SE372378

1275825 Dry cells MATSUSHITA ELECTRIC INDUSTRIAL CO Ltd 24 July 1969 [24 July 1968 31 July 1968] 37249/69 Heading H1B A dry cell comprises a zinc casing forming an anode, a layer of electrolyte paste on the inner surface of the casing, a depolarizer mixture inside the paste layer, a cathode, in contact with the depolarizer and an ion-permeable barrier membrane of polyvinyl alcohol, polyethylene glycol or polyethylene oxide between the depolarizer and the paste layer. The membrane retains its form during storage and the early stages of discharge and prevents the passage of water and paste from the paste layer into the depolarizer and of depolarizer material into the the paste layer. When the zinc ion concentration in the electrolyte layer exceeds a predetermined value the membrane dissolves. The membrane can also include wood pulp, methyl cellulose, methyl ethyl cellulose, carboxymethyl cellulose, hydroxypropyl cellulose, starch, NH 4 Cl, ZnCl 2 , LiCl, KCl, NaCl or CaCl 2 . In the example a Leclanche type cell with the zinc can lined with an electrolyte paste layer composed of polyethylene, polyacrylamide, methyl celullose, wood pulp, starch, NH 4 Cl, ZnCl 2 and H 2 O has the depolarizer wrapped in a membrane composed of polyvinyl alcohol, silica and starch.