JPH10128225A - Formation of coating film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a noble forming method of a coating film excellent in finish appearance such as smoothness of a coating film, sharpness and brightness and an interlaminar adherability of both coating films, capable of preventing a slip down of a water based clear coating material without executing strictly a humidity adjusting, hardly causing a mixed layer of both coating films and hardly causing an after tacking in a forming method of a double layered coating film by a 2-coat and 1-bake system by using a coloring coating material and the water based clear coating material. SOLUTION: In the coating film forming method, a thermoset org. solvent based coloring coating material A containing a neutralized matter of a hydroxy group-containing resin having an acid value of 5-100, and a crosslinking agent selected from among blocked polyisocyanates and amino resins is applied, and then after applying a thermoset water based clear coating material B on the surface of the uncured coating surface, the coating film consisting of the components A and B is cured simultaneously.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-coat one-bake system (2 coats) using an organic solvent-based colored paint and an aqueous clear paint.
C1B).

[0002]

2. Description of the Related Art A multilayer coating film formed of 2C1B using an organic solvent-based coloring paint such as a metallic paint and a solid color paint and an organic solvent-based clear paint has a smoothness, a sharpness, a gloss and a gloss. It has excellent weather resistance and is widely used for the top coating of automobile outer panels.

In recent years, from the viewpoint of air pollution prevention,
It has been proposed to convert the clear paint to an aqueous system.

However, when an organic solvent-based colored paint and a water-based clear paint are applied with 2C1B, the painted surface of the colored paint is usually hydrophobic, and the affinity (wetting property) between the paint and the water-based clear paint is poor. It has a defect that the finished appearance such as smoothness, sharpness, gloss and the like of the multi-layer coating surface and the adhesion between layers of both coating films are not sufficient. Further, if the humidity is not strictly adjusted at the time of applying the water-based clear coating material, the coating film may be displaced, and a great deal of labor is required for the management. In order to eliminate these defects, the colored coating film is preliminarily dried and then the water-based clear paint is applied. However, the number of predrying steps increases, which is not preferable in a practical coating line.

[0005]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned deficiencies in the method of forming a multilayer coating film in 2C1B using an organic solvent-based coloring paint and a water-based clear paint, and provides an affinity (slipperiness) between the two paints. ), Excellent finish appearance and adhesion between layers, etc., water-based clear paint can be applied without strictly adjusting humidity, and a multi-layer coating film with no mixing of both coating films and no mottle phenomenon can be obtained. The present invention relates to a novel coating film forming method.

That is, the present invention relates to a thermosetting organic solvent system containing a neutralized product of a hydroxyl group-containing resin having an acid value of 5 to 100 and a crosslinking agent selected from block polyisocyanates and amino resins. A colored paint (A) is applied, and then a thermosetting water-based clear (B) is applied to the uncured coating surface, and then heated to simultaneously form a multilayer coating film composed of the above (A) and (B). The present invention relates to a coating film forming method characterized by curing.

Hereinafter, the method for forming a coating film of the present invention (hereinafter referred to as “the present method”) will be described in detail.

Colored paint (A): a thermosetting organic solvent containing a neutralized product of a hydroxyl group-containing resin having an acid value of 5 to 100 and a crosslinking agent selected from block polyisocyanate and amino resin Colored paint, thermosetting water-based clear
This is a liquid paint to be applied to an object to be coated prior to the paint (B).

The colored paint (A) is a cross-linking agent (A) selected from a neutralized product of a hydroxyl group-containing resin (A-1) having an acid value of 5 to 100, a block polyisocyanate and an amino resin.
-2) and a coloring pigment (A-3) as essential components, and a thermosetting organic solvent-based coloring paint obtained by mixing these with an organic solvent.

(A-1) is a hydroxyl group-containing resin having an acid value of 5 to 100, and a carboxyl group and a hydroxyl group coexist in one molecule.

The content of the carboxyl group is 5 to 100 mgKOH / g, preferably 10 to 70 mgKOH / g based on the acid value.
KOH / g, more preferably 30 to 50 mg KOH / g
Is within the range. If the acid value is less than 5 mgKOH / g, the water-based clear coating (B) to be subsequently coated has poor affinity (wetting property) with the coating film and the water-absorbing ability of the water-based clear coating film is poor, so that the coating is not suitable. (B) Unevenness, sagging, and the like are generated in the coating film, and when the acid value is larger than 100, the water resistance of the coating film (A) decreases, and neither is preferable.

The hydroxyl group in the resin (A-1) is for imparting crosslinking reactivity with the crosslinking agent (A-2).
Its content is 10 to 150 mg KOH based on the hydroxyl value.
/ G, particularly preferably 30 to 80 mgKOH / g.

Specific examples of the resin (A-1) include acrylic resins, vinyl resins and polyester resins having a carboxyl group and a hydroxyl group.

[0014] The acrylic resin and the vinyl resin are polymers comprising a carboxyl group-containing unsaturated monomer and a hydroxyl group-containing unsaturated monomer as main components, and further using other unsaturated monomers as required. Having a number average molecular weight of about 3,000 to 100,000, especially about 5,000 to 50,000
Is preferred.

The carboxyl group-containing unsaturated monomer is a compound having at least one polymerizable unsaturated double bond and at least one carboxyl group in one molecule, for example, acrylic acid, methacrylic acid, maleic acid, itaconic acid, crotonic acid. Examples include acids and half-monoalkyl esters of these dicarboxylic acids (suitably having 1 to 10 carbon atoms), and one or more of these can be used.

The hydroxyl group-containing unsaturated monomer has at least one polymerizable unsaturated double bond and at least one hydroxyl group in one molecule.
Compound, for example, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, acrylic acid or methacrylic acid such as hydroxypropyl methacrylate and 2 to 2 carbon atoms
Monoesters with 10 glycols, and the like, and one or more of these can be used.

The other unsaturated monomer is a compound having at least one polymerizable unsaturated double bond in one molecule, and is an unsaturated monomer having no carboxyl group or hydroxyl group. Specifically, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate,
Butyl acrylate, butyl methacrylate, pentyl acrylate, pentyl methacrylate, hexyl acrylate, hexyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate,
Monoesters of acrylic acid or methacrylic acid such as lauryl acrylate and lauryl methacrylate with monoalcohols having 1 to 24 carbon atoms; glycidyl group-containing unsaturated monomers such as glycidyl acrylate and glycidyl methacrylate; acrylonitrile, acrylamide, N-methyl Nitrogen-containing unsaturated monomers such as acrylamide, N-methylolacrylamide, N-butoxymethylacrylamide and dimethylaminoethyl methacrylate; aromatic ring-containing unsaturated monomers such as styrene, α-methylstyrene and vinyltoluene; vinyl acetate; Vinyl chloride; and one or more of these can be used.

The acrylic resin is a polymer containing 20% by weight or more of monoesters of acrylic acid or methacrylic acid and a monoalcohol having 1 to 24 carbon atoms, and the vinyl resin has a content of 20% by weight of the monoesters. Less than the polymer.

The polyester resin is an oil-free or oil-modified oil-prepared product prepared by an ester reaction using a polyhydric alcohol and a polybasic acid, and if necessary, a monobasic acid and an oil component (including this fatty acid). It is a polyester resin. The number average molecular weight of the resin is about 500
~ 50,000, especially about 3,000 to 30,000 are preferred.

The polyhydric alcohol is a compound having two or more hydroxyl groups in one molecule, for example, ethylene glycol, diethylene glycol, propylene glycol, butanediol, pentanediol, 2,2-dimethylpropanediol, glycerin, trimethylolpropane. And pentaerythritol and Kajura E (trade name, manufactured by Shell Chemical Co., Ltd.), and one or more of these can be used. A polybasic acid is a compound having two or more carboxyl groups in one molecule, for example, phthalic acid, isophthalic acid, tetrahydrophthalic acid, hexahydrophthalic acid, maleic acid, succinic acid, adipic acid, sebacic acid, trimellitic acid Examples thereof include acids, pyromellitic acid and anhydrides thereof, and one or more of these can be used.

The monobasic acid is a compound having one carboxyl group in one molecule and includes, for example, benzoic acid and t-butylbenzoic acid. The oil component (including this fatty acid) is castor oil, dehydrated Castor oil, safflower oil,
Examples include soybean oil, linseed oil, tall oil, coconut oil, and fatty acids thereof, and one or more of these can be used.

In the polyester resin, the carboxyl group may be, for example, a polycarboxylic acid such as trimellitic acid and pyromellitic acid having three or more carboxyl groups in one molecule, or a dicarboxylic acid may be half-esterified. And the hydroxyl group is glycerin,
It can be easily introduced by using a polyhydric alcohol having three or more hydroxyl groups in one molecule such as trimethylolpropane or pentaerythritol.

As the resin (A-1), a graft polymer obtained by grafting an acrylic resin or a vinyl resin to a polyester resin can also be used, and its number average molecular weight is 500 to 4
0000 is suitable. The graft polymer is obtained by reacting the above unsaturated monomer with a polyester resin having a polymerizable unsaturated group.

The neutralization of the carboxyl group in the resin (A-1) is preferably carried out with a basic substance before mixing with the crosslinking agent (A-2).

The basic substance is preferably water-soluble, for example, ammonia, methylamine, ethylamine, propylamine, isopropylamine, butylamine, 2-ethylhexylamine, cyclohexylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine , Trimethylamine, triethylamine, triisopropylamine, tributylamine, ethylenediamine, morpholine, N-alkylmorpholine, pyridine, monoisopropanolamine, methylethanolamine, methylisopropanolamine,
Examples thereof include dimethylethanolamine, diisopropanolamine, diethanolamine, triethanolamine, diethylethanolamine and triethanolamine, and one or more of these can be used. The amount of the neutralizing agent to be used is 0.1 to 2.0 equivalents, particularly 0.3 to 1.0 equivalent to the carboxyl group in the resin (A-1).
Two equivalents are suitable.

The crosslinking agent (A-2) is selected from a block polyisocyanate and an amino resin, and reacts with the hydroxyl group of the neutralized resin (A-1) to apply the metallic coating (A). The film is cross-linked and cured in three dimensions.

The block polyisocyanate is a compound obtained by blocking the isocyanate group of a polyisocyanate compound with a blocking agent such as phenols, alcohols, oximes and lactams.
When heated above 60 ° C.), the blocking agent dissociates to regenerate free isocyanate groups, which undergo a crosslinking reaction with the hydroxyl groups of the resin (A-1).

The polyisocyanate compound contains 2 per molecule.
Compounds having at least two isocyanate groups, such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, Free methylene bis (cyclohexyl isocyanate), isophorone diisocyanate, and free isocyanate groups obtained by reacting these polyisocyanates with low or high molecular weight polyols in excess of isocyanate groups. And prepolymers. The molecular weight of the block polyisocyanate is preferably from 200 to 10,000.

Examples of the amino resin include a methylolated amino resin in which an imino group obtained by condensation reaction of formaldehyde with some or all of the amino groups of an amino compound such as melamine, benzoguanamine or urea may remain. An imino group or a methylol group obtained by etherification with one or more alcohols selected from monoalcohols having 1 to 10 carbon atoms remains in all or a part of the methylol groups of the methylolated amino resin. And alkyl etherified amino resins that may be present. The number average molecular weight of the alkyl etherified amino resin is preferably from 400 to 3,000.

The neutralized resin (A-1) and the crosslinking agent (A-
The ratio to 2) is based on the solid content, and the former is suitably 50 to 90% by weight, particularly 60 to 80% by weight, and the latter is suitably 50 to 10% by weight, particularly 40 to 20% by weight.

The coloring pigment (A-3) is a pigment for forming a solid tone or metallic tone coating film, and is a known solid color pigment and metallic pigment (interference pigment) known per se used in paints. ) Can be applied. Examples of solid color pigments include inorganic pigments such as titanium oxide, zinc white, carbon black, cadmium red, molybdenum red, chrome ero, chromium oxide, prussian blue, and cobalt blue; azo pigments, phthalocyanine pigments, Quinacridone pigments, isoindoline pigments, sullen pigments,
Organic pigments such as perylene pigments; as metallic pigments, for example, flaky aluminum, mica, mica coated with metal oxide, mica-like iron oxide, silver-plated glass flake, titanium-coated graphite, metal titanium flake,
And phthalocyanine flakes.

The amount of the coloring pigment (A-3) can be arbitrarily selected according to the purpose and is not limited.

The colored coating (A) in the present method is obtained by mixing a neutralized product of the resin (A-1), a crosslinking agent (A-2) and a coloring pigment (A-3) with an organic solvent. Can be

As the organic solvent, any of the known organic solvents for coatings can be used, for example, esters, ethers, alcohols, amides, ketones, aliphatic hydrocarbons, alicyclic hydrocarbons and aromatics. Examples thereof include hydrocarbon solvents, and one or more solvents selected from these solvents can be used.
In particular, among them, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether acetate,
Diethylene glycol monoethyl ether acetate, dioxane, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether,
Diethylene glycol diethyl ether, diethylene glycol monobutyl ether, propylene glycol monoethyl ether, dipropylene glycol monomethyl ether, methyl alcohol, ethyl alcohol, allyl alcohol, n-propyl alcohol, isopropyl alcohol, tertiary butyl alcohol, ethylene glycol, 1,2-propylene It is preferable to use a hydrophilic organic solvent such as glycol, 1,3-butylene glycol, 2,3-butylene glycol, hexylene glycol, hexanediol, dipropylene glycol, acetone, and acetone alcohol. One or two or more of these hydrophilic organic solvents can be used. The hydrophilic organic solvent is easily dissolved in water, and is an organic solvent that dissolves at 50 ° C. or more at 100 ° C. at 20 ° C., for example. The proportion of the hydrophilic organic solvent is suitably 20% by weight or more, especially 40 to 100% by weight, based on the total weight of the organic solvent contained in the colored coating material (A) at the time of coating.

In the colored coating (A), a part of these organic solvents is replaced by water such as deionized water to form a mixed system of an organic solvent and water, and a coating obtained by mixing the above components is also included. It is. In a mixed system of an organic solvent and water, the content of the organic solvent is preferably in the range of 50 to 100% by weight, and the content of water is preferably in the range of 0 to 50% by weight.

The coloring paint (A) may further contain a structural viscosity imparting agent, an extender pigment and the like as needed. The non-volatile matter concentration of the colored coating material (A) at the time of coating is usually 15 to 50% by weight, but the amount of the organic solvent is reduced to 25 to 45% by weight, particularly 35 It is preferably a high solid type adjusted to ~ 45% by weight.

In the present method, the colored paint (A) can be directly applied to an object to be coated such as an automobile outer plate (made of metal or plastic), but may be a cationic or anionic electrodeposition paint. It is preferable to apply a primer and an intermediate coating paint on the cured coating surface.

The coating of the colored paint (A) has a viscosity of 1 when applied.
3-30 seconds / Ford cup # 4/20 ° C, preferably 15-20 seconds / Ford cup # 4/20 ° C,
By air spray, airless spray, electrostatic coating, etc., the film thickness based on the cured coating film is 5 to 25 μm, especially 10 to 10 μm.
It is preferable to apply the coating so as to have a thickness of 20 μm. The coating film of the colored coating (A) is left at room temperature for 1 to 20 minutes as needed without being heated and cured, and then a thermosetting water-based clear coating (B) is applied to the uncured coating surface. .

Water-based clear paint (B): A water-based liquid paint applied to the uncured coating surface of the colored paint (A). The base resin (B-1) and the crosslinking agent (B-2) are mixed and dispersed in water. It becomes. Examples of the base resin (B-1) include an acrylic resin having a carboxyl group and a hydroxyl group, a vinyl resin, and a polyester resin.

The carboxyl group makes the resin easy to dissolve or disperse in water.
150 mgKOH / g, especially 30-100 mgKOH /
g is suitable. The hydroxyl group imparts crosslinking reactivity with the crosslinking agent (B-2), and its content is from 10 to 150 mgKOH / g, particularly from 30 to 80 mgK, based on the hydroxyl value.
OH / g is preferred. Among these base resins, acrylic resin and vinyl resin have a number average molecular weight of about 3,000 to
100,000, especially about 5,000 to 50,000, polyester resin about 500 to 50,000, especially about 3,000 to 50,000
30,000 is preferred.

The acrylic resin, the vinyl resin and the polyester resin (base resin B-1) use the same components as described for the resin (A-1) of the colored coating material (A) and have a hydroxyl value, an acid value and a molecular weight. Although it is obtained by solution polymerization in an organic solvent so as to fall within the above range, it can also be produced by emulsion polymerization in the presence of an aqueous dispersion stabilizer solution.

Examples of the dispersion stabilizer used in the emulsion polymerization include a nonionic surfactant and an anionic surfactant, and an acid value of 20 to 150 and a number average molecular weight of 5,000 to 3,000.
An aqueous solution of an aqueous resin such as 0000 acrylic resin can be suitably used.

The emulsion polymerization itself can be carried out by a known method. Among them, an emulsion produced by a multi-stage polymerization method using a carboxyl group-containing unsaturated monomer is preferable because of excellent workability in coating. That is, first, polymerization is carried out in a system containing no or almost no carboxyl group-containing unsaturated monomer (usually 3% by weight or less in all monomers), and then a large amount of carboxyl group-containing unsaturated monomer (usually (5 to 30% by weight in the monomer), and polymerization and neutralization are preferable, because the viscosity of the emulsion increases, and there is no sagging or unevenness and the coating workability is excellent. As the neutralizing agent, the substances exemplified for the resin (A-1) can be used, and the amount of the neutralizing agent to be used is 0.1 to 2.0 equivalents, particularly 0.3 to 1.0 equivalent to the carboxyl group in the polymer. Two equivalents are suitable.

Further, as the base resin (B-1), polyisocyanate, polyether polyol or polyester polyol having a number average molecular weight of 500 to 5,000, low molecular weight polyol having a molecular weight of less than 500 and dimethylol alkanoic acid For example, polyurethane obtained by subjecting a compound to a urethane reaction can be used.

The crosslinking agent (B-2) reacts three-dimensionally with hydroxyl groups of the base resin (B-1) to form a cured coating film of the water-based clear coating material (B). One or more selected from amino resins can be used. As the block polyisocyanate and the amino resin, a crosslinking agent (A-2) for the colored coating (A) is used.
One or more selected from those exemplified above can be used.

The ratio of the base resin (B-1) to the crosslinking agent (B-2) was 5% based on the total weight of the two components.
0-90%, especially 60-75%, crosslinker 50-50
%, Particularly preferably 40 to 25%.

The water-based clear paint (B) is a base resin (B-
It is obtained by mixing and dispersing 1) and the crosslinking agent (B-2) in water. In the water-based clear paint (B), a part of water can be replaced by the hydrophilic organic solvent exemplified in the colored paint (A), and the content of the organic solvent is 5 to 50 based on the total amount of water. % By weight is suitable.

The aqueous clear paint (B) may further contain a thixotropic agent, a solid color pigment, a metallic pigment, an extender pigment, and the like, if necessary, to the extent that the transparency of the coating film is not impaired. it can. Further, an ultraviolet absorber, a light stabilizer, a surface conditioner, and the like can be added.

The non-volatile content of the aqueous clear coating composition (B) at the time of application is usually preferably 30 to 70% by weight, and the single coating film is a colorless and transparent coating, or a transparent solid or transparent metallic coating. Here, the transparent coating is 30
The light transmittance of the cured coating film of μ is 50% or more.

The water-based clear paint (B) is applied to the uncured colored paint (A) which has been left at room temperature for 1 to 20 minutes as required. The viscosity at the time of application of the water-based clear paint (B) is 2
0-60 seconds / Ford cup # 4/20 ° C, preferably 30-50 seconds / Ford cup # 4/20 ° C,
The film thickness based on the cured coating film is 25 to 50 μm, particularly 30 by air spray, airless spray, electrostatic coating or the like.
It is preferable to apply the coating so as to have a thickness of about 40 μm.

In the present method, the water-based clear paint (B) is applied to the uncured coating surface of the colored paint (A), and then about 100 to 1
The method is accomplished by heating both coatings simultaneously at 80C, preferably 120-160C for about 10-40 minutes.

The technical effects of the method of the present invention are as follows.

1. Compared with 2C1B using an organic solvent-based coloring paint and an organic solvent-based clear paint, the use of a water-based paint as the clear paint contributed to the prevention of air pollution.

2. The neutralized product in the uncured coating film of the colored coating (A) has a strong water absorption property. When the water-based clear coating (B) is applied to the coated surface, the water content in the coating (B) coating film is reduced. Is rapidly absorbed into the coating film of the paint (A) and the viscosity increases,
Deviation, dripping, unevenness, etc. could be prevented. Therefore, the water-based clear coating material (B) can be applied without being influenced by the surrounding humidity, and the finished appearance is hardly deteriorated. That is, it is not necessary to strictly control the humidity at the time of applying the water-based clear paint (B). Therefore, the step of pre-drying the colored paint (A) before applying the water-based clear paint (B) is not particularly necessary.

3. As described above, the water content in the clear paint (B) coating film is rapidly absorbed into the coloring paint (A) coating film and the viscosity increases, so that the affinity (sliminess) of both paints is reduced. In addition, the finished appearance such as smoothness, sharpness, gloss and the like of the multi-layer coating surface and the adhesion between layers of both coating films were improved.

Examples and comparative examples according to the present invention will be described below. All parts and percentages are based on weight.

1. Sample Production Example 1) Acrylic resin solution (a-1) Monomer component-1 (Note 1) was added to 60 parts of butyl cellosolve heated to 120 ° C. over 3 hours and copolymerized.
Acid value 40, hydroxyl value 52 and number average molecular weight about 1000
Acrylic resin solution having a nonvolatile content of 60% (a-1)
I got

Note 1: Monomer component-1 30 parts of methyl methacrylate, ethyl acrylate 23
Parts, 30 parts of butyl acrylate, 12 parts of hydroxyethyl methacrylate, 5 parts of acrylate, and 2 parts of α, α′-azobisisobutyronitrile.

2) Acrylic resin solution (a-1N) 3.5 parts of dimethylaminoethanol was added to 100 parts of acrylic resin solution (a-1) to neutralize the mixture, and then isopropyl alcohol was added to form an acrylic resin having a nonvolatile content of 50%. A resin solution (a-1N) was obtained.

3) Polyester resin solution (b-1) 0.7 mol of neopentyl glycol, 0.3 mol of trimethylolpropane, 0.4 mol of phthalic anhydride and 0.5 mol of adipic acid are placed in a reaction vessel, and ~ 230 ° C
For 5 hours, then trimellitic anhydride 0.03
After the addition by mol and further reacting at 180 ° C. for 1 hour, butyrocellosolve was added thereto, and a polyester resin solution (b-1) having an acid value of 40, a hydroxyl value of 70, and a 70% nonvolatile matter having a number average molecular weight of about 6000 (b-1) I got

4) Polyester resin solution (b-1N) 100 parts of the polyester resin solution (b-1) was neutralized by adding 4 parts of dimethylaminoethanol, and then isopropyl alcohol was added to obtain a polyester resin solution having a nonvolatile content of 60%. (B-1N) was obtained.

5) Acrylic resin emulsion (c-1) 140 parts of deionized water and 30% "Newco
l707SF "(surfactant, manufactured by Nippon Emulsifier Co., Ltd.
2.5 parts of trade name) and 1 part of the following monomer component-2 (Note 2) are added, mixed in a nitrogen stream, and 3 parts of a 3% ammonium persulfate aqueous solution is added at 60 ° C. Then, after heating to 80 ° C., 79 parts of monomer component-2 (Note 2), 30% “N
ewcol 707SF "2.5 parts, a monomer emulsion comprising 4 parts of a 3% aqueous solution of ammonium persulfate and 42 parts of deionized water were added to the reaction vessel over 4 hours using a metering pump. After completion of the addition, it is aged for 1 hour.

Further, at 80 ° C., the following monomer components:
3 (Note 3) 20.5 parts and 4 parts of a 3% aqueous solution of ammonium persulfate are simultaneously dropped in parallel into the reaction vessel in 1.5 hours. Thereafter, the mixture was aged for 1 hour, diluted with 30 parts of deionized water, and filtered at 30 ° C. with a 200 mesh nylon cloth. Deionized water was further added to the filtrate, and the pH was adjusted to 7.5 with dimethylaminoethanolamine to obtain an acrylic resin emulsion (c-1) having an average particle diameter of 0.1 μm and a nonvolatile content of 20%.

Note 2: Monomer component-2 55 parts of methyl methacrylate, 8 parts of styrene, 9 parts of n-butyl acrylate, 5 parts of 2-hydroxyethyl acrylate, 1,6-hexanediol diacrylate
Consists of 2 parts and 1 part of methacrylic acid.

Note 3: Monomer component-3 5 parts of methyl methacrylate, 7 parts of n-butyl acrylate,
It consists of 5 parts of 2-ethylhexyl acrylate, 3 parts of methacrylic acid and 0.5 part of 30% “Newcol 707SF”.

6) Preparation of Colored Paint (A-1) 70 parts (solid content) of an acrylic resin solution (a-1N), Cymel 370 (trade name, manufactured by Mitsui Cytec Co., Ltd., melamine resin, solid content 88%) 30 parts (solid content), 99.98 parts of titanium dioxide pigment and 0.02 of carbon black
Parts were mixed with isopropanol and uniformly dispersed.
Non-volatile content 40%, viscosity 20 seconds / Ford cup # 4/2
It was 0 ° C.

7) Preparation of Colored Paint (A-2) 70 parts (solid content) of a polyester resin solution (b-1N),
30 parts of Cymel 370 (solid content), titanium dioxide 9
9.98 parts and 0.02 parts of carbon black were mixed with isopropanol and uniformly dispersed. Nonvolatile content 4
5%, viscosity 20 seconds / Ford cup # 4/20 ° C.

8) Preparation of Colored Paint (A-3) 35 parts of acrylic resin solution (a-1N) (solid content), 35 parts of polyester resin solution (b-1N) (solid content), 30 parts of Cymel 370 (solid) Min.) And 15 parts of scaly aluminum pigment were mixed with isopropanol and uniformly dispersed. The nonvolatile content was 35%, and the viscosity was 15 seconds / Ford cup # 4/20 ° C.

9) Preparation of Colored Paint (A-4) (Comparative) 70 parts (solid content) of acrylic resin solution (a-1), 30 parts (solid content) of Cymel 370, titanium dioxide pigment
98 parts and 0.02 parts of carbon black were mixed with isopropanol and uniformly dispersed. Nonvolatile 40
%, Viscosity 20 seconds / Ford cup # 4/20 ° C.

10) Preparation of Colored Paint (A-5) (for Comparison) 35 parts (solid content) of acrylic resin solution (a-1), 35 parts (solid content) of polyester resin solution (b-1), Cymel 370 30 parts (solid content) and 15 parts of flaky aluminum pigment were mixed with isopropanol and uniformly dispersed. The nonvolatile content was 35% and the viscosity was 20 seconds / Ford cup # 4/20 ° C.

11) Preparation of Colored Paint (A-6) (Comparative) 35 parts (solid content) of polyester resin solution (b-1N),
3030 parts (solid content) of Cymel 370, 99.98 parts of titanium dioxide pigment and 0.02 parts of carbon black were mixed with deionized water and uniformly dispersed. Nonvolatile 40
%, Viscosity 25 seconds / Ford cup # 4/20 ° C.

12) Water-based thermosetting clear paint (B-
1) Deionized water 40 in 50 parts of acrylic resin solution (a-1N)
Parts and dispersed, and further, a polyester resin solution (b-
1N) 50 parts and 34 parts of Cymel 370 are mixed,
Then, 100 parts of the acrylic resin emulsion (c-1) was blended, and deionized water was added to obtain an aqueous clear paint having a nonvolatile content of 40% and a viscosity of 40 seconds / Ford cup # 4/20 ° C.

2. Examples and Comparative Examples Degreasing and zinc phosphate treated steel sheets (JIS G314
1, a 400 × 300 × 0.8 mm size cationic electrodeposition paint (“Elecron 9400HB” manufactured by Kansai Paint Co., Ltd., trade name, epoxy resin-based cationic resin using a blocked polyisocyanate compound as a curing agent) By electrodeposition coating to a film thickness of 20 μm (cured coating film), heating at 170 ° C. for 20 minutes for cross-linking and curing, and then applying an intermediate coating material (“Lugabake intermediate coating” Kansai Paint) Co., Ltd., trade name, polyester resin / amino resin type, organic solvent type) was applied so as to have a film thickness of 40 μm (cured coating film), and was heated at 140 ° C. for 30 minutes for crosslinking and curing.

The coated steel sheets thus obtained were coated with the colored coatings (A-1) to (A-6) by using a mini-bell rotating electrostatic coating machine while changing the humidity in the booth. The coating thickness was 20 μm based on the cured coating. After applying the colored paint, leave it in the booth for 1 minute, and then in a wet-on-wet state, apply the water-based thermosetting clear paint (B-1) to the colored paint in one stage using an air atomizing electrostatic coating machine. It was painted with the same booth humidity. The coating thickness is 4 based on the cured coating
It was 0 μm. After applying the clear paint, leave it in the booth for 1 minute, and then heat it in a hot air circulating drying oven at 140 ° C for 30 minutes to simultaneously form a multi-layer coating film composed of the colored paint (A) and the clear paint (B-1). Crosslinked and cured.

Table 1 shows the performance of the coating film coated in the above steps together with the respective steps.

[0076]

[Table 1]

The coating film performance test method is as follows.

Metallic feeling: ALCOPE LMR10
IV value (trade name, manufactured by Fuji Industrial Co., Ltd.) was measured. When this value is increased, it indicates that the metallic feeling is excellent.

Smoothness: Measured with a tension meter manufactured by RENAULT. An increase in this value indicates that the smoothness is excellent.

Sharpness: Sharpness gloss meter P.I. G. FIG. It measured by D-IV. When this value is increased, it indicates that the sharpness is excellent.

Appearance: Unevenness of color and metallic unevenness due to the return phenomenon of the coated surface and the mixture of both coating films were visually observed. ○ indicates no color unevenness or metallic unevenness, Δ indicates slight color unevenness or metallic unevenness, and X indicates remarkable color unevenness or metallic unevenness.

Displacement: The multilayer coating applied in the above process was visually observed to evaluate the displacement of the clear coating.
○ indicates no slippage, Δ indicates slight slippage, and X indicates notable slippage.

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Mikio Shimakawa 4-171-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Prefecture Inside Kansai Paint Co., Ltd. (72) Inventor Hiroaki Oda 4-1-1, Higashi-Hachiman, Hiratsuka-shi, Kanagawa Kansai Paint Co., Ltd.

Claims (1)

[Claims] 1. A thermosetting organic solvent-based colored paint (A) containing a neutralized product of a hydroxyl group-containing resin having an acid value of 5 to 100 and a crosslinking agent selected from block polyisocyanate and amino resin. ), And then applying a thermosetting water-based clear (B) to the uncured coated surface, and then heating to simultaneously cure the multilayer coating film composed of (A) and (B). Characteristic coating film forming method.