Polyaryletherketone copolymer membrane as support for gas separation and pervaporation composite membranes

Abstract

This invention relates to certain porous hollow fiber membranes comprising certain PEDEK-PEEK copolymers, to a method for making said porous hollow fiber membranes, to composite membranes comprising a selective layer and their uses in the separation of gases or liquids.

Description

1 SSPU 2024 / 025DescriptionPOROUS ARTICLES AND USES THEREOFReference To Related ApplicationsThis application claims priority from European patent application 24217922.4 filed on December 5, 2024, the whole content of this application being incorporated herein by reference for all purposes.Technical Field

[0001] This invention relates to certain porous articles comprising certain poly(aryl ether ketone) polymers, in particular hollow fibers characterized by narrow pore size distribution and high strain at break. The invention further relates to hollow fiber membranes suitable for use in separation applications, such as gas separation or pervaporation.Background Art

[0002] Poly(aryl ether ketones) (PAEK), including notably poly(ether ether ketone), or PEEK, displays advantageous chemical and physical properties for many uses. The high melting point, high glass transition temperature, low solubility and high chemical resistance make PAEKs the materials of choice for separations applications for harsh environments.

[0003] PAEKs are not known to be affected by common organic solvents at room temperature. PAEKs are also generally known to be resistant to acids and bases, with the exception of strong acids in high concentrations. The general insolubility of PAEKs, while a useful and advantageous attribute for extending fields of use of PAEKs, including under the form of porous membranes, complicates significantly the formation of useful articles including porous membranes.

[0004] US5064580 discloses a method for preparing a porous membrane from poly(ether ether ketone) (PEEK) polymers and a plasticizer, which is capable of dissolving at least a portion of the PEEK polymer at the extrusion or casting temperature. The method comprises a step consisting in leaching at least a portion of the plasticizer from the membranes.

[0005] US4721732 discloses methods of making porous membranes by leaching (partially or entirely) a soluble component from a part made from a blend2 SSPU 2024 / 025 of miscible polymers; among the blends, mention is specifically made of poly(etherimide) and poly(aryl ether ketone) blends. Mixtures of PEI and PEEK are exemplified for manufacturing films which, after leaching with DMF, provides for membranes with average pore size of 0.03 pm and max size pores of 0.07 pm.

[0006] US6887408 discloses a process for the preparation of porous articles of poly(aryl ether ketone) (PAEK), with PEEK / PEI blends being specifically addressed. The process comprises forming the PEEK / PEI blend, forming a shaped article from the blend by extrusion, molding or casting, decomposing the PEI into low molecular weight fragments in the shaped article by chemical treatment by action of certain organic bases, and removing the low molecular weight fragments from the article. Chemical reagents that removed the PEI fragments include for example ammonia, hydrazine, N-Methyl-2-pyrrolidone (NMP), N,N-dimethyl formamide (DMF), and the like.

[0007] On the other side, while poly(ether ether ketone) (PEEK), having characterizing recurring unit of formula -O-Ph-O-Ph-CO-Ph-, with Ph = para-phenylene, has found broad utility, including as constituent material of porous membranes, its glass transition temperature of about 148°C is somewhat limiting its ability for membranes made therefrom to withstand continuous operations at temperatures of 150°C or beyond.

[0008] Among known poly(aryl ether ketone)s (PAEKs) having increased glass transition temperatures, copolymers comprising a mixture of units -O-Ph- O-Ph-CO-Ph- (I) and -O-Ph-Ph-O-Ph-CO-Ph- (II) have been reported.

[0009] WO2022 / 096373A1 discloses microporous articles comprising copolymers comprising a mixture of units -O-Ph-O-Ph-CO-Ph- (I) and -O-Ph-Ph-O-Ph- CO-Ph- (II). The microporous articles exemplified in WO2022 / 096373A1 are flat membranes having a ratio between the bubble point diameter (BPD) and the mean flow pore diameter (MFD) of 1 .71 to 1 .85 which indicates a fairly uniform distribution of pore sizes.

[0010] It has been now found that it is possible to obtain hollow fiber membranes comprising copolymers comprising a mixture of units -O-Ph-O-Ph-CO-Ph- (I) and -O-Ph-Ph-O-Ph-CO-Ph- (II) having an even higher uniformity of3 SSPU 2024 / 025 pore sizes. The inventive hollow fiber membranes also have higher strain at break compared to previously known membranes.Summary of invention

[0011] An object of the present invention is to provide a porous article in the form of a hollow fiber, said porous article comprising a PEDEK-PEEK-type copolymer and having a narrow pore size distribution. The hollow fiber membrane is also provided with outstanding mechanical properties, in particular high strain at break and high modulus.

[0012] Another object of the present invention is to provide a hollow fiber membrane capable of selectively separating gases as well as liquids.Description of invention

[0013] In the present application:- any description, even though described in relation to a specific embodiment, is applicable to and interchangeable with other embodiments of the present disclosure;- where an element or component is said to be included in and / or selected from a list of recited elements or components, it should be understood that in related embodiments explicitly contemplated here, the element or component can also be any one of the individual recited elements or components, or can also be selected from a group consisting of any two or more of the explicitly listed elements or components; any element or component recited in a list of elements or components may be omitted from such list;- any recitation herein of numerical ranges by endpoints includes all numbers subsumed within the recited ranges as well as the endpoints of the range and equivalents;- the indeterminate article “a” in an expression like “a polymer”, is intended to mean “one or more”, or “at least one” unless indicated otherwise;- the use of brackets “( )” before and after names of compounds, symbols or numbers, e.g. “Layer (BL)”, has the mere purpose of better4 SSPU 2024 / 025 distinguishing that name, symbol or number from the rest of the text; thus, said parentheses could also be omitted.

[0014] A first object of the present invention is a porous hollow fiber membrane comprising at least one poly(aryl ether ketone) copolymer [copolymer (PEDEK-PEEK)] comprising:- recurring units (RPEEK) of formula (I):wherein in above formulae (I) and (II), each of R’ and R”, equal to or different from each other, is independently selected at each occurrence from a C1-C12 group optionally comprising one or more than one heteroatoms; sulfonic acid and sulfonate groups; phosphonic acid and phosphonate groups; amino groups; each of j' and k", equal to or different from each other, is independently selected at each occurrence from 0 and an integer from 1 to 4; wherein the recurring units are comprised in a molar ratio (RPEDEK): (RPEEK) of 55:45 to 99:1 , said porous article having a ratio between the bubble point diameter (BPD) and the mean flow pore diameter (MFD), BPD / MFD, between 1.00 and 2.50, wherein the mean flow pore diameter (MFD) and the bubble point diameter (BPD) are determined according to the Pore Size Determination method detailed in the Examples.

[0015] Another object of the present invention is a method for making said porous hollow fiber membrane. The method comprises a step consisting in5 SSPU 2024 / 025 processing a polymer composition comprising copolymer (PEDEK-PEEK), as above described, and at least one additional polymer [polymer (P)] into an article; a step of thermal treating said article, under conditions to cause at least partial crystallization of the copolymer (PEDEK-PEEK); and a step consisting in removing, at least partially, polymer (P) from the article by contacting the article with a solvent for polymer (P), so as to obtain the porous article.

[0016] Further objects of the invention are defined by the appended claims.

[0017] The porous hollow fiber membrane

[0018] A first object of the invention is hence a porous hollow fiber membrane comprising a copolymer (PEDEK-PEEK), as above detailed.

[0019] The hollow fiber membrane is porous, i.e. it possesses well-defined porosity.

[0020] Porous articles can be generally characterized by their mean flow pore diameter and the porosity, i.e. the fraction of the total article that is porous.

[0021] The hollow fiber membrane advantageously possesses a gravimetric porosity (Em) of 40 to 95 % v / v, preferably of 45 to 90 % v / v, more preferably of 50 to 85 % v / v, even more preferably of 55 to 80 % v / v.

[0022] The term “gravimetric porosity” is used herein to denote the volume fraction of voids over the total volume of the porous membrane.

[0023] Suitable techniques for the determination of the gravimetric porosity in the porous membranes of the invention are described for instance in SMOLDERS K., et al. Terminology for membrane distillation. Desalination. 1989, vol.72, p.249-262.

[0024] The porous hollow fiber membrane has a mean flow pore diameter (MFD), as determined according to the Pore Size Determination method detailed in the Examples, of at least 0.005 pm to at most 0.350 pm, preferably of at least 0.008 pm, more preferably at least 0.010 pm, even more preferably at least 0.015 pm; and / or or preferably of at most 0.300 pm, more preferably of at most 0.280 pm, even more preferably of at most 0.250 pm.

[0025] The porous hollow fiber membrane of the invention is characterized by a narrow distribution of pores sizes. Such a narrow pore size distribution is particularly advantageous for filtration / separation performances. It is generally known that bubble point diameter (BPD) is representative of the6 SSPU 2024 / 025 largest pore opening within the membrane. Hence, the ratio BDP / MFD is of significance for describing the distribution of pores sizes in the porous hollow fiber membrane of the invention. The porous hollow fiber membrane of the invention possesses a distribution of pores sizes such that the ratio between the bubble point diameter (BPD) and the mean flow pore diameter (MFD) (ratio BDP / MFD) is less than 2.50, preferably less than 2.00, still preferably less than 1.70, more preferably less than 1.65, even more preferably less than 1 .50. The ratio BDP / MFD is at least 1 .00, at least 1.02, even at least 1.05. Particularly advantageous ranges are between 1.00 and 1.70, between 1.00 and 1.65, between 1.02 and 1.65, between 1.05 and 1.50.

[0026] Bubble point diameter (BPD) and mean flow pore diameter (MFD) are determined according to ASTM F316-03 as described in detail in the Pore Size Determination method in the Examples.

[0027] The porous hollow fiber membrane of the invention generally has an outer diameter of 5.00 mm or less, 4.00 mm or less, 2.00 mm or less, even 1 .50 mm or less and / or of 0.05 mm or more, even 0.10 mm or more, preferably 0.20 mm or more, even 0.30 or more, 0.40 or more. For certain applications suitable ranges may be 0.10 mm to 2.00 mm, 0.40 mm to 2.00 mm, even from 0.40 mm to 1.50 mm.

[0028] Thickness of the porous hollow fiber membrane can be tuned depending on the target field of use. Generally, the porous hollow fiber membrane has a thickness of at least 10 pm, at least 25 pm, at least 30 pm, at least 50 pm and / or of at most 500 pm, at most 400 pm, even at most 350 pm, at most 300 pm, at most 250 pm, even at most 200 pm. In some instances, the porous hollow fiber membrane may have a thickness in the range of 50 to 300 pm, 100 to 250 pm.

[0029] Further, the porous hollow fiber membrane has very good mechanical properties. It generally has tensile modulus of 100 MPa or higher, preferably exceeding 150 MPa, even exceeding 200 MPa. The tensile modulus is determined at room temperature (23°C), according to ASTM D638 at a stretch speed of 50 mm / min.

[0030] Surprisingly, the porous hollow fiber membrane of the invention has a strain at break which is significantly greater than the strain at break of flat7 SSPU 2024 / 025 porous membranes of the same composition. The higher strain at break is associated with higher ductility. Higher ductility is definitely an advantage when handling the hollow fibers for module assembly.

[0031] The porous hollow fiber membrane of the invention comprises at least one poly(aryl ether ketone) copolymer [copolymer (PEDEK-PEEK)]. The porous hollow fiber membrane of the invention comprises said copolymer (PEDEK-PEEK) as the main constituting element.

[0032] The porous hollow fiber membrane of the invention may comprise other constituting ingredients, other than the copolymer (PEDEK-PEEK). The porous hollow fiber membrane of the invention may comprise additives, fillers, stabilizers, colorants. The amount of copolymer (PEDEK-PEEK) is of at least 60 wt%, preferably at least 70 wt%, more preferably at least 80 wt%, even more preferably at least 85 wt%, with respect to the total weight of the porous hollow fiber membrane of the invention.

[0033] It is generally understood that the porous hollow fiber membrane may comprise residues derived from the template leaching method used for its manufacture. Hence, it may be that the porous hollow fiber membrane may comprise in addition to major amounts of copolymer (PEDEK-PEEK), minor amounts of polymer (P), as below detailed.

[0034] Generally, the amount of polymer (P) is at most 15 wt%, preferably at most 12 wt%, more preferably at most 10 wt%, with respect to the total weight of the porous hollow fiber membrane.

[0035] The porous hollow fiber membrane may essentially consist of a major amount of copolymer (PEDEK-PEEK) and a minor amount of polymer (P). Minor quantities, generally of at most 1 wt% (with respect to the total weight of the porous hollow fiber membrane) of other ingredients, impurities or spurious ingredients may be tolerated, provided that they do not substantially modify the advantageous attributes of the porous hollow fiber membrane.

[0036] The copolymer (PEDEK-PEEK)

[0037] The copolymer (PEDEK-PEEK) comprises recurring units (R PEDEK) and (RPEEK) as above detailed in molar ratio (RPEDEK):(RPEEK) of 55:45 to 99:1 , preferably of 60:40 to 95:5, more preferably of 65:35 to 90:10, and even more preferably of 68:32 to 80:20. Copolymers (PEDEK-PEEK) which8 SSPU 2024 / 025 have been found particularly advantageous are those comprising recurring units (RPEDEK) and (RPEEK) as above detailed in molar ratio of (RPEDEK): (RPEEK) of 70:30 to 80:20. For the avoidance of doubt, the molar ratio is calculated based on the sum of recurring units (R PEDEK)+ (RPEEK) in copolymer (PEDEK-PEEK). The sum of recurring units (RPEDEK)+ (RPEEK) can be less than 100 mol%.

[0038] In copolymer (PEDEK-PEEK), the sum of recurring units (RPEDEK) and (RPEEK) is generally of at least 70 mol%, preferably at least 80 mol%, even more preferably at least 90 mol%, and most preferably at least 95 mol%, with respect to the total number of moles of recurring units.

[0039] The copolymer (PEDEK-PEEK) may additionally comprise recurring units (RPAEK) different from recurring units (RPEEK) and (RPEDEK), as above detailed. In such case, the amount of recurring units (R PAEK) is generally comprised between 0 and 5 mol%, with respect to the total number of moles of recurring units of copolymer (PEDEK-PEEK), while recurring units (RPEEK) and (RPEDEK) will be present in an amount of at least 95 mol%, with respect to the total number of moles of recurring units of copolymer (PEDEK-PEEK).

[0040] When recurring units (RPAEK) different from recurring units (RPEEK) and (RPEDEK) are present in the copolymer (PEDEK-PEEK), these recurring units (RPAEK) generally comply with any of the following formulae (K-A) to (K-M) herein below:9 SSPU 2024 / 02510 SSPU 2024 / 025wherein in each of formulae (K-A) to (K-M) above, each of R’, equal to or different from each other, is independently selected at each occurrence from a C1-C12 alkyl group optionally comprising one or more than one heteroatom; sulfonic acid and sulfonate groups; phosphonic acid and phosphonate groups; amino groups; and each of j’, equal to or different from each other, is independently selected at each occurrence from 0 and an integer from 1 to 4, preferably ]’ being equal to zero.

[0041] It is nevertheless generally preferred for the copolymer (PEDEK-PEEK) to be essentially composed of recurring units (RPEEK) and (RPEDEK), as above detailed. The expression “essentially composed of”, in connection with copolymer (PEDEK-PEEK) is meant to indicate that defects, end groups and monomers' impurities may be present in very minor amounts, preferably amount of less than 1 wt%, in the copolymer (PEDEK-PEEK).

[0042] In recurring units (RPEEK) of formula (I), the connections among phenyl groups are generally in the para positions of each of the phenyl rings. Further, it is generally preferred for each of j’ to be zero, or in other words, for each of the phenyl rings not to bear any further substituents in addition to the catenary ethereal or ketone bridging groups. According to these11 SSPU 2024 / 025 preferred embodiments, recurring units (RPEEK) comply with formula (la):Formula (la)

[0043] Similarly, in recurring units (RPEDEK) of formula (II), the connections among phenyl groups are generally in the para positions of each of the phenyl rings. Further, it is generally preferred for each of k” to be zero, or in other words, for each of the phenyl rings not to bear any further substituents in addition to the catenary ethereal or ketone bridging groups. According to these preferred embodiments, recurring units (RPEDEK) comply with formula (lib):Formula (lib)

[0044] Method of making the porous hollow fiber membrane

[0045] The porous hollow fiber membrane of the invention is advantageously manufactured by a method comprising the steps of:1. processing a polymer composition, [composition (C)], comprising copolymer (PEDEK-PEEK), as above described, and at least one additional polymer, [polymer (P)], into a solid article having the shape of a hollow fiber;2. thermally treating the solid article obtained in step 1. under conditions to cause at least partial crystallization of copolymer (PEDEK-PEEK); and3. at least partially removing polymer (P) from the solid article by contacting the thermally treated article obtained at the end of step 2. with a solvent for polymer (P), to obtain a porous hollow fiber.

[0046] In step 1 . a polymer composition, [composition (C)], is processed into a hollow fiber. This step is performed using techniques known in the art for the preparation of hollow fibers.

[0047] Composition (C) is first prepared by mixing copolymer (PEDEK-PEEK) and polymer (P). Mixing is preferably performed by melt compounding.Generally, melt compounding is carried out in an extruder. Composition (C) is typically extruded through a die at temperatures generally beyond12 SSPU 2024 / 025 the melting point of copolymer (PEDEK-PEEK), thereby providing strands which are typically cut thereby providing pellets.

[0048] Composition (C), preferably in the form of pellets, is then processed by extrusion through an annular capillary nozzle into a hollow fiber shape. A core fluid is used for the purpose of retaining the hollow fiber geometry. The core fluid may be either a gas or a liquid. Typically, the core fluid is a gas, such as air or N2.

[0049] Once the molten extrudate of composition (C) exits the annular capillary nozzle, fiber solidification takes place by airflow or by dipping in a water tank, after solidification the fiber is conveyed by rolls to the collecting spool. The molten extrudate may be stretched either in molten phase or after its solidification upon cooling, for delivering the solid article.

[0050] The solid article obtained in step 1 . may comprise, in addition to the copolymer (PEDEK-PEEK) and the polymer (P), various additives which may be included to give a desired property to the non-leached polymer. For example, stabilizers, flame retardants, pigments, plasticizers, and the like can be present. Other polymers may also be added to give the desired property.

[0051] Nevertheless, it is generally preferred that the solid article obtained at the end of step 1 . essentially consists of copolymer (PEDEK-PEEK) and polymer (P). Minor amounts, e.g. of less than 1 wt% of other ingredients, including impurities or other spurious compounds, may be tolerated, without their presence affecting the overall performances of the solid article.

[0052] The weight percent of polymer (P) in composition (C) is generally from 10 wt% to 90 wt%, preferably from 30 wt% to 75 wt%, more preferably from 40 wt% to 70 wt%, even more preferably from 55 wt% to 68 wt%, based on the combined weight of polymer (P) and copolymer (PEDEK-PEEK). Polymer (P) is the component of composition (C) to be leached out.

[0053] Conversely, the weight percent of the copolymer (PEDEK-PEEK), i.e. of the target constituent material of the porous article, is generally from 90 wt% to 10 wt% and preferably from 70 wt% to 25 wt%, more preferably from 60 wt% to 30 wt%, even more preferably from 45 wt% to 32 wt%,13 SSPU 2024 / 025 based on the combined weight of polymer (P) and copolymer (PEDEK- PEEK).

[0054] In step 2. the hollow fiber obtained by extrusion of composition (C) is submitted to a thermal treatment, under conditions to cause at least partial crystallization of copolymer (PEDEK-PEEK).

[0055] As an outcome of the thermal treatment in step 2., the non-leachable polymer, i.e. the copolymer (PEDEK-PEEK), will be in a partly crystalline state. Having the copolymer (PEDEK-PEEK) in a partly crystalline state was found to be particularly advantageous to reduce or control the shrinkage of the pore size in the final porous article.

[0056] The thermal treatment of step 2. is carried out at a temperature of at least 200°C, preferably of at least 220°C, more preferably of at least 230°C and / or at a temperature of at most 350°C, preferably of at most 330°C, more preferably of at most 320°C.

[0057] The thermal treatment of step 2. is carried out for a period of at least 1 minute, preferably at least 2 minutes, more preferably at least 3 minutes; and / or for a period of at most 120 minutes, preferably at most 60 minutes, more preferably at most 30 minutes.

[0058] In step 3. the thermally treated hollow fiber obtained from step 2. is contacted with a solvent capable of dissolving polymer (P) to remove at least partially polymer (P) from the hollow fiber to obtain a porous hollow fiber.

[0059] In step 3. the thermally treated hollow fiber is contacted with a solvent which is a solvent for the polymer (P) and a non-solvent for copolymer (PEDEK-PEEK). The step of contacting the thermally treated hollow fiber with the solvent is performed at the temperature and time conditions required to dissolve at least a part of polymer (P). Preferably the major part of polymer (P) is dissolved in the solvent and is removed upon removal of the solvent.

[0060] The solvent selected for step 3. should not substantially dissolve copolymer (PEDEK-PEEK). It may, however, cause the copolymer (PEDEK-PEEK) to swell. It is within the scope of the invention that the non-solvent may remove low molecular weight fractions of the copolymer (PEDEK-PEEK).14 SSPU 2024 / 025

[0061] Treatment with the solvent preferably takes place by immersing the thermally treated hollow fiber in a bath containing the solvent. The thermally treated hollow fiber is immersed in the bath for a period of time sufficient to remove the desired amount of the polymer (P). Generally, the thermally treated hollow fiber will be maintained in contact with the solvent for about 1 minute to about 8 hours or more, preferably from about 10 minutes to about 4 hours. Alternatively, the thermally treated hollow fiber may be suspended in the vapors of the boiling solvent.

[0062] The temperature at which the solvent treatment step is carried out depends on the solvent used and the nature of polymer (P). In most instances the solvent will be maintained at temperatures from about ambient temperature to about below the boiling point of the solvent.

[0063] Those skilled in the art will readily be able to select solvents which are non-solvents for copolymer (PEDEK-PEEK). For example, methylene chloride, dimethylsulfoxide (DMSO), dimethylacetamide (DMAC), dimethylformamide (DMF), N-methylpyrrolidone, N-ethylpyrrolidone N- butylpyrrolidone, as well as nontoxic solvents such as methyl l-lactate, ethyl lactate, propylene carbonate, tributyl o-acetylcitrate, tributyl citrate, triethyl phosphate, and y-butyrolactone (GBL) could be used to extract polymer (P).

[0064] When polymer (P) is polymer (PEI), N-methylpyrrolidone (NMP), N- ethylpyrrolidone, N-butylpyrrolidone, methylene chloride and y- butyrolactone (GBL), dimethylsulfoxide (DMSO), dihydrolevoglucosenone, dimethyl isosorbide are possible solvents, which can be used in step 3.

[0065] Generally, it is desirable to leach out substantially all the soluble polymer (P) resulting in a porous article having the physical and mechanical properties of the copolymer (PEDEK-PEEK).

[0066] Preferably, the porous hollow fiber membrane of the invention contains at most 10 wt% of polymer (P), based on the weight of the porous article.

[0067] Polymer (P)

[0068] Composition (C) comprises copolymer (PEDEK-PEEK) and at least one additional polymer, referred to as polymer (P). The choice of polymer (P) will be made by one of ordinary skills in the art considering solubility differentiation which is required in the method of the present invention.15 SSPU 2024 / 025

[0069] In view of solubility requirements, polymer (P) will be advantageously selected from amorphous polymers, i.e. from polymers having a heat of fusion of less than 5 J / g when measured by DSC according to ASTM D3418 at a cooling rate of 20 °C / min. Yet, embodiments whereas the polymer (P) possesses a semi-crystalline character are still possible.

[0070] Generally, polymer (P) will be selected among those that are capable of forming homogeneous or compatible blends with copolymer (PEDEK- PEEK).

[0071] Polymer (P) is preferably selected from polymers which can form compatible blends with copolymer (PEDEK-PEEK). The expression “compatible blend” is used herein with respect to composition (C) to refer to polymer blends, which are immiscible polymer blends that exhibit macroscopically uniform physical properties, caused by sufficiently strong interactions between the component polymers.

[0072] According to other embodiments, polymer (P) is selected from polymers which can form miscible blends, i.e. polymers (P) which, when combined with copolymer (PEDEK-PEEK), provide for blends having a single amorphous phase exhibiting a single glass transition temperature.

[0073] Polymer (P) is advantageously at least one of polyimide, poly(ether imide); as well as poly(aryl ether ketone)s different from copolymer (PEDEK- PEEK), such as notably PEK (i.e. a polymer having units (K-B) as described above) or PEKEKK (i.e. a polymer having units (K-G), as described above).

[0074] Polymer (P) is advantageously a polyimide polymer or, preferably, a poly(ether imide) polymer [polymer (PEI)]. The expressions “poly(ether imide)” and / or “polymer (PEI)” denotes a polymer comprising at least 50 mol%, based on the total number of moles in the polymer, of recurring units (RPEI) comprising at least one aromatic ring, at least one imide group, as such and / or in its amic acid form, and at least one ether group. Recurring units (RPEI) may optionally further comprise at least one amide group which is not included in the amic acid form of an imide group.

[0075] Preferably, polymer (PEI) is a polymer comprising at least 50 mol%, based on the total number of moles in the polymer, of recurring units (RPEI) of16 SSPU 2024 / 025 formula (I):where- R is selected from the group consisting of substituted and unsubstituted divalent organic radicals, for example selected from the group consisting of(a) aromatic hydrocarbon radicals having 6 to 20 carbon atoms and halogenated derivatives thereof;(b) straight or branched chain alkylene radicals having 2 to 20 carbon atoms;(c) cycloalkylene radicals having 3 to 20 carbon atoms, and(d) divalent radicals of formula (II):where- Y is selected from the group consisting of alkylenes of 1 to 6 carbon atoms, for example -C(CHs)2 and -CnH2n- (n being an integer from 1 to 6); perfluoroalkylenes of 1 to 6 carbon atoms, for example -C(CFs)2 and - CnF2n- (n being an integer from 1 to 6); cycloalkylenes of 4 to 8 carbon atoms; alkylidenes of 1 to 6 carbon atoms ; cycloalkylidenes of 4 to 8 carbon atoms; -O- ; -S- ; -C(O)- ; -SO2- ; -SO-, and- R” is selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, alkynyl, aryl, alkoxy, carboxylic acid, ester, amide, imide, alkali earth metal sulfonate, alkaline earth metal sulfonate, alkyl sulfonate, alkali earth metal phosphonate, alkaline earth metal phosphonate, alkyl phosphonate, amine and quaternary ammonium and- i, for each R”, is independently zero or an integer ranging from 1 to 4,- T can either be - O - or - O - Ar” - O - wherein the divalent bonds of the - O - or the - O - Ar” - O - group can be in the 3,3', 3,4', 4,3', or the 4,4' positions, wherein Ar” is a aromatic moiety selected from the group consisting of a substituted or unsubstituted,17 SSPU 2024 / 025 saturated, unsaturated or aromatic monocyclic and polycyclic group having 5 to 50 carbon atoms, for example a substituted or unsubstituted phenylene, a substituted or unsubstituted cyclohexyl group, a substituted or unsubstituted biphenyl group, a susbtituted or unsubstituted naphtalene group or a moiety comprising two substituted or unsubstituted phenylene.

[0076] Ar” has general formula (II), as detailed above. For example, Ar” has formula (III):

[0077] The polymer (PEI) according to this preferred embodiment may be prepared by any of the methods well-known to those skilled in the art, including the reaction of a diamino compound of formula (IV):H2N-R-NH2 (IV) where R is as defined before, with any aromatic bis(ether anhydride)s of formula (V):where T is as defined above.

[0078] The aromatic bis(ether anhydride)s of formula (V) can be chosen from the group consisting of m-phenylenediamine, p-phenylenediamine, 2,2-bis(p- aminophenyl)propane, 4,4'-diaminodiphenyl-methane, 4,4'- diaminodiphenyl sulfide, 4,4'-diamino diphenyl sulfone, 4,4'- diaminodiphenyl ether, 1 ,5-diaminonaphthalene, 3,3'-dimethylbenzidine, 3,3'-dimethoxybenzidine, and mixtures thereof.

[0079] Preferably, the organic diamines of formula (IV) are chosen from the group consisting of m-phenylenediamine and p-phenylenediamine and mixtures thereof.

[0080] Advantageously, polymer (PEI) is a polymer comprising at least 50 mol%, based on the total number of moles in the polymer, of recurring units (RPEI)18 SSPU 2024 / 025 of formulas (VI) or (VII), in imide forms, or their corresponding amic acid forms and mixtures thereof:(VII).

[0081] In a preferred embodiment, at least 50 mol%, at least 60 mol%, at least 70 mol%, at least 80 mol%, at least 90 mol%, at least 95 mol%, at least 99 mol% or all of the recurring units in the PEI are recurring units (RPEI) of formulas (VI) or (VII), in imide forms, or their corresponding amic acid forms and mixtures thereof.

[0082] Such aromatic polyimides are notably commercially available from Sabie Innovative Plastics as ULTEM® poly(ether imide) polymers.

[0083] Use of the hollow fiber membrane and composite membranes

[0084] The porous hollow fiber membranes of the invention may be used in many fields of use. They may be used as such, that is as physical separators to maintain the separation between objects (e.g. fluids) having different compositions.

[0085] Alternatively, they can be used to selectively separate one component from others in a composition. Non-limiting examples of suitable field of use are detailed below.

[0086] The hollow fiber membranes of the invention have pore sizes which render them suitable for ultrafiltration applications. They could be used as they are (i.e. without any coating) as ultrafiltration membranes for water purification to remove particles, bacteria, and viruses. They could be used for the ultrafiltration of any aggressive stream or even an organic solvent.19 SSPU 2024 / 025

[0087] Due to their excellent chemical resistance, the inventive fiber membranes could be used to treat organic solvent streams, in particular in pharmaceutical processes. The technique is oftentimes referred to as organic solvent nanofiltration (OSN).

[0088] Alternatively, the hollow fiber membranes of the invention may be used in pervaporation applications. In such applications a membrane is used as a barrier for separation of a liquid feed. When a liquid mixture is in contact with a membrane one of the components of the feed will preferentially permeate due to its higher affinity and / or higher diffusivity. Usually in the downstream side a vacuum is applied to keep a high concentration difference across the membrane.

[0089] The inventive hollow fibers could be used in Condensed Phase Membrane Introduction Mass Spectrometry CP-MIMS when coated with an opportune selective dense layer. In the above application the analytes in the sample are usually pre-concentrated by a hollow fiber membrane depending on their physicochemical properties and directly transferred, using different acceptor phases (gas, liquid or vacuum) to the mass spectrometer. The advantage of such a composite fiber would be the possibility to combine a very thin selective layer (hence increasing the flux of the analytes) with the chemical resistance of the inventive hollow fibers allowing the use of a wide range of solvents as carrier phase.

[0090] Another possible use of these fibers, thanks to the relatively low pore size and to the chemical stability of the polymer, is in so-called “membrane contactors”. In a membrane contactor system, membrane separation is combined with a phase contacting process, like extraction or absorption, and those processes are fully integrated into one single equipment. For example by using those fibers, fluids can be contacted at one of the two sides of the membranes (either shell or lumen) and a gas liquid interface is created at the pore entrance. A possible use is the removal of acid gases like CO2, H2S and other acid gases coming from combustion of fossil fuels, natural gas and effluent flue gas in general.

[0091] In certain of the applications detailed above it may be advantageous to provide the porous membrane with a selective layer. A selective layer is a20 SSPU 2024 / 025 layer, typically made of a polymeric material, allowing only selected molecules or ions to pass through it.

[0092] Composite membranes

[0093] Another object of the invention is therefore a composite membrane comprising the porous hollow fiber and a selective polymer layer. The selective polymer layer is non-porous.

[0094] For the avoidance of doubt, the indeterminate article “a” in the expression like “a selective polymer layer”, is intended to mean “one or more”, or “at least one” unless indicated otherwise.

[0095] The selective polymer layer will be selected depending on the nature of the separation process to be performed.

[0096] For instance, the selective polymer layer may be selected among materials that allow separating CO2 from a gas mixture comprising CO2.

[0097] The selective polymer layer may advantageously be made of a polyethylene oxide)-poly(butylene terephthalate) block copolymer (PEO- PBT), such as those commercially available by PolyVation, NL, under the trade name PolyActive™.

[0098] Other candidates as polymers for the selective layer are: block copolymers obtained by polycondensation of a carboxylic acid polyamide with an alcohol terminated polyethylene glycol (PEG), such as those known under the trade name PEBAX® or VESTAM ID®; sulfonated PEEK; 2, 3,5,6- tetrafluoro-4-pyridinecarbonitrile-3,3,3',3'-tetramethyl-1 , 1 '-spirobisindane- 5,5',6,6'-tetrol co-polymers, known as PIM-py supplied by Sigma Aldrich; and polymethylpentene such as TPX® supplied by Mitsui Chemicals.

[0099] Further candidates as selective layers are amorphous fully fluorinated polymers, such as copolymers of tetrafluorethylene and perfluoro-2,2- dimethyl-1 ,3-dioxole or copolymers of tetrafluoroethylene and 2,2,4- trifluoro-5-trifluoromethoxy-1 ,3-dioxole, such as Hyflon® AD supplied by Syensqo Specialty Polymers Italy SpA and Teflon® AF supplied by Chemours, or Cytop® supplied by AGC Chemicals.

[0100] For use in pervaporation applications to remove ethanol from a water / ethanol stream, the inventive hollow fiber membrane might be provided with a selective layer made of polydimethylsiloxane polymers (PDMS). Alternatively, for use in the dehydration of alcohols a selective21 SSPU 2024 / 025 layer of a hydrophilic polymer, such as poly(vinyl alcohol) polymers, optionally crosslinked, or hydrophilic polyurethanes, may be used.

[0101] The selective polymer layer may have any suitable thickness. For example, the selective polymer layer may have a thickness of less than or equal to 3 pm. In particular, the thickness of the selective layer may be 100-1000 nm, 150-950 nm, 200-900 nm, 250-850 nm, 300-800 nm, 350- 750 nm, 400-700 nm, 450-650 nm, 500-600 nm. Even more in particular, the thickness of the selective layer may be about 230-260 nm, preferably about 200 nm.

[0102] The composite membrane of the invention may further comprise a so- called gutter layer in addition to the selective layer. For membranes with thin selective layers, a gutter layer is usually required to prevent pore penetration in the selective layers. The gutter layer is thus positioned in contact with the porous surface of the hollow fiber membrane and one of the surfaces of the selective polymer layer.

[0103] Gutter layer materials are selected among polymers which are provided with high permeability, to minimize transport resistance.

[0104] The polymer used in the gutter layer may be selected from the group consisting of poly(1 -trimethylsilyl-1 -propyne) polymers or polydimethylsiloxane polymers. The polydimethylsiloxane polymers may conveniently be cross-linked.

[0105] Notable non-limiting examples of suitable polydimethylsiloxane polymers are supplied by Dow Corning under the trade name Sylgard® or by Momentive.

[0106] The composite membrane can be made by any method known in the art. In particular the method comprises a step of coating a surface of the porous hollow fiber membrane with a solution comprising the selective polymer; and optionally drying.

[0107] When the gutter layer is present, the process advantageously comprises a step of coating a surface of the porous hollow fiber membrane with a solution comprising the polymer for the gutter layer; drying; followed by a step of coating the surface of the gutter layer with a solution comprising the selective polymer; and optionally drying.22 SSPU 2024 / 025

[0108] The surface on which the selective polymer layer and optionally the gutter layer are applied may be the internal surface of the hollow fiber or alternatively the external surface.

[0109] A further object of the invention is thus the use of the porous hollow fiber membrane, in particular the composite membranes, of the invention in a process for the separation of gases.

[0110] An example of such a process is the separation of CO2 from a mixed gaseous stream. The mixed gaseous feed stream used in the process of the invention may be any gas stream comprising a mixture of at least two gases, wherein one of these gases is CO2. The use of flue gas or biogas is especially preferred. In a preferred embodiment, the feed stream comprises nitrogen (N2) and CO2. In an alternative preferred embodiment, the feed stream comprises methane (CH4) and CO2. In a further alternative embodiment, the feed stream comprises hydrogen (H2) and CO2.

[0111] The removal of water vapor from a gaseous stream is a further example of a gas separation process that may be conveniently performed using the composite membranes of the invention.

[0112] Alternatively, the hollow fiber membrane of the invention may be used for the separation of liquids. An example of a process for the separation of liquids is pervaporation.

[0113] The following examples are representative of the invention but are not intended to be limiting.

[0114] Examples

[0115] Raw materials

[0116] Copolymer (PEDEK-PEEK): a PEDEK-PEEK copolymer derived from the polycondensation of 4,4’-difluorobenzophenone (DFBP), 4,4’- dihydroxydiphenyl, also known as biphenol, and hydroquinone, possessing a PEDEK-PEEK mole ratio of 75:25 and a melt viscosity of 345 Pa s at 420 °C and 1000 s-1, measured using a capillary rheometer according to ASTM D3835 (copolymer PEDEK-PEEK, hereinafter).

[0117] Polymer (PEI): ULTEM® 1000 PEI from SABIC; the manufacturer reports a melt flow rate of about 9 g / 10 min as measured using a melt index apparatus according to ASTM D1238 at 377 °C and using a 6.6 kg weight.23 SSPU 2024 / 025

[0118] PDMS1 : Sylgard® 184, Dow Corning

[0119] PDMS2 : Momentive RTV-615

[0120] PEO-PBT copolymer (PolyActive™, PolyVation, NL) for membrane fabrication. The copolymer contains 77 wt% of PEO (1500 g mol-1) and 23 wt% of PBT

[0121] Measurement of Gas Permeation

[0122] Gas permeation measurements were performed with a home built constant gas pressure permeation set up for single gas measurements of N2 and CO2. A maximum of 4 bar upstream pressure (CO2 and N2) was applied and the permeate pressure was always at atmospheric pressure. The feed was fed onto the shell side of the fiber and permeate was collected on the lumen side. The permeate flow is measured using a Horiba VP-1 U Soap Film Flow meter. The flow was determined after 30 minutes of stabilization and as an average of 3 flow measurements. The permeation was measured of a single fiber with a length of~10cm. The temperature was set at 35° C. For each type of fiber, at least 3 single fibers were measured.

[0123] As sample preparation, the fibers were glued into a stainless steel tubing (~3 cm) using 3M DP100 Epoxy adhesives.

[0124] Permeance (permeability divided by the thickness of the membrane) is expressed in GPU. Selectivity is the ratio of permeances of single gases.

[0125] Measurement of Tensile Properties

[0126] Mechanical properties of hollow fiber membranes were assessed at room temperature (23°C) following ASTM D 638 standard procedure (type V, grip distance = 25.4 mm, initial length Lo = 21 .5 mm; speed 50 min / min). The values determined are the averages of repeated measurements carried out on 5 specimens of each sample.

[0127] Pore Size Determination

[0128] Determination of bubble point diameter (i.e. corresponding to the size of largest pores), smallest pore sizes and mean flow pore sizes were determined following the ASTM F0316-03 method.

[0129] A Capillary Flow Porometer “Porolux 1000” (Porometer-Belgium) was used.24 SSPU 2024 / 025

[0130] The wetting liquid was Fluorinert® FC 43, which is a fluorinated fluid (tris(perfluorobutyl)amine) with a surface tension of 16 dyne / cm at 25°C. The gas was nitrogen.

[0131] For each determination, membrane disk samples (diameter=25 mm) were initially fully wetted using the wetting liquid and then placed in the sample holder of the instrument. Inert gas (nitrogen) was fed to the sample with increasing pressure. Quoted values in Table 2 are the average of repeated measurements performed on 3 different specimens.

[0132] Preparative Example 1 (a) - Compounding of Copolymer (PEDEK- PEEK) / polymer (PEI) blend

[0133] The blend of copolymer (PEDEK-PEEK) and polymer (PEI) was prepared under the form of pellets by melt compounding using a 26 mm Coperion® co-rotating partially intermeshing twin screw extruder having an L / D ratio of 48:1 . The extruder had 12 barrel sections with barrel sections 2 through 12 being heated with a temperature setting of 380 °C. A 3-mm diameter pin-hole die was used, with a die temperature setting also of 380 °C. The extruder was operated at a throughput rate of 13-14 kg / hr and 225 rpm screw speed, and the extruder torque reading was maintained in the range of about 75-85% during compounding of all the compositions. Vacuum venting with a vacuum level >85 kPa was applied at barrel section 10 during compounding to strip off moisture and any possible residual volatiles from the compound. The extrudate from each of the runs was stranded and cooled in a water trough and then pelletized into pellets approximately 2.7 mm in diameter and 3.0 mm in length.

[0134] A blend of 35 wt% copolymer (PEDEK-PEEK) and 65 wt% polymer (PEI) was prepared.

[0135] Preparative example 1(b) - Hollow fiber (“precursor”) extrusion of Copolymer (PEDEK-PEEK)Zpolymer (PEI) 35 / 65 wt% blend

[0136] Pellets of the blend prepared as described in Ex. 1 (a) were dried overnight at 130°C before extrusion. Hollow fiber precursor was extruded using a FET draw line with a 25 mm diameter extruder and general-purpose screw through a single hole spinneret (pipe-in-pipe) with air feed through spinneret. Size of annulus: max. diameter 3.1 mm; min. diameter: 2.3 mm. The fiber was produced using a large water quench bath with a long draw25 SSPU 2024 / 025 height and guide rollers to keep the filament stable. Samples were collected on a DIN-spool using a low torque winder. Processing conditions are reported in Table 1 for the preparation of precursor fibers to membranes M1 and M2.Table 1 : Processing conditions for preparative Example 1(b)26 SSPU 2024 / 025

[0137] Preparative example 1(c) Fiber (“precursor”) annealing

[0138] Annealing of the fiber was carried out in a ventilated oven.The precursor hollow fiber was heat treated at a temperature of 250°C for a period of 60 minutes, to increase crystalline fraction, which may be measured by DSC.

[0139] Preparative example 1(d) - Extraction to get porous hollow fiber membrane M1

[0140] The annealed precursor hollow fiber obtained as detailed in Ex. 1 (c) was immersed in a bath of dichloromethane at room temperature for a duration of two hours. Subsequently the fiber was rinsed several times in isopropanol (I PA) to remove residual CH2CI2. The porous hollow fiber obtained at the end of the rinsing step was dried at room temperature in a fume hood.

[0141] Preparative example 1(e) - Extraction to get porous hollow fiber membrane M2

[0142] The annealed precursor hollow fiber obtained as detailed in Ex. 1 (c) was immersed in a bath of N-butylpyrrolidone / ethanolamine (95 / 5 wt) at 105°C for two hours. Subsequently the fiber was rinsed several times in water and then isopropanol (IPA) to remove residual solvents. The porous hollow fiber obtained at the end of the rinsing step was dried at room temperature in a fume hood.

[0143] The properties of hollow fiber membranes M1 and M2 are reported in Table 2.Table 2: Properties of porous membranes27 SSPU 2024 / 025

[0144] The bubble point diameter (BPD) is the largest pore opening within the membrane. The mean flow pore diameter (MFD) is an average pore size calculated by the half dry method as described in ASTM F316-03. The ratio of these two quantities BPD / MFD is representative of the uniformity of the pore size distribution, the smaller such ratio, the more uniform the pore size distribution, and hence more favorable the filtration / separation performances of the porous membrane.

[0145] Example 2: Preparation of composite membranes

[0146] Example 2(a): Coating of the gutter layer

[0147] Membrane M2-PDMS1 : Samples of the hollow fiber membrane M2 were soaked in IPA and then soaked in water for over 24 h. A magnetic stirrer was used to mix solutions of 3, 6, 9, and 15 wt% PDMS1 in n-hexane with a crosslinking agent at a 10:1 ratio by weight for 30 min at over 800 rpm. Each solution was cast at room temperature onto a pre-wetted M2 membrane by using an automated bar coating machine. Crosslinking was performed by holding the coated membranes at 80 °C for 2 h.Membrane M2-PDMS2: a solution of PDMS2 at 15 wt% in n-hexane was prepared, after 2:30 hours at 60°C it was diluted to 7.5 wt%, after 1 :30 hours at 60°C it was diluted to 3.75 wt%. The solution was cooled down to28 SSPU 2024 / 025 room temperature. The solution was cast at room temperature onto a prewetted M2 membrane by using an automated bar coating machine (speed2 m / min). After coating, the membranes were held in the oven for 18 hours at 40°C with nitrogen flow.

[0148] CO2 / N2 selectivity was determined for M2-PDMS1 and M2-PDMS2 to be 7.5-8.0. The results showed a CO2 / N2 selectivity higher than that of the original porous hollow fiber which indicates the uniformity of the gutter layer on the porous fiber.

[0149] Example 3: Pervaporation tests with M2-PDMS2

[0150] Following the procedure of Example 2(a) fibers comprising the porous fiber M2 and three coating layers of PDMS2 were prepared. Between each coating layer the fibers were held in an oven for 2h and 15 min for curing. After coating the last layer, the fibers were left in the oven for 18 hours to fully cure. Oven was set at 40°C with a N2 flow. Velocity up and down was3 m / min, the down time was 0 second.

[0151] A module with 5 fibers was assembled. The pervaporation test feed was composed of 2.46 w / w% ethanol in H2O. Tests were performed at two temperatures (40 and 60°C). Feed pressure was set at 100 kPa, vacuum was applied in the lumen. Table 3 below summarizes the test outcome.Table 3

[0152] Separation factors were calculated according to formula 9.2-Chapt 19- Membrane Technology and Applications, Second Edition. Richard W. Baker 2004 John Wiley & Sons, Ltd.

[0153] Example 4 : Pervaporation tests with M2-PDMS1

[0154] Following the procedure of Example 2(a) fibers comprising the porous fiber M2 and PDMS1 were prepared.PDMS solution preparation: PDMS1 20 wt% in n-hexane was prepared and kept at 60°C for 6.5hrs, afterwards the solution was diluted to 7%,29 SSPU 2024 / 025 cross linking continued for a total of 22 hrs. The solution was cooled down to room temperature.Dip coating conditions: RH = 56%, T: 21 °C, V-down 2m\min, down time 1 second, velocity up 0.5 m\min. After coating the fibers were kept in an oven for 5.5 hrs at 45°C under nitrogen flow.

[0155] Pervaporation test conditions: Feed solution composition: ethanol (6 % w / w) / H2O (94% w / w), Temp=21 .5 °C, Pressure was 100 kPa upstream, vacuum (40-50 Pa) on downstream (lumen). Table 4 below summarizes the test outcome.Table 4

[0156] The results show a good capability of the membranes to separate ethanol from water.

[0157] Example 5: Preparation of composite membranes

[0158] Example 5(a): Coating of the gutter layerFollowing the procedure of Example 2(a) a solution of PDMS2 at 1 .35 wt% in n-hexane was cast at room temperature onto a pre-wetted M2 membrane by using an automated bar coating machine (speed 0.5 m / min). Two coating layers were applied.

[0159] CO2 permeance was 2015 GPU and CO2 / N2 selectivity was 8. The results showed a CO2 / N2 selectivity higher than that of the original porous hollow fiber which indicates the uniformity of the gutter layer on the porous fiber.

[0160] Example 5(b): Coating of the selective layer PEO-PBT

[0161] Fibers M2-PDMS2-5 obtained in Example 5(a) were further coated with two coating layers of PEO-PBT as follows.

[0162] 1 wt% solution of PEO-PBT in toluene was coated on fiber M2-PDMS2-5 using an automated bar coating machine at 35°C (speed down and up were 1 m / min). After coating the fibers were left to dry overnight in the fume hood.

[0163] CO2 permeance was 658 GPU and CO2 / N2 selectivity was 40.

[0164] CO2 / CH4 separation

[0165] The fibers obtained in Example 5(b) show a CO2 / CH4 selectivity of 12.

Claims

30 SSPU 2024 / 025Claims1 . A porous hollow fiber membrane comprising at least one poly(aryl ether ketone) copolymer [copolymer (PEDEK-PEEK)] comprising:- recurring units (RPEEK) of formula (I):wherein in above formulae (I) and (II), each of R’ and R”, equal to or different from each other, is independently selected at each occurrence from a C1-C12 group optionally comprising one or more than one heteroatoms; sulfonic acid and sulfonate groups; phosphonic acid and phosphonate groups; amino groups; each of j' and k", equal to or different from each other, is independently selected at each occurrence from 0 and an integer from 1 to 4; wherein the recurring units are comprised in a molar ratio (R PEDEK): (RPEEK) of 55:45 to 99:1 ; and the porous hollow fiber membrane has a ratio between the bubble point diameter (BPD) and the mean flow pore diameter (MFD), ratio BPD / MFD, between 1 .00 and 2.50, wherein the mean flow pore diameter and the bubble point diameter are determined according to the Pore Size Determination method in the Examples.

2. The porous hollow fiber membrane of claim 1 in which the ratio BPD / MFD is between 1.00 and 1.70.

3. The porous hollow fiber membrane of claim 1 or 2 having a mean flow pore diameter (MFD), as determined according to the Pore Size Determination method in the Examples, of at least 0.005 pm to at most 0.350 pm, preferably31 SSPU 2024 / 025 of at least 0.008 pm, more preferably at least 0.010 pm, even more preferably at least 0.015 pm; and / or preferably of at most 0.300 pm, more preferably of at most 0.280 pm, even more preferably of at most 0.250 pm.

4. The porous hollow fiber membrane of any one of the preceding claims which has an outer diameter of 5.00 mm or less, 4.00 mm or less, 2.00 mm or less, even 1.50 mm or less and / or of 0.05 mm or more, even 0.10 mm or more, preferably 0.20 mm or more, even 0.30 or more, 0.40 or more.

5. The porous hollow fiber membrane of any one of the preceding claims which has an outer diameter in the range of 0.10 to 2.00 mm, 0.40 to 1.50 mm.

6. The porous hollow fiber membrane of any one of the preceding claims which has a thickness of at least 10 pm, at least 25 pm, at least 30 pm, at least 50 pm and / or of at most 500 pm, at most 400 pm, even at most 350 pm, at most 300 pm, at most 250 pm, at most 200 pm.

7. The porous hollow fiber membrane of any one of the preceding claims which has a thickness in the range of 50 to 300 pm, 100 to 250 pm.

8. The porous hollow fiber membrane of any one the preceding claims, wherein: the copolymer (PEDEK-PEEK) comprises recurring units (RPEDEK) and (RPEEK) in molar ratio (RPEDEK): (RPEEK) of 60:40 to 95:5, more preferably of 65:35 to 90:10, and even more preferably of 68:32 to 80:20, even more preferably of 70:30 to 80:20.

9. The porous hollow fiber membrane of any one the preceding claims wherein the sum of recurring units (RPEDEK) and (RPEEK) in copolymer (PEDEK-PEEK) is of at least 70 mol%, preferably at least 80 mol%, even more preferably at least 90 mol%, and most preferably at least 95 mol%, with respect to the total number of moles of recurring units; and / or- the copolymer (PEDEK-PEEK) may additionally comprise recurring units (RPAEK) different from recurring units (RPEEK) and (RPEDEK), which are selected from the group consisting of recurring units (RPAEK) complying with any of the following formulae (K-A) to (K-M) herein below:32 SSPU 2024 / 02533 SSPU 2024 / 025wherein in each of formulae (K-A) to (K-M) above, each of R’, equal to or different from each other, is independently selected at each occurrence from a C1-C12 group optionally comprising one or more than one heteroatoms; sulfonic acid and sulfonate groups; phosphonic acid and phosphonate groups; amino groups; and each of j’, equal to or different from each other, is independently selected at each occurrence from 0 and an integer from 1 to 4, preferably ]’ being equal to zero.

10. The porous hollow fiber membrane according to any one of the preceding claims wherein copolymer (PEDEK-PEEK) is essentially composed of recurring units (RPEEK) and (RPEDEK).11 . The porous hollow fiber membrane of any one the preceding claims wherein in recurring units (RPEEK) of formula (I), the connections among phenyl groups are in the para positions of each of the phenyl rings; preferably recurring units (RPEEK) comply with formula (la):Formula (la)34 SSPU 2024 / 02512. The porous hollow fiber membrane of any one the preceding claims wherein in recurring units (RPEDEK) of formula (II), the connections among phenyl groups are in the para positions of each of the phenyl rings; preferably recurring units (RPEDEK) comply with formula (lib): Formula (lib)13. A process for making the porous hollow fiber membrane of any one of claims 1 to 12, said method comprising the steps of:

1. processing a polymer composition comprising copolymer (PEDEK-PEEK), and at least one additional polymer [polymer (P)] into a solid article having the shape of a hollow fiber;2. thermally treating the solid article obtained in step 1. under conditions to cause at least partial crystallization of the copolymer (PEDEK-PEEK), and3. at least partially removing polymer (P) from the solid article by contacting the thermally treated article obtained at the end of step 2. with a solvent for polymer (P), to obtain a porous hollow fiber.

14. The process of claim 13, wherein polymer (P) is a polymer comprising at least 50 mol%, based on the total number of moles in the polymer, of recurring units (RPEI) of formula (I):where- R is selected from the group consisting of substituted and unsubstituted divalent organic radicals, for example selected from the group consisting of(a) aromatic hydrocarbon radicals having 6 to 20 carbon atoms and halogenated derivatives thereof;(b) straight or branched chain alkylene radicals having 2 to 20 carbon atoms;(c) cycloalkylene radicals having 3 to 20 carbon atoms, and(d) divalent radicals of formula (VI):35 SSPU 2024 / 025where- Y is selected from the group consisting of alkylenes of 1 to 6 carbon atoms, for example -C(CHs)2 and -CnH2n- (n being an integer from 1 to 6); perfluoroalkylenes of 1 to 6 carbon atoms, for example -C(CFs)2 and -Cn F2n- (n being an integer from 1 to 6); cycloalkylenes of 4 to 8 carbon atoms; alkylidenes of 1 to 6 carbon atoms ; cycloalkylidenes of 4 to 8 carbon atoms; - O- ; -S- ; -C(O)- ; -SO2- ; -SO-, and- R” is selected from the group consisting of hydrogen, halogen, alkyl, alkenyl, alkynyl, aryl, ether, thioether, carboxylic acid, ester, amide, imide, alkali earth metal sulfonate, alkaline earth metal sulfonate, alkyl sulfonate, alkali earth metal phosphonate, alkaline earth metal phosphonate, alkyl phosphonate, amine and quaternary ammonium and- i, for each R”, is independently zero or an integer ranging from 1 to 4,- T can either be - O - or - O - Ar” - O - wherein the divalent bonds of the - O - or the - O - Ar” - O - group can be in the 3,3', 3,4', 4,3', or the 4,4' positions, wherein Ar” is an aromatic moiety selected from the group consisting of a substituted or unsubstituted, saturated, unsaturated or aromatic monocyclic and polycyclic group having 5 to 50 carbon atoms, for example a substituted or unsubstituted phenylene, a substituted or unsubstituted cyclohexyl group, a substitued or unsubstituted biphenyl group, a susbtituted or unsubstituted naphtalene group or a moiety comprising two substituted or unsubstituted phenylene; and wherein Ar” is preferably of formula (III):

15. A composite membrane comprising the porous hollow fiber membrane of any one of claims 1 to 12 and a selective polymer layer applied on at least one of the surfaces of the hollow fiber membrane.36 SSPU 2024 / 02516. The composite membrane of claim 15 further comprising a gutter layer positioned between and in contact with the surface of the hollow fiber membrane and the selective polymer layer.

17. The composite membrane of claim 15 or 16 wherein the selective polymer layer is selected from the group consisting of polyethylene oxide)- poly(butylene terephthalate) block copolymers, block copolymers obtained by polycondensation of a carboxylic acid polyamide with an alcohol terminated polyethylene glycol, sulfonated PEEK polymers, 2,3,5,6-tetrafluoro-4- pyridinecarbonitrile-3,3,3',3'-tetramethyl-1 , 1 '-spirobisin dane-5,5',6,6'-tetrol copolymers, poly(vinyl alcohol), optionally cross-linked, hydrophilic polyurethanes, polydimethylsiloxane polymers, optionally cross-linked, polymethylpentene, copolymers of tetrafluorethylene and perfluoro-2,2- dimethyl-1 ,3-dioxole or copolymers of tetrafluoroethylene and 2 ,2 ,4-trifl uoro-5- trifluoromethoxy-1 ,3-dioxole.

18. The composite membrane of claim 16 or 17 wherein the polymer of the gutter layer is selected from the group consisting of poly(1 -trimethylsilyl-1 -propyne) polymers and polydimethylsiloxane polymers, optionally cross-linked.

19. The composite membrane of any one of claims 16 to 18 wherein the selective polymer layer is selected from the group consisting of polyethylene oxide)- poly(butylene terephthalate) block copolymers and sulfonated PEEK polymers and the polymer of the gutter layer is a polydimethylsiloxane polymer, optionally cross-linked.

20. Use of the hollow fiber membrane of any one of claims 1 to 12 or of the composite membrane of claims 15 to 19 in a process for the separation of gases.21 . Use of the hollow fiber membrane of any one of claims 1 to 12 or of the composite membrane of claims 15 to 19 in a process for the separation of liquids.

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