GB825929A - Production of chlorocyanuric acids - Google Patents

Abstract

Di- and/or tri-chlorocyanuric acid is produced by intimately admixing an aqueous solution of di-alkali metal cyanurate and/or tri-sodium cyanurate and at least the stoichiometric proportion of gaseous chlorine in an aqueous reaction medium at a temperature not exceeding 25 DEG C., the conditions of mixing being such that the pH is maintained below 4.5, preferably 3-4.5. The di- and/or tri-chlorocyanuric acid is isolated from the reaction mixture in commercial operation after a residence time in the reaction zone sufficiently limited to produce a yield of at least 75%, preferably 85% to prevent appreciable decomposition. In the production of tri-chlorocyanuric acid the pH of the reaction mixture is more preferably 3-4.3. It is preferred to employ a 5-20%, more preferably a 10-15%, stoichiometric excess of chlorine. Alkali metals specified are sodium and potassium. The reaction temperature is preferably 10-25 DEG C. (which temperature is preferably maintained by cooling the cyanurate solution to -5 DEG to 10 DEG C.), but temperatures as low as -9 DEG C. may be employed. A continuous process in which the reaction product is periodically or continuously removed from the reaction zone is preferably employed, and the volume of solution in the reaction zone is preferably maintained substantially constant. The solid chlorocyanuric acid produced may be removed from solution by filtration, decantation or centrifugation with less than 40%, preferably with less than 15% of water, and dried to a water content of less than 4%, preferably below 1.5%. Specification 634,801 is referred to.