JPH09143444A - Acrylic emulsion type adhesive - Google Patents

Abstract

(57) Abstract: To provide an acrylic emulsion type pressure-sensitive adhesive having further excellent water resistance. SOLUTION: The general formula CH ₂ = CR ₁ -COOR ₂ (wherein R ₁ is hydrogen or a methyl group, and R ₂ has 4 to 14 carbon atoms).
90 to 98% by weight of one or more (meth) acrylic acid esters represented by the formula (1), and 2 to 10% by weight of one or more monomers selected from a carboxyl group-containing monomer, an amide group-containing monomer and a hydroxyl group-containing monomer. % 0.5 to 5 parts by weight of a reactive nonionic emulsifier is continuously added dropwise to 100 parts by weight of a mixed monomer with 100% by weight, and emulsion polymerization is carried out at a polymerization temperature of 75 ° C. or lower. .

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an acrylic emulsion type adhesive having excellent water resistance.

[0002]

2. Description of the Related Art In recent years, acrylic adhesives having excellent balance of physical properties and durability have been widely used in place of natural rubber and synthetic rubber adhesives. In particular, acrylic emulsion type adhesives have been widely used because they can avoid pollution and environmental problems. However,
Since the acrylic emulsion-type pressure-sensitive adhesive uses an emulsifier, it has poor water resistance, and there is a problem that the pressure-sensitive adhesive force and cohesive force are deteriorated or white turbidity occurs during immersion in water or high humidity.

Japanese Examined Patent Publication No.
No. 13207 discloses a water-dispersible resin composition of a copolymer, which is a rust preventive coating, but is obtained by emulsion polymerization of a (meth) acrylic acid alkyl ester-based monomer in the presence of a reactive emulsifier. There is. Since it has excellent gloss, water resistance, sprayability, etc., it is used as a vehicle for anticorrosion paints.

[0004]

According to the water-dispersible resin composition described in the above publication, since the reactive emulsifier is used, the water resistance is considerably improved, but after coating and drying this on the object, Also, an ionic functional group remains in the adhesive. Therefore, the water resistance is not sufficient to withstand immersion in water.

An object of the present invention is to solve the above-mentioned conventional problems, and to provide an acrylic emulsion-type pressure-sensitive adhesive which is excellent in water resistance and stability and hardly causes whitening.

[0006]

The acrylic emulsion type pressure-sensitive adhesive of the present invention according to claim 1 has the general formula CH ₂ = CR.
_1- COOR ₂ (wherein R ₁ is hydrogen or a methyl group, R
₂ represents an alkyl group having 4 to 14 carbon atoms) 90 to 98% by weight of one or more (meth) acrylic acid ester represented by
And 0.5 to 5 parts by weight of a reactive nonionic emulsifier to 100 parts by weight of a mixed monomer of 2 to 10% by weight of one or more monomers selected from a carboxyl group-containing monomer, an amide group-containing monomer and a hydroxyl group-containing monomer. It is characterized in that the emulsified emulsified monomer is continuously dropped and emulsion-polymerized at a polymerization temperature of 75 ° C. or lower.

Further, the acrylic emulsion type pressure-sensitive adhesive of the present invention according to claim 2 is characterized in that the reactive nonionic emulsifier according to claim 1 is at least one of the following general formulas [1] and [2]. To do.

[0008]

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[0009]

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However, R1 and R2 are each an alkyl group having 6 to 18 carbon atoms, an alkenyl group, or a substituted aralkyl group. m and n are integers of 20 to 100 A is an alkylene group having 2 to 4 carbon atoms or a substituted alkylene group

In the present invention, the alkyl group has 4 to 4 carbon atoms.
Examples of the alkyl acrylate which is 14 include n-butyl acrylate, 2-ethylhexyl acrylate, isooctyl acrylate, isononyl acrylate, lauryl acrylate, etc.
The acrylic ester is used in the range of 90 to 98% by weight based on the total amount of the monomers. When the amount of the (meth) acrylic acid ester is less than 90% by weight, the adhesive force of the pressure-sensitive adhesive is reduced, and when it exceeds 98% by weight, the cohesive force of the pressure-sensitive adhesive is reduced.

As the carboxyl group-containing monomer,
(Meth) acrylic acid, maleic acid, itaconic acid and the like can be mentioned. Examples of the amide group-containing monomer include (meth) acrylamide, N-isopropylacrylamide, N-vinylpyrrolidone and N-vinylcaprolactam. Examples of the hydroxyl group-containing monomer include 2-hydroxyethyl (meth) acrylate and 4-hydroxybutyl acrylate. One or more kinds of monomers selected from these are used in an amount of 2 to 10% by weight based on all monomers. If the amount of these polar monomers is less than 2% by weight, the cohesive force will be low, and if it exceeds 10% by weight, the cohesive force will be too high and the adhesive force will be reduced.

If necessary, a copolymerizable monomer such as styrene, vinyl acetate, methyl (meth) acrylate, ethyl (meth) acrylate may be copolymerized with the above monomer. Further, the macromonomer may be copolymerized. However, the macromonomer should be 25% by weight or less based on all the monomers.

As the reactive nonionic emulsifier, any one having a copolymerizable unsaturated group can be used, but it is necessary to use at least one kind represented by the following general formulas [1] and [2]. Is.

[0015]

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[0016]

[Chemical 6]

Here, m and n in the formula are integers of 20 to 100. When the values of m and n are less than 20, the cloud point of the emulsifier becomes low and the surface-active ability decreases due to heating during polymerization.
Polymerization stability is significantly deteriorated. The amount of the reactive emulsifier added is 0.5 to 5 parts by weight, preferably 0.5 to 3 parts by weight, based on 100 parts by weight of all the monomers. If it is less than 0.5 parts by weight, the polymerization stability will be lowered, and if it exceeds 5 parts by weight, the water resistance will be lowered.

The temperature for emulsion polymerization is 75 ° C. or lower. If it exceeds 75 ° C, the surface-active ability of the nonionic emulsifier is lowered and the polymerization stability is remarkably deteriorated.

As the polymerization initiator, a persulfate such as ammonium persulfate, a water-soluble azo compound such as azobiscyanovaleric acid, or a redox type polymerization initiator in which hydrogen peroxide and the like are used in combination can be preferably used. The amount of the polymerization initiator used is 0.01 to 1 with respect to 100 parts by weight of all the monomers.
Weight part is preferable, and more preferably 0.03 to 0.5 weight part. Use caution when using a water-soluble azo compound, because the cyano group may remain.

The acrylic emulsion pressure-sensitive adhesive of the present invention may be adjusted in molecular weight using a chain transfer agent such as dodecyl mercaptan, or may be copolymerized with a polyfunctional (meth) acrylate. Further, a viscosity modifier such as polyacrylic acid or a water-soluble urethane resin, a preservative, etc. may be added. Furthermore, a tackifying resin such as a rosin-based resin, a rosin ester-based resin, a terpene-based resin, or a petroleum resin-based resin may be added depending on the application of the pressure-sensitive adhesive.

Since the acrylic emulsion type pressure-sensitive adhesive of the present invention is an aqueous dispersion, it improves physical stability and causes coating defects such as streaks and unevenness due to formation of aggregates during coating. To prevent this, use a PH adjuster
It is necessary to adjust to 6-9.

The pressure-sensitive adhesive of the present invention may be crosslinked by adding a crosslinking agent. As a cross-linking agent, aziridine
Blocks, self-emulsifying isocyanate-based, carbodiimide-based, metal-based and the like are used.

The use of the acrylic emulsion type pressure-sensitive adhesive of the present invention is not particularly limited, and examples thereof include pressure-sensitive adhesive tapes, pressure-sensitive adhesive sheets, pressure-sensitive adhesive labels, double-sided pressure-sensitive adhesive tapes and the like. The base material is not particularly limited, and examples thereof include films such as polyethylene terephthalate and stretched polypropylene, foams such as polyurethane, polyethylene and rubber, and paper, cloth and non-woven fabric.

(Function) Since the acrylic emulsion type pressure-sensitive adhesive of the present invention uses only a nonionic emulsifier as an emulsifier, the coating film formed after coating and drying this emulsifier has an ionic functional group by the emulsifier. The group does not exist. Further, since the nonionic emulsifier is reactive, there is no liberated emulsifier in the formed coating film. Due to these facts, the pressure-sensitive adhesive layer formed by coating and drying has remarkably improved water resistance. Furthermore, since the emulsifier does not have an ionic functional group, aggregates due to ion shock do not form. As a result, a good coating film is formed.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the acrylic emulsion type pressure-sensitive adhesive of the present invention will be described below. (Example 1) 60 parts by weight of ion-exchanged water in which 0.1 part by weight of ammonium persulfate was dissolved was placed in a reaction vessel of 1 liter equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen gas inlet tube, and nitrogen was added. It was heated to 70 ° C. under a gas atmosphere. The following were prepared as a monomer mixture. n-Butyl acrylate 76 parts by weight 2-Ethylhexyl acrylate 20 parts by weight Acrylic acid 2 parts by weight Methacrylic acid 2 parts by weight n-dodecyl mercaptan 0.05 parts by weight

1 part by weight of the above mixed monomer as a reactive nonionic emulsifier, a propenyl group-added polyoxyethylene nonyl phenyl ether (manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., trade name "Aqualon RN-30", EO addition mole number 30), ion 40 parts by weight of exchanged water was added, and the emulsified monomer emulsified by mixing and stirring was placed in a dropping funnel. 70 in the reaction vessel
While maintaining the temperature at 0 ° C, the emulsified monomer was added dropwise over 3 hours to carry out polymerization. After the dropping of the emulsified monomer, 70 ℃
The temperature was maintained for 1 hour, and the mixture was further reacted at 75 ° C. for 3 hours. After cooling the above-mentioned polymerization liquid to 30 ° C. or lower, it was neutralized with 25% aqueous ammonia to obtain an acrylic emulsion-type pressure-sensitive adhesive of the present invention. The solid content was 50%.

(Example 2) An acrylic emulsion pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that the propenyl group-added polyoxyethylene nonylphenyl ether was changed to 2 parts by weight.

Example 3 A reactive nonionic emulsifier was used as an allyl group-added polyoxyethylene nonyl phenyl ether (trade name "Adecaria Soap NE-2" manufactured by Asahi Denka Co., Ltd.
0 ", EO addition mole number 20) An acrylic emulsion pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that 1 part by weight was used.

(Comparative Example 1) Propenyl group-added polyoxyethylene nonyl phenyl ether sulfate ammonium salt as a reactive anionic emulsifier (Daiichi Kogyo Seiyaku Co., Ltd., trade name "Aqualon HS-10", EO addition mole number 10) An acrylic emulsion type pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that 1 part by weight was used.

Comparative Example 2 When the emulsion monomer was dropped, the reaction was carried out for 3 hours while maintaining the reaction temperature at 70 ° C.
An acrylic emulsion type pressure-sensitive adhesive was obtained in the same manner as in Example 1 except that the temperature was kept at 1 ° C for 1 hour and then at 80 ° C for 2 hours.

The emulsion characteristics of the pressure-sensitive adhesives obtained in Examples 1 to 3 and Comparative Examples 1 and 2 were measured according to the following methods. (1) Emulsion characteristics Measurement of solid content Take 1.5 g of emulsion in an aluminum cup and
After drying at 10 ° C for 3 hours, the solid content was calculated by the following formula. Solid content (%) = (dry weight (g) /1.5 (g)) × 100 Polymerization stability The emulsion was filtered through a 100-mesh stainless steel wire net, dried at 110 ° C. for 3 hours, and then left on the wire net. Of the total solid content was calculated by the following formula. Physical stability Add 25 g of ion-exchanged water to 25 g of emulsion to obtain 50
g and 10 kg / c using a Marlon type mechanical stability tester (Kyowa Interface Science Co., Ltd., trade name "Emulsion / Latex Mechanical Stability Measurement-Recorder CMS-A type")
After rotating at a rotation speed of 1000 rpm for 5 minutes under a pressure of m ² , the aggregate in the container was filtered through a 100-mesh wire net and dried at 110 ° C. for 3 hours. Was calculated.

Whitening Resistance Test Acrylic emulsion type adhesives obtained in Examples 1 to 3 and Comparative Examples 1 and 2 are applied to a polyethylene terephthalate film (thickness 38 μm) and dried to have an adhesive layer 25 μm in thickness. Create an adhesive tape, attach the same polyethylene terephthalate film to the adhesive layer surface,
A whitening resistance test was conducted using this sample.

A sample was cut into a size of 100 mm × 25 mm, and a haze meter (manufactured by Tokyo Denshoku Co., Ltd., trade name “MOD”) was used.
Haze value was measured using EL TC-H111DP "). Then, the above sample was immersed in water at 23 ° C. for 48 hours, and the haze value immediately after being taken out was measured. Table 1 shows the above results.

[0034]

[Table 1]

According to Table 1, those of Examples 1 to 3 are comparable with each other in all evaluation items. However, Comparative Example 1 uses a reactive anionic emulsifier and thus has a large whitening resistance, and Comparative Example 2 is a polymer which is polymerized at a high polymerization temperature, and thus it is understood that the polymerization stability is poor.

[0036]

The acrylic emulsion type pressure-sensitive adhesive of the present invention has the above-mentioned constitution, and since only the reactive nonionic emulsifier is used as the emulsifier, an ionic functional group is contained in the pressure-sensitive adhesive layer using this. Not present and free emulsifier is not present. Therefore, the adhesive layer has significantly improved water resistance. Furthermore, since the emulsifier does not have an ionic functional group, an agglomerate due to ion shock is not formed, so that a good coating film is formed. Therefore, since an adhesive tape or the like using this adhesive has high water resistance, it can be used in a field which cannot be applied by the conventional one using the acrylic adhesive.

Claims (2)

[Claims] 1. A general formula CH ₂ ═CR ₁ —COOR ₂ (wherein R ₁ is hydrogen or a methyl group, and R ₂ has 4 to 14 carbon atoms.
90 to 98% by weight of one or more (meth) acrylic acid esters represented by the formula (1), and 2 to 10% by weight of one or more monomers selected from a carboxyl group-containing monomer, an amide group-containing monomer and a hydroxyl group-containing monomer. % 0.5% by weight of a reactive nonionic emulsifier to 100 parts by weight of a mixed monomer, and continuously added dropwise an emulsified monomer which is emulsified and emulsion-polymerized at a polymerization temperature of 75 ° C. or less. Acrylic emulsion type adhesive. 2. The acrylic emulsion-type pressure-sensitive adhesive according to claim 1, wherein the reactive nonionic emulsifier is at least one of the following general formulas [1] and [2]. ## STR1 ## [Chemical formula 2] However, R1 and R2 are each an alkyl group having 6 to 18 carbon atoms, an alkenyl group or a substituted aralkyl group. m and n are integers of 20 to 100 A is an alkylene group having 2 to 4 carbon atoms or a substituted alkylene group