Patent ID: 6413588
Filing Date: 2002-07-02
Classification: B05D

Abstract:
A process for producing a durable coating on a difficult-to-coat substrate made of aluminum or steel, said process comprising:subjecting the surface of said difficult-to-coat substrate to an adhesion promoting treatment, which comprises: cleaning said surface of said difficult-to-coat substrate, applying a film of a silane adhesion promoter on said clean surface of said substrate, said film having a dry thickness in the range of from 100 Ã¥ to 2500 Ã¥, said adhesion promoter comprising: a solution of one or more silanes having the following formula: â€ƒwherein x is an integer between 1 and 3, R is the same or different alkyl having 1 to 3 carbons, a is 0 or an integer between 1 and 3, b equals 3-a, and R1 is selected from the group consisting of: â€ƒH2N, H2N(CH2)2NH, H2N(CH2)2NH(CH2)2NH, and H2N[(CH2)2NH]z â€ƒwherein z is 0 or an integer of 1 to 3; said silane being present in a concentration in the range of 0.001 to 10.0 percent by weight of the solution, removing any excess amount of said silane adhesion promoter from said surface; and drying said surface having said film of said silane adhesion promoter thereon; applying an intermediate layer of a flexible primer on said adhesion promoted surface of said difficult-to-coat substrate, said flexible primer consisting essentially of: a polyester copolymer and a crosslinker, said polyester copolymer being produced through a two-stage polymerization process, said polyester copolymer having a linear segment with terminal hydroxyl groups and a GPC number average molecular weight (Mn) in the range of from 500 to 3000, and a branched segment with lateral hydroxyl groups and a GPC number average molecular weight (Mn) in the range of from 750 to 1500; applying a mar resistant top layer of a clear coating composition on said intermediate layer to produce said durable coating on said difficult-to-coat substrate, said clear coating composition comprising: â€ƒa polyisocyanate binder, fluorinated polyisocyanate binder, an acrylic fluorocarbon binder or a combination thereof.