A preparation method of a homogeneous anion exchange membrane, the homogeneous anion exchange membrane prepared by the method and applications thereof

Abstract

The application provides a preparation method of a homogeneous anion exchange membrane, the homogeneous anion exchange membrane prepared by the method and application, and relates to the technical field of ion exchange membranes. The preparation method of the homogeneous anion exchange membrane comprises the following steps: mixing a quaternary amine polymer, a crosslinking agent and an organic solvent to obtain a casting solution; coating the casting solution on a support layer to obtain a wet membrane piece; and performing heat treatment on the wet membrane piece by using a gradient heating mode to obtain the homogeneous anion exchange membrane. The preparation method of the homogeneous anion exchange membrane has the advantages of simple operation process, significantly enhanced mechanical strength and stability of the membrane, reduced swelling, and improved overall structural stability of the membrane.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ion exchange membrane, in particular to a preparation method of homogeneous anion exchange membrane, the homogeneous anion exchange membrane prepared by the method and the application. BACKGROUND

[0002] Electrodialysis is a membrane separation technology that can realize desalination, concentration and material separation by the migration of anions and cations in the solution under the action of electric field force. Compared with the traditional membrane separation technology such as reverse osmosis, electrodialysis has strong ion selectivity and extremely low pressure, so it has higher efficiency and economy when dealing with water bodies with high salt content. Ion exchange membranes can be divided into heterogeneous membranes, semi-homogeneous membranes and homogeneous membranes according to their membrane structures. The homogeneous ion exchange membrane has low resistance and excellent electrochemical performance, and as a key component in the electrodialysis system, it has higher structural stability and more consistent performance than non-homogeneous membranes and semi-homogeneous membranes, so it has great application potential. However, the production process of the homogeneous ion exchange membrane is complex, the production cost is high, and it has high technical difficulty, which limits its production and promotion.

[0003] At present, the main method for preparing homogeneous anion exchange membranes that have been commercialized and applied is the base film impregnation method. In this method, a polyolefin base film is impregnated in a styrene-divinylbenzene monomer, an initiator is added, and then the mixture is heated and pressurized to polymerize. After that, the surface of the membrane is functionalized (chloromethylation and quaternary amination) to obtain an anion exchange membrane. Although this method has been widely used, it still has some shortcomings. First, the base film impregnation method involves multiple steps, including impregnation of the base film, polymerization, functionalization and post-treatment, etc. These steps not only increase the production time, but also require strict control of the conditions between each step and complex operation process. Second, due to the limited cross-linking degree of the membrane during polymerization, especially the insufficient tightness of the combination between the base film and the polymer, the mechanical strength of the final anion exchange membrane is low. In the membrane preparation process, the surface functionalization treatment steps such as chloromethylation and quaternary amination require strict control of the conditions, and the reaction efficiency is low, which is easy to cause incomplete functionalization, resulting in uneven hydrophilicity and ion exchange performance of the membrane surface, thereby affecting the overall performance of the membrane.

[0004] CN102179186A discloses a kind of homogeneous anion exchange membrane based on monomer in situ polymerization and its preparation method, the preparation method is: in every 4mL chloromethyl styrene monomer 0.08~0.80mL divinyl benzene is added, then 0.5~2g phenolphthalein base polyether ketone and 0.04~0.20g dibenzoyl peroxide or azobisisobutyronitrile are added, and are uniformly mixed to form casting solution, uniformly coated on reinforcing fabric, heated at 70~130℃ for 6~48h in situ polymerization;The base film obtained is soaked in 10~40% mass fraction triethylamine aqueous solution and quaternary ammonium reaction for 6~48h, washed, dried (placed in air at room temperature and dried naturally), to obtain homogeneous anion exchange membrane.

[0005] CN105903357A discloses a kind of homogeneous anion exchange membrane and its preparation method, which first dissolves high molecular weight reinforcing agent in the mixed solution composed of p-chloromethyl styrene and styrene, then sequentially adds imidazole small molecule with terminal alkenyl and imidazole small molecule without terminal alkenyl, stirs uniformly to obtain quaternary ammonium membrane liquid;Then the membrane liquid is coated on the coating plate, and heated and solidified (dried at 100℃ for 12h), to obtain anion exchange membrane.

[0006] It can be seen that the currently disclosed homogeneous anion exchange membrane at least has the following three problems:

[0007] (1) The membrane preparation method is complex and the conditions are uncontrollable: the preparation method of the currently commercialized homogeneous anion exchange membrane includes multiple steps, first part of the monomer needs to be chloromethylated, then the chloromethylated monomer is polymerized with other monomers, then the polymer is quaternized, and finally post-processing is carried out. This process flow is complex, the reaction conditions are harsh, the production cycle is prolonged, and the operation difficulty is increased. Because of the complex preparation route and high technical difficulty, the production and promotion are limited.

[0008] (2) Poor mechanical strength: the currently commercialized homogeneous anion exchange membrane has low mechanical strength because the material has insufficient crosslinking ability during membrane solidification and the structure is relatively fragile during synthesis and crosslinking, so the membrane is prone to cracking and other situations during long-term use, the performance decreases, and the service life is short.

[0009] (3) The membrane sheet is easy to swell and separate from the support layer: the anion exchange membrane prepared by the traditional method has insufficient adhesion between the coating layer and the support layer, and the material compatibility is poor, so that the combination is not tight enough. Therefore, due to the repeated swelling of the membrane during long-term use, the support layer and the coating layer are prone to separation, which seriously affects the service life of the ion exchange membrane.

[0010] Therefore, the present application is proposed. SUMMARY

[0011] The application aims to provide a preparation method of a homogeneous anion exchange membrane, the homogeneous anion exchange membrane prepared by the preparation method and application.

[0012] In order to achieve the above-mentioned purpose of the application, the following technical solutions are adopted:

[0013] In a first aspect, the application provides a preparation method of a homogeneous anion exchange membrane, which comprises the following steps:

[0014] The quaternary aminated polymer, the crosslinking agent and the organic solvent are mixed to obtain a casting solution;

[0015] The casting solution is coated on a support layer to obtain a wet membrane sheet;

[0016] The wet membrane sheet is subjected to heat treatment by using a gradient heating mode to obtain the homogeneous anion exchange membrane.

[0017] The preparation method of the homogeneous anion exchange membrane of the application directly performs membrane preparation by using a new type of quaternary aminated polymer material, and the membrane is prepared by one-step method, so the process is simple, the operation is convenient, and the preparation conditions are easy to control. The homogeneous anion exchange membrane of the application directly dissolves in an organic solvent to form a casting solution by using the combination of the new type of quaternary aminated polymer material and the crosslinking agent, and the crosslinking density of the membrane is improved by optimizing the heat treatment process, so the toughness and tensile strength of the membrane are enhanced, the mechanical strength of the homogeneous anion exchange membrane is further improved by the increased lining net, the active site distribution of the material selected by the preparation method of the application is uniform, the crosslinking density of the membrane is increased by adding the crosslinking agent, so the structural stability of the membrane is enhanced, the swelling property of the membrane is reduced, the compatibility of the coating solution and the support layer is improved, the heat treatment mode of first gradient heating and then gradient cooling is used to prevent the deformation and cracking of the membrane sheet, so the coating layer and the support layer are less likely to separate.

[0018] More specifically, the preparation method of the application has at least the following two advantages:

[0019] (1) The application adopts a new type of quaternary amine polymer direct membrane preparation method, which saves the traditional process of chloromethylation, polymerization and quaternary ammonium of the material monomer on the production line, reduces the membrane preparation process, and is simple to operate and easy to automate. The preparation of the new type of quaternary amine polymer adopts a quaternary amine method, which avoids the instability of the quaternary amine position in the process of quaternary ammonium treatment, and easily produces chain breaking, branching and side reactions, so that the quaternary amine groups in the polymer are more evenly distributed. The prepared membrane has a more uniform electric field distribution, thereby enhancing the selective transmission ability of ions; uniform distribution of quaternary amine groups reduces the swelling risk of the membrane in water, so that it maintains stable size and shape under wet conditions or working conditions, and improves the service life of the membrane.

[0020] (2) Gradient heat treatment process: a unique gradient temperature rising and falling heat treatment process and time control are adopted, so that the crosslinking and curing of the membrane are more uniform, and the mechanical strength and conductivity of the membrane are significantly improved. If the temperature is too high, the polymer will be degraded or crosslinked too much, which will weaken the activity of the sulfonic acid group, reduce the ion exchange performance, and also cause the deformation of the liner, thereby reducing the product yield. If the temperature is too low, the crosslinking will not be sufficient, and the mechanical properties of the membrane will be insufficient. Therefore, through this gradual heat treatment method, the uniformity of crosslinking is ensured, the formation of internal stress is effectively controlled, the deformation amount of the liner is reduced, the swelling phenomenon of the membrane is reduced, and the long-term stability of the membrane is enhanced. Meanwhile, if the heat treatment time is too long, the membrane will be over-cured and the flexibility will be reduced; if the time is too short, the crosslinking will not be sufficient and the membrane structure will be unstable. The time is controlled within 10-120 min to balance the crosslinking effect and the flexibility of the membrane, and to ensure the mechanical strength and conductivity.

[0021] Preferably, the casting solution comprises the following components by mass percentage: quaternary amine polymer 10-60%, crosslinking agent 0.1-10%, and the balance is an organic solvent.

[0022] Preferably, the quaternary amine polymer is selected from any one or a combination of at least two of quaternary amine polyether ketone, quaternary amine polyether ether ketone, quaternary amine polyether ketone ketone, quaternary amine polyether ether ketone ketone, quaternary amine polyether ketone ether ketone ketone, quaternary amine polysulfone, quaternary amine polyether sulfone, quaternary amine polyphenyl sulfone, or quaternary amine polyaryl sulfone.

[0023] Preferably, the degree of quaternization of the quaternary amine polymer is 10-60%.

[0024] Preferably, the crosslinking agent is selected from any one or a combination of at least two of polyvinyl alcohol, polyvinylpyrrolidone, divinylbenzene, formaldehyde, maleic acid or glutaraldehyde.

[0025] Preferably, the organic solvent is selected from any one or a combination of at least two of dimethyl sulfoxide, 1,2-dichloroethane, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, dichloromethane or trichloromethane.

[0026] Preferably, during the preparation of the casting solution, the temperature of the mixing is 30-50℃, and the time of the mixing is 12-48h.

[0027] Preferably, the support layer comprises any one of a mesh cloth, a non-woven cloth or a porous membrane.

[0028] Preferably, the material of the support layer is selected from any one of polypropylene, polyethylene, polyvinyl chloride, polytetrafluoroethylene, polyethylene terephthalate, nylon or glass fiber.

[0029] Preferably, the thickness of the support layer is 10-200μm.

[0030] Preferably, the thickness of the wet film coated on the support layer is 0.2-1.0mm.

[0031] Preferably, the procedure of the gradient temperature rising is as follows:

[0032] firstly rising the temperature to 50-80℃ for 10-15min, then rising the temperature to 80-100℃ for 5-10min, and finally rising the temperature to 110-140℃ for 1-5min.

[0033] Preferably, after the heat treatment, the film is further treated by gradient temperature falling.

[0034] Preferably, the procedure of the gradient temperature falling is as follows:

[0035] firstly falling the temperature to 80-100℃ for 5-10min, then falling the temperature to 50-80℃ for 1-5min.

[0036] In the second aspect, the present application provides a homogeneous anion exchange membrane, which is prepared by the method for preparing a homogeneous anion exchange membrane as described in the first aspect.

[0037] Preferably, the thickness of the homogeneous anion exchange membrane is 0.1-0.3mm.

[0038] Preferably, the electric resistance of the homogeneous anion exchange membrane is 2-5Ω·cm. 2 .

[0039] Preferably, the water content of the homogeneous anion exchange membrane is 25% or less.

[0040] Preferably, the ion exchange capacity of the homogeneous anion exchange membrane is 1.8 mmol / g or more.

[0041] Preferably, the burst strength of the homogeneous anion exchange membrane is > 0.50 MPa.

[0042] In a third aspect, the present application provides a use of the homogeneous anion exchange membrane according to the second aspect in the preparation of an anion exchange membrane for electrodialysis.

[0043] Compared with the prior art, the present application has the following beneficial effects:

[0044] (1) Simplified preparation process and reduced cost: The method for preparing the homogeneous anion exchange membrane used in the present application uses a novel quaternary aminated polymer mixed with a crosslinking agent as a membrane precursor, dissolves it with an organic solvent, and then coats it to form a film after gradient heat treatment. The operation process is simple and easy to automate. At the same time, the use of a novel quaternary aminated polymer directly eliminates the complex functionalization step in the traditional method, simplifying the preparation process. Combined with the optimized coating and heat treatment process, the operation difficulty and cycle in production are reduced, the production cost is reduced, and the production efficiency is improved.

[0045] (2) Enhanced mechanical strength and improved long-term stability: Gradient heat treatment forms a high-density crosslinked network in the membrane, significantly improving the mechanical strength of the membrane, reducing the risk of damage in actual application, and prolonging the service life of the membrane.

[0046] (3) Significantly reduced swelling: The gradient heat treatment process effectively enhances the crosslinking degree of the membrane. Through uniform crosslinking structure and precise material ratio, the swelling phenomenon of the membrane prepared by the present application in water environment is effectively controlled, the swelling is reduced, the dimensional stability of the membrane in water environment is ensured, and the dimensional and performance stability of the membrane is ensured. This makes the membrane more stable under long-term use conditions and suitable for long-term application.

[0047] (4) Strong combination of membrane and support layer: The coating technology and heat treatment process ensure the firm combination between the membrane and the support layer, avoid the problem of separation between the membrane and the support layer during use, significantly enhance the bonding force between the membrane and the support layer, and reduce the risk of separation between the membrane layer and the support layer. At the same time, the ion exchange groups of the membrane are uniformly distributed, the ion exchange performance and the selectivity of the membrane are improved, and thus the efficiency and stability of the membrane in separation and electrochemical process are improved.

[0048] (5) Environmental protection and economy: The simplified preparation process and the direct use of quaternary aminated polymer reduce the solvent and energy consumption, reduce the production cost, and make the process more environmentally friendly. BRIEF DESCRIPTION OF DRAWINGS

[0049] In order to more clearly illustrate the technical solutions in the specific embodiments of the present application or the prior art, the accompanying drawings needed to be used in the specific embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort.

[0050] Figure 1 The preparation flow chart of the homogeneous anion exchange membrane provided by the present application. DETAILED DESCRIPTION

[0051] Unless otherwise defined herein, scientific and technical terms used in connection with the present application shall have the meanings that are commonly understood by those of ordinary skill in the art. Clear indications to the contrary are needed to establish that any term in this application shall be interpreted differently than its plain meaning. Unless defined otherwise, the use of the term "or" in this application is meant to include "and / or", unless otherwise indicated. In addition, the use of the term "including", as well as other forms such as "includes" and "included", is not limiting.

[0052] It should be noted that specific details are set forth in the following description in order to provide a thorough understanding of the application. However, the present application can be practiced with different and / or alternative methods, steps, procedures, materials, and components, and in many different ways from those

[0053] The embodiments of the present application will be described in detail below with reference to the embodiments and examples, but those skilled in the art will understand that the following embodiments and examples are only used to illustrate the present application and should not be regarded as limiting the scope of the present application. Based on the examples in the present application, all other examples obtained by those skilled in the art without any creative effort shall fall within the scope of the present application. If the specific conditions are not specified, the conventional conditions or the conditions recommended by the manufacturer are used. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased on the market.

[0054] In a first aspect, the present application provides a preparation method of a homogeneous anion exchange membrane, as shown in the following scheme: Figure 1 The preparation method of the homogeneous anion exchange membrane comprises the following steps:

[0055] Mixing the quaternary amine polymer, the crosslinking agent and the organic solvent to obtain a casting solution;

[0056] Coating the casting solution on a support layer to obtain a wet membrane piece;

[0057] Performing heat treatment on the wet membrane piece by using gradient temperature rising to obtain the homogeneous anion exchange membrane.

[0058] In the present application, a preparation method of a homogeneous anion exchange membrane is provided, which uses a novel quaternary aminated polymer as a membrane preparation precursor, dissolves with an organic solvent, and coats a film after adding a certain amount of a crosslinking agent, and then performs a gradient heating-gradient cooling heat treatment to form a film. The operation process is simple and easy to control automatically. After the heat treatment is completed, a high-strength, swelling-resistant homogeneous anion exchange membrane is prepared, which ensures its long-term stability in water treatment and electrochemical applications.

[0059] First, in the process of preparing the casting solution, the novel quaternary aminated polymer and the crosslinking agent are dissolved in the organic solvent in a specific ratio, and defoaming is performed to obtain a uniform casting solution. This step ensures uniform distribution of the membrane material, avoids the multi-step functionalization operation in the traditional method, and improves the simplicity of the preparation process. At the same time, the preparation process flow is simplified, and the production equipment investment is reduced: the novel quaternary aminated polymer is used directly, avoiding the post-functionalization steps such as chloromethylation and quaternary amination in the traditional method, making the preparation process simpler and more efficient. By reducing the process steps, the production cycle is shortened, and the equipment investment is reduced. In addition, the use of novel quaternary aminated polymer as raw material makes the anion exchange groups uniformly distributed in the membrane, ensuring that the membrane has high ion exchange capacity.

[0060] Second, the casting solution is uniformly coated on the support layer, and the thickness and uniformity of the film are controlled by precise blade coating technology. This step not only improves the structural integrity of the film, but also enhances the bonding force between the film and the support layer, avoiding the problem that the film layer is easy to separate.

[0061] Third, the wet film sheet is then heat treated using a gradient heating method to promote the solidification and crosslinking of the film. During the heating process, the film material is gradually crosslinked to form a stable structure, and the progressive change of temperature avoids the generation of stress. This treatment significantly enhances the mechanical strength of the film and reduces its swelling. At the same time, the use of gradient heat treatment and the addition of a support layer enhances the crosslinking degree of the film, forms a stable network structure, more significantly improves the mechanical strength and stability of the film, reduces the deformation degree of the film, and reduces the damage of the film.

[0062] As an optional embodiment, the casting solution includes the following components by mass percentage: quaternary aminated polymer 10-60%, crosslinking agent 0.1-10%, and the balance is organic solvent.

[0063] As an optional embodiment, the content of the quaternary aminized polymer is 10-60% based on the total mass of the casting solution, for example, it can be 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 23%, 24%, 25%, 26%, 27%, 28%, 29%, 30%, 31%, 32%, 33%, 34%, 35%, 36%, 37%, 38%, 39%, 40%, 45%, 50%, 55%, 60%, etc.

[0064] As an optional embodiment, the content of the crosslinking agent is 0.1-10% based on the total mass of the casting solution, for example, it can be 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, 1.2%, 1.4%, 1.5%, 1.6%, 1.8%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, etc.

[0065] In the present application, the ratio of the membrane preparation raw materials is optimized to improve the performance of the membrane: the quaternary aminization ratio of the new quaternary aminized polymer is controlled between 10-60%, which ensures that the membrane has good mechanical strength and dimensional stability while efficiently conducting ions; the concentration of the crosslinking agent is optimized to 0.1-10%, which makes the membrane have good conductivity, mechanical strength and flexibility, further reduces the swelling phenomenon of the membrane, and prolongs the service life of the membrane; the proportion of the solvent is optimized to 70-90%, which ensures that the casting solution has appropriate viscosity, uniform coating, high membrane layer density, and the membrane surface is smooth and defect-free after the solvent volatilizes.

[0066] As an optional embodiment, the quaternary aminized polymer is selected from any one or a combination of at least two of quaternary aminized polyether ketone, quaternary aminized polyether ether ketone, quaternary aminized polyether ketone ketone, quaternary aminized polyether ether ketone ketone, quaternary aminized polyether ketone ether ketone ketone, quaternary aminized polysulfone, quaternary aminized polyether sulfone, quaternary aminized polyphenyl sulfone, or quaternary aminized polyaryl sulfone.

[0067] As an optional embodiment, the degree of quaternary aminization of the quaternary aminized polymer is 10-60%, for example, it can be 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, etc.

[0068] As an optional embodiment, the crosslinking agent is selected from any one or a combination of at least two of polyvinyl alcohol, polyvinylpyrrolidone, divinylbenzene, formaldehyde, maleic acid, or glutaraldehyde.

[0069] In the present application, the above-mentioned selected film-forming raw materials (quaternary amine polymer) all have the characteristics of high stability and high strength, and the addition of the above-mentioned crosslinking agent makes the overall material structure more compact and stable, so that the prepared homogeneous anion exchange membrane has the advantage of high mechanical strength. And can be coated on the support mesh cloth, further increasing its mechanical strength. In addition, the crosslinking agent can form a more compact structure between the molecular chains of the polymer, thereby reducing the influence and damage of the external environment on the molecular chains of the polymer.

[0070] As an optional embodiment, the organic solvent is selected from any one or a combination of at least two of dimethyl sulfoxide, 1,2-dichloroethane, N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, dichloromethane or trichloromethane.

[0071] As an optional embodiment, during the preparation of the casting solution, the temperature of the mixing is 30-50°C, for example, it can be 30°C, 32°C, 34°C, 35°C, 36°C, 38°C, 40°C, 42°C, 44°C, 45°C, 46°C, 48°C, 50°C, etc., and the mixing time is 12-48h, for example, it can be 12h, 13h, 14h, 15h, 16h, 17h, 18h, 20h, 22h, 24h, 25h, 26h, 28h, 30h, 32h, 33h, 34h, 35h, 36h, 38h, 40h, 42h, 44h, 45h, 46h, 48h, etc.

[0072] As an optional embodiment, the support layer includes any one of a mesh cloth, a non-woven fabric or a porous membrane.

[0073] As an optional embodiment, the material of the support layer is selected from any one of polypropylene, polyethylene, polyvinyl chloride, polytetrafluoroethylene, polyethylene terephthalate, nylon or glass fiber.

[0074] As an optional embodiment, the thickness of the support layer is 10-200μm, for example, it can be 10μm, 20μm, 40μm, 50μm, 60μm, 80μm, 100μm, 120μm, 140μm, 150μm, 160μm, 180μm, 200μm, etc.

[0075] As an optional embodiment, the thickness of the wet film coated on the support layer is 0.2-1.0mm, for example, it can be 0.2mm, 0.3mm, 0.4mm, 0.5mm, 0.6mm, 0.7mm, 0.8mm, 0.9mm, 1.0mm, etc.

[0076] As an optional embodiment, the program of the gradient temperature rise is:

[0077] First, the temperature is raised to 50-80℃ for 10-15min, then raised to 80-100℃ for 5-10min, and finally raised to 110-140℃ for 1-5min.

[0078] In the first stage of the gradient temperature rising process, the holding temperature of the heat treatment is 50-80℃, for example, it can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, etc.; the holding time of the heat treatment is 10-15min, for example, it can be 10min, 11min, 12min, 13min, 14min, 15min, etc.

[0079] In the second stage of the gradient temperature rising process, the holding temperature of the heat treatment is 80-100℃, for example, it can be 80℃, 85℃, 90℃, 95℃, 100℃, etc.; the holding time of the heat treatment is 5-10min, for example, it can be 5min, 6min, 7min, 8min, 9min, 10min, etc.

[0080] In the third stage of the gradient temperature rising process, the holding temperature of the heat treatment is 110-140℃, for example, it can be 80℃, 85℃, 90℃, 95℃, 100℃, etc.; the holding time of the heat treatment is 1-5min, for example, it can be 1min, 2min, 3min, 4min, 5min, etc.

[0081] As an optional embodiment, in the process of the gradient temperature rising, the second stage is raised by 20-30℃ relative to the first stage, for example, it can be 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, etc.; the third stage is raised by 20-40℃ relative to the second stage, for example, it can be 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, etc.

[0082] As an optional embodiment, in the process of the gradient temperature rising, the second stage is reduced by 5-8min relative to the first stage, for example, it can be 5min, 5.5min, 6min, 6.5min, 7min, 7.5min, 8min, etc.; the third stage is reduced by 2-4min relative to the second stage, for example, it can be 2min, 2.5min, 3min, 3.5min, 4min, etc.

[0083] As an optional embodiment, after the heat treatment is completed, the film after the heat treatment is further processed by using a gradient cooling method.

[0084] In the present application, the heat treatment of gradient temperature rising is completed, and the post-treatment of the film after the heat treatment is preferably carried out by the way of gradient temperature falling, which is more conducive to the formation of stable film structure, and the generation of stress is avoided by the gradual change of the temperature falling, and this treatment can further enhance the mechanical strength of the film and reduce its swelling.

[0085] As an optional embodiment, the procedure of the gradient temperature falling is as follows:

[0086] firstly falling to 80-100℃ for 5-10min, and then falling to 50-80℃ for 10-15min.

[0087] In the first stage of the gradient temperature falling process, the holding temperature of the heat treatment is 80-100℃, for example, it can be 80℃, 85℃, 90℃, 95℃, 100℃, etc.; and the holding time of the heat treatment is 5-10min, for example, it can be 5min, 6min, 7min, 8min, 9min, 10min, etc.

[0088] In the second stage of the gradient temperature falling process, the holding temperature of the heat treatment is 50-80℃, for example, it can be 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃, etc.; and the holding time of the heat treatment is 1-5min, for example, it can be 1min, 2min, 3min, 4min, 5min, etc.

[0089] As an optional embodiment, in the process of the gradient temperature falling, the temperature of the second stage is lowered by 20-40℃ compared with the first stage, for example, it can be 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, 35℃, 36℃, 37℃, 38℃, 39℃, 40℃, etc.

[0090] As an optional embodiment, in the process of the gradient temperature falling, the processing time of the temperature falling of the second stage is reduced by 5-8min compared with the first stage, for example, it can be 5min, 5.5min, 6min, 6.5min, 7min, 7.5min, 8min, etc.

[0091] In the second aspect, the present application provides a homogeneous anion exchange membrane, which is prepared by the preparation method of the homogeneous anion exchange membrane as described in the first aspect.

[0092] As an optional embodiment, the thickness of the homogeneous anion exchange membrane is 0.1 to 0.3 mm, for example, it can be 0.1 mm, 0.12 mm, 0.14 mm, 0.15 mm, 0.16 mm, 0.18 mm, 0.2 mm, 0.22 mm, 0.24 mm, 0.25 mm, 0.26 mm, 0.28 mm, 0.3 mm, etc.

[0093] As an optional embodiment, the electrical resistance of the homogeneous anion exchange membrane is 2 to 5 Ω·cm 2 , for example, it can be 2 Ω·cm 2 , 2.2 Ω·cm 2 , 2.4 Ω·cm 2 , 2.6 Ω·cm 2 , 2.8 Ω·cm 2 , 3 Ω·cm 2 , 3.2 Ω·cm 2 , 3.4 Ω·cm 2 , 3.5 Ω·cm 2 , 3.6 Ω·cm 2 , 3.8 Ω·cm 2 , 4 Ω·cm 2 , 4.2 Ω·cm 2 , 4.4 Ω·cm 2 , 4.6 Ω·cm 2 , 4.8 Ω·cm 2 , 5 Ω·cm 2 , etc.

[0094] As an optional embodiment, the water content of the homogeneous anion exchange membrane is 25% or less, for example, it can be 25%, 24%, 23%, 22%, 21%, 20%, 19%, 18%, 17%, 16%, 15%, etc.

[0095] As an optional embodiment, the ion exchange capacity of the homogeneous anion exchange membrane is 1.8 mmol / g or more, for example, it can be 1.8 mmol / g, 1.82 mmol / g, 1.84 mmol / g, 1.85 mmol / g, 1.86 mmol / g, 1.88 mmol / g, 1.9 mmol / g, 1.92 mmol / g, 1.94 mmol / g, 1.95 mmol / g, 1.96 mmol / g, 1.98 mmol / g, 2 mmol / g, 2.02 mmol / g, 2.04 mmol / g, 2.05 mmol / g, 2.06 mmol / g, 2.08 mmol / g, 2.1 mmol / g, 2.12 mmol / g, 2.14 mmol / g, 2.15 mmol / g, etc.

[0096] As an optional embodiment, the homogeneous anion exchange membrane has a burst strength of > 0.50 MPa.

[0097] In a third aspect, the present application provides use of the homogeneous anion exchange membrane according to the second aspect in the preparation of an anion exchange membrane for electrodialysis.

[0098] The present application is further illustrated by the following specific examples and comparative examples, but it should be understood that these examples are only used to illustrate in more detail and should not be understood as limiting the present application in any form.

[0099] Example 1

[0100] The present embodiment provides a preparation method of a homogeneous anion exchange membrane, the preparation method of the homogeneous anion exchange membrane comprising the following steps:

[0101] (1) 200 g of quaternary aminated polyphenylsulfone with a quaternary amination degree of 20%, 20 g of polyvinyl alcohol, and 2000 g of N,N-dimethylacetamide are mixed, stirred at 40°C for 20 h, and completely dissolved to obtain a casting solution;

[0102] (2) 100 mL of the casting solution is uniformly sprayed on a PET mesh (with an area of 1000 cm 2 , and a thickness of 40 μm) to obtain a wet film piece;

[0103] (3) The wet film piece is placed in an oven, and a gradient temperature rising and gradient temperature falling program is set for curing treatment, then taken out from the oven and cooled to room temperature to obtain the homogeneous anion exchange membrane;

[0104] The curing treatment is in turn: rising to 50°C for 15 min, rising to 80°C for 7 min, rising to 120°C for 5 min; and then falling to 80°C for 7 min, falling to 50°C for 2 min.

[0105] Example 2

[0106] The present embodiment provides a preparation method of a homogeneous anion exchange membrane, the preparation method of the homogeneous anion exchange membrane comprising the following steps:

[0107] (1) 200 g of quaternary aminated polyphenylsulfone with a quaternary amination degree of 20%, 20 g of polyvinyl alcohol, and 2000 g of N,N-dimethylacetamide are mixed, stirred at 40°C for 20 h, and completely dissolved to obtain a casting solution;

[0108] (2) 100 mL of the casting solution is uniformly sprayed on a PET mesh (with an area of 1000 cm 2 , and a thickness of 40 μm) to obtain a wet film piece;

[0109] (3) placing the wet membrane sheet into an oven, setting a gradient temperature rising and gradient temperature falling procedure to perform curing treatment, and then taking out from the oven and cooling to room temperature to obtain the homogeneous anion exchange membrane;

[0110] The curing treatment is sequentially: rising temperature to 65°C for 12 min, rising temperature to 90°C for 6 min, and rising temperature to 110°C for 3 min; and then falling temperature to 90°C for 6 min, and falling temperature to 65°C for 5 min.

[0111] Example 3

[0112] The embodiment provides a preparation method of a homogeneous anion exchange membrane, and the preparation method of the homogeneous anion exchange membrane comprises the following steps:

[0113] (1) mixing 200 g of quaternary aminated polyether ether ketone with a quaternary amination degree of 40%, 20 g of divinylbenzene and 2000 g of dimethyl sulfoxide, stirring at 40°C for 20 h, and obtaining a casting solution after complete dissolution;

[0114] (2) uniformly spraying 100 mL of the casting solution on PET non-woven fabric (with an area of 1000 cm 2 and a thickness of 70 μm) to obtain a wet membrane sheet;

[0115] (3) placing the wet membrane sheet into an oven, setting a gradient temperature rising and gradient temperature falling procedure to perform curing treatment, and then taking out from the oven and cooling to room temperature to obtain the homogeneous anion exchange membrane;

[0116] The curing treatment is sequentially: rising temperature to 80°C for 10 min, rising temperature to 100°C for 5 min, and rising temperature to 140°C for 1 min; and then falling temperature to 100°C for 5 min, and falling temperature to 80°C for 1 min.

[0117] Example 4

[0118] The embodiment provides a preparation method of a homogeneous anion exchange membrane, and the preparation method of the homogeneous anion exchange membrane comprises the following steps:

[0119] Example 5

[0120] The embodiment provides a preparation method of a homogeneous anion exchange membrane, and only difference from the embodiment 1 is that the casting solution of step (1) is prepared by mixing 500g of quaternary aminated polyphenylsulfone with a quaternary aminated degree of 20%, 20g of polyvinyl alcohol and 2000g of N,N-dimethylacetamide, stirring at 40 DEG C for 20h, and obtaining the casting solution after complete dissolution; and other steps are consistent with the embodiment 1.

[0121] Embodiment 6

[0122] The embodiment provides a preparation method of a homogeneous anion exchange membrane, and only difference from the embodiment 1 is that the quaternary aminated degree of quaternary aminated polyphenylsulfone in step (1) is 10%; and other steps are consistent with the embodiment 1.

[0123] Embodiment 7

[0124] The embodiment provides a preparation method of a homogeneous anion exchange membrane, and only difference from the embodiment 1 is that the quaternary aminated degree of quaternary aminated polyphenylsulfone in step (1) is 70%; and other steps are consistent with the embodiment 1.

[0125] Embodiment 8

[0126] The embodiment provides a preparation method of a homogeneous anion exchange membrane, and only difference from the embodiment 1 is that the temperature gradient program in step (2) is that the temperature is first increased to 40 DEG C and kept for 20min, then increased to 70 DEG C and kept for 15min, and finally increased to 100 DEG C and kept for 10min; and other steps are consistent with the embodiment 1.

[0127] Embodiment 9

[0128] The embodiment provides a preparation method of a homogeneous anion exchange membrane, and only difference from the embodiment 1 is that the temperature gradient program in step (2) is that the temperature is first increased to 80 DEG C and kept for 5min, then increased to 100 DEG C and kept for 7min, and finally increased to 120 DEG C and kept for 15min; and other steps are consistent with the embodiment 1.

[0129] Embodiment 10

[0130] The embodiment provides a preparation method of a homogeneous anion exchange membrane, and only difference from the embodiment 1 is that the temperature gradient program in step (2) is that the temperature is first decreased to 70 DEG C and kept for 20min, then decreased to 40 DEG C and kept for 5min; and other steps are consistent with the embodiment 1.

[0131] Embodiment 11

[0132] The embodiment provides a preparation method of a homogeneous anion exchange membrane, which is different from the embodiment 1 only in that, in step (2), the gradient cooling procedure is that: first cooling to 110 DEG C and keeping for 15 min, and then cooling to 90 DEG C and keeping for 3 min; and other steps are consistent with the embodiment 1.

[0133] Example 12

[0134] The embodiment provides a preparation method of a homogeneous anion exchange membrane, which is different from the embodiment 1 only in that, in step (2), the gradient cooling procedure is that: first cooling to 110 DEG C and keeping for 15 min, and then cooling to 90 DEG C and keeping for 3 min; and other steps are consistent with the embodiment 1.

[0135] Comparative Example 1

[0136] The comparative example provides a preparation method of an anion exchange membrane, and the preparation method of the anion exchange membrane comprises the following steps:

[0137] (1) 200g of polyphenylsulfone, 20g of polyvinyl alcohol and 2000g of N,N-dimethylacetamide are mixed, stirred at 40 DEG C for 20h, and completely dissolved to obtain a casting solution;

[0138] (2) 100mL of the casting solution is uniformly sprayed on a PET mesh (with an area of 1000cm 2 , and a thickness of 40um) to obtain a wet film piece;

[0139] (3) the wet film piece is placed in an oven, gradient temperature rising and gradient temperature lowering procedures are set for curing treatment, and then the wet film piece is taken out from the oven and cooled to room temperature to obtain a dry film piece;

[0140] Wherein, the curing treatment is in sequence: temperature rising to 50 DEG C and keeping for 15 min, temperature rising to 80 DEG C and keeping for 7 min, and temperature rising to 120 DEG C and keeping for 5 min; and then temperature lowering to 80 DEG C and keeping for 7 min, and temperature lowering to 50 DEG C and keeping for 15 min;

[0141] (4) the dry film piece is soaked in a 20% trimethylamine aqueous solution for quaternary ammonium reaction for 24h, washed by deionized water, and placed in air for natural drying at room temperature to obtain the anion exchange membrane.

[0142] Comparative Example 2

[0143] The comparative example provides a preparation method of an anion exchange membrane, and the preparation method of the anion exchange membrane comprises the following steps:

[0144] (1) 200 g of quaternary aminated polyphenylsulfone with a quaternary amination degree of 20%, 20 g of polyvinyl alcohol and 2000 g of N,N-dimethylacetamide were mixed, stirred at 40 °C for 20 h, and completely dissolved to obtain a casting solution;

[0145] (2) 100 mL of the casting solution was uniformly sprayed on a PET mesh (1000 cm 2 in area, 40 μm in thickness) to obtain a wet film piece;

[0146] (3) The wet film piece was placed in an oven, heated to 80 °C, and subjected to constant temperature curing treatment for 2 h, then taken out of the oven and cooled to room temperature to obtain the anion exchange membrane.

[0147] Test Example 1

[0148] Test sample: the homogeneous anion exchange membrane provided in Examples 1-12, the anion exchange membrane provided in Comparative Examples 1-2, commercial membrane 1 and commercial membrane 2.

[0149] Test method: in addition to the comparison of the basic performance of the ion exchange membrane with two commercial ion membranes, the prepared membrane and the commercial membrane were compared in the same time and the same concentration ratio by using a self-made micro-ED device for concentration (membrane logarithm 10 groups), the initial NaCl concentration of the dilution liquid and the concentrated liquid was 1 mol / L, and the energy consumption of the prepared membrane and the commercial membrane was 612 and 573 kwh / t NaCl, respectively. The energy consumption of the prepared membrane and the commercial membrane was also compared in the same time and the same concentration ratio.

[0150] The specific test results are shown in Table 1 below:

[0151] Table 1

[0152]

[0153] As shown in Table 1, the thickness of the homogeneous anion exchange membrane prepared by the preparation method of the present application is 0.1-0.3 mm; the electrical resistance of the homogeneous anion exchange membrane is 4.5-5 Ω·cm 2 ; the water content of the homogeneous anion exchange membrane is 25% or less; the ion exchange capacity of the homogeneous anion exchange membrane is 1.8 mmol / g or more; the burst strength of the homogeneous anion exchange membrane is >0.50 MPa; and the energy consumption of the homogeneous anion exchange membrane is 540-581 kwh / t·NaCl.

[0154] Therefore, it is fully illustrated that the method for preparing the homogeneous anion exchange membrane used in the present application uses a novel quaternary aminated polymer as a membrane preparation precursor, uses an organic solvent for dissolution, and after adding a certain amount of a crosslinking agent, a film is coated, and then a film is formed after gradient temperature rising and falling heat treatment, the operation process is simple and easy to automatically control. The raw materials used for film preparation all have the characteristics of high stability and high strength, and the added crosslinking agent makes the entire material structure more compact and stable, so the prepared membrane has the advantage of high mechanical strength. And it can be coated on the supporting mesh cloth to further increase its mechanical strength. In addition, the crosslinking agent can form a more compact structure between the molecular chains of the polymer, thereby reducing the influence and damage of the external environment on the molecular chains of the polymer.

[0155] Test Example 2

[0156] Test sample: homogeneous anion exchange membranes provided by Examples 1-12, anion exchange membranes provided by Comparative Examples 1-2.

[0157] Test method: the obtained ion membrane sample is respectively immersed in 0.1M hydrochloric acid solution and 0.1M sodium hydroxide solution for 24h, and repeated for 30 cycles, and whether separation occurs between the surface coating and the supporting layer of the ion membrane is observed.

[0158] The specific test results are shown in Table 2 as follows:

[0159] Table 2

[0160]

[0161]

[0162] As shown in Table 2, the homogeneous anion exchange membrane obtained by the preparation method of the present application does not have separation phenomenon between the surface coating and the supporting layer after acid and alkali immersion.

[0163] Therefore, it is fully illustrated that the method for preparing the homogeneous anion exchange membrane used in the present application uses a novel quaternary aminated polymer as a membrane preparation precursor, uses an organic solvent for dissolution, and after adding a certain amount of a crosslinking agent, a film is coated, and then a film is formed after gradient temperature rising and falling heat treatment, the operation process is simple and easy to automatically control. The raw materials used for film preparation all have the characteristics of high stability and high strength, and the added crosslinking agent makes the entire material structure more compact and stable, so the prepared membrane has the advantage of high mechanical strength. And it can be coated on the supporting mesh cloth to further increase its mechanical strength. In addition, the crosslinking agent can form a more compact structure between the molecular chains of the polymer, thereby reducing the influence and damage of the external environment on the molecular chains of the polymer.

[0164] In summary, the preparation method of the homogeneous anion exchange membrane of the present application has the following advantages:

[0165] 1. Simple membrane preparation process and controllable conditions: The method for preparing a homogeneous anion exchange membrane used in the present application uses a novel quaternary aminated polymeric material that has been quaternized and a crosslinking agent mixed as a membrane precursor, dissolves in an organic solvent, and then coats the film, which can be formed after heat treatment. The process is simple, reduces process complexity, improves process repeatability, and is easy to automate.

[0166] 2. High mechanical strength: The method used in the present application selects a novel quaternary aminated polymer with excellent mechanical properties, high strength, and good impact resistance as the raw material for membrane preparation. The functional sites are uniformly distributed, and the addition of a crosslinking agent promotes the formation of covalent bonds or ionic bonds between polymer molecules, making the structure of the ion exchange membrane more stable and enhancing its mechanical properties. Coating on a reinforcing mesh further increases the strength and has no significant effect on the conductivity of the membrane, prolonging the service life of the membrane and reducing the frequency of membrane replacement.

[0167] 3. Low swelling, improved compatibility of coating and support layer: The method for preparing an anion exchange membrane in the present application increases the crosslinking density of the membrane by using a novel quaternary aminated polymeric material and a crosslinking agent, thereby enhancing the structural stability of the membrane, reducing its swelling, and improving the compatibility of the coating and support layer, thereby improving their binding. The use of a gradient heat treatment method of first heating and then cooling prevents the membrane from deforming and cracking due to thermal expansion and contraction during preparation, so the coating and support layer are not easily separated during long-term use, significantly improving the stability of the membrane.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, and are not limiting; although the present application has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can modify the technical solutions described in the above embodiments, or make equivalent substitutions for some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solution to deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a homogeneous anion exchange membrane, characterized in that, The preparation method of the homogeneous anion exchange membrane includes the following steps: The quaternized polymer, crosslinking agent, and organic solvent are mixed to obtain the casting solution; The casting solution is applied to the support layer to obtain a wet film. The wet membrane sheet is heat-treated by gradient heating to obtain the homogeneous anion exchange membrane; The gradient heating procedure is as follows: first heat to 50~80℃ and hold for 10~15 min, then heat to 80~100℃ and hold for 5~10 min, and finally heat to 110~140℃ and hold for 1~5 min. After the heat treatment is completed, the process also includes post-treatment of the heat-treated film by using a gradient cooling method. The gradient cooling procedure is as follows: first, cool down to 80~100℃ and hold for 5~10 min, then cool down to 50~80℃ and hold for 1~5 min.

2. The method for preparing a homogeneous anion exchange membrane according to claim 1, characterized in that, The casting solution comprises the following components by mass percentage: 10-60% quaternary ammonium polymer, 0.1-10% crosslinking agent, and the balance being organic solvent.

3. The method for preparing a homogeneous anion exchange membrane according to claim 1 or 2, characterized in that, The quaternized polymer is selected from any one or a combination of at least two of the following: quaternized polyether ketone, quaternized polyether ether ketone, quaternized polyether ketone ketone, quaternized polyether ether ketone ketone, quaternized polyether ketone ether ketone ketone, quaternized polysulfone, quaternized polyether sulfone, quaternized polyphenylsulfone, or quaternized polyarylsulfone.

4. The method for preparing a homogeneous anion exchange membrane according to claim 1 or 2, characterized in that, The degree of quaternization of the quaternized polymer is 10-60%.

5. The method for preparing a homogeneous anion exchange membrane according to claim 1 or 2, characterized in that, The crosslinking agent is selected from any one or a combination of at least two of polyvinyl alcohol, polyvinylpyrrolidone, divinylbenzene, formaldehyde, maleic acid, or glutaraldehyde.

6. The method for preparing a homogeneous anion exchange membrane according to claim 1 or 2, characterized in that, The organic solvent is selected from dimethyl sulfoxide, 1,2-dichloroethane, etc. N,N -Dimethylformamide, N,N -Dimethylacetamide, N Any one or a combination of at least two of 2-methyl-2-pyrrolidone, dichloromethane, or trichloromethane.

7. The method for preparing a homogeneous anion exchange membrane according to claim 1, characterized in that, During the preparation of the casting solution, the mixing temperature is 30~50℃ and the mixing time is 12~48 h.

8. The method for preparing a homogeneous anion exchange membrane according to claim 1, characterized in that, The support layer includes any one of mesh fabric, non-woven fabric, or porous membrane.

9. The method for preparing a homogeneous anion exchange membrane according to claim 1, characterized in that, The material of the support layer is selected from any one of polypropylene, polyethylene, polyvinyl chloride, polytetrafluoroethylene, polyethylene terephthalate, nylon, or glass fiber.

10. The method for preparing a homogeneous anion exchange membrane according to claim 1, characterized in that, The thickness of the support layer is 10~200 μm.

11. The method for preparing a homogeneous anion exchange membrane according to claim 1, characterized in that, The thickness of the wet film coated on the support layer is 0.2~1.0 mm.

12. A homogeneous anion exchange membrane, characterized in that, The homogeneous anion exchange membrane is prepared by the method for preparing a homogeneous anion exchange membrane as described in any one of claims 1 to 11.

13. The homogeneous anion exchange membrane according to claim 12, characterized in that, The thickness of the homogeneous anion exchange membrane is 0.1~0.3 mm.

14. The homogeneous anion exchange membrane according to claim 12, characterized in that, The resistance of the homogeneous anion exchange membrane is 2~5 Ω·cm. 2 .

15. The homogeneous anion exchange membrane according to claim 12, characterized in that, The homogeneous anion exchange membrane has a water content of less than 25%.

16. The homogeneous anion exchange membrane according to claim 12, characterized in that, The homogeneous anion exchange membrane has an ion exchange capacity of 1.8 mmol / g or higher.

17. The homogeneous anion exchange membrane according to claim 12, characterized in that, The burst strength of the homogeneous anion exchange membrane is >0.50 MPa.

18. The use of a homogeneous anion exchange membrane according to any one of claims 12 to 17 in the preparation of anion exchange membranes for electrodialysis.

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