Exploration of Surface Strengthening Agents for Pigmentizing of Precipitated Calcium Carbonate

In the papermaking industry, several studies on greenhouse emission reduction have been subjected. Among the studies, filler loading is the widely used method to reduce greenhouse emission by reducing fiber raw material and drying energy. Especially, precipitated calcium carbonate (PCC), as a typical filler, can improve physical and optical properties of paper as well as reduce carbon dioxide by reusing carbon dioxide during its synthesis. However, excessive internal filler loading causes side effect such as weakening of paper strength. In this study, in order to overcome the problems caused by excessive internal filler loading, some of fillers were separately applied to surface of paper as the pigmentizing. The pigmentizing is the technology of adding fillers to surface sizing agent, and carried as same as existed surface sizing process. The pigmentizing technology can increase the filler content without losses of the paper strength, at the same time, improve the optical properties which is decreased after surface sizing process. So in this study, we applied PCC synthesized diverse size and shape to the pigmentizing technology and evaluated surface properties of paper. In addition, in order to overcome dust problem caused by detached filler from surface, several polymers were applied to surface sizing agent and surface strengthening effect was evaluated. As a result, rhombohedral type of PCC was suitable for the pigmentizing in term of surface strength and optical properties. Surface strengthening agents were applied to scalenohedral type of PCC, among them, cationic polyacrylamide and anionic polyacrylamide critically increased the surface strength of pigmentized paper, when the polymers added below the level of flocculation of filler. In case of poly(ethylene oxide), surface strength was increased at the addition amount of 1% on filler, and it did not affect the viscosity of surface sizing agent and the flocculation of filler.