Aqueous emulsion polymerization of fluorinated monomers using a perfluoropolyether surfactant

Abstract

The invention relates to an aqueous emulsion polymerization of fluorinated monomers using perfluoropolyethers of the following formula (I) or (II). In particular, the perfluoropolyether surfactants correspond to formula (I) or (II) CF 3 —(OCF 2 ) m —O—CF 2 —X  (I) wherein m has a value of 1 to 6 and X represents a carboxylic acid group or salt thereof, CF 3 —O—(CF 2 ) 3 —(OCF(CF 3 )—CF 2 ) z —O-L-Y  (II) wherein z has a value of 0, 1, 2 or 3, L represents a divalent linking group selected from —CF(CF 3 )—, —CF 2 — and —CF 2 CF 2 — and Y represents a carboxylic acid group or salt thereof. The invention further relates to an aqueous dispersion of a fluoropolymer having the aforementioned perfluoropolyether surfactant(s).

1 . Method for making a fluoropolymer comprising an aqueous emulsion polymerization of one or more fluorinated monomers wherein said aqueous emulsion polymerization is carried out in the presence of a perfluoropolyether as an emulsifier, said perfluoropolyether being selected from the group consisting of perfluoropolyethers according to formula (I):  
       CF 3 —(OCF 2 ) m —O—CF 2 —X  (I)  wherein m has a value of 1 to 6 and X represents a carboxylic acid group or salt thereof, perfluoropolyethers according to formula (II):      CF 3 —O—(CF 2 ) 3 —(OCF(CF 3 )—CF 2 ) z —O-L-Y  (II)    wherein z has a value of 0, 1, 2 or 3, L represents a divalent linking group selected from —CF(CF 3 )—, —CF 2 — and —CF 2 CF 2 — and Y represents a carboxylic acid group or salt thereof, and    mixtures of perfluoropolyethers according to formula (I), (II), or combination thereof.    
   
   
       2 . Method according to  claim 1  wherein said one or more fluorinated monomers comprise one or more gaseous fluorinated monomers.  
   
   
       3 . Method according to  claim 1  wherein said one or more fluorinated monomers comprise perfluorinated monomers.  
   
   
       4 . Method according to  claim 1  wherein said aqueous emulsion polymerization is carried out in the presence of a fluorinated liquid and wherein said fluorinated liquid is emulsified using said perfluoropolyether as an emulsifier.  
   
   
       5 . Method according to  claim 1  wherein said aqueous emulsion polymerization is carried out using said perfluoropolyether as the only emulsifier.  
   
   
       6 . Method according to  claim 1  wherein the amount of said perfluoropolyether is between 0.01 and 5% by weight based on the amount of water in the emulsion polymerization.  
   
   
       7 . A dispersion comprising an aqueous dispersion of a fluoropolymer and a perfluoropolyether as an emulsifier, said perfluoropolyether being selected from the group consisting of perfluoropolyethers according to formula (I):  
       CF 3 —(OCF 2 ) m —O—CF 2 —X  (I)  wherein m has a value of 1 to 6 and X represents a carboxylic acid group or salt thereof,    perfluoropolyethers according to formula (II):      CF 3 —O—(CF 2 ) 3 —(OCF(CF 3 )—CF 2 ) z —O-L-Y  (II)    wherein z has a value of 0, 1, 2 or 3, L represents a divalent linking group selected from —CF(CF 3 )—, —CF 2 — and —CF 2 CF 2 — and Y represents a carboxylic acid group or salt thereof, and    mixtures of perfluoropolyethers according to formula (I), (II), or combination thereof.    
   
   
       8 . A dispersion according to  claim 7  wherein said dispersion is free of perfluoroalkanoic acids or salts thereof.  
   
   
       9 . A dispersion according to  claim 7  wherein the amount of said perfluoropolyether is between 0.001 and 5% by weight based on the fluoropolymer solids.  
   
   
       10 . A dispersion according to  claim 7  wherein the amount of fluoropolymer solids is between 10 and 30% by weight.  
   
   
       11 . A dispersion according to  claim 7  wherein the amount of solids is more than 30 and up to 70% by weight.  
   
   
       12 . A dispersion according to  claim 7  wherein the dispersion further comprises a non-ionic surfactant.  
   
   
       13 . A method comprising coating or impregnating a substrate using an aqueous dispersion as defined in  claim 7.