| 摘要 |
PROBLEM TO BE SOLVED: To industrially, inexpensively and easily produce polyvinyl alcohol resin of a low degree of polymerization. SOLUTION: In the polymerization of vinyl ester, the pressure in the polymerization tank is raised higher than the atmospheric one with the unreacting vinyl ester, the vapor of the polymerization solvent or noncondensable gas introduced from the outside of the polymerization tank and the monomer is polymerized at a temperature 2-80 deg.C higher than the boiling point of the reaction solution under atmospheric pressure and the resultant vinyl ester polymer is saponified.
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