| 摘要 |
<p>1,212,726. Microporous films and membranes. SOC. CRYLOR. 28 June, 1968 [30 June, 1967], No. 31055/68. Heading B5B. [Also in Divisions C3 and D1] A microporous film, membrane or similar sheet is prepared by shaping, e.g. by casting or extruding, a thin film from a solution of a high polymer, e.g. acrylonitrile polymer, a segmented polyurethane or a polyvinyl alcohol polymer or a mixture of two or more polymers, which is insoluble in cold water, then coagulating and washing the film, freezing, without intermediate drying, the water impregnated film by rapid cooling to a temperature equal to or below -10‹ C., and drying the resulting material by slow and progressive heating in a vacuum. Suitable polymer solvents are dimethylformamide (DMF), dimethylsulphoxide (DMS) and water and suitable coagulating baths are a mixture of water-DMF, water-DMS, water, or an aqueous saturated salt solution, e.g. sodium sulphate depending upon the polymer.</p> |
