Polyelectrolyte and process for producing the polyelectrolyte

Abstract

The present invention provides an electrolyte having high conductivity even under high-temperature low-humidification conditions (e.g. at a temperature of 100 to 120° C. and a humidity of 20 to 50% RH) and thereby makes it possible to realize a higher performance fuel cell. The present invention is a fluoropolymer electrolyte having an equivalent weight (EW) of not less than 250 but not more than 700 and a proton conductivity of not lower than 0.10 S/cm as measured at a temperature of 110° C. and a relative humidity of 50% RH and comprising a COOZ group- or SO 3 Z group-containing monomer unit, wherein Z represents an alkali metal, an alkaline earth metal, hydrogen atom or NR 1 R 2 R 3 R 4 in which R 1 , R 2 , R 3 and R 4 each independently represents an alkyl group containing 1 to 3 carbon atoms or hydrogen atom.

1 .- 7 . (canceled) 
     
     
         8 . An electrolyte membrane constituted of a fluoropolymer electrolyte having an equivalent weight (EW) of not less than 250 but not more than 700 and a proton conductivity of not lower than 0.10 S/cm as measured at a temperature of 110° C. and a relative humidity of 50% RH and
 which comprises a COOZ group- or SO 3 Z group-containing monomer unit, wherein Z represents an alkali metal, an alkaline earth metal, hydrogen atom or NR 1 R 2 R 3 R 4  in which R 1 , R 2 , R 3  and R 4  each independently represents an alkyl group containing 1 to 3 carbon atoms or hydrogen atom. 
 
     
     
         9 . An electrolyte solution containing the fluoropolymer electrolyte according to  claim 8 . 
     
     
         10 . A membrane-electrode assembly comprising the fluoropolymer electrolyte according to  claim 8 . 
     
     
         11 . A solid polymer fuel cell comprising the membrane-electrode assembly according to  claim 10 . 
     
     
         12 . A production method for a fluoropolymer electrolyte, comprising a step (1) of obtaining a fluoropolymer electrolyte precursor by emulsion polymerization and a step (2) of obtaining said fluoropolymer electrolyte by subjecting said fluoropolymer electrolyte precursor to a chemical treatment,
 said fluoropolymer electrolyte having an equivalent weight (EW) of not less than 250 but not more than 700 and a proton conductivity of not lower than 0.10 S/cm as measured at a temperature of 110° C. and a relative humidity of 50% RH and   comprising a COOZ group- or SO 3 Z group-containing monomer unit, wherein Z represents an alkali metal, an alkaline earth metal, hydrogen atom or NR 1 R 2 R 3 R 4  in which R 1 , R 2 , R 3  and R 4  each independently represents an alkyl group containing 1 to 3 carbon atoms or hydrogen atom.   
     
     
         13 . The production method according to  claim 12 ,
 wherein the step (1) comprises carrying out the emulsion polymerization at a temperature of not lower than 0° C. but not higher than 40° C.   
     
     
         14 . The production method according to  claim 12 ,
 wherein the fluoropolymer electrolyte precursor has a group convertible to COOZ or SO 3 Z (wherein Z represents an alkali metal, an alkaline earth metal, hydrogen atom or NR 1 R 2 R 3 R 4  in which R 1 , R 2 , R 3  and R 4  each independently represents an alkyl group containing 1 to 3 carbon atoms or hydrogen atom) by the chemical treatment, is melt-flowable and has a melt flow rate of 0.01 to 100 g/10 minutes.