Flat thermoplastic film with uniform thickness prodn - by stepwise cooling of molten film, stretching film transversely and solidifying

摘要

Flat thermoplastic film extruded from wide slot dies is obtd. with a more uniform profile contg. fewer thicker parts by (a) effecting stepwise cooling of the molten film to a temp. above the solidification temp., (b) effecting stretching of the film across the direction of extrusion, and (c) cooling the molten film to a solid film. Method enables thin films, e.g. with a final thickness of 2-50 mu to be produced with a more uniform thickness.