Peelable polyester film with self-venting, process for its production and its use

May 1, 2007

Patented is a coextruded, biaxially oriented polyester film with a base layer and a coextruded, uncoated heatsealable outer layer that can be peeled from APET/CPET and from CPET. The outer layer comprises a) from 80 to 98% by weight of polyester and b) from 2 to 10% by weight of inorganic and/or organic particles with a median diameter d50 of from 3 to 12 μm. The polyester used to form the layer is composed of from 12 to 89 mol % of units derived from at least one aromatic dicarboxylic acid and of from 11 to 88 mol % of units derived from at least one aliphatic dicarboxylic acid. The total of the dicarboxylic-acid-derived molar percentages is 100. The ratio calculated from the particle size d50 of the particles and the layer thickness of the outer layer is greater than or equal to 1.5. The shrinkage of the film, at least in one direction, is more than 5% measured at 100°C over a period of 15 minutes and the film does not tear during removal from CPET, based on a sealing temperature of 160°C. The top layer exhibits a surface roughness, Ra, ranging from greater than 120 to 400 nm, as determined via DIN 4768.