Process aid for melt processable polymers
View Patent ↗Extrusion processability of non-fluorinated melt-processable polymers is improved by introducing a fluoropolymer process aid by means whereby the weight average particle size of the fluoropolymer is greater than 2 microns as it reaches the extruder die entrance.
1. A process aid composition for use in an extrudable non-fluorinated melt processable polymer at an extrusion temperature, said process aid composition comprising:
A) at least 1 weight percent, based on total weight of said process aid composition, of a fluoroelastomer having a Mooney viscosity, measured per ASTM D1646 at 121° C., large rotor, condition ML 1+10 minutes, of 60 to 80; and
B) at least 1 weight percent, based on total weight of said process aid composition, of an interfacial agent in an amount no more than a 5:1 weight ratio of interfacial agent to fluoroelastomer, said interfacial agent being a thermoplastic polymer chemically distinct from said fluoroelastomer and said interfacial agent having a melting point less than said extrusion temperature.
2. The composition of claim 1 wherein said interfacial agent is an aliphatic polyester.
3. The composition of claim 2 wherein said interfacial agent is a polycaprolactone having a number average molecular weight between 1000 and 32000.
4. The composition of claim 3 wherein said interfacial agent is a polycaprolactone having a number average molecular weight between 2000 and 10000.
5. The composition of claim 4 wherein said interfacial agent is a polycaprolactone having a number average molecular weight between 2000 and 4000.
6. The composition of claim 1 wherein said interfacial agent is a poly(oxyalkylene) polymer.
7. The composition of claim 6 wherein said poly(oxyalkylene) polymer is a polyethylene glycol.
8. The process aid composition of claim 1 wherein the interfacial agent at the extrusion temperature wets the surface of the fluoroelastomer particles.
9. The process aid composition of claim 1 wherein the interfacial agent is a thermoplastic polymer in a molten state at the extrusion temperature and has a melt viscosity lower than that of the fluoroelastomer.
10. The process aid composition of claim 1 wherein the interfacial agent comprises a fatty acid ester.
11. The process aid composition of claim 1 wherein the interfacial agent comprises a silicone-polyether copolymer.
12. The process aid composition of claim 1 wherein the fluoroelastomer has a glass transition temperature below room temperature.
13. The process aid composition of claim 1 wherein the fluoroelastomer is an amorphous fluoropolymer.
14. The process aid composition of claim 1 wherein the fluoroelastomer is selected from the group consisting of copolymers of i) vinylidene fluoride and hexafluoropropylene; ii) vinylidene fluoride and chlorotrifluoroethylene; iii) vinylidene fluoride and 1-hydropentafluoropropylene; iv) vinylidene fluoride and 2-hydropentafluoropropylene; v) vinylidene fluoride, hexafluoropropylene and tetrafluoroethylene; vi) vinylidene fluoride, 1-hydropentafluoropropylene and tetrafluoroethylene; vii) vinylidene fluoride, 2-hydropentafluoropropylene and tetrafluoroethylene; viii) tetrafluoroethylene and propylene; and ix) tetrafluoroethylene, propylene and vinylidene fluoride.
15. The process aid composition of claim 14 wherein the fluoroelastomer is a copolymer of vinylidene fluoride and hexafluoropropylene.