Patent Application
20220328871
The present disclosure relates to a power storage device packaging material and a power storage device using the same.
Known power storage devices include secondary batteries such as lithium-ion batteries, nickel hydride batteries and lead batteries, and electrochemical capacitors such as electric double layer capacitors. Due to miniaturization of mobile devices, limitation of installation spaces, or the like, further miniaturization of power storage devices is sought, and thus attention is given to lithium-ion batteries for their high energy density. Metal cans that have been used for packaging materials for lithium-ion batteries are being replaced by multilayer films due to their light weight, high heat dissipation, and low manufacturing cost.
Lithium-ion batteries using such a multilayer film as a packaging material are called laminated lithium-ion batteries. The packaging material covers the battery contents (e.g., cathode, separator, anode, electrolyte solution) and prevents moisture from infiltrating into the battery. Laminated lithium-ion batteries are manufactured by, for example, forming a recess in part of the packaging material by cold forming, accommodating the battery contents in the recess, folding back the remaining part of the packaging material, and sealing the edge portions by heat-sealing (see, for example, PTL 1).
[Citation List] [Patent Literature] [PTL 1] JP 2013-101765 A.
As the next generation batteries replacing lithium-ion batteries, research and development have been made on power storage devices called fully solid-state batteries. The fully solid-state batteries are characterized in that they use a solid electrolyte as an electrolytic substance, instead of an organic electrolyte solution. While the lithium-ion batteries cannot be used under temperature conditions higher than the boiling point of their electrolyte solution (about 80° C.), the fully solid-state batteries can be used under temperature conditions higher than 100° C. and can enhance the conductivity of lithium ions when the batteries are used under high temperature conditions (e.g., 100° C. to 150° C. or 100° C. to 170° C.).
However, in manufacturing of laminated fully solid-state batteries using the above-mentioned multilayer film as a packaging material, the adhesion between layers in a high temperature environment may not be achieved if the packaging material has insufficient heat resistance. This causes a deterioration in lamination strength, leading to a decrease in sealing performance of the package of fully solid-state batteries. As described in PTL 1, for example, the packaging material has a structure in which a substrate layer, a metal foil layer (barrier layer) and a sealant layer are laminated via an adhesive layer or the like. In this case, the adhesion between the substrate layer and the metal foil layer are likely to be deteriorated in a high temperature environment. In addition, epoxy adhesives are known as heat-resistant adhesives, but cured epoxy adhesives tend to be brittle and are likely to be insufficient to provide deep drawing formability required for packaging materials and lamination strength under a room temperature environment.
In view of the above issue, first to third objects of the present disclosure are to provide a power storage device packaging material capable of exhibiting excellent lamination strength in both room temperature environment and high temperature environment and having excellent deep drawing formability, and a power storage device using the power storage device packaging material.
Furthermore, in manufacturing of laminated fully solid-state batteries using the above-mentioned multilayer film as a packaging material, delamination may occur between layers in the packaging material (in particular, between the substrate layer and the barrier layer or between the sealant layer and the barrier layer) due to the packaging material having insufficient heat resistance, which may cause insufficient sealing performance of the package of fully solid-state batteries.
In view of the above issue, a fourth object of the present disclosure is to provide a packaging material having excellent heat resistance.
Furthermore, in the above fully solid-state batteries, more battery contents can be stored by increasing the depth of the recess formed by cold forming, and thus higher energy density can be achieved. Therefore, a packaging material made of a multilayer film is required to have deep drawing formability sufficient to form a recess of a desired depth.
In view of the above issue, a fifth object of the present disclosure is to provide a packaging material having excellent heat resistance and sufficient deep drawing formability.
In order to achieve the first object, the present disclosure provides a power storage device packaging material including: a laminate at least including a substrate layer, a barrier layer, and a sealant layer, which are disposed in this order; and an adhesive layer interposed between the substrate layer and the barrier layer, the adhesive layer containing a polyurethane-based compound made of a reaction product of at least one polyester polyol resin and at least one polyfunctional isocyanate compound, wherein the polyfunctional isocyanate compound contains an isocyanurate of isophorone diisocyanate, and a content of isocyanate groups derived from the isocyanurate of isophorone diisocyanate in the polyfunctional isocyanate compound is 5 mol % to 100 mol % relative to a total amount of isocyanate groups contained in the polyfunctional isocyanate compound of 100 mol %.
In a cured film (adhesive layer) of an adhesive using a polyfunctional isocyanate compound containing a polyester polyol resin as a base resin and an isocyanurate of isophorone diisocyanate (hereinafter, also referred to as an “IPDI-isocyanurate”) as a hardener at a specific ratio, relaxation of molecular chain mixing is unlikely to occur even when exposed to high temperatures because of the bulky molecular structure of the IPDI-isocyanurate. Therefore, adhesion between the layers is not likely to decrease even in a high temperature environment, and sufficient lamination strength between the substrate layer and the barrier layer via the above adhesive layer can be obtained. In addition, the above adhesive layer has toughness higher than that of a cured film of epoxy-based adhesive, and can exhibit excellent deep drawing formability and excellent lamination strength in a room temperature environment. Therefore, according to the power storage device packaging material of the present disclosure having the above configuration, excellent lamination strength in both room temperature environment and high temperature environment can be achieved, and deep drawing formability can be improved. Further, since the IPDI-isocyanurate has an alicyclic structure and does not have an aromatic ring, the adhesive layer using the IPDI-isocyanurate as a hardener has an advantage that it is not likely to cause yellowing (deterioration in appearance) even when exposed to a high temperature environment for a long period of time.
In the above power storage device packaging material, a ratio of a number of isocyanate groups contained in the polyfunctional isocyanate compound to a number of hydroxyl groups contained in the polyester polyol resin may be 2 to 60.
When the ratio (NCO/OH) of the number of isocyanate groups to the number of hydroxyl groups is 2 or more, lamination strength in a high temperature environment can be further improved. The reason is as follows. When the amount of the hardener is large relative to the base resin, the hardeners react with each other to produce by-products such as urea resin and biuret resin. These resins contain active hydrogen groups, which interact with polar groups in each layer, increasing the interfacial adhesion. Accordingly, the heat resistance is considered to be improved. On the other hand, the ratio (NCO/OH) of 60 or less can prevent occurrence of insufficient curing caused by an excessively high ratio of the hardener. Accordingly, lamination strength in a room temperature environment and a high temperature environment can be further improved. Further, an excessively high ratio of the hardener, which causes an excessively high ratio of urea resin or biuret resin in the cured film, may cause the cured film to be brittle and have poor formability. Such a problem can be avoided by setting the ratio (NCO/OH) to 60 or less.
In the above power storage device packaging material, the polyfunctional isocyanate compound may further contain an adduct of tolylene diisocyanate (hereinafter, referred to a “TDI-adduct”). The TDI-adduct has intermolecular interaction (π-π stacking) and urethane bonds, and has high cohesive force. Accordingly, the TDI-adduct has relatively good heat resistance, although lower than that of the IPDI-isocyanurate. Further, the TDI-adduct can exhibit adhesion strength in a room temperature environment and deep drawing formability higher than those of the IPDI-isocyanurate. Therefore, by using the IPDI-isocyanurate and the TDI-adduct in combination, excellent lamination strength in both a room temperature environment and a high temperature environment at a high level in a balanced manner can be obtained, and deep drawing formability can be further improved.)
In the above power storage device packaging material, a ratio of a number of isocyanate groups derived from the isocyanurate of isophorone diisocyanate to a number of isocyanate groups derived from the adduct of tolylene diisocyanate contained in the polyfunctional isocyanate compound may be 0.05 to 20. When the ratio (NCOA/NCOB) of the number of isocyanate groups (NCOA) derived from the IPDI-isocyanurate to the number of isocyanate groups (NCOB) derived from the TDI-adduct is 0.05 or more, a sufficient heat resistance improvement effect of the IPDI-isocyanurate can be achieved, and sufficient lamination strength in a high temperature environment can be obtained. Further, when the ratio (NCOA/NCOB) is 0.05 or more, occurrence of delamination when the packaging material is exposed to a high temperature after the deep drawing can be sufficiently prevented. On the other hand, when the ratio (NCOA/NCOB) is 20 or less, a sufficient adhesion improvement effect of the TDI-adduct in room temperature can be achieved, and lamination strength in a room temperature environment and deep drawing formability can be further improved.
In the above power storage device packaging material, a mass per unit area of the adhesive layer may be 2.0 g/m2 to 6.0 g/m2. When the mass per unit area is 2.0 g/m2 or more, the adhesive layer can have a sufficient thickness, whereby the rigidity of the adhesive layer becomes close to that of the substrate layer and the barrier layer. Accordingly, the deep drawing formability and the lamination strength in both a room temperature environment and a high temperature environment can be further improved. On the other hand, when the mass per unit area is larger than 6.0 g/m2, it is difficult to further improve deep drawing formability and lamination strength. Therefore, from the viewpoint of preventing the film thickness and the cost from increasing, the mass per unit area is preferably 6.0 g/m2 or less.
In the above power storage device packaging material, an anticorrosion treatment layer may be provided on one or both surfaces of the barrier layer. The anticorrosion treatment layer can prevent corrosion of the barrier layer, and further enhance adhesion between the barrier layer and a layer adjacent thereto. In fully solid-state batteries, a sulfide-based material may be used for the electrolyte. When water infiltrates into the packaging material, a sulfide-based compound reacts with water to generate hydrogen sulfide (WS). The EFS may deteriorate adhesion between the barrier layer and a layer adjacent thereto. However, when the aforementioned power storage device packaging material is used as a packaging material of fully solid-state batteries, the anticorrosion treatment layer provided on a surface of the barrier layer can impart EFS resistance to the barrier layer, preventing deterioration in adhesion between the barrier layer and a layer adjacent thereto.
In the above power storage device packaging material, the substrate layer may be made of a polyamide film or a polyester film. When a polyamide film or a polyester film is used as the substrate layer, the deep drawing formability can be further improved. Further, when a polyethylene terephthalate film is used as the substrate layer, adhesion to the adhesive layer is further improved. As a result, the heat resistance and the deep drawing formability tend to be further improved.
The above power storage device packaging material may be for use with a fully solid-state battery.
Furthermore, the present disclosure provides a power storage device including: a power storage device main body; a current extraction terminal extending from the power storage device main body; and the power storage device packaging material of the above disclosure, the power storage device packaging material sandwiching and holding the current extraction terminal and accommodating the power storage device main body. The above power storage device may be a fully solid-state battery.
In order to achieve the second object, the present disclosure provides a power storage device packaging material including: a laminate at least including a substrate layer, a first adhesive layer, a barrier layer, a second adhesive layer, and a sealant layer, which are disposed in this order, wherein, when the first adhesive layer is exposed by removing the substrate layer to measure an outermost surface of the exposed first adhesive layer using an attenuated total reflection-Fourier transform infrared spectroscopy, a baseline transmittance T0, a minimum transmittance T1 in a range of 2100 cm−1 to 2400 cm−1, and a minimum transmittance T2 in a range of 1670 cm−1 to 1700 cm−1 satisfy a relationship of 0.06≤(T0−T1)/(T0−T2)≤0.4.
When the relationship of 0.06≤(T0−T1)/(T0−T2)≤0.4 is satisfied, the values of tensile strength and elongation at break of the first adhesive layer become close to those of each layer (mainly the barrier layer and the substrate), resulting in an increase in formability. Further, when a formed product using the packaging material of the present disclosure is exposed to a high temperature environment (150° C.), reaction between the unreacted hardeners is expedited to increase Tg of the first adhesive layer, which improves the heat resistance.
In the above power storage device packaging material, the first adhesive layer may contain a polyfunctional isocyanate compound, and the polyfunctional isocyanate compound may be composed of at least one polyfunctional isocyanate compound selected from the group consisting of an alicyclic isocyanate polymer and an isocyanate polymer containing an aromatic ring in a molecular structure. When the structure of the isocyanate compound is specified as an alicyclic compound and a benzene ring-containing compound, initial adhesion and heat resistance can be improved.
In the above power storage device packaging material, the first adhesive layer may contain a urethane resin made of at least one polyol selected from the group consisting of polyester polyol, acrylic polyol and polycarbonate diol, and the polyfunctional isocyanate polymer. When the polyol component is selected from the group consisting of polyester polyol, acrylic polyol and polycarbonate diol (PCD), heat resistance and formability are improved. In particular, polyester polyols are preferred.
In the above power storage device packaging material, a ratio of a number of isocyanate groups contained in the polyfunctional isocyanate polymer to a number of hydroxyl groups contained in the polyol may be 5 to 60. When the NCO/OH ratio is within the above range, lamination strength in a high temperature environment is improved, and deterioration in formability can be prevented.
In the above power storage device packaging material, a dry coating weight of the urethane resin may be 2.0 g/m2 or more and 6.0 g/m2 or less. When the coating amount is smaller than 2.0 g/m2, the adhesive layer has a small thickness, leading to a decrease in stress dispersion and thus a decrease in formability. On the other hand, when the coating amount increases, the adhesive layer has a large thickness, increasing the formability due to increased stress dispersion or the like. However, the formability does not greatly increase even when the coating amount becomes larger than 6.00 g/m2. Accordingly, from the viewpoint of cost and the like, the upper limit of the coating amount is preferably 6.00 g/m2.
In the above power storage device packaging material, the barrier layer may be an aluminum foil. This leads to excellent overall balance of barrier properties, drawability, cost, and the like.
In the above power storage device packaging material, the barrier layer may have a thickness of 15 μm to 100 μm. This leads to good formability and reduction in the cost.
In the above power storage device packaging material, the barrier layer may be provided with an anticorrosion treatment layer, the anticorrosion treatment layer is provided either between the first adhesive layer and the barrier layer or between the second adhesive layer and the barrier layer, or both thereof. This leads to improvement in chemical adhesion to the adhesive layer, increasing the formability. In addition, this provides corrosion resistance to hydrogen sulfide generated when sulfide is used as the solid electrolyte.
In the above power storage device packaging material, the substrate may be made of a polyamide film or a polyester-based film. Using the substrate having excellent toughness and heat resistance can improve heat resistance and formability.
The above power storage device packaging material may be for use with a fully solid-state battery.
Furthermore, the present disclosure provides a power storage device including: a power storage device main body; a current extraction terminal extending from the power storage device main body; and the power storage device packaging material of the above disclosure, the power storage device packaging material sandwiching and holding the current extraction terminal and accommodating the power storage device main body. The above power storage device may be a fully solid-state battery.
In order to achieve the third object, the present disclosure provides a power storage device packaging material including: a laminate at least including a substrate layer, a barrier layer, and a sealant layer, which are disposed in this order; and an adhesive layer interposed between the substrate layer and the barrier layer, the adhesive layer containing a polyurethane-based compound and a polyamide-imide resin.
The adhesive layer containing the polyurethane-based compound has toughness higher than a cured film of epoxy-based adhesive, and can exhibit excellent deep drawing formability and excellent lamination strength in a room temperature environment. However, the lamination strength in a high temperature environment, for example, 170° C. or higher is not sufficient. A polyurethane-based compound made of a reaction product of polyester polyol and an isocyanurate (IPDI-n) of isophorone diisocyanate has relatively excellent heat resistance. However, in this case as well, the lamination strength in a high temperature environment, for example, 170° C. or higher cannot be regarded as being sufficient.
The polyamide-imide resin is relatively brittle and therefore inferior in toughness, but has excellent heat resistance. Accordingly, when the adhesive layer is prepared by formulating the polyamide-imide resin and the polyurethane-based compound, it exhibits sufficient lamination strength in a high temperature environment, for example, 170° C. or higher, and also has excellent deep drawing formability. Further, it can maintain high lamination strength in a high temperature environment after the deep drawing.
When the solid content of the polyamide-imide resin to the solid content of the polyurethane-based compound in the adhesive layer is defined as A mass %, the content preferably satisfies 1.0 mass %<A. On the other hand, when the solid content A of the polyamide-imide resin to the solid content of the polyurethane-based compound is 1.0 mass % or less, the lamination strength in a high temperature environment may be insufficient. Further, the content preferably satisfies A<20.0 mass %. On the other hand, when the solid content A of the polyamide-imide resin to the solid content of the polyurethane-based compound is 20.0 mass % or higher, the deep drawing formability may be poor.
The polyamide-imide resin preferably has a number average molecular weight Mn of 3,000<Mn<36,000. On the other hand, when the number average molecular weight Mn of the polyamide-imide resin is 3,000 or less, the polyamide-imide resin has a low glass transition temperature or softening temperature, which may cause insufficient lamination strength in a high temperature environment. When the number average molecular weight Mn of the polyamide-imide resin is 36,000 or more, the polyamide-imide resin is not likely to dissolve in a solvent, and it is difficult to apply and form an adhesive layer.
The polyurethane-based compound may also be made of a reaction product of at least one polyol resin and at least one polyfunctional isocyanate compound. In this case, as the polyol resin, at least one polyol resin selected from the group consisting of polyester polyol, acrylic polyol and polycarbonate polyol can be used. When the polyol resin is composed of polyester polyol, acrylic polyol or polycarbonate polyol, both the lamination strength in a high temperature environment and the formability are improved.
Further, as the polyfunctional isocyanate compound, at least one isocyanate polymer selected from the group consisting of an alicyclic isocyanate polymer and an isocyanate polymer containing an aromatic ring in the molecular structure can be used. When the polyfunctional isocyanate compound is composed of an alicyclic isocyanate polymer or an isocyanate polymer containing an aromatic ring in the molecular structure, both the lamination strength and the formability are improved. The reason for this is not clear, but seems to be that, due to the alicyclic isocyanate polymer having a bulky molecular structure, relaxation of molecular chain mixing is unlikely to occur even in a high temperature environment. In addition, it seems that, in an isocyanate polymer containing an aromatic ring in the molecular structure, the cohesive force increases due to the intermolecular interaction, leading to an increase in heat resistance of the cured film itself, and thus an increase in lamination strength.
The ratio (NCO/OH) of the number of isocyanate groups contained in the polyfunctional isocyanate compound to the number of hydroxyl groups contained in the polyol resin is preferably 1.5<NCO/OH<40.0.
When the number of isocyanate groups contained in the hardener (polyfunctional isocyanate compound) of a polyurethane-based compound is very large relative to the number of hydroxyl groups contained in the base resin (polyol resin) (NCO/OH>>1.0), the heat resistance is improved. When the amount of the NCO group is sufficiently larger than the OH groups, the hardeners react with each other to produce by-products such as urea resin and biuret resin. The urea resin and biuret resin contain active hydrogen groups, which interact with polar groups in each interface, increasing the interfacial adhesion. Accordingly, the heat resistance is considered to be improved.
In order to achieve the fourth object, the present disclosure provides a power storage device packaging material including: a laminate structure including a substrate layer, a first adhesive layer, a barrier layer, a second adhesive layer, and a sealant layer, which are disposed in this order, wherein at least one of the first adhesive layer and the second adhesive layer contains a urea-based compound which is a reaction product of an amine-based resin and a polyisocyanate compound, and, when an infrared absorption spectrum peak intensity in a range of 1680 cm−1 to 1720 cm−1 is A1 and an infrared absorption spectrum peak intensity in a range of 1590 cm−1 to 1640 cm−1 is B1 in a layer containing the urea-based compound among the first adhesive layer and the second adhesive layer, X1 defined by the following formula (1-A) is 10 to 99:
X1={B1/(A1+B1)}×100 (1-A).
The above power storage device packaging material has excellent heat resistance. The inventors of the present disclosure consider the reason why the above effects are achieved to be as follows. In the urea-based compound, a urea group has a very high cohesive force. In addition, since the urea group has active hydrogen in the molecule, hydrogen bonds are generated between the interface of a target to be adhered and the active hydrogen, increasing the interfacial adhesion. Further, in the adhesive layer, when X1 calculated by using the infrared absorption spectrum peak intensity in 1680 cm-1 to 1720 cm-1 derived from a urethane group and the infrared absorption spectrum peak intensity in 1590 cm-1 to 1640 cm-1 derived from a urea group is 10 or more, the urea group of the urea-based compound exhibits a high cohesive force, and when X1 is 99 or less, the adhesive layer can be prevented from excessively hardening. Accordingly, the adhesive layer has high adhesiveness. As a result, the above power storage device packaging material has excellent heat resistance.
In the present disclosure, an isocyanate group of the polyisocyanate compound may be bonded to a blocking agent. Further, the blocking agent may be dissociated from an isocyanate group of the polyisocyanate compound at 60° C. to 120° C. As a result, the obtained packaging material has excellent curling resistance.
In the present disclosure, an anticorrosion treatment layer may further be provided at least between the second adhesive layer and the barrier layer. As a result, the heat resistance is further improved.
In the present disclosure, only the second adhesive layer among the first adhesive layer and the second adhesive layer may contain the urea-based compound. As a result, the obtained packaging material has excellent heat resistance, and the first adhesive layer has rigidity that is easily mitigated to achieve excellent deep drawing formability. Further, since only the second adhesive layer contains a urea-based compound, corrosion of the barrier layer due to hydrogen sulfide generated from the battery contents in the packaging material can be suppressed.
In the present disclosure, the sealant layer may contain at least one of a polyolefin-based resin and a polyester-based resin. Due to the sealant layer containing at least one of a polyolefin-based resin and a polyester-based resin having a high melting point, heat resistance is further improved.
In the present disclosure, at least one of the first adhesive layer and the second adhesive layer may contain a hydrogen sulfide adsorbent. As a result, the obtained packaging material has high resistance to hydrogen sulfide, which reduces occurrence of delamination between the barrier layer and the substrate layer and between the barrier layer and the sealant layer even when hydrogen sulfide is generated from the power storage device or when hydrogen sulfide is present outside the packaging material.
The present disclosure may be for use with a fully solid-state battery. Since the packaging material of the present disclosure has excellent heat resistance, it is suitable for use with fully solid-state batteries that are expected to be used in a high temperature environment.
In order to achieve the fifth object, the present disclosure provides a power storage device packaging material (hereinafter, may also be simply referred to as a “packaging material”) including: a laminate structure including a substrate layer, a first adhesive layer, a metal foil layer, a second adhesive layer, and a sealant layer, which are disposed in this order, wherein the first adhesive layer and the second adhesive layer contain a urethane-based compound which is a reaction product of a polyol-based resin and a polyisocyanate compound, and, when an infrared absorption spectrum peak intensity in a range of 2250 cm−1 to 2290 cm−1 is A2 and an infrared absorption spectrum peak intensity in a range of 1680 cm−1 to 1720 cm−1 is B2 in the first adhesive layer and the second adhesive layer, X2 defined by the following formula (1-B) is 10 to 90, and a glass transition temperature of the first adhesive layer and the second adhesive layer is 60° C. to 80° C.:
X2={B2/(A2+B2)}×100 (1-B).
The above power storage device packaging material has excellent heat resistance and sufficient deep drawing formability. The inventors of the present disclosure consider the reason why the above effects are achieved to be as follows.
That is, in the urethane-based compound, a urethane group has a very high cohesive force. In addition, since the urethane group has active hydrogen in the molecule, hydrogen bonds are generated between the interface of a target to be adhered and the active hydrogen, increasing the interfacial adhesion. Further, in the adhesive layer, when X2 calculated by using the infrared absorption spectrum peak intensity in 1680 cm−1 to 1720 cm−1 derived from a urethane group and the infrared absorption spectrum peak intensity in 2250 cm−1 to 2290 cm−1 derived from an isocyanate group as the raw material is 10 or more, the urethane group of the urethane-based compound exhibits a high cohesive force, and when X2 is 90 or less, the adhesive layer can be prevented from excessively hardening. Accordingly, the adhesive layer has high adhesiveness.
Further, when X2 defined by the above general formula (1-B) is 10 to 90 and the glass transition temperature is 60 to 80° C., the adhesive layer has sufficient crosslinking density and has a strength sufficient to withstand the shear stress applied when the adhesive layer is stretched in deep drawing. Further, when X2 defined by the above general formula (1-B) and the glass transition temperature are within the above range, the adhesive layer is prevented from being excessively rigid, and follows the stretching of the substrate layer and the metal foil layer when the adhesive layer is stretched in deep drawing. Accordingly, occurrence of fine cracks in the adhesive layer can be prevented.
Thus, the above packaging material in which both the first adhesive layer and the second adhesive layer contain a urethane-based compound, X2 is 10 to 90, and the glass transition temperature is 60 to 80° C. has excellent heat resistance and sufficient deep drawing formability.
In the present disclosure, the polyol-based resin may be a polyester polyol-based resin. The polyester polyol-based resin tends to have a large number of esters derived from dicarboxylic acids (polar groups) in the molecules and therefore has a high hydrogen bonding force compared with the polyol-based resin. Accordingly, adhesion of the adhesive layer to the substrate layer, the sealant layer and the metal foil layer is improved. As a result, the obtained packaging material has further improved deep drawing formability.
In the present disclosure, an anticorrosion treatment layer may further be provided at least between the second adhesive layer and the metal foil layer. As a result, the obtained packaging material has further improved deep drawing formability and further improved heat resistance, which reduces occurrence of delamination between layers of the packaging material (in particular, between the metal foil layer and the substrate layer or between the metal foil layer and the sealant layer) under high temperature conditions (e.g., 100 to 150° C.).
In the present disclosure, the sealant layer may contain at least one of a polyolefin-based resin and a polyester-based resin, and may contain a polyester-based resin. When the sealant layer contains a polyolefin-based resin having a high melting point, the obtained packaging material has excellent heat resistance, and when the sealant layer contains a polyester-based resin having a higher melting point, the obtained packaging material has more excellent heat resistance.
In the present disclosure, the polyisocyanate compound may contain an aromatic polyisocyanate compound, and may contain an adduct of an aromatic polyisocyanate compound. When the polyisocyanate compound contains these compounds, π-π stacking action between aromatic rings or it-H interaction between molecules occurs, improving the cohesive force of the adhesive layer. Therefore, when the polyisocyanate compound contains an aromatic polyisocyanate compound or an adduct thereof, the obtained packaging material has excellent heat resistance. In addition, since an adduct of an aromatic polyisocyanate compound contains active hydrogen in the molecule, hydrogen bonds are generated between the interface of a target to be adhered and the active hydrogen, increasing the interfacial adhesion. As a result, the obtained packaging material has further improved heat resistance.
In the present disclosure, at least the second adhesive layer may contain a hydrogen sulfide adsorbent. As a result, the obtained packaging material has high resistance to hydrogen sulfide, which reduces occurrence of delamination between the metal foil layer and the sealant layer even when hydrogen sulfide is generated from the power storage device.
The present disclosure may be for use with a fully solid-state battery. Since the packaging material of the present disclosure has excellent heat resistance and sufficient deep drawing formability, it is suitable for use with fully solid-state batteries in which a recess is formed by cold forming, and the battery contents are accommodated in the recess.
According to first to third aspects of the present disclosure, a power storage device packaging material capable of exhibiting excellent lamination strength in both room temperature environment and high temperature environment and having excellent deep drawing formability, and a power storage device using the power storage device packaging material can be provided.
According to a fourth aspect of the present disclosure, a power storage device packaging material having excellent heat resistance can be provided.
According to a fifth aspect of the present disclosure, a power storage device packaging material having excellent heat resistance and sufficient deep drawing formability can be provided.
Embodiments of the present invention will be described below with reference to the drawings. In the following description of the drawings to be referred, components or functions identical with or similar to each other are given the same or similar reference signs, unless there is a reason not to. It should be noted that the drawings are only schematically illustrated, and thus the relationship between thickness and two-dimensional size of the components, and the thickness ratio between the layers, are not to scale. Therefore, specific thicknesses and dimensions should be understood in view of the following description. As a matter of course, dimensional relationships or ratios may be different between the drawings.
Further, the embodiments described below are merely examples of configurations for embodying the technical idea of the present invention. The technical idea of the present invention does not limit the materials, shapes, structures, arrangements, and the like of the components to those described below. The technical idea of the present invention can be modified variously within the technical scope defined by the claims. The present invention is not limited to the following embodiments within the scope not departing from the spirit of the present invention. For the sake of clarity, the drawings may be illustrated in an exaggerated manner as appropriate.
In any group of successive numerical value ranges described in the present specification, the upper limit value or lower limit value of one numerical value range may be replaced with the upper limit value or lower limit value of another numerical value range. In the numerical value ranges described in the present specification, the upper limit values or lower limit values of the numerical value ranges may be replaced with values shown in examples. The configuration according to a certain embodiment may be applied to other embodiments.
The embodiments of the present invention are a group of embodiments based on a single unique invention. The aspects of the present invention are those of the group of embodiments based on a single invention. Configurations of the present invention can have aspects of the present disclosure. Features of the present invention can be combined to form the configurations. Therefore, the features of the present invention, the configurations of the present invention, the aspects of the present disclosure, and the embodiments of the present invention can be combined, and the combinations can have a synergistic function and exhibit a synergistic effect.
<<First Aspect>>
The following description will be given of a power storage device packaging material, a method of producing the packaging material and a power storage device according to a first aspect of the present disclosure.
[Power Storage Device Packaging Material]
In the packaging material 10 of the present embodiment, at least one of the first adhesive layer 12a and the second adhesive layer 12b is a layer containing a polyurethane-based compound made of a reaction product of at least one polyester polyol resin and at least one polyfunctional isocyanate compound. The polyfunctional isocyanate compound contains an isocyanurate of isophorone diisocyanate (IPDI-isocyanurate), and the content of isocyanate groups derived from the IPDI-isocyanurate in the polyfunctional isocyanate compound is 5 mol % to 100 mol % relative to the total amount of isocyanate groups contained in the polyfunctional isocyanate compound of 100 mol %.
In the following description, each of layers constituting the packaging material 10 will be specifically described.
<Substrate Layer 11>
The substrate layer 11 imparts heat resistance to the packaging material in the sealing step during production of the power storage device, and prevents pinholes from occurring during forming processing or distribution. Particularly in the case of a packaging material for a large power storage device, the substrate layer 11 can also impart scratch resistance, chemical resistance, insulating properties, and the like.
The substrate layer 11 is preferably formed of a resin film made of a resin having insulating properties. Examples of the resin film include stretched or unstretched films such as polyester films, polyamide films, polyimide films, and polypropylene films. The substrate layer 11 may be a monolayer film made of one of these resin films, or a laminated film made of two or more of these resin films.
The substrate layer 11 is preferably made of, among the above resin films, a polyester film or a polyamide film, and more preferably a polyester film from the perspective of having excellent formability. These films are preferably biaxially stretched. A polyester resin constituting the polyester film may be, for example, polyethylene terephthalate (PET). A polyamide resin constituting the polyamide film may be, for example, Nylon-6, Nylon-6,6, a copolymer of Nylon-6 and Nylon-6,6, Nylon-6,10, polymetaxylylene adipamide (MXD6), Nylon-11, Nylon-12, or the like. Among the polyamide films, nylon 6 (ONy) is preferred from the perspective of having good heat resistance, piercing strength and impact strength.
The stretching method used for the biaxially stretched film may be, for example, sequential biaxial stretching, tubular biaxial stretching, simultaneous biaxial stretching, or the like. From the perspective of obtaining better deep drawing formability, the biaxially stretched film is preferably stretched using a tubular biaxial stretching method.
Preferably, the substrate layer 11 has a peak melting temperature higher than that of the sealant layer 16. When the sealant layer 16 has a multilayer structure, the peak melting temperature of the sealant layer 16 refers to that of the layer having a maximum peak melting temperature. The peak melting temperature of the substrate layer 11 is preferably 290° C. or higher, and more preferably 290° C. to 350° C. The resin film that can be used as the substrate layer 11 and has a peak melting temperature within the above range may be a nylon film, PET film, polyamide film, polyimide film, polyphenylene sulfide film (PPS film), or the like. The substrate layer 11 may be a commercially available film, or may be a coating film (obtained by applying and drying a coating liquid). The substrate layer 11 may have a single layer structure or a multilayer structure, or may be formed by applying a thermosetting resin. Further, the substrate layer 11 may contain various additives (e.g., a flame retardant, slip agent, anti-blocking agent, antioxidant, photostabilizer, and tackifier).
When the peak melting temperature of the substrate layer 11 is expressed as T11 and that of the sealant layer 16 is expressed as T16, the difference between them (T11−T16) is preferably 20° C. or more. When the temperature difference is 20° C. or more, deterioration in appearance of the packaging material 10 due to heat-sealing can be more sufficiently prevented.
The substrate layer 11 preferably has a thickness of 5 μm to 50 μm, more preferably 6 μm to 40 μm, still more preferably 10 μm to 30 μm, and particularly preferably 12 μm to 30 μm. When the thickness of the substrate layer 11 is 5 μm or more, there is a tendency to improve pinhole resistance and insulation properties of the power storage device packaging material 10. When the substrate layer 11 has a thickness of greater than 50 μm, the total thickness of the power storage device packaging material 10 increases, and the electrical capacity of the battery may have to be reduced, which is not desirable.
<First Adhesive Layer 12a>
The first adhesive layer 12a bonds the substrate layer 11 and the barrier layer 13. In the packaging material 10 of the present embodiment, the first adhesive layer 12a (hereinafter, also referred to as a “specific adhesive layer”) is a layer containing a polyurethane-based compound made of a reaction product of at least one polyester polyol resin and at least one polyfunctional isocyanate compound, in which the polyfunctional isocyanate compound contains IPDI-isocyanurate, and the content of isocyanate groups derived from the IPDI-isocyanurate in the polyfunctional isocyanate compound is 5 mol % to 100 mol % relative to the total amount of isocyanate groups contained in the polyfunctional isocyanate compound of 100 mol %.
In the specific adhesive layer, the content of isocyanate groups derived from the IPDI-isocyanurate in the polyfunctional isocyanate compound is 5 mol % to 100 mol %, preferably 25 mol % to 95 mol %, and more preferably 50 mol % to 75 mol % relative to the total amount of isocyanate groups contained in the polyfunctional isocyanate compound of 100 mol %. When the content is 5 mol % or more, lamination strength in a high temperature environment can be obtained, and occurrence of delamination when the packaging material is exposed to a high temperature after the deep drawing can be prevented. On the other hand, the above content may be 100 mol %, or may be less than 100 mol % when a polyfunctional isocyanate compound other than the IPDI-isocyanurate is used in combination with the IPDI-isocyanurate. When the content is 95 mol % or less, lamination strength in a room temperature environment and deep drawing formability tend to be further improved due to the effect of combined use of other polyfunctional isocyanate compounds.
In the specific adhesive layer, the polyfunctional isocyanate compound may include, in addition to the IPDI-isocyanurate, at least one selected from the group consisting of an adduct of tolylene diisocyanate (TDI-adduct), an adduct of hexamethylene diisocyanate, a biuret and an isocyanurate of hexamethylene diisocyanate, a biuret and an isocyanurate of tolylene diisocyanate, an adduct, a biuret and an isocyanurate of diphenylmethane diisocyanate, and an adduct, a biuret and an isocyanurate of xylylene diisocyanate, or may include TDI-adduct. When such a polyfunctional isocyanate compound is used together with the IPDI-isocyanurate, lamination strength in a room temperature environment and deep drawing formability can be further improved.
When the polyfunctional isocyanate compound contains a TDI-adduct, a ratio (NCOA/NCOB) of the number of isocyanate groups (NCOA) derived from the IPDI-isocyanurate to the number of isocyanate groups (NCOB) derived from the TDI-adduct may be 0.05 to 20. From the viewpoint of heat resistance, the ratio (NCOA/NCOB) may be 0.3 to 6, preferably 2 to 4, and more preferably 3. Further, the ratio (NCOA/NCOB) may also be 7 to 20. When the ratio is 0.05 or more, sufficient lamination strength in a high temperature environment can be obtained, and occurrence of delamination when the packaging material is exposed to a high temperature after the deep drawing can be sufficiently prevented. When the ratio is 20 or less, lamination strength in a room temperature environment and deep drawing formability can be further improved.
In the specific adhesive layer, a ratio (NCO/OH) of the number of isocyanate groups contained in the polyfunctional isocyanate compound to the number of hydroxyl groups contained in the polyester polyol resin may be 2 to 60, preferably 5 to 50, and more preferably 10 to 30. When the ratio is 2 or more, lamination strength in a high temperature environment can be further improved. When the ratio is 60 or less, lamination strength in a room temperature environment and a high temperature environment can be further improved.
The thickness of the first adhesive layer 12a is not specifically limited, but may be, for example, preferably 1 μm to 10 and more preferably 3 μm to 7 μm from the perspective of obtaining desired adhesive strength, conformability, processability, and the like.
When the first adhesive layer 12a is the specific adhesive layer, a mass per unit area of the first adhesive layer 12a may be 2.0 g/m2 to 6.0 g/m2, preferably 2.5 g/m2 to 5.0 g/m2, and more preferably 3.0 g/m2 to 4.0 g/m2 from the perspective of ensuring further improved lamination strength in a room temperature environment and a high temperature environment, and obtaining further improved deep drawing formability.
<Barrier Layer 13>
The barrier layer 13 has water vapor barrier properties to prevent moisture from infiltrating into the power storage device. Further, the barrier layer 13 has ductility and malleability for deep drawing. The barrier layer 13 can be made of, for example, various metal foils such as an aluminum, stainless steel and copper, or a metal vapor deposition film, an inorganic oxide vapor deposition film, a carbon-containing inorganic oxide vapor deposition film, or a film having these vapor deposition films. Examples of the film having a vapor deposition film include an aluminum vapor deposition film and an inorganic oxide vapor deposition film. These can be used singly or in combination of two or more. The barrier layer 13 is preferably made of a metal foil, and more preferably made of an aluminum foil from the viewpoint of the weight (specific gravity), moisture resistance, processability, and cost.
The aluminum foil may be a soft aluminum foil, particularly one subjected to an annealing treatment from the perspective of imparting desired ductility and malleability during forming. It is more preferable to use an iron-containing aluminum foil for the purpose of further imparting pinhole resistance, ductility and malleability during forming. The iron content in the aluminum foil is preferably 0.1 mass % to 9.0 mass %, and more preferably 0.5 mass % to 2.0 mass % relative to 100 mass % of the aluminum foil. The iron content of 0.1 mass % or more can improve pinhole resistance, ductility and malleability of a packaging material 10. The iron content of 9.0 mass % or less can improve flexibility of a packaging material 10. Although an untreated aluminum foil may also be used as the aluminum foil, an aluminum foil subjected to a degreasing treatment is preferably used from the perspective of imparting electrolyte resistance. When the aluminum foil is degreased, only one surface of the aluminum foil may be degreased, or both surfaces may be degreased.
The thickness of the barrier layer 13 is not specifically limited, but is preferably 9 μm to 200 μm, and more preferably 15 μm to 100 μm from the perspective of barrier properties, pinhole resistance and processability. The thickness less than 15 μm may decrease formability. Further, the thickness greater than 100 μm tends to decrease the weight energy density of the battery, leading to a high cost.
<First and Second Anticorrosion Treatment Layers 14a, 14b>
The first and second anticorrosion treatment layers 14a and 14b are disposed on respective surfaces of the barrier layer 13 to prevent corrosion of the metal foil (metal foil layer) or the like constituting the barrier layer 13. The first anticorrosion treatment layer 14a enhances adhesion between the barrier layer 13 and the first adhesive layer 12a. Further, the second anticorrosion treatment layer 14b enhances adhesion between the barrier layer 13 and the second adhesive layer 12b. The first and second anticorrosion treatment layers 14a and 14b may have the same configuration or different configurations. The first and second anticorrosion treatment layers 14a and 14b (hereinafter, also simply referred to as “anticorrosion treatment layers 14a and 14b”) may be formed by, for example, degreasing treatment, hydrothermal modification treatment, anodic oxidation treatment, chemical conversion treatment, or a combination of these treatments.
The degreasing treatment may be acid degreasing or alkaline degreasing. The acid degreasing may be a method using an inorganic acid, such as sulfuric acid, nitric acid, hydrochloric acid or hydrofluoric acid, alone or in combination. The acid degreasing may include use of an acid degreasing agent obtained by dissolving a fluorine-containing compound such as monosodium ammonium difluoride with the aforementioned inorganic acid. Specifically when an aluminum foil is used as the barrier layer 13, use of this acid degreasing agent is effective in terms of corrosion resistance, for its contribution to forming a fluoride of aluminum in a passive state, in addition to obtaining the effect of degreasing aluminum. The alkaline degreasing may be a method using sodium hydroxide or the like.
The hydrothermal modification treatment may be, for example, a boehmite treatment in which an aluminum foil is immersed in boiling water to which triethanolamine has been added.
The anodic oxidation treatment may be, for example, an alumite treatment.
The chemical conversion treatment may be an immersion type or a coating type. Examples of the immersion type chemical conversion treatment include chromate treatment, zirconium treatment, titanium treatment, vanadium treatment, molybdenum treatment, calcium phosphate treatment, strontium hydroxide treatment, cerium treatment, ruthenium treatment, and various chemical conversion treatments of mixed phases thereof. On the other hand, examples of the coating type chemical conversion treatment include a method of applying a coating agent having a corrosion prevention performance to the barrier layer 13.
Of these anticorrosion treatments, when any of the hydrothermal modification treatment, anodic oxidation treatment, and chemical conversion treatment is used to form at least part of the anticorrosion treatment layer, degreasing treatment is preferably performed in advance. Further, when a degreased metal foil such as an annealed metal foil is used as the barrier layer 13, it is not necessary to perform degreasing treatment again in forming the anticorrosion treatment layers 14a and 14b.
The coating agent used for the coating type chemical conversion treatment preferably contains trivalent chromium. Further, the coating agent may contain at least one polymer selected from the group consisting of a cationic polymer and an anionic polymer described later.
Of the treatments mentioned above, the hydrothermal modification treatment and the anodic oxidation treatment, in particular, dissolve a surface of an aluminum foil with a treating agent to form an aluminum compound (such as boehmite or alumite) having good corrosion resistance. These treatments are included in the definition of the chemical conversion treatment since a co-continuous structure is formed from the barrier layer 13 made of an aluminum foil to the anticorrosion treatment layers 14a and 14b. On the other hand, the anticorrosion treatment layers 14a and 14b can also be formed only by a pure coating method, which is not included in the definition of the chemical conversion treatment, as will be described later. For example, this coating method may use a rare-earth oxide sol such as cerium oxide with a mean particle size of 100 nm or less as a material exhibiting an anticorrosion effect (inhibitor effect) for aluminum and preferable in terms of environmental aspects. Use of this method makes it possible to impart an anticorrosion effect to a metal foil such as an aluminum foil even when using an ordinary coating method.
Examples of the rare-earth oxide sol include sols using various solvents such as an aqueous solvent, an alcohol-based solvent, a hydrocarbon-based solvent, a ketone-based solvent, an ester-based solvent, an ether-based solvent, and the like. Of these sols, an aqueous sol is preferred.
To stabilize dispersion, the rare-earth oxide sol may contain, as a dispersion stabilizer, an inorganic acid such as nitric acid, hydrochloric acid, phosphoric acid, or the like or a salt thereof, or an organic acid such as acetic acid, malic acid, ascorbic acid, lactic acid, or the like. Of these dispersion stabilizers, phosphoric acid, in particular, is expected to impart the packaging material 10 with features of (1) stabilizing dispersion of the sol, (2) improving adhesion to the barrier layer 13 making use of an aluminum chelate ability of phosphoric acid, and (3) improving cohesive force of the anticorrosion treatment layers 14a and 14b (oxide layers) by readily inducing dehydration condensation of phosphoric acid even at low temperature, and the like.
The phosphoric acid or a salt thereof may be orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, or an alkali metal salt or an ammonium salt thereof. Of these phosphoric acids or salts thereof, a condensed phosphoric acid such as trimetaphosphoric acid, tetrametaphosphoric acid, hexametaphosphoric acid or ultrametaphosphoric acid, or an alkali metal salt thereof or an ammonium salt thereof is preferred for functional development in the packaging material 10. Further, considering the dry film forming properties (drying capacity and heat quantity) in formation of the anticorrosion treatment layers 14a and 14b made of a rare-earth oxide by various coating methods using the above rare-earth oxide sol, a sodium salt is more preferred from the perspective of exhibiting good dehydrating condensation at low temperature. The phosphate is preferably a water-soluble salt.
The content of the phosphoric acid (or a salt thereof) in the rare-earth oxide is preferably 1 part by mass to 100 parts by mass relative to 100 parts by mass of the rare-earth oxide. When the above content of the phosphoric acid or a salt thereof is 1 part by mass or more relative to 100 parts by mass of the rare-earth oxide, the rare-earth oxide sol becomes more stable and the function of the packaging material 10 becomes much better. The above content is more preferably 5 parts by mass or more relative to 100 parts by mass of the rare-earth oxide. Further, when the above content is 100 parts by mass or less relative to 100 parts by mass of the rare-earth oxide, the function of the rare-earth oxide sol is enhanced. The above content is preferably 50 parts by mass or less, and more preferably 20 parts by mass or less, relative to 100 parts by mass of the rare-earth oxide.
Since the anticorrosion treatment layers 14a and 14b formed of the rare-earth oxide sol are aggregates of inorganic particles, the cohesive force of these layers may be lowered even after being dry-cured. Therefore, the anticorrosion treatment layers 14a and 14b in this case are preferably compounded with an anionic polymer or a cationic polymer described below in order to supplement the cohesive force.
The anionic polymer may be a polymer having a carboxy group. For example, poly(meth)acrylic acid (or a salt thereof), or a copolymer containing poly(meth)acrylic acid as a main component may be used. The copolymerization component of the copolymer includes an alkyl (meth)acrylate monomer (having a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a t-butyl group, a 2-ethylhexyl group, a cyclohexyl group, etc. as an alkyl group); an amide group-containing monomer such as (meth)acrylamide, N-alkyl (meth)acrylamide, or N,N-dialkyl (meth)acrylamide (having a methyl group, an ethyl group, an n-propyl group, an i-propyl group, an n-butyl group, an i-butyl group, a t-butyl group, a 2-ethylhexyl group, a cyclohexyl group, etc. as an alkyl group), N-alkoxy (meth)acrylamide, or N,N-dialkoxy (meth)acrylamide (having a methoxy group, an ethoxy group, a butoxy group, an isobutoxy group, etc. as an alkoxy group), N-methylol (meth)acrylamide, or N-phenyl (meth)acrylamide; a hydroxyl group-containing monomer such as 2-hydroxyethyl (meth)acrylate, or 2-hydroxypropyl (meth)acrylate; a glycidyl group-containing monomer such as glycidyl (meth)acrylate, or allyl glycidyl ether; a silane-containing monomer such as (meth)acryloxypropyltrimethoxysilane or (meth)acryloxypropyltriethoxysilane; or an isocyanate such as (meth)acryloxypropyl isocyanate.
These anionic polymers improve the stability of the anticorrosion treatment layers 14a and 14b (oxide layers) obtained using the rare-earth element oxide sol. The improvement is achieved by the effect of protecting a hard and brittle oxide layer with an acrylic resin component, and the effect of capturing ion contamination (particularly sodium ions) derived from the phosphate contained in the rare-earth oxide sol (cation catcher). That is, if the anticorrosion treatment layers 14a and 14b obtained using the rare-earth oxide sol contain alkali metal ions such as sodium ions or alkaline earth metal ions in particular, the anticorrosion treatment layers 14a and 14b are likely to be deteriorated starting from the ion-containing site. Therefore, the sodium ion or the like contained in the rare-earth oxide sol is fixed with the anionic polymer to improve the durability of the anticorrosion treatment layers 14a and 14b.
The anticorrosion treatment layers 14a and 14b obtained by combining the anionic polymer and the rare-earth oxide sol have anticorrosion performance equivalent to that of the anticorrosion treatment layers 14a and 14b formed by applying chromate treatment to an aluminum foil. The anionic polymer preferably has a structure in which a polyanionic polymer which is essentially water-soluble is crosslinked. The crosslinking agent used for forming this structure may be a compound having, for example, an isocyanate group, a glycidyl group, a carboxy group or an oxazoline group.
Examples of the compound having an isocyanate group include diisocyanates such as tolylene diisocyanate, xylylene diisocyanate or a hydrogenated product thereof, hexamethylene diisocyanate, 4,4′-diphenylmethane diisocyanate or a hydrogenated product thereof, and isophorone diisocyanate; polyisiocyanates such as an adduct obtained by reacting these isocyanates with a polyhydric alcohol such as trimethylolpropane, a biuret obtained by reacting the isocyanates with water, or an isocyanurate as a trimer; and a blocked polyisocyanate obtained by blocking these polyisocyanates with an alcohol, a lactam, an oxime, or the like.
Examples of the compound having a glycidyl group include epoxy compounds obtained by permitting epichlorohydrin to act on a glycol such as ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,4-butanediol, 1,6-hexanediol or neopentyl glycol; epoxy compounds obtained by permitting epichlorohydrin to act on a polyhydric alcohol such as glycerin, polyglycerin, trimethylolpropane, pentaerythritol or sorbitol; and epoxy compounds obtained by permitting epichlorohydrin to act on a dicarboxylic acid such as phthalic acid, terephthalic acid, oxalic acid or adipic acid.
Examples of the compound having a carboxy group includes various aliphatic or aromatic dicarboxylic acids and the like. Also, poly(meth)acrylic acid or an alkali (earth) metal salt of poly(meth)acrylic acid may be used.
Examples of the compound having an oxazoline group include low molecular weight compounds having two or more oxazoline units, or when using a polymerizable monomer such as isopropenyloxazoline, compounds obtained by copolymerizing with acrylic monomers such as (meth)acrylic acid, (meth)acrylic acid alkyl ester and hydroxyalkyl (meth)acrylate.
Further, the crosslinking point may be a siloxane bond by reacting an anionic polymer with a silane coupling agent, more specifically, by selectively reacting a carboxy group of an anionic polymer with a functional group of a silane coupling agent. In this case, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, γ-chloropropylmethoxysilane, vinyltrichlorosilane, γ-mercaptopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, N-β(aminoethyl)-γ-aminopropyltrimethoxysilane, γ-isocyanatopropyltriethoxysilane, or the like may be used. Of these materials, an epoxy silane, aminosilane or isocyanate silane is preferable in terms of reactivity with an anionic polymer or a copolymer thereof in particular.
The ratio of these crosslinking agents to the anionic polymer is preferably 1 part by mass to 50 parts by mass, and more preferably 10 parts by mass to 20 parts by mass, relative to 100 parts by mass of the anionic polymer. When the ratio of the crosslinking agent is 1 part by mass or more relative to 100 parts by mass of the anionic polymer, a sufficiently crosslinked structure is likely to be formed. When the ratio of the crosslinking agent is 50 parts by mass or less relative to 100 parts by mass of the anionic polymer, the pot life of the coating solution improves.
The method used for crosslinking the anionic polymer may be a method of forming an ionic crosslinkage using titanium, zirconium compound or the like, and is not limited to the use of the crosslinking agents mentioned above.
The cationic polymer may be a polymer having an amine, including polyethyleneimine, an ionic polymer complex composed of a polymer having polyethyleneimine and a carboxylic acid, a primary amine graft acrylic resin obtained by grafting a primary amine to an acrylic backbone, polyallylamine or derivatives thereof, and aminophenol. Examples of the polyallylamine include homopolymers or copolymers of allylamine, allylamine amide sulfate, diallylamine, dimethylallylamine, and the like. These amines may be free amines or may be ones stabilized with acetic acid or hydrochloric acid. Maleic acid, sulfur dioxide or the like may be used as a copolymer component. Furthermore, a primary amine may be used after being partially methoxylated to impart crosslinking properties thereto, or aminophenol may also be used. In particular, allylamine or derivatives thereof are preferable.
The cationic polymer is preferably used in combination with a crosslinking agent having a functional group, such as a carboxy group or a glycidyl group, capable of reacting with an amine/imine. The crosslinking agent to be used in combination with the cationic polymer may be polymers having carboxylic acid that forms an ionic polymer complex with polyethyleneimine. Examples of such a crosslinking agent include polycarboxylic acid (salt) such as polyacrylic acid or ionic salts thereof, copolymers having a comonomer introduced thereto, polysaccharides having a carboxy group such as carboxymethyl cellulose or ionic salts thereof, and the like.
The cationic polymer is a more preferable material from the perspective of improving adhesiveness. Since the cationic polymer is water-soluble similarly to the anionic polymer mentioned above, it is more preferable to impart water resistance by permitting it to form a crosslinked structure. The crosslinking agent that can be used for forming a crosslinked structure in the cationic polymer may include ones mentioned in the section on the anionic polymer. When a rare-earth oxide sol is used as the anticorrosion treatment layers 14a and 14b, a cationic polymer may be used as a protective layer, instead of using the anionic polymer mentioned above.
The anticorrosion treatment layer is a chemical conversion treatment layer obtained through chemical conversion treatment represented by a chromate treatment, and can form a gradient structure on the aluminum foil in which the chemical conversion treatment layer is formed on the aluminum foil by treating the aluminum foil using, in particular, a chemical conversion treating agent containing hydrofluoric acid, hydrochloric acid, nitric acid, sulfuric acid, or a salt thereof, followed by permitting it to react with a chromium- or non-chromium-based compound. However, the chemical conversion treatment, which uses an acid as a chemical conversion treating agent, causes deterioration of the working environment and corrosion of the coating device. In this regard, the coating-type anticorrosion treatment layers 14a and 14b mentioned above do not need to form a gradient structure on the barrier layer 13 of an aluminum foil, unlike the anticorrosion treatment layer obtained through the chemical conversion treatment represented by a chromate treatment. Therefore, the properties of the coating agent are not restricted in terms of acidity, alkalinity, neutrality and the like, and a good working environment can be achieved. The coating-type anticorrosion treatment layers 14a and 14b are preferred since chromate treatment using a chromium compound requires alternatives in terms of environmental health.
From the above description, coating-type anticorrosion treatments as mentioned above can be combined as follows, for example: (1) rare-earth oxide sol alone, (2) anionic polymer alone, (3) cationic polymer alone, (4) rare-earth oxide sol+anionic polymer (laminated composite), (5) rare-earth oxide sol+cationic polymer (laminated composite), (6) rare-earth oxide sol+anionic polymer (laminated composite)/cationic polymer (multilayered), (7) rare-earth oxide sol+cationic polymer (laminated composite)/anionic polymer (multilayered). Of these combinations, (1) and (4) through (7) are preferred, and (4) through (7) are more preferred. However, the present embodiment is not limited to the above combinations. For example, an anticorrosion treatment may be selected as follows. Specifically, the cationic polymer is a highly preferable material in terms of having good adhesion to a modified polyolefin resin, as will be described in the section of adhesive resin layer. Therefore, when the adhesive resin layer is formed of a modified polyolefin resin, it is possible to design it that the cationic polymer is provided on the surface contacting the adhesive resin layer (e.g., configurations (5) and (6)).
The anticorrosion treatment layers 14a and 14b are not limited to the layer mentioned above. For example, the anticorrosion treatment layers may be formed using a treating agent prepared by blending a phosphoric acid and a chromium compound with a resin binder (such as aminophenol) as in a coating-type chromate based on known art. When this treating agent is used, the resultant layer will have both the corrosion-preventing function and adhesion. Although it is necessary to consider stability of a coating solution, a coating agent may be prepared in advance by integrating a rare-earth oxide sol with a polycationic polymer or a polyanionic polymer, and using this coating agent, the anticorrosion treatment layers may be formed being imparted with both the corrosion-preventing function and adhesion.
Regardless of having a multilayer structure or a monolayer structure, the anticorrosion treatment layers 14a and 14b preferably have mass per unit area of 0.005 g/m2 to 0.200 g/m2, and more preferably 0.010 g/m2 to 0.100 g/m2. When the mass per unit area is 0.005 g/m2 or more, a corrosion-preventing function can be readily imparted to the barrier layer 13. Even if the mass per unit area exceeds 0.200 g/m2, there is little change in the corrosion-preventing function. If a rare-earth oxide sol is used and if the coating film is thick, heat-curing during drying may be insufficient, and may decrease the cohesive force. The thickness of the anticorrosion treatment layers 14a and 14b can be calculated from their specific gravity.
From the perspective of enhancing adhesion between the sealant layer and the barrier layer, the anticorrosion treatment layers 14a and 14b may contain, for example, cerium oxide, 1 part by mass to 100 parts by mass of phosphoric acid or phosphate relative to 100 parts by mass of the cerium oxide, and a cationic polymer, or may be formed by applying a chemical conversion treatment to the barrier layer 13, or may contain a cationic polymer and be formed by applying a chemical conversion treatment to the barrier layer 13.
<Second Adhesive Layer 12b>
The second adhesive layer 12b bonds the barrier layer 13, on which the second anticorrosion treatment layer 14b is formed, to the sealant layer 16. The second adhesive layer 12b may be a general purpose adhesive for bonding a barrier layer to a sealant layer. Specifically, examples of the material used for forming the second adhesive layer 12b include a polyurethane resin prepared by reacting a bifunctional or higher functional isocyanate compound with a main resin such as a polyester polyol, polyether polyol, acrylic polyol, carbonate polyol, or the like.
These various polyols can be used singly or in combination of two or more, according to the functions and performance sought in the packaging material.
Moreover, other various additives and stabilizers may be added to the polyurethane resin mentioned above depending on the performance required of the adhesive.
In the packaging material 10 of the present embodiment, the second adhesive layer 12b may be the specific adhesive layer described above.
The thickness of the second adhesive layer 12b is not particularly limited, but from the perspective of obtaining a desired adhesive strength, processability and the like, the thickness is preferably 1 μm to 10 μm, and more preferably 3 μm to 7 μm.
When the second adhesive layer 12b is the specific adhesive layer, a mass per unit area of the second adhesive layer 12b may be 2.0 g/m2 to 6.0 g/m2, preferably 2.5 g/m2 to 5.0 g/m2, and more preferably 3.5 g/m2 to 4.5 g/m2 from the perspective of ensuring further improved lamination strength in a room temperature environment and a high temperature environment, and obtaining further improved deep drawing formability.
<Sealant Layer 16>
The sealant layer 16 imparts sealing properties to the packaging material 10 due to heat-sealing. The sealant layer 16 may be a resin film made of a polyolefin-based resin or a polyester-based resin. These resins (hereinafter, also referred to as “base resins”) constituting the sealant layer 16 may be used singly or in combination of two or more.
Examples of the polyolefin-based resin include: low density, medium density or high density polyethylenes; ethylene-α olefin copolymers; polypropylenes; block or random copolymers containing propylene as a copolymerization component; and propylene-α olefin copolymers.
Examples of the polyester-based resin include polyethylene terephthalate (PET) resin, polybutylene terephthalate (PBT) resin, polyethylene naphthalate (PEN) resin, polybutylene naphthalate (PBN) resin, polytrimethylene terephthalate (PTT) resin, and the like.
The sealant layer 16 may contain a polyolefin-based elastomer. The polyolefin-based elastomer may or may not have miscibility with the base resin described above, or may contain both a miscible polyolefin-based elastomer having miscibility and an immiscible polyolefin-based elastomer having no miscibility. Having miscibility (miscible system) means that the polyolefin-based elastomer is dispersed with a dispersed phase size of 1 nm or more and less than 500 nm in the base resin. Having no miscibility (immiscible system) means that the polyolefin-based elastomer is dispersed with a dispersed phase size of 500 nm or more and less than 20 μm in the base resin.
When the resin is a polypropylene-based resin, the miscible polyolefin-based elastomer may be, for example, propylene-butene-1 random copolymer, and the immiscible polyolefin-based elastomer may be, for example, ethylene-butene-1 random copolymer. The polyolefin-based elastomers can be used singly or in combination of two or more.
Further, the sealant layer 16 may contain additive components such as a slip agent, an anti-blocking agent, an antioxidant, a photostabilizer, and a flame retardant. The content of these additive components is preferably 5 parts by mass or less when the total mass of the sealant layer 16 is 100 parts by mass.
The thickness of the sealant layer 16 is not specifically limited, but may be preferably in the range of 5 to 100 more preferably in the range of 10 to 100 and still more preferably in the range of 20 to 80 μm from the perspective of reducing the film thickness and enhancing the heat seal strength in a high temperature environment.
The sealant layer 16 may be either a single-layer film or a multi-layer film, and may be suitably selected according to the required function.
Although the preferred embodiments of the power storage device packaging material of the present embodiment have been specifically described above, the present disclosure is not limited to the specific embodiments and can be modified or changed in various ways within the spirit of the present disclosure recited in the claims.
For example,
<Adhesive Resin Layer 15>
The adhesive resin layer 15 is substantially composed of an adhesive resin composition as the main component and additive components, if necessary. The adhesive resin composition is not particularly limited, but preferably contains a modified polyolefin resin.
The modified polyolefin resin is preferably a polyolefin resin graft-modified with an unsaturated carboxylic acid derivative derived from any of an unsaturated carboxylic acid, acid anhydride thereof and ester thereof.
Examples of the polyolefin resin include low density, medium density and high density polyethylenes, ethylene-α olefin copolymers, homopolypropylenes, blocked polypropylenes, random polypropylenes, and propylene-α olefin copolymers.
The modified polyolefin resin is preferably a polyolefin resin modified with maleic anhydride. For example, “ADMER” manufactured by Mitsui Chemicals, Inc., “MODIC” manufactured by Mitsubishi Chemical Corporation, and the like are suitable for the modified polyolefin resin. Such a modified polyolefin resin excels at reactivity with various metals and polymers having various functional groups, and thus can impart adhesion to the adhesive resin layer 15 making use of the reactivity and can accordingly improve electrolyte resistance. Further, the adhesive resin layer 15 may contain, if necessary, various miscible and immiscible elastomers and various additives such as flame retardants, slip agents, anti-blocking agents, antioxidants, photostabilizers and tackifiers.
The thickness of the adhesive resin layer 15 is not specifically limited, but preferably equal to or less than that of the sealant layer 16 from the perspective of stress relaxation and moisture/electrolyte permeation.
Further, the total thickness of the adhesive resin layer 15 and the sealant layer 16 in the power storage device packaging material 20 is preferably in the range of 5 μm to 100 μm, and more preferably 20 μm to 80 μm from the perspective of reducing the film thickness and enhancing the heat seal strength in a high temperature environment.
[Method of Producing Packaging Material]
Next, an example of a method of producing the packaging material 10 shown in
The method of producing the packaging material 10 of the present embodiment includes a step of laminating the anticorrosion treatment layers 14a and 14b on respective sides of the barrier layer 13, a step of bonding the substrate layer 11 and the barrier layer 13 using the first adhesive layer 12a, a step of preparing a laminate by further laminating the sealant layer 16 via the second adhesive layer 12b, and, if necessary, a step of aging the resultant laminate.
(Step of Laminating Anticorrosion Treatment Layers 14a and 14b on Barrier Layer 13)
In the present step, the anticorrosion treatment layers 14a and 14b are formed on the barrier layer 13. As described above, the method may include applying a degreasing treatment, hydrothermal modification treatment, anodic oxidation treatment, or chemical conversion treatment to the barrier layer 13, or applying a coating agent having a corrosion prevention performance to the barrier layer 13.
If the anticorrosion treatment layers 14a and 14b are multilayers, for example, a coating liquid (coating agent) that serves as a lower layer-side (barrier layer 13-side) anticorrosion treatment layer may be applied to the barrier layer 13, followed by baking to form a first layer, and then, a coating liquid (coating agent) that serves as an upper layer-side anticorrosion treatment layer may be applied to the first layer, followed by baking to form a second layer.
The degreasing treatment may be performed by spraying or immersion. The hydrothermal conversion treatment and the anodic oxidation treatment may be performed by immersion. The chemical conversion treatment may be selected from among immersion, spraying and coating depending on the type of chemical conversion treatment.
Various methods such as gravure coating, reverse coating, roll coating and bar coating may be used as the method of applying the coating agent having corrosion prevention performance.
As described above, the various treatments may be applied to either side or both sides of the metal foil. In the case of a single-side treatment, the treatment is preferably applied to the surface on which the sealant layer 16 is to be laminated. If needed, the treatment mentioned above may also be applied to the surface of the substrate layer 11.
The amounts of the coating agents for forming the first and second layers are preferably 0.005 g/m2 to 0.200 g/m2, and more preferably 0.010 g/m2 to 0.100 g/m2.
If necessary, dry curing may be carried out within a base material temperature range of 60° C. to 300° C. depending on the drying conditions of the anticorrosion treatment layers 14a and 14b used.
(Step of Bonding Substrate Layer 11 and Barrier Layer 13)
In the present step, the barrier layer 13 provided with the anticorrosion treatment layers 14a and 14b on respective sides is bonded to the substrate layer 11 via the first adhesive layer 12a. These layers are bonded to each other using the material constituting the first adhesive layer 12a described above by a bonding method such as dry lamination, non-solvent lamination or wet lamination. The dry coating weight of the first adhesive layer 12a is in the range of 1 g/m2 to 10 g/m2, and more preferably 2 g/m2 to 6 g/m2.
(Step of Laminating Second Adhesive Layer 12b and Sealant Layer 16)
In the present step, the sealant layer 16 is bonded to the second anticorrosion treatment layer 14b-side of the barrier layer 13 via the second adhesive layer 12b. The bonding method may be wet processing, dry lamination, or the like.
If wet processing is used, a solution or a dispersion of the adhesive forming the second adhesive layer 12b is applied to the second anticorrosion treatment layer 14b, and the solvent is vaporized at a predetermined temperature, followed by drying, which may be further followed by baking, if necessary, to thereby form a film. Then, the sealant layer 16 is laminated, thereby preparing the packaging material 10. The coating method may be any of the various coating methods mentioned above. The preferred dry coating weight of the second adhesive layer 12b is the same as that of the first adhesive layer 12a.
In this case, the sealant layer 16 can be produced, for example, using a resin composition for forming a sealant layer, containing a constituent component of the sealant layer 16 described above by using a melt extrusion molding machine. The processing rate of the melt extrusion molding machine may be set to 80 m/min or more from the viewpoint of productivity.
(Step of Aging)
In the present step, the laminate is aged (cured). Aging of the laminate can expedite adhesion between the barrier layer 13/the second anticorrosion treatment layer 14b/the second adhesive layer 12b/the sealant layer 16. Aging may be conducted in the range of room temperature to 100° C. Aging time may be, for example, 1 day to 10 days.
In this manner, the packaging material 10 of the present embodiment as shown in
Next, an example of a method of producing the packaging material 20 shown in
The method of producing the packaging material 20 of the present embodiment includes a step of laminating the anticorrosion treatment layers 14a and 14b on respective sides of the barrier layer 13, a step of bonding the substrate layer 11 and the barrier layer 13 using the first adhesive layer 12a, a step of preparing a laminate by further laminating the adhesive resin layer 15 and the sealant layer 16, and, if necessary, a step of heating the resultant laminate. The steps up to the step of bonding the substrate layer 11 and the barrier layer 13 can be performed in the same manner as in the method of producing the packaging material 10.
(Step of Laminating Adhesive Resin Layer 15 and Sealant Layer 16)
In the present step, the adhesive resin layer 15 and the sealant layer 16 are formed on the second anticorrosion treatment layer 14b formed in the previous step. The method includes sandwich-laminating the adhesive resin layer 15 together with the sealant layer 16 using an extrusion laminator. Further, tandem lamination or co-extrusion by which the adhesive resin layer 15 and the sealant layer 16 are extruded can also be used. The components of the adhesive resin layer 15 and the sealant layer 16 may be formulated, for example, to meet the above-mentioned configurations of the adhesive resin layer 15 and the sealant layer 16. The sealant layer 16 is formed by using the above resin composition for forming a sealant layer.
According to the present step, there can be obtained a laminate, as shown in
When laminating the adhesive resin layer 15, materials that are dry-blended so as to have the composition of the material formulation mentioned above may be directly laminated using an extrusion laminator. Alternatively, when laminating the adhesive resin layer 15, granules obtained in advance by melt-blending materials using a melt kneading device such as a single-screw extruder, twin-screw extruder or Brabender mixer may be laminated using an extrusion laminator.
When laminating the sealant layer 16, materials that are dry-blended so as to have the composition of the material formulation mentioned above, as a resin composition for forming a sealant layer, may be directly laminated using an extrusion laminator. Alternatively, when laminating the adhesive resin layer 15 and the sealant layer 16, granules obtained in advance by melt-blending materials using a melt kneading device such as a single-screw extruder, twin-screw extruder or Brabender mixer may be used to laminate the adhesive resin layer 15 and the sealant layer 16 by tandem lamination or co-extrusion using an extrusion laminator. Moreover, a sealant monolayer film may be formed in advance as a cast film using a resin composition for forming a sealant layer, and the film may be laminated by sandwich-lamination together with an adhesive resin. The formation rate (processing rate) of the adhesive resin layer 15 and the sealant layer 16 may be set to 80 m/min or more from the viewpoint of productivity.
(Step of Heating)
In the present step, the laminate is heat-treated. Heat-treatment of the laminate can improve adhesion between the barrier layer 13/the second anticorrosion treatment layer 14b/the adhesive resin layer 15/the sealant layer 16. The heat-treatment is preferably performed at a temperature at least higher than the melting point of the adhesive resin layer 15.
In this manner, the packaging material 20 of the present embodiment as shown in
Although the preferred embodiments of the power storage device packaging material of the present disclosure have been specifically described above, the present disclosure is not limited to the specific embodiments and can be modified or changed in various ways within the spirit of the present disclosure recited in the claims.
The power storage device packaging material of the present disclosure can be suitably used as a packaging material for power storage devices including, for example, secondary batteries such as a lithium-ion battery, a nickel-hydrogen battery and a lead storage battery, and electrochemical capacitors such as an electric double layer capacitor. In particular, the power storage device packaging material of the present disclosure is suitable as a packaging material for fully solid-state batteries using a solid electrolyte.
[Power Storage Device]
The battery element 52 is formed by interposing an electrolyte between a positive electrode and a negative electrode. The metal terminal 53 is a part of a current collector extending out from the packaging material 10, and made of a metal foil such as a copper foil or an aluminum foil.
The power storage device 50 of the present embodiment may be a fully solid-state battery. In this case, a solid electrolyte such as a sulfide solid electrolyte may be used as the electrolyte of the battery element 52. Since the power storage device 50 of the present embodiment uses the packaging material 10 of the present embodiment, excellent lamination strength can be achieved even when the power storage device 50 is used in a high temperature environment.
<<Second Aspect>>
The following description will be given of a power storage device packaging material according to a second aspect of the present disclosure. The description of the same elements as those in the power storage device packaging material of the first aspect will be omitted. Since a power storage device and a method of producing a power storage device according to the second aspect are the same as those in the first aspect, the description thereof will be omitted.
[Power Storage Device Packaging Material]
The power storage device packaging material according to the second aspect and the power storage device packaging material according to the first aspect are different in the first adhesive layer 12a.
<First Adhesive Layer 12a>
The first adhesive layer 12a bonds the substrate layer 11 and the barrier layer 13. In the packaging material 10 of the present embodiment, the first adhesive layer 12a contains a urethane resin made of at least one polyol selected from the group consisting of polyether polyol, polyester polyol, acrylic polyol and polycarbonate diol, and a polyfunctional isocyanate compound, and the polyfunctional isocyanate compound is composed of at least one polyfunctional isocyanate compound selected from the group consisting of an alicyclic isocyanate polymer and an isocyanate polymer containing an aromatic ring in the molecular structure.
Further, when the first adhesive layer 12a is exposed by removing the substrate layer 11 to measure the outermost surface of the exposed first adhesive layer 12a using the attenuated total reflection-Fourier transform infrared spectroscopy, a baseline transmittance T0, a minimum transmittance T1 in the range of 2100 cm−1 to 2400 cm−1, and a minimum transmittance T2 in the range of 1670 cm−1 to 1700 cm−1 satisfy the relationship of 0.06≤(T0−T1)/(T0−T2)≤0.4.
In the IR spectrum obtained by the attenuated total reflection-Fourier transform infrared spectroscopy, a peak in the range of 2100 cm−1 to 2400 cm−1 is a peak of a carbonyl group derived from an isocyanate group, and a peak in the range of 1670 cm−1 to 1700 cm−1 is a peak of a carbonyl group derived from a urethane bond. When the ratio between the isocyanate group and the urethane bond satisfies 0.06≤(T0−T1)/(T0−T2)≤0.4, a urea resin and a biuret resin generated by reaction between unreacted isocyanate groups and part of the hardener are present in the adhesive layer. Due to the active hydrogen groups present in the urea resin and the biuret resin, the values of tensile strength and elongation at break of the adhesive layer become close to those of each layer (mainly the barrier layer and the substrate), resulting in an increase in formability. Further, when a formed product of the present disclosure is exposed to a high temperature environment (150° C.), reaction between the unreacted hardeners is expedited. As the urea resin and the biuret resin increase, the Tg of the adhesive layer increases, improving the heat resistance.
On the other hand, when (T0−T1)/(T0−T2)≤0.06, there are two cases where the base resin and the hardener quantitatively have reacted with each other under the condition of NCO/OH≈1.0, and where the hardeners have reacted with each other under the condition of NCO/OH>1.0. In the former case, the Tg of the adhesive layer significantly decreases compared with that in a high temperature environment (150° C.), which causes cohesive failure of the adhesive layer. In the latter case, most of the hardener has reacted at the step of aging. Accordingly, the adhesive layer has increased brittleness compared with the case where 0.06≤(T0−T1)/(T0−T2)≤0.4 is satisfied, and thus has a significantly decreased formability.
Further, when (T0−T1)/(T0−T2)>0.4, excess unreacted hardener may be present in the adhesive layer. When such an adhesive layer is exposed to high temperature environment, foaming may occur due to a reaction between the excess hardeners. This may cause delamination in a high temperature environment, and reduce the heat resistance.
The polyfunctional isocyanate compound used in the first adhesive layer 12a is the same as that in the first aspect. In the first adhesive layer 12a, the ratio (NCO/OH) of the number of isocyanate groups contained in the polyfunctional isocyanate compound to the number of hydroxyl groups contained in the polyester polyol resin is the same as that in the first aspect. The thickness of the first adhesive layer 12a is the same as that in the first aspect. The mass per unit area of the first adhesive layer 12a is the same as that in the first aspect.
<<Third Aspect>>
The following description will be given of a power storage device packaging material and a power storage device according to a third aspect of the present disclosure. The description of the same elements as those in the power storage device packaging material and the power storage device of the first aspect will be omitted. Since a method of producing a power storage device according to the third aspect is the same as that in the first aspect, the description thereof will be omitted.
[Power Storage Device Packaging Material]
The power storage device packaging material according to the third aspect and the power storage device packaging material according to the first aspect are different in the first adhesive layer 12a.
<First Adhesive Layer 12a>
The first adhesive layer 12a bonds the substrate layer 11 and the barrier layer 13. In the present disclosure, the first adhesive layer 12a needs to contain a polyurethane-based compound and a polyamide-imide resin. The adhesive layer containing the polyurethane-based compound has high toughness, and is excellent in deep drawing formability and lamination strength in a room temperature environment. On the other hand, a polyamide-imide resin has good heat resistance. Therefore, when the adhesive layer is prepared by formulating the polyamide-imide resin and the polyurethane-based compound, it is possible to obtain sufficient lamination strength between the substrate layer 11 and the barrier layer 13 in a high temperature environment, for example, 170° C. or higher, and excellent deep drawing formability of the packaging material 10, and further possible to maintain the lamination strength between the substrate layer 11 and the barrier layer 13 in a high temperature environment in the packaging material 10 after the deep drawing.
When the solid content of the polyamide-imide resin to the solid content of the polyurethane-based compound is defined as A mass %, the content preferably satisfies 1.0 mass %<A<20.0 mass %, and more preferably 10.0 mass %<A<20.0 mass %. Further, the number average molecular weight Mn of the polyamide-imide resin is preferably 3,000<Mn<36,000.
The polyurethane-based compound may also be made of a reaction product of at least one polyol resin and at least one polyfunctional isocyanate compound. The type of the polyol resin is not specifically limited, but at least one polyol resin selected from the group consisting of polyester polyol, acrylic polyol and polycarbonate polyol can be preferably used. In this case, both the lamination strength between the substrate layer 11 and the barrier layer 13 in a high temperature environment and the formability of the packaging material 10 are improved.
Further, the type of the polyfunctional isocyanate compound is not specifically limited, but at least one isocyanate polymer selected from the group consisting of an alicyclic isocyanate polymer and an isocyanate polymer containing an aromatic ring in the molecular structure can be preferably used. In this case, both the lamination strength and the formability are improved.
Examples of the alicyclic isocyanate polymer include an isocyanurate of isophorone diisocyanate (IPDI-isocyanurate).
Examples of the isocyanate polymer containing an aromatic ring in the molecular structure include an adduct of tolylene diisocyanate (TDI-adduct). Further, an adduct, a biuret and an isocyanurate of diphenylmethane diisocyanate may be used. Further, an adduct, a biuret and an isocyanurate of xylylene diisocyanate may also be used.
Preferably, the polyurethane-based compound is a reaction product of a polyol resin at least partially made of polyester polyol and a polyfunctional isocyanate compound at least partially made of IPDI-isocyanurate. Thus, the packaging material 10 having the first adhesive layer 12a containing a polyurethane-based compound made of a reaction product of polyester polyol and IPDI-isocyanurate is particularly excellent in lamination strength between the substrate layer 11 and the barrier layer 13 in a high temperature environment and the formability of the packaging material 10.
In the specific adhesive layer, the content of isocyanate groups derived from the IPDI-isocyanurate in the polyfunctional isocyanate compound is the same as that in the first aspect.
In the specific adhesive layer, the ratio (NCO/OH) of the number of isocyanate groups contained in the polyfunctional isocyanate compound to the number of hydroxyl groups contained in the polyol resin is preferably 1.5<NCO/OH<40.0. When the number of isocyanate groups contained in the hardener (polyfunctional isocyanate compound) of a polyurethane-based compound is very large relative to the number of hydroxyl groups contained in the base resin (polyol resin) (NCO/OH>>1.0), the heat resistance is improved. When the polyurethane-based compound is made of a reaction product of polyester polyol and IPDI-isocyanurate, the optimum value of the above NCO/OH is 20.
[Power Storage Device]
Other configurations of the power storage device according to the third aspect are the same as those in the first aspect.
<<Fourth Aspect>>
The following description will be given of a power storage device packaging material, a method of producing the packaging material and a power storage device according to a fourth aspect of the present disclosure.
[Power Storage Device Packaging Material]
<Substrate Layer 11>
The substrate layer 11 imparts heat resistance to the packaging material in the sealing step during production of the power storage device, and prevents pinholes from occurring during forming processing or distribution. Particularly in the case of a packaging material for a large power storage device, the substrate layer 11 can also impart scratch resistance, chemical resistance, insulating properties, and the like.
Preferably, the substrate layer 11 has a peak melting temperature higher than that of the sealant layer 16. When the substrate layer 11 has a peak melting temperature higher than that of the sealant layer 16, the appearance of the packaging material is prevented from being impaired due to melting of the substrate layer 11 (outer layer) during heat-sealing. When the sealant layer 16 has a multilayer structure, the peak melting temperature of the sealant layer 16 refers to that of the layer having a maximum peak melting temperature. The peak melting temperature of the substrate layer 11 is preferably 290° C. or higher, and more preferably 290° C. to 350° C. The resin film that can be used for the substrate layer 11 and has a peak melting temperature within the above range may be a nylon film, PET film, polyamide film, polyphenylene sulfide film (PPS film), polyimide film, polyester film, or the like. The peak melting temperature refers to a value obtained according to the method described in JIS K 7121-1987.
The substrate layer 11 may be a commercially available film, or may be a coating film (obtained by applying and drying a coating liquid). The substrate layer 11 may have a single layer structure or a multilayer structure, or may be formed by applying a thermosetting resin. Further, the substrate layer 11 may contain various additives (e.g., a flame retardant, slip agent, anti-blocking agent, antioxidant, photostabilizer, and tackifier).
When the peak melting temperature of the substrate layer 11 is expressed as T11 and that of the sealant layer 16 is expressed as T16, the difference between them (T11−T16) is preferably 20° C. or more. When the temperature difference is 20° C. or more, deterioration in appearance of the packaging material 20 due to heat-sealing can be more sufficiently prevented. The thickness of the substrate layer 11 is preferably 5 μm to 50 μm, and more preferably 12 μm to 30 μm.
<First Adhesive Layer 12 and Second Adhesive Layer 17>
In the following description, the first adhesive layer 12 and the second adhesive layer 17 are specifically described.
(First Adhesive Layer 12)
The first adhesive layer 12 bonds the barrier layer 13, on which the anticorrosion treatment layer 14a is formed, to the substrate layer 11. The first adhesive layer 12 has an adhesive force needed to firmly adhere the substrate layer 11 to the barrier layer 13 and also has conformability for reducing or preventing breakage of the barrier layer 13 by the substrate layer 11 during cold forming. The conformability refers to an ability by which the first adhesive layer 12 remains on a member without being detached, even when the member is deformed due to expansion or contraction.
The first adhesive layer 12 may be made of adhesive components such as a urea-based compound, a urethane-based compound, and the like. These compounds may be used singly or in combination of two or more. The urea-based compound is obtained by reacting an amine-based resin as a base resin with a polyisocyanate compound as a hardener. The urethane-based compound is obtained by reacting a polyol as a base resin with a polyisocyanate compound as a hardener.
Examples of the amine-based resin include polyacrylic amine, and the like.
Examples of the polyol include polyester polyol, polyether polyol, acrylic polyol, and the like.
Examples of the polyester polyol include polyester polyol obtained by reaction of one or more dicarboxylic acids and a diol.
Examples of the polyether polyol include those produced by addition polymerization of ethylene oxide or propylene oxide with propylene glycol, glycerin, pentaerythritol, or the like.
Examples of the acrylic polyol include copolymers obtained by copolymerizing at least a hydroxyl group-containing acrylic monomer and (meth)acrylic acid. In this case, a structural unit derived from (meth)acrylic acid is preferably contained as a main component. The hydroxyl group-containing acrylic monomer may be 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, or the like.
The polyisocyanate compound contains a plurality of isocyanate groups and crosslinks the amine-based resin or polyol. The polyisocyanate compounds may be used singly or in combination of two or more. Examples of the polyisocyanate compound include aliphatic polyisocyanate compound, alicyclic polyisocyanate compound and aromatic polyisocyanate compound.
Examples of the aliphatic polyisocyanate compound include hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), and the like. Examples of the alicyclic polyisocyanate compound include isophorone diisocyanate (IPDI), and the like. Examples of the aromatic polyisocyanate compound include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and the like. As the polyisocyanate compound, a polymer (for example, trimer) of these compounds can be used, and specifically, an adduct, a biuret, an isocyanurate, and the like can be used.
In the polyisocyanate compound, the isocyanate group is preferably bonded to a blocking agent for improving the pot life. Examples of the blocking agent include methylethylketoxime (MEKO), and the like. The temperature at which the blocking agent is dissociated from the isocyanate group of the polyisocyanate compound may be 50° C. or higher, and preferably 60° C. or higher for further improving the pot life. The temperature at which the blocking agent is dissociated from the isocyanate group of the polyisocyanate compound may be 140° C. or less, and preferably 120° C. or less for improving curling resistance of the packaging material.
In order to lower the dissociation temperature of the blocking agent, a catalyst for lowering the dissociation temperature may be used. Examples of the catalyst for lowering the dissociation temperature include tertiary amines such as triethylene diamine and N-methylmorpholine, and metal organic acid salts such as dibutyltin dilaurate.
In the urea-based compound, a molar ratio of the isocyanate groups of the polyisocyanate compound to the amine groups of the amine-based resin is preferably 1 to 10, and more preferably 2 to 5. In the urethane-based compound, a molar ratio of the isocyanate groups of the polyisocyanate compound to the hydroxyl groups of the polyol is preferably 1 to 50, and more preferably 10 to 30.
The first adhesive layer 12 preferably contains a hydrogen sulfide adsorbent for preventing corrosion of the barrier layer 13 due to hydrogen sulfide present outside the packaging material. Examples of the hydrogen sulfide adsorbent include zinc oxide, potassium permanganate, and the like. Since corrosion of the barrier layer 13 due to hydrogen sulfide present outside the packaging material can be prevented due to the first adhesive layer 12 containing a hydrogen sulfide adsorbent, the content of the hydrogen sulfide adsorbent is preferably 1 mass % to 50 mass % of the total amount of the first adhesive layer 12.
The thickness of the first adhesive layer 12 is preferably 1 μm to 10 μm, and more preferably 2 μm to 6 μm from the perspective of obtaining desired adhesive strength, conformability, processability, and the like.
The first adhesive layer 12 is obtained by, for example, coating with a composition containing a base resin and a hardener of the above-mentioned adhesive components. The coating can be performed by known methods such as gravure direct, gravure reverse (direct, kiss) and micro gravure.
When the first adhesive layer 12 contains a urea-based compound, the content of the amine-based resin in the composition containing the amine-based resin and the polyisocyanate compound is preferably 1 mass % to 10 mass % relative to the total amount of the amine-based resin and the polyisocyanate compound.
When the first adhesive layer 12 contains a urethane-based compound, the content of the polyol in the composition containing the polyol and the polyisocyanate compound is preferably 50 mass % to 80 mass % relative to the total amount of the polyol and the polyisocyanate compound.
(Second Adhesive Layer 17)
The second adhesive layer 17 bonds the barrier layer 13, on which the anticorrosion treatment layer 14b is formed, to the sealant layer 16.
The adhesive component forming the second adhesive layer 17 may be ones, for example, similar to those mentioned for the first adhesive layer 12.
The second adhesive layer 17 preferably contains a hydrogen sulfide adsorbent for preventing corrosion of the barrier layer 13 due to hydrogen sulfide generated from the battery contents in the packaging material. Examples of the hydrogen sulfide adsorbent may be ones similar to those mentioned for the first adhesive layer 12. The content of the hydrogen sulfide adsorbent is preferably 0.1 mass % to 50 mass % of the total amount of the second adhesive layer 17.
The second adhesive layer 17 is obtained by the same method as that for the first adhesive layer 12. When the second adhesive layer 17 contains a urea-based compound, the content of the amine-based resin in the composition containing the amine-based resin and the polyisocyanate compound may be the same as that of the first adhesive layer 12. When the second adhesive layer 17 contains a urethane-based compound, the content of the polyol in the composition containing the polyol and the polyisocyanate compound may be the same as that of the first adhesive layer 12.
The thickness of the second adhesive layer 17 is preferably 1 μm to 5 μm. When the thickness of the second adhesive layer 17 is 1 μm or more, sufficient adhesion strength between the barrier layer 13 and the sealant layer 16 can be easily obtained. When the thickness of the second adhesive layer 17 is 5 μm or less, occurrence of cracking in the second adhesive layer 17 can be reduced.
At least one of the first adhesive layer 12 and the second adhesive layer 17 contains a urea-based compound which is a reaction product of an amine-based resin and a polyisocyanate compound, and, when an infrared absorption spectrum peak intensity at 1680 cm−1 to 1720 cm−1 is A1 and an infrared absorption spectrum peak intensity at 1590 cm−1 to 1640 cm−1 is B1 in a layer containing the urea-based compound among the first adhesive layer 12 and the second adhesive layer 17, X1 defined by the following formula (1-A) is 10 to 99, and preferably 20 to 80:
X1={B1/(A1+B1)}×100 (1-A).
The infrared absorption spectrum peak intensity at 1680 cm−1 to 1720 cm−1 and the infrared absorption spectrum peak intensity at 1590 cm−1 to 1640 cm−1 in the layer containing the urea-based compound among the first adhesive layer 12 and the second adhesive layer 17 can be measured by FT-IR (ATR method (total reflection absorption infrared spectroscopy)).
Both the first adhesive layer 12 and the second adhesive layer 17 may contain a urea-based compound, or only the first adhesive layer 12 or only the second adhesive layer 17 among the first adhesive layer 12 and the second adhesive layer 17 may contain a urea-based compound. It is preferred that the first adhesive layer 12 does not contain a urea-based compound and only the second adhesive layer 17 contains a urea-based compound since the obtained packaging material has excellent heat resistance and the first adhesive layer has rigidity that is easily mitigated to achieve excellent deep drawing formability. When the first adhesive layer 12 contains a urea-based compound, the urea group of the urea-based compound exhibits a cohesive force so that hydrogen sulfide present outside the packaging material does not easily pass through the first adhesive layer 12, which prevents corrosion of the barrier layer 13 due to the hydrogen sulfide. When the second adhesive layer 17 contains a urea-based compound, the urea group of the urea-based compound exhibits a cohesive force so that hydrogen sulfide generated from the battery contents in the packaging material does not easily pass through the second adhesive layer 17, which prevents corrosion of the barrier layer 13 due to the hydrogen sulfide. Accordingly, the second adhesive layer 17 preferably contains the urea-based compound.
<Barrier Layer 13>
The barrier layer 13 has water vapor barrier properties to prevent moisture from infiltrating into the power storage device. Further, the barrier layer 13 has ductility and malleability for deep drawing. The barrier layer 13 can be made of, for example, various metal foils such as an aluminum, stainless steel and copper, or a metal vapor deposition film, an inorganic oxide vapor deposition film, a carbon-containing inorganic oxide vapor deposition film, or a film having these vapor deposition films. Examples of the film having a vapor deposition film include an aluminum vapor deposition film and an inorganic oxide vapor deposition film. These can be used singly or in combination of two or more. The barrier layer 13 is preferably made of a metal foil, and more preferably made of an aluminum foil from the viewpoint of the weight (specific gravity), moisture resistance, processability, and cost.
The aluminum foil may be a soft aluminum foil, particularly one subjected to an annealing treatment from the perspective of imparting desired ductility and malleability during forming. It is more preferable to use an iron-containing aluminum foil for the purpose of further imparting pinhole resistance, ductility and malleability during forming. The iron content in the aluminum foil is preferably 0.1 mass % to 9.0 mass %, and more preferably 0.5 mass % to 2.0 mass % relative to 100 mass % of the aluminum foil (e.g., aluminum foil made of the material 8021 or 8079 according to Japanese Industrial Standards). The iron content of 0.1 mass % or more leads to a packaging material 25 having better pinhole resistance, and ductility and malleability. The iron content of 9.0 mass % or less enables a packaging material 25 having much better flexibility.
In order to obtain desired electrolyte resistance, the metal foil used for the barrier layer 13 may be preferably subjected to, for example, degreasing treatment. Further, in order to simplify the production process, the metal foil preferably has a surface that is not etched. In particular, from the perspective of imparting electrolyte resistance, it is preferred to use a degreased aluminum foil as the metal foil used for the barrier layer 13. It should be noted that when the aluminum foil is degreased, only one surface of the aluminum foil may be degreased, or both surfaces may be degreased. The degreasing treatment may be, for example, a wet type or dry type. However, dry degreasing treatment is preferred from the perspective of simplifying the production process.
The dry degreasing treatment may be performed by, for example, extending a treatment time in the step of annealing the metal foil. Adequate electrolyte resistance can be obtained with the degreasing treatment that is carried out simultaneously with the annealing treatment for softening the metal foil.
The dry degreasing treatment may also be flame treatment or corona treatment instead of annealing treatment. Further, the dry degreasing treatment may be one that oxidatively decomposes and removes contaminants using active oxygen generated by irradiating the metal foil with ultraviolet light at a specific wavelength.
The wet degreasing treatment may be, for example, acid degreasing treatment, alkaline degreasing treatment, or the like. Examples of the acid used for the acid degreasing treatment include inorganic acids such as sulfuric acid, nitric acid, hydrochloric acid, or hydrofluoric acid. These acids may be used singly or in combination of two or more. Examples of the alkali used for the alkaline degreasing treatment include sodium hydroxide having strong etching effects. Further, alkaline degreasing treatment may also be performed using a material containing a weakly alkaline material, and a surfactant or the like. The wet degreasing treatment described above can be performed, for example, by immersion or spraying.
From the perspective of barrier properties, pinhole resistance, and processability, the barrier layer 13 preferably has a thickness of 9 μm to 200 μm, more preferably 15 μm to 150 μm, and still more preferably 15 μm to 100 μm. The barrier layer 13 with a thickness of 9 μm or more may be able to make the layer less fragile even when stress is applied thereto during forming. The barrier layer 13 with a thickness of 200 μm or less curbs an increase in mass of the packaging material and minimizes a decrease in weight energy density of the power storage device.
<Anticorrosion Treatment Layers 14a and 14b>
The anticorrosion treatment layers 14a and 14b are disposed on the respective surfaces of the barrier layer 13 to prevent corrosion of the metal film or the like constituting the barrier layer 13. The anticorrosion treatment layer 14a increases the adhesive force between the barrier layer 13 and the first adhesive layer 12. The anticorrosion treatment layer 14b increases the adhesive force between the barrier layer 13 and the second adhesive layer 17. The anticorrosion treatment layers 14a and 14b may have the same configuration or different configurations. In the present embodiment, the anticorrosion treatment layer is each provided between the barrier layer 13 and the first adhesive layer 12 and between the barrier layer 13 and the second adhesive layer 17. However, the anticorrosion treatment layer may be provided only between the barrier layer 13 and the second adhesive layer 17.
The anticorrosion treatment layers 14a and 14b can be formed by, for example, performing degreasing treatment, hydrothermal conversion treatment, anodizing treatment, chemical conversion treatment, or coating-type anticorrosion treatment of applying a coating agent having anticorrosion ability, for layers serving as base materials for the anticorrosion treatment layers 14a and 14b, or a combination of these treatments.
Of the treatments mentioned above, degreasing treatment, hydrothermal conversion treatment, and anodic oxidation treatment, specifically, the hydrothermal conversion treatment and the anodic oxidation treatment, are treatments for dissolving a surface of the metal foil (aluminum foil) with a treatment agent to form a metal compound (aluminum compound (such as boehmite or alumite)) having good corrosion resistance. These treatments may be included in the definition of the chemical conversion treatment since a co-continuous structure is formed from the barrier layer 13 to the anticorrosion treatment layers 14a and 14b.
The degreasing treatment may be acid degreasing or alkaline degreasing. The acid degreasing may be a method using the inorganic acid mentioned above, such as sulfuric acid, nitric acid, hydrochloric acid or hydrofluoric acid, alone or in combination. Further, use of an acid degreasing agent, as the acid degreasing treatment, obtained by dissolving a fluorine-containing compound, such as monosodium ammonium bifluoride, with the above inorganic acid can not only exert the effects of degreasing the barrier layer 13, but also form a passive metal fluoride, and is thus effective in terms of hydrofluoric acid resistance. The alkaline degreasing may be a method using sodium hydroxide or the like.
The hydrothermal conversion treatment may be, for example, boehmite treatment using boehmite obtained by immersing the barrier layer 13 in boiling water with triethanolamine added thereto. The anodic oxidation treatment may be, for example, alumite treatment. Further, the chemical conversion treatment may be, for example, chromate treatment, zirconium treatment, titanium treatment, vanadium treatment, molybdenum treatment, calcium phosphate treatment, strontium hydroxide treatment, cerium treatment, ruthenium treatment, or treatment that is a combination of two or more of these treatments. When performing the hydrothermal conversion treatment, anodic oxidation treatment or chemical conversion treatment, the degreasing treatment described above is preferably performed in advance.
The chemical conversion treatment is not limited to a wet type, but may be one, for example, in which treatment agents used for the treatment are mixed with a resin component and applied. The anticorrosion treatment may preferably be of a coating type chromate treatment because it maximizes the anticorrosion effect and is convenient for liquid waste disposal.
The coating agent used in the coating type anticorrosion treatment may be one which contains at least one selected from the group consisting of a rare-earth oxide sol, an anionic polymer and a cationic polymer. Particularly, a method using a coating agent containing a rare-earth oxide sol is preferred.
The anticorrosion treatment layers 14a and 14b preferably have mass per unit area of 0.005 g/m2 to 0.200 g/m2, and more preferably 0.010 g/m2 to 0.100 g/m2. When the mass per unit area is 0.005 g/m2 or more, a corrosion-preventing function can be readily imparted to the barrier layer 13. The mass per unit area exceeding 0.200 g/m2 will saturate the corrosion-preventing function and no further effect can be expected. Although the above description has been given using mass per unit area, the specific gravity, if available, can be used in terms of thickness.
From the perspective of anticorrosive and anchoring functions, the anticorrosion treatment layers 14a and 14b may each preferably have a thickness of, for example, 10 nm to 5 μm, and more preferably 20 nm to 500 nm.
<Sealant Layer 16>
The sealant layer 16 imparts sealing properties to the packaging material 25 due to heat-sealing. The sealant layer 16 is located on the inside of the power storage device and heat sealed when the power storage device is assembled.
The sealant layer 16 may be, for example, a resin film made of an acrylic resin, a polyolefin-based resin or a polyester-based resin. The sealant layer 16 is preferably a film made of a polyolefin-based resin or a polyester-based resin, and more preferably a film made of a polyester-based resin due to a high melting point for further improving heat resistance of the packaging material.
Examples of the acrylic resin include polymethyl methacrylate resin (PMMA), and the like. These acrylic resins may be used singly or in combination of two or more.
Examples of the polyolefin-based resin include: low density, medium density and high density polyethylenes; ethylene-α olefin copolymers; polypropylenes; and propylene-α olefin copolymers. The polyolefin resin in the form of copolymer may be a block copolymer or a random copolymer.
Examples of the polyester-based resin include polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and the like. These polyester-based resins may be used singly or in combination of two or more.
The sealant layer 16 may be a single layer film or may be a multilayer film, and may be selected according to the required properties. When the sealant layer 16 has a multilayer configuration, the layers may be laminated by co-extrusion or dry lamination.
The sealant layer 16 may contain various additives, such as a flame retardant, a slip agent, an anti-blocking agent, an antioxidant, a photostabilizer, and a tackifier.
The sealant layer 16 preferably has a thickness of 10 μm to 100 μm, and more preferably 20 μm to 60 μm. The sealant layer 16 with a thickness of 10 μm or more achieves adequate heat seal strength. The sealant layer 16 with a thickness of 100 μm or less reduces the amount of water vapor penetrating from an end of the packaging material.
The peak melting temperature of the sealant layer 16 is preferably 200° C. to 280° C. for improving the heat resistance.
[Method of Producing Packaging Material]
Next, a method of producing the packaging material 25 will be described. It should be noted that the method of producing the packaging material 25 should not be limited to the methods described below.
The method of producing the packaging material 25 may include, for example, the following steps S11 to S13 in this order.
Step S11: Forming an anticorrosion treatment layer 14a on a surface of the barrier layer 13 and forming an anticorrosion treatment layer 14b on the other surface of the barrier layer 13.
Step S12: Bonding a surface of the anticorrosion treatment layer 14a on a side opposite to that facing the barrier layer 13 to the substrate layer 11 via the first adhesive layer 12.
Step S13: Forming a sealant layer 16 on a surface of the anticorrosion treatment layer 14b on a side opposite to that facing the barrier layer 13 via the second adhesive layer 17.
<Step S11>
At step S11, an anticorrosion treatment layer 14a is formed on a surface of the barrier layer 13 and an anticorrosion treatment layer 14b is formed on the other surface of the barrier layer 13. The anticorrosion treatment layers 14a and 14b may be formed separately or simultaneously. Specifically, for example, an anticorrosion treatment agent (base material of the anticorrosion treatment layers) is applied to both surfaces of the barrier layer 13, sequentially followed by drying, curing, and baking to simultaneously form anticorrosion treatment layers 14a and 14b. Alternatively, an anticorrosion treatment agent may be applied to a surface of the barrier layer 13, sequentially followed by drying, curing, and baking to form the anticorrosion treatment layer 14a; and then the anticorrosion treatment layer 14b may be similarly formed on the other surface of the barrier layer 13. The order of forming the anticorrosion treatment layers 14a and 14b is not particularly limited. The anticorrosion treatment agent may be different or the same between the anticorrosion treatment layers 14a and 14b. Examples of the method of applying the anticorrosion treatment agent include, but are not limited to, gravure coating, gravure reverse coating, roll coating, reverse roll coating, die coating, bar coating, kiss coating, comma coating, and small-diameter gravure coating.
<Step S12>
At step S12, a surface of the anticorrosion treatment layer 14a on a side opposite to that facing the barrier layer 13 is bonded to the substrate layer 11 by dry lamination or the like using an adhesive for forming the first adhesive layer 12. At step S12, heat treatment may be performed to expedite adhesiveness of the first adhesive layer 12. The temperature in the heat treatment is preferably 140° C. or less for improving curling resistance of the packaging material, and preferably 60° C. or more for improving the pot life of the blocking agent.
<Step S13>
Subsequent to step S12, in the laminate in which the substrate layer 11, the first adhesive layer 12, the anticorrosion treatment layer 14a, the barrier layer 13 and the anticorrosion treatment layer 14b are laminated in this order, a surface of the anticorrosion treatment layer 14b on a side opposite to that facing the barrier layer 13 is bonded to the sealant layer 16 via an adhesive forming the second adhesive layer 17 by dry lamination or the like. In step S13, heat treatment may be performed to expedite adhesiveness of the second adhesive layer 17. The temperature in the heat treatment is preferably 140° C. or less, and more preferably 120° C. or less for improving curling resistance of the packaging material, and preferably 60° C. or more for improving the pot life of the blocking agent.
The packaging material 25 is obtained through the steps S11 to S13 described above. The order of steps in the method of producing the packaging material 25 is not limited to that of the above method in which steps S11 to S13 are sequentially performed. The order of steps may be appropriately changed. For example, step S12 may be followed by step S11.
[Power Storage Device]
Next, a power storage device having the packaging material 25 as a container will be described. The power storage device includes a battery element 1 including electrodes, leads 2 extending from the electrodes, and a container holding the battery element 1. The container is formed of the power storage device packaging material 25, with the sealant layer 16 located on the inside. The container may be obtained by overlapping two packaging materials with the sealant layers 16 face-to-face, and heat-sealing the edge portions of the overlapped packaging materials 25, or may be obtained by folding back a single packaging material so that the surfaces are overlapped with each other and similarly heat-sealing the edge portions of the packaging material 25. The leads 2 are sandwiched and held, and hermetically sealed by the packaging material 25, forming the container with the sealant layer 16 located on the inside. The leads 2 may be sandwiched and held by the packaging material 25 via a tab sealant.
The packaging material of the present embodiment can be used for various power storage devices. Examples of the power storage devices include secondary batteries such as lithium-ion batteries, nickel hydride batteries, lead batteries and fully solid-state batteries, and electrochemical capacitors such as electric double layer capacitors. The packaging material 25 of the present embodiment can maintain excellent heat-sealability when used in a high temperature environment after it is heat-sealed. Accordingly, the packaging material 25 is suitable for use with fully solid-state batteries that are expected to be used in such an environment.
[Method of Producing Power Storage Device]
Next, a method of producing a power storage device using the packaging material 25 will be described. The following description will be given of an example in which a secondary battery 40 is produced using an embossed packaging material 30.
The secondary battery 40, which is a single-sided battery, can be produced through steps S21 to S26 below, for example.
Step S21: Providing a packaging material 25, a battery element 1 including electrodes, and leads 2 extending from the electrodes.
Step S22: Obtaining an embossed packaging material 30 by forming a recess 32 on one side of the packaging material 25 for accommodating the battery elements 1 (see
Step S23: Placing the battery element 1 in the formed area (recess 32) of the embossed packaging material 30, folding back the embossed packaging material 30 to cover the recess 32 with a cover portion 34, and heat-sealing one side of the embossed packaging material 30 so that the leads 2 extending from the battery element 1 are sandwiched and held by the packaging material (see
Step S24: Heat-sealing another side of the embossed packaging material 30, leaving one side other than the side where the leads 2 are sandwiched and held unsealed, injecting an electrolyte through the unsealed side, and heat-sealing the unsealed side in a vacuum (see
Step S25: Performing charging and discharging while setting the current value, voltage value, environmental temperature, etc., to predetermined values to induce chemical changes (chemical conversion).
Step S26: Trimming the ends of the heat-sealed sides other than the side where the leads 2 are sandwiched and held, and turning up the end portions towards the formed area (recess 32) (
<Step S21>
At step S21, a packaging material 25, a battery element 1 including electrodes, and leads 2 extending from the electrodes are provided. The packaging material 25 is provided according to the embodiment described above. The battery element 1 and the leads 2 are not particularly limited, but a known battery element 1 and known leads 2 may be used.
<Step S22>
At step S22, a recess 32 for accommodating the battery element 1 is formed by shaping the sealant layer 16-side of the packaging material 25. The recess 32 has a shape such as a rectangular shape in plan view conforming to the shape of the battery element 1. The recess 32 may be formed by, for example, pressing a pressing member having a rectangular pressing surface against part of the packaging material 25 in the thickness direction thereof. The position to be pressed, i.e., the position where the recess 32 is to be formed, is a position offset from the center of the packaging material 25, which has been cut in a rectangular shape, to one end of the packaging material 25 in the longitudinal direction. After the recess 32 is formed, the other end portion having no recess 32 is folded back to provide a cover (cover portion 34).
More specifically, the method of forming the recess 32 may be one using a die (deep drawing). The forming method may be one that uses a female die and a male die arranged with a gap equal to or greater than the thickness of the packaging material 25 therebetween, so that the male die together with the packaging material 25 is pressed into the female die. The depth (deep drawing degree) of the recess 32 can be adjusted as desired by adjusting the pressing amount of the male die. With the recess 32 being formed in the packaging material 25, an embossed packaging material 30 is obtained. The embossed packaging material 30 has a shape, for example, as illustrated in
<Step S23>
At step S23, the battery element 1 including a cathode, a separator, an anode, and the like is disposed in the formed area (recess 32) of the embossed packaging material 30. The leads 2 extending from the battery element 1 and respectively joined to the cathode and the anode are drawn out of the formed area (recess 32). The embossed packaging material 30 is then folded back at the approximate center thereof in the longitudinal direction so that surfaces of the sealant layer 16 are located on the inside and overlaid with each other, followed by heat-sealing the side of the embossed packaging material 30 where the leads 2 are sandwiched and held. The heat-sealing is controlled by three conditions of temperature, pressure and time, which are appropriately set. The heat-sealing temperature is preferably not less than the temperature at which the sealant layer 16 is melted, and can be specifically 180° C. or higher.
After the heat-sealing, a curing step is performed to heat the entire sealant layer 16. This promotes crystallization of the portions other than the heat-sealed portion so that the entire packaging material 25 has heat resistance. The curing step can be performed at 80° C. to 150° C.
The thickness of the sealant layer 16 before being heat-sealed is preferably 40% or more and 80% or less of the thickness of the leads 2. With the thickness of the sealant layer 16 being not less than the lower limit, the resin constituting the sealant layer 16 tends to adequately fill the end portions of the leads 2. With the thickness of the sealant layer 16 being not more than the upper limit, the thickness of the end portions of the packaging material 25 of the secondary battery 40 can have a moderate thickness, reducing the amount of moisture penetrating from the end portions of the packaging material 25.
<Step S24>
At step S24, a side of the packaging material is heat-sealed, leaving one side other than the side where the leads 2 are sandwiched and held unsealed. An electrolyte is then injected through the unsealed side, which is then heat-sealed in vacuum. The heat-sealing conditions are similar to those of step S23.
<Step S25>
At step S25, the secondary battery 40 obtained at step S23 is charged and discharged to induce chemical changes (chemical conversion: for 3 days in 40° C. environment). Then, the secondary battery 40 is opened once to remove gas generated by the chemical conversion and refill the electrolyte. Thereafter, final sealing is performed. Step S25 can be omitted.
<Step S26>
The end portions of the heat-sealed sides except for the side where the leads 2 are sandwiched and held are trimmed to remove the portion of the sealant layer 16 extending out of the end portions. Then, the heat-sealed portions are turned up toward the formed area 32 to form turned-up portions 42. Thus, the secondary battery 40 is obtained.
Preferred embodiments of the power storage device packaging material of the invention have been specifically described above. However, the present invention should not be construed as limited to such specific embodiments, and can be modified or altered in various ways within the scope of the present invention recited in the claims.
<<Fifth Aspect>>
The following description will be given of a power storage device packaging material, a method of producing the packaging material and a power storage device according to a fifth aspect of the present disclosure. The description of the same elements as those in the power storage device packaging material, the power storage device, and the method of producing the power storage device of the fourth aspect will be omitted. Since a method of producing a power storage device according to the fifth aspect is the same as that in the fourth aspect, the description thereof will be omitted.
[Power Storage Device Packaging Material]
The power storage device packaging material according to the fifth aspect differs from the power storage device packaging material according to the fourth aspect in that a metal foil layer 13 is provided on the first adhesive layer 12 on a side opposite to that facing the substrate layer 11 in the power storage device packaging material according to the fifth aspect, instead of the barrier layer 13 in the power storage device packaging material according to the fourth aspect. Further, the power storage device packaging material according to the fifth aspect and the power storage device packaging material according to the fourth aspect are different in the first adhesive layer 12.
(First Adhesive Layer 12)
The first adhesive layer 12 bonds the metal foil layer 13, on which the anticorrosion treatment layer 14a is formed, to the substrate layer 11. The first adhesive layer 12 has an adhesive force needed to firmly adhere the substrate layer 11 to the metal foil layer 13 and also has conformability for reducing or preventing breakage of the metal foil layer 13 by the substrate layer 11 during cold forming. The conformability refers to an ability by which the first adhesive layer 12 remains on a member without being detached, even when the member is deformed due to expansion or contraction.
The first adhesive layer 12 may be made of adhesive components such as a urethane-based compound, a polyolefin-based resin, and the like. These adhesive components may be used singly or in combination of two or more. The urethane-based compound is obtained by reacting a polyol-based resin as a base resin with a polyisocyanate compound as a hardener.
Examples of the polyol-based resin include polyester polyol-based resin, polyether polyol-based resin, and acrylic polyol-based resin. The polyol-based resin is preferably a polyester polyol-based resin from the viewpoint of improvement in adhesion between the adhesive layer and the sealant layer and between the adhesive layer and the metal foil layer so that the resultant packaging material has further improved deep drawing formability.
Examples of the polyester polyol-based resin include those obtained by reaction of one or more dicarboxylic acids and a diol.
Examples of the polyether polyol-based resin include those produced by addition polymerization of ethylene oxide or propylene oxide with propylene glycol, glycerin, pentaerythritol, or the like.
Examples of the acrylic polyol-based resin include copolymers obtained by copolymerizing at least a hydroxyl group-containing acrylic monomer and (meth)acrylic acid. In this case, a structural unit derived from (meth)acrylic acid is preferably contained as a main component. The hydroxyl group-containing acrylic monomer may be 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, or the like.
Examples of the polyolefin-based resin include low density, middle density and high density polyethylenes, ethylene-α olefin copolymers, homopolypropylenes, blocked polypropylenes, random polypropylenes, and propylene-α olefin copolymers.
The polyolefin-based resin may be one obtained by introducing an acidic group into a polyolefin resin in order to improve adhesion between the substrate layer 11 and the metal foil layer 13. Examples of the introduced acidic group include a carboxy group, sulfonic acid group, and the like. The carboxy group is particularly preferred.
Examples of the acid-modified polyolefin-based resin obtained by introducing a carboxy group into a polyolefin resin include an acid-modified polyolefin-based resin obtained by graft-modifying a polyolefin-based resin with an unsaturated carboxylic acid or an acid anhydride thereof, or esters of unsaturated carboxylic acid or acid anhydride thereof in the presence of a radical initiator.
Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, tetrahydrophthalic acid, bicyclo[2,2,1]hepto-2-ene-5,6-dicarboxylic acid, and the like.
Examples of the acid anhydride of unsaturated carboxylic acid include maleic anhydride, itaconic anhydride, citraconic anhydride, tetrahydrophthalic anhydride, bicyclo[2,2,1]hepto-2-ene-5,6-dicarboxylic anhydride, and the like.
Examples of the esters of unsaturated carboxylic acid or acid anhydride thereof include methyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, dimethyl maleate, monomethyl maleate, diethyl fumarate, dimethyl itaconate, diethyl citraconate, dimethyl tetrahydrophthalic anhydride, dimethyl bicyclo[2,2,1]hepto-2-ene-5,6-dicarboxylic anhydride, and the like.
The ratio of the graft compound in the acid-modified polyolefin-based resin is preferably 0.2 parts by mass to 100 parts by mass relative to 100 parts by mass of the polyolefin-based resin.
The polyisocyanate compound contains a plurality of isocyanate groups and crosslinks the above polyol-based resin. The polyisocyanate compounds may be used singly or in combination of two or more. Example of the polyisocyanate compound include aliphatic polyisocyanate compound, alicyclic polyisocyanate compound and aromatic polyisocyanate compound. From the perspective of improving the heat resistance of the obtained packaging material, an aromatic polyisocyanate compound is preferred.
Examples of the aliphatic polyisocyanate compound include hexamethylene diisocyanate (HDI), xylylene diisocyanate (XDI), and the like. Examples of the alicyclic polyisocyanate compound include isophorone diisocyanate (IPDI), and the like. Examples of the aromatic polyisocyanate compound include tolylene diisocyanate (TDI), diphenylmethane diisocyanate (MDI), and the like. As the polyisocyanate compound, a polymer (for example, trimer) of these compounds can be used, and specifically, an adduct, a biuret, an isocyanurate, and the like can be used. The polyisocyanate compound is preferably an adduct since it enhances interfacial adhesion between the adhesive layer and a target to be adhered and improves the heat resistance of the obtained packaging material.
In the urethane-based compound, a molar ratio of the isocyanate groups of the polyisocyanate compound to the hydroxyl groups of the polyol is preferably 1 to 50, and more preferably 10 to 30.
In a reaction between the polyol-based resin as a base resin and the polyisocyanate compound as a hardener, a catalyst may be used to control the reaction. The polyisocyanate compound reacts with water in a composition containing a base resin and a hardener or in the atmosphere to hydrolyze and produce an amine-based compound, which in turn may react with the polyisocyanate compound to cause self-condensation. The progress of such a side reaction can be suppressed by the use of a catalyst. As a result, a ratio of urethane groups in the urethane-based compound in the first adhesive layer can be increased. Examples of such a catalyst include organic tin compounds such as a dibutyltin compound and a dioctyltin compound, organic titanium compounds, and organic zirconium compounds.
The first adhesive layer 12 preferably contains a hydrogen sulfide adsorbent for preventing corrosion of the metal foil layer 13 due to hydrogen sulfide present outside the packaging material. Examples of the hydrogen sulfide adsorbent include zinc oxide, potassium permanganate, and the like. Since corrosion of the metal foil layer 13 due to hydrogen sulfide present outside the packaging material can be prevented due to the first adhesive layer 12 containing a hydrogen sulfide adsorbent, the content of the hydrogen sulfide adsorbent is preferably 1 mass % to 50 mass % of the total amount of the first adhesive layer 12.
The thickness of the first adhesive layer 12 is preferably 1 μm to 10 μm, and more preferably 2 μm to 6 μm from the perspective of obtaining desired adhesive strength, conformability, processability, and the like.
The first adhesive layer 12 is obtained by, for example, coating with a composition containing a base resin and a hardener of the above-mentioned adhesive components. The coating can be performed by known methods such as gravure direct, gravure reverse (direct, kiss) and micro gravure.
When the first adhesive layer 12 contains a urethane-based compound, the content of the polyol-based resin in the composition containing the polyol-based resin and the polyisocyanate compound is preferably 50 mass % to 90 mass % relative to the total amount of the polyol-based resin and the polyisocyanate compound.
When the first adhesive layer 12 contains a urethane-based compound, and a catalyst is used in the reaction between the polyol-based resin and the polyisocyanate compound, the content of the catalyst in the composition containing the polyol-based resin, the polyisocyanate compound and the catalyst is preferably 0.1 mass % to 20 mass % relative to the total amount of the polyisocyanate compound.
When the first adhesive layer 12 contains an epoxy-based resin, the content of the polymer having two or more epoxy groups in a molecule in a composition containing the polymer having two or more epoxy groups in a molecule and a compound having a functional group that reacts with the epoxy groups is preferably 30 mass % to 60 mass % relative to the total amount of these compounds.
<Metal Foil Layer 13>
Various types of metal foil such as of aluminum and stainless steel may be used as the metal foil layer 13. The metal foil layer 13 is preferably aluminum foil from the perspective of processability such as moisture resistance, ductility and malleability, and cost. The aluminum foil may be a general soft aluminum foil, but aluminum foil containing iron is preferred for exhibiting good pinhole resistance, ductility and malleability when formed.
The aluminum foil (100 mass %) containing iron, the iron content is preferably 0.1 mass % to 9.0 mass %, and more preferably 0.5 mass % to 2.0 mass % (e.g., aluminum foil made of the material 8021 or 8079 according to the Japanese Industrial Standards). The iron content of 0.1 mass % or more leads to a packaging material 25 having better pinhole resistance, and ductility and malleability. The iron content of 9.0 mass % or less enables a packaging material 25 having much better flexibility.
Further, the aluminum foil may be more preferably an annealed soft aluminum foil from the perspective of imparting desired ductility and malleability during forming.
In order to obtain desired electrolyte resistance, the metal foil used for the metal foil layer 13 may be preferably, for example, degreased. Further, in order to simplify the production process, the metal foil preferably has a surface that is not etched. The degreasing treatment may be, for example, a wet type or dry type. However, dry degreasing treatment is preferred from the perspective of simplifying the production process.
The dry type degreasing treatment is the same as that of the power storage device according to the fourth aspect. The wet type degreasing treatment is the same as that of the power storage device according to the fourth aspect. The thickness of the metal foil layer 13 is the same as that of the power storage device according to the fourth aspect.
[Method of Producing Packaging Material]
The method of producing a packaging material according to the fifth aspect and the method of producing a packaging material according to the fourth aspect are different in step S12 and step S13.
<Step S12>
At step S12, a surface of the anticorrosion treatment layer 14a on a side opposite to that facing the metal foil layer 13 is bonded to the substrate layer 11 by dry lamination or the like using an adhesive for forming the first adhesive layer 12. At step S12, heat treatment may be performed to expedite adhesiveness of the first adhesive layer 12. The temperature in the heat treatment is not particularly limited, but may be, for example, 40° C. to 120° C.
<Step S13>
Subsequent to step S12, in the laminate in which the substrate layer 11, the first adhesive layer 12, the anticorrosion treatment layer 14a, the metal foil layer 13 and the anticorrosion treatment layer 14b are laminated in this order, a surface of the anticorrosion treatment layer 14b on a side opposite to that facing the metal foil layer 13 is bonded to the sealant layer 16 via an adhesive forming the second adhesive layer 17 by dry lamination or the like. In step S13, heat treatment may be performed to expedite adhesiveness of the second adhesive layer 17. The temperature in the heat treatment is not particularly limited, but may be, for example, 40° C. to 120° C.
[Power Storage Device]
Since the packaging material 25 has excellent deep drawing formability, it is suitable for use with fully solid-state batteries in which a recess is formed by cold forming, and the battery contents are accommodated in the recess.
The present disclosure will be described below in more detail by way of examples. However, the present disclosure should not be limited to the following examples.
<<First Examination>>
[Materials Used]
Materials used in examples and comparative examples are described below.
<Substrate Layer (25 μm Thickness)>
Ny: Nylon (Ny) film (manufactured by Toyobo Co., Ltd.) having one surface subjected to a corona treatment was used.
PET: a polyethylene terephthalate film having one surface subjected to a corona treatment was used.
<First Adhesive Layer>
The base resin and the hardener shown in Table 1 were used to prepare a first adhesive. The hardener was blended with the base resin at the NCO/OH ratio or the epoxy group/OH shown in the table, and the mixture was diluted with ethyl acetate to the solid content of 26 mass %. When two types of hardeners were used, the hardeners were mixed so that the ratio of the NCO groups of each hardener relative to the total NCO groups of the hardener was the value shown in Table 1. The details of each component constituting the first adhesive are as follows.
(Base Resin)
A-1: Polyester polyol (manufactured by Hitachi Chemical Company, Ltd., trade name: TESLAC 2505-63, hydroxyl group value: 7 to 11 mgKOH/g)
A-2: Acrylic polyol (manufactured by Taisei Fine Chemical Co., Ltd., trade name: 6KW-700, hydroxyl group value: 10 mgKOH/g)
(Hardener)
B-1: Isocyanurate of isophorone diisocyanate (manufactured by Mitsui Chemicals, Inc., trade name: TAKENATE 600)
B-2: Adduct of tolylene diisocyanate (manufactured by Mitsui Chemicals, Inc., trade name: TAKENATE 500)
B-3: Adduct of hexamethylene diisocyanate (manufactured by Asahi Kasei Corp., trade name: DURANATE P301-75E)
B-4: Epoxy-based resin (manufactured by ADEKA Corporation, trade name: ADEKA RESIN EP4100)
<First Anticorrosion Treatment Layer (Substrate Layer-Side) and Second Anticorrosion Treatment Layer (Sealant Layer-Side)>
(CL-1): A Sodium polyphosphate stabilized cerium oxide sol was used after being adjusted to a solid concentration of 10 mass % by using distilled water as a solvent. The sodium polyphosphate stabilized cerium oxide sol was obtained by formulating 10 parts by mass of Na salt of phosphoric acid per 100 parts by mass of cerium oxide.
(CL-2): A composition having 90 mass % of polyallylamine (manufactured by Nitto Boseki Co., Ltd) and 10 mass % of polyglycerol polyglycidyl ether (manufactured by Nagase Chemtex Corp.) was used after being adjusted to a solid concentration of 5 mass % using distilled water as a solvent.
<Barrier Layer (40 μm Thickness)>
An annealed and degreased soft aluminum foil (8079 Material manufactured by Toyo Aluminum K.K.) was used.
<Second Adhesive Layer (Coating Amount 3 g/m2)>
A polyurethane-based adhesive obtained by blending a polyisocyanate with an acid-modified polyolefin dissolved in a mixed solvent of toluene and methylcyclohexane was used.
<Sealant Layer (80 μm Thickness)>
A polyolefin film (a non-stretched polypropylene film having a second adhesive layer-side surface subjected to a corona treatment) was used.
The barrier layer was dry laminated to the substrate layer using the first adhesive (first adhesive layer). For lamination of the barrier layer to the substrate layer, the first adhesive was applied to one surface of the barrier layer at a dry coating weight (mass per unit area) shown in Table 1, followed by drying at 80° C. for 1 minute, and the surface was then laminated to the substrate layer. The laminate was aged at 80° C. for 120 hours.
Then, a surface of the barrier layer on a side opposite to that facing the substrate layer was dry laminated to the sealant layer (80 μm thickness) using a polyurethane-based adhesive (second adhesive layer). For lamination of the barrier layer to the sealant layer, the polyurethane-based adhesive was applied to a surface of the barrier layer on a side opposite to that facing the substrate layer at a dry coating weight (mass per unit area) of 3 g/m2, followed by drying at 80° C. for 1 minute, and the surface was then laminated to the sealant layer. The laminate was aged at 120° C. for 3 hours. By the method described above, a packaging material (laminate of the substrate layer/first adhesive layer/barrier layer/second adhesive layer/sealant layer) was produced.
Packaging materials (laminates of the substrate layer/first adhesive layer/barrier layer/second adhesive layer/sealant layer) of Examples A-2 to A-16 were produced in the same manner as in Example A-1 except that at least one of the composition of the first adhesive and the coating amount of the first adhesive was changed as shown in Table 1.
First, the first and second anticorrosion treatment layers were respectively provided on the barrier layer through the following procedure. That is, (CL-1) was applied to both surfaces of the barrier layer by micro gravure coating at a dry coating weight of 70 mg/m2, followed by baking at 200° C. in a drying unit. Next, (CL-2) was applied to the obtained layer by micro gravure coating at a dry coating weight of 20 mg/m2, thereby forming a composite layer made of (CL-1) and (CL-2) as first and second anticorrosion treatment layers. The composite layer developed corrosion prevention performance by compounding two materials (CL-1) and (CL-2).
Next, the first anticorrosion treatment layer-side of the barrier layer provided with the first and second anticorrosion treatment layers was dry laminated to the substrate layer using the first adhesive (first adhesive layer). Next, the second anticorrosion treatment layer-side of the barrier layer provided with the first and second anticorrosion treatment layers was dry laminated to the sealant layer (80 μm thickness) using a polyurethane-based adhesive (second adhesive layer). The conditions for laminating the barrier layer and the substrate layer, and the conditions for laminating the barrier layer and the sealant layer were the same as those in Example A-1. By the method described above, a packaging material (laminate of the substrate layer/first adhesive layer/first anticorrosion treatment layer/barrier layer/second anticorrosion treatment layer/second adhesive layer/sealant layer) was produced.
A packaging material (laminate of the substrate layer/first adhesive layer/first anticorrosion treatment layer/barrier layer/second anticorrosion treatment layer/second adhesive layer/sealant layer) of Example A-18 was produced in the same manner as in Example A-17 except that the substrate layer was changed to PET.
Packaging materials (laminates of the substrate layer/first adhesive layer/barrier layer/second adhesive layer/sealant layer) of Comparative Examples A-1 to A-5 were produced in the same manner as in Example A-1 except that the composition of the first adhesive was changed as shown in Table 1.
[Measurement of Lamination Strength]
(Lamination Strength in Room Temperature Environment)
The packaging material was cut to a width of 15 mm, and the lamination strength between the barrier layer and the substrate layer in a room temperature environment (25° C.) was measured by a 90 degree peel test using a tensile tester (manufactured by Shimadzu Corporation) under the condition of a tension rate of 50 mm/min. Based on the obtained lamination strength, evaluation was performed according to the following criteria. Table 2 shows the results.
A: Lamination strength is 6.0 N/15 mm or more.
B: Lamination strength is 4.5 N/15 mm or more and less than 6.0 N/15 mm.
C: Lamination strength is 3.0 N/15 mm or more and less than 4.5 N/15 mm.
D: Lamination strength is less than 3.0 N/15 mm.
(Lamination Strength in High Temperature Environment)
The packaging material was cut to a width of 15 mm and left in a high temperature environment of 150° C. for 5 minutes. Then, the lamination strength between the barrier layer and the substrate layer of the packaging material in the environment of 150° C. was measured by a 90 degree peel test using a tensile tester (manufactured by Shimadzu Corporation) under the condition of a tension rate of 50 mm/min. Based on the obtained lamination strength, evaluation was performed according to the following criteria. Table 2 shows the results.
A: Lamination strength is 3.5 N/15 mm or more.
B: Lamination strength is 2.5 N/15 mm or more and less than 3.5 N/15 mm.
C: Lamination strength is 2.0 N/15 mm or more and less than 2.5 N/15 mm.
D: Lamination strength is less than 2.0 N/15 mm.
[Evaluation of Deep Drawing Formability]
The drawing depth at which deep drawing was possible for the packaging material was evaluated by the following method. The packaging material was deep drawn with the drawing depth of the drawing device being set to 1.00 mm to 5.00 mm in steps of 0.25 mm. The presence or absence of breakage and pinholes in the sample after the deep drawing was visually checked by irradiating the packaging material with light to obtain a maximum drawing depth with which the packaging material has been successfully deep drawn causing neither breakage nor pinholes. The drawing depth was evaluated according to the following criteria. Table 2 shows the results.
A: The maximum drawing depth is 4.00 mm or more.
B: The maximum drawing depth is 3.50 mm or more and less than 4.00 mm.
C: The maximum drawing depth is 3.00 mm or more and less than 3.50 mm.
D: The maximum drawing depth is less than 3.00 mm.
[Evaluation of Environmental Reliability]
The samples having the drawing depth of 2.00 mm (5 samples for each example) prepared in the above evaluation of deep drawing formability were left in an environment of 150° C. for 1 week. Then, a portion of the sample near the convexity formed by deep drawing was irradiated with light to visually check whether delamination has occurred between the substrate layer and the barrier layer. The environmental reliability was evaluated according to the following criteria. Table 2 shows the results.
A: No delamination occurred in any of the 5 samples.
D: Delamination occurred in 1 or more of the 5 samples.
<<Second Examination>>
[Materials Used]
Materials used in examples and comparative examples are described below.
<Substrate Layer (25 μm Thickness)>
Ny: Nylon (Ny) film (manufactured by Toyobo Co., Ltd.) having one surface subjected to a corona treatment was used.
PET: a polyethylene terephthalate film having one surface subjected to a corona treatment was used.
<First Adhesive Layer>
The base resin and the hardener shown in Table 3 were used to prepare a first adhesive. The hardener was blended with the base resin at the NCO/OH ratio shown in the table, and the mixture was diluted with ethyl acetate to the solid content of 26 mass %. When two types of hardeners were used, the hardeners were mixed so that the ratio of the NCO groups of each hardener relative to the total NCO groups of the hardener was the value shown in Table 3. The details of each component constituting the first adhesive are as follows.
(Base Resin)
(Hardener)
<First Anticorrosion Treatment Layer (Substrate Layer-Side) and Second Anticorrosion Treatment Layer (Sealant Layer-Side)>
(CL-1): A Sodium polyphosphate stabilized cerium oxide sol was used after being adjusted to a solid concentration of 10 mass % by using distilled water as a solvent. The sodium polyphosphate stabilized cerium oxide sol was obtained by formulating 10 parts by mass of Na salt of phosphoric acid per 100 parts by mass of cerium oxide.
(CL-2): A composition having 90 mass % of polyallylamine (manufactured by Nitto Boseki Co., Ltd) and 10 mass % of polyglycerol polyglycidyl ether (manufactured by Nagase Chemtex Corp.) was used after being adjusted to a solid concentration of 5 mass % using distilled water as a solvent.
<Barrier Layer (40 μm Thickness)>
Either an annealed and degreased soft aluminum foil (8079 Material manufactured by Toyo Aluminum K.K.) or a copper foil (manufactured by JX Nippon Mining & Metals Corporation, model number: HA) was used.
<Second Adhesive Layer (Coating Amount 3 g/m2)>
A polyurethane-based adhesive obtained by blending a polyisocyanate with an acid-modified polyolefin dissolved in a mixed solvent of toluene and methylcyclohexane was used.
<Sealant Layer (80 μm Thickness)>
A polyolefin film (a non-stretched polypropylene film having a second adhesive layer-side surface subjected to a corona treatment) was used.
The barrier layer (aluminum foil) was dry laminated to the substrate layer (Nylon) using the first adhesive (first adhesive layer). For lamination of the barrier layer to the substrate layer, the first adhesive was applied to one surface of the barrier layer at a dry coating weight (mass per unit area) shown in Table 3, followed by drying at 80° C. for 3 minutes, and the surface was then laminated to the substrate layer. The laminate was aged at 80° C. for 120 hours.
Then, a surface of the barrier layer on a side opposite to that facing the substrate layer was dry laminated to the sealant layer (80 μm thickness) using a polyurethane-based adhesive (second adhesive layer). For lamination of the barrier layer to the sealant layer, the polyurethane-based adhesive was applied to a surface of the barrier layer on a side opposite to that facing the substrate layer at a dry coating weight (mass per unit area) of 3 g/m2, followed by drying at 80° C. for 1 minute, and the surface was then laminated to the sealant layer. The laminate was aged at 120° C. for 3 hours. By the method described above, a packaging material (laminate of the substrate layer/first adhesive layer/barrier layer/second adhesive layer/sealant layer) was produced.
Packaging materials (laminates of the substrate layer/first adhesive layer/barrier layer/second adhesive layer/sealant layer) of Examples B-2 to B-17 were produced in the same manner as in Example B-1 except that at least one of the composition of the first adhesive and the coating amount of the first adhesive was changed as shown in Table 3.
A packaging material (laminates of the substrate layer/first adhesive layer/barrier layer/second adhesive layer/sealant layer) of Examples B-18 was produced in the same manner as in Example B-1 except that the barrier layer was made of a copper foil (Cu), and the composition of the first adhesive and the coating amount of the first adhesive were changed as shown in Table 3.
Packaging materials (laminates of the substrate layer/first adhesive layer/barrier layer/second adhesive layer/sealant layer) of Examples B-19 to B-21 were produced in the same manner as in Example B-18 except that the barrier layer was made of an aluminum foil, and the thickness thereof was changed as shown in Table 3.
A packaging material (laminates of the substrate layer/first adhesive layer/barrier layer/second adhesive layer/sealant layer) of Example B-22 was produced in the same manner as in Example B-16 except that the barrier layer was configured to have no anticorrosion treatment layer.
A packaging material (laminates of the substrate layer/first adhesive layer/barrier layer/second adhesive layer/sealant layer) of Example B-23 was produced in the same manner as in Example B-16 except that the substrate was made of PET.
Packaging materials (laminates of the substrate layer/first adhesive layer/barrier layer/second adhesive layer/sealant layer) of Comparative Examples B-1 and B-2 were produced in the same manner as in Example B-1 except that the composition of the first adhesive was changed as shown in Table 3.
[IR Measurement]
The packaging material was cut to an appropriate size, and delaminated at the interface between the substrate layer and the barrier layer from the edge of the packaging material. A surface of the substrate layer or the barrier layer on which more adhesive layer was left was subjected to attenuated total reflection (ATR)-Fourier transform infrared (FT-IR) spectroscopy, by which a transmittance T0 at a baseline of wavenumber of infrared radiation, a minimum transmittance T1 in the range of 2200 cm−1 to 2300 cm−1, and a minimum transmittance T2 in the range of 1670 cm−1 to 1710 cm−1 were calculated.
It was evaluated whether the calculated values satisfied the relationship of 0.06≤(T0−T1)/(T0−T2)≤0.4. Table 3 shows the results.
<Measurement Conditions>
Prism: Germanium
Wavenumber resolution: 4 cm−1
Number of accumulations: 4 times
Baseline: Average intensity between the wavenumbers of 2500 cm−1 and 2700 cm−1
<Measurement Device>
Spectrum Spotlight 400 manufactured by PerkinElmer
[Evaluation of Heat Resistant Lamination Strength of Packaging Material]
The packaging material was cut to a width of 15 mm and delaminated at the interface between the barrier layer and the substrate layer. The measurement was performed by a 90 degree peel test using a tensile tester (manufactured by Shimadzu Corporation) under the condition of a tension rate of 50 mm/min. In the following evaluations, an evaluation of C or higher was judged as a pass.
(Lamination Strength in Room Temperature Environment)
The lamination strength in a room temperature environment (25° C.) was measured. Based on the obtained lamination strength, evaluation was performed according to the following criteria. Table 4 shows the results.
A: Lamination strength is 6.0 N/15 mm or more.
B: Lamination strength is 4.5 N/15 mm or more and less than 6.0 N/15 mm.
C: Lamination strength is 3.0 N/15 mm or more and less than 4.5 N/15 mm.
D: Lamination strength is less than 3.0 N/15 mm.
(Lamination Strength in High Temperature Environment)
The packaging material was cut to a width of 15 mm and left in a high temperature environment of 150° C. for 5 minutes. Then, the lamination strength in an environment of 150° C. was measured. Based on the obtained lamination strength, evaluation was performed according to the following criteria. Table 4 shows the results.
A: Lamination strength is 3.5 N/15 mm or more.
B: Lamination strength is 2.5 N/15 mm or more and less than 3.5 N/15 mm.
C: Lamination strength is 2.0 N/15 mm or more and less than 2.5 N/15 mm.
D: Lamination strength is less than 2.0 N/15 mm.
[Evaluation of Deep Drawing Formability]
The drawing depth at which deep drawing was possible for the packaging material was evaluated by the following method. The packaging material was deep drawn with the drawing depth of the drawing device being set to 1.00 mm to 5.00 mm in steps of 0.25 mm. The presence or absence of breakage and pinholes in the sample after the deep drawing was visually checked by irradiating the packaging material with light to obtain a maximum drawing depth with which the packaging material has been successfully deep drawn causing neither breakage nor pinholes. The drawing depth was evaluated according to the following criteria. Table 4 shows the results.
A: The maximum drawing depth is 5.00 mm or more.
B: The maximum drawing depth is 4.00 mm or more and less than 5.00 mm.
C: The maximum drawing depth is 3.00 mm or more and less than 4.00 mm.
D: The maximum drawing depth is less than 3.00 mm.
[Evaluation of Deep Drawing Reliability]
The samples having the drawing depth of 2.00 mm (5 samples for each example) prepared in the above evaluation of deep drawing formability were left in an environment of 150° C. for 1 week. Then, a portion of the sample near the convexity formed by deep drawing was irradiated with light to visually check whether delamination has occurred between the substrate layer and the barrier layer. The environmental reliability was evaluated according to the following criteria. Table 4 shows the results.
A: No delamination occurred in any of the 5 samples.
D: Delamination occurred in 1 or more of the 5 samples.
<<Third Examination>>
[Materials Used]
Materials used in examples and comparative examples are described below.
A 25-μm thick nylon (Ny) film (manufactured by Toyobo Co., Ltd.) having one surface subjected to a corona treatment was used as the substrate layer 11.
Next, as the material constituting the first adhesive layer 12a, five types of polyamide-imides having different number average molecular weights (Mn) were prepared.
The number average molecular weight (Mn) of each polyamide-imide was 2,000, 5,000, 20,000, 30,000 and 40,000, respectively.
In addition, as the base resin (polyol resin) of the polyurethane-based compound constituting the first adhesive layer 12a, polyether polyol, polyester polyol, acrylic polyol and polycarbonate polyol (PCD) were prepared. Further, as the hardener (polyfunctional isocyanate compound) of the polyurethane-based compound, an adduct of hexamethylene diisocyanate (HDI-a), an isocyanurate of isophorone diisocyanate (IPDI-n) and an adduct of tolylene diisocyanate (TDI-a) were prepared.
A soft aluminum foil (8079 Material manufactured by Toyo Aluminum K.K.) provided with the anticorrosion treatment layers 14a and 14b on respective sides was used as the barrier layer 13. The anticorrosion treatment layers 14a and 14b were formed by using a sodium polyphosphate stabilized cerium oxide sol prepared by blending 10 parts by mass of Na salt of phosphoric acid with 100 parts by mass of cerium oxide.
Next, as the adhesive constituting the second adhesive layer 12b, a polyurethane-based adhesive prepared by blending a polyisocyanate with an acid-modified polyolefin dissolved in a mixed solvent of toluene and methylcyclohexane was used. The second adhesive layer 12b was formed at the coating amount of 3 g/m2.
A polyolefin film (a non-stretched polypropylene film having a second adhesive layer-side surface subjected to a corona treatment) was used as the sealant layer 16. The thickness of the sealant layer 16 was 80 μm.
The packaging material 10 of this example was produced as follows. Table 5 shows the number average molecular weight (Mn) and the formulation amount (solid content of polyamide-imide resin relative to the solid content of polyurethane-based compound) A of the polyamide-imide used, the base resin and the hardener of the polyurethane-based compound, and the ratio (NCO/OH) of the number of isocyanate groups contained therein.
That is, the barrier layer 13 was dry laminated to the substrate layer 11 using the first adhesive (first adhesive layer) 12a. For lamination of the barrier layer 13 to the substrate layer 11, the first adhesive was applied to one surface of the barrier layer 13, followed by drying at 80° C. for 1 minute, and the surface was then laminated to the substrate layer 11. The laminate was aged at 80° C. for 120 hours.
Then, a surface of the barrier layer 13 on a side opposite to that facing the substrate layer 11 was dry laminated to the sealant layer (80 μm thickness) 16 using a polyurethane-based adhesive (second adhesive layer) 12b. For lamination of the barrier layer 13 to the sealant layer 16, the polyurethane-based adhesive was applied to a surface of the barrier layer 13 on a side opposite to that facing the substrate layer 11, followed by drying at 80° C. for 1 minute, and the surface was then laminated to the sealant layer. The laminate was aged at 120° C. for 3 hours. By the method described above, a packaging material (laminate of the substrate layer 11/first adhesive layer 12a/barrier layer 13/second adhesive layer 12b/sealant layer 16) 10 was produced.
Comparative examples C-1 to C-4 were compared with Example C-1, in which polyamide-imide was formulated, to examine the effect of the presence or absence of the polyamide-imide. Table 5 shows the number average molecular weight (Mn) and the formulation amount A of the polyamide-imide used in the comparative examples, the base resin and the hardener of the polyurethane-based compound, and NCO/OH thereof.
These examples were compared with Example C-1 to examine the effect of the formulation amount A of the polyamide-imide. Table 5 shows the number average molecular weight (Mn) and the formulation amount A of the polyamide-imide, the base resin and the hardener of the polyurethane-based compound, and NCO/OH thereof.
These examples were compared with Example C-1 to examine the effect of the number average molecular weight (Mn) of the polyamide-imide. Table 5 shows the number average molecular weight (Mn) and the formulation amount A of the polyamide-imide, the base resin and the hardener of the polyurethane-based compound, and NCO/OH thereof.
These examples were compared with Example C-1 to examine the effect of the type of the base resin of the polyurethane-based compound. Table 5 shows the number average molecular weight (Mn) and the formulation amount A of the polyamide-imide, the base resin and the hardener of the polyurethane-based compound, and NCO/OH thereof.
These examples were compared with Example C-1 to examine the effect of the type of the hardener of the polyurethane-based compound. Table 5 shows the number average molecular weight (Mn) and the formulation amount A of the polyamide-imide, the base resin and the hardener of the polyurethane-based compound, and NCO/OH thereof.
These examples were compared with Example C-1 to examine the effect of NCO/OH of the polyurethane-based compound. Table 5 shows the number average molecular weight (Mn) and the formulation amount A of the polyamide-imide, the base resin and the hardener of the polyurethane-based compound, and NCO/OH thereof.
[Evaluation of Packaging Material 10]
For the packaging materials 10 produced in the examples and the comparative examples, the following four points were evaluated. That is, evaluation by measurement of lamination strength in a room temperature environment, evaluation by measurement of lamination strength in a high temperature environment (170° C.), evaluation of deep drawing formability, and evaluation of reliability (formation reliability) of the packaging material 10 in a high temperature environment (170° C.) after deep drawing were performed.
(Measurement of Lamination Strength in Room Temperature Environment)
The packaging material was cut to a width of 15 mm, and the lamination strength between the barrier layer and the substrate layer in a room temperature environment (25° C.) was measured by a 90 degree peel test using a tensile tester (manufactured by Shimadzu Corporation) under the condition of a tension rate of 50 mm/min. Based on the obtained lamination strength, evaluation was performed according to the following criteria. Table 5 shows the results.
A: Lamination strength is 6.0 N/15 mm or more.
B: Lamination strength is 4.5 N/15 mm or more and less than 6.0 N/15 mm.
C: Lamination strength is 3.0 N/15 mm or more and less than 4.5 N/15 mm.
D: Lamination strength is less than 3.0 N/15 mm.
(Measurement of Lamination Strength in High Temperature Environment)
The packaging material was cut to a width of 15 mm and left in a high temperature environment of 170° C. for 5 minutes. Then, the lamination strength between the barrier layer and the substrate layer of the packaging material in the environment of 150° C. was measured by a 90 degree peel test using a tensile tester (manufactured by Shimadzu Corporation) under the condition of a tension rate of 50 mm/min. Based on the obtained lamination strength, evaluation was performed according to the following criteria. Table 5 shows the results.
A: Lamination strength is 3.0 N/15 mm or more.
B: Lamination strength is 2.0 N/15 mm or more and less than 3.0 N/15 mm.
C: Lamination strength is 1.0 N/15 mm or more and less than 2.0 N/15 mm.
D: Lamination strength is less than 1.0 N/15 mm.
(Evaluation of Deep Drawing Formability)
The drawing depth at which deep drawing was possible for the packaging material was evaluated by the following method. The packaging material was deep drawn with the drawing depth of the drawing device being set to 1.00 mm to 5.00 mm in steps of 0.25 mm. The presence or absence of breakage and pinholes in the sample after the deep drawing was visually checked by irradiating the packaging material with light to obtain a maximum drawing depth with which the packaging material has been successfully deep drawn causing neither breakage nor pinholes. The drawing depth was evaluated according to the following criteria. Table 5 shows the results.
A: The maximum drawing depth is 4.00 mm or more.
B: The maximum drawing depth is 3.50 mm or more and less than 4.00 mm.
C: The maximum drawing depth is 3.00 mm or more and less than 3.50 mm.
D: The maximum drawing depth is less than 3.00 mm.
[Evaluation of Formation Reliability]
The samples having the drawing depth of 2.00 mm (5 samples for each example) prepared in the above evaluation of deep drawing formability were left in an environment of 170° C. for 1 week. Then, a portion of the sample near the convexity formed by deep drawing was irradiated with light to visually check whether delamination has occurred between the substrate layer and the barrier layer. The formation reliability was evaluated according to the following criteria. Table 5 shows the results.
A: No delamination occurred in any of the 5 samples.
B: Delamination occurred in 1 or 2 of the 5 samples.
C: Delamination occurred in 3 or more of the 5 samples.
[Discussion]
(Discussion of Effect of Presence or Absence of Formulation of Polyamide-imide)
As seen from the results of Example C-1 and Comparative Examples C-1 to C-4, there is no significant difference in lamination strength in a room temperature environment depending on the presence or absence of formulation of polyamide-imide, whereas the lamination strength in a high temperature environment and the deep drawing formability are greatly improved by formulating polyamide-imide. Further, the same applies to the reliability (formation reliability) of the packaging material 10 in a high temperature environment after the deep drawing.
Although polyurethane-based compound made of a reaction product of polyester polyol and IPDI-n is considered to have relatively high heat resistance, Example C-1 in which polyamide-imide is formulated is excellent in lamination strength in a high temperature environment and formation reliability compared with Comparative Examples C-3 and C-4 containing the polyurethane-based compound. Moreover, Example C-1 is superior to Comparative Example C-4, even though Comparative Example C-4 has larger NCO/OH to further improve heat resistance.
(Discussion of Formulation Amount A of Polyamide-imide)
As seen from the results of Examples C-1 to C-4, the larger the formulation amount of polyamide-imide (solid content of polyamide-imide resin relative to the solid content of polyurethane-based compound) A, the higher the lamination strength in a high temperature environment and the formation reliability. However, in Example C-5 having the formulation amount A of 20.0 mass %, the lamination strength in a high temperature environment is lowered and the deep drawing formability is greatly reduced compared with those in Examples C-1 to C-4 having the formulation amount A of 15.0 mass % or less.
Therefore, it is found that, in order to achieve both the lamination strength in a high temperature environment and the formation reliability, the formulation amount A of the polyamide-imide should be 1.0 mass %<A<20.0 mass %. The lamination strength in a high temperature environment is particularly excellent when the formulation amount A is 10.0 mass % to 15.0 mass %.
(Discussion of Number Average Molecular Weight (Mn) of Polyamide-imide)
As seen from the results of Examples C-1 and C-6 to C-9, the polyamide-imide resin exhibits excellent lamination strength in a high temperature environment when it has the number average molecular weight (Mn) satisfying 3,000<Mn<36,000 (Examples C-6 to C-8). Within this range, the smaller the number average molecular weight (Mn), the better the lamination strength. The reason for this is not clear, but seems to be that, for example, the polyamide-imide resin having a low molecular weight excels at interfacial adhesion since it has a large number of functional groups per unit mass.
Further, when the number average molecular weight (Mn) is smaller than 5,000 (Example C-1), the lamination strength in a high temperature environment is lower than that in the examples having the number average molecular weight of 5,000 or more (Examples C-6 to C-9). The reason for this seems to be that the brittleness of the polyamide-imide increases with an increase in the number of functional groups per unit mass when the number average molecular weight (Mn) is smaller than 5,000, and the melting point, glass transition temperature, softening point, or the like of the polyamide-imide decreases and thus the heat resistance thereof decreases.
Further, when the number average molecular weight (Mn) of the polyamide-imide is larger than 36,000 (Example C-9), a polyamide-imide having such a high molecular weight does not dissolve in a solvent. Accordingly, an adhesive containing such polyamide-imide cannot be used.
(Discussion of Type of Base Resin of Polyurethane-based Compound)
As seen from the results of Examples C-1 and C-10 to C-12, the examples in which a polyol resin selected from the group consisting of polyester polyol, acrylic polyol and polycarbonate polyol (PCD) is used as the base resin (polyol resin) of the polyurethane-based compound (Examples C-10 to C-12) are excellent in lamination strength in a high temperature environment compared with the example in which polyether polyol is used (Example C-1). Among Examples C-10 to C-12, the lamination strength in a high temperature environment is higher when polyester polyol is used (Example C-10) than when acrylic polyol or PCD is used (Examples C-11 and C-12). In addition, these examples are also excellent in deep drawing formability and formation reliability.
(Discussion of Type of Hardener of Polyurethane-based Compound)
As seen from the results of Examples C-1, C-13 and C-14, the examples in which alicyclic IPDI-n or TDI-a containing an aromatic ring in the molecular structure is used as the hardener (polyfunctional isocyanate compound) of the polyurethane-based compound (Examples C-13 and C-14) are excellent in lamination strength in a high temperature environment compared with the example in which aliphatic HDI-a is used (Example C-1). In addition, these examples are also excellent in deep drawing formability and formation reliability.
(Discussion of NCO/OH of Polyurethane-Based Compound)
As seen from the results of Examples C-1 and C-15 to C-19, when NCO/OH of the polyurethane-based compound satisfies 1.5<NCO/OH<40.0 (Examples C-1 and C-15 to C-19), both the lamination strength in a high temperature environment and the deep drawing formability can be improved. In particular, when NCO/OH is 10.0 to 30.0 (Examples C-16 to C-18), both the lamination strength in a high temperature environment and the deep drawing formability are excellent.
<<Fourth Examination>>
[Materials Used]
Materials used in examples and comparative examples are described below.
<Substrate Layer (25 μm Thickness)>
A polyethylene terephthalate film having one surface subjected to a corona treatment was used.
<First Adhesive Layer (4 μm Thickness) and Second Adhesive Layer (3 μm Thickness)>
Adhesives in which the base resin, the hardener and the hydrogen sulfide adsorbent shown in Table 6 were formulated in the proportions shown in Table 7 were used. The details of the base resin and the hardener shown in Tables 6 and 7 are as follows. Further, as the hydrogen sulfide adsorbent, the compound described below was used.
{Base Resin}
{Hardener}
{Hydrogen Sulfide Adsorbent}
<Anticorrosion Treatment Layer>
A sodium polyphosphate stabilized cerium oxide sol was used after being adjusted to a solid concentration of 10 mass % by using distilled water as a solvent. The sodium polyphosphate stabilized cerium oxide sol was obtained by formulating 10 parts by mass of Na salt of phosphoric acid per 100 parts by mass of cerium oxide.
<Barrier Layer (35 μm Thickness)>
An annealed and degreased soft aluminum foil (8079 Material manufactured by Toyo Aluminum K.K.) was used.
<Sealant Layer (40 μm Thickness)>
A film shown in Table 6 was used as the sealant layer.
[Production of Packaging Material]
The barrier layer was dry laminated to the substrate layer using an adhesive (first adhesive layer). Then, a surface of the barrier layer on a side opposite to that to which the first adhesive layer was adhered was dry laminated to the sealant layer using an adhesive (second adhesive layer).
The laminate thus obtained was heat-treated under the conditions shown in Table 7 to produce a packaging material (substrate layer/first adhesive layer/barrier layer/second adhesive layer/sealant layer).
First, the sodium polyphosphate-stabilized cerium oxide sol was applied to both sides of the barrier layer by gravure coating. Then, the applied sodium polyphosphate-stabilized cerium oxide sol was dried, followed by baking, to form an anticorrosion treatment layer on both sides of the barrier layer. The baking conditions were the temperature of 150° C. and the treatment time of 30 seconds.
Then, one of the surfaces of the barrier layer on which the anticorrosion treatment layer was formed was dry laminated to the substrate layer using the adhesive (first adhesive layer). The other of the surfaces of the barrier layer on which the anticorrosion treatment layer was formed was dry laminated to the sealant layer using the adhesive (second adhesive layer).
The laminate thus obtained was heat-treated under the conditions shown in Table 7 to produce a packaging material (substrate layer/first adhesive layer/anticorrosion treatment layer/barrier layer/anticorrosion treatment layer/second adhesive layer/sealant layer).
[Measurement of Urea Abundance Ratio]
<First Adhesive Layer>
The barrier layer and the substrate layer bonded to the first adhesive layer were removed to expose the first adhesive layer. The infrared absorption spectrum peak intensity of the exposed first adhesive layer was measured by infrared spectroscopy (IR). With the infrared absorption spectrum peak intensity at 1680 cm−1 to 1720 cm−1 represented as A1 and the infrared absorption spectrum peak intensity at 1590 cm−1 to 1640 cm−1 represented as B1, a urea abundance ratio (X1) was calculated by the following formula (2-A). Table 6 shows the results.
Urea abundance ratio(X1)={B1/(A1+B1)}×100 (2-A)
<Second Adhesive Layer>
The barrier layer and the sealant layer bonded to the second adhesive layer were removed to expose the second adhesive layer. A urea abundance ratio in the exposed second adhesive layer was calculated in the same manner as for the first adhesive layer. Table 6 shows the results.
[Evaluation of Heat Resistant Lamination Strength on Sealant Layer-Side]
<Measurement Method>
The packaging material was cut to a width of 15 mm, and the lamination strength between the barrier layer and the sealant layer of the packaging material was measured under any one of the conditions 1 to 3. The 90° peeling was performed at a peeling rate of 50 mm/min.
Condition 1: After the packaging material was heated at 80° C. for 5 minutes, the lamination strength was measured while heating at 80° C.
Condition 2: After the packaging material was heated at 150° C. for 5 minutes, the lamination strength was measured while heating at 150° C.
Condition 3: After the packaging material was exposed to hydrogen sulfide having a concentration of 20 ppm for 1 week while being heated at 100° C., the lamination strength was measured in the same manner as in Condition 2.
<Evaluation Criteria>
The lamination strength was evaluated according to the following criteria, and C or higher was judged as a pass. Table 8 shows the results.
A: Lamination strength is 2.5 N/15 mm or more.
B: Lamination strength is 2.0 N/15 mm or more and less than 2.5 N/15 mm.
C: Lamination strength is 1.5 N/15 mm or more and less than 2.0 N/15 mm.
D: Lamination strength is less than 1.5 N/15 mm.
[Deep Drawing Formability]
<Measurement Method>
The drawing depth at which deep drawing was possible for the packaging material obtained in each example was evaluated by the following method. The presence or absence of breakage and pinholes in the sample that has been deep drawn with the drawing depth of the drawing device being set to 1.00 mm to 5.00 mm in steps of 0.25 mm was visually checked by irradiating the packaging material with light to obtain a maximum drawing depth with which the packaging material was successfully deep drawn causing neither breakage nor pinholes. The drawing depth was evaluated according to the following criteria. Table 8 shows the results.
<Evaluation Criteria>
A: The maximum drawing depth is 4.00 mm or more.
B: The maximum drawing depth is 3.50 mm or more and less than 4.00 mm.
C: The maximum drawing depth is 3.00 mm or more and less than 3.50 mm.
D: The maximum drawing depth is less than 3.00 mm.
[Heat Resistance after Deep Drawing]
The packaging materials (5 samples for each example) having the drawing depth of 2.00 mm obtained in the above evaluation of the [Deep Drawing Formability] were stored for 1 week while being heated at 80° C. or 150° C. Then, a portion of the sample near the convexity formed by deep drawing was irradiated with light to visually check whether delamination has occurred between the substrate layer and the barrier layer. This test was evaluated according to the following criteria. Table 8 shows the results.
<Evaluation Criteria>
A: Delamination occurred in 0 or 1 of the 5 samples.
B: Delamination occurred in 2 to 4 of the 5 samples.
D: Delamination occurred in all the 5 samples.
[Pot Life]
The pot life was evaluated from the gel fraction of the adhesive coating liquid at predetermined time intervals. The gel fraction was measured by the following method. The gel fraction was evaluated according to the following criteria. Table 8 shows the results.
<Measurement of Gel Fraction>
Step A) A part of the adhesive coating liquid was collected after 4 hours elapsed from the preparation of the coating liquid, and the solvent of the coating liquid was dried.
Step B) The weight (referred to as w1) of a mesh on which the sample was to be placed was measured, and the total weight (referred to as w2) of the mesh with the dried coating film of Step A placed thereon was measured.
Step C) The dried coating film of Step A was immersed in xylene, and stored at room temperature for 1 week.
Step D) The xylene solution of Step C was filtered through the mesh used in Step B, and the residue was washed with a large amount of xylene.
Step E) The residue of Step D was dried and weighed (referred to as w3).
Step F) From the weight data obtained above, the gel fraction was calculated by the following formula.
Gel fraction=(w3−w1)/(w2−w1)
<Evaluation Criteria>
A: Gel fraction is less than 40%
B: Gel fraction is 40% or more and less than 50%
C: Gel fraction is 50% or more and less than 60%
D: Gel fraction is 60% or more
[Curling Resistance]
The packaging material having the drawing depth of 2.00 mm obtained in the above evaluation of the [Deep Drawing Formability] was placed on a flat surface. The packaging material was placed with the recessed side of the packaging material being in contact with the flat surface. For each packaging material placed on the flat surface, the curl heights from the flat surface at four corners of the packaging material were measured, and a total value was calculated. The total value was evaluated according to the following evaluation criteria. Table 8 shows the results.
<Evaluation Criteria>
A: The total value of curl heights of four corners is less than 40 mm.
B: The total value of curl heights of four corners is 40 mm or more and less than 100 mm.
D: The total value of curl heights of four corners is 100 mm or more.
[Heat Resistant Seal Strength]
The packaging material was cut to a size of 120 mm×60 mm, folded in half with the sealant layer inside, and an end opposite to the fold is heat-sealed to a width of 10 mm at 190° C./0.5 MPa/3 seconds, and stored at room temperature for 6 hours. Then, a size of 15 mm width×300 mm length was cut out from a longitudinal center part of the heat-sealed portion to prepare a sample for measuring heat seal strength. The sample was left in a test environment of 150° C. for 5 minutes, and the heat-sealed portion in the sample was subjected to a T-peel test using a tensile tester (manufactured by Shimadzu Corporation) under the condition of a tension rate of 50 mm/min. The heat seal strength was evaluated according to the following evaluation criteria. Table 8 shows the results.
<Evaluation Criteria>
A: Heat seal strength is 15 N/15 mm or more
B: Heat seal strength is 10 N/15 mm or more and less than 15 N/15 mm
C: Heat seal strength is 5 N/15 mm or more and less than 10 N/15 mm
D: Heat seal strength is less than 5 N/15 mm
As seen from the measurement results of the heat resistant lamination strength on the sealant layer-side when heated at 80° C. and 150° C., the examples in which the urea abundance ratio (X1) is 10 to 99 (Examples D-1 to D-12) are excellent in heat resistance compared with the examples in which the urea abundance ratio (X1) is less than 10 or greater than 99 (Comparative Examples D-1 to D-3). Further, as seen from the evaluation of the heat resistance after the deep drawing, the examples in which the urea abundance ratio (X1) is 10 to 99 (Examples D-1 to D-12) are excellent in heat resistance compared with the examples in which the urea abundance ratio (X1) is less than 10 or greater than 99 (Comparative Examples D-1 to D-3).
<<Fifth Examination>>
[Materials Used]
Materials used in examples and comparative examples are described below.
<Substrate Layer (25 μm Thickness)>
A polyethylene terephthalate film having one surface subjected to a corona treatment was used.
<First Adhesive Layer (4 μm Thickness) and Second Adhesive Layer (3 μm Thickness)>
Adhesives in which the base resin, the hardener, the catalyst and the hydrogen sulfide adsorbent shown in Table 1 were formulated in the proportions shown in Table 10 were used. The details of the base resin and the hardener shown in Tables 9 and 10 are as follows. Further, as the catalyst and the hydrogen sulfide adsorbent, the compound described below was used.
{Base Resin}
{Hardener}
{Catalyst}
{Hydrogen Sulfide Adsorbent}
<Anticorrosion Treatment Layer>
A sodium polyphosphate stabilized cerium oxide sol was used after being adjusted to a solid concentration of 10 mass % by using distilled water as a solvent. The sodium polyphosphate stabilized cerium oxide sol was obtained by formulating 10 parts by mass of Na salt of phosphoric acid per 100 parts by mass of cerium oxide.
<Metal Foil Layer (35 μm Thickness)>
An annealed and degreased soft aluminum foil (8079 Material manufactured by Toyo Aluminum K.K.) was used.
<Sealant Layer (40 μm Thickness)>
A film shown in Table 9 was used as the sealant layer.
The metal foil layer was dry laminated to the substrate layer using an adhesive (first adhesive layer). Then, a surface of the metal foil layer on a side opposite to that to which the first adhesive layer was adhered was dry laminated to the sealant layer using an adhesive (second adhesive layer).
The laminate thus obtained was heat-treated under the conditions shown in Table 10 to produce a packaging material (substrate layer/first adhesive layer/metal foil layer/second adhesive layer/sealant layer).
First, the sodium polyphosphate-stabilized cerium oxide sol was applied to both sides of the metal foil layer by gravure coating. Then, the applied sodium polyphosphate-stabilized cerium oxide sol was dried, followed by baking, to form an anticorrosion treatment layer on both sides of the metal foil layer. The baking conditions were the temperature of 150° C. and the treatment time of 30 seconds.
Then, one of the surfaces of the metal foil layer on which the anticorrosion treatment layer was formed was dry laminated to the substrate layer using the adhesive (first adhesive layer). The other of the surfaces of the metal foil layer on which the anticorrosion treatment layer was formed was dry laminated to the sealant layer using the adhesive (second adhesive layer).
The laminate thus obtained was heat-treated under the conditions shown in Table 10 to produce a packaging material (substrate layer/first adhesive layer/anticorrosion treatment layer/metal foil layer/anticorrosion treatment layer/second adhesive layer/sealant layer).
[Measurement of Urethane Abundance Ratio]
<First Adhesive Layer>
The metal foil layer and the substrate layer bonded to the first adhesive layer were removed to expose the first adhesive layer. The infrared absorption spectrum peak intensity of the exposed first adhesive layer was measured by infrared spectroscopy (IR). With the infrared absorption spectrum peak intensity at 2250 cm−1 to 2290 cm−1 represented as A2 and the infrared absorption spectrum peak intensity at 1680 cm−1 to 1720 cm−1 represented as B2, a urethane abundance ratio (X2) was calculated by the following formula (2-B). Table 9 shows the results.
Urethane abundance ratio(X2)={B2/(A2+B2)}×100 (2-B)
<Second Adhesive Layer>
The metal foil layer and the sealant layer bonded to the second adhesive layer were removed to expose the second adhesive layer. A urethane abundance ratio in the exposed second adhesive layer was calculated in the same manner as for the first adhesive layer. Table 9 shows the results.
[Measurement of Glass Transition Temperature Tg]
<First Adhesive Layer and Second Adhesive Layer>
The glass transition temperatures Tg of the first adhesive layer and the second adhesive layer were determined by differential scanning calorimetry (DSC) measurement under the conditions of a measurement temperature of 20 to 300° C. and a heating rate of 10° C./min. Table 9 shows the results.
[Evaluation of Heat Resistant Lamination Strength on Sealant Layer-Side]
<Measurement Method>
The packaging material was cut to a width of 15 mm, and the lamination strength between the metal foil layer and the sealant layer of the packaging material was measured under any one of the conditions 1 to 3. The 90° peeling was performed at a peeling rate of 50 mm/min.
Condition 1: After the packaging material was heated at 80° C. for 5 minutes, the lamination strength was measured while heating at 80° C.
Condition 2: After the packaging material was heated at 150° C. for 5 minutes, the lamination strength was measured while heating at 150° C.
Condition 3: After the packaging material was exposed to hydrogen sulfide having a concentration of 20 ppm for 1 week while being heated at 100° C., the lamination strength was measured in the same manner as in Condition 2.
<Evaluation Criteria>
The lamination strength was evaluated according to the following evaluation criteria. Table 11 shows the results.
A: Lamination strength is 2.5 N/15 mm or more.
B: Lamination strength is 2.0 N/15 mm or more and less than 2.5 N/15 mm.
C: Lamination strength is 1.5 N/15 mm or more and less than 2.0 N/15 mm.
D: Lamination strength is less than 1.5 N/15 mm.
[Deep Drawing Formability]
<Measurement Method>
The drawing depth at which deep drawing was possible for the packaging material obtained in each example was evaluated by the following method. The presence or absence of breakage and pinholes in the sample that has been deep drawn with the drawing depth of the drawing device being set to 1.00 mm to 5.00 mm in steps of 0.25 mm was visually checked by irradiating the packaging material with light to obtain a maximum drawing depth with which the packaging material was successfully deep drawn causing neither breakage nor pinholes. The drawing depth was evaluated according to the following criteria, and C or higher was judged as a pass. Table 11 shows the results.
<Evaluation Criteria>
A: The maximum drawing depth is 4.00 mm or more.
B: The maximum drawing depth is 3.50 mm or more and less than 4.00 mm.
C: The maximum drawing depth is 3.00 mm or more and less than 3.50 mm.
D: The maximum drawing depth is less than 3.00 mm.
[Heat Resistance After Deep Drawing]
The packaging materials (5 samples for each example) having the drawing depth of 2.00 mm obtained in the above evaluation of the [Deep Drawing Formability] were stored for 1 week while being heated at 80° C. or 150° C. Then, a portion of the sample near the convexity formed by deep drawing was irradiated with light to visually check whether delamination occurred between the substrate layer and the metal foil layer. This test was evaluated according to the following criteria. Table 11 shows the results.
<Evaluation Criteria>
A: Delamination occurred in 0 or 1 of the 5 samples.
C: Delamination occurred in 2 to 4 of the 5 samples.
D: Delamination occurred in all the 5 samples.
[Heat Resistant Seal Strength]
The packaging material was cut to a size of 120 mm×60 mm, folded in half with the sealant layer inside, and an end opposite to the fold is heat-sealed to a width of 10 mm at 190° C./0.5 MPa/3 seconds, and stored at room temperature for 6 hours. Then, a size of 15 mm width×300 mm length was cut out from a longitudinal center part of the heat-sealed portion to prepare a sample for measuring heat seal strength. The sample was left in a test environment of 150° C. for 5 minutes, and the heat-sealed portion in the sample was subjected to a T-peel test using a tensile tester (manufactured by Shimadzu Corporation) under the condition of a tension rate of 50 mm/min. The heat seal strength was evaluated according to the following evaluation criteria. Table 11 shows the results.
<Evaluation Criteria>
A: Heat seal strength is 15 N/15 mm or more
B: Heat seal strength is 10 N/15 mm or more and less than 15 N/15 mm
C: Heat seal strength is 5 N/15 mm or more and less than 10 N/15 mm
D: Heat seal strength is less than 5 N/15 mm
According to the present disclosure, a power storage device packaging material capable of exhibiting excellent lamination strength in both room temperature environment and high temperature environment and having excellent deep drawing formability, and a power storage device using the power storage device packaging material are provided.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2019-239358 | Dec 2019 | JP | national |
| 2019-239385 | Dec 2019 | JP | national |
| 2020-068509 | Apr 2020 | JP | national |
| 2020-071561 | Apr 2020 | JP | national |
| 2020-119066 | Jul 2020 | JP | national |
This application is a continuation application filed under 35 U.S.C. § 111(a) claiming the benefit under 35 U.S.C. §§ 120 and 365(c) of International Patent Application No. PCT/JP2020/047213, filed on Dec. 17, 2020, which in turn claims the benefit of JP 2019-239358, filed Dec. 27, 2019; of JP 2019-239385, filed Dec. 27, 2019; of JP 2020-068509, filed Apr. 6, 2020; of JP 2020-071561, filed Apr. 13, 2020; of JP 2020-119066, filed Jul. 10, 2020; the disclosures of all which are incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/JP2020/047213 | Dec 2020 | US |
| Child | 17845176 | US |
