A process for the production of biaxially stretched and the length after stretched tubular film of polyethylene terephthalate.

摘要

1478645 Stretched polyethylene terephthalate film HOECHST AG 23 Aug 1974 [30 Aug 1973] 37156/74 Heading B5B PET film is biaxially stretched and then subsequently longitudinally stretched. Biaxial stretching may be simultaneous or first longitudinally then transversely at a tube temperature of 84-86‹ C. the longitudinal and transverse stretching ratios being 3À3-4À2 and 4À0- 4-7 respectively and subsequent longitudinal stretching at 148-152‹ C. and a stretching ratio of 1À05-2À5. Stretched PET film has a tensile strength of 36-60 kg./mm.SP2/SP in the longitudinal direction and an elongation at break of 340-800% in the transverse direction. The film has a wall thickness between 15 and 50 Ám. and may be in the form of a tube of diameter (outside) of 10-150 mm. Shrinkage at 90‹ C. in the transverse direction is less than 5%.