Patent EA-000808-B1 (EA)
Title: Asbestos-free cathodic element suitable for electrolysis of sodium chloride solution
Inventor: BACQUET GERARD
IPC: C25B11/04
Filed: 1996-12-27
Abstract: 1. An asbestos-free cathodic element obtained by deposition after filtration through a porous medium of an aqueous suspension comprising of electrically conductive fibers, at least one catonic polymer, at least one electrocatalytic agent, at least one pore-forming agent and at least one binder selected from among the flouropolymers. 2. A cathodic element as claimed in claim 1, characterized in that electrically-conductive fibers are carbon or graphite fibers. 3. A cathodic element as claimed in claim 2, characterized in that the length of fibers is at least 80%, preferably 90% corresponds to the average length +- 10%. 4. A cathodic element as claimed in any of claims 1-3, characterized in that the electrocatalytic agent is a Raney metal or a preceding product of this metal, or particles comprising ruthenium oxide, platinum oxide, iridium oxide or palladium oxide or a mixture of these oxides and particles comprising electrically conductive medium having a coating in the form of ruthenium oxide, platinum oxide, iridium oxide or palladium oxide or a mixture thereof. 5. A cathodic element as claimed in any of claims 1-4, characterized in that a porous-forming agent eliminated by a chemical or thermal treatment is selected from derivatives based on silica or systems with nanoparticles which are destroyed thermically , such as nanolattices or lattices of less 100 μm. 6. A cathodic element as claimed in any of claims 1-5, characterized in that the catonic polymer is selected from organic polymers, such as synthetic polymers selected from epychlorhydrine, polyimines, polyacrylamides or polymers of natural origin, such as, in particular, cationic amidons or cationic kieselguhrs. 7. A cathodic element as claimed in any of claims 1-6, characterized in that the catonic polymer is selected from organic polymers, such as clays, bentonites, aluminium sulfate or aluminium polychloride. 8. A cathodic element as claimed in any of claims 1-7, characterized in that a suspension further comprises fibrous material, selected from fibers based on cellulose, fibers based on cellulose with positively-charged ions, glass fibers or calcium silicate. 9. A cathodic element as claimed in any of claims 1-8, characterized in that said element is associated with a diaphragm. 10. A cathodic element as claimed in any of claims 1-8, characterized in that said element is associated with a membrane. 11. A method for preparing a cathodic element as claimed in any of claims 1-8, characterized in that comprises the following steps: (a) preparing aqueous suspension comprising of electrically conductive fibers, at least one catonic polymer, at least one electrocatalytic agent, at least one pore-forming agent and at least one binder selected from among the flouropolymers, (b) deposing said suspension on the porous medium by filtration in a programmed control vacuum, (c) dehydrating and drying, if necessary, a bed obtained thereafter, (d) agglomerating the obtained compound at a temperature higher or equal to the fuse or softening temperature of the binder. 12. A method as claimed in claim 11, characterized in that the aqueous suspension comprises 20 to 100 weight parts of the electrically conductive fibers. 13. A method as claimed in claim 11 or 12, characterized in that the aqueous suspension comprises 10 to 60 weight parts of the binder. 14. A method as claimed in claims 11-13, characterized in that the aqueous suspension comprises 30 to 200 weight parts of the pore-forming agent if the latter is eliminated by a chemical treatment, or 10 to 200 weight parts of the pore-forming agent if the latter is eliminated by a thermal treatment, or 30 to 200 weight parts if pore-forming agent is a mixture of agents which are eliminated chemically or thermally. 15. A method as claimed in claims 11-14, characterized in that the aqueous suspension comprises 20 to 200 weight parts of the electrocatalytic agent. 16. A method as claimed in claims 11-15, characterized in that the aqueous suspension comprises at least one cationic polymer in such amount that the measured turbidity of the fluid produced above after clarification of the suspension is more or equal 50, wherein the same measurement for pure water is 100. 17. A method as claimed in claims 11-16, characterized in that the aqueous suspension comprises not more than 60 weight parts on conversion to dry base of fibers base on cellulose and, in particular, 10 to 40 weight parts of such fibers, wherein said fibers can be or can not be positively charged.