JP2021107081A - Bilayer coating film formation method - Google Patents

Abstract

To provide a bilayer coating film formation method that can form a metal-tone coating film excellent in lacquer blackness, metal-tone glossiness and water resistance.SOLUTION: A bilayer coating film formation method is a method for forming a bilayer coating film by successively performing the steps of the present disclosure (1)-(4), where a brilliant pigment disperser (Y) contains water, a surface regulator (A), an evaporation chrome flake pigment (B) and a viscosity adjustment agent (C). The surface regulator (A) is a surface regulator (A) having a contact angle of 8-20° with a tin plate when measured 10 seconds after dripping 10 μL on the pre-defatted tin plate (made by PALTECH CO. LTD.) while regulating liquid mixing an isopropanol/water/surface regulator (A) at a ratio of 4.5/95/1 so that viscosity at a rotor rotation speed of 60 rpm is 150 mPa s at a temperature of 20°C with a B-type viscometer. A light ray transmittance ratio of a film obtained by coating the brilliant pigment disperser (Y) so that a resulting dry film has a thickness of 0.2 μm is 0.1-40% at a wavelength of 550 nm.SELECTED DRAWING: None

Description

(Cross-reference of related applications)
This application claims priority based on Japanese Patent Application No. 2015-254000 filed on December 25, 2015. These documents are incorporated herein by reference in their entirety.
(Technical field)
The present invention relates to a method for forming a multi-layer coating film having a metallic luster and capable of forming a coating film having jet blackness and high water resistance.

The purpose of applying paint is mainly to protect the material and give it an aesthetic appearance. In industrial products, aesthetics, especially "texture", is important from the viewpoint of enhancing the product power. There are various textures of industrial products that consumers demand, but in recent years, in the fields of automobile outer panels, automobile parts, home appliances, etc., a glossy feeling like metal or pearl is required (hereinafter, "" Notated as "metallic luster").

Metallic luster means that the surface does not have a grainy appearance like a mirror surface, and when viewed in a state close to perpendicular to the coated plate (highlight), it shines brightly, and when viewed from diagonally above the coated plate (shade). ) Is a texture characterized by appearing dark, that is, having a large difference in brightness between the highlight region and the shade region.

Techniques for imparting such metallic luster to the surface of industrial products include metal plating treatment and metal vapor deposition treatment (for example, Patent Document 1). However, if metallic luster can be imparted by painting, convenience and cost can be achieved. It is advantageous from the viewpoint.

Patent Document 2 discloses a method for forming a metallic coating film, which comprises coating an uncured coated surface with a composition containing non-leaving aluminum flakes and an organic solvent, and then applying a clear paint. ..

Further, Patent Document 3 describes a metallic paint base containing a non-volatile solid content containing a bright material and a resin and a solvent at a dilution ratio of 150 to 500% using a diluent composed of a high boiling point solvent and a low boiling point solvent. Disclosed is a metallic coating material obtained by diluting with and adding 5 to 10 parts by weight of a viscous resin to 100 parts by weight of the resin content in the metallic coating material base.

Patent Document 4 describes a solid content containing 10 to 30% of a bright material, 10 to 50% of a cellulose acetate butyrate resin having a molecular weight of 25,000 to 50,000 (MWn), and an acrylic-melamine resin as a remaining amount. A metallic paint obtained by diluting a barrel paint base material with an ester solvent and / or a ketone solvent at a dilution ratio such that the solid content is 1 to 10% is disclosed.

Patent Document 5 discloses a method for forming a multi-layer coating film using a bright material-containing base coating material containing a noble metal and / or colloidal particles containing a metal, and further containing a coating film-forming resin and a specific mixed solvent. ing.

Patent Document 6 uses a specific bright material-containing base coating material containing a noble metal and / or colloidal particles containing a metal and a coating film-forming resin, and forms a multi-layer coating film to be used in combination with a specific coating method. The method is disclosed.

The paints disclosed in Patent Documents 2 to 6 are solvent-based paints. However, in recent years, from the viewpoint of low environmental load and the like, water-based coating has been required in the field of metallic paints as well.

Patent Document 7 includes a brilliant pigment obtained by crushing a vapor-deposited metal film into metal pieces and an aqueous cellulose derivative having an acid value of 20 to 150 mgKOH / g (solid content), and the main binder is the aqueous cellulose derivative. A water-based base coating composition which is made of a resin and has a content of the bright pigment of 20 to 70% by mass in PWC is disclosed.

However, the coating film formed by the paint described in Patent Document 7 has insufficient metallic luster. Further, there is a problem in terms of cost in that a binder resin is required.

Japanese Unexamined Patent Publication No. 63-272544 Japanese Unexamined Patent Publication No. 11-90318 Japanese Unexamined Patent Publication No. 2003-313500 Japanese Unexamined Patent Publication No. 2005-120249 Japanese Unexamined Patent Publication No. 2009-28690 Japanese Unexamined Patent Publication No. 2009-28693 Japanese Unexamined Patent Publication No. 2009-155537

A coating film having a costume close to that of a real metal, that is, a smooth metallic luster (that is, a feeling of less particles of the obtained coating film) and a sharp brilliance and shadow (that is, a high coating film obtained) as compared with a conventional coating film. There is a demand for a coating film that also has flip-flop properties.

Furthermore, in addition to being close to real metal, a design with a profound feeling is required by giving it a jet-blackness. However, in the conventional technique of simply adding a black pigment to a bright pigment, the obtained coating film becomes yellowish (that is, the b * value of the obtained coating film is high), and the desired design can be obtained. Can not.

An object of the present invention is to provide a method for forming a multi-layer coating film capable of forming a metallic coating film having excellent jet blackness, metallic luster and water resistance.

According to one aspect of the present invention, the following steps (1) to (4):
(1) A step of applying a colored paint (X) on an object to be coated to form a colored coating film.
(2) A step of coating the bright pigment dispersion (Y) on the colored coating film formed in the step (1) to form a bright coating film.
(3) A step of applying a clear coating film (Z) on the glittering coating film formed in the step (2) to form a clear coating film.
(4) By heating the uncured colored coating film, the uncured brilliant coating film, and the uncured clear coating film formed in the steps (1) to (3), these three coating films are cured at the same time. It is a method of forming a multi-layer coating film by sequentially performing the steps of making the coating film.
The glitter pigment dispersion (Y) contains water, a surface conditioner (A), a vapor-deposited chrome flake pigment (B) and a viscosity conditioner (C).
A liquid in which the surface conditioner (A) is mixed at a ratio of isopropanol / water / surface conditioner (A) = 4.5 / 95/1 is mixed at a temperature of 20 ° C. and a rotor rotation speed of 60 rpm with a B-type viscometer. The surface has a contact angle of 8 to 20 ° with respect to the tin plate when 10 μL is dropped onto a tin plate (manufactured by Partec) that has been degreased in advance and measured after 10 seconds. It is a regulator and
A method for forming a multi-layer coating film having a light transmittance of 0.1 to 40% at a wavelength of 550 nm of a film obtained by coating a glitter pigment dispersion (Y) so as to have a dry film thickness of 0.2 μm. Provided.

According to the method for forming a multi-layer coating film of the present invention, a coating film having an appearance excellent in jet blackness, metallic luster and water resistance can be obtained.

1. 1. Process (1)
The step (1) is a step of applying the colored paint (X) on the object to be coated to form a colored coating film.
Object to be coated In the method for forming a multi-layer coating film of the present invention, the object to be coated includes metals such as iron, zinc and aluminum, metal materials such as alloys containing these, molded products made of these metals, and glass. Examples thereof include molded products made of plastic or foam. Depending on these materials, degreasing treatment or surface treatment can be appropriately performed to obtain an object to be coated. Examples of the surface treatment include phosphate treatment, chromate treatment, composite oxide treatment and the like. Further, when the material of the object to be coated is a metal, it is preferable that an undercoat coating film is formed on the surface-treated metal material by a cationic electrodeposition coating material. When the material of the object to be coated is plastic, it is preferable that a primer coating film is formed on the degreased plastic material by the primer coating material.
Colored paint (X)
As the coloring paint (X), specifically, a thermosetting paint known per se, which contains a vehicle-forming resin, a pigment, and a solvent such as an organic solvent and / or water as a main component, can be used. Examples of the thermosetting paint include intermediate coating paints and base paints.

Examples of the vehicle-forming resin used in the colored coating material (X) include thermosetting resins and room temperature curable resins. From the viewpoints of water resistance, chemical resistance, weather resistance, etc., the vehicle-forming resin is a thermosetting resin. Is desirable. The vehicle-forming resin is preferably produced by using a substrate resin and a cross-linking agent in combination.

The base resin is preferably a resin having good weather resistance, transparency and the like, and specific examples thereof include acrylic resin, polyester resin, epoxy resin and urethane resin.

Examples of the acrylic resin include (meth) acrylic acid esters having functional groups such as α, β-ethylenically unsaturated carboxylic acids, hydroxyl groups, amide groups, and methylol groups, and other (meth) acrylic acid esters and styrene. Examples thereof include a resin obtained by copolymerizing with the above.

As the polyester resin, a polyester resin obtained by subjecting a polybasic acid, a polyhydric alcohol, or a modified oil to a condensation reaction by a conventional method can be used.

Epoxy resins include, for example, a method of synthesizing an epoxy ester by reacting an epoxy group with an unsaturated fatty acid and adding α, β-unsaturated acid to the unsaturated group, a hydroxyl group of the epoxy ester, and phthalic acid. Examples thereof include an epoxy ester resin obtained by a method of esterifying a polybasic acid such as trimellitic acid.

Examples of the urethane resin include those obtained by reacting the above-mentioned acrylic resin, polyester resin or epoxy resin with a diisocyanate compound to increase the molecular weight.

The colored paint (X) may be either a water-based paint or a solvent-based paint, but is preferably a water-based paint from the viewpoint of reducing VOC of the paint. When the coloring paint (X) is a water-based paint, the base resin has a sufficient amount of hydrophilic groups such as a carboxyl group, a hydroxyl group, a methylol group, an amino group, and a sulfonic acid to make the resin water-soluble or water-dispersed. A resin containing a carboxyl group, such as a group or a polyoxyethylene bond, is used, and the hydrophilic group is neutralized to an alkali salt to make the base resin water-soluble or water-dispersible. Can be done. The amount of the hydrophilic group, for example, the carboxyl group at that time is not particularly limited and can be arbitrarily selected depending on the degree of water solubility or water dispersion, but generally, about 10 mgKOH / based on the acid value. It can be in the range of g or more, preferably 30 to 200 mgKOH / g. Examples of the alkaline substance used for neutralization include sodium hydroxide, an amine compound and the like.

The aqueous dispersion of the resin can also be carried out by emulsion polymerization of the monomer component in the presence of a surfactant or a water-soluble resin. Further, it can also be obtained by dispersing the above resin in water in the presence of, for example, an emulsifier. In this water dispersion, the hydrophilic group may not be contained at all in the substrate resin, or may be contained in a smaller amount than the water-soluble resin.

The cross-linking agent is a component for cross-linking and curing the base resin by heating. For example, an amino resin, a polyisocyanate compound, a blocked polyisocyanate compound, an epoxy group-containing compound, a carboxyl group-containing compound, a carbodiimide group-containing compound, and hydrazide. Examples thereof include group-containing compounds and semicarbodiide group-containing compounds. Of these, an amino resin capable of reacting with a hydroxyl group, a polyisocyanate compound, a blocked polyisocyanate compound; and a carbodiimide group-containing compound capable of reacting with a carboxyl group are preferable. As the polyisocyanate compound and the blocked polyisocyanate compound, those described in the section of clear coating material (Z) described later can be used. The above-mentioned cross-linking agent can be used alone or in combination of two or more.

Specifically, an amino resin obtained by condensing or cocondensing melamine, benzoguanamine, urea or the like with formaldehyde, or further etherifying with a lower monohydric alcohol is preferably used. Further, a polyisocyanate compound or a blocked polyisocyanate compound can also be preferably used.

The ratio of each of the above components in the colored paint (X) can be arbitrarily selected as needed, but from the viewpoint of water resistance, finishability, etc., the substrate resin and the cross-linking agent are generally composed of both components. Based on the total mass, the former is preferably in the range of 60 to 90% by mass, particularly 70 to 85% by mass, and the latter is preferably in the range of 10 to 40% by mass, particularly 15 to 30% by mass.

The pigment imparts color and base hiding property to the colored coating film formed by the colored paint (X). By adjusting the type and blending amount of the pigment, the lightness L * value of the coating film obtained by the colored paint (X) is 0.1 to 80, preferably 0.1 to 70, and more preferably 0.1 to 1. It can be adjusted to be within the range of 60. Examples of the pigment include metallic pigments, rust preventive pigments, coloring pigments, extender pigments, etc. Among them, it is preferable to use coloring pigments, and a coating film having excellent base hiding property and metallic luster can be obtained. From the viewpoint of, it is more preferable to use a black pigment.

The pigments can be used in an appropriate combination according to the light transmittance, the hiding property of the base, the desired color, etc., and the amount used is based on the colored paint (X) from the viewpoint of the hiding property of the base, weather resistance, etc. An amount in which the light transmittance in the wavelength range of 400 to 700 nm in the cured coating film having a film thickness of 15 μm is 10% or less, preferably 5% or less is appropriate.

The light transmittance of the coating film is such that the coating material is applied to a glass plate so as to have a predetermined film thickness based on the cured coating film, cured, and then immersed in warm water at 60 to 70 ° C. to obtain the coating film. This is the spectral transmittance when measured in the wavelength range of 400 to 700 nm using a self-recording spectrophotometer (manufactured by Hitachi, Ltd., EPS-3T type) using the coating film obtained by peeling and drying as a sample. When there is a difference depending on the wavelength to be measured (400 to 700 nm), the maximum value is used as the light transmittance.

An organic solvent can also be used for the coloring paint (X), if necessary. Specifically, those normally used in paints can be used, for example, hydrocarbons such as toluene, xylene, hexane and heptane; ethyl acetate, butyl acetate, ethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether. Esters such as acetate and diethylene glycol monobutyl acetate; ethers such as ethylene glycol monomethyl ether, ethylene glycol diethyl ether, diethylene glycol monomethyl ether and diethylene glycol dibutyl ether; alcohols such as butanol, propanol, octanol, cyclohexanol and diethylene glycol; methyl ethyl ketone and methyl isobutyl ketone , Cyclohexanone, isophorone and other ketone organic solvents. These can be used alone or in combination of two or more.

Of the above, organic solvents such as esters, ethers, alcohols and ketones are preferable from the viewpoint of solubility.

The cured film thickness of the colored coating film obtained by the colored coating material (X) is 15 μm or more, preferably 15 to 30 μm, and more preferably 15 from the viewpoints of light transmittance, underlying hiding property, metallic glossiness, and the like. It is ~ 25 μm.

The coating of the colored coating material (X) can be carried out according to a usual method. When the colored coating material (X) is a water-based coating material, for example, the colored coating material (X) is coated with defoaming water, and if necessary, a thickener. After adjusting the solid content to about 10 to 60% by mass and the viscosity to 200 to 5000 cps / 6 rpm (B-type viscometer) by adding an additive such as a defoamer, the surface to be coated is spray-painted and rotated. It can be done by atomization coating or the like. At the time of painting, electrostatic application can be performed if necessary.

From the viewpoint of color stability and the like, the colored paint (X) has a black-and-white concealing film thickness of preferably 40 μm or less, more preferably 5 to 35 μm, and even more preferably 10 to 30 μm. In the present specification, the “black and white concealment film thickness” refers to the film thickness after the black and white checkered concealment rate test paper specified in 4.1.2 of JIS K5600-4-1 is attached to a steel sheet. After the paint is graded and dried or cured so that the film thickness changes continuously, the coated surface is visually observed under diffuse daylight, and the black-and-white boundary of the checkered pattern on the concealment test paper becomes invisible. It is a value measured by an electromagnetic film thickness meter.

2. Process (2)
The step (2) is a step of coating the bright pigment dispersion (Y) on the colored coating film formed in the step (1) to form a bright coating film.

The film obtained by coating the glitter pigment dispersion (Y) so as to have a dry film thickness of 0.2 μm has a light transmittance of 0.1 to 40%, preferably 0.5 to 35% at a wavelength of 550 nm. More preferably, it is 1.0 to 30% from the viewpoint of excellent metallic luster and water resistance of the obtained coating film. When the light transmittance at a wavelength of 550 nm is 0.1% or more, the coating film obtained even when the dry film thickness of the bright pigment dispersion (Y) is 0.2 μm has excellent metallic luster. When the light transmittance at a wavelength of 550 nm is 40% or less, the coating film obtained even when the dry film thickness of the bright pigment dispersion (Y) is 0.2 μm has excellent water resistance.

The light transmittance is self-recorded spectrophotometric lightness using a coating film obtained by coating an OHP sheet with a bright pigment dispersion (Y) so as to be 0.2 μm based on a cured coating film and drying at 80 ° C. for 3 minutes as a sample. It is the transmittance when measured in the wavelength range of 550 nm using a meter (Solid Spec 3700 manufactured by Shimadzu Corporation).
Bright pigment dispersion (Y)
The glitter pigment dispersion (Y) contains water, a surface conditioner (A), a vapor-deposited chrome flake pigment (B) and a viscosity conditioner (C).
Surface conditioner (A)
The surface conditioner (A) helps to uniformly orient the vapor-deposited chrome flake pigment (B) dispersed in water on the object to be coated when the bright pigment dispersion is applied to the object to be coated. Used to do.

The surface conditioner (A) is a liquid obtained by mixing isopropanol / water / surface conditioner (A) = 4.5 / 95/1 at a temperature of 20 ° C. and a rotor rotation speed of 60 rpm with a B-type viscometer. The contact angle with respect to the tin plate is 8 to 20 °, preferably 9 when 10 μL is dropped onto a tin plate (manufactured by Partec) that has been adjusted so that the viscosity of the tin plate is 150 mPa · s and degreased in advance, and measured after 10 seconds. Any surface conditioner having a temperature of ~ 19 °, more preferably 10-18 ° can be used without particular limitation.

The isopropanol / water / surface conditioner (A) ratio of 4.5 / 95/1 corresponds to the ratio of the components of the bright pigment dispersion (Y) for evaluation of the surface conditioner. The viscosity of 150 mPa · s at a rotor rotation speed of 60 rpm with a B-type viscometer is a normal value at the time of coating on an object to be coated. Further, the contact angle of 8 to 20 ° with respect to the tin plate indicates the wet spread of the liquid under standard coating conditions. When the contact angle is 8 ° or more, the liquid is coated on the object to be coated without spreading too much, and when the contact angle is 20 ° or less, the liquid is uniformly coated on the object to be coated without repelling too much.

Examples of the surface conditioner (A) include silicone-based, acrylic-based, vinyl-based, and fluorine-based surface conditioners. The above surface conditioners can be used alone or in combination of two or more as appropriate.

Commercially available products of the surface conditioner (A) include, for example, BYK series manufactured by Big Chemie, Tego series manufactured by Evonic, Granol series manufactured by Kyoeisha Chemical Co., Ltd., Polyflow series, and Disparon series manufactured by Kusumoto Kasei Co., Ltd. Be done.

As the surface conditioner (A), a silicone-based surface conditioner is preferable from the viewpoint of metallic luster and water resistance of the obtained coating film. As the silicone-based surface conditioner, polydimethylsiloxane or modified silicone modified from the polydimethylsiloxane is used. Examples of the modified silicone include a modified product of polyether, a modified product of acrylic, and a modified product of polyester.

The surface conditioner (A) preferably has a dynamic surface tension of preferably 50 to 70 mN / m, more preferably 53 to 68 mN / m, and even more preferably 55 to 65 mN / m. In the present specification, the dynamic surface tension refers to the surface tension value at a frequency of 10 Hz by the maximum bubble pressure method. The dynamic surface tension was measured using a SITA measuring device (SITA t60, Eiko Seiki Co., Ltd.).

The static surface tension of the surface conditioner (A) is preferably 15 to 30 mN / m, more preferably 18 to 27 mN / m, and even more preferably 20 to 24 mN / m. The static surface tension was measured using a surface tension measuring machine (Eiko Seiki Co., Ltd. DCAT 21).

Further, the surface conditioner (A) has a lamella length of preferably 6.0 to 9.0 mm, more preferably 6.5 to 8.5 mm, still more preferably 7.0 to 8.0 mm.

The content of the surface conditioner (A) is 0.1 to 10% by mass based on 100 parts by mass of the total amount of water, the surface conditioner (A), the vapor-deposited chromium flake pigment (B) and the viscosity conditioner (C). Parts, preferably 0.2 to 8 parts by mass, more preferably 0.4 to 6 parts by mass.
Thin-film chrome flake pigment (B)
The vapor-deposited chromium flake pigment (B) in the bright pigment dispersion (Y) is obtained by depositing a chromium film on a base base material, peeling off the base base material, and then pulverizing the vapor-deposited chromium film. Examples of the base material include a film and the like.

Examples of commercially available products that can be used as the thin-film vapor-deposited chrome flake pigment include the "Metalure Liquid Black" series (trade name, manufactured by Ecult Co., Ltd.) and the like.

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

The average thickness of the vapor-deposited chrome flake pigment is preferably 0.01 to 1.0 μm, more preferably 0.01 to 0.1 μm.
Viscosity modifier (C)
As the viscosity adjusting agent (C) in the glitter pigment dispersion (Y), known ones can be used. For example, a silica-based fine powder, a mineral-based viscosity adjusting agent, a barium sulfate atomized powder, and a polyamide-based viscosity adjusting agent can be used. , Organic resin fine particle viscosity adjusting agent, diurea type viscosity adjusting agent, urethane association type viscosity adjusting agent, acrylic swelling type polyacrylic acid type viscosity adjusting agent, cellulose type viscosity adjusting agent and the like. Among them, it is particularly preferable to use a mineral-based viscosity modifier, a polyacrylic acid-based viscosity modifier, and a cellulose-based viscosity modifier from the viewpoint of obtaining a coating film having excellent metallic luster.

Examples of the mineral viscosity modifier include a swellable layered silicate having a 2: 1 type structure in its crystal structure. Specifically, smectite clay minerals such as natural or synthetic montmorillonite, saponite, hectorite, stivensite, biderite, nontronite, bentonite, and laponite, Na-type tetrasilicic fluorine mica, and Li-type tetrasilicic fluorine mica. , Na salt-type fluorine teniolite, swellable mica clay minerals such as Li-type fluorine teniolite and vermiculite, substitutions and derivatives thereof, or mixtures thereof.

Examples of the polyacrylic acid-based viscosity modifier include sodium polyacrylate, a polyacrylic acid- (meth) acrylic acid ester copolymer, and the like.

The acid value of the active ingredient of the polyacrylic acid-based viscosity modifier can be in the range of 30 to 300 mgKOH / g, preferably 80 to 280 mgKOH / g. As commercially available products, for example, "Primal ASE-60", "Primal TT615", "Primal RM5" (above, trade name) manufactured by Dow Chemical Co., Ltd., "SN Thickener 613", "SN Thickener 618" manufactured by San Nopco Ltd., Examples thereof include "SN thickener 630", "SN thickener 634", and "SN thickener 636" (hereinafter referred to as product names).

Examples of the cellulosic viscosity modifier include carboxymethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, cellulose nanofibers, and the like, and among them, a coating film having excellent metallic luster can be obtained. From the viewpoint, it is preferable to use cellulose nanofibers.

The cellulose nanofibers may also be referred to as cellulose nanofibrils, fibrated celluloses, or nanocellulose crystals.

From the viewpoint of obtaining a coating film having excellent metallic luster, the cellulose nanofibers have a number average fiber diameter of preferably in the range of 2 to 500 nm, more preferably 2 to 250 nm, and further preferably 2 to 150 nm. The number average fiber length is preferably in the range of 0.1 to 20 μm, more preferably 0.1 to 15 μm, and even more preferably 0.1 to 10 μm. The aspect ratio, which is a value obtained by dividing the number average fiber length by the number average fiber diameter, is preferably in the range of 50 to 10000, more preferably 50 to 5000, and further preferably 50 to 1000.

For the number average fiber diameter and the number average fiber length, for example, a sample obtained by diluting cellulose nanofibers with water is dispersed and cast on a carbon film-coated grid that has been hydrophilized, and this is cast on a transmission electron microscope (transmission electron microscope). It is measured and calculated from the image observed by TEM).

As the cellulose nanofiber, one obtained by defibrating a cellulose raw material and stabilizing it in water can be used.

Further, the cellulose raw material can be anion-modified by a known method, subjected to various treatments, and an aqueous dispersion liquid dispersed in an aqueous solvent can be used. For example, a group such as a carboxyl group or a carboxylmethyl group is introduced into a cellulose raw material by a known method, and the obtained modified cellulose is washed to prepare a dispersion of modified cellulose, and a mechanical shearing force is applied to the dispersion. Cellulose nanofibers can be used by adding and defibrating.

Examples of commercially available cellulose nanofibers include Leocrysta (registered trademark) manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd. In the present invention, for example, cellulose nanofibers prepared as follows can be used.

The cellulose nanofibers can be produced, for example, by the following methods.

A group such as a carboxyl group or a carboxylmethyl group is introduced into a cellulose raw material by a known method, and the obtained modified cellulose is washed to prepare a dispersion of modified cellulose, and a mechanical shearing force is applied to this dispersion. And defibrate.

Here, the cellulose raw material means various forms of materials mainly composed of cellulose, and specifically, for example, pulp (wood pulp, jute, Manila hemp, herbaceous pulp such as Kenaf, etc.); produced by microorganisms. Natural cellulose such as cellulose; regenerated cellulose spun after dissolving cellulose in some solvent such as copper ammonia solution and morpholin derivative; and hydrolysis, alkali hydrolysis, enzymatic decomposition, blasting treatment, vibration ball mill, etc. Examples thereof include fine cellulose obtained by depolymerizing cellulose by mechanical treatment or the like.

The method for defibrating the cellulose raw material is not particularly limited as long as the cellulose raw material maintains the fibrous state. Methods such as treatment and biological treatment using microorganisms can be mentioned.

Further, as the cellulose nanofibers, anion-modified cellulose nanofibers can also be used. Examples of the anion-modified cellulose nanofibers include carboxylated cellulose nanofibers and carboxylmethylated cellulose nanofibers. In the anion-modified cellulose nanofiber, for example, a functional group such as a carboxyl group or a carboxylmethyl group is introduced into a cellulose raw material by a known method, and the obtained modified cellulose is washed to prepare a dispersion liquid of the modified cellulose. This dispersion can be obtained by defibrating. The carboxylated cellulose is also called oxidized cellulose.

The above-mentioned cellulose oxide is obtained, for example, by oxidizing the cellulose raw material in water with an oxidizing agent in the presence of a compound selected from the group consisting of N-oxyl compounds, bromides, and iodides or mixtures thereof. be able to.

The amount of the N-oxyl compound used is not particularly limited as long as it is a catalytic amount capable of converting cellulose into nanofibers. The amount of bromide or iodide used can be appropriately selected as long as the oxidation reaction can be promoted.

As the oxidizing agent, known ones can be used, and for example, halogens, hypochlorous acids, hypochlorous acids, perhalogenic acids or salts thereof, halogen oxides, peroxides and the like can be used. It is preferable to set the condition so that the amount of carboxyl groups in the cellulose oxide is 0.2 mmol / g or more with respect to the solid content mass of the cellulose oxide. The amount of carboxyl groups can be adjusted by adjusting the oxidation reaction time; adjusting the oxidation reaction temperature; adjusting the pH during the oxidation reaction; adjusting the amount of N-oxyl compound, bromide, iodide, oxidizing agent, etc. added. ..

The introduction of the carboxymethyl group can be carried out as follows.

The cellulose raw material and the solvent are mixed, and 0.5 to 20 times mol of alkali metal hydroxide per glucose residue of the cellulose raw material is used as a mercerizing agent, the reaction temperature is 0 to 70 ° C., and the reaction time is 15 minutes to. Mercerization is performed in about 8 hours. Then, 0.05 to 10.0 times the molar amount of carboxymethylating agent is added per glucose residue, and the reaction is carried out at a reaction temperature of 30 to 90 ° C. and a reaction time of 30 minutes to 10 hours to add a carboxymethyl group to the hydroxyl group in the cellulose molecule. Can be introduced.

The degree of carboxymethyl substitution per glucose unit in the modified cellulose obtained by introducing a carboxymethyl group into the cellulose raw material is preferably 0.02 to 0.50.

The modified cellulose obtained as described above can be defibrated using a pulverizer after being prepared as a dispersion in an aqueous solvent. The crusher used may be any of high-speed shear type, collision type, bead mill type, high-speed rotary type, colloid mill type, high-pressure type, roll mill type, and ultrasonic type. Further, a plurality of these can be used in combination. Among these, it is preferable to use a high-speed shearing type, a collision type, or a high-speed rotating type defibrating device from the viewpoint that a stronger shearing force can be processed under conditions where the risk of contamination by media is low.

The content of the cellulosic viscosity modifier in the bright pigment dispersion (Y) is 2 to 150 mass by mass based on 100 parts by mass of the vapor-deposited chrome flake pigment content from the viewpoint of obtaining a coating film having excellent metallic luster. It is preferably in the range of parts, more preferably in the range of 3 to 120 parts by mass, and particularly preferably in the range of 4 to 100 parts by mass.

These viscosity modifiers can be used alone or in combination of two or more as appropriate.

The glittering pigment dispersion (Y) further includes an organic solvent, a pigment other than the vapor-deposited chrome flake pigment (B), a pigment dispersant, an anti-precipitation agent, a defoaming agent, an ultraviolet absorber, and the surface thereof, if necessary. A surface conditioner or the like other than the adjuster (A) may be appropriately added.

The bright pigment dispersion (Y) can contain a substrate resin and a cross-linking agent from the viewpoint of the adhesiveness of the obtained coating film, but the effect of the present invention can be exhibited even if these are not substantially contained. can.

Examples of the base resin include acrylic resin, polyester resin, alkyd resin, urethane resin and the like.

Examples of the cross-linking agent include melamine resin, melamine resin derivative, urea resin, (meth) acrylamide, polyaziridine, polycarbodiimide, and polyisocyanate compounds which may or may not be blocked. These may be used alone or in combination of two or more.

When the bright pigment dispersion (Y) contains a base resin and / or a cross-linking agent, the vapor-deposited chromium flake pigment (B) / (total of the base resin and the cross-linking agent) = 1/1 to 100 based on the solid content mass. It is in the range of 1/1, preferably 3/1 to 50/1, and more preferably 5/1 to 10/1.

Blending Amount of Each Component of Bright Pigment Dispersion (Y) The bright pigment dispersion (Y) contains water, a surface conditioner (A), a vapor-deposited chrome flake pigment (B) and a viscosity conditioner (C). The blending ratio (mass of solid content) of each component in the bright pigment dispersion (Y) is preferably within the following range from the viewpoint of obtaining a coating film having excellent metallic luster.

Based on 100 parts by mass of the total amount of water, surface conditioner (A), vapor-deposited chrome flake pigment (B) and viscosity conditioner (C).
Water: 70 to 99 parts by mass, preferably 80 to 99 parts by mass, more preferably 90 to 99 parts by mass,
Surface modifier (A): 0.1 to 10 parts by mass, preferably 0.2 to 8 parts by mass, more preferably 0.4 to 6 parts by mass.
Vapor-deposited chrome flake pigment (B): 0.05 to 3.0 parts by mass, preferably 0.1 to 2.0 parts by mass, more preferably 0.15 to 1.0 parts by mass Viscosity adjuster (C): 0 .1 to 30 parts by mass, preferably 0.5 to 20 parts by mass, more preferably 1.0 to 10 parts by mass.

Alternatively or additionally, the blending ratio (solid content mass) of each component is preferably within the following range from the viewpoint of obtaining a coating film having excellent metallic luster.

For the bright pigment dispersion (Y)
Water: 70-99% by mass, preferably 80-99% by mass, more preferably 90-99% by mass,
Surface conditioner (A): 0.1 to 10% by mass, preferably 0.2 to 8% by mass, more preferably 0.4 to 6% by mass,
Thin-film chrome flake pigment (B): 0.05 to 3.0% by mass, preferably 0.1 to 2.0% by mass, more preferably 0.15 to 1.0% by mass.
Viscosity modifier (C): 0.1 to 30% by mass, preferably 0.5 to 20% by mass, more preferably 1.0 to 10% by mass.

The contact angle of the bright pigment dispersion (Y) is 8 to 20 °, preferably 10 to 18 °, from the viewpoint of obtaining a coating film having excellent metallic luster. At this time, the contact angle meter used is CA-X150 manufactured by Kyowa Interface Science Co., Ltd., and the viscosity of the bright pigment dispersion (Y) is 150 mPa · s at a rotor rotation speed of 60 rpm with a B-type viscometer. Refers to the value measured after 10 seconds have passed by dropping 10 μL onto a tin plate (manufactured by Partec) that has been degreased in advance.

Coating of Bright Pigment Dispersion (Y) The bright pigment dispersion (Y) is prepared by mixing and dispersing the above-mentioned components. From the viewpoint of obtaining a coating film having excellent metallic luster, the solid content at the time of coating is set to 0.1 to 15% by mass, preferably 0.2 to 5.0, based on the bright pigment dispersion (Y). It is preferable to adjust the mass%.

The viscosity of the bright pigment dispersion (Y) is the viscosity after 1 minute at 60 rpm measured by a B-type viscometer at a temperature of 20 ° C. from the viewpoint of obtaining a coating film having excellent metallic luster (in the present specification, "B60 value". ”) Is 60 to 1500 mPa · s, preferably 60 to 1000 mPa · s, and more preferably 60 to 500 mPa · s. At this time, the viscometer used is LVDV-I (trade name, manufactured by BROOKFIELD, B-type viscometer).

The glitter pigment dispersion (Y) can be coated by a method such as electrostatic coating, air spray, or airless spray. In the method for forming a multi-layer coating film of the present invention, rotary atomization type electrostatic coating is particularly preferable.

It is preferable that the glitter coating film obtained by coating the glitter pigment dispersion (Y) is dry. The method for drying the brilliant coating film is not particularly limited, and examples thereof include a method of leaving at room temperature for 15 to 30 minutes, a method of preheating at a temperature of 50 to 100 ° C. for 30 seconds to 10 minutes, and the like.

The film thickness 30 seconds after the glitter pigment dispersion (Y) adheres to the object to be coated is preferably 3 to 25 μm, more preferably 4 to 24 μm, from the viewpoint of obtaining a coating film having excellent metallic luster. More preferably, it is 5 to 23 μm.

The thickness of the brilliant coating film is preferably 0.02 to 2.0 μm, more preferably 0.04 to 2.0 μm as a dry film thickness.
3. 3. Process (3)
The step (3) is a step of applying the clear coating film (Z) on the brilliant coating film formed in the step (2) to form a clear coating film.
Clear paint (Z)
As the clear paint (Z), any known thermosetting clear coat paint composition can be used. Examples of the thermosetting clear coat coating composition include an organic solvent type thermosetting coating composition containing a base resin having a crosslinkable functional group and a curing agent, an aqueous thermosetting coating composition, and powder thermosetting. Sexual paint compositions and the like can be mentioned.

Examples of the crosslinkable functional group contained in the substrate resin include a carboxyl group, a hydroxyl group, an epoxy group, and a silanol group. Examples of the type of the base resin include acrylic resin, polyester resin, alkyd resin, urethane resin, epoxy resin, fluororesin and the like. Examples of the curing agent include polyisocyanate compounds, blocked polyisocyanate compounds, melamine resins, urea resins, carboxyl group-containing compounds, carboxyl group-containing resins, epoxy group-containing resins, and epoxy group-containing compounds.

The combination of the base resin / curing agent of the clear paint (Z) includes a carboxyl group-containing resin / epoxy group-containing resin, a hydroxyl group-containing resin / polyisocyanate compound, a hydroxyl group-containing resin / blocked polyisocyanate compound, and a hydroxyl group-containing resin / melamine resin. Etc. are preferable
Further, the clear paint (Z) may be a one-component paint or a multi-component paint such as a two-component urethane resin paint.

Among them, the clear coating material (Z) is preferably a two-component clear coating material containing a hydroxyl group-containing resin and an isocyanate group-containing compound from the viewpoint of the adhesiveness of the obtained coating film.

When a two-component clear paint containing a hydroxyl group-containing resin and an isocyanate group-containing compound is used as the clear paint (Z), it is preferable that the hydroxyl group-containing resin and the polyisocyanate compound are separated from each other in terms of storage stability. , Both are mixed and prepared immediately before use.

When a one-component paint is used as the clear paint (Z), the combination of the base resin / curing agent in the one-component paint includes a carboxyl group-containing resin / epoxy group-containing resin, a hydroxyl group-containing resin / blocked polyisocyanate compound, and a hydroxyl group. There are contained resin / melamine resin and the like. When a one-component paint is used as the clear paint (Z), it is preferable that the clear paint (Z) contains a self-crosslinking component from the viewpoint of adhesiveness.

Examples of the self-crosslinking component include melamine resin, melamine resin derivative, (meth) acrylamide, polyaziridine, polycarbodiimide, polyisocyanate which may or may not be blocked, and the like. These may be used alone or in combination of two or more.

If necessary, a solvent such as water or an organic solvent, a curing catalyst, an antifoaming agent, an additive such as an ultraviolet absorber, and the like can be appropriately added to the clear paint (Z).
Hydroxy Group-Containing Resin As the hydroxyl group-containing resin, conventionally known resins can be used without limitation as long as they contain hydroxyl groups. Examples of the hydroxyl group-containing resin include a hydroxyl group-containing acrylic resin, a hydroxyl group-containing polyester resin, a hydroxyl group-containing polyether resin, and a hydroxyl group-containing polyurethane resin, and preferred examples thereof include a hydroxyl group-containing acrylic resin and a hydroxyl group-containing polyester resin. A hydroxyl group-containing acrylic resin can be mentioned as a particularly preferable one.

The hydroxyl value of the hydroxyl group-containing acrylic resin is preferably in the range of 80 to 200 mgKOH / g, and more preferably in the range of 100 to 180 mgKOH / g. When the hydroxyl value is 80 mgKOH / g or more, the crosslink density is high and the scratch resistance is sufficient. Further, when it is 200 mgKOH / g or less, the water resistance of the coating film is maintained.

The weight average molecular weight of the hydroxyl group-containing acrylic resin is preferably in the range of 2,500 to 40,000, and more preferably in the range of 5,000 to 30,000. When the weight average molecular weight is 2500 or more, the coating film performance such as acid resistance is good, and when it is 40,000 or less, the smoothness of the coating film is maintained, so that the finish is good.

In this specification, the average molecular weight is a value calculated from a chromatogram measured by a gel permeation chromatograph based on the molecular weight of standard polystyrene. As the gel permeation chromatograph, "HLC8120GPC" (manufactured by Tosoh Corporation) was used. As columns, four columns, "TSKgel G-4000HXL", "TSKgel G-3000HXL", "TSKgel G-2500HXL", and "TSKgel G-2000HXL" (all manufactured by Tosoh Corporation, trade name) were used. Mobile phase; tetrahydrofuran, measurement temperature; 40 ° C., flow rate; 1 cc / min, detector; RI conditions.

The glass transition temperature of the hydroxyl group-containing acrylic resin is preferably in the range of −40 ° C. to 20 ° C., particularly preferably −30 ° C. to 10 ° C. When the glass transition temperature is −40 ° C. or higher, the coating film hardness is sufficient, and when the glass transition temperature is 20 ° C. or lower, the coating surface smoothness of the coating film is maintained.
Polyisocyanate compound A polyisocyanate compound is a compound having at least two isocyanate groups in one molecule, and is, for example, an aliphatic polyisocyanate, an alicyclic polyisocyanate, an aromatic aliphatic polyisocyanate, an aromatic polyisocyanate, or the like. Examples thereof include derivatives of polyisocyanates.

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, and 1,3. An aliphatic diisocyanate such as −butylene diisocyanate, 2,4,4- or 2,2,4-trimethylhexamethylene diisocyanate, diisocyanate dimerate, methyl 2,6-diisocyanatohexanate (common name: lysine diisocyanate); 2 , 6-Diisocyanatohexanoic acid 2-isocyanatoethyl, 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, etc. Can be mentioned.

Examples of the alicyclic polyisocyanate include 1,3-cyclopentenediisocyanate, 1,4-cyclohexanediisocyanate, 1,3-cyclohexanediisocyanate, and 3-isocyanatomethyl-3,5,5-trimethylcyclohexylisocyanate (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 (isocyanato) Alicyclic diisocyanates such as methyl) cyclohexane (common name: hydrogenated xylylene diisocyanate) or a mixture thereof, methylenebis (4,1-cyclohexanediyl) diisocyanate (common name: hydrogenated MDI), norbornan 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) Examples of alicyclic triisocyanates such as heptane can be mentioned.

Examples of the aromatic aliphatic polyisocyanate include methylenebis (4,1-phenylene) diisocyanate (common name: MDI), 1,3- or 1,4-xylylene diisocyanate or a mixture thereof, ω, ω'-diisocyanato-. Arophilic aliphatic diisocyanates such as 1,4-diethylbenzene, 1,3- or 1,4-bis (1-isocyanato-1-methylethyl) benzene (common name: tetramethylxylylene diisocyanate) or a mixture thereof; 1,3 , 5-Arophilic aliphatic triisocyanates such as triisocyanatomethylbenzene can be mentioned.

Examples of the aromatic polyisocyanate include m-phenylene diisocyanate, p-phenylenedi isocyanate, 4,4'-diphenyldiisocyanate, 1,5-naphthalenediisocyanate, and 2,4-tolylene diisocyanate (common name: 2,4-tolylene diisocyanate). TDI) or 2,6-tolylene diisocyanate (common name: 2,6-TDI) or a mixture thereof, aromatic diisocyanates such as 4,4'-toluene diisocyanate, 4,4'-diphenyl ether diisocyanate; triphenylmethane-4 , 4', 4''-triisocyanate, 1,3,5-triisocyanatobenzene, 2,4,6-triisocyanatotoluene and other aromatic triisocyanates; 4,4'-diphenylmethane-2,2' , 5, 5'-Aromatic tetraisocyanates such as tetraisocyanates can be mentioned. Examples of the polyisocyanate derivative include the above-mentioned polyisocyanate dimer, trimmer, biuret, allophanate, uretdione, uretoimine, isocyanurate, oxadiazine trione, and polymethylene polyphenyl polyisocyanate (Crude MDI, Polymeric MDI). , Crude TDI and the like. The polyisocyanate derivative may be used alone or in combination of two or more.

The polyisocyanate and its derivatives may be used alone or in combination of two or more.

Hexamethylene diisocyanate compounds can be preferably used among the aliphatic diisocyanates, and 4,4'-methylenebis (cyclohexyl isocyanate) can be preferably used among the alicyclic diisocyanates. Among them, the hexamethylene diisocyanate derivative is particularly suitable from the viewpoint of adhesion, compatibility and the like.

Further, as the polyisocyanate compound, the polyisocyanate and its derivative are reacted with a compound capable of reacting with the polyisocyanate, for example, a compound having an active hydrogen group such as a hydroxyl group or an amino group, under a condition of excess isocyanate group. Prepolymers may be used. Examples of the compound capable of reacting with the polyisocyanate include polyhydric alcohols, low molecular weight polyester resins, amines, water and the like.

Further, as the polyisocyanate compound, a blocked polyisocyanate compound which is a compound in which the isocyanate group in the polyisocyanate and its derivative is blocked with a blocking agent can also be used.

Examples of the blocking agent include phenol-based agents such as phenol, cresol, xylenol, nitrophenol, ethylphenol, hydroxydiphenyl, butylphenol, isopropylphenol, nonylphenol, octylphenol, and methyl hydroxybenzoate; Oximes such as γ-butyrolactam and β-propiolactam; aliphatic alcohols such as methanol, ethanol, propyl alcohol, butyl alcohol, amyl alcohol and lauryl alcohol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono Ether systems such as butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, propylene glycol monomethyl ether, and methoxymethanol; benzyl alcohol, glycolic acid, methyl glycolate, ethyl glycolate, butyl glycolate, lactic acid, methyl lactate, ethyl lactate, lactic acid. Alcohols such as butyl, methylolurea, methylolmelamine, diacetone alcohol, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate; formamide oxime, acetamide oxime, acetoxime, methyl ethyl ketooxime, diacetyl monooxime, benzophenone oxime, cyclohexane oxime, etc. Oxime-based; active methylene-based 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, ethylthiophenol; acidamides such as acetoanilide, acetoaniside, acetotolide, acrylamide, methacrylicamide, acetateamide, stearate amide, benzamide; succinide imide, phthalateimide, maleateimide, etc. Imid system; amine system such as diphenylamine, phenylnaphthylamine, xylidine, N-phenylxylidine, carbazole, aniline, naphthylamine, butylamine, dibutylamine, butylphenylamine; imidazole system such as imidazole, 2-ethylimidazole; urea, thio Urea, ethylene urea, ethylenethiourea, dipheni Urea-based such as luurea; carbamic acid ester-based such as phenyl N-phenylcarbamic acid; imine-based such as ethyleneimine and propyleneimine; sulfite-based such as sodium bisulfite and potassium bisulfite; azole-based compounds, etc. Be done. Examples of the azole compound 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 , 2-Pyrazole imidazoline and other imidazoline derivatives and the like. When blocking (reacting the blocking agent), a solvent can be added as needed. The solvent used for the blocking reaction may be one that is not reactive with the isocyanate group. For example, acetone, ketones such as methyl ethyl ketone, esters such as ethyl acetate, and N-methyl-2-pyrrolidone (NMP). Such solvents can be mentioned.

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

The polyisocyanate compound can be used alone or in combination of two or more.

When a two-component clear paint containing a hydroxyl group-containing resin and an isocyanate group-containing compound is used as the clear paint (Z), the hydroxyl group of the hydroxyl group-containing resin and the polyisocyanate compound are used from the viewpoint of curability and scratch resistance of the coating film. The isocyanate group equivalent ratio (NCO / OH) of is preferably in the range of 0.5 to 2.0, more preferably 0.8 to 1.5.

The clear paint (Z) can appropriately contain a coloring pigment as long as the transparency is not impaired. As the coloring pigment, one kind or a combination of two or more kinds of pigments conventionally known for inks and paints can be used. The amount to be added may be appropriately determined, but is preferably 30 parts by mass or less, more preferably 0.01 to 10 parts by mass, based on 100 parts by mass of the vehicle-forming resin composition in the clear paint (Z). be.

The form of the clear coating material (Z) is not particularly limited, but it is usually used as an organic solvent type coating composition. As the organic solvent used in this case, various organic solvents for coating materials, for example, aromatic or aliphatic hydrocarbon solvents; ester solvents; ketone solvents; ether solvents and the like can be used. As the organic solvent to be used, the one used at the time of preparation of the hydroxyl group-containing resin or the like may be used as it is, or may be further added as appropriate.

The solid content concentration of the clear coating material (Z) is preferably in the range of about 30 to 70% by mass, more preferably in the range of about 40 to 60% by mass.

The above-mentioned clear paint (Z) is applied onto the brilliant coating film. The clear paint (Z) is not particularly limited and can be applied by the same method as the base coat paint. For example, the clear paint (Z) can be applied by a coating method such as air spray, airless spray, rotary atomization coating, or curtain coating coating. .. These coating methods may be electrostatically applied, if necessary. Of these, rotary atomization coating by electrostatic application is preferable. The amount of the clear paint (Z) applied is usually preferably such that the cured film thickness is about 10 to 50 μm.

Further, in the coating of the clear coating material (Z), the viscosity of the clear coating material (Z) is set to a viscosity range suitable for the coating method, for example, in the rotary atomization coating by electrostatic application, the Ford Cup No. 4 It is preferable to appropriately adjust the viscosity by using a solvent such as an organic solvent so that the viscosity range is about 15 to 60 seconds as measured by a viscometer.

After the clear paint (Z) is applied to form a clear coating film, preheating may be performed at a temperature of about 50 to 80 ° C. for about 3 to 10 minutes in order to promote the volatilization of volatile components. ..
4. Process (4)
In step (4), these three coating films are formed by heating the uncured colored coating film, the uncured brilliant coating film, and the uncured clear coating film formed in steps (1) to (3). Is a step of curing at the same time.

Heating can be performed by known means, and for example, a drying furnace such as a hot air furnace, an electric furnace, or an infrared induction heating furnace can be applied.

The heating temperature is preferably in the range of 70 to 150 ° C, preferably 80 to 140 ° C.

The heating time is not particularly limited, but is preferably in the range of 10 to 40 minutes, more preferably 20 to 30 minutes.

A multi-layer coating film is formed by sequentially performing the above steps (1) to (4).

The appearance of the obtained multi-layer coating film can be evaluated by graininess, mirror gloss (60 ° gloss), water resistance, visual metallic appearance, and the like. Further, the jet blackness can be evaluated by the L * 45 value and the b * 15 value.

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

Details of the surface conditioner (A) used for producing the glitter pigment dispersion (Y) described later are shown below. (A-1) to (A-4) are all commercially available surface conditioners.
(A-1) Product name "BYK348", manufactured by BYK, silicone-based surface conditioner, contact angle 13 °, dynamic surface tension 63.9 mN / m, static surface tension 22.2 mN / m, lamella length 7.45 mm , Non-volatile content 100% by mass
(A-2) Product name "BYK346", manufactured by BYK, silicone-based surface conditioner Contact angle 12 °, dynamic surface tension 51.5 mN / m, static surface tension 21.6 mN / m, lamella length 7.40 mm , Non-volatile content 100% by mass
(A-3) Product name "BYK347", manufactured by BYK, silicone-based surface conditioner, contact angle 14 °, dynamic surface tension 68.7 mN / m, static surface tension 21.9 mN / m, lamella length 7.46 mm , Non-volatile content 100% by mass
(A-4) Product name "BYK381", manufactured by BYK, acrylic surface conditioner, contact angle 39 °, dynamic surface tension 71.3 mN / m, static surface tension 38.8 mN / m, lamella length 7.55 mm , Non-volatile content 100% by mass
The contact angle is the viscosity of a liquid mixed with isopropanol / water / surface conditioner (A) = 4.5 / 95/1 at a temperature of 20 ° C. and a rotor rotation speed of 60 rpm with a B-type viscometer. Adjust to 150 mPa · s, drop 10 μL on a pre-defatted tin plate (manufactured by Paltec), and measure using a contact angle meter (CA-X150, trade name, manufactured by Kyowa Interface Science Co., Ltd.) after 10 seconds. It is the contact angle with respect to the tin plate when it is used.
1. 1. Production of Bright Pigment Dispersion (Y) Production Example 1
95 parts by mass of distilled water, 1.0 part by mass of surface conditioner (A-1), Metalule Liquid Black (aqueous vaporized chrome flake pigment, manufactured by Eckart, solid content: 10%, internal solvent: propylene glycol monomethyl ether, average Particle size D50: 14 μm, thickness: 0.03 μm,) 5.5 parts by mass (0.55 parts by solid content), Acrysol ASE-60 (polyacrylic acid viscosity modifier, manufactured by Dow Chemical Co., Ltd., solid content: (28%) 1.8 parts by mass (0.49 parts by mass in terms of solid content) and 0.18 parts by mass of dimethylethanolamine were mixed and mixed by stirring to prepare a brilliant pigment dispersion (Y-1).

Production Examples 2 to 17
Glitter pigment dispersions (Y-2) to (Y-17) were obtained in the same manner as in Production Example 1 except for the formulations shown in Table 1. Each component in the table is shown by mass, and the value in parentheses at the bottom is the actual content. The viscosity (B60 value) of each of the obtained brilliant pigment dispersions and the wavelength of 550 nm of the film obtained by coating each of the obtained brilliant pigment dispersions (Y) so as to have a dry film thickness of 0.2 μm. The light transmittance of is also shown in Table 1.

The details of the resin in the table are as follows.
"Simel 325" Product name: Ornex Japan, melamine resin "Implafix 2794XP" Product name: Sumika Bayer Urethane, blocked polyisocyanate compound "HR517" Product name: Mitsubishi Rayon, Butoxyacrylamide Production Example 18
A brilliant pigment dispersion (Y-18) was obtained in the same manner as in Production Example 1 except for the formulations shown in Table 1. The viscosity (B60 value) of each of the obtained brilliant pigment dispersions and the wavelength of 550 nm of the film obtained by coating each of the obtained brilliant pigment dispersions (Y) so as to have a dry film thickness of 0.2 μm. The light transmittance of is also shown in Table 1.

Production example 19
A brilliant pigment dispersion (Y-18) was obtained in the same manner as in Production Example 1 except for the formulations shown in Table 1. The viscosity (B60 value) of each of the obtained brilliant pigment dispersions and the wavelength of 550 nm of the film obtained by coating each of the obtained brilliant pigment dispersions (Y) so as to have a dry film thickness of 0.2 μm. The light transmittance of is also shown in Table 1.

The substrate resin in the table of Production Example 19 was produced as follows.

A mixed solvent of 27.5 parts of methoxypropanol and 27.5 parts of isobutanol was put in a reaction vessel equipped with a thermometer, a thermostat, a stirrer, a reflux cooler and a dropping device, heated to 110 ° C, and then kept at 110 ° C. However, 25 parts of styrene, 27.5 parts of n-butyl methacrylate, 20 parts of branched higher alkyl acrylate (trade name "isostearyl acrylate", manufactured by Osaka Organic Chemical Industry Co., Ltd.), 7.5 parts of 4-hydroxybutyl acrylate, below. 121.5 parts of a mixture consisting of 15 parts of a phosphoric acid group-containing polymerizable monomer, 12.5 parts of 2-methacryloyloxyethyl acid phosphate, 10 parts of isobutanol and 4 parts of tert-butylperoxyoctanoate was added over 4 hours. The mixture was added dropwise to the mixed solvent, and a mixture consisting of 0.5 part of tert-butylperoxyoctanoate and 20 parts of isopropanol was further added dropwise for 1 hour. Then, it was stirred and aged for 1 hour to obtain a phosphoric acid group-containing resin solution having a solid content of 50%. The phosphoric acid group-containing resin had an acid value of 83 mgKOH / g, a hydroxyl value of 29 mgKOH / g, and a weight average molecular weight of 10,000.

Phosphoric acid 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, a thermostat, a stirrer, a reflux condenser and a dropping device, and the temperature was raised to 90 ° C. Then, 42.5 parts of glycidyl methacrylate was added dropwise over 2 hours, and the mixture was further stirred and aged for 1 hour. Then, 59 parts of isopropanol was added to obtain a phosphate group-containing polymerizable monomer solution having a solid content of 50%. The acid value of the obtained monomer was 285 mgKOH / g.
2. Preparation of the object to be coated 1 The cationic electrodeposition paint "Eleklon 9400HB" (trade name: Kansai Paint Co., Ltd., amine-modified epoxy resin type) is applied to a steel plate (JISG3141, size 400 x 300 x 0.8 mm) that has been degreased and treated with zinc phosphate. A cationic resin using a block polyisocyanate compound as a curing agent) is electrodeposited based on a cured coating film so as to have a film thickness of 20 μm, heated at 170 ° C. for 20 minutes, crosslinked and cured, and the object to be coated 1 Got
3. 3. Preparation of test plate Example 1
Colored paint (X-1) "WP-522H N-2.0 Dark Gray" (trade name, manufactured by Kansai Paint Co., Ltd., polyester resin-based water-based intermediate coating paint, L * value of the obtained coating film) on the object to be coated 1. : 20) was electrostatically coated using a rotary atomization type bell-type coating machine so that the cured film thickness was 20 μm, left for 3 minutes, preheated at 80 ° C. for 3 minutes, and further, as described above. The brilliant pigment dispersion (Y-1) prepared as described above was adjusted to the coating viscosity shown in Table 1, and dried and coated using a robot bell manufactured by ABB under the conditions of a booth temperature of 23 ° C. and a humidity of 68%. The film was coated so as to have a thickness of 0.1 μm. Then, it was left at 80 ° C. for 3 minutes, and then the clear paint (Z-1) "KINO6500" (trade name: Kansai Paint Co., Ltd., hydroxyl group / isocyanate group curable acrylic resin / urethane resin type) was applied to this dry coated surface. The two-component organic solvent type paint) was coated with a robot bell manufactured by ABB as a dry coating film at a booth temperature of 23 ° C. and a humidity of 68% so as to have a thickness of 25 to 35 μm. After coating, the mixture was left at room temperature for 15 minutes and then heated at 140 ° C. for 30 minutes using a hot air circulation type drying oven to simultaneously dry the multi-layer coating film to obtain a test plate.

Here, the film thickness of the dry coating film shown in Table 2 was calculated from the following formula. The same applies to the following examples.
x = sc / sg / S * 10000
x: Film thickness [μm]
sc: Coated solid content [g]
sg: Coating film specific density [g / cm ³ ]
S: Evaluation area of coated solid content [cm2]

Examples 2 to 13, Comparative Examples 1 to 7
A test plate was obtained in the same manner as in Example 1 except that the objects to be coated and the paint shown in Table 2 were used. The clear paints (Z-2) to (Z-5) in the table are as follows.
(Z-2): "KINO1210" (trade name: Kansai Paint Co., Ltd., acid / epoxy curable acrylic resin-based one-component organic solvent type paint).
(Z-3): A coating material in which 0.2 part of Cymel 325 is added as a solid content to 100 parts by mass of the resin solid content contained in the above (Z-2).
(Z-4): "TC-71" (trade name: Kansai Paint Co., Ltd., hydroxyl group-containing resin / melamine resin-based one-component organic solvent type paint).
(Z-5): "KINO 6500 Black Color Clear" (Product name: Kansai Paint Co., Ltd., hydroxyl group / isocyanate group curable acrylic resin / urethane resin two-component organic solvent type paint, containing black pigment)
.. Evaluation of coating film The appearance and performance of the coating film were evaluated for each test plate obtained as described above, and the results are shown in Table 2. The appearance of the coating film was evaluated by graininess, mirror gloss (60 ° gloss), L * 45 value, b * 15 value, visual inspection, and water resistance.

As shown in Table 2, in Comparative Examples 1 to 4, the graininess and visual graininess of the coating film were inferior to those of the coating films of Examples 1 to 13. In Comparative Example 5, the visual graininess of the coating film was inferior to that of the coating films of Examples 1 to 13. Further, the coating films of Comparative Examples 2 to 5 were inferior in jet blackness. In Comparative Example 6, a dry coating film of a bright pigment dispersion having a thickness of 2.1 μm was required to exhibit the same metallic luster, water resistance and jet blackness as in Example 1. The coating film of Comparative Example 7 was inferior in water adhesion resistance.
Particle feeling The particle feeling is represented by a Hi-light Grainines value (hereinafter, abbreviated as “HG value”). The HG value is one of the measures of the microscopic brilliance when the coating film surface is microscopically observed, and is an index showing the graininess in the highlight. The HG value is calculated as follows. First, the coating surface is photographed with a CCD camera at an incident angle of light of 15 degrees and a light receiving angle of 0 degrees, and the obtained digital image data (two-dimensional luminance distribution data) is subjected to two-dimensional Fourier transform processing to obtain power. Obtain a spectral image. Next, the measurement parameters obtained by extracting only the spatial frequency region corresponding to the grain feeling from this power spectrum image are further taken with a numerical value of 0 to 100, and a linear relationship with the grain feeling is established. The value converted so as to be maintained is the HG value. The HG value is a value in which 0 is defined as having no graininess of the glittering pigment, and 100 is defined as having the largest graininess of the glittering pigment.

When the graininess HG is 10 to 40, it is preferable from the viewpoint of the density of the metallic coating film.
Mirror gloss (60 ° gloss)
The 60 ° gloss value of the test plate obtained above was measured using a gloss meter (micro-TRI-gloss, manufactured by BYK-Gardner). The higher the value, the better the metallic luster.

When the 60-degree mirror glossiness of the multi-layer coating film obtained by forming a brilliant coating film on the colored coating film and further forming the coating film on the colored coating film is 150 to 240 degrees, a high glossiness point is obtained. Is preferable.
L * 45 value The L * 45 value refers to the brightness of the (face) in the L * a * b * color system, and refers to a multi-angle spectrophotometer (“MA-68II”, trade name, manufactured by X-Light Co., Ltd.). It is the L * value measured for the light received at an angle of 45 ° from the normal reflection angle to the direction of the measurement light by irradiating the measurement light from an angle of 45 ° with respect to the axis perpendicular to the surface to be measured. If the L * 45 value is 30 or less, it means that the face of the coating film is dark and jet-black.
b * 15 value The b * 15 value refers to the yellowish and bluish highlights in the L * a * b * color system, and is a multi-angle spectrophotometer (“MA-68II”, trade name, X-light Co., Ltd.). The b * value measured for the light received at an angle of 15 ° in the direction of the measurement light from the normal reflection angle by irradiating the measurement light from an angle of 45 ° to the axis perpendicular to the measurement target surface. Is. The smaller the b * 15 value, the less yellowish the coating film is and the better the jet blackness is.
Immerse the water resistance test plate in warm water at 80 ° C for 5 hours, and immediately after pulling it up, cut the multi-layer coating film of the test plate in a grid pattern with a cutter so that it reaches the substrate, and make 100 Goban eyes with a size of 2 mm x 2 mm. make. Subsequently, an adhesive cellophane tape was attached to the surface thereof, and the residual state of the Goban-grain coating film after the tape was rapidly peeled off at 20 ° C. was examined, and the water resistance was evaluated according to the following criteria. Pass is acceptable and File is unacceptable.
Pass: 100 Goban-mesh coatings remain, and no small borders of the coating film occur at the cut edge of the cutter File: The number of Goban-mesh coatings remaining is 99 or less.
Visual metallic feeling The test plate obtained above was observed outdoors on a sunny day at different angles with respect to external light, and the grain feeling and the difference in brightness between the highlight region and the shade region were evaluated. The smaller the graininess and the larger the difference in brightness (flip-flop property: FF property) between the highlight region and the shade region, the better the metallic tone of the coating film. The evaluation was made by a total of 5 people, 2 designers and 3 engineers who have been engaged in color development for 3 years or more, with a maximum of 5 points, and the average score was adopted.
5: Small graininess (HG <45), excellent FF property, and neutral color change (b * ≤ 0) from highlight to shade like tantalum 4: Slightly small graininess (HG <45) , Excellent FF property, neutral color change (b * ≤ 0) from highlight to shade like tantalum 3: Large grain feeling (HG ≥ 45), excellent FF property, highlight like tantalum Neutral color change (b * ≦ 0) from to shade 2: The graininess is small (HG <45), the FF property is inferior, and the color changes from highlight to shade. Especially the highlight is yellowish (b *> 0).
1: The graininess is large (HG ≧ 45), the FF property is inferior, and the color changes from the highlight to the shade. Especially the highlight is yellowish (b *> 0).

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 based on the technical idea of the present invention are possible.

For example, the configurations, methods, processes, shapes, materials, numerical values, etc. given in the above-described embodiments and examples are merely examples, and if necessary, different configurations, methods, processes, shapes, materials, numerical values, etc. May be used.

In addition, the configurations, methods, processes, shapes, materials, numerical values, and the like of the above-described embodiments can be combined with each other as long as they do not deviate from the gist of the present invention.

In addition, the present invention can also adopt the following configurations.
[1] The following steps (1) to (4):
(1) A step of applying a colored paint (X) on an object to be coated to form a colored coating film.
(2) A step of coating the bright pigment dispersion (Y) on the colored coating film formed in the step (1) to form a bright coating film.
(3) A step of applying a clear coating film (Z) on the glittering coating film formed in the step (2) to form a clear coating film.
(4) By heating the uncured colored coating film, the uncured brilliant coating film, and the uncured clear coating film formed in the steps (1) to (3), these three coating films are cured at the same time. It is a method of forming a multi-layer coating film by sequentially performing the steps of making the coating film.
The glitter pigment dispersion (Y) contains water, a surface conditioner (A), a vapor-deposited chrome flake pigment (B) and a viscosity conditioner (C).
A liquid in which the surface conditioner (A) is mixed at a ratio of isopropanol / water / surface conditioner (A) = 4.5 / 95/1 is mixed at a temperature of 20 ° C. and a rotor rotation speed of 60 rpm with a B-type viscometer. Surface adjustment that the contact angle with the tin plate is 8 to 20 ° when 10 μL is dropped onto a tin plate (manufactured by Partec) that has been degreased in advance and measured after 10 seconds. Agent (A)
A method for forming a multi-layer coating film having a light transmittance of 0.1 to 40% at a wavelength of 550 nm of a film obtained by coating a glitter pigment dispersion (Y) so as to have a dry film thickness of 0.2 μm.
[2] The compound according to [1], wherein the bright pigment dispersion (Y) has a viscosity (B60) of 60 to 1500 mPa · s at a rotor rotation speed of 60 rpm with a B-type viscometer at a temperature of 20 ° C. Layer coating method.
[3] Described in [1] or [2], wherein the surface conditioner (A) is a silicone-based surface conditioner, an acrylic-based surface conditioner, a vinyl-based surface conditioner, or a fluorine-based surface conditioner. Method for forming a multi-layer coating film.
[4] The method for forming a multi-layer coating film according to any one of [1] to [3], wherein the surface conditioner (A) is a silicone-based surface conditioner.
[5] The method for forming a multi-layer coating film according to any one of [1] to [4], wherein the surface conditioner (A) has a dynamic surface tension of 50 to 70 mN / m.
[6] The content of the vapor-deposited chrome flake pigment (B) is 0.05 based on 100 parts by mass of the total amount of water, the surface conditioner (A), the vapor-deposited chrome flake pigment (B) and the viscosity adjuster (C). The method for forming a multilayer coating film according to any one of [1] to [5], which is ~ 3.0 parts by mass.
[7] The multi-layer coating according to any one of [1] to [6], wherein the viscosity modifier (C) is at least one selected from a polyacrylic acid-based viscosity modifier and a cellulose-based viscosity modifier. Membrane formation method.

[8] The content of water is 70 to 99 parts by mass based on 100 parts by mass of the total amount of water, the surface conditioner (A), the vapor-deposited chromium flake pigment (B) and the viscosity conditioner (C) [1]. ] To [7]. The method for forming a multi-layer coating film according to any one of the items.
[9] The method for forming a multilayer coating film according to any one of [1] to [8], wherein the content of water is 70 to 99% by mass with respect to the bright pigment dispersion (Y).
[10] The content of the surface conditioner (A) is 0.1 to 0 based on 100 parts by mass of the total amount of water, the surface conditioner (A), the vapor-deposited chrome flake pigment (B) and the viscosity conditioner (C). The method for forming a multilayer coating film according to any one of [1] to [9], which is 10 parts by mass.
[11] The content of the viscosity adjusting agent (C) is 0.1 to 0 based on 100 parts by mass of the total amount of water, the surface adjusting agent (A), the vapor-deposited chrome flake pigment (B) and the viscosity adjusting agent (C). The method for forming a multilayer coating film according to any one of [1] to [9], which is 30 parts by mass.
[12] The method for forming a multi-layer coating film according to any one of [1] to [11], wherein the brilliant coating film has a cured film thickness of 0.02 to 5.0 μm.
[13] The method for forming a multi-layer coating film according to any one of [1] to [12], wherein the brilliant coating film has a cured film thickness of 0.04 to 5.0 μm.
[14] The method for forming a multi-layer coating film according to any one of [1] to [13], wherein the clear coating material (Z) is a two-component clear coating material containing a hydroxyl group-containing resin and a polyisocyanate compound.

The method for forming a multi-layer coating film of the present invention can be applied to various industrial products, particularly inner and outer panels of automobile bodies and automobile parts.

Claims (7)

The following steps (1) to (4):
(1) A step of applying a colored paint (X) on an object to be coated to form a colored coating film.
(2) A step of coating the bright pigment dispersion (Y) on the colored coating film formed in the step (1) to form a bright coating film.
(3) A step of applying a clear coating film (Z) on the glittering coating film formed in the step (2) to form a clear coating film.
(4) By heating the uncured colored coating film, the uncured brilliant coating film, and the uncured clear coating film formed in the steps (1) to (3), these three coating films are cured at the same time. It is a method of forming a multi-layer coating film by sequentially performing the steps of making the coating film.
The glitter pigment dispersion (Y) contains water, a surface conditioner (A), a vapor-deposited chrome flake pigment (B) and a viscosity conditioner (C).
A liquid in which the surface conditioner (A) is mixed at a ratio of isopropanol / water / surface conditioner (A) = 4.5 / 95/1 is mixed at a temperature of 20 ° C. and a rotor rotation speed of 60 rpm with a B-type viscometer. Surface adjustment that the contact angle with the tin plate is 8 to 20 ° when 10 μL is dropped onto a tin plate (manufactured by Partec) that has been degreased in advance and measured after 10 seconds. Agent (A)
A method for forming a multi-layer coating film having a light transmittance of 0.1 to 40% at a wavelength of 550 nm of a film obtained by coating a glitter pigment dispersion (Y) so as to have a dry film thickness of 0.2 μm. The multi-layer coating film according to claim 1, wherein the bright pigment dispersion (Y) has a viscosity (B60) of 60 to 1500 mPa · s at a rotor rotation speed of 60 rpm with a B-type viscometer at a temperature of 20 ° C. Forming method. The method for forming a multi-layer coating film according to claim 1 or 2, wherein the surface conditioner (A) is a silicone-based surface conditioner. The method for forming a multi-layer coating film according to any one of claims 1 to 3, wherein the surface conditioner (A) has a dynamic surface tension of 50 to 70 mN / m. The content of the thin-film vapor-deposited chrome flake pigment (B) is 0.05 to 3. The method for forming a multilayer coating film according to any one of claims 1 to 4, which is 0 parts by mass. The method for forming a multi-layer coating film according to any one of claims 1 to 5, wherein the glittering coating film has a cured film thickness of 0.02 to 5.0 μm. The method for forming a multi-layer coating film according to any one of claims 1 to 6, wherein the clear coating material (Z) is a two-component clear coating material containing a hydroxyl group-containing resin and a polyisocyanate compound.