DE2551234A1 - FRAME FOR AN ELECTROLYSIS CELL MADE OF A SYNTHETIC ORGANIC POLYMER AND A PROCESS FOR ITS MANUFACTURING - Google Patents

Description

Patent attorneys Dipl.-Ing, Γ. Veickmann,

Dipl.-Ing. H. Wr-ICKMANN, Dipl.-Phys. Dr. K. Fincke Dipl.-Ing. F.A.Veickmann, Dipl.-Chem. B. Huber

8 MUNICH 86, DEN

PO Box 860 820

MÖHLSTRASSE 22, CALL NUMBER 98 39 21/22

3423 / H / KW

Hooker Chemicals & Plastics Corp.
Niagara Falls, New York 14302 / USA

Frame for an electrolytic cell made from a synthetic, organic polymer and process for its manufacture

The invention relates to a cell frame or a cell frame for the production of electrolysis cells and assemblies of that. The invention particularly relates to a frame for an electrolytic cell from a deformed synthetic organic polymers, the molded parts and passages to hold the cell elements and for charging and removing cell fluids and for aligning and securing the cell frames having with each other in compilations.

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For the production of chlorine, sodium hydroxide and hydrogen from aqueous sodium chloride solutions are hitherto Electrolysis cells, either of the diaphragm or mercury cell type, have been used. In the In recent years, due to the increase in the cost of mercury and pollution problems associated with associated with its use, diaphragm cells have become increasingly important. Most of these cells have hitherto been made of concrete, but the use of linings made of various polymeric materials such as polyvinyl chloride and polypropylene have been proposed.

With the availability of dimensionally stable anodes and effective permselective membranes, it is now possible has become to increase the productivity of membrane cell assemblies. Because flat electrodes with an intermediate thin separating membrane can be used, is now the production of thin Cell combinations have become possible. Therefore, massive cell wall constructions are no longer necessary or expedient and further efforts have been made to find materials of construction which are suitable for the production of satisfactory electrolytic cells and which are thin are quickly produced can and are able to do so, the electrolysis conditions, the starting materials and the end products to resist. Attempts have already been made to make cells and cell frames from synthetic organic materials polymeric materials, however, such devices are often expensive and the products are at

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not resistant to the conditions of electrolysis, what possibly on stresses that arise in the plastic during processing, or on thereby generated Material weaknesses is due. The machining of filled polymers sets the surfaces of the filler free, which can be undesirable for long-term electrolytic purposes, in particular in Presence of an electrolyte and cell products elevated temperatures or when temperatures vary over a range wide enough to cause expansion and causing contractions upon exposure of the filler in the surface of the filled polymer Can develop signs of weakening.

Polypropylene has already been used as an acid-resistant and alkali-resistant material. It is also with various high-temperature-resistant materials, e.g. talc, mica and asbestos, as fillers been transferred. For making molded frames of the present type for connection to assemblies of electrolytic cells, however, it has not yet been used. Such Products are relatively easy to make, assemble and use and they have a long lifespan, wherein the frame during the electrolysis of aqueous sodium chloride solutions against a hindrance, Warping, expanding, contracting, creeping and other warping are highly resistant.

According to the invention, a frame for an electrolytic cell made of a synthetic organic poly-

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meren as a housing for an anode and a cathode and provided for carrying a membrane. This frame forms together with a matching adjoining Frame that has an electrode with opposite sign than that of the existing frame is closer, contains an electrolytic cell which has an anode, a cathode and an intermediate one Has membrane. The frame - contains inlets and outlets for electrolytic process fluids in the anolyte and catholyte compartments, so that the two adjacent frame formed cell at least one inlet in the anolyte part, at least one outlet from the anolyte compartment, at least one inlet into the catholyte compartment and at least one outlet from the Has catholyte compartment, each of the inlets and outlets with the respective headers or manifolds integral with the cell frame stands. In preferred embodiments of the invention, the synthetic organic polymer is polypropylene, which contains a filler such as asbestos, mica, potassium silicate, talc or mixtures thereof, the frame Injection molded, integral outer alignment and fastening devices to a variety of frames to hold together in a cell assembly, contains and deformed fastening devices, to keep different cell parts in the desired positions. The invention also relates to an electrolysis process using electrolysis cells which contain the frame according to the invention, and a method of manufacturing these frames and intermediate mounts or frames

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for electrodes in order to keep them in the desired positions in the frame according to the invention.

The invention will become apparent with reference to the accompanying drawings
explained in more detail. Show it:

1 is a perspective view of a cell assembly comprising a plurality of frames according to of the invention,

Fig. 2 is a partially cut away vertical transverse

sectional view of a pair of frames according to the invention and parts of other frames,
adjoining it, with two complete frames combined to form an electrolytic cell
are,

3 shows a partially cut-off cross-sectional

elevation view along plane 3-3 of Figure 2, and

Fig. 4 is a partial vertical cross-sectional view of a T-shaped rectangular "picture frame" which is an intermediate mounting means around
to attach an electrode to the plastic frame according to the invention.

The electrolysis cell assembly 11 shown in Figure 1 contains a base 13 _f individual cell frames 15, which are arranged with seals in between (not shown) for sealing purposes, pressure front and back plate parts 17 and 19, horizontal side support rods 21 and 23, the

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are held at the base 13 and above it by vertical members 25, 27, 29 and 31, and bars 33, 35, 37, 39 and 41, each of which is threaded at both ends and each of which is clamping nuts possesses to compress the end plates and in this way the frames in a liquid-tight manner To maintain relationship with each other, which is usually done with the aid of the seals in between. The threaded ends 43 and 45 and the tension nuts 47 and 49 on the rod 41 are and it will be seen that the other rods also have similar threaded ends and tension nuts contain.

A roller, indicated by the reference numeral 51, serves as a bearing to allow the sliding movement of the plate to facilitate. The plates 17 and 19 contain passages therein or are connected thereto to the tension rods to hold in position and to transfer tension forces to the plates. The cell frames 15, their structures described in more detail in Figures 2 and 3 include an external alignment device 53, the outer parts which are integral with the frame and which are molded (at 54) are included to attach to the support rod 23 and to lie on it in order to facilitate the assembly of the cell frames, as will be described in more detail later in connection with FIGS. 2 and 3 will.

FIG. 2 shows combinations of the cell frames with the formation of electrolytic cells. With the exception of

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electrical connections, the outer parts are not shown. For a better illustration are also the upper inlet and outlet passages and manifolds not shown (these are shown in Figure 3). at the arrangement of Figure 2 are the cell frames 15 with the intermediate seal 61 or a Multiple seals held together in liquid-tight contact, creating an electrolytic cell is formed when the electrodes and an interposed membrane are in place. the Frames 15 have walls 63 which delimit the cell formed by the connection of the frames, whereby leakage into the next adjacent cells 65 and 67 is prevented. Cell 69, through connection the frame 15 is formed, includes an anode 71, a cathode 73 and a membrane 75 attached to the inner inactive side of the anode 71 is held. The anode 71 is electrically and mechanically (by welding) on connected to conductor 77 and cathode 73 is connected to conductor 79 in a similar manner. These both conductors are arranged substantially vertically and they have upper ends that pass through openings 81 and 83 pass into the frame and which are in contact with conductors 85 and 87 through which electricity the cell 69 is fed from the cathode lead of the cell 67 and from the cell 69 to the anode lead of the Cell 65 is transferred. Sealing devices 89 and 91 are provided to provide a liquid-tight seal to prevent the loss of gas or liquid.

As shown for the anode lead exit from cell 65, the seal comprises a plurality of

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resilient neoprene sealing rings or O-rings 93, which are connected to each other be pressed against a stop 95 by pulling a cap 97 through a threaded end Collar 99 is clamped against the force-transmitting rigid sealing ring 101. Thus, the sealing rings or O-rings or fasteners of other suitable types, e.g., wedges, pressed against the anode lead and hold it firmly in place, preventing fluid loss from the cell.

The conductors 77 and 79 and through these electrodes 71 and 73 are secured in place by beam brackets 103 and 105 which are attached by screws 107 and 109 molded projections 111 and 113 are attached. The ladder can be attached to the brackets for further support welded on or otherwise positively attached.

As shown, the cathode 73 fits into a prepared opening in the frame at the cathode ends and is additionally supported by the pressure of the gasket against it when the cell frames are braced together. In order to improve the rigidity of the anode, it is placed on an angle frame or a series of angle brackets 115, which frame is in place with respect to the body frame 15 by suitable means such as screws, cement or glue, pressure retention by the gasket 61 etc. and is held in place. The use of the bracket 115 or the "T-shaped" picture frame ¹¹ as an intermediate mounting device, as shown in Figure 4, and as it is interchangeable with the current bracket, serves to give further strength,

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and prevents undesired bending of the anode material.

The membrane 75, which in the embodiment shown is supported against the anode 71, is in place held at which they are between the angle 115, "the frame parts 117, 119 and 121 and also in suitable Channels or grooves, e.g., as at 123 and 125, the holding parts 127 and 129, which are secured by screws in the frame 15, is sealed in place. It will be seen that in the illustration shown the membrane is not perfectly vertical in all positions, but is pressed against it by the anode will be used to aid fixation in place. It is important that the distance between the Electrodes are kept constant for best electrolytic effects, and it is also important to that the membrane is kept tight against the anode in order to prevent chlorine gas, which at the active Side of the anode, away from the membrane, accumulates between the anode and the membrane. Likewise the distance between the membrane and the cathode should be kept constant to avoid interference with the distance to prevent the generated hydrogen gas and allow a free flow of the electrolyte. It it will be seen that in other embodiments of the invention in which the membrane is between the two electrodes is arranged with distances between the membrane and the electrode, it may be appropriate that the active side of the anode of the membrane is facing or that both sides of the anode are active or that if

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the membrane is to be placed against the cathode, the structure used must be modified accordingly can.

An important feature of the present invention is the deformation of the various devices for the Addition and removal of liquid from the manufactured electrolytic cells so that it is not necessary to drill such passages into the frame. In Figure 2, the only such passages are shown for loading the anolyte and catholyte compartments and for the anolyte loading head or distributor. Other loading headers and unloading passages and headers are shown in FIG. The anolyte head piece 131, which is inserted into the frame 15 is formed in, stands through the passage 133 with the anolyte compartment 135 of the cell 69 in communication. At the end of passage 133 near the anolyte compartment an opening stopper 137 is screwed into the previously formed thread in the frame 15 or other Manner so that the passage to the opening shown at 139 is limited. In a similar way there is a manifold 134 for the catholyte feed (Figure 3) through passage 141 with the catholyte compartment 143 in connection and is limited by the opening 145. Use of the openings shared with others of different sizes · are interchangeable it is to regulate the flow rates into the cell.

In Figure 3, a cell frame 15 and a cell 69 are shown, another optional loading

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manifold 147, a chlorine outlet manifold 151, a hydrogen outlet manifold 149, sodium hydroxide solution take-off headers 153, and a take-off head piece 155 for the depleted anolyte included. It can be seen that overflow passages 157 and 159 represent the respective Catholyte and anolyte effluents to the head pieces from the anolyte 161 and the catholyte 163 (behind the membrane). The frame 15 also includes a optional anolyte feed header 167 and an optional catholyte feed header 165, the both can be connected to the interior of the cell by channels or passages not shown. Such passages can be drilled into the frame, if desired, feedings from the top of the cell or they can be molded and plugged when not in use. Likewise, if it is not desired to use bottom charges, passages 133 and 141 are plugged. The use of a manifold 147 is useful when a variety of membranes are to be used, thereby forming a buffer compartment into which the charge is introduced. As above with regard to the running other optional headers, a passage can be opened or closed depending on the intended purpose be plugged.

Although not shown in detail, it is within the scope of the invention, feed and Outlet flows with curved passages apply, so that the resistance of the flow through which a flow leakage could take place is increased. With regard to the charging of liquids through openings

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The resistance becomes due to the smaller currents larger and current leakage is reduced. This becomes particularly effective with respect to the upper loading points when openings are used which are sufficiently small that droplets of the feed liquids are produced which are discontinuous are when they are through the chlorine and hydrogen gas phases fall above the electrolyte in the anode or cathode compartment. Such discontinuous flows result in a very high resistance to a leakage of (electrical) current.

Similarly, such intermittent streams can be created with the overflowing product decreasing is, with the cell fluid and the depleted anolyte from the cell electrolyte levels up lower levels drop. In this way, discontinuously falling streams are generated. Naturally The electrolytes can also be broken up when they are removed from the cell bank to a Prevent seepage through them. In this regard, it is polymeric plastic construction material suitable for the cell frame because it is non-conductive.

In Figure -4 is part of a T-shaped picture frame intermediate mount for holding an electrode, e.g. the expanded mesh anode 71 of FIGS. 2 and 3 are shown on the frame 15. In Figure 2, the framework 115 is shown as an angle and in Figure 4 it is a T-element 169, the one horizontal foot portion 171 and an upper vertical tip portion 173 and a lower vertical tip

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part 175 owns. The top of the T-tip element . 173 is supported on a body part of the frame 15 and the lower portion has attached thereto the expanded mesh anode 177. As shown, is between the anode 177 and the membrane 179 that is between the top of the T-element and the gasket 181 is held, a gap is formed. Naturally, by changing the proportions and the Positions it can be achieved that this distance is larger, smaller or not present at all.

With modifications to the structure shown, a monopolar type of cell is easily made by using just changed the electrical connections so that each cell is independent of the electrolysis voltage is loaded. Similarly, the electrical connections between bipolar cells can be held internally outside the cell. Instead of having electrical connections at the top of the Cell provides, these can also be on your side. The main separators in the cell, which are called vertical central structural parts of the frame shown can be replaced by a variety of such parts which are both thinner to save plastic. You can go to either side of the cell border be moved, but it is preferred, as mentioned, to have them arranged essentially centrally, to divide the cell into roughly equal compartments and to provide greater strength and dimensional stability of the molded plastic frame. Instead of using neoprene sealing rings that tight against

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the electrode conductors by compression of a clamping nut are pressed, other forms of seals can also be used, e.g. individual O-rings, cylinders, hollow conical wedges etc. Such materials can be made from Neoprene or other suitable polymers, e.g. polytetrafluoroethylene and other fluorinated polymers, "instead of using positive retention devices, to hold the membrane and / or the electrodes in place, elastic Devices, e.g. neoprene tapes, which seal or other parts against the frame during assembly press and which possibly fit into the cavities in the frame, can be used. Such Temporary facilities can be used up the various frames during construction the cell assembly are tightly pressed together. Alternatively, instead of using such Devices use an adhesive, such as a neoprene adhesive, to secure the seals, electrodes and temporarily holds the membranes in place. Such an adhesive should be strong enough that he holds the various parts together in proper relation until they are pressed together by pressing the various parts together Frames are permanently attached. Once taken apart, the glue would be different Do not bind parts so tightly that they cannot be removed without permanent damage. In some cases it may be possible to dispense with the use of seals and opposite parts of the Use polypropylene frames that are so tight due to the compression device for putting them together be held together so that the various intermediate

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placed parts are in the desired permanent relationship without the need for a there is a softer sealing material to prevent seepage. If you do without the neoprene seals, then the elasticity of the polypropylene frame can be increased by changing the molding composition Rubber or other elastomeric materials are added, for example in amounts of 5 to 25 percent of the ethylene propylene elastomer.

The cells shown in Figures 2 and 3 are those of a central portion of the row assembly. It will be seen that the end frames are of different construction, being essentially half-cell frames whose outer sides are bare. It does not seem necessary to go into detail about such structures as they are obvious to the expert.

The only material of construction for the cell frames of the invention that has been found to be satisfactory and which can easily be injection molded is polypropylene and especially polypropylene, that is filled with a suitable filler, e.g. asbestos, mica, calcium silicate, talc or mixtures thereof is. The mixtures of the fillers mentioned can consist of two, three or four components, with it is considered particularly favorable that both calcium silicate and mica in such mixtures are included. In some cases, known equivalent fillers can also be used. if only one of the fillers should be used then

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it is preferred that this be calcium silicate, with the fibrous form being considered the best. The polypropylene can be a normal resin intended for injection molding purposes, e.g. an unmodified one, a copolymerized one, one filled with an inert filler or an impact-resistant (rubber) modified one Be polypropylene, which provides products described in "Modern Plastics Encyclopedia" 1973 to 1974, page 552, have specified properties. Therefore, when such resins are used in accordance with the procedures set out on pages 338-410 of this publication - the methods expressly referred to herein - are injection molded, then suitable electrolytic cell frames are obtained suitable for "filter press" assemblies with about 10 to about 60 such frames are suitable for the electrolysis of aqueous sodium chloride solutions.

The frames described are resistant to the electrolyte and the electrolysis products and they are ^{satisfactorily dimensionally stable during the electrolysis, even with temperature fluctuations from 40 to 95 °} C. and pH fluctuations from 3 to 14. Although it is possible to use a polypropylene resin containing no copolymer and rubber, provided that the desired content of fillers improves dimensional stability, heat resistance, etc. enough to make the material satisfactory for industrial chlorine cells, one usually becomes one Use a mixture of a homopolymer and a copolymer. In such a mixture, the composition is normally 10 to 10% copolymer, such as that sold by Shell Chemical Company as Shell 7525.

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ben is, and 10 to h0% homopolymer, the total proportion of these components being 40 to 90% of the end product. Instead of the homopolymer, copolymers with other materials can also be used, for example propylene / acrylic acid copolymers such as Exxon D-561. The level of rubber impact modifiers can range from 0 to 20-6. However, it is preferably present and is typically 3 to Λ5% of the product. The term "polypropylene" used herein in the general sense is intended to include copolymers and copolymers of homopolymers and crosslinking agents such as unsaturated lower organic acids, "e.g. acrylic acid, methacrylic acid and other monoalkene carboxylic acids having 3 to 6 carbon atoms and their equivalents, as well as homopolymers.

The filler, which can be talc, asbestos, calcium silicate or mica or a mixture thereof, preferably contains Calcium silicate fibers, such as wollastonite fibers or synthetic calcium silicate fibers. The filler can preferably also contain mica flakes or flakes. The calcium silicate fibers, either natural or synthetic in origin, asbestos and talc can be a variety in commercially available fashion of diameters, e.g. 180 α for chrysotile asbestos fibers up to 1 mm, although the diameters are usually less than 0.1 mm, e.g. 0.001 to 0.05 mm. The fiber lengths are usually in the range of the 10 to 1,000,000 times the diameter, preferably des 20 to 1000 times. They are usually in the range of 1 mm to 2 cm. Similarly, the mica used is usually sufficiently finely divided,

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that he is through a sieve with a mesh size of 0.105 mm, preferably through a sieve with a clear mesh size of 0.074 mm passes through it. Although these sizes are given here as guidelines, it will be seen that in some cases it may be useful to have different dimensions of the materials to use to create special effects.

The proportion of the described inorganic filler material in the injection molded frame of the invention is 10 to 60%, preferably 15 to 50%, more preferred 20 to 40%. Preferably 50 to 100% of this is calcium silicate fibers. In some embodiments of the invention, however, 10 to 30% asbestos with 90 up to 70% polypropylene homopolymers or 5 to 20% mica flakes, 10 to 30% asbestos fibers, 15 to 50% polypropylene homopolymer and 20 to 60% polypropylene copolymer can be used and give satisfactory results. Instead of a part of the calcium silicate, an equal proportion of 10 to 50% of it can be taken from talc powder. Also can the calcium silicate and / or the talc are treated with silanes or silicones to form the silanol and siloxane groups to modify and vary the properties of the molded polypropylene. It can also various rubber impact modifiers of the known types for their obvious Purposes. As rubbers, any of those normally used can be used are suitable for this purpose in polymer technology, mixtures thereof also being used. However, elastomers based on polyethylene

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len or polypropylene preferred as well as those based on of both such polymers.

Various other additives may also be present in small proportions, usually to an extent of no more than 10% and preferably no more than 5% _f, in the molded products contemplated by the invention, such as colorants, mold release agents and flame retardant chemicals. Such materials, such polymers, fillers and rubbers which are used for the preparation of the injection molded polypropylene resin composition according to the invention are described in more detail in "Modern Plastics Encyclopedia" 1973/1974 and in the 1972/1973 edition of this manual. They are therefore not further described here.

The frames are injection molded according to known procedures for molding large objects (The dimensions of the frame are about 1.1m by 1.1m by 9 cm and the distance between the anode and the cathode in the cell formed by fitting two frames together is usually about 1 cm). A description of such a shape can be found, for example, in the work "Giant, Thick-Sectioned Plastic Parts Achieved by New Method, ”published in the May 1972 issue of“ Product Engineering ” is, as well as in a work "Unusual Technique Makes 'Impossible' Parts", which was published in the September 1971 issue has been published by "Modern Plastics". Such deformation techniques are from Eimco Envirotech. developed and been carried out. Details about suitable deformation methods are given in this work, • stated that are expressly referred to herein,

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ΪΟ -

The molded frame is softened, although it is made of thermoplastic materials, at the operating temperatures of the present invention contemplated electrolytic cells, which can reach up to 95 ⁰ C, do not. The cells work continuously over longer periods of time, for example six months, without discarding, cracking, becoming unusable, sagging or other disturbing signs of a lack of dimensional stability becoming apparent. Without the inorganic reinforcing filler materials, while the results are not as satisfactory, the molded frames are still useful. It is believed that the deformation process, which tends to cover any fibrous materials near the surface of the molded article, thereby prevents exposure of the reinforcement material to the constituent parts of the electrolytic cell, thereby helping to stabilize the injection molded frame. Such products are therefore considered to be superior to similar products in which the cell frame is made from a bulk material of reinforced polypropylene.

The materials of construction of the various components of the cells of the present invention are of concern selected for their resistance to the respective environmental conditions. The anode that is preferably consists of an extended titanium mesh, although other valve metals are also suitable, e.g. Tantalum, and those on their active surface with a noble metal or a noble metal oxide, ζ.B. Ruthenium oxide, can be coated is opposite to the chlorine

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and the acid salt solution of the anolyte compartment. The ladder bars used in such a compartment are preferably made of copper because of their good conductivity and they are plated with titanium, so that they are resistant to the electrolyte. Of the

2 The open part of the anode has openings of 2 to 700 mm,

preferably 100 to 600 mm, and the ratio of the openings to the nominal single major surface area of the anode is in the range of about 25 to 70%, preferably 40 to 70%. The mesh is usually 0.2 to 2.5 mm, preferably 1 to 2 mm thick and the strand or cross-sectional width is 0.7 to 2.5 mm, preferably 1 to 2 mm. The anode is preferably activated with ruthenium oxide on its rear surface facing away from the membrane.

The cathodes used can consist of any electrically conductive material that is opposite is resistant to attack by the cell fluid, which has a relatively high sodium hydroxide content. Suitable cathodes are made of a steel mesh and they are connected to a copper conductor. It However, other cathode materials and conductor materials can also be used, e.g. iron, graphite, Lead dioxide on graphite, lead dioxide on titanium and precious metals such as platinum, iridium, ruthenium and rhodium. The precious metals can be used as surfaces on conductive substrates, e.g. on those made of copper, silver, aluminum, Steel and iron to be deposited. The cathodes used are preferably a sieve or a drawn one Metal mesh and they are flat like the anodes or have other adapted shapes, so that the inter-electrode spacing is roughly the same. The opening

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Genes in the cathode screen or mesh are normally at least 25% of the surface area of a front side of the cathode, preferably 30 to 80%, most preferably about 45 to 65%. The area of the openings is

2 2

homely 0.5 to 1000 mm, preferably 2 to 100 mm.

If a wire screen is used, the strands used are preferably about in diameter 0.5 to 3 mm. Both electrodes are usually perfectly vertical, or substantially more vertical Position held, usually not more than 10 ° from the vertical, preferably not more than 5 ° of which are arranged.

The currently preferred cation permeable membrane consists of a hydrolyzed copolymer of a perfluorinated hydrocarbon and a fluorosulfonated perfluorovinyl ether. The perfluorinated hydrocarbon is preferably tetrafluoroethylene, although other perfluorinated and saturated and unsaturated hydrocarbons having 2 to 5 carbon atoms can be used, of which the monoolefinic hydrocarbons are preferred, especially those having 2 to 4 carbon atoms and most particularly those having 2 to 3 Carbon atoms such as tetrafluoroethylene and hexafluoropropylene. The sulfonated perfluorovinyl ether that is most suitable has the formula FSO ₂ CF ₂ CF ₂ OCf (CF ₅ ) CF ₂ OCF = CF ₂ . Such a material, which is referred to as perfluoro [2- (2-fluorosulfonylethoxy) propylvinylether], and which will hereinafter be abbreviated as PSEPVE, can be modified into equivalent monomers by, for example, the inner perfluorosulfonylethoxy component to the corresponding

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Propoxy component is modified and by changing propyl to ethyl or butyl and in addition the substitution sites of sulfonyl on it to be rearranged or by adding isomers of the perfluoro lower alkyl groups to be favoured. However, it is most preferred to use PSEPVE.

The method of preparing the hydrolyzed copolymer is described, for example, in Example XVII of U.S. Patent 3,282,865. An alternative method is described in Canadian Patent 849,670, which also uses of the finished membrane for fuel cells, which are referred to therein as electrochemical cells will. Both patents are incorporated herein by reference. The copolymer can be im essentially be prepared by PSEPVE or its equivalent with tetrafluoroethylene or its Equivalent in the desired proportions in water at elevated temperatures and pressures above one Time of more than 1 h reacted with each other. After this period the mixture is cooled. It separates into a lower perfluoroether layer and an upper layer of an aqueous medium with the dispersed therein desired polymers. The molecular weight cannot be determined, but it is the equivalent weight about 900 to 1600, preferably 1100 to 1400, and the percentage of PSEPVE or the equivalent Compound is about 10 to 30%, preferably 15 to 20%, most preferably about 17%. The non-hydrolyzed Copolymers can be compression-molded at high temperature and high pressure to form sheets or membranes that have a thickness of 0.02 to 0.5 mm

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ben. These are then further treated to convert the attached -SC ^ F groups to -SO ^ H groups, for example by treatment with 10% sulfuric acid or by the processes of the patents cited above. The presence of the -SCUH groups can be detected by titration, as it is in de.r Canadian Patent is described. Further details of the various stages of the process are given in the Canadian U.S. Patent 752-427 and U.S. Patent 3,041,317, incorporated herein by reference will.

Improved types of the above-described copolymers can by chemical treatment of their surfaces, for example by treatments to to modify the -SO ^ groups located on it. For example, the sulfonic acid group on the membrane can be changed to create a concentration gradient generate, or they can be partially replaced with a phosphoric acid or phosphonic acid part. Such Changes can be made in the manufacturing process or after the membrane has been manufactured. if the treatment is carried out as a subsequent surface treatment of the membrane, then the treatment depth is usually 0.001 to 0.01 mm. In some cases it may be useful to use the sulfonyl or To convert sulfonic acid group of the membrane on one side (e.g. the anode side) into a sulfonamide group, which is more hydrophilic, as disclosed in US Pat. No. 3,784,399, which is expressly incorporated herein by reference is taken, can be made. The membrane can also be in laminated form, which is currently the case

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is most preferred. The layers have a thickness in the range from 0.07 to 0.17 mm on the anode side and from 0.01 to 0.07 mm on the cathode side. The layers have equivalent weights in the area from 1000 to 1200 and 1350 to 1600. A preferred thickness for the layer on the anode side is in the range from 0.07 to 0.12 mm, with a thickness of about 0.1 mm being most preferred. The preferred thickness of the layer on the cathode side is 0.02 to 0.07 mm, with a thickness of about 0.05 mm being most preferred will. The preferred and most preferred equivalent weights or equivalent weights are 1,050 up to 1150 and 1100 or 1450 to 1550 and 1500. The higher the equivalent weight of the individual layer, the smaller the preferred thickness to be used within the specified ranges.

It has also been found that in addition to the previously described copolymers and their modifications Another type of membrane material in the method according to the invention, the films according to the State of the art is superior. Although it appears as if tetrafluoroethylene (TFE) polymers, which have been successively styrenated and sulfonated, would not be suitable to achieve satisfactory cation-active permselective membranes for use in the electrolytic process of the invention to produce, it has been shown that a perfluorinated ethylene propylene polymer (FEP) that styrenates and has been sulfonated gives a suitable membrane. The sulfostyrenated FEP products are against hardening and other failure

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when used under the conditions of the invention Surprisingly resistant to the process.

Examples of suitable membranes which are produced by the process described are products of RAI Research Corporation, Hauppauge, New York, referred to as 18ST12S and 16ST13S. The former product is 18% styrenated and 2/3 · of its phenyl groups are monosulphonated. The latter product is too 16% styrenated and 13/16 of the phenyl groups are monosulphonated. To get 18% styrenation, a solution of 17 1/2% styrene in methylene chloride is used, while to obtain a 16% styrenation a solution of 16% styrene in methylene chloride is used.

The membrane walls usually have a thickness of 0.02 to 0.5 mm, preferably 0.07 to 0.4 mm, most preferably from 0.1 to 0.2 mm. Thickness ranges for the parts of the laminated membranes previously described are has already been specified. If you use polytetrafluoroethylene asbestos, -titan or another suitable network to be mounted for wearing, then have the threads or fibers of the network usually have a thickness of 0.01 to 0.5 mm, preferably 0.05 to 0.15 mm, accordingly up to the thickness of the membrane. It is often preferred that the thickness of the fibers be less than half that the film thickness, but threads of greater thickness than the film can also be used with success, e.g. with 1.1 to 5 times the film thickness. The networks, sieves or cloths have a percentage opening area of about 8 to 80%, preferably 10 to 70%, most important

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preferably 30 to 70%. In general, the cross-sections are of the threads are circular, but other shapes such as ellipses, squares and rectangles are suitable. The carrier network is preferably a sieve or cloth and it will, although it may be glued to the membrane, preferred that it be attached to this by a high temperature, high pressure compaction prior to hydrolysis of the copolymer is melted. The composite structure of membrane and network can then be put in place clamped or otherwise fastened to a holder or to a carrier. At the distances you want Seals are used to maintain between the membrane and one, the other, or both electrodes and / or vertical wires or strips made of a suitable plastic material, e.g. polytetrafluoroethylene, used. In general, the cell width is 0.3 to 1 cm and the distance from the anode to the membrane is 1.5 to 6 mm, but can also be 0 mm. Similar measurements also apply to the distances between the Cathode and the membrane.

After the cell frame has been injection molded at an elevated temperature and pressure, the frame closes Cells and put together to form a cell assembly, as shown in FIGS. 1 to 4. if in place a T or right angle picture frame is used to hold the electrode (and possibly also the membrane), then it is made of a material that withstands the electrolyte with which it is brought in contact. So when the frame is on is located on the anode side, it is often made of titanium or a material clad with titanium, and if it is

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is on the cathode side, then it is usually made of mild steel. Similar rules apply to the various deformation devices, beam clamps etc.

After assembling the frames into cells and after tensioning these parts into a cell assembly, as shown in Figure 1, the cells are charged with electrolyte and electrolysis is carried out began.

The anode compartment is filled with a nearly saturated saline solution or a saline solution with a sodium chloride content of about 25% charged and the cathode compartment is charged with water, which is a little at the beginning Contains amount of salt or saline solution to improve its conductivity. The power is switched on and the chlorine and hydrogen generated in the cells are continuously decreased. In some embodiments of the invention, the chlorine and anolyte will be removed after removal the cell instead of previously separated. Usually sodium hydroxide becomes continuous during electrolysis removed, but it can also be removed after the completion of an electrolysis cycle. The depleted Anolyte is passed through a resaturation device, in which the sodium chloride content is increased, whereupon it is returned to the anode compartment. In general, the sodium chloride content is the same as that of the withdrawn Anolyte about 22 wt .-% and that of the returned from the resaturator about 25%. The anolyte can be acidified and has preferential

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wise one. pH in the range of 1 to 6, more preferred 1 to 5 and most preferably 3 to 4.5, e.g. 3.9 to 4.3. The pH value of the catholyte is naturally about 14, which is due to the high content of sodium hydroxide.

The temperature of the electrolyte is maintained at less than and is preferably from 20 ° to 95 ° C., more preferably about 80 to 95 ° C. The electrolyte temperatures can be adjusted by recirculating parts of it, through regulation the feed rates for the different zones and by changing the temperatures of the feeds to be controlled. Ice cooling and other cooling measures can also be used.

The voltage applied per cell is usually 2.3 to 5 or 6 V, and it is preferably in the range from 3.3 to 4.3V. In a preferred method, it can sometimes be as high as 4.5V. It will be the most it is preferred that the voltage be 3.3 to 4.1 volts. The current density is generally 0.2 to 0.5 A / cm, preferably 0.3 A / cm. The decrease in alkali hydroxide from the catholyte compartment takes place at such a rate that the alkali with a concentration from 5 to 45%, preferably from 5 to 25%, most preferably from about 8 to 12%, is obtained.

The examples illustrate the invention. All parts therein are based on weight.

example 1

A frame of the type shown in Figures 2 and 3 is used

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■ 7.

ü -

injection-molded according to the Eimco-Envirotech process for the injection molding of large pieces of plastic, in which case the injection molding temperature and pressure are normally increased. The mold is designed so that passages, protrusions, channels, edges, ribs, manifolds, alignment and tensioning devices are molded into the formed frame. If possible, threaded or partially threaded openings are also molded in so that they are available and receiving for threaded openings or other parts of the cell frame. The frames are made from a blend of 25% calcium silicate fibers, 10 % EP rubber impact modifier, 37.5% Exxon D-561 propylene / acrylic acid polymers, and 27.5% Shell 7525 polypropylene copolymers and the products obtained are tested and tested. It is found that the surfaces of the frames are richer in resin than the interior parts and that few or no fibers of the inorganic material on the surfaces are uncovered by the resin. Therefore, when tested in respective aqueous electrolytes suitable for use in electrolytic cells for the production of chlorine and alkali hydroxide from sodium chloride solution, the frames do not show significant fatigue, possibly due to the absence of cracks or spots where the calcium silicate is present is exposed. Also when testing for dimensional stability at temperatures in the range of 40 to 95 ° C, which temperatures are used in normal electrolysis with this cell type, the frames are stable and they do not warp, they do not crack and they do not warp other art.

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The frames are assembled into cells using neoprene gaskets, intermediate titanium picture frame brackets for the anodes and similar steel picture frame brackets for the cathode, and nylon screws and rectangular polypropylene ring pieces used to hold the membrane in and tightly against the membrane to hold the anode. The anode used is a drawn titanium mesh anode and the cathode is a steel screen. The conductor to the anode is copper plated with titanium and that to the cathode is copper the strand width is about 2 mm. The net has a diamond-like shape, the longitudinal axis being horizontal, and it has an open area of about 50% on its surface. The distances across the diamond-like structures are 0.75 cm and 1.25 cm The anode is coated on the side facing away from the membrane with an active coating of ruthenium oxide with a thickness of 0.07 mm. The coating is applied according to the known methods for producing dimensionally stable anodes. The cathode is a wire mesh made of mild steel with an equivalent diameter of about 2.0 mm and with an open area of about 50%.

The membrane is of the PSEPVE type (hydrolyzed) like him described above, and it is a laminate having a thickness of 0.17 mm. Corresponding to the thickness 2/3 an equivalent weight of about 1100 and 1/3 an equivalent weight of about 1500. The side of the membrane with the high molecular weight is opposite the cathode and the flatter, thicker side with the lower

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higher molecular weight with a polytetrafluoroethylene support network from threads with a diameter of about 0.3 mm is deposited, which becomes a Sieve or cloth with a percent open area of about 22% will be woven tightly against pressed the anode.

The frames and the cell walls have the dimensions of about 1.1 m by 1.1 m and the cells are about 11 cm thick. The cell walls and the other plastic parts of them in the cell, e.g. the protrusions, the walls that hold the Defining headers, and the passageways, as well as the rims and channels, are usually of a thickness of 1 to 3 cm.

Between the cathode and the membrane is a series of vertical flexible polytetrafluoroethylene separation cylinders or linings, each with a diameter of 2.5 mm, which act as vertical spacers used every 15 cm across the gap between the membrane and the cathode and together with the seal, which has a thickness such that a gap of about 2.5 mm is created between the cathode and the membrane will. These means keep the membrane at a regular distance from the cathode and hold it firmly against the Anode.

In the cell assembly, the various frames are on the temporary aligner or -bar placed, the electrodes are attached and the membranes are fixed by the temporary adhesive (Velcro or other suitable temporary

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or permanent sealant can also be used) and later through the seals in place and held in place. Before sealing the various frames together with the membrane it is usually Treated in place on the frame with a suitable solvent, e.g. glycerine, which has a Prevents drying of the membrane during the assembly of the cell and that, as in the present case, especially useful when connecting a plurality of cells (35) in a cell assembly.

After assembling the cells in the desired position in a filter press-like arrangement these are tightened tightly so that the seepage of liquid is prevented. FIG. 1 shows a view of the assembled cell stack or cell bank. Then the compilation of sources for the feeds and for the electricity and connected to a discharge pipe.

The anode compartments are then filled with a nearly saturated acidified salt solution of one concentration of about 25% and filled with a pH of about 4.1 and the cathode compartment is filled with water, which is initially used to improve conductivity Contains a small amount of sodium hydroxide. The current is switched on and a current density results of 0.3 A / cm. The voltage drop across each source will be during equilibrium of the aqueous Sodium hydroxide solution, chlorine and hydrogen recorded. Under such conditions, the cell voltage drop is about 4 V, the charge is about

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3 kA and the total voltage is about 120V DC. At the operating temperature of about 90 ⁰ C and at other temperatures in the range of 85 to 95 ° C, the stack or the cells compilation provides about 3 t per day chlorine with a chlorine power of about 96% with the addition of acid. The alkali hydroxide performance is about 90% at an alkali hydroxide concentration of 80 to 100 g / l. The chlorine output without the addition of acid is around 90%. After 6 months of operation under the conditions described above, the cell stack is opened and the electrodes, membrane, frame, seals and fasteners are checked. The electrodes and membrane are still operational and the frame shows no signs of significant weakening or warping. Despite the fact that the normal operation of the cells contains some interruptions, the temperature varies over a range of 40 to 95 ° C. The neoprene adhesive is still easily removable from the membrane and frame wall so that the membranes can be reused. In a modification of this approach, when Velcro fasteners are used to hold the membranes in place, they are easily separable and the membranes can be removed without damage.

In variations of this approach, a filled polypropylene resin is used used, which consists of a resin mixture of 30% of the calcium silicate fibers described above, 10% EP rubber impact modifier, 45% Exxon D-561 propylene / acrylic acid copolymer blend

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C0982170760

and 15% Shell 7525 polypropylene copolymers. The results obtained are almost as good as with the composition given above, with the exception that it is found that the frame under extreme conditions are slightly more sensitive to cracking. Another variation is 20% asbestos and 80% Polypropylene homopolymer is used. Although this too Frame, it is not as good as the frame described at the beginning. An improvement is obtained if a resin mixture of 20% asbestos, 10% mica, 40% homopolymers and 30% copolymers is used, which is prepared and examined in the same manner as described above.

Example 2

The procedure of Example 1 is repeated using a mixture of 30% calcium silicate fibers, 10% EP rubber impact strength modifier, 45% Exxon D-561 propylene / acrylic acid copolymer resin and 15% Shell 7525 polypropylene copolymer is used, however a non-laminated hydrolyzed PSEPVE copolymer with a thickness of about 0.2 mm as a membrane with the same type of reinforcement polytetrafluoroethylene screen is used. Similarly, Research Corporation Diaphragms used are designated as 18ST12S and 16ST13S and which have a uniform thickness. Work using a current of 0.3 A / cm in all of these cases the cells satisfactorily without the frame material either by the acidic Anolyte or the alkaline catholyte is damaged.

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When the cells are modified, the ruthenium oxide on the titanium anode is changed in such a way that it is present on all surfaces of which is active and the distance between cathode and membrane is reduced to 2 mm. In such conditions effective electrolysis is effected without damaging the frame material.

If further the electrodes by T-shaped intermediate support parts are held, then they can sag less easily than if they are only held by the seals, although angle frames also are satisfactorily rigid.

The cells of this example also work satisfactorily when the membranes are held against the cathodes or if they are placed halfway between the anodes and cathodes and in the desired locations are held by 1.5mm diameter Teflon liner spacers.

Example 3

Using the method of Example 1, frames are made from a mixture of 35% polypropylene homopolymers and 35% polypropylene copolymers and the remainder (there are no impact modifiers present), mica flakes (0.074 mm), calcium silicate fibers (wollastonite), calcium silicate fibers (synthetic), talc or asbestos (chroysotile) manufactured. There are also unmodified homopolymers, copolymers and 5O: 5O blends of homopolymers and copolymers are used. Frames are formed from all of these mixtures. When testing in practice

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using electrolytes at electrolysis conditions, it is found that the use of calcium silicate fibers in a homopolymer / copolymer blend is best and that the filled polymers in terms of their physical properties, especially dimensional stability and heat resistance, are superior to the unfilled materials. While these differences are important, they are possible to use all frames made of filled polypropylene in technical operation and also the frames made of unfilled polypropylene are still in service although they are inferior. Frames made of other polymers, e.g., polyvinyl chloride, polytetrafluoroethylene and polyethylene, although for long-term use normally technically unacceptable for short term use in electrolytic cells suitable and they are advantageous when in this, if applicable, by the usual injection molding techniques various headers, passages, openings, alignment, honing and fastening devices of the devices according to the invention have been deformed into it.

Still the combination of a polypropylene frame and a cationic permselective membrane of the DuPont Nafion XR type, especially if the membrane is directly without any seals in between is held on the frame in terms of dimensional stability, chemical resistance and the long service life is best and it is preferred.

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Example 4

The process steps of Example 1 are carried out at the temperatures, voltages and pH values described of the various processes within the given ranges from 20 to 95 ° C, from 3.3 to 4.3 V, one Anolyte pH from 3 to 4.5 and from 0.2 to 0.4 A / cm repeated. The electrodes are also based on the size of the open area and the proportional areas and the distances between the electrodes that were previously used specified varies. In such cases, usable electrolysis is obtained and the frames are sufficiently stable that they are technically acceptable. When operating these cells, no significant occur Problems on and the manufacturing costs of the frame are significantly reduced because the frame easily through Injection molding can be produced. Furthermore, the previously molded projections, edges, channels etc. in the frame makes it easier to put the parts together and they can be done within a shorter period of time can be performed, thereby reducing the cost of cell assembly. The invention Cells therefore represent a considerable advantage for the electrolysis of aqueous halide solutions.

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Claims (12)

-3B- claims 1. Frame for an electrolytic cell made of a synthetic organic polymers to form a housing for an anode and a cathode and as a support element for a membrane, characterized in that the frame together with a matching adjacent frame, which has an electrode of opposite sign to that of the first frame is closer, contains, an electrolytic cell (69) forms which an anode (71), a cathode (73) and a membrane (75) disposed therebetween, the frame (15) inlets (159) and outlets (157) for the electrolytic process fluids in anolyte compartments (135) and catholyte compartments (143), so that the two adjacent frames (15) formed Cell at least one inlet (133) into the anolyte compartment, at least one outlet (159) from the anolyte compartment, at least one inlet (141) into the catholyte compartment and at least one outlet (157) from the catholyte compartment having, the individual inlets and outlets with the respective head pieces or manifolds (147, 151, 149, 153, 155) integral with the cell frame. 2. Frame according to claim 1 for use for the electrolysis of aqueous halide solutions, characterized characterized in that the synthetic organic polymer is polypropylene with a Filler from the group of asbestos, mica, calcium silicate, talc and mixtures thereof. -40- 609821/0760 - uo - ■ 3. Frame according to claim 2, characterized in that it has a mold or compression mold construction in such a way that its surfaces are richer in polymer than the interior, in order to ensure durability of the frame compared to the electrolyte in contact with it. 4. Frame according to claim 3> characterized in that the construction material is approximately 15 to 50% calcium silicate fibers, mica flakes or contains a mixture thereof and that the frame when used in an electrolytic cell for the production of chlorine and sodium hydroxide is resistant to warping from aqueous sodium hydroxide solutions. 5. Frame according to claim 3, characterized in that the molded frame is integral has external alignment and fastening means (53) to position a tie rod (33) in the correct position which is used to bring a plurality of frames (15) into filter press relationship in an assembly to keep with multiple cells. 6. Frame according to claim 5, characterized that integral outer alignment devices separate from the alignment and fastening devices are provided around the frame (15) on a plurality of horizontally extending Straps to wear during assembly. 7. Frame according to claim 3, characterized in that the frame molded-in holding -41- 609821/0760 has approximately devices to hold electrical conductors (77, 79) for the electrodes in desired positions, and in that it has support means for an intermediate support for an electrode in place and Place to hold. 8. Frame according to claim 7, characterized in that the intermediate bracket of a rectangular T-shaped picture frame shape, with the leg of the top of the T being horizontal and the top is vertical, with a portion of the top being adapted to be attached to the frame and the other is adapted to be attached to the electrode, causing the electrode to pass through the T-frame is made rigid and held in this way in the desired position. 9. A method for producing a frame for an electrolytic cell for the electrolysis of aqueous sodium chloride solutions, characterized in that the frame is made from a mixture of polypropylene and a filler therefor, the filler being made of selected from the group of asbestos, mica, calcium silicate, talc and mixtures thereof, in the form of an integral Elements molded from parts of two different cells, each frame attached to a different frame can be connected to form a complete cell and wherein the frame and the cells formed molded in feed and discharge passages and fixtures to hold the cell parts, contain. -42- 609821/0760 10. Rectangular frame for an electrode of an electrolytic cell for the production of chlorine, sodium hydroxide and hydrogen from aqueous sodium chloride solutions, characterized in that it is so is designed to be attached to a part of a cell frame and to the electrode for reinforcing the electrode can be attached and that it has a T-shaped cross-section with the leg of the top of the T being horizontal and the top thereof being vertical. 11. Process for the electrolysis of aqueous sodium chloride solutions, characterized in that the solution has an electrolysis voltage of 2.3 to 6 V between an anode and a cathode at a temperature of about 80 to 95 ° C in a membrane cell subject, wherein the walls of the cell are made of molded polypropylene that is made with a filler of the group asbestos, mica, calcium silicate, talc and mixtures thereof. 12. The method according to claim 10, characterized in that g e k e η η draw et that the wall surfaces are richer in polypropylene than the interior to ensure durability compared to the electrolyte in contact therewith, and that the filled polypropylene contains about 15 to 50% calcium silicate fibers, mica flakes or mixtures thereof and is resistant to warping when in use is. 609821/0760