Method of forming multi-layered coating film

Abstract

This invention provides a method for forming multi-layered coating film excelling in appearance, corrosion resistance and chipping resistance, which comprises applying a first coloring paint (B), second coloring paint (C) and clear paint (D) onto cured coating film of a specific electrodeposition paint (A) of low weight loss under heating, wet-on-wet by the order stated; and heat-curing the three-layered coating film simultaneously.

Description

TECHNICAL FIELD

[0001] This invention relates to a method for forming multi-layered coating film excelling in appearance, corrosion resistance and chipping resistance, which comprises applying a first coloring paint, second coloring paint and clear paint onto cured coating film of an electrodeposition paint, wet-on-wet by the order stated; and heat-curing the three-layered coating film simultaneously. BACKGROUND ART

[0002] Coating of metallic shaped articles such as automobile bodies, metallic parts of two-wheeled vehicles, house electric appliances, steel furnitures and the like is normally conducted by the steps of applying an electrodeposition paint, baking the resulting coating film, applying an intermediate coat thereon and baking the same, and then applying a top coat and baking the same to form a multi-layered coating film. However, when baking is performed after application of each of those paints, not only high energy costs are incurred for the baking but also great labor a...

Examples

production example 1

Preparation of Base Resin No. 1

[0145] A flask equippel with a stirrer, thermometer, dropping funnel and a reflux condenser was charged with 155 parts of EHPE-3150 (note 5), 70 parts of diethanolamine and the whole amount of the following phenolic hydroxyl-containing product, which were reacted at 160° C. for 5 hours. Thereafter 692 parts of methyl propanol was added to provide base resin No. 1 having a hydroxyl equivalent of 443, amine value of 63 mgKOH / g and a solid content of 60%.

[0146] Phenolic Hydroxyl-Containing Compound: [0147] A product obtained by mixing 475 parts of bisphenol A diglycidyl ether having an epoxy equivalent of 190, 285 parts of bisphenol A, 53 parts of diethanolamine and 80 parts of carbitol, dissolving the mixture by heating and causing the reactants to react by maintaining them at 130° C. for 3 hours. [0148] (Note 5) EHPE-3150: tradename, Daicel Chemical Industries, Ltd., an epoxy resin having at least two epoxy-containing functional groups per molecule on...

production example 2

Preparation of Curing Agent No. 1

[0149] Two (2) parts of azobisdimethylvaleronitrile was dissolved in 33.4 parts of CYCLOMER M100 (3,4-epoxycyclohexylmethyl methacrylate). The solution was dropped into a 100° C. mixed solvent of 10 parts of methyl isobutyl ketone and 10 parts of ethylene glycol monobutyl ether over 2 hours, aged for an hour, given a temperature raise to 125° C. and aged for an additional hour to provide curing agent No. 1 having an epoxy equivalent of 196 and solid content of 60%.

production example 3

Preparation of Base Resin No. 2 (for Comparative Example)

[0150] To 1010 parts of EPICOAT 828 EL (tradename, Japan Epoxy Resin Co., an epoxy resin), 390 parts of bisphenol A and 0.2 part of dimethylbenzylamine were added, and reacted at 130° C. until the epoxy equivalent reached 800.

[0151] Then 74 parts of dimethylolbutyric acid, 63 parts of diethanolamine and 95 parts of ketiminated product of diethylenetriamine were added and reacted at 120° C. for 4 hours, followed by addition of 330 parts of ethylene glycol monobutyl ether. Thus base resin No. 2 having an amine value of 43 mgKOH / g and solid content of 80% was obtained.

TECHNICAL FIELD

[0001] This invention relates to a method for forming multi-layered coating film excelling in appearance, corrosion resistance and chipping resistance, which comprises applying a first coloring paint, second coloring paint and clear paint onto cured coating film of an electrodeposition paint, wet-on-wet by the order stated; and heat-curing the three-layered coating film simultaneously. BACKGROUND ART

[0002] Coating of metallic shaped articles such as automobile bodies, metallic parts of two-wheeled vehicles, house electric appliances, steel furnitures and the like is normally conducted by the steps of applying an electrodeposition paint, baking the resulting coating film, applying an intermediate coat thereon and baking the same, and then applying a top coat and baking the same to form a multi-layered coating film. However, when baking is performed after application of each of those paints, not only high energy costs are incurred for the baking but also great labor a...

Examples

production example 1

Preparation of Base Resin No. 1

[0145] A flask equippel with a stirrer, thermometer, dropping funnel and a reflux condenser was charged with 155 parts of EHPE-3150 (note 5), 70 parts of diethanolamine and the whole amount of the following phenolic hydroxyl-containing product, which were reacted at 160° C. for 5 hours. Thereafter 692 parts of methyl propanol was added to provide base resin No. 1 having a hydroxyl equivalent of 443, amine value of 63 mgKOH / g and a solid content of 60%.

[0146] Phenolic Hydroxyl-Containing Compound: [0147] A product obtained by mixing 475 parts of bisphenol A diglycidyl ether having an epoxy equivalent of 190, 285 parts of bisphenol A, 53 parts of diethanolamine and 80 parts of carbitol, dissolving the mixture by heating and causing the reactants to react by maintaining them at 130° C. for 3 hours. [0148] (Note 5) EHPE-3150: tradename, Daicel Chemical Industries, Ltd., an epoxy resin having at least two epoxy-containing functional groups per molecule on...

production example 2

Preparation of Curing Agent No. 1

[0149] Two (2) parts of azobisdimethylvaleronitrile was dissolved in 33.4 parts of CYCLOMER M100 (3,4-epoxycyclohexylmethyl methacrylate). The solution was dropped into a 100° C. mixed solvent of 10 parts of methyl isobutyl ketone and 10 parts of ethylene glycol monobutyl ether over 2 hours, aged for an hour, given a temperature raise to 125° C. and aged for an additional hour to provide curing agent No. 1 having an epoxy equivalent of 196 and solid content of 60%.

production example 3

Preparation of Base Resin No. 2 (for Comparative Example)

[0150] To 1010 parts of EPICOAT 828 EL (tradename, Japan Epoxy Resin Co., an epoxy resin), 390 parts of bisphenol A and 0.2 part of dimethylbenzylamine were added, and reacted at 130° C. until the epoxy equivalent reached 800.

[0151] Then 74 parts of dimethylolbutyric acid, 63 parts of diethanolamine and 95 parts of ketiminated product of diethylenetriamine were added and reacted at 120° C. for 4 hours, followed by addition of 330 parts of ethylene glycol monobutyl ether. Thus base resin No. 2 having an amine value of 43 mgKOH / g and solid content of 80% was obtained.

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