WO2024043248A1

WO2024043248A1 - Method for forming multilayered coating film

Info

Publication number: WO2024043248A1
Application number: PCT/JP2023/030220
Authority: WO
Inventors: 信彦成田; 健次酒井; 隆小澤
Original assignee: 関西ペイント株式会社
Priority date: 2022-08-24
Filing date: 2023-08-23
Publication date: 2024-02-29

Abstract

A method for forming a multilayered coating film which comprises the following steps (1) to (3): step (1) in which a glitter coating composition (Y) containing indium particles (y1) is applied to an object to be coated, thereby forming a glitter coating film; step (2) in which a clear coating composition (Z) comprising a hydroxylated acrylic resin (z1) and a polyisocyanate compound (z2) is applied to the glitter coating film obtained in the step (1), thereby forming a clear coating film; and step (3) in which the glitter coating film formed in the step (1) and the clear coating film formed in the step (2) are heated separately or simultaneously to cure the coating films. The hydroxylated acrylic resin (z1) has a hydroxyl value in the range of 10-75 mgKOH/g.

Description

Multi-layer coating formation method

The present invention relates to a method for forming a multilayer coating film.

The purpose of applying paint is mainly to protect the material and add beauty. For industrial products, aesthetic appearance, especially ``texture,'' is important in order to enhance their product appeal. Consumers want a variety of textures in industrial products, but in recent years, there has been a demand for metal-like luster in fields such as automobile exterior panels, automobile parts, and home appliances (hereinafter referred to as "metallic luster"). ”).

Metallic luster is a mirror-like surface with no graininess, and when viewed perpendicularly to the painted plate (highlight), it shines, and when viewed from diagonally above the painted plate (shade). ) is a texture characterized by a dark appearance, that is, a large difference in brightness between the highlight area and the shade area.

Techniques for imparting such metallic luster to the surface of industrial products include metal plating treatment and metal vapor deposition treatment (for example, see Patent Document 1), but if metallic luster can be imparted by painting, it will be easier and cheaper. This is advantageous from the point of view.

Patent Document 2 discloses that a metallic paint base containing a glittering material, a non-volatile solid content including a resin, and a solvent is diluted at a dilution rate of 150 to 500% using a diluent consisting of a high boiling point solvent and a low boiling point solvent. According to a metallic paint characterized by diluting and adding 5 to 10 parts by weight of a viscous resin to 100 parts by weight of the resin in the metallic paint base, a good metallic appearance can be achieved. is listed.

However, the appearance formed by the above metallic paint had insufficient metallic luster.

In addition, coatings are required to not only give an aesthetic appearance but also protect the material, which requires excellent coating performance such as high adhesion.

Japanese Patent Publication No. 63-272544 Japanese Patent Application Publication No. 2003-313500

An object of the present invention is to provide a method for forming a multilayer coating film that can form a multilayer coating film that has excellent metallic luster and can exhibit high coating performance.

The present invention includes the subject matter described in the following sections.

Item 1. The following steps (1) to (3):
Step (1): a step of coating a glittering paint composition (Y) containing indium particles (y1) on the object to be coated to form a glittering coating film;
Step (2): A clear coating composition (Z) containing a hydroxyl group-containing acrylic resin (z1) and a polyisocyanate compound (z2) is applied onto the glitter coating film obtained in step (1) to form a clear coating. Step (3) of forming a film: Curing the glitter coating formed in step (1) and the clear coating formed in step (2) by heating them separately or simultaneously. A method for forming a multilayer coating film, comprising the steps of:
A method for forming a multilayer coating film, wherein the hydroxyl value of the hydroxyl group-containing acrylic resin (z1) is within the range of 10 to 75 mgKOH/g.

Section 2. Item 2. The method for forming a multilayer coating according to Item 1, wherein the glitter coating composition (Y) further contains a hydroxyl group-containing resin (y2).

Section 3. Item 3. The method for forming a multilayer coating according to Item 1 or 2, wherein the glitter coating composition (Y) further contains a melamine resin (y3).

Section 4. In the clear coating composition (Z), the equivalent ratio (NCO/OH) of the total mol of isocyanate groups of the polyisocyanate compound (z2) to the total mol of hydroxyl groups of the hydroxyl group-containing acrylic resin (z1) is 0.7 to The method for forming a multilayer coating film according to any one of Items 1 to 3, which is within the range of 1.5.

According to the method for forming a multilayer coating film of the present invention, it is possible to form a multilayer coating film that has excellent metallic luster and exhibits excellent coating performance such as adhesion.

The multilayer coating film forming method of the present invention includes the following steps (1) to (3):
Step (1): a step of coating a glittering paint composition (Y) containing indium particles (y1) on the object to be coated to form a glittering coating film;
Step (2): A clear coating composition (Z) containing a hydroxyl group-containing acrylic resin (z1) and a polyisocyanate compound (z2) is applied onto the glitter coating film obtained in step (1) to form a clear coating. Step (3) of forming a film: Curing the glitter coating formed in step (1) and the clear coating formed in step (2) by heating them separately or simultaneously. A method for forming a multilayer coating film, comprising the steps of:
In this method, the hydroxyl value of the hydroxyl group-containing acrylic resin (z1) is within the range of 10 to 75 mgKOH/g.

Process (1)
According to the method for forming a multilayer coating film of the present invention, first, a glitter coating composition (Y) containing indium particles (y1) is applied onto an object to be coated to form a glitter coating film.

Object to be coated The object to be coated with the glitter coating composition (Y) is not particularly limited. Examples of the object to be coated include the outer panels of automobile bodies such as passenger cars, trucks, motorcycles, and buses; automobile parts such as bumpers; and the outer panels of household electrical appliances such as mobile phones and audio equipment. can. Among these, outer panels of automobile bodies and automobile parts are preferred.

The materials of these objects to be coated are not particularly limited. For example, metal materials such as iron, aluminum, brass, copper, tinplate, stainless steel, galvanized steel, zinc alloy (Zn-Al, Zn-Ni, Zn-Fe, etc.) plated steel; polyethylene resin, polypropylene resin, acrylonitrile- Resins such as butadiene-styrene (ABS) resin, polyamide resin, acrylic resin, vinylidene chloride resin, polycarbonate resin, polyurethane resin, and epoxy resin; plastic materials such as various FRP; inorganic materials such as glass, cement, and concrete; wood ; Examples include fibrous materials such as paper and cloth. Among these, metal materials and plastic materials are preferred.

Surfaces to which multi-layer coatings are applied include phosphate treatment, chromate treatment, The material may be subjected to surface treatment such as surface treatment or complex oxide treatment.

A coating film may be further formed on the object, which may or may not be surface-treated. For example, the base material to be coated may be optionally subjected to surface treatment, and an undercoat film and/or intermediate coat film may be formed thereon. The undercoat film and/or intermediate coat film is, for example, when the object to be coated is an automobile body, a coating composition for undercoat and/or intermediate coat known per se that is commonly used in the painting of automobile bodies. It can be formed using objects.

As the undercoat paint composition for forming the above-mentioned undercoat film, for example, an electrodeposition paint, preferably a cationic electrodeposition paint can be used. The intermediate coating composition for forming the intermediate coating film includes a base resin such as an acrylic resin, a polyester resin, an alkyd resin, a urethane resin, and an epoxy resin having a crosslinkable functional group such as a carboxyl group or a hydroxyl group; A coating made of an amino resin such as a melamine resin or a urea resin, or a crosslinking agent such as an optionally blocked polyisocyanate compound together with a pigment, a thickener, and other optional components can be used. .

Glitter paint composition (Y)
The glitter paint composition (Y) is a glitter paint composition containing indium particles (y1).

The glitter coating composition (Y) preferably contains indium particles (y1), and further contains a surface conditioner, and water and/or an organic solvent.

Indium particles (y1)
The indium particles (y1) are flaky particles. The flaky particles may also be referred to as scale particles, tabular particles, flake particles, or the like.

In the present invention, a flaky particle means a particle having a substantially flat surface and having a substantially uniform thickness in the direction perpendicular to the substantially flat surface. The term "flake-like particles" refers to particles having a very thin thickness and a substantially flat surface having a very long length. Note that the length of the substantially flat surface is the diameter of a circle having the same projected area as the flaky particle.

The shape of the substantially flat surface is not particularly limited and can be selected as appropriate depending on the purpose, for example, substantially rectangular, substantially square, substantially circular, substantially oval, substantially triangular, substantially quadrilateral, substantially pentagonal, and substantially Examples include polygons such as hexagons, approximately heptagons, and approximately octagons, and random irregular shapes. Among these, a substantially circular shape is preferable.

The indium particles (y1) may have a single layer, or two or more layers may be laminated to form a primary particle. Moreover, the primary particles of the indium particles (y1) may aggregate to form secondary particles.

Note that the indium particles (y1) are made of indium with a purity of 95% or more, and may contain trace amounts of impurities, but do not contain alloys with other metals.

The above indium particles (y1) can be manufactured by performing a peeling layer forming step, a vacuum evaporation step, a peeling step, and further other steps as necessary.

<Peeling layer formation process>
The release layer forming step is a step of providing a release layer on the base material.

The above-mentioned base material is not particularly limited as long as it has a smooth surface, and various materials can be used. Among these, resin films, metal foils, and composite films of metal foils and resin films having flexibility, heat resistance, solvent resistance, and dimensional stability can be used as appropriate. Examples of the resin film include polyester film, polyethylene film, polypropylene film, polystyrene film, and polyimide film. Examples of the metal foil include copper foil, aluminum foil, nickel foil, iron foil, and alloy foil. Examples of composite films of metal foil and resin film include those obtained by laminating the above resin film and metal foil.

As the peeling layer, various organic substances that can be dissolved in the subsequent peeling process can be used. It is preferable to appropriately select the organic material constituting the release layer, since the organic material attached and remaining on the adhesion surface of the island-like structure film can function as a protective layer for the indium particles (y1).

The protective layer has a function of suppressing agglomeration, oxidation, elution into a solvent, etc. of the indium particles (y1). In particular, it is preferable to use the organic substance used in the release layer as a protective layer, since it eliminates the need for a separate surface treatment step.

Examples of organic substances constituting the release layer that can be used as a protective layer include cellulose acetate butyrate (CAB), other cellulose derivatives, polyvinyl alcohol, polyvinyl butyral, polyethylene glycol, polyacrylic acid, polyacrylamide, and acrylic acid copolymers. Examples include polymerized nylon resins, modified nylon resins, polyvinylpyrrolidone, urethane resins, polyester resins, polyether resins, and alkyd resins. These may be used alone or in combination of two or more. Among these, cellulose acetate butyrate (CAB) is preferred because of its high functionality as a protective layer.

The method for forming the release layer is not particularly limited and can be appropriately selected depending on the purpose, for example, an inkjet method, a blade coating method, a gravure coating method, a gravure offset coating method, a bar coating method, a roll coating method. , knife coating method, air knife coating method, comma coating method, U comma coating method, AKKU coating method, smoothing coating method, micro gravure coating method, reverse roll coating method, 4 roll coating method, 5 roll coating method, dip coating method, curtain coating method, slide coating method, die coating method, etc. These may be used alone or in combination of two or more.

<Vacuum deposition process>
The vacuum deposition step is a step of vacuum depositing a metal layer containing indium particles (y1) on the release layer.

The average deposition thickness of the metal layer containing indium particles (y1) is preferably 60 nm or less, more preferably 55 nm or less, even more preferably 50 nm or less, and particularly preferably 45 nm or less. Note that the average deposition thickness of the metal layer containing the indium particles (y1) is the same as the average thickness of the indium particles (y1).

When the average deposition thickness of the metal layer is 60 nm or less, there is an advantage that the surface roughness Ra of the coating film is reduced and excellent metallic gloss can be expressed. The average deposition thickness is the average value obtained by observing a cross section of the metal layer using, for example, a scanning electron microscope (SEM) and measuring the thickness of the metal layer at 5 to 10 locations.

It is preferable that the metal layer is an island-like structured film. The island structure film can be formed by various methods such as vacuum evaporation, sputtering, and plating. Among these, the vacuum evaporation method is preferred.

The vacuum evaporation method is preferable to the plating method in that it can form a film even on resin substrates and does not produce waste liquid, and is preferable to the plating method in that it can achieve a higher degree of vacuum and has a faster film formation rate (evaporation rate). preferable to law.

The vapor deposition rate in the vacuum evaporation method is preferably 10 nm/sec or more, more preferably 10 nm/sec or more and 80 nm/sec or less.

<Peeling process>
The peeling process is a process of peeling the metal layer from the base material by dissolving the peeling layer. The solvent that can dissolve the release layer is not particularly limited as long as it is a solvent that can dissolve the release layer, and can be appropriately selected depending on the purpose, but it may be used as it is as a solvent for the glitter coating composition (Y). Those that can be used are preferred.

Examples of solvents that can dissolve the release layer include alcohol solvents such as methanol, ethanol, propanol, isopropanol, butanol, octanol, dodecanol, ethylene glycol, and propylene glycol; ether solvents such as tetrahydrone; acetone, methyl ethyl ketone, Ketone solvents such as acetylacetone; ester solvents such as methyl acetate, ethyl acetate, butyl acetate, phenyl acetate; ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol Monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol monomethyl ether, triethylene Glycol ether solvents such as glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate; phenol, cresol, etc. Phenolic solvents; aliphatic or aromatic such as pentane, hexane, heptane, octane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, octadecane, octadecene, benzene, toluene, xylene, trimesine, nitrobenzene, aniline, methoxybenzene, trimesine, etc. Hydrocarbon solvents; aliphatic or aromatic chlorinated hydrocarbon solvents such as dichloromethane, chloroform, trichloroethane, chlorobenzene, dichlorobenzene; sulfur-containing compound solvents such as dimethyl sulfoxide; dimethylformamide, dimethylacetamide, acetonitrile, propionitrile, Examples include nitrogen-containing compound solvents such as benzonitrile. These may be used alone or in combination of two or more.

By dissolving the release layer, the island-like structure film is separated from the base material, the island-like structure is split, and the individual islands become indium particles (y1). As a result, an indium particle (y1) dispersion can be obtained without any particular pulverization step, but the primary particles of indium particles (y1) may be pulverized and classified as necessary. Moreover, when the primary particles of the indium particles (y1) are aggregated, they may be crushed as necessary.

Further, as necessary, various treatments may be performed to recover the indium particles (y1) and adjust the physical properties. For example, the particle size of the indium particles (y1) may be adjusted by classification, the indium particles (y1) may be recovered by methods such as centrifugation or suction filtration, or the solid content concentration of the dispersion may be adjusted. good. Further, solvent substitution may be performed, and viscosity adjustment may be performed using additives.

<Other processes>
Other steps include, for example, a step of taking out the peeled metal layer as a dispersion liquid, a step of recovering the island-shaped metal layer from the dispersion liquid as indium particles (y1), and the like.

The cumulative 50% volume particle diameter D50 of the indium particles (y1) obtained by performing the above-mentioned release layer forming step, vacuum evaporation step, peeling step, and other steps as necessary has an excellent metallic luster. From the viewpoint of forming a multilayer coating film having It is particularly preferable.

As the indium particles (y1), commercially available products can be used. Examples of such commercial products include "Leaf Powder 49CJ-1120", "Leaf Powder 49CJ-1150", "Leaf Powder 49BJ-1120", and "Leaf Powder 49BJ-1150" (all manufactured by Oike Kogyo Co., Ltd.). Can be mentioned.

The content of indium particles (y1) in the glitter coating composition (Y) of the present invention is determined by adjusting the solid content of 100 parts by mass of the glitter coating composition (Y) from the viewpoint of obtaining a coating film with excellent metallic gloss. As a standard, it is preferably 50 parts by mass or more, more preferably 70 parts by mass or more, even more preferably in the range of 80 to 99.9 parts by mass, and even more preferably in the range of 90 to 99.9 parts by mass. Particularly preferably within

Examples of the surface conditioning agents include surface conditioning agents such as silicone surface conditioning agents, acrylic surface conditioning agents, vinyl surface conditioning agents, fluorine surface conditioning agents, and acetylene diol surface conditioning agents. From the viewpoint of obtaining a coating film with excellent gloss control, it is preferable to include a fluorine-based surface conditioner. The above-mentioned surface conditioners can be used alone or in an appropriate combination of two or more.

Examples of the fluorine-based surface conditioner include fluorine-based polymers and fluorine-based oligomers having perfluoroalkyl groups and polyalkylene oxide groups, fluorine-based polymers and fluorine-based oligomers having perfluoroalkyl ether groups and polyalkylene oxide groups Oligomers can be mentioned.

Commercially available products of the above-mentioned fluorine-based surface conditioners include "LE-604", "LE-605" (all manufactured by Kyoeisha Chemical Co., Ltd.), "F-444", and "F-554" (all manufactured by DIC Co., Ltd.), etc.

When the glitter coating composition (Y) of the present invention contains a surface conditioner, the content is determined by the solid content of the glitter coating composition (Y) from the viewpoint of obtaining a coating film with excellent metallic gloss. Based on 100 parts by mass, it is preferably 0.01 to 2.0 parts by mass, more preferably 0.05 to 1.5 parts by mass, and 0.1 to 1.0 parts by mass. is even more preferable.

As the organic solvent, those commonly used in paints can be used. Specifically, for example, alcohol solvents such as methanol, ethanol, propanol, isopropanol, butanol, octanol, dodecanol, ethylene glycol, and propylene glycol; ether solvents such as tetrahydrone; ketone solvents such as acetone, methyl ethyl ketone, and acetylacetone. Ester solvents such as methyl acetate, ethyl acetate, butyl acetate, phenyl acetate; Ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol Monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, Glycol ether solvents such as ethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate; Phenol solvents such as phenol and cresol; Pentane , hexane, heptane, octane, dodecane, tridecane, tetradecane, pentadecane, hexadecane, octadecane, octadecene, benzene, toluene, xylene, trimesine, nitrobenzene, aniline, methoxybenzene, aliphatic or aromatic hydrocarbon solvents such as trimesine; dichloromethane , aliphatic or aromatic chlorinated hydrocarbon solvents such as chloroform, trichloroethane, chlorobenzene, and dichlorobenzene; sulfur-containing compound solvents such as dimethyl sulfoxide; nitrogen-containing solvents such as dimethylformamide, dimethylacetamide, acetonitrile, propionitrile, and benzonitrile. Examples include compound solvents. These may be used alone or in combination of two or more.

The organic solvent preferably contains at least one solvent selected from glycol ether-based organic solvents and alcohol-based organic solvents, from the viewpoint of obtaining a coating film with excellent metallic gloss. It is even more preferable.

When the glitter coating composition (Y) of the present invention contains an organic solvent, the content should be determined based on the sum of all components of the glitter coating composition (Y) from the viewpoint of obtaining a coating film with excellent metallic gloss. It is preferably within the range of 85 to 99.9 parts by mass, more preferably within the range of 90 to 99.5 parts by mass, and preferably within the range of 95 to 99 parts by mass relative to 100 parts by mass. It is even more preferable.

Other Components The glitter coating composition (Y) may optionally include pigments other than indium particles (y1), viscosity modifiers, binder resins, crosslinking components, pigment dispersants, antisettling agents, and ultraviolet absorbers. A light stabilizer and the like may be added as appropriate.

Examples of pigments other than the indium particles (y1) include colored pigments, glitter pigments other than the indium particles (y1), extender pigments, and the like. These pigments can be used alone or in combination of two or more. Examples of the color pigments include titanium oxide, zinc oxide, carbon black, molybdenum red, Prussian blue, cobalt blue, azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, threne pigments, and perylene pigments. , dioxazine pigments, diketopyrrolopyrrole pigments, and the like. Examples of the glitter pigment other than the indium particles (y1) include vapor-deposited metal flake pigments other than the indium particles (y1), aluminum flake pigments, optical interference pigments, and the like. Examples of the extender pigment include clay, kaolin, barium sulfate, barium carbonate, calcium carbonate, talc, silica, and alumina white.

When the glitter coating composition (Y) of the present invention contains a pigment other than the indium particles (y1), the content is determined from the viewpoint of obtaining a coating film with excellent metallic gloss. Based on 100 parts by mass of solid content of Y), it is preferably within the range of 0.01 to 30 parts by mass, more preferably within the range of 0.05 to 20 parts by mass, and 0.1 to 15 parts by mass. It is more preferably within the range of parts by mass.

Examples of the viscosity modifier include silica-based fine powder, mineral-based viscosity modifier, barium sulfate atomized powder, polyamide-based viscosity modifier, organic resin fine particle viscosity modifier, diurea-based viscosity modifier, and urethane-based viscosity modifier. acrylic swelling type polyacrylic acid-based viscosity modifiers, cellulose-based viscosity modifiers, and the like.

Examples of the binder resin include hydroxyl group-containing resin (y2).

The above hydroxyl group-containing resin (y2) is a resin having at least one hydroxyl group in one molecule. As the hydroxyl group-containing resin (y2), a wide variety of known resins can be used, such as acrylic resins having hydroxyl groups, polyester resins having hydroxyl groups, acrylic modified polyester resins having hydroxyl groups, polyether resins having hydroxyl groups, and polycarbonates having hydroxyl groups. Examples include resins such as polyurethane resins having hydroxyl groups, epoxy resins having hydroxyl groups, and alkyd resins having hydroxyl groups. These can be used alone or in combination of two or more. Among these, the hydroxyl group-containing resin (y2) preferably contains a hydroxyl group-containing acrylic resin (y2-1) from the viewpoint of adhesion of the formed coating film.

The hydroxyl group-containing acrylic resin (y2-1) can be produced, for example, by copolymerizing a hydroxyl group-containing polymerizable unsaturated monomer and other polymerizable unsaturated monomers (polymerizable unsaturated monomers other than the hydroxyl group-containing polymerizable unsaturated monomer). Obtainable.

The above-mentioned hydroxyl group-containing polymerizable unsaturated monomer is a compound having one or more hydroxyl groups and one or more polymerizable unsaturated bonds in one molecule. Examples of the hydroxyl group-containing polymerizable unsaturated monomer include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate. Monoesterified product of (meth)acrylic acid and dihydric alcohol having 2 to 8 carbon atoms; ε-caprolactone modified product of monoesterified product of (meth)acrylic acid and dihydric alcohol containing 2 to 8 carbon atoms; ( Adducts of meth)acrylic acid and epoxy group-containing compounds (for example, "Cardura E10P" (trade name), manufactured by Momentive Specialty Chemicals, neodecanoic acid glycidyl ester); N-hydroxymethyl (meth)acrylamide; allyl alcohol; , (meth)acrylate having a polyoxyethylene chain whose molecular terminal is a hydroxyl group, and the like.

As other polymerizable unsaturated monomers that can be copolymerized with the above hydroxyl group-containing polymerizable unsaturated monomer, for example, the monomers shown in (1) to (6) below can be used. These polymerizable unsaturated monomers can be used alone or in combination of two or more.

(1) Acid group-containing polymerizable unsaturated monomer An acid group-containing polymerizable unsaturated monomer is a compound having one or more acid groups and one or more polymerizable unsaturated bonds in one molecule. Examples of the monomer include carboxyl group-containing monomers such as (meth)acrylic acid, crotonic acid, itaconic acid, maleic acid and maleic anhydride; sulfonic acid group-containing monomers such as vinylsulfonic acid and 2-sulfoethyl (meth)acrylate. Acidic acids such as 2-(meth)acryloyloxyethyl acid phosphate, 2-(meth)acryloyloxypropyl acid phosphate, 2-(meth)acryloyloxy-3-chloropropyl acid phosphate, 2-methacryloyloxyethyl phenyl phosphate, etc. Examples include phosphoric acid ester monomers. These can be used alone or in combination of two or more.

(2) Esterified products of acrylic acid or methacrylic acid and monohydric alcohol having 1 to 20 carbon atoms. Specifically, methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, ) acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, isooctyl (meth)acrylate, isomyristyl (meth)acrylate, stearyl (meth)acrylate, isostearyl acrylate, lauryl ( Examples include meth)acrylate, tridecyl(meth)acrylate, tetrahydrofurfuryl(meth)acrylate, cyclohexyl(meth)acrylate, isobornyl(meth)acrylate, and the like.

(3) Aromatic vinyl monomer Specific examples include styrene, α-methylstyrene, vinyltoluene, and the like.

By using an aromatic vinyl monomer as a constituent component, the glass transition temperature of the resulting resin increases, and a hydrophobic coating film with a high refractive index can be obtained, which improves the finished appearance by improving the gloss of the coating film. It is possible to obtain the improvement effect of

When an aromatic vinyl monomer is used as a constituent component, its blending ratio is preferably 3 to 50% by mass, particularly preferably 5 to 40% by mass, based on the total amount of monomer components.

(4) Glycidyl group-containing polymerizable unsaturated monomer A glycidyl group-containing polymerizable unsaturated monomer is a compound having one or more glycidyl groups and one or more polymerizable unsaturated bonds in one molecule. Acrylate, glycidyl methacrylate, etc. can be mentioned.

(5) Polymerizable unsaturated bond-containing nitrogen atom-containing compound For example, (meth)acrylamide, N,N-dimethyl(meth)acrylamide, N-[3-(dimethylamino)propyl](meth)acrylamide, N-butoxymethyl Examples include (meth)acrylamide, diacetone (meth)acrylamide, N,N-dimethylaminoethyl (meth)acrylate, vinylpyridine, vinylimidazole, acrylonitrile, and methacrylonitrile.

(6) Other vinyl compounds Examples include vinyl acetate, vinyl propionate, vinyl chloride, vinyl versatate, and the like. Examples of versatile vinyl esters include commercially available products such as "Beova 9" and "Beova 10" (trade names, manufactured by HEXION).

As other polymerizable unsaturated monomers, one or more of the monomers shown in (1) to (6) above can be used.

In the present invention, the polymerizable unsaturated monomer refers to a monomer having one or more (for example, 1 to 4) polymerizable unsaturated groups. A polymerizable unsaturated group means an unsaturated group that can undergo radical polymerization. Examples of such polymerizable unsaturated groups include vinyl group, (meth)acryloyl group, (meth)acrylamide group, vinyl ether group, allyl group, propenyl group, isopropenyl group, and maleimide group.

As used herein, "(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.

The hydroxyl value of the hydroxyl group-containing acrylic resin (y2-1) is preferably from 30 to 200 mgKOH/g, more preferably from 40 to 180 mgKOH/g, from the viewpoint of curability and water resistance, and more preferably from 50 to 180 mgKOH/g. Particularly preferred is a range of 150 mgKOH/g.

The acid value of the hydroxyl group-containing acrylic resin (y2-1) is preferably 0.5 to 15 mgKOH/g, more preferably 1 to 12 mgKOH/g, from the viewpoint of curability and water resistance, etc. Particularly preferred is a range of 2 to 10 mgKOH/g.

The weight average molecular weight of the hydroxyl group-containing acrylic resin (y2-1) is preferably within the range of 2,000 to 50,000, and 3,000 to 45, from the viewpoint of finished appearance and curability of the coating film. ,000, and even more preferably 5,000 to 40,000.

Note that in this specification, the average molecular weight is a value calculated from a chromatogram measured by gel permeation chromatography based on the molecular weight of standard polystyrene. As a gel permeation chromatograph, "HLC8120GPC" (manufactured by Tosoh Corporation) was used. Four columns were used: "TSKgel G-4000HXL", "TSKgel G-3000HXL", "TSKgel G-2500HXL", and "TSKgel G-2000HXL" (all manufactured by Tosoh Corporation, product names), and the mobile phase The measurement was carried out under the following conditions: tetrahydrofuran, measurement temperature: 40°C, flow rate: 1 cc/min, detector: RI.

The glass transition temperature of the hydroxyl group-containing acrylic resin (y2-1) is preferably -50 to 60°C, more preferably -20 to 50°C, from the viewpoint of the hardness of the coating film and the finished appearance, etc. Particularly preferred is a temperature range of 0 to 45°C.

In this specification, the glass transition temperature (°C) of the acrylic resin was calculated using the following formula.

1/Tg(K)=(W1/T1)+(W2/T2)+・・・(1)
Tg (℃) = Tg (K) - 273 (2)
In each formula, W1, W2, . . . represent the respective mass fractions of the monomers used in the copolymerization, and T1, T2, . . . represent the Tg (K) of the homopolymer of the respective monomers.
Note that T1, T2, . . . are values according to Polymer Hand Book (Second Edition, edited by J. Brandup and E.H. Immergut) III-139 to 179. In addition, when the Tg of the monomer homopolymer is not clear, the glass transition temperature (°C) is determined as the static glass transition temperature, and for example, using a differential scanning calorimeter "DSC-220U" (manufactured by Seiko Instruments Inc.), After placing the sample in a measuring cup and completely removing the solvent by vacuum suction, the change in calorific value was measured in the range of -20°C to +200°C at a heating rate of 3°C/min. The point of change was defined as the static glass transition temperature.

The copolymerization method for copolymerizing the above monomer mixture to obtain the hydroxyl group-containing acrylic resin (y2-1) is not particularly limited, and any known copolymerization method can be used. A solution polymerization method in which polymerization is carried out in an organic solvent in the presence of a polymerization initiator can be suitably used.

Examples of organic solvents used in the solution polymerization method include aromatic solvents such as toluene, xylene, and Swasol 1000 (manufactured by Cosmo Oil Co., Ltd., trade name, high-boiling petroleum solvent); ethyl acetate, butyl acetate, Ester solvents such as propylpropionate, butylpropionate, 1-methoxy-2-propyl acetate, 2-ethoxyethylpropionate, 3-methoxybutyl acetate, ethylene glycol ethyl ether acetate, propylene glycol methyl ether acetate; Examples include ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and methyl amyl ketone, and alcohol solvents such as isopropanol, n-butanol, isobutanol, and 2-ethylhexanol.

These organic solvents can be used alone or in combination of two or more, but from the viewpoint of solubility of the acrylic resin, it is preferable to use ester-based solvents and ketone-based solvents. Furthermore, aromatic solvents may be suitably combined with these organic solvents.

Examples of polymerization initiators that can be used in the copolymerization of the hydroxyl group-containing acrylic resin (y2-1) include 2,2'-azobisisobutyronitrile, benzoyl peroxide, di-t-butyl peroxide, di-t- - Known radical polymerization initiators such as amyl peroxide, t-butyl peroctoate, 2,2'-azobis(2-methylbutyronitrile), 2,2'-azobis(2,4-dimethylvaleronitrile), etc. can be mentioned.

When the glitter coating composition (Y) of the present invention contains a hydroxyl group-containing acrylic resin (y2-1) as the hydroxyl group-containing resin (y2), the content is such that it has excellent metallic gloss and From the viewpoint of forming a multilayer coating film exhibiting excellent coating film performance such as adhesion, it is preferably within the range of 50 to 100% by mass, based on the solid content of the hydroxyl group-containing resin (y2), and 55 It is more preferably within the range of ~100% by mass, and even more preferably within the range of 60~100% by mass.

When the glitter coating composition (Y) of the present invention contains the hydroxyl group-containing resin (y2), the content is such that it has excellent metallic gloss and excellent coating film performance such as adhesion. From the viewpoint of forming a multilayer coating film shown in the figure, the amount is preferably within the range of 0.1 to 15 parts by mass, and 0.5 to 15 parts by mass, based on 100 parts by mass of the solid content of the glitter coating composition (Y). It is more preferably within the range of 12 parts by mass, and even more preferably within the range of 1 to 10 parts by mass.

Examples of the crosslinkable component include melamine resin (y3), melamine resin derivatives, urea resins, (meth)acrylamide, polyaziridine, polycarbodiimide, and polyisocyanate compounds that may or may not be blocked. Among them, it is preferable to include melamine resin (y3) from the viewpoint of adhesion of the formed coating film.

As the melamine resin (y3), a partially methylolated melamine resin or a fully methylolated melamine resin obtained by a reaction between a melamine component and an aldehyde component can be used. Examples of the aldehyde component include formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde.

Furthermore, as the melamine resin (y3), it is also possible to use one in which the methylol group of the above-mentioned methylolated melamine resin is partially or completely etherified with an appropriate alcohol. Examples of the alcohol used for etherification include methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol, i-butyl alcohol, 2-ethyl-1-butanol, 2-ethyl-1 -Hexanol, etc.

The melamine resin (y3) is a methyl etherified melamine resin in which the methylol groups of a partially or completely methylolated melamine resin are partially or completely etherified with methyl alcohol, and a methyl etherified melamine resin in which the methylol groups of a partially or fully methylolated melamine resin are partially or completely etherified with butyl alcohol. butyl etherified melamine resin partially or completely etherified with methyl alcohol and butyl alcohol, and methyl-butyl mixed etherified melamine resin partially or completely etherified with methyl alcohol and butyl alcohol. Preferably, methyl-butyl mixed etherified melamine resin is more preferable.

The weight average molecular weight of the melamine resin (y3) is preferably 400 to 6,000, more preferably 500 to 4,000, and even more preferably 600 to 3,000.

Commercially available products can be used as the melamine resin (y3). Examples of commercially available product names include "Cymel 202", "Cymel 203", "Cymel 204", "Cymel 211", "Cymel 212", "Cymel 238", "Cymel 251", "Cymel 253", "Cymel 254", "Cymel 303", "Cymel 323", "Cymel 324", "Cymel 325", "Cymel 327", "Cymel 350", "Cymel 370", "Cymel 380", "Cymel 385", "Cymel 1156", "Cymel 1158", "Cymel 1116", "Cymel 1130" (manufactured by Allnex Japan Co., Ltd.); "Regimin 735", "Regimin 740", "Regimin 741", "Regimin 745", “Regimin 746”, “Regimin 747” (manufactured by Monsanto); “Yuban 120”, “Yuban 20HS”, “Yuban 20SE”, “Yuban 2021”, “Yuban 2028”, “Yuban 28-60” (and more) , manufactured by Mitsui Chemicals Co., Ltd.); "Sumimar M55", "Sumimar M30W", and "Sumimar M50W" (all manufactured by Sumitomo Chemical Co., Ltd.); and the like.

When the glitter coating composition (Y) of the present invention contains the melamine resin (y3), the content is such that it has excellent metallic luster and exhibits excellent coating performance such as adhesion. From the viewpoint of forming a multilayer coating film, it is preferably within the range of 0.1 to 10 parts by mass, and 0.3 to 8 parts by mass, based on 100 parts by mass of the solid content of the glitter coating composition (Y). It is more preferably within the range of 0.5 to 5 parts by mass, and even more preferably within the range of 0.5 to 5 parts by mass.

Coating with the glitter coating composition (Y) can be carried out according to a conventional method, and examples include methods such as air spray coating, airless spray coating, and rotary atomization coating. When applying the bright paint composition (Y), electrostatic charge may be optionally applied. Among these, electrostatic coating using a rotary atomization method and electrostatic coating using an air spray method are preferable. Particularly preferred is the electrostatic coating method.

In the case of air spray coating, airless spray coating or rotary atomization coating, the glitter coating composition (Y) may contain water and/or an organic solvent and optionally additives such as an antifoaming agent. It is preferable to adjust the solid content and viscosity to be suitable for coating.

The solid content of the glitter coating composition (Y) of the present invention is determined from the viewpoint of forming a multilayer coating film that has excellent metallic gloss and exhibits excellent coating film performance such as adhesion. The content is preferably from 0.1 to 15% by weight, preferably from 0.5 to 10% by weight, and more preferably from 1 to 5% by weight.

The viscosity of the glitter coating composition (Y) is Ford Cup No. 1 from the viewpoint of forming a multilayer coating film that has excellent metallic gloss and exhibits excellent coating film performance such as adhesion. 3 viscometer, the time at 20° C. is preferably about 8 to 30 seconds, particularly preferably about 10 to 25 seconds.

The cured film thickness of the bright coating film is preferably about 0.01 to 2 μm from the viewpoint of forming a multilayer coating film that has excellent metallic luster and exhibits excellent coating performance such as adhesion. , more preferably about 0.025 to 1 μm, still more preferably about 0.05 to 0.5 μm.

Process (2)
According to the multilayer coating film forming method of the present invention, next, a clear coating composition containing a hydroxyl group-containing acrylic resin (z1) and a polyisocyanate compound (z2) is applied on the glitter coating film obtained in step (1). The object (Z) is painted and a clear coating film is formed.

Hydroxyl group-containing acrylic resin (z1)
The hydroxyl group-containing acrylic resin (z1) is an acrylic resin having at least one hydroxyl group in one molecule, and has a hydroxyl value within the range of 10 to 75 mgKOH/g. If the content of the hydroxyl group-containing acrylic resin (z1) is less than 10 mgKOH/g, the adhesion of the multilayer coating film to be formed will be poor. If the amount of the hydroxyl group-containing acrylic resin (z1) exceeds 75 mgKOH/g, the adhesion of the multilayer coating film formed will deteriorate. Among these, the hydroxyl value of the hydroxyl group-containing acrylic resin (z1) is within the range of 12 to 70 mgKOH/g from the viewpoint of adhesion of the multilayer coating film to be formed and compatibility with the polyisocyanate compound (z2). It is preferably within the range of 15 to 65 mgKOH/g, and more preferably within the range of 15 to 65 mgKOH/g.

The hydroxyl group-containing acrylic resin (z1) can be obtained by, for example, using a hydroxyl group-containing polymerizable unsaturated monomer and other polymerizable unsaturated monomers (polymerizable unsaturated monomers other than the hydroxyl group-containing polymerizable unsaturated monomer) by a method known per se. For example, it can be produced by copolymerization using a solution polymerization method in an organic solvent, an emulsion polymerization method in water, or the like.

As the hydroxyl group-containing polymerizable unsaturated monomer and other polymerizable unsaturated monomers, the compounds described in the description column of hydroxyl group-containing acrylic resin (y2-1) can be used.

The weight average molecular weight of the hydroxyl group-containing acrylic resin (z1) is preferably in the range of 2,000 to 50,000, preferably 3,000 to 45, from the viewpoint of adhesion of the multilayer coating film to be formed. ,000, and even more preferably 5,000 to 40,000.

The acid value of the hydroxyl group-containing acrylic resin (z1) is 30 mgKOH/g or less, especially 1 to 20 mgKOH, from the viewpoint of the finished appearance of the multilayer coating film to be formed, adhesion, and the pot life of the clear paint composition (Z). It is preferably within the range of /g.

The glass transition temperature of the hydroxyl group-containing acrylic resin (z1) is preferably -50 to 60°C, more preferably -30 to 50°C, from the viewpoint of adhesion, chipping resistance, finished appearance, etc. of the multilayer coating film to be formed. °C, particularly preferably within the range of -10 to 45 °C.

Among the copolymerization methods for copolymerizing the above polymerizable unsaturated monomer mixture to obtain the hydroxyl group-containing acrylic resin (z1), there is a solution polymerization method in which polymerization is carried out in an organic solvent in the presence of a polymerization initiator. can be suitably used.

Examples of the organic solvent used in the above solution polymerization method include alcohol solvents such as methanol, ethanol, propanol, isopropanol, butanol, octanol, dodecanol, ethylene glycol, and propylene glycol; ether solvents such as tetrahydrone; acetone; Ketone solvents such as methyl ethyl ketone and acetylacetone; ester solvents such as methyl acetate, ethyl acetate, butyl acetate, and phenyl acetate; ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, Ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, ethylene glycol monohexyl ether, ethylene glycol monophenyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol monomethyl ether, Glycol ether solvents such as triethylene glycol monoethyl ether, triethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, diethylene glycol monomethyl ether acetate; phenol; Phenolic solvents such as cresol; aliphatic or Aromatic hydrocarbon solvents include aliphatic or aromatic chlorinated hydrocarbon solvents such as dichloromethane, chloroform, trichloroethane, chlorobenzene, and dichlorobenzene.

Examples of polymerization initiators that can be used in the copolymerization of the hydroxyl group-containing acrylic resin (z1) include 2,2'-azobisisobutyronitrile, benzoyl peroxide, di-t-butyl peroxide, and di-t-amyl. Known radical polymerization initiators such as peroxide, t-butyl peroctoate, 2,2'-azobis(2-methylbutyronitrile), and 2,2'-azobis(2,4-dimethylvaleronitrile) are listed. be able to.

The above hydroxyl group-containing acrylic resin (z1) can be used alone or in combination of two or more.

Polyisocyanate compound (z2)
The polyisocyanate compound (z2) is a compound having at least two isocyanate groups in one molecule, and includes, for example, aliphatic polyisocyanate, alicyclic polyisocyanate, araliphatic polyisocyanate, aromatic polyisocyanate, etc. Examples include derivatives of polyisocyanate.

Examples of the aliphatic polyisocyanate include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 1,2-butylene diisocyanate, 2,3-butylene diisocyanate, 1,3 - Aliphatic diisocyanates such as butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, dimer acid diisocyanate, methyl 2,6-diisocyanatohexanoate (common name: lysine diisocyanate); 2 , 2-isocyanatoethyl 6-diisocyanatohexanoate, 1,6-diisocyanato-3-isocyanatomethylhexane, 1,4,8-triisocyanatooctane, 1,6,11-triisocyanatoundecane, 1 , 8-diisocyanato-4-isocyanatomethyloctane, 1,3,6-triisocyanatohexane, 2,5,7-trimethyl-1,8-diisocyanato-5-isocyanatomethyloctane, and other aliphatic triisocyanates. can be mentioned.

Examples of the alicyclic polyisocyanate include 1,3-cyclopentene diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (common name) : isophorone diisocyanate), 4-methyl-1,3-cyclohexylene diisocyanate (common name: hydrogenated TDI), 2-methyl-1,3-cyclohexylene diisocyanate, 1,3- or 1,4-bis(isocyanate) Alicyclic diisocyanates such as methyl)cyclohexane (common name: hydrogenated xylylene diisocyanate) or mixtures thereof, methylenebis(4,1-cyclohexanediyl) diisocyanate (common name: hydrogenated MDI), norbornane diisocyanate; 1,3,5 -triisocyanatocyclohexane, 1,3,5-trimethylisocyanatocyclohexane, 2-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 2- (3-isocyanatopropyl)-2,6-di(isocyanatomethyl)-bicyclo(2.2.1)heptane, 3-(3-isocyanatopropyl)-2,5-di(isocyanatomethyl)- Bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 6-(2 -isocyanatoethyl)-2-isocyanatomethyl-3-(3-isocyanatopropyl)-bicyclo(2.2.1)heptane, 5-(2-isocyanatoethyl)-2-isocyanatomethyl-2- (3-isocyanatopropyl)-bicyclo(2.2.1)-heptane, 6-(2-isocyanatoethyl)-2-isocyanatomethyl-2-(3-isocyanatopropyl)-bicyclo(2.2 .1) Alicyclic triisocyanates such as heptane can be mentioned.

Examples of the araliphatic polyisocyanate include methylene bis(4,1-phenylene) diisocyanate (common name: MDI), 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω,ω'-diisocyanato- Aroaliphatic diisocyanates such as 1,4-diethylbenzene, 1,3- or 1,4-bis(1-isocyanato-1-methylethyl)benzene (common name: tetramethylxylylene diisocyanate) or mixtures thereof; 1,3 , 5-triisocyanatomethylbenzene and other aromatic aliphatic triisocyanates.

Examples of the aromatic polyisocyanate include m-phenylene diisocyanate, p-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 2,4-tolylene diisocyanate (common name: 2,4- Aromatic diisocyanates such as 2,6-tolylene diisocyanate (common name: 2,6-TDI) or mixtures thereof, 4,4'-toluidine diisocyanate, 4,4'-diphenyl ether diisocyanate; triphenylmethane-4 , 4',4''-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene; 4,4'-diphenylmethane-2,2' , 5,5'-tetraisocyanate and other aromatic tetraisocyanates.

Examples of the polyisocyanate derivatives include the above-mentioned polyisocyanate dimer, trimer, biuret, allophanate, uretdione, uretimine, isocyanurate, oxadiazinetrione, polymethylene polyphenyl polyisocyanate (crude MDI, polymeric MDI), crude Examples include TDI.

The above polyisocyanates and their derivatives may be used alone or in combination of two or more.

Among the aliphatic diisocyanates, hexamethylene diisocyanate-based compounds and among the alicyclic diisocyanates, 4,4'-methylenebis(cyclohexyl isocyanate) can be preferably used. Among these, derivatives of hexamethylene diisocyanate are particularly suitable from the viewpoints of adhesion, compatibility, and the like.

As the polyisocyanate compound (z2), the polyisocyanate and its derivatives are reacted with a compound having an active hydrogen group such as a hydroxyl group or an amino group, which can react with the polyisocyanate, under conditions where there are an excess of isocyanate groups. A prepolymer consisting of: Examples of compounds that can react with the polyisocyanate include polyhydric alcohols, low molecular weight polyester resins, amines, and water.

Further, as the polyisocyanate compound (z2), it is also possible to use a blocked polyisocyanate compound, which is a compound in which the isocyanate groups in the above polyisocyanate and its derivatives are blocked with a blocking agent.

Examples of the blocking agent include phenols such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and methyl hydroxybenzoate; ε-caprolactam, δ-valerolactam, Lactams such as γ-butyrolactam and β-propiolactam; aliphatic alcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, amyl alcohol, lauryl alcohol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono Ethers such as butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, methoxymethanol; benzyl alcohol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate, lactic acid, methyl lactate, ethyl lactate, lactic acid Alcohols such as butyl, methylol urea, methylol melamine, diacetone alcohol, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate; formamide oxime, acetamid oxime, acetoxime, methyl ethyl ketoxime, diacetyl monoxime, benzophenone oxime, cyclohexane oxime, etc. Oxime series; active methylene series such as dimethyl malonate, diethyl malonate, ethyl acetoacetate, methyl acetoacetate, acetylacetone; butyl mercaptan, t-butyl mercaptan, hexyl mercaptan, t-dodecyl mercaptan, 2-mercaptobenzothiazole, thio Mercaptans such as phenol, methylthiophenol and ethylthiophenol; acidamides such as acetanilide, acetanisidide, acetotoluide, acrylamide, methacrylamide, acetamide, stearamide and benzamide; succinimide, phthalimide, maleimide, etc. imide series; amine series such as diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, butylphenylamine; imidazole series such as imidazole, 2-ethylimidazole; urea, thio Urea types such as urea, ethylene urea, ethylene thiourea, and diphenyl urea; Carbamate ester types such as phenyl N-phenylcarbamate; Imine types such as ethylene imine and propylene imine; Sulfite types such as sodium bisulfite and potassium bisulfite. ; Examples include azole compounds. Examples of the azole compounds include pyrazole, 3,5-dimethylpyrazole, 3-methylpyrazole, 4-benzyl-3,5-dimethylpyrazole, 4-nitro-3,5-dimethylpyrazole, 4-bromo-3, Pyrazole or pyrazole derivatives such as 5-dimethylpyrazole, 3-methyl-5-phenylpyrazole; imidazole or imidazole derivatives such as imidazole, benzimidazole, 2-methylimidazole, 2-ethylimidazole, 2-phenylimidazole; 2-methylimidazoline and imidazoline derivatives such as 2-phenylimidazoline.

When blocking (reacting the blocking agent), a solvent can be optionally added.

The polyisocyanate compounds (z2) can be used alone or in combination of two or more.

In the clear coating composition (Z), the equivalent ratio (NCO/OH) between the total mol of isocyanate groups of the polyisocyanate compound (z2) and the total mol of hydroxyl groups of the hydroxyl group-containing acrylic resin (z1) is determined by From the viewpoint of forming a multilayer coating film exhibiting excellent coating performance, it is preferably within the range of 0.70 to 1.50, more preferably within the range of 0.75 to 1.40, More preferably, it is within the range of 0.8 to 1.20.

The clear coating composition (Z) optionally contains a solvent such as water and an organic solvent, a resin other than the hydroxyl group-containing acrylic resin (z1), a curing agent other than the polyisocyanate compound (z2), a curing catalyst, and an antifoaming agent. , ultraviolet absorbers, rheology control agents, antisettling agents, and other paint additives may be appropriately blended.

In the clear coating composition (Z), color pigments can be used as appropriate within the range that does not impair the transparency of the coating film. As the coloring pigment, pigments known per se for use in inks or paints can be used alone or in combination of two or more. The blending amount varies depending on the type of coloring pigment used, etc., but is usually 30% by mass or less, preferably 0.05 to 20% by mass, based on the total solid content of the resin component of the clear paint composition (Z). %, more preferably within the range of 0.1 to 10% by weight.

The clear coating composition (Z) can be applied by electrostatic coating, air spraying, airless spraying, etc., and the thickness of the clear coating film is preferably about 10 to 60 μm based on the cured coating film. The thickness is about 15 to 50 μm, more preferably about 20 to 40 μm.

The solid content of the clear coating composition (Z) is within the range of 10 to 65% by mass, preferably 15 to 55% by mass, and more preferably 20 to 50% by mass. The viscosity of the clear paint composition (Z) is adjusted to a range suitable for painting, usually Ford Cup No. Using water and/or an organic solvent, adjust as appropriate so that the time is preferably within the range of about 15 to 60 seconds, particularly preferably about 20 to 50 seconds, at 20° C. using a viscometer.

Process (3)
According to the method for forming a multilayer coating film of the present invention, next, the glitter coating film formed in the step (1) and the clear coating film formed in the step (2) are heated separately or simultaneously. to harden it.

The heating means can be, for example, hot air heating, infrared heating, high frequency heating, etc. The heating temperature is preferably 80 to 160°C, more preferably 100 to 140°C. The heating time is preferably 10 to 60 minutes, more preferably 15 to 40 minutes. Optionally, before performing the heat curing, directly or indirectly, for about 1 to 60 minutes, preferably at a temperature of about 50 to about 110 °C, more preferably about 60 to about 90 °C, by preheating, air blowing, etc. Heating may be performed.

The present invention also includes the following embodiments.
Item 1.
The following steps (1) to (3):
Step (1): a step of coating a glittering paint composition (Y) containing indium particles (y1) on the object to be coated to form a glittering coating film;
Step (2): A clear coating composition (Z) containing a hydroxyl group-containing acrylic resin (z1) and a polyisocyanate compound (z2) is applied onto the glitter coating film obtained in step (1) to form a clear coating. Step (3) of forming a film: Curing the glitter coating formed in step (1) and the clear coating formed in step (2) by heating them separately or simultaneously. A method for forming a multilayer coating film, comprising the steps of:
A method for forming a multilayer coating film, wherein the hydroxyl value of the hydroxyl group-containing acrylic resin (z1) is within the range of 10 to 75 mgKOH/g.
Item 2.
Item 2. The method for forming a multilayer coating according to Item 1, wherein the glitter coating composition (Y) further contains a hydroxyl group-containing resin (y2).
Item 3.
Item 3. The method for forming a multilayer coating according to item 1 or 2, wherein the glitter coating composition (Y) further contains a melamine resin (y3).
Item 4.
In the clear coating composition (Z), the equivalent ratio (NCO/OH) of the total mol of isocyanate groups of the polyisocyanate compound (z2) to the total mol of hydroxyl groups of the hydroxyl group-containing acrylic resin (z1) is 0.7 to The method for forming a multilayer coating film according to any one of Items 1 to 3, which is within the range of 1.5.
Item 5.
Any of Items 1 to 4, wherein the content of indium particles (y1) in the glitter paint composition (Y) is 50 parts by mass or more based on 100 parts by mass of solid content of the glitter paint composition (Y). The method for forming a multilayer coating film according to item 1.
Item 6.
Any one of items 1 to 5, wherein the content of the hydroxyl group-containing resin (y2) is within the range of 0.1 to 15 parts by mass based on 100 parts by mass of the solid content of the glitter coating composition (Y). The method for forming a multilayer coating film described in .
Section 7.
Item 7. The multilayer coating film forming method according to item 6, wherein the hydroxyl group-containing resin (y2) contains a hydroxyl group-containing acrylic resin (y2-1).
Section 8.
Forming a multilayer coating according to Item 3, wherein the content of the melamine resin (y3) is within the range of 0.1 to 10 parts by mass based on 100 parts by mass of the solid content of the glitter coating composition (Y). Method.
Item 9.
Item 9. The method for forming a multilayer coating film according to any one of Items 1 to 8, wherein the glitter coating composition (Y) further contains a surface conditioner.
Item 10.
10. The method for forming a multilayer coating film according to item 9, wherein the surface conditioning agent contains a fluorine-based surface conditioning agent.
Item 11.
Item 11. The multilayer coating according to Item 9 or 10, wherein the content of the surface conditioner is within the range of 0.01 to 0.2 parts by mass based on 100 parts by mass of the solid content of the glitter coating composition (Y). Film formation method.
Item 12.
Item 12. The method for forming a multilayer coating film according to any one of Items 1 to 11, wherein the glitter coating composition (Y) further contains an organic solvent.
Item 13.
Item 13. The method for forming a multilayer coating film according to item 12, wherein the content of the organic solvent is within the range of 85 to 99.9 parts by mass based on 100 parts by mass of solid content of the glitter coating composition (Y).
Section 14.
Item 14. The method for forming a multilayer coating film according to any one of Items 1 to 13, wherein the bright coating film has a solid content of 0.1 to 15% by mass.
Item 15.
Item 15. The method for forming a multilayer coating film according to any one of Items 1 to 14, wherein the cured film thickness of the glitter coating film is 0.01 to 2 μm.
Section 16.
Item 16. The method for forming a multilayer coating film according to any one of Items 1 to 15, wherein the object to be coated includes an outer panel of an automobile body and an automobile part.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited only to these examples. Note that both "parts" and "%" are based on mass.

1. Preparation of base material A cationic electrodeposition paint "Electron GT-10" (trade name: Kansai Paint Co., Ltd., epoxy resin polyamine type) was applied to a degreased and zinc phosphate treated steel plate (JIS G3141, size 400 mm x 300 mm x 0.8 mm) A cationic resin using a block polyisocyanate compound as a curing agent) was electrodeposited to a film thickness of 20 μm based on the cured coating, heated at 170°C for 20 minutes to crosslink and cure, and then electrodeposited. A film was formed.

"TP-65-2" (trade name, manufactured by Kansai Paint Co., Ltd., a polyester resin and amino resin-based organic solvent type intermediate coating composition) was applied to the electrodeposited surface of the obtained steel plate using a rotary atomization method. Using an electrostatic coating machine, electrostatic coating was applied so that the cured film thickness was 35 μm, and the coating was cured by heating at 140° C. for 30 minutes to form an intermediate coating film, thereby preparing a coated object.

2. Preparation of paint Production of hydroxyl group-containing acrylic resin (y2-1) Production example 1
In a reaction vessel equipped with a thermometer, a thermostat, a stirring device, a reflux condenser, a nitrogen inlet tube, and a dropping device, 22 parts of "Swazol 1000" (trade name, manufactured by Maruzen Petrochemical Co., Ltd., aromatic petroleum solvent) and butyl acetate were added. After charging 10 parts and raising the temperature to 125°C, at the same temperature, 17 parts of 2-hydroxyethyl acrylate, 25 parts of styrene, 8 parts of n-butyl acrylate, 34.35 parts of isobutyl methacrylate, 15 parts of 2-ethylhexyl acrylate, A monomer mixture consisting of 0.65 parts of acrylic acid, 1 part of di-tert-amyl peroxide (polymerization initiator), and 20 parts of "Swazol 1000" was added dropwise over 3 hours, and the mixture was aged for 2 hours after the addition was completed. Next, as an additional catalyst, a mixed solution consisting of 0.5 part of di-tert-amyl peroxide and 8 parts of "Swazol 1000" was added dropwise over 1 hour, and after the addition was completed, the solid content was maintained at 125°C for 1 hour. A 60% hydroxyl group-containing acrylic resin solution (y2-1) was obtained. The obtained hydroxyl group-containing acrylic resin (y2-1-1) had a hydroxyl value of 82 mgKOH/g, an acid value of 5 mgKOH/g, a weight average molecular weight of 28,000, and a glass transition temperature of 17°C.

Production example 2 of glittering paint composition (Y)
In a stirring mixing container, 100 parts of "Leaf Powder 49CJ-1120" (trade name, manufactured by Oike Kogyo Co., Ltd., indium particles, solid content 20%, dispersed in propylene glycol monomethyl ether) (solid content 20 parts), "LE- 605" (trade name, manufactured by Kyoeisha Chemical Co., Ltd., fluorine-based surface conditioner, solid content 30%) 0.27 parts (solid content 0.08 parts), hydroxyl group-containing acrylic resin (y2-1-1) 2.3 (solid content 1.4 parts), "Cymel 327" (trade name, manufactured by Allnex, imino group-containing melamine resin, solid content 90%) 0.66 parts (solid content 0.59), and propylene glycol monomethyl ether 1701 1.0 parts were added and mixed with stirring to produce a glitter coating composition (Y-1) with a solids content of 1.2% by mass.

Production examples 3 to 9
Glitter coating compositions (Y-2) to (Y-8) were obtained in the same manner as in Production Example 2 except that the formulation and solid content were as shown in Table 1.

(*1) "METALURE L-71011AE": Trade name, manufactured by Ecart, vapor-deposited aluminum flake pigment, solid content 10%, dispersed in ethyl acetate.

Production example 10 of hydroxyl group-containing acrylic resin (z1)
In a reaction vessel equipped with a thermometer, thermostat, stirring device, reflux condenser, nitrogen inlet tube, and dropping device, 27 parts of "Swazol 1000" (trade name, manufactured by Cosmo Oil Co., Ltd., aromatic organic solvent) and propylene glycol were added. 5 parts of monomethyl ether acetate were charged. The charge solution was stirred at 150°C while blowing nitrogen gas into the reaction vessel, and 20 parts of styrene, 10.5 parts of n-butyl acrylate, 3.5 parts of 2-hydroxyethyl methacrylate, 50 parts of isobutyl methacrylate, and 2 - A monomer mixture consisting of 15 parts of ethylhexyl acrylate, 1.0 part of acrylic acid, and 1.5 parts of ditertiary amyl peroxide (polymerization initiator) was added dropwise at a uniform rate over 4 hours. Thereafter, the mixture was aged at 150° C. for 1 hour, cooled, and further diluted by adding 21 parts of isobutyl acetate to obtain a hydroxyl group-containing acrylic resin (z1-1) solution with a solid content concentration of 65% by mass. The obtained hydroxyl group-containing acrylic resin (z1-1) had a hydroxyl value of 15 mgKOH/g, an acid value of 8 mgKOH/g, a weight average molecular weight of 30,000, and a glass transition temperature of 24°C.

Production examples 11 to 15
In Production Example 10, a solution of hydroxyl group-containing acrylic resins (z1-2) to (z1-6) with a solid content concentration of 65% by mass was prepared in the same manner as in Production Example 10, except that the composition was as shown in Table 2. Obtained. Table 2 also shows the acid value, hydroxyl value, weight average molecular weight, and glass transition temperature of each hydroxyl group-containing acrylic resin.

Manufacturing example 16 of clear paint composition (Z-1)
144.9 parts of the hydroxyl group-containing acrylic resin (z1-1) solution obtained in Production Example 10 (solid content 94.2 parts), "BYK-300" (trade name, manufactured by BYK Chemie Co., Ltd., surface conditioner, active ingredient 52%) ) 0.4 part (solid content 0.2 part) of the base agent uniformly mixed,
As a curing agent, 5.8 parts of "Sumidur N3300" (trade name, manufactured by Sumika Covestro Urethane Co., Ltd., isocyanurate of hexamethylene diisocyanate, solid content 100%) (solid content 5.8 parts) was uniformly mixed immediately before coating, and further, butyl acetate was added, and Ford Cup No. 1 was heated at 20°C. A clear paint composition (Z-1) was obtained by adjusting the viscosity according to No. 4 to 30 seconds.

Production examples 17 to 23
Clear coating compositions (Z-2) to (Z-8) were obtained in the same manner as in Production Example 16 except for using the formulations shown in Table 3.

3. Creation of test board Creation of test board Example 1
The bright paint composition (Y-1) produced in the above "2. Preparation of the paint" was applied onto the base material prepared in the above "1. Preparation of the base material" using a mini-bell type rotary electrostatic coating machine. , under the conditions of a booth temperature of 23°C and humidity of 63%, the cured coating was applied to a film thickness of 0.05 μm, left at room temperature for 15 minutes, and then heated at 140°C in a hot air circulation drying oven. The mixture was heated for 30 minutes to dry and cure to obtain a glitter coating film.

Next, the clear paint composition (Z-2) prepared in "2. Preparation of paint" above was applied onto the bright coating film using a mini-bell rotary electrostatic coating machine at a booth temperature of 23°C and humidity. Example 1 A test plate was prepared.

Here, the film thickness of the dry coating film of the glitter coating film was calculated from the following formula. The same applies to the following examples.
x=sc/sg/S*10000
x: Film thickness [μm]
sc: Coating solid content [g]
sg: Paint film specific gravity [g/cm ³ ]
S: Evaluation area of coated solid content [cm ² ]

Examples 2-7, 9-13 and Comparative Examples 1-3
A test plate was obtained in the same manner as in Example 1 except that the coating material and film thickness were as shown in Table 4.

Example 8
The bright paint composition (Y-2) produced in "2. Preparation of paint" above was applied onto the base material prepared in "1. Preparation of base material" above using a mini-bell type rotary electrostatic coating machine. , under conditions of a booth temperature of 23°C and humidity of 63%, the cured coating was applied to a film thickness of 0.1 μm, left at room temperature for 15 minutes, and then heated to 80°C in a hot air circulation drying oven. Preheating was performed for 3 minutes to obtain an uncured glitter coating film.

Next, the clear paint composition (Z-2) prepared in "2. Preparation of Paint" above was applied onto the uncured glitter coating film using a mini-bell rotary electrostatic coating machine at a booth temperature of 23. ℃ and 68% humidity to give a cured coating film of 35 μm. After leaving it at room temperature for 7 minutes, it was heated at 140℃ for 30 minutes in a hot air circulation drying oven to form a bright coating film. A test plate of Example 8 was prepared by drying and curing the clear coating film and the clear coating film at the same time.

Coating film evaluation The coating film of each test plate obtained as described above was evaluated by the following method, and the results are shown in Table 4.

Initial water resistance adhesion The test board was immersed in warm water at 40°C for 240 hours, pulled out, wiped with a cloth to remove water droplets and dirt, and within 10 minutes at a room temperature of 23°C, cut the multilayer coating on the test board to reach the substrate. Make 100 goblets of 2mm x 2mm in size by cutting in a grid pattern. Subsequently, an adhesive cellophane tape was attached to the surface, and after the tape was rapidly peeled off, the remaining state of the rough coating film was examined, and the water-resistant adhesion was evaluated according to the following criteria. A and B pass.
A: 100 scratched coatings remain, and there are no small edge chips of the coating at the edges of the cutter's incisions.
B: 100 coating films remain, but small edges of the coating film are chipped at the edges of the cuts of the cutter, and there are less than 10 remaining coating films with chipped edges.
C: 100 coating films remain, but small edges of the coating film are chipped at the edges of the cuts of the cutter, and there are 10 or more remaining coating films with chipped edges.
D: 90 to 99 rough coating films remain.
E: The number of remaining rough coating films is 89 or less.

Water resistance adhesion after accelerated weathering test For the accelerated weathering test, a super xenon weatherometer (trade name, manufactured by Suga Test Instruments Co., Ltd.) specified in JIS B 7754 was used, and a xenon arc was applied for 1 hour and 42 minutes. One cycle consisted of lamp irradiation and 2 hours of irradiation with the same lamp under rain conditions for 18 minutes, and after 2000 hours, the same operation as the above water resistant adhesion test was performed. A, B and C are passed.

Specular gloss (60° gloss)
The 60° gloss value was measured using a gloss meter (micro-TRI-gloss, manufactured by BYK-Gardner). The larger the value, the better the metallic luster. A score of 280 or higher is considered passing.

Although the embodiments and examples of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications can be made based on the technical idea of the present invention.

For example, the configurations, methods, processes, shapes, materials, numerical values, etc. mentioned in the above embodiments and examples are merely examples, and different configurations, methods, processes, shapes, materials, numerical values, etc. may be used. good.

Further, the configurations, methods, processes, shapes, materials, numerical values, etc. of the above-described embodiments can be combined with each other without departing from the gist of the present invention.

Claims

The following steps (1) to (3):
Step (1): a step of coating a glittering paint composition (Y) containing indium particles (y1) on the object to be coated to form a glittering coating film;
Step (2): A clear coating composition (Z) containing a hydroxyl group-containing acrylic resin (z1) and a polyisocyanate compound (z2) is applied onto the glitter coating film obtained in step (1) to form a clear coating. Step (3) of forming a film: Curing the glitter coating formed in step (1) and the clear coating formed in step (2) by heating them separately or simultaneously. A method for forming a multilayer coating film, comprising the steps of:
A method for forming a multilayer coating film, wherein the hydroxyl value of the hydroxyl group-containing acrylic resin (z1) is within the range of 10 to 75 mgKOH/g.
The method for forming a multilayer coating film according to claim 1, wherein the glitter coating composition (Y) further contains a hydroxyl group-containing resin (y2).
The method for forming a multilayer coating film according to claim 1 or 2, wherein the glitter coating composition (Y) further contains a melamine resin (y3).
In the clear coating composition (Z), the equivalent ratio (NCO/OH) of the total mol of isocyanate groups of the polyisocyanate compound (z2) to the total mol of hydroxyl groups of the hydroxyl group-containing acrylic resin (z1) is 0.7 to The method for forming a multilayer coating film according to any one of claims 1 to 3, which is within the range of 1.5.