JPH0665551A - Aqueous pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To obtain an aqueous pressure-sensitive adhesive composition of good water resistance. CONSTITUTION:This adhesive composition is prepared from a copolymer emulsion obtained by emulsion-polymerizing 60-99.9wt.% alkyl (meth)acrylate having a 1-14 C alkyl with 0.1-40wt.% ethylenically unsaturated monomer having at least one functional group and 0.1-20 pts.wt., per 100 pts.wt. total of the above monomers, copolymerizable emulsifier terminated with a copolymerizable ethylenic group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a water-based pressure-sensitive adhesive composition composed of a water-based acrylic copolymer used for pressure-sensitive adhesive sheets, pressure-sensitive adhesive labels and the like. More specifically, a film of polyester, vinyl chloride or the like is used as a support. The present invention relates to an aqueous pressure-sensitive adhesive composition having good water resistance.

[0002]

Conventionally, solvent-type acrylic copolymers have been used for film supports. However, since these solvent-type acrylic pressure-sensitive adhesives are synthesized in an organic solvent, volatilization of the solvent at the time of coating is an environmental problem, and conversion to an aqueous acrylic copolymer is being attempted. However, since an aqueous acrylic copolymer is generally synthesized by emulsion polymerization, the emulsifier serves as a medium for permeating moisture into the adhesive layer and cannot maintain an effective adhesive force. There is a problem with using it in place. Therefore, the water-based acrylic copolymer has never been used in applications requiring water resistance.

[0003]

Due to the above-mentioned problems, solvent-type acrylic copolymers are mainly used for this application, and water-based acrylic copolymers have not been used. The advent of adhesives was desired.

The present invention overcomes the drawbacks of these conventional water-based acrylic copolymers and provides a water-based pressure-sensitive adhesive composition having water resistance equivalent to that of solvent-based acrylic copolymers. .

[0005]

That is, the present invention relates to (meth) acrylic acid alkyl ester (a) having an alkyl group having 1 to 14 carbon atoms in an amount of 60 to 99.9% by weight, and at least one or more functional groups. 0.1-40% by weight of the ethylenically unsaturated monomer (b) and 100 parts by weight of the above (a) and (b) in total, a copolymerizable emulsifier having a terminal copolymerizable ethylene group. (C) A water-based pressure-sensitive adhesive composition comprising a copolymer emulsion obtained by emulsion polymerization using 0.1 to 20% by weight.

The (meth) acrylic acid alkyl ester (a) is an alkyl ester having an alkyl group having 1 to 14 carbon atoms, and more specifically, the following compounds can be exemplified. Methyl acid, ethyl acrylate, propyl acrylate, iso-propyl acrylate, butyl acrylate, iso-butyl acrylate,
Acrylic esters of linear or branched aliphatic alcohols such as hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, decyl acrylate, dodecyl acrylate, and corresponding methacrylic acid esters. Preferably, the (meth) acrylic acrylic acid alkyl ester used is an alkyl ester having an alkyl group with 4 to 12 carbon atoms, and the (meth) acrylic acid alkyl ester is a (meth) acrylic copolymer. 50-99.
It is contained in an amount of 9% by weight and is contained in one kind or two or more kinds.

The ethylenically unsaturated monomer (b) having at least one functional group used in the (meth) acrylic copolymer of the present invention means a carboxyl group, a hydroxyl group, a methylol group and an amino group. , An amide group, a glycidyl group, a phosphoric acid group, a sulfonic acid group, an ethyleneimine group, an isocyanate group, and the like. More specifically, there are the following compounds.

Unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic anhydride, maleic acid, maleic acid monoester, itaconic acid and crotonic acid, 2-hydroxypropyl (meth) acrylic acid, (meth) acrylic acid 2
-Hydroxyl ethyl, polyethylene glycol acrylate, glycidyl acrylate, glycidyl methacrylate, mono- (2-hydroxyl ethyl-α-chloro acrylate) acid phosphate, vinyl blocked isocyanate, etc., N-methylol acrylamide,
N-methylol methacrylamide, N-methylaminoethyl acrylate, N-tributylaminoethyl acrylate, N, N-dimethylaminoethyl acrylate,
N, N-dimethylaminoethyl methacrylate, N, N
-Diethylaminoethyl methacrylate, acrylamide, methacrylamide, vinylpyrrolidone, etc. The functional group-containing ethylenically unsaturated monomer is contained in an amount of 0.1 to 40% by weight of the (meth) acrylic copolymer, and is contained in one kind or two or more kinds.

The (meth) acrylic copolymer of the present invention may contain a copolymerizable vinyl monomer other than the above. Vinyl ester, vinyl pyridine, vinyl acetate,
Vinyl propionate, styrene, acrylonitrile, methacrylonitrile, butadiene, chloroprene, etc. The vinyl monomer is from 0.01 to (meth) acrylic copolymer.
It is contained in an amount of 20% by weight and is contained in one kind or two or more kinds.

Examples of the copolymerizable emulsifier used in the present invention include compounds represented by the following general formulas (1) to (3).

General formula (1)

[Chemical 1]

General formula (2)

[Chemical 2]

General formula (3)

[Chemical 3]

Specific examples of the compounds represented by the general formulas (1) to (3) include Latemur S-120 manufactured by Kao Corporation.
Examples thereof include A, Latemur S-180, Latemuru S-180A, Aqualon HS-10 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., and Eleminor JS-2 manufactured by Sanyo Kasei Co., Ltd.

The above copolymerizable emulsifier has 1 to 14 carbon atoms.
0.1 to 20% by weight with respect to the (meth) acrylic acid alkyl ester (a) having an alkyl group, and the ethylenically unsaturated monomer (b) having at least one or more functional groups.
It is contained, and 1 type or 2 or more types are contained. In addition, an emulsifier having no copolymerizability can be used together if necessary.

The water-based pressure-sensitive adhesive composition of the present invention, when polymerized,
If necessary, a polymerization initiator, a buffer, a chain transfer agent, and other additives which are generally used for water-based pressure-sensitive adhesives can be used in combination.

Examples of the polymerization initiator include inorganic peroxides such as potassium persulfate and ammonium persulfate, and organic initiators such as tert-butyl benzoate, dilauryl peroxide, benzoyl peroxide and tert-butyl hydroperoxide. To be Further, it may be used in a redox type in combination with a reducing agent such as sodium sorbitanate.

As the buffer, sodium acetate, sodium citrate, sodium bicarbonate or the like can be used.

As the chain transfer agent, mercaptans such as stearyl mercaptan and t-dodecyl mercaptan can be used.

As other additives, a tackifying resin, a thickener, a wetting agent, a defoaming agent and the like can be used as necessary when adjusting the gelatinization.

In the water-based pressure-sensitive adhesive composition of the present invention, a curing agent such as a blocked isocyanate compound, an epoxy compound, an aziridinyl compound or a melamine compound can be used if necessary.

The water-based pressure-sensitive adhesive composition of the present invention is applied to a film support such as polyester, polyolefin such as polypropylene, or vinyl chloride in an amount of 1 to 50 μm. The pressure-sensitive adhesive sheet obtained is used as a pressure-sensitive adhesive for labels and sheets, tapes, building materials, and packaging materials, and it has effective adhesiveness even when used in locations where water resistance is required, such as locations subject to water drops. And is useful as a general-purpose adhesive.

[0023]

EXAMPLES The present invention will be described in more detail based on examples. In the examples, "part" is "part by weight".

Example 1 Potassium persulfate 0.6 part 2-Ethylhexyl acrylate 60 parts Methyl methacrylate 20 parts Acrylic acid 5 parts Ethyl acrylate 15 parts Copolymerizable emulsifier (Latemur S-120A manufactured by Kao Corporation) 4 parts Polyoxyethylene nonylphenyl ether 1 part Ion-exchanged water 95 parts The above mixture was placed in a flask equipped with a stirrer, thermometer, nitrogen gas inlet tube, condenser and dropping funnel, and 0.6 part of potassium persulfate and ion-exchanged water. 50 parts were charged and 60 parts of 2-ethylhexyl acrylate preliminarily emulsified at an internal temperature of 80 ° C., 20 parts of methyl methacrylate, 5 parts of acrylic acid,
15 parts ethyl acrylate, 4 parts copolymerizable emulsifier [1],
1 part of polyoxyethylene nonylphenyl ether and 45 parts of ion-exchanged water were added dropwise at a constant rate for 3 hours. After the dropwise addition was completed, the reaction was terminated by maintaining the temperature for 2 hours as it was to obtain a (meth) acrylic copolymer.

Example 2 Potassium persulfate 0.6 part 2-Ethylhexyl acrylate 10 parts Butyl acrylate 60 parts Acrylic acid 5 parts Ethyl acrylate 25 parts Copolymerizable emulsifier (Aqualon HS-10 Daiichi Kogyo Seiyaku Co., Ltd.) 3 parts Polyoxyethylene nonylphenyl ether 1 part Ion-exchanged water 95 parts The above mixture was emulsified in the same manner as in Example 1 in a flask equipped with a stirrer, a thermometer, a nitrogen gas introducing tube, a condenser and a dropping funnel. Polymerization was performed to obtain a (meth) acrylic copolymer.

Comparative Example 1 0.6 part potassium persulfate 0.6 part 2-ethylhexyl acrylate 60 parts Methyl methacrylate 20 parts Acrylic acid 5 parts Ethyl acrylate 15 parts Polyoxyethylene nonylphenyl ether 3 parts Ion-exchanged water 95 parts The above mixture Emulsion polymerization was carried out in the same manner as in Example 1 in a flask equipped with a stirrer, a thermometer, a nitrogen gas introduction tube, a condenser, and a dropping funnel to obtain a (meth) acrylic copolymer.

Comparative Example 2 0.6 part potassium persulfate 0.6 part 2-ethylhexyl acrylate 10 parts Butyl acrylate 60 parts Acrylic acid 5 parts Ethyl acrylate 25 parts Polyoxyethylene nonylphenol ether 4 parts Ion-exchanged water 95 parts The above mixture Emulsion polymerization was performed in the same manner as in Example 1 in a flask equipped with a stirrer, a thermometer, a nitrogen gas introduction tube, a condenser, and a dropping funnel to obtain a (meth) acrylic copolymer.

Comparative Example 3 Azoisobutyronitrile 0.3 parts Butyl acrylate 80 parts Acrylic acid 5 parts 2-Ethylhexyl acrylate 15 parts Ethyl acetate 145 parts The above mixture was stirred, a thermometer, a nitrogen gas inlet pipe, A flask equipped with a condenser and a dropping funnel is charged with half of azoisobutyronitrile, a monomer, and ethyl acetate, and the remaining half of the mixture is dropped under heating and refluxing at a constant rate for 1 hour. After completion of dropping, the mixture was heated under reflux for 1.5 hours to complete the reaction. A (meth) acrylic copolymer was obtained. This (meth) acrylic copolymer 1
1 part of an isocyanate compound (manufactured by Nippon Polyurethane Company, trade name: Coronate L) was mixed with a solution containing 00 parts to obtain a pressure-sensitive adhesive composition.

The pressure-sensitive adhesive compositions obtained in Examples 1 and 2 and Comparative Examples 1 and 2 were adjusted to pH 7.2 to 7.5 with ammonia water, and Primal ASE-60 (manufactured by Rohm & Haas). ) Is used to thicken around 10,000 cps. The pressure-sensitive adhesive composition obtained in Comparative Example 3 was directly applied to a commercially available polyethylene laminated high-quality paper separator to obtain a dry weight of 2
5 g / Coating and reversing to commercially available polyethylene terephthalate film 25μ to prepare a coated product, 23 ° C.-65
The coating that was left for 1 week at% RH was subjected to a water resistance test.

In the water resistance test, the adherend is kept at 23 ° C. for 30 minutes or more.
After leaving it at 65% RH, it is attached to an adherend and reciprocated once with a 2 kg roll. After standing for 30 minutes, in water at 23 ° C for 24 hours
put. Then, after air-drying in an atmosphere of 23 ° C.-65% RH for 1 hour, the adhesive strength and whitening degree are measured. The adherend uses a stainless steel plate for adhesion and a glass plate for whiteness. Haze (haze value) was tested with a haze meter (manufactured by Suga Test Instruments Co., Ltd.) after the coated product was attached to a glass plate. The measurement results are shown in Table 1. As shown in Table 1, the examples show good results with respect to the water-based comparative examples 1 and 2 with no decrease in adhesive strength and no whitening observed visually or by HAZE. Also, the results are comparable to those of the solvent-type Comparative Example 3, and the copolymerizing emulsifier has a great effect.

[0031]

[Table 1]

[0032]

According to the present invention, a pressure-sensitive adhesive label sheet having good water resistance on a film support was obtained by using an aqueous pressure-sensitive adhesive composition.

Claims (1)

[Claims] 1. A (meth) acrylic acid alkyl ester (a) having an alkyl group having 1 to 14 carbon atoms (a) 60 to 99.9.
% By weight, 0.1 to 40% by weight of an ethylenically unsaturated monomer (b) having at least one or more functional groups, and 100 parts by weight of the total of (a) and (b) above, at the end. Copolymerizable emulsifier having copolymerizable ethylene group (c) 0.1
A water-based pressure-sensitive adhesive composition comprising a copolymer emulsion obtained by emulsion polymerization using 20 to 20% by weight.