Claims
- 1. A process for forming a densified nonwoven web comprising the steps of:
forming an open structure comprising at least about 5 wt-% of cellulosic materials; heating the open structure to a temperature of at least about 40° C. while substantially maintaining moisture present in the open structure; compressing at least a portion of the heated open structure to form the densified nonwoven web having portions with a local density of greater than about 0.2 g/cm3; and releasing the densified nonwoven web from compression.
- 2. The process of claim 1 wherein the open structure comprises at least about 15 wt-% of cellulosic materials.
- 3. The process of claim 1 wherein the open structure further comprises at least about 5 wt-% non-cellulosic polymeric materials.
- 4. The process of claim 1 comprising heating the open structure to a temperature of at least about 45° C.
- 5. The process of claim 4 comprising heating the open structure to a temperature of at least about 60° C.
- 6. The process of claim 1 wherein the step of heating the open structure comprises maintaining at least about 2 wt-% moisture in the open structure.
- 7. The process of claim 1 wherein the step of compressing the heated open structure forms portions having a local density of about 0.25 to about 0.35 g/cm3.
- 8. The process of claim 1 wherein the cellulosic materials comprise cellulosic fibers.
- 9. The process of claim 3 wherein the non-cellulosic polymeric materials comprise fibers.
- 10. The process of claim 3 wherein the non-cellulose polymeric materials comprise superabsorbent materials.
- 11. The process of claim 10 wherein the superabsorbent materials are particulate.
- 12. The process of claim 10 wherein the superabsorbent materials are fibers.
- 13. The process of claim 1 wherein the step of heating the open structure comprises moving heated air through the open structure.
- 14. The process of claim 13 wherein the heated air is humidified.
- 15. The process of claim 1 wherein the step of heating the open structure comprises transmitting electromagnetic energy to the open structure.
- 16. The process of claim 15 wherein the electromagnetic energy is selected from the group consisting of radio frequency energy, infrared energy, ultrasonic energy, and microwave energy.
- 17. The process of claim 1 further comprising the step of placing the densified nonwoven web between a liquid-pervious cover and a liquid impervious barrier.
- 18. The process of claim 1 wherein the at least a portion of the heated open structure comprises substantially all of the heated open structure, and the densified nonwoven web has a substantially uniform density of greater than about 0.2 g/cm3.
- 19. The process of claim 1 wherein the at least a portion of the heated open structure comprises one or more discrete portions that form embossed portions of the densified nonwoven web.
- 20. The process of claim 19 wherein the emobossed portions of the densified nonwoven web are lines.
- 21. An absorbent structure comprising a densified nonwoven fibrous web comprising at least about 5 wt-% of cellulosic materials, having a local density of greater than about 0.2 g/cm3, and a density relaxation of less than about 20% in densified portions.
- 22. The absorbent structure of claim 21 wherein the nonwoven fibrous web comprises at least about 15 wt-% of cellulosic materials.
- 23. The absorbent structure of claim 21 wherein the cellulosic materials comprise cellulosic fibers.
- 24. The absorbent structure of claim 21 wherein the nonwoven fibrous web further comprises at least about 5 wt-% non-cellulosic polymeric materials.
- 25. The absorbent structure of claim 24 wherein the non-cellulosic polymeric materials comprise fibers.
- 26. The absorbent structure of claim 24 wherein the non-cellulosic polymeric materials comprise superabsorbent materials.
- 27. The absorbent structure of claim 26 wherein the superabsorbent materials are particulate.
- 28. The absorbent structure of claim 21 wherein the nonwoven fibrous web has a moisture content of at least about 2 wt-%.
- 29. The absorbent structure of claim 21 wherein the nonwoven fibrous web has a density of greater than about 0.4 g/cm3.
- 30. The absorbent structure of claim 21 wherein the nonwoven fibrous web is enclosed between a liquid-pervious cover and a liquid impervious barrier.
- 31. Apparatus for forming a densified absorbent web comprising:
an open structure support an open structure heater a press that is suitable to compress the open structure into a densified absorbent web and that has an open structure infeed and a densified absorbent web outfeed wherein the open structure support is associated with the open structure infeed and the open structure heater is associated with the open structure support whereby the open structure can be heated to a temperature significantly above ambient temperatures prior to introduction into the press.
- 32. Apparatus of claim 31 wherein the open structure support is arranged and configured to support a continuous fibrous web.
- 33. Apparatus of claim 32 wherein the open structure support is substantially planar.
- 34. Apparatus of claim 31 wherein the press is the nip between a pair of rolls.
- 35. Apparatus of claim 34 wherein the rolls are smooth.
- 36. Apparatus of claim 34 wherein at least one roll is profiled.
- 37. Apparatus of claim 36 wherein the rolls are embossing rolls.
- 38. Apparatus of claim 34 wherein the open structure support is one of the pair of rolls.
- 39. Apparatus of claim 31 wherein the open structure heater comprises an enclosure for the open structure support.
- 40. Apparatus of claim 39 wherein the open structure heater further comprises a heating element associated with the press.
- 41. Apparatus of claim 40 wherein the open structure heater comprises a heated calendar roll contained within the enclosure for the open structure support.
- 42. Apparatus of claim 41 wherein the open structure support is the heated calendar roll.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This invention is related to the following copending application: U.S. Ser. No. ______, filed Jun. 25, 2002, entitled “Compressed Absorbent Tampon” (Att'y Docket, PPC-841).