PURPOSE: To prevent scale deposition, to improve operating efficiency, and to obtain a high-quality product, by using a specified mercapto compound, a water- soluble polyvalent metallic salt, and a nitrite in a specific ratio in suspension polymerization of vinyl chloride.
CONSTITUTION: 100 parts by wt. of a monomer mixture is blended with 0.001W 0.01 parts by wt. of a water-soluble mercapto compound having a hydroxy group and four or less carbon atoms, three or more functional water-soluble polyvaleic metallic salt and an organic or inorganic nitrite. An amount of the salt is 0.001W 0.1 part by wt. based on 100 parts by wt. of a water medium and an amount of the nitrite is 0.005W50 ppm, preferably 0.01W10 ppm based on the water medium. Tioacetic acid and its alkyl ester may be cited as the water-soluble mercapto compound. A polymerizer can be used not less than 15 times continuously by this method without removing scales, operating efficiency is improved, and quality fall caused by mixing of released scales can be prevented.
MURAMATSU HIDEKAZU
KOBAYASHI MASAHIRO
TAKESHITA ISAO
