| 摘要 |
A rigid cellular product is formed by heating a mixture of polyvinyl chloride base, polyisocyanate, blowing agent and one or more polymerizable monomers, in an airtight mould under pressure, removing the cellular product from the mould between 90 DEG and 140 DEG C. and then reacting it with hot water or steam. The starting mixture may also contain an anhydride of an ethylenic carboxylic acid and a halogenated alkane. The term "polyvinyl chloride base" includes the homopolymer as well as copolymers of vinyl chloride containg less than 25% of vinylidene monomers such as vinylidene chloride or vinyl monomers such as vinyl acetate. Blowing agents used are those which liberate nitrogen on heating, e.g. azodi-isobutyronitrile. Polymerizable monomers specified are styrene, acrylonitrile, methyl acrylate, ethyl acrylate, octyl acrylate, methyl methacrylate, ethyl methacrylate maleic anhydride and fluoro- and halo-derivatives of these compounds. Specified anhydrides are maleic, acrylic, itaconic and citraconic anhydrides. |
