Polyalkyldiallylamine-epihalohydrin resins as wet strength additives for papermaking and process for making the same

A process for forming a polyalkyldiallylamine-epihalohydrin resin comprising the steps of:

• (a) forming a polyalkyldiallylamine polymer by the free-radical polymerization or copolymerization in a first aqueous solution of a hydrohalide salt of an alkyldiallylamine monomer, said alkyldiallylamine polymer having a reduced specific viscosity less than or equal to about 0.20 dL/g and a residual alkyldiallylamine monomer content of less than about 2.0%;
• and
• (b) reacting the alkyldiallylamine polymer with an epihalohydrin in a second aqueous solution, wherein the ratio of epihalohydrin to alkyldiallylamine polymer amine functionality is from about 0.90 to 1.10, comprising the steps of:
• (i) mixing an epihalohydrin and the polyalkyldiallylamine polymer at a total solids content of about 10 to 30% and a temperature of about 25 to 45° C., resulting in a reaction mixture;
• (ii) simultaneously with step (i), adding an aqueous alkaline solution to the reaction mixture to maintain a pH between about 8.0 and 9.0 over a time period of about 4 to 14 hours;
• (iii) adjusting the pH of the reaction mixture to 1.0 to 3.0 with a mineral acid;
• (iv) heating the reaction mixture to between 70 to 90° C. for about 0.5 to 3.0 hours;
• and
• (v) simultaneously with step (iv), maintaining the pH of the reaction mixture at 1.0 to 3.0 by the addition of mineral acid.