Dicarboxylic acids and dicarboxylic acid esters of the formula ##STR1## wherein both R.sub.1 each denote hydrogen, alkyl with 1 to 4 C atoms or phenyl, both R.sub.2 each denote hydrogen or alkyl with 1 to 10 C atoms and, if the two R.sub.2 each denote hydrogen, the two n represent numbers from 2 to 12 and, if the two R.sub.2 each denote an alkyl group with 1 to 10 C atoms, the two n represent numbers from 1 to 12, R.sub.3 denotes hydrogen, methyl or ethyl and R.sub.4 denotes methyl, ethyl, propyl or isopropyl, are prepared by reacting 1 mol of a 1,1'-methylene-bis-hydantoin of the formula ##STR2## or its disodium or dipotassium salt with 2 mols of a compound of the formula ##STR3## wherein Y.sub.1 denotes a chlorine or bromine atom. The dicarboxylic acid compounds are characterized by a high stability to heat and therefore very suitable for the manufacture of polycondensates by the melt condensation process.
                            公式为##STR1##的二
羧酸和二
羧酸酯,其中R.sub.1均表示氢、1至4个碳原子的烷基或苯基,R.sub.2均表示氢或1至10个碳原子的烷基,如果两个R.sub.2均表示氢,则两个n表示2至12的数字,如果两个R.sub.2均表示1至10个碳原子的烷基,则两个n表示1至12的数字,R.sub.3表示氢、甲基或乙基,R.sub.4表示甲基、乙基、丙基或异丙基。通过将公式为##STR2##的1,1'-亚甲基双
肼或其二钠盐或二
钾盐与公式为##STR3##的化合物的2摩尔反应制备这些二
羧酸化合物,其中Y.sub.1表示
氯或
溴原子。这些二
羧酸化合物具有高热稳定性,因此非常适合通过熔融缩聚法制造聚缩酸。