Fluoropolymer coating compositions
Blended fluoropolymer compositions that, in one exemplary application, may be applied as a coating to a substrate and, optionally, may be applied to a substrate that has been previously coated with a primer or basecoat and/or a midcoat. In one embodiment, the composition is a blend of at least one high molecular weight trace modified polytetrafluoroethyelene (TMHPTFE) and at least one melt-processible fluoropolymer (MPF). After being applied to the substrate, optionally over a primer or basecoat and/or midcoat, and then cured, the present compositions form coatings that demonstrate improved abrasion resistance and/or improved release characteristics and/or increased translucency/transparency and/or improved impermeability. The present compositions may also be used to produce films having a high degree of clarity and impermeability. The present compositions in powder form may be melt or paste extruded to form articles with improved impermeability.
1. A fluoropolymer composition, comprising:
at least one high molecular weight polytetrafluoroethylene which has been trace modified with a modifying co-monomer (TMHPTFE) and having a number average molecular weight (M n ) of at least 500,000 and a first melt temperature (Tm) of less than 342° C., said modifying co-monomer present in an amount of less than 1 wt. %, based on the weight of said TMHPTFE, said at least one TMHPTFE present in an amount of between 50 wt. % and 90 wt. % based on the total solids weight of all fluoropolymers in said composition;
at least one melt-processible fluoropolymer (MPF) selected from perfluoroalkoxy (PFA) and methylflouroalkoxy (MFA), said MPF present in an amount of between 10 wt. % and 50 wt. % based on the total solids weight of all fluoropolymers in said composition, and having a melt flow index (MFI) greater than 10 g/10 min; and
wherein said composition lacks low molecular weight polytetrafluoroethylene (LPTFE) having a number average molecular weight (M n ) of less than 500,000.
2. The composition of claim 1 , wherein said modifying co-monomer is perfluoropropylvinylether (PPVE).
3. The composition of claim 1 , wherein said at least one MPF has a first melt temperature (Tm) of less than 312° C.
4. The composition of claim 1 , wherein said at least one TMHPTFE is present in an amount of between 82 wt. % and 90 wt. % and said at least one MPF is present in an amount of between 10 wt. % and 18 wt. %, based on the combined solids weight of said at least one TMHPTFE and said at least on MPF.
5. The composition of claim 1 , wherein said at least one TMHPTFE and said at least one MPF are each in the form of an aqueous dispersion.
6. The composition of claim 1 , wherein said composition lacks fillers.
7. A method of coating a substrate, comprising the steps of:
applying a fluoropolymer composition to the substrate, comprising:
at least one high molecular weight polytetrafluoroethylene which has been trace modified with a modifying co-monomer (TMHPTFE), having a number average molecular weight (M n ) of at least 500,000 and a first melt temperature (Tm) of less than 342° C., said modifying co-monomer present in an amount of less than 1 wt. %, based on the weight of said TMHPTFE, the at least one TMHPTFE present in an amount of between 50 wt. % and 90 wt. % based on the total solids weight of all fluoropolymers in the composition; and
at least one melt-processible fluoropolymer (MPF) selected from perfluoroalkoxy (PFA) and methylflouroalkoxy (MFA), the MPF present in an amount of between 10 wt. % and 50 wt. % based on the total solids weight of all fluoropolymers in the composition, and having a melt flow index (MFI) greater than 10 g/10 min.; and
wherein the composition lacks low molecular weight polytetrafluoroethylene (LPTFE) having a number average molecular weight (M n ) of less than 500,000.
8. The method of claim 7 , further comprising, after said applying step, the additional step of curing the composition to form a coating.
9. The method of claim 7 , wherein said applying step further comprises applying the fluoropolymer composition in the form of an aqueous dispersion to the substrate.
10. The method of claim 7 , wherein said applying step further comprises spraying the fluoropolymer composition in particulate form onto the substrate.
11. The composition of claim 1 , wherein said TMHPTFE is obtained from emulsion polymerization.
12. The composition of claim 1 , wherein said TMHPTFE is obtained from suspension polymerization.
13. The composition of claim 1 , wherein said MPF has a melt flow index (MFI) greater than 15 g/10 min.
14. The method of claim 7 , wherein the fluoropolymer composition is a topcoat and further comprising, prior to said applying step, the additional steps of:
applying and curing a basecoat; and
applying and curing midcoat.
15. The method of claim 7 , wherein the MPF has a melt flow index (MFI) greater than 15 g/10 min.
16. The method of claim 7 , wherein the composition lacks fillers.
17. A fluoropolymer composition, comprising:
at least one high molecular weight polytetrafluoroethylene which has been trace modified with a modifying co-monomer (TMHPTFE) and having a number average molecular weight (M n ) of at least 500,000 and a first melt temperature (Tm) of less than 342° C., said modifying co-monomer present in an amount of less than 1 wt. %, based on the weight of said TMHPTFE, said at least one TMHPTFE present in an amount of between 85 wt. % and 92 wt. % based on the total solids weight of all fluoropolymers in said composition;
at least one melt-processible fluoropolymer (MPF) selected from perfluoroalkoxy (PFA) and methylflouroalkoxy (MFA), said MPF present in an amount of between 8 wt. % and 15 wt. % based on the total solids weight of all fluoropolymers in said composition, and having a melt flow index (MFI) greater than 10 g/10 min; and
wherein said composition lacks low molecular weight polytetrafluoroethylene (LPTFE) having a number average molecular weight (M n ) of less than 500,000.
18. The composition of claim 17 , wherein said modifying co-monomer is perfluoropropylvinylether (PPVE).
19. The composition of claim 17 , wherein said MPF has a melt flow index (MFI) greater than 15 g/10 min.
20. The composition of claim 17 , wherein said at least one TMHPTFE and said at least one MPF are each in the form of an aqueous dispersion.
21. The composition of claim 17 , wherein said composition lacks fillers.
22. The composition of claim 17 , wherein said TMHPTFE is obtained from emulsion polymerization.
23. A fluoropolymer composition, comprising:
a blend of fluoropolymers in aqueous dispersion form, said fluoropolymers consisting of:
at least one high molecular weight polytetrafluoroethylene which has been trace modified with a modifying co-monomer (TMHPTFE) and having a number average molecular weight (M n ) of at least 500,000 and a first melt temperature (Tm) of less than 342° C., said modifying co-monomer present in an amount of less than 1 wt. %, based on the weight of said TMHPTFE, said at least one TMHPTFE present in an amount of between 50 wt. % and 90 wt.% based on the total solids weight of all fluoropolymers in said composition; and
at least one melt-processible fluoropolymer (MPF) selected from perfluoroalkoxy (PFA) and methylflouroalkoxy (MFA), said MPF present in an amount of between 10 wt. % and 50 wt. % based on the total solids weight of all fluoropolymers in said composition, and having a melt flow index (MFI) greater than 10 g/10 min; and
optional additives.
24. The composition of claim 23 , wherein said modifying co-monomer is perfluoropropylvinylether (PPVE).
25. The composition of claim 23 , wherein said MPF has a melt flow index (MFI) greater than 15 g/10 min.
26. The composition of claim 23 , wherein said composition lacks fillers.
27. The composition of claim 23 , wherein said TMHPTFE is obtained from emulsion polymerization.