Maintaining Coated Paper Performance While Varying Coating Color Solids with Engineered Carbonates, 2004 Coating and Graphic Arts Conference

There currently exist many structured and engineered pigments for paper coating, with new technologies for producing these pigments emerging frequently. As they become available for use, the knowledge of how to use these special pigments is imperative. Thus, a solids-performance relation was examined for precipitated calcium carbonate and ground calcium carbonate pigments, including a narrow particle size distribution (psd) aragonite precipitated calcium carbonate, a narrow psd calcite precipitated calcium carbonate, and ground products consisting of a narrow psd ground calcium carbonate, and a broad ground calcium carbonate. The results of this study indicated that there were no appreciable effects of the dilution of coating colors on optical coated paper performance when using high levels of precipitated calcium carbonate or ground calcium carbonate coating colors. The coated paper properties remained consistent over a 4%-units solids decrease. Previous work had demonstrated a decline in optical performance with lower coating color solids. By controlling the key properties such as viscosity, water holding and immobilization in this study, the performance of each pigment could be maintained despite coating color dilution. These results demonstrate that narrow particle distribution pigments such as precipitated calcium carbonate can give enhanced coated sheet performance, even when used at lower coating solids, if attention is given to the rheology and water holding character of the coating. This means that different calcium carbonates can perform well with less than maximum applicable coating color solids.