METHOD AND APPARATUS FOR PRODUCING A SHRINKABLY STRETCHED FLEXIBLE TUBE

摘要

1387030 Stretching tubular films NATURINWERK BECKER & CO 14 June 1972 [29 June 1971] 27809/72 Heading B5B A thermoplastic tubular film is biaxially stretched in apparatus illustrated in Fig. 1. The film passes between nip rollers 1, which expel air, and then over the stretching mandrel 2 which tapers towards the receiving end. The mandrel is steadied against axial movement by at least one pair of rollers 5 outside the film. The mandrel has an optional centering ring 6 and an essential expansion ring 8. Heater 7 heats the tube as it passes over expansion ring 8 and preferably also heats the space between centering ring 6 and expansion ring 8. The film is then cooled by cooling means 9 and longitudinally stretched by pull-off rolls 11, which rotate more rapidly than rolls 5. The invention is illustrated for Nylon 12 films.