Water-thinnable polyurethane with at least two free OH groups obtainable from a first conversion of a primary and/or secondary alkanolamine with a NCO compound giving an intermediate product, followed by the addition of a cyclic carboxylic anhydride to the intermediate product; with the NCO compound exhibiting at least one free NCO group and no blocked NCO group; all alkanolamine being converted during the first conversion to the intermediate product such that the nitrogen atom of the alkanolamine reacts with one of the free NCO groups of the prepolymer to form a urea bond; and the cyclic carboxylic anhydride reacting, with ring opening, with the OH group, originating from the alkanolamine, of the intermediate product; and its use for the production of hot curing coating compositions.