| 摘要 |
1,064,272. Films. BRITISH CELLOPHANE Ltd. July 31, 1964 [Aug. 1, 1963], No. 30636/63. Heading B5B. A film of a molten thermoplastic material which emits volatile products at melt extrusion temperatures is extruded on to a rotating polished, chilled roller and at least a substantial proportion of the vapours emitted by the molten thermoplastic material are removed from the vicinity of the roller by suction. Suitably the mixture of air and vapours formed in the converging space between the film and the roller is removed by suction at a rate of at least 10 cu. ft. per minute per inch of film width. The film may be extruded at a rate of 70-180 feet per minute. Specified film materials include polyethylene, polypropylene and nylon. In apparatus as shown, film 2 is extruded from extrusion head 1 on to the surface of a highly polished rotatable hollow roller 3 which is chilled by a cooling fluid circulated through the roller by pipes 4, 5. The film 2 is thus rapidly cooled below the melting point to form a solid film which is drawn from the rollers over a guide roller 7 to take-up means (not shown). A suction box 8 extends over the entire width of the film and is connected to suction means via pipe 9, so that substantially all the vapours emitted from the film 2 or from the orifice of the head 1 are drawn away from the converging space formed between the film 2 and roller surface 3 and are thus prevented from condensing on the surface of roller 3. |
