GB761371A - Improvements in or relating to the manufacture of sodium perborate - Google Patents

Abstract

Sodium perborate is prepared by mixing anhydrous sodium tetraborate or an impure mineral sodium borate or boric acid with a sodium hydroxide solution, if necessary with heating, to form a solution containing 300-1000gm/l. of sodium metalborate at a temperature (e.g. 30-95 DEG C.) which prevents it from crystallizing, if necessary filtering this solution, and then reacting it with or without dilution with a sodium peroxide or hydrogen peroxide solution. It is preferred to employ a cyclic process in which the sodium hydroxide is present in a mother liquor from a previous precipitation, and after removing precipitated perborate the whole or a part of the residual liquor is recycled. If desired the hot concentrated metaborate solution and the peroxide solution may be run simultaneously into water or a mother liquor from a previous process, when a portion of mother liquor is not recycled, as when using a dilute hydrogen peroxide solution, e.g. 4 per cent w/w, it may be treated with sodium chloride to salt out additional product. In examples, temperatures were maintained at 25 DEG C. and magnesium sulphate added as a stabilizer during the addition of hydrogen peroxide.