JPS6013436B2 - How to install an ion exchange membrane - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for mounting an ion exchange membrane on a filter press type electrolytic cell.

In recent years, ion-exchange membranes have been developed using resins made from fluorinated or fluorine-substituted vinyl compound monomers as a base material, with perfluorovinyl ether in the side chain, and with ion-exchange membranes such as sulfonic acids and carboxylic acids. With the advent of substances with added groups, progress towards commercialization is rapidly progressing.

Particularly in the field of producing chlorine and caustic alkali by electrolyzing aqueous alkali chloride solutions, commercial production methods have been developed as electrolytic methods to correct the shortcomings of conventional mercury and diaphragm methods, such as water pollution, air pollution, and low energy efficiency. being done.

Conventionally, when applying the selective permselectivity of ion exchange membranes to electrochemical operations, they have been provided in sheet form for convenience in membrane production and ease of handling. In particular, although many efforts have been made to develop Furuhata polymers,
Many of them are in sheet form because of the difficulty in processing them.
In general, as a type of electrolytic cell that uses a sheet-like ion-exchange membrane to carry out actual electrochemical operations, the ion-exchange membrane is placed between a substantially flat chamber frame, and a filter press is constructed using a press-furnace method. type electrolyzer is selected. In alkaline chloride electrolysis, a filter press method is used in which a large number of unit cells are sandwiched between an anode chamber frame with an anode installed and a cathode chamber frame with a cathode, with intestinal ion exchange membranes sandwiched between the gaskets on the outer periphery of each chamber frame (flassage surface). The components are tightened and assembled, and electrolysis is performed while supplying alkali chloride as a raw material to the anode chamber, and the desired caustic alkali and hydrogen gas are obtained from the cathode chamber, and chlorine gas is obtained from the anode chamber as products.

In this case, the ion-exchange membrane is subjected to pre-treatment for the purposes of making full use of its performance, ensuring a smooth start, and preventing wrinkles from forming during {31 operation. . As this treatment agent, an alkaline aqueous solution, hydrochloric acid, or an organic solvent is generally used. The inventors of the present invention installed this treated membrane as it is in the above-mentioned filter press type electrolytic cell, and tightened it to prevent leakage of the polar chamber liquid to the outside from the packing surface with each chamber frame. With the conventional method of mounting ion exchange membranes, we have often experienced tears in the surface where the ion exchange membrane is fastened to the chamber frame. This causes a large economic loss as the ion exchange membrane, which still has sufficient electrochemical life remaining, must be replaced due to mechanical damage to a part of the outer circumference of the ion exchange membrane. On the other hand, with ion-exchange membrane electrolytes, it is not possible to extremely increase the area of the unit cell due to manufacturing constraints of commercial ion-exchange membranes, and due to the electrochemical properties of ion-exchange membranes, production on a commercial scale is difficult. , due to constraints such as not being able to increase the production amount per unit membrane area,
It is equipped with multiple membranes. For this reason, due to membrane replacement due to damage to one membrane, other ion exchange membranes that can continue electrolytic operation will also have to be stopped, resulting in a large to medium drop in production and the ability of the entire plant to guarantee constant production. It disappears. In addition, in order to suppress fluctuations in the production amount, a large number of preliminary electrolyzers are required, which makes production on a commercial scale uneconomical. Furthermore, a rupture in the ion exchange membrane causes mixing of the liquid and gas in the electrode chamber, resulting in a product with reduced purity.If the mixture of gases causes a problem, not only the electrolytic cell but the entire plant may be destroyed by an explosion. I refute it.

In order to prevent this from happening, a huge amount of investment and great care must be taken, such as installing a detection device in each ion exchange membrane or each unit cell electrode chamber. Therefore, there is a need for a drastic improvement in the method for installing an ion exchange membrane into a filter press type electrolytic cell that can solve these problems. The present invention is a method for installing an ion exchange membrane that improves these problems, and eliminates the possibility of tearing when tightening the ion exchange membrane. When forming the chamber, the leakage of substances in the electrode chamber to the outside is virtually eliminated, and when setting up the ion exchange membrane in a filter press, it is possible to ensure a secure seal without going through complicated processes or methods. An object of the present invention is to provide a method for installing an ion exchange membrane that can prevent the ion exchange membrane from being damaged.

That is, the present invention uses a filter press type electrolytic cell,
To provide a method for attaching an ion exchange membrane treated in advance with an aqueous alkali solution, hydrochloric acid, an organic solvent, etc. between a cathode and an anode via a packing, by drying the part that comes into contact with the packing. To give an example of the method, m
Do not perform the above treatment on the parts that come into contact with the packing.
2} First, the entire surface of the ion exchange membrane to be used is treated, and the part that will come into contact with the packing is dried before installation.

The intestinal ion exchange membrane used in the present invention is preferably one obtained from a perfluorocarbon polymer, and as the exchange group, sulfonic acid, carboxylic acid, phosphoric acid, sulfonamide, etc. are used.

Of course, it can also be applied to perfluorocarbon vehicle composite membranes of various types. If the hardness of the packing is too hard, the airtightness will be insufficient, while if it is too soft, the compressive strain will increase when the electrolytic cell is tightened, so these are undesirable. Shore hardness of 40 to 9, preferably 50 to 80 is undesirable. used.

The packing can have various shapes such as flat, V-shaped, U-shaped, uneven, O-ring, etc. The tightening strength of the chamber frame is 5 to 90k9/ground, preferably 10 to 70k9/ground.

Although it is not clear why membrane tearing can be prevented when the method of the present invention is applied, it can be explained as follows.

Generally, ion exchange membranes obtained from perfluorocarbon polymers swell extremely well in water, alkaline aqueous solutions, or organic solvents.

As a result, the ion exchange membrane becomes soft, and if it is tightened in this state, the packing will dig in and cover the membrane.

The present invention will be specifically explained below using Examples.

Example 1 An anode chamber frame having an external dimension of the chamber frame of 106Q and a chamber thickness of 50mm was manufactured using titanium.

A sealing surface of 3 mm was provided on the outer periphery of the chamber frame so that the effective membrane area would be the first. The electrodes are made of expanded metal made of titanium plated with platinum, with conductive electrodes made of titanium bonded to copper. An inlet for electrolytic raw materials and an outlet for products were attached to the anode chamber frame. A cathode chamber frame with a similar structure was made of iron. As the cathode, an iron wide span metal was used, and an iron conductive member was attached.

A chloroprene packing having a Shore hardness of 60 and containing no filler such as calcium carbonate was attached to the sealing surface.
E. as a cation exchange membrane. I. Nafio manufactured by DuPont
After n390 was treated in 10% caustic soda at 90oo for 20 hours, the outer periphery in contact with the packing part was dried with a dryer.

The cation exchange membrane thus treated was placed in an electrolytic cell and set at a tightening pressure of 50 kg/flow per packing area. Add a saturated aqueous solution of sodium chloride to the anode chamber and 20% to the cathode chamber.
% caustic soda was added.

Since no leakage was detected from the packing surface, electrolysis was started. Electrolysis was continued at 8500 for 160 days, but no abnormality was observed.

The electrolytic cell was disassembled and the packing surface of the cation exchange membrane was inspected, but no damage to the membrane was found. Comparative Example 1 When the operation was carried out in the same manner as in Example 1 except that the outer peripheral part in contact with the packing part of the intestinal ion exchange membrane was not dried, it was observed that the packing surface was broken after 70 days.

Example 2 A cation exchange membrane (Nafion 290 manufactured by E.I. DuPont) was soaked in ethanol at room temperature for 20 hours, and after removing the ethanol from the membrane, it was soaked in a 20% ether solution of butadiene-1-carboxylic acid. Soaked at room temperature for 2 years.

Next, the membrane was taken out, the surface was wiped clean, and the membrane was placed between a smooth plate and partially polymerized at 110 mm for 2 hours, followed by immersion in propylene glycol at room temperature for 2 hours.

After soaking, the membrane was again placed between smooth plates and heat-treated at 110 oo for 48 hours. A cation exchange membrane was prepared by soaking the membrane in an aqueous solution of 60% potassium hydroxide.
The cation exchange membrane was taken out, and the part that came into contact with the packing was thoroughly wiped with a cloth, and then dried with a hair dryer. An electrolytic cell similar to that used in Example 1 was used and set at a tightening force of 40k9/unit per packing area. The anode chamber was filled with a saturated aqueous solution of sodium chloride, and the cathode chamber was filled with 30% caustic soda. The same operation as in Example 1 was performed. 160
Electrolysis was continued at 85°C on the same day, but no abnormalities were observed.

The electrolytic cell was disassembled and the packing surface of the cation exchange membrane was inspected, but no damage was found. Comparative Example 2 The same cation exchange membrane as used in Example 2 was operated in the same manner as in Example 2, except that the outer peripheral part in contact with the packing part was not dried.

After 80 days, the electrolytic cell was disassembled and the membrane was inspected for tearing, and it was found that the membrane on the bottom surface was torn.

Claims (1)

[Claims] 1. An ion exchange membrane characterized in that when installing the ion exchange membrane in a filter press type electrolytic cell, the part that comes into contact with the packing installed on the flange surfaces of the anode chamber frame and the cathode chamber frame is dried. How to install.