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1. (WO1979000258) THE PRODUCTION OF ELECTROLYTIC MANGANESE DIOXIDE
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CLAIMS

1. In the manufacture of electrolytic manganese dioxide (EMD), a method of detaching the EMD from an electrode on which it has been anodically deposited, characterized by

cathodically polarizing said electrode.

2. The method of claim 1,

characterized in

that the current is passed through the cathodicallypolarized electrode at a current density of at least

100 A/m2 to detach a substantial part of the deposited

EMD.

3. The method of claim 2,

characterized in

that the current density during removal of the EMD is at least 500 A/m2.

4. The method of claim 1,

characterized in

that the deposited EMD is contacted with electrolyte so as to impregnate the EMD deposit with electrolyte before the electrode is cathodically polarized in Order to effect removal of the EMD.

5. The method of claim 1, 2, 3 or 4, characterized in

that removal of the EMD deposit is assisted by impact or by Vibration.

6. In the manufacture of electrolytic manganese dioxide (EMD) by electrolyzing a manganese-containing aqueous electrolyte between electrodes-, to deposit EMD on the electrode(s) acting as anode, and detaching the EMD deposit from said electrode(s) in the form of a solid product for further processing, an improved method of detaching the EMD deposit from said electrode(s), the method being

characterized by

cathodically polarizing said electrode(s).

7. The method of claim 6,

characterized in

that the electrode(s) is or are cathodically polarized by short circuiting with the other electrode(s).

8. The method of claim 6,

characterized in

that the electrode(s) is or are cathodically polarized after a rest period during which the electrode(s) is or are disconnected.

9. The method of claim 6, 7 or 8, characterized in

that removal of the EMD deposit is assisted by impact or by Vibration.

10. A process of producing electrolytic manganese dioxide (EMD), comprising electrolyzing a manganesecontaining aqueous electrolyte between electrodes to deposit EMD on the electrode(s) acting as anode, characterized by

reversing the polarity of at least the electrode(s) connected as anode to detach a substantial part of the deposited EMD from said electrode(s).

11. The process of claim 10,

characterized in

that the polarity of the electrodes is reversed periodically at regulär intervals.

12. The process of claim 11,

characterized in

that the polarity of the electrodes is reversed each time the anodic deposit reaches a thickness in the range from 50 to 150Q micron.

13. The process of claim 10,

characterized in

that the polarity of the electrodes is reversed after a given time during which an EMD deposit has built up on the anodically-polarized electrode(s) and is held reversed to detach the EMD deposit during a period shorter than said given time, whereupon the initial polarity is reinstated.

14. The process of claim 10,

characterized in

that the polarity of all electrodesis reversed in order to detach the deposited EMD from said electrode(s) acting as anode.

15. The process of claim 10,

characterized in

that the polarity of only the or those electrode(s) connected as anode to deposit EMD thereon is reversed using one or more auxiliary electrodes connected as anode during the removal phase.

16. The process of claim 10, 11, 12, 13, 14 or 15, characterized in

that the electrodes are supplied at substantially constant voltage to produce a current peak at the moment of reversal.

17. The process of claim 10, 11, 12, 13, 14, 15 or

characterized in

that electrolytic deposition of EMD is discontinued for a rest period when the anodic deposit has reached a given thickness and is resumed with reversed polarity after the rest period,

18. The process of claim 17,

characterized in

that the electrode(s) connected as anode for the deposition of EMD thereon is or are short-circuited during the rest period with the electrode(s) v/hich were connected as cathodes.

19. The process of claim 10, 11, 12, 13, 14, 15, 16, 17 or 18,

characterized in

that removal of the EMD deposit is assisted by impact or by Vibration.

20. Electrolytic manganese dioxide obtained by the method or process of any preceding claim.

21. A primary cell

characterized by

containing, as depolarizer, a powder of the electrolytic manganese dioxide of claim 20.

22. An apparatus for carrying out the process of any of Claims 10 to 19,

characterized in

that such apparatus comprises the combination of an electrolytic cell including a plurality of electrodes immersed, in use, in a manganese-containing electrolyte, a rectifier for supplying current to the electrodes, and means for reversing the polarity of the electrodes at selected times or when the anodically-deposited EMD has reached a selected thickness.