JP2002121462A - Primer for plastic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a primer for plastics capable of forming a film having excellent adhesion, recoat adhesion, etc., and to provide a method for coating a plastic molded product using the primer. SOLUTION: This primer for the plastics is characterized as comprising (A) a chlorinated polyolefin having 16-22 wt.% chlorine content, <=80 deg.C melting point and 30,000-120,000 weight-average molecular weight, (B) a blocked polyisocyanate prepared by blocking an isocyanurate type aliphatic and/or alicyclic polyisocyanate with a dialkyl malonate and an acetoacetic ester and (C) a polyol resin. The method for coating the plastic molded product is characterized by coating the plastic molded product with the primer for the plastics and then coating the resultant coated surface with a color base coating and a clear coating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic primer for forming a coating film having excellent adhesion and recoat adhesion, and a method for coating a plastic molded article using the primer.

[0002]

2. Description of the Related Art Molded products of polyolefins containing olefins such as ethylene and propylene are widely used in place of metals as members for automobile outer panels, home electric appliances and the like. Then, in applying a two-pack type topcoat containing a polyisocyanate compound to these molded products, a primer containing a chlorinated polyolefin is previously applied in order to improve the adhesion between the topcoat film and the molded products. ing.

[0003] However, rubber components (for example, styrene-butadiene rubber, isoprene rubber, etc.) and hydroxyl group-containing polyolefins which have been contained in polyolefin molded articles up to now are often reduced or not added at all. There is a defect that the adhesion to the molded product is reduced.

[0004] In some cases, after a polyolefin molded article is coated with a primer and a top coat, repair coating is performed. Specifically, the coating is usually polished (sanding) to remove dirt, lumps, etc., and then the primer and the topcoat are re-coated (recoated) on the portion. It has been pointed out that there is a defect that the interlayer adhesion between the top coat and the primer coat applied by the repair coating is insufficient.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a coating film having improved adhesion to a polyolefin molded article or the like to which a rubber component and a hydroxyl group-containing polyolefin have been reduced or not added at all, and improved recoat adhesion. As a result of intensive research on the plastic primer to be formed,
It has been found that a primer using a specific chlorinated polyolefin and a blocked polyisocyanate and using them in combination with a polyol resin achieves the object, and has completed the present invention.

That is, according to the present invention, a chlorinated polyolefin (A) having a chlorine content of 16 to 22% by weight, a melting point of 80 ° C. or less and a weight average molecular weight of 30,000 to 120,000, an isocyanurate type aliphatic And / or a polyol (C) containing a blocked polyisocyanate (B) and a polyol resin (C) obtained by blocking an alicyclic polyisocyanate with a dialkyl malonate ester and an acetoacetate ester. Is provided.

Further, the present invention provides a method for coating a plastic molded article (hereinafter referred to as the present method), which comprises applying the primer to a plastic molded article and then applying a colored base paint and a clear paint on the coated surface. ).

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present primer and the present method according to the present invention will be specifically described.

[0009] Plastic molded articles as objects to be coated with the primer include, for example, bumpers, spoilers,
Examples include plastic molded products used for the outer skin of automobiles such as grills and fenders, as well as the outer skin of household appliances, and these materials include, for example, carbon atoms such as ethylene, propylene, butylene, and hexene. Polyolefins obtained by polymerizing one or two or more olefins selected from olefins having 2 to 10 are particularly suitable. In addition to these, the present primer is also applied to polycarbonate, ABS resin, urethane resin, nylon and the like. can do.

These plastic molded products can be appropriately subjected to degreasing treatment, water washing treatment and the like by a method known per se before coating of the present primer.

The primer has a chlorine content of 16 to 22.
Weight%, melting point is 80 ° C. or less, and weight average molecular weight is 3
A chlorinated polyolefin (A) having a molecular weight of 0000 to 120,000, a blocked polyisocyanate (B) obtained by blocking an isocyanurate type aliphatic and / or alicyclic polyisocyanate with a dialkyl malonate and an acetoacetate, and a polyol resin (C). It can be prepared by mixing and dispersing these in an organic solvent, and further includes using a coloring pigment, an extender pigment, a conductive filler, and the like, if necessary.

Component (A): a chlorine content of 16 to 22% by weight, a melting point of 80 ° C. or less, and a weight average molecular weight of 3000
It is a chlorinated polyolefin included in the range of 0 to 120,000.

The polyolefin serving as the base of the component (A) is obtained by polymerizing one or two or more olefins having 2 to 10 carbon atoms, such as ethylene, propylene, butylene, and hexene. ) It is a polymer.
Further, copolymerization is carried out with other polymerizable monomers such as unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid and fumaric acid, alkyl esters of (meth) acrylic acid, styrene and acrylonitrile according to known methods. Alternatively, a graft-modified polyolefin can also be used. These polymerizable monomers are suitably used in an amount of 50% by weight or less, particularly 30% by weight or less based on the olefins.

[0014] The chlorination of these polyolefins (including copolymers with other polymerizable monomers and graft polymers, the same applies hereinafter) can be performed, for example, by blowing chlorine gas into these organic solvent solutions or dispersions. And the reaction temperature is 5
It is preferably carried out at 0 to 120 ° C., and the chlorine content in the component (A) (solid content) is in the range of 16 to 22% by weight, preferably 18 to 20% by weight. Component (A) has a melting point of 80 ° C. or lower, preferably 50 to 75 ° C., and a weight average molecular weight of 30,000 to 120,000, preferably 5000.
Suitably, it is included in the range of 0 to 80000. If the chlorine content, melting point or weight average molecular weight of the component (A) deviates from these ranges, the object of the present invention is not achieved, which is not preferred.

The melting point of the component (A) is determined by a thermomechanical analyzer "T
MA-50H type "(manufactured by Shimadzu Corporation, trade name)
The chlorinated polyolefin was heated at 80 ° C. to form a sample film, the displacement was measured at a load of 1 g / cm ² , and the temperature was raised at a rate of 3 ° C./min. The melting point can be adjusted by changing the composition of the polyolefin, especially the amount of ethylene and α-olefin monomer.

Component (B): a blocked polyisocyanate obtained by blocking an isocyanurate type aliphatic and / or alicyclic polyisocyanate with a dialkyl malonate and an acetoacetate.

The component (B) is a blocked polyisocyanate in which the free isocyanate groups of an isocyanurated aliphatic and / or alicyclic polyisocyanate compound are blocked with both a dialkyl malonate and an acetoacetate. .

The polyisocyanate compound before blocking may be modified with a hydroxyl compound. This modification is a urethanization reaction between a hydroxyl group and an isocyanate group, and is performed before or after the isocyanuration reaction of the polyisocyanate. Either way, modification is preferably performed before the isocyanuration reaction.

The polyisocyanate compound used for isocyanuration is preferably an aliphatic and / or alicyclic diisocyanate compound having two isocyanate groups in one molecule. Examples thereof include tetramethylene diisocyanate, pentamethylene diisocyanate, and hexamethylene diisocyanate. Examples include methylene diisocyanate, trimethylhexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, bis (isocyanatomethyl) cyclohexane, dicyclohexylmethane diisocyanate, and among them, hexamethylene diisocyanate and isophorone diisocyanate have excellent weather resistance of the coating film. It is preferred.

The hydroxy compound used for the modification is a compound having one or more hydroxyl groups in one molecule,
For example, methanol, ethanol, isopropanol,
Monohydroxy compounds such as phenol, ethylene glycol, propylene glycol, butanediol, pentanediol, hexanediol, cyclohexanediol, dimethylolcyclohexane, dihydroxyl compounds such as neopentylglycol, trimethylpentanediol, trimethylolpropane, glycerin, pentaerythritol And the like. Polyhydric hydroxy compounds, hydroxyl group-containing acrylic resins, hydroxyl group-containing polyester resins, hydroxyl group-containing polyether resins, and the like.

The amount of modification with the hydroxy compound is such that the amount of hydroxyl groups based on isocyanate groups is 0.1 to 20 equivalent%,
Preferably 0.5-15 equivalent%, more preferably 1-10
Equivalent% is suitable. The urethanization reaction between the hydroxy compound and the isocyanate group can be performed in a temperature range of -20 to 150C.

The isocyanuration reaction can be carried out by a known method. To accelerate the reaction, for example, a tetraalkylammonium hydroxide or an organic acid salt such as tetramethylammonium, tetraethylammonium or tetrabutylammonium; Hydroxyalkylammonium hydroxides and organic acid salts such as trimethylhydroxyethylammonium, trimethylhydroxypropylammonium, triethylhydroxyethylammonium and triethylhydroxypropylammonium; alkali metals of alkylcarboxylic acids such as acetic acid, caproic acid, octylic acid and myristic acid Salts; and metal salts of the above-mentioned alkyl carboxylic acids such as tin, zinc and lead; and compounds such as aminosilyl group-containing compounds such as hexamethylene disilazane. It can be used. This catalyst concentration is 10 ppm to 1.
A range of 0% by weight is suitable.

The isocyanuration reaction can be carried out irrespective of the presence or absence of an organic solvent. It is necessary to use a solvent inert to the isocyanate group as the organic solvent. The reaction temperature is usually 20-160 ° C, preferably 40-130 ° C. When the reaction reaches the end point, it is preferable to stop the reaction by deactivating the catalyst with, for example, sulfonic acid, phosphoric acid, or the like. Then, the unreacted substances and the organic solvent are removed to obtain an isocyanurate-type polyisocyanate.

As a blocking agent for the thus obtained isocyanurate-type polyisocyanate (modified with a hydroxy compound if necessary), a dialkyl malonate and an acetoacetate are used in combination. Examples of the dialkyl malonate include dimethyl malonate, diethyl malonate, diisopropyl malonate, and dimalonate.
Butyl, diethyl methylmalonate, benzylmethyl malonate, diphenyl malonate, etc., as acetoacetates, for example, methyl acetoacetate, ethyl acetoacetate, isopropyl acetoacetate, n-propyl acetoacetate, benzyl acetoacetate, Phenyl acetate and the like. The dialkyl malonate is used in an amount of 30 to 90% by weight, particularly 50 to 80% by weight, based on the isocyanate group, and the acetoacetate is used in an amount of 1 to 10% by weight based on the isocyanate group.
A range of 0 to 30 equivalent%, particularly 20 to 50 equivalent% is suitable. In addition to these two types of blocking agents, for example,
Alcohol-based, phenol-based, oxime-based, amine-based,
An acid amide, imidazole, pyridine or mercaptan type blocking agent is
It can be used within the range of 0 equivalent% or less. The blocking reaction of the isocyanate group can be performed by a known method.

Component (C): a polyol resin. This (C)
The component is a compound having two or more hydroxyl groups in one molecule, and does not include the components (A) and (B) described above. Specifically, a polyester resin and an acrylic resin having two or more hydroxyl groups in one molecule can be suitably used.

The hydroxyl group-containing polyester resin is, for example,
Polybasic acids and polyhydric alcohols are known in a manner known per se,
It can be obtained by carrying out an esterification reaction with an excess of hydroxyl groups. Polybasic acid is a compound having two or more carboxyl groups in one molecule, for example, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, pyromellitic acid, itaconic acid, adipic acid , Sebacic acid, azelaic acid, hymic acid,
Often, succinic acid, hetic acid and anhydrides thereof are mentioned. Polyhydric alcohol is a compound having two or more hydroxyl groups in one molecule, for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, butylene glycol, hexanediol, trimethylolethane,
Trimethylolpropane, pentaerythritol, dipentaerythritol, sorbitol and the like.
Introduction of a hydroxyl group can be performed, for example, by using a polyhydric alcohol having three or more hydroxyl groups in one molecule. Further, as the polyester resin, a fatty acid-modified polyester resin modified with a fatty acid such as soybean oil fatty acid and dehydrated castor oil fatty acid can also be used.

The hydroxyl value of the hydroxyl-containing polyether resin is 1
0-100, especially 50-85, acid value is 50 or less, especially 1
And a number average molecular weight of from 2,000 to 100,000, particularly from 3,000 to 30,000 is suitable.

The hydroxyl group-containing acrylic resin can be obtained by polymerizing a hydroxyl group-containing monomer, an acrylic monomer and, if necessary, other monomers. The hydroxyl group-containing monomer is a compound having a hydroxyl group and a polymerizable unsaturated bond in one molecule, for example, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate,
(Meth) such as hydroxybutyl (meth) acrylate
Monoesters of acrylic acid and an alkylene glycol having 2 to 10 carbon atoms are exemplified. Acrylic monomer is
Monoesterified products of (meth) acrylic acid and a monoalcohol having 1 to 20 carbon atoms include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, (meth)
Examples thereof include propyl acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, and stearyl (meth) acrylate. Other monomers, other than this hydroxyl group-containing monomer and acrylic monomer,
Compounds having one or more polymerizable unsaturated bonds in one molecule, for example, (meth) acrylic acid, maleic acid, (meth) glycidyl acrylate, (meth) acrylamide,
Acrylonitrile, styrene, vinyl acetate, vinyl chloride and the like can be mentioned. The polymerization reaction of these monomers can be performed by a known method, for example, solution polymerization or the like. The hydroxyl value of the hydroxyl group-containing acrylic resin is 10 to 10
0, especially 50 to 80, the acid value is 50 or less, especially 1 to 30,
The number average molecular weight is 2,000 to 100,000, particularly 3,000
A range of ５０50,000 is suitable.

The primer is a component (A) described above: a chlorinated polyolefin having a chlorine content of 16 to 22% by weight, a melting point of 80 ° C. or less and a weight average molecular weight of 30,000 to 120,000, and a component (B): A blocked polyisocyanate obtained by blocking an isocyanurate-type aliphatic and / or alicyclic polyisocyanate with a dialkyl malonate and an acetoacetate; and component (C): a polyol resin as an essential component. The composition ratio can be arbitrarily selected according to the purpose. For example, based on the total solid content of the three components, component (A) is 20 to 80% by weight, particularly 40 to 60% by weight, and component (B) is 3%. It is suitable that the content is in the range of 20 to 20% by weight, particularly 5 to 15% by weight, and the component (C) is in the range of 10 to 50% by weight, especially 20 to 30% by weight.

The primer of the present invention comprises these components (A)
It is obtained by dissolving or dispersing the component (B) and the component (C) in an organic solvent, but may further contain a coloring pigment, an extender pigment, a catalyst, and the like, if necessary.

As coloring pigments, titanium oxide, carbon black, graphite, loess, yellow iron oxide, Hansa yellow, pigment yellow, chrome orange, chrome vermilion,
Examples include, but are not limited to, solid color pigments such as permanent orange, amber, permanent red, brilliant carmine, fast violet, methyl violet lake, ultramarine, navy blue, cobalt blue, phthalocyanine blue, pigment green, and naphthol green. One or more of these can be used.

The primer is adjusted to a viscosity of 8 to 20 seconds / Ford cup # 4/20 ° C., and can be applied to a plastic molded product by air spray coating, airless spray coating, electrostatic coating, dip coating, or the like. The coating thickness is suitably in the range of 10 to 40 μm based on the cured coating film. The coating film itself of the primer can form a cured coating film that has undergone a three-dimensional crosslinking reaction by heating at 60 to 120 ° C., preferably 80 to 100 ° C., for about 5 to 40 minutes.

The present invention relates to a method for coating a plastic molded article, which comprises applying the primer of the present invention to a plastic molded article, and then applying a colored base paint and a clear paint to the coated surface.

Specifically, in the present method, the primer is applied to a plastic molded product as described above, and after the coating film is cured, or without curing, a top coat is applied to the coated surface. It is done by doing.

With respect to the plastic molded product, the primer and the method of coating the primer in the present method, those described in the present primer can be applied.

The top coating is a coating to be applied to the cured or uncured coating surface of the primer, and known coatings for plastics can be used. For example, coloring base coatings (Y) and 2 containing a hydroxyl group-containing acrylic resin can be used. A liquid type acrylic resin-based clear paint (Z) can be mentioned, and a multi-layer top coat obtained by applying both paints is particularly preferable.

The coloring base paint (Y) contains a hydroxyl group-containing acrylic resin and a coloring pigment, and is a paint for forming a colored coating film by mixing these with an organic solvent. The cross-linking agent is not substantially contained, and the single coating film of the paint (Y) does not undergo three-dimensional curing due to a cross-linking reaction.

The hydroxyl group-containing acrylic resin is exemplified as the polyol resin (C) of the above primer.
A hydroxyl group-containing monomer, an acrylic monomer, and, if necessary, a hydroxyl group-containing acrylic resin obtained by polymerizing another monomer can be suitably used, and the hydroxyl value is 20.
-100, especially 40-60, acid value under 20, especially 5-1
0, weight average molecular weight of 4000 to 40,000, especially 60
A range of 00 to 20000 is suitable.

Examples of the coloring pigment include, in addition to the solid color pigments exemplified in the present primer, glittering metallic pigments such as aluminum, aluminum oxide, and vapor-deposited aluminum; and light interference such as mica flakes coated with titanium oxide or iron oxide. Thus, a coating film of the colored base paint (Y) can form a solid color coating film, a metallic coating film, or a light interference coating film.

The colored base paint (Y) has a viscosity of 10 to 20.
Seconds / Ford Cup # 4/20 ° C, can be applied to the cured or uncured primer of plastic molded products by air spray coating, airless spray coating, electrostatic coating, dip coating, etc. it can. The coating thickness is suitably in the range of 10 to 40 μm based on the cured coating film. The coating film itself of the colored base paint (Y) does not form a cured coating film that has undergone a three-dimensional crosslinking reaction even when heated.

Two-component acrylic resin clear paint (Z)
Is a clear paint containing a hydroxyl group-containing acrylic resin and a polyisocyanate, which forms a colorless transparent or colored transparent coating film.

The acrylic resin in the clear paint (Z) has a hydroxyl value of 100 to 180, preferably 120 to 1
40, and the weight average molecular weight is 4000-15000,
Preferably, it is an acrylic resin in the range of 6,000 to 8,000.

Specifically, it can be prepared, for example, by copolymerizing a hydroxyl group-containing unsaturated monomer and an acrylic monomer and, if necessary, using another unsaturated monomer in combination.

The hydroxyl group-containing unsaturated monomer is a compound having at least one hydroxyl group and at least one polymerizable unsaturated double bond in one molecule. Examples thereof include hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate. And an equimolar addition product of an alkylene glycol having 2 to 10 carbon atoms such as hydroxybutyl (meth) acrylate and (meth) acrylic acid.

The acrylic monomer is a monoester of meth) acrylic acid and a monoalcohol having 1 to 24 carbon atoms, and specifically, methyl (meth) acrylate,
Ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, hexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate And so on.

Other unsaturated monomers are other than the above-mentioned hydroxyl-containing unsaturated monomers and acrylic monomers, and have at least one polymerizable unsaturated double bond in one molecule. Compounds, for example, acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, fumaric acid, 2-carboxyethyl (meth) acrylate, 2-carboxypropyl (meth) acrylate, 5-carboxypentyl (meth) acrylate Carboxyl group-containing unsaturated compounds such as glycidyl (meth) acrylate and allyl glycidyl ether; perfluorobutylethyl (meth) acrylate, perfluoroisononylethyl (meth) acrylate; For example, perfluorooctylethyl (meth) acrylate Fluoroalkyl (meth) acrylate; styrene, alpha-methyl styrene, vinyl toluene, vinyl aromatic compounds such as alpha-chlorostyrene;
N, N-dimethylaminoethyl (meth) acrylate,
N, N-diethylaminoethyl (meth) acrylate,
Nitrogen-containing alkyl (meth) acrylates such as Nt-butylaminoethyl (meth) acrylate; acrylamide, methacrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-methylol (meth) acrylamide; N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N-dimethylaminoethyl (meth) Polymerizable amides such as acrylamide; 2-vinylpyridine, 1
-Aromatic nitrogen-containing monomers such as -vinyl-2-pyrrolidone and 4-vinylpyridine; and polymerizable nitriles such as acrylonitrile and methacrylonitrile. These can be used alone or in combination of two or more.

The acrylic resin is copolymerized with the above-mentioned unsaturated monomer containing a hydroxyl group, an acrylic monomer and, if necessary, other unsaturated monomers in a known manner such as solution polymerization. Can be prepared.

The polyisocyanate is a compound having two or more isocyanate groups in one molecule, and this isocyanate group is not substantially blocked and used in a free state. Specifically, one or more selected from aliphatic polyisocyanate compounds, alicyclic polyisocyanate compounds, aromatic polyisocyanate compounds, and the like can be used. Among them, as the aliphatic polyisocyanate compound and the alicyclic polyisocyanate compound, those described in the present primer can be suitably used. Examples of the aromatic polyisocyanate compound include xylylene diisocyanate, meta-xylylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, and phenylene diisocyanate. Further, these polyisocyanate compounds and ethylene glycol, propylene glycol, 1,
4-butylene glycol, polyalkylene glycol,
Products obtained by reacting a polyol such as trimethylolpropane or hexanetriol in a ratio in which an isocyanate group is in excess with respect to a hydroxyl group of a polyol, a buret type adduct thereof, an isocyanuric ring type adduct thereof, and the like are also polyisocyanates. Can be used.

The clear paint (Z) is a paint that forms the colorless transparent or colored transparent coating film containing the above-mentioned acrylic resin and polyisocyanate. They can be contained to the extent that they do not interfere, and can be obtained by mixing these with an organic solvent.

The ratio of each component in the clear paint (Z) can be arbitrarily selected according to the purpose, but the former is 50 to 9 based on the total solid content ratio of the acrylic resin and polyisocyanate.
0% by weight, especially 60-80% by weight, the latter component being 10-5%
0% by weight, preferably in the range of 20 to 40% by weight.

In the clear paint (Z), the hydroxyl groups of the acrylic resin and the isocyanate groups of the polyisocyanate are liable to react at room temperature. Therefore, when storing for a long time, these components are separated in advance and mixed immediately before coating. It is preferable to use it.

The clear paint (Z) has a viscosity of 14 to 18 seconds /
The temperature can be adjusted to Ford cup # 4/20 ° C., and the uncured surface of the colored base paint (Y) can be applied by air spray coating, airless spray coating, electrostatic coating, dip coating, or the like. The coating thickness is 15-8 based on the cured coating.
A range of 0 μm is suitable. The coating film of the clear paint (Z) itself is at room temperature to 120 ° C, preferably 80 to 100 ° C.
By heating for about 5 to 60 minutes, a cured coating film that has undergone a three-dimensional crosslinking reaction can be formed.

When the clear paint (Z) is applied to the uncured painted surface of the colored base paint (Y), the clear paint (Z)
The polyisocyanate compound contained in the coating film of (1) penetrates into the uncured coating film of the colored base coating material (Y), and the coating film of the coloring base coating material (Y) can be simultaneously three-dimensionally cross-linked and cured. That is, by applying a colored base paint (Y), applying a clear paint (Z) on the uncured coated surface, and then heating at room temperature to 120 ° C, preferably 80 to 100 ° C for about 5 to 60 minutes. It is possible to form a multi-layer top coat by simultaneously performing a three-dimensional cross-linking and curing reaction of these two coats.

Therefore, according to the present method, the primer coating film and the overcoating film have a temperature of 120 ° C. or less, preferably 80 to
Since it can be cured by heating at 100 ° C. for about 5 to 60 minutes, the plastic molded article as the object to be coated does not undergo any thermal deformation or deterioration.

Then, even if dusts and bumps are generated in this coating process, after 3 to 7 days or more have passed since both coatings were cured, the portion was polished and removed, and the portion and its surroundings were removed. In the part, the interlayer adhesion with the coating film formed by repair coating using the primer, the colored base paint (Y) and the clear paint (Z) was remarkably excellent.

[0056]

EXAMPLES Examples and comparative examples according to the present invention will be described below. All parts and percentages are based on weight, and the film thickness of the coating is based on the cured coating.

1. Preparation of sample 1) Chlorinated polyolefin (A) (A-1): It was carried out according to the description in the examples of Japanese Patent No. 2790621. 4 kg of isotactic polypropylene having a melt index of 14 g / 10 min (measurement method: ASTM D123-62T) is uniformly dissolved under pressure in 80 liters of carbon tetrachloride. A chlorinated polyolefin having a chlorine content of 20% by weight, a melting point of 75 ° C. and a weight average molecular weight of 60,000 was obtained by blowing gas and performing chlorination.

(A-2): In the same manner as in (A-1), using isotactic polypropylene having a different composition and a different melt index, a chlorine content of 20% by weight and a melting point of 6 were used.
A chlorinated polyolefin having a weight average molecular weight of 55000 at 0 ° C. was obtained.

(A-3): In the same manner as in (A-1), using isotactic polypropylene having a different composition and a different melt index, a chlorine content of 20% by weight and a melting point of 1 were used.
A chlorinated polyolefin having a weight average molecular weight of 70,000 at 00 ° C was obtained. (Comparative) 2) Blocked polyisocyanate (B) (B-1): Under a nitrogen atmosphere, 100 parts of 1,6 hexamethylene diisocyanate and 1.2 parts of butanediol were charged into a flask and stirred at 80 ° C at 80 ° C. Hold for 2 hours. Thereafter, the temperature was maintained at 60 ° C., tetrabutylammonium acetate was added, and when the yield reached 30%, phosphoric acid was added to stop the reaction. After filtering the reaction solution, unreacted 1,6 hexamethylene diisocyanate was removed using a thin film evaporator, and the viscosity at 25 ° C was 38.
A polyisocyanate having 00 mPas and an isocyanate content of 21.0% was obtained.

Under a nitrogen atmosphere, 100 parts of this polyisocyanate and 39 parts of xylene were charged into a flask, and 42 parts of diethyl malonate, 34 parts of ethyl acetoacetate, 28%
A mixture of 0.8 parts of sodium methylate solution was slowly added at room temperature. After completion of the addition, the reaction was continued at 60 ° C. for 6 hours. Thereafter, 14 parts of butanol was added and the mixture was sufficiently stirred. A blocked polyisocyanate solution having a resin content of 75% and a blocked isocyanate group content (as NCO) of 9.1% was obtained. Even if this blocked polyisocyanate solution was stored at 5 ° C. for 2 weeks, it did not crystallize and maintained in a solution state.

3) Polyol resin (C) (C-1): 240 parts of phthalic anhydride, 230 parts of trimethylolpropane and 175 parts of coconut oil fatty acid are subjected to an esterification reaction by a conventional method to give a hydroxyl value of 80, an acid value of 15, A fatty acid-modified polyester polyol resin having a number average molecular weight of 8,000 was obtained.

4) One-component type base paint (Y) "SOFLEX 415" (trade name, manufactured by Kansai Paint Co., Ltd.)
Organic solvent-based metallic paint containing a hydroxyl group-containing acrylic resin as a main component and does not contain a crosslinking agent).

5) Two-part clear paint (Z) "SOFLEX 415" (trade name, manufactured by Kansai Paint Co., Ltd.)
Organic solvent-based clear coatings containing a hydroxyl group-containing acrylic resin and a polyisocyanate compound as main components).

2. Examples and Comparative Examples Example 1 Chlorinated polyolefin (A-1) 50 parts (solid content), blocked polyisocyanate (B-1) 10 parts (solid content), polyol resin (C-1) 40 parts (solid content) ) And 80 parts of titanium white pigment were mixed and dispersed in a mixed solvent of xylene / toluene = 1/1 (weight ratio) to obtain a primer adjusted to a viscosity of 13 seconds / Ford cup # 4/20 ° C.

Example 2 50 parts (solid content) of chlorinated polyolefin (A-2), 10 parts (solid content) of blocked polyisocyanate (B-1), 40 parts (solid content) of polyol resin (C-1), 80 parts of titanium white pigment was mixed and dispersed in a mixed solvent of xylene / toluene = 1/1 (weight ratio) to obtain a primer adjusted to a viscosity of 13 seconds / Ford cup # 4/20 ° C.

Comparative Example 1 50 parts (solid content) of chlorinated polyolefin (A-3), 10 parts (solid content) of blocked polyisocyanate (B-1), 40 parts (solid content) of polyol resin (C-1) 80 parts of titanium white pigment was mixed and dispersed in a mixed solvent of xylene / toluene = 1/1 (weight ratio) to obtain a primer adjusted to a viscosity of 13 seconds / Ford cup # 4/20 ° C.

Comparative Example 2 60 parts (solid content) of chlorinated polyolefin (A-2), 40 parts (solid content) of polyol resin (C-1), and 80 parts of titanium white pigment were mixed with xylene / toluene = 1/1 (weight). Ratio) mixed solvent and dispersed, viscosity 13 seconds / Ford cup # 4
A primer adjusted to / 20 ° C was obtained.

Example 3 The primer obtained in Example 1 was applied to a polypropylene (degreasing-treated) of an automotive body exterior grade having a thickness of 15 μm.
Spray paint so that it becomes, leave it at room temperature for 3 minutes, then apply one-pack base paint (Y)
Spray coat “Soflex 415” to a thickness of 15 μm, leave at room temperature for 3 minutes,
Spray painting of liquid type clear paint (Z) “Soflex 415” was performed so that the film thickness became 35 μm.
The coatings were simultaneously cured by heating at 00 ° C. for 30 minutes.

Example 4 The primer obtained in Example 2 was applied to a car body exterior grade polypropylene (degreased) having a thickness of 15 μm.
Spray paint so that it becomes, leave it at room temperature for 3 minutes, then apply one-pack base paint (Y)
Spray coat “Soflex 415” to a thickness of 15 μm, leave at room temperature for 3 minutes,
Spray painting of liquid type clear paint (Z) “Soflex 415” was performed so that the film thickness became 35 μm.
The coatings were simultaneously cured by heating at 00 ° C. for 30 minutes.

COMPARATIVE EXAMPLE 3 The primer obtained in Comparative Example 1 was applied to an automotive body exterior grade polypropylene (degreased) having a thickness of 15 μm.
Spray paint so that it becomes, leave it at room temperature for 3 minutes, then apply one-pack base paint (Y)
Spray coat “Soflex 415” to a thickness of 15 μm, leave at room temperature for 3 minutes,
Spray painting of liquid type clear paint (Z) “Soflex 415” was performed so that the film thickness became 35 μm.
The coatings were simultaneously cured by heating at 00 ° C. for 30 minutes.

COMPARATIVE EXAMPLE 4 The primer obtained in Comparative Example 2 was applied to a polypropylene for automobile body exterior grade (degreased) to a thickness of 15 μm.
Spray paint so that it becomes, leave it at room temperature for 3 minutes, then apply one-pack base paint (Y)
Spray coat “Soflex 415” to a thickness of 15 μm, leave at room temperature for 3 minutes,
Spray painting of liquid type clear paint (Z) “Soflex 415” was performed so that the film thickness became 35 μm.
The coatings were simultaneously cured by heating at 00 ° C. for 30 minutes.

3. Performance tests were performed on the multilayer coating films formed in Examples 3 and 4 and Comparative Examples 3 and 4. The results are shown in Table 1.

[0073]

[Table 1]

The performance test method is as follows.

Adhesion: A cut line was made with a cutter so as to reach the base of the coating film, 100 squares of 2 mm × 2 mm were made, and an adhesive cellophane tape was adhered to the surface, and the adhesive was cut at 20 ° C. The number of remaining coatings in the squares after abruptly peeling off was checked and others. ○: 100 remaining, △: 99 ~
95 pieces remaining, x shows 94 pieces or less remaining.

Water adhesion: A part of the coated bumper was cut out, immersed in warm water of 40 ° C. for 10 days, pulled up and dried, and then subjected to an adhesion test in the same manner as the above adhesion test. The evaluation criteria are the same.

Recoat adhesion: The multilayer coating films formed in Examples and Comparative Examples were allowed to stand at room temperature for 7 days, the same paint was re-applied on the coated surface, cured, and then allowed to stand at room temperature for 3 days. An adhesion test was performed in the same manner as the above adhesion test. The evaluation criteria are the same.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C08J 7/04 CES C08J 7/04 CESSZ C09D 5/00 C09D 5/00 D 175/04 175/04 // C08L 23:10 C08L 23:10 (72) Inventor Keita Ono, Daiji, Miyoshi-cho, Nishi-kamo-gun, Aichi Prefecture, 1st floor, Azaji, Kansai Paint Co., Ltd. F term (reference) 4D075 AE03 CA13 CB06 DA23 DB35 DB36 DB37 DB42 DB48 DB50 DB53 DC11 DC18 EA07 EA10 EA41 EA43 EB13 EB14 EB20 EB22 EB35 EB38 EB45 EB52 EC11 4F006 AA12 AA14 AB13 AB24 AB35 AB37 BA01 CA04 4J038 CB031 CB032 PA CB091 CB121 CP12 DG CB091 PC08

Claims (2)

[Claims] 1. A chlorine content of 16 to 22% by weight and a melting point of 8%.
0 ° C. or less and a weight average molecular weight of 30,000 to 120
A chlorinated polyolefin (A), a blocked polyisocyanate (B) obtained by blocking an isocyanurate type aliphatic and / or alicyclic polyisocyanate with a dialkyl malonate and an acetoacetate, and a polyol resin (C). A primer for plastics, characterized in that: 2. A method for coating a plastic molded article, comprising coating a plastic molded article with the primer for plastic according to claim 1, and then applying a colored base paint and a clear paint on the coated surface.