| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a porous vinyl chloride-based polymer excellent in absorption of a plasticizer, and hardly causing fish eye when molding the polymer, by using a large-scale polymerizer, in high productivity without causing both of the lowering of the quality, and the problem in operation by the foaming under polymerization even in a producing method accompanying the heat-removal by a reflux condenser. SOLUTION: This producing method of a vinyl chloride-based polymer comprises using water at 40-90 deg.C as an aqueous medium, and further using three kinds of (A) a partially saponified polyvinyl alcohol having 300-1,000 polymerization degree, and 65-75 mol% saponification degree, having a mercapto group at least at one terminal of the molecular chain, (B), and (C) partially saponified polyvinyl alcohols having specific polymerization degrees and saponification degrees in specific amounts as a dispersing agent. The polymerization is carried out while regulating the removed quantity of the heat by a reflux condenser under polymerization so as to be 30%-80% of all heat quantity generated by the polymerization.
|
