Proton-conducting membrane and the use of the same

Abstract

The present invention relates to a novel proton-conducting polymer membrane based on polyazoles which can, because of its excellent chemical and thermal properties, be used in a variety of ways and is particularly useful as polymer electrolyte membrane (PEM) to produce membrane electrode units for PEM fuel cells.

1 - 22 . (cancelled).  
     
     
         23 . A proton-conducting polymer membrane based on polyazoles which has a concentration of phosphoric acid expressed as mol of acid per mol of recurring unit of the polymer of from 12 to 20 and is obtainable by a process comprising the steps 
 A) dissolving a polyazole polymer in polyphosphoric acid to form a solution,    B) heating the solution obtainable as described in step A) to temperatures of up to 400° c, under inert gas,    C) formulating a membrane on a support using the solution of the polyazole polymer from step B), and    D) treating the membrane formed in step C) in the presence of moisture at temperatures and for a time which are sufficient for the membrane to become self-supporting so that it can be detached from the support without damage.    
     
     
         24 . A membrane as claimed in  claim 23 , characterized in that the polyphosphoric acid used in step A) has an assay calculated as P 2 O 5  (acidimetric) of at least 85%.  
     
     
         25 . A membrane as claimed in  claim 23 , characterized in that a dispersion/suspension instead of a solution of the polymer is produced in step A).  
     
     
         26 . A membrane as claimed in  claim 23 , characterized in that the polymer used in step A) comprises recurring azole units of the formula (I) and/or (II)  
       
         
           
           
               
               
           
         
       
       where 
 Ar are identical or different and are each a tetravalent aromatic or heteroaromatic group which may have one or more rings,  
 Ar 1  are identical or different and are each a divalent aromatic or heteroaromatic group which may have one or more rings,  
 Ar 2  are identical or different and are each a divalent or trivalent aromatic or heteroaromatic group which may have one or more rings,  
 X are identical or different and are each oxygen, sulfur or an amino group bearing a hydrogen atom, a group having 1-20 carbon atoms, a branched or unbranched alkyl or alkoxy group, and an aryl group as further radical.  
 
     
     
         27 . A membrane as claimed in  claim 26 , wherein 
 X are identical or different and a branched or unbranched alkyl or alkoxy group.    
     
     
         28 . A membrane as claimed in  claim 23 , characterized in that a polymer selected from the group consisting of polybenzimidazole, poly(pyridines), poly(pyrimidines), polyimidazoles, polybenzothiazoles, polybenzoxazoles, polyoxadiazoles, polyquinoxalines, polythiadiazoles and poly(tetrazapyrenes) is used in step A).  
     
     
         29 . A membrane as claimed in  claim 23 , characterized in that the polymer used in step A) comprises one or more recurring benzimidazole units of the formula  
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
       where n and m are each an integer greater than or equal to 10.  
     
     
         30 . A membrane as claimed in  claim 29 , where n and m are each an integer greater than or equal to 100.  
     
     
         31 . A membrane as claimed in  claim 23 , characterized in that the viscosity is adjusted by addition of phosphoric acid after step B) and before step C).  
     
     
         32 . A membrane as claimed in  claim 23 , characterized in that the membrane produced in step C) is treated in the presence of moisture at temperatures and for a time until the membrane is self-supporting and can be detached from the support without damage.  
     
     
         33 . A membrane as claimed in  claim 23 , characterized in that the treatment of the membrane in step D) is carried out at temperatures of from >0° C. to 150° C. in the presence of moisture or water, dilute phosphoric acid and/or water vapor.  
     
     
         34 . A membrane as claimed in  claim 33 , characterized in that the treatment of the membrane in step D) is carried out at temperatures of from 10° C. to 120° C.  
     
     
         35 . A membrane as claimed in  claim 34 , characterized in that the treatment of the membrane in step D) is carried out at temperatures of from room temperature (20° C.) to 90° C.  
     
     
         36 . A membrane as claimed in  claim 23 , characterized in that the treatment of the membrane in step D) is carried out for from 10 second to 300 hours.  
     
     
         37 . A membrane of  claim 36 , characterized in that the treatment of the membrane in step D) is carried out for from 1 minute to 200 hours.  
     
     
         38 . A membrane as claimed in  claim 23 , characterized in that subsequent to the treatment in step D) the membrane is crosslinked by action of IR or NIR.  
     
     
         39 . A membrane as claimed in  claim 23 , characterized in that an electrode is chosen as the support in step C).  
     
     
         40 . A membrane as claimed in  claim 23 , characterized in that the membrane formed in step C) has a thickness of from 20 to 2000 μm.  
     
     
         41 . A membrane as claimed in  claim 40 , characterized in that the membrane formed in step C) has a thickness of from 30 to 1500 μm.  
     
     
         42 . A membrane as claimed in  claim 41 , characterized in that the membrane formed in step C) has a thickness of from 50 to 1200 μm.  
     
     
         43 . A membrane as claimed in  claim 23 , characterized in that the membrane formed in step D) has a thickness of from 15 to 400 μm and is self-supporting.  
     
     
         44 . A membrane as claimed in  claim 43 , characterized in that the membrane formed in step D) has a thickness of from 20 to 200 μm.  
     
     
         45 . A membrane as claimed in  claim 44 , characterized in that the membrane formed in step D) has a thickness of from 20 to 150 μm.  
     
     
         46 . A membrane as claimed in  claim 23 , characterized in that it has a layer comprising a catalytically active component.  
     
     
         47 . An electrode provided with a proton-conducting polymer coating based on polyazoles which has a concentration of phosphoric acid expressed as mol of acid per mol of recurring unit of the polymer of from 12 to 20 which membrane is obtainable by a process comprising the steps 
 A) dissolving a polyazole polymer in polyphosphoric acid to form a solution,    B) heating the solution obtainable as described in step A) to temperatures of up to 400° C., under inert gas,    C) applying a layer to an electrode using the solution of the polyazole polymer from step B), and    D) treating the layer formed in step C) at temperatures of from 0° C. to 150° C. in the presence of moisture.    
     
     
         48 . An electrode as claimed in  claim 47 , characterized in that the coating has a thickness of from 2 to 300 μm.  
     
     
         49 . An electrode as claimed in  claim 48 , characterized in that the coating has a thickness of from 5 to 250 μm.  
     
     
         50 . An electrode as claimed in  claim 49 , characterized in that the coating has a thickness of from 10 to 100 μm.  
     
     
         51 . A membrane-electrode unit comprising: 
 at least one electrode provided with a proton-conducting polymer coating based on polyazoles which has a concentration of phosphoric acid expressed as mol of acid per mol of recurring unit of the polymer of from 12 to 20 which membrane is obtainable by a process comprising the steps 
 i) dissolving a polyazole polymer in polyphosphoric acid to form a solution,  
 ii) heating the solution obtainable as described in step i) to temperatures of up to 400° C., under inert gas,  
 iii) applying a layer to an electrode using the solution of the polyazole polymer from step ii), and  
 iv) treating the layer formed in step iii) at temperatures of from 0° C. to 150° C. in the presence of moisture; and  
   at least one proton-conducting polymer membrane based on polyazoles which has a concentration of phosphoric acid expressed as mol of acid per mol of recurring unit of the polymer of from 12 to 20 and is obtainable by a process comprising the steps 
 A) dissolving a polyazole polymer in polyphosphoric acid to form a solution,  
 B) heating the solution obtainable as described in step A) to temperatures of up to 400° C., under inert gas,  
 C) formulating a membrane on a support using the solution of the polyazole polymer from step B), and  
 D) treating of the membrane formed in step C) in the presence of moisture at temperatures and for a time which are sufficient for the membrane to become self-supporting so that it can be detached from the support without damage.  
   
     
     
         52 . A membrane-electrode unit comprising: 
 at least one electrode, and    at least one proton-conducting polymer membrane based on polyazoles which has a concentration of phosphoric acid expressed as mol of acid per mol of recurring unit of the polymer of from 12 to 20 and is obtainable by a process comprising the steps 
 A) dissolving a polyazole polymer in polyphosphoric acid to form a solution,  
 B) heating the solution obtainable as described in step A) to temperatures of up to 400° C., under inert gas,  
 C) formulating a membrane on a support using the solution of the polyazole polymer from step B), and  
 D) treating of the membrane formed in step C) in the presence of moisture at temperatures and for a time which are sufficient for the membrane to become self-supporting so that it can be detached from the support without damage.  
   
     
     
         53 . A membrane-electrode unit as claimed in  claim 52 , characterized in that the polyphosphoric acid used in step A) has an assay calculated as P 2 O 5  (acidimetric) of at least 85%.  
     
     
         54 . A membrane-electrode unit as claimed in  claim 52 , characterized in that a dispersion/suspension instead of a solution of the polymer is produced in step A).  
     
     
         55 . A membrane as claimed in  claim 52 , characterized in that the polymer used in step A) comprises recurring azole units of the formula (I) and/or (II)  
       
         
           
           
               
               
           
         
       
       where 
 Ar are identical or different and are each a tetravalent aromatic or heteroaromatic group which may have one or more rings,  
 Ar 1  are identical or different and are each a divalent aromatic or heteroaromatic group which may have one or more rings,  
 Ar 2  are identical or different and are each a divalent or trivalent aromatic or heteroaromatic group which may have one or more rings,  
 X are identical or different and are each oxygen, sulfur or an amino group bearing a hydrogen atom, a group having 1-20 carbon atoms, a branched or unbranched alkyl or alkoxy group, and an aryl group as further radical.  
 
     
     
         56 . A membrane-electrode unit as claimed in  claim 55 , wherein 
 X are identical or different and a branched or unbranched alkyl or alkoxy group.    
     
     
         57 . A membrane-electrode unit as claimed in  claim 52 , characterized in that a polymer selected from the group consisting of polybenzimidazole, poly(pyridines), poly(pyrimidines), polyimidazoles, polybenzothiazoles, polybenzoxazoles, polyoxadiazoles, polyquinoxalines, polythiadiazoles and poly(tetrazapyrenes) is used in step A).  
     
     
         58 . A membrane-electrode unit as claimed in  claim 52 , characterized in that the polymer used in step A) comprises one or more recurring benzimidazole units of the formula  
       
         
           
           
               
               
           
         
         
           
           
               
               
           
         
       
       where n and m are each an integer greater than or equal to 10.  
     
     
         59 . A membrane-electrode unit as claimed in  claim 58 , where n and m are each an integer greater than or equal to 100.  
     
     
         60 . A membrane-electrode unit as claimed in  claim 52 , characterized in that the viscosity is adjusted by addition of phosphoric acid after step B) and before step C).  
     
     
         61 . A membrane-electrode unit as claimed in  claim 52 , characterized in that the membrane produced in step C) is treated in the presence of moisture at temperatures and for a time until the membrane is self-supporting and can be detached from the support without damage.  
     
     
         62 . A membrane-electrode unit as claimed in  claim 52 , characterized in that the treatment of the membrane in step D) is carried out at temperatures of from >0° C. to 150° C. in the presence of moisture or water, dilute phosphoric acid and/or water vapor.  
     
     
         63 . A membrane-electrode unit as claimed in  claim 62 , characterized in that the treatment of the membrane in step D) is carried out at temperatures of from 10° C. to 120° C.  
     
     
         64 . A membrane-electrode unit as claimed in  claim 63 , characterized in that the treatment of the membrane in step D) is carried out at temperatures of from room temperature (20° C.) to 90° C.  
     
     
         65 . A membrane-electrode unit as claimed in  claim 52 , characterized in that the treatment of the membrane in step D) is carried out for from 10 second to 300 hours.  
     
     
         66 . A membrane-electrode unit as claimed in  claim 65 , characterized in that the treatment of the membrane in step D) is carried out for from 1 minute to 200 hours.  
     
     
         67 . A membrane-electrode unit as claimed in  claim 52 , characterized in that subsequent to the treatment in step D) the membrane is crosslinked by action of IR or NIR.  
     
     
         68 . A membrane-electrode unit as claimed in  claim 52 , characterized in that an electrode is chosen as the support in step C).  
     
     
         69 . A membrane-electrode unit as claimed in  claim 52 , characterized in that the membrane formed in step C) has a thickness of from 20 to 2000 μm.  
     
     
         70 . A membrane-electrode unit as claimed in  claim 69 , characterized in that the membrane formed in step C) has a thickness of from 30 to 1500 μm.  
     
     
         71 . A membrane-electrode unit as claimed in  claim 70 , characterized in that the membrane formed in step C) has a thickness of from 50 to 1200 μm.  
     
     
         72 . A membrane-electrode unit as claimed in  claim 52 , characterized in that the membrane formed in step D) has a thickness of from 15 to 400 μm and is self-supporting.  
     
     
         73 . A membrane-electrode unit as claimed in  claim 72 , characterized in that the membrane formed in step D) has a thickness of from 20 to 200 μm.  
     
     
         74 . A membrane-electrode unit as claimed in  claim 73 , characterized in that the membrane formed in step D) has a thickness of from 20 to 150 μm.  
     
     
         75 . A membrane-electrode unit as claimed in  claim 52 , characterized in that the membrane has a layer comprising a catalytically active component.  
     
     
         76 . A membrane-electrode unit as claimed in  claim 52 , characterized in that the unit comprises at least one further polymer membrane based on polyazoles and/or a polymer blend membrane comprising at least one polymer based on polyazoles.  
     
     
         77 . A fuel cell comprising one or more membrane-electrode units, wherein the unit includes: 
 at least one electrode, and    at least one proton-conducting polymer membrane based on polyazoles which has a concentration of phosphoric acid expressed as mol of acid per mol of recurring unit of the polymer of from 12 to 20 and is obtainable by a process comprising the steps 
 A) dissolving a polyazole polymer in polyphosphoric acid to form a solution,  
 B) heating the solution obtainable as described in step A) to temperatures of up to 400° C., under inert gas,  
 C) formulating a membrane on a support using the solution of the polyazole polymer from step B), and  
 D) treating the membrane formed in step C) in the presence of moisture at temperatures and for a time which are sufficient for the membrane to become self-supporting so that it can be detached from the support without damage.