Anion exchange membrane

Abstract

An anion exchange membrane, particularly suitable for use in electrolytic cells and fuel cells, includes a polyolefin support and an active copolymer containing monomeric units derived from an acrylic monomer having a long saturated linear alkyl chain. A saturated linear alkyl chain of a monomer unit derived from an acrylic monomer having a sufficient length of the active copolymer interacts with a similar saturated linear chain exposed on the surface of a polyolefin support, resulting in: adhesion of the active copolymer on the support, thereby allowing an anion exchange membrane having high mechanical properties and durability to be obtained; the positive charge of the active copolymer is isolated within the pores of the polyolefin support, promoting the formation of positively charged ion channels, thereby promoting the migration of hydroxide ions and allowing high performance of electrochemical cells to be achieved. The anion exchange membrane according to the invention can be obtained in an economically advantageous manner by a special process comprising promoting polymerization of a monomer mixture in a reactor, activating the copolymer by piperidine tertiary amine and / or pyrrolidine tertiary amine, promoting formation of quaternary ammonium salts and promoting adhesion of the copolymer to a polyolefin support.

Description

Technical Field

[0001] This invention relates to anion exchange membranes, particularly anion exchange membranes for use in electrolyzers and fuel cells.

[0002] This invention also relates to a method for producing anion exchange membranes. Background Technology

[0003] There are four main types of electrolyzers used for hydrogen production: alkaline electrolyzers (AEL), polymer solid electrolyte membrane (PEM) electrolyzers, anion exchange membrane (AEM) electrolyzers, and solid oxide electrolyzers (SOEC). The first two types of electrolyzers dominate the market, with their fuel cell stacks (a set of electrochemical cells that break down water molecules into oxygen and hydrogen) having power outputs in the MW range. The other two types of electrolyzers have fuel cell stack power outputs in the kW range and shorter lifespans.

[0004] AEL electrolyzers operate at low temperatures and are inexpensive. As a widely used technology, it has a well-established supply chain and production capacity. However, its response to fluctuations in power input is limited, making it difficult to integrate with renewable energy sources.

[0005] PEM electrolysis systems use solid electrolytes. They offer faster dynamic response, more compact design, and improved energy efficiency. The proton exchange membrane significantly restricts hydrogen permeation and allows for high-pressure operation, reducing the energy required for hydrogen compression and storage. However, PEM systems have a high baseline energy consumption, making them unsuitable for use in conjunction with renewable energy sources, especially solar power, due to nighttime energy consumption.

[0006] The AEM electrolyzer combines the advantages of PEM and AEL systems. It uses low-cost materials and offers energy density and efficiency comparable to PEM technology. While AEM electrolyzers currently reach a maximum power of 2.4 kW, the insufficient stability of existing membranes limits its widespread adoption in electrolysis applications.

[0007] Finally, the advantage of SOEC electrolyzers lies in their ability to achieve high efficiency while operating at high pressure and using non-precious metal catalysts. They offer good development potential, but their commercial application is currently limited due to their short lifespan caused by high operating temperatures.

[0008] PEM and AEM systems typically use polymer membranes placed between the anode and cathode, which function to transport ions from one half-cell to the other. Therefore, systems operating in acidic environments use membranes capable of migrating H+ ions (proton exchange membranes, PEMs), while those operating in alkaline environments use membranes capable of circulating hydroxide ions (anion exchange membranes, AEMs).

[0009] AEMs are obtained by synthesizing positively charged ionic polymers responsible for migrating negatively charged hydroxide ions. Given the unique operating characteristics of these devices, very stringent requirements are placed on the properties of the polymer materials used. First, they must possess high operating pH stability to avoid undesirable degradation that could lead to uncontrolled membrane rupture. Furthermore, to optimize electrochemical performance, the resulting polymer materials and membranes must exhibit high ionic conductivity. Finally, mechanical properties are also crucial, ensuring operation even under pressure gradients between the two half-cells.

[0010] Compared to the two types of electrolyzers mentioned above, AEM diffusion is limited because the AEM film is more restrictive, especially in terms of stability and mechanical properties. Incidentally, this limits the size of the fuel cell stack to a few kilowatts.

[0011] Given the above, AEM electrolyzers are primarily used in conjunction with renewable energy sources. However, due to limitations in stack size, when they must be used in conjunction with renewable energy plants with capacities of MW or even GW, a large number of modular AEM electrolyzer stacks are required, which leads to a significant increase in both production and operating costs.

[0012] In almost all known AEM membranes, the positive charge responsible for hydroxide ion migration is acquired through the formation of quaternary ammonium salts. AEM anion exchange membranes operate in highly alkaline environments, at which pH, ​​one of the most well-known degradation mechanisms of quaternary ammonium salts is Hoffmann elimination. This occurs by removing a hydrogen atom from the β-position of the nitrogen atom, leading to the formation of a double bond and the elimination of the amine.

[0013] Furthermore, hydroxide ions can nucleophilically substitute the nitrogen atom in ammonium. This mechanism leads to the loss of the quaternary ammonium salt and the formation of alcohols (which are not good at conducting ions) on the polymer chain, inhibiting ion transport activity. The solution to this problem is to spatially impede the chemical environment of the nitrogen atom.

[0014] These phenomena reduce the number of active sites responsible for hydroxide ion (OH-) migration over time, leading to a loss of ionic conductivity.

[0015] Although ammonium salts are generally subject to such limitations, these limitations can be prevented by using amines without hydrogen at the β-position or amines that are not easily removed due to steric hindrance (D. Henkensmeier, M. Najibah, C. Harms, J. Zitka, J. Hnát, K. Bouzek, J. Electrochem. Energy Convers. Storage 2021, 18, 024001).

[0016] Recent studies have shown that piperidine ammonium salts, although difficult to prepare, can provide high chemical resistance (MGMarino, KD Kreuer, ChemSusChem 2015, 8, 513).

[0017] US2020 / 0030787 A1 anticipates the possibility of manufacturing anion exchange membranes in which ammonium salts are obtained as reaction products of piperidine compounds.

[0018] Numerous scientific documents also document the use of polymers containing heteroatoms in the main chain. However, the use of such polymers creates sites that are vulnerable to hydroxyl ion attack, leading to main chain breakage and thus reducing the average molecular weight (Merle G, Wessling M, Nijmeijer K (2011) J Membr Sci, 377:1-35).

[0019] During the use of AEM in batteries, degradation of the polymer backbone leads to a loss of mechanical properties, causing membrane rupture and a rapid decline in the performance of the electrochemical device.

[0020] For electrochemical reactions to occur, the membrane needs to be permeated with water molecules in addition to hydroxide ions. However, an excess of water molecules within the membrane can lead to problems such as: - Swelling; - Changes in polymer film size; - Reduced mechanical strength.

[0021] Excessive dimensional deviations can lead to poor adhesion between the membrane and the electrode, resulting in device failure. Conversely, reduced mechanical strength can cause membrane rupture, especially in devices operating under pressure. To achieve the desired mechanical properties of the membrane, a polymer chain crosslinking strategy is typically used. However, these strategies are difficult to control; excessive crosslinking can impart excessive rigidity to the membrane, making it prone to rupture. (TY Son, TH Ko, V. Vijayakumar, K. Kim, SY Nam, Solid StateIonics 344 (2020), 115153.) In addition, the known manufacturing process of AEM membranes involves laborious and complex synthesis using inexpensive reagents (Kimberly FL Hagesteijn1, Shanxue Jiang1, and Bradley P. Ladewig1, J MaterSci (2018) 53:11131-11150).

[0022] For example, it is known to prepare hydrophilic polymer composite membranes and hydrophobic polymeric porous supports. In these approaches, although mechanical properties are improved, the inertness of the polymer support degrades membrane performance, making it difficult for hydroxyl ions to pass through. Furthermore, the chemical difference between commonly used hydrophobic supports and positively charged polymers leads to low affinity and the formation of weak bonds between the two polymer phases. To address this issue, the surface of the polymer support can be chemically and physically modified to expose functional groups capable of covalently binding with the polymer responsible for hydroxyl ion migration. According to known techniques, these operations require complex techniques (e.g., plasma, corona discharge); however, these techniques cannot penetrate deeply into the pores of the substrate, resulting in ineffective or uncontrollable modifications. (TY Son, TH Ko, V. Vijayakumar, K. Kim, SY Nam, Anion exchange composite membranes composed of poly(phenylene oxide) quaternary ammonium and polyethylene support for alkalineanion membrane exchange fuel cell containing applications, Solid State Ionics 344 (2020), 115153).

[0023] To achieve good conductivity for hydroxide ions without excessively increasing the number of active sites, it is necessary to explore the dissociation of positive charges to form "ion channels," which are continuous positively charged regions across the membrane that serve as preferred pathways for hydroxide ions. Although the importance of ion channels has been recognized in the literature, there is currently no simple and effective method to obtain them (G. Arges et al. vj. Mater. Chem. A, 2017, 5, 5619).

[0024] LUO Y ET AL: “Quaternized poly(methyl methacrylate-co-butyl acrylate-co-vinylbenzyl chloride) membrane for alkaline fuel cells”, JOURNAL OF POWERSOURCES, ELSEVIER, AMSTERDAM, NL, vol. 195, No. 12, June 15, 2010 (2010-06-15), pp. 3765-3771 describes a method for preparing a membrane by copolymerizing a specific functional monomer derived from a random poly(methyl methacrylate-co-butyl acrylate-co-vinylbenzyl chloride) copolymer. The synthesis steps involve copolymerization, quaternization, and finally “membrane casting,” thus eliminating the need for any type of support. The copolymer is free of styrene units and ammonium salts derived from pyrrolidine piperidine units. PTFE is used only as a component in the preparation of electrochemical cell electrodes and not as a support for the active membrane copolymer.

[0025] Given the interest in AEM devices, particularly due to their advantages in combination with renewable resources, there is a need to develop alternatives to AEM membranes, preferably exhibiting mechanical strength and durability, along with high ion conductivity. Summary of the Invention

[0026] The purpose of this invention is to provide an anion exchange membrane (AEM) that exhibits good mechanical strength and durability, along with high ionic conductivity.

[0027] Another object of the present invention is to provide an anion exchange membrane that combines high performance in terms of mechanical strength, durability and conductivity with very low production cost.

[0028] Another object of the present invention is to provide a method for realizing anion exchange membranes that allows for the realization of high-performance membranes at very low production costs.

[0029] Another object of the present invention is to provide a method for realizing anion exchange membranes that allows for the low-cost production of large-format membranes with high mechanical properties, durability and conductivity.

[0030] According to a first aspect of the invention, the aforementioned object is achieved by an anion exchange membrane comprising a multifunctional copolymer and a porous polyolefin material support for increasing mechanical strength. The multifunctional copolymer contains positively charged monomer units (non-acrylic) capable of hydroxyl ion migration and alkane groups of monomer units derived from acrylic monomers having straight-chain saturated alkyl chains with three or more carbon atoms. Therefore, in addition to providing a positive charge for OH- migration, the copolymer can also chemically bond with the support in the polyolefin material (alkane) through hydrophobic interactions.

[0031] The porous polyolefin material carrier ensures the membrane exhibits high mechanical resistance. The active copolymer is a multifunctional copolymer comprising a positively charged monomer unit (non-acrylic) capable of hydroxyl ion migration and an alkane group of a monomer unit derived from an acrylic monomer having a straight-chain saturated alkyl chain with three or more carbon atoms. Therefore, in addition to providing the positive charge for OH- migration, the copolymer can chemically bond with the polyolefin material (alkane) carrier through hydrophobic interactions.

[0032] The saturated straight-chain alkyl chain (alkanes) of the monomer unit derived from acrylic monomers with sufficient copolymer length interacts with similar saturated straight chains exposed on the surface of the polyolefin support, achieving two effects: - The active copolymer adheres to the carrier, thereby obtaining anion exchange membranes with high mechanical properties and durability; - Two phases are formed, one hydrophobic and the other conductive hydrophilic. The positive charge of the active copolymer is separated within the pores of the polyolefin support, promoting the formation of positively charged ion channels, which facilitates the migration of hydroxide ions and allows for high performance in electrochemical cells.

[0033] Advantageously, the active copolymer consists of alkyl acrylate units, styrene units, and vinyl benzyl units with benzyl-linked substituents, which belong to the piperidine and / or pyrrolidine family, preferably N-alkylpiperidine and / or N-alkylpyrrolidine.

[0034] Piperidine and / or pyrrolidine are bonded to the chloromethyl group of the vinylbenzene unit to form a positively charged quaternary ammonium group.

[0035] The use of quaternary ammonium piperidine and / or pyrrolidine, due to their cyclic nature, makes them difficult to attack by hydroxide ions, thus allowing for a combination of high ion exchange capacity and conductivity with high durability.

[0036] It is still advantageous that the living copolymer consists of the polymerization product of at least the following substances with piperidine tertiary amine and / or pyrrolidine tertiary amine: a. Acrylic monomers having a saturated straight-chain alkyl chain with 3 or more carbon atoms; b. Vinyl benzyl monomers having a chloromethyl group bonded to an aromatic ring; c. and vinyl aromatic monomers.

[0037] Advantageously, the piperidine tertiary amine and / or pyrrolidine tertiary amine includes one of the following: 1-methylpiperidine, 1-ethylpiperidine, 1-propylpiperidine, 1-butylpiperidine, 1,2,6-trimethylpiperidine, 1,2,6-triethylpiperidine, 1,2,6-tripropylpiperidine, 1,2,2,6,6-pentamethylpiperidine, 1-methylpyrrolidine, 1-ethylpyrrolidine, 1-propylpyrrolidine, 1,2,5-trimethylpyrrolidine.

[0038] Advantageously, acrylic monomers are esters of acrylic acid, which combine the straight chain of a saturated hydrocarbon with an external oxygen atom.

[0039] It remains advantageous that the acrylic monomers include at least one of the following: propyl acrylate, butyl acrylate, pentyl acrylate, hexyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, undecyl acrylate, dodecyl acrylate, tridecyl acrylate, tetradecyl acrylate, vinadecanyl acrylate, hexadecyl acrylate, heptadecanyl acrylate, octadecyl acrylate, nonadecanyl acrylate, ecicoacrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, vinadecanyl methacrylate, hexadecyl methacrylate, heptadecanyl methacrylate, octadecyl methacrylate, nonadecanyl methacrylate, and ecicoacrylate.

[0040] The vinylbenzyl unit with a positively charged substituent is generated by reacting a vinylbenzyl group containing a chloromethyl group bonded to an aromatic ring with at least one piperidine tertiary amine and / or pyrrolidine tertiary amine containing an alkyl group bonded to a nitrogen atom. This forms a quaternary ammonium salt.

[0041] The hydrophobic interactions established between the linear aliphatic chains of the active copolymer and the support allow for the formation of a hydrophobic phase. This hydrophobic phase contacts the more hydrophilic phase and exposes the quaternary ammonium salt within the pores of the support, resulting in the formation of positively charged hydrophilic domains. This leads to the acquisition of positively charged ion channels through which hydroxyl anions present in an alkaline solution surrounded by the hydrophobic phase can easily enter, preventing excessive water accumulation in the membrane and its weakening mechanical strength.

[0042] Advantageously, the copolymer contains 3% to 10% acrylic units, 40% to 79% vinyl aromatic units and 20% to 50% substituted vinyl benzyl units in molar terms.

[0043] It is still advantageous that the copolymer has an average degree of polymerization between 200 and 500.

[0044] Advantageously, copolymers are obtained by using peroxide radical initiators to promote the polymerization reaction.

[0045] In a preferred structural configuration, the polyolefin carrier is made of a polyethylene-based material selected from LDPE, HDPE, or UHMWPE.

[0046] In alternative structural forms, the polyolefin carrier is a polypropylene-based material.

[0047] Compared to membranes obtained by casting a single active polymer, the use of a polyolefin support allows for a significant improvement in the mechanical properties of the membrane, as is the case in the production of many anion exchange membranes using known techniques.

[0048] The degradation problem under alkaline conditions can be solved by using active polymers and carriers that do not contain heteroatoms in the main chain, because all the bonds in the main chain, carrier and active copolymer are carbon-carbon sp3 covalent bonds, which cannot be linked by OH anions.

[0049] In a preferred configuration, the polyolefin carrier has a porosity between 40% and 95% and an average pore size between 0.2 µm and 1.2 µm.

[0050] Advantageously, the adhesion of the copolymer to the carrier of the polyolefin material is promoted by free radical initiators and / or free radical stabilizers, particularly at least one olefin having aromatic and / or heteroaromatic groups.

[0051] More specifically, by grafting the active polymer onto a support activated with a free radical initiator and an auxiliary agent capable of stabilizing primary free radicals, the adhesion of the copolymer to the polyolefin support can be enhanced, thereby facilitating the reaction combination and preventing degradation. Specifically, this effect can be achieved by using at least one olefin appropriately substituted with aromatic and / or heteroaromatic groups, such as 1-phenylmethacrylate or 1-furanylmethacrylate.

[0052] Due to the presence of a polyolefin carrier, the membrane exhibits high tensile strength, with a Young's modulus between 4800 MPa and 5800 MPa and an elongation greater than 10%; this allows its use in electrolyzers operating at high pressures (greater than 30 bar) without the occurrence of rupture that would lead to a short circuit in the electrolyzer.

[0053] The linear expansion (less than 10%) caused by the membrane absorbing moisture allows it to be used in fuel cells operating with atmospheric oxygen input, preventing membrane separation from the electrodes in the event of humidity changes.

[0054] According to another aspect of the present invention, the above-mentioned objective of the present invention is achieved by a method for implementing an anion exchange membrane, the method comprising the following stages: - Promoting the polymerization of a mixture by at least one peroxide radical initiator, said mixture comprising: ii. Acrylic monomers having a saturated straight-chain alkyl chain with 3 or more carbon atoms; iii. Vinyl benzyl monomers having an aromatic ring chloromethyl group, and iv. Vinyl aromatic monomers, - The obtained copolymer is activated by promoting the formation of quaternary ammonium salts by substituting at least one vinylbenzyl chloride monomer with piperidine tertiary amines and / or pyrrolidine tertiary amines. - In the presence of a polar solvent, the film of the polyolefin carrier is immersed in a liquid solution of the copolymer to promote the bonding between the copolymer and the polyolefin carrier.

[0055] The method of this invention enables the production of anion exchange membranes with performance and mechanical properties comparable to those obtained by using gamma rays to promote the grafting of active polymers onto a polymer matrix with high mechanical properties, with a simple process, safety, and economy. The use of gamma rays is extremely costly, especially due to stringent safety restrictions. These limitations make it economically unprofitable to manufacture anion exchange membranes larger than a certain size, and therefore limit the possibility of realizing high-power devices using this technology without the use of a large number of low-power electrochemical cells. Compared to well-known techniques that allow for the production of anion exchange membranes with comparable performance, the method of this invention also allows for the production of much larger anion exchange membranes at a highly competitive cost, thereby making it possible to manufacture electrolyzers with greater power than those currently known in AEM electrolyzers.

[0056] In a preferred embodiment of the method of the present invention, the copolymer activation stage occurs before the stage of promoting the bonding of the copolymer with the polyolefin carrier, and the polyolefin carrier is based on polyethylene.

[0057] In this scenario, when the polyethylene carrier is immersed in the copolymer in solution, the saturated straight-chain alkyl chains of the monomer units derived from acrylic monomers with sufficient copolymer length interact with similar saturated straight chains exposed on the surface of the polyolefin carrier, and as the solvent present in the solution evaporates, a hydrophobic chemical bond is formed between the active copolymer and the carrier.

[0058] In a preferred embodiment, the stage of promoting the bonding of the copolymer with the polyolefin support occurs by adding a peroxide radical activator and a radical stabilizer composed of olefins having aromatic and / or heteroaromatic groups to a liquid solution containing the copolymer and the porous polyolefin support.

[0059] The addition of free radical activators and free radical stabilizers allows for the formation of covalent bonds between the polyolefin support (which in this case can advantageously be polypropylene) and the active copolymer. Furthermore, in this case, adhesion of the copolymer to the polyolefin support can also be promoted prior to copolymer activation. Attached Figure Description

[0060] Other features and advantages of the invention will become apparent from the following description of implementations given by way of example rather than limitation, with reference to the accompanying drawings, in which: - Figure 1 The main chemical reactions for obtaining anion exchange membranes according to the present invention are illustrated schematically. - Figure 2 This is a Cartesian plot showing the polarization curves of an electrolytic cell including the anion exchange membrane of the present invention at different temperatures; - Figure 3 A table showing the results of measurements of water absorption (at 20°C and 80°C), thickness gain (at 20°C and 80°C), and linear expansion (at 20°C and 80°C) performed according to ISO standards.

[0061] - Figure 4 The table shows the results of measurements of tensile strength, Young's modulus and elongation of the anion exchange membrane according to the present invention, in accordance with ISO 153-7. Detailed Implementation

[0062] In the following description of specific embodiments of the invention, it should be understood that the composition of the membrane according to the invention is not limited to the specific reagents mentioned, and the implementation process is represented only by its basic steps, as those skilled in the art will recognize that the tools, methods, and reagents used may vary and are not intended to limit the scope of the process. Also note that unless the context clearly indicates otherwise, the singular form used herein and in the appended claims also includes plural indicators. Thus, for example, "solvent" refers to one or more solvents and their equivalents known to those skilled in the art. Similarly, the combination of "and / or" is used to indicate that one or both of the statements may occur, for example, A and / or B includes (A and B) and (A or B). Unless otherwise defined, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the process pertains.

[0063] Before describing specific embodiments of the present invention, definitions of some terms used herein are given.

[0064] definition Anion exchange membrane: A membrane composed of polymers that, when placed in an alkaline bath between the electrodes of an electrochemical cell, exposes a positive charge that enables the migration of hydroxide ions.

[0065] Polyolefin materials: Materials based on polyethylene and / or polypropylene.

[0066] Positively charged units: Units in a polymer chain that contain ammonium salts.

[0067] Acrylic monomers: monomers including acrylates and methacrylates with various substituents. Peroxide radical initiators: Radical initiators are molecules containing oxygen-oxygen bonds that are particularly weak at homolytic cleavage, thus serving as a source of free radicals and initiators in radical polymerization or grafting reactions. Peroxides, compounds with the general formula RO-OR, are the most commonly used radical initiators. Heating peroxides causes the weak OO bonds to homolytically cleave, forming two RO radicals. These radicals can attach to the double bonds of olefin compounds to initiate polymerization, or extract hydrogen atoms from organic compounds to form secondary radicals on the molecule. The two radicals can interact to form covalent bonds (bonding reactions).

[0068] Free radical stabilizers are molecules added to stabilize primary free radicals through resonance (delocalization of unpaired electrons on molecules). They prevent polymer degradation by blocking the removal of hydrogen atoms from the chain (bitback), and can also lead to bonding reactions between two free radicals.

[0069] In this invention, the free radical stabilizer is a molecule used to promote grafting because stabilizing free radicals increases the likelihood of covalently binding the active polymer to the support through the recombination of two free radicals.

[0070] Grafting: Generally, grafting refers to the process of attaching molecules to certain polymers to functionalize them. Here, it refers to the formation of covalent bonds between a polyolefin support chain and an active polymer through a free radical reaction, and then "grafting" the polymer onto the support.

[0071] Activation of copolymers: The polymer is converted into a positively charged ionic polymer by reacting a tertiary amine with a benzyl halide.

[0072] Example 1 refer to Figure 1 Anion exchange membranes include: - A carrier made of porous polyolefin material; and - Copolymer, containing: i. Positively charged monomeric units enable the migration of hydroxide ions. ii. A monomeric unit derived from an acrylic monomer having a saturated straight-chain alkyl chain with 3 or more carbon atoms, and iii. Monomer units derived from vinyl aromatic monomers, By joining: - 56% styrene by molar concentration - 34% 4-vinylchlorobenzene (by molar weight) - 9% octadecyl acrylate by molar weight - 1% benzoyl peroxide by molar amount, The reactor was kept at 73°C and under a conditioned atmosphere for about 10 hours to obtain the desired result. Acetone (CH3-CO-CH3) was added in an amount equivalent to 300% (molecular weight) of the initial mixture in the reactor, and stirring was continued until the polymer was completely dissolved.

[0073] Subsequently, 20% N-methylpiperidine (relative to the reactor mixture) was added by molar amount, and the mixture was stirred for another 10 hours by adding 160% ethanol (CH3-CH2-OH) by molar amount to obtain the active copolymer in solution.

[0074] Finally, a support composed of a polyethylene sheet with a porosity of 60% and an average pore size of 0.6 µm is immersed in the obtained solution and held until the solvent is completely evaporated. During this stage, the hydrocarbon chains of the active copolymer crystallize on the support surface, causing positive charges to be exposed and separated within the pores of the support, thereby obtaining the anion exchange membrane according to the invention.

[0075] Using a platinum-based cathode and a Ni / Fe / Co oxide-based anode, polarization curves were plotted at different temperatures to measure the performance of the anion exchange membrane obtained in the electrolytic cell. The measurement results are presented in... Figure 2 The information is provided in the text.

[0076] The ion exchange capacity (IEC) of the obtained anion exchange membrane is measured by alkaline acid titration according to the following steps: - Activate the membrane in 1 M KOH for 24 hours; - Dry in an inert atmosphere; - Weigh until constant weight is achieved; - Immerse the membrane in a known amount of 0.01 M HCl for 24 hours; - Perform reverse titration of an acidic solution with KOH of known concentration; - Calculate the ion exchange capacity using the following formula: IEC = [(molf HCl - number of HCl moles) / m] 1000 in: - molf HCl indicates the final number of moles of HCl after membrane immersion. - The number of HCl moles indicates the initial number of HCl moles before membrane immersion. - m represents dry film quality - Results are expressed in millimoles per gram.

[0077] The average IEC of the five repeated experiments was 1.9 mmol / g.

[0078] The resistance of the anion exchange membrane and the resulting ionic conductivity are calculated using the following procedure: - The membrane was activated in KOH for 24 hours and then assembled in a 5 cm² electrolytic cell with nickel-based electrodes. - Electrolyze for 1 minute (at 10 ma / cm2), then measure the resistance using a HIOKI 3560 at 20°C and 60°C.

[0079] The same type of measurement was performed on the same membrane-free electrolytic cell, and the obtained value was subtracted from the previous value to obtain the effective resistance (Rm) of the membrane using the following formula: Rm = (R1-R2) A in: - R1 represents the total resistance of the battery containing the membrane. - R2 represents the resistance of the membrane-free battery. - A represents the area of ​​the electrode.

[0080] Then the ionic conductivity (Y) is obtained according to the following formula: γ = S / (Rm A) Where S represents the thickness of the membrane.

[0081] The membrane conductivity was found to be 35 ms / cm at 20℃ and 75 ms / cm at 60℃.

[0082] According to ISO 62:2008 (E), the water absorption rate (at 20℃ and 80℃), thickness gain rate (at 20℃ and 80℃), and linear expansion rate (at 20℃ and 80℃) of anion exchange membranes were measured. The results are as follows: Figure 3 As shown in the table.

[0083] The tensile strength, Young's modulus, and elongation of the anion exchange membrane were measured according to ISO 153-7. The measurements were performed using a Shimadzu AGS-X SKN instrument. The results are as follows: Figure 4 As shown in the table.

[0084] Example 2 An anion exchange membrane, comprising: - A carrier made of porous polyolefin material; and - Copolymer, containing: i. Positively charged monomeric units enable the migration of hydroxide ions, and ii. A monomeric unit derived from an acrylic monomer having a saturated straight-chain alkyl chain with 3 or more carbon atoms, and iii. Monomer units derived from vinyl aromatic monomers, By joining: 54% styrene by molar concentration 30% 4-chloroethylene (by molar weight) 15% Esil-methacrylate by molar ratio 1% benzoyl peroxide (by molar) The reactor was then kept under a conditioned atmosphere for approximately 20 hours.

[0085] Then, acetone (CH3-CO-CH3) in an amount of 300% (compared to the mixture in the reactor) was added to the reactor, and stirring was continued until the polymer was completely dissolved.

[0086] Add 1-methylpyrrolidine (relative to the reactor mixture) in molar amounts and stir for another 40 hours, then add 150% ethanol in molar amounts.

[0087] Subsequently, it was added to a solution containing 1% benzoyl peroxide and 2% olefins containing heterocyclic aromatic groups by molar amount. Then, a carrier consisting of polypropylene sheets with a porosity of 50% and an average pore size of 0.5 µm was immersed in the resulting solution and the whole was kept at 73 °C and under a conditioned atmosphere for about 10 hours.

[0088] The membrane according to the invention comprises a polypropylene carrier, to which an active copolymer is chemically bonded, and the membrane is obtained by evaporating a solvent.

[0089] The membrane has characteristics suitable for use in alkaline electrolyzers, particularly regarding mechanical properties, high ion exchange and conductivity, and high durability in alkaline environments.

Claims

1. An anion exchange membrane comprising: a. a support of polyolefin material; and b. an active copolymer containing monomeric units with positive charge, capable of migrating hydroxyl ions; said anion exchange membrane being characterized in that said active copolymer further contains: c. monomeric units derived from an acrylic monomer having a saturated linear alkyl chain with a carbon number equal to or greater than 3, d. styrene units, and e. vinylbenzyl units with a benzyl binding substituent belonging to the piperidine and / or pyrrolidine family, so that said copolymer is capable of chemically binding to the support of polyolefin material through hydrophobic interactions.

2. The anion exchange membrane according to claim 1, characterized by, said piperidine and / or pyrrolidine is an N-alkylpiperidine and / or N-alkylpyrrolidine.

3. An anion exchange membrane according to one of the preceding claims, characterized in that said active copolymer consists of the polymerization product of at least: - an acrylic monomer having a saturated linear alkyl chain with a carbon number equal to or greater than 3; - a vinylbenzyl monomer having a chloromethyl group bound to an aromatic ring; and - a vinyl aromatic monomer.

4. The anion exchange membrane according to the preceding claim, characterized in that, said piperidine and / or pyrrolidine tertiary amine includes at least one of: 1-methylpyridine, 1- ethylpyridine, 1-propylpiperidine, 1-butylpiperidine, 1,2,6-trimethylpyridine, 1,2,6-triethylpiperidine, 1,2,6-tripropylpiperidine, 1,2,2,6,6-pentamethylpiperidine, 1-methylpyrrolidine, 1- ethylpyrrolidine, 1-propylpyrrolidine, 1-butylpyrrolidine, 1,2,5-trimethylpyrrolidine.

5. The anion exchange membrane according to claim 3 or 4, characterized in that, said acrylic monomer is an ester of acrylic acid, wherein a linear saturated hydrocarbon chain is bound to the ester oxygen atom.

6. The anion exchange membrane according to the preceding claim, characterized in that, said acrylic monomer includes at least one of: propyl acrylate, butyl acrylate, pentyl acrylate, heptyl acrylate, octyl acrylate, nonyl acrylate, acrylate, acrylate, dodecyl acrylate, tridecyl acrylate, tetradecyl acrylate, pentadecyl acrylate, hexadecyl acrylate, heptadecyl acrylate, octadecyl acrylate, nonadecyl acrylate, eicosyl acrylate, propyl methacrylate, butyl methacrylate, pentyl methacrylate, hexyl methacrylate, heptyl methacrylate, octyl methacrylate, nonyl methacrylate, decyl methacrylate, undecyl methacrylate, dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecyl methacrylate, octadecyl methacrylate, nonadecyl methacrylate, eicosyl methacrylate.

7. An anion exchange membrane according to one of the preceding claims, characterized in that said copolymer contains, in moles, 3% to 10% of acrylic units, 40% to 79% of vinyl aromatic units, and 20% to 50% of vinylbenzyl units with a substituent.

8. An anion exchange membrane according to one of the preceding claims, characterized in that said support of polyolefin material consists of a polyethylene-based material selected from PE, LDPE, HDPE, or UHMWPE.

9. The anion exchange membrane according to one of claims 1 to 7, characterized in that said support of polyolefin material consists of a polypropylene-based material.

10. A method for building an anion exchange membrane comprising the following stages: a) promoting the polymerization of a mixture comprising: i) acrylic monomers having saturated linear alkyl chains with carbon number equal to or greater than 3; ii) vinylbenzyl monomers having a chloromethyl group bound to an aromatic group, and iii) vinyl aromatic monomers, b) activating the copolymer obtained by promoting the formation of quaternary ammonium salts through the substitution of at least one vinylbenzyl chloride monomer with piperidine tertiary amines and / or pyrrolidine tertiary amines, and c) promoting the binding of the copolymer to the polyolefin support by immersing a thin film of the polyolefin support in a liquid solution of the copolymer in the presence of a polar solvent.

11. Method for the realization of an anion exchange membrane according to the preceding claims, wherein: - the phase of activation of the copolymer occurs before the phase of promoting the binding of the copolymer to the polyolefin support; - the polyolefin support is based on polyethylene.

12. The method of implementing an anion exchange membrane according to claim 10, wherein, The phase of promoting the binding of the copolymer to the polyolefin support occurs by adding to the liquid solution containing the copolymer and the porous polyolefin support a peroxyl radical activator consisting of olefins with aromatic and / or heteroaromatic groups and a radical stabilizer.

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