Blended fluoropolymer compositions
Blended fluoropolymer compositions are provided, in which a liquid dispersion of a first fluoropolymer is blended with a liquid dispersion of a second fluoropolymer. The first fluoropolymer may be polytetrafluoroethylene (PTFE), such as a low molecular weight PTFE (LPTFE) in the form of an aqueous dispersion having a mean particle size of less than 1.0 microns (μm) and a first melt temperature (T m ) of 332° C. or less. The second fluoropolymer may be a melt processable fluoropolymer (MPF), such as methylfluoroalkoxy (MFA), fluorinated ethylene propylene (FEP), or perfluoroalkoxy (PFA), for example, in the form of an aqueous dispersion having a mean particle size of less than 1.0 microns (μm). When the blended fluoropolymer composition is dried, a crystal structure representing a true alloy of the fluoropolymers is formed, having melt characteristics that differ from those of the individual fluoropolymers.
1. A method of forming a fluoropolymer powder composition, comprising the steps of:
providing a blended fluoropolymer composition comprising:
perfluorinated low molecular weight polytetrafluoroethylene (LPTFE) having a number average molecular weight (M n ) less than 500,000 and a first melt temperature (T m ) of 332° C. or less, in the form of a liquid dispersion of particles having a mean particle size of 1.0 microns (μm) or less, the liquid dispersion of LPTFE particles including less than 1.0 wt. % surfactant, based on the weight of the LPTFE liquid dispersion,
perfluoroalkoxy (PFA) in the form of a liquid dispersion of particles having a mean particle size of 1.0 microns (μm) or less and having a melt flow rate (MFR) of at least 4.0 g/10 min;
the blended fluoropolymer composition comprising a PFA content of 37 wt. % to 65 wt. % and a LPTFE content of 35 wt. % to 63 wt. %, based on the total solids of the LPTFE and PFA; and
drying the blended fluoropolymer composition to form a powder.
2. The method of claim 1 , wherein said drying step comprises freeze drying.
3. The method of claim 1 , wherein the blended fluoropolymer composition comprises a PFA content of 43 wt. % to 63 wt. % and a LPTFE content of 37 wt. % to 57 wt. %, based on the total solids of the LPTFE and PFA.
4. The method of claim 1 , wherein the blended fluoropolymer composition comprises a PFA content of 50 wt. % to 60 wt. % and a LPTFE content of 40 wt. % to 50 wt. %, based on the total solids of the LPTFE and PFA.
5. The method of claim 1 , wherein said low molecular weight polytetrafluoroethylene (LPTFE) dispersion has a mean particle size of 0.75 microns (μm) or less.
6. The method of claim 1 , wherein said low molecular weight polytetrafluoroethylene (LPTFE) dispersion has a mean particle size of 0.5 microns (μm) or less.
7. The method of claim 1 , wherein said low molecular weight polytetrafluoroethylene (LPTFE) has a first melt temperature (T m ) of 329° C. or less.
8. The method of claim 1 , wherein said low molecular weight polytetrafluoroethylene (LPTFE) has a first melt temperature (T m ) of 326° C. or less.
9. The method of claim 1 , wherein said low molecular weight polytetrafluoroethylene (LPTFE) dispersion is obtained via emulsion polymerization and without being subjected to agglomeration, thermal degradation, or irradiation.
10. The method of claim 1 , wherein said low molecular weight polytetrafluoroethylene (LPTFE) includes a modifying co-monomer in an amount less than 0.1 wt. % based on the weight of said low molecular weight polytetrafluoroethylene (LPTFE).
11. The method of claim 1 , wherein the low molecular weight polytetrafluoroethylene (LPTFE) is LPTFE homopolymer.
12. The method of claim 1 , wherein:
the blended fluoropolymer composition comprises a PFA content of 43 wt. % to 63 wt. % and a LPTFE content of 37 wt. % to 57 wt. %, based on the total solids of the LPTFE and PFA;
said low molecular weight polytetrafluoroethylene (LPTFE) dispersion has a mean particle size of 0.75 microns (μm) or less; and
said low molecular weight polytetrafluoroethylene (LPTFE) dispersion has a first melt temperature (T m ) of 329° C. or less.
13. The method of claim 12 , wherein the blended fluoropolymer composition comprises a PFA content of 50 wt. % to 60 wt. % and a LPTFE content of 40 wt. % to 50 wt. %, based on the total solids of the LPTFE and PFA.
14. The method of claim 1 , wherein said providing step further comprises mixing the liquid dispersions of LPTFE and PFA particles without coagulation of the particles.
15. A method of forming a fluoropolymer powder composition, comprising the steps of:
providing a blended fluoropolymer composition comprising:
low molecular weight polytetrafluoroethylene (LPTFE) having a number average molecular weight (M n ) less than 500,000 and a first melt temperature (T m ) of 332° C. or less, in the form of a liquid dispersion of particles having a mean particle size of 1.0 microns (μm) or less, the liquid dispersion of LPTFE particles includes less than 1.0 wt. % surfactant, based on the weight of the LPTFE liquid dispersion; and
methylfluoroalkoxy (MFA) in the form of a liquid dispersion of particles having a mean particle size of 1.0 microns (μm) or less;
the blended fluoropolymer composition comprising a MFA content of 35 wt. % to 90 wt. % and a LPTFE content of 10 wt. % to 65 wt. %, based on the total solids of the LPTFE and MFA; and
drying the blended fluoropolymer composition to form a powder.
16. The method of claim 15 , wherein said drying step comprises freeze drying.
17. The method of claim 15 , wherein the blended fluoropolymer composition comprises a MFA content of 45 wt. % to 76 wt. % and a LPTFE content of 24 wt. % to 65 wt. %, based on the total solids of the LPTFE and MFA.
18. The method of claim 15 , wherein the blended fluoropolymer composition comprises a MFA content of 56 wt. % to 76 wt % and a LPTFE content of 24 wt. % to 44 wt. %, based on the total solids of the LPTFE and MFA.
19. The method of claim 15 , wherein the blended fluoropolymer composition comprises a MFA content of 63 wt. % to 70 wt. % and a LPTFE content of 30 wt. % to 37 wt. %, based on the total solids of the LPTFE and MFA.
20. The method of claim 15 , wherein said low molecular weight polytetrafluoroethylene (LPTFE) dispersion has a mean particle size of 0.75 microns (μm) or less.
21. The method of claim 15 , wherein said low molecular weight polytetrafluoroethylene (LPTFE) dispersion has a mean particle size of 0.5 microns (μm) or less.
22. The method of claim 15 , wherein said low molecular weight polytetrafluoroethylene (LPTFE) has a first melt temperature (T m ) of 329° C. or less.
23. The method of claim 15 , wherein said low molecular weight polytetrafluoroethylene (LPTFE) has a first melt temperature (T m ) of 326° C. or less.
24. The method of claim 15 , wherein said low molecular weight polytetrafluoroethylene (LPTFE) dispersion is obtained via emulsion polymerization and without being subjected to agglomeration, thermal degradation, or irradiation.
25. The method of claim 15 , wherein said low molecular weight polytetrafluoroethylene (LPTFE) includes a modifying co-monomer in an amount less than 0.1 wt. % based on the weight of said low molecular weight polytetrafluoroethylene (LPTFE).
26. The method of claim 15 , wherein said MFA has a melt flow rate (MFR) of at least 4.0 g/10 min.
27. The method of claim 15 , wherein the low molecular weight polytetrafluoroethylene (LPTFE) is LPTFE homopolymer.
28. The method of claim 15 , wherein the low molecular weight polytetrafluoroethylene (LPTFE) is perfluorinated.
29. The method of claim 15 , wherein:
the blended fluoropolymer composition comprises a MFA content of 56 wt. % to 76 wt. % and a LPTFE content of 24 wt. % to 44 wt. %, based on the total solids of the LPTFE and MFA;
said low molecular weight polytetrafluoroethylene (LPTFE) dispersion has a mean particle size of 0.75 microns (μm) or less; and
said low molecular weight polytetrafluoroethylene (LPTFE) dispersion has a first melt temperature (T m ) of 329° C. or less.
30. The method of claim 29 , wherein the blended fluoropolymer composition comprises a MFA content of 63 wt. % to 70 wt. % and a LPTFE content of 30 wt. % to 37 wt. %, based on the total solids of the LPTFE and MFA.
31. The method of claim 15 , wherein said providing step further comprises mixing the liquid dispersions of LPTFE and PFA particles without coagulation of the particles.