JPH08290102A - Coating method - Google Patents

Abstract

PURPOSE: To apply a water intermediate coating, a water base coating and a clear coating without degrading finished appearance or the like. CONSTITUTION: This coating method is a method for coating with the thermosetting water intermediate coating (A), the thermosetting water base coating (B) and thermosetting clear coating (C) and for applying the coating (A) and the coating (B) by wet-on-wet method. The neutralization value of the base resin of the intermediate coating (A) is controlled to 10-40 (KOHmg/g) and the neutralization value of the base resin of the base coating is controlled to be 10-20 (KOHmg/g) larger than that of the water intermediate coating (A).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating an aqueous intermediate coating composition, an aqueous base coating composition and a clear coating composition without deteriorating the finished appearance.

[0002]

2. Description of the Related Art It has already been practiced to coat a water-based intermediate coating composition, cure it, and then coat the water-borne base coating composition and the clear coating composition by the 3-coat 2-bake method.

However, in order to shorten the process, for example, these three types of paints are wet-on-wet (w
/ W) and simultaneously curing these three-layer coatings by heating once (3C1B) is strongly desired. However, even if the above coating is simply coated by the 3C1B method, an aqueous intermediate coating film is applied. It was not practical because it was reversed or mixed between the layers of the water-based base coat and the water-based base coat, and the finished appearance such as gloss, gloss and sharpness of the coat was deteriorated.

[0004]

The object of the present invention is to eliminate the above-mentioned deficiencies, and as a result of intensive research, as a water-based intermediate coating composition and a water-based base coating composition which are coated by a wet-on-wet system, neutralization of a specific range is achieved. It has been found that the object can be achieved by incorporating a base resin having a valence, and the present invention has been completed.

That is, the present invention uses a thermosetting aqueous intermediate coating composition (A), a thermosetting aqueous base coat (B) and a thermosetting clear coating composition (C), and the aqueous intermediate coating composition (A) and A method of coating an aqueous base coat (B) by a wet-on-wet method, wherein the neutralization value of the base resin of the aqueous intermediate coating paint (A) is 10 to 40 (KOHmg / g), and the aqueous base coat paint (B) The coating method is characterized in that the neutralization value of the base resin of (1) is made 10 to 20 larger than that of the water-based coating (A).

The present invention will be described in more detail below.

Thermosetting water-based intermediate coating material (A) : This is a coating material to be coated on the surface to be coated prior to the coating of the thermosetting water-based coating material (B). It is a base resin, a cross-linking agent, a coloring pigment and an extender pigment. Is a thermosetting water-based intermediate coating composition in which various additives, organic solvents, and the like are further mixed and dispersed in water.

The base resin is a main component for forming the coating film of the waterborne intermediate coating composition (A), has a functional group capable of reacting with a crosslinking agent and a carboxyl group in its molecule, and has a specific neutralization value. Known materials can be used as long as they have them. Of these, the carboxyl group is for neutralizing and making it aqueous. Examples of the functional group capable of reacting with the crosslinking agent include a hydroxyl group, an epoxy group, an isocyanate group, an amino group and the like, and these may be used alone or in combination of two or more. Further, it is preferable that two or more of the crosslinkable functional groups are bonded to one molecule of the base resin, and the introduction of these carboxyl group and crosslinkable functional group is carried out by a known method. As the base resin, for example, one or more selected from acrylic resins, polyester resins, alkyd resins, urethane resins, epoxy resins and modified resins thereof having these functional groups can be preferably used. Has a number average molecular weight of about 1,000
0-100,000, especially about 2,000-30,000
The range is suitable. Further, as the base resin, an aqueous emulsion of a granular resin obtained by three-dimensionally crosslinking and having a carboxyl group and a crosslinkable functional group can also be used.

In the present invention, it is necessary that the neutralization value of the base resin of the waterborne intermediate coating composition (A) is within the range of 10-40, preferably 20-30. When the neutralization number of the base resin is less than 10, the water dispersion stability is reduced and the layer easily mixes or reverses with the coating film of the aqueous base coat paint (B), while when it is more than 40, the coating workability and the water resistance of the coating film are reduced. It is not preferable because it deteriorates the properties.

In the present invention, the "neutralization value" of the base resin means the amount of the neutralized carboxyl groups among the carboxyl groups contained in 1 g of the base resin, converted into mg of KOH. . This neutralization may be all or some of the carboxyl groups of the base resin.

That is, the unneutralized carboxyl group is not introduced into this neutralization value. Therefore, when all the carboxyl groups of the base resin are neutralized, the neutralization value of the base resin becomes a value equal to its acid value. When a part of the base resin is neutralized, the neutralization value is smaller than the acid value.

The neutralization value can be adjusted by the following method.

(I) The unneutralized total acid value (KOHmg / g) is measured. The oxidation of all neutralizable COOH contained in the resin is measured. Oxidation is preferably within the range of 10-50.

(Ii) The neutralization value is selected (determined). It is within the range of 10 to 40 for the paint (A).

(Iii) These are applied to the following.

[0016]

[Equation 1]

(Iv) When the resin of (i) is neutralized with the amount of the neutralizing agent obtained in (iii), a base resin having a neutralization value of (ii) is obtained.

The amount of carboxyl groups in the base resin of the waterborne intermediate coating composition (A) is 10 to 50 based on the acid value in the unneutralized state.
It is preferably KOHmg / g, especially 20 to 30 KOHmg / g. Then, by neutralizing a part or all of the carboxyl groups and adjusting the neutralization value within the above range, a base resin applicable to the water-based paint (A) is obtained. This neutralization is easily performed using an amino compound or an alkali metal hydroxide.

Amino compounds used as the neutralizing agent include ammonia; ethylamine, propylamine, butylamine, benzylamine, monoethanolamine,
Neopentanolamine, 2-aminopropanol, 3
-Primary monoamines such as aminopropanol; diethylamine, diethanolamine, di-n- or di-is
Secondary monoamines such as o-propanolamine, N-methylethanolamine and N-ethylethanolamine; tertiary such as dimethylethanolamine, trimethylamine, triethylamine, triisopropylamine, methyldiethanolamine and dimethylaminoethanol.
Grade monoamine; diethylenetriamine, hydroxyethylaminoethylamine, ethylaminoethylamine, methylaminopropylamine, etc., and hydroxides include alkali such as sodium hydroxide, potassium hydroxide, lithium hydroxide, calcium hydroxide, barium hydroxide. Metal or alkaline earth metal hydroxides are preferred.

The cross-linking agent is for three-dimensionally cross-linking and curing the above-mentioned base resin, and one or more kinds selected from, for example, amino resins and polyisocyanate compounds can be used. Here, as the amino resin, a methylolated amino resin obtained by reacting an amino component such as melamine, urea, or benzoguanamine with formaldehyde, or part or all of the methylol group of the resin is changed to a monoalcohol having 1 to 5 carbon atoms. Examples thereof include etherified products. Examples of the polyisocyanate compound include aliphatic, alicyclic and aromatic polyisocyanate compounds having two or more isocyanate groups in one molecule. A blocked polyisocyanate compound obtained by reacting these compounds with a blocking agent may be used.

Known base resins and cross-linking agents can be used in the waterborne intermediate coating composition (A), and the mixing ratio of both components is not particularly limited, but the base resin is based on the total weight of both components. Is 50 to 90% by weight, preferably 60 to 80% by weight, and the cross-linking agent is 50 to 10% by weight, preferably 40 to 20% by weight.

As the color pigment, organic or inorganic color pigments for paints; scaly aluminum, copper,
Examples include bright metallic pigments such as mica, coated mica, and mica-like iron oxide. One or more selected from these can be used.

The waterborne intermediate coating composition (A) can be directly applied to a metal or plastic object to be coated such as an automobile, and the object to be coated may be a primer (for example, a cationic electrodeposition coating material) if necessary. Etc.) is preferably painted in advance. The aqueous intermediate coating composition (A) is adjusted to have a viscosity of 20 to 80 seconds / Fordcup # 4/20 ° C., especially 30 to 60 seconds, and is 10 to 60 μm based on the cured coating film by spray coating, electrostatic coating or the like. It is preferable to apply a coating having a film thickness of. Also, electrodeposition coating is possible.

Thermosetting water-based base coat paint (B) : This is a paint to be applied on the uncured coating surface of the above-mentioned water-based paint (A), and the base resin, crosslinking agent and color pigment are dissolved or dispersed in water. And if necessary, extender pigment,
Additives, organic solvents and the like can be added.

The base resin is a main component for forming the coating film of the aqueous base coat paint (B), and those known per se having a functional group capable of reacting with a crosslinking agent and a carboxyl group in the molecule can be used. . The carboxyl group is for neutralizing and making it aqueous. Examples of the functional group capable of reacting with the crosslinking agent include a hydroxyl group, an epoxy group, an isocyanate group, an amino group and the like, and these may be used alone or in combination of two or more. It is preferable that two or more carboxyl groups and crosslinkable functional groups are bonded per molecule of the base resin, and the introduction of these functional groups is performed by a known method. Examples of the base resin include acrylic resins, polyester resins, alkyd resins, urethane resins having these functional groups,
One or more selected from epoxy resins and modified resins thereof can be preferably used, and their number average molecular weights are about 1,000 to 100,000, particularly about 5,0.
A range of 00-60,000 is suitable. Further, as the base resin, an emulsion formed by three-dimensionally crosslinking and having a carboxyl group and a crosslinkable functional group and dispersing this in water can also be used.

In the present invention, an aqueous base coat paint (B)
It is necessary that the neutralization value of the base resin is 10 to 20 KOHmg / g higher than that of the above waterborne intermediate coating composition (A). If the difference between the neutralization value of the base resin of the water-based base coat paint (B) and the neutralization value of the base resin of the water-based intermediate coating paint (A) is less than 10 KOHmg / g, the two coating films tend to be mixed or inverted, while If the difference is more than 20 KOHmg / g, the coating workability and the water resistance of the coating film are deteriorated, which is not preferable.

The amount of carboxyl groups in the base resin of the aqueous base coat paint (B) is preferably 20 to 60 KOHmg / g, particularly 30 to 50 KOHmg / g based on the acid value in the unneutralized state. Then, by neutralizing a part or all of the carboxyl groups and adjusting the neutralization value within the above range, a base resin applicable to the aqueous base coat paint (B) can be obtained. This neutralization is easily performed using the amino compound or the alkali metal hydroxide.

The cross-linking agent is for three-dimensionally cross-linking and curing the above-mentioned base resin, and is, for example, an amino resin,
Particularly, one or more selected from partially or completely alkyl etherified melamine resins and polyisocyanate compounds (including blocked compounds) can be used.

As the base resin and the cross-linking agent in the water-based base coat paint (B), known ones can be used, and the mixing ratio of the both components is not particularly limited, but the base resin is based on the total weight of the both components. 50 to 90% by weight, preferably 60 to 80% by weight, the crosslinking agent is 50 to 10% by weight,
It is preferably 40 to 20% by weight.

As the color pigment, one or more selected from the color pigments for paints and the metallic pigments exemplified in the above waterborne intermediate coating composition (A) can be used.

The aqueous base coat (B) is applied to the uncured coating surface of the aqueous intermediate coating composition (A) (wet on wet system). For example, it is preferable to apply the water-based paint (A), leave it at room temperature for several minutes, and then apply the water-based paint (B).

The water-based base coat paint (B) has a viscosity of 20.
-80 seconds / Fordcup # 4/20 ° C., particularly 30 to 60 seconds, and preferably 10 to 60 μm based on the cured coating film by spray coating, electrostatic coating or the like.

Thermosetting clear coat paint (C) : This is a paint to be applied to the coating surface of the thermosetting base coat paint (B), which contains a base resin and a crosslinking agent as main components. Is dissolved or dispersed in an organic solvent and / or water. You can use powder paint.

The base resin is a main component forming the clear coat coating film, and a resin known per se having a functional group capable of reacting with a crosslinking agent in its molecule can be used. Examples of the functional group include a hydroxyl group, an epoxy group, an isocyanate group, an amino group, and the like, and it is preferable that one or two or more selected from these groups have two or more in one molecule. Further, a carboxyl group may coexist in order to form an aqueous paint. Examples of the base resin include acrylic resins, polyester resins, alkyd resins, fluorine-containing resins, silicon-containing resins and urethane resins having these functional groups. The number average molecular weight of these resins is about 100 to 100,000, especially 2,000.
A range of 0 to 50,000 is suitable, but a larger range is acceptable.

The cross-linking agent is one which can be cross-linked and hardened by reacting with these base resins, for example, melamine resin,
Urea resins, polyisocyanate compounds (including blocked compounds), epoxy group-containing compounds, carboxyl group-containing compounds and the like can be used.

The mixing ratio of the base resin and the crosslinking agent is not particularly limited, but the base resin is 50 to 90% by weight, preferably 60 to 80% by weight, and the crosslinking agent is 50 to 50% by weight, based on the total weight of both components. 10% by weight, preferably 40-20% by weight
Range.

The thermosetting clear coat paint (C) is applied to the uncured or cured coating surface of the thermosetting base coat paint (B). For example, it is preferable to apply the clear coating composition (C) after coating the coating composition (B) and leaving it at room temperature or 100 ° C. or lower for several minutes, or after heat curing at 100 to 180 ° C.

When the clear coating composition (C) is a liquid containing an organic solvent and / or water as a solvent or a dispersion medium, its viscosity is 15 to 40 seconds / Fordc in an organic solvent system.
up # 4/20 ℃, especially 20-30 seconds, water system 20-80 seconds
/ Fordcup # 4/20 ° C, especially 30-60 seconds is suitable. The coating can be performed by spray coating, electrostatic coating, or the like, and the film thickness is preferably in the range of 20 to 200 μm based on the cured coating film.

The coating method of the present invention comprises: (1) sequentially coating the above-mentioned thermosetting aqueous intermediate coating composition (A), thermosetting aqueous base coat (B) and thermosetting clear coat (C) in a wet-on-wet system. After about 120 to about 18
By heating at 0 ° C. for 20 to 40 minutes to simultaneously cure the three-layer coating film (3C1B method), or (2) thermosetting aqueous intermediate coating composition (A) and thermosetting aqueous base coat (B).
Is sequentially applied by the wet-on-wet method, approximately 120-
Heat at about 180 ° C. for 20 to 40 minutes to simultaneously cure the two-layer coating film, then apply thermosetting clear coat (C), and heat at about 120 to about 180 ° C. for 20 to 40 minutes to cure. By doing (3C2B method), the coating method of the present invention is completed.

Further, in the present invention, an aqueous intermediate coating composition (A) for forming a coating film having a cosmetic color tone is used, and a metallic pigment is further blended to form a glittering coating film with a low hiding property. Coating with the above 3C1B method or 3C2B method using the above-mentioned water-based base coat (B) is also included. Even in this coating system, the aqueous intermediate coating composition (A) can be applied directly to the object to be coated or on the surface of the primer coating, without performing ordinary intermediate coating.

[0041]

【The invention's effect】

1. Water-based intermediate coatings, water-based base coatings and clear coatings can be applied and cured by the 3-coat 1-bake method, and the heating process can be partially omitted, so the process can be shortened.

Even if a water-based coating [for example, the above-mentioned water-based intermediate coating (A) and water-based base coat (B)] is applied by wet-on-wetting in the 2.3-coat method, the finished appearance such as gloss and sharpness is obtained. Does not reduce.

Next, examples of the present invention and comparative examples will be described. Parts and percentages are as a rule by weight.

I Preparation of Sample Thermosetting waterborne intermediate coating composition ( A) (A-1): Polyester resin (* 1) 1,000 parts (solid content weight), dimethylaminoethanol (* 2) 4
0 part, melamine resin (* 3) 300 parts (solid content weight),
1,500 parts of titanium white pigment (* 4) and 4.5 parts of carbon black (* 5) were mixed and dispersed in deionized water to obtain an intermediate coating composition (A-1). Viscosity 40 seconds / Ford cup # 4/20
° C.

(* 1) Polyester resin: Neopentyl glycol (0.75 mol), trimethylolpropane (0.25 mol), adipic acid (0.4 mol) and phthalic anhydride (0.5 mol) reacted In addition to the container, 220 ℃
After reacting at room temperature for 5 hours, add trimellitic anhydride to 0.0
A polyester resin having a number average molecular weight of about 6,000, an acid value of 25, and a hydroxyl value of 110, which is obtained by adding 35 mol and reacting at 160 ° C. for 1 hour.

(* 2) Dimethylaminoethanol: manufactured by Nippon Emulsifier Co., Ltd., trade name "Amino alcohol 2 Mab"
s ”was used. As a result, polyester resin (*
1 equivalent of the carboxyl group (acid value 25) of 1) is neutralized (neutralization value 25).

(* 3) Melamine resin: Mitsui Cytec Co., Ltd., trade name "Cymel 703" (amino group-containing methyl etherified melamine resin) (* 4) Titanium white pigment: Sakai Chemical Industry Co., Ltd., product Name "R-41" (* 5) Carbon black: Mitsubishi Chemical Co., Ltd., trade name "Mitsubishi Carbon Black M-100" thermosetting water-based base coat paint (B) (B-1): Aluminum pigment concentrate ( * 6) 48 copies,
Crosslinking agent (* 7) 37.5 parts, acrylic emulsion (*
8) 100 parts, 100 parts of water-soluble acrylic resin (* 9) and 160 parts of deionized water were blended, stirred for 1 hour, and further, "Acrysol ASE-60" (Rohm and Haas Co., thickener ) And dimethylaminoethanolamine were added to adjust the viscosity to 40 seconds and the pH to 8.0 to obtain a thermosetting aqueous base coat paint (B-1).

(* 6) Aluminum pigment concentrated liquid: aluminum paste (metal content 65%) in a stirring and mixing container.
It was obtained by adding 23 parts and 25 parts of butyl cellosolve and stirring and mixing for 1 hour.

(* 7) Crosslinking agent: Hydrophilic melamine resin "Cymel-325" (manufactured by Mitsui Toatsu Chemicals, Inc., trade name, solid content 80%) (* 8) Acrylic emulsion: in reaction vessel , 140 parts of deionized water, 30% "Newcol 707SF"
(Surfactant, manufactured by Nippon Emulsifier Co., Ltd., trade name) 2.5 parts and 1 part of the following monomer mixture (1) were added, and the mixture was stirred and mixed in a nitrogen stream, and then heated to 60 ° C. 3% at the same temperature
Add 3 parts aqueous ammonium persulfate solution. Then 80
After the temperature was raised to ℃, 79 parts of the following monomer mixture (1),
A monomer emulsion consisting of 2.5 parts of 30% "Newcol 707SF", 4 parts of 3% ammonium persulfate aqueous solution and 42 parts of deionized water is added to the reaction vessel using a metering pump over 4 hours. After completion of the addition, aging is carried out at the same temperature for 1 hour. Further, at 80 ° C., the following monomer mixture (2) 2
0.5 parts and 4 parts of a 3% ammonium persulfate aqueous solution are simultaneously dropped into the reaction vessel in parallel over 1.5 hours. After completion of dropping, the mixture was aged at the same temperature for 1 hour, diluted with 30 parts of deionized water, and filtered at 200C with a 200 mesh nylon cloth. Deionized water was further added to this filtrate, pH was adjusted to 7.5 with dimethylaminoethanolamine, and an acrylic resin emulsion having an average particle diameter of 0.1 μm, a solid content of 20%, and an acid value of 40.

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 methacryl. Mixture consisting of 1 part acid.

Monomer mixture (2): 5 parts methyl methacrylate, 5 parts n-butyl acrylate, 5 parts 2-ethylhexyl acrylate, 6.7 parts methacrylic acid and 30%.
A mixture consisting of 0.5 parts of "Newcol 707SF".

(B-2): Aluminum pigment concentrated liquid (*
6) 48 parts, crosslinking agent (* 7) 37.5 parts, acrylic emulsion (* 10) 100 parts, water-soluble acrylic resin (*
9) 100 parts and 180 parts of deionized water were blended, stirred for 1 hour, and then "Acrysol ASE-60" (a thickener made by Rohm and Haas Co.) and dimethylaminoethanolamine were added, and the viscosity was 40 seconds, Adjust to pH 8.0,
A thermosetting water-based base coat paint (B-2) was obtained.

(* 10) Acrylic emulsion: The following monomer mixture (3) is used in place of the above-mentioned (* 8) acrylic emulsion monomer mixture (2), and otherwise the same as (* 8). It was made to react in the process of. The pH was adjusted to 7.5 with dimethylaminoethanolamine and the average particle size was 0.1.
Acrylic resin emulsion with μm, solid content 20% and acid value 45.

Monomer mixture (3): 3 parts methyl methacrylate, 4.7 parts n-butyl acrylate, 2-acrylic acid
3 parts ethylhexyl, 6.9 parts methacrylic acid and 30
% 0.5 "Newcol 707SF" 0.5 part mixture.

(B-3): Aluminum pigment concentrated liquid (*
6) 48 parts, crosslinking agent (* 7) 37.5 parts, acrylic emulsion (* 11) 100 parts, water-soluble acrylic resin (*
9) Mix 100 parts and 150 parts of deionized water, stir for 1 hour, then add "Acrysol ASE-60" (a thickener made by Rohm and Haas Co.) and dimethylaminoethanolamine to obtain a viscosity of 40 seconds, Adjust to pH 8.0,
A thermosetting water-based base coat paint (B-3) was obtained.

(* 11) Acrylic emulsion: The following monomer mixture (4) is used in place of the above-mentioned (* 8) acrylic emulsion monomer mixture (2), and otherwise the same as (* 8). It was made to react in the process of. The pH was adjusted to 7.5 with dimethylaminoethanolamine and the average particle size was 0.1.
Acrylic resin emulsion with μm, solid content 20% and acid value 20.

Monomer mixture (4): 3 parts methyl methacrylate, 7 parts n-butyl acrylate, 5 parts 2-ethylhexyl acrylate, 3 parts methacrylic acid and 30% "Ne".
wcol 707SF "0.5 part mixture.

(B-4): Aluminum pigment concentrated liquid (*
6) 48 parts, crosslinking agent (* 7) 37.5 parts, acrylic emulsion (* 12) 100 parts, water-soluble acrylic resin (*
9) Mix 100 parts and 150 parts of deionized water, stir for 1 hour, then add "Acrysol ASE-60" (a thickener made by Rohm and Haas Co.) and dimethylaminoethanolamine to obtain a viscosity of 40 seconds, Adjust to pH 8.0,
A thermosetting water-based base coat paint (B-4) was obtained.

(* 12) Acrylic Emulsion The following monomer mixture (5) was used in place of the monomer mixture (2) of the above (* 8) acrylic emulsion, and otherwise the same as (* 8). It was made to react in the process. An acrylic resin emulsion adjusted to pH 7.5 with dimethylaminoethanolamine, having an average particle size of 0.1 μm, a solid content of 20% and an acid value of 30.

Monomer mixture (5): 5 parts methyl methacrylate, 7 parts n-butyl acrylate, 5 parts 2-ethylhexyl acrylate, 5 parts methacrylic acid and 30% "Ne".
wcol 707SF "0.5 part mixture.

II Examples and Comparative Examples The thermosetting aqueous intermediate coating composition (A-1) and the thermosetting aqueous base coat coating compositions (B-1) to (B-4) obtained above.
Was applied in accordance with the process described in Table 1 below by a 3-coat 1-coat method.

The surface was treated with "Bondelite # 3030" (a zinc phosphate treating agent manufactured by Nippon Parker Rising Co., Ltd.), and then "ELECRON # 9800" was used as a primer.
A steel sheet obtained by coating (hardening film thickness: 25 μm) with an epoxy resin type cationic electrodeposition coating manufactured by Kansai Paint Co., Ltd. was used as an object to be coated. On this steel sheet, a thermosetting water-based intermediate coating material (A-1), a thermosetting water-based base coat (B-1) to
(B-4) and thermosetting clear coat paint ("Magiclon Clear # 80" manufactured by Kansai Paint Co., Ltd., thermosetting acrylic resin / melamine resin clear coat paint)
(C-1) was applied wet-on-wet by a 3-coat 1-bake method.

That is, the thermosetting water-based intermediate coating composition (A-1) was sprayed onto the steel sheet to give a film thickness of 30 to 30 based on the cured coating film.
The coating is applied so as to have a thickness of 35μ, and the coating is left at room temperature for 5 minutes, and then the thermosetting water-based base coat paints (B-1) to (B-4) are sprayed on the wet coated surface to give a film thickness based on the cured coating film. It is coated so as to have a thickness of 15 to 20 μm, left at room temperature for 5 minutes, and then a thermosetting clear coat coating composition (C-1) is sprayed on the coated surface to give a coating film thickness of 30 to 30 based on the cured coating film.
The coating was applied so as to have a thickness of 35 μ, and the coating was left at room temperature for 7 minutes and then heated at 140 ° C. for 30 minutes to simultaneously cure these three-layer coating films.

[0064]

[Table 1]

Test method Luster: Visual evaluation ○: Good Δ: Slightly inferior ×: Inferior Gloss: 60 degree specular reflectance (%) Visibility: Image clarity measuring device (IMAGE CLARITY METER: manufactured by Suga Test Instruments Co., Ltd.) It is the result measured by. The numbers in the table are I
The CM value takes a value in the range of 0 to 100, and the larger the numerical value, the better the image clarity (image clarity), and the ICM value of 80 or more indicates that the image clarity is extremely excellent.

Impact resistance: Using a DuPont type impact tester, the impact core is 1/2 inch, and the weight is 500 with the coated surface facing up.
The weight of g was dropped, and the drop distance (height cm) at which the coating film was not cracked was measured.

Moisture resistance: 7 at 50 ° C. and 95% humidity
The appearance and adhesion of the coating film after standing for 2 hours were examined.

Criteria for evaluating the appearance of the coating film: ○ means no abnormality,
△ indicates a little swelling and peeling, and × indicates a lot of swelling and peeling.

Adhesion was evaluated by a tape peeling test (100 squares having a size of 1 × 1 mm), and it is shown that 90 or more goggles coating films remain.

Claims (1)

[Claims] 1. A thermosetting water-based intermediate coating composition (A), a thermosetting aqueous base coating (B) and a thermosetting clear coating composition (C) are used, and the aqueous intermediate coating composition (A) and the aqueous base coating (B) are used. In a wet-on-wet system, wherein the neutralizing value of the base resin of the waterborne intermediate coating composition (A) is 10 to 40 (KOHmg / g), and the base resin of the waterborne basecoat coating composition (B). The coating method is characterized in that the neutralization value of is larger than that of the water-based paint (A) by 10 to 20.