| 摘要 |
PURPOSE:To reduce wrinkling and distortion of a film, etc., at the time of shrink packaging and to contrive to improve working properties of the film by giving certain specific physical properties to a biaxially oriented film. CONSTITUTION:After polyester or copolymer polyester containing the proper quantity of inorganic particles, etc., as lubricant has been dried by the use of hopper dryer, paddle dryer, vacuum dryer, etc., the extraction of the polyester is performed at the temperature of 200-320 deg.C. Non-oriented film obtained by quenching after the extraction is first oriented 1.5-5.0 times uniaxially and then oriented 2.5-5.0 times in the direction perpendicularly intersection to the uniaxial direction so as to be gradually formed into a biaxially oriented film, and a heat treatment at 60-130 deg.C for 0.01-60 seconds is applied to the film. Thus, the film is prepared in such manner that the degree of face orientation (DELTAP) of the film is in the range of 0.070-0.150 on both surfaces of the film and the rate of shrinkage after treatment in 97 deg.C hot water for 30 seconds is 15-50% in one direction and the rate of shrinkage in the direction perpendicularly intersecting to the one direction is somewhat smaller than the former rate, i.e., 5-30% and the tear strength is 700g/mm or over. |
