| 摘要 |
1,056,636. Semi - permeable membranes. REGENTS OF THE UNIVERSITY OF CALIFORNIA. March 22, 1965 [March 25, 1964], No. 12029/65. Heading B5B. A semi-permeable membrane is made by casting a film from a solution containing (1) a cellulose ether or ester having anhydroglucose units of formula wherein R 1 , R 2 and R 3 are alkyl groups containing 1-8 carbon atoms or a group of formula COR 5 where R 5 is an alkyl group containing 1-7 carbon atoms, and (2) a substantially water-soluble liquid amide of formula R 6 CONR 7 R 8 in which R 6 is H, methyl or ethyl and R, and R 8 are hydrogen, methyl, ethyl or propyl; evaporating a portion of the liquid amide; immersing the cast membrane in water, and finally heating the membrane to reduce its porosity. In one embodiment the solution is made by dissolving the cellulosic derivative and the amide in an organic solvent. Alternatively, the cellulosic derivative may be dissolved in the liquid amide alone, in which case R 7 and R 8 of the amide are not both hydrogen. The casting of the solution, e.g. on. to a glass plate, and subsequent evaporation, may be carried out at -10‹ to 22-23‹ C. The immersion of the cast membrane may be effected in ice-water for e.g. 1 hour, and the subsequent heating may be carried out in water at 23-95‹ C. for e.g. 4 minutes. Specified cellulosic derivatives are acetate, acetatebutyrate, propionate or ethyl cellulose. The liquid amide may be formamide, dimethylformamide, methyl formamide or ethyl formamide. Suitable organic solvents are acetone, dioxan, tetrahydrofuran, methyl ethyl ketone, ethyl alcohol, methyl alcohol, acetic acid and formic acid. Inorganic salts may be added to the solution, or the cast membrane may be immersed in aqueous solutions of such salts. The membranes are used for recovering potable water from sea-water. |
