Effects of precoating color formulation with coarse ground calcium carbonate and porous precipitated calcium carbonate on paperboard properties and printability

To identify suitable pigments for the precoating of paperboard, the rheological properties of coating colors and their effects on the surface and printing properties of coated paperboard were evaluated with respect to the type and combination of coating pigments. The investigation included porous precipitated calcium carbonate (PCC) and four types of coarse ground calcium carbonate (GCC) of different sizes. As the GCC particle size increased, the viscosity of the coating color decreased in the low-shear region, and the degree of dehydration increased. Coatings containing PCC, which comprised relatively small and highly porous particles, were found to be less dehydrated than coatings containing only GCC. The surface roughness of the coated paperboard increased as the GCC particle size increased, leading to reduced paper gloss. However, increasing the GCC particle size decreased the binder usage and increased surface strength. In conclusion, it is believed that the use of 55-grade GCC rather than the smaller size of 60-grade GCC can reduce costs and enhance surface strength by reducing binder and energy.