Patent Application
20250066962
The present invention relates to a method for manufacturing a thermally adhesive fiber web and a thermally adhesive fiber web produced thereby.
In general, electrospinning is a method of manufacturing nanofibers by using an electric field formed by applying an electric field to a polymer solution. Specifically, as the surface tension of the polymer solution is overcome by the electric field applied to the spinning nozzle, the discharged polymer solution forms a jet, and as this jet flies to a collector by a whipping mechanism, the solvent evaporates and the polymer solidifies to form a fibrous structure.
Electrospun nanofibers manufactured through the above method are fused and composited with woven or nonwoven fabrics, knitted fabrics, paper, etc., and are applied to filters, moisture-permeable and waterproof materials, separators for various batteries, bio-medical materials, vents for electronic devices, etc.
In this case, the process of fusion and composite formation of nanofibers with heterogeneous materials such as woven or nonwoven fabrics and/or different structural specifications is carried out through a processing process such as fusion through heat or ultrasound or a calendar using an adhesive or binder or the like. However, there are problems in that the use of a separate binder or hot melt material results in blocking the pores of the web formed of nanofibers, which causes reduced air permeability, etc., and the excellent physical properties of the web formed of nanofibers cannot be fully expressed. In addition, the use of separate adhesives or hot melt materials entails additional materials and processes, which ultimately has a negative impact on carbon emissions and energy.
To solve these problems, research has been conducted so that two polymer compounds with different melting points are blended and electrospun to allow the nanofibers produced through electrospinning to self-fuse without a separate adhesive or hot melt material. However, most polymer compounds for electrospinning have poor compatibility between heterogeneous types, making it difficult to obtain uniformly blended nanofibers due to phase separation.
In addition, to solve this problem, attempts have been made to fuse and composite with nanofibers by configuring woven or nonwoven fabrics that are fused and composited to be made of sheath-core type low-melting point composite fibers or to contain some low-melting point composite fibers, but since it is difficult to achieve interfacial bonding between nanofibers and conventional low-melting-point composite fibers, there is a problem that nanofibers are partially detached from the composite, or only woven or nonwoven fabrics containing low-melting-point composite fibers can be used for the composite, so there are limitations in the selection of woven or nonwoven fabrics.
The present invention has been devised in view of the above problems, and is directed to providing a method for manufacturing a thermally adhesive fiber web capable of easily performing interfacial bonding through heat fusion of heterogeneous materials having different material and structural specifications since the fiber web itself has thermally-adhesive properties without a separate adhesive or hot melt material, and a thermally adhesive fiber web manufactured thereby.
In addition, the present invention is also directed to providing a thermally adhesive fiber web in which the initial physical properties, such as air permeability and water pressure resistance, of the thermally adhesive fiber web are fully maintained and expressed even after the interfacial thermal bonding, by preventing the closure of pores initially present during the interfacial thermal bonding with heterogeneous materials and thereby exhibiting excellent thermal bonding performance.
In order to solve the above-mentioned problems, the present invention provides a method for manufacturing a thermally adhesive fiber web, including (1) preparing respectively a first spinning solution in which a support component, which is a first polymer compound, is dissolved, and a second spinning solution in which a thermally adhesive component, which is a second polymer compound, is dissolved, the second polymer compound having a melting point at least 50° C. lower than that of the first polymer; (2) after transferring the first spinning solution and the second spinning solution to the end of a discharge port of one spinning nozzle of an electrospinning device through different flow passages to avoid blending of the spinning solutions, performing electrospinning such that the first spinning solution is discharged to a portion of the end surface of the discharge port and the second spinning solution is discharged to the remaining portion, thereby accumulating side-by-side type thermally adhesive composite fibers having a diameter of less than 1 μm; and (3) applying heat to the accumulated side-by-side type thermally adhesive composite fibers to prepare a thermally adhesive fiber web.
According to one embodiment of the present invention, the first spinning solution and the second spinning solution may contain the same type of solvent.
In addition, the first polymer compound may include one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polybenzyl imidazole (PBI), and high-melting point polyethersulfone (PES), and the second polymer compound may include one or more of low-melting point polyethersulfone and polyvinyl butyral.
In addition, the solvent may be at least one solvent of dimethylformamide and dimethylacetamide, or a solvent in which at least one of dimethylformamide and dimethylacetamide is mixed with acetone or alcohol.
In addition, in step (3), heat may be applied at a temperature higher than the glass transition temperature of the second polymer compound and lower than the melting point.
In addition, the present invention provides a thermally adhesive fiber web, formed by accumulating side-by-side type thermally adhesive composite fibers with a diameter of less than 1 μm wherein a support portion formed of a first polymer compound and a thermally adhesive portion formed of a second polymer compound having a melting point of at least 50° C. lower than that of the first polymer compound are placed adjacent to each other in a cross-section thereof, and having a three-dimensional network structure welded between surfaces of thermally adhesive composite fibers in contact.
According to one embodiment of the present invention, the area of the thermally adhesive portion within a cross-section of the thermally adhesive composite fiber may be 50% or less of the area of the cross-section.
In addition, the area of the thermally adhesive portion may be 10 to 30% of the area of the cross-section.
In addition, the first polymer compound may include polyvinylidene fluoride and the second polymer compound may include polyvinyl butyral.
In addition, the present invention provides a side-by-side type thermally adhesive composite fiber having a diameter of less than 1 μm wherein a support portion formed of a first polymer compound and a thermally adhesive portion formed of a second polymer compound having a melting point of at least 50° C. lower than that of the first polymer compound are placed adjacent to each other in a cross-section thereof.
In addition, provided is a waterproof and dustproof sound-transmitting sheet having a thermally adhesive fiber web according to the present invention.
The method for manufacturing a thermally adhesive fiber web according to the present invention can implement a side-by-side type thermally adhesive fiber in which separation does not occur at the interface formed by two types of spun polymer compounds that are adjacent, and through this, it is suitable to implement a thermally adhesive fiber web capable of easily performing interfacial bonding through heat fusion of heterogeneous materials having different material and structural specifications since the fiber web itself has thermally-adhesive properties without a separate adhesive or hot melt material. In addition, the thermally adhesive fiber web manufactured by the present invention can be widely used as a thermally adhesive member or can be widely used itself in various applications such as a membrane for water treatment or a membrane for electronic devices since the initial physical properties, such as air permeability and water pressure resistance, of the thermally adhesive fiber web are fully maintained and expressed even after the interfacial thermal bonding, by preventing the closure of pores initially present during the interfacial thermal bonding with heterogeneous materials and thereby exhibiting excellent thermal bonding performance.
Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily perform the present invention. The present invention may be implemented in many different forms and is not limited to the embodiments described herein. In the drawings, in order to clarify the present invention, parts that are not related to description are omitted and like reference numerals represent like or similar elements throughout the specification.
The thermally adhesive fiber web according to an exemplary embodiment of the present invention may be produced by including the steps of: (1) preparing respectively a first spinning solution in which a support component, which is a first polymer compound, is dissolved, and a second spinning solution in which a thermally adhesive component, which is a second polymer compound, is dissolved, the second polymer compound having a melting point at least 50° C. lower than that of the first polymer compound; (2) after transferring the first spinning solution and the second spinning solution to the end of a discharge port of one spinning nozzle of an electrospinning device through different flow passages to avoid blending of the spinning solutions, performing electrospinning such that the first spinning solution is discharged to a portion of the end surface of the discharge port and the second spinning solution is discharged to the remaining portion, thereby accumulating side-by-side type thermally adhesive composite fibers having a diameter of less than 1 μm; and (3) applying heat to the accumulated side-by-side type thermally adhesive composite fibers to prepare a thermally adhesive fiber web.
As step (1) according to the present invention, performed is a step of preparing respectively a first spinning solution in which a support component, which is a first polymer compound, is dissolved, and a second spinning solution in which a thermally adhesive component, which is a second polymer compound, is dissolved, the second polymer compound having a melting point at least 50° C. lower than that of the first polymer compound.
The support component is a component that performs a support function in the spun side-by-side type thermally adhesive composite fibers and the thermally adhesive fiber web implemented by them. In addition, the thermally adhesive component is a component that exhibits thermal adhesive properties at the interface between side-by-side type thermally adhesive composite fibers, or between these composite fibers and heterogeneous materials.
Among the known polymer compounds known to be electrospun, a combination of polymer compounds having a melting point difference of 50° C. or more may be used without limitation as the support component and the thermally adhesive component. In addition, homogeneous polymer compounds having a melting point difference of 50° C. or higher may be used as the support component and the thermally adhesive component, respectively. If the difference in melting points is less than 50° C., it may be difficult to achieve the purpose of the present invention, as the thermal adhesiveness at the interface may be weakened. In addition, the difference in melting points may preferably be 100° C. or less. In addition, as an example, the support component may be a first polymer compound including one or more selected from the group consisting of high-melting point (or high-polymer) polyurethane, polyacrylonitrile (PAN), polyetherimide (PEI), polymethyl methacrylate, polyvinyl chloride (PVC), polycarbonate (PC), polyethylene terephthalate, polyamide, polyvinylidene fluoride (PVDF), polybenzyl imidazole (PBI), and high-melting point polyethersulfone (PES).
In addition, the thermally adhesive component may be a second polymer compound including one or more of low-melting point (low-polymer) polyurethane, polystyrene (PS), polyvinyl alcohol (PVA), polymethyl methacrylate (PMMA), polylactic acid (PLA), polyethylene oxide (PEO), polyvinylacetate (PVAc), polyacrylic acid (PAA), polycaprolactone (PCL), polyvinyl fluoride (PVDF), polyvinylpyrrolidone (PVP), polyacrylonitrile (PAN), polycarbonate (PC), low-melting point polyethersulfone, and polyvinyl butyral.
Preferably, a side-by-side type composite fiber may be implemented by combining the first polymer compound including one or more selected from the group consisting of polyvinylidene fluoride (PVDF), polybenzyl imidazole (PBI), and high-melting point polyethersulfone (PES), and the second polymer compound including one or more of low-melting point polyethersulfone and polyvinyl butyral, and more preferably, the first polymer compound may include polyvinylidene fluoride, and the second polymer compound may include polyvinyl butyral, which may be advantageous in achieving the purpose of the present invention.
The first polymer compound and the second polymer compound described above are each dissolved in a solvent to form a first spinning solution and a second spinning solution. If homogeneous or heterogeneous polymer compounds with different melting points are mixed and spun with a single spinning solution, the ratio of the low-melting point polymer compound exposed to the surface of the spun fiber is not uniform even if the ratio of the low-melting point polymer compound is increased, and furthermore, the exposure ratio may be low, and thus, it is recommended that they be manufactured with different spinning solutions and that the two spinning solutions not be mixed until just before spinning.
The first spinning solution and the second spinning solution may each include a solvent capable of dissolving the first polymer compound and the second polymer compound, respectively. As the above solvent, any known solvent suitable for dissolving a selected polymer compound and used in the production of a spinning solution for electrospinning can be used without limitation. For example, the solvent contained in the first spinning solution and the solvent contained in the second spinning solution may each independently use at least one solvent of dimethylformamide and dimethylacetamide, or a solvent in which at least one of dimethylformamide and dimethylacetamide is mixed with acetone or alcohol.
However, preferably, the solvents used in each of the first spinning solution and the second spinning solution may be the same kind of solvent, and further, may be substantially the same solvent. If the same kind of or substantially the same solvent is not used, a single spinning nozzle may become clogged or spinnability may decrease due to solidification caused when the two spinning solutions meet at the tip of the single spinning nozzle, and even when a side-by-side type composite fiber is realized, the area ratio between the region formed with the first polymer compound and the region formed with the second polymer compound may be different from the initially designed area ratio, resulting in insufficient thermal bonding performance or closure of pores after thermal bonding.
In addition, it is preferable that the first spinning solution and the second spinning solution contain 10 to 30 wt % of the first polymer compound and the second polymer compound, respectively, and preferably 10 to 20 wt %, and if it is contained at less than 10 wt %, it may not be spun in the form of fibers during spinning but may be sprayed in the form of droplets, and even if spinning occurs, many beads are formed and the solvent does not volatilize well, which may cause pores to become clogged during the calendering process described later. In addition, if the fiber-forming component exceeds 30 wt %, the viscosity may increase and solidification may occur on the surface of the solution, making long-term spinning difficult, and the fiber diameter may increase, making it difficult to manufacture composite fibers having a diameter size of less than or equal to micrometers.
Next, as step (2) according to the present invention, performed is (2) a step of after transferring the first spinning solution and the second spinning solution to the end of a discharge port of one spinning nozzle of an electrospinning device through different flow passages to avoid blending of the spinning solutions, performing electrospinning such that the first spinning solution is discharged to a portion of the end surface of the discharge port and the second spinning solution is discharged to the remaining portion, thereby accumulating side-by-side type thermally adhesive composite fibers having a diameter of less than 1 μm.
Describing referring to
In addition, the electrospun side-by-side type thermally adhesive composite fibers may have a diameter of less than 1 μm, preferably 100 to 700 nm, through which the thermally adhesive fiber web implemented exhibits excellent water pressure resistance, while increasing the interface in contact with the heterogeneous materials to be fused and composited, which may be advantageous in terms of thermal bonding performance.
Meanwhile, composite fibers having a sheath-core type cross-section can also be implemented through a single spinning nozzle divided into different portions at the end of the discharge port, that is, the core portion and the sheath portion surrounding it, but a spinning nozzle for manufacturing a sheath-core type composite fiber is more complex than a spinning nozzle for manufacturing a side-by-side type composite fiber, and even when the region to be discharged during spinning is designed differently, the low-melting point polymer compound may not be exposed to the outside, and the area of the interface between heterogeneous polymer compounds is larger than that of a side-by-side type composite fiber, so there is a concern that a separation phenomenon may occur between regions formed by heterogeneous polymer compounds. In addition, the fiber web in which spun sheath-core type thermally adhesive composite fibers are accumulated frequently has the problem of pore clogging during heat pressing.
On the other hand, in the case of a thermally adhesive fiber web, in which support fibers and thermally adhesive fibers are mixed, manufactured by spinning the first spinning solution and the second spinning solution through different spinning nozzles, it may not be mixed uniformly between the support fibers and the thermally adhesive fibers, and the ratio of thermally adhesive fibers exposed to the outside of the thermally adhesive fiber web may not be uniform, so there is a concern that at the interface with the heterogeneous materials that are fused and composited, there is insufficient thermal adhesion or partially insufficient region, and thus, this type of thermally adhesive fiber web may also be undesirable compared to the thermally adhesive fiber web formed by accumulating side-by-side type thermally adhesive composite fibers.
The above step (2) can utilize a conventionally known electrospinning device, and the conditions for electrospinning can also be performed within a known condition range considering the type of polymer compound selected, so the present invention is not particularly limited thereto. For example, the discharge amount of each spinning solution may be independently 0.01 to 5 cc/g per minute for each spinning nozzle, the applied voltage may be 0.5 to 100 kV, the air gap, which is the distance from the nozzle to the collector, may be 5 to 50 cm, the spinning atmosphere may have a relative humidity of 20 to 80% and a temperature of 20 to 40° C.
Next, as step (3) according to the present invention, a step of applying heat to the accumulated side-by-side type thermally adhesive composite fibers to prepare a thermally adhesive fiber web is performed.
Step (3) is performed so that the thermally adhesive fiber web has a three-dimensional network structure and possesses the desired porosity, pore size, basis weight, etc., and heat, or heat and pressure, may be applied to the accumulated side-by-side type thermally adhesive composite fibers to implement the thermally adhesive fiber web. The heat or heat and pressure may be applied by a known device, for example, calendering, and the heat applied at this time may be applied at a temperature higher than the glass transition temperature of the second polymer compound and lower than the melting point, and the specific temperature varies depending on the type of the second polymer compound selected, and therefore the present invention is not particularly limited thereto. For example, when the first polymer compound is polyvinylidene fluoride and the second polymer compound is polyvinyl butyral, the applied temperature may be 70 to 130° C.
In addition, when the calendering process is performed, it may be performed once or multiple times, and for example, after performing a drying process to remove solvent remaining in the fiber through the first calendering, a second calendering may be performed to control pores and improve strength. In this case, the degree of heat and/or pressure applied in each calendering process may be the same or different.
As shown in
The thermally adhesive fiber web can be welded (A) at the interface formed with the fiber 200 in the heterogeneous material to which the thermally adhesive composite fiber 100 is fused and composited, as shown in
Preferably, the area of the thermally adhesive portion 20 in the cross-section of the thermally adhesive composite fiber 100, 101 may be 50% or less of the cross-section area, and if the area of the thermally adhesive portion 20 exceeds 50%, the pores may become clogged during the manufacturing process of the thermally adhesive fiber web or during the thermal bonding process with heterogeneous material to be fused and composited, and in this case, there is a concern that the physical properties such as air permeability and water pressure resistance may deteriorate and a uniform pore structure distribution may not be achieved. More preferably, the area of the thermally adhesive portion 20 may be 10 to 30% of the cross-sectional area, through which the adhesive performance may be significantly improved through linear contact with the heterogeneous materials to be fused and composited. However, if the thermally adhesive portion 20 is contained at less than 10%, there is a concern that the thermal bonding performance may be significantly reduced, which is not desirable.
Meanwhile, the area of the thermally adhesive portion in the cross-section of the thermally adhesive composite fiber may be implemented by controlling the concentration and supply speed of the polymer compound in the first spinning solution and the second spinning solution.
The above-described thermally adhesive fiber web may have a thickness of 10 to 100 μm, but is not limited thereto.
In addition, the thermally adhesive fiber web may be used to manufacture a sound-transmitting and waterproof sheet. The sound-transmitting and waterproof sheet may include layers provided in known sound-transmitting and waterproof sheets, such as a water-repellent layer, a waterproof layer, an acoustic layer, and a protective layer, and the thermally adhesive fiber web according to an exemplary embodiment of the present invention may be used as a waterproof and dustproof layer and/or an acoustic layer. Meanwhile, as specific examples of sound-transmitting and waterproof sheets, patent application numbers 10-2019-0151233 and 10-2021-0021153 by the same applicant of the present invention are incorporated by reference into the present invention.
The present invention will be described in more detail through the following examples, but the following examples are not intended to limit the scope of the present invention, which should be construed to aid understanding of the present invention.
Polyvinylidene fluoride (PVDF) as a first polymer compound, which is a support component, was dissolved in a mixed solvent of DMAc (dimethylacetamide)/Acetone (mixing ratio of 80:20 in weight %) to prepare a first spinning solution for the PVDF to be 15 wt % based on the total weight of the spinning solution. In addition, polyvinyl butyral (PVB), which has a melting point about 100° C. lower than that of the first polymer compound as a second polymer compound, which is a thermally adhesive component, was dissolved in a mixed solvent of DMAc (dimethylacetamide)/Acetone (mixing ratio of 80:20 in weight %) to prepare a second spinning solution for the PVB to be 15 wt % based on the total weight of the spinning solution.
The prepared first spinning solution and second spinning solution were transferred to a spinning nozzle pack, and electrospinning was performed in a spinning atmosphere of a discharge amount of 0.05 cc/ghole per minute, an applied voltage of 20 kV, a distance of 20 cm between a spinning nozzle tip and a collector, a temperature of 30° C., and a relative humidity of 60%, respectively, through the first flow passage 31 and the second flow passage 32 in the one spinning nozzle 30 of
Through
A thermally adhesive fiber web shown in
As shown in
A thermally adhesive fiber web was prepared with side-by-side type thermally adhesive composite fibers having an area of a thermally adhesive portion as shown in Table 1 below in the same manner as in Example 1, but by adjusting the supply speed of the first spinning solution and the second spinning solution.
The following physical properties were evaluated for the thermally adhesive fiber webs according to Examples 1 to 5, and are shown in Table 1 below.
The mechanical strength was measured by a tensile tester according to ASTM D882-95a for the thermally adhesive fiber webs according to Examples 1 to 5, and the specimen area was evaluated with a width of 0.5 cm, a gauge length of 6.0 cm, and a cross-head speed of 10 mm/min. In addition, the evaluation results were expressed as a relative percentage based on the measurement value of Example 1 as 100.
In order to confirm the rate of change in pores due to thermal fusion, the air permeability (initial air permeability) was measured using an air permeability measuring device (MODEL FX-3300, TEXTEST), and then, heat and pressure of 120° C. were applied twice to each specimen for each example, and the air permeability (final air permeability) was measured again under the same pressure conditions, and then the rate of change in air permeability was calculated using the following equation. The greater the rate of change in air permeability, the greater the pore change due to thermal compression can be evaluated.
Rate of change in air permeability (%)=[(initial air permeability (ccs)−final air permeability (ccs))/initial air permeability (ccs)]×100 [Equation]
As can be seen in Table 1, even in the case of a thermally adhesive fiber web formed with side-by-side type composite fibers, it can be confirmed that there is a difference in the mechanical strength and rate of change in air permeability depending on the area of the thermally adhesive portion within the composite fibers, and it can be seen that the fiber webs according to Examples 1, 4, and 5 can simultaneously achieve mechanical strength and rate of change in air permeability compared to Examples 2 and 3.
Although exemplary embodiments of the present invention have been described above, the idea of the present invention is not limited to the embodiments set forth herein. Those of ordinary skill in the art who understand the idea of the present invention may easily propose other embodiments through supplement, change, removal, addition, etc. of elements within the scope of the same idea, but the embodiments will be also within the idea scope of the present invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2021-0186131 | Dec 2021 | KR | national |
This application is a 35 U.S.C. § 371 National Stage of International Patent Application No. PCT/KR2022/021061, filed Dec. 22, 2022, claiming benefit from Korean Patent Application No. 10-2021-0186131, filed Dec. 23, 2021, the disclosures of which are incorporated herein in their entirety by reference, and priority is claimed to each of the foregoing.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2022/021061 | 12/22/2022 | WO |
