To provide a dispersion stabilizer for suspension polymerization for paeparing a vinyl chloride-based polymer with extremely low levels of fish eyes and defects derived from foreign matter, and a method for producing a vinyl chloride-based polymer by using the stabilizer.
The dispersion stabilizer contains a hydroxypropylmethylcellulose with a degree of methoxy group substitution of 27-30 mass% and a degree of hydroxypropoxy group substitution of 5-12 mass% and has the following characteristics: the viscosity at 20C of a 2 mass% aqueous solution of the hydroxypropylmethyl cellulose is 5-1,600 mPa s; in 2 ml of a 0.2 mass% solution of the hydroxypropylmethyl cellulose, the number of undissolved fibers with a particle size of 8-200 m, as measured by a Coulter counter method, is 1,000 or less; and the number of undissolved fibers with a particle size of 50 m or greater measured using the same method is 20 or less. The method for producing a vinyl chloride-based polymer uses the dispersion stabilizer.
AMANO TADASHI
SHIGEMITSU MINORU
NIINOBE SHINGO
