Wet and dry coating structure of calcium carbonate pigments with narrow particle size distribution

Natural ground calcium carbonate pigments with narrow particle size distributions have had successful use for paper coating during the last four years. Their combination of high brightness with high opacity and excellent coverage provides smoothness and high gloss. Using these pigments has offered development opportunities for coated paper and board producers. The variation in particle size distribution causes different coating color properties such as faster dewatering, higher immobilization rates, and increased high shear viscosity. These properties cause higher blade pressure during coating. Optimization of blade coater runnability requires reduction of solids levels. This means higher dewatering and more drying energy are necessary. Both factors are undesirable for a paper producer. This paper demonstrates how specially designed latex dispersions help to control coating color rheology.