1276036 Starch compositions in dry batteries SOC DES ACCUMULATEURS FIXES ET DE TRACTION 21 April 1970 [22 April 1969 29 Jan 1970] 15017/70 Heading C3U [Also in Division H1] A gelatinized electrolyte suitable for use in dry zinc-manganese dioxide cells comprises an ammonium chloride-free aqueous solution of zinc chloride and an organic gelling agent consisting of starch modified so that granules of the starch have a decreased tendency to swell in aqueous solution. The modified starch may consist of corn, wheat, potato or rice starches treated with epichlorhydrin, formaldehyde, acrolein or phosphorus oxychloride. A dry battery may be formed from negative zinc electrodes 1, Fig. 2, coated on the downward face with a conductive varnish 2 and bearing on the other face a depolarizer mass 4 consisting of the zinc chloride solution, manganese dioxide and about 9% of carbon black. A separator made e.g. of kraft paper, coated on both faces with layers of the modified starch is interposed between each electrode 1 and depolarizer mass 4. The stack of cells thus formed is put under pressure by means of adhesive strips 5 and is then coated with a layer of microcrystalline wax 6. A covering of a thin sheet of plastics material or paraffined paper may be provided. Alternatively, an extensible P.V.C. sheath having initial longitudinal dimensions which are smaller than those of the stack, may be used to maintain the pressure.
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