JPH032293A - Production of acrylic adhesive - Google Patents

Abstract

PURPOSE:To obtain the subject adhesive having low viscosity and excellent wettability to releasing paper, etc., by polymerizing a monomer component containing a specific acrylic acid ester in an aqueous medium in the presence of a polymerizable emulsifier while adding a basic aqueous solution to the system. CONSTITUTION:The objective adhesive can be produced by polymerizing a monomer component containing an acrylic acid ester having a 4-12C alkyl group in an aqueous medium in the presence of a polymerizable emulsifier having one or more polymerizable functional groups [e.g. the emulsifier expressed by formula I to III (R is alkyl; n is normally 2-20)] while adding a basic aqueous solution such as an aqueous solution of ammonia to the system. The other monomer of the above monomer component is e.g. (meth)acrylic acid or acrylamide.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to a method for producing an acrylic adhesive, and more particularly to a method for producing an emulsion-type pressure-sensitive adhesive containing an acrylic resin as a main component.

Technical background of the invention and its problems Acrylic resins have been used as pressure-sensitive adhesives and the like.

When such an acrylic resin is used as a pressure-sensitive adhesive, the acrylic resin is usually applied in the form of an emulsion onto a release paper or the like. It is desirable that the acrylic adhesive used in this manner has excellent wettability (repellency resistance) to release paper and the like.

Furthermore, acrylic adhesives with low viscosity tend to be easier to apply uniformly than those with high viscosity. However, if the viscosity of the acrylic adhesive is lowered, its wettability to release paper etc. will be lowered.

Therefore, when such an acrylic adhesive is used, it is generally used after adjusting the wettability by adding a surfactant or the like.

However, the addition of such a surfactant may deteriorate the properties of the acrylic adhesive as an adhesive. That is, there is a problem in that the addition of a surfactant makes the adhesive hydrophilic and further deteriorates properties such as tackiness and adhesive strength. Further, the use of a surfactant causes the acrylic adhesive to become foamy, resulting in a problem that the workability when applying the acrylic adhesive is reduced.

Purpose of the Invention The present invention aims to solve the above-mentioned problems associated with the prior art, and aims to produce an acrylic adhesive that has low viscosity and excellent wettability to release paper, etc. The purpose is to provide a method to do so.

A further object of the present invention is to provide a method for producing an acrylic adhesive that has the above-mentioned excellent properties and generates less foaming during production and application.

Summary of the Invention The method for producing an acrylic adhesive according to the present invention is a method for producing an acrylic adhesive in which a basic aqueous solution is added in an aqueous medium in the presence of a polymerizable emulsifier having one or more polymerizable functional groups. ~
It is characterized in that a monomer component containing an acrylic ester having 12 alkyl groups is polymerized.

According to the method for producing an acrylic adhesive according to the present invention, a polymerizable emulsifier is used as described above, and since the monomer components are polymerized while adding a basic aqueous solution, the nonvolatile content is It is possible to produce an acrylic adhesive that has high viscosity, low viscosity, and excellent wettability to release paper and the like.

Moreover, since a polymerizable emulsifier is used, foaming can be suppressed during polymerization and during application of the acrylic resin.

DETAILED DESCRIPTION OF THE INVENTION Next, the present invention will be specifically explained with reference to a method for producing an acrylic adhesive.

In the method for producing an acrylic adhesive of the present invention, a monomer component containing an acrylic ester having an alkyl group having a specific number of carbon atoms is used.

The acrylic ester used in the present invention has an alkyl group having 2 to 12 carbon atoms, preferably 4 to 8 carbon atoms.

Examples of such acrylic esters include ethyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, octyl acrylate, and diacrylate.
- Ethylhexyl, isobutyl acrylate, isopentyl acrylate, isononyl acrylate, isodecyl acrylate and decyl acrylate.

Among these acrylic esters, it is particularly preferable to use butyl acrylate and 2-ethylhexyl acrylate. Such acrylic esters can be used alone or in combination.

The monomer component used in the present invention may contain other monomer components in addition to the above-mentioned acrylic ester.

As the monomer component having the above ability used in the present invention, there can be mentioned a compound having a reactive double bond copolymerizable with an acrylic acid ester.

Examples of such compounds include α,β-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and itaconic acid; Mention may be made of alkyl esters, acrylamide, acrylonitrile, vinyl acetate and styrene.

Among other such compounds, methacrylic acid,
Acrylic acid and acrylamide are preferably used.

In the present invention, the content of acrylic ester in the monomer components is usually 50 to 100% by weight, preferably 50 to 70% by weight. Therefore, the content of other monomer component units in the monomer component is 0 to 50% by weight.

This copolymerization is carried out in the presence of a polymerizable emulsifier having one or more polymerizable functional groups.

The polymerizable emulsifier that can be used in the present invention has at least one polymerizable functional group, and also has a hydrophobic group and a hydrophilic group.

Examples of such polymerizable emulsifiers include the following formulas [I] to [
Examples include emulsifiers represented by m].

However, in the above formulas [I] to [I[[], R represents an alkyl group, and n is usually an integer of 2 to 20.

The above polymerizable emulsifiers can be used alone or in combination.

Such a polymerizable emulsifier is generally used in an amount of 0.5 to 5 parts by weight, preferably 1 to 3 parts by weight, per 100 parts by weight of the monomer components.

Further, in the present invention, ordinary emulsifiers can be used in combination with the above-mentioned polymerizable emulsifiers.

As such other emulsifiers, anionic emulsifiers and nonionic emulsifiers can be used.

Examples of anionic emulsifiers that can be preferably used in the present invention include fatty acid soaps, n-acyl amyl acids and their salts, alkyl ester carboxylates, carboxylates such as acylated peptides; polyoxyethylene lauryl ether sulfate. Polyoxyethylene alkyl ether sulfates such as sodium; alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate; alkylnaphthalenesulfonates; salt formalin condensates of naphthalenesulfonic acid; dialkylsulfosuccinate ester salts; alkylsulfoacetates:
and α-olefin sulfonates, and examples of nonionic emulsifiers include polyoxyalkyl esters, single chain length polyoxyethylene alkyl ethers, polyoxyethylene secondary alcohol ethers, polyoxyethylene Alkyl phenyl ether, polyoxyethylene lanolin derivative, ethylene oxide derivative of alkylphenol formalin condensate, polyoxyethylene polyoxypropylene alkyl ether; polyoxyethylene glycerin fatty acid ester, polyoxyethylene castor oil and hydrogenated castor oil, polyoxyethylene sorbitan Fatty acid ester, polyoxysorbitol fatty acid ester; include polyethylene glycol fatty acid ester, fatty acid monoglyceride, polyglycerin fatty acid ester, sorbitan fatty acid ester, propylene glycol fatty acid ester and fatty acid alkanolamine, polyoxyethylene fatty acid amide, polyoxyethylene alkylamine, etc. I can do it.

When such other emulsifier is used, the amount of the other emulsifier is usually 0.5 to 100 parts by weight of the monomer component.
It is used in an amount of 5% by weight, preferably 0.5-3% by weight.

Polymerization using the above monomer components, a polymerizable emulsifier, and other emulsifiers blended as desired is carried out in an aqueous medium. As the aqueous medium, deionized water or distilled water is usually used.

The aqueous medium is generally used in an amount of 80 to 130 parts by weight, preferably 100 to 110 parts by weight, based on 100 parts by weight of the monomer components.

In the method of the present invention, the reaction can be carried out by adding a predetermined amount of the monomer component, a polymerizable emulsifier, other emulsifiers, etc. to an aqueous medium to prepare a dispersion of the monomer component. Preference is given to carrying out the reaction in the manner described.

First, an aqueous monomer dispersion containing a monomer component and an emulsifier is prepared.

In this case, the emulsifier used to prepare the monomer aqueous dispersion can be based on a normal emulsifier other than a polymerizable emulsifier, or a polymerizable emulsifier and a normal emulsifier may be mixed together. It can also be used as Moreover, a polymerizable emulsifier can also be used alone.

In this monomer aqueous dispersion, the monomer component and the emulsifier are preferably used in a weight ratio within the range of 100:0.5 to 100:5, particularly 100:0.5 to 100:
It is preferable to use the weight ratio within the range of :3. Further, the solid content in this monomer aqueous dispersion is usually adjusted within the range of 50 to 85% by weight, preferably 60 to 75% by weight.

Separately from the above monomer aqueous dispersion, an aqueous reaction mother liquor containing a reaction initiator and the like is prepared.

There is no particular restriction on the reaction initiator that can be used in the present invention, and ordinary reaction initiators can be used. Such reaction initiators include potassium persulfate, ammonium persulfate and azobiscyanovaleric acid. The amount of such a reaction initiator used is usually 0.00 parts by weight per 100 parts by weight of monomer components in the aqueous dispersion.
05 to 0.5 parts by weight.

Further, an emulsifier can also be blended into this aqueous reaction mother liquor.

In this case, it is preferable to use a polymerizable emulsifier as the emulsifier used to prepare the aqueous reaction mother liquor.

Further, a small amount of monomer components can also be blended into this aqueous reaction mother liquor. As the monomer component used in this case, it is preferable to use acrylic ester.

The concentration of the monomer components added to this aqueous reaction mother liquor is usually 10% by weight or less, preferably 5% by weight or less.

The solid content in this aqueous reaction mother liquor is usually 2 to 2.
It is adjusted within the range of 20% by weight, preferably 4 to 10% by weight.

In the present invention, when the aqueous reaction mother liquor contains a monomer component, the aqueous reaction mother liquor prepared as described above is heated, and when it does not contain a monomer component, it is heated. The reaction is initiated by adding the aqueous monomer dispersion to the aqueous reaction mother liquor. Then, a basic aqueous solution is added to this solution immediately after the start of this polymerization reaction. Examples of the method for adding the basic aqueous solution include a method of dropping the basic aqueous solution, a method of spraying the basic aqueous solution, and the like. Among these methods, it is particularly preferable to adopt the method of dropping a basic aqueous solution.

Examples of the basic aqueous solution used in the present invention include aqueous solutions of alkali metal hydroxides, alkaline earth metal hydroxides, ammonia, and amines. Particularly in the present invention, it is preferable to use an ammonia aqueous solution.

The concentration of the basic aqueous solution used here is usually 0.1 to
2.5% by weight, preferably in the range 0.2-1.0% by weight.

The aqueous monomer dispersion is added dropwise at a uniform rate.

The reaction time is usually 1 to 5 hours, preferably 2 to 5 hours.
It is 3 hours.

The basic aqueous solution described above can be added even after the polymerization reaction is completed, but it is usually added until at least 97% by weight, preferably at least 99% by weight of the monomer components to be reacted. It is desirable to continue adding.

Note that the above polymerization reaction is preferably performed in an inert gas atmosphere such as nitrogen gas.

The reaction solution thus obtained can be used as is as an acrylic adhesive. This acrylic adhesive usually has a solid content of 45 to 60% by weight, and the viscosity at 25°C measured using a BM type viscometer (NcL4-6 rpm) is usually 10 to 100%.
The viscosity is within the range of P/25°C, and the viscosity is usually about 50 to 100% lower than when no basic aqueous solution is added. Furthermore, this reaction solution has excellent wettability to release paper and the like. Therefore, the acrylic adhesive can be coated on the release paper without adding any component that improves wettability, such as a surfactant.

Effects of the Invention The method for producing an acrylic adhesive according to the present invention uses a polymerizable emulsifier as described above and polymerizes the monomer components while adding a basic aqueous solution, so it has a low viscosity. Moreover, it is possible to produce an acrylic adhesive that has excellent wettability to release paper and the like.

Furthermore, in the production method of the present invention, since a polymerizable emulsifier is used, foaming is less likely to occur during polymerization and when applying the obtained acrylic adhesive onto a release paper.

Next, the present invention will be explained by showing examples and comparative examples.
The present invention should not be construed as being limited by these. In the Examples and Comparative Examples shown below, the expression "1 part" means "part by weight j" unless otherwise specified.

Example 1 An emulsifier aqueous solution prepared by dissolving 1 part of sodium polyoxyethylene lauryl ether sulfate in 50 parts of deionized water,
94 parts of butyl acrylate, 3 parts of acrylic acid, and 1 part of acrylamide were dispersed under stirring to form a monomer aqueous dispersion 14.
9 parts were prepared.

Additionally, 0.0% of a 25% ammonia aqueous solution is added to 10 parts of deionized water.
5 parts were mixed to prepare 10.5 parts of a basic aqueous solution.

Separately, in a glass reactor equipped with a stirrer, a thermometer, a dropping funnel, a nitrogen gas inlet, and a reflux condenser, 40 parts of deionized water was added, and 0.2 parts of potassium persulfate was added.
The polymerizable emulsifier represented by the formula [11] (Anlox H5-
60, Nippon Nyukazai ■) 2 parts and butyl acrylate 2 parts
An aqueous reaction mother liquor was prepared.

Next, nitrogen gas was introduced into the glass reactor to replace the air in the reactor with nitrogen gas, and then the aqueous reaction mother liquor was heated to 82° C. to initiate the reaction.

Immediately after the reaction started, 149 parts of the aqueous monomer dispersion and 10.5 parts of the basic aqueous solution were added dropwise from this dropping funnel over 180 minutes to carry out emulsion polymerization. During this time, the temperature of the reaction solution was maintained at 82°C.

After 180 minutes, the temperature of the reaction solution was increased to 82℃ for another 120 minutes.
The polymerization reaction was completed by maintaining the temperature at °C. After cooling the reaction solution to 25° C., the pH value of the reaction solution was adjusted to around 7.0.

Reaction liquid obtained as above (acrylic adhesive)
The viscosity was measured using a BM type viscometer (Nn4-6 rpm).

The results are shown in Table 1.

In addition, the obtained acrylic adhesive was applied to release paper so that the film thickness after drying was 25 μm, and then at room temperature (23 ° C.
), and the state of the film thus formed was observed to evaluate the wettability of the acrylic adhesive.

The results are also listed in Table 1.

The meanings of the symbols added to Table 1 are as follows.

A: A film is uniformly formed over the entire surface of the release paper.

B: There is a part on the release paper where no film is formed.

C: There is a fairly wide area on the release paper where no film is formed.

In the present invention, the viscosity and wettability were measured or evaluated as described above.

Example 2 In Example 1, 1 part of sodium polyoxyethylene lauryl ether sulfate and a polymerizable emulsifier (Anl) were added to 50 parts of deionized water instead of 149 parts of the aqueous monomer dispersion.
96 parts of butyl acrylate and 3 parts of acrylic acid were added to an emulsifier aqueous solution in which 2 parts of oXH3-60% (manufactured by Nippon Nyukazai ■) were dissolved.
An aqueous reaction mother liquor was prepared using 153 parts of an aqueous monomer dispersion in which 1 part of acrylamide was dispersed under stirring, and 0.2 parts by weight of potassium persulfate was dissolved in 40 parts of deionized water. .

The aqueous reaction mother liquor as described above was heated to 82°C, and then the monomer aqueous dispersion and the basic aqueous solution were each dropped into the aqueous reaction mother liquor over 60 minutes. Polymerization was carried out in the same manner as in Example 1, except that the temperature was maintained at 0.degree. C., to produce an acrylic adhesive.

The viscosity and wettability of the obtained acrylic adhesive are listed in Table 1.

Example 3 In Example 1, the amount of acrylic acid in the aqueous monomer dispersion was 8 parts, and the amount of acrylic acid in the aqueous basic solution was 25%.
An acrylic adhesive was produced by polymerization in the same manner except that the amount of ammonia water used was 1.3 parts.

The viscosity and wettability of the obtained acrylic adhesive are listed in Table 1.

Example 4 In Example 1, the polymerizable emulsifier represented by formula [1] was used instead of the polymerizable emulsifier represented by formula [I] (Eleminol 15-2, manufactured by Sanyo Chemical Industries, Ltd.). , Polymerization was carried out in the same manner to produce an acrylic adhesive.

The viscosity and repellency resistance of the obtained acrylic adhesive are listed in Table 1.

Example 5 Same as in Example 1 except that U Frontier Nl77E1 (manufactured by Daiichi Kogyo Seiyaku ■) was used as the polymerizable emulsifier represented by formula [111] instead of the polymerizable emulsifier represented by formula [I]. Polymerization was carried out to produce an acrylic adhesive.

The viscosity and wettability of the obtained acrylic adhesive are listed in Table 1.

Comparative Example 1 In Example 1, 2 parts of sodium dodecylbenzenesulfonate was used instead of 2 parts of the polymerizable emulsifier represented by formula [I], and 0.5 part of the 25% ammonia aqueous solution was not used. , Polymerization was carried out in the same manner to produce an acrylic adhesive.

The viscosity and wettability of the obtained acrylic adhesive are listed in Table 1.

Comparative Example 2 An acrylic adhesive was produced in the same manner as in Example 1, except that 0.5 part of the 25% ammonia aqueous solution was not used.

The viscosity and wettability of the obtained acrylic adhesive are listed in Table 1.

Comparative Example 3 An acrylic adhesive was produced in the same manner as in Example 2, except that 0.5 part of the 25% ammonia aqueous solution was not used.

The viscosity and wettability of the obtained acrylic adhesive are listed in Table 1.

Table 1

Claims (3)

[Claims] (1) In the presence of a polymerizable emulsifier having one or more polymerizable functional groups, in an aqueous medium while adding a basic aqueous solution,
A method for producing an acrylic adhesive, which comprises polymerizing a monomer component containing an acrylic ester having an alkyl group having 4 to 12 carbon atoms. (2) The method for producing an acrylic adhesive according to claim 1, wherein the basic aqueous solution is an ammonia aqueous solution. (3) The monomer component contains one or more compounds among methacrylic acid, acrylic acid, and acrylamide, in addition to the acrylic ester having an alkyl group having 4 to 12 carbon atoms. The method for producing an acrylic adhesive according to claim 1.