JP2002265858A - Powder coating composition and coating film forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an extremely practical powder coating composition and a coating film forming method which are excellent in the smoothness and scratch resistance of the coating film and also excellent in the recoating property of the coating film. thing. SOLUTION: An epoxy group-containing vinyl copolymer having a glass transition temperature of 40 ° C. or more, a cellulose ester,
A powder coating composition comprising, as essential components, an epoxy group-containing vinyl copolymer having a glass transition temperature of not higher than ° C and a polyvalent carboxylic acid.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a novel and useful powder coating composition applicable to various uses such as automobile bodies and parts, home electric appliances, vending machines, inorganic building materials, building interior and exterior materials, and the like. The present invention relates to a coating film forming method. In more detail, it is excellent in smoothness, sharpness and finished appearance,
In addition, the present invention relates to a powder coating composition and a coating film forming method capable of forming a coating film having excellent interlayer adhesion and recoating properties.

[0002]

2. Description of the Related Art Powder coatings are widely used in all metal coatings as environmentally friendly coatings in which organic solvents do not evaporate into the atmosphere during coating. Above all, powder coatings in the form of using an epoxy group-containing vinyl copolymer as a resin component and a polyvalent carboxylic acid compound as a curing agent component,
It is widely applied and used because it can form a coating film having excellent weather resistance.

[0003] However, this type of powder coating has a drawback that it is inferior in scratch resistance and the like. In order to improve such scratch resistance and the like, particularly, the finished appearance of the coating film and the like are reduced. It ’s easy to fall, and eventually
It was extremely difficult to balance the various performances.

[0004] On the other hand, a composition for a powder coating material having excellent finished appearance and scratch resistance and a coating method thereof have been disclosed. (Japanese Unexamined Patent Publication (Kokai) No. 09-227799) By using the powder coating composition, a coating film having excellent finished appearance and scratch resistance can be obtained. It is also promising to expand to applications such as those for top-clear automobiles, for which the use of powder coatings was difficult due to performance problems.

[0005] Automotive top clear coatings are required to have many coating properties in addition to the finished appearance and scratch resistance. In a coating film for an automobile, a coating film formed by the top clear coating may have coating film defects such as dents. In order to repair the defective part, top clear paint is applied again, but at that time,
Adhesion with the original coating, so-called recoating, is also one of the important coating properties.

In general, powder coatings are inferior in recoating properties. If powder coatings are to be used for top clearing, special treatment of the coating film surface is required to repair coating film defects, resulting in poor workability. It decreases significantly. This problem cannot be solved by the powder coating composition having excellent finish appearance and scratch resistance and its coating method (Japanese Patent Application Laid-Open No. 09-227799), and the powder coating is developed for use in top clear automobiles. It is a big problem on the above.

[0007]

However, the present inventors have solved the above-mentioned problems in the prior art,
It is excellent in the finished appearance and scratch resistance of the coating film formed by applying it on the object to be coated, and in addition, it is also excellent in the recoating property of the coating film, extremely practical, powder coating composition and In order to obtain a method for forming a coating film, the research was started earnestly.

Accordingly, an object of the present invention is to provide an extremely practical powder coating composition which is excellent in smoothness and abrasion resistance of a coating film, and particularly excellent in recoating property of a coating film. An object of the present invention is to provide a coating film forming method.

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, have found that the temperature is 40 ° C.
An epoxy group-containing vinyl copolymer (A) having the above glass transition temperature, a cellulose ester (B), an epoxy group-containing vinyl copolymer (C) having a glass transition temperature of 0 ° C. or lower, and a polycarboxylic acid ( It has been found that a coating film formed using a powder coating composition, characterized by containing D) as an essential component, is excellent in smoothness, scratch resistance, and particularly excellent in recoating property. Here, the present invention has been completed.

That is, the present invention relates to an epoxy group-containing vinyl copolymer (A) having a glass transition temperature of 40 ° C. or higher, a cellulose ester (B), and an epoxy group-containing vinyl copolymer having a glass transition temperature of 0 ° C. or lower. A powder coating composition, comprising: a coalescence (C) and a polycarboxylic acid (D) as essential components.

[0010] A coating film forming method for forming a single-layer or multiple-layer coating film on an object to be coated, wherein the powder coating composition is used as a top coat coating material, Alternatively, a base coat paint [I]
And a top coat paint [II] is further coated thereon, wherein the powder coating composition is used as the top coat paint [II]. ,

[0011] The present invention also provides a coated article on which a coating film is formed by the above coating film forming method.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be specifically described below. First, among the essential components in the powder coating composition of the present invention, a glass transition temperature of 4
The epoxy group-containing vinyl copolymer (A) at 0 ° C. or higher will be described.

The epoxy group-containing vinyl copolymer (A) having a glass transition temperature of 40 ° C. or more is defined as having an average of two or more epoxy groups in one molecule and having a glass transition temperature of 40.
The term refers to a vinyl copolymer having a temperature of not less than ° C.

The epoxy group-containing vinyl copolymer (A)
A known and commonly used method can be applied to prepare the epoxy group-containing vinyl monomer, and if necessary, further using other copolymerizable vinyl monomers, these monomers are used. Polymerization of the compounds in an organic solvent is recommended because it is the simplest method. As the polymerization initiator and the solvent used at that time, known and commonly used ones can be used as they are.

If only particularly typical examples of the epoxy group-containing vinyl monomer used in the preparation of the epoxy group-containing vinyl copolymer (A) are given below,

Various epoxy group-containing monomers such as glycidyl (meth) acrylate, ゜ -methylglycidyl (meth) acrylate, glycidyl vinyl ether and allyl glycidyl ether; (2-oxo-1,3-oxolane) methyl ( (2-oxo-1,3-oxolane) group-containing vinyl monomers such as (meth) acrylate;
Various alicyclic epoxy group-containing vinyl monomers such as 3,4-epoxycyclohexyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, and 3,4-epoxycyclohexylethyl (meth) acrylate There is.

Other vinyl monomers copolymerizable with the epoxy group-containing vinyl monomer include (meth)
Acrylic acid or crotonic acid or esters thereof, and various known and commonly used monomers containing an ethylenically unsaturated bond can also be used. These may be used alone or in combination of two or more.

If only particularly typical examples of the above-mentioned (meth) acrylic acid esters are given as examples,
Methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate,
Isobutyl (meth) acrylate, t (meth) acrylate
tert-butyl or n-hexyl (meth) acrylate,

Cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, isooctyl (meth) acrylate,
Alkyl (meth) acrylates such as 2-ethyloctyl (meth) acrylate, dodecyl (meth) acrylate, isodecyl (meth) acrylate, lauryl (meth) acrylate or stearyl (meth) acrylate;

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

Alternatively, various alkyl carbitols (meth) such as ethyl carbitol (meth) acrylate
In addition to acrylates and the like, further, isobornyl (meth) acrylate, dicyclopentanyl (meth) acrylate, dicyclopentenyl (meth) acrylate or dicyclopentenyloxyethyl (meth) acrylate;

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

Polyethylene glycol mono (meth) acrylate or polypropylene glycol mono (meth)
Acrylates and the like, and various hydroxyl group-containing (meth) acrylates as described above, e.
A so-called lactone-modified hydroxyl-containing (meth) acrylate in the form of a ring-opening reaction with caprolactone.

In addition, for example,?-(Meth) acryloyloxypropyltrimethoxysilane,?-
Various hydrolyzable silyl group-containing monomers, such as (meth) acryloyloxypropyltriethoxysilane or?-(Meth) acryloyloxypropylmethyldimethoxysilane;

Various fluorine-containing a-olefins such as vinyl fluoride, vinylidene fluoride, trifluoroethylene, tetrafluoroethylene, chlorotrifluoroethylene, bromotrifluoroethylene, pentafluoropropylene and hexafluoropropylene. And,

Alternatively, perfluoroalkyl / perfluorovinyl ether or (per) fluoroalkyl vinyl ether such as trifluoromethyl trifluorovinyl ether, pentafluoroethyl trifluorovinyl ether or heptafluoropropyl trifluorovinyl ether (provided that the alkyl group has 1
１８18. )
Such as various fluorine-containing vinyl monomers,

Further, a vinyl monomer having a phosphate ester group, such as mono [(meth) acryloyloxyethyl] phosphate, acidic (meth) acrylic acid ester or phenyl (meth) acryloyloxyethyl phosphate, and the like. .

As the other ethylenically unsaturated monomers, only typical ones are exemplified, and various polyvalent carboxyl groups such as fumaric acid, maleic acid and itaconic acid are exemplified. Mono- or diesters of a monomer contained and a monoalkyl alcohol having 1 to 18 carbon atoms; various aromatic vinyl compounds such as styrene, vinyltoluene, a-methylstyrene or p-tert-butylstyrene;

(Meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, Nn-propyl (meth) acrylamide, Ni
so-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-amyloxymethylacrylamide, N-hexyloxy (meth) acrylamide,
N-heptyloxymethyl (meth) acrylamide, N-
Octyloxymethyl (meth) acrylamide, N-2-
Various amino group-containing amide vinyl monomers such as 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 , Aziridinylethyl (meth) acrylate, pyrrolidinylethyl (meth) acrylate, piperidinylethyl (meth) acrylate, (meth) acryloylmorpholine, N-vinyl-2-pyrrolidone, N-
Various nitrogen-containing vinyl monomers such as vinylcaprolactam, N-vinyloxazoline or (meth) acrylonitrile;

Vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caproate, vinyl caprylate, vinyl caprate, vinyl laurate, C ₉ branched (branched) aliphatic vinyl carboxylate, C Various aliphatic vinyl carboxylate such as ₁₀ branched (branched) aliphatic vinyl carboxylate, C ₁₁ branched (branched) aliphatic vinyl carboxylate or vinyl stearate;

Vinyl esters of various carboxylic acids having a cyclic structure, such as vinyl cyclohexanecarboxylate, vinyl methylcyclohexanecarboxylate, vinylbenzoate 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;

Such as vinyl chloride or vinylidene chloride,
Examples include various halogenated olefins other than the above-mentioned fluoroolefins, or various a-olefins such as ethylene, propylene or butene-1.

The epoxy group-containing vinyl copolymer (A)
The radical polymerization initiator used in the preparation of
Various known and commonly used compounds can be used.

Of these, particularly representative ones will be exemplified only, 2,2'-azobisisobutyronitrile, 2,2'-azobis-methylbutyronitrile, 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-t
tert-butylazo-2-cyanopropane, 2,2′-
Azobis (2-methyl-propionamide) dihydrate,
2,2′-azobis [2- (2-imidazolin-2-yl) propene] or 2,2′-azobis (2,2,4
Various azo compounds, such as -trimethylpentane);

Alternatively, benzoyl peroxide, methyl ethyl ketone peroxide, cumene hydroperoxide, potassium persulfate, tert-butyl peroxy neodecanoate, tert-butyl peroxypivalate, tert-butyl peroxy-2-ethylhexano Ethate, tert-butylperoxyisobutyrate, 1,1-bis-tert-butylperoxy-
3,3,5-trimethylcyclohexane or tert
-Butyl peroxy-laurate,

Tert-butyl peroxyisophthalate, tert-butyl peroxyacetate, tert
Various ketone peroxides, such as -butylperoxybenzoate, dicumyl peroxide or di-tert-butyl peroxide; peroxyketals; hydroperoxides; dialkyl peroxides; diacyl peroxides; Esters; peroxydicarbonates; or hydrogen peroxide.

As the organic solvent used for preparing the epoxy group-containing vinyl copolymer (A), known organic solvents can be used.

If only typical examples of such organic solvents are given as examples, methanol, ethanol, n-
Alkyl alcohols such as propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, n-pentanol, isopentanol;

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

Aromatic hydrocarbons such as benzene, toluene, xylene and ethylbenzene; Exxon Aromatic Naphtha No. Mixed hydrocarbons containing aromatic hydrocarbons, such as 2 (manufactured by Exxon, USA); n-pentane, n
Aliphatic hydrocarbons, such as hexane, n-octane;
Isopar C, Isopar E, Exor DSP100
/ 140, Exol D30 (all manufactured by Exxon, USA) and IP Solvent 1016 (manufactured by Idemitsu Petrochemical Co., Ltd.) such as mixed hydrocarbons containing aliphatic hydrocarbons; cyclopentane, cyclohexane, methylcyclohexane,
Alicyclic hydrocarbons such as ethylcyclohexane;

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

If necessary, a chain transfer agent may be used. Of these, only typical ones are exemplified. Dodecyl mercaptan, lauryl mercaptan, thioglycolic acid ester, mercapto ester Ethanol or a-methylstyrene dimer.

As described above, the epoxy equivalent in the epoxy group-containing vinyl copolymer (A) having a glass transition temperature of 40 ° C. or higher is from about 250 to about 450, more preferably from 300 to 450.
It is desirable to be within the range of 400.

The epoxy group-containing vinyl copolymer (A) has a number average molecular weight of about 1,000 to about 1
It is appropriate to be within the range of 0000, and furthermore, 1.5
A range from 00 to 6,000 is appropriate.

Next, the cellulose ester (B) will be described. Cellulose ester (B)
Is a derivative obtained by appropriately esterifying three hydroxyl groups per C ₆ units of cellulose with acids, and nitric acid, acetic acid,
Examples include esterified products of propionic acid, butyric acid, and other higher fatty acids, and mixed esterified products of acetic acid and butyric acid. In addition, diesters are preferred because they have excellent solvent solubility and are easy to handle.

If only typical examples of the cellulose ester (B) are given as examples, examples thereof include cellulose acetate, cellulose acetate butyrate and cellulose acetate propionate.
Among them, the use of cellulose acetate butyrate is desirable because of its high effect of improving the recoating property.

The cellulose ester (B) exhibits an effect of improving the recoating property when added to the powder coating composition. The amount of the cellulose ester (B) used is based on the total amount of the powder coating composition.
The range of 0.01 to 5% by weight is appropriate.

The above-mentioned epoxy group-containing vinyl copolymer (A) is preferably polymerized in the presence of a cellulose ester (B) in advance. By performing polymerization of the epoxy group-containing vinyl copolymer (A) in the presence of the cellulose ester (B), recoatability can be further improved.

Next, the epoxy group-containing vinyl copolymer (C) having a glass transition temperature of 0 ° C. or lower will be described. The epoxy group-containing vinyl copolymer (C) is prepared by using an epoxy group-containing vinyl monomer and, if necessary, other vinyl monomers, and converting these monomers into an organic solvent. It is prepared by a method of polymerizing with. As the vinyl monomers used at that time, the above glass transition temperature is 4
Vinyl monomers such as those used for preparing the epoxy group-containing vinyl copolymer (A) at 0 ° C. or higher can be used.

Further, in the vinyl monomers used, the ratio of the alkyl methacrylate (c-1) having an alkyl group having 4 or more carbon atoms to the total amount of the vinyl monomers used is expressed as follows. , 30 to 90% by weight, more preferably 40 to 80% by weight. The proportion of the alkyl methacrylate (c-1) having an alkyl group having 4 or more carbon atoms in the total amount of the vinyl monomers used is 30 to 90% by weight, more preferably 40 to 80% by weight. By the above, not only the smoothness of the coating film formed by the powder coating composition finally obtained, not only the scratch resistance is improved, it is particularly possible to obtain a coating film excellent in moisture resistance, water resistance. it can.

As the alkyl methacrylate (c-1) having an alkyl having 4 or more carbon atoms, among methacrylic acid alkyl esters, those having an alkyl group having 4 or more carbon atoms can be used. If only examples are given, n-butyl methacrylate, isobutyl methacrylate, tert-butyl methacrylate, n-hexyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, n-methacrylic acid
-Octyl, isooctyl methacrylate, 2-ethyloctyl methacrylate, n-decyl methacrylate, isodecyl methacrylate, lauryl methacrylate, stearyl methacrylate, eicosyl methacrylate, tetraeicosyl methacrylate and the like. These carbon number 4
The alkyl methacrylate (c-1) having the above alkyl may be used alone or in combination of two or more.

Among these alkyl methacrylates (c-1) having an alkyl group having 4 or more carbon atoms, use of 2-ethylhexyl methacrylate, lauryl methacrylate, and stearyl methacrylate is particularly preferred.

As the polymerization initiator and the solvent, the epoxy group-containing vinyl monomer and the other vinyl monomer, which are used in the preparation of the above-mentioned epoxy group-containing vinyl copolymer (A), are used. The monomer and the radical polymerization initiator, and further, the chain transfer agent can be used as they are.

The epoxy equivalent of the epoxy group-containing vinyl copolymer (C) is preferably 1500 or less, more preferably 800 or less. The epoxy equivalent of the epoxy group-containing vinyl copolymer (C) is 1500
Below, more preferably 800 or less, the abrasion resistance of the obtained coating film is improved.

The epoxy group-containing vinyl copolymer (C) has a number average molecular weight of about 2,000 to about 2,000.
It is appropriate that the value is in the range of 0.000, more preferably,
Preferably it is in the range of 4,000 to 15,000.

The epoxy group-containing vinyl copolymer (C)
The addition amount of (A) is suitably in the range of about 0.1 to about 10% by weight based on the component (A), and is preferably 0.5% by weight.
In the range of from 5 to 5% by weight, more preferably from 1 to 4% by weight.
A weight percent range is appropriate. Furthermore, the epoxy group-containing vinyl copolymer (A) and the epoxy group-containing vinyl copolymer (C) are substantially compatible with each other within the range of the addition amount of the epoxy group-containing vinyl copolymer (C). Desirably not. Here, "substantially incompatible" means that the epoxy-containing vinyl copolymer (A) and the epoxy-containing vinyl copolymer (C) were mixed and heated in the above-described range to melt both. Thereafter, when a film is formed by cooling, the film is turbid.

In order to make the epoxy group-containing vinyl copolymer (A) and the epoxy group-containing vinyl copolymer (C) substantially incompatible, the epoxy group-containing vinyl copolymer (A) And the difference in SP value between the epoxy group-containing vinyl copolymer (C) and the epoxy group-containing vinyl copolymer (C) is preferably in the range of 1.0 to 6.0. It preferably has a lower SP value than the epoxy group-containing vinyl copolymer (A).

Here, the SP value is a parameter indicating the polarity of the resin, and is determined by the following method.

0.5 g of the sample resin was weighed into a 100 ml Meyer flask, and tetrahydrofuran (THF) 1
Add 0 ml to dissolve the resin. Dissolve the solution at a temperature of 2
While maintaining the temperature at 5 ° C. and stirring with a magnetic stirrer, hexane was added dropwise using a 50 ml burette, and the amount of drop (v _h ) at the point where the solution became turbid (turbid point) was determined.

Next, the drop amount (v _d ) at the turbid point when deionized water is used instead of hexane is determined.

Based on v _h and v _d , the SP value δ of the resin is SUH, CL
ARKE [J. Polym. Sci. A-1, Vol.5, 1671-1681 (1967)]
Can be obtained as follows using the equation shown by. 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 cloudy point (φ _h = v _h / (v _h +10), φ _d = / (v _d +10)) δ _h , Δ _d , δ _t ; Hexane, deionized water, THF SP
Values _{V h, V d, V t} ; hexane, deionized water, THF molecular volume (ml / mol)

Further, the ratio of the number average molecular weight of the epoxy group-containing vinyl copolymer (C) to the number average molecular weight of the epoxy group-containing vinyl copolymer (A) ((number average molecular weight of C) / (number of A) (Average molecular weight) is preferably in the range of 1.5 to 5.0, more preferably 2.5 to 5.0.
It is preferably in the range of 5.0.

The ratio of the epoxy equivalent of the epoxy group-containing vinyl copolymer (C) and the epoxy group-containing vinyl copolymer (A) ((epoxy equivalent of C) / (epoxy equivalent of A)) is as follows:
It is preferably in the range of 1.2 to 7.0, more preferably in the range of 1.2 to 2.5.

Next, as the above-mentioned polycarboxylic acid (D), aliphatic or aromatic polycarboxylic acids can be mainly used. If we decide to exemplify only those that are particularly representative,

Succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, brassic acid, dodecane diacid, eicosane diacid, tetraeicosane diacid, maleic acid, citraconic acid, itaconic acid or Glutaconic acid;

Further, phthalic acid, isophthalic acid, trimellitic acid, pyromellitic acid, tetrahydrophthalic acid,
Hexahydrophthalic acid or cyclohexene-1,2-
Dicarboxylic acids; or acid anhydrides thereof.

Further, a urethane-modified compound obtained by reacting the above-mentioned polycarboxylic acid or its anhydride with a polyisocyanate compound can also be used. These polycarboxylic acids (C) may be used alone or in combination of two or more. Among these, aliphatic dibasic acids are preferred because of excellent coating film properties and storage stability.
In particular, dodecane diacid can be suitably used because of its excellent properties.

Here, the mixing ratio of the epoxy group-containing polyfunctional vinyl copolymers (A) and (C) and the polyvalent carboxylic acid (D) is as follows. Of the epoxy group in (C) and the carboxyl group in the polycarboxylic acid (D) by ((A) + (C)) /
(D) With an equivalent ratio of from about 0.5 to about 1.5, more preferably from about 0.8 to about 1.2 is appropriate and should be within such a range. It is desirable to use them in an appropriate ratio.

The powder coating composition of the present invention thus obtained further comprises an epoxy resin, a polyester resin,
Including various synthetic resins such as urethane resin or polyamide resin,

Curing catalysts; flow regulators; antiblocking agents; ultraviolet absorbers; light stabilizers; benzoin; various commonly used coating additives or pigments such as antistatic agents or antioxidants. , Can be used in addition as needed.

Among such additives, ultraviolet absorbers,
To exemplify only typical light stabilizers or antioxidants, 2,4-dihydroxybenzophenone (“Seesorb 100”), 2,2 ′, 4,
4′-tetrahydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone (“Seesorb 10
1 "), 2,2'-dihydroxy-4,4'-methoxybenzophenone or 2-hydroxy-4-methoxy-5
Various benzophenones, such as sulfobenzophenone;

2- (3,5-di-tert-amyl-2)
-Hydroxyphenyl) benzotriazole ("Tinuvin 328"), 2- (2'-hydroxy-5'-methyl-phenyl) benzotriazole ("Tinuvin
P "), 2- [2-hydroxy-3,5-di (1,1-
Various benzotriazoles, such as dimethylbenzyl) phenyl] -2Hbenzotriazole (“Tinuvin 900”); phenyl salicylate (“Seesorb 2”)
01 "), various salicylates;

Various substituted acrylonitrile systems, such as ethyl-2-cyano-3,3'-diphenyl acrylate ("Seesorb 501");2-ethoxy-2'-ethyloxazac acid bisanilide ("Tinuvin 3
12 "), various oxalic anilides; [2,
2'-thiobis (4-tert-octylphenolate)]-2-ethylhexylamine-nickel (II)
Various nickel complex systems, such as ("Seesorb 612NH");

Bis (1,2,2,6,6-pentamethyl-4-piperidyl) sebacate (“Tinuvin 29
2 "), bis (2,2,6,6-tetramethyl-4-
Piperidyl) sebacate ("Tinuvin 770"), 2
Bis (1,2,2,2- (3,5-di-tert-butyl-4-hydroxybenzyl) -2-n-butylmalonate
6-pentamethyl-4-piperidyl) ("Tinuvin 1
44)) various hindered amines;

3,5-di-tert-butyl-4-hydroxytoluene ("BHT Swannox"), tetrakis- [methylene- (3,5-di-tert-butyl-4)
-Hydroxyhydrocinnamate)] (“Irganox 1010”).

Specific examples of the curing catalyst include phosphines such as triphenylphosphine, imidazoles such as 2-methylimidazole, and ammonium salts such as tetrabutylammonium chloride.

Examples of particularly typical pigments include various inorganic pigments such as titanium oxide, red iron oxide, chromium titanium yellow, yellow iron oxide, and carbon black, and phthalocyanine-based pigments such as phthalocyanine blue and phthalocyanine green. , Anthraquinones such as induslen blue and dianthraquinonyl red, azos such as quinacridone, lake red, fast yellow, disazo yellow and permanent red, nitros such as naphthol yellow, and nitrosos such as pigment green B and naphthol green. Various known organic pigments, various known conventional extenders, and further, aluminum
Various known and brilliant (metallic) pigments such as flakes and mica flakes are used.

In order to prepare the powder coating composition according to the present invention, any of the known and commonly used methods can be employed, but usually, after mixing the above-mentioned various components, The purpose is to sufficiently melt-mix at a temperature of about 50 to about 130 ° C. with various melt-kneaders such as a heating roll or an extruder, cool, and then pulverize and classify. The method used for powder coating is adopted.

The coating method is carried out by coating the substrate to be coated with various known and commonly used methods such as electrostatic spraying or fluidized immersion. The baking may be performed at a temperature of about 250 ° C., so that a coating film by powder coating can be obtained.

The powder coating composition of the present invention comprises a coating film forming method for forming a single-layer or multiple-layer coating film on an object to be coated,
It can be suitably used as a top coat paint. Particularly, in a coating film forming method in which a base coat paint [I] is applied on an object to be coated, and a top coat paint [II] is further applied thereon, the top coat paint [II] ] Can be more preferably used. More preferably, the base coat paint [I] is a colored base coat paint, and the top coat paint [II] is a transparent top coat paint.

Here, the object to be coated refers to a substrate to which the paint is applied, and specifically, an unpainted metal material such as an unpainted steel plate, an untreated or chemically treated aluminum substrate. And base materials used for road vehicles such as automobile bodies and two-wheeled vehicle bodies, and base materials used for automobile parts such as aluminum wheels, and in a state where electrodeposition coating has been applied. And base materials used for road vehicles such as automobile bodies. Further, base materials used in home electric appliances, vending machines, steel furniture, etc., such as electrogalvanized steel sheets, hot-dip galvanized steel sheets, tiles; glass; or various inorganic building materials; gates or fences And various building materials such as aluminum sashes.

[0086] These substrates may be processed into a shape suitable for the final use, or may be in a form to which a PCM (pre-coated metal) coating method is applied, that is, a roughly plate-shaped cut plate-shaped substrate. 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, or may be completely post-processed such as coil coating. The substrate used in the provided coating system may be used.

If necessary, a coating film formed of an intermediate coating material on these substrates can also be suitably used as an object to be coated. Here, the intermediate coating is a coating that is applied on the above-described substrate to improve the smoothness, chipping resistance, interlayer adhesion, and the like of the finally obtained multilayer coating film. As such an intermediate coating, an alkyd resin, a polyester resin, an acrylic resin, an epoxy resin, a variety of main components such as a cellulose resin, and a curing agent component such as an amino resin or a polyisocyanate compound, an organic solvent type, Any non-aqueous, powder, water-soluble or water-dispersible thermosetting or room temperature curable coating can be used.

The above-mentioned basecoat paint [I] means a paint mainly using water or an organic solvent as a medium. A typical example of a medium using water is (1)
An aqueous resin as a binder, (2) a dispersion (water dispersion) type resin as a binder,
And (3) those using an emulsion polymer as a binder. Examples of the type (1) include those obtained by copolymerizing a vinyl monomer having a carboxyl group to make the acrylic resin containing an acid group, and further neutralizing the amine to make the resin completely water-soluble. The type (3) includes a water-dispersible polyurethane resin having an anion-forming group (disclosed in Japanese Patent Publication No. 3-45755). The type (3) includes a crosslinkable polymer fine particle. Emulsion polymers (disclosed in JP-A-56-157358).

Typical examples of paints using an organic solvent as a medium include a polymer soluble in an organic solvent such as toluene and xylene, for example, an organic solvent solution of a vinyl resin having a hydroxyl group, and a vinyl copolymer. Coatings formed by combining aminoplasts, polyisocyanates, blocked polyisocyanates, and the like that react with the hydroxyl groups in the coalescence are exemplified.

Among these basecoat paints [I],
A paint mainly comprising water or an organic solvent as a medium, and a combination of a vinyl copolymer having a hydroxyl group and an aminoplast, a polyisocyanate, and a blocked polyisocyanate that react with a hydroxyl group in the vinyl copolymer are preferable. However, a paint obtained by combining a vinyl copolymer having a hydroxyl group and aminoplast is particularly preferable because the effect of improving the adhesion to an object to be coated is remarkable.

These base paints [I] using water or an organic solvent as a medium may be used in addition to these resin components, inorganic pigments such as titanium oxide, extenders, organic pigments, aluminum flakes and mica flakes. Additives such as glittering (metallic) pigments such as lacquer, curing accelerators, and leveling agents.

Examples of pigments or inorganic or organic fillers include various known and commonly used ones. Of those, particularly representative ones are exemplified. is benzidine Yellow, such as Hanza yellow or Rekiddo 4R, various insoluble azo pigments; Rekiddo C, such as soluble azo pigments Carmine 6B or Bordeaux 10;

Various copper phthalocyanine pigments, such as phthalocyanine blue or phthalocyanine green; various chlorinated dyeing lakes, such as rhodamine lake or methyl violet lake; various mordant dye pigments, such as quinoline lake or fast sky blue;

Or various vat dye pigments such as anthraquinone, thioindigo or perinone pigments; various quinacridone pigments such as synchasia red B;
Various oxazine pigments such as oxazine violet; various condensed azo pigments such as chromophtal; and aniline black.

Next, as the inorganic filler, various chromates such as graphite, zinc chromate or molybdate orange; various ferrocyan compounds such as navy blue; titanium oxide, zinc white, mapico yellow, iron oxide, Various metal oxides, such as red iron oxide or chrome green oxide;

Various sulfides or selenides, such as cadmium yellow, cadmium red or mercury sulfide;
Various sulfates, such as barium sulfate or lead sulfate; various silicate salts, such as calcium silicate or ultramarine; various carbonates, such as calcium carbonate or magnesium carbonate; cobalt violet or manganese purple;
Various phosphates;

Various metal powder pigments such as aluminum powder, gold powder, silver powder, copper powder, bronze powder or brass powder; or metal flake pigments and mica flake pigments; mica powder coated with metal oxide; Flake pigments, a class of metallic pigments such as mica-like iron oxide pigments, and pearl pigments,

Further, the extender pigments include precipitated barium sulfate, powder, gypsum, alumina white, clay, silica, silica white, talc, precipitated magnesium carbonate, kaolin, and the like. Can also be used as pigments of this type.

Top coat paint [II] to be applied on top
The powder coating composition of the present invention is preferably used. By using the powder coating composition, it is possible to obtain a coating film which is excellent in the smoothness and sharpness of the coating film, is excellent in scratch resistance and the like, and is particularly excellent in recoating property.

The topcoat paint [II] in the present invention includes those which are not transparent, but when the basecoat paint [I] is a colored basecoat paint, a transparent topcoat paint is preferred. The transparent top coat paint may be colored with a pigment as long as it is transparent.

As described above, the powder coating composition of the present invention is applied to various substrates to be coated as described above by a conventional method, and then baked and dried according to a conventional method. By doing so, it is possible to give a coating film having excellent curability, appearance, weather resistance, mechanical properties and the like.

[0102]

Next, the present invention will be described in more detail with reference to Reference Examples, Examples and Comparative Examples, but it goes without saying that the present invention is not limited only to these Examples.
In the following, all “parts” mean “parts by weight” unless otherwise specified.

Reference Example 1 [Preparation of Epoxy Group-Containing Vinyl Copolymer (A)] A reaction vessel equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet was charged with 100 parts of xylene. The temperature was raised to.

To this were added 45 parts of glycidyl methacrylate and 5 parts of n-butyl methacrylate as monomers.
Parts, 35 parts of methyl methacrylate and 1 part of styrene
A mixture consisting of 5 parts and 7.5 parts of tert-butylperoxy-2-ethylhexanoate as a polymerization initiator was added dropwise over 5 hours.

After the completion of the dropwise addition, the temperature was maintained at the same temperature for another 10 hours to continue the polymerization reaction to complete the reaction, whereby the epoxy-containing vinyl copolymer (A-
A solution (A'-1) of 1) was obtained. Further, 30 parts of the resulting copolymer solution (A'-1), and held under a reduced pressure of about 20 Torr, to obtain an epoxy-containing vinyl copolymer by removing the xylene (A-1). Epoxy-containing vinyl copolymer (A-1) and its solution (A'-1)
Are shown in Table 1.

Reference Example 1 [Preparation of Epoxy Group-Containing Vinyl Copolymer (A)] In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser and a nitrogen inlet, "CA" was prepared as cellulose ester (B).
B551-0.01 "(trade name of cellulose acetate butyrate manufactured by Eastman Chemical Company, USA) and 100 parts of xylene were added, and the temperature was raised to 130 ° C.

To this were added 40 parts of glycidyl methacrylate and 20 parts of n-butyl methacrylate as monomers.
Parts, 25 parts of methyl methacrylate and 1 part of styrene
A mixture consisting of 5 parts and 4.0 parts of tert-butyl peroxy-2-ethylhexanoate as a polymerization initiator was added dropwise over 5 hours.

After completion of the dropping, the polymerization was continued at the same temperature for 10 hours to complete the reaction, thereby completing the epoxy-containing vinyl copolymer (A-
A solution (A'-2) of 2) was obtained. Further, 30 parts of the obtained copolymer solution (A'-2) was kept under reduced pressure of about 20 Torr, and xylene was removed to obtain an epoxy-containing vinyl copolymer (A-2). Epoxy-containing vinyl copolymer (A-2) and its solution (A'-2)
Are shown in Table 1.

Reference Example 3 [Preparation of Epoxy Group-Containing Vinyl Copolymer (A)] As shown in Table 1, a modification was made so as to use a monomer, a cellulose ester (B), and a polymerization initiator. Except for the above, a target solution (A′-3) of an epoxy group-containing vinyl copolymer (A-3) was obtained in the same manner as in Reference Example 2. Further, 30 parts of the copolymer solution (A′-3) was added to about 2 parts.
The xylene was removed under a reduced pressure of 0 Torr to obtain an epoxy-containing vinyl copolymer (A-3). Table 1 shows the properties of the copolymer (A-3) and its solution (A'-3).

[0110]

[Table 1]

<< Note >>"CAB551-0.01": trade name of cellulose acetate butyrate manufactured by Eastman Chemical Company, USA "CAB551-0.2": same as above

Reference Example 4 [Preparation of Epoxy Group-Containing Vinyl Copolymer (C)] In a reaction vessel equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet, 100 parts of xylene was added. The temperature was raised to.

In addition, as shown in Table 2,
A mixture consisting of the monomer and the polymerization initiator was added dropwise over 4 hours. After the completion of the dropwise addition, the solution was kept at the same temperature for 10 hours to continue the polymerization reaction to complete the reaction, thereby obtaining a solution (C′-1) of the epoxy-containing vinyl copolymer (C-1). .

Further, the obtained copolymer solution (C′-
30 parts of 1) was kept under reduced pressure of about 20 Torr, and xylene was removed to obtain an epoxy-containing vinyl copolymer (C-1). The property values of the epoxy-containing vinyl copolymer (C-1) and its solution (C'-1)
It is shown in the table.

Reference Examples 5, 6 [Preparation of Epoxy Group-Containing Vinyl Copolymer (C)] As shown in Table 2, a mixture comprising a monomer and a polymerization initiator was used. Except for the change, in the same manner as in Reference Example 1, the solution (C′-) of the desired epoxy group-containing vinyl copolymer (C-2) and (C-3) was prepared.
2) and (C′-3) were obtained. Further, 30 parts of each copolymer solution (C ′) was kept under reduced pressure of about 20 Torr, and xylene was removed to obtain epoxy-containing vinyl copolymers (C-2) and (C-3). . Table 2 shows the properties of each copolymer (C) and its solution (C ′).

[0116]

[Table 2]

<< Note >>"AcryesterSL": manufactured by Mitsubishi Rayon Co., Ltd.
Trade name of a mixture of a methacrylic acid alkyl ester having a C12 alkyl group in a side chain and a methacrylic acid alkyl ester having a C13 alkyl group in a side chain

Reference Example 7 [Preparation Example of Mixture (S) of Epoxy Group-Containing Vinyl Copolymer (A) and Epoxy-Containing Vinyl Copolymer (B) Containing Cellulose Ester (B)] Table 3 At such a mixing ratio, the solution (A'-1) of the epoxy-containing vinyl copolymer (A) obtained in Reference Example 1
And the solution (B'-1) of the epoxy-containing vinyl copolymer (B) obtained in Reference Example 1, and "CAB551-
0.01 "(trade name of cellulose acetate butyrate manufactured by Eastman Chemical Company, USA) was charged into a container, stirred and mixed, and kept under reduced pressure of about 20 Torr to remove xylene. 99.5%
The above mixture (S-1) was obtained.

Reference Examples 8 to 11 [Examples of Preparation of Mixture (S) of Epoxy Group-Containing Vinyl Copolymer (A) and Epoxy-Containing Vinyl Copolymer (B) Containing Ethrose Ester (B)] The epoxy-containing vinyl copolymer (A) solution (A'-
2), solutions (B'-1) of (A'-3) and the epoxy-containing vinyl copolymer (B) obtained in Reference Examples 4 to 6;
Charge (B'-3) into a container, stir and mix, about 20 T
By removing xylene while maintaining the pressure under a reduced pressure of orr, the mixture (S-2) to (S-2) having a nonvolatile content of 99.5% or more was removed.
-5) was obtained.

Reference Example 12 [Preparation of a mixture (S-6) of an epoxy group-containing vinyl copolymer (A) and an epoxy group-containing vinyl copolymer (B) which does not contain a cellulose ester (B) for comparison. Example] A mixture for comparison (S-6) (99.7% non-volatile content) was obtained in the same manner as in Reference Example 7, except that the cellulose ester (B) was not used.

[0121]

[Table 3]

[0122]

[Table 4]

Examples 1 to 6 (Examples of Preparation of Powder Coating Composition According to the Present Invention) Each of the components was mixed with a "Henschel mixer" (Mitsui Miike Koki Co., Ltd., a mixing machine), and the mixture is further referred to as “MP-20”.
15 "(a twin-screw extrusion kneader manufactured by APV Chemical Machinery, USA).

Next, the various kneaded materials thus obtained are cooled, pulverized, and classified, so that the average particle size is 15 to 35 micrometers (Om).
Various powder coatings (X-1) to (X-
6) was prepared.

Comparative Reference Example 1 An epoxy group-containing vinyl copolymer solution (A'-4) was prepared in the same manner as in Reference Example 3, except that the cellulose ester (B) was not used. An epoxy-containing vinyl copolymer (A) and an epoxy-containing vinyl copolymer (B) were prepared in the same manner as in Reference Example 10, except that the obtained epoxy-containing vinyl copolymer solution (A'-4) was used. Mixture of (S-
7) was prepared and this epoxy-containing vinyl copolymer (A)
And a mixture of epoxy group-containing vinyl copolymer (B) (S-
A powder coating for comparison (X-7) was prepared in the same manner as in Example 4 except that 7) was used.

Comparative Reference Example 2 Example 1 was repeated except that the mixture (S-6) of the epoxy-containing vinyl copolymer (A) and the epoxy-containing vinyl copolymer (B) obtained in Reference Example 12 was used. A powder coating for comparison (X-8) was prepared in the same manner as described above.

[0127]

[Table 5]

[0128]

[Table 6]

<< Note >>"CAB551-0.01": a brand name of cellulose acetate butyrate manufactured by Eastman Chemical Company in the United States "Motaflow P2000": an acrylic relinking agent manufactured by Monsanto, USA "KP322": a product name of silicon-based relinking agent manufactured by Shin-Etsu Chemical Co., Ltd. "CR-90": a rutile-type titanium oxide "Thaipeak CR-90" manufactured by Ishihara Sangyo Co., Ltd.

[0130] [used in coating film forming method of the invention, the preparation examples of the water-soluble resin] Reference Example 13 in advance, 250 parts of styrene, 1 methyl methacrylate
A liquid mixture comprising 57 parts, 63 parts of 2-hydroxyethyl methacrylate, 30 parts of methacrylic acid, and 8 parts of tert-butyl peroxyoctate (abbreviated as TBPO) is prepared.

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, and placed under a nitrogen seal. While stirring, 30 minutes at 75 ° C.
After holding for a minute, the remaining mixture was added dropwise over 2 hours.

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

Next, this acrylic resin solution was dissolved in
After adding 31 parts of dimethylaminoethanol to 0 parts, water was added to obtain a 55% concentration water-soluble acrylic resin solution. Hereinafter, this is abbreviated as water-soluble resin (E-1).

Reference Example 14 (same as above) A solid content of 45% was obtained in the same manner as in Reference Example 15, except that the acrylic monomer component to be used was changed as described below.
Thus, a milky white stable dispersion of an aqueous dispersion type acrylic resin containing crosslinkable fine particles insoluble in a solvent was obtained. Hereinafter, this is abbreviated as water-dispersible resin (E-2).

Methyl methacrylate 450 parts Ethyl acrylate 350 parts 2-hydroxyethyl methacrylate 150 parts Acrylic acid 20 parts Ethylene glycol dimethacrylate 30 parts n-octyl mercaptan 5 parts Ammonium persulfate 4 parts "Triton X-200" 15 parts "Emulgen 840s" 10 parts Deionized water 530 parts

<< Note >>"TritonX-200"; trade name of anionic surfactant manufactured by Rohm & Haas, USA; "Emulgen 840s"; nonionic surfactant manufactured by Kao Atlas Co., Ltd. Trade name of surfactant

Reference Example 15 (Preparation Example of Thickener) 64 of “Acryl ASE-60” (trade name of a thickener manufactured by Rohm and Haas Company; solid content = 28%)
The desired thickener having a solid content of 3% was obtained by adding 6 parts of dimethylethanolamine and deionized water to the parts. Hereinafter, this is abbreviated as (P).

REFERENCE EXAMPLE 16 [Preparation Example (1) of aqueous base coat paint] 100 parts of the water-soluble resin (E-1) obtained in Reference Example 13 and the thickener (P ) And 10 parts,
6 parts of "Cymel 300" (supra), 1.0 part of p-toluenesulfonic acid, "Aluminum paste dispersion # 4
919 "[trade name of aluminum pace manufactured by Toyo Aluminum Co., Ltd.] and" Aluminum paste dispersion # 5
5-519 "(product of the same company) and 12 parts of isopropanol were mixed and mixed with deionized water to give 20 parts.
Ford cup no. 4 with a viscosity of 16
Adjusted to seconds. Hereinafter, this is referred to as an aqueous base coat paint [I
-1].

Reference Example 17 [Preparation Example (2)] 100% of the water-dispersible resin (E-2) obtained in Reference Example 14
Parts, 10 parts of the thickener (P) obtained in Reference Example 15,
5 parts of "Cymel 300", 1.0 part of p-toluenesulfonic acid, "Aluminum paste dispersion # 4919"
3 parts and “Aluminum paste dispersion # 55-51
9 "and 12 parts of isopropanol were mixed and mixed with deionized water at 20 ° C.
Cup No. The viscosity according to 4 was adjusted to 16 seconds. Less than,
This is abbreviated as water-based base coat paint [I-2].

Example 7 The powder coating (X-4) obtained in Example 4 was zinc-phosphate treated with a 0.8 mm thick matte steel plate using an electrostatic spray coating machine for powder coating. Paint on top and then 16
By baking at 0 ° C. for 20 minutes, various test plates on which a cured coating film was formed were obtained. Table 5 shows the evaluation results of the coating films.

Comparative Example 1 The powder paint for comparison (X-coating) obtained in Comparative Reference Example 1 was used.
Except using 7), it carried out similarly to Example 7, and obtained various test plates in which the cured coating film was formed. Table 5 shows the evaluation results of the coating films.

[0142]

[Table 7]

<< Procedure for Evaluation of Various Properties of Coating Film >>

Film thickness: Measured with an electromagnetic film thickness meter.

Smoothness: Five-level evaluation judgment was made by visual judgment.

Evaluation “5”: In the case of a very smooth and smooth coating surface Evaluation “4”: In the case of a small round Evaluation “3”: In the case of a large round Evaluation “2” -When there is a large round and many fine dust skins are recognized Evaluation "1" ... When there is a large round and the fine dust skin is remarkable and the appearance of the coating film is significantly impaired

Scratch resistance: Cleanser resistance was measured. The measuring method was such that a 5% aqueous dispersion of cleanser was immersed in flannel cloth and rubbed 50 times.

Then, the 20-degree gloss (20-degree specular reflectance:%) before and after the rubbing was measured.
Evaluation was made in five stages based on the so-called gloss retention (%).

Evaluation “5”; Gloss retention of 90% or more Evaluation “4”; Gloss retention of 80% or more and less than 90% Evaluation “3”; Gloss retention of 65% or more and less than 80% Evaluation “2”; Gloss retention 50% or more and less than 65% Evaluation "1"; Gloss retention rate less than 50%

Recoating property: The coating film baked and cured at 140 ° C. for 20 minutes is overbaked at 140 ° C. for 20 minutes, and then the powder coating used for forming the coating film on the coated plate is electrostatically coated again. Baked at 140 ° C. for 20 minutes. A cross-cut adhesion test of 2 mm width and 10 × 10 was performed on the obtained coating film, and after the test, evaluation was determined based on the number of squares remaining without peeling. When no peeling was observed, the value was 100, indicating that the coating film had excellent recoating properties. Conversely, when all are peeled, the value is 0, indicating that the coating film has poor recoating properties.

Example 8 The powder coating (X-1) obtained in Example 1 was used in accordance with a so-called multilayer coating film forming method as described below.
Two coats and one bake coating were performed to form a coating film, and various performances were evaluated and judged. The object to be coated substrate at that time, was used subjecting the following pretreatment.

That is, "Bondelight # 3030"
An epoxy resin-based cationic electrodeposition paint is electrodeposited on mild steel sheet treated with [trade name of zinc phosphate treating agent manufactured by Nippon Parkerizing Co., Ltd.], and then,
An amino-polyester resin-based intermediate paint was used.

First, the aqueous metallic paint [I-1] obtained in Reference Example 16 was dried under a coating atmosphere at a temperature of 25 ° C. and a relative humidity of 65 to 70% to a dry film thickness of 2%.
Coating was carried out twice in each case so as to obtain 0 m.

Between these two coatings, setting was performed for 2 minutes. At the time of the first coating, the air pressure of the spray gun was set to 5 kg / cm ² , the flow rate of the coating was set to 400 m / min, and at the time of the second coating, the flow rate of the coating was set to 200 m / min. The distance from the spray gun was 40 cm.

The substrate to be coated was held so that the surface to be coated on the substrate to be coated was always vertical.

After the two coatings, the coating was air-dried at a temperature of 30 ° C. for 5 minutes. Next, after cooling to room temperature, the powder coating (X-1) was applied using an electrostatic spray coating machine for powder coating, and then the coated plate was heated at 140 ° C. for 20 minutes. By baking, a test plate on which a cured coating film was formed was obtained. Table 6 shows the evaluation results of the coating films.

Examples 9 to 12 Except that the powder coating and the water-based metallic coating used were changed as shown in Table 6, a test plate having a cured coating film was obtained in the same manner as in Example 9. Was. Table 6 shows the evaluation results of the coating films.

Comparative Example 2 A test plate having a cured coating film was obtained in the same manner as in Example 8 except that the powder coating (X-8) prepared in Comparative Reference Example 2 was used. Table 6 shows the evaluation results of the coating films.

[0159]

[Table 8]

[0160]

[Table 9]

<< Procedure for Evaluation of Physical Properties of Coating Film >>

Film thickness: Measured with an electromagnetic film thickness meter.

Smoothness: Five-level evaluation judgment was made by visual judgment.

Evaluation “5”: In the case of a very smooth and smooth coating surface Evaluation “4”: In the case of a small round Evaluation “3”: In the case of a large round Evaluation “2”: There is a large round, fine dust When a lot of skin is observed Evaluation "1"; When there is a large round, fine dust skin is remarkable, and the appearance of the coating film is significantly impaired

Scratch resistance: The cleanser resistance was measured. The measuring method was such that a 5% aqueous dispersion of cleanser was immersed in flannel cloth and rubbed 50 times.

Then, the 20-degree gloss (20-degree specular reflectance:%) before and after the rubbing was measured, and the value was determined.
The evaluation was evaluated in five steps based on the so-called gloss retention (%).

Evaluation “5”; Gloss retention of 90% or more Evaluation “4”; Gloss retention of 80% or more and less than 90% Evaluation “3”; Gloss retention of 65% or more and less than 80% Evaluation “2”; Gloss retention 50% or more and less than 65% Evaluation "1"; Gloss retention less than 50%

Recoating property: The coating film baked and cured at 140 ° C. for 20 minutes is overbaked at 140 ° C. for 20 minutes, and then the powder coating used for forming the coating film on the coated plate is electrostatically applied again. Baked at 140 ° C. for 20 minutes. A cross-cut adhesion test of 2 mm width and 10 × 10 was performed on the obtained coating film, and after the test, evaluation was determined based on the number of squares remaining without peeling. When no peeling was observed, the value was 100, indicating that the coating film had excellent recoating properties. Conversely, when all are peeled, the value is 0, indicating that the coating film has poor recoating properties.

[0169]

【The invention's effect】

As has been clarified in detail above, the powder coating composition and the coating film forming method according to the present invention are particularly excellent in recoating property and, in addition, have good smoothness and coating property. The various effects aimed at by the present invention, which are excellent in film gloss and scratch resistance, are exhibited.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C09D 101/10 C09D 101/10 F term (Reference) 4J026 AA02 BA05 BA09 BA10 BA11 BA16 BA19 BA20 BA25 BA27 BA29 BA30 BA31 BA32 BA40 BA41 BA43 BA50 BB01 BB02 BB07 BB08 DB02 DB12 DB15 DB26 GA08 4J036 AK11 AK14 BA02 DB15 DB17 DB18 DB21 DB22 FA01 FB10 FB11 FB13 FB18 JA03 4J038 BA042 DB211 DB212 DB221 DB222 MA13 NA12 PA04 PB05P

Claims (8)

[Claims] 1. An epoxy group-containing vinyl copolymer having a glass transition temperature of 40 ° C. or more (A), a cellulose ester (B), and an epoxy group-containing vinyl copolymer having a glass transition temperature of 0 ° C. or less (C). And a polyvalent carboxylic acid (D) as an essential component. 2. The method according to claim 1, wherein the epoxy group-containing vinyl copolymer (A) is used in the presence of the cellulose ester (B).
The powder coating composition according to claim 1, which is obtained by polymerizing an epoxy group-containing vinyl monomer and other vinyl monomers. 3. The epoxy group-containing vinyl copolymer (A) is the same as the epoxy group-containing vinyl copolymer (A).
The SP value of the epoxy group-containing vinyl copolymer (A) is lower than that of the epoxy group-containing vinyl copolymer (C) by 1.0 to 4.0. Or 2
The powder coating composition according to item 1. 4. The powder coating composition according to claim 1, wherein the epoxy equivalent of the epoxy group-containing vinyl copolymer (C) is 800 or less. 5. A coating film forming method for forming a single-layer or multiple-layer coating film on an object to be coated, wherein the powder coating composition according to claim 1 is coated with a top coat. A method for forming a coating film, which is used as a paint. 6. A method for forming a coating film comprising applying a base coat paint [I] on an object to be coated, and further applying a top coat paint [II] thereon, wherein the top coat paint [II] is used. A method for forming a coating film, comprising using the powder coating composition according to any one of claims 1 to 4. 7. The method according to claim 6, wherein the base coat paint [I] is a colored base coat paint, and the top coat paint [II] is a transparent top coat paint. 8. A coated article on which a coating film is formed by the coating film forming method according to any one of claims 5 to 7.