The invention relates to biuret compounds of the idealized general formula in which R1 is a (C1-C22)-alkylene, (C3-C22)-alkenylene, (C5-C15)-cycloalkylene, arylene, (C7-C12)-aralkylene, a polyoxyalkylene radical or is a polyester radical, R2 is a (C1-C22)-alkyl, hydroxy-(C1-C22)-alkyl, (C3-C18)-alkenyl, aryl, (C7-C12)-aralkyl, or (C5-C12)-cycloalkyl radical, a hydroxy-, (C1-C22)-alkoxy-, (C5-C12)-cycloalkoxy-, or (C7-C12)-aralkoxy-polyoxyalkylene radical, or a polyester radical prepared starting from a (C1-C22)-alkanol, (C5-C12)-cycloalkanol, or (C7-C12)-aralkanol or from a (C1-C22)-alkoxy-, (C6-C12)-cycloalkoxy-, or (C7-C12)-aralkoxy-polyoxyalkylene, Y stands for identical or different radicals O, NH, CO—NH—NH or NH—NH—CO, R3, R4 and R5 independently of one another are a (C2-C40)-alkylene, (C3-C40)-alkenylene, (C5-C40)-cyclo-alkylene, arylene, (C7-C40)-aralkylene or polyoxy-alkylene radical or are a polyester radical, R6 is a (C1-C30)-alkyl, (C3-C22)-alkenyl, hydroxyalkyl and hydroxyalkenyl, (C4-C13)-cycloalkyl, aryl or (C7-C12)-aralkyl radical, Z stands for one or more of the following groups COO, OCO, NHCO, CONH, NHCOO, OOCNH and NHCONH, and a is a number from 1 to 19, and also to processes for preparing them and to their use for rheology control and for thixotroping coating systems, as anti-sag agents and/or as anti-settling agents.