Coating composition comprising chain-extendable crosslinkable polyol and diblocked diisocyanate

A resin composition comprising:

• chain-extendable, crosslinkable polyol of molecular weight about 100 to about 1000, having at least three hydroxyl group, selected from polyhydroxy functional straight or branched chain saturated or unsaturated hydrocarbons, optionally comprising one or more oxy or ester moieties and optionally comprising one or more heterocyclic atoms, aromatic and/or heterocyclic rings, the heterocyclic atom(s) being selected from N, O and S;
• and
• chain-extendable, diblocked diisocyanate of molecular weight about 200 to 2000, wherein said diblocked diisocyanate is the reaction product of an organic diisocyanate with a monofunctional blocking agent selected from alcohol, amide, ketoxime, phenol and a mixture of any of them, in molar ratio of about 1:2, respectively, the blocking group of which diblocked diisocyanate has a de-blocking temperature of about 100.degree. C. to about 190.degree. C.;
• and
• crosslinking agent reactive with the hydroxy functinality of said polyol and substantially unreactive with de-blocked isocyanate functionality of said diblocked diisoycanate, wherein said crosslinking agent and said polyol are present in a molar equivalent ratio of about 1:1 to about 1:15, respectively.