A process for preparing binders for one-component paint systems has the following steps: (I) preparation of a polyurethane-alkyd resin component (A) composed of a mixture (a) of (a1) an unsaturated C.sub.6 -C.sub.30 fatty acid with at least two non-conjugated double bonds, and (a2) an unsaturated C.sub.6 -C.sub.30 fatty acid with at least two conjugated double bonds as esterified side polymer chains of the polyurethane-alkyd component (A); and (b) polyurethane units with anionic groups and/or groups which can be converted into anionic groups as main polymer chains of the polyurethane-alkyd resin component (A); (II) optional neutralisation of the groups in the polyurethane-alkyd resin component (A) which can be converted into anionic groups and their transfer into the aqueous dispersion or solution; and (III) polymerising at least one ethylenically unsaturated, radically polymerisable monomer (c) which has substantially no other reactive functional groups besides the C--C-- double bond in the dispersion prepared as under step (II) in the presence of a radical builder as polymerisation initiator.