Surgery – Means and methods for collecting body fluids or waste material – Absorbent pad for external or internal application and...
Reexamination Certificate
1999-09-14
2002-04-09
Acquah, Samuel A. (Department: 1711)
Surgery
Means and methods for collecting body fluids or waste material
Absorbent pad for external or internal application and...
C528S481000, C528S491000, C528S495000, C528S496000, C528S499000, C528S50200C, C528S503000, C428S304400, C428S308400, C524S081000, C524S356000, C604S358000, C604S385230
Reexamination Certificate
active
06369293
ABSTRACT:
BACKGROUND OF THE INVENTION
The use of 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, preferably of about 20, and often of up to 100 times their weight in a test liquid, such as water or a saline solution. 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 has 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. One characteristic common among such absorbent materials is that they are water-swellable and water-insoluble. In order to achieve such a water-swellable, water-insoluble characteristic, the absorbent material will generally be crosslinked. The amount of crosslinking will generally be above a minimum amount sufficient to make the material water-insoluble but also below some maximum amount so as to allow the material to be sufficiently water swellable so that the water-swellable, water-insoluble material absorbs a desired amount of liquid.
Crosslinking of a material may generally be achieved by either of two different types of crosslinking agents. The first type of crosslinking agent is a polymerizable crosslinking agent. Suitable polymerizable crosslinking agents are generally reactive to a monomer or monomers used to prepare the material and, thus, generally comprise at least two functional groups that are capable of reacting with the monomers. The second type of crosslinking agent is a latent crosslinking agent. Latent crosslinking agents generally do not take part in an overall polymerization process but, instead, are reactive to a polymer at a later point in time when a proper crosslinking condition is provided. Suitable post treatment conditions include using heat treatment, exposure to high energy radiation such as ultraviolet light, x-rays, beta-rays, or gamma-rays, exposure to microwaves, steam or high humidity treatment, high pressure treatment, or treatment with an organic solvent.
Such crosslinking processes inherently result in the use of a separate crosslinking agent or reaction condition thereby increasing the costs of manufacturing the chemically crosslinked material. Additionally, the use of certain crosslinking agents typically requires specialized handling procedures, further increasing the costs of manufacturing, and potentially limiting the applications for which the chemically crosslinked material may be used. Another disadvantage concerning the use of chemical crosslinking agents is that they are often based on chemicals which exhibit certain degrees of toxicity.
SUMMARY OF THE INVENTION
In one aspect, the present invention concerns an absorbent composition comprising an uncrosslinked polymer wherein the absorbent composition is able to absorb or immobilize a relatively large quantity of the liquid.
One embodiment of the present invention concerns an absorbent composition comprising an uncrosslinked polymer, wherein the uncrosslinked polymer has a weight average molecular weight greater than about 1,000,000 and wherein the absorbent composition exhibits a Free Swell value that is at least about 15 grams of water per gram of absorbent composition and a Centrifuge Retention Capacity value that is at least about 8 grams of water per gram of absorbent composition, wherein the time period used to determine both the Free Swell value and the Centrifuge Retention Capacity value is about 19 hours.
In another aspect, the present invention concerns a process for preparing an absorbent composition comprising an uncrosslinked polymer, wherein the absorbent composition exhibits desired absorbent properties.
One embodiment of the present invention concerns a process for preparing an absorbent composition comprising an uncrosslinked polymer, the process comprising the following steps:
a. preparing a mixture of a solvent soluble, uncrosslinked polymer that has a molecular weight greater than about 1,000,000 and a solvent in which the uncrosslinked polymer is soluble, wherein the soluble, uncrosslinked polymer dissolves into the solvent; and
b. recovering the uncrosslinked polymer from the mixture,
wherein the absorbent composition exhibits a Free Swell value that is at least about 15 grams of water per gram of absorbent composition and a Centrifuge Retention Capacity value that is at least about 8 grams of water per gram of absorbent composition, wherein the time period used to determine both the Free Swell value and the Centrifuge Retention Capacity value is about 19 hours.
In another aspect, the present invention concerns a disposable absorbent product comprising an absorbent composition of the present invention that exhibits desired absorbent properties.
In one embodiment of the present invention, a disposable absorbent product comprises a liquid-permeable topsheet, a backsheet attached to the topsheet, and an absorbent structure positioned between the topsheet and the backsheet wherein the absorbent structure comprises an uncrosslinked polymer of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention relates to an absorbent composition comprising an uncrosslinked, high molecular weight polymer, wherein the absorbent composition exhibits desirable absorbent properties. Specifically, the present invention relates to an absorbent composition having the ability to absorb or immobilize a large quantity of liquid. The absorbent composition is useful in disposable absorbent products, such as those disposable absorbent products that are used to absorb or immobilize bodily liquids.
The present invention also provides an absorbent composition that absorbs or immobilizes a liquid with about the same final capacity as compared to commercially available synthetic, crosslinked superabsorbent materials. In one embodiment of the present invention, an absorbent composition is provided which spontaneously degrades over time so that the absorbent composition offers environmental advantages in comparison to existing absorbent compositions.
As used herein, the term “immobilant”, “immobilize”, or other similar terms, is intended to refer to a material, or the effects of such a material, that impedes the movement or flow of a liquid. In the present invention, an effectively entangled, solvent-insoluble uncrosslinked, relatively high molecular weight polymer is generally believed to act as an immobilant for many liquids, by which a liquid becomes entrapped within the network of entangled polymer chains, as well as an absorber of the liquid. Whether an effectively entangled, solvent-insoluble uncrosslinked, relatively high molecular weight polymer actually absorbs or simply immobilizes a liquid is not considered to be important for purposes of the present invention as long as the effectively entangled, solvent-insoluble uncrosslinked, relatively high molecular weight polymer effectively impedes the movement or flow of a liquid so as to exhibit the desired liquid handling properties described herein, such as, for example, Free Swell, Absorbency Under Load, and Centrifuge Retention Capacity.
It has now been discovered that an absorbent composition comprising an uncrosslinked, relatively high molecular weight polymer may be prepared
Dupuis Mary Jeanne
Jorgenson Thomas Patrick
Kepner Eric Scott
Reeves William Grover
Richmond Gerald Lee
Acquah Samuel A.
Kimberly--Clark Worldwide, Inc.
Pugliese, III Sebastian
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