Characteristics of Hybrid Calcium Carbonate Prepared from Ground and Precipitated Calcium Carbonate

Hybrid calcium carbonate (HCC), which is prepared by preflocculation of two components such as ground calcium carbonate (GCC) and calcium oxide in the first step, and next, by injecting carbon dioxide into the preflocculated flocs, is known to increase the bulk, stiffness, and tensile strength of printing paper greatly and simultaneously when compared with GCC. Post-calcium carbonate (pHCC) is different from HCC in that calcium oxide is added to the preflocculated single component, GCC, and carbon dioxide is injected later. Handsheets made of pHCC and HCC showed very similar properties. When the GCC was replaced with precipitated calcium carbonate (PCC) in the preparation of HCC and pHCC, the bulk of the paper increased further, but bonding properties were lowered. By selecting GCC or PCC and by controlling their proportion in the preparation of HCC and pHCC, papermakers may produce papers with desired physical properties. The possibility of extensive replacement of wood fibers by the use of HCC and pHCC while satisfying essential paper quality, and the effect of storage time of the fillers, is also discussed.