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1. WO2007142888 - CONCENTRATED FLUOROPOLYMER DISPERSIONS STABILIZED WITH ANIONIC POLYELECTROLYTE DISPERSING AGENTS

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[ EN ]

CLAIMS
What is claimed is:
1. An aqueous fluoropolymer dispersion comprising
fluoropolymer particles having an average particle size of about 10 to about 400 nm, said dispersion having a solids content of about 35 to about 70 wt% and comprising about 0.03 wt% to about 10 wt% anionic
polyelectrolyte dispersing agent based on the weight of fluoropolymer solids, said dispersion being substantially free of nonionic surfactant and having a Gel Time of at least about 100 seconds.
2. The dispersion of claim 1 further comprising acrylic polymer of acid content of 20% or more by weight.
3. The dispersion of claim 1 wherein said fluoropolymer particles have an average particle size of about 100 to about 350 nm.
4. The dispersion of claim 1 wherein the solids content of the dispersion is about 50 to about 70 wt%.
5. The dispersion of claim 1 wherein said anionic polyelectrolyte dispersing agent is present in an amount of about 0.1 wt% to about 10 wt% based on the weight of fluoropolymer solids.
6. The dispersion of claim 2 wherein said acrylic polymer of acid content of 20% or more is present in an amount of about 0.01 to about 0.5 wt% based the weight of the aqueous portion of the dispersion.
7. The dispersion of claim 2 wherein said acrylic polymer of acid content of 20% or more is present in an amount of about 0.02 to about 0.4 wt% based the weight of the aqueous portion of the dispersion.
8. The dispersion of claim 1 wherein said dispersion contains less than about 300 ppm fluorosurfactant based on the weight of said dispersion
9. The dispersion of claim 1 wherein said dispersion contains less than about 100 ppm fluorosurfactant based on the weight of said dispersion.
10. The dispersion of claim 1 wherein said dispersion contains less than about 50 ppm fluorosurfactant based on the weight of said dispersion.

11. The dispersion of claim 1 wherein said dispersion has a Ge! Time of at least 300 seconds.
12. The dispersion of claim 1 wherein said dispersion has a Gel Time of at least 500 seconds.
13. The dispersion of claim 1 further comprising anionic surfactant.
14. The dispersion of claim 13 wherein said anionic surfactant is present in an amount of about 0.05 to about 10 wt% based on the weight of fluoropolymer solids.
15. The dispersion of claim 1 having a pH of at least about 9.0.

16. The dispersion of claim 1 having a pH of at least about 9.5.

17. The dispersion of claim 1 having a surface tension of greater than about 35 mS/cm.
18. The dispersion of claim 1 wherein the anionic polyelectrolyte dispersing agent is an anionic polymer, having a linear or branched structure, with anionic groups distributed along the polymeric chain.
19. The dispersion of claim 1 wherein the anionic polyelectrolyte dispersing agent has an equivalent weight greater than about 150.
20. The dispersion of claim 1 wherein the equivalent weight of the anionic polyelectrolyte dispersing agent is less than about 50,000.
21. The dispersion of claim 1 wherein the number average molecular weight of the anionic polyelectrolyte dispersing agent is at least about 500.
22. The dispersion of claim 1 wherein the anionic polyelectrolyte dispersing agent contains at least 2 anionic functional groups per molecule. .
23. The dispersion of claim 1 wherein the anionic polyelectrolyte dispersing agent contains anionic functional groups selected from carboxylates, sulphates, sulphonates, phosphates, and phosphonates.
24. The dispersion of claims 1 wherein the anionic polyelectrolyte dispersing agent does not contain fluorine atoms.
25. The dispersion of claims 1 wherein the anionic polyelectrolyte dispersing agents are selected from anionic homopolymers or copolymers of monomers selected from acrylic or vinyl monomers.

26. The dispersion of claim 25 wherein the acrylic monomers are selected from (meth)acrylamide, (meth)acrylic acid in the form of the corresponding salts, (meth)acrylonitrile, linear or branched C1-C4 hydroxyesters of the (meth)acrylic acid, Ci -C12 alkyl(meth)acrylates, wherein the alkyl can be linear or branched, compounds of the following general formula:



wherein: Ri is H or CH3; R2 and R3, equal or different, are H or Ci-Ce alkyl, optionally branched; M is an alkaline or alkaline-earth metal or ammonium and A is NH, O or NCH3.
27. The dispersion of claim 25 wherein said anionic
polyelectrolyte dispersing agent is an acrylic copolymer.
28. The dispersion of claim 27 wherein said anionic polyelectrolye dispersing agent is present in an amount of about 0.5 wt% to about 5.5 wt% based on the weight of fluoropolymer solids.
29. The dispersion of claim 27 wherein said acrylic copolymer dispersing agent has a molecular weight of about 2,000 to about 100,000.

30. The dispersion of claim 27 wherein said acrylic copolymer dispersing agent is hydrophobic.
31. The dispersion of claim 27 wherein said acrylic copolymer dispersing agent comprises methacrylic acid/butyl methacrylate
copolymer.
32. The dispersion of claim 31 wherein said methacrylic acid/butyl methacrylate copolymer comprises about 30 to about 50 mol% methacrylic acid units and about 50 to about 70 mol% butyl methacrylate units.
33. The dispersion of claim 25 wherein the vinyl monomers are selected from vinylaromatic monomers, C1-C12 alkyl vinylethers, and vinyl esters of Ci -Cis aliphatic monocarboxylic acids.
34. The dispersion of claim 33 wherein said vinylaromatic monomers are selected from styrene and its derivatives obtained by substituting one or more hydrogen atoms of the aromatic ring with a hydroxyl or a methyl and/or of vinyl with a methyl.
35. The dispersion of claim 1 wherein the anionic polyelectrolyte dispersing agent comprise polyamic acids.
36. The dispersion of claim 35 wherein the anionic polyelectrolyte dispersing agent comprise polyamic acids selected from aromatic polyamic acids or polyamidoamic acids.
37. The dispersion of claim 35 wherein the polyamic acids contain the following units:


wherein R" is a divalent arylene radical.
38. The dispersion of claims 1 wherein the anionic polyelectrolyte dispersing agent comprise carboxyalkyl celluloses, wherein alkyl comprises from 1 to 5 carbon atoms.
39. A process for reducing the fluorosurfactant content of and concentrating an aqueous fluorosurfactant-containing fluoropolymer dispersion comprising:
stabilizing fluoropolymer dispersion comprising fluoropolymer particles having an average size of about 10 to about 400 nm and a solids content of about 15 to about 55 wt% with anionic polyelectrolyte dispersing agent;
contacting said stabilized fluorosurfactant-containing aqueous fluoropolymer dispersion with an anion exchange resin to reduce fluorosurfactant content to a predetermined level;

separating said anion exchange resin from said dispersion after the fluorosurfactant content has been reduced to produce a reduced-fluorosurfactant dispersion; and
concentrating said dispersion to at least about 35 % by weight using a method which produces dispersion substantially free of nonionic surfactants.
40. The process of claim 39 wherein said concentrating is performed by adding acrylic polymer of acid content of 20% or more by weight to said reduced-fluorosurfactant dispersion in an amount of about 0.01 to about 1 wt% based on aqueous content of said dispersion and subjecting said dispersion to conditions causing said dispersion to separate into a lower phase high in fluoropolymer solids and an upper phase low in fluoropolymer solids and recovering said lower phase as concentrated reduced fluorosurfactant dispersion.
41. The process of claim 40 wherein the pH of said stabilized fluoropolymer dispersion is at least about 6 when said adding of acrylic polymer of acid content of 20% or more is performed.
42. The process of claim 40 wherein the pH of said stabilized fluoropolymer dispersion is at least about 9 when said adding of acrylic polymer of acid content of 20% or more is performed.
43. The process of claim 40 wherein the pH of said stabilized fluoropolymer dispersion is at least about 9.5 when said adding of acrylic polymer of acid content of 20% or more is performed.
44. The process of claim 39 wherein said concentrating is performed by electrodecantation.
45. The process of claim 39 wherein said concentrated reduced fluorosurfactant dispersion recovered has a solids content of about 35 to about 70 wt%.
46. The process of claim 39 wherein said concentrated reduced fluorosurfactant dispersion recovered comprises less than about 300 ppm fluorosurfactant.
47. A process for applying fluoropolymer to a substrate comprising: providing a concentrated aqueous fluoropolymer dispersion comprising fluoropolymer particles and having a solids content of about 35 to about 70 wt%, said dispersion comprising about 0.03 wt% to about 10 wt% anionic polyelectrolyte dispersing agent based on the weight of fluoropolymer solids and containing less than about 300 ppm
fluorosurfactant based on the weight of said dispersion, said dispersion being substantially free of nonionic dispersion;
applying said dispersion to said substrate; and
heating said substrate coated with dispersion to coalesce said fluoropolymer particles on said substrate.
48. The process of claim 47 wherein said substrate is metal.
49. The process of claim 47 wherein said aqueous dispersion further comprises chromic acid.
50. The process of claim 47 wherein said substrate is catheter guide wire.
51. A coating composition comprising the dispersion of claim 1 further comprising chromic acid.