METHOD FOR PRODUCING POLYVINYL ALCOHOL RESIN HAVING HIGH DEGREE OF SAPONIFICATION

摘要

Provided are a method for preparing a poly(vinyl alcohol) resin for optical use easily and economically, a poly(vinyl alcohol) resin prepared by the method having a high degree of saponification, and an optical film comprising the resin. The method comprises the step of reacting a poly(vinyl alcohol) resin having a degree of saponification less than 99.5 mol% by using water as a reaction solvent to prepare a poly(vinyl alcohol) resin having a degree of saponification of 99.95-99.99 mol%. Preferably the reaction solvent comprises further an organic solvent. The prepared poly(vinyl alcohol) resin has a degree of polymerization of 2,000-5,000 and a melting point of 230 deg.C or more.