Fluorinated surfactants for making fluoropolymers

Abstract

The invention provides a method for making a fluoropolymer and a method for preparing a fluorinated surfactant.

What is claimed is: 
     
         1 . A method for making a fluoropolymer comprising:
 aqueous emulsion polymerizing of a fluorinated monomer in the presence of water,
 wherein the polymerizing further takes place in the presence of one or more first fluorinated surfactant having the general formula:
   [R f —(O) t —CHF—(CF2) n —COO—] i X i+ 
 
 
 wherein R f  represents a fluorinated aliphatic group, t is 0 or 1, and n is 0 or 1, and 
 further wherein X i+  represents a cation having a valence of i, and i is 1, 2, or 3. 
   
     
     
         2 . The method of  claim 1 , wherein R f  contains one or more ether oxygen atoms. 
     
     
         3 . The method of  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. 
     
     
         4 . The method of  claim 1 , wherein the polymerizing takes place in the presence of the one or more first fluorinated surfactant being present in an amount of from 0.001 to 5 percent by weight based on the weight of the water. 
     
     
         5 . The method of  claim 1 , wherein the polymerizing takes place in the further presence of one or more second fluorinated surfactant other than the first fluorinated surfactant defined in  claim 1 . 
     
     
         6 . The method of  claim 5  wherein the second fluorinated surfactant is a perfluorinated polyether surfactant. 
     
     
         7 . The method of  claim 1 , wherein the polymerizing results in an aqueous composition that comprises a fluoropolymer particle. 
     
     
         8 . The method of  claim 7 , wherein the fluoropolymer particle has an average diameter of from 40 nm to 400 nm. 
     
     
         9 . The method of  claim 7 , wherein the amount of fluoropolymer particle in the aqueous composition has a first concentration of from 15 to 70 percent by weight based on the weight of the water. 
     
     
         10 . The method of  claim 9 , further comprising increasing the amount of fluoropolymer particle in the aqueous composition from a first concentration to a second concentration, wherein the second concentration is greater than the first concentration. 
     
     
         11 . The method of  claim 7 , further comprising adding a non-ionic, non-fluorinated surfactant to the aqueous composition. 
     
     
         12 . The method of  claim 11 , wherein the non-ionic, non-fluorinated surfactant has the general formula:
   R 1 —O—[CH 2 CH 2 O] n —[R 2 O] m —R 3  
   wherein R 1  represents an aromatic or aliphatic hydrocarbon group having at least 8 carbon atoms, R 2  represents an alkylene group having 3 carbon atoms, R 3  represents an alkyl group having from 1 to 3 carbon atoms, n has a value of from 0 to 40, m has a value of from 0 to 40, and the sum of n +m is at least 2.   
     
     
         13 . The method of  claim 7 , further comprising applying the aqueous composition to a substrate. 
     
     
         14 . The method of  claim 1 , wherein the fluorinated monomer comprises a mixture of tetrafluoroethylene, hexafluoropropylene and a perfluorinated vinyl ether. 
     
     
         15 . The method of  claim 14 , wherein the perfluorinated vinyl ether is CF 3 CF 2 CF 2 —O—CF(CF 3 )—CF 2 —O—CF═CF 2.    
     
     
         16 . The method of  claim 14 , wherein the polymerizing takes place at 35° C. 
     
     
         17 . The method of  claim 14 , further comprising coagulating the aqueous composition with hydrochloric acid to give a coagulated material. 
     
     
         18 . The method of  claim 17 , further comprising agglomerating the coagulated material with gasoline to give an agglomerated material. 
     
     
         19 . The method of  claim 18 , further comprising drying the agglomerated material at 200° C. 
     
     
         20 . The method of  claim 14 , wherein the polymerizing results in an aqueous composition that comprises a fluoropolymer particle having a z-average particle size of from 100 to 150 nm. 
     
     
         21 . The method of  claim 14 , wherein the polymerizing results in an aqueous composition that comprises a fluoropolymer particle having a standard specific gravity of from 2.16 to 2.17. 
     
     
         22 . A method for preparing a fluorinated surfactant, the process comprising:
 carrying out a free radical reaction of a fluorinated olefin with a hydrocarbon alcohol and oxidizing the resulting reaction product,   wherein the fluorinated olefin has the formula:
   R f —(O) t —CF═CF2
 
   wherein R f  represents a fluorinated aliphatic group, t is 0 or 1,   and further wherein the fluorinated surfactant has the general formula:
   [Rf—(O) t —CHF—(CF 2 )—COO − ] i X i+ 
 
   wherein R f  and t are as defined above, and X i−  represents a cation having a valence i, and i is 1, 2, or 3.