Blended fluoropolymer compositions

Abstract

Blended fluoropolymer compositions are provided. In one embodiment, 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) that has been polymerized via a dispersion or emulsion polymerization process, and which has not been agglomerated, irradiated, or thermally degraded. The LPTFE may be in the form of an aqueous dispersion, having a mean particle size of less than 1.0 microns (μm), with the LPTFE having a first melt temperature (T m ) of 332° C. or less. The second fluoropolymer may be a melt processible fluoropolymer (MPF), such as perfluoromethylvinvyl ether (MFA), fluorinated ethylene propylene (FEP), or perfluoropropylvinvyl ether (PFA), for example, in the form of an aqueous dispersion, and having a mean particle size of less than 1.0 microns (μm). Blending of the dispersions facilitates interaction of the LPTFE and MPF on a submicron level to facilitate intimate blending such that, 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. The blended fluoropolymer composition may be used to provide a coating having improved impermeability, stain resistance, abrasion resistance, smoothness, and higher contact angles.

What is claimed is: 
     
         1 . A blended fluoropolymer dispersion, comprising:
 polytetrafluoroethylene (PTFE) having 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; and   a melt processible fluoropolymer (MPF) in the form of a liquid dispersion of particles having a mean particle size of 1.0 microns (μm) or less.   
     
     
         2 . The blended fluoropolymer composition of  claim 1 , wherein said polytetrafluoroethylene (PTFE) dispersion has a mean particle size selected from the group consisting of 0.9 microns (μm) or less, 0.75 microns (μm) or less, 0.5 microns (μm) or less, 0.4 microns (μm) or less, 0.3 microns (μm) or less, and 0.2 microns (μm) or less. 
     
     
         3 . The blended fluoropolymer composition of  claim 1 , wherein said polytetrafluoroethylene (PTFE) has a first melt temperature (T m ) selected from the group consisting of 330° C. or less, 329° C. or less, 328° C. or less, 327° C. or less, 326° C. or less, and 325° C. or less. 
     
     
         4 . The blended fluoropolymer composition of  claim 1 , wherein said polytetrafluoroethylene (PTFE) dispersion is obtained via emulsion polymerization and without being subjected to agglomeration, thermal degradation, or irradiation. 
     
     
         5 . The blended fluoropolymer composition of  claim 1 , wherein said polytetrafluoroethylene (PTFE) dispersion includes less than 1.0 wt. % surfactant, based on the weight of said polytetrafluoroethylene (PTFE) dispersion. 
     
     
         6 . The blended fluoropolymer composition of  claim 1 , wherein said melt processible fluoropolymer (MPF) is selected from the group consisting of perfluoroalkyl vinyl ethers and fluorinated ethylene propylene. 
     
     
         7 . The blended fluoropolymer composition of  claim 1 , wherein said melt processible fluoropolymer (MPF) has a melt flow rate (MFR) of at least 4.0 g/10 min. 
     
     
         8 . The blended fluoropolymer composition of  claim 1 , wherein said melt processible fluoropolymer (MPF) is perfluoropropylvinvyl ether (PFA), said composition having a PFA content of 37 wt. % to 80 wt. % and a PTFE content of 20 wt. % to 63 wt. %, based on the total solids of said PTFE and PFA. 
     
     
         9 . The blended fluoropolymer composition of  claim 1 , wherein said melt processible fluoropolymer (MPF) is perfluoropropylvinvyl ether (PFA), said composition having a PFA content of 37 wt. % to 65 wt. % and a PTFE content of 35 wt. % to 63 wt. %, based on the total solids of said PTFE and PFA. 
     
     
         10 . The blended fluoropolymer composition of  claim 1 , wherein said melt processible fluoropolymer (MPF) is perfluoropropylvinvyl ether (PFA), said composition having a PFA content of 43 wt. % to 63 wt. % and a PTFE content of 37 wt. % to 57 wt. %, based on the total solids of said PTFE and PFA. 
     
     
         11 . The blended fluoropolymer composition of  claim 1 , wherein said melt processible fluoropolymer (MPF) is perfluoropropylvinvyl ether (PFA), said composition having a PFA content of 50 wt. % to 60 wt. % and a PTFE content of 40 wt. % to 50 wt. %, based on the total solids of said PTFE and PFA. 
     
     
         12 . The blended fluoropolymer composition of  claim 1 , wherein said melt processible fluoropolymer (MPF) is perfluoromethylvinvyl ether (MFA), said composition having a MFA content of 35 wt. % to 90 wt. % and a PTFE content of 10 wt. % to 65 wt. %, based on the total solids of said PTFE and MFA. 
     
     
         13 . The blended fluoropolymer composition of  claim 1 , wherein said melt processible fluoropolymer (MPF) is perfluoromethylvinvyl ether (MFA), said composition having a MFA content of 45 wt. % to 76 wt. % and a PTFE content of 24 wt. % to 65 wt. %, based on the total solids of said PTFE and MFA. 
     
     
         14 . The blended fluoropolymer composition of  claim 1 , wherein said melt processible fluoropolymer (MPF) is perfluoromethylvinvyl ether (MFA), said composition having a MFA content of 56 wt. % to 76 wt. % and a PTFE content of 24 wt. % to 44 wt. %, based on the total solids of said PTFE and MFA. 
     
     
         15 . The blended fluoropolymer composition of  claim 1 , wherein said melt processible fluoropolymer (MPF) is perfluoromethylvinvyl ether (MFA), said composition having a MFA content of 63 wt. % to 70 wt. % and a PTFE content of 30 wt. % to 37 wt. %, based on the total solids of said PTFE and MFA. 
     
     
         16 . The blended fluoropolymer composition of  claim 1 , wherein said melt processible fluoropolymer (MPF) is fluorinated ethylene propylene (FEP), said composition having a FEP content of 25 wt. % to 90 wt. % and a PTFE content of 10 wt. % to 75 wt. %, based on the total solids of said PTFE and FEP. 
     
     
         17 . The blended fluoropolymer composition of  claim 1 , wherein said melt processible fluoropolymer (MPF) is fluorinated ethylene propylene (FEP), said composition having a FEP content of 35 wt. % to 90 wt. % and a PTFE content of 10 wt. % to 65 wt. %, based on the total solids of said PTFE and FEP. 
     
     
         18 . The blended fluoropolymer composition of  claim 1 , wherein said melt processible fluoropolymer (MPF) is fluorinated ethylene propylene (FEP), said composition having one of a FEP content of 35 wt. % to 55 wt. % and a PTFE content of 45 wt. % to 65 wt. % and a FEP content of 60 wt. % to 90 wt. % and a PTFE content of 10 wt. % to 40 wt. %, based on the total solids of said PTFE and FEP. 
     
     
         19 . The blended fluoropolymer composition of  claim 1 , wherein said melt processible fluoropolymer (MPF) is fluorinated ethylene propylene (FEP), said composition having one of a FEP content of 40 wt. % to 50 wt. % and a PTFE content of 50 wt. % to 60 wt. % and a FEP content of 75 wt. % to 85 wt. % and a PTFE content of 15 wt. % to 25 wt. %, based on the total solids of said PTFE and FEP. 
     
     
         20 . A method of forming a blended fluoropolymer dispersion, comprising the step of mixing the components of  claim 1 . 
     
     
         21 . A fluoropolymer powder, obtained from the blended fluoropolymer composition of  claim 1 . 
     
     
         22 . A method of forming a fluoropolymer powder, comprising the step of drying the blended fluoropolymer composition of  claim 1 . 
     
     
         23 . A method of forming a fluorpolymer powder, comprising the step of freeze drying the blended fluoropolymer composition of  claim 1 . 
     
     
         24 . A method of coating a substrate, comprising:
 applying the blended fluoropolymer composition of  claim 1  to the substrate; and   heat curing the blended fluoropolymer composition.   
     
     
         25 . A method of forming a blended fluoropolymer composition, comprising the steps of:
 providing a first liquid dispersion of polytetrafluoroethylene (PTFE) particles having a first melt temperature (T m ) of 332° C. or less and a mean particle size of 1.0 microns or less;   providing a second liquid dispersion of particles of a melt processible fluoropolymer (MPF) having a mean particle size of 1.0 microns or less; and   mixing the first and second dispersions together.   
     
     
         26 . The method of  claim 25 , further comprising the additional step of:
 drying the blended fluoropolymer composition to form a powder.   
     
     
         27 . The method of  claim 26 , wherein said drying step comprises freeze drying. 
     
     
         28 . The method of  claim 25 , further comprising the additional step of:
 applying the blended fluoropolymer composition to a substrate; and   heat curing the blended fluoropolymer composition.