Effects of Polyelectrolytes and Their Complexes on the Paper Strength Properties

Polyelectrolytes such as starch and carboxymethyl cellulose (CMC) were added in variable manners to investigate the possible mechanisms for their effects on the drainage and paper strength improvement and to seek optimized conditions of their addition. The pulps used were old corrugated containerboard (OCC) and bleached hardwood kraft pulp (BHKP). The polyelectrolytes studied included a cationic starch, tapioca starch, wheat starch and CIVIC. The mode of addition entailed individual, dual, varied addition sequences and polyelectrolyte complexes. We evaluated the effects of various polyelectrolytes and/or their complexes and modes of additions on the drainage and paper strength. Overall, the effects of variables on the BHKP paper were more pronounced than those on the OCC paper. The effects were quite variable depending on the types of polymer- polyelectrolytes and the modes of addition. For the BHKP, when cationic starch and tapioca starch or wheat starch were added in sequence, the paper strengths, particularly tear and burst were markedly improved. As for the OCC paper, on the other hand, polyelectrolyte complexes contributed to better paper strengths than those using individual or dual sequential addition of agents.