| 摘要 |
<p>A process for preparing rigid cross-linked infusible objects in materials containing a vinyl chloride polymer, comprising homo- or co-polymers of vinyl chloride or mixtures thereof and which are insoluble in solvents for polyvinyl chloride comprises the steps of mixing together said vinyl chloride polymer, a polyisocyanate, a gasification or blowing agent which decomposes on heating to produce a gas, at least one vinylidenic monomer, and an ethylenic anhydride capable of polymerizing with this monomer, heating the mixture in a mould to form an intermediate cellular object, cooling the mould under pressure, removing the intermediate cellular object from the mould and heating it in the presence of water or water vapour to increase both the size and the cell size thereof. It is supposed that anhydride groups of the copolymer from maleic anhydride and vinylidenic monomer (which has been fixed by grafting on to the molecules of vinyl chloride polymer) are hydrolysed by reaction with the water or water vapour and the acid groups thus formed react with some of the polyisocyanate to link the different grafted polyvinyl chloride molecules. In examples the ingredients are formed into a paste which is heated to 170 DEG C. under pressure in a mould. After cooling, the intermediate cellular object is removed from the mould and placed in a humid enclosure at 100 DEG C. to increase the size of the object and the cell size, until a stable volume is obtained. The ingredients used are polyvinyl chloride, toluene - 2,4 - diisocyanate, a ,a 1 - azo - bis - iso - butyronitrile, maleic anhydride and (9) and (17) acrylonitrile, (10) styrene, (11) vinyl acetate, (12) and (18) methyl methacrylate, (13) ethyl acrylate, (14) a mixture of vinyl-pyridine and butyl methacrylate. In comparison examples cellular products are obtained from (1) P.V.C., maleic anhydride and azobisisobutyronitrile; (2) polyvinyl chloride, toluene-2,4-diisocyanate, azobisisobutyronitrile and maleic anhydride; (3) to (8) polyvinyl chloride, phthalic anhydride, toluene diisocyanate and (3) acrylonitrile, (4) styrene, (5) vinyl acetate, (6) methyl methacrylate, (7) ethyl acrylate, (8) a mixture of vinylpyridine and butyl methacrylate. Other specified polyisocyanates are triphenylmethane triiso-cyanate and diphenyl methane diisocyanate. Alternative vinylidenic monomers are those which contain a CH2=C< or CF2=C< grouping. Specified are butadiene, isoprene, dimethyl butadiene, chloroprene, 3-cyano-1,3-butadiene, piperylene, myrcene, vinylidene chloride, styrene, p-chlorostyrene, 3,5-dichlorostyrene, p-methoxystyrene, esters, nitriles and amides, e.g. octyl acrylate, lauryl methacrylate, methyl or chloracrylonitrile, dimethylacrylamide, vinylpyridine, vinyl benzoate, vinyl ketones, vinyl carbazole, ethylene, propylene, isobutylene, divinylbenzene, vinyl acetylene and vinyl ethinyl carbinol. Specification 660,358 is referred to.</p> |
