Polyphenylene sulfide fiber, method for producing same, woven or nonwoven fabric, diaphragm for alkaline water electrolysis, and electrolytic tank for alkaline water electrolysis

Abstract

In order to obtain a polyphenylene sulfide fiber having hygroscopicity while maintaining the excellent heat resistance and chemical resistance of polyphenylene sulfide, a method for producing the polyphenylene sulfide fiber, a woven or nonwoven fabric containing the polyphenylene sulfide fiber, a diaphragm for alkaline water electrolysis, and an electrolytic cell for alkaline water electrolysis, the polyphenylene sulfide fiber of the present invention includes polyphenylene sulfide as a main component, and has a dispersed phase of at least one thermoplastic resin selected from polyphenylene ether, polycarbonate, polyether sulfone, polyphenylene sulfone, polyether imide, and polysulfone, and the average dispersion diameter of the dispersed phase is 0.01-5 μm.

Description

Polyphenylene sulfide fiber, its manufacturing method, woven or nonwoven fabric, diaphragm for alkaline water electrolysis, and electrolytic cell for alkaline water electrolysis

[0001] The present invention relates to polyphenylene sulfide fibers, a method for producing the same, a woven or nonwoven fabric, a diaphragm for alkaline water electrolysis, and an electrolytic cell for alkaline water electrolysis.

[0002] Polyphenylene sulfide (PS) possesses excellent heat resistance, chemical resistance, electrical insulation, and flame retardancy, as well as excellent mechanical properties and moldability. Therefore, it is widely used as a metal replacement material and a material that can withstand extreme environments. Similarly, PP fiber has been utilized in applications such as bag filters, papermaking canvas, electrical insulating paper, battery separators, and various diaphragms, leveraging these properties. In particular, by combining the heat resistance and chemical resistance of PP with the ion permeability and gas separation properties of woven and nonwoven fabrics, PP fiber is being utilized for hydrogen production equipment diaphragms, fuel cell diaphragms, and membrane reinforcements. Taking advantage of PP's heat resistance and chemical resistance, PP fiber is being explored for use in diaphragms for hydrogen production equipment, which are attracting attention as a new energy source.

[0003] Hydrogen production equipment operates in a high-temperature, strongly alkaline environment. Therefore, it is known that improving the moisture absorption of the diaphragm is effective in improving operating efficiency and reducing electrical resistance. However, although polyphenylene sulfide has excellent heat resistance and chemical resistance, it has low moisture absorption, so it is necessary to improve its moisture absorption to further improve operating efficiency.

[0004] To address this issue, for example, polyphenylene sulfide fibers that have been hydrophilized by plasma and / or sulfonation have been proposed (Patent Document 1). It is described that the hydrophilization by plasma and / or sulfonation enhances gas barrier properties.

[0005] On the other hand, a polymer alloy fiber in which polyphenylene sulfide is blended with polyethylene terephthalate has been proposed (Patent Document 2). It is described that the resulting polymer alloy fiber has island component polyphenylene sulfide uniformly dispersed in the sea component.

[0006] Furthermore, a core-sheath type composite fiber has been proposed in which the core component is made of polyester and the sheath component is made of a blend polymer of polyester and polyphenylene sulfide (Patent Document 3). It describes that by controlling the proportion of the blend polymer, a core-sheath type composite fiber having an appropriate dispersion diameter and fiber properties can be obtained.

[0007] Furthermore, fibers made of a blend polymer of polyarylene sulfide and polyalkylene terephthalate have been proposed (Patent Document 4). It is described that by controlling the blend ratio of polyalkylene terephthalate, polyarylene sulfide fibers with excellent dimensional stability, chemical resistance, and heat resistance can be obtained.

[0008] JP-T-2018-534441 A JP-A-2008-63716 A JP-A-2015-140487 A JP-A-2011-106060

[0009] However, the technology disclosed in Patent Document 1 may not be able to maintain its hygroscopicity in a strongly alkaline environment over an extremely long period of time, such as when the hydrogen production device is operated for several decades, resulting in a problem of reduced performance of the hydrogen production device.

[0010] Furthermore, the technology disclosed in Patent Document 2 provides fibers with a highly uniform dispersion diameter, but has the problem that the sea component is polyethylene terephthalate, and therefore the chemical resistance is significantly reduced compared to polyphenylene sulfide.

[0011] Furthermore, the technology disclosed in Patent Document 3 provides fibers with excellent strength and elongation by disposing polyphenylene sulfide on the fiber surface, but has the problem of reduced chemical resistance and heat resistance due to the high polyester content.

[0012] On the other hand, in Patent Document 4, a fiber excellent in chemical resistance and heat resistance is obtained by blending a small amount of polyalkylene terephthalate with polyarylene sulfide, but there is a problem that the actual chemical resistance and heat resistance are lower than those of polyarylene sulfide.

[0013] An object of the present invention is to overcome the problems of the conventional art and to provide a polyphenylene sulfide fiber that has moisture absorption while maintaining the excellent heat resistance and chemical resistance of polyphenylene sulfide, a method for producing the same, a woven or nonwoven fabric containing the polyphenylene sulfide fiber, a diaphragm for alkaline water electrolysis, and an electrolytic cell for alkaline water electrolysis.

[0014] As a result of extensive research, the inventors have found that blending polyphenylene sulfide with a resin that has excellent compatibility with polyphenylene sulfide and is more hygroscopic than polyphenylene sulfide is effective in achieving the hygroscopicity, heat resistance, and alkali resistance required of a diaphragm for a hydrogen production device. The blended resin must also have high heat resistance and chemical resistance. Furthermore, they have found that while the hygroscopic effect can be efficiently achieved by positioning the dispersed phase of a polymer alloy fiber blended with a resin on the fiber surface, a dispersed phase located inside the fiber is less likely to contribute to improving hygroscopicity. Regarding this issue, they have found that controlling the dispersed particle diameter facilitates the placement of the blended components near the fiber surface, further contributing to improved hygroscopicity, leading to the completion of the present invention.

[0015] The present invention aims to solve the above problems and adopts the following means. (1) A polyphenylene sulfide fiber containing polyphenylene sulfide as a main component and having a dispersed phase of at least one thermoplastic resin selected from polyphenylene ether, polycarbonate, polyether sulfone, polyphenylene sulfone, polyetherimide, and polysulfone, wherein the average dispersed diameter of the dispersed phase is 0.01 μm or more and 5.0 μm or less. (2) A polyphenylene sulfide fiber according to (1), having an average fiber diameter of 0.5 μm or more and 15.0 μm or less. (3) A polyphenylene sulfide fiber according to (1) or (2), having an average dispersed diameter of the dispersed phase of 0.1 μm or more and 5.0 μm or less. (4) A polyphenylene sulfide fiber according to (2), having an average dispersed diameter / average fiber diameter ratio of 0.04 to 0.75. (5) The polyphenylene sulfide fiber according to any one of (1) to (4), having a moisture absorption rate of 0.10% or more. (6) The polyphenylene sulfide fiber according to any one of (1) to (5), wherein the polyphenylene sulfide component accounts for 60% by mass or more of the entire fiber. (7) The polyphenylene sulfide fiber according to any one of (1) to (6), wherein the molar ratio O / S determined by SEM-EDX measurement is 0.10 or more and 0.50 or less. (8) The polyphenylene sulfide fiber according to any one of (1) to (7), which is a core-sheath fiber, wherein the core component is polyphenylene sulfide and the sheath component contains a component (A) having a dispersed phase composed of polyphenylene sulfide and another thermoplastic resin. (9) A woven fabric or nonwoven fabric comprising the polyphenylene sulfide fiber according to any one of (1) to (8). (10) A diaphragm for alkaline water electrolysis, comprising the woven fabric or nonwoven fabric according to (9). (11) An electrolytic cell for alkaline water electrolysis, comprising the diaphragm for alkaline water electrolysis according to (10). (12) A method for producing a polyphenylene sulfide fiber according to any one of (1) to (8), comprising melt-kneading polyphenylene sulfide and at least one thermoplastic resin selected from polyphenylene ether, polycarbonate, polyether sulfone, polyphenylene sulfone, polyetherimide, and polysulfone at a melting temperature of 300°C to 350°C, and spinning the mixture through a spinneret.(13) The method for producing polyphenylene sulfide fibers according to (12) above, wherein the spinning draft (the ratio of the spinning speed to the extrusion linear speed at the spinneret) is 30 or more and 2,000 or less.

[0016] According to the present invention, it is possible to obtain polyphenylene sulfide fibers that have moisture absorption properties while maintaining excellent heat resistance and chemical resistance. The method for producing polyphenylene sulfide fibers of the present invention makes it possible to control the dispersion diameter of blend polymers. The woven or nonwoven fabric of the present invention has high hydrophilicity, making it possible to obtain diaphragms for alkaline water electrolysis and electrolytic cells for alkaline water electrolysis that have excellent electrolysis efficiency.

[0017] The fiber of the present invention is a polyphenylene sulfide fiber containing polyphenylene sulfide as a main component and having a dispersed phase of at least one thermoplastic resin selected from polyphenylene ether, polycarbonate, polyether sulfone, polyphenylene sulfone, polyetherimide, and polysulfone, and having an average dispersed particle diameter of the dispersed phase of 0.01 μm or more and 5.0 μm or less.

[0018] The present invention will be described in detail below, but the present invention is not limited to the scope of the following description as long as it does not deviate from the gist of the invention.

[0019] <Polyphenylene sulfide fiber> Polyphenylene sulfide, which is the main component of the present invention, is a resin composed of phenylene sulfide units such as p-phenylene sulfide units and m-phenylene sulfide units represented by structural formula (1) as main repeating units.

[0020]

[0021] The polyphenylene sulfide in the present invention preferably contains p-phenylene sulfide units in an amount of 60 mol % or more. The p-phenylene sulfide units are preferably 60 mol % or more, more preferably 70 mol % or more, even more preferably 80 mol % or more, and most preferably 100 mol %. By keeping the p-phenylene sulfide units within the above range, a fiber with high heat resistance and high strength can be obtained.

[0022] Furthermore, copolymerized units may be contained within the range that does not impair the effects of the present invention, but the amount of copolymerized units is preferably 20 mass % or less relative to the total mass of the polyphenylene sulfide resin.

[0023] The polyphenylene sulfide in the present invention is heated at 320°C for 100 seconds. －１ It is preferable that the melt viscosity at 2000 kJ / min is 50 Pa sec or more and 1000 Pa sec or less. If the melt viscosity is lower than 50 Pa sec, the degree of polymerization is too low, making it impossible to obtain fibers with sufficiently strong mechanical properties, and in addition, there may be frequent yarn breakage during drawing. On the other hand, if the melt viscosity is higher than 1000 Pa sec, the degree of polymerization is too high, making it necessary to increase the spinning temperature during spinning, which accelerates thermal degradation of the polyphenylene sulfide resin and makes it impossible to obtain fibers with high mechanical properties.

[0024] The term "main component" as used herein refers to a component that is contained in an amount of more than 50% by mass. The polyphenylene sulfide fiber of the present invention preferably contains 60% by mass or more of polyphenylene sulfide relative to the total mass of the fiber. This is more preferably 70% by mass or more, even more preferably 80% by mass or more, particularly preferably 85% by mass or more, and most preferably 87% by mass or more. The lower limit is preferably 95% by mass or less, and more preferably 93% by mass or less. By containing polyphenylene sulfide in the fiber within the above range, the fiber will have high heat resistance and chemical resistance. Furthermore, the high uniformity of the resin will result in high fiber orientation during spinning and drawing, resulting in a fiber with high mechanical properties.

[0025] The polyphenylene sulfide fiber of the present invention has a dispersed phase composed of a thermoplastic resin other than polyphenylene sulfide. The thermoplastic resin is at least one selected from polyphenylene ether, polycarbonate, polyethersulfone, polyphenylene sulfone, polyetherimide, and polysulfone. These thermoplastic resins can be used alone or in combination. Known polycarbonates, polyphenylene ethers, polyethersulfones, polyphenylene sulfones, polyetherimides, and polysulfones can be used. From the viewpoint of compatibility with polyphenylene sulfide, polyphenylene ethers, polyethersulfones, polyphenylene sulfones, and the like, which have molecular structures similar to those of polyphenylene sulfide, are more preferred as the thermoplastic resin. The content of the thermoplastic resin is preferably 40% by mass or less, more preferably 30% by mass or less, and even more preferably 20% by mass or less, based on the total mass of the fiber. By making the content more preferably 5% by mass or more and 15% by mass or less, and even more preferably 7% by mass or more and 13% by mass or less, sufficient moisture absorption is maintained, spinnability is stabilized, and balance of strength can be maintained.

[0026] The average dispersed diameter of the dispersed phase of the polyphenylene sulfide fiber of the present invention is 0.01 μm or more and 5.0 μm or less. If the average dispersed diameter of the dispersed phase is greater than 5.0 μm, thread breakage and the like are likely to occur during spinning and drawing, and insufficient drawing is not possible, resulting in a deterioration in the mechanical properties of the fiber. Furthermore, if the average dispersed diameter is large, the dispersed phase is likely to be located in the center of the fiber, where shear stress is less likely to be applied during spinning. In other words, the dispersed phase is less likely to be located on the fiber surface, which may result in an insufficient moisture absorption effect. The average dispersed diameter of the dispersed phase of the polyphenylene sulfide fiber is preferably 4.0 μm or less, more preferably 3.0 μm or less. If the average dispersed diameter of the dispersed phase is less than 0.01 μm, the dispersed phase is likely to be pushed in by the surface tension of the polyphenylene sulfide resin near the fiber surface, making it difficult for the dispersed phase to be exposed to the fiber surface, resulting in an insufficient moisture absorption effect. The average dispersed diameter of the dispersed phase of the polyphenylene sulfide fibers is preferably 0.1 μm or more, more preferably 0.2 μm or more, even more preferably 0.3 μm or more, and most preferably 0.5 μm or more.

[0027] The average dispersion diameter of the dispersed phases is determined by observing the cross section of the fiber with a transmission electron microscope (TEM) and measuring the area (μm) formed by the cross section contours of 50 or more randomly selected dispersed phases. ２ ) is measured, the diameter of a perfect circle having the same area as this area is calculated, and the average value thereof is taken as the average dispersion diameter.

[0028] The average dispersed particle diameter can be set within the above range by adjusting the kneading conditions and the viscosity of the resin.

[0029] The average fiber diameter of the polyphenylene sulfide fiber of the present invention is preferably 0.5 μm or more and 15.0 μm or less. By having an average fiber diameter of 15.0 μm or less, the dispersed phase is more likely to be located on the surface layer of the fiber, which is more likely to be subjected to shear stress during spinning, that is, the dispersed layer is more likely to be located on the surface layer of the fiber, and a sufficient moisture absorption effect is obtained. The average fiber diameter is preferably 13.0 μm or less, and more preferably 10.0 μm or less.

[0030] When the average fiber diameter is 0.5 μm or more, thread breakage and the like are unlikely to occur during spinning and drawing, and productivity is excellent. The average fiber diameter is preferably 0.6 μm or more, and more preferably 0.7 μm or more.

[0031] The average fiber diameter (μm) of the fibers referred to here can be determined by the following procedures. Step 1: The fibers are embedded in an embedding agent such as epoxy resin, and an ultrathin section of the fiber cross section is cut perpendicular to the fiber axis using a microtome equipped with a diamond knife. Step 2: An image of the cross section of one fiber is taken using a scanning electron microscope. The magnification is set to a magnification that allows the cross section of one fiber to be observed and measured with high accuracy. Step 3: Using the taken image, the area (μm) formed by the cross-sectional profile of a single fiber is determined using image analysis software. ２ Step 4: The above measurement is carried out on 100 randomly selected fibers, the number average is calculated, and the average fiber diameter (μm) is calculated and rounded off to one decimal place.

[0032] The average fiber diameter of the fibers can be adjusted to the above range by adjusting the spinning output and draw ratio, but other methods may also be used as long as they do not impede the object of the present invention.

[0033] In the polyphenylene sulfide fiber of the present invention, the ratio of the average dispersed diameter (μm) to the average fiber diameter (μm) (average dispersed diameter / average fiber diameter) is preferably 0.04 or more and 0.75 or less.

[0034] By setting the ratio of average dispersion diameter to average fiber diameter to be 0.75 or less, yarn breakage and the like are less likely to occur during spinning and drawing, improving productivity, and in addition, sufficient drawing is possible, and the fibers are highly oriented, resulting in fibers with high mechanical properties. The ratio of average dispersion diameter to average fiber diameter is more preferably 0.70 or less, and even more preferably 0.65 or less.

[0035] On the other hand, by setting the ratio of average dispersed diameter to average fiber diameter to be 0.04 or more, the average dispersed diameter becomes large relative to the average fiber diameter, and the dispersed phase is located near the fiber surface, thereby improving the moisture absorption rate. The ratio of average dispersed diameter to average fiber diameter is more preferably 0.05 or more.

[0036] The average dispersed diameter / average fiber diameter can be set within the above range by adjusting the kneading conditions, the compatibility between resins, the viscosity of the resins, and the spinning output and draw ratio. －１ The melt viscosity ratio (melt viscosity of thermoplastic resin other than polyphenylene sulfide / melt viscosity of polyphenylene sulfide) is preferably 0.7 or more and 23.0 or less. By making the melt viscosity ratio more preferably 1.0 or more, and even more preferably 3.0 or more, the average dispersed diameter of the dispersed phase relative to the fiber diameter can be increased, improving moisture absorption. By making the melt viscosity ratio more preferably 20.0 or less, even more preferably 15.0 or less, and particularly preferably 10.0 or less, yarn breakage is suppressed and the mechanical properties of the fiber are improved.

[0037] The cross-sectional shape of the polyphenylene sulfide fiber of the present invention is not limited to a round cross section, and may be any irregular cross section such as a multi-lobal 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 cross section, or a hollow cross section.

[0038] The polyphenylene sulfide fiber of the present invention may be composed solely of the aforementioned component (A) having a dispersed phase composed of polyphenylene sulfide and another thermoplastic resin; it may be a composite fiber obtained by combining polyphenylene sulfide with component (A); it may be a composite fiber obtained by combining component (A) with component (B), which has a different blending ratio of polyphenylene sulfide to thermoplastic resin other than polyphenylene sulfide compared to component (A); or it may be a composite fiber obtained by combining component (A) with component (C), which contains one or more thermoplastic resins other than polyphenylene sulfide that are different from the constituent polymer of component (A). The composite structure is not particularly limited as long as it does not impair the effects of the present invention, and any fiber structure can be used, such as a core-sheath structure, a sea-island structure, a side-by-side structure, or an eccentric core-sheath structure. It is preferable that component (C) has good compatibility with component (A). As the thermoplastic resin other than polyphenylene sulfide constituting component (C), specifically, polyphenylene ether, polyether sulfone, polyphenylene sulfone, etc., which have a molecular structure similar to that of polyphenylene sulfide, are more preferred. The good compatibility between the resins leads to a good fiber structure formation during conjugate spinning. In particular, a fiber having a core-sheath structure, in which the core component is polyphenylene sulfide and the sheath component is component (A) having a dispersed phase composed of polyphenylene sulfide and another thermoplastic resin, is preferred. By using component (A) as the sheath component, the dispersed phase is more likely to be arranged on the fiber surface, improving the moisture absorption effect.

[0039] The molar ratio O / S of the polyphenylene sulfide fiber of the present invention, as determined by SEM-EDX, is preferably 0.10 or more and 0.50 or less. By achieving a molar ratio O / S of 0.10 or more, a sufficient amount of thermoplastic resin other than polyphenylene sulfide is present to impart moisture absorption to component (A), thereby improving moisture absorption. The molar ratio O / S is preferably 0.12 or more, more preferably 0.15 or more. By achieving a molar ratio O / S of 0.50 or less, the content of the polyphenylene sulfide component increases, thereby improving fiber strength. The molar ratio O / S is preferably 0.40 or less, more preferably 0.35 or less. The molar ratio O / S determined by SEM-EDX can be adjusted to fall within the above range by adjusting the type and blending ratio of the thermoplastic resin other than polyphenylene sulfide in component (A), the amount of the dispersion layer near the fiber surface, and the like.

[0040] From a practical standpoint, the polyphenylene sulfide fiber of the present invention preferably has a tensile strength of 2.0 cN / dtex or more. The tensile strength is more preferably 2.3 cN / dtex or more, even more preferably 2.5 cN / dtex or more, or 2.8 cN / dtex or more. By setting the tensile strength within the above range, the mechanical properties of the resulting woven fabrics and nonwoven fabrics are improved. Furthermore, thread breakage and tearing during the manufacturing process are less likely to occur. Furthermore, the resulting woven fabrics and nonwoven fabrics are less likely to tear even when tensile stress is applied during subsequent processes or during use. Furthermore, there is no particular upper limit to the tensile strength, but the upper limit that can be achieved industrially is approximately 7.0 cN / dtex.

[0041] The tensile strength of polyphenylene sulfide in the present invention refers to a value measured by the method described in the Examples section.

[0042] The moisture absorption rate of the polyphenylene sulfide fiber of the present invention is preferably 0.10% or more. The moisture absorption rate is more preferably 0.13% or more, and even more preferably 0.15% or more. By setting the moisture absorption rate within the above range, when used as a diaphragm in a hydrogen production device, it is effective in improving the operating efficiency and reducing the electrical resistance. A higher moisture absorption rate is more effective in improving the operating efficiency, but fibers with a high moisture absorption rate exhibit a decrease in mechanical properties when absorbing moisture, so the upper limit of the moisture absorption rate is preferably 5.0%.

[0043] The moisture absorption rate of the polyphenylene sulfide fiber in the present invention refers to a value measured by the method described in the Examples section. The moisture absorption rate within the above range can be achieved by blending polyphenylene sulfide with a resin having a higher moisture absorption rate than polyphenylene sulfide.

[0044] The polyphenylene sulfide fiber of the present invention preferably has a strength retention rate of 80% or more after heat treatment at 180°C for 24 hours. A strength retention rate of 85% or more is more preferable, and even more preferably 90% or more is preferred, as this provides good thermal dimensional stability for woven and nonwoven fabrics. A higher upper limit is preferable, with 100% being ideal, but in reality, it is 99% or less. The heat resistance of the polyphenylene sulfide fiber in the present invention refers to a value measured by the method described in the Examples section. The above range can be achieved by blending polyphenylene sulfide with a highly heat-resistant resin, but other methods may be used as long as they do not impede the object of the present invention.

[0045] The polyphenylene sulfide fiber of the present invention preferably has a strength retention of 90% or more when immersed in a 30% by mass potassium hydroxide aqueous solution at 90°C for 24 hours. More preferably, it is 93% or more, and even more preferably, it is 95% or more. A higher upper limit is preferable, with 100% being ideal, but in reality, it is 99% or less. By achieving this range, strength can be maintained even in an alkaline environment, enabling long-term use as a hydrogen production device. Polyphenylene sulfide fibers are inherently highly resistant to alkali. However, when polyphenylene sulfide fibers are mixed with resins with low alkali resistance, the alkali decomposes components other than polyphenylene sulfide, tending to reduce the strength of the fiber. However, the polyphenylene sulfide fiber of the present invention successfully maintains alkali resistance by incorporating a highly chemical-resistant resin into the fiber as a dispersed phase with a specified dispersion diameter. The alkali resistance of the polyphenylene sulfide fiber in the present invention refers to a value measured by the method described in the Examples section.

[0046] The woven fabric of the present invention is a woven fabric containing the polyphenylene sulfide fiber of the present invention. The weave of the woven fabric may be plain weave, twill weave, satin weave, or a combination of these, or a modified pile weave or figured weave. Plain weave is preferred because it has the greatest number of weaving points and can achieve a high density. The nonwoven fabric of the present invention is a nonwoven fabric containing the polyphenylene sulfide fiber of the present invention. The type of nonwoven fabric in the nonwoven fabric of the present invention is not particularly limited, and examples include spunbond nonwoven fabrics, meltblown nonwoven fabrics, spunlace nonwoven fabrics, needlepunched nonwoven fabrics, and wetlaid nonwoven fabrics. However, wetlaid nonwoven fabrics are preferred because they can provide nonwoven fabrics with both high airtightness and uniformity.

[0047] <Method for Producing Polyphenylene Sulfide Fiber> Next, the method for producing the polyphenylene sulfide fiber of the present invention will be specifically described.

[0048] Examples of a method for producing polyphenylene sulfide used in the present invention include a method in which an alkali metal sulfide such as sodium sulfide is reacted with p-dichlorobenzene and, optionally, m-dichlorobenzene in an organic amide solvent such as N-methyl-2-pyrrolidone to obtain polyphenylene sulfide.

[0049] The method for producing the fiber of the present invention is not particularly limited, but examples include blending in a spinning machine and melt-kneading polyphenylene sulfide and a thermoplastic resin other than polyphenylene sulfide in advance, followed by fiberization. In particular, blending polyphenylene sulfide and a thermoplastic resin other than polyphenylene sulfide in advance to form a blend polymer and then fiberizing the blend polymer is more preferred, as this makes it easier to obtain the fiber of the present invention. Among these, a method is preferred in which polyphenylene sulfide and at least one thermoplastic resin selected from polyphenylene ether, polycarbonate, polyether sulfone, polyphenylene sulfone, polyetherimide, and polysulfone are melt-kneaded at a melting temperature of 280°C to 350°C, preferably 300°C to 350°C, and then spun from a spinneret.

[0050] The form of the polyphenylene sulfide raw material used in the production of the fiber of the present invention is not particularly limited. For example, the resin may be in the form of granules or powder depending on the known production method, but it may be used as is regardless of the form. It may also be used after being formed into flakes or pellets.

[0051] The polyphenylene sulfide and thermoplastic resins other than polyphenylene sulfide used in the present invention are subjected to 320°C for 100 seconds. －１ The melt viscosity ratio (melt viscosity of thermoplastic resin other than polyphenylene sulfide / melt viscosity of polyphenylene sulfide) is preferably 0.7 or more and 23.0 or less, and more preferably 20 or less. By setting the melt viscosity ratio within the above range, the average dispersed diameter of the dispersed phase relative to the fiber diameter can be appropriately increased, improving moisture absorption. By setting the melt viscosity ratio to be more preferably 15.0 or less, and particularly preferably 10.0 or less, yarn breakage is suppressed and the mechanical properties of the fiber are improved.

[0052] The shape of the thermoplastic resin other than polyphenylene sulfide used in the present invention is not particularly limited, and examples thereof include pellets, flakes, granules, and powder.

[0053] For melt kneading, a known heating melt mixing device can be used. Examples of heating melt mixing devices that can be used include a single-screw extruder, a twin-screw extruder, a multi-screw extruder equipped with three or more screws, a multi-screw extruder formed by combining these, and a kneader-ruder. Among these, a twin-screw extruder is preferably used because it improves the dispersibility of polyphenylene sulfide and thermoplastic resins other than polyphenylene sulfide, thereby improving spinnability. Additionally, the average dispersion diameter of the dispersed phase can be adjusted by adjusting the screw rotation speed of the twin-screw extruder. The faster the screw rotation speed, the better the dispersibility and the smaller the average dispersion diameter of the dispersed phase.

[0054] In the melt-kneading method, the method for feeding polyphenylene sulfide and thermoplastic resins other than polyphenylene sulfide to the kneader during kneading is not particularly limited. Examples include a method in which polyphenylene sulfide and thermoplastic resins other than polyphenylene sulfide are blended in advance and fed to the kneader, a method in which polyphenylene sulfide and thermoplastic resins other than polyphenylene sulfide are individually metered and fed to the kneader, and a method in which the thermoplastic resin other than polyphenylene sulfide is fed to the kneader via a side feed. The melt-kneading temperature is preferably 280 to 350°C, preferably 300 to 350°C. Here, the temperature refers to the temperature of the resin at the kneading section or the tip of the kneader. This temperature can usually be measured using a thermometer attached to the tip of the kneader. Setting the melt-kneading temperature within this range is preferred because it improves the spinning stability and the quality, such as the strength and color tone, of the resulting fiber.

[0055] The kneading time is not particularly limited, but is preferably 0.5 to 30 minutes. By setting the kneading time within this range, it is possible to achieve both the dispersibility of the thermoplastic resin and the suppression of thermal decomposition of the polyphenylene sulfide, and it is preferable because this results in good spinning stability and good quality, such as strength and color tone, of the obtained fiber.

[0056] The polyphenylene sulfide fiber of the present invention is preferably obtained by melt-kneading the blend polymer as described above and then melt-spinning the blend polymer.

[0057] The blend polymer used in the present invention is preferably dried before being subjected to melt spinning in order to prevent water contamination and remove oligomers, in order to improve spinnability. Drying conditions usually include vacuum drying at 100 to 200°C for 1 to 24 hours.

[0058] From the viewpoint of productivity, the polyphenylene sulfide fiber of the present invention is preferably a multifilament fiber, and the fineness of the multifilament fiber is preferably 20 dtex or more.

[0059] In melt spinning, a melt spinning technique using an extruder such as a pressure melter, a single-screw extruder, or a twin-screw extruder (twin-screw extruder) can be applied. The extruded blend polymer passes through a pipe, is metered by a metering device such as a gear pump, passes through a filter to remove foreign matter, and is then introduced to a spinneret. At this time, the temperature from the resin pipe to the spinneret (spinning temperature) is preferably 280°C or higher to increase fluidity, and preferably 380°C or lower to suppress thermal decomposition of the resin.

[0060] The spinneret used for extrusion preferably has a nozzle hole diameter D of 0.1 mm or more and 0.6 mm or less, and in a preferred embodiment, L / D, defined as the quotient obtained by dividing the land length L of the nozzle hole (the length of the straight tube portion having the same diameter as the nozzle hole) by the hole diameter, is 1 or more and 10 or less.

[0061] The blend polymer fiber discharged from the spinneret hole passes through a heat-retaining region and is then cooled and solidified by blowing cooling air (air). Since an excessively long heat-retaining region deteriorates spinnability, it is preferably up to 200 mm from the spinneret surface, more preferably up to 100 mm, and an even more preferred embodiment is a heat-retaining region up to 50 mm. The heat-retaining region may be a non-heat-retaining region, or the ambient temperature may be increased using a heating means. The temperature range is preferably 100°C or higher and 500°C or lower, more preferably 200°C or higher and 400°C or lower. The temperature of the cooling air can be determined in consideration of the cooling efficiency, taking into account the balance with the cooling air speed, and a preferred embodiment is 30°C or lower. By setting the cooling air temperature to preferably 30°C or lower, the solidification behavior upon cooling is stabilized, resulting in polyphenylene sulfide fiber with a high fiber diameter uniformity.

[0062] The cooling air is preferably blown in a direction substantially perpendicular to the undrawn fibers discharged from the spinneret. In this case, the speed of the cooling air is preferably 10 m / min or more from the viewpoints of cooling efficiency and uniformity of fineness, and is preferably 100 m / min or less from the viewpoint of spinning stability.

[0063] The cooled and solidified undrawn fibers are taken up by a roller (godet roller) rotating at a constant speed. The take-up speed is preferably 300 m / min or more to improve linear uniformity and productivity, and preferably 2000 m / min or less to prevent yarn breakage.

[0064] The spinning draft in the spinning step is expressed by the following formula, and is preferably in the range of 30 or more and 2000 or less: Spinning draft = Vs / V0, where Vs is the spinning speed (m / min), V0 is the linear discharge speed (m / min), V0 = Q / (S × ρ × 100), Q is the single-hole discharge rate (g / min), and S is the single-hole area (cm ２ ) ρ: Melt density (g / cm ３By setting the spinning draft to preferably 30 or more, more preferably 50 or more, it is possible to prevent the polymer flow discharged from the spinneret hole from remaining directly below the spinneret for a long period of time, and to suppress contamination of the spinneret surface, thereby stabilizing spinnability. Furthermore, by setting the spinning draft to preferably 2000 or less, it is possible to suppress yarn breakage due to excessive spinning tension, and it is preferable because fibers can be obtained with stable spinnability. It is even more preferable that it is 100 to 1000. The melt density is the value of polyphenylene sulfide (1.18 g / cm ３ ) is used.

[0065] The undrawn fiber thus obtained is subjected to a drawing step after being wound up or taken up. Drawing is carried out by running the fiber over a heated first roller or a heating device provided between the first and second rollers, such as a heating bath or a hot plate. Drawing conditions are determined based on the mechanical properties of the undrawn fiber. The drawing temperature is determined by the temperature of the heated first roller or the heating device provided between the first and second rollers, and the draw ratio is determined by the ratio of the peripheral speeds of the first and second rollers. The draw ratio can be appropriately selected depending on the elongation of the fiber before drawing and the tensile strength and elongation of the fiber after drawing, but is preferably 1.02 to 5.0 times. A draw ratio of preferably 2.0 times or more, more preferably 2.5 times or more, can improve the mechanical properties of the fiber by drawing. Furthermore, by setting the draw ratio to preferably 4.7 times or less, more preferably 4.4 times or less, yarn breakage during drawing can be suppressed, and stable drawing can be achieved.

[0066] The temperature of the heated first roller or heating device in the drawing step is preferably 80° C. or higher and 130° C. or lower. A temperature of 80° C. or higher fixes the drawing point, enabling stable drawing, while a temperature of 130° C. or lower can suppress yarn breakage and improve processability. Furthermore, from the viewpoint of fixing the drawing point, the temperature of the second roller is preferably the temperature of the heated first roller or heating device + 20° C. or lower.

[0067] Furthermore, after passing through the second roller, the drawn fiber must be heated and heat-set by a heated third roller or a heating device provided between the second roller and the third roller. The heat-setting temperature in the heat-setting process is preferably 110°C or higher and 250°C or lower. By setting the heat-setting temperature to preferably 140°C or higher, more preferably 160°C or higher, thermal crystallization is promoted, resulting in polyphenylene sulfide fiber with excellent mechanical properties. Furthermore, by setting the heat-setting temperature to preferably 240°C or lower, more preferably 235°C or lower, fusion of the fiber to the rollers is suppressed. In this manner, drawn fiber is obtained.

[0068] <Method for producing woven fabric> The method for producing the woven fabric of the present invention is as follows, but is not limited to this: The obtained polyphenylene sulfide fibers are used as warp and weft yarns, and after warping, healding, and reed insertion, the fabric is woven using a gripper loom or a heavy rapier loom.

[0069] The produced woven fabric is scoured at a water bath temperature of 90 to 95°C and a speed of 20 to 40 m / min. A scouring temperature of 90°C or higher facilitates the removal of dirt from the fabric, while a scouring temperature of 95°C or lower reduces energy consumption. A scouring speed of 20 m / min or higher increases production efficiency, while a scouring speed of 40 m / min or lower allows the scouring liquid to sufficiently contact the filter fabric, completely cleaning the dirt from the fabric. During scouring, it is preferable to add a scouring agent such as soda ash to remove hydrophobic impurities. After rinsing, a heat-setting speed of 5 m / min or higher can suppress shrinkage, wrinkle formation, and deterioration of texture of the woven fabric. A heat-setting speed of 15 m / min or lower can increase heat-setting efficiency. In this manner, a woven fabric can be obtained.

[0070] <Method for producing nonwoven fabric> The nonwoven fabric of the present invention is a nonwoven fabric containing the polyphenylene sulfide fiber of the present invention. The method for producing the nonwoven fabric of the present invention is not particularly limited, and examples thereof include a spunbond method, a meltblowing method, a spunlace method, a needlepunch method, and a wet papermaking method. However, a wet nonwoven fabric represented by a wet papermaking method is preferred because it can produce a nonwoven fabric with high airtightness and high uniformity.

[0071] <Method for producing wetlaid nonwoven fabric> The obtained polyphenylene sulfide fibers can be cut to a predetermined length with a cutter to obtain cut fibers.

[0072] The cut fibers obtained by the above method are dispersed in an aqueous medium. Here, aqueous medium refers to a liquid whose main component is water. These dispersions are mixed in the desired ratio to prepare a papermaking dispersion. Binder fibers may be mixed into the papermaking fiber dispersion as an adhesive between the fibers.

[0073] The papermaking fiber dispersion may contain a surfactant as a dispersant, a water-soluble polymer as a thickener, and an antifoaming agent to suppress foam generation.

[0074] The papermaking dispersion prepared as described above is made into paper using a cylinder, fourdrinier, or inclined wire papermaking machine or a hand-made papermaking machine, and the paper is dried using a Yankee dryer, rotary dryer, or the like to form a dry web, which is then subjected to a heat and pressure treatment to obtain a wetlaid nonwoven fabric.

[0075] The temperature conditions for the heat and pressure treatment are preferably a temperature equal to or higher than the glass transition temperature of the binder fiber and equal to or lower than the melting point of the polyphenylene sulfide fiber, thereby obtaining a wetlaid nonwoven fabric.

[0076] The electrical resistance of the woven or nonwoven fabric of the present invention is preferably 25 mΩ or less. Electrical resistance is a physical property that indicates ion permeability, and lower electrical resistance indicates higher ion permeability. By setting the electrical resistance within the above range, sufficient ion permeability is exhibited and the energy cost for water electrolysis is reduced. It is more preferably 20 mΩ or less, and even more preferably 15 mΩ or less.

[0077] The thus obtained woven or nonwoven fabric of the present invention has excellent heat resistance, chemical resistance and hydrophilicity and can therefore be suitably used as a diaphragm for alkaline water electrolysis. Furthermore, an electrolytic cell for alkaline water electrolysis comprising such a diaphragm for alkaline water electrolysis has excellent electrolysis efficiency.

[0078] The polyphenylene sulfide fiber of the present invention will be described in more detail below with reference to examples. However, the present invention is not limited to these examples. Various modifications and alterations are possible within the scope of the present invention. The respective property values ​​in the examples were determined by the following methods.

[0079] [Measurement and Evaluation Methods] (1) Average Fiber Diameter Measurements were carried out as follows using a scanning electron microscope "S-5500" manufactured by Hitachi High-Technologies Corporation as the scanning electron microscope and "WinROOF2015" manufactured by Mitani Shoji Co., Ltd. as the image analysis software. Step 1: The fibers are embedded in a bisphenol-based epoxy resin embedding agent, and an ultrathin section of the fiber cross section is cut perpendicular to the fiber axis using a microtome equipped with a diamond knife. Step 2: An image of the cross section of one fiber is taken with the scanning electron microscope. The magnification is set to a magnification that allows the cross section of one fiber to be observed and measured with high accuracy. Step 3: Using the taken image and image analysis software, the area Af (μm) formed by the cross-sectional profile of a single fiber is calculated. ２ Step 4: The above measurement is carried out on 100 randomly selected fibers, the number average is calculated, and the average fiber diameter (μm) is calculated, and the result is rounded to one decimal place.

[0080] (2) Average Dispersed Diameter The fiber cross section was observed using a transmission electron microscope (JEM-1400Plus manufactured by JEOL Ltd.) under an accelerating voltage of 100 kV at a magnification that allowed for observation and accurate measurement of the dispersed phase in the fiber cross section, and photographs were taken. First, the fiber was embedded in a bisphenol-based epoxy resin embedding agent, and an ultrathin section of the fiber cross section was cut perpendicular to the fiber axis using a microtome equipped with a diamond knife and used for the above-mentioned photographing. From the fiber cross section photograph, the area (μm ) formed by the cross-sectional contour of the dispersed phase was calculated using image processing software (WINROOF). ２ The diameter of a perfect circle having the same area as the measured area was calculated. The diameters of 50 randomly selected dispersed phase particles were measured, and the average value was calculated to obtain the average dispersed diameter (μm).

[0081] (3) Melt Viscosity The melt viscosity measurement method for calculating the melt viscosity ratio between polyphenylene sulfide and a thermoplastic resin other than polyphenylene sulfide is as follows. The chip-shaped polymer was dried to a moisture content of 200 ppm or less using a vacuum dryer, and the melt viscosity was measured using a Capillograph manufactured by Toyo Seiki Seisakusho Co., Ltd., while gradually changing the shear rate. The measurement temperature was 330°C, and the time from the time the sample was placed in a heating furnace under a nitrogen atmosphere to the start of measurement was 5 minutes. The shear rate was 100 sec. －１ The melt viscosity of the thermoplastic resin other than polyphenylene sulfide was evaluated as the melt viscosity of the polymer. Furthermore, the melt viscosity of the thermoplastic resin other than polyphenylene sulfide was divided by the melt viscosity of polyphenylene sulfide, and the value was rounded to two decimal places to obtain the melt viscosity ratio of polyphenylene sulfide to the thermoplastic resin other than polyphenylene sulfide.

[0082] (4) Molar ratio O / S The surface of polyphenylene sulfide fiber was measured using a scanning electron microscope (SEM-EDX) Hitachi High-Technologies scanning electron microscope (SU1510) with a scanning electron microscope. Samples of fibers were collected and refined for 30 minutes in a water bath containing 0.2% by mass of soda ash at 80 ° C. before measurement. The fiber surface was vapor-deposited with a platinum-palladium alloy and the mass ratio of sulfur atoms to oxygen atoms was measured under an acceleration voltage of 15 kV. The molar ratio of oxygen atoms to 1 mole of sulfur atoms was calculated from the results. The simple number average of three measurements was calculated and the value was rounded to two decimal places.

[0083] (5) Tensile Strength The tensile strength of the polyphenylene sulfide fiber was measured five times per level using "TENSILON" (registered trademark) (UTM-III-100 manufactured by Orientec Co., Ltd.) in accordance with "Chapter 8.5 Tensile Strength and Elongation" of JIS L1013:2010 under the conditions of a sample length of 200 mm and a pulling speed of 200 mm / min, and the arithmetic average value was determined as the tensile strength (cN / dtex).

[0084] (6) Moisture Absorption Rate The fiber was dried at 90°C for 12 hours or more in a hot air dryer, and then returned to room temperature in the dryer. A 2-4 g sample was taken and precisely weighed, and the mass was designated W1. The sample was then placed in a thermo-hygrostat chamber adjusted to a temperature of 30°C and a relative humidity of 90% RH for 24 hours, and the mass was precisely weighed and designated W2. The moisture absorption rate was calculated using the following formula: Moisture absorption rate (%) = (W2 - W1) / W1 × 100. (7) Heat Resistance The fiber was left in an oven adjusted to a temperature of 180°C for 24 hours. The tensile strength of the fiber after the heat treatment was measured, and the ratio (100 × tensile strength after treatment / initial tensile strength) to the initial tensile strength (the tensile strength measured in (5) above; the same applies below) was calculated as the strength retention rate (%).

[0085] (8) Alkali Resistance A fiber was immersed in a 30% by mass aqueous solution of potassium hydroxide. The aqueous solution of potassium hydroxide was then heated to 90°C and heat-treated for 24 hours. The tensile strength of the fiber that had been dried at 90°C for 12 hours or more after the heat treatment in the aqueous solution of potassium hydroxide was measured, and the strength retention (%) was calculated as a ratio to the initial tensile strength (100 × tensile strength after treatment / initial tensile strength).

[0086] (9) Number of twists The number of twists in the present invention refers to a value measured in accordance with "8.13.1 Number of twists" of JIS L1013:2021 "Testing methods for chemical fiber filament yarns."

[0087] (10) Electrical Resistance Measurement was performed in accordance with the provisions of JIS C2313:1995 "Separators for Lead-Acid Batteries." The measurement equipment and conditions were as follows: A potassium hydroxide aqueous 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 electrodes was 23 mm, and the woven or nonwoven fabric with a length of 4 cm and a width of 2 cm was placed between the electrodes. The electrical resistance was measured using an "LCR Meter ZM2371" manufactured by NF Corporation, and an applied voltage was 10 mV. The product of the output impedance (Z) value and the diaphragm area was taken as the electrical resistance, and the value was rounded to the nearest integer.

[0088] [Example 1] Polyphenylene sulfide and polyether sulfone, each consisting of only p-phenylene sulfide units as repeating units, were mixed in proportions of 90% by mass and 10% by mass, in a twin-screw kneader (twin-screw extruder) at a melt temperature of 320°C and a screw rotation speed of 300 min －１ The polyphenylene sulfide and polyether sulfone used were melt-kneaded for 2 minutes at 320°C for 100 seconds to obtain a blend polymer. －１ The melt viscosities at 160 Pa sec and 1600 Pa sec, respectively, were obtained. The resulting blend polymer was vacuum dried at 150°C for 12 hours and then melt-spun at a spinning temperature of 320°C. In the melt spinning, the blend polymer was melt-extruded using a twin-screw extruder and supplied to a spinning pack while being metered using a gear pump. The blend polymer was then extruded from a spinneret having 36 holes, each with a hole diameter D of 0.23 mm and a land length L of 0.3 mm, at a single-hole extrusion rate of 0.36 g / min.

[0089] The blend polymer extruded from the spinneret was passed through a 50 mm non-heated insulation zone and then air-cooled over 1.0 m using a uniflow cooling device at 25°C and an air speed of 18 m / min. An oil was then applied, and 36 filaments were wound on a winder via a first godet roller and a second godet roller at 1000 m / min to obtain undrawn fibers. The spinning draft was 136.

[0090] The undrawn fiber was taken up by a feed roller equipped with a nip roller, tension was applied to the undrawn fiber between the first roller and the first roller, and then the fiber was heated and drawn six times around the first and second rollers heated to 90°C and 100°C, respectively. The fiber was then heated and drawn six times around the third roller heated to 230°C, and heat-set. The total draw ratio was 3.8 times. After the third roller, the fiber was taken up by an unheated roller at a peripheral speed of 400 m / min and then wound on a winder to obtain polyphenylene sulfide fiber containing a dispersed phase of polyethersulfone with an average dispersed diameter of 0.5 μm. The results are shown in Table 1.

[0091] Examples 2 and 3 Polyphenylene sulfide fibers were obtained in the same manner as in Example 1, except that various conditions were changed as shown in Table 1.

[0092] [Examples 4 and 5] Polyphenylene sulfide fibers were obtained in the same manner as in Example 1, except that the melt viscosity of polyphenylene sulfide or polyether sulfone was changed so as to achieve the various conditions and melt viscosity ratios shown in Table 1.

[0093] [Example 6] Screw rotation speed: 200 min －１ Polyphenylene sulfide fibers were obtained in the same manner as in Example 1, except that various conditions were changed as shown in Table 1.

[0094] [Example 7] Polyphenylene sulfide fibers were obtained in the same manner as in Example 1, except that the hole diameter D of the spinneret was changed to 0.30 mm, the land length L to 0.35 mm, and the single-hole output rate was changed to 1.90 g / min, thereby changing the average fiber diameter to that shown in Table 1. The spinning draft was 44.

[0095] [Example 8] Polyphenylene sulfide consisting only of p-phenylene sulfide units as repeating units and polyether sulfone were mixed in proportions of 90% by mass and 10% by mass, respectively, in a twin-screw kneader (twin-screw extruder) at a melt temperature of 320°C and a screw rotation speed of 300 min －１ The polyphenylene sulfide and polyether sulfone used were melt-kneaded at 320°C for 100 seconds to obtain a blend polymer. －１The melt viscosities at these temperatures were 160 Pa sec and 1600 Pa sec, respectively. The resulting blend polymer was vacuum dried at 150°C for 12 hours, and melt spun at a spinning temperature of 305°C using the blend polymer as the island component and polyethylene terephthalate copolymerized with 5.0 mol% of 5-sodium sulfoisophthalic acid as the sea component. In the melt spinning, the polymers were melt extruded at 320°C by a twin-screw extruder using an islands-in-sea composite spinneret (1000 islands) with round island component shapes, with a sea / island component ratio of 40 / 60, and the polymers were supplied to a spinning pack while being metered by a gear pump. The polymers were then extruded at a single-hole throughput rate of 3.44 g / min through a spinneret having eight holes, each with a hole diameter D of 0.6 mm and a land length L of 0.9 mm.

[0096] The polymer extruded from the spinneret was passed through a 50 mm non-heated insulation zone and then air-cooled over 1.0 m using a uniflow cooling device at 25°C and an air speed of 18 m / min. An oil was then applied, and the polymer was passed through a first godet roller and a second godet roller at 1000 m / min and wound on a winder to obtain an undrawn fiber. The spinning draft was 97.

[0097] The unstretched fiber was taken up by a feed roller equipped with a nip roller, tension was applied to the unstretched fiber between the first roller and the first roller, and the unstretched fiber was then heated and drawn six times around the first roller and the second roller heated to 90°C and 100°C, respectively. The fiber was then further heated and drawn six times around the third roller heated to 180°C, and heat-set. The total draw ratio was 3.8 times, and the fiber was taken up by an unheated roller after the third roller at a peripheral speed of 400 m / min and then wound on a winder to obtain a drawn fiber.

[0098] The obtained drawn fiber was subjected to a treatment to dissolve the sea component in a 3 mass % aqueous sodium hydroxide solution (bath ratio 1 / 100) heated to 90°C, thereby obtaining a polyphenylene sulfide fiber containing a dispersed phase of polyethersulfone having an average dispersed diameter of 0.2 µm.

[0099] [Examples 9 to 10] Polyphenylene sulfide fibers were obtained in the same manner as in Example 8, except that the melt viscosity of polyphenylene sulfide or polyether sulfone was changed to achieve the various conditions and melt viscosity ratios shown in Table 2.

[0100] [Example 11] A polyphenylene sulfide fiber was obtained in the same manner as in Example 8, except that the number of islands in the islands-in-sea composite spinneret was 32, the number of spinneret holes was 12, the hole diameter D was 0.3 mm, the land length L was 0.3 mm, and the throughput rate per hole was 1.37 g / min. The spinning draft was 61.

[0101] Example 12 Polyphenylene sulfide fibers were obtained in the same manner as in Example 1, except that various conditions were changed as shown in Table 2.

[0102] Example 13 Polyphenylene sulfide and polyether sulfone, each consisting solely of p-phenylene sulfide units as repeating units, were mixed in proportions of 90% by mass and 10% by mass, and mixed in a twin-screw kneader (twin-screw extruder) at a melt temperature of 320°C and a screw rotation speed of 300 min. －１ The polyphenylene sulfide and polyether sulfone used were melt-kneaded for 2 minutes at 320°C for 100 seconds to obtain a blend polymer. －１ The melt viscosities at these temperatures were 160 Pa sec and 1600 Pa sec, respectively. The resulting blend polymer was vacuum dried at 150°C for 12 hours, and melt-spun at a spinning temperature of 320°C using the blend polymer as the sheath component and polyphenylene sulfide as the core component. In the melt spinning, the blend polymer was melt-extruded using a twin-screw extruder and supplied to a spinning pack while being metered using a gear pump. The blend polymer was then extruded from a spinneret having 36 holes, each with a hole diameter D of 0.25 mm and a land length L of 0.35 mm, at a single-hole extrusion rate of 0.36 g / min.

[0103] The blend polymer extruded from the spinneret was passed through a 50 mm non-heated insulation zone and then air-cooled over 1.0 m using a uniflow cooling device at 25°C and an air speed of 18 m / min. An oil was then applied, and the 36 filaments were passed through a first godet roller and a second godet roller at 1000 m / min and wound on a winder to obtain undrawn fibers. The spinning draft was 161.

[0104] The undrawn fiber was taken up by a feed roller equipped with a nip roller, tension was applied to the undrawn fiber between the first roller and the first roller, and then the fiber was heated and drawn six times around the first and second rollers heated to 90°C and 100°C, respectively. The fiber was then heated and drawn six times around the third roller heated to 230°C, and heat-set. The total draw ratio was 3.8 times. After the third roller, the fiber was taken up by an unheated roller at a peripheral speed of 400 m / min and then wound on a winder to obtain polyphenylene sulfide fiber containing a dispersed phase of polyethersulfone with an average dispersed diameter of 0.5 μm. The results are shown in Table 1.

[0105] Example 14 Polyphenylene sulfide consisting only of p-phenylene sulfide units as repeating units and polyether sulfone were mixed in proportions of 90% by mass and 10% by mass, respectively, in a twin-screw kneader (twin-screw extruder) at a melt temperature of 320°C and a screw rotation speed of 300 min －１ The polyphenylene sulfide and polyether sulfone used were melt-kneaded for 2 minutes at 320°C for 100 seconds to obtain a blend polymer. －１ The melt viscosities at 160 Pa sec and 1600 Pa sec, respectively, were obtained. The resulting blend polymer was vacuum dried at 150°C for 12 hours. Using a round spinneret having 1200 holes, each with a hole diameter D of 0.23 mm and a land length L of 0.30 mm, the melt was extruded at a spinning temperature of 320°C and a single-hole throughput of 0.29 g / min, and then taken up at a spinning speed of 1000 m / min to obtain an undrawn fiber. The spinning draft was 169. The undrawn fiber was then super-drawn 4 times in ethylene glycol at 110°C, followed by neck drawing 2.5 times in water at 98°C to obtain a drawn fiber.

[0106] The resulting drawn fibers were cut to obtain polyphenylene sulfide short fibers having a fiber length of 51 mm.

[0107] The obtained staple fibers were subjected to processes of blending, carding, drawing, roving, fine spinning, rewinding, and heat setting to obtain a single spun yarn with a twist number of 300 T / m, which was then twisted into a four-ply yarn at 100 T / m to obtain a spun yarn (staple fiber) of polyphenylene sulfide containing a dispersed phase of polyethersulfone with an average dispersed diameter of 0.5 μm (in Table 3, the twist number is expressed as 300-100 T / m).

[0108] The resulting spun yarn was used as the warp and weft to weave a plain weave fabric at a warp density of 36 threads / 2.54 cm and a weft density of 25 threads / 2.54 cm. The resulting greige fabric was scoured at 20 m / min in a water bath containing 0.2 mass% soda ash at a bath ratio of 1:20 and a temperature of 70°C. The scoured fabric was dried and heat-set at 180°C to obtain a polyphenylene sulfide fabric as a diaphragm for alkaline water electrolysis. The results are shown in Table 3.

[0109] Example 15 The drawn fibers obtained in Example 11 and the undrawn fibers obtained in Example 8 were cut with a cutter to the fiber lengths listed in Table 4, and then treated with 3 wt % aqueous sodium hydroxide solutions (bath ratio 1 / 100) heated to 90°C and 65°C, respectively, to obtain fiber dispersions. The resulting fiber dispersions were then weighed out to achieve the basis weight and blend ratio listed in Table 1, and the fibers were dispersed so that the fiber concentration in the dispersion was 0.0002 wt %, to obtain a fiber dispersion for papermaking. To this fiber dispersion for papermaking, 0.02 wt % of a dispersant (Y-258 manufactured by Yoshimura Oil Chemical Co., Ltd.) and 0.0003 wt % of a thickener (Meipam manufactured by Meisei Chemical Industry Co., Ltd.) were added, and the mixture was thoroughly stirred. This fiber dispersion for papermaking was used to make paper using a square sheet machine (250 mm square) manufactured by Kumagai Riki Kogyo Co., Ltd., and the paper was dried in a rotary dryer with a roller temperature set to 120°C to obtain a dry web, which was then subjected to thermal calendering at an iron roll surface temperature of 220°C, a linear pressure of 490 N / cm, and a roll rotation speed of 3 m / min to obtain a wetlaid nonwoven fabric. The results are shown in Table 4.

[0110] Comparative Example 1 Polyphenylene sulfide fibers were obtained in the same manner as in Example 1, except that various conditions were changed as shown in Table 2.

[0111] [Comparative Example 2] The single-hole discharge rate was changed to 0.57 g / min, and the polyphenylene sulfide and polyether sulfone used were subjected to a test at 320°C for 100 seconds. －１ Polyphenylene sulfide fibers were obtained in the same manner as in Example 1, except that the melt viscosities at 100 Pa sec and 2500 Pa sec were set to 100 Pa sec and 2500 Pa sec, respectively, and various conditions were changed as shown in Table 2. The spinning draft was 86.

[0112] Comparative Examples 3 and 4 Polyphenylene sulfide fibers were obtained in the same manner as in Example 1, except that the melt-kneading temperature was changed to 300° C. and various conditions were changed as shown in Table 2.

[0113]

[0114]

[0115]

[0116]

[0117] As can be seen from Tables 1 and 2, the polyphenylene sulfide fibers of Examples 1 to 13 had high moisture absorption while maintaining high strength, alkali resistance, and heat resistance. In contrast, the fibers of Comparative Examples 1 to 4 had low properties in any of these areas.

[0118] A comparison of Examples 1 to 3 reveals that as the polyethersulfone content increases, the O / S molar ratio increases and the moisture absorption rate also increases. A comparison of Examples 1, 4, and 5 reveals that as the melt viscosity ratio increases, the average dispersed diameter increases and the moisture absorption rate also increases. A comparison of Examples 1 and 6 reveals that lowering the screw rotation speed can further increase the average dispersed diameter and thus increase the moisture absorption rate. A comparison of Examples 1 and 7 reveals that as the average fiber diameter increases, the dispersed phase tends to be located at the center of the fiber during spinning, which tends to lower the O / S molar ratio and further decrease the moisture absorption rate. Examples 8 to 11 are sea-island composite fibers that have been treated to dissolve the sea component. Since the average fiber diameter is small, the dispersed phase tends to be located on the fiber surface, resulting in a high O / S molar ratio and a high moisture absorption rate. A comparison of Examples 1 and 12 reveals that when polyethersulfone is used as the thermoplastic resin other than polyphenylene sulfide, the O / S molar ratio is higher and the moisture absorption rate is higher than when polyphenylene sulfone is used. Example 13 is a sheath-core fiber, and since the dispersed phase is likely to be located on the fiber surface, it is understood that the molar ratio O / S is high and further the moisture absorption rate is high.

[0119] Since Comparative Example 1 is a fiber made of a single component of polyphenylene sulfide, the molar ratio O / S is 0, and it is clear that the moisture absorption rate is low. Comparative Example 2 has a larger average dispersed diameter than Example 1 and is outside the range of claim 1, so the dispersed phase is more likely to be located at the center of the fiber during spinning, and therefore the molar ratio O / S is low and the moisture absorption rate is also low. In addition, the tensile strength, which is a mechanical property, is also low. As for Comparative Example 3, since polyethylene terephthalate and polybutylene terephthalate are used as thermoplastic resins other than polyphenylene sulfide, the moisture absorption rate is high but the alkali resistance and heat resistance are poor.

Claims

1. A polyphenylene sulfide fiber having polyphenylene sulfide as a main component and having a dispersed phase of at least one thermoplastic resin selected from polyphenylene ether, polycarbonate, polyether sulfone, polyphenylene sulfone, polyether imide and polysulfone, wherein the average dispersed diameter of the dispersed phase is 0.01 μm or more and 5.0 μm or less.

2. The polyphenylene sulfide fiber according to claim 1, having an average fiber diameter of 0.5 μm or more and 15.0 μm or less.

3. Polyphenylene sulfide fiber according to claim 1 or 2, wherein the average dispersed diameter of the dispersed phase is from 0.1 μm to 5.0 μm.

4. The polyphenylene sulfide fiber according to claim 2, wherein the ratio of average dispersed diameter to average fiber diameter is 0.04 or more and 0.75 or less.

5. Polyphenylene sulfide fiber according to claim 1 or 2, which has a moisture absorption rate of 0.10% or more.

6. A polyphenylene sulfide fiber according to claim 1 or 2, in which the polyphenylene sulfide component is 60% by mass or more of the entire fiber.

7. The polyphenylene sulfide fiber according to claim 1 or 2, wherein the molar ratio O / S determined by SEM-EDX measurement is 0.10 or more and 0.50 or less.

8. A polyphenylene sulfide fiber according to claim 1 or 2, which is a core-sheath fiber, the core component being polyphenylene sulfide, and the sheath component being provided with a component (A) having a dispersed phase composed of polyphenylene sulfide and another thermoplastic resin.

9. A woven or nonwoven fabric comprising the polyphenylene sulfide fiber according to claim 1 or 2.

10. A diaphragm for alkaline water electrolysis, comprising the woven or nonwoven fabric according to claim 9.

11. An electrolytic cell for alkaline water electrolysis comprising the diaphragm for alkaline water electrolysis according to claim 10.

12. A method for producing polyphenylene sulfide fiber according to claim 1 or 2, in which polyphenylene sulfide and at least one thermoplastic resin selected from polyphenylene ether, polycarbonate, polyether sulfone, polyphenylene sulfone, polyether imide and polysulfone are melt-kneaded at a melting temperature of 300°C to 350°C and spun from a spinneret.

13. A method for producing polyphenylene sulfide fibers according to claim 12, wherein the spinning draft (the ratio of the spinning speed to the extrusion linear speed at the spinneret) is 30 or more and 2,000 or less.

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