POLYELECTROLYTE AND PROCESS FOR PRODUCING THE POLYELECTROLYTE

• US 20110020728A1
• Filed: 03/12/2009
• Published: 01/27/2011
• Est. Priority Date: 03/19/2008
• Status: Active Grant

• Current Assignee: Asahi Kasei Kabushiki Kaisha (Asahi Kasei Corporation), Daikin Industries Ltd
• Original Assignee: Asahi Kasei E-materials Corporation (Asahi Kasei Corporation), Daikin Industries Ltd
• Inventors: Miyake, Naoto, Kondo, Masahiro, Yoshimura, Takashi, Nakazawa, Masaharu, Shinoki, Noriyuki, Ino, Tadashi, Sakamoto, Naoki, Murai, Takahiko, Kita, Kohei
• Granted Patent: US 8,993,682 B2
• Time in Patent Office: Days
• US Class Current: 429/483
• CPC Class Codes: C08F 14/185 Monomers containing fluorine not covered by the groups C08F14/20 - C08F14/28
• CPC Class Codes: C08F 14/26 Tetrafluoroethene
• CPC Class Codes: C08F 2/16 Aqueous medium
• CPC Class Codes: C08F 2/26 anionic
• CPC Class Codes: C08F 20/04 Acids, Metal salts or ammonium salts thereof
• CPC Class Codes: C08F 214/26 Tetrafluoroethene
• CPC Class Codes: C08F 214/262 with fluorinated vinyl ethers
• CPC Class Codes: C08F 216/1475 Monomers containing sulfur and oxygen
• CPC Class Codes: C08F 28/02 by a bond to sulfur
• CPC Class Codes: C08F 2800/10 as molar percentages
• CPC Class Codes: C08F 2810/00 Chemical modification of a polymer
• CPC Class Codes: C08F 2810/50 wherein the polymer is a copolymer and the modification is taking place only on one or more of the monomers present in minority
• CPC Class Codes: C08F 6/22 Coagulation
• CPC Class Codes: C08F 8/12 Hydrolysis
• CPC Class Codes: C08F 8/22 by reaction with free halogens
• CPC Class Codes: C08F 8/26 Removing halogen atoms or halogen-containing groups from the molecule
• CPC Class Codes: C08F 8/44 Preparation of metal salts or ammonium salts
• CPC Class Codes: C08J 2327/18 Homopolymers or copolymers of tetrafluoroethylene
• CPC Class Codes: C08J 5/2237 containing fluorine
• CPC Class Codes: C08L 27/18 Homopolymers or copolymers or tetrafluoroethene
• CPC Class Codes: H01B 1/122 : Ionic conductors
• CPC Class Codes: H01M 8/1023 : having only carbon, e.g. polyarylenes, polystyrenes or polybutadiene-styrenes
• CPC Class Codes: H01M 8/1039 : halogenated, e.g. sulfonated polyvinylidene fluorides
• CPC Class Codes: Y02E 60/50 : Fuel cells

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 SO₃Z group-containing monomer unit, wherein Z represents an alkali metal, an alkaline earth metal, hydrogen atom or NR¹R²R³R⁴ in which R¹, R², R³ and R⁴ each independently represents an alkyl group containing 1 to 3 carbon atoms or hydrogen atom.

Claims

1. 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 SO₃Z group-containing monomer unit, wherein Z represents an alkali metal, an alkaline earth metal, hydrogen atom or NR¹R²R³R⁴ in which R¹, R², R³ and R⁴ each independently represents an alkyl group containing 1 to 3 carbon atoms or hydrogen atom.

2. The fluoropolymer electrolyte according to claim 1,

which comprises a repeating unit (α

) derived from a COOZ group- or SO₃Z group-containing monomer represented by the general formula (I);

CF₂═

CF(CF₂)_k—

O_l—

(CF₂CFY¹—

O)_n—

(CFY²)_m-A¹ 

 

(I)

wherein Y¹ represents F, Cl or a perfluoroalkyl group;

k represents an integer of 0 to 2, l represents 0 or 1, and n represents an integer of 0 to 8 and n atoms or groups of Y¹ may be the same or different;

Y² represents F or Cl;

m represents an integer of 0 to 6 provided that when m=0, l=0 and n=0;

m atoms of Y² may be the same or different; and

A¹ represents COOZ or SO₃Z in which Z represents an alkali metal, an alkaline earth metal, hydrogen atom or NR¹R²R³R⁴ in which R¹, R², R³ and R⁴ each independently represents an alkyl group containing 1 to 3 carbon atoms or hydrogen atom, and a repeating unit (β

) derived from an ethylenic fluoromonomer copolymerizable with said COOZ group- or SO₃Z group-containing monomer,

the content of the repeating unit (α

) being 10 to 95 mole percent and the content of the repeating unit (β

) being 5 to 90 mole percent, with the sum of the repeating unit (α

) content and the repeating unit (β

) content being 95 to 100 mole percent.

3. The fluoropolymer electrolyte according to claim 2,

wherein k is 0, l is 1, Y¹ is F, n is 0 or 1, Y² is F, m is 2 or 4 and A¹ is —

SO₃H.

4. The fluoropolymer electrolyte according to claim 3,

wherein n is 0 and m is 2.

5. The fluoropolymer electrolyte according to claim 1,

wherein the distance between ionic clusters at 25°

C. and a relative humidity of 50% RH as calculated from the formula (1) given below following small angle X-ray measurement is not shorter than 0.1 nm but not longer than 2.6 nm;

d=λ

/2/sin(θ

m) 

 

(1)

wherein d is said distance between ionic clusters, λ

is wavelength of incident X ray used in small angle X-ray scattering measurement and θ

m is peak-showing Bragg angle.

6. The fluoropolymer electrolyte according to claim 1,

which is obtained by a chemical treatment of a fluoropolymer electrolyte precursor,

wherein said fluoropolymer electrolyte precursor has a group convertible to COOZ or SO₃Z (wherein Z represents an alkali metal, an alkaline earth metal, hydrogen atom or NR¹R²R³R⁴ in which R¹, R², R³ and R⁴ each independently represents an alkyl group containing 1 to 3 carbon atoms or hydrogen atom) upon said chemical treatment, is melt-flowable and has a melt flow rate of 0.01 to 100 g/10 minutes.

7. The fluoropolymer electrolyte according to claim 6,

wherein the chemical treatment comprises immersion in an basic reacting liquid.

8. An electrolyte membrane constituted of the fluoropolymer electrolyte according to claim 1.

9. An electrolyte solution containing the fluoropolymer electrolyte according to claim 1.

10. A membrane-electrode assembly comprising the fluoropolymer electrolyte according to claim 1.

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 SO₃Z group-containing monomer unit, wherein Z represents an alkali metal, an alkaline earth metal, hydrogen atom or NR¹R²R³R⁴ in which R¹, R², R³ and R⁴ 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 SO₃Z (wherein Z represents an alkali metal, an alkaline earth metal, hydrogen atom or NR¹R²R³R⁴ in which R¹, R², R³ and R⁴ 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.