Method of making absorbent structure having three-dimensional topography

1. A method of making an absorbent structure having a three-dimensional topography comprises:

placing at least a portion of the absorbent structure between opposed mold surfaces, at least one of the mold surfaces having a three-dimensional topography; and

imparting the three-dimensional topography of the mold surface onto the absorbent structure so that the absorbent structure has a three-dimensional topography corresponding to the three-dimensional topography of the mold surface, the three-dimensional topography imparted onto the absorbent structure comprising a plurality of discrete peaks surrounded by interconnected valleys, the absorbent structure having the three-dimensional topography imparted thereon having a surface with a projected area and a vertical area, a ratio of the vertical area per projected area being in a range between 0.1 cm 2 /cm 2 and 0.5 cm 2 /cm 2 as determined by a Topography Analysis Method.

2. The method of claim 1 wherein each of the mold surfaces has a three-dimensional topography to impart a three-dimensional topography on both upper and lower surfaces of the absorbent structure.

3. The method of claim 2 wherein the locations of the peaks imparted to the upper surface correspond to the locations of the peaks imparted onto the lower surface and the locations of the valleys imparted onto the upper surface correspond to the locations of the valleys imparted onto the lower surface.

4. The method of claim 2 wherein the locations of the peaks imparted onto the upper surface correspond to the locations of the valleys imparted onto the lower surface and the locations of the valleys imparted onto the upper surface correspond to the locations of the peaks imparted onto the lower surface.

5. The method of claim 2 wherein the locations of the peaks and valleys imparted onto the upper surface generally do not correspond to the locations of the peaks and valleys imparted onto the lower surface.

6. The method of claim 1 wherein the opposed mold surfaces comprise a first mold surface having a plurality of bumps and a second mold surface having a plurality of depressions, each of the depressions in the second mold surface being suitably sized and shaped to receive a respective one of the bumps of the first mold surface.

7. The method of claim 1 wherein the absorbent structure having the three-dimensional topography imparted thereon has a longitudinal axis, a lateral axis and a z-direction axis normal to the longitudinal and lateral axes, the absorbent structure comprising longitudinally opposite ends, laterally opposite side edges, an upper surface, and a lower surface, the upper surface having the three-dimensional topography relative to the longitudinal and lateral axes and defining the plurality of discrete peaks and interconnected valleys of the upper surface relative to the z-direction.

8. The method of claim 1 further comprising forming the absorbent structure from absorbent fibers and a binder material using an airlaying technique.

9. The method of claim 8 wherein the binder material is heat activatable binder material.

10. The method of claim 9 further comprising heating the absorbent structure to a temperature sufficient to activate the heat activatable binder material.

11. The method of claim 1 wherein imparting the three-dimensional topography of the mold surface onto the absorbent structure comprises compressing the absorbent structure between the mold surfaces.

12. The method of claim 1 wherein imparting the three-dimensional topography of the mold surface onto the absorbent structure comprises passing the absorbent structure between a nip defined by two opposed rolls.