PREPARATION OF BORIC ACID ESTER FOR BRAKE FLUID

PURPOSE:To produce a compound useful as a brake fluid having excellent corrosionproofing property to metal and stability in moisture absorption, by neutralizing an alkali catalyst used in the production of a polyether with a specific neutralizing agent, and reacting the product with a boron compound. CONSTITUTION:A polyether is prepared by adding 1-10mol of a 2-4C alkylene oxide to a compound having active hydrogen (e.g. methanol, propanol, butanol, etc.) based on the active hydrogen, and reacting at 80-150 deg.C in the presence of an alkali catalyst (e.g. potassium hydroxide). The alkali catalyst is neutralized with 0.5-1.5 equivalent of a hydroxy acid (e.g. glucolic acid, lactic acid, etc.) (based on 1 equivalent of the alkali catalyst) in an inert gas stream such as nitrogen gas at 20-90 deg.C. the reaction product is added with a born compound (e.g. boric acid, triphenoxyboron, etc.), and subjected to the dehydration reaction or ester exchange reaction at 80-150 deg.C to obtain the objective compound.