JP3014727B2 - Water dispersion - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an aqueous dispersion, and more particularly, to an undercoating of a green product to improve the adhesion of a coating material to the surface of a molded product and an organic solvent. The present invention relates to an aqueous dispersion suitable as a primer, which can maintain a favorable working environment because it does not contain any.

<Conventional technology> Conventionally, the surface of a molded article of polyolefin such as polypropylene is painted, or another resin layer is formed,
The added value is being increased. But,
In general, polyolefin has poor polarity and poor adhesion to paints and other resins. Therefore, conventionally, it has been attempted to improve the coating adhesion by treating the surface of a molded article in advance with chromic acid, flame, corona discharge, plasma, a solvent, or the like to increase the polarity of the surface. However, in these treatments, there are disadvantages that complicated treatments are required and dangers are involved due to the use of corrosive chemicals.

In addition, there is a disadvantage that strict process control is required to obtain a stable processing effect.

Therefore, as an effective means to improve these disadvantages,
There is a method of coating the surface of a molded article or the like with a primer, and various surface treatment agents used as the primer have been proposed. For example, the present applicant has previously described a modified α-olefin copolymer obtained by graft copolymerizing at least one selected from maleic acid and its anhydride, and a monoolefin dicarboxylic acid monoalkyl ester onto a specific α-olefin copolymer. A polymer dissolved in an organic solvent,
A surface treating agent excellent in adhesion and storage stability of a coating film was proposed (Japanese Patent Publication No. Sho 62-21027, Japanese Patent Publication No. Sho 11-11250).

<Problems to be Solved by the Invention> However, any of the conventional ones including this surface treatment agent contains or is dissolved in an organic solvent and used. There is a drawback that the working environment during use is deteriorated. Therefore, in recent years, it has been demanded to reduce the amount of volatile organic solvent used in order to maintain a good working environment in a factory.

Accordingly, an object of the present invention is to provide a coating film having sufficient peel strength and adhesion, and to contain no organic solvent, since the resin molding product has excellent adhesion to a polyolefin molding product such as polypropylene. An object of the present invention is to provide an aqueous dispersion suitable as a primer which can maintain a favorable working environment because it is an aqueous system.

<Means for Solving the Problems> In order to solve the above problems, the present invention provides an α-olefin copolymer containing 0.1 to 25% by weight of an α, β-unsaturated vinyl monomer having a hydroxyl group. The present invention provides an aqueous dispersion obtained by dispersing in a water a modified polymer obtained by graft-copolymerizing a polymer.

Further, the α-olefin copolymer is propylene
It is preferably at least one selected from butene-ethylene copolymer, propylene-ethylene copolymer and propylene-butene copolymer.

The α, β-unsaturated vinyl monomer having a hydroxyl group is preferably a monohydric alcohol (meth) acrylate or a polyhydric alcohol mono (meth) acrylate.

 Hereinafter, the aqueous dispersion of the present invention will be described in detail.

The modified polymer which is a main component of the aqueous dispersion of the present invention contains an α-olefin copolymer as a main component. The α-olefin copolymer is, for example, a copolymer of ethylene and / or propylene and another α-olefin other than ethylene and propylene. Examples of other α-olefins include 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene,
-Octene and the like. In the present invention, one or more of these other α-olefins may be included in the α-olefin copolymer. When the α-olefin copolymer contains another α-olefin, its content is usually about 5 to 50 mol%.

Preferred examples of the α-olefin copolymer include:
Propylene-butene-ethylene copolymer, propylene
Examples include an ethylene copolymer and a propylene / butene copolymer. In particular, as a propylene-butene-ethylene copolymer, for a propylene content of 50 mol or more,
A random copolymer having a butene / ethylene content ratio of 45/5 to 5/45 in a molar ratio is exemplified.

Further, as a particularly preferable example of the propylene / ethylene copolymer, a random copolymer having a propylene / ethylene content ratio of 30/70 to 90/10 in a molar ratio can be mentioned.

Further, as a particularly preferable example of the propylene / butene copolymer, a random copolymer having a propylene / butene content ratio of 50/50 to 90/10 in a molar ratio can be mentioned.

The α-olefin copolymer preferably has an MFR of 0.15 or more from the viewpoint of high cohesion and good adhesion of the resulting aqueous dispersion.

The aqueous dispersion of the present invention is obtained by graft copolymerizing an α, β-unsaturated vinyl monomer having a hydroxyl group (hereinafter, simply referred to as “vinyl monomer”) to the α-olefin copolymer as described above. The modified polymer is dispersed in water.

Examples of the vinyl monomer include hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, and 3-hydroxypropyl (meth) acrylate. (Meth) acrylic acid ester of monohydric alcohol such as chloro-2-hydroxypropyl (meth) acrylate; glycerin mono (meth)
Polyhydric alcohols such as acrylate, pentaerythritol mono (meth) acrylate, trimethylolpropane mono (meth) acrylate, tetraethylolethane mono (meth) acrylate, butanediol mono (meth) acrylate, and polyethylene glycol mono (meth) acrylate Mono (meth) acrylate; 10-undecene-1-ol, 1-octen-3-ol,
-Methanolbornene, 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, a monohydric alcohol (meth) acrylate or a polyhydric alcohol mono (meth) acrylate is preferable, and 2-hydroxypropyl acrylate is particularly preferable.

The amount of the vinyl monomer is 0.1 to 25% by weight, preferably 0.5 to 25% by weight.
The modified copolymer is graft-copolymerized with the above block copolymer so as to be contained in an amount of about 15% by weight. By using such a modified polymer, it is possible to obtain an aqueous dispersion that forms a coating film selected for adhesion and water resistance.

The production of the modified polymer which is a component of the aqueous dispersion of the present invention can be performed according to various known methods. For example, the polymerization can be carried out by graft copolymerizing the vinyl monomer with the block copolymer in the presence of a radical polymerization initiator, in the presence or absence of an inert solvent.

As a method of graft copolymerization in the presence of an inert solvent, for example, an α-olefin copolymer is dissolved in an inert solvent to prepare a solution, and a vinyl monomer and a radical polymerization initiator are added thereto. And reacting by heating while stirring; impregnating the powdered α-olefin copolymer with a solution obtained by dissolving a vinyl monomer and a radical polymerization initiator in an inert solvent; For example, a method in which the reaction is carried out by heating to a temperature that does not occur.

At this time, the usage ratio of the radical polymerization initiator / vinyl monomer is usually 1/100 to 60/100, preferably 1/100, in molar ratio.
It is in the range of / 20 to 1/2. The reaction is preferably carried out with heating and stirring. The reaction temperature is preferably equal to or higher than the melting point of the α-olefin copolymer, particularly in the range of 120 to 160 ° 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.

As a method of performing the graft copolymerization in the absence of an inert solvent, for example, an α-olefin copolymer is heated and melted, a vinyl monomer and a radical polymerization initiator are added, and the mixture is reacted while stirring. Method: a method in which an α-olefin copolymer, a vinyl monomer, and a radical polymerization initiator are mixed in advance, and the mixture is heated and melted by an extruder, and graft copolymerization is performed while extruding the mixture. 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, dichlorobenzoyl oxide, dicumyl peroxide, di-t-
Butyl peroxide, 2,5-dimethyl-2,5-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-butylperacetate, t-butylbenzoate, t-butylperphenylacetate, t-butylperisobutyrate, t-butylper-sec-octoate, t-butylperpiate Organic peresters such as barate, cumyl perpivalate and t-butyl perdiethyl acetate; azo compounds such as azobisisobutyronitrile and dimethylazoisobutyronitrile; Of these, organic peroxides and organic peresters are preferred, and especially dicumyl peroxide, di-t-butyl peroxide, 2,5-dimethyl-2,5-di (t-butylperoxy) hexyne-3,2,5 -Dimethyl-2,5-di (t-butylperoxy) hexane, 1,4-bis (t-
Dialkyl peroxides such as butylperoxyisopropyl) benzene are preferred.

When an inert solvent is used, specific examples thereof include aromatic hydrocarbons such as benzene, toluene, and xylene; aliphatic hydrocarbons such as hexane, heptane, octane, and decane; trichloroethylene, perchlorethylene, and dichloroethylene. And halogenated hydrocarbons such as chlorobenzene. Among them, aromatic hydrocarbons are preferable, and alkyl group-substituted aromatic hydrocarbons are particularly preferable.

The aqueous dispersion of the present invention is obtained by dispersing the modified polymer obtained as described above in water. Examples of a method for producing the water dispersion of the present invention by dispersing the modified polymer in water include, for example, a drum emulsification method in which the externally modified polymer, water and a surfactant are mixed and emulsified at once; A pulverization method in which the modified polymer is charged and dispersed in water together with a surfactant; a solvent replacement method in which the modified polymer dissolved in an organic solvent is mixed with the surfactant and water, and then the organic solvent is removed. A homomixer method in which dispersion is performed using a homomixer; a phase inversion method, and the like, which are appropriately selected depending on 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 aryl ether, polyoxyethylene sorbitan ester, and polyoxyethylene alkylamine ether. Examples of the anionic surfactant include fatty acid salts, higher alcohol sulfates, sodium alkylbenzenesulfonate, formalin condensate of naphthalenesulfonic acid, polyoxyethylene alkyl ether sulfate, and the like, with sodium alkylbenzenesulfonate being particularly preferred.

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. Further, when the aqueous dispersion of the present invention is applied to the surface of a molded product by spray coating, uneven coating does not occur on the coated surface, the coating film adhesion does not vary, and the smoothness of the coated film after coating is applied. It is preferable that the surfactant is used in an amount of 3 to 45% by weight with respect to the modified polymer in that the above-mentioned is preferable.

The mixing ratio of the modified polymer and water in the aqueous dispersion of the present invention is not particularly limited, and can be appropriately selected according to the molded article to be applied, the surface properties thereof, the properties of the top coat used, and the like. In particular, when spray-coating the aqueous dispersion of the present invention, coating unevenness is less likely to occur on the coated surface, variation in the adhesion of the coating film is less likely to occur, and the formed coating film layer does not become thicker. 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.

In addition, a thickener, a basic substance, an antifoaming agent, and the like can be added to the aqueous dispersion of the present invention as needed. Further, in order to improve the wettability with the material to be applied, a small amount of an organic solvent may be added as 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.

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

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

Further, the aqueous dispersion of the present invention, besides 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 be used for molded articles, for example, molded articles such as bumpers for automobiles, and also for surface treatment of steel sheets, steel sheets for electrodeposition treatment, and the like. In addition, acrylic resin, acrylic-modified alkyd resin, polyurethane resin, fatty acid-modified polyester resin, oil-free polyester resin, melamine resin, epoxy resin and the like as a main component paint, primer, undercoating on the surface coated with an adhesive,
It is used not only to improve the adhesion of paint and the like to the surface, but also to form a coating film having excellent clarity, low-temperature impact resistance and the like.

Further, the molded article to which the aqueous dispersion of the present invention is applied, the above-mentioned various polymers or resins are prepared by any of known molding methods such as injection molding, compression molding, hollow molding, extrusion molding, and rotational molding. It may be formed.

The aqueous dispersion of the present invention is a molded article to which it is applied, talc, zinc white, glass fiber, titanium white, inorganic fillers such as magnesium sulfate, pigments and the like are blended, especially for coating films. A primer coating film having good adhesion can be formed. Further, a molded article to which the aqueous dispersion of the present invention is applied,
In addition to the above, various stabilizers, ultraviolet absorbers, hydrochloric acid absorbers and the like may be contained.

As a preferably used stabilizer, for example, 2,6-
Di-tert-butyl-4-methylenephenol, 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,
Phenol-based 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.

As a method for applying the aqueous dispersion of the present invention to the surface of a molded article, spray coating is suitable. For example, the aqueous dispersion is sprayed on the surface of the molded article by a spray gun. What is necessary is just to perform application | coating to a molded article at normal temperature, and after apply | coating, it dries by appropriate methods, such as natural drying and heating forced drying, and can form a coating film.

As described above, after applying the aqueous dispersion of the present invention to the surface of a molded article and drying, the surface of the molded article is subjected to electrostatic coating,
The coating can be applied by a method such as spray coating or brush coating.

The application of the paint may be performed by a method of applying an undercoat and then applying an overcoat. After applying paint, nichrome wire, infrared,
The coating film is cured according to a normal method of heating by high frequency or the like, and a molded article having a desired coating film 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.

Further, the aqueous dispersion of the present invention, by utilizing the characteristics of excellent adhesiveness, peel strength and water resistance, in addition to the use as a primer of the molded article, can be applied to a wide range of applications, for example, Needless to say, it can be applied to uses such as additives for adhesives and paints.

<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.

Substrate test In accordance with the basic test method described in JIS K5400, a test specimen with a base is prepared and a cellophane tape (Nichiban Co., Ltd., trade name) is stuck on the base of the test specimen. After that, it was quickly pulled in the direction of 90 ° to be peeled off, and the number of bases that were not peeled out of the bases 100 was counted and 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.

After immersing the test piece in water at 40 ° C. for 240 hours, the test piece is subjected to a basement test to evaluate the adhesion.

(Example 1) 75 g of a propylene / ethylene copolymer (propylene content: 60 mol%, MFR (190 ° C): 0.6, density: 0.9) was placed in a reaction vessel.
And 240 ml of toluene, and the atmosphere in the reaction vessel was replaced with nitrogen for 1 hour. After heating the temperature of the reaction system to 145 ° C. and completely dissolving the propylene / ethylene copolymer,
A solution of 7 g of hydroxypropyl acrylate dissolved in 30 ml of toluene, and di-t-butyl peroxide
A solution prepared by dissolving 2.4 g in 30 ml of toluene was simultaneously added dropwise over 4 hours, and allowed to react. Next, the reaction was further continued for 2 hours while maintaining the temperature at 145 ° C. After the temperature was returned to room temperature, a large excess of methanol was added to the reaction mixture to precipitate the resulting modified polymer. The precipitated modified polymer was separated by filtration, washed repeatedly with methanol, and dried to obtain a modified polymer graft-modified with 2-hydroxypropyl acrylate.

When the content (graft amount) of 2-hydroxypropyl acrylate in the obtained modified polymer was measured, it was 3.
It was 2% by weight.

Toluene was added to this modified polymer to prepare a polymer solution having a modified polymer concentration of 125 g /. 500 of this polymer solution
g, distilled water 500 g and sodium dodecylbenzenesulfonate (Neoperex F-25, manufactured by Kao Corporation) 1.44
g was stirred at 10,000 rpm and mixed. Then
Carboxymethyl cellulose (Daiichi Kogyo Chemical Co., Ltd.)
HE-600) was added and stirred and mixed to obtain an emulsion.
The toluene in the obtained emulsion was distilled off under reduced pressure using an evaporator, and the modified polymer (particle size: 5 μm) concentration: 20% by weight
Was obtained.

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

This square plate was dried by heating at 100 ° C. for 30 minutes in an air oven, and then subjected to a base test and evaluation of water resistance.

 Table 1 shows the results.

(Example 2) In the same manner as in Example 1, after applying an aqueous dispersion to a polypropylene square plate, a urethane-based paint (R-271, manufactured by Nippon Bee Chemical Co., Ltd.) was further overcoated to a dry film thickness of 60 µm. did. Next, baking was performed in an oven at 100 ° C. for 30 minutes.

The obtained coating film was subjected to a base test, a measurement of peel strength, and an evaluation of water resistance. Table 1 shows the results.

(Example 3) As in Example 1, after applying an aqueous dispersion to a polypropylene square plate, a urethane-based paint (Planit # 800, manufactured by Dainippon Paint Co., Ltd.) was further dried to a dry film thickness of 60 µm. Was overcoated. Next, baking was performed in an oven at 100 ° C. for 30 minutes.

The obtained coating film was subjected to a base test, a measurement of peel strength, and an evaluation of water resistance. Table 1 shows the results.

Example 4 2 kg of the same propylene / ethylene copolymer as used in Example 1 and 2-hydroxypropyl acrylate 60
g, and 8 g of 2,5-dimethyl-2,5'-di (t-butylperoxy) hexane were previously mixed in a Henschel mixer, and the resulting mixture was fed to a twin-screw extruder to give a resin temperature of 230 ° C. The mixture was heated and kneaded at a rotation speed of 260 rpm to cause a reaction to obtain a modified polymer. When the content (graft amount) of 2-hydroxypropyl acrylate in the obtained modified polymer was measured, it was 1.3% by weight.

Example 1 was prepared using this modified polymer (particle size: 5.5 μm).
A water dispersion was obtained in the same manner as described above.

Next, coating was performed in the same manner as in Example 2, and the obtained coating film was subjected to a base test, a measurement of peel strength, and an evaluation of water resistance. Table 1 shows the results.

(Example 5) A sample produced by washing a molded product obtained by injection molding of an olefin-based thermoplastic elastomer (a mixture of polypropylene and an ethylene / propylene copolymer) with steam of 1,1,1-trichloroethane. Then, the aqueous dispersion obtained in Example 1 was spray-coated so as to be 200 g / m ² . This was heated and dried in an air oven at 100 ° C. for 30 minutes, and then coated in the same manner as in Example 2, and the obtained coating film was subjected to a base test, a measurement of peel strength, and an evaluation of water resistance. Table 1 shows the results.

(Example 6) Instead of the propylene / ethylene copolymer, a propylene / butene / ethylene copolymer (propylene / butene /
A modified polymer was obtained in the same manner as in Example 4 except that the ethylene content ratio was 70/20/10). When the content (graft amount) of 2-hydroxypropyl acrylate in the obtained modified polymer was measured, it was 1.6% by weight.

Using this modified polymer (particle size: 4 μm), an aqueous dispersion was obtained in the same manner as in Example 1.

Next, coating was performed in the same manner as in Example 2, and the obtained coating film was subjected to a base test, a measurement of peel strength, and an evaluation of water resistance. Table 1 shows the results.

(Example 7) Instead of a propylene / ethylene copolymer, an ethylene / propylene copolymer (ethylene content: 50 mol%)
A modified polymer was obtained in the same manner as in Example 4 except for using. When the content (graft amount) of 2-hydroxypropyl acrylate in the obtained modified polymer was measured, it was 1.
It was 8% by weight.

Using this modified polymer (particle size: 6 μm), an aqueous dispersion was obtained in the same manner as in Example 1.

Next, coating was performed in the same manner as in Example 2, and the obtained coating film was subjected to a base test, a measurement of peel strength, and an evaluation of water resistance. Table 1 shows the results.

(Comparative Example 1) An aqueous dispersion was prepared using the propylene / ethylene copolymer used in Example 1 without modification with 2-hydroxypropyl acrylate, and used as it was, except that this aqueous dispersion was used. Coating was performed in the same manner as in Example 2, and the obtained coating film was subjected to a base test and a measurement of peel strength. Table 1 shows the results.

(Comparative Example 2) A water dispersion was prepared using the same ethylene-propylene copolymer as used in Example 7 without modifying it with 2-hydroxypropyl acrylate, and using this water dispersion as it was. Was applied in the same manner as in Example 2, and the obtained coating film was subjected to a base test and a measurement of peel strength. Table 1 shows the results.

* Comparative Example: Baseline test X / 100 peeling strength g / cm peeled between primer and paint layer Note “-” in the reference column indicates that measurement was not performed.

<Effect of the Invention> The aqueous dispersion of the present invention is obtained by dispersing a modified polymer obtained by graft copolymerizing an α, β-unsaturated vinyl monomer having a hydroxyl group to an α-olefin copolymer in water. It is a resin molded product, in particular, because it has excellent adhesion with a molded product of polyolefin such as polypropylene, it is possible to obtain a coating film having sufficient peel strength and adhesion,
Since it is an aqueous system containing no organic solvent, it is suitable as a primer that can maintain a favorable working environment.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-47-43520 (JP, A) JP-A-1-123812 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 3/03 C08L 1/00-101/14 C08J 7/00-7/18

Claims (3)

(57) [Claims] A modified polymer obtained by graft copolymerizing an α-olefin copolymer so as to contain 0.1 to 25% by weight of an α, β-unsaturated vinyl monomer having a hydroxyl group is dispersed in water. Aqueous dispersion for surface application of molded articles. 2. The method according to claim 1, wherein the α-olefin copolymer is at least one selected from propylene / butene / ethylene copolymer, propylene, ethylene copolymer and propylene / butene copolymer. Water dispersion. 3. The method according to claim 1, wherein the α, β-unsaturated vinyl monomer having a hydroxyl group is a monohydric alcohol (meth) acrylate or a polyhydric alcohol mono (meth) acrylate. An aqueous dispersion as described in the above.