Claims
- 1. A method for making fibers comprising a) extruding filaments of fiber-forming material; b) directing the filaments through a processing chamber defined by two parallel walls, at least one of the walls being instantaneously movable toward and away from the other wall and being subject to movement means for providing instantaneous movement during passage of the filaments; and c) collecting the processed filaments.
- 2. A method of claim 1 further characterized in that the movement means comprises biasing means for resiliently biasing the at least one movable wall toward the other wall, the biasing means providing a biasing force that establishes a dynamic equilibrium between the pressure within the processing chamber and the biasing force such that the wall moves away from the other wall in response to increases in pressure within the chamber but is quickly returned to the equilibrium position by the biasing force upon resumption of the original pressure within the chamber.
- 3. A method of claim 1 further characterized in that the movement means comprises oscillating means for oscillating the at least one movable wall at a rapid rate so as to release extrudate that may accumulate on the walls of the chamber.
- 4. A method of claim 1 in which both parallel walls are instantaneously movable toward and away from one another and subject to movement means for providing instantaneous movement.
- 5. A method of claim 1 in which a fluid stream is established to direct the filaments through the processing chamber, and at least part of the fluid stream flows through one or more narrow slots disposed within the processing chamber and has a vector component along the longitudinal axis through the processing chamber.
- 6. A method of claim 1 in which the parallel walls have a length transverse to the direction of filament movement through the chamber substantially greater than the spacing between the walls.
- 7. A method of claim 6 in which the processing chamber is free of side walls at the ends of the transverse length of the parallel walls.
- 8. A method of claim 1 controlled so that at least a majority of the filaments solidify before entering the processing chamber, whereupon the solidified filaments are subjected to a lengthwise orienting stress within the chamber.
- 9. A method of claim 1 controlled so that at least a majority of the filaments solidify after they enter the processing chamber but before they exit the chamber.
- 10. A method of claim 1 controlled so that at least a majority of the fibers solidify after they exit the processing chamber.
- 11. A method of claim 1 controlled so that at least a majority of the fibers are sufficiently liquid when collected that fibers become adhered at points of fiber intersection.
- 12. A method of claim 1 in which fibers are collected at an apparent filament speed of at least 8000 meters per minute.
- 13. A method of claim 1 in which the fiber-forming material is extruded through a plurality of die orifices arranged side-by-side in at least one row, and the individual filaments are attenuated into microfibers having an average fiber diameter of about 10 micrometers or less.
- 14. A method for making fibers comprising a) extruding filaments of fiber-forming liquid through orifices in a die, b) directing the filaments through an attenuation chamber defined by two parallel walls, at least one of the walls being instantaneously movable toward and away from the other wall and being resiliently biased toward the other wall; c) establishing a fluid stream that carries the filaments between the walls and attenuates them into fibers; d) selecting a biasing force on the at least one movable wall that establishes a dynamic equilibrium between the pressure within the attenuation chamber and the biasing force such that the wall moves away from the other wall in response to increases in pressure within the chamber but is quickly returned to the equilibrium position by the biasing force upon resumption of the original pressure within the chamber; and e) collecting the formed fibers.
- 15. A method of claim 14 in which both parallel walls are instantaneously movable toward and away from one another and connected to biasing means for providing such instantaneous movement.
- 16. Apparatus for forming fibers comprising a) an extrusion head for extruding filaments of fiber-forming material through orifices in a die, b) a processing chamber aligned to receive the extruded filaments for passage through the chamber, the chamber being defined by two parallel walls, at least one of the walls being instantaneously movable toward and away from the other wall; and c) movement means for providing instantaneous movement of at least one wall.
- 17. Apparatus of claim 16 in which the movement means comprises biasing means for resiliently biasing the wall toward the other wall, movement of the wall toward and away from the other wall being sufficiently easy and rapid that the wall will move away from the other wall in response to increases in pressure within the chamber but will be quickly returned to its original position by the biasing means upon resumption of the original pressure within the chamber.
- 18. Apparatus of claim 17 in which the biasing means comprises an air cylinder having a sliding piston connected to said at least one wall, and the pressure applied to the piston can be adjusted to adjust the force biasing said wall toward the other wall.
- 19. Apparatus of claim 16 in which the movement means comprises oscillating means for oscillating the wall at a rapid rate.
- 20. Apparatus of claim 16 in which both parallel walls are instantaneously movable toward and away from one another and connected to movement means for providing instantaneous movement.
- 21. Apparatus of claim 16 which further includes one or more air knives disposed within the processing chamber and providing a fluid stream having a vector component along the longitudinal axis of the processing chamber to increase the velocity of filaments passing through the chamber.
- 22. Apparatus of claim 16 in which the at least one movable wall is segmented into parts that can move individually toward and away from the other wall.
- 23. Apparatus of claim 16 in which the width of the chamber is narrower near the entry to the chamber than toward the exit of the chamber.
- 24. A nonwoven web comprising a collected mass of fibers that includes fibers randomly interrupted by isolated fiber segments that comprise oriented polymer chains but differ in morphology from the main portion of the fiber.
- 25. A nonwoven web of claim 24 in which the difference in morphology is represented by a difference in at least melting point, cold-crystallization temperature, or glass transition temperature, as measured by differential scanning calorimetry, or crystallinity index or a difference in crystallinity type as measured by X-ray scattering.
- 26. A nonwoven web of claim 24 in which the interrupting segment is fiber-like as opposed to globular and is less than 300 micrometers in diameter, but larger in diameter than the main portions of the fiber.
- 27. A nonwoven web of claim 24 in which the interrupting fiber segment comprises a broken end of the interrupted fiber.
- 28. A nonwoven web of claim 24 in which the interrupting fiber segment comprises an entanglement of the interrupted fiber with itself or another fiber.
- 29. A nonwoven web of claim 24 in which the interrupted fibers have an average diameter of about 10 micrometers or less.
- 30. A nonwoven web of claim 24 in which the main portion of the interrupted fiber exhibits multiple melting peaks during differential scanning calorimetry, with the different melting peaks representing molecular fractions within the fiber that differ in degree of crystalline order.
- 31. A nonwoven web of claim 24 in which the main portion of the interrupted fiber exhibits a dual melting peak during differential scanning calorimetry, with one melting peak representing a chain-extended crystalline portion.
REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation-in-part of Application Ser. No. 09/716,786, filed Nov. 20, 2000.
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
09716786 |
Nov 2000 |
US |
Child |
09835904 |
Apr 2001 |
US |