Water-dispersible binders for cationic electrocoating finishes, and process for their preparation

摘要

The invention relates to water-dispersible binders for cationic electrocoating finishes, which are obtained by reaction of P P(A) epoxy resins containing low molecular weight aromatic groups and having an epoxide equivalent weight of less than 375 with P P(B) aliphatic and/or alicyclic polyfunctional alcohols or carboxylic acids having a number average molecular weight of less than 350, further reaction of the product of (A) and (B) withPP (C) a polyfunctional alcohol having a molecular weight of more than 350, addition at the epoxide groups taking place so that the reaction products of (A) and (B) contain an amount of aromatic groups of from 10 to 45% by weight, calculated as phenylene groups, and further modification of the resulting intermediate withPP(D) primary and/or secondary amines or ammonium salts in order to achieve the required water- dispersibility. The binders contain, as component (C), 5 to 40% by weight, based on the total binder, of a linear polyalkylene ether diol which has on average one terminal primary and one terminal secondary hydroxyl group per molecule and corresponds to the general formula ##STR1## in which n denotes 1 to 4, preferably 1, and m denotes 4 to 35, preferably 5 to 20.