| 摘要 |
1,162,432. Photopolymerization process. CESKOSLOVENSKA AKADEMIE VED. 3 March, 1967 [8 March, 1966], No. 10204/67. Heading C3P. Ethylenically unsaturated monomers are photopolymerized in the presence, as free radical-forming initiator, of a coloured azo compound having an absorption maximum in the visible light region from 3800-5000A and corresponding to the formula R 1 N = N-R 2 where R 1 is an optionally substituted aromatic nucleus directly bonded to the indicated azo group, and R 2 is either (a) an aliphatic hydrocarbon residue bound to the azo group by a tertiary carbon atom, optionally substituted by one or more aryl, aralkyl, nitrile or carbalkoxy groups, or (b) a nitrile group directly linked to the azo group. (The term "aromatic nucleus " includes aromatic, heterocyclic nuclei). Examples illustrate the homopolymerization, in bulk, of methyl methacrylate, acrylonitrile, vinyl chloride, tetrafluoroethylene and styrene, and also the copolymerization of styrene and methyl methacrylate in two stages; in the first stage a prepolymer syrup is formed and, in the second, the syrup is polymerized in dispersion in aqueous polyvinyl alcohol to form a pearl copolymer. |
