| 摘要 |
PURPOSE:To form the titled polymer excellent in melt moldability and drawability, by copolymerizing ethylene with vinyl acetate under at least two specified conditions varied in a stepwise manner and saponifying the resulting copolymer. CONSTITUTION:The copolymerization of ethylene with vinyl acetate is conducted under conditions satisfying the relationships I and II [wherein T is a temperature ( deg.C), and P is an ethylene pressure (kg/cm<2>.G)] in such a manner that the temperature difference between two successive different polymerization conditions is at least 10 deg.C and/or the difference in ethylene pressure therebetween is at least 5kg/cm<2>, the polymerization condition is stepwise shifted from one to the other, and the amount of a polymer formed under each reaction condition is at least 10wt%, based on the total polymer formed. The resulting copolymer is saponified with an alkali catalyst at about 60-175 deg.C to obtain a saponified ethylene/vinyl acetate copolymer (ethylene content of 25-45mol% and degree of saponification >=95%). |
