Process for the manufacture of products from reinforced polyester

Claim 1

A process for the manufacture of a molded, reinforced polyester resin polymeric product comprising the steps of: (a) forming by intensively mixing a readyto-mold SMC or TMC resin and reinforcement composite of an unsaturated polyester resin reactant, a cross-linking monomer, reinforcing material, and microcapsules of from 5 to 200 microns in diameter containing a liquid phase including an initiator for cross-linking of the polyester resin reactant and the monomer, said microcapsules isolating said initiator from said resin until a predetermined elevated temperature of at least about 108° C. is reached in the process; (b) aging said composite until a control viscosity of from 20,000,000 up to 60,000,000 centipoises at 22° C. is reached; (c) introducing a predetermined amount of said composite into a cavity of a mold; (d) applying heat and pressure to said composite to fill said mold cavity uniformly with mixture prior to any significant initiator-induced cross-linking during a first portion of the molding cycle; (e) causing said microcapsules to release said initiator at said predetermined elevated temperature by using the vapor pressure of the liquid phase within the microcapsules, and thereby terminating said first portion of the molding cycle and commencing a second exothermic portion of the molding cycle, said microcapsules having a wall thickness and strength sufficient to withstand the vapor pressure of said liquid phase up to the internal pressure developed in the microcapsules at said predetermined elevated temperature; (f) effecting substantially all initiatorinduced cross-linking during said second exothermic portion of the molding cycle whereby said first portion of said molding cycle is substantially prolonged by maintaining said initiator in said microcapsules and the prolongation of the first portion of said molding cycle permits the use of increased molding temperatures and a net reduction in the overall molding cycle as compared with the use of such initiator in the composite in a conventional non-encapsulated form; and (g) removing the cured composite from said mold cavity to provide said polymeric product.