Stock material or miscellaneous articles – Coated or structually defined flake – particle – cell – strand,... – Particulate matter
Reexamination Certificate
1999-12-06
2002-05-28
Morris, Terrel (Department: 1771)
Stock material or miscellaneous articles
Coated or structually defined flake, particle, cell, strand,...
Particulate matter
C428S296100, C428S402000, C428S408000, C428S913000, C604S365000, C604S367000, C604S368000, C604S375000
Reexamination Certificate
active
06395395
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to superabsorbent materials and compositions containing superabsorbent materials exhibiting enhanced blood absorbence properties and methods for enhancing the blood absorbence properties of such superabsorbent materials and compositions. More specifically, the present invention relates to superabsorbent materials exhibiting enhanced blood absorbence properties for use in disposable, superabsorbent products such as feminine hygiene articles and medical articles.
BACKGROUND OF THE INVENTION
Superabsorbent polymers have been developed in recent years that are capable of absorbing many times their own weight of liquid. These polymers, which are also known as water insoluble hydrogels, have been used to increase the absorbency of sanitary products, such as diapers and sanitary napkins. Superabsorbent polymers are often provided in the form of particulate powders, granules, or fibers that are distributed throughout superabsorbent cellulosic products to increase the absorbency of the product. Superabsorbent particles are described, for example, in U.S. Pat. Nos. 4,160,059; 4,676,784; 4,673,402; 5,002,814; and U.S. Pat. No. 5,057,166. Products such as diapers that incorporate superabsorbent hydrogels are shown in U.S. Pat. Nos. 3,669,103 and 3,670,731.
Superabsorbents have not found widespread use in superabsorbent sanitary articles, such as sanitary napkins, surgical wipes, and other articles used to absorb blood and other serous body fluids, because the superabsorbent materials do not absorb blood readily, nor do they have a high capacity for blood. The low blood absorbent capacity of the superabsorbent material means that large amounts of the superabsorbent material must be incorporated into blood absorbent articles, a factor which increases the production and materials cost for such superabsorbent articles.
U.S. Pat. Nos. 4,190,563 and 4,435,172 describe methods for improving the dispersability of particulate superabsorbent materials within blood. The '563 patent describes improving blood dispersability of superabsorbent materials by surface treating the material with one or more high molecular weight polyethers. The '563 patent describes that the polyethers can be used in amounts ranging from about 1% to about 35% by weight. The '563 patent describes that the polyether coated superabsorbent materials exhibited improved dispersability in blood. The '172 patent describes superabsorbent articles wherein the blood absorption rate is increased by the addition of amido compounds and non-ionic surfactants to water-soluble hydrophillic polymers. Such treated water-soluble hydrophillic polymers tend to be prone to potential risks of toxicity of the polymer and surfactants during use and after disposal (i.e., leaching of unused polymer or surfactant).
A superabsorbent for blood and serous body fluids is disclosed in U.S. Pat. No. 4,693,713. The disclosed superabsorbent composition includes component A, which is described as a water swellable synthetic or natural polymer or copolymer, and component B, which is described as an inorganic or organic compound that at normal temperature is present in the form of a pourable powder and is water soluble. The relatively high levels of component B described in the '713 patent contribute to processing, handling, use (from a toxicity standpoint) and disposal problems.
U.S. Pat. No. 4,381,784 describes an superabsorbent article for absorbing blood that includes a water soluble blood gelling agent to thicken and bind menstrual fluid within the superabsorbent article. According to the '784 patent, the blood gelling agents react with the protein present in blood or menstrual fluid, form particulate disordered structures according to the fourth class of gels defined by Flory, which are essentially completely water soluble, essentially completely linear, and which when placed in water will not form a Class 4 gel without the presence of blood protein. Such water soluble gelling agents are susceptible to the same risks as the water-soluble hydrophillic polymers discussed above with respect to the '784 patent.
U.S. Pat. No. 5,241,009 describes polycarboxyl group containing superabsorbents wherein neutralization of said carboxyl groups with potassium or lithium is described as providing a polymeric composition specifically adapted to absorb proteinaceous fluids, such as blood.
It would be advantageous to provide a superabsorbent material and composition which can be used in sanitary superabsorbent articles, such as sanitary napkins, and surgical wipes, which have a blood absorbent capacity and blood retention properties that would make them suitable choices for improving the blood absorbency of such articles. It would further be advantageous to provide such superabsorbent materials in a manner that is compatible with existing methods of producing such materials and incorporating them into absorbent articles. It would also be advantageous to provide such superabsorbent materials that do not suffer from the drawbacks of prior materials for absorbing serious fluids, such as blood.
SUMMARY OF THE INVENTION
The foregoing and other advantages are provided by the superabsorbent materials and compositions and methods of producing the superabsorbent materials and compositions in accordance with the present invention. Applicants have found that certain of the binders described in the earlier filed applications referenced above, when combined with superabsorbent materials as described below, surprisingly enhance the blood absorbence properties of the superabsorbent material and compositions containing the superabsorbent material and enhancing agents. The advantages of the present invention are obtained by providing superabsorbent materials in combination with enhancing agents that enhance the blood absorbence properties such as free swell blood absorbent capacity and after load blood absorbent capacities, of the superabsorbent materials, and compositions containing the same.
In accordance with the present invention, the enhancing agents can be provided with the superabsorbent materials in several ways, e.g., at least partially coating the superabsorbent material with the enhancing agent, at least partially embedding the enhancing agent in the superabsorbent material, or providing a mixture of superabsorbent material and a fibrous material at least partially coated with the enhancing agent. The enhancing agents can be polymeric enhancing agents, non-polymeric organic enhancing agents, or nonreactive combinations thereof with each other.
In one aspect of the present invention, when the polymeric enhancing agent is to be applied to the superabsorbent material, it includes enhancing agent molecules that have at least one functional group capable of forming a hydrogen bond or a coordinate covalent bond with the superabsorbent material. The enhancing agent is applied to the superabsorbent material to at least partially coat the superabsorbent material, and/or partially embed the enhancing agent in the superabsorbent material, and enhance the blood absorbence properties, such as free swell blood capacity and after load blood capacity, of the superabsorbent material.
In a preferred embodiment of this aspect of the present invention, the polymeric enhancing agent is present in an amount ranging from about 0.01% to about 3% of the weight of the superabsorbent material; more preferably about 0.01% to about 1.0% and the free swell blood absorbent capacity of the treated superabsorbent material is preferably at least 1.15 times, and more preferably at least 1.5 times the free swell blood absorbent capacity of the untreated superabsorbent material. In another preferred embodiment, the after load blood absorbent capacity of the treated superabsorbent material is preferably at least 1.15, and more preferably 1.5 times the after load blood absorbent capacity of the untreated superabsorbent material.
In still another preferred embodiment of this aspect of the present invention, the superabsorbent materi
Halabisky Donald D.
Hansen Michael R.
Morris Terrel
Ruddock Ula C.
Weyerhaeuser Company
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