Stock material or miscellaneous articles – Web or sheet containing structurally defined element or... – Composite having voids in a component
Reexamination Certificate
2003-05-01
2004-10-26
Pezzuto, Helen L. (Department: 1713)
Stock material or miscellaneous articles
Web or sheet containing structurally defined element or...
Composite having voids in a component
C428S131000, C428S314200, C428S317100, C428S913000, C442S118000, C442S119000, C442S154000, C442S155000, C442S156000
Reexamination Certificate
active
06808801
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention is directed to an absorbent structure including a fluid intake layer, a support layer, and a self-forming absorbent binder layer holding the fluid intake layer and the support layer together.
Adhesives, or binders, are a necessary element of many absorbent products. While adhesives beneficially hold products together, adhesives may also have a tendency to interfere with the absorbency of fluids in absorbent products. Adhesives are typically hydrophobic and therefore are not conducive to absorbency or liquid transfer functions. Furthermore, most adhesives are non-absorbent and thus serve no liquid retention function.
Hydrophilic adhesives are known, such as adhesives formulated from water-soluble polymers such as poly(vinyl alcohol), poly(vinyl methyl ether), poly(vinyl pyrrolidone), poly(ethylene oxide), or cellulose derivatives such as hydroxypropyl cellulose. Dextrans, starches and vegetable gums have been used to provide hydrophilic adhesives. These materials provide adhesion under dry conditions. However, upon exposure to aqueous fluids, these materials lose bonding capability because they are substantially soluble in aqueous fluids.
A known approach for making hydrophilic adhesives more functional upon exposure to aqueous fluid is to crosslink the water-soluble polymers. As a result of crosslinking, the material becomes swellable, and no longer soluble, in aqueous fluid. However, crosslinked polymers are difficult to apply to substrates or to establish intimate contact with surfaces because the crosslinked polymers are solid materials and have little or no ability to flow. Some of the crosslinked materials are fairly stiff, and inhibit the flexibility of the absorbent product.
What is therefore needed is a hydrophilic binder or coating that has latent crosslinking capability and which can be produced at attractive cost. Such binder or coating could be easily applied, like a water-soluble polymer, since the hydrophilic binder or coating would be capable of flow prior to crosslinking. Latent crosslinking capability would also provide a simple means of crosslinking the polymer after the polymer has established intimate contact with substrates or has formed a desired final shape or form. There is also a need or desire for such a binder which has a high level of flexibility.
Post-application crosslinking techniques are well known. Typical means of inducing the formation of crosslinks include high temperature “curing” or exposure to radiation, such as ultraviolet or gamma radiation. Another known means of post-application crosslinking is moisture-induced crosslinking.
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.
Anderson et al., in U.S. Pat. No. 5,196,470, reported an alcohol-based, water-soluble binder composition. Because this composition is water-soluble and not cross-linked, it has no absorbency.
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-processable, 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.
U.S. Pat. No. 5,204,404 to Werner reported crosslinkable hydrophobic acrylate ester copolymers including 0.1 to 10% acrylic acid. The resultant cross-linked polymers were reported to be useful for painting and refinishing the exterior of automobiles.
These examples of moisture-induced crosslinking are applied to substantially hydrophobic polymers. 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, and for painting and refinishing the exterior of automobiles, it would be expected that they are durable coatings for which properties such as water absorbency would be a disadvantage.
Conventional personal care absorbent articles including diapers, training pants, sanitary napkins, adult incontinence garments and the like, have a relatively complex structure and manufacturing procedure. Personal care absorbent articles typically include a liquid-permeable bodyside liner, a surge (compensation) layer which receives and distributes liquid received through the liner, a single-layer or multiple-layer absorbent core which receives and stores liquid that passes through the compensation layer, and a liquid-impermeable outer cover that prevents liquid in the absorbent article and provides a substantially dry outer surface. Each of these layers is separately manufactured. The layers are then combined using adhesive bonding, thermal bonding, ultrasonic bonding and other techniques which must be tailored to sufficiently bond the layers together without compromising their respective functions. There is a need or desire for absorbent articles having simpler structures that can be manufactured using simpler, less expensive techniques.
SUMMARY OF THE INVENTION
This invention is directed to a three-layer absorbent structure and to absorbent articles containing it. The three-layer absorbent structure includes the following layers, in sequence, with no additional adhesive or other layers in between them:
a) a liquid-permeable fluid intake layer,
b) a flexible absorbent binder layer, and
c) a support layer.
The flexible absorbent binder layer serves as a fluid storage (absorbent) layer and also bonds the fluid intake layer to the support layer. The absorbent article may contain additional layers, so long as the above three layers of the absorbent structure occur in sequence. In some absorbent articles, the three-layer absorbent structure may not be accompanied by additional layers.
The three-layer absorbent structure is formed by applying an absorbent binder composition to one or both facing surfaces of the fluid intake layer and the support layer, bringing the fluid intake layer and support layer together, and crosslinking the absorbent binder composition to form the flexible absorbent binder layer. Because the flexible absorbent binder layer is formed (crosslinked) while the absorbent binder composition is in contact with the other layers, the flexible absorbent binder layer serves both as an
George Russell Paul
Laumer Jason Matthew
Soerens Dave Allen
Uttecht Cathleen Mae
Kimberly--Clark Worldwide, Inc.
Pauley Petersen & Erickson
Pezzuto Helen L.
LandOfFree
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