KR20130129328A - Mechanically stabilized polyazoles - Google Patents

Abstract

The present invention comprises the steps of treating I) at least one polyazole having at least one amino group in a repeating unit with a solution comprising (i) at least one strong acid and (ii) at least one stabilizing reagent, wherein The total content of stabilizing reagents in solution ranges from 0.01 to 30% by weight),
II) conducting the stabilization reaction directly and / or in a subsequent processing step, carrying out the stabilization reaction by heating to a temperature above 25 ° C.,
A method for preparing mechanically stabilized polyazoles using at least one high functional polyether as said stabilizing reagent.
The polyazoles thus obtained are of particular note of high conductivity and very good mechanical stability. Thus, they are particularly suitable for applications in fuel cells.

Description

Mechanically stabilized polyazoles

The present invention relates to mechanically stabilized polyazoles, in particular acid-doped mechanically stabilized polyazoles, processes for their preparation, and to the polymer electrolyte membrane (PEM), membrane electrode unit (MEU) and PEM fuel, which are of particular importance in the context of the present invention. To its use in batteries. In addition, the mechanically stabilized polyazoles can be advantageously used in many further applications.

Polymer electrolyte membranes (PEM) are already known and in particular used in fuel cells. Often sulfonic acid-modified polymers, in particular perfluorinated polymers, are used. An important example of this is Nafion ^TM from DuPont de Nemour, Wilmington, USA. Proton conduction requires a relatively high water content in the membrane, which is typically 4-20 molecules of water per sulfonic acid group. The required water content, but the stability of the polymer with acidic water and hydrogen and oxygen reactant gases, typically limits the operating temperature of the PEM fuel cell stack to 80-100 ° C. Under pressure, the operating temperature may increase above 120 ° C. In contrast, higher operating temperatures cannot be achieved without loss in the performance of the fuel cell.

However, for system reasons, high operating temperatures above 100 ° C. in fuel cells are preferred. The membrane electrode unit (MEU) is remarkably good at high operating temperatures. More particularly, when using what is called a reformate from hydrocarbons, different amounts of carbon monoxide are present in the reforming gas, which must normally be removed by syngas treatment or gas purification. At high operating temperatures, the catalyst's resistance to CO impurities rises to several volume percent of CO.

In addition, heat is released in the operation of the fuel cell. However, cooling these systems below 80 ° C. can be very expensive and inconvenient. Depending on the power output, the cooling device can be much simpler. This means that in fuel cell systems operating at temperatures above 100 ° C., waste heat can be used much better, and thus fuel cell system efficiency can be improved by power-thermal coupling.

In order to achieve these temperatures, membranes with novel conductive mechanisms are generally used. One way for these purposes is to use a membrane that exhibits electrical conductivity without the use of water. The first development in this direction is detailed, for example, in WO 96/13872. For example, WO 96/13872 discloses the use of acid doped polybenzimidazole membranes produced by a casting process.

Novel production of acid-containing polyazole membranes which also exhibit electrical conductivity without the use of water is described in WO 02/088219. The acid containing polyazole membranes disclosed in WO 02/088219 exhibit excellent profile of properties.

However, due to the intended use of the PEM fuel, the mechanical properties of the acid containing polyazole membranes need to be improved consistently. For example, such membranes are still relatively soft, and thus have only limited mechanical durability, and mechanical stability decreases with increasing temperature, which can lead to stability problems in the upper range of typical operating windows (about 160-180 ° C.). have. Accordingly, there is a need to improve mechanical properties, in particular film stability, at the same time as high conductivity.

Mechanical stability by bridging or crosslinking reactions is already well known in the polymer art. However, the problem here is that even if the polymer itself has sufficient mechanical stability, as a result of impregnation / doping with a strong acid for the purpose of imparting proton conductivity, the mechanical stability of the polymer may sometimes decrease to an unsuitable degree. Can be.

The first approach to improving the mechanical stability of acid containing polyazole membranes can be found in WO 00/44816 and WO 02/070592. This involves first preparing a solution of the polyazole polymer in a protic polar organic solvent and providing a bridging reagent to the solution. After the film is formed, the organic solvent is removed and a bridging reaction is performed. The film is then doped with a strong acid and used. The acid-containing polyazole membranes obtained exhibit good conductivity and improved mechanical stability at the same time as compared to the unbridged acid-containing polyazole membranes.

However, with the help of currently known methods, bridging or crosslinking of polyazole polymers is possible, but the use of protic polar organic solvents has been found to cause new limitations. In particular, high molecular weight polyazoles have only limited solubility and are insoluble in the organic solvent and thus cannot be treated.

It is therefore an object of the present invention to propose better options for the mechanical stabilization of polyazoles, preferably acid doped polyazoles, in particular polyazole based acid doped membranes. In addition, the good property profiles of polyazoles, preferably acid doped polyazoles, more preferably acid containing polyazole membranes, must be maintained or improved, especially with regard to conductivity. A further object is to improve the compressive stability of polyazoles, preferably acid doped polyazoles, more preferably membranes, especially at temperatures in the range of 20 to 200 ° C. In addition, polyazoles, preferably acid doped polyazoles, more preferably membranes, should be produceable at minimal cost in a relatively simple manner. Finally, another object is a very safe solution from the health point of view.

These and further objects which are immediately evident from the above mentioned relations are achieved by a method having all the features of claim 1 herein. The dependent claims are a particularly suitable variant of the method of the invention. In addition, the stabilizing polymers, membrane and membrane electrode assemblies obtainable by the process of the invention and their preferred fields of use are protected.

Therefore,

The present invention comprises the steps of treating I) at least one polyazole having at least one amino group in a repeating unit with a solution comprising (i) at least one strong acid and (ii) at least one stabilizing reagent, wherein The total content of stabilizing reagents in solution ranges from 0.01 to 30% by weight),

II) conducting the stabilization reaction directly and / or in a subsequent processing step, carrying out the stabilization reaction by heating to a temperature above 25 ° C.,

A method for preparing mechanically stabilized polyazoles using at least one high functional polyether as said stabilizing reagent.

The present invention discloses particularly advantageous options for the mechanical stability of polyazoles, preferably acid doped polyazoles, in particular acid containing and modulator conductive polyazole membranes. The high molecular weight polyazoles known to date have been destabilized and the polyazoles modified by bridging and / or crosslinking and known to date do not comprise high molecular weight polyazoles.

In addition, according to the invention, polyazoles, in particular acid containing proton conductive high molecular weight polyazole polymers, with improved elastic modulus and improved elongation at break can be obtained for the first time. Both properties are of particular importance for use in polymer electrolyte membranes for fuel cells.

In addition, the conductivity of the polymer of the invention, which is preferably in the form of a membrane comprising at least one polymer of the invention, is particularly high.

Moreover, the polymers of the invention, preferably present in the form of membranes comprising at least one polymer of the invention, are particularly marked for improved compression stability at temperatures in the range from 20 ° C to 200 ° C.

Finally, the achievement of the present invention can be carried out in a relatively simple manner at an inexpensive scale on an industrial scale and is completely safe from a health standpoint.

Polyazole (s)

Polyazoles in the context of the present invention are understood to mean polyazole polymers in which the repeating unit in the polymer preferably comprises at least one aromatic ring having at least one nitrogen atom. The aromatic ring is preferably a 5 or 6 membered ring having 1 to 3 nitrogen atoms, which can be fused with another ring, in particular another aromatic ring. Individual nitrogen heteroatoms may also be substituted with oxygen, phosphorus and / or sulfur atoms. Heterocyclic aromatic rings are preferably present in the main polymer chain, but may also be present in the side chain. Particular preference is given to these basic polymers comprising in the repeating unit an unsaturated 5- or 6-membered aromatic unit comprising 1 to 5 nitrogen atoms or nitrogen atoms as well as one or more other heteroatoms in the ring.

Polyazoles of the invention have at least one amino group in the repeating unit. The amino group can be represented by a primary amino group (NH ₂ group), secondary amino group (NH group) or tertiary group, which is a cyclic, optionally part of an aromatic structure or part of a substituent on an aromatic unit.

Due to the amino group in the repeating unit, the polymer is basic and the repeating unit may preferentially react with the stabilizing reagent (polyether) via the amino group. In view of the reactivity to the stabilizing reagent, the amino group in the repeating unit is preferably a primary or secondary amino group, more preferably a cyclic secondary amino group, which suitably forms part of the ring of the azole repeating unit.

The process according to the invention is especially used for producing mechanical stabilized polymer membranes based on polyazoles.

In a first particularly preferred variant, the method according to the invention

a) producing a film comprising at least one polyazole having at least one amino group in a repeating unit,

b) treating the film from step (a) with a solution comprising (i) at least one strong acid and (ii) at least one stabilizing reagent, wherein the total content of stabilizing reagent in the solution is from 0.01 to 30 weight % Range),

c) performing the stabilization reaction directly on the membrane obtained in step (b) or by heating to a temperature above 25 ° C. in a subsequent membrane treatment step,

d) optionally further doping the membrane obtained in step (c) with a strong acid or removing the water present to concentrate the strong acid present,

At least one high functional polyether is used as a stabilizing reagent.

The production of films or foils comprising polyazoles is already known. The preparation is carried out, for example, as described in WO 2004/024797,

A) at least one aromatic tetraamino compound is mixed with at least one aromatic carboxylic acid or ester thereof containing at least two acid groups per carboxylic acid monomer, or at least one aromatic and / or heteroaromatic diaminocarboxylic acid is mixed in polyphosphoric acid Forming a solution and / or dispersion,

B) applying the layer to the support using the mixture from step (A),

C) heating the flat structure / layer obtainable according to step (B) to a temperature of 350 ° C. or lower, preferably 280 ° C. or lower, under inert gas to form a polyazole polymer,

D) hydrolyzing (until self-supporting) the polymer formed in step (C),

E) separating the polymer film formed in step (D) from the support and

F) removing and drying the polyphosphoric acid or phosphoric acid present.

The aromatic and heteroaromatic tetraamino compounds used according to the invention are preferably 3,3 ', 4,4'-tetraaminobiphenyl, 2,3,5,6-tetraaminopyridine, 1,2,4, 5-tetraaminobenzene, 3,3 ', 4,4'-tetraaminodiphenyl sulfone, 3,3', 4,4'-butetraaminodiphenyl ether, 3,3 ', 4,4'-tetra Aminobenzophenone, 3,3 ', 4,4'-tetraaminodiphenylmethane and 3,3', 4,4'-tetraaminodiphenyldimethylmethane and salts thereof, in particular mono-, di-, tri- And tetrahydrochloride and tetrahydrochloride derivatives.

The aromatic carboxylic acids used according to the invention are dicarboxylic acids and tricarboxylic acids and tetracarboxylic acids, or esters or anhydrides or acid anhydrides thereof. The term "aromatic carboxylic acid" likewise encompasses heteroaromatic carboxylic acids. The aromatic carboxylic acid is preferably isophthalic acid, terephthalic acid, phthalic acid, 5-hydroxyisophthalic acid, 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-fluoroterephthalic acid, tetrafluorophthalic acid, tetrafluoroisophthalic acid, tetrafluoro Roterephthalic 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, diphenyl Von 4,4'-dicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, 4-trifluoromethylphthalic acid, 2,2-bis (4-carboxyphenyl) hexafluoropropene, 4,4'- Stilbendicarboxylic acid and 4-carboxycinnamic acid, or a C 1 -C 20 -alkyl ester or C 5 -C 12 -aryl ester or acid anhydride or acid chloride thereof. Aromatic tri-, tetracarboxylic acids or C1-C20-alkyl esters or C5-C12-aryl esters or acid anhydrides or acid chlorides thereof are preferably 1,3,5-benzenetricarboxylic acid (trimethic acid); 1,2,4-benzenetricarboxylic acid (trimellitic acid); (2-carboxyphenyl) iminodiacetic acid, 3,5,3'-biphenyltricarboxylic acid; 3,5,4'-biphenyltricarboxylic acid.

Aromatic tetracarboxylic acids or their C1-C20-alkyl esters or C5-C12-aryl esters or acid anhydrides or acid chlorides thereof are preferably 3,5,3 ', 5'-biphenyltetracarboxylic acid, benzene-1,2 , 4,5-tetracarboxylic acid, benzophenonetetracarboxylic acid, 3,3 ', 4,4'-biphenyltetracarboxylic acid, 2,2', 3,3'-biphenyltetracarboxylic acid, 1,2,5,6 Naphthalene tetracarboxylic acid, 1,4,5,8-naphthalene tetracarboxylic acid.

Heteroaromatic carboxylic acids used according to the invention are heteroaromatic dicarboxylic acids and tricarboxylic acids and tetracarboxylic acids, or esters or anhydrides thereof. Heteroaromatic carboxylic acid is understood to mean an aromatic system containing at least one nitrogen, oxygen, sulfur or phosphorus atom in the aromatic ring. These are preferably pyridine-2,5-dicarboxylic acid, pyridine-3,5-dicarboxylic acid, pyridine-2,6-dicarboxylic acid, pyridine-2,4-dicarboxylic acid, 4-phenyl-2,5-pyridinedi Carboxylic acid, 3,5-pyrazoledicarboxylic acid, 2,6-pyrimidinedicarboxylic acid, 2,5-pyrazinedicarboxylic acid, 2,4,6-pyridinetricarboxylic acid, benzamidazole-5,6-dicarboxylic acid, and also C1-C20-alkyl esters or C5-C12-aryl esters thereof, or acid anhydrides thereof or acid chlorides thereof.

The tricarboxylic acid or tetracarboxylic acid (based on the dicarboxylic acid used) is 0 to 30 mol%, preferably 0.1 to 20 mol%, in particular 0.5 to 10 mol%.

The aromatic and heteroaromatic diaminocarboxylic acids according to the invention are preferably diaminobenzoic acids and their mono- and dihydrochloride derivatives.

Preferably, in step (A), a mixture of at least two different aromatic carboxylic acids is used. Particular preference is given to using mixtures which comprise not only aromatic carboxylic acids but also heteroaromatic carboxylic acids. The mixing ratio of aromatic carboxylic acid to heteroaromatic carboxylic acid is 1:99 to 99: 1, preferably 1:50 to 50: 1.

These mixtures are in particular mixtures of N-heteroaromatic dicarboxylic acids with aromatic dicarboxylic acids. Non-limiting examples thereof 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, diphenyl sulfone 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-pyrazoledicarboxylic acid, 2,6-pyrimidinedicarboxylic acid, 2,5-pyrazinedicarboxylic acid.

The polyphosphoric acid used in step (A) includes, for example, commercial polyphosphoric acid available from Riedel-de Haen. Polyphosphoric acid H _{n + 2} P _n O _{3n + 1} (n> 1) usually has a content of at least 83% calculated by P ₂ O ₅ (by acid titration means). Instead of a solution of monomers, it is also possible to produce dispersions / suspensions. The mixture obtained in step (A) has a weight ratio of polyphosphoric acid to the sum of all monomers from 1:10 000 to 10 000: 1, preferably from 1: 1000 to 1000: 1, in particular from 1: 100 to 100: 1.

The layer is formed by means known per se (casting, spraying, knife-coating) in step (B), which is known in the art for producing polymer films. Suitable supports are all supports which can be described as inert under these conditions. However, in addition to these inert supports, polymeric films, wovens and nonwovens are suitable, in combination with other supports such as the layer formed in step (B) to form a laminate. To adjust the viscosity, phosphoric acid (concentrated phosphoric acid, 85%) may optionally be added to the solution. This can adjust the viscosity to the desired value and can promote the formation of the film. The layer obtained in step (B) has a thickness corresponding to the subsequent use, and there is no limitation. Typically, the formed layer has a thickness of 1 to 5000 μm, preferably 1 to 3500 μm, in particular 1 to 100 μm.

The polyazole-based polymer formed in step (C), like the other polyazoles preferably used in connection with the present invention, has the formula I and / or formula II and / or formula III and / or formula IV and / or formula V and / Or a repeating azole unit of Formula VI and / or Formula VII and / or Formula VIII and / or Formula IX and / or Formula X and / or Formula XI and / or Formula XII and / or Formula XIII and / or Formula XIV. :

(I)

≪ RTI ID = 0.0 &

[Formula III]

(IV)

(V)

(VI)

(VII)

(VIII)

(IX)

(X)

(XI)

(XII)

(XIII)

(XIV)

In Formulas I to XIV,

Ar is a tetravalent aromatic or heteroaromatic group, which may be the same or different and may be monocyclic or polycyclic, respectively,

Ar ¹ is the same or different and is a divalent aromatic or heteroaromatic group, which may each be monocyclic or polycyclic,

Ar ² is the same or different and is a divalent or trivalent aromatic or heteroaromatic group which may be monocyclic or polycyclic, respectively,

Ar ³ is the same or different and is a trivalent aromatic or heteroaromatic group, which may each be monocyclic or polycyclic,

Ar ⁴ is the same or different and is a trivalent aromatic or heteroaromatic group, which may each be monocyclic or polycyclic,

Ar ⁵ is the same or different and is a tetravalent aromatic or heteroaromatic group, which may each be monocyclic or polycyclic,

Ar ⁶ is the same or different and is a divalent aromatic or heteroaromatic group, which may each be monocyclic or polycyclic,

Ar ⁷ is the same or different and is a divalent aromatic or heteroaromatic group, which may each be monocyclic or polycyclic,

Ar ⁸ is the same or different and is a trivalent aromatic or heteroaromatic group, which may each be monocyclic or polycyclic,

Ar ⁹ is the same or different and is a divalent or trivalent or tetravalent aromatic or heteroaromatic group which may be monocyclic or polycyclic, respectively,

Ar ¹⁰ is the same or different and is a divalent or trivalent aromatic or heteroaromatic group which may be monocyclic or polycyclic, respectively,

Ar ¹¹ is the same or different and is a divalent aromatic or heteroaromatic group, which may each be monocyclic or polycyclic,

X is the same or different and is an amino group comprising oxygen, sulfur or hydrogen atoms, groups having 1 to 20 carbon atoms, preferably branched or unbranched alkyl or alkoxy groups, or aryl groups as further radicals,

R is the same or different and is hydrogen, an alkyl group or an aromatic group,

n and m are each an integer of 10 or more, preferably 100 or less.

Preferred aromatic or heteroaromatic groups include benzene, naphthalene, biphenyl, diphenyl ether, diphenylmethane, diphenyldimethylmethane, bisphenone, diphenylsulfone, quinoline, pyridine, bipyridine, Pyridazine, pyrimidine, pyrazine, triazine, tetraazine, pyrrole, pyrazole, anthracene, benzopyrrole, benzotriazole, benzoxathiadiazole, benzoxadiazole, benzopyridine, benzopyrazine, benzopyrazidine, Benzopyrimidine, benzopyrazine, benzotriazine, indolizine, quinolyzine, lipidopyridine, imidazopyrimidine, pyrazinopyrimidine, carbazole, acridine, phenazine, benzoquinoline, phenoxazine, phenoxazine It is derived from notthiazine, acridizin, benzopteridine, phenanthroline and phenanthrene.

The substitution patterns of Ar ¹ , Ar ⁴ , Ar ⁶ , Ar ⁷ , Ar ⁸ , Ar ⁹ , Ar ¹⁰ and Ar ¹¹ are as required; In the case of phenylene, for example, Ar ¹ , Ar ⁴ , Ar ⁶ , Ar ⁷ , Ar ⁸ , Ar ⁹ , Ar ¹⁰ and Ar ¹¹ may be 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, for example methyl, ethyl, n- or i-propyl and tert-butyl groups.

Preferred aromatic groups are phenyl or naphthyl groups. Alkyl groups and aromatic groups may be substituted.

Preferred substituents are halogen atoms such as fluorine, amino groups, hydroxy groups or short chain alkyl groups such as methyl or ethyl groups.

Preference is given to polyazoles in which X has the same repeating unit of formula (I) in one repeating unit.

Polyazoles in principle also have different repeating units, for example, in which their X radicals are different. However, preferably only one X unit has the same X radical.

Further preferred polyazole polymers include polyimidazole, polybenzothiazole, polybenzoxazole, polyoxadiazole, polyquinoxaline, polythiadiazole, poly (pyridine), poly (pyrimidine) and poly (tetraaza). Pyrene).

In a further aspect of the invention, the polymer comprising repeating azole units is a copolymer or blend comprising at least two units of the formulas I to XIV different from each other. The polymer may be in the form of block copolymers (diblock, triblock), random copolymers, periodic copolymers and / or alternating polymers.

In a particularly preferred embodiment of the invention, the polymer comprising repeating azole units is a polyazole comprising only units of formula (I) and / or (II).

The number of repeating azole units in the polymer is preferably an integer of 10 or more. Particularly preferred polymers comprise at least 100 repeating azole units.

In the context of the present invention, polymers comprising repeat benzimidazole units are preferred. Some examples of very suitable polymers containing repeat benzimidazole units are represented by the following formula:

In the final formula, the azole units and the two fluorinated components may be combined with one another in any order. The preparation can be carried out as a polymer, a random copolymer or a block copolymer.

In addition, n and m may each independently be an integer of 10 or more, preferably 100 or less.

The teachings of the present invention are in principle suitable for all polyazoles regardless of molecular weight. However, it has been found to be particularly useful for the stabilization of high molecular weight polyazoles which cannot be obtained in any other way. High molecular weight polyazoles, but especially polybenzimidazoles, when measured as intrinsic viscosity, have a significant high molecular weight of at least 1.8 dl / g, preferably at least 2.0 dl / g, particularly preferably at least 2.5 dl / g. The upper limit is preferably 8.0 dl / g or less, more preferably 6.8 dl / g or less, particularly preferably 6.5 dl / g or less. Therefore, molecular weight is more than the molecular weight of commercial polybenzimidazole (IV <1.1 dl / g).

Intrinsic viscosity is measured as follows: For this purpose, the polymer is first dried at 160 ° C. over 2 hours. 100 mg of this dried polymer is then dissolved in 100 ml of concentrated sulfuric acid (minimum 96% by weight) at 80 ° C. over 4 hours. Intrinsic viscosity is measured from this solution with a Ubbelode viscometer at a temperature of 25 ° C. according to ISO 3105 (DIN 51562, ASTM D2515).

If the mixture according to step (A) also comprises tricarboxylic acid or tetracarboxylic acid, this achieves branching / crosslinking of the polymer formed along the main chain. This contributes to the improvement of the mechanical properties.

In one variant of the method, heating the mixture from step (A) to a temperature of 350 ° C. or less, preferably 280 ° C. or less may already result in the formation of oligomers and / or polymers. Depending on the temperature and duration selected, this may be partially or completely dispersed by the heating in step (C). This variant is also suitable for the production of the film required in step (a), preferably comprising high molecular weight polyazoles.

In addition, aromatic dicarboxylic acids (or heteroaromatic dicarboxylic acids) such as isophthalic acid, terephthalic acid, 2,5-dihydroxyterephthalic acid, 4,6-dihydroxyisophthalic acid, 2,6-dihydroxyiso Phthalic acid, diphenic acid, 1,8-dihydroxynaphthalene-3,6-dicarboxylic acid, diphenyl ether 4,4'-dicarboxylic acid, benzophenone-4,4'-dicarboxylic acid, diphenyl sulfone 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 , When pyridine-2,4-dicarboxylic acid, 4-phenyl-2,5-pyridinedicarboxylic acid, 3,5-pyrazoledicarboxylic acid, 2,6-pyrimidinedicarboxylic acid, 2,5-pyrazinedicarboxylic acid , The preferred temperature in step (C) (or if the formation of oligomers and / or polymers is required early as in step (A)) is no greater than 300 ° C., preferably in the range of 100 ° C. to 250 ° C. The.

The polymer layer obtained in step (C) can be treated to produce the film required in step (b) in several ways.

In one variant (Modification A), the polyphosphoric acid or phosphoric acid present remains in the membrane since it is not destroyed in further processing. In this case, the polymer layer produced in step (C) is treated in the presence of moisture for a temperature and for a period of time sufficient for the layer to have sufficient strength for the desired end use. This treatment is carried out to such an extent that the membrane is self supporting, which can be separated from the support without damage (step E). Steps (D) and (E) can also be performed simultaneously or in rapid succession. It is also possible to combine steps (D) and (E) with steps (b), (c) and optionally (d). For example, the hydrolysis in step (D) can be carried out by treating the polymer film formed in step (C) with a solution comprising (i) at least one strong acid and (ii) at least one stabilizing reagent. (Wherein the total content of stabilizing reagents in the solution ranges from 0.01 to 30% by weight). The performance of the stabilization reaction in step (c) can be combined with thermal drying or concentration of the acid present.

The polymer film may be subjected to moisture or water and / or water vapor and / or Up to 85% in the presence of water containing phosphoric acid. The treatment is preferably carried out under standard pressure, but can also be carried out under pressure. The treatment is essential to be carried out in the presence of sufficient moisture as a result of the polyphosphoric acid present contributing to the strengthening of the polymer film as a result of partial hydrolysis to form low molecular weight polyphosphoric acid and / or phosphoric acid. As a result of the hydrolysis step, a sol-gel transition occurs that is found to be involved in certain types of membranes.

Partial hydrolysis of the polyphosphoric acid in step (D) leads to strengthening of the polymer film, making it self supporting and also reducing the layer thickness.

The internal and intermediate molecular structures present in the polyphosphoric acid layer according to step (B) form a series of films found in step (C) to be involved in the good properties of the formed polymer film.

The upper temperature limit of the treatment in step (D) is generally 180 ° C. In the case of the extremely short action of moisture, for example overheated steam, such steam can also be hotter. An essential factor for the upper temperature limit is the treatment period.

Partial hydrolysis (step D) can also be carried out in a climate controlled chamber in which the hydrolysis is controlled under the action of moisture. In this case, the water content can be adjusted in a controlled manner through the temperature or saturation of the contact environment, for example, gas such as air, nitrogen, carbon dioxide or other suitable gas or water vapor. The processing time depends on the selected parameter.

The treatment time for the film also depends on the thickness.

In general, the treatment time is, for example, several seconds to several minutes under the action of superheated steam, or one day at room temperature and low air relative humidity, for example under air. The treatment time is preferably 10 seconds to 300 hours, in particular 1 minute to 200 hours.

When partial hydrolysis is performed at room temperature (20 ° C.) with ambient air having an air relative humidity of 40-80%, the treatment time is 1 to 200 hours.

The polymer film obtained in step (D) is preferably arranged to be self-supporting, ie it can be separated without damage from the support in step (E) and then optionally further processed directly.

The polymer film obtained in step (C) may be further processed on a support, for example to be fully or partially dispersed in step (D) to the extent that it provides a composite membrane.

The treatment of the film in step (b) can be carried out in a hydrolysis bath similar to step (D), to the extent that the polyphosphoric acid or phosphoric acid present after step (C) remains in the membrane (Variation A). In this case, the polyphosphoric acid or phosphoric acid present in the membrane is completely or at least partially substituted with a solution comprising (i) at least one strong acid and (ii) at least one stabilizing reagent. The stabilization reaction in step (c) can be carried out in a hydrolysis bath or preferably immediately after. Depending on the stability of the membrane, the treatment in the hydrolysis bath can be carried out on the support, or the support can be removed in advance, whereby step (E) can optionally be dispensed or predistributed.

This variant also forms part of the subject matter of the present invention.

In a further variant (variant B), the polyphosphoric acid or phosphoric acid present is removed from the membrane. To this end, the polymer layer obtained in step (C) is treated in the presence of moisture for a temperature and for a time sufficient to cause the layer to have sufficient strength for further handling. Thus, the hydrolysis in step (D) and the separation in step (E) can also be carried out simultaneously. This simplification of the hydrolysis is particularly possible when the fresh solution comprising the strong acid is subsequently fed in step (b), since the present polyphosphoric acid or phosphoric acid must be completely removed and not present for treatment in step (b). Do.

To the extent that the polyphosphoric acid or phosphoric acid present in the polymer film must be removed in step F, this can be achieved by the treatment liquid in the temperature range (at standard pressure) between room temperature (20 ° C.) and the boiling point of the treatment liquid.

Treatment liquids used in connection with the present invention are in liquid form at room temperature (ie 20 ° C.) and are used in alcohols, ketones, alkanes (aliphatic and cycloaliphatic), ethers (aliphatic and cycloaliphatic), glycols, esters, carboxylic acids ( In this case, the group members may be halogenated), water and mixtures thereof.

C1-C10 alcohols, C2-C5 ketones, C1-C10-alkanes (aliphatic and cycloaliphatic), C2-C6 ethers (aliphatic and cycloaliphatic), C2-C5 esters, C1-C3 carboxylic acids, dichloromethane, water and their Preference is given to using mixtures.

Then, the processing liquid introduced in step F is again removed. This is preferably done by drying, in which case the parameters of temperature and ambient pressure are selected as a function of the partial vapor pressure of the treatment liquid. Typically, drying is performed at a temperature of 20 ° C. to 200 ° C. and standard pressure. Mild drying can also be carried out under reduced pressure. Instead of drying, the membrane can also be patted dry to remove excess treatment liquid. The order is not important.

Films comprising polyazoles can also be produced by variations of the above methods. In this case, the following steps are performed:

i) at least 350C, preferably at least one aromatic tetraamino compound in melt with at least one aromatic carboxylic acid or ester thereof or at least one aromatic and / or heteroaromatic diaminocarboxylic acid comprising at least two acid groups per carboxylic acid monomer Reacting at a temperature of 300 ℃ or less,

ii) dissolving the solid prepolymer obtained in step (i) in polyphosphoric acid,

iii) heating the solution obtainable in step (ii) to an inert gas at a temperature of no greater than 300 ° C., preferably no greater than 280 ° C. to form a dissolved polyazole polymer,

(iv) forming a film on the support using a solution of the polyazole polymer according to step (iii) and

(v) treating the film formed in step (iv) until self-supporting.

In addition to the above modifications, the formation may also be prepared by the following steps:

I) dissolving the polymer, in particular polyazole, in polyphosphoric acid,

II) heating the solution obtainable in step (I) to a temperature of up to 400 ° C. under an inert gas,

III) forming a film on the support using a solution of the polymer according to step (II) and

IV) treating the membrane formed in step (III) until self-supporting.

In this variant, steps (v) and (IV) are accompanied by steps (E) and (F), and two variants (A) and (B) are possible.

Preferred embodiments of specific raw material and method parameters are detailed for steps (A), (B), (C) and (D), and such modifications are also effective.

In a further particularly preferred variant, the process according to the invention comprises the following steps:

A ') preparing a solution or dispersion of at least one polyazole having at least one amino group in a repeating unit in orthophosphoric acid and / or polyphosphoric acid,

B ') mixing the solution or dispersion from step (A') with a solution comprising (i) at least one strong acid and (ii) at least one stabilizing reagent, wherein the total content of stabilizing reagent in the solution is 0.01 to 30% by weight),

C ') performing the stabilization reaction directly in the solution or dispersion obtained in step (B'), or in a subsequent treatment step, by heating to a temperature above 25 ° C and

D ') optionally further doping the polymer obtained in step (C') with a strong acid or removing the water present to concentrate the strong acid present,

At least one high functional polyether is used as a stabilizing reagent.

In connection with this variant of the invention, the use of the preferred polyazoles described above is particularly advantageous.

Solutions or dispersions can be prepared in step (A ') by simply mixing the components. Or, it may also be considered dilute, that is removed or the feed of the P ₂ O ₅ concentration is low H ₃ PO ₄ and / or poly concentrated or P ₂ O ₅ concentration of the acid-containing composition are relatively high such compositions.

In this regard, however, it should be noted that in some cases, especially at low temperatures and / or high solids content, the dissolution or dispersion of polyazoles in orthophosphoric acid and / or polyphosphoric acid is inhibited mechanically. The composition is then in non-uniform form. At higher temperatures above 100 ° C., water further evaporates out of the composition, as a result of which the concentration of H ₃ PO ₄ and / or polyphosphoric acid changes over time.

Thus, suitably, the solution or dispersion is removed in step (A ').

a ') dissolving and / or dispersing at least one polyazole in orthophosphoric acid and / or polyphosphoric acid, calculated as P ₂ O ₅ based on the total amount of H ₃ PO ₄ and / or polyphosphoric acid and / or water The concentration of H ₃ PO ₄ and / or polyphosphoric acid is selected to be less than 72.0%, preferably less than 71.7%, more preferably less than%, even more preferably less than 71.0%, especially less than 70.5%,

b ') a water phase (a' removed from the solution or dispersion of a), at which time H ₃ PO ₄ and / or poly-phosphoric acid and / or based on the total amount of water to the calculated H as P ₂ O _{5 3} PO ₄ and / Or the concentration of polyphosphoric acid is preferably prepared by increasing the concentration to at least 0.1%, more preferably at least 0.5%, particularly preferably at least 1.0%, in particular at least 1.5%.

The solution or dispersion from step (a ') can generally be obtained by a method known per se, for example by mixing the components. Further preparation methods are described in WO 02/08829.

More preferably, the solution or dispersion from step (a ') is obtained by hydrolyzing a solution or dispersion comprising at least one polyazole and polyphosphoric acid. Such solutions or dispersions can be prepared by polymerizing the monomers described above in polyphosphoric acid.

The solution or dispersion from step (a ') is preferably at least 1.8% by weight, more preferably based on its total weight, having an intrinsic viscosity measured in at least 96% by weight sulfonic acid in the range of 3.0 to 8 g / dL. Preferably at least 2.0% by weight, in particular at least one pyrazole in the range of 2.2 to 2.5% by weight. The amounts of orthophosphoric acid, water and optionally phosphoric acid are preferably in the range 98.2% by weight and more preferably in the range 90.0 to 98.0% by weight, in particular in the range 95.0 to 97.8% by weight.

The water is removed in step (b '), preferably by evaporation, in particular by heating the composition from step (a') above 100 ° C. and / or applying reduced pressure. The composition from step (a ') is in the range above 120 ° C. to 240 ° C., in particular in the range 120 ° C. to 160 ° C., suitably for a time in the range of at least 1 hour up to 48 hours, in particular at least 2 hours up to 24 hours. Particularly preferred is a heating step.

In a further preferred variant of the invention, the composition is

I ') a solution or dispersion of polyazoles having an intrinsic viscosity ranging from 3.0 to 8.0 g / dL, measured in at least 96% by weight sulfuric acid, in polyphosphoric acid is above 160 ° C, preferably above 180 ° C, in particular between 180 and 240 ° C charging initially at a temperature and (where, H ₃ PO ₄ and / or the concentration of the polyphosphate is, H ₃ PO ₄ and / or poly-phosphoric acid and / or based on the total amount of water to P ₂ O ₅ (by acid amount appropriate means Greater than 72.4%, preferably greater than 73.0%, more preferably greater than 74.0%, even more preferably greater than 75.0%, especially greater than 75.45%),

II ') water, orthophosphoric acid and / or polyphosphoric acid, the mixture being calculated as P ₂ P ₅ (by acid titration means), based on the total amount of H ₃ PO ₄ and / or polyphosphoric acid and / or water, 70.5 H ₃ PO _{4 in the} range from% to 75.45%, preferably in the range from 71.0% to 75.0%, more preferably in the range from 71.5% to 74.0%, more preferably in the range from 71.7% to 73.0%, in particular in the range from 72.0% to 72.5% And / or to the solution or dispersion until it has a total content of polyphosphoric acid,

III ') prepared by homogenizing the mixture while maintaining the total amount of H ₃ PO ₄ and / or polyphosphoric acid in the range specified in step (II').

The solution or dispersion from step (I ′) can generally be obtained in a manner known per se, for example by mixing the components. Further preparation methods are described in WO 02/08829.

The solution or dispersion from step (I ′) is more preferably obtained by polymerizing the monomer in polyphosphoric acid.

The solution or dispersion from step (I ′), based on its total weight,

At least one polyazole having an intrinsic viscosity measured in at least 96% by weight sulfuric acid in the range from 3.0 to 8 g / dl, preferably at least 1.8% by weight, more preferably at least 2.0% by weight, in particular in the range from 2.2 to 2.5% by weight. , And

-Polyphosphoric acid and optionally orthophosphoric acid and / or water, preferably in the range 98.2% by weight, more preferably in the range 90.0 to 98.0%, in particular in the range 95.0 to 97.8% by weight.

The polyphosphoric acid used may be, for example, commercial polyphosphoric acid available from Riedel-de Haen. The polyphosphoric acid H _{n + 2} P _n O _{3n + 1} (n> 1) preferably has a content of at least 83%, calculated by P ₂ O ₅ (by acid titration means).

Conventional hydrolysis of such compositions leads to compositions with degraded flow behavior that are no longer processable under standard conditions. Therefore, it is preferable to carry out steps (II ') and (III').

The addition in step (II ′) can be carried out either separately or continuously.

After the addition, the mixture is based on its total weight,

At least one polyazole having an intrinsic viscosity measured at least 96% by weight sulfuric acid in the range from 3.0 to 8 g / dL, preferably at least 1.6% by weight, more preferably at least 1.8% by weight, in particular in the range from 2.0 to 2.3% by weight. And

Preferably up to 98.4% by weight, preferably in the range of 90.0 to 98.2% by weight, in particular in the range of 95.0 to 98.0% by weight and optionally orthophosphoric acid and / or water.

As a result of the addition in step (II ′), a heterogeneous mixture is first formed. "Heterogeneity" refers to a change in optical or physical properties that alters the identity of a property or the appearance homogeneity of the solution over a full range of systems. Typically, the homogeneity change of the solution is evident by the formation of an interface (separation of the liquid from the viscous material), a change of color (usually from green to yellow), or the separation of apparent visible or solid particles from the mild solution. The solution is considered homogeneous when it appears to be the same as a solution or dispersion of polyazole in polyphosphoric acid; Any difference is only in viscosity.

Homogenization in step (III ′) is performed, for example in an autoclave, preferably in a closed system. It is also particularly preferred to condense any water to evaporate and to feed it back to the mixture, preferably by condensing the evaporating water in at least one reflux condenser, preferably directly bonded to the reaction vessel.

Surprisingly, the solution is homogenized within a certain time, preferably less than 4 hours, in particular within 2 hours. The solution viscosity of the mixture is lowered and a useful composition of the present invention is formed.

In a further particularly preferred embodiment of the invention, orthophosphoric acid is added in step (II ′).

The method comprising steps (A '), (B'), (C ') and (D') is preferably used for the production of acid doped polyazole membranes. To this end, the method is suitably

i) forming a film on the support using the polyazole composition from step (A '), (B'), (C ') or (D'), and

(ii) treating the membrane formed in step (i) until self-supporting.

Preferred process parameters for these steps are described in detail above and apply to this variant of the invention.

Additional Blend Ingredients

In addition to the preferred high molecular weight polyazoles described above, blends of one or more preferred high molecular weight polyazoles with additional polymers may also be used. Blend components essentially serve to improve mechanical properties and reduce material costs. Preferred blend components are the polyether sulfones described in German Patent Application No. 10052242.4.

Preferred polymers that can be used as blend components include polyolefins such as poly (chloroprene), polyacetylene, polyphenylene, poly (p-xylylene), polyarylmethylene, polyamethylene, 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, perfluoropropyl vinyl ether, trifluoronitrosomethane, sulfonyl fluoride vinyl ether, carboalkoxyperfluoroalkoxyvinyl ether; Polychlorotrifluoroethylene, polyvinyl fluoride, polyvinylidene fluoride, polyacrolein, polyacrylamide, polyacrylonitrile, polycyanoacrylate, polymethacrylimide, cycloolefin-based copolymers, in particular Copolymers of bornen; Polymers having a CO bond in the main chain, for example polyacetal, polyoxymethylene, polyether, polypropylene oxide, polyepichlorohydrin, polytetrahydrofuran, polyphenylene oxide, polyether ketones, polyesters, in particular Polyhydroxyacetic acid, polyethylene terephthalate, polybutyl terephthalate, polyhydroxybenzoate, polyhydroxypropionic acid, polypivalolactone, polycaprolactone, polymalonic acid, polycarbonate; Polymers having a C-S bond in the main chain, such as polysulfide ether, polyphenylene sulfide, polyether sulfone; Polymers having C-N bonds in the main chain, such as polyimines, polyisocyanides, polyetherimines, polyanilines, polyamides, polyhydrazides, polyurethanes, polyimides, polyazoles, polyazines; Liquid crystal polymers, in particular Vectra and inorganic polymers such as polysilane, polycarbosilane, polysiloxane, polysilic acid, polysilicate, cyrylcone, polyphosphazene and polythiazyl.

For use in fuel cells with sustained use temperatures above 100 ° C., the glass transition temperature or Vicat softening point VST / A / 50 is at least 100 ° C., preferably at least 150 ° C. and most preferably at least 180 ° C. These blend polymers are preferred. Preference is given to polysulfones having a Vicat softening point VST / A / 50 of 180 ° C to 230 ° C.

Preferred polymers include polysulfones, especially polysulfones having aromatic rings in the main chain. In certain embodiments of the invention, the preferred polysulfone and polyethersulfone are melt volume flow rate MVR 300 / 21.6 This was measured by the ISO 1133, 40cm ^3/10 minutes or less, especially 30cm ^3/10 minutes or less, and more preferably from 20cm ^3/10 minutes or less.

Additional additives

In order to further improve the performance properties thereafter, additional fillers, in particular proton conductive fillers, may preferably be added to the high molecular weight polyazoles.

Non-limiting examples of proton conductive fillers include

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 ,

Polyacids, for example 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 ₁₁ , HTaWO ₆ , HNbO ₃ , HTiNbO ₅ , HTiTaO ₅ , HSbTeO ₆ , H ₅ Ti ₄ O ₉ , HSbO _3, H ₂ MoO ₄

Selenite 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 ,

Phosphides such as ZrP, TiP, HfP

Oxides, for example Al ₂ O ₃ , Sb ₂ O ₅ , ThO ₂ , SnO ₂ , ZrO ₂ , MoO ₃

Silicates, such as zeolites, zeolite (NH ₄ +), sheet silicates, silicate skeleton, H- or trawl light, H- mordenite, NH ₄ - Anal Shin, NH ₄ - sodalite, NH ₄ - gallate, H-montmorillonite; Other condensation products of orthosalicylic acid Si (OH) ₄ and salts and esters thereof; Polysiloxanes of the formula H ₃ Si- (O-SiH _2- ) _n -O-SiH ₃ , and in particular other clay minerals, for example montmorillonite, bentonite, kaolinite, pyrophyllite, talc, chlorite, mousse Cobite, mica, smectite, halosite, vermiculite and hydrotalcite

Acids such as HClO ₄ , SbF ₅

Fillers, such as carbides, preferably based on polyazoles and partially crosslinked, in particular SiC, Si ₃ N ₄ , fibers, in particular glass fibers, glass powders and / or polymer fibers.

These additives may be present in conventional amounts, but the positive properties such as the high conductivity, high lifetime and high mechanical stability of the polyazoles, in particular the membranes, should not be so markedly impaired by the addition of excessively large amounts of additives.

In general, polyazoles, in particular membranes, comprise at least 80% by weight of additives, preferably at least 50% by weight and more preferably at most 20% by weight of additives. The additives may be present in different particle forms and particle sizes, or as mixtures, but most preferably in nanoparticle form.

stabilize

The polyazole is treated in step (I) with a solution comprising (i) at least one strong acid and (ii) at least one stabilizing reagent.

Suitable stabilizing reagents in this connection preferably include all compounds which are particularly capable of mechanically stabilizing high molecular weight polyazoles.

Organic compounds used as stabilizing reagents should have sufficient stability against strong acids in the solution. In addition, they have sufficient solubility in strong acids, whereby the total content of stabilizing reagents in solution in step (I) is suitably 0.01 to 20% by weight, preferably 0.1 to 15% by weight, more preferably 0.25 to 10 It should be present in the range of% by weight, in particular 1 to 5% by weight. To the extent that the stabilizing reagent does not have sufficient solubility in strong acids, it may also add small amounts of additional inert solubilizers.

Overall, however, the solubility is preferably in the range in which the solution in step (I) has a total content of stabilizing reagent in the range of 0.01 to 100 mol% (based on the polyazoles present in the film (per repeat unit of the polyazole polymer)), preferably Preferably it should be sufficient to be a reagent in the range of 10 to 80 mol%, in particular 15 to 65 mol%.

If the proportion of stabilizing reagent is too low, the mechanical strength of the polyazole, especially the polymer membrane, is not sufficiently improved, and if the ratio selected is too high, the polyazole, in particular the membrane, becomes brittle, and the characteristic profile of the polyazole, in particular the membrane, is inadequate.

In addition, it is possible to introduce the electrolyte through a crosslinking reaction. The stabilizing reagents may partially or fully react or interact with the electrolyte. This reaction or interaction also leads to mechanical and / or chemical stabilization of the membrane and also to stabilization with respect to the phosphoric acid environment. Introduction of the electrolyte into the stabilization reaction can lead to a decrease in acid strength here.

The proton conductivity of the stabilized polyazole, in particular the stabilized membrane, at 160 ° C. is suitably 30 to 300 mS / cm, preferably 90 to 250 mS / cm.

Proton conductivity is measured by an impedance spectrometer (Zahner IM5 or IM6 spectrometer) and a four point test cell. Specific processes are as follows.

For sample preparation, a piece of about 3.5 × 7 cm size is appropriately cut and the membrane sample is rolled a total of 10 times to a roller-shaped weight of 500 g to remove excess acid. The thickness of the sample was preferably measured at three points and averaged with a Mitutoyo "Absolute, Digmatic" thickness measuring device (early, middle and end of the sample strip). The sample is suitably fixed in the test cell as shown in FIG. 1.

The numbers indicate the following:

(1): I _-

(3): U ₊

(5): U _-

(7): I ₊

(9): connector

(11): Pt wire

(13): sealed

(15): membrane

(17): Pt plate

The screw of the test cell is preferably tightened by hand and the cell is preferably transferred to a controlled oven operating through a temperature-frequency program according to Table 1.

[Table 1]

The oven program is initiated and the impedance spectrum is 20-160 ° C., and vice versa from 160 ° C. to 20 ° C., preferably in 20 ° C. steps, preferably with a 4-point dry test cell with a residence time of 10 minutes before measurement. Measured with Zahner-Elektrik IM6 impedance spectrometer at The spectra are stored and preferably evaluated by the Bode and Niquist literature method. Proton conductivity is calculated by the following equation:

I (distance between contacts) = 2 cm, b (membrane width) = 3.5 cm, d = film thickness in cm, R = measured resistance in ohms.

In the context of the present invention, at least one highly functional polyether, preferably at least one polyetherol, is used as stabilizing reagent.

In the context of the present invention, a highly functional polyetherol is a product having at least three, preferably at least six and more preferably at least ten OH groups in pendant or terminal positions as well as ether groups forming the polymer backbone. It should be understood as meaning. The polymer backbone can be linear or branched. The upper limit on the number of terminal or pendant functional groups is in principle not limited, but a product having a very high number of functional groups may have undesirable properties such as high viscosity or poor solubility. Highly functional polyetherols used in connection with the present invention usually have up to 500 terminal or pendant functional groups, preferably up to 100 terminal or pendant OH functional groups. The highly functional polyetherols for use according to the invention preferably have an average of at least 3, more preferably at least 4, further preferably at least 5 and in particular at least 6 di-, tri- or higher Condensation products formed from functional alcohols. In this case, it is further preferred that it is a condensation product formed from an average of at least six, more preferably at least four, in particular at least five and in particular at least six tri- or higher functional alcohols.

In a preferred embodiment, the high functional polyether is hyperbranched polyetherol. In the context of the present invention, highly branched polyetherpolyols are understood to mean uncrosslinked polymer molecules having hydroxyl and ether groups that are structurally and molecularly heterogeneous. On the other hand, they may have a structure similar to a dendrimer proceeding from the central molecule but with branches of heterogeneous chain length. On the other hand, they may also have linear regions with functional side chain groups. Definitions of dendrimers and hyperbranched polymers are described in P. J. Flory, J. Am. Chem. Soc. 1952, 74, 2718 and H.'Frey et al., Chem. Eur. J. 2000, 6, 15 No. 14, 2499.

In the context of the present invention, "hyperbranching" refers to the degree of branching (DB), i.e., the average number of dendritic bonds per molecule plus the average number of terminal groups divided by the sum of the average number of dendritic, linear and terminal bonds, multiplied by 100. It is understood that the value is 10 to 99.9%, preferably 20 to 99% and more preferably 20 to 95%. In the context of the present invention, "dendrimerity" is understood to mean that the degree of branching is from 99.9 to 100%. Definitions of branching can be found in H. Frey et al., Acta Polym. 1997, 48, 30.

The trifunctional and higher functional alcohols used may be, for example, triols such as trimethylolmethane, trimethylolethane, trimethylolpropane (TMP), 1,2,4-butanetriol. Tetrols such as bistrimethylolpropane (di-TMP) or pentaerythritol can also be used. In addition, higher functional polyols such as bispentaerythritol (di-penta) or inositol can be used. It is also possible to use alkoxylated products of the above-mentioned alcohols and glycerol, preferably having 1 to 40 alkylene oxides per molecule. Trifunctional and higher functional alcohols include aliphatic alcohols and especially those having primary hydroxyl groups, for example trimethylolmethane, trimethylolethane, trimethylolpropane, di-TMP, pentaerythritol, 1 to per molecule Particular preference is given to using di-penta and alkoxylates having 30 ethylene oxide units, and glycerol ethoxylates having 1 to 30 ethylene oxide units per molecule. Very particular preference is given to using trimethylolpropane, pentaerythritol and its ethoxylates having an average of 1 to 20 ethylene oxide units per molecule, and glyceryl ethoxylates having 1 to 20 ethylene oxide units per molecule. . It is also possible to use the alcohols mentioned in the mixture.

As tri- and high-functional alcohols, compounds containing OH groups on two immediately adjacent carbon atoms are less suitable. Under the conditions of the present invention, these compounds tend to remove reactants which may be desirable over etherification reactions. Under the etherification conditions of the present invention, unsaturated compounds forming by-products lead to reaction products that are not useful in the relevant industrial formulations. More particularly, this side reaction occurs in the case of glycerol.

Trifunctional and higher functional alcohols may be used in admixture with difunctional alcohols. Examples of suitable compounds having two OH groups are ethylene glycol, diethylene glycol, triethylene glycol, 1,2- and 1,3-propanediol, dipropylene glycol, tripropylene glycol, neopentyl glycol, 1,2- , 1,3- and 1,4-butanediol, 1,2-, 1,3- and 1,5-pentanediol, hexanediol, dodecanediol, cyclopentanediol, cyclohexanediol, cyclohexanedimethanol, bis (4-hydroxycyclohexyl) methane, bis (4-hydroxycyclohexyl) ethane, 2,2-bis (4-hydroxycyclohexyl) propane; Difunctional polyetherpolyols based on ethylene oxide, propylene oxide, butylene oxide or mixtures thereof, or polytetrahydrofuran. It should also be appreciated that difunctional alcohols can be used in the mixture.

Diols are used to make fine adjustments to the properties of polyetherpolyols. When difunctional alcohols are used, the ratio of difunctional alcohols to trifunctional and higher functional alcohols is determined by one of ordinary skill in the art depending on the desired properties of the polyether. Generally the amount of difunctional alcohol (s) is from 0 to 99 mol%, preferably from 0 to 80 mol%, more preferably from 0 to 75 mol% and most preferably from 0 to 50 mol%, based on the total amount of all alcohols. to be. By addition of trifunctional and higher functional alcohols and diols which vary in the course of the reaction, it is also possible to obtain block copolyethers, for example diol-terminated polyethers.

According to the invention, it is also possible to precondense bifunctional alcohols to OH-terminated oligomers and then to add trifunctional or higher functional alcohols. In this way, it is also possible to obtain hyperbranched polymers with linear block structures.

Moreover, monools may be added to control OH functionality during or after the conversion of tri- and higher-functional alcohols. Such monools can be, for example, straight or branched aliphatic or aromatic monools. They preferably have more than 3 and more preferably more than 6 carbon atoms. As monools, monofunctional polyetherols are suitable. Preferably, up to 50 mol% monool, based on the total amount of trifunctional and higher functional alcohols, is added.

Very particularly suitable polyethers in the context of the present invention are 1:10 to 10: 1, more preferably 1: 5 to 5: 1, even more preferably 1: 2 to 2: 1, especially 1.5: 1 to It can be obtained by reaction of triethylene glycol and pentaerythritol from a triethylene glycol / pentaerythritol mixture preferably having a molar ratio in the range of 1: 1.5, most preferably 1: 1.

For the purposes of the present invention, the polyethers preferably have a number average molecular weight in the range of 100 g / mol to 5000 g / mol, in particular in the range of 700 g / mol to 1500 g / mol. Its weight average molecular weight is suitably in the range from 1000 g / mol to 100,000 g / mol, in particular in the range from 5000 g / mol to 50,000 g / mol.

These molecular weights can be determined by gel permeation chromatography using methods known per se, in particular using appropriate criteria.

Further details on such highly functional polyethers and methods for their preparation are described in WO 2009/101141, the disclosure of which is expressly incorporated by reference.

In a further preferred embodiment of the present invention, high functional polyethers based on glycerol are used as stabilizing reagents. The preparation of polyethers based on glycesol is also described. For example, US Pat. No. 3,932,532 and German Patent Application DE DE 103 3 07 07 172 disclose the preparation of high functional polyethers based on glycerol, which provides oligomeric polyethers catalyzed by strong alkalis, International Publication No. WO 2004/074346 discloses its modification with monofunctional alcohols.

Furthermore, German patent application DE 103 07 172 also discloses 5 to 15 at a temperature of 200 to 280 ° C. in the absence of water in the presence of an acidic catalyst, for example HCl, H ₂ SO ₄ , sulfonic acid or H ₃ PO ₄ . Initiate the polycondensation of glycerol over time.

EP EP141253, German DE DE 44446877 and US Pat. No. 5,728,796 disclose the reaction of tri- and higher-functional alcohols under acidic reaction conditions in the presence of acetone or epoxy compounds. The product obtained is a low molecular weight modified alcohol.

International Publication No. WO 2004/074346 discloses alkali polycondensation of glycerol and subsequent reaction of condensation products obtained with acidic conditions with fatty alcohols. This gives fatty alcohol-modified polyglycerols.

Hyperbranched polyglyceryl ethers are also described in German patent applications DE # 199 47 631 and DE # 102 11 664. The preparation is carried out by ring opening reaction of glycidol, optionally in the presence of a polyfunctional initiating molecule.

In a further preferred embodiment of the invention, high functional polyethers based solely on trimethylolpropane units and / or based solely on pentaerythritol units are used as stabilizing reagents.

Hyperbranched polyetherols can also be prepared by ring-opening polymerization of 1-ethyl-1-hydroxymethyloxetane with a specific catalyst, as described, for example, in WO-00 / 56802. The polymer structure here consists solely of trimethylolpropane units. In addition, 3,3-bis (hydroxymethyl) oxetane is reacted by a ring-opening reaction according to Nishikubo et al., Polymer Journal 2004, 36 (5) 413, which is the only pentaerythritol unit. Highly branched polyethers can be obtained.

See Chen et. al., J. Poly. Sci. Part A: Polym. Chem. 2002, 40, 1991 describe a synthesis method of ring-opening polymerization of 1-ethyl-1-hydroxymethyloxetane and 3,3-bis (hydroxymethyl) oxetane together. This gives a polyether consisting of a mixture of trimethylolpropane and pentaerythritol units.

In step (II), the polyazole has a temperature of more than 25 ° C., preferably more than 50 ° C., more preferably more than 100 ° C., suitably more than 100 ° C. to 180 ° C., in particular from 120 ° C. to 160 ° C. The temperature is preferably stabilized by heating for a period of 5 to 120 minutes, preferably 15 to 100 minutes, more preferably 60 minutes. Optionally, the stabilizing film may be postconditioned for 10 to 60 minutes in an acid containing solution at a temperature of 20 ° C. to 80 ° C., more preferably 60 ° C.

Strong acids used according to the invention are aprotic acids, preferably phosphoric acid and / or sulfuric acid.

In the context of the present disclosure, “phosphate” refers to polyphosphoric acid, phosphonic acid (H ₃ PO ₃ ), orthophosphoric acid (H ₃ PO ₄ ), pyrophosphoric acid (H ₄ P ₂ O ₇ ), triphosphate (H ₅ P ₃ O ₁₀ ), metaphosphoric acid and derivatives, in particular organic derivatives, for example cyclic organophosphoric acid and derivatives thereof, for example acid esters. The phosphoric acid, in particular orthophosphoric acid, is preferably at least 80% by weight, more preferably at least 90% by weight, even more preferably at least 95% by weight and most preferably at least 98% by weight. The concentration calculation is based on the effective concentration of the acid in the membrane or hydrolysis.

In further control for subsequent use, the stabilization in step (II) may involve further doping of the polyazoles, in particular the membranes. In this case, the abovementioned additives can be added or other degree of doping can be carried out by further addition of the strong acids mentioned. In addition, the water present can be recovered from the polyazole, in particular the membrane, for example by concentrating the strong acid present. The required catalyst can also be added to the stabilization reaction and to mixtures of different stabilizers of this group.

The invention also provides a membrane comprising at least one mechanically stabilized polyazole obtainable by the process according to the invention.

The acid containing polyazole membranes of the present invention based on stabilized, preferably high molecular weight polyazole polymers form acid-based complexes with acids and are therefore proton conductive in the absence of water. Such a mechanism, referred to as Grotthus conductive mechanism, makes it possible to use in high temperature fuel cells with sustained operating temperatures of at least 120 ° C, preferably at least 140 ° C, in particular at least 160 ° C. Thus, the membranes of the present invention can be used as electrolytes for electrochemical cells, in particular fuel cells.

The acid containing polyazole membranes of the present invention based on stabilized, preferably high molecular weight polyazole polymers, are marked by improved mechanical properties. For example, the film of the present invention exhibits an elastic modulus of at least 3 MPa, suitably at least 4 MPa, more preferably at least 6 MPa, preferably 7 MPa, in particular at least 8 MPa. The membranes of the invention also exhibit an elongation at break of at least 150%, preferably at least 200%, in particular at least 250%.

Tensile strain properties are preferably measured with a Zwick Z010 standard tensile tester, and subsequent processes have been found to be useful. The sample is first properly cut into strips 1.5 cm wide and 12 cm long. Preferably, two to three samples are prepared, evaluated per sample, and then the results averaged. The thickness of the sample is preferably measured at three points and averaged (preferably at the beginning, middle and end of the strip) with a Mitutoyo Absolute Digmatic thickness measuring device. The measurement is preferably carried out as follows. The sample strip is clamped and held at an introduction force of 0.1 N for 1 minute. The measurement is then carried out automatically at RT (25 ° C.), preferably at a tension rate of 5 mm / min, until the modulus of elasticity MPa is measured (automatic process by Zwick software TextExpert (version 11)). The measurement then continues at a tensile rate of preferably 30 mm / min until the sample strip tears. After completion of the measurement, the fracture toughness (kJ / m ² ) and the elongation at break (%) are measured.

The conductivity of the acid-containing polyazole membranes of the invention, which are based on stabilized, preferably high molecular weight polyazole polymers, is preferably at least 50 mPa / cm, more preferably at least 100 mPa / cm, in particular at least 150 mPa / cm.

The acid containing polyazole membranes of the present invention, which are based on stabilized, preferably high molecular weight polyazole polymers, are further remarkable in their increased stability when used as proton conductive membranes in high temperature fuel cells. In the case of the operation of such a system, in particular in the case of phosphoric acid systems, it has been found that the stability of the acid containing polyazole membranes should be further improved. The membrane of the present invention is remarkable for this improved stability and is preferably insoluble in 99% phosphoric acid in the temperature range of 85 ° C to 180 ° C. In this regard, "insoluble" means that the swelling does not exceed 300% and dissolution of the self supporting film does not occur at all in the excess acid present.

In addition, the acid containing polyazole membranes of the present invention, which are based on stabilized, preferably high molecular weight polyazole polymers, have improved compressibility. The relative reduction in film thickness is typically less than 40% at 160 ° C., 120 minutes according to the Weiser Imprint Test, compared to approximately 80% relative reduction in film thickness for the corresponding destabilizing film under the same conditions. . The Bayesian imprint test to measure compressibility is performed as follows:

To measure the characteristic membrane indentation performance, a membrane sample having an area of 4.91 cm ² (2.5 cm in diameter) was punctured and placed on a hot plate with a Kapton film as a substrate. A metal die guided by a metal guide and having three studs (d = 1 mm) was placed on the membrane sample, and the thickness reduction of the membrane sample was measured by a Mitutoyo DC III thickness measuring device over a period of 120 minutes at a hotplate temperature of 160 ° C. Record as. The measured thickness is normalized to the standard thickness and plotted as a graph over time.

The stabilizing membrane of the present invention is further marked with further improved long term stability.

Further applications also include use as display members, electrochromic members or as electrolytes for various sensors.

The invention also provides a preferred use of the polymer electrolyte membrane of the invention in a single cell for fuel cells (MEU).

 A single cell for a fuel cell comprises at least one inventive membrane and two electrodes, between which a proton conductive membrane is arranged in a sandwich manner.

The electrodes each have a catalytically active layer and a gas diffusion layer for supplying the reaction gas to the catalytically active layer. The gas diffusion layer is porous enough to allow the reactive gas to pass through it.

The polymer electrolyte membrane of the present invention can be used as an electrolyte membrane. It is also possible to prepare electrolyte membranes and precursors for a single cell (MEU) having one or both catalytically active layers. Single cells can also be made by immobilizing a gas diffusion layer on the precursor.

The present invention further provides a fuel cell comprising a plurality of single cells (MEU), wherein each single cell comprises a membrane and two electrodes prepared by the above process, between which the membranes are arranged in a sandwich-like manner. It is.

Stabilization of the invention can also be performed after the generation of MEU from the membrane. For this purpose, the doping of the membrane with a stabilizer is carried out as described above. However, in step (II) or (c) the stabilization reaction or activation of stabilizing components occurs subsequently in the MEU arranged in a sandwich manner.

More preferably, stabilization occurs at temperatures in the range above 100 ° C. to 180 ° C., in particular in the range 120 ° C. to 160 ° C. The reaction time is from several minutes to several hours depending on the reactivity of the reagents. The stabilization reaction in the MEU can be carried out in one or more stages (temperature ramp). In the following the invention is further illustrated by some embodiments without forcing any limitation of the concept of the invention.

Example 1 Preparation of Polyether Polyols Based on Pentaerythritol and Triethylene Glycol

General process

The polymerization was carried out in a 4 L glass flask equipped with a stirrer, reflux condenser and distillation unit with vacuum appendages. The mixture of pentaerythritol, triethylene glycol and catalyst was drained according to the amounts in Table 2 and gradually heated by an oil bath to 180 ° C. at a pressure of 200 to 300 mbar. As the reaction temperature increases, the reaction mixture is stirred and water is removed with a distillation system. Distilled water was collected in a cold round bottom flask, weighed and the conversion measured as a percentage of the theoretically complete conversion possible.

The reaction mixture was then cooled under reduced pressure. For neutralization, KOH was added to the reaction solution. Then the mixture was removed and cooled.

Example 2: Preparation of Polyether Polyols Based on Pentaerythritol, Triethylene Glycol and Neopentyl Glycol

The polymerization was carried out in a 4 L glass flask equipped with a stirrer, reflux condenser and distillation unit with vacuum appendages. The mixture of pentaerythritol, neopentyl glycol, triethylene glycol and catalyst was drained according to the amounts in Table 2 and gradually heated by an oil bath to 180 ° C. at a pressure of 200 to 300 mbar. As the reaction temperature increases, the reaction mixture is stirred and water is removed with a distillation system. Distilled water was collected in a cold round bottom flask, weighed and the conversion measured as a percentage of the theoretically complete conversion possible.

The reaction mixture was then cooled under reduced pressure. For neutralization, KOH was added to the reaction solution. Then the mixture was removed and cooled.

Example 3: Preparation of Polyether Polyols Based on Ethoxylated Trimethylolpropane and Triethylene Glycol

The polymerization was carried out in a 4 L glass flask equipped with a stirrer, reflux condenser and distillation unit with vacuum appendages. The mixture of ethoxylated trimethylolpropane, triethylene glycol and catalyst was withdrawn in accordance with the amounts in Table 2 and gradually heated by an oil bath to 180 ° C. at a pressure of 200 to 300 mbar. As the reaction temperature increases, the reaction mixture is stirred and water is removed with a distillation system. Distilled water was collected in a cold round bottom flask, weighed and the conversion measured as a percentage of the theoretically complete conversion possible.

The reaction mixture was then cooled under reduced pressure. For neutralization, KOH was added to the reaction solution. Then the mixture was removed and cooled.

The product of the present invention was analyzed by gel permeation chromatography using a refractometer as detector. The mobile phase used was hexafluoroisopropanol (HFIP) and the criterion used for molecular weight determination was polymethyl methacrylate (PMMA). OH values were measured according to DIN 53240.

[Table 2]

Feed and End Product

TMP × 3EO: ethoxylated trimethylolpropane

Example 4 Performance of Stabilization of the Invention (Path 1)

Preferably about 800 mL of a preferably 1-5% by weight solution of hyperbranched polyether in 50% to 85% phosphoric acid (preferably based on pentaerythritol and triethylene glycol as listed in Table 2) is added to 1000 mL short Duran ( Schott Duran) manufactured in glass bottles.

A piece of reference polyazole membrane of about A5 size having a thickness of 350 μm (CD114), a phosphoric acid concentration of about 50% by weight and a solids content of about 5% by weight of polyazole, is added to the H ₃ PO ₄ solution and hyperbranched polyether Heated to 60 ° C. with 1-5% by weight. The residence time in solution was 1 hour. The membrane was then removed from the solution and treated in the oven for one hour between two support materials, preferably at 120 to 160 ° C. After the stabilization is performed, the membrane is preferably placed in 50% phosphoric acid for a period of 15 to 30 minutes.

Example 4a) Performance of Stabilization of the Invention (Path 2.1)

Preferably from 1 to 5% by weight of hyperbranched polyethers (preferably based on pentaerythritol and triethylene glycol as listed in Table 2), preferably high molecular weight polyazole 2.0 in 99 to 103% phosphoric acid Stir in a solution consisting of 2.5% by weight and the mixture is heated at 80-120 ° C., preferably with stirring for 1 hour.

The reaction solution is then used to obtain a film of about 350 μm in thickness using a coating knife. The latter is treated in the oven for 30 minutes between two support materials, preferably at 120 to 160 ° C. After the stabilization is performed, the membrane is preferably placed in 50% phosphoric acid for a period of 15 to 30 minutes.

Example 4b) Performance of Stabilization of the Invention (Path 2.2)

Preferably from 1 to 5% by weight of hyperbranched polyethers (preferably based on pentaerythritol and triethylene glycol as listed in Table 2), preferably high molecular weight polyazole 2.0 in 99 to 103% phosphoric acid Stir in a solution consisting of 2.5% by weight and the mixture is heated at 80-120 ° C., preferably with stirring for 1 hour.

The reaction solution is then used to obtain a film of about 350 μm in thickness using a coating knife. The latter is preferably placed in 50% phosphoric acid for a period of 15 to 30 minutes. The membrane is then removed from the solution and treated in the oven for 30 minutes between two support materials, preferably at 120 to 160 ° C.

For the use of 1% by weight of hyperbranched polyether No. 3 (Table 1), at stirring temperatures of 80 ° C. and oven temperatures of 160 ° C., the following properties are achieved by route 2.2:

-Cost of membrane from 99 ℃ phosphoric acid, in 160 ℃

-Proton conductivity at 160 ℃: 196.4 mS / cm

Elastic modulus: 3.5 MPa

Compressibility: Relative decrease in film thickness of 30% or less after 120 minutes at 160 ° C. (Beiger Imprint Test)

For 1 wt% use of hyperbranched polyether number 2 (Table 1), at 85% phosphoric acid and an oven temperature of 160 ° C., the following properties are achieved by route 1:

-Cost of membrane from 99 ℃ phosphoric acid, in 160 ℃

Elastic modulus: 29: MPa

Compressibility: Relative decrease in film thickness of 30% or less after 120 minutes at 160 ° C. (Beiger Imprint Test)

For the 5 wt% use of hyperbranched polyether No. 5 (Table 1), at 85% phosphoric acid and an oven temperature of 160 ° C., the following properties are achieved by route 1:

-Cost of membrane from 99 ℃ phosphoric acid, in 160 ℃

Modulus of elasticity: 26 MPa

Compressibility: Relative decrease in film thickness of 30% or less after 120 minutes at 160 ° C. (Beiger Imprint Test)

Comparative: Unstable Polyazole-Phosphate Membrane:

-Cost of membrane from 99 ℃ phosphoric acid, in 160 ℃

Elastic modulus: 3.5 MPa

Compressibility: relative reduction in film thickness of about 80% after 120 minutes at 160 ° C. (Beiger Imprint Test)

Claims (15)

I) treating at least one polyazole having at least one amino group in a repeating unit with a solution comprising (i) at least one strong acid and (ii) at least one stabilizing reagent, wherein the stabilizing reagent in the solution Total content of is in the range of 0.01 to 30% by weight),
II) conducting the stabilization reaction directly and / or in a subsequent processing step, carrying out the stabilization reaction by heating to a temperature above 25 ° C.,
A method of making mechanically stabilized polyazoles using at least one high functional polyether as said stabilizing reagent. The method of claim 1, wherein the polyazole has a molecular weight (measured as an intrinsic viscosity) of at least 1.8 dl / g. 3. The process according to claim 1, wherein the solution of step (I) comprises at least one protic strong acid, in particular protic strong acid based on phosphoric acid and / or sulfuric acid. The method of claim 3, wherein the phosphoric acid is polyphosphoric acid, phosphonic acid (H ₃ PO ₃ ), orthophosphoric acid (H ₃ PO ₄ ), pyrophosphoric acid (H ₄ P ₂ O ₇ ), triphosphate (H ₅ P ₃ O ₁₀ ), Metaphosphoric acid and derivatives, in particular organic derivatives, such as cyclic organophosphates, and derivatives thereof, such as acid esters. The process according to any one of claims 1 to 4, wherein the polyether can be prepared from triethylene glycol and pentaerythritol. The method of claim 5, wherein the polyether may be prepared from a triethylene glycol / pentaerythritol mixture in a molar ratio of 1:10 to 10: 1. 7. The process of claim 1, wherein the polyether has a number-average molecular weight in the range of 100 g / mol to 5000 g / mol. 8. 8. The method of claim 1, wherein the polyether has a weight-average molecular weight in the range of 1000 g / mol to 100,000 g / mol. 9. The method according to any one of claims 1 to 8,
a) producing a film comprising at least one polyazole having at least one amino group in a repeating unit,
b) treating the film from step (a) with a solution comprising (i) at least one strong acid and (ii) at least one stabilizing reagent, wherein the total content of stabilizing reagent in the solution is from 0.01 to 30 weight % Range),
c) performing a stabilization reaction directly on the membrane obtained in step (b) or by heating to a temperature above 25 ° C. in a subsequent membrane treatment step,
d) optionally further doping the membrane obtained in step (c) with a strong acid or removing the water present to concentrate the strong acid present,
A process for preparing mechanically stabilized polyazoles using at least one high functional polyether as a stabilizing reagent. The method according to any one of claims 1 to 8,
A ') preparing a solution or dispersion of at least one polyazole having at least one amino group in a repeating unit in orthophosphoric acid and / or polyphosphoric acid,
B ') mixing the solution or dispersion from step (A') with a solution comprising (i) at least one strong acid and (ii) at least one stabilizing reagent, wherein the total content of stabilizing reagent in the solution is 0.01 to 30% by weight),
C ') performing the stabilization reaction directly in the solution or dispersion obtained in step (B') or in a subsequent treatment step by heating to a temperature above 25 ° C. and
D ') optionally further comprising doping the polymer obtained in step (C') with a strong acid or removing the water present to concentrate the strong acid present,
A process for preparing mechanically stabilized polyazoles using at least one high functional polyether as a stabilizing reagent. Membrane comprising at least one mechanically stabilized polyazole obtainable by the process according to claim 1. The membrane of claim 11 having a solubility of less than 0.5% by weight polyazole polymer in 99% phosphoric acid over a temperature range of 85 ° C. to 120 ° C. 13. Use of the membrane according to claim 11 or 12 for producing a membrane electrode unit. A membrane electrode unit comprising at least one membrane according to claim 11. Use of the membrane electrode unit according to claim 14 for producing a fuel cell.

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