Thickening Agent Based on Polyurethane

A thickener based on an aqueous preparation of a nonionic, water-dispersible or water-soluble polyurethane is provided, where the polyurethane is obtainable by reacting: (a) one or more hydrophilic polyols containing per molecule at least two OH groups and at least two functional groups selected from ether and ester, the molecular weight being at least 300; (b) one or more hydrophobic compounds containing at least one zerewitinoff-active hydrogen atom per molecule, the molecular weight ranging from about 100 to about 500 with at least one linear or branched, saturated or unsaturated alkyl chain per molecule, the alkyl chain having at least five consecutive carbon atoms and is not linked to a hetero atom; and (c) one or more at least difunctional isocyanates, where the components are reacted in ratios of OHa):ZHb):COc) of 1:(1+x):2(1+y), with the provisos that x is 0.05 - 1.2 and y is ( 0.2 - 1.05 )x. A thickener concentrate is also provided.