JP2021014503A - Powder coating composition - Google Patents

Abstract

To provide a powder coating composition capable of forming a matte coating film having excellent finish properties, coating film hardness, weatherability and adhesiveness to a base material and having a small glossiness fluctuation range due to a film thickness variation.SOLUTION: There is provided a powder coating composition which comprises: a binder component containing a hydroxyl group-containing fluororesin (A), a polyester resin (B) having an acid value of 10 mgKOH/g or less and a hydroxyl value of 10 to 100 mgKOH/g and a blocked polyisocyanate (C); acrylic fine particles (D) having a volume average particle diameter of 21 to 45 μm; calcium carbonate (E) having a volume average particle diameter of 10 to 40 μm; and a color pigment (F) and contains 20 to 55 pts.mass of the component (A), 20 to 55 pts.mass of the component (B), 10 to 40 pts.mass of the component (C), 1 to 40 pts.mass of the acrylic fine particles (D), 1 to 70 pts.mass of the calcium carbonate (E) and 0.5 to 100 pts.mass of the color pigment (F) based on 100 pts.mass of the total solid content of the binder.SELECTED DRAWING: None

Description

The present invention relates to a powder coating composition capable of obtaining a matte coating film having excellent finishability, coating film hardness, weather resistance and adhesion, and having a small gloss fluctuation range due to film thickness fluctuation.

In recent years, there has been an increasing demand in the paint industry for powder paints that do not contain volatile organic compounds at all, do not require exhaust treatment or wastewater treatment, and can be recovered and reused as alternatives to conventional organic solvent-type paints. ..

For example, Patent Document 1 describes a matte powder containing (A) fluororesin, (B) polyester resin, (C) pigment, (D) crosslinked resin particles, (E) epoxy resin, and (F) isocyanate compound. The coating composition is disclosed. Further, it is disclosed that a matte coating film or a coating film having excellent finishability can be obtained by using the (D) crosslinked resin particles. However, although the matte coating film obtained from the powder coating composition described in Patent Document 1 has excellent adhesion to a substrate, it may have insufficient weather resistance. In addition, the matte coating film obtained from the powder coating composition may cause yuzu skin.

In addition, Patent Document 2 describes a powder coating composition containing (A) a fluororesin, (B) a polyester resin, (C) a pigment, and (D) core-shell type acrylic resin particles having a functional group on the surface. The thing is disclosed. However, with the powder coating composition described in Patent Document 2, it was not possible to obtain a matte coating film having no yuzu skin and having a good finish.

Further, the coating film obtained by the powder coating composition described in Patent Documents 1 and 2 has a problem that the gloss varies due to the fluctuation of the film thickness, and a matte coating film having a stable glossiness cannot be obtained.

Against this background, there is a demand for a powder coating composition capable of forming a matte coating film having excellent finishability, coating film hardness, weather resistance, and adhesion to a substrate, and having a small gloss fluctuation range due to film thickness fluctuation. Was there.

Japanese Unexamined Patent Publication No. 2012-41383 Japanese Unexamined Patent Publication No. 2013-76019

An object to be solved by the present invention is to provide a powder coating composition capable of forming a matte coating film having excellent finishability, coating film hardness, weather resistance and adhesion, and having a small gloss fluctuation range due to film thickness fluctuation. Is.

As a result of diligent studies to solve the above problems, the present inventors have made a hydroxyl group-containing fluororesin (A), a polyester resin (B) having an acid value of 10 mgKOH / g or less and a hydroxyl value of 10 to 100 mgKOH / g, and blocking. Powder coating material containing a binder component containing a polyisocyanate (C), acrylic fine particles (D) having a volume average particle diameter of 21 to 45 μm, calcium carbonate (E) having a volume average particle diameter of 10 to 40 μm, and a coloring pigment (F). We have found that the composition can solve the problem, and have completed the present invention.

That is, the present invention relates to the following aspects.

1. 1. Binder component containing hydroxyl group-containing fluororesin (A), polyester resin (B) having an acid value of 10 mgKOH / g or less and a hydroxyl value of 10 to 100 mgKOH / g, and blocked polyisocyanate (C), having a volume average particle diameter of 21 to 45 μm. A powder coating composition containing acrylic fine particles (D), calcium carbonate (E) having a volume average particle diameter of 10 to 40 μm, and a coloring pigment (F), based on a total solid content of 100 parts by mass of the binder component. The component (A) is 20 to 55 parts by mass, the component (B) is 20 to 55 parts by mass, the component (C) is 10 to 40 parts by mass, the acrylic fine particles (D) are 1 to 40 parts by mass, and calcium carbonate. A powder coating composition containing 1 to 70 parts by mass of (E) and 0.5 to 100 parts by mass of the coloring pigment (F).

2. 2. A coated article having a 60-degree mirror surface gloss of 50 or less obtained by coating the powder coating composition according to the above item 1.

The powder coating composition of the present invention is excellent in finishability, coating film hardness, weather resistance and adhesion, has a small gloss fluctuation range due to film thickness variation, and has a 60-degree mirror surface gloss of 50 or less, preferably 30 or less. It is possible to provide a painted article having a matte coating film of.

The powder coating composition of the present invention is a binder containing a hydroxyl group-containing fluororesin (A), a polyester resin (B) having an acid value of 10 mgKOH / g or less and a hydroxyl value of 10 to 100 mgKOH / g, and a blocked polyisocyanate (C). It contains components, acrylic fine particles (D) having a volume average particle diameter of 21 to 45 μm, calcium carbonate (E) having a volume average particle diameter of 10 to 40 μm, and a coloring pigment (F). The details will be described below.

Hydroxy group-containing fluororesin (A)
The hydroxyl group-containing fluororesin (A) (hereinafter, also referred to as “component (A)”) is a polymer having a polymerization unit based on a fluoroolefin. As the component (A), various hydroxyl group-containing fluororesins known for paints can be used. The hydroxyl group-containing fluororesin (A) may be a copolymer of a fluoroolefin and a monomer having a hydroxyl group, but in addition to a polymerization unit based on the fluoroolefin and the monomer having a hydroxyl group, a single amount copolymerizable with these monomers. It may be a copolymer containing a polymerization unit based on the body.

The hydroxyl group-containing fluororesin (A) can form a crosslinked bond by reacting the hydroxyl group contained in the resin with the blocked polyisocyanate (C). The hydroxyl group-containing fluororesin (A) may have a group such as a thiol group, a carboxyl group, an amino group, an amide group, an epoxy group, an isocyanate group and an allyl group in addition to the hydroxyl group.

The hydroxyl value of the hydroxyl group-containing fluororesin (A) is 10 to 200 mgKOH / g, preferably 20 to 150 mgKOH / g, and the number average molecular weight is in the range of 1,000 to 30,000, preferably 3,000 to 15,000. desirable.

One type of the hydroxyl group-containing fluororesin (A) may be used, or two or more types may be used in combination. When the hydroxyl group-containing fluororesin (A) is a mixture of two or more kinds, the hydroxyl value and the number average molecular weight of each fluororesin constituting the mixture are within the above ranges for finishability and weather resistance. Is preferable.

In the present specification, the number average molecular weight is a value obtained by converting the number average molecular weight measured by gel permeation chromatography (GPC) with reference to the molecular weight of standard polystyrene. Specifically, "HLC8120GPC" (manufactured by Tosoh Corporation, trade name) is used in the measurement of the gel permeation chromatograph, and the columns are "TSKgel G-4000HXL", "TSKgel G-3000HXL", and "TSKgel G". -Measurement is performed under the conditions of mobile phase tetrahydrofuran, measurement temperature 40 ° C., flow velocity 1 mL / min, and detector RI using four "-2,500HXL" and "TSKgel G-2000HXL" (above, manufactured by Tosoh Corporation, trade name). be able to.

The hydroxyl group-containing fluororesin (A) in the present invention is a fluorine-containing copolymer containing a polymerization unit based on a fluoroolefin and a polymerization unit based on a monomer having a hydroxyl group.

Examples of the fluoroolefin include tetrafluoroethylene, vinylidene fluoride, chlorotrifluoroethylene, trifluoroethylene, hexafluoropropylene, pentafluoropropylene and the like. As the fluoroolefin, one type may be used, or two or more types may be used.

The content of the fluoroolefin-based polymerization unit in the hydroxyl group-containing fluororesin (A) is preferably 30 to 70 mol% with respect to the total polymerization units.

Examples of the monomer having a hydroxyl group include allyl alcohol, 2-hydroxyethyl vinyl ether, 3-hydroxypropyl vinyl ether, 4-hydroxybutyl vinyl ether, 4-hydroxycyclohexyl vinyl ether, 2-hydroxyethyl allyl ether, 3-hydroxypropyl allyl ether, and the like. 4-Hydroxybutyl allyl ether, 4-hydroxycyclohexyl allyl ether, 2-hydroxyethyl (meth) acrylate, hydroxyvinyl acetate, vinyl hydroxyisobutyrate, vinyl hydroxypropionate, vinyl hydroxybutyrate, vinyl hydroxyvalerate, 4-hydroxycyclohexyl Examples thereof include vinyl esters of hydroxy-substituted fatty groups such as vinyl carboxylate.

The content of the polymerization unit based on the monomer having a hydroxyl group in the hydroxyl group-containing fluororesin (A) is preferably 1 to 50 mol% with respect to the total polymerization units.

A monomer H other than the above may be copolymerized with the hydroxyl group-containing fluororesin (A). Examples of the monomer H include alkyl vinyl ethers having a cycloalkyl group or a branched alkyl group, alkyl vinyl ethers having a linear alkyl group, vinyl ethers such as glycidyl vinyl ether, and vinyl silanes such as vinyl trimethoxysilane and vinyl triethoxysilane. , Vinyl esters of organic acids such as vinyl acetate, vinyl propionate, vinyl butyrate, alkylallyl ethers such as ethylallyl ether, propylallyl ether and butylallyl ether, olefins such as ethylene, propylene and butylene. These monomers may be used alone or in combination of two or more.

Examples of the alkyl vinyl ether having a cycloalkyl group or a branched alkyl group include cyclohexyl vinyl ether, cyclopentyl vinyl ether, 2-ethylhexyl vinyl ether, tert-butyl vinyl ether, isobutyl vinyl ether, 3-methylbutyl vinyl ether and the like.
Examples of the alkyl vinyl ether having a linear alkyl group include methyl vinyl ether, ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, and pentyl vinyl ether.

As the hydroxyl group-containing fluororesin (A), a commercially available product can be used, and a copolymer of fluoroolefins such as Lumiflon (trade name, manufactured by Asahi Glass Co., Ltd.) and vinyl ethers has good paint stability and weather resistance. Is preferable in that

Polyester resin (B)
The polyester resin (B) having an acid value of 10 mgKOH / g or less and a hydroxyl value of 10 to 100 mgKOH / g (hereinafter, may be abbreviated as "polyester resin (B)") used in the powder coating composition of the present invention is used. Usually, it can be produced by an esterification reaction or a transesterification reaction with a polybasic acid component and a polyhydric alcohol component. As the polybasic acid component, for example, an alicyclic polybasic acid component, an aliphatic polybasic acid component, an aromatic polybasic acid component, or the like can be used.

The alicyclic polybasic acid component generally includes a compound having one or more alicyclic structures (mainly 4- to 6-membered rings) and two or more carboxyl groups in one molecule, and an acid anhydride of the compound. And an esterified product of the compound. Examples of the alicyclic polybasic acid component include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, 3-. Alicyclic polyvalent carboxylic acids such as methyl-1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid Anhydrous of these alicyclic polyvalent carboxylic acids; lower alkyl esterified products of these alicyclic polyvalent carboxylic acids and the like. The alicyclic polybasic acid component can be used alone or in combination of two or more.

Examples of the alicyclic polybasic acid component include 1,2-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid anhydride, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and 4-cyclohexene-. 1,2-Dicarboxylic acid and 4-cyclohexane-1,2-dicarboxylic acid anhydride can be preferably used. Of the above, 1,2-cyclohexanedicarboxylic acid and 1,2-cyclohexanedicarboxylic acid anhydride can be particularly preferably used from the viewpoint of hydrolysis resistance.

The aliphatic polybasic acid component is generally an aliphatic compound having two or more carboxyl groups in one molecule, an acid anhydride of the aliphatic compound, and an esterified product of the aliphatic compound, for example, Kohaku. Aliphatic polyvalent carboxylic acids such as acids, glutaric acid, adipic acid, pimeric acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassic acid, octadecanedioic acid, citric acid; Anhydrous of valent carboxylic acid; lower alkyl esterified products of these aliphatic polyvalent carboxylic acids and the like. The aliphatic polybasic acid component can be used alone or in combination of two or more.

As the aliphatic polybasic acid component, it is preferable to use a dicarboxylic acid having an alkylene chain having 4 to 18 carbon atoms. Examples of the dicarboxylic acid having an alkylene chain having 4 to 18 carbon atoms include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassic acid, octadecanedioic acid and the like. Among them, adipic acid can be preferably used. The aromatic polybasic acid component is generally an aromatic compound having two or more carboxyl groups in one molecule, an acid anhydride of the aromatic compound, and a lower alkyl esterified product of the aromatic compound. For example, aromatic polyvalent carboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, trimellitic acid, pyromellitic acid; and anhydrides of these aromatic polyvalent carboxylic acids. Examples thereof include lower alkyl esterified products of these aromatic polyvalent carboxylic acids. The aromatic polybasic acid component can be used alone or in combination of two or more.

As the polyhydric alcohol component, a polyhydric alcohol having two or more hydroxyl groups in one molecule can be preferably used. Examples of the polyhydric alcohol include alicyclic diols, aliphatic diols, aromatic diols, and trihydric or higher polyhydric alcohols.

The alicyclic diol is generally a compound having one or more alicyclic structures (mainly 4- to 6-membered rings) and two hydroxyl groups in one molecule. Examples of the alicyclic diol include dihydric alcohols such as 1,4-cyclohexanedimethanol, tricyclodecanedimethanol, hydrogenated bisphenol A, and hydrogenated bisphenol F; these dihydric alcohols include ε-caprolactone and the like. Examples thereof include polylactone diols to which a lactone compound is added, and these can be used alone or in combination of two or more.

The aliphatic diol is generally an aliphatic compound having two hydroxyl groups in one molecule. Examples of the aliphatic diol include ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, and 2,3. -Butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-pentanediol, 1,5-pentanediol , 1,4-Pentanediol, 2,4-Pentanediol, 2,3-Dimethyltrimethylene glycol, Tetramethylene glycol, 3-Methyl-1,5-Pentanediol, 2,2,4-trimethyl-1,3 -Pentandiol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, 1,9-nonanediol, 1,10-decanediol, 1,12- Dodecanediol, neopentyl glycol; polyetherdiol compounds such as polyethylene glycol, polypropylene glycol and polybutylene glycol can be mentioned, and these can be used alone or in combination of two or more.

The aromatic diol is generally an aromatic compound having two hydroxyl groups in one molecule. Examples of the aromatic diol include an ester diol compound such as bis (hydroxyethyl) terephthalate; an alkylene oxide adduct of bisphenol A, and the like, and these can be used alone or in combination of two or more.

Examples of the trihydric or higher polyhydric alcohol include glycerin, trimethylolethane, trimethylolpropane, diglycerin, triglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, sorbitol, and mannit. Trivalent or higher alcohols; polylactone polyol compounds obtained by adding a lactone compound such as ε-caprolactone to these trihydric or higher alcohols; tris (2-hydroxyethyl) isocyanurate, tris (2-hydroxypropyl) isocyanurate, Examples thereof include tris (hydroxyalkyl) isocyanurate such as tris (2-hydroxybutyl) isocyanurate. Of these, trimethylolpropane is particularly preferable.

The production of the polyester resin (B) used in the present invention is not particularly limited, and can be carried out according to a usual method. For example, it is produced by reacting an acid component containing the polybasic acid component as an essential component and a polyhydric alcohol component in a nitrogen stream at 150 to 250 ° C. for 5 to 10 hours to carry out an esterification reaction or a transesterification reaction. can do.

In the esterification reaction or transesterification reaction, the acid component and the alcohol component may be added at once or may be added in several batches. Further, after first synthesizing the carboxyl group-containing polyester resin, a part of the carboxyl groups in the carboxyl group-containing polyester resin may be esterified using the alcohol component. Further, the hydroxyl group-containing polyester resin may be first synthesized and then reacted with an acid anhydride to half-esterify the hydroxyl group-containing polyester resin.

In the esterification or transesterification reaction, a catalyst may be used to accelerate the reaction. As the catalyst, known catalysts such as dibutyltin oxide, antimony trioxide, zinc acetate, manganese acetate, cobalt acetate, calcium acetate, lead acetate, tetrabutyl titanate, and tetraisopropyl titanate can be used.

Further, the polyester resin (B) can be modified with a fatty acid, a fat or oil, a monoepoxy compound, a monoalcohol compound, a polyisocyanate compound or the like during the preparation of the resin, or after the transesterification reaction or the transesterification reaction.

Examples of the fatty acids include palm oil fatty acid, cotton seed oil fatty acid, hemp seed oil fatty acid, rice bran oil fatty acid, fish oil fatty acid, tall oil fatty acid, soybean oil fatty acid, linseed oil fatty acid, tung oil fatty acid, rapeseed oil fatty acid, castor oil fatty acid, and dehydrated castor bean paste. Fatty acids such as oil fatty acids and safflower fatty acids; lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid and the like can be mentioned.

Examples of fats and oils include coconut oil, cottonseed oil, hemp seed oil, rice bran oil, fish oil, tall oil, soybean oil, flaxseed oil, tung oil, rapeseed oil, castor oil, dehydrated castor oil, safflower oil and the like.

Examples of the polyisocyanate compound used for the above modification include aliphatic diisocyanate compounds such as lysine diisocyanate, hexamethylene diisocyanate, and trimethylhexane diisocyanate; hydrogenated xylylene diisocyanate, isophorone diisocyanate, methylcyclohexane-2,4-diisocyanate, and methylcyclohexane. Alicyclic diisocyanate compounds such as −2,6-diisocyanate, 4,4′-methylenebis (cyclohexylisocyanate), 1,3- (isocyanatomethyl) cyclohexane; aromatics such as tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate Diisocyanate compound; organic polyisocyanate such as trivalent or higher valent polyisocyanate such as lysine triisocyanate itself, or an adduct of each of these organic polyisocyanates with polyhydric alcohol, low molecular weight polyester resin, water, etc. Examples thereof include cyclized polymers of organic diisocyanates (for example, isocyanurate) and billet-type adducts. These can be used alone or in combination of two or more.

The number average molecular weight of the polyester resin (B) is preferably 2,000 to 30,000, particularly in the range of 3,000 to 25,000, from the viewpoint of coating film hardness, processability, and finishability of the obtained coating film. Is preferable.

The acid value of the polyester resin (B) is 10 mgKOH / g or less, preferably 1 to 6 mgKOH / g from the viewpoint of finishability. The hydroxyl value is in the range of 10 to 100 mgKOH / g, preferably 20 to 70 mgKOH / g from the viewpoint of coating film hardness and adhesion.

Blocked polyisocyanate (C)
The blocked polyisocyanate (C) in the powder coating composition of the present invention is, for example, an aromatic compound having two or more isocyanate groups in one molecule, tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, naphthalene diisocyanate and the like. Group diisocyanate; aliphatic diisocyanate such as tetramethylene diisocyanate, hexamethylene diisocyanate, dimerate diisocyanate, lysine diisocyanate; alicyclic diisocyanate such as methylenebis (cyclohexylisocyanate), isophorone diisocyanate, methylcyclohexanediisocyanate, cyclohexanediisocyanate and cyclopentanediisocyanate; Biuret type adduct, allophanate type adduct, isocyanurate ring type adduct of polyisocyanate; these polyisocyanates and low molecular weight or high molecular weight polyol compounds (for example, acrylic polyol, polyester polyol, polyether polyol, etc.) are isocyanated. Examples thereof include a blocked polyisocyanate compound in which a free isocyanate group is blocked by a blocking agent for a polyisocyanate such as an isocyanate group-containing prepolymer formed by reacting with an excess of groups.

Examples of the blocking agent include phenol compounds, oxime compounds, active methylene compounds, lactam compounds, alcohol compounds, mercaptan compounds, acid amide compounds, imide compounds, amine compounds, imidazole compounds, urea compounds, and carbamates. Examples thereof include system compounds and imine compounds.

The powder coating composition of the present invention contains 100 parts by mass of a total solid content of the binder component containing the hydroxyl group-containing fluororesin (A), polyester resin (B), and blocked polyisocyanate (C). (A) 20 to 55 parts by mass, preferably 30 to 45 parts by mass, component (B) 20 to 55 parts by mass, preferably 30 to 45 parts by mass, and component (C) 10 to 40 parts by mass, preferably 15 to 15 to 40 parts by mass. 30 parts by mass is preferable from the viewpoint of coating film hardness and adhesion.

Acrylic fine particles (D)
The powder coating composition of the present invention is excellent in finishability, coating film hardness, weather resistance and adhesion by containing acrylic fine particles (D) having a volume average particle diameter of 21 to 45 μm, and is a matte coating film. Can be obtained.

The method for producing the acrylic fine particles (D) is not particularly limited, and is polymerizable unsaturated by a polymerization method known per se, for example, suspension polymerization, solution polymerization, emulsion polymerization, bulk polymerization, or the like. It can be obtained by reacting the monomers. Among these polymerization methods, suspension polymerization is particularly preferable.

Examples of the polymerizable unsaturated monomer include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth) acrylate. , Tart-butyl (meth) acrylate, 2-ethylhexyl acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, tridecyl (meth) acrylate, octadecyl (meth) acrylate, isostearyl (meth) acrylate, etc. 1 to 24 alkyl (meth) acrylates; styrene, vinyl acetate; acrylic acid, methacrylic acid, acrylonitrile, methacrylonitrile; carboxyl group-containing monomers such as maleic acid, maleic anhydride, crotonic acid, and itaconic acid; N, N Nitrogen-containing alkyl (meth) acrylates such as −dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, Nt-butylaminoethyl (meth) acrylate; acrylamide, methacrylicamide, N-methyl ( Meta) acrylamide, N-ethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N, N-dimethyl (meth) acrylamide, N, Polymerizable amides such as N-dimethylaminopropyl (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylamide; nitrogen such as 2-vinylpyridine, 1-vinyl-2-pyrrolidone, 4-vinylpyridine, allylamine Containing monomer: Multivalent such as 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, 2,3-dihydroxybutyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and polyethylene glycol mono (meth) acrylate. Monoesteride of alcohol and acrylic acid or methacrylic acid; hydroxyl group-containing monomer such as a compound obtained by ring-opening polymerization of ε-caprolactone on the monoesteride of polyhydric alcohol and acrylic acid or methacrylic acid; 2 pieces in 1 molecule Examples of the monomers having the above polymerizable unsaturated group can be mentioned.

These polymerizable unsaturated monomers can be used alone or in combination of two or more.

In the present specification, "(meth) acrylate" means acrylate or methacrylate, "(meth) acrylic acid" means acrylic acid or methacrylic acid, and "(meth) acrylamide" means acrylamide or methacrylic acid. Means amide.

It is desirable that the acrylic fine particles (D) used in the powder coating composition of the present invention are acrylic fine particles containing a copolymer of a monomer mixture containing methyl (meth) acrylate in order to improve weather resistance. Further, the acrylic fine particles (D) may be crosslinked.

The volume average particle diameter of the acrylic fine particles (D) is 21 to 45 μm, and more preferably 25 to 40 μm, so that a matte coating film having a 60-degree mirror surface gloss of 50 or less, preferably 30 or less, is excellent in finish. Suitable for obtaining. The volume average particle diameter of the acrylic fine particles (D) in the present specification was measured using a Microtrack MT3300 (Microtrack Bell, wet particle size distribution measuring device).

Specific examples of the commercially available acrylic fine particles (D) include Ganzpearl GB-22S (manufactured by Aika Kogyo Co., Ltd., trade name, volume average particle diameter 22 μm, acrylic resin particles), techpolymer SSX-127 ( Sekisui Kasei Kogyo Co., Ltd., trade name, volume average particle diameter 27 μm, polymethylmethacrylate resin particles), Techpolymer MBX-30 (Sekisui Kasei Kogyo Co., Ltd., trade name, volume average particle diameter 30 μm, polymethacrylic Methyl acid acid particles), Techpolymer MBX-40 (manufactured by Sekisui Kasei Kogyo Co., Ltd., trade name, volume average particle diameter 40 μm, polymethyl methacrylate resin particles), Techpolymer MB20X-30 (manufactured by Sekisui Kasei Kogyo Co., Ltd.) , Product name, volume average particle diameter 30 μm, polymethyl methacrylate resin particles), tough tick AR-650M (manufactured by Toyo Spinning Co., Ltd., trade name, volume average particle diameter 30 μm, polymethyl methacrylate resin particles), tough tick AR-650MX (Manufactured by Toyo Spinning Co., Ltd., trade name, volume average particle diameter 40 μm, polymethyl methacrylate resin particles) and the like.

The blending ratio of the acrylic fine particles (D) is acrylic with respect to 100 parts by mass of the total solid content of the binder component containing the hydroxyl group-containing fluororesin (A), polyester resin (B) and blocked polyisocyanate (C). When the system fine particles (D) are in the range of 1 to 40 parts by mass and further 5 to 25 parts by mass, a matte coating film having excellent finishability, coating film hardness, weather resistance and adhesion to a substrate can be obtained. Is suitable for

Further, if the blending amount of the acrylic fine particles (D) is less than 1 part by mass, a matte coating film may not be obtained, and if the blending amount of the acrylic fine particles (D) exceeds 20 parts by mass, the finished product is finished. May impair sex and weather resistance.

Calcium carbonate (E)
The powder coating composition of the present invention is excellent in finishability, coating film hardness, weather resistance and adhesion by containing calcium carbonate (E) having a volume average particle diameter of 10 to 40 μm, and has gloss due to film thickness variation. A matte coating film having a small fluctuation range can be obtained.

The volume average particle size of calcium carbonate (E) is in the range of 10 to 40 μm, preferably in the range of 12 to 35 μm, and further in the range of 15 to 30 μm for finishability and gloss due to film thickness variation. It is particularly preferable to obtain a matte coating film having a small fluctuation range.

The volume average particle size was measured using a Microtrack MT3300 (Microtrack Bell, wet particle size distribution measuring device).

The blending ratio of calcium carbonate (E) is based on 100 parts by mass of the total solid content of the binder component containing the hydroxyl group-containing fluororesin (A), polyester resin (B) and blocked polyisocyanate (C). ) Is in the range of 1 to 70 parts by mass, further 10 to 50 parts by mass, and more particularly 15 to 40 parts by mass, which is excellent in finishability, coating film hardness, weather resistance, and adhesion to a substrate. It is suitable for obtaining a matte coating film having a small range of gloss fluctuation due to fluctuation.

Color pigment (F)
Examples of the coloring pigment (F) include titanium dioxide, carbon black, quinacridone, diketopyrrolopyrrole, isoindolinone, indanslone, perylene, perinone, anthraquinone, dioxazine, benzoimidazolone, triphenylmethanequinophthalone, and anthra. Pyrimidine, yellow lead, pearl mica, transparent pearl mica, colored mica, interfering mica, phthalocyanine, halogenated phthalocyanine, azo pigments (azomethine metal complex, condensed azo, etc.), iron oxide, copper phthalocyanine, condensed polycyclic pigments, etc. be able to.

Specific examples of the commercially available titanium dioxide pigment include Ti-Pure R960 (manufactured by DuPont, trade name), Typake CR-95 (manufactured by Ishihara Sangyo Co., Ltd., trade name) and the like.

The amount of the coloring pigment (F) to be blended is 100 parts by mass in total of the solid content of the binder component containing the hydroxyl group-containing fluororesin (A), the polyester resin (B) and the blocked polyisocyanate (C). It is preferable that F) is contained in an amount of 0.5 to 100 parts by mass, preferably 1 to 60 parts by mass, from the viewpoint of finishability and weather resistance.

Constituent Pigments The powder coating composition of the present invention may contain known extender pigments, if necessary. Examples of the extender pigment include barium sulfate, hydrous magnesium silicate (talc), magnesium carbonate, calcium sulfate (gypsum), diatomaceous earth, mica (mica powder), silica, and Neuburg diatomaceous earth.

When the extender pigment is blended, the blending amount thereof is based on 100 parts by mass of the total solid content of the binder component containing the hydroxyl group-containing fluororesin (A), polyester resin (B) and blocked polyisocyanate (C). It is desirable to contain 1 to 50 parts by mass, preferably 2 to 30 parts by mass of the pigment from the viewpoint of improving the finish of the obtained matte coating film.

Other Ingredients The powder coating composition of the present invention contains, as other ingredients, a rust preventive pigment, a surface conditioner, a fluidity adjuster, an acrylic resin, a phenol resin, an epoxy resin, a silicone resin, and a curing catalyst, if necessary. , Antifoaming agent, pigment dispersant, ultraviolet absorber, light stabilizer, antioxidant, magnetic powder, leveling agent, anti-armpit agent such as benzoin, plasticizer, charge control agent, silane coupling agent, etc. Can be done.

Examples of the rust preventive pigment include zinc oxide, a phosphate compound, a phosphate compound, a molybdenate compound, a bismuth compound, and metal ion exchange silica.

Examples of the curing catalyst include metal compounds such as tin and bismuth, organic acid compounds, and organic base compounds.

Examples of the epoxy resin include bisphenol A type diglycidyl ether resin, bisphenol F type diglycidyl ether resin, aminoglycidyl ether resin, bisphenol AD type diglycidyl ether resin, novolak type epoxy resin and the like. Examples of the novolac type epoxy resin include phenol novolac type epoxy resin and cresol novolac type epoxy resin. From the viewpoint of weather resistance of the obtained coating film, the content of the epoxy resin is preferably less than 1 part by mass with respect to 100 parts by mass of the powder coating composition of the present invention. In the composition of the present invention, a coating film having sufficient adhesion to the substrate can be obtained even when the epoxy resin is not contained.

Commercially available products of the surface conditioner include Acronal 4F (manufactured by BASF, trade name), Polyflow S (manufactured by Kyoeisha Chemical Co., Ltd., trade name), Regifflow LV, Regifflow P67 (above, manufactured by ESTRONCHEMICAL, trade name), Modaflow III (manufactured by Monsanto, trade name) and the like are preferably used.

As the fluidity adjusting agent, hydrophobic silica, hydrophilic silica, aluminum oxide and the like can be applied.

The method for producing the powder coating composition of the present invention is not particularly limited, and a known method can be adopted. For example, hydroxyl group-containing fluororesin (A), polyester resin (B), blocked polyisocyanate (C), acrylic fine particles (D), calcium carbonate (E), coloring pigment (F), and, if necessary, constitution. The pigment and other components can be produced by dry-blending with a mixer, blender or the like, then heating, melting and kneading, cooling, coarsely pulverizing, finely pulverizing, and filtering.

Further, for example, a hydroxyl group-containing fluororesin (A), a polyester resin (B), a blocked polyisocyanate (C), calcium carbonate (E), a coloring pigment (F), and, if necessary, an extender pigment and other components. May be produced by dry-blending with a mixer, blender or the like, heat-melting and kneading, cooling, and then dry-blending the acrylic fine particles (D), coarsely pulverizing, finely pulverizing, and filtering.

Coating Film Forming Method The powder coating composition of the present invention can be applied to a conventionally used substrate. Examples of the base material include zinc, iron, aluminum, magnesium, steel and alloys thereof, metal base materials such as zinc-plated steel plates, those having a chemical conversion coating formed on their metal surfaces, and these metal surfaces. Examples thereof include those that have been anodized, and coated metal substrates that have been subjected to primer coating, electrodeposition coating, or the like, if necessary, on these metal substrates. Examples of the chemical conversion treatment liquid used for forming the chemical conversion treatment coating include a phosphate treatment liquid, a zirconium treatment liquid, and a chromate treatment liquid.

The powder coating composition of the present invention can be coated by an electrostatic powder coating method, specifically, a corona charging type, a triboelectric charging type, or the like, and has a dry film thickness of 20 to 150 μm, preferably a dry film. It can be coated in a thickness range of 30 to 80 μm. The baking of the powder coating composition of the present invention can be carried out at 150 to 250 ° C. for 10 to 60 minutes, preferably 170 to 230 ° C. for 10 to 30 minutes.

Hereinafter, the present invention will be described in more detail with reference to Production Examples, Examples and Comparative Examples, but the present invention is not limited thereto. In each example, "part" indicates a mass part and "%" indicates a mass%.

(Production Example 1) Acrylic fine particle No. Production Example of 1 According to the following steps 1 and 2, the acrylic fine particle No. I got 1.
Step 1: Synthesis of polyacrylonitrile-based resin before pulverization An aqueous solution prepared by dissolving 10 parts of polyvinyl alcohol (PVA217 manufactured by Kuraray), 10 parts of sodium sulfate, and 1 part of copper sulfate / pentahydrate in 778 parts of deionized water is made of glass. Charge in the reaction tank. Next, 160 parts of acrylonitrile, 40 parts of methyl methacrylate, and 2 parts of 2,2'-azobis (2-methylvaleronitrile) dissolved as a catalyst were added to the reaction vessel as a monomer, and the mixture was stirred. An aqueous dispersion of a polyacrylonitrile-based resin was obtained by raising the liquid temperature to 50 ° C. and keeping the temperature for 5 hours. Then, the aqueous dispersion of the polyacrylonitrile resin was solid-liquid separated and dried in a hot air dryer at 70 ° C. to obtain a polyacrylonitrile resin.

Step 2: Production of acrylic fine particles of resin by crushing The polyacrylonitrile-based resin obtained in step 1 is crushed with a vertical mill (manufactured by Ishikawajima Harima Heavy Industries, SH-75 type), and acrylic fine particles with a volume average particle diameter of 24 μm No. .. I got 1.

(Production Example 2) Acrylic fine particle No. Production Example of No. 2 Acrylic fine particle No. I got 2.

Step 1: Synthesis of polymethylmethacrylate resin before crushing An aqueous solution prepared by dissolving 7 parts of polyvinyl alcohol (manufactured by Kuraray, PVA217), 10 parts of sodium sulfate, and 1 part of copper sulfate pentahydrate in 831 parts of deionized water. Place in a glass reaction tank. Next, 135 parts of methyl methacrylate, 15 parts of ethylene glycol dimethacrylate, and 1 part of 2,2'-azobis (2-methylvaleronitrile) dissolved as a catalyst were added to the reaction vessel as a monomer, and the mixture was stirred. While raising the liquid temperature to 50 ° C. and keeping the temperature for 5 hours, an aqueous dispersion of a polymethyl methacrylate-based resin was obtained. Then, the polymethyl methacrylate-based resin was dried in a hot air dryer at 70 ° C. to obtain a polymethyl methacrylate-based resin.

Step 2: Production of acrylic fine particles of resin by crushing The polymethyl methacrylate-based resin obtained in step 1 is crushed with a vertical mill (manufactured by Ishikawajima Harima Heavy Industries, SH-75 type), and acrylic having a volume average particle diameter of 18 μm. Fine particle No. I got 2.

Examples and Comparative Examples
Example 1 Powder coating composition No. Production of Lumiflon 710 (Note 1) 41 parts (solid content), Iupica Coat GV-560 (Note 2) 41 parts (solid content), Bestagon B1530 (Note 5) 18 parts (solid content), Techpolymer MBX-30 (solid content) Note 9) 10 parts (solid content), Ti-PureR960 (Note 16) 35 parts, heavy calcium carbonate FP-300 (Note 19) 15 parts, Polyflow S (Note 22) 0.8 parts (solid content) and 0.6 part of benzoin was put into a high speed mixer (manufactured by Fukae Kogyo Co., Ltd., trade name, capacity 2 liters), and stirred uniformly for 1 minute under the conditions of agitator 500 rpm and chopper 4000 rpm.

Next, the mixture was melt-kneaded at 120 ° C. using an extrusion kneader (Busconider PR46, manufactured by Buss AG, trade name) and discharged into a metal vat. After cooling to 50 ° C. or lower, finely pulverized with a hammer type impact crusher and classified with a wire mesh of 150 mesh, the powder coating composition No. 1 having an average particle diameter of 40 μm was obtained. 1 was manufactured.

Examples 2 to 17 Powder coating composition No. 2-No. Production No. 1 of each powder coating composition No. 17 was carried out in the same manner as in Example 1 except that the blending contents of Table 1 and Table 1 were continued. 2-No. 17 was manufactured.

Comparative Examples 1 to 17 Powder coating composition No. 18-No. Production of No. 34 Each powder coating composition No. 34 was prepared in the same manner as in Example 1 except that the contents of Table 2 and Table 2 were continued. 18-No. 34 was manufactured.

(Note 1) Lumiflon 710: manufactured by Asahi Glass Co., Ltd., trade name, hydroxyl group-containing fluororesin, which is a copolymer of fluoroolefins and vinyl ethers, hydroxyl value 46 mgKOH / g
(Note 2) Yupika Coat GV-560: Made by Japan U-Pica Company, trade name, polyester resin, acid value 5 mgKOH / g, hydroxyl value 50 mgKOH / g
(Note 3) Finedec A-239-X: manufactured by DIC Corporation, trade name, polyester resin, acid value 14 mgKOH / g, hydroxyl value 22 mgKOH / g
(Note 4) Polyester resin A: Made in-house, acid value 20 mgKOH / g, hydroxyl value 50 mgKOH / g
(Note 5) Bestagon B1530: Degussa, trade name, isophorone diisocyanate blocked with ε-caprolactam (Note 6) JER 1001: Mitsubishi Chemical's bisphenol A type epoxy resin Epoxy equivalent 450-500, softening point 64 ° C
(Note 62) JER 1004: Mitsubishi Chemical's bisphenol A type epoxy resin Epoxy equivalent 875-975, softening point 97 ° C.
(Note 7) Ganzpearl GB-22S: Aika Kogyo Co., Ltd., trade name, volume average particle diameter 22 μm, acrylic cross-linked resin particles (Note 8) Techpolymer SSX-127: Sekisui Kasei Kogyo Co., Ltd., trade name , Volume average particle diameter 27 μm, Polymethyl methacrylate-based cross-linked resin particles (Note 9) Techpolymer MBX-30: Sekisui Kasei Kogyo Co., Ltd., trade name, Volume average particle diameter 30 μm, Polymethyl methacrylate-based cross-linked resin particles (Note 10) Techpolymer MBX-40: Sekisui Kasei Kogyo Co., Ltd., trade name, volume average particle diameter 40 μm, polymethyl methacrylate-based crosslinked resin particles (Note 11) Tuftic AM: Toyo Spinning Co., Ltd., trade name , Volume average particle diameter 10 μm, Polyacrylic nitrile resin particles (Note 12) Ganzpearl GM10K: Aika Kogyo Co., Ltd., trade name, Volume average particle diameter 10 μm, Polypolymethyl methacrylate resin particles (Note 13) Tuftic AR650ML: Toyo Spinning Co., Ltd. Company, trade name, average particle size 80 μm, polymethyl methacrylate resin particles (Note 14) Tuftic AR650L: manufactured by Toyo Spinning Co., Ltd., trade name, average particle size 100 μm, polymethyl methacrylate resin particles (Note 15) Tuftic FH -S0005: Made by Toyo Spinning Co., Ltd., trade name, volume average particle size 5 μm
(Note 16) Ti-PureR960: Chemours Co., Ltd., product name, titanium white (Note 17) Typek CR-97: Ishihara Sangyo Co., Ltd., product name, titanium white (Note 18) Calcium carbonate # 200: Sankyo Made by Seiko Co., Ltd., trade name, volume average particle diameter 4 μm
(Note 19) Heavy calcium carbonate FP-300: manufactured by Calfan, trade name, volume average particle diameter 27 μm
(Note 20) Barium sulfate W-1, manufactured by Takehara Chemical Industry Co., Ltd., trade name,
(Note 21) P talc: manufactured by Takehara Chemical Industry Co., Ltd., product name, talc (Note 22) Polyflow S: manufactured by Kyoeisha Chemical Co., Ltd., product name, surface conditioner
Making a test board
A zirconium-based chemical conversion treatment liquid was applied to a cold-rolled steel sheet (70 mm × 150 mm × 0.8 mm) to form a chemical conversion treatment film. Next, on the chemical conversion treatment film, each powder coating composition is subjected to electrostatic powder using an electrostatic coating machine PG-1 (manufactured by Asahi Sanac Co., Ltd., trade name) so that the dry film thickness becomes 40 μm. I painted it. Next, each test plate was obtained by heating and drying under the condition that the surface temperature of the object to be coated was 200 ° C. and the holding time was 20 minutes.

Coating film performance test
The above test plate was used and subjected to a coating film performance test according to the test conditions described below. The results are also shown in Tables 1 and 2.

(Note 23) Finishability: The finishability of the coating film was evaluated according to the following criteria.

◎ indicates that the coated surface is in good condition with no yuzu skin, glossiness, repellent, bumps, or dents.

○ indicates that some of the skin is yuzu, glossy, repellent, lumpy, or dented, but there is no problem in practical use.

In Δ, any of yuzu skin, glossy skin, repellent, bumps, and dents is recognized.

X indicates that any of yuzu skin, glossy skin, repellent, bumps, and dents is remarkable.

(Note 24) Weather resistance: An exposure test was conducted using a carbon arc lamp type accelerated weather resistance tester Sunshine Weather Meter (based on JIS K 5600-7-7), and the gloss retention rate for the coating film gloss before the exposure test. The weather resistance of the coating film was evaluated by the time when the value was 80%.

◎ indicates that the time when the gloss retention rate is less than 80% is 4,000 hours or more.

◯ indicates that the time when the gloss retention rate is less than 80% is 2,500 hours or more and less than 4,000 hours.

Δ indicates a time in which the gloss retention rate is less than 80% for 1,500 hours or more and less than 2,500 hours.

X indicates a time when the gloss retention rate is less than 80% and less than 1,500 hours.

(Note 25) Adhesion:
Using the above test plate, the test plate was immersed in warm water at 40 ° C. and pulled up after 240 hours according to JIS K 5600-6-2 (1999). Then, according to the JIS K 5600-5-6 (1999) grid-tape method, use a knife to reach the substrate on the coated surface of the coated plate at intervals of about 2 mm, 11 in parallel in each of the vertical and horizontal directions. The cuts of the book were made to form 100 goban stitches, a cellophane adhesive tape was attached to the surface thereof, and the goban stitch coated surface after the tape was rapidly peeled off was evaluated according to the following criteria.

In ◎, no peeling of the coating film is observed.

○ indicates that a part of the coating film on the corner of the knife scratch is slightly peeled off.

In Δ, 1 to 20 of the 100 Goban eyes are all peeled off.

X indicates that 21 or more of the 100 Goban eyes are all peeled off.

(Note 26) 60-degree mirror gloss: The degree of gloss of the test plate is measured according to the 60-degree mirror gloss of JIS K 5600-4-7 (1999), and the reflectance when the incident angle is 60 degrees is measured. , It was expressed as a percentage when the glossiness of the reference surface of the mirror surface glossiness was set to 100.

⊚ indicates that the 60-degree mirror glossiness is 1 or more and 30 or less.

◯ indicates that the 60-degree mirror glossiness exceeds 30 and is 50 or less.
Δ indicates that the 60-degree mirror glossiness exceeds 50 and is 70 or less.

X indicates that the 60-degree mirror glossiness exceeds 70.

(Note 27) 60-degree mirror gloss stability: The degree of gloss of the test plate is measured according to the 60-degree mirror gloss of JIS K 5600-4-7 (1999), and the reflectance when the incident angle is 60 degrees is measured. Then, it was expressed as a percentage when the glossiness of the reference surface of the mirror surface glossiness was set to 100. Each test plate having a dry film thickness of 100 μm was also prepared in the same manner as the above-mentioned test plate, and the difference in 60-degree mirror gloss between the 40 μm test plate and the 100 μm test plate was calculated.

⊚ indicates that the difference in glossiness is 5 or less.

◯ indicates that the difference in glossiness exceeds 5 and is 10 or less.
Δ indicates that the difference in glossiness exceeds 10 and is 15 or less.

X indicates that the difference in glossiness exceeds 15.

It is possible to provide a coated plate having a matte coating film which is excellent in finish property, coating film hardness, weather resistance and adhesion, and has a small gloss fluctuation range due to film thickness fluctuation.

Claims (2)

Binder component containing hydroxyl group-containing fluororesin (A), polyester resin (B) having an acid value of 10 mgKOH / g or less and a hydroxyl value of 10 to 100 mgKOH / g, and blocked polyisocyanate (C), having a volume average particle diameter of 21 to 45 μm. A powder coating composition containing acrylic fine particles (D), calcium carbonate (E) having a volume average particle diameter of 10 to 40 μm, and a coloring pigment (F), based on a total solid content of 100 parts by mass of the binder component. The component (A) is 20 to 55 parts by mass, the component (B) is 20 to 55 parts by mass, the component (C) is 10 to 40 parts by mass, the acrylic fine particles (D) are 1 to 40 parts by mass, and calcium carbonate. A powder coating composition containing 1 to 70 parts by mass of (E) and 0.5 to 100 parts by mass of the coloring pigment (F). A coated article having a 60-degree mirror surface gloss of 50 or less obtained by coating the powder coating composition according to claim 1.