Apertured polymer sheets incorporating nanoparticles

Abstract

Apertured polymer layers, sheets, meshes or films are provided for a variety of different applications. The polymer sheets include at least one polymer layer having one or more openings for the flow of gas or liquid, and a plurality of nanoparticles disposed within the polymer layer such that the nanoparticles are disposed between a first surface of the polymer layer and a second surface opposite the first surface. These nanoparticles filter contaminants passing through the polymer sheet. In certain embodiments, these apertured sheets constitute a support membrane for a gas or liquid filter. The nanoparticles reduce the total pressure drop across the support membrane to improve the efficiency of such filters.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 63 / 328,959, filed April 8, 2022, the entire disclosure of which is incorporated by reference herein for any purpose. This application is also related to commonly assigned, co-pending U.S. Provisional Patent Applications Nos. 63 / 328,970, 63 / 328,983, 63 / 328,998, 63 / 329,009, 63 / 329,018, 63 / 329,137, 63 / 329,146, 63 / 329,155, 63 / 329,158, 63 / 329,161 and 63 / 329,162 (all filed April 8, 2022), the entire disclosures of which are incorporated herein by reference in their entireties for any purpose.

[0002] Technical Field SUMMARY This specification relates generally to apertured polymer sheets, support members and other materials incorporating nanoparticles, and filters formed from such materials. [Background technology]

[0003] Apertured polymeric sheets or films are lightweight nonwoven materials that contain apertures, pores, or perforations. The apertures may be embossed with a pattern (circles, diamonds, hexagons, ellipses, triangles, rectangles, etc.) and then stretched until the apertures form in the thinned areas created by the embossing. Such apertured substrates can be formed from many polymers, such as polypropylene, polyethylene, high density polyethylene ("HDPE"). The polymer layer can include, for example, an extruded film. Aperture films are used in many applications such as finger bandages, surgical gowns, drapes, masks, tooth whitening strips, hydrogel scrims, nasal supports, electrode support products, filters, food processing, packaging and textile applications, agricultural products, food packaging such as cheese making nets, etc. Aperture films are commercially available and sold under the trademark DelNet®.

[0004] One particularly useful application of apertured films is as a support product for air and liquid filtration equipment. Support sheets or membranes are often used in filters to provide structural support to the filter layers. These sheets often have apertures to allow filtrate to pass through the sheet to the underlying filter media. Generally, when filtration is performed at a certain rate, a cross-flow pressure drop across the support membrane may be observed, which indicates an increase in the force required to force the fluid through the filter. Minimizing the cross-flow pressure drop across a support membrane can reduce the operating costs of filtration. There is therefore a need for improved support membranes and filters containing such membranes. To improve the efficiency of such filters, it is desirable to reduce the total pressure drop across the support membrane. Summary of the Invention

[0005] The following presents a simplified summary of the claimed subject matter in order to provide a basic understanding of some aspects of the claimed subject matter. This summary is not an extensive overview of the claimed subject matter. It is not intended to identify key or critical elements of the claimed subject matter, nor to delineate the scope of the claimed subject matter. Its sole purpose is to present some concepts of the claimed subject matter in a simplified form as a prelude to the more detailed description that is presented later. Apertured polymer layers, sheets, meshes or films are provided that include one or more openings, pores or perforations and incorporate nanoparticles within the polymer layer. In certain embodiments, the apertured sheets constitute the support membrane of a gas filter or liquid filter. The apertured polymer sheets can provide support for, for example, a filter medium, or can have another layer attached to provide the necessary structural support. The nanoparticles trap contaminants and reduce the total pressure drop of the support membrane, improving the efficiency of such filters.

[0006] In one embodiment, the polymer sheet includes at least one polymer layer having one or more openings for the flow of gas or liquid, and a plurality of nanoparticles disposed within the polymer layer such that the nanoparticles are disposed between a first surface of the polymer layer and a second surface opposite the first surface, the nanoparticles filtering contaminants passing through the polymer sheet. In certain embodiments, the polymer sheet is an extruded film. The openings may include holes or perforations. The openings may have any suitable shape, such as diamonds, circles, hexagons, squares, or combinations thereof. In certain embodiments, the sheet has a plurality of pleats extending across the surface of the polymer layer. Multiple types of sheets may be combined, and one or more layers may be used. Sheets of different materials may be combined. The polymer layer may be selected from the group consisting of polypropylene film, high density polyethylene film, and polylactic acid film. The polymer sheet may further comprise a mesh, net, cloth, knit, or woven fabric.

[0007] In certain embodiments, the polymeric layer is a substantially rigid support layer for a gas filter. In other embodiments, the polymeric layer is a flexible surface layer for a face mask. In further embodiments, the polymeric layer is a flexible surface layer for a finger bandage pad. The polymer layers may be coextruded to form an adhesive bonding layer. The polymer layer may have a first surface and a second surface opposite the first surface, and the nanoparticles may form a gradient within the polymer layer such that the density of the nanoparticles decreases from the first surface to the second surface. In embodiments, the nanoparticles are substantially uniformly dispersed throughout the polymer layer. In some embodiments, nanoparticles may be loaded onto the substrate from both the first surface and the second surface. In these embodiments, the area density or "loading" on the first surface and the second surface may be substantially equal to each other or may be different depending on the application. In these embodiments, the area density or "loading" present in the center of the substrate is lower than that on the outer surface. For example, the area density of the center of the substrate may be about 75% of the area density of the outer surface, or may be about 50%, 40%, or 25%.

[0008] In certain embodiments, the nanoparticles have a density of about 0.1 grams / m 2 ~ approx. 20 grams / m 2 , preferably at least about 2.0 grams / m 2 The specific loading or areal density may vary depending on the application. For example, applicants have found that the higher the areal density or loading, the more efficient the nonwoven material is at filtering contaminants. In certain embodiments, the nanoparticles are deposited on the substrate through the first surface. The nanoparticles penetrate through the first surface to the "depth" of the substrate between the first surface and the second surface. As used herein, the term "depth" means that the nanoparticles are dispersed beyond the first surface of the polymer sheet such that at least a portion of the nanoparticles are disposed between the first surface and the opposing second surface of the internal structure of the polymer sheet. In other embodiments, the nanoparticles penetrate substantially the entire substrate from the first surface to the second surface. In other embodiments, the nanoparticles are dispersed in a portion of the polymer sheet from the first surface to a location between the first surface and the second surface. In some embodiments, the nanoparticles penetrate at least 25% of the width or thickness, or more preferably at least about 50% of the thickness, from the first surface between the first surface and the second surface.

[0009] In some embodiments, the nanoparticles are distributed three-dimensionally in space relative to the supporting fibers, which can increase the fiber surface area and the microvolume within the polymer sheet. The three-dimensional distribution also provides resistance to complete blockage of certain portions of the polymer sheet, which is particularly useful in filter media, as it allows fluids (e.g., air and other gases) to pass through the filter, thereby reducing the total pressure drop of the filter. In certain embodiments, the polymer sheet has a thickness from the first surface to the second surface, and the nanoparticles are disposed within the polymer sheet at least 70% of the width from the first surface to the second surface, and in some examples, the nanoparticles are disposed within the polymer sheet at least 90% of the thickness from the first surface to the second surface. In certain embodiments, the nanoparticles are singulated in a fluid and dispersed on the first surface of the polymer sheet. The fluid can be, for example, a gaseous medium such as air, helium, nitrogen, oxygen, carbon dioxide, etc. The nanoparticles can be dispersed from the gaseous medium by gas flow, aerosol, vaporizer, nebulizer, or other suitable delivery mechanism.

[0010] The nanoparticles may comprise any suitable material, such as glass, biosoluble glass, ceramic materials, acrylic, carbon, metals, such as alumina, polymers (e.g., nylon, polyethylene terephalate, etc.), polyvinyl chloride (PVC), polyolefins, polyacetals, polyesters, cellulous ethers, polyalkylene sulfides, poly(arylene oxides), polysulfones, modified polysulfone polymers and polyvinyl alcohols, polyamides, polystyrenes, polyacrylonitriles, polyvinylidene chloride, polymethyl methacrylate, polyvinylidene fluoride, and any combination thereof. The fibers of the substrate may be produced by any method including, but not limited to, airlaid, spinneret, gel spinning, melt spinning, wet spinning, dry spinning, islands-in-a-sea staple or spunbond, segmented pie staple or spunbond, etc. The fibers contemplated may have many cross-sectional shapes including, but not limited to, round, kidney bean, dog bone, trefoil, barbell, bowtie, star, Y-shaped, etc.

[0011] The fibers may be man-made or natural. Suitable materials for the fibers include, but are not limited to, polypropylene, polyester (PET), PEN polyester, PCT polyester, polypropylene, PBT polyester, copolyamide, polyethylene, high density polyethylene ("HDPE"), LLDPE, cross-linked polyethylene, polycarbonate, polyacrylate, polyacrylonitrile, polyfumaronitrile, polystyrene, styrene maleic anhydride, polymethylpentene, cycloolefin copolymers or fluorinated polymers, polytetrafluoroethylene, perfluorinated ethylene and hexyfluoropropylene, or copolymers with PVDF such as P(VDF-TrFE) or P(VDF). -TrFE-CFE), terpolymers, propylene, polyimides, polyetherketones, cellulose esters, nylons and polyamides, polymethacrylics, poly(methyl methacrylate), polyoxymethylene, polysulfonates, acrylics, styrenated acrylics, preoxidized acrylics, fluorinated acrylics, vinyl acetate, vinyl acrylics, ethylene vinyl acetate, styrene-butadiene, ethylene / vinyl chloride, vinyl acetate copolymers, latex, polyester copolymers, carboxylated styrene acrylics or vinyl acetates, epoxies, acrylic multipolymers, phenolics, polyurethanes, cellulose, styrenes, or any combination thereof. Other conventional fiber materials are also contemplated.

[0012] The fibers may include fibers of different sizes, with the fibers generally having diameters ranging from about 1 to about 1000 microns and lengths ranging from about 1.27 to 7.62 centimeters (0.5 to 3 inches). In certain embodiments, the fiber is a biocomponent fiber having a core and a sheath. In some embodiments, the core is eccentric to the sheath. In other embodiments, the core is concentric with the sheath. In certain embodiments, the nanoparticles are singulated in the fluid and dispersed on a first surface of the polymer layer. The polymer layer may include fibers having an electrostatic charge. The nanoparticles may be selected from the group consisting of carbon fibers, glass fibers, polypropylene fibers, nylon fibers, polylactide fibers, and combinations thereof.

[0013] In certain embodiments, the polymer sheet (i.e., fibers and / or nanoparticles) can be electrostatically charged, for example, so that contaminants are captured by both mechanical and electrostatic filtration. The adhesion between the fibers and the nanoparticles can also be enhanced by electrostatically charging the nanoparticles, the fibers, or both. For example, in certain embodiments, the fibers are electrostatically charged so that mechanical filtration can be achieved by the nanoparticles and electrostatic filtration can be achieved by the electret substrate. The electrostatic substrate or electret substrate can be a high-loft triboelectric filter medium made by carding and needling. In one embodiment, the nanoparticles are preferably deposited on the substrate before needling, and then both the electrostatic fibers and the nanoparticles are needled together. In certain embodiments, the polymer sheet further comprises a binder within the polymer layer that adheres the nanoparticles to the polymer layer. The binder may comprise a material selected from the group consisting of starch, dextrin, guar gum, PVOH, and synthetic resins.

[0014] In another aspect, a gas filter includes a filter medium and a substantially rigid support layer adhered to the filter medium. The support layer includes fibers and a plurality of nanoparticles disposed within the support layer. The nanoparticles are configured to filter contaminants passing through the support layer. The support layer may include at least one extruded polymer film having one or more openings for the flow of gas or liquid. In certain embodiments, the polymer film has a first surface and a second surface opposite the first surface, and at least a portion of the nanoparticles are disposed between the first surface and the second surface. The polymer film may include at least one fold to form a pleat in the sheet. The opening may include a pore or perforation. The opening may have a shape such as a hexagon, circle, square, or diamond. In one embodiment, the support layer is substantially porous, hi certain exemplary embodiments, the support layer has a porosity of at least 0.5 or 50%, preferably at least 0.8 or 80%, and more preferably about 0.86 or 86%.

[0015] In certain embodiments, the gas filter further comprises a plurality of pleats extending across a surface of the polymer layer. The polymer film may be selected from the group consisting of a polypropylene film, a high density polyethylene film, and a polylactic acid film. The gas filter may further comprise a mesh, net, cloth, knit, or woven fabric. In certain embodiments, the nanoparticles are singulated in the fluid and dispersed on the first surface of the polymer layer. The support layer may include fibers having an electrostatic charge. The nanoparticles may be selected from the group consisting of carbon fibers, glass fibers, polypropylene fibers, nylon fibers, polylactide fibers, and combinations thereof. In certain embodiments, the gas filter further comprises a binder within the polymer layer that adheres the nanoparticles to the polymer layer. The binder may comprise a material selected from the group consisting of starch, dextrin, guar gum, PVOH, and synthetic resins.

[0016] In another embodiment, a composite material includes a substrate having pores within its internal structure and a plurality of nanoparticles within the internal structure of the substrate, the nanoparticles forming a gradient within the substrate such that the density of the nanoparticles decreases from a first surface to an opposing second surface of the substrate. The substrate can include a fibrous material. The fibrous material can be a plurality of microfibers, the microfibers having a diameter of 1 micrometer or greater. In certain embodiments, the microfibers are formed by a process selected from the group consisting of spunbonding, meltblown, and electrospinning.The nanoparticles extend below the surface by a distance of about 1 millimeter to about 3 millimeters. The description herein of desirable objects met by various embodiments of the present specification is not meant to imply or suggest that any or all of these objects are present as essential features, either individually or collectively, in the most general embodiment of the present specification or in any of its more specific embodiments. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 shows a gas filter comprising first and second support membranes and a filter medium. [Figure 2A-2B] 2A and 2B show an apertured film for use as a support membrane. [Figure 3A-3E] 3A-3E show various embodiments of apertured films having nanoparticles incorporated into the film. [Figure 4] FIG. 4 shows a dual layer filter medium. [Diagram 5] FIG. 5 shows a pleated nonwoven filter medium. [Figure 6] FIG. 6 shows a typical air filter. [Figure 7] FIG. 7 shows a gas filter. [Figure 8] FIG. 8 illustrates a schematic of a system for producing a nonwoven material within a substrate. [Figure 9]FIG. 9 shows a schematic of a system for converting clusters of nanofibers into individual nanoparticles. [Figure 10A-10C] 10A-10C are photographs of a macrocluster of nanofibers, a smaller cluster of nanofibers, and individually isolated nanoparticles, respectively. [Figure 11] FIG. 11 shows the exhaust arrangement of the system of FIG. [Figure 12] FIG. 12 shows the reactor of the system of FIG. [Figure 13] FIG. 13 shows another embodiment of a system for converting clusters of nanofibers into individual nanoparticles. [Figure 14] FIG. 14 illustrates a system for producing a dual layer nonwoven material. [Figure 15] FIG. 15 is a side view of a nonwoven material having nanoparticles dispersed throughout a portion of the material. [Figure 16] FIG. 16 is a side view of a nonwoven material having nanoparticles dispersed throughout the material. [Figure 17] FIG. 17 is a side view of a nonwoven material having nanoparticles dispersed in a gradient throughout the material. [Figure 18] FIG. 18 shows a nonwoven material with nanoparticles dispersed through the depth of the material. [Figure 19] FIG. 19 shows a nonwoven material having nanoparticles dispersed through the depth of the material and a scrim layer overlying the nanoparticles. [Figure 20] FIG. 20 shows a dual-layer nonwoven material with nanoparticles dispersed on the inner surface of the two layers. [Figure 21] FIG. 21 illustrates another embodiment of a system for producing a nonwoven material in a fluid stream. [Figure 22A] FIG. 22A is a photograph of a nonwoven material without the use of a binder. [Figure 22B] FIG. 22B is a photograph of a nonwoven material using a binder. [Figure 23A] FIG. 23A is a photograph of a nonwoven material with nanoparticles dispersed as clumps or clusters throughout the material. [Figure 23B] FIG. 23B is a photograph of a nonwoven material with nanoparticles substantially uniformly dispersed throughout the material. [Figures 24A-24C] 24A-24C show biocomponent fibers incorporated into a nonwoven material. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] This specification and the accompanying drawings show exemplary embodiments and should not be considered limiting, with the claims defining the scope of this specification, including equivalents. Various mechanical, compositional, structural, and operational changes can be made without departing from the scope of this specification and claims, including equivalents. In some cases, well-known structures and techniques have not been shown or described in detail to avoid obscuring the description. Like numbers in two or more figures represent the same or similar elements. Furthermore, elements and their associated aspects described in detail with reference to one embodiment may, where possible, be included in other embodiments where they are not specifically shown or described. For example, even if an element is described in detail with reference to one embodiment and not described with reference to a second embodiment, it can still be said that the element is included in the second embodiment. Furthermore, the depictions in this specification are for illustrative purposes and do not necessarily reflect the actual shape, size, or dimensions of the system or illustrated parts.

[0019] It should be noted that, as used in this specification and the appended claims, the singular forms "a," "an," and "the," as well as the use of the singular form of any word, include plural referents unless expressly and unambiguously limited to one referent. As used herein, the term "include" and grammatical variations thereof are intended to be open-ended, and the recitation of items in a list does not exclude other similar items that may be substituted for or added to the listed items. Unless otherwise indicated, all quantitative values ​​are approximations, whether or not preceded by words such as "about" or "approximately." The materials, methods, and examples described herein are illustrative only and are not intended to be limiting.

[0020] Apertured polymer layers, sheets, meshes or films are provided that contain one or more openings, pores or perforations and incorporate nanoparticles within the polymer layer. The apertured films can be configured for use in many applications, such as finger dressings, surgical gowns, drapes, masks, teeth whitening strips, hydrogel scrims, nasal supports, electrode support products, filters, food processing, packaging and textile applications, agricultural products, food packaging such as cheese making nets, etc. In certain embodiments, the apertured sheet comprises a support membrane of a gas or liquid filter, and the nanoparticles improve the efficiency of such filters by reducing the total pressure drop across the support membrane. As used herein, the term "nanoparticle" refers to a particle having a size of less than 1 micron in at least one axis or dimension. For example, a fiber having a diameter or width of less than 1 micrometer and a length of more than 1 micrometer is a nanoparticle as used herein.

[0021] In certain embodiments, each individual nanoparticle can be a small particle with a size ranging from about 1 to about 1000 nanometers, preferably from about 1 to about 650 nanometers. At least half of the particles in a number size distribution can measure 100 nanometers or less. The majority of nanoparticles are usually composed of only a few hundred atoms. Material properties change as the size of nanoparticles approaches the atomic scale. This is because the surface area to volume ratio becomes large and the surface atoms of the material dominate the material performance. Because of their very small size, nanoparticles have a very large surface area to volume ratio compared to bulk materials such as powders, plates, sheets, or large fibers. This feature allows nanoparticles to have unexpected optical, physical, and chemical properties because they are small enough to confine electrons and create quantum effects. In some embodiments, the nanoparticles comprise nanofibers that have at least one dimension (i.e., diameter, width, height, etc., depending on the cross-sectional shape of the fiber) that is less than 1 micron. The nanofibers may have a continuous length, or the nanofibers may have discrete lengths, such as between 1 and 100,000 microns, preferably between about 100 and 10,000 microns.

[0022] The substrates described herein may include structures of individual fibers or threads that are overlapped, interlocked, or bonded to one another. Nonwovens may include sheet or web structures that are bonded together by mechanically, thermally, or chemically entangling fibers or filaments (and by perforating films). They may be substantially flat, porous sheets made from separate fibers or directly from molten plastic or plastic films. Examples of suitable nonwoven materials include, but are not limited to, meltblown, spunbonded or spunlaced, heat-bonded, bonded carded, airlaid, wetlaid, co-molded, needle punched, stitched, hydraulically entangled fibers, layers, or webs, and the like. In certain embodiments, the substrate may include knitted and / or woven materials. Knitted materials may include any knit pattern suitable for the desired application. Knitted materials suitable for filter applications include weft knit, warp knit, knit mesh panels, compressed knit mesh, and the like. Woven materials suitable for filter applications include woven filter media such as monofilament woven fabrics, multifilament woven fabrics, nylon mesh, polyester mesh, polypropylene mesh, and the like. Woven fabrics can be used, for example, in mesh filter press cloths, woven filter pads and other die-cut pieces, centrifuge filter bags, liquid filter bags, dust collector bags, bed dryer bags, rotary drum filters, filter belts, leaf filters, roll media, and the like.

[0023] In some embodiments, the substrate may comprise a structure comprising intertwined or entangled short-cut fibers and / or filaments. As used herein, short-cut fibers refer to fibers of finite length. As used herein, filaments refer to fibers having a substantially continuous length. In some embodiments, the substrate may comprise short-cut coarse fibers, microfibers and / or fine fibers. As used herein, "fine fibers" refer to fibers having a diameter less than 1 micron, "coarse fibers" refer to fibers having a diameter greater than 10 microns, and microfibers are synthetic fibers having a diameter less than 10 microns. In certain embodiments, the nanoparticles are "depth-wise" dispersed within the substrate. As used herein, the term "depth-wise" means that the nanoparticles are dispersed beyond a first surface of the substrate such that at least a portion of the nanoparticles are disposed within the internal structure of the substrate or medium between the first surface and an opposing second surface. In certain embodiments, the nanoparticles are dispersed substantially throughout the medium from the first surface to the opposing second surface. In other embodiments, the nanoparticles are dispersed in a portion of the medium from the first surface to a location between the first surface and the second surface.

[0024] In some embodiments, the nanoparticles are distributed three-dimensionally in space relative to the support substrate, which can increase the fiber surface area and microvolume within the nonwoven material. The three-dimensional distribution also provides resistance to complete blockage of certain portions of the nonwoven material, which is particularly useful in filter media, as it allows fluids (e.g., air and other gases) to pass through the filter, thereby reducing the total pressure drop of the filter. In other embodiments, the nanoparticles are arranged to create a density gradient through the thickness of the substrate, with higher density nanoparticles located near one surface than the opposite surface, or with higher density nanoparticles located at the surface compared to the central portion of the substrate. The density gradient may be substantially linear, may decrease in a series of discrete steps, or may be random (i.e., a general decrease in density that is neither linear nor step-wise). This density gradient provides a number of advantageous features for certain applications, such as filters (discussed below).

[0025] The nanoparticles may comprise any suitable material, such as glass, biosoluble glass, ceramic materials, acrylic, carbon, metals, such as alumina, polymers (e.g., nylon, polyethylene terephalate, etc.), polyvinyl chloride (PVC), polyolefins, polyacetals, polyesters, cellulous ethers, polyalkylene sulfides, poly(arylene oxides), polysulfones, modified polysulfone polymers and polyvinyl alcohols, polyamides, polystyrenes, polyacrylonitriles, polyvinylidene chloride, polymethyl methacrylate, polyvinylidene fluoride, and any combination thereof. In some embodiments, nanoparticles can be produced as bicomponent segmented pie and islands-in-a-sie. The filaments are then stretched to obtain submicron filaments. The continuous filament nanofibers are cut to the desired length, preferably about 100 to about 10,000 microns.

[0026] In some embodiments, the nanoparticles are absorbents and adsorbents. In some embodiments, the nanoparticles are activated carbon fibers or activated carbon powder. In some embodiments, the nanoparticles are catalytic particles or catalytic fibers. In some embodiments, the nanoparticles can be obtained by feeding a submicron fiber nonwoven fabric into a shredder or grinder or edge trimmer machine where the bonded nonwoven fabric goes in and short cut fibers come out. For example, low mass biocomponent meltblown or nano meltblown fibers can be fed into a shredder to obtain submicron nanoparticles. In some embodiments, different nanoparticles may be mixed. For example, nanofibers and nanobeads can be mixed. Two different nanofibers with different melting points can also be mixed, such that a low melting point nanoparticle acts as a binder for a high melting point nanofiber. Similarly, nanoparticles with different diameters and lengths can also be mixed. In some embodiments, the nanoparticles are selected from environmentally sustainable sources. The nanoparticles may be biosoluble glass nanofibers, biodegradable nanoparticles, compostable nanoparticles, or recyclable compositions.

[0027] Different types of nanoparticles can be combined. Some of the nanoparticles can be functional nanoparticles. For example, the functional nanoparticles can include activated carbon and / or antibacterial materials deposited and / or attached to the fibers in the nonwoven material. This can improve the gas absorption efficiency and bacteria killing effect of the fibers. Also, a composite product with glass and carbon nanoparticles deposited on an apertured sheet can provide filtering and odor removal functions as a filter medium. In some embodiments, the nanoparticles are attached to the substrate via mechanical entanglement. This mechanical adhesion can be supplemented with binders and / or adhesives, as discussed in more detail below. In certain embodiments, the nanoparticles are not crimped (i.e., do not contain significant wavy, bent, curled, coiled sawtooth, or similar shapes associated with nanoparticles in a relaxed state). In other embodiments, the nanoparticles can have a crimped structure with discrete lengths. For example, when these crimped nanofibers with discrete lengths are attached to a substrate, they entangle with themselves, on, and around the substrate. In other embodiments, attachment of the nanofibers to the substrate is achieved via electrostatic charge attraction and / or van der Waals forces between the substrate and the nanoparticles.

[0028] Filter media and filters, such as air filters, face masks, gas turbine and compressor intake filters, panel filters, and the like, are also provided, which include nanoparticles distributed in depth within the filter media. In some embodiments, the filters include one or more support layers attached to the filter media. The support layers and / or filter media may include nanoparticles distributed in depth within the layer. In some embodiments, polymer layers, membranes, or films are provided that include one or more openings for gas or liquid flow, in which the nanoparticles are disposed in depth within the polymer layer. In other embodiments, the substrate includes a nonwoven material that forms a flexible surface layer for finger bandage pads, face masks, and the like. Provided herein are systems, devices, and methods for manufacturing composite materials and products (e.g., gas filters) that include the composite materials. Systems and methods are also provided for singulating individual nanoparticles in a gaseous medium, such as air, helium, nitrogen, oxygen, carbon dioxide, etc. (instead of liquid), which can be dispersed into another product, film, layer, or substrate via gas flow, aerosol, vaporizer, sprayer, or other suitable delivery mechanism.

[0029] Although the following description is presented primarily with respect to composites and filtration media, it should be understood that the devices and methods disclosed herein can be readily adapted for use in a variety of other applications. For example, the composites disclosed herein can be useful in household cleaning products, roofing and flooring products, automotive interiors and headliners, reusable bags, wallpaper, filtration devices, insulation, and the like. Furthermore, the isolated and generated individual nanoparticles can be utilized in various coatings, composites, and / or additives in, for example, polymers, food packaging, flame retardants, fuel cells, batteries, capacitors, nanoceramics, lighting, materials manufacturing, manufacturing methods, composite reinforcement, cement and other materials, medical diagnostic applications, medical treatment devices or therapies, tissue engineering such as scaffolds for bone or tissue repair, drinking water, industrial process fluids, food and beverage products, pharmaceutical and biological agents, tissue imaging, medical therapy delivery, environmental applications such as biodegradable compounds, and the like.

[0030] 1, a composite filter element 114 includes an inner filter substrate 112 and one or more filter support members or membranes 110. The support member 110 may be formed from an extruded sheet of a polymer, such as polypropylene film, high density polyethylene film, polylactic acid film, or a thermoplastic polymer material, such as an extrudable fluoroplastic material, in some embodiments, a perfluoroalkoxyalkane (PFA) copolymer made from the comonomers polytetrafluoroethylene and perfluoroalkylvinylether. However, other polymer materials, such as fluoroplastics, e.g., ethylene chlorotrifluoroethyl (ECTFE); ethylene tetrafluoroethylene (ETFE) of polyvinylidene fluoride (PVDF), may also be used. In certain embodiments, the support membrane 110 includes individual nanoparticles dispersed throughout the depth of the membrane 110. The nanoparticles enable the support membrane to filter at least a portion of the contaminants that pass through the filter membrane 114, i.e., in addition to the filtration provided by the inner filter substrate 112. In other embodiments, the filter substrate 112 and / or the support membrane 110 include such nanoparticles. Fluoroplastic materials such as PFA are highly desirable for use in filters intended for cleaning semiconductor components and other environments where extreme cleanliness is required and the potential for contamination is minimized. Such supported membranes are designed to direct the fluid to be filtered along their surface while simultaneously directing the fluid through their structure to the underlying filter substrate, removing undesirable particles from the filtrate.

[0031] As shown in Figures 2A and 2B, the support film 110 may include a plurality of apertures 128. The apertures are preferably circular, although it will be appreciated that other shapes are possible, such as square, rectangular, hexagonal, triangular, etc. The substrate may be wound into a roll and then unwound and passed through a punch press to form the apertures 128 through in the Z direction in the desired predetermined pattern (Figure 2A). Alternatively, the sheet may be set and then passed through a punch press in a continuous operation to form the predetermined pattern of apertures 128. 2B, after aperture, the filter support member can be stretched in the machine direction, as indicated by double-headed arrow 141, to expand the openings 128 to provide a larger open area for the passage of fluid to be filtered by the filter media or substrate 112. The apertured substrate can be made using any suitable method known in the art. A more complete description of such composite filter media can be found in PCT Application No. US2021 / 011217, the entire disclosure of which is incorporated herein by reference in its entirety for any purpose. In another embodiment, the support membrane 110 may be porous (i.e., instead of or in addition to having openings 128). In this embodiment, additional fluid flow can be achieved with a substantially porous support membrane. In an exemplary embodiment, the support membrane has a porosity of at least 0.5 or 50%, preferably at least 0.8 or 80%, and more preferably about 0.86 or 86%. Porosity is defined as the volume fraction of non-solid or pores relative to the total volume of the material.

[0032] The filter support membrane can be made by any method known to those skilled in the art. In one example shown in Figures 2A and 2B, the support membrane includes ribs. For example, the support membrane can be made by extruding the polymeric material into a sheet and then passing the sheet through a nip area provided by opposing rollers, at least one of which has countersunk grooves on its outer surface. The countersunk grooves of one roller are aligned with the outer surface or countersunk grooves of the other roller in the nip area to form a ribbed sheet with ribs rising from at least one surface of the sheet. Alternatively, the ribs may be formed during the extrusion process or known embossing methods. Once the ribs are formed, the support membrane can be wound into a roll and then unwound and passed through a press to form openings through it in the Z direction in a desired predetermined pattern. Alternatively, as best shown in Figure 2A, the support membrane can be set and then passed through a punch press in a continuous operation to form openings in a predetermined pattern. The punch press can be continuously passed through to form openings in a predetermined pattern. Optionally, the support membrane can be stretched in the machine direction (indicated by the double-headed arrow in FIG. 2B), e.g., to stretch the openings to provide a larger open area for the passage of fluid to be filtered by the filter layer or substrate.

[0033] 3A-3E show some examples of apertured films that can be used as a composite substrate. The apertures can be provided in a variety of patterns having one or more shapes. Multiple types of sheets can be combined and one or more layers may be used. Sheets of different materials can also be combined. The apertured polymer sheet can provide support for, for example, a filter medium, or another layer may be attached to provide the necessary structural support. In certain embodiments, the substrate can be included in a thin film or layer that includes apertures, pores, or perforations. The apertures can be embossed with a pattern (circles, diamonds, hexagons, ellipses, triangles, rectangles, etc.) and then stretched until the apertures are formed in the thinned areas created by the embossing. Such apertured substrates can be formed from many polymers, such as polypropylene, polyethylene, high density polyethylene ("HDPE"). The polymer layer can include, for example, an extruded film. Apertured films are commercially available and are sold under the trademark DelNet®. The substrate is provided in a roll and the nanofibers are deposited on the substrate in a roll-to-roll process. FIGS. 3A-3E show examples of apertured films that can be formed by the methods described herein.

[0034] In certain embodiments, the composite material is formed from an apertured sheet substrate, and the nanoparticles are deposited in the apertured sheet. The substrate has a first surface, a second surface opposite the first surface, and a width or thickness defined between the first surface and the second surface. In certain embodiments, the nanoparticles are deposited on the substrate through the first surface. The nanoparticles penetrate "in-depth" through the first surface to between the first and second surfaces of the substrate. In some embodiments, the nanoparticles penetrate at least 25% of the width or thickness between the first and second surfaces from the first surface, or more preferably at least about 50% of the thickness. In other embodiments, the nanoparticles penetrate substantially the entire substrate from the first surface to the second surface. The nanoparticles preferably comprise individual nanoparticles that have been broken down, separated, and singulated from one another prior to dispersion in the substrate (as shown in FIG. 23B). Thus, the nanoparticles are not layered in the composite product and do not have significant clumps or bundles of nanofibers (as shown in FIG. 23A). This results in greater dispersion of the nanoparticles throughout the substrate, which in some applications, such as gas filters, provides more efficient filtration capacity to filter contaminants. Furthermore, this results in a composite material with a greater nanoparticle areal density (grams per square meter (gsm)) or "loading" within the material. The term "loading" is used herein to mean the areal density (gsm) of material, fibers, or particles in a thin layer, sheet, or film of material.

[0035] In certain embodiments, the nanoparticles have a density of about 0.1 grams / m 2 ~ approx. 20 grams / m 2 , preferably at least about 2.0 grams / m 2 The specific loading or areal density may vary depending on the application. For example, applicants have found that the higher the areal density or loading, the more efficient the nonwoven material is at filtering contaminants. Thus, the specific loading of nanoparticles may vary depending on the desired efficiency of the filter media. In certain embodiments, the composite material comprises a substrate and nanoparticles that permeate the entire width of the substrate. In certain embodiments, the nanoparticles are dispersed substantially throughout the substrate. In certain embodiments, the density of nanoparticles located at the first surface differs by less than 50% from the density of nanoparticles dispersed within the central portion of the substrate. In some embodiments, the difference is less than 25%, preferably less than 10%. In certain embodiments, the amount or number of individual nanoparticles dispersed within the central portion of the substrate is at least about 50%, preferably at least about 75%, more preferably at least about 90% of the amount of individual nanoparticles dispersed at or near the first surface. In other embodiments, the nanoparticles 14 are arranged to create a density gradient from the first surface to the second surface. Contemplated nanoparticles can be made by any method including, but not limited to, airlaid, spinneret, gel spinning, melt spinning, wet spinning, dry spinning, island-in-a-seat staple or spunbond, segmented pie staple or spunbond, and others. Such methods are described in U.S. Patent Nos. 4,406,950, 6,338,814, 6,616,435, 6,861,142, 7,252,493, 7,300,272, 7,309,430, 7,422,071, 7,431,869, 7,504,348, 7,774,077, 9,522,357, 9,993,761, and U.S. Patent Publication No. 2009 / 266,759, the entire disclosures of which are incorporated herein by reference for any purpose.

[0036] FIG. 4 shows a dual layer filter medium including a first substrate 240 having a first surface 242 and a second surface 244 opposite the first surface. A second substrate 250 has a first surface 252 and a second surface 254 opposite the first surface. The second surface 244 of the substrate 240 is adhered to the second surface 254 of the first substrate by any method known to those skilled in the art. The substrates may include polymeric sheets, nonwoven materials, knits, woven fabrics, meshes, and the like. For example, the first substrate 240 may include an apertured polymeric sheet and the second substrate 250 may include a microfiber nonwoven material. In another example, the first substrate 240 includes fibers 246 having a relatively low linear density, e.g., on the order of 3 denier or less, and the second substrate 250 includes fibers 256 having a relatively high linear density, e.g., on the order of 3 denier or more, e.g., on the order of 5 denier, 6 denier or more. One or both of the substrates include individual nanoparticles (not shown) dispersed throughout, adhered to, and / or carried by the substrate. In certain embodiments, a bilayer composite can be formed using the polymer sheet described above attached to a composite formed from a nonwoven substrate, where one or both substrates have nanoparticles adhered thereto and deposited through the depth of the substrate or substrates. The first substrate 240 is configured to filter contaminants primarily with the fibers 46, although as previously described, the first substrate 240 may also include nanoparticles. The second substrate 250 is configured to filter contaminants with both the fibers 256 and the nanoparticles.

[0037] In some embodiments, the substrate may be detrimental to additives such as antimicrobial and / or antiviral compositions, such as silver, zinc, copper, organosilicone, tributyltin, organic compounds containing chlorine, bromine, or fluorine compounds. In certain embodiments, the composite material (i.e., the substrate and / or the nanoparticles) can be electrostatically charged, for example, so that contaminants are captured by both mechanical and electrostatic filtration. The adhesion between the substrate and the nanoparticles can also be enhanced by electrostatically charging the nanoparticles, the substrate, or both. For example, in certain embodiments, the substrate is electrostatically charged so that mechanical filtration can be achieved by the nanoparticles and electrostatic filtration can be achieved by the electret substrate.

[0038] The substrate, the nanoparticles, or both can be electrostatically charged using tribocharging, corona discharge, electrostatic fiber spinning, hydrocharging, charging bars, or other known methods. Corona charging is suitable for charging monopolymer fibers or fiber blends, or fabrics. Tribocharging can be suitable for charging fibers of different electronegativities. Electrostatic fiber spinning combines polymer charging and fiber spinning in a one-step process. One suitable method for tribocharging is described in U.S. Pat. No. 9,074,301, the entire disclosure of which is incorporated herein by reference for any purpose. Nanoparticles can be selected to have different triboelectric properties relative to the substrate in order to use the triboelectric effect to enhance particle removal. In this way, the nanoparticles produced are formed in an electric field and are less susceptible to contamination by chemicals that may mitigate the triboelectric effect.

[0039] The composite material may include a binding agent or material, such as an adhesive or binder, to facilitate attachment of the nanoparticles and / or retention of the nanoparticles within the substrate such that the nanoparticles may be attached to or otherwise held by the substrate to form a stable matrix. The binding agent or material is preferably present in a relatively small amount to adhere the individual nanoparticles to the substrate. Binders may include a variety of conventional materials including naturally based materials such as starch, dextrin, guar gum, etc., or synthetic resins such as EVA, PVA, PVOH, SBR, polyglycolide, etc. In certain embodiments, a solvent based adhesive is used, where adhesion occurs upon solvent evaporation. In one preferred embodiment, the binder or binding material comprises dextrin. In yet another embodiment, the binder comprises a composition of various substances such as water, 2-hexoxyethanol, isopropanolamine, sodium dodecylbenzenesulfonate, lauramine oxide, and ammonium hydroxide. In yet another embodiment, the binder comprises at least PVOH. The binder can be a solution, emulsion, suspension, hot melt, curable, neat, and / or combinations thereof.

[0040] In some embodiments, an adhesive resin is used, which may undergo crosslinking after application of the adhesive on the substrate. Adhesion (water / solvent resistance) may be promoted by self-crosslinking as the solvent in the adhesive formulation evaporates or by thermal activation during the drying process. For certain adhesives, crosslinking may be achieved by high energy wavelengths of electromagnetic radiation, including but not limited to RF, UV, or electron beam. The amount of adhesive may be controlled by adjusting the nozzle size of the spray coater 140 or by controlling the flow rate of the adhesive composition. The bonding agent may be applied using a spray nozzle, dip coating, or other methods. In some embodiments, the binder or bonding material may include a surfactant to reduce the surface or interfacial tension of the binder, thereby enhancing its dispersion and wetting properties and allowing the binder to more easily penetrate the depth of the substrate.Suitable surfactants for use with the adhesives disclosed herein include nonionic, anionic, cationic, and amphoteric surfactants, such as sodium stearate, 4-(5-dodecyl)benzenesulfonate, sodium dodecylbenzenesulfonate wetting agent, docusate (dioctyl sodium sulfosuccinate), alkyl ether phosphates, benzalkonium chloride (BAC), perfluorooctane sulfonate (PFOS), and the like. In some embodiments, the substrate includes its own binder composition. In these embodiments, a binder or binding material may or may not be added to the substrate. In one such embodiment, the substrate includes a biocomponent fiber, and one of the components includes an outer sheath at least partially surrounding an inner core, as further described below.

[0041] Figure 22A is a magnified image of a composite product in which nanoparticles have been deposited without the use of a binder material, and Figure 22B is a magnified image of a composite product in which nanoparticles have been attached to the fibers using a binder material of dextrin and water. As shown, the nanoparticles are more uniformly attached to the substrate when a binder is used. FIG. 22A shows a substrate with biosoluble glass nanofibers deposited in layers only on the surface of the substrate and relying on electrostatic forces to hold the nanofibers. Nanofiber clumping and poor nanofiber retention can be seen in FIG. 22A. The substrate can be a polymer sheet, knit, woven, mesh, or nonwoven material. Composite materials having one or more polymer sheets as substrates can, in further embodiments, include a binder material used to hold the nanoparticles using the materials described above. In a further example, any of the binder materials disclosed herein can be used. Additionally, nanoparticles of biosoluble glass are deposited into the depth of the substrate. In this example, the substrate itself has a MERV rating in the range of 4-10, which can be achieved using any of the methods described herein. The nanoparticles are deposited into the depth of the substrate and electrostatically charged, producing a composite product with a MERV of 13 in one example, using a substrate originally with a MERV of 8. In another example, a composite product with a MERV of 15 is produced using a substrate originally with a MERV of 6. The substrate is provided in a roll, and the composite product can be produced on a commercial scale in a roll-to-roll continuous process, such as any of the processes and methods described herein. In one example, the roll-to-roll process was operated at 30 feet per minute.

[0042] In certain embodiments, the composite materials described herein may be included as part of a filter device that captures or absorbs contaminants, such as liquid filters, gas filters for home and commercial air filtration, surgical masks or other face coverings, etc. The filter device may be a mechanical filter, an absorption filter, a sequestration filter, an ion exchange filter, a reverse osmosis filter, a surface filter, a depth filter, etc., and can be designed to remove many different types of contaminants from air, water, etc. In one such embodiment, the composite material is incorporated into an air filter that removes particles and contaminants from the air, such as a HEPA filter (i.e., pleated mechanical air filter), UV light filter, electrostatic filter, washable filter, media filter, spun glass filter, pleated or non-pleated air filter, activated carbon filter, pocket filter, V-bank compact filter, filter sheet, flat cell filter, filter cartridge, etc. The composite material may include a filter medium for air filtration, may be supported by a support layer, a scrim layer, or may be included in other layers or materials. Applicants have discovered that by incorporating nanoparticles into the depth of the composite material as described herein, the efficiency of the air filter is substantially increased without compromising other factors such as pressure drop (i.e., airflow) of the filter. Furthermore, these materials improve the overall dust holding capacity and therefore the life of the filter, especially compared to filters that rely solely or primarily on electrostatic effects to increase efficiency.

[0043] Traditional residential and commercial air filters are typically rated by the filter's ability to capture particles between approximately 0.3 and 10 microns. This rating, called the Minimum Efficiency Reporting Value, or MERV, was developed by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE). MERV ratings range from 1 to 16, with higher numbers indicating greater efficiency in capturing a particular type of particle. Traditional mechanical air filters typically report a MERV rating for their filter media of around 8. Air filters are generally rated based on their initial efficiency (i.e., the efficiency of the air filter before use) and their efficiency over time. This latter efficiency is generally tested through a conditioning step called ASHRAE Standard 52.2 Appendix J. The air filters provided herein have an initial MERV rating of greater than about 10 and a pressure drop of less than 0.5 inches of water. In some cases, the initial MERV rating is about 11 with a pressure drop of about 0.17 inches of water or less, or an initial MERV rating is about 13 with a pressure drop of about 0.36 inches of water or less, or an initial MERV rating is about 14 with a pressure drop of about 0.5 inches of water or less.

[0044] The gas filters provided herein have a MERV rating of 10 or greater after the gas filters are conditioned to ASHRAE Standard 52.2 Appendix J. In some embodiments, the MERV rating is 13 or greater after the gas filters are conditioned to ASHRAE Standard 52.2, ISO Standard 16890, or any other acceptable standard in the industry. The MERV ratings of the filter media described herein vary based on many factors, including the type and size of fibers used in the filter media, the density of the individual nanoparticles within the filter media, the width of the filter media, the number and size of the pleats (if any), etc. MERV ratings can be measured for composite products formed as pleated filter media as well as for sheets of composite products, each of which may have different pressure drops. Similarly, the pressure drop of the filter media also depends on many factors, including those mentioned above.

[0045] One factor that affects both the MERV rating and pressure drop is the density or loading of nanoparticles in the substrate relative to the density of fibers in the substrate. In certain embodiments, the filter media described herein have a nanoparticle loading of about 0.1 grams / m 2 ~ approx. 20 grams / m 2 , preferably at least about 2 grams / m 2 has a nanoparticle areal density of The efficiency or MERV rating of the filter increases with increasing nanoparticle loading. In particular, Applicant has determined that the nanoparticle loading is at least 2 g / m 2 They found that a filter with a MERV rating of about 10 could be achieved with a loading of 4 or 6 g / m 2A loading of 10 g / m results in filters with MERV ratings of approximately 12 and 13, respectively. 2 These dosages will result in a filter with a MERV rating of 15 or higher.

[0046] An example of a pleated filter media 390 is shown in Figure 5. The filter 390 may include about 0-3.9 pleats per centimeter (about 0-10 pleats per inch) depending on the application. The filter media can be mounted on a cardboard or metal frame for easy replacement filter products (Figure 6). As shown, a gas filter 394 made from the composite materials described herein includes a pleated filter media 396 and a support layer 398 that provides rigidity and structure to the filter media 396. 7 shows a gas filter 309 made with the composite materials described herein. The gas filter 309 includes a substrate and nanoparticles dispersed through the depth of the substrate. The substrate can then be rolled into a cylinder, cone, or other suitable shape and used in applications such as gas turbine and compressor intake filters, panel filters, and the like. Other types of filters that can be developed using the composite materials disclosed herein include conical filter cartridges, square end cap filter cartridges, pocket filters, V-bank compact filters, panel filters, flat cell filters, pleated or non-pleated bag cartridge filters, and the like.

[0047] The composite products disclosed herein can be used in medical masks or other medical applications, such as respirator cartridges. Medical masks are designed to protect medical personnel and / or patients from microorganisms and other substances. For example, medical masks can block bacteria, which may have dimensions of, for example, about 3 microns, as well as viruses, which may have dimensions of, for example, about 0.1 microns. The masks are made with multiple layers of composite material and have ear loops, ties, or other structures for attaching the mask to a person's face. Some of the layers can include composite material with nonwoven substrates, polymer sheets or layers, or the like. At least the top of the mask can incorporate wires so that at least a portion of it conforms to the person's face. The masks can include rigid polymer structures designed to hold the multi-layer composite material to the front of the person's face. In one example, the mask has three layers. The outer and inner layers include nonwoven materials, such as spunbond polypropylene, that provide breathability, although any of the materials mentioned herein can be used. The intermediate layer is disposed between the inner and outer layers and includes a polymeric apertured sheet substrate with nanoparticles deposited in the depth direction of the substrate to provide an initial MERV of 8 or more, preferably a MERV of 10 or more, more preferably a MERV of 13 or more. The pressure drop through the mask is 3-6mm of water, more preferably 4mm of water for breathability. It is desirable for the mask to have an efficiency of about 95%. Other examples of masks have 4 or more layers. Multiple layers of composite products can also be combined into one mask.

[0048] 8 illustrates generally an overall system 410 for producing the composite materials and other products described above. As shown, the system 410 includes a feeder 420 for advancing a substrate 430, such as a polymer sheet or other material, through a manufacturing process. The system 400 further includes a coater 440, a fiberization system 450, and a heating and / or drying device 460. In certain embodiments, the system 400 further includes a vacuum or other negative pressure source 470 underneath the substrate 430 opposite the fiberization system 450. In one embodiment, the feeder 420 includes a winder 424 at a downstream end of the process and an unwinder 422 at an upstream end to continuously wind the substrate 430 through the system 400. In certain embodiments, the feeder 420 may further include a support surface (not shown) extending between the winders to support the substrate 430 as it moves downstream through the system 400. In other embodiments, the substrate is unwound directly from the unwinder 422 to the winder 424 without a separate support surface.

[0049] The coater 440 is configured to spray droplets of a binding agent or material, such as an adhesive or other binder, onto the substrate 430 so that the nanoparticles can adhere to the substrate 430 and form a stable matrix. The binding agent is preferably present in a relatively small amount to adhere the individual nanoparticles to the fibers throughout the substrate 430. In a preferred embodiment, the coater 440 includes a spray nozzle sized to produce droplets of adhesive having a diameter of about 20-30 microns to increase the penetration depth of the adhesive through the substrate 430. Of course, the droplet size can be affected by numerous other parameters including air pressure, volume of air, air temperature, humidity, spray horn design, adhesive rheology / viscosity, carrier, etc. Of course, it will be appreciated that coating the substrate with a binder or binding material can be accomplished by other coating methods including ultrasonic spraying, dip coating, spin coating, gravure coating, kiss roll coating, screen coating, powder coating, electrostatic coating, sputter coating, or similar coating techniques.

[0050] As mentioned above, binders can include a variety of conventional materials, including naturally-based materials such as starch, dextrin, guar gum, etc., or synthetic resins such as EVA, PVA, PVOH, SBR, etc. In certain embodiments, solvent-based adhesives are used where adhesion occurs upon solvent evaporation. In one preferred embodiment, the binder comprises dextrin. In another embodiment, the binder comprises a composition of various substances such as water, 2-hexoxyethanol, isopropanolamine, sodium dodecylbenzenesulfonate, lauramine oxide, and ammonium hydroxide. In yet another embodiment, the binder comprises PVOH. The binder can be a solution, emulsion, suspension, hot melt, curable, neat, and / or combinations thereof.

[0051] In some embodiments, an adhesive resin is used, which may undergo crosslinking after coating of the adhesive to the substrate 430. Adhesion (water / solvent resistance) may be promoted by self-crosslinking as the solvent in the adhesive formulation evaporates or by thermal activation during the drying process. For certain adhesives, crosslinking can be achieved by high energy wavelengths of electromagnetic radiation, including but not limited to RF, UV, or electron beam. The amount of adhesive can be controlled by adjusting the nozzle size of the spray coater 440 or by controlling the flow rate of the adhesive composition. In some embodiments, the binder may include a surfactant to reduce the surface or interfacial tension of the binder, thereby enhancing its dispersion and wetting properties and allowing the binder to more easily penetrate the depth of the substrate.Suitable surfactants for use with the binders disclosed herein include nonionic, anionic, cationic, and amphoteric surfactants, such as sodium stearate, 4-(5-dodecyl)benzenesulfonate, sodium dodecylbenzenesulfonate wetting agent, docusate (dioctyl sodium sulfosuccinate), alkyl ether phosphates, benzalkonium chloride (BAC), perfluorooctane sulfonate (PFOS), and the like.

[0052] In some embodiments, the spray coater 440 is positioned upstream of the fiberization system 450 so that the binder is sprayed before the nanoparticles are deposited. In other embodiments, the spray coater 440 is positioned downstream of the fiberization system 450 so that the binder can be sprayed after the nanoparticles are deposited. In other embodiments, the system 400 includes two spray coaters, one located upstream of the fiberization system 450 and a second spray coater (not shown) located downstream of the fiberization system 450 to coat the substrate 430 with a secondary binder after the nanoparticles are deposited. In some embodiments, there are two or more nozzle heads with each spray coater 440. The nozzle heads may be arranged in series, for example, to obtain better uniformity or to increase the spray width of the fibers. Alternatively, the nozzle heads may be arranged in parallel, i.e., across the width of the substrate, to ensure that the binder is coated across the entire width of the substrate. In some embodiments, the substrate includes its own binder composition. In these embodiments, the binder may or may not be added to the substrate. The binder material incorporated into the substrate may be used in conjunction with other binder materials sprayed onto the substrate.

[0053] In a preferred embodiment, a negative pressure or vacuum source is positioned beneath the substrate opposite the spray coater 440 to increase the penetration depth and uniformity of the binder. The negative pressure source can be any suitable suction device that draws the binder through the substrate, such as a suction pump. The substrate may comprise a material that adheres to the nanoparticles. For example, the substrate may comprise a material that becomes sticky and / or flowable upon heating and / or drying. During the heating / drying process, the substrate is heated to its melting point until it becomes sticky and / or flowable in order to adhere the nanoparticles to the substrate. In a preferred embodiment, adhesion and drying are performed simultaneously in drying apparatus 460.

[0054] FIG. 9 shows a schematic of a fiberization system 450 for converting nanofiber clumps or clusters into individual nanoparticles. The term "fiberization," as used herein, means converting (e.g., opening, separating, singulating, and / or individualizing) clusters, clumps, or other groups of nanoparticles, which may or may not be entangled with one another, into individual nanoparticles having at least one dimension less than 1 micron. FIGS. 10A-10C show examples of macroclusters of entangled nanofibers (FIG. 10A), small clusters of entangled nanofibers (FIG. 10B), and individual nanoparticles (FIG. 10C). As shown, fiberization system 450 includes a feeder 500, such as a hopper, for introducing large or macro-clusters / agglomerates of nanoparticles (see FIG. 10A) into system 450. Feeder 500 may include any suitable hopper device known to those skilled in the art, and is preferably configured to introduce macro-clusters of particles into the process at a specific rate that depends on the downstream fiberization rate. Nanoparticles may be introduced continuously at a specific rate or may be introduced at intervals at a specific rate. Bundled macro-clusters of nanoparticles may be broken down prior to introduction into feeder 500. It should be appreciated that the nanoparticles can be introduced to the fiberizer 450 in many different forms. For example, raw nanofibers can be produced as long, discrete fibers. In this form, the nanofibers may be cut to obtain a desired length / diameter ratio.

[0055] The system 450 further includes a separator 510, such as a blender, to separate or break down macroclusters / agglomerates of nanoparticles into smaller clusters / agglomerates of nanoparticles (see FIG. 10B). The feeder 500 transfers the nanofibers to the separator 510 by any mechanical means in a steady-state, continuous manner. The rate of transfer depends on a variety of factors, including the speed of the substrate 430 along the feeder 420, the rate of fiberization of the nanoparticles, etc. By controlling the amount of nanoparticles that fall into the separator 510, the amount of nanoparticles that are dispersed into the substrate can be controlled to create a continuous manufacturing process. In one embodiment, the separator 510 includes a housing 512 having a first opening 514 connected to the feeder 500 and a second opening 516 connected to a downstream process. The second opening 516 is preferably sized to allow only clusters of nanofibers having a certain size to pass through. The separator 510 may include a number of rotatable blades (not shown) designed to rotate about a vertical axis within the housing 512 to separate and release coarse clusters of nanofibers. The blades may have the same or different pitch and camber to sequentially break down or "open" entangled fibers as they pass from the first opening 514 to the second opening 516.

[0056] Fiberization system 450 further includes a gas flow that extends throughout the system from separator 510 to nozzle 520 (described in more detail below). The gas flow (along with a series of pumps described below) provides the motive force to move the nanofibers through system 450. In one embodiment, the gas flow is created using an air compressor 530 configured to provide compressed air to the system, although it will be appreciated that other forms of gas may be used to move the nanofibers through system 450. The system 450 includes one or more pumps for moving the nanofiber clusters, and thus the individual nanoparticles, through the system. The pumps may include any suitable pump, such as positive displacement, centrifugal, axial, etc. In one embodiment, the first pump 540 includes a first inlet fluidly connected to the air compressor 530 by a first flow path 542 and a second inlet fluidly connected to the separator 510 by a second flow path 544. Compressed air is drawn into the first pump 540, which creates a negative pressure (e.g., vacuum) that draws the nanofiber clusters from the separator 510 into the pump (discussed in more detail below). The system 550 may further include second and third pumps 550, 560, each fluidly connected to an outlet of the first pump 540. In a similar manner, the second and third pumps 550, 560 create a negative pressure that draws the nanofiber clusters through the third flow path 552.

[0057] In a particular embodiment, the pump 540 includes an eductor 600. As shown in FIG. 11, the eductor 600 includes a motive fluid inlet 602 and a nanofiber inlet 604, each of which is connected to an outlet 606 via a flow passage 608. The flow passage 608 includes a convergent inlet nozzle 610, a diffuser throat 612, and a divergent outlet diffuser 614. The high pressure, low velocity air is converted to low pressure, high velocity air, creating the pressure difference required for suction. Based on the Venturi effect and Bernoulli's principle, a primary fluid medium (e.g., compressed air) is used to create a vacuum to draw the nanofibers into the eductor 600 and out through the outlet 606. The diameter of the eductor 600 depends on the volumetric flow rate of the compressed air, the suction requirements, the pressure loss, and the fluid pressure of the compressed air. Returning to FIG. 9 , the third flow path 552 includes a junction 554 that splits the third flow path 552 into two separate flow paths that lead to the second and third pumps 550, 560, respectively. The junction 554 preferably includes a surface or wall that is disposed substantially perpendicular to the third flow path 552 to form a T-shaped intersection. As the nanofiber clusters travel through the third flow path 552, they are propelled against this surface or wall by the negative pressure applied by the second and third pumps 550, 560. This velocity of the nanofibers relative to the junction 554 creates collisions with sufficient kinetic energy to break down at least a portion of the nanofiber clusters into smaller nanofiber clusters and / or into individual nanoparticles having at least one dimension less than 1 micron.

[0058] To create the kinetic energy necessary to break down the nanofiber clusters, air is propelled through the system 450 at a velocity of about 500 feet per minute (fpm) to about 10,000 feet per minute, preferably about 2,000 fpm to about 6,000 fpm. The system 450 includes a sufficient amount of suction pressure, preferably at least about 20 psi. This suction pressure creates a pressure throughout the system of at least about 100 psi. In certain embodiments, the system 450 further includes fourth and fifth flow paths 562, 564 connecting the outlets of the second and third pumps 550, 560 to the reactor 570. As shown in FIG. 12, the reactor 570 includes a top surface 572, a bottom surface 574, and an interior annular chamber 576 extending from the top surface 572 to the bottom surface 574. The reactor 570 further includes a central tube 575 having an open top inlet 578 and an outlet 580. The reactor 570 may further include one or more top outlets 582. The reactor 570 may be coupled to an energy source (not shown) configured to generate a swirling gas vortex within the annular chamber 576. The energy source may include any suitable energy source, such as a pump, a compressor, a generator, etc. The swirling gas preferably flows from the bottom to the top of the reactor 570 around the central tube 575 , moving the nanofiber clusters and individual nanoparticles upward from the bottom surface 575 to the top surface 572 .

[0059] In another embodiment, the vortex is formed without a separate energy source. In this embodiment, nanofiber clusters 590 and individual nanoparticles 592 enter the reactor 570 through bottom inlets 584, 585, 586, 587. The inlets 584, 585, 586, 587 are angled upward to facilitate movement of the nanofibers and nanoparticles around the central tube 575. In a preferred embodiment, at least one of the inlets 584, 585, 586, 587 is angled such that the nanofibers and nanoparticles enter the reactor 570 substantially tangentially to the central tube 575. As the nanofibers and nanoparticles enter the annular chamber 576, their velocity vectors (speed and direction) create vortices within the reactor 570 that cause the nanofibers and nanoparticles to spin around the central tube 575 and rise to the top of the chamber 576. The swirling gas preferably flows from the bottom to the top of reactor 570 around central tube 575, moving the nanofiber clusters and individual nanoparticles upward from bottom surface 575 to top surface 572. Without interruption, nanofibers 590 and nanoparticles 592 are blown up from the bottom to the top of the reactor. The vortex within chamber 576 can further break down (e.g., open, separate, and / or individualize) the nanofiber clusters 590 as they pass through reactor 570. In some embodiments, reactor 570 may also be coupled to an energy source (not shown) configured to create a swirling gas vortex within annular chamber 576. The energy source may include any suitable energy source, such as a pump, a compressor, a generator, etc.

[0060] The system 410 may further include another pump or negative pressure source (see, e.g., FIG. 13) connected to the top outlet 582. This negative pressure draws the fibers 590 through the outlet 582 as they exit the reactor 570. Because the individual nanoparticles 592 are much lighter than the entangled nanofibers 590 that are still clustered together, these individual nanoparticles 592 are drawn into the top inlet 578 of the central tube 575. Meanwhile, the larger and heavier nanofiber clusters 590 that have not yet been broken down are drawn through the top outlet 584. The top outlet 584 may be connected to another pump (not shown) or to the first pump 540. In this way, the nanofiber clusters 590 are sent back through the process to be further broken down, forming a re-feed system for further breaking down the remaining nanofiber clusters. An outlet 580 of the central tube 575 is connected to the nozzle 220 (see FIG. 9). The individual nanoparticles are drawn into the nozzle 520 where they are dispersed onto the surface of the substrate or into the fiber stream (discussed below). The nozzle 520 may include any suitable nozzle known to those of skill in the art. In one embodiment, the nozzle 520 has multiple outlets with outer dimensions tailored to the size (i.e., area) of the substrate passing under the nozzle 520. The nozzle 520 disperses the nanoparticles onto the substrate at a rate driven by the pressure of the system.

[0061] In certain embodiments, the system 400 includes two or more nozzles coupled to the outlet 580 of the reactor 570. The nozzles may be arranged in any suitable configuration on the substrate, for example, in parallel, in series, in parallel, etc. It will be appreciated that pump 540, or pumps 550, 560, may also feed the nanofiber / air mixture stream directly to nozzle 520 (i.e., bypassing reactor 570). In this embodiment, the pressure within the system is designed to generate sufficient kinetic energy to break down or open up substantially all of the nanofibers into individual nanoparticles such that reactor 570 is not required to separate the nanoparticles from larger clusters of fibers.

[0062] 13, which illustrates another embodiment of a fiberization system 620. As shown, the fiberization system 620 includes a separator 625 for separating large or macro-clusters of nanofibers into smaller clusters of nanofibers that pass through the system 620. A first ejector 626 is coupled to the outlet of the separator 625 and serves to draw the nanofibers from the separator 625 into the system 620. An air compressor (not shown) is also coupled to the ejector 626 to provide motive fluid, as described above. As in the previous embodiment, second and third ejectors 630, 640 are connected to the outlet of the first ejector 626. The nanofibers are drawn from the first ejector 320 and propelled against a surface of the T-intersection 650 to break down at least a portion of the nanofibers into smaller clusters or individual nanoparticles. The second and third ejectors 630, 640 each have an outlet connected to a further T-shaped intersection 660, 670. As described above, the nanofibers are propelled against the surface of the T-shaped intersection 660, 670 for further break-up. The T-shaped intersections 660, 670 each are connected to two flow paths that enter the bottom 680 of the reactor. The bottom 680 of the reactor thus has four separate inlets 682, 684, 686, 688 for the passage of the nanofibers. Each of these inlets is preferably angled upwards and located at opposite corners of the reactor. This causes the nanofibers to enter the vortex of the reactor and swirl upwards to the top 690 of the reactor.

[0063] As previously described with reference to FIG. 12, the reactor includes an annular chamber with a central tube with open upper and lower ends connected to a nozzle. Nanofibers that have been sufficiently broken down into individual nanoparticles flow through the open upper end into the central tube for dispersion through the nozzle. Heavier clusters of nanoparticles that have not yet been broken down exit the reactor through one of four separate outlets 692, 694, 696, 698. Ejectors 710, 720 provide the power to draw the nanofibers from the reactor 400, as described above. Each of the outlets 792, 794 is connected to the ejector 710 via a T-shaped intersection 712, and each of the outlets 396, 398 is connected to the ejector 720 via a T-shaped intersection 722. In this case, the nanofibers flow from two flow paths into one flow path as they pass through the intersections 712, 722. The ejectors 710, 720 are connected to T-junctions 730, 740, respectively. As mentioned above, the nanofibers are propelled to the T-junctions 730, 740 to be further broken down into individual nanoparticles. The T-junctions 730, 740 are then connected to the bottom 780 of the reactor 700 (via inlets 732, 734, 742, 744), respectively. This allows the nanofibers to be passed back through the reactor 700 for further processing. This process continues until each cluster of nanofibers is completely broken down into nanoparticles and passes through the nozzle through the central tube. As a final step, the individualized nanofibers are air-sprayed from the nozzle onto any substrate or mixed with any fiber spin stream. In this process, the suction force is up to 20 psi and the pressure is up to 100 psi.

[0064] In certain embodiments, the fiberization system may include a separate control system that monitors the nanofibers to determine when they have broken down into individual nanoparticles suitable for passing through the nozzle. This control system may, for example, simply monitor the pressure of the system to ensure that sufficient pressure is being applied to the nanofibers to break them down into nanoparticles. Alternatively, this control system may include a variety of different sensors located in the system to detect properties of the nanoparticles, such as mass or size. Sensors may be located within the reactor 700, for example, so that the control system can control various parameters of the reactor 700, such as the negative pressure applied to the outlets 692, 694, 696, 698, the speed of the vortex passing around the annular chamber, or the pressure applied to the central tube that draws the nanoparticles into the nozzle. 14 illustrates another embodiment of a system 750 for manufacturing multiple layers of composite material. As shown, the system 750 includes first and second unwinders 752, 754 and a single winder 756 for winding first and second substrates 760, 762 downstream through the system 750. As with the previous embodiment, the system 750 may further include a support surface (not shown) for each of the substrates 760, 762. The first and second unwinders 752, 754 serve to advance the first and second substrates 760, 762 to a process where they are bonded to one another and then wound on the single winder 756, as described below. The substrates may include nonwoven materials, meshes, knits, wovens, polymeric sheets, and the like, as described above.

[0065] The system 750 includes first and second spray coaters 770, 772 disposed downstream of the first and second unwinders 752, 754, respectively, for applying a binder to the first and second substrates 760, 762. The system 700 further includes first and second fiberization systems / apparatuses 780, 782 disposed downstream of each spray gun 770, 772. As previously described, the fiberization apparatuses 780, 782 generate individual nanoparticles and disperse the nanoparticles onto the substrates 760, 762. Once the nanoparticles are dispersed on the substrates 760, 762, the two substrates are joined to one another at a junction 790 and advanced downstream together. The two substrates may be glued to one another at this point, or may simply be layered one on top of the other. The system 750 further includes a heating / drying device, such as an IR oven 792, downstream of the junction 790 of the two substrates. The heating / drying device heats and dries the two substrates to bond them together and to bond the nanoparticles to the fibers within the substrates. The substrates may be, for example, stacked on top of one another.

[0066] In certain embodiments, the nanoparticles are dispersed on both substrates 760, 762. In one such embodiment, the system 500 is designed such that the nanoparticles are dispersed on a first surface of each substrate. The substrates can then be bonded together with the first surfaces facing each other. Alternatively, the first surfaces may be facing away from each other (i.e., bonding the substrates at a second, opposing surface of each substrate). In yet another embodiment, the first surface of the first substrate is bonded to the second surface of the second substrate. In further embodiments, other substrates can be used to form the composite material. Figures 15 and 16 show further embodiments of nanofiber deposited composite materials, where the substrate is a microfiber nonwoven material. The nanoparticles can be substantially distributed throughout the thickness of the substrate in certain embodiments. In other embodiments, the composite material can include nanoparticles having a density gradient across the thickness of the substrate.

[0067] For example, Figure 17 illustrates a substrate 830 in which the nanoparticles 814 form a density gradient such that there is a higher density of nanoparticles 814 disposed near the first surface 816 than the second surface 818. In certain embodiments, the density of the nanoparticles disposed at the first surface 816 differs from the density of the nanoparticles dispersed at the second surface 818 by more than about 75%. In some embodiments, the difference is greater than 50%. In some embodiments, the difference is greater than 25%. In certain embodiments, the amount or number of individual nanoparticles dispersed at or near the second surface 818 is less than about 50%, preferably less than about 25%, and more preferably less than about 10% of the amount of individual nanoparticles dispersed at or near the first surface 816. 17 may be substantially linear from the first surface 816 to the second surface 818. Alternatively, the density of the nanoparticles 814 may decrease in a series of discrete steps from the first surface 816 to the second surface 18, or the gradient may be random (i.e., a general decrease in density that is neither linear nor step-like). The substrate of the composite material may be a polymeric apertured sheet, woven, knit, mesh, nonwoven, or the like.

[0068] The distribution of nanoparticles through the thickness of the composite material can be measured, for example, using imaging techniques. Using electron microscopy or other techniques, a magnified view of the composite product taken at the center of the thickness of the product at a horizontal cross section of the product can be compared to an image taken at the top or bottom of the product, or all three images can be compared to determine how much the nanoparticle deposition varies. Computer image analysis processes can be employed. For example, in FIG. 17, a cross section AA can be taken and a cross section BB can be taken. The top image of each cross section can be taken by an electron microscope, a scanning electron microscope, or other microscope. For example, the top image of the cross section taken at the AA cross section can be compared to the top image taken at the BB cross section. The number of microfibers, the number of nanoparticles, or both in samples of the same two-dimensional size can be evaluated and compared. Additionally, imaging techniques can be used for three-dimensional samples. These techniques can be used to evaluate fiber orientation and other characteristics. These techniques can be used to determine whether nanoparticles are deposited in the depth direction of the substrate, across a substantial portion of the substrate, to substantially the entire depth, or to a portion of the substrate depth.

[0069] In other embodiments, the nanoparticles may be loaded onto the substrate from both the first and second surfaces 816, 818. In these embodiments, the area density or "loading" at the first and second surfaces 816, 818 may be substantially equal to one another or may differ depending on the application. In these embodiments, the area density or "loading" at the center of the substrate is lower than that at the surfaces 816, 818. For example, the area density at the center of the substrate may be about 75% of the area density at the surfaces 816, 818, or may be about 50%, 40%, or 25%. FIG. 18 shows a filter product 900 including a filter medium 910 of a nonwoven material including fibers 922 and nanoparticles 920 dispersed in at least a portion of the filter medium 910. As shown, the filter medium 910 has a first top surface 912 and a second bottom surface 914. The nanoparticles are distributed throughout and beyond the top surface 912 to extend into the depth of the filter medium 910, as described above. The filter product 900 further includes a support layer 930, which may be any suitable support layer known in the art, such as a substantially rigid polymer that provides support for the filter media 910, or an apertured film having a plurality of openings for the passage of gas or fluid (as described above). The fibers of the nonwoven substrate for forming the composite material as disclosed herein can be formed using known methods such as meltblown, spunbond, or other methods mentioned above. The contemplated fibers can have many cross-sectional shapes, including but not limited to round, kidney bean, dog bone, trefoil, barbell, bowtie, star, Y-shaped, and others. These shapes and / or other conventional shapes may be used in conjunction with these embodiments to obtain desired performance characteristics. The fibers in the substrate remain connected to each other, such as by thermal bonding, chemical bonding, intertwining with each other, using a binder such as an adhesive, and the like.

[0070] The fibers of the nonwoven substrate may be man-made or natural. Suitable materials for the fibers include, but are not limited to, polypropylene, polyester (PET), PEN polyester, PCT polyester, polypropylene, PBT polyester, copolyamide, polyethylene, high density polyethylene ("HDPE"), LLDPE, cross-linked polyethylene, polycarbonate, polyacrylate, polyacrylonitrile, polyfumaronitrile, polystyrene, styrene maleic anhydride, polymethylpentene, cycloolefin copolymers or fluorinated polymers, polytetrafluoroethylene, perfluorinated ethylene and hexyfluoropropylene, or copolymers with PVDF such as P(VDF-TrFE) or P(VDF). -TrFE-CFE), terpolymers, propylene, polyimides, polyetherketones, cellulose esters, nylons and polyamides, polymethacrylics, poly(methyl methacrylate), polyoxymethylene, polysulfonates, acrylics, styrenated acrylics, preoxidized acrylics, fluorinated acrylics, vinyl acetate, vinyl acrylics, ethylene vinyl acetate, styrene-butadiene, ethylene / vinyl chloride, vinyl acetate copolymers, latex, polyester copolymers, carboxylated styrene acrylics or vinyl acetates, epoxies, acrylic multipolymers, phenolics, polyurethanes, cellulose, styrene, or any combination thereof. Other conventional fiber materials are also contemplated.

[0071] The fibers of the nonwoven substrate can include fibers of different sizes, with the fibers generally having diameters ranging from about 1 to about 1000 microns and lengths ranging from about 0.5 to 3 inches. The fibers may be configured as a gradient density medium with decreasing pore size from the top (upstream) to the bottom (downstream) of the filter to increase capture efficiency and dust retention capacity. This configuration also allows different amounts of nanoparticles to be dispersed at different depths of the filter medium. For example, the upstream side of the filter medium can have the largest fiber size to allow for more voids and a higher density of nanoparticles, while the downstream side of the filter medium can have smaller sized fibers to provide a lower density of nanoparticles. Alternatively, this structure can be reversed to provide a higher density of nanoparticles in the downstream portion of the filter medium. The fibers of the nonwoven substrate, as part of a composite material, may remain connected to other fibers by being thermally bonded, chemically bonded, or intertwined with each other. Bicomponent fibers are sometimes used especially in mechanical filtration and are formed by extruding two polymers from the same spinneret with both polymers contained within the same filament. Suitable materials for bicomponent fibers include, but are not limited to, polypropylene (PP) / polyethylene (PE), polyethylene terephthalate (PET) / polypropylene (PP), etc.

[0072] In some embodiments, the substrate may comprise a "high loft" nonwoven material, including spunbond or air-through bond carded nonwoven fibers. As used herein, the term "high loft" means that the volume of voids is greater than the volume of all solids. With air-through bond carded nonwoven fibers, the loft of the substrate may be controlled by various means known to those skilled in the art. For example, loft may be increased by reducing the compressive force exerted on the medium during bonding. In another example, high loft nonwoven materials may be produced using thicker fibers, such as greater than 3 denier, e.g., 5 denier or greater, 6 denier or greater in thickness (discussed in more detail below). In other embodiments, loft may be increased by using eccentric biocomponent fibers, as shown in FIG. 24C and discussed in more detail below. The fibers of the nonwoven substrate can have a thickness suitable for the application. In some embodiments, these fibers have at least one dimension in the range of about 1 to about 10,000 micrometers, or about 1 to about 1,000 micrometers, or about 10 to about 100 micrometers. The thickness of the fibers can also be measured in denier, which is a unit of measurement of the linear mass density of the fiber. In some embodiments, the fibers can have a linear density of about 1 denier to about 10 denier. The nanoparticles are fibers with at least one dimension in the range of about 1 to about 1,000 nanometers, or about 1 to about 100 nanometers. The above dimensions of the fibers and nanoparticles can be diameter or width, depending on the shape of the fiber or nanoparticle.

[0073] For gas filters, such as pleated or non-pleated air filters, the fibers may have a linear density ranging from about 1 denier to about 10 denier. The filter media may include fibers having the same or different linear densities. Air filter fibers generally have a linear density of about 3 denier or less to ensure that the fibers are small enough to capture contaminants passing through the filter. Applicant has surprisingly discovered that by using nanoparticles dispersed in the filter media, the fibers can have a greater linear density, for example, greater than 3 denier. This is because the nanoparticles provide significant filtering capacity. In some cases, the fibers can have a linear density greater than 3 denier, greater than 5 denier, greater than 6 denier, or even 7-10 denier. Applicant has also discovered that in some applications, fibers having a greater linear density than those used in conventional filters (e.g., greater than about 3 denier) provide more open space or pores within the filter media, which allows for a greater density of nanoparticles to be dispersed therein. Although this may be contrary to common knowledge to those skilled in the art, Applicant has discovered that fibers having a greater linear density incorporating nanoparticles actually improve the overall efficiency of the filter.

[0074] In certain embodiments, the filter medium may include at least two different fiber thicknesses or linear densities to provide at least two different filter layers within the same filter medium. For example, in some cases, one portion of the filter medium includes fibers with a linear density greater than 3 denier, such as 5 denier or more or 6 denier or more. Another portion of the filter medium includes fibers with a more standard linear density of 3 denier or less. This dual-layer filter medium forms a first filter portion that primarily filters contaminants with nanoparticles with a high density in the thicker fibers, and a second filter portion that primarily filters contaminants with fibers with a lower linear density, although both portions may include nanoparticles dispersed throughout the fibers. In certain embodiments, the filter medium may include three or more separate portions or layers with different denier fiber ranges within each portion.

[0075] 19 illustrates another filter product 940 that includes a filter media 910 of a nonwoven material that includes fibers 922 and nanoparticles 920 dispersed throughout a portion of the filter media 910. In this embodiment, the product 940 includes a scrim layer 950 adhered to a support layer 930. FIG. 20 shows a dual layer filter product 960 including first and second filter media 962, 964 bonded together. As shown, nanoparticles 920 are distributed throughout the depth of each filter media 962, 964. In this embodiment, the nanoparticles 920 are distributed on the inner surfaces 966, 968 of the filter media 962, 964. In another embodiment (not shown), the nanoparticles are distributed on the outer surfaces 970, 972 of the filter media 962, 964. In yet another embodiment, the nanoparticles 920 can be deposited on the inner surface 966 of the filter media 962 and the outer surface 972 of the filter media 964. Filter products similar to those of FIGS. 19 and 20 can incorporate composites with apertured polymer sheets or any other substrates mentioned herein. Filter products having a combination of composites with different substrates can be used.

[0076] FIG. 21 illustrates an apparatus for incorporating nanoparticles into one or more fiber streams, for example during a fiber spinning process. In one such embodiment, the nanoparticles are dispersed between two meltblowing dies, and the molten polymer is extruded through small holes to form fibers. When the nanoparticles meet the fibers while still tacky, they mechanically entangle with the fibers and thermally bond to the fibers. Thus, in some embodiments, no additional bonding step is required. 21, an apparatus 1600 for forming a fibrous nonwoven structure includes a fiberization system 1610 similar to one of the systems and apparatus described above. The fiberization system 1610 includes a nozzle 1620 or similar device for dispersing individual nanoparticles into a first stream 1630. The apparatus 1600 further includes a system for generating one or more streams of fibers that are combined with the stream of individual nanoparticles 1630. The system may include any system known in the art, such as spunbond, carded, extrusion, etc.

[0077] In one example, the system may include a spunbond line, where filaments are formed by spinning molten polymer and drawing the molten filaments. Fiber bundles of filaments are separated, spread out, and then laid on a net to form a web. The fibers are bonded in the form of a sheet by thermal bonding and embossing. The first stream 630 may be introduced, for example, before the attenuation zone or before the bonding (consolidation) step. In another embodiment, the system may include two carding machines arranged in series with each other. The first stream 1630 can be introduced at any point after the first carding line and before the second carding line, so that the nanoparticles are sandwiched between the two carded fiber webs. Then, all the fibers containing the nanoparticles are bonded together (the nanoparticles are thermally interlocked) in an air-through bonding oven.

[0078] In another embodiment, the apparatus includes first and second feeders, such as hoppers 1640, 1642 coupled to first and second extruders 1650, 1652. Each extruder may include, for example, an extrusion screw (not shown) driven by a conventional drive motor (not shown). As the polymer advances through the extruders 1650, 1652, it is gradually heated to a molten state by the rotation of the extrusion screw by the drive motor. Heating the thermoplastic polymer to a molten state may be accomplished in multiple discrete stages where its temperature gradually increases as it advances through discrete heating zones of the extruders 1650, 1652 toward two meltblowing dies 1660, 1662, respectively. The meltblowing dies 1660, 1662 may be in yet another heating zone where the temperature of the thermoplastic resin is maintained at an elevated level for extrusion. Each meltblowing die 1660, 1662 is configured such that two attenuating gas streams per die converge to form a single gas stream that entrains and attenuates the molten threads as they exit the small holes or orifices 1672 of the meltblowing die. The molten threads are attenuated into small diameter fibers, typically smaller than the diameter of the orifice 1672, or into microfibers, depending on the degree of attenuation. Thus, each meltblowing die 1660, 1662 has a corresponding single primary air stream 1680, 1690 of gas that contains the entrained and attenuated polymeric fibers.

[0079] The primary air streams 1680, 1690 containing polymeric fibers are aligned to converge at the forming section 1700. Additionally, a first stream 630 of individual nanoparticles is added to the two primary air streams 1680, 1690 of thermoplastic polymeric fibers or microfibers at the forming section 1030. The introduction of the individual nanoparticles into the two primary air streams 1680, 1690 of fibers is designed to create a distribution of secondary fibrous material 1032 within the combined primary air streams 1680, 1690 of fibers. This can be achieved by merging the first stream 1630 of individual nanofibers between the two primary air streams 1680, 1690 and causing all three gas streams to converge in a controlled manner. Examples of suitable meltblowing dies that may be utilized to produce nonwoven materials are described in more detail in U.S. Pat. Nos. 6,972,104, and 8,017,534 and 7,772,456, and U.S. Patent Application No. US20200216979A1, the entire disclosures of which are incorporated herein by reference in their entireties for any purpose. 24A-24C show various examples of biocomponent fibers that can be used with the nonwoven substrates disclosed herein. FIG. 24A shows a fiber 60 having a core fiber 62 and a surrounding sheath fiber 64. In this embodiment, the core 62 is substantially concentric with the sheath. FIG. 24B shows a biocomponent fiber 70 having first and second fibers 72, 74 arranged side-by-side. FIG. 24C shows a biocomponent fiber 80 having a core fiber 82 and a sheath fiber 84. In this embodiment, the core 82 is off-center with respect to the longitudinal axis of the sheath 84, which increases the overall loft of the biocomponent fiber. Of course, other configurations are possible. For example, the core may include shapes other than circular, such as a dog bone shape, square, triangle, diamond, etc. Alternatively, the fiber may include multiple cores or be divided into three, four or more quadrants.

[0080] Embodiment 1 is a polymer sheet comprising at least one polymer layer having one or more openings for the flow of gas or liquid, and a plurality of nanoparticles disposed within the polymer layer, the nanoparticles having at least one dimension less than 1 micron.Embodiment 2 is the sheet of embodiment 1, wherein the polymer layer has a first surface and a second surface opposite the first surface, at least a portion of the nanoparticles disposed between the first surface and the second surface.Embodiment 3 is the sheet of any one of embodiment 1 or 2, wherein the polymer layer includes at least one fold to form a pleat in the sheet. Embodiment 4 is the sheet of any one of embodiments 1-3, wherein the polymer layer is an extruded film.Embodiment 5 is the sheet of any one of embodiments 1-4, wherein the openings comprise pores or perforations.Embodiment 6 is the sheet of any one of embodiments 1-5, wherein the openings are hexagonal, square, or diamond shaped.

[0081] Embodiment 7 is the sheet of any one of embodiments 1-6, further comprising a plurality of pleats extending across a surface of the polymer layer.Embodiment 8 is the sheet of any one of embodiments 1-7, wherein the polymer layer is selected from the group consisting of polypropylene film, high density polyethylene film, and polylactic acid film.In any of the embodiments disclosed herein, the polymer sheet comprises at least one polymer layer having one or more openings for gas or liquid flow, and a plurality of nanoparticles disposed within the polymer layer, the nanoparticles having at least one dimension less than 1 micron, further the openings comprise pores or perforations, and further the polymer layer is selected from the group consisting of polypropylene film, high density polyethylene film, and polylactic acid film. Embodiment 9 is the sheet of any one of embodiments 1-8, further comprising a mesh, net, cloth, knit, or woven.Embodiment 10 is the sheet of any one of embodiments 1-9, wherein the polymer layer is a substantially rigid support layer for a gas filter. Embodiment 11 is a sheet according to any one of embodiments 1 to 10, wherein the polymer layer is a flexible surface layer for a face mask.Embodiment 12 is a sheet according to any one of embodiments 1 to 11, wherein the polymer layer is a flexible surface layer for a finger bandage pad.

[0082] Embodiment 13 is the sheet of any one of embodiments 1-12, wherein the polymer layers are coextruded to form an adhesive tie layer. Embodiment 14 is the sheet of any one of embodiments 1-13, wherein the nanoparticles form a gradient in the polymer layer such that the density of nanoparticles decreases from the first surface to the second surface.Embodiment 15 is the sheet of any one of embodiments 1-14, wherein the nanoparticles are substantially uniformly dispersed in the polymer layer. Embodiment 16 is a sheet according to any one of embodiments 1 to 15, wherein the nanoparticles are isolated within a fluid and dispersed on the first surface of the polymer layer.

[0083] Embodiment 17 is the sheet of any one of embodiments 1-16, wherein the polymer layer comprises fibers having a static charge. In any of the embodiments disclosed herein, the polymer sheet comprises at least one polymer layer having one or more openings for gas or liquid flow, and a plurality of nanoparticles disposed within the polymer layer, the nanoparticles having at least one dimension less than 1 micron, further the openings comprise pores or perforations, and further the polymer layer, the nanoparticles, or both have a static charge. Embodiment 18 is the sheet of any one of embodiments 1-17, wherein the nanoparticles are selected from the group consisting of carbon fibers, glass fibers, polypropylene fibers, nylon fibers, polylactide fibers, and combinations thereof. Embodiment 19 is the sheet of any one of embodiments 1-18, further comprising a binder in the polymer layer that adheres the nanoparticles to the polymer layer.Embodiment 20 is the sheet of any one of embodiments 1-19, further comprising a binder, the binder comprising a material selected from the group consisting of starch, dextrin, guar gum, PVOH, and synthetic resins.

[0084] Embodiment 21 is a gas filter comprising a filter medium and a substantially rigid support layer adhered to the filter medium, the support layer comprising fibers and a plurality of nanoparticles disposed within the support layer, the nanoparticles having at least one dimension less than 1 micron.Embodiment 22 is the gas filter of embodiment 21, wherein the nanoparticles are configured to filter contaminants passing through the support layer. Embodiment 23 is the gas filter of any one of embodiments 21-22, wherein the support layer comprises at least one extruded polymer film having one or more openings for the flow of gas or liquid.Embodiment 24 is the gas filter of any one of embodiments 21-23, wherein the polymer film has a first surface and a second surface opposite the first surface, and at least a portion of the nanoparticles are disposed between the first surface and the second surface. Embodiment 25 is the gas filter of any one of embodiments 21 to 24, wherein the polymer film includes at least one fold to form a pleat in the sheet.

[0085] Embodiment 26 is the gas filter according to any one of embodiments 23 to 25, wherein the openings comprise pores or perforations.Embodiment 27 is the gas filter according to any one of embodiments 23 to 26, wherein the openings are hexagonal, square, or diamond shaped. Embodiment 28 is the gas filter of any one of embodiments 21-27, further comprising a plurality of pleats extending across a surface of the filter medium. Embodiment 29 is the gas filter according to any one of embodiments 23 to 28, wherein the polymer film is selected from the group consisting of a polypropylene film, a high-density polyethylene film, and a polylactic acid film. Embodiment 30 is the gas filter of any one of embodiments 21 to 29, further comprising a mesh, net, cloth, knit, or woven fabric.

[0086] Embodiment 31 is the gas filter of any one of embodiments 21 to 30, wherein the nanoparticles are isolated within a fluid and dispersed on the first surface of the filter medium. Embodiment 32 is the gas filter of any one of embodiments 21-31, wherein the support layer comprises fibers having an electrostatic charge. In any of the embodiments disclosed herein, the support layer, the nanoparticles, or both, have an electrostatic charge. Embodiment 33 is the gas filter of any of embodiments 21-32, wherein the nanoparticles are selected from the group consisting of carbon fibers, glass fibers, polypropylene fibers, nylon fibers, polylactide fibers, and combinations thereof. Embodiment 34 is the gas filter of any one of embodiments 21 to 33, further comprising a binder to adhere the nanoparticles to the support layer.Embodiment 35 is the gas filter of any one of embodiments 21 to 34, wherein the binder further comprises a material selected from the group consisting of starch, dextrin, guar gum, PVOH, and synthetic resins.

[0087] Embodiment 36 is a composite material comprising a substrate having pores within an internal structure and a plurality of nanoparticles within the internal structure of the substrate, the nanoparticles having at least one dimension less than 1 micron, the nanoparticles forming a gradient within the substrate such that the density of the nanoparticles decreases from a first surface to an opposing second surface of the substrate.Embodiment 37 is the composite material of embodiment 36, wherein the substrate comprises a fibrous material. Embodiment 38 is the composite material of embodiment 37, wherein the fibrous material comprises a plurality of microfibers, the microfibers having one dimension equal to or greater than 1 micron. Embodiment 39 is the composite material of any one of embodiments 36-38, wherein the microfibers are formed by a process selected from the group consisting of spunbonding, meltblowing, and electrospinning.

[0088] Embodiment 40 is the composite material of any one of embodiments 36-39, wherein the nanoparticles extend below the surface a distance of about 1 millimeter to about 3 millimeters. Embodiment 41 is a gas filter having the composite material according to any one of embodiments 36 to 40. Embodiment 42 is a liquid filter having the composite material according to any one of embodiments 36 to 41. Embodiment 43 is a face mask having the composite material of embodiment 36. EXAMPLES

[0089] Example 1 A bicomponent microfiber substrate with an inner circular portion of polyester and an outer concentric portion of HDPE was prepared in a roll. In a roll-to-roll process, the substrate was sprayed with adhesive and nanofibers of biosoluble glass fibers or nanoparticles were deposited on it. The nonwoven product was then heated in an oven and the cooled nonwoven product was collected on another roll. The nanoparticles are deposited according to the steps described in Figures 12-16 below. Biosoluble glass nanofibers are used in the experiments. The nanofibers have a diameter of about 700 nm and a length of about 500 microns. In the following examples, a carded air-through bonded nonwoven fabric made from bicomponent fibers is used as the substrate. Flat sheet media samples were tested at a filtration rate of 110 fpm. Sample size was 12 in. x 12 in. (30.48 cm x 30.48 cm). NaCl salt particles ranging from 0.3 to 10 microns were used as the contaminant.

[0090] Example 2 A carded nonwoven fabric made from 3 denier PET / PE bicomponent fibers is used as the substrate. A composition containing water, 2-hexoxyethanol, isopropanolamine, sodium dodecylbenzenesulfonate, lauramine oxide, and ammonium hydroxide is used as the binder. Different nanofiber loadings are controlled by adjusting the line speed. [Table 1] This example shows that by controlling the amount of nanoparticles added, the MERV rating is increased from MERV 7 to MERV 13.

[0091] Example 3 A high loft air-through carded nonwoven with 5 denier bicomponent fibers is used as the substrate. A typical starch binder is diluted and sprayed prior to nanofiber deposition. Once the solvent evaporates and drying occurs under an IR heater, the starch adheres the nanofibers well. [Table 2]

[0092] Example 4 The substrates used were spunbond or meltblown media with nanoparticles incorporated into the substrate as described herein after IPA discharge. The spunbond fibers were made from molten polymer that was spun and drawn to produce filaments. The substrates had an average basis weight of about 90 gsm and an average thickness of about 0.57 mm. A base sample was used with no nanoparticles incorporated. Four separate samples were prepared with nanoparticles incorporated into the substrate as described herein. In sample 2, nanoparticles were incorporated into the meltblown fibers after IPA discharge. In samples 1, 3, and 4, nanoparticles were incorporated into the spunbond fibers after IPA discharge. The test results are shown in Table 3 below. [Table 3] As shown, the efficiency of the nanoparticle-incorporated media samples increased over the base sample for all three particle groups, with significant increases seen for the E2 and E3 particle groups. The overall MERV rating of the samples increased from MERV 7 (base sample) to MERV 12-MERV 16 when nanoparticles were used. The base sample without nanoparticles had a pressure drop of 0.07 inches of water. Samples 1-4 had a slight increase in pressure drop ranging from 0.17-0.41 inches of water. Sample 2, where nanoparticles were incorporated into the meltblown fibers, had a MERV rating of 14 and a pressure drop of 0.24 inches of water.

[0093] Example 5 5 denier air-through carded fiber was used as the substrate. A base sample was used without nanoparticles incorporated. Two separate samples were prepared with nanoparticles incorporated into the substrate as described herein. The results of this test are shown in Table 4 below. [Table 4] As shown, the efficiency of the nanoparticle-incorporated filter media samples increased substantially over the base sample for all three particle groups. The overall MERV rating of the samples increased from MERV 6 (base sample) to MERV 13 with nanoparticles. The base sample without nanoparticles had a pressure drop of 0.0762 cm (0.03 inches) of water. Samples 1 and 2 had a slight increase in pressure drop ranging from 0.7874 to 0.8382 cm (0.31 to 0.33 inches).

[0094] Example 6 Meltblown fibers were used as the substrate. The substrate had an average basis weight of about 24 gsm and an average thickness of about 0.4 mm. A base sample was used that did not incorporate adhesives such as nanoparticles or PVOH. Sample 1 included meltblown fibers with the belt side up. PVOH was sprayed onto the fibers, but no nanoparticles were incorporated. Sample 2 included meltblown fibers with the fuzzy side up. PVOH was sprayed onto the fibers, but no nanoparticles were incorporated. Sample 3 included meltblown fibers sprayed with PVOH and with nanoparticles incorporated into the fibers as described herein. The results of this testing are shown below in Table 5. [Table 5] As shown, the efficiency of Sample 3 incorporating nanoparticles was increased over the other three base samples for all three particle groups, especially the E1 particle group. The total MERV rating of Sample 3 increased from MERV 13 or 14 (base samples) to MERV 15 when nanoparticles were used. The PVOH added to Samples 2 and 3 did not substantially increase the pressure drop (i.e., 0.35 for the base sample, 0.38 and 0.41 for Samples 1 and 2). The pressure drop for Sample 3 increased from 0.40 inches of water to 1 inch of water. Sample 3, where nanoparticles were incorporated into the meltblown fibers, had a MERV rating of 15 and a pressure drop of 1.02 inches of water.

[0095] Example 7 A 5 denier air-through carded fiber was used as the substrate. A base sample was used that did not incorporate nanoparticles. Seven additional samples were prepared that included 5 denier carded fiber with nanoparticles incorporated into the substrate as described herein. The results of this testing are shown in Table 6 below. [Table 6] As shown, the efficiency of the seven samples incorporating nanoparticles increased over the base sample for all three particle groups, especially for the E2 and E3 particle groups. The total MERV rating increased from MERV 6 (base sample) to MERV 7-MERV 13 with nanoparticles. The pressure drop only increased from 0.0762 cm (0.03 inches) of water to a maximum of 0.8128 cm (0.32 inches) of water.

[0096] Example 8 High loft spunbond fiber was used as the substrate on the continuous fiber line. Two different versions were included in this test: 205-6 and 205-2, and the continuous fiber line setup was altered to prepare two substrates with different masses and thicknesses. For each version (205-6 and 205-2), a base sample was used that did not incorporate nanoparticles. Six additional samples were prepared containing 205-6 and 205-2 fibers with nanoparticles incorporated into the substrate as described herein. The results of this test are shown in Table 7 below. [Table 7] As shown, the efficiency of the six samples incorporating nanoparticles was substantially improved over the base sample for all three particle groups. The total MERV rating increased from MERV 6 (base sample) to MERV 11-MERV 14 with nanoparticles. The pressure drop only increased from 0.04 inches of water to a maximum of 0.87 inches of water. The pressure drop for the 205-2 sample only increased to a maximum of 0.48 inches of water.

[0097] Example 9 Spunbond and meltblown fibers were used as substrates. The average basis weight of the substrates was about 70 gsm for the spunbond fibers and about 24 gsm for the meltblown fibers. The average thickness of the substrates was about 0.75 mm. A base sample was used that did not incorporate nanoparticles. Five additional samples were prepared that included spunbond and meltblown fibers with nanoparticles incorporated into the fibers as described herein. In Samples 1-3, nanoparticles were sprayed onto the meltblown fibers. In Samples 4 and 5, nanoparticles were sprayed onto the spunbond fibers. Additionally, in Samples 1 and 2, the substrates were not sprayed with the adhesive PVOH. Samples 3-5 were sprayed with PVOH. The test results are shown in Table 8 below. [Table 8] As shown, the efficiency of the five samples incorporating nanoparticles was substantially improved over the base sample for all three particle groups. The total MERV rating increased from MERV 5 (base sample) to MERV 16 with nanoparticles. The pressure drop only increased from 0.07 inches of water to a maximum of 0.56 inches of water. For samples 3-5 (PVOH sprayed on substrate), the pressure drop only increased to a maximum of 0.4 inches of water.

[0098] Example 10 Five denier air-through carded glass fiber was used as the substrate. A base sample was used that did not incorporate nanoparticles. Three additional samples were prepared that contained five denier carded glass fiber that incorporated nanoparticles. The test results are shown in Table 9 below. [Table 9] As shown, the efficiency of the three samples incorporating nanoparticles was substantially improved over the base sample for all three particle groups. The total MERV rating increased from MERV 6 (base sample) to MERV 12 or MERV 13 when nanoparticles were used. The pressure drop only increased from 0.03 inches of water to a maximum of 0.27 inches of water.

[0099] Example 11 A fiber blend of 5 denier and 7 denier air-through carded glass fiber was used as the substrate. The media was air-through bonded. A base sample was used that did not incorporate nanoparticles. Nineteen additional samples were prepared that included a fiber blend of 5 denier and 7 denier carded glass fiber that incorporated nanoparticles. The test results are shown in Table 10 below. [Table 10] As shown, the efficiency of all 19 samples incorporating nanoparticles was substantially improved over the base sample for all three particle groups. The overall MERV rating increased from MERV 6 (base sample) to MERV 10-MERV 13 with nanoparticles (the majority of samples were rated MERV 13). Pressure drop only increased from 0.03 inches of water to a maximum of 0.31 inches of water.

[0100] Although the devices, systems, and methods have been described in detail herein in accordance with certain preferred embodiments thereof, numerous modifications and variations therein may be made by those skilled in the art, and therefore the foregoing description should not be construed as limited thereby, but rather should be construed as including such obvious modifications of the foregoing, and only as limited by the spirit and scope of the following claims.

Claims

1. At least one polymer layer having one or more openings for the flow of gas or liquid, and Multiple nanoparticles, at least one of which has a dimension of less than 1 micron, are arranged within the polymer layer. A polymer sheet containing [a specific component].

2. The sheet according to claim 1, wherein the polymer layer has a first surface and a second surface opposite to the first surface, and at least a portion of the nanoparticles are disposed between the first surface and the second surface.

3. The sheet according to claim 1, wherein the polymer layer includes at least one fold for forming pleats within the sheet.

4. The sheet according to claim 1, wherein the polymer layer is an extruded film.

5. The sheet according to claim 1, wherein the opening includes hexagonal, square, or rhombic pores or perforations.

6. The sheet according to claim 1, wherein the polymer layer is selected from the group consisting of polypropylene film, high-density polyethylene film, and polylactic acid film.

7. The sheet according to claim 1, wherein the polymer layer is a substantially rigid support layer for a gas filter.

8. The sheet according to claim 1, wherein the polymer layer is a flexible surface layer for a face mask or a finger bandage pad.

9. The sheet according to claim 2, wherein the nanoparticles form a gradient within the polymer layer such that the density of the nanoparticles decreases from the first surface to the second surface.

10. The sheet according to claim 1, wherein the nanoparticles are substantially uniformly dispersed in the polymer layer.

11. The sheet according to claim 1, wherein the polymer layer includes fibers having an electrostatic charge.

12. The polymer layer further contains a binder that adheres the nanoparticles to the polymer layer, The sheet according to claim 1, wherein the binder comprises a material selected from the group consisting of starch, dextrin, guar gum, PVOH, and synthetic resin.

13. filter media, and A substantially rigid support layer bonded to the filter material. A gas filter comprising a support layer comprising fibers and a plurality of nanoparticles disposed within the support layer, wherein at least one of the nanoparticles has a dimension of less than 1 micron.

14. The gas filter according to claim 13, wherein the nanoparticles are configured to filter contaminants passing through the support layer.

15. The gas filter according to claim 13, wherein the support layer comprises at least one extruded polymer film having one or more openings for the flow of gas or liquid.

16. The gas filter according to claim 15, wherein the polymer film has a first surface and a second surface opposite to the first surface, and at least a portion of the nanoparticles are disposed between the first surface and the second surface.

17. The gas filter according to claim 15, wherein the opening includes hexagonal, square, or rhomboid pores or perforations.

18. The gas filter according to claim 15, wherein the polymer film is selected from the group consisting of polypropylene film, high-density polyethylene film, and polylactic acid film.

19. The gas filter according to claim 13, wherein the support layer includes fibers having an electrostatic charge.

20. The support layer further contains a binder that adheres the nanoparticles to the support layer, The gas filter according to claim 13, wherein the binder comprises a material selected from the group consisting of starch, dextrin, guar gum, PVOH, and synthetic resin.

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