JP2001002979A - Coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating material capable of forming a coating film with high finishability providing hardly any color of the resin, excellent in polishing and after-tack-proofness and also in luster feeling and smoothness. SOLUTION: This coating composition is obtained by including (A) a copolymer with a weight-average molecular weight of 3,000-40,000 and hydroxyl number of 40-160 mgKOH/g, and with monomer components as constituent composed of (a) 10-50 wt.% of styrene, (b) 10-50 wt.% of at least one kind of monomer selected from isobornyl (meth)acrylate and tricyclodecanyl (meth)acrylate, (c) 10-70 wt.% of a monomer selected from a 8-20C alkyl ester of methacrylic acid and 4-20C alkyl ester of acrylic acid, (d) 10-40 wt.% of hydroxyl group- containing polymerizable unsaturated monomer and (e) 0-60 wt.% of another polymerizable unsaturated monomer with no carboxyl group, and (B) a polyisocyanate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition which hardly discolors a resin, is excellent in abrasion properties, resistance to non-uniformity in return, and is capable of forming a coating film having an excellent finish. The present invention relates to a suitable coating composition and a method for forming a coating film using the coating composition.

[0002]

2. Description of the Related Art
As a clear paint for repairing automobile bodies, etc., a clear paint for repair which is a combination of a hydroxyl group-containing acrylic resin and a polyisocyanate is often used, and the hydroxyl group-containing acrylic resin contains an internal part for curing by a urethane-forming reaction. Usually, a carboxyl group is introduced as a catalyst. When a carboxyl group is introduced into a hydroxyl group-containing acrylic resin, there is a problem that the resin viscosity tends to increase and the number of colors of the resin increases.

[0003] As a clear coating for repairing automobile bodies and the like, a coating film having excellent polishing properties can be formed, and the resistance to uneven return of a colored base coating such as a metallic base coating during wet-on-wet coating is good. In addition, in recent years, it has been demanded that the paint be made high solid and a coated film having a high finish can be formed.

[0004] The object of the present invention is to hardly color the resin,
An object of the present invention is to provide a paint which is excellent in polishing properties and resistance to non-uniformity in return, and which can form a highly finished coating film having excellent gloss and smoothness.

It is another object of the present invention to provide a repair coating method which is excellent in polishing properties and resistance to non-uniformity in return, and which can form a highly finished coating film.

[0006]

The present inventors have made styrene, isobornyl (meth) acrylate, tricyclodecanyl (meth) acrylate and a specific alkyl (meth) acrylate part of the constituent monomer component, and The inventors have found that the above object can be achieved by using a hydroxyl group-containing copolymer containing no carboxyl group-containing monomer in the monomer component as a base resin, and have completed the present invention.

Thus, the present invention relates to (A) 10 to 50% by weight of (a) styrene, and (b) at least one monomer selected from isobornyl (meth) acrylate and tricyclodecanyl (meth) acrylate. 50% by weight, (c) at least one monomer selected from the group consisting of methacrylic acid having 8 to 20 carbon atoms and the acrylic acid having 4 to 20 carbon atoms.
70% by weight, (d) hydroxyl-containing polymerizable unsaturated monomer 1
0-40% by weight and (e) above (a), (b), (c)
And 0 to 60% by weight of another polymerizable unsaturated monomer copolymerizable with the component (d) and having no carboxyl group.
Having a weight average molecular weight of 3,000 to 40,000 and a hydroxyl value of 40 to 160.
An object of the present invention is to provide a coating composition comprising a copolymer in the range of mgKOH / g and (B) a polyisocyanate.

Further, the present invention is characterized in that a liquid colored base paint is applied, and then the above-mentioned paint composition is applied on the base coat and dried while the base coat is in an uncured state. A method for forming a repair coating film is provided.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the coating composition of the present invention will be described in detail. The coating composition of the present invention is a coating composition containing the following copolymer (A), copolymer (B), curing agent (C) and organic solvent (D) as essential components.

Copolymer (A) In the composition of the present invention, the copolymer (A) is at least one selected from the group consisting of (a) styrene, (b) isobornyl (meth) acrylate and tricyclodecanyl (meth) acrylate. At least one monomer selected from the group consisting of (c) an alkyl ester of 8 to 20 carbon atoms of methacrylic acid and an alkyl ester of 4 to 20 carbon atoms of acrylic acid (hereinafter, “specific alkyl (meth) acrylate”). And (d) a hydroxyl group-containing polymerizable unsaturated monomer, (e) the above (a), (b),
A hydroxyl group-containing copolymer which is copolymerizable with the components (c) and (d) and has a monomer component comprising another polymerizable unsaturated monomer having no carboxyl group as a constituent component.

In the present invention, "(meth) acrylate" means "acrylate or methacrylate". That is, for example, the isobornyl (meth) acrylate in the component (b) means isobornyl acrylate or isobornyl methacrylate.

Examples of the alkyl ester having 8 to 20 carbon atoms of methacrylic acid in the specific alkyl (meth) acrylate (c) include n-octyl methacrylate, 2-ethylhexyl methacrylate, nonyl methacrylate, decyl methacrylate, dodecyl methacrylate, and the like. Tetradecyl methacrylate, hexadecyl methacrylate, octadecyl methacrylate, and the like, and examples of the C4 to C20 alkyl ester of acrylic acid include n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, pentyl acrylate, hexyl acrylate, Heptyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, dodecyl Acrylate, tetradecyl acrylate, hexadecyl acrylate, and octadecyl acrylate.

Examples of the hydroxyl-containing polymerizable unsaturated monomer (d) include, for example, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2,3-dihydroxybutyl (meth) acrylate, 4-hydroxybutyl Monoesters of polyhydric alcohol and acrylic acid or methacrylic acid, such as (meth) acrylate and polyethylene glycol mono (meth) acrylate; ε-caprolactone is added to the monoester of polyhydric alcohol and acrylic acid or methacrylic acid. Ring-opening polymerized compounds such as "Placcel FA
-1 "," Placcel FA-2 "," Placcel FA-
3 "," Placcel FA-4 "," Placcel FA-
5 "," Placcel FM-1 "," Placcel FM-
2 "," Placcel FM-3 "," Placcel FM-
4 "and" Placcel FM-5 "(both of which are manufactured by Daicel Chemical Co., Ltd., trade names) and the like. These can be used alone or in combination of two or more.

The other polymerizable unsaturated monomer (component (e)) (hereinafter sometimes abbreviated as “other monomer”) is the same as component (a), component (b), component (c) and component (d). It is a polymerizable unsaturated monomer having no carboxyl group other than the components (a), (b), (c) and (d), which can be copolymerized.

[0015] Other monomers as component (e) include, for example, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl. C such as methacrylate and cyclohexyl methacrylate
_1-7 alkyl methacrylate; methyl acrylate,
C _1-3 alkyl acrylates such as ethyl acrylate, n-propyl acrylate and isopropyl acrylate; epoxy group-containing polymerizable unsaturated monomers such as glycidyl (meth) acrylate and 3,4-epoxycyclohexylmethyl (meth) acrylate; N, N Aminoalkyl (meth) acrylates such as -dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate; acrylamide, methacrylamide, N, N-dimethyl Aminoethyl (meth)
Acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N-methylolacrylamide, N-methylolacrylamide methyl ether, N
-(Meth) acrylamide such as methylolacrylamide butyl ether or a derivative thereof; acrylonitrile, methacrylonitrile, vinyl acetate, beoba monomer (manufactured by Shell Chemical Co., Ltd.), vinyl toluene, α-methylstyrene, and the like. These compounds can be used alone or in combination of two or more. In the present invention, “(meth) acrylamide” means acrylamide or methacrylamide.

In the composition of the present invention, the mixing ratio of each monomer constituting the copolymer (A) is preferably within the following range based on all the constituting monomers.

Component (a): 10 to 50% by weight, preferably 20 to 45%
% By weight, component (b): 10 to 50% by weight, preferably 20 to 40%
Component (c): 10 to 70% by weight, preferably 15 to 40%
% By weight, component (d): 10 to 40% by weight, preferably 15 to 30%
Component (e): 0 to 60% by weight, preferably 5 to 50%
weight%.

The amount of styrene is preferably in the range of 10 to 50% by weight from the viewpoint of the glossiness of the resulting coating film and the resistance to nonuniformity in return. It is preferable that the amount of isobornyl (meth) acrylate and / or tricyclodecanyl (meth) acrylate is in the range of 10 to 50% by weight from the viewpoint of the polishing properties of the coating film, the resistance to nonuniformity in return, and the like. . It is preferable that the amount of the specific alkyl (meth) acrylate (c) is in the range of 10 to 70% by weight from the viewpoints of finishability, coating film abrasion, and the like. The amount of the hydroxyl group-containing polymerizable unsaturated monomer is preferably in the range of 10 to 40% by weight from the viewpoint of curability, coating film hardness, coating film finish, and the like.

The copolymer (A) has a weight average molecular weight of 3,000 to 40,000, preferably 5,000 to 40,000.
Within the range of 15,000, the finish of the coating film,
It is suitable from the viewpoint of resistance to non-uniformity in return and has a hydroxyl value of 40.
~ 160mgKOH / g, preferably 80 ~ 130mg
It is preferable that the ratio is in the range of KOH / g from the viewpoints of curability, coating film hardness, finish of the coating film, and the like, and it is preferable that the glass transition temperature is in the range of 20 to 70 ° C. .

In the present invention, the weight average molecular weight is measured by gel permeation chromatography (GPC) using a standard polystyrene calibration curve, and the glass transition temperature (Tg) is determined by differential thermal analysis (DTA). Things.

The polymerization method for obtaining the copolymer (A) by polymerizing the above monomer component is not particularly limited, and a polymerization method known per se, for example, a bulk polymerization method in the presence of a radical polymerization initiator, may be used. Among them, a solution polymerization method can be preferably used, such as a polymerization method, a solution polymerization method, a bulk-suspension two-stage polymerization method in which suspension polymerization is performed after bulk polymerization.

Examples of the radical polymerization initiator include ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide and methylcyclohexanone peroxide; and 1,1-bis (tert-butylperoxy). ) -3,
3,5-trimethylcyclohexane, 1,1-bis (te
rt-butylperoxy) cyclohexane, n-butyl-
4,4-bis (tert-butylperoxy) valerate,
2,2-bis (4,4-ditert-butylperoxycyclohexyl) propane, 2,2-bis (4,4-ditert
-Amyl peroxycyclohexyl) propane, 2,2
-Bis (4,4-ditert-hexylperoxycyclohexyl) propane, 2,2-bis (4,4-ditert-octylperoxycyclohexyl) propane, 2,2-
Peroxyketals such as bis (4,4-dicumylperoxycyclohexyl) propane; hydroperoxides such as cumene hydroperoxide and 2,5-dimethylhexane-2,5-dihydroperoxide;
1,3-bis (tert-butylperoxy-m-isopropyl) benzene, 2,5-dimethyl-2,5-di (tert
Dibutyl peroxides such as -butylperoxy) hexane, diisopropylbenzene peroxide and tert-butylcumyl peroxide; diacyl peroxides such as decanoyl peroxide, lauroyl peroxide, benzoyl peroxide and 2,4-dichlorobenzoyl peroxide Oxides; Peroxycarbonates such as bis (tert-butylcyclohexyl) peroxydicarbonate; Peroxyesters such as tert-butylperoxybenzoate and 2,5-dimethyl-2,5-di (benzoylperoxy) hexane And organic azo polymerization initiators such as 2,2'-azobisisobutyronitrile and 1,1-azobis (cyclohexane-1-carbonitrile).

The polymerization method by the solution polymerization method includes:
For example, there can be mentioned a method in which the monomer mixture is dissolved or dispersed in an organic solvent, and the mixture is heated with stirring at a temperature of usually about 80 ° C. to 200 ° C. in the presence of the radical polymerization initiator. The reaction time is usually 1 to 24
Time is appropriate.

Examples of the organic solvent include hydrocarbon solvents such as heptane, toluene, xylene, octane and mineral spirit; esters such as ethyl acetate, n-butyl acetate, isobutyl acetate, ethylene glycol monomethyl ether acetate, diethylene glycol monobutyl ether acetate, and the like. Ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone and cyclohexanone; alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, sec-butanol and isobutanol; n-butyl ether, dioxane, ethylene glycol monomethyl Ethers, ethers such as ethylene glycol monoethyl ether and the like; Swazole 310, Swazole 1000, Swazole 1500 (or more, Both are manufactured by Cosmo Oil), SH
ELLSOL A (Shellsol A, manufactured by Shell Chemical Company)
And other aromatic petroleum solvents. These organic solvents can be used alone or in combination of two or more.

The copolymer (A) may be composed of one type of copolymer, or may be composed of two or more types of copolymers. For example, if the weight average molecular weight is 3,000 or more,
And less than 20,000 and a hydroxyl value of 50 to 160
a copolymer (a-1) having a weight average molecular weight of 20,000 to 40,000 and a hydroxyl value of 40 to 100 mgKOH / g in a range of mgKOH / g and a constituent monomer component composition in the above range. g, and a mixture with the copolymer (a-2) whose constituent monomer component composition is within the above range. The above copolymer (a-
In the relationship between 1) and the copolymer (a-2), the weight average molecular weight is such that the copolymer (a-2) is a copolymer (a-
5,000 or more larger than 1), and even 10,000
It is preferably larger than 00 from the viewpoints of finishability of the coating film, sagging resistance and the like, and the hydroxyl value of the copolymer (a
-1) is 0 to 60 mgKOH /
g range is large, and further 10 to 40 mgKOH /
It is preferable that the range of g is large from the viewpoint of the finish of the coating film and the hardness of the coating film. The mixing ratio of the copolymer (a-1) and the copolymer (a-2) is (a-1) / (a-
The solid content ratio of 2) is suitably in the range of 95/5 to 50/50.

Polyisocyanate (B) In the present invention, the polyisocyanate as the component (B) is capable of forming a cured coating film by reacting with the hydroxyl group in the copolymer (A). Group 2
Or more. This isocyanato group may be blocked with a blocking agent.

Examples of the polyisocyanate not blocked with a blocking agent include aliphatic diisocyanates such as lysine diisocyanate, hexamethylene diisocyanate, and trimethylhexane diisocyanate; hydrogenated xylylene diisocyanate, isophorone diisocyanate, and methylcyclohexane-2,4. Cycloaliphatic diisocyanates such as (or 2,6) -diisocyanate, 4,4'-methylenebis (cyclohexylisocyanate), 1,3- (isocyanatomethyl) cyclohexane; tolylene diisocyanate, xylylene diisocyanate, diphenylmethane Aromatic diisocyanates such as diisocyanate; organic polyisomers such as trivalent or higher polyisocyanate such as lysine triisocyanate Anate itself, or an adduct of each of these organic polyisocyanates with a polyhydric alcohol, a low molecular weight polyester resin or water, or a cyclized polymer of each organic diisocyanate as described above (eg, isocyanurate), biuret type And adducts. Of these, isocyanurate of hexamethylene diisocyanate is preferred.
These can be used alone or in combination of two or more.

When the composition of the present invention is used as a low-temperature curable paint at room temperature or about 100 ° C. or lower, such as a repair paint, it is preferable to use the above unblocked polyisocyanate as the curing agent (C). But 10
Under baking conditions exceeding 0 ° C., blocked polyisocyanates can also be suitably used.

The blocked polyisocyanate compound is obtained by blocking the isocyanate group of the polyisocyanate with a blocking agent. Examples of the blocking agent include phenols such as phenol, cresol and xylenol; ε-caprolactam;
Lactams such as valerolactam, γ-butyrolactam, β-propiolactam; methanol, ethanol, n-
Or i-propyl alcohol, n-, i- or t-butyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether,
Alcohols such as benzyl alcohol; oximes such as formamidoxime, acetoaldoxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime; dimethyl malonate, diethyl malonate, ethyl acetoacetate, ethyl acetoacetate, methyl acetoacetate, acetylacetone A blocking agent such as an active methylene type can be suitably used. The isocyanate group of the polyisocyanate can be easily blocked by mixing the polyisocyanate with the blocking agent.

The coating composition of the present invention contains the above-mentioned copolymer (A) and polyisocyanate (B) as essential components. The mixing ratio of the component (A) and the component (B) is such that the free or blocked isocyanate group (NCO) is changed to the hydroxyl group (OH) in the copolymer (A).
To the equivalent ratio of NCO / OH, usually 0.2 to
It is suitably within the range of 2.0, preferably 0.5 to 1.5.

When the polyisocyanate (B) is an unblocked polyisocyanate,
When the copolymer (A) and the polyisocyanate are mixed, a reaction between the two occurs. Therefore, it is preferable to form a two-pack paint in which the copolymer (A) and the polyisocyanate are separated, and to mix the two at the time of use.

The coating composition of the present invention comprises the above components (A) and (B) as essential components, and further, if necessary, an organic solvent, a curing catalyst, and a pigment; an ultraviolet absorber, a coating surface adjuster, and an antioxidant. , A fluidity adjusting agent, a wax and the like can be appropriately contained.

The coating composition of the present invention is usually an organic solvent type coating composition. In this case, an organic solvent which can dissolve or disperse each component of the coating can be used.
The above-mentioned organic solvents listed as usable when solution-polymerizing the copolymer (A) can be used as they are,
Further, various similar organic solvents may be appropriately added.

The above-mentioned curing catalyst optionally added to the composition of the present invention promotes the curing reaction of the composition of the present invention, and suitable curing catalysts include, for example, tin octylate and dibutyltin dibutyltin. Organometallic catalysts such as (2-ethylhexanoate), dioctyltin di (2-ethylhexanoate), dioctyltin diacetate, dibutyltin dilaurate, dibutyltin oxide, dioctyltin oxide, lead 2-ethylhexanoate, etc. Can be mentioned.

The coating composition of the present invention swells with a polar solvent such as for repairing automotive coatings and for repairing architectural exterior coatings.
When coating on easily soluble coatings, plastic materials with poor solvent resistance, or when applying wet-on-wet on uncured colored base coatings,
It is preferable to reduce or eliminate the use amount of the polar solvent in terms of preventing lifting of the lower layer coating film, preventing generation of solvent cracks in the plastic material, and preventing return unevenness of the colored base coating film. Examples of low-polar or non-polar solvents that are not polar solvents include hydrocarbon solvents, ether solvents, and aromatic petroleum solvents.

The coating composition of the present invention comprises iron, aluminum, brass, copper plate, stainless steel plate, tin plate, galvanized steel plate, alloyed zinc (Zn-Al, Zn-Ni, Zn-
Metals such as plated steel sheets, such as Fe); surface-treated metals obtained by subjecting these metal surfaces to chemical conversion treatments such as phosphate treatment and chromate treatment; directly or directly on materials to be coated such as plastic, wood, concrete, and mortar It can be applied to the cured coating surface or uncured coating surface of a coating material in which a primer and / or a middle coating and / or a top coating base is applied to the material to be coated, and is excellent in abrasiveness and resistance to nonuniformity by baking. In addition, a highly-finished coating film having excellent gloss and smoothness can be formed.

The coating composition of the present invention may be a colored coating composition or a clear coating composition. The coating composition of the present invention is excellent in polishing properties, resistance to nonuniformity in return, and glossiness, since it can form a highly finished coating film having excellent smoothness, it is used as a repair paint, especially as a clear paint for repair. By doing so, the effects of the present invention can be maximized. In the coating composition of the present invention, since the copolymer (A) does not have a carboxyl group-containing monomer such as acrylic acid or methacrylic acid as a constituent monomer component, the copolymer (A) can be a resin having almost no coloring. Also, there is no problem of curability deterioration due to the absence of a carboxyl group in the resin.

When the coating composition of the present invention is used as a clearing material for repair, a water-based or solvent-type liquid colored base coating material is usually applied to the repaired part whose base has been adjusted as necessary. In a state where the coating film is in an uncured state, a repair coating can be suitably formed by applying a repair clear on the base coating film and drying it. After applying the colored base paint, after curing the base coat, a clear for repair may be applied on the base coat and dried.

The coating film thickness of the coating composition of the present invention is not particularly limited, but usually the cured coating film thickness is 3 to 60 μm.
m, preferably about 5 to 50 μm, and drying conditions are not particularly limited as long as the coating film is cured, and are usually in the range of room temperature to 120 ° C. for 1 minute to 10 days. Is preferred.

[0040]

The present invention will now be described more specifically with reference to examples and comparative examples. Hereinafter, “parts” and “%” are based on weight unless otherwise specified.

Production of Hydroxyl-Containing Copolymer Production Example 1 60 parts of xylene was charged into a reaction vessel equipped with a stirrer, thermometer, reflux condenser, thermostat and dropping pump, and the temperature was raised to 125 ° C. while stirring. Then, 106.5 parts of a mixture of a monomer and a polymerization initiator shown in Table 1 below was dropped at a constant rate over 3 hours using a dropping pump. After completion of the dropwise addition, the mixture was aged at the same temperature for 2 hours to complete the reaction. The obtained hydroxyl group-containing copolymer solution was a uniform transparent solution having a nonvolatile content of 60% and a Gardner foam viscosity U. The copolymer had a weight average molecular weight of about 9,000 and a hydroxyl value of 118 m.
gKOH / g.

Production Examples 2 to 12 The same procedures as in Production Example 1 were carried out except that the amount of xylene charged, the reaction temperature, and the mixture of the monomer and the polymerization initiator were changed to the formulations shown in Table 1 below. A copolymer solution was obtained. Table 1 shows the properties of each of the obtained copolymer solutions and copolymers.

[0043]

[Table 1]

Examples 1 to 8 and Comparative Examples 1 to 4 Using the hydroxyl group-containing copolymer solutions obtained in the above Production Examples,
The mixture was uniformly mixed with the composition shown in Table 2 below to prepare a clear paint.

(Note) in Table 2 has the following meaning.

(* 1) Duranate TPA100: Isocyanurate of hexamethylene diisocyanate, manufactured by Asahi Kasei Corporation, NCO content 23.1%, nonvolatile content 100
%.

Preparation of Test Coated Plate The obtained clear paint was mixed with a mixed solvent having a composition of xylene / butyl acetate / Shellsol A (Note 1) = 60/20/20 (weight ratio) for about 14 seconds (Ford Cup # 4, 25
° C) to obtain a viscous clear paint. "Retan PG2K No.123" (Note 2) is applied at 20 ° C to the process coated plate on which the clear paint for new vehicles is baked.
After setting for 10 minutes, the viscous clear paint was spray-coated thereon so that the dry film thickness of the clear coating film became about 40 μm, and dried at 60 ° C. for 30 minutes to obtain a test coated plate.

(Note 1) Shellsol A: a product of Shell Chemical Company, trade name, aromatic petroleum solvent. (Note 2) Rethane PG2K No. 123: Acrylic / urethane two-pack type colored base paint, metallic color, manufactured by Kansai Paint Co., Ltd.

Using the obtained test coated plate, each test of finish, resistance to uneven return, pencil hardness and abrasion of the coating film was carried out according to the following test methods. Further, the paint condition of each viscous clear paint at the time of painting was also tested. The test results are shown in Table 2 below.

Test Method Paint State: The state of the viscous clear paint at the time of coating was visually evaluated.

：: Colorless and transparent, good Δ: Colored slightly yellow ×: Colored considerably yellow.

Finishing property of coating film: The glossiness, smoothness and transparency of the coating film of the test coated plate were visually judged and evaluated according to the following criteria (metallic return unevenness was evaluated separately).

：: good Δ: slightly bad ×: bad

Nonuniformity in return resistance: The unevenness of the metallic appearance of the coating film of the test coated plate was visually evaluated. ：: Good metallic appearance, good return unevenness resistance Δ: Slight unevenness in the metallic appearance, slightly poor return unevenness ×: Remarkable unevenness in the metallic appearance, poor poor return unevenness .

Pencil hardness: The test coated plate dried at 60 ° C. for 30 minutes is further allowed to stand in a constant temperature and humidity room at a temperature of 20 ° C. and a humidity of 60% for 7 days, and then JIS K5400.
A pencil scratch test specified in 8.4.2 (1990) was performed, and evaluation was performed by a tear method.

Abrasiveness: The test coated plate dried at 60 ° C. for 30 minutes was further left for 2 hours in a constant temperature / humidity room at a temperature of 20 ° C. and a humidity of 60%, and then a fine polishing compound was applied to the coating surface of the test coated plate. Was applied to a towel buff and polished for 2 minutes to polish the coating film, and then the scratches on the coating film surface and the finished gloss were visually evaluated according to the following criteria. ：: almost no scratches and good glossiness Δ: considerably scratches and considerably reduced glossiness ×: many scratches and little glossiness.

[0057]

[Table 2]

[0058]

EFFECT OF THE INVENTION The coating composition of the present invention can form a coating film having excellent polishing properties and resistance to nonuniformity in return, and can form a coating film having excellent gloss and smoothness. It can be suitably used as a paint, especially as a clear paint for repair. Further, the coating composition of the present invention, as a monomer component constituting the copolymer resin, does not contain a carboxyl group-containing monomer, can eliminate the coloring of the resin can be a paint or coating not colored yellow. Since it can be obtained and the viscosity can be reduced, it is advantageous also from the aspect of high solid differentiation of the paint.

Further, a liquid colored base paint is applied,
Then, in a state where the base coating film is in an uncured state, the method for forming a repair coating film of the present invention in which the coating composition of the present invention is coated on the base coating film and dried is excellent in abrasion, excellent in return unevenness resistance, and excellent Finished coating film can be formed. In this case, even when the colored base coating is a metallic base coating, a highly finished coating film having a good metallic appearance can be formed since the anti-return unevenness is excellent.

Continued on the front page F-term (reference) 4J034 BA03 BA07 DA01 DB07 DP03 DP13 DP17 DP18 GA03 GA33 GA43 GA44 HA01 HA07 HA08 HB05 HB08 HB11 HC03 HC08 HC12 HC16 HC17 HC22 HC52 HC61 HC71 HC73 HD02 HD03 HD04 HD05 HD12 HD15 JA02 JA14 JA32 KC17 K18 RA07 4J038 CC071 CC072 CC081 CC082 CG141 CG142 CG161 CG162 CG171 CG172 CH031 CH032 CH041 CH042 CH171 CH172 CH201 CH202 CJ031 CJ032 CJ131 CJ132 DG262 MA14 NA01 PA07 PB12 PC02 PC04 PC06 PC08

Claims (5)

[Claims] (A) 10 to 50% by weight of (a) styrene, (b) 10 to 50% by weight of at least one monomer selected from isobornyl (meth) acrylate and tricyclodecanyl (meth) acrylate, c) at least one monomer selected from C8 to C20 alkyl esters of methacrylic acid and C4 to C20 alkyl esters of acrylic acid;
(D) 10 to 40% by weight of a hydroxyl group-containing polymerizable unsaturated monomer and (e) copolymerizable with the above components (a), (b), (c) and (d), and having a carboxyl group. A monomer component consisting of 0 to 60% by weight of another polymerizable unsaturated monomer which has a weight average molecular weight of 3,000 to 4
A coating composition comprising: (B) a polyisocyanate and a copolymer having a hydroxyl value in the range of 40 to 160 mgKOH / g. 2. The copolymer (A) comprises the following copolymer (a-
The coating composition according to claim 1, which is a mixture of 1) and a copolymer (a-2). Copolymer (a-1): within the range of copolymer (A) and having a weight average molecular weight of 3,000 or more and 20,000
0 and a hydroxyl value of 50 to 160 mgKOH / g
Copolymer (a-2): within the range of the copolymer (A) and having a weight average molecular weight of 20,000 to 40,000
A copolymer having a hydroxyl value in the range of 40 to 100 mgKOH / g. 3. The compounding amount of the polyisocyanate (B) is as follows:
The hydroxyl group (OH) in the copolymer (A) is compared with the isocyanate group (NCO) in the polyisocyanate (B).
The coating composition according to claim 1, wherein the content of NCO / OH is in the range of 0.2 to 2.0 in terms of equivalent ratio of NCO / OH. 4. A liquid colored base paint is applied, and the paint composition according to any one of claims 1 to 3 is applied on the base paint in an uncured state. A method for forming a repair coating film, characterized by painting and drying. 5. The method for forming a repair coating film according to claim 4, wherein the liquid colored base paint is a liquid metallic base paint containing a glitter pigment.