JPS61281890A - Fluorine-containing ion exchange membrane for electrolysis - Google Patents

Abstract

PURPOSE:To develop an ion exchange membrane having excellent mechanical strength and dimensional stability by using a laminate of fluoropolymer films to constitute the ion exchange membrane of an ion exchange membrane electrolytic cell for electrolysis of an aq. NaCl soln. CONSTITUTION:The ion exchange membrane of the ion exchange membrane electrolytic cell for producing gaseous NaOH and Cl by electrolyzing an aq. NaCl soln. is constituted of the fluorine-contg. ion exchange membrane. The ion exchange membrane is made into the double construction on the cathode chamber side constituted of the fluoropolymer film contg. a carboxylic acid group and the fluoropolymer film contg. the carboxylic group having a large ion exchange capacity. The anode side thereof is constituted of the laminated construction with the fluoropolymer film contg. the sulfonic acid group. The porous base material made of the perfluoropolymer having 10-300 denier yarn size and 40 pieces/inch yarn density is exposed into such fluorine-contg. ion exchange membrane at 1/100-2/3 of 10-300mum thickness thereof from the membrane surface and a hydrophilic coating is provided on the surface thereof.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a fluorine-containing ion exchange membrane for electrolysis, and more specifically, to an electrolysis membrane having high mechanical strength, dimensional stability, and low electrical resistance. The present invention relates to a fluorine-containing ion exchange membrane for use.

[Prior art] Fluorine-containing ion exchange membranes are used for electrolysis of aqueous alkali chloride solutions to produce alkali hydroxide and chlorine, water electrolysis,
It is widely used as a diaphragm for electrolysis such as hydrochloric acid electrolysis and valuable metal recovery because of its excellent heat resistance, chemical resistance, mechanical strength, etc., and its use has also been proposed.

When a fluorine-containing ion-exchange membrane is put into practical use for electrolysis, it is generally made using 1, for example, polytetrafluoroethylene (PT) to improve its mechanical strength and dimensional stability.
A porous substrate such as a woven fabric made of a fluorine-containing polymer such as FE) is inserted into the membrane as a reinforcing material to support the membrane. (JP-A-53-58192, JP-A-58-37188, JP-A-58-37187, etc.) However, the fluorine-containing ion exchange membrane reinforced in this way has The result is that the substrate blocks ion transmission (current flow), thereby increasing membrane resistance. Such an increase in membrane resistance becomes more pronounced as the porous substrate is inserted more closely into the ion exchange membrane to improve the mechanical strength and dimensional stability of the membrane.

Due to the contradictory phenomenon between the mechanical properties and electrochemical properties of the ion exchange membrane, conventionally, it has been necessary to use a porous base material with a density that does not excessively increase the membrane resistance. For this reason, the thread density of the woven fabric or the like of the porous base material inevitably becomes sparse, and the thread diameter of the woven fabric inevitably becomes large in order to provide strength.

An increase in the thread diameter of the woven fabric causes an increase in the thickness of the ion exchange membrane, and a sparse opening also means that the P
With TFE yarn, it is difficult to manufacture woven fabrics with uniform thread density, and as a result, special woven fabrics such as leno weave (Japanese Patent Application Laid-open No. 5
No. 5-75428.

Utility Model Publication No. 58-81301, etc.), which in turn leads to an increase in the thickness of the ion exchange membrane, creating a vicious cycle.

[Problems to be Solved by the Invention] It is an object of the present invention to have high mechanical strength and dimensional stability, which cannot be achieved with the above conventional techniques, and to reduce the film thickness. The present invention provides a fluorine-containing ion exchange membrane for electrolysis with low electrical resistance.

More specifically, a porous substrate such as a woven fabric is inserted into the membrane at a high density to provide high mechanical strength and dimensional stability, but this also does not increase the membrane resistance and reduces the M thickness. The present invention provides an ion exchange membrane for electrolysis that does not increase in size.

[Means for solving the problems] The present invention has been made to achieve the above object,
The feature is that it is made of a fluorine-containing polymer system with a thread diameter of 10 to 300 denier (De), and a high-density porous base material with a thread density of 40 wood/inch or more, which partially extends from the anode side surface of the membrane. A fluorine-containing ion exchange membrane for electrolysis is embedded in a fluorine-containing polymer film constituting the membrane so as to be exposed, and at least the exposed surface of the porous base material has a wood-philic coating.

In the present invention, the thread diameter is 10 to 300 Da and the thread density is 40
A porous base material with a high density of wood/inch or more is used as a reinforcing material, but such a high density porous base material has never been used before, and therefore has unprecedented mechanical strength and Dimensional stability is achieved.

As described above, in the present invention, the porous substrate is inserted so as to be exposed from the anode side surface of the membrane.

Conventionally, when the reinforcing material is exposed from the membrane surface, it has been considered undesirable because gas and the like will adhere to the reinforcing material and the resistance will increase. On the other hand, exceptionally, the reinforcing material is removed from the membrane surface by -f! l! Japanese Patent Laid-Open No. 58-37188 describes inserting it so that it is exposed. but.

The porous base material used in this case has a small thread density of 10 to 30 threads/inch, similar to conventional ones, and therefore has a large thread diameter, as well as porous bases exposed from the membrane, which is essential in the present invention. There is no disclosure of providing wood with a wood-loving coating.

In the present invention, when a porous base material with a small opening and a high vE degree is used, the above object can only be achieved by providing a hydrophilic coating to the portion exposed from the membrane. this is,
The mechanism is not necessarily clear, as will be made clear from the examples shown later.As it seems, in the present invention, the porous substrate having a wood-loving coating on the surface is The high-density porous base material that penetrates into the interior of the membrane through the electrolyte and is embedded in the membrane also has an electrolytic solution nearby, which reduces the current shielding effect of the porous base material. This is thought to prevent an increase in membrane resistance.

The porous substrate used in the present invention is preferably made of woven or knitted fabric, has a thread diameter of 10 to 300 Da, preferably 50 to 100 [1e], and a thread density of 40 threads/inch or more, particularly A high density of 50 to 150 lines/inch is used. When expressed as a planar open area ratio, it is usually 60% or less, preferably 50 to 30%, although it varies depending on the thread diameter. The thickness of the porous base material varies depending on the thickness of the ion exchange membrane, but is preferably 3/2 of the membrane thickness.
~115 and a layer of 50 to 200μ is used.

Porous substrates maintain a high degree of mechanical strength and dimensional stability in terms of electrolytic applications.

It is preferable to have heat resistance and chemical resistance.

Examples of these include PTFE, tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer, tetrafluoroethylene-perfluoroacrylate copolymer, tetrafluoroethylene-ethylene copolymer, and vinylidene fluoride. Fluorine-containing polymers such as polymers, particularly perfluoropolymers, are preferred.

The woven fabric or knitted fabric constituting the porous base material is monofilament or multifilament, yarn thereof, slit yarn, etc., and the weaving method may be plain weave,
Appropriate weaving methods such as leno weaving, twill weaving, cord weaving, sashakka, and knitting are used. In some cases, the porous base material may be a blended yarn or mixed fiber yarn of a fluorine-containing polymer yarn and a yarn of rayon, polyethylene terephthalate, cellulose, etc., which is a so-called sacrificial yarn that is soluble under electrolysis. . In this case, the amount of sacrificial yarn mixed is preferably 6% to 85%, particularly 30% to BO%, based on the weight of the total amount.

The woven fabric or knitted fabric is a so-called flat porous base material whose cross section is flattened and the ratio of positive/longitudinal diameter of the yarn cross section is preferably 2 to 10, as shown in JP-A No. 58-37187. can also be used.

The fluorine-containing ion exchange membrane of the present invention is made of a fluorine-containing polymer having a carboxylic acid group, a sulfonic acid group, or a phosphoric acid group as an ion exchanger. Ion exchange capacity is preferably 0.5-4
．． 0 milliequivalent 7g dry resin, especially 0.8-2.0
Milliequivalents/g dry resin is suitable, thickness preferably 30
A small one of ~300μ, particularly 100~250μ is preferable in terms of membrane resistance.

The fluorine-containing ion exchange membrane can be formed from a single layer of fluoropolymer film, but it can also be an 81-layer membrane of the same or different type. The ion exchange membrane having a preferable laminated structure includes a first layer made of a fluorine-containing polymer having a carboxylic acid group as an ion exchange group, and a fluorine-containing polymer having a cation exchange group supported by a porous base material. and a second layer located on the anode side of the first layer and having a low electrical resistance and a large thickness of 75 to 220 μm.

It is necessary for the first layer to have a carboxylic acid group as an ion exchange group in order to provide high current efficiency, and the ion exchange capacity is preferably 0.5 to 2.0 1/m/mm. g dry resin, especially 0.8 to 1.3 meq. 7 g dry resin is used. This first layer preferably has an electrical resistance (specific resistance) of 180 to 180 compared to the second layer.
Since it is as large as 250 Ω·cm, its thickness is preferably comprised of a fluoropolymer film having a layer thickness of 10 to 70 μm, particularly an amount of 15 to 40 μm.

The second layer preferably has, but is not limited to, a sulfonic acid group, a carboxylic acid group, or a phosphoric acid group as a cation exchange group, and also has a lower electrical resistance than the first layer. It preferably has 20-200 Ω・C, especially 30-150 Ω・C, and has a thickness of 75-200 Ω・C.
It is formed from a fluoropolymer film having a thickness of 220 μm, particularly 80 to 200 μm. Like the first layer, the second fluorine-containing polymer does not necessarily have to be formed from one type of polymer, and may have different types of ion exchange groups and/or ion exchange capacities as necessary. It can be formed from two or more types of fluorine-containing polymers.

For example, if the film is composed of a film with a carboxylic acid group on the 1wk electrode side and a film with a sulfonic acid group on the anode side, or both have a sulfonic acid group or a carboxylic acid group,
Examples include two or more types of films having a large ion exchange capacity on one pole side.

When a fluorine-containing polymer film having a sulfonic acid group or two or more films including the film and a film having a carboxylic acid group are used as the second layer, a film having a sulfonic acid group and a film having a carboxylic acid group are used. A layer of a fluoropolymer having both a sulfonic acid group and a carboxylic acid group or a fluoropolymer having a sulfonic acid group is preferably added to the laminated interface with the film in order to improve bonding properties between the two. A third layer consisting of a blend layer of a polymer and a fluorine-containing polymer having a carboxylic acid group and having a thickness of preferably 5 to 50 μm, particularly 10 to 40 μm can be interposed.

The ion exchange capacity of the fluorine-containing polymer having a cation exchange group in the second layer or the third layer is preferably 0.
5-2.5 meq/g dry resin, especially 0.8-2.
0 meq/g dry resin.

The fluorine-containing polymer constituting the first to third layers is preferably formed from a perfluoropolymer, which is composed of a copolymer of at least two types of monomers, preferably a primary It consists of a copolymer having the polymerized units of (a) and (b).

Kokote, x, x゛ are -F, -CI, -1 (or -
CF3 with Te, A is -503M, -000M or -P
O3H (M is hydrogen.

(representing an alkali metal or a group that is converted into these groups by hydrolysis), Y is selected from the primary ones, where:
Z, z'' are -F or a perfluoroalkyl group having 1 to 10 carbon atoms, and X, !, and Z each represent an integer of 1 to 10.

-(CF2)X, -0-(CFt arrow., (0-CF
2-CF Chi.

In addition, the composition ratio of (a)/(b) forming the above polymer (
molar ratio) is selected such that the fluoropolymer forms the above ion exchange capacity.

The above-mentioned fluoropolymer is preferably a perfluoropolymer, and a preferable example thereof is CF2-CF2
and CF2-CFOCFz CF CC, Fs ) OCF
Copolymer with z 0F2So2F, CF2 +++Cp
2 and CF2mCFO (copolymer of CF2h-ssOzF, CF2-CF2 and CF2-CFO (CF2)
+ -s Copolymer with COOCH3, furthermore CF2
w-CF2 and CFt-CF-OCFzCF (CF
3) A copolymer with OCFzCF2COOCH3 is exemplified.

When inserting a porous base material into a fluoropolymer film constituting a membrane, the porous base material is superimposed on the fluoropolymer film and heated and press-fitted. When using the above multilayer fluoropolymer film, the first layer, if necessary, the third layer, the second layer, and then the porous substrate are layered in this order and heated. Press-fitted. The temperature is selected to be at least the softening point of the fluorine-containing polymer, preferably at least the melting point, for example 100 to 250°C, and under such heating, the objects are preferably stacked one on top of the other and exposed from the outside at a weight of 1 to 80 kg/cm.
At step 2, the porous substrate is inserted into the polymer film by applying pressure using a press or the like.

In the present invention, the porous substrate is inserted and embedded in the fluoropolymer film so that a portion of the porous substrate is exposed from the anode side surface of the ion exchange membrane. That is, the porous substrate does not need to be exposed over the entire surface of the embedded membrane;
Preferably, as many parts as possible are exposed from the membrane surface.

The degree of exposure is such that the porous base material is embedded in the fluoropolymer film, preferably at least 10μ layer, preferably 50 to 100μ layer, and preferably 10μ layer.
m or more, particularly 20 to 50 μm, are exposed from the anode side surface of the membrane. Excessively small embedding of the porous substrate is undesirable because the mechanical strength and dimensional stability of the membrane will not be sufficient, while excessive embedding will lead to an increase in membrane resistance, especially if exposed parts of the porous substrate If it is small, a significant increase in membrane resistance will result.

In the present invention, the porous base material is required to have a wood-philic coating on at least the surface of the exposed portion thereof. Various methods can be used to apply the wood-loving coating to the porous substrate. For example, after inserting and embedding the porous substrate into the membrane,
Possible methods include spraying a solution or dispersion of an inorganic or organic lignifying agent onto the exposed portion, or immersing the porous substrate in this solution or dispersion, followed by drying or firing. . The concentration of the lignifying agent in the solution or dispersion is preferably selected to be 5 to 30% by weight, and the drying and firing are preferably carried out at 50 to 200°C for 0.1 to 1 hour.

The above-mentioned inorganic hydrophilic agent is titanium.

Oxides, chlorides, oxychlorides, nitrates, silicon carbide, etc. of zirconium, niobium, tantalum, vanadium, manganese, molybdenum, tin, etc. are used. When such an inorganic wood-loving agent is used, the same fluorine-containing polymer as that constituting the porous substrate described above is preferably added to the solution or dispersion in an amount of 2 to 25% by weight. , it is possible to improve the adhesion between the inorganic hydrophilic agent and the porous substrate.

As the organic hydrophilizing agent mentioned above, a fluorine-containing polymer having a parent group such as a carboxylic acid group or a phosphoric acid group is used. As such a fluorine-containing polymer, the same kind as the fluorine-containing polymer forming the above-mentioned ion exchange membrane can be used, but in this case, a low molecular weight one having a molecular weight of 500 to 10,000 can be used.

Another method for applying a hydrophilic coating to a porous substrate is to spray a solution or dispersion of a fluorine-containing polymer having a tree parent group, which is the organic tree parent agent mentioned above, onto the porous base material. or by immersing a porous substrate in these solutions or dispersions;
Next.

A woodphilic coating can be produced by polymerizing the above-mentioned hexamers. Still another method is to incorporate the ion exchange membrane embedded with the porous substrate into the electrolytic cell, and then add the above-mentioned hydrophilic agent, preferably ZrO(N), to the anolyte.
O3)2. A so-called wood-loving coating can also be applied on-site by adding an inorganic wood-loving agent such as Zr0C+2°FeCl2 and dipping these hydrophilic agents into the porous substrate.

The lignophilic coating on the porous substrate needs to be applied to a portion of the exposed portion of the porous substrate from the membrane, preferably the entire surface, but in some cases, it may also be applied to the portion embedded in the membrane. It can be applied to the entire surface of the porous substrate. In this case as well, the process is carried out in the same manner by applying the above-mentioned wood-philic coating before embedding the porous base material in the membrane.

The process conditions for electrolyzing an aqueous alkali chloride solution using the ion exchange membrane of the present invention are
For example, the anode chamber is preferably 2.5 to 5.
A 0N alkali chloride aqueous solution is supplied, and water or diluted alkali hydroxide is supplied to the cathode chamber, preferably 50N.
Electrolysis is carried out at ~120° C. and a current density of 10 to 100 A/d.

In such a case, heavy metal ions such as calcium and magnesium in the aqueous alkali chloride solution cause deterioration of the ion exchange membrane, so it is preferable to minimize them as much as possible. can be added to the aqueous alkali chloride solution.

In the present invention, the electrolytic cell may be of a monopolar type or a bipolar type as long as it has the above configuration, and the material constituting the electrolytic cell may be, for example, in the case of an anode chamber in the case of electrolysis of an aqueous alkali chloride solution.

Materials resistant to aqueous alkali chloride and chlorine, such as valve metal and titanium, are used; in the case of the cathode chamber, iron, stainless steel, or nickel, which are resistant to alkali hydroxide and hydrogen, are used.

In the case of arranging the electrodes in the present invention, the electrodes may be arranged in contact with the multilayer membrane or at appropriate intervals, but in particular in the case of the present invention, the electrodes may be arranged in contact with the diaphragm accompanied by low membrane resistance without any hindrance,
Advantageous sliding voltages can be achieved.

In the above, the diaphragm of the present invention was mainly used for the electrolysis of aqueous alkali chloride solutions, but it goes without saying that it can be similarly applied to the electrolysis of water, halogen acids (hydrochloric acid, hydrobromic acid), and alkali carbonate. be.

Next, the present invention will be explained with reference to Examples, but it goes without saying that the present invention includes various embodiments within its scope.
For example, the ion exchange membrane in which the porous base material of the present invention is embedded may contain porous particles that are permeable to gas and liquid and have no electrode activity on the surface or both surfaces of the anode side or the cathode side, as necessary. layer (JP-A-58-75583 and JP-A-5
7-39185) or a porous layer containing gas- and liquid-permeable particles with electrode activity (Japanese Patent Laid-Open No. 54-112)
No. 398) can be provided to further improve the sliding voltage under electrolysis.

[Example] Example 1 and Comparative Example 1 A plain-woven fabric A with a thread density of 100 wood/inch was obtained by using multifilaments with a denier number of 80, which are made by aligning and twisting eight 10-denier monofilaments made of PTFE, as warp and weft threads. Ta.

The open area ratio of this woven fabric was 35%, the thickness at the intersection of the threads measured with a dial gauge was SOμ, and the cross-sectional shape of the threads was observed under a microscope, and the oblateness ratio of the threads was approximately 1.0. Ta. A part of the woven fabric A was cut to a size of 20 cm x 20 cm, and a sample containing 18% Zr0Ch and a copolymer of tetrafluoroethylene and methyl perfluoro-3-oxa-1-heptenoate with an ion exchange capacity of 2.0 meq. The fabric B was immersed in an ethanol solution containing 3%/g of polymer for 20 minutes and then dried in an air oven at 70°C for 30 minutes to obtain a woven fabric B having a hydrophilic coating on its surface.

On the other hand, a copolymer of tedrafluoroethylene and methyl perfluoro-3-oxa-1-heptenoate, which has an ion exchange capacity of 1.50 milliequivalents/gram, is molded by T-die extrusion to a thickness of A fluoropolymer film having a diameter of 140 μm was obtained.

Next, the two types of woven fabrics A and B were layered on the fluorine-containing polymer film cut into a size of 20 cm x 2 Gcm, sandwiched between two biaxially stretched polyester films, and pressed at 5 kg/cm using a flat plate press in each case. Rin 2
．． After pressing at 180°C for 10 minutes, the polyester film for mold release was peeled off and two types of ion exchange membrane A (comparison Example 1) and ion exchange membrane B (
Example 1) was obtained.

Next, these ion-exchange membranes were immersed in a 25% by weight aqueous sodium hydroxide solution at 80°C for 18 hours, and after hydrolysis, samples of 5c intestine x 5c intestine were cut out from ion-exchanged HA and B, respectively. Anode and R made of Rum2/T i02 with the exposed surface facing the anode side.
It was installed in an electrolytic cell having a low overvoltage cathode made of u/Xi, and electrolysis of saline water was carried out at 80° C. and 25 A/dm2.

The concentration of salt water on the anode side was maintained at 3.5N, and the concentration of produced caustic soda was maintained at 35% while supplying water to the cathode side. After 7 days, the sliding voltage of the electrolytic cell was 3.21 V for ion exchange membrane A and 3.18 V for ion exchange membrane B, demonstrating the superiority of ion exchange membrane B of the present invention. The current efficiency was 84.0% in all cases.

Comparative Example 2 Tetrafluoroethylene and perfluoro-3-oxa-
A fluoropolymer copolymer with methyl 1-heptenoate and having an ion exchange capacity of 1.55 milliequivalents/gram was obtained by T-die extrusion molding to obtain a fluoropolymer film a having a thickness of 110 μm, In the same manner, a fluoropolymer film b having a thickness of 30 μm was obtained.

In the same manner as in Example 1, a fluoropolymer film,
Woven fabric B and film b were laminated in this order to obtain an ion exchange membrane in which woven fabric B was completely embedded.

Using a membrane obtained by hydrolyzing this membrane in the same manner as in Example 1, electrolysis of saline water was performed. The sliding voltage of the electrolytic cell after 7 days was 3.28V.

Current efficiency was 93.5%.

Example 1 and Comparative Example 2 (woven fabric is completely embedded)
Comparing the results, it was found that the sliding voltage of Example 1 was lower by about 120 mV.

Example 2 Using the ion exchange membrane B produced in Example 1, a paste of ZrO2 fine particles with a particle size of 1 to 10 μm was made into a paste using an aqueous solvent was spray coated on both sides of the membrane, and then dried.
After adhering Z r02 of g/s2, it was pressed with a pair of roll presses heated to 140°C, and Z r0 was applied to the film surface.
A porous layer consisting of 2 particles was formed.

Next, electrolysis of saline solution was performed using the membrane obtained by hydrolysis in the same manner as in Example 1. After 7 days, the sliding voltage of the electrolytic cell was 2.98V, and the current efficiency was 94%.The 0M rotation, which had continued stable operation for 80 days, was stopped, the electrolytic cell was disassembled, and the membrane was observed. There was no peeling or cracks or pinholes in the fluoropolymer film.

Example 3 Tetrafluoroethylene and perfluoro-3=oxa-
It is a copolymer with methyl 1-heptenoate and has an ion exchange capacity of 1.20 mm! /g of film a with a thickness of 30μ and the same ion exchange capacity of 1.55 milliequivalents/
Film b with a thickness of 140 μm and an ion exchange capacity of 1.15 meq/g of tetrafluoroethylene and perfluoro(3,8-dioxa-4-methyl-7-
octensulfonyl fluoride) and a copolymer of tetrafluoroethylene and methyl perfluoro-3-oxa-1-heptenoate from a 2=3 weight ratio blend with an ion exchange capacity of 1.55 meq/g. A fluorine-containing polymer laminated film in the above order was obtained by extrusion molding a film having a thickness of 20 μm.

Next, 10 PTFE monofilaments (10 denier) were twisted together to form warp and weft multifilaments with a denier of 100, to obtain a plain-woven fabric with a density of 85 threads/inch.

The open area ratio of this woven fabric was 48%, and the thread intersection thickness measured with a dial gauge was 110 to 120 μm. A part of the woven fabric was cut into a size of 20cm x 200mm and mixed with 20% lithium perfluoro-n-octoate, tetrafluoroethylene and perfluoro(3,8-dioxa-4-methyl-7-octensulfonic acid). The sample was immersed in an ethanol solution containing 5% of a copolymer with an ion exchange capacity of 1.2 meq/g for 15 minutes, and then dried in an air oven at 50°C for 1 hour to form a wood-philic coating on the surface. Obtained woven fabric.

Next, the above-mentioned woven fabric was stacked on the blend layer side, sandwiched between two stretched polyester films, and pressed using a flat plate press at 5 kg/cm2 at 200°C for 5 minutes, cooled, and the Ill type polyester film was peeled off. An ion exchange membrane was obtained in which the woven fabric was exposed over the entire surface of the membrane by an average of 7 to 8 μm.

Next, this membrane was immersed in a 25% weight sodium hydroxide aqueous solution at 30° C. for 16 hours to be hydrolyzed.

A sample of 5cs
It is installed in an electrolytic cell with two anodes and a low overvoltage cathode made of Ru/Ru, and the distance between the two electrodes is 0.55 m or less, and salt is heated at a current density of 30 A/d while maintaining the liquid temperature at 80°C. Performed water electrolysis.

The liquid concentrations in the negative and positive polarity chambers were the same as in Example 1. The sliding voltage of the electrolytic cell after 7 days is 3. llV and current efficiency are both 87
．． It was 0%.

Example 4 A plain-woven cloth with a weaving density of 150 wood/inch was obtained by using multifilaments of 30 denier monofilaments made of PTFE and twisting them together as warp and weft threads and 80 threads.

The open area ratio of this woven fabric was 24%, the thickness of the woven fabric measured with a dial gauge was 80 μm, and the thickness at the intersection of the threads was 120 μm. Cut a part of the woven fabric to 20cm x 20cm,
20% lithium perfluoro-n-octoate, tetrafluoroethylene and perfluoro(3,8-dioxa-
It was immersed for 15 minutes in an ethanol solution containing 5% of the polymer with an ion exchange capacity of 1.2 meq/g, and then heated in an air oven at 50°C for 1 hour. After drying for hours, a woven fabric with a hydrophilic coating on one surface was obtained.

On the other hand, T
A fluoropolymer film having a thickness of 150 μm was obtained by molding by die extrusion.

Next, the woven fabric was layered on the fluorine-containing polymer cut into 20cm x 20cm squares, sandwiched between two stretched polyester films, and pressed at 2,200°C for 5 minutes using a flat plate press, followed by cooling. Peel off the mold release polyester film, and the woven fabric covers the entire surface of the film.
An ion exchange membrane with only 10 μm exposed was obtained.

Next, this membrane was immersed in a 25% by weight aqueous sodium hydroxide solution at 90° C. for 18 hours to be hydrolyzed.

The ion exchange membrane cut out from the sample of the 5c layer
It was assembled into an electrolytic cell having two anodes and a low overvoltage cathode made of Ru/i, and electrolysis of saline water was carried out at 80° C. and 20 A/d2.

The concentration of salt water on the anode side was maintained at 3.5N, and the concentration of produced caustic soda was maintained at 35% while supplying water to the cathode side. 7
After several days, the sliding voltage of the electrolytic cell was 3.31 V, and the current efficiency was 85.0%.

Example 5 The floating fabric described in Example 4 was used, but with an average particle size of 0.2μ
It consists of 35% β-silicon carbide, a copolymer of tetrafluoroethylene and perfluoro(3,8-dioxa-4-methyl-7-octensulfonic acid), and has an ion exchange capacity of 1.0 meq/ grams of polymer 4%
The fabric was immersed in an ethanol solution containing the following for 15 minutes and then dried in an air oven at 50°C for 1 hour to obtain a woven fabric with a hydrophilic coating on its surface.

Using a membrane prepared in the same manner as in Example 4 except for using the above-mentioned woven fabric, saline solution electrolysis was performed. As a result, the sliding voltage of the electrolytic cell after 3 days was 3.30 V, and the current efficiency was 85 .0
%Met.

Example 6 An ion exchange membrane with the same specifications as in Example 4 except that the woven fabric was exposed to 80 to 70 μm over the entire membrane was prepared, and as a result of electrolysis of saline water using this membrane, an electrolytic cell was obtained after 3 days. The sliding voltage was 3.28V, and the current efficiency was 35.5%.

Example 7 A plain-woven cloth with a weaving density of 100 filaments/inch was obtained using multifilaments with a denier number of 50 made by aligning and twisting five monofilaments of 10 denier made of PTFE as warp and weft yarns.

The open area ratio of this woven fabric was 41%, the thickness of the woven fabric measured with a dial gauge was 70 μm layer, and the thickness at the intersection of threads was 80 μm.

An ion exchange membrane was prepared in the same manner as in Example 4 except for using this woven fabric, and the result of electrolysis of saline solution was that the sliding voltage of the electrolytic cell after 1 day was 3.21 V, and the current efficiency was was 95.5%.

Example 8 10 denier monofilament 10 made of PTFE
A plain-woven cloth with a weave density of 70 wood/inch was obtained by using multifilaments of denier 100, which were made by pulling and twisting books, as warp and weft threads.

The open area ratio of this woven fabric was 42%, and the thread intersection thickness measured with a dial gauge was 85 μm.

On the other hand, T A fluoropolymer film having a thickness of 35 μm and 80 ILm was obtained by molding using the die pressing method.

The above two types of films were laminated at a temperature of 180° C. using a roll press to obtain a two-layered fluoropolymer film.

Next, the woven fabric is layered on the polymer side of a two-layered fluoropolymer film having an ion exchange capacity of 1.50 meq/g, and sandwiched between biaxially stretched polyester films.
After pressing at 5 kg/cm2 using a flat plate press at 200° C. for 5 minutes, the film was cooled and the release polyester film was peeled off to obtain a film in which the woven fabric was exposed by an average of 5 μm over the entire surface of the film.

15% Zr0Ch on both sides of the film thus obtained.

An aqueous ethanol solution containing 5% of a copolymer of tetrafluoroethylene and perfluoro(3,8-dioxa-4-methyl-7-octenoic acid sulfonic acid) was spray applied and dried on both sides of the membrane.

15g/+s2 (1) After attaching Zr0Ch,
The membrane was dried in an air oven at 90°C for 40 minutes to obtain an ion exchange membrane having a wood-philic coating on the surface of the membrane and woven fabric.

Next, this membrane was immersed in a 25% by weight aqueous sodium hydroxide solution at 90°C for 18 hours to be hydrolyzed, and then 5cm
c The ion exchange membrane from which the intestine sample was cut was placed in an electrolytic cell with a RuO2/TiO2 anode and a low overvoltage cathode made of Ru/Old, with the exposed surface of the woven fabric facing the anode side, and heated at 90°C and 30A/dm2. Saline electrolysis operation was carried out at

The concentration of salt water on the anode side was maintained at 3.5N, and the concentration of produced caustic soda was maintained at 35% while supplying water to the cathode side. 7
After a few days, the sliding voltage of the electrolytic cell was 2.98V, and the current efficiency was 8B, 5%.

Example 9 A membrane was produced in the same manner as in Example 8, except that the woven fabric was exposed from the shoe surface by an average of 40μ, and electrolysis of saline water was performed using the membrane obtained by hydrolysis under the same conditions. The sliding voltage of the electrolytic cell after 4 days was 2.114V, and the current efficiency was 88.5%.
Met.

Example 1O 10 denier monofilament 10 made of PTFE
A plain-woven cloth with a weave density of 40 threads/inch was obtained by using multifilaments of denier 100, which were made by pulling and twisting books, as warp and weft threads.

This woven fabric had an open area ratio of 63%, and the thread intersection thickness measured with a dial gauge was 85 μm layer.

A membrane was produced in exactly the same manner as in Example 8, except for using the above-mentioned woven fabric, and this membrane was hydrolyzed under the same conditions, and the resulting membrane was used for electrolysis of saline solution. The sliding voltage of the electrolytic cell after 4 days was 2.93 V, and the current efficiency was 86.0%.

Example 11 20 denier monofilament made of PTFE A multifilament of denier A8O made by aligning and twisting four pieces of wood was used as the weft, and a denier number of 40 was made by aligning and twisting four pieces of wood and a 10 denier monofilament made of PTFE.
Multifilaments were used as warp threads to obtain entangled fabrics having warp and weft weave densities of 3B/inch and 45 threads/inch, respectively.

On the other hand, T Fluoropolymer films having a thickness of 30 μm and a thickness of 100 μm were obtained by molding by die extrusion.

The above two types of films were rolled into m layers at a temperature of 200° C. to obtain a two-layered fluoropolymer film.

Next, the woven fabric is layered on the polymer side of a two-layered fluoropolymer film having an ion exchange capacity of 1.60 meq/g, and sandwiched between biaxially stretched polyester films.
After pressing at 5 kg/c for 5 minutes using a flat plate press at 2,200°C, it was cooled and the release polyester film was peeled off to obtain a film in which the woven fabric was exposed by an average of 5 μ over the entire surface of the film. .

Zr with a particle size of 1 to 10 μm is coated on both sides of the film thus obtained.
After making a paste of O2 fine particles with an aqueous solvent, spray coating, drying, and depositing 20 g/layer 2 of Zr(h) on both sides of the membrane, the membrane surface was pressed with a pair of rolls heated to 140°C. A non-conductive porous layer of ZrO2 was formed in a semi-buried state.

Next, this membrane was immersed in a 25% by weight aqueous sodium hydroxide solution at 80°C for 18 hours to be hydrolyzed, and then
The ion exchange membrane cut out from the sample of the table was placed in an electrolytic cell with a RuO2/TiO2 anode and a low overvoltage cathode made of Ru/Old, with the side where the woven fabric was exposed facing the anode side, and heated to 80°C and 30A/da2. electrolysis of saline solution was carried out.

The concentration of salt water on the anode side was maintained at 3.5N, and the concentration of produced caustic soda was maintained at 35% while supplying water to the cathode side. 7
The sliding voltage of the electrolytic cell after 3 days. OOV, and the current efficiency was 88.0%.

Example 12 Using the woven fabric described in Example 11, Zr0C1218%
, is a copolymer of tetrafluoroethylene and methyl perfluoro-3-oxa-1-heptenoate, and has an ion exchange capacity of 2.0 meq/g. It is immersed in an ethanol solution containing 5% polymer for 20 minutes, and then immersed in air. The fabric was dried in an oven for 30 minutes to obtain a woven fabric with a wood-loving coating on the surface.

An ion exchange membrane was prepared in the same manner as in Example 11 except that the above-mentioned woven fabric was used, and the membrane was hydrolyzed in the same manner as in Example 11 to perform electrolysis of saline solution. After 7 days, the sliding voltage of the electrolytic cell was 2.15 V, and the current efficiency was 88.0%.

Example 13 An ion exchange membrane was prepared in the same manner as in Example 12 except that the woven fabric was exposed at a height of 40 to 50 μm. Electrolysis of saline solution was carried out using a hydrolyzed membrane according to the method. The sliding voltage of the electrolytic cell after 7 days was 2.93V, the current efficiency was 8B,
It was 0%.

Example 14 A 100-denier monofilament made of PTFE was twisted to form warp and weft yarns to obtain a tangle-woven fabric with warp and weft weave densities of 52 yarns/inch and 26 yarns/inch, respectively. The open area ratio of this woven fabric was 56%, and the thickness at the intersection of the threads measured with a dial gauge was 150 μm. Film formation was carried out in the same manner as in Example 12, except that the above woven fabric was used.
Electrolysis of saline solution was performed using the membrane obtained by hydrolysis. The sliding voltage of the electrolytic cell after 3 days was 2.98 V, and the current efficiency was 86.5%.

Claims (7)

[Claims] (1) A high-density porous base material made of fluorine-containing polymer threads with a thread diameter of 10 to 300 deniers and a thread density of 40 threads/inch or more, with a part of it exposed from the anode side surface of the membrane. embedded in the fluoropolymer film that makes up the membrane,
A fluorine-containing ion exchange membrane for electrolysis, characterized in that at least the exposed surface of the porous base material has a hydrophilic coating. (2) the porous base material has a thickness of 10 to 300 μm,
The membrane according to claim (1), in which 1/100 to 2/3 of the membrane is exposed from the membrane surface. (3) The membrane according to claim (1) or (2), wherein the hydrophilic coating on the surface of the porous substrate is an inorganic oxide. (4) The membrane according to claim (1), (2) or (3), wherein the fluorine-containing polymer film constituting the membrane is made of a fluorine-containing polymer having a carboxylic acid group and/or a sulfonic acid group. (5) The fluorine-containing polymer film constituting the membrane has a fluorine-containing polymer film having a carboxylic acid group facing the cathode side and a carboxylic acid group located on the anode side having a larger ion exchange capacity than the above. Claims (1), (2) or (3) having a laminated structure with a fluoropolymer film
) membrane. (6) The fluoropolymer film constituting the membrane has a laminated structure of a fluoropolymer film with carboxylic acid groups facing the cathode side and a fluoropolymer film with sulfonic acid groups located on the anode side. Claims with (1)
), (2) or (3). (7) The membrane according to any one of claims (1) to (6), wherein the fluorine-containing ion exchange membrane is used for alkali chloride electrolysis to produce alkali hydroxide and chlorine.