Patent ID: 6375820
Filing Date: 2002-04-23
Classification: B05D,Y10T

Abstract:
A method for forming a multi-layer paint film, comprising:applying a cationic electrodeposition paint (A) containing a block polyisocyanate compound as a cross-linking agent on a surface of a painted matter, applying a water based intermediate coat paint (B) containing a block polyisocyanate compound as a cross-linking agent on the electrodeposition paint film surface without curing the electrodeposition paint film to form an intermediate coat paint film, and then heating to cure both of the electrodeposition paint film and the intermediate coat paint film at the same time to thereby form a multi-layer paint film, wherein said cationic electrodeposition paint (A) contains a base resin (A-1) having a hydroxyl group and a cationic group, a block polyisocyanate compound (A-2), a tin base catalyst (A-3) of at least 10 parts by weight per 100 parts by weight of the resin solid content, and a bismuth-containing compound (A4) in a form of an aqueous dispersion paste of bismuth obtained by mixing and dispersing a water-insoluble bismuth compound and an aliphatic carboxylic acid shown by the following formula (I) in an aqueous medium:R1â€”CH(Oâ€”R2)â€”(CH2)nâ€”COOHâ€ƒâ€ƒ(I) wherein R1 represents a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; R2 represents a hydrogen atom or an alkyl group having 1 to 10 carbon atoms; and n represents 0 or 1, and a cross-linking curing reaction in the electrodeposition paint film is controlled so that it starts earlier than a cross-linking curing reaction in the intermediate coat paint film.