Isocyanate prepolymers having an NCO content of 1.5 to 5.0 wt. % and a monomeric diisocyanate content of less than 0.5 wt. % which are the reaction products ofA) aromatic or cycloaliphatic diisocyanates withB) mixtures ofB1) polyether polyols having a molecular weight of 1000 to 3000 andB2) polyester carbonate diols having a molecular weight of 700 to 3000,wherein components B1) and B2) are present in a weight ratio of 0.25:1 to 1.5:1;a process for the preparation of these isocyanate prepolymers by reacting the preceding starting materials at an NCO/OH equivalent ratio of at least 1.5:1 and optionally with subsequent removing unreacted monomeric diisocyanate by distillation; and the use of these isocyanate prepolymers as binders for sealing or coating compositions.