JPS6026495B2 - Homogeneous cation exchange membrane with multilayer structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an economically advantageous homogeneous intestinal ion exchange membrane for use in ion exchange membrane process alkaline chloride electrolysis.

More specifically, a multilayer structure of two or three or more layers with different equivalent weights (dry resin weight containing one equivalent of ion exchange groups) and/or types of ion exchange groups used in ion exchange membrane method alkaline chloride electrolysis. This invention relates to a homogeneous intestinal ion exchange membrane with low electrolysis voltage and high current efficiency, characterized in that at least the end layer with a low water content among both end layers of the membrane is a phase surface. be. The homogeneous cation exchange membrane referred to in the present invention is an intestinal ion exchange membrane formed solely from an ion exchange resin without blending a thermoplastic resin having no ion exchange groups.

Conventionally, in heterogeneous ion exchange membranes made by mixing ion exchange resin and thermoplastic resin, the membrane surface is roughened by brushing or flame treatment in order to reduce membrane resistance. It has been proposed to expose the ion exchange resin (for example, see Hakama Kaisho 52-4759).

However, in a homogeneous ion exchange membrane made only of ion exchange resin, the ion exchange resin is originally exposed on the membrane surface, so the membrane resistance does not decrease even if such surface reduction treatment is performed.

No. 52-2098 of Homura Mochiseki discloses that the surface of the membrane is subjected to electrical discharge treatment, radiation treatment, or flame treatment, but the purpose of this is to convert intestinal ion exchange groups into ones that do not have ion exchange ability. However, there is no description or suggestion regarding the shape of the membrane surface that improves the current efficiency.

When the intestinal ion exchange groups on the membrane surface are modified in this way, the resistance of the membrane increases and the electrolytic voltage increases, which is not preferable. The present invention lowers the electrolytic voltage by roughening the membrane surface without denaturing intestinal ion exchange groups. Furthermore, it is known that with homogeneous intestinal ion exchange membranes, if the cathode surface of the membrane is not smooth, hydrogen gas bubbles generated at the cathode during electrolysis will adhere to the membrane surface, increasing the electrolytic voltage.
Conventionally, it has been common practice to incorporate a membrane with at least one smooth surface into an electrolytic cell so that the smooth side faces the cathode side (see, for example, Tokokukan Sho 51-113148y). Usually, the thickness of the intestinal ion exchange membrane used for ion exchange membrane method chloride alkali electrolysis is 1000 microns or less, preferably 200 microns or less in order to reduce membrane resistance, and because the membrane strength is insufficient, support fibers are used. Addition of pus strength has been made.

A method for embedding support fibers in an intestinal ion exchange membrane is, for example, a method in which a heat-melting ion exchange membrane intermediate manufactured by extrusion molding and support fibers are layered and hot pressed, and the support fibers are embedded in the membrane (heat-pressing). Press lamination method), after hydrolyzing only one side of a heat-fusible ion-exchange membrane intermediate produced by extrusion to make it heat-insoluble, a support fiber is brought into contact with the opposite heat-fusible side, Examples include a method of embedding the support fibers in the membrane by reducing the pressure on the side in contact with the support fibers while heating the whole (vacuum lamination method, Samurai Kosho No. 52-1467). In the heat press lamination method, both sides are smooth, and in the vacuum lamination method, the surface that has been hydrolyzed in advance is smoothed, and conventionally, the electrolytic cell was assembled with this smooth surface facing the cathode side. . Furthermore,
In recent years, intestinal ion exchange membranes having a multilayer structure consisting of a layer with a low water content and a layer with a high water content have been proposed in order to maintain high current efficiency and reduce the electrolysis voltage in the production of alkali hydroxide.

For example, a membrane consisting of two layers, a layer with a large equivalent weight and a layer having a 4-layer structure (Tokubatsu 51-141 Private No.), a membrane consisting of two layers, a layer having a sulfonic acid group and a layer having a weak acid group ( Japanese Patent Application Publication No. 5
2-120999) etc. have been proposed for use in salt electrolysis. At this time, it is essential to incorporate the layer into the electrolytic cell so that the layer having a low water content, the layer having a large equivalent weight, or the layer having a weak acid group is on the cathode side. When embedding supporting fibers in such a multilayered cation exchange membrane, the supporting fibers are embedded from the side of the layer with a high water content, and at least the side of the layer with a low water content is smooth. I was worried. However, as a result of detailed observation of the electrolytic state, the present inventors surprisingly found that when the cathode surface of the homogeneous intestinal ion exchange membrane was moderately dregsed, hydrogen gas bubbles generated at the cathode due to electrolysis were observed. It was found that the amount of film surface adhesion was the smallest and the electrolytic voltage was the lowest.

That is, the object of the present invention is to further reduce the electrolytic voltage while maintaining a high current efficiency of a homogeneous cation exchange membrane having a multilayer structure with different equivalent weights and/or types of ion exchange groups. The object can be efficiently achieved by the present invention, in which the surface of the intestinal ion exchange membrane with a low water content is used as the lees surface.
The surface-roughened multilayer cation exchange membrane of the present invention is economically advantageous because hydrogen gas bubbles generated at the cathode hardly adhere to the membrane surface, and the electrolysis voltage is low and the current efficiency is high. It is a membrane. In ion exchange membrane method alkaline chloride electrolysis, the anode chamber and cathode chamber are divided by a single cation exchange membrane.
The chamber method is advantageous, and a fluorine-based homogeneous intestinal ion exchange membrane having excellent heat resistance, chemical resistance, mechanical strength, etc. is usually used as the intestinal ion exchange membrane.

The present invention is particularly effective for fluorine-based intestinal ion-exchange membranes, perhaps because gases tend to adhere to them more easily than hydrocarbon-based intestinal ion-exchange membranes. Each layer of the cation exchange membrane of the present invention, which has a multilayer structure with different water contents, is distinguished from other layers by equivalent weight and/or type of ion exchange group. Equivalent weight and/or
Alternatively, an ion exchange group may be present.

However, the proportion thereof is preferably 50% or less, more preferably 25% or less. Also, at the boundaries between layers, there may be a continuous change in the density of different equivalent weights and/or ion exchange groups present in adjacent layers. Further, ion exchange resins having different equivalent weights and/or types of ion exchange groups may be uniformly mixed in each layer, and each layer may be distinguished by the difference in composition ratio. The boundaries between each layer are dyed by appropriately changing the dyeing temperature, dyeing time, or dyeing solution pH.The infrared absorption spectrum of the surface is measured while scraping the film from the surface, and the density of various exchange groups changes as the depth of scraping increases. This can be observed by tracking changes.

The water content of the intestinal ion exchange membrane is measured by the following method.

The cation exchange membrane was immersed in 0.1N caustic soda at 90°C for two periods, and then washed with pure water. Wipe off the water droplets adhering to the surface of the pus with paper and measure the weight (W, g). The membrane is then vacuum dried and weighed (W.g). Moisture content =
Jiju and X1oo (%) For fiber-reinforced cation exchange membranes, water that has entered the fibers will cause measurement errors in water content, so measurements must be compared with membranes that are not reinforced with fibers.

The reason why the electrolytic voltage decreases when the layer with a low moisture content of such a multilayered cation exchange membrane is roughened and installed in the electrolytic cell with the roughened surface facing the cathode is that This is because it is difficult for the hydrogen gas bubbles generated at the cathode to adhere to the cathode surface of the membrane, and the voltage increase due to the hydrogen gas bubbles adhering to the cathode surface is due to electrical shielding by the attached bubbles, ■ electrical shielding by the attached bubbles, and ■ membrane - This is due to a decrease in the diffusion rate of highly concentrated caustic soda at the liquid interface.

On the other hand, chlorine gas generated at the anode by electrolysis has a considerably larger bubble diameter than hydrogen gas, so it is difficult to adhere to the anode surface of the homogeneous intestinal ion exchange membrane.

Therefore, roughening the anode surface of the homogeneous cation exchange membrane is not necessarily necessary to lower the electrolytic voltage. In the present invention, the term "rough surface" refers to a mirror surface.

The rough surface preferably has one unevenness on the membrane surface with a maximum height of 0.05 microns or more and a roughness of 0.05 microns or more.
It is sufficient if the amount is 2 or more per skin. More preferably, the maximum height is 0.05 to 5 microns and the roughness is 0.
If 30 to 25 irregularities of 0.05 micron or more are present per skin, gas adhesion to the film surface is extremely small.
When the maximum height of the rough surface is 0.05 microns, the effect of preventing gas from adhering to the membrane surface is low. Furthermore, when the unevenness with a roughness of 0.05 microns or more is less than 2 roughness per side, the effect of preventing gas adhesion to the film surface is small. To confirm the extent of gas adhesion to the membrane surface, the membrane may be assembled in a transparent electrolytic cell made of acrylic resin or the like, electrolyzed, and the membrane surface observed.

The surface roughness of the cation exchange membrane can be measured by a stylus method using a universal surface profile measuring device (Type Surfcom 6 Tsukuda Tokyo Seimitsu KK). That is, when the stylus is placed on the membrane surface and moved, the stylus moves up and down according to the unevenness of the membrane surface.
This vertical movement is converted into an electrical signal and recorded on recording paper.
Normally, the intestinal ion exchange membrane is flexible and easily deformed by the stylus, so when measuring surface texture, use a pickup with a stylus tip shape of loAm or more and a measuring force of 0.1 or less. is desirable. In the present invention, the stylus end shape is 1.
Measurements were taken in Mt. 3 using a pickup with a measuring force of 0.07 m. In addition, cation exchange membranes are often strengthened with support fibers, and in this case, the membrane surface has large irregularities (surface waviness) caused by the support fibers.In order to distinguish between surface waviness and surface roughness, It is desirable to pass the electrical signal of motion through an electrical filter to cut off wavelengths longer than a specific wavelength. In the present invention, the cutoff value is 0.
Measurements were made with the setting set to 032 skin. The maximum height referred to in the present invention is determined by the following method in accordance with the JIS standard (JISB0601).

In other words, when a standard length of 0.1 skin is sampled from a roughness curve measured with a cutoff value of 0.032 skin, and the sampled area is sandwiched between two straight lines that are balanced with the average line, the interval between these two straight lines is the roughness curve. Measure in the direction of vertical magnification. For example, in Fig. 1, the distance Rmax between the straight line passing through the highest mountain peak P, and the straight line passing through the deepest valley V, among the straight lines parallel to the average line of the part from which the standard length of 0.1 leg has been removed, is defined as the maximum height. call.
Measurement is performed at different locations within the same sample, and the obtained values are averaged. In addition, when determining the maximum height, a standard length is extracted from an area that is considered to be a flaw, such as an exceptionally high mountain or deep valley. Also, the roughness according to the present invention is 0.
．． The number of unevenness per piece of 0.05 microns or more is US S.
It was determined in accordance with the AE standard (SAEJ911) using the following method.

In other words, 2 levels of (10) 0.025 microns and (1) 0.025 microns with respect to the average line of the part extracted from the standard length 0.1 side from the roughness curve measured at the cutoff value 0.032 side. Draw a straight line on the book (P line and V line respectively),
Tell them that the mountain that passes through the V line and then the P line is one mountain, and find the number per 0.1 fence. For example, in FIG. 2, the number of peaks that pass through line P after passing through line V is three, a, b, and c. Measurements are made in groups of 1m at different locations within the same sample, and the obtained values are averaged to determine the number per willow. In the present invention, the homogeneous cation exchange membrane with a grain layer structure, which is used by roughening at least the end layer with a low water content among the end layers, substantially prevents the passage of the anolyte or catholyte through the membrane by hydraulic flow. A homogeneous cation exchange membrane of a fluorine type is preferred. Passage of the anolyte or catholyte through the membrane by hydraulic flow is undesirable because it degrades the quality of products produced by salt water electrolysis. Examples of the fluorine-based homogeneous intestinal ion exchange membrane include: ■ sulfonic acid type intestinal ion exchange membrane, ■ sulfonamide type cation exchange membrane, ■ carboxylic acid type cation exchange membrane, and ■ phosphate type intestinal ion exchange membrane. I can do it. However, the present invention is not limited to these, but is applicable to all homogeneous cation exchange membranes. In order to manufacture an intestinal ion exchange membrane having a multilayer structure of two or more layers having different equivalent weights and/or ion exchange groups, for example, ■ two or three layers having different equivalent weights and/or ion exchange capacities; Examples include a method in which the above layers are stacked and laminated, and (2) a method in which only one side of the cation exchange membrane is treated to change the equivalent weight and/or type of ion exchange group.

However, the method is not limited to these methods. Intestinal ion exchange membranes with a multilayer structure preferred for the present invention are listed below.

■Tetrafluoroethylene and CF2: CFOCF2CF (
CF3) OCF2CF2S02F copolymer (A polymer), a sulfonic acid membrane laminated with two types of films with different equivalent weights (Japanese Patent Publication No. 189/1989), ■Tetrafluoroethylene and CF2=CF○( CF2)nA or CF2=CFOCF2fCFXOCF2)-(CF
X) Previous (CF20CFX″ChinAkuA is CN, C〇F,
C〇〇day, C〇〇R,, C〇NR2R3・,;X, X'
, X″ is a copolymer of F or CF3), and is a carboxylic acid film laminated with two films with different equivalent weights,
■A membrane in which only one side of the polymer film is heat-treated, UV-treated, reagent-treated, etc. to desulfonate a portion of the ion exchange groups (Samurai Seki No. 51-122677, No. 53-55, No. 3 to 53- 58493), ■ A sulfonamide membrane in which only one side of the polymer film is treated with ammonia, alkyl monoamine or diamine (Special Seki No. 48-4436, No. 50-66488, No. 51-64495, No. 51-64496) , ■ A membrane obtained by treating the sulfonamide membrane with nitrites to convert the sulfonamide groups into carboxylic acid groups (
Samurai Seki Sho 53-11411), ■ A carboxylic acid film obtained by reducing only one side of a polymer film (Japanese Unexamined Patent Publication No. Sho 52-24)
No. 175, No. 52-24176, No. 52-24177)
, ■ Carboxylic acid film in which only one side of the A polymer film is oxidized with organic solvent vapor (Special Kankaira No. 54-183932);
■A membrane containing a mixture of carboxylic acid groups and sulfonamide groups, which is obtained by treating only one side of the polymer film with a basic aqueous solution containing an ammonium ion-containing compound or ammonium ions (JP-A-54-121478, 54- 41287), ■ Phosphoric acid film in which only one side of the A polymer was reacted with iodine in the presence of a radical generator and then treated with an IJ compound (
Special Seki Shokyu-No. 82684).

However, the invention is not limited to these membranes. Methods for roughening a homogeneous cation exchange membrane include: (1) using a molding die with a predetermined uneven portion when extrusion molding the ion exchange membrane; A method in which the ion exchange membrane is passed through a matte rotating roll with uneven parts; ■ A method in which the ion exchange membrane is layered with a molding material such as cloth, paper, or organic or inorganic powder; ■ A method in which the surface of the ion exchange membrane is polished. ■ Method of polishing the ion exchange membrane with sand vapor, ■ Method of passing the ion exchange membrane between rotating rolls with sand vapor wrapped around the surface, ■ Method of spraying the abrasive material onto the ion exchange membrane with compressed air (dry plast method), Water A method in which an abrasive suspended in water is sprayed onto an ion exchange membrane using compressed air (liquid honing method), ■ A method in which the surface of an ion exchange membrane is polished with a metal brush, ■ A method in which electric discharge treatment such as arc discharge or glow discharge is used, ■method of irradiating the membrane surface with ultraviolet rays, X-rays, electron beams, radiation, etc.; ■method of treatment with gas flames, heated air, etc.; ■method of treating ion exchange membranes with solvents; ■method of manufacturing with ion exchange resin. mesh,
Methods such as attaching a nonwoven fabric or the like to the membrane surface may be used, but the method is not limited to these methods.

In order to uniformly roughen the surface of the intestinal ion exchange membrane which has surface undulations due to support fibers, a method using a heat pressing method, a dry blasting method, a liquid honing method or a glow treatment is preferable.

Although the surface roughening treatment may be performed on both sides of the ion exchange membrane, the desired reduction in electrolytic voltage can be achieved by performing the surface roughening treatment only on the surface with a low water content. The surface roughening treatment of the present invention is also applied to ion exchange membrane intermediates, and after the surface roughening treatment, the ion exchange membrane intermediates are subjected to treatments such as hydrolysis and introduction of ion exchange groups to remove intestinal ions. Used as an exchange membrane. Examples of the alkali chloride of the present invention include lithium chloride, sodium chloride, potassium chloride, and the like.

Furthermore, examples of the alkali hydroxide include lithium hydroxide, sodium hydroxide, potassium hydroxide, and the like. The most important thing when implementing the electrolysis method of the present invention is to incorporate the homogeneous cation exchange membrane into the electrolytic cell so that the rough surface faces the cathode side.

When installed in an electrolytic cell with the rough surface facing the anode,
A reduction in electrolytic voltage cannot be achieved. An electrolytic cell and electrolytic conditions preferred for the present invention will be described.

Salt water is supplied to the anode chamber, and water or dilute alkali hydroxide solution is supplied to the cathode chamber while electrolysis is carried out to adjust the concentration of alkali hydroxide at the outlet of the cathode chamber. The salt water supplied to the anode chamber is purified using the same machine as the conventional chloride alkali electrolysis method.

In other words, the return salt water that circulates from the anode chamber and returns to boiling water is
Dechlorination, saturated dissolution of alkali chloride, precipitation separation of magnesium, calcium, iron, etc., and neutralization operations are performed, and these steps are performed in the same manner as in conventional methods. However, if necessary, it may be desirable to further purify the feed brine with a particulate ion exchange resin, particularly a chelating resin, to bring the calcium to an acceptable limit, preferably below IPPm. The concentration of the salt water is preferably thick and close to saturation.
The utilization rate of alkali chloride supplied to the anode chamber is 5 to 95%.
Although this value varies depending on the current density and heat removal method, it is generally desirable to have a higher value.

Electrolysis can be carried out at a temperature of 0 to 150q0.

Since heat is generated by electrolysis, the anolyte or a portion of the catholyte is cooled to remove the heat.

Chlorine and hydrogen are generated in the anode chamber and the cathode chamber, respectively.

In particular, an electrolytic cell designed to guide the generated gas to the back side of the electrode and raise it has the effect of lowering the electrolysis voltage and reducing the power consumption. The flow rate in each chamber is preferably such that the liquid in the chamber is controlled by the gas generated in the cathode chamber and the anode chamber in addition to the flow rate supplied from the outside, and for this purpose,
It is desirable to use an electrode with many voids, such as a metal mesh electrode, to move and circulate the liquid in each chamber with the upward flow of gas.

From the viewpoint of overvoltage, the electrode is preferably iron or iron plated with nickel or a nickel compound as a cathode.
The anode is generally preferably a metal mesh electrode coated with an oxide of a noble metal such as ruthenium. Examples will be specifically described below, but the present invention is not limited thereto.

Example 1 Tetrafluoroethylene and perfluoro-3,6-dioxy-4-methyl-7-octensulfonyl fluoride in 1,1,2-trichloro-1,2,2-trifluoroethane and perfluoropropionyl peroxide. Copolymerization was carried out using tetrafluoroethylene as a polymerization initiator at a polymerization temperature of 4yo while maintaining a pressure of 5K9/G.

This will be referred to as Polymer 1. In the same operation, copolymerization of tetrafluoroethylene was carried out while maintaining the pressure at 3k9/SuG. This will be referred to as Polymer 2. Polymers 1 and 2 were heat-molded to form films of 100 microns each, and then hydrolyzed, and the water content and equivalent weight were measured by titration.

The water content of polymers 1 and 2 is 10% and 21%, respectively,
The equivalent weight was 15001110, respectively. Polymer 1,
2 were heated and molded to a thickness of 50 microns and 100 microns, respectively.
A sulfonic acid type ion exchange membrane was obtained by saponifying the composite material, which was made into a two-layer laminate of microns, and further embedded with Teflon and (1) woven fabric from the side of the polymer 2 by a vacuum lamination method.

The sulfonic acid type cation exchange membrane was subjected to hammer surface treatment using a hot press method.

A silicone rubber sheet (upper part) with a thickness of 3, a layer of light magnesium oxide powder (manufactured by Wako Pure Chemical Industries KK) with a thickness of 1, and a wet sulfonic acid type cation exchange membrane (equivalent weight of 1500)
side (side A) facing up), a silicone rubber sheet with a thickness of 3 sails, and a wire mesh of 60 mesh (bottom) are stacked to form a 28
It was hot pressed for 10 minutes at a pressure of 10k9/m while heating to 0. Next, magnesium oxide adhering to the film was dissolved and removed with hydrochloric acid. A of the roughened cation exchange membrane
When the surface roughness was measured, the maximum height was 0.6 microns, and each sail had about 49 irregularities with a roughness of 0.05 microns or more. The membrane thus obtained was placed in a transparent electrolytic cell made of acrylic resin with side A facing the cathode, and salt electrolysis was performed at a current density of 5 M/dm2 and an electrolysis temperature of 90°C.

The anode is a dimensionally stable electrode made of a titanium substrate coated with ruthenium oxide, and the cathode is an iron wire mesh. In the anode chamber, PH
The second chamber supplied saline, and the cathode chamber was supplied with caustic soda. The electrolysis voltage is 3.75V, and the current efficiency is
It was 80%. There were no hydrogen gas bubbles attached to the cathode surface of the membrane. The resistance of the membrane is 6.30. It was.

Comparative Example 1 Instead of the heat-pressed and roughened membrane of Example-1, a membrane without roughening treatment was produced in the same manner as in Example-2 and electrolyzed in the same manner.

The electrolysis voltage is 4.05V, and the current efficiency is 79.5
%Met.

Hydrogen gas bubbles were heavily attached to the cathode surface of the membrane that had not been roughened. The resistance of the film that has not been subjected to surface roughening treatment is 6.30. It was.

Examples 2 to 5, Comparative Example 2 Tetrafluoroethylene and perfluoro 3,6-dioxy-4-methyl-7-octensulfonyl fluoride were copolymerized in the same manner as in Example 1 to obtain an equivalent weight of 1350 at a water content of 14%. (polymer 1) and water content 22%
A polymer (polymer 2) having an equivalent weight of 1090 was obtained.

These polymers were heat-molded to form a two-layer laminate with a thickness of 35 microns (polymer 1) and 100 microns (polymer 2), and then a Teflon woven fabric was placed under vacuum from the surface of polymer 2. It was embedded using the lamination method.

Only the surface of the polymer 1 of the sulfonic acid type intestinal ion exchange membrane obtained by saponifying the laminate was subjected to a ring treatment to convert it into a carboxyl group (side A). Next, the A side of the cation exchange membrane was roughened by a liquid honing method.

The liquid honing method is a method of polishing by spraying an abrasive material suspended in water onto the workpiece using compressed air. In this example, emery powder (trade name: FO
#1200, manufactured by Fujimi Abrasives Industry KK) was suspended in an aqueous solution and sprayed with 3 kg/ground of compressed air.

The spraying time is 10, 30, 60 and 1 per waist ldm2.
2 sand. The surface texture of side A of the roughened film thus obtained was measured.

The results are shown in Table 1. In addition, these membranes were assembled into an electrolytic cell with the A side facing the cathode side, electrolyzed in the same manner as in Example 1, and the state of gas adhesion to the membrane surface, electrolytic voltage, and current efficiency were measured. . The results are shown in Table 1. Table 1 Example 6 Tetrafluoroethylene and perfluoro-3, . 6-Dioxy-4-methyl-7-octensulfonyl fluoride was copolymerized to obtain a polymer having a water content of 18% and an equivalent weight of 1200.

The polymer was heat formed into a 125 micron thick film and then treated with n-butylamine on one side to give a 20.
A micron sulfonamide layer was produced (side A). Next, a Teflon woven fabric was embedded from the opposite side of side A using a vacuum lamination method, followed by saponification treatment to obtain a sulfonamide type cation exchange membrane. Separately, the water content was measured using a membrane in which a sulfonamide layer was formed over the entire thickness of the film and found to be 8%. The surface of the intestinal ion exchange membrane was roughened by dry blasting.

The dry blasting method is a method of polishing by spraying an abrasive onto the object to be ground using compressed air. ) was sprayed onto side A with 2k9/ground compressed air. The spraying time was 1 minute per waist ldm2. As a result of the phase formation treatment, approximately 49 irregularities with a maximum height of 0.5 microns and a roughness of 0.05 microns or more were formed on the membrane surface per rib. The rough surface of the cation exchange membrane thus obtained (A
Example 1
Electrolyzed in the same manner as. In this example, the current density was 3 M/dm2. The electrolysis voltage was 3.6V, and the current efficiency was 84%. There were no hydrogen gas bubbles attached to the cathode surface of the intestinal ion exchange membrane. Comparative Example 3 In place of the roughened sulfonamide type intestinal ion exchange membrane of Example 6, a sulfonamide type cation exchange membrane without roughening treatment was used, and electrolysis was carried out in the same manner as in Example 5. .

The electrolysis voltage was 3.85V, and the current efficiency was 83.5%.

Hydrogen gas bubbles were heavily attached to the cathode surface of the cation exchange membrane. Example 7 Tetrafluoroethylene and perfluoro-3,6-dioxer-4-methyl-7-octensulfonyl fluoride were copolymerized in the same manner as in Example 1 to produce a polymer (polymer) with a water content of 14% and an equivalent weight of 1350. 1) and a polymer (Polymer 2) having a water content of 22% and an equivalent weight of 1090.

These polymers were heat molded to form a two-layer laminate with a thickness of 35 microns (polymer 1) and 100 microns (polymer 2), and then a Teflon woven fabric was vacuum laminated from the side of polymer 2. Embedded by law.

The laminate was saponified to obtain a sulfonic acid type cation exchange membrane. Next, the intestinal ion exchange membrane was roughened by a glow discharge method.

That is, the dried intestinal ion exchange membrane was placed on the side of polymer 1 (A
The film was placed on the cathode with the surface facing upward, and a glow discharge was caused between the film and the anode facing upward, and only the A side of the film was subjected to surface roughening treatment. Glow discharge is performed by reducing the pressure of the device to 10-ITom, then blowing argon gas to make it 10-ITom.
Discharge power 0.6W/200W. It was performed at a discharge power amount of sec/enemy. As a result of the surface roughening treatment, approximately 6M of unevenness was formed on side A with a maximum height of 0.7 microns and a roughness of 0.05 microns or more per rib. Only the A side of the thus obtained roughened membrane was subjected to reduction treatment to obtain a carboxylic acid type cation exchange membrane.

The sample was assembled into an electrolytic cell with side A facing the cathode, and electrolyzed in the same manner as in Example 1. Electrolysis voltage is 3.75V
The current efficiency was 96%. There were no hydrogen gas bubbles attached to the cathode surface of the intestinal ion exchange membrane.

[Brief explanation of the drawing]

Figure 1 shows the method of determining the maximum height from the recorded roughness curve, and Figure 2 shows the method for determining the maximum height from the recorded roughness curve.
．． This is a method of determining the number of unevenness of 0.05 microns or more. Figure 1 Figure 2

Claims (1)

[Scope of Claims] 1. In a homogeneous cation exchange membrane having a multilayer structure of two or three or more layers having different equivalent weights and/or types of ion exchange groups, at least one of the two end layers of the membrane has a low water content. A cation exchange membrane characterized by a rough edge layer. 2. The cation exchange membrane according to claim 1, wherein the cation exchange membrane is a fluorine-based cation exchange membrane. 3 The cation exchange membrane has a maximum height of 0.05 micron or more and a roughness of 1 mm or more and a roughness of 0.05 micron or more.
The cation exchange membrane according to claim 1 or 2, which is a cation exchange membrane having 20 or more rough surfaces per cation exchange membrane. 4. Claim 1, wherein the cation exchange membrane is a membrane whose surface has been roughened by a method of stacking the membrane and a molding material and heat pressing them.
The cation exchange membrane according to any one of Items 1 to 3. 5. The cation exchange membrane according to any one of claims 1 to 3, wherein the cation exchange membrane is a membrane roughened by dry blasting. 6. The cation exchange membrane according to any one of claims 1 to 3, wherein the cation exchange membrane is a membrane roughened by a liquid honing method. 7. The cation exchange membrane according to any one of claims 1 to 3, wherein the cation exchange membrane is a membrane roughened by a glow discharge method.