According to the invention, oxyalkylates of aliphatic or cyclic, primarily primary diamines or polyamines, or block polymers (having recurring structural units of the abovementioned oxyalkylate type) produced by prior linking of such oxyalkylates with dicarboxylic acids, are converted into novel substances which are suitable for a very wide variety of areas of application in the field of interface-active agents and can be employed, for example, in the preparation of azo pigments to improve the coloristic properties, by esterification of the terminal hydroxyl group in these aminoxyalkylates using fatty acids or aromatic carboxylic acids and/or resin acids, and, if appropriate, subsequent reaction of free hydroxyl groups which are still present with dicarboxylic acids and sulfite to form the corresponding monoester (containing anionic radicals).