GB611439A - Improvements in or relating to the production of alkali metal perborate compositions - Google Patents

Abstract

Alkali metal perborate compositions are prepared by mixing boric acid (i.e. boric oxide, ortho- or pyro-boric acid) or an alkali metal borate, e.g. borax, with hydrogen peroxide, an alkali metal peroxide or hydroxide and sufficient water to cause reaction between the boron compound and the peroxide and to form a substantially homogeneous solution, and rapidly dehydrating the solution until a homogeneous solid product is obtained. The dehydration, the temperature of which is not lower than 100 DEG C. and preferably is between 100 DEG and 150 DEG C., may be continued until the residual water content of the product is not more than 5 per cent in excess of that required to be equivalent to the H2O2 content as calculated from the active oxygen content. The proportion employed may be from 0.2 to 0.96 mol. and preferably from about 0.8 to 0.96 mol. of Na2O2 for each mol. of Na2B4O7. Other salts of boric acid, i.e. metaborates or tetraborates, may be used instead of borax. The stability in storage and in solution may be increased by addition of sodium pyrophosphate or of sodium silicate and magnesium sulphate.