Surgery – Means and methods for collecting body fluids or waste material – Absorbent pad for external or internal application and...
Reexamination Certificate
2002-07-26
2004-11-23
Moore, Margaret G. (Department: 1712)
Surgery
Means and methods for collecting body fluids or waste material
Absorbent pad for external or internal application and...
C604S365000, C524S733000, C524S837000, C442S118000, C442S119000, C428S326000, C428S331000, C428S323000
Reexamination Certificate
active
06822135
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention is directed to a fluid storage material, and a method of making a fluid storage material, in which particles are secured to one another and/or to a substrate with a crosslinkable binder composition.
Personal care absorbent products typically include an absorbent layer or an absorbent assembly to absorb and retain liquids, and a number of non-absorbent structural layers and non-absorbent structural components to maintain the absorbent layer in a desired location or to enhance the functionality of the absorbent layer. Each component in the absorbent product serves a specific purpose. As more features and functions are added to the product, the bulk of the product tends to increase.
An absorbent layer with a high absorbent capacity is typically bulkier than an absorbent layer with a lower absorbent capacity. For purposes of discretion and comfort, it is desirable to have as thin an absorbent layer as possible, without sacrificing absorbent capacity. Superabsorbent materials make it possible for absorbent layers to be thin while maintaining a high absorbent capacity, but even garments containing absorbent layers of superabsorbent material may be relatively bulky due to all of the additional features of the garment included to prevent leakage, such as surge layers and additional absorbent material in target areas.
Containment flaps are often included around leg openings to capture any excess fluid around the leg openings, while waist dams may be included around the waist opening to prevent the escape of any excess fluid through the waist opening. Although these additional components may be somewhat absorbent, these components typically do not contain the high absorbency of superabsorbent particles (SAP) because of the difficulty in keeping superabsorbent particles attached to a substrate, particularly in a swollen or wet condition.
Various techniques are known for creating additional absorbency in personal care absorbent articles. For example, it is known to use alkoxysilane-grafted poly(ethylene oxide) as an absorbent coating, thereby creating absorbency on non-absorbent surfaces. However, the resulting absorbent surfaces have less absorbent capacity than SAP.
As another example, it is known to produce an absorbent material by applying a water-softened superabsorbent to a supporting substrate without any additional adhesives. However, use of water alone does not provide for attachment in the wet condition.
As yet another example, it is known to react SAP with a polyhydroxy organic compound, such as glycerol, to form covalent bonds with the SAP. These covalent bonds attach the particles to each other and to a suitable substrate. Formation of covalent bonds with the SAP is expected to create stresses during the swelling process that would either inhibit swelling of the SAP or rupture the membrane coating.
Also, it is known to create individual superabsorbent fibers having high absorbent capacity. Such fibers can be formed by combining a superabsorbent resin with a binder component and adding the combination to a fiber base material in a non-bonded web form. The individual fibers have considerable absorbent capacity.
Furthermore, it is known to create absorbent composites containing fine, hydratable microfibril fibers obtained from cellulose or derivatives capable of swelling in water. These fibers can be used to coat superabsorbent particles. The microfibrilar cellulose fiber coating provides a measure of binding to a supporting sheet, such as a nonwoven fabric. Since the microfibrilar cellulose fibers coat the superabsorbent particles, the fibers tend to inhibit migration of the superabsorbent particles but do not form durable attachments, especially when wet. Conventional adhesive materials used to increase or enhance durability of attachment tend to limit access of liquids to the superabsorbent or create significant constraining forces that limit superabsorbent swelling and therefore ultimate capacity.
U.S. Pat. No. 6,403,857 to Gross et al. describes an absorbent structure including an integral layer of superabsorbent polymer particles. The water-swellable superabsorbent polymer particles are adhered to an absorbent layer using a water-based polymeric binder that is latex bonded and/or thermally bonded. Gross et al. also describe a binder that may be a carboxylic polyelectrolyte in admixture with a crosslinking agent. The crosslinking agent has the property of reacting with carboxylic or carboxylate groups of the polyelectrolyte.
Other recent development efforts have provided coating materials for a variety of uses. For example, U.S. Pat. No. 6,054,523, to Braun et al., describes materials that are formed from organopolysiloxanes containing groups that are capable of condensation, a condensation catalyst, an organopolysiloxane resin, a compound containing a basic nitrogen, and polyvinyl alcohol. The materials are reported to be suitable for use as hydrophobic coatings and for paints and sealing compositions.
Others have reported the production of graft copolymers having silane functional groups that permitted the initiation of cross-linking by exposure to moisture. Prejean (U.S. Pat. No. 5,389,728) describes a melt-processible, moisture-curable graft copolymer that was the reaction product of ethylene, a 1-8 carbon alkyl acrylate or methacrylate, a glycidyl containing monomer such as glycidyl acrylate or methacrylate, onto which has been grafted N-tert-butylaminopropyl trimethoxysilane. The resulting copolymers were reported to be useful as adhesives and for wire and cable coatings.
Furrer et al., in U.S. Pat. No. 5,112,919, reported a moisture-crosslinkable polymer that was produced by blending a thermoplastic base polymer, such as polyethylene, or a copolymer of ethylene, with 1-butene, 1-hexene, 1-octene, or the like; a solid carrier polymer, such as ethylene vinylacetate copolymer (EVA), containing a silane, such as vinyltrimethoxysilane; and a free-radical generator, such as an organic peroxide; and heating the mixture. The copolymers could then be cross-linked by reaction in the presence of water and a catalyst, such as dibutyltin dilaurate, or stannous octoate.
U.S. Pat. No. 4,593,071 to Keough reported moisture cross-linkable ethylene copolymers having pendant silane acryloxy groups. The resultant cross-linked polymers were reported to be especially resistant to moisture and to be useful for extruded coatings around wires and cables. The same group has reported similar moisture curable polymers involving silanes in U.S. Pat. Nos. 5,047,476, 4,767,820, 4,753,993, 4,579,913, 4,575,535, 4,551,504, 4,526,930, 4,493,924, 4,489,029, 4,446,279, 4,440,907, 4,434,272, 4,408,011, 4,369,289, 4,353,997, 4,343,917, 4,328,323, and 4,291,136. Since the cured products of these formulations are reported to be useful for coverings for wire and cable, and for non-conductive coatings for electrical conductors, it would be expected that they are durable coatings for which properties such as water absorbency and biodegradability would be a disadvantage.
Water-swellable polymers have reportedly been produced by cross-linking water soluble polymers, such as poly(ethylene oxide). It is known that poly(alkylene oxides), such as poly(ethylene oxide), can be cross-linked through gamma irradiation. Depending upon the degree of irradiation and the degree of cross-linking, the properties of the cross-linked polymer can range from a water soluble material to a hard solid with no appreciable water absorbency. Materials that are substantially non-water soluble, but still absorbent can be made. However, the use of gamma rays requires expensive equipment and time consuming procedures due to safety concerns, and the degree of cross-linking that is obtained is often difficult to control.
Several references have reported the use of chemical cross-linking groups as a method of avoiding the dangers and costs associated with the use of ionizing radiation. U.S. Pat. No. 3,963,605 to Chu reported a water-swellable, cross-linked poly(alkylene oxide) that was produced by h
Laumer Jason Matthew
Makoui Kambiz Bayat
Qin Jian
Sawyer Lawrence Howell
Soerens Dave Allen
Kimberly--Clark Worldwide, Inc.
Moore Margaret G.
Pauley Petersen & Erickson
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