| 摘要 |
969,689. Preventing contamination of extrudates. IMPERIAL CHEMICAL INDUSTRIES Ltd. June 7, 1963 [June 20, 1962], No. 23745/62. Heading B5A. A process for preventing contamination of an extruded profile of thermoplastic polymeric material by a discoloured collar or fragments thereof, temporarily adherent to the die face surrounding the extrusion orifice comprises cooling the orifice and/or its adherent material, by a directed blast of cooling gas supplied at such a rate as to maintain the adhering material at a temperature below that of substantial thermal degradation or at which thermally induced reaction with the gas can occur. The collar or fragments thereof, once detached, may travel with the profile, which is cooled until at least its surface has solidified, until shear, compression or impact forces are applied to separate the collar or fragments from the profile and so prevent or reduce irregularities in the latter. The gas used may be air, carbon dioxide or nitrogen. The apparatus used comprises nozzles 2 discharging flat jets towards the collars 3 and the die face 1 which is tapered to approach the extrudate tangentially. Alternatively the die face may be flat, whilst other forms of nozzles, including an annular nozzle, may be used. The process may be used for moulding pellets of polyhexamethylene adipamide/glass fibre. Specification 950,656 is referred to. |
