Cationic Starch Preflocculated Filler for Improvement in Filler Bondability and Composite Tensile Index of Paper

Inorganic fillers, the second largest component of the papermaking process, have poor bondability with cellulosic fibers, interfere in interfiber bonding, and reduce paper strength. Filler preflocculation/modification is a practical method for enhancing interactions between the filler particles and fibers. This article reports on the effects of filler content and preflocculation on the filler bondability factor calculated based on first-pass ash retention and paper strength properties such as the tensile, Z-direction tensile, and composite tensile indexes. Talc filler preflocculated using 0.1-0.8% dosages of cooked cationic starch based on the dry weight of filler was loaded in paper to obtain varying filler contents of 15-24%. The filler bondability factor (FBF) and various tensile properties of paper were calculated and analyzed for all experiments. FBF and paper strength were reduced with increasing filler content in paper, whereas they were improved upon addition of preflocculated filler in paper. Noticeably, preflocculated filler resulted in increases in FBF and composite tensile index of 13-24% and 7-15%, respectively, at a 24% filler content in paper.