Patent ID: 6521162
Filing Date: 2003-02-18
Classification: B29C,B29K,D04H,Y10T

Abstract:
A process for making molded parts having a density of 0.8 to 1.85 grams per cm3 and a shrinkage of less than 1 millimeter per compared with the dimensions of the cold mold, comprising the following steps:(a) admixing a low pressure molding compound consisting essentially of unsaturated thermosetting resin, shrink control additive, fumed silica thixotrope, free radical initiator, alkaline earth oxide or hydroxide thickening agent and monomer, (b) forming a paste, (c) dispensing said paste above and below a bed of chopped roving glass, forming a molding sheet, (d) consolidating said sheet, (e) enveloping said sheet in a carrier film, (f) maturing said sheet until a matured molding viscosity of 3 million to 18 million centipoises is attained and said sheet is non-tacky, (g) releasing said sheet from said carrier film, (h) compression molding said sheet into a part in a mold at a temperature of 85 to 170 degrees Centrigrade and a pressure of 80 to 500 psi ) 0.6 to 3.5 MPa) whereby a uniform flow of resin, filler and glass occurs outward to the said part, and (i) removing said molded part, said part having shrunk less than 1 millimeter per meter in comparison with said mold.