The present invention relates to a process for preparing polyurethanes, which comprise at least three hydrophilic sections, at least four hydrophobic sections, optionally allophanate segments and/or isocyanurate segments and which are prepared in the presence of alkali(ne earth) metal carboxylates. The process may comprise using at least one carboxylic acid salt of at least one metal selected from the group consisting of the alkali metals, the alkaline earth metals and mixtures thereof. Furthermore, the present invention relates to the polyurethanes per se obtainable in this way, to the use thereof as thickeners for aqueous preparations, and to preparations comprising polyurethanes of this type.
