Polymerization of vinyl chloride with t-butyl peroxyneoheptanoate and

Abstract

There is provided a process of producing a vinyl chloride polymer wherein vinyl chloride monomer or a monomeric mixture containing vinyl chloride monomer is suspension polymerized in the presence of an oil-soluble polymerization initiator and a suspending agent in an aqueous medium in a polymerization vessel, said process comprising providing, as the oil-soluble polymerization initiator, a mixture of (A) t-butyl peroxyneoheptanoate with (B) a perester peroxide other than said t-butyl peroxyneoheptanoate, said perester peroxide being such that a 10-hour half-life period temperature of a benzene solution of said peroxide dissolved in an amount of 0.1 mole per 1 liter of benzene is 44 to 55.degree. C.; and completing the polymerization at a temperature higher than a preset temperature for the polymerization by from 10 to 20.degree. C. when or after the internal pressure of the polymerization vessel begin to drop at the terminal stage of the polymerization reaction. According to this process, it is possible to obtain a vinyl chloride polymer good in quality, particularly with low initial discoloration when processed into formed products, at a good yield in a short period of polymerization time.