EVOH generally has higher crystallinity because of its very strong intermolecular forces due to hydrogen bonds between hydroxyl groups present at its side chains. Further, a film containing EVOH prevents transmission of gas molecules because the inter-molecular forces are strong even in an amorphous part of the EVOH. For this reason, the EVOH-containing film is generally excellent in gas barrier property. Therefore, EVOH is conventionally widely used for a packaging material because of its excellent gas barrier property and higher transparency.
An example of packaging material is a multilayer film structure which includes an intermediate layer of EVOH-containing film, and inner and outer layers of a thermoplastic resin respectively provided on opposite sides of the EVOH-containing film layer. The multilayer structure is formed into a film, a sheet or a container such as a bottle for a food packaging material, a medicine packaging material, an industrial chemical packaging material, an agricultural packaging material and other packaging material with advantageous use of its excellent gas barrier property and transparency.
However, the multilayer structure, which is highly transparent, transmits not only visible light but also ultraviolet radiation, so that a product contained in the packaging material is problematically liable to be deteriorated by the ultraviolet radiation. Particularly, it is known that, where the multilayer structure is used as food packaging material, food contained in the packaging material is exposed to ultraviolet radiation of a wavelength range of shorter than 320 nm such as UV-B and UV-C and, as a result, is significantly deteriorated. To cope with this, it is proposed to add a water-soluble UV absorber to a film of a resin such as a polyvinyl alcohol having a gas barrier property to thereby impart the resin film with a higher transparency and prevent the photodegradation of the contained product due to the transmitted ultraviolet radiation (see, for example, PTL 1).