Production of aqueous solutions of cationic thermosetting resins

A process for producing an aqueous solution of a thermosetting resin, consisting essentially of

• (i) heating an aliphatic dicarboxylic acid and a polyalkylenepolyamine to obtain a polyamidopolyamine, the molar ratio of the aliphatic dicarboxylic acid to the polyalkylenepolyamine being 1:1.0 to 1.2, and the heating being continued until the viscosity at 25.degree. C. of a 50% aqueous solution of the resulting polyamidopolyamine reaches 400 to 1,000 cps,
• (ii) reacting the polyamidopolyamine with epichlorohydrin in an aqueous medium, the amount of epichlorohydrin being 1.6 to 1.7 moles per mole of the secondary amino group present in the polyamidopolyamine, the concentration of said reactants in the aqueous medium being 15 to 50% by weight, and the reaction being continued until the viscosity at 25.degree. C. of a 15% aqueous solution of the reaction product reaches 30 to 150 cps,
• (iii) adjusting the aqueous solution to pH 3 to 5 at 25.degree. C., and
• (iv) controlling the concentration of the aqueous reaction product solution to 15 to 30% by weight.