Epichlorohydrin-based polymers containing primary amino groups used as additives in papermaking

Abstract

Disclosed is a method for manufacture and application of a polymeric papermaking additive, which can be used in paper manufacture as an agent for improving retention, drainage, product strength and paper machine operation. The additive according to this disclosure is a polymer of epichlorohydrin and contains primary amino groups. Under neutral or acidic conditions these primary amino groups become cationic, which assures good adsorption of the polymer onto anionic fibers and fines of pulps used for production of paper or paperboard. By adsorbing on several fibers or fines, the polymer can increase the retention of fines and fillers. Primary amino groups of this polymer can also form chemical bonds with carbonyl groups of cellulose, lignin and hemicellulose, which are especially abundant in the fibers and fines of mechanical pulps. The cross-linking of fibers and fines by chemical bonds can increase the initial strength of wet web and the strength of rewetted paper. Mechanical pulps contain high negative charge and tend to deactivate many conventional cationic polymers. Because of its high cationic charge and the ability to form chemical bonds with mechanical pulp, novel papermaking additive according to this invention is particularly suitable for improving the retention and the strength of paper made from fibrous pulp suspensions that contain at least a portion of mechanical pulp. If the polymer has a high molecular weight it can be use as a single component retention and strength additive. If the polymer has a relatively low molecular weight, it can be conveniently used as coagulant and can be combined with a high-molecular-weight, low-charge-density polymer that serves as a flocculent.