FLUOROOLEFIN/VINYL ALCOHOL COPOLYMER AND PROCESS FOR ITS PRODUCTION
To provide a process for producing a fluoroolefin/vinyl alcohol copolymer with sufficiently high productivity and excellent heat resistance, whereby a quality loss by coloration is prevented, and a fluoroolefin/vinyl alcohol copolymer obtainable by such a process. A process for producing a fluoroolefin/vinyl alcohol copolymer, which comprises a polymerization step of copolymerizing a specific fluoroolefin and a vinyl ether having a hydrogen atom of a hydroxy group of a vinyl alcohol substituted with a protective group which can be deprotected, and a deprotection step of substituting the protective group in polymerized units based on the vinyl ether in the copolymer obtained in the polymerization step, with a hydrogen atom to form a hydroxyl group, and the fluoroolefin/vinyl alcohol copolymer obtainable by such a process.
1 . A process for producing a fluoroolefin/vinyl alcohol copolymer, which comprises a polymerization step of copolymerizing a fluoroolefin represented by the following formula (1) and a vinyl ether represented by the following formula (2), and a deprotection step of substituting R 1 in polymerized units based on the vinyl ether in the copolymer obtained in the polymerization step, with a hydrogen atom to form a hydroxy group:
CF 2 ═CFX (1)
CH 2 ═CHOR 1 (2)
wherein X is a fluorine atom, a chlorine atom, a trifluoromethyl group or —OC a F 2a+1 (wherein a is an integer of from 1 to 3), and R 1 is a protective group to be substituted with a hydrogen atom by a deprotection reaction.
2 . The process for producing a fluoroolefin/vinyl alcohol copolymer according to claim 1 , wherein R 1 in the formula (2) is —CR 2 R 3 R 4 (wherein each of R 2 , R 3 and R 4 which are independent of one another, is a C 1-3 alkyl group), a C 1-6 alkoxymethyl group, a tetrahydrofuryl group, a tetrahydropyranyl group or a trialkylsilyl group (—Si(R 5 ) 3 wherein R 5 is a C 1-6 alkyl group or an aryl group).
3 . The process for producing a fluoroolefin/vinyl alcohol copolymer according to claim 1 , wherein the compound represented by the formula (2) is t-butyl vinyl ether.
4 . The process for producing a fluoroolefin/vinyl alcohol copolymer according to claim 1 , wherein R 1 is substituted with a hydrogen atom by an acid.
5 . The process for producing a fluoroolefin/vinyl alcohol copolymer according to claim 1 , wherein in the polymerization step, the molar ratio of the fluoroolefin represented by the formula (1) to the vinyl ether represented by the formula (2) i.e. (fluoroolefin)/(vinyl ether) is from 45/55 to 55/45.
6 . The process for producing a fluoroolefin/vinyl alcohol copolymer according to claim 1 , wherein a vinyl ether represented by the following formula (3) is further copolymerized:
CH 2 ═CHOR 6 (3)
wherein R 6 is a group which is not susceptible to a deprotection reaction in the deprotection step.
7 . A fluoroolefin/vinyl alcohol copolymer having an alternating copolymerization rate of a fluoroolefin represented by the following formula (1) and vinyl alcohol being at least 95%:
CF 2 ═CFX (1)
wherein X is a fluorine atom, a chlorine atom, a trifluoromethyl group or —OC a F 2a+1 (wherein a is an integer of from 1 to 3).
8 . The fluoroolefin/vinyl alcohol copolymer according to claim 7 , which has a 10 mass % thermal decomposition starting temperature of at least 340° C.