Process for the preparation of impact-modified polymer compositions comprising A) from 10 to 98 parts by weight, based on the sum of components A+B+C+D+E, of at least one polymer selected from the group of the aromatic polycarbonates, aromatic polyester carbonates and aromatic polyesters, as well as mixtures thereof, B) from 0.5 to 50.0 parts by weight, based on the sum of components A+B+C+D+E, of at least one pulverulent rubber-modified vinyl (co)polymer, C) from 0 to 80 parts by weight, based on the sum of components A+B+C+D+E, of at least one component selected from rubber-modified vinyl (co)polymers in granulate form and rubber-free vinyl (co)polymers, D) from 0.002 to 0.200 part by weight, based on the sum of components A+B+C+D+E, of at least one Brönsted acid, E) from 0.1 to 40.0 parts by weight, based on the sum of components A+B+C+D+E, of additives, with the exception of the acids according to component D that are conventionally added, wherein the sum of the parts by weight of components A+B+C+D+E in the composition is 100, comprising the steps: (i) preparing a solution of the acidic compound according to D with a concentration of from 0.5 to 8 wt.%, (ii) physically blending the solution of the acidic compound D from step (i) with the total amount or a partial amount of the graft polymer powder according to component B and optionally with the total amount or a partial amount of one or more further pulverulent components of the polycarbonate-ABS composition, (iii) melting, mixing and dispersing in one another the mixture from step (ii) with the further residual components A, B, C, and E of the composition, which have optionally likewise been premixed, in a compounding unit, wherein the solvent that has been added to the composition by the solution of the acidic compound is removed again in a degassing zone of the compounding unit by application of a low pressure, and the polymer melt so prepared is subsequently solidified by cooling and then granulated. A) from 10 to 98 parts by weight, based on the sum of components A+B+C+D+E, of at least one polymer selected from the group of the aromatic polycarbonates, aromatic polyester carbonates and aromatic polyesters, as well as mixtures thereof, B) from 0.5 to 50.0 parts by weight, based on the sum of components A+B+C+D+E, of at least one pulverulent rubber-modified vinyl (co)polymer, C) from 0 to 80 parts by weight, based on the sum of components A+B+C+D+E, of at least one component selected from rubber-modified vinyl (co)polymers in granulate form and rubber-free vinyl (co)polymers, D) from 0.002 to 0.200 part by weight, based on the sum of components A+B+C+D+E, of at least one Brönsted acid, E) from 0.1 to 40.0 parts by weight, based on the sum of components A+B+C+D+E, of additives, with the exception of the acids according to component D that are conventionally added, (i) preparing a solution of the acidic compound according to D with a concentration of from 0.5 to 8 wt.%, (ii) physically blending the solution of the acidic compound D from step (i) with the total amount or a partial amount of the graft polymer powder according to component B and optionally with the total amount or a partial amount of one or more further pulverulent components of the polycarbonate-ABS composition, (iii) melting, mixing and dispersing in one another the mixture from step (ii) with the further residual components A, B, C, and E of the composition, which have optionally likewise been premixed, in a compounding unit, wherein the solvent that has been added to the composition by the solution of the acidic compound is removed again in a degassing zone of the compounding unit by application of a low pressure, and the polymer melt so prepared is subsequently solidified by cooling and then granulated.