Process for producing fluorinated olefin/vinyl alcohol copolymer and film made by forming a composition containing the copolymer

1. A process for producing a fluorinated olefin/vinyl alcohol copolymer, comprising:

(1): emulsion polymerizing a fluorinated olefin of formula (1) and a vinyl ether of formula (2) in an aqueous medium comprising an emulsifier to obtain a fluorinated olefin/vinyl ether copolymer, wherein the mass ratio of the vinyl ether of formula (2) to the aqueous medium is from 5/95 to 70/30:

CF 2 ═CFX 1   (1)

CH 2 ═CHOR 1   (2)

wherein

in formula (1), X 1 is selected from the consisting of a fluorine atom, a chlorine atom, a trifluoromethyl group and —OC a F 2a+1a wherein a is an integer of from 1 to 3, and

in formula (2), R 1 is a group selected from the group consisting of a C 4-12 tertiary alkyl, a C 4-12 tertiary alkoxyalkyl group, a C 4-6 alicyclic hydrocarbon group which has an etheric oxygen atom, a C 6-10 aryl group and —Si(R 5 ) 3 , wherein R 5 is a C 1-10 alkyl group or an aryl group,

wherein said fluorinated olefin and said vinyl ether have an alternating copolymerization ratio of at least 95%; and

(2): converting said fluorinated olefin/vinyl ether copolymer to a fluorinated olefin/vinyl alcohol copolymer by substituting R 1 with a hydrogen atom.

2. The process for producing a fluorinated olefin/vinyl alcohol copolymer according to claim 1 , wherein R 1 is a t-butyl group.

3. The process for producing a fluorinated olefin/vinyl alcohol copolymer according to claim 1 , wherein (2) is carried out in the presence of an acid.

4. The process for producing a fluorinated olefin/vinyl alcohol copolymer according to claim 1 , wherein in the fluorinated olefin/vinyl ether copolymer obtained in (1), the molar ratio of the repeating units based on the fluorinated olefin represented by the formula (1) to the repeating units based on the vinyl ether represented by the formula (2) is from 40/60 to 60/40.

5. The process for producing a fluorinated olefin/vinyl alcohol copolymer according to claim 1 , wherein in (1), a vinyl ether of formula (3) is further copolymerized:

CH 2 ═CHOR 6   (3)

wherein R 6 is a group selected from the group consisting of an unsubstituted C 1-6 primary alkyl group, an unsubstituted C 1-6 secondary alkyl group, an unsubstituted C 6-12 cycloalkyl group, a C 1-6 primary alkyl group having at least one substituent, a c 1-6 secondary alkyl group having at least one substituent, and a C 6-12 cycloalkyl group having at least one substituent, wherein said substituent is a hydroxy group or a fluorine atom,

wherein said fluorinated olefin and said vinyl ether (2) and (3) have an alternating copolymerization ratio (1):((2)+(3)) of at least 95%.

6. The process for producing a fluorinated olefin/vinyl alcohol copolymer according to claim 1 , wherein the emulsifier is a compound represented by formula (4):

R 7 —(CH 2 ) n —COOX 2   (4)

wherein R 7 is a C 1-9 perfluoroalkyl group which may have an etheric oxygen atom, n is an integer of from 0 to 2, and X 2 is a hydrogen atom, NH 4 or an alkaline metal atom.

7. The process for producing a fluorinated olefin/vinyl alcohol copolymer according to claim 1 , wherein (1) is carried out in the presence of a basic compound.

8. The process for producing a fluorinated olefin/vinyl alcohol copolymer according to claim 1 , wherein the fluorinated olefin/vinyl alcohol copolymer has a weight average molecular weight of from 50,000 to 1,000,000.

9. A film made by forming a composition uprising the fluorinated olefin/vinyl alcohol copolymer obtained by the production process as defined in claim 1 .

10. The film according to claim 9 , wherein the forming is a casting method.