Wet strengthened fiber products, wet strengthening resins, and methods for making and using same

A method for forming a wet strengthened fiber product, comprising:

• combining a wet strengthening resin with a plurality of fibers to produce a fiber mixture,
• wherein the wet strengthening resin comprises a polyamide-epihalohydrin resin and about 5 wt % to about 95 wt % of a cationic styrene maleimide resin, based on the combined weight of the polyamide-epihalohydrin resin and the cationic styrene maleimide resin,
• wherein the polyamide-epihalohydrin resin comprises a reaction product of a polyamidoamine and an epihalohydrin, and
• wherein the cationic styrene maleimide resin comprises a reaction product of a styrene maleic anhydride copolymer and an amine compound and has a weight average molecular weight of about 500 to about 200,000 and a styrene to maleimide molar ratio of about 1:1 to about 5:1;
• forming a fiber web from the fiber mixture, wherein the fiber web comprises the fibers, the polyamide-epihalohydrin resin, and the cationic styrene maleimide resin;
• and
• at least partially curing the polyamide-epihalohydrin resin and the cationic styrene maleimide resin in the fiber web to form the wet strengthened fiber product, wherein the wet strengthening resin is present in the wet strengthened fiber product in an amount of about 0.05 wt % to about 5 wt %, based on a combined weight of the polyamide-epihalohydrin resin and the cationic styrene maleimide resin relative to a dried weight of the wet strengthened fiber product.