Stock material or miscellaneous articles – Sheet including cover or casing – Complete cover or casing
Patent
1986-11-03
1989-02-21
Epstein, Henry F.
Stock material or miscellaneous articles
Sheet including cover or casing
Complete cover or casing
428138, 428323, 428534, A61F 316, A61F 318
Patent
active
048064084
DESCRIPTION:
BRIEF SUMMARY
The invention covers an absorbent structure for disposable articles such as a baby's nappy, a sanitary pad or any other article intended to absorb and retain body secretions and be discarded after use.
This type of article generally comprises a mass absorbing the liquids placed between a permeable web on the body side and an impermeable sheet of polyethylene on the external side.
The absorbent mass usually consists of one or several cellulose fibre layers of cellulose fibres obtained by dry defibration of paper pulp sheets or rolls.
In order to improve the absorbent power of the pad and limit its volume improved retention additives known also as superabsorbents are incorporated in it. These additives, which are in the form of fibres, film or more generally granule particles or pellets are compounds which swell in the presence of the liquid to be absorbed, but they are not solubilized. The liquid is then absorbed quasi-irreversibly, at least under the usual utilization conditions, and form with the compound a gel whose volume can be several tens of times greater than that of the dry additive.
According to most of the known methods the superabsorbent particles are fixed on the surface of the pad or incorporated in its mass. The terms "fixed" and "incorporated" mean that there is a rigid bond between a particle and the pad obtained by the presence of an additive providing adhesion.
For example, from FR Pat. No. 2,402,474 it is known that there is method for the manufacture of an absorbent structure in which an improved retention additive is combined with a substrate, and then fixed by the deposition of a binder by spraying or transfer. The substrate can be a synthetic film or a fibrous material constituting the external face. According to one of the forms of embodiment of the patent the additive layer is covered with a second fibrous pad before the permeable web on the body side is placed in position.
According to FR Pat. No. 2,446,357, the additive is contained, without being fixed, between two fibrous layers bonded to one another along lines of the points of cohesion. These layers thereby delimit a number of receptacles in which the gel can develop freely.
According to another known method a nappy for babies is made by successively placing on a sheet of soft tissue, a pad of foamed cellulose, then a layer of superabsorbent in a narrow, central strip and a sheet permeable to liquids of the size of the superabsorbent strip. The lateral edges of the sheet of soft tissue and the pad not covered with superabsorbent are then folded over one another onto the permeable sheet. A layer with a cross-section in the form of a snail is thereby obtained, with a triple thickness of cellulose foam enclosing the superabsorbent.
These various methods allow the products with a good liquid absorption capacity to be produced.
However it has been found in a certain percentage of articles comprising one of the structures described above that the gel becomes visible after normal usage. This occurs when the additive is incorporated in the mass in depth in a manner such as to leave on the body side immediately under the permeable sheet a cellulose foam layer free from or poor in additive allowing the diffusion of the liquid towards the layers next to the impermeable external sheet.
The fact that the gel becomes visible may be due to the loss in cohesion of this layer facilitated by the baby's movements. This may also be due to the migration of the gel through this layer. When a permeable sheet is introduced between the additive and the upper fluff layer an improvement is found; but it is not significant, migration also takes place through the meshes or the perforations of the sheet, or else the gel circumvents it. Such migration is not desirable as it promotes pilling of the layer to the detriment of the comfort of the user. In addition poor distribution results in a barrier effect by the gel formed in certain places thereby increasing the risks of leaks. Under extreme utilisation conditions the gel can pass through the permeable web
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Brellmann Jean
Pierre Michel
Ruppel Remy
Beghin-Say SA
Breiner A. W.
Epstein Henry F.
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