Photoluminescent pigment dispersion liquid, photoluminescent coating material composition, and method for forming multilayer coating film

Abstract

Provided is a photoluminescent pigment dispersion liquid which contains: a silica-treated aluminum pigment (A) having an amino group at the surface; a first dispersing resin (B); and water. The solids content in the silica-treated aluminum pigment (A) having an amino group at the surface is 90 mass% or more. The first dispersing resin (B) is a polymer of a composition containing: an acidic functional group-containing polymerizable unsaturated monomer (b1); a polyoxyalkylene chain-containing non-ionic polymerizable unsaturated monomer (b2); and another polymerizable unsaturated monomer (b3). The water content is 90 mass% or more relative to the amount of solvent in the photoluminescent pigment dispersion liquid.

Description

Glitter pigment dispersion, glitter paint composition, and method for forming multilayer coating film

[0001] The present invention relates to a glitter pigment dispersion, a glitter coating composition, and a method for forming a multilayer coating film.

[0002] In recent years, from the perspective of protecting the global environment, there has been a demand to reduce the amount of volatile organic compounds (VOCs) emitted from paints, and the replacement of solvent-based paints with water-based paints is progressing rapidly in various fields.

[0003] Furthermore, there has been a recent demand to reduce the amount of volatile organic compounds (VOCs) contained in water-based paints.

[0004] On the other hand, the coating film formed by applying paint is required to protect the object being painted and also to give it a design (beautiful appearance), and metallic paint colors in particular are very popular as they exude a sense of luxury.

[0005] However, when the amount of organic solvent is reduced in order to reduce the amount of volatile organic compounds (VOCs) in metallic paint colors, the dispersibility of the aluminum pigment deteriorates, making it difficult to obtain a paint film with high brilliance.

[0006] Patent Document 1 describes an aluminum pigment composition for aqueous paints that contains at least an aluminum pigment, a rheology control agent, and an organic solvent, wherein the organic solvent has a solubility parameter of 6 to 12 and a solubility in water at 20°C of 30% by mass or less, and the rheology control agent is added in an amount of 2.5 parts by mass per 100 parts by mass of the solids in a resin emulsion, and the viscosity is measured using a Brookfield viscometer. The viscosity at 60 revolutions, B60, and the viscosity at 6 revolutions, B6, are both within the range of 0.3 to 30 Pa s, and the thixotropic index, B6 / B60, which is the ratio of B6 to B60, is 1 to 60. This aluminum pigment composition for aqueous paints is characterized by the improved orientation of the aluminum pigment after application, thereby improving metallic unevenness and thereby achieving a color tone and appearance comparable to those of organic solvent-based paints.

[0007] Although the aluminum pigment composition for aqueous paint has good luster, in recent years, there has been a demand for further reduction in the amount of volatile organic compounds (VOCs).

[0008] Japanese Patent Application Publication No. 2009-242457

[0009] An object of the present invention is to provide a bright pigment dispersion that can be used to produce a bright coating composition that has a low content of volatile organic compounds (VOCs) and is capable of forming a coating film with excellent brightness.

[0010] According to the present invention, there are provided a bright pigment dispersion, a bright coating composition, and a method for forming a multilayer coating film, which include the following aspects.

[0011] Item 1. A brilliant pigment dispersion containing a silica-treated aluminum pigment (A) having amino groups on its surface, a first dispersing resin (B), and water, wherein the solids content of the silica-treated aluminum pigment (A) having amino groups on its surface is 90 mass% or more, and the first dispersing resin (B) is a polymer of a composition containing a polymerizable unsaturated monomer (b1) having an acidic functional group, a nonionic polymerizable unsaturated monomer (b2) having a polyoxyalkylene chain, and another polymerizable unsaturated monomer (b3), and the water content is 90 mass% or more based on the amount of solvent in the brilliant pigment dispersion.

[0012] Item 2. The brilliant pigment dispersion according to Item 1, wherein the silica-treated aluminum pigment (A) having amino groups on its surface includes a silica-treated aluminum pigment (A1) having amino groups and alkyl groups on its surface.

[0013] Item 3. The bright pigment dispersion liquid according to Item 1 or 2, wherein the polymerizable unsaturated monomer (b1) containing an acidic functional group includes a polymerizable unsaturated monomer containing a carboxyl group.

[0014] Item 4. The brilliant pigment dispersion liquid according to any one of Items 1 to 3, further comprising a second dispersing resin (C) that is a polymer of a composition containing a polymerizable unsaturated monomer (c1) containing at least one functional group selected from the group consisting of a tertiary amino group and a quaternary ammonium salt group, a nonionic polymerizable unsaturated monomer (c2) having a polyoxyalkylene chain, and another polymerizable unsaturated monomer (c3).

[0015] Item 5. A glittering coating composition comprising the glittering pigment dispersion according to any one of Items 1 to 4 and a film-forming resin.

[0016] Item 6. A method for forming a multilayer coating film, comprising the following steps (1) to (4): step (1): applying a colored coating composition (X) onto a substrate to form a colored coating film, step (2): applying the glittering coating composition (Y) described in item 5 onto the colored coating film obtained in step (1) to form a glittering coating film, step (3): applying a clear coating composition (Z) onto the glittering coating film obtained in step (2) to form a clear coating film, and step (4): heating the multilayer coating film comprising the colored coating film, glittering coating film, and clear coating film formed in steps (1), (2), and (3), respectively, to simultaneously cure the multilayer coating film.

[0017] By using the bright pigment dispersion of the present invention, it is possible to produce a bright coating composition that has a low content of volatile organic compounds (VOCs) and is capable of forming a coating film with excellent brightness.

[0018] In this specification, "comprise" is a concept that encompasses "consist essentially of" and "consist only of." In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. Furthermore, the upper or lower limit of a numerical range described in this specification, including the claims, may be replaced with the upper or lower limit shown in the examples or a value that can be unambiguously derived from the examples. Furthermore, in this specification, a numerical value connected with "to" means a numerical range that includes the numbers before and after "to" as the lower and upper limits.

[0019] The bright pigment dispersion of the present invention will be described in more detail below.

[0020] Brilliant pigment dispersion The brilliant pigment dispersion of the present invention is a brilliant pigment dispersion containing a silica-treated aluminum pigment (A) having amino groups on its surface, a first dispersing resin (B), and water, wherein the solids content of the silica-treated aluminum pigment (A) having amino groups on its surface is 90 mass% or more, and the first dispersing resin (B) is a polymer of a composition containing a polymerizable unsaturated monomer (b1) having an acidic functional group, a nonionic polymerizable unsaturated monomer (b2) having a polyoxyalkylene chain, and another polymerizable unsaturated monomer (b3), and the water content is 90 mass% or more based on the amount of solvent in the brilliant pigment dispersion.

[0021] From the viewpoint of producing a bright coating composition with a low content of volatile organic compounds (VOCs), the water content is preferably 92 mass% or more, and more preferably 94 mass% or more, based on the amount of solvent in the bright pigment dispersion. Examples of the solvent include water and organic solvents. The amount of solvent in the bright pigment dispersion is the total amount of one or more solvents contained in the bright pigment dispersion.

[0022] Silica-treated aluminum pigment (A) having amino groups on its surface The silica-treated aluminum pigment (A) having amino groups on its surface has a solids content of 90% by mass or more. In particular, from the viewpoint of producing a bright coating composition with a low content of volatile organic compounds (VOCs), the solids content is preferably 95% by mass or more, and more preferably 99% by mass or more.

[0023] The silica-treated aluminum pigment (A) having amino groups on its surface can be produced by reacting a silica-treated aluminum pigment with a silane coupling agent. Such modification of silica-treated aluminum pigments with amino groups is known.

[0024] The silica-treated aluminum pigment (A) having amino groups on its surface interacts with the acidic functional groups of the first dispersing resin (B), improving the dispersibility of the silica-treated aluminum pigment (A), and enabling a bright coating composition containing the silica-treated aluminum pigment (A) to form a coating film with excellent brightness.

[0025] From the viewpoint that a bright coating composition containing the silica-treated aluminum pigment (A) forms a coating film with excellent brightness, the silica-treated aluminum pigment (A) preferably has an average particle size in the range of 1 to 100 μm, more preferably in the range of 5 to 50 μm, and even more preferably in the range of 7 to 30 μm. The thickness is preferably in the range of 0.01 to 1.0 μm, and even more preferably in the range of 0.02 to 0.5 μm.

[0026] From the viewpoints of dispersibility and the water resistance and luster of the coating film formed, the silica-treated aluminum pigment (A) having amino groups on its surface preferably includes a silica-treated aluminum pigment (A1) having amino groups and alkyl groups on its surface.

[0027] The silica-treated aluminum pigment (A1) having amino and alkyl groups on its surface can be produced by reacting a silane coupling agent with an aluminum pigment whose surface has been silica-treated. Such modification of silica-treated aluminum pigments with amino and alkyl groups is known.

[0028] From the viewpoint of producing a glittering coating composition that has a low content of volatile organic compounds (VOCs) and is capable of forming a coating film with excellent glitter, the content of the silica-treated aluminum pigment (A) having amino groups on its surface in the glittering pigment dispersion of the present invention is preferably 60 to 95 parts by mass, more preferably 65 to 93 parts by mass, and even more preferably 70 to 90 parts by mass, based on 100 parts by mass of the solids content in the glittering pigment dispersion.

[0029] First Dispersion Resin (B) The first dispersion resin (B) is a polymer of a composition containing a polymerizable unsaturated monomer (b1) containing an acidic functional group, a nonionic polymerizable unsaturated monomer (b2) having a polyoxyalkylene chain, and another polymerizable unsaturated monomer (b3).

[0030] Examples of the polymerizable unsaturated monomer (b1) containing an acidic functional group include a polymerizable unsaturated monomer containing a carboxyl group, a polymerizable unsaturated monomer containing a phosphoric acid group, and a polymerizable unsaturated monomer containing a sulfonic acid group, and among these, it is preferable to include a polymerizable unsaturated monomer containing a carboxyl group.

[0031] The carboxyl group-containing polymerizable unsaturated monomer is a compound having one or more carboxyl groups and one polymerizable unsaturated group in one molecule, and examples thereof include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, maleic acid, maleic anhydride, etc. These may be used alone or in combination of two or more.

[0032] The polymerizable unsaturated monomer having a phosphate group is a compound having one or more phosphate groups and one polymerizable unsaturated group in one molecule, and examples thereof include acid phosphooxyethyl (meth)acrylate, acid phosphooxypropyl (meth)acrylate, acid phosphooxypoly(oxyethylene)glycol (meth)acrylate, acid phosphooxypoly(oxypropylene)glycol (meth)acrylate, etc. These may be used alone or in combination of two or more.

[0033] The polymerizable unsaturated monomer containing a sulfonic acid group is a compound having one or more sulfonic acid groups and one polymerizable unsaturated group in one molecule, and examples thereof include 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl (meth)acrylate, allylsulfonic acid, 4-styrenesulfonic acid, etc.; sodium salts and ammonium salts of these sulfonic acids; and these can be used alone or in combination of two or more.

[0034] In this specification, the term "polymerizable unsaturated group" refers to an unsaturated group that can undergo radical polymerization. Examples of such polymerizable unsaturated groups include vinyl groups and (meth)acryloyl groups.

[0035] In addition, in this specification, "(meth)acrylate" means acrylate or methacrylate. "(meth)acrylic acid" means acrylic acid or methacrylic acid. "(meth)acryloyl" means acryloyl or methacryloyl. "(meth)acrylamide" means acrylamide or methacrylamide.

[0036] The proportion of the polymerizable unsaturated monomer (b1) containing an acidic functional group in the monomers constituting the first dispersion resin (B) is preferably 1 to 30 mass%, more preferably 3 to 25 mass%, and even more preferably 5 to 20 mass%, based on the total amount of the polymerizable unsaturated monomer (b1) containing an acidic functional group, the nonionic polymerizable unsaturated monomer (b2) having a polyoxyalkylene chain, and the other polymerizable unsaturated monomer (b3).

[0037] The nonionic polymerizable unsaturated monomer (b2) having a polyoxyalkylene chain 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, and a block chain of polyoxyethylene and polyoxypropylene.

[0038] The molecular weight of the polyoxyalkylene chain is preferably in the range of 150 to 3,000, and more preferably in the range of 300 to 2,500.

[0039] Examples of the nonionic polymerizable unsaturated monomer (b2) having a polyoxyalkylene chain include those represented by the following formula (1): CH═C(R 3 ) COO (C n H 2n O) m -R 4 (1) (wherein, R 3 represents a hydrogen atom or a methyl group, R 4 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, m is an integer of 4 to 60, preferably 6 to 50, and n is 2 or 3, preferably 2, wherein m oxyalkylene units (C n H 2n O) may be the same or different from each other).

[0040] Specific examples of the nonionic polymerizable unsaturated monomer (b2) having a polyoxyalkylene chain include tetraethylene glycol (meth)acrylate, methoxytetraethylene glycol (meth)acrylate, ethoxytetraethylene glycol (meth)acrylate, n-butoxytetraethylene glycol (meth)acrylate, tetrapropylene glycol (meth)acrylate, methoxytetrapropylene glycol (meth)acrylate, ethoxytetrapropylene glycol (meth)acrylate, n-butoxytetrapropylene glycol (meth)acrylate, polyethylene glycol (meth)acrylate, polypropylene glycol (meth)acrylate, methoxypolyethylene glycol (meth)acrylate, and ethoxypolyethylene glycol (meth)acrylate, and these may be used alone or in combination of two or more.

[0041] The proportion of the nonionic polymerizable unsaturated monomer (b2) having a polyoxyalkylene chain in the monomers constituting the first dispersion resin (B) is preferably 50 to 95 mass%, more preferably 55 to 93 mass%, and even more preferably 60 to 90 mass%, based on the total amount of the polymerizable unsaturated monomer (b1) containing an acidic functional group, the nonionic polymerizable unsaturated monomer (b2) having a polyoxyalkylene chain, and the other polymerizable unsaturated monomer (b3).

[0042] The other polymerizable unsaturated monomer (b3) is a compound having one polymerizable unsaturated bond per molecule other than the above-mentioned monomers (b1) and (b2), and specific examples thereof are listed below. (i) Alkyl or cycloalkyl (meth)acrylates: for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, 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 (meth)acrylate, cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, tricyclodecanyl (meth)acrylate, and the like. (ii) Polymerizable unsaturated monomers having an isobornyl group: isobornyl (meth)acrylate, etc. (iii) Polymerizable unsaturated monomers having an adamantyl group: adamantyl (meth)acrylate, etc. (iv) Polymerizable unsaturated monomers having a tricyclodecenyl group: tricyclodecenyl (meth)acrylate, etc. (v) Polymerizable unsaturated monomers containing an aromatic ring: benzyl (meth)acrylate, styrene, α-methylstyrene, vinyltoluene, etc. (vi) Polymerizable unsaturated monomers having an alkoxysilyl group: vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, γ-(meth)acryloyloxypropyltrimethoxysilane, γ-(meth)acryloyloxypropyltriethoxysilane, etc. (vii) Polymerizable unsaturated monomers having a fluorinated alkyl group: perfluoroalkyl (meth)acrylates such as perfluorobutylethyl (meth)acrylate and perfluorooctylethyl (meth)acrylate; fluoroolefins, etc. (viii) Polymerizable unsaturated monomers having a photopolymerizable functional group such as a maleimide group.(ix) Vinyl compounds: N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate, etc. (x) Nitrogen-containing polymerizable unsaturated monomers: (meth)acrylonitrile, (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylamide, methylene bis(meth)acrylamide, ethylene bis(meth)acrylamide, adducts of glycidyl (meth)acrylate and amine compounds, etc. (xi) Polymerizable unsaturated monomers having two or more polymerizable unsaturated groups in one molecule: allyl (meth)acrylate, ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, etc. (xii) Epoxy group-containing 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, and the like. (xiii) Polymerizable unsaturated monomers having an ultraviolet-absorbing functional group: 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-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole, etc.(xiv) Light-stable polymerizable unsaturated monomers: 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-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, and the like. (xv) polymerizable unsaturated monomers having a carbonyl group: acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formylstyrene, vinyl alkyl ketones having 4 to 7 carbon atoms (for example, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone), etc. (xvi) polymerizable unsaturated monomers having an acid anhydride group: maleic anhydride, itaconic anhydride, citraconic anhydride, etc. (xvii) hydroxyl group-containing polymerizable unsaturated monomers: monoesters of polyhydric alcohols and (meth)acrylic acid (other than the nonionic polymerizable unsaturated monomer (b2) having a polyoxyalkylene chain), such as 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 2,3-dihydroxybutyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate; compounds obtained by ring-opening polymerization of the above monoesters of polyhydric alcohols and (meth)acrylic acid with ε-caprolactone, etc.

[0043] The proportion of the other polymerizable unsaturated monomer (b3) in the monomers constituting the first dispersion resin (B) is preferably 1 to 25 mass%, more preferably 2 to 15 mass%, and even more preferably 3 to 10 mass%, based on the total amount of the polymerizable unsaturated monomer (b1) containing an acidic functional group, the nonionic polymerizable unsaturated monomer (b2) having a polyoxyalkylene chain, and the other polymerizable unsaturated monomer (b3).

[0044] The polymerization of the monomers constituting the first dispersion resin (B) can be carried out by a method known per se, such as solution polymerization in an organic solvent or emulsion polymerization in water, among which solution polymerization is preferred. An example of a polymerization method using solution polymerization is a method in which a mixture of a polymerizable unsaturated monomer (b1) containing an acidic functional group, a nonionic polymerizable unsaturated monomer (b2) having a polyoxyalkylene chain, and other polymerizable unsaturated monomers (b3) and a radical polymerization initiator is dissolved or dispersed in an organic solvent, and then heated with stirring at a temperature of about 80°C to about 200°C for about 1 to 10 hours to polymerize the mixture.

[0045] Examples of the organic solvent include hydrocarbon solvents such as heptane, toluene, xylene, octane, and mineral spirits; ester solvents such as ethyl acetate, n-butyl acetate, isobutyl acetate, ethylene glycol monomethyl ether acetate, and diethylene glycol monobutyl ether acetate; ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, diisobutyl ketone, and cyclohexanone; alcohol solvents such as methanol, ethanol, isopropanol, n-butanol, sec-butanol, and isobutanol; ether solvents such as n-butyl ether, dioxane, ethylene glycol monomethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monopropyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monobutyl ether, and tripropylene glycol monomethyl ether; and aromatic petroleum solvents such as Swazol 310, Swazol 1000, and Swazol 1500 manufactured by Cosmo Oil Co., Ltd. These organic solvents can be used alone or in combination of two or more.

[0046] Examples of the radical polymerization initiator include ketone peroxides such as cyclohexanone peroxide, 3,3,5-trimethylcyclohexanone peroxide, and methylcyclohexanone peroxide; peroxyketals such as 1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, 1,1-bis(tert-butylperoxy)cyclohexane, and n-butyl-4,4-bis(tert-butylperoxy)valerate; hydroperoxides such as cumene hydroperoxide and 2,5-dimethylhexane-2,5-dihydroperoxide; 1,3-bis(tert-butylperoxy-m-isopropyl)benzene, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, diisopropylbenzene peroxide, and tert-butyl peroxyketals. Examples of the initiator include dialkyl peroxides such as tirucumyl peroxide; diacyl peroxides such as decanoyl peroxide, lauroyl peroxide, benzoyl peroxide, and 2,4-dichlorobenzoyl peroxide; peroxycarbonates such as bis(tert-butylcyclohexyl)peroxydicarbonate; organic peroxide polymerization initiators such as peroxyesters such as tert-butyl peroxybenzoate and 2,5-dimethyl-2,5-di(benzoylperoxy)hexane; and azo polymerization initiators such as 2,2'-azobisisobutyronitrile, 2,2'-azobis(2-methylpropionate)dimethyl, 1,1-azobis(cyclohexane-1-carbonitrile), azocumene-2,2'-azobismethylvaleronitrile, and 4,4'-azobis(4-cyanovaleric acid). The amount of these radical polymerization initiators used is not particularly limited, but is preferably 0.1 to 15 parts by weight, and more preferably 0.3 to 10 parts by weight, per 100 parts by weight of the total amount of polymerizable monomers.

[0047] From the viewpoint of the curability and water resistance of the resulting coating film, the hydroxyl value of the first dispersion resin (B) is preferably in the range of 0.1 to 20 mgKOH / g, more preferably in the range of 0.5 to 15 mgKOH / g, and even more preferably in the range of 1 to 10 mgKOH / g.

[0048] From the viewpoint of interaction with the amino groups of the silica-treated aluminum pigment (A) having amino groups on its surface, the acid value of the first dispersing resin (B) is preferably within the range of 5 to 200 mgKOH / g, more preferably within the range of 15 to 180 mgKOH / g, and even more preferably within the range of 30 to 150 mgKOH / g.

[0049] From the viewpoint of dispersion stability, etc., the weight average molecular weight of the first dispersion resin (B) is preferably in the range of 1,000 to 50,000, more preferably in the range of 2,000 to 40,000, and even more preferably in the range of 3,000 to 30,000.

[0050] From the viewpoint of producing a glittering coating composition that has a low content of volatile organic compounds (VOCs) and is capable of forming a coating film with excellent glittering properties, the content of the first dispersion resin (B) in the glittering pigment dispersion of the present invention is preferably 0.1 to 20.0 parts by mass, more preferably 0.2 to 15.0 parts by mass, and even more preferably 0.3 to 10.0 parts by mass, based on 100 parts by mass of the solid content in the glittering pigment dispersion.

[0051] From the viewpoint of producing a glittering coating composition that has a low content of volatile organic compounds (VOCs) and can form a coating film with excellent glittering properties, it is preferable that the glittering pigment dispersion of the present invention further contains a second dispersing resin (C).

[0052] Second Dispersion Resin (C) The second dispersion resin (C) is a polymer of a composition containing a polymerizable unsaturated monomer (c1) containing at least one functional group selected from the group consisting of a tertiary amino group and a quaternary ammonium salt group, a nonionic polymerizable unsaturated monomer (c2) having a polyoxyalkylene chain, and another polymerizable unsaturated monomer (c3).

[0053] In the present invention, when a dispersing resin corresponds to both the first dispersing resin (B) and the second dispersing resin (C), it is considered to be included in the first dispersing resin (B).

[0054] Examples of polymerizable unsaturated monomers containing a tertiary amino group include N,N-dialkylaminoalkyl (meth)acrylates such as N,N-dimethylaminoethyl (meth)acrylate, N,N-diethylaminoethyl (meth)acrylate, N,N-dimethylaminopropyl (meth)acrylate, N,N-di-t-butylaminoethyl (meth)acrylate, and N,N-dimethylaminobutyl (meth)acrylate; and N,N-dialkylaminoalkyl (meth)acrylamides such as N,N-dimethylaminoethyl (meth)acrylamide, N,N-diethylaminoethyl (meth)acrylamide, and N,N-dimethylaminopropyl (meth)acrylamide.

[0055] Furthermore, examples of the quaternary ammonium base-containing polymerizable unsaturated monomer include (meth)acryloyloxyalkyltrialkylammonium salts such as 2-(methacryloyloxy)ethyltrimethylammonium chloride, 2-(methacryloyloxy)ethyltrimethylammonium bromide, and 2-(methacryloyloxy)ethyltrimethylammonium dimethylphosphate; and (meth)acryloylaminoalkyltrialkylammonium salts such as methacryloylaminopropyltrimethylammonium chloride and methacryloylaminopropyltrimethylammonium bromide.

[0056] The polymerizable unsaturated monomer (c1) containing at least one functional group selected from the group consisting of a tertiary amino group and a quaternary ammonium salt group preferably contains a polymerizable unsaturated monomer containing a tertiary amino group, from the viewpoint of producing a glittering coating composition that has a low content of volatile organic compounds (VOCs) and is capable of forming a coating film with excellent glitter.

[0057] The proportion of the polymerizable unsaturated monomer (c1) containing at least one functional group selected from the group consisting of a tertiary amino group and a quaternary ammonium salt group in the monomers constituting the second dispersion resin (C) is preferably 0.1 to 20 mass%, more preferably 0.5 to 15 mass%, and even more preferably 1 to 10 mass%, based on the total amount of the polymerizable unsaturated monomer (c1) containing at least one functional group selected from the group consisting of a tertiary amino group and a quaternary ammonium salt group, the nonionic polymerizable unsaturated monomer (c2) having a polyoxyalkylene chain, and the other polymerizable unsaturated monomer (c3).

[0058] As the nonionic polymerizable unsaturated monomer having a polyoxyalkylene chain (c2), the compounds described in the explanation section for the nonionic polymerizable unsaturated monomer having a polyoxyalkylene chain (b2) can be used.

[0059] The proportion of the nonionic polymerizable unsaturated monomer (c2) having a polyoxyalkylene chain in the monomers constituting the second dispersion resin (C) is preferably 1 to 50 mass %, more preferably 3 to 40 mass %, and even more preferably 5 to 30 mass %, based on the total amount of the polymerizable unsaturated monomer (c1) having at least one functional group selected from the group consisting of a tertiary amino group and a quaternary ammonium salt group, the nonionic polymerizable unsaturated monomer (c2) having a polyoxyalkylene chain, and the other polymerizable unsaturated monomer (c3).

[0060] The other polymerizable unsaturated monomer (c3) is a compound having one polymerizable unsaturated bond per molecule other than the above-mentioned monomers (c1) and (c2), and specific examples thereof are listed below. (i) Alkyl or cycloalkyl (meth)acrylates: for example, methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, 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 (meth)acrylate, cyclohexyl (meth)acrylate, methylcyclohexyl (meth)acrylate, t-butylcyclohexyl (meth)acrylate, cyclododecyl (meth)acrylate, tricyclodecanyl (meth)acrylate, and the like. (ii) Polymerizable unsaturated monomers having an isobornyl group: isobornyl (meth)acrylate, etc. (iii) Polymerizable unsaturated monomers having an adamantyl group: adamantyl (meth)acrylate, etc. (iv) Polymerizable unsaturated monomers having a tricyclodecenyl group: tricyclodecenyl (meth)acrylate, etc. (v) Polymerizable unsaturated monomers containing an aromatic ring: benzyl (meth)acrylate, styrene, α-methylstyrene, vinyltoluene, etc. (vi) Polymerizable unsaturated monomers having an alkoxysilyl group: vinyltrimethoxysilane, vinyltriethoxysilane, vinyltris(2-methoxyethoxy)silane, γ-(meth)acryloyloxypropyltrimethoxysilane, γ-(meth)acryloyloxypropyltriethoxysilane, etc. (vii) Polymerizable unsaturated monomers having a fluorinated alkyl group: perfluoroalkyl (meth)acrylates such as perfluorobutylethyl (meth)acrylate and perfluorooctylethyl (meth)acrylate; fluoroolefins, etc. (viii) Polymerizable unsaturated monomers having a photopolymerizable functional group such as a maleimide group.(ix) vinyl compounds: N-vinylpyrrolidone, ethylene, butadiene, chloroprene, vinyl propionate, vinyl acetate, etc. (x) carboxyl group-containing polymerizable unsaturated monomers: (meth)acrylic acid, maleic acid, crotonic acid, β-carboxyethyl (meth)acrylate, etc. (xi) hydroxyl group-containing polymerizable unsaturated monomers: monoesters of polyhydric alcohols and (meth)acrylic acid (other than the nonionic polymerizable unsaturated monomer (b2) having a polyoxyalkylene chain), such as 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, 2,3-dihydroxybutyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, etc.; compounds obtained by ring-opening polymerization of the above monoesters of polyhydric alcohols and (meth)acrylic acid with ε-caprolactone, etc. (xii) Polymerizable unsaturated monomers having two or more polymerizable unsaturated groups in one molecule: allyl (meth)acrylate, ethylene glycol di(meth)acrylate, 1,4-butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, etc. (xiii) Epoxy group-containing 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, etc. (xiv) Polymerizable unsaturated monomers having a sulfonic acid group: 2-acrylamido-2-methylpropanesulfonic acid, 2-sulfoethyl (meth)acrylate, allylsulfonic acid, 4-styrenesulfonic acid, etc.; sodium salts and ammonium salts of these sulfonic acids, etc. (xv) Polymerizable unsaturated monomers having a phosphoric acid group: acid phosphooxyethyl (meth)acrylate, acid phosphooxypropyl (meth)acrylate, acid phosphooxypoly(oxyethylene)glycol (meth)acrylate, acid phosphooxypoly(oxypropylene)glycol (meth)acrylate, etc.(xvi) Polymerizable unsaturated monomers having an ultraviolet absorbing functional group: 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-[2-(methacryloyloxy)ethyl]phenyl]-2H-benzotriazole, etc. (xvii) Light-stable polymerizable unsaturated monomers: 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-2,2,6,6-tetramethylpiperidine, 1-crotonoyl-4-crotonoyloxy-2,2,6,6-tetramethylpiperidine, and the like. (xviii) Polymerizable unsaturated monomers having a carbonyl group: acrolein, diacetone acrylamide, diacetone methacrylamide, acetoacetoxyethyl methacrylate, formyl styrene, vinyl alkyl ketones having 4 to 7 carbon atoms (e.g., vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone), etc. (xix) Polymerizable unsaturated monomers having an acid anhydride group: maleic anhydride, itaconic anhydride, citraconic anhydride, etc.

[0061] The proportion of the other polymerizable unsaturated monomer (c3) in the monomers constituting the second dispersion resin (C) is preferably 45 to 90 mass %, more preferably 55 to 87 mass %, and even more preferably 65 to 85 mass %, based on the total amount of the polymerizable unsaturated monomer (c1) containing at least one functional group selected from the group consisting of a tertiary amino group and a quaternary ammonium salt group, the nonionic polymerizable unsaturated monomer (c2) having a polyoxyalkylene chain, and the other polymerizable unsaturated monomer (c3).

[0062] The monomers constituting the second dispersion resin (C) can be polymerized by a conventionally known method. From the viewpoint of the dispersibility of the silica-treated aluminum pigment (A) having amino groups on its surface, the second dispersion resin (C) is preferably an AB block polymer obtainable by addition-fragmentation chain transfer polymerization using an addition-fragmentation chain transfer agent. Specifically, a block polymer can be produced by addition-fragmentation chain transfer polymerization of the monomer components constituting the block in the presence of the addition-fragmentation chain transfer agent. The addition-fragmentation chain transfer polymerization can be carried out, for example, by solution polymerization in an organic solvent or emulsion polymerization in water. Furthermore, during polymerization, a known radical polymerization initiator can be optionally used in combination with the addition-fragmentation chain transfer agent.

[0063] As the addition-fragmentation chain transfer agent, for example, 2,4-diphenyl-4-methyl-1-pentene (sometimes abbreviated as "α-methylstyrene dimer" or "MSD") can be suitably used. MSD is preferably used in the first polymerization.

[0064] The AB block polymer preferably comprises an A block containing the polymerizable unsaturated monomer (c1) containing at least one functional group selected from the group consisting of a tertiary amino group and a quaternary ammonium salt group and another polymerizable unsaturated monomer (c3), and a B block containing the nonionic polymerizable unsaturated monomer (c2) having a polyoxyalkylene chain and another polymerizable unsaturated monomer (c3).

[0065] In the AB block polymer, the ratio (mass ratio) of the total amount of monomers constituting the A block to the total amount of monomers constituting the B block is preferably 10 / 90 to 60 / 40, and more preferably 20 / 80 to 50 / 50, from the viewpoint of the dispersibility of the silica-treated aluminum pigment (A) having amino groups on its surface.

[0066] From the viewpoint of the curability and water resistance of the resulting coating film, the second dispersion resin (C) preferably has a hydroxyl value in the range of 10 to 100 mgKOH / g, more preferably in the range of 20 to 80 mgKOH / g, and even more preferably in the range of 30 to 60 mgKOH / g.

[0067] From the viewpoint of the interaction with the silica-treated aluminum pigment (A) having amino groups on its surface and the first dispersing resin (B), the second dispersing resin (C) preferably has an amine value in the range of 1 to 30 mgKOH / g, more preferably in the range of 3 to 25 mgKOH / g, and even more preferably in the range of 5 to 20 mgKOH / g.

[0068] From the viewpoint of dispersion stability, etc., the weight average molecular weight of the second dispersion resin (C) is preferably in the range of 1,000 to 50,000, more preferably in the range of 2,000 to 40,000, and even more preferably in the range of 3,000 to 30,000.

[0069] From the viewpoint of producing a glittering coating composition that has a low content of volatile organic compounds (VOCs) and is capable of forming a coating film with excellent glittering properties, the content of the second dispersing resin (C) in the glittering pigment dispersion of the present invention is preferably 1 to 25 parts by mass, more preferably 3 to 23 parts by mass, and even more preferably 5 to 20 parts by mass, based on 100 parts by mass of the solid content in the glittering pigment dispersion.

[0070] Other Components The bright pigment dispersion of the present invention may further contain, as necessary, an organic solvent, a pigment other than the silica-treated aluminum pigment (A) having amino groups on its surface, a viscosity adjuster, an anti-settling agent, an ultraviolet absorber, a light stabilizer, and the like.

[0071] From the viewpoint of producing a glittering coating composition that has a low content of volatile organic compounds (VOCs) and is capable of forming a coating film with excellent glitter, the solids content of the glittering pigment dispersion of the present invention is preferably in the range of 10 to 50 mass %, and more preferably in the range of 20 to 40 mass %.

[0072] Glittering Paint Composition (Y) The glittering paint composition (Y) of the present invention is a glittering paint composition containing the glittering pigment dispersion of the present invention and a film-forming resin.

[0073] From the viewpoint of producing a glittering coating composition (Y) having a low content of volatile organic compounds (VOCs), the water content in the glittering coating composition (Y) of the present invention is preferably 70% by mass or more, more preferably 80% by mass or more, and even more preferably 85% by mass or more, based on the amount of solvent in the glittering coating composition (Y). Examples of the solvent include water and organic solvents. The amount of solvent in the glittering coating composition (Y) is the total amount of one or more solvents contained in the glittering coating composition (Y).

[0074] Examples of the film-forming resin include acrylic resin, polyester resin, epoxy resin, and urethane resin.

[0075] Examples of the acrylic resin include resins obtained by copolymerizing α,β-ethylenically unsaturated carboxylic acid, (meth)acrylic acid esters having functional groups such as hydroxyl groups, amide groups, methylol groups, and epoxy groups, other (meth)acrylic acid esters, styrene, and the like.

[0076] Examples of the polyester resin that can be used include polyester resins obtained by a condensation reaction between a polyhydric alcohol such as ethylene glycol, propylene glycol, butylene glycol, 1,6-hexanediol, trimethylolpropane, or pentaerythritol and a polycarboxylic acid component such as adipic acid, isophthalic acid, terephthalic acid, phthalic anhydride, hexahydrophthalic anhydride, or trimellitic anhydride.

[0077] The epoxy resin may be, for example, a so-called bisphenol A type epoxy resin, which is produced by a condensation reaction between bisphenol A and epichlorohydrin.

[0078] Examples of the urethane resin include compounds obtained by an addition reaction between a diisocyanate compound and a polyhydric alcohol, and polymerized resins obtained by reacting the above-mentioned acrylic resin, polyester resin, or epoxy resin with a diisocyanate compound.

[0079] The film-forming resin preferably has a sufficient amount of hydrophilic groups to be water-soluble or water-dispersible.

[0080] Examples of the hydrophilic group include a carboxyl group, a hydroxyl group, a methylol group, an amino group, a sulfonic acid group, and a polyoxyethylene bond, with a carboxyl group being preferred among these.

[0081] The hydrophilic group is preferably neutralized with sodium hydroxide, an amine compound, or the like to form an alkali salt.

[0082] The resin can also be dispersed in water by emulsion polymerization of the polymerizable component in the presence of a surfactant or a water-soluble resin. Furthermore, the resin can also be dispersed in water in the presence of an emulsifier, for example. In this case, the base resin does not need to contain the hydrophilic group.

[0083] The film-forming resins can be used alone or in combination of two or more. From the viewpoint of forming a coating film with excellent brilliance, the content of the film-forming resin in the glittering coating composition (Y) of the present invention is preferably in the range of 30 to 85 parts by mass, more preferably in the range of 35 to 80 parts by mass, based on 100 parts by mass of the total solids in the glittering coating composition (Y).

[0084] The bright coating composition (Y) of the present invention preferably further contains a curing agent.

[0085] Examples of the curing agent include amino resins, polyisocyanate compounds, blocked polyisocyanate compounds, etc. The curing agents may be used alone or in combination of two or more.

[0086] When the bright coating composition (Y) of the present invention contains the above-mentioned curing agent, the content of the film-forming resin and the curing agent is preferably within the range of 50 to 90 mass %, particularly preferably 60 to 85 mass %, of the former, and preferably 10 to 50 mass %, particularly preferably 15 to 40 mass %, of the latter, based on the total mass of both components.

[0087] In addition to the above components, the glittering coating composition (Y) of the present invention may optionally contain a coloring pigment, an extender pigment, a glittering pigment other than the silica-treated aluminum pigment (A) having amino groups on its surface, a curing catalyst, an ultraviolet absorber, an antifoaming agent, a viscosity modifier, a surface modifier, an organic solvent, etc.

[0088] Examples of the color pigment include titanium oxide, zinc oxide, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, threne pigments, perylene pigments, dioxazine pigments, and diketopyrrolopyrrole pigments, and among these, carbon black is preferably included.

[0089] When the glittering coating composition (Y) of the present invention contains the above-mentioned coloring pigment, the content of the coloring pigment is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, based on 100 parts by mass of the resin solid content in the glittering coating composition (Y).

[0090] Examples of the extender pigment include barium sulfate, talc, clay, kaolin, barium carbonate, calcium carbonate, silica, and alumina white.

[0091] When the glittering coating composition (Y) of the present invention contains the above-mentioned extender pigment, the content of the extender pigment is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, based on 100 parts by mass of the resin solids in the glittering coating composition (Y).

[0092] Examples of the luster pigment other than the silica-treated aluminum pigment (A) having amino groups on its surface include aluminum (including vapor-deposited aluminum) other than the silica-treated aluminum pigment (A) having amino groups on its surface, copper, zinc, brass, nickel, glass flakes, aluminum oxide, mica, aluminum oxide coated with titanium oxide and / or iron oxide, and mica coated with titanium oxide and / or iron oxide.

[0093] When the glittering coating composition (Y) of the present invention contains a glittering pigment other than the silica-treated aluminum pigment (A) having amino groups on its surface, the content of the glittering pigment is preferably 0.1 to 30 parts by mass, more preferably 0.5 to 20 parts by mass, based on 100 parts by mass of the resin solids in the glittering coating composition (Y).

[0094] Examples of the curing catalyst include tin octylate, dibutyltin diacetate, dibutyltin di(2-ethylhexanoate), dibutyltin dilaurate, dioctyltin diacetate, dioctyltin di(2-ethylhexanoate), dibutyltin oxide, dibutyltin sulfide, dioctyltin oxide, dibutyltin fatty acid salts, lead 2-ethylhexanoate, zinc octylate, zinc naphthenate, zinc fatty acids, bismuth octanoate, bismuth 2-ethylhexanoate, bismuth oleate, bismuth neodecanoate, and bismuth versatic acid. Examples of compounds that can be used include organometallic compounds such as bismuth, bismuth naphthenate, cobalt naphthenate, calcium octoate, copper naphthenate, and tetra(2-ethylhexyl)titanate; sulfonic acid group-containing compounds such as paratoluenesulfonic acid, dodecylbenzenesulfonic acid, and dinonylnaphthalenesulfonic acid; and phosphate group-containing compounds such as monobutyl phosphate, dibutyl phosphate, mono-2-ethylhexyl phosphate, di-2-ethylhexyl phosphate, alkyl ether phosphate, polyoxyethylene alkyl ether phosphate, and phosphate group-containing resins.

[0095] When used, the glittering coating composition (Y) of the present invention can be diluted with water and / or an organic solvent, etc., if necessary, to adjust the viscosity to an appropriate level before application.

[0096] The appropriate viscosity varies depending on the coating composition, but it is preferable to adjust the viscosity, for example, using water and / or an organic solvent so that it is within the range of 2000 to 7000 mPa s when measured using a Brookfield viscometer at 20°C and a rotation speed of 6 rpm. Furthermore, in the above, the coating solids concentration of the glitter coating composition (Y) is preferably 3 to 30 mass%, and more preferably about 5 to 25 mass%.

[0097] The glittering coating composition (Y) of the present invention may be either a one-component coating or a multi-component coating, but is preferably a one-component coating from the viewpoints of excellent productivity due to the absence of a coating mixing step and simplification of maintenance of coating machines.

[0098] The glittering coating composition (Y) of the present invention can be applied to a substrate by a known method, such as air spray coating, airless spray coating, rotary atomization coating, curtain coating, etc., and electrostatic application may be performed during application. Among these, air spray coating, rotary atomization coating, etc. are preferred. Furthermore, such application methods can be performed once or several times until the desired film thickness is obtained.

[0099] The amount of the glittering coating composition (Y) of the present invention to be applied is preferably an amount that results in a cured film thickness of 0.5 to 20 μm, more preferably 1 to 15 μm, and even more preferably 2 to 10 μm.

[0100] Method for forming a multilayer coating film The method for forming a multilayer coating film of the present invention comprises the following steps (1) to (4): step (1): applying a colored coating composition (X) onto an object to be coated to form a colored coating film; step (2): applying a glittering coating composition (Y) of the present invention onto the colored coating film obtained in step (1) to form a glittering coating film; step (3): applying a clear coating composition (Z) onto the glittering coating film obtained in step (2) to form a clear coating film; and step (4): heating the multilayer coating film comprising the colored coating film, glittering coating film and clear coating film formed in steps (1), (2) and (3), respectively, thereby simultaneously curing the multilayer coating film.

[0101] The substrate is not particularly limited, and examples thereof include outer panels of automobile bodies such as passenger cars, trucks, motorcycles, and buses; automobile parts; and outer panels of household electrical appliances such as mobile phones and audio equipment. Of these, outer panels of automobile bodies and automobile parts are preferred.

[0102] The material of these substrates is not particularly limited. Examples include metal materials such as iron, aluminum, brass, copper, tinplate, stainless steel, zinc-plated steel, and zinc alloy (Zn-Al, Zn-Ni, Zn-Fe, etc.)-plated steel; resins such as polyethylene resin, polypropylene resin, acrylonitrile-butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, and epoxy resin; plastic materials such as various FRPs; inorganic materials such as glass, cement, and concrete; wood; and fibrous materials such as paper and cloth. Of these, metal materials and plastic materials are preferred.

[0103] Furthermore, the surface of the object to which the multilayer coating film is applied may be a metal surface such as an outer panel of an automobile body, an automobile part, a household electrical appliance, or a metal substrate such as the steel plate that constitutes these, which has been subjected to a surface treatment such as phosphate treatment, chromate treatment, or composite oxide treatment.

[0104] A coating film may be further formed on an object that may or may not have been surface-treated. For example, a substrate to be coated may be subjected to a surface treatment as needed, and a primer coating film and / or intermediate coating film may be formed thereon. For example, when the substrate to be coated is an automobile body, the primer coating film and / or intermediate coating film may be formed using a known primer and / or intermediate coating composition that is commonly used in painting automobile bodies.

[0105] The undercoat paint composition for forming the undercoat paint film can be, for example, an electrodeposition paint, preferably a cationic electrodeposition paint. The intermediate paint composition for forming the intermediate paint film can be a paint prepared by mixing a base resin having a crosslinkable functional group such as a carboxyl group, a hydroxyl group, or the like, such as an acrylic resin, a polyester resin, an alkyd resin, a urethane resin, or an epoxy resin, with a crosslinking agent such as an amino resin such as a melamine resin or a urea resin, or an optionally blocked polyisocyanate compound, together with a pigment, a thickener, and optionally other components.

[0106] As the colored coating composition (X), a thermosetting colored coating composition known for use in coating automobile bodies, etc., can be used, and for example, a thermosetting coating composition containing a base resin having a crosslinkable functional group, a crosslinking agent, a color pigment, and an extender pigment can be suitably used. Furthermore, a luster pigment can also be contained.

[0107] Examples of the crosslinkable functional group contained in the base resin include a carboxyl group, a hydroxyl group, and an epoxy group.

[0108] Examples of the base resin include acrylic resin, polyester resin, alkyd resin, and urethane resin.

[0109] Examples of the crosslinking agent include melamine resins, polyisocyanate compounds, and blocked polyisocyanate compounds.

[0110] As the colored coating composition (X), either an aqueous coating composition or an organic solvent-based coating composition may be used, but from the viewpoint of reducing the environmental load, an aqueous coating composition is preferred.

[0111] The method for applying the colored coating composition (X) is not particularly limited, but a wet coating film can be formed by, for example, air spray coating, airless spray coating, rotary atomization coating, curtain coating, or other coating methods. In these coating methods, electrostatic application may be performed as necessary. Of these, air spray coating or rotary atomization coating is particularly preferred. The amount of colored coating composition (X) applied is preferably an amount that results in a cured film thickness of 5 to 30 μm, more preferably an amount that results in a cured film thickness of 7 to 20 μm.

[0112] When air spray coating, airless spray coating, or rotary atomization coating is performed, the viscosity of the colored coating composition (X) is adjusted as appropriate using a solvent such as water or an organic solvent so that it falls within a viscosity range suitable for the coating, preferably within a viscosity range of about 15 to 60 seconds, particularly preferably about 20 to 50 seconds, at 20°C as measured using a Ford Cup No. 4 viscometer.

[0113] As the clear coating composition (Z), any known thermosetting clear coating composition for use in painting automobile bodies and the like can be used, such as an organic solvent-based thermosetting coating composition containing a base resin having a crosslinkable functional group and a curing agent, an aqueous thermosetting coating composition, or a powder thermosetting coating composition.

[0114] Examples of crosslinkable functional groups possessed by the base resin include carboxyl groups, hydroxyl groups, epoxy groups, silanol groups, etc. Types of base resins include acrylic resins, polyester resins, alkyd resins, urethane resins, epoxy resins, fluororesins, etc. Examples of curing agents 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.

[0115] Preferred combinations of base resin / curing agent for the clear coating composition (Z) include carboxyl group-containing resin / epoxy group-containing resin, hydroxyl group-containing resin / polyisocyanate compound, hydroxyl group-containing resin / blocked polyisocyanate compound, hydroxyl group-containing resin / melamine resin, etc.

[0116] The clear coating composition (Z) may be a one-component coating, or may be a multi-component coating such as a two-component urethane resin coating.

[0117] Furthermore, the above-mentioned clear coating composition (Z) may contain coloring pigments, luster pigments, dyes, etc., as needed, to the extent that transparency is not impaired, and may further contain extender pigments, ultraviolet absorbers, light stabilizers, antifoaming agents, thickeners, rust inhibitors, surface conditioners, etc., as appropriate.

[0118] The application method of the clear coating composition (Z) is not particularly limited, but a wet coating film can be formed by, for example, air spray coating, airless spray coating, rotary atomization coating, curtain coating, or other coating methods. In these coating methods, electrostatic application may be performed as necessary. Of these, air spray coating or rotary atomization coating is particularly preferred. The amount of clear coating composition (Z) applied is preferably an amount that results in a cured film thickness of 10 to 50 μm, more preferably an amount that results in a cured film thickness of 20 to 40 μm.

[0119] When air spray coating, airless spray coating, or rotary atomization coating is performed, the viscosity of the clear coating composition (Z) is adjusted appropriately using a solvent such as an organic solvent so that it falls within a viscosity range suitable for such coating, preferably within a viscosity range of about 15 to 60 seconds, particularly preferably within a viscosity range of about 20 to 50 seconds, at 20°C as measured using a Ford Cup No. 4 viscometer.

[0120] The heating can be carried out by known means, for example, a drying oven such as a hot air oven, an electric oven, or an infrared induction heating oven. The heating temperature is preferably within the range of 70 to 160°C, more preferably 90 to 150°C. The heating time is not particularly limited, but is preferably within the range of 10 to 60 minutes, more preferably 20 to 40 minutes.

[0121] The present invention will be explained in more detail below with reference to Production Examples, Examples, and Comparative Examples. Note that these Production Examples, Examples, and Comparative Examples are merely illustrative and are not intended to limit the scope of the present invention. In the Production Examples, Examples, and Comparative Examples, "parts" and "%" are based on mass unless otherwise specified. Furthermore, the film thickness of the coating film is based on the cured coating film.

[0122] 1. Preparation of coated object A degreased and zinc phosphate-treated steel plate (JIS G3141, size 400 mm x 300 mm x 0.8 mm) was electrodeposited with the cationic electrodeposition paint "Elecron GT-10" (product name: manufactured by Kansai Paint Co., Ltd., which uses an epoxy resin polyamine-based cationic resin and a blocked polyisocyanate compound as a curing agent) so that the film thickness based on the cured coating was 20 μm, and the coating was then heated at 170°C for 20 minutes to crosslink and cure, thereby forming an electrodeposition coating.

[0123] On the electrodeposition coated surface of the steel plate obtained, "WP-523H" (product name: acrylic-melamine resin-based water-based intermediate coating paint, manufactured by Kansai Paint Co., Ltd.) was applied using an air spray so that the film thickness based on the cured coating film was 20 μm. After leaving it for 3 minutes, the plate was preheated at 80°C for 3 minutes to form an uncured intermediate coating film, thereby preparing a coated article.

[0124] 2. Preparation of Paint Preparation of Hydroxyl-Containing Acrylic Resin Emulsion (1) Production Example 1 A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, and dropping device was charged with 70.7 parts of deionized water and 0.52 parts of "Aqualon KH-10" (trade name, Dai-ichi Kogyo Seiyaku Co., Ltd., emulsifier, active ingredient 97%), stirred and mixed in a nitrogen stream, and heated to 80°C. Next, 1% of the total amount of the monomer emulsion described below and 5 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 was added dropwise over 3 hours to the reaction vessel maintained at the same temperature. After completion of the dropwise addition, the reaction vessel was allowed to age for 1 hour, and then cooled to 30°C while gradually adding 40 parts of a 5% aqueous 2-(dimethylamino)ethanol solution. The mixture was then discharged while filtering through a 100-mesh nylon cloth, yielding a hydroxyl-containing acrylic resin emulsion (1) with a solids concentration of 45%. The resulting hydroxyl group-containing acrylic resin emulsion (1) had a hydroxyl value of 43 mgKOH / g and an acid value of 12 mgKOH / g.

[0125] Monomer emulsion: 50 parts of deionized water, 10 parts of styrene, 40 parts of methyl methacrylate, 35 parts of ethyl acrylate, 3.5 parts of n-butyl methacrylate, 10 parts of 2-hydroxyethyl methacrylate, 1.5 parts of acrylic acid, 1.0 part of "Aqualon KH-10," and 0.03 parts of ammonium persulfate were mixed and stirred to obtain a monomer emulsion.

[0126] Preparation of Hydroxyl-Containing Polyester Resin (2) Preparation Example 2: A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, and water separator was charged with 174 parts of trimethylolpropane, 327 parts of neopentyl glycol, 352 parts of adipic acid, 109 parts of isophthalic acid, and 101 parts of 1,2-cyclohexanedicarboxylic anhydride. The mixture was heated from 160 ° C. to 230 ° C. over 3 hours, and the resulting condensed water was distilled off using a water separator while maintaining the temperature at 230 ° C. until the acid value reached 3 mg KOH / g or less. 59 parts of trimellitic anhydride was added to the reaction product, and the mixture was subjected to an addition reaction at 170 ° C. for 30 minutes. The mixture was then cooled to 50 ° C. or less, and neutralized by adding an equivalent amount of 2-(dimethylamino)ethanol relative to the acid groups. Deionized water was then added gradually to obtain a hydroxyl-containing polyester resin (2) solution with a solids concentration of 45% and a pH of 7.2. The resulting hydroxyl-containing polyester resin (2) had a hydroxyl value of 128 mgKOH / g, an acid value of 35 mgKOH / g, and a weight-average molecular weight of 13,000.

[0127] Preparation of Color Pigment Dispersion Paste Preparation Example 3 56 parts of the hydroxyl group-containing polyester resin (2) solution obtained in Preparation Example 2 (25 parts solids), 60 parts of "JR-806" (trade name, rutile titanium dioxide, manufactured by Teika Corporation), 1 part of "Carbon MA-100" (trade name, carbon black, manufactured by Mitsubishi Chemical Corporation), 15 parts of "Variace B-35" (trade name, barium sulfate powder, manufactured by Sakai Chemical Industry Co., Ltd.), and 5 parts of deionized water were mixed, and the pH was adjusted to 8.0 with 2-(dimethylamino)ethanol. Next, the resulting mixture was placed in a wide-mouth glass bottle, and glass beads with a diameter of approximately 1.3 mm were added as a dispersion medium, the bottle was sealed, and the mixture was dispersed for 30 minutes using a paint shaker to obtain a color pigment dispersion paste (P-1).

[0128] Preparation of Colored Coating Composition (X) Preparation Example 4 137 parts of the colored pigment dispersion paste (P-1) obtained in Preparation Example 3, 25 parts (11 parts solids) of the hydroxyl group-containing acrylic resin emulsion (1) obtained in Preparation Example 1, 20 parts (9 parts solids) of the polyester resin solution (2) obtained in Preparation Example 2, 78 parts (30 parts solids) of "Bayhydur VPLS2310" (trade name, manufactured by Sumika Covestro Urethane Co., Ltd., blocked polyisocyanate compound, 38% solids), and 72 parts (25 parts solids) of "U-coat UX-8100" (trade name, manufactured by Sanyo Chemical Industries, Ltd., urethane emulsion, 35% solids) were uniformly mixed. Next, to the resulting mixture, "UH-752" (trade name, manufactured by ADEKA Corporation, thickener), 2-(dimethylamino)ethanol, and deionized water were added, and the mixture was subjected to a Ford Cup No. test at pH 8.0, paint solids content 48%, and 20 ° C. A colored coating composition (X-1) having a viscosity of 30 seconds according to the method of Example 4 was obtained.

[0129] Preparation of First Dispersion Resin (B) Preparation Example 5: A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, nitrogen inlet tube, and dropping device was charged with 75 parts of propylene glycol monomethyl ether and heated to 95°C. A mixture of 2 parts of styrene, 1.5 parts of n-butyl methacrylate, 1.5 parts of hydroxyethyl methacrylate, 12 parts of methacrylic acid, 83 parts of methoxypolyethylene glycol methacrylate (molecular weight approximately 496), 120 parts of propylene glycol monomethyl ether, and 10 parts of 2,2'-azobis(2-methylbutyronitrile) was added dropwise over 4 hours, and the mixture was aged for 30 minutes after completion of the dropwise addition. Thereafter, a mixture of 10 parts of propylene glycol monomethyl ether and 0.5 parts of 2,2'-azobis(2-methylbutyronitrile) was added dropwise over 1 hour, and the mixture was aged for 1 hour after completion of the dropwise addition. Thereafter, the mixture was desolvated under reduced pressure, and the propylene glycol monomethyl ether was removed until the solids content was 90% by mass. The resulting first dispersion resin (B-1) had a weight average molecular weight of 5,000, an acid value of 78 mgKOH / g, and a hydroxyl value of 6.5 mgKOH / g.

[0130] Production Examples 6 to 13 Solutions of first dispersion resins (B-2) to (B-9) with a solid content of 90% by mass were obtained in the same manner as in Production Example 5, except that the blending compositions in Production Example 5 were as shown in Table 1. The weight average molecular weight, acid value, and hydroxyl value of each first dispersion resin are also shown in Table 2.

[0131]

[0132]

[0133] Production of Second Dispersion Resin (C) Production Example 14: Into a reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, and a dropping device, 18.2 parts of ethylene glycol monobutyl ether and 11.8 parts of 2,4-diphenyl-4-methyl-1-pentene were charged, and the mixture was stirred and mixed in a nitrogen stream until the temperature reached 120°C. Then, the following monomer mixture I was added dropwise over 6 hours, and the mixture was aged at 120°C for 30 minutes. <Composition of Monomer Mixture I> Methyl methacrylate 87 parts N,N-dimethylaminoethyl methacrylate 12 parts Tridecyl methacrylate 0.5 parts Lauryl methacrylate 0.5 parts 2,2'-Azobis(2-methylbutyronitrile) 3 parts Ethylene glycol monobutyl ether 6 parts Next, to the above aged product was added dropwise the following additional catalyst mixture over 1 hour, and after aging at 120°C for 1 hour, 18 parts of ethylene glycol monobutyl ether and 22.7 parts of propylene glycol monobutyl ether were added so that the solids concentration was 60%, thereby obtaining a solution of Polymer A, a macromonomer. The weight average molecular weight of the obtained Polymer A was approximately 3000. <Additional catalyst mixture> 2,2'-azobis(2-methylbutyronitrile) 0.5 parts Ethylene glycol monobutyl ether 9 parts Next, 41.7 parts of the macromonomer polymer A were charged into a reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, and a dropping device, and the mixture was stirred and mixed in a nitrogen stream until the temperature reached 95°C. Then, monomer mixture II and monomer mixture III shown below were added dropwise over 3 hours, and the mixture was aged at 95°C for 30 minutes.<Composition of Monomer Mixture II> Methyl methacrylate 45 parts 2-hydroxyethyl methacrylate 10 parts 2,2'-azobis(2-methylbutyronitrile) 0.9 parts Propylene glycol monobutyl ether 5 parts <Composition of Monomer Mixture III> Methoxypolyethylene glycol methacrylate (molecular weight approximately 2080) 20 parts Deionized water 20 parts Ethylene glycol monobutyl ether 5 parts Next, to the above aged product, the following additional catalyst mixture was added dropwise over 1 hour, and after aging at 95°C for 1 hour, 36 parts of propylene glycol monobutyl ether was added to achieve a solids concentration of 53%, to obtain a solution of a second dispersion resin (C-1), which is an AB block polymer. The resulting polymer had a weight average molecular weight of approximately 15,000, an amine value of 9.5 mgKOH / g, and a hydroxyl value of 43 mgKOH / g. <Additional catalyst mixture> 2,2'-azobis(2-methylbutyronitrile) 0.375 parts Propylene glycol monobutyl ether 6 parts Production of carboxylic acid group-containing dispersion resin (3) Production Example 15 A reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux condenser, a nitrogen inlet tube, and a dropping device was charged with 35 parts of propylene glycol monopropyl ether, and the temperature was raised to 85°C. Then, a mixture of 30 parts of methyl methacrylate, 20 parts of 2-ethylhexyl acrylate, 29 parts of n-butyl acrylate, 15 parts of 2-hydroxyethyl acrylate, 6 parts of acrylic acid, 15 parts of propylene glycol monopropyl ether, and 2.3 parts of 2,2'-azobis(2,4-dimethylvaleronitrile) was added dropwise over 4 hours, and the mixture was aged for 1 hour after completion of the dropwise addition. Then, 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, and the mixture was aged for 1 hour after the completion of the dropwise addition. 7.4 parts of diethanolamine was added to obtain a carboxylic acid group-containing dispersion resin (3) solution with a solids content of 55%. The obtained carboxylic acid group-containing dispersion resin (3) had an acid value of 47 mg KOH / g, a hydroxyl value of 72 mg KOH / g, and a weight average molecular weight of 58,000.

[0134] Preparation of Phosphate Group-Containing Dispersion Resin (4) Preparation Example 16 A mixed solvent of 27.5 parts of methoxypropanol and 27.5 parts of isobutanol was placed in a reaction vessel equipped with a thermostat, a stirrer, a reflux condenser, and a dropping device, and heated to 110°C. 121.5 parts of a mixture consisting of 25 parts of styrene, 27.5 parts of n-butyl methacrylate, 20 parts of "Isostearyl acrylate" (trade name, branched higher alkyl acrylate, manufactured by Osaka Organic Chemical Industry Ltd.), 7.5 parts of 4-hydroxybutyl acrylate, 15 parts of the following phosphoric acid group-containing polymerizable monomer, 12.5 parts of 2-methacryloyloxyethyl acid phosphate, 10 parts of isobutanol, and 4 parts of t-butyl peroxyoctanoate was added to the mixed solvent over 4 hours, and a mixture of 0.5 parts of t-butyl peroxyoctanoate and 20 parts of isopropanol was added dropwise over 1 hour. The mixture was then stirred and aged for 1 hour to obtain a phosphate group-containing dispersion resin (4) solution with a solids concentration of 50%. The acid value due to the phosphate group of this resin was 83 mg KOH / g, the hydroxyl value was 29 mg KOH / g, and the weight average molecular weight was 10,000.

[0135] Phosphate group-containing polymerizable monomer: 57.5 parts of monobutyl phosphate and 41 parts of isobutanol were placed in a reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, and dropping device, and the mixture was heated to 90°C. 42.5 parts of glycidyl methacrylate was added dropwise over 2 hours, and the mixture was then stirred and aged for an additional 1 hour. Subsequently, 59 parts of isopropanol was added to obtain a phosphate group-containing polymerizable monomer solution with a solids content of 50%. The acid value due to the phosphate group of the resulting monomer was 285 mgKOH / g.

[0136] Preparation of Nonionic Polymerizable Unsaturated Monomer-Containing Dispersion Resin (5) Having Amino Groups and Polyoxyalkylene Chains Preparation Example 17 20 parts of ethylene glycol monobutyl ether was charged into a four-necked flask equipped with a stirrer, thermometer, condenser, and nitrogen gas inlet, and the temperature was raised to 95°C under nitrogen gas aeration. After reaching 95°C, the nitrogen gas aeration was stopped, and a mixture consisting of 10 parts of styrene, 40 parts of methyl methacrylate, 10 parts of 2-hydroxyethyl acrylate, 10 parts of dimethylaminoethyl methacrylate, 30 parts of methoxypolyethylene glycol methacrylate (molecular weight approximately 1000), 65 parts of ethylene glycol monobutyl ether, and 1 part of 2,2'-azobisisobutyronitrile was added dropwise over 3 hours. The mixture was aged for 2 hours while aerating nitrogen gas at 95°C, then cooled to 60°C and diluted with 15 parts of ethylene glycol monobutyl ether to obtain a 50% solids solution of nonionic polymerizable unsaturated monomer-containing dispersion resin (5) having amino groups and polyoxyalkylene chains. The resulting dispersion resin (5) containing a nonionic polymerizable unsaturated monomer having an amino group and a polyoxyalkylene chain had an amine value of 35.5 mgKOH / g, a hydroxyl value of 48.4 mgKOH / g, and a number average molecular weight of 6,500.

[0137] Preparation of a glittering pigment dispersion Example 1 In a stirring and mixing vessel, 30 parts (solids content: 30 parts) of aluminum pigment A (a silica-treated aluminum pigment having amino groups and alkyl groups on the surface, an average particle size (d50) of 19 μm, an average thickness of 0.40 μm, and a solids concentration of 100%), 80 parts of deionized water, and 2 parts (solids content: 1.8 parts) of the first dispersion resin (B-1) obtained in Production Example 5 were uniformly mixed to obtain a glittering pigment dispersion (P-2).

[0138] Examples 2 to 10 and Comparative Examples 1 to 4 Bright pigment dispersions (P-3) to (P-15) were obtained in the same manner as in Example 1, except that the formulations shown in Table 2 were used.

[0139]

[0140]

[0141] Preparation of Hydroxyl-Containing Acrylic Resin Emulsion (6) Preparation Example 18 A reaction vessel equipped with a thermometer, thermostat, stirrer, reflux condenser, and dropping device was charged with 130 parts of deionized water and 0.52 parts of "Aqualon KH-10." The mixture was stirred and mixed in a nitrogen stream and heated to 80°C. Next, 1% of the total amount of the monomer emulsion (1) described below and 5.3 parts of a 6% aqueous ammonium persulfate solution were introduced into the reaction vessel and the mixture was maintained at 80°C for 15 minutes. Thereafter, the remaining monomer emulsion (1) was added dropwise over 3 hours to the reaction vessel maintained at the same temperature, and after completion of the addition, the mixture was aged for 1 hour. Thereafter, the monomer emulsion (2) described below 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 a 5% aqueous dimethylethanolamine solution to the reaction vessel. The mixture was then discharged while being filtered through a 100-mesh nylon cloth, yielding a hydroxyl-containing acrylic resin emulsion (6) with a solids concentration of 30%. The resulting hydroxyl group-containing acrylic resin emulsion (6) had a hydroxyl value of 25 mgKOH / g and an acid value of 33 mgKOH / g.

[0142] Monomer emulsion (1): 42 parts of deionized water, 0.72 parts of "Aqualon KH-10", 2.1 parts of methylenebisacrylamide, 2.8 parts of styrene, 16.1 parts of methyl methacrylate, 28 parts of ethyl acrylate, and 21 parts of n-butyl acrylate were mixed and stirred to obtain a monomer emulsion (1).

[0143] Monomer emulsion (2): A monomer emulsion (2) was obtained by mixing and stirring 18 parts of deionized water, 0.31 parts of "Aqualon KH-10", 0.03 parts of ammonium persulfate, 5.1 parts of methacrylic acid, 5.1 parts of 2-hydroxyethyl acrylate, 3 parts of styrene, 6 parts of methyl methacrylate, 1.8 parts of ethyl acrylate, and 9 parts of n-butyl acrylate.

[0144] Preparation of Acrylic Resin (7) for Dispersing Color Pigments Preparation Example 19: 48 parts of ethylene glycol monobutyl ether was charged into a conventional acrylic resin reaction vessel equipped with a stirrer, thermometer, and reflux condenser, and the mixture was heated and stirred to maintain the temperature at 110°C. A mixture consisting of 10 parts of styrene, 40 parts of methyl methacrylate, 25 parts of n-butyl methacrylate, 10 parts of 2-hydroxyethyl methacrylate, 3 parts of methacrylic acid, 5 parts of N,N-dimethylaminoethyl methacrylate (solids content, dissolved in 10 parts of deionized water), 10 parts of polyethylene glycol monomethacrylate (molecular weight approximately 350), 4 parts of azobisisobutyronitrile, and 20 parts of isobutyl alcohol was added dropwise thereto 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 consisting of 25 parts of ethylene glycol monobutyl ether and 0.5 parts of azobisisobutyronitrile was added dropwise thereto over 1 hour. The mixture was then aged at 110°C for 1 hour and then cooled to obtain a solution of acrylic resin (7) for dispersing color pigments with a solid content of 50%. The acrylic resin (7) for dispersing color pigments had a hydroxyl value of 43 mgKOH / g and a weight average molecular weight of about 20,000.

[0145] Preparation of Hydroxyl-Containing Polyester Resin (8) Preparation Example 20: 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, and heated. The temperature was raised from 160°C to 230°C over 3 hours, and then the mixture was subjected to a condensation reaction at 230°C for 4 hours. Next, in order to add carboxyl groups to the resulting condensation reaction product, 38.3 parts of trimellitic anhydride was added, and the mixture was reacted at 170°C for 30 minutes. The mixture was then diluted with 2-ethyl-1-hexanol to obtain a hydroxyl-containing polyester resin (8) solution with a solids concentration of 70%. The resulting hydroxyl-containing polyester resin (8) had a hydroxyl value of 150 mgKOH / g, an acid value of 46 mgKOH / g, and a weight-average molecular weight of 6,400.

[0146] Production of Color Pigment Dispersion Paste (P-16) Production Example 21 16 parts (8 parts in terms of solids content) of the acrylic resin (7) for dispersing color pigments obtained in Production Example 19, 5 parts of "RAVEN 5000 ULTRA III BEADS" (trade name, carbon black pigment, manufactured by COLUMBIAN CARBON CO.), and 70 parts of deionized water were mixed and dispersed for 2 hours using a paint shaker to obtain a color pigment dispersion paste (P-16) with a solids content of 14.3%.

[0147] 11. Production of Glittering Paint Composition (Y) Example 11 112 parts of the glittering pigment dispersion (P-2) obtained in Example 1 (solid content 31.8 parts), 91 parts of the colored pigment dispersion paste (P-16) obtained in Production Example 21 (solid content 13 parts), 83.3 parts of the hydroxyl group-containing acrylic resin emulsion (6) obtained in Production Example 18 (solid content 25 parts), 35.7 parts of the hydroxyl group-containing polyester resin (8) solution obtained in Production Example 20 (solid content 25 parts), "Cymel 325" (trade name, manufactured by Allnex Co., Ltd., melamine resin, solid content 80%) 37.5 parts (solid content 30 parts) and 20.4 parts of the phosphate group-containing dispersion resin (4) solution obtained in Production Example 16 (solid content 10.2 parts) were uniformly mixed. Next, to the resulting mixture was added "Primal ASE-60" (trade name, manufactured by Rohm and Haas, thickener, solids content 28%), 2-(dimethylamino)ethanol and deionized water to obtain a glittering coating composition (Y-1) having a pH of 7.8, a coating solids content of 14%, and a viscosity of 2000 mPa·s when measured at 20°C and 6 rpm using a Brookfield viscometer. The water content in glittering coating composition (Y-1) was 89 mass% based on the amount of solvent in glittering coating composition (Y).

[0148] Examples 12 to 21, Comparative Examples 5 to 8 Each of the glitter coating compositions (Y-2) to (Y-15) was obtained in the same manner as in Example 11, except that the blending compositions were as shown in Table 3 below.

[0149]

[0150]

[0151] 3. Preparation of Test Plate Example 22 On the substrate prepared in "1. Preparation of Substrate" above, the colored coating composition (X-1) obtained in Production Example 4 was electrostatically coated using a rotary atomization bell-type coating machine to a cured film thickness of 12 μm, and left for 2 minutes to form a colored coating film. Furthermore, on this colored coating film, the glitter coating composition (Y-1) obtained in Example 11 was applied using a robot bell manufactured by ABB Corporation under conditions of a booth temperature of 23°C and humidity of 68% to a dried coating film thickness of 4 μm. After leaving for 3 minutes, the coating was preheated at 80°C for 3 minutes to form a glitter coating film. Next, on this glossy coating film, clear coating composition (Z-1) "Magicron KINO-1210TW" (trade name, manufactured by Kansai Paint Co., Ltd., an acrylic resin-based organic solvent-based clear coating composition containing a carboxyl group-containing resin and an epoxy group-containing resin) was applied using a robot bell manufactured by ABB Corporation at a booth temperature of 23 ° C. and a humidity of 68% to form a dry coating film of 35 μm to form a clear coat coating film. After coating, the plate was left at room temperature for 7 minutes and then heated at 140 ° C. for 30 minutes in a hot air circulation drying oven to simultaneously dry the multi-layer coating film and prepare a test panel.

[0152] Examples 23 to 32 and Comparative Examples 9 to 12 Test panels were obtained in the same manner as in Example 22, except that the paints shown in Table 4 were used.

[0153]

[0154]

[0155]

[0156] Coating Film Evaluation Each test panel obtained as described above was evaluated for the following items, and the results are shown in Table 4.

[0157] Brilliance grade Sg (15°) value: A CCD chip was placed in the direction perpendicular to the planar direction of the measurement surface of each test plate to capture an image of the measurement surface. Light was irradiated onto the measurement surface from an angle of 15° to the perpendicular direction, and the CCD chip captured an image of the measurement surface. The resulting images were analyzed with an image analysis algorithm using a brightness level histogram to evaluate the brilliance grade Sg (15°) value. A multi-angle colorimeter (BYK, product name: BYK-mac i) was used for the measurement. The smaller the value, the less graininess there was. A score of 10 or less was considered acceptable.

[0158] FF value: Using a multi-angle colorimeter BYK-mac i (product name, manufactured by BYK-Gardner), L ＊ Value (L ＊ 15 values) and L of 110 degrees of light reception angle ＊ Value (L ＊ The FF value is calculated using the following formula. The larger the value, the greater the change in brightness depending on the observation angle, and the more excellent the sense of brilliance. A value of 50 or more is considered acceptable. FF value = L at a light receiving angle of 15 degrees ＊ Value (L ＊ 15 values) - L with a light receiving angle of 110 degrees ＊ Value (L ＊ 110 value). The test plates of Examples 22-32 passed both the brilliance grade Sg value and FF value, and the multi-layer coating films had excellent brilliance. In contrast, the test plates of Comparative Examples 9 and 10 failed the brilliance grade Sg value, and Comparative Examples 11 and 12 failed the FF value.

Claims

1. A brilliant pigment dispersion comprising a silica-treated aluminum pigment (A) having an amino group on its surface, a first dispersing resin (B), and water, The solid content of the silica-treated aluminum pigment (A) having an amino group on its surface is 90 mass% or more, and The first dispersion resin (B) is a polymer of a composition containing a polymerizable unsaturated monomer (b1) having an acidic functional group, a nonionic polymerizable unsaturated monomer (b2) having a polyoxyalkylene chain, and another polymerizable unsaturated monomer (b3), A brilliant pigment dispersion, the content of water being 90 mass % or more based on the amount of the solvent in the brilliant pigment dispersion.

2. 2. The brilliant pigment dispersion according to claim 1, wherein the silica-treated aluminum pigment (A) having an amino group on its surface comprises a silica-treated aluminum pigment (A1) having an amino group and an alkyl group on its surface.

3. 3. The brilliant pigment dispersion according to claim 1, wherein the polymerizable unsaturated monomer (b1) containing an acidic functional group includes a polymerizable unsaturated monomer containing a carboxyl group.

4. 3. The brilliant pigment dispersion according to claim 1 or 2, further comprising a second dispersing resin (C) which is a polymer of a composition containing a polymerizable unsaturated monomer (c1) containing at least one functional group selected from the group consisting of a tertiary amino group and a quaternary ammonium salt group, a nonionic polymerizable unsaturated monomer (c2) having a polyoxyalkylene chain, and another polymerizable unsaturated monomer (c3).

5. A glittering paint composition comprising the glittering pigment dispersion according to claim 1 or 2 and a film-forming resin.

6. The following steps (1) to (4): Step (1): A step of applying a colored coating composition (X) onto an object to be coated to form a colored coating film; Step (2): A step of applying the glittering coating composition (Y) according to claim 5 onto the colored coating film obtained in step (1) to form a glittering coating film; Step (3): A step of applying a clear coating composition (Z) onto the glossy coating film obtained in step (2) to form a clear coating film; Step (4): A method for forming a multilayer coating film, comprising a step of simultaneously curing the multilayer coating film including the color coating film, the glossy coating film and the clear coating film formed in steps (1), (2) and (3), respectively, by heating the multilayer coating film.