Layered absorbent structure with wicking performance
The present invention relates to a layered absorbent structure in the form of a laminate including liquid storage layers comprising particulate superabsorbent material and adhesive fibers. Notably, the absorbent structure includes a wicking layer positioned between the liquid storage layers, with the wicking layer desirably acting to improve fluid spreading and rewet performance of the absorbent structure. The wicking layer preferably comprises airlaid cellulosic fibrous material such as wood pulp, and may optionally include superabsorbent polymer. A bonding pattern of the wicking layer is oriented to enhance wicking and rewet performance.
1. A layered absorbent structure, comprising:
a central wicking layer, and a first liquid storage layer positioned in a liquid-transferring relationship on a first side of said central wicking layer,
said central wicking layer comprising hydrogen-bonded cellulosic fibrous material that comprises a plurality of a cellulosic fibers bonded together by hydrogen bonds within the central wicking layer, said central wicking layer having a corduroy bonding pattern having parallel bonded lines and unbonded space between the parallel bonded lines, the parallel bonded lines having a width of approximately 1 millimeter (mm), and where an area of a surface of said central wicking layer that corresponds to the parallel bonded lines is 5% of a total area of the surface of said central wicking layer,
said first liquid storage layer comprising a matrix of adhesive filaments and absorbent particles, said adhesive filaments adhering said first liquid storage layer to said first side of said central wicking layer,
said first liquid storage layer comprising a cellulosic fiber tissue layer adhered to the matrix of adhesive filaments and absorbent particles on the side of the matrix opposite said central wicking layer.
2. A layered absorbent structure in accordance with claim 1 , wherein
said central wicking layer is comprised of a hydrogen-bonded, airlaid cellulosic fibrous material bonded by applying heat and pressure.
3. A layered absorbent structure in accordance with claim 1 , wherein said layered absorbent structure exhibits a Vertical Delamination Strength greater than 4N.
4. A layered absorbent structure in accordance with claim 1 , further comprising a second liquid storage layer positioned in a liquid-transferring relationship on a second side of said central wicking layer, said second side opposite to said first side, said second liquid storage layer comprising a matrix of adhesive filaments and absorbent particles, said adhesive filaments adhering said second liquid storage layer to said second side of said central wicking layer, and said second liquid storage layer comprising a cellulosic fiber tissue layer adhered to the matrix of adhesive filaments and absorbent particles on the side of the matrix opposite said central wicking layer.
5. A layered absorbent structure in accordance with claim 4 , wherein said first and second liquid storage layers are of equal basis weight.
6. A layered absorbent structure in accordance with claim 1 , wherein
said central wicking layer comprises a central portion formed from hydrogen-bonded wood pulp fibers, and a first tissue layer and a second tissue layer that are both hydrogen-bonded to respective opposite sides of said central portion.
7. A layered absorbent structure in accordance with claim 3 , wherein said central wicking layer contains up to 20% by weight of superabsorbent polymer.
8. A layered absorbent structure in accordance with claim 1 , wherein said layered absorbent structure exhibits an average Gurley Stiffness of no more than 400.
9. A layered absorbent structure in accordance with claim 1 , wherein said wicking layer includes bonded and unbonded regions, wherein said wicking layer presents more bonded regions in a direction transversely of said absorbent structure.
10. A layered absorbent structure, comprising:
a central wicking layer, and a first liquid storage layer positioned in a liquid-transferring relationship on a first side of said central wicking layer,
said central wicking layer comprising hydrogen-bonded cellulosic fibrous material that comprises a plurality of a cellulosic fibers bonded together by hydrogen bonds within the central wicking layer,
said first liquid storage layer comprising a matrix of adhesive filaments and absorbent particles, said adhesive filaments adhering said first liquid storage layer to said first side of said central wicking layer,
said first liquid storage layer comprising a cellulosic fiber tissue layer adhered to the matrix of adhesive filaments and absorbent particles on the side of the matrix opposite said central wicking layer;
where:
a. the vertical delamination strength of the layered absorbent structure exceeds 4N;
b. the central wicking layer has a corduroy bonding pattern having parallel bonded lines and unbonded space between the parallel bonded lines, the parallel bonded lines having a width of approximately 1 millimeter (mm), and an area of a surface of the central wicking layer that corresponds to the parallel bonded lines being 5% of a total area of the surface of the central wicking layer;
c. the central wicking layer has a density in the range of 0.08 g/cc to 0.25 g/cc; and
d. the caliper of the layered absorbent structure is 3 mm or less.
11. The layered absorbent structure in claim 10 wherein the corduroy bonding pattern suppresses wicking in the transverse direction by requiring liquid that wicks in that direction to repeatedly cross between bonded and unbonded regions while liquid wicking in the longitudinal direction does not have to traverse between bonded and unbonded regions.
12. The layered absorbent structure in claim 11 where the central wicking layer contains up to 20% by weight of superabsorbent polymer (SAP).
13. A layered absorbent structure in accordance with claim 1 , where the unbonded space between the parallel bonded lines is approximately 2.9 mm.
14. A layered absorbent structure in accordance with claim 1 , where the parallel bonded lines extend in a longitudinal direction, and where the corduroy bonding pattern is configured to reduce wicking in a transverse direction.
15. A layered absorbent structure in accordance with claim 1 , where the central wicking layer comprises hydrogen-bonded airlaid material comprising cellulosic fibrous material and superabsorbent polymer (SAP), the hydrogen-bonded airlaid material comprising less than 20% by weight of the SAP.
16. A layered absorbent structure in accordance with claim 1 , where the caliper of the layered absorbent structure is 3 mm or less.
17. A layered absorbent structure in accordance with claim 1 , where said adhesive filaments comprise a pressure-sensitive, thermoplastic adhesive composition.
18. A layered absorbent structure in accordance with claim 17 , where said pressure-sensitive, thermoplastic adhesive composition comprises a synthetic rubber-based pressure-sensitive adhesive.