Process for the preparation of a sulfonated poly(ether nitrile) polymer (SPEN)

Abstract

The present invention relates to a process for the preparation of a sulfonated poly(ether nitrile) polymer (sPEN), wherein the process comprises step I) converting a reaction mixture (RG) comprising as components (A) at least one benzonitrile compound according to formula (I), (B1a) at least one non-sulfonated aromatic dihydroxy compound according to formula (II), (B1b) optionally at least one non-sulfonated aromatic dihydroxy compound according to formula (III), (B2) 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. The present invention further relates to a sulfonated poly(ether nitrile) polymer (sPEN) obtained by the inventive process and to the use of the sulfonated poly(ether nitrile) polymer (sPEN) in a membrane (M). Moreover, the present invention relates to a membrane comprising the sulfonated poly(ether nitrile) polymer (sPEN) and to a method for the preparation of the membrane (M).

Description

[0001] Process for the preparation of a sulfonated poly(ether nitrile) polymer (sPEN)

[0002] Description

[0003] The present invention relates to a process for the preparation of a sulfonated poly(ether nitrile) polymer (sPEN), wherein the process comprises step I) converting a reaction mixture (RG) comprising as components (A) at least one benzonitrile compound according to formula (I), (B1a) at least one non-sulfonated aromatic dihydroxy compound according to formula (II), (B1b) optionally at least one non-sulfonated aromatic dihydroxy compound according to formula (III), (B2) 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. The present invention further relates to a sulfonated poly(ether nitrile) polymer (sPEN) obtained by the inventive process and to the use of the sulfonated poly(ether nitrile) polymer (sPEN) in a membrane (M). Moreover, the present invention relates to a membrane comprising the sulfonated poly(ether nitrile) polymer (sPEN) and to a method for the preparation of the membrane (M).

[0004] Today, poly(aryl sulfone) polymers are most frequently used as matrix materials in ultra / microfiltration (LIF / MF) membranes for water treatment applications. To counter fouling processes during operation and to maintain productivity, the MF / LIF membranes are regularly cleaned by oxidative treatment, for example, by an oxidative treatment using sodium hypochlorite NaOCI (Panglisch et. al, Separation Purification Technology 2020, 251 , 117345). However, due to these NaOCI cleaning procedures, the poly(aryl sulfone) polymers are degraded by attack of the sulfonyl moieties (V. Gitis et.al, Journal of Membrane Science 2002, 305, 176-184; J.-L. Gardette et. al., Polymer Degradation and Stability 2013, 98, 1164-1172).

[0005] 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.

[0006] Therefore, the object of the present invention was to provide an improved polymer which can be used in an ultra / microfiltration (UF / MF) membrane for water treatment applications. The polymer or the membrane (M), respectively, should be chemically and mechanically stable and easy to produce at relatively low costs.

[0007] This object is achieved by a process for the preparation of a sulfonated poly(ether nitrile) polymer (sPEN) comprising step I) converting a reaction mixture (RG) comprising as components

[0008] (A) at least one benzonitrile compound according to formula (I) wherein

[0009] X1and X2are independently selected from a halogen, and

[0010] X3is H or a halogen,

[0011] (B1a) at least one non-sulfonated aromatic dihydroxy compound according to formula (II) wherein

[0012] R1and R2are independently selected from H, nitro and OR, wherein R is selected from C C6alkyl and C6-C12aryl, and

[0013] 8 X is a direct bond or O,

[0014] (B1b) optionally at least one non-sulfonated aromatic dihydroxy compound according to formula (III) wherein

[0015] R3and R4are independently selected from H, nitro and OR, wherein R is selected from C C6alkyl and C6-C12aryl,

[0016] (B2) at least one sulfonated aromatic dihydroxy component according to formula (IV) wherein

[0017] R5is selected from H, halogen, nitro and OR, wherein R is selected from Ci-C6alkyl and C6-Ci2aryl, and

[0018] Y is H, Na or K,

[0019] (C) at least one carbonate component, and

[0020] (D) at least one aprotic polar solvent.

[0021] This object is further achieved by a process for the preparation of a sulfonated poly(ether nitrile) polymer (sPEN) comprising step

[0022] I) converting a reaction mixture (RG) comprising as components

[0023] (A) at least one benzonitrile compound according to formula (I) wherein

[0024] X1and X2are independently selected from a halogen, and

[0025] X3is H or a halogen,

[0026] (B1a) at least one non-sulfonated aromatic dihydroxy compound according to formula (II) wherein

[0027] R1and R2are independently selected from H, nitro and OR, wherein R is selected from C C6alkyl and C6-C12aryl, and

[0028] X is a direct bond or O,

[0029] (B1b) optionally at least one non-sulfonated aromatic dihydroxy compound according to formula (III) wherein

[0030] R3and R4are independently selected from H, nitro and OR, wherein R is selected from C Ce alkyl and C6-C12aryl,

[0031] (B2) at least one sulfonated aromatic dihydroxy component according to formula (IV) wherein

[0032] R5is selected from H, halogen, nitro and OR, wherein R is selected from aryl, and

[0033] Y is H,

[0034] (C) at least one carbonate component, and

[0035] (D) at least one aprotic polar solvent, wherein the obtained sulfonated poly(ether nitrile) polymer (sPEN) is used in an ultra / microfiltration (LIF / MF) membrane for water treatment applications.

[0036] It has surprisingly been found that the inventive sulfonyl free sulfonated poly(ether nitrile) polymers (sPEN) produced by the inventive process can be successfully processed to MF / LIF membranes using at least one pore forming additive (P) by a non-solvent induced phase separation process.

[0037] By using the components (A), (B1a), (B1b) and (B2), also the use of the endocrine disruptors bisphenol S and bisphenol A as monomers can be avoided. All monomers used in the inventive preparation process are REACH registered and commercially available.

[0038] The sulfonyl free sulfonated poly(ether nitrile) polymers (sPEN) show high glass transition temperatures and can be produced in existing assets for producing poly(aryl sulfone) polymers which is very cost-effective.

[0039] The MF / LIF membranes comprising the inventive sulfonated poly(ether nitrile) polymers (sPEN) show an improved fouling propensity and oxidation resistance. They are also stable to basic environment.

[0040] The present invention will be described in more detail hereinafter. Process for the of a sulfonated

[0041] The process for the preparation of a sulfonated poly(ether nitrile) polymer (sPEN) comprises step I) converting a reaction mixture (RG) comprising the components (A), (B1a), optionally (B1 b), (B2), (C) and (D) described above.

[0042] The components (A), (B1a), optionally (B1 b), and (B2) enter a polycondensation reaction.

[0043] Component (D) acts as a solvent and component (C) acts as a base to deprotonate components (B1a), optionally (B1b), and (B2) during the condensation reaction.

[0044] The reaction mixture (RG) is understood to mean the mixture that is used according to the present invention for preparing the sulfonated poly(ether nitrile) polymer (sPEN). 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 (A1), (B1a), optionally (B1 b), and (B2) to give the target product, the sulfonated poly(ether nitrile) polymer (sPEN). The mixture obtained after the polycondensation which comprises the sulfonated poly(ether nitrile) polymer (sPEN) 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 component (B2) to deprotonate component (B1 a) and / or optionally component (B1 b) and / or component (B2). Deprotonated components (B1a) and / or optionally (B1b), and / or (B2) then react with component (A), wherein the halide compound is formed. This process is known to the person skilled in the art.

[0045] 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.

[0046] 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 components (B1a) and / or optionally (B1b), and / or component (B2) and also the condensation reaction between components (A), (B1a), optionally (B1 b), and (B2) takes place in a single reaction stage without isolation of the intermediate products, for example the deprotonated species of components (B1a) and / or optionally (B1 b), and / or (B2). 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.

[0047] 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).

[0048] 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.

[0049] Another object of the present invention is therefore also a process wherein the reaction mixture (RG) does not comprise any substance which forms an azeotrope with water.

[0050] The ratio of component (A), component (B1a), optionally component (B1 b), and 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.

[0051] Preferably, the molar ratio of component (A) to components (B1a), optionally (B1 b), and (B2) is 1.

[0052] Preferably, the conversion in the polycondensation reaction is at least 0.9.

[0053] Process step I) for the preparation of the sulfonated poly(ether nitrile) polymer (sPEN) 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.

[0054] The isolation of the sulfonated poly(ether nitrile) polymer (sPEN) 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 sulfonated poly(ether nitrile) polymer (sPEN) is carried out by precipitation of the product mixture (PG) in water. The precipitated sulfonated poly(ether nitrile) polymer (sPEN) 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.

[0055] It is possible to filter the product mixture (PG) after step I). The halide compound can thereby be removed.

[0056] The present invention therefore also provides a process wherein the process furthermore comprises step

[0057] II) filtration of the product mixture (PG) obtained in step I).

[0058] In a preferred embodiment, the reaction mixture (RG) comprises component (A) in an amount of 50 mol-%, component (B1a) in an amount of from 25 to 49 mol-%, preferably of from 30 to 45 mol- %, component (B1b) 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 1 to 7.5 mol-%, preferably of from 1 to 5 mol-%, based on the sum of the mol-% of components (A), (B1a), (B1b) and (B2).

[0059] Therefore, another object of the present invention is also a process wherein the reaction mixture (RG) comprises component (A) in an amount of 50 mol-%, component (B1a) in an amount of from 25 to 49 mol-%, component (B1b) in an amount of from 0 to 17.5 mol-%, and component (B2) in an amount of from 1 to 7.5 mol-%, based on the sum of the mol-% of components (A), (B1a), (B1b) and (B2).

[0060] The reaction mixture (RG) comprises as component (A) at least one benzonitrile compound according to formula (I) wherein

[0061] X1and X2are independently selected from a halogen, and

[0062] X3is H or a halogen.

[0063] 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).

[0064] 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.

[0065] 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).

[0066] Another object of the present invention is therefore also a process wherein component (A) is 2,6-dichloro-benzonitrile.

[0067] 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.

[0068] 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).

[0069] 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.

[0070] “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).

[0071] In a further preferred embodiment, component (A) consists of 2,6-dichloro-benzonitrile.

[0072] Component (B1a)

[0073] The reaction mixture (RG) comprises as component (B1a) at least one non-sulfonated aromatic dihydroxy compound according to formula (II) wherein

[0074] R1and R2are independently selected from H, nitro and OR, wherein R is selected from CrCe alkyl and C6-C12aryl, and

[0075] X is a direct bond or O.

[0076] 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 (B1a) means precisely one non-sulfonated aromatic dihydroxy compound according to formula (II).

[0077] “Non-sulfonated” within the context of the present invention means that the nonsulfonated aromatic dihydroxy compound (B1a) does not comprise any -SO2X group, wherein X is selected from the group consisting of Cl and O' combined with one cation equivalent.

[0078] “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 NH4+.

[0079] 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 (B1a).

[0080] Since the reaction mixture (RG) comprises at least one carbonate component (C), the hydroxyl groups of component (B1a) in the reaction mixture (RG) may be present partially in deprotonated form.

[0081] Component (B1 a) is preferably used as a monomer. This means that the reaction mixture (RG) comprises component (B1a) preferably as monomer and not as prepolymer.

[0082] 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.

[0083] Preferably, component (B1a) is 4,4’-dihydroxybiphenyl.

[0084] In a preferred embodiment, component (B1a) 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 (B1a) in reaction mixture (RG).

[0085] In a further particularly preferred embodiment, component (B1a) consists essentially of a non-sulfonated aromatic dihydroxy compound according to formula (II). What is meant herein by "consisting essentially of' is that component (B1a) 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 (B1a) in reaction mixture (RG).

[0086] In a further preferred embodiment, component (B1a) consists of a non-sulfonated aromatic dihydroxy compound according to formula (II), preferably of 4,4’- dihydroxybiphenyl.

[0087] Component (B1 b)

[0088] The reaction mixture (RG) optionally comprises as component (B1b) at least one non- sulfonated aromatic dihydroxy compound according to formula (III) wherein

[0089] R3and R4are independently selected from H, nitro and OR, wherein R is selected from CrCe alkyl and C6-C12aryl.

[0090] 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 (B1b) means precisely one non-sulfonated aromatic dihydroxy compound according to formula (III).

[0091] “Non-sulfonated” within the context of the present invention also means that the non- sulfonated aromatic dihydroxy compound (B1b) does not comprise any -SO2X group, wherein X is selected from the group consisting of Cl and O' combined with one cation equivalent.

[0092] “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 NH4+. 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 (B1b).

[0093] 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.

[0094] 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.

[0095] 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.

[0096] Preferably, component (B1b) 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.

[0097] Therefore, the present invention accordingly also provides a process wherein component (B1a) is 4,4’-dihydroxybiphenyl and component (B1b) is hydroquinone.

[0098] In a preferred embodiment, component (B1b) 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 (B1b) in reaction mixture (RG).

[0099] In a further particularly preferred embodiment, component (B1b) consists essentially of a non-sulfonated aromatic dihydroxy compound according to formula (III).

[0100] 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).

[0101] In a further preferred embodiment, component (B1b) consists of a non-sulfonated aromatic dihydroxy compound according to formula (III), preferably of hydroquinone. Component (B2)

[0102] The reaction mixture (RG) comprises as component (B2) at least one sulfonated aromatic dihydroxy component according to formula (IV), wherein

[0103] R5is selected from H, halogen, nitro and OR, wherein R is selected from C Ce alkyl and C6-C12aryl, and

[0104] Y is H, Na or K.

[0105] 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.

[0106] “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.

[0107] “Cation equivalent” within the context of the present invention means a cation of a single positive charge, for example, Na+or K+.

[0108] The reaction mixture (RG) preferably comprises from 1 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), (B1a), optionally (B1 b), and (B2).

[0109] The sum of the mol-% of components (A), (B1a), optionally (B1 b), and (B2) usually is 100 mol-%.

[0110] 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. Component (B2) is preferably selected from 2,5-dihydroxybenzene sulfonic acid or 2,5- dihydroxybenzene sulfonic acid potassium salt.

[0111] Therefore, another object of the present invention is also a process wherein component (B2) is 2,5-dihydroxybenzene sulfonic acid or 2,5-dihydroxybenzene sulfonic acid potassium salt.

[0112] 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 (RG).

[0113] 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).

[0114] 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.

[0115] “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).

[0116] In a further particularly preferred embodiment, component (B2) consists of 2,5- dihydroxybenzene sulfonic acid or 2,5-dihydroxybenzene sulfonic acid potassium salt.

[0117] 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. 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.

[0118] 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).

[0119] Another object of the present invention is therefore also a process wherein component (C) comprises at least 50 % by weight of potassium carbonate, based on the total weight of component (C).

[0120] In a preferred embodiment component (C) consists essentially of potassium carbonate.

[0121] “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).

[0122] In a particularly preferred embodiment component (C) consists of potassium carbonate.

[0123] Potassium carbonate having a volume weighted average particle size of less than 200 pm 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.

[0124] In a preferred embodiment, the reaction mixture (RG) does not comprise any alkali metal hydroxides or alkaline earth metal hydroxides.

[0125] Component (D)

[0126] 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.

[0127] Preferably, component (D) is selected from the group consisting of N-methylpyrrolidone, N-butylpyrrolidone, N-tert-butylpyrrolidone, N-dimethylacetamide, dimethyl sulfoxide, sulfolane and N,N-dimethylformamide. N-methylpyrrolidone is particularly preferred as component (D). Another object of the present invention is therefore also a process wherein component (D) is selected from the group consisting of N-methylpyrrolidone, N- butylpyrrolidone, N-tert-butylpyrrolidone, N-dimethylacetamide, dimethyl sulfoxide, sulfolane and N,N-dimethylformamide.

[0128] 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 N,N- dimethylformamide, based on the total weight of component (D) in the reaction mixture (RG). N-methylpyrrolidone is particularly preferred as component (D).

[0129] In a further preferred embodiment, component (D) consists essentially of N-methylpyrrolidone.

[0130] “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- butylpyrrolidone, N-dimethylacetamide, dimethyl sulfoxide, sulfolane and N,N- dimethylformamide with preference given to N-methylpyrrolidone.

[0131] In a preferred embodiment, component (D) consists of N-methylpyrrolidone. N-methylpyrrolidone is also referred to as NMP or N-methyl-2-pyrrolidone.

[0132] Sulfonated polyfether nitrile) polymer (sPEN)

[0133] A further object of the present invention is a sulfonated poly(ether nitrile) polymer (sPEN) obtained by the above-described process.

[0134] The sulfonated poly(ether nitrile) polymer (sPEN) obtainable by the above-described process can comprise units that are derived from component (A) and from component (B1a) and / or optionally component (B1b), as well as units that are derived from component (A) and from component (B2). In a preferred embodiment, the sulfonated poly(ether nitrile) polymer (sPEN) consists of units that are derived from component (A) and from component (B1a) and / or optionally component (B1 b), as well as of units that are derived from component (A) and from component (B2).

[0135] Preferred sulfonated poly(ether nitrile) polymer (sPEN) comprise repeating units of the general formula (V): wherein k = 0.01 to 0.3, m = 0 to 0.4, and n = 0.1 to 0.9.

[0136] Therefore, a further object of the present invention is a sulfonated poly(ether nitrile) polymer (sPEN), wherein the sulfonated poly(ether nitrile) polymer (sPEN) comprise repeating units of the general formula (V): wherein k = 0.01 to 0.3, m = 0 to 0.4, and n = 0.1 to 0.9.

[0137] In a preferred embodiment, k = 0.01 to 0.3, m = 0.01 to 0.4, and n = 0.1 to 0.9.

[0138] The sulfonated poly(ether nitrile) polymer (sPEN) obtained by the process described above has a glass transition temperature (TG). Preferably, the sulfonated poly(ether nitrile) polymer (sPEN) has a glass transition temperature (TG) in the range from 190 to 230 °C obtained by differential scanning calorimetry (DSC) according to ISO 11357-1 (2017) and 11357-2 (2020) at 20 K / min.

[0139] The sulfonated poly(ether nitrile) polymer (sPEN) obtained by the process described above preferably also has a viscosity number of 100 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). 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 Kriiss DSA100 (A. KRUSS Optronic GmbH, Hamburg, Germany) at 23°C placing 8 to 10 drops of deionized water with a volume of approximately 2 L on the sample.

[0140] Therefore, another object of the present invention is a sulfonated poly(ether nitrile) polymer (sPEN), wherein the sulfonated poly(ether nitrile) polymer (sPEN) has a glass transition temperature from 190 to 230 °C obtained by DSC according to ISO 11357-1 (2017) and 11357-2 (2020) at 20 K / min and a viscosity number from 100 to 270 ml / g according to ISO 1628-5 (1998) in a 1 wt.-% polymer solution in N-methylpyrrolidone, and a monolithic film of the poly(ether nitrile) polymer (PEN) has water contact angle from 55 to 70 °.

[0141] The weight average molecular weight (Mw) of the sulfonated poly(ether nitrile) polymer (sPEN) is generally in the range from 30 000 to 130 000 g / mol, preferably in the range from 50 000 to 110 000 g / mol and more preferably in the range from 60 000 to 105 000 g / mol. The weight average molecular weights (Mw) are measured using gel permeation chromatography (GPC). Dimethylacetamide (DMAc) and 0.5 wt.-% LiBrwere used as solvent and narrowly distributed polymethyl methacrylate was used as standard in the measurement.

[0142] In addition, the sulfonated poly(ether nitrile) polymer (sPEN) preferably has a polydispersity MW / MNin the range from 2 to 2.8.

[0143] 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.

[0144] Membrane (M)

[0145] The sulfonated poly(ether nitrile) polymer (sPEN) obtained by the process described above can be comprised in a membrane (M).

[0146] Therefore, another object of the present invention is also a membrane (M) comprising the inventive sulfonated poly(ether nitrile) polymer (sPEN).

[0147] Another object of the present invention is therefore also the use of the inventive sulfonated poly(ether nitrile) polymer (sPEN) in a membrane (M), especially in an ultra / microfiltration (LIF / MF) membrane for water treatment applications. The membrane (M) comprises preferably at least 50 % by weight of the sulfonated poly(ether nitrile) polymer (sPEN), more preferably at least 70 % by weight and most preferably at least 90 % by weight of the sulfonated poly(ether nitrile) polymer (sPEN), based on the total weight of the membrane (M).

[0148] In a further preferred embodiment, the membrane (M) consists essentially of the sulfonated poly(ether nitrile) polymer (sPEN).

[0149] “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 sulfonated poly(ether nitrile) polymer (sPEN), based on the total weight of the membrane (M).

[0150] During the formation of the membrane (M) the sulfonated poly(ether nitrile) polymer (sPEN) is separated from at least one solvent. Therefore, the obtained membrane (M) is essentially free from the at least one solvent.

[0151] “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).

[0152] 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).

[0153] 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.

[0154] Membrane preparation

[0155] A membrane (M) can be prepared from the sulfonated poly(ether nitrile) polymer (sPEN) according to the present invention by any method known to the skilled person.

[0156] Preferably, the membrane (M) comprising the sulfonated poly(ether nitrile) polymer (sPEN) is prepared by a method comprising the steps i) providing a solution (S) which comprises the sulfonated poly(ether nitrile) polymer (sPEN), 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).

[0157] Another object of the present invention is therefore a method for the preparation of a membrane (M), wherein the method comprises the steps i) providing a solution (S) which comprises the sulfonated poly(ether nitrile) polymer (sPEN), 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).

[0158] Step i)

[0159] In step i) a solution (S) is provided which comprises the sulfonated poly(ether nitrile) polymer (sPEN), at least one pore forming additive (P) and at least one solvent.

[0160] “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.

[0161] 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 sulfonated poly(ether nitrile) polymer (sPEN) and the at least one pore forming additive (P) in the at least one solvent.

[0162] The dissolution of the sulfonated poly(ether nitrile) polymer (sPEN) 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.

[0163] 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.

[0164] The solution (S) preferably comprises the sulfonated poly(ether nitrile) polymer (sPEN) 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 sulfonated poly(ether nitrile) polymer (sPEN) and the at least one pore forming additive (P). Therefore, the sulfonated poly(ether nitrile) polymer (sPEN) and the at least one pore forming additive (P) preferably cannot be separated from the at least one solvent by filtration.

[0165] The solution (S) preferably comprises from 10 to 25 % by weight of the sulfonated poly(ether nitrile) polymer (sPEN), 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 sulfonated poly(ether nitrile) polymer (sPEN), 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).

[0166] Optionally, the solution (S) can comprise from 0 to 15 % by weight, preferably from 8 to 12 % by weight of a non-solvent, based on the total weight of the solution (S). The nonsolvent can, for example, be 1 ,2-propanediol.

[0167] Another object of the present invention is therefore also a method, wherein the solution (S) provided in step i) comprises in the range from 10 to 25 wt.-% of the sulfonated poly(ether nitrile) polymer (sPEN), 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).

[0168] As the at least one solvent, any solvent known to the skilled person for the sulfonated poly(ether nitrile) polymer (sPEN) 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.

[0169] Another object of the present invention is therefore also a method 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. 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).

[0170] The solution (S) provided in step i) furthermore comprise at least one pore forming additive (P) for the membrane preparation.

[0171] Suitable pore forming additives (P) are poly(alkylene oxides) and poly(vinyl pyrrolidone).

[0172] Examples for suitable poly(alkylene oxides) are poly(ethylene oxide), polypropylene oxide) and poly(ethylene oxide)-poly(propylene oxide) copolymer. Preferred poly(alkylene oxides) are poly(ethylene oxides) PEO 200 to 2,000,000 g / mol.

[0173] As poly(vinyl pyrrolidone) poly(vinyl pyrrolidone) K12 to 90 is preferred.

[0174] As pore forming additive (C), poly(vinyl pyrrolidone) is preferred.

[0175] Another object of the present invention is therefore also a method for the preparation of a membrane (M), wherein the at least one pore forming additive (P) is selected from the group consisting of poly(alkylene oxides) and poly(vinyl pyrrolidone).

[0176] 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).

[0177] To the person skilled in the art, it is clear that the percentages by weight of the sulfonated poly(ether nitrile) polymer (sPEN), 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.

[0178] 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 sulfonated poly(ether nitrile) polymer (sPEN) and the at least one pore forming additive (P) in the at least one solvent.

[0179] For the sulfonated poly(ether nitrile) polymer (sPEN) comprised in the solution (S) the embodiments and preferences given for the sulfonated poly(ether nitrile) polymer (sPEN) obtained in the process described above hold true.

[0180] Step ii) 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).

[0181] 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).

[0182] 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).

[0183] 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.

[0184] 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.

[0185] 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.

[0186] Another object of the present invention is therefore also a method for the preparation of a membrane (M), wherein the separation in step ii) is performed by a phase inversion process.

[0187] 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.

[0188] Therefore, another object of the present invention is a membrane (M), wherein the membrane (M) is a porous membrane (M).

[0189] As a person skilled in the art knows, the porous membrane (M) typically has a top layer and a supporting structure at the bottom, wherein the top layer is the active filtration layer. The top layer, as well as the supporting structure typically comprise pores, wherein the pore size distribution of the top layer is actually the only decisive factor for the properties of the membrane. In general, the pore size of the top layer is smaller than the pore size of the supporting structure at the bottom.

[0190] Preferably, the pore size of the membrane (M) increases from the top layer, which is used for separation, to the bottom of the membrane (M). Therefore, such a membrane (M) is also called an asymmetric membrane (M).

[0191] A further object of the present invention is therefore a membrane (M), wherein the membrane (M) is asymmetric.

[0192] The minimal pore diameter of the membrane (M) is preferably < 5 nm.

[0193] The supporting structure can have diameters up to 10 pm.

[0194] A phase inversion process within the context of the present invention means a process wherein the dissolved sulfonated poly(ether nitrile) polymer (sPEN) 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 sulfonated poly(ether nitrile) polymer (sPEN). The person skilled in the art knows suitable phase inversion processes.

[0195] The phase inversion process can, for example, be performed by cooling down the solution (S). During this cooling down, the sulfonated poly(ether nitrile) polymer (sPEN) comprised in the solution (S) precipitates. Another possibility to perform the phase inversion process is to bring the solution (S) in contact with a vapour that is a non-solvent for the sulfonated poly(ether nitrile) polymer (sPEN). The sulfonated poly(ether nitrile) polymer (sPEN) will then as well precipitate. Suitable vapours, that are non-solvents for the sulfonated poly(ether nitrile) polymer (sPEN), are, for example, protic polar solvents described hereinafter in their gaseous state. Another phase inversion process, which is preferred within the context of the present invention, is the phase inversion by immersing the solution (S) into at least one protic polar solvent.

[0196] Therefore, in one embodiment of the present invention, in step ii), the at least one pore forming additive (P) and the at least one solvent comprised in the solution (S) are separated from the sulfonated poly(ether nitrile) polymer (sPEN) comprised in the solution (S) by immersing the solution (S) into at least one protic polar solvent.

[0197] This means that the membrane (M) is formed by immersing the solution (S) into at least one protic polar solvent. Suitable protic polar solvents are known to the skilled person. The at least one protic polar solvent is preferably a non-solvent for the sulfonated poly(ether nitrile) polymer (sPEN).

[0198] Preferred at least one protic polar solvents are water, methanol, ethanol, n-propanol, isopropanol, glycerol, ethylene glycol and mixtures thereof. Preferably, the at least one protic polar solvent is water.

[0199] Therefore, another object of the present invention is a method for the preparation of a membrane (M), wherein the at least one protic polar solvent is water.

[0200] The at least one protic polar solvent is usually comprised in a coagulation bath. The coagulation bath preferably also comprises further components, for example, the same solvent as comprised in the solution (S).

[0201] Step ii) usually comprises a provision of the solution (S) in a form that corresponds to the form of the membrane (M) which is obtained in step ii).

[0202] Therefore, in one embodiment of the present invention step ii) comprises a casting of the solution (S) to obtain a film of the solution (S).

[0203] Therefore, in one preferred embodiment of the present invention, 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) immersing the film of the solution (S) into at least one protic polar solvent, wherein the sulfonated poly(ether nitrile) polymer (sPEN) comprised in the film of 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 the film of the solution (S) to obtain a membrane (M1) which is in the form of a film, and ii-3) washing the membrane (M1) with water, wherein the sulfonated poly(ether nitrile) polymer (sPEN) comprised in the membrane (M1) is completely separated from the at least one pore forming additive (P) and the at least one solvent comprised in the membrane (M1) to obtain the membrane (M).

[0204] 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 sulfonated poly(ether nitrile) polymer (sPEN), based on the total weight of the sulfonated poly(ether nitrile) polymer (sPEN) comprised in the film of the solution (S), are separated from the at least one pore forming additive (P) and the at least one solvent.

[0205] 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 sulfonated poly(ether nitrile) polymer (sPEN), based on the total weight of the sulfonated poly(ether nitrile) polymer (sPEN) comprised in the membrane (M1), are separated from the at least one pore forming additive (P) and the at least one solvent.

[0206] In step ii-1) the solution (S) can be cast by any method known to the skilled person. Usually, the solution (S) is cast with a casting knife that is heated to a temperature in the range from 20 to 100 °C, preferably in the range from 40 to 80°C.

[0207] Therefore, another object of the present invention is a method for the preparation of a membrane (M), wherein step ii-1) is carried out at a temperature in the range of 40 to 80°C.

[0208] The solution (S) is usually cast on a substrate that does not react with the sulfonated poly(ether nitrile) polymer (sPEN), the at least one pore forming additive (P) or the at least one solvent comprised in the solution (S).

[0209] Suitable substrates are known to the skilled person and are, for example, selected from glass plates and polymer fabrics such as non-woven materials.

[0210] In step ii-2), the film of the solution (S) is preferably immersed into at least one protic polar solvent at a temperature in the range of 20 to 80°C, more preferably at a temperature in the range of 20 to 60°C. For the at least one protic polar solvent, the same definitions, embodiments and preferences as described above apply.

[0211] In step ii-3), the membrane (M1) is preferably washed at a temperature in the range of 20 to 100°C, more preferably at a temperature in the range of 50 to 70°C.

[0212] Before washing, the membrane (M) can also be exposed to a water bath containing a NaOCI solution at 60 °C and a pH of 9.5.

[0213] The membrane (M) obtained in step ii-3) is preferably a flat sheet membrane.

[0214] For the production of 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 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.

[0215] The membrane (M) has preferably a pure water permeation (PWP) > 100 kg nr2bar1IT1, a MWCO < 30 kDa and a PEO retention / fouling propensity > 85 %.

[0216] The present invention is further elucidated by the following examples without limiting it thereto.

[0217] Examples

[0218] Components used

[0219] Component (A): 2,6-Dichlorobenzonitrile (26DCBN, CAS 1194-65-6), Alzchem

[0220] Group AG, Trostberg, Germany

[0221] Component (B1a): 4,4'-Dihydroxybiphenyl (DHBP, CAS 92-88-6)

[0222] Component (B1 b): Hydroquinone (HC, CAS 123-31-9), Sigma-Aldrich Chemie GmbH, Taufkirchen, Germany

[0223] Component (B2): 2,5-Dihydroxybenzenesulfonic acid potassium salt (HCS, CAS 21799-87-1), Alfa Aesar, 2 Radcliff Rd Tewksbury, MA 01876, USA

[0224] Component (C): Potassium carbonate (K2CO3), anhydrous

[0225] Component (D): N-methylpyrrolidone (NMP, CAS 872-50-4), Th. Geyer GmbH &

[0226] Co. KG, Dornierstr. 4-6, 71272 Renningen, Germany

[0227] General procedures

[0228] The proportion of HC and HCS units are determined by1H-NMR-spectroscopy in CDCI3at 400 MHz.

[0229] 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 11357-1 (2017) and 11357-2 (2020) at 20 K / min.

[0230] The molecular weight is determined by gel permeation chromatography (GPC) in dimethylacetamide (DMAc) and 0.5 wt.-% LiBr using a PMMA standard.

[0231] Comparative Example C1 : non-sulfonated polyfether nitrile) polymer (PEN)

[0232] 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.

[0233] 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.

[0234] 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.

[0235] Example 2: sulfonated polyfether nitrile) polymer (sPEN)

[0236] 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.

[0237] 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.

[0238] 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 (sPEN) are summarized in table 1.

[0239] Table 1

[0240] As can be seen from table 1 , the inventive sulfonated poly(ether nitrile) polymer (sPEN) shows a higher glass transition temperature compared to the glass transition temperature of the non-sulfonated poly(ether nitrile) polymer. Preparation of membranes

[0241] Components used

[0242] PEN: non-sulfonated poly(ether nitrile) polymer according to CE1 sPEN: sulfonated poly(ether nitrile) polymer according to E2 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; which is abbreviated as “E6020P”

[0243] Luvitec® K90: polyvinylpyrrolidone with a molecular weight Mwof 1 000 000 to

[0244] 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”

[0245] Luvitec® K30: polyvinylpyrrolidone with a molecular weight Mwof 44 000 to

[0246] 540 000 g / mol and a solution viscosity characterized by the K- value of 30, determined according to the method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932 (58)); which is abbreviated as “K30”

[0247] General procedure

[0248] 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 g membrane polymer and 5 or 6 g Luvitec® polyvinylpyrrolidone in 75 or 80 g 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.

[0249] Table 2: Compositions of polyethernitrile and Ultrason® E 6020 P solutions prepared with PVP in NMP

[0250] After that, the membrane solution was reheated at 60 °C for 2 hours and casted onto a glass plate with a casting knife (300 microns) at 60 °C using an Erichsen Coating machine (Coatmaster 510, Erichsen GmbH & Co KG, Hemer, Germany) operating at a speed of 5 mm / s. The membrane film was allowed to rest for 30 seconds before immersion at 25 °C for 10 minutes in a water-based coagulation bath consisting of a mixture of the same solvent used for the preparation of the above-mentioned polymer solution and water at a ratio of 60:40 based on weight. After the membrane had detached from the glass plate, the membrane was exposed to a water bath containing a 2000 ppm NaOCI solution at 60 °C and a pH of 9.5 for 2 h. The membrane was then washed with water at 60 °C and one time with a 0.5wt.-% solution of sodium bisulfite to remove active chlorine. After the posttreatment the membranes are stored in a wet state.

[0251] Membrane characterization

[0252] • Solution viscosity

[0253] 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 5 to 100 rpm.

[0254] • Solution Turbidity

[0255] 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).

[0256] • Determination of the membrane water permeability

[0257] The pure water permeability (PWP) of the membranes is tested using a pressure cell with a diameter of 74 mm using ultrapure water (salt-free water, filtered by a Millipore UF-system) at 23 °C and 1 bar water pressure. The pure water permeability (PWP) is calculated as follows (equation (1)):

[0258] PWP: pure water permeability [kg / bar h m2] m: mass of permeated water [kg]

[0259] A: membrane area [m2]

[0260] P: pressure [bar] t: time of the permeation experiment [h],

[0261] • Determination of the membrane’s molecular weight cut-off (MWCO)

[0262] In a subsequent test, solutions of poly(ethylene oxide)-standards with increasing molecular weight are used as feed to be filtered by the membrane at a pressure of 0.15 bar. By GPC-measurement of the feed and permeate, the molecular weight of the permeate of each poly(ethylene oxide)-standard used is determined.

[0263] • Determination of the membrane’s fouling propensity

[0264] The pure water permeability is measured after the MWCO determination again, wherein PWPAis obtained. Together with the pure water permeability measured before the membranes'exposure to the solution of poly(ethylene oxide)-standards (PWPB), the fouling propensity is calculated (equation (2)):

[0265] PWP : pure water permeance after MWCO measurement [kg I bar h m2]

[0266] PWPB: pure water permeance before MWCO measurement [kg I bar h m2] R: fouling propensity [%].

[0267] Table 3: Properties of the membranes prepared from solutions according to table

[0268] 2; coagulation water-NMP (60 / 40 wt / wt) Permeance retention: PWPA / PWPB* 100 [%]

[0269] As can be seen from table 3, sPEN polymers are forming under comparable non-solvent induced phase separation conditions tighter fine porous ultrafiltration membranes with lower flux (MWCO < 20 kDa; PWP < 500 kg / h m2bar) compared to membranes based on PEN (MWCO < 30 kDa; PWP > 700 kg / h m2bar) and PESU (MWCO < 50 kDa; PWP > 700 kg / h m2bar). The sPEN based membranes according to the invention are showing a reduced fouling propensity with permeation retention rates of higher than 85 % compared to PEN with lower than 80 % and PESU having only 70 % as closest state of the art.

[0270] Figure 1 shows a cross-section of the membrane of inventive example Ex. M2. Figure 2 shows a cross-section of the membrane of comparative example Ex. MC4 and figure 3 shows a cross-section of the membrane of comparative example Ex. MC5 (all figures 1500 x magnification). As can be seen from the figures, sPEN polymers are forming under comparable non-solvent induced phase separation conditions tighter fine porous ultrafiltration membranes without maco-voids compared to membranes based on PEN and PESU.

Claims

Claims1. Process for the preparation of a sulfonated poly(ether nitrile) polymer (sPEN) comprising stepI) converting a reaction mixture (RG) comprising as components(A) at least one benzonitrile compound according to formula (I)whereinX1and X2are independently selected from a halogen, and X3is H or a halogen,(B1a) at least one non-sulfonated aromatic dihydroxy compound according to formula (II)whereinR1and R2are independently selected from H, nitro and OR, wherein R is selected from C C6alkyl and C6-C12aryl, andX is a direct bond or O,(B1b) optionally at least one non-sulfonated aromatic dihydroxy compound according to formula (III)whereinR3and R4are independently selected from H, nitro and OR, wherein R is selected from Ci-C6alkyl and C6-Ci2aryl,(B2) at least one sulfonated aromatic dihydroxy component according to formula (IV)whereinR5is selected from H, halogen, nitro and OR, wherein R is selected from aryl, andY is H,(C) at least one carbonate component, and(D) at least one aprotic polar solvent, wherein the obtained sulfonated poly(ether nitrile) polymer (sPEN) is used in an ultra / microfiltration (LIF / MF) membrane for water treatment applications.

2. The process according to claim 1 , wherein component (A) is 2,6-dichloro- benzonitrile.

3. The process according to claim 1 or claim 2, wherein component (B1a) is 4,4’- dihydroxybiphenyl and component (B1b) is hydroquinone.

4. The process 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 process 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 process 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 process 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 25 to 49 mol-%, component (B1b) in an amount of from 0 to 17.5 mol-%, and component (B2) in an amount of from 1 to 7.5 mol-%, based on the sum of the mol-% of components (A), (B1a), (B1b) and (B2).

8. Sulfonated poly(ether nitrile) polymer (sPEN) obtained by a process according to any one of claims 1 to 7.

9. Sulfonated poly(ether nitrile) polymer (sPEN) according to claim 8, wherein the sulfonated poly(ether nitrile) polymer (sPEN) comprise repeating units of the general formula (V):wherein k = 0.01 to 0.3,m = 0 to 0.4, and n = 0.1 to 0.9.

10. Sulfonated poly(ether nitrile) polymer (sPEN) according to claim 8 or 9, wherein the sulfonated poly(ether nitrile) polymer (sPEN) has a glass transition temperature from 190 to 230 °C obtained by DSC according to ISO 11357-1 (2017) and 11357-2 (2020) at 20 K / min and a viscosity number from 100 to 270 ml / g according to ISO 1628-5 (1998) in a 1 wt.-% polymer solution in N- methylpyrrolidone, and a monolithic film of the poly(ether nitrile) polymer (PEN) has water contact angle from 55 to 70 °.

11. A membrane (M) comprising a sulfonated poly(ether nitrile) polymer (sPEN) according to any of claims 8 to 10.

12. The membrane (M) according to claim 11 , wherein the membrane (M) is a porous membrane (M).

13. The membrane (M) according to claim 11 or claim 12, wherein the membrane (M) is asymmetric.

14. A method for the preparation of a membrane (M) according to any one of claims 11 to 13, wherein the method comprises the steps i) providing a solution (S) which comprises the sulfonated poly(ether nitrile) polymer (sPEN), 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).

15. The method according to claim 14, 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, gammavalerolactone, dihydrolevoglucosenone, methyl 5-(dimethylamino)-2-methyl-5- oxopentanoate and sulfolane.

16. The method according to claim 14 or claim 15, wherein the solution (S) provided in step i) comprises in the range from 10 to 25 wt.-% of the sulfonated poly(ether nitrile) polymer (sPEN), 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).

17. The method according to any one of claims 14 to 16, wherein the separation in step ii) is performed by a phase inversion process.

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