GCC vs. PCC as the Primary Filler for Coated and Uncoated Woodfree Paper, 1998 Papermakers Conference Proceedings

The debate continues regarding the choice of filler for woodfree papers. PCC is generally seen as an opacifying pigment with its downside being slower drainage and drying. GCC is generally seen as a pigment providing drainage, strength and filler-for-fiber substitution potential with normally lower bulk. The economics of fiber substitution tend to be the strong driving force for the use of GCC. Data are presented on several grades of GCC compared to a typical scalenohedral PCC in the manufacture of both coated and uncoated woodfree papers. A pilot paper machine trial was carried out, producing coating base stock using GCC or PCC as a primary filler. All the rolls produced were subsequently coated, calendered and sheet-fed offset printed. The general results show that in a coated sheet the end properties of a calendered gloss grade are similar and the filler-for-fiber economics will drive a conversion to higher filler levels. There were no print quality differences depending on the filler. Another pilot paper machine trial was conducted while changing the blend of filler in an uncoated woodfree sheet. The conditions went from 100 % GCC to 100 % PCC. Paper properties were compared at each level. Commercial data are also presented supporting the findings from the pilot paper machine. For uncoated papers GCC by itself or GCC/PCC blends increase the potential for higher filler levels, improve drainage and drying which may allow production improvements on dryer- limited machines, and decrease sizing chemical usage.