| 摘要 |
An alkenyl aromatic compound is polymerized in an aqueous medium containing 0,023 to 0,4% of a salt of a sulphonated polyvinyl toluene, until from 8 to 60% of monomer is polymerized and before agglomeration occurs, and then an anionic or nonionic surface active agent is added and polymerization continued to give a non-sticky granular product. Optionally 0,5 to 0,01% of a divinyl aromatic compound may be present. The presence of neopentane, pentane, hexane, heptane, iso-octane, or dichlorodifluoromethane gives products which expand to a cellular mass on heating. Polymerization is accelerated by the use of a peroxygen catalyst or mixtures thereof and in examples other ingredients used are potassium dichromate, ammonium sulphate, sodium sulphate, and ammonium or sodium hydroxide for adjusting pH to 6.ALSO:Products which can be foamed on heating, e.g. by steam, are obtained by polymerizing an alkenyl aromatic compound in an aqueous medium containing 2 to 25% based on the monomers of neopentane, pentane, hexane, heptane, iso-octane, dichlordifluoromethane or dichlorodifluoromethane, and also containing 0,023 to 0,4% of a salt of a sulphonated polyvinyl toluene, the polymerization being carried out until from 8 to 60% of monomer is polymerized and before agglomeration occurs, and then polymerization being continued in the presence of an anionic or nonionic surface active agent whereby a non-sticky granular product is obtained. Optionally 0,5 to 0,01% of a divinyl aromatic compound is present and polymerization is accelerated by the use of peroxygen catalysts. In examples the monomers used are styrene, ethylvinylbenzene and divinyl benzene, and the pH of the media used are adjusted to 6.
|
