U.S. Pat. No. 4,228,281 describes dicarboxylic acids which contain polymeric triazine rings and are of the general formula III (see formulae), in which R1, R2 , R3 and R5 are each hydrogen or a C1 -C22 -alkyl hydrocarbon radical, R4 is a C2 -C18 -hydrocarbon diradical and R6 is a C1 -C12 -hydrocarbon diradical, which acids are used for the synthesis of polyesters having a glass transition temperat