Process for the production of biaxially stretched films and apparatus for implementation of the process

摘要

In the process for the production of thin, biaxially stretched films from polypropylene, the latter is melted in an extruder and extruded from a slot die over the surface of a take-off roll. The plastic melt cooled on the surface of the take-off roll into an intermediate film is temperature-treated in the region of the take-off roll in a zone and the intermediate film is subsequently biaxially stretched and heat-set in a known way. At a take-off roll temperature TW of between 10 DEG C. and 100 DEG C., blowing air of a temperature TL greater than/equal to 30 DEG C. is blown onto the film surface on the air side not in contact with the circumferential surface of the take-off roll, the duration for this temperature treatment being at least 1.5 seconds.