Patent Application
20080145269
Absorbent feminine care articles, such as sanitary napkins, panty containers, labial pads, and other types of catamenial devices, are used to absorb menses and other body fluids. These absorbent products are used during a women's menstrual cycle or between menstrual cycles for light incontinence purposes. Regardless, the absorbent articles are primarily designed for a single use, after which they are discarded into a toilet pail or trash receptacle. Unfortunately, however, storage in a toilet pail located in a bathroom or in some other trash receptacle may rapidly result in the development of disagreeable odors. As such, a need currently exists for a method for reducing the odor produced by personal care absorbent articles, particularly after they are disposed.
In accordance with one embodiment of the present invention, a deodorizing container is disclosed that comprises a resiliently deformable substrate having an inner surface and an outer surface that define therebetween an interior space. An odor control ink is present on the inner surface of the substrate, the odor control ink comprising a plurality of nanoparticles modified with a transition metal.
In accordance with another embodiment of the present invention, a method for reducing the odor associated with an article that contains a bodily fluid (e.g., urine, menses, etc.) is disclosed. The method comprises disposing the article (e.g., personal care absorbent article) into an interior space defined between an inner surface an outer surface of a deodorizing container. An odor control ink is present on the inner surface of the container, the odor control ink comprising a plurality of nanoparticles modified with a transition metal. The modified nanoparticles are configured to adsorb a malodorous compound associated with the bodily fluid.
Other features and aspects of the present invention are discussed in greater detail below.
A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, which makes reference to the appended figures in which:
Repeat use of references characters in the present specification and drawings is intended to represent same or analogous features or elements of the invention.
Reference now will be made in detail to various embodiments of the invention, one or more examples of which are set forth below. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations may be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment, may be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.
As used herein, the term “absorbent article” generally refers to any article capable of absorbing water or other fluids. Examples of some absorbent articles include, but are not limited to, personal care absorbent articles, such as diapers, training pants, absorbent underpants, incontinence articles, feminine hygiene products (e.g., sanitary napkins), swim wear, baby wipes, and so forth; medical absorbent articles, such as garments, fenestration materials, underpads, bedpads, bandages, absorbent drapes, and medical wipes; food service wipers; clothing articles; and so forth. Various absorbent article configurations are described, for instance, in U.S. Pat. No. 5,649,916 to DiPalma, et al.; U.S. Pat. No. 6,110,158 to Kielpikowski; U.S. Pat. No. 6,663,611 to Blaney, et al.; U.S. Pat. No. 4,886,512 to Damico et al.; U.S. Pat. No. 5,558,659 to Sherrod et al.; U.S. Pat. No. 6,888,044 to Fell et al.; and U.S. Pat. No. 6,511,465 to Freiburger et al., as well as U.S. Patent Application Publication No. 2004/0060112 A1 to Fell et al., all of which are incorporated herein in their entirety by reference thereto for all purposes.
As used herein, the term “Zeta Potential” generally refers to the potential gradient that arises across an interface. Zeta Potential measurements may be taken using, for instance, a Zetapals instrument available from the Brookhaven Instrument Corporation of Holtsville, N.Y. Zeta Potential measurements may be conducted by adding one to three drops of a sample into a cuvet containing 1 millimolar KCl solution, using the instrument's default functions preset for aqueous solutions.
As used herein, the term “nonwoven web” refers to a web having a structure of individual fibers that are randomly interlaid, not in an identifiable manner as in a knitted fabric. Nonwoven webs include, for example, meltblown webs, spunbond webs, carded webs, wet-laid webs, airlaid webs, coform webs, hydraulically entangled webs, etc. The basis weight of the nonwoven web may generally vary, but is typically from about 5 grams per square meter (“gsm”) to 200 gsm, in some embodiments from about 10 gsm to about 150 gsm, and in some embodiments, from about 15 gsm to about 100 gsm.
As used herein, the term “meltblown” web or layer generally refers to a nonwoven web that is formed by a process in which a molten thermoplastic material is extruded through a plurality of fine, usually circular, die capillaries as molten fibers into converging high velocity gas (e.g. air) streams that attenuate the fibers of molten thermoplastic material to reduce their diameter, which may be to microfiber diameter. Thereafter, the meltblown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed meltblown fibers. Such a process is disclosed, for example, in U.S. Pat. No. 3,849,241 to Butin, et al.; U.S. Pat. No. 4,307,143 to Meitner, et al.; and U.S. Pat. No. 4,707,398 to Wisneski, et al., which are incorporated herein in their entirety by reference thereto for all purposes. Meltblown fibers may be substantially continuous or discontinuous, and are generally tacky when deposited onto a collecting surface.
As used herein, the term “spunbond” web or layer generally refers to a nonwoven web containing small diameter substantially continuous filaments. The filaments are formed by extruding a molten thermoplastic material from a plurality of fine, usually circular, capillaries of a spinnerette with the diameter of the extruded filaments then being rapidly reduced as by, for example, eductive drawing and/or other well-known spunbonding mechanisms. The production of spunbond webs is described and illustrated, for example, in U.S. Pat. No. 4,340,563 to Appel. et al., U.S. Pat. No. 3,692,618 to Dorschner, et al., U.S. Pat. No. 3,802,817 to Matsuki, et al., U.S. Pat. No. 3,338,992 to Kinney, U.S. Pat. No. 3,341,394 to Kinney, U.S. Pat. No. 3,502,763 to Hartman, U.S. Pat. No. 3,502,538 to Levv, U.S. Pat. No. 3,542,615 to Dobo, et al., and U.S. Pat. No. 5,382,400 to Pike, et al., which are incorporated herein in their entirety by reference thereto for all purposes. Spunbond filaments are generally not tacky when they are deposited onto a collecting surface. Spunbond filaments may sometimes have diameters less than about 40 micrometers, and are often between about 5 to about 20 micrometers.
Generally speaking, the present invention is directed to a deodorizing container for the disposal of absorbent articles, such as sanitary napkins, diapers, wipes, etc. More specifically, the container includes an odor control ink that contains nanoparticles. The nanoparticles may possess various forms and shapes depending upon the desired result, such as a sphere, crystal, rod, disk, tube, string, etc. Regardless, the average particle size (e.g., diameter or width) of the nanoparticles is about 5 micrometers or less, in some embodiments about 1 micrometer or less, in some embodiments about 100 nanometers or less, in some embodiments from about 1 to about 50 nanometers, and in some embodiments, from about 2 to about 25 nanometers. Further, the surface area is typically about 50 square meters per gram (m2/g) or more, in some embodiments from about 100 m2/g to about 1000 m2/g, and in some embodiments, from about 150 m2/g to about 600 m2/g. Surface area may be determined by the physical gas adsorption (B.E.T.) method of Bruanauer, Emmet, and Teller, Journal of American Chemical Society, Vol. 60, 1938, p. 309, with nitrogen as the adsorption gas. Due to their small size and high surface area, it is believed that the nanoparticles provide an increased area for adsorbing malodorous compounds commonly associated with biological fluids (e.g., menses, urine, etc.). This increases the statistical likelihood of contact between the particle surface and malodorous compounds, thereby enhancing the overall odor reduction provided by the ink.
If desired, the nanoparticles may also be relatively nonporous or solid. That is, the nanoparticles may have a pore volume that is less than about 0.5 milliliters per gram (ml/g), in some embodiments less than about 0.4 milliliters per gram, in some embodiments less than about 0.3 ml/g, and in some embodiments, from about 0.2 ml/g to about 0.3 ml/g. Without intending to be limited by theory, it is believed that the solid nature, i.e., low pore volume, of the nanoparticles may enhance the uniformity and stability of the nanoparticles, without sacrificing their odor adsorption characteristics.
Any of a variety of nanoparticles may generally be employed in the present invention. One particularly suitable class of nanoparticles includes inorganic oxides, such as silica, alumina, zirconia, magnesium oxide, titanium dioxide, iron oxide, zinc oxide, copper oxide, zeolites, clays (e.g., smectite clay), combinations thereof, and so forth. Various examples of such nanoparticles are described in U.S. Patent Application Publication Nos. 2003/0203009 to MacDonald; 2005/0084412 to MacDonald, et al.; and 2005/0085144 to MacDonald. et al., which are incorporated herein in their entirety by reference thereto for all purposes. If desired, the nanoparticles may be selected to have a zeta potential that facilitates ionic bonding with certain compounds (e.g., odor control agent, malodorous compounds, etc.), a substrate, and so forth. For example, the nanoparticles may possess a negative zeta potential, such as less than about 0 millivolts (mV), in some embodiments less than about −10 mV, and in some embodiments, less than about −20 mV. Examples of nanoparticles having a negative zeta potential include silica nanoparticles, such as Snowtex-C, Snowtex-O, Snowtex-PS, and Snowtex-OXS, which are available from Nissan Chemical of Houston, Tex. Alternatively, the nanoparticles may have a positive zeta potential, such as greater than about 0 millivolts, in some embodiments greater than about +20 millivolts (mV), in some embodiments greater than about +30 mV, and in some embodiments, greater than about +40 mV. The nanoparticles may, for instance, be formed entirely from a positively charged material, such as alumina. Examples of commercially available alumina nanoparticles include, for instance, Aluminasol 100, Aluminasol 200, and Aluminasol 520, which are available from Nissan Chemical Industries Ltd. The positive zeta potential may also be imparted by a continuous or discontinuous coating present on the surface of a core material. In one particular embodiment, for example, the nanoparticles are formed from silica nanoparticles coated with alumina. A commercially available example of such alumina-coated silica nanoparticles is Snowtex-AK, which is available from Nissan Chemical of Houston, Tex.
Although the nanoparticles themselves possess a certain degree of odor reducing properties, they are nevertheless modified with a transition metal to improve their odor control properties. Without being limited by theory, it is believed that the transition metal provides one or more active sites for capturing and/or neutralizing a malodorous compound. The active sites may be free, or may be weakly bound by water molecules or other ligands so that they are replaced by a malodorous molecule when contacted therewith. In addition, the nanoparticles still have the large surface area that is useful in adsorbing other malodorous compounds. Examples of some suitable transition metals that may be used in the present invention include, but are not limited to, scandium, titanium, vanadium, chromium, manganese, iron, cobalt, nickel, copper, zinc, and so forth. Single metallic, as well as dinuclear, trinuclear, and cluster systems may be used. The ratio of the transition metal to the nanoparticles may be selectively varied to achieve the desired results. In most embodiments, for example, the molar ratio of the transition metal to the nanoparticles is at least about 10:1, in some embodiments at least about 25:1, and in some embodiments, at least about 50:1.
Due to the addition of the transition metal, the modified nanoparticles may sometimes exhibit a Zeta Potential that is different than the Zeta Potential of the nanoparticles prior to modification. The addition of positively-charged metal ions may, for instance, increase the Zeta Potential of the unmodified nanoparticles by at least about 1.0 millivolt, and in some embodiments, by at least about 5.0 millivolts. Of course, the particular difference in Zeta Potential, if any, is related in part to the quantity and type of transition metal employed. For instance, the addition of a dilute solution of copper chloride to a silica nanoparticle solution may result in a change in Zeta Potential of the silica suspension from −25 millivolts to a higher Zeta Potential, such as in the range of about −5 millivolts to −15 millivolts.
The transition metal may be applied to the nanoparticles in a variety of ways. For instance, nanoparticles may simply be mixed with a solution containing the appropriate transition metal in the form of a salt, such as those containing a copper ion (Cu+2), iron (III) ion (Fe+3), and so forth. Such solutions are generally made by dissolving a metallic compound in a solvent resulting in free metal ions in the solution. Generally, the metal ions are drawn to and adsorbed onto the nanoparticles due to their electric potential differences, i.e., they form an “ionic” bond. In many instances, however, it is desired to further increase the strength of the bond formed between the metal and nanoparticles through the formation of a coordinate and/or covalent bond. Although ionic bonding may still occur, the presence of coordinate or covalent bonding may have a variety of benefits, such as reducing the likelihood that any of the metal will remain free during use (e.g., after washing). Further, a strong adherence of the metal to the nanoparticles also optimizes odor adsorption effectiveness.
Numerous techniques may be utilized to form a stronger bond between the transition metal and nanoparticles. For example, silica sols are generally considered stable at a pH of greater than about 7, and particularly between a pH of 9-10. When dissolved in water, salts of transition metals are acidic (e.g., copper chloride has a pH of approximately 4.8). Thus, when such an acidic transition metal salt is mixed with a basic silica sol, the pH is lowered and the metal salt precipitates on the surface of the silica particles. This compromises the stability of the silica particles. Further, at lower pH values, the number of silanol groups present on the surface of the silica particles is reduced. Because the transition metal binds to these silanol groups, the capacity of the particles for the transition metal is lowered at lower pH values. Thus, to ameliorate the pH-lowering affect caused by the addition of an acidic transition metal salt (e.g., copper chloride), certain embodiments of the present invention employ selective control over the pH of the silica particles during mixing with the transition metal.
The selective control over pH may be accomplished using any of a variety of well-known buffering systems known in the art. One such buffering system utilizes urea thermal decomposition (i.e., pyrolysis) to increase pH to the desired value. The pyrolysis of urea is well known, and has been described in, for instance, Study of the Urea Decomposition (Pyrolysis) Reaction and Importance to Cyanuric Acid Production, Peter M. Shaber, et al., American Laboratory (August 1999), which is incorporated herein in its entirety by reference thereto for all purposes. For instance, to initiate the pyrolysis reaction, urea is first heated to its melting point of approximately 135° C. With continued heating to approximately 150° C., the urea is vaporized (Eq. 1) and is then decomposed into ammonia and isocyanic acid (Eq. 2). The urea also reacts with the isocyanic acid byproduct to form biuret (Eq. 3).
H2N—CO—NH2(m)+heatH2N—CO—NH2(g) (1)
H2N—CO—NH2(g)+heatNH3(g)+HNCO(g) (2)
H2N—CO—NH2(m)+HNCO(g)H2N—CO—NH—CO—NH2(s) (3)
H2N—CO—NH—CO—NH2(m)+HNCO(g)CYA(s)+NH3(g) (4)
H2N—CO—NH—CO—NH2(m)+HNCO(g)ammelide(s)+H2O(g) (5)
As the temperature is further increased, other reactions begin to occur. For instance, biuret may decompose back into urea and isocyanic acid. The urea produced is unstable at higher temperatures, and thus, will further decompose into ammonia and isocyanic acid. Urea and the byproducts of the pyrolysis reaction will continue to react and further decompose as the reaction mixture is heated.
One advantage of using urea decomposition to control the pH of the transition metal/silica mixture is the ability to easily manipulate pH as the metal and silica are mixed together. For instance, as indicated above, the pyrolysis of urea produces ammonia (NH3) as a byproduct. In some embodiments of the present invention, the presence of this ammonia byproduct may be used to increase the pH of the transition metal/silica mixture to the desired level. The amount of ammonia present in the mixture may be easily controlled by selectively varying the amount of urea reactant and the temperature to which the urea is heated. For instance, higher pyrolysis temperatures generally result in a greater amount of resulting ammonia due to the greater extent to which the urea and its byproducts are decomposed.
Besides urea decomposition, other well-known buffering systems may also be employed in the present invention to increase the pH of the transition metal/silica mixture to the desired level. For instance, in one embodiment, the buffering system may use an alkali metal bicarbonate and an alkali metal carbonate in a certain molar ratio. The alkali metal cations may be, for instance, sodium and/or potassium. In one particular embodiment, the buffering system employs sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3). In other embodiments of the present invention, the buffering system may simply involve adding a certain amount of a basic compound to the mixture, such as sodium hydroxide, potassium hydroxide, ammonium hydroxide, and so forth. Regardless of the technique for increasing the pH of the transition metal/silica mixture, it is believed that the adjustment allows stronger bonds to be formed between the transition metal and silica particles. Specifically, without intending to be limited by theory, it is believed that the transition metal is capable of forming covalent bonds with the silanol groups present on the silica particle surface. In addition, the higher pH increases the number of silanol groups available for binding and reduces salt precipitation, thereby enhancing bonding efficiency. Of course, due to the opposite charge of the transition metal and some types of silica particles, some binding via electrostatic attraction will also be present.
Apart from pH adjustment, other techniques may also be utilized to further enhance the strength of the bonds formed between the transition metal and the nanoparticles, such as the use of coupling agents (e.g., organofunctional silanes), bifunctional chelating agents (e.g., EDTA), and so forth. Examples of such techniques are described in more detail in U.S. Patent Application Publication Nos. 2005/0084438 to Do, et al.; 2005/0084474 to Wu, et al.; and 2005/0084464 to McGrath, et al., which are incorporated herein in their entirety by reference thereto for all purposes.
If desired, more than one type of transition metal may be bound to a particle. This has an advantage in that certain metals may be better at removing specific malodorous compounds than other metals. Likewise, different types of nanoparticles may be used in combination for effective removal of various malodorous compounds. In one embodiment, for instance, copper-modified silica nanoparticles are used in combination with manganese-modified silica nanoparticles. By using two different nanoparticles in combination, numerous malodorous compounds may be more effectively removed. For example, the copper-modified particle may be more effective in removing sulfur and amine odors, while the manganese-modified particle may be more effective in removing carboxylic acids.
The odor control ink may also contain other components to facilitate application of the ink. For example, the ink may contain a binder for increasing the durability of the nanoparticles on the container, even when present at high levels. Suitable binders may include, for instance, those that become insoluble in water upon crosslinking. Crosslinking may be achieved in a variety of ways, including by reaction of the binder with a polyfunctional crosslinking agent. Examples of such crosslinking agents include, but are not limited to, dimethylol urea melamine-formaldehyde, urea-formaldehyde, polyamide epichlorohydrin, etc. In some embodiments, a polymer latex may be employed as the binder. The polymer suitable for use in the lattices typically has a glass transition temperature of about 30° C. or less so that the flexibility of the resulting container is not substantially restricted. Moreover, the polymer also typically has a glass transition temperature of about −25° C. or more to minimize the tackiness of the polymer latex. For instance, in some embodiments, the polymer has a glass transition temperature from about −15° C. to about 15° C., and in some embodiments, from about −10° C. to about 0° C. For instance, some suitable polymer lattices that may be utilized in the present invention may be based on polymers such as, but are not limited to, styrene-butadiene copolymers, polyvinyl acetate homopolymers, vinyl-acetate ethylene copolymers, vinyl-acetate acrylic copolymers, ethylene-vinyl chloride copolymers, ethylene-vinyl chloride-vinyl acetate terpolymers, acrylic polyvinyl chloride polymers, acrylic polymers, styrene-acrylic copolymers (e.g., Jonrez FV2080, available from MeadWestvaco Corporation, Charleston S.C.), nitrile polymers, and any other suitable anionic polymer latex polymers known in the art. The charge of the polymer lattices described above may be readily varied, as is well known in the art, by utilizing a stabilizing agent having the desired charge during preparation of the polymer latex.
Although polymer lattices may be effectively used as binders in the present invention, such compounds sometimes result in a reduction in drapability and an increase in residual odor. Thus, water-soluble organic polymers may also be employed as binders to alleviate such concerns. One class of water-soluble organic polymers found to be suitable in the present invention is polysaccharides and derivatives thereof. Polysaccharides are polymers containing repeated carbohydrate units, which may be cationic, anionic, nonionic, and/or amphoteric. In one particular embodiment, the polysaccharide is a nonionic, cationic, anionic, and/or amphoteric cellulosic ether. Suitable nonionic cellulosic ethers may include, but are not limited to, alkyl cellulose ethers, such as methyl cellulose and ethyl cellulose; hydroxyalkyl cellulose ethers, such as hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl hydroxybutyl cellulose, hydroxyethyl hydroxypropyl cellulose, hydroxyethyl hydroxybutyl cellulose and hydroxyethyl hydroxypropyl hydroxybutyl cellulose; alkyl hydroxyalkyl cellulose ethers, such as methyl hydroxyethyl cellulose, methyl hydroxypropyl cellulose, ethyl hydroxyethyl cellulose, ethyl hydroxypropyl cellulose, methyl ethyl hydroxyethyl cellulose and methyl ethyl hydroxypropyl cellulose; and so forth. Suitable cellulosic ethers may include, for instance, those available from Akzo Nobel of Covington, Virginia under the name “BERMOCOLL.” Still other suitable cellulosic ethers are those available from Shin-Etsu Chemical Co., Ltd. of Tokyo, Japan under the name “METOLOSE”, including METOLOSE Type SM (methycellulose), METOLOSE Type SH (hydroxypropylmethyl cellulose), and METOLOSE Type SE (hydroxyethylmethyl cellulose). One particular example of a suitable nonionic cellulosic ether is ethyl hydroxyethyl cellulose having a degree of ethyl substitution (DS) of 0.8 to 1.3 and a molar substitution (MS) of hydroxyethyl of 1.9 to 2.9. The degree of ethyl substitution represents the average number of hydroxyl groups present on each anhydroglucose unit that have been reacted, which may vary between 0 and 3. The molar substitution represents the average number of hydroxethyl groups that have reacted with each anhydroglucose unit. One such cellulosic ether is BERMOCOLL E 230FQ, which is an ethyl hydroxyethyl cellulose commercially available from Akzo Nobel. Other suitable cellulosic ethers are also available from Hercules, Inc. of Wilmington, Del. under the name “CULMINAL.” The ink may also include various other components as is well known in the art, such as colorants, colorant stabilizers, photoinitiators, solvents, surfactants, humectants, biocides or biostats, electrolytic salts, pH adjusters, etc. For example, various components for use in an ink are described in U.S. Pat. No. 5,681,380 to Nohr, et al. and U.S. Pat. No. 6,542,379 to Nohr, et al., which are incorporated herein in their entirety by reference thereto for all purposes. Examples of suitable humectants include, for instance, ethylene glycol; diethylene glycol; glycerine; polyethylene glycol 200, 400, and 600; propane 1,3 diol; propylene-glycolmonomethyl ethers, such as Dowanol PM (Gallade Chemical Inc., Santa Ana, Calif.); polyhydric alcohols; or combinations thereof. Other additives may also be included to improve ink performance, such as a chelating agent to sequester metal ions that could become involved in chemical reactions over time, a corrosion inhibitor to help protect metal components of the printer or ink delivery system, a biocide or biostat to control unwanted bacterial, fungal, or yeast growth in the ink, and a surfactant to adjust the ink surface tension.
To form the odor control ink, its components may be initially dissolved or dispersed in a solvent. For example, one or more of the above-mentioned components may be mixed with a solvent, either sequentially or simultaneously, to form an ink that may be easily applied to a substrate. Any solvent capable of dispersing or dissolving the components is suitable, for example water; alcohols such as ethanol or methanol; dimethylformamide; dimethyl sulfoxide; hydrocarbons such as pentane, butane, heptane, hexane, toluene and xylene; ethers such as diethyl ether and tetrahydrofuran; ketones and aldehydes such as acetone and methyl ethyl ketone; acids such as acetic acid and formic acid; and halogenated solvents such as dichloromethane and carbon tetrachloride; as well as mixtures thereof. The concentration of solvent in the ink is generally high enough to allow easy application, handling, etc. If the amount of solvent is too large, however, the amount of modified nanoparticles deposited on the container might be too low to provide the desired odor reduction. Although the actual concentration of solvent employed will generally depend on the type of modified nanoparticles and the substrate on which it is applied, it is nonetheless typically present in an amount from about 40 wt. % to about 99 wt. %, in some embodiments from about 50 wt. % to about 95 wt. %, and in some embodiments, from about 60 wt. % to about 90 wt. % of the ink (prior to drying).
The solids content and/or viscosity of the ink may be varied to achieve the extent of odor reduction desired. For example, the ink may have a solids content of from about 5% to about 90%, in some embodiments from about 10% to about 80%, and in some embodiments, from about 20% to about 70%. By varying the solids content of the ink, the presence of the modified nanoparticles and other components in the odor control ink may be controlled. For example, to form an odor control ink with a higher level of modified nanoparticles, the ink may be provided with a relatively high solids content so that a greater percentage of the modified nanoparticles are incorporated into the odor control ink during the application process. Generally, the viscosity is less than about 2×106 centipoise, in some embodiments less than about 2×105 centipoise, in some embodiments less than about 2×104 centipoise, and in some embodiments, less than about 2×103 centipoise, such as measured with a Brookfield viscometer, type DV-I or LV-IV, at 60 rpm and 20° C. If desired, thickeners or other viscosity modifiers may be employed in the ink to increase or decrease viscosity.
Once formed, the odor control ink of the present invention may be applied to the inner surface of a resiliently deformable substrate used to form the container so that it is able to readily contact malodorous compounds associated with any absorbent article disposed within the container. One benefit imparted by the odor control ink of the present invention is that it generally forms a durable coating that is not readily removed from the substrate upon application. Thus, the substrate may be pre-treated with the ink and subsequently incorporated into the container without substantial loss of its odor control properties. This allows the ink to more readily applied to certain areas of the container (e.g., inside surface) without substantial difficulty. Of course, it should be understood that the odor control ink may also be applied to the substrate after it is incorporated into the container.
The substrate may include one or multiple layers, and may be constructed from a variety of materials, such as films, nonwoven webs, paper webs, foams, etc. In one particular embodiment, the substrate includes a generally liquid impermeable film formed from a thermoplastic polymer, such as polyolefins (e.g., polyethylene, polypropylene, etc.), ethylene vinyl acetate, ethylene ethyl acrylate, ethylene acrylic acid, ethylene methyl acrylate, ethylene normal butyl acrylate, nylon, ethylene vinyl alcohol, polystyrene, polyurethane, and so forth. Such films may be mono- or multi-layered. The thickness of the film may vary depending upon the desired use. In most embodiments, however, the film has a thickness of about 50 micrometers or less, in some embodiments from about 1 to about 40 micrometers, in some embodiments from about 2 to about 35 micrometers, and in some embodiments, from about 5 to about 30 micrometers.
In addition to film forming polymer(s), other additives may also be incorporated into the film, such as melt stabilizers, processing stabilizers, heat stabilizers, light stabilizers, antioxidants, heat aging stabilizers, whitening agents, antiblocking agents, bonding agents, lubricants, fillers, etc. Fillers, for example, are particulates or other forms of material that may be added to the film polymer extrusion blend and that will not chemically interfere with the extruded film, but which may be uniformly dispersed throughout the film. Fillers may serve a variety of purposes, including enhancing film opacity and/or breathability (i.e., vapor-permeable and substantially liquid-impermeable). For instance, filled films may be made breathable by stretching, which causes the polymer to break away from the filler and create microporous passageways. Breathable microporous elastic films are described, for example, in U.S. Pat. Nos. 5,997,981; 6,015,764; and 6,111,163 to McCormack, et al.; U.S. Pat. No. 5,932,497 to Morman, et al.; U.S. Pat. No. 6,461,457 to Taylor, et al., which are incorporated herein in their entirety by reference thereto for all purposes. Further, hindered phenols are commonly used as an antioxidant in the production of films. Some suitable hindered phenols include those available from Ciba Specialty Chemicals under the trade name “Irganox®”, such as Irganox® 1076, 1010, or E 201. Moreover, bonding agents may also be added to the film to facilitate bonding of the film to additional materials (e.g., nonwoven webs). Examples of such bonding agents include hydrogenated hydrocarbon resins. Other suitable bonding agents are described in U.S. Pat. No. 4,789,699 to Kieffer et al. and U.S. Pat. No. 5,695,868 to McCormack, which are incorporated herein in their entirety by reference thereto for all purposes.
Besides films, the substrate may also contain a nonwoven web, such as spunbond webs, meltblown webs, bonded carded webs, air-laid webs, coform webs, hydraulically entangled webs, and so forth. Nonwoven webs may be formed by a variety of different materials. For instance, suitable polymers for forming nonwoven webs may include polyolefins, polyamides, polyesters, polycarbonates, polystyrenes, thermoplastic elastomers, fluoropolymers, vinyl polymers, and blends and copolymers thereof. Suitable polyolefins include, but are not limited to, polyethylene, polypropylene, polybutylene, and so forth; suitable polyamides include, but are not limited to, nylon 6, nylon 6/6, nylon 10, nylon 12 and so forth; and suitable polyesters include, but are not limited to, polyethylene terephthalate, polybutylene terephthalate, polytrimethyl terephthalate, polylactic acid, and so forth. Particularly suitable polymers for use in the present invention are polyolefins including polyethylene, for example, linear low density polyethylene, low density polyethylene, medium density polyethylene, and high density polyethylene; polypropylene; polybutylene; as well as copolymers and blends thereof.
The fibers used to form the nonwoven web may be in the form of substantially continuous fibers, staple fibers, and so forth. Substantially continuous fibers, for example, may be produced by known nonwoven extrusion processes, such as, for example, known solvent spinning or melt-spinning processes. In one embodiment, the nonwoven web contains substantially continuous melt-spun fibers formed by a spunbond process. The spunbond fibers may be formed from any melt-spinnable polymer, co-polymers or blends thereof. The denier of the fibers used to form the nonwoven web may also vary. For instance, in one particular embodiment, the denier of polyolefin fibers used to form the nonwoven web is less than about 6, in some embodiments less than about 3, and in some embodiments, from about 1 to about 3.
Nonwoven laminates may also be employed in some embodiments of the present invention. In one embodiment, the nonwoven laminate contains a meltblown layer positioned between two spunbond layers to form a spunbond/meltblown/spunbond (“SMS”) laminate. Various techniques for forming SMS laminates are described in U.S. Pat. No. 4,041,203 to Brock et al.; U.S. Pat. No. 5,213,881 to Timmons, et al.; U.S. Pat. No. 5,464,688 to Timmons, et al.; U.S. Pat. No. 4,374,888 to Bornslaeger; U.S. Pat. No. 5,169,706 to Collier, et al.; and U.S. Pat. No. 4,766,029 to Brock et al., as well as U.S. Patent Application Publication No. 2004/0002273 to Fitting, et al., all of which are incorporated herein in their entirety by reference thereto for all purposes. Of course, the nonwoven laminate may have other configuration and possess any desired number of meltblown and spunbond layers, such as spunbond/meltblown meltblown/spunbond laminates (“SMMS”), spunbond/meltblown laminates (“SM”), etc.
If desired, the substrate may be subjected to one or treatments that enhance the resulting durability of the odor control ink. For instance, because the odor control ink may be aqueous-based, the substrate may be subjected to a hydrophilic treatment to improve its affinity for the ink. For example, the substrate may be subjected to corona field that results in morphological and chemical modifications of the surface of the substrate. The term “corona field” generally refers to a corona field of ionized gas. The dose or energy density to which the substrate is exposed may range from about 1 to about 500 watt-minute per square foot (w-min/ft2), in some embodiments from about 15 to about 350 w-min/ft2, and in some embodiments, from about 20 to about 80 w-min/ft2. The corona field may be applied to the substrate under ambient temperature and pressure; however, higher or lower temperature and pressures may be used. Various suitable corona discharge treatments are described, for instance, in U.S. Pat. No. 4,283,291 to Lowther; U.S. Pat. No. 3,754,117 to Walter; U.S. Pat. No. 3,880,966 to Zimmerman, et al.; and U.S. Pat. No. 3,471,597 to Schirmer, which are incorporated herein in their entirety by reference thereto for all purposes. In addition to or in conjunction with corona discharge treatment, the substrate may also be applied with a hydrophilic compound. One class of suitable hydrophilic compounds includes polysaccharides, such as described above.
Any of a variety of techniques may be employed in the present invention to apply the odor control ink to the substrate. For instance, the ink may be applied using rotogravure or gravure printing, either direct or indirect (offset). Gravure printing encompasses several well-known engraving techniques, such as mechanical engraving, acid-etch engraving, electronic engraving and ceramic laser engraving. Such printing techniques provide excellent control of the composition distribution and transfer rate. Gravure printing may provide, for example, from about 10 to about 1000 deposits per lineal inch of surface, or from about 100 to about 1,000,000 deposits per square inch. Each deposit results from an individual cell on a printing roll, so that the density of the deposits corresponds to the density of the cells. A suitable electronic engraved example for a primary delivery zone is about 200 deposits per lineal inch of surface, or about 40,000 deposits per square inch. By providing such a large number of small deposits, the uniformity of the deposit distribution may be enhanced. Suitable gravure printing techniques are also described in U.S. Pat. No. 6,231,719 to Garvey, et al., which is incorporated herein in its entirety by reference thereto for all purposes. Moreover, besides gravure printing, it should be understood that other printing techniques, such as flexographic printing, may also be used to apply the ink.
Still another suitable contact printing technique that may be utilized in the present invention is “screen printing.” Screen printing is performed manually or photomechanically. The screens may include a silk or nylon fabric mesh with, for instance, from about 40 to about 120 openings per lineal centimeter. The screen material is attached to a frame and stretched to provide a smooth surface. The stencil is applied to the bottom side of the screen, i.e., the side in contact with the substrate upon which the fluidic channels are to be printed. The ink is painted onto the screen, and transferred by rubbing the screen (which is in contact with the substrate) with a squeegee.
Ink-jet printing techniques may also be employed in the present invention. Ink-jet printing is a non-contact printing technique that involves forcing the ink through a tiny nozzle (or a series of nozzles) to form droplets that are directed toward the substrate. Two techniques are generally utilized, i.e., “DOD” (Drop-On-Demand) or “continuous” ink-jet printing. In continuous systems, ink is emitted in a continuous stream under pressure through at least one orifice or nozzle. The stream is perturbed by a pressurization actuator to break the stream into droplets at a fixed distance from the orifice. DOD systems, on the other hand, use a pressurization actuator at each orifice to break the ink into droplets. The pressurization actuator in each system may be a piezoelectric crystal, an acoustic device, a thermal device, etc. The selection of the type of ink jet system varies on the type of material to be printed from the print head. For example, conductive materials are sometimes required for continuous systems because the droplets are deflected electrostatically. Thus, when the sample channel is formed from a dielectric material, DOD printing techniques may be more desirable.
In addition to the printing techniques mentioned above, any other suitable application technique may be used in the present invention. For example, other suitable printing techniques may include, but not limited to, such as laser printing, thermal ribbon printing, piston printing, spray printing, flexographic printing, etc. Still other suitable application techniques may include bar, roll, knife, curtain, spray, slot-die, dip-coating, drop-coating, extrusion, stencil application, etc. Such techniques are well known to those skilled in the art.
The odor control ink may be cover an entire surface of the substrate or it may be applied in a pattern. For example, the pattern may cover from about 10% to about 95%, in some embodiments from about 12% to about 90%, and in some embodiments, from about 15% to about 50% of the area of a surface of the substrate. The patterned application of the odor control ink may provide a variety of benefits, such as presenting a stark and highly visible contrast against a different color (e.g., the color of the background) and thus changing the overall appearance of the substrate. For example, the odor control ink may have a dark color and applied against a contrasting light background. Alternatively, a differently colored foreground may contrast with a dark background provided by the odor control ink. The relative degree of contrast between the odor control ink and the other color may be measured through a gray-level difference value. In a particular embodiment, the contrast may have a gray level value of about 45 on a scale of 0 to about 255, where 0 represents “black” and 255 represents “white.” The analysis method may be made with a Quantimet 600 Image Analysis System (Leica, Inc., Cambridge, UK). This system's software (QWIN Version 1.06A) enables a program to be used in the Quantimet User Interactive Programming System (QUIPS) to make the gray-level determinations. A control or “blank” white-level may be set using undeveloped Polaroid photographic film. An 8-bit gray-level scale may then be used (0-255) and the program allowed the light level to be set by using the photographic film as the standard. A region containing the other color (e.g., background or foreground) may then be measured for its gray-level value, followed by the same measurement of the ink. The routine may be programmed to automatically calculate the gray-level value of the odor control ink. The difference in gray-level value between the odor control ink and the other color may be about 45 or greater on a scale of 0-255, where 0 represents “black” and 255 represents “white.” The particular type or style of odor control ink pattern may include any arrangement of stripes, bands, dots, or other geometric shape. The pattern may include indicia (e.g., trademarks, text, and logos), floral designs, abstract designs, any configuration of artwork, etc.
The patterned application of odor control ink may also have various other functional benefits, including optimizing flexibility or some other characteristic of the substrate. The patterned application of odor control ink may provide different odor control properties to multiple locations of the substrate. For example, in one embodiment, the substrate may be treated with two or more regions of odor control ink that may or may not overlap. The regions may be on the same or different surfaces of the substrate. In one embodiment, one region of a substrate is coated with a first odor control ink, while another region is coated with a second odor control ink. If desired, one region may be configured to reduce one type of odor, while another region may be configured to reduce another type of odor. Alternatively, one region may possess a higher level of an odor control ink than another region or substrate to provide different levels of odor reduction.
Regardless of the method of application, the substrate may be dried at a certain temperature to drive the solvent from the odor control ink. For example, the substrate may be heated to a temperature of at least about 50° C., in some embodiments at least about 70° C., and in some embodiments, at least about 80° C. By minimizing the amount of solvent in the odor control ink, a larger surface area of the modified nanoparticles may be available for contacting malodorous compounds, thereby enhancing odor reduction. It should be understood, however, that relatively small amounts of solvent may still be present. For example, the dried ink may contain a solvent in an amount less than about 10% by weight, in some embodiments less than about 5% by weight, and in some embodiments, less than about 1% by weight.
When dried, the relative percentages and solids add-on level of the resulting modified nanoparticles may vary to achieve the desired level of odor control. The “solids add-on level” is determined by subtracting the weight of the untreated substrate from the weight of the treated substrate (after drying), dividing this calculated weight by the weight of the untreated substrate, and then multiplying by 100%. One particular benefit of the present invention is that high solids add-on levels are achievable without a substantial sacrifice in durability of the ink and flexibility of the substrate. In some embodiments, for example, the add-on level of the ink is at least about 2%, in some embodiments from about 4% to about 40%, and in some embodiments, from about 6% to about 35%. The concentration of the modified nanoparticles in the odor control ink is generally tailored to facilitate odor control without adversely affecting other properties of the resulting substrate, such as flexibility. For instance, the modified nanoparticles are typically present in the ink (after drying) in an amount of about 50 wt. % or more, in some embodiments from about 50 wt. % to about 98 wt. %, and in some embodiments, from about 60 wt. % to about 95 wt. %.
The configuration of the deodorizing container of the present invention is not particularly critical. Referring to
The effectiveness of the deodorizing container of the present invention may be measured in a variety of ways. For example, the percent of a malodorous compound adsorbed by the odor control ink may be determined in accordance with the headspace gas chromatography test set forth herein. In some embodiments, for instance, the container is capable of adsorbing at least about 25%, in some embodiments at least about 45%, and in some embodiments, at least about 65% of a particular malodorous compound, such as mercaptans (e.g., ethyl mercaptan), ammonia, amines (e.g., trimethylamine (TMA), triethylamine (TEA), etc.), sulfides (e.g., hydrogen sulfide, dimethyl disulfide (DMDS), etc.), ketones (e.g., 2-butanone, 2-pentanone, 4-heptanone, etc.) carboxylic acids (e.g., isovaleric acid, acetic acid, propionic acid, etc.), aldehydes, terpenoids, hexanol, heptanal, pyridine, and so forth. The effectiveness of the ink in removing odors may also be measured in terms of “Relative Adsorption Efficiency”, which is determined using headspace gas chromatography and measured in terms of milligrams of odor adsorbed per gram of the ink. It should be recognized that the chemistry of any one type of odor control ink may not be suitable to reduce all types of malodorous compounds, and that low adsorption of one or more malodorous compounds may be compensated by good adsorption of other malodorous compounds.
The present invention may be better understood with reference to the following examples.
Quantitative odor adsorption was determined in the Examples using a test known as “Headspace Gas Chromatography.” Headspace gas chromatography testing was conducted on an Agilent Technologies 5890, Series II gas chromatograph with an Agilent Technology 7694 headspace sampler (Agilent Technologies, Waldbronn, Germany). Helium was used as the carrier gas (injection port pressure: 87.5 kPa; headspace vial pressure: 108.9 kPa; supply line pressure is at 413.4 kPa). A DB-624 column was used for the malodorous compound that had a length of 30 meters and an internal diameter of 0.25 millimeters. Such a column is available from J&W Scientific, Inc. of Folsom, Calif. The operating parameters used for the headspace gas chromatography are shown below in Table 1:
The test procedure involved placing a sample in a headspace vial. Using a syringe, an aliquot of the relevant malodorous compound (ethyl mercaptan or triethylamine) was also placed in the vial. Each sample was tested in triplicate. The vial was then sealed with a cap and a septum and placed in the headspace gas chromatography oven at 37° C. After two (2) hours, a hollow needle was inserted through the septum and into the vial. A 1-cubic centimeter sample of the headspace (air inside the vial) was then injected into the gas chromatograph. Initially, a control vial with only the aliquot of malodorous compound was tested to define 0% malodorous compound adsorption. To calculate the amount of headspace malodorous compound removed by the sample, the peak area for the malodorous compound from the vial with the sample was compared to the peak area from the malodorous compound control vial.
Modified silica particles were prepared for treatment of a film. The silica particles were Snowtex-OXS, which are colloidal silica nanoparticles commercially available from Nissan Chemical America of Houston, Tex. The particles have an average particle size of between 4 to 6 nanometers and a surface area between 200 to 500 square meters per gram as measured using the BET (Brunauer, Emmett and Teller) method. The silica particles were modified with a transition metal as follows. A solution of iron (III) chloride hexahydrate (FeCl3.6H2O) (78.1 grams, 0.289 moles) in water (500 milliliters) was added to 2.4 liters of an aqueous solution of Snowtex-OXS (10 wt. % solids, 2.89×10−3 moles SiO2 particles). The suspension was stirred until the iron salt dissolved in the solution. Water (2 liters) was then added to the mixture. While vigorously stirring the suspension, a solution of sodium bicarbonate (NaHCO3) (26.8 grams NaHCO3 in 3.6 liters of water, 0.32 moles NaHCHO3) was added. The resulting FeOXS supsension was stirred at room temperature for 1 hour. A corona-treated polyethylene film (Pliant Corp.) was then laid flat onto an Accu-Lab™ Drawdown Machine (UV Process Supply, Inc.; Chicago, Ill.). The FeOXS suspension (2 milliliters) was transferred to one end of the film and evenly spread over the entire film surface using a pull down bar (with grooves) and moving it in a single direction. The treated film was allowed to dry in air.
The ink-coated film of Example 1 was assessed for its ability to adsorb ethyl mercaptan using the above-described headspace gas chromatography (GC) test. Specifically, three (3) strips of the FeOXS treated polyethylene film (0.0738 grams, 0.0750 grams, and 0.0786 grams, respectively) were each transferred to different headspace GC sample vials. Ethyl mercaptan (1 mL, 839 mg) was injected into each sample vial; and the vial was sealed immediately. The sample vials were transferred to the headspace GC instrument for data collection. Three (3) untreated polyethylene film samples (0.0754 g, 0.0713 g, and 0.0742 g) were also assessed for comparison. The results are set fort below in Table 2 in terms of the average milligrams of ethyl mercaptan removed per gram of the sample.
The ink-coated film of Example 1 was assessed for its ability to adsorb triethylamine using the above-described headspace gas chromatography (GC) test. Specifically, three (3) strips of the FeOXS treated polyethylene film (0.0703 grams, 0.0805 grams, and 0.0798 grams, respectively) were each transferred to different headspace GC sample vials. Triethylamine (1 mL, 726 mg) was injected into each sample vial; and the vial was sealed immediately. The sample vials were transferred to the headspace GC instrument for data collection. Three (3) untreated polyethylene film samples (0.0846 g, 0.0863 g, and 0.0910 g) were also assessed for comparison. The results are set fort below in Table 3 in terms of the milligrams of triethylamine removed per gram of the sample.
While the invention has been described in detail with respect to the specific embodiments thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing, may readily conceive of alterations to, variations of, and equivalents to these embodiments. Accordingly, the scope of the present invention should be assessed as that of the appended claims and any equivalents thereto.
