Peroxide curable fluoropolymers obtainable by polymerization using non-fluorinated polyhydroxy emulsifiers

1. Method of making a curable fluoropolymer comprising (i) repeating units derived from vinylidene fluoride and (ii) at least one perfluorinated monomer selected from hexafluoropropene, tetrafluoroethene, a perfluorovinyl ether, a perfluoroallylether, and a combination thereof,

said method comprising polymerizing the monomers in an aqueous medium in a radical reaction containing (a) a first material selected from one or more reaction initiators, one or more chain transfer agent containing one or more halogens selected from iodine, bromine and a combination thereof, and (b) one or more non-fluorinated aliphatic polyhydroxy emulsifier containing at least one polyhydroxy unit having at least two adjacent hydroxyl groups and at least one long chain unit containing from 4 to 40 carbon atoms and,

wherein the polymerization is carried out without adding a fluorinated emulsifier; and

wherein the curable fluoropolymer has a CF 2 CH 2 I to CF 2 CH 2 OH group ratio of at least 10.

2. The method of claim 1 wherein the at least one polyhydroxy unit is cyclic and contains a six-membered ring and/or a five-membered ring.

3. The method of claim 1 wherein the polyhydroxy emulsifier is selected from alkyl(poly)glycosides, alkyoxy(poly)glycosides, polyoxyalkyl(poly)glycosides, and combinations thereof.

4. The method of claim 1 wherein the polyhydroxy emulsifier is selected from alkylglucosides according the general formula

wherein m represents an integer of from 1 to 10, and R represents an alkyl chain that may be interrupted by one or more oxygen atoms.

5. The method according claim 1 wherein the at least one polyhydroxy unit is acyclic.

6. The method of claim 5 wherein the at least one non-fluorinated aliphatic polyhydroxy emulsifier is represented by the general formula (III):

R 1 —C(═O)—N(R 3 )—Z  (III)

wherein R 3 is H or a linear or branched aliphatic residue containing from 1 to 8 carbon atoms, wherein the carbon chain of the aliphatic residue may optionally be interrupted by one or more than one ether oxygen atom and wherein R 1 represents a linear or branched aliphatic residue containing from 5 to 31 carbon atoms, and Z represents an acyclic polyhydroxy hydrocarbyl moiety having at least 2 hydroxy groups directly bonded to the carbon chain.

7. The method of claim 6 wherein Z contains an acyclic unit represented by the general formula

—(CHOH) n —,

wherein n represents an integer of from 2 up to and including 8.

8. The method of claim 1 wherein the chain transfer agent is selected from (a) alpha-omega diiodo alkanes, (b) alpha-omega diiodo fluoroalkanes and (c) alpha-omega diiodo perfluoroalkanes, each of (a) through (c) having from 1 to 12 carbon atoms.

9. The method of claim 1 wherein the polymerization is carried out in the presence of an iodine-containing cure-site monomer.

10. The method of claim 1 wherein the curable polymer contains from 14 to 80% wt of vinylidene fluoride comonomer.

11. The method of claim 1 wherein the curable fluoropolymer contains from about 0.1 to about 0.6% wt of iodine based on the total weight of the polymer.

12. The method of claim 1 wherein the curable fluoropolymer is present in an aqueous dispersion and has a Z-average particle size of from about 20 to about 300 nm.

13. The method of claim 1 wherein the curable fluoropolymer has a Mooney viscosity (ML 1+10 at 121° C.) of from about 20 to about 80.