Device and process for producing plastic films

摘要

A device and a process are described for extruding plastic material into tubular form which is expanded by blowing in air (13) which is introduced at the extruder die (12) of the extruder (11). The expanded tube is cooled (30) and is formed in a forming unit consisting of a pressure chamber (20) and a vacuum-cooling chamber (60), in which the expansion of the tube is prevented by the pressure chamber (60) and the longitudinal movement of the tube as a result of the suction action of a vacuum. Subsequently the cooled tube is heated (50), is stretched in the longitudinal direction by the tension between the vacuum-cooling chamber (60) and a take-off roll pair (80) and in the transverse direction by further expansion, without further blowing devices being necessary upstream of the reheating device. The further expansion is brought about by the blown air which causes the original expansion of the tube during its emergence from the extruder die (Fig. 2).