| 摘要 |
A process for the production of porous masses and shaped articles from polymeric resins consists in heating finely-grained resin containing an organic volatile liquid, which does not dissolve or only swells the resin and which has a lower boiling point than the softening point of the resin, in homogeneous dispersion, in moulds to temperatures above the boiling point of the liquid, the amount of resin-liquid dispersion being such that on foaming up it completely fills the moulds and exerts an excess pressure on the inner walls of the mould. Already foamed-up resin may be co-employed and the resin-liquid dispersion may be first incompletely foamed by heating. Specified resins are polystyrene (which may be dissolved in monostyrene), polyvinyl pyrrolidone (which may be mixed with monostyrene and subjected to polymerization conditions), and polymethyl methacrylate (containing its monomer), while petroleum ether, pentane, hexane, heptane, cyclopentane, cyclohexane, methanol, methylene chloride, ethyl benzene and cyclopentadiene are specified volatile organic liquids. The homogeneous dispersion may be produced by bead or emulsion polymerization in which the organic liquid is employed. The heating may be carried out with hot air, moist hot air, steam, by infra-red radiation, in electric high frequency fields or by contact with hot liquids which do not dissolve the polymeric resins, e.g. water, ethylene glycol and glycerine. Specification 695,826 is referred to. |
