| 摘要 |
PROBLEM TO BE SOLVED: To obtain a polyvinyl alcohol(PVA)-based thermoplastic copolymer comprising an aliphatic polyester-grafted PVA, excellent in flexibility, water resistance, moldability, gas barrier property and safety, and suitable for films, etc., by subjecting a lactone to a ring-opening polymerization in the presence of the PVA. SOLUTION: A PVA-based thermoplastic copolymer is obtained by subjecting a ring-opening-polymerizable lactone having three to ten carbon atoms in the ring, such asε-caprolactone to a ring-opening polymerization reaction in a mixture comprising PVA having a saponification degree of >=60mol.% preferably in an amount of 2-98wt.% and the lactone preferably in an amount of 98-2wt.%. The ring-opening polymerization is preferably performed under a solvent-free condition.
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