WO2012055743A1

WO2012055743A1 - Polymers based on polyazoles

Info

Publication number: WO2012055743A1
Application number: PCT/EP2011/068296
Authority: WO
Inventors: Maria Leute; Martin Bortenschlager; Tobias Halbach; Eckhard Hanelt; Stefan Haufe
Original assignee: Wacker Chemie Ag
Priority date: 2010-10-26
Filing date: 2011-10-20
Publication date: 2012-05-03
Also published as: DE102010042957A1

Abstract

The invention relates to polymers based on polyazoles, containing at least one grouping selected from formulas (I) and (II), wherein the groups and indices have the meanings indicated in claim 1, with the proviso that nitrogen must not be the aromatic ring ring-forming element in formulas (I) and (II). The invention also relates to methods for producing and using said polymers, in particular for preparing polymer electrolyte membranes.

Description

Polymers based on polyazoles

The invention relates to polymers based on polyazoles, processes for their preparation and their use, in particular for the preparation of polymer electrolyte membranes.

Polyazoles, especially polybenzimidazole (PBI), as well as membranes and fibers made therefrom, have long been known. Polybenzimidazole is characterized by high thermal and chemical resistance. PBI fibers are therefore used, among other things, for refractory fabrics. Crosslinked polymer films of PBI are used, for example, as semipermeable membranes or as polymer electrolyte membranes for fuel cells. In polymer membranes for gas separation, crosslinking often leads to an improvement in the selectivity with simultaneously reduced permeability. However, US Pat. No. 6,946,015 shows that cross-linking of PBI does not adversely affect the ratio of selectivity to permeability. The C0 ₂ / CH ₄ selectivity decreases in this case in the crosslinked

PBI membrane with increasing permeability even less than the uncrosslinked membrane.

In a fuel cell, controlled oxidation of a fuel, such as hydrogen gas, converts chemical energy into electrical energy. For this purpose, the fuel and an oxidant, such as oxygen, are supplied to two opposing electrodes which are separated by an electronically insulating membrane. The membrane contains an electrolyte which is permeable to protons but not to the reactive gases. Materials used for this purpose are, for example, perfluorosulfonic acid polymers which are mixed with water. are bulky or basic polymers containing strong acids as a liquid electrolyte.

EP-A 787 369 describes a process for preparing proton-conducting polymer electrolyte membranes in which a basic polymer such as polybenzimidazole is doped with a strong acid such as phosphoric acid or sulfuric acid. Since then, numerous similar membranes of various polyazoles or polyazines have been developed for this application. The advantage of a fuel cell with such a membrane is that it can be operated at temperatures above 100 ° C to about 200 ° C, because the polymer is sufficiently stable and the boiling point of the acid is well above 100 ° C. By increased compared to a fuel cell with a membrane of perfluorosulfonic acid polymer and water operating temperature, the catalyst activity is increased at the electrodes, reduces the sensitivity of the catalysts against carbon monoxide contamination in the fuel gas and made the waste heat with higher temperature technically better usable. The disadvantage of doping the polymer with a liquid electrolyte is that the mechanical stability of the membrane is considerably reduced. This can be partially compensated by crosslinking of the polymer as described in EP-B 1 165 670. So that the service life is not limited by this networking, there is a requirement that the long-term stability of the crosslinking in the hot and strongly acidic environment of a fuel cell membrane corresponds to the stability of the polybenzimidazole.

Polymer electrolyte membranes of PBI are commonly used as described, for example, in Q. Li et al. "High temperature proton ex- change membranes based on polybezimidazoles for fuel cells ^w, Progress co- using bifunctional reactive additives described in Polymer Science, 34 (2009) p 459 ~ 460 valent or ionically crosslinked by additives with polar groups. For this purpose, a solution which contains the basic polymer and a bridging reagent is used and then the bridging is carried out. The main target groups for the bridging reagents are the NH groups of the imidazole. Preferred bridging reagents for a covalent bond are diglycidyl ethers, polyfunctional organic acids or their halides and anhydrides, multiply halogenated organic compounds, dialdehydes or divinyl compounds. Numerous studies show, however, that when using bridging reagents, the long-term stability of the bridging is often lower than that of the thermally and chemically exceptionally stable polyazole. Therefore, the mechanical stability of such a networked membrane can slowly decrease, especially in an aggressive environment such as in a fuel cell. The selection of the polyazole chains bridging groups must therefore be carried out very carefully. In addition, the process step necessary for bridging should be cost-effective with as little time and equipment as possible.

Rode et al. (Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya 11, (1968), 2662-2663) describe the reaction of ring nitrogen atoms in PBI with formaldehyde, whereby two imidazole units are linked via a methylene bridge.

H. Xu. et al. describe the crosslinking of polybenzimidazoles via terminal amino groups with terephthalic aldehyde (Journal of Membrane Science 288 (2007) 255-260), resulting in Schiff's bases. The present invention relates to polymers based on polyazoles, the at least one group selected from -NR ² -CRVNR ² - (I) and

contain, where

R ^{1 may be the} same or different and is hydrogen or hydrogen radicals, the carbon chain may be interrupted by non-adjacent - (CO) -, -O-, -S- or ~ NR ⁴ ~ groups and may be substituted by -CN or halogen,

R ^{2 may be the} same or different and has the meaning of hydrogen tom or a hydrocarbon radical in which the carbon chain is interrupted by non-adjacent - {C0) ~, -O-, -S- or -NR ⁴ groups and - CN or halogen can be substituted, wherein the rest can form a ring with the nitrogen via a further binding site,

R ^{3 has} the meaning of hydrogen atom or a hydrocarbon radical in which the carbon chain may be interrupted by non-adjacent - {CO) -, -O-, -S- or -NR ⁴ groups and may be substituted by - CN or halogen, wherein the Rest can form a ring with the nitrogen via another binding site, and

R ^{4 may be the} same or different and is optionally substituted hydrocarbon radicals,

with the proviso that no nitrogen in the formulas (I) and (II) may be a ring-forming element of an aromatic ring.

Examples of radicals R ¹ are alkyl radicals, such as the methyl,

Ethyl, n-propyl, iso-propyl, 1-n-butyl, 2-n-butyl, iso ~ Butyl, tert. Butyl, n-pentyl, iso-pentyl, neo-pentyl, tert. -Pentyl radical, hexyl radicals such as the n-hexyl radical, heptyl radicals such as the n-heptyl radical, octyl radicals such as the n ~ octyl radical and iso-octyl radicals such as the 2, 2, 4-trimethylpentyl radical, nonyl radicals such as the n-nonyl radical, decyl radicals such as the n-decyl radical, dodecyl radicals, such as the n-dodecyl radical, and octadecyl radicals, such as the n-octadecyl radical; Cycloalkyl radicals, such as cyclopentyl, cyclohexyl, cyclohephenyl and methylcyclohexyl radicals; Alkenyl radicals such as the vinyl, 5-hexenyl, cyclohexenyl, 1-propenyl, allyl, 3-butenyl and 4-pentenyl radicals; Alkynyl radicals, such as the ethynyl, propargyl and 1-propynyl radicals; Aryl radicals, such as the phenyl, naphthyl, anthryl and phenanthryl radicals; Alkaryl radicals, such as o-, m-, p-tolyl radicals, xylyl radicals and ethylphenyl radicals; and aralkyl radicals, such as the benzyl radical, the - and the .beta.-phenylethyl radical.

1

R is preferably hydrogen or hydrocarbon radicals having 1 to 20 carbon atoms, particularly preferably hydrogen or alkyl or aryl radicals having 1 to 10 carbon atoms, in particular hydrogen.

Examples of radicals R ² and R ³ are the radicals given above for R ¹ and divalent radicals, such as the methylene or ethylene radical

2 3

R and R are, independently of one another, hydrogen, alkyl, cycloalkyl, alkenyl, aryl, alkaryl or arylalkyl radicals having 1 to 20 carbon atoms and also divalent radicals, such as methylene or ethylene radicals, particularly preferably Hydrogen atom or methylene bridges, wherein the hydrocarbon radical can form a ring with the nitrogen via another binding site.

Examples of radicals R ⁴ are the radicals given above for R ¹ . R is preferably an alkyl, cycloalkyl,

Alkenyl, aryl, alkaryl or arylalkyl radical having 1 to 20 carbon atoms, particularly preferably alkyl radicals having 1 to 6 carbon atoms, in particular the methyl radical.

Examples of groupings of the formula (I) are -NH-CH ₂ -NH-, -N (CH ₂ -) -CH ₂ -NH-, -N (CHa-) -CH ₂ -N (CH ₂ -) -, -N (CH ₃ ) -CH ₂ -NH-,

-N (CH ₂ -) -CH ₂ -N (CH ₃₎ -N {CH ₃₎ - (CH ₂ N {CH ₃₎ ™ NH ~ CH CH ₃₎ -NH-,

-N (CH ₂ -) -CH (CH ₃ ) -NH-, -N (CH ₂ -) -CH (CH ₃ ) -N (CH ₂ -) -, wherein -NH-CH ₂ --NH-, - N (CH ₂ -) -CH ₂ -H-, -N (CH -) -CH ₂ -N (CH ₂ -) -, -N (CH ₃ ) -CH ₂ -NH -, -N (CH ₂ - } -CH ₂ -N (CH ₃ ) -, -N (CH ₃ ) -CH ₂ -N (CH ₃ ) - preferred and

-NH-CH ₂ -NH-, -N (CH ₂ -) -CH ₂ -NH ~ and -N (CH ₂ -) -CH-N (CH ₂ -) - are particularly preferred.

Examples of groupings of the formula (II) are -NH-CH ₂ -0-, -N (CH ₂ -) -CH ₂ -0-, -N (CH ₃ ) -CH ₂ -O-, -NH-CH { CH ₃ ) -O-,

-N (CH ₂ -) -CH (CH ₃ ) -O-, wherein -NH ~ CH ₂ -O-, -N (CH ₂ -) -CH ₂ -O-,

-N (CH ₃ ) -CH ₂ -O- preferred and -NH-CH ₂ ~0-, -N (CH ₂ -) -CH ₂ -O- are particularly preferred.

The polymers according to the invention can only have groupings of the formula {I), only groups of the formula (II) or both groups of the formula (I) and also groups of the formula (II). The polymers according to the invention are preferably those which contain groups of the formula (I) and, if appropriate, also groups of the formula (II), in particular those which contain exclusively groups of the formula (I).

The polymers according to the invention are preferred in terms of their polyazole content at 130 ° C. and 1000 hPa in N, -dimethylacetamide. zugt 0 to 20 wt.%, Particularly preferably 0 to 10 wt.%, In particular 0 to 5 wt.%, Soluble.

The erfindungsgeraäßen polymers are preferably solids of any color at room temperature and the pressure of the surrounding atmosphere. The glass transition point of the polymers according to the invention is preferably above 150 ° C., more preferably above 200 ° C., in particular in the range from 250 ° C. to 500 ° C. The polymers of the invention have the advantage that they are characterized by excellent hydrolysis stability and retain their structural integrity, even when stored in strong acids. The polymers of the invention have the advantage that they have good mechanical stability even at high temperatures.

Furthermore, the polymers according to the invention have the advantage that they are long-lasting under the usual conditions for the applications described.

Another object of the present invention is a process for the preparation of the polymers according to the invention, in which polyazoles (A), which contain at least one primary or secondary amino group, are reacted with aldehyde reagents (B).

In the process according to the invention, component (A) is preferably mixed with (B) and optionally further substances, the mixture is given a mold and reacted, or component {A) is mixed with optionally further substances mixed, the mixture is given a mold and then doped with (B) and reacted.

The polyazoles (A) used according to the invention may be any and all known polyazoles which, in addition to the azole building block, contain at least one further aromatic or heteroaromatic compound.

Examples of the polyazoles (A) used in accordance therewith are those based on building blocks selected from pyrrole, pyrazole, benzpyrazole, oxazole, benzoxazole, thiazole, benzothiazole, imidazole and benzimidazole and additionally aromatic or heteroaromatic groups, such as benzene, naphthalene , Pyridine, pyrimidine or pyrazine groups, wherein the building blocks may be substituted, such as by sulfonic acid, alkyl, alkenyl and fluoroalkyl radicals. The different groups may also be linked via imide, ether, thioether, sulfone or direct C-bonds. Preferred examples of polyazoles (A) are all described in Q. Li et al. Progress in Polymer Science, 34, p. 453 (Scheme 1), 455 (Scheme 5, 6), 456 (Scheme 7) and 457 (Scheme 8) "High temperature proton exchange membranes based on polybenzimidazoles for fuel cells". (2009) mentioned polymers, which are to be fenoffenungsgehalt of the present invention.

The polyazoles (A) used in accordance with the invention are particularly preferably those which are built up from building blocks selected from imidazole, benzimidazole, pyridine, benzene and naphthalene, the different groups being replaced by imide, ether, sulfone or direct C.sub.2 Bonds are linked and wherein the blocks may be substituted, such as by sulfonic acid, alkyl, alkenyl and Fluoroalkylreste. The polyazoles (A) used according to the invention and processes for their preparation are known. For example, see Q. Li et al. "High temperature proton exchange membranes based on polybenzimidazoles for fuel cells", Progress in Polymer Science, 34, pp. 449-477 (2009).

The polyazoles (A) carry as end groups usually those of the monomers used for the preparation, such as amino and / or carboxylic acid groups and / or their esters, or by subsequent chemical reaction any introduced end groups, such as alkyl, aryl , Alkenyl, OH ~, epoxide, keto, aldehyde, ester, thiol, thioester, silyl, oxime, amide ™, imide, urethane ™, and urea groups. In the inventively used polyazoles (A) are preferably those having a primary or secondary amino and / or carboxylic acid end groups, particularly preferably NH ₂ - and / or COOH end groups, in particular more than 50% of all terminal groups NH ₂ radicals are.

In particular, the polyazoles (A) used according to the invention are polybenzimidazoles, as described, for example, in Q. Li et al. "High temperature proton exchange membranes based on polybenzimidazoles for fuel cells", Progress in Polymer

Science, 34, p. 453 (Scheme 1), 455 (Scheme 5, 6), 456 (Scheme 7), 457 (Scheme 8) (2009), most preferably Poly ~ 2, 2 '- (m ~ Phenylene) -5,5'-dibenzimidazole having primary or secondary amino and / or carboxylic acid end groups, more preferably having NH ₂ and / or COOH end groups, in particular more than 50% of all end groups being NH ₂ radicals.

Polybenz midazole (A) can be prepared by various and known methods, such as by polymerization of diamonds. minobenzidine and isophthalic acid and / or their esters. Polybenzimidazoles {A) may contain amino groups and / or carboxylic acid groups and / or their esters as end groups, or end groups introduced by subsequent chemical reaction, such as, for example, alkyl, aryl, alkenyl, OH, epoxide, keto , Aldehyde, ester, thiol, thioester, silyl, oxime, amide, imide, urethane and urea groups.

The polyazoles (A) used according to the invention may have a different number of amino and / or carboxylic acid end groups. The polyazoles (A) are particularly preferably those which have at least 3 amino groups of the general formula -NHR ⁵ (III) per molecule, where

R ^{s is} a hydrogen atom, a hydrocarbon radical, a - (CO) - OR ⁶ - group or a - (CO) ™ NR ⁸ R ⁷ group, wherein the carbon chain by non-adjacent - (CO) -, -O- , -S- or -NR ⁴ - groups may be interrupted and substituted by -CN or -halogen,

R ^{s is} a hydrocarbon radical, wherein the carbon chain can be interrupted by non-adjacent - (CO) -, -O-, ~ S ~ or -NR ⁴ groups and can be substituted by -CN or -halogen,

R ^{7 is} a hydrogen atom or a hydrocarbon radical, wherein the carbon chain can be interrupted by non-adjacent - (CO) -, -O-, -S- or -NR ⁴ groups and can be substituted by -CN or -halogen, and by R ⁸ covalently can be connected

R ^{8 is} a hydrogen atom or a hydrocarbon radical, wherein the carbon chain is interrupted by non-adjacent - (CO) -, -O-, -S- or -NR groups and with -CN or -halogen may be substituted and may be covalently bonded to R ⁷ , and

R ^{4 has} one of the meanings given above. Examples of radical R ^s are the radicals given above for radical R ¹ above.

5

The radical R is preferably hydrogen, in order to

Alkyl, cycloalkyl, alkenyl, aryl, alkaryl or arylalkyl radicals having 1 to 20 carbon atoms, more preferably hydrogen atom.

The polyazoles (A) used according to the invention have an inherent viscosity of preferably> 0.1 dl / g, particularly preferably from 0.1 to 2.5 dl / g, in particular from 0.3 to 1.5 dl / g, in each case measured on a 0.4% w / v solution, ie 0.4 g / 100 ml, of polyazole in H ₂ SO (95-97% by weight) with an Ubbelohde viscometer at a temperature of 25 ° C and a pressure of 1000 hPa.

The component (A) used according to the invention has a molecular weight Mw of preferably 1,000 to 300,000 g / mol, particularly preferably 4,000 to 150,000 g / mol, in each case measured as absolute molar mass by GPC coupled with static light scattering {eluent: DMAc mixed with 1 wt.% LiBr).

Most preferably, (A) is poly-2,2 ^! - (m-phenylene) -5, 5'-dibenzimidazole having on average per molecule at least 3 amino end groups of the formula (III) and an inherent viscosity of 0.3 to 1.5 dl / g measured on a

0.4% (w / v) solution, ie 0.4 g / 100 ml, of polyazole in H ₂ S0 ₄ (95-97% by weight) with an Ubbelohde viscometer at a temperature of 25 ° C. and a pressure of 1000 hPa. The aldehyde reagents (B) used according to the invention may be any and all known aldehyde reagents.

As aldehyde reagents (B) are preferably used according to the invention are e.g. at 20 ° C and the pressure of the surrounding atmosphere, ie between 900 and 1100 hPa, monomeric forms of formaldehyde, such as formaldehyde gas and aqueous or organic solutions of aldehydes, as well as formaldehyde in condensed form such as paraformaldehyde, Trio ™ xan or other aldehyde condensates. However, the aldehyde (B) may also be present in latent form and only be released in the reaction according to the invention. There are, for example, all previously known aldehyde-releasing agents.

The aldehyde reagent (B) used in accordance with the invention may be gases, liquids or solids.

If the aldehyde reagents are gaseous, they are preferably pure gases, such as formaldehyde gas, or mixed with inert gases, such as argon or nitrogen. If a gas mixture (B) is used, it preferably contains more than 5% by weight of aldehyde mixed with an inert gas. The gas mixture (B) preferably contains 0 to

0.01% by weight of oxygen and more preferably no oxygen.

If the aldehyde reagents (B) used in the process according to the invention are solids, they are preferably used as the solution. Preferred solvents are liquids which at 20 ° C and 1013 hPa 1 to 50 wt.% AI- dissolve dehydreagenz, and are compatible with the process conditions. Examples of particularly preferred solvents for preparing the aldehyde solutions {B) are water, polar aprotic solvents, such as N, N-dimethyacetamide, dimethylformamide, dimethyl sulfoxide and N-methylpyrrolidone, as well as orthophosphoric acid and polyphosphoric acid. Aqueous stabilizers (B) may be added as stabilizer alcohols, such as methanol. Particularly preferred aqueous aldehyde solutions (B) are formalin solutions which preferably contain 10 to 50% by weight of formaldehyde, 3 to 20% by weight of methanol and 30 to 87% by weight of water.

If the aldehyde reagents (B) used in the process according to the invention are solids, they can also be added directly as a solid to a solution which contains the polyazoles (A) used according to the invention and optionally further constituents.

Component (B) is preferably formaldehyde, paraformaldehyde or trioxane, if appropriate in a mixture with inert gas or a solvent.

In the method according to the invention, the aldehyde reagent (B) is preferably used in an amount such that the molar ratio of aldehyde groups in (B) to primary or secondary amino groups in component (A) is between 0.1 and 10, more preferably between 0 , 5 and 8, in particular between 1 and 5.

In addition to polyazole (A) and aldehyde reagents (B), solvents (C) and further components (D) which are different from components (A) and (B) can be used in the process according to the invention. Examples of the solvents (C) which may optionally be used according to the invention are all polar aprotic solvents which do not react with the further mixture constituents (A) under the process conditions, and acids and in particular polyacids, provided that the polyazole (A) is more adequate for the process Solve the quantity.

Preferred examples of solvent (C) are N, N-dimethylacetamide, dimethylformamide, dimethylsulfoxide, N-methylpyrrolidone and polyphosphoric acid, with N, N-dimethylacetamide and polyphosphoric acid being particularly preferred.

Polyphosphoric acid is often used as a solvent already in the preparation of polyazoles, so that polyazole (A) in the process according to the invention may optionally already be used in admixture with polyphosphoric acid, if not previously separated in the preparation of the polyazole, in which case the polyphosphoric acid the component (C) corresponds.

The term solvent does not mean that all components of the mixture must dissolve completely in it.

In addition to components (A), (B) and (C), further constituents (D) can now be used in the process according to the invention. The optionally used further constituents (D) can be any desired and previously known substances, as described, for example, in US Pat. also been used in connection with polyazoles.

The optionally used further substances (D) preferably contain no groups reactive toward NH or primary or secondary amino groups. However, it can also be chemical Compounds are used, which are covalently incorporated into the Hetzwerk for example, contained therein NH or OH groups. Examples of such compounds are alcohols which carry at least two OH groups and which, together with the aldehyde reagents (B), lead to NCO bridges of the formula (II) between the polyazoles.

Examples of optionally used further substances (D) are additives which increase the crosslinking density; Filler, for example, change the mechanical properties or the absorption capacity for a liquid electrolyte in the polymer film according to the invention; Fabrics that are removed after film formation and leave pores in the film; Low concentration additives that can serve to modify the properties of the surface of the polymer film, such as surface tension; Additives that improve the durability of the mixture or the film; or additives that serve process optimization. Examples of additives which increase the crosslinking density, (D) are low molecular weight or polymeric crosslinker building blocks or particles which are not based on polyazoles and which carry more than one amino group or hydroxyl group. Examples of preferred low molecular weight crosslinker building blocks (D) are di-, tri- and tetrahydroxy compounds, such as ethylene glycol, dihydroxybenzene, glycerol, trihydroxybenzene and pentaerythritol, or compounds having more than two amino groups, such as diaminobenzidine or melamine. An example of a compound having NH and OH groups is hydroxyanil. Examples of fillers (D) are polymers which are not based on polyazoles having amino groups, or inorganic components such as metal oxides. Examples of optionally used as fillers polymers (D) are

Polyolefins, such as polyethylene, polypropylene, polyisobutylene, polynorbornene, polymethylpentene, poly (1,4-isoprene), poly (3,4-isoprene), poly (1,4-butadiene), poly (1,2-butadiene),

Styrene {co) polymers such as polystyrene, poly (methylstyrene),

Poly (trifluorostyrene), poly (pentafluorostyrene),

N-basic polymers such as polyvinylcarbazole, polyethylenimine, poly {2-vinylpyridine}, poly (3-vinylpyridine), poly (4-vinylpyridine),

- (Het) ryl main chain polymers, such as polyether ketone PEK, polyether ether ketone PEEK, polyether ether ketone ketone PEEKK, polyether ketone ether ketone ketone PEKEK,

Polyethersulfones such as polysulfone, polyphenylsulfone, polyether-ether sulfone, polyethersulfone PES, polyphenylene ethers such as poly (2,6-dimethyloxyphenylene), poly {2,6-diphenyloxyphenylene), polyphenylene sulfide and

- perfluorinated polymers.

Examples of inorganic components (D) which may be used as fillers are silicon oxides, silicates such as framework or layer silicates or silicic acids, zeolites, aluminosilicates, titanium oxides, titanates, zirconium oxides, zirconium phosphates and heteropolyacids such as tungstophosphoric acid. These inorganic components (D) may also be in the form of particles which may be mesoporous and may be modified on the surface or in the pores by functional inorganic or organic groups such as, for example, sulfone, phosphono, amino or imidazole groups. The polymeric and inorganic components {D) listed above may be endowed with OH groups and / or primary or secondary amino groups to later enable covalent crosslinking with component (A). In this way, for example, particles whose surfaces are functionalized with NH or OH groups are integrated into the polymer network. Examples of pore formers (D) are ammonium salts or salts of alkali metals and alkaline earth metals, esters of mono- and dicarboxylic acids, esters of phosphoric acid, esters of saccharides and fatty acids, alkanols, glycols, polydialkylsiloxanes, phenyl / alkylsiloxanes, cyclic siloxanes or Organosilanes.

Examples of additives (D) are surfactants, adhesion promoters or preservatives substances.

Examples of additives (D) used for process optimization are catalysts, initiators or stabilizers.

The type and amount of further constituents (D) which may be used depends primarily on the specific applications or conditions of the polymers prepared according to the invention or prepared according to the invention.

The components used according to the invention may each be one type of such a component as well as a mixture of at least two types of a respective component.

The process of the invention is preferably carried out at the pressure of the surrounding atmosphere, ie 900 to 1100 hPa. The process according to the invention is preferably carried out at temperatures in the range from 10 ° C. to 300 ° C., particularly preferably from 20 ° C. to 200 ° C.

Any desired shaped articles can be produced by the process according to the invention, such as solid blocks, woven fabrics, nonwovens, textiles, coatings, films or fibers, films being preferred.

A preferred variant of the process according to the invention (variant 1) is characterized in that

in a first step

a mixture comprising polyazole (A) which contains at least one primary or secondary amino group, aldehyde reagent (B), solvent (C) and optionally further substances (D),

in a second step

the mixture obtained in the first step is shaped, preferably applied to a support

and

in a third step

Polyazole (A) with aldehyde reagent (B) is reacted, with or without solvent is partially or completely removed.

A further preferred variant of the method according to the invention (variant 2) is characterized in that

in a first step

a mixture comprising polyazole (A) which contains at least one primary or secondary amino group, solvent (C) and optionally further substances {D} is prepared,

in a second step the mixture obtained in the first step is shaped, preferably applied to a support

and

in a third step

the film obtained in the second step is contacted with aldehyde reagent (B) and polyazole (A) is reacted with aldehyde reagent {B), with or without the removal of any or all solvents. The mixture according to the first step of variants 1 and 2 according to the invention preferably contains at least 1% by weight, more preferably at least 5% by weight, in particular at least 10% by weight, of polyazole (A). The mixture preferably contains at most

90% by weight, particularly preferably at most 70% by weight, in particular at most 50% by weight, of polyazole (A).

The mixture according to the first step of variants 1 and 2 according to the invention contains solvent (C) in amounts of preferably 10 to 99% by weight, more preferably 30 to 95% by weight, in particular 50 to 90% by weight.

If component (D) is used in the first step of variants 1 and 2 according to the invention, these are amounts of preferably 1 to 200 parts by weight, more preferably 10 to 100 parts by weight, in each case based on 100 parts by weight of component (A). Preferably, no component (D) are used.

The mixture according to the first step of Variants 1 and 2 according to the invention preferably contains no further substances beyond components (A), (B), (C) and (D). The mixture according to the first step of the variants 1 and 2 according to the invention can be prepared by any known methods, such as by simply mixing the individual components and optionally stirring, preferably polyazole (A) with solvent (C) to a premix (M ) and then the remaining ingredients are added in any order to this premix. In this case, the other constituents, such as the aldehyde reagent (B) used in variant 1 or optionally used further substances (D) can be separately dissolved in one part of the solvent (C) and subsequently added to the premix (M).

To prepare the premix (M) in the first step of the variants 1 and 2 according to the invention, the mixture is preferably stirred until the polyazole (A) is preferably more than 90% by weight, particularly preferably completely, in the solvent ( C) has solved. Thereafter, optionally used aldehyde reagents (B) or further substances (D) can be added. If desired, proportions of component (A), (B)

and / or other substances (D) which have not dissolved in solvent {C) remain in the solution or are filtered off.

The preparation of this premix (M) in the first step according to the invention is carried out at temperatures of preferably 50 to 350.degree. C., particularly preferably 100 to 300.degree. C., in particular 150 to 250.degree.

The addition of the optionally remaining constituents to the premix (M) in the first step of variants 1 and 2 according to the invention can be carried out at the temperatures at which the premix (M) was prepared or at higher or lower temperatures, wherein the aldehyde reagent (B) before - added at low temperatures, such as 10 to 40 ° C, to avoid premature reactions.

The first step of the invention is preferably carried out in the variants 1 and 2 at the pressure of the surrounding atmosphere, ie 900 to 1100 hPa. It can also be performed at lower or higher pressures.

The first step of variants 1 and 2 according to the invention is preferably carried out in an inert gas atmosphere, such as under argon or nitrogen purge.

The first step of variants 1 and 2 according to the invention can be carried out continuously or batchwise.

The mixture according to the first step of variants 1 and 2 according to the invention is preferably a solution, a suspension or a paste. In the case of the solution, the polyazole (A) and optionally used aldehyde reagents (B) and / or further substances (D) are dissolved in the solvent (C). in the

In the case of the suspension, particles of the polyazole (A), the optionally used aldehyde reagents (B) and / or the other substances (D) are dispersed in the solvent used as the continuous phase. The mixture of the first step is particularly preferably a solution, in particular having a honey-type viscosity.

The application of the mixture obtained in the first step of the invention on a support can be carried out with all suitable, previously known discontinuous and continuous application methods. Preferably, the application is carried out by pouring out the mixture on a planar substrate, by application with a roller or slot die, through the doctor blade. process or spin coating. The chosen application method also depends on the desired layer thickness of the dry polymer film according to the third step of variants 1 or 2 according to the invention.

Examples of carriers which can be used in the second step of variants 1 and 2 according to the invention are all previously known carriers which are well wetted by the mixtures according to the invention, are largely resistant to the components contained in the mixtures and have dimensional stability in the temperature range used. Examples of such carriers are polymer films such as poly (ethylene terephthalate), polyimide, polyethyleneimide, polytetrafluoroethylene and polyvinylidene fluoride films, metal surfaces such as stainless steel strips, glass surfaces and siliconized papers.

In particular, when the polymer film is to be removed from the carrier after the preparation, carriers are preferred which are chemically inert to the mixture according to the first step of variants 1 and 2 according to the invention.

The application can also be carried out on a functional carrier, which is part of the respective application. For example, in the case of manufacturing a semi-permeable membrane, the mixture may be applied to an open-pored film or backing fabric. When used as a fuel cell membrane, the mixture can be applied directly to the gas diffusion layer or the electrode thereon.

The carriers used are preferably those which are wetted by the mixture according to the first step of variants 1 and 2 according to the invention, the contact angle being of the mixture on the carrier is preferably less than 90 °, particularly preferably less than 30 °, in each case measured with inert gas as the surrounding phase.

The second step according to the invention can be carried out continuously or discontinuously in variants 1 and 2.

For continuous application methods, polymer films such as poly (ethylene terephthalate) films or metal strips such as stainless steel are preferably used. For the batch process, glass plates are preferably used.

The second step of variants 1 and 2 according to the invention is preferably carried out at the pressure of the surrounding atmosphere, ie 900 to 1100 hPa. It can also be performed at lower or higher pressures.

The second step of variants 1 and 2 according to the invention is preferably carried out at temperatures below the boiling point of the solvent (C), particularly preferably in the temperature range from 10 to 80 ° C., in particular 15 to 40 ° C. If a polyacid is used as the solvent {C), the application of the

25 carried out on the support preferably in the temperature range of 150 ° C to 200 ° C.

The second step of variants 1 and 2 according to the invention is preferably carried out in air in a low-dust environment or in a clean room environment, which helps to ensure a constant film quality. The solvent which can optionally be removed in the third step of variants 1 and 2 according to the invention is solvent (C) and optionally solvent contained in the aldehyde reagent. If the mixture from the first step also contains a polar aprotic solvent (C), this is preferably completely or partially removed in the third step. If the mixture from the first step contains a polyacid as solvent (C), it preferably remains in the film and is optionally later converted into an acid by hydrolysis.

If solvents are to be removed in the third step of the process according to the invention, then the customary processes known from the prior art for drying can be used. In this case, the polymer film is preferably heated to the extent that the solvent or solvent mixture escapes without forming gas bubbles in the film.

The drying of the film in the third step of variant 1 according to the invention is preferably carried out at temperatures below the

Boiling point of the solvent (C) carried out, preferably at 40 to 150 ° C, more preferably at 60 to 130 ° C, in particular at temperatures at which a crosslinking reaction is not or only delayed takes place. Drying can be accelerated by reducing the ambient pressure below 900 hPa. By subsequently increasing the temperature to preferably not more than 250 ° C., more preferably not more than 200 ° C., the reaction of the polyazole (A) with the aldehyde reagent (B) can be started or accelerated.

In the third step of process variant 2 according to the invention aldehyde reagent (B) is added so as to allow the reaction of the polyazole (A) with the aldehyde reagent (B), wherein the optionally carried out drying before or after the addition of component (B). If, in the third step of process variant 2, solvent is to be removed completely or partially, this is preferably carried out before addition of aldehyde reagent (B).

The drying of the film in the third step of variant 2 of the invention is preferably carried out at temperatures of 40 to 250 ° C, more preferably at 80 to 200 ° C, in particular at 80 to 150 ° C. By reducing the ambient pressure below 900 hPa, drying can be accelerated. If the film is to be dried only after the addition of component (B), which is not preferred, rather low temperatures are selected at which a crosslinking reaction is not or only delayed takes place.

In the third step of process variant 2 according to the invention, aldehyde reagent (B) is added, for example by immersion, spraying or by gassing of the polymer film obtained in the second step, if appropriate after preceding drying. Subsequently, the crosslinking reaction can be accelerated by raising the temperature to preferably not more than 250 ° C., more preferably not more than 200 ° C. Preferably, in the third process step of variant 2 according to the invention, the optionally completely or partially dried film is immersed on the support or as a self-supporting film in a bath containing an aldehyde reagent (B) (variant 2a), or it is dissolved in a formaldehyde gas containing atmosphere (variant 2b). A bath according to variant 2a preferably contains an aqueous solution with 10 to 50% by weight of aldehyde, which is optionally stabilized with alcohol. The bath may also contain an acid such as orthophosphoric acid, contain. Immersion in the bath may be carried out in an inert gas atmosphere, such as under argon or nitrogen purge, or even in the presence of oxygen, for example in air. In variant 2b, the atmosphere containing formaldehyde gas preferably consists of more than 5% by weight of formaldehyde in one

Inert gas, such as argon or nitrogen, and preferably contains 0 wt.% To 0.01 wt.% Of oxygen, and more preferably no oxygen. Storage in a formaldehyde gas-containing atmosphere may also be carried out after the film has been wholly or partially dried and then doped with a strong acid such as orthophosphoric acid.

The necessary duration of treatment of the film with aldehyde reagents (B) in the third step of variant 2 according to the invention is determined by the rate of diffusion of the aldehyde reagent into the film and can not be stated as a whole. The optimum duration can be determined experimentally depending on the temperature, the concentration of the aldehyde in the bath or the atmosphere and the material composition and thickness of the film.

The reaction according to the invention in the third step of variants 1 and 2 is preferably carried out in an inert gas atmosphere, such as under argon or nitrogen purge, but can also be carried out in the presence of oxygen, for example in air, if no formaldehyde gas (B ) is used. The substeps carried out in air in the third step of process variants 1 and 2 according to the invention are carried out in a low-dust environment or in a clean room environment. leads, which helps to ensure a constant film quality.

The desired thickness of the polymer film after the third step depends on the requirements of the particular application. As semipermeable membranes thin layers between 1 and 20 μηι are preferred, especially when the film is mechanically supported by a porous support. As a self-supporting film, such as when used as a polymer electrolyte membrane, the thickness of the dry polymer film is preferably between 20 and 200 μπι. If the polymer film contains polyphosphoric acid after the third step, the film thickness is preferably between 30 and 500 μm. In the third step of process variants 1 and 2 according to the invention, preference is given to producing polymer films having a thickness of from 1 to 500 .mu.m, more preferably from 5 to 200 .mu.m.

As soon as the polymer film has sufficient mechanical stability, it can be detached from the carrier. This can be done after completion of the third step or after the optional drying in the third step. The polymer film may also remain on the support if desired for the application.

The heating of the polymer film in the third step of process variants 1 and 2 according to the invention can be carried out by any desired methods known hitherto, for example in a hot-air oven or by contact with hot surfaces.

The third step according to the invention of variant 1 as well as variant 2 can be carried out at different pressures. the, preferably at the pressure of the surrounding atmosphere, ie at 900 to 1100 hPa.

The third step according to the invention can be carried out continuously or discontinuously. If the third step according to the invention is to be carried out continuously, for example, a drying oven or heated rolls / belts, e.g. made of stainless steel or sintered metal, or a floating dryer can be used.

In the third step of variants 1 and 2 according to the invention, polymer films are now obtained which, in addition to the polyazoles, optionally have a residual amount of solvent and also all other substances. The quality of crosslinking of the polymer films obtained can be determined by determining the in N, N

Dimethylacetamide soluble proportions of polyazole in the polymer film can be assessed.

The selection of the process variant according to the invention depends on the intended use of the polymers of the invention and in particular on whether they are used as a rather massive material or as thin films or fibers. For example, for the crosslinking of a solid shaped body, the aldehyde reagent (B) is preferably introduced in the first step into a mixture with the polyazole (A), that is to say variant 1 is preferably carried out. If thin films or fibers are to be produced from the polyazole, the aldehyde reagent (B) according to process variant 2 can also be supplied in the third step, for example by immersion or spraying with a solution containing an aldehyde reagent, or by gassing with formaldehyde. The method according to the invention has the advantage that it is easy to carry out.

The process according to the invention has the advantage that it can be carried out under mild temperature conditions and thus subsequent embrittlement of the polymers is avoided. Also, the choice of other materials (D) for modifying the film properties is less limited than a process in which the films are subjected to severe thermal stress.

Furthermore, the method according to the invention has the advantage that it allows a hydrolytically and oxidatively stable crosslinking based on a simple and inexpensive crosslinker.

Due to the variability of the method used, the procedure can be customized depending on the desired end product and preferred production management. The polymer films according to the invention or produced according to the invention can now be used for all purposes for which polymer films have hitherto also been used.

Depending on the intended use, the polymer film according to the invention can be modified in further process steps by methods known per se. For use as a polymer electrolyte membrane, the polymer film obtained in the third step of process variants 1 and 2 can be doped with a strong acid in a further step, if appropriate, unless it has already been used as solvent in a preceding process step. As strong acids should here acids with a pK _s of preferably less than 4 are understood. It is also possible to have one such further Verfhenensschritt to summarize with the third step of the process variant 2 and so for example to introduce the aldehyde reagent (B) together with a strong acid in the polymer film.

Another object of the invention are polymer electrolyte membranes of polymers based on polyazoles, the at least one group selected from

-NR ² -CR ¹ 2-NR ² (I) and

wherein the radicals and indices have the abovementioned meaning, with the proviso that no nitrogen may be in the groupings of the formula (I) and (II) ring-forming element of an aromatic ring, which are doped with a strong acid. Another object of the present invention is a process for the preparation of polymer electrolyte membranes, characterized in that polyazoles (A) containing at least one primary or secondary amino group are reacted with aldehyde reagents (B) and then in a doping step with a strong acid can be doped.

With regard to the stability of the polymer film and the safety precautions required for handling strong acids at high temperatures, doping in the doping step optionally carried out is preferably carried out below 200 ° C., more preferably at 20 to 160 ° C., in particular 35 to 130 ° C. According to a variant of the optional doping step, the polymer film according to the invention is immersed in a highly concentrated strong acid over a period of preferably not more than 5 hours and more preferably 1 minute to 1 hour, with a higher temperature shortening the immersion time.

The amount of acid used in the doping step optionally carried out in this variant is usually from 5 to 10,000 times, preferably from 6 to 5,000 times, more preferably from 6 to 1,000 times, in each case based on weight of the polymer (A) in the polymer film. Alternatively, according to another variant of the doping step, a strong acid may be metered onto the polymer film and the film heated until the film has completely absorbed the acid. The amount of acid used in the doping step which may optionally be carried out according to the invention in this variant is usually 2 to 10 times, preferably 3 to 8 times, in each case based on the weight of the polymer film.

According to a further variant of the optional doping step, the polymer film is pressed between two acid-impregnated gas diffusion electrodes for the production of a membrane electrode assembly. The amount of acid used in the doping step optionally carried out according to the invention in this variant is usually 2 to 10 times, preferably 3 to 8 times, in each case based on the weight of the polymer film. As strong acids in the doping step according to the invention are protic strong acids, such as phosphorus-containing acids and sulfuric acid. In the context of the present invention, "phosphorus-containing acids" is understood as meaning polyphosphoric acid, phosphonic acid (H ₃ PO ₃ ), orthophosphoric acid

(H ₃ PO ₄ ), pyrophosphoric acid {H ₄ P ₂ 0 ₇ ), triphosphoric acid (H ₅ P ₃ Oi ₀ ) and metaphosphoric acid.

Since the polymer in the film according to the invention can be impregnated with a larger number of molecules of strong acid with increasing concentration of the strong acid, the phosphorus-containing acid, in particular orthophosphoric acid, preferably has a concentration of at least 70% by weight and more preferably at least 85% by weight. % in water.

The optionally performed doping step according to the invention is carried out at the pressure of the surrounding atmosphere, ie 900 to 1100 hPa. It can also be performed at lower or higher pressures.

The polymer electrolyte membrane obtained according to the invention in the doping step is proton-conducting and can therefore be used preferably as an electrolyte for fuel cells or electrolysis cells. The polymer electrolyte is not limited to the use for cells, but can also be used, for example, as the electrolyte for a display element, an electrochromic element or various sensors.

Each individual cell in a fuel cell usually contains a polymer electrolyte membrane according to the invention and two

Electrodes between which the polymer electrolyte membrane is sandwiched. The electrodes each have one catalytically active layer and a porous gas diffusion layer.

Another object of the invention is the use of the invention or inventively produced polymer electrolyte membranes for the production of membrane electrode assemblies for fuel cells or electrolysis cells.

Another object of the invention is a membrane-electrode assembly containing at least one electrode and at least one inventive or inventively prepared polymer electrolyte membrane.

The polymers and polymer films according to the invention have the advantage that they have high mechanical stability and excellent long-term thermal and chemical stability. Especially when using polyazoles having predominantly amino groups as end groups which are crosslinked via these end groups, particularly homogeneous and flexible films are obtained.

Due to the different permeabilities and selectivities of the polymer films according to the invention for liquids and gases, they are outstandingly suitable as semipermeable membranes. The invention therefore also relates to the use of the polymer films according to the invention or the polymer films produced according to the invention as a semipermeable membrane for the separation of liquids and gases. Because of the high temperature or corrosion resistance, the polymers of the invention are also particularly suitable for the production of coatings, fibers, fabrics, nonwovens or textiles, where these properties are required. To the known processes for the production of fibers include, in particular, spinning or extrusion. If these processes are carried out in the second step of the process according to the invention instead of the preferred application to a support, instead of the film according to the invention thin fibers based on polyazoles according to the invention are obtained, the mechanical properties of which differ significantly from those of uncrosslinked polyazoles due to the covalent crosslinking ,

If, in contrast, a carrier is used in the second step of the process according to the invention which is not removed after the third step according to the invention, for example a woven, non-woven or textile, a coating is obtained. Preference is given to those substrates which allow covalent attachment of the coating to the substrate by the aldehyde reagent (B) due to the presence of hydroxyl or amino groups.

In the following examples, all parts and percentages are by weight unless otherwise specified. Unless otherwise indicated, the following examples are air at ambient atmospheric pressure, ie, at about 1000 hPa, and at room temperature, ie, about 2Q ° C, or a temperature obtained by combining the reactants at room temperature without additional heating or Cooling stops, carried out. The air used in the experiments contains 23% by weight of oxygen and 50% relative humidity. All viscosity data given in the examples refer to a temperature of 25 ° C.

Inherent viscosity was measured in the following examples as follows: The polymer is first dried at 160 ° C for 2 h, 400 mg of the thus dried polymer are then dissolved for 4 hours at 80 ° C in 100 ml of concentrated sulfuric acid (concentration 95- 97 wt.%). The inherent viscosity is made from this 0.4% (w / v) solution according to ISO 3105 with an Ubbelohde

Viscometer determined at a temperature of 25 ° C.

The solubility of the polyazole portion of the polymer films produced was determined in the following examples as follows {"Solubility Test"):

The membrane piece is dried at 150 ° C, weighed and extracted for one hour at 130 ° C and 1000 hPa in N, N-dimethylacetamide. Thereafter, the membrane is again dried at 150 ° C to constant weight and then weighed.

The hydrolysis stability of the polymer films produced was determined in the following examples as follows:

An approximately 2 cm ² sample of the finished film is stored in 100 ml of 85% orthophosphoric acid in a closed glass vessel at 150 ° C for 240 h. After the test, the condition of the samples is assessed visually.

example 1

Preparation of amine-terminated polybenzimidazole

107.1 g of 3,3'-diaminobenzidine (0.5 mol) and 79.5 g of isophthalic acid (0.475 mol) (molar ratio 1.053, amine excess) were stirred into 2.0 kg of polyphosphoric acid and introduced into a heatable reactor (5 l The batch was heated to 190 ° C. (jacket temperature) and stirred for 20 hours The reaction product was precipitated in water, washed with it and suspended in 550 g of a 10% strength by weight sodium bicarbonate solution The polybenzimidazole was then washed again with water, filtered off, at Dried at 130 ° C in a vacuum and ground with an electric mill. The yield was 132.3 g.

The polybenzimidazole thus prepared had an inherent viscosity of 0.70 dl / g.

Preparation and characterization of a crosslinked polybenzimidazole film with aldehyde reagent in the solution

la) 15.0 g of the polybenzimidazole (PBI) prepared above were dissolved in 85.0 g of N, N-dimethylacetamide (DMAc) in a pressure reactor (Buchi iniclave, 200 ml) with stirring at a temperature of 200 ° C. After cooling to room temperature, 0.3 g of paraformaldehyde was added. Subsequently, the solution was stirred for a few minutes until the paraformaldehyde had completely dissolved.

After filtration and degassing, the solution was applied at room temperature by means of a film-drawing device with a gap of 0.4 mm to a polyethylene terephthalate (PET) support film having a thickness of 0.175 mm (commercially available under the trade name "Melenex O" from Pütz GmbH, Germany). Thereafter, the film was heated for 6 hours at 130 ° C. in a circulating-air drying oven, then separated from the carrier film and then heated for a further 6 hours at 180 ° C. in a circulating air drying oven The thickness of the film thus obtained was 30 to 35 μm.

With this film, a solubility test and a hydrolysis test were carried out according to the methods described above. The

Weight loss after one hour in 130 ° C hot N, -Dimethylacetamid was 4%. The hydrolysis test in 150 ° C hot phosphoric acid showed that although the film swells, but otherwise retains its shape. 1b) 12.0 g of the polybenzimidazole PBI prepared above were dissolved in 88.0 g of DMAc in a pressure reactor (Büchi miniclave, 200 ml) with stirring at a temperature of 200 ° C. After cooling to room temperature, 3.24 g of methanol-containing formalin solution (37% by weight of formaldehyde, 12% by weight of methanol, 51% by weight of water) were added dropwise with stirring.

Thereafter, the solution was applied at room temperature by means of a film applicator (0.4 mm gap height) on a carrier film of polyethylene terephthalate (PET) with a thickness of 0.175 mm (commercially available under the trade name "Melinex 0 at Pütz GmbH, Germany). After drying (each 10 minutes at 80 ° C, 100 ° C and 30 min at 150 ° C), the film was separated from the carrier film. Subsequently, the film was heated in a convection oven for 2 h in 200 ° C hot air. The film thickness was 30 to 35 μm.

With this film, a solubility test and a hydrolysis test were carried out according to the methods described above. The weight loss after one hour in 130 ° C hot N, -Dimethyl- acetamide was 5%. The hydrolysis test in 150 ° C hot phos- phoric acid showed that the film swells, but otherwise retains its shape.

Example 2

Preparation and characterization of a PBI - crosslinked film during swelling in phosphoric acid

12.0 g of PBI according to Example 1 were dissolved in 88.0 g of DMAc in a pressure reactor (Büchi Miniclave, 200 ml) with stirring at a temperature of 200 ° C. After filtration and degassing, the solution at room temperature by means of a film applicator (0.4 mm gap height) on a support film of polyethylene terephthalate (PET) with a thickness of 0.175 mm (commercially available under the trade name "Melinex O" at Pütz GmbH, Germany ) applied. After drying (each 10 minutes at 80 ° C, 100 ° C and 30 min at 150 ° C), the film was separated from the carrier film. It was then placed for 1 h in a 130 ° C hot aqueous solution of 85 wt.% Ortho-phosphoric acid with 2 wt,% paraformaldehyde. The swollen film was removed from the acid bath, dried and then annealed at 130 ° C. for a further 6 hours for complete crosslinking.

From a sample of this film, the phosphoric acid was removed again to be able to carry out a solubility test according to the method described above. For this purpose, the sample was first washed in water, then in aqueous Na ₂ C0 ₃ solution and finally again in water, dried and weighed. The weight loss after one hour in 130 ° C hot N, N-dimethylacetamide was 5%. The hydrolysis test in 150 ° C hot phosphoric acid showed that although the film swells, but otherwise retains its shape.

Example 3

Preparation and characterization of a PBI - crosslinked film after swelling in phosphoric acid

12.0 g of PBI according to Example 1 were dissolved in 88.0 g of DMAc in a pressure reactor (Büchi Miniclave, 200 ml) with stirring at a temperature of 200 ° C. After filtration and degassing, the solution at room temperature by means of a film applicator (0.4 mm gap height) on a support film of polyethylene terephthalate (PET) with a thickness of 0.175 mm {commercially available under the trade name "Melinex 0" at Pütz GmbH, Germany After drying (10 minutes at 80 ° C., 100 ° C. and 30 minutes at 150 ° C.), the film was separated from the carrier film and then immersed in a 130 ° C. hot aqueous solution containing 85% by weight. The swollen film was removed from the acid bath and dried The film was stored for 15 minutes at 120 ° C in a vessel which was filled with a gas mixture of 12 wt.% Formaldehyde and 88 wt.% Argon.

From a sample of this film, the phosphoric acid was removed again to be able to carry out a solubility test according to the method described above. For this purpose, the sample was first washed in water, then in aqueous Na ₂ C0 ₃ solution and finally again in water, dried and weighed. The weight loss after one hour in 130 ° C hot N, N ~ Dirnethylacetamid was 2%. The hydrolysis test in 150 ° C hot phosphoric acid showed that although the film swells, but otherwise retains its shape.

Example 4

Preparation and characterization of a film from the crude PBI solution - Crosslinking with aldehyde reagent in the crude PBI solution

107.1 g of 3,3'-diaminobenzidine (0.5 mol) and 79.5 g of isophthalic acid (0.475 mol) (molar ratio 1.053, amine excess) were stirred into 2.0 kg of polyphosphoric acid and introduced into a heatable reactor {5 1), which was purged with inert gas argon. The batch was heated to 190 ° C. (jacket temperature) and stirred for 20 hours, then the batch was admixed with 2% by weight paraformaldehyde (based on PBI), knurled at 170 ° C. on a glass plate to give a 120 μm thick film, and 12 h at 130 ° C. The polyphosphoric acid was then hydrolyzed by storage in air at 22 ° C. and 50% relative humidity.

From a sample of this film, the phosphoric acid was removed again to be able to carry out a solubility test according to the method described above. For this purpose, the sample was first washed in water, then in aqueous Na ₂ C0 ₃ solution and finally again in water, dried and weighed. The weight abnähme after one hour in 130 ° C hot N, -Dimethylacetamid was 3. The hydrolysis test in 150 ° C hot phosphoric acid showed that although the film swells, but otherwise retains its shape.

Example 5

Preparation and characterization of a film from the crude PBX solution followed by crosslinking with formalin solution

107.1 g of 3, 3 ¹ -Diaminobenzidin {0.5 mol) and 79.5 g of isophthalic re {0.475 mole) (1.053 molar ratio, excess of amine) were stirred in 2.0 kg äure polyphosphoric and (in a heated reactor 5 The reaction mixture was heated to 190 ° C. (jacket temperature) and stirred for 20 hours, after which the product obtained was laced at 170 ° C. on a glass plate to give a 50 μm thick film, cooled to room temperature and then immersed in an aqueous methanol-stabilized formal solution (37% by weight of formaldehyde, 12% by weight of methanol, 51% by weight of water) together with the glass plate for 1. Thereby, the film came off the glass plate Annealed at 150 ° C in air for 3 h.

From a sample of this film, the phosphoric acid was removed again to be able to carry out a solubility test according to the method described above. For this purpose, the sample was first washed in water, then in aqueous Na ₂ C0 ₃ solution and finally again in water, dried and weighed. The weight loss after one hour in 130 ° C hot N, -Dimethylacetamid was 5%. The hydrolysis test in 10% phosphoric acid showed that the film swells, but otherwise retains its shape.

Example 6 Producing and characterizing a FBI film with crosslinking with formalin solution

6a) 12.0 g PBI according to Example 1 were dissolved in 88.0 g D Ac in a pressure reactor (Büchi miniclave, 200 ml) with stirring at a temperature of 200 ° C. After filtration and degassing, the solution was applied to a PET support film (Melinex O, 0.175 mm) at room temperature using a film applicator (0.4 mm gap height). After drying (each 10 minutes at 80 ° C, 100 ° C and 30 min at 150 ° C), the film was separated from the carrier film. He was then 1 h in a 70 ° C hot methanol-stabilized formalin {37 wt.% Formaldehyde, 12 wt.% Methanol, 51 wt.% Water) inserted. Thereafter, the film was heated in a fresh air oven for 5 min in 250 ° C hot air. The film thickness was 30 to 35 μπκ. The film thus obtained will hereinafter be called film 6a.

With this film, a solubility test and a hydrolysis test were carried out according to the methods described above. The weight loss after one hour in 130 ° C hot N, N-dimethylacetamide was 2%. The hydrolysis test in 150 ° C hot phos- phoric acid showed that the film swells, but otherwise retains its shape.

6b) In order to be able to assess the mechanical stability of the polymer film film 6a obtained above in a), tensile stress measurements were carried out. For this purpose, film samples with a length of 6 cm and a width of 1 cm were placed in a measuring apparatus of the

Zwick GmbH & Co. (model Z010 TN, sample holder 8106) clamped and pulled apart at a speed of 5 cm / min. The polymer film cracked at a voltage of

140 N / mm ² and an elongation of 5%.

Example 7 Doping a membrane with phosphoric acid and determining the

conductivity

7a) From a piece (6 6 cm ² ) of the film 6a prepared in Example 6, the weight and the thickness were determined. Subsequently, the film piece was placed in a Petri dish, with

85 wt.% Phosphoric acid in water in the Petri dish and heated for 30 min at 150 ° C in a drying oven. The film was allowed to cool to room temperature and with paper towels. From the swollen film, the weight and the thickness were again determined. He had taken six times his weight. The degree of doping {mass increase based on the weight of the swollen membrane) was 85% by weight. The thickness was 55 μΓΠ.

7b) A piece (20 × 10 mm ² ) of the swollen membrane prepared above under a) was placed in a one-point conductivity cell {available under the name "Type BT110" from BekkTech LLC, USA) and in one Convection oven heated to 150 ° C. By means of an impedance analyzer (available under the name "Model IM6ex" from Zahner-Elektrik,

Germany) the membrane impedance was determined. The sample geometry (thickness, area) yields a membrane conductivity of 5 S / m at 150 ° C.

Example 8

Producing a membrane electrode assembly

The 6 x 6 cm ² piece of the swollen with phosphoric acid membrane of Example 7 was so between two commercially he ^"hältliche gas diffusion electrodes (each 3.0 mg / cm ² platinum loading Fa. Johnson Matthey, Type 3 mg Pt Blk, no electro lyte, on Toray TGP-H-090, U) that the platinum catalyst layers contacted the membrane. This membrane-electrode assembly was allowed to stand for 4 hours between plane-parallel plates a temperature of 160 ° C and a force of 1.3 kN compressed to a membrane-electrode assembly.

Example 9

Fuel cell test of the membrane-electrode assembly

The membrane electrode assembly of Example 8 was installed in a conventional arrangement in a test cell {quickCONNECT F25 Fa. Baltic-FuelCells GmbH, Germany) and sealed with a pressing force of 3.5 kN. The operation of the test cell was carried out on a MILAN test stand of the company. Magnum Fuel Cell AG, Figure 1 shows the course of the current-voltage curve at 160 ° C. The gas flow for hydrogen was 196 nml / min and for air

748 nml / min. Unhumidified gases with atmospheric pressure were used. At a current of 0.8 A / cm ² , a cell voltage of 0.500 mV was measured. Under the test conditions indicated, the MEA, at a measurement frequency of 16 kHz, exhibited an impedance of 4.1 m2 over a 25 cm ^{2 area} .

Current [A / cm ² ] Figure 1: Polarization curve of a membrane-electrode unit according to the invention in the Brennsto elle

Comparative Example 1

The procedure described in Example la was repeated with the modification that no paraformaldehyde was added.

The thickness of the film thus obtained was 30 to 35 μm.

With this film, a solubility test and a hydrolysis test were carried out according to the methods described above. Both tests resolved the movie completely.

Comparative Example 2

a) Preparation of carboxylic acid-terminated polybenzimidazole 101.8 g of 3,3'-diaminobenzidine {0.475 mol) (commercially available from Sigma-Aldrich, Germany) and 83.7 g of isophthalic acid

(0.5 mol) (molar ratio 0.95, excess acid) were dissolved in

2 kg of polyphosphoric acid were stirred in and introduced into a heatable reactor (5 l), which was purged with protective gas argon. The batch was heated to 190 ° C (jacket temperature) and stirred for 20 hours. The reaction product was precipitated in water, washed with it and neutralized in 550 g of a 10% strength by weight sodium bicarbonate solution. Thereafter, the polybenzimidazole was washed again with water, filtered off, dried at 130 ° C in a vacuum and ground with an electric mill. The yield was 132.3 g.

The polybenzimidazole thus prepared had an inherent viscosity of 0.43 dl / g. b) Preparation and characterization of a film of carboxylic acid-terminated polybenzimidazole and aldehyde reagent in the solution

15.0 g of the PBI prepared above were dissolved in 85.0 g of DMAc in a pressure reactor (Buchi Miniclave, 200 ml) with stirring at a temperature of 200 ° C. After cooling to room temperature, 0.3 g of paraformaldehyde was added. Subsequently, the solution was stirred for a few minutes until the paraformaldehyde had completely dissolved.

After filtration and degassing, the solution was applied to a 0.755 mm (Melinex O, 0.175 mm) PET support film using a 0.4 mm gap film applicator. Thereafter, the film was heated for 6 hours at 130 ° C. in a circulating air drying cabinet, then separated from the carrier film and then heated for a further 6 hours at 180 ° C. in a circulating air drying cabinet. The thickness of the film thus obtained was 30 to 35 μτη.

With this film, a solubility test and a hydrolysis test were carried out according to the methods described above. The weight loss after one hour in 130 ° C hot N, N-dimethyl-acetamide was 22.5%. During the hydrolysis test in 150 ° C hot phosphoric acid, the film dissolved completely after a few hours.

Comparative Example 3

a) Preparation of polybenzimidazole with phenyl end groups

10,714 g of 3, 3 ¹ -Diaminobenzidin (0.05 mol) of {commercially available from Sigma-Aldrich, Germany) and 7.95 g of isophthalic acid

(0.0475 mol) (molar ratio 1.053, amine excess) were stirred into 200 g of polyphosphoric acid and heated under argon protective gas atmosphere to 190 ° C and stirred for 20 hours. Subsequently, 2 g of benzoic acid (0.016 mol, 3.2-fold excess based on NH _{2 end} groups of the PBI) was added and stirred at 190 C for a further 3 h. The reaction product was precipitated in water, washed with it and neutralized in 55 g of a 10% strength by weight sodium bicarbonate solution. Thereafter, the poly ™ benzimidazole was again washed with water, filtered, dried at 130 ° C in vacuo and ground with an electric mill. The yield was 15.3 g. 1H NMR studies showed that 82% of the terminal NH ₂ groups of the PBI were reacted with benzoic acid and a phenyl-terminated PBI was obtained.

The polybenzimidazole thus prepared had an inherent viscosity of 0.497 dl / g.

b) Preparation and characterization of a film of polybenzimidazole with phenyl end groups and with aldehyde reagent in the suspension

15.0 g of PBI according to Comparative Example 3a were dissolved in 85.0 g of DMAc in a pressure reactor {Büchi Minielave, 200 ml) with stirring at a temperature of 200 ° C. After cooling to room temperature, 0.3 g of paraformaldehyde was added. Subsequently, the solution was stirred for a few minutes until the paraformaldehyde had completely dissolved.

After filtration and degassing, the solution was applied by means of a 0.4 mm gap film applicator to a PET support film having a thickness of 0.175 mm (Melinex O, 0.175 mm). Thereafter, the film was heated for 6 h at 130 ° C in a circulating rocker cabinet, then separated from the carrier film and then heated for a further 6 h at 180 ° C in a convection oven. The thickness of the film thus obtained was 30 to 35 μm.

Claims

claims

1. Polymers based on polyazoles, the at least one group selected from -NR ² -CRVNR ² - (I) and

contain, where

1 may be the same or different and is hydrogen or methyl radicals, the carbon chain may be interrupted by non-adjacent - (CO) -, -O-, -S ~ or -NR ⁴ groups and may be substituted by -CN or halogen,

R ^{2 may be the} same or different and has the meaning of hydrogen atom or a hydrocarbon radical in which the carbon chain interrupted by non-adjacent - {CO) -, -O-, -S- or -NR ⁴ groups and with -CN or halogen may be substituted, the remainder being able to form a ring with the nitrogen via an additional bonding site,

R ^{3 has} the meaning of hydrogen atom or a hydrocarbon radical in which the carbon chain may be interrupted by non-adjacent - (CO) -, -O-, -S- or -NR ⁴ groups and may be substituted by -CN or halogen, wherein the Rest can form a ring with the nitrogen via another binding site, and

2. Polymers according to claim l, characterized in that they are soluble in terms of their Polyazolgehalt at 130 ° C and 1000 hPa in N, N-dimethylacetamide 0 to 20 wt.%. 3. Polymers according to claim 1 or 2, characterized in that they have a glass transition point of over 150 ° C. , Process for the preparation of the polymers according to one or more of Claims 1 to 3, in which polyazoles (A) which contain at least one primary or secondary amino group are reacted with aldehyde reagents (B).

5. Process according to Claim 4, characterized in that the polyazoles (A) are polybenzimidazoles.

6. The method according to claim 4 or 5, characterized in that component (B) is formaldehyde, paraformaldehyde or trioxane. 7. polymer electrolyte membranes of polymers based on polyazoles, the at least one grouping selected from

-NR ² -CRVNR ² ~ (I) and

wherein the radicals and indices have the abovementioned meaning, with the proviso that no nitrogen may be in the groups of the formula (I) and (II) ring-forming element of an aromatic ring, which are doped with a strong acid.

8. A process for the preparation of polymer electrolyte membranes, characterized in that polyazoles (A) containing at least one primary or secondary amino group are reacted with aldehyde reagents (B) and then doped in a doping step with a strong acid.

9. Use of the polymer electrolyte membranes according to claim 7 or produced according to claim 8 for the production of membrane electrode assemblies for fuel cells or Elektrolysezel- len.

10. Membrane electrode unit comprising at least one electrode and at least one polymer electrolyte membrane according to claim 7 or produced according to claim 8.

11. Use of the polymer films according to one or more of claims 1 to 3 or prepared according to one or more of claims 4 to 6 as a semipermeable membrane for the separation of liquids and gases.