Method for preparing high-polymerization-degree polyvinyl alcohol through water-phase precipitation polymerization

The invention provides a method for preparing high-polymerization-degree polyvinyl alcohol through water-phase precipitation polymerization, which comprises the following steps: preparing polyvinyl acetate through water-phase precipitation polymerization, and carrying out alcoholysis on the prepared polyvinyl acetate to obtain the high-polymerization-degree polyvinyl alcohol. Wherein the step of preparing polyvinyl acetate through aqueous phase precipitation polymerization comprises the following steps: mixing vinyl acetate with azodiisobutyronitrile to obtain a mixed solution, then dropwise adding the mixed solution into deionized water, keeping the reaction temperature in the dropwise adding process, continuing to stir and react after the dropwise adding is finished, and collecting a solid product, so as to obtain the polyvinyl acetate with high polymerization degree. According to the technical scheme, the polymerization product polyvinyl acetate is directly separated out of water, high-polymerization-degre