Surgery – Means and methods for collecting body fluids or waste material – Absorbent pad for external or internal application and...
Reexamination Certificate
2001-11-06
2004-03-16
Lo, Weilun (Department: 3761)
Surgery
Means and methods for collecting body fluids or waste material
Absorbent pad for external or internal application and...
C604S385010
Reexamination Certificate
active
06706946
ABSTRACT:
1. FIELD OF THE INVENTION
The present invention relates to absorbent articles for retaining body fluids such as urine, menses, or faecal material, and in particular to their ability to acquire and retain aqueous based materials. The invention further relates to disposable absorbent articles such as baby diapers or training pants, adult incontinence products, and feminine hygiene products.
2. BACKGROUND
Disposable absorbent articles are well know from the art for receiving and retaining bodily discharges, such as urine, menstrual fluids, or faecal materials. Thereby, two basic mechanisms are relied on. First, the containment of such discharges is generally achieved by a gasketing functionality, such as through impermeable materials or construction of sealings between the article and—in most cases—the skin of the wearer. The other key mechanism is to retain the discharges within the absorbent article, generally achieved by using an absorbent structure to pick up the discharges. In most cases, the absorption mechanism is directed towards handling of the aqueous components of the discharges.
One of the key performance criteria against which a absorbent article has to deliver is the acquisition speed. Obviously, a fast liquid acquisition warrants a short time span between exudation and storage of the exudate. Another key performance criterion is the dryness of the user facing surface of the absorbent article. To match the wearing comfort of regular underwear, a dry touch of the user facing surface is desired.
Thereby, one of the key basis transport and storage phenomena is related to the capillary effects of the structures, whereby two properties of the materials used for constructing such structures are of critical importance. First, the porosity of the structure respectively of the materials comprised in that structure. A great number of prior art has been directed against optimising the porosity, or pore size, be this in fibrous structures, or foamed structures, or structures essentially made of particulate materials, or combinations thereof.
Second, the surface tension effects. Also here, a great number of prior art has been dealing with the surface energy of the materials used in such structures. Thereby it is generally accepted, that the “ultimate storage materials” have to be relatively hydrophilic, whereas the “initial acquisition” materials can be less hydrophilic to allow better rewetting properties. This, however, has to be balanced with pore size requirements to still allow rapid fluid pick up into the article. It has also been recognised in the prior art, that these properties have to be considered not only for the first wetting instance, but that also subsequent loadings have to be taken in consideration.
As a consequence, a number of prior art deals with creating “gradient structures” have been disclosed, whereby—in direction of the fluid flowing into the absorbent structure—the materials exhibit different degrees of hydrophilicity—optionally in combination with other parameter impacting on the capillary transport properties, such as porosity or pore size. This aims at allowing easy penetration of the fluid into the article whilst reducing the ability for rewetting.
The hydrophilicity requirement was readily fulfilled for natural fibre based structures, such as cellulose of fluff based structures. Also, “semi-synthetic” materials like viscose/rayon maintained a intrinsic hydrophilicity throughout the material making process until the use in such structures. Further, a certain family of synthetic materials exhibit a natural hydrophilicity like polyester-based materials or polyacrylate materials. However, a number of materials being otherwise suitable for applications in such structures were hydrophobic by nature, for example polyolefinic resins, such as polyethylene or polypropylene from which webs to be used as topsheet could be made.
Consequently, a significant effort was spent against rendering such materials sufficiently hydrophilic at least on their surface so as to allow good wettability. One approach is to apply surfactants to the surface only, and often these were readily removable from this surface. This was thought to be beneficial for rewetting properties, however, for subsequent loadings the surface was left hydrophobic, with the risk of poor performance such as leakage.
Such structures and materials are for example disclosed in EP-A-0.469.591 (Hamajima); EP-A-0.312.118 (Meyer); EP-A-0.670.154 (Everett); EP-A-0.257.280 (Luceri); EP-A-0.359.501 (Cadieux); WO 91/14414 (Newkirk); U.S. Pat. No. 3,614,055 (Mesek); U.S. Pat. No. 4,077,410 (Butterworth);
Attempts to bind specific surfactants more strongly to the surface are described in EP-A-0.598.204 (Garavaglia) or WO 95/10648 (Everhardt).
One further approach in the prior art attempting to address this issue was to incorporate surfactants into the resins of such polymers, and/or by “attaching” the surfactants more firmly to the surface to maintain the hydrophilicity over subsequent loadings, such as described in EP-0.340.763 (Hansen).
In WO 96/28602 (Quincy), wettable materials such as films or fibrous webs are described, with a hydrophobic surface having coating which includes a surface free energy modifier, such as a protein, and a surface-active agent, such as a polyethoxylated alkylphenol. Such materials aim at optimising the wettability and penetration of porous materials by fluids wetting such films or fibrous webs.
However, none of the aforementioned prior art documents provided an absorbent article that features a permanently hydrophobic topsheet and still exhibits fast liquid acquisition and a low rewet. In this context, it is to be noted that topsheets comprising a skin care composition have become very popular recently such as for example those taught in WO 96/16682 (Roe et al.). The user facing surface of these topsheets is—due to the hydrophobic nature of the skin care compositions—at least partially hydrophobic over the entire usage period.
To further improve the liquid handling properties of absorbent article comprising such hydrophobic topsheets, it has been taught in PCT/US97/20842 (Roe) to use an apertured carrier covered with skin care composition as the topsheet allowing to cover the entire area in between the apertures with a skin care composition.
Independent of the above liquid handling aspects, it has been another recent trend in the absorbent article field to provide absorbent articles with apertured topsheets over open structures in order to be able to acquire and store faecal materials such as for example those described in WO 95/05139 (Roe). Such open structures have large open pores to store faecal material. On the other hand, such large open pores limit the liquid handling capabilities of such open structures by reducing their capillary suction. More specifically, such open structures are less efficient in acquiring liquid from a overlying topsheet thereby drying out that topsheet.
It is an object of the present invention to provide an absorbent article which overcomes the problems posed by the prior art absorbent articles.
It is a further object of the present invention to provide an absorbent article with improved liquid handling performance having an fibrous, apertured topsheet.
It is a further object of the present invention to provide an absorbent article with improved liquid handling having a hydrophobic topsheet.
It is a further object of the present invention to provide an absorbent article with improved liquid handling having a low retention liquid in the topsheet.
It is a further object of the present invention to provide an absorbent article with improved liquid handling having a topsheet comprising a skin care composition.
It is a further object of the present invention to provide an absorbent article having a structure having large open pores under an apertured topsheet.
3. SUMMARY OF THE INVENTION
The present invention provides a disposable absorbent article having a transverse centerline, a first region, and a second region, said front region being positioned forwa
Lankhof John Peter
Schmidt Mattias
Hughett Eileen L.
Kidwell Michele
Lo Weilun
Milbrada Edward J.
Patel Ken K.
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