A process for preparing porous and hydrophilic diaphragms for electrochemical cells, in particular diaphragms for fuel elements

摘要

1,203,487. Porous diaphragms. SIEMENS A.G. 8 Aug., 1968 [18 Aug., 1967], No. 38003/68. Headings C3C and C3P. Porous diaphragms are made by forming a solution of homo- or co-polymer (which may be cross-linked or non-cross-linked), containing both hydrophobic and hydrophilic groups, there being at least 12 carbon atoms in the molecule per hydrophilic group, and precipitating the polymer from the solution in the form of a porous plate so as to form the diaphragm which is suitable for use in an electrochemical cell. In examples solutions of copolymers of methyl or butyl methacrylate and methacrylic acid, or of hydrolysed vinyl acetate and vinyl chloride, in dimethylformamide, aq. alcoholic KOH or tetrahydrofuran were spread out on a glass plate (or injected into water) and precipitation occurred by evaporation of the solvent and/or contacting the solution with water, isopropanol, tetrahydrofuran or aq. KOH.