Dupont Teijin Films U.S. Ltd.

Brian John Farmer, Legal Representative

William Alasdair MacDonald

Kenneth Evans

Julian Peter Attard

Pierre Georges Osborne Moussalli

David Boyce

Christopher Charles Naylor

David Edward Robins, Legal Representative

A process for the production of a polymeric film comprising a copolyester having an acid component and a diol component, said acid component comprising a dicarboxylic acid and a sulfomonomer containing a sulfonate group attached to the aromatic nucleus of an aromatic dicarboxylic acid, said process comprising the steps of: (i) melt-extruding a layer of said copolyester; (ii) stretching the extrudate in at least one direction; (iii) heat-setting the film by raising the temperature of the stretched film to a temperature Tin a first heating zone such that (T-T) is in the range of from 5 to 30&#xb0; C., and then raising the temperature of the film to a temperature Tin a second heating zone such that (T-Tis in the range of from 0 to 10&#xb0; C., wherein Tis the peak melting temperature of the polymeric film; wherein Tis greater than T; and wherein the times which a transverse section of the film spends in the first and second heating zones are defined by tand t, respectively, such that the ratio of tto tis at least 2:1; and a polymeric film obtainable thereby having an ultimate tensile strength at destruction in the range of 2 to 15 kgf/mmin the machine direction and 2.5 to 17 kgf/mmin the transverse direction.

Process for the production of brittle polymeric film

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Staffordshire, United Kingdom

Brian John Farmer, Legal Representative