Optimized binder systems for natural calcium carbonate pigments with narrow particle size distribution

Natural Ground Calcium Carbonate pigments with narrow particle size distribution provide a combination of high brightness, high opacity and excellent coverage offer new development opportunities for coated paper and board producers. The difference in particle size distribution results in different coating color properties such as faster dewatering, higher immobilization rate and increased high shear viscosity. These properties can lead to higher blade pressures and faster coating color dewatering. In general the solids levels are reduced to optimize the blade coater runnability. However lower solids content means higher dewatering and more drying energy, which can be undesirable for the paper and board producer. This paper will give fundamental explanations for the basic mechanisms of the runnability differences between Ground Calcium Carbonates with broad and narrow particle size distributions. Based on these considerations the application examples from a woodfree double coated paper and a board pre-coat will demonstrate how specially designed latex dispersions help to control coating color rheology. These latex dispersions will improve the coater runnability of Ground Calcium Carbonate pigments with narrow particle size distribution without sacrificing the optical and physical properties of the coated paper and board.