DE10330461A1 - Production of polymer membrane, used in membrane electrode unit for fuel cell, uses phosphorus and/or sulfur oxy-acid in liquid for hydrolyzing membrane made by heating mixture of polyphosphoric acid and polyazole or precursors - Google Patents

Abstract

Production of proton-conducting polymer membranes comprises (a) producing a mixture of polyphosphoric acid, polyazole(s) and/or compound(s) forming polyazoles on heating in step (b), (b) heating the mixture under inert gas up to 400[deg]C; (c) applying a layer of the mixture from (a) and/or (b) to a substrate; and (d) treating the resultant membrane, the novelty is that (d) uses a hydrolysis liquid comprising phosphorus and/or sulfur oxyacid(s). Independent claims are also included for the following: (1) proton-conducting polymer membrane produced by this process, which has a phosphoric acid concentration of at least 85 wt.% at a breaking stress of at least 30 kJ/m 2>; (2) proton-conducting polymer membrane comprising phosphoric acid, polyazole(s) and monomer(s) (I) capable of free radical polymerization and having phosphonic and/or sulfonic acid groups, in which the weight ratio of the sum of phosphoric acid, polyphosphoric acid and polyphosphoric acid hydrolysis products to (I) is >= 1:2.

Description

The The present invention relates to processes for the production of proton-conducting Polymer membranes as well as improved polymer membranes due to Their excellent chemical and thermal properties are widely used can be and in particular as a polymer electrolyte membrane (PEM) in so-called PEM fuel cells are suitable.

proton-conducting Polymer membranes with good properties are known. So describe For example, the documents DE No. 10117686.4 and DE No. 10117687.2 Membranes that have a high phosphoric acid content. These Membranes are obtained by containing a soft polyphosphoric acid Layer is solidified to a membrane comprising phosphoric acid. The solidification is achieved by the hydrolysis of polyphosphoric acid to phosphoric acid.

in the In general, the hydrolysis can be achieved by atmospheric moisture. The disadvantage here, however, is that the moisture content varies can. This is going on the hydrolysis uneven, causing no consistent product quality can be achieved. at very low humidity can be a phase separation occur.

The Hydrolysis can according to the above Publications also be made under conditioned conditions. Problematic is, however, that the hydrolysis proceeds very slowly to a high acid content to reach. It should be remembered that a climatic chamber is right is expensive.

Furthermore Hydrolysis begins unilaterally from a surface, with hydrolysis beginning at a point. However, it is recommended to hydrolyze the membrane until a homogeneous membrane is formed, otherwise the membrane is relatively unstable is, so this when peeling from an inert carrier to be damaged can.

Furthermore Although it was found that a fairly short hydrolysis to a Membrane with a high phosphoric acid content leads, but this membrane a has very low mechanical stability.

Becomes the hydrolysis is longer executed although the mechanical stability increases, but the phosphoric acid content decreases.

Of the The present invention is therefore based on the object method to provide for the production of polymer electrolyte membranes, to solve the tasks outlined above. In particular, that should Process a cost-effective Production of polymer electrolyte membranes at high, constant Enable product quality. About that In addition, it was therefore an object of the present invention to polymer electrolyte membranes create a high mechanical performance in relation to their performance stability exhibit. Furthermore, the membranes should have high performance, in particular a high conductivity over a wide Show temperature range.

Be solved these objects by a process for the production of proton-conducting Polymer membranes with all features of claim 1. Regarding the polymer membranes of claim 18 provides a solution of underlying task.

• A) Herstellung einer Mischung umfassend Polyphosphorsäure, mindestens ein Polyazol und/oder mindestens ein oder mehrere Verbindungen, die unter Einwirkung von Wärme gemäß Schritt B) zur Bildung von Polyazolen geeignet sind,
• B) Erwärmen der Mischung erhältlich gemäß Schritt A) unter Inertgas auf Temperaturen bis zu 400°C,
• C) Aufbringen einer Schicht unter Verwendung der Mischung gemäß Schritt A) und/oder B) auf einem Träger,
• D) Behandlung der in Schritt C) gebildeten Membran, dadurch gekennzeichnet, dass die Behandlung der Membran mit einer Hydrolyseflüssigkeit erfolgt, die Sauerstoffsäuren des Phosphors und/oder Sauerstoffsäuren des Schwefels umfasst.

The present invention accordingly provides a proton-conducting polymer membrane comprising polyazole blends obtainable by a process comprising the steps

• A) preparation of a mixture comprising polyphosphoric acid, at least one polyazole and / or at least one or more compounds which are suitable for forming polyazoles under the action of heat in step B),
• B) heating the mixture obtainable according to step A) under inert gas to temperatures of up to 400 ° C.,
• C) applying a layer using the mixture according to step A) and / or B) on a support,
• D) treatment of the membrane formed in step C), characterized in that the treatment of the membrane is carried out with a hydrolysis liquid comprising oxygen acids of phosphorus and / or oxygen acids of sulfur.

According to the present invention, the membrane may be passed directly after doctoring into a hydrolyzing liquid having, for example, a predetermined concentration of phosphoric acid. Here through an automated production of high-performance membranes is possible. By varying the acid concentration, one can set the hydrolysis rate and membrane properties (H ₃ PO ₄ content, conductivity) in a targeted manner. Here, phase separation, which may occur upon hydrolysis in a low humidity environment, can be substantially eliminated.

The Hydrolysis time of the membrane can additionally by increasing the Temperature significantly reduced become. Through these advantages can the membranes are made more controlled, making it a particularly consistent high quality is achieved.

By the inventive method In particular, membranes are available, at a very high acid concentration a high mechanical stability exhibit.

Furthermore can especially the membranes obtained by the present process simply by welding in an acid-stable Film, for example a polyethylene or polypropylene film, for a long time be stored.

A inventive membrane shows over a big Temperature range high conductivity, even without a additional Humidification is achieved. In this case, a membrane according to the invention a relatively high mechanical stability.

Of Further, these membranes show a surprisingly long life.

The according to step B) composition comprises polyazoles. These polymers can already added in step A). Furthermore, these can Polymers also from the polymer underlying monomers, oligomers and / or prepolymers during heating according to step B).

worin
Ar gleich oder verschieden sind und für eine vierbindige aromatische oder heteroaromatische Gruppe, die ein- oder mehrkernig sein kann,
Ar¹ gleich oder verschieden sind und für eine zweibindige aromatische oder heteroaromatische Gruppe, die ein- oder mehrkernig sein kann,
Ar² gleich oder verschieden sind und für eine zwei oder dreibindige aromatische oder heteroaromatische Gruppe, die ein- oder mehrkernig sein kann,
Ar³ gleich oder verschieden sind und für eine dreibindige aromatische oder heteroaromatische Gruppe, die ein- oder mehrkernig sein kann,
Ar⁴ gleich oder verschieden sind und für eine dreibindige aromatische oder heteroaromatische Gruppe, die ein- oder mehrkernig sein kann,
Ar⁵ gleich oder verschieden sind und für eine vierbindige aromatische oder heteroaromatische Gruppe, die ein- oder mehrkernig sein kann,
Ar⁶ gleich oder verschieden sind und für eine zweibindige aromatische oder heteroaromatische Gruppe, die ein- oder mehrkernig sein kann,
Ar⁷ gleich oder verschieden sind und für eine zweibindige aromatische oder heteroaromatische Gruppe, die ein- oder mehrkernig sein kann,
Ar⁸ gleich oder verschieden sind und für eine dreibindige aromatische oder heteroaromatische Gruppe, die ein- oder mehrkernig sein kann,
Ar⁹ gleich oder verschieden sind und für eine zwei- oder drei- oder vierbindige aromatische oder heteroaromatische Gruppe, die ein- oder mehrkernig sein kann,
Ar¹⁰ gleich oder verschieden sind und für eine zwei- oder dreibindige aromatische oder heteroaromatische Gruppe, die ein- oder mehrkernig sein kann,
Ar¹¹ gleich oder verschieden sind und für eine zweibindige aromatische oder heteroaromatische Gruppe, die ein- oder mehrkernig sein kann,
X gleich oder verschieden ist und für Sauerstoff, Schwefel oder eine Aminogruppe, die ein Wasserstoffatom, eine 1–20 Kohlenstoffatome aufweisende Gruppe, vorzugsweise eine verzweigte oder nicht verzweigte Alkyl- oder Alkoxygruppe, oder eine Arylgruppe als weiteren Rest trägt
R gleich oder verschieden für Wasserstoff, eine Alkylgruppe und eine aromatische Gruppe steht und
n, m eine ganze Zahl größer gleich 10, bevorzugt größer gleich 100 ist.Polymers based on polyazole contain recurring azole units of the general formula (I) and / or (II) and / or (III) and / or (IV) and / or (V) and / or (VI) and / or (VII) and / or (VIII) and / or (IX) and / or (X) and / or (XI) and / or (XII) and / or (XIII) and / or (XIV) and / or (XV) and / or or (XVI) and / or (XVI) and / or (XVII) and / or (XVIII) and / or (XIX) and / or (XX) and / or (XXI) and / or (XXII)

wherein
Ar are the same or different and represent a tetravalent aromatic or heteroaromatic group which may be mononuclear or polynuclear,
Ar ^{1 are the} same or different and represent a divalent aromatic or heteroaromatic group which may be mononuclear or polynuclear,
Ar ^{2 are the} same or different and represent a two- or three-membered aromatic or heteroaromatic group which may be mononuclear or polynuclear,
Ar ^{3 are the} same or different and represent a trivalent aromatic or heteroaromatic group which may be mononuclear or polynuclear,
Ar ^{4 are the} same or different and represent a trivalent aromatic or heteroaromatic group which may be mononuclear or polynuclear,
Ar ^{5 are the} same or different and represent a tetravalent aromatic or heteroaromatic group which may be mononuclear or polynuclear,
Ar ^{6 are the} same or different and represent a divalent aromatic or heteroaromatic group which may be mononuclear or polynuclear,
Ar ^{7 are the} same or different and represent a divalent aromatic or heteroaromatic group which may be mononuclear or polynuclear,
Ar ^{8 are the} same or different and represent a trivalent aromatic or heteroaromatic group which may be mononuclear or polynuclear,
Ar ^{9 are the} same or different and represent a bi- or tri- or tetravalent aromatic or heteroaromatic group which may be mononuclear or polynuclear,
Ar ^{10 are the} same or different and represent a divalent or trivalent aromatic or heteroaromatic group which may be mononuclear or polynuclear,
Ar ^{11 are the} same or different and represent a divalent aromatic or heteroaromatic group which may be mononuclear or polynuclear,
X is the same or different and is oxygen, sulfur or an amino group which carries a hydrogen atom, a 1-20 carbon atom group, preferably a branched or unbranched alkyl or alkoxy group, or an aryl group as a further radical
R is the same or different hydrogen, an alkyl group and an aromatic group, and
n, m is an integer greater than or equal to 10, preferably greater than or equal to 100.

According to the invention preferred aromatic or heteroaromatic groups are derived from benzene, naphthalene, Biphenyl, diphenyl ether, diphenylmethane, diphenyldimethylmethane, Bisphenone, diphenylsulfone, thiophene, furan, pyrrole, thiazole, oxazole, Imidazole, isothiazole, isoxazole, pyrazole, 1,3,4-oxadiazole, 2,5-diphenyl-1,3,4-oxadiazole, 1,3,4-thiadiazole, 1,3,4-triazole, 2,5-diphenyl-1,3,4-triazole, 1,2,5-triphenyl-1,3,4-triazole, 1,2, 4-oxadiazole, 1,2,4-thiadiazole, 1,2,4-triazole, 1,2,3-triazole, 1,2,3,4-tetrazole, benzo [b] thiophene, Benzo [b] furan, indole, benzo [c] thiophene, benzo [c] furan, isoindole, Benzoxazole, benzothiazole, benzimidazole, benzisoxazole, benzisothiazole, Benzopyrazole, benzothiadiazole, benzotriazole, dibenzofuran, dibenzothiophene, Carbazole, pyridine, bipyridine, pyrazine, pyrazole, pyrimidine, pyridazine, 1,3,5-triazine, 1,2,4-triazine, 1,2,4,5-triazine, tetrazine, quinoline, Isoquinoline, quinoxaline, quinazoline, cinnoline, 1,8-naphthyridine, 1,5-naphthyridine, 1,6-naphthyridine, 1,7-naphthyridine, phthalazine, pyridopyrimidine, Purine, pteridine or quinolizine, 4H-quinolizine, diphenyl ether, anthracene, Benzopyrrole, benzooxathiadiazole, benzooxadiazole, benzopyridine, benzopyrazine, Benzopyrazidine, benzopyrimidine, benzotriazine, indolizine, pyridopyridine, Imidazopyrimidine, pyrazinopyrimidine, carbazole, aciridine, phenazine, Benzoquinoline, phenoxazine, phenothiazine, acridizine, benzopteridine, Phenanthroline and phenanthrene, which may also be substituted could be.

Here, the substitution pattern of Ar ¹ , Ar ⁴ , Ar ⁶ , Ar ⁷ , Ar ⁸ , Ar ⁹ , Ar ¹⁰ , Ar ^{11 is} arbitrary, in the case of phenylene, for example, Ar ¹ , Ar ⁴ , Ar ⁶ , Ar ⁷ , Ar ⁸ , Ar ⁹ , Ar ¹⁰ , Ar ^{11 are} ortho, meta and para-phenylene. Particularly preferred groups are derived from benzene and biphenylene, which may optionally also be substituted.

preferred Alkyl groups are short-chain alkyl groups having 1 to 4 carbon atoms, such as For example, methyl, ethyl, n- or i-propyl and t-butyl groups.

preferred Aromatic groups are phenyl or naphthyl groups. The alkyl groups and the aromatic groups can be substituted.

preferred Substituents are halogen atoms such as. As fluorine, amino groups, hydroxy groups or short chain alkyl groups such as. For example, methyl or ethyl groups.

Prefers are polyazoles with repeating units of the formula (I) at where X is the same within a repeating unit are.

The Polyazoles can in principle also have different repeating units that are for example, in their remainder X differ. Preferably, however it has only the same radicals X in a repeating unit.

Further preferred polyazole polymers are polyimidazoles, polybenzimidazole ether ketone, polybenzothiazoles, polybenzoxazoles, polyoxadiazoles, polyquinoxalines, polythiadiazoles, poly (pyridines), poly (pyrimidines), and poly (tetrazapyrene).

In a further embodiment In the present invention, the polymer is containing recurring Azole units a copolymer or a blend containing at least two Contains units of the formula (I) to (XXII) which differ from each other. The polymers can as block copolymers (diblock, triblock), random copolymers, periodic copolymers and / or alternating polymers are present.

In a particularly preferred embodiment In the present invention, the polymer is containing recurring Azoleinheiten a polyazole, the units of formula (I) and / or (II).

The Number of repeating azole units in the polymer is preferred an integer greater than or equal 10. Particularly preferred polymers contain at least 100 recurring Azole units.

wobei n und m eine ganze Zahl größer gleich 10, vorzugsweise größer gleich 100 ist.In the context of the present invention, polymers containing recurring benzimidazole units are preferred. Some examples of the most useful polymers containing benzimidazole recurring units are represented by the following formulas:

where n and m is an integer greater than or equal to 10, preferably greater than or equal to 100.

The polyazoles used in step A), but in particular the polybenzimidazoles are characterized by a high molecular weight. Measured as intrinsic viscosity, this is preferably in Be rich from 0.3 to 10 dl / g, in particular 1 to 5 dl / g.

Of others can the polyazoles are also prepared in step B) by heating. For this can the mixture according to step A) one or more compounds added under the action of Heat according to step B) are suitable for the formation of polyazoles.

For this are suitable mixtures containing one or more aromatic and / or heteroaromatic tetra-amino compounds and one or more aromatic and / or heteroaromatic carboxylic acids or their derivatives which at least two acid groups per carboxylic acid monomer include. Furthermore, you can one or more aromatic and / or heteroaromatic diaminocarboxylic acids for Production of polyazoles can be used.

To the aromatic and heteroaromatic tetra-amino compounds belong inter alia 3,3 ', 4,4'-tetraaminobiphenyl, 2,3,5,6-tetraaminopyridine, 1,2,4,5-tetraaminobenzene, 3,3 ', 4,4'-tetraaminodiphenylsulfone, 3,3 ', 4,4'-tetraaminodiphenyl ether, 3,3', 4,4'-tetraaminobenzophenone, 3,3 ', 4,4'-tetraaminodiphenylmethane and 3,3', 4,4'-tetraaminodiphenyldimethylmethane as well their salts, in particular their mono-, di-, tri- and tetrahydrochloride derivatives. Of these, 3,3 ', 4,4'-tetraaminobiphenyl, 2,3,5,6-tetraaminopyridine and 1,2,4,5-tetraaminobenzene particularly preferred.

Of Further, the mixture A) aromatic and / or heteroaromatic carboxylic acids include. These are dicarboxylic acids and tricarboxylic acids and Tetracarboxylic acids or their esters or their anhydrides or their acid halides, in particular their acid halides and / or acid bromides. Preferably, the aromatic dicarboxylic acids are um isophthalic acid, terephthalic acid, phthalic acid, 5-hydroxyisophthalic, 4-hydroxyisophthalic acid, 2-hydroxyterephthalic acid, 5-aminoisophthalic acid, 5-N, N-dimethylaminoisophthalic acid, 5-N, N-diethylaminoisophthalic acid, 2,5-dihydroxyterephthalic acid, 2,6-dihydroxyisophthalic acid, 4,6-dihydroxyisophthalic acid, 2,3- Dihydroxyphthalic acid, 2,4-dihydroxyphthalic acid, 3,4-dihydroxyphthalic acid, 3-fluorophthalic acid, 5-fluoroisophthalic acid, 2-fluoroterphthalic acid, tetrafluorophthalic acid, tetrafluoroisophthalic acid, tetrafluoroterephthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diphenic acid, 1,8-dihydroxynaphthalene-3,6-dicarboxylic acid, diphenylether-4,4'-dicarboxylic acid, benzophenone-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, biphenyl-4 , 4'-dicarboxylic acid, 4-trifluoromethylphthalic acid, 2,2-bis (4-carboxyphenyl) hexafluoropropane, 4,4'-stilbenedicarboxylic acid, 4-carboxycinnamic acid, or their C1-C20 alkyl esters or C5-C12 aryl esters, or their acid anhydrides or their acid chlorides.

at the aromatic tricarboxylic acids or their C 1 -C 20 -alkyl esters or C 5 -C 12 -aryl esters or their acid anhydrides or their acid chlorides it is preferably 1,3,5-benzenetricarboxylic acid (Trimesic acid), 1,2,4-benzenetricarboxylic acid (Trimellitic acid), (2-carboxyphenyl) iminodiacetic acid, 3,5,3'-biphenyltricarboxylic acid, 3,5,4'-biphenyltricarboxylic acid.

at the aromatic tetracarboxylic acids or their C 1 -C 20 -alkyl esters or C 5 -C 12 -aryl esters or their acid anhydrides or their acid chlorides it is preferably 3,5,3 ', 5'-biphenyltetracarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, benzophenonetetracarboxylic acid, 3,3', 4,4'-biphenyltetracarboxylic acid, 2,2 ', 3,3' Biphenyltetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid, 1,4,5,8-naphthalenetetracarboxylic acid.

at the heteroaromatic carboxylic acids are heteroaromatic dicarboxylic acids and tricarboxylic acids and Tetracarboxylic acids or their esters or their anhydrides. As heteroaromatic carboxylic acids aromatic systems understood which at least one nitrogen, Oxygen, sulfur or phosphorus atom contained in the aromatic. Preferably these are pyridine-2,5-dicarboxylic acid, pyridine-3,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, pyridine-2,4-dicarboxylic acid, 4-phenyl-2,5-pyridinedicarboxylic acid, 3,5- Pyrazoledicarboxylic acid, 2,6-pyrimidinedicarboxylic acid, 2,5-pyrazinedicarboxylic acid, 2,4,6-pyridinetricarboxylic acid, benzimidazole-5,6-dicarboxylic acid. Such as their C1-C20 alkyl esters or C5-C12 aryl esters, or their acid anhydrides or their acid chlorides.

Of the Content of tricarboxylic acid or tetracarboxylic acids (based on the dicarboxylic acid used) is between 0 and 30 mol%, preferably 0.1 and 20 mol%, in particular 0.5 and 10 mol%.

Of Furthermore, the mixture A) may also be aromatic and heteroaromatic Diaminocarboxylic acids included. Belongs to these including diaminobenzoic acid, 4-phenoxycarbonyl-3, '4'-diaminodiphenyl and their mono- and dihydrochloride derivatives.

Prefers in step A) mixtures of at least 2 different aromatic carboxylic acids use. Particular preference is given to using mixtures which in addition to aromatic carboxylic acids also heteroaromatic carboxylic acids contain. The mixing ratio of aromatic carboxylic acids to heteroaromatic carboxylic acids is between 1:99 and 99: 1, preferably 1:50 to 50: 1.

at these mixtures are in particular mixtures of N-heteroaromatic dicarboxylic acids and aromatic dicarboxylic acids. Nonlimiting examples of dicarboxylic acids are isophthalic acid, terephthalic acid, phthalic acid, 2,5-dihydroxyterephthalic acid, 2,6-dihydroxyisophthalic acid, 4,6-dihydroxyisophthalic acid, 2,3-dihydroxyphthalic acid, 2,4-dihydroxyphthalic acid. 3,4-dihydroxyphthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diphenic acid, 1,8-dihydroxynaphthalene-3,6-dicarboxylic acid, diphenyl ether-4,4 ' dicarboxylic acid, benzophenone-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, 4-trifluoromethylphthalic acid, pyridine-2,5-dicarboxylic acid, pyridine-3,5-dicarboxylic acid, Pyridine-2,6-dicarboxylic acid, pyridine-2,4-dicarboxylic acid, 4-phenyl-2,5-pyridinedicarboxylic acid, 3,5-pyrazoldicarboxylic acid, 2,6-pyrimidinedicarboxylic acid, 2,5-pyrazinedicarboxylic acid.

Should one possible high molecular weight can be achieved, so is the molar ratio of Carboxylic acid groups to amino groups in the reaction of tetra-amino compounds with one or more aromatic carboxylic acids or their esters, the at least two acid groups contain per carboxylic acid monomer, preferably in the vicinity from 1: 2.

The in step A) preferably comprises at least 0.5 wt .-%, in particular 1 to 30 wt .-% and particularly preferably 2 to 15% by weight of monomers for the preparation of polyazoles.

insofar the mixture according to step A) also tricarboxylic acids or tetracarboxylic acid contains This is a branching / crosslinking of the polymer formed achieved. This wears to improve the mechanical property.

According to one Another aspect of the present invention includes those in step A) mixture prepared compounds under the action of Heat according to step B) are suitable for the formation of polyazoles, these compounds by reaction of one or more aromatic and / or heteroaromatic Tetra-amino compounds with one or more aromatic and / or heteroaromatic carboxylic acids or their derivatives, the at least two acid groups per carboxylic acid monomer contained, or of one or more aromatic and / or heteroaromatic diamino in the melt at temperatures of up to 400 ° C, in particular up to 350 ° C, preferably up to 280 ° C are available. The for the preparation of these prepolymers compounds to be used have been previously set forth.

The polyphosphoric acid used in step A) are commercially available polyphosphoric acids, such as are obtainable, for example, from Riedel-de Haen. The polyphosphoric acids N _{n + 2} P _n O _{3n + 1} (n> 1) usually have a content calculated as P ₂ O ₅ (acidimetric) of at least 83%. Instead of a solution of the monomers, it is also possible to produce a dispersion / suspension.

According to one particular aspect of the present invention, the in step A) and / or step B) produced at least one added to another polymer which is not a polyazole (polymer (B)). This polymer may be dissolved, dispersed or suspended, inter alia available.

in this connection can the weight ratio from polyazole to polymer (B), in particular in the range from 0.1 to 50, preferably from 0.2 to 20, more preferably from 1 to 10 lie. If the polyazole is formed only in step B) can the weight ratio calculated from the weight of the monomers to form the polyazole whereby the compounds liberated in the condensation, for example, to consider water are.

Among the preferred polymers include polyolefins, such as
Poly (chloroprene), polyacetylene, polyphenylene, poly (p-xylylene), polyarylmethylene, polyarmethylene, polystyrene, polymethylstyrene, polyvinyl alcohol, polyvinyl acetate, polyvinyl ether, polyvinylamine, poly (N-vinylacetamide), polyvinylimidazole, polyvinylcarbazole, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl chloride, polyvinylidene chloride , Polytetrafluoroethylene, polyhexafluoropropylene, copolymers of PTFE with hexafluoropropylene, with perfluoropropyl vinyl ether, with trifluoronitrosomethane, with sulfonyl fluoride vinyl ether, with carbalkoxyperfluoroalkoxy vinyl ether, polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyacrolein, polyacrylamide, polyacrylonitrile, polycyanoacrylates, polymethacrylimide, cycloolefinic copolymers, in particular of norbornene;
Polymers having CO bonds in the main chain, for example, polyacetal, polyoxymethylene, polyether, polypropylene oxide, polyepichlorohydrin, polytetrahydrofuran, polyphenylene oxide, polyether ketone, polyesters, especially polyhydroxyacetic acid, polyethylene terephthalate, polybutylene terephthalate, polyhydroxybenzoate, polyhydroxypropionic acid, polypivalolactone, polycaprolactone, polymalonic acid, polycarbonate;
Polymeric CS bonds in the backbone, for example, polysulfide ethers, polyphenylene sulfide, polyethersulfone;
Polymeric CN bonds in the backbone, for example polyimines, polyisocyanides, polyetherimine, polyaniline, polyamides, polyhydrazides, polyurethanes, polyimides, polyazoles, polyazines;
Liquid crystalline polymers, especially Vectra and
Inorganic polymers, for example polysilanes, polycarbosilanes, polysiloxanes, polysilicic acid, polysilicates, silicones, polyphosphazenes and polythiazyl.

Of Furthermore, the polymers (B) also include polymers with covalently bonded Acid groups. These acid groups especially include sulfonic acid groups. The sulfonic acid groups Modified polymers preferably have a content of sulfonic acid groups in the range of 0.5 to 3 meq / g. This value is over the so-called ion exchange capacity (IEC) determined.

to Measuring the IEC, the sulfonic acid groups are converted into the free acid. For this the polymer is treated in a known manner with acid, wherein excess acid Washing is removed. So the sulfonated polymer is first 2 hours treated in boiling water. Subsequently, excess water abgetupt and the sample while 15 hours at 160 ° C in a vacuum drying oven at p <1 mbar dried. Then the dry weight of the membrane is determined. The thus-dried polymer is then dissolved in DMSO at 80 ° C for 1 h solved. The solution is then titrated with 0.1 M NaOH. From the consumption of Acid up to the equivalent point and the dry weight is then the ion exchange capacity (IEC) calculated.

such Polymers are known in the art. So can sulfonic acid groups containing polymers, for example by sulfonation of polymers getting produced. Methods for sulfonating polymers are in F. Kucera et. al. Polymer Engineering and Science 1988, Vol. 38, No 5, 783-792 described. Here you can the sulfonation conditions are chosen so that a lower Sulfonierungsgrad arises (DE-A-19959289).

So became another class of non-fluorinated polymers by sulfonation developed by high temperature stable thermoplastics. So are sulfonated Polyether ketones (DE-A-4219077, WO96 / 01177), sulfonated polysulfones (J. Membr. Sci. 83 (1993) p.211) or sulfonated polyphenylene sulfide (DE-A-19527435).

US-A-6110616 describes copolymers of butadiene and styrene and their subsequent Sulfonation for use for Fuel cells.

Of others can Such polymers are also obtained by polyreactions of monomers become the acid groups include. So can perfluorinated polymers as described in US-A-5422411 by copolymerization made from trifluorostyrene and sulfonyl-modified trifuorostyrene become.

These include, among others Perfluorosulfonsäurepolymeren Nafion ^® (US Patent 3,692,569). This polymer can be solubilized as described in US-A-4453991 and then used as an ionomer.

To the preferred polymers with acid groups belong including sulfonated polyether ketones, sulfonated polysulfones, sulfonated polyphenylene sulfides, perfluorinated sulfonic acid group-containing Polymers as described in US-A-3692569, US-A-5422411 and US-A-6110616.

to Application in fuel cells with a continuous service temperature above 100 ° C preference is given to those polymers (B) which have a glass transition temperature or Vicat softening temperature VST / A / 50 of at least 100 ° C, preferably at least 150 ° C and most preferably at least 180 ° C have.

in this connection are polysulfones having a Vicat softening temperature VST / A / 50 from 180 ° C up to 230 ° C prefers.

In addition, preferred are polymers (B) which have a low solubility and / or degradability in phosphoric acid. According to a particular embodiment of the present invention is increasing the weight by treatment with 85% phosphoric acid only insignificantly. Preferably, the weight ratio of the plate after the phosphoric acid treatment to the weight of the plate before the treatment is greater than or equal to 0.8, in particular greater than or equal to 0.9, and particularly preferably greater than or equal to 0.95. This value is measured on a sheet of polymer (B) which is 2 mm thick, 5 cm long and 2 cm wide. This plate is placed in phosphoric acid, wherein the weight ratio of phosphoric acid to plate is 10. Subsequently, the phosphoric acid is heated with stirring for 24 hours at 100 ° C. The plate is then freed from excess phosphoric acid by washing with water and dried. After this, the plate is weighed again.

Preferred polymers include polysulfones, especially polysulfone having aromatics in the backbone. Have According to a particular aspect of the present invention, preferred polysulfones and polyether sulfones have a melt volume rate MVR 300 / 21.6 smaller or equal to 40 cm ^3/10 min, especially less than or equal to 30 cm ^3/10 min and particularly preferably less than or equal to 20 cm ³ / 10 min measured to ISO 1133.

The obtained in step A) is heated to a temperature according to step B) up to 400 ° C, in particular up to 350 ° C, preferably up to 280 ° C, especially 100 ° C up to 250 ° C and more preferably heated in the range of 180 ° C to 250 ° C. This is a Inert gas, for example nitrogen or a noble gas, such as neon, Argon, used. This step serves, depending on the starting material, either to dissolve, to disperse Polyazoles, or to form polyazoles from monomers or polymers Precursors of polyazoles.

In a variant of the method, the heating according to step B) after the formation a flat Building according to step C).

The In addition, in step A) and / or step B) prepared mixture organic solvents contain. these can positively influence the processability. So, for example the rheology of the solution be improved so that it is easier to extrude or knife can be.

to further improvement of the performance characteristics of the Membrane in addition still fillers, in particular proton-conducting fillers, as well as additional acids be added. The addition can be carried out, for example, in step A), Step B) and / or step C) take place. Furthermore, these additives, if these are in liquid Form are present, even after the polymerization according to step D) are added. Furthermore, you can these additives of the hydrolysis fluid added become.

Non-limiting examples of proton-conductive fillers are
Sulfates such as: CsHSO ₄ , Fe (SO ₄ ) ₂ , (NH ₄ ) ₃ H (SO ₄ ) ₂ , LiHSO ₄ , NaHSO ₄ , KHSO ₄ , RbSO ₄ , LiN ₂ H ₅ SO ₄ , NH ₄ HSO ₄ ,
Phosphates such as Zr ₃ (PO ₄ ) ₄ , Zr (HPO ₄ ) ₂ , HZr ₂ (PO ₄ ) ₃ , UO ₂ PO ₄ .3H ₂ O, H ₈ UO ₂ PO ₄ , Ce (HPO ₄ ) ₂ , Ti ( HPO ₄ ) ₂ , KH ₂ PO ₄ , NaH ₂ PO ₄ , LiH ₂ PO ₄ , NH ₄ H ₂ PO ₄ , CsH ₂ PO ₄ , CaHPO ₄ , MgHPO ₄ , HSbP ₂ O ₈ , HSb ₃ P ₂ O ₁₄ , H ₅ Sb ₅ P ₂ O ₂₀ ,
Polyacid such as H ₃ PW ₁₂ O ₄₀ .nH ₂ O (n = 21-29), H ₃ SiW ₁₂ O ₄₀ .nH ₂ O (n = 21-29), H _x WO ₃ , HSbWO ₆ , H ₃ PMo ₁₂ O ₄₀ , H ₂ Sb ₄ O ₄₀ , HTaWO ₆ , HNbO ₃ , HTiNbO ₅ , HTiTaO ₅ , HSbTeO ₆ , H ₅ Ti ₄ O ₉ , HSbO ₃ , H ₂ MoO ₄
Selenites and arsenides such as (NH ₄ ) ₃ H (SeO ₄ ) ₂ , UO ₂ AsO ₄ , (NH ₄ ) ₃ H (SeO ₄ ) ₂ , KH ₂ AsO ₄ , Cs ₃ H (SeO ₄ ) ₂ , Rb ₃ H (SeO ₄ ) ₂ ,
Oxides such as Al ₂ O ₃ , Sb ₂ O ₅ , ThO ₂ , SnO ₂ , ZrO ₂ , MoO ₃
Silicates such as zeolites, zeolites (NH ₄ +), phyllosilicates, framework silicates, N-natrolites, H-mordenites, NH ₄ -alanecines, NH ₄ -sodalites, NH ₄ -gallates, H-montmorillonites
Acids such as HClO ₄ , SbF ₅
Fillers such as carbides, in particular SiC, Si ₃ N ₄ , fibers, in particular glass fibers, glass powders and / or polymer fibers, preferably based on polyazoles.

These Additives can be contained in the proton-conducting polymer membrane in conventional amounts, wherein however, the positive properties, such as high conductivity, high durability and high mechanical stability of the membrane by adding from too big Amounts of additives should not be affected too much. In general comprises the membrane after the treatment according to step D) at most 80 wt .-%, preferably at most 50 wt .-% and particularly preferably at most 20 wt .-% additives.

Furthermore, this membrane may also contain perfluorinated sulfonic acid additives (preferably 0.1-20% by weight, preferably 0.2-15% by weight, very preferably 0.2-10% by weight). These additives improve performance near the cathode to increase oxygen solubility and oxygen diffusion and reduce the adsorption of phosphoric acid and phosphate to platinum. Gang, Xiao; Hjuler, HA; Olsen, C., Berg, RW; Bjerrum, NJ Chem. Dep. A, Tech., Univ., Denmark, Lyngby, Den, J. Electrochem. Soc. (1993), 140 (4), 896-902 and perfluorosulfonimides as Additive in phosphoric acid fuel cell. Razaq, M .; Razaq, A .; Yeager, E .; DesMarteau, Darryl D .; Singh, S. Case Cent. Electrochem. Sci., Case West. Reserve Univ, Cleveland, OH, USA. J. Electrochem. Soc. . (1989), 136 (2), 385-90) Non-limiting examples of persulfonated additives are: trifluoromethanesulfonic acid, potassium trifluoromethanesulfonate, sodium trifluoromethanesulfonate, lithium trifluoromethanesulfonate, Ammoniumtrifluormethansulfonat, Kaliumperfluorohexansulfonat, Natriumperfluorohexansulfonat perfluorohexanesulphonate, lithium, ammonium perfluorohexanesulphonate, perfluorohexanesulphonic acid, potassium nonafluorobutanesulfonate, Natriumnonafluorbutansulfonat, Lithiumnonafluorbutansulfonat, Ammoniumnonafluorbutansulfonat, Cesium nonafluorobutanesulfonate, triethylammonium perfluorohexasulfonate, perflurosulfoimides and Nafion.

The Formation of the plane Building according to step C) takes place by means of measures known per se (casting, spraying, doctoring, Extrusion) from the prior art for polymer film production are known. As a carrier are all suitable under the conditions as inert carrier to be designated. To these carriers belong in particular films of polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyhexafluoropropylene, copolymers of PTFE with hexafluoropropylene, Polyimides, polyphenylene sulfides (PPS) and polypropylene (PP).

to Adjustment of viscosity can the solution optionally with an easily evaporable organic solvent be offset. This allows the viscosity to the desired Value adjusted and the formation of the membrane can be facilitated.

The Thickness of the plane Building according to step C) is preferably between 10 and 4000 μm, preferably between 15 and 3500 μm, in particular between 20 and 3000 microns, more preferably between 30 and 1500 microns and most preferably between 50 and 1200 microns.

The Treatment of the membrane in step D) takes place in particular at temperatures in the range of 0 ° C and 150 ° C, preferably at temperatures between 10 ° C and 120 ° C, in particular between room temperature (20 ° C) and 90 ° C, by a hydrolysis liquid, the water and at least one oxygen acid of the phosphor and / or Sulfur includes. The treatment is preferably carried out under normal pressure, but can also be done under the influence of pressure.

The hydrolysis can be a solution represent, wherein the liquid may also contain suspended and / or dispersed components. The viscosity the hydrolysis liquid can be within a wide range, with an addition to adjust the viscosity of solvents or a temperature increase can be done. Preferably, the dynamic viscosity is in the range from 0.1 to 10,000 mPa.s, in particular from 0.2 to 2000 mPa · s, these values are measured, for example, according to DIN 53015 can.

The Treatment according to step D) can be done by any known method. For example, the in step C) are immersed in a liquid bath. Furthermore, the hydrolysis liquid can be sprayed on the membrane. Furthermore, the hydrolysis via the Membrane to be poured. The latter methods have the advantage that the concentration of acid in the hydrolysis liquid while the hydrolysis remains constant. However, the first method is often less expensive in the execution.

To the oxygen acid Phosphorus and / or sulfur include in particular phosphinic acid, phosphonic acid, phosphoric acid, hypodiphosphonic acid hypodiphosphoric acid, oligophosphoric acids, sulfurous Acid, sulphurous acid and / or sulfuric acid. These acids can used singly or as a mixture.

The hydrolysis includes water, the concentration of water in general not very critical. According to a particular aspect of present invention, the hydrolysis liquid comprises 5 to 80 wt .-%, preferably 8 to 70 wt .-% and particularly preferably 10 to 50 wt .-% water. The amount of water that is formally contained in the oxygen acids is not taken into account in the water content of the hydrolysis liquid.

From the aforementioned acids are phosphoric acid and / or sulfuric acid particularly preferred, these acids in particular 5 to 70 Wt .-%, preferably 10 to 60 wt .-% and particularly preferably 15 to 50% by weight of water.

The partial hydrolysis of the polyphosphoric acid in step D) leads to a solidification of the membrane and to a decrease in the layer thickness and formation of a membrane. The solidified membrane generally has a thickness between 15 and 3000 microns, preferably 20 and 2000 microns, in particular between 20 and 1000 microns, wherein the membrane is self-supporting.

The upper temperature limit of the treatment according to step D) is in the Usually 150 ° C. In extremely short action, the hydrolysis liquid also hotter as 150 ° C be. Essential for the upper temperature limit is the duration of the treatment. According to one particular aspect of the present invention, the membrane is in the hydrolysis liquid cooled to room temperature.

The Duration of treatment can vary widely, with duration in particular the water concentration of the hydrolysis liquid dependent is. Furthermore, the treatment time is the thickness of the membrane dependent.

In the rule is the treatment time between 10 seconds and 20 hours, in particular 1 minute to 10 hours.

The according to step D) obtained membrane can be made self-supporting, i. she can from the carrier without damage solved and subsequently if necessary, directly further processed or stored.

On the Degree of hydrolysis, i. the duration, temperature and hydrolysis fluid, is the concentration of phosphoric acid and thus the conductivity the polymer membrane according to the invention adjustable. According to the invention Concentration of phosphoric acid as a mole of acid indicated per mole of repeat unit of the polymer. As part of the present invention is a concentration (moles of phosphoric acid based on a repeat unit of formula (III), i. Polybenzimidazole) between 10 and 100, in particular between 12 and 95, preferred. Such high doping levels (concentrations) are by doping polyazoles with commercially available ortho-phosphoric acid only very difficult or not accessible at all.

in the Following the treatment according to step D), the membrane can by exposure to heat in the presence of oxygen still be networked. This hardening the membrane additionally improves the properties of the membrane. For this purpose, the membrane to a temperature of at least 150 ° C, preferably at least 200 ° C and particularly preferably at least 250 ° C are heated. The oxygen concentration is usual in this process step in the range of 5 to 50% by volume, preferably 10 to 40% by volume, without this is a limitation should be done.

The Crosslinking can also be effected by the action of IR or NIR (IR = infra red, d. H. Light with one wavelength greater than 700 nm; NIR = near IR, d. H. Light with a wavelength in the range from about 700 to 2000 nm or an energy in the range of about 0.6 to 1.75 eV). Another method is the irradiation with β-rays. The radiation dose is here between 5 and 200 kGy.

ever after desired Degree of crosslinking can increase the duration of the crosslinking reaction in one wide range. In general, this reaction time is in the range of 1 second to 10 hours, preferably 1 minute to 1 hour, without this being a limitation.

The inventive polymer membrane has improved material properties over the previously known doped Polymer membranes on. In particular, they show in comparison with known doped polymer membranes perform better. This is justified in particular by an improved proton conductivity. This is at temperatures of 120 ° C at least 0.1 S / cm, preferably at least 0.11 S / cm, in particular at least 0.12 S / cm. If the membranes of the invention polymers with sulfonic acid groups include the membranes show a high even at a temperature of 70 ° C. Conductivity. The conductivity depends among other things from sulfonic acid group content the membrane. The higher this one Proportion, the better the conductivity at low temperatures. Here, a membrane according to the invention be moistened at low temperatures. For this purpose, for example the compound used as an energy source, for example hydrogen, be provided with a proportion of water. In many cases, however, it is enough also the water formed by the reaction to moistening to achieve.

The specific conductivity is measured by means of impedance spectroscopy in a 4-pole arrangement in the potentiostatic mode and using platinum electrodes (wire, 0.25 mm diameter). The distance between the current-collecting electrodes is 2 cm. The spectrum obtained is compared with a simple model consisting of a parallel arrangement of an ohmic resistor and a Capacitor evaluated. The sample cross-section of the phosphoric acid-doped membrane is measured immediately prior to sample assembly. To measure the temperature dependence, the measuring cell is brought to the desired temperature in an oven and controlled by a Pt-100 thermocouple placed in the immediate vicinity of the sample. After reaching the temperature, the sample is held at this temperature for 10 minutes before starting the measurement.

According to a particular embodiment of the present invention, the membranes have a high mechanical stability. This size results from the hardness of the membrane, which is determined by means of microhardness measurement according to DIN 50539. For this purpose, the membrane is loaded with a Vickers diamond successively within 20 s up to a force of 3 mN and the penetration depth is determined. Accordingly, the hardness at room temperature is at least 5 mN / mm ² , preferably at least 50 mN / mm ² and very particularly preferably at least 200 mN / mm ² , without this being a restriction. Subsequently, the force is kept constant at 3 mN for 5 s and the creep is calculated from the penetration depth. For preferred membranes, creep C _HU 0.003 / 20/5 under these conditions is less than 30%, preferably less than 15%, and most preferably less than 5%. The module determined by means of microhardness measurement is YHU at least 0.1 MPa, in particular at least 2 MPa and very particularly preferably at least 5 MPa, without this being intended to limit it.

in the Comparison to known Polyazolmembranen, according to the applications DE No. 10117686.4 and DE No. 10117687.2 those according to the inventive method obtained membranes particularly good mechanical properties. So is the fracture toughness surprising at a high phosphoric acid content high.

Thus, new polymer electrolyte membranes are provided which have a phosphoric acid concentration of at least 85 wt .-% at a fracture toughness of at least 30 kJ / m ² , in particular 50 kJ / m ² and particularly preferably 100 kJ / m ² .

Of Furthermore, preferred polymer electrolyte membranes show a high Elongation at break of at least 60%, in particular at least 80% and particularly preferably at least 100% at a phosphoric acid concentration of at least 85% by weight.

Particularly powerful new polymer electrolyte membranes are obtained according to the invention which have a fracture toughness of at least 10 kJ / m ² , in particular 20 kJ / m ² and particularly preferably 30 kJ / m ² , at a phosphoric acid concentration of at least 95% by weight.

The Measurement of elongation at break / stress (fracture toughness) can be obtained on strip-shaped samples with a width of 15 mm and length of 120 mm on the device Zwick Z010 performed become. The tensile test can be carried out at a temperature of 25 ° C with a Strain rate of 50 mm / min done.

To potential Fields of application of the polymer membranes according to the invention belong to the use in fuel cells, electrolysis, in capacitors and in battery systems.

The The present invention also relates to a membrane-electrode assembly, which has at least one polymer membrane according to the invention. The membrane-electrode unit has a high performance even with a low content of catalytically active substances, such as platinum, ruthenium or palladium on. For this can with a catalytically active layer provided gas diffusion layers be used.

The Gas diffusion layer generally exhibits electron conductivity. Become common therefor area, electrically conductive and acid resistant Structures used. These include, for example, carbon fiber papers, graphitized carbon fiber papers, Carbon fiber fabrics, graphitized carbon fiber fabrics and / or sheet formations, made conductive by the addition of carbon black were.

The catalytically active layer contains a catalytically active substance. These include precious metals, in particular platinum, palladium, rhodium, iridium and / or ruthenium. These substances can also be used in the form of alloys with each other. Furthermore, these substances can also be used in alloys with base metals such as Cr, Zr, Ni, Co and / or Ti. In addition, it is also possible to use the oxides of the abovementioned noble metals and / or base metals. According to a particular aspect of the present invention, the catalytically active compounds are used in the form of particles, preferably having a size in the range from 1 to 1000 nm, in particular especially 10 to 200 nm and preferably 20 to 100 nm.

Of Further, the catalytically active layer may contain conventional additives. These include including fluoropolymers such as e.g. Polytetrafluoroethylene (PTFE) and surface-active Substances.

According to one particular embodiment the present invention is the weight ratio of fluoropolymer to catalyst material, comprising at least one noble metal and optionally one or several carrier materials, greater than 0.1, this ratio preferably in the range of 0.2 to 0.6.

According to one particular embodiment According to the present invention, the catalyst layer has a thickness in the range of 1 to 1000 μm, in particular from 5 to 500, preferably from 10 to 300 μm. This Value represents an average obtained by measuring the layer thickness in the cross section of recordings can be determined with a Scanning electron microscope (SEM) can be obtained.

According to a particular embodiment of the present invention, the noble metal content of the catalyst layer is 0.1 to 10.0 mg / cm ² , preferably 0.3 to 6.0 mg / cm ² and more preferably 0.3 to 3.0 mg / cm ² , These values can be determined by elemental analysis of a flat sample.

For further information on membrane-electrode assemblies, reference is made to the specialist literature, in particular to the patent applications WO 01/18894 A2, DE 195 09 748 . DE 195 09 749 WO 00/26982, WO 92/15121 and DE 197 57 492 directed. The disclosure contained in the abovementioned references with regard to the construction and production of membrane-electrode assemblies, as well as the electrodes to be selected, gas diffusion layers and catalysts is also part of the description.

In a further variant can be applied to the membrane according to the invention a catalytically active layer are applied and these with a gas diffusion layer are connected.

Also The subject of the present invention is a membrane-electrode assembly which is at least a polymer membrane according to the invention optionally in combination with another polymer membrane based of polyazoles or a polymer blend membrane.

In a further variant can be applied to the membrane according to the invention a catalytically active layer are applied and these with a gas diffusion layer are connected. This is done according to the steps A) to D) formed a membrane and applied the catalyst. These structures are also the subject of the present invention.

Furthermore can the formation of the membrane according to the steps A) to D) also on a support or a carrier film take place, which already has the catalyst. After removing the carrier or the carrier film the catalyst is on the membrane according to the invention. These structures are also the subject of the present invention.

Also The subject of the present invention is a membrane-electrode assembly which is at least a coated electrode and / or at least one polymer membrane according to the invention in combination with another polymer membrane based on polyazoles or a polymer blend membrane containing at least one polymer based on polyazoles.

Examples 1-5

to Preparation of the membrane was a poly (2,2 '- (p-phenylene) -5,5'-bibenzimidazole-co-poly ((6-6'-bibenzimidazole-2,2'-dyl) -2,5-pyridine ) Solution in PPA made as follows.

5.283 g of 2,5-pyridinedicarboxylic acid (125 mmol), 15.575 g of terephthalic acid (375 mmol), 26.785 g of TAB (0.5 mol) and 468 g of PPA were placed in a 500 ml three-necked flask. The reaction suspension was heated to 120 ° C for 2h then to 150 ° C for 4h, then to 190 ° C for 6h then to 220 ° C for 20 ° C. Thereafter, the reaction solution was diluted at 220 ° C with 600 g of 85% H ₃ PO ₄ , and then stirred at 240 ° C for 6 hours.

A small part of the solution was precipitated with water. The precipitated resin was filtered, washed three times with H ₂ O, neutralized with ammonium hydroxide, then washed with H ₂ O and dried at 100 ° C for 24 hours at 0.001 bar. From a 0.2 g / dL polymer solution in 100 ml of 96% H ₂ SO ₄ was added the inh rente viscosity η _inh measured. η _inh = 3.2 dL / g at 30 ° C

The high-viscosity solution was knife-coated at 200 ° C. with a preheated doctor blade on a polyethylene terephthalate film (PET film) with a 500 μm thick membrane. In each case a membrane piece with the size 20 × 30 cm was placed in 1 l of H ₃ PO ₄ with the following concentration.

• Example 1: 40% H ₃ PO ₄
• Example 2: 50% H ₃ PO ₄
• Example 3: 60% H ₃ PO ₄
• Example 4: 70% H ₃ PO ₄
• Example 5: 80% H ₃ PO ₄

Then The membranes became 15 min, 30 min, 1 h, 2 h, 4 h, 6 h, and 20 h at RT in these hydrolysis baths hydrolyzed. Thereafter, the membranes were titrated with 0.1 N NaOH, around the acid number per repeat unit to determine. Below in Table 1 are Results of the hydrolysis shown.

Table 1:

Examples 6-8

The high-viscosity solution was knife-coated at 160 ° C. with a preheated doctor blade on a PET film having a thickness of 500 μm. In each case a membrane piece with the size 20 × 30 cm was hydrolyzed in 1 l of H ₃ PO _{4 with the} following concentration and time.
Comparison 1: hydrolysed with humidity, 24 hours at room temperature

• Example 6: in 50% H ₃ PO ₄ 20 min.
• Example 7: in 60% H ₃ PO ₄ 1 h
• Example 8: in 70% H ₃ PO ₄ 2h

The Membranes were titrated with 0.1 N NaOH to give the acid number per repeat unit to determine. Below in Table 2 are summarized the titration results.

Table 2

The material properties were determined by tensile strain measurement and compared with Comparative Example 1 (Table 3). The elongation at break / stress (fracture toughness) measurement is carried out on 15 mm wide and 120 mm long specimens on the Zwick Z010 instrument. The train Such is carried out at a temperature of 25 ° C with a strain rate of 50 mm / min.

Table 3:

From these membranes, 50 cm ² MEAs (Membrane Electrode Assembly) were then prepared and measured with H ₂ / air. The values (resting potential (OCV), mV at 0.2 A / cm ² , mV at 0.6 A / cm ² at 160 ° and 0 bar) are compared with sample 0 at the bottom of Table 4.

Table 4:

The Resting potential is directly related to the permeability of the membrane to the Fuel linked. The higher this permeability the lower the resting potential. Therefore, a high rest potential means a low hydrogen permeability (See Handbook of Fuel Cell's Fundamentals, Technology and Application, Editors: W. Vielstich; A. Lamb, H.A. Gasteiger).

Claims (21)

A process for the preparation of proton-conducting polymer membranes comprising the steps A) preparation of a mixture comprising polyphosphoric acid, at least one polyazole and / or at least one or more compounds which are suitable for forming polyazoles under the action of heat in step B), B) heating the mixture obtainable according to step a) under under inert gas to temperatures of up) to 400 ° C, C applying a layer using the mixture from step a) and / or B) on a support, D) treating the membrane formed in step C), characterized in that the treatment of the membrane is carried out with a hydrolysis liquid which comprises oxygen acids of phosphorus and / or oxygen acids of sulfur. Method according to claim 1; characterized in that the mixture prepared in step A) comprises compounds comprising, under the action of heat in step B) for the formation of Polyazoles are suitable, these compounds one or more aromatic and / or heteroaromatic tetra-amino compounds and one or more aromatic and / or heteroaromatic carboxylic acids or their derivatives containing at least two acid groups per carboxylic acid monomer include, and / or one or more aromatic and / or heteroaromatic diamino include. A method according to claim 1, characterized in that the mixture prepared in step A) comprises compounds which are suitable under the action of heat in step B) for the formation of polyazoles, which compounds by reaction of one or more aromatic and / or heteroaromatic Tetra Amino compounds with one or more aromatic and / or heteroaromatic carboxylic acids or their derivatives which contain at least two acid groups per carboxylic acid monomer, or of one or more aromatic and / or heteroaromatic diaminocarboxylic acids in the Melt at temperatures of up to 400 ° C are available. Method according to claim 2 or 3, characterized in that the formation of polyazoles suitable compounds as aromatic and / or heteroaromatic Tetra-amino compound includes compounds which are selected from the group consisting of 3,3 ', 4,4'-tetraaminobiphenyl, 2,3,5,6-tetraaminopyridine and / or 1,2,4,5-tetraaminobenzene. Method according to claim 2, 3 or 4, characterized in that suitable for the formation of polyazoles Compounds as aromatic and / or heteroaromatic carboxylic acids or their derivatives containing at least two acid groups per carboxylic acid monomer include compounds which are selected from the group consisting from isophthalic acid, terephthalic acid, phthalic acid, 5-hydroxyisophthalic, 4-hydroxyisophthalic acid, 2-hydroxyterephthalic acid, 5-aminoisophthalic acid, 5-N, N-dimethylaminoisophthalic acid, 5-N, N-diethylaminoisophthalic acid, 2,5-dihydroxyterephthalic acid, 2,5-dihydroxyisophthalic acid, 2,3-dihydroxyisophthalic acid, 2,3- Dihydroxyphthalic acid, 2,4-dihydroxyphthalic acid. 3,4-dihydroxyphthalic acid, 3-fluorophthalic acid, 5-fluoroisophthalic acid, 2-fluoroterphthalic acid, tetrafluorophthalic acid, tetrafluoroisophthalic acid, tetrafluoroterephthalic acid, 1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, diphenic acid, 1,8-dihydroxynaphthalene-3,6-dicarboxylic acid, diphenyl ether-4,4'-dicarboxylic acid, benzophenone-4,4'-dicarboxylic acid, diphenylsulfone-4,4'-dicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, 4- Trifluoromethylphthalic acid, 2,2-bis (4-carboxyphenyl) hexafluoropropane, 4,4'-stilbenedicarboxylic acid, 4-carboxycinnamic acid, or their C 1 -C 20 -alkyl esters or C 5 -C 12 -aryl esters, or their acid anhydrides or their acid chlorides. Method according to claim 2, 3, 4 or 5, characterized in that the formation of Polyazoles suitable compounds aromatic tricarboxylic acids whose C1-C20-alkyl-esters or C5-C12-aryl-esters or their acid anhydrides or their acid halides or tetracarboxylic acids, their C1-C20-alkyl esters or C5-C12-aryl esters or their acid anhydrides or their acid halides include. Method according to claim 6, characterized in that the aromatic tricarboxylic acids compounds include that selected are selected from the group consisting of 1,3,5-benzenetricarboxylic acid (trimesic acid); 2,4,5-benzenetricarboxylic acid (trimellitic acid); (2-carboxyphenyl) iminodiacetic acid, 3,5,3'-biphenyl tricarboxylic acid; 3,5,4'-biphenyl tricarboxylic acid 2,4,6-pyridine tricarboxylic acid, benzene-1,2,4,5-tetracarboxylic acids; Naphthalene-1,4,5,8-tetracarboxylic acids, 3,5,3 ', 5'-biphenyltetracarboxylic acids, benzophenonetetracarboxylic acid, 3,3', 4,4'-biphenyltetracarboxylic acid, 2,2 ', 3,3'-biphenyltetracarboxylic acid, 1,2,5,6-naphthalenetetracarboxylic acid and / or 1,4,5,8-naphthalene. Method according to claim 6 or 7, characterized in that the content of tricarboxylic acid and / or Tetracarboxylic acids between 0 and 30 mol%, preferably 0.1 and 20 mol%, in particular 0.5 and 10 mol%, based on the dicarboxylic acid used. Method according to one or more of the claims 2 to 8, characterized in that the formation of polyazoles suitable compounds heteroaromatic dicarboxylic acids, tricarboxylic acids and / or Tetracarboxylic acids which include at least one nitrogen, oxygen, sulfur or phosphorus atom in the aromatic. Method according to claim 9, characterized in that pyridine-2,5-dicarboxylic acid, pyridine-3,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, pyridine-2,4-dicarboxylic acid, 4-phenyl-2,5-pyridinedicarboxylic acid, 3, 5-pyrazoldicarboxylic acid, 2,6-pyrimidinedicarboxylic acid, 2,5-pyrazinedicarboxylic acid, 2,4,6-pyridinetricarboxylic acid, benzimidazole-5,6-dicarboxylic acid, and their C1-C20-alkyl esters or C5-C12 aryl esters, or their acid anhydrides or their acid chlorides be used. Method according to claim 2 or 3, characterized in that suitable for the formation of polyazoles Compounds diaminobenzoic acid and / or their mono- and dihydrochloride derivatives. Method according to one of the preceding claims, characterized in that in step A) and / or step B) available Composition at least one further polymer (polymer B), the no polyazole, added is, the weight ratio of polyazole to polymer B ranges from 0.1 to 50. Method according to one of the preceding claims, characterized in that the heating according to step B) after formation a flat Building according to step C) Method according to one of the preceding claims, characterized in that the treatment according to step D) at temperatures in the range of 0 ° C and 150 ° C he follows. Method according to one of the preceding claims, characterized characterized in that the hydrolysis liquid is phosphorous acid, phosphonic acid, phosphoric acid, hypodiphosphonic acid hypodiphosphoric acid, oligophosphoric acids, sulfurous Acid, sulphurous acid and / or sulfuric acid includes. Method according to one of the preceding claims, characterized characterized in that the hydrolysis liquid water in a concentration from 5 to 80% by weight. Method according to one of the preceding claims, characterized in that phosphoric acid is used as the hydrolysis fluid which comprises 10 to 60% by weight of water. Proton-conducting polymer membrane obtainable by a process of claims 1 to 17, characterized in that the membrane has a phosphoric acid concentration of at least 85 wt .-% at a breaking stress of at least 30 kJ / m ² . Proton-conducting polymer membrane obtainable by a process of claims 1 to 17, characterized in that the membrane has a phosphoric acid concentration of at least 95 wt .-% at a breaking stress of at least 10 kJ / m ² . Membrane electrode unit containing at least a polymer membrane according to claim 18 or 19. Fuel cell containing one or more membrane electrode assemblies according to claim 20th