JPH0439314A - Aqueous dispersion - Google Patents

Abstract

PURPOSE:To obtain an aqueous dispersion suitable as primers for coatings, adhesives, etc., by carrying out graft copolymerization of a styrene.butadiene block copolymer (hydrogenated polymer) with a specific amount of a hydroxyl group-containing alpha,beta-unsaturated vinyl monomer and dispersing the resultant graft polymer in water. CONSTITUTION:Graft copolymerization of styrene.butadiene block copolymer [preferably a block copolymer expressed by the structural formula of the formula (S is styrene polymer block; D is butadiene copolymer block; m is 0 or 1)] or hydrogenated copolymer thereof with 0.05-25wt.%, preferably 0.5-10wt.% hydroxyl group-containing alpha,beta-unsaturated vinyl monomer [e.g. hydroxyethyl (meth)acrylate]. The resultant modified polymer in an amount of 5-70pts.wt. is then dispersed in 95-30pts.wt. water to afford the objective aqueous dispersion especially suitable as primers for coatings, adhesives, etc., of molded polyolefin products.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to an aqueous dispersion, and particularly to an aqueous dispersion that can be used as an undercoat for a molded article to improve the adhesion of a paint to the surface of the molded article.

<Prior Art> Conventionally, the surface of a molded product made of polyolefin such as polypropylene is coated to increase its added value. However, polyolefins generally have poor polarity and poor paint adhesion. Therefore, conventionally, the surface of the molded article is treated with a brimer in advance to improve the adhesion and adhesion of the paint.

Therefore, as a binder for a paint that can be applied in one coat directly to molded products without the need for a brimer, styrene-butadiene-styrene block copolymer (meth) Resin compositions for coatings obtained by polymerizing acrylic esters, particularly vinyl monomers having hydroxyl groups, have been proposed.

(Unexamined Japanese Patent Publication No. 63-51477) <Problems to be Solved by the Invention> However, even if the resin composition for paint described in JP-A No. 63-51477 is used, the resulting coating film is Peel strength is not sufficient. Additionally, all conventional brimers, including this composition, contain organic solvents or are used after being dissolved in organic solvents, which poses the problem of deteriorating the working environment during manufacture and use. .

Therefore, the present invention has excellent adhesion to resin molded articles, especially polyolefin molded articles such as polypropylene, so it is possible to obtain a coating film with sufficient peel strength, and since it is an aqueous system that does not use organic solvents, The object of the present invention is to provide an aqueous dispersion suitable as a primer that can maintain a good working environment.

<Means for Solving the Problems> In order to solve the above problems, the present invention provides a styrene-butadiene block copolymer or a hydrogenated product thereof with zero α,β-unsaturated vinyl monomers having hydroxyl groups. .05~2
An aqueous dispersion obtained by dispersing in water a modified polymer obtained by graft copolymerization so as to contain 5% by weight, the aqueous dispersion containing 95 to 30 parts by weight of water to 5 to 70 parts by weight of the modified polymer. It provides a dispersion.

Further, it is preferable that the α,β-unsaturated vinyl monomer having a hydroxyl group is a (meth)acrylic ester of a monohydric alcohol or a mono(meth)acrylic ester of a polyhydric alcohol.

The present invention will be explained in detail below.

The styrene-butadiene block copolymer, which is the main component of the modified polymer that is a constituent component of the aqueous dispersion of the present invention, is
It is a copolymer containing a styrene polymer block which is a repeating structural unit derived from one or more styrene and a butadiene polymer block which is a repeating structural unit derived from one or more butadiene, for example, the general formula %. % (In the formula, S represents a styrene polymer block, D represents a butadiene polymer block, and n is an integer of 1 or more.) Preferably, < is the following formula.

-D-3- (wherein S and D are the same as above, and m is 0 or 1).

This styrene-butadiene block copolymer is described, for example, in U.S. Pat.
Examples include those manufactured by the method described in Japanese Patent No. 192743 and the like. Specific examples of this styrene-butadiene block copolymer include those commercially available as Kraton 1101 and 1102 (both manufactured by Shell Chemical Co., Ltd.).

Further, the hydrogenated product of this styrene-butadiene block copolymer can be produced by the method described in, for example, Japanese Patent Publication No. 43-6636, Japanese Patent Publication No. 45-20504, Japanese Patent Publication No. 48-3555, etc. Examples include things that are done. As a specific example of the hydrogenated product of this styrene-butadiene block copolymer, Kraton G-
Examples include those commercially available as 1652 (Shell Chemical Co., Ltd.).

These styrene-butadiene block copolymers or their hydrogenated products are suitable for gel permeation at 40°C using tetrahydrofuran as a solvent, from the viewpoint of peel strength and solid content concentration of the coating film of the aqueous dispersion of the present invention. The number average molecular weight measured by chromatography is lXl0'~
18X10' is preferred, especially 1.5X1
Preferably, it is 0' to 12X10'. In addition, the styrene content is determined by the adhesion of the coating film of the aqueous dispersion of the present invention,
10 to 6 in terms of peel strength, low temperature properties, stickiness, etc.
Preferably 0% by weight, especially 12-55% by weight
It is preferable that

The aqueous dispersion of the present invention comprises a styrene-butadiene block copolymer or a hydrogenated product thereof (hereinafter simply referred to as a block copolymer) containing an α,β-unsaturated vinyl monomer having a hydroxyl group. It is made by dispersing in water a modified polymer obtained by graft copolymerizing vinyl monomers (hereinafter simply referred to as vinyl monomers).

Examples of this vinyl monomer include hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 2-hydroxy-3-phenoxypropyl (
(meth)acrylic acid esters of monohydric alcohols such as meth)acrylate, 3-chloro-2-hydroxypropyl(meth)acrylate; glycerin mono(meth)acrylate, pentaerythritol mono(meth)acrylate, trimethylolpropane mono( Mono(meth)acrylic acid esters of polyhydric alcohols such as meth)acrylate, tetraethylolethane mono(meth)acrylate, butanediol mono(meth)acrylate, polyethylene glycol mono(meth)acrylate; 10-undecen-1-ol , 1-octen-3-ol, 2
-Methanol norbornene, hydroxystyrene, hydroxyethyl vinyl ether, hydroxyethyl vinyl ether, N-methylol acrylamide, 2-(meth)acryloyloxyethyl acid phosphate, glycerin monoallyl ether, allyl alcohol, allyloxyethanol and the like. Among these, (meth)acrylic esters of monohydric alcohols or mono(meth)acrylic esters of polyhydric alcohols are preferably used.

This vinyl monomer is graft copolymerized to the above-mentioned block copolymer to form a modified polymer in an amount of 0.05 to 25% by weight, preferably 0.5 to 10% by weight. By using such a modified polymer, it is possible to obtain an aqueous dispersion that forms a coating film with excellent adhesion and water resistance.

The production of the modified polymer which is a constituent component of the aqueous dispersion of the present invention can be carried out, for example, by adding the vinyl monomer to the block copolymer in the presence of a radical polymerization initiator, in the presence or absence of an inert solvent. It can be obtained by graft copolymerization.

As a method for graft copolymerization in the presence of an inert solvent, for example, 10 m of a block copolymer is added to 1 m of an inert solvent.
~3000kg, preferably 20~], OOOkg
After dissolving and preparing a solution, a vinyl monomer is sequentially added thereto at a rate of 0.5 to 100 mmol/min, preferably 1 to 20 mmol/min, per 1 kg of block copolymer in the solution. There is a method of reacting by sequentially adding a radical polymerization initiator at a rate of 5X10-' to 50 mmol/min, preferably 1X10-' to 5 mmol/min per 1 kg of block copolymer. The molar ratio of initiator/vinyl monomer is usually 1/100 to 315, preferably 1/20 to 1.
/2 range. In addition, the reaction is preferably carried out under heating and stirring, and the reaction temperature is 50°C or higher, particularly 80°C to
The temperature range is preferably 00°C, and the reaction time is about 2 to 10 hours. The reaction method may be either a batch method or a continuous method, but a batch method is preferable in order to perform the graft copolymerization uniformly.

In addition, as a method for performing graft copolymerization in the absence of an inert solvent, for example, the block copolymer is A method may be mentioned in which the reaction is carried out by heating and melting the copolymer and stirring it vigorously. Furthermore, the block copolymer, the vinyl monomer, and the radical polymerization initiator can be mixed in advance, and the mixture can be heated and melted in an extruder and graft copolymerized while being extruded. In the method carried out in the absence of these inert solvents, the amount of vinyl monomer and radical polymerization initiator used, the ratio of both, etc. are the same as the method carried out in the presence of the above-mentioned inert solvent. .

Examples of the radical polymerization initiator used in the graft copolymerization include benzoyl peroxide, dichlorobenzoyl peroxide, dicumyl peroxide, di-t
-butyl peroxide, 2,5-dimethyldi(peroxybenzoate) hexyne-3,1,4-bis(1-
butylperoxyisopropyl)benzene, lauroylperoxide, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3,2,5-dimethyl-
Organic peroxides such as 2,5-di(1-butylperoxy)-hexane: t-butylberacetate, t-butylberbenzoate, t-butylberphenylacetate, t-butylperisobutylene-1, t- Organic bersesters such as butylbery S-octoate, t-butyl bibarate, cumylberbivalate, t-butylberdiethyl acetate; azo compounds such as azobisisobutyronitrile, dimethylazoisobutyronitrile, etc.; Preferred are organic peroxides and organic bersesters.

The aqueous dispersion of the present invention is obtained by dispersing the modified polymer obtained as described above in water. Methods for producing the aqueous dispersion of the present invention by dispersing a modified polymer in water include, for example, a drum emulsification method in which the modified polymer, water, and a surfactant are mixed together and emulsified; The pulverization method involves dispersing the modified polymer in water together with a surfactant, and the solvent replacement method involves mixing the modified polymer dissolved in an organic solvent with a surfactant and water, and then removing the organic solvent. ; a homomixer method in which dispersion is carried out using a homomixer; a phase inversion method, etc., which are appropriately selected depending on the physical properties of the modified polymer used.

As the surfactants used, mention may be made of nonionic and anionic surfactants. Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene alkyl ether, polyoxyethylene alkylamine ether, and the like.
Examples of the anionic surfactant include fatty acid salts, higher alcohol sulfates, sodium alkylbenzenesulfonates, naphthalenesulfonic acid formalin condensates, polyoxyethylene alkyl ether sulfates, and sodium alkylbenzenesulfonates are particularly preferred.

The amount of this surfactant used is usually 0.05% based on the amount of the modified polymer, in order to ensure a good dispersion state of the modified polymer and good adhesion of the resulting aqueous dispersion to the molded product. ~1
It is preferably about 0% by weight, particularly preferably 0.1 to 7% by weight.

The ratio of modified polymer and water used in the aqueous dispersion of the present invention is 95 to 3 parts by weight of water to 5 to 70 parts by weight of modified polymer.
The proportion is appropriately selected within the range of 0 parts by weight. In particular, when spraying the aqueous dispersion of the present invention, uneven coating occurs on the coated surface, and variations in the adhesion of the coating film are less likely to occur, and the formed coating layer is The content is preferably 3 to 45% by weight, since it does not become thick and the smoothness of the coated film is good when used as a primer, for example.

Further, a thickener, a basic substance, an antifoaming agent, etc. can be added to the aqueous dispersion of the present invention, if necessary.

Examples of thickeners include mineral thickeners such as ammonium alginate, sodium alginate, and bentonite clay; acrylic acid thickeners such as sodium polyacrylate, ammonium polyacrylate, and crosslinked acrylic emulsion copolymers: Examples include cellulose derivatives such as carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose, and hydroxyethylcellulose, with carboxymethylcellulose being particularly preferred.

Examples of antifoaming agents include vegetable oils such as castor oil, soybean oil, and linseed oil; mineral oils such as spindle oil and liquid paraffin; fatty acids such as nistearic acid and oleic acid; oleyl alcohol, polyoxyalkylene glycol, octyl alcohol, etc. Alcohols; Fatty acid esters such as ethylene glycol distearate and polyoxyethylene sorbitan monolaurate; Phosphate esters such as tributyl phosphate and sodium octyl phosphate; Amides such as polyoxyalkylene amide; Aluminum stearate, potassium oleate , metal soaps such as calcium stearate; silicones such as dimethyl silicone and polyether-modified silicone; and amines such as cyamylamine and polyoxypropylene alkylamine.

Furthermore, an organic solvent such as alcohol or toluene may be added as necessary to improve wetting with the material.

Furthermore, in addition to the above, the aqueous dispersion of the present invention may optionally contain various stabilizers such as antioxidants, weathering stabilizers, and heat-resistant inhibitors; coloring agents such as titanium oxide and organic compounds; carbon black, ferrite, etc. It may contain conductivity imparting agents such as.

The aqueous dispersion of the present invention is applied to the surface of a molded article made of polyolefin or other polymer, and used as a brimer or the like to improve the adhesion of paint to the surface. In particular, the aqueous dispersion of the present invention may be made of polyolefins such as high-pressure polyethylene, medium-low pressure polyethylene, polypropylene, poly-4-methyl-1-pentene, poly-1-butene, polystyrene, and ethylene-propylene copolymers. , olefin copolymers such as ethylene/butene copolymers, propylene/butene copolymers, and the like.

Furthermore, in addition to the above-mentioned polyolefins and their copolymers, the aqueous dispersion of the present invention can also be made of molded products made of polypropylene and synthetic rubber, polyamide resins, unsaturated polyester resins, polybutylene terephthalate resins, polycarbonate resins, etc. It can also be used for surface treatment of molded products such as automobile bumpers, and furthermore, steel plates and steel plates for electrodeposition treatment. In addition, undercoat the surface coated with paints, primers, adhesives, etc. whose main components are polyurethane resin, fatty acid-modified polyester resin, oil-free polyester resin, melamine resin, epoxy resin, etc. to improve the adhesion of the paint, etc. to the surface. It is also used to improve the image quality and form coatings with excellent image clarity and low-temperature impact resistance.

The aqueous dispersion of the present invention can be applied to molded products containing inorganic fillers such as talc-zinc white, glass fiber, titanium white, magnesium sulfate, pigments, etc. A brimer coating film with good adhesion can be formed. Furthermore, the molded article coated with the aqueous dispersion of the present invention may contain various stabilizers, ultraviolet absorbers, hydrochloric acid absorbers, etc. in addition to the above.

Preferably used stabilizers include, for example, 2,6-
Di-t-butyl-4-methylphenol, tetrakis[methylene(3,5-di-t-butyl-4-hydroxyhydrocinnamate)]methane, metaoctadecyl-3
-(4'-Hydoxy-3,5-di-t-butylphenyl)propionate, 2,2'-methylenebis(4-methyl-6-t-butylphenol)4,4'-butylidenebis(3-methyl-6- t-butylphenol), 4
4'-thiobis(3-methyl-6-t-butylphenol), 2.2-thiobis(4-methyl-6-t-butylphenol), 1.3.5-trimethyl-2,4,6
-1 Lis(3,5-di-t-butyl-4-hydroxybenzyl)benzene,],]3,5-tris2-methyl-
Phenol stabilizers such as 4-hydroxy-5-t-butylphenol)butane; Sulfur stabilizers such as dilaurylthiodipropionate and distearylthiodipropionate; Tridecyl phosphite, trinonylphenyl phosphite, etc. Examples include phosphorus stabilizers.

Further, as the ultraviolet absorber used, for example, 2-
Examples thereof include hydroxy-4-octoxybenzophenone, 2-ethylhexyl-2-cyano-3,3-diphenylacrylate, and roseoctylphenyl salicylate.

An example of the hydrochloric acid absorbent is calcium stearate.

The aqueous dispersion of the present invention is suitable for spray application to a molded article, for example, by spraying onto the surface of the molded article with a spray gun. The coating on molded articles can be carried out using 1B, and after coating, it can be dried by an appropriate method such as natural drying or forced drying under heat to form a coating film.

As described above, after the aqueous dispersion of the present invention is applied to the surface of a molded article and dried, the surface of the molded article is coated with electrostatic coating,
The paint can be applied by spraying, painting, brushing, or other methods. The paint may be applied by applying an undercoat and then a topcoat. After applying the paint,
A molded article having a desired coating film on its surface can be obtained by curing the coating film according to a conventional heating method using nichrome wire, infrared rays, high frequency waves, or the like. The method for curing the coating film is appropriately selected depending on the material and shape of the molded article, the properties of the paint used, etc.

<Examples> Hereinafter, the present invention will be specifically explained with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited to these Examples in any way.

Further, in the following, the physical properties of the coating film were evaluated according to the following method.

A test piece with a base grain was prepared according to the base grain test method described in JIS K5400, and a piece of sellotape made by Chiban (trade name) was pasted on the base grain of the test piece. Thereafter, this was quickly pulled in a 90° direction to peel it off, and the number of base grains that were not peeled out of 100 base grains was counted and used as an index of adhesion.

Prepare a coating film on the base material, make a cut with a cutter blade to a width of 1c until the blade reaches the base material, peel off the edge, and then cut the edge of the peeled coating film with a 50mm cutter. The peel strength was measured by pulling the coating film in a direction of 180° at a speed of mm/min until it peeled off.

After immersing a test piece of No. 1 wood in water at 40° C. for 240 hours, it was subjected to a substrate test to evaluate adhesion.

(Example 1) (Production of modified polymer) In an autoclave with a capacity of 1.5β equipped with a stirring device, Kraton G-1652 (manufactured by Shell Chemical Co., Ltd., number average Molecular weight = 8.8X10', styrene content: 31% by weight)
Charge 250 parts by weight and 500 parts by weight of toluene, and raise the temperature to 160°C while stirring.

Next, 25 parts by weight of 2-hydroxypropyl acrylate and 6.5 parts by weight of di-t-butyl peroxide,
After adding in portions over 5 hours each, add 16
The reaction was allowed to proceed at 0°C for 2 hours with stirring.

The content of 2-hydroxypropyl acrylate in the obtained modified polymer was measured and found to be 344% by weight.

(Production of aqueous dispersion) Toluene was further added to the toluene solution containing the modified polymer obtained in the above reaction to bring the concentration of the modified polymer to 125 g.
Adjusted to /ff.

500g of this modified polymer solution 500g of distilled water, j
: i and 1.44 g of sodium dodecylbenzenesulfone (Neoperex F-25, manufactured by Kao Corporation) were mixed,
The mixture was stirred for 15 minutes at a rotational speed of 10,000 rpm. Then,
0.72 g of carboxyl methyl cellulose (HE-600, manufactured by Daiichi Kogyo Yakuhin) was added and mixed with stirring. Toluene in the obtained emulsion was distilled off under reduced pressure using an evaporator.
An aqueous dispersion with a modified polymer concentration of 20% by weight was obtained.

(Coating) This aqueous dispersion was spray-coated to a polypropylene square plate (X 440, manufactured by Mitsui Petrochemical Industries, Ltd.) that had been cleaned with 1,1.1-trichloroethane vapor at a density of 200 g/m2. .

This square plate was heated and dried in an air oven at 100° C. for 30 minutes, and then subjected to a base grain test, peel strength measurement, and water resistance test. The results are shown in Table 1.

(Example 2).

In the same manner as in Example 1, the aqueous dispersion was applied to a polypropylene square plate, and then a top coat (R-271, manufactured by Nippon B Chemical Co., Ltd.) was applied to give a dry film thickness of 60 μm. After being left to cool at room temperature for 10 minutes, it was baked in an oven at 100° C. for 30 minutes. The resulting coating film was subjected to a base grain test, peel strength measurement, and water resistance test. The results are shown in Table 1.

(Example 3) An aqueous dispersion was applied in the same manner as in Example 1, except that instead of cleaning with 1.1.1-trichloroethane vapor, a polypropylene square plate whose surface had been wiped with white gasoline was used. Thereafter, a top coat was applied in the same manner as in Example 2 to obtain a coating film.

The obtained coating film was subjected to a base grain test, a peel strength test, and a water resistance test.

(Example 4) 3 kg of the same styrene-butadiene block copolymer produced in Example 1, 120 g of 2-hydroxyethyl acrylate, and 12 g of 2,5-dimethyldi(t-butylperoxy)hexane were mixed in advance in a Henschel mixer. After that, a twin-screw extruder (PCM-4 manufactured by Ikegai Iron Works)
5), granulation was carried out at a resin temperature of 230° C. and a rotation speed of 26 Orpm.

The content of 2-hydroxyethyl acrylate in the obtained modified polymer was 2.9% by weight.

An aqueous dispersion of this tempered polymer was prepared in the same manner as in Example 1, and subjected to a base grain test, peel strength measurement, and water resistance test in the same manner as in Example 1. The results are shown in Table 1.

(Example 5) The aqueous dispersion prepared in Example 4 was applied to a polypropylene square plate in the same manner as in Example 4, and then a top coat was applied in the same manner as in Example 2.

The obtained coating film was subjected to a substrate grain test, peel strength measurement, and water resistance test. The results are shown in Table 1.

(Comparative Example 1) A sample coated with a top coat was prepared in the same manner as in Example 2 except that the aqueous dispersion was not coated, and was subjected to a base grain test and peel strength measurement. The results are shown in Table 1.

*Substrate grain test:
- It is made by dispersing in water a modified polymer made by graft copolymerizing an unsaturated vinyl monomer, and it has excellent workability when coating molded products, and can be made into fine particles, so it is effective only for paint adhesion. First, it is possible to form a coating film with excellent image clarity. Furthermore, since no organic solvent is used, a good working environment can be maintained during manufacturing and coating operations.

Claims (2)

[Claims] (1) A modified polymer obtained by graft copolymerizing a styrene-butadiene block copolymer or its hydrogenated product so that it contains 0.05 to 25% by weight of an α,β-unsaturated vinyl monomer having a hydroxyl group. An aqueous dispersion comprising 95 to 30 parts by weight of water per 5 to 70 parts by weight of the modified polymer. (2) The α,β-unsaturated vinyl monomer having a hydroxyl group is a (meth)acrylic ester of a monohydric alcohol or a mono(meth)acrylic ester of a polyhydric alcohol. Aqueous dispersion.