| 摘要 |
1,141,376. Foaming thermoplastic resins. MONSANTO CHEMICALS Ltd. 20 Sept., 1967 [1 Nov., 1966], No. 48833/66. Headings C3C and C3P. Thermoplastic resins are foamed by a process in which the heat-softened resin containing orthoboric acid as nucleating agent is mixed under pressure with a volatile blowing agent and extruded into a zone of lower pressure to allow foaming of the resin, the extrusion conditions being such that the orthoboric acid is thermally decomposed so as to provide nucleation sites for cell formation. Conventional nucleating agents, e.g. silica and talc, may also be present. The resin may be a polymer of ethylene, propylene, butadiene, styrene, vinyl toluene, α-methyl styrene, acrylonitrile, vinyl chloride, vinyl acetate, methyl acrylate, ethyl acrylate or methyl methacrylate The blowing agent may be an aliphatic hydrocarbon or halogenated hydrocarbon, acetone, carbon dioxide or nitrogen. Examples describe the preparation of foamed sheets of polyethylene, polystyrene and an ethylene/vinyl acetate. |
