Production of nanofibers by melt spinning

• US 20080242171A1
• Filed: 03/18/2008
• Published: 10/02/2008
• Est. Priority Date: 03/29/2007
• Status: Active Grant

• Current Assignee: Cummins Filtration Incorporated (Cummins Incorporated)
• Original Assignee: E. I. du Pont de Nemours and Company (Corteva, Inc.)
• Inventors: Huang, Tao, Avgousti, Marios, Armantrout, Jack Eugene, Marshall, Larry R., Mueller, Tim, Yembrick, Scott, Dunn, willliam H., Wetzel, Mark David, Oconnor, James M.
• Granted Patent: US 8,277,711 B2
• Time in Patent Office: Days
• US Class Current: 442/51
• CPC Class Codes: D01D 5/0023 the material being a polymer melt
• CPC Class Codes: D01D 5/0985 by means of a flowing gas (e.g. melt-blowing)
• CPC Class Codes: D01D 5/18 by means of rotating spinnerets
• CPC Class Codes: D01F 6/04 from polyolefins
• CPC Class Codes: Y10T 428/2931 Fibers or filaments nonconcentric [e.g., side-by-side or eccentric, etc.]
• CPC Class Codes: Y10T 442/186 Comprising a composite fiber

Abstract

A process and apparatus for forming nanofibers from a spinning melt utilizing a high speed rotating distribution disc. The fibers can be collected into a uniform web for selective barrier end uses. Fibers with an average fiber diameter of less that 1,000 nm can be produced.

Claims

1. A nanofiber forming process comprising the steps of:

supplying a spinning melt of at least one thermoplastic polymer to an inner spinning surface of a heated rotating distribution disc having a forward surface fiber discharge edge;

issuing the spinning melt along said inner spinning surface so as to distribute the spinning melt into a thin film and toward the forward surface fiber discharge edge; and

discharging separate molten polymer fibrous streams from the forward surface discharge edge to attenuate the fibrous streams to produce polymeric nanofibers that have mean fiber diameters of less than about 1,000 nm.

2. The process of claim 1, wherein the polymer is selected from the group consisting of polyolefins, polyesters, polyamides, polyaramids, polycarbonates, poly(meth)acrylates, polystyrene-based polymers, biopolyesters, thermotropic liquid crystal polymers, cellulose esters, thermoplastic cellulose, acrylonitrile-butadiene-styrene resins, acetals, acrylics, chlorinated polyethers, fluoropolymers, vinyl polymers, biodegradable polymers, bio-based polymers, bicomponent engineering polymers, embedded nanocomposite containing polymers, natural polymers, and copolymers and combinations thereof.

3. The process of claim 1, wherein the spinning melt has a viscosity from about 1,000 cP to about 100,000 cP.

4. The process of claim 1, wherein the spinning melt is supplied at a throughput rate from about 0.1 g/min to about 500 g/min.

5. The process of claim 1, wherein the rotational speed of the rotating distribution disc is between about 1,000 rpm and about 100,000 rpm.

6. The process of claim 1, wherein the rotating distribution disc is heated by indirect heating selected from infrared heating, induction heating or radiation heating.

7. The process of claim 1, wherein the molten polymer fibrous streams discharged from the forward surface discharge edge are directed into a hot blowing gas stream and away from the rotating distribution disc.

8. The process of claim 1, wherein the blowing gas has a temperature at or above the melting point of the polymer.

9. The process of claim 1, which forms nanofibers having a mean fiber diameter less than about 500 nm.

10. The process of claim 1, further comprising cooling the nanofibers with a cooling gas having a temperature below the melting point of the polymer.

11. The process of claim 1, further comprising collecting the fibers onto a collector to form a fibrous web.

12. The process of claim 11, further comprising applying a vacuum through the collector to pull the fibers onto the collector to form a fibrous web.

13. The process of claim 11, wherein a voltage potential is maintained between the rotating distribution disc and the collector.

14. The process of claim 13, wherein the voltage potential is maintained between the rotating distribution disc and an electrode positioned between the rotating distribution disc and the collector.

15. The process of claim 13, wherein the voltage potential is maintained between the collector and an electrode positioned between the rotating distribution disc and the collector.

16. The process of claim 13, wherein the voltage potential is between about 1 kV to about 150 kV.

17. A melt spinning apparatus for making polymeric nanofibers, comprising:

a molten polymer supply tube having an inlet portion and an outlet portion and at least one molten polymer outlet nozzle at the outlet portion thereof, said supply tube positioned axially through said melt spinning apparatus;

a spinneret comprising a rotatable molten polymer distribution disc, having an inner spinning surface inlet portion surrounding and in fluid communication with said outlet portion of said molten polymer supply tube, and a forward surface discharge edge portion; and

an indirect heating source directed at said rotatable molten polymer distribution disc.

18. The melt spinning apparatus of claim 17, further comprising an annular hot blowing gas ring having blowing gas nozzles disposed on the circumference thereof, said blowing gas ring disposed annular to said molten polymer supply tube, with said blowing gas nozzles positioned to direct hot blowing gas over said forward surface fiber discharge edge.

19. The melt spinning apparatus of claim 17, further comprising a porous collection surface downstream of said forward surface discharge edge.

20. The melt spinning apparatus of claim 17, wherein said rotatable molten polymer distribution disc has a concave inner spinning surface.

21. The melt spinning apparatus of claim 17, wherein said rotatable molten polymer distribution disc has a flat inner spinning surface.

22. The melt spinning apparatus of claim 17, wherein the molten polymer distribution disc diameter is about 10 mm to about 200 mm.

23. The melt spinning apparatus of claim 20, wherein the angle between said forward surface fiber discharge edge and said inner spinning surface is between greater than 0 degrees and about 90 degrees.

24. The melt spinning apparatus of claim 17, further comprising a stationary shear disc, disposed annular to said outlet portion of said molten polymer supply tube and parallel to and separated by a gap from the surface of the rotatable molten polymer distribution disc.

25. The melt spinning apparatus of claim 17, wherein the forward surface discharge edge is serrated.

26. The melt spinning apparatus of claim 19, further comprising at least one cooling gas nozzle disposed between said hot blowing gas ring and said collection surface.

27. The melt spinning apparatus of claim 17, further comprising a high voltage charging device connected between said molten polymer distribution disc and said collection surface.

28. The melt spinning apparatus of claim 17, wherein said collection surface is disposed annular to said spinneret.

29. A collection of nanofibers comprising polyolefin, having mean fiber diameters of less than about 500 nm.

30. The collection of nanofibers of claim 29, having a median fiber diameter of less than or equal to about 400 nm.

31. The collection of nanofibers of claim 30, having a mean fiber diameter of less than about 400 nm and a median fiber diameter of less than about 400 nm.

32. The collection of nanofibers of claim 31, having a median fiber diameter of less than about 360 nm.

33. The collection of nanofibers of claim 29, in the form of a nonwoven web.

34. The collection of nanofibers of claim 29, wherein the polyolefin is polypropylene.

35. The collection of nanofibers of claim 29, wherein the polyolefin is polyethylene.

36. The collection of nanofibers of claim 33, wherein said nonwoven web is collected on a fibrous scrim.