Patent Application
20050192550
The present invention relates to an absorbent article such as a diaper, an incontinence protector, a sanitary towel or the like, having a transverse direction, a longitudinal direction and a centre axis extending in the longitudinal direction, and a direction of thickness, the article comprising a liquid-permeable cover sheet arranged on an upper surface of the article, a backing sheet arranged on a lower surface of the article, and an absorbent structure enclosed between these sheets, the absorbent structure having, in the longitudinal direction, a middle portion and two opposite end portions and having, in the transverse direction, a central portion and two opposite edge portions.
An absorbent structure for absorbent articles, such as diapers, incontinence protectors and sanitary towels which are intended to be used once and disposed of, is usually made up of one or more sheets of hydrophilic fibres, for example cellulose fluff pulp. Superabsorbents are also often included, which are polymers with an ability to absorb many times their own weight of water or body fluid. In addition, the absorbent structure can also contain further components, for example in order to improve its liquid-spreading properties or to increase its stability and its ability to withstand deformation during use.
An important problem encountered primarily in the case of diapers and incontinence protectors for adults, intended to receive and absorb relatively large amounts of fluid, is that these often leak before their total absorption capacity has been fully utilized. Since, when urinating, large amounts of fluid are often released in the space of a few seconds, this can lead to the absorbent structure being locally saturated with liquid in the liquid-receiving zone, i.e. the liquid does not have time to spread to other parts of the absorbent structure. This means that additional liquid released by the user leaks out of the diaper. This kind of early leakage is of course a source of considerable irritation both for the user and for the person caring for the user. The leakage problem is accentuated upon repeated wetting.
EP 0,254,476 describes an absorbent structure which, in a zone substantially in front of the wetting area, has a lower weight per unit area and a lower density compared to surrounding portions of the absorbent structure. In this way, a high liquid absorption capacity in the wetting area is achieved, after which the liquid can spread out farther and is stored in the surrounding areas of the absorbent structure.
GB 2,082,643 further describes an absorbent structure with a substantially uniform weight per unit area, but with a density gradient in the longitudinal direction, such that the density increases towards the end portions of the absorbent structure.
U.S. Pat. No. 4,413,996 describes an absorbent structure for diapers which has a liquid-collecting recess or well in the wetting area. A porous wadding can be arranged, if appropriate, in this well.
However, there is still room for improvement as regards the liquid absorption capacity and the spreading ability, in particular in the case of products which are intended to take up large amounts of liquid in a short period of time.
With the present invention, an article of the type discussed at the start has been obtained which substantially eliminates the problems which have been associated with previously known articles of this kind.
An absorbent article according to the invention is characterized principally in that the edge portions in the absorbent structure's middle portion, within at least part of the direction of thickness, have a first mean pore size, and in that the central portion in the absorbent structure's middle portion has a second mean pore size within at least part of the direction of thickness, the first mean pore size being greater than the second mean pore size, and in that the absorbent article can be folded along the longitudinal centre axis (II) so that a part of the article, on one side of the centre line (II) extending in the longitudinal direction, is brought to lie against a corresponding part of the article on the other side of the centre line (II) extending in the longitudinal direction on the upper surface of the article, and the portions which have the greater, first mean pore size constitute a liquid-receiving zone when the article is in use. The criterion that the first mean pore size is greater than the second mean pore size applies at least in the dry state, but the first mean pore size is preferably greater than the second mean pore size both in the dry state and in the wet state. Having a difference in mean pore size permits draining of liquid from the liquid-receiving zone to the areas with the second, lesser mean pore size.
With the present invention, an absorbent article is obtained which is intended to be used in a folded state. Folded state means that the article is folded along its longitudinal centre axis, at least in the middle portion of the article, so that parts of the article on each side of the longitudinal centre axis are folded towards one another. The advantage of such an article is that in the folded state it can take up a large amount of liquid in a short space of time, which substantially reduces the risk of the absorbent structure becoming locally saturated with liquid in the liquid-receiving zone, which in turn reduces the risk of leakage. Another advantage of an article according to the invention is that the article when in use, i.e. in the folded state, has a narrow crotch area. The narrow crotch area creates a good fit and means that the risk of the article chafing against the user's thighs during use is reduced. By virtue of the fact that the article is folded when in use, it is also possible to design an article which, before folding, is wider than a conventional diaper. This means that the total absorption capacity in the crotch area of the article can be very high.
According to one embodiment, the liquid-permeable cover sheet, on one side of the longitudinal centre axis (II), is connected to the liquid-permeable cover sheet on the other side of the longitudinal centre axis (II). The cover sheet can, for example, be connected by adhesive bonding or by thermal welding. The connection is preferably intermittent, for example at two or more points. The advantage of this design is that the article is permanently in a correctly folded state and the risk of the article being wrongly folded or of its unfolding during use is eliminated.
According to one embodiment, the absorbent structure has an upper surface directed towards the liquid-permeable cover sheet and a lower surface directed towards the backing sheet, the absorbent structure being folded along the longitudinal centre axis (II) so that at least a part of the upper surface on one side of the longitudinal centre axis (II) in the middle portion of the absorbent structure lies against a part of the upper surface on the other side of the longitudinal centre axis (II).
To ensure that, in the folded state, the bearing of the upper surface on each side of the longitudinal centre axis in the middle portion of the absorbent structure is permanent, in one embodiment the upper surface on one side of the longitudinal centre axis in the middle portion of the absorbent structure is connected to the upper surface on the other side of the longitudinal centre axis. The connection can be obtained, for example, by adhesive bonding or by thermal welding. The advantage of such an embodiment is that the absorbent structure is permanently in a folded state and the risk of the absorbent structure unfolding is eliminated.
According to one embodiment, the edge portions in the middle portion of the absorbent structure have the first mean pore size throughout the entire thickness of the absorbent structure. This means that the liquid-receiving zone, i.e. the area with material having the greater pore size, covers the whole crotch portion in that part of the absorbent structure that is directed towards the user. By virtue of the fact that the article is folded when in use, the absorbent structure can be wider than an absorbent structure in an unfolded diaper. This means that both the liquid-receiving capacity and the storing capacity of an absorbent structure according to this embodiment is very high.
According to another embodiment, the edge portions of the end portions in the absorbent structure also have the first mean pore size, within at least part of the direction of thickness. The advantage of this embodiment is that the liquid-receiving zone in the longitudinal direction of the article is longer. A further advantage of such an embodiment is that such an absorbent structure is easier to produce.
In the direction of thickness, the absorbent structure can be made up of a first sheet and a second sheet. The first sheet can have a smaller extent in the longitudinal direction than the second sheet.
According to a preferred embodiment, the absorbent structure has a first mean pore size which is at least 1.1 times as great as the second mean pore size.
According to yet another embodiment, the absorbent structure has a first mean pore size which is at least 1.3 times as great as the second mean pore size.
According to one embodiment, the liquid-receiving zone has a lower density than the area comprising the second, lesser mean pore size. For example, the liquid-receiving zone has a density of between 0.02 and 0.2 g/cm3, and the density is preferably between 0.06 and 0.15 g/cm3. In such a structure, the area having the second, lesser mean pore size has a density of between 0.1 and 1.0 g/cm3, preferably between 0.12 and 0.6 g/cm3.
a shows a cross section through the absorbent structure shown in
b shows a cross section through the absorbent structure shown in
a shows a cross section through an alternative embodiment of an absorbent structure according to the invention.
b shows a cross section through the absorbent structure shown in
The fibre material in the liquid-receiving zone 110 consists, for example, of synthetic fibres, for example of polyethylene, polypropylene, polyester or copolymers thereof. It is also possible for the synthetic fibres to be two-component fibres. Another example of fibre material in the liquid-receiving zone is cellulose fibres of mechanical pulp, thermomechanical pulp or chemi-thermomechanical pulp (CTMP). These pulps have relatively coarse fibres with residual lignin, as a result of which they have a relatively large pore volume and high wetting resilience and are comparatively easy to drain of liquid. A high wetting resilience means that the fluff pulp substantially retains its structure even after wetting. Other fluff pulps too with similar properties can be used, for example chemically stiffened cellulose fibres. Another example of a suitable material is a fibrous layer comprising polyacrylate-based particles or a polyacrylate-based coating bound to the fibrous layer. A further example of a suitable material is a superabsorbent foam, for example a polyacrylate-based foam. A polyacrylate-based foam is produced by means of a solution, which at least consists of monomer, crosslinking agent, initiator and surfactant, being saturated and pressurized with carbon dioxide in a vessel under agitation. When the solution is removed from the vessel through a nozzle, the solution expands and a foamed structure is obtained. The foamed structure is then locked by initiating polymerization and cross-linking, for example by UV radiation.
A further example of a suitable material in the liquid-receiving zone 110 is a layer of continuous fibres which have been bonded to one another in a bonding pattern at points or along lines or in some regions, but otherwise are essentially non-bonded to one another. Such a material can also be used as an integrated cover sheet/liquid-receiving sheet in the liquid-receiving zone.
The difference in pore size, between the liquid-receiving zone with the first, greater mean pore size and the area which has the second, lesser mean pore size, is obtained, for example, by a difference in density between the different materials, although the desired difference in pore size can also be obtained at the same density but with different types of material.
The second sheet 106 is a liquid-storing sheet. The liquid-storing sheet is preferably a fibre structure which contains superabsorbent, i.e. polymers with the ability to absorb many times their own weight of water or body fluid. The superabsorbent is in the form of powder, flakes, fibres, granules or the like. The superabsorbent can be mixed with the fibre material or can be applied in the form of one or more layers between layers of fibre. The superabsorbent can also be a foam structure. Moreover, the second sheet 106 can also comprise a liquid-spreading layer.
The superabsorbent is, for example, particulate and is either uniformly distributed in the liquid-storing sheet or is distributed with varied concentration in the longitudinal direction and/or direction of thickness of the absorbent structure. It is also conceivable to have a substantially pure layer of superabsorbent as storing sheet. In order not to block and prevent spread of liquid, it is possible for example to have a superabsorbent material which is also able to swell under normally occurring pressure forces. The feature which characterizes such a superabsorbent is a high degree of crosslinking which makes it more difficult to compress compared to a gel with a lower degree of crosslinking. The liquid-storing sheet can of course also be completely free of superabsorbent or can contain several different types of superabsorbents. The superabsorbent material can also be formed to give a foam.
The body fluid released, for example urine, is quickly taken up in the liquid-receiving zone and is spread out farther to the area having the second, lesser pore size and to the second sheet, i.e. the liquid-storing sheet 106. The liquid-receiving zone is drained of liquid and is then ready to accept the next dose of liquid. The liquid-storing sheet 106 has the capacity to store several doses of liquid.
a shows a cross section of the absorbent structure 100 shown in
b shows a cross section of the absorbent structure shown in
a shows a cross section, on a transverse centre line I, through an alternative embodiment of an absorbent structure 300 according to the invention.
b shows a cross section of the absorbent structure 300 shown in
The two end portions 402 of the first sheet 405 also have the second mean pore size. The first mean pore size is greater than the second mean pore size. When the absorbent structure is used in an absorbent article, the absorbent structure 400 is intended to be folded on the longitudinal centre line II such that the upper face 408 on one side of the longitudinal centre line II in the inner edge portion 411 of the middle portion 401 lies against the upper face on the other, opposite side of the longitudinal centre line II in the inner edge portion 411 of the middle portion 401, and the portions which have the greater, first mean pore size constitute a liquid-receiving zone 410. During use of the absorbent article, the inner edge portions 411 of the absorbent structure in the middle portion 401 constitute the part of the absorbent structure that is placed in the area in the absorbent structure 400 which is first wetted, namely the liquid-receiving zone 410. According to another alternative, an absorbent article which comprises the absorbent structure 400 is folded when it is placed on the user. In this case, the whole article is folded along the longitudinal centre axis of the article, so that at least parts of the liquid permeable cover sheet on each side of the longitudinal centre axis are folded onto one another.
The two end portions 502 of the first sheet 505 in
When the absorbent structure is used in an absorbent article, the absorbent structure is intended to be folded on its longitudinal centre axis II such that the upper face 508 on one side of the longitudinal centre line II in the inner edge portion 511 of the middle portion 501 lies against the upper face on the other, opposite side of the longitudinal centre axis II in the inner edge portion 511 of the middle portion 501, and the portions which have the greater, first mean pore size constitute a liquid-receiving zone 510. During use of the absorbent article, the inner edge portions 511 of the absorbent structure in the middle portion 501 constitute the part of the absorbent structure that is placed in the area in the absorbent structure which is first wetted, namely the liquid-receiving zone 510. According to another alternative, an absorbent article which comprises the absorbent structure 500 is folded when it is placed on the user. In this case, the whole article is folded along the longitudinal centre axis II of the article, so that at least parts of the liquid permeable cover sheet on each side of the longitudinal centre axis II are folded onto one another.
The incontinence protector shown in
The incontinence protector 6 is intended to surround the lower part of the user's trunk in the manner of a pair of absorbent pants. The incontinence protector 6 has a front end portion 613 intended to be directed forwards on the user during use of the incontinence protector, and a rear end portion 614 intended to be directed rearwards on the user during use, and a narrower crotch portion 615 which is located between the front end portion 613 and the rear end portion 614 and is intended to be arranged between the user's legs.
The incontinence protector 6 moreover has elastic members. These elastic members in the incontinence protector 6 constitute raised elastic liquid barriers 616, waist elastic 617 and leg elastic 618.
The elastic raised liquid barriers 616 are fixed to the liquid-permeable cover sheet 611 and are designed to prevent leakage of liquid. The elastic raised liquid barriers are made of a liquid-tight material, for example a hydrophobic nonwoven sheet, and comprise one or more elastic threads, which elastic threads ensure that the liquid barriers have elasticity and, during use, are raised from the liquid-permeable cover sheet 611.
The waist elastic 617 in the incontinence protector 6 is made of an elastic tape material and is placed slightly in from the front end edge of the article. The leg elastic 618 of the incontinence protector 6 consists of elongate elastic members, such as one or more elastic threads or an elastic tape element. The elongate elastic members are placed along the longitudinal edges of the article, at least along the crotch portion of the article, and constitute leg bands. The elastic threads or elastic tapes are pretensioned, i.e. stretched to a certain extent before the elastic threads or tapes are anchored to the liquid-permeable cover sheet 611. In this way, the elastic threads are drawn together and the material to the inside of the elastic threads is pleated slightly so as to give a tighter fit around the user's legs during use of the incontinence protector.
To allow the incontinence protector 6 to be fastened together to give the desired pants shape, the incontinence protector 6 comprises a fastening arrangement for joining the incontinence protector together to give a pants shape. The fastening arrangement comprises a first member 620 and a second member 621. In the incontinence protector 6 shown in
