| 摘要 |
1295205 Tubular films SHOWA DENKO KK 19 July 1971 [24 July 1970 8 Dec 1970] 33802/71 Heading B5B A process for the production of a tubular film of thermoplastic resin, comprising the steps of introducing a tubularly inflated film 2 of thermoplastic resin, extruded through the annular slit of a die 1 into an annular water cooling tank 6 having a central cooling channel lined with a pliable water-retentive element 10 and composed of a cooling zone 7, a sizing zone 8 and a draining zone 9, cooling the film to a temperature immediately above that at which crystallization would begin by means of the pliable element in the cooling zone, causing the film to be pressed against the inner wall of the cooling channel by means of inflation pressure and suction exerted in the sizing zone (as shown by means of suction orifices 12 formed on the inner wall of suction chamber 5), so as to confer tubular form on the film and allow the film to undergo crystallization, and removing remaining water adhering to the outer surface of the film in the draining zone. Specified film-forming materials include polyolefins, especially polyethylene and polypropylene. In the apparatus of Fig. 1, the suction chamber and the draining chamber are formed integrally and the combined suction and draining chamber communicates with a pipe 20 incorporating a vacuum pump so as to maintain the chamber in the state of a partial vacuum. Thus the cooling channel is composed of cooling zone 7, sizing zone 8 and draining zone 9 and these zones correspond to the inner walls respectively of the water-cooling chamber 4, suction orifices 12 and draining chamber 5. The inner wall of the cooling channel is fitted with a pliable water-retentive element 10. This may be made of felty material, non-woven fabric, tufty material, or spongy material, e.g. viscose sponge. The upper end of the cooling element is immersed into the water-cooling chamber 4 so that the entire cooling element can be sufficiently wetted with the cooling water. Water-feeding pipe 11 keeps the water at constant level. A suitable inflation pressure is maintained in the film by orifices 22, and as the film slides over the surface of the cooling element 10, it begins to undergo cooling by the cold water retained in said element 10. While passing this cooling zone, the film is still in an uncrystallized state. As the film begins to slide over sizing zone, 8, it is attracted toward the wall and held fast against element 10 because of the suction exerted through a plurality of suction orifices 12 formed on the inner wall of suction chamber 5. Thus the film is shaped, cooled and crystallized by the cold water. The apparatus of Fig. 3 incorporates a cooling mandrel. |
