| 摘要 |
1,064,390. Extrusion/injection moulding; extrusion nozzles. BRITISH VISQUEEN Ltd. Aug. 20, 1965 [Sept. 23, 1964], No. 38795/64. Headings B5A and B5B. The die orifice of an extrusion moulding machine, or the injection nozzle of an injection moulding machine, used in the moulding of polyolefinic material, in particular polyethylene, are isolated from the atmosphere at the beginning or end of a " shut-down " period by maintaining a non-oxidizing gas, e.g. nitrogen, therearound. In particular such a gas is utilized until the die or nozzle has cooled to at least 100‹ C. and, on starting the moulding operation, is used before the die or nozzle reaches a temperature of 100‹ C. A cover may be placed over the die or nozzle to act as a gas chamber and at the beginning of a " shut-down " period external polymeric residue is removed prior to introduction of the gas. The gas may be fed continuously, or if the chamber is sealable, at intervals during the cooling period. With extrusion, the cover may be retained at the end of a " shutdown " period until the extrudate impinges upon and lifts the cover. With injection moulding, the chamber may be formed by the closed injection mould. The invention particularly relates to apparatus for the extrusion of flat or tubular films. |
