process for preparing a white non-transparent microvoided biaxially stretched film

Disclosed is a process for preparing a non-transparent microvoided axially stretched film including i) mixing a linear polyester having monomer components consisting essentially of an aromatic dicarboxylic acid, an aliphatic diol and optionally an aliphatic dicarboxylic acid, a non-crosslinked random SAN-polymer and one or more additional ingredients to produce a mixture, ii) forming the mixture produced in step i) in a thick film followed by quenching; iii) stretching the thick film at a temperature between the glass transition temperature of the SAN-polymer and the glass transition temperature of said linear polyester to at least twice the initial length, and (iv) further stretching the film at an angle substantially 90° to the previous stretching process to at least twice the initial length and at 90° C. or below.