Thickening agent based on polyurethane

a)b)c) c) a) b)Disclosed is a thickener based on an aqueous preparation of a nonionic, water-dispersible or water-soluble polyurethane, obtained by reacting: (a) hydrophilic polyols containing at least two OH groups and at least two functional groups selected from ether and ester, of molecular weight at least 300; (b) hydrophobic compounds containing at least one zerewitinoff-active hydrogen atom, of molecular weight about 100 to about 500, with at least one linear or branched, saturated or unsaturated alkyl chain having at least five consecutive carbon atoms not linked to a hetero atom; and (c) at least difunctional isocyanates, where the components are reacted in equivalent ratios OH:ZH:NCOof 1:(1+x):2(1+y), with the provisos that x is 0.05-1.2, y is (0.2-1.05)x, and more than one equivalent of NCOis present versus the sum of OHand ZH.