Surgery – Means and methods for collecting body fluids or waste material – Absorbent pad for external or internal application and...
Reexamination Certificate
2001-01-16
2002-12-03
Calvert, John J. (Department: 3765)
Surgery
Means and methods for collecting body fluids or waste material
Absorbent pad for external or internal application and...
C604S358000
Reexamination Certificate
active
06489533
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a water-decomposable absorbent article for pantiliners, sanitary napkins, incontinence pads, diapers, etc.
2. Description of the Related Art
Recently, water-decomposable absorbent articles disposable in flush toilets have come available, including, for example, pantiliners, sanitary napkins, incontinence pads, diapers, etc. Such a water-decomposable absorbent article comprises a water-decomposable top sheet to face the skin of a wearer (i.e., the top sheet serves as a body facing surface), a water-decomposable back sheet to face an external support such as an underwear (i.e., the back sheet serves as a garment facing surface), and a water-decomposable absorbent core sandwiched between the top sheet and the back sheet. In general, the back sheet is provided with an adhesive layer via which the absorbent article is fitted to the external support such as an underwear, and the adhesive layer is covered with a release sheet so as not to degrade its adhesiveness until use. Before use, the release sheet is peeled off to expose the adhesive layer outside, and the absorbent article is fitted to the external support via the thus-exposed adhesive layer.
Water-decomposable absorbent articles have self-sustaining strength enough to keep their shape during use, and, after used, they are disposed of in toilets and readily decomposed in water. However, the release sheet which is to be peeled off before use, is made of a resin sheet or-a cardboard sheet coated thick with silicone, and is very troublesome since it must be treated as wastes. If the release sheet is also made from a water-decomposable material, it can be disposed of in toilets without requiring treating as wastes, and thereby being convenient to users.
In that situation, Japanese Unexamined Patent Publication (Kokai) No. Heisei 11-47187 discloses a water-decomposable individual packaging absorbent article, for which is used a water-decomposable release sheet. The water-decomposable release sheet used for it is made of a water-soluble resin film or a water-soluble paper coated with a silicone or Teflon for release treatment, and the absorbent article is individually wrapped with the release sheet.
However, the water-soluble resin film coated with a silicone or Teflon for release treatment is problematic in that, when it is stored for a long period of time in high-humidity environments, the film absorbs water and swells, and, as a result, the strength of the wrapping bag of the film is lowered. Another problem with it is that the swollen film will cause surface defects such as pin holes through the release treatment portion of silicone or the like. Such surf-ace defects tend to zip the release sheet when the release sheet is released from the adhesive layer of the absorbent article, and, as a result, smoothly releasing the release sheet from the adhesive layer will be often difficult. In case where the water-soluble resin film is made thick to increase its wet strength, such a thick film will gel in water when disposed of in flush toilets, and will clog drainpipes. The water-soluble paper coated with the lubricant (silicone) is also problematic in that the hydrophobic, three-dimensionally crosslinking release layer of silicone or Teflon will bond fibers of the water-soluble paper to each other, and, as a result, the release sheet will be poorly or hardly decomposable in water.
Japanese Unexamined Patent Publication (Kokai) No. Heisei 8-48950 discloses a release sheet prepared by sizing a water-decomposable paper with a water-soluble sizing agent followed by coating a surface thereof with silicone. However, the invention disclosed in this patent publication is essentially directed to a technique of recycling used paper for regenerated paper, and not to a technique of ensuring rapid decomposition in water of silicone-coated water-decomposable paper and of preventing the surface defects of the coating film of silicone. Japanese Unexamined Patent Publication (Kokai) No. Heisei 6-218006 discloses a water-degradable release liner prepared by coating water-degradable paper with a solution of polyvinylpyrrolidone, drying it, and further coating it with a lubricant silicone layer. In the disclosed release liner, however, the polymer material of polyvinylpyrrolidone is not heat-sealable. Therefore, when the release liner is tried to individually wrap absorbent articles with it, it cannot be formed into bags through heat-sealing via polyvinylpyrrolidone.
In those disclosed in the above-mentioned Japanese Unexamined Patent Publication (Kokai) Nos. Heisei 6-218006 and 8-48950, a water-soluble resin is infiltrated into the fiber-to-fiber space in water-decomposable paper, or water-decomposable paper is coated with a water-soluble resin solution thereby to size the paper. However, the composite film of water-decomposable paper and a water-soluble resin, which is produced by infiltrating the water-soluble resin into water-decomposable paper or by coating water-decomposable paper with the water-soluble resin solution in the manner disclosed, is still problematic in that a surface of the composite film tends to be roughened owing to the roughness of the constituent fibers. In case where a release layer of silicone or the like is formed on such a rough surface of the composite film, it could not have a uniform thickness since the underlying composite film does not have a flat surface. As a result, when the water-soluble resin in the composite film has absorbed water to swell, the release layer that overlies the composite film will have surface defects such as pinholes. Still another problem with the composite film produced by coating water-decomposable paper with the water-soluble resin solution is that the composite film is often warped in the step of drying it after coated with the resin solution, owing to the difference in the wet expansion coefficient between the water-decomposable paper and the water-soluble resin. As a result, when a release layer of crosslinked silicone or the like is formed on such a warped composite film, it will be cracked or will have surface defects such as pin holes.
Through the surface defects (cracks and pin holes) of the release layer, water will penetrate into the underlying water-soluble resin layer to swell or gel it, and the thus-swollen or gelled resin layer will be exposed outside through the surface defects of the release layer. If so, the release properties of the release layer for facilitating easy release of the release sheet from an adhesive layer will be thereby lowered, and, as a result, smoothly peeling the release sheet from the adhesive layer of an absorbent article will be difficult.
SUMMARY OF THE INVENTION
An object of the invention is to provide a water-decomposable absorbent article provided with an adhesive layer to which is fitted a water-decomposable release sheet, wherein the release sheet is improved so that its release layer is flat and is resistant to water, that it is well decomposable in water and that its releasability from the adhesive layer is surely kept for a long period of time.
Another object of the invention is to provide such a water-decomposable absorbent article, in which the release sheet can be formed into a bag for packaging the absorbent article and it can be heat-sealed via a water-soluble polymer layer that underlies the release layer.
According to one aspect of the invention, a water-decomposable absorbent article may comprise: an absorbent body that includes a water-decomposable top sheet, a water-decomposable back sheet, a water-decomposable adsorbent core sandwiched between the top sheet and the back sheet, and an adhesive layer provided on the back sheet to fit the absorbent article to an external support; and a water-decomposable release sheet for protecting the adhesive layer before use with covering the adhesive layer, wherein;
the release sheet includes a release layer that faces the adhesive layer, a water-decomposable fibrous layer, and a water-soluble polymer layer sandwich
Imai Shigeo
Suzuki Sachiyo
Calvert John J.
Darby & Darby
Grayson Angela J
Uni-Charm Corporation
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