Process for the preparation of a multilayer film

摘要

A continuous process for preparation of a multilayer film from thermoplastic material comprising processing in an extruder, feeding into a film blowing die having several concentric slots, stretching, blowing, bonding and winding up wherein the layers are bonded together when the exterior layer has been oriented to the desired extent in the longitudinal direction by stretching and the interior layer in the transverse direction by blowing by means of gas medium and, optionally, in the longitudinal direction by stretching, but before any of the material layers has been cooled to a temperature which corresponds to the frost point of the material in question and otherwise before any of the material has lost its viscous flowability, and wherein one or more interior layers may be used.