Fiber-Loading: A Progress Report, 1994 Recycling Symposium Proceedings

John Klungness, Daniel Caulfield, Irving Sachs, Freya Tan, Marguerite Sykes, Richard Shilts

Recent conversion of many papermaking systems from acid to neutral or alkaline sizing has created new opportunities for papermaking process development. For example, calcium carbonate can now be used as a paper filler as well as a paper coating pigment. The objective of this study was to investigate the potential for producing calcium carbonate within, and as an integral part of, the stock preparation process. This might reduce manufacturing costs and extend our nation’s forest resources.

Our investigations show that fiber loading with calcium carbonate can be accomplished by an in situ reaction between calcium hydroxide and carbon dioxide in high consistency pulps under mechanical shear. A pressurized disc refiner adequately serves as reaction chamber and a means for obtaining good dispersion of filler and fiber.

In some respects, properties of handsheets prepared with fiber-loaded pulp out-performed those made by conventional direct-loading. This permits less expensive calcium carbonate to be substituted for higher cost fiber without compromising paper strength or optical properties. These results warrant further investigation to determine potential economic and paper property benefits.