JPH10120966A - Thermosetting coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermosetting coating composition giving a coating film having excellent interlaminar adhesive strength, stainproofness and corrosion resistance by compounding a specific acrylic copolymer with an amino resin and an epoxy resin. SOLUTION: This coating composition is composed of (A) an acrylic copolymer having a hydroxyl value of 20-100mgKOH/g, an acid value of 0.1-40mgKOH/ g and a weight-average molecular weight of 3,000-100,000 and produced by the copolymerization of (i) 0.1-10wt.% of a (meth)acrylic monomer of the formula I (R<1> to R<3> are each H or methyl; Z is O atom or imino; R<4> is a 1-4C alkyl, a ureido ring, etc.), (ii) 5-50wt.% of an OH-containing vinyl monomer, (iii) 0.2-10wt.% of a carboxyl-containing monomer of the formula II or III (R<5> and R<6> are each H or a 1-12C hydrocarbon substituent), (iv) 5-94.7wt.% of a (meth) acrylic acid ester of the formula IV (R<7> is H or methyl; R<8> is a 1-8C hydrocarbon substituent) and (v) 0-80wt.% of other vinyl monomers, (B) an amino resin and (C) an epoxy resin. The amounts of the components A, B and C are 50-94 pts.wt., 5-50 pts.wt. and 1-40 pts.wt. based on 100 pts.wt. of A+B+C, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel thermosetting coating composition useful for industrial applications, and more particularly, to an automobile, a home appliance, a building material, a pre-coated metal, etc., having excellent stain resistance, corrosion resistance, and exfoliation resistance. The present invention relates to a thermosetting coating composition useful for applications.

[0002]

2. Description of the Related Art An acrylic thermosetting coating composition using an amino resin as a curing agent is used in automobiles, home appliances, building materials due to its excellent film properties such as weather resistance, chemical resistance, water resistance and solvent resistance. Are widely used for various applications such as In addition, since it has good storage stability and can be handled with one liquid, it is particularly suitable for coating industrial metal products which are to be commercialized by line coating.

[0003] However, when a coating material comprising the same thermosetting coating composition is further applied on a cured coating film comprising a thermosetting coating composition using an amino resin as a curing agent, and the coating composition is heated and cured, the peeling property (phase Hagi property) is a performance that has been required for many years from the viewpoint of repair painting for eliminating defective products, but a product that satisfies the market has not yet been obtained.

For example, a thermosetting coating composition using an acrylic copolymer in which a large amount of ethyl acrylate or the like is used and the glass transition temperature is lowered is relatively good in the peelability, but the stain resistance and the like are low. There was a problem that the weather resistance sharply decreased. Accordingly, there has been a strong demand for a thermosetting coating composition that can achieve compatibility between the delamination property, the stain resistance, and the weather resistance of the coating film.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to maintain good performance of the acrylic thermosetting coating composition such as weather resistance, cosmetic properties, hardness, flexibility, etc. in a well-balanced manner, and to have good peelability. Another object of the present invention is to provide a thermosetting coating composition capable of forming a coating film having excellent stain resistance and corrosion resistance.

[0006]

Means for Solving the Problems The present inventors have conducted intensive studies on a thermosetting coating composition in order to achieve the above object, and as a result, have reached the present invention.

That is, the present invention relates to (1) (a) a (meth) acrylic monomer represented by the following general formula (I):
10% by weight,

[0008]

Embedded image [Wherein, R ¹ , R ² and R ³ represent a hydrogen atom or a methyl group, Z represents an oxygen atom or an imino group, and R ⁴ represents an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms. Group or formula (II)

[0009]

Embedded image Represents a ureido ring represented by (B) 5 to 50% by weight of a hydroxyl group-containing vinyl monomer, (c) the following general formula (III)
Or 0.2 to 10% by weight of a carboxyl group-containing monomer represented by (IV),

[0010]

Embedded image HOOCCHＣＯCHCOOR ⁵ (III) (wherein, R ⁵ represents a hydrogen atom or a hydrocarbon substituent having 1 to 12 carbon atoms.)

[0011]

Embedded image _{CH 2 = C (COOH) CH} 2 COOR 6 (IV) ( wherein, R ⁶ represents a hydrogen atom or a hydrocarbon substituent having 1 to 12 carbon atoms.) (D) the following general formula (V 5) to 94.7% by weight of a (meth) acrylate represented by the formula:

[0012]

Embedded image ^{_{CH 2 = C (R 7)}} COOR 8 (V) ( wherein, R ⁷ represents a hydrogen atom or a methyl group, R ⁸
Represents a hydrocarbon substituent having 1 to 8 carbon atoms. ) And (e) a copolymerizable other vinyl-based monomer in an amount of from 0 to 80% by weight, and a hydroxyl value of from 20 to 100 m
50 to 94 parts by weight of an acrylic copolymer (A) having a gKOH / g and an acid value of 0.1 to 40 mgKOH / g and a weight average molecular weight of 3,000 to 100,000; (2) 5 to 50 parts by weight of an amino resin (B) And (3) 1 to 40 parts by weight of the epoxy resin (C) (however, the total amount of the acrylic copolymer (A), the amino resin (B) and the epoxy resin (C) is 100 parts by weight). .) A thermosetting coating composition.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The thermosetting coating composition of the present invention comprises an acrylic copolymer (A), an amino resin (B) and an epoxy resin (C).

Acrylic copolymer (A) in the present invention
Is a (meth) acrylic monomer (a) represented by the above general formula (I), a hydroxyl group-containing vinyl monomer (b), a carboxyl group-containing monomer represented by the above general formula (III) or (IV) A polymer obtained by copolymerizing the monomer (c), the (meth) acrylate (d) represented by the general formula (d), and another copolymerizable vinyl monomer (e). .

The (meth) acrylic monomer (a) represented by the general formula (I) is used in an amount of 0.1 to 10% by weight. If the amount is less than 0.1% by weight, the corrosion resistance and adhesion to the substrate are reduced, and if it exceeds 10% by weight, the aesthetics (especially glossiness) and the corrosion resistance are reduced. Preferably 0.5
-5% by weight.

Specific examples of the (meth) acrylic monomer (a) include N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, Nt-butyl (meth) acrylamide, acrylamidoethylethyleneurea, Methacrylamidoethyl ethylene urea, ethylene urea ethyl methacrylate, ethylene urea ethyl acrylate, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, N
-Butoxymethyl (meth) acrylamide, etc., and acrylamidoethylethyleneurea, methacrylamidoethylethyleneurea, ethyleneureaethylmethacrylate, and ethyleneureaethylacrylate are particularly preferable.

The hydroxyl group-containing vinyl monomer (b) has a content of 5 to
It is used in the range of 50% by weight, but if it is less than 5% by weight, the crosslinked density of the cured coating film is low, the hardness and solvent resistance are low, and if it exceeds 50% by weight, the water resistance and impact resistance are reduced. Become. Preferably it is in the range of 10 to 30% by weight.

Specific examples of the hydroxyl group-containing vinyl monomer (b) include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate,
-Hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 6-hydroxyhexyl (meth) acrylate, 2-hydroxyethyl (meth)
Ε-caprolactone ring-opening addition monomer to acrylate, ε-caprolactone ring-opening addition monomer to 2-hydroxypropyl (meth) acrylate, propylene oxide ring-opening addition monomer to (meth) acrylic acid, to (meth) acrylic acid And hydroxyl group-containing (meth) acrylates such as ethylene oxide ring-opening addition monomers; and hydroxyl group-containing vinyl monomers such as hydroxybutyl vinyl ether and parahydroxystyrene.

The carboxyl group-containing monomer (c) represented by the general formula (III) or (IV) is used in the range of 0.2 to 10% by weight.
The solvent resistance and the stain resistance are low, and if it exceeds 10% by weight, the coating film becomes brittle, the flexibility is lowered and the water resistance is lowered. Preferably it is in the range of 0.5 to 5% by weight.

Specific examples of the carboxyl group-containing monomer (c) include dibasic acid monomers such as maleic acid, fumaric acid and itaconic acid; monomethyl itaconate, monobutyl itaconate, monooctyl itaconate, itaconic acid Monobasic esters of unsaturated double bonds containing unsaturated double bonds such as monophenyl, monobenzyl itaconate, monomethyl fumarate, monobutyl fumarate, monomethyl maleate, monobutyl maleate, monooctyl maleate and monolauryl maleate. Can be

The (meth) acrylic acid ester (d) represented by the general formula (V) is an essential component from the viewpoint of cosmetics and weather resistance, and is used in the range of 5 to 94.7% by weight. If it is less than 5% by weight, weather resistance and chemical resistance are reduced, and
If the content exceeds 4.7% by weight, the hardness and the solvent resistance will decrease. It is preferably in the range of 10 to 70% by weight, and more preferably in the range of 30 to 60% by weight.

Specific examples of (meth) acrylate (d) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, (Meth) acrylic acid n-
Butyl, i-butyl (meth) acrylate, t-butyl (meth) acrylate, sec-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, (meth) Examples thereof include 2-ethylhexyl acrylate, cyclohexyl (meth) acrylate, phenyl (meth) acrylate, benzyl (meth) acrylate, phenylethyl (meth) acrylate, and isobornyl (meth) acrylate.

[0023] Other copolymerizable vinyl monomers (e)
Can be used in an amount of 0 to 80% by weight within a range that does not impair the corrosion resistance, stain resistance, and delamination characteristic of the thermosetting coating composition of the present invention. Preferably it is in the range of 20 to 60% by weight.

Specific examples of other copolymerizable vinyl monomers (e) include monomers having an aromatic hydrocarbon substituent such as styrene and vinyl toluene; and the above-mentioned general formulas such as acrylamide and methacrylamide ( Amide group-containing monomers not included in I); amino group-containing monomers such as dimethylaminoethyl (meth) acrylate and diethylaminoethyl (meth) acrylate; 2,2,3,3-tetrafluoropropyl (meth) (Meth) acrylates having an alkyl group substituted with a fluorine atom, such as acrylate, trifluoroethyl (meth) acrylate, and perfluorooctylethyl (meth) acrylate; lauryl (meth) acrylate, decyl (meth) acrylate;
Tridecyl (meth) acrylate, stearyl (meth)
(Meth) acrylic esters having a hydrocarbon substituent having 9 or more carbon atoms, such as acrylate and nonyl (meth) acrylate; and carboxyl group-containing monomers such as methacrylic acid, acrylic acid, and acrylic acid dimer.

The acrylic copolymer (A) used in the present invention is composed of the above monomers, and has a hydroxyl value of 20 to 100 mgKOH / g and an acid value of 0.1 to 4
0 mgKOH / g and weight average molecular weight of 3000 to 100
It is important that it is 000.

When the hydroxyl value is less than 20 mgKOH / g, the hardness and solvent resistance of the cured coating film are low, while when the hydroxyl value exceeds 100 mgKOH / g, the water resistance, impact resistance and corrosion resistance are poor. When the acid value is less than 0.1 mg KOH / g, the solvent resistance and the stain resistance are low. On the other hand, when the acid value exceeds 40 mg KOH / g, the water resistance and the adhesion to the substrate are reduced. If the weight average molecular weight is less than 3,000, the solvent resistance and weather resistance are low. On the other hand, if the weight average molecular weight is more than 100,000, the cosmetic property is reduced and the amount of non-volatile components during coating is reduced. It is. Preferably the hydroxyl value is 40 to 80
The weight average molecular weight is in the range of 7000 to 50,000 with an mgKOH / g and an acid value of 5 to 20 mgKOH / g.

The acrylic copolymer (A) is prepared by copolymerizing the copolymer components (a) to (e) together with a known initiator by a known polymerization method such as a solution polymerization method, a bulk polymerization method and an emulsion polymerization method. However, it is particularly preferable that the polymer is produced by a solution polymerization method.

The organic solvent used in the solution polymerization may be selected from commonly used organic solvents such as isopropyl alcohol, n-butyl alcohol, toluene and xylene, and the polymerization initiator is azobisisobutyronitrile, It can be selected from commonly used polymerization initiators such as benzoyl peroxide and cumene hydroperoxide.

If necessary, a chain transfer agent such as 2-mercaptoethanol and n-octylmercaptan can be used.

The amount of the acrylic copolymer (A) used in the thermosetting coating composition of the present invention is from 50 to 50 parts by weight of the total amount of the components (A), (B) and (C).
It is 94 parts by weight, and if it is less than 50 parts by weight, the water resistance and weather resistance are low, and if it exceeds 94 parts by weight, the solvent resistance and the corrosion resistance deteriorate. Preferably it is 60 to 85 parts by weight.

In the thermosetting coating composition of the present invention, the amino resin (B) is used as a curing agent component. The amount of the amino resin (B) used is in the range of 5 to 50 parts by weight based on 100 parts by weight of the total amount of the components (A), (B) and (C). When the crosslinking density is low, the hardness and the solvent resistance are not sufficient, and when the amount exceeds 50 parts by weight, the coating film becomes brittle, the weather resistance is reduced, and the metallic feeling of the coating film, gloss, etc. are reduced. Other physical and chemical performance may be poor. Preferably it is 10 to 40 parts by weight.

As a specific example of the amino resin (B), butyl obtained by subjecting aminotriazine, urea, dicyandiamide or N, N-ethyleneurea to methylol and alkyl-etherifying it with cyclohexanol or an alkanol having 1 to 6 carbon atoms can be used. Melamine resins and methylated melamine resins obtained by methyl etherification.

When preparing a thermosetting coating composition using the amino resin (B), 0.05 to 5% by weight of an external acid catalyst based on the total solid content of the resin is optionally used. You may. External acid catalysts that can be used include, for example, phosphoric acid,
Examples include those selected from paratoluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and neutralized products of these amines.

In the thermosetting coating composition of the present invention, the epoxy resin (C) contains the components (A), (B) and (C) for the purpose of improving the adhesion to the substrate and the corrosion resistance. In a range of 1 to 40 parts by weight based on 100 parts by weight of the total amount. If the amount is less than 1 part by weight, the adhesion and corrosion resistance will be low, and if it exceeds 40 parts by weight, the stain resistance and weather resistance will decrease. The preferred use range of the epoxy resin (C) is 5 to 30 parts by weight.

Specific examples of the epoxy resin (C) used include Epicoat 100, which is a condensation reaction product of bisphenol A or bisphenol F with epichlorohydrin.
1, Epicoat 1004, Epicoat 1007, Epicoat 807 (all manufactured by Yuka Shell Epoxy Co., Ltd.) and polyglycidyl ether compounds. Those commercially available under the trade name of Denacol manufactured by Nagase Kasei Co., Ltd., such as Denacol EX-211 and Denacol EX-
611. Examples of the cycloaliphatic epoxy resin include Chissonox CX-221 and Chissonox CX-289, which are commercially available under the trade name of Chissonox manufactured by Chisso Corporation.

In the thermosetting coating composition of the present invention, a volatile organic solvent diluent carrying a binder; inorganic pigments such as titanium oxide and iron oxide; cyanine blue and cyanine green; And organic pigments such as perylene; additives such as surface conditioners, ultraviolet absorbers, light stabilizers, antioxidants and anti-dripping agents; and additives such as alkyd resins, oil-free polyester resins and cellulose resins as required. To be selected and added by a general blending method.

[0037]

The present invention will be described below in detail with reference to examples. Parts and% in Production Examples, Examples and Comparative Examples
Represents parts by weight and% by weight. The evaluation of the coating film performance used in Examples and Comparative Examples was performed using the following method.

(1) Visual Appearance Judgment was made mainly on glossiness and smoothness.

(2) Gloss Digital-deflection gloss meter UGV-4D manufactured by Suga Test Instruments Co., Ltd.
(60 ° G).

(3) Hardness Using a Mitsubishi Pencil Uni, the coating was scratched at an angle of 45 degrees to measure the hardness. Hardness was defined as the highest hardness that did not damage.

(4) Adhesion The coating was cut in 1 cm squares at intervals of 1 mm with a cutter knife to make 100 grids, and a cellophane tape was stuck on the grid, and then peeled off at a stretch without peeling. The adhesion was evaluated based on the number of grids remaining in the following criteria. ：: No peeling Δ: Area remaining without peeling is 80/100 or more ×: Area remaining without peeling is less than 80/100

(5) Erichsen value Using an Erichsen tester, the coated plate was extruded from the back side and the value (mm) containing cracks was defined as the Erichsen value.

(6) Impact Resistance Using a DuPont impact tester, the maximum height (cm) at which cracks did not occur was taken as the impact resistance value (measurement conditions;
Test piece 1/2 ", notched, concave, load 500g).

(7) Solvent Resistance Xylene was immersed in gauze, and the appearance after 16 reciprocal rubbing tests was visually judged.

(8) Boiling Water Resistance The coated plate was immersed in boiling water for 2 hours, pulled up, and visually measured for appearance.

(9) Stain resistance The coating film was coated with an oil-based red magic ink, allowed to stand for 2 hours, and then wiped off with n-butyl alcohol to visually determine the presence of traces and the degree of the traces.

(10) Compatibility The coated film (the first coat) was baked at 180 ° C. for 15 minutes, and then the same paint as the first coat was further applied on the coated film at 160 ° C. For 15 minutes. Then, after making a cross cut with a knife on the two-layer coating film, a cellophane tape peeling test was performed, and the presence or absence and the degree of peeling of the coating film were visually determined according to the following criteria. ◎: No abnormality is observed at all. ○: Peeling of the coating film is slightly observed at the cross-cut portion. △: A considerable amount of coating film is peeled at the cross-cut portion.

(11) Weather resistance Sunshine weatherometer (Suga Test Machine Co., Ltd.)
Manufactured for 500 hours, and the gloss retention (60 ° G,%) of the coating film was measured.

(12) Corrosion resistance A cross-cut was placed on the coated plate with a knife, sprayed with salt water (5% salt solution, test temperature 35 ° C.) for 240 hours, and then peeled off from the cross-cut portion by a cellophane tape peel test. The width (one side, mm) was measured.

The criteria for the visual appearance, solvent resistance, boiling water resistance and contamination resistance were determined according to the following methods. ：: Very good, excellent film performance is maintained. ：: good, having sufficient practical performance △: poor, there is a problem in practical use ×: extremely poor, not practically useable

1. Production Example of Acrylic Copolymer (A) (1) Production of Acrylic Copolymer (A-1) 30 parts of n-butyl alcohol and xylene 70 as a solvent in a container equipped with a stirrer, a temperature controller, and a condenser. And heated it to 100 ° C. while stirring it.
-Methoxymethylacrylamide 5 parts, 2-hydroxyethyl methacrylate 10 parts, monobutyl maleate 7
Parts, methyl acrylate 20 parts, isobornyl acrylate 5 parts, n-butyl acrylate 33 parts, styrene 20 parts,
A mixture of a vinyl monomer comprising 0.5 parts of azobisisobutyronitrile and a polymerization initiator was dropped into the container over 3 hours, and the content was maintained at the same temperature for 3 hours to obtain an acrylic copolymer. A combination (A-1) was obtained. Table 1 shows the characteristics of the obtained acrylic copolymer (A-1).

The properties of the acrylic copolymer (A) shown in Table 1 are measured by the following measurement methods. Viscosity: Measured with a Gardner-Holt foam viscometer. (25
° C). Heating component: Residual ratio (%) when 1 g of acrylic copolymer was sampled on an aluminum dish and dried at 150 ° C. for 1 hour. Hydroxyl value: mg equivalent number of potassium hydroxide equivalent to hydroxyl group contained in 1 g of the solid content of the acrylic copolymer. Acid value: The number of mg of potassium hydroxide required to neutralize 1 g of the solid content of the acrylic copolymer. Weight average molecular weight: Measured by gel permeation chromatography, and shows a value based on polystyrene.

(2) Acrylic copolymer (A-2)
Production of (A-9) Except that the monomer composition is changed as shown in Table 1, polymerization similar to that of the acrylic copolymer (A-1) is performed to produce the acrylic copolymer (A-2) to (A-9) was obtained. The properties of the obtained acrylic copolymers (A-2) to (A-9) are shown in Table 1.

[0054]

[Table 1]

Example 1 (1) Preparation of paint Acrylic copolymer (A-1) obtained in the above production example
140 parts, CR-95 (manufactured by Ishihara Sangyo Co., Ltd., chlorine method titanium oxide) 100 parts, Uban 20SE (manufactured by Mitsui Toatsu Chemicals, butylated melamine resin, nonvolatile content 60%) 3
3.3 parts, Epicoat # 1001 (product of Yuka Shell Epoxy Co., Ltd., epoxy resin) 10 parts, Modaflow (manufactured by Monsanto Co., leveling agent) 0.1 part, cellosolve acetate 30 parts, xylene 30 parts and glass beads 300
Part of the mixture was dispersed in a planetary ball mill (Fritz, Japan) over 30 minutes to remove glass beads, and then Solvesso # 100 (Esso, aromatic petroleum fraction): cellosolve acetate = 80: 20. (Weight ratio) No. 20 seconds in a 4 Ford Cup (20
C.) to obtain a white paint.

(2) Evaluation of coating film performance The above white paint was applied to a 0.8 mm (thickness) × 70 mm × 150 mm zinc phosphate treated dull steel plate (Bondarite 144 dull steel plate, manufactured by Japan Test Panel Co., Ltd.). Air spray coating was performed so that the dry film thickness was 30 μm. 10
After setting at room temperature for 15 minutes, the coated plate was baked at 160 ° C. for 15 minutes to obtain a coated plate. Table 3 shows the results of evaluating the coating film performance of the obtained coated plate.

[Examples 2 to 3, Comparative Examples 1 to 8] Example 1
Various white paints were prepared according to the compounding ratios shown in Table 2 in the same manner as described above. Next, using this white paint, a method similar to that of Example 1 was repeated to obtain a coated plate. Table 3 shows the results of evaluating the coating film performance of the obtained coated plate.

[0058]

[Table 2]

[0059]

[Table 3]

As is clear from Table 3, the coating films of the thermosetting coating compositions of Examples 1 to 3 exhibited excellent coating performance.
On the other hand, the coating films of the thermosetting coating compositions of Comparative Examples 1 to 8 that do not satisfy the conditions specified by the present invention have poor coating film appearance or coating film performance such as corrosion resistance, stain resistance, and delamination property. Was enough.

[0061]

EFFECTS OF THE INVENTION The thermosetting coating composition of the present invention has excellent coating properties such as coating appearance, corrosion resistance, stain resistance, weather resistance, and delamination properties, so that it can be used in various applications such as automobiles, home appliances, It can be widely used for industrial applications such as building materials and pre-coal metal.

Claims (1)

[Claims] (1) (1) (a) 0.1 to 10% by weight of a (meth) acrylic monomer represented by the following general formula (I): [Wherein, R ¹ , R ² and R ³ represent a hydrogen atom or a methyl group, Z represents an oxygen atom or an imino group, and R ⁴ represents an alkyl group having 1 to 4 carbon atoms or an alkoxy group having 1 to 4 carbon atoms. Group or formula (II) Represents a ureido ring represented by (B) 5 to 50% by weight of a hydroxyl group-containing vinyl monomer, (c) the following general formula (III)
Or 0.2 to 10% by weight of a carboxyl group-containing monomer represented by (IV): HOOCCHＯCHCOOR ⁵ (III) (wherein, R ⁵ is a hydrogen atom or a hydrocarbon having 1 to 12 carbon atoms) CH ₂ ＣC (COOH) CH ₂ COOR ⁶ (IV) (wherein R ⁶ represents a hydrogen atom or a hydrocarbon substituent having 1 to 12 carbon atoms) (d) 5) to 94.7% by weight of a (meth) acrylate represented by the following general formula (V): CH ₂ ＣC (R ⁷ ) COOR ⁸ (V) (where R ⁷ is a hydrogen atom or a methyl group, R ⁸
Represents a hydrocarbon substituent having 1 to 8 carbon atoms. ) And (e) a copolymerizable other vinyl-based monomer in an amount of from 0 to 80% by weight, and a hydroxyl value of from 20 to 100 m
50 to 94 parts by weight of an acrylic copolymer (A) having a gKOH / g and an acid value of 0.1 to 40 mgKOH / g and a weight average molecular weight of 3,000 to 100,000; (2) 5 to 50 parts by weight of an amino resin (B) And (3) 1 to 40 parts by weight of the epoxy resin (C) (however, the total amount of the acrylic copolymer (A), the amino resin (B) and the epoxy resin (C) is 100 parts by weight). )) Thermosetting coating composition.