A process for preparing a polymer mixture containing at least two different comb polymers, wherein the comb polymers each have a polymer backbone having side chains attached via ester and/or amide groups, which process includes the steps of: a) providing and/or preparing a reaction mixture containing at least a first base polymer bearing acid groups and a second base polymer bearing acid groups, wherein the two base polymers differ chemically; b) conjointly esterifying and/or amidating the two base polymers with at least one unilaterally hydroxyl-terminated side chain compound and/or with at least one unilaterally amino-terminated side chain compound to obtain at least two different comb polymers.