Composite membranes, methods for preparing same and uses

Abstract

This application discloses a composite membrane, its preparation method, and use. The composite membrane includes a porous layer and a non-porous dense layer disposed on one side of the porous layer. The non-porous dense layer includes a polymer mixture and a nanomaterial. The polymer mixture includes a first polymer and a second polymer, the first polymer including a hydrophilic polymer, and the second polymer including an amphiphilic polymer. The composite membrane of this application has excellent moisture permeability, gas barrier properties, and water resistance, and can be used as a heat exchange membrane. It can be assembled into a total heat exchange element by conventional methods and used in a total heat exchanger.

Description

[Technical Field]

[0001] The examples of the present application are in the field of heat exchange membranes, for example, composite membranes, their preparation methods and uses. [Background technology]

[0002] As energy conservation and emission reduction concepts become more prevalent, industrial operations today require outdoor air intake systems to recover residual heat from indoor air. Heat exchange membrane materials are used in outdoor air exchange systems. These membranes separate the incoming fresh outdoor air from the exhaust indoor air. They must have excellent gas barrier and moisture permeability, i.e., they must be able to effectively block carbon dioxide while allowing water vapor to pass through. They must also achieve relatively high latent heat exchange through water vapor mass transfer. The heat exchange efficiency of a heat exchange membrane depends primarily on latent heat exchange, i.e., the mass transfer of water vapor molecules. Water vapor mass transfer is similar to the dissolution-diffusion-adsorption process in gas heat exchange membrane structures, and the rate of mass transfer significantly determines the latent heat exchange efficiency of the heat exchange membrane. Achieving high water vapor selectivity through a heat exchange membrane is a challenging task in improving latent heat exchange efficiency.

[0003] Conventional heat exchange membrane materials are metal membranes, paper membranes, or polymer membranes. Metal membranes cannot transmit or accumulate water vapor, and only sensible heat exchange occurs, resulting in low latent heat exchange efficiency. Paper membrane materials have weaker sensible heat exchange than metal membrane pieces, and moisture accumulation makes them susceptible to mold deterioration and bacterial growth. Polymer membranes have relatively high selective water vapor permeability, high latent heat exchange efficiency, and are less susceptible to mold deterioration and bacterial growth, making them advantageous for use as total heat exchange membranes.

[0004] However, considering a relatively long service life and high heat exchange efficiency, heat exchange membrane materials are required to have good water resistance and moisture permeability.Since related heat exchange membranes often have a hydrophilic polymer as the main structure of the membrane, improvements in water resistance and structural stability are required.

[0005] Therefore, it is important to develop a composite membrane that has excellent moisture permeability, gas barrier properties, and water resistance. Summary of the Invention

[0006] The invention of the present application is briefly described below, but is not intended to limit the scope of the claims.

[0007] As used herein, the term "and / or" refers to a relationship between related objects and represents a three-way relationship, such as A and / or B, where only A is present, both A and B are present, or only B is present.

[0008] The examples of the present application provide a composite membrane, its preparation method, and use thereof. The composite membrane has excellent moisture permeability, gas barrier properties, and water resistance, and can be used as a heat exchange membrane in a total heat exchanger by assembling it into a total heat exchange element by a conventional method.

[0009] In a first aspect, an embodiment of the present application provides a composite membrane, the composite membrane including a porous layer and a non-porous dense layer disposed on one side of the porous layer, the non-porous dense layer comprises a polymer mixture and a nanomaterial; the polymer mixture includes a first polymer and a second polymer; the first polymer comprises a hydrophilic polymer; The second polymer comprises an amphiphilic polymer.

[0010] In the present application, the porous layer serves as a support layer to provide the composite membrane with relatively good transmembrane pressure resistance, and the non-porous dense layer corresponds to the organic-inorganic hybrid separation membrane, and specifically, the first polymer and the second polymer are the main materials of the non-porous dense layer.

[0011] The first polymer forms a non-porous dense layer through entanglement between chain segments, van der Waals forces, and hydrogen bonding, resulting in relatively excellent gas barrier properties. Gas molecules reach the surface of the dense layer through random collisions, and the hydrophilic polymer chain segment structure interacts and bonds with water vapor molecules due to its hydrophilic nature. This allows water molecules to rapidly adsorb and dissolve on the surface of the dense layer, continuously accumulating to relatively high concentrations. Gas molecules such as carbon dioxide (CO2) are prevented from adsorbing and dissolving by the hydrophilic polymer and are therefore retained outside the dense layer, thereby achieving highly selective separation of water vapor and gas molecules such as CO2. Furthermore, polymer chain segments may not be perfectly folded in an orderly fashion, resulting in atomic-dimensional defects and irregular stacking, resulting in voids. The unoccupied free volume between these polymer chains allows water molecules accumulating on the surface of the non-porous dense layer to reach the other side of the non-porous dense layer by Fickian diffusion driven by concentration differences, thereby enabling latent heat exchange.

[0012] Self-assembly occurs between the second polymer and the nanomaterial. The hydrophobic chain segments of the second polymer interact relatively strongly with the nanomaterial through intermolecular forces such as hydrogen bonding, van der Waals forces, and hydrophobic-hydrophobic interactions, entangling themselves with the nanomaterial's surface. The polymer chains then adsorb to the nanomaterial's surface, forming a non-covalently crosslinked network between the amphiphilic polymers, with the nanomaterial as a "contact point." The hydrophilic chain segments ensure stable dispersion of the amphiphilic polymer in the hydrophilic membrane layer, primarily composed of the first polymer, contributing to the maintenance of a stable membrane layer structure. Furthermore, the crosslinking action improves the tacticity of the polymer chains in the polymer network and the gas barrier properties of the membrane layer.

[0013] Therefore, the composite membrane of the present application has high selective gas blocking properties and high moisture permeability, as well as water resistance, good antibacterial and antifungal properties, and a long service life.

[0014] Preferably, the porous layer is not a nonwoven fabric.

[0015] Preferably, the porous layer comprises: A. The thickness of the porous layer is 5 μm to 50 μm; B. The porosity of the porous layer is 30% to 60%; C. The pore size of the porous layer is 10 nm to 70 nm; D. The stretching strength of the porous layer is 1300 kgf / cm 2 That is all, E. The puncture strength of the porous layer is 300 gf or more; Satisfy one or more of the characteristics A to E.

[0016] The thickness of the porous layer is 5 μm to 50 μm, for example, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, and the like.

[0017] The porosity of the porous layer is 30% to 60%, for example, 35%, 40%, 45%, 50%, 55% and the like.

[0018] The pore size of the porous layer is 10 nm to 70 nm, for example, 20 nm, 30 nm, 40 nm, 50 nm, or 60 nm.

[0019] In the present application, the pore size of the porous layer is not particularly limited, but is preferably within the range of 10 nm to 70 nm, because if the porosity is too high, the transmembrane pressure resistance of the microporous separator decreases, and if the porosity is too low, the effective mass transfer area decreases, which is disadvantageous in improving latent heat exchange efficiency.

[0020] In the present application, the uniformly distributed pore size and appropriate porosity can effectively improve the latent heat efficiency of the composite membrane when used in a total heat exchanger.

[0021] The stretching strength of the porous layer is 1300 kgf / cm 2 For example, 1400 kgf / cm 2 , 1500kgf / cm 2 , 1600kgf / cm 2, 1700kgf / cm 2 And so on.

[0022] The puncture strength of the porous layer is 300 gf or more, for example, 350 gf, 400 gf, 450 gf, or 500 gf.

[0023] In the present application, relatively high stretching strength and puncture strength can ensure good transmembrane pressure resistance of the composite membrane, especially when the composite membrane has an asymmetric structure.

[0024] Preferably, the material of the porous layer comprises a thermoplastic resin.

[0025] Preferably, the thermoplastic resin comprises any one or a combination of at least two of polyethylene, polypropylene, polyvinylidene fluoride, and polysulfone. Representative, non-limiting combinations include a combination of polyethylene and polypropylene, a combination of polypropylene, polyvinylidene fluoride, and polysulfone, a combination of polyethylene, polypropylene, polyvinylidene fluoride, and polysulfone, etc.

[0026] Preferably, the first polymer comprises groups capable of forming hydrogen bonds with water.

[0027] Preferably, the group is any one or a combination of at least two selected from -OH, -C=O-, -NH2, -CN, -CONH, -CON-, -COC-, and -COOH, for example, a combination of -OH and -C=O-, a combination of -NH2, -CN, -CONH, -CON- and -COC-, a combination of -NH2, -CN, -CONH, -CON-, -COC- and -COOH, etc.

[0028] Preferably, the first polymer comprises one or a combination of at least two of polyvinylpyrrolidone, polyethylene oxide, polyacrylamide, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyhydroxyethyl methacrylate, polymaleic anhydride, chitosan, acetylcellulose, ethylcellulose, carboxymethylcellulose, hydroxypropyl methylcellulose, gelatin, or gum arabic. Exemplary, non-limiting combinations include a combination of polyvinylpyrrolidone and polyethylene oxide, a combination of polyacrylamide, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, and polyhydroxyethyl methacrylate, and a combination of ethylcellulose, carboxymethylcellulose, hydroxypropyl methylcellulose, gelatin, and gum arabic.

[0029] Preferably, the molecular weight of the first polymer is 20 kDa to 1000 kDa, for example, 50 kDa, 100 kDa, 200 kDa, 400 kDa, 600 kDa, 800 kDa, and the like.

[0030] In the present application, the molecular weight of the first polymer is preferably within the range of 20 kDa to 1,000 kDa. If the molecular weight is less than 20 kDa, the film-forming ability of the first polymer is relatively poor, the gas barrier properties of the non-porous dense layer are poor, and efficient separation of H2O molecules from other gas molecules cannot be achieved. If the molecular weight is more than 1,000 kDa, the first polymer is difficult to dissolve in a solvent, and the non-porous dense layer has poor water resistance and an unstable structure.

[0031] Preferably, the second polymer comprises any one or a combination of at least two of polyethylene glycol-b-polycaprolactone copolymer, polyethylene glycol-b-polylactic acid copolymer, hydrophobically modified hydroxypropyl methylcellulose, or polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer. Exemplary, non-limiting combinations include a combination of polyethylene glycol-b-polycaprolactone copolymer and polyethylene glycol-b-polylactic acid copolymer, a combination of polyethylene glycol-b-polylactic acid copolymer, hydrophobically modified hydroxypropyl methylcellulose and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, a combination of polyethylene glycol-b-polycaprolactone copolymer, polyethylene glycol-b-polylactic acid copolymer, hydrophobically modified hydroxypropyl methylcellulose and polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer, and the like.

[0032] Preferably, in the second polymer, the molecular weight ratio of the hydrophilic chain segment to the hydrophobic chain segment is 1:(0.2 to 5), where 0.2 to 5 can be 0.5, 1, 2, 3, 4, and the like.

[0033] In the present application, the molecular weight ratio of the hydrophilic chain segment to the hydrophobic chain segment in the second polymer is preferably within the range of 1:(0.2 to 5). This is because, when the molecular weight ratio of the hydrophilic chain segment to the hydrophobic chain segment exceeds 1:0.2, the interaction due to self-assembly of the second polymer and the nanomaterial is relatively weak, the structural stability of the formed non-covalent crosslinked network is relatively poor, and the structural stability of the non-porous dense layer is reduced. When the molecular weight ratio of the hydrophilic chain segment to the hydrophobic chain segment is less than 1:5, the second polymer has relatively strong chain hydrophobicity and poor compatibility with the first polymer, resulting in reduced gas barrier properties of the non-porous dense layer.

[0034] Preferably, the mass ratio of the first polymer to the second polymer is (2-20):1, where 2-20 can be 4, 6, 8, 10, 12, 14, 16, 18, and the like.

[0035] Preferably, the mass ratio of the nanomaterial to the polymer mixture is 1:(0.5-40), where 0.5-40 can be 1, 5, 10, 15, 20, 25, 30, 35, etc.

[0036] In this application, the mass ratio of the nanomaterial to the polymer mixture is preferably within the range of 1:1 (0.5-40). This is because, when the mass ratio of the nanomaterial to the polymer mixture exceeds 1:0.5 (here, this refers to both ratios, i.e., 2, and other similar expressions), the excess nanomaterial on the surface of the composite membrane increases the gas diffusion paths, improving the membrane's gas barrier performance, but it also has a certain effect on the absorption and diffusion rate of water vapor molecules, reducing the membrane's moisture permeability. When the mass ratio of the nanomaterial to the polymer mixture is less than 1:40, the effective entanglement between the nanomaterial and the second polymer results in a relatively poor stability of the non-covalently crosslinked network, resulting in poor gas barrier properties and tacticity of the composite membrane.

[0037] Preferably, the nanomaterial comprises any one or a combination of at least two of silicon dioxide, aluminum oxide, montmorillonite, barium titanate, titanium(IV) oxide, barium titanate, gold, polystyrene, silver, lithium aluminum titanium phosphate, cellulose, hydroxyapatite, or carbon. Exemplary, non-limiting combinations include combinations of silicon dioxide, aluminum oxide, montmorillonite, barium titanate, and titanium(IV) oxide, combinations of titanium(IV) oxide, barium titanate, gold, polystyrene, silver, lithium aluminum titanium phosphate, and cellulose, combinations of silver, lithium aluminum titanium phosphate, cellulose, hydroxyapatite, and carbon, etc.

[0038] Preferably, the nanomaterial is at least one of granular, flake, wire, rod or tubular.

[0039] Preferably, the particle size or diameter of the nanomaterial is between 5 nm and 500 nm, for example, 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, etc.

[0040] In the present application, the particle size or diameter of the nanomaterial is preferably within the range of 5 nm to 500 nm. If the particle size or diameter of the nanomaterial exceeds 500 nm, the nanomaterial will reduce the tacticity and denseness of the non-porous dense layer structure, which is disadvantageous for achieving high gas barrier performance. If the particle size or diameter of the nanomaterial is less than 5 nm, the non-covalent bond interaction between the nanomaterial and the polymer chain segment will be relatively poor, resulting in poor stability of the formed non-covalent cross-linked structure.

[0041] In this application, the particle size of the nanomaterials refers to non-spherical materials, and the diameter of the nanomaterials refers to spherical materials.

[0042] Preferably, the thickness of the non-porous dense layer is 0.01 μm to 20 μm, for example, 0.05 μm, 0.1 μm, 0.5 μm, 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, etc.

[0043] Preferably, the non-porous dense layer further contains a water-soluble inorganic salt.

[0044] In this application, inorganic salt ions uniformly distributed in the nonporous dense layer can effectively improve the hydrophilicity of the surface of the nonporous dense layer, contribute to bonding with water vapor molecules on the surface, and strengthen the adsorption and dissolution of water molecules on the surface of the nonporous dense layer. Furthermore, the water-soluble inorganic salt destroys the crystalline regions of the hydrophilic polymer within the nonporous dense layer, creating more microscopic voids and free volume, which effectively increases the diffusion and transport rate of water molecules within the nonporous dense layer. Gas molecules are adsorbed and dissolved on the surface of the nonporous dense layer, determining the ratio of gas molecules within the layer to the air through this process. Under the action of the mass transfer driving force, the gas molecules diffuse to the other side within the layer, and then desorb from the adsorption, without significantly affecting mass transfer. In the above process, dissolution and diffusion determine the mass transfer efficiency of the composite membrane. In addition, the metal ions of the water-soluble inorganic salt and the carboxylate ion functional groups of the polymer salt form a crosslinked structure through the complex formation action caused by ionic bonds. Such ionic bonds have a relatively strong action force, and the resulting crosslinked structure is relatively stable, interpenetrating as a crosslinked network, which can effectively improve the structural stability of the non-porous dense layer.

[0045] Preferably, the mass ratio of the water-soluble inorganic salt to the polymer mixture is 1:(0.25-40), and 0.25-40 can be 0.5, 1, 2, 5, 10, 15, 20, 25, 30, 35, or the like.

[0046] In the present application, the mass ratio of the water-soluble inorganic salt to the polymer mixture is preferably within the range of 1:(0.25 to 40). If the mass ratio of the water-soluble inorganic salt to the polymer mixture exceeds 1:0.25, the inorganic salt reduces the density of the separation membrane, thereby reducing the gas barrier performance of the separation membrane. If the mass ratio of the water-soluble inorganic salt to the polymer mixture is less than 1:40, the internal voids and free volume are relatively small, the rate of diffusion and transport of water molecules is significantly reduced, and the structural stability of the crosslinked network formed by the inorganic salt and the polymer salt is poor.

[0047] Preferably, the water-soluble inorganic salt comprises any one or a combination of at least two of magnesium chloride, magnesium sulfate, calcium chloride, calcium nitrate, zinc nitrate, zinc chloride, or zinc sulfate. Exemplary, non-limiting combinations include a combination of magnesium chloride, magnesium sulfate, and calcium chloride, a combination of calcium nitrate, zinc nitrate, zinc chloride, and zinc sulfate, a combination of magnesium chloride, magnesium sulfate, calcium chloride, calcium nitrate, zinc nitrate, zinc chloride, and zinc sulfate, etc.

[0048] Preferably, the polymer mixture further comprises a polymer salt.

[0049] Preferably, the polymeric salt comprises a polymeric salt containing a carboxylate ion.

[0050] Preferably, in the polymer salt, the molar ratio of carboxylate ions to the monomers of the polymer used to form the polymer salt is 1:(1-20), where 1-20 is 2, 4, 6, 8, 10, 12, 14, 16, 18, and the like.

[0051] Preferably, the molecular weight of the polymer salt is between 2 kDa and 200 kDa, for example, 5 kDa, 10 kDa, 20 kDa, 40 kDa, 60 kDa, 80 kDa, 100 kDa, 120 kDa, 140 kDa, 160 kDa, 180 kDa, etc.

[0052] In the present application, the molecular weight of the polymer salt is preferably within the range of 2 kDa to 200 kDa. This is because, when the molecular weight is less than 2 kDa, the cross-linking between the carboxylate ion-functionalized polymer salt and the metal ions of the water-soluble inorganic salt is relatively weak, resulting in a decrease in the water resistance of the nonporous dense layer. When the molecular weight is more than 200 kDa, the cross-linking between the carboxylate ion-functionalized polymer salt and the metal ions of the water-soluble inorganic salt is too strong, resulting in an excessively high viscosity of the three-phase mixture and a decrease in the uniformity and density of the nonporous dense layer.

[0053] Preferably, the polymeric salt comprises a monovalent organic salt.

[0054] In the present application, the polymer mixture contains a carboxylate ion-containing polymer salt, more preferably a monovalent organic salt, and the carboxylate ion group in the monovalent organic salt can form crosslinks between the polymers through ionic bonds with divalent and polyvalent ions. The crosslinking action between the carboxylate ion-functionalized polymer salt and the metal ions of the water-soluble inorganic salt can further improve the structural stability and water resistance of the membrane.

[0055] Preferably, the polymer salt comprises one or a combination of at least two of sodium carboxymethylcellulose, sodium alginate, potassium alginate, lithium carboxymethylcellulose, sodium hyaluronate, sodium polymethacrylate, potassium polyacrylate, or sodium polyacrylate. Exemplary, non-limiting combinations include a combination of sodium carboxymethylcellulose, sodium alginate, and potassium alginate, a combination of potassium alginate, lithium carboxymethylcellulose, sodium hyaluronate, and sodium polymethacrylate, a combination of sodium hyaluronate, sodium polymethacrylate, potassium polyacrylate, and sodium polyacrylate, etc.

[0056] Preferably, the mass ratio of the polymer salt to the first polymer is 1:(2-30), where 2-30 can be 5, 10, 15, 20, 25, or the like.

[0057] In the present application, the mass ratio of the polymer salt to the first polymer is preferably within the range of 1:1 (2 to 30). This is because a mass ratio of the polymer salt to the first polymer exceeding 1:2 affects the density of the separation membrane layer, and a mass ratio of the polymer salt to the first polymer less than 1:30 results in poor structural stability of the interpenetrating crosslinked network, poor water resistance, and a significant shortening of the service life of the composite membrane.

[0058] As described above, conventional heat exchange membranes typically undergo UV crosslinking or chemical crosslinking of the separation membrane layer to improve their water resistance. While this improves the membrane's structural stability, it destroys the tacticity of the separation membrane structure, reducing its gas barrier and moisture permeability. The non-porous dense layer in the composite membrane of the present application forms a triple-interpenetrating network structure, utilizing the van der Waals forces between the polymer chains and the inorganic nanomaterial and the electrostatic interactions between the polymer chains and the inorganic salt metal ions to achieve non-covalent crosslinking, thereby achieving a triple-interpenetrating effect of the polymer network. This improves the structural stability of the non-porous dense layer, i.e., the separation membrane layer, and provides the composite membrane with relatively good water resistance. Furthermore, by adjusting the amount and ratio of the polymer chains and the inorganic salt metal ions, the adsorption, dissolution, and diffusion processes of water vapor molecules in the composite membrane can be controlled, thereby easily and effectively controlling the moisture permeability of the heat exchange membrane and achieving flexible control of the heat exchange efficiency of the composite membrane.

[0059] The non-porous dense layer, i.e., the organic-inorganic hybrid separation membrane, is an organic-inorganic hybrid membrane prepared by a method such as solvent dispersion coating of a three-phase mixture, which has a macroscopically dense structure, an internal nano-channel for water molecules, and a triple-interpenetrating network structure formed by non-covalent crosslinking.

[0060] Preferably, a protective layer is further provided on the outside of the non-porous dense layer.

[0061] Preferably, the protective layer comprises: a. the surface contact angle of the protective layer is greater than 90°; b. The thickness of the protective layer is within the range of 5 μm to 150 μm; c. The pore size of the protective layer is 1 μm to 70 μm; The present invention satisfies one or more of the characteristics a to c.

[0062] The surface contact angle of the protective layer is greater than 90°, such as 95°, 100°, 110°, 120°, and the like.

[0063] In this application, the hydrophobic structure of the protective layer can protect the intermediate non-porous dense layer from the destructive effects of liquid water, such as erosion and swelling, and contribute to maintaining the denseness of the non-porous dense layer structure. If the surface contact angle is less than 90°, the protective layer cannot effectively block liquid water, which is detrimental to protecting the dense structure of the non-porous dense layer.

[0064] The thickness of the protective layer is 5 μm to 150 μm, for example, 10 μm, 20 μm, 40 μm, 60 μm, 80 μm, 100 μm, 120 μm, or 140 μm.

[0065] In the present application, the thickness of the protective layer is preferably within the range of 5 μm to 150 μm, because if the thickness of the nonwoven fabric is less than 5 μm, it is too thin and cannot effectively block liquid water, and if the thickness is more than 150 μm, it is too thick and is disadvantageous to the mass transfer of water vapor on the heat exchange membrane surface.

[0066] The pore size of the protective layer is 1 μm to 70 μm, for example, 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, or 60 μm.

[0067] Preferably, the protective layer comprises a nonwoven fabric.

[0068] Preferably, the nonwoven fabric material comprises one or a combination of at least two of polyolefin, polyester, or cellulose. Representative, non-limiting combinations include a combination of polyolefin and polyester, a combination of polyester and cellulose, a combination of polyolefin, polyester, and cellulose, etc.

[0069] Preferably, the nonwoven fabric comprises one or a combination of at least two of polyethylene terephthalate nonwoven fabric, polypropylene nonwoven fabric, polyethylene nonwoven fabric, or cellulose nonwoven fabric. Representative but non-limiting combinations include a combination of polyethylene terephthalate nonwoven fabric and polypropylene nonwoven fabric, a combination of polypropylene nonwoven fabric, polyethylene nonwoven fabric, and cellulose nonwoven fabric, a combination of polyethylene terephthalate nonwoven fabric, polypropylene nonwoven fabric, polyethylene nonwoven fabric, and cellulose nonwoven fabric, etc.

[0070] In a second aspect, an embodiment of the present application provides a method for preparing a composite membrane according to the first aspect, the method comprising the steps of mixing a first polymer, a second polymer, and a nanomaterial to form a dispersion, applying the dispersion to one or both sides of a porous layer, and drying to form a non-porous dense layer to obtain the composite membrane.

[0071] In the present application, the preparation method involves dispersing raw materials for preparing the non-porous dense layer in a solvent, forming a dispersion having a triply interpenetrating network structure through self-organization, applying the dispersion to one side of the porous layer by a coating method (e.g., doctor coating, roll coating, spray coating, etc.), and drying (e.g., heat drying or drying in the shade) to prepare a membrane, thereby forming a dense organic-inorganic hybrid separation membrane layer, i.e., a dense layer, and thus forming the composite membrane.

[0072] More preferably, the protective layer may be selectively combined with the non-porous dense layer by a common method such as rolling or bonding, and the resulting composite membrane has a three-layer structure of porous layer-non-porous dense layer-protective layer.

[0073] Preferably, the preparation method further comprises providing a protective layer on the outside of the non-porous dense layer.

[0074] Preferably, the method of applying the protective layer to the outside of the non-porous dense layer includes rolling and / or gluing.

[0075] Preferably, the dispersion further comprises a solvent and an auxiliary agent.

[0076] Preferably, the solvent comprises any one or a combination of at least two of water, ethanol, or isopropyl alcohol. Exemplary, non-limiting combinations include a combination of water and ethanol, a combination of ethanol and isopropyl alcohol, a combination of water, ethanol, and isopropyl alcohol, etc.

[0077] Preferably, the auxiliary comprises a wetting agent and / or a binder.

[0078] Preferably, when the total mass of the solvent is expressed as 100%, the mass fraction of the wetting agent is 0.1% to 1%, for example, 0.2%, 0.4%, 0.6%, 0.8%, etc.

[0079] Preferably, the wetting agent comprises an anionic surfactant and / or a non-ionic surfactant.

[0080] Preferably, the wetting agent includes a polyether-modified polysiloxane-based compound and / or an acetylene diol-based compound.

[0081] Preferably, when the total mass of the solvent is expressed as 100%, the mass fraction of the binder is 0.5% to 5%, for example, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, and the like.

[0082] Preferably, the binder comprises one or a combination of at least two of a polyvinyl acetate binder, a polyacrylic acid binder, a polyurethane binder, an epoxy resin binder, a phenolic resin binder, or a silicone binder. Representative, non-limiting combinations include a combination of a polyvinyl acetate binder and a polyacrylic acid binder, a combination of a polyurethane binder, an epoxy resin binder, and a phenolic resin binder, a combination of a polyurethane binder, an epoxy resin binder, a phenolic resin binder, and a silicone binder, etc.

[0083] In a third aspect, embodiments of the present application provide an air exchange device comprising a composite membrane according to the first aspect or a composite membrane prepared by the preparation method according to the second aspect.

[0084] In this application, when the composite membrane is used in an outdoor air exchange device, water vapor can be quickly adsorbed and dissolved in the non-porous dense layer, resulting in a fast transmission and permeation rate, while gases such as carbon dioxide are difficult to adsorb and dissolve in the non-porous dense layer, resulting in a slow permeation rate and difficulty in penetrating the surface of the non-porous dense layer into the composite membrane. Through the above process, the composite membrane achieves high selectivity for separation of water vapor and other gases, effectively blocks the mass transfer of gases other than water molecules, prevents indoor exhaust air from contaminating the introduced fresh air, ensures efficient mass transfer of water vapor, achieves efficient latent heat exchange, and further achieves high heat exchange efficiency of the composite membrane.

[0085] Compared with the related art, the embodiments of the present application have the following beneficial effects:

[0086] (1) The composite membranes according to the examples of the present application have excellent moisture permeability, gas barrier properties, and water resistance, and can be assembled into a total heat exchange element by a conventional method as a heat exchange membrane and used in a total heat exchanger.

[0087] (2) The composite membrane according to the embodiment of the present application has a moisture permeability of 510 to 1620 g / (m 2 24 hours), and the breathability is 14100~37000s / 100mL. In the water resistance test, the change in moisture permeability is I~II grade, and the change in gas barrier is A~C grade.

[0088] Other aspects will become apparent after review of the drawings and detailed description.

[0089] The drawings are a part of this application and are intended to aid in understanding the technical solution of the present application, and are intended to interpret the technical solution of the present application together with the examples of the present application, but are not intended to limit the technical solution of the present application. [Brief explanation of the drawings]

[0090] [Figure 1] 1 is a photograph showing the surface morphology of the non-porous dense layer of the composite membrane according to Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0091] The technical solution of the present application will be further described below using specific embodiments. Those skilled in the art will understand that the examples are only for the purpose of understanding the present application, and are not intended to limit the present application.

[0092] In this application, the acquisition information of some raw materials in each embodiment is as follows:

[0093] Polyethylene separator: purchased from Shenzhen Xingyuan Material Technology Co., Ltd., with a thickness of 20 μm, a porosity of 48%, a pore size of 38 nm, and a stretching strength of 1700 kgf / cm 2 This is the result of testing, and the puncture strength is 700gf.

[0094] Polypropylene separator: purchased from Shenzhen Xingyuan Material Technology Co., Ltd., with a thickness of 16 μm, a porosity of 51%, a pore size of 37 nm, and a stretching strength of 110 kgf / cm 2or more, and the puncture strength is 250 gf or more.

[0095] Examples 1 to 22 and Comparative Examples 1 to 3 Examples 1 to 22 and Comparative Examples 1 to 3 provided composite membranes, each of which includes a porous layer, a non-porous dense layer, and a protective layer stacked in this order. Taking Example 1 as an example, a photograph of its surface appearance is shown in Figure 1.

[0096] Specifically, the information for each layer is as follows:

[0097] Porous layer: Except for Example 14, in which a polypropylene separator was used, a polyethylene separator was used in the other cases.

[0098] Protective layer: A nonwoven fabric made of polyethylene terephthalate.

[0099] Non-porous dense layer: 2 μm thick, specific composition shown in Table 1.

[0100] [Table 1-1]

[0101] [Table 1-2]

[0102] [Table 1-3] In Table 1, the mass fractions of the polymer mixtures are based on the total dispersion, as are the inorganic nanomaterials and salts.

[0103] The composite membrane is prepared by the following preparation method, which includes the following steps:

[0104] The raw materials for preparing the non-porous dense layer were dispersed in water in the above-mentioned amounts to form a dispersion having an interpenetrating network structure through self-organization, the dispersion was applied to one side of the porous layer and dried to obtain a non-porous dense layer, and the protective layer was then combined with the non-porous dense layer by rolling to obtain the composite membrane.

[0105] Performance Test The composite membranes of Examples 1 to 22 and Comparative Examples 1 to 3 were subjected to the following tests.

[0106] (1) Moisture permeability: Tests are conducted in accordance with GB / T 2679.2~2015. If the change in moisture permeability is within ±15%, it is classified as Grade I. If it is outside ±15%, it is classified as Grade II. In terms of moisture permeability, Grade I is superior to Grade II.

[0107] (2) Gas barrier properties: Tested according to GB / T 36363-2018. The gas barrier performance is grade A if the drop is less than 10%, grade B if the drop is 10-25%, and grade C if the drop is more than 25%. The performance ranking is A>B>C.

[0108] (3) Water resistance: After the composite membrane was immersed in water for 30 days, its moisture permeability and gas barrier properties were tested.

[0109] The test results are summarized in Table 2.

[0110] [Table 2-1]

[0111] [Table 2-2] As can be seen from analyzing the data in Table 2, the composite membrane according to the present application has a moisture permeability of 510 to 1620 g / (m 2The composite membrane according to the present application has excellent moisture permeability, gas barrier properties and water resistance, and can be assembled into a total heat exchange element by a conventional method as a heat exchange membrane, and can be used in a total heat exchanger.

[0112] As can be seen from the analysis of Comparative Examples 1 to 3 and Example 1, the performance of Comparative Examples 1 to 3 was inferior to that of Example 1, which proved that the composite membrane according to the present application had better performance.

[0113] As can be seen from the analysis of Examples 15-16 and Example 3, Examples 15-16 were inferior to Example 3, which proved that the performance of the composite membrane formed when the mass ratio of the nanomaterial to the polymer mixture was in a preferred range was better.

[0114] As can be seen from the analysis of Examples 17-18 and Example 3, Examples 17-18 were inferior to Example 3, which proves that the performance of the composite membrane formed when the mass ratio of the water-soluble inorganic salt to the polymer mixture was within a preferred range was better.

[0115] As can be seen from the analysis of Examples 19-20 and Example 3, Examples 19-20 were inferior to Example 3, which proves that the performance of the composite membrane formed when the mass ratio of the first polymer to the second polymer was within a preferred range was better.

[0116] As can be seen from the analysis of Examples 21-22 and Example 3, Examples 21-22 were inferior to Example 3, which proves that the performance of the composite membrane formed when the mass ratio of the polymer salt to the first polymer was in the preferred range was better.

[0117] Although the present application has used the above examples to describe the detailed methods of the present application, it is not limited to the above detailed methods, that is, the implementation of the present application does not necessarily depend on the above detailed methods. As can be understood by those skilled in the art, any improvements made to the present application, equivalent replacement of each material of the product of the present application, addition of auxiliary components, selection of specific methods, etc., also fall within the protection scope and disclosure scope of the present application.

Claims

1. A composite membrane comprising: The composite membrane includes a porous layer and a non-porous dense layer provided on one side of the porous layer, the non-porous dense layer comprises a polymer mixture and a nanomaterial; the polymer mixture comprises a first polymer and a second polymer; the first polymer comprises a hydrophilic polymer; The second polymer comprises an amphiphilic polymer. Composite membrane.

2. The porous layer is not a nonwoven fabric. The composite membrane of claim 1 .

3. The porous layer is A. The thickness of the porous layer is 5 μm to 50 μm; B. The porosity of the porous layer is 30% to 60%; C. The pore size of the porous layer is 10 nm to 70 nm; D. The stretching strength of the porous layer is 1300 kgf / cm ２ That is all, E. The puncture strength of the porous layer is 300 gf or more. Satisfy one or more of the characteristics A to E 3. The composite membrane of claim 1 or 2.

4. the material of the porous layer includes a thermoplastic resin; Preferably, the thermoplastic resin comprises any one or a combination of at least two of polyethylene, polypropylene, polyvinylidene fluoride, or polysulfone. The composite membrane according to any one of claims 1 to 3.

5. the first polymer contains a group capable of forming a hydrogen bond with water; Preferably, the group is -OH, -C=O-, -NH ２ , —CN, —CONH, —CON—, —C—O—C—, or —COOH, Preferably, the first polymer comprises any one or a combination of at least two of polyvinylpyrrolidone, polyethylene oxide, polyacrylamide, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyhydroxyethyl methacrylate, polymaleic anhydride, chitosan, acetyl cellulose, ethyl cellulose, carboxymethyl cellulose, hydroxypropyl methyl cellulose, gelatin, or gum arabic; Preferably, the molecular weight of the first polymer is between 20 kDa and 1000 kDa. The composite membrane according to any one of claims 1 to 4.

6. the second polymer comprises any one or a combination of at least two of polyethylene glycol-b-polycaprolactone copolymer, polyethylene glycol-b-polylactic acid copolymer, hydrophobically modified hydroxypropyl methylcellulose, or polyethylene oxide-polypropylene oxide-polyethylene oxide triblock copolymer; Preferably, in the second polymer, the molecular weight ratio of the hydrophilic chain segment to the hydrophobic chain segment is 1:(0.2 to 5). The composite membrane according to any one of claims 1 to 5.

7. the mass ratio of the first polymer to the second polymer is (2 to 20):1; Preferably, the mass ratio of the nanomaterial to the polymer mixture is 1:(0.5-40); Preferably, the nanomaterial comprises any one or a combination of at least two of silicon dioxide, aluminum oxide, montmorillonite, barium titanate, titanium(IV) oxide, barium titanate, gold, polystyrene, silver, lithium aluminum titanium phosphate, cellulose, hydroxyapatite or carbon; Preferably, the nanomaterial is at least one of granular, flake, wire, rod, or tubular; Preferably, the particle size or diameter of the nanomaterial is between 5 and 500 nm. The composite membrane according to any one of claims 1 to 6.

8. the non-porous dense layer has a thickness of 0.01 to 20 μm; Preferably, the non-porous dense layer further contains a water-soluble inorganic salt, Preferably, the mass ratio of the water-soluble inorganic salt to the polymer mixture is 1:(0.25-40); Preferably, the water-soluble inorganic salt comprises any one or a combination of at least two of magnesium chloride, magnesium sulfate, calcium chloride, calcium nitrate, zinc nitrate, zinc chloride, or zinc sulfate. The composite membrane according to any one of claims 1 to 7.

9. the polymer mixture further comprises a polymer salt; Preferably, the polymeric salt comprises a polymeric salt containing a carboxylate ion; Preferably, in the polymer salt, the molar ratio of carboxylate ions to monomers of the polymer used to form the polymer salt is 1:(1 to 20); Preferably, the molecular weight of the polymeric salt is between 2 and 200 kDa; Preferably, the polymeric salt comprises a monovalent organic salt; Preferably, the polymer salt comprises any one or a combination of at least two of sodium carboxymethylcellulose, sodium alginate, potassium alginate, lithium carboxymethylcellulose, sodium hyaluronate, sodium polymethacrylate, potassium polyacrylate, or sodium polyacrylate; Preferably, the mass ratio of the polymer salt to the first polymer is 1:(2 to 30). The composite membrane according to any one of claims 1 to 8.

10. A protective layer is further provided on the outside of the dense layer, Preferably, the surface contact angle of the protective layer is greater than 90°; Preferably, the thickness of the protective layer is 5 μm to 150 μm; Preferably, the pore size of the protective layer is 1 μm to 70 μm, Preferably, the protective layer comprises a nonwoven fabric, Preferably, the material of the nonwoven fabric comprises any one or a combination of at least two of polyolefin, polyester or cellulose; Preferably, the nonwoven fabric comprises any one or a combination of at least two of polyethylene terephthalate nonwoven fabric, polypropylene nonwoven fabric, polyethylene nonwoven fabric, or cellulose nonwoven fabric. The composite membrane according to any one of claims 1 to 9.

11. A method for preparing the composite membrane according to any one of claims 1 to 10, comprising the steps of: mixing a first polymer, a second polymer, and a nanomaterial to form a dispersion, applying the dispersion to one side of a porous layer, and drying the dispersion to form a non-porous dense layer, thereby obtaining the composite membrane. Method for preparing composite membranes.

12. The preparation method further includes providing a protective layer on the outside of the non-porous dense layer; Preferably, the method of applying the protective layer includes rolling and / or gluing. The preparation method according to claim 11.

13. The dispersion further comprises a solvent and an auxiliary agent; Preferably, the solvent comprises any one or a combination of at least two of water, ethanol, or isopropyl alcohol; Preferably, the auxiliary comprises a wetting agent and / or a binder. The preparation method according to any one of claims 11 to 12.

14. The mass fraction of the wetting agent is 0.1% to 1% when the total mass of the solvent is 100%; Preferably, the wetting agent comprises an anionic surfactant and / or a nonionic surfactant; Preferably, the wetting agent comprises a polyether-modified polysiloxane-based compound and / or an acetylene diol-based compound; Preferably, the mass fraction of the binder is 0.5% to 5% when the total mass of the solvent is expressed as 100%; Preferably, the binder includes any one or a combination of at least two of a polyvinyl acetate binder, a polyacrylic acid binder, a polyurethane binder, an epoxy resin binder, a phenolic resin binder, or a silicone binder.

14. The preparation method according to claim 13.

15. A composite membrane according to any one of claims 1 to 10 or a composite membrane prepared by the preparation method according to any one of claims 11 to 14. Fresh air exchange membrane.

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