Pigmentable low shrink thermosetting polyesters

In a process for producing a uniformly pigmented molded part from a low-shrink moldingg resin composition containing tinting pigments dispersed in a thermosetting unsaturated polyester polymer mixed with copolymerizable ethylenically unsaturated monomer, the improvement comprising:

• forming preformed lightly cross-linked polymer particles having an average particle size between about 15 microns and 100 microns, said cross-linked polymer particles being substantially a linear polymer selected from the group consisting of ethylenic addition polymers, polyesters, polyurethanes, polyamides, polyamines, epoxides, alkyd polyesters, polyethers, and polycarbonates, said linear polymer being cross-linked by minor amounts of multifunctional monomer to provide preformed polymer particles having a cross-linking density of between about 0.005 and 2 equivalent cross-linking sites per kilogram of preformed polymer;
• providing a low-shrink molding resin composition mixture comprising by weight at least about 25% of said thermosetting polyester polymer, about 5% to 25% of said lightly cross-linked preformed polymer particles, and about 30% to 70% of said ethylenically unsaturated copolymerizable monomer;
• and curing the moldingg resin composition to form a molded structure having a uniformly pigmented surface.

A pigmentable low-shrink thermosetting unsaturated polyester molding resin composition for thickening with Group II metal oxides, hydroxides, or alkoxides, and curable to form low-profile molded parts, the molding resin composition comprising:

• a resin mixture comprising by weight at least 25% of a thermosetting ethylenically unsaturated polyester polymer, about 5 to 25% of lightly cross-linked preformed polymer particles, and about 30 to 70% of an ethylenically unsaturated monomer copolymerizable with said thermosetting polyester polymer for forming a thermoset matrix binding said preformed polymer particles;
• said lightly cross-linked, preformed polymer particles having an average particle size between about 15 and 100 microns and being a linear polymer selected from the group consisting of ethylenic addition polymers, polyester condensation polymers, polyurethanes, polyamides, polyamines, epoxides, alkyd polyesters, polyethers, and polycarbonates, said linear polymer cross-linked with minor amounts of multifunctional monomer providing cross-linked preformed polymer particles having a cross-linking density of between about 0.005 to 2 equivalent cross-linking sites per kilogram of said preformed polymer whereby said molding resin composition is curable to form a low-profile molded structure.