JPH03134084A - Sprayable pressure-sensitive adhesive composition - Google Patents

Abstract

PURPOSE:To obtain an adhesive which is well sprayable without occurrence of a spider's web when spray coating is performed, by using a dispersion obtd. by the dispersion polymn. of a specified acrylic monomer in an org. solvent in the presence of a dispersant as a base. CONSTITUTION:A pressure-sensitive adhesive compsn. wherein an org. solvent dispersion of internally crosslinked polymer particles obtd. by dispersion- polymerizing 100 pts.wt. acrylic monomer consisting of 100-50 wt.% 4-22C alkyl acrylate and/or methacrylate and 0-50 wt.% copolymerizable unsatd. monomer in the presence of 1-200 pts.wt. dispersant in an org. solvent is used as a base. As the org. solvent used, those which do not dissolve a polymer prepd. from the acrylic monomer can be used and a proper solvent in accordance with the kind of the above described monomer can be used. As the polymn. initiator, an org. peroxide (e.g. benzoyl peroxide) is especially pref. as the polymer particles can be internally crosslinked only by using it.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention provides a sprayable pressure-sensitive adhesive based on an organic solvent dispersion of internally crosslinked acrylic polymer particles obtained by non-aqueous dispersion polymerization. Regarding the composition.

[Prior Art] Pressure-sensitive adhesives have traditionally been used either by being applied directly to the adhesive surface or as pressure-sensitive adhesive tapes being applied to one or both sides of a support such as a paper or plastic film. . In the former case, there are problems in terms of application to porous surfaces and workability, and in the latter case, there is a problem in that it is difficult to apply to uneven surfaces.

As a means to solve these problems, there is a method of using a sprayable J8 pressure adhesive composition and spraying this composition onto the adhesive surface.

Sprayable pressure-sensitive adhesive compositions include Japanese Patent Publication No. 461264
After filtering and drying the crosslinked polymer as seen in Publication No. 0,
Dispersed in organic solvent with high shear force, JP-A-61
It is known that polymer particles produced by emulsion polymerization are redispersed in an organic solvent as seen in Japanese Patent Publication No. 1-12765 (Japanese Patent Publication No. 1-12765). There are also examples where it is used as it is or after being redispersed in an organic solvent.

[Problem to be solved by the invention]

As described above, sprayable pressure-sensitive adhesive compositions have the problem that if they are in a solution type, they tend to form so-called "spider webs" that form rubbery threads during spraying. It has been considered to use it in the form of a dispersion using an aqueous medium or an organic solvent.

However, a dispersion using an aqueous medium has the disadvantage that drying is slow when spray coating.

In addition, in order to redisperse something polymerized in an aqueous medium into an organic solvent to make a dispersion, several steps of separation, washing, drying, and redispersion are required after polymerization, which has the disadvantage of poor work efficiency. There is.

In view of the above-mentioned conventional circumstances, the present invention provides "
The first object of the present invention is to provide a pressure-sensitive adhesive composition that can be sprayed well without producing "spider webs." A second object of the present invention is to directly obtain an organic solvent dispersion, which is the base of such a sprayable pressure-sensitive adhesive composition, without going through steps such as separation and redispersion.

[Means to solve the problem]

As a result of intensive studies to achieve the above object, the present inventors created an organic solvent dispersion containing internally crosslinked polymer particles by non-aqueous dispersion polymerization in an organic solvent, and used this as a base for sensitization. Knowing that by preparing a pressure-sensitive adhesive composition, it is possible to easily obtain a pressure-sensitive adhesive composition that can be sprayed well without producing "cobwebs" during spray coating;
The present invention has now been completed.

That is, the present invention provides 100 to 50% by weight of an acrylic acid alkyl ester and/or a methacrylic acid alkyl ester having an alkyl group having 4 to 22 carbon atoms (hereinafter referred to as (meth)acrylic acid alkyl ester) and copolymerizable therewith. obtained by dispersion polymerizing 100 parts by weight of an acrylic monomer consisting of 0 to 50% by weight of an unsaturated monomer in an organic solvent in the presence of 1 to 200 parts by weight of a dispersion stabilizer.
The present invention relates to a sprayable pressure-sensitive adhesive composition characterized in that it is based on an organic solvent dispersion of internally crosslinked polymer particles.

[Structure and operation of the invention]

The (meth)acrylic acid alkyl ester used as the main component of the acrylic monomer in the present invention has an alkyl group having 4 to 22 carbon atoms, preferably 8 to 18 carbon atoms, and has excellent pressure-sensitive adhesive properties. Furthermore, it is a material that provides polymers with excellent elastic properties. Specifically, butyl acrylate, amyl acrylate, 2-ethylhexyl acrylate, isononyl acrylate, decyl acrylate, lauryl acrylate, stearyl acrylate, and 2-methacrylate.
-Ethylhexyl, lauryl methacrylate, etc., and one or more of these may be used.

Examples of unsaturated monomers copolymerizable with this (meth)acrylic acid alkyl ester include acrylic acid, unsaturated carboxylic acids such as methacrylic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate. Examples include (meth)acrylic acid alkyl esters, glycidyl acrylate, acrylic acid amide, vinyl esters such as vinyl acetate and vinyl propionate, acrylonitrile, and styrene, in which the number of carbon atoms in the alkyl group is outside the above range, and one type of these Or two or more types are used.

In the present invention, an acrylic monomer consisting of 100 to 50% by weight of the above-mentioned (meth)acrylic late alkyl ester and 0 to 50% by weight of an unsaturated monomer copolymerizable therewith is used as a dispersion stabilizer. dispersion polymerization in an organic solvent in the presence of
An organic solvent dispersion of internally crosslinked polymer particles is obtained.

The organic solvent used here may be any organic solvent as long as it does not dissolve the polymer produced from the acrylic monomer, and one or more appropriate solvents may be used depending on the type of the monomer. - For boat fishing, polar solvents such as acetone and ethyl acetate are more suitable than non-polar solvents such as n-hexane, and in particular, those containing lower alcohols such as methanol and ethanol are most suitable.

In addition, when using a large amount of a relatively highly polar monomer such as butyl acrylate or amyl acrylate as the main component of the acrylic monomer, drying during spray coating may be necessary to further increase the polarity of the solvent. A small amount of water may be added within a range that does not impair the properties of the dispersion, thereby ensuring the stability of the dispersion.

When carrying out dispersion polymerization of acrylic monomers in such organic solvents, it is essential to use a dispersion stabilizer in order to ensure polymerization stability and stability of the resulting dispersion of polymer particles. The dispersion stabilizer is preferably a graft or block copolymer of a component that has an affinity with an organic solvent and a component that has an affinity with the generated polymer particles, but is not limited thereto. Any polymer may be used as long as it has an affinity for. However, in order not to impair the properties of a pressure-sensitive adhesive based on polymer particles, it is desirable that the dispersion stabilizer itself has a composition similar to that of a pressure-sensitive adhesive, and more preferably that the dispersion stabilizer itself has a composition of a pressure-sensitive adhesive. .

Examples of suitable dispersion stabilizers include, for example, when the organic solvent is a lower alcohol, acrylic acid alkyl esters such as ethyl acrylate and butyl acrylate, acrylic acid, itaconic acid, and 2-acrylamide-2
- Copolymers with polar group-containing monomers such as methylpropanesulfonic acid can be mentioned.

The amount of the dispersion stabilizer varies depending on the specific content of the polymerization system, but is generally in the range of 1 to 200 parts by weight, more preferably 5 to 100 parts by weight, per 100 parts by weight of the acrylic type or II form. It is better. If it is less than 1 part by weight, sufficient stability cannot be imparted to the dispersion of polymer particles, and if it is more than 200 parts by weight, the viscosity of the dispersion of polymer particles increases, resulting in poor spray coating properties. .

Polymerization initiators used in dispersion polymerization include organic peroxides such as lauroyl peroxide and benzoyl peroxide, 2,2-azobisisobutyronitrile, and 2,2-azobis(2,4-dimethylvaleronitrile). Among these, organic peroxides are particularly preferred because they can internally crosslink the polymer particles by themselves, as will be described later.

The acrylic monomer, polymerization initiator, and organic solvent during dispersion polymerization may be charged all at once at the start of polymerization, or monomers of the same composition or different compositions may be added dropwise one after another during polymerization. Good too.

When an organic peroxide is used as a polymerization initiator, the polymer particles produced by such dispersion polymerization become internally crosslinked within the particles, but when a polymerization initiator made of an azo compound is used, In some cases, such polymer particles may not be obtained at the end of polymerization. In this case, for example, after the completion of polymerization, an organic peroxide or other crosslinking agent may be added, and the same internally crosslinked polymer particles as described above may be produced by absorbing this into the polymer particles and causing the reaction. Can be done. Such appropriate addition means within the polymerization system can be arbitrarily employed in the present invention.

Note that whether or not the polymer particles are internally crosslinked can be easily confirmed by measuring their gel fraction. That is, the polymer particles produced by the dispersion polymerization of the present invention usually have a gel fraction in the range of 30 to 98%, and are clearly internally crosslinked.

In the present invention, the thus obtained organic solvent dispersion of internally crosslinked polymer particles may be directly applied to spray coating as a sprayable pressure-sensitive adhesive composition;
This dispersion may be used as a base for a pressure-sensitive adhesive composition adjusted to a desired composition and concentration.

It is particularly preferred that the dispersion polymerization is carried out at a high concentration and diluted to a suitable solvent composition before spray coating. In this way, the molecular weight of the polymer increases, it is easy to obtain a polymer with excellent adhesive properties, and it is also advantageous for internal crosslinking. Another advantage is that the solvent composition can be adjusted to be easy to spray without lowering the concentration more than necessary.

Unlike the organic solvent used in dispersion polymerization, the diluting solvent is not particularly limited in consideration of the solubility of the polymer particles, and any commonly used organic solvent may be used. Rather, the spray coating properties of the dispersion may be improved by using a relatively less polar solvent that can swell or dissolve the sol in the polymer particles.

In preparing the pressure-sensitive adhesive composition of the present invention as described above, tackifiers commonly used in pressure-sensitive adhesives,
Various additives may also be appropriately blended.

The pressure-sensitive adhesive composition of the present invention obtained in this way is
It can be sprayed well at high solids concentrations without leaving any spider webs.

〔Effect of the invention〕

As described above, the pressure-sensitive adhesive composition of the present invention directly produces an organic solvent dispersion containing internally crosslinked polymer particles by non-aqueous dispersion polymerization in an organic solvent, and can be sprayed using this as a base. A pressure sensitive adhesive composition can be prepared.

Since the pressure-sensitive adhesive composition of the present invention is composed of internally crosslinked polymer particles, it can be sprayed well without producing "spider webs." Furthermore, since it is an organic solvent dispersion, it has excellent drying properties that cannot be achieved with an aqueous medium. Furthermore, unlike in the case of polymerization in an aqueous medium, the organic solvent dispersion liquid that serves as the base can be obtained directly without going through the multiple steps of separation, drying, and redispersion into organic solvents, which improves work efficiency. Problems can be resolved.

〔Example〕

EXAMPLES Below, the present invention will be described in more detail by showing examples, but the present invention is not limited only to these examples. In the examples and comparative examples below, parts mean parts by weight.

Moreover, the gel fraction was measured by the following method.

<Gel fraction> The solid content obtained by drying the polymer under reduced pressure is wrapped in a Teflon membrane with a pore size of 0.2 μm, immersed in toluene, and left at room temperature for IO days. Dry the removed insoluble matter.

Weigh and calculate the gel fraction.

Example 1 120 parts of methanol, 1 part of 2-ethylhexyl acrylate
00 parts of ethyl acrylate-acrylic acid copolymer (weight ratio 9515, weight average molecular weight 580,000) as a dispersion stabilizer, 20 parts of lauroyl peroxide, and 0.4 parts of lauroyl peroxide were charged into four flasks and stirred well. and dissolved.

After nitrogen substitution, the internal temperature was raised to 55°C to initiate polymerization, and the polymerization was carried out at 60°C for 8 hours to obtain a milky white dispersion. The solid content concentration of the obtained organic solvent dispersion was 50% by weight. The gel fraction of the polymer particles was 58%, and the weight average molecular weight of the sol fraction was 930,000.

100 parts of ethyl acetate was added to 100 parts of this organic solvent dispersion and thoroughly stirred to prepare a pressure sensitive adhesive composition having a solid content concentration of 25% by weight. When the pressure-sensitive adhesive composition thus obtained was spray-coated onto a polyester film using a suction-type spray coating device with a nozzle diameter of 0.7, "spider webs" were generated. It was possible to spray well without any problems.

Example 2 40 parts of acetone, 30 parts of methanol, 95 parts of lauryl acrylate, 5 parts of acrylic acid, butyl acrylate-methacrylic acid copolymer as a dispersion stabilizer (weight ratio 90/l)
Four mixtures consisting of 10 parts of O1 (weight average molecular weight: 360,000) and 0.3 part of t-butylperoxyneodecanoate were charged into a flask and stirred to dissolve.

After nitrogen substitution, the bath temperature was raised to 45° C. to initiate polymerization, and the polymerization was carried out at 50° C. for 10 hours to obtain a milky white dispersion. The solid content concentration of the obtained organic solvent dispersion was 60
% by weight. The gel fraction of the polymer particles was 38%, and the weight average molecular weight of the sol fraction was 1) 50,000.

50 parts of ethyl acetate was added to 100 parts of this organic solvent dispersion and thoroughly stirred to prepare a pressure sensitive adhesive composition having a solid content concentration of 40% by weight. When the pressure-sensitive adhesive composition thus obtained was spray coated in the same manner as in Example 1,
It was possible to spray well without producing "spider webs".

Example 3 35 parts of ethyl acetate, 70 parts of methanol, 90 parts of lauryl methacrylate, 10 parts of vinyl acetate, butyl acrylate-acrylic acid copolymer as a dispersion stabilizer (weight ratio 951
A mixture consisting of 5 parts (weight average molecular weight: 400,000) and 0.4 parts of lauroyl peroxide was charged into a fourth flask and stirred well to dissolve.

After purging with nitrogen, the bath temperature was raised to 55° C. to initiate polymerization, and the polymerization was carried out at 60° C. for 10 hours to obtain a milky white dispersion. The solid content concentration of the obtained organic solvent dispersion was 5
It was 0% by weight. The gel fraction of the polymer particles was 34%, and the weight average molecular weight of the sol fraction was 770,000.

100 parts of acetone was added to 100 parts of this organic solvent dispersion and thoroughly stirred to prepare a pressure sensitive adhesive composition having a solid content concentration of 25% by weight. When the pressure-sensitive adhesive composition thus obtained was spray coated in the same manner as in Example 1,
It was possible to spray well without producing "spider webs".

Example 4 100 parts of methanol, 30 parts of stearyl acrylate, 70 parts of isononyl acrylate, 2-ethylhexyl acrylate-acrylic acid copolymer as a dispersion stabilizer (weight ratio 80/20, weight average molecular weight 420,000) ) and 0.5 part of bis(4-t-butylcyclohexyl) peroxydicarbonate were charged into four flasks and stirred well to dissolve.

After purging with nitrogen, the bath temperature was raised to 50'C to initiate polymerization, and polymerization was carried out at 60'C for 10 hours to obtain a milky white dispersion. The solid content concentration of the obtained organic solvent dispersion was 50% by weight. The gel fraction of the polymer particles is 72%,
The weight average molecular weight of the sol component was 640,000.

To 100 parts of this organic solvent dispersion were added 5 parts of ethyl acetate 1) and 5 parts of a terpene phenol resin (Sumilite PR-516038 manufactured by Juju Baklei [1]) and stirred well.
A pressure sensitive adhesive composition having a solid content concentration of 25% by weight was prepared.

When the pressure-sensitive adhesive composition thus obtained was spray coated in the same manner as in Example 1, it was successfully sprayed without generating "spider webs".

Comparative Example 1 In Example 1, polymerization was carried out using 0.4 part of 2,2-azobis(2,4-dimethylvaleronitrile) instead of lauroyl peroxide as a polymerization initiator. The gel fraction of the obtained polymer was 0%, and the weight average molecular weight of the sol fraction was 1.32 million.

A pressure-sensitive adhesive composition was prepared using the liquid after polymerization in the same manner as in Example 1, and this composition was spray-coated in the same manner as in Example 1, but "spider webs" were generated. However, I could not spray it properly.

Claims (6)

[Claims] (1) Acrylic acid consisting of 100 to 50% by weight of an acrylic acid alkyl ester and/or methacrylic acid alkyl ester whose alkyl group has 4 to 22 carbon atoms and 0 to 50% by weight of an unsaturated monomer copolymerizable therewith. System monomer 100
A spray characterized by being based on an organic solvent dispersion of internally crosslinked polymer particles obtained by dispersing and polymerizing 1 to 200 parts by weight of a dispersion stabilizer in an organic solvent. Possible pressure sensitive adhesive compositions. (2) The number of carbon atoms in the alkyl group of the acrylic acid alkyl ester and/or methacrylic acid alkyl ester is 8 or more
18. The sprayable pressure sensitive adhesive composition of claim 1. (3) Claim (1) or (3) wherein the organic solvent is a polar solvent.
The sprayable pressure-sensitive adhesive composition according to item 2). (4) Claim (3) in which the polar solvent contains lower alcohols
The sprayable pressure sensitive adhesive composition described in . (5) The sprayable pressure-sensitive adhesive composition according to any one of claims (1) to (4), wherein the polymerization initiator used in the dispersion polymerization is an organic peroxide. (6) Gel fraction of internally crosslinked polymer particles is 30 to 9
8%. A sprayable pressure sensitive adhesive composition according to any of claims (1) to (5).