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AssigneeShin-Etsu Chemical Co., Ltd.
InventorsHajime Kitamura, Ichiro Kaneko
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A process for preparation of a vinyl chloride polymer comprising the steps of subjecting an aqueous medium containing vinyl chloride monomer or a mixture of vinyl chloride monomer with other vinyl monomer, a polymerization initiator and a dispersant to high-speed shear agitation at a shear rate of 10.sup.4 sec.sup.-1 or above to prepare a suspended dispersion containing fine particles of the monomer(s) dispersed therein, then subjecting the suspended dispersion to low-speed shear agitation at a shear rate of from 10 to 100 sec.sup.-1, and thereafter starting suspension polymerization. Even with a decreased amount of dispersant, the process inhibits the coarsening of the polymer particles, to yield the polymer with a narrow particle diameter distribution. Deposition of scale and formation of fish-eyes are also prevented effectively.
A process for preparation of a vinyl chloride polymer comprising the steps of subjecting an aqueous medium containing vinyl chloride monomer or a mixture of vinyl chloride monomer with other vinyl monomer, a polymerization initiator and a dispersant to high-speed shear agitation at a shear rate of from 10.sup.4 sec.sup.-1 to 10.sup.6 sec -1 at 10.degree. to 30.degree. C. for 0.05 to 5 seconds to prepare a suspended dispersion containing fine particles of the monomer(s) dispersed therein, then subjecting the suspended dispersion to low-speed agitation at a shear rate of from 10 to 100 sec.sup.-1 at 10.degree. to 30.degree. C. for 1 to 30 minutes, and thereafter starting suspension polymerization.
Dependencies are inferred from the claim text.