Method for thickening aqueous systems using hydrophilic polyurethanes

A method for increasing viscosity of an aqueous system which comprises:

• admixing with the aqueous system a nonionic, water soluble, polyurethane having a weight average molecular weight of from 10.000 to 200,000 and consisting essentially of the groups;
• (a) —O—(CH2—CH2O—)n, wherein n is a number of 8-300;
• (b) —CO—NH—X—NH—CO— wherein X is an aliphatic, aromatic or cycloaliphatic group;
• and
• (c) —O—Y—O—, wherein Y comprises a hydrophobic moiety selected from the group consisting of
• (—CH2—CH(CH3)—O)m—CH2—CH(CH3)—,
• (CH2—CH(C2H5)—O)m—CH2—CH(C2H5)—,
• (CH2—CH2—CH2—CH2 O)m—CH2—CH2—CH2—CH2—,
• alkylene groups having from 6 to 44 carbon atoms, cycloalkylene groups having from 6 to 44 carbon atoms and mixtures thereof wherein m is a number of 8 to 500, the nonionic polyurethane forms a homogenous mixture with water;
• the mixture having a specific viscosity of at least 0.4 at a 1% by weight solution in water at 20° C. wherein (c) comprises from 5% to 40% by weight, based on (a)+(c) of the polyurethane.