| 摘要 |
PURPOSE:To obtain a vinyl chloride polymer having a high bulk density and a high rate of absorbing plasticizer, by suspension-polymerizing a vinyl chloride monomer so that the ratio of the degree of polymerization of the final product to that of the polymer in the middle course of polymerization may fall within a specified range. CONSTITUTION:In performing a polymerization reaction by feeding a polymerization vessel with an aqueous medium, a dispersant, a polymerization initiator and a vinyl chloride monomer, said reaction is controlled so that the difference in the average degree of polymerization between the obtained vinyl chloride polymer as the final product and the vinyl chloride polymer at a polymer conversion >=10% may fall within + or -10% of the average degree of polymerization of the final product. Indispensable requirements for practicing this process are to raise the polymerization temperature stepwise or continuously within a range of 10-80 deg.C and to control it so that the average degree of polymerization of the polymer at a polymer conversion >=10% may fall within 90-110% of the average degree of polymerization of the final product. Any change in the average degree of polymerization of the polymer at a polymer conversion <=10% exerts no particular influence upon the quality of the final product.
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