Flocculation of fillers with polyelectrolyte complexes

The objective of this study was a better understanding of the effect of charge density and of the molecular weight of polyelectrolyte complex components on the flocculation of kaolin and precipitated calcium carbonate (PCC) fillers. The results show that the components of the complexes had a major impact on flocculation. In order to achieve an effective flocculation one of the components of the polyelectrolyte complex (PEC) should be a high molecular weight polyelectrolyte so that the PEC could effectively form polymer bridges between filler particles. More specifically, the component in excess of the complex should have a higher molar mass than the other component. When the polyelectrolyte with lower molecular weight is in excess in the PEC, the flocculation efficiency of the PEC decreases significantly. The charge ratio of the PECs has a great effect on the flocculation. With charge ratios other than 1, maximum flocculation was achieved with low dosages, but with complexes near 1:1 ratio the dosing range is broader, and higher maximum flocculation can be achieved. A pre-mixed complex where one component has a high charge density is not beneficial for flocculation. This study showed that a one step addition of PEC could be an effective and robust way for filler flocculation.