DE10316317A1 - Production of a heterocycle-substituted polyarylether sulfone, useful for making polymer electrolyte membranes for fuel cells comprises halogenation, reaction with metal and reaction with a heterocycle - Google Patents

Abstract

Production of a heterocycle-substituted polyarylether sulfone (I) comprises halogenating a polyarylether sulfone (II), reacting the product with a metal and reacting the product with an electrophilic 5-membered heterocyclic compound (III) having at least one ring nitrogen atom, provided that (III) has a carbon-bonded leaving group when (III) has only one ring nitrogen atom. Production of a heterocycle-substituted polyarylether sulfone of formula (I) comprises halogenating a polyarylether sulfone of formula (II), reacting the product with a metal and reacting the product with an electrophilic 5-membered heterocyclic compound (III) having at least one ring nitrogen atom, provided that (III) has a carbon-bonded leaving group when (III) has only one ring nitrogen atom: [Image] n : an integer, preferably 10-150; R1a 5-membered heterocycle having at least one ring N atom, provided that ring atom 1 is a C atom when there is only one ring N atom. An independent claim is also included for (I) produced as above.

Description

The The invention relates to a large scale feasible process for the preparation of N-heterocycles substituted polyarylethersulfones substituted with N-heterocycles, Moisture-free usable polyarylethersulfones, according to this Method available and the use of these substituted with N-heterocycles Polyarylethersulfone, especially as PEM in PEMFC.

Polymer electrolyte membrane fuel cells (PEMFC) have a big one Potential as an environmentally friendly source of energy. fuel cells have been since the sixties of the twentieth century used in space travel, moved but only recently, especially as "green" energy producers in Ahead of commercialization. This fuel cells were particular for the Use in automobiles, in electronic devices and in stationary power plants examined.

Probably the most critical component of a fuel cell is the polymer electrolyte membrane (PEM) or proton exchange membrane. In the last 30 years Nafion ^® (polyperfluorosulfonic) was DuPont as an industry standard for a PEM fuel cell. Nafion ^® membranes have sufficient proton conductivity (about 0.1 S / cm at 80 ° C in water), good chemical resistance and mechanical strength. Disadvantages of these membranes include high cost, reduced high temperature (> 80 ° C) conductivity, and high methanol permeability in direct methanol fuel cells (DMFC).

The Increasing the operating temperature of fuel cells is important for several reasons. For one thing, higher ones diminish Operating temperatures in fuel cells carbon monoxide poisoning the catalysts. Carbon monoxide in concentrations of a few ppm can e.g. the performance of fuel cells at about 80 ° C disadvantageous influence. To increase the other higher Operating temperatures the reaction kinetics of the fuel oxidation, e.g. Hydrogen oxidation, at the anode and especially the oxidant reduction, e.g. Oxygen reduction, at the cathode.

Becomes however, as the operating temperature increases, it becomes increasingly difficult to keep the PEM moist. Dehydrated membranes lose their proton conductivity and lead due to membrane shrinkage, poor contact between the various fuel cell components. It therefore exists a need for membranes that are not sensitive to the temperature range of liquid water limited are.

As a result of the renewed interest in fuel cells and the challenge of the high temperature operation of new membrane materials have been investigated as potential substitutes for Nafion ^®. Previous work focused on sulfonated polystyrenes, styrene-butadiene block copolymers or polyaryl ethers, such as PEEK. Such polymers are typically prepared by sulfonation of the polymer, ie, by introducing sulfonic acid groups into the already existing polymer backbone.

A other, in this context, interesting class are the Polysulfones. Although they have several advantages, including high thermal and chemical stability (especially against acids, lyes and oils), good mechanical properties in the temperature range from -70 to + 150 ° C, high shape and oxidation resistance, heavy flammability. However, they are usually lacking in benefits usable functional groups, so they are usually only for applications be used where their hydrophobic, unreactive character is advantageous, e.g. in pipes and moldings, and as a carrier for membranes for the Ultrafiltration and reverse osmosis.

offenbart, bei dem ein Polyethersulfon der allgemeinen Formel

in einem ersten Schritt metalliert und in einem zweiten Schritt mit einem Elektrophil umgesetzt wird. Als Metallie rungsreagens werden Li, Na, K oder Amalgame oder organische Derivate dieser Metalle angegeben, ggf. in Gegenwart eines Katalysators, wie z.B. TMEDR oder HMPT. Dabei sind lithiumorganische Verbindungen und insbesondere Butyllithium bevorzugt. Hinsichtlich der Reaktionstemperaturen wird angegeben: Nicht größer als 8°C, vorzugsweise –30 bis –70°C. Die Reaktionsansätze bewegen sich im Bereich von 0,005 bis 0,01 mol. Weiter lehrt die Schrift, dass das Metallierungsreagens unter Schutzgas, vorsichtig und unter sorgfältiger Abführung der Reaktionswärme zugegeben werden muss, da sonst, bei Temperaturen von mehr als 8°C an der Eintropf stelle, unlösliche Produkte ausfallen, die durch ihre Unlöslichkeit einer weiteren Umsetzung entzogen sind. Für eine großtechnische Produktion scheint ein Verfahren gemäß dieser Erfindung ungeeignet zu sein.The introduction of functional groups in polyarylethersulfones have hitherto generally been accomplished via a lithiation step. In Scripture US 4,833,219 (National Research Council of Canada), for example, a method for producing aromatic polysulfones of the general formula

disclosed in which a polyethersulfone of the general formula

metallated in a first step and reacted in a second step with an electrophile. As metallization reagent Li, Na, K or amalgams or organic derivatives of these metals are given, optionally in the presence of a catalyst such as TMEDR or HMPT. In this case, organolithium compounds and in particular butyllithium are preferred. With regard to the reaction temperatures, it is stated: not greater than 8 ° C, preferably -30 to -70 ° C. The reactions are in the range of 0.005 to 0.01 mol. Further, the document teaches that the metalating reagent must be added under inert gas, carefully and with careful dissipation of the heat of reaction, otherwise precipitate at temperatures of more than 8 ° C at the dripping, insoluble products that withdrawn by their insolubility further reaction are. For large scale production, a method according to this invention seems to be inappropriate.

In the German Offenlegungsschrift DE 198 36 514 A1 (University of Stuttgart, Chair and Institute of Chemical Process Engineering), several methods for side chain modification of aromatic polyethersulfones are given, wherein the reactant polyethersulfones as in the above US 4,833,219 lithiated with butyl lithium and then reacted with an electrophile. In the present case, however, N-containing electrophiles are used. It also works under inert gas, at temperatures from -30 to -60 ° C and the approaches are in the range of about 0.02 mol. Also this method seems to be unsuitable for the realization in a large-scale production.

Further functionalized polyarylethersulfones are for example from WO 01/84657 A2 (University of Stuttgart) known.

A likewise in this context interesting material class are with N-heterocycles substituted polymers. They exhibit proton conductivity on and can nearly moistening free and z.T. even at elevated temperatures than PEM is set become. Such polymers are, for example, from the spectrum of science, Sept. 2001, pp. 66-69. There are imidazole-substituted Polymers disclosed in which imidazolyl groups via spacer to a polymer backbone are bound. over The production process of such polymers is based on this document but nothing forth.

The abovementioned processes permit the preparation of functionalized polyaryl ether sulfones only on a laboratory scale. Polyarylethersulfones are used only in the range of about 0.005 to 0.02 mol and the yields are also within this range. The amounts of functionalized polyarylethersulfones obtainable by these processes are too low for industrial use of these compounds. An up-scaling of the processes from the laboratory to the pilot scale and finally to the production scale does not seem possible. The reason for this is that these processes use chemicals that are simply too expensive and too dangerous and their use is particular, ie cost and energy tensive measures, such as strict exclusion of air and low temperatures. In particular, the metalating compounds used, such as butyllithium, are problematic. These are only stable at low temperatures for a long time (storage temperature ≤ -18 ° C), are usually stored as a solution in n-hexane (toxic, nerve damaging) and react extremely violent with access of air (danger of fire and explosions). All this makes their handling extremely difficult and dangerous and their use in large-scale production almost impossible.

the across from there is a need for larger quantities functionalized, preferably approximately moisture-free polyarylethersulfones, around them e.g. as competitive Materials for PEMs from PEMFC can be used.

task Therefore, the present invention is a production method for functionalized, nearly to provide moisture-free polyarylethersulfones, their preparation in scale of industrial productions.

Further Objects of the present invention are functionalized, nearly moisture-free polyarylethersulfones to provide as well as possible Uses for the functionalized, approximate to indicate moisture-free polyarylethersulfones.

A Requirements for a for a large-scale For example, realizing a suitable manufacturing process is that it economical is, i. it should u.a. with as possible to carry out cheap chemicals be deliver high yields and require little energy.

A another requirement is that it should be carried out as safely as possible, without excessive accident risk. Manufacturing processes using e.g. overly dangerous chemicals used are therefore generally not suitable for large-scale implementation.

wobei n eine ganze Zahl ist, bevorzugt aus dem Bereich 10 bis 150,
und R₁ ein Fünfring-Heterocyclus mit wenigstens einem Ring-N-Atom,
wobei Ringatom 1 ein C-Atom ist, wenn nur ein Ring-N-Atom vorhanden ist.A first subject of the present invention is accordingly a process for the preparation of a polyarylethersulfone of the general formula I.

where n is an integer, preferably from the range 10 to 150,
and R _{1 is} a five-membered heterocycle having at least one ring N atom,
wherein ring atom 1 is a C atom when only one ring N atom is present.

• a) Bereitstellen eines Polyarylethersulfons der allgemeinen Formel II
  
  wobei n eine ganze Zahl ist, bevorzugt aus dem Bereich 10 bis 150,
• b) Halogenierung des Polyarylethersulfons der allgemeinen Formel II;
• c) Umsetzung des Produktes aus Schritt b) mit einem geeigneten Metall;
• d) Umsetzung des metallierten Produktes aus Schritt c) mit einem elektrophilen Fünfring-Heterocyclus mit wenigstens einem Ring-N-Atom, bei dem die Abgangsgruppe an einem C-Atom sitzt, wenn nur ein Ring-N-Atom vorhanden ist, um ein Polyarylethersulfon der allgemeinen Formel I zu erhalten.

The method according to the invention comprises the following steps:

• a) providing a polyarylethersulfone of the general formula II
  
  where n is an integer, preferably from the range 10 to 150,
• b) halogenation of the polyarylethersulfone of the general formula II;
• c) reaction of the product from step b) with a suitable metal;
• d) reacting the metallated product of step c) with an electrophilic five-membered heterocycle having at least one ring N atom in which the leaving group is attached to a carbon atom when only one ring N atom is present to form a polyaryl ether sulfone to obtain the general formula I.

The N atom (s) can take any of the positions 1, 2, 3, 4 and / or 5 (see formula (I)). However, if the five-membered heterocycle R ₁ has only one ring N atom, then position 1 (see formula (I)) is occupied by a C atom, so that the five-membered heterocycle R _{1 can be} attached to the Polymer backbone is bound. The five-membered heterocycle may also contain one or two double bonds.

Of the Five-heterocyclic will over a corresponding electrophilic compound introduced in educt II. As Electrophiles are suitable, for example: the corresponding ones Carbonyls, organohalogen compounds, alcohols, thiols and the like, preferably the corresponding bromorganic or chloro-organic compounds, e.g. 2-bromobenzimidazole or 2-chlorobenzimidazole.

In Step c) suitable metals are, for example, alkali metals and alkaline earth metals, Metals of the second subgroup, in particular Li, Na, Mg, where Mg is particularly preferred (Grignard reaction).

The inventive method allows the preparation of functionalized polyarylethersulfones in industrial production scale. It can be based on experience in the field of Wurtz and Wurtz-Fittig syntheses resorted become. These syntheses have long been known and in large-scale scale operated processes in which organohalogen compounds with e.g. Na or Mg are reacted.

The inventive method Comes with comparatively inexpensive chemicals, can operated under mild reaction conditions and requires no Use of inert gas, but under dry air or the Solvent vapor can be performed.

On Another advantage is in the big one variability to see the procedure. So have to the starting materials have no acidic protons and as electrophiles in step d) Also compounds are used, which are among the sharp ones Conditions in the use of organolithium compounds would decompose. In addition the dynamic controllability of the reaction is advantageous. So can chosen be whether the starting material at an aromatic nucleus or in a side chain should be functionalized.

On Another advantage is that at no time there is a risk that insoluble ones rainfall and only partially converted products, which is another Remove implementation. Of course, this is associated with another advantage of the method according to the invention, high yields.

Furthermore is to mention that the inventive method burdened with a much lower risk. All used Chemicals are relatively stable and do not respond or only moderately with Air. On the harmful solvent n-hexane can be dispensed with.

A preferred variant of the method according to the invention provides that the halogenation, i. Step b), thermally and under action a reaction accelerating catalyst is carried out. This mainly results in nuclear-halogenated products ("KKK-Regel").

there these are halogenation products in which at least an H atom of the adjacent to the sulfone group phenylene rings a halogen atom is replaced. But it is also possible that in dependence from the reaction conditions (amount of the halogen used, Art the catalyst used, reaction time, etc.) also several or also all H atoms of the phenylene rings adjacent to the sulfone group replaced by halogen atoms.

at the reaction can Both products are formed in which the sulfone group ortho-stationary H atoms replaced (ortho substitution products), as well as products in which the sulfone group contains meta-standing H atoms replaced (meta-substitution products). In practice, product mixtures are obtained which are substantially said ortho-substitution product contain.

On for the inventive method particularly suitable catalyst is Fe. The use of Fe as Catalyst is particularly advantageous, especially for a large-scale Process because Fe is cheap, readily available, environmentally friendly and completely dangerous.

wobei n eine ganze Zahl ist, bevorzugt aus dem Bereich 10 bis 150,
und R₁ ein Fünfring-Heterocyclus mit wenigstens einem Ring-N-Atom,
wobei Ringatom 1 ein C-Atom ist, wenn nur ein Ring-N-Atom vorhanden ist,
die nach dem vorstehend beschriebenen Verfahren erhältlich sind.Another object of the present invention are polyarylethersulfones of the general formula I.

where n is an integer, preferably from the range 10 to 150,
and R _{1 is} a five-membered heterocycle having at least one ring N atom,
where ring atom 1 is a C atom, if only one ring N atom is present,
which are obtainable by the method described above.

The polyarylethersulfones according to the invention are extremely stable thermally and chemically and show through the introduced Five-heterocyclic good proton conductivities with at least one ring N atom on. Your proton conductivity is also approximately independent of its water content, i. they are moistening free used. A good proton conductivity without humidification lies up to temperatures above 110 ° C before, decomposition from about 130 ° C begins. This can be the system technical effort, otherwise in use for the Humidification would be required significantly reduced or even eliminated.

The five-membered heterocycle R ₁ can be bonded directly to the polymer backbone via a C-C bond without the need for a good proton conductivity, a spacer between R ₁ and the polymer backbone. This considerably simplifies the production process for a humidification-free proton conductor.

In preferred polyarylethersulfones, the five-membered heterocycle R ₁ is a member of the group of the azoles, azolidines, diazone, diazolidines, triazoles, triazolidines, tetrazoles and tetrazolidines, wherein the polyarylethersulfone may also contain various representatives of this group. Such polyarylethersulfones have a particularly good proton conductivity under humidification-free conditions.

The above-mentioned five-membered heterocycles R ₁ may have at least one substituent R ₂ , wherein at least one ring N atom is unsubstituted. An example of such a compound is shown by Formula III

such Heterocycles can an improved thermal stability and / or improved proton conductivity have, especially under humid conditions.

In this case, the at least one substituent may be a substituent which improves the proton conductivity, in particular under humidification-free conditions, preferably an amino group, in particular -NH ₂ . Further, the at least one substituent may be a fused aromatic, preferably a benzene ring, whereby the thermal stability of the polyarylethersulfone may be improved. Examples of such compounds are shown by Formulas IV and V

In turn, the fused aromatic may carry at least one substituent which preferably enhances proton conductivity under humidification-free conditions, especially an amino group. An example of such a compound is shown by Formula VI

It is advantageous if the inventive polyarylethersulfone a Substitution degree in the range of 20 to 200 mol%, preferably in the range of 80 to 150 mol% and in particular in the range of 100 to 120 mol%. Polyarylethersulfone of this type are on the one hand good soluble and on the other hand have an advantageously high basicity.

wobei n eine ganze Zahl ist, bevorzugt aus dem Bereich 10 bis 150,
und R₁ ein Fünfring-Heterocyclus mit wenigstens einem Ring-N-Atom,
wobei Ringatom 1 ein C-Atom ist, wenn nur ein Ring-N-Atom vorhanden ist,
die nach dem vorstehend beschriebenen Verfahren erhältlich sind,
in Elektrolyten, Ionenaustauschern, katalytisch aktiven Substanzen, Polymerblends und/oder neuen Werkstoffen.A third object of the present invention is the use of polyarylethersulfones of the general formula I.

where n is an integer, preferably from the range 10 to 150,
and R _{1 is} a five-membered heterocycle having at least one ring N atom,
where ring atom 1 is a C atom, if only one ring N atom is present,
obtainable by the method described above,
in electrolytes, ion exchangers, catalytically active substances, polymer blends and / or new materials.

With particular advantage can the above-mentioned polyarylethersulfones are used for membranes, preferably for Polymer electrolyte membranes (PEM), in particular for PEM for fuel cells. such Membranes have good thermal and mechanical properties, such as. high mechanical stability and heat resistance, and at the same time good proton conductivities, especially under humid conditions. The membranes are also good in boiling water. They are special with that for the Use in fuel cells suitable.

The present invention will be explained in more detail with reference to the figure described below. The figure shows the steps of the inventive method, starting from the polyaryl ether sulfone UDEL ^® (1).

The synthesis starts from the polyarylethersulfone UDEL ^® (1) (company BPAmoco). (1) is thermally / catalytically brominated in a conventional manner. Essentially, the intermediate (2) brominated ortho to the sulfone group on a phenylene ring is formed. The intermediate (2) is subsequently reacted in THF first with Mg and then with an organohalogen compound as electrophile, in this example, 2-chlorobenzimidazole (3), wherein substantially the polyarylethersulfone (4) functionalized on the phenylene ring in ortho position to the sulfone group.

For the reactions, a polyaryl ether sulfone UDEL ^® (1) was used - hereinafter referred to as PAES. The PAES is available from BPAmoco. Before use, the PAES was dried in a high vacuum at 130 ° C. for 8 h. The electrophile used was 2-chlorobenzimidazole (3). The solvents THF (tetrahydrofuran) and diethyl ether were dried by boiling over Na / benzophenone and then distilling off. CHCl ₃ was dried over CaCl ₂ and then distilled off. Mg, Br ₂ and hydrochloric acid were purchased from Merck and used without further pretreatment. 2-Chlorobenzimidazole (3) was purchased from ABCR GmbH and used without further pretreatment.

1. Thermal-catalytic bromination:

The PAES (1) (50 g, 0.113 mol) was dissolved in 500 mL of CHCl ₃ and treated with 225 g of Fe powder. For this purpose, Br ₂ (6.15 cm ³ , 0.12 mol) was added dropwise within 1 h with stirring at room temperature. After completion of the addition, stirring was continued for 2 h at room temperature. The reaction product was crystallized out with cooling, washed with aqueous Na ₂ CO ₃ solution and subsequently with water and then recrystallized once. The yield was 70% of theory. (41.3 g, 0.079 mol) of nuclear-brominated PAES (2).

2nd Grignard and Grignard reaction:

0.079 mol of Mg shavings were placed in 50 ml of THF and stirred with 2 g of the brominated PAES (2) offset. The remaining PAES (2) was dissolved in 100 mL of THF. After Initiation of the reaction was the solution of brominated PAES (2) in THF with stirring dropwise. After the completion of the dropping, the reaction mixture became another 1 h at reflux cooked.

Subsequently, 0.079 mol (12.1 g) of 2-chlorobenzimidazole (3) was dissolved in 50 ml of THF and added dropwise with stirring to the reaction mixture obtained above. After completion of the dropwise addition, the reaction mixture was boiled for 3 h at reflux. Thereafter, the THF was replaced by diethyl ether. The workup was carried out by hydrolysis with ice, neutralization with half-concentrated hydrochloric acid, extraction with diethyl ether, washing the ethereal phase with water, drying the ethereal phase with Na ₂ SO ₄ , crystallization with cooling and recrystallization once. (4) was an almost colorless, microcrystalline powder. The yield was about 72% of theory (31.8 g, 0.057 mol).

The approaches described above are easily enlarged. The chemicals used are cheap and largely harmless. The required temperatures are in usual, easy to control areas, especially measures for cooling, e.g. at temperatures well below 0 ° C, are not required also not when dripping at the dropping point. A fail hardly soluble Intermediates are not observed. The use of inert gas not necessary; dry air or the solvent vapors sufficient. Up-scaling up to production scale, e.g. 1 t per year or more, seems readily possible. In the face of that is the inventive method for one large-scale Production well suited.

Claims (12)

Process for the preparation of a polyarylethersulfone of the general formula I

wherein n is an integer, preferably from the range 10 to 150, and R _{1 is} a five-membered heterocycle having at least one ring N atom, wherein ring atom 1 is a C atom when only one ring N atom is present characterized by the following steps: a) providing a polyaryl ether sulfone of the general formula II

wherein n is an integer, preferably from the range 10 to 150, b) halogenation of the polyarylethersulfone of the general formula II; c) reaction of the product from step b) with a suitable metal; d) reacting the metallated product of step c) with an electrophilic five-membered heterocycle having at least one ring N atom in which the leaving group is attached to a carbon atom when only one ring N atom is present to form a polyaryl ether sulfone to obtain the general formula I. Method according to claim 1, characterized in that the halogenation, i. step b), thermally and under the action of a reaction accelerating Catalyst performed becomes. Method according to claim 2, characterized in that the catalyst is selected from the group of transition metals, where Fe is preferred. Polyarylethersulfone of the general formula I.

wherein n is an integer, preferably from the range 10 to 150, and R _{1 is} a five-membered heterocycle having at least one ring N atom, wherein ring atom 1 is a C atom when only one ring N atom is present obtainable by the process according to any one of claims 1 to 3. Polyaryl ether sulfones according to claim 4, characterized in that that the five-membered heterocycle selected is from the group of azoles, azolidines, diazoles, diazolidines, triazoles, Triazolidines, tetrazoles, tetrazolidines or combinations thereof. Polyarylethersulfones according to claim 4 or 5 characterized characterized in that the five-membered heterocycle bears at least one substituent, wherein at least one ring N atom is unsubstituted. Polyarylethersulfones according to claim 6, characterized that the at least one substituent is the proton conductivity improving substituent, preferably an amino group. Polyarylethersulfones according to Claim 6, characterized that the at least one substituent is a fused aromatic, preferably a benzene ring. Polyarylethersulfones according to claim 8, characterized in that the fused aromatic carries at least one substituent one the proton conductivity improving substituent, particularly preferably an amino group. Polyarylethersulfones according to one of claims 4 to 9, characterized in that it has a degree of substitution in the range from 20 to 200 mol%, preferably from 80 to 150 mol%, particularly preferably from 100 to 120 mol%. Use of polyaryl ether sulfones of the general formula I.

wherein n is an integer, preferably from the range 10 to 150, and R _{1 is} a five-membered heterocycle having at least one ring N atom, wherein ring atom 1 is a C atom when only one ring N atom is present . which are obtainable by the process according to any one of claims 1 to 3, in electrolytes, ion exchangers, catalytically active substances, polymer blends and / or new materials. Use according to claim 11, characterized in that the polyarylethersulfones for membranes be used, preferably for Polymer electrolyte membranes (PEM), particularly preferred for PEM for fuel cells.