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US 5,288,437 AGranted
Process to produce thin film
AssigneeHoechst Aktiengesellschaft
InventorsGuenther Crass, Siegfried Janocha, Gisbert Bammert
Life of this patent
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Abstract
A process is described to produce ultra thin biaxially stretched film made of thermoplastic where at least two film webs are superimposed and stretched together in both the longitudinal and transverse directions. The film webs are subjected to a heat treatment before the first draw step. After stretching, the film webs are separated again from each other.
Claims10
A process for producing biaxially oriented thermoplastic films comprising;
- A) superimposing together unoriented thermoplastic films;
- B) heat treating the superimposed films at a temperature in the range of from about 50.degree. C. to 90.degree. C. to improve the stretchability of the films;
- C) heating the heat treated superimposed films immediately following said heat treating step B) and in the absence of intermediate steps to a temperature sufficient for stretching, and
- D) biaxially stretching the superimposed films to a thickness of about 2 .mu.m or less wherein the films are biaxially oriented.
1 more element
Dependencies are inferred from the claim text.