Calcium borate for use in glass fibre manufacture - is produced e.g. from low grade colemanite mineral by reaction with sulphuric acid to produce boric acid which is then treated with calcium hydroxide

摘要

Calcium borate is produced from a 30-40% boric acids solution by reaction with a Ca compound in a molar ratio of 6 mole B to 1 mole Ca. Also claimed are: (i) method of producing calcium borate from a mineral containing a borate salt by reacting it with H2SO4 to produce boric acid which is crystallised from solution, and then reacting a 30-40% solution of the obtained boric acid with a Ca compound in a molar ratio of 6 mol B to 1 mol Ca; (ii) calcium borate containing 48-61 wt.% B2O3, 19-31 wt.% CaO, 19-23 wt.% H2O and 0-1 wt.% impurities; and further claims for calcium borate obtained by either of the above methods. The colemanite or howlith (sic) mineral is reacted with 20M to 36M H2SO4 with agitation at 90-100[deg]C for 0.25 to 2.5 hours. Boric acid is vacuum crystallised from the solution at 30[deg]C. The boric acid solution is treated with CaO or Ca(OH)2 at 90[deg]C for 1-3 hours. The calcium borate is filtered and dried at 110[deg]C.