In-mold coating composition and method of applying same

A method of providing a compression or injection molded completely cured thermoset article with a coating substantially free of surface defects comprising:

• a. depositing in a mold a thermosetting composition comprising an unsaturated polyester resin, a cross-linkable monomer, a low shrink additive, a filler, glass fibers and a polymerization initiator for said polyester and cross-linkable monomer;
• b. compression or injection molding said thermosetting composition to provide a compression of injection molded completely cured thermoset polyester resin glass fiber article having an integrally molded outer surface, at least one boss and/or at least one rib, said boss and/or said rib being opposite to said surface, and said surface exhibiting as defects sink marks, pores, microcracks, open knit lines and waviness,
• c. opening said mold and placing on said outer surface in said mold a charge of a curable thermosetting coating composition, said charge being sufficient to provide on said surface a coating having a thickness of less than about twenty mils;
• d. closing said mold and applying sufficient pressure to said charge to cause said coating composition to substantially cover uniformly the entire area of and penetrate said surface, said coating composition including a mold release agent and
• (i) an isocyanate-terminated material containing unreacted isocyanate groups, and
• (ii) a composition containing reactive hydrogen atoms for reaction with (i);
• e. curing said coating composition in said mold under heat and pressure to bond said coating composition to said surface;
• and
• f. removing said coated article from said mold, providing said article with a substantially continuous smooth defect-free crosslinked-isocyanate based coating adhered tightly to said surface of said article.

A method of providing a compression or injection molded completely cured reinforced thermoset article with a coating to eliminate surface defects, (1) the composition of said thermoset article comprising a completely cured unsaturated polyester-crosslinkable monomer compound reinforced with glass fibers and containing a low shrink additive and a filler, (2) said article having an outer surface, and (3) said surface having defects comprising pores, comprising:

• a. placing on said outer surface of said article in a mold a charge of a curable thermosetting coating composition, said charge being sufficient to provide on said surface a coating having a thickness of less than about 20 mils;
• b. closing the mold and applying sufficient pressure to said charge to cause the coating composition to substantially uniformly cover and penetrate said surface, the coating composition including a mold release agent and
• (i) an isocyanate-terminated material containing unreacted isocyanate groups, and
• (ii) a composition containing reactive hydrogen atoms for reaction with (i);
• c. curing said coating composition in said mold under heat and pressure to bond said coating composition to said surface;
• and
• d. removing said coated article from said mold, providing said article with a substantially smooth defect-free crosslinked-isocyanate based coating bonded to said surface of said article.

A method of providing a compression or injection molded completely cured thermoset article with a coating substantially free of surface defects comprising:

• a. depositing in a mold a thermosetting composition comprising an unsaturated polyester resin, a cross-linkable monomer, a low shrink additive, a filler, glass fibers and a polymerization initiator for said polyester and crosslinkable monomer;
• b. compression or injection molding said thermosetting composition to provide a compression or injection molded completely cured thermoset polyester resin glass fiber article having an integrally molded outer surface, said surface having defects comprising pores,
• c. opening said mold and placing on said outer surface in said mold a charge of a curable thermosetting coating composition, said charge being sufficient to provide on said surface a coating having a thickness of less than about 20 mils;
• d. closing said mold and applying sufficient pressure to said charge to cause said coating composition to substantially cover uniformly the entire area of and penetrate said surface, said coating composition including a mold release agent and
• (i) an isocyanate-terminated material containing unreacted isocyanate groups, and
• (ii) a composition containing reactive hydrogen atoms for reaction with (i);
• e. curing said coating composition in said mold under heat and pressure to bond said coating composition to said surface;
• and
• f. removing said coated article from said mold, providing said article with a substantially continuous smooth defect-free crosslinked-isocyanate based coating adhered tightly to said surface of said article.