| 摘要 |
Expandable pearls of copolymer based upon a styrene compound which is styrene, substituted styrene or their copolymers are prepared by copolymerizing in aqueous suspension the styrene compound with one or more unsaturated aliphatic hydrocarbons or halogenated hydrocarbons that are gaseous under normal temperature and pressure and are introduced under pressure at any moment of the polymerization time, so that at least one of the hydrocarbons or halogenated hydrocarbons is partially retained as an expanding agent in the pearls. Suitable substituted styrenes are a -methyl-styrene, ethylstyrenes, chlorostyrenes, vinyl toluene and divinyl benzene and suitable copolymers are styrene-acrylonitrile, styrenemethylmethacrylate and styrene - a - methylstyrene. Unsaturated compounds suitable for use are butenes, propene, butadiene and their halogenated derivatives and certain of the vinylidene halides. Conventional catalysts and suspension agents may be added to the polymerization mixture. |
