JPS598307B2 - Netsukoukaseihifufussaibutsu - Google Patents

Description

Detailed Description of the Invention The present invention relates to an aqueous polymer dispersion obtained by emulsion polymerization of a vinyl monomer containing a crosslinkable unsaturated monomer using a water-soluble thermosetting acrylic resin as an emulsifier. It provides a baked coating film with significantly improved mechanical properties, water resistance, and chemical resistance made of amino resin, and also has a small amount of organic solvents in volatile substances, making it effective in preventing air and water pollution. The present invention relates to a curable aqueous coating composition.

Conventionally, thermosetting water-based paints have been widely used as a pollution control measure such as air pollution prevention, but these water-based paints can be roughly divided into water-dispersed types, in which the resin component is dispersed in water, and those in which the resin components are dissolved in water. There are two types of aqueous solutions available, but at the current stage neither is satisfactory and has several drawbacks.

For example, in the water-dispersed water-based paint that is the object of the present invention, the gloss of the resulting paint film is poor, the surfactant used as an emulsifier remains in the paint film, so the water resistance and weather resistance are unsatisfactory, and the water-soluble Even if crosslinking agents such as polyester amino resins are used in combination, curing properties are insufficient due to insufficient fusion and uniform mixing with the dispersed particles in the aqueous dispersion, and generally poor water resistance and anti-oxidant properties. can be given. The present invention was achieved as a result of various studies aimed at improving the above-mentioned drawbacks of conventional emulsion polymer water-based paints using surfactants in order to solve the problems mentioned above.

That is, the present invention provides 5 to 60% by weight of hydroxyalkyl acrylate and/or hydroxyalkyl methacrylate, and 5 to 20% of acrylic acid and/or methacrylic acid.
weight? , the following general formula (wherein R is a hydrogen atom or a methyl group, R is a hydrogen atom or CnH2O+1 and n is 1 to 4
Shows the numbers.

) and at least one copolymerizable monoethylenically unsaturated monomer selected from acrylic acid alkyl esters, methacrylic acid alkyl esters, styrene and styrene derivatives 30-85 weight? Using a hydrophilic copolymer obtained by copolymerizing and neutralizing as an emulsifier, 5 to 50% by weight of the compound (1) and 50 to 95% by weight of the vinyl monomer. An aqueous polymer dispersion obtained by emulsion polymerization of a monomer mixture consisting of (
B) It consists of an amino resin, the content of 8 is 40% by weight or less based on the sum of (8) and (3) as solid content, and the content of organic solvent in the volatile substances contained therein is 3-30 weight? A thermosetting coating composition is provided. The hydroxyalkyl acrylate or hydroxyalkyl methacrylate that is the first component of the emulsifier used in the present invention includes 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, and 2-hydroxypropyl methacrylate. etc. can be used, and the amount is 5 to 60 weight? Preferably 10 to 40 weight? Is it appropriate to use 5 weight? If it is less than 60% by weight, it may be due to a decrease in crosslinking property. If the amount is higher, the water resistance of the coating film will be poor due to an increase in the number of hydrophilic groups.

Further, the second component (acrylic acid and/or methacrylic acid) is used within the range of 5 to 20% by weight, and the particle size of the aqueous polymer dispersion can be arbitrarily adjusted by the amount of the second component and the amount of neutralization thereof. is possible. The second component is 5 weight? If the amount is less, a stable aqueous polymer dispersion cannot be obtained, and if it is more than 20% by weight, the obtained aqueous polymer dispersion becomes viscous and also has poor stability. Further, as the compound () which is the third component of the emulsifier, for example, N-
Monomers having self-crosslinking functional groups such as methylol acrylamide, N-methylol methacrylamide, N-butoxymethyl acrylamide, and N-butoxymethyl methacrylamide can be mentioned, and the amount thereof is 5 to 20% by weight. It is. If it is less than 5% by weight, sufficient water resistance and chemical resistance cannot be obtained, and 20% by weight? If the amount is more, it is not preferable because there is a possibility that the emulsifier will gel during production.

Furthermore, the fourth component of the emulsifier, that is, the water is copolymerized with each of the above-mentioned components. Examples of monoethylenically unsaturated monomers that can form a sexual copolymer (emulsifier) include alkyl acrylates (for example, methyl acrylate, ethyl acrylate, propyl acrylate, n-butyl acrylate, isobutyl acrylate). , 2-ethylhexyl acrylate, lauryl acrylate, cyclohexyl acrylate, etc.), alkyl methacrylates (e.g., methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, 2-ethyl methacrylate) Ethylhexyl, lauryl methacrylate, cyclohexyl methacrylate, etc.) styrene, substituted styrenes, etc.

The emulsifier used in the present invention has the following proportions:
It can be obtained by copolymerizing the components in an organic solvent using a suitable polymerization initiator by a known method and neutralizing the resultant.

Examples of organic solvents used here include alcoholic solvents such as methyl, ethyl, isopropyl, and butyl alcohol;
Ether alcohol thickeners such as methyl cellosolve, cellosolve, butyl cellosolve, methyl carbitol, carbitol, butyl carbitol, ester thickeners such as methyl cellosolve acetate, cellosolve acetate, ketone solvents such as acetone, etc. Freely miscible with water A suitable brewing agent is used. In addition, polymerization initiators include azo compounds such as azobisisobutyronitrile, peroxides such as benzoyl peroxide, peracid esters such as t-butyl perbenzoate, ammonium persulfate, and iron salts. Redox systems can be used. Furthermore, it is possible to introduce some unsaturated groups into such copolymers, and since these unsaturated groups can participate in the copolymerization reaction in emulsion polymerization, a more stable aqueous polymer dispersion can be obtained. Obtainable.

As a method for introducing unsaturated groups, for example, by reacting an amount of glycidyl methacrylate that reacts with a portion of carboxyl groups in the copolymer in the presence of a basic catalyst,
Methacrylic groups can be introduced into copolymer side chains. After distilling off an appropriate amount of the organic solvent from the copolymer solution obtained in this way under normal pressure or reduced pressure, the copolymer is neutralized by at least 50% of the carboxyl groups by adding a basic substance. By diluting it with water to a desired concentration, an emulsifier for the aqueous polymer dispersion used in the present invention can be obtained.

In this case, the amount of neutralization is preferably 70% or more, and the basic substances used include ammonia, methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, dimethylethanolamine,
These include diethanolamine and triethanolamine. The aqueous polymer dispersion used in the present invention can be obtained by emulsion polymerization of a monomer mixture consisting of the compound (1) and a vinyl monomer using the hydrophilic copolymer as an emulsifier.

Is the amount of compound (1) in the monomer mixture 5 to 50% by weight? , preferably 5 to 30% by weight. When the compound (1) is less than 5% by weight, mechanical properties,
The purpose of the present invention, which is to obtain a baked coating film with markedly improved water resistance and chemical resistance, cannot be achieved, and the weight of 50%? If the amount is higher, the mechanical properties and water resistance of the coating film will deteriorate. Furthermore, as the vinyl monomer, in addition to the monoethylenically unsaturated monomer that is the fourth component of the emulsifier, acrylic acid,
Methacrylic acid, hydroxyalkyl acrylate, methac IJ/hydroxyalkyl laceate, etc. can also be mentioned.

The aqueous polymer dispersion of the present invention contains the emulsifier and the monomer mixture in a solid content weight ratio of the former to 5:95 to 40.
:60 ratio and carry out according to the usual emulsion polymerization method.

Incidentally, if necessary, a surfactant commonly used in emulsion polymerization may be used in combination with the emulsifier as long as the performance is not deteriorated. The aqueous polymer dispersion thus obtained has excellent mechanical stability, thermal stability, and good storage stability.

Even if the aqueous polymer dispersion is used alone, it is possible to obtain a baked coating film with significantly improved mechanical properties, water resistance, and chemical resistance, which is the objective of the present invention. By adding resin, the above-mentioned coating film performance can be dramatically improved.

Amino resins with various structures are used, but
For example, di-, tri-, tetra-, bender, or hexamethylolmelamine and its derivatives, urea-
formaldehyde condensate, urea-melamine cocondensation resin,
Examples include benzoguanamine, but melamine resin is particularly preferred. The blending ratio of the aqueous polymer dispersion and amino resin 03) is such that the content of (B) as solid content is 40% by weight relative to the sum of (4) and 8. The amount is in the range of 5 to 30% by weight, preferably 5 to 30% by weight. Blends outside this range will result in defects in coating film performance such as water resistance and anti-pollution properties, and the object of the present invention will not be achieved. Since the aqueous polymer dispersion according to the present invention has affinity for pigments, it does not particularly require other known water-soluble resins as pigment dispersants. It may be added in a proportion of up to 50 parts by weight based on

Furthermore, one of the characteristics of the composition of the present invention is that the proportion of organic solvent in the volatile substance is 3 to 30% by weight. It is in being. If the amount of organic solvent is within this range, there will be no problem in preventing air pollution. Here, volatile substances have a boiling point of 300 at normal pressure.
It refers to substances with temperatures below ℃, specifically water and organic thickening agents. The composition of the present invention may contain various inorganic and organic pigments, various fillers, additives, and the like, as necessary.

As a method for coating the composition of the present invention, various well-known coating methods such as brush coating, dip coating, spray coating, roller coating, or electrodeposition coating can be used.

After coating, the composition of the present invention is cured by heating.

The conditions for heat curing are the content of crosslinkable functional groups in the composition,
It varies depending on the film thickness, type of solvent, etc., but usually 80 to 25
Water resistance,
A coating film with excellent solvent resistance can be formed. Note that NH4Cl, NH4NO3, (NH4)2H is added to the composition in advance.
A common crosslinking catalyst such as P04, (COOH)2, P-toluenesulfonic acid is added in an amount of 0.5 to 0.5 to
It can also be added in an amount of 1.0% by weight, which is effective in lowering the heat curing conditions.

The feature of the present invention is that in the aqueous polymer dispersion, a self-crosslinking monomer [compound (1)] is used not only for the dispersed particles but also for the emulsifier itself. If an amino resin is mixed alone or in an aqueous dispersion of the polymer, a film is formed in the presence or absence of a crosslinking catalyst, and heat-treated, the emulsifier and the polymer (dispersed particles) are formed.
Comrades, because a dense three-dimensional network structure is formed between the emulsifier and the polymer, and further between the dispersed particles and the external crosslinking agent (amino resin), the physical properties of the coating film are significantly improved, and it has sufficient hardness and toughness. It is possible to obtain a glossy coating film with excellent water resistance, chemical resistance, and adhesive resistance.

In addition, since the amount of organic solvent in the volatile substance in the composition of the present invention is 3 to 30% by weight, the amount of organic solvent in the volatile substance is 3 to 30% by weight, compared to the current aqueous solution type paint that requires the use of a large amount of organic thickener. The amount of organic stimulants can be reduced, making it extremely effective in preventing air pollution. Furthermore, the effects obtained by the present invention will be explained in comparison with water-dispersed paints and water-solution paints produced by conventional emulsion polymerization methods. First, in water-dispersed paints obtained by conventional emulsion polymerization methods, surfactants remain in the paint film, so the water resistance and weather resistance of the paint film are unsatisfactory, and the gloss is also poor.

However, in the production of the composition according to the invention, there is no need to use conventional surfactants, and the particle size of the resulting aqueous polymer dispersion is extremely small, so that the above-mentioned disadvantages are not present. In addition, conventional water-liquid type paints require a large amount of carboxyl groups to make the base resin water-soluble, and these remain in the paint film, leading to drawbacks such as poor alkali resistance, water resistance, and weather resistance.

On the other hand, the aqueous polymer dispersion of the present invention requires only a small amount of carboxyl groups based on the total amount, and has almost no drawbacks as described above. Furthermore, it is possible to increase the non-volatile content during painting, which is limited by the current liquid-type paints, and painting workability is also improved. The present invention will be explained below with reference to Examples.

In Examples and Comparative Examples? represents weight %. Production example 1 Hydroxyethyl methacrylate 5 parts by weight Acrylic acid 20 parts by weight N-butoxymethylacrylamide 20 parts by weight Styrene
30 parts by weight ethyl methacrylate
25 parts by weight of 1 part by weight of azobisisobutyronitrile was added dropwise to 100 parts by weight of Cellosolve heated to 120°C, and after polymerization took place for 7 hours, 70 parts by weight of the solvent
Parts by weight were distilled off, an equivalent amount was neutralized with triethylamine, and water was added to make a 15% aqueous solution.

To 100 parts by weight of this aqueous solution, add methyl methacrylate.
24 parts by weight ethyl acrylate
15 parts by weight N-budoxymethylacrylamide 15 parts by weight N-methylolmethacrylamide 3 parts by weight hydroxyethyl methacrylate 3 parts by weight were added and stirred for 1 hour, then 1 part by weight of ammonium persulfate was dissolved in 10 parts by weight of water and added 75 parts by weight. After heating at .degree. C. for 4 hours, an aqueous polymer dispersion with a solids content of 44% and a viscosity of 250 centipoise was obtained.

This dispersion did not change in viscosity even after being left at 40° C. for one month, and remained stable without any aggregates. When 4 parts by weight of butyl cellosolve was added to 100 parts by weight of this aqueous polymer dispersion, diluted with water, and dried in a #4 food cup for 30 seconds, a paint with a solid content of 3970 and an amount of organic anesthetic in volatile substances of 13% was obtained. Ta. This was painted on an iron plate and baked at 160°C for 20 minutes. Example 1 HM-100 (a type of methylated methylol melamine) was added to 179 parts by weight of the aqueous polymer dispersion obtained in Production Example 1.
A paint was prepared by adding 37 parts by weight of 80% butyl cellosolve solution (product name manufactured by Sumitomo Chemical Co., Ltd.) and 10 parts by weight of butyl cellosolve, diluted with water and heated in a #4 food cup for 30 seconds, resulting in a solid content of 34. %, and the amount of organic solvent in volatile substances was 11%.

This was spray painted on an iron plate and baked at 140°C for 30 minutes. Example 2 Euban 20SE, a type of butoxymethylated melamine, was added to 205 parts by weight of the aqueous polymer dispersion obtained in Production Example 1.
(50% n-butanol/xylene mixed solution) [trade name manufactured by Mitsui Toatsu Chemical Co., Ltd.] 10 parts by weight and 1 part by weight of butyl cellosoluble were added to prepare a paint, diluted with water, and poured into a #4 food cup to make a paint. When converted to seconds, the solid content was 35%.
The amount of organic lactic agent in the volatile substances was 12%.

This was spray painted on an iron plate and baked at 140°C for 30 minutes. Example 3 Hydroxyethyl methacrylate 10 parts by weight Acrylic acid 5 parts by weight Methacrylic acid
3 parts by weight styrene
40 parts by weight ethyl methacrylate
42 parts by weight of 2 parts by weight of azobisisobutyronitrile were added dropwise to 100 parts by weight of cellosolve heated to 120°C and polymerization was carried out over 7 hours. 80 parts by weight of the solvent was distilled off and triethylamine Neutralize with water and add water 2
Make a 5% water bottle solution.

Using 80 parts by weight of this milky liquid, titanium white JR-600E
[Product name manufactured by Teikoku Kako Co., Ltd.] 100 parts by weight was dispersed in a ball mill to obtain the polymer aqueous dispersion 114 used in Production Example 1.
A paint was prepared by adding 37 parts by weight of HM-100 and 10 parts by weight of butyl cellosolve, diluted with water, and dried in a #4 food cup for 30 seconds.The solid content was 50%, and the organic content in the volatile substances was 50%. The drug amount was 13%. When this was spray-painted on an iron plate, it showed excellent painting workability and 140
Baked at ℃ for 30 minutes. Example 4 25% water used in Example 3? A paint was prepared by dispersing 5 parts by weight of aluminum pigment in 80 parts by weight of the liquid, adding 114 parts by weight of the aqueous polymer dispersion used in Production Example 1, 37 parts by weight of HM-100, and 10 parts by weight of butyl cellosolve. When diluted with water and dried in a photo cup #4 for 30 seconds, the solid content was 3.
5%, and the amount of organic liqueur in volatile matter was 13%.

When this was spray-coated on an iron plate, the coating workability was excellent, and when baked at 140°C for 30 minutes, a coating film with an excellent metallic feel was obtained. Example 5 Hydroxyethyl acrylate 30 parts by weight Methacrylic acid 10 parts by weight N-methylolacrylamide 5 parts by weight Methyl methacrylate
25 parts by weight butyl acrylate 30 parts by weight azobisisobutyronitrile 1 part by weight were added dropwise to 100 parts by weight of isopropyl alcohol heated to reflux and polymerized over 7 hours. Part was distilled off, neutralized with aqueous ammonia, and water was added to make a 20% aqueous solution.

Styrene was added to 100 parts by weight of this aqueous solution.
12 parts by weight isobutyl methacrylate
After adding 10 parts by weight of N-methylol acrylamide and 5 parts by weight of hydroxyethyl methacrylate and stirring for 1 hour, 1 part by weight of potassium persulfate was added to 10 parts by weight of water.
When the mixture was added to 1 part by weight and heated at 75°C for 4 hours, an aqueous polymer dispersion having a solid content of 36% and a viscosity of 260 centipoise was obtained.

This dispersion did not change in viscosity even after being left at 40° C. for one month, and remained stable without any aggregates. A paint was prepared by adding 37 parts by weight of HM-100 and 10 parts by weight of butyl cellosolve to 194 parts by weight of this aqueous polymer dispersion, diluted with water and dried in a #4 food cup for 30 seconds, resulting in a solid content of 32%.
The amount of organic additives in volatile substances was 11%. This was painted on an iron plate and baked at 140°C for 30 minutes. Example 6 Hydroxyethyl methacrylate 60 parts by weight Acrylic acid 5 parts by weight Methyl methacrylate 30 parts by weight N-methylolacrylamide 5 parts by weight Azobisisobutyronitrile
After dropping 1 part by weight into 100 parts by weight of cellosolve heated to 120°C and polymerizing for 7 hours,
2 parts by weight of glycidyl methacrylate, 0.05 parts by weight of hydroquinone, and 0.5 parts by weight of dimethylaminoethanol were added, and heating was continued for further 6 hours.

70 parts by weight of the bulking agent were distilled off from this solution, neutralized with triethylamine, and then diluted with water to obtain an 8% aqueous solution. Add styrene to 100 parts by weight of this aqueous solution.
40 parts by weight Ethyl acrylate 28 parts by weight N-methylolacrylamide 5 parts by weight When heated for 4 hours, the solid content was 4
An aqueous polymer dispersion with a viscosity of 95 centipoise at 4% was obtained.

This dispersion did not change in viscosity even after being left at 40° C. for one month, and remained stable without any aggregates. A paint was prepared by adding 37 parts by weight of HM-100 and 10 parts by weight of butyl cellosolve to 159 parts by weight of this aqueous polymer dispersion, diluted with water and heated in a #4 food cup for 30 seconds, resulting in a solid content of 35%.
, the amount of organic liqueur in the volatile matter was 10%. This was painted on an iron plate and baked at 140°C for 30 minutes. Comparative Example 1 All of the compounds used in Production Example 1 were prepared in the same manner as in Production Example 1, except that N-butoxymethylacrylamide was replaced with butyl acrylate and N-methylolmethacrylamide was replaced with 2-hydroxyethyl methacrylate. A combined aqueous dispersion was made.

A paint was prepared in the same manner as in Example 2 using this aqueous polymer dispersion. Paint (30 seconds with food cup #4)
The solid content was 34%, and the amount of organic solvent in volatile substances was 11%. This was spray-painted on an iron plate and baked at 140°C for 30 minutes. Comparative Example 2 The emulsifier and the entire dispersed particles of the aqueous polymer dispersion of Production Example 1 were added to 92 parts by weight of a water solution containing 2 parts by weight of sodium dodecylbenzenesulfonate (surfactant) and 0.7 parts by weight of ammonium persulfate. 3.75 parts by weight of hydroxyethyl methacrylate,
3 parts by weight of acrylic acid, 18 parts by weight of N-butoxymethylacrylamide, 4.5 parts by weight of styrene, 3.75 parts by weight of ethyl methacrylate, 24 parts by weight of methyl methacrylate,
When 15 parts by weight of ethyl acrylate and 3 parts by weight of N-methylol methacrylamide were added dropwise and emulsion polymerization was carried out at 80°C, an aqueous dispersion with a solid content of 45% was obtained.

Triethylamine was added to 156 parts by weight of this aqueous dispersion for equivalent neutralization, and 20 parts by weight of Cellosolve and HM-
When a paint prepared by adding 37 parts by weight of 100 was diluted with water and heated in a #4 food cup for 30 seconds, the solid content was 44.
%, organic thickening agent in volatile matter 24%. This was spray-painted on an iron plate and baked at 140°C for 30 minutes. Comparative Example 3 Monomer components constituting the entire emulsifier and dispersed particles of the aqueous polymer dispersion of Production Example 1, namely, 3.75 parts by weight of hydroxyethyl methacrylate, 3 parts by weight of acrylic acid, and 18 parts by weight of N-butoxymethylacrylamide. , 4.5 parts by weight of styrene, 3.75 parts by weight of ethyl methacrylate, 24 parts by weight of methyl methacrylate, 15 parts by weight of ethyl acrylate, 3 parts by weight of N-methylolmethacrylamide, and 0.75 parts by weight of azobisisobutyronitrile. The mixture consisting of 5 parts was added dropwise to 75 parts by weight of cellosolve heated to 120°C, and polymerization was carried out over 7 hours. After that, 35 parts by weight of cellosolve was distilled off, the equivalent amount was neutralized with triethylamine, and water was added. to make a 20% aqueous solution.

Next, 37 parts by weight of HM-100 was added to 350 parts by weight of the aqueous solution, diluted with water, and heated in a #4 food cup for 30 seconds.
It was %. This was spray-painted on an iron plate and baked at 140°C for 30 minutes. Comparative Example 4 22 parts by weight of hydroxyethyl methacrylate, 20 parts by weight of acrylic acid, 3 parts by weight of N-butoxymethylacrylamide, 30 parts by weight of styrene, 25 parts by weight of ethyl methacrylate and 1 part by weight of azobisisobutyronitrile were heated at 120°C. heated to 100
The mixture was added dropwise to part by weight of cellosolve and polymerized over a period of 7 hours, after which 70 parts by weight of cellosolve was distilled off, the equivalent amount was neutralized with triethylamine, and water was added to make a 15% aqueous solution.

A 30-second paint was produced using food cup #4 in the same manner as in Example 2, except that this milky liquid was used. The solids content of the paint is 34%, and the amount of organic lactic agent in volatile substances is 1
It was 1%. Spray this paint onto the iron plate and
Baking was performed at 40°C for 30 minutes. Comparative Example 5 3 parts by weight of hydroxyethyl methacrylate, 20 parts by weight of acrylic acid, 22 parts by weight of N-butoxymethyl acrylamide
Parts by weight, 30 parts by weight of styrene, 25 parts by weight of ethyl methacrylate
parts by weight and 1 part by weight of azobisisobutyronitrile,
It was added dropwise to 100 parts by weight of cellosolve heated to 120°C and polymerized over 7 hours. After that, 70 parts by weight of cellosolve was distilled off, the equivalent amount was neutralized with triethylamine, and water was added to make 15% water. It was made into a liquid.

A 30-second paint was produced using food cup #4 in the same manner as in Example 2, except that this aqueous solution was used. The solids content of the paint was 34%, and the amount of organic solvent in volatile substances was 11%. Spray this paint onto the iron plate,
It was baked at 140°C for 30 minutes. Performance test results: 3 for the food cup #4 obtained in the above examples and comparative examples.
The properties of the composition diluted to 0 seconds and the performance test results of the baked coating are shown in the following table.

Claims (1)

[Scope of Claims] 1 (A) 5 to 60% by weight of hydroxyalkyl acrylate and/or hydroxyalkyl methacrylate, 5 to 20% by weight of acrylic acid and/or methacrylic acid,
Compounds represented by the following general formula ▲ Numerical formulas, chemical formulas, tables, etc. ▼ (In the formula, R is a hydrogen atom or a methyl group, R' is a hydrogen atom, or C_nH_2_n_+_1, where n represents a number from 1 to 4.) (I) 5 to 20% by weight, and 30 to 85% by weight of at least one copolymerizable monoethylenically unsaturated monomer selected from acrylic acid alkyl esters, methacrylic acid alkyl esters, and styrene;
Using a water-soluble copolymer obtained by copolymerizing and neutralizing as an emulsifier, a monomer mixture consisting of 5 to 50% by weight of the compound (I) and 50 to 95% by weight of vinyl monomer was emulsion polymerized. (B) an amino resin, the content of (B) as solid content is 40% by weight or less based on the sum of (A) and (B), and it is contained therein. A thermosetting coating composition characterized in that the content of organic solvent in the volatile substance is 3 to 30% by weight.