The invention relates to a polymer composition, comprising at least one thermoplastic polymer, at least one pigment or at least one filler or a mixture thereof and at least one diester of a linear diol having 2 to 8 C-atoms with a linear or branched, saturated or unsaturated monocarboxylic acid having 6 to 44 C-atoms, wherein the fraction of diesters comprising different fatty acid radicals in a molecule is less than 10% by weight with regard to the total amount of diesters.