Preparation of vinyl chloride polymers using high-speed and low-speed shear agitation

摘要

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 104 sec-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-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.