| 摘要 |
PURPOSE:To raise the thickness accuracy of a film of ethylene-vinyl acetate copolymer saponified product by a method in which the film is heated over 20% or more of the distance between nip rolls in the temperature range of 70-120 deg.C and then stretched to 1.2-2.0 times in areal scale factor in such a way as to cause sufficient orientation of molecules. CONSTITUTION:A tubular EVOH film 9 biaxially stretched (primary stretching) by inflation method is restretched (secondary stretching) by reheating by means of the pressure of inside gas and an external heater 12. In this case, the film is reheated to 70-120 deg.C over 20% or more of the distance between nip rolls and also for the circular cross section of bubble between the nip rolls and then stretched to within 1.2-2.0 times in the areal scale factor in the heating zone. No breakage of the film occurs, no vibratioi and pulsative movement of bubble take place, and therefore, the restretching of the film can be attained in the stabilized state. The film so obtained has high molecular orientation degrees and good accuracy in thickness uniformity. |
