JPH11228866A - Powder coating composition and method for forming multilayer coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating film having good paint safety and, in particular, excellent coating properties such as appearance, weather resistance, mechanical properties, and chipping resistance. To provide a novel powder coating composition and a method for forming a multi-layer coating film having a high level of performance. SOLUTION: Epoxy group-containing vinyl polymer (A)
, A carboxyl group-containing polyester resin (B), and β
-A powder coating composition containing a hydroxyalkylamide curing agent (C) and an epoxy resin (D) as essential film forming components, and a method for forming a multilayer coating film using the same.

Description

DETAILED DESCRIPTION OF THE INVENTION

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel and useful powder coating composition and a method for forming a multilayer coating film. More specifically, the present invention comprises an epoxy group-containing vinyl copolymer, a carboxyl group-containing polyester resin, a β-hydroxyalkylamide curing agent, and an epoxy resin, respectively. , It is safe for the human body, gives a coating film with excellent coating appearance, weather resistance and mechanical properties, and can give a new coating film with excellent chipping resistance. The present invention relates to a high powder coating composition and a method for forming a multilayer coating film, and is also suitable as a coating material for an automobile.

[0001]

2. Description of the Related Art Powder paints are one type of paints that do not contain organic solvents. In recent years, however, their pollution-free properties have been noticed from the viewpoint of environmental problems such as air pollution. , Is increasing year by year. The types of binder resins used in such powder coatings also range in various forms of high molecular compounds depending on the application.

As powder coatings having excellent properties such as coating film appearance, weather resistance or mechanical properties, and storage stability of coatings, there are polyester powder coatings, especially block-isocyanate compounds, tolylene compounds, and the like. A polyester powder coating using glycidyl isocyanurate or the like as a curing agent is mentioned, and is currently widely used.

[0003] However, tolylene glycidyl isocyanurate, a curing agent component, has very low safety.
Has been questioned.

A so-called blocked polyisocyanate compound using ε-caprolactam or the like as a curing agent is scattered during baking and curing, but from the viewpoint of environmental protection and safety. In addition, it has been desired to use a compound having as little a blocking agent as possible, such as ε-caprolactam.

[0005] On the other hand, looking at the conventional techniques for painting an automobile body, the techniques that have been accepted so far include:
Coated objects coated with cationic electrodeposition (such as automobile bodies)
Then, after applying an intermediate coating containing an organic solvent, baking and drying, similarly, a base coating coating containing an organic solvent, and further, a top coating coating containing an organic solvent, sequentially. The mainstream is a coating method which adopts a process of re-coating, baking and curing.

However, in the prior art, as described above, such a coating method is problematic in terms of environmental hygiene because of the evaporation of the organic solvent during coating. Further, as a method of avoiding the volatilization of the organic solvent, it is conceivable to use a powder coating in a form substantially containing no organic solvent, but at present, the powder coating is used as the intermediate coating. In such a case, the resulting multilayer coating film, in particular, had poor mechanical properties and chipping resistance.

[0007] As described above, there is a demand for further improvement of the mechanical properties of the coating material for automobiles, which is a new application for the powder coating material described above. In particular, chipping resistance has been demanded as a new requirement.

By the way, as proposed in Japanese Patent Application Laid-Open No. 9-003369, if an acrylic polymer having a glycidyl group is mainly used as a curing agent, safety or weather resistance, and furthermore, when curing at a low temperature, It is possible to form a coating film having improved mechanical properties and the like.

However, it can be said that further mechanical properties, especially chipping resistance, are sufficient.

[0010] As described above, in any case, the polyester powder coating and the multi-layer coating coating which are extremely practicable, such as satisfying various performances required in recent years for use in automobiles and the like. The reality is that there is no film formation method.

[0011]

However, the present inventors have started research to solve the various problems in the conventional technology as described above. Therefore, the problem to be solved by the present invention is, on the one hand, that the safety of the paint is good, not to mention, in particular, appearance, weather resistance, mechanical properties, etc., and further, chipping resistance The present invention provides a novel powder coating composition having extremely high practicability, which provides a coating film having excellent properties and the like, and particularly provides a powder coating composition and a multilayer coating film forming method suitable for use in automobiles and vehicles. It is in.

[0012]

Means for Solving the Problems Accordingly, the present inventors have:
As a result of diligent and intensive studies, aiming at the problems to be solved by the invention as described above, a carboxyl group-containing polyester resin (B) and a β-hydroxy resin were added to an epoxy group-containing vinyl polymer (A). The powder coating composition [I] obtained by mixing the alkylamide curing agent (C) and the epoxy resin (D), preferably in a specific ratio, is safe, Gives a coating film having excellent weather resistance, mechanical properties, and pitting resistance, and is preferable as a coating composition for automobiles. The epoxy group-containing vinyl polymer (A) has a softening point of 80 to 150 ° C. A vinyl polymer having an epoxy group equivalent of 250 to 700 has a softening point of 80 to 150 ° C. and an acid value of 10 to 2 as a carboxyl group-containing polyester resin (B).
The polyester resin No. 00 is a compound represented by the following general formula (1) as a β-hydroxyalkylamide curing agent (C), and the epoxy resin (D) is a hydrogenated bisphenol A type epoxy resin and / or an alicyclic resin. Formula type epoxy resins are preferred, respectively. Further, as a coating method, after applying the powder coating composition [I] to an object to be coated, a base coat coating [II] and a transparent top coat coating [III] A method of forming a multilayer coating film that is painted in order,
The inventors have found that there is a method for forming a multi-layer coating film for applying the top coat paint [IV], and have completed the present invention.

That is, the present invention provides (1) an epoxy group-containing vinyl polymer (A), a carboxyl group-containing polyester resin (B), a β-hydroxyalkylamide curing agent (C), and an epoxy resin (D). ) Is contained as an essential film-forming component.

(2) An epoxy group-containing vinyl polymer (A) has a softening point of 80 to 150 ° C. and an epoxy group equivalent of 25.
The powder coating composition according to claim 1, which is a vinyl polymer of 0 to 700.

(3) The carboxyl group-containing polyester resin (B) has a softening point of 80 to 150 ° C. and an acid value of 10 to 20.
The powder coating composition according to the above (1) or (2), which is a polyester resin of 0 (mg KOH / g solid content).

(4) The β-hydroxyalkylamide curing agent (C) has the following general formula (1)

[0017]

Embedded image

Wherein R ¹ is a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, R ² is a hydrogen atom or 1 to ² carbon atoms.
5 represents an alkyl group or HOCH (R ¹ ) CH ₂ — (R ¹ is the same as described above), and A represents a divalent hydrocarbon group. The powder coating composition according to the above (1), (2) or (3), which is a compound represented by the formula:

(5) The above (1), (2), (3) wherein the epoxy resin (D) is a hydrogenated bisphenol A type epoxy resin and / or an alicyclic type epoxy resin.
Or the powder coating composition according to (4),

(6) The weight ratio (A / B) between the epoxy group-containing vinyl polymer (A) and the carboxyl group-containing polyester resin (B) is from 60/40 to 97/3, and Total amount of the polymer (A) and the carboxyl group-containing polyester resin (B) (A +
B) The amount of the β-hydroxyalkylamide curing agent (C) used is 1 to 10 parts by weight based on 100 parts by weight,
B) The powder coating composition according to any one of (1) to (5) above, wherein the amount of the epoxy resin (D) used is 2 to 20 parts by weight based on 100 parts by weight;

(7) The powder coating composition according to any one of the above (1) to (6), wherein the powder coating composition is a coating composition for a vehicle.

(8) Any one of the above (1) to (7)
The powder coating composition [I] according to
After curing, apply base coat paint [II],
Furthermore, a method of forming a multilayer coating film, characterized by applying a transparent top coat paint [III], baking and drying, and

(9) The powder coating composition [I] according to any one of (1) to (7) is applied to an object to be coated and cured, and then a top coat coating [IV] is applied. And baking and drying.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the powder coating composition and the method for forming a multilayer coating film of the present invention will be described in detail. First, the powder coating composition [I] of the present invention will be described.

The epoxy group-containing vinyl polymer (A), which is one of the essential components of the powder coating composition of the present invention, includes, for example, an epoxy group at the terminal or side chain of the molecule. Means a vinyl-based copolymer having, for example, a vinyl-based monomer having an epoxy group, together with other vinyl-based monomers that can be copolymerized if necessary. It can be prepared by various methods, such as a method or a method in which an epoxy group is introduced by modifying a vinyl polymer by a conventional method.

Among them, the above-mentioned methods include, for example, a method of synthesizing a vinyl copolymer having an isocyanate group and further reacting the copolymer with glycidol, Although there is a method of converting the glyceryl carbonate group-containing vinyl copolymer obtained by copolymerizing a vinyl monomer having a carbonate group into a copolymer having an epoxy group through a decarboxylation reaction, etc. The above method is simple.

[0027] Among the vinyl monomers having an epoxy group which are used for obtaining the epoxy group-containing vinyl polymer (A) used in the present invention by the above-mentioned method, they are particularly representative. If only a thing is illustrated, various glycidyl esters of (meth) acrylic acid such as glycidyl (meth) acrylate and β-methylglycidyl (meth) acrylate, (meth) allyl glycidyl ether, (meth) Various allyl glycidyl ethers such as allyl methyl glycidyl ether, 3,4-epoxycyclohexyl acrylate,
Various types of alicyclic epoxy group-containing vinyl monomers such as 3,4-epoxycyclohexyl methacrylate, among which copolymerization properties of the epoxy group-containing vinyl copolymer (A) and epoxy groups In consideration of the reactivity of glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexyl acrylate, and 3,4-epoxycyclohexyl methacrylate are preferred.

Further, it is a matter of course that other vinyl monomers which can be copolymerized with the vinyl monomers having an epoxy group can be used. Of those, only typical ones are exemplified, and the following are shown.

Various acrylates, such as methyl acrylate, ethyl acrylate, butyl acrylate or cyclohexyl acrylate;
Various methacrylates, such as methyl methacrylate, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate or benzyl methacrylate;

2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3
-Hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, 3-hydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, polyethylene glycol mono (meth) acrylate or polypropylene glycol mono (meth) acrylate Various hydroxyl group-containing (meth) acrylates; or various (meth) acrylates described above.
An addition reaction product of acrylate and ε-caprolactone;

Various carboxyl group-containing monomers such as (meth) acrylic acid, crotonic acid, itaconic acid, maleic acid or fumaric acid, or various polycarboxylic acids such as itaconic acid, maleic acid or fumaric acid Mono- or polyesters of a group-containing monomer and a monoalkyl alcohol having 1 to 18 carbon atoms; N-dimethylaminoethyl (meth) acrylamide, N-diethylaminoethyl (meth) acrylamide, N-dimethylaminopropyl ( Various amino group-containing amide unsaturated monomers such as (meth) acrylamide or N-diethylaminopropyl (meth) acrylamide;

Various dialkylaminoalkyl (meth) acrylates such as dimethylaminoethyl (meth) acrylate or diethylaminoethyl (meth) acrylate; tert-butylaminoethyl (meth) acrylate, tert-bitylaminopropyl (meth)
Various amino group-containing monomers such as acrylate, aziridinylethyl (meth) acrylate, pyrrolidinylethyl (meth) acrylate or piperidinylethyl (meth) acrylate;

Ethylene, propylene or butene-1
Various halogenated olefins except fluoroolefin such as vinyl chloride or vinylidene chloride; various aromatic vinyl compounds such as styrene, α-methylstyrene or vinyltoluene; 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; Various perfluoroalkyl / perfluorovinyl ethers or (per) fluoroalkyl vinyl ethers such as trifluoromethyl trifluorovinyl ether, pentafluoroethyl trifluorovinyl ether or heptafluoropropyl trifluorovinyl ether (where the carbon number of the alkyl group is Various fluorine-containing vinyl monomers, such as 1 to 18);

Vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, branched aliphatic (branched aliphatic) carboxylic acids having 9 carbon atoms Various aliphatic vinyl carboxylates such as vinyl acrylate, branched aliphatic vinyl carboxylate having 10 carbon atoms, branched aliphatic vinyl carboxylate having 11 carbon atoms or vinyl stearate; vinyl cyclohexanecarboxylate, methylcyclohexane There are various vinyl esters of a carboxylic acid having a cyclic structure, such as vinyl carboxylate, vinyl benzoate or vinyl p-tert-butyl benzoate.

The epoxy group-containing vinyl polymer (A)
In consideration of the mechanical properties of the resulting coating film, especially the chipping resistance, etc., an epoxy equivalent content in the range of 200 to 1,000 is appropriate, and particularly an epoxy group content of 250 to 700. Are particularly preferred.

The number-average molecular weight of the epoxy group-containing vinyl polymer (A) is 300 to 5, taking into account the mechanical properties, chipping resistance and smoothness of the coating film.
000 is appropriate, and among them, 1,000 to
Particularly preferred is a range of 5,000.

The softening point of the epoxy group-containing vinyl polymer (A) by the ring and ball method is 80 to 150 ° C. in consideration of the blocking resistance of the powder coating composition and the smoothness of the coating film. Within the range is appropriate.

To prepare the epoxy group-containing vinyl polymer (A) using various vinyl monomers as exemplified above, various known and commonly used methods can be applied. Above all, the simplest is the solution radical polymerization method.

The carboxyl group-containing polyester resin (B), which is one of the essential components of the present invention, can be obtained, for example, by reacting a polyhydric acid component and a polyhydric alcohol component as main raw materials. And a resin having a carboxyl group as a functional group.

Here, only the typical examples of the above-mentioned polyhydric acids are exemplified, and adipic acid,
Azelaic acid, sebacic acid, dimer acid, glutaric acid (anhydrous), suberic acid, maleic acid, fumaric acid, (anhydrous)
Succinic acid or 1,4-cyclohexanedicarboxylic acid,
(Anhydride) phthalic acid, tetrahydro (anhydride) phthalic acid, hexahydro (anhydride) phthalic acid, methylhexahydro (anhydride) phthalic acid, isophthalic acid, terephthalic acid or 2,6-naphthalenedicarboxylic acid, or 4,4-diphenyldicarboxylic acid Acids such as various dicarboxylic acids (anhydrides) or their dimethyl esters, (anhydrous) trimellitic acid, trimesic acid, cyclopentanetetracarboxylic acid, methylcyclohexentricarboxylic acid or (anhydrous) pyromellitic acid And various compounds.

On the other hand, if only typical examples of the above-mentioned polyhydric alcohols are exemplified, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, dipropylene glycol,
1,3-propanediol, 1,3-butanediol,
1,4-butanediol, 1,5-pentanediol,
1,6-hexanenediol or neopentyl glycol, cyclohexanedimethanol, octanediol, diethylpropanediol, butylethylpropanediol, 2-methyl-1,3-propanediol or 2,2,4-trimethylpentanediol, bis Hydroxyethyl terephthalate, hydrogenated bisphenol A, bisphenol A alkylene oxide adduct or hydrogenated bisphenol A alkylene oxide adduct;

Glycerin, diglycerin, trimethylolpropane, trimethylolethane, pentaerythritol, dipentaerythritol or trishydroxyethyl isocyanurate;

Various monoepoxy compounds such as "Kajura E10" (trade name of glycidyl ester of a branched aliphatic carboxylic acid manufactured by Shell Chemical Company, The Netherlands), and "Denacol EX-211" [Nagase Chemical Co., Ltd.] (stock)
And various polyfunctional epoxy compounds such as “Epiclon 1050” (trade name of bisphenol A type diglycidyl ether manufactured by Dainippon Ink and Chemicals, Inc.). is there.

In addition, dimethylolpropionic acid,
Hydroxypivalyl hydroxypivalate, ε-caprolactone or parahydroxybenzoic acid, etc., can also be used.

Among these, terephthalic acid and / or isophthalic acid and neopentyl glycol are preferably used as essential components in consideration of the mechanical properties and durability of the polyester resin (B).

The acid value of the carboxyl group-containing polyester resin (B) is from 10 to 20 in consideration of the mechanical properties of the coating film, especially the chipping resistance and the water resistance of the coating film.
0 (mg KOH / g solid content; the same applies hereinafter) is preferable, and particularly preferably 20 to 100.

The number average molecular weight of the carboxyl group-containing polyester resin (B) is from 1,000 to 10,000 in consideration of the mechanical properties and chipping resistance of the coating film and the smoothness of the coating film. The range is appropriate, and particularly, the range of 2,000 to 5,000 is particularly preferable.

The softening point of the carboxyl group-containing polyester resin (B) by the ring and ball method is in the range of 80 to 150 ° C. in consideration of the blocking resistance of the powder coating composition and the smoothness of the coating film. Is suitable, and particularly preferably in the range of 90 to 130 ° C.

The β-hydroxyalkylamide curing agent (C), which is one of the further essential components of the present invention, is represented by the following general formula (2):

[0051]

Embedded image [Wherein, R ¹ is a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, R ² is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or HOCH (R ¹ ) CH _2- (R ¹ is as defined above. The same). And a compound having two or more structures represented by the general formula (2) is usually used. Among them, the following general formula (1)

[0052]

Embedded image

Wherein R ¹ is a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, R ² is a hydrogen atom or 1 to ² carbon atoms.
5 represents an alkyl group or HOCH (R ¹ ) CH ₂ — (R ¹ is the same as described above), and A represents a divalent hydrocarbon group. Are preferred. Further, in the formula, R ¹ is a hydrogen atom or a methyl group, and R ² is HOCH (R ¹ ) C
H _2- (R ¹ is a hydrogen atom or a methyl group), and A is preferably an alkylene group having 2 to 10 carbon atoms, particularly preferably an alkylene group having 4 to 8 carbon atoms.

The above-mentioned β-hydroxyalkylamide is prepared, for example, by using a carboxylic acid and / or a carboxylic acid ester and a β-hydroxyalkylamine as a catalyst using an alkoxide such as sodium or potassium.
It is obtained by reacting.

The carboxylic acid and carboxylic acid ester used herein include, for example, succinic acid, adipic acid, glutaric acid, sebacic acid, dodecanoic acid, dimethyl succinate, diethyl succinate, dimethyl adipate, diethyl adipate, glutaric acid Examples thereof include dimethyl, diethyl glutarate, dimethyl sebacate, diethyl sebacate, dimethyl dodecanoate, diethyl dodecanoate, methyl cyclohexanedicarboxylate, diethyl cyclohexanedicarboxylate, dimethyl tetrahydrophthalate, and diethyl tetrahydrophthalate.

Examples of the hydroxyamine include N-methylethanolamine, diethanolamine, N-methylpropanolamine, dipropanolamine and the like.

Various compounds can be obtained by combining the above carboxylic acid and / or carboxylic acid ester with beta-hydroxyalkylamine. However, in consideration of the hardness of the coating film and the stability of the coating material, dimethyl adipate is preferred. A combination of diethanolamine with one or more carboxylic acid esters selected from the group consisting of diethyladipate, dimethyl glutarate, diethyl glutarate, dimethyl sebacate and diethyl sebacate is preferred.

The epoxy resin (D), which is one of the further essential components of the present invention, may be any of various epoxy resins. Particularly, only typical ones are exemplified. A type epoxy resin, for example, Epicron 1050, Epicron 2050, Epicron 3050 [all are Dainippon Ink and Chemicals, Inc.
Product]; hydrogenated bisphenol A type epoxy resin, for example, ST-5080, ST-5100, ZX-1164
[All products are manufactured by Toto Kasei Co., Ltd.]; Alicyclic type epoxy resins, for example, EHPA-3150 [Products of Daicel Chemical Industries, Ltd.], Araldite CY179 [Products of Nippon Ciba Geigy Co., Ltd.]; Polybasic acid glycidyl ester type Epoxy resins, for example, Denacol EX-711 (manufactured by Nagase Kasei Kogyo Co., Ltd.) and the like, hydrogenated bisphenol A type and alicyclic type epoxy resins are preferred if weather resistance is important, and furthermore, A hydrogenated bisphenol A type epoxy resin is preferred because of excellent undercoating of the resulting coating film and excellent adhesion to metal equipment.

As exemplified above, the use ratio of the epoxy group-containing vinyl polymer (A) and the carboxyl group-containing polyester resin (B), which are essential components, is (A) / (B). Copy ratio is 60/40 to 97
/ 3 is desirable.

The amount of the β-hydroxyalkylamide curing agent (C), which is an essential component, is selected in consideration of the effects to be achieved by the present invention and the storage stability of the paint. The range of 1 to 10 parts by weight is appropriate for the total usage of 100 parts by weight of A) and the carboxyl group-containing polyester resin (B), and the range of 1 to 3 parts by weight is particularly preferable.

Further, epoxy resin (D) as an essential component
Considering the desired effect of the present invention and the weather resistance of the coating film, the total amount of the epoxy group-containing vinyl polymer (A) and the carboxyl group-containing polyester resin (B) is 100 parts by weight. The range of 2 to 20 parts by weight is appropriate, and the range of 2 to 10 parts by weight is particularly preferable.

In order to prepare a powder coating composition using each essential component in the present invention as described above, various known and commonly used methods can be applied. As a particularly typical method among them, for example, first, each essential component as described above is mixed, and if necessary, various additive components such as a pigment or a spreading agent are also mixed. There is a so-called mechanical pulverization method in which the mixture is melted and kneaded, and then subjected to a fine pulverization (chemical) step and a classification (chemical) step to obtain a desired powder coating composition.

The powder coating composition of the present invention may further contain an organic or inorganic pigment within a range that does not deviate from the object of the present invention or within a range that does not impair the effects of the present invention. And various additives known in the art, such as flow regulators, light stabilizers, UV absorbers or antioxidants;

Various fibrous derivatives, such as nitrocellulose or cellulose acetate butyrate; or various resins, such as chlorinated polyethylene, chlorinated polypropylene, petroleum resin, or chlorinated rubber, can also be added. Is, of course.

A catalyst can be added for the purpose of accelerating the curing during baking. In such a case, usually, a reaction between the carboxyl group and the epoxy group is accelerated. Also, various basic catalysts such as amine and imidazole can be used.

In particular, when the powder coating composition according to the present invention is used for automobiles, particularly for automobiles, it is intended to improve chipping resistance.
It is effective to add various known and commonly used curing catalysts and further various known and commonly used thermoplastic resins.

Various kinds of thermoplastic resins may be added to the polyester resin in advance and melt-mixed in addition to the addition at the time of blending the paint.

The powder coating composition according to the present invention contains “M” in order to improve the concealing property as an intermediate coating.
It is particularly effective to add an organic pigment such as "A-100" (trade name of carbon black pigment manufactured by Mitsubishi Chemical Corporation).

The powder coating composition according to the present invention thus obtained is applied to various substrates by a conventional method, and then dried and baked in a conventional method to obtain a coating film appearance. In addition, it is possible to provide a coating film having excellent weather resistance, mechanical properties, and chipping resistance.

The powder coating composition according to the present invention thus obtained is used, in particular, as a paint for automotive top coat, or as a paint for automotive middle coat.
Further, it can be widely used and applied as a paint for automobile parts, a paint for building materials, and a paint for various metal products.

In particular, it is suitable for use in automobiles and as a paint for vehicle interior coating.

Next, the method for forming a multilayer coating film of the present invention will be described. The first component, that is, the object to be coated refers to the base materials to which the coating material is to be applied. Yes, specifically, a so-called unpainted metal material such as an unpainted steel sheet, an untreated or chemically treated aluminum-based substrate, such as a car body or a motorcycle body, etc. Examples include base materials used for various road vehicles and base materials used for automobile parts such as aluminum wheels, and also, in a state where an electrodeposition coating is applied, such as an automobile body. Substrates used for such various road vehicles are also included. Further, a base material used for home electric appliances or steel furniture, for example, an electrogalvanized steel sheet or a hot-dip galvanized steel sheet can be exemplified.

These substrates may be processed into a shape suitable for the final use, or may be made of PC
A form in which the M (pre-coat / metal) coating method is applied, that is, a roughly flat plate-shaped base plate,
After the intended multilayer coating film is formed by the multilayer coating method of the present invention, it may be such that it is bent into a predetermined shape according to the purpose, and further, a coil It may be a substrate, such as a coating, which is used completely in a coating system subjected to so-called post-processing.

The powder coating composition [I], which is the second component constituting the method for forming a multilayer coating film according to the present invention, is applied to the above-mentioned object to be coated and baked and cured to form a coating layer [ 1].

Next, the coating layer [2] composed of the base coating material [II], which is a component of the method for forming a multilayer coating film in the present invention, will be described.

The base coat paint [II] which can be used for forming the coating layer [2] includes a paint which can be obtained mainly by using water or an organic solvent as a medium.

First, among these, only typical paints in the form of water as a medium are exemplified. For example, a paint using an aqueous resin as a binder or a dispersion (water dispersion) is used. ) Type resin as a binder, or an emulsion polymer as a binder.

In the above-mentioned type, the acrylic resin having an acid group in the molecule is further neutralized with an amine or the like by copolymerizing a vinyl monomer having a carboxyl group. Depending on the type, there is a completely water-solubilized (completely water-solubilized) form and the like.
There is a water-dispersible polyurethane resin having an anion-forming group as disclosed in JP-A-755-755, and the above-mentioned type is disclosed in JP-A-56-157358.
As disclosed in Japanese Patent Application Laid-Open Publication No. H10-163, there is a method comprising an aqueous solution of an emulsion polymer containing fine particles of a crosslinkable polymer.

As the paint in the form of an organic solvent as a medium, various known and commonly used paints can be used as they are. Of those, only representative ones are exemplified. Obtained by combining an organic solvent solution of a hydroxyl group-containing vinyl copolymer and an aminoplast, a polyisocyanate or a block polyisocyanate, respectively, which reacts with the hydroxyl group-containing vinyl copolymer. And various types of resin compositions as binders.

These various base coat paints [II], which can be obtained using water or an organic solvent as a medium, can be used in addition to these resin components, various commonly used inorganic pigments such as titanium oxide, and phthalocyanine-based paints. Such as anthraquinone-based or quinacridone-based, such as coloring pigments such as known and various organic pigments, or known and commonly used extender pigments, and further, such as aluminum flakes or mica flakes; Various known and commonly used additives such as known and commonly used brilliant (metallic) pigments and the like, and also a curing accelerator and a leveling agent can be contained.

Here, only particularly typical examples of the above-mentioned coloring pigments are exemplified, and titanium oxide, zinc white, carbon black, iron black, copper chromium black, copper / iron / manganese black, yellow Lead, cadmium yellow, ocher, titanium yellow, zinc chromate, red iron oxide, zinc / iron brown, cadmium red, chrome green, chrome oxide green, titanium / cobalt,
Various inorganic pigments such as zinc green, viridian, emerald green, cobalt green, kaolin, bentonite, silica white, aluminum white, gypsum, chalk, precipitated calcium carbonate or barite;

Β-naphthol, β-oxynaphthoic acid, naphthol AS, acetoacetic anilide, phthalocyanine, anthraquinone, indigo, perylene, perinone, dioxazine, quinacridone, isoindolinone, Metal complex salts, such as fluorbin-based or quinophthalone-based, various, organic pigments and the like,

Further, only typical representative examples of the above-mentioned extender pigments may be barium sulfate,
Examples include barium carbonate, magnesium carbonate, silica, alumina or clay.

Further, the above-mentioned brilliancy (metallic tone)
Various metal powders, such as gold powder, silver powder, brass powder, aluminum powder or copper powder, or titanium oxide treatment was applied to scale-like mica if only typical pigments were exemplified. (Post-processing)
There are pigments and the like.

Next, the coating layer [3] obtained from the transparent top coat coating [III], which is a component of the method for forming a multilayer coating film in the present invention, will be described.

The transparent top coat paint [III] which can be used for forming the above-mentioned coating layer [3] and which is used in carrying out the method for forming a multilayer coating film according to the present invention is as follows. As described above, various types of resin compositions can be used, each containing water or an organic solvent as a medium, or various powders in a form substantially free of water or an organic solvent. Body coating compositions can also be used.

The topcoat paint [III] which can be used at that time is itself for forming a so-called transparent coating film. Therefore, if it is transparent, it can be colored. The good thing is, of course.

The coating layer [2] and the coating layer [3] thus obtained, as described above, are applied on the object to be coated as described above in this order. Baked and dried at the same time, resulting in a coating layer [1],
In other words, a so-called multilayer coating film in which the layers [2] and [3] are laminated is formed.

However, after the coating layer [2] of each of these coating layers is applied, and before the coating layer [3] is applied, this coating layer [2] So-called 2C2B (2 coat 2)
Baking) method or a so-called 2C1B (2 coat 1 baking) method which does not employ such a baking step can be used. In addition, a step of drying at a temperature range from room temperature to about 100 ° C. may be adopted.

Next, of the method of forming a multilayer coating film according to the present invention, another type of multilayer coating film forming method different from the above-described method will be described.

That is, the other method of forming a multilayer coating film according to the present invention is, as described above, a coating film obtained by applying a powder coating composition [I] to an object to be coated and baking and curing the same. A coating layer [4] composed of a layer [1] and a top coating paint [IV], and the first constituent element, the above-described coated object and the coating layer [1]. As for the method, the constituent elements and the usage are the same as in the case of the above-described method for forming a multilayer coating film.

By the way, the coating layer [4] refers to a coating layer formed in such a manner that the coating layer [1] is formed by a bake-hardening reaction, then coated and formed thereon. The top coat paint [IV] used at this time is a transparent top coat paint [II] which can be used when forming the above-mentioned coating layer [3].
I] can also be used, but unlike the case of the coating layer [3] as described above, the coating layer [4] itself may be transparent or opaque. That is, it may be.

As the resin composition that can be used as the top coat paint [IV], only typical ones are exemplified. Resin composition, for example, an organic solvent solution of a hydroxyl group-containing vinyl copolymer, such as to react with the hydroxyl group-containing vinyl copolymer, respectively, aminoplast, polyisocyanate or block polyisocyanate There are various resin compositions and the like in a form that can be obtained in combination, and it is also possible to use various resin compositions in a form using the above-mentioned water as a medium. In particular, a powder coating composition that does not contain a powder coating composition can also be exemplified. Further, these resin compositions may include, for example, titanium oxide or carbon black. Do, also that the inclusion of pigments, able is a matter of course.

In carrying out the method for forming a multilayer coating film according to the present invention, there are no particular restrictions on the conditions for forming the coating film in order to sufficiently exhibit chipping resistance and the like. According to the curing conditions,
What is necessary is just to select it.

The dry coating film obtained by performing the method for forming a multilayer coating film according to the present invention has a film thickness of the coating film layer [1] of 10 ~
It is appropriate that the thickness of the multi-layer coating film is 200 μm (micrometer) and the thickness of the multi-layer coating film is 30 to 500 μm.
It is particularly preferably from 0 to 300 μm.

According to the method for forming a multilayer coating film according to the present invention, which has been described in detail above, in particular, the appearance, weather resistance, mechanical properties, A multilayer coating film having excellent chipping resistance and the like can be obtained.

The thus obtained article having an excellent multilayer coating film can be widely used and applied, but the present invention is by no means limited to only the following illustrative examples. .

As various means of transportation or transportation,
Alternatively, various types of untreated steel sheets may be used as examples of so-called base materials to be coated, which are used in manufacturing equipment for agriculture, mining and industry, or construction. Rusted steel plates; various treated steel plates such as galvanized steel plates and tin plates; various alloys such as stainless steel plates; and various metal materials or metal products such as aluminum plates or copper plates.

In particular, for so-called agricultural, mining and construction or construction purposes, such as for automobiles, and also for various vehicle bodies as a means of transportation or transportation such as motorcycles, or for tractors or bulldozers. It is effective for various vehicle bodies as a means.

From the above, it is possible to provide an extremely practical powder coating composition and a method for forming a multilayer coating film, which are low in pollution and excellent in various physical properties. In particular, it is possible to obtain an extremely practical article that is excellent in mechanical properties and the like, and further exhibits a new property of chipping resistance.

[0101]

EXAMPLES Next, the present invention will be described more specifically with reference examples, examples and comparative examples. In the following, parts and% (excluding 60-degree gloss) are by weight. It is assumed that

Reference Example 1 [Preparation Example of Epoxy Group-Containing Vinyl Polymer (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 placed under a nitrogen atmosphere. Then, the temperature was raised to 130 ° C.

There, 250 of methyl methacrylate was added.
Parts, 100 parts of n-butyl methacrylate, 100 parts of glycidyl methacrylate, 50 parts of β-methylglycidyl methacrylate, 3 parts of azobisisobutyronitrile
Part and tert-butyl peroxyoctoate (T
Abbreviated as BPO. ) Was dropped over 4 hours, and after completion of the dropping, the mixture was kept at the same temperature for 10 hours to carry out a polymerization reaction.

After the completion of the polymerization reaction, the polymer resin solution thus obtained is kept under a reduced pressure of 30 Torr, and xylene is distilled off (hereinafter, referred to as “xylene”).
Also called distillation. ), The non-volatile content is 99.5%,
Softening point by ring and ball method (hereinafter also referred to as softening point) is 10
At 2 ° C., a solid of an epoxy group-containing vinyl copolymer having an epoxy equivalent of 515 and a number average molecular weight of 2,500 was obtained. Hereinafter, this is abbreviated as polymer (A-1).

Reference Example 2 (same as above) 150 parts of styrene and 150 parts of methyl methacrylate
In the same manner as in Reference Example 1, except that a mixture of 50 parts of dibutyl fumarate, 150 parts of glycidyl methacrylate, 3 parts of azobisisobutyronitrile and 50 parts of TBPO was used. 9 minutes
9.7% with a softening point of 98 ° C. and an epoxy equivalent of 490
And a solid of an epoxy group-containing vinyl copolymer having a number average molecular weight of 1,600 was obtained. Hereinafter, this is abbreviated as polymer (A-2).

Reference Example 3 [Preparation Example of Carboxyl Group-Containing Polyester Resin (B)] In a reaction vessel equipped with a stirrer, thermometer, condenser and nitrogen gas inlet, 200 parts of ethylene glycol and 1,000 parts of neopentyl glycol were placed. Using a mixture consisting of 500 parts of 1,4-cyclohexanedimethanol, 2,000 parts of dimethyl terephthalate and 1.5 parts of zinc acetate, while removing generated methanol out of the reaction system, alcohol exchange reaction. Was done.

Next, a mixture of 140 parts of trimethylolpropane, 1,500 parts of terephthalic acid and 2 parts of di-n-butyltin oxide was further charged, and the temperature was raised to 240 ° C. The esterification reaction is carried out while distilling off water to form an acid value of 50.
Having a softening point of 100 ° C. and a number average molecular weight of 2.0
Thus, the desired carboxyl group-containing polyester resin was obtained. Hereinafter, this is abbreviated as resin (B-1).

Reference Example 4 (same as above) In a reaction vessel equipped with a stirrer, a thermometer, a condenser and a nitrogen gas inlet, 400 parts of ethylene glycol, 1,300 parts of neopentyl glycol, 1,700 parts of dimethyl terephthalate and Using a mixture consisting of 1.5 parts of zinc acetate, an alcohol exchange reaction was carried out while removing generated methanol outside the reaction system.

Next, 1,000 parts of terephthalic acid, 650 parts of isophthalic acid and di-n-
A mixture consisting of two parts of butyltin oxide was charged,
By raising the temperature to 240 ° C. and performing an esterification reaction while distilling off generated water, the acid value is 27, the softening point is 113 ° C., and the number average molecular weight is 3,100. Was obtained. Hereinafter, this is abbreviated as resin (B-2).

Examples 1 to 7 and Comparative Examples 1 to 3 Each of these examples is an example of preparing a powder coating composition.

First, as shown in Table 1, the polymer (A-1) and the polymer (A-
2), resin (B-1) and resin (B-2), and β-hydroxyalkylamide curing agent “PRIMID XL-
552 "[(the following structural formula manufactured by Rohm and Haas Company, USA)

[0112]

Embedded image

This is hereinafter referred to as a curing agent (C-1). ] And an epoxy resin "ST-5080" [hereinafter, epoxy resin (D-
1)] and the epoxy resin “Epiclon 305
0 "[hereinafter abbreviated as epoxy resin (D-2)];
Furthermore, various resins, curing agents, additives, and pigments used in the preparation of the powder coating are respectively used in the composition ratios shown in Tables 1 (1) to 1 (3). ,
At 90 ° C., the mixture was melt-kneaded with “Coneder PR-46 type” (trade name, manufactured by Bus, Switzerland), then cooled and pulverized.

Next, using a 150-mesh sieve (screen), each of the pulverized fractions passed through the sieve was collected, whereby the powder coating compositions (P-1) to (P- 7) and powder coating compositions (p-1) to (p-3) for comparison were obtained.

Thereafter, evaluation of various performances of each powder coating composition was examined. The criterion of the evaluation test or the criterion of the evaluation judgment at that time is as described later.

That is, each of the powder coating compositions was applied on a zinc phosphate-treated steel sheet by an electrostatic spray coating machine so that the dry film pressure became 60 μm.
By baking at 0 ° C. for 20 minutes, various test plates (that is, coated plates on which the cured coating film was placed) were obtained.

Next, for each coated plate, the second
Evaluation of coating film performance was evaluated over various test items shown in Tables (1) to 2 (3). The results are shown in the same table.

[0118]

[Table 1]

<< Footnote to Table 1 >>"TaipecCR-90" is a trade name of rutile type titanium oxide manufactured by Ishihara Sangyo Co., Ltd. "Acronal 4F" is a product of a flow regulator manufactured by BASF, Germany. Name

[0120]

[Table 2]

[0121]

[Table 3]

<< Footnote to Table 1 >>"M-8020""Fine Dick M"
"-8020", a brand name of a hydroxyl group-containing polyester resin manufactured by Dainippon Ink and Chemicals, Inc. having a hydroxyl value of about 30, "B-1530"... "IPDI- adduc
tB-1530 ", a trade name of a blocked isocyanate compound manufactured by Huls AG, Germany.

[0123]

[Table 4]

<< Footnotes in Table 2 >> The procedure for evaluation judgment was as follows.

60-degree gloss: 60-degree specular reflectance (%)
Evaluation judgment by. Dupont impact value: Evaluation by Dupont impact tester (1 /
2 inches). It was indicated by a height (cm) such that when the load of 500 g was dropped, the coating film did not cause defects such as cracks. The higher the value, the better the impact resistance. Eriksen ... Evaluation by Ericksen tester. The higher the value, the better the flexibility of the coating film. Water resistance test: Determined by measuring the DuPont impact value of a test plate immersed in hot water at 95 ° C. for 2 hours. Weather resistance: Expressed as a gloss retention (%) after exposure for 800 hours using a sunshine weather meter (trade name, manufactured by Suga Test Instruments Co., Ltd.). The higher the value, the better the weather resistance.

[0126]

[Table 5]

[0127]

[Table 6]

Reference Example 5 [Preparation example of aqueous resin (X) for base coat paint [II]] In a reaction vessel equipped with a stirrer, thermometer, condenser and nitrogen gas inlet, 680 parts of deionized water, ammonium persulfate 2 parts and "Triton X-200"
(Trade name of an anionic surfactant manufactured by Rohm and Haas Company, USA) was added and heated to 95 ° C.

Next, the reaction system at 95 ° C. was added with 450 parts of methyl methacrylate, 350 parts of ethyl acrylate, 150 parts of 2-hydroxyethyl methacrylate, 20 parts of acrylic acid, 30 parts of ethylene glycol dimethacrylate, 30 parts of n-octyl mercaptan, 5 parts of ammonium persulfate, and 4 parts of “Triton”. X-200 "15 parts" Emulgen 840s " 10 parts [trade name of nonionic surfactant manufactured by Kao Atlas Co., Ltd.] An aqueous emulsion consisting of 530 parts of deionized water was added dropwise over 4 hours, and after the addition was completed, the same was continued for 3 hours. The temperature was maintained. Thereafter, the reaction solution was cooled, and then 5 parts of dimethylethanolamine and 40 parts of deionized water were added.

Thus, a stable milky white dispersion of an aqueous acrylic resin having a solid content of 45% was obtained. Hereinafter, this is abbreviated as aqueous resin (X).

Reference Example 6 (Preparation Example of Thickener) 64 parts of "Acryzole ASE-60" (trade name of a thickener manufactured by Rohm and Haas Company, USA; solid content = 28%) was added with 64 parts of dimethyl By adding 6 parts of ethanolamine and 530 parts of deionized water, the target substance having a solid content of 3% was obtained. Hereinafter, this is referred to as a thickener (A
Abbreviated as D).

Reference Example 7 [Preparation Example of Base Coating Paint [II]] 100 parts of the aqueous resin (X) obtained in Reference Example 5 and 10 parts of the thickener (AD) obtained in Reference Example 6 5 parts of "Cymel 300" (trade name of hexamethoxymethylated melamine manufactured by Mitsui Sianamide), 1.0 part of p-toluenesulfonic acid, and "Aluminum paste dispersion #
4919 "(Trade name of aluminum paste manufactured by Toyo Aluminum Co., Ltd.) and" Aluminum paste dispersion #
55-519 "(product of the same company) and 12 parts of isopropanol, and then mixed with deionized water at 20 ° C. for Ford Cup No. 1; 4 was adjusted so that the viscosity was 16 seconds. Hereinafter, this is abbreviated as basecoat paint (II-1).

Reference Example 8 [Transparent top coat paint [III]
Preparation Example] In a reaction vessel similar to that of Reference Example 5, 500 parts of xylene was charged and heated to 120 ° C. Then, styrene 1
A mixture of 50 parts, 150 parts of methyl methacrylate, 75 parts of n-butyl acrylate, 125 parts of 2-hydroxyethyl methacrylate, 3 parts of azobisisobutyronitrile and 3 parts of TBPO was added over 4 hours. By dropping and maintaining the same temperature for 10 hours after the completion of dropping, the nonvolatile content is 50.5%,
And, the hydroxyl value is 53 (mg KOH
/ G solid content) for use in the top coat paint [III]. Hereinafter, this resin solution is abbreviated as a top coat paint resin (T-1).

Next, this top coat paint resin (T-
1) 100 copies of “Super Beckamine L-117
-60 [trade name of butyl etherified melamine / formaldehyde resin manufactured by Dainippon Ink and Chemicals, Inc.]
After adding 5.7 parts, using "Solvesso 100" (trade name of an aromatic hydrocarbon organic solvent manufactured by Exxon), 20
Ford cup no. The viscosity according to 4 is 24
Adjusted to seconds. Hereinafter, this is abbreviated as transparent topcoat paint (III-1).

Reference Example 9 (same as above) 400 parts of xylene was charged into the same reaction vessel as in Reference Example 5, and the temperature was raised to 135 ° C. Then, 9 of styrene
A mixture of 0 parts, 240 parts of methyl methacrylate, 30 parts of 2-ethylhexyl acrylate, 240 parts of glycidyl methacrylate and 24 parts of TBPO was added dropwise at the same temperature over 6 hours.

After the completion of the dropwise addition, the reaction was continued at the same temperature for a further 8 hours. After the completion of such a polymerization reaction,
By removing the solvent, a copolymer solid having a softening point by a ring and ball method of 117 ° C., an epoxy equivalent of 380 and a number average molecular weight of 4,700 was obtained. Hereinafter, this is abbreviated as resin for topcoat paint (T-2).

Next, the resin for top coat paint (T
-2) with respect to 76 parts of 24 parts of dodecane diacid (hereinafter, referred to as “part 2”)
Abbreviated as DDA. ) And “Modaflow”
(Trade name of a flow control agent manufactured by Monsanto Co., USA) at 90 ° C. and “Kneader PR”
The mixture was melt-kneaded with a "-46 type" (trade name, manufactured by Buss, Switzerland), cooled, and pulverized.

Next, a powdered top coat / clear paint which can be used as a transparent top coat paint [III] is obtained by collecting each of the crushed and classified products passing through the sieve using a 150 mesh screen (screen). I got Hereafter, this is called transparent top coat paint (III
-2).

Reference Example 10 [Preparation Example of Topcoat Paint [IV]] Resin for Topcoat Paint (T-1) prepared in Reference Example 8
Of titanium oxide was added to 100 parts of the mixture, and the mixture was dispersed using a sand mill. Next, 3 parts of “Super Beckamine L-117-60” was added to the dispersion.
Add 5.7 parts and add Ford Cup N at 20 ° C
o. 4 so that the viscosity according to No. 4 becomes 24 seconds.
By diluting with "00", a top coat paint containing pigment was obtained. Hereinafter, this is abbreviated as topcoat paint [IV].

Examples 8 to 14 and Comparative Examples 4 to 7 Tables 3 (1) to 3 (3) in the same manner as in Examples 1 to 7.
A multilayer coating film was formed from each of the powder coating compositions 1 to 6 and the various coatings obtained in the above Reference Examples 5 to 10 prepared at the composition ratios shown in Tables 1 and 2 and subjected to various tests.

[0141]

[Table 7]

<< Footnote to Table 3 >>"MA-100" A trade name of carbon black manufactured by Mitsubishi Chemical Corporation.

[0143]

[Table 8]

[Description of Method for Forming Multi-Layer Coating Film] The above-mentioned powder coating compositions (P-8) to (P-10) and the above-mentioned powder coating compositions (p-4) to (p-6) ), The base coat paint [II] obtained in Reference Example 7, and the top coat paints [III-1], [III-2] and [IV] obtained in Reference Examples 8 to 10, For inventions and controls,
Various multilayer coating films were produced and prepared by the following methods.

That is, first, as a substrate to be used as an object to be coated, an electrodeposited plate obtained by electrodepositing an epoxy resin-based cationic electrodeposition paint on a mild steel plate manufactured by Nippon Route Service Co., Ltd. was used.

Next, Examples 8 to 12 and Comparative Examples 4 to 6
Each of the powder coating compositions was coated on an object to be coated so that the film thickness after baking was 60 μm, each was subjected to electrostatic powder coating, and then baked at 170 ° C. for 15 minutes. Was performed. Thereafter, each of the objects to be coated thus electrostatic powder-coated (that is, a coated plate having a cured coating film coated with a powder coating composition as an intermediate coating material) was cooled to room temperature. From the base coat paint [II] in a coating atmosphere where the temperature is 25 ° C. and the relative humidity is 70%, so that the dry film thickness becomes 20 μm.
Each was painted twice. Between these two coatings, a setting was performed for 2 minutes.

After the two coatings, the object to be coated is
Air-dried at a temperature of 5 ° C. for 5 minutes, and further cooled to room temperature.
1] or [III-2] was painted and baked. In this case, the top coat paint [III-1] is applied by a usual spray coating method, and the baking temperature is 140 ° C./2.
It was 0 minutes. Also, top coat paint [III-2]
Was applied by electrostatic powder coating to a dry film thickness of 70 μm, and baked at 150 ° C. for 20 minutes.

On the other hand, Examples 13 to 14 and Comparative Examples 7 to
As No. 8, a topcoat paint [IV] was applied and baked on a coated plate on which a cured coating film coated with the powder coating composition was prepared, prepared in the same manner as described above. In this case, the top coat paint [IV] was applied by a usual spray coating method, and the baking temperature was 140 ° C./20 minutes.

The thus obtained cured coating films were evaluated for various properties. The results are collectively shown in Table 4 (1) to Table 4 (3).

[0150]

[Table 9]

[0151]

[Table 10]

[0152]

[Table 11]

The procedure for evaluation evaluation was as follows. Smoothness: Evaluation was visually determined. The criteria are as follows. …: In the case of a very smooth and smooth paint surface…: 場合 In the case where a large round is recognized ×… 場合 In the case where fine dust skin is observed

Metallic feeling: Evaluation was visually judged. The criteria are as follows. ○ …… The arrangement of aluminum flakes is good and the appearance is very beautiful, and depending on the viewing angle, the depth feeling unique to metallic coatings can be fully expressed. △ …… The arrangement of aluminum flakes is generally good, but the brightness of the coating film is poor. × …… The arrangement of aluminum flakes is disturbed.

Chipping resistance: A test plate cooled to -20 ° C., at an angle of 90 °, at 4 atm. The peeling state of the coating film when 50 g of No. 7 crushed stone was applied was visually evaluated and determined using a predetermined atmospheric pressure. The evaluation criteria are as follows. …: When peeling is hardly observed Δ…: When peeling of the coating layer is observed to some extent ×: Large peeling of the powder coating layer is observed, and
When the bottom electrodeposition coating film is also damaged and the metal surface is exposed

Interlayer adhesion: The coated plate was placed in warm water at 40 ° C.
It was immersed for 10 days, and after 30 minutes from the lifting, a cross cut was made and a peeling test using an adhesive tape was performed. The evaluation criteria are as follows. …: When no peeling was observed between any of the coating layers or between the object to be coated and the coating layer, Δ: between any of the coating layers Or, when peeling is partially observed between the object to be coated and the coating film layer x: When delamination is observed over the entire surface

Water resistance: A test plate was placed in warm water of 40 ° C. for 1 hour.
The state of the coated surface after immersion for 0 days was visually evaluated and determined. The evaluation criteria are as follows. ◎: No change is observed on the coated surface.…: A slight decrease in smoothness or gloss is observed on the coated surface. When observed ×: When the coated surface is significantly reduced in smoothness and glossiness

As shown in the various Examples and Comparative Examples as described above, the powder coating composition and the method for forming a multilayer coating film according to the present invention are particularly suitable for the appearance, mechanical properties and resistance to wear. It can be reasonably known to provide an article having a cured coating film having excellent chipping properties.

[0159]

As described above in detail, the powder coating composition and the method for forming a multilayer coating film according to the present invention not only have a particularly excellent appearance and mechanical properties, but also have a new resistance property. It is extremely practical, giving a cured coating film having excellent chipping properties.

[Procedure amendment]

[Submission date] February 17, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

Reference Example 8 [Transparent top coat paint [III]
Preparation Example] In a reaction vessel similar to that of Reference Example 5, 500 parts of xylene was charged and heated to 120 ° C. Then, styrene 1
A mixture of 50 parts, 150 parts of methyl methacrylate, 75 parts of n-butyl acrylate, 125 parts of 2-hydroxyethyl methacrylate, 3 parts of azobisisobutyronitrile and 3 parts of TBPO was added over 4 hours. By dropping and maintaining the same temperature for 10 hours after the completion of dropping, the nonvolatile content is 50.5%,
And, the hydroxyl value is 53 (mg KOH
/ G solid content) for use in the top coat paint [III]. Hereinafter, this resin solution is abbreviated as resin for topcoat paint (T-1).

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

Next, the resin for top coat paint (T
-1) in 100 parts, "Super Beckamine L-11
7-60 [trade name of butyl etherified melamine / formaldehyde resin manufactured by Dainippon Ink and Chemicals, Inc.]
After adding 5.7 parts, using "Solvesso 100" (trade name of an aromatic hydrocarbon organic solvent manufactured by Exxon), 20
Ford cup no. The viscosity according to 4 is 24
Adjusted to seconds. Hereinafter, this is abbreviated as a transparent topcoat paint [III-1] .

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name]

[Correction method] Change

[Correction contents]

Next, a powdered top coat / clear paint which can be used as a transparent top coat paint [III] is obtained by collecting each of the crushed and classified products passing through the sieve using a 150 mesh screen (screen). I got Hereinafter, this is referred to as a transparent top coat paint [III
-2] .

Claims (9)

[Claims] 1. An epoxy group-containing vinyl polymer (A)
, A carboxyl group-containing polyester resin (B), and β
-A powder coating composition comprising a hydroxyalkylamide curing agent (C) and an epoxy resin (D) as essential film-forming components. 2. An epoxy group-containing vinyl polymer (A)
Has a softening point of 80 to 150 ° C and an epoxy group equivalent of 250 to 7
The powder coating composition according to claim 1, which is a vinyl polymer of No. 00. 3. A carboxyl group-containing polyester resin (B) having a softening point of 80 to 150 ° C. and an acid value of 10 to 200.
3. The powder coating composition according to claim 1, which is a polyester resin having a solid content of (mg KOH / g solid content). 4. The β-hydroxyalkylamide curing agent (C) is represented by the following general formula (1): [Wherein, R ¹ is a hydrogen atom or an alkyl group having 1 to 2 carbon atoms, R ² is a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or HOCH (R ¹ ) CH _2- (R ¹ is as defined above. the same),
A represents a divalent hydrocarbon group. The powder coating composition according to claim 1, 2 or 3, which is a compound represented by the formula: 5. The powder coating composition according to claim 1, wherein the epoxy resin (D) is a hydrogenated bisphenol A type epoxy resin and / or an alicyclic type epoxy resin. 6. The epoxy group-containing vinyl polymer (A) and the carboxyl group-containing polyester resin (B) have a weight ratio (A / B) of 60/40 to 97/3, and the epoxy group-containing vinyl polymer. Total amount of polymer (A) and carboxyl group-containing polyester resin (B) used (A + B) 100
The amount of the β-hydroxyalkylamide curing agent (C) to be used is 1 to 10 parts by weight, and the amount (A + B) is 100 parts by weight.
The amount of the epoxy resin (D) used is 2 to 20 parts by weight.
The powder coating composition according to any one of claims 1 to 5, which is in parts by weight. 7. The powder coating composition according to claim 1, wherein the powder coating composition is a coating composition for an automobile. 8. A powder coating composition [I] according to any one of claims 1 to 7, which is applied to an object to be coated and cured, and then a base coat coating [II] is applied. A method for forming a multilayer coating film, which comprises applying a transparent topcoat paint [III], baking and drying. 9. A powder coating composition [I] according to any one of claims 1 to 7, applied to an object to be coated, cured, and then coated with a top coat coating [IV], A method for forming a multilayer coating film, comprising baking and drying.