Fiber Reinforcement for Ion Exchange Composite Membranes

Abstract

Fibers are disclosed that include a composition comprising a fluorinated polymer containing a plurality of ion exchange groups or a precursor thereof and an aromatic polyamide-imide polymer. The fibers are obtained by electrospinning or forced spinning a composition comprising a fluorinated polymer containing a plurality of ion exchange groups or a precursor thereof and an aromatic polyamide-imide polymer. The fibers can be disposed in a web suitable for the preparation of a composite membrane. In particular, it is a composite ion exchange membrane suitable for use in a proton exchange fuel cell or a filtration device.

Description

Technical Field

[0001] The present invention relates to fibers, fibrous materials including fiber webs, and polymer electrolyte membranes including the fibrous materials. The polymer electrolyte membrane of the present invention is particularly suitable for use in electrochemical devices such as fuel cells.

Background Art

[0002] A proton exchange fuel cell is an electrochemical device that generates electricity by a catalyzed combination of a fuel that is hydrogen and an oxidant such as oxygen. In a typical proton exchange fuel cell, the polymer electrolyte membrane is involved in proton conductivity that enables the transport of protons from the anode to the cathode and constitutes an essential component of the electrochemical device. The polymer electrolyte membrane used for a proton exchange fuel cell is required to have excellent proton conductivity, an excellent ability to separate the hydrogen gas supplied to the anode and the oxygen supplied to the cathode, as well as excellent mechanical strength, shape stability, and chemical resistance. To improve characteristics such as dimensional stability, durability, and mechanical strength, reinforced composite membranes including an ion exchange polymer as an electrolyte substance and a porous support are known. Reinforced composite membranes including a porous polytetrafluoroethylene support and a fully fluorinated polymer including an ion exchange group are well-known in the art.

[0003] Examples of fully fluorinated polymers including an ion exchange group are, for example, tetrafluoroethylene and a comonomer including a -SO3M functional group, for example, CF2=CF-(OCF2CF(R F1 )) w -(O-CF2) z -(CF(R F2 )) y SO3M (wherein w is 0, 1, or 2, and R F1 and R F2 are F, Cl, or C optionally substituted with one or more ether oxygens 1~C10independently selected from fluoroalkyl groups, z is 0 or 1, y is an integer from 0 to 6; M is H, Li, Na, K or a quaternary ammonium ion) is a copolymer with

[0004] For fuel cell applications, well-known impregnated membranes include a fully fluorinated ion exchange polymer impregnated into an expanded PTFE (ePTFE) support.

[0005] The search for alternative supports for expanded PTFE (ePTFE) in reinforced membranes for fuel cells has attracted increasing attention. For this purpose, aromatic polymers are promising candidates due to their mechanical properties, but their use is hampered by poor compatibility with fully fluorinated ion exchange polymers, resulting in membranes with poor water management and poor conductivity, especially at low relative humidity. One of the most important features of fuel cells, including polymer electrolyte membranes (hereinafter "PEMFCs"), is to maintain a high water content in the membrane to ensure acceptable ionic conductivity. Therefore, water management in the membrane is extremely important for efficient performance. PEMFCs must operate under conditions where the byproduct water does not evaporate faster than it is produced. The water content of a PEMFC is determined by the balance or transport of water during the reactive operating mode. The water transport process is a function of the current as well as the properties of both the membrane and the electrodes (permeability, thickness, etc.).

[0006] Nanofibers constitute a class of known fillers used in the manufacture of reinforced composite membranes. These nanofiber-structured materials can increase water retention and, as a result, increase the proton conductivity of the membrane.

[0007] Electrospinning is a versatile method for generating ultra-thin nanofiber-based structures. The morphology and diameter of electrospun fibers can be adjusted by controlling various parameters, including not only the intrinsic properties of the solution such as the type of polymer, the viscosity, concentration, elasticity, and surface tension of the solvent, but also the operating conditions such as the electric field applied in the process, the distance between the spinneret and the collector, and the feeding rate for the polymer solution.

[0008] The use of electrospun nanofibers in composite membranes of fully fluorinated ion-exchange polymers such as Nafion®, Fumion®, and Aquivion® PFSA has been studied over the past 15 years. For example, Ballengee, J. B. et al., Macromolecules 2011, 44, 18, 7307-7314 disclosed two distinct membrane structures: (1) a Nafion® film reinforced by a poly(phenylsulfone) nanofiber network structure, and (2) Nafion® nanofibers embedded in an inert / uncharged poly(phenylsulfone) polymer nanofiber network structure. Both membrane structures exhibited similar volume / weight water swelling and proton conductivity, and the conductivity corresponded linearly to the Nafion® volume fraction, and the swelling was smaller than that expected based on the relative amount of Nafion®.

[0009] International Publication No. WO 2012 / 174463 A1 likewise discloses a composite membrane comprising a nonwoven web of a material containing fibers composed of one or more fully aromatic polyimide polymers and an ion-exchange polymer impregnated between opposing surfaces of the composite membrane. In an exemplary embodiment, a composite membrane is disclosed that includes a web made of a polyimide polymer containing PMDA-ODA repeat units and an ion-exchange polymer obtained by hydrolysis of a tetrafluoroethylene / perfluoro-5-sulfonylfluoride-3-oxa-1-pentene copolymer having 737 equivalents. The composite membrane exhibits lower conductivity than the ion-exchange polymer alone but lower swelling properties.

[0010] Completely fluorinated ion-exchange polymers such as Nafion® and short-side-chain Aquivion® PFSA, 3M ionomers, etc. tend to be electrosprayed as beads rather than electrospun into fibers due to the electrostatic interactions arising from their chemical structures. The addition of high molecular weight carrier polymers and the increase in the concentration of the ion-exchange polymer in the dispersion are means to overcome this situation. Some carrier polymers such as poly(ethylene oxide), poly(vinyl pyrrolidone) or poly(acrylic acid) have been used to facilitate the electrospinning of ion-exchange polymers.

[0011] U.S. Patent Application Publication No. 20160322661A discloses a membrane for a proton exchange membrane fuel cell comprising, by weight, 50 to 95% of a cation-exchange fluorinated polymer based on the total weight of the membrane; and 5 to 50% of a hydrocarbon aromatic polymer different from the cation-exchange fluorinated polymer, containing at least one aromatic ring on its polymer chain and containing a sulfonic acid group. U.S. Patent Application Publication No. 20160322661A does not disclose a composition comprising an aromatic polymer without a sulfonic acid group nor fibers prepared therefrom.

[0012] It has now been found that it is possible to obtain composite fibers comprising both an aromatic polymer and a fluorinated ion-exchange polymer that overcome many of the problems encountered in the prior art.

[0013] In particular, it has been found that fibers can be spun from a composition comprising an aromatic polyamide-imide polymer and a fluorinated ion-exchange polymer, characterized by good mechanical properties. The composite fibers make it possible to obtain a support characterized by good conductivity at low relative humidity and can therefore be used without problems in the preparation of ion-exchange membranes. SUMMARY OF THE INVENTION

[0014] A first object of the present invention is a fiber comprising a composition containing a fluorinated polymer containing a plurality of ion exchange groups or a precursor thereof and an aromatic polyamide-imide polymer. The fiber can advantageously be arranged in a web of fibers. The fiber of the present invention is prepared from a composition containing at least one fluorinated polymer containing a plurality of ion exchange groups or a precursor thereof and at least one aromatic polyamide-imide polymer. The composition is also an object of the present invention.

[0015] A second object of the present invention is a process for preparing a fiber, which comprises electrospinning or forced spinning a composition containing a fluorinated polymer containing a plurality of ion exchange groups or a precursor thereof and an aromatic polyamide-imide polymer.

[0016] A third object of the present invention is a composite membrane comprising the fiber of the first object, which can advantageously be arranged in a fiber web or mat, and a fluorinated polymer containing a plurality of ion exchange groups. The fiber can be distributed in a matrix of the fluorinated polymer containing a plurality of ion exchange groups. Alternatively, when the fiber is arranged in a web or mat, the fluorinated polymer containing a plurality of ion exchange groups can be impregnated between the opposing surfaces of the web or mat.

[0017] Among further objects of the present invention are a fuel cell or a filtration device comprising the composite membrane.

Brief Description of the Drawings

[0018]

Figure 1

Modes for Carrying Out the Invention

[0019] As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, "a plurality" means two or more.

[0020] The use of parentheses before and after symbols or numbers identifying a compound, chemical formula, or part of a formula is for the sole purpose of better distinguishing those symbols or numbers from the rest of the text, and thus, the said parentheses may also be omitted.

[0021] Any description, even if related to a specific embodiment, is applicable to and interchangeable with other embodiments of the present invention.

[0022] Any recitation in this specification of a numerical range by endpoints includes all numbers subsumed within the recited range as well as the endpoints and equivalents of the range.

[0023] As used herein, the expressions "ion-exchange polymer" or "ionomer" generally refer to polymers that conduct ions. More precisely, this expression interchangeably refers to polymers containing a plurality of ion-exchange groups.

[0024] A first object of the present invention is a fiber comprising a composition [Composition (C)] comprising at least one fluorinated polymer or a precursor thereof containing a plurality of ion-exchange groups, collectively referred to as [Polymer (I x )], and at least one aromatic polyamide-imide polymer hereinafter referred to as [Polymer (PAI)].

[0025] To avoid ambiguity, the composition comprises one or more polymers (I x ) and one or more polymers (PAI).

[0026] Composition (C) typically contains 0.1 to 95.0 wt%, 0.5 to 75.0 wt% of polymer (I x ) based on the total weight of the composition. Composition (C) may contain at least 1.0 wt%, preferably at least 2.0 wt% of polymer (I x ). Polymer (I x) can be at most 60.0 wt%, at most 50.0 wt%, at most 49.5 wt, at most 45.0 wt%, further at most 30.0 wt% or at most 25.0 wt% of the total weight of the composition.

[0027] The composition contains 5.0 to 99.9 wt%, preferably 25.0 to 99.5 wt% of a polymer (PAI) based on the total weight of the composition. Typically, the polymer (PAI) is at least 40.0 wt%, at least 50.0 wt%, at least 50.5 wt%, further at least 55.0 wt%, preferably at least 60.0 wt%, further at least 75 wt% based on the total weight of the composition.

[0028] In certain embodiments, composition (C) contains 0.01 to 5.0 wt% of a stabilizing additive based on the total weight of the composition.

[0029] In one aspect of the above embodiments, the stabilizing additive is a compound capable of decomposing peroxide radicals. The peroxide decomposition additive is preferably selected from the group consisting of alumina, silica, ceria (CeO2), Ce2O3, titania (TiO2), Ti2O3, zirconium oxide, manganese dioxide, yttrium oxide (Y2O3), Fe2O3, FeO, tin oxide, germanium oxide, copper oxide, nickel oxide, manganese oxide, tungsten oxide and mixtures thereof. Alternatively, the peroxide decomposition additive can be selected from salts of the same metal, particularly salts of manganese or cerium. The salt can contain any suitable anion including chloride, bromide, nitrate, carbonate, etc.

[0030] Advantageously, the peroxide decomposition additive is selected from the group consisting of oxides of cerium and manganese, CeO2, Ce2O3 and MnO2 and salts of cerium and manganese, alone or in combination with other oxides such as silica or alumina.

[0031] The peroxide decomposition additive is thoroughly mixed with the composition or dissolved therein to achieve a substantially uniform distribution.

[0032] The composition (C) preferably contains, based on the total weight of the composition, 0.5 to 75.0% by weight of the polymer (I x ), 25.0 to 99.5% by weight of the polymer (PAI) and optionally 0.01 to 5.0% by weight of a stabilizing additive as defined above.

[0033] The composition (C) may contain, based on the total weight of the composition, 1.0 to 50.0% by weight, 1.0 to 49.5% by weight, 1.0 to 45.0% by weight, and further 1.0 to 25.0% by weight of the polymer (I x ), 50.0 to 99.0% by weight, 50.5 to 99.0% by weight, 55.0 to 99.0% by weight, preferably 75.0 to 99.0% by weight of the polymer (PAI) and optionally 0.01 to 5.0% by weight of a stabilizing additive. The stabilizing additive is preferably selected from the group consisting of oxides of cerium and manganese, CeO2, Ce2O3 and MnO2 and salts of cerium and manganese, either alone or in combination with other oxides such as silica or alumina.

[0034] Preferably, the composition consists essentially of, and preferably consists of, the polymer (I x ), the polymer (PAI) and optionally a stabilizing additive as detailed above. The expression "consists essentially of", when referring to the composition, indicates that the amount of other components other than the polymer (I x ), the polymer (PAI) and the optional stabilizing additive is 10.0% by weight or less, preferably 5.0% by weight or less, more preferably 1.0% by weight or less based on the total weight of the composition.

[0035] Fluorinated polymers containing ion-exchange groups and their precursors [polymer (I X )] [polymer (I X )] is used herein to collectively refer to fluorinated polymers containing a plurality of ion-exchange groups and their precursors containing a plurality of functional groups that can be hydrolyzed to generate ion-exchange groups.

[0036] Polymer (I X) is fluorinated, i.e., it contains repeating units derived from an ethylenically unsaturated monomer containing at least one fluorine atom. It may further contain repeating units derived from at least one hydrogenated monomer, and the term "hydrogenated monomer" is intended to mean an ethylenically unsaturated monomer containing at least one hydrogen atom and no fluorine atoms.

[0037] Polymer (I X ) contains a plurality of ion exchange groups selected from the group consisting of -SO3M, -PO3M and -COOM (wherein M is selected from the group consisting of H, an ammonium group or a metal, preferably a monovalent metal). Examples of preferred monovalent metals include alkali metals, preferably Li, K, Na.

[0038] Polymer (I x ) The precursor of contains a plurality of hydrolyzable groups selected from the group consisting of -SO2X’, -PO2X’’ and -COX’’ (wherein X’ is a halogen, especially F or Cl, and X’’ is -OR, and R is a C1-C5 alkyl group).

[0039] In a preferred embodiment, polymer (I x ) contains the functional group -SO2X.

[0040] Polymer (Ix) can be in the neutral form, and the expression "neutral form" indicates that it contains the hydrolyzable group -SO2X (wherein X = X’, and X’ is selected from the group consisting of F, Cl, Br, I). Preferably, X’ is selected from F or Cl. More preferably, X’ is F.

[0041] Alternatively, polymer (Ix) can be in the ionic (acid or salt) form, and the expression "ionic form" indicates that in the -SO2X functional group, X is OM and M is selected from the group consisting of H, an alkali metal, NH4.

[0042] To avoid ambiguity, the term "alkali metal" is intended herein to mean the following metals: Li, Na, K, Rb, Cs. Preferably, the alkali metal is selected from Li, Na, K.

[0043] The fluorinated polymer containing the -SO3M functional group is typically prepared from a fluorinated polymer containing the -SO2X' functional group, preferably the -SO2F functional group, by a method known in the art.

[0044] The polymer (Ix) can be obtained in its salt form (i.e., in the formula, M is a cation selected from the group consisting of NH4 and alkali metals) by treating the corresponding polymer containing the -SO2X' functional group, typically the -SO2F functional group, with a strong base (e.g., NaOH, KOH).

[0045] Polymer (I x ) can be obtained in its acid form (i.e., in the formula, M is H) by treating the corresponding salt form of the polymer with a concentrated acid solution.

[0046] Suitable polymers (I x ) are those polymers comprising repeating units derived from at least one ethylenically unsaturated fluorinated monomer (monomer (A) as defined below) containing at least one -SO2X' functional group and repeating units derived from at least one ethylenically unsaturated fluorinated monomer (monomer (B) as defined below).

[0047] The phrase "at least one monomer" is used herein with respect to both types of monomers (A) and (B) to indicate that one or more monomers of each type may be present in the polymer. Hereinafter, the term monomer is used to refer to both one and two or more monomers of a given type.

[0048] Non-limiting examples of suitable monomers (A) are - The formula: CF2=CF(CF2) pA sulfonyl halide fluoroolefin of SO2X’ (wherein p is an integer from 0 to 10, preferably from 1 to 6, more preferably p is equal to 1, 2 or 3, and preferably X’ = F); - Formula: CF2=CF-O-(CF2) m A sulfonyl halide fluorovinyl ether of SO2X’ (wherein m is an integer from 1 to 10, preferably from 1 to 6, more preferably from 2 to 4, even more preferably m is equal to 2 or 4, and preferably X’ = F); - Formula: CF2=CF-(OCF2CF(R F1 )) w -O-CF2-(CF(R F2 )) y A sulfonyl halide fluoroalkoxyvinyl ether of SO2X’ (wherein w is 0, 1 or 2, and R and R which are the same as or different from each other are independently F, Cl or a C1-C fluoroalkyl group optionally substituted with one or more ether oxygens, y is an integer from 0 to 6; preferably, w is 1, R is -CF3, y is 1, R is F, and preferably X’ = F); F1 and R F2 are independently F, Cl or a C1-C fluoroalkyl group optionally substituted with one or more ether oxygens, y is an integer from 0 to 6; preferably, w is 1, R is -CF3, y is 1, R is F, and preferably X’ = F); 10 A sulfonyl halide fluoroalkoxyvinyl ether of SO2X’ (wherein w is 0, 1 or 2, and R and R which are the same as or different from each other are independently F, Cl or a C1-C fluoroalkyl group optionally substituted with one or more ether oxygens, y is an integer from 0 to 6; preferably, w is 1, R is -CF3, y is 1, R is F, and preferably X’ = F); F1 is -CF3, y is 1, R F2 is F, and preferably X’ = F); - Formula CF2=CF-Ar-SO2X’ (wherein Ar is a C5-C aromatic or heteroaromatic substituent, and preferably X’ = F) of a sulfonyl halide aromatic fluoroolefin 15 is a sulfonyl halide aromatic fluoroolefin is as follows.

[0049] Preferably, monomer (A) is selected from the group of sulfonyl fluorides (i.e., wherein X’ = F).

[0050] More preferably, monomer (A) is selected from the group of fluorovinyl ethers of the formula CF2=CF-O-(CF2) m -SO2F (wherein m is an integer from 1 to 6, preferably from 2 to 4, more preferably 2 or 4).

[0051] Even more preferably, monomer (A) is CF2=CFOCF2CF2-SO2F (perfluoro-5-sulfonylfluoride-3-oxa-1-pentene).

[0052] Non-limiting examples of suitable ethylenically unsaturated fluorinated monomers of type (B) are - C2-C8 perfluoroolefins such as tetrafluoroethylene (TFE), hexafluoropropylene (HFP), perfluoroisobutylene; - C2-C8 hydrogen-containing fluoroolefins such as trifluoroethylene (TrFE), vinylidene fluoride (VDF), vinyl fluoride (VF), pentafluoropropylene and hexafluoroisobutylene; - C2-C8 chloro-, and / or bromo-, and / or iodo-containing fluoroolefins such as chlorotrifluoroethylene (CTFE) and bromotrifluoroethylene; - Fluoroalkyl vinyl ethers of the formula CF2=CFOR f1 (wherein R f1 is C1-C6 fluoroalkyl, for example -CF3, -C2F5, -C3F7); - Especially fluoroalkoxyalkyl vinyl ethers of the formula CF2=CFOCF2OR f2 (R f2 is a C1-C3 fluoro(oxy)alkyl group such as -CF2CF3, -CF2CF2-O-CF3 and -CF3), including fluoroalkoxyalkyl vinyl ethers of the formula CF2=CFOX0 (wherein X0 is a C1-C 12 fluorooxyalkyl group containing one or more ether oxygen atoms); - Of the formula:

Chemical formula

[0053] Preferably, monomer (B) is - a C2-C8 perfluoroolefin selected from tetrafluoroethylene (TFE) and / or hexafluoropropylene (HFP); - a C2-C8 hydrogen-containing fluoroolefin selected from trifluoroethylene (TrFE), vinylidene fluoride (VDF) and vinyl fluoride (VF); - of the formula:

Chemical formula

[0054] End groups, impurities, defects and other pseudo-units in limited amounts (less than 1 mol% based on the total moles of repeating units) may be present in the preferred polymer (I x ) in addition to the listed repeating units without substantially affecting the properties of the polymer (I x ).

[0055] According to a particular embodiment, at least one monomer (B) is TFE.

[0056] The preferred polymer (I x ) is (1) In an amount of 50 to 99 mol%, preferably 52 to 98 mol%, based on the total moles of the repeating units of polymer (I x ) of repeating units derived from tetrafluoroethylene (TFE); and (2) In an amount of 1 to 50 mol%, preferably 2 to 48 mol%, based on the total moles of the repeating units of polymer (I x ) of, (j) a sulfonyl halide fluorovinyl ether of the formula: CF2=CF-O-(CF2) m SO2X (wherein X is a halogen, preferably F or Cl, more preferably F; m is an integer of 1 to 10, preferably 1 to 6, more preferably 2 to 4, and even more preferably m is equal to 2 or 4); (jj) a sulfonyl fluoride fluoroalkoxy vinyl ether of the formula: CF2=CF-(OCF2CF(R F1 )) w -O-CF2(CF(R F2 )) y SO2X (wherein X is a halogen, preferably F or Cl, more preferably F; w is an integer of 0 to 2; R F1 and R F2 are independently F, Cl or a C1-C 10 fluoroalkyl group optionally substituted with one or more ether oxygens; y is an integer of 0 to 6; preferably, w is 1, R F1 is -CF3, y is 1, and R F2 is F); and (jjj) a mixture thereof comprising at least one hydrolyzed repeating unit containing at least one -SO3M group derived from at least one monomer selected from the group consisting of; (3) In an amount of 0 to 45 mol%, preferably 0 to 40 mol%, based on the total moles of the repeating units of polymer (I x ) of at least one hydrogenated and / or fluorinated monomer different from TFE, preferably hexafluoropropylene, a compound of the formula CF2=CFOR’ f1 (wherein R’ f1is a perfluoroalkyl vinyl ether of C1-C6 perfluoroalkyl, e.g., -CF3, -C2F5, -C3F7); e.g., the formula CF2=CF O CF2OR’ f2 (wherein R’ f2 is a C1-C6 perfluoroalkyl, e.g., -CF3, -C2F5, -C3F7 or a C1-C6 perfluorooxyalkyl having one or more ether groups such as -C2F5-O-CF3) of perfluoroalkyl-methoxy-vinyl ether, and a repeating unit derived from a completely fluorinated monomer usually selected from the group consisting of perfluoro-oxyalkyl vinyl ethers of the formula CF2=CFOR’ O1 (wherein R’ O1 is a C2-C 12 perfluoro-oxyalkyl) and is selected from polymers containing

[0057] Consistently, a preferred precursor polymer (I x ) is (1) 50-99 mol%, preferably 52-98 mol% of repeating units derived from tetrafluoroethylene (TFE) based on the total moles of repeating units of the precursor of polymer (I x ); and (2) 1-50 mol%, preferably 2-48 mol% of x based on the total moles of repeating units of the precursor of polymer (I (j) formula: CF2=CF-O-(CF2) m SO2X X (wherein X X is halogen, preferably F or Cl, more preferably F; m is an integer of 1-10, preferably 1-6, more preferably 2-4, and even more preferably, m is equal to 2 or 4) of sulfonyl halide fluorovinyl ether; (jj) formula: CF2=CF-(OCF2CF(R F1 )) w -O-CF2(CF(R F2 ))X X (wherein X Xis a halogen, preferably F or Cl, more preferably F; w is 0, 1 or 2, and R, which may be the same as or different from each other F1 and R F2 are independently F, Cl or a C1-C 10 fluoroalkyl group optionally substituted with one or more ether oxygens, and y is an integer from 0 to 6; preferably, w is 1, R F1 is -CF3, y is 1, and R F2 is F) of sulfonyl fluoride fluoroalkoxy vinyl ether; and (jjj) a mixture thereof at least one monomer selected from the group consisting of repeating units derived from; (3) 0 to 45 mol%, preferably 0 to 40 mol%, based on the total moles of the repeating units of the precursor of polymer (Ix), of at least one hydrogenated and / or fluorinated monomer different from TFE, preferably hexafluoropropylene, of the formula CF2=CFOR’ f1 (wherein R’ f1 is C1-C6 perfluoroalkyl, such as -CF3, -C2F5, -C3F7) of perfluoroalkyl vinyl ether; for example of the formula CF2=CFOCF2OR’ f2 (wherein R’ f2 is C1-C6 perfluoroalkyl, such as -CF3, -C2F5, -C3F7 or -C2F5-O-CF3, a C1-C6 perfluorooxyalkyl having one or more ether groups) of perfluoroalkyl-methoxy-vinyl ether, including of the formula CF2=CFOR’ O1 (wherein R’ O1 is a C2-C 12 perfluoro-oxyalkyl having one or more ether groups) of perfluoro-oxyalkyl vinyl ether, usually selected from the group consisting of repeating units derived from fully fluorinated monomers and can be obtained from a polymer containing them, selected from them.

[0058] According to a particular embodiment, a preferred polymer (I x ) is (k) 55 to 95 mol%, preferably 65 to 93 mol%, of repeating units derived from TFE; (kk) 5 to 45 mol%, preferably 7 to 35 mol%, of hydrolyzed repeating units containing at least one -SO3M group and derived from monomer (2) as detailed above; (kkk) 0 to 25 mol%, preferably 0 to 20 mol%, of repeating units derived from fluorinated monomer (3) different from TFE as detailed above consisting essentially of, and further consisting of, all percentages being based on the total moles of the repeating units of the polymer (I x ).

[0059] For preferred precursors, the same can be said with modifications where necessary, but units derived from monomer (2) as detailed above are included instead of their corresponding hydrolyzed equivalents.

[0060] Polymer (I X ) and / or its precursor may further contain repeating units derived from at least one bis-olefin [bis-olefin (OF)] of the formula: R A R B =CR C -T-CR D =R E R F (wherein R A , R B , R C , R D , R E and R F are each independently selected from the group consisting of H, F, Cl, C1-C5 alkyl groups and C1-C5 (per)fluoroalkyl groups, and T is preferably a linear or branched C1-C 18 alkylene or cycloalkylene group or (per)fluoropolyoxyalkylene group optionally containing one or more ether oxygen atoms and at least partially fluorinated) and may further contain repeating units derived from at least one bis-olefin [bis-olefin (OF)].

[0061] Bis-olefin (OF) is preferably of formula (OF-1), (OF-2) and (OF-3): (OF-1)

Chemical formula

Chemical formula

Chemical formula

[0062] Polymer (I X) or its precursor further contains a repeating unit derived from at least one bis-olefin (OF), and optionally, the polymer (I X ) or its precursor typically contains the repeating unit of the polymer (I X ) or its precursor in an amount of 0.01 mol% to 1.0 mol%, preferably 0.03 mol% to 0.5 mol%, more preferably 0.05 mol% to 0.2 mol%, based on the total moles of the repeating units of the polymer (I

[0063] ) Optionally, the amount of the ionizable group or hydrolysable group in the polymer (I X ) or its precursor is such that it provides a total amount of ionizable groups or hydrolysable groups of at least 0.55, preferably at least 0.65, more preferably at least 0.75 meq / g, based on the total weight of the polymer (I X ) or its precursor.

[0064] Regarding the maximum amount of the ionizable group or hydrolysable group contained in the polymer (I X ) or its precursor, there is no substantial limitation. Optionally, the ionizable group or hydrolysable group is generally present in an amount of at most 3.50 meq / g, preferably at most 3.20 meq / g, more preferably at most 2.50 meq / g, based on the total weight of the polymer (I x ) or its precursor.

[0065] Polyamide-imide polymer, polymer (PAI) Contains repeating units, and more than 50 mol% of the repeating units [repeating units (R PAI )] contain at least one aromatic ring and at least one amino acid group and / or imide group [polymer (PAI)].

[0066] The repeating unit (R PAI ) is preferably

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0067] The repeating unit (R PAI ) is more preferably units (i), (ii) and (iii) as detailed below:

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Chemical formula

Chemical formula

[0068] The repeating unit (R PAI ) is preferably the repeating unit (i) or a mixture of the repeating units (ii) and (iii).

[0069] Preferably, the polymer (PAI) contains more than 90 mol%, further more than 95 mol% of the repeating unit (R PAI ). Even more preferably, it does not contain repeating units other than the repeating unit (R PAI ).

[0070] Excellent results were obtained with polymers (PAI) consisting of the repeating unit (i) or a mixture of the repeating units (ii) and (iii).

[0071] The amount of the repeating unit containing an amido acid group can be determined by any suitable technique, such as spectroscopic or titration techniques, which are well-known to those skilled in the art.

[0072] Typically, the polymer (PAI) does not contain a sulfonic acid group.

[0073] When the repeating unit (R PAI ) is selected from those of the formulas (R PAI -A), (R PAI -B), (R PAI -C), (R PAI -D), (R PAI -E) detailed above, the molar percentage of the repeating unit (R PAI ) containing at least one amido acid group is

Number

[0074] Typically, 70 mol% or less, more preferably 65 mol% or less, and even more preferably 60 mol% or less of the repeating unit (R PAI ) contains at least one amido acid group.

[0075] The polymer (PAI) can be produced by a process involving a polycondensation reaction between at least an aromatic polycarboxylic acid halide monomer and at least an aromatic diamine.

[0076] The aromatic polycarboxylic acid halide monomer is selected from the group consisting of acid halide derivatives of terephthaloyl chloride, isophthaloyl chloride, phthaloyl chloride, and trimellitic anhydride. Preferably, it is selected from trimellitic anhydride monoacid halides. Among the trimellitic anhydride monoacid halides, trimellitic anhydride monoacid chloride is preferred.

[0077] In some embodiments, the dicarboxylic anhydride monomer can be used in combination with the polycarboxylic acid halide monomer. Suitable dicarboxylic anhydride monomers include pyromellitic anhydride, bis(3,4-dicarboxyphenyl) ether dianhydride, and trimellitic anhydride. When the dicarboxylic anhydride monomer is used in this process, the excess amount of the acid halide monomer relative to the equimolar concentration of the aromatic diamine monomer is calculated taking into account the total moles of the acid halide and the dicarboxylic anhydride monomer.

[0078] The aromatic diamine monomer is selected from the group consisting of 4,4'-diaminodiphenyl ether (ODA), p-phenylenediamine (PDA), m-phenylenediamine (MPDA), diphenyldimethylmethanediamine (DMMDA), 1,3-bis(3-aminophenoxy)benzene (BAPB), 4,4'-bisphenol A ether diamine (BAPP), 4,4'-bis(4-aminophenoxy)diphenyl sulfone (BAPS), 4,4'-bis(4-aminophenoxy)diphenyl ether (BAPE), diaminodiphenyl(methyl)ketone (DABP), 4,4'-diaminotriphenylamine (DATPA), 4,4'-diaminodiphenylmethane (MDA), diaminodiphenyl sulfone (DDS), 3,4'-diaminodiphenyl ether (3,4'-ODA), 3,3'-dimethyl-4,4'-diaminodiphenylmethane (MDI), 4,4'-diamino-diphenoxy-1'',4''-benzene, 4,4'-diamino-diphenoxy-1'',3''-benzene, 3,3'-diamino-diphenoxy-1'',3''-benzene, 4,4'-diamino-diphenyl-4'',4-phenyl-isopropylpropane.

[0079] The aromatic diamine monomer is preferably selected from the group consisting of 4,4'-diaminodiphenyl ether (ODA), p-phenylenediamine (PDA), m-phenylenediamine (MPDA) and mixtures thereof.

[0080] The polycondensation reaction is advantageously carried out using a stoichiometric excess of acid halide monomer under substantially anhydrous conditions in a polar solvent and at a temperature below 150 °C.

[0081] In order to control the molecular weight of the polymer and improve its stability, as is known to those skilled in the art, a monofunctional reactant can be used as an end-capping agent.

[0082] The polymer (PAI) is preferably isolated in solid form by coagulation or precipitation from a polar reaction solvent under mild conditions, preferably by the addition of a miscible non-solvent such as water, lower alkyl alcohol, etc. Optionally, the solid resin is then collected, washed thoroughly with water, and can be centrifuged or pressed to further reduce the water content of the solid without heating. Non-solvents other than water and lower alkyl alcohols are known and are used in the art to precipitate the polymer (PAI) from solutions containing, for example, ethers, aromatic hydrocarbons, ketones, etc.

[0083] The number average molecular weight (Mn) of the polymer (PAI) is preferably at least 1000, more preferably at least 1500, and even more preferably at least 2000.

[0084] The molecular weights (Mw and Mn) of the polymer (PAI) can be measured using gel permeation chromatography (GPC).

[0085] Non-limiting examples of suitable polymers (PAI) are available from Solvay Specialty Polymers under the trade name Torlon® PAI.

[0086] Fibers The fibers of the present invention contain the composition (C) as detailed above. In certain embodiments, the fibers of the present invention consist essentially of the composition (C), and the expression "consist essentially of" is used to indicate that the fibers contain less than 10% by weight, preferably less than 5% by weight, of other components.

[0087] Non-limiting examples of possible other components include, for example, solvents used in the preparation of the fibers or any other additives used to facilitate the manufacture of the fibers.

[0088] The fibers can have a diameter of 50 to 1500 nm (or a similar cross-sectional dimension for non-circular shapes). Typically, the fibers have a diameter of at least 80 nm, preferably at least 100 nm. The fiber diameter is generally less than 1500 nm, more preferably less than 1200 nm. For example, it can be 100, 110, 120, 130, 140, 150, 160, 170, 180, 190, 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, 300, 310, 320, 330, 340, 350, 360, 370, 380, 390, 400, 410, 420, 430, 440, 450, 460, 470, 480, 490, 500, 510, 520, 530, 540, 550, 560, 570, 580, 590, 600, 610, 620, 630, 640, 650, 660, 670, 680, 690, 700, 710, 720, 730, 740, 750, 760, 770, 780, 790, 800, 810, 820, 830, 840, 850, 860, 870, 880, 890, 900, 910, 920, 930, 940, 950, 960, 970, 980, 990 nm.

[0089] The fibers of the present invention can be of various lengths based on an aspect ratio of at least 100, 500, 1000, 5000 or more with respect to the fiber diameter. In one embodiment, the length of the fibers can be at least 0.5 micrometers, more preferably at least 1.0 micrometers, including lengths in the range of about 0.5 micrometers to 10 meters. Further, the fibers can be cut to a desired length using any suitable instrument.

[0090] Method for manufacturing the fibers The fibers can advantageously be obtained by an electrospinning or forced spinning process. Both processes are known in the art for the preparation of fibers. The fibers obtained from these processes can be used to make webs, such as non-woven webs, from the fiber assembly.

[0091] A typical electrospinning setup includes a high voltage source connected to an exit port that is coupled to a source of a fluid fiber-forming material. An electric field is provided to charge the exit port from which the fluid exits. Electrodes for focusing, steering, and guiding the exiting solution are placed below the exit port. These serve to direct / pull the fluid from the exit port and onto the collector as fibers.

[0092] Forced spinning is also a known technique. Fibers can be manufactured using forced expulsion of a selected starting fiber-forming fluid material through an exit port. The exit port is configured with a size and shape to form a fine jet of the fluid material at the exit from the exit port. Due to factors such as surface tension, fluid viscosity, solvent volatility, rotational speed, etc., the expelled material can solidify as ultrafine fibers having a diameter significantly smaller than the inner diameter of the exit port. The jet of the released material is directed towards the collector, where it is collected for use in the final product.

[0093] Regardless of the technique used, whether electrospinning or forced spinning, the collected fiber material forms a two - dimensional or three - dimensional intertwined fiber web that can be processed to the desired surface area and thickness. The surface area and thickness can be controlled by the amount of time the fibers continue to be released onto the collector and can be controlled across the surface area of the collector (e.g., a moving belt as the collector can allow for a sheet of material of unlimited length).

[0094] When ultrafine fibers are overlapped, contact points are created at the intersections and the membranes bind steadily. If any web joining of the contact points is desired, it can be achieved by application of heat (thermal bonding), heat and pressure and / or chemical bonding. The system can include heating elements, pressure - applying devices, and chemical - bonding units for achieving such bonding.

[0095] In some embodiments, the fiber - forming material is supplied to a reservoir as a polymer solution, i.e., a composition (C) dissolved in a suitable solvent. In this embodiment, the method comprises, prior to supplying the fiber - forming material to the reservoir, polymer (I x) may further include dissolving or dispersing the polymer (PAI) and optionally a stabilizing additive in a solvent.

[0096] The liquid composition may advantageously be prepared by a dissolution process in which the polymer (I x ) the polymer (PAI) and optionally the stabilizing additive are contacted with the liquid medium under suitable temperature conditions.

[0097] Suitable liquid media that can be used are polar aprotic organic solvents such as acetone, ketones like methyl ethyl ketone, esters such as methyl acetate, dimethyl carbonate, diethyl carbonate, ethyl acetate, nitriles like acetonitrile, sulfoxides such as dimethyl sulfoxide, amides such as N,N-dimethylformamide, N,N-dimethylacetamide, pyrrolidones such as N-methylpyrrolidone, N-ethylpyrrolidone, etc.

[0098] In other embodiments, the composition (C) is supplied to the reservoir as a polymer melt. In such embodiments, the reservoir is heated to a temperature suitable for melting or softening the polymer (I x ) and the polymer (PAI).

[0099] At the end of the electrospinning or forced spinning process, a plurality of polymer fibers are formed. The plurality of fibers can be of the same diameter or different diameters.

[0100] The fibers are typically randomly arranged to form an aggregate of fibers hereinafter referred to as a "web". In this specification, the term "mat" may also be used to refer to an aggregate of fibers.

[0101] The thickness of the fiber web produced from the electrospinning or forced spinning process may need to be adjusted by pressing the web with a calendering roller or other pressing device, and this pressing operation can be carried out at a temperature that can cause some melting of the fibers at the contact point depending on the materials used.

[0102] Typically, the temperature is kept below the melting point of the fibrous material. The contact points, when fused together, can provide some amount of reinforcement when the fibrous web is used in the preparation of ion-exchange membranes.

[0103] Composite membrane Advantageously, the assembly comprising the fibers of the present invention can be used in the preparation of composite membranes. The composite membranes can be used both as ion-conductive membranes in electrolytic cells or as membranes for filtration or ultrafiltration applications.

[0104] The term "membrane" is used herein in its ordinary meaning to denote a discontinuous, generally thin interface that inhibits the permeation of chemical species in contact therewith.

[0105] The expression "composite membrane" is used herein to refer to a membrane comprising the fibers of the present invention, for example a web of the fibers of the present invention and an ion-exchange polymer.

[0106] Composite membranes typically comprise a first phase that contains, preferably consists of, an ion-exchange polymer, and a second phase that contains composition (C). The first and second phases can be layers of a multilayer structure. The composite membranes can contain two or more phases of the first type and / or two or more phases of the second type.

[0107] Composite membranes can contain fibers distributed in a matrix of an ion-exchange polymer. The fibers can be discrete fibers, i.e., fibers not arranged in a web. The fibers can be chopped.

[0108] Composite membranes can be produced by a process that includes (a) providing a plurality of fibers of the present invention; and (b) mixing the plurality of fibers with a polymer containing a plurality of ion-exchange groups. The mixing can be effected, for example, by providing the fibers to a dispersion of a polymer containing a plurality of ion-exchange groups in a liquid.

[0109] Alternatively, the composite membranes can contain a web produced from the fibers of the present invention and an ion-exchange polymer.

[0110] The ion exchange polymer is applied to the fibrous web. Any conventional method known in the art, such as impregnation, casting, coating, for example, roller coating, gravure coating, reverse roll coating, dip coating, spray coating, etc., can be used to apply the ion exchange polymer to the fibrous web.

[0111] The coating can be carried out by standard techniques known in the art, such as casting, notch bar coating or lamination.

[0112] Alternatively, the composite membrane can be prepared by an impregnation process. Such an impregnation process includes the step of impregnating the fibrous web of the present invention with a liquid composition containing an ion exchange polymer.

[0113] The impregnation can be carried out by dipping the fibrous web into an impregnation container containing the liquid composition, or it can be carried out by applying a suitable amount of the liquid composition by well-known coating techniques such as casting, coating, spraying, brushing, etc. on each side of the porous support simultaneously or in any subsequent coating step. Nevertheless, impregnation by dipping into a container containing the liquid composition is generally understood to be the technique that provides the best results.

[0114] The process for preparing the composite membrane typically includes at least one drying step and / or at least one annealing step.

[0115] The drying step is typically intended to remove the excess liquid medium from the film of the ion exchange polymer. This step is generally carried out at a temperature of 20 - 100 °C, preferably 25 - 90 °C, more preferably 30 - 80 °C.

[0116] The annealing process typically considered to strengthen the ion exchange polymer film is generally carried out at a temperature of at least 150°C, preferably at least 170°C, more preferably at least 180°C, and even more preferably at least 200°C. The maximum temperature is not particularly limited, provided that the fiber web and the ion exchange polymer of the present invention remain stable under these conditions. Generally, the annealing process is carried out at a temperature not exceeding 300°C, preferably not exceeding 270°C, and more preferably not exceeding 250°C.

[0117] The ion exchange polymer can be any polymer containing an ion exchange group.

[0118] The ion exchange polymer can advantageously be a fluorinated ion exchange polymer (I x ). All the definitions and priorities detailed above for the polymer (I x ) used in the preparation of the fibers of the present invention are equally applicable to the polymer (I x ) used in the preparation of the composite membrane.

[0119] The polymer (I x ) used in the preparation of the membrane can be the same as or different from the polymer (I x ) used in the composition (C) for the preparation of the fibers. For example, the polymer can contain the same repeating units but in different relative ratios, or it can contain different repeating units.

[0120] The composite membrane of the present invention has excellent proton conductivity even at low relative humidity and thus exhibits improved performance when used as a polymer electrolyte membrane in a membrane - electrode assembly for a fuel cell.

[0121] According to another embodiment of the present invention, there are provided a membrane - electrode assembly for a fuel cell containing an ion exchange composite membrane as a polymer electrolyte membrane and a fuel cell containing the same.

[0122] Specifically, the membrane-electrode assembly includes an anode and a cathode facing each other, and a composite membrane as a polymer electrolyte membrane disposed between the anode and the cathode.

[0123] The membrane-electrode assembly can be manufactured by a general manufacturing method for a membrane-electrode assembly for a fuel cell, except that the composite membrane is used as the polymer electrolyte membrane.

[0124] According to another embodiment of the present invention, a fuel cell including a membrane-electrode assembly including a composite membrane as a polymer electrolyte membrane is provided.

[0125] The composite membrane of the present invention can also be used in a filtration or ultrafiltration device. Therefore, a further object of the present invention is a filtration or ultrafiltration device including the composite membrane of the present invention.

[0126] If the disclosure of any patent, patent application, and publication incorporated herein by reference makes the terms unclear to the extent that it conflicts with this description, this description shall prevail.

[0127] The present invention is illustrated by the following non-limiting examples.

Examples

[0128] The following raw materials were used in the following examples.

[0129] Ix-1: Aquivion® PFSA PW98, a tetrafluoroethylene-perfluoro(3-oxa-4-pentenesulfonic acid) copolymer having an equivalent weight of 980 g / mol SO3H, available from Solvay Specialty Polymers.

[0130] PAI-1: Torlon® AI-10 LM is a polyamide-imide polymer with an acid value of 82.0 mg KOH / g, available from Solvay Specialty Polymers.

[0131] Comparative Example 1: Preparation of a Web of Forced-Spun Fibers and Polymer PAI PAI-1 was dried in a vented oven at 170 °C. After 4 hours, PAI-1 was dissolved in dimethylacetamide with stirring at room temperature. The dispersion was forced-spun using a FibeRio Cyclone FE with a rotating spinneret equipped with a nozzle of 150 - 500 microns. The forced-spun fibers were placed on a web having a thickness of 30 microns and a basis weight of 3 g / m 2 ².

[0132] Example 1: Preparation of Forced-Spun Fibers of Polymer (I x ) and Polymer PAI PAI-1 was dried in a vented oven at 170 °C while Ix-1 was dried in a vented oven at 100 °C. After 4 hours, PAI-1 and Ix-1 were dissolved in dimethylacetamide with stirring at room temperature to obtain a dispersion containing 10 wt% of Ix-1 and 90 wt% of PAI-1 based on the total amount of the polymers.

[0133] The dispersion was forced-spun using a FibeRio Cyclone FE with a spinneret rotating at 6000 - 8000 rpm and equipped with a nozzle of 150 - 500 microns. The forced-spun fibers were placed on a web having a thickness of 40 microns and a basis weight of 5.8 g / m 2 ².

[0134] Examples 2 and Comparative Example 2: Preparation of Composite Membranes The webs consisting of the forced-spun fibers obtained in Example 1 and Comparative Example 1 were used for the preparation of composite membranes. Each web was attached to a PTFE circular frame having an inner diameter of 100 mm and then immersed in a liquid mixture containing polymer Ix-1 (14 wt%), water (42 wt%), 1-propanol (34 wt%) and N-ethylpyrrolidone (10 wt%) at room temperature for 2 minutes. Then, the specimens were heat-treated in a vented oven at 65 °C for 1 hour, at 90 °C for 1 hour and from 90 °C to 190 °C for 1 hour. The thickness of the obtained membranes was 50 ± 5 microns. The weight ratio of the fibers to the final membranes was about 1.7 wt%.

[0135] Characteristic evaluation of the composite membrane: The in-plane conductivity was measured by a four-electrode Bekk-Tech BT-112 cell operating at 80 °C and in the relative humidity range of 20 - 120%. Humidified hydrogen (1000 sccm) and heating were supplied using a 1 KW Greenlight Power Technologies FCATS-E fuel cell test station. The membrane conductivity was calculated taking into account the geometric parameters of the sample and the cell resistance obtained as the slope of the cell voltage vs. current plot using a Metrohm Autolab PGSTAT-30 potentiostat / galvanostat. The cell was conditioned at the working temperature for 1 hour before measurement.

[0136] The results shown in Figure 1 indicate that the composite membrane obtained using the web of fibers produced from the composition of the present invention (Example 2) as the reinforcing layer has much higher proton conductivity over all ranges of relative humidity, particularly at low values of relative humidity, than the composite membrane obtained with the web of Comparative Example 2.

Claims

1. At least one fluorinated polymer or its precursor containing multiple ion exchange groups [polymer (I ｘ A fiber comprising a composition [composition (C)] containing )] and at least one aromatic polyamide-imide polymer [polymer (PAI)].

2. At least one polymer (I) in an amount of 0.1 to 95.0% by weight, preferably 0.5 to 75.0% by weight, 1.0 to 49.5% by weight, and more preferably 1.0 to 25.0% by weight, relative to the total weight of composition (C). ｘ The fiber according to claim 1, comprising 5.0 to 99.9% by weight, preferably 25.0 to 99.5% by weight, 50.5 to 99.0% by weight, and more preferably 75.0 to 99.0% by weight of at least one polymer (PAI).

3. Polymer (I ｘ )teeth, (1) Polymer (I ｘ ) with 50 to 99 mol%, preferably 52 to 98 mol%, of repeating units derived from tetrafluoroethylene, relative to the total moles of the repeating units; (2) Polymer (I ｘ ) 1 to 50 mol%, preferably 2 to 48 mol%, of at least one -SO ２ A monomer comprising an X group (wherein X is a halogen, preferably F or Cl or -OM, and M is selected from the group consisting of H, an ammonium group or a metal, preferably a monovalent metal), Formula (j): CF ２ = CF - O - (CF ２ ) ｍ SO ２ X (where m is an integer of 1 to 10, preferably 1 to 6, more preferably 2 to 4, and even more preferably, m is equal to 2 or 4); a sulfonyl halide fluorovinyl ether (jj) Formula: CF ２ =CF - (OCF ２ CF(R) Ｆ１ )) ｗ -O-CF ２ (CF(R) Ｆ２ )) ｙ SO ２ X (wherein w is an integer between 0 and 2, and R is equal to or different from each other) Ｆ１ and R Ｆ２ This is C independently and optionally substituted with F, Cl, or one or more ether oxygen atoms. １ ~C １０ It is a fluoroalkyl group, where y is an integer from 0 to 6; preferably, w is 1, and R Ｆ１ -CF ３ And y is 1, and R Ｆ２ is F) sulfonyl fluoride fluoroalkoxy vinyl ether; and (jjj) mixtures of those A monomer selected from the group consisting of; (3) Polymer (I ｘ ) 0 to 45 mol%, preferably 0 to 40 mol%, of at least one hydrogenated and / or fluorinated monomer different from TFE, preferably hexafluoropropylene, formula CF, relative to the total mole of repeating units. ２ = CFOR' ｆ１ (In the formula, R' ｆ１ C １ ~C ６ Perfluoroalkyl, ７ Perfluoroalkyl vinyl ether of formula CF ２ = CFOCF ２ OR' ｆ２ (In the formula, R' ｆ２ C １ ~C ６ C having perfluoroalkyl or one or more ether groups １ ~C ６ Formula CF contains perfluoroalkyl-methoxy-vinyl ethers (which are perfluorooxyalkyls). ２ = CFOR' Ｏ１ (In the formula, R' Ｏ１ C has one or more ether groups. ２ ~C １２ Repeating units derived from fully fluorinated monomers, generally selected from the group consisting of perfluorooxyalkyl vinyl ethers (which are perfluorooxyalkyls) and A fiber according to claim 1, selected from the group consisting of polymers including the following.

4. The polymer (PAI) contains repeating units, and more than 50 mol% of the repeating units contains at least one aromatic ring and at least one amic acid group and / or imide group [repeating unit (R ＰＡＩ )], the repeating unit is preferably, 【Chemistry 1】 Selected from the group consisting of, in the formula, - The symbol → in each formula indicates isomerism such that the group pointed to by the arrow may be located in the position shown or in a swapped position within any repeating unit of the aromatic polyamic acid structure; - Ar is an aromatic tetravalent group that may contain one or more aromatic rings, preferably, 【Chemistry 2】 (In the formula, X is -O-, -C(O)-, -S-, -SO ２ -ien-CH ２ -, -C(CF ３ ) ２ -, - (CF ２ ) ｎ (Selected from the group consisting of -, where n = 0, 1, 2, 3, 4, or 5) It is an aromatic tetravalent group selected from the group consisting of; - R is an aromatic divalent group which may contain one or more aromatic rings, preferably, 【Transformation 3】 (In the formula, Y is -O-, -C(O)-, -S-, -SO ２ -ien-CH ２ -, -C(CF ３ ) ２ -, - (CF ２ ) ｎ (Selected from the group consisting of -, where n = 0, 1, 2, 3, 4, or 5) 【Chemistry 4】 The fiber according to claim 1, wherein the aromatic divalent group is selected from the group consisting of the following.

5. The composition contains 1.0% to 50.0% by weight, 1.0% to 49.5% by weight, and further 1.0% to 25.0% by weight of at least one of the polymers (I ｘ ) and 50.0 to 99.0% by weight, 50.5 to 99.0% by weight, preferably 75.0 to 99.0% by weight of at least one polymer (PAI), and optionally 0.01 to 5.0% by weight of cerium and manganese oxides, CeO, either alone or in combination with other oxides such as silica or alumina. ２ Ce ２ O ３ and MnO ２ The fiber according to claim 1, comprising a stabilizing additive selected from the group consisting of and the group consisting of salts of cerium and manganese.

6. An aggregate, preferably in the form of a web, comprising the fibers according to any one of the multiple claims 1 to 5.

7. A process for preparing the fibers according to any one of claims 1 to 5, comprising the step of electrospinning or forcibly spinning the composition (C) according to any one of claims 1 to 5 through a spinneret.

8. A composite film comprising a fiber according to any one of claims 1 to 5 and a polymer containing a plurality of ion exchange groups.

9. A composite membrane comprising the aggregate described in claim 6 and a polymer containing a plurality of ion exchange groups.

10. A method for producing a composite film according to claim 8, comprising: (a) providing a plurality of fibers according to any one of claims 1 to 5; and (b) mixing the plurality of fibers with a polymer containing a plurality of ion exchange groups.

11. A method for producing the composite film according to claim 9, comprising: (a) providing the aggregate according to claim 6 in the form of a web of fibers; and (b) coating the polymer containing a plurality of ion exchange groups onto the web of fibers.

12. The method according to claim 11, wherein the polymer containing a plurality of ion exchange groups is applied to the fiber web by impregnation, casting, or coating.

13. A membrane-electrode assembly comprising the composite membrane according to claim 8 or 9.

14. A fuel cell comprising a composite membrane according to claim 8 or 9 or a membrane-electrode assembly according to claim 13.

15. A filtration or ultrafiltration device comprising the composite membrane described in claim 8 or 9.

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