Wet and Dry Coating Structure of Calcium Carbonate Pigments with Narrow Particle Size Distribution, 1999 Coating Conference Proceedings

Rainer Knappich

Dow Europe S.A.

Peter Burri

OMYA, Plüss-Staufer AG

Gerold Lohmüller

Dow Deutschland Inc.

Peter Hugener

OMYA, Plüss-Staufer AG

Natural Ground Calcium Carbonate pigments with narrow particle size distributions have been successfully introduced for paper coating during the last 4 years. The combination of high brightness with high opacity and excellent coverage leading to better smoothness and higher gloss has offered new development opportunities for the coated paper and board producers.

The difference in particle size distribution results also in different coating color properties like faster dewatering, higher immobilization rate and increased high shear viscosity. However, these properties lead to higher blade pressure during coating.

In general the solids levels are reduced to optimize the blade coater runnability. Lower solids content means higher dewatering and more drying energy necessary, which can be undesirable for the paper producer.

This paper will demonstrate how specially designed latex dispersions help to control coating color rheology leading to improved coater runnability with Ground Calcium Carbonate pigments with narrow particle size distributions without sacrificing the optical and physical properties of the coated papers.