| 摘要 |
PROBLEM TO BE SOLVED: To obtain a chlorinated vinyl chloride resin excellent in heat stability while improving the polymn. productivity and the drying efficiency in the drying step after post-chlorination by chlorinating a vinyl chloride polymer of a specified polymn. conversion by a water suspension method under the exposure to light. SOLUTION: A vinyl chloride polymer obtd. by polymn. with a monomer conversion of 70-90 wt.% is chlorinated. On chlorination, the reaction temp. is pref. kept relatively low, 0-60 deg.C. Still pref., the reaction temp. from the beginning to the time when the chlorine content reaches 62 wt.% is kept at 0-60 deg.C, and at any time after that, the temp. is increased to higher than 60 deg.C but at most 85 deg.C. A chlorine gas used pref. has an oxygen content of 500 ppm or lower. On chlorination, a catalyst (e.g. a peroxide) may be used. Pref., the chlorine content of the resultant chlorinated vinyl chloride resin is set at 62-70 wt.%. |
