High solids coating composition with oligomeric hydroxyphosphate catalyst-A

Claim 1

A thermosetting coating composition adapted for low temperature bake applications which contains greater than about 60% by weight of nonvolatile solids, and which, exclusive of pigments, solvents and other nonreactive components, consists essentially of: (A) a polyepoxide resin having a number average molecular weight (M n ) of between about 140 and about 3,000; (B) a reactive catalyst comprising at least one oligomeric hydroxy functional organophosphate ester having the formula: ##STR3## wherein n=1 to 2 and R is selected from the group consisting of mono or dihydroxy radicals containing one or more ester linkages and having a molecular weight of between about 120 and about 1500; (C) an amine-aldehyde crosslinking agent; and (D) up to about 45 weight percent based on the total weight of (A), (B), (C) and (D) of a hydroxy functional additive having a number average molecular weight (M n ) of between about 150 and about 6000, said oligomeric organophosphate ester being included in said composition in an amount sufficient to provide between about 0.8 and about 1.5 equivalents of acid functionality for each equivalent of epoxy functionality on said polyepoxide resin, and said amine aldehyde crosslinking agent being included in said composition in an amount sufficient to provide at least about 0.4 equivalents of nitrogen crosslinking functionality for each equivalent of hydroxy functionality included in said composition either as (i) an organic hydroxyl group on said oligomeric organophosphate ester, (ii) a hydroxyl group on said hydroxy functional additive, or (iii) as a result of esterification of said epoxy functionality of said polyepoxide resin during cure of said coating composition.