Process for producing fluoroionomer, method for purification and concentration of the ionomer, and method of film formation

1. A process for producing a fluorinated ionomer block copolymer, comprising the steps of: copolymerizing, in the presence of a polymerization initiator and an iodine compound, (i) a compound represented by Formula (I)

(M) 1/L OSO 2 CFY(CF 2 ) m O(CFXCF 2 O) n CF═CF 2   (I)

wherein M is H or a metal with a valence of L wherein L is 1, 2 or 3, X is F, Cl or CF 3 , Y is a halogen atom, m is 1 to 5, and n is 0 to 5, (ii) tetrafluoroethylene and (iii) at least one third monomer selected from the group consisting of hexafluoropropylene and perfluoroalkyl vinyl ether of structure CF 2 ═CFORf wherein Rf is C 1 to C 5 perfluoroalkyl, to form a fluorine-containing polymer chain segment B containing sulfonic acid groups; and reacting, in the presence of a polymerization initiator, the fluorine-containing polymer chain segment B, tetrafluoroethylene and at least one third monomer selected from the group consisting of hexafluoropropylene, and perfluoroalkyl vinyl ether of structure CF 2 ═CFORf wherein Rf is C 1 to C 5 perfluoroalkyl, to form a fluorine-containing polymer chain segment A which is different from the fluorine-containing polymer chain segment B;

wherein the fluorine-containing polymer chain segment B comprises:

(i) 5 to 49 mole % of repeating units derived from the compound represented by Formula (I),

(ii) 50 to 94 mole % of repeating units derived from tetrafluoroethylene, and

(iii) 0.5 to 20 mole % of repeating units derived from the third monomer(s).

2. The process of claim 1 , further comprising the step of:

dissolving or dispersing the product of the reacting step to form a solution or dispersion; and

subjecting the solution or dispersion to ultrafiltration or dialysis.

3. A method for purifying and concentrating the fluorinated ionomer obtained according to the method of claim 1 , comprising subjecting a fluorinated ionomer solution or dispersion to ultrafiltration or dialysis.

4. A method for forming a film of a fluorinated ionomer, comprising casting on a substrate a concentrated fluorinated ionomer solution or dispersion obtained by the method according to claim 3 .

5. A method according to claim 4 , wherein a cation affinity substance is added as a film-forming aid in the film formation by casting of the concentrated fluorinated ionomer solution or dispersion on a substrate.

6. A method for forming a film of a fluorinated ionomer, comprising the steps of:

1copolymerizing, in the presence of a polymerization initiator, (i) a compound represented by Formula (I)

(M) 1/L OSO 2 CFY(CF 2 ) m O(CFXCF 2 O) n CF═CF 2   (I)

wherein M is H or a metal with a valence of L wherein L is 1, 2 or 3, X is F, Cl or CF 3 , Y is a halogen atom, m is 1 to 5, and n is 0 to 5, (ii) tetrafluoroethylene and (iii) at least one third monomer selected from the group consisting of hexafluoropropylene and perfluoroalkyl vinyl ether of structure CF 2 ═CFORf wherein Rf is C 1 to C 5 perfluoroalkyl, to produce a fluorinated ionomer;

2) subjecting a solution or dispersion of the fluorinated ionomer of step (1) to ultrafiltration or dialysis to produce a concentrated solution or dispersion of the fluorinated ionomer; and

3) casting on a substrate the concentrated solution or dispersion of the fluorinated ionomer, wherein polyethylene glycol is added as a film-forming aid.

7. A process for producing a sulfonic acid functional group-containing fluorinated ionomer comprising 1 to 50 mole % of repeating units derived from a monomer represented by a sulfonic acid functional group-containing perhalogenated monomer of Formula (I)

(M) 1/L OSO 2 CFY(CF 2 ) m O(CFXCF 2 O) n CF═CF 2   (I)

wherein M is H or a metal with a valence of L wherein L is 1, 2 or 3, X is F, Cl or CF 3 , Y is a halogen atom, m is 1 to 5, and n is 0 to 5; 50 to 99 mole % of repeating units derived from tetrafluoroethylene; and 0 to 10 mole % of repeating units derived from a third monomer or monomers copolymerizable therewith; the process comprising carrying out solution polymerization or suspension polymerization in any of the polymerization media (1) to (4):

(1) Solvent A, which is an organic solvent capable of dissolving a sulfonic acid functional group-containing perhalogenated monomer at a concentration of 0.005 mole/L or higher;

(2) a mixed solvent comprising Solvent B and Solvent A, wherein Solvent B is a solvent incompatible with Solvent A;

(3) Solvent D, which is an acid capable of dissolving a sulfonic acid functional group-containing perhalogenated monomer at a concentration of 0.005 mole/L or higher;

(4) a mixed solvent comprising Solvent E and Solvent D, wherein Solvent B is a solvent incompatible with Solvent D.

8. A process according to claim 7 , wherein the polymerization medium is a mixed solvent obtained by adding Solvent C, which is another solvent compatible with Solvent A, to Solvent A or to the mixed solvent comprising Solvent A and Solvent B.

9. A process according to claim 7 , wherein the polymerization medium is a mixed solvent obtained by adding Solvent F, which is another solvent compatible with Solvent D, to Solvent D or to the mixed solvent comprising Solvent D and Solvent E.

10. A process according to claim 7 , wherein m is 1, n is 0 to 5, X is CF 3 and Y is F.

11. A process according to claim 10 , wherein n is 0.

12. A method according to claim 6 , wherein M is H or Na.

13. A method according to claim 7 , wherein Solvent A is an organic solvent having a dielectric constant of 6 to 60.

14. A method according to claim 6 , wherein the fluorinated ionomer comprises:

(i) 5 to 49 mole % of repeating units derived from the compound represented by Formula (I),

(ii) 50 to 94 mole % of repeating units derived from tetrafluoroethylene, and

(iii) 0.5 to 20 mole % of repeating units derived from the third monomer(s).

15. A method for forming a film of a fluorinated ionomer, comprising the steps of:

1) copolymerizing, in the presence of a polymerization initiator and an iodine compound, (i) a compound represented by Formula (I)

(M) 1/L OSO 2 CFY(CF 2 ) m O(CFXCF 2 O) n CF═CF 2   (I)

wherein M is H or a metal with a valence of L wherein L is 1, 2 or 3, X is F, Cl or CF 3 , Y is a halogen atom, m is 1 to 5, and n is 0 to 5, (ii) tetrafluoroethylene and (iii) at least one third monomer selected from the group consisting of hexafluoropropylene and perfluoroalkyl vinyl ether of structure CF 2 ═CFORf wherein Rf is C 1 to C 5 perfluoroalkyl, to form a fluorine-containing polymer chain segment B containing sulfonic acid groups;

2) reacting, in the presence of a polymerization initiator, the fluorine-containing polymer chain segment B, tetrafluoroethylene and at least one third monomer selected from the group consisting of hexafluoropropylene, and perfluoroalkyl vinyl ether of structure CF 2 ═CFORf wherein Rf is C 1 to C 5 perfluoroalkyl, to form a fluorine-containing polymer chain segment A which is different from the fluorine-containing polymer chain segment B, thereby yielding a fluorinated ionomer block copolymer;

3) subjecting a solution or dispersion of the fluorinated ionomer block copolymer of step (2) to ultrafiltration or dialysis to produce a concentrated solution or dispersion of the fluorinated ionomer block copolymer; and

4) casting on a substrate the concentrated solution or dispersion of the fluorinated ionomer block copolymer, wherein polyethylene glycol is added as a film-forming aid.

16. A process according to claim 7 , wherein the ratio of repeating units derived from the third monomer is 0.5 to 10 mole %.

17. A method according to claim 15 , wherein the fluorine-containing polymer chain segment B comprises:

(i) 5 to 49 mole % of repeating units derived from the compound represented by Formula (I),

(ii) 50 to 94 mole % of repeating units derived from tetrafluoroethylene, and

(iii) 0.5 to 20 mole % of repeating units derived from the third monomer(s).