Wetlaid unitary stratified composite

• US 6,670,522 B1
• Filed: 07/21/2000
• Issued: 12/30/2003
• Est. Priority Date: 12/06/1996
• Status: Expired due to Fees

• Current Assignee: National Institute for Strategic Technology Acquisition and Commercialization
• Original Assignee: Weyerhaeuser Company (Weyerhauser)
• Inventors: Miller, Charles E., Mathews, Jeffrey D., Naieni, Shahrokh A., Graef, Peter A., Howard, Fred B., Bunker, Daniel T., Elston, Colin
• Primary Examiner(s): Ruhl, Dennis
• Application Number:
  US09/620,947
• Time in Patent Office: 1,257 Days
• Field of Search: 604/384, 604/383, 604/378, 604/365, 604/370, 604/375, 428/131-140, 428/170-172, 428/284, 428/298, 428/300, 442/402
• US Class Current: 604/370
• CPC Class Codes: A61F 13/531 having a homogeneous composition through the thickness of the pad A61F13/538, A61F13/539 take precedence
• CPC Class Codes: A61F 13/534 having an inhomogeneous composition through the thickness of the pad A61F13/538, A61F13/539 take precedence; homogeneous cores with tissue wrapping A61F13/53
• CPC Class Codes: A61F 13/537 characterised by a layer facilitating or inhibiting flow in one direction or plane, e.g. a wicking layer A61F13/538 takes precedence
• CPC Class Codes: A61F 13/539 characterised by the connection of the absorbent layers with each other or with the outer layers
• CPC Class Codes: B32B 2262/0253 Polyolefin fibres
• CPC Class Codes: B32B 2262/0261 Polyamide fibres
• CPC Class Codes: B32B 2262/0284 Polyethylene terephthalate [PET] or polybutylene terephthalate [PBT]
• CPC Class Codes: B32B 2262/04 Cellulosic plastic fibres, e.g. rayon
• CPC Class Codes: B32B 2307/726 Permeability to liquids, absorption
• CPC Class Codes: B32B 2307/73 Hydrophobic
• CPC Class Codes: B32B 2555/02 Diapers or napkins
• CPC Class Codes: B32B 5/04 characterised by a layer being specifically extensible by reason of its structure or arrangement , e.g. by reason of the chemical nature of the fibres or filaments
• CPC Class Codes: B32B 5/26 another layer next to it also being fibrous or filamentary relative arrangement of fibres or filaments of different layers B32B5/12
• CPC Class Codes: Y10T 428/249943 Fiber is nonlinear [e.g., crimped, sinusoidal, etc.]
• CPC Class Codes: Y10T 428/249949 Two or more chemically different fibers

Abstract

A unitary stratified composite composed of a first stratum and a second stratum integrally connected by a transition zone is disclosed. The first stratum serves as a liquid acquisition stratum that rapidly acquires and then transfers liquid to the second stratum. The second stratum serves to withdraw liquid from the first stratum and further serves as a temporary storage stratum. Methods for forming the unitary stratified composite are also disclosed.

Claims

1. A wetlaid absorbent composite comprising a first stratum, a second stratum, and a transition zone intermediate and coextensive with the first and second strata;

the first stratum comprising synthetic fibers and a bicomponent binding fibers;

the second stratum comprising a bicomponent binding fibers and crosslinked cellulosic fibers; and

the transition zone comprising fibers from the first and second strata commingled substantially uniformly across the composite'"'"'s width and along the composite'"'"'s length.

2. The composite of claim 1 wherein the first stratum is substantially homogeneous.

3. The composite of claim 1 wherein the second stratum is substantially homogeneous.

4. The composite of claim 1 wherein the first stratum has a pore size greater than the pore size of the second stratum.

5. The composite of claim 1 wherein the first stratum has a density in the range from about 0.01 to about 0.3 g/cm³.

6. The composite of claim 1 wherein the second stratum has a density in the range from about 0.03 to about 0.5 g/cm³.

7. The composite of claim 1 wherein the first stratum has a basis weight in the range from about 10 to about 100 gsm.

8. The composite of claim 1 wherein the second stratum has a basis weight in the range from about 10 to about 500 gsm.

9. The composite of claim 1 wherein the first stratum comprises fibers having a length from about 0.25 to about 1.5 inches.

10. The composite of claim 1 wherein the first stratum comprises fibers having denier from about 5 to about 20.

11. The composite of claim 1 wherein the synthetic fibers comprise polyethylene terephthalate fibers.

12. A wetlaid absorbent composite comprising a first stratum, a second stratum, and a transition zone intermediate and coextensive with the first and second strata;

the first stratum comprising polyethylene terephthalate fibers and bicomponent binding fibers;

the second stratum comprising crosslinked cellulosic fibers and a wet strength agent; and

the transition zone comprising fibers from the first and second strata commingled substantially uniformly across the composite'"'"'s width and along the composite'"'"'s length.

13. The composite of claim 12 wherein the first stratum is substantially homogeneous.

14. The composite of claim 12 wherein the second stratum is substantially homogeneous.

15. The composite of claim 12 wherein the first stratum has a pore size greater than the second stratum.

16. The composite of claim 12 wherein the first stratum has a density in the range from about 0.01 to about 0.3 g/cm³.

17. The composite of claim 12 wherein the second stratum has a density in the range from about 0.03 to about 0.5 g/cm³.

18. The composite of claim 12 wherein the first stratum has a basis weight in the range from about 10 to about 100 gsm.

19. The composite of claim 12 wherein the second stratum has a basis weight in the range from about 10 to about 500 gsm.

20. An absorbent composite comprising a first stratum, a second stratum, and a transition zone intermediate and coextensive with the first and second strata;

the first stratum comprising synthetic fibers and a bicomponent binding fibers;

the second stratum comprising a bicomponent binding fibers and crosslinked cellulosic fibers; and

the transition zone comprising fibers from the first and second strata commingled substantially uniformly across the composite'"'"'s width and along the composite'"'"'s length.

21. An absorbent composite comprising a first stratum, a second stratum, and a transition zone intermediate and coextensive with the first and second strata;

the first stratum comprising polyethylene terephthalate fibers and bicomponent binding fibers;

the second stratum comprising crosslinked cellulosic fibers and a wet strength agent; and

the transition zone comprising fibers from the first and second strata commingled substantially uniformly across the composite'"'"'s width and along the composite'"'"'s length.