Process for producing vinyl chloride-based polymer via continuous or intermittent addition of dispersing stabilizer

摘要

A process for suspension polymerizing vinyl chloride or a monomeric mixture containing the same in an aqueous medium comprising the step of adding a partially saponified polyvinyl alcohol having an average polymerization degree of 600 to 800 and a saponification degree of 65 to 75 mol % to a polymerization system, wherein the partially saponified polyvinyl alcohol is added before start of polymerization, and also after-added continuously or intermittently over the period from the start of polymerization to the time when a polymerization conversion of 10 to 30% is reached. By the suspension polymerization process, it is possible to obtain a vinyl chloride-based polymer having high bulk specific gravity, high gelation rate and a certain level of thermal stability and showing an effectively reduced number of fish eyes when formed into shaped products.