Patent Application
20050026778
1. Technical Field
The present invention relates generally to protective fibers, and in particular, to reactive and adsorptive fibers for providing multi-functional protection from chemical and biological agents and methods for providing and using such fibers.
2. Description of Related Art
Historically, activated carbon has been incorporated into textiles for clothing and into filters to provide adsorptive protection. While activated carbon is extremely effective for adsorbing toxic vapors, activated carbon imparts only partial protection against chemical agents, which are captured through physical entrapment within its pores. Since this entrapment is a physical process, activated carbon does nothing to neutralize an absorbed chemical, it simply stores it. Such storage presents a host of problems: these materials may be released over time; the carbon has capacity restrictions and thus cannot be used indefinitely; and storage results in disposal problems after usage. Finally, activated carbon does not provide protection from biological agents (such as anthrax or small pox). Previously, protection against biological contamination has been relegated to barrier methods, i.e. full body suits. In addition to the life support problems associated with hermetic sealing, these barriers present similar disposal problems after being coated with harmful entities.
To fulfill a long standing need to provide biocidal components for protective systems for military and civilian EMS applications, scientists have been developing metal-based nanoparticles. U.S. Pat. No. 6,057,488 discloses effective biocidal properties of metal-oxide nanoparticles when dispersed as a powder or combined in a test tube with biological contaminants. Due to the unique physical properties and size of nanoparticles, it has heretofore been impossible to separate and fix the nanoparticles into a tangible form that could be flexibly integrated into protective systems and combined with conventional adsorbents.
Accordingly, a need exists for an efficient and effective protective entity which has biocidal properties for the destruction of biological agents in addition to reactive properties for the adsorption, decomposition and neutralization of chemical agents.
The present invention is directed to a system and method for providing nanoparticulate-retaining fibers which possess chemically reactive properties, biocidally reactive properties, chemically adsorptive properties, or combinations of such properties. Advantageously, the present invention successfully overcomes significant material handling challenges and results in an entity which can provide efficient and effective adsorption and neutralization of harmful chemical agents as well as biological agents in a form which can be used, for example, to manufacture a protective textile comprising the protective fibers alone, or the protective fibers may be incorporated into other textiles, media, materials or systems.
The fibers may be combined with conventional activated carbon (e.g., in beads or powder form) to produce a protective fiber having enhanced chemical adsorption as well as biocidal properties.
In yet another aspect, any conventional activated carbon (e.g., in beads or powder form) which has been wettlerized may utilized to add the ability to bind/neutralize blood agents.
These and other aspects, features and advantages of the present invention will be described or become apparent from the following detailed description of the preferred embodiments, which is to be read in connection with the accompanying drawings.
The present invention comprises a fiber onto which reactive/adsorptive particulates are adhered for providing a resultant protective entity which has the potential to protect against both chemical and biological warfare threats. For example, these protective fibers may be used to manufacture chemically and biologically protective textiles for use as clothing, shelters or air filtration, or the fibers themselves can be incorporated into other media (filters, fabrics, etc). The reactive/adsorptive particulates used according to the present invention are preferably inorganic, reactive nanoparticulates formed from about 1 nm to about 200 nm sized clusters.
Reactive nanoparticles are environmentally stable nanometer-sized clusters of atoms and molecules with high surface areas and unique morphologies which result in high chemical reactivity. Since these nanoparticles have immense surface areas, they possess extraordinary catalytic and reactive properties, which differentiate them from their bulk-chemical species relatives. In contrast to the bulk-chemical species, nanoparticles have a statiscally significantly higher number of atoms/ions/molecules residing at the surface of the cluster. These reactive nanoparticles are preferably comprised of metal complexes of oxides, metal complexes of hydroxides, metal complexes of hydrates as well as polyoxometallates (POMs).
The reactive nanoparticles preferably used for protective fiber applications according to the present invention are specifically engineered to destructively adsorb chemicals and microorganisms. Such nanoparticles are capable of absorbing and then detoxifying hazardous chemicals by breaking molecular bonds to yield harmless end products. Similarly, such reactive nanoparticles are able to kill or inactivate microorganisms by attacking cell membranes and oxidizing important functional proteins or DNA. The nanoparticles may be enhanced or modified for environmental purposes. Thus, the nanoparticles preferably used according to the present invention include at least one of chemically adsorptive nanoparticles, chemically reactive nanoparticles, and biocidally reactive nanoparticles. Further, the nanoparticles used according to the present invention preferably have a Brunauer-Emmett-Teller (BET) multi-point surface area of at least about 70 m2/g for older nanoparticles to at least about 1200 m2/g or more for more advanced nanoparticles and have an average pore radius of at least about 45 Angstroms to at least about 100 Angstroms.
Exemplary nanoparticles which may be used include metal oxide composites in powder nanoparticulate form. These metal oxide composites comprise metal oxide nanoparticles having oxygen ion moieties on their surfaces with reactive atoms interacted or chemisorbed with those surface oxygen ions. For example, the metal oxide nanoparticles may be taken from the group consisting of oxides of Mg, Ti, Ca, Al, Sn, Fe, Co, V, Mn, Ni, Cr, Cu, Zn, Zr, or mixtures thereof. For example, the metal oxide nanoparticles may comprise MgO, TiO2, CaO, Al2O3, SnO2, Fe2O3, FeO, CoO, V2O5, MnO3, NiO, Cr2O3, CuO, ZnO, ZrO2 and mixtures thereof. Nanoparticles made of metal complexes of hydroxides, metal complexes of hydrates as well as polyoxometallates (POMs) are also suitable. Some of the nanoparticles listed in this paragraph may also be further processed, for example to include reactive halogen atoms, alkali metal atoms, SO2, NO2, ozone or a second different metal oxide. Alternate processing can provide a protective coating to the nanoparticles which are not soluble rendering them waterproof. These advanced processing steps are dislosed in the following U.S. Pat. Nos. 6,057,488 and 5,914,436 and 6,417,423 and 5,990,373 and 5,712,219 and 6,087,294 and 6,093,236 and 5,759,939, and in published U.S. patent application Ser. No. 2002/0035032, the complete disclosures of which are incorporated herein by reference thereto. Any of these products may be incorporated into the multi-functional protective products according to the invention.
These various classes of nanoparticles have been noted for their ability to chemically decompose classical chemical warfare agents as well as many of the toxic industrial chemicals (TICs) and toxic industrial materials (TIMs). The reactive nature of the interaction breaks molecular bonds to reduce chemical species to non-toxic by-products. For example, nanoparticles have been shown effective in chemical destruction of carbon tetrachloride (CCl4), dimethyl-methyl-phosphonate (DMMP), paraoxon (as simulant for VX and GD), 2-chloroethyl-ethyl sulfide (2-CEES, one-armed Mustard), military agents and acid gases. Compared to activated carbon, studies have proven that nanoparticles have a much higher capacity to inactivate chemical warfare simulants. More specifically, nanoparticles chemically decompose mustard (HD) agent, as indicated by the presence of 1,4-Dithiane, a known HD degradation product. In certain instances, the nanoparticles perform the same or better than activated carbon, but in lighter weight materials with more compact volumes.
In providing biological protection, the protective fibers provide protection against biological warfare agents or infectious microorganisms such as, e.g., viruses, (vegetative) bacteria, sporulated bacteria (Anthrax), fungi or protozoa. Utilizing different mechanisms, the reactive nanoparticles instantaneously attack the cell wall, proteins and DNA of the microorganisms, thereby destroying them.
It is to be noted that the term “harmful entities” as used in the present application is defined to include all biological agents and chemical agents described above, singly or in combination.
Additional Activated Carbon Components
The agents of biological warfare can be bacteria, viruses, fungi or spores, wherein some species of spores generate as dormant seeds or genetic progenitors of themselves. These species' principal difference from chemical agents is size, wherein they may measure tenths of microns up to micron size or larger, which can be at least about a thousand times larger than chemical agent species. The pores of activated carbon cannot absorb these entities which are much larger than the pores themselves. The initial wave of these biological entities rapidly blocks the outer pores of the activated carbon thereby preventing the absorption of smaller chemical species that would otherwise be easily trapped within the pores. When a contaminated environment first encounters a network of fibers containing nanoparticles, any biological contaminants contained therein will be caused to undergo lysis. The by-products of lysis are chemical toxins which are more readily absorbed by the downstream activated carbon. Thus, a multi-component protective material containing biocidal nanoparticles can improve the efficacy of activated carbon in environments containing both chemical and biological warfare agents.
While any type of carbon may be used with the present invention, an activated carbonaceous bead (CarboTex bead) with an extraordinarily high surface area (e.g., about 1500 m2/gm) and extraordinary hardness (e.g., from about 2 to about 10 times harder than Rohm & Haas and Kureha beads) comprises the activated carbon bead preferably used according to an aspect of the present invention. The materials and methods used for manufacturing the preferred activated carbon bead used in the present invention are described in published U.S. patent application Ser. No. 2002-0028333 entitled “Spherical High Performance Adsorbents with Microstructure” by Giebelhausen et al. filed on Mar. 8, 2001, U.S. Pat. No. 6,376,404 entitled “Process for the Production of Shaped High-Performance Adsorbents” by Giebelhausen et al. filed on Mar. 15, 2000, and U.S. Pat. No. 6,316,378 entitled “Process for the Production of Shaped Activated Carbon” by Giebelhausen et al. filed on Mar. 15, 2000, the disclosures of which are all incorporated herein by reference thereto.
It is to be noted that in an alternate embodiment, an activated carbon bead which has been loaded with metal ions (e.g., wettlerized) to further impart reactive properties onto the activated carbon for providing protection against blood agents which are in contact therewith, may be used.
Additional Iodinated Resin Components
Iodinated resin is used in filters for air and water purification. It is a micro-biocidal agent that consists of iodine fixed to an ion exchange resin matrix. When a microorganism contacts the iodinated resin, iodine is released. Depending upon the type of microorganism, the iodine may oxidize the cell membrane, vital proteins or DNA, thereby killing it or rendering it incapable of reproduction. Iodinated resin has biocidal efficacy against viruses, bacteria, sporulated bacteria, fungi and protozoa. Iodinated resin is typically sold in bulk in bead, fragment or powder form. Triosyn® resin is one example of a type of iodinated resin preferably used in the present invention. Such iodinated resin may be combined with the nanoparticles.
Fibers
The present invention has overcome the challenge of effectively integrating nanoparticle technology with a fiber entity to produce a resultant protective fiber which would provide chemical and biological protection in a form which can be, for example, manufactured into a protective textile (e.g., as a woven material) or incorporated into other materials or fibers. It is to be noted that this challenge is partially the result of the small size of the nanoparticles themselves. Advantageously, the present invention can effectively incorporate nanoparticles into a fiber entity to attain successful attachment of the nanoparticles to the fiber at the necessary loading and uniformity requirements while not overly occluding the nanoparticles or reducing the reactivity of the nanoparticles being attached. A further aspect of the invention is constructing a nanoparticular filter which can be readily combined with complementary filter media in a practical and flexible manner to address a wide variety of biological and chemical threats. In this manner the invention represents a significant advancement in transforming biocidal nanoparticles from invisible particulate matter to industrial scale fiber-based components.
It is to be noted that the fiber entity may comprise, for example, any type of synthetic or natural fiber material (e,g., polyester, cotton, etc.) or any combination of synthetic and/or natural fibers. In one aspect, the resultant nanoparticle-treated fibers can, for example, be combined and interwoven to form a protective fabric. It is to be noted that such a fabric may be comprised of nanoparticle-treated fibers wherein the fibers themselves may be comprised of various types of materials. In another aspect, a nanoparticle-treated fiber may be incorporated as an addendum into other materials (permeable or non-permeable), such as, e.g., textiles, filters/filtration media, etc. Preferably, engineered fibers are used for receiving nanoparticles. These engineered fibers consist of a core material coated with a polymer having a low melting point (Tg).
Attachment Methodologies
For a given application and desired protection level, activated carbon could be contained within the same fiber layer as the biocidal nanoparticle, or contained in an adjacent layer or further spaced therefrom. Spacing out the layers provides greater residence time of an ambient airflow, while compressed layers provide thinner, lighter protective materials. The iodinated resin and activated carbon powders could be attached to a fiber network according to any of the following exemplary methodologies.
Squeeze-Coating—This method of lamination can utilize, e.g., a Fuller Apparatus. In a preferred embodiment, this apparatus is used to completely wet each fiber (for example polyester) with an adhesive via a dip tank and then to squeeze the excess out with a nip roll. Once the excess adhesive is removed, powders are then applied via, for example, a shaker system onto a wet or partially cured fiber. The fiber is then thoroughly cured followed by vacuuming or forced air to remove any extraneous powders from the surface of the fiber. In an alternate embodiment, the adhesive (for example urethane or acrylic powders) are combined into a slurry and then passed through the Fuller Apparatus.
Pre-Pregging—Pre-pregging involves pre-impregnating a fiber (for example, polyester) with a resin or adhesive prior to additional lamination. The fiber is first completely coated with an adhesive and then nip-rolled to remove the excess. Preferred adhesives should possess the ability to become tacky/molten upon the application of heat after they have been pre-pregged, while at room temperature the pre-pregged materials should remain dry and non-tacky. Exemplary adhesives include a urethane-based adhesive with about 20% to about 25% solids or a hot-melt thermoplastic adhesive having about 30% solids. After coating with an adhesive, the fiber is subsequently dried until it is no longer tacky. The fiber coated with the dried adhesives is then considered “pre-pregged.” Powders are then applied onto the pre-pregged fiber, which is then quickly heated for a short period of time. Since the adhesive becomes tacky with the application of heat, the powder become permanently bonded to the adhesive. The fiber is then cooled, thus rendering the adhesive non-tacky once again. Finally, to remove any extraneous powders, the resultant fiber can be flushed with forced air.
Hot Melt—Hot Melt technology utilizes thermoplastic polymers that are solid at room temperature. These polymers are then heated to their molten form at which time different types of materials can be adhered onto the polymer. The polymers are then set by simple cooling rather than by chemical curing or through evaporation of a solvent, which advantageously makes them more environmentally sound. Hot melt technology can be broken down into two groups: (i) Engineered Fibers; and (ii) Hot Melt Adhesives.
Engineered fibers are fibers coated with a polymer which has a lower melting point that is designed to melt away or become molten. Exemplary hot melt fibers have exteriors made of reinforced or unreinforced thermoplastics such as polyester, polyamide and ethylene vinyl acetate (EVA). Typically, engineered fibers are available in various diameters; it is to be noted that any diameter size may be utilized in the present invention. These engineered fibers can be incorporated into, for example, woven or non-woven substrates to form fabrics. Once molten, the exterior of the engineered fiber can be used as an adhesive to bond materials such as, for example, other fiber, fabrics or particulates. This results in a clean, efficient and highly controllable application of, for example, particulates in comparison with most other application methods (e.g., squeeze-coating).
Hot Melt adhesives are 100% solid thermoplastic adhesives; exemplary types which may be utilized in the present invention are EVAs, polyolefins, polyamides and other suitable adhesives. These adhesives may be applied via heat generating equipment through the use of, for example, hand-held equipment or bulk systems which reduce the solid adhesive to a molten state. The adhesive is then cured by cooling which causes it to form rapid durable double bonds across most substrates. For example, hot melts may be specifically formulated to bond to different substrates.
There are numerous advantages to using hot melt adhesives. For example, since hot melt adhesives are 100% solid systems, this reduces transportation and storage problems. In addition, the instantaneous bond strength supplied by these adhesives allows for faster and more efficient production. Indeed, in comparison with water or solvent-based adhesives, hot melts form strong bonds almost instantaneously and thus reduces the size and amount of equipment used for processing. The reduction in equipment is due to the fact that drying or curing ovens are not required. Further, the high viscosity of hot melt adhesives as compared with solvent-based systems allows them to be used on various porous and non-porous substrates without sacrificing bond strength. Finally, since hot melt adhesives do not set by means of solvent evaporation, they are considered environmentally friendly, which has become increasingly critical in light of more stringent environmental guidelines.
In one embodiment, a powder made from a hot melt adhesive is used to attach activated carbon powder onto fibers. To permanently attach the powder onto/into each fiber of the spacer fabric, each fiber is pre-impregnated or “pre-pregged” with the hot melt adhesive. If the hot melt adhesive is a fine powder, this can be done, for example, by simply sprinkling it onto the surface of the fabric, thus coating each fiber. The powder-coated fibers are then heated to affix the adhesive powder.
To obtain an even distribution and to facilitate ease of handling, it is to be noted that hot melt powder adhesive and/or powders can alternatively be applied via the electrostatically fluidized bed technology (discussed further in Part 2 below). Any un-bonded or extraneous powder and/or adhesive powder may be removed by flushing with forced air.
Electrostatic Attachment
An alternate method for attaching powders onto the surface of a fiber involves electrostatic attachment. In one embodiment, electrostatic attachment utilizes electrostatically charged fluidized bed technology as well as a powder management system to apply powders to various fibers, without the use of adhesives or binders (e.g., activated carbon powder, iodinated resin powder, etc.) While in the present invention, this process of incorporating powdered particulates is used for fibers, it is to be noted that the electrostatic attachment method could also be used for coating particulates on barrier non-wovens, films or membranes.
In the electrostatic fluidized bed process, particulates are aerated in a fluidizing chamber and are electrostatically charged by ionized air. As the particulates become charged, they repel each other. The particles rise above the fluidizing bed, forming a cloud of charged particles. A fiber is then introduced to the cloud of electrostatically charged particulates (e.g., conveyed through it). The charged particulates are attracted to and become attached to the fiber, thus coating it. Since the particulates are more attracted to exposed areas than to areas which are already coated, this provides a uniform coating of powder onto the fiber. Advantageously, the electrostatic fluidized bed process provides uniform powder depositions which can be adjusted to increase or decrease particulate add-on. The coating thickness and the deposition weight can be controlled by adjusting the applied voltage to the charged media as well as the exposure time of the fiber to the cloud of charged particles.
Further details about the electrostatic fluidized bed process are set forth in the following U.S. Patents, the complete disclosures of which are incorporated herein by reference. The references are U.S. Pat. Nos. 5,639,307 and 6,294,222 and 5,486,410 and 5,736,473 and 5,482,773 and 6,024,813 and 4,797,318 and published U. S. patent application Ser. No. 2002/0187258. Details about the electrostatic fluidized bed process are also described in foreign patent JP513 1136, the complete disclosure of which is incorporated herein by reference.
Issues that were addressed by the present invention in incorporating powder onto fibers via electrostatic attachment include:
(a) establishing the best process parameters for the equipment utilized for electrostatic attachment,
(b) selecting ideal substrates for capturing the powders to obtain target loadings of nanoparticles,
(c) optionally, pre-treating the fibers with an adhesive enhancer or binder,
(d) developing a method for permanently attaching the powder after they have been electrostatically attached, and
(e) for enhanced adhesion, optionally down-select a chemical adhesive to improve the attachment of the particles to the fiber.
Examples of Biocidally Reactive Enabled Fibers
While a variety of attachment methodologies have been disclosed for the attachment of resin powders and activated carbon powders, the attachment methods for nanoparticles requires the balancing of numerous special conditions. The successful implementation of these requirements is collectively referred to as “non-occluding retaining means”. We define “non-occluding retaining means” as a modification or control of an attachment process which optimizes certain of the below listed factors to transfer the adsorptive and reactive properties of the free-flowing nanoparticles into a fiber-based network. An exemplary listing of those factors is as follows: maintaining spatial distance between nanoparticulate clusters to avoid occlusion by clumping; matching the nanoparticle to the fiber and to the attachment mechanism to insure compatibility; downselecting an adhesive (e.g. with lowest possible Tg) to avoid physically overwhelming the nanoscale sized particles by a melt flow; to maintain the characteristic nanoparticulate matter structure where a huge portion of the atoms and ions exist at the surface of the nanoparticle even with low rates of agglomeration into popcorn-type clusters; avoiding changes which would erode the surface structure consisting of jagged edges of the atoms/ions which facilitates lysis; and avoiding chemical changes and reactions which would adversely compromise adsorption of chemical entities and reactivity/adsorption toward biological and chemical entities.
While an adhesive may also be used in conjunction with electrostatic attachment, successful bonding of the nanoparticles to a substrate can be achieved via electrostatic attachment alone without any use of additional adhesives. Advantageously, the lack of additional adhesives eliminates the possibility of any unwanted chemical reactions between the adhesives and the nanoparticles in the final product, while simultaneously preventing the over-occluding of the nanoparticles, which would render them unreactive.
In one embodiment, the method of electrostatic attachment can be used to attach nanoparticles to synthetic, bi-component (or multi-component) fibers. Bi-component fibers are comprised of, for example, at least two or more different types of polymers. The polymers may comprise, e.g., polyolefins, polyamides and polyesters. For example, each bi-component fiber may have an inner core comprised of polyester and an outer sheath comprised of a polypropylene or nylon depending upon the properties desired. According to this embodiment, agglomerated nanoparticles are introduced into a fluidizing bed device which uses an electromagnetic/electrostatic mechanism for vigorously impelling the charged nanoparticles onto a bi-component fiber. Once the particulates are spatially distributed onto the surface of the bi-component fiber, heat may optionally be applied, in a carefully controlled manner to permanently affix the particulates. Under microscopy the nanoparticles can be seen to be imbedded in the low Tg thermoplastic fibers. Thus, the polymer of the fiber acts as its own adhesive. Advantageously, this method eliminates the necessity of using of additional adhesives and thus minimizes particulate over-occlusion, unwanted chemical reactions or unintended adsorption from vapors produced during adhesive curing.
The addition of nanoparticulates into a filtration media composed of bi-component fibers has been reduced to practice. Samples were impregnated with Magnesium Oxide nanoparticles (MgO, supplied by Nanoscale Materials Inc.), Triosyn® (supplied Hydro Biotech, Inc.) resin powder and carbon powder by utilizing the electrostatic fluidized bed process. Exemplary microscope photographs at ×100 and ×200 magnification of untreated low-loft filtration media having no MgO nanoparticles are shown in
Following the non-occluding retention of the particulates, it is to be noted that forced air can be used to remove extraneous particulates that were not bonded to the fibers. A resultant fiber treated in this manner would advantageously be able to provide biocidal capability in, for example, a textile construct (e.g., when such treated fibers are woven together or introduced/incorporated into other woven or non-woven material).
Test Data
The chemical agent testing was performed by Calspan University of Buffalo Research Center (CUBRC). The samples were went to CUBRC to be challenged against Liquid/Vapor (L/V) and Vapor/Vapor (V/V) of Mustard (HD) and Soman (GD). The samples were tested in accordance to CUBRC's Standard Operating Procedure, “SOP-AEC-CHEM2-R00”, which consists of a modified version of the procedures described in CRDC-SP-84010, “Laboratory Method for Evaluating Clothing Systems Against Chemical Agents—Mo Jo Waters Method,” June 1984.
The samples were challenged at an ambient temperature (˜23° C.) and 50% relative humidity. Each sample swatch size was 11.4 cm2. All samples were tested with a cover fabric that is standard material used in current chemical protective clothing applications. It is wind resistant nylon/cotton poplin that has been “quarpel” treated. The “quarpel” treatment is a water and oil resistant finish. The cover fabric serves two purposes: low air permeability and greater resistance to liquids. It prevents the chemical agent from instantaneously soaking directly through the fabric and overwhelming the nanoparticles.
Depending upon the agent tested, each sample was challenged with ten (10)—1 μL droplets of MeS, HD or GD, which results in a contamination density of 10 g/m2. The challenge agent was applied to the outer surface of the cover fabric. All samples were tested in triplicate and each sample type included one control sample. The control sample did not contain the reactive-/adsorptive component. A complete list of test parameters is listed is Table 1.
High loft filtration media are non-wovens comprised of synthetic bi-component fibers. Bi-component fibers are made of 2 or more polymers (can have inner/outer cores). The filtration media samples were all tested with a cover fabric.
The high-loft filtration media sample loaded with MgO nanoparticles performed very well compared to the samples without the MgO nanoparticles (control). In the MeS challenge (the results of which are shown in Table 2 below), the test sample had an MeS average permeation rate at 1 hour of only 31.9 nm/min/cm2 as opposed to 324.0 nm/min/cm2 for the control sample.
Table 3 shows the results of the liquid/vapor HD permeation tests with high-loft filtration media loaded with MgO nanoparticles. Surprisingly, these test samples were capable of reducing the cumulative mass of HD by up to 85%.
Table 4 shows a description of a sample tested against not only HD but also the live chemical agent soman (GD) which is a fluorinated organophosphorous compound that is volatile liquid. The test results for this sample in the HD and GD challenges are shown in Tables 5 and 6.
Advantageously, the sample 021902-7 is capable of reducing the cumulative mass of HD by 86%, and is capable of reducing the cumulative mass of GD by 99.8%.
As far as trends, the data in Tables 4-6 above indicate a direct correlation of nanoparticle loading to HD or GD adsorption. Namely, the higher the nanoparticle loading on the filter media, the more HD or GD that was adsorbed.
Descriptions of a nanoparticle-imparted high-loft filtration media sample and a conventional carbon laminate sample submitted for HD and GD vapor/vapor testing are shown in Table 7 below. The purpose of conducting the vapor/vapor test is to determine the adsorptive properties of the nanoparticles only, since vapor/vapor testing eliminates absorptive effects from the cover fabric, any adhesives and the adsorbent's substrate.
The results for the HD and GD vapor/vapor testing for these samples are shown in Tables 8 and 9, respectively, below.
As can be seen from the results of Tables 8 and 9, the test sample 050202-1 exhibited excellent adsorption performance in light of the reduction in cumulative mass of HD and GD being 85% and 99.6%, respectively.
The nanoparticles used in accordance with the invention are those that possess a protective property, i.e. protective nanoparticles or protective nanoparticulate entities. For purposes of this application, the term “protective nanoparticles” encompasses one or more of the following three particular types of nanoparticles: chemically adsorptive nanoparticles; chemically reactive nanoparticles; and biocidally reactive nanoparticles.
Protective nanoparticles are metal-containing nanoparticles or metal-containing nanocrystals. The metals are present as metal oxides, metal hydroxides, metal hydrates, POMs. To enhance their protective properties, such metal-containing protectants may be combined with one of more of a metal oxide, Group I metals, Group IA metals, an alkali metal, a reactive halogen, a metal nitrate, SO2, NO2, or ozone.
It should be noted that a bulk metal-containing particle that is ground down to a powder will not possess the protective properties of the nanoparticles used according to the invention because the ground powder will have conventional surface features. In order to distinguish powders from nanoparticles which may be seemingly in the same size range, the protectants according to the invention are referred to as finely divided nanoparticles or finely divided nanocrystals. Protective nanoparticles are formed from 1 nm to 200 nm sized nanoparticulate clusters. These clusters cling together due to van der Waals forces and therefore have many distinguishable constituent parts. A ground powder is just a single entity, with a uniform exterior surface. In contrast thereto, when the nanometer sized clusters cling together much of their original surface area is preserved providing Brunauer-Emmett-Teller (BET) multi-point surface areas of at least 70 m2/g for early protective nanoparticles and surface areas of at least 1200 m2/g for later versions. These surfaces may contain pores having an average pore radius from 45 Angstroms to 100 Angstroms.
While the structure, surface area and pore size have imbued the nanoparticles with their protective properties, these structural features have also interfered with past attempts to incorporate the nanoparticles into tangible protective filter precursors. Failed attempts have resulted from an inability to control the van der Waals forces resulting in excessive clumping or from an inability to control the adhesive or retaining means resulting in occluding of useful surface areas or pores. The invention is concerned with products and methods that utilize nanoparticles in a flexible manner to readily incorporate one or more of their chemically adsorptive, chemically reactive or biocidally reactive properties.
Although illustrative embodiments of the present invention have been described herein, it is to be understood that the present invention is not limited to those precise embodiments, and that various other changes and modifications may be affected therein by one skilled in the art without departing from the scope or spirit of the present invention. For example, it is expressly intended that all combinations of those carbon beads, metal ions, nanoparticles and/or method steps and/or substrate materials which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or as a general matter of compatibility of application method. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.
This is a division of pending U.S. patent application Ser. No. 10/371,918 filed on Feb. 21, 2003, which in turn claims the priority date benefit of U.S. Provisional Application 60/360,050 filed on Feb. 25, 2002.
| Number | Date | Country | |
|---|---|---|---|
| 60360050 | Feb 2002 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 10371918 | Feb 2003 | US |
| Child | 10847137 | May 2004 | US |
