Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Coated or impregnated woven – knit – or nonwoven fabric which... – Coated or impregnated natural fiber fabric
Reexamination Certificate
1999-12-28
2004-01-13
Juska, Cheryl A. (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Coated or impregnated woven, knit, or nonwoven fabric which...
Coated or impregnated natural fiber fabric
C442S154000, C442S165000, C442S414000, C604S367000, C604S374000, C604S375000
Reexamination Certificate
active
06677256
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to an absorbent structure that forms a superabsorbent composition in situ having the ability to absorb a large quantity of liquid. The structure includes an absorbent material and a fibrous material having an activating agent incorporated therein. The fibrous material releases the activating agent in response to contact with liquid and the activating agent activates the absorbent material so that it becomes a superabsorbent material. The absorbent structure is useful in disposable absorbent products, such as those disposable absorbent products that are used to absorb bodily fluids.
BACKGROUND OF THE INVENTION
The use of water-swellable, generally water-insoluble absorbent materials, commonly known as superabsorbents, in disposable absorbent personal care products is known. Such absorbent materials are generally employed in absorbent products such as diapers, training pants, adult incontinence products, and feminine care products in order to increase the absorbent capacity of such products while reducing their overall bulk. Such absorbent materials are generally present in absorbent products in a fibrous matrix, such as a matrix of wood pulp fluff. A matrix of wood pulp fluff generally has an absorbent capacity of about 6 grams of liquid per gram of fluff. The superabsorbent materials generally have an absorbent capacity of at least about 10, desirably of about 20, and often of up to about 1000 times their weight in water. Clearly, incorporation of such absorbent materials in personal care products can reduce the overall bulk while increasing the absorbent capacity of such products.
A wide variety of materials have been described for use as absorbent materials in personal care products. Such materials include natural-based materials such as agar, pectin, gums, carboxyalkyl starch, and carboxyalkyl cellulose, as well as synthetic materials such as polyacrylates, polyacrylamides, and hydrolyzed polyacrylonitrile. While such natural-based absorbent materials are known for use in personal care products, they have not gained wide usage in such products, at least in part because their absorbent properties are generally inferior compared to the synthetic absorbent materials, such as the sodium polyacrylates. Specifically, many of the natural-based materials tend to form soft, gelatinous masses when swollen with a liquid. When employed in absorbent products, the presence of such soft gelatinous masses tends to prevent the transport of liquid within the fibrous matrix in which the absorbent materials are incorporated. This phenomenon is known as gel blocking. Once gel blocking occurs, the product cannot efficiently absorb subsequent insults of liquid, and the product tends to leak. Further, many of the natural-based materials exhibit poor absorption properties, particularly when subjected to external pressures.
In contrast, synthetic absorbent materials are often capable of absorbing large quantities of liquid while maintaining a generally stiff, non-mucilaginous character. Accordingly, synthetic absorbent materials can be incorporated in absorbent products while minimizing the likelihood of gel blocking.
One property of currently available superabsorbent materials is that such materials typically very rapidly absorb the liquid that comes into contact with the superabsorbent material. While such quick absorbency of the liquid may be desirable in many applications, there are certain applications in which it is not desirable. For example, in an absorbent structure that is insulted with a liquid at only a very localized location, it would generally be desirable to have the liquid distributed throughout the entire volume of the absorbent structure so that the absorbent capacity of the entire absorbent structure is utilized. However, if the superabsorbent material located near the localized insult location absorbs the liquid very quickly, this superabsorbent material may swell and restrict the flow of the liquid throughout the rest of the absorbent structure, possibly resulting in the liquid leaking out of the absorbent structure in the area of the localized insult location. Accordingly, it is often desirable to employ a superabsorbent material in the localized insult location that actually absorbs the liquid at a slow rate. This allows the liquid to be distributed throughout the absorbent structure first and then be subsequently absorbed by the superabsorbent material.
Several methods are known to slow down the liquid absorbing rate of a relatively fast absorbing superabsorbent material. For example, it is possible to coat the fast absorbing superabsorbent material with a material that is nonabsorbent and/or hydrophobic. Such coating materials tend to temporarily shield the underlying superabsorbent material from any liquid and, thus, delay the absorption of the liquid by the superabsorbent material. However, such coating materials often reduce the overall liquid capacity of the superabsorbent material, add to the expense and complexity of preparing the superabsorbent material, and may negatively affect other liquid handling properties of the superabsorbent material.
Commercially available superabsorbents are generally in a substantially neutralized or salt form. This is because, in general, in order to have a relatively high capacity for liquid absorption, a water-swellable, water-insoluble polymer must be a polyelectrolyte. However, such superabsorbents absorb liquid relatively quickly, leading to the above discussed problems. It is known that when an acidic or basic water-swellable, water-insoluble polymer, substantially in its free acid or free base form, respectively, is mixed with a basic second material or an acidic second material, respectively, the resulting absorbent composition will exhibit both a relatively high capacity for liquid absorption as well as a relatively slow liquid absorbing rate. This is believed to be because, as the mixture is placed in an aqueous solution, the acidic or basic water-swellable, water-insoluble polymer, substantially in its free acid or free base form, respectively, reacts with the basic second material or the acidic second material, respectively, and the chemical equilibrium is in favor of converting the acidic or basic water-swellable, water-insoluble polymer from its free acid or free base form, respectively, to its respective salt form. As such, the mixture comprising the converted water-swellable, water-insoluble polymer will now exhibit a relatively high capacity for liquid absorption. However, because the conversion of the water-swellable, water-insoluble polymer, from its free acid or free base form, respectively, to its respective salt form is a relatively slow process of ionization and ion diffusion into the polymer, the water-swellable, water-insoluble polymer will also exhibit a relatively slow liquid absorbing rate. In addition, the conversion of the water-swellable, water-insoluble polymer from its free acid or free base form to its respective salt form in an electrolyte-containing solution, such as an aqueous sodium chloride solution, has a substantial desalting effect on the electrolyte-containing solution, thereby improving the liquid-absorbing performance of the mixture by alleviating the salt-poisoning effect.
WO 98/24832 discloses an absorbent composition that includes a polymeric absorbent material and a second material. The two components are mixed and used in an absorbent article, desirably in conjunction with a fibrous matrix. The second material can be provided in the form of particles, flakes, fibers, films, and nonwoven structures or the two components can be provided as a bi-component fiber. This composition has disadvantages in terms of handling properties and structural integrity.
A single material or polymer comprising both acidic and basic functional groups within its molecular structure will not exhibit the desired absorbent properties described above. This is believed to be because such acidic and basic functional groups within a single molecular struc
Dutkiewicz Jacek
Li Yong
Lonsky Werner
Qin Jian
Sun Tong
Befumo Jenna-Leigh
Charlier Patricia A.
Juska Cheryl A.
Pratt John S.
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