Dispersion stabilizer for suspension polymerization and method of producing vinyl chloride-based polymer using same

摘要

Provided is a dispersion stabilizer for suspension polymerization that contains a hydroxypropylmethylcellulose with a degree of methoxy group substitution of 27 to 30% by mass and a degree of hydroxypropoxy group substitution of 5 to 12% by mass, in which the viscosity at 20°C of a 2% by mass aqueous solution of the hydroxypropylmethylcellulose is within a range from 5 to 1,600 mPa·s, and in 2 ml of a 0.2% by mass solution of the hydroxypropylmethylcellulose, the number of undissolved fibers with a particle size within a range from 8 to 200 µm, as measured by a Coulter counter method, is not more than 1,000, and the number of undissolved fibers with a particle size of 50 µm or greater measured using the same method is not more than 20. By employing a method of producing a vinyl chloride-based polymer that uses this dispersion stabilizer, a vinyl chloride-based polymer with extremely low levels of fish eyes and defects derived from foreign objects can be produced.