| abstract |
【Task】 Provided is a method for producing a vinyl chloride polymer having high porosity, excellent plasticizer absorbability, very little fish eye and high bulk specific gravity with high productivity. [Solution] In aqueous suspension polymerization of vinyl chloride or a monomer mixture containing the same, as a dispersion stabilizer, (A) a methoxy substitution degree of 26 to 30% by mass, a hydroxypropoxy substitution degree of 4 to 15% by mass, and Hydroxypropylmethylcellulose having a viscosity of 5 to 4000 mPa · s at 20 ° C. in a mass% aqueous solution, (B) partially saponified polyvinyl alcohol having a saponification degree of 75 to 85 mol% and an average polymerization degree of 1000 to 3000, and (C) saponification Partially saponified polyvinyl alcohol having a degree of 20 to 57 mol% and an average degree of polymerization of 150 to 600 is used. Suspension polymerization is started in the presence of specific ratios (A), (B) and (C), and (C) is further added to the polymerization reaction system at a polymerization conversion of 15 to 50%. [Selection figure] None |