Wet strength resin composition and method of making same

A process for producing a wet strength resin composition comprising the steps of:

• (a) heating a C.sub.1-3 dialkyl ester of a saturated aliphatic dicarboxylic acid having from 3 to 6 carbon atoms and a polyalkylenepolyamine having two primary amine groups and at least one secondary amine group in a molar ratio of said ester to said polyalkylenepolyamine of up to 1:1 to a temperature of from about 150.degree. C. to about 160.degree. C. and continuing said heating until the reaction temperature drops to from about 110.degree. C. to about 120.degree. C.;
• (b) removing the alcohol formed in said reaction mixture at a temperature of from about 110.degree. C. to about 160.degree. C. until the viscosity at 25.degree. C. of a 50% aqueous solution of resulting polyamidopolyamine reaches at least 700 cps;
• (c) adding epichlorohydrin to an aqueous solution of said polyamidopolyamine at a rate sufficient to maintain the temperature in a range of from about 5.degree. C. to about 30.degree. C. to form a reaction mixture having an E/N ratio of from 0.6 to 1.08;
• (d) maintaining the temperature of said reaction mixture in a range of from about 15.degree. C. to about 35.degree. C. until all of the epichlorohydrin has reacted;
• and (e) adjusting the pH of said reaction mixture to a value of up to about 7.0 to produce a wet strength resin composition comprised of an aqueous solution of an aminopolyamide-epichlorohydrin acid salt resin wherein said composition has total organically bound chlorine of up to 0.7% by weight of said resin.