VERFAHREN ZUR HERSTELLUNG VON POROESEN DIAPHRAGMEN

摘要

1468355 Treating electrolysis diaphragms IMPERIAL CHEMICAL INDUSTRIES Ltd 24 June 1974 [18 July 1973 (2)] 34167/73 and 34168/73 Heading C7B A diaphragm e.g. of PVdC or PTFE for use in an electrolytic cell e.g. an alkali metal chloride cell, is rendered porous in situ in the cell by electrolysis or acid extraction of a particulate additive incorporated in the diaphragm during manufacture. The additive may be maize and/or potato starch, cellulose, cellulose acetate or CaCO 3 . Electrolytic removal may employ e.g. NaCl as electrolyte with a normal working voltage or current density, and a reduced electrolyte flow, e.g. 10-30% of the normal working value, at 50-60‹C. Acid extraction may involve HNO 3 , HCl, H 2 SO 4 or acetic acid containing a corrosion inhibitor for mild steel, e.g. propargyl alcohol, thiourea or KCNS. The polymeric membrane may be made from an aqueous slurry containing the polymer, additive and a permanent filler such as TiO 2 , BaSO 4 , asbestos, graphite or Al 2 O 3 by a process including calendering and lamination, and in which a strengthening gauze of polypropylene may be rolled in. The polymer may be of particle size 0À05-1Á, the removable additive 5-100Á and the filler below 10Á.