Abstract: Vacuum injection molding designed for manufacturing solid plastics. Elimination of gases from the liquid resins gives polymers which are more dimensionally stable, mechanically stronger, and more resistant to thermooxidative action. Among liquid resin systems like allylics, epoxies, polyesters and so on, the polyurethanes belong to systems which are sensitive not only to reactive gases but also to the moisture absorbed. In the vacuum injection molding, a vacuum system is connected to reactant chambers, metering devices, mixing chambers, and molds. To produce solid polyurethane bodies, polyol and a polyisocyanate or similar reactants are provided in each of the reaction chambers and are flowed through metering devices into a mixing chamber by gravity flow or by pressure differential. The system is designed such that the reactants are kept from moisture and air to avoid formation of bubbles and microbubbles in the polymer bodies produced by the mixture of the reactants.

Abstract: Solid, rigid, filled polyurethane composites are prepared by a process comprising admixing a dried polyisocyanate component containing a degreased dust- and solid-impurity-free filler with a dry polyol, degassing said admixture until no further gas evolution occurs and effecting reaction between the polyisocyanate and polyol.