JPH0688056A - Coating composition improved in interlayer adhesion, use thereof, and multilayer coating film - Google Patents

Abstract

PURPOSE:To provide a coating compsn. remarkably improved in the adhesion to an undercoating film, the method for using same, and a mu1tilayer coating film. CONSTITUTION:A coating compsn. remarkably improved in interlayer adhesion contains a film-forming resin, a curative which cures the resin under heating, and a compd. having an 8-18C long-chain alkyl group and an HLB of 3-12 and selected from the group consisting of a phosphoric ester, a sulfonic ester, and a carboxylic acid in an amt. of the compd. of 0.1-5wt.% based on the sum of the resin and the curative.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating composition having improved interlayer adhesion to a lower coating film, its use and a multilayer coating film.

[0002]

2. Description of the Related Art As represented by automobile paints, it is necessary to form a multi-layer coating film in order to protect metal from corrosion and to have a beautiful appearance. In other words, it is often the case that an overcoat paint having a completely different composition and performance is applied onto the undercoat film. In this case, peeling of the coating film often occurs between the undercoating film and the topcoating film due to a decrease in adhesion. On the other hand, a method of increasing the adhesion with the top coating film by sanding the undercoat coating film is often used, but since the step of sanding is involved, the productivity is deteriorated.

Further, in the coating of automobiles, a thermosetting clear base paint (hereinafter simply referred to as "clear paint") is applied on a so-called wet-on-wet without coating a thermosetting colored base paint and baking it. There is a method of coating and baking and curing the colored base coat layer and the clear coat layer at the same time (this step is particularly called a two-coat one-bake system). However, in automobile coating lines, if a defect occurs in the coating film formed by this two-coat one-bake method, the colored base paint and clear paint are applied again by the two-coat one-bake method without sanding the coating film. What is done is being done.

When this is illustrated, a coating film as shown in FIG. 1 is formed. Since different materials are used for the base paint and the clear paint, the adhesion between the first clear coat layer and the second base coat layer is poor, and film peeling may occur.

Phosphorus compounds have been used in the past to improve adhesion. For example, US Pat.
No. 1,841 uses phosphoric acid or alkylbenzene sulfonic acid to improve adhesion, but the alkyl group bonded to this phosphoric acid or alkylbenzene sulfonic acid has 1 to 12 carbon atoms. However, the adhesion to the surface of the undercoat film is not always sufficient. Also used herein is free phosphoric acid, which is different from the phosphoric acid ester compound of the present invention. In addition, in sulfonic acid compounds, the invention does not include aromatics.

In US Pat. No. 4,772,289, although a phosphate ester having a polyether chain is used to improve the adhesion of a coating film to leather products, the adhesion to the coating surface is Is not always sufficient, resulting in the disadvantage of durability based on ether.

US Pat. Nos. 4,839,403 and 4,
No. 801,628 uses a phosphoric acid ester containing a hydroxyl group composed of phosphoric acid and an epoxy compound in order to improve adhesion. However, when this compound is used, the effect of adhesion to the metal surface is recognized, but the adhesion of the coated film surface that is always painted is not always sufficient.

[0008]

DISCLOSURE OF THE INVENTION The present invention provides a coating composition in which the adhesion of the lower coating film is improved by selecting a specific phosphorus compound or other compound, a method of using the same and a multilayer coating film. The purpose is to do.

[0009]

That is, the present invention provides (A)
Coating film-forming resin, (B) a cross-linking agent for heating and curing the resin (A), and (C) a phosphoric acid ester having a long-chain alkyl group having 8 to 18 carbon atoms and having HLB 3 to 12, sulfone An acid or carboxylic acid is contained, and the solid content of the component (C) is 0.1 to the total solid content of the components (A) and (B).
A coating composition with improved interlayer adhesion of 5% by weight is provided.

The present invention also applies a base coat, and after applying a clear coat without curing the base coat,
Provided is a method for forming a coating film, which comprises baking and curing a base coat and a clear coat together.

The present invention also provides a cured coating film comprising a first base coat and a first clear coat formed on the first base coat, and the second base coat without sanding the cured coating film. And a second clear coat is applied without curing the second base coat, and then the second base coat and the second clear coat are baked and cured together to provide a coating film forming method. .

The present invention also provides a multilayer coating film obtained by the above method.

The coating film forming resin of the present invention is not particularly limited, and resins generally used in thermosetting paints can be used. Examples of such materials include acrylic resins, polyester resins, alkyd resins, epoxy resins, urethane resins, or combinations of two or more of these resins. The solvent system of the coating composition of the present invention may be either an aqueous solvent or an organic solvent, but in the case of an aqueous solvent, a group for solubilizing water in the film-forming resin, for example, a carboxyl group or an amino group. And by neutralizing them with a neutralizing agent, they can be dissolved or dispersed in water. Preferred resins include acrylic resins and polyester resins. Particularly preferred are 5 to 40% by weight of amide group-containing ethylenic monomer [eg (meth) acrylamide, N-methylacrylamide, N-butylacrylamide, etc.], acid group-containing ethylenic monomer [eg (meth) acryl). Acid, maleic acid, itaconic acid, etc.] and other ethylenic monomers [eg (meth) acrylates such as methyl (meth) acrylate, butyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate;
Acrylonitrile; aromatic vinyl monomers such as styrene, etc.]. These resins generally have a hydroxyl value of 20 to 200, preferably 30 to 15
Has 0. The hydroxyl group is considered to be the reaction point with the crosslinking agent.
The coating film-forming resin has a number average molecular weight of 1,000 to 50,
000, preferably 1,000 to 20,000.

The crosslinker component (B) is required to heat and cure the above-mentioned coating film forming resin component (A). Examples of such include blocked polyisocyanate compounds, alkoxylated melamine formaldehyde condensates (melamine formaldehyde) or alkoxylated products of condensates with paraformaldehyde (e.g., methoxymethylolmelamine, isobutoxylated methylolmelamine, n.
A cycloaliphatic, aromatic or aliphatic epoxy compound containing butoxylated methylolmelamine) and two or more epoxies (eg Epicoat 828, Epicoat 1001, Epicoat 1004, commercially available from Shell Chemical Company,
Epolite 40E, Epolite 4 commercially available from Kyoei Yushi Co., Ltd.
00E, Epolite No. 1600, Epolite No. 7
21 etc.) and at least one of them is used.

The component (C) used in the present invention has 8 to 18 carbon atoms.
Is a phosphoric acid ester, sulfonic acid, or carboxylic acid having a long-chain alkyl group and having HLB 3 to 12.
The number of carbon atoms in the alkyl chain is preferably from 8 to 18, and if the number of carbon atoms is less than 8, the wettability to the coating film is reduced and the adhesion is poor. Further, if the carbon number exceeds 18, crystal of the compound precipitates in the coating material, causing a problem. More preferably, the number of carbon atoms is 10 to 14, the wettability is better, and the adhesion is improved. HLB of the above compound is represented by a Griffin formula based on the weight fraction: HLB = 20 (M _H / M) [wherein M _H means the molecular weight of the hydrophilic group portion and M means the molecular weight of the activator]. As the molecular weight of the hydrophilic group, the following molecular weights of phosphoric acid ester, sulfonic acid and carboxylic acid were used. HLB is 3 to 12, preferably 4 to 8.
Outside of this range, the wettability decreases, which is not preferable.
When the compound C is represented by the general formula,

[0016]

[Chemical 1]

A compound represented by: or a salt thereof. More preferred compounds include 2-ethylhexyl acid phosphate, mono- or di-diisodecyl acid phosphate, mono- or di-tridecyl acid phosphate, mono- or di-lauryl acid phosphate, mono- or di-nonylphenyl acid phosphate, Examples thereof include lauryl sulfate, nonyl sulfate, stearic acid and lauric acid.

The above components may be formulated as a clear coating composition, or they may be blended with a pigment to form a paint. Although any type of pigment may be used, a coloring pigment, an extender pigment, a metal pigment, mica particles and the like are usually used. Examples of coloring pigments include carbon black, acetylene black, yellow lead, cadmium yellow, yellow iron oxide, mineral fast yellow, navels yellow, benzidine yellow, molybdenum orange, permanent orange GTR, red iron oxide, cadmium red, resole red, permanent. Red 4R,
Fast violet B, methyl violet rake,
Metal phthalocyanine blue, fast sky blue,
Examples include chrome green, chromium oxide, and titanium oxide. Examples of extender pigments include barium carbonate, clay, silica, talc and the like. Aluminum flake is generally used as the metal pigment. Examples of the mica particles include mica particles encapsulated with a metal oxide, typically iron oxide or titanium oxide, and coated (mica pigment).

The blending ratio of the component A and the component B is 5 to 60% by weight, preferably 20 to 40% by weight of the component B based on the total amount of both in terms of solid content. Crosslinking agent (component B) is 5
If it is less than 5% by weight, curing will be poor and water resistance will decrease. On the other hand, if it exceeds 60% by weight, the stability of the coating composition decreases. The content of component C is 0.1 to 5% by weight, preferably 0.5 to 2 based on the total amount of component A and component B based on the solid content.
% By weight. When the content of the component C is 0.1% by weight, the adhesiveness, which is the effect of the present invention, decreases. On the other hand, if it exceeds 5% by weight, the water resistance decreases.

In the coating composition of the present invention, in addition to the above-mentioned components, additives usually added to the coating, such as a surface conditioner,
Viscosity suppressors (for example, water-insoluble particles), thickeners, antioxidants, UV inhibitors, antifoaming agents and the like may be added. The blending amount of these is within the range known to those skilled in the art.

When the composition of the present invention is applied onto a coating film, the long-chain alkyl group of the component (C) is oriented on the lower coating film to improve the wettability of the hydrophobic coating film to form a lower coating film. I think that the adhesion will be improved.

The production of the coating composition is not particularly limited, but the components A,
After thoroughly mixing B, component C is added. The composition can be applied by diluting to an appropriate viscosity with an organic solvent or water, spray coating, dip coating, brush coating, etc.
It is dried at 00 to 200 ° C. for 10 to 60 minutes.

The present invention is particularly excellent as a top coating for automobiles and is very effective as a base coating for a two-coat one-bake coating system for automobiles. If a coating defect occurs in a two-coat one-bake coating system in which a base coating containing a pigment is applied and a clear coating is applied without baking and drying, then a two-coat one-bake coating system is used. When a conventionally known base paint is applied and a clear paint is applied and then baked and dried, sufficient adhesion cannot be ensured between the first base clear coating film and the second base clear coating film. However, when the composition of the present invention is used in a paint, sufficient adhesion can be secured.

[0024]

EFFECTS OF THE INVENTION The coating composition of the present invention has a significantly improved adhesion to a base coating film (the quality of the base coating film is not taken into consideration), and a high interlayer adhesion property can be obtained without sanding the base coating film. Is obtained.

In addition, when there is a defect in the two-coat one-bake coating of the composition of the present invention, the composition of the present invention is added to the second base paint in a coating method in which the two-coat one-bake is overlaid again. With, the extremely excellent adhesion can be obtained without sanding treatment.

[0026]

EXAMPLES The present invention will be described in more detail by way of examples. The invention should not be construed as limited to these examples.

Production Example 1 Synthesis of Acrylic Resin 1 76 parts by weight of methoxypropanol was charged into a 2 liter reaction vessel equipped with a stirrer, a temperature controller and a cooling tube, and the temperature was adjusted to 12
The temperature was 0 ° C. Further, 15 parts by weight of styrene, 63 parts by weight of methyl methacrylate, 48 parts by weight of 2-hydroxyethyl methacrylate, 117 parts by weight of N-butyl acrylate, 27 parts by weight of methacrylic acid, 30 parts by weight of acrylamide, 60 parts by weight of methoxypropanol and t-butylperoxide. A monomer solution consisting of 3 parts by weight of oxy-2-ethylhexanate was dropped into the reaction vessel over 3 hours, and stirring was continued for 1 hour. Further dimethyl ethanolamine 28
And 536 parts of deionized water were added to obtain an acrylic resin having a volatile content of 30% and a resin number average molecular weight of 12,000. The resin had a hydroxyl number of 70 and an acid number of 58.

Production Example 2 (for Pigment Paste) Synthesis of Acrylic Resin 2 As in Production Example 1, 24 parts by weight of styrene, 73 parts by weight of methyl methacrylate, 48 parts by weight of 2-hydroxyethyl methacrylate, 117 parts by weight of N-butyl acrylate. , Methacrylic acid 18 parts by weight, acrylamide 20 parts by weight, methoxypropanol 40 parts by weight, and t-butylperoxy-2-ethylhexanate 3 parts by weight, except that a monomer solution was used. A polymer was synthesized. Furthermore, 19 parts of dimethylethanolamine and 565 parts of deionized water are added to add volatile matter 30
%, The number average molecular weight of the resin was 12,000, and an acrylic resin was obtained. The characteristics of this resin were that it had a hydroxyl number of 70 and an acid number of 40.

Production Example 3 Synthesis of Acrylic Resin 3 In Production Example 1, 350 parts by weight of xylene was charged.
The temperature is raised to 250 ° C., 250 parts by weight of glycidyl methacrylate,
Styrene 25 parts by weight, methyl methacrylate 60 parts by weight, N-butyl methacrylate 165 parts by weight and t-
A monomer initiator solution consisting of 50 parts by weight of butylperoxy-2-hexanoate was added dropwise over 3 hours, and stirring was continued for 2 hours. Nonvolatile content 55%, number average molecular weight 250
0 epoxy group-containing acrylic resin was obtained.

Production Example 4 Synthesis of Polyester Resin In a 2 liter reaction vessel equipped with a stirrer, temperature controller and cooling tube, 67 parts by weight of bishydroxyethyl taurine, 65 parts by weight of neopentyl glycol, 118 parts by weight of azelaic acid,
93 parts by weight of phthalic anhydride and 27 parts by weight of xylene were charged and the temperature was raised. Water generated by the reaction was removed by azeotropic distillation with xylene.

It took about 2 hours from the start of reflux to increase the temperature to 19
The temperature was raised to 0 ° C., stirring and dehydration were continued until the acid value corresponding to the carboxylic acid reached 72.5, and the temperature was cooled to 140 ° C. Then
While maintaining the temperature of 140 ° C., 157 parts by weight of Cadura E10 (manufactured by Shell Co.) was added dropwise over 30 minutes, and then stirring was continued for 2 hours to complete the reaction. Further, 47 parts by weight of dimethylethanolamine was added, and 1100 parts by weight of deionized water was added. The resulting polyester resin has an acid value of 59, a hydroxyl value of 90, a non-volatile content of 30%, and a number average molecular weight of 105.
It was 4.

Production Example 5 Synthesis of Acrylic Resin 700 parts by weight of xylene was charged into the same apparatus as in Production Example 1, and the temperature was raised to 130 ° C. 200 parts by weight of styrene, 2-
A monomer initiator solution consisting of 200 parts by weight of ethylhexyl acrylate, 90 parts by weight of hydroxyethyl methacrylate, 10 parts by weight of methacrylic acid, 100 parts by weight of methyl methacrylate and 36 parts by weight of t-butylperoxy-2-hexanoate was added dropwise over 3 hours, Stirring was continued for another 2 hours, nonvolatile content 45%, number average molecular weight 560
An acrylic resin having an acid value of 0 and an acid value of 10 was obtained.

Production Example 6 Synthesis of Acrylic Resin The same apparatus as in Production Example 1 was charged with 700 parts by weight of butyl acetate and heated to 130 ° C. 200 parts by weight of styrene, n-
A monomer initiator solution consisting of 200 parts by weight of butyl acrylate, 90 parts by weight of 2-hydroxyethyl methacrylate, 10 parts by weight of methacrylic acid, 100 parts by weight of methyl methacrylate and 36 parts by weight of t-butylperoxy-2-hexanoate was added dropwise in 3 hours. Then, stirring was continued for another 2 hours, and the nonvolatile content was 45%, the number average molecular weight was 8000,
An acrylic resin having an acid value of 10 was obtained.

Production Example 7 Synthesis of Acrylic Resin The same apparatus as in Production Example 1 was charged with 350 parts by weight of xylene and 350 parts by weight of methoxypropanol and heated to 130 ° C. Styrene 160 parts by weight, 2-ethylhexyl acrylate 200 parts by weight, hydroxyethyl methacrylate 90 parts by weight, methacrylic acid 50 parts by weight, methyl methacrylate 100 parts by weight and t-butyl peroxy-2.
A monomer initiator solution consisting of 36 parts by weight of hexanoate was added dropwise over 3 hours, and stirring was continued for 2 hours to obtain an acrylic resin having a nonvolatile content of 45%, a number average molecular weight of 5600 and an acid value of 50.

Preparation Example 8 Preparation of Pigment Dispersion Paste 1 54 parts by weight of the acrylic resin prepared in Preparation Example 2, M-11
12 parts by weight of 00 (manufactured by Cablack) and 18 parts by weight of deionized water were mill-dispersed for 3 hours to obtain a pigment paste.

Preparation Example 9 Preparation of Pigment Dispersion Paste 2 100 parts by weight of the acrylic resin prepared in Preparation Example 6 and 15 parts by weight of Maroon R-6424 (manufactured by Harmon Co.) were similarly mill-dispersed to obtain a pigment paste.

Example 1 Preparation of Aqueous Metallic Paint 1 170 parts of acrylic resin of Production Example 1, C-303 (Mitsui Toatsu Chemicals, Inc., methylated melamine solid content 100%) 21
Part, aluminum paste 7160N (Toyo Aluminum) 1
6.3 parts, lauryl acid phosphate (HLB 7.3)
1.6 parts of a 50% xylene solution of was mixed with stirring with a stirrer.

The top coating composition obtained above was diluted with deionized water, and the viscosity was adjusted with a Ford cup # 4 at 20 ° C. for 30 seconds to obtain an aqueous metallic coating.

Example 2 Preparation of Aqueous Paint 2 170 parts of the above acrylic resin of Production Example 1, C-303 (Mitsui Toatsu Chemical Co., Ltd., methylated melamine, solid content 100%)
30 parts, 30 parts of M-1100 pigment paste of Production Example 8,
2.5 parts of a 50% xylene solution of stearyl acid phosphate (HLB5.5) was mixed by stirring with a stirrer.

The top coating composition obtained above was diluted with deionized water and the viscosity was adjusted to 20 seconds at 20 ° C. in Ford cup # 4 to obtain an aqueous coating.

Example 3 Preparation of Solvent-based Paint 3 150 Parts of Acrylic Resin of Production Example 6, U-20N-60
(Mitsui Toatsu Chemical Co., Inc., butylated melamine), 17 parts of Bright Copper (Mica manufactured by Marl Co., Ltd.), 18 parts of Perind Maroon R6424 pigment paste of Production Example 9, 50% xylene of isostearyl acid phosphate (HLB 5.5). 3.2 parts by weight of the solution was mixed by stirring with a stirrer.

The acrylic melamine-based paint obtained above was diluted with a 1: 1 mixture of ethyl acetate and xylene, and the viscosity was adjusted with a Ford cup # 4 for 30 seconds at 25 ° C. to obtain an acrylic melamine-based paint.

Example 4 Preparation of Aqueous Paint 4 180 parts of the polyester resin of Production Example 4, C-303 (Mitsui Toatsu Chemicals, Inc., methylated melamine solid content 100%) 2
5 parts, M-1100 Pigment Paste 16.3 of Preparation Example 8
Part, 5 of lauryl acid phosphate (HLB 7.3)
2.5 parts of 0% xylene solution was mixed by stirring with a stirrer.

The top coating composition obtained above was diluted with deionized water and the viscosity was adjusted to 20 seconds at 20 ° C. in Ford cup # 4 to obtain an aqueous coating.

Example 5 Preparation of Aqueous Metallic Paint 5 170 Parts of Acrylic Resin of Production Example 1, U-20N-60
(Mitsui Toatsu Chemical Co., Ltd., butylated melamine) 20 parts, 10 parts of blocked isocyanate compound obtained by blocking isophorone diisocyanate with methyl ethyl ketone oxime,
Aluminum paste 60-600 (made by Toyo Aluminum Co., Ltd.) 1
6.3 parts, 2-ethylhexyl acid phosphate (H
2.4 parts of a 50% xylene solution of LB9.2) was mixed by stirring with a stirrer.

The top coating composition obtained above was diluted with deionized water and the viscosity was adjusted to 20 seconds at 20 ° C. in Ford cup # 4 to obtain an aqueous metallic coating.

Production Example 10 Preparation of clear paint 1 80 parts of the acrylic resin of Production Example 5 and 15 parts of U-20N-60 (manufactured by Mitsui Toatsu Chemical Co., Inc., butylated melamine) were mixed by stirring with a stirrer.

The acrylic melamine-based clear paint obtained above was diluted with a 1: 1 mixture of Solvesso 100 and Solvesso 150, and the mixture was cooled at 20 ° C. in a Ford cup # 4.
The viscosity was adjusted to 22 seconds to obtain an acrylic melamine-based clear paint.

Production Example 11 Preparation of clear coating 3 500 parts of the acrylic resin of Production Example 7, 100 parts of the epoxy group-containing acrylic resin of Production Example 3, and 7 parts of a 20% methanol solution of tetrabutylammonium bromide were mixed by stirring with a stirrer. did.

The acid epoxy curing type clear paint obtained above was applied to Solvesso 100 and Solvesso 150 1:
Dilute to 1 mixture and ford cup # 4 at 20 ° C for 2
The viscosity was adjusted to 2 seconds to obtain an acid epoxy clear paint.

Production Example 12 Preparation of clear paint 4 50 parts of acrylic resin of Production Example 5 and 20 parts of C-303 (manufactured by Mitsui Toatsu Chemicals, Inc., methylated melamine solid content 100%),
Blocked isocyanate compound 2 in which isophorone diisocyanate is blocked with methyl ethyl ketone oxime
0 parts, dibutyltin dilaurate 5% xylene solution
6 parts were mixed by stirring with a stirrer.

The acrylic-melamine-isocyanate-based clear coating material obtained above was diluted with sorbet 150 and the viscosity was adjusted to 22 seconds at 20 ° C. in Ford cup # 4 to obtain an acrylic-melamine-isocyanate-based clear coating material.

Comparative Example 1 In place of lauryl acid phosphate in Example 1, ethyl acid phosphate (HLB value 15.4) was added to obtain an aqueous metallic coating material.

Comparative Example 2 Instead of lauryl acid phosphate in Example 1, lauryl polyoxyethyl acid phosphate (HLB) was used.
Value 12.1 (n = 4) and HLB value 13.5 (n =
6)) was added to obtain an aqueous paint.

Comparative Example 3 An aqueous paint was obtained by adding 1.6 parts of a reaction product of a bisphenol A type epoxy resin having a molecular weight of 400 and phosphoric acid in place of lauryl acid phosphate in Example 1.

Comparative Example 4 0.16 parts by weight of a 50% xylene solution of lauryl acid phosphate in Example 1 was added to obtain an aqueous paint.

Comparative Example 5 An aqueous paint was obtained by adding 16 parts by weight of a 50% xylene solution of lauryl acid phosphate in Example 1.

Example 6 Method of forming a coating film The coating composition obtained in Example 1 was air-spray coated onto an unsanded intermediate coated steel sheet so that the dry coating film would have a thickness of 15 microns, and after setting for 5 minutes, 80 ° C., 5 It was preheated for a minute, and then the clear paints obtained in Production Examples 10 to 12 were air-sprayed to a dry coating film thickness of 40 microns, set for 7 minutes, and dried at 140 ° C. for 20 minutes. The adhesion of this coating film was evaluated. Table 1 shows the results of the adhesion and the combination of the base coating and the clear coating.

Table 1 Test Plate Base Paint Clear Paint Adhesion * 1 Example 1 Production Example 10 100/100 2 Example 2 Production Example 10 100/100 3 Example 3 Production Example 10 100/100 4 Example 4 Production Example 11 100/100 5 Example 5 Production Example 12 100/100 6 Comparative Example 1 Production Example 12 5/100 7 Comparative Example 2 Production Example 12 8/100 8 Comparative Example 3 Production Example 12 8/100 9 Comparative Example 4 Production Example 12 10/100 10 Comparative Example 5 Production Example 12 10/100 *: 2 mm interval cuts were put in with a cutter knife to make 100 cuts of 2 mm square, and a peeling test using a tape was performed. Numerical values indicate the number / 100 without peeling.

Example 7 Method for forming coating film On the intermediate coated steel sheet, the base paint prepared in Examples 1 to 5 and Comparative Examples 1 to 5, and then the clear paints in Production Examples 10 to 12 were used as dry coating films in the former 15 micron and the latter. Paint the former to 40 microns, then set for 5 minutes, 80
After preheating at 5 ° C for 5 minutes and then painting the latter, 1
I set it for 0 minutes. Dry the coated plate with a dryer at 160 ℃,
A test plate was prepared by baking for 18 minutes.

The same base paint and clear paint were repainted again without sanding this test plate, 1
A two-coat one-bake coating film consisting of four layers was formed by baking at 40 ° C. for 18 minutes. The recoat adhesion of this coating film was evaluated. Table 2 shows the results of the recoat adhesion and the combination of the base coating and the clear coating.

Table 2 Test Plate Base Paint Clear Paint Recoat Adhesion * 1 Example 1 Production Example 10 100/100 2 Example 2 Production Example 10 90/100 3 Example 3 Production Example 10 90/100 4 Example 4 Production Example 11 98/100 5 Example 5 Production Example 12 95/100 6 Comparative Example 1 Production Example 12 5/100 7 Comparative Example 2 Production Example 12 5/100 8 Comparative Example 3 Production Example 12 8/100 9 Comparative Example 4 Production Example 12 15/100 10 Comparative Example 5 Production Example 12 12/100 *: 100 mm cuts of 2 mm square were made by inserting 2 mm interval cuts with a cutter knife, and a tape peeling test was performed. Numerical values indicate the number / 100 without peeling.

[Brief description of drawings]

1 is a cross-sectional view showing a conventional coating film and a multilayer coating film of the present invention.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Reference number within the agency FI Technical display location C09D 5/00 PSD 6904-4J 7/12 PSL 7211-4J (72) Inventor Manabu Yoshioka Osaka Prefecture Neyagawa 19-17 Ikedanaka-cho, Ichi, Japan Paint Co., Ltd. (72) Inventor Hiroshi Miwa 19-17 Ikedanaka-cho, Neyagawa-shi, Osaka Japan Paint Co., Ltd.

Claims (7)

[Claims] 1. A coating film-forming resin (A), (B) a crosslinking agent for heating and curing the resin (A), and (C) a long-chain alkyl group having 8 to 18 carbon atoms, and HL
Containing phosphoric acid ester, sulfonic acid or carboxylic acid having B3 to 12 and having a blending solid content of component (C) of 0.1 to 5% by weight based on the total solid content of components (A) and (B). A coating composition having improved interlayer adhesion. 2. The coating composition according to claim 1, wherein the coating film forming resin (A) is an aqueous resin having an amide group. 3. The film-forming resin (A) is polymerized with 5 to 40% by weight of an amide group-containing ethylenic monomer, 3 to 25% by weight of an acid group-containing ethylenic monomer and other polymerizable ethylenic monomers. The coating composition according to claim 1, which is an acrylic resin prepared by. 4. The coating composition according to claim 1, wherein the component (C) is a phosphoric acid ester having a long-chain alkyl group having 8 to 18 carbon atoms and having HLB 3 to 12. 5. A coating film forming method comprising applying a base coat, applying a clear coat without curing the base coat, and then baking and curing the base coat and the clear coat together, wherein the base coat is any one of claims 1 to 4. A coating film forming method comprising: 6. A cured coating film comprising a first base coat and a first clear coat formed on the first base coat is formed, and a second base coat is applied without sanding the cured coating film. A coating method of baking the second base coat and the second clear coat together after applying the second clear coat without curing the second base coat, wherein the first base coat and the second base coat Is a coating composition according to any one of claims 1 to 4. 7. A multilayer coating film obtained by the method according to claim 5 or 6.