The complex-induced flocculation of semi-dilute calcite dispersions - Influence of the mode of addition of the polyelectrolytes

In this work, the flocculation of calcite dispersions was induced by adding mixtures of high molecular weight cationic starch and low molecular weight anionic sodium polyacrylate (NaPA). The starch is industrially used as a fixative. As the starch forms complexes with anionic substances in the wet end. the complexes strongly influence the flocculation of fibers and fillers. In order to reach further understanding of the complex-induced flocculation in general, the mode of addition of the polyelectrolytes was varied. The effect of changing the mode of addition was moderate. Especially at high ratios of NaPA to starch and high total amounts added, the flocculation behavior was completely determined by the deposition of the large amount of complexes formed in the aqueous phase.