A thermoplastic molding composition, comprising 10 to 98.99% of a thermoplastic polyester, 0.01 to 20% of a hyperbranched polycarbonate, and/or hyperbranched AxBy polyester, wherein Ax and By are different monomers and indices x and y are functional groups in A and B, x is at least 1.1 and y at least 2.1; 1 to 60% of a graft polymer comprising 20 to 80% of a graft base comprising an elastomeric polymer based on alkyl acrylates, 20 to 80% of a graft of 60 to 95% of styrene or of substituted styrenes of formula 1 R is an alkyl radical or hydrogen, R1 is an alkyl radical, n is 1-3, and 5 to 40% by weight of an unsaturated nitrite, 0 to 60% of a copolymer comprising, 60 to 95 of styrene and/or substituted styrenes of formula 1, 5 to 40% of an unsaturated nitrile, 0 to 60% of other additives.