Amphoteric PAMS as Dry Strength Resins, 2005 Papermakers Conference

The use of poly(acrylamide) (PAM) dry strength resins has been widespread in Japan for many years. The demands of papermakers for improved strength have forced the chemical suppliers to develop more effective strength resins. This work demonstrates the superiority of copolymer-type amphoteric PAM (co-AMP-PAM) over cationic starch in a waste furnish with increasing levels of conductivity. The co-AMP-PAM can also be used together with cationic starch. In a fine paper furnish we obtained large strength improvements at very low dosage when co-AMP-PAM was used together with cationic starch. Most chemical additives become less effective as dosage increases. This is usually attributed to saturation of available sites to adsorb on the cellulose. Using Focused Beam Reflectance Measurements (FBRM) we determined the size and the strength of the flocs formed by PAMs. We are able to screen resins using FBRM to predict their effectiveness in handsheets. We tested the combination of a co-AMP-PAM with a PAM grafted starch (G-PAM). The mixture formed a polyion complex more efficiently than either product itself. The optimum ratio was determined by FBRM. They were then tested in handsheets and large increases in dry strength and drainage were observed.