Patent GB-958390-A (GB)
Title: Purification and stabilisation of polyethers
Inventor: GUDGEON HERBERT
IPC: C08G65/30
Filed: 1961-07-11
Abstract: Polyethers as herein defined are purified and stabilized by contact with an aqueous solution of an alkali metal bisulphite or ammonium bisulphite.  The polyethers are those hydroxy group-containing polyethers obtained by polymerizing cyclic oxides or mixtures thereof, optionally in the presence of a compound, e.g. water, ammonia or an organic compound containing one or more active hydrogen atoms. The polymerization is usually effected in the presence of a catalyst, e.g. potassium hydroxide or fluorosulphonic acid. Specific oxides include ethylene, propylene and butylene oxides, oxacyclobutanes, tetrahydrofuran, 3-hydroxymethyl oxacyclobutane, glycidol and diepoxides.  The organic compounds containing active hydrogen include alcohols, glycols, polyols, phenols, primary amines, mono and disecondary amines and monocarboxylic acids, numerous examples being given including sucrose and phenolformaldehyde reaction products. The purification is preferably effected by agitating the polyether with an aqueous bisulphite solution containing at least 24% sulphur dioxide as bisulphite, the amount of solution being 0.05-1.0% by weight of the polyether; the treatment is carried out between 10-150 DEG C.  The bisulphite may be produced in situ by first shaking the polyethers containing the residual alkaline catalyst, with a saturated brine solution and then introducing sulphur dioxide.  The treated ethers may be recovered by separating the aqueous phase if desired with the aid of added neutral salt, e.g. sodium chloride, or a water insoluble solvent for the polyether. Alternatively the water may be evaporated off by means of reduced pressure and/or elevated temperatures followed by filtration to remove precipitated inorganic material. Anti-oxidants may be incorporated in the polyether before or after the treatment or in the starting materials from which the ether is prepared, e.g. various specified phenols, which may be sterically hindered, zinc dialkyl-dithiophosphates, zinc dialkyldithiocarbamates and dialkyldithio dialkylene carboxylates.  The bisulphite treatment may be combined before, during or after with other purification methods, e.g. treatment with organic or inorganic acids, absorbent clays, ion-exchange resins or finally divided carbon.  By reaction with isocyanates the purified polyethers may be converted into polyurethanes of much improved colour.  In examples the purification and stabilization of crude polypropylene glycol using bisulphite liquour, phosphoric acid activated and neutralized wood carbon and 2-(a -methyl)cyclohexyl 4:6-dimethyl phenol is described; the polypropylene glycol (M.W.-2,000) is prepared by the addition of 1:2 propylene oxide to diethylene glycol in the presence of potassium hydroxide.ALSO:Polyethers as herein defined are purified and stabilized by contact with an aqueous solution of an alkali metal bisulphite or ammonium bisulphite.  The polyethers are those hydroxy-group containing poly ethers obtained by polymerising cyclic oxides, or mixtures thereof, optionally in the presence of a compound, e.g. water, ammonia or an organic compound containing one or more active hydrogen atoms. The polymerization is usually effected in the presence of a catalyst, e.g. potassium hydroxide or fluorosulphonic acid. Specific oxides include ethylene, propylene and butylene oxides, oxacyclobutanes, tetrahydrofuran, 3-hydroxymethyloxacyclo butane, glycidol and diepoxides. The organic compounds containing active hydrogen include alcohols, glycols, polyols, phenols, primary amines, mono and di-secondary amines and monocarboxylic acids, numerous examples being given, including sucrose and phenolformaldehyde reaction products. The purification is preferably effected by agitating the polyether with an aqueous bisulphite solution containing at least 24% sulphur dioxide as bisulphite, the amount of solution being 0.05-1.0% by weight of the polyether; the treatment is carried out between 10-150 DEG C.  The bisulphite may be produced in situ by first shaking the polyether, containing the residual alkaline catalyst, with a saturated brine solution and then introducing sulphur dioxide.  The treated ethers may be recovered by separating the aqueous phase, if desired, with the aid of added neutral salt, e.g. sodium chloride, or a water insoluble solvent for the polyether. Alternatively the water may be evaporated off by means of reduced pressure and/or elevated temperatures followed by filtration to remove precipitated inorganic material. Anti-oxidants may be incorporated in the polyether before or after the treatment or in the starting materials from which the ether is prepared, e.g. various specified phenols, which may be stoically hindered, zinc dialkyldithiophosphates, zinc dialkyldithiocarbamates and dialkylthio dialkylene carboxylates. The bisulphite treatment may be combined before, during or after with other purification methods, e.g. treatment with organic or inorganic acids, absorbent clays, ion-exchange resins or finely divided carbon. By reaction with isocyanates the purified polyethers may be converted into polyurethanes of much improved colour. In examples the purification and stabilization of a crude polypropylene glycol using bisulphite liquor, phosphoric acid activated and neutralised wood carbon and 2-(a -methyl)-cyclohexyl 4:6-dimethyl phenol is described; the poly propylene glycol (M.W. 2000) is prepared by the addition of 1:2 propylene oxide to diethylene glycol in the presence of potassium hydroxide. After purification and stabilization this polyether is heated with a mixture of 2:4- and 2:6-tolylene di-isocyanate in a dry nitrogen atmosphere to give a polyurethane.