JPS605678B2 - Inspection method for electrolytic cells incorporating ion exchange membranes - Google Patents

Description

[Detailed Description of the Invention] The present invention provides a method for inspecting an electrolytic cell incorporating an ion exchange membrane;
In particular, the present invention relates to a method for inspecting the presence or absence of pinholes in an ion exchange membrane and the presence or absence of unnecessary holes such as leakage in a seal portion.

The method for obtaining caustic alkali by electrolyzing alkali chloride IJ is as follows:
From the standpoint of pollution prevention, the diaphragm method has become mainstream in place of the mercury method.

The septum method, which usually uses a furnace diaphragm made of asbestos or the like, is currently used industrially.

However, the caustic alkali obtained by the asbestos method has a low concentration and contains alkali chloride as an impurity, so it is usually difficult to use it as is for various uses such as industrial chemicals.

On the other hand, various methods have been proposed in which an ion exchange membrane is used in place of the asbestos diaphragm as a means for directly obtaining higher purity and higher concentration caustic alkali by electrolysis.

In an electrolytic cell that uses an ion exchange membrane, even if there is a pinhole-sized hole in the ion exchange membrane or other sealing parts, the separator fluid will migrate directly into the catholyte, making it no different from an asbestos diaphragm. This results in a product that is contaminated with impurities.

In addition, it is quite difficult to find pinholes with the ion exchange membrane alone, and when it is attached to the electrolytic cell,
It is more realistic to discover any problems after actually using the product.

From this point of view, the inventor of the present invention conducted various studies and examinations with the aim of knowing whether or not there are inconvenient lotus holes after assembling an electrolytic cell. In this method, the electrolytic cell is sealed, and carbon tetrachloride is added to the cathode chamber or the anode chamber, and the corresponding electrode is By introducing air into the chamber so that the pressure in the polar chamber into which the air is introduced is lower than the pressure in the polar chamber into which the carbon tetrachloride is introduced, and by taking out the air and detecting the presence or absence of phosgene with a halogen detection device. ,
It has been found that the above object can be achieved, and this is the gist of the present invention.

In the present invention, carbon tetrachloride may be introduced into either the positive or negative electrode chamber, and air may be introduced into the corresponding electrode chamber.

The polar chamber into which carbon tetrachloride is introduced has an underwater pressure of 150 to 15
It is appropriate to maintain a reduced pressure of 20°C, and in this case, in order to ensure that carbon tetrachloride is sufficiently distributed in the polar chamber, water is introduced from a part of the polar chamber to maintain the above water pressure. Take out the carbon tetrachloride little by little by providing a suitable outlet.
Such carbon tetrachloride is purged to the outside through a suitable exclusion column such as activated carbon.

On the other hand, the corresponding polar chamber is -100 to -16 at underwater pressure.
Air is introduced so as to maintain a reduced pressure of 0 to 20 days, and a suitable outlet is provided to take out the air so as to maintain this pressure.

Because there is a pressure difference between the two electrode chambers, if there is a pinhole in the ion exchange membrane or the seal is incomplete, carbon tetrachloride will flow from there into the air chamber and will be detected by the halogen detector. Ru. It is preferable that the amount of carbon tetrachloride present in the polar chamber is at least 100 chloride, so that the amount of carbon tetrachloride present in the polar chamber is on the 0.1 side. Pinholes up to this point can be detected. The method of the present invention is applied to any type of ion-exchange membrane electrolytic cell, such as a filter press type monopolar or bipolar cell, or a single-polar or bipolar cell in which an existing asbestos cell is improved into an ion-exchange membrane cell. But it doesn't matter. Moreover, the present invention
It can also be applied to various dialysis tanks using ion exchange membranes or reverse osmosis membranes, and the electrolytic tank referred to in the present invention includes these as well.
The ion exchange membrane used in the present invention is made of a polymer containing a cation exchange group such as a carboxyl group, a sulfonic acid group, a phosphoric acid group, or a phenolic hydroxyl group, and such a polymer includes a fluorine-containing polymer. It is particularly preferable to adopt Examples of fluorine-containing polymers containing ion exchange groups include vinyl monomers such as tetrafluoroethylene and chlorotrifluoroethylene, and polymers having reactive groups that can be converted into ion exchange groups such as sulfonic acid, carboxylic acid, and phosphoric acid groups. A copolymer of a fluoro vinyl monomer and a perfluoro vinyl monomer having an ion exchange group such as a sulfonic acid or carboxylic acid t-phosphate group is preferably used. Also usable are membrane polymers of trifluorostyrene to which ion exchange groups such as sulfonic acid groups have been introduced, and styrene divinylbenzene to which sulfonic acid groups have been introduced.

Among these monomers, it is particularly preferable to use monomers that can form the following polymerized units {i, 'o}, since highly pure caustic alkali can be obtained with relatively high current efficiency. . [A) ÷CF2-CXX÷, where × is fluorine, chlorine, hydrogen or -CF3, and X'
is X or CF3(CF2)m, m is 1 to 5, and Y is selected from the following.

-P-A, ” (CF2 left LP, Q, Rna A Here P is 1°C F2 temperature XX' rice CF2★ and Q is 1 {F2 ``[[CXX' side, R is ÷CXX'-.

-CF2Tera, and (P, Q, R) represents arranging at least one of P, Q, and R in any order.
X and X' are the same as above, n = 0 to 1, a, b, c
, d, and e are 0 to 6. A is -COO day or one CN
, one COF, one COOR, one COOM, one CONR2R
Represents a functional group that can be converted into one COOH' by hydrolysis or neutralization. R represents an alkyl group having 1 to 10 carbon atoms, M represents an alkali metal or a quaternary ammonium group, and R2 and R3 represent hydrogen or an alkyl group having 1 to 10 carbon atoms. Preferred representative examples of the above Y include the following, in which A has a structure in which A is bonded to carbon containing fluorine.

x, y, and z are all 1 to 10, z and Rf are a group selected from -F or a perfluoroalkyl group having 1 to 10 carbon atoms, and A is the same as above.

When using a fluorine-containing cation exchange membrane in which the concentration of carboxylic acid groups in the membrane is 0.5 to 2.0 milliequivalents per dry resin made of these copolymers, for example, the concentration of caustic soda is Even if it is over 40%, its current efficiency is 9
It reaches over 0%. When the concentration of carboxylic acid groups in the film per night of the dry resin is 1.1 to 1.7 milliequivalents, it is possible to stably obtain caustic soda at a high concentration as described above over a long period of time with high current efficiency. This is especially preferable because it can be done. In order to achieve such an ion exchange capacity, the above {i) and '. } In the case of a copolymer consisting of polymerized units,
Preferably [Rho's polymerized unit is 1 to 40 mol%, especially 8
A suitable amount is 25 mol %. The preferred ion exchange membrane used in the present invention is obtained by a copolymer of the above-mentioned fluorinated olefin monomer and a polymerizable monomer having a functional group convertible to a carboxylic acid group or a carboxylic acid group. The molecular weight is preferably about 100,000 to 2,000,000, especially about 15
10,000 to 100 is appropriate.

Furthermore, in order to produce such a copolymer, one or more of the above-mentioned monomers may be used, and the resulting film may be modified by further copolymerizing a third monomer. For example, CF2
=CFORf (Rf is a perfluoroalkyl group having 1 to 10 carbon atoms) is used to impart flexibility to the obtained film, or CF2=CF-CF=CF2, CF2
By using divinyl monomers such as =CF◯ (CF2) and ~3CF=CF2 in combination, the resulting copolymer can be crosslinked and mechanical strength can be imparted to the membrane. The copolymerization of the fluorinated olefin monomer with a polymerization monomer having a carboxylic acid group or a functional group convertible to the carboxylic acid group, and further with a third monomer can be carried out by any known method. . That is, polymerization can be carried out by catalytic polymerization, thermal polymerization, radiation polymerization, etc., using a solvent such as a halogenated hydrocarbon, if necessary. Furthermore, there are no particular limitations on the means for forming an ion exchange membrane from the obtained copolymer, such as press molding, roll forming, extrusion molding, solution casting, dispersion molding,
Any known means such as powder molding may be employed as appropriate. The film thus obtained has a thickness of 20 to 500 mm, preferably 50 mm.
It is appropriate to make it 400 Buddhas.

In addition, if the copolymer is not a carboxylic acid group itself but a functional group that can be converted into a carboxylic acid group before or after the copolymer film formation process, preferably after film formation, by appropriate treatment accordingly. , these functional groups are converted to carboxylic acid groups.

For example, one CN, one COF, one COOR,, -COOM
, -CONR2R3 (M, R, ~R3 are the same as above), it is hydrolyzed or neutralized with an acid or alkaline alcohol solution to convert it to a carposo acid group, and when the functional group is a double bond. It is converted into a carboxylic acid group by reacting with -COF2. Furthermore, the intestinal ion exchange membrane used in the present invention may be made of an olefin polymer such as polyethylene or polypropylene, preferably polytetrafluoroethylene, a copolymer of ethylene and tetrafluoroethylene, etc. during membrane formation, if necessary. It is also possible to mix and mold fluorine-containing polymers, or use fabrics such as cloths, nets, nonwoven fabrics, porous films, etc. made of these polymers as a support.
It is also possible to reinforce the membrane using metal wire, silk, or porous material as a support. Next, the present invention will be explained by examples.

In place of the asbestos diaphragm, use polytetrafluoroethylene and CF2=CF○(CF2)3COOC in the asbestos diaphragm method electrolytic cell DS-45 manufactured by Diamond Shamrock Co., Ltd.
Ion exchange capacity 1.48 heq/
A 220 mm thick enteric ion exchange membrane with multi-dry resin was installed by the following method.

First, the membrane was formed into a bag shape with one end open, having dimensions of 6 mm inside, 90 mm long, and 7 mm high, so that each cage-shaped anode could fit inside, and the anode was placed inside the bag. The fixing bolt of the electrode was passed through the bottom of the bag from inside the bag to fix the anode and the bag-like membrane to the bottom of the turtle tank. The open end of the bladder membrane is thus located above the anode. Next, a cathode can with a gap for fitting the anode between the cathode fingers is inserted, the anode covered with a bag-like membrane is inserted between the cathode fingers, and an FEP tube is placed on the upper end of the cathode can. After inserting the anode/anolyte separator and heat-sealing the open end of the bag-shaped waist to it,
The electrolytic cell was assembled by covering it with a salt water holding lid made of RP.

Carbon tetrachloride was continuously introduced into the anode chamber of the electrolytic cell, and while a portion of the carbon tetrachloride was taken out from the chamber, the internal pressure was maintained at an underwater pressure of -IQ and a concentration of 250 kg.

On the other hand, air was introduced into the cathode chamber, and a circulation pump was connected between the inlet and the air outlet of the chamber to increase the circulation amount to 45 cc/cm.
The internal pressure was kept at -300°/min while the air was taken out from the air outlet at a rate of 10°/min.

Then, the air taken out was measured every 15 minutes using a halogen detector (Model S, manufactured by Komyo Rikagaku Kogyo Co., Ltd.) for one hour. As a result, no halogen was detected. Next, one pinhole of 0.5 mm was made in the ion exchange membrane, and measurements were made in the same manner, and approximately 2 strings of phosgene were detected.

Claims (1)

[Scope of Claims] 1. A method for inspecting the presence or absence of unnecessary communication holes such as pinholes in the ion exchange membrane, seal portion, etc. in an electrolytic cell having a cathode and anode chamber partitioned by an ion exchange membrane. , the electrolytic cell is sealed, carbon tetrachloride is introduced into the cathode chamber or the anode chamber, and air is introduced into the corresponding electrode chamber, and the pressure in the electrode chamber into which the air is introduced is lower than the pressure in the electrode chamber into which carbon tetrachloride is introduced. A method for inspecting an electrolytic cell incorporating an ion exchange membrane, which is characterized in that the air is introduced so that the air is removed, and the air is extracted and detected by a halogen detection device. 2 The internal pressure of the polar chamber into which carbon tetrachloride is introduced is +50 to -5
The method according to claim 1, wherein the temperature is 0 mmH_2O. 3 The internal pressure of the polar chamber into which air is introduced is -100 to -600
The method according to claim 1, wherein mmH_2O. 4 The concentration of carbon tetrachloride introduced into the electrode chamber is at least 1
000 ppm.