Fiber laminate and separation membrane composite

Abstract

To provide a fiber laminated body which can achieve a separation membrane composite body that can prevent occurrence of such a problem that wrinkles and cracks are generated in a film layer, is less likely to cause such a problem that passing resistance of gas and liquid or ions are unintentionally increased, and is rich in strength, and a separation membrane composite body having the fiber laminated body.SOLUTION: There are provided a fiber laminated body that is used for reinforcing a film layer by bringing a non-woven fabric layer into contact with the film layer and has a non-woven fabric layer and a fiber base material layer, wherein the non-woven fabric layer contains a fiber containing a fluorine-based resin as a constituent fiber, the fiber base material layer has an average fiber diameter of the constituent fiber larger than that of the non-woven fabric layer, and thereby can solve the above problems; and a separation membrane composite body having the fiber laminated body.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a fiber laminate having a nonwoven fabric layer used to reinforce a film layer and a fiber substrate layer, and a separation membrane composite having a film layer on the nonwoven fabric layer of the fiber laminate. [Background technology]

[0002] In recent years, separation membranes made of films have been used in a variety of industrial applications. For example, separation membranes are used as gas-permeable membranes (e.g., oxygen separation membranes and carbon dioxide separation membranes), liquid-permeable membranes (e.g., water filtration membranes), separators for secondary batteries, capacitors, or redox flow batteries, and electrolyte membranes for fuel cells. Furthermore, as an example of a gas-permeable membrane, it is expected that it will also be used as an oxygen-enrichment membrane used to provide highly concentrated oxygen to fuel cells, as disclosed in JP-A-2003-151585 (Patent Document 1) and JP-A-2012-28017 (Patent Document 2).

[0003] Although there is a demand for thinner separation membranes so that they can be used in a wider variety of industrial applications, thin separation membranes have problems such as poor strength, such as poor shape stability during handling and production, and poor dimensional stability during use. For this reason, preparation of a separation membrane composite by reinforcing the separation membrane with a nonwoven fabric has been investigated.

[0004] As an example of such a separation membrane composite, Japanese Patent Laid-Open No. 2018-23955 (Patent Document 3) discloses a laminate comprising a fiber substrate whose surface is covered with a porous resin body and a separation membrane formed on the porous resin body. Note that Patent Document 3 is characterized in that the surface of the fiber substrate is covered with a porous resin body and smoothed in order to form a thin, uniform separation membrane. Furthermore, Japanese Patent Laid-Open No. 03-108258 (Patent Document 4) discloses, as a comparative example, an oxygen enrichment membrane formed by forming an oxygen-selective permeable membrane on a polypropylene nonwoven fabric.

[0005] Furthermore, Japanese Patent Laid-Open No. 2009-183879 (Patent Document 5) discloses a separation membrane substrate sheet having an ultrafine fiber layer on a support fiber sheet mainly made of fusion fibers, which is used in producing an oxygen enrichment membrane, etc. In addition, Patent Document 5 discloses, as an example, the production of a separation membrane laminate sheet in which a thin film is laminated on an ultrafine fiber layer made of polyacrylonitrile. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent Publication No. 2003-151585 [Patent Document 2] Patent Publication No. 2012-28017 [Patent Document 3] Patent Publication No. 2018-23955 [Patent Document 4] Patent Publication No. 03-108258 [Patent Document 5] Patent Publication No. 2009-183879 Summary of the Invention [Problem to be solved by the invention]

[0007] The applicant of the present application has found that the separation membrane composite disclosed in Patent Document 3 sometimes suffers from an unintended problem of increased resistance to the passage of gases, liquids, or ions through the film layer. In the separation membrane composite disclosed in Patent Document 3, a porous resin body that can prevent the passage of gases, liquids, or ions forms a planar contact portion between the fiber substrate layer and the film layer, and is in contact with the film layer. Therefore, it is believed that the large area of ​​each contact portion makes it difficult for gases, liquids, or ions to pass through the film layer.

[0008] In contrast, in the separation membrane composite disclosed as a comparative example in Patent Document 4, the constituent fibers of the fiber substrate layer, which can prevent the passage of gases, liquids, or ions, contact the film layer without forming point-like or linear contact areas between the fiber substrate layer and the film layer. Therefore, the separation membrane composite disclosed in Patent Document 4, which has this configuration, can have a smaller area of ​​contact than the separation membrane composite disclosed in Patent Document 3, which has no planar contact area. However, the applicant of the present application found that, in the separation membrane composite disclosed in Patent Document 4, if a fiber substrate layer made of constituent fibers with a small average fiber diameter is used to provide a separation membrane composite that is less likely to have the problem of unintended high resistance to passage of gases, liquids, or ions by sufficiently reducing the area of ​​the contact area, the film layer is not sufficiently reinforced, which can result in a separation membrane composite with high strength. On the other hand, when a fiber substrate layer made of constituent fibers with a large average fiber diameter is used to sufficiently reinforce the film layer and provide a separation membrane composite with high strength, the area of ​​each contact portion becomes large, which can unintentionally cause a problem of increased resistance to the passage of gases, liquids, or ions.

[0009] As described above, as long as the conventional technologies disclosed in Patent Documents 3 and 4 are used, it has been difficult to prevent the problem of unintentional increase in resistance to the passage of gases, liquids, or ions, and to provide a separation membrane composite with sufficient reinforcement of the film layer to provide high strength.

[0010] Furthermore, in the prior art, a water surface spreading method, which is also disclosed in Patent Document 5, is sometimes employed as a method for forming a film layer on a fiber web or nonwoven fabric capable of forming a nonwoven fabric layer. The water surface spreading method is a method in which a resin capable of forming a film layer is spread on the water surface to form a film on the water surface, and then the film-like resin is scooped up onto the main surface of the fiber web or nonwoven fabric, forming a film layer on the main surface of the fiber web or nonwoven fabric.

[0011] In the water surface spreading method, a fiber web or nonwoven fabric is immersed in water. At this time, a film layer is formed on the fiber web or nonwoven fabric in a swollen or shrunk state due to water absorption, and then dried. However, during this drying stage, the fiber web or nonwoven fabric may deform, causing problems such as wrinkles and cracks in the film layer. In fact, in the separation membrane-laminated sheet prepared in the examples of Patent Document 5, wrinkles and cracks were likely to occur in the film layer, possibly because the constituent fibers of the ultrafine fiber layer were made of polyacrylonitrile, which has a high water absorption rate.

[0012] The applicant of the present application aims to provide a fiber laminate that can prevent the occurrence of problems such as wrinkles and cracks in the film layer and that can realize a separation membrane composite with high strength that is less likely to cause problems such as unintended high resistance to the passage of gases, liquids, or ions, and a separation membrane composite that includes such a fiber laminate. [Means for solving the problem]

[0013] The present invention provides "(Claim 1) A fiber laminate having a nonwoven fabric layer and a fiber substrate layer, which is used to reinforce a film layer by bringing the nonwoven fabric layer into contact with the film layer, The resin constituting the constituent fibers of the nonwoven fabric layer is only vinylidene fluoride homopolymer or PVDF-HFP, The resin constituting the constituent fibers of the fibrous base material layer is polyethylene terephthalate or polyphenylene sulfide resin only, The average fiber diameter of the constituent fibers of the fiber base material layer is larger than that of the nonwoven fabric layer. Fiber laminate. (Claim 2) A separation membrane composite comprising a fiber laminate having a nonwoven fabric layer and a fiber substrate layer, and a film layer provided on the nonwoven fabric layer, The resin constituting the constituent fibers of the nonwoven fabric layer is only vinylidene fluoride homopolymer or PVDF-HFP, The resin constituting the constituent fibers of the fibrous base material layer is polyethylene terephthalate or polyphenylene sulfide resin only, the nonwoven fabric layer and the film layer are in contact with each other, The average fiber diameter of the constituent fibers of the fiber base material layer is larger than that of the nonwoven fabric layer. Separation membrane complex. ” is. [Effects of the Invention]

[0014] By using the fiber laminate of the present invention, a separation membrane composite can be prepared, which has a film layer in contact with a nonwoven fabric layer in a fiber laminate having a nonwoven fabric layer and a fiber substrate layer whose constituent fibers have a larger average fiber diameter than the nonwoven fabric layer. In this separation membrane composite, the film layer is reinforced by the fiber laminate (in other words, the nonwoven fabric layer reinforced by a fiber substrate layer whose constituent fibers have a larger average fiber diameter than the nonwoven fabric layer).

[0015] In the separation membrane composite according to the present invention, the nonwoven fabric layer and the film layer are in direct contact with each other, so that the constituent fibers of the nonwoven fabric layer form point-like or linear contact areas between the nonwoven fabric layer and the film layer and are in contact with the film layer. Therefore, the area of ​​the contact areas can be made smaller than in the separation membrane composite disclosed in Patent Document 3, which has no planar contact areas, and a separation membrane composite can be provided that is less likely to cause problems such as unintended high resistance to passage of gases, liquids, or ions.

[0016] The fibrous substrate layer is laminated with the nonwoven fabric layer, and the fibrous substrate layer has constituent fibers with a larger average fiber diameter than the nonwoven fabric layer, so that the nonwoven fabric layer is effectively reinforced by the fibrous substrate layer. Therefore, even when a nonwoven fabric layer made of constituent fibers with a small average fiber diameter is used to sufficiently reduce the area of ​​contact between the constituent fibers of the nonwoven fabric layer and the film layer, the film layer can be sufficiently reinforced by the fibrous laminate (in other words, a nonwoven fabric layer reinforced by a fibrous substrate layer whose constituent fibers have a larger average fiber diameter than the nonwoven fabric layer), and a separation membrane composite with excellent strength can be provided.

[0017] Furthermore, the nonwoven fabric layer of the present invention contains fibers containing a fluororesin as a constituent fiber. Therefore, the fiber web or nonwoven fabric that can constitute the nonwoven fabric layer of the present invention has the property of being resistant to swelling or shrinkage upon water absorption. As a result, by using the fiber laminate of the present invention, even when, for example, a water surface spreading method is employed, the problem of wrinkles or cracks in the film layer can be prevented, and a separation membrane composite can be provided.

[0018] As described above, the present invention can prevent the problem of wrinkles and cracks occurring in the film layer, and can provide a separation membrane composite that is strong and is less likely to cause the problem of unintentionally increasing resistance to the passage of gases, liquids, or ions. DETAILED DESCRIPTION OF THE INVENTION

[0019] In the present invention, various configurations can be appropriately selected, such as the following configurations. Note that, unless otherwise specified, the various measurements described in the present invention were performed under atmospheric conditions of normal pressure and 25°C. Furthermore, unless otherwise specified, the various measurement results described in the present invention were measured to a value one digit smaller than the desired value, and the desired value was calculated by rounding off the value one digit smaller. As a specific example, when the desired value is measured to one decimal place, the value was measured to two decimal places, and the obtained value was rounded off to one decimal place to calculate the desired value, and this value was used as the desired value. Furthermore, the upper and lower limits exemplified in the present invention can be combined in any combination.

[0020] The fiber laminate of the present invention serves to reinforce the film layer, and includes a nonwoven fabric layer and a fiber substrate layer.

[0021] The nonwoven fabric layer in contact with the film layer is a sheet-like fiber layer (e.g., a fiber layer derived from a fiber web or nonwoven fabric) in which fibers are randomly entangled. Therefore, between the nonwoven fabric layer and the film layer, the constituent fibers of the nonwoven fabric layer that prevent the passage of gases, liquids, or ions form point-like or linear contact areas and are in uniform contact with the film layer, making it difficult to prevent the passage of gases, liquids, or ions through the film layer. Furthermore, in the nonwoven fabric layer, the shape and size of the voids formed by the constituent fibers can be uniform, so that the passage of gases, liquids, or ions between the nonwoven fabric layer and the film layer is efficient and makes it difficult to prevent the passage of gases, liquids, or ions through the film layer.

[0022] Furthermore, since the constituent fibers of the nonwoven fabric layer form point-like or linear contact areas and are in uniform contact with the film layer, the film layer can also be effectively reinforced by the nonwoven fabric layer, and therefore a separation membrane composite that can be used for various industrial applications can be provided.

[0023] The nonwoven fabric layer contains fibers containing a fluororesin as its constituent fibers. The water absorption rate of the fluororesin is lower than the water absorption rate (0.3%) of the polyacrylonitrile used in the examples of Patent Document 5. The water absorption rate here can be determined by the following method.

[0024] (Method for measuring water absorption rate) (1) Prepare an organic resin to be measured. (2) The organic resin is dried until no weight change occurs due to evaporation of water, and the mass (W1) of the organic resin after drying is measured. (3) After drying, the organic resin is exposed to an atmosphere of 30°C and 90 RH% for 360 hours to absorb moisture, and the mass (W2) of the organic resin after moisture absorption is measured. Note that RH% means the relative humidity, which indicates the ratio to the amount of saturated water vapor. (4) The obtained values ​​of mass (W1) and mass (W2) are substituted into the following formula, and the calculated value is the water absorption rate (α, unit: %) of the organic resin. α=100×(W2-W1) / W1

[0025] The form of the organic resin used in the above-mentioned measurement method can be appropriately selected, and may be in the form of pellets, a film, fibers, or fabric (for example, a web, a nonwoven fabric, a woven fabric, or a knitted fabric). By subjecting the fibers or nonwoven fabric to the above-mentioned measurement, the water absorption rate of the organic resin constituting the fibers or nonwoven fabric can be determined.

[0026] As the fluororesin, for example, a homopolymer or copolymer having fluorine atoms in the molecular structure, such as polytetrafluoroethylene resin or polyvinylidene fluoride resin, can be used. These fluororesins may be either linear or branched polymers, and may be block copolymers or random copolymers. Furthermore, the fluororesin may have any three-dimensional structure or may have any crystallinity. Furthermore, the fluororesin may be one type, or may be a mixture of multiple types of fluororesins, such as a mixed resin.

[0027] In particular, since the nonwoven fabric layer is made of high-strength fibers, the resin constituting the fibers of the nonwoven fabric layer preferably contains a polyvinylidene fluoride resin so that the nonwoven fabric layer can also effectively reinforce the film layer. Note that the term "polyvinylidene fluoride resin" as used herein refers to a resin having a -(CHCF) structure in the molecular structure of the main chain, and examples include vinylidene fluoride homopolymers and vinylidene fluoride copolymers such as PVDF-HFP. Hereinafter, polyvinylidene fluoride resin may be abbreviated as PVDF.

[0028] The mass percentage of PVDF in the resin constituting the fibers of the nonwoven fabric layer can be adjusted as appropriate. However, the higher the mass percentage, the less likely swelling or shrinkage due to water absorption occurs, which can prevent problems such as wrinkles or cracks in the film layer and reduce the risk of unintended increases in resistance to the passage of gases, liquids, or ions, resulting in a separation membrane composite with excellent strength. For this reason, it is preferable that the fibers constituting the nonwoven fabric layer be composed solely of PVDF.

[0029] By making the average fiber diameter of the constituent fibers of the nonwoven fabric layer small, the contact area between the constituent fibers of the nonwoven fabric layer and the film layer can be made sufficiently small, thereby providing a separation membrane composite that is less likely to cause problems such as unintended high resistance to the passage of gases, liquids, or ions.

[0030] From this perspective, the average fiber diameter of the constituent fibers of the nonwoven fabric layer is preferably 1 μm or less, preferably less than 450 nm, and preferably 400 nm or less. While the lower limit can be adjusted as appropriate, a realistic average fiber diameter of the constituent fibers is 10 nm or more, preferably greater than 100 nm, preferably greater than 130 nm, and preferably greater than 150 nm. In this specification, the term "average fiber diameter" refers to the arithmetic mean value of the fiber diameters of 50 fibers measured using a 5000x electron microscope photograph of the cross section or surface of the object being measured. Furthermore, if the fiber diameter is too small to measure, it can be measured using an electron microscope photograph at a magnification greater than 5000x. If the cross section of the fiber is noncircular, the diameter of a circle with the same area as the cross section can be considered to be the fiber diameter.

[0031] The fiber length of the constituent fibers of the nonwoven fabric layer is selected as appropriate, but can be short or long fibers having a specific length, or continuous fibers having a length that makes it difficult to actually measure the fiber length. The small number of fiber ends in the nonwoven fabric layer makes the surface of the nonwoven fabric layer in contact with the film layer smooth, and the nonwoven fabric layer can also effectively reinforce the film layer. Therefore, it is preferable that the constituent fibers contain continuous fibers having a continuous length, and more preferably, the constituent fibers consist solely of continuous fibers. The "fiber length" referred to in the present invention can be measured based on an electron microscope photograph taken at 5000x magnification of the cross section or surface of the object to be measured. If the fiber length is too long to measure, it can be measured based on an electron microscope photograph taken at a magnification lower than 5000x.

[0032] The constituent fibers of the nonwoven fabric layer may be monofilaments, fibrillar fibers, or composite fibers. Examples of composite fibers include core-sheath, sea-island, side-by-side, orange, and bimetal fibers. The constituent fibers may have a cross-sectional shape that is not only approximately circular or elliptical, but also irregular. Examples of irregular cross-sectional fibers include fibers with cross sections that are hollow, polygonal (e.g., triangular), alphabetic (e.g., Y-shaped), irregular, multi-lobed, or symbolic (e.g., asterisk) shapes, or shapes combining multiple of these shapes.

[0033] The method for preparing the fibers constituting the nonwoven fabric layer can be appropriately selected, for example, electrospinning, which is a method of spinning by applying an electric field to a spinning solution obtained by dissolving a resin in a solvent, spinning by using centrifugal force on a spinning solution obtained by dissolving a resin in a solvent, spinning a spinning solution obtained by dissolving a resin in a solvent using an accompanying airflow as disclosed in JP-A-2011-012372, neutralization spinning, which is a type of electrospinning method as disclosed in JP-A-2005-264374, or direct spinning methods such as melt-blowing and spunbonding.

[0034] In addition, by collecting fibers spun using a direct spinning method (particularly an electrostatic spinning method), a fiber web or nonwoven fabric composed only of continuous fibers can be prepared. Furthermore, depending on the spinning conditions, the fiber web or nonwoven fabric prepared using the above-mentioned method may have film-like or granular nonfibrous material called shots attached to the main surface. The presence or absence of nonfibrous material on the main surface of the nonwoven fabric layer, and the number and amount of nonfibrous material, if any, on the main surface of the nonwoven fabric layer can be adjusted appropriately.

[0035] In addition to direct spinning, a nonwoven fabric layer may be formed on a fabric that can form the fiber substrate layer by laminating thin fibers on the fabric using a wet method. Also, a fiber layer formed by stretching a resin sheet may be formed on a fabric that can form the fiber substrate layer.

[0036] The various physical properties of the nonwoven fabric layer, such as basis weight and thickness, can be selected as appropriate. For example, the thickness can be 0.1 to 200 μm, or 0.2 to 150 μm, with the upper limit being 100 μm or less, or 50 μm or less. The "thickness" referred to in the present invention refers to the average value of 10 randomly selected measurements taken using an outside micrometer (0 to 25 mm) specified in JIS B7502:1994, according to the measurement method specified in JIS C2111 5.1(1).

[0037] For example, the basis weight is 0.05 to 10 g / m 2 and the density can be 0.1 to 5 g / m 2 and 0.3 to 3 g / m 2 and 0.5 to 2 g / m 2 The "weight per unit area" in the present invention means a value measured in an area of ​​10 cm x 10 cm in accordance with JIS L1085.

[0038] The fiber substrate layer is a sheet-like fiber layer that serves to reinforce the nonwoven fabric layer. The type of fiber substrate layer can be selected appropriately, and woven or knitted fabrics can be used in addition to fiber webs and nonwoven fabrics. In particular, the fiber substrate layer is preferably a fiber web or nonwoven fabric-derived fiber layer in which fibers are randomly entangled, similar to the nonwoven fabric layer. Because the fiber substrate layer has similar physical properties to the nonwoven fabric layer, as will be described in detail later, the fiber substrate layer and the nonwoven fabric layer can be firmly laminated together, and the nonwoven fabric layer can be effectively reinforced by the fiber substrate layer. In addition, the fiber substrate layer can also exhibit the effects of increasing the diffusibility of liquids or gases, protecting the nonwoven fabric layer or film layer from locally acting liquids or gases, and acting as a cushion to prevent the nonwoven fabric layer or film layer from collapsing.

[0039] Preferred combinations of such nonwoven fabric layers and fibrous substrate layers include a combination of an electrospun nonwoven fabric layer and a spunbond nonwoven fabric, a combination of a meltblown nonwoven fabric and a spunbond nonwoven fabric, and a combination of an electrospun nonwoven fabric layer and a wetlaid nonwoven fabric.

[0040] The type of resin constituting the fiber substrate layer can be appropriately selected, and examples thereof include polyether resins (polyethylene glycol, polypropylene glycol, etc.), polyphenylene sulfide resins, phenolic resins, epoxy resins, polyimide resins, polyamideimide resins, polyamide resins (e.g., aromatic polyamide resins such as aramid resins, aromatic polyetheramide resins, nylon resins, etc.), urethane resins, epoxy resins, polysulfone resins (polysulfone, etc.), polyethersulfone resins (polyethersulfone, sulfonated polyethersulfone, etc.), fluorine resins (polytetrafluoroethylene, polyisopropyl methyl methacrylate, etc.), and the like. The resin may be a known resin such as a vinylidene fluoride resin (such as a polyvinylidene fluoride homopolymer or a polyvinylidene fluoride copolymer), a vinyl alcohol resin (such as polyvinyl alcohol or polyvinyl acetate), polycaprolactone, polyglycolic acid, polyvinylpyrrolidone, polybenzimidazole resin, or an acrylic resin (for example, a polyacrylonitrile resin copolymerized with an acrylic acid ester or a methacrylic acid ester, or a modacrylic resin copolymerized with acrylonitrile and vinyl chloride or vinylidene chloride), and may be one type of resin or multiple types of resins, such as a mixed resin.

[0041] In particular, as will be described in detail later, in order to provide a fiber laminate in which the surface of the fiber base layer and the surface of the constituent fibers of the nonwoven fabric layer are sufficiently welded, the constituent fibers of the fiber base layer preferably contain polyethylene terephthalate (hereinafter sometimes referred to as PET), and the constituent fibers of the fiber base layer preferably consist solely of PET. Furthermore, in order to easily maintain the shape of the fiber base layer even when a heat and pressure treatment is performed when a film layer is provided on the nonwoven fabric layer in the fiber laminate or in the production process of the separation membrane composite, the constituent fibers of the fiber base layer preferably contain polyphenylene sulfide resin, and the constituent fibers of the fiber base layer preferably consist solely of polyphenylene sulfide resin.

[0042] The constituent fibers of the fibrous substrate layer, like the constituent fibers of the nonwoven fabric layer, may be fibrillated fibers or composite fibers in addition to monofilaments. Furthermore, the constituent fibers of the fibrous substrate layer may be fibers with a cross-sectional shape that is not substantially circular or elliptical, but may also be fibers with a modified cross-section. The constituent fibers of the fibrous substrate layer can be prepared in the same manner as the method for preparing the constituent fibers of the nonwoven fabric layer.

[0043] The fiber diameter of the fibers constituting the fibrous substrate layer is appropriately selected, but the average fiber diameter of the fibrous substrate layer can be greater than 1 μm and not more than 1000 μm, can be 2 to 500 μm, or can be 5 to 100 μm. Note that the fibers constituting the fibrous substrate layer may be not only single fibers or composite fibers, but also threads formed by entanglement of multiple fibers.

[0044] In the present invention, the fibrous base material layer is characterized in that the average fiber diameter of the constituent fibers is larger than that of the nonwoven fabric layer. By having the constituent fibers of the fibrous base material layer reinforcing the nonwoven fabric layer larger than the average fiber diameter of the constituent fibers of the nonwoven fabric layer, the nonwoven fabric layer can be effectively reinforced by the fibrous base material layer.

[0045] Therefore, even when a nonwoven fabric layer made of constituent fibers with a small average fiber diameter is used to sufficiently reduce the area of ​​contact between the constituent fibers of the nonwoven fabric layer and the film layer, the film layer can be sufficiently reinforced by the fiber laminate (in other words, a nonwoven fabric layer reinforced by a fiber substrate layer whose constituent fibers have a larger average fiber diameter than the nonwoven fabric layer), thereby providing a separation membrane composite with excellent strength.

[0046] The fiber length of the fibers constituting the fibrous base material layer is appropriately selected, but can be short fibers, long fibers, or continuous fibers, like the fibers constituting the nonwoven fabric layer. Since the number of fiber ends in the fibrous base material layer is small, the surface is smooth, the thickness is uniform, and various physical properties such as mechanical strength are excellent. As a result, the nonwoven fabric layer can be effectively reinforced by the fibrous base material layer, and the fibrous base material layer and the nonwoven fabric layer can be firmly laminated and integrated, and the nonwoven fabric layer can be further effectively reinforced by the fibrous base material layer. Therefore, it is preferable that the fibrous base material layer contains continuous fibers having a continuous length as its constituent fibers, and it is more preferable that the constituent fibers of the fibrous base material layer are only continuous fibers.

[0047] The various physical properties of the fiber substrate layer, such as basis weight and thickness, can be appropriately selected. For example, the thickness can be 10 μm to 2 mm, 12 μm to 1 mm, 15 μm to 0.5 mm, or 20 μm to 0.2 mm. For example, the basis weight can be 2 to 500 g / m 2 and the thickness can be 3 to 200 g / m 2 and the thickness can be 4 to 100 g / m 2 and 5 to 50 g / m 2 It can be.

[0048] The fiber laminate of the present invention is a laminate of the nonwoven fabric layer and the fiber base layer described above. The lamination mode of the nonwoven fabric layer and the fiber base layer can be selected as appropriate. They can be simply overlapped, bonded together by a binder, laminated together by ultrasonic sealing, or laminated together by fiber bonding of the constituent fibers of the nonwoven fabric layer and / or the fiber base layer. In particular, to more effectively reinforce the nonwoven fabric layer with the fiber base layer and prevent unintended increases in the resistance to gas, liquid, or ion passage between the nonwoven fabric layer and the fiber base layer, it is preferable that the constituent fibers of the fiber base layer and the nonwoven fabric layer are welded together at the contacting portions, thereby laminating and integrating the nonwoven fabric layer and the fiber base layer. "Welded" here means that the constituent fibers of the fiber base layer and the constituent fibers of the nonwoven fabric layer are melted and integrated at the contacting portions, with the boundary between the fibers in the fiber base layer and the fibers in the nonwoven fabric layer being unclear and indistinguishable.

[0049] A fiber laminate in which a nonwoven fabric layer and a fiber base layer are laminated together in this manner can be prepared, for example, by forming a nonwoven fabric layer by directly spinning the fiber base layer onto a substrate that can form the fiber base layer using a spinning solution prepared by dissolving the resin that forms the constituent fibers of the nonwoven fabric layer in a solvent (a solvent that can dissolve both the constituent resins of the nonwoven fabric layer and the fiber base layer). In other words, the fiber laminate can be prepared by dissolving the contact areas between the constituent fibers of the fiber base layer and the constituent fibers of the nonwoven fabric layer in the solvent remaining in the nonwoven fabric layer, and then removing the remaining solvent.

[0050] If a nonwoven fabric layer is formed by directly spinning molten resin onto a substrate capable of forming a fiber substrate layer, such as by using a melt-blowing method, the boundary between the fibers of the fiber substrate layer and the fibers of the nonwoven fabric layer can be confirmed at the contact area. In a fiber laminate having such an integrated laminated structure, the nonwoven fabric layer and the fiber substrate layer may not be sufficiently integrated, resulting in the nonwoven fabric layer peeling from the fiber substrate layer. As a result, the fiber substrate layer may not be able to unintentionally reinforce the nonwoven fabric layer sufficiently.

[0051] Whether or not the fiber base material layer and the nonwoven fabric layer are laminated together by welding at the contact points between the constituent fibers of the fiber base material layer and the constituent fibers of the nonwoven fabric layer can be determined by the following method.

[0052] (How to determine whether welding has occurred) 1. A sample (square or rectangular shape) is taken from the fiber laminate to be measured. To facilitate the confirmation process described below, the constituent resin of the sample may be dyed using a dye solution (e.g., Kayastain Q (manufactured by Nippon Kayaku Co., Ltd.)). 2. Take an optical microscope photograph or an electron microscope photograph (hereinafter collectively referred to as a microscope photograph) of the cross section of the sample (photographing area: a square area of ​​3 mm x 3 mm). 3. Use the naked eye to check the areas in the microscopic photograph where the surface of fiber (A) of the same type as the fiber that makes up one main surface of the object to be measured comes into contact with the surface of fiber (B) of the same type as the fiber that makes up the other main surface of the object to be measured. 4. If the boundary between fiber (A) and fiber (B) in the area confirmed in item 3 is not clear and the boundary cannot be confirmed (for example, the surface portion of fiber (A) and the surface portion of fiber (B) are mixed and integrated at the contacting area), the fiber laminate being measured is determined to have a portion where the surface of the fiber base layer and the surface of the constituent fiber of the nonwoven fabric layer are welded together.

[0053] The various physical properties of the fiber laminate, such as the basis weight and thickness, can be selected as appropriate. For example, the thickness can be 10 μm to 2 mm, 12 μm to 1 mm, 15 μm to 0.5 mm, or 20 μm to 0.2 mm. For example, the basis weight can be 2 to 500 g / m 2 and the thickness can be 3 to 200 g / m 2 and the thickness can be 4 to 100 g / m 2 and 5 to 50 g / m 2 It can be.

[0054] Furthermore, the surface roughness (Ra) of the main surface of the fiber laminate on which the nonwoven fabric layer is exposed is preferably 20 μm or less, more preferably 15 μm or less, and most preferably 9 μm or less. A surface roughness of 20 μm or less tends to efficiently reinforce the film layer with the nonwoven fabric layer, making it easier to provide a separation membrane composite with excellent strength that is less likely to experience unintended problems such as increased resistance to the passage of gases, liquids, or ions. The surface roughness (Ra) referred to in the present invention can be measured using a surface roughness tester (Mitutoyo's small surface roughness tester, Surftest (registered trademark) SJ310).

[0055] A fiber laminate having a nonwoven fabric layer derived from an electrospun nonwoven fabric is preferred because it is possible to prepare a fiber laminate having such a desirable surface roughness.

[0056] The air permeability of the fiber laminate is adjusted appropriately to provide the desired separation membrane composite. As a specific example, the air permeability of the fiber laminate can be as follows: 200 cm 3 / cm 2 / s or less, 100 cm 3 / cm 2 / s or less, while the lower limit is higher than 0, but not higher than 1 cm 3 / cm 2 / s or more is realistic.

[0057] Furthermore, by providing a film layer on the nonwoven fabric layer in the fiber laminate satisfying the above-mentioned configuration, a separation membrane composite can be provided in which the nonwoven fabric layer and the film layer are in direct contact with each other.

[0058] The film layer refers to a coating or membrane-like layer that can selectively allow permeation of specific gases such as oxygen and carbon dioxide, specific liquids such as ethyl acetate, methyl ethyl ketone, and isopropanol, specific ions such as sodium ions, calcium ions, and chloride ions, or amino acids and lactic acid, etc., and this film layer serves as the separation membrane in the separation membrane composite. The film layer may be non-porous or porous, but it is preferable to adopt one with a non-porous structure so that specific gases, specific liquids, or specific ions can permeate efficiently as intended.

[0059] The components constituting the film layer can be organic components such as organic resins, or inorganic components. The components constituting the film layer are selected appropriately depending on the application of the separation membrane composite. As organic components, in addition to the resins listed as resins constituting the fibers of the fibrous substrate layer described below, silicone polymers such as polydimethylsiloxane and silicone rubber, ethylene-vinyl alcohol copolymers, perforated low-density polyethylene resins, poly(1-trimethylsilyl-1-propyne), etc. can be used. Furthermore, as inorganic components, silica, palladium, zeolite, etc. can be used.

[0060] In particular, since it is possible to provide a separation membrane composite suitable for an oxygen enrichment membrane, it is preferable that the film layer contains an organic component such as a silicone polymer such as polydimethylsiloxane or silicone rubber, an ethylene-vinyl alcohol copolymer, a perforated low-density polyethylene resin, or poly(1-trimethylsilyl-1-propyne), and it is preferable that the film layer is composed only of the above-mentioned organic component.

[0061] The various physical properties of the film layer, such as basis weight and thickness, can be appropriately selected. For example, the thickness can be 20 to 1000 nm, or 50 to 500 nm. For example, the basis weight can be 0.01 to 1 g / m2 and the thickness can be 0.05 to 0.5 g / m 2 It can be.

[0062] The separation membrane composite according to the present invention is characterized in that a film layer is provided on the nonwoven fabric layer of the fiber laminate. By providing the film layer on the nonwoven fabric layer, the constituent fibers of the nonwoven fabric layer contact the film layer at point-like or linear contact areas between the nonwoven fabric layer and the film layer. As a result, the area of ​​the contact area can be reduced, and the passage of gases, liquids, or ions through the film layer is less likely to be hindered, thereby providing a separation membrane composite that is less likely to cause problems such as unintended high resistance to passage of gases, liquids, or ions.

[0063] The smaller the fiber diameter of the fibers constituting the nonwoven fabric layer, the smaller the curvature of the fibers. As a result, as described above, it is believed that the fibers constituting the nonwoven fabric layer can contact the film layer through point-like or linear contact areas. Furthermore, the smaller the fiber diameter of the fibers constituting the nonwoven fabric layer, the smaller the size of each contact area between the fibers and the film layer and the more likely it is that they will be uniformly dispersed. As a result, it is believed that the nonwoven fabric layer can effectively reinforce the film layer without impeding the passage of gases, liquids, or ions through the film layer, thereby providing a separation membrane composite with excellent strength.

[0064] The mode in which the nonwoven fabric layer and the film layer are in direct contact with each other and laminated can be selected as appropriate, and may include a mode in which they are simply overlapped, a mode in which they are bonded by pressure, a mode in which they are laminated together by ultrasonic sealing or the like, a mode in which they are laminated together by fiber adhesion between the constituent fibers of the nonwoven fabric layer, a mode in which they are laminated together by adhesion between the components that constitute the film layer, and a mode in which the constituent resin of the film layer is spread in a film-like form on the surface of the nonwoven fabric layer and then scooped up and dried to laminate together.

[0065] Next, a method for producing a fiber laminate according to the present invention will be described by taking a specific example of production, with the explanation of the same configuration as that described above being omitted. (1) A step of preparing a fabric capable of constituting a fiber substrate layer; (2) preparing a spinning solution by dissolving a fluororesin in a solvent; (3) feeding the spinning solution to an electrostatic spinning device to thin the spinning solution and spin a fiber containing a fluorine-based resin; (4) collecting the solvent remaining in the spun fibers on the main surface of the fabric, thereby forming a fiber web made of the fibers containing the fluorine-based resin on one main surface of the fabric; (5) a step of removing the solvent remaining in the laminate web to prepare a fiber laminate; and a fiber base material layer having constituent fibers with a larger average fiber diameter than that of the nonwoven fabric layer, which are laminated together. Furthermore, this method for manufacturing a fiber laminate makes it possible to weld the constituent fiber surfaces of a nonwoven fabric layer derived from a fiber web made of fibers containing a fluororesin to the constituent fiber surfaces of a fabric-derived fiber base material layer, thereby producing a fiber laminate in which the nonwoven fabric layer and the fiber base material layer are laminated together.

[0066] First, step (2) will be described. The type of solvent is appropriately selected so as to dissolve the resin that can form the nonwoven fabric layer. Examples include N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, acetonitrile, dimethyl sulfoxide, formic acid, water, alcohol, etc. By using a solvent that can dissolve the resin that can form the fiber base material layer, a fiber laminate in which the nonwoven fabric layer and the fiber base material layer are laminated together can be produced.

[0067] The temperature and viscosity of the spinning solution are selected appropriately so that the desired nonwoven fabric layer can be prepared. The temperature of the spinning solution can be 5 to 40°C, 10 to 35°C, or 15 to 30°C. The viscosity of the spinning solution can be 0.05 to 8 Pa·s, 0.1 to 6 Pa·s, or 0.2 to 5 Pa·s. This "viscosity" is measured using a viscosity measuring device at a temperature of 25°C with a shear rate of 100 s -1 The time value.

[0068] In addition, by selecting a solvent that can also dissolve the constituent resin of the fabric that can form the fiber base layer, the constituent fiber surfaces of the nonwoven fabric layer and the constituent fiber surfaces of the fiber base layer can be welded together to produce a fiber laminate in which the nonwoven fabric layer and the fiber base layer are laminated together.

[0069] Next, steps (3) and (4) will be described. The method of spinning by reducing the diameter of the spinning solution is appropriately selected so as to prepare the desired nonwoven fabric layer, and for example, direct spinning can be used. When electrostatic spinning is used, a voltage is applied to the spinning solution, and an opposite voltage is applied to a counter electrode such as a metal plate spaced from the discharge portion of the spinning solution, causing the spinning solution to fly toward the counter electrode and reduce the diameter. The reduced diameter spinning solution is then collected on the main surface of a fabric placed between the discharge portion and the counter electrode, forming a fiber web made of fibers containing a fluororesin on the fabric.

[0070] When electrospinning is employed, the spinning conditions are appropriately adjusted so that the spun fluororesin-containing fibers with residual solvent can be collected on the main surface of the fabric. Specifically, the spun fluororesin-containing fibers with residual solvent can be easily collected on the main surface of the fabric by using a spinning solution with a high ratio of solvent in the spinning solution, shortening the spinning distance, increasing the spinning amount, maintaining a high concentration of volatilized solvent in the spinning space, adjusting the temperature and humidity of the spinning space so that the solvent does not easily volatilize, etc.

[0071] Next, step (5) will be explained. The method for removing the solvent remaining in the laminate web can be selected as appropriate, and one example is a method of subjecting the laminate web to a heating device. The type of heating device can be selected as appropriate, and for example, a method using a device that heats or heats and presses with a roll, an oven dryer, a far-infrared heater, a dry heat dryer, a hot air dryer, or a device that can heat by irradiating infrared rays can be used. The heating temperature of the heating device is selected as appropriate, and is appropriately adjusted so that the remaining solvent can be volatilized and removed, and that the constituent components such as the constituent fibers do not unintentionally decompose or denature.

[0072] In addition, when adhesive components or crosslinkable resins are present in the constituent fibers of the fabric or fiber web, the fibers may be bonded by the adhesive components or the crosslinkable resin may be crosslinked by subjecting the fabric or fiber web to a heating device.

[0073] The fiber laminate produced as described above may be subjected to a pressure treatment such as calendaring to adjust the thickness, or may be subjected to a hydrophilization treatment such as sulfonation, plasma treatment, or fluorine gas treatment, or may be punched or molded into a desired shape, depending on the intended use or mode of use.

[0074] Furthermore, the fiber laminate can be used alone, but if necessary, it can be laminated with a separately prepared fabric (fiber web or nonwoven fabric, woven or knitted fabric), film (porous or nonporous film), foam, etc. The lamination method can be selected appropriately, and can include simply overlapping, partially melt-bonding the constituent components, laminating and integrating with a binder, integrating by ultrasonic welding, or sewing.

[0075] Next, a method for producing a separation membrane composite according to the present invention will be described by taking a specific production example, with the explanation of the same configuration as in the above items being omitted. (1) preparing a solution in which components capable of constituting a film layer are dissolved in a solvent; (2) preparing a liquid that does not dissolve or that hardly dissolves the component; (3) pouring the solution into a water tank containing the liquid and spreading a film of the component on the surface of the liquid; (4) A step of preparing a fiber laminate in which a nonwoven fabric layer containing fibers containing a fluorine-based resin as a constituent fiber and a fiber substrate layer having constituent fibers with a larger average fiber diameter than that of the nonwoven fabric layer are laminated; (5) a step of immersing the fiber laminate in the water bath and scooping up a film of the component that has spread on the main surface of the fiber laminate where the nonwoven fabric layer is exposed; (6) A step of removing the fiber laminate having the film of the component from the water tank and drying it to form a film layer of the component on the nonwoven fabric layer of the fiber laminate; A method for producing a separation membrane composite comprising the steps of:

[0076] or (1) preparing a film; (2) preparing a fiber laminate in which a nonwoven fabric layer containing fluororesin-containing fibers as constituent fibers and a fiber substrate layer having constituent fibers with a larger average fiber diameter than that of the nonwoven fabric layer are laminated; (3) preparing a laminate by laminating the film on the main surface of the fiber laminate where the nonwoven fabric layer is exposed; (4) a step of heating the laminate to bond the constituent fibers of the nonwoven fabric layer to the film layer, and then allowing it to cool to form a film layer derived from the film on the nonwoven fabric layer in the fiber laminate; A method for producing a separation membrane composite comprising the steps of:

[0077] or, (1) A step of preparing a solution in which components capable of constituting a film layer are dissolved in a solvent, or a dispersion in which a film layer is dispersed in a dispersion medium; (2) preparing a fiber laminate in which a nonwoven fabric layer containing fluororesin-containing fibers as constituent fibers and a fiber substrate layer having constituent fibers with a larger average fiber diameter than that of the nonwoven fabric layer are laminated; (3) applying the solution or dispersion to the exposed main surface of the fiber laminate, where the nonwoven fabric layer is exposed, to form a film; (4) a step of heating the fiber laminate coated with the solution or dispersion, removing the solvent or dispersion medium, and allowing it to cool, thereby forming a film layer made of the components on the nonwoven fabric layer of the fiber laminate; A method for producing a separation membrane composite comprising the steps of:

[0078] The separation membrane composite produced as described above may be subjected to a pressure treatment such as calendaring to adjust the thickness, or may be subjected to a hydrophilization treatment such as sulfonation, plasma treatment, or fluorine gas treatment, or may be punched or molded into a desired shape, depending on the intended use or mode of use.

[0079] Furthermore, the separation membrane composite can be used alone, but if necessary, it can be laminated with a separately prepared fabric (fiber web or nonwoven fabric, woven or knitted fabric), film (porous or nonporous film), foam, etc. The lamination method can be selected appropriately, and examples that can be used include a method of simply stacking the components, a method of partially melt-bonding the components, a method of laminating and integrating the components with a binder, a method of integrating the components by ultrasonic welding, or a method of sewing the components together. [Example]

[0080] Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[0081] (Preparing the substrate) The following substrates were prepared: A polyolefin wet-laid nonwoven fabric (basis weight: 10 g / m²) made by wet-laid papermaking of partially fused, heat-fusible composite fibers (fineness: 0.8 dtex (average fiber diameter: 10 μm), fiber length: 5 mm, water absorption: 0.01%), which consist of a core of polypropylene (high-melting point component, melting point: 168°C) and a sheath of high-density polyethylene (low-melting point component, melting point: 135°C). 2 , thickness: 35μm). PET wet-laid nonwoven fabric (basis weight: 9 g / m2) made by wet-laid PET short fibers (fineness: 0.8 dtex (average fiber diameter: 9 μm), fiber length: 5 mm, water absorption: 0.1%) 2, thickness: 30μm). PET spunbond nonwoven fabric (basis weight: 15g / m2) made of PET continuous fiber (average fiber diameter: 20μm, water absorption rate: 0.1%) 2 , thickness: 80 μm, surface roughness of main surface (Ra): 27.8 μm).

[0082] (Preparing the spinning solution) Polyvinylidene fluoride homopolymer (water absorption: 0.03%) was dissolved in dimethylformamide (hereinafter abbreviated as DMF, boiling point: 153°C) to prepare spinning solution A with a solids concentration of 16 mass %. DMF is a solvent that can dissolve PET but does not dissolve PE. Furthermore, nylon 6 (water absorption: 1.1%) was dissolved in formic acid (boiling point: 101°C) to prepare spinning solution B with a solids concentration of 15 mass %. Note that formic acid is a solvent that does not dissolve PET.

[0083] Example 1 Spinning solution A was subjected to electrospinning under the following spinning conditions, and the spun fibers containing the solvent were collected on one main surface of a polyolefin-based wetlaid nonwoven fabric. In this way, a laminated web was prepared in which a fiber web composed of continuous fibers of polyvinylidene fluoride homopolymer was laminated on a polyolefin-based wetlaid nonwoven fabric. The shape of the metal nozzle (the part that ejects the spinning solution): circular Distance between the tip of the metal nozzle and the collector (metal plate with a substrate that can form a fiber substrate layer): 10 cm Voltage applied to spinning solution: 15 kV Spinning solution discharged from a metal nozzle: 1g / hour Electrospinning environment: Temperature 25℃, humidity 30%RH The prepared laminated web was then brought into contact with a heated roll whose surface temperature was adjusted to 130°C to remove the solvent remaining in the laminated web, thereby forming a fiber laminate (basis weight of the nonwoven fabric layer derived from the fiber web: 1.00 g / m 2 A nonwoven fabric layer derived from a fiber web having a thickness of 3 μm and an average fiber diameter of the fibers constituting the nonwoven fabric layer derived from a fiber web of 200 nm was prepared. In the fiber laminate prepared in Example 1, the surfaces of the constituent fibers of the fiber substrate layer derived from the polyolefin-based wetlaid nonwoven fabric were not welded to the surfaces of the polyvinylidene fluoride homopolymer fibers that were the constituent fibers of the nonwoven fabric layer derived from the fiber web. Furthermore, when the surface roughness of the exposed main surface of the nonwoven fabric layer derived from the fiber web was measured, the surface roughness (Ra) was 2.4 μm.

[0084] Example 2 A fiber laminate was produced in the same manner as in Example 1, except that a PET wetlaid nonwoven fabric was used instead of a polyolefin-based wetlaid nonwoven fabric. That is, electrostatic spinning was performed by subjecting spinning solution A to the same spinning conditions as in Example 1, and the spun fibers containing the solvent were collected on one main surface of a PET wetlaid nonwoven fabric. In this way, a laminate web was prepared in which a fiber web composed of continuous fibers of polyvinylidene fluoride homopolymer was laminated on a PET wetlaid nonwoven fabric. The prepared laminated web was then brought into contact with a heated roll whose surface temperature was adjusted to 130°C to remove the solvent remaining in the laminated web, thereby forming a fiber laminate (basis weight of the nonwoven fabric layer derived from the fiber web: 1.00 g / m 2 A nonwoven fabric layer derived from a fiber web having a thickness of 3 μm and an average fiber diameter of the fibers constituting the nonwoven fabric layer derived from a fiber web of 200 nm was prepared. In the fiber laminate prepared in Example 2, the surfaces of the constituent fibers of the fiber base material layer derived from the PET wetlaid nonwoven fabric and the surfaces of the polyvinylidene fluoride homopolymer fibers, which are the constituent fibers of the nonwoven fabric layer derived from the fiber web, were fused together. Furthermore, when the surface roughness of the exposed main surface of the nonwoven fabric layer derived from the fiber web was measured, the surface roughness (Ra) was found to be 2.1 μm.

[0085] Example 3 A fiber laminate was produced in the same manner as in Example 1, except that a PET spunbond nonwoven fabric was used instead of a polyolefin-based wetlaid nonwoven fabric. That is, electrostatic spinning was performed by subjecting spinning solution A to the same spinning conditions as in Example 1, and the spun fibers containing the solvent were collected on one main surface of the PET spunbond nonwoven fabric. In this way, a laminate web was prepared in which a fiber web composed of continuous fibers of polyvinylidene fluoride homopolymer was laminated on the PET spunbond nonwoven fabric. The prepared laminated web was then brought into contact with a heated roll whose surface temperature was adjusted to 130°C to remove the solvent remaining in the laminated web, thereby forming a fiber laminate (basis weight of the nonwoven fabric layer derived from the fiber web: 1.00 g / m 2 A nonwoven fabric layer derived from a fiber web having a thickness of 3 μm and an average fiber diameter of the fibers constituting the nonwoven fabric layer derived from a fiber web of 200 nm was prepared. In the fiber laminate prepared in Example 3, the surfaces of the constituent fibers of the fiber base layer derived from the PET spunbond nonwoven fabric and the surfaces of the polyvinylidene fluoride homopolymer fibers, which were the constituent fibers of the nonwoven fabric layer derived from the fiber web, were fused together. Furthermore, when the surface roughness of the exposed main surface of the nonwoven fabric layer derived from the fiber web was measured, the surface roughness (Ra) was 9.0 μm.

[0086] Example 4 A solution of polytrimethylsilylpropene in hexane was prepared, and then this solution was dropped onto the surface of pure water using a syringe needle to form a film of polytrimethylsilylpropene on the water surface. The fiber laminate prepared in Example 1 was dropped into pure water, and the fiber laminate was gently pulled out of the water so as to scoop up the polytrimethylsilylpropene film directly onto the nonwoven fabric layer of the fiber laminate. The fiber laminate was then dried to remove water and toluene, thereby preparing a separation membrane composite comprising a film layer made of polytrimethylsilylpropene on the nonwoven fabric layer of the fiber laminate. In the separation membrane composite prepared in this manner, the nonwoven fabric layer derived from the fiber web and the film layer were in direct contact with each other. Furthermore, when the film layer of the prepared separation membrane composite was visually inspected, no wrinkles or cracks were found in the film layer.

[0087] Example 5 A separation membrane composite was prepared in the same manner as in Example 4, except that the fiber laminate prepared in Example 2 was used instead of the fiber laminate prepared in Example 1. In the separation membrane composite prepared in this manner, the nonwoven fabric layer derived from the fiber web and the film layer were in direct contact with each other. Furthermore, when the film layer of the prepared separation membrane composite was visually inspected, no wrinkles or cracks were found in the film layer.

[0088] Example 6 A separation membrane composite was prepared in the same manner as in Example 4, except that the fiber laminate prepared in Example 3 was used instead of the fiber laminate prepared in Example 1. In the separation membrane composite prepared in this manner, the nonwoven fabric layer derived from the fiber web and the film layer were in direct contact with each other. Furthermore, when the film layer of the prepared separation membrane composite was visually inspected, no wrinkles or cracks were found in the film layer.

[0089] (Comparative Example 1) Using the same method as in Example 4, a separation membrane composite was prepared, having a film layer made of polytrimethylsilylpropene on one main surface of a PET spunbond nonwoven fabric. In the separation membrane composite prepared in this manner, the PET spunbond nonwoven fabric and the film layer were in direct contact with each other. Visual inspection of the film layer of the prepared separation membrane composite revealed wrinkles and cracks in the film layer.

[0090] (Comparative Example 2) Spinning solution A was subjected to electrospinning under the spinning conditions described above, and the spun fibers containing the solvent were collected on a collector. In this way, a fiber web composed of continuous fibers of polyvinylidene fluoride homopolymer was prepared on a collector. The prepared fiber web was then recovered and brought into contact with a heated roll whose surface temperature was adjusted to 130°C to remove the solvent remaining in the fiber web, resulting in an electrospun nonwoven fabric (basis weight: 5.00 g / m). 2 The thickness was 15 μm and the average fiber diameter was 200 nm. The surface roughness of the exposed main surface was measured and found to be 2.1 μm (Ra). Using the same method as in Example 4, a separation membrane composite was prepared, having a film layer made of polytrimethylsilylpropene on one main surface of the electrospun nonwoven fabric thus prepared. In the separation membrane composite prepared in this manner, the electrospun nonwoven fabric and the film layer were in direct contact with each other. Furthermore, visual inspection of the film layer of the prepared separation membrane composite revealed no wrinkles or cracks in the film layer.

[0091] (Comparative Example 3) A fiber laminate was produced in the same manner as in Example 3, except that spinning solution B was used instead of spinning solution A. That is, electrostatic spinning was performed by subjecting spinning solution B to the same spinning conditions as in Example 1, and the spun fibers containing the solvent were collected on one main surface of a PET spunbond nonwoven fabric. In this way, a laminate web was prepared in which a fiber web composed of continuous nylon 6 fibers was laminated on a PET spunbond nonwoven fabric. The prepared laminated web was then brought into contact with a heated roll whose surface temperature was adjusted to 130°C to remove the solvent remaining in the laminated web, thereby forming a fiber laminate (basis weight of the nonwoven fabric layer derived from the fiber web: 1.00 g / m 2 The nonwoven fabric layer derived from the fiber web had a thickness of 3 μm and an average fiber diameter of the fibers constituting the nonwoven fabric layer derived from the fiber web of 200 nm. The surface roughness of the exposed main surface of the nonwoven fabric layer derived from the fiber web was measured, and the surface roughness (Ra) was found to be 9.0 μm. In addition, in the fiber laminate prepared in Comparative Example 3, the surface of the constituent fibers of the fiber base material layer derived from the PET spunbond nonwoven fabric and the surface of the nylon 6 fiber, which is the constituent fiber of the nonwoven fabric layer derived from the fiber web, were not welded together.

[0092] Comparative Example 4 A separation membrane composite was prepared in the same manner as in Example 6, except that the fiber laminate prepared in Comparative Example 3 was used instead of the fiber laminate prepared in Example 3. In the separation membrane composite prepared in this manner, the nonwoven fabric layer derived from the fiber web and the film layer were in direct contact with each other. Furthermore, when the film layer of the prepared separation membrane composite was visually inspected, wrinkles and cracks were found to have occurred in the film layer.

[0093] Furthermore, when the thickness of the film layer in the separation membrane composites prepared in the above Examples and Comparative Examples was confirmed using an SEM, the thickness was 500 nm in all cases.

[0094] When the separation membrane composites prepared as described above were compared, the following was found. Compared to the separation membrane composite prepared in Comparative Example 1, in the separation membrane composites prepared in Examples 4 to 6, the nonwoven fabric layer made of constituent fibers with a small average fiber diameter (the nonwoven fabric layer derived from the fiber web prepared using the electrospinning method) was in direct contact with the film layer, and the area of ​​the contact portion was small. The separation membrane composite prepared in Comparative Example 2 had poorer shape stability during handling and manufacturing than the separation membrane composites prepared in Examples 4 to 6, and wrinkles and cracks occurred during handling, resulting in poor strength. The reason for this is thought to be that the electrospun nonwoven fabric, which is made of constituent fibers with a small average fiber diameter, alone is insufficient to reinforce the film layer. In contrast, the separation membrane composites prepared in Examples 4 to 6 had excellent shape stability during handling and manufacturing, and were strong without wrinkles or cracks during handling. The reason for this is thought to be that the film layer was sufficiently reinforced by the presence of a fiber substrate layer comprising a fiber layer with a larger average fiber diameter than the electrospun nonwoven fabric described above. The separation membrane composites prepared in Comparative Examples 1 and 4 had wrinkles and cracks in the film layer, whereas the separation membrane composites prepared in Examples 4 to 6 had no wrinkles or cracks in the film layer. The reason for this is thought to be that the nonwoven fabric layer constituting the separation membrane composite contains fibers containing a fluororesin as a constituent fiber, which prevents the fiber layer (such as the nonwoven fabric layer) adjacent to the film layer from absorbing water and swelling or shrinking. Additionally, the low surface roughness (Ra) of the nonwoven fabric layer forming the film layer is thought to have enabled the film layer to be efficiently reinforced by the nonwoven fabric layer.

[0095] From the above, it has been found that the fiber laminate of the present invention can prevent the problem of wrinkles and cracks in the film layer, and can provide a separation membrane composite with high strength that is less likely to cause the problem of unintentionally increasing resistance to the passage of gases, liquids, or ions. [Industrial Applicability]

[0096] According to the present invention, for example, the separation membrane can be a gas-permeable membrane (e.g., an oxygen separation membrane or a carbon dioxide separation membrane), a liquid-permeable membrane (e.g., a water filtration membrane), a separator for a secondary battery, a capacitor, or a redox flow battery, an electrolyte membrane for a fuel cell, or an oxygen-enrichment membrane used to provide a high concentration of oxygen to a fuel cell.

Claims

1. A fiber laminate having a nonwoven fabric layer and a fiber substrate layer, which is used to reinforce a film layer by bringing the nonwoven fabric layer into contact with the film layer, the resin constituting the constituent fibers of the nonwoven fabric layer is only vinylidene fluoride homopolymer or PVDF-HFP, The resin constituting the constituent fibers of the fibrous base material layer is polyethylene terephthalate or polyphenylene sulfide resin only, The average fiber diameter of the constituent fibers of the fiber base material layer is larger than that of the nonwoven fabric layer. Fiber laminate.

2. A separation membrane composite comprising a fiber laminate having a nonwoven fabric layer and a fiber substrate layer, and a film layer provided on the nonwoven fabric layer, the resin constituting the constituent fibers of the nonwoven fabric layer is only vinylidene fluoride homopolymer or PVDF-HFP, The resin constituting the constituent fibers of the fibrous base material layer is polyethylene terephthalate or polyphenylene sulfide resin only, the nonwoven fabric layer and the film layer are in contact with each other, The average fiber diameter of the constituent fibers of the fiber base material layer is larger than that of the nonwoven fabric layer. Separation membrane complex.