Flocculants for Precipitated Calcium Carbonate in Newsprint Pulps, 1997 Papermakers Conference Proceedings

The retention of precipitated calcium carbonate (PCC) in newsprint pulp (15 wt % semi-bleached kraft + 85 wt % peroxide-bleached mechanical) using polymeric flocculants was investigated in the laboratory. Both commercially available and experimental polymeric flocculants were evaluated and the combination of cationic polyacrylamide and bentonite was found to be the most effective commercial retention aid. However, the experimental poly AM/MPEGMA), a copolymer of acrylamide and methoxy poly(ethylene glycol) methacrylate, when used in conjunction with phenolic resin (PFR), was the most effective retention aid of all. The retention of precipitated calcium carbonate by the PFR/poly(AM/MPEGMA) system was further increased by pretreatment of the pulp furnish with Na2 CO3 or by employing acid-tolerant PCC instead of conventional PCC. Both Na2 C03 -treated pulp and acid-tolerant PCC have lower equilibrium concentrations of Ca ++ ions.