The present invention relates to polyglycerol partial esters of polyhydroxystearic acid and polyfunctional carboxylic acids which are obtainable by esterification of a polyglycerol mixture with polyhydroxystearic acid where N=1 to 10, preferably 2 to 8, in particular 3 to 5 units and dimer fatty acids which have been obtained by catalytic dimerization of unsaturated fatty acids having 12 to 22 C atoms and have an average functionality of 2 to 3, and/or with aliphatic, linear or branched dicarboxylic acids having a chain length of 2 to 16 C atoms and additionally saturated or unsaturated, linear or branched fatty acids having 6 to 22 C atoms, preferably 12 to 18 C atoms, the degree of esterification of the polyglycerol mixture being between 20 and 75%, preferably 40 to 70%.