POLYESTER FILMS USABLE FOR CLOSURES AND PROCESS FOR THEIR PREPARATION

摘要

Polyester films 5-30 microns thick having (i) a degree of crystallinity of greater than or equal to 50 %, (ii) a planar birefringence delta P of less than or equal to 0.160, (iii) a breaking strength in the longitudinal direction (RRMD) and the weakest of the two breaking strengths in diagonal directions (+/- 45 degrees . w.r.t. the longitudinal direction) (RR45) such that (RRMD)-(RR45) is less than or equal to 40 kg/mm<2> (392.4 MPa) and (iv) an elongation at rupture in the longitudinal direction (ARMD) and the highest of the two elongations at rupture in the diagonal directions (+/- 45 degrees w.r.t. the longitudinal direction) (45) such that (ARMD)+(AR45) is greater than or equal to 290 %, and which satisfy the performance requirements of the particular application envisaged.