| abstract |
The preparation of alkaline earth metal carbonates of formula EaCO3, where Ea = Ba, Ca or Sr, in particle form, comprises: (i) reacting an alkaline earth metal hydroxide (Ea(OH)2) solution with a concentration of 0.1-0.75 M with ca. 2-30 l carbon dioxide per l solution; (ii) passing the reaction mixture through a continuously operating mixer reactor, in which relatively high-speed interacting tools subject the mixture to trim, shear and friction forces; and (3) separating the alkaline earth metal carbonate formed and drying. Also claimed are: (i) barium carbonate (BaCO3) particles with a BET unit surface area of 3-30 m2/g, and calcium or strontium carbonate (SrCO3) particles with a BET value of 3-50 m<2>/g, at least 95%, preferably 100%, of the particles have a maximum diameter of 1 mu m, prepared by the above process using a crystal growth inhibitor chosen from (alkyl) ammonium salts of 3-12C carboxylic acids containing at least 2 carboxyl (COOH) or hydroxyl (OH) groups; and (ii) particles similar to those in (i), except that at least 90% of particles have a diameter of 0.1-1 mu m and they are prepared without the use of a crystal growth inhibitor. |