JP2018103082A - Multilayer coating film formation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer coating film formation method capable of forming a multilayer coating film excellent in feeling of luminosity and depth feeling with high chroma.SOLUTION: A multilayer coating film formation method is a method for sequentially coating a first color base coating material, a second color base coating material and a clear coating material onto a base material by a wet-on-wet method to form a multilayer coating film, where the first color base coating material contains an aluminum flake pigment and a vapor-deposited chrome flake pigment, an aluminum flake pigment concentration is in a range of 20-50 pts.mass with respect to 100 pts.mass of a resin solid content contained in the first color base coating material, a vapor-deposited chrome flake pigment concentration is in a range of 1-10 pts.mass with respect to 100 pts.mass of the aluminum flake pigment contained in the first color base coating material, and a coating material solid content concentration is in a range of 2-20 mass% with respect to the total mass of the first color base coating material.SELECTED DRAWING: None

Description

  The present invention relates to a method for forming a multilayer coating film that can form a multilayer coating film that is excellent in glitter, has very high saturation, and excellent depth.

  In exterior colors of industrial products such as automobiles, metallic paint colors whose appearance changes depending on the viewing angle dominate. Among metallic paint colors, highlights (near specularly reflected light) and high brightness, and paint colors with a large color change from highlight to shade (diagonal direction) have the effect of making the applied industrial products more prominent. There is a popular paint color. Furthermore, metallic paint colors with high saturation from highlights to shades and excellent depth are one of the most demanding user colors as high-quality and bright paint colors. As a method for obtaining a highly saturated metallic coating color, a method of laminating a color clear coating on a metallic coating is already known.

  For example, Patent Document 1 discloses a method for forming a metallic coating film in which a metallic base paint, a transparent second base paint, and a clear paint are sequentially applied. However, this method makes it difficult to manage the coating line because the coating color changes greatly due to slight variations in the thickness of the second base coating film having transparency, and the film thickness becomes thicker than the general part. There is a problem that the color of the edge portion that is easy to darken, and a so-called picture frame phenomenon occurs.

  In order to solve the above problem, in Patent Document 2, a metallic base coating containing a colored pigment and a luster pigment is applied to form a metallic base coating film, and a colored base coating containing a coloring pigment is applied thereon for coloring. A method of forming a multi-layer coating film in which a base coating film is formed and further a clear coating film is formed on the uppermost layer and then the entire film is cured, and the lightness L * value of the metallic base coating film is set to 60 or less. A method for forming a multilayer coating film is disclosed in which the light transmittance of a film having a wavelength of 400 nm or more and 700 nm or less is made 30 to 50%. According to this method, it is possible to suppress the occurrence of color unevenness due to film thickness variations, but there is a problem that the saturation at the face of the multilayer film (between highlight and shade) is not sufficient.

  On the other hand, in Patent Document 3, a metallic base coating film formed by a metallic base coating composition containing a coloring pigment (i) and a glitter pigment (ii), a colored base coating film formed by a coloring base coating composition, And a clear coating film, wherein the colored base coating composition comprises an acrylic resin (a), a melamine resin (b), a blocked isocyanate compound (c), and a phosphoric acid compound (d). And the metallic base coating film has a light transmittance of 0.0001 to 0.1% in the wavelength range of 300 nm to 420 nm, and the colored base coating film has a wavelength of 300 nm to 420 nm. The light transmittance in the range is 20 to 70%, and the colored base coating film has a dry film thickness after baking and curing of 21 to 40 μm. A forming method is described. Although a high-design multi-layer coating film that does not deteriorate the coating performance such as light resistance can be obtained, there is a problem that the flip-flop property is insufficient.

WO97 / 47396 JP 2007-167720 A JP-A-2006-185527

  An object of the present invention is to provide a method for forming a multilayer coating film that eliminates the above-mentioned problems, can form a multilayer coating film that is excellent in glitter, has high chroma, and has a deep feeling.

  That is, the present invention is a method for forming a multilayer coating film by sequentially applying a first color base paint, a second color base paint, and a clear paint on a substrate by wet-on-wet, wherein the first color base paint is aluminum. The flake pigment and the vapor deposition chromium flake pigment are contained, the aluminum flake pigment concentration is in the range of 20 to 50 parts by mass with respect to 100 parts by mass of the resin solid content contained in the first color base paint, and the vapor deposition chromium flake pigment concentration is the first color base. In the range of 1 to 10 parts by mass with respect to 100 parts by mass of the aluminum flake pigment contained in the paint, and in the range of 2 to 20% by mass of the solid content concentration of the paint based on the total mass of the first color base paint, The film thickness of the coating film with one color base paint is in the range of 1 to 7 μm based on the cured coating film, and the second color base Fee, to method for forming a multilayer coating film which comprises a coloring pigment.

  According to the method of the present invention, by using a specific amount of two specific glitter pigments as the first color base paint, a multi-layer coating film is formed which suppresses light transmission and is excellent in glitter, high chroma and depth. it can.

  In the method of the present invention, a first color base paint, a second color base paint, and a clear paint are sequentially applied on a substrate by wet-on-wet to form a multilayer coating film.

  Base materials include metals such as iron, zinc, aluminum and magnesium, alloys containing these, molded products plated or vapor-deposited with these metals, and molded products made of glass, plastic, foam, etc. Can be mentioned. Depending on these materials, it can be appropriately degreased or surface treated to form a substrate. In particular, the base material is preferably a metal material itself, various materials plated or vapor-deposited with metal, and those materials subjected to degreasing or surface treatment.

  In addition, an undercoat film or an intermediate coat film can be formed on the material or the like to form a substrate. The undercoating film is formed to conceal the surface of the material or impart anticorrosion and rustproofing properties to the material, and can be obtained by applying an undercoating paint, drying and curing. The undercoat paint type is not particularly limited, and examples thereof include an electrodeposition paint and a primer. The intermediate coating film is formed to conceal the surface of the material or the undercoating film, or to provide adhesion or chipping resistance. The intermediate coating is applied on the surface of the material or the undercoating film. It can be obtained by drying and curing. The type of intermediate coating material is not particularly limited, and known types can be used. For example, an organic solvent-based or water-based intermediate coating material containing a thermosetting resin composition and a pigment as essential components can be used.

  In the present invention, the first color base paint is applied on the substrate and contains an aluminum flake pigment and a vapor-deposited chromium flake pigment.

The above-mentioned aluminum flake pigment is generally produced by pulverizing and grinding aluminum in a ball mill or attritor mill using a pulverization aid in the presence of a pulverizing medium solution, and usually has an average particle diameter (D50) for coatings. The thing of about 1-50 micrometers, especially about 5-20 micrometers is used from the point of the stability in a coating material, or the finish of the coating film formed. The average particle diameter means a long diameter. As the grinding aid, aliphatic amines, aliphatic amides and aliphatic alcohols are used in addition to higher fatty acids such as oleic acid, stearic acid, isostearic acid, lauric acid, palmitic acid and myristic acid. Aliphatic hydrocarbons such as mineral spirits are used as the grinding fluid.
The average thickness of the aluminum flake pigment is 0.05 to 1.0 μm, preferably 0.1 to 0.5 μm. The average particle diameter here means a median diameter of a volume-based particle size distribution measured by a laser diffraction scattering method using a Microtrac particle size distribution measuring device MT3300 (trade name, manufactured by Nikkiso Co., Ltd.). The thickness is defined as an average value of 100 or more measured values by observing a cross section of the coating film containing the scaly aluminum pigment with a microscope and measuring the thickness using image processing software.

  As the aluminum flake pigment, those whose surface is coated with a resin, those whose surface is treated with silica, and those whose surface is treated with phosphoric acid, molybdic acid or silane coupling agent can be used. It is preferable from the viewpoint of obtaining a coating film having excellent storage stability and metallic gloss. The aluminum flake pigment may be a colored aluminum pigment such as a surface coated with a colored pigment and further coated with a resin, or a surface coated with a metal oxide such as iron oxide on the surface of the aluminum flake pigment.

  The vapor-deposited chromium flake pigment is obtained by vapor-depositing a chromium film on a base substrate, peeling the base substrate, and then pulverizing the vapor-deposited chromium film. As said base material, a film etc. can be mentioned, for example.

  As a commercial item which can be used as the said vapor deposition chromium flake pigment, "Metalure Liquid Black" series (A brand name, the product made by Ecarte) etc. can be mentioned, for example.

  The average particle diameter (D50) of the vapor-deposited chrome flake pigment is preferably about 1 to 50 μm, particularly about 5 to 20 μm from the viewpoints of stability in the paint, jet blackness and finish of the formed coating film. is there.

  The average thickness of the vapor-deposited chromium flake pigment is 0.01 to 1.0 μm, preferably 0.01 to 0.1 μm.

  The aluminum flake pigment concentration is preferably in the range of 20 to 50 parts by mass with respect to 100 parts by mass of the resin solid content in the first color base paint from the viewpoint of the concealability of the coating film obtained by coating and the brightness. More preferably, it is 21-49 mass parts, Most preferably, it exists in the range of 22-48 mass parts.

  Moreover, the said vapor deposition chromium flake pigment density | concentration is 1-10 mass parts with respect to 100 mass parts of aluminum flake pigments contained in a 1st color base coating material from the point of the light transmission suppression of the coating film obtained by coating, and the improvement of FF property. It is preferably within the range, more preferably 1.5 to 8 parts by mass, particularly preferably 2 to 7 parts by mass.

  The first color base paint may further contain a conventionally known color pigment as required. Such coloring pigments are not particularly limited, and specifically, composite metal oxide pigments such as titanium oxide pigments, iron oxide pigments, titanium yellow, azo pigments, quinacridone pigments, diketopyrrolopyrrole pigments. Pigment, perylene pigment, perinone pigment, benzimidazolone pigment, isoindoline pigment, isoindolinone pigment, metal chelate azo pigment, phthalocyanine pigment, indanthrone pigment, dioxane pigment, selenium pigment, Any one of indigo pigments and carbon black pigments can be used in combination of one or more.

  When using the said color pigment, it is preferable that the compounding quantity exists in the range of 0.01-30 mass parts with respect to 100 mass parts of resin solid content in a 1st color base coating material, More preferably, it is 1-20 masses. Within the range of the part.

  The said 1st color base coating material can contain an extender as needed. Examples of extender pigments include barium sulfate, barium carbonate, calcium carbonate, aluminum silicate, silica, magnesium carbonate, talc, and alumina white.

  When blending the extender, the blending amount is preferably in the range of 0.1 to 20 parts by weight, more preferably 1 to 15 parts by weight with respect to 100 parts by weight of the resin solid content in the first color base paint. Within the range of the part.

  The second color base paint is applied on the coating film of the first color base paint and contains a color pigment.

  The color pigment used for the second color base paint can be appropriately selected from the color pigments listed in the description of the first color base paint.

  The blending amount of the color pigment is preferably in the range of 0.1 to 20 parts by mass with respect to 100 parts by mass of the resin solid content in the paint from the viewpoint of the light transmittance of the coating film obtained by coating, Preferably it exists in the range of 0.5-10 mass parts.

  In the present invention, the first color base paint and the second color base paint may be either water-based paint or solvent-based paint, and for example, acrylic resin, polyester resin, alkyd resin, polyurethane resin or the like is used as the film-forming resin. it can. These paints are preferably water-based paints containing a film-forming resin (b) other than acrylic resin emulsions (a) and (a) and a curing agent (c), particularly as a film-forming resin component.

  The acrylic resin emulsion (a) is obtained by emulsifying and dispersing an acrylic resin in an aqueous medium, and examples thereof include an emulsion produced by emulsion polymerization of a polymerizable unsaturated monomer mixture.

  The acrylic resin emulsion (a) is particularly preferably a core-shell emulsion comprising a core part of the copolymer (I) and a shell part of the copolymer (II). Further, the copolymer (I) is contained in one molecule. It is obtained by copolymerizing a polymerizable unsaturated monomer (a1) having two or more polymerizable unsaturated groups and a polymerizable unsaturated monomer (a2) other than the polymerizable unsaturated monomer (a1). It is desirable that II) is obtained by copolymerizing a plurality of polymerizable unsaturated monomers (a3) from the viewpoint of improving the appearance and water resistance of the resulting coating film.

  Examples of the polymerizable unsaturated monomer (a1) include ethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, tetraethylene glycol di (meth) acrylate, and 1,6-hexanediol di (meth). Examples include acrylate, allyl (meth) acrylate, divinylbenzene, trimethylolpropane triacrylate, methylene bis (meth) acrylamide, ethylene bis (meth) acrylamide, and combinations thereof.

  In the present specification, “(meth) acrylate” means acrylate and / or methacrylate.

  The polymerizable unsaturated monomer (a2) other than the polymerizable unsaturated monomer (a1) (hereinafter sometimes simply referred to as “polymerizable unsaturated monomer (a2)”) is the polymerizable unsaturated monomer (a1). And a monomer having one polymerizable unsaturated group that can be copolymerized with the monomer, and a compound having a polymerizable unsaturated group such as a vinyl group or a (meth) acryloyl group.

  Specific examples of the polymerizable unsaturated monomer (a2) include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl. (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 (manufactured by Osaka Organic Chemical Industry, trade name), cyclohexyl (meth) acrylate, methylcyclohexyl (meth) acrylate, t-butylcyclohexyl Alkyl or cycloalkyl (meth) acrylate such as ru (meth) acrylate, cyclododecyl (meth) acrylate; polymerizable unsaturated monomer having isobornyl group such as isobornyl (meth) acrylate; adamantyl (meth) acrylate, etc. A polymerizable unsaturated monomer having an adamantyl group; vinyl aromatic compounds such as styrene, α-methylstyrene, vinyltoluene; vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris (2-methoxyethoxy) silane, γ- (meta ) Polymerizable unsaturated monomer having alkoxysilyl group such as acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropyltriethoxysilane; perfluorobutylethyl (meth) acrylate, perfluorooctyl Perfluoroalkyl (meth) acrylates such as chill (meth) acrylate; polymerizable unsaturated monomers having a fluorinated alkyl group such as fluoroolefin; monomers having a photopolymerizable functional group such as maleimide group; N-vinylpyrrolidone, ethylene , Vinyl compounds such as butadiene, chloroprene, vinyl propionate and vinyl acetate; carboxyl group-containing polymerizable unsaturated monomers such as (meth) acrylic acid, maleic acid, crotonic acid and β-carboxyethyl acrylate; (meth) acrylonitrile, ( Nitrogen-containing polymerizable unsaturated monomers such as (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylamide, adducts of glycidyl (meth) acrylate and amines; 2-hydroxye (Meth) acrylic acid such as ru (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, 4-hydroxybutyl (meth) acrylate, etc. Monoesterified product with dihydric alcohol, ε-caprolactone modified product of monoesterified product of (meth) acrylic acid and dihydric alcohol having 2 to 8 carbon atoms, N-hydroxymethyl (meth) acrylamide, allyl alcohol, molecule Hydroxyl-containing polymerizable unsaturated monomers such as (meth) acrylate having a polyoxyethylene chain having a terminal hydroxyl group; glycidyl (meth) acrylate, β-methylglycidyl (meth) acrylate, 3,4-epoxycyclohexylmethyl (meth) Acrylate, 3,4-epoxycyclohexylethyl (meth) Epoxy group-containing polymerizable unsaturated monomers such as acrylate, 3,4-epoxycyclohexylpropyl (meth) acrylate, and allyl glycidyl ether; (meth) acrylate having a polyoxyethylene chain whose molecular terminal is an alkoxy group; 2-acrylamide- 2-methylpropanesulfonic acid, allylsulfonic acid, sodium styrenesulfonate, sulfoethyl methacrylate and its sodium salt or ammonium salt-containing polymerizable unsaturated monomer; 2-acryloyloxyethyl acid phosphate, 2-methacryloyloxy Phosphoric acid group-containing polymerizable unsaturated monomers such as ethyl acid phosphate, 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- (3-acryloyloxy-2-hydroxypropoxy) benzophenone, 2- (2'-hydroxy-5'-methacryloyloxyethylphenyl) -2H-benzo Monomers having a UV-absorbing functional group such as triazole; 4- (meth) acryloyloxy-1,2,2,6,6-pentamethylpiperidine, 4- (meth) acryloyloxy-2,2,6,6- Tetramethylpiperidine, 4-cyano-4- (me ) 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-2, Monomers having UV stability such as 2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine; acrolein, diacetone acrylamide, diacetone methacrylamide , Acetoacetoxyethyl methacrylate, formylstyrene, 4 to 7 carbon atoms That vinyl alkyl ketones (e.g., vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone) carbonyl group-containing monomer compounds, such as, and combinations thereof.

  In producing the copolymer (I), the polymerizable unsaturated monomer (a1) is preferably 0.1 based on the total mass of the polymerizable unsaturated monomer (a1) and the polymerizable unsaturated monomer (a2). -20% by weight, more preferably 0.2-10% by weight, and even more preferably 0.7-4% by weight, and the polymerizable unsaturated monomer (a2) is a polymerizable unsaturated monomer. Based on the total mass of (a1) and the polymerizable unsaturated monomer (a2), it is preferably 80 to 99.9% by mass, more preferably 90 to 99.8% by mass, and even more preferably 96 to 99.%. A range of 3% by mass is preferable from the viewpoints of stability during production, improvement of water resistance and weather resistance of the resulting coating film, and the like.

  The plurality of polymerizable unsaturated monomers (a3) forming the shell portion of the copolymer (II) can be appropriately used from those listed in the polymerizable unsaturated monomer (a2), and the obtained core-shell type From the viewpoint of ensuring the stability of the emulsion in an aqueous medium, the shell portion of the copolymer (II) preferably contains a carboxyl group-containing monomer as the polymerizable unsaturated monomer (a3). As the carboxyl group-containing monomer, acrylic acid and / or methacrylic acid is particularly suitable. The amount of the carboxyl group-containing monomer is preferably 1 on the basis of the total mass of the plurality of polymerizable unsaturated monomers (a3) from the viewpoints of stability of the emulsion resin in an aqueous medium and water resistance of the resulting coating film. A range of -40% by mass, more preferably 6-25% by mass, and still more preferably 7-19% by mass is suitable from the viewpoint of storage stability and improvement of water resistance of the resulting coating film.

  In addition, the plurality of polymerizable unsaturated monomers (a3) forming the shell portion of the copolymer (II) can be used as at least a part of the components from the viewpoint of ensuring the stability of the obtained emulsion resin in an aqueous medium. In order to improve the stability of the emulsion resin in an aqueous medium, it is preferable to contain the hydroxyl group-containing monomer. As the hydroxyl group-containing monomer, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, and 4-hydroxybutyl (meth) acrylate are particularly preferable. The amount of the hydroxyl group-containing monomer is generally based on the total mass of the plurality of polymerizable unsaturated monomers (a3) from the viewpoint of the stability of the emulsion resin in the aqueous medium and the water resistance of the resulting coating film. A range of 1 to 40% by mass, preferably 3 to 25% by mass, and more preferably 4 to 20% by mass is suitable from the viewpoint of storage stability and improvement of water resistance of the resulting coating film.

  The core-shell type emulsion forms, for example, a copolymer (I) by emulsion polymerization of a monomer mixture (1) containing the polymerizable unsaturated monomer (a1) and the polymerizable unsaturated monomer (a2) in the above ratio. Then, a monomer mixture (2) containing a plurality of polymerizable unsaturated monomers (a3) is added and emulsion polymerization is performed. The emulsion polymerization of the monomer mixture (1) can be performed by a method known per se, for example, using a polymerization initiator in the presence of an emulsifier. The monomer mixture (2) can optionally contain components such as a polymerization initiator, a chain transfer agent, a reducing agent, and an emulsifier.

  The core-shell type emulsion has a copolymer (I) formed from a monomer mixture (1) containing a polymerizable unsaturated monomer (a1) and a polymerizable unsaturated monomer (a2) as a core, and a plurality of polymerizable unsaturated monomers. It is a core / shell type emulsion having a copolymer (II) formed from a monomer mixture (2) containing the monomer (a3) as a shell. The ratio of the copolymer (I) to the copolymer (II) in the core-shell type emulsion is generally 5 / in the solid content mass ratio of the copolymer (I) / copolymer (II) from the viewpoint of metallic unevenness of the resulting coating film. It is suitable to be in the range of 95 to 95/5, particularly 30/70 to 92/8, more particularly 40/60 to 90/10. Generally, when the ratio of the copolymer (I) to the copolymer (II) is less than 5/95, the metallic unevenness tends to become prominent, and when it exceeds 95/5, the uniformity of the decorative layer is increased. It may be damaged.

  As the acrylic resin emulsion (a), a single-layer acrylic resin emulsion obtained by emulsion polymerization in one step can also be used.

  The acrylic resin emulsion (a) obtained as described above is preferably from 5 to 90 mgKOH / g, more preferably from 8 to 50 mgKOH / g, and even more preferably from the viewpoints of storability and water resistance of the resulting coating film. It has a resin acid value in the range of ˜35 mg KOH / g. The acrylic resin emulsion (a) is preferably in the range of 1 to 70 mgKOH / g, more preferably 2 to 50 mgKOH / g, and still more preferably 5 to 30 mgKOH / g, from the viewpoint of the water resistance of the resulting coating film. The resin has a hydroxyl value of

  As the film-forming resin (b) other than the acrylic resin emulsion (a), polyester resin, acrylic resin other than (a), alkyd resin, polyurethane resin, silicone resin, epoxy resin and the like can be used.

  The polyester resin is an oil-free or oil-modified carboxyl group-containing polyester resin prepared by an esterification reaction using a polyhydric alcohol and a polybasic acid, and optionally a monobasic acid, an oil component, and the like. Obtained by neutralization.

  The polyester resin preferably contains both hydroxyl groups and carboxyl groups, preferably 10 to 300 mg KOH / g, more preferably 50 to 250 mg KOH / g, and even more preferably 80 to 180 mg KOH / g. Is suitable having an acid value in the range of 1 to 200 mg KOH / g, more preferably 15 to 100 mg KOH / g, and even more preferably 25 to 60 mg KOH / g.

  The polyester resin generally has a number average molecular weight in the range of 1,000 to 50,000, more preferably 1,500 to 20,000.

  In this specification, the number average molecular weight and the weight average molecular weight use tetrahydrofuran as a solvent, use “HLC-8120GPC” (trade name, manufactured by Tosoh Corporation) as a gel permeation chromatograph, and use “ A total of four TSKgel G4000HXL, two TSKgel G3000HXL, and one TSKgel G2000HXL (trade name, all manufactured by Tosoh Corporation) were used as detectors, and a differential refractometer was used. Used, mobile phase: tetrahydrofuran, measurement temperature: 40 ° C., flow rate: 1 mL / min.

  In addition, a basic substance can be used for neutralizing the carboxyl group of the polyester resin. The basic substance is preferably water-soluble, specifically, for example, ammonia, methylamine, ethylamine, propylamine, butylamine, dimethylamine, trimethylamine, triethylamine, ethylenediamine, morpholine, 2- (methylamino) ethanol, Examples include 2- (dimethylamino) ethanol, diethanolamine, triethanolamine, diisopropanolamine, and 2-amino-2-methylpropanol, and combinations thereof.

  The acrylic resin is other than the acrylic resin emulsion (a), for example, a monomer mixture containing a hydrophilic group-containing monomer such as the carboxyl group-containing polymerizable unsaturated monomer, a hydroxyl group-containing polymerizable unsaturated monomer, or the like. A carboxyl group-containing acrylic resin obtained by copolymerization by a solution polymerization method or the like, particularly a weight average molecular weight of 1,000 to 200,000, preferably 2,000 to 100,000, more preferably 3,000. Examples thereof include carboxyl group-containing acrylic resins in the range of ˜80,000, and more preferably in the range of 5,000 to 70,000.

  The carboxyl group of the acrylic resin can be neutralized using the above basic substance. The acrylic resin preferably has a hydroxyl value in the range of 1 to 200 mgKOH / g, more preferably 2 to 100 mgKOH / g, and still more preferably 3 to 80 mgKOH / g, and preferably 1 to 200 mgKOH / g. Preferably have an acid value in the range of 2 to 150 mg KOH / g, and more preferably 5 to 100 mg KOH / g.

  Examples of the curing agent (c) include amino resins, polyisocyanate compounds, blocked polyisocyanate compounds, epoxy group-containing compounds, carboxyl group-containing compounds, carbodiimide group-containing compounds, hydrazide group-containing compounds, and semicarbazide group-containing compounds. It is done. Of these, amino resins that can react with hydroxyl groups, polyisocyanate compounds and blocked polyisocyanate compounds, and carbodiimide group-containing compounds that can react with carboxyl groups are preferred. A hardening | curing agent can be used individually or in combination of 2 or more types.

  In the first color base paint and the second color base paint, the contents of the acrylic resin emulsion (a), the film-forming resin (b) other than the acrylic resin emulsion (a), and the curing agent (c) can be appropriately selected. From the viewpoints of appearance, water resistance, weather resistance, and the like of the resulting coating film, the acrylic resin emulsion (a) is 5 to 50 parts by mass, preferably 10 to 10 parts by mass based on the total resin solids of 100 parts by mass. 45 parts by mass, the film-forming resin (b) other than the acrylic resin emulsion (a) is 5 to 60 parts by mass, preferably 10 to 55 parts by mass, and the curing agent (c) is 5 to 50 parts by mass. Part, preferably 10 to 45 parts by weight.

  The first color base paint and the second color base paint are various paints such as a thickener, a curing catalyst, an ultraviolet absorber, a light stabilizer, an antifoaming agent, a plasticizer, a surface conditioner, and an anti-settling agent as required. Additives can be included.

  In the present invention, from the viewpoint of improving the saturation saturation of the multilayer coating film, it is desirable that the second color base paint contains a pigment dispersion in which a colored pigment is dispersed by a pigment dispersant. It is desirable to contain a pigment dispersion dispersed by a block polymer dispersant.

  As the AB block polymer dispersant, a conventionally known dispersant having a functional site adsorbing to a pigment (amino group, quaternary ammonium base, etc.) can be used without any particular limitation. A block containing a structural unit derived from a saturated monomer and a structural unit derived from a (meth) acrylic acid alkyl ester, a structural unit derived from a polyoxyalkylene chain-containing polymerizable unsaturated monomer, and a (meth) acrylic acid alkyl ester A block polymer having a B block containing a derived structural unit can be suitably used, and a triblock may be used as long as it has these blocks.

  Examples of the polymerizable unsaturated monomer having an amino group include N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N N, N-dialkylaminoalkyl (meth) acrylates such as N, N-di-t-butylaminoethyl (meth) acrylate and N, N-dimethylaminobutyl (meth) acrylate; N, N-dimethylaminoethyl (meth) Tertiary amino group-containing polymerizable unsaturated monomers such as N, N-dialkylaminoalkyl (meth) acrylamides such as acrylamide, N, N-diethylaminoethyl (meth) acrylamide, and N, N-dimethylaminopropyl (meth) acrylamide Can be used.

  Examples of (meth) acrylic acid alkyl esters include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, and isobutyl (meth). Acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, n-octyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, cyclohexyl (meth) acrylate, isobornyl (meth) acrylate, C1-C24 linear or cyclic alkyl (meth) acrylate monomers such as tridecyl (meth) acrylate can be exemplified.

  The polyoxyalkylene chain-containing polymerizable unsaturated monomer is a monomer having a polyoxyalkylene chain and a polymerizable unsaturated group in one molecule. Examples of the polyoxyalkylene chain include a polyoxyethylene chain, a polyoxypropylene chain, a block chain of polyoxyethylene and polyoxypropylene, and the like. The polyoxyalkylene chain preferably has a molecular weight in the range of 200 to 3,000, in particular 300 to 2,500. Specific examples thereof include, for example, tetraethylene glycol (meth) acrylate, methoxytetraethylene glycol (meth) acrylate, ethoxytetraethylene glycol (meth) acrylate, n-butoxytetraethylene glycol (meth) acrylate, tetrapropylene glycol (meta ) Acrylate, methoxytetrapyroprene glycol (meth) acrylate, ethoxytetrapropylene glycol (meth) acrylate, n-butoxytetrapropylene glycol (meth) acrylate, polyethylene glycol (meth) acrylate, polypropylene glycol (meth) acrylate, methoxypolyethylene glycol (Meth) acrylate, ethoxypolyethylene glycol (meth) acrylate, etc. Can.

  Other polymerizable unsaturated monomers may be further used for each block polymer as necessary. Other polymerizable unsaturated monomers include, for example, 2-hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and lactones such as ε-caprolactone in these hydroxyalkyl (meth) acrylate monomers. Hydroxyl group-containing polymerizable unsaturated monomers such as compounds obtained by ring-opening polymerization of polymers; carboxyl group-containing polymerizable unsaturated monomers such as methacrylic acid and acrylic acid; styrene, α-methylstyrene, vinyltoluene, benzyl (meth) acrylate, etc. Aromatic vinyl compounds; (meth) acrylonitrile, vinyl acetate and the like can be mentioned. These polymerizable unsaturated monomers can be used alone or in combination of two or more.

  In the AB block polymer dispersant, the polymerizable unsaturated monomer having an amino group is contained in an amount of 5 to 50% by mass, preferably 10 to 40% by mass, based on the total amount (solid content) of monomers constituting the A block. The polyoxyalkylene chain-containing polymerizable unsaturated monomer is preferably contained in an amount of 10 to 70% by mass, preferably 20 to 45% by mass, based on the total amount (solid content) of monomers constituting the block. Further, the ratio (mass ratio) of the total amount of monomers constituting the A block and the total amount of monomers constituting the B block is 10/90 to 60/40, preferably within the range of 20/80 to 50/50. From the viewpoint of

The AB block polymer dispersant can be produced by a conventionally known technique, and in particular, can be obtained by an addition cleavage type chain transfer polymerization method using an addition cleavage type chain transfer agent. Specifically, a block polymer can be produced by subjecting a monomer component constituting the block to addition-cleavage chain transfer polymerization in the presence of the addition-cleavage chain transfer agent. The addition-cleavage chain transfer polymerization can be performed by, for example, a solution polymerization method in an organic solvent, an emulsion polymerization method in water, or the like. Moreover, in the case of superposition | polymerization, in addition to this addition cleavage type | mold chain transfer agent, a well-known radical polymerization initiator can be used together as needed.
For example, 2,4-diphenyl-4-methyl-1-pentene (sometimes abbreviated as “α-methylstyrene dimer” or “MSD”) is preferably used as the addition-cleavage chain transfer agent. be able to. The MSD is preferably used in the first polymerization.

  The AB block polymer dispersant obtained as described above has a weight average molecular weight of 2000 to 100,000, preferably 3000 to 20000, and an amine value of 50 mgKOH / g or less, preferably 3 to 30 mgKOH / g. Is desirable.

  The pigment dispersion used in the second color base paint is dispersed so that the color pigment is 10 to 200 parts by weight, preferably 20 to 100 parts by weight with respect to 100 parts by weight of the resin solid content of the AB block polymer dispersant. From the viewpoint of improving the saturation of the highlight of the multilayer coating film, it is preferable to obtain it.

  In the present invention, the coating of the first color base paint and the second color base paint is not particularly limited, and examples thereof include air spray coating, airless spray coating, rotary atomization coating, and the like. A wet film can be sequentially formed on the object to be coated. These coating methods may be electrostatically applied as necessary. Among them, rotary atomizing electrostatic coating and air spray electrostatic coating are preferable, and rotary atomizing electrostatic coating is preferable. Particularly preferred.

  In the case of air spray coating, airless spray coating, or rotary atomization coating, the viscosity of each paint is appropriately adjusted using water and / or an organic solvent so that the viscosity range is suitable for the coating. It is preferable to keep it. The first color base paint has a paint solid content concentration of 2 to 20% by mass, preferably 5 to 15% by mass, and the second color base paint has a paint solid content concentration of 10 to 30% by mass, preferably 15 to 25%. It is desirable to be in the range of mass%.

It is preferable to leave an interval of about 30 seconds to 3 minutes without preheating from the end of the application of the first color base paint to the start of the application of the second color base paint.
The first color base coating film has a cured film thickness of 1 to 7 μm, particularly 1 to 4 μm, and the second color base coating film has a cured film thickness of 5 to 20 μm, particularly 7 to 15 μm.

  Since the method of the present invention can form a coating film with excellent glitter, it is suitable for use in the outer plate portion of an automobile body.

  In the car body painting line, coating is usually performed by dividing the zone into zones that use the same type of paint. For example, an automobile painting line is generally divided into an undercoating zone, an intermediate coating zone, a base coat painting zone, and a clear coat painting zone.

  Also, in each coating zone, coating is usually divided into two or more times, and setting (stationary) for about 30 seconds to 3 minutes is performed between each coating to prevent sagging of the paint and the like. Measures for obtaining the coating quality have been taken, and each coating in the same zone is called a first stage, a second stage,.

  Such a coating method is generally referred to as multi-stage coating. For example, when coating in the same zone is performed twice, it is referred to as two-stage coating. Among these, it is preferable to apply the method of the present invention in the base coat coating zone, to apply the first color base paint in the first stage, and to apply the second color base paint in the second stage.

  In the method of the present invention, the first color base paint and the second color base paint are sequentially applied by wet-on-wet, and the clear paint is applied thereon with the resulting multilayer coating film uncured.

  Examples of the clear coating include organic solvent type thermosetting coating compositions, aqueous thermosetting coating compositions, thermosetting powder coating compositions, etc. containing a base resin having a crosslinkable functional group and a curing agent. Can do.

  Examples of the crosslinkable functional group possessed by the base resin include a carboxyl group, a hydroxyl group, an epoxy group, and a silanol group. Examples of the base resin include acrylic resin, polyester resin, alkyd resin, urethane resin, epoxy resin, and fluorine resin. Examples of the curing agent include polyisocyanate compounds, blocked polyisocyanate compounds, melamine resins, urea resins, carboxyl group-containing compounds, carboxyl group-containing resins, epoxy group-containing resins, and epoxy group-containing compounds.

  In addition, the clear paint can contain, if necessary, a color pigment, a bright pigment, a dye, a matting agent, etc. to such an extent that the transparency is not hindered, and an extender pigment, an ultraviolet absorber, a light stabilizer. An antifoaming agent, a thickener, a rust inhibitor, a surface conditioner, and the like can be appropriately contained.

  The clear coating can be applied by a method such as electrostatic coating, air spraying, airless spraying, and the film thickness is suitably in the range of 20 to 50 μm based on the cured coating film.

  In the method of the present invention, the first color base paint, the second color base paint, and the clear paint coating are simultaneously heat-cured. The heating means can be performed by, for example, hot air heating, infrared heating, high-frequency heating, and the like, and the heating temperature is preferably 80 to 140 ° C, more preferably 100 to 120 ° C. The heating time is preferably 10 to 60 minutes, and more preferably 15 to 40 minutes.

  In the present invention, the L * C * h color specification calculated from the spectral reflectance obtained by receiving the light irradiated from the 45-degree angle of the multilayer coating film obtained as described above at an angle of 15 degrees with respect to the regular reflection light. L * C * calculated from the spectral reflectance obtained when the chroma C * in the system was 100 or more and the light irradiated from the 45 ° angle of the multilayer coating film was received at an angle of 75 ° with respect to the regular reflection light It is desirable that C * / L * in the h color system is 2.8 or more.

  The L * C * h color system here is a table devised based on the L * a * b * color system defined by the International Commission on Illumination in 1976 and adopted in JIS Z 8729. In the color system, C * represents saturation, and the geometric distance from the center in the chromaticity diagram is quantified. The larger the value, the higher the saturation.

  In the present specification, the saturation C * in the L * C * h color system is, specifically, a multi-angle spectrophotometer (trade name, MA-68II, manufactured by x-rite) on the obtained coating film. Are used to define the light emitted from an angle of 45 degrees as a numerical value calculated from the spectral reflectance received at 15 degrees with respect to the specularly reflected light. Such C * (also referred to as C * 15 in this specification) represents the saturation of the highlight, and the greater the value, the higher the saturation of the highlight.

  In addition, C * / L * in the above L * C * h color system is specifically a multi-angle spectrophotometer (trade name, MA-68II, manufactured by x-rite) on the obtained coating film. , And the light emitted from an angle of 45 degrees is defined as a numerical value calculated from the spectral reflectance received at 75 degrees with respect to the regular reflection light. Such C * / L * (also referred to as C * 75 / L * 75 in the present specification) represents the depth of the shade, and the greater the value, the greater the depth of the shade.

Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to only these examples. “Part” and “%” are based on mass.

Production of acrylic resin emulsion (a) Production Example 1
A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube and dropping device, 128 parts of deionized water, “ADEKA rear soap SR-1025” (trade name, manufactured by ADEKA, emulsifier, active ingredient 25 %) 2 parts were charged, stirred and mixed in a nitrogen stream, and heated to 80 ° C.

  Next, 1% of the total amount of the following monomer emulsion for core part and 5.3 parts of 6% ammonium persulfate aqueous solution were introduced into the reaction vessel and kept at 80 ° C. for 15 minutes. Thereafter, the remainder of the monomer emulsion for the core part was dropped into a reaction vessel maintained at the same temperature over 3 hours, and aging was performed for 1 hour after completion of the dropping. Next, the following monomer emulsion for shell part was added dropwise over 1 hour, and after aging for 1 hour, it was cooled to 30 ° C. while gradually adding 40 parts of 5% 2- (dimethylamino) ethanol aqueous solution to the reaction vessel, The mixture was discharged while being filtered through a 100 mesh nylon cloth to obtain an acrylic resin emulsion (a) having an average particle diameter of 100 nm and a solid content of 30%. The obtained acrylic resin emulsion had an acid value of 33 mgKOH / g and a hydroxyl value of 25 mgKOH / g.

  Monomer emulsion for core part: 40 parts of deionized water, 2.8 parts of “ADEKA rear soap SR-1025”, 2.1 parts of methylenebisacrylamide, 2.8 parts of styrene, 16.1 parts of methyl methacrylate, 28 of ethyl acrylate The monomer emulsion for the core part was obtained by mixing and stirring the part and 21 parts of n-butyl acrylate.

  Monomer emulsion for shell part: 17 parts of deionized water, 1.2 parts of “ADEKA rear soap SR-1025”, 0.03 part of ammonium persulfate, 3 parts of styrene, 5.1 parts of 2-hydroxyethyl acrylate, 5 parts of methacrylic acid .1 part, 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 for shell part.

Production of film-forming resin (b) other than (a) Production Example 2
A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube and dropping device was charged with 35 parts of propylene glycol monopropyl ether, heated to 85 ° C., then 30 parts of methyl methacrylate, 2-ethylhexyl acrylate 20 Parts, n-butyl acrylate 29 parts, 2-hydroxyethyl acrylate 15 parts, acrylic acid 6 parts, propylene glycol monopropyl ether 15 parts and 2,2′-azobis (2,4-dimethylvaleronitrile) 2.3 parts. The mixture was added dropwise over 4 hours and aged for 1 hour after completion of the addition. Thereafter, a mixture of 10 parts of propylene glycol monopropyl ether and 1 part of 2,2′-azobis (2,4-dimethylvaleronitrile) was added dropwise over 1 hour, followed by aging for 1 hour after completion of the addition. Further, 7.4 parts of diethanolamine was added to obtain a hydroxyl group-containing acrylic resin solution (b-1) having a solid content of 55%. The obtained hydroxyl group-containing acrylic resin had an acid value of 47 mgKOH / g, a hydroxyl value of 72 mgKOH / g, and a weight average molecular weight of 58,000.

Production Example 3
In a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser and water separator, 109 parts of trimethylolpropane, 141 parts of 1,6-hexanediol, 126 parts of 1,2-cyclohexanedicarboxylic acid anhydride and adipine 120 parts of acid was charged, and the temperature was raised from 160 ° C. to 230 ° C. over 3 hours, followed by condensation at 230 ° C. for 4 hours. Next, in order to introduce a carboxyl group, the resulting condensation reaction product was added with 38.3 parts of trimellitic anhydride, reacted at 170 ° C. for 30 minutes, and then diluted with 2-ethyl-1-hexanol. Thus, a hydroxyl group-containing polyester resin solution (b-2) having a solid content of 70% was obtained. The obtained hydroxyl group-containing polyester resin had an acid value of 46 mgKOH / g, a hydroxyl value of 150 mgKOH / g, and a number average molecular weight of 1,400.

Production Example 4 of AB Block Polymer Dispersant Production Example 4
Into a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser and dropping device, 18.2 parts of ethylene glycol monobutyl ether and 11.8 parts of 2,4-diphenyl-4-methyl-1-pentene were charged, After stirring and mixing in a nitrogen stream and reaching 120 ° C., the following monomer mixture I was added dropwise over 6 hours and aged at 120 ° C. for 30 minutes.
<Monomer mixture I composition>
87 parts of methyl methacrylate,
N, N-dimethylaminoethyl methacrylate 12 parts tridecyl methacrylate 0.5 part,
Lauryl methacrylate 0.5 part 2,2'-azobis (2-methylbutyronitrile) 3 parts,
6 parts of ethylene glycol monobutyl ether.

Next, the following additional catalyst mixture was added dropwise over 1 hour and aged at 120 ° C. for 1 hour, and then 18 parts of ethylene glycol monobutyl ether and 22.7 parts of propylene glycol monobutyl ether were added so that the solid concentration was 60%. Thus, a polymer A solution as a macromonomer was obtained. The weight average molecular weight of the obtained polymer A was about 3,000.
<Additional catalyst mixture>
0.5 part of 2,2′-azobis (2-methylbutyronitrile),
9 parts of ethylene glycol monobutyl ether.

Next, 41.7 parts of polymer A, which is a macromonomer, is charged into a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser and dropping device, and after stirring and mixing in a nitrogen stream, the temperature reaches 95 ° C. The following monomer mixture II and monomer mixture III were added dropwise over 3 hours and aged at 95 ° C. for 30 minutes.
<Monomer mixture II composition>
45 parts methyl methacrylate,
10 parts 2-hydroxyethyl methacrylate,
2,2′-azobis (2-methylbutyronitrile) 0.9 part propylene glycol monobutyl ether 5 parts <monomer mixture III composition>
20 parts of methoxypolyethylene glycol methacrylate (molecular weight about 2080),
Deionized water 20 parts ethylene glycol monobutyl ether 5 parts,
Next, the following additional catalyst mixture was added dropwise over 1 hour and aged at 95 ° C. for 1 hour, and then 36 parts of propylene glycol monobutyl ether was added so that the solid content concentration was 53% to obtain an AB block polymer solution. It was. The weight average molecular weight of the obtained polymer was about 15,000.
<Additional catalyst mixture>
2,75'-azobis (2-methylbutyronitrile) 0.375 parts,
6 parts of prolene glycol monobutyl ether.

Production Example 5
In a reaction vessel equipped with a thermometer, a thermostat, a stirring device, a reflux condenser, and a dropping device, 37 parts of ethylene glycol monobutyl ether was charged and stirred at a temperature of 110 ° C. In this, 10 parts of styrene, 35 parts of methyl methacrylate, 20 parts of 2-ethylhexyl methacrylate, 5 parts of N, N-dimethylaminoethyl methacrylate, 10 parts of 2-hydroxyethyl methacrylate, methoxypolyethylene glycol monomethacrylate (molecular weight about 2080) A mixture of 20 parts, 1 part azobisisobutyronitrile and 5 parts isobutyl alcohol was added dropwise over 3 hours. After completion of the dropwise addition, the mixture was aged at 110 ° C. for 30 minutes, and then an additional catalyst mixture composed of 20 parts of ethylene glycol monobutyl ether and 0.5 part of azobisisobutyronitrile was added dropwise over 1 hour. Subsequently, the mixture was aged at 110 ° C. for 1 hour and then cooled to obtain a pigment dispersion resin solution having a solid content of 55%. The weight average molecular weight of the obtained resin was 20,000.

Production of glitter pigment dispersion Production Example 6
In a stirring and mixing container, 40 parts of aluminum flake pigment paste (trade name “GX-180A”, manufactured by Asahi Kasei Metals Co., Ltd., metal content: 74%), vapor-deposited chrome flake pigment paste (trade name “METALURE LiquidBlack”, manufactured by Eckart GmbH (10% metal content) 10 parts, 35 parts 2-ethyl-1-hexanol, 8 parts phosphoric acid group-containing resin solution (Note 1) and 0.2 parts 2- (dimethylamino) ethanol were mixed uniformly. A bright pigment dispersion (P-1) was obtained.

(Note 1) Phosphate group-containing resin solution: Mixing 27.5 parts of methoxypropanol and 27.5 parts of isobutanol in a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube and dropping device The solvent was added and heated to 110 ° C. Next, 25 parts of styrene, 27.5 parts of n-butyl methacrylate, 20 parts of branched higher alkyl acrylate (trade name “isostearyl acrylate” manufactured by Osaka Organic Chemical Co., Ltd.), 7.5 parts of 4-hydroxybutyl acrylate, phosphoric acid 121.5 parts of a mixture comprising 15 parts of a group-containing polymerizable monomer (Note 2), 12.5 parts of 2-methacryloyloxyethyl acid phosphate, 10 parts of isobutanol and 4 parts of t-butylperoxyoctanoate over 4 hours In addition to the above mixed solvent, a mixture of 0.5 part of t-butyl peroxyoctanoate and 20 parts of isopropanol was added dropwise over 1 hour. Thereafter, the mixture was aged while stirring for 1 hour to obtain a phosphate group-containing resin solution having a solid content concentration of 50%. The acid value due to the phosphate group of the phosphate group-containing resin was 83 mgKOH / g, the hydroxyl value was 29 mgKOH / g, and the weight average molecular weight was 10,000.
(Note 2) Phosphoric acid group-containing polymerizable monomer: put 57.5 parts monobutyl phosphoric acid and 41 parts isobutanol in a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube and dropping device, After raising the temperature to 90 ° C., 42.5 parts of glycidyl methacrylate was added dropwise over 2 hours. Then, after further aging with stirring for 1 hour, 59 parts of isopropanol was added to obtain a phosphate group-containing polymerizable monomer solution having a solid concentration of 50%. The acid value due to the phosphate group of the obtained monomer was 285 mgKOH / g.

Production Example 7
In Production Example 6, the amount of the aluminum flake pigment paste was changed from 40 parts to 30 parts, and the amount of the vapor-deposited chrome flake pigment paste was changed from 10 parts to 4 parts in the same manner as in Production Example 6, except that the bright pigment dispersion A liquid (P-2) was obtained.

Production Example 8
In Production Example 6, the bright pigment dispersion liquid was prepared in the same manner as in Production Example 6 except that the amount of aluminum flake pigment paste was changed from 40 parts to 65 parts and the amount of vapor-deposited chromium flake pigment paste was changed from 10 parts to 30 parts. (P-3) was obtained.

Production Example 9
In Production Example 6, the bright pigment dispersion liquid was prepared in the same manner as in Production Example 6 except that the amount of aluminum flake pigment paste was changed from 40 parts to 90 parts and the amount of vapor-deposited chromium flake pigment paste was changed from 10 parts to 67 parts. (P-4) was obtained.
Production Example 10
In Production Example 6, the bright pigment dispersion liquid was prepared in the same manner as in Production Example 6 except that the amount of aluminum flake pigment paste was changed from 40 parts to 14 parts and the amount of vapor-deposited chrome flake pigment paste was changed from 10 parts to 1 part. (P-5) was obtained.

Production and Production Example 11 of Colored Pigment Dispersion
11.8 parts of acrylic resin solution obtained in Production Example 2 (6.5 parts of resin solid content), 20 parts of “PERRIND MAROON 179-229 6440” (trade name, PigmentRed 179, manufactured by Sun Chemical Co., Ltd.) and 50 of deionized water After mixing the parts and adjusting the pH, the mixture was dispersed with a paint shaker for 30 minutes to obtain a colored pigment dispersion (R-1).

Production Example 12
In Production Example 11, a colored pigment dispersion (R-2) was obtained in the same manner as in Production Example 11 except that the amount of “PERRIND MAROON 179-229 6440” was 10 parts.

Production Example 13
AB block polymer solution 5.7 parts obtained in Production Example 4 (resin solid content 3.0 parts), “PERRIND MAROON 179-229 6440” (trade name, PigmentRed 179, manufactured by Sun Chemical Co., Ltd.) 1.5 parts and After mixing 50 parts of deionized water and adjusting the pH, the mixture was dispersed with a paint shaker for 30 minutes to obtain a colored pigment dispersion (R-3).

Production Example 14
After adjusting pH by mixing 5.5 parts of pigment-dispersed resin solution obtained in Production Example 5 (resin solid content: 3.0 parts), 1.5 parts of “PERRIND MAROON 179-229 6440” and 50 parts of deionized water. The mixture was dispersed with a paint shaker for 30 minutes to obtain a colored pigment dispersion (R-4).

Production and production example 15 of first color base paint
In a stirring and mixing container, 65 parts of acrylic resin emulsion (a) obtained in Production Example 1 (solid content 19.5 parts), 57 parts of polyester resin solution (b-2) obtained in Production Example 3 (solid content 40 parts) , 93 parts of the glitter pigment dispersion (P-1) obtained in Production Example 6 (aluminum 29.6 parts, deposited chromium 1.0 part, resin solid content 4 parts), and colored pigment dispersion obtained in Production Example 11 (R-1) 81.8 parts (perylene 20 parts, resin solid content 6.5 parts) and melamine resin (trade name “Cymel 325” manufactured by Nippon Cytec Industries, Ltd., solid content 80%) 37.5 parts ( (Solid content 30 parts) is mixed uniformly, and polyacrylic acid thickener (trade name “Primal ASE-60” manufactured by Rohm and Haas), 2- (dimethylamino) ethanol and deionized water are added. Adjust the viscosity and pH to be suitable for painting. An aqueous first color base paint (X-1) having a solid content of 10% was obtained.

Production Examples 16-23
In Production Example 15, water-based first color base paints (X-2) to (X-9) were obtained in the same manner as in Production Example 15 except that the paint composition and the solid content of the paint were as shown in Table 1.

  In addition, the compounding quantity of Table 1 is a solid content display.

Production example 24 of the second color base paint
In a stirring and mixing container, 78 parts (solid content 23.4 parts) of the acrylic resin emulsion (a) obtained in Production Example 1 and 57 parts (solid content 40 parts) of the polyester resin solution (b-2) obtained in Production Example 3 57.2 parts of colored pigment dispersion (R-3) obtained in Production Example 13 (1.5 parts of perylene, 3.0 parts of resin solid content), and melamine resin (trade name “Cymel 325” Nippon Cytec Industries Ltd.) 37.5 parts (manufactured by 80% solid content) (30 parts solid content) were mixed uniformly, and a polyacrylic acid thickener (trade name “Primal ASE-60” manufactured by Rohm and Haas), 2 -(Dimethylamino) ethanol and deionized water were added to adjust the viscosity and pH to be suitable for coating to obtain an aqueous second color base coating (Y-1) having a coating solid content of 25%.

Production Example 25
In Production Example 25, an aqueous second color base paint (Y-2) was obtained in the same manner as in Production Example 25 except that the coating composition was as shown in Table 2.
In addition, the compounding quantity of Table 2 is a solid content display.

Preparation of test article:
"Electron GT-10" (trade name, manufactured by Kansai Paint Co., Ltd., thermosetting epoxy resin-based cationic electrodeposition paint) is dried on a cold rolled steel sheet treated with zinc phosphate measuring 45cm long x 30cm wide x 0.8mm thick Electrodeposited to a thickness of 20 μm, cured by heating at 170 ° C. for 30 minutes, and then overcoated with “Amirac TP-65-2” (trade name, manufactured by Kansai Paint Co., Ltd., polyester resin Amino resin-based, organic solvent-type intermediate coating) was applied to a dry film thickness of 40 μm, heated at 140 ° C. for 30 minutes and cured to obtain a test article.

Preparation of test coated plate Example 1
On the test object, the water-based first color base paint (X-1) obtained in Production Example 15 is a rotary atomizing bell-type coating machine “ABB cartridge bell coating machine” (trade name, manufactured by ABB Co., Ltd.). ) Was electrostatically applied to a dry film thickness of 5 μm to form a first color 1 base coating film. After an interval of 1 minute, the aqueous second color base paint (Y-1) obtained in Production Example 24 was applied on the first color base coating film so as to have a dry film thickness of 10 μm. A coating film was formed. After an interval of 2 minutes, preheating was performed at 80 ° C. for 3 minutes to form an uncured base coat film, on which a clear coating “KINO6510” (trade name: Kansai Paint Co., Ltd., hydroxyl group / isocyanate group curing) Type acrylic urethane resin-based two-component organic solvent-type paint) to a dry film thickness of 30 μm, left for 7 minutes, then heated at 140 ° C. for 30 minutes to simultaneously cure these coatings A coated plate was prepared.

Examples 2-8 and Comparative Examples 1-6
Each water-based first color base paint and water-based second color base paint in Example 1 is changed to the paint shown in Table 3 below, and the film thickness is also adjusted. 8 and Comparative Test Plates 1 to 6 were prepared. Each test coated plate was evaluated by the following test method. The results are also shown in Table 3.

(* 1) Highlight saturation:
Using a multi-angle spectrocolorimeter “MA-68” (trade name, manufactured by X-Rite) for each test coating plate, the light irradiated from an angle of 45 degrees is received at 15 degrees with respect to the regular reflection light. C * 15 was calculated from the measured spectral reflectance. 100 or more was considered acceptable.

(* 2) Shade depth:
Using a multi-angle spectrocolorimeter “MA-68” (trade name, manufactured by X-Rite) for each test coating plate, light irradiated from an angle of 45 degrees is received at 75 degrees with respect to regular reflection light. C * 75 / L * 75 was calculated from the measured spectral reflectance. 2.8 or higher was accepted.

(* 3) Flip-flop value (FF value):
About each test coating plate, L value (lightness) of the light reception angle of 15 degrees and the light reception angle of 110 degrees was measured using a multi-angle spectrocolorimeter “MA-68” (trade name, manufactured by X-Rite). The FF value was obtained by the following formula. 1.60 or higher is acceptable.
FF value = L value with a light receiving angle of 15 degrees / L value with a light receiving angle of 110 degrees.
The larger the FF value, the larger the change in the L value (brightness) depending on the observation angle (light receiving angle), indicating that the flip-flop property is excellent.

  (* 4) Light transmittance of the water-based first color base paint: The water-based first color base paint was applied as in the examples and comparative examples except that a smooth PTFE plate was used as the test object, and the room temperature was about 20 ° C. After leaving it in the laboratory for 15 minutes, it was dried at 140 ° C. for 30 minutes using a hot air dryer to obtain a cured coating film. The obtained coating film was peeled off to prepare a free film, and the light transmittance at a wavelength of 420 nm was measured using a spectrophotometer UV3700 (trade name, manufactured by Shimadzu Corporation). Accept less than 1.0%.

(* 5) Unevenness: Each test coated plate was visually evaluated for unevenness (color unevenness).
○: Unevenness is not observed.
X: Generation of unevenness was observed.

Claims (6)

A method of forming a multilayer coating film by sequentially applying a first color base paint, a second color base paint, and a clear paint on a substrate by wet-on-wet,
The first color base paint contains an aluminum flake pigment and a vapor deposition chromium flake pigment, and the aluminum flake pigment concentration is in the range of 20 to 50 parts by mass with respect to 100 parts by mass of the resin solid content contained in the first color base paint. The flake pigment concentration is in the range of 1 to 10 parts by mass with respect to 100 parts by mass of the aluminum flake pigment contained in the first color base paint, and the paint solid content concentration is 2 to 20 with respect to the total mass of the first color base paint. In the range of mass%, the film thickness of the coating film by the first color base paint is in the range of 1 to 7 μm based on the cured coating film,
The method for forming a multilayer coating film, wherein the second color base paint contains a color pigment. 2. The multilayer according to claim 1, wherein the first color base paint and the second color base paint are water-based paints containing the acrylic resin emulsion (a), a film-forming resin (b) other than (a), and a curing agent (c). Coating film forming method. The method for forming a multilayer coating film according to claim 1 or 2, wherein the second color base paint contains 0.1 to 20 parts by weight of a color pigment with respect to 100 parts by weight of the resin solid content in the paint. The multilayer coating film forming method according to any one of claims 1 to 3, wherein the second color base paint contains a pigment dispersion obtained by dispersing a color pigment with an AB block polymer dispersant. The method for forming a multilayer coating film according to any one of claims 1 to 4, wherein the film thickness of the coating film by the second color base paint is in the range of 5 to 20 µm based on the cured coating film. Saturation C * in the L * C * h color system calculated from spectral reflectance obtained by receiving light irradiated from a 45 degree angle of the multilayer coating film at an angle of 15 degrees with respect to specular reflection light is 100 or more. And C * / L in the L * C * h color system calculated from the spectral reflectance obtained by receiving light irradiated from a 45-degree angle of the multilayer coating film at an angle of 75 degrees with respect to regular reflection light. The method for forming a multilayer coating film according to any one of claims 1 to 5, wherein * is 2.8 or more.