| 摘要 |
PURPOSE:To reduce anisotropy and provide the film with prominent mechanical strength and dimensional stability against heat by a method wherein the Young's modulus, heat shrinkage factor, humidity expansion coefficient and birefringence rate in the surface of biaxially orientated film of copolymer of 3-methyl-1-butene in the oriented direction thereof are specified. CONSTITUTION:The longitudinal and transversal Young's modulus in the surface of the film is specified to 200kg/mm<2>, the longitudinal and transversal heat shrinkage factor in the surface of the film at 180 deg.C is specified to 4% or less, the longitudinal and transversal humidity expansion coefficient in the surface of the film is specified to 5X10<-6>/%RH or less and the birefringence rate (DELTAn) in the surface of the film is specified to 0.02 or less. The film is manufactured by a method wherein high- molecular copolymer, for example,is passed through a filter and is extruded out of a die, thereafter, rough granular structures and grains are removed and the extruded material is taken of to a cooling drum to manufacture an unoriented film. The first stage simultaneous biaxial orientation of the unoriented film is effected under temperature of 50 deg.C-180 deg.C with 2X-5X magnification in each direction, then the second stage simultaneous biaxial orientation of the same is effected under a temperature higher than the temperature in the first stage with 1.2X-3.5X magnification.
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