Dicalcium phosphate dihydrate preparation from calcium - compounds and phosphoric acid and/or phosphates

摘要

In wet process carried out batchwise or continuously in presence of water and opt. basic cpd., reactants are used with max. plus-or-minus 15 wt. % deviations from stoichiometric amounts, according to equation: 3H+, + PO43- + Ca2+ + 2 OH- right arrow CaHPO4.2H2O. For achieving defined particle size or particle size distribution, reactants are first mixed quickly and intimately in amounts such that pH 2-6 is set up and maintained at temps. below 70 degrees C (25-45 degrees C) for duration of reaction. Smaller particle sizes are obtained by carrying out reaction at higher pH of given range, and adding bal. of Ca cpd. and opt. base after addition of complete amount of H3PO4 and/or phosphate; filtering and processing after pH of reaction mixture has fallen to 6.5-7.5 after a temporary increase. Products are used (pref. stabilised) in cosmetics and medicinal preparations. Stabilisation prevents hardening of toothpastes by reaction with contained glycerol.