Fluorinated surfactants for making fluoropolymers

Abstract

The invention provides a fluorinated surfactant having the general formula: [R f —(O) t —CHF—(CF 2 ) n —COO—] i X i+   (I) wherein R f represents a partially or fully fluorinated aliphatic group optionally interrupted with one or more oxygen atoms, t is 0 or 1 and n is 0 or 1, X i+ represents a cation having a valence i and i is 1, 2 or 3. The surfactant can be used in emulsion polymerization of fluoromonomers to prepare fluoropolymers.

1 . A fluorinated surfactant having the general formula:
   [R f —(O) t —CHF—(CF 2 ) n —COO − ] i X i+   (I)
   
       wherein R f  represents a partially or fully fluorinated aliphatic group optionally interrupted with one or more oxygen atoms, t is 0 or 1 and n is 0 or 1, X′ represents a cation having a valence i and i is 1, 2 or 3. 
     
     
         2 . A fluorinated surfactant according to  claim 1  wherein R f  represents a perfluorinated aliphatic group that is optionally interrupted with one or more oxygen atoms. 
     
     
         3 . A fluorinated surfactant according to  claim 1  wherein t is 1 and wherein R f  is selected from the group consisting of perfluorinated aliphatic groups of 1 to 6 carbon atoms and perfluorinated groups of the formula R f   1 —[OR f   2 ] p —[OR f   3 ] q  wherein R f   1  is a perfluorinated aliphatic group of 1 to 6 carbon atoms, R f   2  and R f   3  each independently represents a linear or branched perfluorinated alkylene of 1, 2, 3 or 4 carbon atoms and p and q each independently represent a value of 0 to 4 and wherein the sum of p and q is at least 1. 
     
     
         4 . 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 one or more fluorinated surfactants as defined in  claim 1 . 
     
     
         5 . Method according to  claim 4  wherein the amount of said one or more fluorinated surfactants is between 0.001 and 5% by weight based on the amount of water in the aqueous phase of the aqueous emulsion polymerization. 
     
     
         6 . Method according to  claim 4  wherein said aqueous emulsion polymerization further comprises one or more fluorinated surfactants other than said fluorinated surfactants defined in  claim 1 . 
     
     
         7 . Method according to  claim 6  wherein said further fluorinated surfactants comprise perfluorinated polyether surfactants. 
     
     
         8 . Aqueous composition comprising one or more fluorinated surfactants as defined in  claim 1 . 
     
     
         9 . Aqueous composition according to  claim 8  wherein said aqueous composition comprises fluoropolymer particles. 
     
     
         10 . Aqueous composition according to  claim 9  wherein said fluoropolymer particles have an average diameter of 40nm to 400nm. 
     
     
         11 . Aqueous composition according to  claims 9  wherein the amount of fluoropolymer particles is between 15 and 70% by weight. 
     
     
         12 . Aqueous composition according to  claim 9  further comprising a non-ionic non-fluorinated surfactant. 
     
     
         13 . Method of applying an aqueous composition as defined in  claim 9  to a substrate. 
     
     
         14 . A process for producing a fluorinated surfactant, the process comprising:
 carrying out a free radical reaction of a fluorinated olefin of formula
   R f —(O) t —CF═CF 2    (II)
 
   
       wherein R f  represents a partially or fully fluorinated aliphatic group optionally interrupted with one or more oxygen atoms, t is 0 or 1 and n is 0 or 1, X i+  represents a cation having a valence i and i is 1, 2 or 3
 with a hydrocarbon alcohol; and 
 oxidizing the resulting reaction product, 
 wherein the fluorinated surfactant has the general formula:
   [R f —(O) t —CHF—(CF 2 ) n —COO − ] i X i+   (I)
 
 
 
       wherein t is 1 and wherein R f  is selected from the group consisting of perfluorinated aliphatic groups of 1 to 6 carbon atoms and perfluorinated groups of the formula R f   1 —[OR f   2 ] p —[OR f   3 ] q — wherein R f   1  is a perfluorinated aliphatic group of 1 to 6 carbon atoms, R f   2  and R f   3  each independently represents a linear perfluorinated alkylene of 1, 2, 3 or 4 carbon atoms and p and q each independently represent a value of 0 to 4 and wherein the sum of p and q is at least 1, and wherein n is 0 or 1, X i+  represents a cation having a valence i and i is 1, 2 or 3.