Effects of Adding Co-ground Talc and Calcium Carbonate on the Retention and Paper Properties of Handsheets

In this study, 2 methods of preparation of talc and calcium carbonate were employed. The 2 minerals were either ground up together with water or the wet-ground calcium carbonate was mixed with dry-ground talc. Then the preparations were added to a typical fine paper furnish to investigate the effects of replacing a portion of calcium carbonate with talc on the first-pass retention (FPR), ash, sizing degree, bulk, tensile strength, smoothness, roughness, brightness, and opacity of the handsheets (with a basis weight 60 g m^(-2)). Handsheets produced with 100% wet-ground calcium carbonate (GCC) and 100% dry-ground talc served as the control groups. The replacement level of talc was 10%, and the dosages examined were 0, 10, 20, and 30%. The results indicated that replacing a portion of GCC with talc enhanced the FPR, ash retention, bulk, sizing degree, tensile index, and brightness of the handsheets at the cost of decreased smoothness and opacity. Comparing the 2 preparations, grinding together the talc and calcium carbonate appeared to produce a more-uniform particle size distribution and smaller average particle diameters than the separately ground and mixed groups. The edges of the platy filler were smoother for the former group as well. Comparing the 2 groups, talc and GCC ground together produced better handsheet filler retention, sizing degree, tensile index, and brightness.