The influence of dextran derivatives on polyethylene oxide and polyacrylamide-induced calcium carbonate flocculation and floc strength

High molecular weight water-soluble polymers (retention aids) are routinely added to improve fines and filler retention during papermaking. However, d issolved and colloidal substances (DCS), associated with mechanical pulps ( MPs) are known to interfere with the retention aid functions. Reported in t his work are both flocculation results and novel filler flee strength measu rements for precipitated calcium carbonate flocs formed in the presence of model DCS polymers. The DCS models include well-defined dextran, dextran su lfate and hydrophobically modified dextran. Depending on the nature of the retention aid, the model DCS polymers can either interfere with or in a few cases improve retention. The results are interpreted in terms of establish ed models of colloid science. (C) 1999 Elsevier Science B.V. All rights res erved.