Composition with latent reactive catalyst

A liquid, thermosetting high solids coating composition which is adapted for low temperature bake applications, which contains greater than about 55% by weight of nonvolatile solids, and which, exclusive of pigments, solvents and other nonreactive components, consists essentially of:

• (A) a bifunctional copolymer bearing hydroxyl functionality and pendent epoxy functionality, having a number average moleculer weight (M.sub.n) of between about 1,500 and about 10,000 and a glass transition temperature (T.sub.g) of between about -25.degree. C. and about 70.degree. C., said copolymer consisting essentially of (i) between about 5 and about 25 weight percent of monoethylenically unsaturated monomers bearing glycidyl functionality and between about 5 and about 25 weight percent of monoethylenically unsaturated monomers bearing hydroxyl functionality, with the total of said glycidyl and hydroxy functional monomers being not greater than about 30 weight percent of other monoethylenically unsaturated monomers in said bifunctional copolymer and (ii) between about 90 and about 70 weight percent of other monoethylencially unsaturated monomers;
• (B) a latent reactive catalyst comprising the reaction product of (i) a monofunctional copolymer bearing pendent epoxy functionality, having a number average molecular weight (M.sub.n) of between about 1,500 and about 10,000 and a glass transition temperature (T.sub.g) of between about -25.degree. C. and about 70.degree. C., said copolymer being prepared from between about 5 and about 30 weight percent of monoethylenically unsaturated monomers bearing glycidyl functionality and between about 70 and about 95 weight percent of other monoethylenically unsaturated monomers;
• and (ii) a sulfonic acid having the formula ##STR5## wherein R is selected from linear or branched alkyl groups and aryl groups, said copolymer bearing pendent epoxy functionality and said sulfonic acid being reacted in such amounts that there are between 0.3 and about 1 acid groups per epoxy in the reaction mixture.
• (C) an amine-aldehyde crosslinking agent;
• and
• (D) up to about 45 weight percent of a hydroxy functional additive having a member average molecular weight (M.sub.n) of between about 150 and about 6,000,
• said latent reactive catalyst being included in said composition in an amount ranging from about 0.5 to about 5 weight percent, said amine-aldehyde crosslinking agent being included in said composition in an amount ranging from about 15 to about 45 weight percent, said weight percents being based on the total weight of (A), (B), (C) and (D).