JPH04211462A - Production of polymer emulsion - Google Patents

Abstract

PURPOSE:To provide a process for producing a polymer emulsion having excellent storage stability, giving a coating film having excellent nature and suitable as a paint. CONSTITUTION:A monomer (A) containing 2 or more polymerizable groups in one molecule and giving a polymer having a glass transition temperature of 50 deg.C or higher is emulsified in water to obtain an aqueous emulsion of the monomer. The monomer (A) is polymerized in the above emulsion together with a monomer (B) giving a polymer having a glass transition temperature of 40 deg.C or lower and a monomer (C) having a hydrophilic group. The polymerization is carried out in the presence of 0.05-0.36 pts.wt. of a water-soluble polymerization initiator while adding 2-50 pts.wt. of the monomer (B) and 0.1-5 pts.wt. of the monomer (C) to 100 pts.wt. of the monomer (A).

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention provides a polymer emulsion that has good storage stability, forms a coating film with excellent properties, and can be suitably used not only as a paint but also as an antistatic coating. Relating to a manufacturing method.

0002

[Prior Art] Water-based emulsion type paints, in which water is used as a dispersion medium, do not use organic solvents, so there is no need to worry about environmental pollution, the viscosity can be easily adjusted, and painting equipment can be easily cleaned with water. It has become widely used because of this.

[0003] The following monomers are generally used in aqueous emulsion type coatings. For example, 1 such as acrylic ester or methacrylic ester
Monomers with one polymerizable group in the molecule, monomers with two or more polymerizable groups in one molecule such as trimethylolpropane triacrylate and neopentyl glycol dimethacrylate as crosslinking agents, epoxy acrylate, Examples include photopolymerizable unsaturated compounds such as urethane-modified acrylates and, if necessary, monomers having hydrophilic groups such as acrylic acid and methacrylic acid.

[0004] In order to develop an aqueous emulsion type paint, the present inventors mixed aqueous emulsions of the various monomers described above, added a photopolymerization initiator to the mixture, and prepared a paint. Then, apply this paint to a PVC board,
It was cured by heating or ultraviolet irradiation.

[0005]

[Problems to be Solved by the Invention] However, the paints obtained in this way tend to suffer from a decrease in the stability of the emulsion and the formation of precipitates during long-term storage, poor film-forming properties, and poor film formation. The surface hardness of the coating film was not fully satisfactory.

[0006]

[Means for Solving the Problems] The present inventors have conducted extensive research in order to obtain a water-based emulsion type paint with excellent storage stability and film properties, and as a result, the glass transition point of the polymer has been Monomers and hydrophilic groups whose glass transition point of the polymer is 40°C or lower at a temperature of 50°C or higher and on the surface of an emulsion obtained by emulsifying a monomer having two or more polymerizable groups in one molecule. The inventors have discovered that the above object can be achieved by partially polymerizing a monomer having the following, and have completed the present invention.

That is, in the present invention, 100 parts by weight of the monomer is added to an aqueous emulsion of a monomer having a glass transition point of 50° C. or higher and having two or more polymerizable groups in one molecule. 2 to 50 parts by weight of a monomer whose glass transition point is 40°C or lower and 0 parts of a monomer having a hydrophilic group.
．． The total monomer to be polymerized is 10 parts by weight, adding 1 to 5 parts by weight.
This is a method for producing a polymer emulsion, characterized in that each of the above monomers is polymerized in the presence of a water-soluble polymerization initiator in an amount of 0.05 to 0.36 parts by weight relative to 0 parts by weight.

[0008] The monomer (hereinafter also simply referred to as monomer (A)) having two or more polymerizable groups in one molecule whose glass transition point is 50°C or higher is used in the present invention. , known compounds may be employed without any restriction. Specific examples are as follows. In the following description, acrylate and methacrylate are collectively referred to as (meth)acrylate. For example, neopentyl glycol diacrylate, trimethylolpropane triacrylate,
Polyfunctional monomers such as pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol hexaacrylate, tripropylene glycol diacrylate: epoxy (meth)acrylate, urethane (meth)acrylate, polyester acrylate, etc. Examples include monomers with relatively large molecular weights. These may be used in combination of two or more types as necessary.

In the present invention, in order to improve the film-forming properties of the resulting polymer emulsion and form a coating film with high surface hardness, the monomer (A) described above must have a glass transition temperature of 50 when polymerized. ℃ or higher, and those having a glass transition temperature of 100°C or higher and a large number of functional groups are more preferably used.

The aqueous emulsion of monomer (A) described above can be obtained by a known method. That is, it is a method in which the monomer (A) described above is added to water in which an emulsifier is dissolved, more preferably a dispersion stabilizer is dissolved, and the mixture is stirred.

[0011] As the emulsifier, anionic surfactants,
Examples include cationic surfactants, nonionic surfactants, and other reactive surfactants. Further, as the dispersion stabilizer, polyvinyl alcohol, hydroxyethyl cellulose, polyethylene glycol, etc. are used. These emulsifiers and dispersion stabilizers can be used directly in the emulsion polymerization step after emulsification.

[0012] The amounts of emulsifiers and dispersion stabilizers to be used are not particularly limited, but generally the above monomer (A) 1
00 parts by weight, 5 to 20 parts by weight and 10 to 10 parts by weight, respectively.
A range of 100 parts by weight is preferred. In addition, the amount of the monomer (A) relative to water should be 100 parts by weight of water in order to increase the stability of the polymer emulsion obtained by the present invention and to provide excellent film-forming properties as a coating material. It is preferable that the amount is in the range of 10 to 50 parts by weight.

Next, as the monomer (hereinafter also referred to as monomer (B)) whose polymer glass transition point is 40° C. or lower, any known compound may be employed without any restriction. Specific examples are as follows. n-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-hexyl (meth)acrylate, n-decyl (meth)acrylate, stearyl (meth)acrylate, glycidyl (meth)acrylate, cyclohexyl (meth)acrylate, Monomers such as lauryl (meth)acrylate are preferably used, and two or more of these may be used in combination if necessary.

[0014] The amount of the monomer having a glass transition point of 40° C. or lower is preferably in the range of 2 to 50 parts by weight per 100 parts by weight of the monomer (A) described above, depending on the properties of the coating film. and from the viewpoint of stability of the polymer emulsion.

[0015] Furthermore, the monomer having a hydrophilic group (hereinafter also referred to as monomer (C)) improves the storage stability of the polymer emulsion obtained by the present invention and the antistatic properties of the coating film. It is an essential ingredient for Examples of hydrophilic groups include hydroxyl groups, carboxyl groups, amino groups, substituted amino groups, phosphoric acid groups, and sulfonic acid groups. Examples of monomers having such hydrophilic groups include (
meth)acrylic acid, butanediol mono(meth)acrylate, N,N-dimethylaminoethyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate,
Examples include hydroxypropyl (meth)acrylate, 2-methoxyethyl (meth)acrylate, N-vinylpyrrolidone, and mono(2-methacryloyloxyethyl)acid phosphate. The amount of the monomer having a hydrophilic group added is 0.1 to 100 parts by weight of monomer (A).
It is preferable to use 5 parts by weight, preferably from 0.5 to 4 parts by weight, from the viewpoint of coating film properties and storage stability. Among the monomers having hydrophilic groups mentioned above, especially when mono(2-methacryloyloxyethyl) acid phosphate is used, it imparts excellent antistatic ability to the coating film formed by the resulting polymer emulsion. Further, it is preferable in the present invention because mono(2-methacryloyloxyethyl) acid phosphate and a monomer having another hydrophilic group are used together to improve the storage stability of the polymer emulsion. It is particularly preferred because it can also exhibit excellent antistatic ability.

Furthermore, in addition to the above-mentioned monomer whose glass transition point is 40° C. or lower and the monomer having a hydrophilic group, a fluorine-based monomer is added to 100 parts by weight of the above-mentioned (A). On the other hand, it is preferable to use 1 to 20 parts by weight in order to impart water repellency to the coating film of the resulting polymer emulsion. As the fluorine monomer, for example, 2
, 2,2-trifluoroethyl (meth)acrylate, 2
, 2,3,3-tetrafluoropropyl (meth)acrylate, 2,2,3,4,4,4-hexafluorobutyl (
Fluorine monomers such as meth)acrylates are preferably used.

In the present invention, the above monomer (A)
Emulsion polymerization is carried out while adding a monomer whose glass transition point is 40° C. or lower and a monomer having a hydrophilic group to the aqueous emulsion. It is not preferable to add a monomer whose glass transition point is 40° C. or less and a monomer having a hydrophilic group all at once, since this will cause aggregation of the emulsion. In order to obtain a stable polymer emulsion, the addition rate of both monomers is generally 0.1 to
It is preferably 2.0 g/min, more preferably in the range of 0.4 to 1.2 g/min. Moreover, these two monomers may be added separately, or a mixture thereof may be added.

[0018] Emulsion polymerization is preferably carried out at a temperature range of 50 to 68°C in order to prevent emulsion agglomeration. In addition, the addition of a monomer having a glass transition point of 40°C or less and a monomer having a hydrophilic group to the polymer described above should be carried out before and during the temperature rise to the temperature for emulsion polymerization. , it is preferable to start after the temperature is raised to prevent agglomeration of the polymer emulsion.

As the initiator used for emulsion polymerization, water-soluble polymerization initiators such as potassium persulfate, ammonium persulfate, and sodium thiosulfate are used. The amount added is from 0.05 to 0.36 parts by weight, preferably from 0.1 to 0.3 parts by weight, and less than 0.05 parts by weight. Polymerization is not initiated and 0
．． If it exceeds 36 parts by weight, the emulsion will aggregate, which is not preferable.

The polymer emulsion obtained according to the present invention contains hydroquinone, hydroquinone monomethyl ether, t-butylcatechol, P-benzoquinone, 2,
It is preferable to incorporate known thermal polymerization inhibitors such as 5-t-butylhydroquinone and phenothiazine. The amount added is 0.00 parts by weight per 100 parts by weight of the polymer emulsion.
The amount is preferably in the range of 0,001 to 0.1 part by weight.

In order to make the polymer emulsion obtained in the present invention photocurable, a photopolymerization initiator is added. Examples of photopolymerization initiators include benzoins such as benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin propyl ether, and α-methylbenzoin; anthraquinones such as 1-chloroanthraquinone and 2-chloroanthraquinone; benzophenone, P-
Benzophenones such as chlorobenzophenone and P-dimethylaminobenzophenone; diphenyl disulfide,
A photopolymerization initiator such as a sulfur-containing compound such as tetramethylthiuram disulfide is mixed. The blending amount of these photopolymerization initiators is 1:1 of the monomer before emulsion polymerization in the emulsion.
The amount is usually 0.05 to 20 parts by weight, preferably 0.5 to 10 parts by weight.

[0022] The method of addition is not particularly limited, but the following method is usually adopted. ■ Method of mixing with monomer (A) before emulsification of monomer (A) ■ Method of adding during emulsification of monomer (A) ■ Method of adding during emulsion polymerization ■ Method of adding after completion of emulsion polymerization At the same time, a tertiary amine can also be used as a photosensitizer to promote photopolymerization.

In addition, when the polymer emulsion obtained in the present invention is made thermosetting, benzoyl peroxide,
Organic peroxides such as diacyl peroxide; azo compounds such as azobisisobutyronitrile and azobisdimethylvaleronitrile are mixed.

[0024] The polymer emulsion obtained according to the present invention can be printed or coated on a substrate by a known method. For example, methods such as spraying, flow coating, dipping, application with a pad or roll, and brush application may be employed. The polymer emulsion coated or printed on the substrate in this manner is pre-dried and then cured to form a good cured coating film by heat curing, curing by ultraviolet irradiation, curing by electron beam irradiation, or the like.

[0025]

Effects of the Invention The polymer emulsion obtained according to the present invention does not precipitate even after long-term storage, and has good storage stability. Furthermore, the coating film obtained with this polymer emulsion has good surface hardness, water resistance, and adhesive strength to the substrate, and also has excellent antistatic ability. Therefore, the polymer emulsion obtained by the present invention can be used, for example, in molded products such as synthetic resin films, etc.
It can also be suitably used for paper, glass, stainless steel, stone, etc., and can be suitably used as a surface protective agent and antistatic agent.

[0026]

[Examples] Examples and comparative examples are listed below to specifically explain the present invention, but the present invention is not limited to these examples. The properties of the coating films obtained in the following Examples and Comparative Examples were evaluated by the following method.

(1) Appearance Visually observe the coating film. If it has good transparency and no sagging, spots, or cloudiness, it is ○, and if it is opaque or has sagging or spots, it is rated ×.
It was displayed in

(2) Pencil Hardness The surface hardness of the coating film was measured according to JIS D 0202 using a pencil hardness meter.

(3) Scratch The surface of the coating film was scratched with a fingernail, and the cases where no scratches were left were marked with ◯, and the cases with scratches were marked with ×.

(4) Adhesion After making 100 squares of 1 mm x 1 mm on the coating film with a sharp cutter knife, commercially available cellophane tape was applied and then quickly peeled off, resulting in the number of squares that remained without being peeled off. showed that.

(5) After immersing a hard polyvinyl chloride board on which a water-resistant coating film has been formed in water for 24 hours, rub the coating film with your fingertips. If no abnormality is observed at all, ○, if even the slightest is observed. is indicated with an x.

(6) Storage stability The prepared polymer emulsion was placed in a sample bottle, protected from light, and stored at room temperature for 90 days. Samples in which no precipitation occurred after storage were indicated by ○, and samples in which precipitation occurred were indicated by x.

(7) Viscosity The prepared polymer emulsion was measured using an E-type viscometer.

(8) The hard polyvinyl chloride plate on which the surface resistivity coating was formed was heated to 23°C and 50%
The sample was kept in an RH atmosphere for 24 hours, and the surface resistivity was measured.

(9) Drop a drop of water on the hard polyvinyl chloride plate on which the contact angle coating has been formed,
The contact angle with respect to water was measured.

Example 1 3 parts of nonionic surfactant (manufactured by Kao Corporation, trade name: Emulgen #950), 3 parts of polyvinyl alcohol, and 10 parts of water were added.
0 parts and stirred uniformly to obtain a polyvinyl alcohol dispersion. Urethane acrylate (manufactured by Daicel UCB Ltd., trade name EB) was added to 525 parts of this dispersion.
Add 100 parts of a mixture of 16.7 parts of ECRYL 1290) and 83.3 parts of trimethylolpropane triacrylate, and uniformly emulsify and disperse the mixture while stirring with a homomixer to form an emulsion of urethane acrylate-trimethylolpropane triacrylate. Obtained. Next, in a flask equipped with a thermometer, a stirrer, and a reflux condenser, 625 parts of the above urethane acrylate-trimethylolpropane triacrylate emulsion and a fluorine-based surfactant (manufactured by Neos Co., Ltd., trade name: Ftardient F- After adding 0.56 parts of 100) and heating to 65° C., 0.22 parts of potassium persulfate and 49 parts of deionized water were added under a nitrogen stream. Furthermore, from the dropping funnel, 2-ethylhexyl acrylate 1
A uniform mixture of 1.2 parts of acrylic acid and 0.7 parts of acrylic acid was added dropwise into the flask over about 20 minutes (addition rate: 0.8 g/min). After completion of the dropping, polymerization was carried out at 65° C. for 5 hours to obtain a polymer emulsion. To 100 parts of the monomer in the polymer emulsion thus obtained, 2 parts of a photopolymerization initiator (manufactured by Merck & Co., trade name: Darocure-1173) was added and mixed uniformly to prepare an emulsion composition. The obtained emulsion composition was coated on a hard polyvinyl chloride plate with a bar coater No. After drying, it was cured by irradiating ultraviolet rays from a height of 20 cm using a high-pressure mercury lamp (80 W/cm). The properties of the obtained coating film were evaluated and the results are shown in Table 1.

Comparative Example 1 0.56 parts of fluorosurfactant and 49 parts of deionized water were added to the urethane acrylate-trimethylolpropane triacrylate emulsion obtained in the same manner as in Example 1, and the mixture was poured into a dropping funnel with stirring. About 20 parts of a mixture of 11.2 parts of 2-ethylhexyl acrylate and 0.7 parts of acrylic acid was added.
It was added dropwise over several minutes and mixed uniformly. A photopolymerization initiator was added to the emulsion thus obtained in the same manner as in Example 1 to prepare an emulsion composition, and then evaluated in the same manner as in Example 1.
The results are shown in Table 1.

Example 2 and Comparative Example 2 In Example 1, the amount of potassium persulfate added was 0.39 parts,
All the same as Example 1 except that it was changed to 0.42 part and 0.45 part.
An emulsion composition was obtained in the same manner as above. Furthermore, the storage stability and coating film properties of this emulsion composition were evaluated in the same manner as in Example 1, and the results are shown in Table 1.

[Table 1]

Example 3 An emulsion composition was prepared in the same manner as in Example 1 except that the addition rates of monomer (B) and monomer (C) were changed as shown in Table 2. The results are shown in Table 2.

[Table 2]

Example 4 and Comparative Example 3 An emulsion composition was obtained in the same manner as in Example 1, except that monomers (A), (B) and (C) shown in Table 3 were used. The evaluation is shown in Table 3.

[Table 3]

Example 5 2-ethylhexyl acrylate and acrylic acid mono(
An emulsion composition was obtained in the same manner as in Example 1, except that 2.3 parts of 2-methacryloyloxyethyl) acid phosphate and a uniformly mixed mixture were added dropwise, and the evaluation thereof is shown in Table 4.

Example 6 2-ethylhexyl acrylate and acrylic acid with 2,
An emulsion composition was obtained in the same manner as in Example 1, except that 2,2-trifluoroethyl methacrylate was added in the amount shown in Table 4 and a uniformly mixed mixture was added dropwise, and the evaluation thereof is shown in Table 4. Ta.

[Table 4]

Claims (1)

[Claims] Claim 1: To an aqueous emulsion of a monomer having a glass transition point of 50° C. or higher and having two or more polymerizable groups in one molecule, based on 100 parts by weight of the monomer, Monomer 2 ~ whose polymer glass transition point is 40°C or less
Water-soluble polymerization of 0.05 to 0.36 parts by weight based on 100 parts by weight of the total monomers to be polymerized, while adding 50 parts by weight and 0.1 to 5 parts by weight of a monomer having a hydrophilic group. A method for producing a polymer emulsion, which comprises polymerizing each of the above monomers in the presence of an initiator.