Method for the preparation of fluoropolymer powdered materials
A method for the preparation of fluoropolymer powdered materials is disclosed. A suspension of solid fluoropolymer particles in a liquid carrier, preferably water, is frozen and the frozen carrier is then removed by sublimation at sub-atmospheric pressure to produce a dry powder of fluoropolymers particles.
1. A method for preparing a modified fluoropolymer powdered material, said method comprising the following steps:
providing a suspension of solid fluoropolymer particles and at least one filler in a water-based liquid carrier;
freezing the suspension; and
sublimating the frozen carrier by phase transition from a solid state directly to a gaseous state, thereby forming the modified fluoropolymer powdered material as a dry powder.
2. The method according to claim 1 , wherein said sublimating the frozen carrier step is accomplished at a sub-atmospheric pressure.
3. The method according to claim 2 , wherein the sub-atmospheric pressure is in a range of from about 0.01 atmospheres to about 0.99 atmospheres.
4. The method according to claim 1 , wherein said sublimating the frozen carrier step is carried out at a temperature below a glass transition temperature of the fluoropolymer.
5. The method according to claim 1 , wherein said sublimating the frozen carrier step is carried out at ambient temperature.
6. The method according to claim 1 , wherein said sublimating the frozen carrier step is carried out at a temperature between ambient temperature and a glass transition temperature of the fluoropolymer.
7. The method according to claim 1 , wherein said freezing step is carried out at a temperature in a range of from about −60° C. to about −20° C.
8. The method according to claim 1 , wherein the suspension of the solid fluoropolymer particles and filler in the water-based liquid carrier is frozen in one or more trays.
9. The method according to claim 1 , wherein the filler is selected from pigments, binders, and combinations thereof.
10. The method according to claim 1 , further comprising the additional step of:
milling the fluoropolymer particles.
11. The method according to claim 1 , further comprising the additional step of:
irradiating the fluoropolymer particles.
12. The method according to claim 1 , wherein the fluoropolymer is fibrillatable.
13. The method according to claim 1 , wherein the fluoropolymer is non-pumpable.
14. The method according to claim 1 , wherein the fluoropolymer is polytetrafluoroethylene (PTFE).
15. The method according to claim 1 , wherein the fluoropolymer is fluorinated ethylene propylene (FEP).
16. The method according to claim 1 , wherein the fluoropolymer is perfluoroalkoxy (PFA).
17. The method according to claim 1 , wherein the fluoropolymer comprises perfluoro methyl vinyl ether.
18. The method according to claim 1 , wherein the dry fluoropolymer material comprises particles having an average particle diameter from 1 μm to 100 μm.
19. The method according to claim 1 , wherein the dry fluoropolymer material comprises particles having an average particle diameter from 20 μm to 30 μm.