JP2950336B2 - Aqueous dispersion - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an aqueous dispersion, and more particularly to an aqueous dispersion which can be applied to 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 article of polyolefin such as polypropylene has been coated to increase its added value. However, polyolefins generally have poor polarity and poor paint adhesion. Therefore, conventionally, the surface of a molded article has been treated with a primer in advance to improve the adhesion and adhesion of the paint.

Therefore, as a binder for a paint that can be applied once directly to a molded article or the like without a primer, it is used in the presence of a hydrogenated styrene-butadiene-styrene block copolymer in an inert organic solvent (meth). A resin composition for a coating obtained by polymerizing an acrylic ester, particularly a vinyl monomer having a hydroxyl group, has been proposed. (JP
<Problems to be Solved by the Invention> However, even when the resin composition for coating described in the above-mentioned JP-A-63-51477 is used, the obtained coating film has sufficient peel strength. Not something. In addition, conventional primers including this composition are used because they contain an organic solvent or are dissolved in an organic solvent, which causes a problem that the working environment during production and use is deteriorated. .

Therefore, the present invention is a resin-based molded article, particularly because it has excellent adhesion with a molded article of polyolefin such as polypropylene, it is possible to obtain a coating film having a sufficient peel strength, and because it is an aqueous system that does not use an organic solvent, An object of the present invention is to provide an aqueous dispersion suitable as a primer, which can maintain a favorable working environment.

<Means for Solving the Problems> In order to solve the above-mentioned problems, the present invention provides a styrene-butadiene block copolymer or a hydrogenated product thereof containing an α, β-unsaturated vinyl monomer having a hydroxyl group in an amount of 0.05%. An aqueous dispersion obtained by dispersing a modified polymer obtained by graft copolymerization so as to contain 〜25% by weight in water, comprising 95 to 30 parts by weight of water with respect to 5 to 70 parts by weight of the modified polymer. An aqueous dispersion is provided.

In addition, it is preferable that the α, β-unsaturated vinyl monomer having a hydroxyl group is a mono (meth) acrylate of a dihydric alcohol or a mono (meth) acrylate of a trivalent or higher alcohol.

 Hereinafter, the present invention will be described in detail.

Styrene-butadiene block copolymer which is a main component of the modified polymer which is a component of the aqueous dispersion of the present invention,
A copolymer comprising one or more styrene polymer blocks, which are repeating structural units derived from styrene, and one or more butadiene polymer blocks, which are repeating structural units derived from butadiene. S-D _n (where S represents a styrene polymer block, D represents a butadiene polymer block, and n is an integer of 1 or more.) Preferably, the following formula: S-D-S _m (where S is And D are the same as those described above, and m is 0 or 1.)

The styrene-butadiene block copolymer is described, for example, in U.S. Pat. No. 3,265,765, JP-A-61-192743.
And those manufactured by the method described in Japanese Patent Application Publication No. Specific examples of the styrene-butadiene block copolymer include those commercially available as Kraton 1101 and 1102 (both manufactured by Shell Chemical Company).

The hydrogenated styrene-butadiene block copolymer is disclosed, for example, in JP-B-43-6636 and JP-B-43-636.
45-20504, JP-B-48-3555 and the like. Specific examples of the hydrogenated styrene-butadiene block copolymer include those commercially available as Kraton G-1652 (manufactured by Shell Chemical Company).

These styrene-butadiene block copolymers or hydrogenated products thereof are subjected to gel permeation chromatography at 40 ° C. using tetrahydrofuran as a solvent in view of the peel strength and the solid content of the coating film of the aqueous dispersion of the present invention. Number average molecular weight measured by 1 × 10 ⁴ -1
It is preferably 8 × 10 ⁴ , particularly 1.5 × 10 ^{4 to} 12 × 10 ⁴
Is preferred. Further, the styrene content is the adhesion of the coating film of the aqueous dispersion of the present invention, peel strength, low-temperature properties,
From the viewpoint of stickiness and the like, the content is preferably 10 to 60% by weight, and particularly preferably 12 to 55% by weight.

The aqueous dispersion of the present invention is a styrene-butadiene block copolymer as described above or a hydrogenating agent thereof (hereinafter, referred to as
These are simply referred to as block copolymers), and a modified polymer obtained by graft copolymerizing an α, β-unsaturated vinyl monomer having a hydroxyl group (hereinafter, simply referred to as a vinyl monomer) is dispersed in water. It becomes.

Examples of the vinyl monomer include hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, Mono (meth) acrylates of dihydric alcohols such as -chloro-2-hydroxypropyl (meth) acrylate; glycerin mono (meth) acrylate, pentaerythritol (meth) acrylate, trimethylolpropane mono (meth) acrylate, tetra Mono (meth) acrylates of tri- or higher-valent alcohols such as ethylolethane (meth) acrylate, butanediol mono (meth) acrylate, and polyethylene glycol mono (meth) acrylate; 10
= Undecen-1-ol, 1-octen-3-ol, 2-methanol norbornene, hydroxystyrene, hydroxyethyl vinyl ether, hydroxybutyl vinyl ether, N-methylol acrylamide, 2
-(Meth) acryloyloxyethyl acid phosphate, glycerin monoallyl ether, allyl alcohol, allyloxyethanol and the like. Among these, mono (meth) acrylate of dihydric alcohol or mono (meth) acrylate of trivalent or higher alcohol is preferably used.

The vinyl monomer is present in an amount of 0.05 to 25% by weight, preferably 0.1%.
The modified copolymer is graft copolymerized with the above block copolymer so as to be contained in an amount of 5 to 10% by weight. By using such a modified polymer, an aqueous dispersion that forms a coating film having excellent adhesion and water resistance can be obtained.

The production of the modified polymer as a component of the aqueous dispersion of the present invention may be performed, for example, in the presence of a radical polymerization initiator, in the presence or absence of an inert solvent, by adding the vinyl monomer to the block copolymer. Can be obtained by graft copolymerization of the polymer.

As a method of graft copolymerization in the presence of an inert solvent, for example, 10 to ³ block copolymer in an inert solvent 1m3
After preparing a solution by dissolving 000 kg, preferably 20 to 1000 kg, a vinyl monomer is added thereto at a rate of 0.5 to 100 mmol / min, preferably 1 to 20 mmol / min per 1 kg of the block copolymer in the solution. A method in which a radical polymerization initiator is added sequentially at a rate of 5 × 10 ⁻⁵ to 50 mmol / min, preferably 1 × 10 ^{−2 to} 5 mmol / min per 1 kg of a block copolymer, and a reaction is performed by sequentially adding the radical polymerization initiator. There is. At this time, the ratio of the radical polymerization initiator / vinyl monomer used is usually
The molar ratio ranges from 1/100 to 3/5, preferably from 1/20 to 1/2. The reaction is preferably carried out with heating and stirring.
The reaction temperature is preferably 50 ° C. or higher, particularly in the range of 80 to 200 ° C., and the reaction time is about 2 to 10 hours. The reaction system may be either a batch system or a continuous system, but a batch system is preferable in order to uniformly carry out the graft copolymerization.

Further, as a method of performing the graft copolymer in the absence of an inert solvent, for example, at a reaction temperature equal to or higher than the softening point of the block copolymer, in the presence of a vinyl monomer and a radical polymerization initiator, A method in which the block copolymer is heated and melted and the reaction is carried out by vigorous stirring can be cited. Further, the block copolymer, the vinyl monomer and the radical polymerization initiator may be mixed in advance, and the mixture may be heated and melted by an extruder and graft copolymerized while being extruded. In the method performed in the absence of these inert solvents, the amount of the vinyl monomer and the radical polymerization initiator used, and the ratio of both used are the same as in the method performed in the presence of the above-described inert solvent. .

Examples of the radical polymerization initiator used for the graft copolymerization include benzoyl peroxide, dichloropendoyl peroxide, dicumyl peroxide, and di-
t-butyl peroxide, 2,5-dimethyl-di (peroxybenzoate) hexyne-3, 1,4-bis (t-butylperoxyisopropyl) benzene, lauroyl peroxide, 2,5-dimethyl-2,5-di (t -Butylperoxy) -hexyne-3,2,5-dimethyl-2,5-di (t
Organic peroxides such as -butylperoxy) -hexane; t-butyl peracetate, t-butyl perbenzoate, t-butyl perphenyl acetate, t-butyl perisobutyrate, t-butyl per-s-octoate, t-butyl pivalate, Cumil perpivalate, t
Organic peresters such as -butylperdiethyl acetate; azo compounds such as azobisisobutyronitrile and dimethylazoisobutyronitrile; and the like, preferably organic peroxides and organic peresters.

The aqueous dispersion of the present invention is obtained by dispersing the modified polymer obtained as described above in water. Examples of the method for producing the aqueous dispersion of the present invention by dispersing the modified polymer in water include, for example, a drum emulsification method in which the modified polymer, water and a surfactant are mixed and emulsified at once; A pulverization method for dispersing the modified polymer that has been put into water together with a surfactant, and dispersing; dissolving the modified polymer dissolved in an organic solvent with the surfactant and water, and then removing the organic solvent. Method; homomixer method in which dispersion is performed using a homomixer; phase inversion method, and the like, which are appropriately selected according to the physical properties of the modified polymer to be used.

Surfactants used include nonionic and anionic surfactants. Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxyethylene alkyl allyl ether, polyoxyethylene sorbitan ester, and polyoxyethylene alkylamine ether.
Examples of the anionic surfactant include fatty acid salts, higher alcohol sulfates, sodium alkylbenzene sulfonate, formalin condensate of naphthalenesulfonic acid, polyoxyethylene alkyl ether sulfate, and the like. Particularly preferred is sodium alkylbenzene sulfonate.

The amount of the surfactant used is generally 0.05 to 10 with respect to the modified polymer, in that the dispersion state of the modified polymer is good, and the adhesion with the molded article of the obtained aqueous dispersion is good. % By weight, preferably 0.1 to 7% by weight.

The proportion of the modified polymer and water used in the aqueous dispersion of the present invention is appropriately selected from the range of 95 to 30 parts by weight of water with respect to 5 to 70 parts by weight of the modified polymer. In particular, when spray-coating the aqueous dispersion of the present invention, coating unevenness is less likely to occur on the coated surface, the adhesion of the coating is less likely to vary, and the amount of the coating formed does not increase, For example, when used as a primer, the content is preferably 3 to 45% by weight from the viewpoint that the smoothness of the coating film after coating becomes good.

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

As the thickener, for example, ammonium alginate,
Mineral thickeners such as sodium alginate, bentonite clay; acrylic thickeners such as sodium polyacrylate, polyammonium acrylate, acrylic emulsion copolymer crosslinked acrylic emulsion copolymer;
Examples thereof include cellulose derivatives such as carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose, and hydroxyethylcellulose, and carboxymethylcellulose is particularly preferable.

Examples of the antifoaming agent 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 stearic acid and oleic acid; oleyl alcohol, polyoxyalkylene glycol, octyl alcohol, and the like. Alcohols; fatty acid esters such as ethylene glycol distearate and polyoxyethylene sorbitan monolaurate; phosphoric acid esters such as tributyl phosphate and sodium octyl phosphate; amides such as polyoxyalkylene amide; aluminum stearate and potassium oleate And metal soaps such as calcium stearate; silicons such as dimethyl silicon and polyether-modified silicon; amines such as diamylamine and polyoxypropylene alkylamine.

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

Furthermore, in addition to the above, the aqueous dispersion of the present invention may further contain, if necessary, various stabilizers such as antioxidants, weather stabilizers, and heat inhibitors; coloring agents such as titanium oxide and organic pigments; carbon black and ferrite. May be included.

The aqueous dispersion of the present invention is applied to the surface of a molded article made of a polyolefin or other polymer, and is used as a primer or the like for improving the adhesion of a paint to the surface. In particular, the aqueous dispersion of the present invention includes, for example, polyolefins such as high-pressure polyethylene, medium-low-pressure polyethylene, polypropylene, poly-4-methyl-1-pentene, poly-1-butene, and polystyrene; ethylene-propylene copolymer It can be suitably used for molded articles composed of olefin copolymers such as ethylene / butene copolymer and propylene / butene copolymer.

Further, the aqueous dispersion of the present invention, in addition to the above-mentioned polyolefin and its copolymer, comprises a molded article composed of polypropylene and synthetic rubber, a polyamide resin, an unsaturated polyester resin, a polybutylene terephthalate resin, a polycarbonate resin and the like. It can also be used for surface treatment of molded articles such as bumpers for automobiles, and also steel sheets and steel sheets for electrodeposition treatment. In addition, a primer, a primer, an adhesive or the like containing polyurethane resin, a fatty acid-modified polyester resin, an oil-free polyester resin, an melamine resin, an epoxy resin, etc. as a main component is applied to the surface, and the paint or the like adheres to the surface. It is also used for forming a coating film which is excellent in sharpness, low-temperature impact resistance, etc.

The aqueous dispersion of the present invention is a molded article to which the talc, zinc white, glass fiber, titanium white, inorganic fillers such as magnesium sulfate, pigments and the like are blended,
In particular, it is possible to form a primer coating film having good adhesion of the coating film. In addition, the molded article to which the aqueous dispersion of the present invention is applied may contain various stabilizers, ultraviolet absorbers, hydrochloric acid absorbers and the like in addition to the above.

As a preferably used stabilizer, for example, 2,6-
Di-tert-butyl-4-methylphenol, tetrakis [methylene (3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane, metaoctadecyl-3-
(4'-hydroxy-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-tris (3,5-di-
t-butyl-4-hydroxybenzyl) benzene, 1,3,
Phenolic stabilizers such as 5-tris (2-methyl-4-hydroxy-5-t-butylphenol) butane; sulfur-based stabilizers such as dilaurylthiodipropionate and distearylthiodipropionate; tridecyl phosphite And phosphorus-based stabilizers such as trinonylphenyl phosphite.

Further, as the ultraviolet absorber used, for example, 2
-Hydroxy-4-octoxybenzophenone, 2-ethylhexyl-2-cyano-3,3-diphenylacrylate, paraoctylphenyl salicylate and the like.

Examples of the hydrochloric acid absorbent include calcium stearate and the like.

The aqueous dispersion of the present invention is suitable for spray application to a molded article, and is sprayed on the surface of the molded article by a spray gun, for example. The coating on the molded article may be performed at room temperature. After the coating, the coating is dried by an appropriate method such as natural drying or forced heating drying 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, a paint is applied to the surface of the molded article by a method such as electrostatic painting, spray painting, or brush painting. can do. After applying the paint,
It may be carried out by a method of overcoating. After applying the paint,
The coating is cured according to a normal method of heating with a nichrome wire, infrared rays, high frequency, or the like, and a molded article having a desired coating on the surface can be obtained. The method for curing the coating film is appropriately selected depending on the material and shape of the molded product, the properties of the paint used, and the like.

<Examples> Hereinafter, the present invention will be described specifically with reference to Examples and Comparative Examples of the present invention, but the present invention is not limited to these Examples. In the following, the physical properties of the coating film were evaluated according to the following methods.

Cross-cut test According to the cross-cut test method described in JIS K5400, a test piece with a cross-cut is prepared, and a cellotape (trade name, manufactured by Nichiban Co., Ltd.) is stuck on the cross-cut of the test piece. After that, this was quickly pulled in the direction of 90 ° to be peeled off, and the number of grids which were not peeled out of the grid 100 was counted, and was used as an index of adhesion.

Peel strength Prepare a coating film on the substrate, cut a 1cm width until the blade reaches the substrate with a cutter blade, after peeling the end,
The peel strength was measured by pulling the edge of the peeled coating film at a speed of 50 mm / min in a direction of 180 ° until the coating film was peeled.

Water Resistance Test After the test piece was immersed in water at 40 ° C. for 240 hours, it was subjected to a grid test to evaluate the adhesion.

Example 1 (Production of Modified Polymer) In a 1.5-volume autoclave equipped with a stirrer, Kraton G-1652 (hydrogenated styrene / butadiene block copolymer; Shell Chemical Co., number average molecular weight: 250 parts by weight of 8.8 × 10 ⁴ , styrene content: 31% by weight) and 500 parts by weight of toluene were charged, and the temperature was raised to 160 ° C. with stirring. Then, 2-hydroxypropyl acrylate
After 25 parts by weight and 6.5 parts by weight of di-t-butyl peroxide were added in portions over 5 hours each,
The reaction was carried out with stirring at 160 ° C. for 2 hours.

When the content of 2-hydroxypropyl acrylate in the obtained modified polymer was measured, it was 3.4% by weight.

(Production of aqueous dispersion) Toluene was further added to the toluene solution containing the modified polymer obtained in the above reaction, and the concentration of the modified polymer was 125 g /
Was adjusted.

500 g of this modified polymer solution, 500 g of distilled water, and sodium dodecylbenzenesulfonate (Neoperex F
-25, manufactured by Kao Corporation) at a speed of 10,000 rpm
For 15 minutes. Next, 0.72 g of carboxymethylcellulose (HE-600, manufactured by Dai-ichi Kogyo Chemical Co., Ltd.) was added and mixed by stirring. The toluene in the obtained emulsion was distilled off under reduced pressure using an evaporator to obtain an aqueous dispersion having a modified polymer concentration of 20% by weight.

(Coating) This aqueous dispersion was spray-coated on a polypropylene square plate (X440, manufactured by Mitsui Petrochemical Industries, Ltd.) washed with 1,1,1-trichloroethane vapor at 200 g / m ² .

After this square plate was dried by heating at 100 ° C. for 30 minutes in an air oven, it was subjected to a grid test, a measurement of peel strength and a water resistance test. Table 1 shows the results.

(Example 2).

In the same manner as in Example 1, after the aqueous dispersion was applied to a polypropylene square plate, a top coat (R-271, manufactured by Nippon Bee Chemical Co., Ltd.) was further applied to a dry film thickness of 60 μm. After leaving to cool at room temperature for 10 minutes,
Baking was performed for 0 minutes. The obtained coating film was subjected to a grid test, a measurement of peel strength, and a water resistance test. Table 1 shows the results.

Example 3 Instead of washing with 1,1,1-trichloroethane vapor,
After the aqueous dispersion was applied in the same manner as in Example 1 except that a polypropylene square plate whose surface was wiped with white gasoline was used, a top coat was further applied in the same manner as in Example 2 to obtain a coating film. .

The obtained coating film was subjected to a grid test, a measurement of peel strength, 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-dimethyl-di- (t-dibutylperoxy) hexane were mixed with a Henschel mixer. After that, the mixture was granulated with a twin-screw extruder (PCM-45 manufactured by Ikegai Iron Works) at a resin temperature of 230 ° C. and a rotation speed of 260 ppm.

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

An aqueous dispersion was prepared from this modified polymer in the same manner as in Example 1, and subjected to a grid test, a measurement of peel strength, and a water resistance test in the same manner as in Example 1. Table 1 shows the results.

(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 grid test, a measurement of peel strength, and a water resistance test. Table 1 shows the results.

(Comparative Example 1) A sample to which an overcoat was applied was prepared in the same manner as in Example 2 except that the aqueous dispersion was not applied, and subjected to a grid test and a measurement of peel strength. Table 1 shows the results.

<Effects of the Invention> The aqueous dispersion of the present invention has a styrene-butadiene block copolymer or a hydrogenated product thereof having an α,
A modified polymer obtained by graft copolymerizing a β-unsaturated vinyl monomer is dispersed in water. It has excellent workability when applying a molded product, and it can be atomized to only adhere to paint. Instead, a coating film having excellent sharpness can be formed. Further, since no organic solvent is used, a favorable working environment can be maintained during production and coating.

──────────────────────────────────────────────────続 き Continuation of front page (72) Inventor Hajime Inagaki 61-2, Waki, Waki-machi, Kuga-gun, Yamaguchi Prefecture Inside Mitsui Petrochemical Industry Co., Ltd. (58) Field surveyed (Int.Cl. ⁶ , DB name ) C08F 287/00 C09D 151/00 C08L 51/00

Claims (2)

(57) [Claims] 1. A modified polymer obtained by graft copolymerizing a styrene / butadiene block copolymer or a hydrogenated product thereof so as to contain 0.05 to 25% by weight of an α, β-unsaturated vinyl monomer having a hydroxyl group. Is an aqueous dispersion obtained by dispersing water in water, wherein the modified polymer is 5-95 parts by weight of water 95
Aqueous dispersion containing up to 30 parts by weight. 2. The α, β-unsaturated vinyl monomer having a hydroxyl group is a mono (meth) acrylate of a dihydric alcohol or a mono (meth) acrylate of a trihydric or higher alcohol. Item 2. The aqueous dispersion according to Item 1.