An aqueous multicomponent system comprising (I) at least one aqueous component comprising dissolved and/or dispersed therein at least one polyurethane-based graft copolymer (P) containing isocyanate-reactive functional groups and preparable by graft copolymerizing at least one polyurethane (P′) selected from the group consisting of hydrophobic or hydrophilic polyurethanes containing on average at least one functional group selected from the group consisting of thiocarbamate groups, thiol groups and sulfide groups with at least one olefinically unsaturated monomer,  or alternatively (II) at least one liquid organic component comprising at least one water soluble and/or dispersible, polyurethane-based graft copolymer (P) and (III) at least one aqueous component, and (IV) at least one liquid organic component comprising or consisting of at least one polyisocyanate, processes for preparing it, and its use.