Process for the preparation of polymer powders

The invention relates to a process for the preparation of polymer powders by evaporating the volatile constituents from aqueous dispersions of film-forming polymers P in the presence of drying aids T, which are selected from the salts of oligomeric arylsulfonic acid-formaldehyde condensation products, which is characterized in that the aqueous polymer dispersion precedes the evaporation of the volatile constituents contains at least 1.5% by weight, preferably at least 1.7% by weight, based on the polymer in the dispersion, of at least one anionic surface-active compound AO which contains at least one C¶6¶-C¶ 32¶-alkyl group, the polymer powders obtainable by the process and their use in mineral binders.