JPS5943033A - Cation exchange membrane - Google Patents

Abstract

PURPOSE:To provide a cation exchange membrane exhibiting high current efficiency during electrolysis of alkali metal salt, consisting of a perfluorocarbon resin having a specified degree of crystal orientation. CONSTITUTION:A perfluorocarbon resin membrane consisting of a sulfonate type cation exchange resin layer having an ion exchange capacity of 0.1-2meq/g of dry resin and a wealky acidic ion exchange group type cation exchange resin layer having an ion exchange capacity of 0.1-2meq/g of dry resin, is mono- or biaxially oriented at a temp. of not lower than 110 deg.C, but not higher than the heat decomposition temp. of the membrane at a drawing rate of 10m/min at least 1.1 times as wide in terms of an areal ratio, and heat-treated at 110 deg.C or higher for one min or longer to obtain a cation exchange membrane having a degree of orientation of 50 or above when the degree of crystalline orientation (pi) as measured by wide angle X-ray scattering method is represented by the formula, wherein H deg. is a half-width of X-ray diffraction intensity distribution on an equatorial line.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention discloses a 9-fluorocarbon system suitable for use with alkali metal electrolyte ratios. This is about Fuji Oitake and its method of making.

For more details, please refer to the Ministry of Education. Hoku crystal leakage: Weakly unique cation exchange Fl
When used for alkali metal salt electrolysis using the so-called germ exchange membrane method, the current efficiency during alkali metal salt electrolysis is high and the diffusion of alkali gold MW is small. The present invention relates to a fluorocarbon-based cation exchange membrane.

Ion Exchange Membrane Method The properties required for a cation exchange membrane in alkali metal salt electrolysis are secondary heat resistance and oxidation resistance as a material. ``Low electrical resistance, high current efficiency 5) {.・・'．
．． ``'$.'ml11・aluminum...force・・reduced diffusion of metal salts, etc.

．． ``Akira?, Ii'-Yai-Y.- '7')'＞;
f. As a car 7, 7 system cation exchange membrane, perfluoroalkylvinyl 21ter sulfonate whose main component is -'e1:fluoro (.'?, A1 dioxer-gourmethyl-couoctenesulfonyl fluoride) is used. After heating and molding the composite into a membrane, the sulfonyl group is modified to a sulfonic acid group (Vc) and the sulfonyl group is modified to form a sulfonic acid group (Vc). Den-based cation exchange membranes are known. et al. '． Ho. : Iric acid type Gosenichiful. Oh! Kaneson's rabbit cation exchange membrane has a high water content in the sulfonic acid groups, so the electrical resistance of the membrane is low, but it has the drawbacks of low current efficiency and large diffusion of alkali metal salts. Overcome your shortcomings
'f 6 TameK As a cation exchange group,
Perfluorocarbon-based cation exchange membranes having both weakly acidic cation exchange groups such as phosphoric acid groups and sulfonamide groups and sulfonic acid groups have been provided. In particular, a method of laminating a layer containing a weakly acidic cation exchange group and a layer containing a sulfonic acid group, or chemical treatment of the sulfonic acid group on one side of the membrane that has only a sulfonic acid group as an ion exchange group, converts Cal to a citric acid group. A fluorocarbon-based cation exchange membrane produced by a method of changing to a weakly acidic cation exchange group or other weakly acidic cation exchange group exhibits excellent effects. And the layer of these membranes whose main component is weakly acidic cation exchange groups. By performing electrolysis toward the cathode side, current efficiency can be improved.

Furthermore, it has been found that by increasing the thickness of the layer in which weakly acidic cation exchange groups are present, the diffusion of alkali metal salts can also be reduced. Furthermore, it has been found that when the layer of weakly acidic cation exchange groups is thick enough to exceed the total film thickness, for example, the decrease is significant. However, introduction of a weakly acidic cation exchange group increases the electrical resistance of the membrane, that is, increases the electrolytic power, so it is desirable that the layer of the weakly acidic cation exchange group be as thin as possible from the viewpoint of improving the power unit consumption. ．． Therefore, the present inventors have conducted intensive research on the 7'i method IC, which reduces the amount of alkali metal salts, especially common salt, in caustic alkali without increasing the electrical resistance of the membrane during electrolysis of alkali metal salts. As a result? By stretching a fluorocarbon-based cation exchange membrane containing both a sulfonic acid group and a weakly acidic cation exchange group at a temperature exceeding the glass transition temperature, an alkali metal salt (hereinafter referred to as common salt) under electrolytic conditions is produced. It has also been found that it is possible to prevent the diffusion of ions in the membrane.

Furthermore, by using this method, further improvement in current efficiency can be expected. Therefore, the present inventors further investigated why such excellent effects can be obtained by stretching, and discovered a wood quality that produces these effects. ′? That is, ゛? The invention is based on the crystal orientation change (・π) defined by the following formula. (However, the half-width of the x-ray diffraction intensity distribution on the equator H0#″j)
It has been found that the objective can be achieved by setting the temperature to 5θ or more, preferably 5s or more.

Here, the degree of crystal orientation? (π) is? What is measured by wide-angle scattering of x-rays? For example, "Cζ" published by Maruzen Co., Ltd., co-authored by Masao Kakuto and Nobutami Kanai, "Kobungo x Shin Diffraction", Notsuki, 1939? Ωθ Nikko's /wa/page ~. It is detailed in the section [Analysis of microcrystal orientation] on page 200.

In the present invention, the main chain of the fluorocarbon-based cation exchange membrane is -CF2=CFX- (where 'X is F
microcrystals exist partially, and by X-ray diffraction measurement, one peak of diffraction intensity is observed between Ωθ=7.6 and /g0. By measuring the distribution of this diffraction intensity on the equator, the orientation characteristics of the crystal can be determined. In this case, for example, when the light is oriented in one direction, an intensity distribution curve in which a λ peak exists between the azimuth angles θ and θ0 is obtained as shown in FIG.

The half-width referred to herein is h1 to h2 in M, which is the H intensity of AS when the diffraction intensity of BC is used as a reference. In the photographic method, the diffraction intensity distribution curve shown in FIG. In addition, the X-ray diffractometer uses a polar figure device, and the graph of azimuth angle and intensity when the polar angle = 4-0 corresponds to that.

In the case of orientation in the co-direction or higher, if the highest degree of orientation is 50 or higher, the original goal of this invention can be achieved.

The reason why the cation exchange membrane of the present invention has low salt diffusion and high current efficiency is not clear, but it is presumed as follows. That is, perfluorocarbons as mentioned above in general? The ion-based cation exchange membrane is not crosslinked, and the presence of a partial crystal structure in the membrane prevents excessive swelling or dissolution of the membrane in a solution. In other words, it is considered that, in addition to the type of ion exchange group and the exchange capacity 1, the crystallinity and coordinating crystalline state of the VC membrane are factors that determine the water content of the membrane. The orientation of the crystals acts on the film as if a type of crosslinking had occurred, so the molecules become denser,
This will further suppress the diffusion of salts and increase the current efficiency, but it is thought that the increase in ideal pressure will hardly occur compared to X7.

In the present invention, the perfluorocarbon-based cation exchange membrane is the above-mentioned cation exchange membrane. It is essential that M be oriented as shown in FIG.

Generally, the means for orienting the film-like material may be stretched at a temperature lower than its melting point. Alternatively, it can also be performed by calendering.

Therefore, the present invention also involves extruding a perfluorinated cation exchange resin or a resin having a functional group that can be converted into an ion exchange group into a membrane by melt extrusion prior to the introduction of an ion exchange group. The resin is stretched uniaxially or biaxially at a temperature between the co-order transition temperature and the melting temperature of the resin, or the thermal decomposition temperature of the resin, preferably under tension on the sides at a temperature of /lθ°C or more. Heat treatment can be carried out by keeping the temperature at or below the melting point or thermal decomposition temperature for 7 minutes or more. After carrying out the stretching treatment as described above, if necessary, ・Ion exchange groups are introduced by a conventional method, or ・A net-like or cloth-like material for packing is applied to one side of the membrane and pressed under heat. The membrane may also be reinforced by embedding at least two portions of the packing material within the membrane.

Furthermore, the present invention makes it possible to improve the performance of a cation exchange membrane whose current efficiency has decreased after being subjected to electrolysis for a long period of time by subjecting it to K stretching (and heat treatment) under the above conditions.

? The effect of stretching in the present invention is effective for perfluorocarzene-based cation exchange membranes, regardless of the type of exchange groups, such as sulfonic acid groups, carbanoic acid groups, or other ion exchange groups. However, special VC resins have two types of cation exchange groups, such as resins with sulfonic acid groups and resins with weakly acidic cation exchange groups such as carpanic acid. It is particularly effective for ion exchange membranes with a layered structure consisting of two types of resins. The reason for this is not necessarily clear, but there is generally a difference in water content between resins with sulfonic acid groups and resins with weakly acidic groups. This may cause cracks in the membrane or breakdown due to uneven distribution of internal stress. Diffusion of common salt and a decrease in current efficiency are thought to occur due to various reasons such as the formation of gaps, but as in the present invention, the above-mentioned oriented salt. In the case of a two-layer structure, it is thought that the above-mentioned defects can be prevented to some extent not only because both layers exist closely but also because of the influence of molecular arrangement.

The cation exchange membrane used in the present invention will be explained below.The cation exchange membrane of the present invention is characterized by having both a sulfonic acid group and a weakly acidic cation exchange group. Examples of acidic cationic substituents include sulfonic azide groups, .carganic acid amide groups, .phosphoric acid groups, phenolic hydroxyl groups, thiol groups, etc., and 0,S-N NaOH.
As mentioned above, a functional group that becomes an anion in a basic atmosphere is used.

Preferred are carboxylic acid groups and sulfonamide groups. It is sufficient that one or more types of cleaved weak acidic groups are present. The state of existence of the sulfonic acid group and the weakly acidic cation exchange group is not particularly limited, but it is preferable that the weakly acidic cation exchange group is unevenly distributed on one side of the membrane. That is, the membrane is:, Sur. Contains a phonic acid group.
From resin. layer and weak acidity. Cation exchange group. Has. layer of resin.・A suitable layer of sulcus consisting of ・etc. Weakly acidic cations that give fruit. Resins with exchange groups have sulfonic acid groups that are weakly acidic. s for the on-exchange group
It may be present in an amount of 0q6 (mol) or less. Similarly, the resin containing sulfonic acid groups may contain weakly acidic cation exchange groups in an amount less than 50 of the total exchange groups. In this way, a resin with a small number of phonic acid groups and a weakly acidic positive acid. The fluorocarbon-based cation exchange membrane, which is integrated with a resin having ion exchange groups, is of the Ω type. Physically bonding a matrix consisting of a resin, e.g. 2 min. This also includes a case in which 21 are unevenly distributed in each case.

゛It is also a fluorocar that has both a sulfonic acid group and a weakly acidic cation exchange group. 'fyn-based cation exchange membrane,
Many cation exchange membranes have been proposed in the past, and the present invention can also be obtained using these known methods for producing cation exchange membranes.

Some examples are given below.

(1) After converting the sulfonic acid group on one side of the sulfonic acid type cation exchange membrane 9 to sulfonyl halide, . Cal? A method of converting into an acid group. The sulfonic acid type cation exchange IIQ mentioned here is a copolymer represented by the following general formula.

That is, tetrafluoroethylene and non-fluoro(3,6
- Dioxada = methyl-7-ocdenesulfonyl fluoride) copolymer, etc. is formed into a film by a thermoforming method (these are collectively referred to as an sulfonic acid precursor film).
.

(2) Sulfo. One side of the phosphoric acid type precursor film is reacted with ammonium or tertiary/bamboo amines to form a sulfonic acid residue on the surface layer of one side of the film, and then the remaining sulfonyl fluoride is hydrolyzed to form sulfonyl fluoride. /Method of converting into phonic acid group. In this case, the sulfonamidation and hydrolysis can be carried out by known methods, such as the method described in Japanese Patent Application Laid-open No. 1996-1616A'lgg. Generally a sulfonamide layer. Thickness / 00 people ~ % of the umbrella membrane thickness ・(
31 At least one side of the precursor film is treated with phosphorus pentachloride or a mixture of phosphorus oxychloride and phosphorus pentachloride to remove -SO? After converting F to -S02CtK, the entire treated surface is treated with an oxidizing agent or a 1':t reducing agent to form a carboxylic acid group as the king of the film on one side in a portion of /008~film thickness. How to make these methods JP-A-S? -/S'l Otsuq issue and JP-A-62=. 2'
The method described in No. 1/'7'7 can be adopted (4) -S by the precursor film or its hydrolysis treatment.
After converting o2F into a sulfonic acid group, one side of the membrane is reduced to sulfinic acid or sulfuryl halide, and then this is reduced or oxidized to convert a caldic acid group to one side of the membrane in the same manner as above. How to form to a thickness of .

This is Japanese Patent Application Publication No. S3-7.32094t.
/ gA 03 and other methods may be adopted. In this case, the remaining sulfinic acid or sulfuryl halide is preferably converted into a sulfonic acid group by oxidation or oxidation and hydrolysis.・(5) A method of laminating the precursor film with the following polymer and hydrolyzing it: k units of -CF2-CF2- and one CF2, provided that
CF, 4 or -CF2→-CF3m is 01 Tapa S number n is / ~ Otsu's number? kSt is a positive number and - is 9~/Yt6 Copolymer consisting of one halon or alkoxy group unit (these are collectively referred to as carboxylic acid M precursor) i6+ Sulfonic acid type precursor film , a method in which a mixture of each unit-forming monomer shown in section (4) or at least the latter monomer is impregnated or coated with 1-j' and then hydrolyzed.In this case, of course, the precursor film is hydrolyzed in advance. You can leave it there.

(7) By sulfonic acid type precursor film or hydrolysis treatment? -S (> 2 F) is converted to sulfonic acid by irradiating it with ultraviolet rays from one side in the presence of nitrogen acid, thereby converting the sulfonic acid into carboxylic acid on one side only. Various other methods have also been adopted. However, compared to the method in which two types of ion exchange resins are formed into membranes and then laminated together, it is possible to form a membrane with a homogeneous phase at once, and then (by chemical treatment, a resin layer with sulfonic acid groups and a weakly It is preferable to use a method of separating the resin layer from the resin layer having an acidic cation exchange group.

In addition, 1. Kamimachijiku employs means for forming crystal orientation, which is a feature of the present invention. Method. at °C - Step of forming the precursor film or precursor into a film shape, applying 9 steps of 11111 water decomposition, or having a sulfonic acid group or a sulfonyl halide group and a carbonyl halide group or a carbo/
At the stage of introducing the acid ester group, other sulfonic acid groups or groups that can be converted to sulfonic acid groups and Cal. Weakly acidic cations such as phosphoric acid groups. Stretching may be carried out at any stage in which an ion exchange group or a group convertible into the same group is present. However, in view of the soft fresivity which will be described later, it is preferable to carry out this process when the ion exchange groups present in the membrane are in the acid type or ammonium oxide type. Optionally, after the first stretching, the Tyflon cloth or mesh may be thermocompression bonded (including press-fitting part or all of it into the membrane). The membrane in which packing is formed in this manner has improved dimensional stability.

In general, it is preferable that such thermocompression bonding be carried out in the presence of predominantly sulfonic acid groups or functional groups that can be converted into sulfonic acid groups.

Another method is to add strength and dimensional stability to the membrane.
- Has it been made into a Sibril? Litetrafluoroethylene I
It can also be achieved by mixing it with the matrix-forming copolymer of I-1 and leaving it in the film forming layer. ? Next, the step for forming crystal orientation in the present invention will be explained. As already mentioned, in order to form the orientation, it is generally necessary to stretch the membrane. In this stretching method, the uniaxial or uniaxial stretching means that are generally used in the process of heating or plastic film are preferred. However, calendering may also be employed. The e-fluorocarbon film of the present invention is preferably stretched at a temperature above the glass transition temperature.

Of course, it is also possible to stretch the film at the glass transition temperature line 1, 20F, but as far as the present invention is concerned, the cation exchange membrane stretched below the glass transition temperature is Therefore, such stretching conditions should be avoided.Also, of course, if the temperature is below the decomposition or melting temperature (often the softening temperature) of the material to be stretched, It is necessary to stretch it by / / q '.
The film may be stretched at a temperature of C or higher and lower than the thermal decomposition temperature of the film.

The stretching ratio may be determined by checking the orientation of crystals in the stretched film, but in general, the area ratio is preferably 7.5 times or more. 1 of the present invention with 7.3 to 3 times stretching
can reach the target. Although the limit value of the stretching speed varies depending on the temperature conditions, it is generally safe to set it to 7 OrIL/min or less.

Furthermore, after stretching, the film is kept under tension or moderate tension at a temperature of 0°C or higher, preferably at a temperature slightly higher than the temperature, cold, or sag during stretching for at least / minutes. It is preferable to perform heat treatment. It is also effective to relieve swelling and lower eyelids. ″′
・Examples will be shown below to specifically explain the present invention, but
The present invention is not limited to these.
・? ·Example/ '
? Tetrafluoroethylene and 74' = 7 fluoro' (
3, Otsu-. Hydrolyzing the copolymerized agricultural product of dioxa←coumethylnikooctenesulfonyl fluoride), the exchange container becomes a sulfonic acid type perfluorocarbon with a dry film thickness of 0.9/millimeter/gram and a thickness of lgθμ. A system cation exchange membrane was obtained. After treating only one side of the membrane with phosphorus pentachloride to convert the sulfonic acid groups to sulfonyl chloride groups, it was immersed in butanol and heated while blowing air. Oxidation treatment was performed to change the sulfonyl chloride group to a butyl ester group of caldic acid. Next, the membrane was hydrolyzed with a caustic soda methanol mixed solution to remove caldicic acid and sulfonic acid. An f-fluorocarbon-based cation exchange membrane was obtained. When this membrane was stained with a crystal violet brewing solution, the surface where caldenic acid groups were present was not stained at all at a thickness of /0μ. It was found that this layer was substantially free of sulfonic acid groups. The cation exchange membrane thus obtained was
The sample was immersed in a mixed solution of N-hydrochloric acid and monomethanol (/:/volume ratio) at room temperature for 6 hours to fully transform the ion exchange group into H+ form. Next, the film was set in a stretching device in an air-dried state, and
/5θ°C, simultaneously in the a-axis direction at a rate of /Ocm/min, respectively. The area was stretched 3 times (area magnification approximately /.k.times). After stretching, the film was heated as it was at a temperature of /gO°C and held for 30 minutes to perform heat treatment. After that, it was cooled to room temperature by standing to cool, and then immersed in a 6N-caustic soda-methanol (l:/volume ratio) mixed solution at room temperature for an hour.
The ion exchange group was Na+ type. Thickness when air-dried is 700
It became μ. The degree of orientation was determined to be 55 by measuring the X-ray diffraction of the membrane obtained using an X-ray pole shape measuring device manufactured by Rigaku Denki ■.

Calculate the obtained cation exchange membrane? The surface containing phosphoric acid groups was directed toward the cathode, and it was reduced to a two-chamber type tank with an effective area of 0.5 dm. The cypress anode is a metal anode made of titanium lath coated with titanium dioxide and ruthenium dioxide, and the cathode is a soft iron wire mesh. Anode room saline solution resistance level 3. sN, so that the generated caustic soda concentration is 9N3/) A /dm2
, KO°C. The electrolysis results are shown in Table I.

Comparative Example/ ・Is the cation exchange membrane having sulfonic acid groups and carboxylic acid groups in Example/ subjected to stretching treatment? The degree of orientation was measured and salt electrolysis was performed in the same manner as in Example. The alignment/direction is 110? Ta. The electrolysis results are also shown in Table ■.

Examples U to G1 Comparative Examples C and 3 The cation exchange membranes containing sulfonic acid groups and caldenic acid groups of Example 1 were prepared by a conventional method. After forming the ionic form as shown in ■, it was stretched under the conditions shown in Table ■. I did it.

Note that the stretching was performed only in the longitudinal direction, with the transverse direction being fixed. The degree of orientation and electrolytic results obtained in the same manner as in Example 1 are shown in Table 3. ? 1. As a comparative example, Table 3 also shows the degree of distribution and electrolysis results of a film subjected to the same thermal history without stretching, and a film subjected to stretching treatment at a temperature below the glass transition temperature.

The following is a yarn example 9.
Noret 7-octensulfonyl fluoride and tetrafluoroethylene were copolymerized, hydrolyzed, and measured. A copolymer of g Otomi IJ equivalent/g dry film was heat molded to obtain a film with a thickness/50 μm. Only one side of this membrane was reacted with ethylenediamine and then subjected to hydrolysis treatment to obtain a fluorocarbon-based cation exchange membrane having sulfonamide groups and sulfonic acid groups.

The membrane was immersed in a mixed solution of /N monohydrochloric acid and methanol (/:/volume ratio) at room temperature for an hour to change the ion exchange group to H+ type. Next, the film was set in a stretching device and heated to 730°C, and then stretched in the 2@ direction. Stretching was performed 3 times.

Next, heat treatment was carried out by increasing the wettability by /70°CK and holding for /hour. After cooling, 6N-caustic soda methanol (/:
/volume ratio) was immersed in the mixed solution at room temperature for g hours to change the ion exchange group to Na'' type.The thickness was qOμ when air-dried.

The degree of orientation of this film was 56. The membrane thus obtained was oriented toward the cathode side containing 1 sulfonamide group. ．． implementation.
example/. Salt electrolysis was performed in a similar manner. The concentration of caustic soda produced was set to gN. Great results. Table ■． Shown below.

Comparative example. llt. ．． ．． ．． ．． I: 11? The sulfonic acid group of Example 9 has a sulfone 7 mido group. Do not stretch or process the cation exchange bleaching process. ．． Please use it. ．． Real tIAf! l! Same as 9. Mulberry sword. ．． Salt poisoning by law. Line 49. . ．． ．． Confrontation. Kakura table. Shown in ■.
．． The degree of orientation of this film was θ. ! ．． Reponylfluoride P) and tetrafluoride'? Together with Ochiren? Perform hydrolysis treatment on Shigetani's armpit sardine! ,．． ．． Exchange capacity is 0. ．． ．． ．． ．． 9 Remi j IJ equivalent/'? "5J. Dry film, thickness /g1.

2, - Completed. Yu, 1. Ho. A phosphoric acid type cation exchange membrane was obtained.・．． Part one. Only one side is irradiated with ultraviolet rays in the presence of nitrogen oxides to form sulfonic acid groups. was converted into a carbic acid group and stained with an acidic solution of Calderic acid. It was confirmed that the basic force i exists in the layer busμ. ? The cation exchange membrane thus obtained was immersed in a 7N hydrochloric acid/methanol mixed solution (/:/volume ratio) in a hawker room for an hour.

' R iTiItik+. stomach. @vc-ty'.
't- L, 1, 1. /． ．． SO". After raising the temperature, the transverse direction was fixed, and longitudinally inward direction was stretched by /. 2 times. Next, heat treatment was performed by raising the temperature to /. 70°C and holding it for 3θ minutes. After cooling, the sample was immersed in a 4N-caustic soda-methanol mixed solution (7 volumes) at room temperature for g hours to convert the ion exchange group into Na'' type. Thickness is 72 when air-dried.
It became 0μ. The degree of orientation of this film was higher than hbs.

A layer containing Calpo≧acid group is placed on the cathode side:Example/. :．
・．． : ・11・-4 Salt electrolysis was performed in the same manner as in 1.

Rewarding the results ・．． ．． Comparative example S' Example/0? A cation exchange membrane containing sulfonic acid groups and sulfonamide groups was subjected to salt electrolysis for one-time measurement without stretching. . Degree of orientation. was 115. The results are shown in Table 1.

Example // The cation exchange membrane containing sulfonic acid groups and calylr acid groups of Example / was subjected to salt electrolysis in the same manner as in Example / without stretching treatment. The degree of orientation was QgolIO. The initial electrolytic performance at that time was a current efficiency of 94%.
li solution voltage 3. 'lSV, NaCt in produced caustic soda
# degree/00 ppm (sO% caustic soda equivalent). Conducted electrolysis for 6 months/year, current efficiency g9, electrolysis voltage 3. Doug■, NaC2 in the produced caustic soda
When the concentration reached /20 ppm, the membrane was removed from the electrolytic cell and a mixed solution of /N monohydrochloric acid and methanol (/:
/volume ratio) at room temperature for an hour to remove impurities in the membrane and change the ion exchange group to H+ type. Next, the film was set in a stretching device and stretched at /50°C by a factor of 7.5 in the machine direction while being fixed in the transverse direction, and then heated to 770°C and heat-treated for 30 minutes. It was immersed in a mixed solution of N-caustic soda and methanol (/:/volume ratio) at room temperature for an hour to change the ion exchange group to Na+ type.

The degree of orientation increased to B/. When electrolysis is performed again, the current efficiency is 93. S%'! The electrolytic voltage is 3, IIsV.
, NaCt#Ifi'SOppm in the produced caustic soda (
50% caustic soda equivalent).

[Brief explanation of the drawing]

FIG. 1 is a diagram related to the measurement and calculation of crystal orientation defined in the invention. This is a clear diagram. In the figure, the vertical axis is the diffraction intensity, and the horizontal axis is the azimuth. :． B, M, h, h21l-i' each represent each point in the figure. ■． : 1 fi'Fi'HiHA,. Tokuyama Soda Co., Ltd.

Claims (1)

[Claims] (11) Made of a perfluorocargin resin having a sulfonic acid group and a weakly acidic cation exchange group, the crystal orientation change (π) measured by wide-angle X-ray scattering is expressed by the following formula: When expressed, the cation exchange membrane has an orientation degree of 50 or more, where H0 is the half width of the X-ray diffraction intensity distribution on the equator. (2) A layer made of a sulfonic acid type cation exchange resin and a weak A cation exchange membrane (3) according to claim 1+, consisting of two layers of an acidic cation exchange group-type cation exchange resin and a good layer, wherein the weakly acidic cation exchange group is a carboxylic acid group. Claim No. {Cation exchange membrane according to claim 11 (41
The capacity of the ion exchange group in the sulfonic acid type cation exchange resin layer is O. /~2maea, /9 dry resin, and the capacity of the ion exchange group in the weakly acidic cation exchange group type cation exchange resin layer is θ. i'=,2meq/. ! The cation exchange membrane (51) according to claim (2), which is a dry resin, has a thickness of 0.05-/ttrm, and the weakly acidic cation exchange group type cation exchange resin layer has a thickness of 7 μm. ~Membrane 1
The cation exchange membrane 1 according to claim 21, which has a thickness of A, has a structure in which the main chain has +CF2-CF10 repeating units, and the side chain has -(-0CF2・CFR+, The cation exchange membrane described in item (!) of the patent application, which is made of a fluorocarbonate bonded with an ion exchange group via F or CF,
．． ) (7) A film-like material made of a perfluorocarbon resin having a sulfonic acid group and a weakly acidic cation exchange group//
Stretching at a temperature of 0° C. or higher and lower than the decomposition temperature of the resin so as to give a degree of orientation such that the degree of crystal orientation (π) measured by wide-angle scattering of X-rays is equal to or higher than sθ when expressed by the following formula. What is the manufacturing method for the characteristic cation exchange membrane? However, H0 is the equator. Above (half price width of ON moromi diffraction strong one bon cloth (8
1. Stretching autumn clothes? The production of a cation exchange membrane according to item 1(7) of the claim, characterized in that the membrane is then subjected to heat treatment at a temperature of 1/θ° C. or higher for at least 1 minute or more. Method