JP2000256486A - Reinforced cation exchange membrane - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a cation exchange membrane made proof against leak of an anolyte from its elution pores when used in an electrolytic cell, by making it contain a plain-weave reinforcing woven fabric comprising reinforcing yarns and sacrifice yarns or comprising reinforcing yarns alone, and making it have a cross section in which the sacrifice yarn elution holes are flat in the direction of the plane of the membrane. SOLUTION: This is an ion exchange membrane containing a plain-weave reinforcing woven fabric made from reinforcing yarns comprising polyetetrafluoroethylene, having an aspect ratio of 2-20 and woven at a mount of 4-20 and sacrifice yarns comprising a polyethylene terephthalate multifilament, having a thickness of 20-50 denier and a filament count of 4-8 in a ratio of the mount of the reinforcing fibers to that of the sacrifice yarns of 1/(2 to 10), having a cross section in which the sacrifice elution holes are flat in the direction of the plane of the membrane, and of which the aperture ratio is made 70-90%. It is desirable that after having been woven, the reinforcing fabric is subjected to a flattening treatment at 200 deg.C or above in order to improve the flatness of a cross section of a sacrifice thread and a cross section of the reinforcing yarn, and therefore it has a thickness of 30-80 μm after it is treated. A multi-layer ion exchange membrane having a high current efficiency and a low electric resistance is useful in alkali electrolysis.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion exchange membrane for electrolysis, and more particularly, to an ion exchange membrane reinforced with a woven fabric composed of a reinforcing yarn and a sacrificial yarn used for electrolysis of an alkali chloride aqueous solution. In particular, the present invention relates to a fluorine-containing ion exchange membrane which is excellent in electrochemical properties and mechanical strength by preventing leakage of anolyte from the sacrificial yarn elution hole in the membrane to the outside.

[0002]

2. Description of the Related Art As a solid electrolyte used for an alkali metal chloride electrolytic membrane, at least two layers of a perfluorocarbon carboxylic acid layer and a perfluorocarbon sulfonic acid are used.
It is known in the art that a laminate film having more than two layers is effective. These ion exchange membranes are required to have high current efficiency, low membrane electric resistance, and easy handling, and for that purpose, it is essential that the membrane has sufficient mechanical strength. However, since these perfluorocarbon films have low tear strength and cannot withstand long-term use as they are, usually a reinforcing material such as a reinforced woven fabric is embedded in the film to improve the tear strength.

However, a general reinforcing material is ion-impermeable, and embedding the reinforcing material in the film results in a decrease in an effective current-carrying area and a corresponding increase in an electrolysis voltage during electrolysis. The tendency becomes more remarkable as the structure is made denser to enhance the reinforcing effect, or as the yarns constituting the reinforcing material are made thicker. Further, thickening the yarn means an increase in the amount of resin of the film for enclosing the yarn itself, which leads to an increase in the electric resistance of the film.

Various attempts have heretofore been made to overcome the relationship between the high mechanical strength of such contradictory films and the low electrical resistance of the films. First, the fabric structure is roughened, and the opening ratio (window (inter-fiber gap) with respect to the entire area of the fabric structure)
(In which the total area is expressed as a percentage) has been attempted. Generally, in alkali metal chloride electrolysis under a high current density, if the aperture ratio is set to 70% or less, the effective energization area of the film becomes insufficient, and not only the electric resistance of the film increases but also the movement of impurities locally increases. As a result, the current efficiency of the film decreases. Therefore, it is generally considered that an aperture ratio of 70% or more is necessary.

[0005] In an attempt to obtain a reinforced woven fabric having both high mechanical strength and a large opening ratio, the woven fabric was used as a woven fabric having high misalignment resistance, and the yarn used was limited to a specific denier yarn of perfluoropolymer multifilament. After weaving a membrane (JP-A-61-7338) and then a plain woven fabric in which a perfluoropolymer reinforcing yarn and a sacrificial yarn dissolvable with an alkaline solution are mixed, the sacrificial yarn is dissolved and only the remaining reinforcing yarn is removed. A method of inserting between laminated films has been proposed (JP-A 64-55393). However, even if these methods are used, the aperture ratio is limited to about 70%, and if an attempt is made to achieve an aperture ratio higher than that, misalignment of the woven fabric opening occurs, and the production of the woven fabric or the lamination film becomes difficult. Insertion becomes difficult.

Further, instead of using a sacrificial yarn, a woven fabric using a commercially available PTFE porous yarn that has been improved to increase the apparent specific gravity has been proposed. There is a limit to the conversion (Japanese Unexamined Patent Publication No. 3-21742).
7). Therefore, a perforated polymer reinforced yarn, and a plain woven woven fabric obtained by mixing sacrifice yarns that can be dissolved in a chemical treatment such as an acid or an alkali when used in an electrolytic cell, is inserted between the laminated films, Thereafter, a method of dissolving the sacrificial yarn in the woven fabric by the above-mentioned chemical treatment has been proposed (Japanese Patent Laid-Open No. 1-3).
08435, JP-A-63-113029). This woven fabric has good misalignment resistance even when the opening ratio of the reinforcing yarn portion is high by mixing the sacrifice yarn. Further, since the sacrificial yarn is dissolved in the film, voids (hereinafter, sacrificial yarn elution holes) are generated in the film in portions originally occupied by the sacrificial yarn. Also, by bringing the position of the woven fabric in the membrane close to the side of the membrane that comes into contact with the anolyte, minute cracks (hereinafter referred to as through holes) on the membrane surface
By introducing the anolyte into the inside of the membrane through the through-holes, it is possible to fill the anolyte in the portion where the permeation of ions is shielded by the reinforcing yarn or in the layer where the sacrificial yarn elution hole is present. Can reduce the electric resistance.

However, these sacrificial yarn elution holes are connected to the entire woven fabric, that is, the entire membrane, and when used in the electrolytic cell, a part of the anolyte is placed outside the flange that fixes the membrane to the electrolytic cell. There is the problem of seepage and anolyte leakage from the edge of the membrane. The leakage of the anolyte outside the cell promotes corrosion of the electrolytic cell and deterioration of the gasket. For this reason,
When mounting the membrane in the electrolytic cell, a method is adopted in which a gasket is coated with a paste-like silicon sealant or fluorine-based grease to block the elution hole in the flange part,
The application takes time depending on the shape of the electrolytic cell, and when the coating thickness is not uniform, there is a problem that the sealant or the grease protrudes into the energized portion or the electrolytic cell.

[0008]

DISCLOSURE OF THE INVENTION The present invention relates to a plain weave reinforced fabric having an elution hole in the membrane in which traces of the dissolution of sacrificial yarn can be formed, and no leakage of anolyte from the elution hole to the outside of the membrane when using an electrolytic cell. It is an object to provide an ion exchange membrane using a cloth.

[0009]

Means for Solving the Problems The inventors of the present invention have made intensive studies to solve the above-mentioned problems, and as a result, have determined that the cross-sectional shape of the elution hole formed in the dissolution trace of the sacrificial yarn constituting the plain-woven reinforced woven fabric is in the direction of the membrane plane. In order to solve the above-mentioned problems, it has been found that the flattening has a remarkable effect, and the present invention has been accomplished.

Hereinafter, the present invention will be described in detail. The plain-woven reinforced woven fabric of the present invention is inserted between layers of the laminated electrolytic membrane as a reinforcing material and plays a role as a reinforcing material for the membrane, and is a woven fabric composed of reinforcing yarns and sacrificial yarns. After dissolving the sacrificial yarn by a method described later, the reinforcing yarn has a function of maintaining strength of the electrolytic membrane and suppressing a dimensional change as a remaining yarn constituting the woven fabric.
In addition, it is preferable that the membrane be used in an electrolytic cell, for example, one that is resistant to high temperature in salt electrolysis and in the presence of chlorine, sodium hypochlorite, and a high concentration of sodium hydroxide. As a yarn satisfying these mechanical properties, heat resistance and chemical resistance, for example, a perfluorocarbon-based yarn is preferable. Further, in consideration of the improvement in the tear strength of the membrane, a preferred form is a 50 to 200 denier tape obtained by slitting a high-strength porous sheet made of polytetrafluoroethylene disclosed in JP-B-56-17216 into a tape shape. Yarn may be used.

The reinforcing yarn cross section preferably has an appropriate aspect ratio (an aspect ratio defined by the width / thickness of the yarn) for the purpose of securing the bending strength of the membrane and reducing the thickness of the reinforced woven fabric. , The ratio of which is 2 to 20, especially 3 to
10 is preferred. The flattening of the yarn is usually performed by calendering between heated metal rolls after weaving. A part or all of the sacrificial yarn is dissolved in use in an electrolytic cell or by an acid or alkali chemical treatment, and pores (sacrificial yarn elution holes) are generated in the dissolution trace. Polyethylene terephthalate, rayon, cellulose or the like is used as a material for the sacrificial yarn, and a wide variety of polyethylene terephthalate multifilaments is particularly preferable.

In order to prevent leakage of the anolyte from the sacrificial thread elution hole, it is necessary to crush the sacrificial thread elution hole at the flange portion of the electrolytic cell and completely close the opening to the outside of the flange. In the present invention, the shape of the sacrificial yarn elution hole which is easily crushed at the electrolytic cell flange portion must be flat in the membrane plane direction. Accordingly, it is necessary to control the aggregate form of the multifilaments so that the cross section of the multifilament sacrificial yarn constituting the reinforced woven fabric is also flat as a whole in the plane direction of the woven fabric. Here, the section that is flat in the membrane (woven cloth) plane direction means that the cross-sectional shape is substantially elliptical, and the major axis that defines the ellipse is substantially parallel to the membrane (woven cloth) plane. means. A particularly preferred form of multifilament assembly is a form in which the filaments are juxtaposed in the plane of the woven fabric without overlapping each other in the thickness direction of the woven fabric, as shown in FIG.

One of the methods for controlling the form of aggregation of the multifilament sacrificial yarn is to determine the number of twists of the sacrificial yarn at the time of weaving. Warp is 1m in consideration of weaving
It is preferred that the weft be woven with 0 to 350 twists per non-twist. If the number of twisted yarns is too large, the overlap between the single yarns due to twisting increases, and the flatness of the sacrificial yarn cross section is lost. The warp can be provided with a gluing or an interlacing if necessary.

Furthermore, by making the number of filaments 4 to 8 and making the cross section circular, the sacrificial yarn after weaving the reinforced woven fabric can be arranged in parallel in the plane of the woven fabric. If the number of filaments is smaller than this, the number of denier per filament increases, and even if the filaments are arranged in parallel, the flatness of the cross section of the sacrificial yarn is inferior. On the other hand, if the number of filaments is too large, the overlap between filaments increases even if the number of twisted yarns is low. Further, in order to increase the number of contact points between the filaments and leave a continuous space in the dissolution trace of the sacrificial yarn, it is desirable that the filament has a circular cross section.

The thickness of the sacrificial yarn varies depending on the thickness and the opening ratio of the whole woven fabric, but is usually preferably 20 to 50 denier. 2
If it is smaller than 0 denier, a sufficient space as an elution hole cannot be obtained. On the other hand, when the denier is larger than 50 denier, the thickness of the whole woven fabric becomes large, and it becomes difficult to crush the sacrificial yarn elution hole. In the woven fabric of the present invention, the number of reinforcing yarns to be driven is 4 to 20 yarns / inch depending on the thickness of the reinforcing yarn to be used and the opening ratio of the target woven fabric. Further, when limited to 100 to 150 denier yarn, 8 to 16 yarns / inch is preferable. In addition, it is essential that the ratio of the number of driving of the reinforcing yarn to the number of the sacrifice yarn is an even-number multiple of the sacrifice yarn. In the case of an odd number, after the sacrificial yarn is melted, the entanglement between the warp and the weft of the reinforcing yarn is lost, and the two only intersect with each other two-dimensionally, which is not practical because a plain weave structure is not formed. The ratio is 2 for 1 reinforcing yarn.
It is 10 times. From the viewpoint of weaving and the problem of misalignment, the total number of reinforcing yarns and sacrificial yarns is preferably 60 to 100 / inch.

The opening ratio of the woven fabric based on the inter-fiber gap of the reinforcing yarn after elution of the sacrificial yarn is preferably 70 to 90%, particularly preferably 80 to 90%.
90% is appropriate. If it is less than 70%, not only does the electrolysis voltage of the membrane increase, but also the substantial current density of the portion separated by the reinforcing yarn increases, which may cause a decrease in current efficiency. On the other hand, if it is more than 90%, the effect of reinforcing the membrane by the woven fabric is reduced.

The aperture ratio can be generally confirmed by taking a photograph using an optical microscope. After weaving, the reinforced woven fabric obtained by the above-mentioned method is preferably subjected to a smoothing treatment at a temperature of 200 ° C. or more, in order to further improve the flatness of the sacrificial yarn cross section and the reinforcing yarn cross section, and the thickness after the treatment is preferable. Is 30 to 80 μm. If the woven fabric is too thick, the flatness of the cross section of the sacrificial yarn may be inferior and the smoothness of the film may be deteriorated. Although there is no particular limitation on the smoothing of the woven fabric, a hot roll, a hot plate or the like is generally used. In particular, a preferred method is a method of continuously passing and rolling between two heated rolls while applying tension in the warp direction of the woven fabric. Furthermore, if the warp and the weft of the polyethylene terephthalate sacrificial yarns have different heat shrinkage rates, it is possible to prevent the multifilament sacrificial yarns that were arranged in parallel at the time of weaving from overlapping with each other due to the heat shrinkage during the smoothing process. For example, since the warp can control the shrinkage by tension, a polyethylene terephthalate yarn having a general boiling water shrinkage of 6% or more can be used, and a low shrinkage polyethylene terephthalate having a boiling water shrinkage of 3% or less can be used for a weft to which no tension can be applied. Yarn can be used.

It is useful for the ion exchange membrane for alkali chloride electrolysis to have a multilayer structure of a layer composed of a carboxylic acid group having a high electric resistance but high current efficiency and a layer composed of a sulfonic acid group having a low electric resistance. Some are well known.
Also, as shown in JP-A-5-98486, a three-layer structure film having a specific water content is important for providing a film having a low electrolytic voltage, high current efficiency and high strength.

The carboxylic acid-containing first layer facing the cathode used in the present invention comprises a copolymer of at least two kinds of monomers selected from the following (formula 1) and (formula 2). . CF ₂ = CXaXb (Formula 1) (where Xa, Xb = F, Cl, H, or CF ₃ ) CF ₂ = CF (OCF ₂ CFXc) nO (CF ₂ ) mY (Formula 2) (where Xc = F Or CF ₃ , m = 1 to an integer of 1 to 3, n
= 0 or 1, Y is a precursor which is hydrolyzed in an alkaline medium to form a carboxylic acid group, and includes a carboxylic acid ester group —COOR (R = lower alkyl group having 1 to 4 carbon atoms), a cyano group —CN, It is selected from acid halide-COZ (Z = halogen atom). Usually, preferably, the following compounds are exemplified as the monomer represented by (Formula 1). As the monomer represented by CF ₂ ＣＦCF ₂ (Formula 2), a carboxylate group is employed. The following are shown as examples. CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ COO
CH ₃ CF ₂ ＣＦCFOCF ₂ CF ₂ COOCH ₃ CF ₂ ＣＦCFOCF ₂ CF ₂ CF ₂ COOCH _{3 As the} ion exchange capacity, high current efficiency and reduction of the salt concentration in the generated alkali hydroxide can be obtained by the following formula (2). )
Although it depends on the structure of the monomer, the hydrolysis conditions and the alkali concentration, for example, a copolymer of CF ₂ = CF ₂ is preferably 0.7 to 0.95 meq / g. Further, the thickness of the first layer is 5 to 40 µ, preferably 10 to 30 µ.

The second layer having a sulfonic acid group is composed of a copolymer of two types of monomers selected from the following (Formula 1) and the following (Formula 3). CF ₂ = CF (OCF ₂ CFXc) nO (CF ₂ ) mW (Formula 3) (where Xc = F, or CF ₃ , m = 1 to ₃ ;
= 0, 1 or 2, and W is a precursor which is hydrolyzed to a sulfonic acid group in an alkaline medium, and is a sulfonyl halide group —SO ₂ Xd (Xd = F, Cl, Br) or an alkyl Sulfonic acid-SO ₂ R (R
= Lower alkyl group having 1 to 4 carbon atoms). Usually, a monomer having a sulfonyl fluoride group is preferably used as the monomer of the formula (3), and the following monomers are shown as typical examples. CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ CF ₂ S
O ₂ F CF ₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ SO ₂ F CF ₂ = CFOCF ₂ CF ₂ CF ₂ SO ₂ F CF ₂ = CFOCF ₂ CF ₂ SO ₂ F for the purpose of reducing the salt concentration in the alkali hydroxide to be produced, the structure and hydrolysis conditions (equation 3), but still different by alkali concentration, for example in a copolymer of CF ₂ = CF ₂ 0.9~ 1.
1 meq / g is preferred. In order to prevent delamination during electrolysis with the first carboxylic acid layer, it is preferable that the difference in ion exchange capacity with the first layer is as small as possible. Further, the thickness of the second layer is 60 to 100 μm, and preferably 70 to 90 μm, because the strength is dominant.

The third layer having a sulfonic acid group is preferably selected from a polymer having the same structure as that of the second layer, and is higher than the second layer in order to reduce the same ion exchange capacity or electrolytic voltage. Ion exchange capacity is preferred. Further, the thickness of the third layer is preferably 10 to 30 μm in order to effectively form through-holes necessary for infiltrating the anolyte into the sacrificial yarn elution holes on the membrane surface. In the case of 30 μm or more, no through hole is formed, and the anolyte is not supplied to the elution hole, so that the membrane resistance increases.

The film of the present invention can be produced by known techniques, for example, hot press molding, roll molding, extrusion molding, and the like. Particularly preferred is a method in which the first layer and the second layer are formed by coextrusion. The third layer is formed into a film by a single-layer extrusion method, and is passed through a flat plate or drum having a heating source and a vacuum source disclosed in Japanese Patent Application Laid-Open No. 56-99234 and having a large number of pores on the surface. A heat-resistant release paper having air temperture is laminated and laminated in the order of a third layer film, a calendered plain woven woven fabric, and a 2/1 composite film, and the air between the layers is reduced under reduced pressure at a temperature at which each polymer melts. It is a method of integrating while removing. Here, co-extrusion of the first layer and the second layer contributes to increasing the adhesive strength at the interface. In addition, the method of integrating under reduced pressure has the advantage that the thickness of the second layer on the reinforced woven fabric is larger than that of the hot press method, and the second layer is sufficiently penetrated into the third layer, so that it is easy to form a through hole in the membrane surface. .

The method of hydrolyzing the integrated laminate to form an ion-exchange membrane can be performed under known conditions. An example of a preferred method is a hydrolysis method using a water-soluble organic compound and MOH (M = alkali metal) as disclosed in JP-A-1-140987. The electrolyte membrane obtained by the above method may have an inorganic coating layer for preventing gas adhesion on the cathode side surface and the anode side surface as needed.
The coating layer can be formed by a known method, for example, a method disclosed in JP-A-3-137136 in which fine particles of an inorganic oxide measured in a binder polymer solution are applied by spraying. Is preferred.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to Examples and Comparative Examples.

[0025]

Example 1 A 900-denier tape yarn made of polytetrafluoroethylene (PTFE) was used as a reinforcing yarn.
Twist / m was twisted to form a thread. As a sacrificial yarn, a polyethylene terephthalate (PET) yarn having a boiling water shrinkage of 6% or more and 30 denier and 6 filaments is twisted at 200 turns / m, and a weft yarn having a boiling water shrinkage of 3% or less and 35 denier and 8 filaments is made of polyethylene terephthalate. (PE
T) The yarn was prepared without twisting. Using these yarns, a plain reinforced woven fabric was prepared in which the reinforcing yarn PTFE was 16 yarns / inch and the sacrificial yarn PET was 64 times / inch, which was four times the PTFE. The thickness of this woven fabric was 100 μ.

After weaving, the thickness of the woven fabric was smoothed to 68 μm by passing between two heated metal rolls. PTF of the woven fabric
The opening ratio of only the E-reinforced yarn was 75%. As a result of observation of the surface and cross section of this woven fabric, the cross-sectional shape of the multifilament sacrificial yarn was flat in the plane direction of the woven fabric, and both warp and weft yarns were in a form in which the filaments were juxtaposed without overlapping each other in the film thickness direction.

CF ₂ = CF ₂ and CF ₂ = CFOCF ₂ CF
(CF ₃ ) OCF ₂ CF ₂ COOCH ₃ copolymer (A) having an equivalent weight of 1100, and CF ₂ ＣＦCF ₂ and CF
₂ = CFOCF ₂ CF (CF ₃ ) OCF ₂ CF ₂ SO ₂ F copolymer (B) having an equivalent weight of 1030, and polymer (C) having an equivalent weight of 950 having the same structure as polymer (B) Prepare and use polymer (A) and polymer (B) with an apparatus equipped with two extruders, a co-extrusion T-die, and a take-off machine.
μ, a two-layer film (a) having a polymer (B) layer thickness of 90 μ was obtained. Further, a film (b) of 25 μm of the polymer (C) was obtained by a single-layer T-die.

Air-permeable release paper, film (b), reinforced woven fabric, and polymer (B) are placed on a woven fabric side on a drum having a heating source and a vacuum source inside and a large number of fine holes on the surface thereof. The two-layer films (a) are sequentially laminated so as to face
At a temperature of 30 ° C. and under a reduced pressure of −600 mmHg, integration was performed while excluding intermediate air to obtain a composite membrane. Equal amounts by weight in a mixed solution of a 50/50 parts by weight of water and ethanol 950 CF ₂ = CF ₂ and _{CF 2 = CFOCF 2 CF (CF} 3)
5 wt% of a fluorinated polymer having a sulfonic acid group obtained by hydrolyzing a copolymer of OCF ₂ CF ₂ SO ₂ F was dissolved. 20 wt% of zirconium oxide having a primary particle size of 0.02 μm was added to the solution, and a suspension was obtained which was uniformly dispersed by a ball mill. This suspension was applied to both surfaces of the composite membrane by a spray method and dried to form an inorganic layer.

This membrane is made of dimethyl sulfoxide (DMS)
O) 30 wt%, potassium hydroxide (KOH) 15 wt%
Is hydrolyzed at a temperature of 90 ° C. for 60 minutes in an aqueous solution containing
After washing with water, equilibration treatment was performed with 2% sodium bicarbonate at 25 ° C. After the hydrolysis, all the sacrificial yarns were dissolved, and the opening ratio of the membrane was 80%. Observation of the cross section of this film showed that the shape of the sacrificial yarn elution hole had the same flat shape as the multifilament sacrificial yarn constituting the reinforced woven fabric.

Further, when the surface of the film (b) was observed with an electron microscope, a fine crack was formed at the intersection of the sacrificial yarns. A low hydrogen overvoltage cathode is placed on the carboxylic acid side of the ion exchange membrane coated with the inorganic layer in the electrolytic cell having a current carrying area of 270 dm ² , and a low chlorine overvoltage anode is placed on the sulfonic acid side, without applying a silicone sealant via a gasket. It was tightened with a hydraulic press at a surface pressure of 18 kg / cm ² . Then, on the anode side, 205 g of aqueous sodium chloride solution
/ L while adjusting the alkali concentration on the cathode side to 32.
%, And electrolysis was performed under the conditions of 40 A / dm ² and a temperature of 90 ° C. During the electrolysis, no leakage of the anolyte solution from the surface and the cross section of the anode side membrane outside the flange was observed.

[0031]

Example 2 A 100-denier tape yarn made of polytetrafluoroethylene (PTFE) was used as a reinforcing yarn.
A plain reinforced woven fabric was woven in the same manner as in "Example 1", except that the yarn was twisted at 0 times / m. The thickness of this woven fabric was 80μ. Then, it was smoothed to 53 μm by a heating roll. The opening ratio of only the PTFE reinforcing yarn of the woven fabric was 78%.

As a result of observation of the surface and cross section of the woven fabric, the cross-sectional shape of the multifilament sacrificial yarn was flat in the plane direction of the woven fabric, and the filaments of both warp and weft yarns were arranged in parallel without overlapping each other in the film thickness direction. Met. Using this woven fabric, a composite membrane was produced under the same method and conditions as in "Example 1". As a result, the opening ratio of the membrane after hydrolysis was 81%. When the cross section of this film was observed, all the sacrificial yarns were dissolved, and the shape of the elution hole had the same flat shape as the multifilament sacrificial yarn constituting the reinforced woven fabric.

Further, when the surface of the film (b) was observed with an electron microscope, a fine crack was formed at the intersection of the sacrificial yarns. Thereafter, electrolysis was performed under the same conditions as in "Example 1". As a result, there was no leakage of the anolyte from the surface and the cross section of the anode-side membrane outside the flange during electrolysis.

[0034]

[Comparative Example 1] A 750-denier tape yarn made of polytetrafluoroethylene (PTFE) was used as a reinforcing yarn.
Twist / m was twisted to form a thread. As sacrificial yarn, 40 warp yarn shrinkage of 3% or less for both warp yarns and 30 denier 12 filament polyethylene terephthalate (PET) yarn
Twist of 0 times / m was applied. Using these yarns, reinforcing yarn P
TFE is 16 / inch, and sacrificial thread PET is 4
A plain woven mixed woven fabric was woven at a rate of 64 lines / inch.
After that, 100 μm is passed between two heated metal rolls.
The thickness was smoothed. The opening ratio of only the PTFE reinforcing yarn of the reinforced woven fabric was 75%.

As a result of observation of the surface and cross section of this woven fabric, the cross-sectional shape of the multifilament sacrificial yarn was not flat in the plane direction of the woven fabric, and the warp and weft yarns were close to a circle in which the filaments overlap in the film thickness direction. there were. Using this woven fabric, a composite membrane was produced under the same method and conditions as in "Example 1". As a result, the opening ratio of the membrane after hydrolysis was 78%.

When the cross section of this membrane was observed, all the sacrificial yarns were dissolved, and the shape of the elution hole had the same circular shape as the multifilament sacrificial yarns constituting the reinforced woven fabric. Further, when the surface of the film (b) was observed with an electron microscope, a minute crack was formed at the intersection of the sacrificial yarns. Thereafter, electrolysis was performed under the same conditions as in "Example 1". As a result, leakage of the anolyte from the anode-side membrane surface and the cross section outside the flange was observed before energization and during electrolysis, and a part thereof was crystallized in an icicle shape. .

[0037]

[Comparative Example 2] A polytetrafluoroethylene (PTFE) 100 denier tape yarn was used as a reinforcing yarn.
Twisting of 00 times / m was performed to form a thread. The sacrificial yarn is twisted at a rate of 200 times / m to a polyethylene terephthalate (PET) yarn having 30 denier 18 filaments and a W-shaped cross section, with a warp shrinkage of 6% or more, and a warp yarn of 6% or more.
The weft was prepared without twisting the same type of polyethylene terephthalate (PET) yarn as the warp. Using these yarns as they are, the reinforcing yarn PTFE is 16 yarns / inch, the sacrificial yarn PE
A plain woven mixed woven fabric was woven such that T was 64 times / inch, four times as large as PTFE. The thickness of this woven fabric was 85 μ.

After weaving, it was smoothed to a thickness of 54 μm by passing between two heated metal rolls. PTFE of the reinforced woven fabric
The opening ratio of only the reinforcing yarn was 75%. As a result of observing the surface and cross section of this woven fabric, the cross-sectional shape of the multifilament sacrificial yarn was not flat in the plane direction of the woven fabric. In addition, the filaments were dispersed and overlapped in the direction of film thickness in both warp and weft yarns, and were not arranged in parallel in the plane direction of the woven fabric. Using this woven fabric, a composite membrane was produced under the same method and conditions as in "Example 1". As a result, the opening ratio of the membrane after hydrolysis was 81%.

When the cross section of this film was observed, all the sacrificial yarns were dissolved, and the shape of the elution hole had the same circular shape as the multifilament sacrificial yarns constituting the reinforced woven fabric. Further, when the surface of the film (b) was observed with an electron microscope, a minute crack was formed at the intersection of the sacrificial yarns. Thereafter, electrolysis was performed under the same conditions as in "Example 1". As a result, leakage of the anolyte from the anode-side membrane surface and the cross section outside the flange was observed before energization and during electrolysis, and a part thereof was crystallized in an icicle shape. .

[0040]

The reinforcing woven fabric of the present invention flattens the shape of the sacrificial yarn elution hole in the plane of the woven fabric, so that the elution hole is easily crushed at the flange portion of the electrolytic cell, and the anolyte is discharged to the outside of the flange. It has the effect of preventing leakage. This eliminates the need for applying a silicone sealant or a fluorine-based grease, which has been conventionally applied, and makes it possible to easily mount the apparatus in an electrolytic cell.

[Brief description of the drawings]

FIG. 1 is a schematic partial cross-sectional view of a pre-hydrolysis ion exchange membrane of Example 1.

FIG. 2 is a schematic partial cross-sectional view of a pre-hydrolysis ion exchange membrane of Comparative Example 1.

FIG. 3 is a schematic partial cross-sectional view of a pre-hydrolysis ion exchange membrane of Comparative Example 2.

[Explanation of symbols]

 1 Polytetrafluoroethylene reinforced yarn 2 Polyethylene terephthalate sacrificial yarn

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) D03D 15/06 D03D 15/06 F-term (Reference) 4D006 GA16 KE12P KE16P KE18P MA03 MA07 MA09 MA10 MA13 MA24 MA31 MA40 MB12 MB15 MC03X MC28X MC30X MC48X MC72X MC74X NA45 NA46 NA50 NA54 PB12 4F071 AA26X AA27C AA27X AA30X AA46C AH19 FA05 FA06 FB01 FC07 4J002 AB01Y BD12W BD15W BD15X BD17W BE04W CF06A FAA14A01A04A04A04A04A04A04A04A14A CA01 DA24 EB04

Claims (6)

[Claims] 1. An ion-exchange membrane having a reinforcing yarn and a sacrificial yarn, or a plain-woven reinforcing woven fabric composed only of the reinforcing yarn, and having a sacrificial yarn elution hole whose cross section is flat in a membrane plane direction. 2. The ion exchange membrane according to claim 1, wherein the sacrificial yarn is made of polyethylene terephthalate multifilament, and a cross section of the sacrificial yarn is flat in a membrane plane direction. 3. The ion exchange membrane according to claim 1, wherein the number of twists of the warp is 0 to 350 times / m, and the weft is non-twisted. 4. The ion exchange membrane according to claim 1, wherein the sacrificial yarn has a thickness of 20 to 50 denier and comprises 4 to 8 circular cross-section filaments. 5. The ion exchange membrane according to claim 1, wherein the sacrificial yarn has a warp boiling water shrinkage of 6% or more and a weft boiling water shrinkage of 3% or less. 6. The ion exchange membrane according to claim 1, wherein the thickness of the plain woven woven fabric is 30 to 80 μm.