Surgery – Means and methods for collecting body fluids or waste material – Absorbent pad for external or internal application and...
Reexamination Certificate
1999-04-29
2001-05-08
Weiss, John G. (Department: 3761)
Surgery
Means and methods for collecting body fluids or waste material
Absorbent pad for external or internal application and...
C604S358000, C604S359000
Reexamination Certificate
active
06229062
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to superabsorbent polymers (SAPs) containing odor-controlling compounds. The odor-controlling SAPs can be incorporated into articles, such as bandages, diapers, sanitary napkins, and other disposable paper products, where the odor-controlling compounds act to reduce and/or eliminate malodors.
BRIEF DESCRIPTION OF RELATED TECHNOLOGY
Water-absorbing resins are widely used in sanitary and hygienic goods, wiping cloths, water-retaining agents, dehydrating agents, sludge coagulants, disposable towels and bath mats, disposable door mats, thickening agents, disposable litter mats for pets, condensation-preventing agents, and release control agents for various chemicals. Water-absorbing resins are available in a variety of chemical forms, including substituted and unsubstituted natural and synthetic polymers, such as hydrolysis products of starch acrylonitrile graft polymers, carboxymethylcellulose, crosslinked polyacrylates, sulfonated polystyrenes, hydrolyzed polyacrylamides, polyvinyl alcohols, polyethylene oxides, polyvinylpyrrolidones, and polyacrylonitriles.
Such water-absorbing resins are termed “superabsorbent polymers,” or SAPs, and typically are lightly crosslinked hydrophilic polymers. SAPs are discussed generally in Goldman et al. U.S. Pat. Nos. 5,669,894 and 5,559,335, the disclosures of which are incorporated herein by reference. SAPs can differ in their chemical identity, but all SAPs are capable of absorbing and retaining amounts of aqueous fluids equivalent to many times their own weight, even under moderate pressure. For example, SAPs can absorb one hundred times their own weight, or more, of distilled water. The ability to absorb aqueous fluids under a confining pressure is an important requirement for an SAP used in a hygienic article, such as a diaper.
As used herein, the term “SAP particles” refers to superabsorbent polymer particles in the dry state, more specifically, particles containing from no water up to an amount of water less than the weight of the particles. The terms “SAP gel,” “SAP hydrogel,” or “hydrogel” refer to a superabsorbent polymer in the hydrated state, more specifically, particles that have absorbed at least their weight in water, and typically several times their weight in water.
Bodily fluids, such as blood, urine, menses, and the like, have an unpleasant odor or develop an unpleasant odor when exposed to air and/or bacteria for prolonged time periods. For example, it is known that human urine contains urea, which in turn is hydrolyzed to yield carbon dioxide and ammonia, the latter having a pungent, unpleasant odor. Ammonia also is an alkaline substance that can irritate skin. Once these bodily fluids are absorbed by the hygienic and sanitary goods containing an SAP, it is important to ensure proper odor control, for example by overcoming the malodor and irritation caused by ammonia, or by preventing the formation of ammonia. Prevention of ammonia formation can be accomplished by inhibiting the action of urease, an enzyme produced by bacteria that catalyzes the hydrolysis of urea to ammonia and carbon dioxide.
For example, cyclodextrin has been found to be an effective compound for controlling malodors. Cyclodextrin is capable of encapsulating molecules, and, therefore, as a dry powder, effectively absorbs odoriferous molecules into its structure. When wet by bodily fluids, cyclodextrin is solubilized, and then is capable of controlling malodors more effectively by forming inclusion complexes with the odoriferous molecules (e.g., ammonia) or precursors thereof (e.g., urea). For example, cyclodextrin, when wet by urine, encapsulates urea and acts as a barrier preventing the catalytic hydrolysis of urea to ammonia by urease. Furthermore, any ammonia formed by the noncatalytic hydrolysis of urea is encapsulated by the cyclodextrin, thereby trapping the malodorous ammonia molecules.
U.S. Pat. Nos. 5,733,272, 5,714,445, and 5,429,628 disclose that cyclodextrin can be incorporated with SAPs by sprinkling, mixing, or distributing a dry cyclodextrin powder onto a fluid absorbent material, e.g., an SAP. More specifically, the patents disclose that cyclodextrin can be distributed by an in situ crystallization technique wherein the fluid absorbent material is impregnated with a saturated aqueous solution of the cyclodextrin. Upon drying, the cyclodextrin crystallizes as small particles adhering to the absorbent material. This process is carried out, for example, by spraying an aqueous solution of the cyclodextrin onto an already formed dry absorbent material, or onto a wet fiber web precursor of the dry absorbent material. Alternatively, the patents disclose that a water-soluble binder can be used to adhere cyclodextrin powder to the fluid absorbent material.
The distribution of cyclodextrin as disclosed in these patents, however, is not uniform throughout a cross section of the absorbent material. A major portion of the cyclodextrin is present near the external surface of the absorbent material (e.g., SAP particle), and a minor portion, if any, of the cyclodextrin is present within the absorbent material particle. When an absorbent material is wet by bodily fluids, the fluids typically penetrate beyond the surface of the absorbent material and soak into the core of the material. With an inadequate amount of cyclodextrin at or near the core of the material (e.g., SAP particle), malodors cannot be controlled or trapped effectively.
Therefore, it would be desirable to provide an SAP that exhibits exceptional odor-reducing and odor-controlling characteristics. Furthermore, it would be desirable to provide an SAP having a uniform distribution of an odor-controlling compound therein. In addition, it would be desirable to provide an odor-controlling SAP that has an ability to absorb liquids quickly, demonstrates good fluid permeability and conductivity into and through the SAP, and has a high gel strength, such that the hydrogel formed from the SAP does not deform or flow under an applied stress or pressure.
SUMMARY OF THE INVENTION
The present invention is directed to an odor-controlling superabsorbent polymer (SAP) and to methods of manufacturing an odor-controlling SAP. More particularly, the present invention is directed to an odor-controlling SAP having an odor-controlling compound homogeneously distributed throughout an SAP particle.
One aspect of the present invention, therefore, is to provide a method of manufacturing an odor-controlling SAP including the steps of polymerizing an &agr;,&bgr;-unsaturated carboxylic acid, such as acrylic acid, either neutralized, unneutralized, or a mixture of both (i.e., DN (degree of neutralization) of 0 to 100), to form a polymeric hydrogel, admixing an odor-controlling compound selected from the group consisting of a cyclodextrin compound, triclosan, an amphoteric surfactant, a water-insoluble phosphate, and mixtures thereof, with the polymeric hydrogel, and then, if necessary or desired, neutralizing the resulting admixture. The resulting odor-controlling hydrogel has the odor-controlling compound homogeneously dispersed throughout the hydrogel.
Another aspect of the invention is to provide a method of making an odor-controlling SAP including the steps of polymerizing a mixture containing water, an &agr;,&bgr;-unsaturated carboxylic acid (either neutralized, unneutralized, or a mixture of both), and an odor-controlling compound selected from the group consisting of a cyclodextrin compound, an amphoteric surfactant, a water-insoluble phosphate, and mixtures thereof, to form a polymeric hydrogel, and thereafter, if necessary or desired, neutralizing the polymeric hydrogel to form an odor-controlling SAP having an odor-controlling compound distributed homogeneously therethrough. The method also includes the optional step of admixing a second odor-controlling compound selected from the group consisting of a cyclodextrin compound, triclosan, an amphoteric surfactant, a water-insoluble phosphate, and mixtures thereof, with t
Darlington, Jr. Jerald W.
Mandell Kathleen
Tomlin Anthony S.
BASF Aktiengesellschaft Corporation
Bogart Michael
Marshall O'Toole Gerstein Murray & Borun
Weiss John G.
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