Alkaline anion exchange blend membrane

Abstract

The present invention relates to an alkaline anion exchange membrane precursor (pAAEM) comprising a blend of at least one first polymer (P1) comprising repeating units derived from acrylonitrile and at least one second polymer (P2) comprising repeating units derived from vinyl lactam, and to an alkaline anion exchange membrane (AAEM) obtained therefrom.

Description

[Technical Field]

[0001] The present invention relates to an alkaline anion exchange membrane precursor (pAAEM) comprising a blend of at least one first polymer (P1) comprising repeating units derived from acrylonitrile and at least one second polymer (P2) comprising repeating units derived from vinyl lactam, and to an alkaline anion exchange membrane (AAEM) obtained therefrom.

[0002] The present invention further relates to a process for preparing an alkaline anion exchange membrane precursor (pAAEM), a process for preparing an alkaline anion exchange membrane (AAEM), an alkaline water electrolysis cell comprising an alkaline anion exchange membrane (AAEM), the use of an alkaline anion exchange membrane (AAEM) in an alkaline water electrolysis cell, and a process for preparing hydrogen using an alkaline exchange membrane (AAEM).

[0003] Politics, society and industry aim to reduce CO2 emissions by decarbonizing industry and mobility. In this context, green hydrogen plays a strategic role as it can replace hydrocarbons in chemical and industrial processes, energy conversion and fuel cell propulsion in mobility applications.

[0004] Furthermore, as the share of renewable resources increases, Germany's energy system is undergoing fundamental change. In accordance with the 2010 Energy Concept, the Federal Government has set the target of reducing greenhouse gas emissions by at least 80% in 2050 compared to 1990 levels. Furthermore, in 2050, 60% of total final energy consumption should be supplied by renewable energies, compared to the 1990 base year. In the first years, the implementation of the 2010 Energy Concept will require an increase in the share of renewable energies in total energy production, but once a significant portion is supplied by renewable sources, technological solutions for the intermediate storage of solar, wind, or hydroelectric energy will be required.

[0005] Power-to-Gas (P2G) as a system solution can convert electricity into hydrogen or methane for use in various areas such as mobility, industry, heat supply, and power generation applications.

[0006] The key element of a P2G system is the water electrolyzer, which exists as either an alkaline exchange membrane electrolyzer system or a proton exchange membrane electrolyzer system. Today, most commercial electrolyzers have a current rating of 1000-3000 A / m 2 It is based on alkaline electrolysis using a 30 wt % KOH aqueous electrolyte (conductivity of 1.5 S / cm at 80 °C) which can operate at current densities in the range of 1000 A / m. However, efficiency decreases at higher current densities, making it technically unsuitable for use at current densities of 1000 A / m. 2 Current densities below 1000 kJ are the norm.

[0007] The porous diaphragm is used to separate the generated oxygen gas and hydrogen gas, but is also used to prevent mixing of the catholyte and anolyte in order to obtain high gas purity and high current efficiency.

[0008] Asbestos is widely used as a diaphragm material at temperatures up to 100°C, while polyantimony acid, nickel oxide, polyphenylene sulfide (Ryton®), and polyphenylene sulfide / zirconium oxide (Zirfon®) are known as modern diaphragm materials.

[0009] The membrane materials described in the state of the art have a thickness of about 500 μm. They exhibit good stability against alkaline aqueous solutions. A drawback of the membrane materials used in the state of the art is that they are not gas-tight. As a result, the evolved gases oxygen and hydrogen can migrate through the membrane material, which leads to a decrease in the efficiency of the electrolysis process. Furthermore, the membrane materials are quite expensive.

[0010] Another approach recently disclosed in the state of the art is the use of alkaline anion exchange membranes in alkaline water electrolysis cells for the preparation of hydrogen.

[0011] "D. Aili, M.R. Kraglund, J. Tavacoli, C. Chatzichristodoulou, and J.O. Jensen, Polysulfone-polyvinylpyrrolidone blend membranes as electrolytes in alkaline water electrolysis, Journal Membrane Science 2020, 598, 117674-117684. DOI: 10.1016 / j.memsci.2019.117674" discloses polysulfone-polyvinylpyrrolidone blend membranes as electrolytes in alkaline water electrolysis. The alkaline anion exchange membranes disclosed in this publication have already demonstrated fairly good performance. However, their long-term stability in strongly alkaline aqueous solutions is not sufficient in all cases. Therefore, there is still room for improvement.

[0012] Therefore, it is an object of the present invention to provide an alkaline anion exchange membrane precursor (pAAEM) from which an anion exchange membrane (AAEM) can be obtained that does not exhibit the drawbacks of the prior art or that exhibit these drawbacks only in a reduced form. The preparation of the alkaline anion exchange membrane precursor (pAAEM) and the alkaline anion exchange membrane (AAEM) obtained therefrom should be easy to carry out. The alkaline anion exchange membrane (AAEM) should be suitable for use in an alkaline aqueous electrolysis cell. Furthermore, the alkaline anion exchange membrane (AAEM) should be suitable for the production of hydrogen and oxygen in an alkaline aqueous electrolysis cell.

[0013] This object is achieved by an alkaline anion exchange membrane precursor (pAAEM) comprising a blend (B) of at least one first polymer (P1) comprising repeating units derived from acrylonitrile and at least one second polymer (P2) comprising repeating units derived from vinyl lactam.

[0014] Furthermore, this object is achieved by an alkaline anion exchange membrane (AAEM) obtained by contacting an alkaline anion exchange membrane precursor (pAAEM) with an alkaline aqueous solution.

[0015] It has been surprisingly found that an alkali anion exchange membrane (AAEM) exhibiting good ionic conductivity, low swelling, and high stability in a strongly alkaline aqueous solution can be obtained from the alkali anion exchange membrane precursor (pAAEM) of the present invention. The alkali anion exchange membrane precursor (pAAEM) of the present invention can provide an alkali anion exchange membrane (AAEM) having a smaller thickness than membrane materials disclosed in the state of the art.

[0016] The alkali anion exchange membrane precursor (pAAEM) and the alkali anion exchange membrane (AAEM) obtained therefrom are gas-tight. Therefore, by using the alkali anion exchange membrane (AAEM) in an alkaline aqueous electrolysis cell, the transfer of evolved gases oxygen and hydrogen (gas crossover) is prevented or at least reduced. This improves the efficiency of the electrolysis process and produces purer hydrogen and oxygen gases. The alkali anion exchange membrane (AAEM) of the present invention also has lower resistance than commercially available membrane materials such as Zirfon® and is stable at operating temperatures above 100°C. [Brief explanation of the drawings]

[0017] [Figure 1] 1 shows a scanning electron microscope photograph (SEM cross section, magnification: 5000 times) of the pAAEM membrane of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0018] The present invention will be described in further detail below.

[0019] Alkaline anion exchange membrane precursor (pAAEM) The blend (B) contained in the alkaline anion exchange membrane precursor (pAAEM) includes at least one first polymer (P1) containing repeating units derived from acrylonitrile and at least one second polymer (P2) containing repeating units derived from vinyl lactam.

[0020] First Polymer (P1) The expression "at least one first polymer (P1)" according to the present invention means exactly one first polymer (P1) and also a mixture of two or more different first polymers (P1). Preferably, exactly one first polymer (P1) is used.

[0021] The terms "at least one first polymer (P1)" and "first polymer (P1)" according to the present invention are used synonymously and interchangeably throughout the present invention.

[0022] The first polymer (P1) contains repeating units derived from acrylonitrile. Acrylonitrile is a monomer having the structure H2=CH-CN and CAS number 107-13-1. Polyacrylonitrile is also known as prop-2-enenitrile.

[0023] The carbon-carbon double bonds contained in acrylonitrile can react by free radical polymerization. The repeating unit derived from acrylonitrile by free radical polymerization has the following formula:

[0024] [ka]

[0025] Suitable polymers that can be used as the at least one first polymer (P1) in the present invention preferably contain at least 50% by weight, more preferably at least 70% by weight, even more preferably at least 80% by weight, and particularly preferably at least 90% by weight of repeating units derived from acrylonitrile, based on the total weight of the at least one first polymer (P1) contained in the blend (B).

[0026] Another object of the present invention is therefore an alkaline anion exchange membrane precursor (pAAEM), in which the at least one first polymer (P1) comprises at least 50% by weight of repeat units derived from acrylonitrile, based on the total weight of the at least one first polymer (P1) contained in the blend (B).

[0027] Suitable first polymers (P1) that can be used in preferred embodiments of the present invention are acrylonitrile homopolymers and acrylonitrile copolymers.

[0028] If an acrylonitrile copolymer is used as the first polymer (P1), the first polymer (P1) comprises at least 50% by weight, more preferably at least 70% by weight, even more preferably at least 80% by weight, and particularly preferably at least 90% by weight, of repeating units derived from acrylonitrile, based on the total weight of the at least one first polymer (P1) contained in the blend (B).

[0029] When an acrylonitrile copolymer is used as the first polymer (P1), the first polymer (P1) comprises repeating units derived from acrylonitrile and one or more, preferably exactly one, repeating units derived from acrylic acid methyl ester, (meth)acrylic acid methyl ester, and styrene.

[0030] In a preferred embodiment, polyacrylonitrile homopolymer and / or polyacrylonitrile-co-polyacrylic acid methyl ester polymer is used as the first polymer (P1).

[0031] Another object of the present invention is therefore an alkaline anion exchange membrane precursor (pAAEM) according to any one of claims 1 to 5, in which the at least one first polymer (P1) is at least one polymer selected from the group consisting of polyacrylonitrile, polyacrylonitrile-co-polyacrylic acid methyl ester and polystyrene acrylonitrile, polyacrylonitrile and polyacrylonitrile-co-polyacrylic acid methyl ester being particularly preferred.

[0032] The first polymer (P1) preferably has a weight average molecular weight (M) in the range of 30 000 to 1 400 000 g / mol, measured by gel permeation chromatography (GPC) according to GPC part 2: N,N-dimethylacetamide (DMAC) as eluent (ISO 13885-2:2020); German version EN ISO 13885-2:2021. w )

[0033] Second polymer (P2) The expression "at least one second polymer (P2)" according to the present invention means exactly one first polymer (P2) and also a mixture of two or more different second polymers (P2). Preferably, exactly one second polymer (P2) is used.

[0034] The terms "at least one second polymer (P2)" and "second polymer (P2)" according to the present invention are used synonymously and interchangeably throughout the present invention.

[0035] The at least one second polymer (P2) is selected from the group consisting of the at least one second polymer (P2) and the at least one second polymer (P2) represented by the formula (I):

[0036] [ka] (In the formula, n is 3 to 12; m is 0 to 3; R 1 is C1~C 10 -Alkyl, C2-C 10 -alkenyl, aryl or aralkyl, R 2 , R 3 and R 4 are each independently hydrogen, C1 to C 10 -Alkyl, C2-C 10 Preferably, the weight of repeating units derived from at least one monomer of the formula (I) is at least 50% by weight, more preferably at least 70% by weight, even more preferably at least 80% by weight, and particularly preferably at least 90% by weight.

[0037] In a preferred embodiment, the at least one second polymer (P2) preferably comprises at least 50% by weight, more preferably at least 70% by weight, even more preferably at least 80% by weight and particularly preferably at least 90% by weight of repeat units derived from exactly one monomer of formula (I), based on the total weight of the at least one second polymer (P2) contained in blend (B).

[0038] In a preferred embodiment, the at least one second polymer (P2) comprises repeat units derived from at least one monomer of formula (I), wherein n is 3-5.

[0039] In another preferred embodiment, the at least one second polymer (P2) comprises repeat units derived from at least one monomer of formula (I), wherein m is 0.

[0040] In another preferred embodiment, the at least one second polymer (P2) comprises repeat units derived from at least one monomer of formula (I), where R 2 , R 3 and R 4 are each hydrogen.

[0041] In a more preferred embodiment, the at least one second polymer (P2) is at least one monomer selected from the group consisting of N-vinylpyrrolidone (N-vinyl-2-pyrrolidone), N-vinylpiperidone (N-vinyl-2-piperidone) and N-vinylcaprolactam.

[0042] Therefore, another object of the present invention is an alkaline anion exchange membrane precursor (pAAEM), wherein the at least one second polymer (P2) is at least one polymer selected from the group consisting of polyvinylpyrrolidone, polyvinylpiperidone and polyvinylcaprolactam.

[0043] The at least one second polymer (P2) preferably has a solution viscosity characterized by a K value, determined according to the method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932(58)), of 17 to 100, more preferably 28 to 95, particularly preferably 85 to 92.

[0044] In a preferred embodiment, the blend (B) contained in the alkaline anion exchange membrane precursor (pAAEM) has a glass transition temperature (T g )

[0045] In another preferred embodiment, the blend (B) contained in the alkaline anion exchange membrane precursor (pAAEM) has a glass transition temperature (T g )

[0046] Glass transition temperature (T g ) is preferably measured in the second heating cycle by differential scanning calorimetry (DSC) at a heating rate of 10 K / min according to ISO 11357-1 (2017) and 11357-2 (2020).

[0047] Therefore, another object of the present invention is an alkaline anion exchange membrane precursor (pAAEM) according to claim 1, wherein the blend (B) has a glass transition temperature, measured by differential scanning calorimetry (DSC), of at least 100°C.

[0048] In a preferred embodiment, the blend (B) contained in the alkaline anion exchange membrane precursor (pAAEM) contains 1 to 50 wt % of the at least one first polymer (P1) and 50 to 99 wt % of the at least one second polymer (P2) based on the total weight of the at least one first polymer (P1) and the at least one second polymer (P2) contained in the blend (B), preferably based on the total weight of the blend (B).

[0049] Another object of the present invention is therefore an alkaline anion exchange membrane precursor (pAAEM) according to claim 1 or 2, in which blend (B) comprises 1 to 50% by weight of at least one first polymer (P1) and 50 to 99% by weight of at least one second polymer (P2), based on the total weight of the at least one first polymer (P1) and the at least one second polymer (P2) contained in blend (B).

[0050] In a more preferred embodiment, the blend (B) contained in the alkaline anion exchange membrane precursor (pAAEM) contains 10 to 50 wt % of the at least one first polymer (P1) and 50 to 90 wt % of the at least one second polymer (P2) based on the total weight of the at least one first polymer (P1) and the at least one second polymer (P2) contained in the blend (B), preferably based on the total weight of the blend (B).

[0051] In a more preferred embodiment, the blend (B) contained in the alkaline anion exchange membrane precursor (pAAEM) contains 20 to 30 wt % of the at least one first polymer (P1) and 70 to 80 wt % of the at least one second polymer (P2) based on the total weight of the at least one first polymer (P1) and the at least one second polymer (P2) contained in the blend (B), preferably based on the total weight of the blend (B).

[0052] In a preferred embodiment, the alkaline anion exchange membrane precursor (pAAEM) and the alkaline anion exchange membrane (AAEM) obtained therefrom comprise at least one mechanical support to improve the mechanical stability of the alkaline anion exchange membrane precursor (pAAEM) and the alkaline anion exchange membrane (AAEM) obtained therefrom.

[0053] Therefore, another object of the present invention is an alkaline anion exchange membrane precursor (pAAEM) according to any one of claims 1 to 7, which comprises at least one mechanical support.

[0054] The expression "at least one mechanical support" in the present invention means exactly one mechanical support, but also a mixture of two or more different mechanical supports. Preferably, exactly one mechanical support is used.

[0055] The terms "at least one mechanical support" and "mechanical support" in the present invention are used synonymously and interchangeably throughout the present invention.

[0056] When the alkaline anion exchange membrane precursor (pAAEM) comprises a mechanical support, the mechanical support is preferably covered with blend (B).

[0057] The mechanical support is preferably a woven or nonwoven fabric.

[0058] Suitable woven fabrics are preferably selected from the group consisting of woven fabric, woven carbon fiber mat, woven polyacrylonitrile mat, woven polyphenylene sulfide mat, and woven polyolefin fiber mat.

[0059] Preferred woven fabrics are woven polyolefin fiber mats such as woven polyethylene, woven polypropylene fiber mats, woven polyacrylonitrile mats, and / or woven polyphenylene sulfide mats.

[0060] Suitable nonwoven fabrics are preferably selected from the group consisting of nonwoven carbon fiber mats, nonwoven polyacrylonitrile mats, nonwoven polyphenylene sulfide mats, and nonwoven polyolefin fiber mats.

[0061] Preferred nonwovens are nonwoven polyolefin fiber mats such as nonwoven polyethylene, nonwoven polypropylene fiber mats, nonwoven polyacrylonitrile mats and / or nonwoven polyphenylene sulfide mats.

[0062] In a preferred embodiment, the alkaline anion exchange membrane precursor (pAAEM) and the alkaline anion exchange membrane (AAEM) obtained therefrom are gas-tight.

[0063] Therefore, another object of the present invention is that the alkaline anion exchange membrane precursor (pAAEM) is gas-tight.

[0064] The term "gas-tight" means that no gas transport (gas crossover) of hydrogen and oxygen occurs through the alkaline anion exchange membrane precursor (pAAEM) or the alkaline anion exchange membrane (AAEM) in the alkaline aqueous electrolysis cell.

[0065] In another preferred embodiment, the alkaline anion exchange membrane precursor (pAAEM) and the alkaline anion exchange membrane (AAEM) obtained therefrom are monolithic.

[0066] In the context of the present invention, the term "monolithic" means that the alkaline anion exchange membrane precursor (pAAEM) and the alkaline anion exchange membrane (AAEM) obtained therefrom preferably do not have pores.

[0067] In another preferred embodiment, the alkaline anion exchange membrane precursor (pAAEM) has a thickness in the range of 10 to 250 μm, preferably in the range of 20 to 200 μm, more preferably in the range of 20 to 150 μm, and particularly preferably in the range of 20 to 100 μm.

[0068] Therefore, another object of the present invention is an alkaline anion exchange membrane precursor (pAAEM) according to any one of claims 1 to 9, having a thickness in the range of 10 to 250 μm.

[0069] In another preferred embodiment, the alkaline anion exchange membrane precursor (pAAEM) and the alkaline anion exchange membrane precursor (AAEM) obtained therefrom have the form of a flat sheet membrane.

[0070] Preparation of alkaline anion exchange membrane precursor (pAAEM) Another object of the present invention is to provide a process for preparing an alkaline anion exchange membrane precursor (pAAEM), comprising: i) providing a solution (S) comprising at least one first polymer (P1), at least one second polymer (P2) and at least one polar solvent; ii) separating at least one polar solvent from the solution (S) to obtain an alkaline anion exchange membrane precursor (pAAEM).

[0071] In step i), a solution (S) is provided. The solution (S) in step i) can be provided by any method known to those skilled in the art. For example, the solution (S) can be provided in step i) in a conventional container that can be equipped with a stirring device and preferably a temperature control device. Preferably, the solution (S) is provided by dissolving at least one first polymer (P1) and at least one second polymer (P2) in at least one polar solvent.

[0072] Dissolving at least one first polymer (P1) and at least one second polymer (P2) in at least one polar solvent to provide a solution (S) is preferably carried out under stirring.

[0073] Step i) is preferably carried out at elevated temperatures, in particular in the range of 30 to 100° C., more preferably in the range of 40 to 80° C. The skilled person will select the temperature depending on the at least one polar solvent.

[0074] The solution (S) provided in step i) preferably comprises at least one first polymer (P1) and at least one second polymer (P2) completely dissolved in at least one polar solvent. This means that the solution (S) preferably does not contain solid particles of the at least one first polymer (P1) and at least one second polymer (P2). Therefore, the at least one first polymer (P1) and at least one second polymer (P2) preferably cannot be separated from the solution (S) by filtration.

[0075] The solution (S) in step i) preferably contains 40 to 84 wt % of at least one polar solvent and 60 to 16 wt % of polymer (i.e., the sum of the weights of at least one first polymer (P1) and at least one second polymer (P2)), each based on the total weight of the solution (S).

[0076] The amounts of the at least one first polymer (P1) and the at least one second polymer (P2) in the solution (S) provided in step i) are selected so that the alkaline anion exchange membrane precursor (pAAEM) obtained in step ii) comprises a blend (B) having the above amounts of the at least one first polymer (P1) and the at least one second polymer (P2), taking into account the blend (B).

[0077] As the at least one polar solvent, any polar solvent known to the person skilled in the art for the at least one first polymer (P1) and for the at least one second polymer (P2) is suitable.

[0078] In a preferred embodiment, the at least one polar solvent is at least one aprotic polar solvent.

[0079] Preferably, the at least one polar solvent is soluble in water. Thus, the at least one solvent is preferably selected from the group consisting of N-alkyl-2-pyrrolidone, preferably N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-butyl-2-pyrrolidone and N-tert-butyl-2-pyrrolidone, 2-pyrrolidone, N-dimethylacetamide, dimethyl sulfoxide, dimethylformamide, N,N-dimethyl-2-hydroxypropanamide, N,N-diethyl-2-hydroxypropanamide, γ-valerolactone, dihydrolevoglucosenone, methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate and sulfolane.

[0080] N-Alkyl-2-pyrrolidone, γ-valerolactone and N-dimethylacetamide are particularly preferred, and N-methylpyrrolidone and N-dimethylacetamide are most preferred as the at least one polar solvent.

[0081] The solution (S) preferably contains the weight of at least one solvent in the range of 40 to 84% by weight, more preferably the weight of at least one polar solvent in the range of 50 to 70% by weight, based on the total weight of the solution (S).

[0082] The duration of step i) can vary within a wide range. The duration of step i) is preferably in the range of 10 minutes to 48 hours (hours), in particular in the range of 10 minutes to 24 hours, more preferably in the range of 15 minutes to 12 hours. The skilled person will select the duration of step i) so as to obtain a homogeneous solution of at least one first polymer (P1) and at least one second polymer (P2) in at least one polar solvent.

[0083] In step ii), the at least one polar solvent (D) is separated from the solution (S) to obtain an alkaline anion exchange membrane precursor (pAAEM).

[0084] After filtering the solution (S) provided in step i), in step ii) it is possible to separate the at least one polar solvent from the solution (S) to obtain a filtered solution (fS).

[0085] The following embodiments and preferred forms for separating at least one polar solvent from the solution (S) apply equally to the case of separating at least one polar solvent from the filtered solution (fS).

[0086] Furthermore, after degassing the solution (S) provided in step i), it is possible to separate at least one polar solvent from the solution (S) in step i) to obtain a degassed solution (dS). This embodiment is preferred. The following embodiments and preferred forms for separating at least one polar solvent from the solution (S) are equally applicable to the case of separating at least one polar solvent from the degassed solution (dS).

[0087] Degassing of solution (S) in step i) can be carried out by any method known to those skilled in the art, for example by vacuum, by ultrasonic treatment or by leaving solution (S) to stand.

[0088] The separation of the at least one polar solvent from the solution (S) can be carried out by any method known to those skilled in the art that is suitable for separating solvents from polymers.

[0089] Preferably, the separation of the at least one polar solvent from the solution (S) is carried out by a phase inversion process.

[0090] Therefore, another object of the present invention is also a process for the preparation of an alkaline anion exchange membrane precursor (pAAEM), wherein the separation of at least one polar solvent in step ii) is carried out by a phase inversion process.

[0091] A phase inversion process within the context of the present invention means a process in which at least one dissolved first polymer (P1) and at least one dissolved second polymer (P2) are converted into a solid phase, which solid phase comprises the blend (B).

[0092] Therefore, the phase inversion process can also be called a precipitation process. According to step ii), the conversion is carried out by separating at least one polar solvent from at least one first polymer (P1) and at least one second polymer (P2). Those skilled in the art are aware of suitable phase inversion processes.

[0093] The phase inversion process can be carried out, for example, by cooling the solution (S), during which the at least one first polymer (P1) and the at least one second polymer (P2) contained in the solution (S) precipitate to form the blend (B).

[0094] In a preferred embodiment, step ii) comprises the following steps: ii-1) casting the solution (S) provided in step i) to obtain a film of the solution (S); ii-2) A step of separating at least one polar solvent from the film of the solution (S) obtained in step ii-1) to obtain an alkaline anion exchange membrane precursor (pAAEM) in the form of a film.

[0095] The separation in step ii-2) is preferably carried out by evaporating at least one polar solvent from the film of solution (S).

[0096] The evaporation of the at least one solvent is preferably carried out under reduced pressure and at elevated temperatures in the range of 30 to 100°C.

[0097] Thus, in a particularly preferred embodiment, step ii) comprises the following steps: ii-1) casting the solution (S) provided in step i) to obtain a film of the solution (S); ii-2) A step of evaporating at least one polar solvent from the film of the solution (S) obtained in step ii-1) to obtain an alkaline anion exchange membrane precursor (pAAEM) in the form of a film.

[0098] This means that the alkaline anion exchange membrane precursor (pAAEM) is formed by evaporating at least one polar solvent from a film of solution (S).

[0099] In step ii-1), the solution (S) can be cast by any method known to those skilled in the art. Typically, the solution (S) is cast using a casting knife, a caster bar, a Mayer bar, a slot die, or a reverse roll that is heated to a temperature in the range of 20 to 150°C, preferably in the range of 40 to 100°C, more preferably in the range of 60 to 85°C.

[0100] In step ii-1), the solution (S) is preferably cast onto a substrate (carrier material) that does not react with the at least one first polymer (P1) and the at least one second polymer (P2) and / or the at least one polar solvent contained in the solution (S).

[0101] Suitable substrates (carrier materials) are, for example, steel belts, drying cylinders or polymer films. The substrate (carrier material) is generally not part of the finished alkaline anion exchange membrane precursor (pAAEM) and is used solely for processing purposes.

[0102] It is also possible to cast the solution (S) onto a porous support layer that will become part of the alkaline anion exchange membrane precursor (pAAEM).

[0103] After step ii), the alkaline anion exchange membrane precursor (pAAEM) can be further processed. The alkaline anion exchange membrane precursor (pAAEM) can be washed, for example, with water.

[0104] Alkaline Anion Exchange Membrane (AAEM) Another object of the present invention is an alkaline anion exchange membrane (AAEM) obtained from an alkaline anion exchange membrane precursor (pAAEM). For the alkaline anion exchange membrane (AAEM), the descriptions and preferred embodiments regarding the alkaline anion exchange membrane precursor (pAAEM) are applied accordingly.

[0105] In a preferred embodiment, the alkaline anion exchange membrane (AAEM) is obtained by contacting an alkaline anion exchange membrane precursor (pAAEM) with an alkaline aqueous solution.

[0106] Therefore, another object of the present invention is an alkaline anion exchange membrane (AAEM) obtained by contacting an alkaline anion exchange membrane precursor (pAAEM) with an alkaline aqueous solution.

[0107] In a preferred embodiment, the alkaline anion exchange membrane (AAEM) is obtained from the alkaline anion exchange membrane precursor (pAAEM) by immersion in an alkaline aqueous solution having a temperature in the range of 20 to 99°C, more preferably in the range of 50 to 95°C, for a time in the range of 1 minute to 10 hours, preferably 10 minutes to 4 hours.

[0108] The alkaline aqueous solution may contain an alkali metal hydroxide and / or an alkaline earth hydroxide. Preferably, the alkaline aqueous solution contains an alkali hydroxide. Among the alkali hydroxides, sodium hydroxide (NaOH) and potassium hydroxide (KOH) are particularly preferred. Potassium hydroxide (KOH) is most preferred.

[0109] The concentration of the aqueous alkali hydroxide solution is preferably in the range of 1 to 10 mol / l, and more preferably in the range of 4 to 8 mol / l.

[0110] When an alkaline aqueous solution containing potassium hydroxide (KOH) is used, the concentration of this solution is preferably in the range of 15 to 40% by weight, more preferably in the range of 15 to 35% by weight.

[0111] Therefore, another object of the present invention is a process for preparing an alkaline anion exchange membrane (AAEM), comprising the step of contacting an anion exchange membrane precursor (pAAEM) with an alkaline aqueous solution.

[0112] In a preferred embodiment, the alkaline anion exchange membrane (AAEM) has a resistance of 0.2 ohm cm in 6 M potassium hydroxide solution at a temperature of 20° C. 2 The film has a specific resistance of less than 0.25 cm 2 The membrane was sandwiched between two gold electrodes. The cell was closed with a torque of 4 Nm, and the conductivity was determined from the impedance spectrum at a phase angle of 0 degrees. The membrane was measured by soaking the film overnight in either a 20 wt % or 30 wt % KOH aqueous solution at room temperature, then either removing it directly from the KOH solution or post-treating it by dipping or immersing it in DI water. The conductivity was determined from the area-specific resistivity determined by this method and the thickness measured with a micrometer.

[0113] Another object of the present invention is the use of an alkaline anion exchange membrane (AAEM) in an alkaline water electrolysis cell.

[0114] Another object of the present invention is a process for the preparation of hydrogen using an alkaline anion exchange membrane (AAEM).

[0115] The present invention will be further elucidated by the following examples, but is not limited thereto. [Example]

[0116] The ingredients used, a first polymer (P1), P1a: Polyacrylonitrile homopolymer with a weight average molecular weight (Mw) of 200,000 g / mol (Dolanit® H-PAN; manufactured by Dolan GmbH) P1b: Polyacrylonitrile-co-polyacrylic acid methyl ester polymer (Dolanit® N-PAN; manufactured by Dolan GmbH) with a weight average molecular weight (Mw) of 80 000 g / mol.

[0117] a second polymer (P2), P2a: molecular weight M of 1,000,000 to 1,500,000 g / mol w and polyvinylpyrrolidone having a solution viscosity characterized by a K value of 90 determined according to the method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932(58)), abbreviated as "K90" (Luvitec® K90 from BASF SE).

[0118] Comparative diaphragms and comparative membrane materials, A membrane comprising polyphenylene sulfide coated with zirconium dioxide (Zirfon® UTP500 membrane from Agfa Gevert NV, Mortsel, Belgium). P1v: Polyethersulfone (Ultrason® E 6020 P from BASF SE) with a glass transition temperature (DSC, 10° C. / min; according to ISO 11357-1 / -2) of 225° C. and a weight average molecular weight (Mw) of 75,000 g / mol.

[0119] Preparation of alkaline anion exchange membrane (AAEM), General Procedures A polymer solution for membrane preparation was prepared containing 5 wt. % of the first polymer (P1a, P1b, or P1v) and 15 wt. % of the second polymer (P2a) dissolved in 80 wt. % N-methyl-2-pyrrolidone (NMP). The polymer solution was homogenized in a Speed ​​Mixer™ DAC 600.1 Vac-P (Hauschild & Co. KG, Hamm, Germany) at speeds of 200, 800, and 1200 rpm within a 30-minute mixing time. Prior to membrane casting, the polymer solution was characterized by dynamic viscosity measurement (Brookfield DI-prime, RV6 spindle, 20 rpm, 60°C).

[0120] To prepare flat-sheet alkaline anion-exchange membrane precursors (pAAEMs), the polymer solutions were spread onto glass substrates at 300 μm thickness at 5 mm / s (0.3 m / min) using a casting knife (Coatmaster 510, Erichsen GmbH & Co. KG, Hemer, Germany) at 60° C. and subsequently dried under vacuum at 50° C. The films were then transferred to a water bath, peeled off from the glass plates, and stored in water.

[0121] For the preparation of alkaline anion exchange membrane (AAEM), alkaline anion exchange membrane precursor (pAAEM) was immersed in a 30 wt % aqueous potassium hydroxide solution.

[0122] The film thicknesses of the alkaline anion exchange membrane precursor (pAAEM) and alkaline anion exchange membrane (AAEM) were measured with a Mitutoyo ID-C112XB (Mitutoyo Corporation, Kawasaki, Japan).

[0123] After storing in a 30 wt% potassium hydroxide aqueous solution at 80°C for 14 days, the electrical resistance (EIS: [ohm]), conductivity (C: [mS / cm]) and specific resistance (R: [ohm cm 2 The results are shown in Table 2.

[0124] Table 1 shows the viscosity of the polymer solution before casting, the film thickness of the alkaline anion exchange membrane precursor (pAAEM), and the alkaline stability.

[0125] [Table 1]

[0126] [Table 2]

[0127] The alkaline anion exchange membrane (AAEM) of the present invention has significantly lower resistance compared to commercially available membrane materials such as Zirfon® UTP500.

[0128] A scanning electron micrograph (SEM cross section) of the pAAEM membrane of Example 1 (magnification: 5000 times) is shown in FIG.

Claims

1. An alkaline anion exchange membrane precursor (pAAEM) comprising a blend (B) of at least one first polymer (P1) comprising repeating units derived from acrylonitrile and at least one second polymer (P2) comprising repeating units derived from vinyl lactam.

2. 2. The alkali anion exchange membrane precursor (pAAEM) of claim 1, wherein the blend (B) has a glass transition temperature of at least 100° C. measured in the second heating cycle by differential scanning calorimetry (DSC) at a heating rate of 10 K / min according to ISO 11357-1 (2017) and 11357-2 (2020).

3. 3. The alkaline anion exchange membrane precursor (pAAEM) according to claim 1 or 2, wherein the blend (B) comprises 1 to 50 wt % of the at least one first polymer (P1) and 50 to 99 wt % of the at least one second polymer (P2), based on the total weight of the at least one first polymer (P1) and the at least one second polymer (P2) contained in the blend (B).

4. The alkali anion exchange membrane precursor (pAAEM) according to any one of claims 1 to 3, wherein the at least one first polymer (P1) comprises at least 50 wt% of repeating units derived from acrylonitrile, based on the total weight of the at least one first polymer (P1) contained in the blend (B).

5. The at least one second polymer (P2) is selected from the group consisting of a hydroxyl group, ... 【Chemistry 1】 (In the formula, n is 3 to 12; m is 0 to 3; R １ is C １ ~C １０ -Alkyl, C ２ ~C １０ alkenyl, aryl or aralkyl, R ２ , R ３ and R ４ are each independently hydrogen, C １ ~C １０ -Alkyl, C ２ ~C １０ 5. The alkaline anion exchange membrane precursor (pAAEM) according to claim 1, comprising at least 50% by weight of repeating units derived from at least one monomer of the formula (I) - alkenyl, aryl or aralkyl.

6. The alkaline anion exchange membrane precursor (pAAEM) according to any one of claims 1 to 5, wherein the at least one first polymer (P1) is at least one polymer selected from the group consisting of polyacrylonitrile and polyacrylonitrile-co-polyacrylic acid methyl ester.

7. The alkali anion exchange membrane precursor (pAAEM) according to any one of claims 1 to 6, wherein the at least one second polymer (P2) is at least one polymer selected from the group consisting of polyvinylpyrrolidone, polyvinylpiperidone and polyvinylcaprolactam.

8. The alkaline anion exchange membrane precursor (pAAEM) according to any one of claims 1 to 7, wherein said alkaline anion exchange membrane precursor (pAAEM) comprises at least one mechanical support.

9. The alkaline anion exchange membrane precursor (pAAEM) according to any one of claims 1 to 8, wherein the alkaline anion exchange membrane precursor (pAAEM) is airtight.

10. The alkaline anion exchange membrane precursor (pAAEM) according to any one of claims 1 to 9, wherein the alkaline anion exchange membrane precursor (pAAEM) has a thickness in the range of 10 to 250 µm.

11. A process for preparing the alkaline anion exchange membrane precursor (pAAEM) according to any one of claims 1 to 10, comprising: i) providing a solution (S) comprising said at least one first polymer (P1), said at least one second polymer (P2), and at least one polar solvent; ii) separating the at least one polar solvent from the solution (S) to obtain the alkaline anion exchange membrane precursor (pAAEM).

12. An alkaline anion exchange membrane (AAEM) obtained by contacting the alkaline anion exchange membrane precursor (pAAEM) according to any one of claims 1 to 10 with an alkaline aqueous solution.

13. The alkaline anion exchange membrane (AAEM) has a specific resistance of 0.2 ohm cm in 6 M potassium hydroxide solution at a temperature of 20°C. ２ 13. The alkaline anion exchange membrane (AAEM) of claim 12, having a resistivity of less than 1000 .mu.m.

14. An alkaline water electrolysis cell comprising the alkaline anion exchange membrane (AAEM) of claim 12 or 13.

15. A process for the preparation of hydrogen, using the alkaline anion exchange membrane (AAEM) according to claim 12 or 13.

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