Precipitated aragonite and a process for producing it

A process for producing a precipitated aragonite calcium carbonate (PACC), which comprises reacting a reaction mixture of an aqueous calcium hydroxide slurry, including at least one active agent selected from the group consisting of carboxylic acids of formula CH3(CH2)nCOOH, where n is 7, 8 or 9, carboxylate salts thereof, esters thereof, anhydrides thereof, acyl halides thereof and ketenes thereof of the formula CH3(CH2)n−1C═C═O, wherein n is as defined previously, with carbon dioxide or a gas containing carbon dioxide, wherein at least one of the active agent added to the reaction mixture or reaction conditions of temperature, pH, mode of operation and reactant concentrations, are selected to yield precipitated aragonite calcium carbonate with a specific gravity of less than 2.5 g/cm3, when determined by a method that comprises:

• a. drying said PACC for 12 hours at 120° C.;
• b. mixing a weighed quantity (Wc) of the dried PACC with a weighed quantity (Wo) of tall oil having a density 0.93 g/cm3;
• c. sonicating the mixture in an ultrasound bath for 20 minutes;
• d. measuring the total volume of the mixture (V) and the total weight of the mixture (W) at 20-22° C. and calculating the density D therefrom from the following equation
• D=W/V;
• and
• e. calculating the specific gravity (S.G.) of the PACC from the following equation:
• 1/D=[Wc(Wo+Wc)]/S.G.+[Wo(Wo+Wc)]/0.93.