JPS6059088A - Method for sealing ion exchange membrane and gasket - Google Patents

Abstract

PURPOSE:To prevent sustainedly a leak of an electrolytic soln. by making a water repellent exist on the surface of an ion exchange membrane to be sealed in an electrolytic cell. CONSTITUTION:When an ion exchange membrane and a gasket are press-sealed, a water repellent is made to exist on the surface of at least the part of the membrane contacting with the gasket by coating, dipping or other method. A leak of an electrolytic soln. from the press-sealed part can be sustainedly prevented. Any water repellent which does not deteriorate the membrane and the gasket and does not contaminate an electrolyzate may be used as said water repellent.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of sealing an ion exchange membrane and a gas nut, and particularly provides a sealing method for preventing leakage of electrolyte in an ion exchange membrane electrolytic cell.

In an ion exchange membrane electrolytic cell, an ion exchange membrane is used as a diaphragm that partitions an anode chamber and a cathode chamber. usually,
The ion exchange membrane is the anode chamber frame.

A gasket is placed on each cathode chamber frame to seal it. However, at the contact surface between the ion exchange membrane and the force socket, the surface of the ion exchange membrane is uneven.

In particular, it is difficult to achieve a complete seal due to the unevenness caused by the banking cloth. The electrolyte is sucked out through the small gap created in the seal by capillary action. This leads to corrosion of the electrolytic solution, busbars, etc., which in turn becomes a factor that impairs electrolysis efficiency. To prevent such troubles, the tightening pressure for filter press type electrolytic cells is generally
For example, it is customary to make it very large, such as one made of 50 or more, but even in such a case, there is still no possibility of leakage of the electrolyte. Another problem is that when the gasket is tightly tightened, the gasket deforms and the ion exchange membrane in contact with it is stretched, which may cause damage to the ion exchange membrane at the backing contact surface.

On the other hand, for example, a flat ion exchange membrane obtained by modifying a filterable diaphragm electrolytic cell in which an anode chamber and a cathode chamber are partitioned by forming an ion exchange membrane into a cylindrical or bag shape and accommodating one electrode. In a tube (pool) type electrolytic cell, there is also a sealing part made up of an ion exchange membrane and a gasket to prevent the anode and cathode compartment liquids from mixing, but there is still the problem of leakage from this area. be.

As a means to improve the sealing performance between the ion exchange membrane and the gasket, it is also possible to remove in advance the ion exchange groups of the ion exchange membrane on the surface that contacts the gasket to make it hydrophobic and prevent electrolyte leakage. However, this is not practical because the physical properties such as elongation of the ion exchange membrane change.

Furthermore, methods have been proposed in which various oil-based chemicals are applied to the sealing surfaces of the ion exchange membrane and gasket to prevent liquid leakage, but few of these methods are satisfactory, especially from the viewpoint of sustainability of the effect.

In order to solve the above-mentioned problems, the present inventors conducted extensive research and found that when press-sealing an ion exchange membrane and a gasket, a water repellent agent was applied in advance to at least the surface of the ion exchange membrane in contact with the gasket 1. The inventors have discovered that leakage of electrolyte in an ion-exchange membrane electrolytic cell can be prevented in a sustained manner by the presence of such an ion-exchange membrane electrolyte, and have thus come to provide the present invention. That is, according to the present invention, leakage of the electrolyte from the part where the ion exchange membrane is press-sealed with the gasket in the ion exchange membrane electrolytic cell can be prevented in a sustained manner.
It is possible to improve electrolysis efficiency.

As the water repellent used in the present invention, any known water repellent can be used without any restrictions as long as it does not damage the ion exchange membrane and gasket materials and does not contaminate the electrolyzed product. In particular, fluorine-based water repellents such as 70 Rogard A silicone-based water repellent such as (manufactured by Co., Ltd., trade name) is preferably used. Among these, fluorine-containing compounds, particularly perfluorocarbon-based silicon compounds, are preferred as stable substances that are not altered by electrolytic products.

In the embodiment of the present invention, it is sufficient to pre-exist the water repellent agent as described above on at least the surface of the sealed portion of the ion exchange membrane, and then press-seal it with the force-sket. By doing so, a uniform coating of the water repellent agent is present on the surface of the ion exchange membrane, so that the effects of the present invention become extremely significant. However, if a water repellent is applied to the surface of the gasket, the above effect may not be achieved, so this is not a preferred embodiment. The method for making a water repellent agent present on the surface of an ion exchange membrane is generally to apply a mixed solution of the water repellent agent and an organic solvent to the ion exchange membrane, or to immerse a desired part of the ion exchange membrane in the solution. A method of attaching the material by attaching the material may be adopted as appropriate. The amount of water repellent present in at least the surface [111] of the ion exchange membrane cannot be determined unconditionally depending on the type of water repellent, etc., but it is generally 05 to 3μ thick, or 003 to 3μ thick.
It is preferable to use the range of 110011I/crI.

In addition, it is necessary to have a water repellent at least on the part of the ion exchange membrane surface that comes into contact with the gasket, but in the electrolysis of aqueous alkali metal chloride solutions, the environment contains chlorine or chlorine-saturated salt water, so it cannot be used for a long period of time. In this case, it is preferable that a water repellent agent be present on all surfaces other than the electrolytic surface.

The battery case to which the present invention is applied is not particularly limited. For example, a battery tank used for concentrating or desalting salt water or other salt solutions, etc.A battery tank that has the function of transferring and separating ions through an ion exchange membrane is suitable, and is also used for electrolysis of aqueous alkali metal salt solutions. It may also be an electrolytic cell. Furthermore, it is also effective for a type of battery that does not supply current from the outside, such as diffusion dialysis. Further, the format of the container is also arbitrary, and may be a filter press type, pool type/finger type, or any other type. The battery case may have a structure in which the ion exchange membrane and the gasket are brought into pressure contact with each other to prevent leakage of the liquid or gas contained therebetween. Furthermore, it will be easily understood that the type and structure of the ion exchange membrane used are not limited in view of the gist of the present invention. The present invention is characterized in that it is particularly effective for ion exchange membranes of the type that use reinforcing fibers such as woven fabrics and have uneven surfaces and are generally difficult to seal. Among technologies using ion exchange membranes, in particular for electrolysis of aqueous alkali metal salt solutions, from the viewpoint of durability of the ion exchange membrane, tetrafluoroethylene and perfluorocarbon vinyl ether having ion exchange groups as pendant groups are generally used. It is a copolymer with , and its characteristic is that it does not have a crosslinked structure. When such a membrane is tightened strongly for the purpose of sealing, for example, if the operation of tightening with high surface pressure is repeated with a product made of 30 or more, the sole part becomes thinner and weaker due to the creep phenomenon. You can't force it.

Therefore, liquid or gas tends to leak from the sealed portion of the ion exchange membrane. The present invention is extremely effective in solving the problem of preventing such leakage.

The gasket (backing) applied to the present invention is not particularly limited. Known backing material.

For example, natural rubber, synthetic rubber, soft polyvinyl chloride, polyethylene, polypropylene, ethylene-fluoroethylene copolymer resin, tetrafluoroethylene, and other elastic or flexible materials can be used.

Examples will be shown below to explain the present invention in detail, but
The present invention is not limited to the following examples.

Example 1 An electrolytic cell made of acrylic resin with an electrode area of 110 crn x 40 cm, the anode of which was coated with a mixture of ruthenium oxide and titanium oxide using a titanium lath material.

The cathode was a test cell using a soft iron mesh, with a 4 tnm thick chloroprene rubber on the anode side and a 2 trm thick chloroprene rubber on the cathode side as a caskerat, and a thin layer of carboxylic acid groups on the cathode side as an ion exchange membrane. Perfluorocarbon-based cation exchange membrane having L-1 and other U sulfonic acid groups (
A product based on Fuion 415 manufactured by DuPont, into which a carboxylic acid group was introduced by Tokuyama Soda Co., Ltd.) was used. The gasket and the ion exchange membrane are tightened so that the surface pressure is 15 degrees.

4.5N saline solution is supplied to the anode chamber, and l0I is supplied to the cathode chamber.
To obtain J's caustic soda, anode chamber 100σ
Water column, cathode chamber is 2OA/d under the condition of 120cm water column.
“ Electrolysis was performed at 80°C.

When Fluoroguard BM-300 was applied to the outer edge of the ion exchange membrane from the gasket contacting surface and used after drying, no liquid leakage occurred during 30 days of electrolysis.

On the other hand, when the above-mentioned treatment was not carried out, it was observed that salt crystals were formed in the casket part from the third day onward and grew day by day.

Example 2 Using ion exchange VC (same type as in Example 1),
It was machined into a box shape with a length of 130 holes, an oak of 7σ, and a depth of 100σ with an open top. (This will be referred to as a bag from now on).

A silicone water repellent (5D-800 manufactured by Toray Silicon Co., Ltd.) is applied up to the upper end 150B of this bag. After drying, the bag was immersed in pure water, stretched, and attached to the anode.

The bag containing the anode was fixed in the electrolytic cell as shown in FIG. That is, Yin 8! i! Bag 2 inserted between 1
At the bottom, the bottom plate 3 also stands up, and the lead 4 penetrates, @pole 5
The anode and the bag are fixed. The upper part is fixed between the electrode frame 6 and the plug 7 via a packing 8. He is 40k with the presser bolt 9
It was held down with a torque of 17 cIn.

Supplying salt water at 3101//l to the @ pole side of the electrolytic cell,
It is operated at a current density of 20 A/cLm and a cell temperature of 80 to 90°C so as to obtain 30% caustic soda from the cathode chamber.

No IJ leakage of salt water was observed at least 30 days after energization.

Example 3 Example 2. Example 2 except that a fluorine-based water repellent (manufactured by Daikin Corporation, trade name: Tex Guard) was used as the water repellent in Example 2. I did exactly the same thing.

No leakage of salt water was observed at least 30 days after energization. Further, in both Examples 2 and 3, the water repellency of the seal portion was the same as before energization.

Comparative Example 1 Example 2 except that the ion exchange membrane was incorporated into the battery case without applying a water repellent. It was conducted under the same conditions.

Salt water leakage occurs when the liquid is filled before energization, and the
Even after this, salt water leakage continues to occur, and Mhol crystals continue to form in the sole. Adding more sealing plugs had little effect. After 30 days of operation, crystals deposited on the seal part accumulated, making it difficult to continue operation unless the seal part was cleaned.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an outline of an electrolytic cell used in an example. In the figure, l is the cathode, 2 is the bag (ion exchange membrane), and 3 is the cathode.
is the bottom plate, 4 is the lead, 5 is the anode, 6 is the electrode frame, 7 is the plug, 8i; i is the packing. 9#i push bolt. Patent Applicant: Tokuyama Soda Co., Ltd. Drawings 2) (No change in content) Figure 1 Procedural Amendments March 1980 η Director-General of the Patent Office Kazuo Wakasugi 1, J> Indication of Patent Application 1982 -165156 No. 2, Title of Invention Method for sealing ion exchange membrane and gasket 3,
Relationship with the case of the person making the amendment Patent applicant address: 1-1-4, Mikage-cho, Tokuyama City, Yamaguchi Prefecture, weight of the amendment order: January 11, 1980, same shipping address: 17+31, 1980 IJ5, subject of amendment: Figure
surface

Claims (1)

[Scope of Claims] 1) A method for sealing an ion exchange membrane and a gas nut, characterized in that a water repellent agent is preliminarily present on the sealing surface of the ion exchange membrane when sealing the ion exchange membrane and the gasket. 2) Method 0 according to claim 1 used in an electrolytic cell for electrolyzing an aqueous alkali metal chloride solution