Method for producing composite film

Abstract

Provided is a method for producing a composite film having high adhesion between porous particles and a substrate.　The method for producing a composite film includes a step in which a substrate is coated with a dispersion containing porous particles, wherein the dispersion includes (A) the porous particles, (B) a polymer which is not a cellulosic polymer and serves as a binder, and (C) an oligomer containing OH groups. It is preferable that the dispersion further contains (D) a cellulosic polymer. The porous particles preferably include at least one component selected from the group consisting of porous metal complexes, zeolite, amorphous silica-alumina, porous silica, porous alumina, and activated carbon.　

Description

Method for manufacturing composite membrane

[0001] The present invention relates to a method for producing a composite membrane having a coating layer comprising porous particles.

[0002] By applying a dispersion containing porous particles to a substrate, a composite membrane can be produced in which the substrate is provided with a coating layer containing porous particles. The porous particles have moisture-absorbing properties, and the substrate provided with the layer containing porous particles is used as a moisture absorbent in a dehumidifier or the like.

[0003] Patent Document 1 discloses a film-like composition to be applied to a substrate, which contains a porous organometallic complex MIL-101(Cr) containing chromium as the metal, an acrylic polymer material as an adhesive curing material, and a urethane polymer material as a thickener. Patent Document 1 also discloses that the film-like composition applied to a substrate can be used, for example, as a dehumidifying material for a desiccant dehumidifier.

[0004] Japanese Patent Application Laid-Open No. 2019-171259

[0005] Patent Document 1 discloses a film-like composition obtained by mixing a porous material, which is a main component material and serves as a moisture absorbent or adsorbent, with an adhesive curing agent (binder) in a solvent, and applying the mixture to a substrate and drying it. Patent Document 1 discloses that a desired film-like composition having high moisture absorption and film strength at the same time cannot be achieved unless the film-like composition is constructed by carefully determining the type and composition of the adhesive curing agent that is compatible with the porous material, which is the main component material, and the substrate.

[0006] An object of the present invention is to provide a method for producing a composite membrane that can be applied to various types of porous particles and has high adhesion between the porous particles and the substrate.

[0007] A first aspect of the present invention proposes a method for producing a composite membrane, which includes a step of coating a substrate with a dispersion liquid containing porous particles, the dispersion liquid containing (A) porous particles, (B) a polymer acting as a binder excluding a cellulose-based polymer, and (C) an oligomer having an OH group.

[0008] The present invention can be applied to various types of porous particles, and can provide a method for producing a composite film having high adhesion between the porous particles and the substrate.

[0009] The present invention will now be described based on embodiments, although the present invention is not limited to the embodiments described below.

[0010] An embodiment of the present invention is a method for producing a composite membrane, which includes a step of coating a substrate with a dispersion liquid containing porous particles, the dispersion liquid including (A) porous particles, (B) a polymer that serves as a binder excluding a cellulose-based polymer, and (C) an oligomer that includes an OH group.

[0011] When the dispersion liquid to be coated on the substrate contains (A) porous particles, (B) a polymer that serves as a binder excluding the cellulose-based polymer, and (C) an oligomer that contains an OH group, the adhesion between the coating layer containing the porous particles and the substrate is increased when the dispersion liquid is cured, and a composite film with high flex resistance can be obtained even when a relatively thick coating layer (for example, 100 μm or more) is formed.

[0012] The (A) porous particles contained in the dispersion preferably include at least one selected from the group consisting of porous metal complexes, zeolites, amorphous silica-alumina, porous silica, porous alumina, and activated carbon. As the (A) porous particles, metal-organic frameworks (hereinafter also referred to as "MOFs") can be used, which are porous metal complexes that combine metal ions with bridging organic ligands that link the metal ions to form a crystalline polymer structure with internal pores. Zeolites are porous crystalline aluminosilicates. The (A) porous particles have a large specific surface area and adsorption capacity, and some function as molecular sieves, making them suitable for use in a variety of fields, such as separation membranes, adsorbents, moisture absorbents, and catalysts.

[0013] The average particle size of the (A) porous particles contained in the dispersion is preferably in the range of 0.01 μm to 1,000 μm, more preferably in the range of 0.1 μm to 500 μm, and even more preferably in the range of 0.5 μm to 200 μm. It may be in the range of 0.5 μm to 100 μm, 0.5 μm to 50 μm, or 0.5 μm to 30 μm. When the average particle size of the (A) porous particles contained in the dispersion is in the range of 0.01 μm to 1,000 μm, a composite film having high adhesion between the coating layer and the substrate can be provided without impairing the specific surface area and adsorption capacity of the porous particles. The average particle size of the (A) porous particles can be evaluated, for example, using a laser diffraction particle size distribution analyzer.

[0014] The (B) polymer contained in the dispersion is a polymer other than a cellulose-based polymer, and serves as a binder that binds the (A) porous particles together or between the porous particles and the substrate. The (B) polymer (hereinafter also referred to as "(B) polymer") that serves as a binder other than a cellulose-based polymer is preferably a polymer of a size that does not enter the pores of the porous particles and does not block the pores of the porous particles.

[0015] The (B) polymer contained in the dispersion preferably has a molecular weight greater than that of the (C) OH group-containing oligomer described below, and has a weight-average molecular weight of 5,000 or greater as measured by gel permeation chromatography (GPC) analysis using polystyrene as the standard. In the present specification, "weight-average molecular weight" refers to the weight-average molecular weight measured by GPC analysis using polystyrene as the standard. The weight-average molecular weight can be measured, for example, using a high-speed GPC device (e.g., product name HLC-8220GPC, manufactured by Tosoh Corporation, using a KF-804 column, toluene as an eluent, and a polymer concentration of 0.05%). The weight-average molecular weight of the (B) polymer contained in the dispersion is more preferably in the range of 8,000 to 1,000,000, even more preferably in the range of 10,000 to 500,000, even more preferably in the range of 20,000 to 100,000, and particularly preferably in the range of 25,000 to 80,000. When the weight-average molecular weight is in the range of 8,000 to 1,000,000, it can function as a binder without blocking the pores of the porous particles. The (B) polymer used in the dispersion of the (B) polymer contained in the dispersion may be a commercially available product. When a commercially available product is used, the catalog value may be used as the weight-average molecular weight of the (B) polymer.

[0016] The (B) polymer contained in the dispersion is preferably a thermoplastic resin or a thermosetting resin. For example, as the thermoplastic resin, a silicone resin, an acrylic resin, polyvinyl alcohol, an acetalized polyvinyl alcohol, etc. can be used. As the thermosetting resin, a polyimide, an epoxy resin, a urethane resin, etc. can be used. The (B) polymer is preferably a resin that is compatible with the (C) oligomer containing an OH group, which will be described later. When the (C) oligomer containing an OH group is a silicone oligomer having a siloxane bond in its main chain, the (B) polymer is preferably a silicone resin having a siloxane bond in its main chain.

[0017] The silicone resin may be methylphenyl silicone, methyl silicone, phenyl silicone, etc. The silicone resin may have a weight average molecular weight of, for example, 30,000 or 45,000.

[0018] The acetalized polyvinyl alcohol resin may be an alkylacetalized polyvinyl alcohol, etc. The acetalized polyvinyl alcohol resin may have a weight average molecular weight of, for example, 200,000.

[0019] When the substrate is made of an inorganic material such as glass or metal, the (C) OH group-containing oligomer contained in the dispersion undergoes hydrogen bonding or condensation reaction with the OH groups present on the surface of the substrate, improving the adhesion between the porous particles and the substrate. Furthermore, when the substrate is made of an organic material such as resin, the OH group-containing reactive group contained in the oligomer forms a chemical bond, such as a hydrogen bond, with the reactive group of the resin constituting the substrate, thereby improving the adhesion between the porous particles and the substrate. For example, even when a primer layer made of an organic material such as resin is present on the surface of the substrate, the OH group-containing reactive group contained in the oligomer forms a chemical bond, such as a hydrogen bond, with the reactive group of the resin constituting the primer layer, thereby improving the adhesion between the porous particles and the primer layer. When the dispersion contains the (C) OH group-containing oligomer, the adhesion between the porous particles and the substrate is improved. Furthermore, by filling the gaps formed between the molecular chains of the (B) polymer with the (C) OH group-containing oligomer, the flexibility of the coating layer obtained by curing the dispersion is improved, thereby improving the flexibility of the coating layer.

[0020] The (C) OH group-containing oligomer contained in the dispersion preferably has a weight-average molecular weight of less than 5,000 as measured by GPC analysis using polystyrene as a standard. If the weight-average molecular weight of the (C) OH group-containing oligomer contained in the dispersion is less than 5,000, it can form chemical bonds such as hydrogen bonds with reactive groups present on the surface of the substrate without inhibiting the binder function of the (B) polymer contained in the dispersion, thereby improving the adhesion between the substrate and the coating layer formed by the dispersion. The weight-average molecular weight of the (C) OH group-containing oligomer contained in the dispersion is more preferably in the range of 100 to 4,900, even more preferably in the range of 1,000 to 4,900, and even more preferably in the range of 2,000 to 4,900. The (C) OH group-containing oligomer used in the dispersion may be a commercially available product. When a commercially available product is used, the weight-average molecular weight of the (C) OH group-containing oligomer may be a catalog value.

[0021] The (C)OH group-containing oligomer contained in the dispersion may be a silicone oligomer, (meth)acrylic oligomer, polyvinyl alcohol oligomer, epoxy oligomer, or the like. Silicone oligomers are oligomers having an Si-O bond (siloxane bond) in the molecular chain, such as methylphenyl silicone oligomer. (Meth)acrylic means acrylic or methacrylic. Acrylic oligomers are oligomers having an acryloyl group or methacryloyl group, such as polybasic acid-modified acrylic oligomers. Examples of polyvinyl alcohol oligomers include poval oligomers. Examples of epoxy oligomers include glycerin diglycidyl ether.

[0022] The dispersion may further contain a polymer compound different from the (B) polymer. For example, it may further contain a synthetic resin. When the dispersion further contains a synthetic resin, the dispersion stability of the porous particles is improved, the leveling properties of the dispersion during coating are improved, and the adhesion between the porous particles and the substrate is also improved. It is preferable to use at least one synthetic resin selected from the group consisting of polyvinyl alcohol (PVA) and polyvinylpyrrolidone.

[0023] The dispersion preferably further contains (D) a cellulose-based polymer. The dispersion contains (A) porous particles, (B) a polymer acting as a binder excluding the cellulose-based polymer, and (C) an oligomer containing an OH group, and further contains (D) a cellulose-based polymer, thereby improving the dispersion stability of the porous particles and improving the leveling properties of the dispersion during coating. In addition, the adhesion between the porous particles or between the porous particles and the substrate is also further improved.

[0024] The cellulose-based polymer (D) is preferably a cellulose derivative containing at least one selected from the group consisting of methyl cellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, hydroxypropyl methyl cellulose, carboxymethyl cellulose, ethyl methyl cellulose, and ethyl cellulose.

[0025] The weight-average molecular weight of the (D) cellulose-based polymer contained in the dispersion, as measured by GPC analysis using polystyrene as a standard, is preferably in the range of 10,000 to 1,000,000. When the weight-average molecular weight of the (D) cellulose-based polymer contained in the dispersion is in the range of 10,000 to 1,000,000, the dispersion stability of the porous particles is improved, and the leveling properties of the dispersion are improved. Furthermore, the adhesion between the porous particles or between the porous particles and the substrate can be further improved while maintaining the flexibility of the coating layer after curing. The weight-average molecular weight of the (D) cellulose-based polymer contained in the dispersion is more preferably in the range of 20,000 to 700,000, even more preferably in the range of 25,000 to 400,000, and even more preferably in the range of 30,000 to 250,000. The (D) cellulose-based polymer used in the dispersion may be a commercially available product. When a commercially available product is used, the weight-average molecular weight of the (D) cellulose-based polymer may be a catalog value.

[0026] The dispersion may contain a solvent. Examples of the solvent contained in the dispersion include water or an organic solvent. The water may be deionized water. The organic solvent may be a water-soluble organic solvent. Examples of water-soluble organic solvents include ethanol, 2-propanol, N-methylpyrrolidone, toluene, hexane, ethyl acetate, ethyl methyl ketone, propylene glycol monomethyl ether, and N,N-dimethylformamide.

[0027] When the dispersion contains a solvent, the content of the (A) porous particles contained in the dispersion is preferably in the range of 50.0 mass % or more and 95.0 mass % or less, and may be in the range of 52.0 mass % or more and 92.0 mass % or less, or may be in the range of 55.0 mass % or more and 90.0 mass % or less, when the total amount of the dispersion excluding the solvent is taken as 100 mass %. When the content of the (A) porous particles contained in the dispersion is in the range of 50.0 mass % or more and 95.0 mass % or less, when the total amount of the dispersion excluding the solvent is taken as 100 mass %, the porous particles can be easily dispersed in the dispersion without moisture or carbon dioxide (CO ２A coating layer is obtained by curing a dispersion containing a sufficient amount of porous particles capable of adsorbing and desorbing the (A) porous particles, (B) a polymer, (C) an oligomer having an OH group, and (D) a cellulose-based polymer. In this specification, when the dispersion is composed of a solvent, (A) porous particles, (B) a polymer, (C) an oligomer having an OH group, and (D) a cellulose-based polymer, the total amount of the dispersion excluding the solvent refers to the total amount of the (A) porous particles, (B) a polymer, (C) an oligomer having an OH group, and (D) a cellulose-based polymer, excluding the solvent.

[0028] When the dispersion contains a solvent, the content of the (B) polymer, which serves as a binder excluding the cellulose-based polymer contained in the dispersion, is preferably in the range of 1.0% by mass to 45.0% by mass, or may be in the range of 3.0% by mass to 42.0% by mass, or may be in the range of 5.0% by mass to 40.0% by mass, when the total amount of the dispersion excluding the solvent is taken as 100% by mass. When the (B) polymer, excluding the cellulose-based polymer contained in the dispersion, is contained in the range of 1.0% by mass to 45.0% by mass, when the total amount of the dispersion excluding the solvent is taken as 100% by mass, a coating layer with high flex resistance can be obtained in which the porous particles are in close contact with each other and with the substrate.

[0029] When the dispersion contains a solvent, the content of the (C) OH group-containing oligomer contained in the dispersion is preferably in the range of 0.1% by mass to 20.0% by mass, more preferably in the range of 0.2% by mass to 18.0% by mass, and may be in the range of 0.3% by mass to 16.0% by mass, or may be in the range of 1.0% by mass to 5.0% by mass, when the total amount of the dispersion excluding the solvent is taken as 100% by mass. When the (C) OH group-containing oligomer contained in the dispersion is contained in the range of 0.1% by mass to 20.0% by mass, the adhesion between the porous particles and between the porous particles and the substrate is further improved. As a result, a coating layer with improved flexibility is obtained by curing the dispersion.

[0030] When the dispersion contains a solvent, the content of the cellulose polymer (D) contained in the dispersion is preferably in the range of 0.2% by mass to 30.0% by mass, and may be in the range of 0.5% by mass to 20.0% by mass, or may be in the range of 0.8% by mass to 10.0% by mass, when the total amount of the dispersion excluding the solvent is taken as 100% by mass. When the cellulose polymer (D) contained in the dispersion is contained in the range of 0.2% by mass to 30.0% by mass, when the total amount of the dispersion excluding the solvent is taken as 100% by mass, the dispersion stability of the porous particles and the leveling ability of the dispersion during coating are improved, and the adhesion between the porous particles or between the porous particles and the substrate is further improved. As a result, a coating layer that maintains flexibility after curing is obtained.

[0031] When the dispersion contains a solvent, the content of the solvent contained in the dispersion may be in the range of 20.0% by mass or more and 90.0% by mass or less, 25.0% by mass or more and 90.0% by mass or less, or 30.0% by mass or more and 85.0% by mass or less, when the total amount of the dispersion containing the solvent is taken as 100% by mass. The content of the solvent contained in the dispersion varies depending on the method of coating the substrate with the dispersion. For example, when the dispersion is coated on the substrate using a coating device such as a knife coater that conveys a film-like substrate with a back roll and applies the dispersion to the substrate with a knife, the content of the solvent contained in the dispersion is preferably in the range of 20.0% by mass or more and 90.0% by mass or less, when the total amount of the dispersion containing the solvent is taken as 100% by mass.

[0032] The substrate on which the dispersion is coated is preferably made of a material with a low specific heat. When the substrate is made of a material with a low specific heat, moisture and carbon dioxide (CO ２After adsorption of the hydroxybenzoates, when the adsorbed substance is desorbed by heating, for example, heat loss is reduced, allowing the adsorbed substance to be desorbed efficiently. Examples of materials with low specific heat used for the substrate include metals. The material used for the substrate may be an inorganic substance with low specific heat or a polymer such as a resin. When the material used for the substrate is a metal or an inorganic substance, examples of the metal or inorganic substance include stainless steel, copper, aluminum, magnesium, titanium, aluminum alloys, magnesium alloys, glass, alumina, etc. When the material used for the substrate is a polymer, examples of the polymer include polyimide, polyvinyl chloride, epoxy resin, paper, etc. When the material used for the substrate is a metal, the specific heat is preferably 1.0 kJ / (kg·K) or less, and may be 0.8 kJ / (kg·K) or less, or may be 0.5 kJ / (kg·K) or less. When the material used for the substrate is a polymer, the specific heat is preferably 2.0 kJ / (kg K) or less, and may be 1.5 kJ / (kg K) or less, or may be 1.2 kJ / (kg K) or less. The substrate may be flexible, such as a sheet or a film. The substrate may be mesh-like. In this specification, the terms sheet and film are not distinguished from each other, and the term film may be used to include substrates also called sheets, and the term sheet is used to include substrates also called films.

[0033] The thickness of the substrate is preferably in the range of 10 μm to 300 μm, and may be in the range of 20 μm to 250 μm, or may be in the range of 50 μm to 250 μm. When the thickness of the substrate is in the range of 10 μm to 300 μm, it is easy to handle and the dispersion liquid can be easily coated on the substrate. In addition, the specific surface area of ​​the composite membrane comprising the substrate and the coating layer is increased, and the adsorption ability can be improved, for example, when the composite membrane is used as a catalyst or moisture absorbent.

[0034] In the step of coating a substrate with a dispersion liquid containing porous particles, the substrate may be coated with the dispersion liquid using a device such as a gravure coater, a dip coater, a reverse coater, a wire bar coater, a die coater, a knife coater, a sprayer, or an inkjet. For example, when a knife coater is used, the film-like substrate may be transported on a back roll while the dispersion liquid is evenly spread on the surface of the film-like substrate with a knife. The film-like substrate may be coated with the dispersion liquid while being transported while applying tension in the transport direction.

[0035] The thickness of the dispersion applied to the substrate is preferably in the range of 1 μm to 1,000 μm after curing, and may be in the range of 1 μm to 500 μm. The thickness of the coating layer before curing is preferably in the range of 1 μm to 2,000 μm, and may be in the range of 10 μm to 1,000 μm. After the step of coating the substrate with the dispersion, the dispersion is cured by, for example, heating at 90° C. to 180° C. or drying in a space of 15° C. to 40° C., thereby obtaining a composite film comprising the substrate and the coating layer.

[0036] The method for producing a composite film may include a step of coating the surface of the substrate with a primer layer composition that will serve as a primer layer before the step of coating the substrate with the dispersion. By providing a primer layer between the substrate and the coating layer made of the dispersion, the adhesion between the substrate and the coating layer can be further improved. The primer layer composition preferably contains at least a polymer. Examples of the polymer include resins, preferably epoxy resins, acrylic resins, urethane resins, silicone resins, etc. The primer layer composition may be coated onto the substrate using a device such as a gravure coater, dip coater, reverse coater, wire bar coater, die coater, knife coater, sprayer, or inkjet. The primer layer composition is preferably coated so that the thickness of the resulting primer layer is in the range of 1 μm to 10 μm, and may be coated so that the thickness is in the range of 1 μm to 5 μm. The thickness of the primer layer before curing is preferably in the range of 1 μm to 30 μm, and may be coated so that the thickness is in the range of 1 μm to 15 μm. After the primer composition is coated on the substrate, the primer composition can be heated at a temperature of 90°C or higher and 180°C or lower, or dried and cured at a temperature of 15°C or higher and 40°C or lower, to obtain a primer layer.

[0037] Embodiments of the present invention encompass the following technical concepts: [1] A method for producing a composite membrane, comprising a step of coating a substrate with a dispersion containing porous particles, the dispersion containing (A) porous particles, (B) a polymer acting as a binder other than a cellulose-based polymer, and (C) an oligomer having an OH group. [2] The method for producing a composite membrane according to [1], wherein the dispersion further contains (D) a cellulose-based polymer. [3] The method for producing a composite membrane according to [1] or [2], wherein the dispersion contains a solvent, and the content of the (A) porous particles in the dispersion is within a range of 50.0 mass% to 95.0 mass% based on the total amount of the dispersion excluding the solvent. [4] The method for producing a composite membrane according to any one of [1] to [3], wherein the dispersion contains a solvent, and the content of the (C) oligomer having an OH group in the dispersion is within a range of 0.1 mass% to 20.0 mass% based on the total amount of the dispersion excluding the solvent. [5] The method for producing a composite membrane according to any one of [1] to [4], wherein the porous particles include at least one selected from the group consisting of porous metal complexes, zeolites, amorphous silica-alumina, porous silica, porous alumina, and activated carbon.

[0038] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0039] (A) Porous particles The following porous particles were prepared: Porous particle 1 (MOF-303, average particle diameter 3 μm) Porous particle 2 (CAU-10, average particle diameter 5 μm) Porous particle 3 (3A type zeolite, average particle diameter 1 μm) Porous particle 4 (silica gel, manufactured by Wako Pure Chemical Industries, Ltd., average particle diameter 5 μm) Porous particle 5 (activated carbon, manufactured by Wako Pure Chemical Industries, Ltd., activated carbon, powder, average particle diameter 15 μm)

[0040] (B) Polymers to be Binders Silicone Resin 1 (methylphenyl silicone, weight average molecular weight 30,000) Silicone Resin 2 (methylphenyl silicone, weight average molecular weight 45,000)

[0041] (C) Oligomer containing OH group Silicone oligomer containing OH group (weight average molecular weight less than 5,000)

[0042] (D) Cellulose-based polymers Methyl cellulose (MC) (weight average molecular weight 40,000) Hydroxypropyl cellulose (HPC) (weight average molecular weight 30,000)

[0043] Substrate Stainless steel (SUS-304) plate (thickness 25 μm, 100 μm) (specific heat: 0.5 kJ / (kg.K)) Stainless steel (SUS-304) mesh 325 (thickness 60 μm) (specific heat: 0.5 kJ / (kg.K), plain weave, wire diameter: 0.035 mm, mesh size: 0.043 mm) Polyimide polymer (Kapton) plate (thickness 100 μm) (specific heat: 1.1 kJ / (kg.K)) In Table 1, if the shape such as mesh is not specified, it means a plate.

[0044] Composition for Primer Layer A composition containing 90 parts by mass of a modified epoxy resin (Modelpics 302, manufactured by Arakawa Chemical Industries, Ltd.) and 10 parts by mass of pure water was used as the composition for primer layer.

[0045] Examples 1 to 14: (A) porous particles, (B) polymers (excluding the cellulose-based polymer) as binders, (C) oligomers containing OH groups, and (D) cellulose-based polymers were placed in a container and stirred to produce dispersions according to the formulations shown in Table 1. In Table 1, the amounts of (A) porous particles, (B) polymers, (C) oligomers containing OH groups, and (D) cellulose-based polymers refer to the amounts when the total amount of the dispersion including the solvent is taken as 100% by mass. The amount of solvent refers to the content of the solvent when the total amount of (A) porous particles, (B) polymers, (C) oligomers containing OH groups, (D) cellulose-based polymers, and solvent is taken as 100% by mass. The primer layer composition was applied to the substrate using a knife coater, and the primer layer composition applied to the substrate was heated at 150°C for 1 minute or more to cure and form a primer layer with a thickness of 5 μm. The obtained dispersion was coated onto the substrate shown in Table 1 from above the primer layer using a knife coater so that the coating layer after curing had the thickness shown in Table 1. The dispersion coated onto the substrate was heated at 150°C for 5 minutes or more, thereby adhering to the primer layer through hydrogen bonding or condensation reaction and curing, forming a coating layer of the thickness shown in Table 1, and a composite film comprising the substrate, primer layer, and coating layer was obtained. When "both sides" is listed for the coating surface in Table 1, a primer layer and a coating layer are provided on each of both sides of the substrate. When "one side" is listed for the coating surface in Table 1, a primer layer and a coating layer are provided on only one side.

[0046] Example 15 A composite membrane comprising a substrate, a primer layer, and a coating layer was obtained in the same manner as in Examples 1 to 14, except that a dispersion liquid was used that did not contain (D) a cellulose-based polymer and instead contained polyvinyl alcohol (PVA, manufactured by Nippon Vinyl Acetate & Poval Co., Ltd., weight average molecular weight 30,000) in the formulation shown in Table 1. The weight average molecular weight of PVA was determined by a catalog value measured by GPC analysis using polystyrene as the standard. In Table 1, the symbol "-" indicates that no corresponding item exists, and in Example 15, both the symbol "-" and "(PVA)" were listed for the (D) cellulose-based polymer item.

[0047] Comparative Example 1 A composite film including a substrate, a primer layer, and a coating layer was obtained in the same manner as in Examples 1 to 14, except that the oligomer containing an OH group (C) was not contained. In Table 1, the symbol "-" indicates that the corresponding item does not exist.

[0048] Comparative Example 2 A composite membrane comprising a substrate, a primer layer, and a coating layer was obtained in the same manner as in Examples 1 to 14, except that the polymer (B) acting as a binder other than the cellulose-based polymer was not included. In Table 1, the symbol "-" indicates that the corresponding item does not exist.

[0049] Tape Peeling: To evaluate the adhesion between the substrate and the coating layer, a tape peeling test was performed. Nichiban Cellotape (registered trademark), item 405, width: 15 mm, thickness: 0.05 mm, adhesive strength: 4.73 N / 10 mm, tensile strength: 48.5 N / 10 mm, was cut into a 5 cm piece and weighed on an analytical balance. A 4 cm portion of the cellotape was attached to the center of the composite film, and the remaining 1 cm was pinched with fingers. The cellotape was peeled off within 1 second while pulling so that the angle between the composite film and the tape was 90 degrees. The weight of the peeled cellotape was measured on an analytical balance. The weight change before and after tape peeling is shown in Table 1 as the tape peeling amount.

[0050] Bending Resistance A vinyl chloride pipe with an outer diameter of 7.62 cm and a length of 20 cm was used for the bending resistance test. A composite membrane cut to a size of 25.4 cm wide and 5.08 cm long was wrapped around the pipe so that one side was in contact with the side of the pipe. The composite membrane was wrapped so that the side of the composite membrane followed the circumference of the pipe. When only one side was coated, the composite membrane was wrapped so that the side without the coating layer was in contact with the pipe. After wrapping, the composite membrane was removed from the pipe. Both sides of the composite membrane were then inspected for cracks or peeling. Cracks in the coating layer were judged to be cracks. Peeling was judged to be present when there was a crack in the coating layer or when the coating layer around the crack had a floating portion that was not in contact with the substrate. A rating of 1 was given if the coating layer had no cracks or peeling, a rating of 2 was given if there was cracking, and a rating of 3 was given if there was only peeling or cracking and peeling. The results of the bending resistance test are shown in Table 1.

[0051]

[0052] The composite membranes of Examples 1 to 15 use various types of porous particles. The composite membranes of Examples 1 to 15 have a tape peel weight of 1.5 mg or less after tape peeling, are free of cracks or peeling after a flex resistance test, have high adhesion between the substrate and the coating film, and have high flexibility of the coating layer, resulting in improved flexibility.

[0053] The composite film of Comparative Example 1 did not contain an oligomer containing a (C)OH group, and therefore the adhesion between the substrate and the coating film was lower than that of the composite films of Examples 1 to 15, and the amount of tape peeled off after tape peeling was significantly greater than that of the composite films of Examples 1 to 15. Furthermore, the composite film of Comparative Example 1 also had lower flexibility of the coating layer, and cracks occurred after the bending resistance test, resulting in a bending resistance rating of 2.

[0054] The composite film of Comparative Example 2 did not contain the polymer (B), and therefore had lower adhesion between the substrate and the coating film than the composite films of Examples 1 to 15, and the amount of tape peeled off after tape peeling was greater than the composite films of Examples 1 to 15. Furthermore, the composite film of Comparative Example 2 had lower flexibility of the coating layer, and peeling occurred after the multiple bending test, resulting in a bending resistance rating of 3.

[0055] The composite membrane produced by the production method of the present disclosure can be used for adsorption and separation of gases, ions, moisture, etc., gas separation, filters, reaction fields such as polymer synthesis, various sensors, etc., and can be used in fields such as separation membranes, adsorbents, moisture absorbents, catalysts, etc.

Claims

1. A method for producing a composite membrane, comprising the step of coating a substrate with a dispersion liquid containing porous particles, the dispersion liquid containing (A) porous particles, (B) a polymer acting as a binder excluding a cellulose-based polymer, and (C) an oligomer containing an OH group.

2. The method for producing a composite membrane according to claim 1, wherein the dispersion further comprises (D) a cellulose-based polymer.

3. A method for producing a composite membrane as described in claim 1 or 2, wherein the dispersion contains a solvent, and the content of the (A) porous particles in the dispersion is within the range of 50.0 mass% or more and 95.0 mass% or less with respect to the total amount of the dispersion excluding the solvent.

4. The method for producing a composite membrane according to claim 1 or 2, wherein the dispersion contains a solvent, and the content of the oligomer containing the (C)OH group in the dispersion is within the range of 0.1 mass % or more and 20.0 mass % or less, based on the total amount of the dispersion excluding the solvent.

5. The method for producing a composite membrane according to claim 1 or 2, wherein the porous particles comprise at least one selected from the group consisting of porous metal complexes, zeolites, amorphous silica-alumina, porous silica, porous alumina, and activated carbon.

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