Patent Application
20050250887
This application claims the priority benefit of Taiwan application serial no. 93112611, filed May 5, 2004.
1. Field of the Invention
The present invention relates to a type of adhesive. More particularly, the present invention relates to an emulsion type, acrylic, pressure sensitive adhesive with the properties of water-whitening resistance and aging resistance.
2. Description of the Related Art
As the society becomes more aware of the significance of environmental protection, industrial products, even the commonly used product, such as adhesive that is harmful to the ecological environment are gradually being replaced and eliminated. The solvent-type of adhesive is steadily going off the market. Among the emulsion type of adhesives the acrylic pressure sensitive adhesive is broadly used, especially in the application of label product. However, when this type of transparent label, which is formed with the emulsion type acrylic pressure sensitive adhesive (simply known as emulsion adhesive) is attached to a bottle, it is desirable that the adhesive can remain transparent even in a high moisture environment for a long period of time.
However, it is difficult to achieve the above-mentioned characteristic. Since, many water sensitive materials are added during the polymerization of emulsion adhesive, for example emulsifier for stabilizing emulsion, polar monomers for enhancing the peel adhesion and mechanical stability (for example, monomers that contain carboxylic acid groups, such as acrylic acid, methyacrylic acid, itaconic acid) and a small amount of electrolytes, such as an initiator. This type of emulsion adhesive forms a transparent film when drying, and an interface still presents between the emulsion particles. The interface provides a channel for water molecules to diffuse into the film. As water diffuses into the film, the refraction index at the interface between the emulsion particles becomes greater, leading to the scattering of light and the whitening of the emulsion adhesive, and adversely affecting the visual appearance of the adhesive.
Asides from the above-mentioned shortcomings, when this type of adhesive is coated on a calcium carbonate (CaCO3) substrate of a synthetic paper, a coated paper or a neutral paper, the adhesive properties, such as loop tack, steel peel adhesion, PE peel adhesion, deteriorate drastically. Since the interior of the calcium carbonate substrate contains moisture, the water molecules and calcium carbonate react and break down into Ca+2 and Co3−2, wherein Ca+2 and COOH in the adhesive further form ˜2COO−Ca+2 due to a chelating effect, leading to the deterioration of the adhesive properties.
Accordingly, the present invention provides an emulsion type acrylic pressure sensitive adhesive. Besides having a high peel adhesion, the adhesive of the present invention also has the properties of water-whitening resistance and aging resistance.
In accordance to the present invention, an emulsion type acrylic pressure sensitive adhesive having the water-whitening resistance and aging resistance properties is provided. The composition of this type of pressure sensitive adhesive includes: (a) 15 to 35 part per hundred of dialkyl dicarboxylate monomers; (b) 15 to 35 part per hundred of vinyl esters monomers; (c) 35 to 65 parts per hundred of alkyl acrylate monomers or alkyl methacrylate monomers; (d) 0.1 to 2.0 parts per hundred of a cross-linker based on the total weight of (a)+(b)+(c); (e) 0.2 to 2.0 parts per hundred of hydroxy alkyl acrylate monomers or hydroxy alkyl mathacrylate; (f) 0.1 to 1.0 parts per hundred of a nonionic surfactant; (g) 0.4 to 3.0 parts per hundred of an anionic surfactant; (h) 0.1 to 0.5 parts per hundred of reactive surfactant. The emulsion type acrylic pressure sensitive adhesive is formed after the above components are reacted with an appropriate amount of deionized water, initiator and buffer. The emulsion type acrylic pressure sensitive adhesive of the present invention has an average particle diameter between about 0.1˜0.5 microns, a glass transition temperature (Tg) between about −50˜−20° C. and a solid content of about 30%-70% by weight (wt. %).
One or part or all of these and other features and advantages of the present invention will become readily apparent to those skilled in this art from the following description wherein there is shown and described a preferred embodiment of this invention, simply by way of illustration of one of the modes best suited to carry out the invention. As it will be realized, the invention is capable of different embodiments, and its several details are capable of modifications in various, obvious aspects all without departing from the invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive.
The emulsion type acrylic pressure sensitive adhesive of the present invention can be produced by an emulsion polymerization method. According to an embodiment, the composition of the emulsion type acrylic pressure sensitive adhesive includes of:
The emulsion type acrylic pressure sensitive adhesive of the present invention can be formed by mixing with different types of surfactants to provide a stable emulsion during the polymerization of the emulsion, and for the end product to have a high peel adhesion, a desirable film forming characteristic, water whitening resistance and aging resistance properties. The various types of surfactant include mixtures of nonionic surfactant, anionic surfactant and reactive surfactant, wherein the content of the surfactant is 0.5 to 4.5 parts per hundred, based on the total weight of (a)+(b)+(c).
The monomer composition of the emulsion type acrylic pressure sensitive adhesive begins to react with each other through at least one initiator, a buffer and deionized water. The amount of the initiator is about 0.1 to 2.0 parts per hundred based on the total weight of (a)+(b)+(c). The initiator can be, for example, sodium persulfate, ammonium persulfate or potassium persulfate. The amount of the buffer is 0.1 to 0.5 parts per hundred based on the total weight of (a)+(b)+(c). The buffer can be, for example, sodium bicarbonate or sodium acetate.
With the presence of the above (f), (g) and (h) surfactant mixtures, an appropriate amount of deionized water, initiator and buffer, the above (a), (b), (c), (d) and (e) monomers in the reaction tank begin to react under heating to form emulsion adhesive particles, under reaction temperature of 50° C.-90° C. for about 5-10 hours of reaction time.
In the aforementioned reaction, the dialkyl maleate monomers or dialkyl furmarate monomers (a), the vinly esters monomers (b), the alkyl acrylate monomers or alkyl methacrylate monomers (c), the cross-linker (d), the hydroxy alkyl acrylate monomers or hydroxy alkyl methacrylate monomers (e), the nonionic surfactant (f), the anionic surfactant (g), the reactive surfactant (h) are used. Deionized water, the initiator and the buffer can be added continuously or semi-continuously. The emulsion adhesive of the present invention has an average particle diameter between about 0.1˜0.5 microns, a glass transit temperature (Tg) between about −50˜−20° C. and a solid content of about 30%-70% by weight (wt. %).
Preparation of the emulsion type, acrylic; pressure sensitive adhesive of the present invention is described as follow.
0.25 g of ammonium•polyoxethyene nonyl phenyl ether sulfate (Chun-Zih Synthesis Company, Taiwan) and 2.74 gm of NE-10 (Asahi Denka Co., Ltd, Japan) are evenly mixed in 40 g of de-ionized water to obtain solution A.
70.5 g of de-ionized water, 3.08 g of polyoxethyene nonyl phenyl ether (Chun-Zih Synthesis Company, Taiwan), 18.22 g of ammonium•polyoxethyene nonyl phenyl ether sulfate, 153.9 g of 2-ethyl hexyl methacrylate monomers, 102.6 g of dioctyl maleate monomers, 85.5 g of vinyl acetate monomers, 3.42 g of hydroxy ethyl acrylate and 1.03 g of ethyl acetoxy ethyl methacrylate monomers are evenly mixed to obtain the solution B.
87.5 g of de-ionized water, 1.8 g of sodium bicarbonate and 0.9 g of potassium persulfate are evenly mixed to prepare solution C.
20.5 g of de-ionized water and 0.9 g of potassium persulfate are mixed to prepare solution D.
The solution A and a half quantity (½) of the solution D are poured into the emulsion and polymerization apparatus, which includes a stirrer, a thermometer, a heater, a reflux condenser, a five neck flask and a one-liter round bottom flask. When the solution is heated to about 69 to 70° C., a mixture of 1/10 of the solution B and ½ of the solution D is steadily fed into the emulsion and polymerization apparatus within 20-30 minutes. The mixture is then heated to 79 to 81° C., and the remaining of solution B ( 9/10 of the weight) and the solution C are slowly fed into the emulsion and polymerization apparatus within 240 minutes. Thereafter, the reaction temperature is increased to 85 to 87° C. and is maintained for 90 minutes, and is then cooled to the room temperature. The resultant emulsion acrylic type, pressure sensitive adhesive has a solid content of about 60%, a pH value of 5.2, a viscosity 14000 cps. The physical properties of the product are shown in Table 1.
0.25 g of ammonium polyoxethyene nonyl phenyl ether sulfate (Chun-Zih Synthesis Company, Taiwan) and 2.74 g of RS-30 (Asahi Denka Co., Ltd, Japan) are evenly mixed in 40 g of de-ionized water to obtain solution A.
70.5 g of de-ionized water, 3.08 g of polyoxethyene nonyl phenyl ether (Chun-Zih Synthesis Company, Taiwan), 18.22 g of ammonium polyoxethyene nonyl phenyl ether sulfate, 153.9 g of 2-ethyl hexyl methacrylate monomers, 102.6 g of dioctyl maleate monomers, 85.5 g of vinyl acetate monomers, 3.42 g of hydroxy ethyl acrylate and 1.03 g of acetoacetoxy ethy methacrylate monomers are evenly mixed to obtain the solution B.
87.5 g of de-ionized water, 1.8 g of sodium bicarbonate and 0.9 g of potassium persulfate are evenly mixed to prepare solution C.
20.5 g of de-ionized water and 0.9 g of potassium persulfate are mixed to prepare solution D.
The solution A and a half quantity (½) of the solution D are poured into the emulsion and polymerization apparatus, which includes a stirrer, a thermometer, a heater, a reflux condenser, a five neck flask and a one-liter round bottom flask. When the solution is heated to about 69 to 70° C., the mixture of 1/10 of the solution B and ½ of the solution D is steadily fed into the emulsion and polymerization apparatus within 20-30 minutes. The mixture is then heated to 79 to 81° C., and the remaining solution B ( 9/10 of the weight) and the solution C are slowly fed into the emulsion and polymerization apparatus within 240 minutes. Thereafter, the reaction temperature is increased to 85 to 87° C. and is maintained for 90 minutes, and is then cooled to the room temperature. The resultant emulsion type, acrylic, pressure sensitive adhesive has a solid content of 60%, pH 4.8, viscosity 9000 cps. The physical properties of this product are shown in Table 1.
0.25 g of ammonium polyoxethyene nonyl phenyl ether sulfate (Chun-Zih Synthesis Company, Taiwan) is evenly mixed in 40 g of de-ionized water to obtain solution A.
70.5 g of de-ionized water, 3.08 g of polyoxethyene nonyl phenyl ether (Chun-Zih Synthesis Company, Taiwan), 18.22 g of ammonium polyoxethyene nonyl phenyl ether sulfate, 153.9 g of 2-ethyl hexyl methacrylate monomers, 102.6 g of dioctyl maleate monomers, 85.5 g of vinyl acetate monomers, 3.42 g of hydroxy ethyl acrylate and 1.03 g of acetoacetoxy ethy methacrylate monomers are evenly mixed to obtain the solution B.
87.5 g of de-ionized water, 1.8 g of sodium bicarbonate and 0.9 g of potassium persulfate are evenly mixed to prepare solution C.
20.5 g of de-ionized water and 0.9 g of potassium persulfate are mixed to prepare solution D.
The solution A and a half quantity (½) of the solution D are poured in to the emulsion and polymerization apparatus, which includes a stirrer, a thermometer, a heater, a reflux condenser, a five neck flask and a one-liter round bottom flask. When the solution is heated to about 69 to 70° C., the mixture of 1/10 of the solution B and ½ of the solution D is steadily fed into the emulsion and polymerization apparatus within 20-30 minutes. The mixture is then heated to 79 to 81° C., and the remaining solution B ( 9/10 of the weight) and the solution C are slowly fed within 240 minutes into the emulsion and polymerization apparatus. Thereafter, the reaction temperature is increased to 85 to 87° C. and is maintained for 90 minutes, and then cooled to the room temperature. The resultant product has a solid content of 60%, a pH value of 5.1, a viscosity of 9500 cps. The physical properties of this product are shown in Table 1.
The product is obtained following the procedures in embodiment 1 with the addition of 3.42 g of acrylic acid of and of methacrylic acid. The physical properties of this product are shown in Table 1.
Coating conditions: the thickness of the PP synthetic paper is 80 μm; the thickness of the adhesive is 22 ± 0.2 μm.
The differences in the products of Embodiment 1, Embodiment 2, Comparison of Embodiment 1, Comparison of Embodiment 2.
∘: with the addition; x without the addition
As shown in Table 1, the product in embodiment 1 contains NE-10 reactive surfactant, the product in embodiment 2 contains RS-30 reactive surfactant, the product in the comparison of embodiment 1 does not contain any reactive surfactant. The product in the comparison of embodiment 2 contains NE-10 reactive surfactant, acrylic acid monomers and methacrylic acid monomers.
Regarding the water-whitening resistance test, please refer to the following “Test Method” section.
According to the table above, the products of embodiment 1 and embodiment 2 display desirable water-whitening resistance property after being subjected to the water-whitening resistance test. The water-whitening resistance of the product of comparison of embodiment 1, in which reactive surfactant is not used, the water-whitening resistance property is undesirable. The product of comparison of embodiment 2, which is the same as the product of embodiment 1 with the addition of acrylic acid and methacrylic acid monomers, displays a less desirable water-whitening resistance property.
Test Methods:
The Effect Tests:
The results of the aging resistance effect of the products of embodiment 1, embodiment 2, comparison of embodiment 1, comparison of embodiment 2 are summarized in Tables 3, 4, 5 and 6.
Coating conditions: the thickness of the synthetic paper is 80 μm; the thickness of the adhesive is 22 ± 0.2 μm.
Coating conditions: the thickness of the synthetic paper is 80 μm; the thickness of the adhesive is 22 ± 0.2 μm.
Coating conditions: the thickness of the synthetic paper is 80 μm; the thickness of the glue is 22 ± 0.2 μm.
Coating conditions: the thickness of the synthetic paper is 80 μm; the thickness of the adhesive is 22 ± 0.2 μm.
As shown in Tables 3, 4, 5, and 6, the products of embodiment 1 and embodiment 2 display desirable aging resistance effect (refer to Table 3 and table 4). The product of the comparison of embodiment 1 displays acceptable aging resistance effect. The product of the comparison of embodiment 2 is the same as that of embodiment 1 with the addition of acrylic acid and methacrylic acid monomers. The loop tack, steel adhesion and PE adhesion become less desirable for the product of the comparison of embodiment 2, while the holding power improves (see table 6).
In accordance to the disclosure above of the present invention, a mixture of appropriate proportions of dialkyl dicarboxylate monomers, vinyl esters monomers, alkyl acrylates (or alkyl methacrylates) monomers, cross-linker, hydroxy alkyl acrylates (or hydroxy alkyl methacrylate) with nonionic surfactant, anionic surfactant and reactive surfactant is heated and reacted to form an emulsion adhesive product, wherein this product not only has a high degree of adhesiveness, it has also the water-whitening resistance and aging resistance properties.
The foregoing description of the preferred embodiment of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form or to exemplary embodiments disclosed. Accordingly, the foregoing description should be regarded as illustrative rather than restrictive. Obviously, many modifications and variations will be apparent to practitioners skilled in this art. The embodiments are chosen and described in order to best explain the principles of the invention and its best mode practical application, thereby to enable persons skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use or implementation contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents in which all terms are meant in their broadest reasonable sense unless otherwise indicated. It should be appreciated that variations may be made in the embodiments described by persons skilled in the art without departing from the scope of the present invention as defined by the following claims. Moreover, no element and component in the present disclosure is intended to be dedicated to the public regardless of whether the element or component is explicitly recited in the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 93112611 | May 2004 | TW | national |
