Polyurethane-based thickeners for aqueous compositions

摘要

The present invention relates to a process for the preparation of polyurethanes suitable for use as thickeners for aqueous compositions by reacting at an NCO/OH equivalent ratio of 0.9:1 to 1.2:1 a) a polyether component having an OH number of 10 to 30 mg KOH/g and obtained by the alkoxylation of a mixture of a1) 30 to 80 mole % of a monofunctional alcohol or alkylphenol having 8 to 30 carbon atoms, a2) 2 to 10 mole % of sodium hydroxide or potassium hydroxide, a3) 10 to 60 mole % of water and a4) 0 to 10 mole % of a trihydric to hexahydric alcohol having a molecular weight of 92 to 600, with ethylene oxide or a mixture of ethylene oxide with up to 20 mole %, based on the total moles of alkylene oxides, of propylene oxide, in which the percentages of a1) to a4) add up to 100, with b) a polyisocyanate component containing at least one organic diisocyanate, optionally in admixture with up to 20 mole %, based on the total moles of component b), of higher than difunctional polyisocyanates. The invention also relates to the polyurethanes obtainable by this method and their use, optionally in combination with other thickeners, for the thickening of aqueous systems.