Coextruded, heat-sealable and peelable polyesterfilm, process for its production and its use

摘要

A polyester film comprises a base layer and a heatsealable top layer which is peelable from amorphous polyethylene terephthalate. The top layer contains 60-97 wt.% polyester and 3-30 wt.% polyester-incompatible polymer. The polyester comprises 25-95 mol.% units derived from aromatic dicarboxylic acid(s) and 5-75 mol.% units derived from aliphatic dicarboxylic acid(s). The layer thickness of the top layer is 0.7-2.5 mu m. An independent claim is also included for a process for producing a sealable and peelable polyester film, comprising feeding polymers for the base layer (B) and the top layer (A) specified above and top layer (C) to separate extruders. The melts are then shaped and layered on top of one another in a multilayer die to give flat melt films. The multilayer film is drawn off with the aid of a chill roll and optionally further rolls, solidified and then biaxially stretch-oriented and heat-set. The biaxial stretching is carried out in succession, first longitudinally (in machine direction) and then transversely (at right angles to machine direction) that the longitudinal stretching is carried out at 60-130[deg]C and the transverse stretching is at 90-140[deg]C, and the longitudinal stretching ratio is set at 2:1 to 5.5:1 and the transverse stretching ratio is at 2.4:1 to 5:1.