| 摘要 |
<p>A METHOD OF PRODUCING ETHYLENE-VINYL ALCOHOL COPOLYMER FILM A method of producing films of ethylene-vinyl alcohol copolymers having an ethylene content of 20-55 mole % and a saponification degree of not less than 96% is provided which is characterized in that biaxial or multiaxial stretching at a low moisture content and at low temperatures, previously thought difficult, is made possible by using unstretched films which are especially low in the degree of crystallinity. The degree of crystallinity of the unstretched film is represented by the density at 25.degree.C thereof and when the ethylene content is X mole %, a film having a lower density value than the value calculated by the formula 1.320 - 4.3 x 10-3 X ( g/ml ) is used. The moisture content is not more than 3.5%, preferably not more than 2.0%, the stretching temperature is 50-150.degree.C, preferably 50.degree.-100.degree.C, and the stretching ratio is 4-20 times. If necessary, heat treatment follows the stretching. Such a method gives excellent packaging films having low levels of oxygen gas permeability, which are moreover less dependent on humidity in the atmosphere.</p> |
