GB892557A - Purification process - Google Patents

Abstract

Polyethers contaminated with basic inorganic materials are purified by treating with an acid of the formula HxMFy where M is an element of Group 3 or 4 of the Periodic Table, x is 1 to 3 and y is 4 to 6. The polyethers are particularly those obtained by polymerizing a b -alkylene oxides, optionally in the presence of a compound containing reactive hydrogen, and in the presence of an alkaline catalyst, e.g. KOH and NaOH. Examples of the fluoro-acids are fluoroboric, fluorosilicic, fluorotitanic and fluoroaluminic acids. They may be added as aqueous solutions or as solutions or suspensions of metal fluoride, e.g.titanium tetrafluoride or aluminium trifluoride, in hydrofluoric acid. The amount of acid is preferably sufficient to produce a pH of 3 to 5. The temperature may be from 25 DEG to 150 DEG C., preferably 90 DEG to 110 DEG C. where the polyether is liquid. The resultant insoluble matter is removed by filtration. Prior to this, a further treatment with an acid-acceptor is preferably effected. Suitable acceptors are basic compounds insoluble in polyethers, e.g. silicates and carbonates of alkaline earth metals. In the examples, the polyethers are prepared from: (1) glycerol and propylene oxide; (2) trimethylolpropane and propylene oxide and then with ethylene oxide; (3) ethylene oxide and isooctanol; (4) trimethylolpropane and propylene oxide. These polyethers have hydroxyl values ranging from 59 to 542 mg. KOH per gm., the upper limit corresponding to a molecular weight of 310.ALSO:Polyethers contaminated with basic inorganic materials are purified by treating with an acid of the formula HxMFy where M is an element of Group 3 or 4 of the Periodic Table, x is 1 to 3 and y is 4 to 6. The polyethers are particularly those obtained by polymerising a b -alkylene oxides, optionally in the presence of a compound containing reactive hydrogen, such as water, monohydric alcohols, e.g. butanol, diols, pentaerythritol, sorbitol, sucrose and others mentioned hereinafter, and in the presence of an alkaline catalyst, e.g. KOH and NaOH. Examples of the fluoro-acids are fluoroboric, flourosilicic, fluorotitanic and fluoroaluminic acids. They may be added as aqueous solutions or as solutions or suspensions of metal fluoride, e.g. titanium tetrafluoride or aluminium trifluoride, in hydrofluoric acid. The amount of acid is preferably sufficient to produce a pH of 3 to 5. The temperature may be from 25 DEG to 150 DEG , preferably 90 DEG to 110 DEG C. where the polyether is liquid. The resultant insoluble matter is removed by filtration. Prior to this, a further treatment with an acid-acceptor is preferably effected, suitable acceptors being basic compounds insoluble in polyethers, e.g. silicates and carbonates of alkaline earth metals. In the examples, the polyethers are prepared from (1) glycerol and propylene oxide; (2) trimethyl propane and propylene oxide and then with ethylene oxide; (3) ethylene oxide and isooctanol; (4) trimethylpropane and propylene oxide. These polyethers have hydroxyl values ranging from 59 to 542 mg.K.O.H. per gm., the upper limit corresponding to a molecular weight of 310.