| abstract |
Process for producing particles comprising ball-shaped spherical surface-modified calcium carbonate comprising the steps of: a) providing at least one aqueous suspension of calcium carbonate-containing mineral; b) providing at least one acid soluble in water; c) optionally providing additional gaseous CO2 via an external route; d) contacting the aqueous suspension of calcium carbonate-containing mineral from step a) with the acid from step b) and with the CO2 generated in situ and / or supplied externally of step c) under stirring conditions; e) optionally dehydrating the aqueous suspension; wherein at least one processing agent is added before, during or after said mineral aqueous suspension containing calcium carbonate from step a) is contacted with said acid from step b) and with said CO2 generated in situ and / or externally supplied from step c), the processing agent is dosed in one or more steps to said mineral aqueous suspension containing calcium carbonate, the processing agent is added in amounts of up to 8% by weight based on dry weight of the suspension, and the at least one processing agent is selected from the group comprising ferrous sulfate, ferric sulfate, ferrous chloride, ferric chloride, aluminum sulfate and / or its hydrated forms, silicates, water soluble cationic polymers, amphoteric polymers soluble in water, soluble nonionic polymers and combinations thereof, as well as seeds of precipitated calcium carbonate (PCC), or calcium carbonate with surface reaction, or mineral comprising calcium carbonate with reaction on the surface in the form of a ball. |