	US 7,541,064 B2
	Method of forming multilayer coating film including water-borne basecoat on automobile substrate
Tsuyoshi Harakawa, Anjo (Japan); Hideaki Ogawa, Sakai (Japan); Shigeyuki Sasaki, Nara (Japan); Takashi Nakano, Kyoto (Japan); and Hirofumi Oi, Kyoto (Japan)
Assigned to Nippon Paint Co., Ltd., Osaka (Japan)
Filed on Nov. 14, 2005, as Appl. No. 11/273,786.
Application 11/273786 is a division of application No. 10/364594, filed on Feb. 11, 2003, granted, now 7,034,066.
Claims priority of application No. 2002-034552 (JP), filed on Feb. 12, 2002.
Prior Publication US 2006/0079604 A1, Apr. 13, 2006
Int. Cl. B05D 3/02 (2006.01); C09D 5/02 (2006.01); C08K 3/22 (2006.01)

U.S. Cl. 427—372.2 [427/407.1]

4 Claims

1. A method of forming a multilayer coating film which comprises applying a water-borne base coating composition to an article to be coated and applying a clear coating composition thereon, followed by curing by heating, said water-borne base coating composition comprising:

(a) an emulsion resin obtained by emulsion polymerization of an α,β-ethylenically unsaturated monomer mixture having an acid value of 3 to 50 and comprising at least 65% by mass, based on a total weight of said α,β-ethylenically unsaturated monomer mixture, of a (meth)acrylate ester whose ester moiety contains one or two carbon atoms,

(b) a coloring component comprising an optically coherent flaky pigment, and

(c) an acrylic polymer compound having a weight average molecular weight of 400,000 to 1,500,000 and represented by the general formula (1):

wherein in the formula, A and B are the same or different and each represents a molecular terminal group resulting from a polymerization reaction producing a resin of the general formula (1), a terminal group resulting from hydrolysis thereof, a hydrogen atom or a hydroxyl group; M represents a carboxylic acid group or a carboxylic acid group neutralized with ammonia or a primary, secondary or tertiary amine compound, N represents a carboxylic acid group, a carboxylic acid ester group whose ester, moiety contains one or more carbon atoms, or a carboxylic acid group neutralized with ammonia or a primary, secondary or tertiary amine compound; m is an integer of not less than 1 and n is an integer of not less than 0, provided that m/9 is not less than n; and R is a hydrogen atom or a methyl group,

the content of said acrylic polymer compound on the solid basis being 0.3 to 4.0% by mass relative to the resin solids in the coating composition.