JP5081608B2 - Multi-layer coating formation method - Google Patents

Description

  The present invention is a three-coat one-bake method comprising sequentially coating a first colored paint, a water-based second colored paint and a clear paint on an object to be coated, and simultaneously heat-curing the resulting three-layer coating film. By this, it is related with the method of forming the multilayer coating film which has the outstanding external appearance.

  As a method of forming a coating film on an automobile body, an electrodeposition coating film is formed on an object to be coated, and then an intermediate coating paint → baking cure → base coat paint coating → clear paint coating → baking cure 3 coat 2 bake ( 3C2B) The method of forming a multilayer coating film by the method has been widely adopted. However, in recent years, from the viewpoint of energy saving, the baking and curing step after coating the intermediate coating is omitted, and the electrodeposition coating is applied to the object to be coated. Then, a method of forming a multilayer coating film by a three-coat one-bake (3C1B) system in which an intermediate coating is applied, a base coating is applied, a clear coating is applied, and a baking and curing is attempted.

  However, since the coating by the 3C1B method tends to cause a mixed layer of the first colored coating film and the second colored coating film, the smoothness and sharpness of the resulting coating film are likely to be lower than the 3C2B method, In addition, when a paint containing a bright pigment is used as the second colored paint, there is a problem that a flip-flop property is deteriorated and metallic unevenness is likely to occur, and it is difficult to obtain a sufficient bright feeling.

  For example, Patent Document 1 discloses a coating film comprising a step of sequentially applying an intermediate coating, a base coating and a clear coating on an electrodeposited material, and a step of baking and curing the three layers formed at a time. In the forming method, as an intermediate coating material, 10 to 70% by mass of a hydroxyl group-containing resin, 10 to 70% by mass of a curing agent capable of reacting with a hydroxyl group, and 18 to 50 of a non-aqueous dispersion resin in a solid content ratio based on the total solid content of the resin. By using a paint having a volume shrinkage of 45% or less when it is cured at 140 ° C. for 30 minutes after coating, it has an excellent finished appearance. It is disclosed that a film can be formed. However, the coating film obtained by the coating film forming method may be inferior in smoothness, water resistance and flip-flop properties, or may have metallic unevenness, particularly when an aqueous coating material is used as the base coating material. There is a problem that sufficient smoothness, water resistance and flip-flop properties cannot be obtained.

  Further, Patent Document 2 discloses an acrylic resin emulsion, a curing agent, and an organic substance-treated titanium dioxide as a water-based intermediate coating in a three-coat one-bake coating method using an aqueous intermediate coating, an aqueous base coating, and a clear coating. It is disclosed that when a paint containing a pigment is used, a multilayer coating film excellent in chipping resistance and gloss can be formed. However, the coating film obtained by the coating film forming method has problems such as inferior smoothness, water resistance and flip-flop properties, and metallic unevenness.

  Further, Patent Document 3 discloses a method for forming a coating by a three-coat one-bake method using an organic solvent-type or non-aqueous dispersion-type thermosetting paint, a thermosetting aqueous metallic paint, and a transparent thermosetting paint. As a mold or non-water dispersion type thermosetting paint, a neutralized polycarboxylic acid resin having an acid value of 5 to 100 mg KOH / g and an amino resin are essential components, and the viscosity after coating is 10 poise (20 ° C. ) When using a coating that has been adjusted to the above, and applying a thermosetting water-based metallic paint on the coating film, a multilayered coating film with a uniform metallic feel and excellent gloss and sharpness It is disclosed that it can be formed. However, there is a problem that the coating film obtained by the coating film forming method may be inferior in smoothness and water resistance.

JP 2002-35677 A Japanese Patent Laid-Open No. 2004-289836 Japanese Patent Laid-Open No. 61-141969

  The main object of the present invention is to apply a first colored paint, a water-based second colored paint, and a clear paint on an object to be coated in sequence, and simultaneously heat cure the resulting three-layered multi-layer coating film. In the method for forming a multilayer coating film according to the present invention, it is preferable to provide a method capable of forming a coating film excellent in smoothness, sharpness and water resistance, particularly when the second colored paint contains a glitter pigment. An object of the present invention is to provide a method capable of forming a coating film having an excellent appearance with high flip-flop properties and little metallic unevenness.

  As a result of intensive studies to achieve the above-mentioned object, the present inventors, as a result of this, in the method for forming a multilayer coating film by the 3C1B method, a hydroxyl group-containing resin, a curing agent, and a specific polymer are used as the first colored paint. When a paint containing fine particles is used, even when an aqueous paint is used as the second colored paint, a multilayer coating film excellent in smoothness, sharpness and water resistance can be formed. It has been found that when the colored paint contains a bright pigment, a multi-layer coating film having an excellent appearance with high flip-flop properties and little metallic unevenness can be formed, and the present invention has been completed.

Thus, in the present invention, the first colored coating film, the second colored coating (X), the aqueous second colored coating (Y), and the clear coating (Z) are sequentially coated on the object to be coated. Comprising simultaneously baking and curing the colored coating and the clear coating,
The first colored paint (X) contains a hydroxyl group-containing resin (A), a curing agent (B) and polymer fine particles (C), and the polymer fine particles (C) are present in the presence of the polyester resin (a). The polymerizable unsaturated monomer (b) is an organic that dissolves the polyester resin (a) and the polymerizable unsaturated monomer (b) but does not substantially dissolve the polymer formed from the polymerizable unsaturated monomer (b). Obtained by polymerizing in a solvent,
The polyester resin (a) is obtained by the reaction of the acid component (a-1) and the alcohol component (a-2), and the acid component (a-1) and the alcohol component (a-2) The total amount of the acid component (a-1) and the alcohol component (a-2) is the total of the cyclic polybasic acid (a-1-1) and the alicyclic polyhydric alcohol (a-2-1). The present invention provides a multilayer coating film forming method characterized by containing at least 5 mol% as a reference.

  According to the multilayer coating film forming method of the present invention, a coating film excellent in smoothness, sharpness and water resistance is formed in the 3C1B system in which the first colored paint, the aqueous second colored paint and the clear paint are sequentially applied. can do. In particular, when an aqueous paint containing a bright pigment is used as the aqueous second colored paint, a multilayer coating film having an excellent appearance with high flip-flop properties and little metallic unevenness can be formed.

  Hereinafter, the multilayer coating film forming method of the present invention will be described in further detail in order for each step.

Embodiments of the Invention

Application of the first colored paint (X) According to the multilayer coating film forming method of the present invention, first, the first colored paint (X) is applied onto the article to be coated.

The material of the coating object to which the method of the present invention can be applied is not particularly limited, for example, iron, aluminum, brass, copper, stainless steel, tinplate, galvanized steel, alloyed zinc (Zn -Al, Zn-Ni, Zn-Fe, etc.) Metal materials such as plated steel; polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin Resin such as epoxy resin and various plastic materials such as FRP; inorganic materials such as glass, cement and concrete; wood; fiber materials (paper, cloth, etc.), among others, metal materials and plastic materials Is preferred.

  In addition, the object to which the method of the present invention can be applied is not particularly limited, and examples thereof include an outer plate portion of an automobile body such as a passenger car, a truck, a motorcycle, and a bus; an automobile part; An outer plate portion of an electric product can be used, and among them, an outer plate portion of an automobile body and an automobile part are preferable.

  The object to be coated may be one in which a surface treatment such as a phosphate treatment, a chromate treatment, or a complex oxide treatment is performed on the metal material or a metal surface such as a vehicle body formed from the metal material. Further, the object to be coated may be one in which an undercoat film such as various electrodeposition paints is formed on the metal material or the vehicle body, and in particular, the undercoat film is formed by a cationic electrodeposition paint. A vehicle body is particularly suitable.

First colored paint (X)
As the first colored paint (X) applied on the object to be coated, an organic solvent-type paint or aqueous paint containing a hydroxyl group-containing resin (A), a curing agent (B) and polymer fine particles (C) is used. can do.

Hydroxyl-containing resin (A)
The hydroxyl group-containing resin (A) is a resin having at least one hydroxyl group in one molecule, and the hydroxyl value is generally 2 to 300 mgKOH / g, particularly 5 to 250 mgKOH / g from the viewpoint of water resistance of the resulting coating film. g, more particularly in the range of 10 to 180 mg KOH / g is preferred.

  Further, the hydroxyl group-containing resin (A) can have an acid group in the molecule. Examples of the acid group include a carboxyl group, a sulfonic acid group, and a phosphoric acid group. Among them, it is preferable to have a carboxyl group. The acid value of the hydroxyl group-containing resin (A) is generally from 1 to 200 mgKOH / g, particularly from 2 to 150 mgKOH / g, more particularly from 3 to 100 mgKOH / g, from the viewpoint of storage stability of the paint and water resistance of the resulting coating film. It is preferable to be within the range.

  The content of the hydroxyl group-containing resin (A) is generally 2 to 95 parts by weight, particularly 20 to 70 parts by weight, more particularly 30 to 60 parts by weight, based on 100 parts by weight of the resin solid content in the first colored paint (X). It is preferable to be within the range of the part. Here, the resin solid content in the first colored paint (X) is the total amount of the hydroxyl group-containing resin (A), the curing agent (B), and the polymer fine particles (C).

Examples of the hydroxyl group-containing resin (A) include resins having a hydroxyl group, such as polyester resin, acrylic resin, polyether resin, polycarbonate resin, polyurethane resin, epoxy resin, and alkyd resin. It can be used in combination of more than one species. Among these, the hydroxyl group-containing resin (A) is preferably a hydroxyl group-containing polyester resin (A1) and / or a hydroxyl group-containing acrylic resin (A2), particularly a hydroxyl group-containing polyester resin (A1).

  The hydroxyl group-containing polyester resin (A1) can be usually produced by an esterification reaction or an ester exchange reaction of an acid component (a1-1) and an alcohol component (a1-2).

  As the acid component (a1-1), a compound usually used as an acid component in the production of a polyester resin can be used. For example, an aliphatic polybasic acid (a1-1-1), an alicyclic polybasic An acid (a1-1-2), an aromatic polybasic acid (a1-1-3), etc. can be used.

  The aliphatic polybasic acid (a1-1-1) generally includes 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. Specifically, for example, fats such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassic acid, octadecanedioic acid, citric acid, etc. An aliphatic polycarboxylic acid anhydride; an aliphatic polycarboxylic acid anhydride; a lower alkyl esterified product of the aliphatic polycarboxylic acid. These aliphatic polybasic acids can be used alone or in combination of two or more.

  The alicyclic polybasic acid (a1-1-2) is generally 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. Specifically, for example, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene -1,2-dicarboxylic acid, 3-methyl-1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid And alicyclic polyvalent carboxylic acids such as acids; anhydrides of the alicyclic polyvalent carboxylic acids; and lower alkyl esterified products of the alicyclic polyvalent carboxylic acids. These alicyclic polybasic acids can be used alone or in combination of two or more. As the alicyclic polybasic acid (a1-1-2), from the viewpoint of chipping resistance, 1,2-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic anhydride, 1,3-cyclohexanedicarboxylic acid, 1 , 4-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic anhydride, etc. are preferably used, among which 1,2-cyclohexanedicarboxylic acid and / or It is particularly preferred to use 1,2-cyclohexanedicarboxylic acid anhydride.

  The aromatic polybasic acid (a1-1-3) generally includes an aromatic compound having two or more carboxyl groups in one molecule, an acid anhydride of the aromatic compound, and an esterified product of the aromatic compound. Specifically, for example, aromatic polyvalent carboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, trimellitic acid, pyromellitic acid; An anhydride of a polyvalent carboxylic acid; a lower alkyl esterified product of the aromatic polyvalent carboxylic acid. These aromatic polybasic acids can be used alone or in combination of two or more. As the aromatic polybasic acid (a1-1-3), it is particularly preferable to use phthalic acid, phthalic anhydride, isophthalic acid, trimellitic acid, or trimellitic anhydride.

Moreover, as an acid component (a1-1), an aliphatic polybasic acid (a1-1-1), an alicyclic polybasic acid (a1-1-2), and an aromatic polybasic acid (a1-1-3) Acids other than these can also be used, and such acids are not particularly limited. For example, coconut oil fatty acid, cottonseed oil fatty acid, hempseed oil fatty acid, rice bran oil fatty acid, fish oil fatty acid, tall oil fatty acid, soybean oil fatty acid, Fatty acids such as linseed oil fatty acid, tung oil fatty acid, rapeseed oil fatty acid, castor oil fatty acid, dehydrated castor oil fatty acid, safflower oil fatty acid; lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, benzoic acid Acids, monocarboxylic acids such as p-tert-butylbenzoic acid, cyclohexane acid, 10-phenyloctadecanoic acid; lactic acid, 3-hydroxybutanoic acid, 3-hydroxy-4-ethoxy Such hydroxy carboxylic acids such as benzoic acid. These acid components can be used alone or in combination of two or more.

  As a hydroxyl-containing polyester resin (A1), content of the alicyclic polybasic acid (a1-1-2) in an acid component (a1-1) from a smoothness of a coating film obtained and a viewpoint of chipping resistance. Is a hydroxyl group-containing polyester resin (A1 ′) in the range of at least 30 mol%, in particular 50 to 100 mol%, more particularly 70 to 100 mol%, based on the total amount of the acid component (a1-1). It is preferable to do. Among these, from the viewpoint of chipping resistance of the obtained coating film, the hydroxyl group-containing polyester resin (A1 ′) is 1,2-cyclohexanedicarboxylic acid and / or 1 as the alicyclic polybasic acid (a1-1-2). It is preferable that the polyester resin be a hydroxyl group-containing polyester resin using 2-cyclohexanedicarboxylic acid anhydride.

  The content of the hydroxyl group-containing polyester resin (A1 ′) is generally 2 to 70 parts by mass, particularly 10 to 50 parts by mass, more particularly 15 to 15 parts by mass, based on 100 parts by mass of the resin solid content in the first colored paint (X). It is preferable to be within the range of 40 parts by mass.

  As the alcohol component (a1-2), a polyhydric alcohol having two or more hydroxyl groups in one molecule can be suitably used. Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, Trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 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 2,4-pentanediol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, , 4-hexanediol, 2,5-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, hydrogenated bisphenol A, hydrogenated bisphenol F, and the like; Polylactone diols obtained by adding lactones such as ε-caprolactone to alcohol; ester diols such as bis (hydroxyethyl) terephthalate; alkylene oxide adducts of bisphenol A, polyether diols such as polyethylene glycol, polypropylene glycol, and polybutylene glycol Glycerin, trimethylolethane, trimethylolpropane, diglycerin, triglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, tris (2-hydroxyethyl) isocyanuric acid, sorbitol, mannitol, etc. Trivalent or higher alcohols; polylactone polyols obtained by adding lactones such as ε-caprolactone to these trivalent or higher alcohols.

  Examples of the alcohol component (a1-2) include alcohols other than the above polyhydric alcohols, for example, monoalcohols such as stearyl alcohol and 2-phenoxyethanol; propylene oxide, butylene oxide, “Cardura E10” (trade name, HEXION Specialty Chemicals). Alcohol compounds obtained by reacting acids with monoepoxy compounds such as glycidyl esters of synthetic hyperbranched saturated fatty acids (made by company) can also be used.

  The production of the hydroxyl group-containing polyester resin (A1) is not particularly limited, and can be performed according to an ordinary method. For example, an acid component (a1-1) and an alcohol component (a1-2) are mixed in a nitrogen stream. In this method, heating is carried out at about 150 to about 250 ° C. for about 5 to 10 hours, and the esterification reaction or transesterification reaction of the acid component (a1-1) and the alcohol component (a1-2) can be carried out. .

  When the acid component (a1-1) and the alcohol component (a1-2) are subjected to esterification reaction or transesterification reaction, these may be added at once, or may be added in several portions. Alternatively, after first synthesizing the hydroxyl group-containing polyester resin, the obtained hydroxyl group-containing polyester resin may be reacted with an acid anhydride to be half-esterified, or after first synthesizing the carboxyl group-containing polyester resin, the alcohol component (A1-2) may be added.

  In the esterification or transesterification reaction, as a catalyst for promoting the reaction, for example, dibutyltin oxide, antimony trioxide, zinc acetate, manganese acetate, cobalt acetate, calcium acetate, lead acetate, tetrabutyl titanate, A catalyst known per se, such as tetraisopropyl titanate, can be used.

  In some cases, the hydroxyl group-containing polyester resin (A1) may be modified with a fatty acid, a monoepoxy compound, a polyisocyanate compound or the like during the production of the resin or after the esterification reaction or the transesterification reaction.

  Examples of the fatty acid include coconut oil fatty acid, cottonseed 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, dehydrated castor Oil fatty acid, safflower oil fatty acid and the like can be mentioned, and as the above-mentioned monoepoxy compound, for example, “Cardura E10” (trade name, manufactured by HEXION Specialty Chemicals, glycidyl ester of synthetic highly branched saturated fatty acid) is preferably used. it can.

  Examples of the polyisocyanate compound include aliphatic diisocyanates such as lysine diisocyanate, hexamethylene diisocyanate, and trimethylhexane diisocyanate; hydrogenated xylylene diisocyanate, isophorone diisocyanate, methylcyclohexane-2,4-diisocyanate, and methylcyclohexane-2,6. Alicyclic diisocyanates such as diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), 1,3- (isocyanatomethyl) cyclohexane; aromatic diisocyanates such as tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate; lysine Organic polyisocyanate itself such as triisocyanate or higher polyisocyanate such as triisocyanate Or an adduct of each of these organic polyisocyanates and a polyhydric alcohol, a low molecular weight polyester resin or water, or a cyclized polymer of each organic diisocyanate (for example, isocyanurate), a biuret type adduct, etc. These may be used alone or in combination of two or more.

  The hydroxyl group-containing polyester resin (A1) generally has a hydroxyl value in the range of 10 to 300 mgKOH / g, particularly 50 to 250 mgKOH / g, more particularly 80 to 180 mgKOH / g, and an acid value of 1 to 200 mgKOH / g, The acid value is preferably within the range of 2 to 100 mgKOH / g, more preferably 3 to 40 mgKOH / g. The hydroxyl group-containing polyester resin (A1) generally has a weight average molecular weight in the range of 500 to 50,000, preferably 1,000 to 30,000, more preferably 1,500 to 20,000. It is.

  In addition, the number average molecular weight and the weight average molecular weight in the present specification are based on the number average molecular weight or the weight average molecular weight measured with a gel permeation chromatograph (manufactured by Tosoh Corporation, “HLC8120GPC”) based on the molecular weight of standard polystyrene. It is a converted value. In this measurement, four columns of “TSKgel G-4000HXL”, “TSKgel G-3000HXL”, “TSKgel G-2500HXL”, and “TSKgel G-2000HXL” (both trade names, manufactured by Tosoh Corporation) are used as columns. The conditions were as follows: mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 mL / min, detector: RI.

  The content of the hydroxyl group-containing polyester resin (A1) is generally 2 to 70 parts by mass, particularly 10 to 50 parts by mass, and more particularly 15 to 40 parts by mass, based on 100 parts by mass of the resin solid content in the first colored paint (X). It is preferable to be within the range of parts by mass.

  The hydroxyl group-containing acrylic resin (A2) in the first colored paint (X) is usually copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer (a2-1) and the hydroxyl group-containing polymerizable unsaturated monomer (a2-1). Another polymerizable unsaturated monomer (a2-2) can be produced by copolymerizing by a method known per se, for example, a solution polymerization method in an organic solvent, an emulsion polymerization method in water, or the like. it can.

  The hydroxyl group-containing polymerizable unsaturated monomer (a2-1) is a compound having at least one hydroxyl group and at least one polymerizable unsaturated bond in one molecule. Specifically, for example, 2-hydroxyethyl (meth) Mono of (meth) acrylic acid such as acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and a dihydric alcohol having 2 to 8 carbon atoms Esterified product; ε-caprolactone modified product of monoesterified product of the (meth) acrylic acid and a dihydric alcohol having 2 to 8 carbon atoms; N-hydroxymethyl (meth) acrylamide; allyl alcohol; Examples thereof include (meth) acrylate having a certain polyoxyethylene chain.

Examples of the other polymerizable unsaturated monomer (a2-2) copolymerizable with the hydroxyl group-containing polymerizable unsaturated monomer (a2-1) include methyl (meth) acrylate, ethyl (meth) acrylate, n- Propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl ( (Meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, “isostearyl acrylate” (trade name, Osaka Organic Chemical Industries, Ltd.) ), Cyclohexyl (meth) acryle Alkyl, cycloalkyl (meth) acrylate such as methyl, cyclohexyl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate; isobornyl group such as isobornyl (meth) acrylate A polymerizable unsaturated monomer having an adamantyl group such as adamantyl (meth) acrylate; a vinyl aromatic compound such as styrene, α-methylstyrene, vinyltoluene; vinyltrimethoxysilane, vinyltriethoxysilane , Vinyl tris (2-methoxyethoxy) silane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane, etc. -Perfluoroalkyl (meth) acrylates such as perfluorobutylethyl (meth) acrylate and perfluorooctylethyl (meth) acrylate; Polymerizable unsaturated monomers having fluorinated alkyl groups such as fluoroolefins; Polymerizable unsaturated monomer having a polymerizable functional group; vinyl compounds such as N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate; (meth) acrylic acid, maleic acid, crotonic acid, β-carboxyethyl Carboxyl group-containing polymerizable unsaturated monomers such as acrylate; (meth) acrylonitrile, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, glycidyl (meth) ) Nitrogen-containing polymerizable unsaturated monomers such as adducts of acrylates and amines; one molecule of polymerizable unsaturated group such as allyl (meth) acrylate, 1,6-hexanediol di (meth) acrylate 2 or more polymerizable unsaturated monomers: glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate , 3,4-epoxycyclohexylpropyl (meth) acrylate, epoxy group-containing polymerizable unsaturated monomers such as allyl glycidyl ether; (meth) acrylate having a polyoxyethylene chain whose molecular terminal is an alkoxy group; 2-acrylamide-2 -Methylpropane sulfonic acid, allyl sulfonic acid, Polymerizable unsaturated monomers having a sulfonic acid group such as styrenesulfonic acid sodium salt, sulfoethyl methacrylate and its sodium salt and ammonium salt; 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, 2-acryloyloxypropyl Polymerizable unsaturated monomers having a phosphate group such as acid phosphate and 2-methacryloyloxypropyl acid phosphate; 2-hydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy) benzophenone, 2-hydroxy-4- (3 -Acryloyloxy-2-hydroxypropoxy) benzophenone, 2,2'-dihydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy) benzophenone, 2, UV-absorbing functional groups such as 2'-dihydroxy-4- (3-acryloyloxy-2-hydroxypropoxy) benzophenone and 2- (2'-hydroxy-5'-methacryloyloxyethylphenyl) -2H-benzotriazole Polymerizable unsaturated monomer; 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- Cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1 -(Meth) acryloyl-4-cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperi 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 4-crotonoylamino-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2, UV-stable polymerizable unsaturated monomers such as 2,6,6-tetramethylpiperidine; acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formylstyrol, vinylalkyl having 4 to 7 carbon atoms Examples thereof include polymerizable unsaturated monomer compounds having a carbonyl group such as ketones (for example, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone), and these can be used alone or in combination of two or more.

  The hydroxyl group-containing acrylic resin (A2) is generally in the range of 2 to 200 mgKOH / g, particularly 5 to 150 mgKOH / g, more particularly 10 to 100 mgKOH / g, from the viewpoints of storage stability and water resistance of the resulting coating film. It preferably has a hydroxyl value. The hydroxyl group-containing acrylic resin (A2) is generally from 1 to 200 mgKOH / g, particularly from 2 to 100 mgKOH / g, more particularly from 3 to 60 mgKOH / g, from the viewpoint of the water resistance of the resulting coating film. It is preferable to have Further, the hydroxyl group-containing acrylic resin (A2) generally has a weight average molecular weight in the range of 1,000 to 200,000, particularly 2,000 to 100,000, more particularly 3,000 to 50,000. It is.

The content of the hydroxyl group-containing acrylic resin (A2) in the first colored paint (X) is generally 2 to 70 parts by weight, particularly 10 to 10 parts by weight, based on 100 parts by weight of the resin solid content in the first colored paint (X).
It is preferred that it is in the range of 50 parts by weight, more particularly 15-30 parts by weight.

Curing agent (B)
As the curing agent (B) blended in the first colored paint (X), a compound having a crosslinkable functional group capable of reacting with a hydroxyl group in the hydroxyl group-containing resin (A) can be used. Amino resin (B1), polyisocyanate compound (B2), blocked polyisocyanate compound (B3) and the like can be suitably used. A hardening | curing agent (B) can be used individually or in combination of 2 or more types, respectively.

  Examples of the amino resin (B1) include a partial or completely methylolated amino resin obtained by reacting an amino component such as melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, dicyandiamide and the aldehyde. Examples of the aldehyde include formaldehyde, paraformaldehyde, acetaldehyde, benzaldehyde and the like. In addition, it is also possible to use a methylol group obtained by partially or completely etherifying a methylol group with a suitable alcohol. Examples of alcohols used for etherification include methyl alcohol, ethyl alcohol, n -Propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, 2-ethylbutanol, 2-ethylhexanol and the like.

  As the amino resin (B1), a melamine resin is preferable. Among them, a methyl ether melamine resin (B1-1) obtained by partially or completely etherifying a methylol group of a partially or completely methylol melamine resin with methyl alcohol, Butyl etherified melamine resin (B1-2) in which methylol group of partially or fully methylolated melamine resin is partially or completely etherified with butyl alcohol, methylol group of partially or fully methylolated melamine resin with methyl alcohol and butyl alcohol Partly or completely etherified methyl-butyl mixed etherified melamine resin (B1-3) is particularly preferred.

  The melamine resin generally has a weight average molecular weight in the range of 400 to 5,000, particularly 600 to 4,000, more particularly 1,000 to 3,000.

  Commercially available products can be used as the melamine resin. Examples of commercially available products include “Cymel 202”, “Cymel 203”, “Cymel 238”, “Cymel 251”, “Cymel 303”, “Cymel 323”, “Cymel 324”, “Cymel 325”, “Cymel 327”, “Cymel 350”, “Cymel 385”, “Cymel 1156”, “Cymel 1158”, “Cymel 1116”, “Cymel 1130” , "Uban 120", "Uban 20HS", "Uban 20SE60", "Uban 2021", "Uban 2028", "Uban 28-60" (above, Mitsui Chemicals).

  The melamine resins can be used alone or in combination of two or more.

  When the melamine resin is used as a curing agent, a curing catalyst such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, or a salt of these acids with an amine may be used in combination. it can.

The polyisocyanate compound (B2) is a compound having two or more isocyanate groups in one molecule, for example, aliphatic polyisocyanates such as hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, dimer acid diisocyanate, and lysine diisocyanate, and Burette type adducts, isocyanurate cycloadducts of these polyisocyanates; isophorone diisocyanate, 4,4′-methylenebis (cyclohexyl isocyanate), methylcyclohexane-2,4-diisocyanate, methylcyclohexane-2,6-diisocyanate, 1 , 3-Di (isocyanatomethyl) cyclohexane, 1,4-di (isocyanatomethyl) cyclohexane, 1,4-cyclohexane diisocyanate, 1,3- Cycloaliphatic diisocyanates such as cyclopentane diisocyanate and 1,2-cyclohexane diisocyanate, and burette-type adducts and isocyanurate cycloadducts of these polyisocyanates; xylylene diisocyanate, metaxylylene diisocyanate, tetramethyl xylylene diisocyanate, Tolylene diisocyanate, 4,4′-diphenylmethane diisocyanate, 1,5-naphthalene diisocyanate, 1,4-naphthalene diisocyanate, 4,4′-toluidine diisocyanate, 4,4′-diphenyl ether diisocyanate, m-phenylene diisocyanate, p-phenylene Diisocyanate, 4,4′-biphenylene diisocyanate, 3,3′-dimethyl-4,4′-biphenylene diisocyanate, Aromatic diisocyanate compounds such as bis (4-isocyanatophenyl) sulfone, isopropylidenebis (4-phenylisocyanate), and burette type adducts, isocyanurate cycloadducts of these polyisocyanates; triphenylmethane-4,4 ', 4 "-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene, 4,4'-dimethyldiphenylmethane-2,2', 5,5'-tetraisocyanate Such as polyisocyanates having 3 or more isocyanate groups in one molecule, and burette type adducts, isocyanurate cycloadducts of these polyisocyanates; ethylene glycol, propylene glycol, 1,4-butylene glycol, dimethylol Propionic acid, poly Urethane adducts obtained by reacting a polyisocyanate compound with an excess ratio of isocyanate groups to hydroxyl groups of polyols such as ruylene glycol, trimethylolpropane and hexanetriol, and burette type adducts of these polyisocyanates, isocyanates Examples thereof include a nurate ring adduct.

  The blocked polyisocyanate compound (B3) is obtained by adding a blocking agent to the isocyanate group of the polyisocyanate compound (B2). When the blocking agent is dissociated by heating and the isocyanate group is regenerated. Can react with hydroxyl groups. The dissociation temperature of the blocking agent is usually in the range of about 60 to about 140 ° C, preferably about 70 to about 120 ° C.

Examples of the blocking agent include phenols such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and hydroxybenzoic acid methyl; ε-caprolactam, δ-valerolactam, lactams such as γ-butyrolactam, β-propiolactam; aliphatic alcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, amyl alcohol, lauryl alcohol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono Butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene Ethers such as glycol monomethyl ether and methoxymethanol; benzyl alcohol; glycolic acid; glycolic acid esters such as methyl glycolate, ethyl glycolate and butyl glycolate; lactic acid; lactic acid esters such as methyl lactate, ethyl lactate and butyl lactate; Alcohols such as methylol urea, methylol melamine, diacetone alcohol, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate; oximes such as formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketoxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime Active methylene system such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone; Mercaptans such as butyl mercaptan, t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thiophenol, methylthiophenol, ethylthiophenol; Acid amides such as stearic acid amide and benzamide; Imidos such as succinimide, phthalic acid imide and maleic acid imide; Amines such as butylphenylamine; imidazoles such as imidazole and 2-ethylimidazole; urea, thiourea, ethyl Ureas such as urea, ethylenethiourea and diphenylurea; carbamates such as phenyl N-phenylcarbamate; imines such as ethyleneimine and propyleneimine; sulfites such as sodium bisulfite and potassium bisulfite; 3, Examples thereof include pyrazoles such as 5-dimethylpyrazole, 3-methylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3,5-dimethylpyrazole.

  As the blocked polyisocyanate compound (B3), a polyisocyanate compound blocked with an active methylene blocking agent is preferable, and an isocyanurate of hexamethylene diisocyanate blocked with an active methylene blocking agent is particularly preferably used. be able to.

  Further, as the blocking agent, a hydroxycarboxylic acid having at least one hydroxyl group and at least one carboxyl group, for example, hydroxypivalic acid, dimethylolpropionic acid and the like can also be used. In particular, when the first colored paint (X) is an aqueous paint, the isocyanate group is blocked using the hydroxycarboxylic acid, and then the carboxyl group of the hydroxycarboxylic acid is neutralized to give water dispersibility. A polyisocyanate compound can be suitably used. As a commercial item of such a curing agent, for example, “Baihijoule BL5140” (trade name, manufactured by Sumika Bayer Urethane Co., Ltd.) can be mentioned.

  The content of the curing agent (B) in the first colored paint (X) is generally 5 to 70 parts by mass, particularly 20 based on the total solid content of 100 parts by mass of the hydroxyl group-containing resin (A) and the curing agent (B). It is preferable to be in the range of ˜60 parts by mass, more particularly in the range of 30 to 50 parts by mass.

Polymer fine particles (C)
The polymer fine particles (C) blended in the first colored paint (X) are prepared by mixing the polymerizable unsaturated monomer (b) with the polyester resin (a) and the polymerizable resin in the presence of the specific polyester resin (a). Although the saturated monomer (b) is dissolved, the polymer formed from the polymerizable unsaturated monomer (b) is obtained by polymerization in an organic solvent that does not substantially dissolve.

Polyester resin (a)
The polyester resin (a) used for the production of the polymer fine particles (C) is obtained by the reaction of the acid component (a-1) and the alcohol component (a-2), and the acid component (a-1). And the alcohol component (a-2) are the alicyclic polybasic acid (a-1-1) and the alicyclic polyhydric alcohol (a-2-1) in total, the acid component (a-1) and The polyester resin contains at least 5 mol%, preferably 10 to 70%, more preferably 15 to 40 mol% based on the total amount of the alcohol component (a-2).

The polyester resin (a) includes, for example, an alicyclic polybasic acid (a-1-1) and / or an alicyclic polyhydric alcohol (a-2-1), an alicyclic polybasic acid (a-1). -1) Alcohol component (a-2-2) other than acid component (a-1-2) and alicyclic polyhydric alcohol (a-2-1)
Can be produced by esterification reaction or transesterification reaction.

  The alicyclic polybasic acid (a-1-1) includes a compound having at least one alicyclic structure (mainly 4 to 6-membered ring) and at least two carboxyl groups in one molecule, Acid anhydrides and esterified products of the compounds are specifically included, such as 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene-1, 2-dicarboxylic acid, 3-methyl-1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid, etc. An alicyclic polyvalent carboxylic acid; an anhydride of the alicyclic polyvalent carboxylic acid; a lower alkyl esterified product of the alicyclic polyvalent carboxylic acid, and the like. Alicyclic polybasic acids al can be used either alone or in combination of two or more.

  Examples of the alicyclic polybasic acid (a-1-1) include 1,2-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic anhydride, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid. An acid or the like can be used, and it is particularly preferable to use 1,2-cyclohexanedicarboxylic acid and / or 1,2-cyclohexanedicarboxylic anhydride.

  Moreover, as an acid component (a-1-2) other than alicyclic polybasic acid (a-1-1), an alicyclic polybasic acid (a Compounds other than (1-1) can be used, and examples thereof include aliphatic polybasic acids and aromatic polybasic acids.

  The aliphatic polybasic acid includes an aliphatic compound having at least two carboxyl groups in one molecule, an acid anhydride of the aliphatic compound, and an esterified product of the aliphatic compound. For example, succinic acid, Aliphatic polyvalent carboxylic acids such as glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, octadecanedioic acid, citric acid; An acid anhydride; a lower alkyl esterified product of the aliphatic polyvalent carboxylic acid, and the like. These aliphatic polybasic acids can be used alone or in combination of two or more. As said aliphatic polybasic acid, adipic acid, an adipic anhydride, etc. can be used conveniently, for example.

  The aromatic polybasic acid includes an aromatic compound having at least two carboxyl groups in one molecule, an acid anhydride of the aromatic compound, and an esterified product of the aromatic compound, such as phthalic acid, Aromatic polycarboxylic acids such as isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, 4,4′-biphenyldicarboxylic acid, trimellitic acid, pyromellitic acid; anhydrides of the aromatic polyvalent carboxylic acids; The lower alkyl esterification thing of a carboxylic acid etc. are mentioned, These aromatic polybasic acids can be used individually or in combination of 2 or more types, respectively. As the aromatic polybasic acid, phthalic acid, phthalic anhydride, isophthalic acid, trimellitic acid, or trimellitic anhydride is preferably used.

Examples of the acid component (a-1-2) other than the alicyclic polybasic acid (a-1-1) include coconut oil fatty acid, cottonseed oil fatty acid, hemp oil fatty acid, rice bran oil fatty acid, fish oil fatty acid, tall Fatty acids such as oil fatty acid, soybean oil fatty acid, linseed oil fatty acid, tung oil fatty acid, rapeseed oil fatty acid, castor oil fatty acid, dehydrated castor oil fatty acid, safflower oil fatty acid; lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, Monocarboxylic acids such as linoleic acid, linolenic acid, benzoic acid, p-tert-butylbenzoic acid, cyclohexane acid, 10-phenyloctadecanoic acid; lactic acid, 3-hydroxybutanoic acid, 3-hydroxy-4-ethoxybenzoic acid, etc. Hydroxycarboxylic acid and the like can be used, and these acid components can be used alone or
It can be used in combination of more than one species.

  The alicyclic polyhydric alcohol (a-2-1) includes a compound having at least one alicyclic structure (mainly a 4- to 6-membered ring) and at least two hydroxyl groups in one molecule, For example, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, hydrogenated bisphenol A, hydrogenated bisphenol F, spiroglycol, dihydroxymethyltricyclodecane and the like can be mentioned.

  As the alcohol component (a-2-2) other than the alicyclic polyhydric alcohol (a-2-1), an alicyclic polyhydric alcohol (a A compound other than 2-1) can be used, and for example, a polyhydric alcohol having no alicyclic structure can be preferably used.

  Examples of the polyhydric alcohol having no alicyclic structure include ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1, 3-butanediol, 2,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-pentane Diol, 1,5-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-4,3-pentanediol, 3-methyl -1,5-pentanediol, 2,2,4-trimethyl Dihydric alcohols such as 1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, neopentyl glycol; and the like. Lactones such as ε-caprolactone added thereto; ester diols such as bis (hydroxyethyl) terephthalate; alkylene oxide adducts of bisphenol A, polyether diols such as polyethylene glycol, polypropylene glycol, polybutylene glycol Glycerin, trimethylolpropane, trimethylolethane, diglycerin, triglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, tris (2-hydroxyethyl); ) Trivalent or higher alcohols such as isocyanuric acid, sorbitol and mannitol; and polylactone polyols obtained by adding lactones such as ε-caprolactone to these trivalent or higher alcohols.

  Examples of the alcohol component (a-2-2) other than the polyhydric alcohol having no alicyclic structure include monoalcohols such as stearyl alcohol and 2-phenoxyethanol; propylene oxide, butylene oxide, “Cardura E10” (Trade name, manufactured by HEXION Specialty Chemicals, glycidyl ester of synthetic highly branched saturated fatty acid) and the like, and alcohol compounds obtained by reacting acids.

  When the acid component (a-1) and the alcohol component (a-2) are subjected to an esterification reaction or a transesterification reaction, these may be added at once or in several portions. Alternatively, after first synthesizing the hydroxyl group-containing polyester resin, the obtained hydroxyl group-containing polyester resin may be reacted with an acid anhydride to be half-esterified. Also, after first synthesizing the carboxyl group-containing polyester resin, the alcohol component (A-2) may be added.

In the esterification or transesterification reaction, as a catalyst for promoting the reaction, dibutyltin oxide, antimony trioxide, zinc acetate, manganese acetate, cobalt acetate, calcium acetate, lead acetate, tetrabutyl titanate, tetraisopropyl A catalyst known per se, such as titanate, can also be used.

  The polyester resin (a) preferably has a radically polymerizable unsaturated group, and among them, the polyester resin (a) has a molecular weight of 0.3 to 1.5, particularly 0.8 to 1.2, per molecule. It is particularly preferred to have about 1 radically polymerizable unsaturated group. Introduction of a radically polymerizable unsaturated group into the polyester resin (a) can be performed, for example, by reacting a monoisocyanate group-containing polymerizable unsaturated monomer with a hydroxyl group in the polyester resin (a). Examples of the monoisocyanate group-containing polymerizable unsaturated monomer include equimolar adducts of a diisocyanate compound such as hexamethylene diisocyanate and isophorone diisocyanate and hydroxyalkyl (meth) acrylate.

  The polyester resin (a) can be modified with a fatty acid, a monoepoxy compound, a polyisocyanate compound or the like during the preparation of the resin or after the esterification reaction or the transesterification reaction.

  Examples of the fatty acid include coconut oil fatty acid, cottonseed 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, dehydrated castor Oil fatty acid, safflower oil fatty acid and the like can be mentioned. As the monoepoxy compound, for example, “Cardura E10” (trade name, manufactured by HEXION Specialty Chemicals, a glycidyl ester of a synthetic highly branched saturated fatty acid) can be suitably used. .

  Especially, it is preferable that a polyester resin (a) is a fatty acid modified polyester resin (a ') from a viewpoint of the smoothness of the coating film obtained. The fatty acid-modified polyester resin (a ′) includes a polyester resin modified with a compound derived from a fatty acid such as “Cardura E10” in addition to the polyester resin modified with the fatty acid. The fatty acid-modified polyester resin (a ′) is preferably a polyester resin modified with at least one compound selected from the group consisting of coconut oil fatty acid, tall oil fatty acid, castor oil fatty acid and the above-mentioned “Cardura E10”. In particular, a polyester resin modified with coconut oil fatty acid and / or “Cardura E10” is preferable.

  In the production of the polymer fine particles (C), the amount of the polyester resin (a) in copolymerizing the polymerizable unsaturated monomer (b) is based on 100 parts by mass of the polymerizable unsaturated monomer (b). As a general rule, it is suitable to be in the range of 5 to 200 parts by weight, in particular 10 to 100 parts by weight, more particularly 25 to 70 parts by weight.

  The polyester resin (a) generally has a weight average molecular weight in the range of 500 to 100,000, preferably 1,000 to 50,000, more preferably 1,500 to 30,000, generally 5 to 200 mg KOH / g, preferably Hydroxyl value within the range of 20-160 mg KOH / g, more preferably 50-120 mg KOH / g, and generally acids within the range of 1-70 mg KOH / g, preferably 2-50 mg KOH / g, more preferably 3-30 mg KOH / g. Can have a valence.

Polymerizable unsaturated monomer (b)
There is no restriction | limiting in particular as a polymerizable unsaturated monomer (b) used for manufacture of a polymer fine particle (C), For example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i -Propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (Meth) acrylate, nonyl (meth) acrylate, tridecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, “isostearyl acrylate” (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.), cyclohexyl (meth) Acrylate, methylcyclohexane Polymers having alkyl or cycloalkyl (meth) acrylates such as syl (meth) acrylate, t-butylcyclohexyl (meth) acrylate, cyclododecyl (meth) acrylate; and isobornyl groups such as isobornyl (meth) acrylate Polymerizable unsaturated monomers having an adamantyl group such as adamantyl (meth) acrylate; vinyl aromatic compounds such as styrene, α-methylstyrene and vinyltoluene; 2-hydroxyethyl (meth) acrylate, 2 A monoesterified product of (meth) acrylic acid such as hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate and a dihydric alcohol having 2 to 8 carbon atoms, This (meth) acrylic acid and C2-C8 Hydroxyl-containing polymerizable unsaturated monomers such as ε-caprolactone modified monoester compounds with dihydric alcohol, allyl alcohol, (meth) acrylate having a polyoxyethylene chain having a hydroxyl group at the molecular end; (meth) acrylic acid Carboxyl group-containing polymerizable unsaturated monomers such as maleic acid, crotonic acid, β-carboxyethyl acrylate; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, γ- (meth) acryloyloxypropyl Polymerizable unsaturated monomers having an alkoxysilyl group such as trimethoxysilane and γ- (meth) acryloyloxypropyltriethoxysilane; perfluorobutylethyl (meth) acrylate, perfluorooctylethyl (meth) acrylate and the like Fluoroalkyl (meth) acrylate; polymerizable unsaturated monomer having a fluorinated alkyl group such as fluoroolefin; polymerizable unsaturated monomer having a photopolymerizable functional group such as maleimide group; N-vinylpyrrolidone, ethylene, butadiene, chloroprene, Vinyl compounds such as vinyl propionate and vinyl acetate; (meth) acrylonitrile, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, glycidyl (meth) acrylate -Containing polymerizable unsaturated monomers such as adducts of amines and amines; polymerizable unsaturated groups such as allyl (meth) acrylate and 1,6-hexanediol di (meth) acrylate in one molecule Two or more polymerizable unsaturated monomers; glycidyl (meth) Acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, allyl glycidyl ether Epoxy group-containing polymerizable unsaturated monomers such as (meth) acrylate having a polyoxyethylene chain whose molecular terminal is an alkoxy group; 2-acrylamido-2-methylpropanesulfonic acid, allylsulfonic acid, sodium styrenesulfonate, Polymerizable unsaturated monomers having a sulfonic acid group such as sulfoethyl methacrylate and its sodium salt and ammonium salt; 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acyl Polymerizable unsaturated monomers having a phosphate group such as dophosphate, 2-acryloyloxypropyl acid phosphate, 2-methacryloyloxypropyl acid phosphate; 2-hydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy) benzophenone, 2-hydroxy-4- (3-acryloyloxy-2-hydroxypropoxy) benzophenone, 2,2′-dihydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy) benzophenone, 2,2′-dihydroxy-4- Polymerizable unsaturated molecule having an ultraviolet absorbing functional group such as (3-acryloyloxy-2-hydroxypropoxy) benzophenone, 2- (2′-hydroxy-5′-methacryloyloxyethylphenyl) -2H-benzotriazole 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-cyano-4- (Meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1- (meth) Acryloyl-4-cyano-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 4-crotonoylamino- UV light such as 2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine Qualitatively polymerizable unsaturated monomer; acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formyl styrene, vinyl alkyl ketone having 4 to 7 carbon atoms (for example, vinyl methyl ketone, vinyl ethyl ketone, vinyl Examples thereof include polymerizable unsaturated monomer compounds having a carbonyl group such as butyl ketone, and these can be used alone or in combination of two or more.

  The organic solvent used as the dispersion medium when producing the polymer fine particles (C) does not substantially dissolve the produced dispersion polymer particles, but is based on the polyester resin (a) and the polymerizable unsaturated monomer (b). It is preferable that the organic solvent be a good solvent and substantially immiscible with water. Specific examples of such organic solvents include hexane, heptane, octane, mineral spirits, toluene, xylene, butyl acetate and the like, and these can be used alone or in combination of two or more. In this case, the polymer fine particles (C) are preferably mixed with the first colored paint (X) as a mixed liquid of the polyester resin (a), the organic solvent and the polymer fine particles (C).

  Polymerization of the polymerizable unsaturated monomer (b) in the organic solvent in the presence of the polyester resin (a) uses a method known per se (for example, the method described in JP-A-57-177068). Examples of radical polymerization initiators include organic peroxide polymerization initiators such as benzoyl peroxide; 2,2′-azobisisobutyronitrile, 1,1-azobis (cyclohexane-1) Azo polymerization initiators such as -carbonitrile) and the like. As the reaction temperature during the polymerization, generally a temperature within the range of about 60 to about 160 ° C. can be used, and the reaction usually takes about 4 to 8 hours. Can end. The polymer fine particles (C) may be either crosslinked or uncrosslinked, but preferably crosslinked.

  The polymer fine particles (C) generally have an average particle diameter in the range of 160 to 450 nm, particularly 180 to 400 nm, more particularly 200 to 350 nm. The average particle diameter can be adjusted by a method known per se, for example, by adjusting the amount of the polyester resin (a).

  In the present specification, the average particle diameter of the polymer fine particles is a value measured by a light scattering method using a submicron particle analyzer manufactured by Beckman Coulter.

  The polymer fine particles (C) include a polymerizable unsaturated monomer (b) in the presence of the polyester resin (a) and the copolymer (c) from the viewpoint of smoothness and sharpness of the obtained multilayer coating film. ), The polyester resin (a), the copolymer (c) and the polymerizable unsaturated monomer (b) are dissolved, but the polymer formed from the polymerizable unsaturated monomer (b) is not substantially dissolved. Polymer fine particles (C ′) obtained by polymerization in a solvent can be preferably used.

  The content of the polymer fine particles (C) in the first colored paint (X) is generally 2 to 50 parts by weight, particularly 3 to 35 parts by weight, based on 100 parts by weight of the resin solid content in the first colored paint (X). Part, more particularly in the range of 5 to 25 parts by weight.

Copolymer (c)
As the copolymer (c) used in the production of the polymer fine particles (C ′), a polymerizable unsaturated monomer (c-1) having a self-condensed polyester chain of a hydroxyl group-containing fatty acid and other polymerizable unsaturated monomers ( What is obtained by copolymerizing c-2) is mentioned.

  The polymerizable unsaturated monomer (c-1) having a self-condensed polyester chain of a hydroxyl group-containing fatty acid is, for example, an epoxy group on the carboxyl group of the self-condensed polyester of a hydroxyl group-containing fatty acid such as 12-hydroxyhexadecanoic acid or 12-hydroxyoctadecanoic acid. It can be obtained by addition reaction of the contained unsaturated monomer and introduction of a radically polymerizable unsaturated group. Among them, the polymerizable unsaturated monomer (c-1) is obtained by addition reaction of an epoxy group-containing unsaturated monomer, preferably glycidyl (meth) acrylate, to the carboxyl group of the self-condensed polyester of 12-hydroxyoctadecanoic acid. The polymerizable unsaturated monomer is suitable.

Examples of other polymerizable unsaturated monomer (c-2) include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, and n-butyl (meth). ) Acrylate, i-butyl (meth) acrylate, tert-butyl (meth) acrylate, n-hexyl (meth) acrylate, n-octyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, nonyl (meth) acrylate, tridecyl (Meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, “isostearyl acrylate” (trade name, manufactured by Osaka Organic Chemical Industry Co., Ltd.), cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate , T-Butyl Alkyl or cycloalkyl (meth) acrylates such as rohexyl (meth) acrylate and cyclododecyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxy Monoesterified product of (meth) acrylic acid such as propyl (meth) acrylate and 4-hydroxybutyl (meth) acrylate and a dihydric alcohol having 2 to 8 carbon atoms, the (meth) acrylic acid and 2 to 8 carbon atoms Ε-caprolactone modified monoester product with dihydric alcohol, allyl alcohol, hydroxyl group-containing polymerizable unsaturated monomer such as (meth) acrylate having a polyoxyethylene chain having a hydroxyl group at the molecular end; isobornyl (meth) acrylate, etc. A polymerizable unsaturated monomer having an isobornyl group of Polymerizable unsaturated monomers having an adamantyl group such as adamantyl (meth) acrylate; vinyl aromatic compounds such as styrene, α-methylstyrene and vinyltoluene; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) Polymerizable unsaturated monomers having alkoxysilyl groups such as silane, γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane; perfluorobutylethyl (meth) acrylate, perfluorooctyl Perfluoroalkyl (meth) acrylate such as ethyl (meth) acrylate; polymerizable unsaturated monomer having a fluorinated alkyl group such as fluoroolefin; polymerizable unsaturated having a photopolymerizable functional group such as maleimide group Nomers; vinyl compounds such as N-vinyl pyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate; carboxyl group-containing polymerizable unsaturation such as (meth) acrylic acid, maleic acid, crotonic acid, β-carboxyethyl acrylate, etc. Monomer; (meth) acrylonitrile, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, adduct of glycidyl (meth) acrylate and amines, etc. Nitrogen-containing polymerizable unsaturated monomer; polymerizable unsaturated monomer having two or more polymerizable unsaturated groups in one molecule such as allyl (meth) acrylate and 1,6-hexanediol di (meth) acrylate Glycidyl (meth) acrylate, β-methylglycidyl (medium ) Epoxy group-containing polymerizable monomers such as acrylate, 3,4-epoxycyclohexylmethyl (meth) acrylate, 3,4-epoxycyclohexylethyl (meth) acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, and allyl glycidyl ether (Meth) acrylate having a polyoxyethylene chain whose molecular terminal is an alkoxy group; 2-acrylamido-2-methylpropane sulfonic acid, allyl sulfonic acid, sodium styrene sulfonate, sulfoethyl methacrylate and its sodium salt Polymerizable unsaturated monomer having a sulfonic acid group such as ammonium salt; 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxyethyl acid phosphate, 2-acryloyloxy Polymerizable unsaturated monomers having a phosphate group such as propyl acid phosphate and 2-methacryloyloxypropyl acid phosphate; 2-hydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy) benzophenone, 2-hydroxy-4- ( 3-acryloyloxy-2-hydroxypropoxy) benzophenone, 2,2′-dihydroxy-4- (3-methacryloyloxy-2-hydroxypropoxy) benzophenone, 2,2′-dihydroxy-4- (3-acryloyloxy-2) Polymerizable unsaturated monomer having an ultraviolet absorbing functional group such as -hydroxypropoxy) benzophenone, 2- (2'-hydroxy-5'-methacryloyloxyethylphenyl) -2H-benzotriazole; 4- (meth) acryloyloxy 1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloyloxy-2,2,6,6-tetramethylpiperidine, 4-cyano-4- (meth) acryloylamino-2,2, 6,6-tetramethylpiperidine, 1- (meth) acryloyl-4- (meth) acryloylamino-2,2,6,6-tetramethylpiperidine, 1- (meth) acryloyl-4-cyano-4- (meta ) Acryloylamino-2,2,6,6-tetramethylpiperidine, 4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, 4-crotonoylamino-2,2,6,6-tetramethyl UV-stable polymerizable unsaturated monomers such as piperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine; acrolein , Carbonyl groups such as diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formyl styrene, vinyl alkyl ketone having 4 to 7 carbon atoms (for example, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone) The polymerizable unsaturated monomer compound etc. which have are mentioned, These can be used individually or in combination of 2 or more types, respectively.

  Further, the copolymer (c) preferably contains a radically polymerizable unsaturated group, and among them, 0.3 to 1.5, preferably 0.8 to, per molecule of the copolymer (c). It is preferred to have 1.2, more preferably about 1 radically polymerizable unsaturated groups. The introduction of the radically polymerizable unsaturated group into the copolymer (c) is, for example, by introducing a hydroxyl group into the copolymer (c) and reacting the monoisocyanate group-containing polymerizable unsaturated monomer with the hydroxyl group. A method in which a carboxyl group is introduced into the copolymer (c) and an epoxy group-containing polymerizable unsaturated monomer is reacted with the carboxyl group; an epoxy group is introduced into the copolymer (c). The method can be carried out by a method of reacting a carboxyl group-containing polymerizable unsaturated monomer with the epoxy group. Examples of the epoxy group-containing polymerizable unsaturated monomer include glycidyl (meth) acrylate, and examples of the carboxyl group-containing polymerizable unsaturated monomer include (meth) acrylic acid.

  The copolymer (c) generally has a weight average molecular weight in the range of 1,000 to 200,000, in particular 2,000 to 100,000, more particularly 3,000 to 50,000.

  In the production of the polymer fine particles (C ′), the amount of the polyester resin (a) and the copolymer (c) present when the polymerizable unsaturated monomer (b) is polymerized is determined by the polymerizable unsaturated monomer (b). Based on 100 parts by weight, the polyester resin (a) is generally in the range of 1 to 70 parts by weight, especially 10 to 50 parts by weight, more particularly 20 to 40 parts by weight, and the copolymer (c) is generally 1 It is suitable to be in the range of ˜70 parts by mass, especially 5 to 50 parts by mass, more particularly 8 to 30 parts by mass.

In addition, from the viewpoint of smoothness, sharpness, flip-flip properties and metallic unevenness of the resulting multilayer coating film, the polyester resin (a) and copolymer ( The abundance ratio of c) is 10/90 to 90/10, particularly 50/50 to 85/15, more particularly 60/40 to the resin solid mass ratio of polyester resin (a) / copolymer (c). It is preferable to be within the range of 80/20.

  The first colored paint (X) is for modifying polyurethane resin, polyester resin, acrylic resin, alkyd resin, silicon resin, fluororesin, epoxy resin, etc. that do not have a hydroxyl group in addition to the hydroxyl group-containing resin (A). A resin may further be included. Especially, it is preferable that a polyurethane resin is included from viewpoints of chipping resistance, water resistance, etc. of the coating film obtained. The above modifying resins can be used alone or in combination of two or more. When the first colored paint (X) contains the modifying resin, the content of the modifying resin is 50 parts by mass or less based on 100 parts by mass of the resin solid content in the first colored paint (X). It is preferable that

  Further, the first colored paint (X) is a curing agent (B) when the hydroxyl group-containing resin (A) and / or the modifying resin has a crosslinkable functional group such as a carboxyl group or an epoxy group. A curing agent having a crosslinkable functional group capable of reacting with the functional group can be contained. Examples of such a curing agent include an epoxy group-containing compound, a carboxyl group-containing compound, a carbodiimide group-containing compound and the like that can react with the crosslinkable functional group. Among them, a carbodiimide group-containing compound is preferably used. it can.

  As said carbodiimide group containing compound, what made the carbon dioxide reaction of the isocyanate groups of the above-mentioned polyisocyanate compound (B2) can be used, for example. Examples of commercially available carbodiimide group-containing compounds include “carbodilite V-02”, “carbodilite V-02-L2”, “carbodilite V-04”, “carbodilite E-01”, “carbodilite E-02” ( Product names, both of which are manufactured by Nisshinbo Co., Ltd.).

  In the present invention, the resin solids in the first colored paint (X) include these resins in addition to the resin solids such as the hydroxyl group-containing resin (A), amino resin (B1), and modifying resin. It also includes a solid content of a curing agent such as a cross-linked polyisocyanate compound (B2), a blocked polyisocyanate compound (B3), the epoxy group-containing compound, a carboxyl group-containing compound, and a carbodiimide group-containing compound.

  The first colored paint (X) can further contain polymer fine particles (D).

Polymer fine particles (D)
For example, the polymer fine particles (D) dissolve the polymerizable unsaturated monomer (b) and the copolymer (c) and the polymerizable unsaturated monomer (b) in the presence of the copolymer (c). The polymer formed from the polymerizable unsaturated monomer (b) is a polymer fine particle other than the polymer fine particle (C ′), which can be obtained by polymerizing in a substantially insoluble organic solvent.

  In the production of the polymer fine particles (D), the amount of the copolymer (c) when the polymerizable unsaturated monomer (b) is polymerized is generally based on 100 parts by mass of the polymerizable unsaturated monomer (b). It is suitable to be in the range of 5 to 200 parts by weight, particularly 10 to 100 parts by weight, more particularly 25 to 70 parts by weight.

  The polymer fine particles (D) preferably have an average particle diameter generally in the range of 160 to 450 nm, particularly 180 to 400 nm, and more particularly 200 to 350 nm.

When the first colored paint (X) contains the polymer fine particles (D), the content of the polymer fine particles (D) is based on 100 parts by mass of the resin solid content in the first colored paint (X). Generally 2-50
It can be in the range of 3 parts by weight, preferably 3 to 35 parts by weight, more preferably 5 to 25 parts by weight.

  The first colored paint (X) preferably further contains crosslinked polymer fine particles (E) from the viewpoints of smoothness, sharpness, flip-flop properties and metallic unevenness of the resulting coating film.

Crosslinked polymer fine particles (E)
The crosslinked polymer fine particles (E) are emulsified with a polymerizable monomer (e-1) having at least two radically polymerizable unsaturated groups in the molecule and another polymerizable unsaturated monomer (e-2). Cross-linked polymer fine particles obtained by polymerization are included, and in particular, a polymerizable monomer having at least two radically polymerizable unsaturated groups in the molecule and other polymerizable unsaturated monomers are allylated in the molecule. Crosslinked polymer fine particles obtained by emulsion polymerization in the presence of a reactive emulsifier containing a group (for example, see JP-A-3-66770) can be suitably used.

  Examples of the polymerizable monomer (e-1) having at least two radically polymerizable unsaturated groups in the molecule used for the production of the crosslinked polymer fine particles (E) include ethylene glycol di (meth) acrylate, 1 , 6-hexanediol diacrylate and the like, and as other radical polymerizable unsaturated monomer (e-2), for example, (meth) acrylic acid alkyl ester, hydroxyl group-containing monomer, per se known polymerization such as styrene Sex unsaturated monomers. Moreover, a water-soluble azoamide compound etc. can be used as a polymerization initiator at the time of emulsion polymerization.

  The crosslinked polymer fine particle (E) emulsion obtained by the above emulsion polymerization can be separated in the form of a solid by physical or chemical means such as water evaporation or azeotropy or polymer (particle) precipitation or aggregation. Alternatively, the medium of the target crosslinked polymer fine particle emulsion can be replaced from water with another resin, an organic solvent, or the like by such physical or chemical means.

  The crosslinked polymer fine particles (E) can generally have an average particle diameter in the range of 40 to 200 nm, preferably 50 to 150 nm, and more preferably 70 to 100 nm. The average particle size can be adjusted by a method known per se, for example, by adjusting the type and amount of the reactive emulsifier.

  When the first colored paint (X) contains the crosslinked polymer fine particles (E), the content of the crosslinked polymer fine particles (E) is based on 100 parts by mass of the resin solid content in the first colored paint (X). Generally, it is suitable to be in the range of 2 to 30 parts by weight, particularly 3 to 20 parts by weight, more particularly 5 to 15 parts by weight.

From the viewpoint of the sharpness of the coating film obtained, flip-flop properties, and metallic unevenness, the first colored paint (X) has polymer fine particles (C) and average particle diameters having an average particle diameter in the range of 160 to 450 nm. The ratio of the average particle size of the polymer fine particles (C) to the average particle size of the cross-linked polymer fine particles (E) is: The average particle size of the coalesced fine particles (C)] / [the average particle size of the crosslinked polymer fine particles (E)] is generally 1.2 / 1 to 10/1, particularly 1.5 / 1 to 5/1, more particularly 2 It is preferable that it is in the range of / 1 to 4/1. In such a case, the reason why a coating film excellent in sharpness, flip-flop properties and metallic unevenness is not clear, but by using two kinds of polymer fine particles having different average particle sizes in combination, the first In the colored coating film, a state in which crosslinked polymer fine particles (E) having a relatively small average particle diameter are present is formed between the polymer fine particles (C) having a relatively large average particle diameter. When the aqueous second colored paint (Y) is applied onto the coating film, water penetration from the aqueous second colored paint (Y) to the first colored paint film is suppressed, and the first colored paint film and the second colored paint It is presumed that the mixed layer between the coating films is suppressed.

  The first colored paint (X) preferably further contains a pigment (F). Examples of the pigment (F) include a color pigment (F1), an extender pigment (F2), and a glitter pigment (F3). These pigments may be used alone or in combination of two or more. Can do.

  When the first colored paint (X) contains the pigment (F), the content of the pigment (F) is generally 1 to 200 based on 100 parts by mass of the resin solid content in the first colored paint (X). It is suitable to be in the range of parts by mass, especially 20 to 150 parts by mass.

  Examples of the color pigment (F1) include titanium oxide, zinc white, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigment, phthalocyanine pigment, quinacridone pigment, isoindoline pigment, selenium pigment, and perylene pigment. Among these, titanium oxide and carbon black can be preferably used.

  When the first colored paint (X) contains the colored pigment (F1), the content of the colored pigment (F1) is generally 1 based on 100 parts by mass of the resin solid content in the first colored paint (X). It is suitable to be in the range of ~ 120 parts by mass, especially 10 to 100 parts by mass, more particularly 15 to 50 parts by mass.

  The extender pigment (F2) includes, for example, clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, alumina white, etc. Among them, it is preferable to use barium sulfate and / or talc. .

  The first colored paint (X) is an extender (F2), in particular, barium sulfate having an average primary particle size of 1 μm or less, more preferably sulfuric acid having an average primary particle size in the range of 0.01 to 0.8 μm. Containing barium is preferable because it can provide a multilayer coating film having excellent smoothness and water resistance, high flip-flop properties, and excellent appearance with little metallic unevenness.

  In this specification, the average primary particle diameter of barium sulfate is the average of the maximum diameters of 20 barium sulfates on a straight line obtained by observing barium sulfate with a scanning electron microscope and randomly drawing on an electron micrograph. It is the value.

  When 1st colored paint (X) contains extender pigment (F2), content of extender pigment (F2) is generally 1-100 mass on the basis of 100 mass parts of resin solid content in 1st colored paint. Part, particularly 11 to 60 parts by weight, more particularly 16 to 40 parts by weight. When the first colored paint (X) contains barium sulfate having an average primary particle diameter of 1 μm or less, the content of barium sulfate having an average primary particle diameter of 1 μm or less is the resin solid content in the first colored paint (X). Generally, it is suitable to be in the range of 1 to 100 parts by weight, particularly 11 to 60 parts by weight, more particularly 16 to 40 parts by weight, based on 100 parts by weight of the minute.

  The first colored paint (X) is preferably a colored paint composition containing the colored pigment (F1) and the extender pigment (F2), and is based on 100 parts by mass of the resin solid content in the first colored paint (X). As a coloring pigment (F1) usually 1 to 120 parts by weight, particularly 10 to 100 parts by weight, more particularly 15 to 50 parts by weight, and extender pigment (F2) usually 1 to 100 parts by weight, particularly 11 to 60 parts. It is preferable to contain a mass part, and especially 16-40 mass parts.

The glitter pigment (F3) is a pigment for imparting a glittering glitter or light interference pattern to the coating film. Specifically, for example, non-leafing type or leafing type aluminum (including vapor-deposited aluminum). Copper, zinc, brass, nickel, aluminum oxide, mica, aluminum oxide coated with titanium oxide or iron oxide, mica coated with titanium oxide or iron oxide, or the like can be used. The glitter pigment (F3) is preferably flake shaped. Further, the glitter pigment (F3) has a longitudinal dimension of 1 to 100 μm, particularly 5 to 40 μm, and a thickness of 0.0001 to 5 μm, particularly 0.001 to 2 μm. Is suitable.

  The first colored paint (X) further comprises a curing catalyst, a thickener, an ultraviolet absorber, a light stabilizer, an antifoaming agent, a rust inhibitor, a plasticizer, an organic solvent, a surface conditioner, and an anti-settling agent as necessary. Ordinary paint additives such as agents can be contained alone or in combination of two or more.

  The first colored paint (X) may be either an organic solvent-type paint or an aqueous paint, but is preferably an organic solvent-type paint from the viewpoint of storage stability. In this specification, the water-based paint is a paint whose main component is water, and the organic solvent-type paint is a paint that does not substantially contain water as a solvent.

The first colored paint (X) described above can be applied to the above-mentioned object by a method known per se, for example, air spray, airless spray, rotary atomizer, etc. In this case, electrostatic application may be performed. The coating film thickness is usually 10 to 100 μm, preferably 10 to 50 μm, and more preferably 15 to 35 μm as a cured film thickness.

  The coated first colored paint (X) is coated with the solid content of the paint film by means of, for example, preheating (preheating), air blowing, etc. before applying the aqueous second colored paint (Y). Can be adjusted.

  The preheating is usually performed by directly or indirectly heating the coated object in a drying furnace at a temperature of about 50 to about 110 ° C., preferably about 60 to about 90 ° C. for about 1 to 30 minutes. Moreover, the said air blow can be normally performed by spraying the air heated to normal temperature or the temperature of about 25 to 80 degreeC on the coating surface of the to-be-coated object.

  When an organic solvent-type paint is used as the first colored paint (X), it is preferable not to perform preheating from the viewpoint of energy saving. That is, in the coating film forming method of the present invention, it is possible to use an organic solvent-type paint as the first colored paint (X) and not to perform preheating after the first colored paint (X) is applied. And a multi-layer coating film with excellent smoothness, sharpness, water resistance and flip-flop properties and little metallic unevenness can be formed.

Application of aqueous second colored paint (Y) Next, the aqueous second colored paint (Y) is applied onto the first colored coating film formed as described above.

Water-based second colored paint (Y)
The water-based second colored paint (Y) is generally applied for the purpose of imparting an excellent appearance to the article to be coated. The water-based second colored paint (Y) is, for example, an automobile body. Those known per se that are usually used in painting can be used. Specifically, for example, a base resin such as an acrylic resin, a polyester resin, an alkyd resin, a urethane resin, and an epoxy resin having a crosslinkable functional group such as a carboxyl group and a hydroxyl group, and a polyisocyanate compound that may be blocked, A resin component prepared by dissolving or dispersing a resin component composed of a curing agent such as a melamine resin or a urea resin in water together with a pigment and other additives can be used. Especially, the thermosetting water-based coating material containing the above-mentioned hydroxyl-containing resin (A) and melamine resin can be used conveniently.

  Further, as the pigment, the above-described color pigment (F1), extender pigment (F2), glitter pigment (F3), and the like can be used. Among them, the water-based second colored paint (Y) contains the glitter pigment (F3), which is excellent in smoothness, sharpness and water resistance, high in flip-flop properties, and excellent in metallic unevenness. Since a multilayer coating film having an appearance can be formed, it is particularly suitable.

  Examples of the bright pigment (F3) include non-leafing type or leafing type aluminum (including vapor-deposited aluminum), copper, zinc, brass, nickel, aluminum oxide, mica exemplified in the description of the first colored paint (X). And aluminum oxide coated with titanium oxide or iron oxide, mica coated with titanium oxide or iron oxide, and the like. Among these, aluminum, aluminum oxide, mica, aluminum oxide coated with titanium oxide or iron oxide, mica coated with titanium oxide or iron oxide are preferably used, and aluminum is particularly preferably used. These glitter pigments can be used alone or in combination of two or more. The glitter pigment (F3) is preferably flake shaped. The glitter pigment (F3) has a longitudinal dimension of 1 to 100 μm, particularly 5 to 40 μm, and a thickness of 0.0001 to 5 μm, particularly 0.001 to 2 μm. Is suitable.

  When the aqueous second colored paint (Y) contains the glitter pigment (F3), the content of the glitter pigment (F3) is based on 100 parts by mass of the solid content in the aqueous second colored paint (Y). Generally, it is suitable to be in the range of 1 to 40 parts by weight, particularly 3 to 30 parts by weight, more particularly 5 to 20 parts by weight.

  The aqueous second colored paint (Y) preferably further contains a hydrophobic solvent (G). The hydrophobic solvent (G) is an organic solvent having a mass dissolved in 100 g of water at 20 ° C. of 10 g or less, preferably 5 g or less, more preferably 1 g or less. Hydrocarbon solvents such as mineral spirit, toluol, xylol, solvent naphtha; n-hexanol, n-octanol, 2-octanol, 2-ethylhexanol, n-decanol, benzyl alcohol, ethylene glycol mono-2-ethylhexyl ether, propylene Alcohol solvents such as glycol mono n-butyl ether, dipropylene glycol mono n-butyl ether, tripropylene glycol mono n-butyl ether, propylene glycol mono 2-ethylhexyl ether, propylene glycol monophenyl ether Ester solvents such as n-butyl acetate, isobutyl acetate, isoamyl acetate, methyl amyl acetate, ethylene glycol monobutyl ether; and ketone solvents such as methyl isobutyl ketone, cyclohexanone, ethyl n-amyl ketone, diisobutyl ketone, etc. Can be used alone or in combination of two or more.

  As the hydrophobic solvent (G), an alcohol-based hydrophobic solvent is preferably used from the viewpoint of the smoothness of the resulting multilayer coating film. Among them, alcohol solvents having 7 to 14 carbon atoms such as n-octanol, 2-octanol, 2-ethyl-1-hexanol, ethylene glycol mono 2-ethylhexyl ether, propylene glycol mono n-butyl ether, dipropylene glycol mono n-Butyl ether is particularly preferred.

In the case where the aqueous second colored paint (Y) contains the hydrophobic solvent (G), the content of the hydrophobic solvent (G) is based on 100 parts by mass of the resin solid content in the aqueous second colored paint (Y). , Generally 2-7
It is suitable to be in the range of 0 parts by weight, especially 11-60 parts by weight, more particularly 16-55 parts by weight. The resin solid content in the aqueous second colored paint (Y) is the sum of the base resin and the curing agent.

  If necessary, the water-based second colored paint (Y) may further be, for example, a curing catalyst, a thickener, an ultraviolet absorber, a light stabilizer, an antifoaming agent, a rust inhibitor, a plasticizer, an organic solvent, or a surface conditioner. Ordinary paint additives such as anti-settling agents can be contained alone or in combination of two or more.

The water-based second colored paint (Y) can be applied by a method known per se, for example, air spray, airless spray, rotary atomizing coater, etc. Also good. The coating film thickness is usually 5 to 40 μm, preferably 10 to 30 μm, and more preferably 12 to 20 μm as a cured film thickness.

  The coated film of the water-based second colored paint (Y) is heated for about 1 to 60 minutes at a temperature of about 50 to about 110 ° C., preferably about 60 to about 90 ° C., for example, by preheating, air blowing or the like. Can be dried.

Application of Clear Paint (Z) A clear paint (Z) is further applied onto the uncured coating film of the aqueous second colored paint (Y) formed as described above.

Clear paint (Z)
As the clear paint (Z), for example, those known per se that are usually used in the painting of automobile bodies can be used. Specifically, for example, a base resin such as an acrylic resin, a polyester resin, an alkyd resin, a urethane resin, an epoxy resin, or a fluororesin having a crosslinkable functional group such as a hydroxyl group, a carboxyl group, an epoxy group, or a silanol group, and melamine Resin, urea resin, polyisocyanate compound which may be blocked, carboxyl group-containing compound or resin, epoxy group-containing compound or cross-linking agent such as resin, etc., organic solvent-based thermosetting paint, aqueous thermosetting type A paint, a thermosetting powder paint, or the like can be used. Among these, a thermosetting paint comprising a hydroxyl group-containing acrylic resin and a melamine resin, a thermosetting paint comprising a hydroxyl group-containing acrylic resin and an optionally blocked polyisocyanate compound, or a carboxyl group-containing resin and an epoxy group A thermosetting paint comprising a resin is particularly preferred.

  The clear paint (Z) may be in the form of a one-component paint, or in the form of a two-component paint such as a two-component urethane resin paint.

  If necessary, the clear paint (Z) can contain the above-mentioned color pigment (F1), glitter pigment (F3), dye, etc. to such an extent that the transparency is not hindered. F2), a curing catalyst, a thickener, an ultraviolet absorber, a light stabilizer, an antifoaming agent, a rust inhibitor, a plasticizer, an organic solvent, a surface conditioner, an anti-settling agent and the like can be appropriately contained.

The clear paint (Z) can be applied to the coating surface of the water-based second colored paint (Y) by a method known per se, for example, airless spray, air spray, rotary atomizer, etc. In this case, electrostatic application may be performed. The clear paint (Z) can be applied usually in a dry film thickness of 10 to 60 μm, preferably 25 to 50 μm.

  After the clear paint (Z) is applied, it may be preheated at room temperature for about 1 to 60 minutes, preferably 3 to 20 minutes, or at about 40 to 80 ° C. for 1 to 60 minutes. it can.

Baking A multi-layer coating film composed of three layers of the first colored coating film, the second colored coating film and the clear coating film formed as described above can be obtained by a conventional coating film baking means, for example, It can be cured by heating at a temperature of about 80 to about 170 ° C., preferably about 120 to about 160 ° C. for about 15 to about 40 minutes, by hot air heating, infrared heating, high frequency heating or the like.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited only to these Examples. “Parts” and “%” indicate “parts by mass” and “% by mass”.

Production of hydroxyl group-containing polyester resin solution (A1) Production Example 1
In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and water separator, 89 parts of neopentyl glycol, 20 parts of trimethylolpropane, 83 parts of isophthalic acid, 44 parts of adipic acid and 1,2-cyclohexanedicarboxylic acid After charging 23 parts of acid anhydride and raising the temperature from 160 ° C. to 230 ° C. over 3 hours, the condensed water produced was kept at 230 ° C. while distilling off with a water separator, and the acid value was 3 mg KOH / g. Until the solid content is 60% with a mixed solvent of xylene / swazol 1000 (trade name, manufactured by Cosmo Oil Co., Ltd., petroleum aromatic hydrocarbon solvent) = 50/50 (mass ratio), A hydroxyl group-containing polyester resin solution (A1-1) was obtained. The content of the alicyclic polybasic acid (a1-1-2) in the acid component (a1-1) of the obtained hydroxyl group-containing polyester resin is 16 mol based on the total amount of the acid component (a1-1). The acid value was 3 mgKOH / g, the hydroxyl value was 67 mgKOH / g, and the weight average molecular weight was 10,500.

Production Example 2
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser and water separator, 89 parts of neopentyl glycol, 20 parts of trimethylolpropane, 8.9 parts of phthalic anhydride, 29 parts of adipic acid and 1, 2 -108 parts of cyclohexanedicarboxylic acid anhydride was charged, and the temperature was raised from 160 ° C to 230 ° C over 3 hours, and then the condensed water produced was kept at 230 ° C while distilling off with a water separator, and the acid value was 3 mgKOH The reaction is continued until x / g is reached, so that the solid content is 60% with a mixed solvent of xylene / swazol 1000 (trade name, manufactured by Cosmo Oil Co., Ltd., petroleum aromatic hydrocarbon solvent) = 50/50 (mass ratio). Dilution was performed to obtain a hydroxyl group-containing polyester resin solution (A1-2). The content of the alicyclic polybasic acid (a1-1-2) in the acid component (a1-1) of the obtained hydroxyl group-containing polyester resin is 73 based on the total amount of the acid component (a1-1). The acid value was 3 mgKOH / g, the hydroxyl value was 61 mgKOH / g, and the weight average molecular weight was 12,600.

Production of hydroxyl group-containing acrylic resin solution (A2) Production Example 3
A reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser and dropping device was charged with 72 parts of xylene and 8 parts of n-butanol, stirred at 100 ° C. while blowing nitrogen gas, and 3 parts of styrene therein. , 50 parts of methyl methacrylate, 20 parts of ethyl acrylate, 8.5 parts of n-butyl acrylate, 15 parts of 2-hydroxyethyl methacrylate, 1.5 parts of acrylic acid and 1 part of 2,2′-azobisisobutyronitrile Was dripped at a uniform rate over 3 hours and further aged at the same temperature for 2 hours. Thereafter, a mixture of 10 parts of xylene and 0.5 part of 2,2′-azobisisobutyronitrile was added dropwise to the reaction vessel over 1 hour, and aged for 1 hour after completion of the addition, containing a hydroxyl group having a solid content of 55%. An acrylic resin solution (A2-1) was obtained. The resulting hydroxyl group-containing acrylic resin had an acid value of 3 mgKOH / g, a hydroxyl value of 65 mgKOH / g, and a weight average molecular weight of 35,000.

Production of polyester resin solution (a) Production example 4
In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and water separator, 89 parts neopentyl glycol, 20 parts trimethylolpropane, 15 parts adipic acid, 129 parts 1,2-cyclohexanedicarboxylic anhydride Then, 0.002 part of monobutyltin hydroxide was charged, and the contents were heated to 230 ° C. over 4 hours while stirring. Further, after heating at 230 ° C. for 2 hours, in order to promote the removal of the condensed water by-produced in the esterification reaction, 5% xylene is added to the total charged amount to maintain a temperature of 230 ° C. Heating was continued until 3 mg KOH / g. When the resin acid value reached 3 mgKOH / g, heating was stopped, and the residue was diluted with xylene so that the heating residue was 60% to obtain a polyester resin solution. Next, in 153 parts of the obtained polyester resin solution, 5 parts of xylene, 2.28 parts of a 1: 1 (molar ratio) adduct of isophorone diisocyanate and 2-hydroxyethyl acrylate synthesized by a known method and 4-tert- After adding 0.02 part of butylcatechol and reacting at 90 ° C. for 3 hours and introducing a polymerizable unsaturated group, it was diluted with n-butanol to obtain a polyester resin solution (a-1) having a solid content of 58%. . The total content of the alicyclic polybasic acid (a-1-1) and the alicyclic polyhydric alcohol (a-2-1) in the obtained polyester resin is the acid component (a-1) and the alcohol component. Based on the total amount of (a-2), it was 43 mol%, the acid value was 3 mgKOH / g, the hydroxyl value was 64 mgKOH / g, and the weight average molecular weight was 12,800.

Production Example 5
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser and water separator, 137 parts of trimethylolpropane, 69 parts of isophthalic acid, 75 parts of 1,2-cyclohexanedicarboxylic acid anhydride and monobutyltin hydroxide 0 0.002 part was charged and the contents were heated to 230 ° C. over 3 hours with stirring. Furthermore, after heating at 230 ° C. for 1.5 hours, 105 parts of coconut oil fatty acid is added, and 5% xylene is added to the total charged amount to promote removal of condensed water by-produced in the esterification reaction. The temperature was maintained at 0 ° C., and heating was continued until the resin acid value reached 3 mgKOH / g. When the resin acid value reached 3 mgKOH / g, heating was stopped, and the residue was diluted with xylene so that the heating residue was 60% to obtain a polyester resin solution. Next, in 153 parts of the obtained polyester resin solution, 5 parts of xylene, 2.28 parts of a 1: 1 (molar ratio) adduct of isophorone diisocyanate and 2-hydroxyethyl acrylate synthesized by a known method and 4-tert- After adding 0.02 part of butylcatechol and reacting at 90 ° C. for 3 hours and introducing a polymerizable unsaturated group, it was diluted with n-butanol to obtain a polyester resin solution (a-2) having a solid content of 58%. . The total content of the alicyclic polybasic acid (a-1-1) and the alicyclic polyhydric alcohol (a-2-1) in the obtained polyester resin is determined based on the acid component (a-1) and the alcohol component ( Based on the total amount of a-2), it was 20 mol%, the acid value was 3 mgKOH / g, the hydroxyl value was 111 mgKOH / g, and the weight average molecular weight was 13,500.

Production Example 6
In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and water separator, 41 parts of trimethylolpropane, 53 parts of neopentyl glycol, 12.4 parts of ethylene glycol, 126 parts of phthalic anhydride, coconut oil fatty acid 32 parts and 0.002 part of monobutyltin hydroxide were charged and the contents were heated to 230 ° C. over 4 hours while stirring. After further heating at 230 ° C. for 2 hours, 5% xylene is added to the total charge to maintain the temperature at 230 ° C. to promote the removal of the condensed water by-produced in the esterification reaction, and the acid value is 3 mgK.
Heating was continued until OH / g. When the acid value reached 3 mgKOH / g, heating was stopped and the residue was diluted with xylene so that the heating residue was 60% to obtain a polyester resin solution. Next, in 153 parts of the obtained polyester resin solution, 5 parts of xylene, 2.28 parts of a 1: 1 (molar ratio) adduct of isophorone diisocyanate and 2-hydroxyethyl acrylate synthesized by a known method and 4-tert- After adding 0.02 part of butylcatechol and reacting at 90 ° C. for 3 hours and introducing a polymerizable unsaturated group, it was diluted with n-butanol to obtain a polyester resin solution (a-3) having a solid content of 58%. . The total content of the alicyclic polybasic acid (a-1-1) and the alicyclic polyhydric alcohol (a-2-1) in the obtained polyester resin is determined based on the acid component (a-1) and the alcohol component ( Based on the total amount of a-2), it was 0 mol%, the acid value was 3 mgKOH / g, the hydroxyl value was 103 mgKOH / g, and the weight average molecular weight was 7,500.

Production of polymerizable unsaturated monomer (c-1) having a self-condensed polyester chain of a hydroxyl group-containing fatty acid Production Example 7
A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and water separator was charged with 740 parts of 12-hydroxystearic acid and 132 parts of toluene and heated to 140 ° C., and 12-hydroxystearic acid was completely removed. After dissolution, 1.5 parts of methanesulfonic acid was added, and the dehydration condensation reaction was continued for about 8 hours. A 12-hydroxystearic acid self-condensed polyester having a resin acid value of 30 mgKOH / g and a number average molecular weight of 1,800 was obtained. Obtained. To this resin solution, 0.7 parts of 4-tert-butylcatechol, 89.5 parts of glycidyl methacrylate, and 3 parts of N, N-dimethyl-n-dodecylamine were added, and heating was continued at 140 ° C. for about 8 hours. The reaction was continued until the acid value was 0.3 or less. The reaction product was cooled and then diluted with toluene to obtain a polymerizable unsaturated monomer solution (c-1-1) having a self-condensed polyester chain of a hydroxyl group-containing fatty acid having a solid content concentration of 70%.

Production of copolymer (c) Production Example 8
A reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser and dropping device was charged with 174 parts of butyl acetate, heated to 100 ° C., and then the polymerizable unsaturated monomer solution (c-1) obtained in Production Example 7 -1) A mixture of 297 parts, 196 parts of methyl methacrylate, 19 parts of glycidyl methacrylate, 163 parts of xylene and 9.6 parts of 2,2′-azobisisobutyronitrile was added dropwise to the reaction vessel over 3 hours, and the addition was completed. After 4 hours aging. Thereafter, a mixture of 0.05 part of 4-tert-butylcatechol, 3.8 parts of methacrylic acid and 0.5 part of 2- (dimethylamino) ethanol was added, and the temperature until 140 ° C. was reached until the resin acid value reached 0.5. The reaction was continued for about 5 hours, and then butyl acetate was added to obtain a copolymer (c-1) solution having a solid content of 45% and a weight average molecular weight of 25,000.

Production Example 9
A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and dropping device was charged with 90 parts of butyl acetate, then 38.9 parts of methyl methacrylate, 38.8 parts of stearyl methacrylate, 2-hydroxyethyl acrylate Of the mixed solution consisting of 22.3 parts and 2,2′-azobisisobutyronitrile, 20 parts were added and heated with stirring to raise the temperature. The remaining 85 parts of the above mixed solution was added dropwise at 110 ° C. over 3 hours, and then a solution consisting of 0.5 parts of azoisobutyronitrile and 10 parts of butyl acetate was added dropwise over 30 minutes. The reaction solution was further stirred and refluxed for 2 hours to increase the rate of conversion to resin, and then the reaction was terminated to obtain a copolymer (c-2) solution having a solid content of 50%.

Production of polymer fine particles (C) Production Example 10
Polyester resin (a-1) obtained in Production Example 4 after charging 77 parts of xylene and 63 parts of heptane in a reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser and a dropping device, and raising the temperature to 100 ° C. 69 parts (solid content 40 parts), methyl acrylate 50 parts, methyl methacrylate 10 parts, acrylonitrile 20 parts, 2-hydroxyethyl acrylate 14 parts, glycidyl methacrylate 4 parts, acrylic acid 2 parts, 2,2'-azobisisobuty A mixture 1 of 2 parts of ronitrile and 1 part of 2- (dimethylamino) ethanol was added dropwise to the reaction vessel over 3 hours. After completion of the addition, the mixture was aged for 4 hours, and then xylene was added to give a polymer having a solid concentration of 40%. A fine particle dispersion (C-1) was obtained. The average particle size of the obtained polymer fine particles was 330 nm (manufactured by Beckman Coulter, measured with “COULTER N4 type”).

Production Examples 11-18
In Production Example 10, synthesis was performed in the same manner as in Production Example 10 except that the mixture 1 was formulated as shown in Table 1 below, to obtain polymer fine particle dispersions (C-2) to (C-9). Table 1 below shows solid content concentrations and average particle diameters of the polymer fine particle dispersions (C-2) to (C-9) obtained together with Production Example 10. In addition, the mixing | blending of each mixture shown in Table 1 is solid content mass ratio of each component.

Production of polymer fine particles (D) Production Example 19
A reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser and dropping device was charged with 77 parts of xylene and 63 parts of heptane, heated to 100 ° C., and then the copolymer (c-1) obtained in Production Example 8 ) 89 parts (solid content 40 parts), methyl acrylate 10 parts, methyl methacrylate 50 parts, acrylonitrile 20 parts, 2-hydroxyethyl acrylate 14 parts, glycidyl methacrylate 4 parts, acrylic acid 2 parts, 2,2′-azobisiso A mixture 1 of 2 parts of butyronitrile and 1 part of 2- (dimethylamino) ethanol was added dropwise to the reaction vessel over 3 hours. After completion of the dropwise addition, the mixture was aged for 4 hours, and then xylene was added. A coalesced fine particle dispersion (D-1) was obtained. The average particle size of the obtained polymer fine particles was 190 nm.

Production Example 20
A reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser and dropping device was charged with 77 parts of xylene and 63 parts of heptane, heated to 100 ° C., and then copolymer (c-2) obtained in Production Example 9 ) 80 parts (solid content 40 parts), methyl acrylate 10 parts, methyl methacrylate 50
1 part of acrylonitrile, 20 parts of acrylonitrile, 14 parts of 2-hydroxyethyl acrylate, 4 parts of glycidyl methacrylate, 2 parts of acrylic acid, 2 parts of 2,2′-azobisisobutyronitrile and 1 part of 2- (dimethylamino) ethanol Was added dropwise to the reaction vessel over 3 hours, and after ripening for 4 hours, xylene was added to obtain a polymer fine particle dispersion (D-2) having a solid concentration of 40%. The average particle diameter of the obtained polymer fine particles was 260 nm.

Production of crosslinked polymer fine particles (E) Production Example 21
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser and dropping device, 355 parts of deionized water and "Latemul S-120A" (trade name, manufactured by Kao Corporation, sulfosuccinic acid-based allyl group-containing anionic reaction) 2 parts of an emulsifying emulsifier, 50% aqueous solution) and heated to 90 ° C. with stirring. To this, “VA-086” (trade name, manufactured by Wako Pure Chemical Industries, Ltd., 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propion, which is a water-soluble azoamide polymerization initiator) Amide]) 1.25 parts of an aqueous solution of 50 parts of deionized water was added. After 15 minutes, 5% of a monomer mixture consisting of 30 parts styrene, 40 parts methyl methacrylate, 15 parts n-butyl acrylate, 5 parts 2-hydroxyethyl acrylate and 10 parts 1,6-hexanediol diacrylate was added. Next, after stirring for another 30 minutes, the dropping of the remaining monomer mixture and aqueous polymerization initiator solution was started. The dropwise addition of the monomer mixture was performed for 3 hours, and the dropwise addition of the polymerization initiator aqueous solution was performed for 3.5 hours, while the polymerization temperature was maintained at 90 ° C. Even after completion of the dropwise addition of the polymerization initiator aqueous solution, the mixture was heated for 30 minutes and maintained at 90 ° C., cooled to room temperature, and taken out using a filter cloth to obtain an aqueous dispersion of crosslinked polymer fine particles having a solid content of 20%.

  This aqueous dispersion was dried on a stainless steel vat in an electric hot air dryer at 60 ° C. and taken out as a solid resin. Thereafter, the mixture was dispersed in a mixed solvent of xylene / n-butyl alcohol = 50/50 (mass ratio) heated to 60 ° C. to obtain a crosslinked polymer fine particle dispersion (E-1) having a solid concentration of 15%. . The average particle diameter of the obtained polymer fine particles was 90 nm.

Production Example 22
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser and dropping device, 355 parts of deionized water and "Latemul S-120A" (trade name, manufactured by Kao Corporation, sulfosuccinic acid-based allyl group-containing anionic reaction) 20 parts of water-soluble emulsifier, 50% aqueous solution), and heated to 90 ° C. with stirring. To this, “VA-086” (trade name, manufactured by Wako Pure Chemical Industries, Ltd., 2,2′-azobis [2-methyl-N- (2-hydroxyethyl) -propion, which is a water-soluble azoamide polymerization initiator) Amide]) 1.25 parts of an aqueous solution of 50 parts of deionized water was added. After 15 minutes, 5% of a monomer mixture consisting of 30 parts styrene, 40 parts methyl methacrylate, 15 parts n-butyl acrylate, 5 parts 2-hydroxyethyl acrylate and 10 parts 1,6-hexanediol diacrylate was added. Next, after stirring for another 30 minutes, the dropping of the remaining monomer mixture and aqueous polymerization initiator solution was started. The dropwise addition of the monomer mixture was performed for 3 hours, and the dropwise addition of the polymerization initiator aqueous solution was performed for 3.5 hours, while the polymerization temperature was maintained at 90 ° C. Even after completion of the dropwise addition of the polymerization initiator aqueous solution, the mixture was heated for 30 minutes and maintained at 90 ° C., cooled to room temperature, and taken out using a filter cloth to obtain an aqueous dispersion of crosslinked polymer fine particles having a solid content of 20%.

  This aqueous dispersion was dried on a stainless steel vat in an electric hot air dryer at 60 ° C. and taken out as a solid resin. Thereafter, the mixture was dispersed in a mixed solvent of xylene / n-butyl alcohol = 50/50 (mass ratio) heated to 60 ° C. to obtain a crosslinked polymer fine particle dispersion (E-2) having a solid content concentration of 15%. . The average particle diameter of the obtained polymer fine particles was 50 nm.

Production Example 23
In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and dropping device, 130 parts of deionized water and “Latemul S-120A” (trade name, manufactured by Kao Corporation, sulfosuccinic acid-based allyl group-containing anionic reactivity) 1 part emulsifier, 50% aqueous solution) was added, and the temperature was raised to 80 ° C. with stirring. Next, 1% of the total amount of the following monomer emulsion (1) and 5.3 parts of a 6% aqueous ammonium persulfate solution were introduced into the reaction vessel and maintained at 80 ° C. for 15 minutes. Thereafter, the remaining monomer emulsion (1) was dropped into a reaction vessel maintained at the same temperature over 3 hours, and after aging was completed for 1 hour, it was taken out using a filter cloth, and the solid content was 20%. A crosslinked polymer fine particle aqueous dispersion was obtained.

  This aqueous dispersion was dried on a stainless steel vat in an electric hot air dryer at 60 ° C. and taken out as a solid resin. Thereafter, it was dispersed in a mixed solvent of xylene / n-butyl alcohol = 50/50 (mass ratio) heated to 60 ° C. to obtain a crosslinked polymer fine particle dispersion (E-3) having a solid content concentration of 15%. . The average particle diameter of the obtained polymer fine particles was 230 nm.

  Monomer emulsion (1): 65 parts of deionized water, 2 parts of “Latemul S-120A”, 30 parts of styrene, 40 parts of methyl methacrylate, 15 parts of n-butyl acrylate, 5 parts of 2-hydroxyethyl acrylate and 1,6- 10 parts of hexanediol diacrylate was mixed and stirred to obtain a monomer emulsion (1).

Production of first colored paint (X) Production Examples 24-41
Hydroxyl group-containing polyester resin solutions (A1-1) to (A1-2) obtained in Production Examples 1 and 2 above, hydroxyl group-containing acrylic resin solution (A2-1) obtained in Production Example 3, and melamine resin (B1- 3-1) (Methyl-butyl mixed etherified melamine resin, solid content 60%, weight average molecular weight 2,000), blocked isocyanate compound (B3-1) (hexamethylene diisocyanate isocyanurate diethyl malonate blocked product) , Solid content 60%), polymer fine particles (C-1) to (C-9) obtained in Production Examples 10 to 18, and polymer fine particles (D-1) to (D-1) to (D) obtained in Production Examples 19 to 20 D-2), polymer fine particles (E-1) to (E-3) obtained in Production Examples 21 to 23, JR-806 (trade name, manufactured by Teica, rutile titanium dioxide), carbon MA-100 ( Product name, manufactured by Mitsubishi Chemical Corporation, carbon black), Variace B-34 (trade name, manufactured by Sakai Chemical Industry Co., Ltd., barium sulfate powder, average primary particle size 0.3 μm), MICRO ACE S-3 (trade name, Nippon Talc Co., Ltd.) Manufactured, talc powder, average primary particle size 4.8 μm) with the composition shown in Table 2 below, stirring and mixing with a disper to form a paint, the first colored paint (X-1) to (X-18) Got. In addition, the mixing | blending of the 1st coloring coating material shown in Table 2 is solid content mass ratio of each component. In addition, in blending the pigment component, 7 parts of xylene was added to and mixed with 42 parts of the hydroxyl group-containing polyester resin solution (25 parts of resin solids) in the first colored paint and the amount of pigment shown in the table. The mixture was dispersed for 30 minutes to obtain a pigment dispersion paste, which was then stirred and mixed with other components. By adding a mixed solvent of xylene / swazol 1000 (trade name, manufactured by Cosmo Oil Co., Ltd., petroleum aromatic hydrocarbon solvent) = 50/50 (mass ratio), the first colored paint was further added to Ford Cup No. 4 was used to adjust the viscosity to 20 seconds at 20 ° C.

Production Example of Acrylic Emulsion for Aqueous Second Colored Paint (Y) Production Example 42
A reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser and a dropping device was charged with 130 parts of deionized water and 0.52 parts of Aqualon KH-10 (Note 1), and stirred and mixed in a nitrogen stream. The temperature was raised to ° C. Subsequently, 1% of the total amount of the following monomer emulsion 1 and 5.3 parts of a 6% aqueous ammonium persulfate solution were introduced into the reaction vessel and maintained at 80 ° C. for 15 minutes. Then, the remaining monomer emulsion (1) was dripped in the reaction container hold | maintained at the same temperature over 3 hours, and it age | cure | ripened for 1 hour after completion | finish of dripping. Thereafter, the following monomer emulsion (2) was added dropwise over 1 hour, and after aging for 1 hour, the mixture was cooled to 30 ° C. while gradually adding 40 parts of 5% dimethylethanolamine aqueous solution to the reaction vessel, and 100 mesh nylon It was discharged while being filtered with a cloth, and the average particle size was 100 nm (submicron particle size distribution measuring device “COULTER N4 type” (manufactured by Beckman Coulter), diluted with deionized water and measured at 20 ° C.), solid. An acrylic emulsion having a partial concentration of 30%, an acid value of 33 mgKOH / g, and a hydroxyl value of 25 mgKOH / g was obtained.

(Note 1) Aqualon KH-10: Polyoxyethylene alkyl ether sulfate ester ammonium salt: 97% active ingredient manufactured by Daiichi Kogyo Seiyaku Co., Ltd.
Monomer emulsion (1): 42 parts deionized water, 0.72 parts Aqualon KH-10, 2.1 parts methylenebisacrylamide, 2.8 parts styrene, 16.1 parts methyl methacrylate, 28 parts ethyl acrylate and n- 21 parts of butyl acrylate was mixed and stirred to obtain a monomer emulsion (1).
Monomer emulsion (2): 18 parts deionized water, 0.31 part Aqualon KH-10, 0.03 part ammonium persulfate, 5.1 parts methacrylic acid, 5.1 parts 2-hydroxyethyl acrylate, 3 parts styrene, 6 parts of methyl methacrylate, 1.8 parts of ethyl acrylate and 9 parts of n-butyl acrylate were mixed and stirred to obtain a monomer emulsion (2).

Production of polyester resin solution for aqueous second colored paint (Y) Production Example 43
A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and water separator was charged with 109 parts of trimethylolpropane, 141 parts of 1,6-hexanediol, 126 parts of hexahydrophthalic anhydride and 120 parts of adipic acid. The temperature was raised between 160 ° C. and 230 ° C. over 3 hours, and then a condensation reaction was performed at 230 ° C. for 4 hours. Subsequently, in order to add a carboxyl group to the obtained condensation reaction product, 38.3 parts of trimellitic anhydride was further added and reacted at 170 ° C. for 30 minutes, and then 2-ethyl-1-hexanol (20 ° C. In a polyester resin solution (mass dissolved in 100 g of water: 0.1 g), the acid value is 46 mgKOH / g, the hydroxyl value is 150 mgKOH / g, the solid content concentration is 70%, and the weight average molecular weight is 6,400. PE1) was obtained.

Production Example 44
A polyester resin solution (in the same manner as in Production Example 43) except that 2-ethyl-1-hexanol as a dilution solvent is changed to ethylene glycol mono n-butyl ether (mass dissolved in 100 g of water at 20 ° C .: infinite). PE2) was obtained.

Production Example of Bright Pigment Concentrate Liquid Production Example 45
In the stirring and mixing vessel, 19 parts of aluminum pigment paste “GX-180A” (made by Asahi Kasei Metals Co., Ltd., metal content 74%), 35 parts of 2-ethyl-1-hexanol, resin solution containing phosphate group (Note 2) 8 And 0.2 part of 2- (dimethylamino) ethanol were mixed uniformly to obtain a bright pigment concentrate (P1).

  (Note 2) Phosphate group-containing resin solution: In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and dropping device, a mixed solvent of 27.5 parts of methoxypropanol and 27.5 parts of isobutanol was added, 6. Heat to 110 ° C., 25 parts of styrene, 27.5 parts of n-butyl methacrylate, 20 parts of “isostearyl acrylate” (trade name, Osaka Organic Chemical Industries, Ltd., branched higher alkyl acrylate), 4-hydroxybutyl acrylate 51.5 parts, 15 parts of a phosphoric acid group-containing polymerizable monomer (Note 3), 12.5 parts of 2-methacryloyloxyethyl acid phosphate, 10 parts of isobutanol, 4 parts of t-butyl peroxyoctanoate 121.5 Is added to the above mixed solvent over 4 hours, and 0.5 part of t-butylperoxyoctanoate and A mixture of propanol 20 parts was added dropwise for 1 hour. Thereafter, the mixture was aged and stirred for 1 hour to obtain a phosphate group-containing resin solution having a solid concentration of 50%. The acid value due to the phosphoric acid group of this resin was 83 mgKOH / g, the hydroxyl value derived from 4-hydroxybutyl acrylate was 29 mgKOH / g, and the weight average molecular weight was 10,000.

(Note 3) Phosphoric acid group-containing polymerizable monomer: Into a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and dropping device, put 57.5 parts of monobutyl phosphate and 41 parts of isobutanol and raise the temperature to 90 ° C. After warming, 42.5 parts of glycidyl methacrylate was added dropwise over 2 hours, followed by stirring and aging for another hour. Thereafter, 59 parts of isopropanol was added to obtain a phosphate group-containing polymerizable monomer solution having a solid content concentration of 50%. The acid value due to the phosphate group of the obtained monomer was 285 mgKOH / g.

Production Example 46
A bright pigment concentrate (P2) was obtained in the same manner as in Production Example 45, except that 35 parts of 2-ethyl-1-hexanol was changed to 35 parts of ethylene glycol mono n-butyl ether.

Production of water-based second colored paint (Y) Production Example 47
100 parts of the acrylic emulsion obtained in Production Example 42, 57 parts of the polyester resin solution (PE1) obtained in Production Example 43, 62 parts of the glitter pigment concentrated liquid (P1) obtained in Production Example 45 and “Cymel 325” (trade name) , Nippon Cytec Industries, Inc., melamine resin, solid content 80%) 37.5 parts uniformly mixed, deionized water and 2- (dimethylamino) ethanol added, pH 8.0, solid content concentration 23% Water-based second colored paint (Y-1) was obtained.

Production Example 48
100 parts of the acrylic emulsion obtained in Production Example 42, 57 parts of the polyester resin solution (PE2) obtained in Production Example 44, 62 parts of the bright pigment concentrate (P2) obtained in Production Example 46, and “Cymel 325” (trade name) , Nippon Cytec Industries, Inc., melamine resin, solid content 80%) 37.5 parts uniformly mixed, deionized water and 2- (dimethylamino) ethanol added, pH 8.0, solid content concentration 23% Water-based second colored paint (Y-2) was obtained.

Coating Film Formation Method The first colored paints (X-1) to (X-18) obtained in Production Examples 24 to 41 and the aqueous second colored paint (Y-1) obtained in Production Examples 47 to 48 and ( For Y-2), test plates were prepared and evaluated as follows.

(Preparation of test article)
Electrocolon-coated ELECRON GT-10 (trade name, manufactured by Kansai Paint Co., Ltd., cationic electrodeposition paint) on a cold-rolled steel sheet that has been subjected to zinc phosphate chemical conversion treatment to a cured film thickness of 20 μm, and at 170 ° C. for 30 minutes It was heated and cured to give a test article.

Example 1
In a coating environment at a temperature of 23 ° C. and a humidity of 75%, the first colored paint (X-1) obtained in Production Example 24 was applied to the test object by using a rotary atomizing type coating machine. It was painted to 20 μm and left for 10 minutes. Next, on the first colored coating film, the aqueous second colored paint (Y-1) obtained in Production Example 47 was applied using a rotary atomizing coating machine so as to have a cured film thickness of 15 μm. Preheating was performed at 80 ° C. for 3 minutes. Next, a cured film of Magiclon KINO-1210 (trade name, manufactured by Kansai Paint Co., Ltd., acrylic resin-based solvent-based clear coating, hereinafter referred to as “clear coating (Z-1)”) on the second colored coating film. The film was coated to a thickness of 35 μm and left for 7 minutes, and then heated at 140 ° C. for 30 minutes to simultaneously cure the first colored coating film, the second colored coating film, and the clear coating film to prepare a test plate. .

Examples 2-14, Comparative Examples 1-5
In Example 1, the first colored paint (X-1) obtained in Production Example 24 is any one of the first colored paints (X-2) to (X-23) shown in Table 3, and Production Example 47 A test plate was prepared in the same manner as in Example 1 except that the water-based second colored paint (Y-1) obtained in 1 was changed to the water-based second colored paint (Y-1) or (Y-2) shown in Table 3. Produced.

  Each test plate obtained in Examples 1 to 14 and Comparative Examples 1 to 5 was evaluated by the following test method. The evaluation results are shown in Table 3.

(Test method)
Smoothness: Evaluation was made using a Long Wave (LW) value measured by Wave Scan (trade name, manufactured by BYK Gardner). The Long Wave (LW) value is an index of the amplitude of the surface roughness having a wavelength of about 1.2 to 12 mm, and the smaller the measured value, the higher the smoothness of the coated surface.

  Vividness: Evaluated using the Short Wave (SW) value measured by Wave Scan (trade name, manufactured by BYK Gardner). The Short Wave (SW) value is an index of the amplitude of the surface roughness with a wavelength of about 0.3 to 1.2 mm, and the smaller the measured value, the higher the sharpness of the coating surface.

Water resistance: After immersing the test plate in warm water of 40 ° C. for 240 hours, pulling up and drying at 20 ° C. for 12 hours, the multi-layer coating film of the test plate was cut into a grid shape with a cutter so as to reach the substrate, and the size was 2 mm. Make 100 x 2mm gobang eyes. Subsequently, an adhesive cellophane tape was attached to the surface, and the remaining number of the Gobang eyes coating after the tape was rapidly peeled off at 20 ° C. was examined.
(Double-circle): 100 gobang eyes coatings remain, and the edge of the cutting edge of a cutter does not have a small edge of the coating.
◯: 100 gobanged paint films remain, but small flickering of the paint film occurs at the edge of the cutter.
(Triangle | delta): 90-99 pieces of gobang eyes coating films remain.
X: The remaining number of gobang eyes coatings is 89 or less.

Flip-flop property: Each test plate was visually observed at different angles, and the flip-flop property was evaluated according to the following criteria.
A: The change in the metallic feeling due to the visual angle is remarkable, and it has extremely excellent flip-flop properties.
○: The change in the metallic feeling due to the viewing angle is large, and the flip-flop property is excellent.
Δ: The change in the metallic feeling due to the viewing angle is slightly small, and the flip-flop property is slightly inferior.
X: The change of the metallic feeling by a visual angle is small, and flip-flop property is inferior.

Metallic unevenness: Each test plate was visually observed, and the degree of occurrence of metallic unevenness was evaluated according to the following criteria.
A: Almost no metallic unevenness is observed, and the coating film has a very excellent appearance.
○: Metallic unevenness is slightly observed, but has excellent coating appearance.
(Triangle | delta): Metallic unevenness is recognized and a coating-film external appearance is inferior somewhat.
X: Many metallic unevenness is recognized and the coating-film external appearance is inferior.

Chipping resistance: A test plate was placed on a specimen holder of a stepping stone testing machine JA-400 (chipping test device) manufactured by Suga Test Instruments Co., Ltd., and compressed at 0.392 MPa (4 kgf / cm ² ) at −20 ° C. 50 g of granite crushed stone with a particle size of 7 was sprayed onto the coated surface with air, and the degree of occurrence of scratches on the coating film was visually observed and evaluated.
A: The size of the scratch is extremely small, and the electrodeposition surface and the base steel plate are not exposed.
○: The size of the scratch is small, and the electrodeposition surface and the base steel plate are not exposed.
Δ: Although the size of the scratch is small, the electrodeposition surface and the base steel plate are exposed.
X: The size of the scratches is quite large, and the base steel plate is also greatly exposed.

Claims (14)

A first colored paint (X), a water-based second colored paint (Y), and a clear paint (Z) are sequentially applied on the object to be coated, and a first colored paint film, a second colored paint film, and a clear paint are formed. Comprising simultaneously baking and curing the film,
The first colored paint (X) contains a hydroxyl group-containing resin (A), a curing agent (B) and polymer fine particles (C), and the polymer fine particles (C) are present in the presence of the polyester resin (a). The polymerizable unsaturated monomer (b) is an organic that dissolves the polyester resin (a) and the polymerizable unsaturated monomer (b) but does not substantially dissolve the polymer formed from the polymerizable unsaturated monomer (b). Obtained by polymerizing in a solvent,
The polyester resin (a) is obtained by the reaction of the acid component (a-1) and the alcohol component (a-2), and the acid component (a-1) and the alcohol component (a-2) The total amount of the acid component (a-1) and the alcohol component (a-2) is the total of the cyclic polybasic acid (a-1-1) and the alicyclic polyhydric alcohol (a-2-1). A multilayer coating film forming method characterized by containing at least 5 mol% as a reference.   The method for forming a multilayer coating film according to claim 1, wherein the hydroxyl group-containing resin (A) is a hydroxyl group-containing polyester resin (A1) and / or a hydroxyl group-containing acrylic resin (A2).   The method for forming a multilayer coating film according to claim 1 or 2, wherein the curing agent (B) is an amino resin (B1), a polyisocyanate compound (B2) or a blocked polyisocyanate compound (B3).   The polymer fine particle (C) comprises a polyester resin (a), a polymerizable unsaturated monomer (c-1) having a self-condensing polyester chain of a hydroxyl group-containing fatty acid, and another polymerizable unsaturated monomer (c-2). In the presence of the copolymer (c), the polymerizable unsaturated monomer (b) is dissolved in the polyester resin (a), the copolymer (c) and the polymerizable unsaturated monomer (b). The multilayer coating film according to any one of claims 1 to 3, wherein the polymer formed from the saturated monomer (b) is polymer fine particles (C ') obtained by polymerizing in a substantially insoluble organic solvent. Forming method.   The first colored paint (X) is a copolymer (c) of a polymerizable unsaturated monomer (c-1) having a self-condensing polyester chain of a hydroxyl group-containing fatty acid and another polymerizable unsaturated monomer (c-2). In the presence of the polymerizable unsaturated monomer (b), the polymerizable unsaturated monomer (b) and the copolymer (c) are dissolved, but the polymer formed from the polymerizable unsaturated monomer (b) is The method for forming a multilayer coating film according to any one of claims 1 to 4, further comprising polymer fine particles (D) obtained by polymerization in an organic solvent that does not substantially dissolve.   The method for forming a multilayer coating film according to any one of claims 1 to 5, wherein the polyester resin (a) is a fatty acid-modified polyester resin (a ').   The polyester resin (a) is obtained by the reaction of the acid component (a-1) and the alcohol component (a-2), and the acid component (a-1) and the alcohol component (a-2) The total amount of the acid component (a-1) and the alcohol component (a-2) is the total of the cyclic polybasic acid (a-1-1) and the alicyclic polyhydric alcohol (a-2-1). The method for forming a multilayer coating film according to any one of claims 1 to 6, which contains 10 to 70 mol% as a reference.   The method for forming a multilayer coating film according to any one of claims 1 to 7, wherein the polymer fine particles (C) have an average particle diameter in the range of 160 to 450 nm.   The first colored paint (X) emulsion polymerizes a polymerizable monomer (e-1) having at least two radically polymerizable unsaturated groups in the molecule and other radical polymerizable unsaturated monomers (e-2). The method for forming a multilayer coating film according to any one of claims 1 to 8, further comprising crosslinked polymer fine particles (E) obtained by caking.   The method for forming a multilayer coating film according to claim 9, wherein the crosslinked polymer fine particles (E) have an average particle diameter in the range of 40 to 200 nm.   The first colored paint (X) comprises both polymer fine particles (C) having an average particle diameter in the range of 160 to 450 nm and crosslinked polymer fine particles (E) having an average particle diameter in the range of 40 to 200 nm. The ratio of the average particle diameter of the polymer fine particles (C) to the average particle diameter of the crosslinked polymer fine particles (E): [average particle diameter of the polymer fine particles (C)] / [crosslinked polymer fine particles (E) The average particle diameter] is in the range of 1.2 / 1 to 10/1.   The multilayer coating film forming method according to any one of claims 1 to 11, wherein the first colored paint (X) further contains a pigment (F).   The method for forming a multilayer coating film according to any one of claims 1 to 12, wherein the article to be coated is a vehicle body having an undercoat coating film formed by an electrodeposition coating.   An article coated by the multilayer coating film forming method according to claim 1.