GB989812A - Production of chlorocyanuric acids - Google Patents

Abstract

A process for.producing a chlorocyanuric acid which comprises introducing chlorine into an aqueous alkaline dispersion of an alkaline earth metal salt of cyanuric acid at a temperature in the range from above the freezing point (-5 DEG C.) of the dispersion, and continuing the addition of chlorine until the pH of the dispersion is reduced to a value below 4. Preferably the temperature is at most 50 DEG C. The alkaline earth cyanurate may be prepared as a 10-30% slurry by mixing a 10-35% aqueous slurry of the alkaline earth carbonate, oxide or hydroxide with a 5-25% slurry of cyanuric acid in stoichiometric proportion, which mixture then has a pH of 12.0-12.6 and to which liquid or gaseous chlorine is added with agitation and external cooling to replace the metal atoms of the cyanurate. The mixture is maintained at 10-35 DEG C. and the chloro cyanuric acid separated, e.g. by centrifuging. The process may be continuous, the chlorine and the slurry of cyanurate being introduced into the reaction zone at 0-50 DEG C. at rates to adjust the pH to below 4 and a portion of the mixture is continuously removed from which the chloro cyanuric acid is separated. Trichlorocyanuric acid is prepared from the trialkaline earth metal dicyanurate using 100-200% of the stoichiometric quantity of chlorine and reducing the pH below 3.5. The dichlorocyanuric acid is prepared from the mono alkaline earth metal monocyanurate using 100-120% of the stoichiometric quantity of chlorine and reducing the pH below 2.5.