Improving the Smoothness of Alkaline Bleached Board Using a Novel Precipitated Calcium Carbonate (PCC) Filler, 2003 Spring Technical Conference Proceedings

Increasing the quality of North American solid bleached sulfate board (SBS) while lowering manufacturing costs is a most formidable task for any papermaker. Bleached board producers can draw upon the experience of fine-paper manufacturers, who found they could improve production costs by reducing the amount of bleached fiber used through the addition of mineral fillers such as precipitated calcium carbonate.

For a mineral filler to be effective in SBS board, a balance of bulk, stiffness, smoothness, brightness, runnability, and cost must be achieved to give manufacturers the ability to meet the increasing demands of a competitive paperboard market. With this in mind, a novel precipitated calcium carbonate (PCC) filler has been developed which provides a balance of these properties. This product improves production economics with greater filler for fiber replacement potential than any other mineral filler currently available.

Many fillers fall short in maintaining bulk and stiffness. However, this new PCC particle not only maintains bulk and stiffness, it also provides exceptional surface smoothness upon calendering, due to its particle shape, large size, and extremely low surface area. Better surface smoothness and brightness are important to improving the quality of the substrate for coating applications which will allow coated SBS board to meet the increasing graphic quality demands for printing and appearance.

To this end, a study was performed to show how the properties of paperboard could be improved by using this new PCC filler. This work compared traditional acid bleached board to alkaline bleached board using various calcium carbonate fillers under controlled conditions, focusing on calendering pressure and the impact of calendering pressure on bleached board smoothness, stiffness and other end-use properties.