A process for preparing finely divided mixtures of amphiphilic polymers and polycarboxylates, which comprises mixing(a) aqueous dispersions or colloidal aqueous solutions with at least one amphiphilic polymer, and(b) an aqueous solution of a polycarboxylatein a weight ratio of (a):(b) of from 1:1 to 1:20, each based on the solids, or dispersing at least one amphiphilic polymer in an aqueous solution of a polycarboxylate, and spray-drying the dispersions thus obtainable to form finely divided polymer mixtures, use of the finely divided polymer mixtures as ingredient of detergent and as laundry aftertreatment, and finely divided polymer mixtures having a particle size from 20 .mu.m to 3 mm prepared by the above-indicated process.