Study of using water softening process byproduct, calcium carbonate on fine paper production

purification and softening, a lot of calcium carbonate with other impurities produce and these byproducts gather and bury as mineral sludge.In this research, The quality of calcium carbonate from water softening process in mazandran wood and paper industry (MWPI) mill and effects of loading of this byproduct on fine paper production was investigated and the results were compared with other industrial fillers like grounded calcium carbonate(GCC) and precipitated calcium carbonate(PCC) and also china clay (kaolin).From the paper structural viewpoint, the fine paper that filled with water softening calcium carbonate (derived after water softening process) have more bulk(bulkier) and more porous and rougher surface compare to fine papers that filled with the common industrial fillers.From the paper strength properties viewpoint, the fine paper that filled with water softening calcium carbonate have less decrease in tensile and burst strength but have not suitable tear strength properties. From the paper optical properties viewpoint, the fine paper that filled with water softening calcium carbonate, because of particles size and impurities of this filler have the least light scattering coefficient and consequently have less brightness and opacity.Adding of 10 and 20 percent precipitated calcium carbonate to by water softening calcium carbonate cause paper porosity and strength decreasing but the optical properties of hand sheets was increased.