COMPOSITE SHEET

Abstract

To design a composite sheet in which a metal-organic network is supported within a fiber-based sheet material, exhibiting high gas adsorption performance and where the metal-organic network is resistant to detachment during use. The composite sheet includes a metal-organic network dispersed within a fiber-based sheet material. The fiber comprises a core-sheath structure consisting of a core and a sheath. The metal-organic network is supported by a resin fused to and fixed to the sheath of the core-sheath fiber. The surface exposure ratio of the supported metal-organic network to the sheath of the core-sheath fiber is 50% or greater.

Description

Title of the invention: COMPOSITE SHEET Technical field

[0001] The present invention relates to a composite sheet in which a metal-organic network is supported on a sheet base material. State of the art

[0002] Metal-organic frameworks (MOFs) have attracted attention as high-performance gas adsorption materials because they have uniform pore size, high specific surface area, high separation performance, and the like. In contrast, MOFs are known to be difficult to handle by themselves because they are micron-scale fine powders. To address this, a technology is known that allows a base material such as a non-woven fabric to support MOFs to collectively handle a large amount of MOFs (see, for example, patent literature 1).

[0003] List of quotes

[0004] Patent literature

[0005] Literature Patent 1: Japanese Patent Application Laid Public No. 2021-191913

[0006] Literature Patent 2: US Patent Application Laid Public No. 2021 / 0189620

[0007] Literature Patent 3: Chinese Patent Application Laid Public No. 12002938 Disclosure of the invention Technical problem

[0008] In order to increase the gas adsorption performance, it is necessary for the nonwoven fabric to support a large number of RMOs. For this purpose, it is advantageous to have the RMOs supported not only by the surface layer portion of the nonwoven fabric but also by its interior. However, each particle of the RMO tends to remain on the surface layer portion without penetrating into the interior of the nonwoven fabric in general methods such as a method of spraying RMO particles onto the nonwoven fabric and a method of impregnating the nonwoven fabric with an RMO dispersion liquid.

[0009] The fibers forming the nonwoven fabric do not have a function of fixing the RMO on their surfaces. For this reason, even if an attempt is made to make the nonwoven fabric support a large number of RMOs, the RMOs that are not sufficiently fixed fall off the nonwoven fabric, making it difficult to display sufficient gas adsorption performance during use.

[0010] A technology that uses binders to fix RMOs on the surfaces of fibers forming the nonwoven is known. However, in the technology that relies mainly on binders to fix RMOs, binders stuck to RMO surfaces clog the pores of RMOs, and the original gas adsorption performance of RMOs is easily impaired.

[0011] An object of the present invention is to provide a composite sheet in which a metal-organic network is supported in a sheet base material formed of a fiber, the gas adsorption performance is high, and the metal-organic network hardly falls off during use. Solution to the problem

[0012] A composite sheet according to one embodiment of the present invention includes: a fiber; a sheet base material formed from the fiber; and a metal-organic network dispersed in the sheet base material.

[0013] In one embodiment, the fiber includes a core-cladding fiber having a core-cladding structure that includes a core and a cladding.

[0014] In one embodiment, the metalloorganic network and the sheath of the core-sheath fiber are bonded by a molten and fixed resin of the sheath.

[0015] In one embodiment, a surface exposure ratio of the bonded metal-organic network to the cladding of the core-cladding fiber is 50% or more.

[0016] Advantageous effects of the invention

[0017] According to the present invention, it is possible to provide a composite sheet in which a metal-organic network is supported in a sheet base material formed of a fiber, a gas adsorption performance is high, and the metal-organic network hardly falls off during use. Brief description of the drawings

[0018] [Fig. 1] is a flowchart showing a method of producing a composite sheet according to one embodiment of the present invention. Method(s) of carrying out the invention

[0019] [Basic configuration of composite sheet]

[0020] A composite sheet according to one embodiment of the present invention includes a sheet base material and a metal-organic framework (MOF).

[0021] The sheet base material of the composite sheet according to this embodiment is a base material formed of a fiber in a sheet shape, is typically a nonwoven, but may be a woven, a knit, a mesh or the like.

[0022] The RMO of the composite sheet according to this embodiment is typically a fine powder including a metal ion and an organic ligand, is dispersed in the sheet base material, and is supported on the surface of the fiber forming the sheet base material. It should be noted that such a structure is designated porous coordination polymer (PCP) in some cases, but is referred to as metal-organic framework (MOF) throughout this specification.

[0023] In the composite sheet according to this embodiment, the fiber forming the sheet base material includes a core-sheath fiber. The core-sheath fiber is a composite fiber in which a resin that forms a core and a resin that forms a sheath are different from each other, the sheath covering the core and forming a surface of the fiber.

[0024] In the core-sheath fiber used in this embodiment, the melting point of the core is preferably higher than the melting point of the sheath, and the difference between the melting point of the core and the melting point of the sheath is preferably 10°C or more and 200°C or less, more preferably 60°C or more, and even more preferably 100°C or more. With such a configuration, in the process of producing the composite sheet according to this embodiment, the shape of the fiber is preserved by the core having a high melting point. That is, in step S05 described below, the sheath is melted more reliably, and melting of the core due to overshoot during heating can be more easily prevented. Furthermore, the resin of the sheath having a low melting point is melted and attached to the RMO, thereby supporting the RMO.

[0025] Furthermore, in the core-sheath fiber used in this embodiment, the melting point of the core is preferably 160°C or higher and 280°C or lower, more preferably 200°C or higher, and even more preferably 240°C or higher. In the composite sheet according to this embodiment, by setting the melting point of the core of the core-sheath fiber included in the fiber forming the sheet base material at such a high temperature, it is possible to further expand the range of use, for example, gases in high-temperature exhaust gases generated in factories or the like can be collected.

[0026] Furthermore, in the core-sheath fiber used in this embodiment, the melting point of the sheath is preferably 70°C or higher and lower than 160°C, more preferably 80°C or higher, and even more preferably 100°C or higher. By raising the melting point of the sheath in the core-sheath fiber in this way, it is possible to raise the drying temperature in step S04 described below and to carry out drying in a shorter time.

[0027] The fiber forming the sheet base material in this embodiment preferably includes, for example, a core-sheath fiber that includes a core formed from polyethylene terephthalate and a sheath formed from polyethylene.

[0028] It should be noted that in the core-cladding fiber according to this embodiment, at least one of the core or the cladding may include a plurality of types of resin components. In this case, the melting point of the core indicates the melting point of a resin component included in the core, and the sheath melting point indicates the melting point of a resin component included in the sheath.

[0029] Each particle of the RMO used in the composite sheet according to this embodiment is typically porous with numerous pores having uniform pore sizes and functions as a gas adsorption material by adsorbing and retaining gas molecules in each pore.

[0030] The composite sheet according to this embodiment is a gas adsorption sheet capable of adsorbing, by causing a sheet base material to collectively support a large amount of RMO in a state capable of effectively exhibiting gas adsorption performance, a large amount of gas as all of the RMO supported on the sheet base material.

[0031] In the composite sheet according to this embodiment, an RMO layer is typically formed on the surface of the fiber.

[0032] Here, the RMO layer indicates a state in which aggregates of RMO particles form a layer as a whole. Specifically, the RMO layer includes one or more forms in, for example, the following states: a plurality of RMOs in fine powder form or particle form are deposited / stacked on the surface of the fiber; RMOs in fine powder form or particle form are generated on the surface of the fiber and grow to cover the surface of the fiber; and adjacent RMO particles unite with the generation and growth to cover the surface of the fiber as a unified film.

[0033] The RMO layer is preferably in a state of covering the surface of the fiber in the form of a unified film. This makes it more difficult for the RMO to fall off from the fiber. In addition, it is possible to prevent, when the cladding of the core-cladding fiber melts, the resin forming the melted cladding from sticking to the RMO attached to another core-cladding fiber.

[0034] In the composite sheet according to this embodiment, the particle size of the RMO may be larger or smaller than the fiber diameter of the sheet base material.

[0035] The RMOs that can be used in the composite sheet according to this embodiment have various pore sizes depending on the combination of metal ions and organic ligands. Therefore, in the composite sheet according to this embodiment, the pore size of the RMO to be supported on the sheet base material can be determined in accordance with the molecular size of the gas to be adsorbed. Therefore, in the composite sheet according to this embodiment, it is possible to selectively adsorb a specific gas by the RMO supported on the sheet base material.

[0036] The composite sheet according to this embodiment may comprise the RMO capable of selectively adsorbing carbon dioxide, for example, to recover carbon dioxide known as a greenhouse gas, and then the recovered carbon dioxide can be used as a raw material for chemicals. By using the RMO capable of selectively adsorbing, for example, a hydrocarbon (methane, ethane, propane or the like), hydrogen, hydrogen sulfide, nitrogen or oxygen, in addition to carbon dioxide, the composite sheet according to this embodiment can be configured as a gas adsorption sheet for these gases.

[0037] In the composite sheet according to this embodiment, it is possible to obtain the effects of the present invention even in the case where any of the wide variety of RMOs is used. That is, the RMO is synthesized by self-assembly mainly by a coordination bond between a metal ion and an organic ligand. This reaction mechanism is the same regardless of the type of metal ion and organic ligand. Since RMOs have, in principle, infinite combinations of metal ions and organic ligands, the combination of RMOs offers infinite possibilities. At this stage, the shape of the nano-space to be obtained can be adjusted arbitrarily because the RMO can be synthesized by considering and selecting species of the metal ion, the shape, length and substituent group of a ligand, and the like in accordance with the type of gas to be adsorbed and the adsorption characteristics.From the above, the present invention can accomplish the same effect with an arbitrary RMO.

[0038] [Basic configuration of the production process of the composite sheet]

[0039] (Schematic description)

[0040] The basic configuration of a method for producing a composite sheet according to this embodiment will be described in accordance with the flowchart shown in [Fig.l]. The method for producing a composite sheet according to [Fig.l] comprises step SOI (Prepare raw material solution), step S02 (Impregnate with first raw material solution), step S03 (Impregnate with second raw material solution), step S04 (Dry) and step S05 (Apply heat treatment). Steps SOI to S05 according to this embodiment will be described below.

[0041] (SOI Step: Prepare raw material solution)

[0042] In the SOI step, each of a first raw material solution and a second raw material solution is prepared as a raw material solution of an RMO. The first raw material solution and the second raw material solution are each a solution comprising one of a metal ion and an organic ligand, which are raw materials of the RMO. When these solutions are mixed, the metal ion and the organic ligand react with each other to generate an RMO.

[0043] In this embodiment, the first raw material solution includes a metal ion as a solute, and the second raw material solution includes an organic ligand as a solute.

[0044] In this embodiment, the solvent of the first raw material solution preferably includes water.

[0045] In this embodiment, the solution of the second raw material solution preferably includes ethanol.

[0046] As an example of the SOI step, in the case where the RMO is an ELM-11 (ELM = Elastic Layer-structured Metal organic framework), an aqueous solution of Cu(BF4)2 is prepared as a first raw material solution, and an ethanol solution of 4,4'-bipyridine (bpy) is prepared as a second raw material solution.

[0047] (Step S02: Impregnate with first raw material solution)

[0048] In step S02, a sheet base material is impregnated with the first raw material solution prepared in step SOI.

[0049] The method of impregnating the sheet base material with the first raw material solution in step S02 is not limited to a specific method. For example, a method of impregnating the sheet base material with a sufficient amount of the first raw material solution using one or two or more selected from among dripping with a dropper, spraying, spray coating, potting, curtain coating and dip coating can be used. Among these, one or two or more selected from among dripping with a dropper, spraying, spray coating, potting and curtain coating are preferably used from the viewpoint of preventing contamination in the first raw material solution.

[0050] In step S02, the time for impregnating the sheet base material with the first raw material solution is preferably 0.1 minute or more from the viewpoint of allowing the first raw material solution to penetrate into the central region of the sheet base material.

[0051] Furthermore, the impregnation time of the sheet base material with the first raw material solution is preferably 30 minutes or less from the point of view of ensuring productivity.

[0052] In step S02, it is preferable to uniformly disperse the metal ion included in the first raw material solution with the solvent over the entire sheet base material.

[0053] (Step S03: Impregnate with second raw material solution)

[0054] In step S03, the sheet base material which was impregnated with the first raw material solution in step S02 is impregnated with the second solution of raw material prepared in the SOI stage before the first raw material solution dries.

[0055] This allows the reaction between the solute of the first raw material solution and the solute of the second raw material solution to proceed smoothly even in the case where the solute of the first raw material solution is difficult to dissolve in the solute of the second raw material solution.

[0056] Furthermore, even in the case where the solute of the first raw material solution is dissolved in the solute of the second raw material solution, it is possible to uniformly carry out the reaction between the solute of the first raw material solution and the solute of the second raw material solution.

[0057] The state in which the first raw material solution has not dried in the sheet base material is a state in which the solvent of the first raw material solution remains in the sheet base material, more specifically a state in which 50% or more of the solvent of the first raw material solution remains in the sheet base material compared to that before impregnation. The amount of the second raw material solution is preferably the amount corresponding to the amount of the first raw material solution with which the sheet base material is impregnated in step S02.

[0058] In step S03, the impregnation time of the sheet base material with the second raw material solution is preferably 0.1 minute or more from the viewpoint of allowing the second raw material solution to penetrate into the central region of the sheet base material.

[0059] Furthermore, the impregnation time of the sheet base material with the second raw material solution is preferably 30 minutes or less from the point of view of ensuring productivity.

[0060] The method of impregnating the sheet base material with the second raw material solution in step S03 is not limited to a specific method. For example, a method of adding a sufficient amount of the second raw material solution dropwise into the sheet base material using one or two or more selected from among dripping with a dropper, spraying, spray coating, dipping, curtain coating, and dip coating may be used. Of these, one or two or more selected from among dripping with a dropper, spraying, spray coating, dipping, and curtain coating are preferably used from the viewpoint of preventing contamination in the second raw material solution.

[0061] In step S03, it is preferable to uniformly disperse the organic ligand included in the second raw material solution with the solvent over the entire sheet base material.

[0062] This organic ligand reacts with the metal ion that was previously dispersed in the sheet base material in step S02 to generate an RMO.

[0063] As an example of step S03, in the case where the RMO is ELM-11, Cu(BF4 )2 contained in the first raw material solution and bpy contained in the second raw material solution react with each other according to the following formula to generate ELM-11.

[0064] Cu(BF4)2 + 2bpy -> Cu (bpy)2(BF4)2

[0065] In the general process of producing a composite sheet, an RMO generated in advance is supported on the sheet base material. For this reason, each particle of the RMO tends to remain on the surface layer portion in the vicinity of the surface of the sheet base material because it cannot penetrate inside through interstices of the fiber forming the sheet base material. Namely, in the general process of producing a composite sheet, the RMO tends to be unevenly distributed on the surface layer portion of the sheet base material. Conversely, with a base material configuration in which the RMO is able to penetrate inside the sheet base material, the RMO quickly falls off and it is difficult to increase the amount of supported RMO.

[0066] On the other hand, in the production process of the composite sheet according to this embodiment, typically, raw materials before RMO generation, i.e., a metal ion and an organic ligand, are dispersed in the sheet base material at the molecular level. By subsequently generating RMO particles, it is possible to make not only the surface layer portion of the sheet base material but also the central region in the thickness direction support a large number of RMO.

[0067] It should be noted that the "central region in the thickness direction" refers to the middle portion when the sheet base material is divided equally into three regions in the thickness direction.

[0068] In the production process of the composite sheet according to this embodiment, since the above advantage can be obtained even with a configuration in which the thickness of the sheet base material is large, it is possible to make, by using a sheet base material having a large thickness, the sheet base material bear even more RMO. From this point of view, in this embodiment, the thickness of the composite sheet is preferably 0.2 mm or more, more preferably 0.5 mm or more, and even more preferably 1 mm or more.

[0069] The thickness of the composite sheet is realistically 10 mm or less, preferably 5 mm or less.

[0070] The thickness of the composite sheet is obtained as an average of a total of 5 positions, namely 4 corner positions and 1 central region in plan view, measured with a weight of 3.7 gf / cm2 and making the pressure area of ​​the probe 10 cm2 in accordance with JIS K 6402.

[0071] In the above general process of producing a composite sheet, the amount of RMO particles that wrap around the region on the opposite side of the fiber on the spraying surface or the application surface is small during the process of spraying or applying RMO to the sheet base material. For this reason, it is difficult to support the RMOs uniformly over the entire circumference of the fiber surface.

[0072] On the other hand, in the process of producing the composite sheet according to this embodiment, it is possible to disperse the metal ion and the organic ligand together with the solvent over the entire three-dimensional structure of the sheet base material. For this reason, it is possible to support the RMOs uniformly over the entire circumference of the surface of the fiber forming the sheet base material.

[0073] As an example of a configuration comparative to this embodiment, a production process using a method of drying the sheet base material impregnated with the first raw material solution before step S03 will be described. In the process of producing a composite sheet according to the example of a comparative configuration, the solvent is removed by evaporation from the surface layer side of the sheet base material in the process of drying the sheet base material before step S03. For this reason, the solvent in the central region in the thickness direction of the sheet base material disperses toward the surface layer side together with the metal ion and solidifies.As a result, in the production process of the composite sheet according to the comparative configuration example, the solute of the first raw material solution is unevenly distributed on the surface layer portion in the sheet base material before being impregnated with the second raw material solution. For this reason, the amount of RMO that can be generated in the central region in the thickness direction of the sheet base material is small. Furthermore, in the production process of the composite sheet according to the comparative configuration example, the solute of the first raw material solution is generated as a solid in the sheet base material before being impregnated with the second raw material solution.For this reason, even if the sheet base material is impregnated with the second raw material solution, it is difficult for the solute of the first raw material solution to dissolve in the solvent of the second raw material solution to form metal ions. Therefore, metal ions do not react with the organic ligand and tend to remain as unreacted products.

[0074] In the process of producing the composite sheet according to this embodiment, it is preferable that the sheet base material impregnated with the first raw material solution in step S02 is not dried and that the sheet base material in a state in which the solvent of the first raw material solution is present is impregnated with the second raw material solution in step S03.

[0075] This eliminates the aforementioned problem that arises in the production process of the composite sheet according to the comparative configuration example. Namely, in the production process of the composite sheet according to this embodiment, the metal ion included in the first raw material solution can be made to react with the organic ligand included in the second raw material solution while being uniformly dispersed in the sheet base material.

[0076] Furthermore, in the process of producing the composite sheet according to this embodiment, the reaction occurs when the metal ion and the organic ligand which are present in the solvent without being subjected to a binding force effectively bind to each other. For this reason, it is unlikely that the metal ion and the organic ligand will remain as unreacted products.

[0077] Therefore, in the production process of the composite sheet according to this embodiment, it is possible to make the sheet base material bear more RMO than in the production process of the composite sheet according to the comparative configuration example.

[0078] In the process of producing the composite sheet according to this embodiment, it is conceivable that the reaction between the metal ion and the organic ligand proceeds to heterogeneous nucleation at the interface of the fiber forming the sheet base material. Intermolecular forces act between the RMO generated with heterogeneous nucleation in this manner and the fiber interface. The RMO generated in step S03 is supported directly on the fiber interface by the intermolecular forces without any other components. Therefore, in the process of producing the composite sheet according to this embodiment, it is not necessary to use a binder as an adhesive component in order to support the RMO on the fiber surface.

[0079] It should be noted that in this patent specification, the expression "the RMO is supported directly on the surface of the fiber" refers to the fact that the RMO is attached to the surface of the fiber without any other components than the RMO and the fiber material. Typically, the RMO is attached by intermolecular forces as described above, hydrophobic interactions described below, or the resin on the surface of the fiber, which is melted and attached to the RMO.

[0080] Whether the resin on the surface of the fiber is melted and attached to the RMO can be determined by observing the cross-section of the fiber forming the composite sheet using a scanning electron microscope (SEM). Namely, in the case where the resin of the cladding of the core-cladding fiber is melted and attached to the RMO, the RMO becomes embedded in the cladding of the core-cladding fiber, and thus, it is observed that the contour of the core-cladding fiber, which is initially circular, is deformed at the boundary between the RMO and the core-cladding fiber.

[0081] Therefore, in the composite sheet according to this embodiment, performance degradation due to the presence of binders, such as a decrease in gas adsorption performance of the RMO due to the adhesion of the binder and a decrease in flexibility due to the binder, is less likely to occur. For this reason, in the composite sheet according to the present invention, it is preferable that the RMO is supported directly on the surface of the fiber. Such an effect is accomplished mainly by generation of the RMO by the reaction between the metal ion and the organic ligand as described above and can be effectively accomplished not only with the configuration exemplified in the Examples described below, but also with other configurations.

[0082] In the composite sheet according to this embodiment, the distance between the fibers defined as the dimension of the gap between the fibers forming the sheet base material is preferably 1 μm or more, more preferably 10 μm or more, even more preferably 50 μm or more, and even more preferably 100 μm or more. This ensures structural flexibility of the RMO supported on the fiber surface and prevents the RMO from falling off. That is, it is easier to obtain high flexibility of the composite sheet and it is possible to create a space where the RMO is formed to increase the support ratio.

[0083] Furthermore, the distance between the fibers is preferably 1000 pm or less, more preferably 500 pm or less, even more preferably 400 pm or less, and even more preferably 300 pm or less. This suppresses homogeneous nucleation and more efficiently generates heterogeneous nucleation during the reaction between the metal ion and the organic ligand. That is, the portion where the RMO is formed can be controlled to be the surface of the fiber.

[0084] A method for measuring the distance between fibers of the sheet base material in the composite sheet according to this embodiment will be described. First, an arbitrary surface of the composite sheet to be measured is observed with an SEM to obtain an enlarged image of the surface. In the enlarged image, 50 gaps formed by the respective fibers are selected, and the total of the gaps is measured and divided by the number of gaps (50) to obtain an average gap area per gap. An average fiber-to-fiber diameter when the gap is converted to a circle is obtained based on the average gap-by-gap area obtained in this way using the following formula, and the average fiber-to-fiber diameter is used as the distance between fibers.

[0085] Average fiber-to-fiber diameter = 2 x (average gap area / 3.14)A(l / 2)

[0086] Furthermore, in the composite sheet according to this embodiment, the basis weight of the sheet base material is preferably 10 g / m2 or more, more preferably 20 g / m2 or more, and preferably 100 g / m2 or less, more preferably 80 g / m2 or less. It should be noted that in the case where the sheet base materials are stacked and used as a single sheet base material, it is preferable that the total basis weight of the sheet base material exceeds 100 g / m2.

[0087] (Step S04: Drying)

[0088] In step S04, the sheet base material on which the RMO is supported in step S03 is dried.

[0089] It should be noted that in step S04, during the drying process, the solvent is evaporated from the surface layer side of the sheet base material, and the solvent in the central region in the thickness direction of the sheet base material disperses toward the surface layer side. However, the RMO that has been attached to the surface of the fiber in the central region in the thickness direction of the sheet base material remains on the surface of the fiber with the solvent without moving. For this reason, in the method for producing a composite sheet according to this embodiment, the dispersed state of the RMO supported on the sheet base material in step S04 is maintained.

[0090] In the method for producing a composite sheet according to the present invention, the total number of performing the series of processes of steps S02 to S04 may be one. This means that the series of processes does not necessarily need to be repeated.

[0091] Furthermore, by repeating the processes of steps S02 to S04, it is possible to increase the amount of RMO to be supported on the sheet base material. From this point of view, the total number of performing the processes of steps S02 to S04 is preferably 2 or more, more preferably 3 or more.

[0092] It should be noted that there is a limit to the amount of RMO that can be supported on the sheet base material, the total number of performing steps S02 to S04 is preferably 20 or less in the method for producing a composite sheet according to this embodiment from the viewpoint of production cost and the like.

[0093] (Step S05: Apply heat treatment)

[0094] In step S05, a heat treatment is applied to the sheet base material dried in step S04. The heat treatment of step S05 is preferably carried out at a temperature equal to or higher than the melting point of the sheath and lower than the melting point of the core. For example, the heat treatment in step S05 can be carried out by maintaining it at 140 °C for 2 hours.

[0095] The RMO generated in step S03 being in the hydrated state, it does not have a gas adsorption function.

[0096] In step S05, it is preferable that the solvent component remaining in the sheet base material is completely removed.

[0097] In step S05, by dehydrating the RMO, it is possible that the RMO displays the gas adsorption function. In this way, the composite sheet according to this embodiment is obtained.

[0098] In step S05, by performing heat treatment in the above temperature range, only the sheath having a low melting point in the core-sheath fiber included in the fiber forming the sheet base material melts or softens. As a result, in the composite sheet after heat treatment, the RMO is supported on the surface of the core-sheath fiber by melting and fixing. Namely, in the composite sheet according to this embodiment, it is possible to fix the sheath of the core-sheath fiber to the RMO without separately adding a binder as an adhesive component.

[0099] Furthermore, in step S05, the core having a high melting point is less likely to melt or soften in the heat treatment process. Therefore, even in the composite sheet after heat treatment, the shape of the fiber forming the sheet base material is preserved in the core.

[0100] In the sheet base material used in this embodiment, the more the core-sheath fiber, the more effectively it is possible to prevent RMOs from falling off. From this point of view, in the sheet base material used in this embodiment, the content of the core-sheath fiber is preferably 3 mass% or more, more preferably 10 mass% or more, and even more preferably 30 mass% or more.

[0101] The content of the core-sheath fiber in the sheet base material is less than 100% by mass, preferably less than or equal to 90% by mass, and more preferably less than or equal to 80% by mass.

[0102] The content of the core-sheath fiber in the composite sheet is preferably 1% by mass or more, more preferably 2% by mass or more.

[0103] The content of the core-sheath fiber in the composite sheet is preferably 20% by mass or less, more preferably 18% by mass or less.

[0104] In the process of producing a general composite sheet in which a sheet base material is made to support an RMO generated in advance as described above, melted sheaths in a plurality of core-sheath fibers adjacent to a given RMO tend to adhere to the particles of the given RMO during heat treatment. On the other hand, in the process of producing the composite sheet according to this embodiment, since the sheath forming the surface of the core-sheath fiber is covered by the RMO at step S03, the melted sheath in the core-sheath fiber hardly adheres to the RMO supported on another core-sheath fiber at step S05. Therefore, in the composite sheet according to this embodiment, the RMO supported on the sheet base material is able to more effectively display original gas adsorption performance.

[0105] Furthermore, in the composite sheet according to this embodiment, a high support capacity for RMOs is easily accomplished and the RMO is less likely to fall off from the core-sheath fiber compared with a composite sheet obtained by the process of producing a general composite sheet. This also contributes to effectively exhibiting gas adsorption performance.

[0106] The relationship between the drying temperature in step S04, the heat treatment temperature in step S05, and the configuration of the core-sheath fiber in the method for producing a composite sheet according to this embodiment will be summarized below.

[0107] In the core-cladding fiber according to this embodiment, it is preferable that the melting point of the core is higher than the heat treatment temperature in step S05.

[0108] Further, in the core-sheath fiber, it is preferable that the melting point of the sheath is higher than the drying temperature in step S04 and lower than the heat treatment temperature in step S05.

[0109] In the method for producing a composite sheet according to this embodiment, by setting the melting point of the sheath of the core-sheath fiber at a temperature higher than the drying temperature in step S04, it is possible to prevent the sheath from melting to bring the reaction product into the fiber in step S04. For this reason, it is possible to resolutely continue the RMO generation reaction and increase the reactivity of the RMO generation reaction.

[0110] Furthermore, by setting the melting point of the sheath of the core-sheath fiber at a temperature lower than the heat treatment temperature in step S05, it is possible to fix the RMO to the surface of the fiber more reliably. Furthermore, by setting the melting point of the core of the core-sheath fiber at a temperature higher than the heat treatment temperature in step S05, the shape of the fiber is maintained by the core not melting in step S05. For this reason, the interstices between the fibers of the sheet base material are maintained, and it is possible to increase the reactivity of the RMO generation reaction.

[0111] [Another example of a composite sheet production method configuration]

[0112] The method for producing a composite sheet according to this embodiment is not limited to the above basic configuration. For example, in the method of producing a composite sheet according to this embodiment, it is preferable that in the SOI step, one of the metal ion and the organic ligand, which are raw materials of an RMO, is included in the first raw material solution, and the other is included in the second raw material solution.

[0113] In the SOI step, it is preferable that the first raw material solution includes the metal ion and the second raw material solution includes the organic ligand as described above.

[0114] Further, the first raw material solution may include the organic ligand and the second raw material solution may include the metal ion.

[0115] In the method for producing a composite sheet according to this embodiment, it is preferable that in the SOI step, one of the first raw material solution and the second raw material solution includes water as a solvent, and the other includes an organic solvent as a solvent.

[0116] In the SOI step, it is preferable that water is included as the solvent of the first raw material solution and an organic solvent is included as the solvent of the second raw material solution as described above.

[0117] In addition to this, an organic solvent may be included as a solvent of the first raw material solution and water may be included as a solvent of the second raw material solution.

[0118] Further, in the SOI step, a solvent other than ethanol may be used as the organic solvent. For example, methanol, isopropanol or acetone may be included.

[0119] The organic solvent is preferably a solvent which can be mixed with water in an arbitrary ratio.

[0120] In the method for producing a composite sheet according to this embodiment, it is preferable that in the SOI step, the content of water included in one of the first raw material solution and a second raw material solution, which includes water as a solvent, is 30 mass% or more and 99 mass% or less. Furthermore, in the method for producing a composite sheet according to this embodiment, it is preferable that in the SOI step, the content of an organic solvent included in one of the first raw material solution and the second raw material solution, which includes the organic solvent as a solvent, is 30 mass% or more and 99 mass% or less. Within these numerical ranges, it is easier for the raw material solution to penetrate into the sheet base material and for RMOs to uniformly attach in the thickness direction of the composite sheet.

[0121] The method of producing a composite sheet according to this embodiment may include, if necessary, an additional Step in addition to the above Steps. In addition, in the method of producing a composite sheet according to this embodiment, some of the above Steps may be modified or omitted if necessary.

[0122] For example, in the drying in step S04, the treatment time can be shortened by performing the heat treatment at a temperature higher than room temperature and lower than the heat treatment temperature in step S05.

[0123] Furthermore, for example, by providing a process of drying the sheet base material in the heat treatment in step S05, step S04 immediately before step S05 (the last step S04 in the case where steps S02 to S04 are repeated) can be omitted.

[0124] In the method for producing a composite sheet according to this embodiment, as the fiber forming the sheet base material, a fiber other than the core-sheath fiber may be included. In this case, it is preferable that the fiber other than the core-sheath fiber also includes an organic fiber. Therefore, in the method for producing a composite sheet according to this embodiment, hydrophobic interactions between molecules act between the organic ligand of the RMO and a group present on the surface of the organic fiber, which enables the RMO to be more firmly attached to the surface of the organic fiber.

[0125] It should be noted that such hydrophobic interactions appear not only in hydrophobic organic fibers, but also in hydrophilic organic fibers. Namely, hydrophobic interactions appear even in the organic fiber which is hydrophilic as a whole if it has a hydrophobic portion at a microscopic level. For example, in a cellulose fiber which is a hydrophilic organic fiber, hydrophobic interactions appear because a CH group forming an axial group of the glucopyranose ring is hydrophobic.

[0126] Whether the fiber forming the sheet base material in the composite sheet is hydrophilic or hydrophobic is determined by the effective property of the surface of the fiber, regardless of the initial property of the fiber itself. Namely, in the case of the fiber which has been subjected to a surface treatment, the determination is made for the fiber in the state after the surface treatment. For example, the hydrophobic fiber whose surface has been subjected to a hydrophilic treatment is determined to be a hydrophilic fiber, and the hydrophilic fiber whose surface has been subjected to a hydrophobic treatment is determined to be a hydrophobic fiber.

[0127] In order to evaluate whether the fiber forming the sheet base material in the composite sheet is hydrophilic or hydrophobic, deionized water is sprayed onto the composite sheet, and the contact surface between each fiber and the deionized water is observed using a microscope or a digital microscope. It is determined that the surface of the fiber is hydrophilic in the case where the contact angle between the fiber and deionized water is less than 60°, and the fiber surface is determined to be hydrophobic in the case where the contact angle is 60° or more.

[0128] In the case where a fiber other than the core-sheath fiber is included as the fiber forming the sheet base material, the mass of the core-sheath fiber alone can be obtained as follows. Namely, the fiber type can be identified by identifying the structural formula of the fiber forming the sheet base material in the composite sheet using time-of-flight secondary ion mass spectrometry (TOF-SIMS), infrared (IR) spectroscopy, nuclear magnetic resonance (NMR), energy dispersive X-ray spectroscopy (EDX) or the like, and measuring their melting point using DSC. Then, the mass of the core-sheath fiber included in the composite sheet can be calculated based on the intensity ratio of the NMR spectrum obtained from the 100% aggregate of the corresponding core-sheath fiber and the spectrum obtained from the composite sheet.

[0129] In the method for producing a composite sheet according to this embodiment, it is preferable to use a sheet base material including both a hydrophilic fiber and a hydrophobic fiber. That is, in the sheet base material used in this embodiment, at least one hydrophilic fiber other than the core-sheath fiber that is a hydrophobic fiber is preferably included, and a hydrophobic fiber other than the core-sheath fiber may be included. Therefore, in step S03, the penetration rate of one of the water and the organic solvent into the sheet base material impregnated with the other increases, and thus, RMOs are less likely to be unevenly distributed in the sheet base material.

[0130] The sheet base material according to this embodiment preferably includes, as the hydrophilic organic fiber, one or two or more selected from a cellulose fiber, a regenerated cellulose fiber, a thermoplastic fiber whose surface has been hydrophilized, and the like.

[0131] The regenerated cellulose fiber more preferably includes one or two or more selected from a rayon, a cupra, and the like.

[0132] Examples of methods for hydrophilizing the surface of the thermoplastic fiber include applying a hydrophilizing agent and performing a plasma treatment.

[0133] The thermoplastic fiber preferably includes one or two or more selected from a polyolefin resin, a polyester resin, a vinyl resin, an acrylic resin, a fluoropolymer, a polyamide resin, and the like.

[0134] The polyolefin resin preferably includes one or two or more selected from polyethylene, polypropylene, and the like.

[0135] The polyester resin preferably includes one or two or more selected from polyethylene terephthalate and the like.

[0136] The vinyl resin preferably includes one or two or more selected from polyvinyl chloride, polystyrene, and the like.

[0137] The acrylic resin preferably includes one or two or more selected from polyacrylic acid, polymethyl methacrylate, and the like.

[0138] The fluoropolymer preferably includes one or two or more selected from polyperfluoroethylene and the like.

[0139] Further, the sheet base material according to this embodiment preferably includes, as the hydrophobic organic fiber, one or two or more selected from a synthetic fiber and the like.

[0140] The synthetic fiber preferably includes one or two or more selected from a polyolefin fiber, a polyester fiber, a fluorine fiber, a polyamide fiber, and the like.

[0141] Further, in this embodiment, all or part of the fiber forming the sheet base material may be an inorganic fiber. The sheet base material according to this embodiment preferably includes, as the inorganic fiber, one or two or more selected from a glass fiber, a ceramic fiber, a metal fiber, a carbon fiber, and the like.

[0142] [Detailed configuration of composite sheet]

[0143] (surface coverage)

[0144] In the composite sheet according to this embodiment, the RMO can be supported on the entire three-dimensional structure of the sheet base material including the fiber in step S03. Namely, in the composite sheet according to this embodiment, a large number of RMOs can be supported not only on the surface layer portion of the sheet base material, but also on the central region in the thickness direction. Specifically, in the composite sheet according to this embodiment, the surface coverage defined as the ratio of the region covered by the RMO to the surface area of ​​the fiber in the central region in the thickness direction of the composite sheet is preferably 60% or more, more preferably 70% or more, even more preferably 80% or more, and realistically 100% or less.

[0145] The surface coverage by the RMO in the fiber forming the sheet base material of the composite sheet can be obtained by SEM and EDX. Specifically, the composite sheet is split and unsupported RMOs are removed by a blower or the like. A microstructure photograph of the entire split surface is taken by SEM. In the obtained microstructure photograph, a line perpendicular to a straight line along the width direction of the composite sheet is drawn, and the midpoint between the two end portions in the thickness direction of the composite sheet is determined on the perpendicular line. The part of the straight line along the width passing through the midpoint is defined as the central region in the thickness direction of the composite sheet. Attention is paid to an arbitrary fiber present in the central region in the thickness direction of the composite sheet, a microstructure photograph of one of the fibers is taken by SEM, and an element mapping image is generated by EDX. Therefore, a region where the fiber is present can be identified by the microstructure photograph, and a region where the metal is present can be identified as a region where an RMO is present by the element mapping image. The surface coverage can be calculated as a ratio of the region where an RMO is present to the entire region where a fiber is present.

[0146] (Circumferential coverage)

[0147] In the composite sheet according to this embodiment, the RMO can be supported uniformly over the entire circumference of the surface of the fiber forming the sheet base material. As a result, in the composite sheet according to this embodiment, it is possible to increase the circumferential coverage defined as the ratio of the region covered by the RMO, of the surface of the fiber observed as the contour of the fiber in the orthogonal cross-section to the longitudinal direction of the fiber forming the sheet base material. Specifically, in the composite sheet according to this embodiment, the circumferential coverage by the RMO in at least a portion of the fiber forming the sheet base material is preferably 80% or more, more preferably 85% or more, even more preferably 90% or more, and realistically 100% or less.Still more preferably, the circumferential coverage by the RMO in at least a portion of the fiber forming the middle region when the cross-section of the composite sheet is divided equally into three regions is 80% or more. It should be noted that the shape of the fiber contour is not particularly limited and may be circular, rectangular, triangular, star-shaped or the like. In any case, the circumferential coverage can be calculated by obtaining the length of the entire circumference of the fiber surface using a known method.

[0148] The circumferential coverage by the RMO on the surface of the fiber forming the sheet base material of the composite sheet can be obtained by SEM and EDX. Specifically, a microstructure photograph in the field of view in which the cross section orthogonal to the longitudinal direction of the fiber in the cross section of the composite sheet can be observed is taken by SEM, and an element mapping image is generated by EDX. The length of the entire region of the fiber surface observed as the contour of the fiber in the cross section orthogonal to the longitudinal direction of the fiber and the length of the region covered by the RMO of the fiber surface observed as the contour of the fiber are measured, and the circumferential coverage can be used as its ratio by the following formula.

[0149] Circumferential coverage (%) by RMO = 100 x (length of RMO covered region of fiber surface / length of entire region of fiber surface)

[0150] (Thickness of the fiber covering the RMO layer)

[0151] Whether or not the RMO covers the fiber surface and the thickness of the RMO layer covering the fiber are measured as follows. A two-component curable liquid epoxy resin and a curing agent are mixed, and a sheet to be measured is impregnated with the mixture. Then, the resulting mixture is degassed by vacuuming and then subjected to heat treatment to cure the epoxy resin and the curing agent. In this way, a cured sample with the positions of the fiber and the RMO fixed is obtained.

[0152] The obtained cured sample is cut along the thickness direction of the sheet, and its surface is observed by SEM. A cross-sectional portion of the fiber covered by the RMO is extracted from the obtained cross-sectional image of the composite sheet. An average value of the thicknesses in the radial direction of the fiber of the RMO layer of the fiber-covering portion is used as the thickness of the RMO layer.

[0153] (RMO Content Report)

[0154] In the composite sheet according to this embodiment, by increasing the surface coverage and circumferential coverage by the RMO in the fiber forming the sheet base material as described above, it is possible to support more RMO on the sheet base material, i.e., to increase the RMO content. Specifically, in the composite sheet according to this embodiment, the content ratio of the RMO defined as the ratio of the mass of the RMO to the mass of the entire composite sheet is preferably 80 mass% or more, more preferably 85 mass% or more. Furthermore, in the composite sheet according to this embodiment, the content ratio of the RMO is preferably 99 mass% or less.

[0155] The content ratio of the RMO in the composite sheet can be obtained by analyzing the composite sheet. Specifically, first, gas adsorption measurement, X-ray diffraction (XRD), EDX, NMR, IR, elemental analysis and the like are performed to obtain a pore structure, a crystal lattice size, a crystal structure and a constituent element. The type of RMO, i.e., the metal ion and the organic ligand, is identified by checking these results against a publicly available RMO database. The composite sheet is then thermally decomposed, and the amount of metal included in the remaining ash is measured. Then, the mass of the RMO included in the composite sheet is obtained based on the measured metal amount and the content of metal in the identified RMO. The RMO content ratio is obtained by dividing the obtained mass of the RMO by the mass of the composite sheet.

[0156] (RMO Surface Exposure Report)

[0157] In the composite sheet according to this embodiment, it is not necessary to rely primarily on a binder as an adhesive component. For this reason, in the composite sheet according to this embodiment, it is possible to increase the surface exposure ratio without a binder covering the surface of the RMO. The surface exposure ratio is defined as the ratio of the area where the surface of the RMO is exposed to the area occupied by the RMO supported on the cladding of the core-cladding fiber forming the sheet base material when the composite sheet is viewed in plan (100 x (area of ​​the region where the surface of the RMO is exposed) / (area of ​​the region occupied by the RMO supported on the cladding of the core-cladding fiber forming the sheet base material)).Specifically, in the composite sheet according to this embodiment, the surface exposure ratio of the RMO is preferably 50% or more and 100% or less, more preferably 70% or more, and even more preferably 90% or more.

[0158] In order to measure the surface exposure ratio of the RMO in the composite sheet, firstly, the RMOs which are not supported on the cladding of the core-cladding fiber forming the sheet base material in the composite sheet are removed by a blower or the like. Subsequently, the surface area of ​​the RMO supported on the cladding of the core-cladding fiber forming the sheet base material is analyzed by TOF-SIMS, micro IR or the like and can be evaluated by mapping. Specifically, a part of the RMO to be observed is identified, its area (area of ​​the region occupied by the RMO) is measured, and the surface area of ​​the RMO is analyzed. The area of ​​the region where a spectrum derived from a substance other than the RMO is detected on the RMO is measured by analyzing the surface area of ​​the RMO. The substance other than the RMO is derived from a binder, for example. The area of ​​the region where a spectrum derived from a substance other than RMO is detected is subtracted from the area occupied by RMO.The area of ​​the difference is divided by the area of ​​the RMO, and thus, the surface exposure ratio of the RMO can be calculated.

[0159] (Amount of gas adsorption per unit volume of composite sheet)

[0160] Similarly, in the composite sheet according to this embodiment, the surface of the RMO is not covered by adhesion of a binder. For this reason, the surface exposure ratio of the RMO is high. In addition, in the composite sheet according to this embodiment, there are few unreacted products of the RMO as described in comparison with the comparative configuration example in “Step S03: Impregnating with Second Raw Material Solution” above. For this reason, the gas adsorption performance is less inhibited. As a result, in the sheet composite sheet according to this embodiment, the RMO supported on the sheet base material is capable of effectively displaying the initial gas adsorption performance. Furthermore, it is possible to attach the RMO also to the fiber in the central region of the composite sheet, and the air permeability is high. For this reason, in the composite sheet according to this embodiment, it is possible to increase the gas adsorption amount per unit volume of the composite sheet. Specifically, in the composite sheet according to this embodiment, for example, in the case of using an RMO selectively adsorbing carbon dioxide, the gas adsorption amount per unit volume of the composite sheet is preferably 2 mL / cm3 or more, more preferably 3 mL / cm3 or more, and even more preferably 5 mL / cm3 or more.

[0161] The gas adsorption amount per unit volume of the composite sheet is obtained by dividing the measured gas adsorption amount for the composite sheet by the measured amount of the composite sheet. The gas adsorption amount is measured using a high-precision gas adsorption amount measuring instrument "BELSORP-minill" manufactured by MicrotracBEL Corp.

[0162] (RMO Drop Report)

[0163] In the composite sheet according to this embodiment, it is possible to firmly fix the RMO to the fiber surface by intermolecular forces acting between the fiber surface and the RMO, and it is not necessary to rely primarily on a binder as an adhesive component to fix the RMO to the fiber surface.

[0164] In the composite sheet according to this embodiment, since the RMO is fixed by the fused sheath forming the surface of the core-sheath fiber, a particularly high fixing strength can be obtained on the surface of the core-sheath fiber. For this reason, in the composite sheet according to this embodiment, the RMO is less likely to fall off from the sheet base material.

[0165] In the composite sheet according to this embodiment, the falling ratio of the RMO by shaking evaluation in which the composite sheet is grasped by hand and shaken up and down is preferably 0 mass% or more and 20 mass% or less, more preferably 18 mass% or less, even more preferably 15 mass% or less, and even more preferably 9 mass% or less.

[0166] Therefore, in the composite sheet according to this embodiment, since the amount of RMO supported on the sheet base material is easily retained during transportation and use, the gas adsorption performance is less likely to deteriorate. Furthermore, in the composite sheet according to this embodiment, it It is possible to prevent RMO that has fallen during use from entering the facility as a foreign substance.

[0167] The RMO drop ratio is obtained by dividing the mass of RMO that fell during the shaking evaluation by the mass of RMO included in the composite sheet before the shaking evaluation.

[0168] (Maximum bending stress of the composite sheet)

[0169] In the composite sheet according to this embodiment, high flexibility can be easily achieved with the configuration that does not rely primarily on a binder as an adhesive component for attaching the RMO to the fiber surface. As a result, the composite sheet according to this embodiment is capable of achieving high workability and can be stored and transported in a rolled form.

[0170] In the composite sheet according to this embodiment, the maximum bending stress is preferably 0 MPa or more and 5 MPa or less, more preferably 3 MPa or less, even more preferably 1 MPa or less, even more preferably 0.1 MPa or less.

[0171] The maximum bending stress in the composite sheet can be measured using a measuring device (AG-X plus universal testing machine manufactured by SHIMADZU CORPORATION) in accordance with the three-point bending test of JIS K7017. At this stage, the composite sheet used as a measuring sample is cut as a sample with the dimension of 100 mm (length) x 100 mm (width) and measured.

[0172] In the three-point bending evaluation, the sample is placed on a jig with a distance between the support points of 40 mm, the central region between the support points is pressed at a speed of 10 mm / min, and the amount of pressure and the bending load are measured. The maximum value of the bending stress obtained by this evaluation is used as the maximum bending stress.

[0173] It should be noted that the bending stress is a physical property value calculated by the moment (product of a load and a distance) applied to the sample during the three-point bending test by the section modulus of the sample and is calculated by the following formula.

[0174] Bending stress (MPa) = 3 x bending load (N) x distance between support points (m) / 2 / sample thickness (m) / (sample width (m)2) / 106

[0175] In the case where the sample cannot be cut due to the size of the composite sheet to be measured, a sample having an arbitrary size can be cut and measured.

[0176] (Gurley air permeability of composite sheet)

[0177] It is preferable that the composite sheet according to this embodiment is configured to be able to be crossed by gas with a low pressure loss so that the gas is readily supplied also to the RMO supported on the central region in the thickness direction of the composite sheet. Specifically, in the composite sheet according to this embodiment, the Gurley air permeability is preferably 0 s / 100 mL or more and 10 s / 100 mL or less, more preferably 5 s / 100 mL or less, and even more preferably 0.5 s / 100 mL or less. The Gurley air permeability of the composite sheet can be obtained using a Gurley type air permeability testing machine in accordance with JIS P8117:2009.

[0178] In the composite sheet according to this embodiment, since the Gurley air permeability is high, it is possible to suppress a decrease in the amount of supported RMO due to fixation by the inter-cladding contact of the core-cladding fiber in the heat treatment process in step S05.

[0179] (Identification of the type of fiber forming the base sheet material)

[0180] The type of fiber forming the base sheet material in the composite sheet can be identified using TOF-SIMS, IR, NMR, EDX, differential scanning calorimetry (DSC), and the like. Specifically, the fiber type can be identified by identifying the structural formula of the fiber forming the sheet base material in the composite sheet by TOF-SIMS, IR, NMR, EDX or the like and measuring its melting point by DSC.

[0181] [Other embodiments]

[0182] Although one embodiment of the present invention has been described above, it is understood that the present invention is not limited to the above-mentioned embodiment only and that various modifications may be made without departing from the essence of the present invention.

[0183] For example, in the method for producing a composite sheet according to this embodiment, although it is preferable that one of the solvents used in the first raw material solution and the second raw material solution prepared in the SOI step includes water and the other includes an organic solvent from the viewpoint of the penetration rate of the first raw material solution and the second raw material solution into the sheet base material, a different configuration may be adopted from another viewpoint. For example, in the method for producing a composite sheet according to this embodiment, both solvents used in the first raw material solution and the second raw material solution prepared in the SOI step may include water or an organic solvent.

[0184] Although it is preferable that the composite sheet according to this embodiment does not include a binder, it may include a small amount of binder in the case where, for example, it is necessary to fix the RMO even more firmly to the base material. sheet. However, in the composite sheet according to this embodiment, it is preferable that the ratio of the mass of the binder to the total mass of the RMO and the binder is 0 mass% or more and 5 mass% or less from the viewpoint of ensuring high gas adsorption performance of the RMO and high flexibility.

[0185] Further, in the composite sheet according to this embodiment, the binder content on the mass of the entire composite sheet is 0 mass% or more and 10 mass% or less, preferably 5 mass% or less, and more preferably 1 mass% or less.

[0186] The present invention further includes the configurations shown below.

[0187] <1>

[0188] Composite sheet, comprising:

[0189] a fiber;

[0190] a sheet base material formed from the fiber; and

[0191] a metalloorganic network dispersed in the sheet base material,

[0192] the fiber including a core-cladding fiber having a core-cladding structure that includes a core and a cladding,

[0193] the metalloorganic network and the sheath of the core-sheath fiber being bonded by a molten and fixed resin of the sheath, and

[0194] a surface exposure ratio of the bonded metal-organic network to the sheath of the core-sheath fiber being 50% or more.

[0195] <2>

[0196] Composite sheet according to <1> , in which

[0197] the composite sheet has a circumferential coverage by the metalloorganic network in a cross section orthogonal to a longitudinal direction in at least a portion of the fiber of 80% or more and 100% or less, preferably 85% or more, and more preferably 90% or more.

[0198] <3>

[0199] Composite sheet according to <1> Or <2> , in which

[0200] the core of the core-sheath fiber includes a resin component having a melting point of 160°C or higher and 280°C or lower, preferably 200°C or higher, and more preferably 240°C or higher.

[0201] <4>

[0202] Composite sheet according to any one of <1> has <3> , in which

[0203] the sheath of the core-sheath fiber comprises a resin component having a melting point of 70°C or higher and lower than 160°C, preferably 80°C or higher, and more preferably 100°C or higher.

[0204] <5>

[0205] Composite sheet according to any one of <1> has <4> , in which

[0206] the core of the core-sheath fiber comprises a resin component having a melting point higher than that of the resin component included in the sheath, and a difference between the melting point of the resin component included in the core and the melting point of the resin component included in the sheath is preferably 10°C or more and 200°C or less, more preferably 60°C or more, and even more preferably 100°C or more.

[0207] <6>

[0208] Composite sheet according to any one of <1> has <5> , in which

[0209] the resin component included in the core of the core-cladding fiber has a melting point higher than the melting point of the resin component included in the sheath by 10°C or more.

[0210] <7>

[0211] Composite sheet according to any one of <1> has <6> , in which

[0212] the composite sheet has a metal-organic network drop ratio by shaking evaluation of 20 mass% or less.

[0213] <8>

[0214] Composite sheet according to any one of <1> has <7> , in which

[0215] the composite sheet has a metal-organic network drop ratio by shaking evaluation of 0 mass% or more and 20 mass% or less, preferably 18 mass% or less.

[0216] <9>

[0217] Composite sheet according to any one of <1> has <8> , in which

[0218] a maximum bending stress is 5 MPa or less.

[0219] <10>

[0220] Composite sheet according to any one of <1> has <9> , in which

[0221] the composite sheet has a maximum bending stress of 0 MPa or more and of 5 MPa or less, preferably of 3 MPa or less, and more preferably of 1 MPa or less.

[0222] <11>

[0223] Composite sheet according to any one of <1> has <10> , in which

[0224] the composite sheet has a composite sheet thickness of 0.2 mm or more and of 10 mm or less, preferably of 0.5 mm or more and of 5 mm or less, and more preferably of 1 mm or more.

[0225] <12>

[0226] Composite sheet according to any one of <1> to < 11>, in which

[0227] the composite sheet has a Gurley air permeability of the composite sheet of 0 s / 100 mL or more and 10 s / 100 mL or less, preferably 5 s / 100 mL or less, more preferably 0.5 s / 100 mL or less.

[0228] <13>

[0229] Composite sheet according to any one of <1> has <12> , in which

[0230] the composite sheet has a content ratio of the metal-organic network to a mass of the entire composite sheet of 80 mass% or more and 99 mass% or less, preferably 85 mass% or more.

[0231] <14>

[0232] Composite sheet according to any one of <1> has <13> , in which

[0233] the composite sheet has a fiber forming the central region in the thickness direction of the composite sheet, and

[0234] the fiber forming the central region has a surface coverage by the metalloorganic network of 60% or more and 100% or less, preferably 70% or more, and more preferably 80% or more.

[0235] <15>

[0236] Composite sheet according to any one of <1> has <14> , in which

[0237] the composite sheet has a metal-organic network surface exposure ratio of 50% or more and 100% or less, preferably 70% or more, and more preferably 90% or more.

[0238] <16>

[0239] Composite sheet according to any one of <1> has <15> , in which

[0240] the fiber has a layer of the metalloorganic network formed on a surface of the fiber.

[0241] <17>

[0242] Composite sheet according to <16> , in which

[0243] the metal-organic network layer is a film of the metal-organic network covering the surface of the fiber in the form of a unified film.

[0244] <18>

[0245] Composite sheet according to any one of <1> has <17> , in which

[0246] the metalloorganic network is capable of selectively adsorbing carbon dioxide.

[0247] <19>

[0248] Composite sheet according to any one of <1> has <18> , in which

[0249] the composite sheet does not include a binder.

[0250] <20>

[0251] Composite sheet according to any one of <1> has <19> , in which

[0252] the sheet base material is a nonwoven.

[0253] <21>

[0254] Composite sheet according to any one of <1> has <20> , in which

[0255] a shape of the fiber is preserved in the core.

[0256] <22>

[0257] A method of producing a composite sheet in which a metal-organic network is supported in a sheet base material formed of a fiber including a core-sheath fiber, comprising:

[0258] preparing a first raw material solution and a second raw material solution, wherein

[0259] the first raw material solution includes either a metal ion or an organic ligand which are raw materials of the metal-organic framework, and

[0260] the second raw material solution includes the other;

[0261] impregnating the sheet base material with the first raw material solution;

[0262] impregnating the sheet base material with the second raw material solution before the first raw material solution with which the sheet base material is impregnated dries; and

[0263] applying a heat treatment to the sheet base material impregnated with the second raw material solution.

[0264] <23>

[0265] Method for producing a composite sheet according to <22> , in which

[0266] one of the first raw material solution and the second raw material solution includes water at 30% by mass or more and 99% by mass or less, and the other includes an organic solvent at 30% by mass or more and 99% by mass or less.

[0267] <24>

[0268] Method for producing a composite sheet according to <22> Or <23> , in which

[0269] the first raw material solution includes the metal ion and the second raw material solution includes the organic ligand.

[0270] <25>

[0271] Method for producing a composite sheet according to <24> , in which

[0272] a solvent of the first raw material solution includes water and a solvent of the second raw material solution includes an organic solvent.

[0273] <26>

[0274] A method of producing a composite sheet according to any one of <22> has <25> , including:

[0275] drying the sheet base material which has been impregnated with the second raw material solution before the heat treatment.

[0276] <27>

[0277] Method for producing a composite sheet according to <26> , in which

[0278] a total number of performing a series of the following processes before heat treatment is 1 or more and 20 or less, preferably 2 or more, and more preferably 3 or more,

[0279] the sheet base material is impregnated with the first raw material solution,

[0280] the sheet base material is impregnated with the second raw material solution before the first raw material solution with which the sheet base material is impregnated dries, and

[0281] the sheet base material which has been impregnated with the second raw material solution is dried.

[0282] <28>

[0283] A method of producing a composite sheet according to any one of <22> has <27> , in which

[0284] the metalloorganic network is dehydrated by the heat treatment.

[0285] <29>

[0286] A method of producing a composite sheet according to any one of <22> has <28> , in which

[0287] a resin component included in a core of the core-sheath fiber has a melting point higher than a heat treatment temperature, and

[0288] a resin component included in a sheath of the core-sheath fiber has a melting point higher than a drying temperature and lower than the heat treatment temperature.

[0289] <30>

[0290] A composite sheet produced by the method of producing a composite sheet according to any one of <22> has <29> .

[0291] [Examples and Comparative Examples]

[0292] (Examples 1 and 2)

[0293] As examples of the present invention, composite sheet samples were prepared using the above production method.

[0294] As the sheet base material, an air-laid nonwoven fabric (basic weight of 40 g / m2) including a hydrophilic fiber and a hydrophobic fiber in the mass ratio shown in Table 1 was used. In both Examples 1 and 2, chemical softwood pulp (NBKP) which was a cellulose fiber was used as the hydrophilic organic fiber. Furthermore, as the hydrophobic organic fiber, a core-sheath fiber in which a core was formed of polyethylene terephthalate (PET) having a melting point of 260°C and a sheath was formed of polyethylene (PE) having a melting point of 130°C was used. The core-sheath fiber content in the sheet base material was 70% by mass.

[0295] As RMO, ELM-11 capable of selectively adsorbing carbon dioxide was used.

[0296] Table 1 shows the thickness of the composite sheet, the number of times steps S02 to S04 are performed, and the heat treatment temperature in step S05.

[0297] The specific configurations of steps SOI to S05 are as follows.

[0298] In the SOI step, an aqueous solution of Cu(BF4)2 was diluted with deionized water at 0.125 mol / L to prepare a first raw material solution. In addition, bpy was dissolved with 1 mol / L ethanol to prepare a second raw material solution.

[0299] In step S02, 14 g of the first raw material solution was applied to the 100 x 100 mm sheet base material using a dropper.

[0300] In step S03, 2.4 g of the second raw material solution was applied to the sheet base material to which the first raw material solution was applied in step S02 using a dropper before the sheet base material dried.

[0301] In step S04, the sheet base material on which the second raw material solution was applied in step S03 was dried by drawing overnight.

[0302] Steps S02 to S04 were repeated the number of times indicated in Table 1.

[0303] In step S05, after repeating steps S02 to S04 the number of times indicated in Table 1, the sheet was placed in a drying oven for two hours at the heat treatment temperature indicated in Table 1.

[0304] The RMO content ratio, circumferential coverage, surface exposure ratio and gas adsorption amount per unit volume in each sample of the composite sheet were obtained using the above analysis method. The circumferential coverage was obtained for the fiber forming the central region in the thickness direction of the composite sheet. In more detail, the RMO content ratio and gas adsorption amount per unit volume were obtained as follows.

[0305] • RMO content ratio

[0306] The RMO content ratio was calculated based on the mass of the obtained composite sheet and the mass of the base material sheet alone before supporting the RMO using the following formula.

[0307] RMO content ratio (%) = 100 x (mass of composite sheet - mass of base material sheet alone) / mass of sample

[0308] • Quantity of gas adsorption per unit volume

[0309] The composite sheet sample was cut into an arbitrary size. BELSORP-minill (manufacturer MicrotracBEL Corp.) was used to evaluate the gas adsorption amount. Vacuum degassing treatment was carried out at 100 °C for 12 hours as a pretreatment, and then the carbon dioxide adsorption isotherm was measured. The resulting adsorption amount as the carbon dioxide adsorption amount was divided by the amount of the measured composite sheet sample to calculate the gas adsorption amount per unit volume.

[0310] Table 2 shows the analysis results of the composite sheet samples. As shown in Table 2, in both samples of the composite sheets according to Examples 1 and 2, the circumferential coverage was 100%. As a result, both samples had a high RMO content ratio of 80% by mass or more.

[0311] Furthermore, in both samples, the surface exposure ratio of the RMO was 100% and the gas adsorption amount of the RMO per unit volume was also high. Therefore, it was assumed that a decrease in gas adsorption performance of the RMO due to support by the sheet base material was suppressed.

[0312] Furthermore, the shape of any fiber was preserved. It was determined that the RMO was fixed to the cladding by the molten and fixed resin of the cladding into the core-cladding fiber. In addition, a layer of RMO was formed on the surface of the fiber.

[0313] Then, the RMO drop ratio, maximum bending stress, RMO uniformity, workability and Gurley air permeability in each sample were evaluated. For workability, filling property evaluation and RMO retention evaluation were carried out. In more detail, the RMO uniformity and workability were evaluated as follows.

[0314] • Uniformity of the RMO

[0315] The composite sheet sample was cut in the thickness direction to create a cross-sectional observation surface. Then, a microstructure photograph by SEM and an element mapping image by EDX were generated. At this time, respective regions obtained by dividing the composite sheet sample into three in the thickness direction were made to fall into the observation / analysis region. The content of metal which is the main component of RMO was quantified from the obtained element mapping image, and an average value of the contents of metal which is the main component of RMO in the three divided regions and a uniformity evaluation value were calculated by the following formula.

[0316] Uniformity Assessment Value (%) = 100 x (maximum value of the content of the metal which is the main component of the RMO - minimum value of the content of the metal which is the main component of RMO) / average value of the contents of the metal which is the main component of RMO in the three divided regions.

[0317] The numerical value obtained by rounding the uniformity evaluation value obtained above to the nearest 10 was used as the uniformity evaluation result of the RMO. Namely, it can be seen that in the sample of each composite sheet, the smaller the numerical value of the evaluation result, the higher the uniformity of the RMO, and the larger the numerical value of the evaluation result, the lower the uniformity of the RMO.

[0318] “Workability

[0319] As part of the workability assessment, a filling property assessment and an RMO retention assessment were performed.

[0320] Filling property evaluation

[0321] The composite sheet was cut into a width of 5 cm and a length of 10 cm, and the cut sample was wrapped around a cylinder having a diameter of 1.5 mm along the outer periphery of the circumference.

[0322] The stacked state of the obtained rolled sample was determined and the state of the interstices of the stacked composite sheet sample was determined. For the sample of each composite sheet, the maximum value of the interstices was used as the evaluation result of the filling property. In other words, it can be seen that in the sample of each composite sheet, the smaller the value of the evaluation result, the higher the obtained filling property of the rolled sample.

[0323] RMO Retention Assessment

[0324] The mass of the composite sheet was measured before and after the filling property evaluation test, and the RMO retention ratio was calculated by the following formula.

[0325] Retention ratio RMO (%) = 100 x (mass of composite sheet after filling property evaluation test / mass of composite sheet before filling property evaluation test)

[0326] This RMO retention ratio was used as the evaluation result of the RMO retention evaluation. Namely, it can be seen that in the sample of each composite sheet, the larger the value of the evaluation result, the better the state in which the RMO is supported on the fiber surface when processed into a wound sample is maintained.

[0327] As shown in Table 2, in both samples, the falling ratio of RMO was small, i.e., 10 mass% or less, and the maximum bending stress was small, i.e., 0.03 MPa. Therefore, in both samples, preferable evaluation results for workability were obtained, i.e., the gap in the filling property evaluation was less than 2 mm and the RMO retention evaluation was 97% or more. In addition, in both samples, the numerical value of RMO uniformity was 20% or less, and it was found that the RMO was dispersed with high uniformity over the entire sheet base material. In addition, in both samples, the Gurley air permeability was small, i.e., 0.1 s / 100 mL, and it was found that high air permeability could be obtained. It is conceivable that the high air permeability in each sample contributes to the increase in the gas adsorption amount per unit volume.

[0328] In all examples, the gas adsorption amount per unit volume was higher than that in the following Comparative Example 1. This is presumably due to the fact that the RMO was able to exhibit the initial gas adsorption function without being covered by a resin. Furthermore, in all examples, the maximum bending stress was lower, the gap in the filling property evaluation was smaller, and the Gurley air permeability was greater than in the following Comparative Example 1. These are presumably due to the fact that they were not adversely affected by the melting of the resin.

[0329] It was found that in all the Examples, the numerical value of the uniformity of the RMO was smaller and the dispersibility of the RMO was higher than those of the following Comparative Example 2. This is presumably due to the fact that the RMO was uniformly arranged over the entire sheet base material by forming RMO particles on the sheet base material. It is conceivable that as a result, in all the Examples, the circumferential coverage in the central region in the thickness direction of the composite sheet was higher than that of Comparative Example 2.

[0330] In all examples, the gas adsorption amount per unit volume was higher than that of the following Comparative Example 3. This is probably due to the fact that the RMO supported on the fiber surface was able to display the initial gas adsorption function without being covered by a resin.

[0331] Furthermore, in all Examples, the maximum bending stress was lower and the gaps in the filling property evaluation for workability were smaller than those in Comparative Example 3. These are probably due to the fact that they were not adversely affected by resin melting.

[0332] Furthermore, it was found that in all Examples, the numerical value of the uniformity of the RMO was smaller and the dispersibility of the RMO was higher than those of Comparative Example 3. This is presumably due to the fact that the RMO has was uniformly arranged over the entire sheet base material by forming RMO particles on the sheet base material.

[0333] In all examples, the amount of gas adsorption per unit volume was significantly higher than that of Comparative Example 4. This is likely due to the fact that the RMO was able to exhibit the initial gas adsorption function without being covered by a resin.

[0334] Furthermore, it was found that in all Examples, the numerical value of the uniformity of the RMO was smaller and the dispersibility of the RMO was higher than those of Comparative Example 4. This is presumably due to the fact that the RMO was uniformly arranged over the entire sheet base material by forming RMO particles on the sheet base material. It is conceivable that as a result, in all Examples, the circumferential coverage in the central region in the thickness direction of the composite sheet was higher than that of Comparative Example 4.

[0335] (Comparative Examples 1 to 4)

[0336] Composite sheet samples according to the Comparative Examples were prepared under the conditions shown in Table 1. In addition, for each sample, an analysis and evaluation identical to those of Examples 1 and 2 were carried out. Table 2 shows the analysis result and the evaluation result of each sample. Comparative Examples 1 to 4 will be described in detail below.

[0337] “Comparative Example 1

[0338] In Comparative Example 1, an airlaid nonwoven fabric (grammage of 40 g / m2) formed of a polyethylene (PE) fiber was used as the sheet base material. The core-sheath fiber content in the sheet base material was 0% by mass.

[0339] Instead of steps S02 to S04 according to the above embodiment, RMO particles (average particle size of 5 qm) generated beforehand were spread on both surfaces of the sheet base material so that the RMO content ratio of Table 2 was obtained, pressed at room temperature, and then subjected to a heat treatment at 140°C for 2 hours. In the obtained composite sheet, the PE fiber formed only from PE having a low melting point melted by the heat treatment, the fiber shape was not retained, and the molten resin partially covered the RMO.

[0340] “Comparative Example 2

[0341] In Comparative Example 2, a nonwoven fabric identical to that of Example 1 was used as the sheet base material.

[0342] Instead of steps S02 to S04 according to the above embodiment, previously generated RMO particles (average particle size of 5 qm) were spread on both surfaces of the sheet base material so that the RMO content ratio of Table 2 was obtained, pressed at room temperature, and then subjected to heat treatment at 140°C for 2 hours.

[0343] In Comparative Example 2, the shape of the fiber in the composite sheet was retained.

[0344] “Comparative Example 3

[0345] In Comparative Example 3, a nonwoven fabric identical to that of Example 1 was used as the sheet base material.

[0346] Instead of steps S02 to S04 according to the above embodiment, a dispersion liquid of a previously generated RMO was spread on both surfaces of the sheet base material and then subjected to a heat treatment at 140°C for 2 hours. The configuration of the dispersion liquid of the RMO used in Comparative Example 3 is as follows.

[0347] Average particle size of RMO: 5 qm

[0348] Binder: Water-soluble PVA

[0349] RMO / binder ratio: 1 / 1

[0350] Solvent: deionized water

[0351] Dry matter content: 20%

[0352] In the sample of the composite sheet according to Comparative Example 3, the RMO was not supported directly on the surface of the fiber. In all samples of the composite sheets, the surface of the RMO was partially covered by fusion of the core-sheath fiber sheath or contact with the binder.

[0353] “Comparative Example 4

[0354] In Comparative Example 4, a nonwoven fabric identical to that of Example 1 was used as the sheet base material.

[0355] Instead of steps S02 to S04 according to the above embodiment, RMO particles (average particle size of 5 qm) generated beforehand were spread on both surfaces of the sheet base material so that the RMO content ratio of Table 2 was obtained.

[0356] In Comparative Example 4, since no heat treatment was performed, the RMO particles were not fixed by melting the sheath of the core-sheath fiber. In the obtained composite sheet, a large number of RMOs fell off during the processing and sample preparation when measuring the gas adsorption amount per unit volume.

[0357] (Table 1) Example Example Comparison 1 2 1 2 3 4 Fiber Hydrophilic fiber (% by mass) 30 30 0 30 30 30 Hydrophobic fiber (% by mass) 70 70 100 70 70 70 Composite sheet thickness (mm) 1.5 1.5 1.4 1.5 1.5 1.5 Steps S02 to S04 (time) 3 5 - - - - Heat treatment temperature (°C) 140 140 140 140 100 -

[0358] (Table 2) Example Comparative Example 1 2 1 2 3 4 RMO Content Ratio (wt %) 86 90 90 87 48 12 Circumferential Coverage (%) 100 100 - 60 50 10 RMO Surface Exposure Ratio (%) 100 100 - 100 0 100 Gas Adsorption Ratio (mL / cm3) 6.2 9.7 0.3 6.0 0.1 0.2 With or without RMO attached to sheath portion With With Without With Without With RMO Drop Ratio (%) 4 10 16 33 0 97 Maximum Bending Stress (MPa) 0.03 0.03 10 0.03 0.60 0.06 RMO Uniformity (%) 20 10 - 60 70 90 Workability Filling property assessment (mm) Less than 2 Less than 2 5 or more Less than 2 5 or more Less than 2 R MO Retention Rating (%) 99 97 95 85 100 80 Gurley Air Permeability (s / 100 mL) 0.1 0.1 15 0.1 0.3 0.1

Claims

Claims

1. A composite sheet, comprising: a fiber; a sheet base material formed from the fiber; and a metal-organic network dispersed in the sheet base material, the fiber including a core-sheath fiber having a core-sheath structure that includes a core and a sheath, the metal-organic network and the sheath of the core-sheath fiber being bonded by a molten and fixed resin of the sheath, and a surface exposure ratio of the bonded metal-organic network to the sheath of the core-sheath fiber being 50% or more.

2. The composite sheet of claim 1, wherein the composite sheet has a circumferential coverage by the metal-organic network in a cross section orthogonal to a longitudinal direction in at least a portion of the fiber of 80% or more.

3. A composite sheet according to claim 1 or 2, wherein a layer of the metal-organic network is formed on a surface of the fiber.

4. A composite sheet according to claim 3, wherein the metal-organic network layer is a metal-organic network film covering the surface of the fiber as a unified film.

5. A composite sheet according to claim 1 or 2, wherein a content ratio of the metal-organic framework to a mass of the entire composite sheet is 80 mass% or more.

6. A composite sheet according to claim 1 or 2, wherein the composite sheet has a maximum bending stress of 5 MPa or less.

7. A composite sheet according to claim 1 or 2, wherein the composite sheet has a thickness of 0.2 mm or more.

8. The composite sheet of claim 7, wherein the composite sheet has a thickness of 0.5 mm or more.

9. A composite sheet according to claim 1 or 2, wherein the composite sheet has a Gurley air permeability of 10 s / 100 mL or less.

10. A method of producing a composite sheet in which a metal-organic network is supported in a material of sheet base formed from a fiber including a core-sheath fiber, comprising: the preparation of a first raw material solution and a second raw material solution, wherein the first raw material solution includes either a metal ion or an organic ligand which are raw materials of the metal-organic framework, and the second raw material solution includes the other; impregnating the sheet base material with the first raw material solution; impregnating the sheet base material with the second raw material solution before the first raw material solution with which the sheet base material is impregnated dries; and applying heat treatment to the base sheet material impregnated with the second raw material solution.

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