JPS6040515B2 - Ion exchange membrane electrolyzer - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an ion-exchange membrane electrolytic cell, particularly to an ion-exchange membrane electrolytic cell suitable for electrolyzing an aqueous alkali chloride solution.

In recent years, from the viewpoint of pollution prevention, the method for obtaining caustic alkali and chlorine by electrolyzing an aqueous alkali chloride solution has been replaced by the diaphragm method instead of the mercury method, and a method using an ion exchange membrane for the purpose of obtaining even higher purity and highly concentrated caustic alkali. has been put into practical use.

On the other hand, in this type of electrolysis, it is imperative to reduce the electrolytic voltage as low as possible from the viewpoint of energy saving. The so-called SPE (Solid Poly
merElectroly) type alkali chloride electrolysis (for example, Tokusei No. 53-152297, Tokusei No. 52-78
7 Iso Publication) is known.

This is a method that allows electrolysis to be carried out at a lower voltage than before because it can reduce the electrical resistance of the electrolytic solution and the electrical resistance caused by bubbles generated from hydrogen and chlorine gas, which were previously thought to be unavoidable in this type of technology. This is an excellent method. On the other hand, the present inventors conducted further research and, instead of bonding the above-mentioned electrode to the membrane surface as a porous layer, a porous layer that itself does not have electrode activity, for example, is non-conductive, was attached to the membrane surface. combine,
By providing the electrode through the porous layer, we have developed an electrolytic cell that can reduce the voltage in the cell in substantially the same way as the electrolytic cell provided with the electrode porous layer.

This electrolytic cell has a low cell voltage, has a wide range of selectivity as the electrode material does not come into direct contact with the membrane, and is free from troubles caused by gas generation at the interface between the membrane and the porous layer. It has an additional advantage over an electrolytic cell having a porous electrode layer in that it can be prevented.

By the way, in an ion exchange membrane electrolytic cell that has a porous layer on its surface that does not have electrode activity, the contact between the gas permeable porous layer and the ion exchange membrane surface is an important point that affects the performance of the device. If the thickness of the porous layer is uneven, or if there is insufficient contact between the porous layer and the ion exchange eye, part of the porous layer may easily separate, resulting in an increase in the oar voltage. Alternatively, due to the accumulation of gas or excess liquid at the contact interface, the voltage may increase, and the intended advantages of the device may be reduced or not obtained.

The present invention provides a method for contacting an ion-exchange membrane with a gas- and liquid-permeable porous layer in this type of ion-exchange membrane electrolytic cell.
By adopting a new construction means, an illustrated tank having excellent performance is provided, in which a porous layer of uniform thickness is provided on the ion exchange membrane surface so as to be in sufficient contact with the ion exchange pus.

That is, the present invention provides an electrolytic cell in which an anode and a cathode are partitioned by an ion exchange membrane, wherein at least one of the anode and the cathode is formed on the surface of the ion exchange membrane and has no electrode activity and is permeable to gases and liquids. are arranged through a porous layer of
The present invention provides an ion-exchange membrane electrolytic cell characterized in that the porous layer is formed by adhering particles of a gas-conducting or non-conductive substance to the ion-exchange membrane surface by a roll coating method. be. In the present invention, the gas- and liquid-permeable porous layer formed on the ion-exchange membrane surface may be made of either a conductive material or a non-game-conducting material, as long as it does not act as an electrode, and may be made of either an inorganic material or an organic material. You may.

However, it is preferable to use a material that is corrosion resistant to the polar liquid and has hydrophilic properties. Preferred examples include metals, metal oxides, hydroxides, carbides, nitrides, or mixtures thereof, and hydrophilic polymers, particularly fluorine polymers on the anode side. For example, in the case of electrolysis of an aqueous alkali chloride solution, the porous layer on the anode side is made of group W-A (preferably germanium, tin, lead), group W-B (preferably titanium, titanium, etc.) of the periodic table.
Powders of oxides, hydroxides, nitrides, or carbides of metals of the V-B group (preferably niobium, tantalum), iron group metals (iron, cobalt, nickel), oxides, hydroxides, nitrides, or carbides are used. Ru.

On the other hand, for the porosity layer on the cathode side, ``In addition to the materials used to form the porosity layer on the anode side, ethylene tetrafluoride treated with hydrophilic treatment with silver, zirconium or its alloy, stainless steel, carbon, or potassium titanate, etc. Resin, etc. are used. When forming the porous layer by the roll coating method, the above material preferably has a particle size of 0.01 to 300, particularly 0.1 to 10.
It is used in the form of a 0 ml powder.

The above materials may be used alone or in combination of two or more. For example, an inorganic material may be mixed with an organic material such as polytetrafluoroethylene modified by copolymerizing a small amount of an acid type monomer, or a fluoropolymer for ion exchange membranes described below. In carrying out the method, it is preferable to use a paste containing the particles as described above.

When using paste-like materials, binders such as fluorocarbon polymers such as boritetrafluoroethylene and polytrifluorochloroethylene, and cells such as carboxymethyl cellulose, methyl cellulose, and hydroxyethyl cellulose, if necessary. Thickeners such as water-soluble substances such as bases, polyethylene glycol, polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, polymethyl vinyl ether, casein, and polyacrylamide are used. These binders or thickeners are preferably 0 to 5% by weight, especially 0% by weight, based on the powder.
．． 5-3% by weight is used. In addition, if necessary at this time, the formation of the porous layer can be facilitated by further adding an appropriate surfactant such as a closest-chain hydrocarbon or a fluorinated hydrocarbon.

In any case, the content of said particles in the formed porous layer is between 0.001 and 50 particles/field, especially between 0.01 and 3
It is preferable to set it to about 3/0. The roll coating method (roll coating method), which forms a porous layer on the edge, can be applied continuously to the surface of the largest ion exchange membrane, and is desirable from the viewpoints of workability and uniformity of coating. . In this case, the coater includes a rod coater, blade coater, knife coater, air knife coater, IJ/
Any general-purpose coating method such as a roll coater, a gravure roll coater, a kiss coater, a calendar coater, a nip coater, or a dip coater can be used. Normally, a porous layer can be formed by uniformly applying a paste like the one described above on the surface of an ion exchange membrane and then continuously drying the evaporated components in the paste in a drying oven. . After forming a porous layer on one side of the ion-exchange membrane by roll coating, in the case of a long membrane, it is rolled up once, and then the reverse side is coated with a roll in the same manner, thereby forming a layer on both sides of the ion-exchange membrane. It is also possible to form a porous layer. The amount of solid particles adhered after application and drying depends on the solid content concentration of the paste, the viscosity, the conveyance speed of the ion-exchanged pus to be applied, the rotation speed of each roll, and, in the case of a bar coater method, backup It can be controlled by the distance between the roll and the bar coater.

In the case of a gravure coater, etc., it can also be controlled by an engraved pattern on the gravure roll. In any case, the thickness of the paste to be applied is 0.001 to 5 o/, preferably 0.01 to 30 o/in terms of particle solid content.
It is desirable to apply the coating to a predetermined thickness as uniformly as possible within the range of o'. The applied paste is dried at a temperature within a range that does not cause thermal deterioration of the ion exchange membrane, e.g.
It can be carried out at a temperature of 2 pi or less, and the temperature, time, etc. can be selected depending on the solvent composition in the paste.
In this way, a porous layer with uniform thickness and high adhesion is formed on one or both surfaces of the ion exchange membrane.
Preferably, if necessary, the porous layer is pressed against the membrane surface under pressure.

Such pressing methods include the flat plate pressing method in which the coated film is cut into predetermined dimensions and then pressed between heated flat plates, and the roll is rotated between a pair of heated rolls, especially a metal roll and a rubber roll. It is possible to adopt any roll press method in which the material is pressed continuously while being pressed. In this case, the pressing temperature can be set in a wide range of temperatures from about 100 to about 30,000 so that the film softens to melts. The press pressure is
In the case of a flat plate press, 1 to 1000k9/ground, preferably 1
~200k9/enough, 0.5~2 for roll press
00k9/Koichi roll length, preferably 1-100k9
/ ground - roll length is adopted. In order to obtain good gas and liquid permeability, the porous layer thus formed on the surface of the ion exchange membrane, which has no fin polar activity, preferably has an average pore diameter of 0.01 to 200 r, particularly 0. 1-100
The porosity is preferably 10 to 99%, particularly 25 to 95%, and the thickness is preferably 0.01 to 200.
In particular, it is appropriate to set it to 0.1 to 100 μm.

When a porous layer having no electrode activity is formed on the surface of the ion exchange membrane, the electrode is placed through the porous layer.

As such an electrode, a porous electrode such as silk or expanded metal is used. As such electrode materials, for example, platinum group metals, conductive oxides thereof, or conductive reduced oxides thereof are used as the anode, while platinum group metals, conductive oxides thereof, etc. are used as the cathode. Or iron group metals etc. are used. Examples of platinum group metals include platinum, rhodium, ruthenium, palladium, and iridium, and examples of iron group metals include iron, cobalt, nickel, Raney nickel, and stabilized Raney nickel. If a porous electrode is used, it can be formed from the material itself forming the anode or cathode. However, when platinum group metals or their guiding fin oxides are used, it is preferable to coat the surface of an expanded valve metal such as titanium or tantalum with these substances. Although these anodes or cathodes do not necessarily have to be placed in contact with the porous layer, preferably the electrodes are placed in contact with the porous layer. In addition, when only either the anode or the cathode is disposed via a porous layer having no electrode activity according to the present invention, the opposite electrode, the anode or the cathode, is
The porous electrode described above can be placed directly on the anode side or the cathode side of the ion exchange membrane.

In such a case, these flea electrodes may be provided in contact with the ion exchange membrane surface, or may be provided at intervals. The ion exchange membrane used in the present invention is made of a polymer containing a cation exchange membrane such as a carboxylic acid group, a sulfonic acid group, a phosphoric acid group, a phenolic hydroxyl group, and such a polymer includes a fluorine-containing polymer. It is particularly preferable to employ coalescence.

Examples of fluorine-containing polymers containing ion exchange membranes include combinations of vinyl monomers such as tetrafluoroethylene and chlorotrifluoroethylene with perfluorinated vinyl monomers having ion exchange membranes such as sulfonic acid, carboxyl acid, and phosphoric acid groups. Polymers are preferably used. Further, a membrane-like polymer of trifluorostyrene having an ion exchange membrane such as a sulfonic acid group introduced therein can also be used. Among these, it is particularly preferable to use a polymer having the following polymerized Mr.

{EEK CF2-CXX'NA, where X is F, CI, H or -CF3, and X' is
or CF3(CF2)m, m is 1 to 5, and Y
is selected from the following:

CF2xA, 10tCF2NAxA, x, y, and z are all 0 to 10, and Z and Rr are selected from 1F or a perfluoroalkyl group having 1 to 10 carbon atoms.

In addition, A is -S03M, -COOM or -S02F, -CN, -CO, which can be converted into these groups by hydrolysis.
F or -COOR, M is hydrogen or an alkali metal,
R represents an alkyl group having 1 to 10 carbon atoms. The cation exchange membrane used in the present invention preferably has an ion exchange capacity of 0.5 to 4.0 meq/g dry resin, particularly 0.8 to 2.0 meq/g dry resin. is preferred.

In order to provide such ion exchange capacity, the above
In the case of an ion exchange membrane made of a copolymer consisting of polymerized units of [o], preferably the polymerized units of [o' are preferably 1
Suitably it is from 3 to 25 mol%, especially from 3 to 25 mol%.

The cation exchange membrane used in the present invention does not necessarily need to be formed from only one type of polymer, nor does it need to have only one type of ion exchange membrane.

For example, a laminated membrane of two types of polymers with a smaller ion exchange capacity on the cathode side than on the anode side, the cathode side containing a weakly acidic exchange group such as a carboxylic acid group, and the anode side containing a strongly acidic exchange group such as a sulfonic acid group. Ion-exchange membranes can also be used. These ion-exchange membranes are manufactured by various conventionally known methods, and if necessary, these ion-exchange membranes can be manufactured using fabrics such as cloth or mesh, preferably made of a fluorine-containing polymer such as polytetrafluoroethylene. It can be reinforced with non-woven fabric, metal mesh, porous material, etc.

Further, the thickness of the ion exchange membrane of the present invention is preferably 20
-500 mm, preferably 50-400 mm. The porous layers on the anode and cathode side, which are preferably bonded and formed on the surface of these ion exchange membranes, are formed in an appropriate ion exchange membrane form so as not to cause decomposition of the ion exchange membrane of the ion exchange membrane. , for example, in the case of a carboxylic acid group,
In its ester form, in the case of a sulfonic acid group, -S02
Type F, bonding is achieved through the use of pressure and heat.

The conditions for electrolyzing, for example, an aqueous alkali chloride solution using the electrolytic cell of the present invention are as follows.
Known conditions such as those in Publication No. 23 can be employed.

For example, in the anode chamber, preferably 2.5 to 5 normal (N)
of aqueous alkali chloride is supplied, and water or diluted alkali hydroxide is supplied to the cathode chamber, preferably 80 qo to 12
Electrolysis is carried out at a current density of 10 to 100 A'dm2. In such a case, heavy metal ions such as calcium and magnesium in the aqueous alkali chloride solution cause deterioration of the ion exchange membrane, so it is preferable to keep them as small as possible.
Furthermore, an acid such as hydrochloric acid can be added to the aqueous alkali chloride solution in order to prevent the generation of oxygen at the anode as much as possible. The electrolytic cell in the present invention may be of a monopolar type or a bipolar type as long as it has the above configuration.

In addition, the material used to construct the electrolytic cell is titanium, which is resistant to aqueous alkali chloride and chlorine in the case of the anode chamber, and titanium, which is resistant to high concentrations of alkali hydroxide and hydrogen, in the case of the cathode chamber. Some iron, stainless steel or nickel are used. Further, in the present invention, when an ion exchange membrane with a porous layer attached is used, an electrode is arranged on the outside thereof. For example, in the case of the anode, expanded metal of valve metal coated with precious metals, their alloys or conductive oxides thereof, and in the case of the cathode, silk, mesh or expanded metal of iron, nickel or stainless steel. It consists of Further, these electrodes are preferably brought into contact with the porous layer by pressing them against the porous layer. Although the above description has been made particularly as an electrolytic cell for an aqueous alkali chloride solution, it goes without saying that the electrolytic cell of the present invention can be similarly applied as a fin and scale bath for water, halogen acid, and alkali carbonate.

Next, the present invention will be explained in more detail using examples.

Example 1 Titanium oxide particles with a particle size of 5 or less were added to a mixed solvent in which 93 parts of cyclohexanol and 31 parts of cyclohexanone were uniformly mixed in 600 parts of water containing 11 parts of methylcellulose.
60 days and the surface of polytetrafluoroethylene with a particle size of 1 or less is treated with tetrafluoroethylene and CF2=CF○ (CF
2) 26 particles coated with 3COOC copolymer were added and mixed to prepare a suspension paste.

The paste was applied to one side of the ion exchange membrane using a roll coater having a coater section consisting of a bar coater and a backup roll.

The ion exchange capacity of the ion exchange membrane is 1.43 milliequivalents/
This is an enteric ion exchange membrane made of a copolymer of gram dry resin, tetrafluoroethylene having a thickness of 210 μm, and a ratio of CF2=CF0(CF2)3COOC. The coater gap between the doctor blade and the ion exchange membrane surface is approximately 35r.
The application speed was 3/min and was subsequently dried continuously in a 4-length drying oven maintained at 110°C. After completing the coating and drying on one side in this manner, the coating and drying on the opposite side of the membrane was then carried out under the same conditions. The ion exchange membrane with porous layers formed on both sides was sandwiched between two sheets of stretched saturated polyester film with a thickness of 100 mounds, and then passed between a metal roll with a diameter of 30 arcs heated to 150oC and a silicone rubber lining roll. At the speed of 3 ratio Eno, 40k9/
It was continuously pressed and wound under arc-roll length pressure.

As a result of peeling off the two upper and lower polyester films used as protective films, a composite membrane having porous layers firmly adhered to both surfaces of the ion exchange membrane was obtained. The composite membrane was
The ion exchange membrane was hydrolyzed by immersion in a % by weight aqueous sodium hydroxide solution. Each side of the ion exchange membrane contained about 1 part of titanium oxide on each side. Next, on the anode side of the ion exchange membrane, an anode with a low chlorine overvoltage made of expanded titanium metal (minor axis 2.5 skin, major axis 5 side) coated with Oka solution of ruthenium oxide, iridium oxide, and titanium oxide was placed. In addition, SUS304 expanded metal (minor axis: 2.5 mm, major axis: 5 mm) was etched on the cathode side at 150°C for 5 hours in a 52% caustic soda aqueous solution to ensure low hydrogen overvoltage. 0.
The ion exchange membrane was brought into pressurized contact at a pressure of 0.01 kg/yield, and while supplying a 5N aqueous sodium chloride solution to the anode chamber and water to the cathode chamber, the sodium chloride concentration in the anode chamber was brought to 4N, and the cathode While maintaining the caustic soda concentration in the chamber at 35% by weight, electrolysis was carried out at 9000.4 M/dm2, and the following results were obtained.

Voltage W) Current efficiency (%) 3.07 93.2 Comparative example 1 Electrolysis was carried out in the same manner as in Example 1 without attaching anything to both sides of the ion exchange membrane used in Example 1, and the following Got the results.

Cell voltage W) Current efficiency (%) 3.41 93.8

Claims (1)

[Scope of Claims] 1. An electrolytic cell in which an anode and a cathode are separated by an ion exchange membrane, wherein at least one of the anode and the cathode is formed on the surface of the ion exchange membrane through which gas and liquid permeate and have no electrode activity. The porous layer is formed by adhering particles of a conductive or non-conductive substance to the surface of the ion exchange membrane by a roll coating method. Ion exchange membrane electrolyzer. 2 The porous layer has a porosity of 10 to 99% and a thickness of 0.01 to
The electrolytic cell according to claim 1, having a diameter of 200μ. 3. The electrolytic cell according to claim 1, wherein the conductive or non-conductive substance is made of an inorganic or organic material that has corrosion resistance against the polar liquid. 4. The electrolytic cell according to claim 1, wherein the application of the particles is carried out by applying a thin layer of a paste containing the particles to the surface of the ion exchange membrane. 5 Conductive or non-conductive substance has a particle size of 0.01 to 100
The electrolytic cell according to claim 1, wherein the electrolytic cell is coated on the surface of an ion exchange membrane as μ particles. 6. The electrolytic cell according to claim 1, wherein the ion exchange membrane is a fluorine-containing cation exchange membrane having a carboxylic acid group or a sulfonic acid group. 7. The electrolytic cell according to claim 1, wherein the ion exchange membrane electrolytic cell is an aqueous alkali chloride solution electrolytic cell for producing alkali hydroxide and chlorine.