Surgery – Means and methods for collecting body fluids or waste material – Absorbent pad for external or internal application and...
Reexamination Certificate
1998-12-15
2002-08-06
Weiss, John G. (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
06429351
ABSTRACT:
The present invention relates to an absorbent article that includes a liquid-permeable outer casing sheet mounted on a first surface of the article, a liquid-impermeable outer casing sheet mounted on a second surface of the article, and an absorbent body enclosed between said two casing sheets, wherein the absorbent body includes a liquid-reception or liquid acquisition space consisting of at least one cavity or at least one region of lower density than an acquisition layer of the absorbent body that adjoins said space essentially in the same plane thereas, and wherein the liquid-acquisition layer includes a material which when wetted increases in size in a direction (z-direction) generally perpendicular to the first surface of the article.
One problem with hitherto known absorbent articles, such as diapers, pants-type diapers or trainers, incontinence guards, sanitary napkins and like articles, that are intended to repeatedly receive and absorb body fluid excreted by a user is that the rate at which liquid is able to penetrate into the article is greatly reduced at each renewed wetting occasion. This problem is particularly apparent in diapers and incontinence guards for children and adults, since the article must be capable of receiving and absorbing a relatively large volume of liquid excreted in the course of only a few seconds. It is therewith not unusual, particularly after a first wetting of the article, that liquid which is not immediately absorbed into the article will instead flow across the surface of said article and run past the edges thereof Such body fluid leakages are, of course, highly undesirable because, among other things, they soil and stain clothes, bed linen and mattresses, sometimes destructively.
The reason why the body fluid acquisition rate decreases with repeated wettings of the article is because the absorbent body of the article becomes temporarily saturated with body fluid within a limited area around the point at which the surface of the article is first met by the body fluid, the so-called primary wetting point. As a rule, the absorbent articles include one or more layers of hydrophilic fibres, for instance cellulose fluff pulp, and often also a powerful absorbent hydrocolloidal material, so-called superabsorbents. Liquid transport in such material is relatively slow, since it is primarily, dependent on capillary forces in those cavities present between fibres and particles in the absorbent body of the article. Liquid is transported within the hydrocolloidal materials by diffusion, which is a slower process than that generated by the capillary forces. Thus, the liquid will remain in the primary wetting region of the article for a relatively long period of time, and is then transported only gradually to surrounding parts of the absorbent body of said article.
In recent years, the problem has been accentuated by the development towards absorbent bodies that have been successively compressed to greater extents with the intention of reducing packaging volume and for transportation, storage and environmental reasons.
It is known to guide the transportation of liquid away from the primary wetting region to those parts of the absorbent body in which absorbent material that has still not been utilized is located, by providing the article with liquid transporting means in the form of compressed patterns, e.g. compressed strips, that disperse the liquid in the longitudinal direction of the article. An article that includes such compressed strips is known from PCT/SE94/00835. Liquid transportation in the article is mainly effected as a result of differences in capillary forces between the compressed strips and surrounding material. Although a certain positive effect is obtained in this way, in the form of a directed flow of liquid in the absorbent body, the rate at which the liquid is transported in the article is much too slow in relation to the rate at which body liquid is discharged onto the article. There is thus a risk that liquid will not be absorbed quickly enough and will instead run along the surface of the article and leak over the edges thereof. This risk is particularly applicable to products that are intended for urine absorption, such as diapers and incontinence guards, which must often deal with large volumes of liquid that are discharged within a relatively short time. Furthermore, heavy compression of an article makes the article stiff and imparts thereto parts that are not-readily flexible and that make the article less pliable and less liable to mould to the shape of the wearer's body when worn.
The capacity of an absorbent article to receive and retain large volumes of body liquid can also be enhanced by creating different types of liquid-receiving cavities or basins in the article.
U.S. Pat. No. 3,889,679 describes a diaper that has a plurality of circular holes disposed through the absorbent body of the diaper. However, since wetting of a diaper takes place within a limited region of the diaper, the primary wetting region, only those holes that are located nearest this region can be used to initially receive body liquid. These holes quickly fill with liquid, which is gradually drained by the surrounding absorbent material away from the holes by the suction effect generated by the capillary forces between the fibres in the absorbent material. This is a slow process, as before mentioned, and there is a considerable risk that liquid will still be left in the holes when liquid is discharged on the next wetting occasion. The absorbent material located nearest the primary wetting region of the diaper will gradually become saturated with body liquid and then lose essentially all ability to drain liquid from the holes. Another problem with this absorbent body is that it consists of a material which collapses when wetted and therewith essentially lose its three-dimensional structure. Consequently, the cavity space available in the absorbent body for acquisition of liquid is practically non-existent after a first wetting.
U.S. Pat. No. 4,560,372 describes an absorbent body that includes a resilient fibre layer and a layer of hydrophilic fibres that have been compressed, slit and then drawn apart to form openings. The absorbent body also includes 20-60% superabsorbent material. As a result of its high superabsorbent content, the material will swell in both the z-direction and in the xy-direction when wetted, i.e. the material will swell into the openings at the same time as it swells in the thickness direction of said material, wherewith the area of said openings are greatly reduced after wetting.
Swedish Patent Application No. 9304321-4 describes an absorbent body for absorbent articles such as diapers, incontinence guards and sanitary napkins that is provided with a liquid-acquisition part in the form of a drainage well that is located essentially opposite the contemplated primary wetting region of the absorbent body and that extends down into and through a liquid storage part of the absorbent body. The drainage well is in liquid communication with a liquid dispersion layer located beneath a liquid storage layer and has a greater effective mean pore size than the surrounding liquid storage part.
An absorbent body of this kind will function effectively in respect of receiving a first volume of liquid and even subsequent liquid volumes when the time between liquid discharges is sufficient to enable the well to empty of liquid between the liquid discharge occasions. The absorbent body according to Swedish Patent Application No. 9304321-4 is also dependent on capillary forces in draining liquid from the well. Consequently, the liquid-acquisition well is emptied gradually as liquid is transported from the coarser pores in the well to the finer pores in the surrounding absorbent material. There is also the risk that the well will be too small to accommodate large volumes of liquid and therewith be overfilled.
Prior publications WO 87/01914, U.S. Pat. No. 4,333,462, U.S. Pat. No. 4,333,463, U.S. Pat. No. 4.333,464, U.S. Pat. No. 4,413,996, EP
Buschka Anette
Guidotti Ted
Gustafsson Anders
Widlund Urban
SCA Hygiene Products AB
Webb Jamisue
Weiss John G.
Young & Thompson
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