Process for preparing vinyl chloride polymer.

摘要

Polyvinyl chloride is prepared by suspension polymerization of a monomeric charge of vinyl chloride dispersed and suspended in an aqueous medium while agitating the suspension. An oil-soluble partially saponified polyvinyl alcohol is added to the monomeric charge as a dispersant at the start of polymerization. A water-soluble partially saponified polyvinyl alcohol and/or a hydroxypropylmethyl cellulose is continuously added as a suspending agent from the start of polymerization. The suspending agent is entirely added while the polymerization rate is in the range of 5-50%. The agitating power applied to the aqueous suspension is 50-110 kg.m/s.ton while the suspending agent is being added, and increased above 110 kg.m/s.ton after the completion of addition. The resulting polymer has a high bulk density and a sharp particle size distribution and is susceptible to extrusion.