Surgery – Means and methods for collecting body fluids or waste material – Absorbent pad for external or internal application and...
Patent
1997-01-29
1998-11-03
Weiss, John G.
Surgery
Means and methods for collecting body fluids or waste material
Absorbent pad for external or internal application and...
6043851, 604368, A61F 1315
Patent
active
058302026
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to an absorbent structure comprising an upper layer and a lower layer, each layer comprising absorbent gelling material particles.
The invention also relates to an absorbent structure comprising an upper layer and a lower layer, each layer comprising absorbent gelling material particles, the upper layer comprising an acquisition zone and a storage zone, the average basis weight of absorbent gelling material particles in the acquisition zone being lower than the average basis weight of the absorbent gelling material particles in the storage zone, wherein the lower layer comprises a mixture of absorbent gelling material particles and fibers.
The invention furthermore relates to a method for making such an absorbent structure.
BACKGROUND OF THE INVENTION
From WO 94/02092 (Coles) a sanitary napkin is known having a core which is comprised of a layer of absorbent gelling material sandwiched between two tissue layers. The layer of absorbent gelling material has a central acquisition zone that is substantially free of absorbent gelling material. The central acquisition zone serves to promote longitudinal spread of liquids along the sanitary napkin's core and to reduce side soiling.
U.S. Pat. No. 5,304,161 discloses a multilayer absorbent structure having an upper layer comprising absorbent gelling material and a lower storage layer of absorbent gelling material. A liquid passage way is provided in the upper layer of absorbent gelling material such that the upper and lower layers are in fluid communication. The upper layer may be comprised of two separate strips of absorbent gelling material.
U.S. Pat. Nos. 4,988,344 and 4,988,345 (Reising) and WO92/11831 (Feist) disclose absorbent articles having an upper layer comprising absorbent gelling material overlying a lower layer of absorbent gelling material. A liquid acquisition aperture is provided in the upper layer.
From DE-A-26 36 899 (Unilever) a multilayer sanitary napkin is known comprising three layers of absorbent gelling material. Each layer of absorbent gelling material is sandwiched between two tissue layers. The layers of absorbent gelling material are attached to the tissue layers in a striped pattern to promote longitudinal spread of liquids and to improve vertical uptake of liquid into the lower layers of the sanitary napkin.
In absorbent articles that comprise a mixture of absorbent gelling material particles and fibers, as described in U.S. Pat. No. 4,610,678 (Weisman), it has been found that at relatively high concentrations of absorbent gelling material particles, for instance above about 60% by weight of the mixture, the particles tend to separate from the fibers and collect in the lowest point of the absorbent structure. This has the undesirable effect that in the parts of the absorbent structure from which the particles have separated, insufficient absorbent capacity is present, and that liquids can be squeezed out of these parts. On the other hand, the absorbent efficiency and liquid-handling properties of the absorbent structure are reduced in those areas where the absorbent gelling material particles have collected and where very high local concentrations and basis weights of particles are present.
Furthermore, during formation of absorbent products having a relatively high concentration of absorbent gelling particles mixed into the fiber matrix, the particles that separate from the fiber matrix can contaminate the diaper forming equipment, especially the laydown screens on which the absorbent structures are formed, but also other equipment such as for instance the knifes for cutting side notches in the topsheet and backshet of an absorbent product.
Another negative effect of relatively high concentrations of absorbent gelling material, is that so called `gel blocking` may occur. When the absorbent gelling material particles swell upon being wetted, they will expand into the void spaces between the fibers and will form a resistance for liquids flowing into the absorbent core. On the other hand,
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Bogdanski Michael Scott
Feist Barry Robert
Litchholt John Joseph
Sanchez Liza Marie
Schmidt Mattias
Linman E. Kelly
Rasser Jacobus C.
Roof Carl J.
Ruhl Dennis
The Procter & Gamble & Company
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