| 摘要 |
PURPOSE:To provide excellent dynamical properties to a film and especially enhancing the modulus of elasticity thereof at high temp. and to impart enhanced heat resistance and high temp. dimensional stability thereto, by a method wherein a raw film. which was thermally stretched to the lateral direction, is subjected to zone stretching under tension under local heating and further subjected to one stage or multistage heat treatment while locally heated at temp. in the vicinity of crystallization temp. under high tension. CONSTITUTION:A raw film according to an extrusion method is thermally stretched to the lateral direction to be converted to morphology facilitating zone stretching. By this operation, lamella is arranged in a state stacked in the lateral direction and takes an azimuth wherein a folded chain crystal structure is easily unraveled by external force in the longitudinal direction. Subsequently, zone stretching performed in the orthogonal direction is performed while the film is passed through a narrow heating zone while locally heated. Further, by applying zone heat treatment to the highly stretched and ultimatelly extended chain structure obtained by zone stretching at temp. suitable for crystallization, a film having not only enhanced dimensional stability but also high modulus of elasticity and high strength is obtained.
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