| abstract |
(57) [Summary] [Structure] In a method for producing a vinyl chloride polymer by suspending and dispersing vinyl chloride in an aqueous medium to carry out suspension polymerization, as a dispersant for the suspension dispersion, (A) A combination of partially saponified polyvinyl alcohol having a saponification degree of 20 to 60 mol% and a block character of 0.6 or more and (B) partially saponified polyvinyl alcohol having a saponification degree of 65 to 75 mol% is used in combination with the suspension polymerization. After the initiation, when the polymerization conversion rate reaches 5 to 60%, (C) hydroxypropylmethyl cellulose having a methoxy substitution degree of 26 to 30 weight% and a hydroxypropoxy substitution degree of 4 to 15 weight% is added to the polymerization system. And [Effects] While effectively suppressing the adhesion of polymer scale to the wall surface of the polymerizer, the bulk density is high, the gelation speed is fast, and the fish eye when formed into a molded product is also effectively suppressed. A polymer can be obtained. |