So far films, sheets and other fabricates of resins having gas barrier properties have been used for food packaging, parts packaging, covering and protection materials, and the like. They are used as a substitute for conventional paper or cellophane because of their excellent processability, transparency, light weight, and low price. In recent years, there is a desire to enhance the gas barrier properties of such polymeric materials for film or sheet to a level of those of glass or metallic materials, for the sake of long term preservation of the contents.
For the purpose, ethylene-vinyl alcohol copolymer resins (EVOH), poly (vinyl alcohol) resins, polyamide resins, polyester resins, poly (vinylidene chloride) resins, and other crystalline thermoplastic resins have been used owing to their high gas barrier properties.
In such crystalline gas barrier resins, it is known that increasing crystallinity brings forth the improvement of the gas barrier property and that the application of drawing or rolling also improves the gas barrier property. In fact, these processes have been practiced.
However, the gas barrier properties of these conventionally obtained films and the like are not fully satisfactory, and it is desired to develop materials with higher gas barrier properties.