JPH0867833A - Resin composition for powder coating - Google Patents

Abstract

PURPOSE: To obtain the subject composition containing a specific copolymer and an ester exchange catalyst as essential components and giving cured coating films excellent in appearance, curability, flexibility, weather resistance and physical properties. CONSTITUTION: This resin composition contains (A) a copolymer obtained by copolymerizing (i) a polymerizable monomer of the formula [R1 is H, CH3 ; R2 is a 1-18C alkyl, a cycloalkyl, an aralkyl, a (substituted) phenyl] with (ii) a hydroxyl group-containing vinylic monomer and preferably further with (iii) another vinylic monomer capable of being copolymerized with the component (i) or (ii), and (B) an ester exchange catalyst as essential components. The component B is preferably the combination of a sulfonic acid group-containing compound with a sulfonic acid alkali metal, ammonium or amine group- containing compound, e.g. benzene sulfonic acid sodium salt, and is added in an amount of 0.05-1 pt.wt. per 100 pts.wt. of the resin solid content.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a new and useful resin composition for powder coatings. More specifically, the present invention mainly comprises, as an essential component, a copolymer obtained by copolymerizing a specific polymerizable monomer and a hydroxyl group-containing vinyl monomer, and a transesterification catalyst. In particular, the present invention relates to a resin composition for powder coating, which has a very high practicality and can provide a coating film having excellent coating film appearance, curability, weather resistance and mechanical properties.

[0002]

2. Description of the Related Art Powder coating is one form of coating that does not contain organic solvents. In recent years, its pollution-free property has been attracting attention from the viewpoint of environmental problems such as air pollution, and the amount used is also
It is increasing year by year.

As for the kind of binder resin used in this type of powder coating, various polymer compounds are used depending on the application.

Among them, particularly representative of them are a composition in which a terminal isocyanate group type polyester resin is mixed with a block / isocyanate compound as a curing agent, and an acrylic copolymer having a glycidyl group. The polymer has a composition in which an aliphatic dibasic acid is blended, but the former requires a high baking temperature, and the weather resistance when used outdoors is not sufficient. There is a problem that the latter is inferior to the latter in blocking resistance during storage of powder coating (difficulty of fusion of coating particles) and flexibility of coating film. Have a point.

[0005]

As described above, the conventional powder coating material has advantages and disadvantages, and is a substitute for satisfying and satisfying the various demands currently strongly demanded in the industry. In other words, unfortunately, powder coatings with extremely high practicality, which can provide coating films that are excellent not only in the appearance of the coating film, but also in curability, weather resistance, and mechanical properties, have appeared, unfortunately. The reality is that they have not.

In view of the above-mentioned drawbacks of the prior art, however, the present inventors have diligently started research in order to meet the various demands of the industry as described above. Therefore, the problem to be solved by the present invention depends on one factor, and in particular, it is possible to give a coating film excellent in coating film appearance, curability, weather resistance, mechanical properties, and the like, which is extremely highly practical. The aim is to provide powder coatings.

[0007]

Therefore, the present inventors have
In addition to solving the problems of the above-mentioned conventional techniques, in order to meet the various demands of the present invention as described above, focusing on the problems to be solved by the present invention, as a result of earnestly studying, as a result, from a specific component It was found that a composition obtained by incorporating a transesterification catalyst into a copolymer which can give a coating film excellent in coating film appearance, curability, weather resistance and mechanical properties, among others. Thus, the present invention has been completed here.

That is, the present invention is basically based on the following general formula (1):

[0009]

[Chemical 3]

[Wherein R ₁ is --H or --CH
₃ denote the, R ₂ denote the alkyl group, a cycloalkyl group, an aralkyl group, a phenyl group or substituted phenyl group the number of carbon atoms becomes 1-18. ] A copolymer (A) obtained by copolymerizing the specific polymerizable monomer (a) represented by
And a transesterification catalyst (B) as an essential component, to provide a resin composition for powder coating having extremely high practicality.

The structure of the present invention will be described in detail below.

Here, first, the above-mentioned copolymer (A) means a specific polymerizable monomer (a) and a hydroxyl group-containing vinyl monomer as represented by the above-mentioned general formula (1). The form obtained by copolymerizing the monomer (b) is referred to, or the polymerizable monomer (a) and
A form obtained by copolymerizing a hydroxyl group-containing vinyl monomer (b) with another vinyl monomer (c) copolymerizable with these monomers (a) or (b) Refers to

Among the polymerizable monomers (a) represented by the above-mentioned general formula (1), which are the copolymerization components (comonomers or comonomers) of the copolymer (A), particularly representative. Examples of various methacrylic acid esters such as methylmethacrylate, ethylmethacrylate, butylmethacrylate, isobutylmethacrylate, laurylmethacrylate, cyclohexylmethacrylate or benzylmethacrylate;

Alternatively, various acrylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate or cyclohexyl acrylate may be used.

Here, these acrylic acid esters and / or methacrylic acid esters [hereinafter, these are generically referred to as (meth) acrylic acid esters or (meth) esters]
Also called acrylates. The number of carbon atoms of the alkyl group constituting the above] may be in the range of 1 to 18, but particularly in terms of blocking resistance, the number of carbon atoms in the range of 1 to 4 is It can be used more preferably.

The hydroxyl group-containing vinyl monomer (b), which is a copolymerization component of the copolymer (A), means at least one hydroxyl group and a polymerizable unsaturated double bond in one molecule. , But also includes only 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 2-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether. , 3-hydroxybutyl vinyl ether, 2-hydroxy-2-methylpropyl vinyl ether, 5-hydroxypentyl vinyl ether or 6-hydroxyhexyl vinyl ether, and various vinyl ethers having a hydroxyl group;

Addition reaction products of these various vinyl ethers with ε-caprolactone; 2-hydroxyethyl (meth) allyl ether, 3-hydroxypropyl (meth) allyl ether, 2-hydroxypropyl (meth) allyl ether, 4-hydroxybutyl (meth) allyl ether, 3-hydroxybutyl (meth) allyl ether, 2-hydroxy-2-methylpropyl (meth)
Various hydroxyl group-containing allyl ethers such as allyl ether, 5-hydroxypentyl (meth) allyl ether or 6-hydroxyhexyl (meth) allyl ether;

These various allyl ethers and ε-
Addition reaction product with caprolactone; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth ) Various hydroxyl group-containing (meth) acrylates such as acrylate, 4-hydroxybutyl (meth) acrylate, polyethylene glycol mono (meth) acrylate or polypropylene glycol mono (meth) acrylate; or various (meth) acrylates listed above. And the main component of the addition reaction of ε-caprolactone.

Further, the monomer (c), which is a copolymerization component of the copolymer (A), that is, the other component which can be copolymerized with the above-mentioned component (a) and / or component (b). The vinyl monomer refers to a vinyl-based monomer other than the component (a) and the component (b), but if only typical ones are exemplified, ethylene, propylene or Various α-olefins such as butene-1; various halogenated olefins other than fluoroolefins such as vinyl chloride or vinylidene chloride;
Various aliphatic vinyl compounds such as styrene, α-methylstyrene or vinyltoluene;

Various amino group-containing amide systems such as N-dimethylaminoethyl (meth) acrylamide, N-diethylaminoethyl (meth) acrylamide, N-dimethylaminopropyl (meth) acrylamide or N-diethylaminopropyl (meth) acrylamide. Unsaturated monomers; various dialkylaminoalkyl (meth) acrylates such as dimethylaminoethyl (meth) acrylate or diethylaminoethyl (meth) acrylate; tert-butylaminoethyl (meth) acrylate, tert-bitylamino Propyl (meta)
Various amino group-containing monomers such as acrylate, aziridinylethyl (meth) acrylate, pyrrolidinylethyl (meth) acrylate or piperidinylethyl (meth) acrylate;

Various carboxyl group-containing monomers such as (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid or fumaric acid; glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate or (meth ) Various epoxy group-containing monomers such as allyl glycidyl ether; various α, β-ethylenically unsaturated dicarboxylic acids such as maleic acid or fumaric acid, and monohydric alcohols having 1 to 18 carbon atoms Monoesters (half esters);

Vinyltrimethoxysilane, vinyltriethoxysilane, vinyltripropoxysilane, vinylmethyldiethoxysilane, vinyltris (β-methoxyethoxy) silane, allyltrimethoxysilane, trimethoxysilylethyl vinyl ether, triethoxysilylethyl vinyl ether, Methyldimethoxysilylethyl vinyl ether, trimethoxysilylpropyl vinyl ether, triethoxysilylpropyl vinyl ether,
Methyldiethoxysilylpropyl vinyl ether, γ-
Various hydrolyzable silyl group-containing monomers such as (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane or γ- (meth) acryloyloxypropylmethyldimethoxysilane;

Various fluorine-containing α-olefins such as vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, bromotrifluoroethylene, pentafluoropropylene or hexafluoropropylene; or Various perfluoroalkyl perfluorovinyl ethers such as trifluoromethyl trifluorovinyl ether, pentafluoroethyl trifluorovinyl ether or heptafluoropropyl trifluorovinyl ether and (per) fluoroalkyl vinyl ethers (provided that the carbon number of the alkyl group is 1-1
A range of 8 is preferable. ) Various fluorine atom-containing monomers such as;

Methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, tert-butyl butynyl ether, n-
Various alkyl vinyl ethers or substituted alkyl vinyl ethers such as pentyl vinyl ether, n-hexyl vinyl ether, n-octyl vinyl ether, 2-ethylhexyl vinyl ether, chloromethyl vinyl ether, chloroethyl vinyl ether, benzyl vinyl ether or phenylethyl vinyl ether; cyclopentyl vinyl ether, cyclohexyl vinyl ether Or various cycloalkyl vinyl ethers such as methylcyclohexyl vinyl ether;

Vinyl-2,2-dimethylpropanoate, vinyl-2,2-dimethylbutanoate, vinyl-
2,2-dimethylpentanoate, vinyl-2,2-dimethylhexanoate, vinyl-2-ethyl-2-methylbutanoate, vinyl-2-ethyl-2-methylpentanoate, vinyl-3- Chloro-2,2-dimethylpropanoate, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, C ₉
Branched aliphatic (branched aliphatic) carboxylate vinyl, C
₁₀ branched aliphatic (branched aliphatic) vinyl carboxylate,
Various aliphatic vinyl carboxylates such as C ₁₁ branched aliphatic (branched aliphatic) carboxylates or vinyl stearate;

Alternatively, various vinyl esters of carboxylic acids having various cyclic structures such as vinyl cyclohexanecarboxylate, vinyl methylcyclohexanecarboxylate, vinyl benzoate or vinyl p-tert-butylbenzoate can be used.

As the amount of the polymerizable monomer (a) and the hydroxyl group-containing vinyl monomer (b) as exemplified above, the weight% of the monomer component (a) is X,
(B) When the weight% of the monomer component is Y,
An appropriate range is 5 ≦ X ≦ 95, 5 ≦ Y ≦ 95, and 10 ≦ X + Y ≦ 100, and preferably 10 ≦ X ≦ 90. 10
Satisfies ≦ Y ≦ 70 and 10 ≦ X + Y ≦ 100
It is suitable to be within the range that satisfies

(A) When the amount of the monomer component is less than 5%, the mechanical properties of the coating film are inevitably deteriorated. On the other hand, when it is more than 95%, the same drawbacks are caused. This is not preferable in any case. On the other hand, the same applies to the monomer component (b).

Further, the number average molecular weight of the copolymer (A) is preferably in the range of about 500 to about 50,000, and more preferably 1,000 to 10,000.
It is even more desirable to be within the range. When the number average molecular weight is less than 500, mechanical properties of the coating film are inevitably deteriorated.
When it is larger than 000, the smoothness of the coating film is inevitably deteriorated.

Further, the glass transition temperature of the copolymer (A) is preferably in the range of about 50 ° C. to about 100 ° C. When it is lower than about 50 ° C., the blocking resistance of the powder coating is inevitable. Will be inferior, while about 1
When the temperature is higher than 00 ° C., the smoothness of the coating film is inevitably deteriorated, which is not preferable in any case.

Further, the hydroxyl value of the copolymer (A) is about 10 (mgKOH / g solid content) to about 30.
It is preferably within the range of 0 (mgKOH / g solid content). If the hydroxyl value is less than about 10, the mechanical properties of the coating film will inevitably be inferior.
If it is larger than the above range, the water resistance of the coating film is inevitably deteriorated.

Using the respective monomers (a) and (b) listed above, or the respective monomers (a) to (c) listed above, respectively, the copolymerization A known and commonly used method can be used as it is for the preparation of the coalescence. Among them, the solution radical polymerization method is the most convenient.

The above-mentioned transesterification catalyst (B), which is another essential constituent of the resin composition for powder coating of the present invention, refers to a compound for accelerating the transesterification reaction. For, an acidic or basic compound is used.

Of these, only representative ones are exemplified, and various acidic compounds such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid, phosphoric acid or sulfonic acid; Li
Various basic compounds such as OH, KOH or NaOH; or various metal compounds such as PbO, zinc acetate, lead acetate, antimony trioxide, tetraisopropyl titanate, dibutyltin dilaurate, dibutyltin dioctate or monobutylstannic acid. And so on.

In particular, as a compound capable of sufficiently exerting the effects of the present invention, it is desirable to use a compound having a sulfonic acid group or a compound having a group consisting of an alkali metal salt or amine salt of sulfonic acid.

The above-mentioned compound having a sulfonic acid group refers to a compound having a sulfonic acid group or --SO ₃ H, and a group consisting of an alkali metal salt or amine salt of sulfonic acid described above. the compound having, wherein the salt of a sulfonic acid group or -SO ₃ M [, M is an alkali metal atom, -NH ₄ or -NR ₃
(However, each R is the same or different and represents a hydrogen atom or an alkyl group.). ] Is meant.

Of the various compounds, only typical ones are exemplified, and benzenesulfonic acid, paratoluenesulfonic acid, dodecylbenzenesulfonic acid and their sodium salts, ammonium salts, amine salts, etc. Is mentioned.

It is needless to say that these transesterification catalysts may be used alone or in combination of two or more kinds.

The transesterification catalyst is usually in the range of about 0.01 to about 10 parts by weight, preferably 0.05 to 1 part by weight, based on 100 parts by weight of the resin solid content. It is added within the range. This addition amount is about 0.0
If it is less than 1 part by weight, the curability of the coating film will be inevitably deteriorated, while if it is more than about 10 parts by weight, the storage stability of the paint will be inevitably deteriorated. Therefore, both cases are not preferable.

From the essential constituents listed above,
As a method for preparing the resin composition for powder coating of the present invention, known and commonly used methods are used. As a particularly representative method among them, first, on the basis of the essential constituents of the composition of the present invention, further, if necessary, a pigment or a leveling agent is mixed, and then the mixture thus obtained is mixed. A so-called mechanical pulverization method may be mentioned in which the mixture is melt-kneaded, then finely pulverized, and then subjected to a classification step to obtain a desired powder coating material.

The resin composition for powder coatings of the present invention may further include various known and commonly used pigments such as organic or inorganic pigments, flow regulators, ultraviolet absorbers, antioxidants and the like. Additives; various kinds of fibrin derivatives such as nitrocellulose or cellulose acetate butyrate; or various kinds of resins such as chlorinated polyethylene, chlorinated polypropylene, petroleum resin, epoxy resin or chlorinated rubber You can also

The resin composition for powder coating material of the present invention thus obtained is applied by a conventional method to various base materials to which this type of powder coating material is applied, and then according to a conventional method. By baking and drying, a coating film having excellent appearance, curability, weather resistance and mechanical properties, among others, can be provided.

The resin composition for powder coating of the present invention thus obtained is used for top coating of automobiles, middle coating of automobiles, automobile parts or building materials.
It can be widely used and applied as a paint for various metal products.

[0044]

EXAMPLES Next, the present invention will be explained more specifically with reference to Reference Examples, Examples and Comparative Examples. In the following, all parts and percentages are by weight unless otherwise specified. There is.

Reference Example 1 [Preparation Example of Copolymer (A)] In a reaction vessel equipped with a stirrer, a thermometer, a condenser and a nitrogen gas inlet, 500 parts of xylene was charged, and the mixture was heated to 130 ° C. under a nitrogen atmosphere. To 375 parts of methyl methacrylate and 125 parts of 2-hydroxyethyl methacrylate and 3 parts of azobisisobutyronitrile.
Parts and tert-butyl peroxyoctoate (T
A mixture of 25 parts of BPO) was added dropwise over 4 hours, and the temperature was maintained at the same temperature for 10 hours after the completion of the addition.

Further, from the resin solution thus obtained,
By distilling off xylene under a reduced pressure of about 30 Torr, the nonvolatile content was 99.5%, the softening point by the ring and ball method was 130 ° C., and the number average molecular weight was 5,0.
A solid of the intended copolymer (A) of No. 00 was obtained. Hereinafter, this is abbreviated as polymer (A-1).

Reference Example 2 (same as above), except that a mixture of 150 parts of styrene, 250 parts of n-butyl methacrylate and 100 parts of 4-hydroxybutyl acrylate was used as the monomers, except that the mixture was changed. As in Reference Example 1, the nonvolatile content was 9
9.7%, the softening point by the ring and ball method is 102 ° C., and
A solid of the target copolymer (A) having a number average molecular weight of 4,100 was obtained. Hereinafter, this is abbreviated as a polymer (A-2).

Reference Example 3 (Same as above) As monomers, 125 parts of styrene, 200 parts of methyl methacrylate, 125 parts of n-butyl acrylate,
Use a mixture of 45 parts of "FM-1" [a hydroxyl group-containing vinyl monomer obtained by modifying 2-hydroxyethyl methacrylate with a lactone, manufactured by Daicel Chemical Industries, Ltd.] and 5 parts of acrylic acid. Changed and combined with TB
In the same manner as in Reference Example 1, except that the amount of PO used was changed to 50 parts, the nonvolatile content was 99.8%, the softening point by the ring and ball method was 98 ° C., and the number average molecular weight was 15,000. A solid of the desired copolymer (A) was obtained. Hereinafter, this is abbreviated as a polymer (A-3).

Reference Example 4 [Preparation example of a control copolymer lacking the use of the essential monomer (a) component at all]

The nonvolatile content was 99.8% as in Reference Example 1, except that a mixture of 375 parts of styrene and 125 parts of 2-hydroxyethyl methacrylate was used as the monomer. A control copolymer solid having a softening point of 131 ° C. according to a ring and ball method and a number average molecular weight of 5,500 was obtained. Hereinafter, this is abbreviated as a polymer (A'-1).

Reference Example 5 [Preparation example of control copolymer lacking any use of component (b) as essential monomer]

The procedure of Reference Example 1 was repeated except that a mixture of 200 parts of styrene and 300 parts of n-butyl methacrylate was used as the monomer.
Nonvolatile content is 99.8%, softening point by ring and ball method is 110
A control copolymer solid having a number average molecular weight of 4,800 at 0 ° C. was obtained. Hereafter, the polymer (A'-
2) is abbreviated.

Reference Example 6 [Essential monomer,
Example of Preparation of Control Copolymer, Form of Absent Use of Component (b)

As a monomer, 300 parts of styrene, n-
The nonvolatile content was 99.% as in Reference Example 1 except that a mixture of 500 parts of butyl methacrylate and 200 parts of glycidyl methacrylate was used, and the amount of TBPO used was changed to 50 parts. 5%
Thus, a copolymer solid for control having a softening point by the ring and ball method of 100 ° C. and a number average molecular weight of 1,600 was obtained. Hereinafter, this is abbreviated as a polymer (A'-3).

Examples 1 to 5 and Comparative Examples 1 to 3 The respective components were mixed in the mixing ratios shown in Table 2, and the mixture thus obtained was used as a "co-kneader" (Bus, Switzerland). The mixture was heated and kneaded by a uniaxial kneader “PR-46 type” manufactured by the same company.

Next, various kneaded materials thus obtained were roughly pulverized and then finely pulverized to prepare various powder coatings having an average particle diameter of 30 to 40 μm (μm). .

Thereafter, each of these paints was applied onto a zinc phosphate-treated steel sheet by the electrostatic powder coating method, and then baked and dried at 160 ° C. for 20 minutes to obtain: Various test coated plates were prepared.

Comparative Example 4 Commercially available block / isocyanate compound-curable polyester powder coating materials were used as they were to prepare coated plates for various tests.

With respect to each of the test coated plates obtained in the above, various coating film performances were evaluated. The results are collectively shown in Table 3.

[0060]

[Table 1]

<< Footnotes in Table 1 >> 1) .... Abbreviation of styrene 2) .... Abbreviation of methyl methacrylate

3) ... Abbreviation of n-butyl methacrylate 4) ... Abbreviation of n-butyl acrylate

5) ... Abbreviation of 2-hydroxyethyl methacrylate 6) .... Abbreviation of 4-hydroxybutyl acrylate

7) ... Abbreviation of lactone modified hydroxyl group-containing vinyl monomer manufactured by Daicel Chemical Industries, Ltd. 8) ... Abbreviation of acrylic acid

[0065]

[Table 2]

<< Footnote in Table 1 >> Mn ......... abbreviation of number average molecular weight

[0067]

[Table 3]

<< Footnote in Table 1 >> 9) .... Abbreviation of glycidyl methacrylate

[0069]

[Table 4]

[0070]

[Table 5]

<< Footnotes in Table 2 >>"TaipecCR-90" ...... Titanium dioxide manufactured by Ishihara Sangyo Co., Ltd.

“Modaflow” ………………………… A leveling agent manufactured by Monsanto, USA

[0073]

[Table 6]

<< Footnote in Table 2 >>"Erichsenvalue" ... This value is measured by an Erichsen tester. The larger the value, the better the flexibility of the coating film.

[0075]

[Table 7]

<< Footnote of Table 2 >>"BeckamineP-198" .... Phosphoric acid curing accelerator manufactured by Dainippon Ink and Chemicals, Inc.

[0077]

[Table 8]

[0078]

[Table 9]

[0079]

[Table 10]

[0080]

[Table 11]

[0081]

As is clear from the comparison between each example and each comparative example, the resin composition for powder coating composition of the present invention has, inter alia, a coating film appearance, curability, flexibility and weather resistance. To give an excellent cured coating film.

Claims (5)

[Claims] 1. The following general formula (1): [Wherein R ₁ represents —H or —CH ₃ and R ₂ represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, an aralkyl group, a phenyl group or a substituted phenyl group. To do. ] A copolymer (A) obtained by copolymerizing the polymerizable monomer (a) represented by the formula (1) and a hydroxyl group-containing vinyl monomer (b) and an ester exchange catalyst (B) are essential. A resin composition for powder coating, which is contained as a component. 2. The following general formula (1): [Wherein R ₁ represents —H or —CH ₃ and R ₂ represents an alkyl group having 1 to 18 carbon atoms, a cycloalkyl group, an aralkyl group, a phenyl group or a substituted phenyl group. To do. ] The polymerizable monomer (a) represented by the formula (1), the hydroxyl group-containing vinyl monomer (b), and another vinyl monomer (c) copolymerizable with the component (a) or the component (b). A resin composition for powder coatings, which comprises a copolymer (A) obtained by copolymerization of and a transesterification catalyst (B) as essential components. 3. The resin composition for powder coating according to claim 1 or 2, wherein the transesterification catalyst is at least one compound having a sulfonic acid group. 4. The powder according to claim 1, wherein the transesterification catalyst is at least one compound having a group consisting of an alkali metal salt, an ammonium salt or an amine salt of sulfonic acid. Resin composition for body paint. 5. The above-mentioned transesterification catalyst comprises at least one compound having a sulfonic acid group and at least one compound having a group consisting of an alkali metal salt, ammonium salt or amine salt of sulfonic acid. The resin composition for powder coating according to claim 1 or 2, which is used in combination.