Poly(arylene ether sulfone) polymer membranes

Abstract

The present invention relates to a membrane comprising two different poly(arylene ether sul- fone) polymers (P1) and (P2), manufacturing methods therefor and its uses.

Description

[0001] Poly(arylene ether sulfone) polymer membranes

[0002] Description

[0003] The present invention relates to a membrane comprising two different poly(arylene ether sulfone) polymers (P1) and (P2), manufacturing methods therefor and its uses.

[0004] Membrane technologies have reached a lot of attention during the last decades. In several application areas membranes are used for the energy efficient separation of mixtures. Particularly, membranes are widely used for water purification (J.-C. Schrotter, B. Bozkaya-Sch rotter in ..Membranes for Water Treatment", Ed. K.-V. Peinemann, S. Pereira Nunes, Wiley-VCH, Vol. 4, 2010). Another important field of use for specific membranes is the purification of blood, in particular blood dialysis (hemodialysis) or blood filtration dialysis therapies that are necessary in the treatment of people suffering from renal kidney disease (C.R. Ronco, W.R. Clark, Nature Reviews Nephrology, 14, 2018, 394).

[0005] To be suitable in membrane applications, polymeric materials need to exhibit particular mechanical properties, thermal stability and chemical resistance. One promising class of materials for membrane applications are polyarylene sulfones. They belong to the group of high-performance polymers having high heat resistance, chemical resistance, excellent mechanical properties, and durability (E.M. Koch, H.-M. Walter, Kunststoffe 80 (1990) 1146; E. Dbring, Kunststoffe 80, (1990) 1149, N. Inchaurondo-Nehm, Kunststoffe 98, (2008) 190). For example, they are suitable as material for forming dialysis membranes and ultrafiltration (UF) membranes in general (N. A. Hoenich, K. P. Katapodis, Biomaterials 23 (2002) 3853; S. Savariar, G.S. Underwood, E.M. Dickinson, P.J. Schielke, A.S. Hay, Desalination 144 (2002) 15). Membrane material that is being used for membranes for medical purposes has to fulfill certain criteria and the quality standards for membranes used in medical applications are particularly high. For example; it is often necessary to sterilize the membrane which usually means that the membrane is subjected to higher temperatures. Therefore, the membrane material needs to be temperature resistant in the required temperature range.

[0006] One particular problem connected with ultrafiltration membranes is membrane fouling leading to undesirable decay of membrane performance. A further challenge in membrane technology is the adjustment of an appropriate pore size, in particular for specific membranes such as dialysis membranes. Both issues have been addressed by using the non-solvent induced phase separation (NIPS) process and by utilizing a hydrophilic pore-forming agent such as polyvinylpyrrolidone (PVP) together with the respective membrane-forming polymer. DE 19817364 is directed to a process for the preparation of hydrophilic membranes with high porosity using a first hydrophobic polymer and a second hydrophilic polymer, wherein, for example, the first polymer is a polysulfone and the hydrophilic polymer is a polyvinylpyrrolidone. In particular, DE 19817364 uses two polyvinylpyrrolidones with different molecular weights, leading to membranes with im- proved porosity. In EP 2113298 the same approach is used to make polyethersulfone-based dialysis membranes.

[0007] An approach to produce ultrafiltration membranes without the use of a pore forming component via the NIPS-process is described in EP0344581. EP0344581 uses dope solutions containing a polyarylate and a polysulfone as membrane polymers. One disadvantage of the methods described in the examples of EP0344581 is, however, that the polyarylate polymer turns out to have limited solubility and the components are instable in solvents usually employed in membrane fabrication, such as N-methyl-2-pyrrolidone (NMP), resulting in turbid solutions. Furthermore, polyarylates are polyesters that have limited stability against longer use in aqueous environments. Hence, the applicability of this approach in ultrafiltration membrane technology is quite limited.

[0008] There is need for membranes, particularly ultrafiltration membranes exhibiting an excellent selectivity and high membrane productivity as well as good mechanical properties, particularly suitable for medical applications such as dialysis. Specifically, there is need for ultrafiltration membranes having low molecular weight cut-off and high water permeation rate at the same time as well as good aging stability. Further, the polymer material needs to have good viscosity properties to be suitable to be formed into stable membranes. Also, the membrane material should exhibit certain hydrophilic characteristics to enable the membrane to be wetted by the liquid that needs to pass the membrane. The pore size is also a crucial parameter as the pores need to be wide enough to allow for high flow (PWP = pure water permeability) of the liquid to be purified through the membrane while having selective retention properties. In particular, in case of dialysis, the molecular weight cut off is supposed to be lower than 100 kD in order to avoid proteins to pass through as well. Additionally, the pores need to be connected to account for a high permeate flux. A further objective underlying the present invention was to provide stable polymer solutions for the production of membranes, in particular to be used in the NIPS process, which can thus effectively be used for the preparation of ultrafiltration membranes.

[0009] These objects are successfully addressed by the inventive membrane (M) comprising poly(arylene ether sulfone) polymers (P1) and (P2), wherein (P1) and (P2) comprise at least one structural repeating unit selected from the following units la to Is:

[0010] wherein x is from 0.05 to 1 and n is 1; wherein x is from 0.05 to 1 and n is 1 ; wherein the at least one structural repeating unit of (P2) is different from the at least one structural repeating unit of (P1).

[0011] The membranes according to the invention show excellent selectivity and efficiency and, at the same time, are surprisingly stable and exhibit excellent aging properties and surprising maintenance of membrane performance over time.

[0012] In the context of the present invention, the term “membrane” means a semipermeable structure acting as a selective barrier, allowing some particles, substances or chemicals to pass through, while retaining others. In general, membranes are applied in various liquid and gaseous separations. The membrane may have various geometries such as flat sheet, spiral wound, pillows, tubular, single bore hollow fiber or multiple bore hollow fiber.

[0013] For example, membranes (M) can be nanofiltration (NF) membranes, microfiltration (MF) membranes and ultrafiltration (UF) membranes. These membrane types are generally known in the art.

[0014] NF membranes are normally especially suitable for removing multivalent ions and large monovalent ions. Typically, NF membranes function through a solution / diffusion or / and filtrationbased mechanism. NF membranes are normally used in crossflow filtration processes. Nanofiltration membranes often comprise charged polymers comprising sulfonic acid groups, carboxylic acid groups and / or ammonium groups.

[0015] MF membranes normally have an average pore diameter of 0.05 pm to 10 pm, preferably 1.0 pm to 5 pm, and they are normally suitable for removing particles with a particle size of 0.1 pm and above. Microfiltration can use a pressurized system, but it does not need to include pressure. MF membranes can be hollow fibers, capillaries, flat sheet, tubular, spiral wound, pillows, hollow fine fiber or track etched. They are porous and allow water, monovalent species (Na+, CI-), dissolved organic matter, small colloids, and viruses to pass through but retain particles, sediment, algae or large bacteria.

[0016] UF membranes are normally suitable for removing suspended solid particles and solutes of high molecular weight, for example above 100,000 Da. UF membranes may be particularly suitable for removing bacteria and viruses. Usually, UF membranes have an average pore diameter of 0.5 nm to 50 nm, preferably 1 to 40 nm, more preferably 5 to 20 nm.

[0017] The inventive membrane (M) can be used in any processes known to the skilled person in which membranes are used.

[0018] The skilled person is familiar with the preparation of membranes in general. It is known that during the preparation of the membrane the solvent exchange usually leads to an asymmetric membrane structure.

[0019] The membrane (M) may be a porous membrane. A porous membrane typically comprises pores, wherein the pores usually have a diameter in the range of from 1 nm to 10000 nm, preferably in the range of from 2 to 500 nm and particularly preferably in the of range from 5 to 250 nm determined via filtration experiments using a solution containing different PEG'S covering a molecular weight from 300 to 1000000 g / mol. By comparing the GPC-traces of the feed and the filtrate, the retention of the membrane for each molecular weight can be determined. The molecular weight, where the membrane shows a 90% retention is considered as the molecular weight cutoff (MWCO) for this membrane under the given conditions. Using the known correlation between the Stoke diameters of PEG and their molecular weights, the mean pore size of a membrane can be determined. Details about this method are given in the literature (Chung, J. Membr. Sci. 531 (2017) 27-37). A porous membrane may typically be obtained if the membrane is prepared via a phase inversion process.

[0020] A dense membrane typically comprises virtually no pores. A dense membrane may typically be obtained by a solution casting process in which a solvent comprised in the casted solution is evaporated. Usually the separation layer is casted on a support, which might be another polymer like polysulfone or celluloseacetate. On top of the separation layer sometimes a layer of polydimethylsiloxane is applied.

[0021] In one embodiment of the present invention, the inventive membrane (M) is a dense membrane. In particular, if the membrane is a dense membrane, it is particularly suitable for gas separation.

[0022] The inventive membrane (M) can have any thickness. For example, the thickness of the membrane may be in the range from 2 to 350 pm, preferably in the range from 3 to 200 pm and most preferably in the range from 5 to 100 pm.

[0023] According to one embodiment of the present invention the membrane (M) of the invention is an asymmetric membrane. In a further embodiment, the membrane is porous.

[0024] The membrane (M) of the invention is particularly suitable for nanofiltration, microfiltration and / or ultrafiltration, particularly if the membrane is a porous membrane. Therefore, according to one embodiment of the invention, the membrane (M) is a nanofiltration, ultrafiltration (UF) and / or microfiltration membrane. Typical nanofiltration, ultrafiltration and microfiltration processes are known to the skilled person.

[0025] According to one particular embodiment, the inventive membrane is an ultrafiltration membrane.

[0026] In a further particular embodiment, the inventive membranes (M) are UF membranes that are spiral wound membranes, pillow membranes or flat sheet membranes. In another embodiment the inventive membranes (M) are UF membranes that are tubular membranes.

[0027] In still another embodiment thereof, the membrane (M) is a hollow fiber membrane, wherein it may be a single bore hollow fiber or multiple bore hollow fiber membrane. In a hollow fiber membrane, a semipermeable barrier is in the form of a hollow fiber.

[0028] Multiple channel membranes, also referred to as multi bore membranes, comprise more than one longitudinal channel, also referred to as “channel” or “bore”.

[0029] The number of channels is typically 2 to 19. In one embodiment, the multiple bore hollow fiber membrane comprises two or three channels. In another embodiment, the multiple bore hollow fiber membrane comprises 5 to 9 channels. In one specific embodiment, the multiple bore hollow fiber membrane comprises seven channels. In yet another embodiment, the multiple bore hollow fiber membrane comprises 20 to 100 channels.

[0030] The shape of the bore or bores may vary. Normally, the membranes according to the invention have an essentially circular, ellipsoid or rectangular diameter. Preferably, membranes according to the invention are essentially circular, i.e. the bores have an essentially circular diameter.

[0031] In another embodiment, such bores have an essentially ellipsoid diameter. In yet another embodiment, channels have an essentially rectangular diameter. In some cases, the actual form of such channels may deviate from the idealized circular, ellipsoid or rectangular form.

[0032] Normally, such channels have an outer diameter (for essentially circular diameters), an outer smaller diameter (for essentially ellipsoid diameters) or an outer smaller feed size (for essentially rectangular diameters) of 0.05 mm to 3 mm, preferably 0.5 to 2 mm, more preferably 0.9 to 1.5 mm. In another preferred embodiment, such channels have an outer diameter (for essentially circular diameters), an outer smaller diameter (for essentially ellipsoid diameters) or an outer smaller feed size (for essentially rectangular diameters) in the range from 0.2 to 0.9 mm.

[0033] According to the invention, in one preferred embodiment, the hollow fiber membranes have an outer diameter (for essentially circular diameters), an outer smaller diameter (for essentially ellipsoid diameters) or an outer smaller feed size (for essentially rectangular diameters) of 2 to 10 mm, preferably 3 to 8 mm, more preferably 4 to 6 mm. In another preferred embodiment according to the invention, the hollow fiber membranes have an outer diameter (for essentially circular diameters), an outer smaller diameter (for essentially ellipsoid diameters) or an outer smaller feed size (for essentially rectangular diameters) of 2 to 4 mm.

[0034] The hollow fiber membrane can have any thickness. For example, the thickness of the membrane is in the range from 20 to 150 pm, preferably in the range from 20 to 100 pm and most preferably in the range from 30 to 60 pm. This can be particularly suitable for dialysis membranes.

[0035] If multi-bore hollow fiber membranes contain channels with an essentially rectangular shape, these channels can be arranged in a row. If the channels in a multi-bore hollow fiber membrane have essentially circular shape, these channels are preferably arranged such that a central channel is surrounded by the other channels. In one preferred embodiment, a membrane comprises one central channel and for example four, six or 18 further channels arranged cyclically around the central channel. The wall thickness in such multiple channel membranes is normally from 0.02 to 1 mm at the thinnest position, preferably 30 to 500 pm, more preferably 100 to 300 pm.

[0036] According to one embodiment, in the inventive membrane (M), the at least one repeating structural unit for (P1) and (P2), respectively, is preferably selected from the units la to Io and Is.

[0037] According to a further embodiment, in the inventive membrane (M), the at least one repeating structural unit for (P1) and (P2), respectively, is preferably selected from the units la to Io.

[0038] According to still a further embodiment, in the inventive membrane (M), the at least one repeating structural unit for (P1) and (P2), respectively, is preferably selected from the units la, Ig, Ik, Ip, and Is, more specifically selected from the units la, Ig, Ik, and Is.

[0039] In still a further embodiment of the inventive membrane (M), the at least one repeating structural unit for (P1) and (P2), respectively, is preferably selected from the units la, Ig and Ik.

[0040] The poly(arylene ether sulfone) comprising structural repeating units of formula la is also termed polysulfone (PSU).

[0041] The poly(arylene ether sulfone) comprising structural repeating units of formula Ig is also termed polyphenylene sulfone (PPSLI).

[0042] The poly(arylene ether sulfone) comprising structural repeating units of formula Ik is also termed polyether sulfone (PESLI or PES).

[0043] For the purposes of the present disclosure, abbreviations such as PSU, PPSU, PESU (PES) are in accordance with DIN EN ISO 1043-1:2001. According to one particular embodiment, (P1) comprises the unit la as structural repeating unit and (P2) comprises the unit Ig.

[0044] According to a further particular embodiment, (P1) comprises the unit la as structural repeating unit and (P2) comprises the unit Ik.

[0045] According to still a further particular embodiment, (P1) comprises the unit Ig as structural repeating unit and (P2) comprises the unit Ik.

[0046] According to a further particular embodiment of the invention, (P1) comprises the unit la as structural repeating unit and (P2) comprises the unit Ip.

[0047] According to still a further particular embodiment, (P1) comprises the unit Ig as structural repeating unit and (P2) comprises the unit Ip.

[0048] According to still a further particular embodiment, (P1) comprises the unit Ik as structural repeating unit and (P2) comprises the unit Ip.

[0049] According to a further particular embodiment of the invention, (P1) comprises the unit la as structural repeating unit and (P2) comprises the unit Is.

[0050] According to still a further particular embodiment, (P1) comprises the unit Ig as structural repeating unit and (P2) comprises the unit Is.

[0051] According to still a further particular embodiment, (P1) comprises the unit Ik as structural repeating unit and (P2) comprises the unit Is.

[0052] Other repeating units, in addition to the at least one unit selected from the units la to Is present in (P1) or (P2), respectively, are those in which one or more 1 ,4-phenylene units deriving from hydroquinone have been replaced by 1 ,3-phenylene units deriving from resorcinol, or by naphthylene units deriving from dihydroxynaphthalene.

[0053] The weight-average molar masses Mwof the poly(arylene ether sulfone) polymer (P1) and (P2), respectively, are preferably in the range of from 10 000 to 180 000 g / mol, more preferably in the range from 15 000 to 150 000 g / mol and particularly preferably in the range from 20 000 to 125 000 g / mol, determined by means of gel permeation chromatography in dimethylacetamide as solvent against narrowly distributed polymethyl methacrylate as standard. More specifically, the Mwis from 10 000 to 100 000 g / mol, more specifically from 10 000 to 95 000 g / mol, in particular from 12 000 to 93 000 g / mol, particularly preferably from 14 000 to 90 000 g / mol, determined by means of gel permeation chromatography in dimethylacetamide as solvent against narrowly distributed polymethyl methacrylate as standard.

[0054] The viscosity number (V.N.) of the poly(arylene ether sulfone) polymer (P1) and (P2), respectively, is determined as a 1 % solution in N-methylpyrrolidone at 25 °C. The viscosity number (V.N.) is preferably the range of from 60 to 120 ml / g. It is preferred according to one embodiment, if the poly(arylene ether sulfone) polymers (P1) and / or (P2) used in the inventive membranes (M) have high purity, in particular with respect to the cyclic oligomer content. The “cyclic dimer” is an unwanted side product that can be formed during polycondensation when preparing the polymers. This impurity is measurable by means of the turbidity of the polymer product in solution, using DMF, DMAc, or NMP as solvent. Methods for the measurement of turbidity are well-known to the skilled person.

[0055] Production processes that lead to the abovementioned poly(arylene ether sulfone) polymers are known per se to the person skilled in the art and are described by way of example in Herman F. Mark, "Encyclopedia of Polymer Science and Technology", third edition, volume 4, 2003, chapter “Polsulfones” pages 2 to 8, and also in Hans R. Kricheldorf, "Aromatic Polyethers" in: Handbook of Polymer Synthesis, second edition, 2005, pages 427 to 443.

[0056] The synthesis of the poly(arylene ether sulfone) polymers can generally be done by polycondensation of appropriate monomers in dipolar-aprotic solvents at elevated temperatures.

[0057] An overview of the preparation of poly(arylene ether sulfone) polymers using the hydroxide method and using the carbonate method is given, for example, in R.N. Johnson et.al. , J. Polym. Sci. A-1 5 (1967) 2375 and J.E. McGrath et.al., Polymer 25 (1984) 1827. Moreover, the production of polyarylethersulfone polymers are described in the patent applications US4870153, EP113112, EP297363 and EP135130, which are hereby incorporated by reference. In these patent applications suitable educts, catalysts, solvents and ratios of the used components as well as reaction times and reaction temperatures can be found.

[0058] For the carbonate method, the aromatic dihydroxyl compound and the aromatic dihalogen compound are reacted together in the presence of carbonates, preferably potassium carbonate. In general, N,N-dimethylacetamide, DMF, N-Ethylpyrrolidone or NMP is preferably used as solvent, and toluene or chlorobenzene is added as azeotroping agent for the removal of water. Preference is given to a process without the use of an azeotroping agent.

[0059] Compared to the hydroxide method, the carbonate method has the advantage that the potassium carbonate excess can vary in a comparatively wide regime without decreasing the molecular weights of the polymers formed. The reaction control is thereby simplified in comparison with the hydroxide method. According to the present invention, poly(arylene ether sulfone) polymers produced by any process can be used.

[0060] Particular preference is given to the reaction, in aprotic polar solvents and in the presence of anhydrous alkali metal carbonate, in particular sodium carbonate, potassium carbonate, calcium carbonate, or a mixture thereof, very particularly preferably potassium carbonate, between at least one aromatic compound having two halogen substituents and at least one aromatic compound having two functional groups reactive toward abovementioned halogen substituents. One particularly suitable combination is N-methyl-2-pyrrolidone as solvent and potassium carbonate as base.

[0061] It is preferable that the poly(arylene ether sulfone) polymers (P1) and / or (P2) have either halogen end groups, in particular chlorine end groups, or etherified end groups, in particular alkyl ether end groups, these being obtainable via reaction of the OH or, respectively, phenolate end groups with suitable etherifying agents. Examples of suitable etherifying agents are monofunctional alkyl or aryl halide, e.g. CT -C6-alkyl chloride, C Ce-alkyl bromide, or C C6-alkyl iodide, preferably methyl chloride, or benzyl chloride, benzyl bromide, or benzyl iodide, or a mixture thereof. For the purposes of the polyarylene(ether)sulfones of component A) preferred end groups are halogen, in particular chlorine, alkoxy, in particular methoxy, aryloxy, in particular phenoxy, or benzyloxy.

[0062] The combined % by weight of the poly(arylene ether sulfone) polymers (P1) and (P2) comprised in the inventive membrane (M) is preferably at least 50 % by weight, more preferably at least 70 % by weight and most preferably at least 90 % by weight, based on the total weight of the membrane (M). In a further preferred embodiment, the membrane (M) consists essentially of the poly(arylene ether sulfone) polymers (P1) and (P2). “Consisting essentially of” means that the membrane (M) comprises more than 95% by weight, preferably more than 97.5% by weight and most preferably more than 98% by weight of the poly(arylene ether sulfone) polymers (P1) and (P2), as combined % by weight of (P1) and (P2) and based on the total weight of the membrane.

[0063] According to one embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, in the inventive membrane (M) is 40 to 98% by weight, more specifically 45 to 97% by weight, even more specifically 50 to 96% by weight, even more specifically 60 to 95% by weight, based on the total weight of the membrane (M).

[0064] In the inventive membrane (M), the ratio of poly(arylene ether sulfone) polymers (P1) to (P2), as defined and preferably defined herein, can be any possible weight ratio, such as for example 1 :10 to 10:1, in particular 1:9 to 9:1 , more particularly 1:8 to 8:1 , even more particularly 1:7 to 7:1. According to specific embodiments, the ratio can be 1:6 to 6:1 or 1 :5 to 5:1, in particular 1 :4 to 4:1, more particularly 1:3 to 3:1, even more particularly 1 :2 to 2:1. According to one very particular embodiment of the present invention, (P1) and (P2) may be present in equal or nearly equal amounts (1 :1). Nearly equal amounts” within this context means that the difference in amounts of (P1) and (P2) is only in a neglectable range.

[0065] The membrane of the present invention may also comprise at least one hydrophilic polymer additive (A). In particular, the at least one additive (A) is selected from poly(alkylene oxides), polyvinylpyrrolidone (PVP) and a sulfonated poly(arylene ether sulfone) polymer (SP).

[0066] According to one specific embodiment, the membrane (M) does not contain any additive (A). Polyvinylpyrrolidone is commercially available, e.g. Luvitec® from BASF SE. According to one embodiment, the PVP has a solution viscosity characterized by a K-value of at least 12 (PVP K12), of at least 30 (PVP K30) or of at least 85 (PVP K85). It may be preferred, if the PVP has a solution viscosity characterized by a K-value of at least 80 (PVP K80), such as for example Luvitec® K80. In a further preferred embodiment, the PVP has a solution viscosity characterized by a K-value of at least 85 (PVP K85), such as for example Luvitec® K85. It may be also preferred, if the PVP has a solution viscosity characterized by a K-value of at least 90 (PVP K90), such as for example Luvitec® K90.

[0067] The solution viscosity is determined according to the method of Fikentscher (Fikentscher, Cellu- losechemie 13, 1932 (58).

[0068] The sulfonated poly(arylene ether sulfone) polymer preferably comprises units of formula (I) wherein the definitions of the symbols t, q, Q, T, Y, Ar and Ar1are as follows: t, q independently of one another 0, 1 , 2 or 3;

[0069] Q, T, Y independently of one another a chemical bond or a group selected from -O-, -S-,

[0070] -SO2-, S=O, C=O, -N=N- and -CRaRb-, wherein Raand Rbindependently of one another are a hydrogen atom, (C C12)alkyl, (C C^jalkoxy, (C3-C12)cycloalkyl or a (C6-C18)aryl group, and wherein at least one of Q, T, and Y is present and is -SO2-; and

[0071] Ar and Ar1independently of one another (C6-Ci8)arylene; and where at least one unit (I) comprises an arylene group which is substituted with at least one -SO2X group, wherein X is selected from the group consisting of Cl and O' combined with one cation equivalent, where the cation equivalent is H+, Li+, Na+, K+, Mg2+, Ca2+or NH4+.

[0072] If Q, T or Y, among the abovementioned conditions, is a chemical bond, this is understood to mean that the adjacent group to the left and the adjacent group to the right are bonded directly to one another via a chemical bond. It will be readily appreciated that at least one of the groups consisting of Q, T and Y being -SO2- means that at least one group in formula (I) is -SO2-. Thus, when q is = 0, at least one of T and Y is -SO2-; when, for example, t is = 0, at least one of Q and Y is -SO2- and when q = 0 and t = 0 then Y is SO2.

[0073] According to one preferred embodiment, t and q are independently 0 or 1 . According to one preferred embodiment, Q, T, and Y in formula II are independently selected from a chemical bond, -O-, -SO2- and -CRaRb-, with the proviso that at least one of Q, T, and Y is present and is -SO2-. Furthermore, it may be preferred, if Raand Rbare, independently of one another, hydrogen or (C C^alkyl.

[0074] In -CRaRb-, Raand Rbare preferably independently selected from hydrogen, (C C12)alkyl, (C C12)alkoxy and (C6-C18)aryl.

[0075] (Ci-Ci2)alkyl refers to linear or branched saturated hydrocarbon groups having from 1 to 12 carbon atoms. The following moieties are particularly encompassed: (Ci-C6)alkyl, e.g. methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, 2- or 3-methylpentyl, as well as (C7-Ci2)alkyl , e.g. unbranched heptyl, octyl, nonyl, decyl, undecyl, lauryl, and the singly branched or multibranched analogs thereof.

[0076] The term " C C^-alkoxy" refers to a linear or branched alkyl group having 1 to 12 carbon atoms which is bonded via an oxygen, at any position in the alkyl group, e.g. methoxy, ethoxy, n- propoxy, 1 -methylethoxy, butoxy, 1-methyhpropoxy, 2-methylpropoxy or 1 ,1 -dimethylethoxy.

[0077] (C3-C12)cycloalkyl refers to monocyclic saturated hydrocarbon radicals having 3 to 12 carbon ring members and particularly comprises (C3-C8)cycloalkyl, e.g. cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, cyclopropylmethyl, cyclopropylethyl, cyclopropylpropyl, cyclobutylmethyl, cyclobutylethyl, cyclopentylethyl, -propyl, -butyl, -pentyl, -hexyl, cyclohexylmethyl, -dimethyl, and -trimethyl.

[0078] Ar and Ar1are independently of one another a (C6-C18)-arylene group. It may be preferred that, according to a specific embodiment, Ar1is an unsubstituted (C6-C12)arylene group.

[0079] It may be preferred that Ar and Ar1are independently selected from phenylene, bisphenylene and naphthylene groups, and from arylene groups that derive from anthracene, from phenanthrene, or from naphthacene. For examples, Ar and Ar1are independently selected from 1 ,2-phenylene, 1 ,3-phenylene, 1 ,4-phenylene, 1 ,6-naphthylene, 1 ,7-naphthylene, 2,6-naphthylene and 2,7-naphthylene, 2,7-dihydroxynaphthylene and 4,4'-bisphenylene.

[0080] In particular, it may be preferred that Ar and Ar1are independently selected from phenylene and naphthylene groups, such as independently selected from 1 ,2-phenylene, 1 ,3-phenylene, 1 ,4- phenylene, 1 ,6-naphthylene, 1 ,7-naphthylene, 2,6-naphthylene and 2,7-naphthylene, more specifically independently selected from 1 ,4-phenylene, 1 ,3-phenylene and naphthylene. Furthermore, according to another embodiment of the present invention Ar and Ar1are independently selected from arylene groups that derive from anthracene, from phenanthrene, or from naphthacene. According to still a further embodiment, Ar and Ar1are independently selected from 2,7-dihydroxynaphthylene and 4,4'-bisphenylene. Preferred sulfonated poly(arylene ether sulfone) polymers are those comprising at least one of the units la to Io as repeating structural units as defined and preferably defined herein, wherein at least one unit unit la to Io comprises an arylene group which is substituted with at least one - SO2X group, wherein X is selected from the group consisting of Cl and O' combined with one cation equivalent, where the cation equivalent is H+, Li+, Na+, K+, Mg2+, Ca2+or NH4+:

[0081] According to one embodiment, the sulfonated poly(arylene ether sulfone) polymer comprises at least one unit selected from the units la, Ig and Ik as repeating structural units, wherein at least one of said units comprises an arylene group which is substituted with at least one -SO2X group, wherein X is selected from the group consisting of Cl and O' combined with one cation equivalent, where the cation equivalent is H+, Li+, Na+, K+, Mg2+, Ca2+or NH4+:

[0082] According to one embodiment, the sulfonated poly(arylene ether sulfone) polymer comprises structural repeating units of formula la and is also termed sulfonated polysulfone (sPSU). Therein, unit la comprises an arylene group which is substituted with at least one -SO2X group, wherein X is selected from the group consisting of Cl and O' combined with one cation equivalent, where the cation equivalent is H+, Li+, Na+, K+, Mg2+, Ca2+or NH4+:

[0083] According to a further embodiment, the sulfonated poly(arylene ether sulfone) polymer comprises structural repeating units of formula Ig and is also termed sulfonated polyphenylene sulfone (sPPSU). Therein, unit Ig comprises an arylene group which is substituted with at least one -SO2X group, wherein X is selected from the group consisting of Cl and O' combined with one cation equivalent, where the cation equivalent is H+, Li+, Na+, K+, Mg2+, Ca2+or NH4+:

[0084] According to still a further embodiment, the sulfonated poly(arylene ether sulfone) polymer comprises structural repeating units of formula Ik and is also termed sulfonated polyether sulfone (sPESU or sPES). Therein, unit Ik comprises an arylene group which is substituted with at least one -SO2X group, wherein X is selected from the group consisting of Cl and O' combined with one cation equivalent, where the cation equivalent is H+, Li+, Na+, K+, Mg2+, Ca2+or NH4+:

[0085] Sulfonated poly(arylene ether sulfone) polymers are known since decades (A. Noshay, L.M. Robeson, J. Appl. Polym. Sci. 20 (1976) 1885). While the direct sulfonation of poly(arylene ether sulfone) polymers is leading to side reactions and allows only limited control on the degree of sulfonation, the use of the di-sulfonated dichloro-diphenylsulfone (sDCDPS) as co-monomer allows the synthesis of well-defined sulfonated poly(arylene ether sulfone) polymers (lleda et.al., J. Polym. Sci. A, Polym. Chem. 31 (1993) 853; J.E. McGrath et.al., Macromol. Symp. 175 (2001) 387). Further details about the synthesis of high molecular weight sulfonated poly(arylene ether sulfone) polymers can be found in PCT / EP2023 / 064280.

[0086] According to one embodiment, the additive (A) preferably comprises polyvinylpyrrolidone (PVP). More preferably, the hydrophilic polymer additive (A) comprises at least 50% by weight, preferably at least 60% by weight, in particular at least 70% by weight of PVP in relation to the amount of additive (A) in the membrane. In a preferred embodiment, the hydrophilic polymer additive (A) consists of polyvinylpyrrolidone as defined and preferably herein. In one embodiment, the membrane (M) comprises PVP as defined and preferably defined herein.

[0087] If present, the amount of PVP, as defined and preferably defined herein, in the inventive membrane (M) is preferably from 0.1 to 5% by weight based on the total weight of the membrane, more specifically from 0.2 to 3% by weight, even more specifically from 0.3 to 2% by weight. In a further embodiment, the amount of PVP in the inventive membrane is from 0.4 to 1.5% by weight, more specifically from 0.5 to 1.3% by weight, even more specifically from 0.6 to 1.2% by weight. In still a further embodiment, the amount of PVP is from 0.7 to 1.1% by weight. In particular PVP may be present in an amount of 0.1 to 1% by weight, more specifically 0.3 to 1% by weight.

[0088] According to one specific embodiment of the present invention, the inventive membrane (M) is essentially free from PVP. “Essentially free” within the context of the present invention means that the membrane comprises at most 0.05 % by weight, preferably at most 0.04 % by weight and particularly preferably at most 0.03 % by weight, more specifically at most 0.01 % by weight of PVP based on the total weight of the membrane. According to one very specific embodiment, the inventive membrane (M) does not contain any PVP.

[0089] According to still a further embodiment, the additive (A) preferably comprises a sulfonated poly(arylene ether sulfone) polymer (SP). Preferably, the hydrophilic polymer additive (A) comprises at least 50% by weight, preferably at least 60% by weight, in particular at least 70% by weight of a sulfonated poly(arylene ether sulfone) polymer (SP) in relation to the amount of additive (A) in the membrane. In a preferred embodiment, the hydrophilic polymer additive (A) consists of at least one sulfonated poly(arylene ether sulfone) polymer (SP) as defined and preferably herein. In one embodiment, the membrane (M) comprises at least one sulfonated poly(arylene ether sulfone) polymer (SP) as defined and preferably defined herein.

[0090] If present, the amount of sulfonated poly(arylene ether sulfone) polymer (SP) in the inventive membrane (M) is preferably from 0.1 to 5% by weight based on the total weight of the membrane, more specifically from 0.2 to 3% by weight, even more specifically from 0.3 to 2% by weight. In a further embodiment, the amount of sulfonated poly(arylene ether sulfone) polymer (SP) in the inventive membrane is from 0.4 to 1.5% by weight, more specifically from 0.5 to 1.3% by weight, even more specifically from 0.6 to 1.2% by weight. In still a further embodiment, the amount of sulfonated poly(arylene ether sulfone) polymer (SP) is from 0.7 to 1.1% by weight. In particular, sulfonated poly(arylene ether sulfone) polymer (SP) may be present in an amount of 0.1 to 1% by weight, more specifically 0.3 to 1% by weight. According to one specific embodiment of the present invention, the inventive membrane (M) is essentially free from sulfonated poly(arylene ether sulfone) polymer (SP). “Essentially free” within the context of the present invention means that the membrane comprises at most 0.05 % by weight, preferably at most 0.04 % by weight and particularly preferably at most 0.03 % by weight, more specifically at most 0.01 % by weight of sulfonated poly(arylene ether sulfone) polymer (SP) based on the total weight of the membrane. According to one very specific embodiment, the inventive membrane (M) does not contain any sulfonated poly(arylene ether sulfone) polymer (SP).

[0091] According to a further embodiment of the invention, the membrane (M) comprises polyvinylpyrrolidone (PVP) as defined and preferably defined above and a sulfonated poly(arylene ether sulfone) polymer (SP) as defined and preferably defined above.

[0092] According to still a further embodiment, the at least one additive (A) comprises poly(alkylene oxides), in particular selected from poly(ethylene oxide), polypropylene oxide) and poly(ethylene oxide)-poly(propylene oxide) copolymers.

[0093] According to a further embodiment of the invention, the membrane (M) comprises poly(alkylene oxides) selected from poly(ethylene oxide), polypropylene oxide) and poly(ethylene oxide)- polypropylene oxide) copolymers.

[0094] If present, the amount of poly(alkylene oxides) in the inventive membrane (M) is preferably from 0.1 to 5% by weight based on the total weight of the membrane, more specifically from 0.2 to 3% by weight, even more specifically from 0.3 to 2% by weight. In a further embodiment, the amount of poly(alkylene oxides) in the inventive membrane is from 0.4 to 1.5% by weight, more specifically from 0.5 to 1 .3% by weight, even more specifically from 0.6 to 1 .2% by weight. In still a further embodiment, the amount of poly(alkylene oxides) is from 0.7 to 1.1% by weight. In particular, poly(alkylene oxides) may be present in an amount of 0.1 to 1% by weight, more specifically 0.3 to 1 % by weight.

[0095] As is self-explanatory for the skilled person, all constituents of the membrane (M) add up to 100 % by weight.

[0096] The membrane (M) can be prepared by any method for the preparation of a membrane. A further object of the present invention is a method for the preparation of a membrane (M) comprising the steps: a) providing a composition (C), comprising the poly(arylene ether sulfone) polymers (P1) and (P2) as defined and preferably defined herein, and at least one solvent (D); b) separating the at least one solvent (D) from the composition (C) to obtain the membrane (M). The composition (C) in step a) comprises (P1) and (P2) as defined and preferably defined herein. It may be preferred, if the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 10% by weight or more, based on the total weight of the composition (C). According to a further embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 11% by weight or more, more specifically 12% by weight or more, based on the total weight of the composition (C). According to a specific embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 13% by weight or more, based on the total weight of the composition (C).

[0097] In a particular embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 14% by weight or more, based on the total weight of the composition (C). According to a further embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 15% by weight or more, more specifically 16% by weight or more, based on the total weight of the composition (C). According to a further specific embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 17% by weight or more, based on the total weight of the composition (C).

[0098] Furthermore, it may be preferred according to the invention, if the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 18% by weight or more, based on the total weight of the composition (C). According to still a further embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 19% by weight or more, more specifically 20% by weight or more, based on the total weight of the composition (C). According to still a further specific embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 21% by weight or more, based on the total weight of the composition (C). It may be further preferred according to one embodiment, if the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 22% by weight or more, more specifically 23% by weight or more, even more specifically 24% by weight or more, even more specifically 25% by weight or more based on the total weight of the composition (C).

[0099] According to one embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 10 to 30% by weight, more specifically 13 to 25% by weight, even more specifically 15 to 23% by weight or more, based on the total weight of the composition (C).

[0100] The ratio of poly(arylene ether sulfone) polymers (P1) to (P2), as defined and preferably defined herein, in composition (C) can be any possible weight ratio, such as for example 1:10 to 10:1 , in particular 1:9 to 9:1 , more particularly 1:8 to 8:1 , even more particularly 1:7 to 7:1. According to specific embodiments, the ratio can be 1 :6 to 6:1 or 1 :5 to 5:1 , in particular 1:4 to 4:1 , more particularly 1 :3 to 3:1 , even more particularly 1:2 to 2:1. According to one very particular embodiment of the present invention, (P1) and (P2) may be present in equal or nearly equal amounts (1:1) in compositions (C). Nearly equal amounts” within this context means that the difference in amounts of (P1) and (P2) is only in a neglectable range.

[0101] “At least one solvent” within the context of the present invention means precisely one solvent, and also a mixture of two or more solvents.

[0102] Preferably, the at least one solvent (D) is an aprotic polar solvent. In particular, the at least one solvent (D) is soluble in water.

[0103] According to one embodiment, the at least one solvent (D) is preferably selected from the group consisting of N-alkyl-2-pyrrolidone, preferably N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N- butyl-2-pyrrolidone and N-tert.-butyl-2-pyrrolidone, 2-pyrrolidone, N-dimethylacetamide, dimethylsulfoxide, dimethylformamide, N,N-dimethyl-2-hydroxypropan amide, N,N-diethyl-2- hydroxypropan amide, y-valerolactone, dihydrolevoglucosenone, methyl 5-(dimethylamino)-2- methyl-5-oxopentanoate and sulfolane. N-alkyl-2-pyrrolidone, y-valerolactone and N,N-dimethyl- 2-hydroxypropan amide are particularly preferred. N-methylpyrrolidone is most preferred as the at least one solvent (D).

[0104] According to one embodiment, the composition (C) comprises solvent (D) in an amount such that the total amount of all constituents in the composition add up to 100% by weight.

[0105] The composition (C) preferably comprises in the range of from 50 to 85% by weight of the at least one solvent (D), preferably in the range from 55 to 84% by weight of the at least one solvent (D), more preferably in the range from 60 to 83% by weight of the at least one solvent (D), even more preferably in the range from 67 to 82% by weight of the at least one solvent (D), based on the total weight of the composition (C). According to a particular embodiment, the composition (C) preferably comprises, in the range of from 68 to 75% by weight of the at least one solvent (D), also preferably in the range from 70 to 75% by weight of the at least one solvent (D).

[0106] Further, the composition (C) may also comprise a hydrophilic polymer additive (A) as defined and preferably defined above for the membrane (M). According to one particular embodiment, the composition (C) does not contain any additive (A).

[0107] According to a preferred embodiment, the composition (C) comprises polyvinylpyrrolidone (PVP) as defined and preferably herein.

[0108] If present, the amount of PVP, as defined and preferably defined herein, in the composition (C) is preferably from 0.1 to 8% by weight based on the total weight of the composition (C), more specifically from 0.2 to 6% by weight, even more specifically from 0.3 to 5% by weight. In a further embodiment, the amount of PVP in the composition (C) is from 0.4 to 3% by weight, more specifically from 0.5 to 2.5% by weight, even more specifically from 0.6 to 2.0% by weight. In still a further embodiment, the amount of PVP is from 0.7 to 1.8% by weight. In particular, PVP may be present in an amount of 0.1 to 1 .7% by weight, more specifically 0.3 to 1 .5% by weight.

[0109] According to one specific embodiment of the present invention, the composition (C) is essentially free from PVP. “Essentially free” within the context of the present invention means that the composition (C) comprises at most 0.05 % by weight, preferably at most 0.04 % by weight and particularly preferably at most 0.03 % by weight, more specifically at most 0.01 % by weight of PVP based on the total weight of the composition (C). According to one very specific embodiment, the composition (C) does not contain any PVP.

[0110] According to a further embodiment, the composition (C) preferably comprises a sulfonated poly(arylene ether sulfone) polymer (SP) as defined and preferably defined above for the membrane (M).

[0111] If present, the amount of sulfonated poly(arylene ether sulfone) polymer (SP), as defined and preferably defined herein, in the composition (C) is preferably from 0.1 to 5% by weight based on the total weight of the composition (C), more specifically from 0.2 to 3% by weight, even more specifically from 0.3 to 2% by weight. In a further embodiment, the amount of sulfonated poly(arylene ether sulfone) polymer (SP) in the composition (C) is from 0.4 to 1.5% by weight, more specifically from 0.5 to 1.3% by weight, even more specifically from 0.6 to 1 .2% by weight. In still a further embodiment, the amount of sulfonated poly(arylene ether sulfone) polymer (SP) is from 0.7 to 1.1 % by weight. In particular, the sulfonated poly(arylene ether sulfone) polymer (SP) may be present in an amount of 0.1 to 1 % by weight, more specifically 0.3 to 1 % by weight.

[0112] According to one specific embodiment of the present invention, the composition (C) is essentially free from sulfonated poly(arylene ether sulfone) polymer (SP). “Essentially free” within the context of the present invention means that the composition (C) comprises at most 0.05 % by weight, preferably at most 0.04 % by weight and particularly preferably at most 0.03 % by weight, more specifically at most 0.01 % by weight of sulfonated poly(arylene ether sulfone) polymer (SP), based on the total weight of the composition (C). According to one very specific embodiment, the composition (C) does not contain any sulfonated poly(arylene ether sulfone) polymer (SP).

[0113] According to a further embodiment of the invention, the composition (C) comprises poly(alkylene oxides) selected from poly(ethylene oxide), polypropylene oxide) and poly(ethylene oxide)-poly(propylene oxide) copolymers. If present, the amount of poly(alkylene oxides) in the composition (C) is preferably from 0.1 to 5% by weight based on the total weight of the composition (C), more specifically from 0.2 to 3% by weight, even more specifically from 0.3 to 2% by weight. In a further embodiment, the amount of poly(alkylene oxides) in the composition (C) is from 0.4 to 1.5% by weight, more specifically from 0.5 to 1.3% by weight, even more specifically from 0.6 to 1.2% by weight. In still a further embodiment, the amount of poly(alkylene oxides) is from 0.7 to 1.1% by weight. In particular, poly(alkylene oxides) may be present in an amount of 0.1 to 1% by weight, more specifically 0.3 to 1% by weight.

[0114] The composition (C) in step a) is preferably a solution and can be provided by any method known to the skilled person, for example in customary vessels which may comprise a stirring device and preferably a temperature control device. Preferably, the composition (C) or solution, respectively, is provided by dissolving (P1) and (P2) in the at least one solvent (D), preferably under agitation.

[0115] Step a) 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.

[0116] The composition (C) or solution, respectively, preferably comprises the polymers (P1) and (P2) completely dissolved in the at least one solvent (D). This means that the composition (C) preferably comprises no solid particles of the polymers (P1) and (P2) and that the polymers (P1) and (P2) preferably cannot be separated from the at least one solvent (D) by filtration.

[0117] The duration of step a) may vary in wide limits. The duration of step a) 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 a) preferably so as to obtain a homogeneous solution.

[0118] In step b) of the inventive process the at least one solvent (D) is separated from the composition (C), or solution, respectively, to obtain the membrane (M). It is possible to filter the composition

[0119] (C), or solution, respectively, provided in step a) before the at least one solvent (D) is separated to obtain a filtered solution.

[0120] Moreover, it is possible to degas the composition (C), or solution, respectively, before the at least one solvent (D) is separated in step b), to obtain a degassed solution. This embodiment is preferred. The following embodiments and preferences for separating the at least one solvent

[0121] (D) from the composition (C) or solution, respectively, apply equally for separating the at least one solvent (D) from the degassed solution. The degassing in step a) can be carried out by any method known to the skilled person, for example, via vacuum or by allowing the composition (C) or solution, respectively, to rest. The following embodiments and preferences for separating the at least one solvent (D) from the composition (C), or solution, respectively, apply equally for separating the at least one solvent from the filtered solution which is used in this embodiment of the invention. The separation of the at least one solvent can be performed by any method known to the skilled person which is suitable to separate solvents from polymers. Preferably, the separation is carried out via a phase inversion process.

[0122] A phase inversion process within the context of the present invention means a process wherein the dissolved polymers (P1) and (P2) are transformed into a solid phase. Therefore, a phase inversion process can also be denoted as a precipitation process. The person skilled in the art knows suitable phase inversion processes.

[0123] The phase inversion process can, for example, be performed by cooling down the solution, wherein the polymers (P1) and (P2) comprised in this solution precipitate. Another possibility to perform the phase inversion process is bringing the composition in contact with a gaseous liquid that is a non-solvent for the polymers (P1) and (P2). The polymers (P1) and (P2) will then as well precipitate. Suitable gaseous liquids that are non-solvents for the polymers (P1) and (P2) are for example protic polar solvents described hereinafter in their gaseous state.

[0124] Another phase inversion process which is preferred within the context of the present invention is the phase inversion by immersing the solution into at least one protic polar solvent. Therefore, in one embodiment of the present invention, in step b) the at least one solvent (D) comprised in the composition (C) is separated from the polymers (P1) and (P2) by immersing the solution into at least one protic polar solvent. This leads to the formation of the membrane. Suitable at least one protic polar solvents are known to the skilled person. The at least one protic polar solvent is preferably a non-solvent for the polymers (P1) and (P2). Preferred at least one protic polar solvents are water, methanol, ethanol, n-propanol, iso-propanol, glycerol, ethylene glycol and mixtures thereof.

[0125] In step b) the composition (C) is usually handled such that it is brought into a form that corresponds to the desired shape of the membrane. Therefore, in one embodiment of the present invention step b) comprises casting of the composition to obtain a film of the composition or a passing of the solution through at least one spinneret to obtain at least one hollow fiber of the composition or solution, respectively. Therefore, in one preferred embodiment of the present invention, step b) comprise the following steps: b-1) casting the composition (C) or solution, respectively, provided in step a) to obtain a film of the composition; b-2) evaporating the at least one solvent from the film of the composition obtained in step b-1) to obtain the membrane which is in the form of a film. This means that the membrane is formed by evaporating the at least one solvent from a film of the composition. In step b-1) the composition can be cast by any method known to the skilled person. Usually, the composition is cast with a casting knife that is heated to a temperature in the range from 20 to 150 °C, preferably in the range from 40 to 100°C. The composition is usually cast on a substrate that does not react with the polymers (P1) and (P2) or the at least one solvent (D) comprised in the solution. Suitable substrates are known to the skilled person and are, for example, selected from glass plates and polymer fabrics such as non-woven materials. To obtain a dense membrane, the separation in step b) is typically carried out by evaporation of the at least one solvent (D) comprised in the composition.

[0126] During the formation of the membrane the poly(arylene ether sulfone) polymers (P1) and (P2) are separated from the at least one solvent (D). Therefore, the obtained inventive membrane (M) is essentially free from the at least one solvent (D). “Essentially free” within the context of the present invention means that the membrane comprises at most 1 % by weight, preferably at most 0.5 % by weight and particularly preferably at most 0.1 % by weight of the at least one solvent based on the total weight of the membrane.

[0127] A further object of the invention is a membrane (M) obtainable by the inventive method described above.

[0128] Still a further object of the invention is a separation element, a membrane module, a membrane cartridge or a separation system comprising the inventive membrane (M) as described and preferably described herein.

[0129] Still a further object of the invention is a use of an inventive membrane (M) as described and preferably described herein in an ultrafiltration process.

[0130] The present invention is also directed to a use of a membrane (M) as described and preferably described herein or of the separation element, the membrane module, the membrane cartridge or the separation system comprising the inventive membrane (M) for water treatment applications, treatment of industrial or municipal wastewater, desalination of sea or brackish water, dialysis, plasmolysis and / or food processing.

[0131] In particular, the present invention is also directed to a use of a membrane (M) as described and preferably described herein or of the separation element, the membrane module, the membrane cartridge or the separation system comprising the inventive membrane (M) for dialysis, in particular hemodialysis. According to a specific embodiment, the inventive membrane (M) is used in a dialysis process as a dialysis membrane.

[0132] Further, the present invention is directed to an apparatus for dialysis comprising an inventive membrane (M) as described and preferably described herein or of the separation element, the membrane module, the membrane cartridge or the separation system comprising the inventive membrane (M).

[0133] A further object of the present invention is a composition (C), comprising poly(arylene ether sulfone) polymers (P1) and (P2) and at least one solvent (D), wherein (P1) and (P2), respectively, comprises at least one of the units la to Is as repeating structural units as defined and preferably defined herein, wherein the at least one unit of (P2) is different from the at least one unit of (P1).

[0134] The polymers (P1) and (P2) and the solvent (D), and, if present, the additive (A), are defined and preferably defined above and the embodiments and preferences independently also apply to the inventive composition (C) accordingly.

[0135] According to one embodiment of the inventive composition (C), the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2) in the composition (C) is 10% by weight or more, based on the total weight of the composition (C).

[0136] It may be preferred, if the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 11% by weight or more, based on the total weight of the composition (C). According to a further embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 12% by weight or more, more specifically 13% by weight or more, based on the total weight of the composition (C). According to a specific embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 14% by weight or more, based on the total weight of the composition (C).

[0137] In a particular embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 15% by weight or more, based on the total weight of the composition (C). According to a further embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 16% by weight or more, more specifically 17% by weight or more, based on the total weight of the composition (C). According to a further specific embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 18% by weight or more, based on the total weight of the composition (C).

[0138] Furthermore, it may be preferred according to the invention, if the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 19% by weight or more, based on the total weight of the composition (C). According to still a further embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 20% by weight or more, more specifically 21% by weight or more, based on the total weight of the composition (C). According to still a further specific embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 22% by weight or more, based on the total weight of the composition (C). It may be further preferred according to one embodiment, if the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 23% by weight or more, more specifically 24% by weight or more, even more specifically 25% by weight or more, based on the total weight of the composition (C).

[0139] According to one embodiment, the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2), as defined and preferably defined herein, is 10 to 30% by weight, more specifically 13 to 25% by weight, even more specifically 15 to 23% by weight or more, based on the total weight of the composition (C).

[0140] The ratio of poly(arylene ether sulfone) polymers (P1) to (P2), as defined and preferably defined herein, in the inventive composition (C) can be any possible weight ratio, such as for example 1 :10 to 10:1, in particular 1:9 to 9:1 , more particularly 1:8 to 8:1 , even more particularly 1:7 to 7:1. According to specific embodiments, the ratio can be 1:6 to 6:1 or 5:1 to 1 :5, in particular 1 :4 to 4:1, more particularly 1:3 to 3:1, even more particularly 1 :2 to 2:1. According to one very particular embodiment of the inventive composition (C), (P1) and (P2) may be present in equal or nearly equal amounts in compositions (C). Nearly equal amounts” within this context means that the difference in amounts of (P1) and (P2) is only in a neglectable range.

[0141] According to one embodiment, the composition (C) comprises solvent (D), as defined and preferably defined herein, in an amount such that the total amount of all constituents in the composition add up to 100% by weight.

[0142] Surprisingly, it has been found within the framework of the present invention, that the inventive compositions (C) are outstandingly stable even at high polymer contents of poly(arylene ether sulfone) polymers (P1) and (P2). The inventive compositions (C) are highly suitable for the preparation of membranes, in particular ultrafiltration membranes, particularly in non-solvent induced phase separation processes (NIPS).

[0143] A further object of the present invention is, thus, the use of the inventive composition (C) for the production of a membrane.

[0144] Surprisingly, the specific combination of polymers (P1) and (P2) according to the present invention allows the preparation of selective as well as efficient membranes having good mechanical properties. According to the present invention it is possible to adjust of the pore size and hydrophilicity of the membrane avoiding the drawbacks of known membranes. The inventive membrane forming compositions allow high polymer contents and exhibit favorable viscosity, both crucial for the successful formation of membranes. The inventive membranes are particularly suitable for medical purposes where high quality standards exist, they have a low molecular weight cut-off and high water permeation rates, as well as good aging stability. The present invention is further elucidated by the following working examples without being limited by them.

[0145] Components and abbreviations used:

[0146] PESU-1: Polyethersulfone, V.N. =81 ml / g (1 wt.% NMP, 25°C)

[0147] PPSU: Polyphenylenesulfone, V.N. = 66 ml / g (1 wt.% NMP, 25°C) sPPSU-1 : Polyphenylenesulfone with 4.7 mol% units based on sDCDPS and biphenol, V.N.

[0148] =66.7 ml / g (1 wt.% NMP, 25°C) sPPSU-2: Polyphenylenesulfone with 19.4 mol% units based on sDCDPS and biphenol, V.N. =67.8 ml / g (1 wt.% NMP, 25°C)

[0149] PSU: Polysulfone, V.N. =80 ml / g (1 wt.% NMP, 25°C)

[0150] PAR: Polyarylat, U-100, Unitika, LtD.; V.N. =47.5 ml / g (1 wt.%NMP, 25°C)

[0151] PVP: Polyvinylpyrrolidone, e.g. K85 (BASF, SE)

[0152] NMP: N-methylpyrrolidone, anhydrous

[0153] NTU nephelometric turbidity unit

[0154] PVP K85 Polyvinylpyrrolidone with a solution viscosity characterized by the K-value of 85, determined according to the method of Fikentscher (Fikentscher, Cellulosechemie 13, 1932 (58)

[0155] MWCO molecular weight cut-off

[0156] PWP pure water permeability

[0157] The viscosity number (V.N.) of the poly(arylene ether sulfone) polymers and the polyarylate was measured according to DIN ISO 1628-1 in a 1% by weight NMP solution.

[0158] The polymer solution turbidity was 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.

[0159] Preparation of Membranes, general procedure

[0160] Into a three-neck flask equipped with a magnetic stirrer the components according to the recipes given in Table 1 were added. The mixtures were heated under gentle stirring at 60°C until a homogeneous clear viscous solution was obtained. The solution was degassed overnight at room temperature. Then, the membrane solution was reheated to 60°C for 2 hours and cast- ed onto a glass plate with a casting knife (300 microns) at 60°C using an Erichsen Coating ma- chine operating at a speed of 5 mm / min. The membrane film was allowed to rest for 30 seconds before immersion into a water / NMP 50 / 50 (by weight) bath at 25°C for 10 minutes.

[0161] After the membrane had detached from the glass plate, the membrane was carefully transferred into a water bath for 12 h. Then the membranes were washed with VE-water 3 times for 2.5 h at 75°C, wherein the water was exchanged after every washing step. Then, the membranes were stored wet until characterization started.

[0162] A part of the polymer solution was used for turbidity measurements, see above

[0163] A flat sheet continuous film with micro structural characteristics of UF membranes having dimension of at least 10x15 cm size was obtained. The membrane showed a top thin skin layer (1-10 microns) and a porous layer underneath (thickness: 100-150 microns).

[0164] Membrane characterization:

[0165] Using a pressure cell having a diameter of 60 mm, the pure water permeation of the membranes was tested using ultrapure water (salt-free water, filtered by a Millipore UF-system). In a subsequent test, a solution of different PEG-standards was filtered at a pressure of 0.15 bar. By GPC-measurement of the feed and the permeate, the molecular weight cut-off was determined.

[0166] The heat stability of the membranes was tested by storing a circular membrane piece for 60 h at 100°C in a pressure cooker. Then, the membranes were tested again with respect to their performance. In some cases, the membrane was to brittle to be tested after this treatment.

[0167] Table 1: Membrane forming solution und membrane properties:

[0168] *n.d.=not determined

[0169] **brittle = specimen was too brittle to be subjected to test

[0170] The membranes based on the new composition show higher water permeability at a comparable separation performance than the reference membrane and a much better ageing stability. M1C, M2C and M3C are comparison samples, M4 to M9 are representative for the present invention.

Claims

Claims1. A membrane (M) comprising poly(arylene ether sulfone) polymers (P1) and (P2), wherein (P1) and (P2) comprise at least one structural repeating unit selected from the following units la to Is:wherein x is from 0.05 to 1 and n is 1;wherein x is from 0.05 to 1 and n is 1;wherein x is from 0.05 to 1 and n is 1; wherein said at least one structural repeating unit of (P2) is different from the at least one structural repeating unit of (P1).

2. The membrane of claim 1, wherein the at least one structural repeating unit of (P1) and (P2), respectively, is selected from the units la, Ig and Ik, wherein said at least one structural repeating unit of (P2) is different from the at least one structural repeating unit of (P1).

3. The membrane of claim 1 or 2, wherein the at least one structural repeating unit for (P1) is Ik (PESLI), and the at least one structural repeating unit for (P2) is PSU or PPSLI, comprising structural repeating units la or Ig, respectively.

4. The membrane of any one of claims 1 to 3, wherein the ratio of poly(arylene ether sulfone) polymers (P1) to (P2), is 1 :10 to 10:1.

5. The membrane of any one of claims 1 to 4, further comprising a sulfonated poly(arylene ether sulfone) polymer (SP).

6. The membrane of any one of claims 1 to 4, further comprising polyvinylpyrrolidone (PVP).

7. The membrane of any one of claims 1 to 6, wherein the membrane is a nanofiltration (NF) membrane, microfiltration (MF) membrane or ultrafiltration (UF) membrane.

8. The membrane of any one of claims 1 to 7, wherein the membrane is a flat sheet or hollow fiber membrane.

9. The membrane of any one of claims 1 to 8, wherein the membrane is a dialysis membrane.

10. A method for the preparation of a membrane (M) comprising the steps: a) providing a composition (C), comprising the poly(arylene ether sulfone) polymers (P1) and (P2) as defined in any one of claims 1 to 4, and at least one solvent (D); b) separating the at least one solvent (D) from the composition (C) to obtain the membrane (M).

11. The method of claim 10, wherein the combined amount of poly(arylene ether sulfone) polymers (P1) and (P2) in the composition (C), is 10% by weight or more, based on the total weight of the composition (C).

12. The method of claim 10 or 11 , wherein the ratio of poly(arylene ether sulfone) polymers (P1) to (P2), in the composition (C) is 1 :10 to 10:1.

13. The method of any one of claims 10 to 12, wherein the at least one solvent (D) is selected from the group consisting of N-alkyl-2-pyrrolidone, preferably N-methyl-2-pyrrolidone, N- ethyl-2-pyrrolidone, N-butyl-2-pyrrolidone and N-tert.-butyl-2-pyrrolidone, 2-pyrrolidone, N- dimethylacetamide, dimethylsulfoxide, dimethylformamide, N,N-dimethyl-2-hydroxypropan amide, N,N-diethyl-2-hydroxypropan amide, y-valerolactone, dihydrolevoglucosenone, methyl 5-(dimethylamino)-2-methyl-5-oxopentanoate and sulfolane.

14. The method of any one of claims 10 to 13, wherein the composition (C) also comprises a water-soluble polymer additive (A) comprising polyvinylpyrrolidone (PVP).

15. A membrane obtainable by the method according to any one of claims 10 to 14.

16. A separation element, a membrane module, a membrane cartridge or a separation system comprising the membrane according to any one of claims 1 to 9 or 15.

17. A use of a membrane according to any one of any one of claims 1 to 9 or 15 in an ultrafiltration process.

18. A use of a membrane according to any one any one of claims 1 to 9 or 15 or of the separation element, the membrane module, the membrane cartridge or the separation system according to claim 16 for water treatment applications, treatment of industrial or municipal wastewater, desalination of sea or brackish water, dialysis, plasmolysis and / or food processing.

19. An apparatus for dialysis comprising a membrane according to any one of claims 1 to 9 or 15.

20. A composition (C), comprising poly(arylene ether sulfone) polymers (P1) and (P2) and at least one solvent (D), wherein (P1) and (P2), respectively, comprises at least one of the structural repeating units la to Is as defined in any one of claims 1 to 4, wherein the at least one unit of (P2) is different from the at least one unit of (P1).

21. A use of the composition (C) according to claim 20 for the production of a membrane, in particular in a non-solvent induced phase separation process.

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