Verfahren zur Herstellung von Alginatmembranen

Alginate membranes are prepared by applying a layer of an aqueous solution of an alkyl ammonium alginate to a porous substrate saturated with a solution containing polyvalent cations that form an alginate gel by reaction with the alginate solution, the alginate solution before application to the substrate being mixed with a softener, and after the gel-forming process the gel and the substrate are dried. A hygroscopic liquid which is difficultly volatile is preferably used as softener, e.g. glycerol. When the membrane is washed through e.g. in the case of filtrations, the softener is washed out by water. The partly shrunk alginate membrane on drying is detached from its connection with the substrate and the membrane together with the filter residue from the substrate removed. The membrane may be floated off the substrate. In examples, a sheet of porous filter substrate is saturated with an aqueous solution of AlCl36H2O, or La(NO3)3. 6H2O. A solution of sodium alginate and glycerine is spread over the saturated substrate, whereupon an alginate gel is formed, and the whole is air dried at ambient temperature. The alginate membranes can be used in pressure apparatus.ALSO:Alginate membranes for use as ion-exchange membranes are prepared by applying a layer of an aqueous solution of an alkyl ammonium alginate to a porous substrate, for example a paper or membrane filter saturated with a solution containing polyvalent cations that form an alginate gel by reaction with the alginate solution, the alginate solution before application to the substrate being mixed with a softener, and, after the gel-forming process, the gel and the substrate are dried by being subjected to a drying process. A hygroscopic liquid which is difficultly volatile is preferably used as softener, e.g. glycerol. When the membrane is washed through, e.g. in the case of filtrations, the softener is washed out by water. The partly shrunk alginate membrane on drying is detached from its connection with the substrate and the membrane together with the filter residue from the substrate removed. The membrane may be floated off the substrate. In Example 1, a sheet of porous filter substrate is saturated with an aqueous solution of AlCl3 6H2O. A solution of sodium alginate and glycerine is spread over the saturated substrate, whereupon an alginate gel is formed, and the whole is air dried at ambient temperature. In Example 2, La (NO3)3 6H2O is used instead of AlCl3 6H2O. The alginate membranes can be u