| 摘要 |
1,264,670. Cellulose membrane. DOW CHEMICAL CORP. 17 April, 1969, No. 19736/69. Heading BIX. [Also in Division B5] Permselective membranes are made by forming the membrane from a mixture comprising a cellulose ester, a plasticizer and optionally a polyol i.e. ethylene or propylene glycol or a polyglycol of M.W. up to 20,000 or glycerine, leaching the plasticizer and polyol if present, from the membrane with a liquid which is a solvent for the plasticizer but a non-solvent for the membrane with the proviso that where polyol is absent from the mixture, the membrane is immersed in a solution of plasticizer in water, or a water miscible solvent e.g. methanol or ethanol, or a polyol prior to the leaching step. Suitable plasticizers are dimethyl sulphoxide, dimethyl formamide, butyrolactone, N-methyl formamide, dimethyl acetamide, caprolactam, 2-pyrrolidone, malonitrile, triacetin, tetramethyl sulphone and ring substituted compounds thereof which are preferred. The leaching is generally effected with water or ethanol. The exemplified cellulose ester is a cellulose acetate. Exemplified plasticizers are in example I, tetramethylene, sulphone and polyethylene glycol containing four ethylene oxide units, in Example II, dimethyl phthalate and polyethylene glycol, in Example IV, tetramethylene sulphone and tetraethylene glycol, and in example VI, tetramethylene sulphone and methylene dichloride. In example IV, the membranes are in the form of fine filamentary hollow fibres whilst in all the other examples they are films. |
