2018 Volume 72 Issue 7 Pages 771-778
Several mill trials on Bel-Baie 3 twin wire former suggested that neutral PCC（precipitated calcium carbonate）filled newsprint has high brightness and opacity and is technically feasible. Sheet formation was good, physical properties were acceptable, and print quality such as ink transfer and print through was excellent, however, a large linting propensity was observed. To solve this problem, Prufbau printing tests and EPMA（Electron Probe Micro Analysis）were employed for the evaluation of linting tendency and paper sheet structure. PCC filler retained by mechanical filtration were observed near the paper surface as agglomerates. Laboratory studies found that using a retention aid improved paper two sided ness and distribution of PCC fillers by colloidal forces, and reduced linting propensity. Based upon these results, the next mill trial was performed. For effective use of retention aid, the zeta potential of the paper machine headbox was monitored continuously by an on-line instrument and was controlled into the proper range. Stock inlet pH was stable at 7.5-8 due to the buffering effect of PCC, and no darkening of mechanical pulp was observed. No paper breaks or foaming troubles were observed. The first pass retention was increased and two sided ness and linting of the newsprint were decreased to satisfactory levels.
