| 摘要 |
1287404 Tubular films W & H M GOULD. ING Ltd 11 Sept 1969 [12 Sept 1968] 43324/68 Heading B5B Tubular film is made by extrusion of a melt through an annular orifice 3 defined by a mandrel 1 and a surrounding die 2, the mandrel being fitted with both cooling means 11 and heating means 9, the extruded tube being cooled by an external air blast from ring 10. The mandrel and die are first heated to the extrusion temperature, the mandrel by means of the induction heater 9 housed in a recess in the mandrel adjacent to the extrusion orifice; during extrusion the mandrel is cooled by circulation of fluid, preferably distilled water in stainless steel tubes housed in the cooling block 11, to a temperature in the neighbourhood of that of the die, but above the lower critical temperature of the plastics material at which a sharp increase in viscosity occurs. During extrusion air is blown through the axial duct 6 in the mandrel into the continuous extruded tube 7, and also from the teroidal ducts 10 on to the outside of the tube to cool it. The extruded tube is hauled from the extrusion orifice by a pair of nip rolls 5, which also collapse the tube as an air bubble is trapped between the nip rolls and the extrusion orifice. The apparatus is most suited to the manufacture of polythene films using a running temperature of 160‹ C. for the mandrel and 150‹ C. for the die. |
