AQUEOUS INTERMEDIATE COATING COMPOSITION AND METHOD FOR FORMING MULTILAYER COATING FILM

摘要

The present invention provides an aqueous intermediate coating composition comprising: (A) a resin containing hydroxyl and carboxyl groups with a hydroxyl value of 100 to 200 mg KOH/g and an acid value of 20 to 50 mg KOH/g; (B) at least one curing agent selected from the group consisting of melamine resins and blocked polyisocyanate compounds; and (C) flat pigment particles; the molecular weight distribution of a curable resin component comprising component (A) and component (B) including from 30 to 50% by weight of a component with a molecular weight of less than 1,000, and 10% by weight or less of a component with a molecular weight exceeding 100,000; the proportion of component (C) being from 2 to 15 parts by weight based on 100 parts by weight of the resin component; and when the intermediate coating composition is applied to an undercoating film, pre-dried at 100°C for 30 minutes and then heat-cured at 145°C for 30 minutes, the film thickness shrinkage percentage of the cured coating film being 20% or less based on the film thickness of the coating film after pre-drying. The invention also provides a method for forming a multilayer coating film using the aqueous intermediate coating composition.