PROCESS FOR PRODUCING A LABEL-SHAPED CALCIUM-MAGNESIUM-CARBONATE MIXTURE WITH A BASIC CHARACTER

摘要

Process for mfg. carbonates of calcium and/or magnesium, the novelty being that by heating to 1000-1100 degrees C, dolomite is converted into a mixt. of calcium and magnesium oxides which are suspended in water using 1 pt. wt. of oxides and 20 pts. wt. water and the carbon dioxide is introduced into the suspension to convert the hydroxides into the corresponding carbonates. The initial starting material is pref. natural dolomite calcined in a rotary drum furnace, and the gas fed into the suspension is pref. CO2 or a mixt. of CO2 and N2, esp. the exhaust gas from the drum furnace. Before or during the slaking of the oxides, additional amounts of Ca or Mg oxide, hydroxide or carbonate may be added. Used e.g. for mfr. of basic calcium-magnesium carbonate as a filler or coating for mfg. glossy papers, where the carbonate has a degree of whiteness above 95%.