| 摘要 |
Polyvinyl alcohol is manufactured by the alcoholysis of polyvinyl esters, in particular polyvinyl acetate, in the presence of a basic catalyst and in the presence of an alkanol as the solvent. The degree of polymerization of the polyvinyl ester used as the starting material is normally within the range from 400 to 10,000. The catalyst used is preferably an alkali metal hydroxide or an alkali metal alcoholate. The alcoholysis is effected by first preparing a solution of the polyvinyl ester, which is then trans-esterified at an elevated temperature. The resulting polyvinyl alcohol exhibits a high degree of purity. It is suitable for use as a base material for the production, by thermoplastic methods, of shaped articles, chiefly by compression molding, injection molding and extrusion. |
