CALCIUM DIHYDROGEN PHOSPHATE DIHYDRATE FOR TOOTHPASTE AND ITS MANUFACTURE

摘要

PURPOSE:To obtain the titled salt having very superior cleaning power and kneading characteristics as a base for toothpaste by mixing prismatic or platy crystals and flat crystals of calcium dihydrogen phosphate dihydrate obtd. By reacting alkali metallic phosphate with Ca salt at different pH values. CONSTITUTION:Said prismatic or platy crystals are those having 10-15mum thickness, and said flat crystals are those having 1-2mum thickness. They may be prepared separately and mixed, yet they can be manufactured suitably by a continuous method. In the soln. reaction of alkali metallic phosphate with Ca salt, mineral acid or the like is added to adjust the pH to 2.5-3.5 in the 1st stage, and they are reacted with stirring. The preferred reaction temp. is =40 deg.C. As the double decomposition reaction proceeds, calcium dihydrogen phosphate dihydrate crystals are produced. After finishing the reaction, by adding an alkali substance in the 2nd stage, the pH of the slurry is adjusted to 3.5-5.0 to reduce the solubility of said dihydrate, and crystals of the dehydrate are further deposited. Thus, a deposited mixture of prismatic or platy crystals and flat crystals are obtd. in the former and latter stages.