Fluoroolefin/vinyl alcohol copolymer and process for its production

Abstract

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.