Centrifugal solution spun nanofiber process
The invention relates to a process for forming nanofibers from a spinning solution utilizing a high speed rotating spin disk having a flat surface. The nanofibers can be collected into a uniform web for selective barrier end uses.
1. A nanofiber forming process comprising the steps of: supplying a spinning solution having at least one polymer dissolved in at least one solvent at a temperature between about 100° C. and the freezing point of the solvent to a rotating flat spin disk with a rotational speed between about 4,000 rpm and about 100,000 rpm, the flat spin disk having a flat surface and a forward surface discharge edge located in the plane of the rotating flat spin disk at the circumference of the flat surface; issuing the spinning solution from the flat spin disk along the flat surface so as to fully wet the flat surface of the flat spin disk and to distribute the spinning solution as a film toward the forward surface discharge edge of the flat spin disk; the rotational speed of the flat spin disk propelling the spinning solution along the flat surface of the flat spin disk past the forward surface discharge edge to form separate fibrous streams from the spinning solution in the plane of the flat spin disk while the solvent vaporizes to produce polymeric nanofibers of diameter 800 nm or less; wherein the flat surface defines a plane, the plane is perpendicular to the axis of rotation of the flat spin disk, and the surface and the forward discharge edge are all in the plane.
2. The process of claim 1 , wherein the polymer is selected from the group comprising polyalkylene oxides, poly(meth)acrylates, polyolefins, polystyrene based polymers and copolymers, vinyl polymers and copolymers, fluoropolymers, polyesters and copolyesters, polyurethanes, polyalkylenes, polyamides, polyaramids, thermoplastic polymers, liquid crystal polymers, engineering polymers, biodegradable polymers, bio-based polymers, natural polymers, and protein polymers.
3. The process of claim 1 , wherein the spinning solution has a viscosity from about 10 cP to about 100,000 cP.
4. The process of claim 3 , wherein the spinning solution has a viscosity from about 100 cP to about 75,000 cP.
5. The process of claim 4 , wherein the spinning solution has a viscosity from about 1,000 cP to about 50,000 cP.
6. The process of claim 1 , wherein the spinning solution is supplied at a throughput rate from about 1 cc/min to about 500 cc/min.
7. The process of claim 1 , wherein the rotational speed of the flat spin disk is between about 6,000 rpm and about 100,000 rpm.
8. The process of claim 7 , wherein the rotational speed of the flat spin disk is between about 8,000 rpm and about 100,000 rpm.
9. The process of claim 1 , wherein the average fiber diameter is less than about 500 nm.
10. The process of claim 9 , wherein the average fiber diameter is less than about 100 nm.
11. The process of claim 1 , further comprising flowing a shaping fluid around the flat spin disk to direct the spinning solution away from the flat spin disk.
12. The process of claim 11 , wherein the shaping fluid comprises a gas.
13. The process of claim 12 , wherein the gas is air or nitrogen and can be heated or cooled.
14. The process of claim 1 , further comprising collecting the nanofiber onto a collector to form a fibrous web.
15. The process of claim 14 , further comprising applying a vacuum through the collector to pull the nanofibers onto the collector to form a fibrous web.
16. The process of claim 1 further comprising providing an electric field while forming separate fibrous streams from the spinning solution while the solvent vaporizes to produce polymeric nanofibers.
17. The process of claim 16 , wherein the electrical field has a voltage potential of about 1 kV to about 150 kV.
18. The process of claim 17 , further comprising the step of collecting the fiber on a collector into a fibrous web and applying a vacuum through the collector to pull the nanofibers onto the collector to form the fibrous web.
19. The process of claim 18 , wherein the voltage potential is maintained between the flat spin disk and the collector.
20. The process of claim 18 , wherein the voltage potential is maintained between the flat spin disk and an electrode positioned between the flat spin disk and the collector.