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

In the study, 2 methods of preparation of talc and calcium carbonate were employed. The 2 minerals were either co-ground with water or the wet ground calcium carbonate was mixed with dry ground talc afterward. 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. The handsheets added 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 could enhance 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, co-grinding of talc and calcium carbonate appeared to have more uniform particle size distribution and smaller average particle diameters than the separately ground and mixed group. The edges of the platy filler were smoother for the former group as well. Comparing the 2 groups, the co-ground talc-GCC gave better handsheet filler retention, sizing degree, tensile index and brightness.