Process for preparing polybenzimidazoles

Abstract

The invention relates to a method for preparing polybenzimidazoles of formula (1) or (2) below, wherein n and m are each 1: by polycondensation of corresponding tetracarboxylic acids or dianhydrides and tetraamines by jointly heating the reactants, characterized in that the preparation of polybenzimidazoles of formula (1) or (2) is carried out by using tetracarboxylic acids as starting material and substantially without the formation of any by-products, wherein a) first, a stoichiometric salt is formed from the tetracarboxylic acid and the tetraamine; b) polycondensation is carried out under hydrothermal conditions by heating the stoichiometric salt obtained in step a), in water as a solvent and under pressure, to temperatures above 100° C., wherein the values of n and m and, thus, the molecular weight and/or the extent of cyclization in the polycondensate obtained, are/is regulated by means of the temperature and/or the duration of the polycondensation; and c) optionally, a solvent-free thermal treatment of the polycondensate is carried out in order to achieve complete cyclization.

Dependencies are inferred from the claim text.