Unmodified Starch Granules for Strengthening Mineral-Filled Cellulosic Fiber Networks Promoted by Starch Pretreatment with a Cationic Polymer Flocculant in Combination with the Use of an Anionic Microparticulate Material

The efficient use of renewable resources (e.g., starch) is essential to the green economy. On the basis of commercially available microparticle retention and drainage systems, the process concept of trapping unmodified starch granules in mineral-filled cellulosic fiber networks for strength enhancement by incorporation of cationic polymer flocculant pretreated/bridged starch granules in combination with the use of an anionic microparticulate material was discussed and demonstrated. Specifically, a high molecular weight cationic polyacrylamide and a modified bentonite, which are commercially available in the market, were used as the polymer flocculant and the anionic microparticulate material, respectively. The paper strength loss upon the addition of precipitated calcium carbonate filler particles was significantly mitigated by employing such a concept, which may provide an alternative strategy for improving the strength properties of mineral-filled paper grades.