Aqueous emulsion polymerization process for producing fluoropolymers

Abstract

The present invention provides a method of making a fluoropolymer comprising polymerizing one or more fluorinated monomers in an aqueous emulsion polymerization in the presence of a fluorinated surfactant selected from fluorinated surfactants of formula (I): [R f O-L-CO 2 − ] i X i+   (I) wherein R f is selected from a partially fluorinated alkyl group, a fully fluorinated alkyl group, a partially fluorinated alkyl group that is interrupted with one or more oxygen atoms, and a fully fluorinated alkyl group that is interrupted with one or more oxygen atoms; L is selected from a partially fluorinated alkylene group, a fully fluorinated alkylene group, a partially fluorinated alkylene group that is interrupted with one or more oxygen atoms, and a fully fluorinated alkylene group that is interrupted with one or more oxygen atoms; X i+ represents a cation having the valence i; and i is 1, 2, or 3; further wherein at least part of the fluorinated surfactant is added to the aqueous phase as an aqueous mixture with at least one fluorinated liquid, and further wherein when the fluorinated surfactant is a perfluorinated polyethercarboxylic acid, the fluorinated liquid is not a perfluoropolyether.

1 . A method of making a fluoropolymer comprising polymerizing one or more fluorinated monomers in an aqueous emulsion polymerization in the presence of a fluorinated surfactant selected from fluorinated surfactants of formula (I):
   [R f O-L-CO 2   − ] i X i+   (I)   
     wherein R f  is selected from a partially fluorinated alkyl group, a fully fluorinated alkyl group, a partially fluorinated alkyl group that is interrupted with one or more oxygen atoms, and a fully fluorinated alkyl group that is interrupted with one or more oxygen atoms; L is selected from a partially fluorinated alkylene group, a fully fluorinated alkylene group, a partially fluorinated alkylene group that is interrupted with one or more oxygen atoms, and a fully fluorinated alkylene group that is interrupted with one or more oxygen atoms; X i+  represents a cation having the valence i; and i is 1, 2, or 3, 
     further wherein at least part of the fluorinated surfactant is added to the aqueous phase as an aqueous mixture with at least one fluorinated liquid, and further wherein when the fluorinated surfactant is a perfluorinated polyethercarboxylic acid, the fluorinated liquid is not a perfluoropolyether. 
   
   
       2 . The method of  claim 1  wherein the fluorinated surfactant is selected from:
 i) fluorinated surfactants of formula (II):
   CF 3 —(OCF 2 ) m —O—CF 2 —X  (II) 
   
     wherein m has a value of from 1 to 6 and X represents a carboxylic acid or salt thereof;
 ii) fluorinated surfactants of formula (III):
   CF 3 —O—(CF2) 3 -(OCF(CF 3 )CF 2 ) z —O-L-Y  (III) 
 
 
     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;
 iii) fluorinated surfactants of formula (IV):
   [R f   1 —(O) t —CQH—(CF 2 ) p —O] n —R-G  (IV) 
 
 
     wherein R f   1  represents a partially or fully fluorinated aliphatic group optionally interrupted with one or more oxygen atoms, Q represents F or CF 3 , R is an aliphatic or aromatic hydrocarbon group, G represents a carboxylic or sulfonic acid or salt thereof, t is 0 or 1, and n is 1, 2, or 3;
 iv) fluorinated surfactants of formula (V)
   R f   2 —(O) s —CHF—(CF 2 ) v —X  (V) 
 
 
     wherein R f   2  represents a partially or fully fluorinated aliphatic group optionally interrupted with one or more oxygen atoms, s is 0 or 1, v is 0 or 1, and X is a carboxylic acid or salt thereof;
 v) fluorinated surfactants of formula (VI)
   R f   3 —O—CF 2 CF 2 —X  (VI) 
 
 
     wherein R f   3  represents a linear or branched perfluoroalkyl group having 1, 2, 3, or 4 carbon atoms and X represents a carboxylic acid group or salt thereof. 
   
   
       3 . The method of  claim 1  wherein the fluorinated liquid is perfluorinated. 
   
   
       4 . The method of  claim 1 , wherein the fluorinated liquid is selected from a perfluoroalkane; a perfluorinated N-alkyl substituted morpholine; (R f ′) 3 N, wherein each R f ′ is independently selected from a fluorinated alkyl group having from 1 to 10 carbon atoms; and combinations thereof. 
   
   
       5 . The method of  claim 1  wherein the fluorinated liquid is selected from perfluoropolyethers of formula (VIII):
   R f ″—(—OCF 2 ) x —(OCF 2 CF 2 ) y —(CF(CF 3 )—CF 2 ) z —(OCF(CF 3 )) a -Q  (VIII)   
     wherein R f ″ is selected from perfluoroalkyl groups having from 1 to 10 carbon atoms; Q is selected from R f ″ and R f ″—(OCF 2 ) x —(OCF 2 CF 2 ) y —(CF(CF 3 )—CF 2 ) z —(OCF(CF 3 )) a ; each x, y, z, and a is independently selected from 0 to 10 with the proviso that the sum of x+y+z+a is at least 1. 
   
   
       6 . The method of  claim 1  wherein the fluorinated liquid is selected from fluorinated polyethers of formula (X):
   R f ′″—O—CFH—CF 2 —O—R  (X)   
     wherein R f ′″ is selected from a perfluorinated alkyl group having from 1 to 10 carbon atoms and R is selected from CH 3  and R f ′″, wherein when R is R f ′″, it may be the same or different than the other R f′″.    
   
   
       7 . The method of  claim 1  wherein the fluorinated liquid is selected from fluorinated polyethers of the formula (IX):
   R f ″″—[OC 3 F 6 ] n —O—CHFCF 3   (IX)   
     wherein R f ″″ is selected from a perfluorinated alkyl group having from 1 to 4 carbon atoms, and n is from 1 to 10. 
   
   
       8 . The method of  claim 1  wherein the fluorinated liquid has a boiling point of at least 100° C. 
   
   
       9 . The method of  claim 1  wherein the amount of fluorinated surfactant not more than 1.0% by weight based on the weight of the aqueous dispersion. 
   
   
       10 . The method of  claim 1  wherein the aqueous phase further comprises a second fluorinated surfactant corresponds to the following general formula (XI):
   Y—R F -Z-M  (XI)   
     wherein Y represents hydrogen, Cl or F; R F  represents a linear or branched perfluorinated alkylene having 4 to 10 carbon atoms; Z represents COO— or SO 3 — and M represents a monovalent cation. 
   
   
       11 . The method of  claim 1  wherein the amount of the fluorinated liquid in the aqueous mixture is between 0.1 and 70% by weight relative to the total weight of the aqueous mixture. 
   
   
       12 . The method of  claim 1  wherein the anion of the fluorinated surfactant has a molecular weight of not more than 1000 grams per mole. 
   
   
       13 . The method of  claim 1  wherein the fluorinated surfactant, when administered to a rat, has a renal recovery rate of at least 50% of the administered amount 96 hours after administration and further wherein the renal half-life is not more than 30 hours. 
   
   
       14 . The method of  claim 1  wherein each aliphatic portion of the fluorinated surfactant has not more than three carbon atoms. 
   
   
       15 . The method of  claim 1  wherein the amount of fluorinated surfactant is from 1 to 40% by weight based on the weight of the aqueous mixture. 
   
   
       16 . The method of  claim 1  wherein the fluorinated surfactant forms a microemulsion. 
   
   
       17 . The method of  claim 1  wherein the aqueous mixture comprises droplets having an average particle size of from 5 to 2000 nm. 
   
   
       18 . The method of  claim 1  wherein the amount of fluorinated surfactant is less than 1% by weight based on the weight of the aqueous dispersion. 
   
   
       19 . An aqueous mixture comprising a fluorinated surfactant selected from:
 i) fluorinated surfactants of formula (II):
   CF 3 —(OCF 2 ) m —O—CF 2 —X  (II) 
   
     wherein m has a value of from 1 to 6 and X represents a carboxylic acid or salt thereof;
 ii) fluorinated surfactants of formula (III):
   CF 3 —O—(CF2) 3 -(OCF(CF 3 )CF 2 ) z —O-L-Y  (III) 
 
 
     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;
 iii) fluorinated surfactants of formula (IV):
   [R f   1 —(O) t —CQH—(CF 2 ) p —O] n —R-G  (IV) 
 
 
     wherein R f   1  represents a partially or fully fluorinated aliphatic group optionally interrupted with one or more oxygen atoms, Q represents F or CF 3 , R is an aliphatic or aromatic hydrocarbon group, G represents a carboxylic or sulfonic acid or salt thereof, t is 0 or 1, and n is 1, 2, or 3;
 iv) fluorinated surfactants of formula (V)
   R f   2 —(O) s —CHF—(CF 2 ) v —X  (V) 
 
 
     wherein R f   2  represents a partially or fully fluorinated aliphatic group optionally interrupted with one or more oxygen atoms, s is 0 or 1, v is 0 or 1, and X is a carboxylic acid or salt thereof;
 v) fluorinated surfactants of formula (VI)
   R f   3 —O—CF 2 CF 2 —X  (VI) 
 
 
     wherein R f   3  represents a linear or branched perfluoroalkyl group having 1, 2, 3, or 4 carbon atoms and X represents a carboxylic acid group or salt thereof, the aqueous mixture further comprising at least one fluorinated liquid. 
   
   
       20 . An aqueous mixture comprising a fluorinated surfactant selected from fluorinated surfactants of formula (I):
   [R f O-L-CO 2   − ] i X i+   (I)   
     wherein R f  is selected from a partially fluorinated alkyl group, a fully fluorinated alkyl group, a partially fluorinated alkyl group that is interrupted with one or more oxygen atoms, and a fully fluorinated alkyl group that is interrupted with one or more oxygen atoms; L is selected from a partially fluorinated alkylene group, a fully fluorinated alkylene group, a partially fluorinated alkylene group that is interrupted with one or more oxygen atoms, and a fully fluorinated alkylene group that is interrupted with one or more oxygen atoms; X i+  represents a cation having the valence i; and i is 1, 2, or 3;
 further comprising at least one fluorinated liquid, and further wherein when the fluorinated surfactant is a perfluorinated polyethercarboxylic acid, the fluorinated liquid is not a perfluoropolyether.