Flexible aminoplast-curable film-forming compositions providing films having resistance to acid etching

A method for applying a composite coating to a plastic substrate which is a flexible thermosetting or thermoplastic material which comprises applying to the substrate a colored film-forming composition to form a base coat and applying to said base coat a clear film-forming composition to form a transparent top coat over the base coat wherein the clear film-forming composition comprises a flexible, curable film-forming composition, comprising:

• (i) 10 to 50 percent by weight based on the weight of resin solids of a polyether polymer containing a plurality of terminal or pendant carbamate groups of the structure:
• ##STR6## incorporated into the polyether polymer, wherein said polyether polymer has on average at least two of said terminal or pendant carbamate groups per molecule;
• (ii) 5 to 50 percent by weight based on weight of resin solids of a polymer selected from the group consisting of a polyester polymer, a polyurethane polymer, an acrylic polymer, and mixtures thereof wherein each polymer contains a plurality of terminal or pendant carbamate groups of the structure:
• ##STR7## (iii) 20 to 50 percent based on weight of resin solids of an aminoplast crosslinking agent containing methylol and/or methylol ether groups, wherein the equivalent ratio of said pendant or terminal carbamate groups to methylol or methylol ether groups is from 0.5 to 2:1 and is sufficient to form a crosslinked film.