Horváth Sándor: Iparjogvédelmi ismeretek 5 - Iparjogvédelmi dokumentáció és információ (1982)
Mellékletek
1 561 251 PATENT SPECIFICATION (21) Application No. 7712/77 (22) Filed 23 Feb 1977 (31) Convention Application No 20786 (32) Filed 3 Mar. (33) Italy (IT) (44) Complete Specification Published 13 Feb. 1980 (51) INT. CL.3 B32B 25/02 25/10 25/16 C25B 9/Ó0 // 1/40 (52) Index at Acceptance B5N 2502 2510 2516 C7B 145 218 279 JC (72) Inventor: BRUNO MIRABELL1 (54) COVER FOR ELECTROLYTIC CELLS (71) We, INDUSTRIE PIRELLI SpA, an Italian Company of Centro Pirelli, Piazza Duca d’Aosta No 3, 20100 Milan. Italy do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: 5 This invention relates to a cover for electrolytic cells and especially to a cover for 5 electrolytic cells for the production of caustic soda and chlorine. In conventional electrolytic cells from which chlorine and caustic soda are produced from a sodium chloride solution, mercury is used as the cathode and the anode comprises one or more electrodes made from graphite. These electrodes are suspended inside the cell by 10 being inserted through holes provided in a cover which seals the cell, and are fixed in Ю predetermined positions relative to one another, to the electrolyte and to the cathode in such a way that they may be moved towards the cathode to compensate for wear during the operaton of the cell. In this way the predetermined distance between the anodes and the cathode is maintained 15 In the course of the electrolytic process, chlorine is produced at the anodes, and therefore 15 it is necessary for the cover to provide a seal for this gas, both in the area immediately adjacent the holes through which the anodes are inserted and around the periphery of the cell. In addition, the cover should be sufficiently flexible to allow it to move with the anodes, as these are moved towards the cathode, whilst continuing to act as a seal. Thus, 20 the cover is genially made of an elastomeric material and this material should be one 20 having a working life at last equivalent to that of the anodes. Thus, both the anodes and the cover are replaced at the same time. Since chlorine-generating electrolytic cells operate continuously at relatively high electrolysis temperatures, the elastomeric material must be resistant to hot nascent 25 chlorine. Moreover, since, during electrolysis, there is a strong concentration of ozone in 25 the atmosphere surrounding the cell, it is necessary that the elastomeric material should be resistant to this gas. In addition, owing to the slight vacuum which occurs during operation of the cell, the cover tends to deform by being sucked inwards. 30 When this deformation of the cover between one anode and another, or between an 30 anode and the periphery of the cell, becomes too great, leakage may occur. It is known to use natural rubber to make the surface of the cover which is exposed to nascent chlorine. It is also known to use polymers which are resistant to ozone, such as polychloroprene or copolymers and terpopolymers of ethylene and propylene to make the 35 surface of the cover which is to face outwardly of the cell. It is also known to reinforce the 35 cover with an insert of a textile material, e.g. nylon, polyester or polypropylene, to prevent it from being sucked inwards by the vacuum created in the cell during electrolysis. Technical developments in chlorine-soda cells which have occurred in the last few years include the inroduction of metal (e.g titanium) anodes which have a working life 40 approximately three times that of graphite anodes, and an increase in the dimensions of the 40 cells and hence in the distance between one anode and another and between the anodes and the periphery of the cell. These two developments have brought about the need to increase the working life of the covers from 12 to 18 months (as was required for cells having graphite anodes) to 30 to 36 45 months and to increase the resistance of the cover to deformation. 45 1.1Ю/ a .sz. melléklet (in 1 561 251 75
