A novel predictive method for filler coflocculation with cellulose microfibrils

摘要

Different strategies aimed at reducing the negative impact of fillers on paper strength have been the objective of many studies during the past few decades.Some new strategies have even been patented or commercialized,yet a complete study on the behavior of the filler flocs and their effect on retention,drainage,and formation has not been found in literature.This type of research on fillers is often limited by difficulties in simulating high levels of shear at laboratory scale similar to those at mill scale.To address this challenge,a combination of techniques was used to compare pref locculation(i.e.,filler is flocculated before addition to the pulp)with coflocculation strategies(i.e.,filler is mixed with a binder and flocculated before addition to the pulp).The effect on filler and fiber flocs size was studied in a pilot flow loop using focal beam reflectance measurement(FBRM)and image analysis.FloCs obtained with cationic polyacrylamide(CPAM)and ben-tonite were shown to have similar shear resistance with both strategies,whereas cationic starch(CS)was clearly more advantageous when coflocculation strategy was used.The effect of flocculation strategy on drainage rate,STFI formation,ash retention,and standard strength properties was measured.Coflocculation of filler with CPAM plus bentonite or CS showed promising results and produced sheets with high strength but had a negative impact on wire dewatering,opening a door for further optimization.Application: Papermakers can apply this generalized bench-scale method to optimize the use of CMF with wet-end chemistry in terms of paper properties,dewatering,and retention.Different systems can be optimized in regard to floc stability and filler flocs performance.