Process and apparatus for reducing the sag and/or the different stress profile of by extrusion blowing produced and flattened tubular film

摘要

The invention relates to a process for reducing the sag and/or the varying stress profile of a tubular film of thermoplastic material, produced by the blow-moulding method and laid flat, transversely to its longitudinal direction. To achieve the object of providing such a process by which the sag and/or the different stress states transversely to the tubular film can be reduced or completely eliminated as far as possible in a simple way, the tubular film is heated over its width and subsequently cooled and/or stretched. The invention also relates to an apparatus for carrying out this process.