Absorbent articles with improved leakage safety

Details Absorbent articles with improved leakage safety Absorbent articles with improved leakage safety

2001-12-06

2004-09-14

Lo, Weilun (Department: 3761)

Surgery

Means and methods for collecting body fluids or waste material

Absorbent pad for external or internal application and...

C604S385170

Reexamination Certificate

active

06791005

ABSTRACT:

FIELD OF INVENTION
The present invention relates to an absorbent article, such as a sanitary napkin, a panty liner or an incontinence protector, which is intended to be carried in the crotch region of the wearer inside the wearer's panties or pants, said article having a generally elongated shape with two long sides, two short sides, two end-portions, a central portion located between the end-portions, a liquid-permeable casing sheet or top sheet which is intended to lie proximal to the wearer's body in use, a liquid-impermeable casing sheet or backing sheet intended to lie distal from the wearer's body in use, and between said sheets a drainage sheet and an element which forms a hump on the side of the article that lies proximal to the wearer's body in use, as seen in a direction from the liquid-permeable casing sheet towards the liquid-impermeable casing sheet.
BACKGROUND OF THE INVENTION
Conventional absorbent articles of the aforesaid kind are generally flat. Consequently, when the lower abdomen of the female carrier is not flat problems can occur when donning and wearing such articles. In such cases, abutment of the article with the wearer's body is not of the best and if gaps occur between product and the user's body there is a serious risk that body fluid will leak past the long side-edges of the article. Such leakage is particularly undesirable, since it is very liable to soil the wearer's clothes. Rearward leakage is a particular problem in this respect, which normally occurs when the user lies down, for instance at night.
With the intention of solving this problem, it has been proposed to provide the absorbent articles with a pre-formed hump. Absorbent articles that include humps are described in EP-A-0 419 434, among others. The intention of providing absorbent articles with pre-formed humps is to create contact with the genitals of the wearer in use. Discharged body fluids can be caught immediately on leaving the wearer's body and will be absorbed immediately by the article, without running out over its surface and over the long edges of the article.
Another drawback with flat articles is that when the article is used, it is influenced by forces exerted by the wearer's thighs for instance, so as to wrinkle the product and/or cause the long edges of the product to fold over the liquid-permeable surface thereof. A wrinkled surface and/or inwardly folded long edges of the product will significantly reduce the liquid-permeable surface and in many cases to a size that is insufficient to capture all liquid discharged by the wearer at one time, wherewith leakage may occur.
A conventional way of creating a hump is simply to provide a large amount of absorbent material in the absorbent pad within the area where the hump is desired, and form the hump from this excess material. Humps are most often formed from an absorbent material referred to as cellulose fluff pulp, in other words defibred pulp from, e.g., thermomechanical pulp, chemithermomechanical pulp, or chemical sulphite pulp or sulphate pulp. Such a material, however, is not stable when wet, and consequently a hump comprised of such material will collapse and lose its shape when wet. In order to obtain a hump consisting of cellulose fluff pulp and having sufficient height whilst the article is in use, it is necessary to use so much cellulose fluff pulp in the production of the hump as to cause the hump to be felt uncomfortable by the wearer. Another problem that occurs with an article constructed in accordance with the above description is that control of the liquid dispersion capacity of the article in the z-direction is lost, because the article loses its shape when wetted. It is also known to produce an article which includes a hump that faces towards the wearer, by placing a moulding or shaping element on top of the absorbent core. One drawback in this respect is that the hump results in inertia in liquid transportation down into the product, due to the fact that the shaping element must be filled with liquid before it releases the liquid to the underlying absorption core, said core having a strong liquid suction and absorbing effect and also a liquid retaining absorption effect. Earlier patent documents have also proposed the use of foam material in providing the hump. A problem with the use of foam material in the hump resides in the difficulties in achieving a foam structure that has sufficiently open pores to obtain effective ingress of liquid into the structure, at the same time as the material shall have great ability in retaining the liquid in its structure without liquid being forced therefrom when subjected to load by the wearer, for instance when the wearer sits down. A hump can also be provided on the upper side of the article, by providing a planar article with a shaping element that takes a convex shape in relation to the wearer when the sides of the article in the region of the crotch are subjected to greater loads from the wearer's thighs. The drawback with this solution is that the shaping element returns to its original planar state immediately the wearer does not subject the sides of the article to pressure, e.g. when she stands with her legs apart or sits in a “lotus position”, and also because it is difficult to produce a shape that corresponds essentially to the body shape of the wearer, solely by flexural deformation.
An absorbent article of the kind described in the introduction is known from EP-A1-0 768 072. However, in this case, the hump-forming element also constitutes the element that shall absorb and store discharged liquid and comprises a compressible, resilient and wet-stable material.
The object of the present invention is to provide an absorbent article of the aforesaid kind which conforms well to the wearer's body, makes the risk of leakage slight, and enables the hump-forming element to be manufactured from both absorbent material that is not wet-stable and non-absorbent material.
SUMMARY OF THE INVENTION
This object is achieved in accordance with the invention with an article of the kind described in the introduction that is characterised by an absorbent layer disposed between the drainage layer and the hump-forming element, wherewith the absorbent layer has smaller capillaries than the drainage layer and that part of the hump-forming element that lies against the absorbent layer.
The drainage layer, which has a lower density and therewith larger capillaries than the underlying absorbent layer, is placed on top of the absorbent layer, therewith contributing towards the rapid ingress of liquid in the z-direction down to the absorbent layer, in other words there is obtained a capillary size gradient with large capillaries in the drainage layer and smaller capillaries in the absorbent layer, meaning that the absorbent layer will leach/draw liquid out from the drainage layer. As a result of the difference in the size of the capillaries between the absorbent layer material and the material of the hump-forming element (the absorbent layer has smaller capillaries than the hump-forming material) no natural dispersion of liquid to the underlying hump-forming element will take place, since the capillary forces act in the opposite direction, i.e. the absorbent layer leaches out any liquid present in the hump-forming element. This means that the hump-forming element need not necessarily include material that retains its shape in a wet state, as this element will not be subjected to large amounts of liquid. The construction of the article in this manner makes accessible a wide selection of hydrophobic materials, hydrophilic materials or mixtures thereof for use as hump-forming elements.
The absorbent layer may conveniently extend beyond the contour line of the hump-forming element, but inwardly of the contour line of the drainage layer. The drainage layer is placed on top of the absorbent layer because rapid ingress of the liquid into the hump is desired, wherewith the surface that lies proximal to the wearer in use will be drier and m

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