JPH06264022A - Thermosetting coating composition - Google Patents

Abstract

PURPOSE:To improve the decorative properties, long-term weatherability, gloss, and chipping resistance of the subject compsn. by compounding a specific acrylic copolymer with an amino resin. CONSTITUTION:An acrylic copolymer having a hydroxyl value of 2-100mgKOH/ g, an acid value of 0.1-40mgK0H/g, and a wt. average mol.wt. of 300-150.000 is obtd. by copolymerizing 3-40wt.% (meth)acrylamide monomer of formula I, 5-60wt.% hydroxylated (meth)acrylic ester of formula II [wherein R<4> is H or methyl; and R<5> is a group of formula II, IV, or V (wherein R<6>, R<7>, R<9>, and R<10> are each an optionally branched 1-5C alkylene group; R<8> is H or methyl; (j) is 2-5; (k) and (m) are each 1-10; and (n)is 1-4)], 0.2-15wt.% carboxylated monomer of formula VI or VII, 30-80wt.% (meth)acrylic ester of formula VIII, and 0-50wt.% other vinyl monomers. The compsn. is prepd. by compounding 50-95wt.% the coplymer with 50-5wt.% amino resin.

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 is required to have cosmetic properties such as automobiles and long-term weather resistance. More specifically, the present invention relates to a base coat coating composition and a clear composition containing a coloring agent such as metallic powder or a coloring pigment. The present invention relates to a thermosetting coating composition which is suitable for use as a base coat paint when a coating film is formed by a two-coat one-bake method using a coating paint and which is excellent in chipping resistance.

[0002]

2. Description of the Related Art Acrylic thermosetting coating compositions are used for coating automobile bodies because of their excellent coating properties, especially gloss, weather resistance, chemical resistance and stain resistance.
However, the conventional acrylic thermosetting coating composition has the following problems, and its improvement has been desired. In other words, there is a problem that a coating film on a vehicle body is momentarily damaged by pebbles splashing in a running vehicle, so-called chipping damages the coating film on the automobile and corrodes the body. .

Usually, the coating system for automobiles is composed of the steps of chemical conversion treatment, electrodeposition primer, intermediate coating and top coating, and the chipping resistance is as described in JP-A-62-143978.
As disclosed in Japanese Patent Laid-Open No. 63-59375 and Japanese Patent Laid-Open No. 63-59375, there are many cases in which the intermediate coating film is used for securing.

In order to prevent chipping even in the top coat film of the present invention, an intermediate coat film in which energy generated by impact is absorbed by the coating film in the middle so that it is not transmitted to the base metal. Improvements based on the same idea were also considered.

However, since the topcoat film is intended to impart cosmetic properties and to achieve coating quality such as weather resistance, it has been difficult to achieve both chipping resistance and prior art.

[0006]

The present invention has been completed as a result of intensive studies to solve the above-mentioned conventional problems, and the object of the present invention is to provide the original glossiness of the acrylic thermosetting coating composition, An object of the present invention is to provide an acrylic thermosetting coating composition in which the coating film performance and the chipping resistance of the coating film are improved without impairing the cosmetic properties in the case of containing a metallic powder or a coloring pigment.

[0007]

That is, the thermosetting coating composition of the present invention is prepared by applying a base coat paint containing a colorant, and then applying a clear coat paint again.
A thermosetting coating composition for a base coat paint used in a coating system for obtaining a coating film by heat curing, comprising: (a) CH ₂ = CR ¹ -CO-NH-R ² -OR ³ (I) (In the formula, R ¹ is a hydrogen atom or a methyl group, and R ² has 1 carbon atom.
An alkylene group having 3 to 3 branches and R ³ represents a hydrogen atom or an aromatic, alicyclic or aliphatic hydrocarbon group having 1 to 15 carbon atoms. 3 to 40% by weight of a (meth) acrylamide monomer represented by the formula (b), general formula (II) CH ₂ = CR ⁴ -CO-OR ⁵ (II) (wherein R ⁴ is a hydrogen atom or methyl). Group, R ⁵ is the following general formula
It represents any group represented by (III) to (V). )

[0008]

[Chemical 4]

[0009]

[Chemical 5]

[0010]

[Chemical 6] (In the formula, R ⁶ , R ⁷ , R ⁹ and R ¹⁰ are alkylene groups having 1 to 5 carbon atoms and may have a branch, R ⁸ is a hydrogen atom or a methyl group, j is an integer of 2 to 5, k is an integer from 1 to 10 and m is 1
The integer of -10, n shows the integer of 1-4. 5 to 60% by weight of a hydroxyl group-containing (meth) acrylic acid ester represented by the formula (c) General formula (VI) or (VII) HOOCCH = CHCOOR ¹¹ (VI) CH ₂ = C (COOH) CH ₂ COOR ¹² (VII) (In the formula, R ¹¹ and R ¹² have a hydrogen atom or a carbon number of 1 to
12 hydrocarbon substituents are shown. 0.2 to 15% by weight of a carboxyl group-containing monomer represented by the formula (d):
II) CH ₂ = CR ¹³ -CO-OR ¹⁴ (VIII) (in the formula, R ¹³ represents a hydrogen atom or a methyl group, and R ¹⁴ represents a hydrocarbon substituent having 1 to 20 carbon atoms) ( (Meth) acrylic acid ester 30 to 80% by weight, and
(e) The hydroxyl value obtained by copolymerizing 0 to 50% by weight of another vinyl monomer copolymerizable with the above components (a) to (d) is 2
0 to 100 mgKOH / g, acid value 0.1 to 40 mgKOH / g, weight average molecular weight of 3,000 to 150,000, acrylic copolymer (A) 50 to 95% by weight, and curing agent (B) 5 to 5
0% by weight.

[0011]

The acrylic copolymer (A) used in the thermosetting coating composition of the present invention is composed of the monomers (a) to
(e) (however, the use of the monomer (e) is optional), which is obtained by copolymerizing at a specific ratio and has a hydroxyl value of 20 to
It must be an acrylic copolymer having 100 mgKOH / g, an acid value of 0.1 to 40 mgKOH / g, and a weight average molecular weight of 3,000 to 150,000.

The acrylamide monomer (a) represented by the above general formula (I) is a component which exerts a remarkable effect in improving the chipping resistance of the coating film. The amount of the monomer (a) used is appropriately 3 to 40% by weight. If the amount used is less than 3% by weight, the desired effect of improving the chipping resistance will not be sufficient, and if it exceeds 40% by weight, the water resistance, glossiness and metallic feel of the coating film will deteriorate. Considering the balance between chipping resistance and other physical properties of the coating film, the preferred range of use is 10 to 30% by weight.

Monomer (a) represented by the general formula (I)
Specific examples of N-methylol acrylamide, N
-Methylol methacrylamide, N-methoxymethyl acrylamide, N-methoxymethyl methacrylamide,
N-ethoxymethylacrylamide, N-ethoxymethylmethacrylamide, N-propoxymethylacrylamide, N-propoxymethylmethacrylamide, N-butoxymethylacrylamide, N-butoxymethylmethacrylamide, N-phenoxymethylacrylamide,
Examples thereof include N-phenoxymethyl methacrylamide, N-hexyloxymethyl acrylamide, N-hexyloxymethyl methacrylamide and the like.

The hydroxyl group-containing (meth) acrylic acid ester monomer (b) represented by the general formula (II) is an important component for improving the chipping resistance, and is used in the range of 5 to 60% by weight. It If it is less than 5% by weight, the effect of improving the scratch resistance is not sufficient, and if it exceeds 60% by weight, the coating film hardness is low and the water resistance is also low.

Specific examples of the monomer (b) include 1 mol of γ-butyrolactone adduct to 2-hydroxyethyl methacrylate and ε to 2-hydroxyethyl methacrylate.
-Caprolactone 1 mol adduct, γ-butyrolactone 2 mol adduct to 2-hydroxyethyl acrylate, 2
Examples include adducts of organic lactones with hydroxyl group-containing (meth) acrylates such as ε-caprolactone 2 mol adduct to hydroxyethyl acrylate and ε-caprolactone 1 mol adduct to 2-hydroxypropyl methacrylate. These adducts can be synthesized by a known addition reaction utilizing a transition metal. As specific examples of the monomer (b), ring-opening adducts of ethylene oxide and propylene oxide with 2-hydroxyethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate, and 2-hydroxy. The dimer and trimer of ethyl (meth) acrylate or 2-hydroxypropyl (meth) acrylate are also mentioned, and these may use together 2 or more types.

The carboxyl group-containing monomer (c) represented by the general formula (VI) or (VII) is 0.2 to 1
Used in the range of 5% by weight. If it is less than 0.2% by weight, the effect of improving the chipping resistance is not sufficient, and if it exceeds 15% by weight, the viscosity of the resin solution becomes high, the solid content of the coating becomes low, and the pigment and the curing agent are added. It is not suitable because the storage stability of the contained base coat paint is lowered. The preferable range of the amount used is 1 to 8% by weight.

Specific examples of the monomer (c) include fumaric acid, fumaric acid monomethyl ester, fumaric acid monobutyl ester, maleic acid, maleic acid monomethyl ester, maleic acid monobutyl ester, itaconic acid, itaconic acid monomethyl ester. , Monobutyl ester of itaconic acid.

The (meth) acrylic acid ester (d) represented by the above general formula (VIII) and having a hydrocarbon group having 20 or less carbon atoms contributes to imparting a metallic feeling and a glossy feeling, and at the same time resists the coating film. It also has the property of improving solvent resistance, chemical resistance, weather resistance, etc. Specific examples include methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, sec-butyl (meth) acrylate, t-butyl. (Meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, cetyl (meth) acrylate, stearyl (meth) acrylate,
Examples thereof include cyclohexyl (meth) acrylate, phenyl (meth) acrylate, phenylethyl (meth) acrylate and benzyl (meth) acrylate.
The amount of the (meth) acrylic acid ester (d) used is 30 to 80.
Weight percent is suitable. If it is less than 30% by weight, the above effect is insufficient, and if it exceeds 80% by weight, the chemical resistance and solvent resistance of the coating film are deteriorated, which is not preferable.

Other vinyl monomers (e) copolymerizable with the above components (a) to (d) used in the present invention include acrylic acid,
Carboxyl group-containing monomers such as methacrylic acid; styrene derivatives such as styrene, α-methylstyrene and vinyltoluene; polymerizable unsaturated nitriles such as acrylonitrile and methacrylonitrile; vinyl esters such as vinyl acetate and vinyl propionate. Epoxy group-containing monomers such as glycidyl (meth) acrylate, (meth) allyl glycidyl ether, and metaglycidyl (meth) acrylic acid ester; basic monomers such as dimethylaminoethyl (meth) acrylic acid and diethylaminoethyl (meth) acrylic acid Etc.

Further, a vinyl monomer having a hydroxyl group other than the (meth) acrylic acid ester monomer (b) represented by the general formula (II), for example, 2-hydroxyethyl (meth) acrylate, 2-hydroxy. Propyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, and a carboxyl group-containing vinyl monomer other than the carboxyl group-containing monomer (c) represented by the general formula (VI) or (VII), such as acrylic acid. , Methacrylic acid, etc. can also be used.

These monomers (e) are used in the main applications of the present invention, such as in automotive coatings, in quality performances such as weather resistance, cosmetics, chemical resistance, solvent resistance, water resistance, flexibility and adhesion. Since it affects the properties and the like, it is appropriately selected and used in a range that does not impair these performances. The range of use of the monomer (e) is 0 to 50% by weight, preferably 40% by weight or less.

The acrylic copolymer (A) used in the thermosetting coating composition of the present invention may be polymerized by any known polymerization method such as solution polymerization method, bulk polymerization method and emulsion polymerization method. Particularly, a polymer obtained by a solution polymerization method is preferable. In the case of the solution polymerization method, the mixture of the above monomers is copolymerized in the presence of an organic solvent and a polymerization initiator.
As the organic solvent, a commonly used organic solvent such as isopropyl alcohol, n-butanol, toluene, xylene can be used, and a polymerization initiator such as azobisisobutyronitrile, benzoyl peroxide, cumene hydroperoxide is usually used. The polymerization initiator used can be used. Also,
If necessary, a chain transfer agent such as 2-mercaptoethanol or n-octyl mercaptan can be used.

The acrylic copolymer (A) of the present invention has a hydroxyl value of 20 to 100 mgKOH / g, but a hydroxyl value of 20 mg.
If it is less than KOH / g, the cross-linking density of the cured coating film is low, the solvent resistance is lowered, and the interlayer adhesion with the clear coating film is also lowered.
If it exceeds 100 mgKOH / g, the water resistance of the coating film will decrease. The acid value of the acrylic copolymer (A) is 0.1 to
40 mg KOH / g. When the acid value is less than 0.1 mgKOH / g, the cross-linking density of the cured coating film is low and the solvent resistance and weather resistance decrease, and when the acid value exceeds 40 mgKOH / g, the water resistance decreases, which is not suitable. . Furthermore, the weight average molecular weight of the acrylic copolymer (A) is 3,000 to 150,000. When the weight average molecular weight is less than 3,000, the weather resistance and solvent resistance are reduced, and when the weight average molecular weight is more than 150,000,
It is not suitable because the nonvolatile content at the time of painting will decrease.

The thermosetting coating composition of the present invention contains the amino resin (B) as a curing agent in order to satisfy the above-mentioned quality performance in the automotive coating and the like, which is the main application of the present invention. The amount of amino resin (B) used is 5 to 50% by weight. If it is less than 5% by weight, the weather resistance, solvent resistance, water resistance and the like of the coating film are insufficient, and if it exceeds 50% by weight, the glossiness and metallic feeling of the coating film, physical properties and chemical performance are poor. Not preferable.

Specific examples of the amino resin include aminotriazine, urea, dicyandiamide, and methylolated products of N, N-ethyleneurea which are alkyl etherified with cyclohexanol or an alkanol having 1 to 6 carbon atoms. Obtained from aminotriazine,
For example, methyl etherified melamine resin and butyl etherified melamine resin are suitable. In addition, an external catalyst of an amino resin represented by paratoluenesulfonic acid, dodecylbenzenesulfonic acid, naphthalenesulfonic acid, or an amine neutralized product thereof can be added to the thermosetting coating composition of the present invention.

The thermosetting coating composition of the present invention basically comprises the above-mentioned acrylic copolymer (A) and amino resin (B), but in addition to these, it is excellent in the coating film aimed at by the present invention. In addition, a resin other than an acrylic resin such as a polyester resin, an epoxy resin, or a fibrin resin can be contained within a range that does not impair the chipping resistance. Usually, the amount of these resins used is less than 30% by weight based on the base coat coating composition. If it exceeds 30% by weight, the adhesion to the clear coat coating film after heat curing may be deteriorated or the weather resistance may be deteriorated.

The thermosetting coating composition of the present invention may contain the following conventionally known components when used as a paint. That is, aluminum paste, mica,
Brightness agents such as scaly iron oxide; pigments such as titanium oxide, carbon black, quinacridone, cyanine blue; resins other than acrylic resins such as polyester resins, epoxy resins, fiber resins; surface conditioners, UV absorbers, Auxiliary additives such as antioxidants, pigment settling agents, thixotropic agents, etc .;
Etc.

In the thermosetting coating composition of the present invention, the above-mentioned respective components are compounded by a general compounding method, and mainly a base coat paint is applied, and then a clear coat paint is overcoated, followed by heat curing to form a coating film. It is used as a base coat paint for the resulting coating system. When used as a base coat paint, various dilution solvents are used to adjust the viscosity of the Ford cup No. 4 at 20 ° C to be within the range of 10 to 20 seconds, and this is dried on the base material. The thickness is 10 to 30 μm, or the primer coating film is formed on the substrate in advance so that the dry film thickness is 10 to 30 μm.

Then, after leaving at room temperature for several minutes, for example, an acrylic resin / amino resin type or acrylic resin / isocyanate prepolymer is used as a vehicle, and if necessary, an ultraviolet absorber, a light stabilizer, an anti-sagging agent, etc. A thermosetting clear coat paint prepared by blending auxiliary additives, etc. with a Ford cup No. 4 having a viscosity of 13-
It is adjusted to be within the range of 40 seconds, and this is overcoated on the base coat coating film so that the dry film thickness becomes 20 to 50 μm, and left at room temperature for several minutes. After that, 60 ℃
It is cured in a temperature range of 180 ° C for 10 to 40 minutes. In this way, 2 coats with excellent chipping resistance
A 1-bake cured coating film can be formed.

[0030]

EXAMPLES Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. Parts and% are, unless otherwise specified,
All by weight. <Synthesis of acrylic copolymers B-1 to B-8 for base coat paint> After heating the solvent having the composition shown in Table 1 to 90 ° C,
A mixture of the monomer and the polymerization initiator having the composition shown in Table 1 was added dropwise over 4 hours and then polymerized at the same temperature for 3 hours to synthesize acrylic copolymers B-1 to B-8 for base coat paints.

[0031]

[Table 1] <Synthesis of copolymers C-1 and C-2 for clear coat paint>
After heating the solvent having the composition shown in Table 2 to 130 ° C,
The mixture of the monomer and the polymerization initiator having the composition shown in
The mixture was added dropwise over a period of time and further polymerized at the same temperature for 2 hours to synthesize copolymers C-1 and C-2 for clear coat paint.

[0032]

[Table 2] * 1: Petroleum aromatic hydrocarbon (manufactured by Esso Co.) Example 1 and Comparative Example 1 Preparation of solid color base coat paints Solid color base coat paints BP-1 and BP-2 having the following formulations were prepared. Acrylic copolymer (B-1 or B-2) 160 parts Uban 20SE (Mitsui Toatsu Chemicals Co., Ltd. butylated melamine resin) 33 parts Rubicron 500RG (Tosoh Co., Ltd. red pigment) 5 parts Xylene 20 parts Cellosolve acetate 20 parts Preparation of clear coat paint CP-1 having the following composition was prepared. Copolymer C-1 for clear coat paint 117 parts Uban 20SE 50 parts Solvesso # 150 (aromatic petroleum derivative manufactured by Esso) 20 parts n-butanol 5 parts Tinuvin 328 (UV absorber manufactured by Ciba-Geigy) 0.7 parts Sanol LS-770 (a light stabilizer manufactured by Sankyo Co., Ltd.) 0.4 part Modaflow (a leveling agent manufactured by Monsanto Co., Ltd.) 0.2 part coating test A 0.8 mm x 90 mm x 30 mm dull steel plate that has been subjected to chemical conversion treatment with zinc phosphate, No. 4 Ford was prepared by using a solvent prepared by mixing toluene: ethyl acetate: solveso # 150 at a ratio of 4: 3: 3 (weight) on a test piece obtained by applying cationic electrodeposition, an intermediate coating film, and sanding. A solid color base coat paint, the viscosity of which was adjusted to 14 seconds in a cup, was applied to 20 μm in two stages. After standing at room temperature for 3 minutes, Solvesso # 100: Solvesso # 150
No.4 using the solvent which mixed 2: 1 (weight) ratio
A clear coat paint, the viscosity of which was adjusted to 28 seconds with a Ford cup, was applied to have a thickness of 35 μm, left at room temperature for 10 minutes, and then baked at 140 ° C. for 30 minutes.
Table 3 shows evaluation results of chipping resistance and other coating film performance.

As is clear from Table 3, in the case of Example 1, a two-coat / one-bake coating film having good chipping resistance and other coating film performance could be formed, whereas Comparative Example 1
In the case of No. 1, a lot of delamination was observed between the base coating film and the intermediate coating film, and the chipping resistance was low.

[0034]

[Table 3] * 1) Using a stepping stone tester (JA-400 type, manufactured by Suga Tester Co., Ltd.), at an air pressure of 3 kg / m ² in a constant temperature bath at -30 ° C, 7
Fine stone (500 g) is collided with the coating film at an angle of 45 °, and the peeling condition is visually determined. * 2) Nisseki Regular Gasoline, soaked at room temperature for 24 hours, and judged appearance after pulling. * 3) 10% H ₂ SO ₄ spot After 24 hours at room temperature, the appearance is judged. * 4) Appearance judgment after soaking in 50 ° C warm water for 2 weeks and pulling up. * 5) Sunshine WOM 2000 hours later, 50 ℃, 9
Appearance after 240 hours of humidity resistance at 8% RH. * 6) After the conditions of * 5, a rugged cellophane tape peeling test is performed.
Display the adhesion rate. The symbols in the table have the following meanings. ◎ Very good ○ Good △ Poor × Extremely bad Examples 2 to 4 and Comparative Example 2 Preparation of Metallic Basecoat Paints Metallic basecoat paints BP-3 to BP-6 with the following formulation.
Was prepared. Acrylic copolymer (B-3 to B-6) 60 parts U-Van 20SE 33 parts Alpaste 1109MA (aluminum paste manufactured by Toyo Aluminum Co., Ltd.) 15 parts Xylene 20 parts The above CP-1 is used for the clear coat paint. did.

A 2-coat / 1-bake coating film was formed from the thus obtained metallic base coat paint and clear coat paint by the same steps as those for the solid color. The evaluation results are shown in Table 4.

In the case of Examples 2 to 4, a two-coat / one-bake coating film having good chipping resistance and other coating film performance could be formed, whereas in Comparative Example 2, the chipping resistance was low. Met.

[0037]

[Table 4] * 1 to * 6) Each is in agreement with Table 3.

Example 5 and Comparative Example 3 Preparation of Metallic Base Coating Paint The following composition was used to prepare a metallic basecoat paint BP-7 and
BP-8 was prepared. Acrylic copolymer (B-7 or B-8) 160 parts Sumidule N-75 (Sumitomo Chemical Co., Ltd. isocyanate prepolymer) 25 parts Alpaste 1109MA 15 parts Xylene 20 parts Preparation of clear coat paint A clear coat paint CP-2 was prepared. Copolymer for clear coat paint C-2 120 parts Sumidur N-75 36 parts Xylene 20 parts Tinuvin 328 0.7 parts Sanol LS770 0.4 parts Modaflow 0.2 parts Metallic base coat paints thus obtained and The clear coat paint was mixed with toluene: ethyl acetate: solveso # 150 at a ratio of 6: 3: 1 (weight) on the test piece, and the viscosity was adjusted to 13 seconds with a No. 4 Ford cup. The base coat paint was applied in two stages to a thickness of 20 μm. After leaving it at room temperature for 3 minutes, clear coat paint whose viscosity was adjusted to 22 seconds with a No. 4 Ford cup was applied with Solvesso # 100 to have a thickness of 35 μm, and after leaving it at room temperature for 10 minutes, 140 ° C. Baking was performed for 30 minutes. The evaluation results of chipping resistance and other coating film performance are shown in Table 5.

In Example 5, a two-coat / one-bake coating film having good chipping resistance and other coating film performance was formed, whereas in the coating film of Comparative Example 3, chipping resistance was low. became.

[0040]

[Table 5] * 1 to * 6) Each is in agreement with Table 3.

[0041]

As is apparent from the above examples, the composition of the acrylic base coat paint of the present invention is used to
When the laminated coating film is formed by the coat / one bake method, a coating film having improved chipping resistance while maintaining excellent cosmetic properties and coating film performance can be obtained.

Claims (1)

[Claims] 1. A thermosetting coating composition for a base coat paint, which is used in a coating system in which a base coat paint containing a colorant is applied, and then a clear coat paint is overlaid and then heat cured to obtain a paint film. (a) General formula (I) CH ₂ = CR ¹ -CO-NH-R ² -OR ³ (I) (In the formula, R ¹ is a hydrogen atom or a methyl group, and R ² has 1 carbon atom.
An alkylene group having 3 to 3 branches and R ³ represents a hydrogen atom or an aromatic, alicyclic or aliphatic hydrocarbon group having 1 to 15 carbon atoms. 3 to 40% by weight of a (meth) acrylamide monomer represented by the formula (b), general formula (II) CH ₂ = CR ⁴ -CO-OR ⁵ (II) (wherein R ⁴ is a hydrogen atom or methyl). Group, R ⁵ is the following general formula
It represents any group represented by (III) to (V). ) [Chemical 1] [Chemical 2] [Chemical 3] (In the formula, R ⁶ , R ⁷ , R ⁹ and R ¹⁰ are alkylene groups having 1 to 5 carbon atoms and may have a branch, R ⁸ is a hydrogen atom or a methyl group, j is an integer of 2 to 5, k is an integer from 1 to 10 and m is 1
The integer of -10, n shows the integer of 1-4. 5 to 60% by weight of a hydroxyl group-containing (meth) acrylic acid ester represented by the formula (c) General formula (VI) or (VII) HOOCCH = CHCOOR ¹¹ (VI) CH ₂ = C (COOH) CH ₂ COOR ¹² (VII) (In the formula, R ¹¹ and R ¹² have a hydrogen atom or a carbon number of 1 to
12 hydrocarbon substituents are shown. 0.2 to 15% by weight of a carboxyl group-containing monomer represented by the formula (d):
II) CH ₂ = CR ¹³ -CO-OR ¹⁴ (VIII) (in the formula, R ¹³ represents a hydrogen atom or a methyl group, and R ¹⁴ represents a hydrocarbon substituent having 1 to 20 carbon atoms) ( (Meth) acrylic acid ester 30 to 80% by weight, and
(e) The hydroxyl value obtained by copolymerizing 0 to 50% by weight of another vinyl monomer copolymerizable with the above components (a) to (d) is 2
50 to 95% by weight of an acrylic copolymer (A) having an acid value of 0 to 100 mgKOH / g, an acid value of 0.1 to 40 mgKOH / g, and a weight average molecular weight of 3,000 to 150,000; and an amino resin (B) 5.
A thermosetting coating composition consisting of .about.50% by weight.