| 摘要 |
PURPOSE:To prevent packaging material from blocking by a method wherein convex ribs or concave flutes are formed by drawing a molten film under the state that the temperature unevenness is developed in the molten film by blowing cooling air from a plurality of small diameter nozzles against the molten film. CONSTITUTION:A film 4 extruded from a die 1 is cooled with an air ring 3, a cooling drum 6 and the like. A cooling device 5 consisting in providing a plurality of openings acting as small diameter nozzles 7 onto the side wall part of a tubular air passage or disposing a necessary number of nozzles in an array. A plurality of the nozzles are arranged along the circumference of the film, when the film 4 is of tubular form, and in a straight line, when the film is flat by being extruded through a T-die. comparatively solidified portions and portions in molten state are formed due to the temperature unevenness by unevenly cooling the molten state film 4 with the cooling device 5. By drawing the film under the above-mentioned state, a film with rib-like projections is obtained. When a sack is made of said resultant film, the ribs prevent the film from adhering to each other, resulting in enabling to prevent packaging material from blocking. |
