Process for coating polymeric substrates with mar-resistant coating

Claim 1

A process for coating a polymeric substrate comprising, A. continuously contacting a clean, dust-free polymeric substrate with a mar-resistant coating composition having a viscosity of from about 50 to about 95 centipoises at room temperature, for from about 2 to about 7 minutes, B. continuously removing the resultant coated substrate from said coating composition, C. allowing said coating on said substrate to level, with evaporation of solvent, for from about 30 seconds to about 3 minutes, and D. curing the resultant leveled coating by subjecting it to radiant heat at a temperature of from about 50° C. to about 130° C. for from about 1 to about 20 minutes, said mar-resistant coating composition consisting essentially of a mixture of (1), (2), (3) and (4), in which 1. is a saturated urethane prepolymer having terminal hydroxy groups which is the reaction product of materials consisting essentially of a mixture of (a) and (b), at a molar ratio of 1:2 respectively in which, a. is an isocyanate-terminated urethane which is the reaction product of a mixture consisting essentially of (I) and (II), at a molar ratio of 1:2 respectively in which I. is a saturated diol having a molecular weight of from about 200 to about 3,000, and Ii. is a saturated organic isocyanate, (b) is a monomeric, sterically bulky, polyhydric alcohol containing 2-6 hydroxyl groups and being free of oxyalkylene units, 2. is a polyalkyl ether of a polymethylol melamine, 3. is an acid catalyst and 4. is from about 0.0% to about 5.0%, by weight, based on the total weight of solids in said composition, of an ultraviolet light absorber.