| 摘要 |
Vinyl chloride homo- or copolymers are produced by bulk polymerization of the monomer(s) in two stages, the first stage consisting of a pre-polymerization in a vessel with vigorous agitation of the reactants until 7 to 15% of the monomer(s) has been converted and the second stage being carried out in a different vessel or vessels in which the reaction medium is agitated less vigorously, the first and the second stage being carried out in the presence of different catalysts, the second stage catalyst having a lower rate of decomposition than the first stage catalyst under the reaction conditions prevailing during the second stage. Examples of the first stage catalyst are sulphonyl acetyl cyclohexane peroxide (SACP), dichloroacetyl peroxide and trichloroacetyl peroxide and of the second stage catalyst are (1) azodiisobutyronitrile, (2) lauroyl peroxide and (3) isopropyl peroxydicarbonate. The catalysts are added together in the first stage or the second stage catalyst is added during transfer of the monomer-polymer mixture to the second vessel or directly to said vessel. In the examples polyvinyl chloride and vinyl chloride-vinyl acetate copolymers are produced using a catalyst combination of SACP and (1), (2) or (3), the average particle size of the polymers being in the range 100 to 250 microns.
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