Dispersion assis5tant for suspension polymerization, method for producing vinyl polymer in which said assistant is used, and vinyl chloride resin
The purpose of the present invention is to provide a dispersion assistant with which it is possible to stably obtain an excellent polymeric substance (vinyl resin) with minimal adhering of scale to a polymerization vessel even when the dispersion assistant is used in a large amount in the suspension polymerization of a vinyl compound. The additive for suspension polymerization contains a polyvinyl alcohol polymer (A) that has a gelling degree of 60 mol% or less and has acetal groups (a) having olefinically unsaturated double bonds.