KR100679444B1 - Method for forming multilayered coating film - Google Patents

Abstract

The present invention paints an organic solvent-type hydrophilic coloring paint (A), an aqueous coloring paint (B) and a clear paint (C) sequentially on a coated object, and heats and hardens these coating films. In the method for forming a layer coating film, the hydrophilic coloring paint (A) contains a neutralized product of a carboxyl group-containing resin having an acid value in the range of 5 to 100, a curing agent, an aluminum powder having an average particle diameter of 20 µm or less, and a colored pigment, and The content rate of this aluminum powder exists in the range of 0.1-10 weight part per 100 weight part of resin solid content, It is providing the multilayer coating film formation method characterized by the above-mentioned.

Description

Multi-layer coating method {METHOD FOR FORMING MULTILAYERED COATING FILM}

The present invention relates to a method of sequentially coating an organic solvent-type hydrophilic coloring paint, an aqueous coloring paint and a clear coating to form a multilayer coating film.

Background Art A method of forming a multilayer coating film by sequentially coating an organic solvent-type hydrophilic coloring paint, an aqueous coloring paint and a clear coating is known. The uncured coating film of the organic solvent-type hydrophilic coloring paint has a strong hydrophilicity, and when the aqueous coloring paint is coated on the painted surface, the moisture in the coating film is absorbed and the viscosity rises sharply. Even if the coating is carried out in an atmosphere, it has an effect that a defect such as surface roughening does not occur. Moreover, even if an aqueous metallic paint is used as this aqueous coloring paint, there is an effect of being able to form the coating film excellent in glossiness with no metallic stain, without being influenced by the humidity at the time of coating. On the other hand, the coating film of the organic solvent-type hydrophilic coloring paint has a low light transmittance, excellent concealability, and preferably a thin film, in order to maintain the weather resistance and the plastering property of the multilayer coating film. Therefore, until now, a large amount of colored pigment is contained. As a result, the concealability of the coating film can be ensured, but on the other hand, there is a drawback that the physical performance of the coating film is easily degraded.

Thus, the present inventors have a low content of the coloring pigment of the hydrophilic coloring paint in order to solve the above drawbacks in the method of coating the organic solvent type hydrophilic coloring paint, the aqueous coloring paint and the clear coating to form a multilayer coating film. Further, even in the case of a thin film, a hydrophilic coloring paint is formed that is excellent in concealability and the physical performance of the coating film is not diminished. As a result, this time, it was found out that the object can be achieved by containing a specific amount of aluminum powder having a specific average particle diameter together with the coloring pigment in the hydrophilic coloring paint, thus completing the present invention.

In this way, according to the present invention, the coating material is coated with an organic solvent-type hydrophilic coloring paint (A), an aqueous coloring paint (B) and a clear coating (C) in sequence, and heated to cure these coating films to form a multilayer coating film. In the forming method, the hydrophilic coloring paint (A) contains a neutralized product of a carboxyl group-containing resin having an acid value in the range of 5 to 100, a curing agent, an aluminum powder having an average particle diameter of 20 µm or less, and a coloring pigment. There is provided a method for forming a multilayer coating film, wherein the powder content is in the range of 0.1 to 10 parts by weight per 100 parts by weight of the resin solid content.

In the method of the present invention, when the aqueous colored paint (B) is coated on the uncured coating film surface of the organic solvent-type hydrophilic colored paint (A), the neutralized carboxyl group-containing resin contained in the coating film of the hydrophilic colored paint (A) is strong. Since the water-absorbing property is exhibited, the water in the coating film of the aqueous coloring paint (B) coated on the painted surface is absorbed, and the viscosity thereof rises rapidly, so that the surface is rough even when the aqueous coloring paint is painted in a low humidity atmosphere. Less defects such as losing occur. If a metallic paint is used as the aqueous coloring paint (B), it is possible to form a coating film having excellent glossiness without being affected by the humidity at the time of coating and without metallic staining. In addition, according to the method of the present invention, by containing a specific amount of aluminum powder having a specific average particle diameter together with the coloring pigment in the hydrophilic coloring paint (A), even if the content of the coloring pigment is reduced, the thin film is excellent in concealability. The remarkable effect that a coating film can be formed and that the physical performance of a coating film does not fall can be acquired.

Hereinafter, the coating method of the present invention will be described in more detail.

Examples of the coating material for forming the multilayer coating film according to the coating method of the present invention include, for example, metal products and plastic products, and more specifically, for example, passenger cars and trucks formed using metal products and / or plastics. Car bodies such as bicycles, motorcycles, and buses. It is preferable to perform surface treatment (for example, resin, zinc phosphate treatment etc.) beforehand by these means suitably.

The organic solvent-type hydrophilic coloring paint (A) can be applied directly to these coatings, but it is also possible to coat a primary coating such as a cationic electrodeposition coating, or, if necessary, an intermediate coating and to cure each coating film. It is preferable to coat the hydrophilic coloring paint (A). As these primary and intermediate coatings, those already known as such can be used.                     

According to the present invention, the organic solvent-type hydrophilic coloring paint (A) coated on the coating as described above is a neutralized product of a carboxyl group-containing resin having an acid value in the range of 5 to 100, a curing agent, aluminum powder having an average particle diameter of 20 µm or less, and coloring. It is a organic solvent type coating material which contains a pigment and the content rate of the said aluminum powder exists in the range of 0.1-10 weight part per 100 weight part of resin solid content.

The carboxyl group-containing resin used as the hydrophilic coloring paint (A) is not particularly limited as long as it is a resin for paint containing at least one carboxyl group in the molecule and having an acid value in the range of 5 to 100. Resin can be used. The following resin is mentioned as the representative example.

(i) at least one of the carboxyl group-containing polymerizable monomers of group (a) and at least one of the polymerizable monomers of group (c) copolymerizable with this, and further, if necessary, the hydroxyl group-containing polymerizable group of group (b) Acrylic resin or vinyl resin in which the number average molecular weight obtained by copolymerizing at least 1 sort (s) of a monomer is in the range of about 3000 to about 40000, Preferably it is about 5000 to about 25000.

(a) Group: (alpha), (beta)-ethylenically unsaturated carboxylic acids, such as acrylic acid, methacrylic acid, maleic acid, maleic anhydride, itaconic acid, a crotonic acid.

(b) Group: The hydroxyalkyl ester of 1-8 carbon atoms of (meth) acrylic acid, such as hydroxyethyl (meth) acrylate and hydroxypropyl (meth) acrylate.

(c) group: methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl ( Meth) acrylate, t-butyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, acrylic acid Alkyl or cycloalkyl ester having 1 to 24 carbon atoms in (meth) acrylic acid such as decyl; (Meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, diacetone acrylamide, N-methylol (meth) acrylamide, N-butoxymethyl acrylamide ) Acrylamide; Glycidyl group-containing vinyl monomers such as glycidyl (meth) acrylate, glycidyl (meth) acrylamide and allyl glycidyl ether; Vinyl aromatic compounds such as styrene, vinyltoluene and α-methylstyrene; And other vinyl monomers such as vinyl propionate, vinyl acetate, (meth) acrylonitrile, vinyl propionate, vinyl pivalate, and beobamonomer (manufactured by Shell Chemical).

(ii) polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, butanediol, pentanediol, 2,2-dimethylpropanediol, glycerin, trimethylolpropane, pentaerythritol, and monohydric alcohols or molecules used in combination if necessary Alcohol component consisting of a monoepoxy compound having one glycidyl group, for example, Kajura E (trade name, manufactured by Shell Chemical Co., Ltd.), phthalic anhydride, isophthalic acid, tetrahydro phthalic anhydride, hexahydroxy anhydride Condensation of acid components consisting of polybasic acids such as phthalic acid, maleic anhydride, succinic anhydride, adipic acid, sebacic acid, trimellitic anhydride, pyromellitic anhydride, and monobasic acids such as benzoic acid and t-butyl benzoic acid, if necessary. Oil-alkyd resins having a number average molecular weight of 500 to 10000, in particular 1000 to 7000, obtained by the reaction; Or in addition to the alcohol component and the acid component, the number average molecular weight obtained by reacting at least one of fatty acids derived from castor oil, tung oil, sunflower oil, soybean oil, linseed oil, tor oil, palm oil and their fats and oils is from 500 to 500; Oil-modified alkyd resins in the range of 10000, in particular 1000-7000.

(iii) Graft copolymers having a number average molecular weight in the range of about 5000 to about 40000, in particular about 8000 to about 20000, in which an acrylic resin or a vinyl resin is grafted with an alkyd resin. Such a graft copolymer can be obtained by, for example, reacting an alkyd resin having a polymerizable unsaturated group with a polymerizable monomer as described above in (i).

These carboxyl group-containing resins may have an acid value in the range of 5-100, Preferably it is 10-50, More preferably, it is 30-50. When the acid value of this resin is less than 5, the mismatch with the aqueous coloring paint (B) coated on the coating surface of the organic-solvent hydrophilic coloring paint (A) containing this resin worsens, and the moisture contained in the coating film Since the suction property is lowered, defects such as flow irregularity and sagging of the aqueous coloring paint (B) occur, which tends to deteriorate the plastering properties of the coating film. On the contrary, when the acid value of this resin becomes larger than 100, the water resistance of the coating film itself of a hydrophilic coloring paint (A), etc. tend to fall.

In this carboxyl group-containing resin, a hydroxyl group can be coexisted with a carboxyl group by copolymerizing the hydroxyl group containing polymerizable monomer as described in said (b) group, for example. When these both functional groups are used together, since the hardness, water resistance, weather resistance, etc. of the coating film formed improve, it is preferable. The hydroxyl value of the resin containing both carboxyl and hydroxyl groups is generally in the range of about 10 to about 200, especially 15 to 100, more preferably 25 to 70.

As a neutralizing agent for neutralizing carboxyl group-containing resin, For example, Ammonia; Primary amines such as methylamine and ethylamine; Secondary amines such as dimethylamine, diethylamine and diethanolamine; Basic substances can be used like tertiary amines such as trimethylamine, triethylamine, dimethylethanolamine and triethanolamine. The amount of neutralizing agent used is generally within the range of about 0.1 to about 2 equivalents, especially about 0.3 to about 1.2 equivalents, relative to the carboxyl groups in the resin.

The curing agent used as the organic solvent-type hydrophilic coloring paint (A) is useful for crosslinking and curing the resin, and examples thereof include amino resins and block polyisocyanate compounds.

Examples of the amino resins include condensation or co-condensation products of amine compounds such as melamine, benzoguanamine, triazine-based compounds, urea, and dicyandiamide and formaldehyde, and melamine formaldehyde resins are particularly preferred. Alkyl etherified amino resins formed by reacting mono-alcohols having 1 to 8 carbon atoms with these condensates are preferably used.

A block polyisocyanate compound is a compound in which the isocyanate group of the polyisocyanate compound is blocked with a blocking agent, and the blocking agent is dissociated when heated to the dissociation temperature of the blocking agent (for example, about 100 to about 170 ° C.), and the free isocyanate group is regenerated to crosslink. Can react with a functional group.                     

 A polyisocyanate compound is a compound which has 2 or more isocyanate groups in 1 molecule, For example, aromatic diisocyanate, such as tolylene diisocyanate, diphenylmethane diisocyanate, xylene diisocyanate, naphthalene diisocyanate; Aliphatic diisocyanates such as tetramethylene diisocyanate, hexamethylene diisocyanate, dimer acid diisocyanate and lidin diisocyanate; Alicyclic diisocyanate, such as methylenebis (cyclohexyl isocyanate, isophorone diisocyanate, methylcyclohexane diisocyanate, cyclohexane diisocyanate, cyclopentane diisocyanate; biuret type, isocyanuric ring type, and polyaryl of these polyisocyanate compounds) And a free isocyanate group-containing prepolymer formed by reacting with a phenol, oximes, lactams, active methylenes, alcohols, acid amides, imides, amines, imidazoles, Urea, carbamic acid, imine, mercaptans, etc. The molecular weight of the block polyisocyanate compound is preferably in the range of about 200 to about 10000, particularly about 500 to about 5000.

The mixing ratio of the carboxyl group-containing resin and the curing agent in the hydrophilic coloring paint (A) is generally about 50 to about 90%, preferably about 60 to about 85%, and the curing agent based on the total solids weight of both. Is preferably in the range of about 10 to about 50%, preferably about 15 to about 40%.

The organic solvent-type hydrophilic coloring paint (A), in addition to the neutralizing agent and curing agent of the carboxyl group-containing resin, further comprises aluminum powder and coloring pigment having an average particle diameter of 20 µm or less.                     

As aluminum powder, flaky metal aluminum powder can be used, and the average particle diameter is 20 micrometers or less normally, It is preferable to exist in the range of 15-5 micrometers especially. Here, [average particle diameter] means the median diameter measured by the laser dilution acid activity method (LA-500). In addition, the thickness is preferably in the range of 0.001 to 0.5 µm, particularly 0.01 to 0.3 µm. It is preferable that the mixing ratio of such aluminum powder in the hydrophilic coloring paint (A) is generally in the range of 0.1 to 10 parts by weight, in particular 0.5 to 7 parts by weight, and more particularly 1 to 5 parts by weight, per 100 parts by weight of the resin solid content. .

The coating film formed of a coating material obtained by blending aluminum powder of such a size with the above-mentioned ratio hardly exhibits a glistening glossiness, and the concealability can be remarkably improved, and as a result, the coloring used in combination The compounding quantity of a pigment can be made small. For example, in the case of a paint containing titanium white pigment as a coloring pigment, the compounding amount of titanium white pigment can achieve the same concealability by about half. As a result, the physical performance of the paint, for example, chipping resistance, peeling resistance (impact resistance) and the like can be significantly improved as compared with the case where only the coloring pigment is used.

Colored pigments blended into the hydrophilic coloring paint (A) are used to impart desired color tone and concealability to the coating film, and include dyes as well as ordinary pigments, for example titanium dioxide, carbon black, phthalocyanine blue, phthalocyanine green, and carbazole. Biolet, Anthrapyridine, Azo Orange, Yellow, Flavanslon Yellow, Isoindolin Yellow, Azo Yellow, Indathlon Blue, Dibrom Anzalone Red, Perylene Red, Azored, Anthraquinone Red, Quina Clidone Red Organic or inorganic color pigments such as biot and biot; Azo dyes such as monoazo dyes, polyazo dyes, metal complex azo dyes, pyrazolone azo dyes, stilbene azo dyes, and thiazole azo dyes; Anthraquinone dyes such as anthraquinone derivatives and anthrone derivatives; Indigo dyes such as indigo derivatives and thioindigo derivatives; Phthalocyanine dyes; Diphenylmethane dyes; Carbonium dyes such as triphenyl methane dye, xanthine dye and acridine dye; Quinone imine dyes, such as an azine dye, an oxadine dye, and a thiadine dye; Methine dyes such as polymethine (or cyanine) dye and adimethine dye; And dyes such as quinoline dyes, nitro dyes, nitron dyes, benzoquinones, naphthoquinone dyes, naphthalimide dyes, and pelinone dyes, and these may be used alone or in combination of two or more thereof. The blending ratio of these colored pigments in the hydrophilic coloring paint (A) is not particularly limited and can be blended within a range in which a coating film of a desired color tone can be formed.

The hydrophilic coloring paint (A) can be prepared by dissolving or dispersing the neutralization, the curing agent, the aluminum powder and the coloring pigment of the carboxyl group-containing resin described above in an organic solvent, and the solid content concentration at the time of coating is about 35% by weight or more, Particularly preferred is the so-called high solid type, adjusted to about 40 to about 60% by weight.

Examples of the organic solvents include solvents such as paint esters, ethers, alcohols, amides, ketones, aliphatic hydrocarbons, alicyclic hydrocarbons, and aromatic hydrocarbons. It can be used together. Among them, in particular, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, and diethylene. Glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol diethyl ether, diethylene glycol monobutyl ether, methyl alcohol, ethyl alcohol, allyl alcohol, n-propyl alcohol, isopropyl alcohol, tertiary butyl alcohol, ethylene Glycol, 1,2-propylene glycol and its monoether, 1,3-butylene glycol, 2,3-butylene glycol, hexylene glycol, hexanediol, dipropylene glycol and its monoether, acetone, diacetone alcohol, etc. It is preferable to use the same hydrophilic organic solvent. These hydrophilic organic solvents generally have a water solubility of at least 50 parts by weight, in particular at least 70 parts by weight, per 100 parts by weight of water at 20 ° C. The ratio of the hydrophilic organic solvent to the total organic solvent is suitably in the range of 20% by weight or more, particularly 40 to 100% by weight, based on the total weight of the organic solvent contained in the hydrophilic coloring paint (A) at the time of coating.

The hydrophilic coloring paint (A) containing each of the above components may have a base hiding property within the range of 10 µm or less, particularly 8 to 5 µm, based on the cured coating. Underlying concealability means the film thickness of the thinnest coating film which coats this hydrophilic coloring paint (A) on the surface of a black-and-white checkered pattern, and a pattern cannot be seen through the coating film.

Although the hydrophilic coloring paint (A) can be applied directly to the coating material, it is preferable to coat the primary coating paints such as electrodeposition paints (Anion type, Cation type) and, if necessary, the intermediate coating paints, and then harden these coatings. Do. Coating is preferably carried out in a differentiated manner, and can be performed using, for example, an air spray, an airless spray, an air differentiation or a rotary electrostatic coating machine. It is preferable to adjust the viscosity of the hydrophilic coloring paint (A) at the time of coating within the range of about 15 to about 60 seconds, especially 15 to 35 seconds (20 ° C), with a pod cup # 4. On the basis of this, it is thicker than the covering thickness of the lower extremity, for example, in the range of about 5 to about 25 mu m, especially about 8 to about 20 mu m.

In the present invention, the hydrophilic coloring paint (A) is coated on the coated object and left to stand at room temperature for 1 to 10 minutes as needed without curing the coating film, and then the aqueous colored paint (B) is coated on the uncured coating surface. desirable.

An aqueous coloring paint (B) is an aqueous coating which uses water as its main solvent or dispersion medium, and specifically, an aqueous coloring paint containing an aqueous vinyl resin and / or an aqueous polyester resin, a curing agent and a coloring pigment is preferably used.

As the aqueous vinyl resin in the aqueous coloring paint (B), those already known per se can be used. For example, the number average molecular weight, which is obtained by copolymerizing a carboxyl group-containing polymerizable monomer, a hydroxyl group-containing polymerizable monomer, and other polymerizable monomers, is about 3000 to about 40000, preferably about 5000 to about 20000, and an acid value of about 20 to about An aqueous vinyl resin having about 100, preferably about 30 to about 80, hydroxyl value of about 20 to about 200, preferably about 30 to about 150.

Examples of the carboxyl group-containing polymerizable monomer include monoethylenically unsaturated carboxylic acids such as (meth) acrylic acid, maleic acid, and itaconic acid, and examples of the hydrogen group-containing polymerizable monomer include (meth) acrylic acid 2-. And hydroxyalkyl esters of monoethylenically unsaturated carboxylic acids such as hydroxyethyl and 2-hydroxypropyl (meth) acrylate. As other polymerizable monomers, for example, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, lauryl (meth) acrylate, Alkyl esters of monoethylenically unsaturated carboxylic acids such as (meth) acrylic acid acyl; Acrylamide derivatives, such as (meth) acrylamide, N-methylol (meth) acrylamide, diacetone acrylamide; Glycidyl esters of monoethylenically unsaturated carboxylic acids such as glycidyl (meth) acrylate; Vinyl esters of saturated carboxylic acids such as vinyl acetate and vinyl propionate; Aromatic unsaturated monomers, such as styrene, (alpha) -methylstyrene, and vinyltoluene, are mentioned.

The vinyl resin obtained in this way is neutralized using basic materials, such as ammonia, amines, such as a triethylamine, a monoethanolamine, diethanolamine, a triethanolamine, and dimethylamino ethanol, and a basic substance, such as hydroxide of alkali metals, such as sodium hydroxide, etc. It can be made water-dispersible.

Moreover, the aqueous dispersion which disperse | distributes the copolymer obtained by copolymerizing a hydroxyl group containing polymeric monomer and other polymerizable monomer in water, with or without a carboxyl group-containing polymerizable monomer can also be used as an aqueous vinyl resin.

As an aqueous polyester resin, the acid value is 15-100, especially 20 in the polyester resin obtained by condensation reaction of the alcohol component and acid component which were illustrated about the alkyd resin as carboxyl containing resin in the said hydrophilic coloring paint (A). To 80, and the hydroxyl value is preferably in the range of 20 to 200, especially 30 to 150.

As a hardening | curing agent in an aqueous coloring paint (B), the condensation or co-condensation of formaldehyde, for example with melamine, benzoguanamine, a triazine type compound, urea, dicyandiamide, etc. is further modified with monoalcohols of 1-8 carbon atoms. What was made, carboxyl containing amino resin, etc. are mentioned. Of these, melamine resins obtained by esterification with alcohols are particularly preferred. These curing agents can be used without any problem of hydrophilicity and hydrophobicity.

The mixing ratio of the aqueous vinyl resin and / or the aqueous polyester resin and the curing agent in the aqueous coloring paint (B) is generally about 50 to about 90% by weight, preferably based on the total solids weight of both. From about 60 to about 85 weight percent, and the curing agent component may be in the range of about 10 to about 50 weight percent, preferably about 15 to about 40 weight percent.

The aqueous coloring paint (B) forms a coating film colored with a solid color bath, a metallic bath, an optical interference bath, or the like, and the coloration degree of the color of the coating film of the hydrophilic paint (A) penetrating the coating film and adjacent to the lower layer is Either of them may be transparent enough to be seen or opaque enough not to be visible.

The paint which forms a solid color-like coating film is obtained by mix | blending a coloring pigment (it also contains a dye) as exemplified above with respect to a hydrophilic coloring paint (A). The coating material which forms a metallic-like coating film can be manufactured by mix | blending well-known metallic pigments, such as an aluminum flake. Moreover, the coating material which forms the optical interfering coating film can be manufactured by mix | blending interference color pigments, such as a flaky mica powder which coat | covered the surface with metal oxides, such as titanium oxide.

The aqueous coloring paint (B) can be coated by the same method as the hydrophilic coloring paint (A), and the viscosity at the time of coating is usually about 10 to about 50 seconds (20 ° C), especially about 15 to about pod cup # 4. 30 seconds (20 degreeC), and a coating film thickness is preferably within the range of about 5 to about 30 micrometers, especially about 10 to about 20 micrometers, based on the heat-curing coating film.

In the method of the present invention, the organic solvent-type hydrophilic coloring paint (A) and the aqueous coloring paint (B) are coated in the same manner as above, and left at room temperature for about 1 to 10 minutes, or about 50 to about 100 ° C, preferably Preferably it is preheated at about 60 to about 80 ° C. for about 1 to 20 minutes and then the clear paint (C) is coated.

Clear paint (C) is a paint which forms a transparent coating film coated on the coating surface of the non-hardened aqueous coloring paint (B) preheated as needed, and is a fine cosmetic, final appearance, weather resistance, chemical resistance, water resistance, and water resistance of a multilayer coating. Wet etc. can be improved further. Specifically, the organic solvent type or non-aqueous dispersion type paint which uses the thermosetting resin composition which consists of an acrylic resin (gas resin) and an amino resin (crosslinking agent) as a vehicle component is mentioned, Furthermore, a ultraviolet absorber, a coloring agent, etc. are mix | blended suitably. It may be.

The clear paint (C) preferably has a high solids content from the viewpoint of pollution prevention and resource reduction, and specifically, for example, the non-volatile content concentration at the time of coating is about 35 wt% or more, preferably about 40 to about 80 wt%, more Preferably it is adjusted within the range of about 45 to about 80% by weight.

The clear paint (C) may be coated in the same manner as the hydrophilic coloring paint (A), and the viscosity at the time of coating is about 15 to about 60 seconds (20 ° C.), especially about 20 to about 40 seconds (in the pod cup # 4). 20 degreeC) and it is preferable to coat so that it may become a film thickness within the range of about 5 to about 50 micrometers, especially about 20 to about 45 micrometers based on a cured coating film.

As described above, the coating film formed by superimposing the hydrophilic coloring paint (A), the aqueous coloring paint (B), and the clear coating (C) in turn is about 3 coating 1 bake method or 3 coating 2 bake method. It can be cured by heating for about 15 to about 45 minutes at a temperature of 120 to about 180 ° C., preferably about 130 to about 160 ° C., thereby forming a multilayer coating film according to the present invention.

According to the method of this invention mentioned above, the effect described below is acquired.

(1) A method of coating an organic solvent-type hydrophilic coloring paint (A), an aqueous coloring paint (B) and a clear coating (C) in order to form a multilayer coating film, wherein the neutralized carboxyl group-containing in the hydrophilic coloring paint (A) is contained. Since the resin is hydrophilic, it is excellent in compatibility with the aqueous coloring paint (B) coated on the painted surface, and since the water in the coating film of the aqueous coloring paint (B) is absorbed and the coating viscosity rises rapidly, the aqueous coloring paint (B ) Even when coated in a low humidity atmosphere does not cause defects such as surface roughness.

(2) Even when the metallic aqueous coloring paint (B) is used, the metallic coating film having excellent glossiness without the metallic nonuniformity can be formed because the humidity at the time of coating is not affected.                     

(3) The organic solvent-type hydrophilic coloring paint (A) contains a specific aluminum powder and a coloring pigment, and in particular, by containing a specific amount of aluminum powder, the coating film shows little shiny brightness and its concealability. Since it can remarkably improve, the compounding quantity of the coloring pigment used together can be reduced, As a result, the physical performance of the coating film of a hydrophilic coloring paint (A), for example, chipping and peeling resistance (impact resistance), etc. can be improved.

(4) It is an advantageous coating method for resource saving and pollution prevention, and the multilayer coating film formed by the method of the present invention has excellent finish appearance, design, painting workability, etc. Widely available.

Example

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. Both parts and% are by weight and the film thickness of the coating film is for the cured coating film.

1. Preparation of Sample

1) the object

a: "Electron # 9400" (Kansai Paint Co., Ltd. make, brand name, cationic electrodeposition paint) was electrodeposited-coated by the conventional method, and it heated at 175 degreeC for 30 minutes, and hardened the coating film on the steel plate which carried out the degreasing and zinc phosphate treatment. The film thickness was 20 micrometers. Subsequently, an intermediate coating "Luga Bake Intermediate Coating, Light Gray" (manufactured by Kansai Paint Co., Ltd.) was applied to this coating surface, and heated at 140 ° C for 30 minutes to cure the coating film (film thickness of 20 µm). It was set as.                     

2) Organic solvent type hydrophilic coloring paint (A)

It mixed based on the component and the compounding quantity of following Table 1, and obtained the organic-solvent type hydrophilic coloring paint (A). Adjustment of the viscosity and solid content rate was performed by adding isopropyl alcohol. The compounding quantity is solid secretion.

Hydrophilic Coloring Paint (A) A-1 A-2 A-3 A-4 Acrylic resin neutralization solution (Note 1) 70 - 70 - Polyester resin neutralization solution (Note 2) - 70 - 70 Cymel 370 (Note 3) 30 30 30 30 Arpaste891K (Note 4) 5 5 - - Titanium White Pigment 50 50 55 95 Paint Solids (%) 35 35 35 35 Viscosity (Note 5) 25 25 25 25 Lower cover thickness (Note 6) 10 10 25 10 (Note 1): 30 parts of methyl methacrylate, 23 parts of ethyl acrylate, 30 parts of butyl acrylate, 12 parts of hydroxyethyl methacrylate, and 5 parts of acrylic acid to copolymerize acrylic acid having an acid value of 40, a hydroxyl value of 52, and a number average molecular weight of about 10,000 A resin organic solvent solution (solid content 60%) was obtained. To this solution was added neutralized by addition of dimethylaminoethanol and then diluted with isopropyl alcohol (50% solids). (Note 2): 0.7 mol of neopentyl glycol, 0.3 mol of trimethylolpropane, 0.4 mol of phthalic anhydride and 0.5 mol of adipic acid were esterified, followed by addition of 0.03 mol of trimellitic anhydride, followed by butyl cell. The solution was added to obtain a polyester resin solution having an acid value of 40, a number average molecular weight of about 6,000, and a resin solid content of 70%. Dimethylaminoethanol was added to this polyester resin solution to neutralize it, and then diluted with isopropyl alcohol (50% solids). * 3: Mitsui Cytec Co., Ltd. make, brand name, water-soluble melamine resin. Note 4: Toyo Aluminum Co., Ltd. make, brand name, aluminum paste. Average particle diameter 12 mu m. (Note 5): Second / Pod Cup # 4/20 degreeC. (Note 6): Coverability of the lower extremity is coated with a hydrophilic coloring paint (A) on the surface of the black-and-white intersecting pattern, and the thickness of the thinnest coating film whose appearance cannot be visually confirmed when reflecting the coating film (µm)

3) Aqueous coloring paint (B)

Mixing was performed based on the components and contents shown in Table 2 below to obtain an aqueous coloring paint (B). Adjustment of the viscosity and solid content was performed by adding deionized water. The compounding quantity is solid secretion.

Aqueous coloring paint (B) B-1 B-2 Acrylic resin neutralization solution (Note 1) 50 50 Polyester resin neutralization solution (Note 2) 50 50 Acrylic Emulsion (Note 7) 100 100 Cymel 370 (Note 3) 34 34 Armipaste Note 8 - 2 Blue G316 5 - Paint Solids (%) 25 25 Viscosity (Note 5) 30 30 (Note 7): 140 parts of deionized water, 2.5% of 30% `` Newcol 707SF '' (surfactant, Nippon New Kaze Co., Ltd. product) and 2.5 parts of the following monomer mixture (1) were added and stirred and mixed in a nitrogen gas stream. 3 parts of 3% ammonium persulfate aqueous solution were added, heating at 60 degreeC. Subsequently, after raising the temperature to 80 ° C., a monomer emulsion consisting of 79 parts of the monomer mixture (1), 2.5 parts of “Newcol 707SF”, 4 parts of 3% aqueous ammonium persulfate solution and 42 parts of deionized water was added to the reaction vessel over 4 hours. . Thereafter, it was aged for 1 hour. Then, 20.5 parts of the following monomer mixture (2) and 4 parts of 3% aqueous ammonium persulfate solution were added dropwise to the reaction vessel at 80 ° C. simultaneously for 1.5 hours. It was then aged for 1 hour and diluted with 30 parts of deionized water. Deionized water was added to this filtrate and adjusted to pH7.5 with dimethylaminoethanol to obtain an acrylic resin emulsion having a solid content of 20%. Monomer mixture (1): 55 parts of methyl methacrylate, 8 parts of styrene, 9 parts of n-butyl acrylate, 5 parts of 2-hydroxyethyl acrylate, 2 parts of 1,6-hexanediol diacrylate and 1 part of methacrylic acid Monomer mixture (2): 5 parts of methyl methacrylate, 7 parts of n-butyl acrylate, 5 parts of 2-ethylhexyl acrylate, 3 parts of methacrylic acid, and 0.5 parts of "Newcol 707SF" (Note 8): Armipaste 891K: Oyo aluminum company make, brand name.

4) Clear Paint (C)

(C-1)

57 parts of acrylic resin solution (Note 9), 50 parts of acrylic resin non-aqueous dispersion (Note 10), 30 parts of Cymel 303 (Note 11), 4 parts of 25% dodecylbenzenesulfonic acid solution and BYK-300 (Note 12) to 0.5 part The resultant mixture was adjusted to a viscosity of 30 seconds (Pod Cup # 4/20 ° C) by Swagel # 1000 (manufactured by Cosmo Co., Ltd., product name, aromatic hydrocarbon solvent), and the clear coating (C-1) having a resin solid content of 55% was prepared. Obtained.

(Note 9) Acrylic resin solution: 40 parts of `` swoolzol # 1000 '' are added to the reaction vessel and heated to 120 ° C, and 30 parts of styrene, 35 parts of butyl acrylate, 10 parts of 2-ethylhexyl acrylate, and 25 parts of hydroxyethyl acrylate It is a resin obtained by addition-polymerizing the monomer mixture which consists of 4 parts and 4 parts of (alpha), (alpha) 'azobisisobutyronitrile over 3 hours, and has a hydroxyl value of 120, a number average molecular weight of about 6,000, and resin solid content of 70%.

(Note 10) Acrylic resin non-aqueous dispersion: 58 parts of organic solvent 28-60 (manufactured by Mitsui Totsugaku Co., Ltd., trade name, melamine resin solution, solid content 60%), 30 parts of n-heptane and benzoyl peroxide 0.15 Part was injected and heated to 95 ° C., 15 parts of styrene, 9 parts of acrylonitrile, 13 parts of methyl methacrylate, 15 parts of methyl acrylate, 1.8 parts of n-butyl acrylate, and 2-hydroxyethyl methacrylate 10 A monomer mixture consisting of 1.2 parts of acrylic acid, 0.5 parts of benzoyl peroxide, 5 parts of n-butanol, 30 parts of "Shellzol 140" (trade name, manufactured by Shell Seiki Co., Ltd.) and 9 parts of n-heptane was added dropwise over 3 hours. After 1 hour, 0.65 parts of t-butylperoctoate and 3.5 parts of "shellsol 140" were added dropwise over 1 hour. Then, stirring was continued for 2 hours, maintaining about 95 degreeC, the solvent was removed under reduced pressure, and the acrylic resin non-aqueous dispersion liquid of 60% of resin solid content and varnish viscosity A (Gardner bubble viscosity) was obtained.

(11) Cymel 303: Mitsui Cytec Co., Ltd. product name, mono melamel melamine resin

12) BYK-300: Big Chemical Fan Co., Ltd., brand name, surface conditioner

2. Examples and Comparative Examples

One of the hydrophilic coloring paints (A-1) to (A-4) was applied to the workpiece at a relative temperature of 75% RH with a film thickness of 10 µm, and left to stand at room temperature for about 5 minutes. Subsequently, the aqueous colored coating (B-1) or (B-2) was coated on the uncured coating film surface with an air spray at a film thickness of about 15 μm at a relative temperature of 75% RH, and then preheated at 60 ° C. for 5 minutes. The clear paint (C-1) was coated with an air spray at a film thickness of 35 µm, left at room temperature for about 5 minutes, heated at 140 ° C. for 30 minutes, and the three-layer coating film was simultaneously crosslinked and cured. The performance test results of these coating steps and the obtained multilayer coating film are shown in Table 3 below.

Example Comparative example One 2 3 4 One 2 Hydrophilic Coloring Paint (A) A-1 A-2 A-1 A-2 A-3 A-4 Aqueous coloring paint (B) B-1 B-1 B-2 B-2 B-1 B-2 Clear Paint (C) C-1 C-1 C-1 C-1 C-1 C-1 Performance test results Smoothness 18 17 18 17 18 18 Sunyoung Sung 1.0 1.0 1.0 1.0 1.0 1.0 Water resistance 0 0 0 0 0 0 Adhesion 0 0 0 0 0 0 Impact resistance 0 0 0 0 △ × Chipping resistance 0 0 0 0 △ ×

Test Methods

Smoothness: Measured by a tension meter (manufactured by RENAULY). Larger value means better smoothness.

Sensitivity: It measured by the sedimentation tester NSIC (made by Suga test company). Larger value means better selectivity.

Water resistance: After immersing a sample plate in 40 degreeC warm water for 240 hours, the coating surface state was visually evaluated based on the following reference | standard. 0: No abnormality is observed, Δ: defects such as gloss reduction and swelling are slightly visible, and ×: defects such as gloss reduction and swelling are remarkable.

Water resistance: After immersing the sample plate in 40 ℃ hot water for 10 days, dry the coating film and make 11 cuts at 2mm intervals so as to reach the ground with cutter knife on the painted surface, and then cross them at right angles. 11 pieces were cut at intervals of mm, 100 small pieces of 2 mm × 2 mm were made, and the adhesive cellophane tape was attached to the coated surface at 20 ° C., and then peeled off rapidly. 0: 100 remaining, Δ: 99 to 90 remaining, ×: 89 or less remaining.

Impact resistance: According to JIS K-5400 8.3.2 (1990). Using the impact type having a tip radius of 6.3 mm, the weight of 500 g was dropped from the height of 30 cm to visually observe the cracked and peeled state of the coating film. 0: no cracking or peeling is seen at all, Δ: cracking and peeling partially occurs at the dropping point and its periphery, x: cracking and peeling at the dropping point and its periphery occur a lot.

Chipping resistance: QGR Gravelometer (produced by Q Panel Co., Ltd.) is used, and 0.5 kg of No. 7 whetstone is sprayed with debris on a test plate under an air pressure of 4 kg / ㎠ and a temperature of 20 ° C. The salt spray test was carried out for 48 hours according to the method specified in Z-2371. The status of rust was comprehensively evaluated and the following criteria were indicated. 0: Excellent (2 or less rusts occurred in the test plate of 7 cm × 7 cm), △: slightly inferior (3 to 9 rusts occurred in the 7 cm × 7 cm test board), ×: inferior (7 cm × 7 10 or more rusts) on a test plate of cm).

The present invention relates to a method of sequentially coating an organic solvent-type hydrophilic coloring paint, an aqueous coloring paint, and a clear paint to form a multilayer coating film. According to the present invention, defects such as roughening of the surface even when painted in a low humidity atmosphere are provided. This rarely occurs, and the coating film excellent in glossiness and selectivity without a metallic stain can be formed without being affected by the humidity at the time of coating.

Claims (13)

As a method of forming a multilayer coating film by coating and heating an organic solvent type hydrophilic coloring paint (A), an aqueous coloring paint (B), and a clear paint (C) in order to harden these coating films, The hydrophilic coloring paint (A) contains a neutralized product of a carboxyl group-containing resin having an acid value in the range of 5 to 100, a curing agent, an aluminum powder having an average particle diameter of 20 µm or less, and a colored pigment, and the content of this aluminum powder is 100 parts by weight of the resin solids. It is in the range of 0.1-10 weight part, The multilayer coating film formation method characterized by the above-mentioned. The method according to claim 1, wherein the carboxyl group-containing resin has an acid value in the range of 10 to 50. The method according to claim 1, wherein the carboxyl group-containing resin further contains a hydroxyl group. The method according to claim 3, wherein the carboxyl group-containing resin has a hydroxyl value in the range of 10 to 200. The method of claim 1 wherein the curing agent is an amino resin or a blockpolyisocyanate compound. The method according to claim 1, wherein the aluminum powder is flaky metal aluminum powder. The method of claim 6, wherein the aluminum powder has an average particle diameter in the range of 5-15 μm. The method of claim 6, wherein the aluminum powder has a thickness in the range of 0.001 to 0.5 μm. The method according to claim 1, wherein the aluminum powder is contained in the range of 1 to 5 parts by weight per 100 parts by weight of the resin solids. The method according to claim 1, wherein the organic solvent-type hydrophilic coloring paint (A) has a base hiding property of 10 µm or less. The method according to claim 1, wherein the organic solvent-type hydrophilic coloring paint (A) is a high solid type. The method according to claim 1, wherein the aqueous coloring paint (B) contains a curing agent and a coloring pigment, either or both of an aqueous vinyl resin and an aqueous polyester resin. An article coated by the method of claim 1.