Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Nonwoven fabric
Reexamination Certificate
1999-08-16
2001-08-21
Copenheaver, Blaine (Department: 1771)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Nonwoven fabric
C428S327000, C428S328000, C428S330000
Reexamination Certificate
active
06277772
ABSTRACT:
TECHNICAL AREA
The present invention concerns the utilization of bactericidal zeolites containing metal ions to confer antiodor properties onto superabsorbent hydrophilic polymers.
The superabsorbent polymers (SAP) are used in the manufacture of disposable pants to improve their absorption capacity for liquids, in particular, for urine. When the absorbent article is impregnated with urine, it develops various strong and unpleasant odors, including the odor of ammonia, coming from the hydrolysis of urea by bacterial ureases (Proteus, Acinetobacter, etc.) present in the skin and in the digestive tract.
Search for a solution to the problem of odors is especially pressing because, in our days, the absorption capacity of articles for protection against body fluids has been increasing very significantly by incorporating in them superabsorbent polymers (SAP), in particular, hydrophilic polymers and copolymers of acrylic acid; at the same time, the duration of keeping them in place is increased and all these conditions promote the development of microbial and enzymatic activity and emission of odors which result from that.
PRIOR ART
With the purpose of eliminating these odors, numerous actions were undertaken in the field of hygiene in general; this was done in different ways. For example, odor or ammonia absorbents have been widely used (U.S. Pat. No. 3,340,875 of the Scolt [sic, this is a typo in French text, should be Scott] Paper Company, U.S. Pat. Nos. 4,795,482 and 4,826,497 of Union Carbide) in combination with deodorants, fragrances, etc. The use of oxidizing agents (hydrogen peroxide, chlorine dioxide) as well as bactericides (in particular, quaternary ammonium salts), antibiotics, complexing agents, surfactants, alone or in combinations of these, have also been recommended. These products pose the general problem that they have an irritating action on the skin and the mucosa. The absorbents for odors or ammonia are certainly less dangerous in this regard, but they leave a clear field for bacterial proliferation which remains bothersome and which should be controlled to start with.
DESCRIPTION OF THE INVENTION
Now it was found that it is possible to formulate superabsorbent polymers with zeolite exchanged with metal ions in order to produce absorbent compositions, which, when they are saturated with urine or biological fluids, and are maintained under the conditions of utilization which are propitious for development of bacteria, do not give rise either to large evolution of ammonia or to the emission of repulsive or simply unpleasant odors and which impart this property to the hygiene articles that contain them.
Thus, the invention consists of a superabsorbent composition intended for the production of hygiene articles of the type of pants, diapers, do not develop unpleasant odors, comprising a superabsorbent polymer for water, saline solutions and body fluids and a zeolite exchanged with metal cations having bactericidal properties in the proportion of 0.05% to 10%, preferably 0.01 to 5% with respect to the superabsorbent composition.
Superabsorbent polymers are products which respond to the definition of superabsorbents as it is found in the work “Absorbent Polymer Technology”, “Studies in Polymer Sciences 8, Elsevier 1990”, that is, dry materials which can absorb spontaneously an aqueous fluid at a rate of at least twenty times its own weight. The superabsorbent polymers in the sense of the present invention are polymers which are obtained by the polymerization of water-soluble, ethylenically unsaturated monomers with partial crosslinking, in particular, acrylic acid and methacrylic acid, as well as their alkali salts, which are obtained by a method of polymerization in solution or in suspension. These polymers have a very large capacity of absorption and retention of water and aqueous solutions and today are widely used in the market in the form of powders, the particle sizes being between 100 and 800 &mgr;m. The literature on them is very rich; one can consult, for example, EP-A-0312952 (The Dow Chemical Company) and EP-A-0441507 (Sumitomo Seika Chem.).
Zeolites are microporous crystalline aluminosilicates, the structure of which is that of assemblies of tetrahedral groups of SiO
4
−
and AlO
4
−
and which can be represented by the formula expressed as oxides
x M
2
O; Al
2
O
2
; y SiO
2
; z H
2
O
in which M is an alkali or alkaline-earth cation with the valence n,
x is a number less than or equal to 1,
y is between 2 and 30, and
z is a number which expresses the state of hydration of the zeolite.
The bactericidal properties of zeolites exchanged with certain metal cations, which themselves have bactericidal properties, are known. They have been used to prepare bactericidal fibers that permit the manufacture of articles of current consumption: socks, undergarments, etc., especially in Japan (U.S. Pat. Nos. 4,525,410 and 5,064,599, Kanebo). Recently, the Procter & Gamble Company claimed an absorbent system that controls body odors by incorporating into them zeolites exchanged with silver in the perforated plastic film which envelopes the absorbent (WO 95/24173). Others place a layer of such zeolites in the sandwich manner between two sheets of superabsorbent polymer films (JP 63 156540, Dainippon Printing Co.). Other patents describe the aqueous dispersion of zeolites exchanged with silver in textile layers (JP 63 097,159, Matsui), or they are used by them impregnating confetti dispersed in the absorbent components of hygiene articles (EP 0389015, Procter & Gamble). If one excepts the very curious synergism between a metal zeolite and a ceramic which radiates in the far infrared (JO63-210174, OTA), one does not find any teaching published about compositions containing a superabsorbent polymer and a metal zeolite.
The superabsorbent compositions of the invention are prepared very easily, these being compositions which resist the emission of ammonia and unpleasant odors when they are saturated with body fluids, for example, a mixture of superabsorbent polymer powder with a particle size between 100 and 800 &mgr;m with a zeolite powder exchanged with metal cations, preferably having a particle size between 0.5 and 20 pm, at a rate of 0.05 to 10% and preferably 0.1 to 5% by weight of the exchanged zeolite with respect to the composition.
These exchanged zeolites are themselves prepared in the known manner starting from natural or synthetic zeolites. More particularly, zeolites A (LTA) or faujasites (FAU) or their mixtures are used for this purpose. The zeolite powder is suspended in water under agitation and then an aqueous solution of the metal ion with bactericidal properties, in particular, the Ag
+
, Cu
2+
, Zn
2+
ions, is added to it. It is recommended to disperse the zeolite powder to be exchanged preferably at pH 7-8 to avoid the precipitation of the metal oxide or hydroxide. The useful quantity of Ag
+
ions attached to the zeolite is between 0.01 and 10% by weight with respect to the zeolite, preferably between 0.05% and 5%. The quantity of Cu
2+
and Zn
2+
ions is between 0.1 and 25%, preferably between 0.2 and 15% by weight.
The superabsorbent compositions of the invention gel upon contact with water, aqueous saline solutions or body fluids as the superabsorbents of the prior art, and the gels thus formed behave essentially identically. Thus, one can use them instead of the ordinary superabsorbents in the manufacture of hygiene articles, such as disposable diapers, or disposable pants for babies, children, adults or the elderly of both sexes.
Not suffering from any contraindication, the zeolites exchanged with the metal ions Ag
+, Cu
2+
and Zn
2+
be justly considered as being harmless, on the one hand, because these ions are strongly attached to the inside of the zeolite structure, and, on the other hand, because these ions are traditionally and widely used in antiseptic compositions for the skin (Flanamazinc® and Sicazine® 1%; 1% silver sulfadiazine with a silver content of 0.3%, Dermocuivr
Gancet Christian
Nicolas Serge
Taupin Yves
CECA S.A.
Copenheaver Blaine
Smith , Gambrell & Russell, LLP
Torres Norca L.
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