The invention provides heat-curable thixotropic mixtures containing carbamate and/or allophanate groups, including at least one oligomer and/or polymer containing at least one of carbamate and allophanate groups, and at least one thixotropic agent that is a urea derivative preparable by reacting at least one amine and/or water with at least one isocyanate in the presence of at least one amino resin. The invention further provides processes for preparing the mixtures and coating materials, adhesives and sealing compounds prepared from the mixtures.