Vapor permeation curable polyester resin coating compositions for flexible substrates

A method for coating a flexible substrate with a coating composition which comprises:

• (I) applying said coating composition to said flexible substrate, said coating composition having a pot life of at least about 4 hours in an open pot and comprising:
• (A) an aromatic hydroxyl-functional condensation product having an acid number of less than about 10, having an aromatic hydroxyl-functionality of at least 2, and containing substantially no aliphatic hydroxyl groups, said condensation product made by condensing the following ingredients in the indicated molar proportions or double thereof except for the phenol-functional carboxylic acid:
• (1) between about 3 and 8 moles of a mixture of diols which include a sterically hindered diol, and a diol or mono-epoxide which provides a pendant C.sub.8 -C.sub.22 hydrocarbyl group;
• and
• (2) between about 3 and 6 moles of a mixture of a linear aliphatic dibasic acid and an ortho or meta aromatic dicarboxylic acid, and a phenol-functional carboxylic acid having at least one carbon atom between said phenol group and said carboxyl group;
• (B) a multi-isocyanate cross-linking agent comprising a mixture of aromatic and aliphatic multi-isocyanates, wherein the ratio of aromatic hydroxyl equivalents from said condensation product to the isocyanate equivalents of said multi-isocyanate agent ranges from between about 1:1 and 1:1.7;
• (C) a volatile organic solvent for said condensation product and for said multi-isocyanate;
• and
• (D) a mar-resisting agent of an organic long chain fatty compound physically incompatible in said coating composition and having an effective chain length of at least 12 carbon atoms;
• and
• (II) exposing said coated flexible substrate to a vaporous tertiary amine catalyst to rapidly cure said coating at about room temperature;
• said cured coating having a film thickness of between about 0.1 and about 0.5 mils;
• said cured film of said coating composition possessing a flexibility sufficient for a zero-T bend on metal and a mar resistance of at least about 2,000 grams as borne by the edge of a nickel passed over said cured film.