EP0037140B1 - Process for electrolyzing aqueous alkali metal halide solutions using a pervious diaphragm of a hydrophobic polymeric organic material - Google Patents

Process for electrolyzing aqueous alkali metal halide solutions using a pervious diaphragm of a hydrophobic polymeric organic material Download PDF

Info

Publication number
EP0037140B1
EP0037140B1 EP81200298A EP81200298A EP0037140B1 EP 0037140 B1 EP0037140 B1 EP 0037140B1 EP 81200298 A EP81200298 A EP 81200298A EP 81200298 A EP81200298 A EP 81200298A EP 0037140 B1 EP0037140 B1 EP 0037140B1
Authority
EP
European Patent Office
Prior art keywords
diaphragm
polymeric material
metal oxide
process according
electrolysis
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.)
Expired
Application number
EP81200298A
Other languages
German (de)
French (fr)
Other versions
EP0037140A1 (en
Inventor
Jean Indeherbergh
Edgard Nicolas
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.)
Solvay SA
Original Assignee
Solvay SA
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 Solvay SA filed Critical Solvay SA
Priority to AT81200298T priority Critical patent/ATE8154T1/en
Publication of EP0037140A1 publication Critical patent/EP0037140A1/en
Application granted granted Critical
Publication of EP0037140B1 publication Critical patent/EP0037140B1/en
Expired legal-status Critical Current

Links

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 subject of the present invention is a process for the electrolysis of an aqueous solution of an alkali metal halide, in particular of sodium chloride brines, in which a permeable diphragm of organic polymer material is opened.
  • hydrophilic additives into these diaphragms; these are usually mineral compounds in the particulate state, such as asbestos fibers, mica, talc, or even particles of titanate dioxide, alumina, silica or potassium titanate.
  • a permeable diaphragm for an electrolysis cell obtained by coagulation of a dispersion of polytetrafluoroethylene and an additive.
  • hydrophilic inorganic in the particulate state alumina, silica, titanium oxide
  • a diaphragm of controlled permeability for an electrolysis cell which is obtained by coagulation of a colloidal suspension of a mineral compound hydrophilic (potassium titanate, titanium dioxide, thorium dioxide, zirconium oxide) on cellulosic fibers, coagulation of a colloidal suspension of a fluoropolymer on cellulosic fibers coated with the hydrophilic mineral compound, formation of a sheet with the resulting coagulum, drying the sheet and heating it to melt the polymer and burn the cellulosic fibers. In this way a coherent porous sheet is obtained, the pores of which are lined with the hydrophilic mineral compound.
  • hydrophilic potassium titanate, titanium dioxide, thorium dioxide, zirconium oxide
  • Patent US 4036729 to Patil et al published on July 19, 1977, relates to a permeable diaphragm which consists of a felt formed on the perforated cathode of an electrolysis cell, starting from a dispersion of a polymeric material fibrous and a hydrophilic mineral compound (Asbestos, mica, talc, barium or potassium titanate, titanium dioxide, boron nitride) in an aqueous medium containing acetone and a surfactant.
  • a hydrophilic mineral compound Asbestos, mica, talc, barium or potassium titanate, titanium dioxide, boron nitride
  • these known diaphragms generally have the advantage of being inert with respect to the aggressive chemical media present in electrochemical cells, such as acid brines of sodium chloride or aqueous solutions of sodium hydroxide.
  • a diaphragm for an electrolysis cell by impregnating a support fabric of polymeric material, with a substance containing a compound siliceous.
  • the impregnating substance may optionally also contain an additive intended to improve the ionic conductivity of the diaphragm, such as magnesium oxide or alumina.
  • the siliceous compound of the impregnating substance must moreover be in the form of particles whose diameter must be greater than 1 ⁇ m and is preferably fixed between 1 and 75 ⁇ m.
  • This known diaphragm has the disadvantage of being of delicate and expensive construction; its intrinsic properties, in particular its permeability to aqueous electrolytes, are difficult to reproduce, because they are highly dependent on the nature and the origin of the siliceous compound.
  • the carboxylic functional groups of the fluoropolymer have the function of conferring the desired hydrophilicity on the diaphragms, while the magnesium compound, chemically bonded to the polymer, has the function of improving the stability and the consistency of the properties of the diaphragms.
  • porous sheet-shaped products are described, formed from an aggregate of fibers of organic polymer, inert, hydrophobic and suitable for various applications, such as diaphragms for electrolytic cells, separators for accumulators, fuel cell elements, dialysis membranes and filters.
  • These porous products may optionally contain a wettable additive, examples of which are inorganic oxides and hydroxides such as, in particular, zirconium oxide, titanium oxide, chromium oxide and the oxides and magnesium and calcium hydroxides.
  • a wettable additive examples of which are inorganic oxides and hydroxides such as, in particular, zirconium oxide, titanium oxide, chromium oxide and the oxides and magnesium and calcium hydroxides.
  • zirconium oxide titanium oxide, chromium oxide and the oxides and magnesium and calcium hydroxides.
  • the object of the invention is to provide a process for the electrolysis of an aqueous solution of alkali metal halide in a cell with a permeable diaphragm made of hydrophobic organic polymeric material, which has good mechanical cohesion, which is either a moderate cost which, all other things being equal, ensures improved performance for the electrolysis cells of aqueous solutions of alkali metal halide.
  • the invention therefore relates to a process for the electrolysis of an aqueous alkali metal halide solution in a cell with a permeable diaphragm in which or implements a permeable diaphragm made of hydrophobic organic polymeric material for a cell for the electrolysis of aqueous solutions.
  • the choice of the polymer of the organic polymeric material is dictated by the need to obtain a diaphragm which resists the chemical and thermal conditions normally prevailing in the electrolysis cells. It is possible, for example, to use thermoplastic polymers chosen from polyolefins, polycarbonates, polyesters, polyamides, polyimides, polyphenylenes, polyphenylene oxides, polyphenylene sulfides, polysulfones and mixtures of these polymers. In general, fluorinated polymers are preferably used, according to the invention.
  • Polymers containing fluorinated monomer units derived from ethylene or propylene are advantageously chosen, preferably polymers containing at least 50%, and more particularly at least 75%, of such monomer units.
  • Particularly suitable polymers are those containing only monomeric units derived from ethylene or propylene in which all the hydrogen atoms have been substituted by chlorine or fluorine atoms.
  • polymers which are suitable in the case where the diaphragm according to the invention is intended for the electrolysis of sodium chloride brines are those chosen from polytetrafluoroethylene, polychlortrifluoroethylene, polyvinylidene fluoride, copolymers of ethylene and chlorotrifluoroethylene, copolymers of ethylene and tetrafluoroethylene, copolymers of chlorotrifluoroethylene and vinylidene fluoride, copolymers of hydropentafluorpropylene and vinylidene fluoride, copolymers of hexafluoroisobutylene and vinylidene fluoride, copolymers of tetrafluoroethylene and perfluorvinyl ether sulphonyls, copolymers of tetrafluoroethylene and perfluoralkylvinyl ether.
  • Particularly preferred copolymers are those of tetrafluoroethylene and perfluoroprolylene.
  • a first characteristic of the invention consists in the fact that the hydrophilic additive of the diaphragm is an oxide of a metal chosen from those of group lla of the Periodic Table of the Elements.
  • Magnesium oxide has been found to be especially advantageous. All other things being equal, the performance of the electrolysis cells of aqueous sodium chloride solutions equipped with a diaphragm according to the invention are in fact optimum when the hydrophilic metal oxide is magnesium oxide.
  • the hydrophilic metal oxide is distributed in the form of particles among the organic polymer material. These particles can be in the amorphous state, in the state of single crystals or in the state of polycrystals, and they can have the form of grains or fibers.
  • the hydrophilic metal oxide particles have an average diameter which does not exceed 0.5 ⁇ m, the average diameter of a particle being by definition, the diameter of a sphere having a volume equal to that of the particle.
  • hydrophilic metal oxide particles whose mean diameter is between 0.002 ⁇ m and 0.2 ⁇ m, the values less than 0.1 ⁇ m being preferred.
  • metal oxide particles having an average diameter of between 0.005 and 0.05 ⁇ m have been found to be especially advantageous.
  • the quantity of hydrophilic metal oxide in the diaphragm according to the invention is generally chosen to be sufficient to give the diaphragm a wettability acceptable by aqueous electrolytes but without exceeding a limit value beyond which the cohesion or the mechanical resistance of the diaphragm becomes insufficient for the function for which it is intended.
  • hydrophilic metal oxide The choice of the optimum quantity of hydrophilic metal oxide to be used depends on a large number of parameters, among which appear in particular the nature of the organic polymeric material, the choice of the metal or metals of group lla entering into the composition. oxide metal, the shape and the average diameter of the metal oxide particles, as well as the destination of the diaphragm and the desired performance for the electrolysis cell for which the diaphragm is intended. In general, the optimum amount of hydrophilic metal oxide to be used must be determined in each particular case, by routine work in the laboratory.
  • diaphragms in accordance with the invention which have proved adequate in the majority of cases are those having a weight content of hydrophilic metal oxide at least equal to 5% of the total weight of the diaphragm, and generally between 10 and 80% of this weight. Weight contents of between 20 and 60% are however preferred.
  • the particles of the hydrophilic metal oxide can be distributed in the individual state among the mass of organic polymeric material or, alternatively, they can be contained in situ in the polymeric material, of which they constitute a filler.
  • a part of the particles of the hydrophilic metal oxide of the diaphragm can be distributed individually among the polymeric material, the remaining part of the particles being included in situ in the polymeric material of which it constitutes a filler.
  • the diaphragm according to the invention can be obtained by any technique commonly used for the manufacture of diaphragms made of organic polymeric material.
  • the organic polymeric material is in the fibrous state.
  • the organic polymeric material can be either in the form of fibers or fibrils; alternatively, it can also comprise a mixture of fibers and fibrils.
  • fibrils is intended to denote a specific structure of the polymeric material.
  • the fibrils consist of an aggregate of a multitude of very fine filaments, with a film-like appearance, connected together so as to form a three-dimensional network.
  • the fibrillated aggregates In appearance flaky, the fibrillated aggregates have an oblong shape; their length varies from 0.5 to 50 mm approximately and their diameter from a few microns to approximately 5 mm. They are characterized by a high specific surface, greater than 1 m 2 / g and even, in many cases, 10 m 2 / g.
  • the fibrils used in the context of the invention can, for example, be produced by subjecting a mixture of a polymer in the molten state and of a solvent, to a sudden expansion through an appropriate orifice, as described in particular in French patents 1,596,107 of December 13, 1968, 2,148,449 and 2,148,450 of August 1, 1972 and in Belgian patents 811,778 of March 1, 1974 and 824,844 of January 17, 1975, all in the name of the Applicant.
  • the fibrils used in the context of the invention can also be manufactured by other methods, for example by one or other of the methods described in French patents 1,214,157 or June 10, 1958 and 1,472,989 of September 24, 1965, on behalf of E.1. du Pont de Nemours and Co. In these manufacturing processes, however, continuous fibrillated locks are obtained, which must then be shredded, for example by grinding.
  • the organic polymeric material is in the form of fibers
  • fibers whose diameter is substantially between 0.1 and 25 microns fibers which are very suitable are those having a diameter of between 1 and 15 microns.
  • the hydrophilic metal oxide is contained in situ in the fibrous polymeric material, of which it constitutes a charge. It has in fact been observed that the diaphragms according to this variant of the invention have optimum cohesion and lead to particularly advantageous electrolysis results.
  • the diaphragms which lead to the most advantageous electrolysis results are those in which the polymeric material organic is perfluorinated and in a fibrous state, and in which, according to the invention, the hydrophilic metal oxide is magnesium oxide in particles which have an average diameter of between 0.005 and 0.05 I lm and which are contained in situ in the polymeric material, of which they constitute a filler.
  • the diaphragm can advantageously be in the form of a felt. This is generally obtained by decantation or filtration of a suspension of the fibrous polymeric material and the metal oxide particles in a suitable liquid which does not dissolve the polymeric material or the metal oxide.
  • a felt is formed from a suspension of the polymeric material in the fibrous state and hydrophilic metal oxide particles in water or an aqueous solution.
  • Suitable aqueous solutions include aqueous solutions of sodium chloride and aqueous solutions of sodium hydroxide.
  • Caustic brines containing 150 to 200 g of sodium chloride and 100 to 150 g of sodium hydroxide have been found to be particularly advantageous per liter; they are generally obtained by electrolysis of sodium chloride brines in diaphragm electrolysis cells.
  • a surfactant In order to facilitate the dispersion of the polymeric material and the hydrophilic metal oxide in water or the aqueous solution, it may be desirable to add a surfactant thereto. Fluorinated surfactants have been found to be especially advantageous, such as fluorinated or perfluorinated fatty acids, fluorinated or perfluorinated sulfonic acids and the salts of these acids.
  • the surfactant can be introduced individually in the aqueous solution.
  • the optimum amount of surfactant to be used depends on various factors, among which are in particular the nature of the polymer, the dimensions of the fibers or fibrils of the polymer, the nature of the aqueous solution and the nature of the surfactant. It can be determined in each particular case by routine laboratory work.
  • the surfactant is used in an amount of between 0.5 and 10% of the weight of the polymeric material, the values of between 2 and 7% being however preferred.
  • the felt is sufficient to decant or filter it.
  • the felt by filtering the above suspension directly through an openwork support of the diaphragm by applying a technique analogous to that commonly used for the manufacture of asbestos diaphragms and described in particular in the United States patents. 1 865152 in the name of KE STUART, of June 28, 1932, and 3 344 053 in the name of NEIPERT et al., Of May 4, 1964.
  • the perforated support of the diaphragm can advantageously be the perforated cathode of a diaphragm electrolysis cell .
  • This embodiment has the advantage of making it possible to manufacture the diaphragm in situ on cathodes of complicated shape, with non-developable surface, for example of the type equipping the electrolysis cells described in French patents 2,223,083 of 28 3. 1973 and 2,428,335 of October 14, 1974 in the name of the Claimant.
  • the dispersion of the polymeric material and the metal oxide in water or the aqueous solution and the filtration of the resulting aqueous suspension through the perforated support are executed in a single device, known per se for the manufacture of asbestos diaphragms, and described in French patent 2,308,702 of 25. 4.1975, in the name of the Applicant.
  • the diaphragm according to the invention has the advantage of having good mechanical cohesion and of being of stable dimensions during its use in an electrolysis cell. It has the advantageous property of an excellent wettability by aqueous electrolytes, in particular by sodium chloride brines.
  • the diaphragm according to the invention has the particularly advantageous characteristic of generally having a permeability to aqueous electrolytes of the same order of magnitude as that of asbestos diaphragms normally fitted to the electrolysis cells with sodium chloride brines. , so that it is well suited to be substituted for the asbestos diaphragms of existing electrolysis cells, for example of the type described in French patents 2 164 623 of 12.12.1972, 2 223 083 of 28. 3. 1973 , 2 230 411 dated 27. 3. 1974 and 2 248 335 dated 14.10.1974, all in the name of the Claimant.
  • the diaphragm according to the invention also has the interesting and surprising characteristic of having, from the start of its use, the optimum characteristics required for wettability and permeability.
  • This feature of the diaphragm according to the invention provides the appreciable advantage that the electrolysis cells are henceforth capable of operating under normal conditions, with optimum energy efficiency, from the start of their commissioning with a new diaphragm.
  • the diaphragm according to the invention may optionally contain, in addition to the polymeric material and the hydrophilic metal oxide, other usual constituents of the permeable diaphragms of the aimed at giving it additional properties.
  • some electrolysis tests were carried out in a laboratory cell comprising a vertical anode and a cathode separated by a diaphragm.
  • the anode consisted of a circular titanium plate of 113 cm 2 , carrying an active coating consisting of an equimolar mixture of ruthenium dioxide and titanium dioxide.
  • the cathode was formed from a 113 cm 2 mild steel circular lattice, and bore the diaphragm on its face opposite the anode. The distance between the anode and the cathode was 5 mm.
  • Examples 1 to 3 relate to electrolysis tests with diaphragms in accordance with the invention.
  • the fibrils have an average specific surface of approximately 23 m 2 / g. They were obtained, by subjecting a biphasic mixture of the polymer in the molten state and of an appropriate solvent, to a sudden expansion through an orifice of small section, as described in French patents 1,596,107 of December 13, 1968, 2 148,449 of 2,148,450 of August 1, 1972 and in the Belgian patents 811,778 of March 1, 1974 and 824,844 of January 17, 1975, all in the name of the Applicant.
  • the magnesium oxide particles have an average diameter of between 0.02 and 0.04 ⁇ m.
  • the fibrils and magnesium oxide particles were dispersed in caustic brine containing approximately 8% by weight of sodium hydroxide and 16% by weight of sodium chloride.
  • the caustic brine also contained, per liter, 400 mg of the product known as "Polymin P" (BASF) which is a polyethyleneimine retaining agent.
  • BASF Polymin P
  • the cathode of the cell was immersed therein and the suspension was sucked through it so as to deposit on its surface a felt formed from a mixture of fibrils and particles of magnesium oxide .
  • the felt had a weight corresponding to approximately 1.3 kg / m 3 of cathode surface area, and it contained approximately 68% by weight of fibrils and 32% by weight of magnesium oxide.
  • the felt on the cathode After forming the felt on the cathode, it was immediately mounted in the laboratory cell and there was electrolysis of a brine containing 255 g of sodium chloride per kg, at a constant current density, equal to 2 kA / m 2 of anode. The temperature in the cell was maintained at about 85 ° C for the duration of the test.
  • the magnesium oxide powder and a surfactant were combined with the polymer (copolymer of tetrafluoroethylene and perfluoropropylene) in situ in the fibrils, at the time of their manufacture.
  • the particles of magnesium oxide and the surfactant were incorporated into this mixture.
  • the respective amounts of magnesium oxide and of surfactant used have been adjusted so that the fibrils obtained contain approximately 58% by weight of polymer, 39% by weight of magnesium oxide and 3% by weight of agent. fluorinated surfactant.
  • the magnesium oxide particles used had an average diameter of between 0.02 and 0.04 ⁇ m.
  • the fibrils thus obtained had a specific surface area of approximately 25 m 2 / g.
  • a diaphragm consisting exclusively of such fibrils was deposited on the cathode of the laboratory cell, applying the method described in Example 1, but omitting however to incorporate the retaining agent »Polymin P « in the caustic brine bath. .
  • the weight of the diaphragm obtained corresponded to approximately 1.3 kg / m 2 of the cathode.
  • the diaphragm used in this test consisted of a felt formed from a mixture of individual particles of magnesium oxide identical to those used in Example 1 and of fibrils charged with magnesium oxide and a fluorinated surfactant, identical to the fibrils used in the test of Example 2.
  • the quantities used were adjusted so that the diaphragm formed on the cathode had a weight equivalent to 1.4 kg / m 2 of cathode surface and contained approximately 93% of fibrils loaded with magnesium oxide and surfactant and 7% of individual particles of magnesium oxide.
  • Example 4 relates to an electrolysis test with a diaphragm prior to the invention.
  • fibrils made of a copolymer of tetrafluoroethylene and perfluoropropylene, loaded with a powder of titanium dioxide and a fluorinated surfactant were manufactured.
  • the fibrils were manufactured by a technique comparable to that used to obtain the fibrils of Example 2.
  • the particles of titanium dioxide used in the manufacture of the fibrils had an average diameter equal to approximately 0.02 J lm.
  • the respective amounts of polymer, titanium dioxide and surfactant used were adjusted so that the fibrils obtained contain approximately 48.75% by weight of polymer, 48.75% by weight of titanium dioxide and 2 , 50% by weight of fluorosurfactant.
  • a diaphragm consisting exclusively of such fibrils was deposited on the cathode of the laboratory cell, by applying the method described in Example 2.
  • the weight of the diaphragm obtained corresponded to approximately 1.3 kg / m 2 of the cathode.

Abstract

Permeable diaphragm for a cell for the electrolysis of aqueous solutions of an alkali metal halide, the diaphragm being made from a hydrophobic organic polymeric material containing an oxide of a metal chosen from amongst group IIa of the periodic table of the elements, the oxide being in the form of particles having a mean diameter of at most 0.5 mu m.

Description

La présente invention a pour objet un procédé d'électrolyse d'une solution aqueuse d'halogénure de métal alcalin, notamment de saumures de chlorure de sodium, dans lequel on suet en ouvre un diphragme permeable en matière polymérique organique.The subject of the present invention is a process for the electrolysis of an aqueous solution of an alkali metal halide, in particular of sodium chloride brines, in which a permeable diphragm of organic polymer material is opened.

Il est connu d'utiliser des diaphragmes à base de polymères organiques dans des cellules d'électrolyse.It is known to use diaphragms based on organic polymers in electrolysis cells.

La nature fortement hydrophobe des polymères organiques qui conviennent pour cette application impose d'incorporer à ces diaphragmes des additifs hydrophiles; ceux-ci sont habituellement des composés minéraux à l'état particulaire, tels que des fibres d'amiante, du mica, du talc, ou encore des particules de bioxyde de titanate, d'alumine, de silice ou de titanate de potassium.The highly hydrophobic nature of the organic polymers which are suitable for this application makes it necessary to incorporate hydrophilic additives into these diaphragms; these are usually mineral compounds in the particulate state, such as asbestos fibers, mica, talc, or even particles of titanate dioxide, alumina, silica or potassium titanate.

Ainsi, dans le brevet Etats-Unis 3 702 267 publié le 7 novembre 1972 et cédé à E.I.Du Pont de Nemours, on décrit un diaphragme perméable pour cellule d'électrolyse, obtenu par coagulation d'une dispersion de polytétrafluoréthylène et d'un additif inorganique hydrophile à l'état particulaire (alumine, silice, oxyde de titane), calandrage du coagulum résultant pour le mettre sous la forme d'une feuille et séchage de la feuille.Thus, in the United States patent 3,702,267 published on November 7, 1972 and assigned to EIDu Pont de Nemours, a permeable diaphragm for an electrolysis cell is described, obtained by coagulation of a dispersion of polytetrafluoroethylene and an additive. hydrophilic inorganic in the particulate state (alumina, silica, titanium oxide), calendering of the resulting coagulum to form it into a sheet and drying of the sheet.

Dans le brevet Etats-Unis 3 627 859, publié le 14 décembre 1971 et cédé à Leesona Corp., on décrit un diaphragme de perméabilité réglée pour cellule d'électrolyse, qui est obtenu par coagulation d'une suspension colloidale d'un composé minéral hydrophile (titanate de potassium, dioxyde de titane, dioxyde de thorium, oxyde de zirconium) sur des fibres cellulosiques, coagulation d'une suspension colloidale d'un polymère fluoré sur les fibres cellulosiques revêtues du composé minéral hydrophile, formation d'une feuille avec le coagulum résultant, séchage de la feuille et chauffage de celle-ci pour fondre le polymère et brûler les fibres cellulosiques. On obtient de la sorte une feuille poreuse cohérente, dont les pores sont tapissés du composé minéral hydrophile.In US Patent 3,627,859, issued December 14, 1971 and assigned to Leesona Corp., a diaphragm of controlled permeability for an electrolysis cell is described, which is obtained by coagulation of a colloidal suspension of a mineral compound hydrophilic (potassium titanate, titanium dioxide, thorium dioxide, zirconium oxide) on cellulosic fibers, coagulation of a colloidal suspension of a fluoropolymer on cellulosic fibers coated with the hydrophilic mineral compound, formation of a sheet with the resulting coagulum, drying the sheet and heating it to melt the polymer and burn the cellulosic fibers. In this way a coherent porous sheet is obtained, the pores of which are lined with the hydrophilic mineral compound.

Le brevet Etats-Unis 4036729 de Patil et al, pulbié le 19 juillet 1977, concerne un diaphragme perméable qui consiste en un feutre formé sur la cathode ajourée d'une cellule d'électrolyse, au départ d'une dispersion d'une matière polymérique fibreuse et d'un composé minéral hydrophile (Amiante, mica, talc, titanate de baryum ou de potassium, dioxyde de titane, nitrure de bore) dans un milieu aqueux contenant de l'acétone et un agent tensioactif.Patent US 4036729 to Patil et al, published on July 19, 1977, relates to a permeable diaphragm which consists of a felt formed on the perforated cathode of an electrolysis cell, starting from a dispersion of a polymeric material fibrous and a hydrophilic mineral compound (Asbestos, mica, talc, barium or potassium titanate, titanium dioxide, boron nitride) in an aqueous medium containing acetone and a surfactant.

Grâce à un choix approprié des polymères entrant dans leur constitution, ces diaphragmes connus présentent généralement l'avantage d'être inertes vis-à-vis des milieux chimiques agressifs présents dans les cellules électrochimiques, tels que les saumures acides de chlorure de sodium ou les solutions aqueuses d'hydroxyde de sodium.Thanks to an appropriate choice of polymers entering into their constitution, these known diaphragms generally have the advantage of being inert with respect to the aggressive chemical media present in electrochemical cells, such as acid brines of sodium chloride or aqueous solutions of sodium hydroxide.

Ils présentent néanmoins le grave inconvénient de nécessiter généralement des teneurs excessives en composés minéraux hydrophiles, qui peuvent parfois dépasser 90% du poids global du diaphragme, ce qui complique grandement leur mise en oeuvre et nuit par ailleurs à leur cohésion et à leur résistance mécanique.They nevertheless have the serious drawback of generally requiring excessive contents of hydrophilic mineral compounds, which can sometimes exceed 90% of the overall weight of the diaphragm, which greatly complicates their implementation and also harms their cohesion and their mechanical strength.

On a aussi proposé, dans le brevet belge 870 771, déposé le 26 mars 1979 au nom de Olin Corporation, de fabriquer un diaphragme pour cellule d'électrolyse par imprégnation d'un tissu de support en matière polymérique, avec une substance contenant un composé siliceux. En plus du composé siliceux, la substance d'imprégnation peut éventuellement contenir aussi un additif destiné à améliorer la conductivité ionique du diaphragme, tel que de l'oxyde de magnésium ou de l'alumine. Le composé siliceux de la substance d'imprégnation doit par ailleurs être à l'état de particules dont le diamètre doit être supérieur à 1 Ilm et est de préférence fixé entre 1 et 75 um.It has also been proposed, in Belgian patent 870,771, filed on March 26, 1979 in the name of Olin Corporation, to manufacture a diaphragm for an electrolysis cell by impregnating a support fabric of polymeric material, with a substance containing a compound siliceous. In addition to the siliceous compound, the impregnating substance may optionally also contain an additive intended to improve the ionic conductivity of the diaphragm, such as magnesium oxide or alumina. The siliceous compound of the impregnating substance must moreover be in the form of particles whose diameter must be greater than 1 μm and is preferably fixed between 1 and 75 μm.

Ce diaphragme connu présente le désavantage d'être de construction délicate et coûteuse; ses propriétés intrinsèques, notamment sa perméabilité aux électrolytes aqueux, sont difficilement reproductibles, car elles sont fortement tributaires de la nature et de l'origine du composé siliceux.This known diaphragm has the disadvantage of being of delicate and expensive construction; its intrinsic properties, in particular its permeability to aqueous electrolytes, are difficult to reproduce, because they are highly dependent on the nature and the origin of the siliceous compound.

Dans la demande de brevet européen 79 102 380.7, déposée le 11 juillet 1979 au nom de E.l.du Pont de Nemours & Cy, et publié le 19 mars 1980 sous le no 8 635, on propose pour remédier aux inconvénients précités, de réaliser les diaphragmes en une matière polymérique fluorée contenant des groupes fonctionnels hydrophiles, carboxyliques et d'y incorporer un composé de magnésium choisi parmi les oxyde, hydroxyde, carbonate, oxyhalogénures et hydroxyhalogénures de magnésium, le composé de magnésium étant lié chimiquement à la matière polymérique fluorée. Dans ces diaphragmes connus, les groupes fonctionnels carboxyliques du polymère fluoré ont pour fonction de conférer le caractère hydrophile recherché aux diaphragmes, tandis que le composé de magnésium, lié chimiquement au polymère, a pour fonction d'améliorer la stabilité et la constance des propriétés des diaphragmes.In European patent application 79 102 380.7, filed on July 11, 1979 in the name of Eldu Pont de Nemours & Cy, and published on March 19, 1980 under No. 8,635, it is proposed to remedy the aforementioned drawbacks, to produce the diaphragms into a fluorinated polymeric material containing hydrophilic, carboxylic functional groups and of incorporating therein a magnesium compound chosen from magnesium oxide, hydroxide, carbonate, oxyhalides and hydroxyhalides, the magnesium compound being chemically bonded to the fluorinated polymeric material. In these known diaphragms, the carboxylic functional groups of the fluoropolymer have the function of conferring the desired hydrophilicity on the diaphragms, while the magnesium compound, chemically bonded to the polymer, has the function of improving the stability and the consistency of the properties of the diaphragms.

De tels diaphragmes présentent le désavantage d'être de fabrication difficile et coûteuse.Such diaphragms have the disadvantage of being difficult and expensive to manufacture.

Dans le brevet beige 833 912, déposé le 26 septembre 1975 au nom de Imperial Chemical Industries Limited, on décrit des produits poreux en forme de feuilles, formés d'un aggrégat de fibres en polymère organique, inerte, hydrophobe et convenant pour diverses applications, telles que des diaphragmes pour cellules d'électrolyse, des séparateurs pour accumulateurs, des éléments de piles à combustible, des membranes de dialyse et des filtres. Ces produits poreux peuvent éventuellement contenir un additif mouillable, dont des exemples cités sont les oxydes et hydroxydes inorganiques tels que, notamment, l'oxyde de zirconium, l'oxyde de titane, l'oxyde de chrome et les oxydes et hydroxydes de magnésium et de calcium. En règle générale, on suggère d'utiliser de l'oxyde de titane ou de l'oxyde de zirconium dans tous les exemples d'application des feuilles poreuses comme diaphragmes dans des cellules d'électrolyse de solutions de chlorure de sodium.In beige patent 833,912, filed September 26, 1975 in the name of Imperial Chemical Industries Limited, porous sheet-shaped products are described, formed from an aggregate of fibers of organic polymer, inert, hydrophobic and suitable for various applications, such as diaphragms for electrolytic cells, separators for accumulators, fuel cell elements, dialysis membranes and filters. These porous products may optionally contain a wettable additive, examples of which are inorganic oxides and hydroxides such as, in particular, zirconium oxide, titanium oxide, chromium oxide and the oxides and magnesium and calcium hydroxides. As a general rule, it is suggested to use titanium oxide or zirconium oxide in all the examples of application of the porous sheets as diaphragms in cells for electrolysis of sodium chloride solutions.

On a maintenant observé qu'il était possible d'améliorer grandement les performances des cellules d'électrolyse de solutions aqueuses de chlorure de sodium équipées de diaphragmes en matière polymérique organique hydrophobe, en opérant une sélection bien spécifique parmi les nombreux additifs hydrophiles utilisables dans de tels diaphragmes.It has now been observed that it was possible to greatly improve the performance of the electrolysis cells of aqueous sodium chloride solutions equipped with diaphragms made of hydrophobic organic polymeric material, by making a very specific selection from among the numerous hydrophilic additives usable in such diaphragms.

En conséquence, l'invention a pour objectif de fournir un procédé d'électrolyse d'une solution aqueuse d'halogénure de métal alcalin dans une cellule à diaphragme permeable en matière polymérique organique hydrophobe, qui présente une bonne cohésion mécanique, qui soit d'un coût modéré et qui assure, toutes autres choses étant égales, des performances améliorées aux cellules d'électrolyse des solutions aqueuses d'halogénure de métal alcalin.Consequently, the object of the invention is to provide a process for the electrolysis of an aqueous solution of alkali metal halide in a cell with a permeable diaphragm made of hydrophobic organic polymeric material, which has good mechanical cohesion, which is either a moderate cost which, all other things being equal, ensures improved performance for the electrolysis cells of aqueous solutions of alkali metal halide.

L'invention concerne dès lors un procédé d'électrolyse d'une solution aqueuse d'halogénure de métal alcalin dans une cellule à diaphragme permeable dans lequel ou met en ouvre un diaphragme perméable en matière polymérique organique hydrophobe pour cellule d'électrolyse de solutions aqueuses d'halogénure de métal alcalin, contenant un oxyde métallique hydrophile à l'état de particules; selon l'invention, l'oxyde metallique hydrophile est choisi parmie les oxydes des métaux du groupe lia du Tableau périodique des éléments, à l'état de particules ayant un diamètre moyen égal au maximum à 0,5 Jlm.The invention therefore relates to a process for the electrolysis of an aqueous alkali metal halide solution in a cell with a permeable diaphragm in which or implements a permeable diaphragm made of hydrophobic organic polymeric material for a cell for the electrolysis of aqueous solutions. an alkali metal halide, containing a hydrophilic metal oxide in the form of particles; according to the invention, the hydrophilic metal oxide is chosen from the oxides of the metals of group lia of the Periodic Table of the Elements, in the form of particles having an average diameter equal to at most 0.5 Jlm.

Dans le diaphragme mis en ouvre dans le procédé selon l'invention, le choix du polymère de la matière polymérique organique est dicté par la nécessité d'obtenir un diaphragme qui résiste aux conditions chimiques et thermiques régnant normalement dans les cellules d'électrolyse. On peut par exemple utiliser des polymères thermoplastiques choisis parmi les polyoléfines, les polycarbonates, les polyesters, les polyamides, les polyimides, les polyphénylènes, les oxydes de polyphénylènes, les sulfures de polyphénylènes, les polysulfones et les mélanges de ces polymères. D'une manière générale, on utilise de préférence, selon l'invention, des polymères fluorés. On choisit avantageusement des polymères contenant des unités monomériques fluorées dérivées de l'éthylène ou du propylène, de préférence des polymères contenant au moins 50%, et plus particulièrement au moins 75%, de telles unités monomériques. Des polymères particulièrement adéquats sont ceux ne contenant que des unités monomériques dérivées de l'éthylène ou du propylène dont tous les atomes d'hydrogène ont été substitués par des atomes de chlore ou de fluor.In the diaphragm implemented in the method according to the invention, the choice of the polymer of the organic polymeric material is dictated by the need to obtain a diaphragm which resists the chemical and thermal conditions normally prevailing in the electrolysis cells. It is possible, for example, to use thermoplastic polymers chosen from polyolefins, polycarbonates, polyesters, polyamides, polyimides, polyphenylenes, polyphenylene oxides, polyphenylene sulfides, polysulfones and mixtures of these polymers. In general, fluorinated polymers are preferably used, according to the invention. Polymers containing fluorinated monomer units derived from ethylene or propylene are advantageously chosen, preferably polymers containing at least 50%, and more particularly at least 75%, of such monomer units. Particularly suitable polymers are those containing only monomeric units derived from ethylene or propylene in which all the hydrogen atoms have been substituted by chlorine or fluorine atoms.

A titre d'exemple, des polymères qui conviennent dans le cas où le diaphragme selon l'invention, est destiné à l'électrolyse de saumures de chlorure de sodium, sont ceux choisis parmi le polytétrafluoréthylène, le polychlortrifluoréthylène, le polyfluorure de vinylidène, les copolymères d'éthylène et de chlorotrifluoréthylène, les copolymères d'éthylène et de tétrafluoréthylène, les copolymères de chlorotrifluoréthylène et de fluorure de vinylidène, les copolymères d'hydropentafluorpropylène et de fluorure de vinylidène, les copolymères d'hexafluoroisobutylène et de fluorure de vinylidène, les copolymères de tétrafluoréthylène et de perfluorvinyléther sulfonyles, les copolymères de tétrafluoréthylène et de perfluoralkylvinyléther. Des copolymères particulièrement préférés sont ceux de tétrafluoréthylène et de perfluoroprolylène.By way of example, polymers which are suitable in the case where the diaphragm according to the invention is intended for the electrolysis of sodium chloride brines, are those chosen from polytetrafluoroethylene, polychlortrifluoroethylene, polyvinylidene fluoride, copolymers of ethylene and chlorotrifluoroethylene, copolymers of ethylene and tetrafluoroethylene, copolymers of chlorotrifluoroethylene and vinylidene fluoride, copolymers of hydropentafluorpropylene and vinylidene fluoride, copolymers of hexafluoroisobutylene and vinylidene fluoride, copolymers of tetrafluoroethylene and perfluorvinyl ether sulphonyls, copolymers of tetrafluoroethylene and perfluoralkylvinyl ether. Particularly preferred copolymers are those of tetrafluoroethylene and perfluoroprolylene.

Une première caractéristique de l'invention consiste dans le fait que l'additif hydrophile du diaphragme est un oxyde d'un métal choisi parmi ceux du groupe lla du Tableau périodique des éléments.A first characteristic of the invention consists in the fact that the hydrophilic additive of the diaphragm is an oxide of a metal chosen from those of group lla of the Periodic Table of the Elements.

L'oxyde de magnésium s'est révélé spécialement avantageux. Toutes autres choses étant égales, les performances des cellules d'électrolyse de solutions aqueuses de chlorure de sodium équipées d'un diaphragme conforme à l'invention sont en effet optimum lorsque l'oxyde métallique hydrophile est de l'oxyde de magnésium.Magnesium oxide has been found to be especially advantageous. All other things being equal, the performance of the electrolysis cells of aqueous sodium chloride solutions equipped with a diaphragm according to the invention are in fact optimum when the hydrophilic metal oxide is magnesium oxide.

Dans le diaphragme selon l'invention, l'oxyde métallique hydrophile est distribué à l'état de particules parmi la matière polymère organique. Ces particules peuvent être à l'état amorphe, à l'état de monocristaux ou à l'état de polycristaux, et elles peuvent avoir la forme de grains ou de fibres.In the diaphragm according to the invention, the hydrophilic metal oxide is distributed in the form of particles among the organic polymer material. These particles can be in the amorphous state, in the state of single crystals or in the state of polycrystals, and they can have the form of grains or fibers.

Selon une seconde caractéristique de l'invention, les particules d'oxyde métallique hydrophile ont un diamètre moyen qui n'excède pas 0,5 pm, le diamètre moyen d'une particule étant par définition, le diamètre d'une sphère ayant un volume égal à celui de la particule.According to a second characteristic of the invention, the hydrophilic metal oxide particles have an average diameter which does not exceed 0.5 μm, the average diameter of a particle being by definition, the diameter of a sphere having a volume equal to that of the particle.

En pratique, pour des considérations de coût et de facilité de mise en oeuvre, il n'est pas souhaitable de réduire le diamètre moyen des particules de l'oxyde métallique hydrophile sous 0,001 µm.In practice, for reasons of cost and ease of implementation, it is not desirable to reduce the average diameter of the particles of the hydrophilic metal oxide below 0.001 μm.

Toutes autres choses étant égales, on obtient généralement de bons résultats avec des particules d'oxyde métallique hydrophile dont le diamètre moyen est compris entre 0,002 µm et 0,2 µm, les valeurs inférieures à 0,1 µm étant préférées. En général, les particules d'oxyde métallique ayant un diamètre moyen compris entre 0,005 et 0,05 µm se sont révélées spécialement avantageuses.All other things being equal, good results are generally obtained with hydrophilic metal oxide particles whose mean diameter is between 0.002 μm and 0.2 μm, the values less than 0.1 μm being preferred. In general, metal oxide particles having an average diameter of between 0.005 and 0.05 µm have been found to be especially advantageous.

La quantité d'oxyde métallique hydrophile dans le diaphragme selon l'invention est choisie en général pour être suffisante pour conférer au diaphragme une mouillabilité acceptable par les électrolytes aqueux mais sans excéder une valeur limite au-delà de laquelle la cohésion ou la résistance mécanique du diaphragme devienne insuffisante pour la fonction à laquelle on le destine.The quantity of hydrophilic metal oxide in the diaphragm according to the invention is generally chosen to be sufficient to give the diaphragm a wettability acceptable by aqueous electrolytes but without exceeding a limit value beyond which the cohesion or the mechanical resistance of the diaphragm becomes insufficient for the function for which it is intended.

Le choix de la quantité optimum d'oxyde métallique hydrophile à mettre en oeuvre dépend d'un grand nombre de paramètres, parmi lesquels figurent notamment la nature de la matière polymérique organique, le choix du métal ou des métaux du groupe lla entrant dans la composition de l'oxyde métallique, la forme et le diamètre moyen des particules de l'oxyde métallique, ainsi que la destination du diaphragme et les performances souhaitées pour la cellule d'électrolyse à laquelle on destine le diaphragme. D'une manière générale, la quantité optimum d'oxyde métallique hydrophile à mettre en oeuvre doit être déterminée dans chaque cas particulier, par un travail de routine au laboratoire.The choice of the optimum quantity of hydrophilic metal oxide to be used depends on a large number of parameters, among which appear in particular the nature of the organic polymeric material, the choice of the metal or metals of group lla entering into the composition. oxide metal, the shape and the average diameter of the metal oxide particles, as well as the destination of the diaphragm and the desired performance for the electrolysis cell for which the diaphragm is intended. In general, the optimum amount of hydrophilic metal oxide to be used must be determined in each particular case, by routine work in the laboratory.

En pratique, des diaphragmes conformes à l'invention qui se sont révélés adéquats dans la majorité des cas sont ceux ayant une teneur pondérale en oxyde métallique hydrophile au moins égale à 5% du poids total du diaphragme, et généralement comprise entre 10 et 80% de ce poids. Des teneurs pondérales comprises entre 20 et 60% sont toutefois préférées.In practice, diaphragms in accordance with the invention which have proved adequate in the majority of cases are those having a weight content of hydrophilic metal oxide at least equal to 5% of the total weight of the diaphragm, and generally between 10 and 80% of this weight. Weight contents of between 20 and 60% are however preferred.

Dans le diaphragme selon l'invention, les particules de l'oxyde métallique hydrophile peuvent être distribuées à l'état individuel parmi la masse de matière polymérique organique ou, en variante, elles peuvent être contenues in situ dans la matière polymérique, dont elles constituent une matière de charge. En variante, une partie des particules de l'oxyde métallique hydrophile du diaphragme peuvent être réparties individuellement parmi la matière polymérique, la partie restante des particules étant englobée in situ dans la matière polymérique dont elle constitue une matière de charge.In the diaphragm according to the invention, the particles of the hydrophilic metal oxide can be distributed in the individual state among the mass of organic polymeric material or, alternatively, they can be contained in situ in the polymeric material, of which they constitute a filler. As a variant, a part of the particles of the hydrophilic metal oxide of the diaphragm can be distributed individually among the polymeric material, the remaining part of the particles being included in situ in the polymeric material of which it constitutes a filler.

Le diaphragme selon l'invention peut être obtenu par toute technique communément utilisée pour la fabrication des diaphragmes en matière polymérique organique.The diaphragm according to the invention can be obtained by any technique commonly used for the manufacture of diaphragms made of organic polymeric material.

Il peut notamment se présenter sous la forme d'une feuille mince calandrée, obtenue par exemple par une technique similaire à celles décrites dans les brevets Etats-Unis 3 702 267 et 3 627 859 auxquels il a été fait référence ci-dessus.It can in particular be in the form of a thin calendered sheet, obtained for example by a technique similar to those described in US Patents 3,702,267 and 3,627,859 to which reference has been made above.

Toutefois, dans une forme de réalisation preférée du diaphragme selon l'invention, la matière polymérique organique est à l'état fibreux.However, in a preferred embodiment of the diaphragm according to the invention, the organic polymeric material is in the fibrous state.

Dans cette forme de réalisation préférée de l'invention, la matière polymérique organique peut être indifféremment à l'état de fibres ou de fibrilles; en variante, elle peut aussi comprendre un mélange de fibres et de fibrilles.In this preferred embodiment of the invention, the organic polymeric material can be either in the form of fibers or fibrils; alternatively, it can also comprise a mixture of fibers and fibrils.

On entend désigner par fibrilles une structure spécifique de la matière polymère. Les fibrilles consistent en un agrégat d'une multitude de filaments très ténus, d'aspect pelliculaire, connectés entre eux de manière à former un réseau tridimensionnel. D'aspect floconneux, les agrégats fibrillés ont une forme oblongue; leur longueur varie de 0,5 à 50 mm environ et leur diamètre de quelques microns à 5 mm environ. Ils sont caractérisés par une surface spécifique élevée, supérieure à 1 m2/g et même, dans beaucoup de cas, à 10 m2/g.The term “fibrils” is intended to denote a specific structure of the polymeric material. The fibrils consist of an aggregate of a multitude of very fine filaments, with a film-like appearance, connected together so as to form a three-dimensional network. In appearance flaky, the fibrillated aggregates have an oblong shape; their length varies from 0.5 to 50 mm approximately and their diameter from a few microns to approximately 5 mm. They are characterized by a high specific surface, greater than 1 m 2 / g and even, in many cases, 10 m 2 / g.

Les fibrilles utilisées dans le cadre de l'invention peuvent, par exemple, être fabriquées en soumettant un mélange d'un polymère à l'état fondu et d'un solvant, à une détente brusque au travers d'un orifice approprié, comme décrit notamment dans les brevets français 1 596 107 du 13 décembre 1968, 2 148 449 et 2148 450 du ler août 1972 et dans les brevets belges 811 778 du ler mars 1974 et 824 844 du 17 janvier 1975, tous au nom de la Demanderesse.The fibrils used in the context of the invention can, for example, be produced by subjecting a mixture of a polymer in the molten state and of a solvent, to a sudden expansion through an appropriate orifice, as described in particular in French patents 1,596,107 of December 13, 1968, 2,148,449 and 2,148,450 of August 1, 1972 and in Belgian patents 811,778 of March 1, 1974 and 824,844 of January 17, 1975, all in the name of the Applicant.

En variante, les fibrilles utilisées dans le cadre de l'invention peuvent aussi être fabriquées par d'autres procédés, par exemple par l'un ou l'autre des procédés décrits dans les brevets français 1 214157 ou 10 juin 1958 et 1 472 989 du 24 septembre 1965, au nom de E.1. du Pont de Nemours and Co. Dans ces procédés de fabrication, on obtient toutefois des mèches fibrillées continues, qu'il convient ensuite de déchiqueter, par exemple par broyage.Alternatively, the fibrils used in the context of the invention can also be manufactured by other methods, for example by one or other of the methods described in French patents 1,214,157 or June 10, 1958 and 1,472,989 of September 24, 1965, on behalf of E.1. du Pont de Nemours and Co. In these manufacturing processes, however, continuous fibrillated locks are obtained, which must then be shredded, for example by grinding.

Dans le cas où la matière polymérique organique est à l'état de fibres, il est préférable, suivant l'invention, d'utiliser des fibres dont le diamètre est sensiblement compris entre 0,1 et 25 microns; des fibres qui conviennent bien sont celles ayant un diamètre compris entre 1 et 15 microns.In the case where the organic polymeric material is in the form of fibers, it is preferable, according to the invention, to use fibers whose diameter is substantially between 0.1 and 25 microns; fibers which are very suitable are those having a diameter of between 1 and 15 microns.

Selon une variante spécialement avantageuse de la forme de réalisation préférée de l'invention, dans laquelle la matière polymérique organique est à l'état fibreux, l'oxyde métallique hydrophile est contenu in situ dans la matière polymérique fibreuse, dont il constitue une matière de charge. On a en effet observé que les diaphragmes conformes à cette variante de l'invention présentent une cohésion optimum et conduisent à des résultats d'électrolyse spécialement avantageux.According to a particularly advantageous variant of the preferred embodiment of the invention, in which the organic polymeric material is in the fibrous state, the hydrophilic metal oxide is contained in situ in the fibrous polymeric material, of which it constitutes a charge. It has in fact been observed that the diaphragms according to this variant of the invention have optimum cohesion and lead to particularly advantageous electrolysis results.

Toutes autres choses étant égales, dans le cas où l'invention est appliquée aux cellules à diaphragme pour l'électrolyse des solutions aqueuses de chlorure de sodium, les diaphragmes qui conduisent aux résultats d'électrolyse les plus avantageux sont ceux dans lesquels la matière polymérique organique est perfluorée et à l'état fibreux, et dans lesquels, conformément à l'invention, l'oxyde métallique hydrophile est de l'oxyde de magnésium en particules qui ont un diamètre moyen compris entre 0,005 et 0,05 Ilm et qui sont contenues in situ dans la matière polymérique, dont elles constituent une matière de charge.All other things being equal, in the case where the invention is applied to diaphragm cells for the electrolysis of aqueous sodium chloride solutions, the diaphragms which lead to the most advantageous electrolysis results are those in which the polymeric material organic is perfluorinated and in a fibrous state, and in which, according to the invention, the hydrophilic metal oxide is magnesium oxide in particles which have an average diameter of between 0.005 and 0.05 I lm and which are contained in situ in the polymeric material, of which they constitute a filler.

Dans la forme de réalisation préférée de l'invention où la matière polymérique est à l'état fibreux, le diaphragme peut avantageusement se présenter sous la forme d'un feutre. Celui-ci est généralement obtenu par décantation ou filtration d'une suspension de la matière polymérique fibreuse et des particules d'oxyde métallique dans un liquide adéquat qui ne dissout pas la matière polymérique ni l'oxyde métallique.In the preferred embodiment of the invention where the polymeric material is in the fibrous state, the diaphragm can advantageously be in the form of a felt. This is generally obtained by decantation or filtration of a suspension of the fibrous polymeric material and the metal oxide particles in a suitable liquid which does not dissolve the polymeric material or the metal oxide.

Un mode de fabrication adéquat d'un tel feutre est décrit dans la demande de brevet européen 79 200 411.1 déposée le 19 juillet 1979, au nom de la Demanderesse. Selon ce mode de fabrication, on disperse les fibres ou les fibrilles de la matière polymérique et les particules d'oxyde métallique hydrophile dans un liquide organique, on soumet la suspension résultante à un battage, puis on la décante ou la filtre.An adequate method of manufacturing such a felt is described in European patent application 79 200 411.1 filed on July 19, 1979, in the name of the Applicant. According to this manufacturing method, the fibers or fibrils of the polymeric material and the hydrophilic metal oxide particles are dispersed in an organic liquid, the resulting suspension is subjected to beating, then it is decanted or filtered.

Selon un mode de fabrication préféré du diaphragme selon l'invention, on forme un feutre au départ d'une suspension de la matière polymérique à l'état fibreux et des particules d'oxyde métallique hydrophile dans de l'eau ou une solution aqueuse. Des solutions aqueuses qui conviennent bien sont notamment les solutions aqueuses de chlorure de sodium et les solutions aqueuses d'hydroxyde de sodium. Les saumures caustiques contenant, par litre, de 150 à 200 g de chlorure de sodium et de 100 à 150 g d'hydroxyde de sodium se sont révélées spécialement avantageuses; elles sont généralement obtenues par électrolyse de saumures de chlorure de sodium dans des cellules d'électrolyse à diaphragme. Afin de faciliter la dispersion de la matière polymérique et de l'oxyde métallique hydrophile dans l'eau ou la solution aqueuse, il peut être souhaitable d'y ajouter un agent tensioactif. Les agents tensioactifs fluorés se sont révélés spécialement avantageux, tels que les acides gras fluorés ou perfluorés, les acides sulfoniques fluorés ou perfluorés et les sels de ces acides.According to a preferred method of manufacturing the diaphragm according to the invention, a felt is formed from a suspension of the polymeric material in the fibrous state and hydrophilic metal oxide particles in water or an aqueous solution. Suitable aqueous solutions include aqueous solutions of sodium chloride and aqueous solutions of sodium hydroxide. Caustic brines containing 150 to 200 g of sodium chloride and 100 to 150 g of sodium hydroxide have been found to be particularly advantageous per liter; they are generally obtained by electrolysis of sodium chloride brines in diaphragm electrolysis cells. In order to facilitate the dispersion of the polymeric material and the hydrophilic metal oxide in water or the aqueous solution, it may be desirable to add a surfactant thereto. Fluorinated surfactants have been found to be especially advantageous, such as fluorinated or perfluorinated fatty acids, fluorinated or perfluorinated sulfonic acids and the salts of these acids.

L'agent tensioactif peut être introduit à l'état individuel dans la solution aqueuse.The surfactant can be introduced individually in the aqueous solution.

Il s'est toutefois avéré spécialement avantageux d'introduire l'agent tensioactif in situ dans la matière polymérique fibreuse, au moment de sa fabrication, de sorte qu'il constitue une matière de charge de la matière polymérique.However, it has been found to be particularly advantageous to introduce the surfactant in situ into the fibrous polymeric material, at the time of its manufacture, so that it constitutes a filler for the polymeric material.

La quantité optimum d'agent tensioactif à mettre en oeuvre dépend de divers facteurs, parmi lesquels figurent notamment la nature du polymère, les dimensions des fibres ou fibrilles du polymère, la nature de la solution aqueuse et la nature de l'agent tensioactif. Elle peut être déterminée dans chaque cas particulier par un travail de routine au laboratoire.The optimum amount of surfactant to be used depends on various factors, among which are in particular the nature of the polymer, the dimensions of the fibers or fibrils of the polymer, the nature of the aqueous solution and the nature of the surfactant. It can be determined in each particular case by routine laboratory work.

D'une manière générale, on obtient de bons résultats lorsque l'agent tensioactif est utilisé en quantité comprise entre 0,5 et 10% du poids de la matière polymérique, les valeurs comprises entre 2 et 7% étant toutefois préférées.In general, good results are obtained when the surfactant is used in an amount of between 0.5 and 10% of the weight of the polymeric material, the values of between 2 and 7% being however preferred.

Pour former le feutre au départ de la suspension aqueuse de la matière polymérique fibreuse et de l'oxyde métallique hydrophile, il suffit de la décanter ou de la filtrer. On peut par exemple filtrer la suspension aqueuse à travers une toile ajourée à mailles fines, sécher le feutre formé de la sorte sur la toile, puis le retirer de la toile et le disposer tel quel à titre de diaphragme dans une cellule d'électrolyse.To form the felt from the aqueous suspension of the fibrous polymeric material and the hydrophilic metal oxide, it is sufficient to decant or filter it. One can for example filter the aqueous suspension through a perforated canvas with fine mesh, dry the felt formed in this way on the canvas, then remove it from the canvas and place it as it is as a diaphragm in an electrolysis cell.

On préfère toutefois, selon l'invention, former le feutre en filtrant la suspension précitée directement à travers un support ajouré du diaphragme en appliquant une technique analogue à celle communément utilisée pour la fabrication de diaphragmes en amiante et décrite notamment dans les brevets Etats-Unis 1 865152 au nom de K. E. STUART, du 28 juin 1932, et 3 344 053 au nom de NEIPERT et al., du 4 mai 1964. Le support ajouré du diaphragme peut avantageusement être la cathode ajourée d'une cellule d'électrolyse à diaphragme. Ce mode de réalisation présente l'avantage de permettre la fabrication du diaphragme in situ sur des cathodes de forme compliquée, à surface non développable, par exemple du type de celles équipant les cellules d'électrolyse décrites dans les brevets français 2 223 083 du 28. 3. 1973 et 2 428 335 du 14.10.1974 au nom de la Demanderesse.However, it is preferred, according to the invention, to form the felt by filtering the above suspension directly through an openwork support of the diaphragm by applying a technique analogous to that commonly used for the manufacture of asbestos diaphragms and described in particular in the United States patents. 1 865152 in the name of KE STUART, of June 28, 1932, and 3 344 053 in the name of NEIPERT et al., Of May 4, 1964. The perforated support of the diaphragm can advantageously be the perforated cathode of a diaphragm electrolysis cell . This embodiment has the advantage of making it possible to manufacture the diaphragm in situ on cathodes of complicated shape, with non-developable surface, for example of the type equipping the electrolysis cells described in French patents 2,223,083 of 28 3. 1973 and 2,428,335 of October 14, 1974 in the name of the Claimant.

Selon une variante avantageuse de ce mode de fabrication du diaphragme selon l'invention, la dispersion de la matière polymérique et de l'oxyde métallique dans l'eau ou la solution aqueuse et la filtration de la suspension aqueuse résultante à travers le support ajouré sont exécutées dans un appareil unique, connu en soi pour la fabrication des diaphragmes en amiante, et décrit dans le brevet français 2 308 702 du 25. 4.1975, au nom de la Demanderesse.According to an advantageous variant of this method of manufacturing the diaphragm according to the invention, the dispersion of the polymeric material and the metal oxide in water or the aqueous solution and the filtration of the resulting aqueous suspension through the perforated support are executed in a single device, known per se for the manufacture of asbestos diaphragms, and described in French patent 2,308,702 of 25. 4.1975, in the name of the Applicant.

Dans le cas particulier où ce mode de fabrication préféré est utilisé pour former le feutre du diaphragme in situ sur un treillis cathodique profilé en forme de doigts parallèles, par exemple de type de ceux équipant les cellules d'électrolyse décrites dans les brevets français 2 223 083 et 2 248 335 précités, il est souhaitable d'utiliser la technique décrite dans le brevet Etats-Unis 3 970 041 déposé le 2.4.1975, au nom de Morton S. Kircher, qui consiste à engager des éléments de séparation entre les doigts cathodiques successifs pendant la formation de feutre.In the particular case where this preferred manufacturing method is used to form the diaphragm felt in situ on a cathode mesh profiled in the shape of parallel fingers, for example of the type equipping the electrolysis cells described in French patents 2,223 083 and 2 248 335 cited above, it is desirable to use the technique described in United States patent 3,970,041 filed on 2.4.1975, in the name of Morton S. Kircher, which consists of engaging separation elements between the fingers successive cathodics during felt formation.

Le diaphragme selon l'invention présente l'avantage d'avoir une bonne cohésion mécanique et d'être de dimensions stables pendant son utilisation dans une cellule d'électrolyse. Il possède la propriété avantageuse d'une excellente aptitude à la mouillabilité par les électrolytes aqueux, notamment par les saumures de chlorure de sodium.The diaphragm according to the invention has the advantage of having good mechanical cohesion and of being of stable dimensions during its use in an electrolysis cell. It has the advantageous property of an excellent wettability by aqueous electrolytes, in particular by sodium chloride brines.

Outre ces propriétés avantageuses, le diaphragme selon l'invention, présente la caractéristique particulièrement intéressante d'avoir généralement une perméabilité aux électrolytes aqueux de même ordre de grandeur que celle de diaphragmes en amiante équipant normalement les cellules d'électrolyse de saumures de chlorure de sodium, de sorte qu'il convient bien pour être substitué aux diaphragmes en amiante des cellules d'électrolyse existantes, par exemple du type de celles décrites dans les brevets français 2 164 623 du 12.12.1972, 2 223 083 du 28. 3. 1973, 2 230 411 du 27. 3. 1974 et 2 248 335 du 14.10.1974, tous au nom de la Demanderesse.In addition to these advantageous properties, the diaphragm according to the invention has the particularly advantageous characteristic of generally having a permeability to aqueous electrolytes of the same order of magnitude as that of asbestos diaphragms normally fitted to the electrolysis cells with sodium chloride brines. , so that it is well suited to be substituted for the asbestos diaphragms of existing electrolysis cells, for example of the type described in French patents 2 164 623 of 12.12.1972, 2 223 083 of 28. 3. 1973 , 2 230 411 dated 27. 3. 1974 and 2 248 335 dated 14.10.1974, all in the name of the Claimant.

Le diaphragme selon l'invention présente par ailleurs la particularité intéressante et surprenante d'avoir, dès le début de son utilisation, les caractéristiques optimum requises de mouillabilité et de perméabilité. Cette particularité du diaphragme suivant l'invention apporte l'avantage appréciable que les cellules d'électrolyse sont dorénavant capables de fonctionner en régime normal, avec un rendement énergétique optimum, dès le début de leur mise en service avec un nouveau diaphragme. Le diaphragme selon l'invention peut éventuellement contenir, en plus de la matière polymérique et de l'oxyde métallique hydrophile, d'autres constituants habituels des diaphragmes perméables destinés à lui conférer des propriétés supplémentaires.The diaphragm according to the invention also has the interesting and surprising characteristic of having, from the start of its use, the optimum characteristics required for wettability and permeability. This feature of the diaphragm according to the invention provides the appreciable advantage that the electrolysis cells are henceforth capable of operating under normal conditions, with optimum energy efficiency, from the start of their commissioning with a new diaphragm. The diaphragm according to the invention may optionally contain, in addition to the polymeric material and the hydrophilic metal oxide, other usual constituents of the permeable diaphragms of the aimed at giving it additional properties.

L'intérêt de l'invention va ressortir des quelques exemples d'application suivants.The advantage of the invention will emerge from the following examples of application.

Dans ces exemples d'application, on a procédé à quelques essais d'électrolyse dans une cellule de laboratoire comprenant une anode et une cathode verticales séparées par un diaphragme. L'anode a consisté en une plaque circulaire en titane de 113 cm2, portant un revêtement actif constitué d'un mélange équimolaire de dioxyde de ruthénium et de dioxyde de titane. La cathode était formée d'un treillis circulaire en acier doux de 113 cm2, et portait le diaphragme sur sa face en regard de l'anode. La distance entre l'anode et la cathode était de 5 mm.In these application examples, some electrolysis tests were carried out in a laboratory cell comprising a vertical anode and a cathode separated by a diaphragm. The anode consisted of a circular titanium plate of 113 cm 2 , carrying an active coating consisting of an equimolar mixture of ruthenium dioxide and titanium dioxide. The cathode was formed from a 113 cm 2 mild steel circular lattice, and bore the diaphragm on its face opposite the anode. The distance between the anode and the cathode was 5 mm.

Première série d'essais (conformes à l'invention)First series of tests (in accordance with the invention)

Les exemples 1 à 3 concernent des essais d'électrolyse avec des diaphragmes conformes à l'invention.Examples 1 to 3 relate to electrolysis tests with diaphragms in accordance with the invention.

Exemple 1Example 1

On a utilisé dans la cellule un diaphragme formé d'un mélange de 68% en poids de fibrilles en copolymère de tétrafluoréthylène et de perfluoropropylène et de 32% en poids de particules d'oxyde de magnésium.A diaphragm formed from a mixture of 68% by weight of fibrils made of a copolymer of tetrafluoroethylene and perfluoropropylene and 32% by weight of magnesium oxide particles was used in the cell.

Les fibrilles ont une surface spécifique moyenne d'environ 23 m2/g. Elles ont été obtenues, en soumettant un mélange biphasique du polymère à l'état fondu et d'un solvant approprié, à une détente brusque à travers un orifice de faible section, comme décrit dans les brevets français 1 596107 du 13 décembre 1968, 2 148 449 de 2 148 450 du ler août 1972 et dans les brevets belges 811 778 du ler mars 1974 et 824 844 du 17 janvier 1975, tous au nom de la Demanderesse.The fibrils have an average specific surface of approximately 23 m 2 / g. They were obtained, by subjecting a biphasic mixture of the polymer in the molten state and of an appropriate solvent, to a sudden expansion through an orifice of small section, as described in French patents 1,596,107 of December 13, 1968, 2 148,449 of 2,148,450 of August 1, 1972 and in the Belgian patents 811,778 of March 1, 1974 and 824,844 of January 17, 1975, all in the name of the Applicant.

Les particules d'oxyde de magnésium ont un diamètre moyen compris entre 0,02 et 0,04 µm.The magnesium oxide particles have an average diameter of between 0.02 and 0.04 µm.

Pour fabriquer le diaphragme, on a dispersé les fibrilles et les particules d'oxyde de magnésium dans une saumure caustique contenant approximativement 8% en poids d'hydroxyde de sodium et 16% en poids de chlorure de sodium. La saumure caustique contenait en outre, par litre, 400 mg du produit connu sous le nom »Polymin P« (BASF) qui est un agent rétenteur à base de polyéthylèneimine.To make the diaphragm, the fibrils and magnesium oxide particles were dispersed in caustic brine containing approximately 8% by weight of sodium hydroxide and 16% by weight of sodium chloride. The caustic brine also contained, per liter, 400 mg of the product known as "Polymin P" (BASF) which is a polyethyleneimine retaining agent.

Après homogénéisation de la suspension, on y a immergé la cathode de la cellule et on a aspiré la suspension à travers celle-ci de manière à déposer à sa surface un feutre formé d'un mélange des fibrilles et des particules d'oxyde de magnésium. Le feutre avait un poids correspondant approximativement à 1,3 kg/m3 de surface de la cathode, et il contenait approximativement 68% en poids de fibrilles et 32% en pids d'oxyde de magnésium.After homogenization of the suspension, the cathode of the cell was immersed therein and the suspension was sucked through it so as to deposit on its surface a felt formed from a mixture of fibrils and particles of magnesium oxide . The felt had a weight corresponding to approximately 1.3 kg / m 3 of cathode surface area, and it contained approximately 68% by weight of fibrils and 32% by weight of magnesium oxide.

Après formation du feutre sur la cathode, on a monté immédiatement celle-ci dans la cellule de laboratoire et on y a procédé à l'électrolyse d'une saumure contenant 255 g de chlorure de sodium par kg, sous une densité de courant constante, égale à 2 kA/m2 d'anode. La température dans la cellule a été maintenue à environ 85° C pendant toute la durée de l'essai.After forming the felt on the cathode, it was immediately mounted in the laboratory cell and there was electrolysis of a brine containing 255 g of sodium chloride per kg, at a constant current density, equal to 2 kA / m 2 of anode. The temperature in the cell was maintained at about 85 ° C for the duration of the test.

On a consigné au Tableau 1 qui suit, l'évolution, au cours du temps, de la perméabilité du diaphragme, de la teneur en hydroxyde de sodium dans le catholyte, de la tension d'électrolyse aux bornes de la cellule et du rendement de courant à l'anode. La perméabilité du diaphragme exprimée en h-1, est définie par la relation suivante:

Figure imgb0001
où:

  • Q désigne le débit de saumure à travers le diaphragme (en cm3/h);
  • S désigne la section du diaphragme (en cm2);
  • H désigne la pression hydrostatique de saumure sur le diaphragme,

exprimée en cm de colonne de saumure.
Figure imgb0002
 The evolution, over time, of the diaphragm permeability, the content of sodium hydroxide in the catholyte, the electrolysis voltage at the terminals of the cell and the yield of current at the anode. The permeability of the diaphragm expressed in h- 1 , is defined by the following relation:
Figure imgb0001
 or:
  • Q denotes the flow of brine through the diaphragm (in cm 3 / h);
  • S denotes the section of the diaphragm (in cm 2 );
  • H denotes the hydrostatic brine pressure on the diaphragm,

expressed in cm of brine column.
Figure imgb0002

Exemple 2Example 2

Dans l'essai qui va suivre, la poudre d'oxyde de magnésium et un agent tensioactif ont été associés au polymère (copolymère de tétrafluoréthylène et de perfluoropropylène) in situ dans les fibrilles, au moment de la fabrication de celles-ci. A cet effet, avant de fabriquer les fibrilles par détente du mélange biphasique du polymère et du solvant comme décrit dans l'exemple 1, on a incorporé à ce mélange les particules d'oxyde de magnésium et l'agent tensioactif. Les quantités respectives d'oxyde de magnésium et d'agent tensioactif mises en oeuvre ont été réglées pour que les fibrilles obtenues contiennent environ 58% en poids de polymère, 39% en poids d'oxyde de magnésium et 3% en poids d'agent tensioactif fluoré. Les particules d'oxyde de magnésium mises en oeuvre avaient un diamètre moyen compris entre 0,02 et 0,04 µm.In the following test, the magnesium oxide powder and a surfactant were combined with the polymer (copolymer of tetrafluoroethylene and perfluoropropylene) in situ in the fibrils, at the time of their manufacture. To this end, before manufacturing the fibrils by expansion of the two-phase mixture of the polymer and the solvent as described in Example 1, the particles of magnesium oxide and the surfactant were incorporated into this mixture. The respective amounts of magnesium oxide and of surfactant used have been adjusted so that the fibrils obtained contain approximately 58% by weight of polymer, 39% by weight of magnesium oxide and 3% by weight of agent. fluorinated surfactant. The magnesium oxide particles used had an average diameter of between 0.02 and 0.04 μm.

Les fibrilles ainsi obtenues avaient une surface spécifique égale à environ 25 m2/g.The fibrils thus obtained had a specific surface area of approximately 25 m 2 / g.

On a déposé sur la cathode de la cellule de laboratoire un diaphragme constitué exclusivement de telles fibrilles, en appliquant la méthode décrite à l'exemple 1, mais en omettant toutefois d'incorporer l'agent rétenteur »Polymin P« au bain de saumure caustique. Le poids du diaphragme obtenu correspondait à environ 1,3 kg/m2 de la cathode.A diaphragm consisting exclusively of such fibrils was deposited on the cathode of the laboratory cell, applying the method described in Example 1, but omitting however to incorporate the retaining agent »Polymin P« in the caustic brine bath. . The weight of the diaphragm obtained corresponded to approximately 1.3 kg / m 2 of the cathode.

On a ensuite répété les conditions d'électrolyse mises en oeuvre dans l'essai de l'exemple 1. Les résultats obtenus sont mentionnés au Tableau II.

Figure imgb0003
The electrolysis conditions used in the test of Example 1 were then repeated. The results obtained are listed in Table II.
Figure imgb0003

Exemple 3Example 3

Le diaphragme utilisé dans cet essai a consisté en un feutre formé d'un mélange de particules individuelles d'oxyde de magnésium identiques à celles utilisées dans l'exemple 1 et de fibrilles chargées d'oxyde de magnésium et d'un agent tensioactif fluoré, identiques aux fibrilles utilisées dans I'essai de l'exemple 2. Les quantités mises en oeuvre ont été réglées pour que le diaphragme formé sur la cathode ait un poids équivalent à 1,4 kg/m2 de surface de la cathode et contienne environ 93% de fibrilles chargées d'oxyde de magnésium et d'agent tensioactif et 7% de particules individuelles d'oxyde de magnésium.The diaphragm used in this test consisted of a felt formed from a mixture of individual particles of magnesium oxide identical to those used in Example 1 and of fibrils charged with magnesium oxide and a fluorinated surfactant, identical to the fibrils used in the test of Example 2. The quantities used were adjusted so that the diaphragm formed on the cathode had a weight equivalent to 1.4 kg / m 2 of cathode surface and contained approximately 93% of fibrils loaded with magnesium oxide and surfactant and 7% of individual particles of magnesium oxide.

L'essai d'électrolyse, pour lequel on a répété les conditions des exemples 1 et 2, a abouti aux résultats consignés au Tableau III.

Figure imgb0004
The electrolysis test, for which the conditions of Examples 1 and 2 were repeated, led to the results recorded in Table III.
Figure imgb0004

Essai comparatifComparative essay

L'exemple 4 concerne un essai d'électrolyse avec un diaphragme antérieur à l'invention.Example 4 relates to an electrolysis test with a diaphragm prior to the invention.

Exemple 4Example 4

En prévision de l'essai d'électrolyse dont la description va suivre, on a fabriqué des fibrilles en copolymère de tétrafluoréthylène et de perfluoropropylène, chargées d'une poudre de bioxyde de titane et d'un agent tensioactif fluoré. Les fibrilles ont été fabriquées par une technique comparable à celle mise en oeuvre pour l'obtention des fibrilles de l'exemple 2. Les particules de bioxyde de titane mises en oeuvre dans la fabrication des fibrilles avaient un diamètre moyen égal à environ 0,02 Jlm. Les quantités respectives de polymère, de bioxyde de titane et d'agent tensioactif mises en oeuvre ont été réglées de manière que les fibrilles obtenues contiennent approximativement 48,75% en poids de polymère, 48,75% en poids de bioxyde de titane et 2,50% en poids d'agent tensioactif fluoré.In anticipation of the electrolysis test, the description of which will follow, fibrils made of a copolymer of tetrafluoroethylene and perfluoropropylene, loaded with a powder of titanium dioxide and a fluorinated surfactant, were manufactured. The fibrils were manufactured by a technique comparable to that used to obtain the fibrils of Example 2. The particles of titanium dioxide used in the manufacture of the fibrils had an average diameter equal to approximately 0.02 J lm. The respective amounts of polymer, titanium dioxide and surfactant used were adjusted so that the fibrils obtained contain approximately 48.75% by weight of polymer, 48.75% by weight of titanium dioxide and 2 , 50% by weight of fluorosurfactant.

On a déposé sur la cathode de la cellule de laboratoire un diaphragme constitué exclusivement de telles fibrilles, en appliquant la méthode décrite à l'exemple 2. Le poids du diaphragme obtenu correspondait à environ 1,3 kg/m2 de la cathode.A diaphragm consisting exclusively of such fibrils was deposited on the cathode of the laboratory cell, by applying the method described in Example 2. The weight of the diaphragm obtained corresponded to approximately 1.3 kg / m 2 of the cathode.

On a appliqué les mêmes conditions d'électrolyse que dans les essais des exemples 1 à 3. Les résultats obtenus sont mentionnés au Tableau IV.

Figure imgb0005
The same electrolysis conditions were applied as in the tests of Examples 1 to 3. The results obtained are mentioned in Table IV.
Figure imgb0005

Une comparaison des résultats des essais des exemples 1 à 3 avec ceux de l'essai comparatif de l'exemple 4 fait apparaître immédiatement que les diaphragmes conformes à l'invention ont une meilleure perméabilité, permettent des tensions d'électrolyse plus basses et procurent des rendements de courant plus élevés.A comparison of the results of the tests of Examples 1 to 3 with those of the comparative test of Example 4 immediately shows that the diaphragms according to the invention have better permeability, allow lower electrolysis voltages and provide higher current yields.

Claims (10)

1. Process for the electrolysis of an aqueous solution of an alkali metal halide in a cell having a permeable diaphragm, in which process a porous sheet is used, for the diaphragm, which consists of hydrophobic organic polymeric material and containing a hydrophilic metal oxide in particle form, characterized in that a porous sheet is used in which the metal oxide is chosen from amongst the oxides of the metals of group 11a of the periodic table of the elements, the oxide being in the form of particles having a mean diameter at most equal to 0.5 microns.
2. Process according to claim 1, characterized in that the metal oxide is magnesium oxide.
3. Process according to claim 1 or 2, characterized in that the metal oxide particles have a mean diameter of between 0.002 and 0.2 microns.
4. Process according to any one of claims 1 to 3, characterized in that the metal oxide is used in an amount of between 20 and 60% of the total weight of the diaphragm.
5. Process according to any one of claims 1 to 4, characterized in that the organic polymeric material is used in a fibrous form.
6. Process according to any one of claims 1 to 5, characterized in that a sheet is used in which the metal oxide is present in situ in the organic polymeric material and constitutes a filler thereof.
7. Process according to claim 6, characterized in that a sheet is used which comprises a surface-active agent present in situ in the organic polymeric material and constitutes a filler thereof.
8. Process according to claim 7, characterized in that the surface active agent is used in amount of between 2 and 7% of the weight of organic polymeric material.
9. Process according to any one of claims 1 to 8, characterized in that a sheet is used in which the organic polymeric material is a copolymer of tetrafluoroethylene and of perfluoropropylene.
10. Process according to any one of claims 5 to 9, characterized in that the sheet is used in the form of a felt obtained in situ, on a perforated support, from an aqueous suspension of the polymeric material, which is in a fibrous form, and of the hydrophilic metal oxide.
EP81200298A 1980-03-27 1981-03-17 Process for electrolyzing aqueous alkali metal halide solutions using a pervious diaphragm of a hydrophobic polymeric organic material Expired EP0037140B1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
AT81200298T ATE8154T1 (en) 1980-03-27 1981-03-17 METHOD FOR THE ELECTROLYSIS OF AQUEOUS ALKALI HALIDE SOLUTIONS USING A PERMEABLE DIAPHRAGM OF ORGANIC HYDROPHOBIC POLYMERIC MATERIAL FOR A CELL APPROPRIATE FOR THE ELECTROLYSIS OF AQUEOUS ALKALI HALIDE SOLUTIONS.

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FR8006919 1980-03-27
FR8006919A FR2485041A1 (en) 1980-03-27 1980-03-27 PERMAABLE DIAPHRAGM IN ORGANIC POLYMERIC MATERIAL FOR ELECTROLYSIS CELL OF AQUEOUS ALKALINE METAL HALIDE SOLUTIONS

Publications (2)

Publication Number Publication Date
EP0037140A1 EP0037140A1 (en) 1981-10-07
EP0037140B1 true EP0037140B1 (en) 1984-06-27

Family

ID=9240217

Family Applications (1)

Application Number Title Priority Date Filing Date
EP81200298A Expired EP0037140B1 (en) 1980-03-27 1981-03-17 Process for electrolyzing aqueous alkali metal halide solutions using a pervious diaphragm of a hydrophobic polymeric organic material

Country Status (13)

Country Link
US (1) US4482441A (en)
EP (1) EP0037140B1 (en)
JP (1) JPS56150193A (en)
AT (1) ATE8154T1 (en)
AU (1) AU6865481A (en)
BR (1) BR8101810A (en)
DE (1) DE3164380D1 (en)
ES (1) ES500728A0 (en)
FI (1) FI68671C (en)
FR (1) FR2485041A1 (en)
NO (1) NO811030L (en)
PT (1) PT72734B (en)
ZA (1) ZA811739B (en)

Families Citing this family (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4853101A (en) * 1984-09-17 1989-08-01 Eltech Systems Corporation Porous separator comprising inorganic/polymer composite fiber and method of making same
MX169225B (en) * 1984-09-17 1993-06-24 Eltech Systems Corp COMPOSITE OF NON-ORGANIC FIBERS / POLYMER METHOD FOR PREPARING IT AND USING IT, INCLUDING A DIMENSIONALLY STABLE SEPARATOR
ZA856924B (en) * 1984-09-17 1986-05-28 Eltech Systems Corp Non-organic/polymer fiber composite,method of making same and use including dimensionally stable separator
US4707228A (en) * 1986-06-06 1987-11-17 Treadwell Corporation Diaphragm for electrolytic and electrochemical cells
WO1993016217A2 (en) * 1992-02-13 1993-08-19 The Dow Chemical Company Separators for electrolytic cells and processes for making
EP1528126A1 (en) * 2003-10-30 2005-05-04 Vandenborre Hydrogen Systems N.V. An integrated electrolyser module with an internal gas/liquid separator

Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE833912A (en) * 1974-09-26 1976-03-26 Ici Ltd POROUS PRODUCTS

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1865152A (en) * 1930-01-31 1932-06-28 Hooker Electrochemical Co Production of electrolytic cathode-diaphragm structures
DE1771457C3 (en) * 1968-05-28 1974-12-05 Rheinisch-Westfaelisches Elektrizitaetswerk Ag, 4300 Essen Process for the production of a zinc dendrite barrier membrane made of metal oxide and plastic
US3930886A (en) * 1971-11-11 1976-01-06 Leesona Corporation Porous fluoro-carbon polymer matrices
IT1019598B (en) * 1973-05-18 1977-11-30 Comp Generale Electricite ELECTROCHEMICAL ELEMENTS WITH THIN LAYERS
JPS5064739A (en) * 1973-10-12 1975-06-02
US4036729A (en) * 1975-04-10 1977-07-19 Patil Arvind S Diaphragms from discrete thermoplastic fibers requiring no bonding or cementing
US4007059A (en) * 1975-08-20 1977-02-08 General Motors Corporation Electrochemical cell electrode separator and method of making it and fuel cell containing same
US4126536A (en) * 1976-12-27 1978-11-21 Basf Wyandotte Corporation Diaphragms for chlor-alkali cells
US4238303A (en) * 1978-08-14 1980-12-09 E. I. Du Pont De Nemours And Company Diaphragm modifier for chlor-alkali cell
US4173526A (en) * 1978-11-21 1979-11-06 E. I. Du Pont De Nemours And Company Chlor-alkali cell diaphragm and its treatment
US4330602A (en) * 1979-07-13 1982-05-18 W. R. Grace & Co. Battery separator
US4253935A (en) * 1979-09-19 1981-03-03 Ppg Industries, Inc. Method of preparing a diaphragm having a gel of a hydrous oxide or zirconium in a porous matrix

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE833912A (en) * 1974-09-26 1976-03-26 Ici Ltd POROUS PRODUCTS

Also Published As

Publication number Publication date
FI68671C (en) 1985-10-10
NO811030L (en) 1981-09-28
JPS56150193A (en) 1981-11-20
AU6865481A (en) 1981-10-01
BR8101810A (en) 1981-09-29
ES8207592A1 (en) 1982-09-16
ZA811739B (en) 1982-04-28
PT72734B (en) 1982-03-22
PT72734A (en) 1981-04-01
ES500728A0 (en) 1982-09-16
ATE8154T1 (en) 1984-07-15
FR2485041B1 (en) 1983-11-04
FR2485041A1 (en) 1981-12-24
EP0037140A1 (en) 1981-10-07
DE3164380D1 (en) 1984-08-02
FI68671B (en) 1985-06-28
US4482441A (en) 1984-11-13
FI810932L (en) 1981-09-28

Similar Documents

Publication Publication Date Title
US4720334A (en) Diaphragm for electrolytic cell
CA2023032C (en) Diagphragm, association of said diaphragm with a cathodic element, and method of production therefor
CA1165276A (en) Electrolysis diaphragm, and its production
US4680101A (en) Electrolyte permeable diaphragm including a polymeric metal oxide
EP0132425A1 (en) Material based on conductive fibres, its manufacture and its use, in particular in the production of cathode elements
CA1182257A (en) Diaphragm, its preparation and its use in a electrolytic process
CA2241230C (en) Asbestos-free cathodic element suitable for electrolysis of sodium chloride solution
EP0037140B1 (en) Process for electrolyzing aqueous alkali metal halide solutions using a pervious diaphragm of a hydrophobic polymeric organic material
CN1015270B (en) Method for production of alkali metal hydroxide
EP0296076B1 (en) Production of an electroactive material based on conductive fibers and its use in the production of cathode elements
FR2706912A1 (en)
CA1125464A (en) Membranes
FR2808289A1 (en) PROCESS FOR THE PREPARATION OF A DIAPHRAGM FOR AN ELECTROLYTIC CELL
FR2808290A1 (en) PROCESS FOR THE EXPLOITATION OF ELECTROLYTIC CELLS WITH ALKALI CHLORINE
EP0007674B1 (en) Method of elektrolysis of an aqueous alkali metal chloride solution in a diaphragm cell
EP0412916B1 (en) Diaphragm comprising asbestos fibres, association of such a diaphragm with a cathodic element and process of manufacture
EP0222671A1 (en) Microporous material, process for its preparation and its uses, especially in producing cathodic elements
CH621583A5 (en)
EP0319517B1 (en) Material based on conductive fibres, its manufacture and its use, in particular in the production of cathode elements
EP0642602A1 (en) Method for the preparation of a microporous diaphragm
FR2803309A1 (en) ASBESTOS-FREE DIAPHRAGM, COMPRISING NON-FIBROUS MINERAL PARTICLES COMPRISING THE SAME, ITS OBTAINING AND USE
FR2590276A1 (en) Synthetic diaphragm and processes for its manufacture and use.
EP0018034A1 (en) Process for manufacturing a porous diaphragm for an electrolytic cell

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

AK Designated contracting states

Designated state(s): AT BE CH DE FR GB IT LI LU NL SE

17P Request for examination filed

Effective date: 19820329

ITF It: translation for a ep patent filed

Owner name: BARZANO' E ZANARDO MILANO S.P.A.

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Designated state(s): AT BE CH DE FR GB IT LI LU NL SE

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: SE

Effective date: 19840627

REF Corresponds to:

Ref document number: 8154

Country of ref document: AT

Date of ref document: 19840715

Kind code of ref document: T

REF Corresponds to:

Ref document number: 3164380

Country of ref document: DE

Date of ref document: 19840802

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LU

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 19850331

Ref country code: LI

Effective date: 19850331

Ref country code: CH

Effective date: 19850331

PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
GBPC Gb: european patent ceased through non-payment of renewal fee
REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: AT

Payment date: 19870310

Year of fee payment: 7

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: AT

Effective date: 19880317

BERE Be: lapsed

Owner name: SOLVAY & CIE (S.A.)

Effective date: 19880331

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19881118

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: BE

Effective date: 19890331

REG Reference to a national code

Ref country code: FR

Ref legal event code: CD

NLT1 Nl: modifications of names registered in virtue of documents presented to the patent office pursuant to art. 16 a, paragraph 1

Owner name: SOLVAY (SOCIETE ANONYME) TE BRUSSEL, BELGIE.

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: FR

Payment date: 19990223

Year of fee payment: 19

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: NL

Payment date: 20000331

Year of fee payment: 20

Ref country code: DE

Payment date: 20000331

Year of fee payment: 20

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Free format text: LAPSE BECAUSE OF NON-PAYMENT OF DUE FEES

Effective date: 20001130

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: NL

Free format text: LAPSE BECAUSE OF EXPIRATION OF PROTECTION

Effective date: 20010317

NLV7 Nl: ceased due to reaching the maximum lifetime of a patent

Effective date: 20010317