Thermoplastic polyester moulding compositions with good toughness properties

Claim 1

A mixture of (1) 60 to 99% by weight of a thermoplastic polyester and (2) 1 to 40% by weight of a polyolefin graft polymer obtainable from (a) 70 to 99% by weight of a graft base consisting of a polymer of at least one member selected from the group consisting of aliphatic and aromatic mono-olefins, said polymer containing up to 50% by weight of polymerized other mono-olefinically unsaturated radically polymerizable compounds, or said polymer containing up to 5% by weight of polymerized diolefins and (b) 1 to 30% by weight of a radically graftable ethylenically unsaturated compound, the percentages for (1) and (2) being based on the sum of (1) and (2), the percentages of (a) and (b) being based on the sum of components (a) and (b) and the remaining percentages set forth under (a) being based on the sum of the starting monomers used for the production of the graft base, such polyolefin graft polymer having been produced by contacting a melt of graft base (a) with oxygen or oxygen-containing gas for at most 10 minutes with intensive mixing under a pressure of from 1 to 150 bars and at a temperature of from 80° to 300° C., adding the ethylenically unsaturated compound to be grafted immediately after said contact with oxygen or oxygen-containing gas with intensive mixing in the absence of oxygen or oxygen-containing gas and removing residual monomers after graft polymerization reaction.