Absorbent single use hygiene item

Details Absorbent single use hygiene item Absorbent single use hygiene item

2000-01-27

2002-07-02

Vanatta, Amy (Department: 3765)

Surgery

Means and methods for collecting body fluids or waste material

Absorbent pad for external or internal application and...

C604S370000, C604S368000, C604S367000, C604S358000, C604S374000

Reexamination Certificate

active

06414216

ABSTRACT:

BACKGROUND OF THE INVENTION
The invention concerns an absorbent single use hygiene item having a liquid tight back sheet, a liquid permeable cover sheet, an absorbent body comprising a suitable super absorbing polymer material (SAP material) disposed between the cover and the back for absorbing body fluids, in particular urine, and with a liquid absorbing intermediate layer comprising a top stratum (
18
) made from synthetic fibers and a bottom stratum (
20
), wherein the average pore volume of the top stratum (
18
) is larger than the average pore volume of the intermediate layer (
8
) bottom stratum (
20
) and wherein the intermediate layer (
8
) is disposed between the absorbent body (
6
) and the cover sheet (
2
).
A hygiene item of this kind has been disclosed in DE 92 18 991 U1. EP 0 689 818 A2 discloses a hygiene item with which the intermediate layer is manufactured together with the absorbent layer using a multi-layer flat material comprising a liquid tight back sheet, a cover sheet which is permeable to liquids, and an absorbent body containing a super-absorbent polymer material and disposed between the sheets which is suitable for the storage of body liquids, in particular urine. A two-ply liquid absorbing and distributing intermediate layer consists essentially of a top stratum made from synthetic fibers and a bottom stratum, wherein the average pore volume of the top stratum is larger than the average pore volume of the bottom stratum. The intermediate layer is disposed between the absorbent body and the cover sheet.
Hygiene items, in particular diapers or incontinence inlays, containing SAP materials in their absorbent body are susceptible to so-called gel blocking. The SAP materials swell in the region of liquid discharge to impair additional liquid acceptance in particular in response to repeated liquid discharge in these regions. The intermediate layer disposed between the cover sheet and the absorbent body is thereby intended to act as a kind of intermediate buffer for absorbing the incident liquid, for distributing the liquid within intermediate layer, and for passing the liquid into the absorbent body. Liquids in the vicinity of liquid discharge can thereby be transported to remote locations of the absorbent body or to SAP materials contained therein which are still present in an “unused” state.
WO 91/11162 discloses a hygiene item having a liquid acceptance and distribution layer located above the absorbent body and comprising cross-linked cellulose fibers.
The chemical cross-linkage of the cellulose molecules is present within the cellulose fibers through cross-linkage of the cellulose molecules within a single fiber only and is not active between fibers. In consequence thereof, these fibers are relatively stiff, textured, and elastic. The intramolecular absorption capacity of the fibers is reduced. Such fibers are better suited for processing repeated discharge of liquid streams than are the non-chemically cross-linked cellulose fibers of the absorbent body. They are better suited for rapid absorption, containment, internal distribution and passage thereof to the absorbent body. In addition to the chemically cross-linked cellulose fibers, the intermediate layer of the conventional hygiene item contains a thermoplastic bonding material in the form of an admixture of thermoplastic fibers. Heating of the fiber mixture leads to melting of the thermoplastic fibers and to glue-like mutual bonding and securing of the chemically cross-linked cellulose fibers. This is reported as being particularly advantageous.
EP 0 397 110 A1 describes a diaper having a synthetic fiber-based, voluminous bonded fiber fabric which is disposed as an intermediate layer between the absorbent body and the cover sheet to provide temporary liquid absorption. The layer must however have an area density of at least 60 g/m
2
for adequate intermediate storage and distribution of the discharged liquid. Materials used in the voluminous, bonded fiber fabric layer are expensive, create logistic problems, and are difficult to integrate into high speed machinery, since a continuous roll of this material having finite, conventional usable diameter can only have a very limited working length and frequent exchange of the rolls is necessary.
Departing from the above described prior art, it is the underlying purpose of the invention to create a hygiene item having a high fraction of super-absorbing polymer materials in the absorbent body whose storage capacity can be better and more completely used than that of the hygiene article disclosed in WO 91/11162. In addition, the hygiene item must be inexpensive to produce. Departing from the hygiene item categorizing the invention, it is the underlying purpose of the present invention to create a hygiene item of simple construction which is therefore inexpensive to manufacture, whose liquid absorption performance and whose liquid storage performance is improved, in particular, in response to repeated application of liquids. The hygiene item user should also not feel the liquid remaining in the intermediate layer, e.g. as a result of body weight pressure on the skin following repeated liquid discharge.
SUMMARY OF THE INVENTION
This purpose is achieved in accordance with the invention with a hygiene item of the above mentioned kind, wherein the bottom stratum is made from chemically cross-linked cellulose fibers and the longitudinal end sections of the top stratum overlap the longitudinal ends of the bottom stratum, with the hydrophilicity of the chemically cross-linked cellulose fibers of the bottom stratum being larger than that of the synthetic fibers of the top stratum.
In accordance with the invention, the lower stratum of the intermediate layer is made solely from chemically cross-linked cellulose fibers. The good performance of the two stratum intermediate layer constructed in accordance with the invention results from a synergetic interaction which can be explained as follows. The gradient of the average pore volume (as seen in a direction towards the absorbent body, perpendicular to the plane of the cover sheet) initially provides a relatively large-pored liquid acceptance volume for liquids incident on the top stratum of the intermediate layer. The liquid can then gain access into the absorbent body via the bottom stratum of the intermediate layer. The reduced hydrophilicity of the synthetic fibers in the top stratum of the intermediate layer compared to that of the chemically cross-linked cellulose fibers of the bottom stratum of the intermediate layer and, in addition, its preferentially lower hydrophilicity compared to the non-cross-linked cellulose fibers of the absorbent body, support the desired direction of liquid transport. The bottom stratum of the intermediate layer made from chemically cross-linked cellulose fibers has a certain liquid guidance capacity due to the capillary absorption action of the fibers so that liquids passing through the top stratum of the intermediate layer and into the bottom stratum are distributed through the plane thereof into regions removed from the point of liquid incidence for further transport into the underlying absorbent body at these locations. Following repeated discharge of liquids, the storage capacity of the absorbent body is nevertheless nearly exhausted in the regions at which liquids are incident. This point in time is critical for the function of the hygiene item. The bottom stratum of the intermediate storage layer can then store additional incident liquid, at least to a limited extent. This storage capacity is effected by the remaining molecular bonding capacity of the cross-linked fibers and by the pore volume remaining between the fibers. The bottom stratum of the intermediate layer thereby provides reserve storage capacity. The amount of liquid stored therein which is pressed out to the surface of the diaper, i.e. to the skin of the diaper user, is thereby substantially reduced, since the upper large pore stratum of the intermediate storage layer has synthetic fibers with reduced hydrophili

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