Fluoropolymer latex, process for its production, and fluoropolymer

Abstract

To provide a process for producing a fluoropolymer latex, which is excellent in the productivity of the fluoropolymer latex, and which can produce a fluoropolymer latex excellent in the storage stability, and to provide such a fluoropolymer latex. A process for producing a fluoropolymer latex, which comprises emulsion polymerizing a fluoromonomer in an aqueous medium containing from 0.001 to 10.0 mass % of a fluorine-containing emulsifier represented by the formula (1): F(CF 2 ) n O(CF 2 CF 2 O) m CF 2 COOA (wherein A is a hydrogen atom, an alkali metal or NH 4 , n is an integer of from 3 to 10, and m is 0 or an integer of from 1 to 3) to obtain the fluoropolymer latex.

1 . A fluoropolymer latex characterized by comprising a fluoropolymer and a fluorine-containing emulsifier represented by the formula (1): F(CF 2 ) n O(CF 2 CF 2 O) m CF 2 COOA (wherein A is a hydrogen atom, an alkali metal or NH 4 , n is an integer of from 3 to 10, and m is 0 or an integer of from 1 to 3).  
   
   
       2 . The fluoropolymer latex according to  claim 1 , wherein the fluoropolymer is a polymer of at least one fluoromonomer selected from the group consisting of tetrafluoroethylene, vinylidene fluoride, hexafluoropropylene, CF 2 ═C(OR f ) n F 2-n (wherein R f  is a C 1-8  perfluoroalkyl group or a perfluorooxyalkylene group containing at least one ether bond per molecule, n is 1 or 2, and any of carbon chains may be a straight chain, may contain a branched chain or may have a cyclic structure) and chlorotrifluoroethylene, if necessary with at least one monomer selected from the group consisting of CH 2 ═CHOR (wherein R is a C 1-8  alkyl group or an oxyalkylene group containing at least one ether bond, and any of carbon chains may be a straight chain, may contain a branched chain or may have a cyclic structure), propylene and ethylene, and if necessary with at most 10 mol % of crosslinking group-containing monomer.  
   
   
       3 . The fluoropolymer latex according to  claim 1 , wherein the fluoropolymer is at least one member selected from the group consisting of a tetrafluoroethylene polymer, a tetrafluoroethylene/chlorotrifluoroethylene copolymer, a tetrafluoroethylene/propylene copolymer, a tetrafluoroethylene/hexafluoropropylene copolymer, a vinylidene fluoride/hexafluoropropylene copolymer, a tetrafluoroethylene/vinylidene fluoride/hexafluoropropylene copolymer, a tetrafluoroethylene/CF 2 ═CFOCF 3  copolymer, a tetrafluoroethylene/CF 2 ═CFOC 3 F 7  copolymer, a tetrafluoroethylene/CF 2 ═CFOCF 3 /CF 2 ═CFOC 3 F 7  copolymer, a tetrafluoroethylene/CF 2 ═C(OC 2 F 5 ) 2  copolymer, a tetrafluoroethylene/methyl vinyl ether copolymer, a tetrafluoroethylene/ethyl vinyl ether copolymer, a tetrafluoroethylene/n-butyl vinyl ether copolymer, a tetrafluoroethylene/ethyl vinyl ether/n-butyl vinyl ether copolymer, a vinylidene fluoride/CF 2 ═CFOC 3 F 7  copolymer, an ethylene/hexafluoropropylene copolymer and a tetrafluoroethylene/propylene/vinylidene fluoride copolymer.  
   
   
       4 . The fluoropolymer latex according to  claim 1 , wherein the fluoropolymer is at least one member selected from the group consisting of a tetrafluoroethylene polymer, a tetrafluoroethylene (from 40 to 60 mol %)/propylene (from 60 to 40 mol %) copolymer, a tetrafluoroethylene (from 40 to 70 mol %)/CF 2 ═CFOCF 3  (from 60 to 30 mol %) copolymer, a tetrafluoroethylene (from 40 to 70 mol %)/CF 2 ═CFOC 3 F 7  (from 60 to 30 mol %) copolymer, a tetrafluoroethylene (from 40 to 70 mol %)/CF 2 ═C(OC 2 F 5 ) 2  (from 60 to 30 mol %) copolymer, a tetrafluoroethylene (from 70 to 30 mol %)/methyl vinyl ether (from 30 to 70 mol %) copolymer, a tetrafluoroethylene (from 70 to 30 mol %)/ethyl vinyl ether (from 30 to 70 mol %) copolymer, a tetrafluoroethylene (from 70 to 30 mol %)/n-butyl vinyl ether (from 30 to 70 mol %) copolymer, a tetrafluoroethylene (from 60 to 30 mol %)/ethyl vinyl ether (from 1 to 69 mol %)/n-butyl vinyl ether (from 1 to 69 mol %) copolymer, a vinylidene fluoride (from 40 to 70 mol %)/CF 2 ═CFOC 3 F 7  (from 60 to 30 mol %) copolymer, an ethylene (from 40 to 60 mol %)/hexafluoropropylene (from 60 to 40 mol %) copolymer and a tetrafluoroethylene (from 30 to 60 mol %)/propylene (from 20 to 50 mol %)/vinylidene fluoride (from 1 to 40 mol %) copolymer.  
   
   
       5 . The fluoropolymer latex according to  claim 1 , wherein the fluorine-containing emulsifier is F(CF 2 ) n OCF 2 CF 2 OCF 2 COOA (wherein A is a hydrogen atom, an alkali metal or NH 4 , and n is 3 or 4).  
   
   
       6 . A process for producing a fluoropolymer latex, which comprises emulsion polymerizing a fluoromonomer in an aqueous medium containing from 0.001 to 10.0 mass % of a fluorine-containing emulsifier represented by the formula (1): F(CF 2 ) n O(CF 2 CF 2 O) m CF 2 COOA (wherein A is a hydrogen atom, an alkali metal or NH 4 , n is an integer of from 3 to 10, and m is 0 or an integer of from 1 to 3) to obtain the fluoropolymer latex.  
   
   
       7 . The process for producing a fluoropolymer latex according to  claim 6 , wherein the fluoromonomer is at least one fluoromonomer selected from the group consisting of tetrafluoroethylene, vinylidene fluoride, hexafluoropropylene, CF 2 ═C(OR f ) n F 2-n  (wherein R f  is a C 1-8  perfluoroalkyl group or a perfluorooxyalkylene group containing at least one ether bond per molecule, n is 1 or 2, and any of carbon chains may be a straight chain, may contain a branched chain or may have a cyclic structure) and chlorotrifluoroethylene, and, if necessary, at least one monomer selected from the group consisting of CH 2 ═CHOR (wherein R is a C 1-8  alkyl group or an oxyalkylene group containing at least one ether bond, and any of carbon chains may be a straight chain, may contain a branched chain or may have a cyclic structure), propylene and ethylene is copolymerized and if necessary, at most 10 mol % of crosslinking group-containing monomer is copolymerized.  
   
   
       8 . The process for producing a fluoropolymer latex according to  claim 6 , wherein the fluorine-containing emulsifier is F(CF 2 ) n OCF 2 CF 2 OCF 2 COOA (wherein A is a hydrogen atom, an alkali metal or NH 4 , and n is 3 or 4).  
   
   
       9 . A fluoropolymer latex which is obtained by concentrating a fluoropolymer latex obtained by the process as defined in  claim 6 , to a fluoropolymer concentration of at least 30 mass %.  
   
   
       10 . A fluoropolymer which is obtained by coagulating a fluoropolymer latex obtained by the process as defined in  claim 6.