Application of Amphoteric Polyacrylamide Solely or with the Combination of Cationic Starch for Paper Strength Improvement

Abstract

Water-soluble amphoteric polyacrylamide (AmPAM) has been widely used in papermaking as one of the agents for the improvement of dry strength. In this investigation, AmPAM was used, solely or with the combination of cationic starch (CS), for the strength improvement of paper sheets made from kraft hardwood fiber (KHW) and recycled old corrugated container (OCC) fiber. The results showed that AmPAM achieved better performance than CS as the dry strength additive of paper on the condition of the same dosage, especially for secondary fibers. AmPAM improved the breaking length of paper sheets made from virgin KHW by 25%, while by 80% for OCC, when at the dosage of 0.5% (wt% to mass of oven dried pulp). When AmPAM was applied with the combination of CS, a negative synergism was observed. Besides strength improvement, there were many additional benefits obtained from adding AmPAM, especially in the absence of cationic starch, e.g. decreased slurry conductivity, decreased beating degree, and increased retention. In this aspect, AmPAM is an efficient, multi-beneficial dry strength agent for the papermaking process, especially for secondary fibers.