| 摘要 |
An apparatus for manufacturing tubular film from thermoplastic resinous materials comprises a tube die to extrude the film downwardly, means beneath the die for flattening the freshly extruded tube, means for applying to the outer surface of the film tube immediately upon extrusion an enveloping, cascading column of a temperature regulating liquid and means for withdrawing and taking up the flattened tube from the flattening means. The method of producing film claimed comprises continuously applying to the outer surface of the film tube the said column of liquid, immediately after the extrusion and prior to the flattening step. Preferably, means are provided for circulating a dust-laden gas within the film tube so that dust is deposited on its inner surface prior to flattening. Guiding and forming means may be provided beneath the die either circumferentially around the freshly extruded film tube or within it; in the latter case, the said means is preferably a solid mandrel (e.g. generally cylindrical, or alternatively disc-like) which may have a diameter either smaller or larger than the extruding diameter of the tube die, so that the film tube is respectively contracted or expanded. Numerous suitable resinous materials are listed in the Specification, but crystalline homo- and copolymers of vinylidene chloride, (e.g. containing 15% vinyl chloride) are preferred. Specification 656,735 and U.S.A. Specifications 2,461,975, 2,488 571, 2,641,022 and 2,720,680 are referred to. |
