PROCESS FOR THE PRODUCTION OF A FILLING MATERIAL FOR THE PAPER INDUSTRY

摘要

Fillers for use in the paper industry are made by forming a is not 75 wt.% suspension of CaCO3 (opt. contg. impurities) in water and adjusting the pH of the suspension to 5-12 with organic and/or inorganic acid(s). The pH may be adjusted in two or more stages with different acids, or in several stages with a single acid. Process is esp. useful for treating the causticising sludge obtd. as a by-prod. in the regeneration of sulphate cellulose, and consisting mainly of CaCO3 contaminated with K,Na,Mg,OH,S and silicate ions, to give a material which can be used as a filler in papermaking. The slurry of causticising sludge may be mixed with a calcium hypochlorite slurry, using is not 25 pts. wt. Ca in the hypochlorite per 100 pts. wt. Ca in the causticising sludge. Up to 10 wt.% water glass may be added to the suspension before adding the acid.