A total heat exchange membrane and a preparation method thereof, and a total heat exchanger

Abstract

The application discloses a total heat exchange film and a preparation method and a total heat exchanger thereof. The total heat exchange film comprises a porous support film and an active layer crosslinked on the surface of the porous support film. The porous support film comprises polybenzimidazole, a high-temperature-resistant polymer and a pore-forming agent. The obtained porous support film has excellent water absorption, high-temperature resistance and high moisture permeability. The active layer comprises chitosan, a crosslinking agent, a hydrophilic polymer and a moisture absorbent. The chitosan has high moisture permeability, mildew resistance and antibacterial property. Through physical crosslinking or chemical crosslinking, the chitosan, the hydrophilic polymer and the porous support film form a three-dimensional network structure, so that the total heat exchange film has excellent gas resistance and washing resistance. The total heat exchange film can be cleaned, and the performance of the film is not affected after cleaning, so that the film can be recycled, cost is saved and the film has more market competitiveness.

Description

Technical Field

[0001] This invention relates to the field of heat exchanger technology, and more specifically to a total heat exchange membrane, its preparation method, and a total heat exchanger. Background Technology

[0002] Total heat exchange membranes are used in the core of fresh air total heat exchange systems to achieve simultaneous exchange of sensible heat and latent heat (water vapor) between fresh air and stale air, while preventing carbon dioxide and VOCs from entering the fresh air side of the stale air. Therefore, total heat exchange membranes are required to have certain porosity, pore size, and membrane thickness, as well as good moisture permeability and gas barrier properties.

[0003] The core frame of a total heat exchanger is generally made of polystyrene plastic, with a melting point of approximately 166℃. However, the melting point of widely used polyolefin porous membrane materials (below 145℃) is lower than this temperature, making it difficult to meet the requirements of automated production, and labor costs drive up the core cost. Therefore, total heat exchange membranes are required to be resistant to high temperatures.

[0004] To extend the service life of the core, internal dust can be removed by washing with water while ensuring that enthalpy efficiency does not decrease. Therefore, the total heat exchange membrane must be washable and have water-resistant properties.

[0005] Fresh air and stale air may carry bacteria, mold, and other microorganisms that adhere to the surface of the core membrane. In humid conditions, these microorganisms multiply rapidly, forming biofilms or mold spots on the paper or polyolefin membrane surface, leading to fresh air pollution, odor generation, and reduced enthalpy efficiency (increased moisture and air resistance). Therefore, total heat exchange membranes are required to have antibacterial and anti-mold functions.

[0006] The main types of total heat exchange membranes on the domestic market are paper membranes and polymer material membranes. Polymer materials are primarily hygroscopic materials such as polyvinyl alcohol, polyacrylic acid, and polyvinylpyrrolidone. However, some polymer materials, such as polyacrylic acid and polyvinylpyrrolidone, are carcinogenic and unsuitable for use as total heat exchange membranes. Furthermore, the water vapor adsorption and diffusion performance (hygroscopicity) of single polymer materials needs further improvement. In recent years, some total heat exchange membranes have enhanced their hygroscopic properties by doping the polymer materials with hygroscopic metal salts, such as lithium chloride, sodium chloride, potassium chloride, and calcium chloride. However, these hygroscopic agents are prone to deliquescence after absorbing moisture, and deliquescent total heat exchange membranes are more likely to become breeding grounds for microorganisms. Regarding membrane antibacterial properties, some patents (such as CN110016814A and CN103877870B) propose adding antibacterial materials during the membrane material preparation process. These antibacterial agents are mainly compounds containing metal ions such as silver, copper, and zinc. However, these antibacterial agents contain heavy metals, which can cause environmental pollution. Since antibacterial agents do not have hygroscopic properties, they reduce the hygroscopicity of the total heat exchange membrane, thereby reducing the latent heat recovery efficiency.

[0007] The information disclosed in this background section is only intended to enhance the understanding of the background technology of this application, and therefore may include prior art that is not known to those skilled in the art. Summary of the Invention

[0008] In view of the problems pointed out in the background art, the purpose of the present invention is to provide a total heat exchange membrane and its preparation method, and a total heat exchanger. The total heat exchange membrane has excellent high moisture permeability, anti-mildew and antibacterial properties, gas barrier properties, and washability.

[0009] To achieve the above-mentioned objectives, the present invention employs the following technical solution: This invention provides a total heat exchange membrane, comprising: a porous support membrane and an active layer, wherein the active layer is cross-linked on the surface of the porous support membrane; the porous support membrane comprises polybenzimidazole, polyamide, and a porogen; the mass fraction of polybenzimidazole is W1, W1≥1%, W1≤10%; the mass fraction of the porogen is W3, W3≥0.1%, W3≤1%; the active layer comprises chitosan, a cross-linking agent, a hydrophilic polymer, and a hygroscopic agent; the mass fraction of chitosan is W4, W4≥0.1%, W4≤3%; the degree of deacetylation of chitosan is T, T>70%; the thickness of the active layer is D2, D2≥0.1 μm, D2≤3 μm.

[0010] In some embodiments of this application, the thickness of the porous support membrane is D1, where D1 ≥ 10 micrometers and D1 ≤ 80 micrometers; and the porosity of the porous support membrane is K, where K ≥ 45% and K ≤ 90%.

[0011] In some embodiments of this application, the mass fraction of polyamide is W2, where W2≥0.5% and W2≤5%.

[0012] In some embodiments of this application, the pore-forming agent includes at least one of polyethylene glycol, lithium chloride, and sodium chloride.

[0013] In some embodiments of this application, the molecular weight of chitosan is M, where M ≥ 100,000 and M ≤ 2,000,000.

[0014] In some embodiments of this application, the mass fraction of the hygroscopic agent is W6, where W6 ≥ 0.1‰ and W6 ≤ 1‰; the hygroscopic agent includes at least one of lithium chloride, anhydrous calcium chloride, zinc chloride, silica gel, and nano-montmorillonite.

[0015] In some embodiments of this application, the crosslinking agent includes at least one of formaldehyde, glyoxal, epichlorohydrin, and genipin.

[0016] In some embodiments of this application, the mass fraction of the hydrophilic polymer is W5, where W5 ≥ 0.1% and W5 ≤ 1%; the hydrophilic polymer includes at least one of polyvinyl alcohol, polyacrylic acid, polyvinylpyrrolidone, polyacrylamide, and polysulfonated betaine methacrylate.

[0017] This application also provides a method for preparing the total heat exchange membrane, the method comprising: (1) Dissolve the polybenzimidazole, the polyamide and the pore-forming agent in an organic solvent to obtain a homogeneous polymer casting solution; (2) The polymer casting solution is degassed to form a liquid film, and the liquid film is then used to form a base film; (3) The base membrane is placed in deionized water to wash away excess organic solvent, and then the pore-forming agent in the base membrane is dissolved and desorbed, and dried to obtain a porous support membrane; (4) Dissolve the chitosan in an aqueous solution containing acetic acid, add the crosslinking agent, the hydrophilic polymer, and the hygroscopic agent, heat and stir until uniformly dissolved to prepare a coating solution; (5) The coating liquid is coated on the surface of the porous support membrane to obtain the total heat exchange membrane.

[0018] This application also provides a total heat exchanger, including the aforementioned total heat exchange membrane.

[0019] Compared with existing technologies, the advantages and positive effects of this invention are as follows: This invention provides a total heat exchange membrane and its preparation method, as well as a total heat exchanger. The total heat exchange membrane of this invention comprises a porous support membrane and an active layer cross-linked on the surface of the porous support membrane. The porous support membrane comprises polybenzimidazole, a high-temperature resistant polymer, and a pore-forming agent, resulting in a porous support membrane with excellent water absorption, high temperature resistance, and high moisture permeability. The active layer comprises chitosan, a cross-linking agent, a hydrophilic polymer, and a hygroscopic agent. Chitosan has high moisture permeability and antifungal and antibacterial properties. Through physical or chemical cross-linking, chitosan, the hydrophilic polymer, and the porous support membrane can form a three-dimensional network structure, giving the total heat exchange membrane excellent gas barrier and water washability. The total heat exchange membrane is washable without affecting its performance, thus allowing for recycling, cost savings, and greater market competitiveness. Detailed Implementation

[0020] The technical solutions in the embodiments of this application will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0021] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0022] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0023] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0024] The following disclosure provides many different embodiments or examples for implementing various structures of the invention. To simplify the disclosure, specific examples of components and arrangements are described below. These are merely examples and are not intended to limit the invention. Furthermore, reference numerals and / or letters may be repeated in different examples; such repetition is for simplification and clarity and does not in itself indicate a relationship between the various embodiments and / or arrangements discussed. In addition, examples of various specific processes and materials are provided in this invention, but those skilled in the art will recognize the application of other processes and / or the use of other materials.

[0025] [Total Heat Exchange Membrane] The total heat exchange membrane of the present invention comprises: a porous support membrane and an active layer, wherein the active layer is cross-linked on the surface of the porous support membrane.

[0026] The porous support membrane comprises polybenzimidazole, a high-temperature resistant polymer, and a pore-forming agent. The resulting porous support membrane exhibits excellent hydrophilicity, thermal stability, mechanical strength, and high moisture permeability.

[0027] The active layer comprises chitosan, a cross-linking agent, a hydrophilic polymer, and a hygroscopic agent. Chitosan possesses high moisture permeability and antifungal and antibacterial properties. Through physical or chemical cross-linking, chitosan, hydrophilic polymers, and a porous support membrane can form a three-dimensional network structure, giving the total heat exchange membrane excellent gas barrier and water wash resistance.

[0028] In summary, the total heat exchange membrane of this application has excellent hydrophilicity, high temperature resistance, high moisture permeability, mildew and antibacterial properties, and water washability. The total heat exchange membrane can be washed without affecting its performance, thus enabling it to be recycled, saving costs and making it more competitive in the market.

[0029] Specifically: Porous support membranes include polybenzimidazole, polyamide, and porogens.

[0030] Polybenzimidazole (PBI) is an aromatic polymer with excellent thermal stability, high mechanical strength, good chemical stability, and excellent flame retardancy, and its benzimidazole backbone has high hydrophilicity. Polyamide (PA) contains hydrophilic amide groups, and intramolecular hydrogen bonding gives it a high melting point and excellent mechanical properties. Using PBI and PA as membrane substrates, microporous thin-film membranes prepared by phase inversion can impart excellent hydrophilicity, thermal stability, and mechanical strength to porous support membranes, as well as excellent flame retardant and self-extinguishing properties.

[0031] If the mass fraction W1 of polybenzimidazole is too low, the mechanical strength and thermal stability of the resulting porous supported membrane will be significantly reduced. Therefore, the mass fraction W1 of polybenzimidazole is made greater than the first parameter value. For example, the first parameter value can be 1% or 2%. A suitable specific parameter should be selected in the specific design, and no specific restriction is made here.

[0032] If the mass fraction W1 of polybenzimidazole is too high, the polybenzimidazole will be difficult to dissolve in the casting solution, resulting in an excessively thick porous support film with low porosity, which is detrimental to heat transfer. Therefore, the mass fraction of polybenzimidazole should be less than the value of the second parameter. For example, the value of the second parameter can be 8% or 10%. A suitable specific parameter should be selected during the design process, and no specific restrictions are imposed here.

[0033] This invention can ensure that the porous support membrane has excellent mechanical strength, thermal stability and hydrophilicity by optimizing the mass fraction W1 of polybenzimidazole, without affecting the permeability of the porous support membrane to organic solvents.

[0034] Preferably, in this invention, the mass fraction W1 of polybenzimidazole can be greater than or equal to 1%, and W1 can be less than or equal to 10%. Within this range, the porous support membrane can be ensured to have excellent mechanical strength, heat transfer performance and hydrophilicity.

[0035] If the mass fraction W2 of polyamide is too low, the mechanical strength and hydrophilicity of the resulting porous support membrane will be significantly reduced. Therefore, the mass fraction W2 of polyamide is made greater than the first parameter value. For example, the first parameter value can be 0.5% or 0.6%. A suitable specific parameter should be selected in the specific design, and no specific restriction is made here.

[0036] If the mass fraction of polyamide, W2, is too high, the polyamide will be difficult to dissolve in the casting solution, resulting in an excessively thick porous support film with low porosity, which is detrimental to heat transfer. Therefore, the mass fraction of polyamide, W2, should be less than the value of the second parameter. For example, the value of the second parameter can be 5% or 4.5%. A suitable specific parameter should be chosen during the design process, and no specific limitation is imposed here.

[0037] This invention can ensure that the porous support membrane has excellent mechanical strength, thermal stability and hydrophilicity by optimizing the mass fraction W2 of polyamide.

[0038] Preferably, in this invention, the mass fraction of polyamide W2 can be greater than or equal to 0.5%, and W2 can be less than or equal to 5%. Within this range, it can be ensured that the porous support membrane has excellent mechanical strength, heat transfer performance and hydrophilicity.

[0039] In other preferred embodiments, polyetherimide, polyimide or polysulfone may be used instead of polyamide, and no specific limitation is made here.

[0040] The porogen used in this application is water-soluble. After the water-soluble porogen is added, it will be deposited in large quantities in the membrane on the side of the plate. Washing the membrane material with boiling water can dissolve the water-soluble porogen from the membrane material, thereby forming a pore structure on the membrane on the side of the plate, resulting in a porous support membrane. This can effectively ensure the porosity of the membrane close to the side of the plate, and ensure the high moisture permeability and low moisture resistance of the porous support membrane.

[0041] If the mass fraction W3 of the porogen is too low, it cannot guarantee the formation of sufficient pore structures on the porous support membrane, resulting in low porosity on the side of the support membrane close to the plate, thus failing to ensure the high moisture permeability and low moisture resistance performance of the porous support membrane. Therefore, the mass fraction W3 of the porogen is greater than the first parameter value. For example, the first parameter value can be 0.1% or 0.15%. A suitable specific parameter should be selected during the specific design process, and no specific limitation is made here.

[0042] If the mass fraction W3 of the porogen is too high, it will lead to excessive porosity on the support membrane, which will significantly reduce the mechanical strength of the support membrane. Therefore, the mass fraction W3 of the porogen should be less than the value of the second parameter. For example, the value of the second parameter can be 1% or 1.5%. A suitable specific parameter should be selected during the specific design, and no specific restriction is made here.

[0043] This invention can optimize the mass fraction W3 of the pore-forming agent to achieve an appropriate porosity in the porous support membrane without reducing its high moisture permeability and low moisture resistance, and without affecting its mechanical strength.

[0044] Preferably, in this invention, the mass fraction W3 of the pore-forming agent can be greater than or equal to 0.1%, and W3 can be less than or equal to 1%. Within this range, the pore-forming agent can make the porosity of the porous support membrane appropriate, without reducing the high moisture permeability and low moisture resistance performance of the porous support membrane, and without affecting the mechanical strength of the porous support membrane.

[0045] If the thickness D1 of the porous support membrane is too low, the mechanical strength of the support membrane will decrease significantly. Therefore, the thickness D1 of the porous support membrane is made greater than the first parameter value. For example, the first parameter value can be 10 micrometers or 9 micrometers. A suitable specific parameter should be selected during the specific design, and no specific restriction is made here.

[0046] If the thickness D1 of the porous support membrane is too high, it will significantly reduce the thermal conductivity and moisture permeability of the membrane. Therefore, the thickness D1 of the porous support membrane is made smaller than the value of the second parameter. For example, the value of the second parameter can be 80 micrometers or 76 micrometers. In specific design, a suitable specific parameter should be selected, and no specific restriction is made here.

[0047] This invention can optimize the thickness D1 of the porous support membrane, thereby enabling the porous support membrane to have excellent thermal conductivity and moisture permeability; on the other hand, it can ensure the strength of the porous support membrane, giving it excellent mechanical strength.

[0048] Preferably, in this invention, the thickness D1 of the porous support membrane can be greater than or equal to 10 micrometers, and D1 can be less than or equal to 80 micrometers. Within this range, on the one hand, the porous support membrane can have excellent thermal conductivity and high moisture permeability; on the other hand, the strength of the porous support membrane can be guaranteed, so that the porous support membrane has excellent mechanical strength.

[0049] If the porosity K of the porous support membrane is too low, it will hinder water vapor transport, leading to a significant decrease in the membrane's thermal conductivity and moisture permeability. Therefore, the porosity K of the porous support membrane should be greater than the first parameter value. For example, the first parameter value can be 45% or 46%. A suitable specific parameter should be chosen during the design process, and no specific limitation is imposed here.

[0050] If the porosity K of the porous support membrane is too high, it will lead to a significant decrease in the mechanical strength of the porous support membrane. Therefore, the porosity K of the porous support membrane should be less than the value of the second parameter. For example, the value of the second parameter can be 90% or 85%. In specific design, a suitable specific parameter should be selected, and no specific restriction is made here.

[0051] This invention can optimize the porosity K of the porous support membrane, thereby enabling the porous support membrane to have excellent thermal conductivity and ensuring its strength, thus giving it excellent mechanical strength.

[0052] Preferably, in this invention, the porosity K of the porous support membrane can be greater than or equal to 45%, and K can be less than or equal to 90%. Within this range, on the one hand, it can facilitate the passage of water vapor through the porous support membrane, giving the porous support membrane excellent thermal conductivity and high moisture permeability; on the other hand, it can ensure the strength of the porous support membrane, giving the porous support membrane excellent mechanical strength.

[0053] The pore-forming agent includes at least one of polyethylene glycol, lithium chloride, and sodium chloride, without any specific limitation.

[0054] In this invention, the porogen may include polyethylene glycol (PEG) and lithium chloride, with a mass ratio of PEG to lithium chloride of 1:1. Both PEG and lithium chloride are readily soluble in water and exhibit excellent water solubility. PEG is an organic porogen, and lithium chloride is an inorganic porogen. By using a combination of organic and inorganic porogens, the porosity K and thickness D1 of the porous support membrane can be effectively adjusted. This ensures that the thickness D1 of the porous support membrane is greater than or equal to 10 micrometers and less than or equal to 80 micrometers, and that the porosity K of the porous support membrane is greater than or equal to 45% and less than or equal to 90%. This ensures that the porous support membrane possesses excellent water absorption, high moisture permeability, high temperature resistance, and flame-retardant self-extinguishing properties.

[0055] If the thickness D2 of the active layer is too low, gases such as carbon dioxide can easily permeate through the membrane material, resulting in low membrane strength and easy damage. Therefore, the thickness D2 of the active layer is made greater than the first parameter value. For example, the first parameter value can be 0.1 micrometers or 0.08 micrometers. A suitable specific parameter should be selected during the specific design, and no specific restriction is made here.

[0056] If the thickness D2 of the active layer is too high, gases such as carbon dioxide will not permeate the membrane material quickly, and the membrane material will not be easily damaged. Therefore, the thickness D2 of the active layer should be less than the value of the second parameter. For example, the value of the second parameter can be 3 micrometers or 2.8 micrometers. In specific design, a suitable specific parameter should be selected, and no specific limitation is made here.

[0057] This invention can optimize the thickness D2 of the active layer to ensure that gases such as carbon dioxide cannot quickly pass through the membrane material while making the active layer as thin as possible.

[0058] Preferably, in this invention, the thickness D2 of the active layer can be greater than or equal to 0.1 micrometers, and D2 can be less than or equal to 3 micrometers. This ensures that gases such as carbon dioxide cannot quickly pass through the membrane material, while improving the gas barrier performance of the total heat exchange membrane and making the active layer as thin as possible.

[0059] Chitosan has strong hygroscopic properties, with a moisture absorption rate exceeding 500%, more than twice that of cellulose. The synergistic effect of chitosan and hydrophilic polymers enables the total heat exchange membrane to possess high moisture permeability and low moisture resistance. Furthermore, the amino groups in the chitosan molecule possess long-lasting antibacterial and antifungal properties, giving the total heat exchange membrane excellent antibacterial and antifungal functions.

[0060] In this embodiment, the hydrophilic polymer can be polyvinyl alcohol (PVA). As a hydrophilic compound, polyvinyl alcohol has multiple hydroxyl groups, which can be chemically crosslinked with chitosan and porous support membrane respectively. Moreover, polyvinyl alcohol (PVA) is insoluble in cold water, which is beneficial to give the heat exchange membrane excellent water-washing resistance.

[0061] In other preferred embodiments, the hydrophilic polymer includes at least one of polyacrylic acid, polyethylene glycol, polyvinylpyrrolidone, polyacrylamide, and polysulfonated betaine methacrylate, without any specific limitation herein.

[0062] The macromolecular chains of chitosan contain hydroxyl and amino groups, the molecular chains of polybenzimidazole (PBI) contain imidazole groups, and the molecular chains of polyamide (PA) contain hydrophilic amide groups. These groups can form intermolecular and intramolecular hydrogen bonds, resulting in a stable physical cross-linked structure. This makes the prepared total heat exchange membrane insoluble in water, organic solvents, and alkaline solutions, improving its washability and ease of cleaning. Furthermore, the addition of the chemical cross-linking agent glutaraldehyde can achieve covalent cross-linking between these groups, such as co-crosslinking of chitosan with chitosan, co-crosslinking of chitosan with polyvinyl alcohol (PVA), and co-crosslinking of chitosan / PVA with a porous support membrane. This forms a stable chemical cross-linked structure, making the prepared total heat exchange membrane insoluble in water, organic solvents, and alkaline solutions. Through physical or chemical cross-linking, chitosan, polyvinyl alcohol (PVA), and porous support membranes can form a three-dimensional network structure, making chitosan and PVA difficult to dissolve in organic solvents, water, and alkaline solutions, thus giving the total heat exchange membrane excellent gas barrier and water wash resistance.

[0063] If the chitosan mass fraction W4 is too low, chitosan cannot fully exert its hygroscopic, antifungal, and antibacterial properties, and it cannot achieve sufficient cross-linking between chitosan and chitosan, between chitosan and polyvinyl alcohol (PVA), or between chitosan / PVA and the porous support membrane, thus failing to form a stable chemical cross-linked structure. Therefore, the chitosan mass fraction W4 should be greater than the first parameter value. For example, the first parameter value can be 0.1% or 0.15%. A suitable specific parameter should be chosen during the design process; no specific limitation is imposed here.

[0064] If the chitosan mass fraction W4 is too high, it will be difficult to stir and mix the chitosan evenly. Therefore, the chitosan mass fraction W4 should be less than the second parameter value. For example, the second parameter value can be 3% or 3.5%. A suitable specific parameter should be chosen during the design process; no specific limitation is made here.

[0065] This invention optimizes the mass fraction W4 of chitosan, allowing it to fully exert its hygroscopic, antifungal, and antibacterial properties, while also ensuring that the chitosan is easy to stir and mix evenly.

[0066] Preferably, in this invention, the mass fraction W4 of chitosan can be greater than or equal to 0.1%, and W4 can be less than or equal to 3%. Within this range, chitosan can fully exert its hygroscopic, antifungal, and antibacterial properties, and chitosan is easy to stir and mix evenly. In addition, it can also ensure sufficient cross-linking of chitosan with chitosan, cross-linking of chitosan with polyvinyl alcohol (PVA), and cross-linking of chitosan / PVA with the porous support membrane, thereby forming a stable chemical cross-linked structure.

[0067] If the degree of deacetylation (T) of chitosan is too low, chitosan cannot provide a high level of amino exposure, resulting in fewer cross-linking groups and hindering stable and effective cross-linking polymerization on the porous support membrane surface. Furthermore, a low degree of deacetylation (T) prevents chitosan from fully utilizing its hygroscopic, antifungal, and antibacterial properties, thus failing to improve the antibacterial and antifungal performance of the total heat exchange membrane. Therefore, the degree of deacetylation (T) of chitosan should be greater than the first parameter value. For example, the first parameter value could be 70% or 65%. A suitable specific parameter should be chosen during the design process, and no specific limitation is imposed here.

[0068] In this invention, the degree of deacetylation T of chitosan can be greater than 70%, which allows chitosan to maintain a high amino exposure level, increases the cross-linking groups of chitosan, and enables the active layer to be stably and effectively cross-linked and polymerized on the surface of the porous support membrane. Furthermore, a degree of deacetylation greater than 70% also allows chitosan to fully exert its hygroscopic, antifungal, and antibacterial properties, thereby improving the antibacterial and antifungal performance of the total heat exchange membrane.

[0069] If the molecular weight M of chitosan is too low, it cannot provide a high level of amino exposure, resulting in fewer cross-linking groups and hindering stable and effective cross-linking polymerization on the porous support membrane surface. Furthermore, a low molecular weight M prevents chitosan from fully utilizing its hygroscopic, antifungal, and antibacterial properties, thus failing to improve the antibacterial and antifungal performance of the total heat exchange membrane. Therefore, the molecular weight M of chitosan is greater than the first parameter value. For example, the first parameter value could be 100,000 or 90,000; a suitable specific parameter should be chosen during the design process, and no specific limitation is imposed here.

[0070] If the molecular weight (M) of chitosan is too high, it will be difficult to stir and mix evenly. Therefore, the molecular weight (M) of chitosan should be less than the value of the second parameter. For example, the value of the second parameter can be 2 million or 1.95 million. A suitable specific parameter should be chosen during the design process; no specific limitation is imposed here.

[0071] This invention optimizes the molecular weight M of chitosan, enabling it to provide a higher amino exposure and increase the cross-linking groups, thus allowing the active layer to stably and effectively cross-link and polymerize on the porous support membrane surface. It also allows chitosan to fully utilize its hygroscopic, antifungal, and antibacterial properties, thereby improving the antibacterial and antifungal performance of the total heat exchange membrane.

[0072] Preferably, in this invention, the molecular weight M of chitosan can be greater than or equal to 100,000, and M can be less than or equal to 2 million. Within this range, chitosan can provide a higher amino exposure, increasing the cross-linking groups of chitosan, so that the active layer can be stably and effectively cross-linked and polymerized on the surface of the porous support membrane. In addition, chitosan can also fully exert its hygroscopic, antifungal, and antibacterial properties to improve the antibacterial and antifungal performance of the total heat exchange membrane.

[0073] If the mass fraction W5 of the hydrophilic polymer is too low, the hydrophilic polymer cannot fully exert its hydrophilic and hygroscopic properties, and cannot provide enough cross-linking groups to ensure sufficient intermolecular and intramolecular hydrogen bonding (physical cross-linking). Therefore, the mass fraction W5 of the hydrophilic polymer should be greater than the first parameter value. For example, the first parameter value can be 0.1% or 0.15%. A suitable specific parameter should be selected during the specific design process, and no specific restriction is made here.

[0074] If the mass fraction W5 of the hydrophilic polymer is too high, it will be difficult to stir and mix evenly. Therefore, the mass fraction W5 of the hydrophilic polymer should be less than the value of the second parameter. For example, the value of the second parameter can be 1% or 0.9%. A suitable specific parameter should be selected during the design process, and no specific limitation is made here.

[0075] This invention optimizes the mass fraction W5 of the hydrophilic polymer, ensuring sufficient cross-linking groups to guarantee adequate intermolecular and intramolecular hydrogen bonding (physical cross-linking). This makes the total heat exchange membrane less soluble in water, organic solvents, and alkaline solutions. Furthermore, it improves the moisture permeability of the total heat exchange membrane.

[0076] Preferably, in this invention, the mass fraction W5 of the hydrophilic polymer can be greater than or equal to 0.1%, and W5 can be less than or equal to 1%. Within this range, the hydrophilic polymer can provide sufficient crosslinking groups to ensure sufficient intermolecular and intramolecular hydrogen bonding (physical crosslinking), making the total heat exchange membrane difficult to dissolve in water, organic solvents, and alkaline solutions. In addition, it can also improve the moisture absorption capacity of the total heat exchange membrane.

[0077] If the mass fraction W6 of the desiccant is too low, the desiccant cannot fully exert its hygroscopic properties. Therefore, the mass fraction W6 of the desiccant should be greater than the first parameter value. For example, the first parameter value can be 0.1‰ or 0.05‰. In specific design, a suitable specific parameter should be selected, and no specific restriction is made here.

[0078] If the mass fraction W6 of the desiccant is too high, it will lead to an increase in the membrane resistance of the active layer. Therefore, the mass fraction W6 of the desiccant should be less than the value of the second parameter. For example, the value of the second parameter can be 1‰ or 0.5‰. In specific design, a suitable specific parameter should be selected, and no specific limitation is made here.

[0079] This invention can optimize the mass fraction W6 of the desiccant to ensure that the desiccant effectively improves the moisture absorption capacity of the total heat exchange membrane and helps reduce the membrane resistance of the active layer.

[0080] Preferably, in this invention, the mass fraction W6 of the desiccant can be greater than or equal to 0.1‰, and W6 can be less than or equal to 1‰. Within this range, the desiccant can effectively improve the moisture absorption capacity of the total heat exchange membrane and help reduce the membrane resistance of the active layer.

[0081] The hygroscopic agent includes at least one of lithium chloride, anhydrous calcium chloride, zinc chloride, silica gel and nano-montmorillonite, without any specific limitation.

[0082] The hygroscopic agent is an auxiliary component, mainly intended to improve moisture absorption capacity. Higher moisture absorption capacity helps reduce the resistance of the dense layer membrane. The active layer is the dense layer, which generally serves as a gas barrier, ensuring that gases such as carbon dioxide cannot quickly pass through the membrane material while keeping the dense layer as thin as possible. The thickness of the dense layer is determined by the concentration of the coating solution.

[0083] Crosslinking agents include at least one of formaldehyde, glyoxal, epichlorohydrin, and genipin, without specific limitations.

[0084] To enhance the antibacterial and antifungal properties of the total heat exchange membrane, antibacterial and antifungal agents can be added to the active layer components, such as chitosan quaternary ammonium salt, 2-pyridinethiol-1-zinc oxide, silver nanoparticles, etc.

[0085] [Preparation method of total heat exchange membrane] The method for preparing the total heat exchange membrane of the present invention includes: (1) Polybenzimidazole, polyamide and pore-forming agent are dissolved in an organic solvent at 80°C to obtain a homogeneous polymer casting solution; The organic solvent can be N,N-dimethylformamide (DMF), which can fully dissolve and mix the polybenzimidazole, high-temperature polymer and porogen.

[0086] The temperature at which polybenzimidazole, polyamide, and porogen dissolve in an organic solvent is T1, where T1 ≥ 70℃ and T1 ≤ 90℃. Within this temperature range, polybenzimidazole, high-temperature resistant polymer, and porogen can be fully dissolved and mixed uniformly.

[0087] (2) After degassing the polymer casting solution, a liquid film is prepared, and the liquid film is then used to prepare a base film; The temperature for preparing the base film is T2, where T2≥50℃ and T2≤80℃. Within this temperature range, the base film can achieve good uniformity, smoothness, and high strength.

[0088] The relative humidity for preparing the base film is S, where S≥50% and S≤95%; within this humidity range, the base film can achieve good uniformity, flatness, and high strength.

[0089] The preparation time for the base film is E, where E≥10min and E≤50min; within this humidity range, the base film can achieve good uniformity, smoothness, and high strength.

[0090] If air bubbles are present in the polymer casting solution, they will affect the uniformity, flatness, and strength of the film. By degassing, air bubbles in the polymer casting solution can be removed, resulting in a base film with good uniformity, flatness, and high strength.

[0091] Degassing methods can include ultrasonic degassing, static degassing, vibration degassing, etc., and no specific restrictions are made here.

[0092] (3) The base membrane is placed in deionized water to wash away excess organic solvent, and then the pore-forming agent in the base membrane is dissolved in boiling water and dried to obtain a porous support membrane. (4) Dissolve chitosan in an aqueous solution containing acetic acid, add crosslinking agent, hydrophilic polymer and hygroscopic agent, heat and stir until dissolved to prepare coating solution; Chitosan contains amino groups and is only soluble in acidic solutions (Ph: 1-2). This invention uses acetic acid solution, which is a weak acid, easily volatilized, and will not remain on the membrane material, thus not affecting the membrane material forming.

[0093] (5) Coating liquid is applied to the surface of porous support membrane to obtain total heat exchange membrane.

[0094] The preparation process of the total heat exchange membrane of the present invention is simple and easy to operate, which can realize the mass production of total heat exchange membrane, save costs, and make it more competitive in the market.

[0095] The total heat exchange membrane of this invention comprises a porous support membrane and an active layer cross-linked on the surface of the porous support membrane. The porous support membrane comprises polybenzimidazole, a high-temperature resistant polymer, and a pore-forming agent, resulting in a porous support membrane with excellent water absorption, high temperature resistance, and high moisture permeability. The active layer comprises chitosan, a cross-linking agent, a hydrophilic polymer, and a hygroscopic agent, enabling the active layer to possess high moisture permeability and antifungal and antibacterial properties. Through physical or chemical cross-linking, chitosan, the hydrophilic polymer, and the porous support membrane can form a three-dimensional network structure, giving the total heat exchange membrane excellent gas barrier and water washability. The total heat exchange membrane is washable without affecting its performance, thus allowing for recycling, cost savings, and enhanced market competitiveness.

[0096] Total heat exchanger The total heat exchanger of the present invention includes the total heat exchange membrane of the present invention, which can be assembled into a total heat exchange element according to known methods and used in a total heat exchanger.

[0097] The total heat exchange membrane of this invention comprises a porous support membrane and an active layer cross-linked on the surface of the porous support membrane. The porous support membrane comprises polybenzimidazole, a high-temperature resistant polymer, and a pore-forming agent, resulting in a porous support membrane with excellent water absorption, high temperature resistance, and high moisture permeability. The active layer comprises chitosan, a cross-linking agent, a hydrophilic polymer, and a hygroscopic agent, enabling the active layer to possess high moisture permeability and antifungal and antibacterial properties. Through physical or chemical cross-linking, chitosan, the hydrophilic polymer, and the porous support membrane can form a three-dimensional network structure, giving the total heat exchange membrane excellent gas barrier and water washability. The total heat exchange membrane is washable without affecting its performance, thus allowing for recycling, cost savings, and enhanced market competitiveness.

[0098] The total heat exchanger of this invention has excellent moisture permeability and harmful gas barrier properties. It can provide fresh air to the room, remove polluted air, and improve indoor air quality, while recovering HVAC energy (simultaneously recovering sensible heat and latent heat). This will effectively promote the national "energy conservation and emission reduction" process and has profound strategic significance and good social benefits. Example

[0099] The preparation method of the total heat exchange membrane in this embodiment includes: (1) Dissolve 5% polybenzimidazole, 1% modified polyamide and 0.5% porogen polyethylene glycol in organic solvent N,N-dimethylformamide (DMF) at 80°C to obtain a homogeneous polymer casting solution; (2) After degassing the polymer casting solution, a liquid film is formed by using a scraper film forming machine. The liquid film is placed in air at a temperature of 60℃ and a relative humidity of 95% for 30 minutes to form a base film. (3) The base membrane is placed in deionized water to wash away excess organic solvent, and then the pore-forming agent in the membrane material is dissolved in boiling water and dried to obtain a porous support membrane. (4) Dissolve 1% chitosan in an aqueous solution containing 0.5% acetic acid, add 5% crosslinking agent glutaraldehyde, 0.5% polyvinyl alcohol, and 0.5‰ hygroscopic agent calcium chloride, heat and stir until dissolved to prepare a coating solution; (5) Coating liquid is applied to the surface of porous support membrane to obtain total heat exchange membrane. Example

[0100] The preparation method of the total heat exchange membrane in this embodiment includes: (1) Dissolve 5% polybenzimidazole, 1% modified polyamide and 0.5% pore-forming agent (polyethylene glycol and lithium chloride in a mass ratio of 1:1) in organic solvent N,N-dimethylformamide (DMF) at 80°C to obtain a homogeneous polymer casting solution. (2) After degassing the polymer casting solution, a liquid film is formed by using a scraper film forming machine. The liquid film is placed in air at a temperature of 60℃ and a relative humidity of 95% for 30 minutes to form a base film. (3) The base membrane is placed in deionized water to wash away excess organic solvent, and then the pore-forming agent in the membrane material is dissolved in boiling water and dried to obtain a porous support membrane. (4) Dissolve 1% chitosan in an aqueous solution containing 0.5% acetic acid, add 5% crosslinking agent glutaraldehyde, 0.5% polyvinyl alcohol, and 0.5‰ hygroscopic agent calcium chloride, heat and stir until dissolved to prepare a coating solution; (5) Coating liquid is applied to the surface of porous support membrane to obtain total heat exchange membrane. Example

[0101] The preparation method of the total heat exchange membrane in this embodiment includes: (1) Dissolve 10% polybenzimidazole, 2% modified polyamide and 0.8% porogen polyethylene glycol in organic solvent N,N-dimethylformamide (DMF) at 80°C to obtain a homogeneous polymer casting solution; (2) After degassing the polymer casting solution, a liquid film is formed by using a scraper film forming machine. The liquid film is placed in air at a temperature of 60℃ and a relative humidity of 95% for 30 minutes to form a base film. (3) The base membrane is placed in deionized water to wash away excess organic solvent, and then the pore-forming agent in the membrane material is dissolved in boiling water and dried to obtain a porous support membrane. (4) Dissolve 2% chitosan in an aqueous solution containing 0.5% acetic acid, add 5% crosslinking agent glutaraldehyde, 0.5% polyvinyl alcohol, and 0.2‰ hygroscopic agent calcium chloride, heat and stir until dissolved to prepare a coating solution; (5) Coating liquid is applied to the surface of porous support membrane to obtain total heat exchange membrane.

[0102] The preparation method of the total heat exchange membrane in this embodiment includes: (1) Dissolve 5% polybenzimidazole, 1% modified polyamide and 0.5% porogen polyethylene glycol in organic solvent N,N-dimethylformamide (DMF) at 80°C to obtain a homogeneous polymer casting solution; (2) The polymer casting solution was poured onto cellulose paper and allowed to stand to obtain a porous support membrane. (3) Dissolve 1% chitosan in an aqueous solution containing 0.5% acetic acid, add 5% crosslinking agent glutaraldehyde, 0.5% polyvinyl alcohol, and 0.5‰ hygroscopic agent calcium chloride, heat and stir until dissolved to prepare a coating solution; (4) Coating liquid is applied to the surface of porous support membrane to obtain total heat exchange membrane.

[0103] The performance of the total heat exchange membranes obtained in Examples 1-3 and Comparative Example 1 was tested, and the results are shown in Table 1.

[0104]

[0105] The results show that, compared with the membrane of Comparative Example 1, the total heat exchange membrane of the present invention significantly increases water vapor permeability and significantly reduces carbon dioxide permeability. Therefore, the total heat exchange membrane of the present invention possesses excellent moisture permeability and harmful gas barrier properties, providing fresh air to the room, removing polluted air, and improving indoor air quality while recovering HVAC energy (simultaneously recovering sensible and latent heat). This contributes to energy conservation and emission reduction in building HVAC systems, effectively promoting the national "energy conservation and emission reduction" process, and has profound strategic significance and good social benefits.

[0106] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0107] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A total heat exchange membrane, characterized in that, The total heat exchange membrane includes: A porous support membrane and an active layer, wherein the active layer is cross-linked on the surface of the porous support membrane; The porous support membrane is prepared by a polymer casting solution, which includes polybenzimidazole, polyamide, and a pore-forming agent. The mass fraction of polybenzimidazole is W1, where W1 ≥ 1% and W1 ≤ 10%. The mass fraction of the pore-forming agent is W3, where W3 ≥ 0.1% and W3 ≤ 1%. The active layer is prepared by a coating liquid, which includes chitosan, a crosslinking agent, a hydrophilic polymer, and a hygroscopic agent. The mass fraction of chitosan is W4, where W4 ≥ 0.1% and W4 ≤ 3%. The thickness of the active layer is D2, where D2 ≥ 0.1 micrometers and D2 ≤ 3 micrometers.

2. The total heat exchange membrane according to claim 1, characterized in that, The thickness of the porous support membrane is D1, where D1 ≥ 10 micrometers and D1 ≤ 80 micrometers; The porosity of the porous support membrane is K, where K≥45% and K≤90%.

3. The total heat exchange membrane according to claim 1, characterized in that, The mass fraction of polyamide is W2, where W2 ≥ 0.5% and W2 ≤ 5%.

4. The total heat exchange membrane according to claim 1, characterized in that, The pore-forming agent includes at least one of polyethylene glycol, lithium chloride, and sodium chloride.

5. The total heat exchange membrane according to claim 1, characterized in that, The degree of deacetylation of chitosan is T, where T > 70%; The molecular weight of chitosan is M, where M≥100,000 and M≤2,000,000.

6. The total heat exchange membrane according to claim 1, characterized in that, The mass fraction of the desiccant is W6, where W6 ≥ 0.1‰ and W6 ≤ 1‰; The hygroscopic agent includes at least one of lithium chloride, anhydrous calcium chloride, zinc chloride, silica gel, and nano-montmorillonite.

7. The total heat exchange membrane according to claim 1, characterized in that, The crosslinking agent includes at least one of formaldehyde, glyoxal, epichlorohydrin, and genipin.

8. The total heat exchange membrane according to claim 1, characterized in that, The mass fraction of the hydrophilic polymer is W5, where W5 ≥ 0.1% and W5 ≤ 1%. The hydrophilic polymer includes at least one of polyvinyl alcohol, polyacrylic acid, polyvinylpyrrolidone, polyacrylamide, and polysulfonated betaine methacrylate.

9. The method for preparing the total heat exchange membrane according to any one of claims 1-8, characterized in that, The method for preparing the total heat exchange membrane includes: (1) Dissolve the polybenzimidazole, the polyamide and the pore-forming agent in an organic solvent to obtain a homogeneous polymer casting solution; (2) The polymer casting solution is degassed to form a liquid film, and the liquid film is then used to form a base film; (3) The base membrane is placed in deionized water to wash away excess organic solvent, and then the pore-forming agent in the base membrane is dissolved and desorbed, and dried to obtain a porous support membrane; (4) Dissolve the chitosan in an aqueous solution containing acetic acid, add the crosslinking agent, the hydrophilic polymer, and the hygroscopic agent, and heat and stir until uniformly dissolved to prepare a coating solution; (5) The coating liquid is coated on the surface of the porous support membrane to obtain the total heat exchange membrane.

10. A total heat exchanger, characterized in that, Includes the total heat exchange membrane according to any one of claims 1-8.

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