EP1242655A1 - Asbestos-free diaphragm, comprising non-fibrous mineral particles, combination comprising same, method for obtaining same and use thereof - Google Patents

Asbestos-free diaphragm, comprising non-fibrous mineral particles, combination comprising same, method for obtaining same and use thereof

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Publication number
EP1242655A1
EP1242655A1 EP00990842A EP00990842A EP1242655A1 EP 1242655 A1 EP1242655 A1 EP 1242655A1 EP 00990842 A EP00990842 A EP 00990842A EP 00990842 A EP00990842 A EP 00990842A EP 1242655 A1 EP1242655 A1 EP 1242655A1
Authority
EP
European Patent Office
Prior art keywords
diaphragm
fibers
dispersion
diaphragm according
pore
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP00990842A
Other languages
German (de)
French (fr)
Inventor
Jean-Guy Le Helloco
Jean-Maurice Perineau
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Chloralp SAS
Original Assignee
Chloralp SAS
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Chloralp SAS filed Critical Chloralp SAS
Publication of EP1242655A1 publication Critical patent/EP1242655A1/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25B—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR
    • C25B13/00—Diaphragms; Spacing elements
    • C25B13/04—Diaphragms; Spacing elements characterised by the material

Definitions

  • the present invention relates to a diaphragm obtained by depositing a fibrous sheet free of asbestos fibers and titanate fibers, a combination comprising it. It also relates to the preparation of the diaphragm and of said combination, as well as the use of the latter for obtaining an alkali metal hydroxide solution by electrolysis of aqueous solutions of alkali metal halides.
  • the diaphragms In general, it is known to prepare the diaphragms by depositing asbestos fibers on a support, consolidating them with a polymer inert with respect to the electrolyte and optionally adding a blowing agent which is eliminated in end of preparation, so as to give the diaphragms the necessary porosity.
  • asbestos-free diaphragms have been described, obtained from suspensions comprising, in addition to the fluoropolymer used as binder and the blowing agent, a mixture of fibers and optionally a gel of 'oxohydroxide of a metal.
  • the fiber mixture comprises on the one hand, polytetrafluoroethylene fibers and on the other hand, mineral fibers which are chosen from carbon, graphite and titanate fibers. Note that the carbon fiber and graphite content must be limited so that the resulting diaphragm has an appropriate resistivity.
  • the object of the present invention is to provide a diaphragm which is both free of asbestos fibers and titanate fibers.
  • a first object of the invention relates to a microporous diaphragm capable of being obtained by filtration, through a porous support, of an aqueous dispersion devoid of asbestos fibers . and titanate fibers, comprising organic fibers, at least one binder 'selected from halogen-containing polymers, at least one blowing agent and inorganic particles of non fibrous structure.
  • a second object of the invention consists of a combination comprising said diaphragm and a precathode consisting of a fibrous sheet capable of being obtained by depositing, by filtration through a porous support, of a dispersion comprising fibers, part of which is electrically conductive, at least one binder chosen from halogenated polymers, at least one electrocatalytic agent, at least one pore-forming agent.
  • a third object of the invention relates to a process for the preparation of the diaphragm consisting in implementing the following steps: a) a dispersion is prepared comprising organic fibers, at least one binder chosen from halogenated polymers, at least one agent porogenic and inorganic particles of non-fibrous structure, b) depositing by vacuum filtration, through a porous support, the dispersion thus obtained, c) removing the liquid and, if necessary, drying the fibrous sheet formed, d) the fibrous sheet is sintered, e) the pore-forming agent is eliminated, if necessary.
  • an aqueous dispersion is prepared comprising the fibers, part of which is electrically conductive, at least one binder chosen from halogenated polymers, at least one electrocatalytic agent, at least a blowing agent, b) a fibrous sheet is deposited by filtration under programmed vacuum of said dispersion through a porous support, c) the liquid is removed and the fibrous sheet formed, constituting the precathode is dried, if necessary ) optionally sintering the precathode, e) optionally eliminating the pore-forming agent, f) depositing on the precathode, by programmed vacuum filtration, an aqueous dispersion, comprising organic fibers, at least one binder chosen from halogenated polymers, at least one pore-forming agent, mineral particles of non-fibrous structure, g) the liquid is eliminated and the diaphra
  • the present invention relates to the use of the diaphragm or of a combination comprising it, for the electrolysis of aqueous solutions of alkali metal halides.
  • the diaphragm according to the invention can be obtained by depositing, by filtration through a porous support, a dispersion comprising organic fibers, at least one binder chosen from - halogenated polymers, at least one pore-forming agent and mineral particles of non-fibrous structure.
  • the organic fibers are preferably based on a halogenated polymer chosen from homopolymers or copolymers derived at least in part from olefinic monomers substituted by fluorine atoms or substituted by a combination of fluorine atoms and at least one chlorine, bromine or iodine atoms per monomer.
  • homopolymers or fluorinated copolymers may be constituted by polymers or copolymers derived from tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, bromotrifluoroethylene
  • Such fluorinated polymers can also contain up to 75 mol% of units derived from other ethylenically unsaturated monomers containing at least as many fluorine atoms as carbon atoms, such as for example vinylidene (di) fluoride, vinyl and perfluoroalkyl esters, such as perfluoroalkoxyethylene.
  • the organic fibers are polytetrafluoroethylene fibers.
  • the organic fibers used in the context of the present invention can have variable dimensions.
  • the diameter is between 10 and 500 ⁇ m
  • the length is it that the length / diameter ratio varies between 5 and
  • fibers whose average dimensions are between 50 and 200 ⁇ m for the diameter and 1 to 10 mm for the length.
  • the content of organic fibers in the dispersion represents 100 parts by weight.
  • the contents indicated, unless otherwise stated, are expressed in dry weight of the compound concerned.
  • the diaphragm may include carbon or graphite fibers.
  • these fibers are in the form of filaments whose diameter is generally less than 1 mm and more particularly between 10 ⁇ 3 and 0.1 mm and whose length is greater than 0.5 mm and more especially between 1 and 20 mm.
  • said fibers have, according to a particular embodiment, a distribution of monodispersed length, that is to say a distribution such that the length of at least 80% and advantageously of at least 90%, of the fibers. , corresponds to the average length to within ⁇ 10%.
  • the content of carbon fibers, graphite, or their mixture, if they are present, is such that it does not give the diaphragm a conductive character (the resistivity of the diaphragm is greater than or equal to 4 ⁇ .cm). More specifically, the content is between 2 and 10 parts by weight per 100 parts by weight of organic fibers.
  • the dispersion from which the diaphragm according to the invention can be obtained further comprises a binding agent chosen from halogenated polymers.
  • the halogenated polymer used as a binder is polytetrafluoroethylene.
  • the binding agent is more particularly in the form of a dispersion of polymer particles, the dry extract of which varies between 30 and 70% by weight.
  • the content of binder represents more particularly 20 to 50 parts by weight, per 100 parts by weight of organic fibers.
  • the dispersion used to obtain the diaphragm comprises a blowing agent. It is understood that when use is made of blowing agents, the final material in principle no longer contains such agents and the porosity of said material, under the effect of the decomposition or elimination of these blowing agents, is controlled.
  • pore-forming agents By way of illustration of the pore-forming agents, mention may be made of mineral salts, which can then be eliminated chemically (leaching, decomposition) or thermally.
  • the blowing agent is chosen from the compounds which can be eliminated chemically or thermally, or a mixture of such compounds.
  • the blowing agent is chosen from compounds which can be eliminated by chemical means.
  • alkali or alkaline earth salts such as halides, sulfates, sulfonates, bisulfites, phosphates, carbonates, bicarbonates. Mention may also be made of amphoteric alumina. Still in this category of blowing agent, a preferred variant consists in using silica. This pore-forming agent is subsequently removed with an alkaline treatment, during the first use of the material (or the diaphragm) or before it.
  • silicas are suitable for this use and more particularly precipitated silicas or combustion silicas.
  • the specific surface of the silica used is more particularly between 100 and 300 m 2 / g.
  • the quantity and particle size of the blowing agents are closely linked to the application for which the materials are intended. Simply as an order of magnitude, the particle size of the blowing agents most often varies between 1 and 50 ⁇ m and preferably between 1 and 15 ⁇ m. As for the quantity, and always by way of illustration, it is chosen as a function of the desired porosity, which can reach 90% or even more (according to standard ASTM D 276-72).
  • the pore-forming agent is chosen from compounds which can be eliminated thermally, such as for example nanoparticulate systems (latex of size less than 100._nm).
  • the content of blowing agent is more particularly between 20 and 100 parts by weight, per 100 parts by weight of organic fibers.
  • the diaphragm includes mineral particles of non-fibrous structure.
  • said particles have a particle size such that their average size is less than 150 ⁇ m. More specifically, the average size of particles is at least 10 ⁇ m. According to a preferred embodiment of the invention, the average particle size is between 10 and 50 ⁇ m.
  • the particles are based on hydrated silicates comprising at least magnesium and / or aluminum and / or potassium.
  • silicates and without intending to be limited thereto, mention may be made of talc, kaolin, mica, attapulgite, vermiculite.
  • the mineral particles used in the composition of the dispersion have a platelet structure.
  • the particles used are more precisely particles of mica.
  • the content of mineral particles in the dispersion more particularly, between 30 and 100 parts by weight, per 100 parts by weight of organic fibers.
  • the dispersion from which the diaphragm according to the invention can be obtained can comprise additives conventional in the field, such as for example at least one surfactant, or at least one thickening agent, or mixtures thereof.
  • suitable surfactants which are preferably nonionic surfactants, mention may be made of ethoxylated alcohols or fluorocarbon compounds with functionalized groups, alone or as a mixture; these alcohols or these fluorocarbon compounds generally have carbon chains from C 6 to C Q.
  • ethoxylated alcohols are used which are ethoxylated alkylphenols, such as in particular octoxynols.
  • the amount introduced into the dispersion generally represents from 1 to 10 parts by weight, per 100 parts by weight of organic fibers.
  • thickening agents As regards the thickening agents, according to the present invention is meant a compound which increases the viscosity of the dispersion and which exhibits water-retaining properties.
  • Natural or synthetic polysaccharides are generally used. Mention may in particular be made of the biopolymers obtained by fermentation of a carbohydrate under the action of microorganisms.
  • xanthan gum is used. Xanthan gum is synthesized using bacteria belonging to the genus Xanthomonas and more particularly to the species described in Bergey's manual of determination bacteriology (8th edition - 1974 - Williams N. Wilkins C ° Baltimore). The species Xanthomonas campesths is particularly suitable for the synthesis of xanthan gum.
  • bacteria belonging to the genus Arthrobacter to the genus Erwinia, to the genus Azobacter, to the genus Agrobacter or to fungi belonging to the genus Sclerotium.
  • the dispersion comprises thickening agents
  • their content generally represents between 1 and 10 parts by weight per 100 parts by weight of organic fibers. It should be noted that the overall dry matter content of the dispersion from which the diaphragm can be obtained is usually between 1 and 10% by weight.
  • the dispersion which has just been described is deposited by filtration through a porous support.
  • said support can be either another fibrous sheet (also called precathode), which will be described in detail below, or a metal surface having openings whose size is between 20 ⁇ m and 5 mm (also called cathode elementary), or the combination of these two types of support.
  • a metal surface used as a porous support can more particularly consist of fabrics or grids whose void, the perforations or the porosity can be included in the range indicated above. It can likewise have one or more flat or cylindrical surfaces, commonly called “thermowell", having an open surface.
  • This metallic, conductive surface can, among other things, be composed of iron, nickel, alloys such as stainless steel, or any other material treated so as to make it even less sensitive to the corrosivity of the medium, such as by example of the iron on which a nickel deposit would have been made.
  • the present invention relates to a combination comprising the diaphragm and another fibrous sheet (precathode) capable of being obtained by deposition by filtration through a porous support of a dispersion comprising fibers, part of which is electrically conductive, at least one binder chosen from halogenated polymers, at least one electrocatalytic agent and at least one pore-forming agent.
  • a porous support on which this other fibrous sheet is deposited is constituted by a metal surface having openings the size of which is between 20 ⁇ m and 5 mm (elementary cathode). The characteristics concerning the elementary cathode detailed previously remain valid.
  • the association is such that one finds from one face towards the other, the diaphragm according to the invention, the precathode as defined above, the elementary cathode.
  • the precathode preferably has a resistivity equal to or less than 0.4 ⁇ .cm.
  • said sheet comprises electrically conductive fibers. These can be chosen from intrinsically conductive fibers or else treated so as to make them such.
  • these fibers are in the form of filaments whose diameter is generally less than 1 mm and more particularly between 10 "3 and 0.1 mm and whose length is greater than 0.5 mm and more especially between 1 and 20 mm.
  • the fibers used in the composition of the sheet are intrinsically conductive fibers, such as in particular carbon or graphite fibers.
  • the conductive fibers preferably have a distribution of monodispersed length, that is to say a distribution such that the length of at least 80% and advantageously at least 90%, of the fibers, corresponds to the length average to within ⁇ 10%.
  • fibers from material which is not electrically conductive but which are made conductive by treatment it is possible to use fibers from material which is not electrically conductive but which are made conductive by treatment.
  • material which is not electrically conductive but which are made conductive by treatment By way of example, mention may be made of zirconia fibers made conductive by chemical or electrochemical deposition of a metal such as nickel.
  • the content of conductive fibers is determined so that the overall resistivity of the precathode fibrous web is less than or equal to 0.4 ⁇ .cm.
  • the dispersion more particularly comprises 20 to 100 parts by weight of conductive fibers. According to a preferred variant, the content of conductive fibers is between 50 and 90 parts by weight.
  • the dispersion may likewise contain, in association with the conductive fibers, non-conductive fibers. These fibers are generally in the form of filaments whose size is similar to that given for the conductive fibers.
  • non-conductive fibers By way of illustration of non-conductive fibers, mention may in particular be made of organic fibers, such as polypropylene or polyethylene fibers, optionally halogenated and in particular fluorinated, polyhalo-vinylidene fibers and in particular polyvinylidene fluoride, or even fibers of fluorinated polymers.
  • organic fibers such as polypropylene or polyethylene fibers
  • Such fibers when present, are preferably polytetrafluoroethylene fibers. Reference may be made to the corresponding passage in the description, giving details of the structure of such fibers.
  • the proportion of non-conductive fibers is such that the resistivity of the precathode is at most 0.4 ⁇ .cm.
  • the content of non-conductive fibers when used here, can represent up to 90% by weight and preferably be between 20 and 70% by weight of the mixture of conductive fibers and non-conductive fibers.
  • the dispersion also comprises at least one binder chosen from halogenated polymers. What has been said about the binder used in the composition of the dispersion from which the diaphragm can be obtained remains valid.
  • the binder is polytetrafluoroethylene.
  • the content of binder in the dispersion is more particularly between 10 and 60 parts by dry weight.
  • the dispersion from which this precathode layer is obtained further comprises at least one electrocatalytic agent.
  • electrocatalytic agent Any type of metal known in the art can be used as the electrocatalytic agent to activate the electrolysis reaction.
  • a Raney metal is used, such as preferably nickel, or else a precursor of this Raney metal, consisting in fact of an alloy based on said metal associated with another than one can easily eliminate. More particularly, it is an alloy comprising aluminum which can be leached for example by a basic treatment.
  • This type of electrocatalytic agent has in particular been described in European patent EP 296 076 to which reference may be made on this subject.
  • electrocatalytic agent particles comprising an oxide of ruthenium, platinum, iridium, palladium, or a mixture of these oxides.
  • mixture particles comprising in themselves a mixture of oxides, but also particles, based on a metal oxide, mixed with other particles comprising a different oxide.
  • Said agent can also be in the form of particles consisting of an electrically conductive support, comprising a coating in the form of ruthenium oxide, platinum, iridium, palladium; these oxides being alone or in admixture in the sense which has just been explained. It would not be departing from the scope of the present invention to combine these two variants, that is to say particles based on oxide or coated with an oxide.
  • the electrocatalytic agent according to the invention is in the form of a coating of a support such as in particular iron, cobalt, nickel, Raney iron, Raney cobalt, Raney nickel, the elements of columns IVA and VA of the periodic table, carbon, graphite.
  • a support such as in particular iron, cobalt, nickel, Raney iron, Raney cobalt, Raney nickel, the elements of columns IVA and VA of the periodic table, carbon, graphite.
  • the content of electrocatalytic agent in the dispersion is more precisely between 20 and 200 parts by weight. Preferably, it is between 60 and 120 parts by weight.
  • the dispersion likewise comprises a blowing agent. What has been indicated above concerning the nature of this blowing agent remains valid, both for the general definition of this compound and for the preferred variants, and will not be repeated here.
  • this content is generally between 30 and 200 parts. More particularly, the amount of blowing agent is between 30 and 100 parts by weight.
  • the amount of this type of compound is more particularly between 10 and 200 parts by weight.
  • said sheet comprises a cationic polymer.
  • suitable cationic polymers two categories of polymers may be mentioned, organic polymers and inorganic polymers, the latter being able to be used alone or as a mixture.
  • polymers from the first category synthetic polymers chosen from epychlorohydrin, polyimines, polyacrylamides, polyacrylamines are polymers capable of entering into the composition of the suspension used in the invention .
  • Polymers of natural origin such as, in particular, cationic starches and cationic guars are compounds which are suitable for the invention.
  • inorganic polymers mention may be made, without intending to be limited, of clays, bentonites, aluminum sulphate, aluminum polychloride.
  • the polymer is chosen from polyacrylamines, sold in particular under the name FLOERGER® by the company Floerger, cationic starches, such as hot-soluble cationic starches (cationic HI-CAT® starches, sold by the company Roquette), as well as cold soluble cationic starches, of the type of cationic guars sold under the brand MEYPRO® by the company Meyhall; these polymers can be present alone or as a mixture.
  • the content of cationic polymer is such that the measurement of the turbidite of the supernatant liquid after settling of the dispersion is greater than or equal to 50, preferably 75 (the measurement of the turbidite is carried out by transmission to 630 nm on a Methrom 662 Photometer® type turbidimeter; that of pure water gives a value of 100). Furthermore, the content of cationic polymer is such that there is no excessive difficulty in filtering the suspension.
  • the content varies between 10 and 80 parts by dry weight, and preferably; between 20 and 40 parts by dry weight.
  • the dispersion of the precathode layer preferably comprises conductive fibers (without non-conductive fibers), a blowing agent, a cationic polymer, and optionally other additives.
  • fibrous material more particularly the type of fibers ⁇ based on cellulose, or cellulose-based fibers which have been given a positive ionic charge.
  • the suspension comprises fibers based on cellulose, charged or not positively charged, as fibrous material, their content is at most 60 parts by dry weight, and preferably between 10 and 40 parts by weight.
  • the dispersion may also include usual additives, but not compulsory, such as surfactants, thickening agents. Those used in the composition of the dispersion allowing access to the diaphragm according to the invention can be used to obtain the first layer
  • the diaphragm can be obtained by implementing the following steps: a) a dispersion is prepared comprising organic fibers, at least one binder chosen from halogenated polymers, at least one pore-forming agent and mineral particles of non-fibrous structure, b) depositing by vacuum filtration, and through a porous support, the dispersion thus obtained, c) removing the liquid and, if necessary, drying the fibrous web formed, d) sintering the fibrous web, e) eliminates, if necessary, the blowing agent.
  • the preparation of the dispersion is carried out by mixing the various elements which constitute it, in an aqueous solution.
  • the contents of the various components of the dispersion are such that they satisfy the conditions indicated above.
  • Stage b) of filtration is carried out under vacuum.
  • this vacuum is programmed.
  • the sheet is deposited on the porous support by programmed vacuum filtration.
  • the filtration of the dispersion can be carried out vertically, which represents a particularly advantageous advantage for exploitation on an industrial scale, or horizontally.
  • step d) of filtration the vacuum is maintained so as to eliminate the liquid.
  • the resulting sheet can be dried, for example by bringing the temperature to a value below 150 ° C.
  • the resulting fibrous web is then the subject of a sintering or consolidation step (step d).
  • the fibrous sheet constituting the diaphragm according to the invention can, if necessary, be the subject of a step of elimination of the pore-forming agent.
  • step e) takes place by carrying out a chemical treatment of the diaphragm, of the sheet or of their combination, with an alkaline solution.
  • step e) can be carried out by contacting the diaphragm with an alkali metal hydroxide solution having a concentration of between 40 and 200 g / l. Furthermore, the temperature is more particularly between 20 and 95 ° C.
  • step e) can take place before the use of the diaphragm or in situ, that is to say during the first use of the diaphragm or of the association.
  • an aqueous dispersion is prepared comprising the fibers, part of which is electrically conductive, at least one binder chosen from halogenated polymers, at least one electrocatalytic agent, at least one pore-forming agent, b) a fibrous sheet is deposited by filtration under programmed vacuum of said dispersion through a porous support, c) the liquid is removed and dries, if necessary, the fibrous sheet formed, constituting the precathode, d) optionally sintering the precathode, e) optionally eliminating the pore-forming agent, f) depositing on the precathode, by filtration under programmed vacuum, an aqueous dispersion, comprising organic fibers, at least one binder chosen from halogenated polymers, at least one pore-forming agent, mineral particles of non-fibrous structure, g) the liquid is eliminated and dried possibly the diaphragm
  • the first step is carried out in a similar manner to that used for the preparation of the dispersion used to obtain the diaphragm.
  • this dispersion is deposited on a metal support having openings whose size is between 20 ⁇ m and 5 mm.
  • the deposition by filtration of the dispersion takes place under a programmed vacuum, the conditions of which have been explained for the deposition of the sheet constituting the diaphragm.
  • step c) The conditions of step c) are moreover similar to those implemented for obtaining the diaphragm.
  • the precathode layer can be sintered by heating to a temperature greater than or equal to the softening temperature of the binder.
  • the elimination of the pore-forming agent can take place at this stage, according to a method identical to that described when obtaining the diaphragm. However, preferably, this step is only carried out at the end of the process (step i).
  • Steps f) to i) correspond to those described above for obtaining the diaphragm.
  • a final object of the invention consists of the use of the diaphragm or of a combination comprising it, in the electrolysis of aqueous solutions of alkali metal halides, more particularly of sodium chloride solutions.
  • a dispersion is prepared from the following elements: ° permuted water, the amount of which is calculated to obtain approximately 4 liters of dispersion and a dry extract of approximately 3.2% by weight, ° 100 parts by weight of carbon fibers whose diameter is approximately
  • the suspension obtained is filtered, after having stirred it, under vacuum, on a braided iron mesh and rolled steel type "Gantois" whose opening is 2 mm and whose wire diameter is 2 mm, the deposition area being 1.21 dm 2 .
  • the vacuum is established to reach in stages a value between 300.10 2 and 450.10 2 Pa.
  • the maximum vacuum is maintained for approximately 15 minutes.
  • the whole is then dried.
  • Triton X 100 from the company Rohm and Haas.
  • the required volume of dispersion is taken so that it presents the quantity of dry extract that we intend to deposit (here 1.3 kg / m 2 ; 1.53 kg / m 2 ; 1.8 kg / m m 2 ).
  • the dispersion is carried out under programmed vacuum on the precathode layer obtained previously. The vacuum is established to reach in stages a value between 300.10 2 and 450.10 2 Pa. The maximum vacuum is maintained for approximately 15 minutes. The combination is then sintered at 350 ° C in air for 7 minutes.
  • the cell operating conditions are as follows D Current density: 2.5 kA / m 2 ° Temperature: 85 ° C
  • H is the hydraulic head reduced to a flow rate of 100.
  • ⁇ It corresponds to the ratio of the difference between the levels of Panolyte and catholyte and the flow rate (expressed in ml / h); the ratio being multiplied by 100.
  • RF is the Faraday yield (sodium hydroxide concentration: 3N).

Abstract

The invention concerns a microporous diaphragm obtainable by filtering through a porous support, an aqueous dispersion free of asbestos fibres and titanate fibres, comprising organic fibres, at least a binding agent selected among halogenated polymers, at least a pore-forming agent and mineral particles with non-fibrous structure. The invention also concerns a combination comprising said diaphragm and a fibrous mat obtainable by filtration deposit through a porous support of a dispersion comprising fibres whereof part is electrically conductive, at least a binding agent selected among halogenated polymers, at least an electrolytic agent, at least a pore-forming agent. The invention further concerns the preparation of the diaphragm and the combination, and the use thereof to obtain an alkali metal hydroxide solution by electrolysis of aqueous alkali metal halide solutions.

Description

DIAPHRAGME EXEMPT D'AMIANTE, COMPRENANT DES PARTICULES ASBESTOS-FREE DIAPHRAGM COMPRISING PARTICLES
MINERALES NON FIBREUSES, ASSOCIATION LE COMPRENANT, SONNON-FIBROUS MINERALS, ASSOCIATION INCLUDING SAME
OBTENTION ET SON UTILISATIONOBTAINING AND USING IT
La présente invention a pour objet un diaphragme obtenu par dépôt d'une nappe fibreuse exempte de fibres d'amiante et de fibres de titanate, une association le comprenant. Elle concerne de même la préparation du diaphragme et de ladite association, ainsi que l'utilisation de ces derniers pour l'obtention de solution d'hydroxyde de métal alcalin par électrolyse de solutions aqueuses d'halogénures de métal alcalin.The present invention relates to a diaphragm obtained by depositing a fibrous sheet free of asbestos fibers and titanate fibers, a combination comprising it. It also relates to the preparation of the diaphragm and of said combination, as well as the use of the latter for obtaining an alkali metal hydroxide solution by electrolysis of aqueous solutions of alkali metal halides.
De manière générale, il est connu de préparer les diaphragmes en déposant sur un support, des fibres d'amiante, en les consolidant par un polymère inerte vis-à- vis de l'électrolyte et en ajoutant éventuellement un agent porogène qui est éliminé en fin de préparation, de manière à conférer aux diaphragmes la porosité nécessaire.In general, it is known to prepare the diaphragms by depositing asbestos fibers on a support, consolidating them with a polymer inert with respect to the electrolyte and optionally adding a blowing agent which is eliminated in end of preparation, so as to give the diaphragms the necessary porosity.
Ces diaphragmes, s'ils ont des avantages en matière de performances, présentent toutefois l'inconvénient de comprendre, parmi leurs éléments constitutifs, des fibres d'amiante.These diaphragms, if they have performance advantages, have the disadvantage of including, among their constituent elements, asbestos fibers.
• Dans le brevet européen EP 41 917, on a décrit des diaphragmes exempts d'amiante et obtenus à partir de suspensions comprenant, outre le polymère fluoré utilisé en tant que liant et l'agent porogène, un mélange de fibres et éventuellement un gel d'oxohydroxyde d'un métal. Le mélange de fibres comprend d'une part, des fibres de polytétrafluoroéthylène et d'autre part, des fibres minérales qui sont choisies parmi les fibres de carbone, de graphite et de titanate. Notons que la teneur en fibres de carbone et de graphite doit être limitée de manière à ce que le diaphragme résultant possède une résistivité appropriée.• In European patent EP 41 917, asbestos-free diaphragms have been described, obtained from suspensions comprising, in addition to the fluoropolymer used as binder and the blowing agent, a mixture of fibers and optionally a gel of 'oxohydroxide of a metal. The fiber mixture comprises on the one hand, polytetrafluoroethylene fibers and on the other hand, mineral fibers which are chosen from carbon, graphite and titanate fibers. Note that the carbon fiber and graphite content must be limited so that the resulting diaphragm has an appropriate resistivity.
La présente invention a pour objet de proposer un diaphragme qui soit à la fois exempt de fibres d'amiante et de fibres de titanate.The object of the present invention is to provide a diaphragm which is both free of asbestos fibers and titanate fibers.
Ainsi, un premier objet de l'invention concerne un diaphragme microporeux susceptible d'être obtenu par filtration au travers d'un support poreux, d'une dispersion aqueuse dépourvue de fibres d'amiante .et de fibres de titanate, comprenant des fibres organiques, au moins un liant 'choisi parmi les polymères halogènes, au moins un agent porogène et des particules minérales de structure non fibreuse. Un deuxième objet de l'invention est constitué par une association comprenant ledit diaphragme et une précathode constituée d'une nappe fibreuse susceptible d'être obtenue par dépôt par filtration à travers un support poreux, d'une dispersion comprenant des fibres dont une partie est conductrice de l'électricité, au moins un liant choisi parmi les polymères halogènes, au moins un agent électrocatalytique, au moins un agent porogène.Thus, a first object of the invention relates to a microporous diaphragm capable of being obtained by filtration, through a porous support, of an aqueous dispersion devoid of asbestos fibers . and titanate fibers, comprising organic fibers, at least one binder 'selected from halogen-containing polymers, at least one blowing agent and inorganic particles of non fibrous structure. A second object of the invention consists of a combination comprising said diaphragm and a precathode consisting of a fibrous sheet capable of being obtained by depositing, by filtration through a porous support, of a dispersion comprising fibers, part of which is electrically conductive, at least one binder chosen from halogenated polymers, at least one electrocatalytic agent, at least one pore-forming agent.
Un troisième objet de l'invention a trait à un procédé de préparation du diaphragme consistant à mettre en œuvre les étapes suivantes : a) on prépare une dispersion comprenant des fibres organiques, au moins un liant choisi parmi les polymères halogènes, au moins un agent porogène et des particules minérales de structure non fibreuse, b) on dépose par filtration sous vide, à travers un support poreux, la dispersion ainsi obtenue, c) on élimine le liquide et, si nécessaire, on sèche la nappe fibreuse formée, d) on fritte la nappe fibreuse, e) on élimine, si nécessaire, l'agent porogène.A third object of the invention relates to a process for the preparation of the diaphragm consisting in implementing the following steps: a) a dispersion is prepared comprising organic fibers, at least one binder chosen from halogenated polymers, at least one agent porogenic and inorganic particles of non-fibrous structure, b) depositing by vacuum filtration, through a porous support, the dispersion thus obtained, c) removing the liquid and, if necessary, drying the fibrous sheet formed, d) the fibrous sheet is sintered, e) the pore-forming agent is eliminated, if necessary.
L'obtention de l'association précitée constitue un autre objet de la présente invention. Cette dernière consiste à mettre en œuvre les étapes suivantes : a) on prépare une dispersion aqueuse comprenant les fibres, dont une partie est conductrice de l'électricité, au moins un liant choisi parmi les polymères halogènes, au moins un agent électrocatalytique, au moins un agent porogène, b) on dépose une nappe fibreuse par filtration sous vide programmé de ladite dispersion à travers un support poreux, c) on élimine le liquide et l'on sèche, si nécessaire, la nappe fibreuse formée, constituant la précathode, d) on fritte éventuellement la précathode, e) on élimine éventuellement l'agent porogène, f) on dépose sur la précathode, par filtration sous vide programmé, une dispersion aqueuse, comprenant des fibres organiques, au moins Un liant choisi parmi les polymères halogènes, au moins un agent porogène, des particules minérales de structure non fibreuse, g) on élimine le liquide et l'on sèche éventuellement le diaphragme ainsi formé, h) on fritte l'ensemble, i) on élimine si nécessaire l'agent porogène.Obtaining the above-mentioned association constitutes another object of the present invention. The latter consists in implementing the following steps: a) an aqueous dispersion is prepared comprising the fibers, part of which is electrically conductive, at least one binder chosen from halogenated polymers, at least one electrocatalytic agent, at least a blowing agent, b) a fibrous sheet is deposited by filtration under programmed vacuum of said dispersion through a porous support, c) the liquid is removed and the fibrous sheet formed, constituting the precathode is dried, if necessary ) optionally sintering the precathode, e) optionally eliminating the pore-forming agent, f) depositing on the precathode, by programmed vacuum filtration, an aqueous dispersion, comprising organic fibers, at least one binder chosen from halogenated polymers, at least one pore-forming agent, mineral particles of non-fibrous structure, g) the liquid is eliminated and the diaphragm thus formed is optionally dried, h) it is fried the whole, i) if necessary, the blowing agent is eliminated.
Enfin, la présente invention concerne l'utilisation du diaphragme ou de l'association le comprenant, pour l'électrolyse de solutions aqueuses d'halogénures de métal alcalin.Finally, the present invention relates to the use of the diaphragm or of a combination comprising it, for the electrolysis of aqueous solutions of alkali metal halides.
On a constaté de manière surprenante que l'emploi de particules de structure non fibreuse, associées à des fibres organiques, à base notamment d'un polymère halogène, permettait d'obtenir un diaphragme dont les propriétés mécaniques, telles que les résistances à l'allongement, à la rupture, sont similaires à celles obtenues avec des diaphragmes comprenant des fibres organiques et minérales. De plus, les caractéristiques de porosité correspondent aussi aux critères d'utilisation dans les cellules d'électrolyse de solutions aqueuses d'halogénures de métaux alcalins.It has been found, surprisingly, that the use of particles of non-fibrous structure, associated with organic fibers, based in particular on a halogenated polymer, makes it possible to obtain a diaphragm whose mechanical properties, such as resistance to elongation, at break, are similar to those obtained with diaphragms comprising organic and mineral fibers. In addition, the porosity characteristics also correspond to the criteria for use in the electrolysis cells of aqueous solutions of alkali metal halides.
Or rien ne conduisait l'homme de l'art à imaginer qu'un diaphragme ne comprenant que des fibres organiques et des particules minérales de structure non fibreuse, puisse atteindre de tels objectifs.However, nothing led those skilled in the art to imagine that a diaphragm comprising only organic fibers and mineral particles of non-fibrous structure could achieve such objectives.
En effet, auparavant, on avait cherché à remplacer les fibres d'amiante par des matériaux de structure fibreuse, c'est-à-dire présentant un rapport longueur / diamètre d'au moins 10, comme notamment les fibres de titanate. Il était donc loin d'être évident pour l'homme de l'art que des particules de morphologie aussi radicalement différente de celle des fibres, puissent avoir des propriétés de renfort satisfaisantes.Indeed, before, we had sought to replace asbestos fibers with fibrous structure materials, that is to say having a length / diameter ratio of at least 10, such as in particular titanate fibers. It was therefore far from obvious to those skilled in the art that particles of morphology as radically different from that of the fibers could have satisfactory reinforcing properties.
Mais d'autres caractéristiques et avantages de la présente invention apparaîtront plus clairement à la lecture de la description et des exemples qui vont suivre. Ainsi que cela a été indiqué auparavant, le diaphragme selon l'invention est susceptible d'être obtenu par dépôt par filtration à travers un support poreux, d'une dispersion comprenant des fibres organiques, au moins un liant choisi parmi les - polymères halogènes, au moins un agent porogène et des particules minérales de structure non fibreuse. Les fibres organiques sont de préférence à base d'un polymère halogène choisi parmi les homopolymères ou copolymères dérivés au moins en partie de monomères oléfiniques substitués par des atomes de fluor ou substitués par une combinaison d'atomes de fluor et de l'un au moins des atomes de chlore, de brome ou d'iode par monomère. Des exemples d'homopolymères ou de copolymères fluorés peuvent être constitués par des polymères ou copolymères dérivés de tétrafluoroéthylène, d'hexafluoropropylène, de chlorotrifluoroéthylène, de bromotrifluoroéthylèneHowever, other characteristics and advantages of the present invention will appear more clearly on reading the description and the examples which follow. As indicated above, the diaphragm according to the invention can be obtained by depositing, by filtration through a porous support, a dispersion comprising organic fibers, at least one binder chosen from - halogenated polymers, at least one pore-forming agent and mineral particles of non-fibrous structure. The organic fibers are preferably based on a halogenated polymer chosen from homopolymers or copolymers derived at least in part from olefinic monomers substituted by fluorine atoms or substituted by a combination of fluorine atoms and at least one chlorine, bromine or iodine atoms per monomer. Examples of homopolymers or fluorinated copolymers may be constituted by polymers or copolymers derived from tetrafluoroethylene, hexafluoropropylene, chlorotrifluoroethylene, bromotrifluoroethylene
De tels polymères fluorés peuvent aussi contenir jusqu'à 75 moles % de motifs dérivés d'autres monomères éthyléniquement insaturés contenant au moins autant d'atomes de fluor que d'atomes de carbone, comme par exemple le (di)fluorure de vinylidène, les esters de vinyle et de perfluoroalkyle, tel que le perfluoroalcoxyéthylène.Such fluorinated polymers can also contain up to 75 mol% of units derived from other ethylenically unsaturated monomers containing at least as many fluorine atoms as carbon atoms, such as for example vinylidene (di) fluoride, vinyl and perfluoroalkyl esters, such as perfluoroalkoxyethylene.
On peut naturellement utiliser dans l'invention plusieurs homopolymères ou copolymères fluorés tels que définis ci-avant. II va sans dire qu'on ne sortirait pas du cadre de la présente invention en associant à ces polymères fluorés une faible quantifié, par exemple jusqu'à 10 ou 15 % en poids, de polymère dont la molécule ne renferme pas d'atomes de fluor, comme par exemple du polypropylène. Selon un mode de réalisation préféré de l'invention, les fibres organiques sont des fibres de polytétrafluoroéthylène.It is naturally possible to use in the invention several homopolymers or fluorinated copolymers as defined above. It goes without saying that it would not be departing from the scope of the present invention to combine with these fluorinated polymers a low quantification, for example up to 10 or 15% by weight, of polymer whose molecule does not contain atoms of fluorine, such as polypropylene. According to a preferred embodiment of the invention, the organic fibers are polytetrafluoroethylene fibers.
Les fibres organiques utilisées dans le cadre de la présente invention peuvent présenter des dimensions variables. Généralement, le diamètre est compris entre 10 et 500 μm, la longueur est elle que le rapport longueur/diamètre évolue entre 5 etThe organic fibers used in the context of the present invention can have variable dimensions. Generally, the diameter is between 10 and 500 μm, the length is it that the length / diameter ratio varies between 5 and
500. De préférence, on recourt à des fibres dont les dimensions moyennes sont comprises entre 50 et 200 μm pour le diamètre et 1 à 10 mm pour la longueur.500. Preferably, use is made of fibers whose average dimensions are between 50 and 200 μm for the diameter and 1 to 10 mm for the length.
Leur préparation est décrite notamment dans le brevet américain 4 444 640.Their preparation is described in particular in US patent 4,444,640.
Par convention, la teneur en fibres organiques dans la dispersion représente 100 parties en poids. Dans ce qui va suivre, les teneurs indiquées, sauf mention contraire, sont exprimées en poids sec du composé concerné.By convention, the content of organic fibers in the dispersion represents 100 parts by weight. In what follows, the contents indicated, unless otherwise stated, are expressed in dry weight of the compound concerned.
Si nécessaire, le diaphragme peut comprendre des fibres de carbone ou de graphite.If necessary, the diaphragm may include carbon or graphite fibers.
Plus particulièrement, ces fibres se présentent sous une forme de filaments dont le diamètre est généralement inférieur à 1 mm et plus particulièrement compris entre 10~3 et 0,1 mm et dont la longueur est supérieure à 0,5 mm et plus spécialement comprise entre 1 et 20 mm.More particularly, these fibers are in the form of filaments whose diameter is generally less than 1 mm and more particularly between 10 ~ 3 and 0.1 mm and whose length is greater than 0.5 mm and more especially between 1 and 20 mm.
Par ailleurs, lesdites fibres présentent, selon un mode de réalisation particulier, une distribution de longueur monodispersée, c'est-à-dire une distribution telle que la longueur d'au moins 80 % et avantageusement d'au moins 90 %, des fibres, correspond à la longueur moyenne à ± 10 % près.Furthermore, said fibers have, according to a particular embodiment, a distribution of monodispersed length, that is to say a distribution such that the length of at least 80% and advantageously of at least 90%, of the fibers. , corresponds to the average length to within ± 10%.
La teneur en fibres de carbone, de graphite, ou leur mélange, si elles sont présentes, est telle qu'elle ne confère pas au diaphragme un caractère conducteur (la résistivité du diaphragme est supérieure ou égale à 4 Ω.cm). Plus précisément, la teneur est comprise entre 2 et 10 parties en poids pour 100 parties en poids de fibres organiques.The content of carbon fibers, graphite, or their mixture, if they are present, is such that it does not give the diaphragm a conductive character (the resistivity of the diaphragm is greater than or equal to 4 Ω.cm). More specifically, the content is between 2 and 10 parts by weight per 100 parts by weight of organic fibers.
La dispersion à partir de laquelle le diaphragme selon l'invention est susceptible d'être obtenu, comprend de plus un agent liant choisi parmi les polymères halogènes.The dispersion from which the diaphragm according to the invention can be obtained, further comprises a binding agent chosen from halogenated polymers.
Ce qui vient d'être décrit au sujet de la nature du polymère halogène constituant les fibres organiques, reste valable et ne sera pas repris ici.What has just been described concerning the nature of the halogenated polymer constituting the organic fibers, remains valid and will not be repeated here.
Selon un mode de réalisation préféré de l'invention, le polymère halogène employé en tant que liant, est le polytétrafluoroéthylène.According to a preferred embodiment of the invention, the halogenated polymer used as a binder, is polytetrafluoroethylene.
L'agent liant se présente plus particulièrement sous la forme d'une dispersion de particules de polymère dont l'extrait sec varie entre 30 et 70% en poids. La teneur en agent liant représente plus particulièrement 20 à 50 parties en poids, pour 100 parties en poids de fibres organiques.The binding agent is more particularly in the form of a dispersion of polymer particles, the dry extract of which varies between 30 and 70% by weight. The content of binder represents more particularly 20 to 50 parts by weight, per 100 parts by weight of organic fibers.
Comme cela a été indiqué auparavant, la dispersion mise en œuvre pour l'obtention du diaphragme comprend un agent porogène. Il est entendu que lorsqu'il est fait appel à des agents porogènes, le matériau final ne renferme en principe plus de tels agents et la porosité dudit matériau, sous l'effet de la décomposition ou de l'élimination de ces agents porogènes, est contrôlée.As indicated above, the dispersion used to obtain the diaphragm comprises a blowing agent. It is understood that when use is made of blowing agents, the final material in principle no longer contains such agents and the porosity of said material, under the effect of the decomposition or elimination of these blowing agents, is controlled.
A titre d'illustration des agents porogènes on peut mentionner des sels minéraux, qui pourront être ensuite éliminés par voie chimique (lixiviation, décomposition) ou par voie thermique.By way of illustration of the pore-forming agents, mention may be made of mineral salts, which can then be eliminated chemically (leaching, decomposition) or thermally.
L'agent porogène est choisi parmi les composés que l'on peut éliminer par voie chimique ou par voie thermique, ou un mélange de tels composés.The blowing agent is chosen from the compounds which can be eliminated chemically or thermally, or a mixture of such compounds.
Selon un premier mode de réalisation de l'invention, l'agent porogène est choisi parmi les composés éliminables par voie chimique.According to a first embodiment of the invention, the blowing agent is chosen from compounds which can be eliminated by chemical means.
A titre de tels composés, on peut notamment citer les sels alcalins ou alcalino- terreux, tels que les halogénures, les sulfates, les sulfonates, les bisulfites, les phosphates, les carbonates, les bicarbonates. On peut également citer l'alumine amphotère. Toujours dans cette catégorie d'agent porogène, une variante préférée consiste à utiliser la silice. Cet agent porogène est éliminé par la suite avec un traitement alcalin, lors de la première utilisation du matériau (ou du diaphragme) ou avant celle- ci.Mention may in particular be made, as such compounds, of alkali or alkaline earth salts, such as halides, sulfates, sulfonates, bisulfites, phosphates, carbonates, bicarbonates. Mention may also be made of amphoteric alumina. Still in this category of blowing agent, a preferred variant consists in using silica. This pore-forming agent is subsequently removed with an alkaline treatment, during the first use of the material (or the diaphragm) or before it.
Tous les types de silices conviennent à cette utilisation et plus particulièrement les silices précipitées ou les silices de combustion.All types of silicas are suitable for this use and more particularly precipitated silicas or combustion silicas.
La surface spécifique de la silice mise en œuvre est plus particulièrement comprise entre 100 et 300 m2/g.The specific surface of the silica used is more particularly between 100 and 300 m 2 / g.
La quantité et la granulométrie des agents porogènes sont étroitement liées à l'application à laquelle les matériaux sont destinés. A titre simplement d'ordre de grandeur, la granulométrie des agents porogènes varie le plus souvent entre 1 et 50 μm et de préférence entre 1 et 15 μm. Quant à la quantité, et toujours à titre d'illustration, elle est choisie en fonction de la porosité désirée, celle-ci pouvant atteindre 90 %, voire davantage (selon la norme ASTM D 276-72).The quantity and particle size of the blowing agents are closely linked to the application for which the materials are intended. Simply as an order of magnitude, the particle size of the blowing agents most often varies between 1 and 50 μm and preferably between 1 and 15 μm. As for the quantity, and always by way of illustration, it is chosen as a function of the desired porosity, which can reach 90% or even more (according to standard ASTM D 276-72).
Selon un deuxième mode de réalisation de l'invention, l'agent porogène est choisi parmi les composés éliminables thermiquement, comme par exemple les systèmes nanoparticulaires (latex de taille inférieure à 100._nm).According to a second embodiment of the invention, the pore-forming agent is chosen from compounds which can be eliminated thermally, such as for example nanoparticulate systems (latex of size less than 100._nm).
La teneur en agent porogène est plus particulièrement comprise entre 20 et 100 parties en poids, pour 100 parties en poids de fibres organiques.The content of blowing agent is more particularly between 20 and 100 parts by weight, per 100 parts by weight of organic fibers.
Ainsi que cela a été indiqué plus haut, le diaphragme comprend des particules minérales de structure non fibreuse.As indicated above, the diaphragm includes mineral particles of non-fibrous structure.
Plus particulièrement, lesdites particules présentent une granulométrie telle que leur taille moyenne est inférieure à 150 μm. Plus particulièrement, la taille moyenne des particules est d'au moins 10 μm. Selon un mode de réalisation préféré de l'invention, la taille moyenne des particules est comprise entre 10 et 50 μm.More particularly, said particles have a particle size such that their average size is less than 150 μm. More specifically, the average size of particles is at least 10 μm. According to a preferred embodiment of the invention, the average particle size is between 10 and 50 μm.
En outre, selon un mode de réalisation particulier de la présente invention, les particules sont à base de silicates hydratés comprenant au moins du magnésium et/ou de l'aluminium et/ou du potassium.In addition, according to a particular embodiment of the present invention, the particles are based on hydrated silicates comprising at least magnesium and / or aluminum and / or potassium.
A titre de silicates convenables, et sans intention de s'y limiter, on peut citer le talc, le kaolin, le mica, l'attapulgite, la vermiculite.As suitable silicates, and without intending to be limited thereto, mention may be made of talc, kaolin, mica, attapulgite, vermiculite.
Selon une variante particulièrement avantageuse et préférée de l'invention, les particules minérales entrant dans la composition de la dispersion présentent une structure plaquettaire.According to a particularly advantageous and preferred variant of the invention, the mineral particles used in the composition of the dispersion have a platelet structure.
A ce titre, les particules mises en œuvre sont plus précisément des particules de mica.As such, the particles used are more precisely particles of mica.
La teneur en particules minérales dans la dispersion plus particulièrement, comprise entre 30 et 100 parties en poids, pour 100 parties en poids de fibres organiques.The content of mineral particles in the dispersion more particularly, between 30 and 100 parts by weight, per 100 parts by weight of organic fibers.
La dispersion à partir de laquelle le diaphragme selon l'invention est susceptible d'être obtenu, peut comprendre des additifs classiques dans le domaine, comme par exemple au moins un tensioactif, ou au moins un agent épaississant, ou leurs mélanges. Parmi les tensioactifs convenables, qui sont de préférence des tensioactifs non ioniques, on peut citer les alcools éthoxylés ou des composés fluorocarbonés à groupes fonctionnalisés, seuls ou en mélange ; ces alcools ou ces composés fluorocarbonés présentent généralement des chaînes carbonées de C6 à C Q. De préférence, on utilise des alcools éthoxylés qui sont des alkylphénols éthoxylés, tels que notamment les octoxynols.The dispersion from which the diaphragm according to the invention can be obtained, can comprise additives conventional in the field, such as for example at least one surfactant, or at least one thickening agent, or mixtures thereof. Among the suitable surfactants, which are preferably nonionic surfactants, mention may be made of ethoxylated alcohols or fluorocarbon compounds with functionalized groups, alone or as a mixture; these alcohols or these fluorocarbon compounds generally have carbon chains from C 6 to C Q. Preferably, ethoxylated alcohols are used which are ethoxylated alkylphenols, such as in particular octoxynols.
Au cas ou un tensioactif est utilisé, la quantité introduite dans la dispersion représente en général de 1 à 10 parties en poids, pour 100 parties en poids de fibres organiques.In the case where a surfactant is used, the amount introduced into the dispersion generally represents from 1 to 10 parts by weight, per 100 parts by weight of organic fibers.
En ce qui concerne les agents épaississants, on entend selon la présente invention, un composé qui augmente la viscosité de la dispersion et qui présente des propriétés rétentrices d'eau.As regards the thickening agents, according to the present invention is meant a compound which increases the viscosity of the dispersion and which exhibits water-retaining properties.
On utilise généralement des polysaccharides naturels ou synthétiques. On peut notamment citer les biopolymères obtenus par fermentation d'un hydrate de carbone sous l'action de micro-organismes. On utilise avantageusement la gomme xanthane. La gomme xanthane est synthétisée à l'aide de bactéries appartenant au genre Xanthomonas et plus particulièrement aux espèces décrites dans Bergey's manual of détermination bacteriology (8ème édition - 1974 - Williams N. Wilkins C° Baltimore). L'espèce Xanthomonas campesths convient tout particulièrement bien pour la synthèse de la gomme xanthane.Natural or synthetic polysaccharides are generally used. Mention may in particular be made of the biopolymers obtained by fermentation of a carbohydrate under the action of microorganisms. Advantageously, xanthan gum is used. Xanthan gum is synthesized using bacteria belonging to the genus Xanthomonas and more particularly to the species described in Bergey's manual of determination bacteriology (8th edition - 1974 - Williams N. Wilkins C ° Baltimore). The species Xanthomonas campesths is particularly suitable for the synthesis of xanthan gum.
Parmi les autres micro-organismes capables de produire des polysaccharides de propriétés similaires, on peut citer les bactéries appartenant au genre Arthrobacter, au genre Erwinia, au genre Azobacter, au genre Agrobacter ou les champignons appartenant au genre Sclerotium.Among the other microorganisms capable of producing polysaccharides with similar properties, mention may be made of bacteria belonging to the genus Arthrobacter, to the genus Erwinia, to the genus Azobacter, to the genus Agrobacter or to fungi belonging to the genus Sclerotium.
Dans le cas où la dispersion comprend des agents épaississants, leur teneur représente en général, entre 1 et 10 parties en poids pour 100 parties en poids de fibres organiques. II est à noter que la teneur en matières sèches globale de la dispersion à partir de laquelle le diaphragme est susceptible d'être obtenu, est habituellement comprise entre 1 et 10 % en poids.In the case where the dispersion comprises thickening agents, their content generally represents between 1 and 10 parts by weight per 100 parts by weight of organic fibers. It should be noted that the overall dry matter content of the dispersion from which the diaphragm can be obtained is usually between 1 and 10% by weight.
La dispersion qui vient d'être décrite est déposée par filtration à travers un support poreux. II est à noter que ledit support peut être soit une autre nappe fibreuse (appelée aussi précathode), qui sera décrite en détail plus bas, soit une surface métallique présentant des ouvertures dont la taille est comprise entre 20 μm et 5 mm (appelé aussi cathode élémentaire), soit la combinaison de ces deux types de support.The dispersion which has just been described is deposited by filtration through a porous support. It should be noted that said support can be either another fibrous sheet (also called precathode), which will be described in detail below, or a metal surface having openings whose size is between 20 μm and 5 mm (also called cathode elementary), or the combination of these two types of support.
Dans le cas d'une surface métallique employée comme support poreux, cette dernière peut être plus particulièrement constituée par des toiles ou des grilles dont le vide de maille, les perforations ou la porosité peuvent être compris dans la gamme indiquée auparavant. Elle peut de même présenter une ou plusieurs surfaces planes ou cylindriques, appelées communément "doigt de gant", présentant une surface ouverte. Cette surface métallique, conductrice, peut entre autres être composée de fer, de nickel, d'alliages comme par exemple l'acier inoxydable, ou encore de tout matériau traité de manière à le rendre encore moins sensible à la corrosivitό du milieu, comme par exemple du fer sur lequel on aurait réalisé un dépôt de nickel.In the case of a metal surface used as a porous support, the latter can more particularly consist of fabrics or grids whose void, the perforations or the porosity can be included in the range indicated above. It can likewise have one or more flat or cylindrical surfaces, commonly called "thermowell", having an open surface. This metallic, conductive surface can, among other things, be composed of iron, nickel, alloys such as stainless steel, or any other material treated so as to make it even less sensitive to the corrosivity of the medium, such as by example of the iron on which a nickel deposit would have been made.
Ainsi que cela a été mentionné auparavant, la présente invention concerne une association comprenant le diaphragme et une autre nappe fibreuse (précathode) susceptible d'être obtenue par dépôt par filtration à travers un support poreux d'une dispersion comprenant des fibres, dont une partie est conductrice de l'électricité, au moins un liant choisi parmi les polymères halogènes, au moins un agent électrocatalytique et au moins un agent porogène. Plus particulièrement, le support poreux sur lequel cette autre nappe fibreuse est déposée, est constitué par une surface métallique présentant des ouvertures dont la taille est comprise entre 20 μm et 5 mm (cathode élémentaire). Les caractéristiques concernant la cathode élémentaire détaillée auparavant restent valables.As mentioned previously, the present invention relates to a combination comprising the diaphragm and another fibrous sheet (precathode) capable of being obtained by deposition by filtration through a porous support of a dispersion comprising fibers, part of which is electrically conductive, at least one binder chosen from halogenated polymers, at least one electrocatalytic agent and at least one pore-forming agent. More particularly, the porous support on which this other fibrous sheet is deposited, is constituted by a metal surface having openings the size of which is between 20 μm and 5 mm (elementary cathode). The characteristics concerning the elementary cathode detailed previously remain valid.
Selon un mode de réalisation préféré de l'invention, l'association est telle que l'on trouve d'une face vers l'autre, le diaphragme selon l'invention, la précathode telle que définie ci-dessus, la cathode élémentaire.According to a preferred embodiment of the invention, the association is such that one finds from one face towards the other, the diaphragm according to the invention, the precathode as defined above, the elementary cathode.
La nappe fibreuse constituant la précathode va maintenant être décrite. Tout d'abord, il est à noter que la précathode présente de préférence une résistivité égale ou inférieure à 0,4 Ω.cm.The fibrous web constituting the precathode will now be described. First of all, it should be noted that the precathode preferably has a resistivity equal to or less than 0.4 Ω.cm.
Comme cela a été indiqué plus haut, ladite nappe comprend des fibres conductrices de l'électricité. Celles-ci peuvent être choisies parmi les fibres intrinsèquement conductrices ou bien traitées de façon à les rendre telles.As indicated above, said sheet comprises electrically conductive fibers. These can be chosen from intrinsically conductive fibers or else treated so as to make them such.
Plus particulièrement, ces fibres se présentent sous une forme de filaments dont le diamètre est généralement inférieur à 1 mm et plus particulièrement compris entre 10"3 et 0,1 mm et dont la longueur est supérieure à 0,5 mm et plus spécialement comprise entre 1 et 20 mm.More particularly, these fibers are in the form of filaments whose diameter is generally less than 1 mm and more particularly between 10 "3 and 0.1 mm and whose length is greater than 0.5 mm and more especially between 1 and 20 mm.
Selon un premier mode de réalisation de l'invention, préféré, les fibres entrant dans la composition de la nappe sont des fibres intrinsèquement conductrices, comme notamment les fibres de carbone ou de graphite.According to a first preferred embodiment of the invention, the fibers used in the composition of the sheet are intrinsically conductive fibers, such as in particular carbon or graphite fibers.
Par ailleurs, les fibres conductrices présentent de préférence une distribution de longueur monodispersée, c'est-à-dire une distribution telle que la longueur d'au moins 80 % et avantageusement d'au moins 90 %, des fibres, correspond à la longueur moyenne à ± 10 % près.Furthermore, the conductive fibers preferably have a distribution of monodispersed length, that is to say a distribution such that the length of at least 80% and advantageously at least 90%, of the fibers, corresponds to the length average to within ± 10%.
Selon un second mode de réalisation de l'invention, on peut utiliser des fibres issues de matériau non conducteur de l'électricité mais rendues conductrices par un traitement. On peut à titre d'exemple citer les fibres de zircone rendues conductrices par dépôt chimique ou électrochimique d'un métal tel que le nickel.According to a second embodiment of the invention, it is possible to use fibers from material which is not electrically conductive but which are made conductive by treatment. By way of example, mention may be made of zirconia fibers made conductive by chemical or electrochemical deposition of a metal such as nickel.
La teneur en fibres conductrices est déterminée de manière à ce que la résistivité globale de la nappe fibreuse précathodique soit inférieure ou égale à 0,4 Ω.cm. La dispersion comprend plus particulièrement 20 à 100 parties en poids de fibres conductrices. Selon une variante préférée, la teneur en fibres conductrices est comprise entre 50 et 90 parties en poids.The content of conductive fibers is determined so that the overall resistivity of the precathode fibrous web is less than or equal to 0.4 Ω.cm. The dispersion more particularly comprises 20 to 100 parts by weight of conductive fibers. According to a preferred variant, the content of conductive fibers is between 50 and 90 parts by weight.
La dispersion peut de même contenir, en association avec les fibres conductrices, des fibres non conductrices. Ces fibres se présentent généralement sous forme de filaments dont la taille est analogue à celle donnée pour les fibres conductrices.The dispersion may likewise contain, in association with the conductive fibers, non-conductive fibers. These fibers are generally in the form of filaments whose size is similar to that given for the conductive fibers.
A titre d'illustration de fibres non conductrices, on peut notamment citer les fibres organiques, telles que les fibres de polypropylène ou de polyéthylène, éventuellement halogène et notamment fluoré, les fibres de polyhalogéno-vinylidène et notamment de polyfluorure de vinylidène, ou encore les fibres de polymères fluorés.By way of illustration of non-conductive fibers, mention may in particular be made of organic fibers, such as polypropylene or polyethylene fibers, optionally halogenated and in particular fluorinated, polyhalo-vinylidene fibers and in particular polyvinylidene fluoride, or even fibers of fluorinated polymers.
De telles fibres, lorsqu'elles sont présentes, sont de préférence des fibres de polytétrafluoroéthylène. On pourra se référer au passage correspondant de la description, donnant les détails de structure de telles fibres.Such fibers, when present, are preferably polytetrafluoroethylene fibers. Reference may be made to the corresponding passage in the description, giving details of the structure of such fibers.
Dans une association de fibres conductrices et non conductrices, la proportion de fibres non conductrices est telle que la résistivité de la précathode est d'au plus 0,4 Ω.cm. Notons que la teneur en fibres non conductrices, lorsqu'elles sont utilisées ici, peut représenter jusqu'à 90 % en poids et de préférence être comprise entre 20 et 70 % en poids du mélange fibres conductrices, fibres non conductrices.In a combination of conductive and non-conductive fibers, the proportion of non-conductive fibers is such that the resistivity of the precathode is at most 0.4 Ω.cm. Note that the content of non-conductive fibers, when used here, can represent up to 90% by weight and preferably be between 20 and 70% by weight of the mixture of conductive fibers and non-conductive fibers.
La dispersion comprend de plus, au moins un liant choisi parmi les polymères halogènes. Ce qui a été dit au sujet du liant entrant dans la composition de la dispersion à partir de laquelle le diaphragme est susceptible d'être obtenu reste valable.The dispersion also comprises at least one binder chosen from halogenated polymers. What has been said about the binder used in the composition of the dispersion from which the diaphragm can be obtained remains valid.
De préférence, le liant est le polytétrafluoroéthylène.Preferably, the binder is polytetrafluoroethylene.
La teneur en liant dans la dispersion est plus particulièrement comprise entre 10 et 60 parties en poids sec. La dispersion à partir de laquelle cette nappe précathodique est obtenue, comprend en outre au moins un agent électrocatalytique.The content of binder in the dispersion is more particularly between 10 and 60 parts by dry weight. The dispersion from which this precathode layer is obtained, further comprises at least one electrocatalytic agent.
On peut employer, en tant qu'agent électrocatalytique tous les types de métaux connus dans le domaine pour activer la réaction d'électrolyse.Any type of metal known in the art can be used as the electrocatalytic agent to activate the electrolysis reaction.
Cependant selon une première variante particulière de l'invention, on utilise un métal de Raney, comme de préférence le nickel, ou bien encore un précurseur de ce métal de Raney, consistant en fait en un alliage à base dudit métal associé à un autre que l'on peut facilement éliminer. Plus particulièrement, il s'agit d'un alliage comprenant de l'aluminium qui peut être lessivé par exemple par un traitement basique. Ce type d'agent électrocatalytique a notamment été décrit dans le brevet européen EP 296 076 auquel on pourra se référer à ce sujet.However, according to a first particular variant of the invention, a Raney metal is used, such as preferably nickel, or else a precursor of this Raney metal, consisting in fact of an alloy based on said metal associated with another than one can easily eliminate. More particularly, it is an alloy comprising aluminum which can be leached for example by a basic treatment. This type of electrocatalytic agent has in particular been described in European patent EP 296 076 to which reference may be made on this subject.
Selon une seconde variante, on peut utiliser comme agent électrocatalytique, des particules comprenant un oxyde de ruthénium, de platine, d'iridium, de palladium, ou un mélange de ces oxydes.According to a second variant, it is possible to use as electrocatalytic agent, particles comprising an oxide of ruthenium, platinum, iridium, palladium, or a mixture of these oxides.
Par mélange, on entend des particules comprenant en elles-mêmes, un mélange d'oxydes, mais aussi des particules, à base d'un oxyde métallique, mélangées à d'autres particules comprenant un oxyde différent. Bien évidemment, les combinaisons intermédiaires entre ces deux possibilités sont tout à fait envisageables. Ledit agent peut se présenter en outre sous la forme de particules constituées d'un support conducteur de l'électricité, comprenant un revêtement sous forme d'oxyde de ruthénium, de platine, d'iridium, de palladium ; ces oxydes étant seuls ou en mélange au sens qui vient d'être explicité. On ne sortirait pas du cadre de la présente invention en combinant ces deux variantes, c'est-à-dire particules à base d'oxydé ou revêtues d'un oxyde.By mixture is meant particles comprising in themselves a mixture of oxides, but also particles, based on a metal oxide, mixed with other particles comprising a different oxide. Obviously, the intermediate combinations between these two possibilities are quite conceivable. Said agent can also be in the form of particles consisting of an electrically conductive support, comprising a coating in the form of ruthenium oxide, platinum, iridium, palladium; these oxides being alone or in admixture in the sense which has just been explained. It would not be departing from the scope of the present invention to combine these two variants, that is to say particles based on oxide or coated with an oxide.
De préférence l'agent électrocatalytique selon l'invention se présente sous la forme d'un revêtement d'un support tel que notamment le fer, le cobalt, le nickel, le fer de Raney, le cobalt de Raney, le nickel de Raney, les éléments des colonnes IVA et VA de la classification périodique, le carbone, le graphite. Ici et pour toute la description qui va suivre, la classification périodique des éléments à laquelle il est fait référence est celle publiée dans le supplément au Bulletin de la Société Chimique de France (no.1 - 1966).Preferably the electrocatalytic agent according to the invention is in the form of a coating of a support such as in particular iron, cobalt, nickel, Raney iron, Raney cobalt, Raney nickel, the elements of columns IVA and VA of the periodic table, carbon, graphite. Here and for all the description which follows, the periodic classification of the elements to which reference is made is that published in the supplement to the Bulletin de la Société Chimique de France (no.1 - 1966).
Ce type d'agent électrocatalytique est notamment décrit dans la demande de brevet internationale WO 95/21950.This type of electrocatalytic agent is described in particular in international patent application WO 95/21950.
Il est à noter, là encore, que la combinaison des deux types d'agents électrocatalytiques décrits auparavant est possible.Again, it should be noted that the combination of the two types of electrocatalytic agents described above is possible.
La teneur en agent électrocatalytique dans la dispersion est plus précisément comprise entre 20 et 200 parties en poids. De préférence, elle est comprise entre 60 et 120 parties en poids.The content of electrocatalytic agent in the dispersion is more precisely between 20 and 200 parts by weight. Preferably, it is between 60 and 120 parts by weight.
La dispersion comprend de même un agent porogène. Ce qui a été indiqué plus haut concernant la nature de cet agent porogène reste valable, tant pour la définition générale de ce composé que pour les variantes préférées, et ne sera pas repris ici.The dispersion likewise comprises a blowing agent. What has been indicated above concerning the nature of this blowing agent remains valid, both for the general definition of this compound and for the preferred variants, and will not be repeated here.
Dans le cas où l'agent porogène est éliminable par un traitement chimique, comme c'est le cas de la silice notamment, cette teneur est en général comprise entre 30 et 200 parties. Plus particulièrement, la quantité d'agent porogène est comprise entre 30 et 100 parties en poids.In the case where the blowing agent can be removed by chemical treatment, as is the case with silica in particular, this content is generally between 30 and 200 parts. More particularly, the amount of blowing agent is between 30 and 100 parts by weight.
Dans le cas où l'agent porogène est éliminable thermiquement, tel que pour les systèmes nanoparticulaires, la quantité de ce type de composé est plus particulièrement comprise entre 10 et 200 parties en poids.In the case where the blowing agent is thermally removable, such as for nanoparticulate systems, the amount of this type of compound is more particularly between 10 and 200 parts by weight.
Une combinaison de ces deux possibilités est envisageable. Dans ce dernier cas, la quantité d'agents porogènes correspondant à un mélange d'agents éliminables chimiquement et thermiquement est comprise plus particulièrement entre 30 et 200 parties en poids. Selon une variante particulière de la présente invention, ladite nappe comprend un polymère cationique. Parmi les polymères cationiques convenables, on peut mentionner deux catégories de polymères, les polymères organiques et les polymères inorganiques, ceux-ci pouvant être utilisés seuls ou en mélange.A combination of these two possibilities is possible. In the latter case, the amount of blowing agents corresponding to a mixture of chemically and thermally eliminable agents is more particularly between 30 and 200 parts by weight. According to a particular variant of the present invention, said sheet comprises a cationic polymer. Among the suitable cationic polymers, two categories of polymers may be mentioned, organic polymers and inorganic polymers, the latter being able to be used alone or as a mixture.
A titre d'exemple de polymères de la première catégorie, les polymères de synthèse choisis parmi l'épychlorhydrine, les polyimines, les polyacrylamides, les polyacrylamines sont des polymères susceptibles d'entrer dans la composition de la suspension mise en œuvre dans l'invention. Les polymères d'origine naturelle comme notamment les amidons cationiques, les guars cationiques sont des composés convenables à l'invention. Parmi les polymères inorganiques, on peut citer sans intention de se limiter les argiles, les bentonites, le sulfate d'aluminium, le polychlorure d'aluminium.By way of example of polymers from the first category, synthetic polymers chosen from epychlorohydrin, polyimines, polyacrylamides, polyacrylamines are polymers capable of entering into the composition of the suspension used in the invention . Polymers of natural origin such as, in particular, cationic starches and cationic guars are compounds which are suitable for the invention. Among the inorganic polymers, mention may be made, without intending to be limited, of clays, bentonites, aluminum sulphate, aluminum polychloride.
Selon un mode de réalisation préférée, le polymère est choisi parmi les polyacrylamines, commercialisées notamment sous la dénomination FLOERGER® par la société Floerger, les amidons cationiques, comme les amidons cationiques solubles à chaud (amidons cationiques HI-CAT®, commercialisés par la société Roquette), ainsi que les amidons cationiques solubles à froid, du type des guars cationiques commercialisés sous la marque MEYPRO® par la société Meyhall ; ces polymères pouvant être présents seuls ou en mélange.According to a preferred embodiment, the polymer is chosen from polyacrylamines, sold in particular under the name FLOERGER® by the company Floerger, cationic starches, such as hot-soluble cationic starches (cationic HI-CAT® starches, sold by the company Roquette), as well as cold soluble cationic starches, of the type of cationic guars sold under the brand MEYPRO® by the company Meyhall; these polymers can be present alone or as a mixture.
La teneur en polymère cationique, s'il est présent, est telle que la mesure de la turbidite du liquide surnageant après décantation de la dispersion est supérieure ou égale à 50, de préférence à 75 (la mesure de la turbidite est effectuée par transmission à 630 nm sur un turbidimètre de type Methrom 662 Photometer® ; celle de l'eau pure donne une valeur de 100). Par ailleurs, la teneur en polymère cationique est telle que l'on ne rencontre pas de difficulté excessive pour la filtration de la suspension.The content of cationic polymer, if present, is such that the measurement of the turbidite of the supernatant liquid after settling of the dispersion is greater than or equal to 50, preferably 75 (the measurement of the turbidite is carried out by transmission to 630 nm on a Methrom 662 Photometer® type turbidimeter; that of pure water gives a value of 100). Furthermore, the content of cationic polymer is such that there is no excessive difficulty in filtering the suspension.
Dans le cas plus particulier de l'amidon cationique, la teneur varie entre 10 et 80 parties en poids sec, et de préférence; entre 20 et 40 parties en poids sec.In the more specific case of cationic starch, the content varies between 10 and 80 parts by dry weight, and preferably; between 20 and 40 parts by dry weight.
Selon une variante préférée, la dispersion de la nappe précathodique comprend de préférence des fibres conductrices (sans fibres non conductrices), un agent porogène, un polymère cationique, et éventuellement d'autres additifs.According to a preferred variant, the dispersion of the precathode layer preferably comprises conductive fibers (without non-conductive fibers), a blowing agent, a cationic polymer, and optionally other additives.
Parmi les additifs utilisables dans le cas de cette , variante, on peut citer les matériau fibreux, plus particulièrement du type des fibres^ à base de cellulose, ou des fibres à base de cellulose auxquelles on a donné une charge ionique positive.Among the additives used in the case of this variant, there may be mentioned fibrous material, more particularly the type of fibers ^ based on cellulose, or cellulose-based fibers which have been given a positive ionic charge.
Comme fibres de cellulose chargées positivement, on peut citer les fibres BECOFLOC ®.Mention may be made, as positively charged cellulose fibers, of BECOFLOC® fibers.
Dans le cas particulier où la suspension comprend des fibres à base de cellulose, chargées ou non positivement, en tant que matériau fibreux, leur teneur est d'au plus 60 parties en poids sec, et de préférence comprise entre 10 et 40 parties en poids.In the particular case where the suspension comprises fibers based on cellulose, charged or not positively charged, as fibrous material, their content is at most 60 parts by dry weight, and preferably between 10 and 40 parts by weight.
Bien évidemment, la dispersion peut aussi comprendre des additifs usuels, mais non obligatoires, comme les tensioactifs, les agents épaississants. Ceux entrant dans la composition de la dispersion permettant d'accéder au diaphragme selon l'invention peuvent être mis en œuvre pour l'obtention de la première nappeObviously, the dispersion may also include usual additives, but not compulsory, such as surfactants, thickening agents. Those used in the composition of the dispersion allowing access to the diaphragm according to the invention can be used to obtain the first layer
Une telle nappe fait notamment l'objet d'une demande de brevet internationale WO 97/24774. Un mode de préparation du diaphragme selon l'invention va maintenant être décrit.Such a sheet is in particular the subject of an international patent application WO 97/24774. A method of preparing the diaphragm according to the invention will now be described.
Ainsi, le diaphragme peut être obtenu en mettant en œuvre les étapes suivantes : a) on prépare une dispersion comprenant des fibres organiques, au moins un liant choisi parmi les polymères halogènes, au moins un agent porogène et des particules minérales de structure non fibreuse, b) on dépose par filtration sous vide, et à travers un support poreux, la dispersion ainsi obtenue, c) on élimine le liquide et, si nécessaire, on sèche la nappe fibreuse formée, d) on fritte la nappe fibreuse, e) on élimine, si nécessaire, l'agent porogène.Thus, the diaphragm can be obtained by implementing the following steps: a) a dispersion is prepared comprising organic fibers, at least one binder chosen from halogenated polymers, at least one pore-forming agent and mineral particles of non-fibrous structure, b) depositing by vacuum filtration, and through a porous support, the dispersion thus obtained, c) removing the liquid and, if necessary, drying the fibrous web formed, d) sintering the fibrous web, e) eliminates, if necessary, the blowing agent.
La préparation de la dispersion est réalisée en mélangeant les divers éléments qui la constituent, dans une solution aqueuse.The preparation of the dispersion is carried out by mixing the various elements which constitute it, in an aqueous solution.
Les teneurs des divers éléments constitutifs de la dispersion sont telles qu'elles vérifient les conditions indiquées auparavant.The contents of the various components of the dispersion are such that they satisfy the conditions indicated above.
Bien évidemment, dans le but d'obtenir une dispersion homogène, la préparation de la dispersion a lieu sous agitation.Obviously, in order to obtain a homogeneous dispersion, the preparation of the dispersion takes place with stirring.
L'étape b) de filtration est réalisée sous vide. De préférence, ce vide est programmé. La nappe est déposée sur le support poreux par filtration sous vide programmé.Stage b) of filtration is carried out under vacuum. Preferably, this vacuum is programmed. The sheet is deposited on the porous support by programmed vacuum filtration.
Celui-ci est réalisé de manière connue en soi et peut être.effectué en continu ou par paliers, à une dépression finale de 1 ,5 .10^ à 5.10^ Pa. 'This is carried out in a manner known per se and can be carried out continuously or in stages, at a final depression of 1.5 × 10 5 to 5.10 Pa.
La filtration de la dispersion peut être effectuée verticalement, ce qui représente un avantage particulièrement intéressant pour une exploitation à l'échelle industrielle, ou horizontalement.The filtration of the dispersion can be carried out vertically, which represents a particularly advantageous advantage for exploitation on an industrial scale, or horizontally.
A l'issue de l'étape b) de filtration, on maintient le vide de manière à éliminer le liquide. Eventuellement la nappe résultante peut être séchée par exemple en portant la température à une valeur inférieure à 150°C. La nappe fibreuse résultante fait ensuite l'objet d'une étape de frittage ou de consolidation (étape d).At the end of step b) of filtration, the vacuum is maintained so as to eliminate the liquid. Optionally, the resulting sheet can be dried, for example by bringing the temperature to a value below 150 ° C. The resulting fibrous web is then the subject of a sintering or consolidation step (step d).
Ce frittage est réalisé de manière connue, à une température supérieure au point de ramollissement du polymère halogène employé en tant que liant. Une fois consolidée, la nappe fibreuse constituant le diaphragme selon l'invention, peut si nécessaire, faire l'objet d'une étape d'élimination de l'agent porogène.This sintering is carried out in a known manner, at a temperature above the softening point of the halogenated polymer used as a binder. Once consolidated, the fibrous sheet constituting the diaphragm according to the invention can, if necessary, be the subject of a step of elimination of the pore-forming agent.
Notons que cette étape peut avoir lieu lors de l'opération de frittage, dans le cas où l'agent porogène employé est dégradable thermiquement. Dans le cas où l'agent porogène mis en œuvre est, au moins en partie, choisi parmi les agents éliminables par voie chimique, l'étape e) a lieu en effectuant un traitement chimique du diaphragme, de la nappe ou de leur association, avec une solution alcaline.Note that this step can take place during the sintering operation, in the case where the blowing agent used is thermally degradable. In the case where the pore-forming agent used is, at least in part, chosen from the agents which can be eliminated by chemical means, step e) takes place by carrying out a chemical treatment of the diaphragm, of the sheet or of their combination, with an alkaline solution.
Il est particulièrement intéressant d'utiliser la solution d'hydroxyde de métal alcalin obtenue par l'électrolyse de la solution d'halogénure alcalin. Ainsi, l'étape e) peut être effectuée en contactant le diaphragme avec une solution d'hydroxyde de métal alcalin présentant une concentration comprise entre 40 et 200 g/l. Par ailleurs, la température est plus particulièrement comprise entre 20 et 95°C.It is particularly advantageous to use the alkali metal hydroxide solution obtained by the electrolysis of the alkali halide solution. Thus, step e) can be carried out by contacting the diaphragm with an alkali metal hydroxide solution having a concentration of between 40 and 200 g / l. Furthermore, the temperature is more particularly between 20 and 95 ° C.
Il est à noter que l'étape e) peut avoir lieu préalablement à l'utilisation du diaphragme ou in situ, c'est-à-dire lors de la première utilisation du diaphragme ou de l'association.It should be noted that step e) can take place before the use of the diaphragm or in situ, that is to say during the first use of the diaphragm or of the association.
En ce qui concerne l'obtention de l'association au sens de la présente invention, on met en œuvre les étapes suivantes : a) on prépare une dispersion aqueuse comprenant les fibres, dont une partie est conductrice de l'électricité, au moins un liant choisi parmi les polymères halogènes, au moins un agent électrocatalytique, au moins un agent porogène, b) on dépose une nappe fibreuse par filtration sous vide programmé de ladite dispersion à travers un support poreux, c) on élimine le liquide et l'on sèche, si nécessaire, la nappe fibreuse formée, constituant la précathode, d) on fritte éventuellement la précathode, e) on élimine éventuellement l'agent porogène, f) on dépose sur la précathode, par filtration sous vide programmé, une dispersion aqueuse, comprenant des fibres organiques, au moins un liant choisi parmi les polymères halogènes, au moins un agent porogène, des particules minérales de structure non fibreuse, g) on élimine le liquide et l'on sèche éventuellement le diaphragme ainsi formé, h) on fritte l'ensemble, i) on élimine si nécessaire l'agent porogène.With regard to obtaining the association within the meaning of the present invention, the following steps are implemented: a) an aqueous dispersion is prepared comprising the fibers, part of which is electrically conductive, at least one binder chosen from halogenated polymers, at least one electrocatalytic agent, at least one pore-forming agent, b) a fibrous sheet is deposited by filtration under programmed vacuum of said dispersion through a porous support, c) the liquid is removed and dries, if necessary, the fibrous sheet formed, constituting the precathode, d) optionally sintering the precathode, e) optionally eliminating the pore-forming agent, f) depositing on the precathode, by filtration under programmed vacuum, an aqueous dispersion, comprising organic fibers, at least one binder chosen from halogenated polymers, at least one pore-forming agent, mineral particles of non-fibrous structure, g) the liquid is eliminated and dried possibly the diaphragm thus formed, h) the whole is sintered, i) if necessary, the blowing agent is eliminated.
La première étape est réalisée de manière similaire à celle mise en œuvre pour la préparation de la dispersion mise en œuvre pour l'obtention du diaphragme.The first step is carried out in a similar manner to that used for the preparation of the dispersion used to obtain the diaphragm.
Les divers éléments constitutifs de cette nappe précathodique, de même que la proportion de chacun d'entre eux, a été détaillée auparavant. Il suffit donc de s'y référer.The various constituent elements of this precathode layer, as well as the proportion of each of them, has been detailed before. So just refer to it.
De manière avantageuse, cette dispersion est déposée sur un support métallique présentant des ouvertures dont la taille est comprise entre 20 μm et 5 mm.Advantageously, this dispersion is deposited on a metal support having openings whose size is between 20 μm and 5 mm.
Le dépôt par filtration de la dispersion à lieu sous un vide programmé dont les conditions ont été explicitées pour le dépôt de la nappe constituant le diaphragme.The deposition by filtration of the dispersion takes place under a programmed vacuum, the conditions of which have been explained for the deposition of the sheet constituting the diaphragm.
Les conditions de l'étape c) sont de plus similaires à celles mises en œuvre pour l'obtention du diaphragme.The conditions of step c) are moreover similar to those implemented for obtaining the diaphragm.
La nappe précathodique peut être frittée par chauffage à une température supérieure ou égale à la température de ramollissement du liant. L'élimination de l'agent porogène peut avoir lieu à ce stade, selon une méthode identique à celle décrite lors de l'obtention du diaphragme. Cependant, de préférence, cette étape n'est réalisée qu'en fin de procédé (étape i).The precathode layer can be sintered by heating to a temperature greater than or equal to the softening temperature of the binder. The elimination of the pore-forming agent can take place at this stage, according to a method identical to that described when obtaining the diaphragm. However, preferably, this step is only carried out at the end of the process (step i).
Notons que l'on pourra se référer à la demande internationale WO 97/24474 pour ce qui concerne le procédé de préparation de la nappe précathodique. Les étapes f) à i) correspondent à celles décrites auparavant pour l'obtention du diaphragme.It should be noted that reference may be made to international application WO 97/24474 with regard to the process for preparing the precathode layer. Steps f) to i) correspond to those described above for obtaining the diaphragm.
Un dernier objet de l'invention est constitué par l'utilisation du diaphragme ou de l'association le comprenant, dans l'électrolyse de solutions aqueuses d'halogénures de métal alcalin, plus particulièrement de solutions de chlorure de sodium.A final object of the invention consists of the use of the diaphragm or of a combination comprising it, in the electrolysis of aqueous solutions of alkali metal halides, more particularly of sodium chloride solutions.
Un exemple concret mais non limitatif de l'invention va maintenant être présenté.A concrete but nonlimiting example of the invention will now be presented.
EXEMPLEEXAMPLE
1/ Préparation d'une association comprenant le diaphragme selon l'invention1 / Preparation of an association comprising the diaphragm according to the invention
Sauf précision contraire, le parties en poids sont données en poids sec du composé considéré.Unless otherwise specified, the parts by weight are given in dry weight of the compound considered.
On prépare une dispersion à partir des éléments suivants : ° eau permutée, dont la quantité est calculée pour obtenir environ 4 litres de dispersion et un extrait sec d'environ 3,2 % en poids, ° 100 parties en poids de fibres de carbone dont le diamètre est d'environA dispersion is prepared from the following elements: ° permuted water, the amount of which is calculated to obtain approximately 4 liters of dispersion and a dry extract of approximately 3.2% by weight, ° 100 parts by weight of carbon fibers whose diameter is approximately
10 mm et dont la longueur moyenne est de 1 ,5 mm, ° 35 parties en poids de polytétrafluoroéthylène sous forme de latex à 60% d'extrait sec, » 20 parties en poids de guar cationique (MEYPRO®, commercialisé par la société Meyhall), ° 200 parties en poids de silice précipitée sous forme de particules de granulométrie moyenne de 3 mm et dont la surface B.E.T. est de10 mm, the average length of which is 1.5 mm, 35 parts by weight of polytetrafluoroethylene in the form of latex with 60% dry extract, ”20 parts by weight of cationic guar (MEYPRO®, sold by the company Meyhall ), ° 200 parts by weight of silica precipitated in the form of particles with an average particle size of 3 mm and whose BET surface is of
250 m2.g-1 , ° 1 ,8 parties en poids de Triton X 100 ® de la société Rohm et Haas, π 180 parties en poids de nickel de Raney sous forme de poudre de 10 μm250 m 2 .g- 1 , ° 1, 8 parts by weight of Triton X 100 ® from the company Rohm and Haas, π 180 parts by weight of Raney nickel in the form of 10 μm powder
(Ni 20 commercialisé par la Société Procatalyse).(Ni 20 sold by the company Procatalyse).
On introduit dans l'eau permutée et sous agitation, le guar cationique puis les autres éléments constitutifs de la dispersion.Is introduced into permuted water and with stirring, the cationic guar and then the other constituent elements of the dispersion.
On filtre la suspension obtenue, après l'avoir agitée, sous vide, sur un grillage de fer tressé et laminé d'acier type "Gantois" dont l'ouverture est de 2 mm et dont le diamètre de fils est de 2 mm, la surface de dépôt étant de 1 ,21 dm2.The suspension obtained is filtered, after having stirred it, under vacuum, on a braided iron mesh and rolled steel type "Gantois" whose opening is 2 mm and whose wire diameter is 2 mm, the deposition area being 1.21 dm 2 .
La dépression est établie pour atteindre par paliers une valeur comprise entre 300.102 et 450.102 Pa. La dépression maximaie est maintenue pendant environ 15 minutes.The vacuum is established to reach in stages a value between 300.10 2 and 450.10 2 Pa. The maximum vacuum is maintained for approximately 15 minutes.
L'ensemble est alors séché.The whole is then dried.
On prépare, sous agitation, 4 litres d'une dispersion présentant un extrait sec d'environ 6,3 % et comprenant : α 100 parties en poids de fibres de polytétrafluoroéthylène,4 liters of a dispersion having a dry extract of approximately 6.3% and comprising: α 100 parts by weight of polytetrafluoroethylene fibers are prepared, with stirring,
° 30 parties en poids de polytétrafluoroéthylène sous forme de latex à 60% d'extrait sec, ° 40 parties en poids de mica WG 333 (Kaolins d'Arvor, broyé à une taille de 30 μm),° 30 parts by weight of polytetrafluoroethylene in the form of latex with 60% of dry extract, ° 40 parts by weight of mica WG 333 (Kaolins d'Arvor, ground to a size of 30 μm),
D 50 parties en poids de silice précipitée sous forme de particules de granulométrie moyenne de 3 mm et dont la surface B.E.T. est de 250 m2.g-1 , D 50 parts by weight of silica precipitated in the form of particles with an average particle size of 3 mm and whose BET surface area is 250 m 2 .g- 1 ,
(H)(H)
3,6 parties en poids de Triton X 100 de la société Rohm et Haas.3.6 parts by weight of Triton X 100 from the company Rohm and Haas.
On prélève le volume de dispersion requis de manière à ce qu'il présente la quantité d'extrait sec que l'on compte déposer (ici 1,3 kg/m2 ; 1,53 kg/m2 ; 1 ,8 kg/m2). On effectue sous vide programmé le dépôt de la dispersion sur la nappe précathodique obtenue auparavant. La dépression est établie pour atteindre par paliers une valeur comprise entre 300.102 et 450.102 Pa. La dépression maximale est maintenue pendant environ 15 minutes. L'association est ensuite frittée à 350°C sous air pendant 7 minutes.The required volume of dispersion is taken so that it presents the quantity of dry extract that we intend to deposit (here 1.3 kg / m 2 ; 1.53 kg / m 2 ; 1.8 kg / m m 2 ). The dispersion is carried out under programmed vacuum on the precathode layer obtained previously. The vacuum is established to reach in stages a value between 300.10 2 and 450.10 2 Pa. The maximum vacuum is maintained for approximately 15 minutes. The combination is then sintered at 350 ° C in air for 7 minutes.
2/ Evaluation des performances de l'association2 / Evaluation of the association's performance
Les performances de l'association ainsi obtenue sont évaluées dans une cellule d'électrolyse présentant les caractéristiques suivantes :The performance of the combination thus obtained is evaluated in an electrolysis cell having the following characteristics:
° Anode en titane déployé laminé revêtu de Tiθ2- uθ2° Rolled expanded titanium anode coated with Tiθ2- uθ2
° Cathode élémentaire en acier inox doux tressé et laminé ; fils de 2 mm ; maille de 2 mm ; recouverte de la nappe précathodique et du diaphragme° Elementary cathode in braided and laminated mild stainless steel; 2 mm wires; 2 mm mesh; covered with the precathode layer and the diaphragm
D Distance anode - association/cathode élémentaire : 6 mm ° Surface active de l'électrolyseur : 0,5 dm2 D Distance anode - association / elementary cathode: 6 mm ° Active surface of the electrolyser: 0.5 dm 2
° Cellule assemblé selon le type filtre-presse.° Cell assembled according to the filter press type.
Les conditions de fonctionnement de la cellule sont les suivantes D Densité de courant : 2,5 kA / m2 ° Température : 85°CThe cell operating conditions are as follows D Current density: 2.5 kA / m 2 ° Temperature: 85 ° C
-1-1
Fonctionnement à chlorure anodique constant : 4,8 mole.lOperation with constant anodic chloride: 4.8 mole.l
Les résultats sont rassemblés dans le tableau ci-dessousThe results are collated in the table below
H est la charge hydraulique ramenée à un débit de 100.^Elle correspond au rapport de la différence entre les niveaux de Panolyte et du catholyte et du débit (exprimé en ml/h) ; le rapport étant multiplié par 100.H is the hydraulic head reduced to a flow rate of 100. ^ It corresponds to the ratio of the difference between the levels of Panolyte and catholyte and the flow rate (expressed in ml / h); the ratio being multiplied by 100.
RF est le rendement Faraday (concentration en soude : 3N). Les résultats apparaissant dans ce tableau indiquent que les performances des cellules comprenant le diaphragme selon l'invention sont au moins aussi bonnes que celles atteintes par les cellules comprenant des diaphragmes connus.RF is the Faraday yield (sodium hydroxide concentration: 3N). The results appearing in this table indicate that the performance of the cells comprising the diaphragm according to the invention is at least as good as that achieved by the cells comprising known diaphragms.
Ces essais montrent de plus qu'il est possible d'adapter le diaphragme à différentes conditions de fonctionnement de la cellule, en fonction du poids déposé.These tests also show that it is possible to adapt the diaphragm to different operating conditions of the cell, depending on the weight deposited.
En outre, les tests mécaniques en rupture des diaphragmes et des associations ont montré que les valeurs de l'allongement à la rupture, la contrainte maximale, la force maximale, rendent compatibles de tels diaphragmes et associations, avec l'utilisation dans des cellules d'électrolyse de solutions aqueuses d'halogénures de métaux alcalins. In addition, mechanical tests in rupture of diaphragms and associations have shown that the values of elongation at break, maximum stress, maximum force, make such diaphragms and associations compatible, with the use in d cells. electrolysis of aqueous solutions of alkali metal halides.

Claims

REVENDICATIONS
1. Diaphragme microporeux susceptible d'être obtenu par filtration au travers d'un support poreux, d'une dispersion aqueuse dépourvue de fibres d'amiante et de fibres de titanate, comprenant des fibres organiques, au moins un liant choisi parmi les polymères halogènes, au moins un agent porogène et des particules minérales de structure non fibreuse.1. Microporous diaphragm capable of being obtained by filtration, through a porous support, of an aqueous dispersion devoid of asbestos fibers and titanate fibers, comprising organic fibers, at least one binder chosen from halogenated polymers , at least one pore-forming agent and mineral particles of non-fibrous structure.
2. Diaphragme selon la revendication précédente, caractérisé en ce que les particules minérales présentent une granulométrie telle que leur taille moyenne est inférieure à 150 μm.2. Diaphragm according to the preceding claim, characterized in that the mineral particles have a particle size such that their average size is less than 150 μm.
3. Diaphragme selon la revendication précédente, caractérisé en ce que les particules minérales les particules présentent une granulométrie telle que leur taille moyenne est d'au moins 10 μm, et de préférence comprise entre 10 et 50 μm.3. Diaphragm according to the preceding claim, characterized in that the inorganic particles the particles have a particle size such that their average size is at least 10 μm, and preferably between 10 and 50 μm.
4. Diaphragme selon l'une quelconque des revendications précédentes, caractérisé en ce que les particules sont des particules de silicates hydratés comprenant au moins du magnésium et/ou de l'aluminium et/ou du potassium.4. Diaphragm according to any one of the preceding claims, characterized in that the particles are particles of hydrated silicates comprising at least magnesium and / or aluminum and / or potassium.
5. Diaphragme selon la revendication 4, caractérisé en ce que les particules sont des particules de talc ou de mica.5. Diaphragm according to claim 4, characterized in that the particles are talc or mica particles.
6. Diaphragme selon l'une des revendications précédentes, caractérisé en ce que les particules minérales présentent une structure plaquettaire.6. Diaphragm according to one of the preceding claims, characterized in that the mineral particles have a platelet structure.
7. Diaphragme selon l'une quelconque des revendications précédentes, caractérisé en ce que la teneur en particules minérales est comprise entre 30 et 100 parties en poids, pour 100 parties en poids de fibres organiques.7. Diaphragm according to any one of the preceding claims, characterized in that the content of mineral particles is between 30 and 100 parts by weight, per 100 parts by weight of organic fibers.
8. Diaphragme selon l'une quelconque des revendications précédentes, caractérisé en ce que les fibres organiques sont à base d'un polymère halogène choisi parmi les homopolymères ou copolymères dérivés au moins en partie de monomères oléfiniques substitués par des atomes de fluor ou substitués par une combinaison d'atomes de fluor et de l'un au moins des atomes de chlore, de brome ou d'iode par monomère, et de préférence, le polytétrafluoroéthylène. 8. Diaphragm according to any one of the preceding claims, characterized in that the organic fibers are based on a halogenated polymer chosen from homopolymers or copolymers derived at least in part from olefinic monomers substituted by fluorine atoms or substituted by a combination of fluorine atoms and at least one of chlorine, bromine or iodine atoms per monomer, and preferably polytetrafluoroethylene.
9. Diaphragme selon l'une quelconque des revendications précédentes, caractérisé en ce que le polymère halogène mis en œuvre en tant que liant est choisi parmi les homopolymères ou copolymères dérivés au moins en partie de monomères oléfiniques substitués par des atomes de fluor ou substitués par une combinaison d'atomes de fluor et de l'un au moins des atomes de chlore, de brome ou d'iode par monomère, et de préférence le polytétrafluoroéthylène.9. Diaphragm according to any one of the preceding claims, characterized in that the halogenated polymer used as a binder is chosen from homopolymers or copolymers derived at least in part from olefinic monomers substituted by fluorine atoms or substituted by a combination of fluorine atoms and at least one of chlorine, bromine or iodine atoms per monomer, and preferably polytetrafluoroethylene.
10. Diaphragme selon l'une quelconque des revendications précédentes, caractérisé en ce que la teneur en liant représente plus particulièrement 20 à 50 parties en poids, pour 100 parties en poids de fibres organiques.10. Diaphragm according to any one of the preceding claims, characterized in that the content of binder represents more particularly 20 to 50 parts by weight, per 100 parts by weight of organic fibers.
11. Diaphragme selon l'une quelconque des revendications précédentes, caractérisé en ce que l'agent porogène est choisi parmi les composés que l'on peut éliminer par voie chimique ou par voie thermique, ou un mélange de tels composés.11. Diaphragm according to any one of the preceding claims, characterized in that the pore-forming agent is chosen from the compounds which can be eliminated chemically or thermally, or a mixture of such compounds.
12. Diaphragme selon la revendication précédente, caractérisé en ce que l'agent porogène est la silice.12. Diaphragm according to the preceding claim, characterized in that the blowing agent is silica.
13. Diaphragme selon la revendication 11 , caractérisé en ce que l'agent porogène est choisi parmi les systèmes nanoparticulaires (latex de taille inférieure à 100 nm).13. A diaphragm according to claim 11, characterized in that the pore-forming agent is chosen from nanoparticulate systems (latex of size less than 100 nm).
14. Diaphragme selon l'une quelconque des revendications précédentes, caractérisé en ce que la teneur en agent porogène est comprise entre 20 et 100 parties en poids, pour 100 parties en poids de fibres organiques.14. Diaphragm according to any one of the preceding claims, characterized in that the content of blowing agent is between 20 and 100 parts by weight, per 100 parts by weight of organic fibers.
15. Diaphragme selon l'une quelconque des revendications précédentes, caractérisé en ce que la dispersion comprend au moins un tensioactif, ou au moins un agent épaississant, ou leurs mélanges.15. Diaphragm according to any one of the preceding claims, characterized in that the dispersion comprises at least one surfactant, or at least one thickening agent, or their mixtures.
16. Diaphragme selon l'une quelconque des revendications précédentes, caractérisé en ce que la dispersion comprend des fibres de carbone ou de graphite.16. Diaphragm according to any one of the preceding claims, characterized in that the dispersion comprises carbon or graphite fibers.
17. Diaphragme selon la revendication précédente, caractérisé en ce que la teneur en fibres de carbone, de graphite, ou leur mélange, est comprise entre 2 et 10 parties en poids pour 100 parties en poids de fibres organiques.17. Diaphragm according to the preceding claim, characterized in that the content of carbon fibers, of graphite, or their mixture, is between 2 and 10 parts by weight per 100 parts by weight of organic fibers.
18 Diaphragme selon l'une quelconque des revendications précédentes, caractérisé en ce que le support poreux peut être une autre nappe fibreuse, une surface métallique présentant des ouvertures dont la taille est comprise entre 20 μm et 5 mm, ou bien la combinaison de ces deux types de support.18 Diaphragm according to any one of the preceding claims, characterized in that the porous support can be another fibrous sheet, a metal surface with openings between 20 μm and 5 mm in size, or a combination of these two types of support.
19. Association caractérisée en ce quelle comprend le diaphragme selon l'une des revendications 1 à 18 et une nappe fibreuse, ou précathode, susceptible d'être obtenue par dépôt par filtration à travers un support poreux d'une dispersion comprenant des fibres dont une partie est conductrice de l'électricité, au moins un liant choisis parmi les polymères halogènes, au moins un agent électrocatalytique, au moins un agent porogène.19. Association characterized in that it comprises the diaphragm according to one of claims 1 to 18 and a fibrous sheet, or precathode, capable of being obtained by deposition by filtration through a porous support of a dispersion comprising fibers including one part is electrically conductive, at least one binder chosen from halogenated polymers, at least one electrocatalytic agent, at least one pore-forming agent.
20. Association selon la revendication précédente, caractérisée en ce que le support poreux est constitué par une surface métallique présentant des ouvertures dont la taille est comprise entre 20 μm et 5 mm, ou cathode élémentaire.20. Association according to the preceding claim, characterized in that the porous support is constituted by a metal surface having openings whose size is between 20 μm and 5 mm, or elementary cathode.
21. Association selon l'une des revendications 19 ou 20, caractérisée en ce que l'on trouve d'une face vers l'autre, le diaphragme, la précathode, le support constitué par la cathode élémentaire.21. Association according to one of claims 19 or 20, characterized in that one finds from one face towards the other, the diaphragm, the precathode, the support constituted by the elementary cathode.
22. Préparation du diaphragme selon l'une quelconque des revendications 1 à 18, caractérisé en ce que l'on met en œuvre les étape suivantes : a) on prépare une dispersion comprenant des fibres organiques, au moins un liant choisi parmi les polymères halogènes, au moins un agent porogène et des particules minérales de structure non fibreuse, b) on dépose par filtration sous vide, et à travers un support poreux, la dispersion ainsi obtenue, c) on élimine le liquide et, si nécessaire, on sèche la nappe fibreuse formée, d) on fritte la nappe fibreuse, e) on élimine, si nécessaire, l'agent porogène.22. Preparation of the diaphragm according to any one of claims 1 to 18, characterized in that the following steps are carried out: a) a dispersion is prepared comprising organic fibers, at least one binder chosen from halogenated polymers , at least one blowing agent and inorganic particles of non-fibrous structure, b) depositing by vacuum filtration, and through a porous support, the dispersion thus obtained, c) removing the liquid and, if necessary, drying the fibrous web formed, d) sintering the fibrous web, e) eliminating, if necessary, the blowing agent.
23. Préparation de l'association selon l'une quelconque des revendication 19 à 21 , caractérisé en ce que l'on met en œuvre les étapes suivantes : a) on prépare une suspension aqueuse comprenant les fibres, dont une partie est conductrice de l'électricité, au moins un liant choisi parmi les polymères halogènes, au moins un agent électrocatalytique, au moins un agent porogène, b) on dépose une nappe fibreuse par filtration sous vide programmé de ladite dispersion à travers un support poreux, c) on élimine le liquide et l'on sèche, si nécessaire, la nappe fibreuse formée, constituant la précathode, d) on fritte éventuellement la précathode, e) on élimine éventuellement l'agent porogène, f) on dépose sur la précathode, par filtration sous vide programmé, une dispersion aqueuse, comprenant des fibres organiques, au moins un liant choisi parmi les polymères halogènes, au moins un agent porogène et des particules minérales de structure non fibreuse, g) on élimine le liquide et l'on sèche éventuellement le diaphragme ainsi formé, h) on fritte l'ensemble, i) on élimine si nécessaire l'agent porogène.23. Preparation of the association according to any one of claims 19 to 21, characterized in that the following steps are implemented: a) an aqueous suspension is prepared comprising the fibers, part of which is conductive of the electricity, at least one binder chosen from halogenated polymers, at least one electrocatalytic agent, at least one pore-forming agent, b) a fibrous sheet is deposited by filtration under programmed vacuum of said dispersion through a porous support, c) it is eliminated the liquid and the fibrous web formed, constituting the precathode, is dried, if necessary d) optionally sintering the precathode, e) optionally eliminating the pore-forming agent, f) depositing on the precathode, by programmed vacuum filtration, an aqueous dispersion, comprising organic fibers, at least one binder chosen from halogenated polymers , at least one pore-forming agent and mineral particles of non-fibrous structure, g) the liquid is eliminated and the diaphragm thus formed is optionally dried, h) the whole is sintered, i) the pore-forming agent is eliminated if necessary .
24. Procédé selon l'une quelconque des revendications 22 ou 23, caractérisé en ce que l'élimination de l'agent porogène a lieu en effectuant un traitement chimique du diaphragme, de la nappe ou de leur association, avec une solution alcaline.24. Method according to any one of claims 22 or 23, characterized in that the elimination of the pore-forming agent takes place by carrying out a chemical treatment of the diaphragm, of the sheet or of their combination, with an alkaline solution.
25. Procédé selon l'une quelconque des revendication 22 à 24, caractérisé en ce que l'élimination de l'agent porogène a lieu lors de la première utilisation du diaphragme ou de l'association.25. Method according to any one of claims 22 to 24, characterized in that the elimination of the blowing agent takes place during the first use of the diaphragm or of the combination.
26. Procédé selon l'une quelconque des revendication 22 à 25, caractérisé en ce que l'élimination de l'agent porogène a lieu en mettant en œuvre un traitement thermique, de préférence celui correspondant à l'étape de frittage.26. Method according to any one of claims 22 to 25, characterized in that the elimination of the pore-forming agent takes place by implementing a heat treatment, preferably that corresponding to the sintering step.
27. Utilisation du diaphragme selon l'une quelconque des revendications 1 à 18, ou d'une association selon l'une quelconque des revendications 19 à 22, pour l'électrolyse de solutions aqueuses d'halogénure de métal alcalin. 27. Use of the diaphragm according to any one of claims 1 to 18, or a combination according to any one of claims 19 to 22, for the electrolysis of aqueous solutions of alkali metal halide.
EP00990842A 1999-12-30 2000-12-28 Asbestos-free diaphragm, comprising non-fibrous mineral particles, combination comprising same, method for obtaining same and use thereof Withdrawn EP1242655A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9916752 1999-12-30
FR9916752A FR2803309B1 (en) 1999-12-30 1999-12-30 ASBESTOS-FREE DIAPHRAGM COMPRISING NON-FIBROUS MINERAL PARTICLES, ASSOCIATION COMPRISING THE SAME, OBTAINING AND USING THE SAME
PCT/FR2000/003732 WO2001049902A1 (en) 1999-12-30 2000-12-28 Asbestos-free diaphragm, comprising non-fibrous mineral particles, combination comprising same, method for obtaining same and use thereof

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EP1242655A1 true EP1242655A1 (en) 2002-09-25

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JP6215010B2 (en) * 2013-11-15 2017-10-18 池上通信機株式会社 Small molded article conveying apparatus and lever-like member used in the apparatus

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US4720334A (en) * 1986-11-04 1988-01-19 Ppg Industries, Inc. Diaphragm for electrolytic cell
FR2650843B1 (en) * 1989-08-10 1992-01-17 Rhone Poulenc Chimie DIAPHRAGM, ASSOCIATION OF SUCH A DIAPHRAGM WITH A CATHODE ELEMENT AND PROCESS FOR OBTAINING SAME
WO1993016217A2 (en) * 1992-02-13 1993-08-19 The Dow Chemical Company Separators for electrolytic cells and processes for making
FR2727102B1 (en) * 1994-11-21 1997-08-01 Rhone Poulenc Chimie PROCESS FOR THE REMOVAL OF METAL IMPURITIES BY ELECTROCHEMICAL ROUTE
US5683749A (en) * 1995-07-26 1997-11-04 Ppg Industries, Inc. Method for preparing asbestos-free chlor-alkali diaphragm
US5685755A (en) * 1995-09-07 1997-11-11 The Dow Chemical Company Non-asbestos diaphragm separator
FR2743090B1 (en) * 1995-12-29 1998-02-06 Rhone Poulenc Chimie ASBESTOS-FREE CATHODE ELEMENT FOR USE IN SODIUM CHLORIDE SOLUTION ELECTROLYSIS

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FR2803309A1 (en) 2001-07-06
RU2002120187A (en) 2004-03-27

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