BIAXIALLY ORIENTED POLYESTER FILM AND ITS PRODUCTION

摘要

PROBLEM TO BE SOLVED: To produce the subject film useful as packaging bags having functional properties excellent in gas barrier properties by bringing the film to contain ethylene terephthalate units and ethylene isophthalate units in a specific ratio. SOLUTION: This biaxially oriented polyester film is brought to contain 15-50 mole % of ethylene terephthalate unit and 85-50 mole % of ethylene isophthalate unit. The film is preferably produced by melting and mixing a polyethylene terephthalate with a copolymer of a polyethylene terephthalate/ ethylene isophthalate to form a non-drawn sheet, then biaxially orienting the sheet simultaneously. The copolymer has preferably (5/95)-(35/65) molar ratio of ethylene terephthalate/ethylene. The film preferably has <=30 ml/m2/24 hr/atm oxygen permeability and >=2.0 kgf cm impact strength.