Abstract: 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 T1 in a first heating zone such that (TM-T1) is in the range of from 5 to 30° C., and then raising the temperature of the film to a temperature T2 in a second heating zone such that (TM-T2 is in the range of from 0 to 10° C.