Woven fabric and manufacturing method for the same, diaphram for alkaline water electrolysis, and electrolytic cell for alkaline water electrolysis

Abstract

To provide a woven fabric that exhibits excellent ion permeability, ion permeability sustainability, and gas barrier property when used as a diaphragm for alkaline water electrolysis, and a method for manufacturing the same.SOLUTION: A woven fabric having a multifilament mainly composed of polyphenylene sulfide has an average single yarn diameter of the multifilament of 0.2 μm or more and 5.0 μm or less, and the number of single yarns is 5,000 or more and 400,000 or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a fabric, a diaphragm for alkaline water electrolysis using the same, and an electrolytic cell for alkaline water electrolysis.

Background Art

[0002] Polyphenylene sulfide (hereinafter sometimes abbreviated as PPS) has high heat resistance, chemical resistance, electrical insulation, and flame retardancy, and in addition, has excellent mechanical properties and moldability. Therefore, it is widely used as a metal substitute material and a material that can withstand extreme environments. Fibers made of polyphenylene sulfide utilize the above characteristics and are used in applications such as bag filters, papermaking canvases, electrical insulating papers, battery separators, and various diaphragms. In particular, by combining the heat resistance and chemical resistance of polyphenylene sulfide against high-concentration alkaline solutions and other characteristics with the self-supporting property, ion permeability, gas barrier property, and other characteristics of fabric materials, it is known that a fabric made of polyphenylene sulfide fibers can be used for diaphragms for alkaline water electrolysis.

[0003] Patent Document 1 proposes a PPS fiber structure made of a fabric of PPS fibers, and it is described that it has high gas barrier properties and excellent hydrophilicity as a separator cloth.

[0004] Further, Patent Document 2 proposes an electrolytic diaphragm using multifilament yarns having a specific fineness and a woven fabric having a specific cover factor, and describes the effects of improving electrolysis efficiency and being applicable to various treatment conditions.

[0005] Furthermore, Patent Document 3 proposes a polyphenylene sulfide fabric for water electrolysis having a specific functional group and element content, and it is described that it has excellent gas barrier properties as a diaphragm for an electrolytic cell for water electrolysis.

Prior Art Documents

Patent Documents

[0006] Patent Document 1 Japanese Patent Publication No. 2018-534441 Patent Document 2 Japanese Unexamined Patent Application Publication No. 2008-088449 Patent Document 3 Japanese Patent Publication No. 2019-513902 Summary of the Invention Problems to be Solved by the Invention

[0007] The PPS fiber structure described in Patent Document 1 achieves high performance in gas barrier properties and ion permeability by taking advantage of the bulkiness characteristic of staple fibers. However, as a result of investigations by the present inventors, it has been found that when used for a long time as a diaphragm for alkaline water electrolysis, the ion permeability tends to decrease.

[0008] In addition, although the electrolysis diaphragm made of a woven fabric described in Patent Document 2 improves the electrolysis efficiency by using a multifilament fabric having a specific configuration, the fabric having such a configuration has a high air permeability because it has voids between warp yarns and / or between weft yarns. Therefore, when used as a diaphragm for alkaline water electrolysis, the gas barrier property is not sufficient, and there is a problem that the purity of hydrogen gas is low due to the mixing of oxygen gas and hydrogen gas generated in the electrolytic cell. There is also a problem that a hydrogen explosion may occur.

[0009] Furthermore, although the multifilament fabric described in Patent Document 3 has high gas barrier properties, since it is composed of multifilaments having a large fineness, the unevenness formed between multifilaments and / or between single filaments is remarkable, so that bubbles of oxygen gas and / or hydrogen gas generated in the electrolytic cell easily adhere to the fabric. That is, the ion permeability tends to decrease over time.

[0010] An object of the present invention is to provide a fabric and a method for manufacturing the same, which exhibit excellent effects in terms of ion permeability, ion permeation persistence, and gas barrier properties when used as a diaphragm for alkaline water electrolysis. And this fabric can be suitably used for a diaphragm for alkaline water electrolysis and an electrolytic cell for alkaline water electrolysis.

Means for Solving the Problems

[0011] As a result of studying a diaphragm for alkaline water electrolysis using a fabric made of staple fibers disclosed in Patent Document 1 by the present inventors, it was presumed that the ion permeability might decrease over time due to the fuzz on the staple fibers. That is, it was presumed that bubbles of oxygen gas and / or hydrogen gas generated in the electrolytic cell adhered to the fuzz of the diaphragm, and the permeation of ions was inhibited as the bubbles increased around the diaphragm over time.

[0012] Therefore, as a result of studying based on this hypothesis, the present inventors found that when filaments (long fibers) were used instead of staple fibers (short fibers) that are likely to generate fuzz, the fuzz of the fabric was suppressed, and a decrease in ion permeability over time as a diaphragm could be suppressed. Furthermore, as a result of intensive studies by the present inventors, it was found that by using a multifilament having an average single-filament diameter and the number of single filaments within a specific range as the filament, excellent gas barrier properties and ion permeability are also obtained, and the present invention has been completed.

[0013] In order to solve the above problems, the present invention employs any of the following means. (1) A fabric having a multifilament mainly composed of polyphenylene sulfide, wherein the average single-filament diameter of the multifilament is 0.2 μm or more and 5.0 μm or less, and the number of single filaments is 5000 or more and 400000 or less. (2) The fabric according to (1), wherein in the multifilament, when the average single-filament diameter is d [μm] and the number of single filaments is N [pieces], the product (d × N) of d and N is 50000 μm·pieces or more and 250000 μm·pieces or less. (3) The fabric according to (1) or (2), wherein the ten-point average roughness (Rz) measured in accordance with JIS B0601:1994 "Surface Roughness - Definition and Representation" of the fabric is 600 μm or more and 1000 μm or less. (4) The fabric according to any one of (1) to (3), wherein the multifilament includes drawn fibers and undrawn fibers, and the mass ratio of the drawn fibers to the undrawn fibers is in the range of 99:1 to 50:50. (5) The fabric according to any one of (1) to (4), wherein the twist number of the multifilament is 0 T / m or more and 200 T / m or less. (6) The fabric according to any one of (1) to (5), wherein the warp direction weave density of the fabric is 30 threads / 2.54 cm or more and 55 threads / 2.54 cm or less, and the weft direction weave density is 20 threads / 2.54 cm or more and 45 threads / 2.54 cm or less. (7) The fabric according to any one of (1) to (6), wherein the cover factor of the fabric is 2000 or more and 2800 or less. (8) A diaphragm for alkaline water electrolysis comprising the fabric according to any one of (1) to (7). (9) An electrolytic cell for alkaline water electrolysis comprising the diaphragm for alkaline water electrolysis according to (8). (10) A step of obtaining undrawn fibers having a sea-island type composite cross-section obtained by melt-extruding from the discharge holes of a sea-island type composite die, with polyphenylene sulfide as the island component and copolymerized polyethylene terephthalate as the sea component, A step of obtaining drawn fibers by drawing the undrawn fibers, A step of obtaining a mixed multifilament by combining the drawn fibers and the undrawn fibers so that the mass ratio of the drawn fibers to the undrawn fibers is in the range of 99:1 to 50:50, A step of obtaining a fabric using the mixed multifilament as warp and weft, The method for manufacturing a fabric according to any one of (1) to (7), comprising: (11) The method for manufacturing a fabric according to (10), wherein after the step of obtaining the fabric, a sea-removing treatment is performed. (12) The method for manufacturing a fabric according to (10) or (11), wherein in the step of obtaining the mixed multifilament, the twist number of the mixed multifilament is 0 T / m or more and 200 T / m or less.

Advantages of the Invention

[0014] According to the present invention, when used as a diaphragm for alkaline water electrolysis, a fabric and a method for manufacturing the same can be provided, which exhibit excellent effects in terms of ion permeability, ion permeation persistence, and gas barrier properties. And this fabric can be suitably used for a diaphragm for alkaline water electrolysis and an electrolytic cell for alkaline water electrolysis.

Embodiments for Carrying Out the Invention

[0015] 〔Fabric〕 The fabric of the present invention has multifilaments mainly composed of polyphenylene sulfide, the average single-filament diameter of the multifilaments is 0.2 μm or more and 5.0 μm or less, and the number of single filaments is 5000 or more and 400000 or less.

[0016] <Single filament> The fabric of the present invention has multifilaments mainly composed of polyphenylene sulfide. Here, the main component means a component that is more than 50 mol% of the resin constituting the fabric of the present invention. The polyphenylene sulfide according to the present invention is a polymer composed of diphenylene sulfide units composed of p-phenylene sulfide units and / or m-phenylene sulfide units as main repeating units.

[0017] In the polyphenylene sulfide according to the present invention, the p-phenylene sulfide unit is preferably 60 mol% or more, more preferably 70 mol% or more, and still more preferably 80 mol% or more. By setting it within the above range, fibers excellent in heat resistance, heat and humidity resistance, chemical resistance, and dimensional stability can be obtained.

[0018] The polyphenylene sulfide according to the present invention may contain copolymer units other than the diphenylene sulfide units as long as the effects of the present invention are not impaired. Examples of the copolymer units other than the diphenylene sulfide units include aromatic sulfides such as triphenylene sulfide and biphenylene sulfide, and their alkyl-substituted products or halogen-substituted products.

[0019] The polyphenylene sulfide fiber according to the present invention may be a single-component fiber or a composite fiber in which two or more resins are combined. When the polyphenylene sulfide fiber is a composite fiber, the composite form is not particularly limited as long as the effects of the present invention are not impaired, and it can be appropriately selected from a core-sheath type, a sea-island type, a side-by-side type (bimetal type), an eccentric core-sheath type, a blend type, etc. Further, when the polyphenylene sulfide fiber is made into a composite fiber, the resin to be combined with the polyphenylene sulfide is preferably a polyphenylene sulfide having a different copolymerization ratio of p-phenylene sulfide units and m-phenylene sulfide units from the viewpoint of process stability and flexibility in the manufacturing process. For example, in the case of a core-sheath type composite fiber, a polyphenylene sulfide composed only of p-phenylene sulfide units can be used as the core component, and a polyphenylene sulfide obtained by copolymerizing m-phenylene sulfide units with p-phenylene sulfide units can be used as the sheath component. Also, in the case of a sea-island type composite fiber, a polyphenylene sulfide composed only of p-phenylene sulfide units can be used as the sea component, and a polyphenylene sulfide obtained by copolymerizing m-phenylene sulfide units with p-phenylene sulfide units can be used as the island component.

[0020] The average single-filament diameter of the polyphenylene sulfide fiber according to the present invention is 0.2 μm or more and 5.0 μm or less. When the average single-filament diameter is 0.2 μm or more, an interval through which ions can permeate is formed between the single filaments, thereby improving the ion permeability. Therefore, the average single-filament diameter is preferably 0.3 μm or more, more preferably 0.5 μm or more. Further, when the average single-filament diameter is 5.0 μm or less, the gap between the single filaments becomes small, the gas barrier property of the formed fabric as a diaphragm is improved, the purity of hydrogen gas is maintained at a high level, and / or the risk of hydrogen explosion during the hydrogen production process is reduced. Therefore, the average single-filament diameter is preferably 3.0 μm or less, more preferably 1.0 μm or less.

[0021] The average single-filament diameter referred to here is determined as follows. (1) Select a magnification at which the cross-section of the single filament can be observed with a scanning electron microscope and take an image. (2) Using the taken image, measure the area Af [μm 2 formed by the cross-sectional contour of the single filament, and calculate the diameter of a perfect circle having the same area as this area Af. (3) Measure 100 arbitrarily extracted fibers, calculate the number average, and round off the third decimal place to obtain the average single-filament diameter [μm].

[0022] In addition, when the polyphenylene sulfide fiber according to the present invention includes drawn fibers and undrawn fibers as described later, 100 drawn fibers and 100 undrawn fibers are taken out from the multifilament respectively by measuring the orientation parameter described later, and after obtaining the average single-filament diameter of each, the average single-filament diameter of the entire multifilament is obtained as follows. The undrawn yarn mixing ratio is calculated by the method described in the examples. (Average single-filament diameter [μm]) = (Average single-filament diameter of drawn fibers [μm]) × {100 - (Undrawn yarn mixing ratio [%])} ÷ 100 + (Average single-filament diameter of undrawn fibers [μm]) × (Undrawn yarn mixing ratio [%]) ÷ 100.

[0023] The cross-sectional shape of the polyphenylene sulfide fiber according to the present invention is not limited in any way, and can be any irregular cross-sectional shape such as a round cross-section, a multi-lobed cross-section such as a Y-shaped cross-section or a triangular cross-section, a flat cross-section, an S-shaped cross-section, a cross-shaped cross-section, or a hollow cross-section.

[0024] The polyphenylene sulfide according to the present invention may contain various additives such as inorganic substances such as titanium oxide, silica, barium oxide, calcium carbonate, colorants such as carbon black, dyes and pigments, flame retardants, fluorescent brighteners, antioxidants, or ultraviolet absorbers, as long as the effects of the present invention are not impaired.

[0025] <Multifilament> It is important that the fabric of the present invention has multifilaments. In the present invention, a multifilament refers to a long fiber composed of two or more single filaments. Multifilaments have higher strength than staple fibers and also have higher shape stability of the fabric. And since staple fibers are formed by twisting short fibers, there are many hairy fibers on the surface, whereas multifilaments, which are long fibers, are less likely to generate hairy fibers and have the characteristic that the fabric surface becomes smoother. Therefore, when loaded into an electrolytic cell for alkaline water electrolysis as a diaphragm, bubbles of oxygen gas and / or hydrogen gas generated in the electrolytic cell are less likely to adhere to the diaphragm, and it is possible to suppress a decrease in ion permeability over time due to bubble adhesion to the diaphragm.

[0026] The number of monofilaments in the multifilament according to the present invention is 5,000 or more and 400,000 or less. In the present invention, the number of monofilaments refers to the number of monofilaments constituting the multifilament. When the number of monofilaments is 5,000 or more, the gas barrier property as a diaphragm of the formed fabric is improved, the purity of hydrogen gas is maintained at a high level, and / or the risk of hydrogen explosion in the hydrogen production process is reduced. Therefore, the number of monofilaments is preferably 160,000 or more, more preferably 200,000 or more. Also, when the number of monofilaments is more than 400,000, the electrical resistance as a diaphragm of the formed fabric may be large and the energy cost in hydrogen production may increase. Therefore, the number of monofilaments is preferably 320,000 or less, more preferably 280,000 or less.

[0027] The number of monofilaments according to the present invention is determined by measuring the mass [g] of a 1 m long multifilament and dividing the mass by the mass [g] of a 1 m long monofilament. The calculation method of the mass of a 1 m long monofilament is as follows. (Mass of a 1 m long monofilament [g / m]) = { (Average monofilament diameter [cm]) / 2} 2 × π × (Resin density [g / cm 3 ) × 100 Resin density: 1.38 [g / cm 3 .

[0028] In the multifilament according to the present invention, when the average single-filament diameter is d [μm] and the number of single filaments is N [pieces], the product of d and N (d×N) is preferably 50,000 μm·pieces or more and 250,000 μm·pieces or less. When the product of d and N (d×N) is 50,000 μm·pieces or more, it becomes difficult for bubbles of oxygen gas and / or hydrogen gas to pass through, the purity of hydrogen gas is maintained at a high level, and / or the risk of hydrogen explosion due to the mixing of oxygen gas and hydrogen gas may be reduced. Therefore, the product of d and N (d×N) is more preferably 100,000 μm·pieces or more, and even more preferably 125,000 or more. On the other hand, when the product of d and N (d×N) is 250,000 μm·pieces or less, an ion-permeable interval is generated between single filaments and between multifilaments, so the ion permeability increases, and the electrical resistance as a diaphragm of the formed fabric becomes small, thereby reducing the energy cost in hydrogen production. Therefore, the product of d and N (d×N) is more preferably 200,000 μm·pieces or less, and even more preferably 175,000 μm·pieces or less. The product of d and N (d×N) can be within the above range by appropriately adjusting the average single-filament diameter and the number of single filaments.

[0029] The multifilament according to the present invention preferably contains drawn fibers and undrawn fibers. As will be described later, the multifilament according to the present invention is heat-treated and heat-shrinks in the desalting process and the heat-setting process in spinning and / or weaving. At this time, by including drawn fibers and undrawn fibers, the multifilament becomes bulky due to the difference in their heat shrinkage rates, and the voids formed near the tissue points of the fabric become small, so that when applied to a diaphragm, a fabric excellent in gas barrier properties is obtained. In addition, since the multifilament becomes bulky, voids are generated between single filaments and between multifilaments, resulting in a fabric excellent in ion permeability.

[0030] The desalting process referred to in the present invention means obtaining ultrafine fibers by extracting and removing the sea component from composite fibers including spun sea-island fibers using a solvent. The details of the desalting process will be described later.

[0031] The mass ratio of drawn fibers to undrawn fibers contained in the multifilament according to the present invention (mass of drawn fibers: mass of undrawn fibers) is preferably in the range of 99:1 to 50:50. By setting it in this range, sufficient heat shrinkage occurs when the fabric is heat-treated in the sea-removal step or heat-setting step, and the bulk and voids near the weaving points of the fabric are in the optimum range, resulting in a fabric with excellent gas barrier properties when used as a diaphragm. Furthermore, since the proportion of undrawn yarns is not too high, the tension of the multifilament can be maintained, allowing it to be woven at a high weave density. Therefore, the mass ratio of drawn fibers to undrawn fibers is more preferably in the range of 80:20 to 50:50, and even more preferably in the range of 70:30 to 50:50.

[0032] In the present invention, fibers with an orientation parameter of 1.0 or more and less than 2.0 are called undrawn fibers, and fibers with an orientation parameter of 2.0 or more are called drawn fibers. The orientation parameter is a value that indicates the orientation of the molecular chains of polyphenylene sulfide, and the larger the orientation parameter, the higher the orientation of the molecular chains. The orientation parameter is a value measured by laser Raman spectroscopy.

[0033] The orientation parameter was measured by irradiating a polarized laser beam onto a single yarn under the following conditions and detecting the polarized Raman scattered light. -1 The peak intensity near (the stretching vibration mode of the phenyl ring - S (sulfur atom)) is I 1080 and 740cm -1 The peak intensity near I (out-of-plane bending vibration mode of the phenyl ring-S) 740 When the polarization direction is the same as the longitudinal direction of the fiber, it is called parallel polarization, and when it is perpendicular, it is called perpendicular polarization. The intensity ratio of parallel polarization (I 1080 / I 740 ) is the parallel intensity ratio, and the perpendicular polarization intensity ratio (I 1080 / I 740 ) is the perpendicular intensity ratio, the ratio of the parallel intensity ratio to the perpendicular intensity ratio (parallel intensity ratio / perpendicular intensity ratio) is called the orientation parameter. ·Device: Near-infrared Raman spectrometer · Conditions: Measurement mode: Microscopic Raman Objective lens: 100x Beam diameter: 1 μm Cross slit: 1 mm Light source: YAG laser / 1064 nm Laser power: 1 W Diffraction grating: Single ٣٠٠ gr / mm Slit: 100 μm Detector: InGaAs The twist number of the multifilament according to the present invention is preferably 0 T / m or more and 200 T / m or less. Here, 0 T / m means not applying twist to the multifilament. By setting it to 200 T / m or less, the bulkiness of the multifilament can be maintained, the voids near the weave points of the fabric become smaller, so the gas barrier property of the separator is excellent, and the porosity between single filaments is improved, contributing to the improvement of ion permeability. More preferably, it is 150 T / m or less, and even more preferably, it is 100 T / m or less. Also, by improving the strength and elongation of the multifilament and suppressing the hairiness, it becomes easier to increase the weaving density, and the process passability during weaving is improved. Therefore, it is more preferably 25 T / m or more, and even more preferably 50 T / m or more. The method of setting the twist number within the above range is not particularly limited, and examples include a method of twisting using a twisting machine. The twist number in the present invention refers to the value measured according to "8.13.1 Twist number" in JIS L1013:2021 "Test Methods for Chemical Fiber Filament Yarns".

[0034] <Fabric> The weave of the fabric of the present invention may be plain weave, twill weave, satin weave, or any combination or modified pile weave or figured weave of these. However, since it has the most weave points and the highest tightness, plain weave is preferred. By plain weave, the unevenness on the fabric surface can be reduced. When loaded into a hydrogen production device as a separator, bubbles of oxygen gas and / or hydrogen gas generated in the electrolytic cell are less likely to adhere to the separator.

[0035] The ten-point average roughness (Rz) of the fabric of the present invention in accordance with JIS B0601:1994 "Surface Roughness - Definition and Representation" is preferably 600 μm or more and 1000 μm or less. By setting the ten-point average roughness (Rz) to 600 μm or more, appropriate unevenness is formed on the fabric surface, so that the surface area in contact between the diaphragm and the bubbles becomes small. Therefore, the effect of reducing the adhesiveness of the bubbles in the electrolytic solution can be obtained. The ten-point average roughness (Rz) is more preferably 650 μm or more, and even more preferably 700 μm or more. Further, by setting the ten-point average roughness (Rz) to 1000 μm or less, since the unevenness present on the surface is large, when the bubbles generated in the electrolytic solution come into contact with the unevenness on the fabric surface, the buoyancy acting on the bubbles is likely to be decomposed in a direction other than the vertical direction, so that the separation of the bubbles is likely to be inhibited. The ten-point average roughness (Rz) is more preferably 900 μm or less, and even more preferably 800 μm or less. By being in the above range, not only the adhesiveness due to the surface free energy of the fabric surface is suppressed, but also since there is little unevenness on the fabric surface, the separation of the bubbles is less likely to be inhibited.

[0036] The ten-point average roughness (Rz) of the fabric referred to here can be measured by the following method. Prepare the target fabric and install it on the sample stage so as to stretch the wrinkles. The surface of the fabric installed on the sample stage is photographed as a three-dimensional image with a laser microscope in a size of 4 mm in the vertical direction and 5 mm or more in the horizontal direction of the observation field. The three-dimensional image is photographed at a total of 5 positions at arbitrary positions on the fabric, and the ten-point average roughness (Rz) in the above observation field is measured according to the method described in JIS B0601:1994 "Surface Roughness - Definition and Representation". Round off the decimal part of the average value to obtain the ten-point average roughness (Rz) of the fabric of the present invention (unit: μm). As a method for setting the ten-point average roughness (Rz) of the fabric within the above range, for example, it can be achieved by using a fabric made of multifilament consisting of an average single-filament diameter and the number of single filaments within a specific range.

[0037] The fabric density of the fabric of the present invention preferably has a warp direction fabric density of 30 threads / 2.54 cm or more and 55 threads / 2.54 cm or less, and a weft direction fabric density of 20 threads / 2.54 cm or more and 45 threads / 2.54 cm or less. Here, the fabric density in the present invention is the number of multifilaments per unit length in the warp direction or weft direction of the fabric, which is different from the number of single filaments. By setting the warp direction fabric density to 30 threads / 2.54 cm or more and the weft direction fabric density to 20 threads / 2.54 cm or more, sufficient tightness is generated between the multifilaments of the fabric, resulting in a smaller gap, improving the gas barrier property of the formed fabric as a diaphragm, maintaining a high level of hydrogen gas purity, and / or reducing the risk of hydrogen explosion in the hydrogen production process. More preferably, the warp direction fabric density is 39 threads / 2.54 cm or more and the weft direction fabric density is 29 threads / 2.54 cm or more. Even more preferably, the warp direction fabric density is 43 threads / 2.54 cm or more and the weft direction fabric density is 34 threads / 2.54 cm or more. On the other hand, by setting the warp direction fabric density to 55 threads / 2.54 cm or less and the weft direction fabric density to 45 threads / 2.54 cm or less, an interval through which ions can permeate is generated between the multifilaments, increasing the ion permeability and reducing the electrical resistance of the formed fabric as a diaphragm, thereby reducing the energy cost in hydrogen production. More preferably, the warp direction fabric density is 51 threads / 2.54 cm or less and the weft direction fabric density is 41 threads / 2.54 cm or less. Even more preferably, the warp direction fabric density is 47 threads / 2.54 cm or less and the weft direction fabric density is 38 threads / 2.54 cm or less.

[0038] The cover factor of the fabric of the present invention is preferably 2,000 or more and 2,800 or less. The cover factor is a value characterizing the tightness of the fabric. By setting the cover factor to 2,000 or more, sufficient tightness is generated between the multifilaments of the fabric, so that the gaps become small, the gas barrier property as the diaphragm of the formed fabric is improved, the purity of hydrogen gas is maintained at a high level, and / or the risk of hydrogen explosion in the hydrogen production process is reduced. More preferably, it is 2,100 or more, and still more preferably, it is 2,200 or more. Also, by setting the cover factor to 2,800 or less, an interval through which ions can permeate is generated between the multifilaments, so that the ion permeability is increased, and the electrical resistance as the diaphragm of the formed fabric is reduced, thereby reducing the energy cost in hydrogen production. More preferably, it is 2,700 or less, and still more preferably, it is 2,600 or less.

[0039] The cover factor of the fabric referred to here can be calculated by the following method.

[0040]

Equation

[0041] Here, CF is the cover factor (unitless), N w is the warp direction weave density of the fabric [ends / 2.54 cm], D w is the fineness of the multifilament in the warp direction of the fabric [dtex], N f is the weft direction weave density of the fabric [ends / 2.54 cm], D f is the fineness of the multifilament in the weft direction of the fabric [dtex]. The fineness of the multifilament is measured by preparing cops for 100 turns using a measuring machine with a frame circumference of 1.0 m and measuring the fineness according to the following formula. Fineness [dtex] = weight of cops for 100 turns [g] × 100.

[0042] The film thickness (thickness of the fabric) of the fabric of the present invention is preferably 0.35 mm or more and 1.00 mm or less. When the film thickness of the fabric is 0.35 mm or more, oxygen gas and / or hydrogen gas generated in the electrolytic cell become less likely to pass locally. That is, the gas barrier property is improved, the purity of hydrogen gas is maintained at a high level, and / or the risk of hydrogen explosion in the hydrogen production process is reduced. The film thickness of the fabric is more preferably 0.40 mm or more, and even more preferably 0.45 mm or more. When the film thickness of the fabric is 1.00 mm or less, the path through which ions permeate becomes shorter, so that a decrease in ion permeability can be suppressed. The film thickness of the fabric is more preferably 0.90 mm or less, and even more preferably 0.80 mm or less.

[0043] The bubble point of the fabric of the present invention is preferably 0.5 kPa or more. The bubble point is an index of the maximum pores of the fabric and is an index by which the gas barrier property of the diaphragm can be evaluated. By setting the bubble point within the above range, local passage of oxygen gas and / or hydrogen gas generated in the electrolytic cell through the maximum pores of the fabric becomes less likely to occur. That is, the gas barrier property is improved, the purity of hydrogen gas is maintained at a high level, and / or the risk of hydrogen explosion in the hydrogen production process is reduced. The bubble point of the fabric is more preferably 0.8 kPa or more, and even more preferably 1.2 kPa or more. On the other hand, the bubble point is preferably 100 kPa or less. By setting it within the above range, both the gas barrier property and the ion permeability can be achieved.

[0044] The bubble point of the fabric referred to here can be measured by the following method. Using a porous material automatic pore measurement system Perm-Porometer (manufactured by PMI), the pressure is calculated according to the bubble point method (based on ASTM F316-86). The measurement sample diameter is 25 mm, and the value obtained by rounding the third decimal place of the bubble point obtained by automatic calculation to the second decimal place is used in the pore size distribution measurement using a measurement liquid with a known surface tension.

[0045] The maximum pore diameter at the bubble point of the fabric of the present invention is preferably 130 μm or less. By setting it within the above range, it becomes difficult for oxygen gas and / or hydrogen gas generated in the electrolytic cell to pass through locally. That is, the gas shielding property is improved, the purity of hydrogen gas is maintained at a high level, and / or the risk of hydrogen explosion is reduced during the hydrogen production process. More preferably, it is 80 μm or less, and even more preferably, it is 40 μm or less. On the other hand, the maximum pore diameter at the bubble point of the fabric is preferably 0.5 μm or more. By setting it within the above range, it is possible to achieve both gas shielding property and ion permeability.

[0046] The maximum pore diameter at the bubble point of the fabric referred to here can be measured by the following method. Using a porous material automatic pore size measurement system Perm-Porometer (manufactured by PMI), calculate the pore size according to the bubble point method (based on ASTM F316-86). Assuming the measurement sample diameter is 25 mm, use the value obtained by rounding the second decimal place of the maximum pore diameter at the bubble point obtained by automatic calculation to the first decimal place through the measurement of the pore size distribution using a measurement liquid with a known surface tension.

[0047] The average pore diameter of the fabric of the present invention is preferably 30 μm or less. While the above maximum pore diameter at the bubble point is the diameter of the pores through which oxygen gas and / or hydrogen gas most easily pass in the fabric, the average pore diameter is an index for evaluating the average gas shielding property of the entire diaphragm. By setting the average pore diameter of the fabric within the above range, it becomes difficult for oxygen gas and / or hydrogen gas generated in the electrolytic cell to pass through the entire diaphragm. That is, the gas shielding property is improved, the purity of hydrogen gas is maintained at a high level, and / or the risk of hydrogen explosion is reduced during the hydrogen production process.

[0048] The average pore diameter of the fabric mentioned here can be measured by the following method. Using a porous material automatic pore size measurement system Perm-Porometer (manufactured by PMI), the pore size is calculated according to the bubble point method (based on ASTM F316-86). The measured sample diameter is 25 mm, and the average flow diameter obtained by automatic calculation from the pore size distribution measurement using a measurement liquid with a known surface tension is used as the average pore diameter, and the value obtained by rounding the second decimal place to the first decimal place is used.

[0049] The electrical resistance of the fabric of the present invention is 260 mΩ·cm 2 The following is preferable. Electrical resistance is a physical property indicating ion permeability, and the lower the electrical resistance, the higher the ion permeability. By setting the electrical resistance within the above range, sufficient ion permeability is exhibited, and the energy cost in water electrolysis is reduced. More preferably, it is 200 mΩ·cm 2 or less, and even more preferably 160 mΩ·cm 2 or less.

[0050] The electrical resistance of the fabric mentioned here can be measured by the following method. It is measured in accordance with the provisions of JIS C2313:1995 "Separator for lead-acid batteries". The measuring device and measuring conditions are as follows. As the electrolyte, an aqueous potassium hydroxide solution with a concentration of 30% by mass and a temperature of 60 °C is used, and pure silver is used as the electrode. The distance between both electrodes is 23 mm, and the fabric with a length of 4 cm and a width of 2 cm is installed between both electrodes. Subsequently, the electrical resistance is measured using "LCR meter ZM2371" manufactured by NF Circuit Design Block Co., Ltd., and the applied voltage is 10 mV. The product of the value of the output impedance (Z) and the diaphragm area is used as the electrical resistance, and the first decimal place is rounded to use an integer value.

[0051] The bubble rising angle of the fabric of the present invention is preferably 70° or less. The bubble rising angle in the present invention indicates the discreteness of bubbles with respect to the diaphragm in water, and is a physical property indicating that the smaller the value, the more excellent the discreteness of bubbles. By setting it within the above range, bubbles hardly adhere to the diaphragm with the electrolytic solution, and it is possible to suppress the increase in the amount of adhered bubbles over time, so that the ion permeation persistence is increased. The bubble rising angle of the fabric is more preferably 55° or less, and even more preferably 40° or less.

[0052] The bubble rising angle of the fabric referred to here is measured by the following method. Prepare a fabric to be measured in a square shape with a side length of 10 cm, and attach it to a smooth plate such as an iron plate so as to stretch out the wrinkles. With the surface on which the fabric is attached facing down, the plate is horizontally submerged in water at a water temperature of 20°C. Attach 5 mL of bubbles to the fabric in the water, and with one side of the plate as the axis, gradually lift the opposite side of the plate. The lifting speed is such that the angular velocity at the angle formed by the water surface and the plate is π / 180 (=0.017) rad / s. Measure the angle formed by the water surface and the plate at the moment when the bubbles detach from the fabric and float in the water during the process. The measurement is performed 10 times in each of the four directions of the front and back surfaces and the vertical and horizontal directions of the fabric. Round off the decimal part of the average value of the angles in each direction, and take the lowest value as the bubble rising angle of the fabric of the present invention.

[0053] [[Alkaline water electrolysis diaphragm and alkaline water electrolysis cell]] The fabric of the present invention can be suitably used as a diaphragm in alkaline water electrolysis.

[0054] As the alkaline water electrolysis diaphragm of the present invention, the above-described fabric of the present invention may be used as it is, or a hydrophilic treatment may be performed within a range that does not inhibit the effects of the present invention. By performing the hydrophilic treatment, the permeability of the electrolytic solution can be improved, and the electrolysis efficiency can be improved.

[0055] In addition, the electrolytic cell for alkaline water electrolysis of the present invention may be any one that includes an electrolytic cell, a plurality of anodes, and cathodes, and in particular, it may be one that uses the diaphragm for alkaline water electrolysis of the present invention as the diaphragm disposed between the anode and the cathode. By using the diaphragm for alkaline water electrolysis of the present invention, high-purity hydrogen gas can be obtained with high electrolysis efficiency. The electrolytic cell for alkaline water electrolysis of the present invention may be an electrolytic cell for alkaline water electrolysis having any structure including a zero-gap structure or a gap structure, and the operating pressure and capacity are not particularly limited either. For example, these electrolytic cells for alkaline water electrolysis may operate at atmospheric pressure or may be pressurized, that is, they can operate at a pressure exceeding atmospheric pressure. The above electrodes are not particularly limited, and known electrodes can be used. For example, those including a conductive substrate containing nickel or a nickel alloy, etc. can be mentioned.

[0056] 〔Method for manufacturing a fabric〕 As an example, the fabric of the present invention has a step of obtaining undrawn fibers having a sea-island composite cross-section obtained by melt-extruding from the discharge holes of a sea-island type composite spinneret with polyphenylene sulfide as the island component and copolymerized polyethylene terephthalate as the sea component, a step of obtaining drawn fibers by drawing the undrawn fibers, a step of obtaining a mixed-filament multifilament having a mass ratio of drawn fibers to undrawn fibers in the range of 99:1 to 50:50, and a step of obtaining a fabric using the mixed-filament multifilament as warp and weft. It can be manufactured by a manufacturing method having these steps.

[0057] <Step of obtaining undrawn fibers> Next, a method for manufacturing a multifilament made of polyphenylene sulfide, which is a component of the fabric of the present invention, is shown, but this is not the limit.

[0058] The polyphenylene sulfide to be used is preferably dried before being subjected to melt spinning for the purpose of preventing moisture from mixing in and removing oligomers in order to improve the yarn-making property. As the drying conditions, vacuum drying at 100°C to 200°C for 1 hour to 24 hours is usually used.

[0059] The polyphenylene sulfide fiber according to the present invention can be obtained by removing the polymer of the sea component of a sea-island type composite fiber having a sea-island type composite cross-section in which polyphenylene sulfide is arranged in the island component.

[0060] An easily soluble polymer is preferably used for the sea component of the above sea-island type composite fiber. The easily soluble polymer referred to here is selected from, for example, melt-moldable polymers such as polyethylene terephthalate, polyethylene naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, polyolefin, polycarbonate, polyacrylate, polyamide, polylactic acid, thermoplastic polyurethane, and copolymers thereof. Among them, from the viewpoint of simplifying the elution process of the sea component, the sea component is preferably a copolyester, polylactic acid, polyvinyl alcohol, etc. that show easy elution in an aqueous solvent or hot water. A polyester copolymerized with 5-sodium sulfoisophthalic acid, or a polyester copolymerized with ethylene glycol to further improve the elution property is preferred. On the other hand, when thermal decomposition of the easily soluble polymer progresses during spinning, the cross-section formability and spinnability of the composite fiber deteriorate, so high heat resistance, that is, resistance to thermal decomposition at the above spinning temperature, is required. From such a viewpoint, a polyester copolymerized with 5-sodium sulfoisophthalic acid is more preferred.

[0061] When a polyester copolymerized with 5-sodium sulfoisophthalic acid is used for the sea component, from the viewpoint of achieving both solubility in an aqueous solvent and heat resistance, the copolymerization amount of 5-sodium sulfoisophthalic acid is preferably 2 mol% or more and 20 mol% or less. By setting the copolymerization amount of 5-sodium sulfoisophthalic acid to preferably 2 mol% or more, more preferably 3 mol% or more, the solubility in an aqueous solvent is improved, so that when used for the sea component of the sea-island type composite fiber, the sea component can be easily removed. Also, by setting the copolymerization amount of 5-sodium sulfoisophthalic acid to preferably 20 mol% or less, more preferably 15 mol% or less, a polymer having excellent heat resistance is obtained.

[0062] The sea-island composite fiber used in the present invention is obtained by melting polyphenylene sulfide and other component polymers separately using an extruder such as a pressure melt type, single-screw or twin-screw extruder, followed by metering with a known metering device such as a gear pump via a polymer pipe, passing through a filter for foreign matter removal, and then guiding them to a spinneret respectively. Each polymer guided to the spinneret is shape-regulated into an arbitrary composite form within the spinneret and merged, and is discharged from the die hole as a sea-island composite fiber. At this time, the temperature from the polymer pipe to the spinneret (spinning temperature) is preferably 290°C or higher to enhance fluidity, and preferably 380°C or lower to suppress thermal decomposition of the polymer.

[0063] The spinneret used for extrusion preferably has a die hole diameter D of 0.1 mm or more and 0.6 mm or less, and the ratio L / D of the land length L of the die hole (the length of the straight pipe part having the same diameter as the die hole diameter) to the hole diameter D is preferably 1 or more and 10 or less.

[0064] The shape and cross-sectional area of the island component in the sea-island composite fiber may be the same as the area of the fiber cross-section calculated from the above fiber shape and average single-filament diameter. For example, by making the polyphenylene sulfide, which is the island component, into a round shape with a diameter of 2.0 μm, a round cross-section fiber with an average single-filament diameter of 2.0 μm can be obtained after the sea-removing treatment. The multifilament having an average single-filament diameter within the above range can be obtained, for example, by removing the polymer of the sea component of the sea-island composite fiber having a sea-island composite cross-section with polyphenylene sulfide arranged in the island component. Also, by appropriately adjusting conditions such as cooling, heat preservation, take-up, and drawing, in addition to the polymer species used in the sea-island composite fiber, the pore diameter of the island component of the sea-island composite die, the sea-island ratio during spinning, and the spinning machine temperature, a multifilament having an average single-filament diameter within the above range can be obtained.

[0065] The number of island components in the sea-island composite fiber is not particularly limited, but is preferably 20 or more and 4000 or less. By making the number of island components more preferably 100 or more, and even more preferably 200, the diameter of the island components can be reduced, and it becomes possible to reduce the average single-filament diameter of the polyphenylene sulfide fiber. Further, by making the number of island components more preferably 3000 or less, the fiber cross-section formability becomes good, and fibers with a small variation in single-filament diameter can be obtained.

[0066] The sea-island composite fiber discharged from the spinneret holes is cooled and solidified by blowing cooling air (air). The temperature of the cooling air can be determined in balance with the cooling air speed from the viewpoint of cooling efficiency, and is preferably 30°C or less. By preferably setting the temperature of the cooling air to 30°C or less, the solidification behavior due to cooling becomes stable, and fibers with high uniformity in average single-filament diameter are obtained.

[0067] Also, the cooling air is preferably flowed in a direction substantially perpendicular to the fiber axis to the undrawn fiber discharged from the spinneret. At this time, the speed of the cooling air is preferably 10 m / min or more from the viewpoints of cooling efficiency and uniformity of fineness, and preferably 100 m / min or less from the viewpoint of spinning stability.

[0068] The cooled and solidified undrawn fiber is taken up by a roller (godet roller) rotating at a constant speed. The take-up speed is preferably 300 m / min or more for linear uniformity and productivity improvement, and preferably less than 5000 m / min so as not to promote the orientation of the molecular chains, more preferably 30000 m / min or less, and even more preferably 1500 m / min or less. If it is 5000 m / min or more, high orientation proceeds, and the orientation parameter may become 2.0 or more. In the definition of the present invention, it becomes a drawn fiber.

[0069] The above is the method for manufacturing an undrawn fiber. By continuing the subsequent manufacturing method, a drawn fiber can be obtained.

[0070] <Process for obtaining drawn fiber> After once winding up or taking out the obtained undrawn fibers, they are continuously subjected to a drawing process. The drawing is performed by running them on a heated first roller or a heating device provided between the first roller and the second roller, for example, in a heating bath or on a hot plate. The drawing conditions are determined by the mechanical properties of the obtained undrawn fibers. The drawing temperature is determined by the temperature of the heated first roller or the heating device provided between the first roller and the second roller, and the draw ratio is determined by the ratio of the peripheral speeds of the first roller and the second roller.

[0071] The temperature of the heated first roller or the heating device in the drawing process is preferably 80°C or higher and 130°C or lower. By setting it to 80°C or higher, the drawing point is fixed and stable drawing becomes possible. By setting it to 130°C or lower, yarn breakage can be suppressed and the process throughput is improved. Also, from the viewpoint of fixing the drawing point, the temperature of the second roller is preferably (heated first roller) + 20°C or lower or (temperature of the heating device) + 20°C or lower.

[0072] Furthermore, after passing through the second roller, the drawn fibers may be heated by a heated third roller or a heating device provided between the second roller and the third roller to perform heat setting. When performing heat setting, the heat setting temperature is preferably 150°C to 240°C. By setting the heat setting temperature to 150°C or higher, in addition to high orientation, heat crystallization can be performed to obtain high-strength fibers, and a fabric excellent in dimensional stability and mechanical strength can be obtained. Also, by setting the heat setting temperature to 240°C or lower, fusion of the fibers to the roller can be suppressed and deterioration of the process throughput can be prevented.

[0073] <Step of obtaining mixed multifilament> Subsequently, it is preferable to obtain sea-island type composite fibers of any fineness by running and winding up any amount of the obtained drawn fibers or any amount of drawn fibers and undrawn fibers together on an unheated roller. As described above, it is preferable to obtain a mixed multifilament by mixing the drawn fibers and the undrawn fibers in a mass ratio range of 99:1 to 50:50.

[0074] The obtained sea-island composite fiber composed of drawn fibers and / or undrawn fibers may be woven after the sea component removal treatment to obtain a fabric mainly composed of polyphenylene sulfide, or may be subjected to the sea component removal treatment after being made into a fabric composed of the sea-island composite fiber. In the present embodiment, it is preferable to perform the sea component removal treatment after making a fabric composed of the sea-island composite fiber. By performing the sea component removal treatment after making the sea-island composite fiber into a fabric, the multifilaments become bulky after weaving and fill the voids formed near the weave points of the fabric. Therefore, when applied to a diaphragm, it becomes a fabric excellent in gas barrier properties. The following method for manufacturing a fabric describes the latter method.

[0075] <Step of obtaining a fabric> An example of the method for manufacturing the fabric of the present invention is shown below, but it is not limited thereto.

[0076] The obtained sea-island composite fiber is twisted in the range of 0 T / m or more and 200 T / m or less, and then used as warp and weft, and after warping, threading through heddles, and reed insertion, weaving is performed using a gripper loom or a heavy rapier loom.

[0077] The produced fabric is scoured at a bath temperature of 90°C to 95°C and a speed of 20 m / min to 40 m / min for 30 minutes to 60 minutes. By setting the scouring temperature at 90°C or higher, it becomes easier to remove the dirt on the fabric, and by setting it at 95°C or lower, the energy consumption can be suppressed. By setting the scouring speed at 20 m / min or higher, the production efficiency can be increased. On the other hand, by setting the scouring speed at 40 m / min or lower, the scouring liquid can sufficiently contact the filter cloth, and the dirt on the fabric can be completely washed. When scouring, it is preferable to add a scouring agent such as soda ash to remove hydrophobic impurities. After washing with water, a desalting treatment of the fabric is performed. The conditions for the desalting treatment are preferably a bath temperature of 80°C to 100°C, a sodium hydroxide aqueous solution concentration of 3 wt% to 5 wt%, and 30 minutes to 60 minutes. After the desalting treatment, it is washed with water and dried. By setting the bath temperature at 80°C or higher, the sea components can be completely eluted. By setting the sodium hydroxide aqueous solution concentration at 3 wt% or higher, the sea components are easily eluted, and by setting it at 5 wt% or lower, the production cost can be suppressed. By setting the treatment time at 30 minutes or longer, the sea components can be completely eluted, and by setting it at 60 minutes or shorter, the production cost can be suppressed. Also, it is preferable to perform an acid treatment with maleic acid before the alkali treatment with the sodium hydroxide aqueous solution. After the desalting treatment, heat setting is performed at a heat setting temperature of 150°C to 200°C and a heat setting speed of 5 m / min to 15 m / min for 30 seconds to 5 minutes. By setting the heat setting temperature at 150°C or higher, the heat setting efficiency can be increased, and the shrinkage of the non-drawn fibers can be expressed. By setting the heat setting temperature at 200°C or lower, the production cost can be suppressed. By setting the heat setting speed at 5 m / min or higher, the shrinkage, wrinkle formation, and deterioration of the texture of the fabric can be suppressed. By setting the heat setting speed at 15 m / min or lower, the heat setting efficiency can be increased.

[0078] A hydrophilization treatment may be performed within a range that does not inhibit the effects of the present invention. By performing the hydrophilization treatment, the permeability of electrolytes and ion permeability are improved. Examples of the hydrophilization treatment include sulfonation treatment and plasma processing.

Example

[0079] Next, the present invention will be described in detail based on examples. However, the present invention is not limited only to these examples. In addition, in the measurement of each physical property, those without special description were measured based on the above-described methods.

[0080] (1) Average single filament diameter Using a scanning electron microscope "S-5500" manufactured by Hitachi High-Technologies Corporation as a scanning electron microscope and "WinROOF2015" manufactured by Mitani Trading Co., Ltd. as image analysis software, the measurement was performed as described above.

[0081] (2) Number of single filaments It was calculated by measuring the mass [g] of a 1 m long multifilament and dividing the mass by the mass [g] of a 1 m long single filament. The calculation method of the mass of a 1 m long single filament is as follows. (Mass of a 1 m long single filament [g / m]) = {(Average single filament diameter [cm]) / 2} 2 × π × (Resin density [g / cm 3 ) × 100 (3) Orientation parameter Using the following apparatus, the orientation parameter was measured by the above-described method. · Apparatus: Near-infrared Raman spectrometer (manufactured by Photon Design Co., Ltd.) · Detector: InGaAs / manufactured by Nippon Loepar Co., Ltd. (3-2) Undrawn fiber mixing ratio Measure the average single filament diameter of 100 fibers randomly extracted from the multifilaments forming the fabric as described above. After measuring the orientation parameter of the extracted fibers and separating the drawn fibers and undrawn fibers, from the measurement method of the average single filament diameter in (1), measure the average single filament diameter of all the extracted drawn fibers and undrawn fibers. From the obtained average single filament diameter, calculate the fineness of each fiber, and calculate the sum (W1) of the fineness of the drawn fibers and the sum (W2) of the fineness of the undrawn fibers. Then, the undrawn fiber mixing ratio was calculated by the following calculation method. (Undrawn fiber mixing ratio [mass%]) = (W2) / (W1 + W2) × 100.

[0082] (4) Twist number The twist number in the present invention refers to the value measured in accordance with "8.13.1 Twist Number" of JIS L1013:2021 "Test Methods for Chemical Fiber Filament Yarns".

[0083] (5) Ten-point average roughness (Rz) Prepare the target fabric and install it on the sample stage so as to stretch out the folds. Observe the surface of the fabric installed on the sample stage with a laser microscope (shape measurement laser microscope VK-X210 manufactured by Keyence Corporation) and take three-dimensional images with a size of 4 mm in the vertical direction and 5 mm or more in the horizontal direction of the observation field. The three-dimensional images are taken at five arbitrary positions on the fabric, and using the company's analysis application (VK-H1XA), in accordance with the method described in JIS B0601:1994 "Surface Roughness - Definitions and Expressions", perform ten-point average roughness (Rz) surface roughness measurement for 4 mm in the vertical direction × 5 mm in the horizontal direction of each image. Round off the decimal part of the simple average to obtain the ten-point average roughness (Rz) of the fabric of the present invention.

[0084] (6) Cover factor The calculation formula for the cover factor of the fabric is as follows.

[0085] [Number]

[0086] Here, N w is the warp direction weave density of the fabric [ends / 2.54 cm], D w is the fineness [dtex] of the multifilament made of polyphenylene sulfide in the warp direction of the fabric, N f is the weft direction weave density of the fabric [ends / 2.54 cm], D f is the fineness [dtex] of the weft direction filaments (multifilaments made of polyphenylene sulfide) in the fabric. The fineness of the filaments (multifilaments made of polyphenylene sulfide) was measured by preparing cops for 100 turns using a measuring machine with a frame circumference of 1.0 m and according to the following formula. Fineness [dtex] = Weight of cops for 100 turns [g] × 100 (7) Bubble point The pressure was calculated using the bubble point method (based on ASTM F316-86) using a Perm-Porometer (PMI), an automatic porous material pore measurement system. The measurement sample diameter was 25 mm, and Galwick (surface tension 16 mN / m) was used as the measurement liquid with a known surface tension. The bubble point was automatically calculated using the measurement, and the value was rounded to two decimal places. Furthermore, the gas barrier properties of the membrane were evaluated based on the results of the physical properties according to the criteria shown in Table 1 below.

[0087] (8) Maximum pore size at bubble point The pore size was calculated using the Perm-Porometer (PMI) automatic porous material pore measurement system according to the bubble point method (based on ASTM F316-86). The measurement sample diameter was 25 mm, and the pore size distribution was measured using Galwick (surface tension 16 mN / m) as the measurement liquid with a known surface tension. The bubble point maximum pore diameter was automatically calculated and rounded to one decimal place.

[0088] (9) Average pore size Pore size was calculated using the bubble point method (based on ASTM F316-86) using a Perm-Porometer (PMI), an automatic porous material pore measurement system. The sample diameter was 25 mm, and the pore size distribution was measured using Galwick (surface tension 16 mN / m) as the measurement liquid with a known surface tension. The mean flow diameter was automatically calculated as the mean pore size, and the value was rounded to one decimal place.

[0089] (10) Electrical resistance The measurement was carried out in accordance with the provisions of JIS C2313:1995 "Separator for Lead-Acid Batteries". The measuring device and measuring conditions are as follows. An aqueous potassium hydroxide solution with a concentration of 30% by mass and a temperature of 60 °C was used as the electrolyte, and pure silver was used as the electrodes. The distance between the two electrodes was 23 mm, and the fabric with a length of 4 cm and a width of 2 cm was placed between the two electrodes. The electrical resistance was measured using the "LCR Meter ZM2371" manufactured by NF Circuit Design Block Co., Ltd., and the applied voltage was 10 mV. The product of the value of the output impedance (Z) and the diaphragm area was taken as the electrical resistance, and the first decimal place was rounded off to use an integer value. Also, based on the results of these physical properties, the ion permeability of the diaphragm was determined according to the criteria shown in Table 1 below.

[0090] (11) Bubble rising angle The target fabric was prepared in a square size with a side length of 10 cm and attached to a smooth plate such as an iron plate so as to stretch out the wrinkles. With the surface on which the fabric was attached facing down, the plate was horizontally submerged in water at a water temperature of 20 °C. 5 mL of bubbles were attached to the fabric in the water, and with one side of the plate as the axis, the opposite side was gradually lifted. The lifting speed was set such that the angular velocity at the angle formed by the water surface and the plate was π / 180 (=0.017) rad / s. During that process, the angle formed by the water surface and the plate at the moment when the bubble detached from the fabric and floated in the water was measured. The measurement was carried out 10 times in each of the 4 directions, namely the front and back surfaces and the longitudinal and transverse directions of the fabric. The decimal part of the average value of the angles in each direction was rounded off, and the lowest value was taken as the bubble rising angle of the fabric of the present invention.

[0091]

Table 1

[0092] [Example 1] Using a sea-island type composite die (number of islands: 1000) with polyphenylene sulfide consisting only of p-phenylene sulfide units as the island component and polyethylene terephthalate copolymerized with 5.0 mol% of 5-sodium sulfoisophthalic acid as the sea component, with the shape of the island component being round, the composite ratio of the sea / island components was set to 30 / 70, and the fibers were melt-extruded at a single-hole discharge rate of 1.43 g / min. After cooling and solidifying the fibers, an oil agent was applied, and they were wound up at a spinning speed of 1000 m / min to obtain undrawn fibers having a sea-island type composite cross-section.

[0093] The obtained undrawn fibers were taken up by a feed roller equipped with nip rollers, tension was applied to the undrawn fibers between them and the first roller, and then they were wound around the first roller and the second roller heated to 90 °C and 100 °C respectively for 6 turns to perform heat drawing. Further, they were wound around the third roller heated to 180 °C for 6 turns to perform heat setting. The draw ratio was 3.7 times, and after the third roller, they were taken up by a non-heated roller with a peripheral speed of 400 m / min to obtain drawn fibers having a sea-island type composite cross-section.

[0094] While combining 184 obtained drawn fibers and 48 undrawn fibers, they were taken up by a non-heated roller with a peripheral speed of 100 m / min to obtain a mixed multifilament having a sea-island type composite cross-section.

[0095] Using the obtained mixed multifilament as warp and weft, after twisting only the warp at 50 T / m, weaving was performed with a warp-wise weaving density of 45 threads / 2.54 cm and a weft-wise weaving density of 35 threads / 2.54 cm to produce a plain woven greige fabric. The obtained greige fabric was scoured at 20 m / min in a hot bath with a liquor ratio of 1:20, a temperature of 70 °C, and 0.2 mass% of soda ash added. After treating the scoured fabric at 60 m / min with a 0.2 mass% maleic acid aqueous solution at a liquor ratio of 1:20 and a temperature of 130 °C, the fabric was treated at 60 m / min with a 4 mass% sodium hydroxide aqueous solution at a liquor ratio of 1:20 and a temperature of 98 °C to perform de-sea processing of the fabric. The de-sea processed fabric was dried and heat set at 180 °C to obtain a polyphenylene sulfide fabric as a diaphragm for alkaline water electrolysis.

[0096] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 2.

[0097] [Example 2] Undrawn fibers and drawn fibers having a sea-island composite cross-section were obtained in the same manner as in Example 1, except that the single-hole discharge amount during melt spinning was changed to 3.67 g / min.

[0098] While combining 80 drawn fibers and 16 undrawn fibers obtained, they were taken up by an unheated roller with a peripheral speed of 100 m / min to obtain a mixed multifilament having a sea-island composite cross-section.

[0099] A polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from the mixed multifilament obtained in the same manner as in Example 1.

[0100] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 2.

[0101] [Example 3] Undrawn fibers and drawn fibers having a sea-island composite cross-section were obtained in the same manner as in Example 1, except that the single-hole discharge amount during melt spinning was changed to 8.25 g / min.

[0102] While combining 32 drawn fibers and 8 undrawn fibers obtained, they were taken up by an unheated roller with a peripheral speed of 100 m / min to obtain a mixed multifilament having a sea-island composite cross-section.

[0103] A polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from the mixed multifilament obtained in the same manner as in Example 1.

[0104] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 2.

[0105] [Example 4] Undrawn fibers and drawn fibers having a sea-island composite cross-section were obtained in the same manner as in Example 1, except that the number of islands of the sea-island composite die was 32, the number of die holes was 12, and the single-hole discharge amount was changed to 1.88 g / min.

[0106] While combining 384 drawn fibers and 96 undrawn fibers obtained, they were taken up by a non-heated roller with a peripheral speed of 100 m / min to obtain a mixed multifilament having a sea-island type composite cross-section.

[0107] A polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from the mixed multifilament obtained in the same manner as in Example 1.

[0108] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 2.

[0109] [Example 5] Undrawn fibers and drawn fibers having a sea-island type composite cross-section were obtained in the same manner as in Example 1, and a mixed multifilament having a sea-island type composite cross-section was also obtained.

[0110] A polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from the mixed multifilament obtained in the same manner as in Example 1, except that the warp direction weaving density during weaving was changed to 41 threads / 2.54 cm and the weft direction weaving density was changed to 31 threads / 2.54 cm.

[0111] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 2.

[0112] [Example 6] Undrawn fibers and drawn fibers having a sea-island type composite cross-section were obtained in the same manner as in Example 1, and a mixed multifilament having a sea-island type composite cross-section was also obtained.

[0113] A polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from the mixed multifilament obtained in the same manner as in Example 1, except that the warp direction weaving density during weaving was changed to 49 threads / 2.54 cm and the weft direction weaving density was changed to 39 threads / 2.54 cm.

[0114] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 2.

[0115] [Example 7] An undrawn fiber and a drawn fiber having a sea-island composite cross-section were obtained in the same manner as in Example 1, and a mixed multifilament having a sea-island composite cross-section was also obtained.

[0116] A polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from the mixed multifilament obtained in the same manner as in Example 1, except that the warp weaving density during weaving was changed to 35 threads / 2.54 cm and the weft weaving density was changed to 25 threads / 2.54 cm.

[0117] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 2.

[0118] [Example 8] An undrawn fiber and a drawn fiber having a sea-island composite cross-section were obtained in the same manner as in Example 1, and a mixed multifilament having a sea-island composite cross-section was also obtained.

[0119] A polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from the mixed multifilament obtained in the same manner as in Example 1, except that the warp weaving density during weaving was changed to 53 threads / 2.54 cm and the weft weaving density was changed to 43 threads / 2.54 cm.

[0120] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 2.

[0121] [Example 9] An undrawn fiber and a drawn fiber having a sea-island composite cross-section were obtained in the same manner as in Example 1.

[0122] While combining 274 drawn fibers and 24 undrawn fibers obtained, they were taken up by a non-heated roller with a peripheral speed of 100 m / min to obtain a mixed multifilament having a sea-island composite cross-section.

[0123] A polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from the obtained mixed multifilament in the same manner as in Example 1.

[0124] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 2.

[0125] [Example 10] An undrawn fiber and a drawn fiber having a sea-island composite cross-section were obtained in the same manner as in Example 1.

[0126] While combining 274 drawn fibers and 1 undrawn fiber obtained, they were taken up by a non-heated roller with a peripheral speed of 100 m / min to obtain a mixed multifilament having a sea-island composite cross-section.

[0127] From the obtained mixed multifilament, a polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained in the same manner as in Example 1.

[0128] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 2.

[0129] [Example 11] An undrawn fiber and a drawn fiber having a sea-island composite cross-section were obtained in the same manner as in Example 1.

[0130] While combining 360 drawn fibers obtained, they were taken up by a non-heated roller with a peripheral speed of 100 m / min to obtain a multifilament composed of 360 drawn fibers.

[0131] A polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from 360 drawn multifilaments obtained in the same manner as in Example 1.

[0132] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 2.

[0133] [Example 12] An undrawn fiber and a drawn fiber having a sea-island composite cross-section, and a mixed multifilament having a sea-island composite cross-section were obtained in the same manner as in Example 1.

[0134] While combining 136 drawn fibers and 32 undrawn fibers obtained, they were taken up by a non-heated roller with a peripheral speed of 100 m / min to obtain a mixed multifilament having a sea-island composite cross-section.

[0135] A polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from the mixed fiber multifilament obtained in the same manner as in Example 1, except that the warp direction weaving density during weaving was changed to 60 threads / 2.54 cm and the weft direction weaving density was changed to 50 threads / 2.54 cm.

[0136] Physical property evaluation of the obtained fabric was carried out. The evaluation results are shown in Table 3.

[0137] [Example 13] Undrawn fibers and drawn fibers having a sea-island composite cross-section were obtained in the same manner as in Example 1.

[0138] While combining 128 drawn fibers and 64 undrawn fibers obtained, they were taken up by a non-heated roller with a peripheral speed of 100 m / min to obtain a mixed fiber multifilament having a sea-island composite cross-section.

[0139] A polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from the mixed fiber multifilament obtained in the same manner as in Example 1, except that the warp direction weaving density during weaving was changed to 40 threads / 2.54 cm and the weft direction weaving density was changed to 30 threads / 2.54 cm.

[0140] Physical property evaluation of the obtained fabric was carried out. The evaluation results are shown in Table 3.

[0141] [Example 14] Undrawn fibers and drawn fibers having a sea-island composite cross-section, and also a mixed fiber multifilament having a sea-island composite cross-section were obtained in the same manner as in Example 1.

[0142] Before weaving, only the warp threads were twisted at 120 T / m, and then a polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from the mixed fiber multifilament obtained in the same manner as in Example 1.

[0143] Physical property evaluation of the obtained fabric was carried out. The evaluation results are shown in Table 3.

[0144] [Example 15] An undrawn fiber and a drawn fiber having a sea-island composite cross-section were obtained in the same manner as in Example 1, and a mixed multifilament having a sea-island composite cross-section was also obtained.

[0145] Before weaving, only the warp yarns were twisted at 170 T / m, and then a polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from the mixed multifilament obtained in the same manner as in Example 1.

[0146] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 3.

[0147] [Example 16] An undrawn fiber and a drawn fiber having a sea-island composite cross-section were obtained in the same manner as in Example 1, and a mixed multifilament having a sea-island composite cross-section was also obtained.

[0148] Before weaving, the warp yarns were twisted at 50 T / m and the weft yarns were twisted at 50 T / m, and then a polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from the mixed multifilament obtained in the same manner as in Example 1.

[0149] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 3.

[0150] [Comparative Example 1] Polyphenylene sulfide composed only of p-phenylene sulfide units was melt-spun using a circular die having 1200 discharge holes at a single-hole discharge rate of 0.29 g / min, and the resulting undrawn fiber was taken up at a spinning speed of 1000 m / min. The fiber was drawn 4-fold in ethylene glycol at 110°C as super-draw stretching and 2.5-fold in water at 98°C as neck stretching to obtain a drawn fiber.

[0151] The obtained drawn fiber was cut to obtain polyphenylene sulfide short fibers having a fiber length of 51 mm.

[0152] The obtained short fibers were subjected to the processes of mixing with cotton, carding, drawing, roving, spinning, winding back, and heat setting. After obtaining a single spun yarn with a denier of 14s and a twist of 300 T / m, four of them were combined and twisted at 100 T / m to obtain a spun yarn (staple fiber) of polyphenylene sulfide (in Table 3, the twist is denoted as 300 - 100 T / m).

[0153] Using the obtained spun yarns as warp and weft, a plain weave gray fabric was woven with a warp density of 36 threads / 2.54 cm and a weft density of 25 threads / 2.54 cm. The obtained gray fabric was scoured at 20 m / min in a hot bath with a bath ratio of 1:20 and a temperature of 70 °C, to which 0.2 mass% of soda ash was added. The scoured fabric was dried and heat set at 180 °C to obtain a polyphenylene sulfide fabric as a diaphragm for alkaline water electrolysis.

[0154] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 3.

[0155] [Comparative Example 2] Polyphenylene sulfide consisting only of p-phenylene sulfide units was melt extruded through a round die with 36 orifices at a single orifice discharge rate of 0.58 g / min. After cooling and solidifying the extruded fibers, an oil agent was applied, and the fibers were wound up at a spinning speed of 1000 m / min to obtain 36 - filament undrawn fibers.

[0156] From the obtained undrawn fibers, drawn fibers were obtained in the same manner as in Example 1.

[0157] While combining 686 of the obtained drawn fibers, they were taken up by an unheated roller with a peripheral speed of 100 m / min to obtain a multifilament of 686 drawn fibers.

[0158] Using the obtained multifilaments as warp and weft, only the warp was twisted at 50 T / m, and then woven with a warp direction weaving density of 45 threads / 2.54 cm and a weft direction weaving density of 35 threads / 2.54 cm to produce a plain woven greige fabric. The obtained greige fabric was scoured at 20 m / min in a hot bath with a bath ratio of 1:20 and a temperature of 70 °C containing 0.2 mass% of soda ash. The scoured fabric was dried and heat set at 180 °C, and finally a polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained.

[0159] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 3.

[0160] [Comparative Example 3] An undrawn fiber and a drawn fiber having a sea-island composite cross-section were obtained in the same manner as in Example 1, and a mixed multifilament having a sea-island composite cross-section was also obtained.

[0161] A polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from the mixed multifilament obtained in the same manner as in Example 1 except that the sea-island removal process was not performed.

[0162] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 3.

[0163] [Comparative Example 4] An undrawn fiber and a drawn fiber having a sea-island composite cross-section were obtained in the same manner as in Example 4.

[0164] While combining 128 drawn fibers and 32 undrawn fibers obtained, they were taken up by a non-heated roller with a peripheral speed of 100 m / min to obtain a mixed multifilament having a sea-island composite cross-section.

[0165] A polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from the mixed multifilament obtained in the same manner as in Example 4 except that the warp direction weaving density during weaving was changed to 75 threads / 2.54 cm and the weft direction weaving density was changed to 65 threads / 2.54 cm.

[0166] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 3.

[0167] [Comparative Example 5] Undrawn fibers and drawn fibers having a sea-island composite cross-section were obtained in the same manner as in Example 1.

[0168] While combining 400 drawn fibers and 96 undrawn fibers obtained, they were taken up by a non-heated roller with a peripheral speed of 100 m / min to obtain a mixed multifilament having a sea-island composite cross-section.

[0169] A polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained from the mixed multifilament obtained in the same manner as in Example 4, except that the warp direction weaving density during weaving was changed to 35 threads / 2.54 cm and the weft direction weaving density was changed to 25 threads / 2.54 cm.

[0170] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 3.

[0171] [Comparative Example 6] Polyphenylene sulfide consisting only of p-phenylene sulfide units was melt-spun at a single-hole discharge rate of 11.56 g / min using a round die having two discharge holes, and the fibers were immediately cooled and solidified in warm water at 80°C to obtain undrawn fibers. Subsequently, the above undrawn fibers were drawn in the first stage at 3.60 times in a temperature atmosphere of 100°C, and further drawn in the second stage at 1.25 times in a temperature atmosphere of 130°C to make the total draw ratio 4.50 times. Then, in a temperature atmosphere of 180°C, heat setting was performed at a ratio of 0.95 times to obtain drawn fibers of monofilaments.

[0172] From the obtained drawn fibers, a polyphenylene sulfide fabric as a diaphragm for alkaline electrolysis was obtained in the same manner as in Example 1, except that the warp direction weaving density during weaving was changed to 50 threads / 2.54 cm and the weft direction weaving density was changed to 40 threads / 2.54 cm while remaining as monofilaments.

[0173] The physical properties of the obtained fabric were evaluated. The evaluation results are shown in Table 3.

[0174]

Table 2

[0175] [Table 3]

[0176] The polyphenylene sulfide fabric as the diaphragm for alkaline water electrolysis obtained in Examples 1 to 10 is a fabric having multifilaments with an average single filament diameter in a specific range and a specific number of single filaments, and it can be seen that all of the gas barrier property, ion permeability, and ion permeation persistence are good.

[0177] On the other hand, the fabric made of staple fibers obtained in Comparative Example 1 had a large ten-point average roughness (Rz), and as a result, the bubble rising angle was large, that is, the ion permeation persistence was poor.

[0178] In the fabric obtained in Comparative Example 2, since multifilaments with a thick fineness of an average single filament diameter of 12 μm were used, gaps were likely to occur between the multifilaments, resulting in a small bubble point and poor gas barrier property. Also, the ten-point average roughness (Rz) was large, and as a result, the bubble rising angle was large, that is, the ion permeation persistence was poor.

[0179] In the fabric obtained in Comparative Example 3, since fibers that had not undergone the desalination process were used, the multifilaments had a thicker fineness than in Comparative Example 2, and for the same reasons as in Comparative Example 2, the gas barrier property and ion permeation persistence were poor.

[0180] In the fabric obtained in Comparative Example 4, the number of fibers of the multifilaments used in the fabric was less than the range of Claim 1. For thinning, the ion permeability was improved, but because of that, the bubbles were more likely to penetrate, resulting in poor gas barrier property.

[0181] In the fabric obtained in Comparative Example 5, the number of fibers of the multifilament used in the fabric was larger than the range of Claim 1, resulting in a thick fabric. Therefore, the gas barrier property was improved, but the ion permeability was deteriorated accordingly.

[0182] In the fabric obtained in Comparative Example 6, the number of fibers of the multifilament used in the fabric was smaller than the range of Claim 1, and furthermore, it was a monofilament. Therefore, since the gaps between the fibers were large, the gas barrier property was poor. Also, since it was not a multifilament, the space through which ions permeated was limited, so it was not excellent in exchange for the gas barrier property. In addition, since it was a monofilament fabric with a thick fineness, air bubbles were likely to get caught between the warp threads and / or the weft threads, resulting in poor ion permeation persistence.

Claims

1. A fabric having multifilaments mainly composed of polyphenylene sulfide, wherein the average single-filament diameter of the multifilaments is 0.2 μm or more and 5.0 μm or less, and the number of single filaments is 5,000 or more and 400,000 or less.

2. The fabric according to claim 1, wherein in the multifilaments, when the average single-filament diameter is d [μm] and the number of single filaments is N [pieces], the product of d and N (d × N) is 50,000 μm·pieces or more and 250,000 μm·pieces or less.

3. The fabric according to claim 1 or 2, wherein the ten-point average roughness (Rz) measured in accordance with JIS B0601:1994 "Surface roughness - Definition and representation" of the fabric is 600 μm or more and 1000 μm or less.

4. The fabric according to claim 1 or 2, wherein the multifilaments include drawn fibers and undrawn fibers, and the mass ratio of the drawn fibers to the undrawn fibers is in the range of 99:1 to 50:

50.

5. The fabric according to claim 1 or 2, wherein the twist number of the multifilaments is 0 T / m or more and 200 T / m or less.

6. The fabric according to claim 1 or 2, wherein the warp direction weave density of the fabric is 30 threads / 2.54 cm or more and 55 threads / 2.54 cm or less, and the weft direction weave density is 20 threads / 2.54 cm or more and 45 threads / 2.54 cm or less.

7. The fabric according to claim 1 or 2, wherein the cover factor of the fabric is 2000 or more and 2800 or less.

8. A diaphragm for alkaline water electrolysis comprising the fabric according to claim 1 or 2.

9. An electrolytic cell for alkaline water electrolysis comprising the diaphragm for alkaline water electrolysis according to claim 8.

10. A step of obtaining undrawn fibers having a sea-island composite cross-section obtained by melt-extruding from the discharge holes of a sea-island type composite spinneret, with polyphenylene sulfide as the island component and copolymerized polyethylene terephthalate as the sea component; A step of obtaining drawn fibers by drawing the undrawn fibers; A step of obtaining mixed multifilaments by combining the drawn fibers and the undrawn fibers so that the mass ratio thereof is in the range of 99:1 to 50:50; A step of obtaining a fabric using the mixed multifilaments as warp and weft; The method for manufacturing a fabric according to claim 1 or 2, comprising the above steps.

11. The method for manufacturing a fabric according to claim 10, wherein after the step of obtaining the fabric, a sea-removing treatment is performed.

12. The method for manufacturing a woven fabric according to claim 10, wherein in the step of obtaining the mixed-filament multifilament, the twist number of the mixed-filament multifilament is 0 T / m or more and 200 T / m or less.

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