| 摘要 |
PURPOSE:To make it possible to give high heat shrinkage factor and comparatively low heat shrinkage stress to a film by a method wherein copolymer composition of epsilon-caprolactam and lauryl lactam is employed as the major constituent of raw resin. CONSTITUTION:A biaxially oriented film which employs copolymer consisting of 90-65mol% of epsilon-caprolactam and 10-35mol% of lauryl lactam as raw resin is formed so as to have the shrinkage factor at 100 deg.C by hot water of 30% or more both in longitudinal direction and in lateral direction and at the same time the heat shrinkage stress of 100-500g/mm<2>. In this case, the biaxially orienting temperature is preferably 120 deg.C or lower and the necessary draw ratio is 250% or more longitudinally and laterally in order to obtain the drawing effect necessary for molecular orientation, heat shrinkability and the like. Because the film is excellent in heat shrinkability and the heat shrinkage stress of the shrunk film is comparatively low, the film is suitable for the shrink wrapping of even matters to be packaged which is liable to get out of shape. Further, the film has low moisture and water absorption properties and consequently the slack due to moisture absorption after packaging is small. |
