Foamed plastics prodn. - by normal foam-prodn. processes, using liq. ammonia or liq. carbon di:oxide as blowing agent

摘要

Foamed plastics (I) are produced by incorporating a liquefied blowing agent (II) under pressure into a thermoplastic (III) which is softened or melted by heating; when the pressure is released (II) expands to produce a plastic foam; (II) is liq. ammonia or liq. CO2. Pref. (III) is polyethylene or polypropylene, esp. LDPE,. polystyrene, PVC or thermorubber, or a polyurethane- or epoxy-based reactive resin; the liq. ammonia contains dissolved organic cpds; mol. ratio ammonia:CO2 = (1:10)-(10:1), pref. (1:1)-1:5). USE/ADVANTAGE - The process is useful for the prodn. of foamed sheet, sections and tubes (claimed). (II) are safe to handle, non-flammable and environmentally harmless (contrast prior-art hydrocarbon and CFC blowing agents), and can be readily recovered from foam prods. for possible recycling.