Plastic and nonmetallic article shaping or treating: processes – Vacuum treatment of work – To degas or prevent gas entrapment
Patent
1980-10-22
1984-03-27
Pavelko, Thomas P.
Plastic and nonmetallic article shaping or treating: processes
Vacuum treatment of work
To degas or prevent gas entrapment
2643286, 26432818, 26432819, 425543, 425546, B29F 100
Patent
active
044393865
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. After combining in the mixing chamber, the reaction mixture is flowed into molds by gravity or injected into them by vacuum differential so as to form appropriately shaped bodies of solid polyurethane or the like for applications where other structural materials were heretofore used. Extreme care in avoiding moisture and air to the reactants and the reaction mixture minimizes bubble formation to such a degree that polyurethane bodies of greatly enhanced physical characteristics are produced.
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