JPH023404A - Preparation of aqueous dispersion of copolymer - Google Patents

Abstract

PURPOSE:To obtain an aq. dispersion having excellent adhesiveness to polyesters, papers, etc., and being capable of forming a self-adhesive film by performing emulsion-polymn. of a specified mixture of vinyl monomers in the presence of a water-soluble compd. CONSTITUTION:100 pts.wt. monomer mixture consisting of 60-99.8wt.% acrylate of a 4-8C aliph. alcohol (A) (e.g., butyl acrylate), 0.2-10wt.%, pref. 0.5-5wt.% functional monomer (B) selected from alpha,beta-unsatd. carboxylic acids (and its anhydrides), 2-hydroxyalkyl (meth)acrylates, (meth)acrylamide and methylol(meth) acrylamide and 0-30wt.% vinyl monomer except A and B is emulsion- polymerized in the presence of 0.01-10 pts.wt. water-soluble compd. selected from dihydrofuran, dihydropyran, methylcyclohexenedicarboxylic acid and norbornenedicarboxylic acid to obtain an aq. dispersion of a copolymer having a Tg of -10 to -90 deg.C.

Description

Detailed Description of the Invention (a) Object of the Invention (Field of Industrial Application) The present invention relates to a method for producing an aqueous copolymer dispersion, particularly a film having excellent adhesion to polyester, paper, and labels, especially adhesive. The present invention relates to a method for producing an aqueous copolymer dispersion that can form a drug film.

(Prior art) Conventionally, an aqueous dispersion of a copolymer with a low glass transition temperature of 11θ°C to -90°C obtained by emulsion polymerization of vinyl monomers has been used to form adhesive films and adhesive films. However, the film has the disadvantage of poor adhesion when the adherend has a surface with low polarity, such as polyethylene or polypropylene. A tackifier such as rosin or rosin ester was added to the copolymer dispersion after it was heated. However, when this tackifier was added, there was a problem in that the cohesive force was significantly reduced.

In order to improve the adhesion of a film formed from an aqueous copolymer dispersion obtained by emulsion polymerization of this type of vinyl monomer, t-dodecylmercaptan was added during emulsion polymerization.
It is known that the molecular weight of the resulting copolymer is controlled by the presence of a thiol-based chain transfer agent such as 3-mercaptopropionic acid. The chain transfer agent is contained in the polymer, and its odor becomes a problem. Although various proposals have been made to remove the odor of such chain transfer agents, it is well known that it is practically difficult to completely remove the odor from the resulting copolymer. Furthermore, it has been reported that the use of this type of chain transfer agent (sulfur-containing compound) reduces the durability of the resulting polymer because the sulfur-containing compound is bonded to the resulting polymer (% opening/closing 61 -228006
Publication No.).

Further, although the adhesive film of the aqueous dispersion of the copolymer obtained using this thiol-based chain transfer agent has good adhesive strength, it has a drawback of weak cohesive strength when a load is applied.

(Il! Problem to be Solved by the Invention) The present invention is directed to forming a film for an adhesive or pressure-sensitive adhesive that has excellent adhesive or pressure-sensitive adhesive performance and has high cohesive force (holding force). The purpose of the present invention is to provide a method for producing an aqueous copolymer dispersion of a vinyl monomer.

Φ) Structure of the invention (means for solving the problem) In the present invention, in the presence of a water-soluble dicarboxylic acid or its anhydride and a water-soluble unsaturated ether compound, a specific heptamer is added in a specific ratio. This goal was achieved by emulsion polymerization of the vinyl monomer mixture used in .

That is, the method for producing the copolymer aqueous dispersion of the present invention is as follows: (A 70 to 94% by weight of acrylic ester of aliphatic saturated alcohol having 4 to 8 carbon atoms, CB) α,β-unsaturated carboxylic acid, α , β-unsaturated Kahlua? 0.2 to 10% by weight of a monomer having a functional group selected from acid anhydride, 2-hydroxyalkyl acrylate, 2-hydroxyalkyl methacrylate, acrylamide, methacrylamide, methylol acrylamide, and methylol methacrylamide, and C) the above. 100 parts by weight of a vinyl monomer mixture consisting of 0 to 30% by weight of vinyl monomers other than ω) and ω) selected from dihydropyran, dihydrofuran, methylcyclohexenedicarboxylic acid, norbornenedicarboxylic acid, and acid anhydrides thereof. Water soluble compound 0.01-10
The present invention provides a method for producing an aqueous copolymer dispersion, which is characterized by carrying out emulsion polymerization in the presence of parts by weight.

The water-soluble compound present during the emulsion polymerization of the present invention is represented by the following structural formula, for example.

Since the water-soluble compound having a double bond is allowed to exist during the emulsion polymerization of the present invention, the compound having the double bond acts as a chain transfer agent in the polymerization reaction.
The molecular weight of the produced copolymer can be effectively lowered, and the adhesive strength and adhesive force of the produced copolymer can be improved without causing a decrease in the cohesive strength of the produced copolymer. Moreover, these water-soluble compounds having double bonds are bound to the produced copolymer and included in the copolymer, but like thiol-based chain transfer agents,
There is no risk of imparting a bad odor to the resulting copolymer.

Furthermore, since this water-soluble compound having a double bond is allowed to exist during the emulsion polymerization of the present invention, the copolymer of the aqueous dispersion produced contains these digmene, and is a base material for polyester, paper, etc. Adhesion to materials is significantly improved.

Although water-insoluble compounds having double bonds, such as cyclohexene and cyclopeptene, have chain transfer ability, it is not possible to obtain a polymer that has high adhesive strength and exhibits excellent cohesive strength.

The amount of the compound having a water-soluble double bond used in the present invention is 0 parts by weight based on 100 parts by weight of the total amount of vinyl monomers.
．． 01 to 10 parts by weight, preferably o, i to 3 parts by weight. If the proportion of the compound used is too small, the chain transfer effect will not be sufficient, and the amount of the compound contained in the resulting copolymer will be too small, resulting in a copolymer with poor performance as an adhesive or pressure-sensitive adhesive. They will coalesce and the cohesive force will decrease.

In addition, if the proportion of the compound used is too high, the chain transfer effect becomes too high, resulting in the molecules of the resulting copolymer being cut and having an extremely small molecular weight9, making it unsuitable for adhesives and pressure-sensitive adhesives. This results in a copolymer with poor performance.

The monomer used in the present invention has 4 to 8 carbon atoms.
is an acrylic ester of aliphatic saturated alcohol,
This monomer is a monomer that provides a homopolymer with a glass transition point of 130°C or lower. Specific examples include butyl acrylate, 2-ethylhexyl acrylate, and the like. The amount of monomer (4) used is 70 to 94% by weight based on the total monomer weight. If the amount of monomer (A) decreases too much, the flexibility of the film will be lost.

Furthermore, the monomer (B) used in the present invention is α,
-COOH, -OH selected from β-unsaturated carboxylic acid, α9β-unsaturated carboxylic acid anhydride, 2-hydroxyalkyl acrylate, 2-hydroxyalkyl methacrylate, acrylamide, methacrylamide, methylolacrylamide and methylmethacrylamide ,−
It is a monomer having an NH2 functional group. Examples of α,β-unsaturated carboxylic acids include acrylic acid, methacrylic acid, and itaconic acid. In addition, the alkyl group in 2-hydroxyalkyl acrylate and 2-hydroxyalkyl methacrylate has 1 to 5 carbon atoms.
Examples include alkyl groups. The amount of monomer 03) used is 0.2 to 10% by weight, preferably 0.5 to 5% by weight, based on the total amount of monomers. If the amount used is too large, the water resistance of the film will deteriorate, and if it is too small, the adhesive performance will be reduced.

In the present invention, the vinyl monomer 0 has a carbon number of 1.
~4 aliphatic saturated alcohol methacrylic acid ester and vinyl monomers other than the components (1) and @) above. Specific examples thereof include methyl methacrylate, ethyl methacrylate, propyl methacrylate, butyl methacrylate, acrylonitrile, vinyl acetate, styrene, and methyl acrylate. Generally, if the homopolymer uses too much vinyl monomer which gives a polymer with a glass transition point of 60°C or higher, the copolymer becomes unsuitable for adhesives or pressure-sensitive adhesives, so the amount of monomer 0 used is The amount of 30i should be 5 or less per 1 By of total monomers.

In the production method of the present invention, the above monomers (4) to C
) By appropriately adjusting the type and combination of copolymers, the glass transition point (Tg) of the copolymer of the resulting copolymer dispersion can be set to -10 to -90°C. Aqueous dispersions of polymers are particularly suitable as dispersions for forming adhesive films.

In the present invention, the monomer mixture (ioo parts by weight) using the above monomers (1) to (0) in respective proportions is converted into a compound selected from dihydrofuran, dihydrobilane, methylcyclohexenedicarboxylic acid, norbornenedicarboxylic acid, and anhydrides thereof. Emulsion polymerization is carried out in the presence of 1 part of o, o i to 10i, and the emulsion polymerization itself can be carried out by various methods including known methods. For example,
As the polymerization initiator, inorganic peroxides such as sodium persulfate, potassium persulfate, and ammonium persulfate; organic peroxides such as tertiary hydroperoxide, benzoyl peroxide, and ditertiary butyl peroxide; Conjugate oxidation using a reducing agent
Reductive initiator; active azo compounds such as azobisisobutyronitrile are used. Further, as the emulsifier, an emulsifier used in ordinary emulsion polymerization can be used.

(Examples etc.) Below, Examples and Comparative Examples will be given and further explained in detail. "Parts" in these examples mean parts by weight.

Example 1 Temperature regulator, anchor type stirrer, reflux condenser, supply container,
330 parts of water in a reactor equipped with a thermometer and a nitrogen inlet tube;
1 part of IJum (and persulfuric acid) was charged.

Separately, the following was prepared as feed ■Feed I 2-ethylhexyl acrylate 1300 parts Methyl methacrylate 130 parts Vinyl acetate
130 parts acrylonitrile
30 parts acrylic acid 30 parts dihydropyran 8 parts water
650 parts 20 moles of ethylene oxide 106 parts of a 30% by weight aqueous solution of the sodium salt of the sulfuric ester of p-nonylphenol (anionic emulsifier) reacted An initiator solution was prepared.

After purging the inside of the reactor into which the above initiator solution had been charged in advance with nitrogen gas, 10% by weight of the above feed 1 was added into the same reactor, and the mixture was heated to 90°C. After 10% by weight of (1) was injected into the same reactor, feed (1) and the remainder of feed (2) were gradually and uniformly fed into the same reactor in parallel over a period of 3 to 3.5 hours. After the supply was finished, emulsion polymerization was carried out by keeping the temperature at 90°C for 1.5 hours to obtain a copolymer dispersion.The copolymer concentration of the copolymer dispersion was about 5
I won 7 weights.

Examples 2 to 4 Aqueous copolymer dispersions were produced according to the method of Example 1 except that the monomer composition and chain transfer agent were changed as shown in Table 1.

Comparative Example 1 Example 1 except that dihydropyran was not used at all.
An aqueous copolymer dispersion was prepared in the same manner as described above.

Comparative Examples 2 to 3 A copolymer dispersion was produced in the same manner as in Example 1 except that t-dodecylmercaptan or 3-mercaptopropionic acid was used instead of dihydrofuran.

=3・ Notes to Table 1: The method and evaluation of each test are as follows.

■ Preparation of test pieces First, add 1f of the thickener Latecol D [trade name of Mitsubishi Yuka Perdice ■] to 200f of each copolymer aqueous dispersion.
was added to silicone release paper using a wire bar so that the solid content was 259/rrl, and after drying at 100°C for 2 minutes, high-quality paper (got/m") was pasted and a test piece was prepared. It was created.

■ Adhesion test (*l) The above test piece (2.5 x 1 om) was glued to a polished stainless steel plate (SUS) or a polyethylene plate, and the bond was tested using an Instron tensile tester. Power tested.

■ Cohesive force (holding force) test The above test piece (2 x 2 m) was glued to a surface-polished stainless steel plate (SUS), a load of 1# was applied, and the temperature was 40°C.
#Toho (time until t9 falls) was measured under conditions of 65% humidity.

■ Odor test The odor of the above dried test piece was examined with the nose and evaluated according to the following criteria: ◎...Almost no odor.

Q...There is an odor.

X: Significant odor.

(e) Effects of the invention The copolymer aqueous dispersion obtained by the production method of the invention can form a film with excellent pressure-sensitive adhesive and adhesive properties,
In particular, the film has excellent adhesion to the surface of low-value materials such as polyolefin. Further, the film has no odor unlike the films of aqueous copolymer dispersions obtained using conventional thiol-based chain transfer agents.

Patent applicant Mitsubishi Yuka Pardische Co., Ltd. Agent
Patent Attorney Masahisa Hase Agent Patent Attorney Takaya Yamamoto

Claims (1)

[Scope of Claims] 1) (A) 60 to 99.8% by weight of acrylic ester of aliphatic saturated alcohol having 4 to 8 carbon atoms, (B) α,β-unsaturated carboxylic acid, α,β-unsaturated Saturated carboxylic anhydride, 2-hydroxyalkyl acrylate,
0.2 to 10% by weight of a monomer having a functional group selected from 2-hydroxyalkyl methacrylate, acrylamide, methacrylamide, methylol acrylamide, and methylol methacrylamide, and (C) a vinyl type other than the above (A) and (B). Monomer 0
100 parts by weight of a vinyl monomer mixture consisting of ~30% by weight, 0.01 to 10 parts by weight of a water-soluble compound selected from dihydropyran, dihydrofuran, methylcyclohexenedicarboxylic acid, norbornenedicarboxylic acid, and acid anhydrides thereof. A method for producing an aqueous copolymer dispersion, comprising emulsion polymerization in the presence of. 2) The glass transition point of the copolymer of the aqueous dispersion is -10 to -
The manufacturing method according to claim 1, wherein the temperature is 90°C.