JPS6112775A - Pressure-sensitive adhesive - Google Patents

Abstract

PURPOSE:The titled adhesive, obtained by incorporating two kinds of alkyl (met) acrylate based multicomponent polymers having different elastic moduli in a specific proportion, having improved adhesive force and improved cutting property, and useful for processing tapes, labels, etc. CONSTITUTION:A pressure-sensitive adhesive obtained by incorporating (A) 50- 90pts.wt. based on the solid, alkyl (meth)acrylate based multicomponent copolymer emulsion prepared by copolymerizing (i) 0.5-10wt% acrylic acid with (ii) 0-25wt% vinyl acetate and (iii) 5-50wt% 1-12C alkyl (meth)acrylate, preferably ethyl acrylate in the presence of a chain transfer agent consisting of a 1- 12C alkyl mercaptan with (B) 5-40pts.wt., based on the solid, emulsion prepared copolymerizing (i) 0.5-10wt% component (i) with 0-25wt% component (ii), 70- 95wt% component (iii) and (iv) 0.1-1wt% copolymerizable crosslinking monomer.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an adhesive mainly composed of an acrylic polymer that has excellent adhesive strength and excellent cutting processability, and more specifically relates to an adhesive having different elastic moduli. The present invention relates to a tape with excellent adhesive strength and improved cutting workability obtained by blending two types of acrylic polymers in a fixed ratio, and 2. A pressure-sensitive adhesive for sealing and sealing processing. .

[Prior art]

Conventionally, various pressure-sensitive adhesive products for processing tapes, labels, and seals have been widely used in fields such as printing, packaging, food, medicine, electronics, and automobiles. Rubber-based and acrylic-based polymers are used as pressure-sensitive adhesives, and acrylic-based pressure-sensitive adhesives are especially used for sealing and lining processing.

[Problem that the invention seeks to solve]

However, the acrylic pressure-sensitive adhesive has adhesive properties,
In particular, the current situation is that adhesiveness to adherends such as films and molded articles made of polyolefin or polybutadiene resins 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 such as lunding water dispersants, but all of them have drawbacks such as the pressure-sensitive adhesive protruding 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. In addition, natural rubber-based pressure-sensitive adhesives have drawbacks such as poor weather resistance and staining of blades during slitting and cutting.

Conventional pressure-sensitive adhesives for stickers and labels are categorized according to their uses, such as those for frozen foods, those for measuring labels, strong adhesive types, and removable types. Pressure-sensitive adhesives, which are said to be highly adhesive, have a strong adhesion force and adhere well to non-polar adherends, but they are pressure-sensitive to the guillotine blade during the slitting, cutting, and punching processes of adhesive labels, tapes, etc. Adhesion of adhesive becomes a problem.

In addition, many strong adhesive pressure-sensitive adhesives are natural rubber emulsion type or natural rubber solvent type, and these have poor weather resistance. In addition, the quality of acrylic pressure-sensitive adhesives has conventionally been generally controlled by using a polymerization degree regulator, and those with a high degree of polymerization have weak adhesive strength but have good cutting properties.・Although it shows strong adhesive strength, it was thought that cutting workability was poor. Furthermore, even if a pressure-sensitive adhesive with a polymerization degree intermediate between the two was synthesized, a pressure-sensitive adhesive with excellent adhesive strength and cutting processability could not be obtained, and there was a demand for the development of such a pressure-sensitive adhesive.

[Object of the present invention]

An object of the present invention is to provide a pressure-sensitive adhesive that has excellent adhesive strength and improved cutting processability.

Another object of the present invention is to use two types of acrylic polymers,
It has excellent adhesion to adherends such as films and molded products made of resins such as polyolefin and polybutadiene, which is better than conventional pressure-sensitive adhesives that are said to have strong adhesive properties, and is easy to process on a cutting machine. Another objective is to provide a pressure-sensitive adhesive with excellent adhesive strength (adhesive to non-polar adherends, excellent weather resistance, and less staining of the blade during guillotine cutting. The object of the present invention is to provide a pressure-sensitive adhesive that causes less blade staining when cutting slits and has good cutting properties when printing stickers.

Still other purposes will become clear from the description below.

[Means for solving problems]

The present invention includes (A) (al acrylic acid 05-10% by weight, FA)
Vinyl acetate 0 to 25% by weight, (c) at least selected from the group consisting of alkyl acrylates in which the alkyl group has 1 to 12 carbon atoms, and alkyl methacrylates in which the alkyl group has 1 to 12 carbon atoms; 5 to 50% by weight of one type of monomer and, if necessary, 5% by weight or less of a monomer having a functional group copolymerizable with these monomers, as a chain transfer agent. 150 to 90 parts by weight (solid content basis) of a low elasticity alkyl acrylate and/or alkyl methacrylate multi-component copolymer emulsion obtained by copolymerizing with 01 to 1% by weight of alkyl mercaptan having ~12 alkyl mercaptans. (B) (σ) Acrylic acid 0.5-10% by weight, (hl vinyl acetate O-25% by weight, (c) Alkyl acrylate in which the alkyl group has 1 to 12 carbon atoms and the number of carbon atoms in the alkyl group 70 to 95% by weight of at least one monomer selected from the group consisting of alkyl methacrylates having 1 to 12 pieces, and (d) 0.0% by weight of a crosslinkable monomer copolymerizable with these monomers. 1 to 3%, and if necessary, up to 5% by weight of a monomer having a functional group that can be copolymerized with these monomers, and if necessary, up to 0.1% by weight of the carbon of the alkyl group. 5 to 40 parts by weight of a highly elastic alkyl acrylate and/or meth, alkyl lylate multicomponent copolymer emulsion obtained by copolymerizing an alkyl mercaptan having 1 to 12 alkyl mercaptans as a chain transfer agent (solid The present invention relates to an emulsion-type pressure-sensitive adhesive characterized in that the active ingredient is

The present inventors pursued a pressure-sensitive adhesive with excellent adhesive strength and improved cutting processability, and as a result of repeated research, we found that the factors that have a large effect on these properties are It has been found that it is not the polymerization degree of the system polymer, but its elastic modulus.

The elastic modulus of the acrylic polymer is 10 mm in length and 0 in cross-sectional area.
．． A film of 25 mm2 is prepared, stretched at 1000%/min, and the relationship between stress and elongation is determined. The maximum stress is 2.
0 x 102 dyne/cLIL2 or more and elongation at break of 2000% or less is considered a high elastic copolymer, and the maximum stress is 5. A low elasticity copolymer is defined as a copolymer having OX 101 dyne /cT12 or less and an elongation at break of 3000% or more.

According to the present inventors, when a highly elastic copolymer is used, cutting workability is good, but adhesiveness is poor.

On the other hand, in the case of a copolymer with low elasticity, although the adhesive strength is excellent, the cutting processability cannot be said to be good.

Therefore, in order to obtain an adhesive that has both properties, copolymers with an intermediate elastic modulus were manufactured and studied, but it was not possible to obtain a desirable product with a good balance of both properties. In order to be used in pressure-sensitive adhesives, acrylic copolymers must exhibit viscoelasticity within a specific elastic modulus range, but as mentioned above, depending on the intermediate elasticity copolymer, cutting processability, Unable to obtain one that maintains the proper balance of adhesion. Therefore, the present inventors changed their point of view and tried blending the above-mentioned high elasticity copolymer and low elasticity copolymer in a specific ratio, and unexpectedly found a balance between both adhesive strength and cutting workability. They also discovered that an excellent pressure-sensitive adhesive can be obtained.

The present invention provides an emulsion of a low elasticity alkyl acrylate and/or alkyl methacrylate multi-component copolymer represented by FA) and a high elasticity represented by (B), the former being 5
The present invention relates to an emulsion-type pressure-sensitive adhesive obtained by blending the latter in a ratio of 0 to 90 parts by weight, and the latter in a ratio of 5 to 40 parts by weight, but its effects are not necessarily clear. However, by mixing low- and high-elasticity copolymers at the molecular or particle level and creating an apparent distribution of elastic modulus, it is possible to control the balance between the adhesive strength and cutting workability of pressure-sensitive adhesives. It is believed that we were able to provide a pressure-sensitive adhesive with adhesive strength and cutting processability that cannot be achieved with a single polymeric material.

Acrylic polymers with low elasticity are used as polymerization degree regulators (chain transfer agents) during polymerization in order to lower the degree of polymerization and reduce the entanglement of polymer chains. 12 alkyl mercaptans 0.1
It is necessary to use ~1 part by weight.

In addition, the highly elastic acrylic copolymer is crosslinked and increases the degree of polymerization, increasing the entanglement of polymer chains.
In order to obtain high elasticity, it is necessary to include 01 to 3% by weight of crosslinking monomers such as ethylene glycol dimethacrylate, glycidyl methacrylate, and divinylbenzene in the copolymerization component. 0.01% by weight or less of an alkyl mercaptan whose alkyl group has 1 to 12 carbon atoms may be used in combination.

In the low elasticity and high elasticity alkyl acrylate and/or alkyl methacrylate multi-component copolymer used in the present invention, the alkyl group to be copolymerized with the acrylic acid or vinyl acetate monomer has 1 to 12 carbon atoms. Monomer (c) includes methyl (meth)acrylate, ethyl (meth)acrylate, propylene (meth)acrylate, butyl (meth)acrylate, amyl (meth)acrylate, and (meth)acrylic acid. hexyl, hebutyl (meth)acrylate, octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate,
(meth)acrylic acid del/dyl and (meth)acrylic acid lauryl, etc., but particularly desirable ones have 2 to 2 carbon atoms.
It is an alkyl (meth)acrylate having 8 alkyl groups.

In addition, in these multi-component copolymers, if necessary, a monomer having a functional group copolymerizable with the above-mentioned monomer can be used as a copolymerization component. acids, α,β-unsaturated carboxylic acids such as methacrylic acid, crotonic acid, itaconic acid, maleic acid and hyfumaric acid;
Monomers having a human 90-xyl group such as human 80-xyethyl (meth)acrylate and hydroxyzolopyl (meth)acrylate; monomers having a glycidyl group such as glycidyl (meth)acrylate; Unsaturated carboxylic acid amides having an amide group such as acrylamide, N-methylol (meth)acrylamide, N-butoxymethyl (meth)acrylamide and diacetone (meth)acrylamide, and furthermore, amine groups such as melamine and vinylpyridine. There are monomers with

FA) low elasticity acrylic copolymer in the present invention is produced by combining the above monomer mixture with a suitable emulsifier, a dispersant such as a protective colloid, a radical polymerization initiator, and an alkyl group having 1 to 12 carbon atoms. Mercaptan 01-1% by weight
It can be produced by emulsion copolymerization in the presence of (chain transfer agent).

The high modulus acrylic copolymers of the present invention can likewise be produced as emulsion copolymers or solution copolymers.

The polymerization initiator for emulsion polymerization is potassium persulfate, and other inorganic peroxides may be used.

Polymerization initiators for solution polymerization include α, α'-azodiisobutyronitrile, penzoinope peroxide, acetyl peroxide, and t.
-butylhydro to ruoxy F, cumencht 50 to luoxoto, di-t-methyl peroxide, azodicyclohexylcarbonitrile α, α'-dimethyl azodiisobutyrate,
Co-phosphoric acid peroxide, dicumene peroxide, dichlorobenzoyl peroxide, etc. can be used.

The preferred solvent is ethyl acetate, but butyl acetate, benzene,
Other organic solvents such as cyclohexane, carbon tetrachloride, methanol, and toluene may also be used.

The pressure-sensitive adhesive composition of the present invention contains 50 to 90 parts by weight of the low modulus copolymer emulsion and 5 to 40 parts by weight of the high modulus copolymer emulsion (all based on solid content). ). Highly elastic copolymer is 4
If the amount is more than 0 parts by weight, the adhesive strength will decrease. In order to maintain good adhesion to polyolefin films and molded articles, which are non-polar and difficult to adhere, the content is desirably 30% by weight or less. On the other hand, when the amount of the low elastic copolymer is 90 parts by weight or more and the amount of the high elastic copolymer is 5 parts by weight or less.

When cutting with a guillotine, the adhesion to the blade increases, resulting in poor cutting performance.

The emulsion type pressure sensitive adhesive of the present invention can be used as is;
Or, if necessary, plasticizer, tackifier, thickener, pH
Conditioners, wetting agents, antifungal agents, and the like can be added.

Usually, in order to apply an emulsion-type pressure-sensitive adhesive, it is necessary to increase the viscosity to about 10,000 to 20,000 Cp, T. In this case, the thickeners include cellulose, polyvinyl alcohol, polyacrylate,
Polymer surfactants, alkali-thickened acrylic resins, and the like are useful.

Supports to which the emulsion-type pressure-sensitive adhesive of the present invention is coated include papers such as high-quality paper, art paper, coated paper, metallized paper, and kraft paper, HoIJ ethylene, polypropylene, polyester, acetate, and Examples include films such as H-solivinyl chloride and composites thereof.

〔Effect of the invention〕

The pressure-sensitive adhesive of the present invention, which is made by blending a low-modulus acrylic copolymer and a high-modulus acrylic copolymer in a specific ratio, is a pressure-sensitive adhesive with excellent adhesive strength and excellent cutting processability. It adheres particularly well to non-polar adherends, has excellent weather resistance, has little blade staining when cutting guillotines and slits, has good cutting properties when printing stickers, and has excellent adhesion and cutting workability. It has become possible to provide a pressure-sensitive adhesive that has both properties.

〔Example〕

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 2-ethylhexyl acrylate 80%, vinyl acetate 4%
, 15% methyl acrylate, 1% acrylic acid and 0.2% hydrodecyl mercaptan, 100% water, 1% potassium persulfate as a polymerization initiator, and Emar NO (+n lyoxyethylene alkylphenol ether sulfate) as an emulsifier. Add 5% of sodium (manufactured by Kako Atlas Co., Ltd.),
Copolymer emulsion (A) was synthesized by heating at 70°G for 20 hours in a flask equipped with a reflux condenser. Similarly synthesized or 79% 2-ethylhexyl acrylate to 70 parts of copolymer emulsion (A) (solid content 50%);
Add 30 parts of an acrylic copolymer emulsion (B) (solid content 50%) consisting of 4% vinyl acetate, 15% methyl methacrylate, 1% acrylic acid and 1% ethylene glycol dimethacrylate, and stir for 30 minutes to form an emulsion. A mold pressure sensitive adhesive was obtained.

The resulting adhesive had a solids content of 50%, a pH of 3.5, and a viscosity of 750 cps. Table 1 summarizes the results of the physical property evaluation described below for this adhesive. 10 minutes) at 20℃
Figure 1 shows the relationship between elongation and elongation stress when elongated at 1000%/min.

Copolymer A has a large elongation at break, low tensile stress, low elasticity, and high adhesiveness, but poor cutting workability.

Copolymer B has low elongation at break, high tensile stress, high elasticity, and low adhesiveness, but good cutting workability.

The product of the present invention (A1B, Lund product) has a breaking elongation of copolymer B.
It is equivalent to copolymer A, has better cutting workability than copolymer A, has significantly lower elongation stress and higher adhesive strength than copolymer B, and is a pressure-sensitive adhesive with a good balance of both properties.

Example 2 Acrylic copolymer emulsion (A) obtained by polymerizing 80% 2-ethylhexyl acrylate, 15% methyl methacrylate, 5% acrylic acid, and 0.5% dodecyl mercaptan in the same manner as in Example 1. An acrylic copolymer emulsion consisting of 78% 2-ethylhexyl acrylate, 15% methyl methacrylate, 5% acrylic acid, 2% divinylbenzene, and 0.05% dodecyl mercaptan based on 90 parts (solid content 50%) B) (Solid content 50%) 1
0 parts were mixed to obtain an emulsion type pressure sensitive adhesive. The solid content of this product is 50%, the pH is 40, and the viscosity is so
It was o cps. The results of these physical property evaluations are summarized in Table 1.

The physical properties of each emulsion-type pressure-sensitive adhesive obtained as described above were evaluated as follows.

A thickener (Blymar AEJ Knee 108, manufactured by Nippon Acrylic Co., Ltd.) was added to each of these, and the viscosity was adjusted to 15,000 to 20,000 using 25% ammonia water. Ocps (B
type viscometer, 6 rpm). Coat 25 to 30.97 m2 (after drying) of this emulsion-type pressure-sensitive adhesive on release paper, dry at 110°C for 2 minutes, and then apply
7 m2) to obtain adhesive paper.

This adhesive paper was tested for adhesive strength (
Adhesive strength) was determined by the 180 degree peeling method using a high-density polyethylene plate as the adherend at a peeling rate of 30 mV min at 20°C and 88°C.
The cutting processability was evaluated by stacking 100 samples and cutting them using an office guillotine cutting machine. Also, for comparison, strong adhesive tank paper for rough surfaces (Modern Plastic Co., Ltd.)
) as a control 1, strong adhesive tack paper (Fujishiko Co., Ltd. PZ2)
Comparison 2: Weighing label paper (Souken Kako Co., Ltd. PM-70)
0B) was used as Control 3, and similar tests were conducted on these as well. Table 1 shows the evaluation results of their physical properties.

As is clear from Table 1, the pressure-sensitive adhesives of Examples 1 and 2 have a high adhesive strength, and are particularly excellent in adhesion to adherends made of polyolefin, and also have excellent cutting workability. On the other hand, Control 1゜2 has excellent adhesion strength at °C, but the guillotine blade is heavily stained, and Control 3 has good cutting workability, but there is little guillotine blade stain and the adhesive strength is insufficient.

[Brief explanation of drawings]

FIG. 1 is a graph showing the relationship between elongation and tensile stress of copolymers A and B synthesized in Example 1 and the adhesive of the present invention obtained by mixing them.

Claims (3)

[Claims] (1) (A) (a) 0.5-10% by weight of acrylic acid, (
b) 0 to 25% by weight of vinyl acetate, and (c) selected from the group consisting of alkyl acrylates in which the alkyl group has 1 to 12 carbon atoms and alkyl methacrylates in which the alkyl group has 1 to 12 carbon atoms. at least one monomer 5
Alkyl acrylate and/or alkyl methacrylate obtained by copolymerizing ~50% by weight with 0.1 to 1% by weight of an alkyl mercaptan whose alkyl group has 1 to 12 carbon atoms as a chain transfer agent. Multi-component copolymer emulsion 50-90 parts by weight (solid content basis) and (B) (a) 0.5-10% by weight of acrylic acid, (b) 0-25% by weight of vinyl acetate, (c) carbon of alkyl group 70 to 95% by weight of at least one monomer selected from the group consisting of alkyl acrylates having 1 to 12 carbon atoms and alkyl methacrylates having 1 to 12 carbon atoms in the alkyl group; and (d) 5 to 40 parts by weight of an alkyl acrylate and/or alkyl methacrylate multicomponent copolymer emulsion obtained by copolymerizing 0.1 to 3% of a crosslinkable monomer copolymerizable with these monomers ( An emulsion-type pressure-sensitive adhesive characterized by having a solid content base) as an active ingredient. (2) The multi-component copolymer of either (A), (B) or both may further contain, as a copolymerization component, a monomer having a functional group copolymerizable with the monomer component described above. 5% by weight
The emulsion type pressure-sensitive adhesive according to claim 1, which contains the following: (3) A patent claim in which the multi-component copolymer of (B) further contains 0.1% by weight or less of an alkyl mercaptan whose alkyl group has 1 to 12 carbon atoms as a copolymerization component. The emulsion-type pressure-sensitive adhesive according to item 1 or 2.