| 摘要 |
PURPOSE:To eliminate generation of cracks, by a method wherein after stretching of a specified styrene resin film in a longitudinal direction, the same is stretched a little laterally. CONSTITUTION:A film whose mixture ratio of styrene/butadiene/block copolymer resin composed of 60-85wt.% styrene content and 40-15wt.% butadiene content with polyetyrene is styrene/butadiene/block copolymer resin:polystyrene =95:5-50:50 pts.wt. is stretched 2.0-5.0 times in a longitudinal direction, and orientation treatment of the film has been performed 1.05-1. 2 times laterally. When the content of styrene/butadiene/block copolymer is less than the range, it becomes that cracks are apt to occur and when it is much more than the range, stiffness is reduced due to deterioration of the tensile modulus of elasticity and thinning of the film becomes difficult. When a lateral draw ratio is made lower than the range, a prevention effect of the cracks is eliminated and when the same is made higher, the film is apt to generate creases due to shrinkage in a lateral direction at the time when the film is shrinked over a bottle and wrapping height becomes unequal. |
