Disposable absorbent articles typically comprise three basic components: a liquid permeable topsheet that is located closest to the skin of the wearer when the article is in use, an absorbent core, and a liquid impermeable barrier sheet which is located on the opposite side of the absorbent core. Other components such as fastening tapes, leg and waist elastics, etc. are also commonly used.
The absorbent core receives and retains liquids that pass through the liquid permeable topsheet and typically comprises a batt of wood fluff fibers. Superabsorbent materials, typically in powder form, are often distributed within the absorbent core to enhance its liquid holding capacity and liquid retention properties.
One problem associated with absorbent articles is the inefficient utilization of the total absorptive capacity of the absorbent core material. This is due in part because absorbent articles normally have an elongated rectangular or hourglass shape and the liquid introduction or insult and spreading of liquid is often confined to the central area of the absorbent core.
Another problem associated with absorbent articles is the inability of the absorbent core to absorb liquids rapidly enough when large amounts of liquid are discharged into the absorbent core over short periods of time. This often results in undesirable side leakage.
To improve the liquid acquisition and lateral spreading properties of absorbent articles, many products have utilized a wicking layer of tissue or crepe. This wicking layer can be located between the liquid permeable topsheet and the absorbent core, in the center of the absorbent core, or in the absorbent core in a location closer to the liquid impermeable barrier sheet. However, tissue and crepe tend to promote isotropic spreading of liquids. That is, liquid tends to spread at similar rates in both the lengthwise and width directions of the absorbent article. As a result, in many instances where the core is elongate, the liquid will leak beyond the side edges of the absorbent article before it has an opportunity to spread to the ends of the absorbent core.
Numerous other approaches have been suggested for improving the liquid distribution and absorption properties of absorbent articles. Most of these approaches have involved the use of channels, reservoirs, apertures, etc. that have been introduced into the wood fluff absorbent core or tissue wicking layer by embossing or corrugation techniques. See, for example, U.S. Pat. Nos. 4,676,786 (Nishino), 4,678,464 (Holtman), 4,655,759 (Romans-Hess et al.), and 5,030,229 (Yang).
U.S. Pat. No. 4,735,624 (Mazars) discloses a disposable diaper comprising an absorbent pad constituted by an absorbent material consisting essentially of hydrophilic fibers joined to one another to form a coherent mass. The pad is narrow in the crotch area and widens out in the front and rear areas of the diaper with branches.
Other approaches have been taken such as the use of nonwoven inserts as flow control zones, as disclosed in U.S. Pat. Nos. 4,795,453 (Wolfe) and 4,908,026 (Sukiennik et al.), or the use of a plastic netting material to promote the unidirectional spreading of liquids in absorbent pads, as disclosed in European patent 0 174 152 B1. The use of certain complex shaped fibers, in tow or staple form, that are capable of spontaneously transporting liquid in absorbent articles is disclosed in European patent application 0 391 814 A2 (Phillips et al.).
U.S. Pat. No. 4,798,604 (Carter) discloses a contoured polymeric film which is apertured and contains a pattern of raised areas that may be employed to form the body contacting surface, i.e, topsheet, in absorbent devices.
Despite these previously known technologies, additional improvements to obtain more efficient and speedier absorption by absorbent cores without leaking are desired.