JPH0148953B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to an emulsion-type pressure-sensitive adhesive having excellent adhesion to non-polar adherends such as films or molded articles made of polyethylene, polypropylene, polybutadiene, etc. Conventional pressure-sensitive adhesives are mainly made of natural rubber or synthetic rubber, to which tackifiers, plasticizers, fillers, anti-aging agents, etc. are added, or they are made of acrylic ester copolymers, etc. Solution-type products were the mainstream. However, since these solution-type pressure-sensitive adhesives use organic solvents, there are various problems in terms of fire occurrence, occupational health, and pollution such as air pollution. Therefore, in recent years, water-based pressure-sensitive adhesives have attracted attention from the viewpoint of resource saving, non-pollution, and safety and hygiene. Among them, emulsion-type pressure-sensitive adhesives containing acrylic acid ester copolymers as the main component are widely used. ing. Pressure-sensitive adhesives are used in a wide range of applications such as tapes, labels, stickers, and stickers, and the adherend materials include plastic films and molded products, metals, glass, ceramics, paper, cloth, and fruit. In particular, the demand for plastic products is increasing, and the proportion of resins such as polyethylene, polypropylene, and polybutadiene has increased significantly due to safety and hygiene considerations, and they are now widely used in tableware, containers, toys, wrapping paper, bags, etc. . However, the acrylic emulsion type pressure-sensitive adhesive has disadvantages in drying properties, water resistance, adhesive properties, etc. compared to conventional solution-type pressure-sensitive adhesives. The current situation is that the adhesion to adherends such as films and molded articles made of polyester is poor. Methods for improving adhesion to these adherends include softening the pressure-sensitive adhesive or reducing its molecular weight to lower its cohesive force and improve its adhesion, or using tackifiers, plasticizers, rubber, etc. There are methods of blending water dispersants, but all of them have drawbacks such as extrusion of the pressure-sensitive adhesive from the support due to a decrease in cohesive force, penetration or slits, staining of the blade during sealing, and a decrease in weather resistance. occurs. Various proposals have been made to improve the drawbacks of such acrylic emulsion type pressure-sensitive adhesives.
For example, an acrylic pressure-sensitive adhesive emulsion mixed with an ethylene-vinyl acetate copolymer emulsion (see JP-A-52-151326) or a vinyl acetate-ethylene-vinyl acetate emulsion used as an adhesion modifier for an acrylic pressure-sensitive adhesive emulsion. Those using vinyl chloride copolymer (see JP-A-54-78738)
However, since the glass transition point of the modifying polymer is high in both cases, pressure-sensitive adhesives blended with these have a problem in practical use because their adhesion at low temperatures decreases. It has also been proposed to use an ethylene-vinyl ester copolymer containing acrylic acid ester as a pressure-sensitive adhesive (Japanese Patent Laid-Open No. 73235/1983).
However, these polymers have poor anchoring properties to supports such as paper and film, have low cohesive strength as pressure-sensitive adhesives, and have poor adhesive properties. It has drawbacks such as poor secondary processing properties such as slitting, cutting, and punching of tapes or sheets. The present invention was made in view of the current situation, and its purpose is to improve the above-mentioned drawbacks and to provide superior properties to adherends such as films or molded products made of resins such as polyolefin and polybutadiene. An object of the present invention is to provide an emulsion-type pressure-sensitive adhesive having properties such as adhesive properties. The present invention has the following configuration to achieve the above object. That is, the emulsion-type pressure-sensitive adhesive of the present invention (first invention) comprises (A) 100 parts by weight (solid content basis) of an acrylic pressure-sensitive adhesive emulsion, and (B) (a) 5 to 30 parts by weight of ethylene. Weight %, (b)
20-90% by weight of vinyl acetate and (c) 5-50% by weight of at least one monomer selected from the group consisting of alkyl acrylates and alkyl methacrylates, the alkyl group having 1-12 carbon atoms. The active ingredient is an ethylene-vinyl acetate-alkyl acrylate and/or alkyl methacrylate multicomponent copolymer emulsion obtained by copolymerizing with 5 to 35 parts by weight (solid content basis), and The emulsion-type pressure-sensitive adhesive of the present invention (second invention) comprises (A) 100 parts by weight (solid content basis) of an acrylic pressure-sensitive adhesive emulsion, and (B) 5 to 30 parts by weight of (a) ethylene. %, (b) 20 to 90% by weight of vinyl acetate, (c) at least one monomer selected from the group consisting of alkyl acrylates and alkyl methacrylates, in which the alkyl group has 1 to 12 carbon atoms. 5-50% by weight
and (d) an ethylene-vinyl acetate-alkyl acrylate and/or alkyl methacrylate-based multicomponent copolymer obtained by copolymerizing 0.1 to 5% by weight of a monomer having a functional group that can be copolymerized with these monomers. It is characterized by containing 5 to 35 parts by weight (based on solid content) of a polymer emulsion as an active ingredient. As a result of intensive research to improve the above-mentioned drawbacks, the present inventors have developed an ethylene-vinyl acetate-alkyl acrylate and/or alkyl methacrylate multi-component copolymer into the acrylic pressure-sensitive adhesive emulsion (A). By mixing the combined emulsion (B),
It can be applied to films and molded products made of polyolefin and polybutadiene resins without sacrificing the advantages of acrylic pressure-sensitive adhesives, such as adhesion at low temperatures and secondary processability such as slitting, cutting, and punching. The present invention was achieved by discovering that adhesiveness can be significantly improved. The acrylic pressure-sensitive adhesive emulsion (A) in the present invention is generally known as a pressure-sensitive adhesive, and uses an alkyl ester of acrylic acid and/or methacrylic acid as the main monomer component,
It can be obtained by subjecting this to emulsion polymerization with a copolymerizable α,β-unsaturated carboxylic acid and, if necessary, other copolymerizable monomers in the presence of an emulsifier and a radical polymerization initiator. Desirable monomer compositions of the acrylic pressure-sensitive adhesive emulsion (A) in the present invention include the following. The main monomer component, acrylic ester or methacrylic ester (hereinafter the terms acrylic and methacrylic are collectively referred to as (meth)acrylic), includes (meth)acrylic acid n
-butyl, 2-ethylhexyl (meth)acrylate, etc., and it is effective to use at least one of these in an amount of 50 to 99% by weight, preferably 65 to 99% by weight, based on the total amount of monomers. Monomers that can be copolymerized with these monomers include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, vinyl acetate, vinyl propionate, vinyl chloride, and styrene. and acrylonitrile, and at least one of these is contained in an amount of 0 to 50% by weight, preferably 0 to 35% by weight based on the total amount of monomers.
Weight percentages are valid. Further, examples of α,β-unsaturated carboxylic acids include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid, and at least one of these is added in an amount of 0.1 to 10% by weight based on the total amount of monomers. %, preferably even 0.5 to 5% by weight. Furthermore, if necessary, hydroxyethyl (meth)acrylate,
Hydroxypropyl (meth)acrylate, (meth)
Monomers having functional groups such as glycidyl acrylate, (meth)acrylamide, and N-methylol (meth)acrylamide can be used, and at least one of these is added in an amount of 0 to 10% based on the total amount of monomers.
It is advantageous to use % by weight, preferably 0 to 5% by weight. Further, the solid content of the acrylic pressure-sensitive adhesive emulsion (A) in the present invention is preferably 40% by weight or more, preferably 45% by weight or more, from the viewpoint of coating properties and drying properties. On the other hand, in the present invention, ethylene-vinyl acetate-
The (meth)alkyl acrylate multicomponent copolymer emulsion (B) may or may not itself have the performance as a pressure-sensitive adhesive. However, the proportion of the copolymerization composition of the emulsion is extremely important, and the glass transition temperature (Tg) of the copolymer must be -10°C or lower, preferably -15°C or lower. That is, the monomer composition of this copolymer is ethylene (a),
It consists of vinyl acetate (b) and at least one monomer (c) selected from the group consisting of alkyl (meth)acrylates in which the alkyl group has 1 to 12 carbon atoms; Invention) Furthermore, these ingredients,
A carboxyl group that can be copolymerized with these monomers,
Added at least one monomer (d) selected from the group consisting of monomers having a functional group such as a hydroxyl group, a glycidyl group, an amide group, or an amino group (second invention) This is effective. Monomer (c) of alkyl (meth)acrylate having an alkyl group having 1 to 12 carbon atoms in the present invention
Examples include methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate,
Butyl (meth)acrylate, amyl (meth)acrylate, hexyl (meth)acrylate, heptyl (meth)acrylate, octyl (meth)acrylate,
(meth)acrylic acid 2-ethylhexyl, (meth)
Examples include decyl acrylate and uralyl (meth)acrylate, and particularly desirable one is alkyl (meth)acrylate having an alkyl group having 2 to 8 carbon atoms. Further, in the present invention, at least one monomer (d) selected from the group consisting of monomers having various functional groups described above includes acrylic acid, methacrylic acid,
α,β-unsaturated carboxylic acids such as crotonic acid, itaconic acid, maleic acid and fumaric acid; monomers with hydroxyl groups such as hydroxyethyl (meth)acrylate and hydroxypropyl (meth)acrylate; (meth) Monomers with glycidyl groups such as glycidyl acrylate, (meth)acrylamide,
Unsaturated carboxylic acid amides having an amide group such as N-methylol(meth)acrylamide, N-butoxymethyl(meth)acrylamide and diacetone(meth)acrylamide, and further monomers having an amino group such as melamine and vinylpyridine. I have a body. The above ethylene-vinyl acetate- in the present invention
The composition ratio of each of the above monomers in the alkyl (meth)acrylate multicomponent copolymer emulsion (B) is extremely important. In other words, it is appropriate that the content of ethylene (a) be 5 to 30% by weight, preferably 10 to 25% by weight; if it is less than 5% by weight, the flexibility and water resistance of the polymer will be poor, and the polymer will become non-polar. Adhesiveness to substances is not sufficiently exhibited. Moreover, if the content exceeds 30% by weight, tack and cohesive force will be impaired. In addition, vinyl acetate (b) is a component that contributes to adhesive force and cohesive force, and its content is 20
It is appropriate to set the amount to 90% by weight, preferably 30 to 80% by weight. If this content is less than 20% by weight, adhesive and cohesive strength will be insufficient, and if it exceeds 90% by weight,
Polymer flexibility, water resistance, and alkali resistance are poor.
In addition, the content of alkyl (meth)acrylate (c) is
It is appropriate to set it as 5 to 50% by weight, and 5% by weight
If the amount is less than 50% by weight, the blending with the acrylic pressure-sensitive adhesive emulsion (A) will not be effective and the tackiness will be insufficient. The disadvantage is the loss of adhesion to non-polar plastics. In particular, as alkyl (meth)acrylates, those containing 5 to 40% by weight of a monomer having an alkyl group having 2 to 8 carbon atoms and a homopolymer glass transition temperature (Tg) of -10°C or less are used. It has an excellent blending effect with the acrylic pressure-sensitive adhesive emulsion (A), and is desirable in terms of performance such as adhesive strength, cohesive strength, and tack. In the present invention, it is effective to add at least one monomer (d) of the above-mentioned functional group as a fourth component in addition to the above-mentioned components (a), (b) and (c). These monomers stabilize the emulsion,
It is used to improve properties such as imparting reactivity and crosslinking properties, and a small content of 0.1 to 5% by weight is sufficient. The ethylene-vinyl acetate-alkyl (meth)acrylate multicomponent copolymer emulsion (B) in the present invention is prepared by combining the above monomer mixture with a suitable emulsifier, a dispersant such as a protective colloid, a radical polymerization initiator, and a pH adjustment agent. It can be obtained by emulsion copolymerization under pressure in the presence of a polymerization agent and, if necessary, a degree of polymerization regulator. Further, the solid content in the multi-component copolymer emulsion (B) in the present invention is 40% by weight or more, preferably 45% by weight or more.
It is desirable to have a high solids content of at least % by weight without reducing the solids content of the acrylic pressure-sensitive adhesive emulsion (A), which is the main component, and from the viewpoint of coating properties and drying properties. In the present invention, the acrylic pressure-sensitive adhesive emulsion (A) includes the ethylene-vinyl acetate-
By mixing (meth)alkyl acrylate multi-component copolymer emulsion (B) in a specific ratio,
Acrylic pressure-sensitive adhesive emulsion has excellent adhesion at low temperatures and secondary processability such as slitting, cutting and punching properties for adhesive labels and tapes.
It is possible to obtain an emulsion-type pressure-sensitive adhesive having excellent adhesion to films, molded articles, etc. made of polyolefin and polybutadiene resin without sacrificing the advantage of (A). and both (A) and (B)
The appropriate blending ratio of (B) to 100 parts by weight (based on solid content) of (A) is 5 to 35 parts by weight, preferably 10 to 30 parts by weight. If this amount is less than 5 parts by weight, the adhesion to the object will be poor, and if it exceeds 35 parts by weight, low-temperature adhesion and tackiness will deteriorate.
The advantages of acrylic pressure-sensitive adhesives, such as anchoring properties to substrates, cohesive strength, and secondary processability such as cutting and punching properties, become insufficient. The emulsion-type pressure-sensitive adhesive of the present invention having the above structure can be used as is, but if necessary, it may be added with a plasticizer, tackifier, thickener, PH regulator, wetting agent, anti-mold agent, etc. It can be added and used. Normally, in order to apply an emulsion-type pressure-sensitive adhesive, it is necessary to increase the viscosity to about 10,000 to 20,000 cps. In this case, useful thickeners include celluloses, polyvinyl alcohol, polyacrylates, polymeric surfactants, and alkali thickening acrylic resins. Supports to which the emulsion-type pressure-sensitive adhesive of the present invention is coated include papers such as wood-free paper, art paper, coated paper, metallized paper, and kraft paper, polyethylene, polypropylene, polyester, acetate, and polychloride. Examples include films such as vinyl and composites thereof. Next, the present invention will be explained with reference to Examples, but the present invention is not limited to these in any way. Note that parts and % in the text mean parts by weight and % by weight, respectively. Example 1 Acrylic pressure-sensitive adhesive emulsion (A) consisting of 85% 2-ethylhexyl acrylate, 13% methyl acrylate and 2% acrylic acid (solid content 50%,
PH2.5, viscosity 500cps) 20 parts of ethylene (a)
%, vinyl acetate (b) 65%, and 2-ethylhexyl acrylate (c) 15% ethylene-vinyl acetate-alkyl acrylate multi-component copolymer emulsion (B) (solid content 50%, PH5.0 (viscosity 100 cps) were mixed to obtain an emulsion-type pressure-sensitive adhesive. The solid content of this stuff is 50%, the PH is 3.0, and the viscosity is 350cps
It was hot. Also, for comparison, the above (A) component only (Control 1) and the above (B) for 100 parts of the above (A) component
A mixture of 40 parts of ingredients (Control 2: solid content 50%,
PH2.8, viscosity 250cps) was also produced. Evaluation of these physical properties will be summarized below. Example 2 Acrylic pressure-sensitive adhesive emulsion (A) consisting of 87% 2-ethylhexyl acrylate, 10% methyl methacrylate, 1% glycidyl methacrylate and 2% acrylic acid (solid content 50%, PH 3.0, viscosity
Ethylene-vinyl acetate-alkyl acrylate multi-component copolymer emulsion (B) consisting of 15% ethylene (a), 55% vinyl acetate (b) and 30% ethyl acrylate (c) to 100 parts (1000cps) Solid content 50%, PH5.0,
(viscosity 150 cps) were mixed to obtain an emulsion-type pressure-sensitive adhesive. The solid content of this product is 50%, and the pH is
3.2, and the viscosity was 850 cps. Also, for comparison, only the above (A) ingredient (Control 3) and the above (A) ingredient
Ethylene-vinyl acetate copolymer emulsion (manufactured by Sumitomo Chemical Co., Ltd., Sumikaflex #400) (solid content 55%, PH4.5-6.5, viscosity 1100-100 parts)
A mixture of 15 parts (1700 cps, Tg 0°C) (Control 4: solid content 50.5%, PH 3.5, viscosity 900 cps) was also prepared. Evaluation of these physical properties will be summarized below. Example 3 Acrylic pressure-sensitive adhesive emulsion (A) consisting of 40% 2-ethylhexyl acrylate, 38% n-butyl acrylate, 20% vinyl acetate, and 2% acrylic acid (solid content 48%, PH 2.7, Ethylene-vinyl acetate consisting of 15% ethylene (a), 65% vinyl acetate (b), 17% n-butyl acrylate (c), and 3% N-methylolacrylamide (d) per 100 parts (viscosity 850 cps) 15 parts of alkyl acrylate multi-component copolymer emulsion (B) (solid content 50%, pH 5.0, viscosity 150 cps) were mixed to obtain an emulsion type pressure sensitive adhesive.
The solid content of this product is 48.3%, the pH is 3.0, and the viscosity is
It was 750cps. For comparison, a product containing only the above component (A) (Control 5) was also prepared. Evaluation of these physical properties will be summarized below. The physical properties of each emulsion-type pressure-sensitive adhesive obtained above were evaluated as follows. For each of these, a thickener (manufactured by Nippon Acrylic Co., Ltd.,
Add Primal ASE-108) and use 25% ammonia water to obtain a viscosity of 15,000 to 20,000 cps (B-type viscometer,
6 rpm). This emulsion-type pressure-sensitive adhesive was coated on release paper at 25 to 30 g/m ² (after drying), and after drying at 110°C for 2 minutes, it was coated on high-quality paper (64 g/m ² ).
were pasted together to obtain adhesive paper. Physical properties of this adhesive paper were measured based on JIS-Z-0237. In other words, the adhesive strength (adhesive strength) is 180
The holding force (cohesive force) was measured by the degree peeling method at 20℃ and RH65%, and the holding force (cohesive force) was determined by the falling time
mm×25mm (vs. stainless steel), load 1Kg, 40℃,
Measurements were made under the conditions of RH65%, and tack (adhesiveness) was measured using the ball rolling method under the conditions of 20°C and RH65%.
Regarding low-temperature adhesion, adhesion to various films at 0°C was evaluated by a sensory test.
(〇 indicates good, × indicates poor) The obtained results are shown in the table below.

【table】

[Table] As is clear from the table, Examples 1, 2, and 3 have a well-balanced adhesive property, and have particularly excellent adhesion to adherends made of polyolefin and polybutadiene. Adhesion is also good, and there are no problems with anchoring to the base material. On the other hand, Controls 1, 3, and 5 have low adhesion to polyethylene and polypropylene, and Controls 2 and 4 have slightly improved adhesion but are not satisfactory, and have poor anchoring ability and low-temperature adhesion to the substrate. is defective. As explained above, the emulsion-type pressure-sensitive adhesive of the present invention has excellent adhesion to non-polar adherends such as films or molded products made of polyolefin and polybutadiene, and also has excellent adhesive properties for slit cutting and punching. It is a useful product with good secondary processability.

Claims (1)

[Claims] 1 (A) Acrylic pressure-sensitive adhesive emulsion 100
Parts by weight (solid content basis) and (B) (a) ethylene 5 to 30
(b) 20-90% by weight of vinyl acetate, and (c) at least one monomer selected from the group consisting of alkyl acrylates and alkyl methacrylates, in which the alkyl group has 1 to 12 carbon atoms. The active ingredient is an ethylene-vinyl acetate-alkyl acrylate and/or alkyl methacrylate multi-component copolymer emulsion obtained by copolymerizing 5-50% by weight of ethylene-vinyl acetate-alkyl acrylate and/or alkyl methacrylate. An emulsion-type pressure-sensitive adhesive characterized by: 2 (A) Acrylic pressure sensitive adhesive emulsion 100
Parts by weight (solid content basis) and (B) (a) ethylene 5 to 30
(b) 20-90% by weight of vinyl acetate, (c) at least one monomer selected from the group consisting of alkyl acrylates and alkyl methacrylates, in which the alkyl group has 1 to 12 carbon atoms. body 5-50% by weight and (d)
Ethylene-vinyl acetate-alkyl acrylate and/or alkyl methacrylate multicomponent copolymer emulsion 5 obtained by copolymerizing 0.1 to 5% by weight of a monomer having a functional group that can be copolymerized with these monomers. An emulsion-type pressure-sensitive adhesive characterized by containing ~35 parts by weight (based on solid content) as an active ingredient.