Use of a membrane (m) comprising a poly(ether nitrile) polymer (PEN) in a membrane humidifier (MH) for fuel cells (FCS)

Abstract

The present invention relates to the use of a membrane (M) in a membrane humidifier (MH) for fuel cells (FCs), wherein the membrane (M) comprises a poly(ether nitrile) polymer (PEN). The poly(ether nitrile) polymer (PEN) is prepared by a process comprising the step I) converting a reaction mixture (RG) comprising as components (A) at least one benzonitrile compound according to formula (I), (B1a) at least one first non-sulfonated aromatic dihydroxy compound according to formula (II), (B1b) optionally at least one second non-sulfonated aromatic dihydroxy compound according to formula (III), (B2) optionally at least one sulfonated aromatic dihydroxy component according to formula (IV), (C) at least one carbonate component, and (D) at least one aprotic polar solvent.

Description

[0001] Use of a membrane (M) comprising a poly(ether nitrile) polymer (PEN) in a membrane humidifier (MH) for fuel cells (FCs)

[0002] Description

[0003] The present invention relates to the use of a membrane (M) in a membrane humidifier (MH) for fuel cells (FCs), wherein the membrane (M) comprises a poly(ether nitrile) polymer (PEN). The poly(ether nitrile) polymer (PEN) is prepared by a process comprising the step I) converting a reaction mixture (RG) comprising as components (A) at least one benzonitrile compound according to formula (I), (B1 a) at least one first non-sulfonated aromatic dihydroxy compound according to formula (II), (B1 b) optionally at least one second non-sulfonated aromatic dihydroxy compound according to formula (III), (B2) optionally at least one sulfonated aromatic dihydroxy component according to formula (IV), (C) at least one carbonate component, and (D) at least one aprotic polar solvent.

[0004] A fuel cell (FC) is a power generation cell that combines hydrogen and oxygen to generate electricity. Such a fuel cell (FC) has advantages in that it is possible to continuously generate electricity as long as hydrogen and oxygen are supplied, unlike a general chemical cell, and in that there is no heat loss. In addition, the fuel cell (FC) directly converts chemical energy generated by combination of hydrogen and oxygen into electrical energy, whereby the volume of a discharged pollutant is small. As a result, the fuel cell (FC) is environmentally friendly and a concern about depletion of resources due to an increase in energy consumption can be reduced.

[0005] There are different types of fuel cells (FCs), whereby the polymer electrolyte membrane fuel cell (PEMFC) is known as being the most favourable to a transportation system as well as small-scale stationary power generation equipment, since the polymer electrolyte membrane fuel cell (PEMFC) is operated at a lower temperature than the other fuel cells (FCs) and the output density of the polymer electrolyte membrane fuel cell (PEMFC) is high, whereby it is possible to miniaturize the polymer electrolyte membrane fuel cell (PEMFC).

[0006] One of the most important factors to maintain the performance of a polymer electrolyte membrane fuel cell (PEMFC) is to supply a predetermined amount of moisture to a polymer electrolyte membrane (PEM) (also referred to as a proton exchange membrane) of a membrane electrode assembly (MEA) in order to retain moisture content. The reason for this is that, in the case in which the polymer electrolyte membrane (PEM) becomes dry, its ability to conduct protons is lowered and as consequence power generation efficiency is reduced.

[0007] One method to supply a predetermined amount of moisture to a polymer electrolyte membrane (PEM) is the membrane humidification method, wherein water vapor is provided to a gas that is supplied to the polymer electrolyte membrane (PEM) using a membrane configured to selectively transmit only water vapor included in an exhaust gas in order to humidify the polymer electrolyte membrane (PEM). This method shows the advantage that it is possible to reduce the weight and size of a humidifier. The used selective membranes are preferably hollow fibre membranes which have a high index of permeation area per unit volume in case of module formation. As materials for the hollowfibre membranes perfluorinated sulfonic acid polymers (PFSA), polyimides or polyarylsulfones such as polyethersulfone (PESU) or polysulfone (PSU) are used.

[0008] US 2021 / 0154624 A1 , for example, discloses a composite hollow fiber membrane for a fuel cell membrane humidifier, wherein the composite hollow fiber membrane comprises: a hollow fiber membrane; and a pollutant entrapping layer coated on an inner surface of the hollow fiber membrane, the pollutant entrapping layer being configured to remove a pollutant from air flowing along a lumen of the hollow fiber membrane, the pollutant comprising nitrogen oxide, sulfur oxide, ammonia, or a mixture of two or more thereof. The hollow fiber membrane may include polyethersulfone and the pollutant entrapping layer may include poly(perfluorosulfonic acid).

[0009] US 2023 / 0323567 A1 discloses a hollow fiber membrane material for a high-humidification hydrogen fuel cell humidifier and a preparation method and application thereof. The preparation method includes mixing and dissolving sulfonated polyarylene ether nitrile resin, a pore-forming agent, a modified nano-filler and a solvent for still standing; performing vacuumizing; coagulating a spinning fluid in an internal coagulant bath and an external coagulant bath; and washing and drying an obtained crude product to obtain the hollow fiber membrane material.

[0010] Nevertheless, the membranes of the state of the art used in membrane humidifiers often show a dissatisfying selectivity and oxidation stability.

[0011] The object of the present invention therefore was to provide an improved membrane (M) which can be used in a membrane humidifier (MH) for fuel cells (FCs). The membrane (M) should be chemically and mechanically stable and easy to produce at relatively low costs. In addition, it should show a high water-vapor transmission.

[0012] This object is achieved by the use of a membrane (M) in a membrane humidifier (MH) for fuel cells (FCs), wherein the membrane (M) comprises a poly(ether nitrile) polymer (PEN) and the poly(ether nitrile) polymer (PEN) is prepared by a process comprising the step

[0013] I) converting a reaction mixture (RG) comprising as components

[0014] (A) at least one benzonitrile compound according to formula (I) wherein X1and X2are independently selected from a halogen, and

[0015] X3is H or a halogen,

[0016] (B1 a) at least one first non-sulfonated aromatic dihydroxy compound according to formula (II) wherein

[0017] R1and R2are independently selected from H, nitro and OR, wherein R is selected from Ci-Ce alkyl and C6-C12 aryl, and

[0018] X is a direct bond or 0,

[0019] (B1 b) optionally at least one second non-sulfonated aromatic dihydroxy compound according to formula (III) wherein

[0020] R3and R4are independently selected from H, nitro and OR, wherein R is selected from Ci-Ce alkyl and C6-C12 aryl,

[0021] (B2) optionally at least one sulfonated aromatic dihydroxy component according to formula (IV) wherein

[0022] R5is selected from H, halogen, nitro and OR, wherein R is selected from Ci-Ce alkyl and C6-C12 aryl, and

[0023] Y is H, Na or K,

[0024] (C) at least one carbonate component, and

[0025] (D) at least one aprotic polar solvent.

[0026] This object is further achieved by the use of a membrane (M) in a membrane humidifier (MH) for fuel cells (FCs), wherein the membrane (M) comprises a poly(ether nitrile) polymer (PEN) and the poly(ether nitrile) polymer (PEN) is prepared by a process comprising the step

[0027] I) converting a reaction mixture (RG) comprising as components

[0028] (A) at least one benzonitrile compound according to formula (I) wherein

[0029] X1and X2are independently selected from a halogen, and

[0030] X3is H or a halogen, (B1 a) at least one first non-sulfonated aromatic dihydroxy compound according to formula (II) wherein

[0031] R1and R2are independently selected from H, nitro and OR, wherein R is selected from Ci-Ce alkyl and C6-C12 aryl, and

[0032] X is a direct bond or 0,

[0033] (B1 b) at least one second non-sulfonated aromatic dihydroxy compound according to formula (III) wherein

[0034] R3and R4are independently selected from H, nitro and OR, wherein R is selected from Ci-Ce alkyl and C6-C12 aryl,

[0035] (B2) optionally at least one sulfonated aromatic dihydroxy component according to formula (IV) wherein

[0036] R5is selected from H, halogen, nitro and OR, wherein R is selected from Ci-Ce alkyl and Ce-

[0037] C12 aryl, and

[0038] Y is H, Na or K, (C) at least one carbonate component, and

[0039] (D) at least one aprotic polar solvent, wherein component (B1 b) is hydroquinone.

[0040] It has surprisingly been found that a membrane (M) comprising a poly(ether nitrile) polymer (PEN), wherein the poly(ether nitrile) polymer (PEN) is prepared by a process comprising step I), can successfully be used in a a membrane humidifier (MH) for fuel cells (FCs).

[0041] The membrane (M) shows a higher or comparable water vapor transmission and a higher oxidative stability at 80 to 90 °C compared to the water vapor transmission and oxidative stability of commercial membranes used in membrane humidifiers (MH) for fuel cells (FCs).

[0042] A further advantage of the inventive membranes (M) is their much lower production costs compared to the production costs of, for example, Nation® membranes.

[0043] The present invention will be described in more detail hereinafter.

[0044] Process for the nitril

[0045] The process for the preparation of the poly(ether nitrile) polymer (PEN) comprises step I) converting a reaction mixture (RG) comprising component (A), component (B1 a), optionally component (B1 b), optionally component (B2), component (C) and component (D) described above.

[0046] The components (A), (B1 a), optionally (B1 b) and optionally (B2) enter a polycondensation reaction.

[0047] Component (D) acts as a solvent and component (C) acts as a base to deprotonate components (B1 a), optionally (B1 b) and optionally (B2) during the condensation reaction.

[0048] The reaction mixture (RG) is understood to mean the mixture that is used according to the present invention for preparing the poly(ether nitrile) polymer (PEN). In the present case all details given with respect to the reaction mixture (RG) thus, relate to the mixture that is present prior to the polycondensation. The polycondensation takes place during the process in which the reaction mixture (RG) reacts by polycondensation of components (A), (B1 a), optionally (B1 b) and optionally (B2) to give the target product, the poly(ether nitrile) polymer (PEN). The mixture obtained after the polycondensation which comprises the poly (ether nitrile) polymer (PEN) target product is also referred to as product mixture (PG). The product mixture (PG) usually furthermore comprises the at least one aprotic polar solvent (component (D)) and a halide compound. The halide compound is formed during the conversion of the reaction mixture (RG). During the conversion first, component (C) reacts with component (B1 a) and / or optionally component (B1 b) and / or optionally component (B2) to deprotonate component (B1 a) and / or optionally component (B1b) and / or optionally component (B2). Deprotonated components (B1 a), optionally (B1 b) and / or optionally (B2) then react with component (A), wherein the halide compound is formed. This process is known to the person skilled in the art.

[0049] The components of the reaction mixture (RG) are generally reacted concurrently. The individual components may be mixed in an upstream step and subsequently be reacted. It is also possible to feed the individual components into a reactor in which these are mixed and then reacted.

[0050] In the process, the individual components of the reaction mixture (RG) are generally reacted concurrently in step I). This reaction is preferably conducted in one stage. This means, that the deprotonation of component (B1 a) and / or optionally (B1 b) and / or optionally component (B2) and also the condensation reaction between components (A), (B1 a), optionally (B1 b) and optionally (B2) takes place in a single reaction stage without isolation of the intermediate products, for example the deprotonated species of component (B1 a) and / or optionally (B1 b) and / or optionally (B2).

[0051] The process according to step I) of the invention is carried out according to the so called “carbonate method”. The process is not carried out according to the so called “hydroxide method”. This means, that the process according to the invention is not carried out in two stages with isolation of phenolate anions. Therefore, in a preferred embodiment, the reaction mixture (RG) is essentially free from sodium hydroxide and potassium hydroxide. More preferably, the reaction mixture (RG) is essentially free from alkali metal hydroxides and alkali earth metal hydroxides.

[0052] The term “essentially free” in the present case is understood to mean that the reaction mixture (RG) comprises less than 100 ppm, preferably less than 50 ppm of sodium hydroxide and potassium hydroxide, preferably of alkali metal hydroxides and alkali earth metal hydroxides, based on the total weight of the reaction mixture (RG).

[0053] It is furthermore preferred that the reaction mixture (RG) does not comprise toluene. It is particularly preferred that the reaction mixture (RG) does not comprise any substance which forms an azeotrope with water.

[0054] Another object of the present invention is therefore also a use wherein the reaction mixture (RG) does not comprise any substance which forms an azeotrope with water.

[0055] The ratio of component (A), component (B1 a), optionally component (B1 b) and optionally component (B2) derives in principle from the stoichiometry of the polycondensation reaction which proceeds with theoretical elimination of hydrogen chloride and is established by the person skilled in the art in a known manner.

[0056] Preferably, the molar ratio of component (A) to components (B1 a), optionally (B1 b) and optionally (B2) is 1.

[0057] Preferably, the conversion in the polycondensation reaction is at least 0.9. Process step I) for the preparation of the poly(ether nitrile) polymer (PEN) is typically carried out under conditions of the so called “carbonate method”. This means that the reaction mixture (RG) is reacted under the conditions of the so called “carbonate method”. The reaction (polycondensation reaction) is generally conducted at temperatures in the range from 80 to 250 °C, preferably in the range from 100 to 220 °C. The upper limit of the temperature is determined by the boiling point of the at least one aprotic polar solvent (component (D)) at a pressure in the range from 200 to 400 mbar. The reaction is preferably carried out over a time interval of 5 min to 4 h.

[0058] The isolation of the poly (ether nitrile) polymer (PEN) obtained in the process according to the present invention in the product mixture (PG) may be carried out for example by precipitation of the product mixture (PG) in water, in an alcohol or mixtures of water with an alcohol. Preferably, the isolation of the obtained poly(ether nitrile) polymer (PEN) is carried out by precipitation of the product mixture (PG) in water. The precipitated poly(ether nitrile) polymer (PEN) can subsequently be extracted with water and then be dried. In one embodiment of the invention, the precipitate can also be taken up in an acidic medium. Suitable acids are for example organic or inorganic acids for example carboxylic acid such as acetic acid, propionic acid, succinic acid or citric acid and mineral acids such as hydrochloric acid, sulfuric acid or phosphoric acid.

[0059] It is possible to filter the product mixture (PG) after step I). The halide compound can thereby be removed.

[0060] The present invention therefore also provides a use wherein the process furthermore comprises step

[0061] II) filtration of the product mixture (PG) obtained in step I).

[0062] In a preferred embodiment, the reaction mixture (RG) comprises component (A) in an amount of 50 mol-%, component (B1 a) in an amount of from 25 to 50 mol-%, preferably of from 30 to 45 mol-%, component (B1 b) in an amount of from 0 to 17.5 mol-%, preferably of from 4 to 15 mol-%, and component (B2) in an amount of from 0 to 7.5 mol-%, preferably of from 1 to 5 mol-%, based on the sum of the mol-% of components (A), (B1 a), (B1 b) and (B2).

[0063] In another preferred embodiment, the reaction mixture (RG) comprises component (A) in an amount of 50 mol-%, component (B1 a) in an amount of from 30 to 45 mol-%, component (B1 b) in an amount of from 5 to 20 mol-%, and component (B2) in an amount of from 0 to 7.5 mol-%, based on the sum of the mol-% of components (A), (B1 a), (B1 b) and (B2).

[0064] Therefore, another object of the present invention is also a use wherein the reaction mixture (RG) comprises component (A) in an amount of 50 mol-%, component (B1 a) in an amount of from 25 to 50 mol-%, component (B1 b) in an amount of from 0 to 17.5 mol-%, and component (B2) in an amount of from 0 to 7.5 mol-%, based on the sum of the mol-% of components (A), (B1 a), (B1 b) and (B2).

[0065] Component (A)

[0066] The reaction mixture (RG) comprises as component (A) at least one benzonitrile compound according to formula (I) wherein

[0067] X1and X2are independently selected from a halogen, and

[0068] X3is H or a halogen.

[0069] The term “at least one benzonitrile compound according to formula (I)” in the present case, is understood to mean exactly one benzonitrile compound according to formula (I) and also mixtures of two or more benzonitrile compounds according to formula (I).

[0070] The bonding lines in formula (I) with which the substituents CN, X2and X3are linked to the benzene ring, and which extend into the benzene ring, in the present case, are understood to mean that the substituents CN, X2and X3can have any possible position on the benzene ring.

[0071] The at least one benzonitrile compound according to formula (I) (component (A)) is preferably selected from the group consisting of 2,6-dichloro-benzonitrile, 2,6-difluoro-benzonitrile, 2,5-dichloro-benzonitrile, 2,4-dichloro-benzonitrile, 2,3- dichloro-benzonitrile, 3,5-dichloro-benzonitrile and 3-bromo-2,6-difluoro-benzonitrile. 2,6-dichloro-benzonitrile is particularly preferred as component (A). Another object of the present invention is therefore also a use wherein component (A) is 2,6-d ichloro-benzon itrile.

[0072] Component (A) is preferably used as a monomer. This means that the reaction mixture (RG) comprises component (A) preferably as a monomer and not as a prepolymer.

[0073] In a particularly preferred embodiment, component (A) comprises at least 80 % by weight, preferably at least 90 % by weight, more preferably at least 98 % by weight, of at least one benzonitrile compound according to formula (I) selected from the group consisting of 2,6-dichloro-benzonitrile, 2,6-difluoro-benzonitrile, 2,5-dichloro-benzonitrile, 2,4-dichloro- benzonitrile, 2,3-dichloro-benzonitrile, 3,5-dichloro-benzonitrile and 3-bromo-2,6-difluoro-benzonitrile, based on the total weight of component (A) in the reaction mixture (RG).

[0074] In a further particularly preferred embodiment, component (A) consists essentially of at least one benzonitrile compound according to formula (I) selected from the group consisting of 2,6-dichloro-benzonitrile, 2,6-difluoro- benzonitrile, 2,5-dichloro-benzonitrile, 2,4-dichloro-benzonitrile, 2,3-dichloro-benzonitrile, 3,5-dichloro-benzonitrile and 3-bromo-2,6-difluoro-benzonitrile.

[0075] “Consisting essentially of’, in the present case is understood to mean that component (A) comprises more than 99 % by weight, preferably more than 99.5 % by weight, particularly preferably more than 99.9 % by weight of at least one benzonitrile compound according to formula (I) selected from the group consisting of 2,6-dichloro-benzonitrile, 2,6- difluoro-benzonitrile, 2,5-dichloro-benzonitrile, 2,4-dichloro-benzonitrile, 2,3-dichloro-benzonitrile, 3,5-dichloro- benzonitrile and 3-bromo-2,6-difluoro-benzonitrile, based in each case on the total weight of component (A) in the reaction mixture (RG). In these embodiments, 2,6-dichloro-benzonitrile is particularly preferred as component (A).

[0076] In a further preferred embodiment, component (A) consists of 2,6-dichloro-benzonitrile.

[0077] Component (B1 a)

[0078] The reaction mixture (RG) comprises as component (B1 a) at least one non-sulfonated aromatic dihydroxy compound according to formula (II)

[0079] Wherein

[0080] R1and R2are independently selected from H, nitro and OR, wherein R is selected from Ci-Ce alkyl and C6-C12 aryl, and is a direct bond or 0. The term “at least one non-sulfonated aromatic dihydroxy compound according to formula (II)” in the present case, is understood to mean exactly one non-sulfonated aromatic dihydroxy compound according to formula (II) and also mixtures of two or more non-sulfonated aromatic dihydroxy compounds according to formula (II). Preferably, component (B1 a) means precisely one non-sulfonated aromatic dihydroxy compound according to formula (II).

[0081] “Non-sulfonated” within the context of the present invention means that the non-sulfonated aromatic dihydroxy component (B1 a) does not comprise any -SO2X group, wherein X is selected from the group consisting of Cl and O- combined with one cation equivalent.

[0082] “One cation equivalent” within the context of the present invention means one cation of a single positive charge or one charge equivalent of a cation with two or more positive charges, for example, H+, Li+, Na+, K+, Mg2+, Ca2+or NHT.

[0083] The at least one non-sulfonated aromatic dihydroxy compound according to formula (II) may here be used in pure form or as a technical-grade product, which may comprise up to 2 wt%, preferably up to 1 wt% and more preferably up to 0.5 wt% of impurities, all based on the overall weight of the at least one non-sulfonated aromatic dihydroxy compound according to formula (II). Any impurities present are included in the wt% percentages relating to component (B1 a).

[0084] Since the reaction mixture (RG) comprises at least one carbonate component (C), the hydroxyl groups of component (B1 a) in the reaction mixture (RG) may be present partially in deprotonated form.

[0085] Component (B1 a) is preferably used as a monomer. This means that the reaction mixture (RG) comprises component (B1 a) preferably as monomer and not as prepolymer.

[0086] The bonding lines in formula (II) with which the substituents R1, X, R2and OH are each linked to a benzene ring, and which each extend into a benzene ring, in the present case, are understood to mean that the substituents R1, X, R2and OH can have any possible position on the respective benzene ring.

[0087] Preferably, component (B1 a) is 4, 4’ -dihydroxybiphenyl.

[0088] Another object of the present invention is therefore also a use wherein component (B1 a) is 4, 4’ -dihydroxybiphenyl.

[0089] In a preferred embodiment, component (B1 a) comprises not less than 80 wt%, preferably not less than 90 wt% and more preferably not less than 98 wt% of a non-sulfonated aromatic dihydroxy compound according to formula (II), based on the overall weight of component (B1 a) in reaction mixture (RG).

[0090] In a further particularly preferred embodiment, component (B1 a) consists essentially of a non-sulfonated aromatic dihydroxy compound according to formula (II). What is meant herein by "consisting essentially of" is that component (B1 a) comprises more than 99 wt%, preferably more than 99.5 wt% and more preferably more than 99.9 wt% of a non-sulfonated aromatic dihydroxy compound according to formula (II), based on the overall weight of component (B1 a) in reaction mixture (RG).

[0091] In a further preferred embodiment, component (B1a) consists of a non-sulfonated aromatic dihydroxy compound according to formula (II), preferably of 4,4’-dihydroxybiphenyl.

[0092] Component (B1 b)

[0093] The reaction mixture (RG) optionally comprises as component (B1 b) at least one non-sulfonated aromatic dihydroxy compound according to formula (III) wherein

[0094] R3and R4are independently selected from H, nitro and OR, wherein R is selected from Ci-Ce alkyl and C6-C12 aryl.

[0095] The term “at least one non-sulfonated aromatic dihydroxy compound according to formula (III)” in the present case, is understood to mean exactly one non-sulfonated aromatic dihydroxy compound according to formula (III) and also mixtures of two or more non-sulfonated aromatic dihydroxy compounds according to formula (III). Preferably, component (B1 b) means precisely one non-sulfonated aromatic dihydroxy compound according to formula (III).

[0096] “Non-sulfonated” within the context of the present invention also means that the non-sulfonated aromatic dihydroxy compound (B1 b) does not comprise any -SO2X group, wherein X is selected from the group consisting of Cl and O’ combined with one cation equivalent.

[0097] “One cation equivalent” within the context of the present invention means one cation of a single positive charge or one charge equivalent of a cation with two or more positive charges, for example, H+, Li+, Na+, K+, Mg2+, Ca2+or NHT.

[0098] The at least one non-sulfonated aromatic dihydroxy compound according to formula (III) may here be used in pure form or as a technical-grade product, which may comprise up to 2 wt%, preferably up to 1 wt% and more preferably up to 0.5 wt% of impurities, all based on the overall weight of the at least one non-sulfonated aromatic dihydroxy compound according to formula (III). Any impurities present are included in the wt% percentages relating to component (B1 b).

[0099] Since the reaction mixture (RG) comprises at least one carbonate component (C), the hydroxyl groups of component (B1 b) in the reaction mixture (RG) may be present partially in deprotonated form.

[0100] Component (B1 b) is preferably used as a monomer. This means that the reaction mixture (RG) comprises component (B1 b) preferably as monomer and not as prepolymer.

[0101] The bonding lines in formula (III) with which the substituents R3, R4and OH are linked to the benzene ring, and which extend into the benzene ring, in the present case, are understood to mean that the substituents R3, R4and OH can have any possible position on the benzene ring.

[0102] Preferably, component (B1 b) is selected from the group consisting of hydroquinone (benzene-1 ,4-diol), resorcinol (benzene-1 ,3-diol), 2-methoxyhydroquinone and 2,6-dimethoxyhydroquinone. Hydroquinone is particularly preferable.

[0103] Therefore, the present invention accordingly also provides a use wherein component (B1 b) is hydroquinone.

[0104] In a preferred embodiment, component (B1 b) comprises not less than 80 wt%, preferably not less than 90 wt% and more preferably not less than 98 wt% of a non-sulfonated aromatic dihydroxy compound according to formula (III), based on the overall weight of component (B1 b) in reaction mixture (RG).

[0105] In a further particularly preferred embodiment, component (B1 b) consists essentially of a non-sulfonated aromatic dihydroxy compound according to formula (III).

[0106] What is meant herein by "consisting essentially of" is that component (B1 b) comprises more than 99 wt%, preferably more than 99.5 wt% and more preferably more than 99.9 wt% of a non-sulfonated aromatic dihydroxy compound according to formula (III), based on the overall weight of component (B1 b) in reaction mixture (RG).

[0107] In a further preferred embodiment, component (B1 b) consists of a non-sulfonated aromatic dihydroxy compound according to formula (III), preferably of hydroquinone.

[0108] Component (B2)

[0109] The reaction mixture (RG) optionally comprises as component (B2) at least one sulfonated aromatic dihydroxy component according to formula (IV), wherein

[0110] R5is selected from H, halogen, nitro and OR, wherein R is selected from Ci-Ce alkyl and C6-C12 aryl, and

[0111] Y is H, Na or K.

[0112] The term “at least one sulfonated aromatic dihydroxy component” in the present case, is understood to mean exactly one sulfonated aromatic dihydroxy component and also mixtures of two or more sulfonated aromatic dihydroxy components.

[0113] “Sulfonated” within the context of the present invention means that the aromatic dihydroxy component comprises a group resulting from the sulfonation of the aromatic dihydroxy component. The sulfonation of aromatic dihydroxy components is known to the skilled person. In particular, “sulfonated” means that the aromatic dihydroxy component comprises one -SO3Y group wherein Y is hydrogen or a cation equivalent.

[0114] “Cation equivalent” within the context of the present invention means a cation of a single positive charge, for example, Na+or K+.

[0115] The reaction mixture (RG) preferably comprises from 0 to 7.5 mol-%, more preferably from 1 to 5 mol-% of at least one sulfonated aromatic dihydroxy component as component (B2), based on the sum of the mol-% of components (A), (B1 a), optionally (B1 b), and optionally (B2).

[0116] The sum of the mol-% of components (A), (B1 a), optionally (B1 b), and optionally (B2) usually is 100 mol-%.

[0117] The bonding lines in formula (IV) with which the substituents R5, SO3Y and OH are linked to the benzene ring, and which extend into the benzene ring, in the present case, are understood to mean that the substituents R5, SO3Y and OH can have any possible position on the benzene ring.

[0118] Component (B2) is preferably selected from 2,5-dihydroxybenzene sulfonic acid or 2,5-dihydroxybenzene sulfonic acid potassium salt.

[0119] Therefore, another object of the present invention is also a use wherein component (B2) is 2,5-dihydroxybenzene sulfonic acid or 2,5-dihydroxybenzene sulfonic acid potassium salt. The present invention therefore also relates to a process wherein component (B2) comprises at least 50 % by weight of at least one sulfonated aromatic dihydroxy component selected from 2,5-dihydroxybenzene sulfonic acid or 2,5- dihydroxybenzene sulfonic acid potassium salt, based on the total weight of component (B2) in the reaction mixture ( G).

[0120] In a particularly preferred embodiment component (B2) comprises at least 80 % by weight, preferably at least 90 % by weight, more preferably at least 98 % by weight of at least one sulfonated aromatic dihydroxy component selected from 2,5-dihydroxybenzene sulfonic acid or 2,5-dihydroxybenzene sulfonic acid potassium salt, based on the total weight of component (B2) in the reaction mixture (RG).

[0121] In a further particularly preferred embodiment component (B2) consists essentially of at least one sulfonated aromatic dihydroxy component selected from 2,5-dihydroxybenzene sulfonic acid or 2,5-dihydroxybenzene sulfonic acid potassium salt.

[0122] “Consisting essentially of” in the present case is understood to mean that component (B2) comprises more than 95 % by weight, preferably more than 97 % by weight, particularly preferably more than 99 % by weight of at least one sulfonated aromatic dihydroxy component selected from 2,5-dihydroxybenzene sulfonic acid or 2,5-dihydroxybenzene sulfonic acid potassium salt, based on the total weight of component (B2) in the reaction mixture (RG).

[0123] In a further particularly preferred embodiment, component (B2) consists of 2,5-dihydroxybenzene sulfonic acid or 2,5- dihydroxybenzene sulfonic acid potassium salt.

[0124] In case the reaction mixture (RG) comprises component (B2), the resulting poly(ether nitrile) polymer (PEN) is a sulfonated poly(ether nitrile) polymer (sPEN).

[0125] Component (C)

[0126] The reaction mixture (RG) comprises at least one carbonate component as component (C). The term “at least one carbonate component” in the present case, is understood to mean exactly one carbonate component and also mixtures of two or more carbonate components. The at least one carbonate component is preferably at least one metal carbonate. The metal carbonate is preferably anhydrous.

[0127] Preference is given to alkali metal carbonates and / or alkaline earth metal carbonates as metal carbonates. At least one metal carbonate selected from the group consisting of sodium carbonate, potassium carbonate and calcium carbonate is particularly preferred as metal carbonate. Potassium carbonate is most preferred. For example, component (C) comprises at least 50 % by weight, more preferred at least 70 % by weight and most preferred at least 90 % by weight of potassium carbonate based on the total weight of the at least one carbonate component in the reaction mixture (RG).

[0128] Another object of the present invention is therefore also a use wherein component (C) comprises at least 50 % by weight of potassium carbonate, based on the total weight of component (C).

[0129] In a preferred embodiment component (C) consists essentially of potassium carbonate.

[0130] “Consisting essentially of” in the present case is understood to mean that component (C) comprises more than 99 % by weight, preferably more than 99.5 % by weight, particular preferably more than 99.9 % by weight of potassium carbonate based in each case on the total weight of component (C) in the reaction mixture (RG).

[0131] In a particularly preferred embodiment component (C) consists of potassium carbonate.

[0132] Potassium carbonate having a volume weighted average particle size of less than 200 m is particularly preferred as potassium carbonate. The volume weighted average particle size of the potassium carbonate is determined in a suspension of potassium carbonate in N-methylpyrrolidone using a particle size analyser.

[0133] In a preferred embodiment, the reaction mixture (RG) does not comprise any alkali metal hydroxides or alkaline earth metal hydroxides.

[0134] Component (D)

[0135] The reaction mixture (RG) comprises at least one aprotic polar solvent as component (D). “At least one aprotic polar solvent”, according to the invention, is understood to mean exactly one aprotic polar solvent and also mixtures of two or more aprotic polar solvents.

[0136] Preferably, component (D) is selected from the group consisting of N-methylpyrrolidone, N-butylpyrrolidone, N-tert- butylpyrrolidone, N-dimethylacetamide, dimethyl sulfoxide, sulfolane and dimethylformamide. N-methylpyrrolidone is particularly preferred as component (D).

[0137] Another object of the present invention is therefore also a use wherein component (D) is selected from the group consisting of N-methylpyrrolidone, N-butylpyrrolidone, N-tert-butylpyrrolidone, N-dimethylacetamide, dimethyl sulfoxide, sulfolane and dimethylformamide.

[0138] It is preferred that component (D) comprises at least 50 % by weight of at least one solvent selected from the group consisting of N-methylpyrrolidone, N-butylpyrrolidone, N-tert-butylpyrrolidone, N-dimethylacetamide, dimethyl sulfoxide, sulfolane and dimethylformamide, based on the total weight of component (D) in the reaction mixture (RG). N-methylpyrrolidone is particularly preferred as component (D).

[0139] In a further preferred embodiment, component (D) consists essentially of N-methylpyrrolidone.

[0140] “Consist essentially of’, in the present case, is understood to mean that component (D) comprises more than 98 % by weight, particularly preferably more than 99 % by weight, more preferably more than 99.5 % by weight, of at least one aprotic polar solvent selected from the group consisting of N-methylpyrrolidone, N-butylpyrrolidone, N-tert- butylpyrrol idone, N-dimethylacetamide, dimethyl sulfoxide, sulfolane and dimethylformamide with preference given to N-methylpyrrolidone.

[0141] In a preferred embodiment, component (D) consists of N-methylpyrrolidone. N-methylpyrrolidone is also referred to as NMP or N-methyl-2-pyrrol idone.

[0142] Polyfether nitrile) polymer (PEN)

[0143] The poly(ether nitrile) polymer (PEN) obtainable by the above-described process can comprise units that are derived from component (A) and from component (B1 a) and / or optionally component (B1 b), as well as optionally units that are derived from component (A) and from component (B2). In a preferred embodiment, the poly(ether nitrile) polymer (PEN) consists of units that are derived from component (A) and from component (B1 a) and / or optionally component (B1 b), as well as optionally of units that are derived from component (A) and from component (B2).

[0144] Preferred poly(ether nitrile) polymers (PEN) comprise repeating units of the general formula (V): wherein k = 0 to 0.3, m = 0 to 0.4, and n = 0.1 to 0.9.

[0145] Therefore, a further object of the present invention is a use, wherein the poly (ether nitrile) polymer (PEN) comprises repeating units of the general formula (V): wherein k = 0 to 0.3, m = 0 to 0.4, and n = 0.1 to 0.9.

[0146] In a more preferred embodiment, k = 0 to 0.3, m = 0.01 to 0.4, and n = 0.1 to 0.9.

[0147] In a most preferred embodiment, k = 0.01 to 0.3, m = 0.01 to 0.4, and n = 0.1 to 0.9.

[0148] The poly(ether nitrile) polymer (PEN) obtained by the process described above has a glass transition temperature (TG). Preferably, the poly(ether nitrile) polymer (PEN) has a glass transition temperature (TG) in the range from 190 to 230 °C obtained by differential scanning calorimetry (DSC) according to ISO 1 1357-1 (2017) and 1 1357-2 (2020) at 20 K / min.

[0149] The poly(ether nitrile) polymer (PEN) obtained by the process described above preferably also has a viscosity number of 25 ml / g to 270 ml / g. This viscosity number is quantified according to DIN EN ISO 1628-5 (1998) in a 1 wt.-% solution of N-methylpyrrolidone (NMP).

[0150] A monolithic film of the poly(ether nitrile) polymer (PEN) obtained by the process described above preferably has a water contact angle in the range from 55 to 70 °. The contact angle is determined by time-resolved automated image analysis by Kruss DSA100 (A. KRUSS Optronic GmbH, Hamburg, Germany) at 23°C placing 8 to 10 drops of deionized water with a volume of approximately 2 pL on the sample.

[0151] The weight average molecular weight (Mw) of the poly(ether nitrile) polymer (PEN) is generally in the range from 30

[0152] 000 to 130 000 g / mol, preferably in the range from 50 000 to 1 10 000 g / mol and more preferably in the range from 60 000 to 105000 g / mol. The weight average molecular weights (Mw) are measured using gel permeation chromatography (GPC). Dimethylacetamide (DMAc) and 0.5 wt.-% LIBr were used as solvent and narrowly distributed polymethyl methacrylate was used as standard in the measurement.

[0153] In addition, the poly(ether nitrile) polymer (PEN) preferably has a polydispersity MW / MN in the range from 2 to 3.5, more preferably from 2.2 to 2.7.

[0154] In case component (B2) is present in the preparation process, the proportion of HCS is preferably < 30 mol-%, more preferably in the range from 1 to 20 mol-%. The proportion of HCS units is determined by1H-NMR-spectroscopy in CDCI3at 400 MHz.

[0155] Membrane (M)

[0156] The poly(ether nitrile) polymer (PEN) obtained by the process described above is comprised in the membrane (M).

[0157] The membrane (M) comprises preferably at least 50 % by weight of the poly(ether nitrile) polymer (PEN), more preferably at least 70 % by weight and most preferably at least 90 % by weight of the poly(ether nitrile) polymer (PEN), based on the total weight of the membrane (M).

[0158] In a further preferred embodiment, the membrane (M) consists essentially of the poly(ether nitrile) polymer (PEN).

[0159] “Consisting essentially of” means that the membrane (M) comprises more than 93% by weight, preferably more than 95% by weight and most preferably more than 97% by weight of the poly(ether nitrile) polymer (PEN), based on the total weight of the membrane (M).

[0160] During the formation of the membrane (M) the poly (ether nitrile) polymer (PEN) is separated from at least one solvent. Therefore, the obtained membrane (M) is essentially free from the at least one solvent.

[0161] “Essentially free” within the context of the present invention means that the membrane (M) comprises at most 7 % by weight, preferably at most 5 % by weight and particularly preferably at most 3 % by weight of the at least one solvent based on the total weight of the membrane (M). The membrane (M) comprises at least 0.0001 % by weight, preferably at least 0.001 % by weight and particularly preferably at least 0.01 % by weight of the at least one solvent based on the total weight of the membrane (M).

[0162] To the person skilled in the art, it is clear, that, if a pore forming additive (P) is used in the preparation of the membrane (M), then the membrane (M) usually furthermore comprises the pore forming additive (P). For example, the membrane (M) then comprises in the range from 1 to 15 % by weight, preferably in the range from 2 to 10 % by weight and most preferably in the range from 3 to 8 % by weight of the at least one pore forming additive (P), based on the total weight of the membrane (M).

[0163] In case a pore forming additive (P) is used in the preparation of the membrane (M) then the membrane (M) is preferably a porous membrane.

[0164] Membrane

[0165] A membrane (M) can be prepared from the poly(ether nitrile) polymer (PEN) according to the present invention by any method known to the skilled person.

[0166] Preferably, the membrane (M) comprising the poly(ether nitrile) polymer (PEN) is prepared by a method comprising the steps i) providing a solution (S) which comprises the poly(ether nitrile) polymer (PEN), at least one pore forming additive (P) and at least one solvent, ii) separating the at least one pore forming additive (P) and the at least one solvent from the solution (S) to obtain the membrane (M).

[0167] Another object of the present invention is therefore a use, wherein the membrane (M) is prepared by a method comprising the steps i) providing a solution (S) which comprises the poly(ether nitrile) polymer (PEN), at least one pore forming additive (P) and at least one solvent, ii) separating the at least one pore forming additive (P) and the at least one solvent from the solution (S) to obtain the membrane (M).

[0168] Step i)

[0169] In step i) a solution (S) is provided which comprises the poly(ether nitrile) polymer (PEN), at least one pore forming additive (P) and at least one solvent.

[0170] “At least one pore forming additive (P)” within the context of the present invention means precisely one pore forming additive (P), and also a mixture of two or more pore forming additives (P). “At least one solvent” within the context of the present invention means precisely one solvent, and also a mixture of two or more solvents. The solution (S) can be provided in step i) by any method known to the skilled person. For example, the solution (S) can be provided in step I) in customary vessels which may comprise a stirring device and preferably a temperature control device. Preferably, the solution (S) is provided by dissolving the poly(ether nitrile) polymer (PEN) and the at least one pore forming additive (P) in the at least one solvent.

[0171] The dissolution of the poly(ether nitrile) polymer (PEN) and the at least one pore forming additive (P) in the at least one solvent to provide the solution (S) is preferably effected under agitation.

[0172] Step I) is preferably carried out at elevated temperatures, especially in the range from 20 to 120 °C, more preferably in the range from 40 to 100 °C. A person skilled in the art will choose the temperature in accordance with the at least one solvent.

[0173] The solution (S) preferably comprises the poly(ether nitrile) polymer (PEN) and the at least one pore forming additive (P) completely dissolved in the at least one solvent. This means that the solution (S) preferably comprises no solid particles of the poly(ether nitrile) polymer (PEN) and the at least one pore forming additive (P). Therefore, the poly (ether nitrile) polymer (PEN) and the at least one pore forming additive (P) preferably cannot be separated from the at least one solvent by filtration.

[0174] The solution (S) preferably comprises from 10 to 25 % by weight of the poly(ether nitrile) polymer (PEN), from 1 to 15 % by weight of the at least one pore forming additive (P) and from 60 to 89 % by weight of the at least one solvent, based on the total weight of the solution (S). More preferably, the solution (S) in step I) comprises from 14 to 20 % by weight of the poly(ether nitrile) polymer (PEN), from 5 to 7 % by weight of the at least one pore forming additive (P) and from 73 to 81 % by weight of the at least one solvent, based on the total weight of the solution (S).

[0175] Optionally, the solution (S) can comprise from 0 to 15 % by weight, preferably from 8 to 12 % by weight of a nonsolvent, based on the total weight of the solution (S). The non-solvent can, for example, be 1 ,2-propanediol.

[0176] Another object of the present invention is therefore also a use, wherein the solution (S) provided in step I) comprises in the range from 10 to 25 wt.-% of the poly(ether nitrile) polymer (PEN), 1 to 15 wt.-% of the at least one pore forming agent (P) and 60 to 89 wt.-% of the at least one solvent, based on the total weight of the solution (S).

[0177] As the at least one solvent, any solvent known to the skilled person for the poly (ether nitrile) polymer (PEN) and the at least one pore forming additive (P) is suitable. Preferably, the at least one solvent is soluble in water. Therefore, the at least one solvent is preferably selected from the group consisting of N-methylpyrrolidone, N-butylpyrrolidone, N-tert- butylpyrrolidone N-(2’-hydroxyethyl)-2-pyrrolidone. N-dimethylacetamide, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethyllactamide, gamma-valerolactone, dihydrolevoglucosenone, methyl 5-(dimethylamino)-2-methyl-5- oxopentanoate and sulfolane. N-methylpyrrolidone and N-dimethyllactamide are particularly preferred. Another object of the present invention is therefore also a use wherein the at least one solvent is selected from the group consisting of N-methylpyrrolidone, N-butylpyrrolidone, N-tert-butylpyrrolidone N-(2’-hydroxyethyl)-2-pyrrolidone. N-dimethylacetamide, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethyllactamide, gamma-valerolactone, dihydrolevoglucosenone, methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate and sulfolane.

[0178] The solution (S) preferably comprises in the range from 60 to 89 % by weight of the at least one solvent, more preferably in the range from 73 to 81 % by weight, of the at least one solvent, based on the total weight of the solution (S).

[0179] The solution (S) provided in step I) furthermore comprise at least one pore forming additive (P) for the membrane preparation.

[0180] Suitable pore forming additives (P) are poly(alkylene oxides) and poly(vinyl pyrrolidone).

[0181] Examples for suitable poly(alkylene oxides) are polyethylene oxide), polypropylene oxide) and polyethylene oxide)- poly(propylene oxide) copolymer. Preferred poly(alkylene oxides) are poly(ethylene oxides) PEO 200 to 2,000,000 g / mol.

[0182] As poly(vinyl pyrrolidone) poly(vinyl pyrrolidone) K12 to 90 is preferred.

[0183] As pore forming additive (C), poly(vinyl pyrrolidone) is preferred.

[0184] Another object of the present invention is therefore also a use wherein the at least one pore forming additive (P) is selected from the group consisting of poly(alkylene oxides) and poly(vinyl pyrrolidone).

[0185] The solution (S) can comprise the at least one pore forming additive (P), for example, in an amount of from 1 to 15 % by weight, preferably in the range from 5 to 7 % by weight, based on the total weight of the solution (S).

[0186] To the person skilled in the art, it is clear that the percentages by weight of the poly(ether nitrile) polymer (PEN), the at least one pore forming additive (P), the at least one solvent and the optionally comprised non-solvent comprised in the solution (S) typically add up to 100 % by weight.

[0187] The duration of step I) may vary between wide limits. The duration of step I) is preferably in the range from 10 min to 48 h (hours), especially in the range from 10 min to 24 h and more preferably in the range from 15 min to 12 h. A person skilled in the art will choose the duration of step I) so as to obtain a homogeneous solution of the poly(ether nitrile) polymer (PEN) and the at least one pore forming additive (P) in the at least one solvent. For the poly (ether nitrile) polymer (PEN) comprised in the solution (S) the embodiments and preferences given for the poly(ether nitrile) polymer (PEN) obtained in the process described above hold true.

[0188] Step ii)

[0189] In step ii), the at least one pore forming additive (P) and the at least one solvent are separated from the solution (S) to obtain the membrane (M).

[0190] It is possible to filter the solution (S) provided in step I) before the at least one pore forming additive (P) and the at least one solvent are separated from the solution (S) in step ii) to obtain a filtered solution (fS). The following embodiments and preferences for separating the at least one pore forming additive (P) and the at least one solvent from the solution (S) apply equally for separating the at least one pore forming additive (P) and the at least one solvent from the filtered solution (fS).

[0191] Moreover, it is possible to degas the solution (S) in step I) before the at least one pore forming additive (P) and the at least one solvent are separated from the solution (S) in step ii) to obtain a degassed solution (dS). This embodiment is preferred. The following embodiments and preferences for separating the at least one pore forming additive (P) and the at least one solvent from the solution (S) apply equally for separating the at least one pore forming additive (P) and the at least one solvent from the degassed solution (dS).

[0192] The degassing of the solution (S) in step I) can be carried out by any method known to the skilled person, for example via vacuum or by allowing the solution (S) to rest.

[0193] The separation of the at least one pore forming additive (P) and the at least one solvent from the solution (S) can be performed by any method known to the skilled person which is suitable to separate pore forming additives and solvents from polymers.

[0194] Preferably, the separation of the at least one pore forming additive (P) and the at least one solvent from the solution (S) is carried out via a phase inversion process.

[0195] Another object of the present invention is therefore also a use, wherein the separation in step ii) is performed by a phase inversion process.

[0196] If the separation of the at least one pore forming additive (P) and the at least one solvent is carried out via a phase inversion process, the obtained membrane (M) is typically a porous membrane.

[0197] The membrane (M) obtained in step ii) is preferably a hollow fiber membrane. Another object of the present invention is therefore also a use, wherein the membrane (M) is a hollow fiber membrane.

[0198] As a person skilled in the art knows, a porous hollow fiber membrane (M) preferably has an inner layer and a supporting structure, wherein the inner layer is the active filtration layer. The inner layer, as well as the supporting structure, typically comprise pores, wherein the pore size distribution of the inner layer is actually the only decisive factor for the properties of the hollow fiber membrane. In general, the pore size of the inner layer is smaller than the pore size of the outer layer (inside-out configuration).

[0199] Preferably, the pore size of the membrane (M) increases from the inner layer, which is used for separation, to the outer layer of the membrane (M). Therefore, such a membrane (M) is also called an asymmetric membrane (M).

[0200] The minimal pore diameter of the membrane (M) is preferably < 5 nm.

[0201] The supporting structure can have diameters up to 10 pm.

[0202] A phase inversion process within the context of the present invention means a process wherein the dissolved poly(ether nitrile) polymer (PEN) is transformed into a solid phase. Therefore, a phase inversion process can also be denoted as precipitation process. According to step II), the transformation is performed by separation of the at least one pore forming additive (P) and the at least one solvent from the poly(ether nitrile) polymer (PEN). The person skilled in the art knows suitable phase inversion processes.

[0203] To produce single bore hollow fibers or multiple bore hollow fibers step II) may be performed by extruding the solution (S) through an extrusion nozzle with the required number of hollow needles. The coagulating liquid or center fluid (CF) is then injected through the hollow needles into the extruded polymer during extrusion, so that parallel continuous channels extending in extrusion direction are formed in the extruded polymer. Preferably, the pore size on an outer surface of the extruded membrane is controlled by bringing the outer surface after leaving the extrusion nozzle in contact with a mild coagulation agent such that the shape is fixed without active layer on the outer surface and subsequently the membrane is brought into contact with a strong coagulation agent.

[0204] Therefore, in one preferred embodiment of the present invention, step II) comprises the following step: ii-1) passing the solution (S) provided in step I) and a center fluid (CF) through a spinning die into a precipitation bath (PB) to obtain the membrane (M).

[0205] Preferably, before step ii-1 ), the solution (S) is reheated to a temperature in the range of 40 to 80°C.

[0206] The center fluid CF) preferably comprises water and at least one solvent selected from the group consisting of N- methylpyrrolidone, N-butylpyrrolidone, N-tert-butylpyrrolidone N-(2’-hydroxyethyl)-2-pyrrolidone. N- dimethylacetamide, dimethyl sulfoxide, N,N-dimethylformamide, N, N-dimethyllactamide, gamma-valerolactone, dihydrolevoglucosenone, methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate and sulfolane. N-methylpyrrolidone and N-dimethyllactamide are particularly preferred.

[0207] The precipitation bath (PB) preferably comprises at least one protic polar solvent.

[0208] Suitable protic polar solvents are known to the skilled person. The at least one protic polar solvent is preferably a nonsolvent for the poly (ether nitrile) polymer (PEN).

[0209] Preferred protic polar solvents are water, methanol, ethanol, n-propanol, iso-propanol, glycerol, ethylene glycol and mixtures thereof. Preferably, the at least one protic polar solvent is water.

[0210] Therefore, another object of the present invention is a use, wherein the at least one protic polar solvent is water.

[0211] In a preferred embodiment, the spinning die has a temperature in the range of 40 to 80°C.

[0212] The precipitation bath (PB) preferably has a temperature in the range of 50 to 90°C.

[0213] The distance between the die and the precipitation bath is preferably in the range of from 40 to 80 cm.

[0214] After step ii-1 ), the membrane (M) is preferably wound on a winding reel.

[0215] In a preferred embodiment, after step ii-1), and after the membrane (M) is optionally wound on a winding reel, the membrane (M) can also be exposed to a water bath containing a NaOCI solution at a pH of 9.5.

[0216] After step ii-1 ) and after the optional exposure to a water bath containing a NaOCI solution at a pH of 9.5, the membrane (M) is preferably washed in a step ii-2). In a preferred embodiment, in step ii-2), the membrane (M) is treated with a water extraction, preferably at a temperature in the range from 70 to 90 °C, with subsequent drying.

[0217] During step ii-1 ), preferably, the poly(ether nitrile) polymer (PEN) comprised in the solution (S) is at least partly separated from the at least one pore forming additive (P) and the at least one solvent comprised in solution (S) to obtain the membrane (M).

[0218] In step ii-2), the poly(ether nitrile) polymer (PEN) comprised in the membrane (M) is preferably completely separated from the at least one pore forming additive (P) and the at least one solvent comprised in the membrane (M).

[0219] The term “at least partly” within the context of the present invention means that preferably at least 50% by weight, more preferably at least 60% by weight, of the poly (ether nitrile) polymer (PEN), based on the total weight of the poly (ether nitrile) polymer (PEN) comprised in the solution (S), are separated from the at least one pore forming additive (P) and the at least one solvent.

[0220] The term “completely” within the context of the present invention means that preferably at least 90% by weight, more preferably at least 95% by weight, of the poly (ether nitrile) polymer (PEN), based on the total weight of the poly (ether nitrile) polymer (PEN) comprised in the membrane (M), are separated from the at least one pore forming additive (P) and the at least one solvent.

[0221] The present invention is further elucidated by the following examples without limiting it thereto.

[0222] Components used

[0223] Component (A): 2,6-Dichlorobenzonitrile (26DCBN, CAS 1194-65-6), Alzchem

[0224] Group AG, Trostberg, Germany

[0225] Component (B1a): 4,4'-Dihydroxybiphenyl (DHBP, CAS 92-88-6)

[0226] Component (B1b): Hydroquinone (HC, CAS 123-31 -9), Sigma-Aldrich Chemie

[0227] GmbH, Taufkirchen, Germany

[0228] Component (B2): 2,5-Dihydroxybenzenesulfonic acid potassium salt (HCS, CAS

[0229] 21799-87-1), Alfa Aesar, 2 Radcliff Rd Tewksbury, MA 01876, USA

[0230] Component (C): Potassium carbonate (K2CO3), anhydrous

[0231] Component (D): N-methylpyrrolidone (NMP, CAS 872-50-4), Th. Geyer GmbH &

[0232] Co. KG, Dornierstr. 4-6, 71272 Renningen, Germany

[0233] General procedures

[0234] The proportion of HC and HCS units are determined by1H-NMR-spectroscopy (Proton nuclear magnetic resonance spectroscopy) in CDCI3 at 400 MHz.

[0235] The viscosity number (V.N.) of the polymers is determined in a 1 wt.-% solution in NMP based on ISO 1628-5 (1998). The glass transition temperature (TG) is determined by differential scanning calorimetry (DSC) according to ISO 1 1357-1 (2017) and 1 1357-2 (2020) at 20 K / min.

[0236] The molecular weight is determined by gel permeation chromatography (GPC) in dimethylacetamide (DMAc) and 0.5 wt.-% LiBr using a PMMA standard.

[0237] Example 1 : non-sulfonated poly(ether nitrile) polymer (PEN)

[0238] In a 4 L vessel equipped a with stirrer, Dean-Stark-trap, nitrogen inlet and temperature control 344.1 g (2.0 mol) of 2,6- dichlorobenzonitrile (26DCBN), 283.6 g (1.523 mol) of dihydroxydiphenyl (DHDP) and 50.06 g (0.50 mol) of hydrochinone (HC) were dissolved, under nitrogen (30L / h), in 1000 ml of N-methylpyrrolidone (NMP) and mixed with 290.24 g (2.1 mol) of anhydrous potassium carbonate at a stirring rate of 130 rpm.

[0239] The reaction mixture was firstly heated at 180 °C, for 1 h at a pressure of 300 mbar, the water of reaction and N- methylpyrrolidone being continuously distilled off, and then reacted for 0.5 h at 190° C.

[0240] After adding 1000 ml of N-methylpyrrolidone, the mixture was cooled to 80 °C and inorganic constituents were filtered off. Subsequently the polymer was then isolated by precipitation in water. After extraction with water for 20 h at 80 °C (160L / h water flux), the product was dried under reduced pressure at 140 ° C, giving a white powder (PEN). The properties of the obtained non-sulfonated poly (ether nitrile) polymer (PEN) are summarized in table 1 .

[0241] Example 2: sulfonated polyfether nitrile) polymer (PEN)

[0242] In a 4 L vessel equipped a with stirrer, Dean-Stark-trap, nitrogen inlet and temperature control 344.1 g (2.0 mol) of 2,6- dichlorobenzonitrile (26DCBN), 279.32 g (1.50 mol) of dihydroxydiphenyl (DHDP), 22.83 g (0.10 mol) 2,5- dihydroxybenzenesulfonic acid potassium salt (HCS) and 44.04 g (0.40 mol) of hydrochinone (HC) were dissolved, under nitrogen (30L / h), in 1000 ml of N-methylpyrrolidone (NMP) and mixed with 290.24 g (2.1 mol) of anhydrous potassium carbonate at a stirring rate of 130 rpm.

[0243] The reaction mixture was firstly heated at 180 °C, for 1 h at a pressure of 300 mbar, the water of reaction and N- methylpyrrolidone being continuously distilled off, and then reacted for 0.5 h at 190° C.

[0244] After adding 1000 ml of N-methylpyrrolidone, the mixture was cooled to 80 °C and inorganic constituents were filtered off. Subsequently the polymer was then isolated by precipitation in water. After extraction with water for 20 h at 80 °C (160L / h water flux), the product was dried under reduced pressure at 140 ° C, giving a white powder (sPEN). The properties of the obtained sulfonated poly (ether nitrile) polymer (PEN) are summarized in table 1 . Table 1

[0245] Preparation of membranes Components used

[0246] PEN: non-sulfonated poly(ether nitrile) polymer according to E1 sPEN: sulfonated poly(ether nitrile) polymer according to E2

[0247] Ultrason® E 6020 P: polyether sulfone with a viscosity number (measured based on ISO 1628-5 (1998) in a 1 wt.-% polymer solution in N-methyl-pyrrolidone) of 81 ml / g; a glass transition temperature (DSC, 10 K / min, according to ISO 11357-1 (2017) and 11357-2 (2020)) of 225 °C; a molecular weight Mw(GPC in THF, PS standard) of 75 000 g / mol; and Mw / Mn= 3.4; which is abbreviated as “E6020P”

[0248] Luvitec® K90: polyvinylpyrrolidone with a molecular weight Mwof 1 000 000 to 1 500 000 g / mol and a solution viscosity characterized by the K-value of 90, determined according to the method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932 (58)); which is abbreviated as “K90”

[0249] General procedure

[0250] The amounts given in this general procedure are general ranges, the exact amount for the respective experiment can be found in table 2. A clear viscous solution, usually referred to as solution of 15 or 19 wt% membrane polymer and 5 or 6 wt% Luvitec® polyvinylpyrrolidone in 75 or 80 wt% NMP was prepared using a SpeedMixer® DAC 600.1 Vac-P (Hauschild & Co. KG, Hamm, Germany) at speeds of 200, 800 and 1200 rpm within 30 minutes of mixing. The solution was degassed overnight at room temperature. A center fluid was prepared by mixing distilled water and N- Methyl pyrrol idone (NMP). The weight fraction of the two components in the center fluid was: water : NMP = 60 wt %: 40 wt %.

[0251] A hollow fiber membrane was formed by reheating the polymer solution at 60°C for 2 hours and passing the solution as well as the center fluid through a spinning die. The diameter of the spinning die was 0.33 mm - 0.62 mm - 1 .3 mm. The temperature of the die was 60° C. The hollow fiber membrane was formed at a spinning speed of 18 to 20 cm / min. The polymer solution was leaving the die with 3.5 ml / min while the center fluid was leaving the die with 4.0 ml / min. The liquid capillary was passed into a water bath having a temperature of 70° C. The distance between the die and the precipitation bath was 60 cm. The hollow fiber membrane formed was guided through one water bath and subsequently was wound onto a winding reel. Afterwards the membrane was treated with 2000 ppm aqueous sodiumhypochlorite (NaOCI) at pH 9.5 for 3 hours and 20 hours water extraction at 80 °C with subsequent drying.

[0252] Table 2: Compositions and properties of PEN and Ultrason® E 6020 P solutions prepared with PVP in NMP

[0253] Membrane characterization Solution viscosity

[0254] The polymer solution viscosity is measured with a Brookfield Viscometer DV-I Prime (Brookfield Engineering Laboratories, Inc. Middleboro, USA) with RV 6 spindle at 60 °C with 20 rpm.

[0255] • Solution Turbidity

[0256] The polymer solution turbidity is measured with a turbidimeter 2100AN (Hach Lange GmbH, Dusseldorf, Germany) employing a filter of 860 nm at 60 °C and expressed in nephelometric turbidity units (NTU). NTU values below 1 are preferred.

[0257] • Water vapor transmission rate (WTR)

[0258] The water vapor transmission rate (WTR, expressed in g / s m2) is tested on mini modules comprising 8 to 10 hollow fibers of 10 cm length at 80 °C at a given water flux (WET-IN, expressed in g / s m2). Also, the nitrogen permeability (expressed in L / m2h bar) at a pressure of 2 bar is assessed before and after WTR measurements at 80 and 90 °C. A high WTR in combination with low nitrogen leakage is desired.

[0259] • BET surface assessment

[0260] Solvent exchanged and dried membrane samples are used for Brunauer-Emmet-Teller (BET) surface assessment. The wet membrane samples are stored for 12 h subsequently in water / ethanol (1 :1 wt / wt), water / ethanol (1 :2 wt / wt), ethanol / n-hexane (1 : 1 wt / wt) and finally n-hexane before drying at 60 °C under vacuum.

[0261] The BET surface is determined by gas-adsorption-desorption (GAD) experiments with nitrogen by 5-point method with ASAP 2420 (Fa. Micromeritics, Norcross, USA). The samples are activated at 130 °C for 15 min before measurement.

[0262] • Fenton

[0263] The hollow fiber samples are subjected to reaction with Fenton reagent with 2000 ppm Fe and 3500 ppm H2O2 at 60 °C for 6 h in a glass sample vial. Table 3: Properties of the membranes prepared from solutions according to table 2

[0264] As can be seen from table 3, sPEN and PEN based hollow fiber humidifiers have compared to a PESU hollow fiber humidifier lower nitrogen permeability before and after the water transmission testing. Also, sPEN and PEN based hollow fiber humidifiers show higher BET surfaces of more than 20 m2 / g.

[0265] Figures 1 a and 1 b show cross-sections of the membrane of comparative example Ex. MC3. Figures 2a and 2b show cross-sections of the membrane of inventive example Ex. M 1 , and figures 3a and 3b show cross-sections of the membrane of inventive example Ex. M2 (all figures 150 x and 1500 x magnification, respectively). As can be seen from the figures, sPEN and PEN based hollow fiber humidifiers show similar to a PESU hollow fiber humidifier similar dimensions with identical wall thickness and increasing pore sizes from the inner to the outer side.

[0266] Figure 4 shows the results of the Water transmission rate. It can be seen that sPEN and PEN based hollow fiber humidifiers have compared to a PESU hollow fiber humidifier membranes comparable or higher water transmission rates at 80 °C.

[0267] In table 4, the results of the Fenton treatment are shown.

[0268] Table 4: Number-averaged molecular weight Mnand polydispersity before and after Fenton treatment

[0269] It can be seen from table 4 that PEN / sPEN hollow fiber humidifiers show less degradation in molecular weight as shown from upon treatment with the fenton reagent than the polyethersulfone based hollow fiber.

Claims

Claims1. The use of a membrane (M) in a membrane humidifier (MH) for fuel cells (FCs), wherein the membrane (M) comprises a poly(ether nitrile) polymer (PEN) and the poly(ether nitrile) polymer (PEN) is prepared by a process comprising the stepII) converting a reaction mixture (RG) comprising as components(B) at least one benzonitrile compound according to formula (I)whereinX1and X2are independently selected from a halogen, andX3is H or a halogen,(B1 a) at least one first non-sulfonated aromatic dihydroxy compound according to formula (II)whereinR1and R2are independently selected from H, nitro and OR, wherein R is selected from Ci-Ce alkyl and C6-C12 aryl, andX is a direct bond or 0,(B1 b) at least one second non-sulfonated aromatic dihydroxy compound according to formula (III)whereinR3and R4are independently selected from H, nitro and OR, wherein R is selected from Ci-Ce alkyl and C6-C12 aryl,(B2) optionally at least one sulfonated aromatic dihydroxy component according to formula (IV)whereinR5is selected from H, halogen, nitro and OR, wherein R is selected from Ci-Ce alkyl and C6-C12 aryl, andY is H, Na or K,(C) at least one carbonate component, and(D) at least one aprotic polar solvent, wherein component (B1 b) is hydroquinone.

2. The use according to claim 1 , wherein component (A) is 2, 6-d ichloro-benzon itrile.

3. The use according to claim 1 or claim 2, wherein component (B1 a) is 4, 4’ -dihydroxybiphenyl.

4. The use according to any of claims 1 to 3, wherein component (B2) is 2,5-dihydroxybenzene sulfonic acid or 2,5-dihydroxybenzene sulfonic acid potassium salt.

5. The use according to any of claims 1 to 4, wherein component (C) comprises at least 50 wt.-% of potassium carbonate, based on the total weight of component (C).

6. The use according to any of claims 1 to 5, wherein component (D) is selected from the group consisting of N-methylpyrrolidone, N-butylpyrrolidone, N-tert-butylpyrrolidone, N-dimethylacetamide, dimethyl sulfoxide, sulfolane and dimethylformamide.

7. The use according to any of claims 1 to 6, wherein the reaction mixture (RG) comprises component (A) in an amount of 50 mol-%, component (B1a) in an amount of from 30 to 45 mol-%, component (B1 b) in an amount of from 4 to 15 mol-%, and component (B2) in an amount of from 1 to 5 mol-%, based on the sum of the mol-% of components (A), (B1 a), (B1 b) and (B2).

8. The use according to any of claims 1 to 7, wherein the poly(ether nitrile) polymer (PEN) comprises repeating units of the general formula (V):wherein k = 0 to 0.3, m = 0.01 to 0.4, and n = 0.1 to 0.9.

9. The use according to any one of claims 1 to 8, wherein the membrane (M) is prepared by a method comprising the steps i) providing a solution (S) which comprises the poly(ether nitrile) polymer (PEN), at least one pore forming additive (P) and at least one solvent,ii) separating the at least one pore forming additive (P) and the at least one solvent from the solution (S) to obtain the membrane (M).

10. The use according to claim 9, wherein the solution (S) provided in step I) comprises in the range from 10 to 25 wt.-% of the poly(ether nitrile) polymer (PEN), 1 to 15 wt.-% of the at least one pore forming agent (P) and60 to 89 wt.-% of the at least one solvent, based on the total weight of the solution (S).11 . The use according to claim 9 or 10, wherein the separation in step II) is performed by a phase inversion process.

12. The use according to any one of claims 9 to 11, wherein the at least one solvent is selected from the group consisting of N-methylpyrrolidone, N-butylpyrrolidone, N-tert-butylpyrrolidone N-(2’-hydroxyethyl)- 2-pyrrolidone. N-dimethylacetamide, dimethyl sulfoxide, N,N-dimethylformamide, N,N-dimethyllactamide, gamma-valerolactone, dihydrolevoglucosenone, methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate and sulfolane.

13. The use according to any one of claims 9 to 12, wherein the at least one pore forming additive (P) is selected from the group consisting of poly(alkylene oxides) and poly(vinyl pyrrolidone).

14. The use according to any one of claims 9 to 12, wherein the membrane (M) is a hollow fiber membrane.

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