JP2005015768A - Powder coating composition and method of forming coating film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a powder coating composition which, in various applications usable of a powder coating composition, can form a coating film excellent in smoothness, scuff resistance, etc., even when the coating film is thin, and, in particular, when it is applied as a transparent topcoating material onto a coating film formed by applying an aqueous base coating material and subsequently baking the resultant coating film, the baked coating film exhibits an excellent smoothness; and to provide a method for forming a coating film. <P>SOLUTION: The powder coating composition is formed by containing (A) an epoxy group-containing vinyl copolymer having a glass transition temperature of ≥40°C and a number average molecular weight of 1,000-5,000, (B) a hydroxy group-containing vinyl copolymer having a glass transition temperature of ≤0°C and (C) a polyvalent carboxylic anhydride. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The powder coating composition of the present invention and the method for forming a coating film can be applied to various fields such as the automobile field and the household electrical appliance field. More specifically, the powder coating composition of the present invention is applied to an automobile. When used as a transparent topcoat paint, it can be suitably used on a coating obtained by coating a topcoat paint, particularly an aqueous basecoat paint.

Conventionally, powder coating compositions have been widely used in general metal coatings as environmentally friendly coatings that do not volatilize organic solvents into the atmosphere during coating. In recent years, whether a powder coating composition can be used as a coating for a transparent top coat (top clear) having an enormous market scale in place of a solvent-based coating has been studied and some have been implemented. If the powder coating is used entirely as an automotive top clear coating, the volatilization of the organic solvent can be reduced.
Furthermore, if the powder coating composition is used entirely as a transparent top coat paint on a coating obtained by applying a water base coat paint as a base coat, it will greatly reduce the global environment caused by volatilization of organic solvents. The load can be reduced.

  As a powder coating composition, for example, a powder coating composition having excellent weather resistance, which contains an epoxy group-containing vinyl copolymer and a polyvalent carboxylic acid as a curing agent has been reported (for example, Patent Documents). 1). However, in general, the powder coating composition including the powder coating composition is insufficient in the finished appearance of the resulting coating film as compared with the solvent-based coating.

  Accordingly, a powder coating material comprising a polyfunctional vinyl copolymer having a glass transition temperature of 40 ° C. or higher, a polycarboxylic acid and a polyfunctional vinyl copolymer having a glass transition temperature of 0 ° C. or lower. Compositions have been developed, and it has been reported that the resulting coated film is excellent in finished appearance and scratch resistance (see, for example, Patent Documents 2 and 3).

  Although the performance of the powder coating composition has been greatly improved by the above technical progress, in order to ensure the same performance as that of the solvent-based coating, further improvement of the performance, that is, the finished appearance of the obtained coating film There is a strong demand from the market for improved scratch resistance. In particular, with respect to scratch resistance, even a slight difference in scratches on the surface of the coating film greatly affects the commercial value, so that further improvement is strongly demanded.

  On the other hand, conventionally, in order to form a coating film having an excellent finished appearance comparable to that of a solvent-based paint with a powder coating composition, the film thickness of the coating film obtained by using the solvent-based paint is changed. It needs to be thicker than the thickness. For example, the film thickness of a coating film formed using a solvent-based coating as an automotive transparent top coat coating is generally about 40 μm, whereas the coating film formed using a powder coating composition is The film thickness is generally 60 to 80 μm. The need to increase the film thickness when using a powder coating composition is not appropriate from the viewpoint of the complexity of the coating operation, the amount of powder coating used, the amount of energy consumed, the economy, etc. There is a strong need for a solution.

  Furthermore, in order to drastically reduce organic solvents, a solvent-based thin film is used when a powder coating composition is used as a transparent top coat coating, particularly on a coating obtained by applying a water base coat coating. It is important to form a coating film with an excellent finished appearance that is comparable to paint, but with multi-layer coating films when using aqueous base coat paints, sufficient smoothness to meet the recently increasing demand for appearance improvements Is not obtained.

JP-A-52-69936 (Claim 1) JP 09-227799 A (Claim 1) JP 2002-146278 A (Claim 1)

  The problem to be solved by the present invention is to obtain a coating film excellent in smoothness and scratch resistance, etc. even in a thin film, particularly by applying a coating for an aqueous base coat in various applications where the powder coating composition can be used. Another object of the present invention is to provide a powder coating composition and a coating film forming method capable of providing a coating film having excellent smoothness when coated and baked as a transparent top coat coating on the coated film.

The present invention uses a hydroxyl group-containing vinyl copolymer (B) newly in a curing system based on an epoxy-containing vinyl copolymer and a polyvalent carboxylic acid. Furthermore, 1) the polyvalent carboxylic acid is converted into an anhydride. 2) By further using a compound (E) having a crosslinking reactivity with a hydroxyl group, the reaction of a conventional epoxy group and a carboxylic acid and 1) the reaction of a polyvalent carboxylic acid anhydride and a hydroxyl group, 2) It has been found that the scratch resistance can be further improved without impairing excellent smoothness due to the combined reaction of the hydroxyl group and the compound (E).
Furthermore, when a powder coating composition is applied and baked onto an aqueous base coat, if a hydroxyl group-containing compound having a hydrophilic functional group is used, the coating film having a high affinity with the aqueous coat and an excellent appearance can be obtained. Considering that there is a possibility of obtaining it, we proceeded with the examination.

That is, the present inventor uses a hydroxyl group-containing vinyl copolymer (B) completely newly in a curing system based on an epoxy-containing vinyl copolymer and a polyvalent carboxylic acid,
1) Limit polyvalent carboxylic acid to anhydride, or
2) By further using the compound (E) having a crosslinking reactivity with a hydroxyl group, a coating film not only having excellent scratch resistance but also excellent appearance and smoothness particularly when using an aqueous base paint is provided. The inventors have found that a powder coating composition that can be obtained is obtained, and have completed the present invention.

  That is, the present invention relates to an epoxy group-containing vinyl copolymer (A) having a glass transition temperature of 40 ° C. or higher and a number average molecular weight of 1000 to 5000, and a hydroxyl group-containing vinyl having a glass transition temperature of 0 ° C. or lower. A powder coating composition comprising a copolymer (B) and a polyvalent carboxylic acid anhydride (C) is provided.

  The present invention also relates to an epoxy group-containing vinyl copolymer (A) having a glass transition temperature of 40 ° C. or higher and a number average molecular weight of 1000 to 5000, and a hydroxyl group-containing vinyl having a glass transition temperature of 0 ° C. or lower. A powder coating composition comprising a copolymer (B), a polyvalent carboxylic acid (D), and a compound (E) having a crosslinking reactivity with a hydroxyl group is provided.

  Moreover, this invention provides the formation method of the coating film characterized by apply | coating the above-mentioned powder coating composition as a coating material for topcoats on a base material, and baking it.

  Furthermore, the present invention applies the above-mentioned powder coating composition as a top coat paint on a base coat paint, particularly a paint film obtained by painting a water-based colored base coat paint, Then, a method for forming a multilayer coating film characterized by baking is provided.

  Moreover, this invention provides the coating material obtained by apply | coating the above-mentioned powder coating composition on a base material, and baking it.

  According to the present invention, it is possible to obtain a coating film excellent in smoothness, coating film gloss, scratch resistance, etc., particularly when forming a thin film, without releasing the organic solvent into the environment.

Hereinafter, embodiments of the present invention will be described in detail.
First, the epoxy group-containing vinyl copolymer (A) having a glass transition temperature of 40 ° C. or higher and a number average molecular weight of 1000 to 5000 used in the present invention will be described.

The epoxy group-containing vinyl copolymer (A) is a vinyl polymer having an epoxy group in the molecule, but preferably has an average of two or more epoxy groups in one molecule.
When the average number of epoxy groups is less than 2 in one molecule, the coating film is not sufficiently crosslinked at the time of baking and curing.

  The epoxy group-containing vinyl copolymer (A) has a glass transition temperature of 40 ° C. or higher. This is because if the glass transition temperature of the epoxy group-containing vinyl copolymer (A) is less than 40 ° C., the storage stability (blocking resistance) of the powder coating composition may be adversely affected. From this viewpoint, the glass transition temperature is more preferably in the range of 50 ° C to 90 ° C.

  The number average molecular weight of the epoxy group-containing vinyl copolymer (A) is preferably in the range of 1000 to 5000, more preferably in the range of 1500 to 3000, when measured by gel permeation chromatography with a tetrahydrofuran-soluble content. By adjusting to such a range, even if the film thickness of the obtained coating film is reduced, a coating film excellent in smoothness, scratch resistance, etc. can be obtained.

  The epoxy group-containing vinyl copolymer (A) can be produced by a known and usual method, but the epoxy group-containing vinyl monomer and other vinyls that can be copolymerized with the monomer as required. The method of polymerizing these in an organic solvent using monomers is preferred because it is the simplest. In that case, it is possible to use a well-known and usual polymerization initiator and a solvent.

  Here, examples of the epoxy group-containing vinyl monomer that can be used for producing the epoxy group-containing vinyl copolymer (A) include glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, glycidyl vinyl ether, Various epoxy group-containing monomers such as allyl glycidyl ether; (2-oxo-1,3-oxolane) group-containing vinyl monomers such as (2-oxo-1,3-oxolane) methyl (meth) acrylate In addition, various alicyclic epoxy group-containing vinyls such as 3,4-epoxycyclohexyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, and 3,4-epoxycyclohexylethyl (meth) acrylate. And monomers.

  Examples of other vinyl monomers that can be copolymerized with the epoxy group-containing vinyl monomer include various commonly used vinyl monomers such as (meth) acrylic acid, crotonic acid, or esters thereof. These can be used, and these can be used alone or in combination of two or more.

  Examples of the ester of (meth) acrylic acid described above include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, and (meth) acrylic acid n. -Butyl, isobutyl (meth) acrylate, tert-butyl (meth) acrylate or n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, (meth) acrylate n -Octyl, isooctyl (meth) acrylate, 2-ethyloctyl (meth) acrylate, dodecyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate or stearyl (meth) acrylate ( (Meth) acrylic acid alkyl esters,

  Benzyl (meth) acrylate, phenyl (meth) acrylate, phenoxyethyl (meth) acrylate or tetrahydrofurfuryl (meth) acrylate,

  Alternatively, various alkyl carbitol (meth) acrylates such as ethyl carbitol (meth) acrylate, and further, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate or Dicyclopentenyloxyethyl (meth) acrylate;

  Hydroxyl-containing (meth) acrylic acid esters such as 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate or 4-hydroxybutyl (meth) acrylate ;

  Polyethylene glycol mono (meth) acrylate, polypropylene glycol mono (meth) acrylate, and the like, and further, a so-called form in which the above-mentioned various hydroxyl group-containing (meth) acrylic esters are subjected to a ring-opening reaction with ε-caprolactone. Examples include lactone-modified hydroxyl group-containing (meth) acrylates.

  Furthermore, as other vinyl monomers, various kinds such as γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane, or γ- (meth) acryloyloxypropylmethyldimethoxysilane, etc. A hydrolyzable silyl group-containing monomer of

  Various fluorine-containing α-olefins such as vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, bromotrifluoroethylene, pentafluoropropylene or hexafluoropropylene;

  Perfluoroalkyl / perfluorovinyl ether or (per) fluoroalkyl vinyl ether such as trifluoromethyl trifluorovinyl ether, pentafluoroethyl trifluorovinyl ether or heptafluoropropyl trifluorovinyl ether (wherein the alkyl group has 1 to 18 carbon atoms) Various fluorine-containing vinyl monomers, such as

  Phosphoric ester group-containing vinyl monomers such as mono [(meth) acryloyloxyethyl] phosphate, acidic phosphoric acid (meth) acrylic acid ester or (meth) acryloyloxyethyl phenyl phosphate;

  Mono- or diesters of various polyvalent carboxyl group-containing monomers such as fumaric acid, maleic acid or itaconic acid, and monoalkyl alcohols having 1 to 18 carbon atoms; styrene, vinyltoluene, α -Various aromatic vinyl compounds such as methylstyrene or p-tert-butylstyrene;

  (Meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, Nn-propyl (meth) acrylamide, N-iso-propyl (meth) acrylamide, Nn-butyl (meth) acrylamide N-iso-butyl (meth) acrylamide, N-tert-butyl (meth) acrylamide, N-amyl (meth) acrylamide, N- (meth) acrylamide, N-hexyl (meth) acrylamide, N-heptyl (meth) Acrylamide or N-2-ethylhexyl (meth) acrylamide,

  N, N-dimethyl (meth) acrylamide, N, N-diethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, Nn- Propoxymethyl (meth) acrylamide, N-iso-propoxymethyl (meth) acrylamide or Nn-butoxymethyl (meth) acrylamide,

  Alternatively, N-iso-butoxymethyl (meth) acrylamide, N-tert-butoxymethyl (meth) acrylamide, N-amyloxymethyl acrylamide, N-hexyloxy (meth) acrylamide, N-heptyloxymethyl (meth) acrylamide, N -Various amino group-containing amide vinyl monomers such as octyloxymethyl (meth) acrylamide, N-2-ethyl-hexyloxymethyl (meth) acrylamide or diacetone (meth) acrylamide;

  Various dialkylaminoalkyl (meth) acrylates such as dimethylaminoethyl (meth) acrylate or diethylaminoethyl (meth) acrylate; tert-butylaminoethyl (meth) acrylate, tert-butylaminopropyl (meth) acrylate, aziridini Ruethyl (meth) acrylate, pyrrolidinylethyl (meth) acrylate, piperidinylethyl (meth) acrylate, (meth) acryloylmorpholine, N-vinyl-2-pyrrolidone, N-vinylcaprolactam, N-vinyloxazoline or Various nitrogen-containing vinyl monomers such as (meth) acrylonitrile;

Vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, C ₉ becomes branched (branched) aliphatic carboxylic acid vinyl, C ₁₀ composed branch Various aliphatic vinyl carboxylates such as a branched (branched) aliphatic carboxylate, C ₁₁ branched (branched) aliphatic carboxylate or vinyl stearate;

  Vinyl esters of various carboxylic acids having a cyclic structure, such as vinyl cyclohexanecarboxylate, vinyl methylcyclohexanecarboxylate, vinyl benzoate or vinyl p-tert-butylbenzoate;

  Various alkyl vinyl ethers such as ethyl vinyl ether, hydroxyethyl vinyl ether, hydroxy n-butyl vinyl ether, hydroxyisobutyl vinyl ether, cyclohexyl vinyl ether or lauryl vinyl ether;

  Various halogenated olefins other than the above-mentioned fluorine-containing α-olefins such as vinyl chloride or vinylidene chloride, or various α-olefins such as ethylene, propylene, and butene-1 can be used.

  Examples of the polymerization initiator that can be used when the various monomers described above are copolymerized in an organic solvent include 2,2′-azobisisobutyronitrile and 2,2′-azobis-methylbutyrate. Ronitrile, 2,2′-azobis-2,4-dimethylvaleronitrile, 1,1′-azobis-cyclohexanecarbonitrile, dimethyl-2,2′-azobisisobutyrate, 4,4′-azobis-4 -Cyanovaleric acid, 2,2'-azobis- (2-amidinopropene) dihydrochloride, 2-tert-butylazo-2-cyanopropane, 2,2'-azobis (2-methyl-propionamide) dihydrate Various azo compounds such as 2,2′-azobis [2- (2-imidazolin-2-yl) propene] or 2,2′-azobis (2,2,4-trimethylpentane);

  Alternatively, benzoyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, potassium persulfate, tert-butyl peroxyneodecanoate, tert-butyl peroxypivalate, tert-butyl peroxy-2-ethylhexanoate, tert -Butylperoxyisobutyrate, 1,1-bis-tert-butylperoxy-3,3,5-trimethylcyclohexane or tert-butylperoxylaurate,

  Various ketone peroxides such as tert-butyl peroxyisophthalate, tert-butyl peroxyacetate, tert-butyl peroxybenzoate, dicumyl peroxide or di-tert-butyl peroxide; peroxyketal; hydroperoxide Dialkyl peroxides; diacyl peroxides; peroxyesters; peroxydicarbonates; or hydrogen peroxide.

  As the organic solvent that can be used when the various monomers described above are copolymerized in an organic solvent, known and commonly used solvents can be used. For example, methanol, ethanol, n-propanol, isopropanol, alkyl alcohols such as n-butanol, isobutanol, sec-butanol, tert-butanol, n-pentanol, isopentanol;

  Glycol ethers such as methyl cellosolve, ethyl cellosolve, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monopropyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether;

  Aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; Exon aromatic naphtha no. 2 (manufactured by Exxon, Inc.) and other aromatic hydrocarbons; aliphatic hydrocarbons such as n-pentane, n-hexane, and n-octane; Isopar C, Isopar E, Exol DSP 100/140, Mixed hydrocarbons containing aliphatic hydrocarbons such as Exol D30 (both manufactured by Exxon USA) and IP Solvent 1016 (manufactured by Idemitsu Petrochemical Co.); Alicyclic rings such as cyclopentane, cyclohexane, methylcyclohexane and ethylcyclohexane Group hydrocarbons;

  Ethers such as tetrahydrofuran, dioxane, diisopropyl ether, di-n-butyl ether; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone; ketones; methyl acetate, ethyl acetate, n-propyl acetate, isopropyl acetate, n-butyl acetate, isobutyl acetate And esters such as n-amyl acetate, isoamyl acetate, hexyl acetate, ethyl propionate, and butyl propionate.

  Moreover, a chain transfer agent can also be used as needed, for example, dodecyl mercaptan, lauryl mercaptan, thioglycolic acid ester, mercaptoethanol, or α-methylstyrene dimer.

  The epoxy equivalent of the epoxy group-containing vinyl copolymer (A) used in the present invention is in the range of 250 to 1000 from the viewpoint of low temperature curability of the powder coating composition and scratch resistance of the resulting coating film. Is preferable, and the range of 300-600 is more preferable.

  In the epoxy group-containing vinyl copolymer (A), it is preferable to introduce a hydroxyl group in addition to the epoxy group from the viewpoint of scratch resistance.

  Next, the hydroxyl group-containing vinyl copolymer (B) having a glass transition temperature of 0 ° C. or less used in the present invention will be described.

  The hydroxyl group-containing vinyl copolymer (B) is a vinyl copolymer having a hydroxyl group in the molecule, but preferably has a hydroxyl value in the range of 20 to 400, more preferably in the range of 50 to 200. If the hydroxyl value is within such a range, the resulting coating film has good scratch resistance. Further, from the viewpoint of production of a hydroxyl group-containing vinyl copolymer, it is substantially difficult to obtain a hydroxyl group-containing vinyl copolymer having a hydroxyl value exceeding 400.

  The glass transition temperature of the hydroxyl group-containing vinyl copolymer (B) is 0 ° C. or lower, more preferably −10 ° C. or lower. If the glass transition temperature of the hydroxyl group-containing vinyl copolymer (B) is within such a range, the resulting coating film has good scratch resistance.

  Such a hydroxyl group-containing vinyl copolymer (B) can be produced by a publicly known and commonly used method. For example, a hydroxyl group-containing vinyl monomer and, if necessary, other monomers copolymerizable with the monomer can be used. The method of polymerizing a vinyl monomer in an organic solvent is mentioned.

  Examples of the hydroxyl group-containing vinyl monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, or 4- (meth) acrylic acid 4- Hydroxyl-containing (meth) acrylic acid esters such as hydroxybutyl;

  Examples include polyethylene glycol mono (meth) acrylate or polypropylene glycol mono (meth) acrylate, and further, a form in which the above-mentioned various hydroxyl group-containing (meth) acrylic esters are subjected to a ring-opening reaction with ε-caprolactone. It is preferable to use a so-called lactone-modified hydroxyl group-containing (meth) acrylate, and it is more preferable to use a lactone-modified hydroxyl group-containing (meth) acrylate.

  As other vinyl monomers, it is possible to use the same vinyl monomers as exemplified above as those that can be used when producing the epoxy group-containing vinyl copolymer (A). it can. At this time, it is preferable to use together the methacrylic acid alkylester (b-1) which has a C8-C24 alkyl group, and an epoxy-group-containing monomer.

  Here, as a methacrylic acid alkyl ester (b-1) which has a C8-C24 alkyl group, when manufacturing the said epoxy-group-containing vinyl copolymer (A), for example, it can be used. Among the exemplified methacrylic acid alkyl esters, the alkyl group has 8 to 24 carbon atoms. More specifically, 2-ethylhexyl methacrylate, n-octyl methacrylate, isooctyl methacrylate, 2-ethyloctyl methacrylate, n-decyl methacrylate, isodecyl methacrylate, lauryl methacrylate, stearyl methacrylate, methacrylic acid Examples include eicosyl and tetraeicosyl methacrylate, and these can be used alone or in combination of two or more.

  Among the methacrylic acid alkyl esters (b-1) having an alkyl group having 8 to 24 carbon atoms, those having an alkyl group having 12 or more carbon atoms, such as lauryl methacrylate and stearyl methacrylate are more preferable. preferable.

  In one molecule of the hydroxyl group-containing vinyl copolymer (B), 30 to 90% by weight of a structural unit derived from a methacrylic acid alkyl ester (b-1) having an alkyl group having 8 to 24 carbon atoms is contained. It is preferable that it is contained in the range of 40 to 80% by weight. By adjusting to such a range, particularly the moisture resistance of the coating film obtained using the powder coating composition of the present invention can be improved, and when the coating film thickness is reduced, smoothness is improved. In addition, a coating film having excellent scratch resistance can be obtained.

  In addition, radical polymerization initiators, organic solvents, chain transfer agents that can be used when the above-mentioned hydroxyl group-containing vinyl monomer and other monomers copolymerizable therewith are copolymerized in an organic solvent. Can use the same thing as what was illustrated as what can be used when manufacturing the said epoxy-group-containing vinyl copolymer (A), respectively.

  The number average molecular weight of the hydroxyl group-containing vinyl copolymer (B) used in the present invention is preferably in the range of 2,000 to 20,000, as determined by gel permeation chromatography of tetrahydrofuran-soluble matter, A range of 000 to 15,000 is more preferable. Within such a range, the moisture resistance and the smoothness of the coating film will be good.

As a usage-amount of a hydroxyl-containing vinyl copolymer (B), the range of 0.1-10 weight% is preferable with respect to an epoxy-group-containing vinyl copolymer (A), The range of 0.5-5 weight% Is more preferable, and the range of 1 to 4% by weight is most preferable.
Within such a range, improved curing of smoothness and scratching properties can be obtained sufficiently, and no good repellency, dents, etc. occur and a good appearance can be obtained.
Further, within the above-mentioned range, when the epoxy group-containing vinyl copolymer (A) and the hydroxyl group-containing vinyl copolymer (B) are mixed, the epoxy group-containing vinyl copolymer (A) and the hydroxyl group-containing vinyl copolymer are mixed. It is preferable that the blend (B) is not substantially compatible from the viewpoint that the smoothness of the obtained coating film, particularly the scratch resistance can be improved.

  Here, substantially incompatible means that the epoxy group-containing vinyl copolymer (A) and the hydroxyl group-containing vinyl copolymer (B) were mixed and heated in the above-described range to melt both. After that, when the coating film is formed by cooling, the coating film is turbid. In order to prevent the epoxy group-containing vinyl copolymer (A) and the hydroxyl group-containing vinyl copolymer (B) from being substantially compatible, the SP value of the epoxy group-containing vinyl copolymer (A), The difference from the SP value of the hydroxyl group-containing vinyl copolymer (B) is preferably in the range of 1.0 to 4.0, and the hydroxyl group-containing vinyl copolymer (B) contains an epoxy group. It is preferable to have an SP value lower than that of the vinyl copolymer (A).

  Here, the SP value is a parameter representing the polarity of the resin and can be obtained by the following method.

0.5 g of the hydroxyl group-containing vinyl copolymer (B) or epoxy group-containing vinyl copolymer (A) described above is weighed into a 100 ml Meyer flask and 10 ml of tetrahydrofuran (THF) is added and dissolved. While the dissolved solution is maintained at a liquid temperature of 25 ° C. and stirred with a magnetic stirrer, hexane is added dropwise using a 50 ml burette, and the dropping amount (v _h ) of the point at which the solution becomes cloudy (turbid point) Ask for.
Next, the dropping amount (v _d ) at the cloud point when deionized water is used instead of hexane is determined.

From v _h and v _d , the SP value δ of various vinyl copolymers was determined by SUH, CLARKE [J. Polym. Sci. A-1, Vol. 5, 1671-1681 (1967)] can be obtained as follows.

δ = ((V _mh ) ^(1/2) δ _mh + (V _md ) ^(1/2) δ _md ) / (V _mh ) ^(1/2) + (V _md ) ^(1/2) )
here,
V _mh = (V _h · V _t ) / (φ _h · V _t + φ _t · V _h ),
V _md = (V _d · V _t ) / (φ _d · V _t + φ _t · V _d )
δ _mh = φ _h · δ _h + φ _t · δ _t ,
δ _md = φ _d · δ _d + φ _t · δ _t
φ _h , φ _d , φ _t ; volume fraction of hexane, deionized water, and THF at the cloud point (φ _h = v _h / (v _h +10), φ _d = / (v _d +10))
δ _h , δ _d , δ _t ; SP value of hexane, deionized water, THF V _h , V _d , V _t ; molecular volume of hexane, deionized water, THF (ml / mol)

Next, the polyvalent carboxylic acid anhydride (C) and the polyvalent carboxylic acid (D) used in the present invention will be described.
The polycarboxylic acid anhydride (C) is mainly an anhydride of an aliphatic or aromatic polycarboxylic acid. Typical examples include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, brassic acid, dodecane diacid, hexadecane diacid, octadecane diacid, eicosane diacid, tetraeico. Sun diacid, maleic acid, citraconic acid, itaconic acid or glutaconic acid;

  Examples include phthalic acid, isophthalic acid, trimellitic acid, pyromellitic acid, tetrahydrophthalic acid, hexahydrophthalic acid, and cyclohexene-1,2-dicarboxylic acid anhydride. These may be used alone or in combination of two or more. .

  Typical examples of the polyvalent carboxylic acid (D) include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, brassic acid, dodecanedioic acid, hexadecanedioic acid, and octadecane. Diacid, eicosane diacid, tetraeicosane diacid, maleic acid, citraconic acid, itaconic acid or glutaconic acid; phthalic acid, isophthalic acid, trimellitic acid, pyromellitic acid, tetrahydrophthalic acid, hexahydrophthalic acid, cyclohexene 1,2-dicarboxylic acid can be mentioned, and these can be used alone or in combination of two or more.

  Among these, since the coating film appearance, storage stability, and particularly coating film properties are excellent, an anhydride of dodecanedioic acid is used as the polyvalent carboxylic acid anhydride (C), and dodecanedioic acid is used as the polyvalent carboxylic acid (D). Particularly preferred.

  The powder coating composition of the present invention uses a completely new hydroxyl group-containing vinyl copolymer (B) in a curing system based on an epoxy-containing vinyl copolymer and a polyvalent carboxylic acid. The carboxylic acid is limited to an anhydride, or 2) a compound (E) having a crosslinking reactivity with a hydroxyl group is further used. Next, a compound (E) having a crosslinking reactivity with a hydroxyl group is used. Will be described in detail.

  The compound (E) having a crosslinking reactivity with a hydroxyl group reacts with the hydroxyl group of the hydroxyl group-containing vinyl copolymer (B) or when the epoxy group-containing vinyl copolymer (A) has a hydroxyl group. For example, at least one compound selected from the group consisting of amino resins, blocked isocyanates, and N-alkoxymethyl group-containing acrylic resins can be suitably used.

  As the amino resin, for example, amino group-containing compounds such as melamine, urea, acetoguanamine, benzoguanamine, steroguanamine, spiroguanamine, and aldehyde compounds such as formaldehyde, paraformaldehyde, acetaldehyde, glyoxal, and the like are known and commonly used methods. The condensates obtained by reacting with each other or those obtained by etherifying each condensate with alcohols can be used. In particular, those partially or completely etherified with alcohols having 1 to 4 carbon atoms are preferred. Specific examples of such amino resins include hexamethyl etherified methylol melamine, hexabutyl etherified methylol melamine, methyl butyl. Examples thereof include mixed etherified methylol melamine, methyl etherified methylol melamine, butyl etherified methylol melamine, isobutyl etherified methylol melamine, and condensates thereof. The amino resin is preferably solid at room temperature, but any amino resin that is not solid at room temperature can be used as long as it is used for coatings.

  Examples of the blocked isocyanate include aliphatic diisocyanates such as hexamethylene diisocyanate and trimethylhexamethylene diisocyanate; cyclic aliphatic diisocyanates such as xylylene diisocyanate and isophorone diisocyanate; tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate and the like. Organic diisocyanates such as aromatic diisocyanates; or adducts of these organic diisocyanates with polyhydric alcohols, low molecular weight polyester resins (polyester polyols) or water; and polymers of the aforementioned organic diisocyanates (isocyanurates) Various polyisocyanates such as isocyanate and biuret bodies), and known and commonly used blocks. Agents, lactams, and the like those obtained allowed blocked with an oxime, such as active hydrogen-containing compound can be used. Examples of commercially available products include VESTANAT B1358 / 100, VESTAGON B1065, B1530 (block polyisocyanate manufactured by Degussa, Germany), Clelan UI, and Clelan TPLS2122 (block polyisocyanate manufactured by Sumitomo Bayer Urethane Co., Ltd.). Net). As the polyisocyanate, a so-called self-block type compound having a uretdione bond in the molecule can also be used.

  Examples of the N-alkoxymethyl group-containing acrylic resin include N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide, Nn-propoxymethyl (meth) acrylamide, and N-iso-propoxymethyl (meth). A monomer having an N-alkoxymethyl group such as acrylamide, Nn-butoxymethyl (meth) acrylamide, N-iso-butoxymethyl (meth) acrylamide, N-tert-butoxymethyl (meth) acrylamide, and the like, if necessary An acrylic resin obtained by copolymerizing with other monomers by a known and usual method can be used.

  Of the amino resin, blocked isocyanate, and N-alkoxymethyl group-containing acrylic resin, it is particularly preferable to use an N-alkoxymethyl group-containing acrylic resin from the viewpoint of excellent scratch resistance of the resulting coating film. The amount of the N-alkoxymethyl group-containing monomer used is preferably in the range of 5 to 100% by weight based on the total amount of monomers used when producing the N-alkoxymethyl group-containing acrylic resin. More preferably, it is within the range of 70% by weight.

  In the case of the powder coating composition containing the epoxy group-containing vinyl copolymer (A), the hydroxyl group-containing vinyl copolymer (B) and the polyvalent carboxylic acid anhydride (C), The epoxy group contained in each of the epoxy group-containing vinyl copolymer (A) and the hydroxyl group-containing vinyl copolymer (B), and the value obtained by adding up the equivalents of the hydroxyl group and the carbonyl group contained in the polyvalent carboxylic acid anhydride (C). The ratio to the equivalent [(equivalent of epoxy group + equivalent of hydroxyl group) / equivalent of carbonyl group]] is preferably in the range of 0.5 to 1.5, more preferably in the range of 0.7 to 1.2.

  Also, the epoxy group-containing vinyl copolymer (A) and the hydroxyl group-containing vinyl copolymer (B), the polyvalent carboxylic acid (D), and a compound (E) having crosslinking reactivity with the hydroxyl group are contained. In the case of the powder coating composition, the epoxy group-containing vinyl copolymer (A) has a compounding ratio of the epoxy group-containing vinyl copolymer (A) and the polyvalent carboxylic acid (D). The ratio of the equivalent of the carboxyl group of the polyvalent carboxylic acid (D) to the equivalent of the group [equivalent of carboxyl group / equivalent of epoxy group] is preferably in the range of 0.7 to 2.0, 0 More preferably within the range of 8-1.3.

  The amount of the compound (E) having cross-linking reactivity with a hydroxyl group is 0.5 to 100 parts by weight with respect to a total of 100 parts by weight of the epoxy group-containing vinyl copolymer (A) and the hydroxyl group-containing vinyl copolymer (B). It is preferably within the range of 30 parts by weight, and more preferably within the range of 1 to 10 parts by weight.

  The powder coating composition of the present invention further includes various synthetic resins such as epoxy resins, polyester resins, urethane resins or polyamide resins, curing catalysts, flow regulators, antiblocking agents, ultraviolet absorbers, Various commonly used paint additives or pigments such as light stabilizers, benzoin, antistatic agents, antioxidants and the like can be added as necessary.

  Among these additives, examples of the ultraviolet absorber include benzophenone and benzotriazole.

  As the light stabilizer or antioxidant, hindered amines, phenols, phosphites, and the like can be used.

  Examples of the curing catalyst include tertiary amines such as dimethylcocoamine, phosphines such as triphenylphosphine, imidazoles such as 2-methylimidazole, ammonium salts such as tetrabutylammonium chloride, tributylphosphonium bromide, and the like. Phosphonium salts can be preferably used.

  As pigments, various inorganic pigments such as titanium oxide, petal, chrome titanium yellow, yellow iron oxide, carbon black, phthalocyanine series such as phthalocyanine blue and phthalocyanine green, anthraquinone series such as indanthrene blue and dianthraquinonyl red, quinacridone Various organic pigments known in the art, such as azo, such as azo-type, lake red, first yellow, disazo yellow, permanent red, etc., nitro-type such as naphthol yellow, nitroso-type such as pigment green B, naphthol green, etc. Various extender pigments such as aluminum flakes, mica flakes, and the like can be used.

  The powder coating composition of the present invention is preferably produced by a so-called melt-kneading method from the viewpoint of quality stability and stable mass productivity. The powder coating composition is, for example, a mixture of an epoxy group-containing vinyl copolymer (A) and a hydroxyl group-containing vinyl copolymer (B), or a solution of an epoxy group-containing vinyl copolymer (A) and a hydroxyl group-containing vinyl. Mixing the copolymer (B) solution and removing the solvent, the polycarboxylic acid anhydride (C) and other various raw materials described above are mixed, and a heating roll or an extruder. The desired powder coating composition can be obtained by sufficiently melting and mixing at a temperature of 50 to 130 ° C. using a melt kneader such as the above, and then cooling, pulverizing and classifying.

  In addition, the compound (E) having a crosslinking reactivity with a hydroxyl group that is a raw material of the powder coating composition may cause a curing reaction to proceed during coating production by heating such as an N-alkoxymethyl group-containing acrylic resin. In the case of using a compound, it is effective to produce a solution containing various raw materials (hereinafter referred to as a powder coating material solution) and use a technique such as a spray drying method or a freeze drying method. In particular, it is preferable to apply a spray drying method capable of producing a powder coating composition at a low temperature and in a high yield.

  The powder coating composition of the present invention can be used for applications such as automobiles, motorcycles and other vehicle coatings that require high appearance and scratch resistance, and particularly top coatings for automobiles.

Next, a method for forming a coating film using the powder coating composition of the present invention will be described.
The above-described powder coating composition of the present invention is used as a top coat coating [II], and is applied to various substrates by a known and common method such as electrostatic spraying or fluid dipping, and then preferably 100 By baking at a temperature of ˜250 ° C., a coating film excellent in various properties can be formed.

  Also, the base coat paint [I] is applied on the base material, and then the powder coating composition of the present invention is applied as the top coat paint [II] on the base coat paint film, and then baked. Can also be formed.

  Here, the top coat paint [II] refers to a paint applied on the paint film on which the base coat paint [I] is applied, and protects the paint film made of the base coat paint [I], It bears the function of giving glossiness and the like.

  As described above, by using the powder coating composition of the present invention as the top coat paint [II], it is excellent in smoothness and sharpness, and in addition, is excellent in scratch resistance and the like, and is also water and moisture resistant. An excellent coating film can be obtained.

  As the top coat paint [II], a non-transparent paint can be used. However, when using a colored base coat paint, a transparent top coat paint should be used so as not to impair the aesthetics of the paint film. It is preferable to use it. At this time, the transparent top coat paint may be colored with a pigment as long as it is transparent.

  The base coat paint [I] is a paint to be applied directly on various base materials described later or on a coating film made of an undercoat or an intermediate paint provided on the base. The material has a function of imparting design properties such as hue and aesthetics to the material, and further imparting adhesion between the top coat paint [II] coated thereon and the base.

  As the base coat paint [I], a known solvent-based paint or water-based paint can be used.

  Solvent-based paints that can be used as base coat paints include polymers soluble in organic solvents such as toluene and xylene, such as organic solvent solutions of vinyl resins having hydroxyl groups and / or acid groups, and this vinyl copolymer. A combination of a hydroxyl group and a reactive aminoplast, polyisocyanate, block polyisocyanate, and / or an epoxy resin reactive with an acid group of this vinyl copolymer, an epoxy group-containing acrylic resin, etc. Examples include paints.

Examples of the water-based paint that can be used as a base coat paint include (1) a water-soluble resin obtained by dissolving a resin in water, such as an amine neutralized acid group-containing acrylic resin, as a binder,
(2) What contains a dispersion (water dispersion) type resin as a binder, such as a water dispersible polyurethane resin,
(3) What contains the emulsion etc. which contain a crosslinkable polymer as a binder are mentioned.

  The above water-based paint is a combination of aminoplasts reactive with hydroxyl groups in the binder, polyisocyanates, block polyisocyanates, and / or epoxy resins reactive with acid groups in the binder, epoxy group-containing acrylic resins, etc. It becomes.

  Among these, a water-based paint formed by combining a vinyl copolymer having a hydroxyl group and an aminoplast, polyisocyanate, or block polyisocyanate having reactivity with the hydroxyl group of the vinyl copolymer is preferable. In particular, a coating material obtained by combining a vinyl copolymer having a hydroxyl group and aminoplast is preferable.

  In particular, by combining the aqueous base coat paint and the powder paint composition of the present invention, the amount of organic solvent scattered can be greatly reduced as compared with conventional solvent-based paints, and excellent smoothness even in thin films. A coating film having properties is obtained.

  These base coat paints [I] contain various conventional pigments such as organic pigments, inorganic pigments, extender pigments, glitter (metallic tone) pigments, additives such as curing accelerators and leveling agents. Can do.

The base coat [I] and the top coat [II] are coated with an unpainted metal material such as an unpainted steel plate, an untreated or chemically treated aluminum substrate, and an automobile. The base material used for road vehicles, such as a vehicle body and a two-wheeled vehicle body, the base material used for motor vehicle parts, such as an aluminum wheel, can be used.
Moreover, the base material used for road vehicles, such as a motor vehicle body by which electrodeposition coating was given, can also be used. In addition, base materials used in home appliances, vending machines, steel furniture, etc., such as electrogalvanized steel sheets, hot-dip galvanized steel sheets, tiles, various inorganic building materials such as glass, gates or fences Various building materials such as building materials and aluminum sashes can also be used.

  These base materials may be processed into a shape corresponding to the end use, or a form to which a PCM (pre-coat metal) coating method is applied, that is, a flat plate-like base material. After the multilayer coating film is formed by the method of the present invention, it may be bent into a predetermined shape according to the purpose. Furthermore, it may be a base material used in a coating system such as coil coating that is completely subjected to post-processing.

  Moreover, what formed the coating film by the intermediate coating material on these base materials as needed can be used.

  Here, the intermediate coating is a coating applied on a substrate in order to improve the smoothness, chipping resistance, interlayer adhesion and the like of the finally obtained multilayer coating film. As such an intermediate coating, for example, it consists of various main ingredient components such as alkyd resin, polyester resin, acrylic resin, epoxy resin, cellulose resin, and curing agent component such as amino resin or polyisocyanate compound, and is an organic solvent type. A non-aqueous dispersion type, powder, water-soluble type or water-dispersion type thermosetting or room temperature curable coating can be used.

  Next, the present invention will be described more specifically with reference examples, examples and comparative examples. In the following description, unless otherwise specified, all “parts” mean “parts by weight”.

Reference Example 1 [Preparation Example of Epoxy Group-Containing Vinyl Copolymer]
In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet, 100 parts of xylene was placed and heated to 130 ° C.

  As an epoxy group-containing vinyl monomer, 45 parts of glycidyl methacrylate, as other vinyl monomers, 5 parts of n-butyl methacrylate, 35 parts of methyl methacrylate and 15 parts of styrene, as a polymerization initiator Of tert-butylperoxy-2-ethylhexanoate was added dropwise over 5 hours.

  After completion of the dropwise addition, the solution is kept at the same temperature for 10 hours, and the polymerization reaction is continued to complete the reaction, whereby the epoxy group-containing vinyl copolymer (A-1) solution (A′-1 ) Further, 30 parts of the obtained epoxy group-containing vinyl copolymer solution (A′-1) was kept under reduced pressure at 180 ° C. and 20 Torr, and xylene was removed to remove the epoxy group-containing vinyl copolymer ( A-1) was obtained. Table 1 shows the property values of the epoxy group-containing vinyl copolymer (A-1) and the solution (A′-1) thereof.

Reference Example 2 [Preparation Example of Epoxy Group-Containing Vinyl Copolymer]
As shown in Table 1, the target epoxy group-containing vinyl copolymer was used in the same manner as in Reference Example 1 except that a mixture comprising a vinyl monomer and a polymerization initiator was used. A solution (A′-2) of the combined (A-2) was obtained. Further, 30 parts of the obtained epoxy group-containing vinyl copolymer solution (A′-2) was kept under reduced pressure at 180 ° C. and 20 Torr, and xylene was removed to remove the epoxy group-containing vinyl copolymer (A−). 2) was obtained. Table 1 shows the property values of the epoxy group-containing vinyl copolymer (A-2) and the solution (A′-2) thereof.

Reference Example 3 [Preparation Example of Epoxy Group-Containing Vinyl Copolymer for Comparison]
As shown in Table 1, the target epoxy group-containing vinyl copolymer was used in the same manner as in Reference Example 1 except that a mixture comprising a vinyl monomer and a polymerization initiator was used. A solution (A′-3) of the union (A-3) was obtained. Further, 30 parts of the epoxy group-containing vinyl copolymer solution (A′-3) thus obtained was kept at 180 ° C. under a reduced pressure of 20 Torr to remove xylene, thereby removing the epoxy group-containing vinyl copolymer (A−). 3) was obtained. Table 1 shows the property values of the epoxy group-containing vinyl copolymer (A-3) and the solution (A′-3) thereof.

[Glass transition temperature (℃)]
A numerical value obtained by converting the temperature (K) calculated by the following Fox equation into (° C.).
100 / Tg = W1 / Tg1 + W2 / Tg2 + W3 / Tg3 + W4 / Tg4
-In formula, W1, W2 ... shows the mass fraction (mass%) of various components.
-In formula, Tg1, Tg2, ... shows the glass transition temperature (K) of the homopolymer of various components. Here, the glass transition temperature of the homopolymer used was the value described in Polymer Handbook (Second Edition, edited by J, Brandrup E, H, Immergut). )

[Number average molecular weight]
Number average molecular weight by molecular weight measurement in gel permeation chromatography of tetrahydrofuran solubles.

[SP value]
Value obtained by the method described in detail in paragraphs “0060” to “0062” in “Embodiments of the Invention” in the present specification.

Reference Example 4 [Preparation Example of Hydroxyl-Containing Vinyl Copolymer]
In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet, 100 parts of xylene was placed and heated to 120 ° C.

  To this, a mixture comprising a vinyl monomer and a polymerization initiator, as shown in Table 2, was added dropwise over 4 hours. After completion of the dropwise addition, the solution was maintained at the same temperature for 10 hours, and the polymerization reaction was continued to complete the reaction, thereby obtaining a solution (B′-1) of the hydroxyl group-containing vinyl copolymer (B-1). .

  Furthermore, 30 parts of the obtained hydroxyl group-containing vinyl copolymer solution (B′-1) was maintained at 180 ° C. under a reduced pressure of 20 Torr, and xylene was removed to remove the hydroxyl group-containing vinyl copolymer (B—). 1) was obtained. Table 2 shows the property values of the hydroxyl group-containing vinyl copolymer (B-1) and the solution (B′-1) thereof.

Reference Example 5 [Preparation Example of Hydroxyl-Containing Vinyl Copolymer]
As shown in Table 2, the target hydroxyl group-containing vinyl copolymer was obtained in the same manner as in Reference Example 4 except that a mixture comprising a vinyl monomer and a polymerization initiator was used. A solution (B′-2) of (B-2) was obtained. Furthermore, 30 parts of each hydroxyl group-containing vinyl copolymer solution (B′-2) was held at 180 ° C. under a reduced pressure of 20 Torr, and xylene was removed to obtain a hydroxyl group-containing vinyl copolymer (B-2). It was. Table 2 shows the properties of each hydroxyl group-containing vinyl copolymer (B-2) and its solution (B′-2).

Reference Examples 6 and 7 [Preparation Example of Hydroxyl-Containing Vinyl Copolymer for Comparison]
As shown in Table 2, a hydroxyl group-containing vinyl copolymer for comparison was used in the same manner as in Reference Example 4 except that a mixture comprising a vinyl monomer and a polymerization initiator was used. Solutions (B'-3) and (B'-4) of union (B-3) and (B-4) were obtained. Further, 30 parts of each hydroxyl group-containing vinyl copolymer solution (B′-3) and (B′-4) were kept under a reduced pressure of 20 Torr, and xylene was removed to prepare the hydroxyl group-containing vinyl copolymer. Respective (B-3) and (B-4) were obtained. The properties of the copolymers (B-3) and (B-4) and their solutions (B′-3) and (B′-4) are shown in Table 2.

“Acryester SL”: trade name of a mixture of a methacrylic acid alkyl ester having a C12 alkyl group in the side chain and a methacrylic acid alkyl ester having a C13 alkyl group in the side chain, manufactured by Mitsubishi Rayon Co., Ltd.

Reference Examples 8 to 10 [Preparation Example of Mixture (S) of Epoxy Group-Containing Vinyl Copolymer and Hydroxyl Group-Containing Vinyl Copolymer]
In the compounding ratio as shown in Table 3, the epoxy group-containing vinyl copolymer solutions (A′-1) and (A′-2) obtained in Reference Examples 1 and 2 and Reference Examples 4 and 5 The solution (B′-1) and (B′-2) of the obtained hydroxyl group-containing vinyl copolymer was charged into a container, stirred and mixed, and kept under a reduced pressure of 20 Torr to remove xylene. Mixtures (S-1) to (S-3) having a content of 99.5% or more were obtained.

Reference Example 11 [Preparation Example of Mixture of Epoxy Group-Containing Vinyl Copolymer and Hydroxyl Group-Containing Vinyl Copolymer]
The epoxy group-containing vinyl copolymer solution (A′-3) obtained in Reference Example 3 and the hydroxyl group-containing vinyl copolymer solution (B) obtained in Reference Example 4 at a blending ratio as shown in Table 3 '-1) was charged into a container, stirred and mixed, and kept under a reduced pressure of 20 Torr to remove xylene, thereby obtaining a mixture (S-4) having a nonvolatile content of 99.8%.

Reference Example 12 [Preparation Example of Mixture of Epoxy Group-Containing Vinyl Copolymer and Comparative Hydroxyl Group-Containing Vinyl Copolymer]
The epoxy group-containing vinyl copolymer solution (A′-2) obtained in Reference Example 2 and the hydroxyl group-containing vinyl copolymer solution (B) obtained in Reference Example 6 at a blending ratio as shown in Table 3 The mixture (S-6) having a non-volatile content of 99.7% was obtained in the same manner as in Comparative Reference Example 1 using '-4).

Reference Example 13 [Preparation Example of Mixture of Epoxy Group-Containing Vinyl Copolymer and Comparative Epoxy Group-Containing Vinyl Copolymer]
The epoxy group-containing vinyl copolymer solution (A′-2) obtained in Reference Example 2 and the epoxy group-containing vinyl copolymer solution obtained in Reference Example 7 (with a blending ratio as shown in Table 3) B'-4) was charged into a container, stirred and mixed, and kept under a reduced pressure of 20 Torr to remove xylene, thereby obtaining a mixture (S-6) having a nonvolatile content of 99.8%.

Reference Example 14 [Preparation Example of Compound N-Alkoxymethyl Group-Containing Acrylic Resin (D-1) Having Crosslinking Reactivity with Hydroxyl Group]
In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet, 75 parts of methyl ethyl ketone was placed and heated to 85 ° C.

  A mixture comprising 40 parts of methyl methacrylate, 40 parts of Nn-butoxymethylacrylamide, 92 parts of methyl ethyl ketone, and 10 parts of azobisisobutyronitrile as a polymerization initiator was added dropwise over 6 hours. After completion of the dropwise addition, the compound was maintained at the same temperature for 8 hours to complete the polymerization reaction, thereby obtaining a compound solution (D′-1) having a cross-linking reactivity with a hydroxyl group having a nonvolatile component of 35%.

  Next, the compound solution (D'-1) is an explosion-proof vertical downward co-current type spray drying apparatus equipped with a solvent recovery device, and the powdered compound (D-1) is sprayed using a two-fluid nozzle method as a spray method. Obtained.

Examples 1 to 5 (Preparation examples of the powder coating composition of the present invention)
Each component shown in Table 4 was mixed with a “Henschel mixer” (mixer manufactured by Mitsui Miike Processing Co., Ltd.) at the blending ratio shown in Table 4, and the mixture was mixed with “MP-2015. "(A twin-screw extrusion kneader manufactured by APV Chemical Machinery, USA) was kneaded with heat to obtain kneaded materials.

  Subsequently, the various kneaded materials obtained are cooled, pulverized, and further classified, whereby various target powder coating compositions (X-) having an average particle diameter of 15 to 35 micrometer (μm) are obtained. 1) to (X-5) were prepared.

Comparative Reference Example 1
Instead of the mixture (S-1) of the epoxy group-containing vinyl copolymer (A′-1) and the hydroxyl group-containing vinyl copolymer (B′-1) obtained in Reference Example 8, it was obtained in Reference Example 1. A comparative powder coating composition (X-6) was prepared in the same manner as in Example 1 except that only the epoxy group-containing vinyl copolymer (A-1) was used.

Comparative Reference Example 2
Instead of the mixture (S-1) of the epoxy group-containing vinyl copolymer (A′-1) and the hydroxyl group-containing vinyl copolymer (B′-1) obtained in Reference Example 8, it was obtained in Reference Example 11. A powder coating composition (X-7) for comparison was prepared in the same manner as in Example 1 except that the mixture (S-4) was used.

Comparative Reference Example 3
Instead of the mixture (S-1) of the epoxy group-containing vinyl copolymer (A′-1) and the hydroxyl group-containing vinyl copolymer (B′-1) obtained in Reference Example 12, it was obtained in Reference Example 12. A comparative powder coating composition (X-8) was prepared in the same manner as in Example 5 except that the mixture (S-5) was used.

Comparative Reference Example 4
In place of the mixture (S-3) of the epoxy group-containing vinyl copolymer (A′-2) and the hydroxyl group-containing vinyl copolymer (B′-1) obtained in Reference Example 12, it was obtained in Reference Example 13. A comparative powder coating composition (X-9) was prepared in the same manner as in Example 5 except that the mixture (S-6) was used.

Comparative Reference Example 5
A comparative powder coating composition (X-10) was prepared in the same manner except that the type and ratio of the curing agent of Example 1 were changed.

《註》
“Additol VXL-1381”: polyanhydride of dodecanic acid manufactured by UCB “Troyl EX-570”: trade name “B-1358 / 100” of leveling agent manufactured by TROY CHEMICAL, blocked isocyanate, manufactured by Degussa Product name of curing agent “DBTDL”: Dibutyltin dilaurate

Reference Example 15 [Preparation Example of Water-Soluble Resin Used for Water-Based Basecoat Paint]
A liquid mixture consisting of 250 parts of styrene, 157 parts of methyl methacrylate, 63 parts of 2-hydroxyethyl methacrylate and 30 parts of methacrylic acid and 8 parts of tert-butyl peroxyoctate (abbreviated as TBPO) was previously prepared. Prepare.

  Next, 75 parts of this mixed solution and 500 parts of methyl ethyl ketone (MEK) were charged into a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet, while stirring under a nitrogen seal, After maintaining at 75 ° C. for 30 minutes, the remaining mixture was added dropwise over 2 hours.

  Furthermore, by continuing the reaction for 12 hours at the same temperature, the nonvolatile content is 50%, the solution acid value is 20, the solution hydroxyl value is 25, and the Gardner viscosity at 25 ° C. (hereinafter the same) is Z. An acrylic resin solution was obtained.

  Next, after adding 31 parts of dimethylaminoethanol to 1,000 parts of this acrylic resin solution, 600 parts of water was added and then the solvent was removed to obtain a water-soluble acrylic resin solution having a nonvolatile content of 55%. Hereinafter, this is abbreviated as a water-soluble resin (E-1).

Reference Example 16 [Preparation Example of Water Dispersible Resin Used for Water-Based Basecoat Paint]
A water-dispersed acrylic resin having a solid content of 45% and containing crosslinkable fine particles insoluble in a solvent, except that the acrylic monomer component used was changed as follows. A milky white stable dispersion was obtained. Hereinafter, this is abbreviated as water-dispersible resin (E-2).

[Acrylic monomer components used]
450 parts of methyl methacrylate
350 parts of ethyl acrylate
150 parts of 2-hydroxyethyl methacrylate
Acrylic acid 20 parts
30 parts of ethylene glycol dimethacrylate
n-octyl mercaptan 5 parts
4 parts ammonium persulfate
"Triton X-200" 15 copies
"Emargen 840s" 10 copies
530 parts of deionized water

《註》
“Triton X-200”: Product name of anionic surfactant “Rum & Haas” manufactured by Rohm & Haas, USA “Emulgen 840s”: Product of nonionic surfactant manufactured by Kao Atlas Co., Ltd. Name

Reference Example 17 (Example of thickener preparation)
By adding 6 parts of dimethylethanolamine and deionized water to 64 parts of “Acrisol ASE-60” (Rohm and Haas, brand name of thickener; solid content = 28%), A target thickener having a solid content of 3% was obtained. Hereinafter, this is abbreviated as (P).

Reference Example 18 [Preparation Example of Aqueous Base Coat Paint (1)]
100 parts of the water-soluble resin (E-1) obtained in Reference Example 17, 10 parts of the thickener (P) obtained in Reference Example 19, and 6 parts of “Cymel 300” (supra), 1.0 part of p-toluenesulfonic acid, 3 parts of “aluminum paste dispersion # 4919” [trade name of aluminum pace manufactured by Toyo Aluminum Co., Ltd.] and “aluminum paste dispersion # 55-519” (the company Product) and 12 parts of isopropanol and mixed with deionized water at 20 ° C. for Ford Cup No. The viscosity according to 4 was adjusted to 16 seconds. Hereinafter, this is abbreviated as an aqueous base coat paint [I-1].

Reference Example 19 [Preparation Example of Water-Based Basecoat Paint (2)]
100 parts of the water-dispersible resin (E-2) obtained in Reference Example 18, 10 parts of the thickener (P) obtained in Reference Example 19, 5 parts of “Cymel 300”, p-toluene 1.0 part of sulfonic acid, 3 parts of “aluminum paste dispersion # 4919” and 1.5 parts of “aluminum paste dispersion # 55-519” and 12 parts of isopropanol are mixed together with deionized water. Ford Cup No. 20 at 20 ° C. The viscosity according to 4 was adjusted to 16 seconds. Hereinafter, this is abbreviated as an aqueous base coat paint [I-2].

Examples 6-9
Each of the obtained powder coating compositions (X-1), (X-2), (X-4), and (X-5) obtained in Examples 1 to 4 was subjected to electrostatic spray coating for powder coating. Then, coating was performed on a 0.8 mm thick satin steel plate treated with zinc phosphate, followed by baking at 140 ° C. for 20 minutes to obtain various test plates having a cured coating film formed thereon. Table 5 summarizes the evaluation results of these coating films.

Comparative Examples 1-4
Except that the powder coating compositions (X-6), (X-7), (X-9) and (X-10) for comparison and control obtained in Comparative Reference Examples 1 to 5 were used. In the same manner as in Example 6, various test plates on which a cured coating film was formed were obtained. Table 5 summarizes the evaluation results of these coating films.

《Guidelines for evaluation of physical properties of coating film》

Film thickness: Measured with an electromagnetic film thickness meter.

Smoothness: A five-step evaluation determination was performed by visual determination.
Evaluation “5”: In the case of a smooth and smooth coated surface Evaluation “4”: In the case where there are small rounds Evaluation “3”: In the case where there are large rounds Evaluation “2”: There are large rounds and many fine chilli skin Case where rating is "1": When there is a large round, fine dusty skin is noticeable, and the appearance of the paint film is significantly impaired

Film gloss: Measures 60 ° specular reflectance

Scratch resistance: Cleanser resistance was measured. As a measuring method, a 5% cleanser aqueous dispersion was immersed in flannel cloth and rubbed 50 times. The 20-degree gloss (20-degree specular reflectance:%) before and after the rubbing was measured, and the so-called gloss retention (%) obtained from this was evaluated and judged in 5 stages.
Evaluation “5”: Gloss retention 90% or more Evaluation “4”: Gloss retention 80% or more but less than 90% Evaluation “3”: Gloss retention 65% or more but less than 80% Evaluation “2”: Gloss retention 50% or more Less than 65% evaluation "1": Gloss retention less than 50%

Example 10
Using the powder coating composition (X-1) obtained in Example 1, a coating film is formed by performing two-coat one-bake coating according to a so-called multilayer coating film forming method as shown below. Then, various performances were evaluated and judged. As the base material at that time, a substrate subjected to the following pretreatment was used.

  That is, an epoxy resin-based cationic electrodeposition coating was electrodeposited on a mild steel sheet treated with “Bondelite # 3030” (trade name of zinc phosphate-based processing agent manufactured by Nippon Parkerizing Co., Ltd.), and then An amino-polyester resin-based intermediate coating was applied on top.

  The aqueous base coat paint [I-1] obtained in Reference Example 18 was subjected to a coating atmosphere in which the temperature was 25 ° C. and the relative humidity was 65 to 70% so that the dry film thickness was 20 μm. Painted in two portions.

Between the two paintings, a setting for 2 minutes was performed. The air pressure of the spray gun at the first coating is 5 kg / cm ² , the flow rate of the paint is 400 m / min, the flow rate of the paint is 200 m / min at the second coating, The distance was 40 cm.
The coated surface on the substrate was always vertical.

  After painting twice, it was air-dried at a temperature of 30 ° C. for 5 minutes. Next, after cooling to room temperature, the powder coating composition (X-1) is applied with an electrostatic spray coating machine for powder coating, and then this coated plate is baked at 140 ° C. for 20 minutes. A test plate on which a cured coating film was formed was obtained. Table 6 shows the evaluation results of the coating film.

Examples 11-14
A test plate on which a cured coating film was formed was obtained in the same manner as in Example 10 except that the powder coating composition and the aqueous base coat coating used were changed as shown in Table 6. Table 6 summarizes the evaluation results of these coating films.

Comparative Examples 6-8
Test plate on which a cured coating film was formed in the same manner as in Examples 10 and 11 except that the powder coating compositions (X-6) to (X-8) prepared in Comparative Reference Examples 1 to 3 were used. Got. Table 6 shows the evaluation results of the coating film.

《Guidelines for evaluation of physical properties of coating film》

Film thickness: Measured with an electromagnetic film thickness meter.

Smoothness: A five-step evaluation determination was performed by visual determination.
Evaluation “5”: In the case of a smooth and smooth coated surface Evaluation “4”: In the case where there are small rounds Evaluation “3”: In the case where there are large rounds Evaluation “2”: There are large rounds and many fine chilli skin Case where rating is "1": When there is a large round, fine dusty skin is noticeable, and the appearance of the paint film is significantly impaired

Film gloss: Measures 60 ° specular reflectance

Scratch resistance: Cleanser resistance was measured. In the measurement method, an 8% cleanser aqueous dispersion was immersed in flannel cloth and rubbed 50 times. The 20-degree gloss (20-degree specular reflectance:%) before and after the rubbing was measured, and a five-step evaluation judgment was performed based on the so-called gloss retention (%) obtained from this.
Evaluation “5”: Gloss retention 90% or more Evaluation “4”: Gloss retention 80% or more but less than 90% Evaluation “3”: Gloss retention 65% or more but less than 80% Evaluation “2”: Gloss retention 50% or more Less than 65% evaluation "1": Gloss retention less than 50%

Moisture resistance: Gloss retention obtained by measuring 20 degree gloss (20 degree specular reflectance:%) after leaving the coated plate at 40 ° C. and 100% relative humidity for 20 days, and obtaining the gloss value before and after the test. Evaluation was made in five stages by rate (%).
Evaluation “5”: Gloss retention 90% or more Evaluation “4”: Gloss retention 80% or more but less than 90% Evaluation “3”: Gloss retention 65% or more but less than 80% Evaluation “2”: Gloss retention 50% or more Less than 65% evaluation "1": Gloss retention less than 50%

Claims (11)

Epoxy group-containing vinyl copolymer (A) having a glass transition temperature of 40 ° C. or higher and a number average molecular weight of 1000 to 5000, and a hydroxyl group-containing vinyl copolymer (B) having a glass transition temperature of 0 ° C. or lower. And a powder coating composition comprising the polyvalent carboxylic acid anhydride (C). Epoxy group-containing vinyl copolymer (A) having a glass transition temperature of 40 ° C. or higher and a number average molecular weight of 1000 to 5000, and a hydroxyl group-containing vinyl copolymer (B) having a glass transition temperature of 0 ° C. or lower. , A polyvalent carboxylic acid (D), and a powder coating composition comprising a compound (E) having a crosslinking reactivity with a hydroxyl group. The hydroxyl group-containing vinyl copolymer (B) has 30 to 90% by weight of structural units derived from an alkyl methacrylate (b-1) having an alkyl group having 8 to 24 carbon atoms in one molecule. Or the powder coating composition of 2. The powder coating composition according to claim 1 or 2, wherein the hydroxyl group-containing vinyl copolymer (B) has a hydroxyl value of 20 to 400. The powder coating composition according to claim 1 or 2, wherein the hydroxyl group-containing vinyl copolymer (B) has an SP value smaller by 1.0 to 4.0 than the epoxy group-containing vinyl copolymer (A). object. The powder coating material according to claim 2, wherein the compound (E) having a crosslinking reactivity with a hydroxyl group is at least one selected from the group consisting of an amino resin, a blocked isocyanate, and an N-alkoxymethyl group-containing acrylic resin. Composition. A method of forming a coating film, comprising: applying a powder coating composition according to claim 1 or 2 as a top coat coating on a substrate, and then baking the coating composition. The powder coating composition according to claim 1 or 2 is applied as a top coating [II] onto the coating obtained by applying the base coating [I] onto the substrate, and then baked. The formation method of the multilayer coating film characterized by the above-mentioned. The powder coating composition according to claim 1 or 2 is applied as a transparent topcoat coating [IIb] onto a coating film obtained by coating a colored basecoat coating [Ib] on a substrate, Next, a method for forming a multilayer coating film characterized by baking. The method for forming a multilayer coating film according to claim 9, wherein the colored base coat paint [Ib] is an aqueous colored base coat paint. A coated product obtained by coating the powder coating composition according to claim 1 or 2 on a substrate and then baking.