Electrostatic filtration filter

Abstract

A filter media, triboelectrically charged fibers thereof, and methods thereof are described. The filter media may include a first plurality of fibers and / or a second plurality of fibers. The first plurality of fibers may be triboelectrically charged by the second plurality of fibers. The first plurality of fibers and the second plurality of fibers may include polylactic acid fibers and acrylic acid fibers, respectively. The first plurality of fibers and the second plurality of fibers may also include acrylic fibers and polypropylene fibers, respectively. The filter media may include one or more charging additives. A method for preparing the filter media may include contacting the first plurality of fibers with the second plurality of fibers, whereby contacting the first plurality of fibers with the second plurality of fibers triboelectrically charges the first plurality of fibers.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Patent Application No. 63 / 410,729, filed September 28, 2022, and U.S. Provisional Patent Application No. 63 / 410,731, filed September 28, 2022, the contents of which are incorporated by reference herein to the extent not inconsistent with this disclosure.

[0002] FIELD OF THE INVENTION This disclosure relates generally to electrostatic filtration media, and more particularly to gas filters incorporating triboelectrically charged fibers. [Background technology]

[0003] Conventional filters, such as liquid filters and gas filters, often utilize or are fabricated from nonwoven materials (e.g., nonwoven and / or porous materials, fibers, fabrics, sheets, meshes, etc.) that are capable of or configured to separate or remove contaminants and particulates (e.g., dust, pollen, mold, bacteria, etc.) from air. Filtration devices incorporating nonwoven materials are classified into two types: surface filters and depth filters. Surface filters (e.g., membranes, films, etc.) act or function as a barrier to prevent the passage of contaminants. Surface filters typically have submicron pore sizes, a relatively narrow pore size distribution, and relatively high particle capture efficiencies. However, surface filters have a relatively high pressure drop, which reduces airflow through the filter. Surface filters also have a relatively low contaminant (e.g., particle) capture capacity, which significantly reduces the filter's lifespan. As a result, the use of surface filters is generally limited. Depth filters have relatively moderate to high efficiency, relatively low pressure drop, and relatively high contaminant capture capacity. Depth filters typically use one or more types of fibers in the form of a nonwoven sheet, forming tortuous paths between the fibers to retain or capture contaminants. While conventional surface and depth filters are relatively effective at separating contaminants, physical filtration of contaminants is often limited by the pore size and / or tortuous paths formed in the nonwoven sheet. In view of the above, electrostatic or "electret" filter media are often prepared by preparing the fibers of a nonwoven material or sheet from electrostatically charged fibers to further separate contaminants through electrostatic interactions. Electrostatically charged filter media are described in U.S. Pat. Nos. 10,571,137 and 9,802,187, the disclosures of which are incorporated herein by reference to the extent such disclosures are not inconsistent with the present application. Electrostatic or "electret" filter media improves filtration efficiency without increasing the amount of force required to push air through the filter media.

[0004] Conventional methods for electrostatically charging fibers include, but are not limited to, fiber treatment, passing fibers through a corona ("corona discharge"), hydrocharging, electrospinning, and tribocharging. Tribocharging, in particular, involves bringing two materials into contact, such as by rubbing them together, and then separating the materials from each other. While filters utilizing triboelectrically charged filters show promise, recent trends have sought to increase the charge density, or the amount of charge that can be generated and maintained on fibers, without compromising lifetime, collection capacity, pressure drop, or flow rate through the filter. Summary of the Invention

[0005] The following is intended to present only a simplified summary of some aspects of one or more implementations of the subject matter described herein. Further areas of applicability of the subject matter will become apparent from the detailed description provided below. This summary is not an extensive overview and is not intended to identify key or critical elements of the present teachings or to delineate the scope of the subject matter. Rather, it is merely intended to present one or more concepts in a simplified form as a prelude to the more detailed description that follows.

[0006] The foregoing and / or other aspects and benefits described herein may be achieved by providing a filter media comprising a first plurality of fibers, the first plurality of fibers being triboelectrically charged. The first plurality of fibers may comprise polylactic acid (PLA) fibers or acrylic fibers. In one aspect, the filter media can include a second plurality of fibers. The first plurality of fibers can be triboelectrically charged by the second plurality of fibers. In one embodiment, at least a portion of the second plurality of fibers may include a friction-negative material. In one embodiment, at least a portion of the second plurality of fibers can include a tribopositive material. The tribopositive material can include a relatively lower positive charge than the first plurality of fibers. In one embodiment, at least a portion of the second plurality of fibers may comprise polypropylene (PP) fibers. In one embodiment, the polypropylene fibers can include an elongation of about 25% to about 100%, a tensile strength of about 25 cN / tex to about 100 cN / tex, or a combination thereof.

[0007] In one embodiment, the first plurality of fibers can include acrylic fibers. In one embodiment, the first plurality of fibers may include PLA fibers and at least a portion of the second plurality of fibers may include acrylic fibers. In one embodiment, the first plurality of fibers may further comprise polyhydroxyalkanoate (PHBV). In one embodiment, the weight ratio of the first plurality of fibers to the second plurality of fibers can be about 1:1. In one embodiment, the first plurality of fibers and the second plurality of fibers can be nonwoven fibers. In one embodiment, the first plurality of fibers can be present in an amount of at least 10% by weight of the total weight of the filter media. In one embodiment, the PLA fibers may comprise poly-L-lactic acid (PLLA). In one embodiment, the first plurality of fibers, the second plurality of fibers, or a combination thereof may include a spin finish of about 2% or less. In one embodiment, the first plurality of fibers can include continuous fibers. In one embodiment, the first plurality of fibers can include non-continuous fibers. In one embodiment, the first plurality of fibers can have a diameter of from about 0.1 μm to about 200 μm. In one embodiment, the first plurality of fibers can have a linear density of from about 0.5 denier to about 50 denier. In one embodiment, the first plurality of fibers, the second plurality of fibers, or a combination thereof may include one or more nucleating agents. In one aspect, the first plurality of fibers, the second plurality of fibers, or a combination thereof may include one or more charge additives, or a combination thereof, configured to modify the charge of the first plurality of fibers and increase the stability of the charge of the first plurality of fibers.

[0008] In one embodiment, the one or more charging additives may include one or more of triphenylmethane, ammonium compounds, immonium compounds, fluorinated ammonium compounds, fluorinated immonium compounds, biscationic acid amides, polymeric ammonium compounds, diallylammonium compounds, aryl sulfide derivatives, phenol derivatives, phosphonium compounds, fluorinated phosphonium compounds, calix(n)arene, metal complex compounds, benzimidazolone, azine, thiazine, oxazine, or any combination thereof. In one embodiment, the one or more charge additives may include a nucleating agent. In one aspect, the one or more charging additives may comprise a relatively higher electronegative charge than the first plurality of fibers or the second plurality of fibers. In one embodiment, the one or more charging additives can include a relatively higher dielectric constant than the first plurality of fibers or the second plurality of fibers. In one embodiment, the first plurality of fibers may include one or more charge control agents. In one aspect, the filter media may be formed by carding and needling. In one embodiment, the first plurality of fibers and the second plurality of fibers can comprise a spunbond electrostatically charged medium. In one embodiment, the first plurality of fibers and the second plurality of fibers can comprise a meltblown electrostatically charged medium. In one aspect, the first plurality of fibers can be triboelectrically charged by rubbing the first plurality of fibers with one or more machines. The one or more machines can include one or more of a carding machine, a needling machine, or a combination thereof. In one embodiment, the first plurality of fibers can include PLA fibers. The first plurality of fibers can be triboelectrically charged by hydrocharging.

[0009] In one embodiment, the second plurality of fibers can include one or more biodegradable fibers. In one aspect, the one or more biodegradable fibers may comprise one or more of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), polyhydroxybutyrate (PHB), polybutylene succinate (PBS), poly(butylene adipate-co-terephthalate) (PBAT), poly(3-hydroxybutyrate-co-e-hydroxyvalerate) (PHBV), polyhydroxyalkanoate (PHA), polycaprolactone (PCL), or any combination thereof. In one aspect, the one or more biodegradable fibers may be selected from the group consisting of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), polyhydroxybutyrate (PHB), polybutylene succinate (PBS), poly(butylene adipate-co-terephthalate) (PBAT), poly(3-hydroxybutyrate-co-e-hydroxyvalerate) (PHBV), polyhydroxyalkanoates (PHAs), polycaprolactone (PCL), and combinations thereof. In one embodiment, the one or more biodegradable fibers can include PHBH. These and / or other aspects and benefits described herein may be achieved by providing an air filter product including any of the filter media described above or herein.

[0010] The foregoing and / or other aspects and benefits described herein may be achieved by providing a method of manufacturing a filter media. The method may include contacting a first plurality of fibers, which may include polylactic acid (PLA) fibers or acrylic fibers, with a second plurality of fibers. Contacting the first plurality of fibers with the second plurality of fibers may triboelectrically charge the first plurality of fibers. In one embodiment, the second plurality of fibers can include a friction-negative material. In one embodiment, the second plurality of fibers can include a tribopositive material. The tribopositive material can include a relatively lower positive charge than the first plurality of fibers. In one embodiment, the second plurality of fibers can be polypropylene (PP). In one embodiment, the first plurality of fibers can be acrylic fibers. In one embodiment, the first plurality of fibers can include PLA fibers, and the second plurality of fibers can include acrylic fibers. In one embodiment, the first plurality of fibers may further comprise polyhydroxyalkanoate (PHBV). In one embodiment, the weight ratio of the first plurality of fibers to the second plurality of fibers can be about 1:1. In one embodiment, the first plurality of fibers and the second plurality of fibers can be nonwoven fibers. In one embodiment, the filter media may include PLA fibers in an amount of at least 50% by weight. In one embodiment, the PLA fibers may comprise poly-L-lactic acid (PLLA).

[0011] In one embodiment, the method can include carding the first plurality of fibers and the second plurality of fibers. In one embodiment, the method can include spunbonding a first plurality of fibers and a second plurality of fibers. In one embodiment, the method can include meltblowing a first plurality of fibers and a second plurality of fibers. In one embodiment, the method can include contacting one or more nucleating agents with the first plurality of fibers, the second plurality of fibers, or a combination thereof. In one embodiment, the method can include contacting one or more charging additives with a first plurality of fibers, a second plurality of fibers, or a combination thereof. In one embodiment, the method can include contacting one or more charge control agents with the first plurality of fibers, the second plurality of fibers, or a combination thereof. These and / or other aspects and benefits described herein may be achieved by providing an air filter product prepared according to any of the methods described above.

[0012] Further areas of applicability of the subject matter will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating some exemplary aspects of the subject matter, are intended for purposes of illustration only and are not intended to limit the scope thereof. The description herein of desirable objects that may be met by various embodiments herein is not meant to imply or suggest that any or all of these objects may be present as essential features, individually or collectively, in either the most general embodiment herein or its more specific embodiments. DETAILED DESCRIPTION OF THE INVENTION

[0013] This specification and the accompanying drawings illustrate exemplary embodiments and should not be construed as limiting, with the claims defining the scope of this specification, including equivalents. Various mechanical, compositional, structural, and operational changes may be made without departing from the scope of this specification and claims, including equivalents. In some instances, well-known structures and techniques have not been shown or described in detail to avoid obscuring the description. Like numbers in two or more drawings represent the same or similar elements. Furthermore, elements and their related aspects described in detail with reference to one embodiment may, whenever practical, be included in other embodiments in which they are not specifically shown or described. For example, if an element is described in detail with reference to one embodiment but not with reference to a second embodiment, the element may still be claimed to be included in the second embodiment. Furthermore, the description herein is for illustrative purposes only and does not necessarily reflect the actual shape, size, or dimensions of the systems or illustrated components.

[0014] 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 the use is expressly and unambiguously limited to one referent. As used herein, the term "include" and its grammatical variations are intended to be open-ended, and the listing 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, quantitative values ​​are approximate, whether or not indicated by words such as "about" or "approximately." The materials, methods, and examples described herein are illustrative only and are not intended to be limiting.

[0015] Ranges are used throughout this disclosure as a shorthand for describing any and all values ​​within a range. It should be understood that descriptions in range format are merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the embodiments or implementations disclosed herein. Accordingly, disclosed ranges should be construed as specifically disclosing all possible subranges and individual numerical values ​​within that range. As such, any value within the range may be selected as a range terminus. For example, a description of a range of 1 to 5 should be considered to specifically disclose subranges such as 1.5 to 3, 1 to 4.5, 2 to 5, 3.1 to 5, etc., as well as individual numerical values ​​within that range, e.g., 1, 2, 3, 3.2, 4, 5, etc. This applies regardless of the breadth of the range.

[0016] Furthermore, all numerical values ​​are "about" or "approximate" indicators, taking into account experimental error and variations that one of ordinary skill in the art would expect. All numerical values ​​and ranges disclosed herein should be understood to be approximate values ​​and ranges, regardless of whether "about" is used in conjunction with them. As used herein, the term "about," when used in conjunction with a number, should also be understood to refer to a value that may be ±0.01% (inclusive), ±0.1% (inclusive), ±0.5% (inclusive), ±1% (inclusive), ±2% (inclusive) of that number, ±3% (inclusive) of that number, ±5% (inclusive) of that number, ±10% (inclusive) of that number, or ±15% (inclusive) of that number. It should also be understood that when a numerical range is disclosed herein, any number falling within that range is specifically disclosed. As used herein, "free" or "substantially free" of a material can refer to the material being present in a composition, component, or phase in an amount less than 10.0 wt.%, less than 5.0 wt.%, less than 3.0 wt.%, less than 1.0 wt.%, less than 0.1 wt.%, less than 0.05 wt.%, less than 0.01 wt.%, less than 0.005 wt.%, or less than 0.0001 wt.% of the total weight of the composition, component, or phase. All references cited herein are incorporated by reference in their entirety. In the event of a conflict between a definition in this disclosure and a definition in a reference, the present disclosure controls.

[0017] The inventors have surprisingly and unexpectedly discovered that polylactic acid (PLA) and / or fibers thereof exhibit and / or possess relatively high tribopositive properties. Accordingly, the inventors have surprisingly and unexpectedly discovered that rubbing, handling, or otherwise contacting the PLA fibers with another fiber or material (e.g., a tribonegative fiber or material) creates or generates significant polarization and / or charge on the PLA fibers. The generation of charge creates and / or enhances local electric field gradients in or within the filter media and / or its PLA fibers, thereby increasing particle removal by electrostatic forces and, consequently, improving the filtration efficiency of the filter media. The inventors have also surprisingly and unexpectedly discovered that the charge on the PLA fibers is retained even after several days. The inventors have further surprisingly and unexpectedly discovered that it is possible to prepare a fully or substantially biodegradable filter media from a fiber blend of PLA fibers and one or more biodegradable fibers, such as PHBV. The inventors have also surprisingly and unexpectedly discovered that a fiber blend of PLA fibers and one or more biodegradable fibers exhibits improved filtration efficiency compared to conventional, non-biodegradable filter media.

[0018] Disclosed are filter media, filters, and / or fibers thereof that capture particles through electrostatic forces. Exemplary filters may be or include, but are not limited to, gas filters, liquid filters, face masks, CPAP filters, vacuum bags, cabin air filters, HVAC furnace filters, gas turbine and compressor intake filters, panel filters, residential air filters, commercial air filters, etc. Systems and methods for manufacturing the filter media, filters, and / or fibers thereof are also disclosed.

[0019] The filter media may include a plurality of fibers. The fibers may be electret fibers. As used herein, the term or phrase "electret fibers" may refer to fibers comprising a dielectric material having a quasi-permanent state of electric polarization. The plurality of fibers of the filter media may be formed into a substrate, such as a sheet, layer, film, perforated film, mesh, netting, etc., or any combination thereof. The substrate may include one or more nonwoven materials. For example, the substrate may include fibers or threads that may be interleaved, interlocked, glued, or otherwise bonded to one another. Exemplary nonwoven materials may be or include, but are not limited to, fibers, layers, sheets, or fabrics that are adhered or bonded to one another using mechanical, thermal, and / or chemical means or methods. The substrate or its nonwoven material may be meltblown, spunbonded, spunlaced, heat-sealed, adhesive-carded, airlaid, wet-laid, co-formed, needlepunched, stitched, hydroentangled, etc., or any combination thereof. The substrate may be flat or substantially flat. The substrate may be or may include a porous sheet prepared from discrete fibers, fused plastic or plastic film, or a combination thereof.

[0020] The fibers of the filter media may be bonded to one another by mechanical (e.g., entanglement), thermal, and / or chemical means. For example, the fibers may be bonded to one another by thermal bonding (e.g., heating). In another example, the fibers may be bonded to one another by one or more chemical bonds. In at least one embodiment, the filter media or its fibers may include one or more binders, such as adhesives, capable of or configured to bond the fibers to one another.

[0021] The substrate and / or its fibers may be or include a "high loft" nonwoven material. For example, the substrate and / or its fibers may be or include a high loft nonwoven material, including spunbond nonwoven fibers and / or air-through-bonded, carded nonwoven fibers. As used herein, the term or phrase "high loft" may refer to a nonwoven material or fiber in which the volume of voids is relatively greater than the volume of the material or solids. It should be understood that in air-through-bonded, carded nonwoven fibers, the loftiness or loft of the substrate may be controlled by various means known to those skilled in the art. For example, the loft of the material and / or fibers may be increased by reducing the compressive force applied to the filter media or its fibers during one or more processes (e.g., bonding).

[0022] The substrate and / or its fibers may be or include knitted and / or woven fabrics. Knitted fabrics may include any knit pattern suitable for the desired application, particularly filter applications. Knitted fabrics suitable for filter applications may be or include, but are not limited to, weft knits, warp knits, knit mesh panels, compressed knit meshes, etc., or any combination thereof. Woven fabrics suitable for filter applications may be or include woven filter media such as monofilament woven fabrics, multifilament woven fabrics, nylon mesh, polyester mesh, polypropylene mesh, etc. Woven fabrics may 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, fluidized bed dryer bags, rotary drum filters, filter belts, leaf filters, roll media, etc.

[0023] The filter media may include a plurality of fibers that are triboelectrically charged. The triboelectric effect (also known as friction, tribocharging, triboelectricity, or tribocharging) should be understood to describe the transfer of charge between two objects that rub, scrape, or otherwise contact each other. It should also be understood that the extent of the triboelectric effect (e.g., the polarity and / or strength of the resulting charge) may depend, at least in part, on the respective materials and / or their properties, surface morphology (e.g., roughness, smoothness, etc.), temperature, strain (e.g., elastic strain), etc. The triboelectric series is a function of the charge density (nC / cm) of each of the materials. 2 It should further be understood that the present invention may provide a list of materials ordered according to one or more respective characteristics, such as relative distance or position of two materials on the triboelectric series, with a corresponding increase in charge transfer between the two materials.

[0024] The filter media or its fibers can be or include polylactic acid (PLA), a non-PLA polymer, or a combination thereof. For example, the fibers of the filter media can be or include, but are not limited to, polylactic acid (PLA) fibers, one or more non-PLA fibers, or a combination thereof. The PLA fibers can be present in an amount of about 10% to 100% by weight of the total weight of the filter media and / or its fibers. For example, the PLA fibers can be present in an amount of about 10%, about 20%, about 30%, about 40%, or about 50% to about 60%, about 70%, about 80%, about 90%, about 95%, or more by weight of the total weight of the filter media or its fibers. In at least one embodiment, at least about 10% of the fibers can be PLA fibers. Exemplary PLA fibers may be or include, but are not limited to, racemic polylactic acid, such as poly-L-lactide (PLLA), poly-D-lactide (PDLA), poly-DL-lactic acid (PDLLA), or combinations thereof. The PLA polymer or copolymer may be prepared from lactic acid monomers. The lactic acid monomer may be or include one or more of an isomer of lactic acid, such as L-lactic acid, D-lactic acid, or mixtures thereof; an anhydride of any isomer of lactic acid, such as L-lactide, D-lactide, meso-lactide, or mixtures thereof; cyclic dimers of such lactic acid and / or lactide; or any combination thereof. In an exemplary embodiment, the PLA polymer may be a polymer prepared from both L-lactic acid and D-lactic acid monomers.

[0025] As used herein, the term or phrase "PLA-based surface" may refer to a surface of a fiber, fabric, film, etc., made or composed of at least 50% PLA-based resin. It should be understood that the remainder of the PLA-based surface may be or may consist of other resins, such as polyhydroxybutyrate (PHB), other biodegradable materials, nucleating agents, antioxidants, charge enhancers, or any combination thereof. In at least one embodiment, the fiber is entirely or substantially PLA resin. For example, the fiber may be about 98% or more PLA resin, about 99% or more PLA resin, or 100% PLA resin. In at least one embodiment, at least a portion of the fiber has a PLA-based surface. For example, one or more of the fibers has a surface comprising at least 50% PLA-based resin.

[0026] The filter media may include a first plurality of fibers and a second plurality of fibers. The first plurality of fibers may be or include PLA fibers, one or more non-PLA fibers, or a combination thereof. The second plurality of fibers may be or include PLA fibers, one or more non-PLA fibers, or a combination thereof. The first and second plurality of fibers may be formed into a substrate, such as a sheet, layer, film, perforated film, mesh, netting, or the like. The substrate may include one or more nonwoven materials. The nonwoven material may have a structure that may interleave individual fibers or threads. Exemplary nonwoven materials may be or include, but are not limited to, fibers, layers, or weaves that may be meltblown, spunbond, adhesive carded, airlaid, wet-laid, co-formed nonwoven structures, hydroentangled, or the like, or any combination thereof. The substrate may also be or include, but is not limited to, spun yarn, felt, knitted fabric, woven fabric, or the like, or any combination thereof.

[0027] The first and second pluralities of fibers discussed herein may be included as part of a filter device that separates, traps, captures, or otherwise absorbs contaminants. Exemplary filter devices may be or include, but are not limited to, liquid filters, residential and commercial air filtration gas filters, surgical masks or other face coverings, etc. Filter devices may be mechanical filters, absorption filters, sequestration filters, ion exchange filters, reverse osmosis filters, surface filters, depth filters, etc., and may be designed to remove many different types of contaminants from air, water, etc.

[0028] In exemplary embodiments, the first and second pluralities of fibers may be incorporated into an air filter that removes or otherwise separates particles and / or contaminants from air, such as a Minimum Efficiency Reporting Value (MERV) filter, a UV light filter, a washable filter, a media filter, a spun glass filter, a pleated air filter, a non-pleated air filter, an activated carbon filter, a pocket filter, a V-bank compact filter, a filter sheet, a flat cell filter, a filter cartridge, etc. The first and second fibers may comprise a filter media for the air filter, may be supported by a support layer, a scrim layer, or may be included in another layer or material.

[0029] In at least one embodiment, the first plurality of fibers (i.e., the "first fibers") can comprise or consist of PLA and / or its derivatives. In another embodiment, the first plurality of fibers (i.e., the "first fibers") can comprise a mixture or combination of PLA and one or more additional materials or fibers (e.g., non-PLA materials or fibers). In yet another embodiment, the first plurality of fibers can comprise or consist of one or more non-PLA materials or fibers (e.g., polypropylene fibers). The additional materials or fibers can be or consist of, but are not limited to, one or more melt-spun non-polylactic acid fibers, non-melt-spun non-polylactic acid fibers in the form of continuous fibers, staple fibers, bicomponent fibers, acrylic fibers, etc., or any combination thereof. In at least one embodiment, the PLA fibers or compositions thereof can comprise one or more of an amine stabilizer, compatibilizer, lubricant, antibacterial agent, antiviral agent, dispersant, antioxidant, plasticizer, coupling agent, nucleating agent, charge-enhancing additive, etc., or any combination thereof. The PLA may be present in the first plurality of fibers in an amount of at least about 30% by weight, at least about 40% by weight, at least 50% by weight, at least 60% by weight, at least 80% by weight, at least 90% by weight, or more, of the total weight of the first plurality of fibers.

[0030] In at least one embodiment, the first fibers may comprise a mixture or combination of PLA fibers and polyhydroxyalkanoate (PHBV) fibers, and the PLA may be present in the first plurality of fibers in an amount of at least about 50% by weight of the first fibers. The first fibers comprising a mixture or combination of PLA fibers and PHBV fibers may have a charge density of about 0.5 nC / cm. 2 It could be more than that. In at least one embodiment, the first plurality of fibers comprises polypropylene (PP) fibers and the second plurality of fibers comprises acrylic fibers. Thus, the filter media or fibers thereof comprises a first plurality of fibers comprising PP fibers and a second plurality of fibers comprising acrylic fibers, and the filter media or fibers thereof further comprises one or more charging additives as further discussed herein.

[0031] In at least one embodiment, the first and / or second fibers have a tenacity or tensile strength of about 25 cN / tex to about 100 cN / tex. For example, the first and / or second fibers can have a tensile strength of about 25 cN / tex, about 35 cN / tex, or about 45 cN / tex to about 50 cN / tex, about 70 cN / tex, about 80 cN / tex, or about 100 cN / tex. In other examples, the first and / or second fibers can have a tensile strength of about 25 cN / tex to about 100 cN / tex, about 35 cN / tex to about 60 cN / tex, or about 45 cN / tex. In at least one embodiment, the first plurality of fibers comprises PP fibers, and the first plurality of fibers or the PP fibers have a tensile strength of about 25 cN / tex to about 100 cN / tex, about 30 cN / tex to about 60 cN / tex, or about 45 cN / tex. As used herein, the term or phrase "tensile strength" can refer to mass stress at break.

[0032] In at least one embodiment, the first and / or second plurality of fibers have an elongation of about 10% to about 150%. For example, the first and / or second fibers can have an elongation of about 10%, about 20%, about 30%, or about 35% to about 40%, about 50%, about 70%, about 80%, or about 150%. In other examples, the first and / or second fibers can have an elongation of about 10% to about 100%, about 20% to about 70%, about 30% to about 40%, or about 35%. In at least one embodiment, the first and / or second fibers comprise PP fibers, and the first and / or second fibers have an elongation of about 10% to about 150%, about 20% to about 100%, about 30% to about 40%, or about 35%. As used herein, the term or expression "elongation" may refer to the amount of stretch or elongation that a fiber or fibre can tolerate before breaking.

[0033] In exemplary embodiments, the first and / or second plurality of fibers have a tensile strength of about 25 cN / tex to about 100 cN / tex, about 30 cN / tex to about 60 cN / tex, or about 45 cN / tex, and an elongation of about 25% to about 100%, about 30% to about 50%, or about 35%. The inventors have surprisingly and unexpectedly discovered that fibers having a tensile strength of about 30 cN / tex to about 60 cN / tex, or about 45 cN / tex, and an elongation of about 30% to about 40%, or about 35%, exhibit improved effectiveness in retaining and / or generating triboelectric charges. Without being bound by theory, it is believed that a relatively high tensile strength and / or a relatively low elongation increases the stretching of the fibers relative to normal. The increased stretching of the fibers is believed to affect crystallization. In particular, a relative increase in fiber drawing is believed to increase the amount or rate of crystallization, resulting in more ordered or oriented crystals, and the orientation of the crystals relatively improves the fiber's ability to generate and / or retain triboelectric charges. In at least one embodiment, the first fiber and / or the second fiber may contain 2% or less of a spin finish, and preferably may be free or substantially free of a spin finish (e.g., bare fibers). As used herein, the term or phrase "spin finish" may refer to a liquid, solid, or emulsion composition applied to the surface of a fiber to improve processing of the fiber, such as in short-staple or long-staple spinning.

[0034] The first plurality of fibers, which may include PLA fibers, may be continuous or discontinuous. Exemplary discontinuous fibers may be or include, but are not limited to, staple fibers. The first plurality of fibers (e.g., staple and / or continuous fibers) may have a length of about 1 mm to about 200 mm, about 5 mm to about 150 mm, or about 30 mm to about 70 mm. The first plurality of fibers may have a diameter of about 0.1 μm to about 200 μm, or about 5 μm to about 50 μm. The first plurality of fibers may have a linear density of about 5.6×10 -2 It can be from about 0.5 denier to about 50 denier (Tex to about 5.6 Tex).

[0035] In at least one embodiment, the second plurality of fibers may be or may include, but is not limited to, a friction-negative or friction-positive material that comprises or has a relatively low charge density compared to the first plurality of fibers (e.g., PLA fibers). As noted above, the inventors have surprisingly and unexpectedly discovered that PLA and its fibers are relatively high friction-positive materials. For example, PLA has a charge density of about 0.5-1.0 nC / cm. 2 Thus, PLA is a relatively improved material for transferring charge with tribonegative materials, and when a first plurality of fibers, which may include PLA fibers, is rubbed or contacted with a second plurality of fibers, which may include fibers or materials sufficiently distant from the PLA in the triboelectric series, significant polarization and charge is generated in the PLA fibers.

[0036] The non-PLA fibers and / or the second plurality of fibers (ie, the "second fibers") may be or may include man-made fibers, natural fibers, or a combination thereof. Exemplary materials and / or fibers for the non-PLA fibers and / or the second plurality of fibers include polypropylene, polyester (PET), polyethylene naphthalate (PEN) polyester, polycyclohexylene dimethylene terephthalate (PCT) polyester, polypropylene (PP), polybutylene terephthalate (PBT) polyester, copolyamide, polyethylene, high density polyethylene (HDPE), linear low density polyethylene (LLDPE), cross-linked polyethylene, polycarbonate, polyacrylate, polyacrylonitrile (PAN), polyfumaronitrile, polymers prepared from fumaronitrile, polystyrene (PS), styrene maleic anhydride, polymethylpentene, cycloolefin copolymers, fluorinated polymers, polytetrafluoroethylene, perfluorinated ethylene and hexafluoropropylene, or copolymers with PVDF, such as P(VDF-TrFE) or poly(vinylidene fluoride-co-trifluoroethylene) copolymers containing 80 mol% VDF. The fiber may be or may include, but is not limited to, a polymer or terpolymer such as P(VDF-TrFE-CFE), propylene, polyimide (PI), Kevlar, polyether ketone, cellulose esters, cotton, ramie, chitosan, wool, cupra, lyocell, nylon, polyamide, silk, polyether-polyurea copolymer, Lycra, elastane, polymethacrylic acid polymer, poly(methyl methacrylate), polyoxymethylene, polysulfonate, acrylic, modacrylic, styrenated acrylic, pre-oxidized acrylic, fluorinated acrylic, vinyl acetate, vinyl acrylic, ethylene vinyl acetate, styrene-butadiene, ethylene / vinyl chloride, vinyl acetate copolymer, latex, polyester copolymer, carboxylated styrene acrylic or vinyl acetate, epoxy, acrylic multipolymer, phenolic, polyurethane, cellulose, polytetrafluoroethylene (PTFE), styrene, or any combination thereof. It should be understood that other conventional fiber materials are also contemplated.

[0037] The filter media and / or its fibers may be biodegradable or substantially biodegradable. As used herein, the term "biodegradable" may refer to materials or substances that can be decomposed by microorganisms. The filter media and / or its fibers may also be biobased or substantially biobased. As used herein, the term or phrase "biobased material" may refer to materials or substances made or prepared from substances derived from living (or once-living) organisms. For example, biobased materials may refer to materials and substances derived from plant and animal biomass. Exemplary biobased materials may be or include, but are not limited to, materials derived from and / or prepared from starch, sugars, lipids, or any combination thereof extracted from corn, sugarcane, sugar beets, vegetable oils, etc.

[0038] In at least one embodiment, the non-PLA fibers and / or the second plurality of fibers can be or include, but are not limited to, one or more bio-based and / or biodegradable fibers. For example, the non-PLA fibers and / or a portion of the second plurality of fibers can be or include, one or more bio-based and / or biodegradable fibers. In another example, the non-PLA fibers and / or the second plurality of fibers can be substantially or entirely bio-based and / or biodegradable fibers. Exemplary bio-based and / or biodegradable fibers may be or may include, but are not limited to, poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), polyhydroxybutyrate (PHB), polybutylene succinate (PBS), poly(butylene adipate-co-terephthalate) (PBAT), poly(3-hydroxybutyrate-co-e-hydroxyvalerate) (PHBV), polyhydroxyalkanoate (PHA), polycaprolactone (PCL), polycaprolactone butylene succinate (PCL-BS), polybutylene succinate adipate (PBSA), polyethylene terephthalate succinate (PETS), cellulose acetate (CA), one or more petroleum-based biodegradable polymers, derivatives thereof, copolymers thereof, or any combination thereof.

[0039] In an exemplary embodiment, a filter medium may include a first plurality of fibers including biobased and biodegradable PLA fibers, and a second plurality of fibers may include one or more additional biobased and / or biodegradable fibers. For example, the filter medium may include a mixture of PLA fibers and one or more additional biobased and / or biodegradable fibers. In another example, the filter medium may include a mixture of PLA fibers and additional biobased and / or biodegradable fibers including one or more of PHBH, PHB, PBS, PBAT, PHBV, and PHA, or any combination thereof. In yet another example, the filter medium may include a mixture of PLA fibers and one or more additional biobased and / or biodegradable fibers selected from the group consisting of PHBH, PHB, PBS, PBAT, PHBV, PHA, and combinations thereof. In another example, the filter medium may include a mixture of PLA fibers and PHBH.

[0040] The non-PLA fibers and / or the second plurality of fibers or second fibers can have a thickness or diameter of about 1 μm to about 10,000 μm, about 1 μm to about 1,000 μm, or about 10 μm to about 100 μm. For example, the second fibers can have a diameter of about 0.1 μm to about 200 μm, or about 5 μm to about 50 μm.

[0041] In exemplary embodiments, the first plurality of fibers may be or include PLA and / or PLA fibers, and the second plurality of fibers may be or include polypropylene fibers, acrylic fibers, or a combination thereof. It should be understood that PLA has several properties or characteristics similar to PP, PE, and PS, including, but not limited to, dielectric constant, loss tangent, and surface resistivity. However, PLA transfers relatively more charge when rubbed or contacted with PP fibers than acrylic fibers. Similarly, PLA transfers relatively more charge when rubbed or contacted with acrylic fibers than PP fibers. Therefore, utilizing a first plurality of fibers including PLA or PLA fibers in conjunction with one or more sufficiently tribo-negative materials and / or a second plurality of fibers including tribo-negative fibers improves the effectiveness of the filter media without compromising other properties / qualifications of the filter media, such as lifespan, collection capacity (e.g., dust holding capacity), pressure drop, airflow through the filter media, etc., or any combination thereof. It should also be understood that PLA has a relatively high electrical resistance and a relatively low coefficient of friction compared to polypropylene (PP). PLA and its fibers are also hydrophobic. PLA is also biodegradable. PLA can be made or prepared using existing manufacturing equipment, such as that used for petrochemical plastics. Therefore, producing PLA and / or its fibers can be relatively cost-effective compared to other polymers (e.g., PP, PS, PE, etc.).

[0042] The first and second pluralities of fibers may have the same linear mass density, measured in denier or den (D). The first and second pluralities of fibers may have different linear mass densities. In at least one embodiment, the second pluralities of fibers have a linear mass density of about 5.6×10 -2 Tex to approximately 5.6 Tex (approximately 0.5 denier or den (D) to approximately 50D), approximately 1.1 x 10 -2 It can be Tex to about 1.1 Tex (about 1D to about 10D). The first fibers and second fibers can be present in the filter media in a weight ratio of about 10:1 (e.g., about 10 to about 1), about 5:1, about 3:1, about 2:1, about 1:1, about 1:2, about 1:3, about 1:5 to about 1:10. In an exemplary embodiment, the weight ratio of the first fibers to the second fibers is about 1:1. The first fibers and second fibers can be present in the filter media in a total surface area ratio of about 10:1, about 5:1, about 3:1, about 2:1, about 1:1, about 1:2, about 1:3, about 1:5, or about 1:10. In an exemplary embodiment, the total surface area ratio of the first fibers to the second fibers is about 1:1.

[0043] PLA has several important properties similar to those of PP, such as dielectric constant, loss tangent, and surface resistivity. However, when PLA is rubbed against PP, it transfers more charge than, for example, acrylic fibers rubbed against PP. Similarly, when PLA is rubbed against acrylic fibers, it transfers more charge than, for example, acrylic fibers rubbed against PP. That is, PLA has a higher triboelectric charge density than PP and acrylic fibers. Therefore, PLA improves the overall effectiveness of triboelectrically charged filters without compromising other functions, such as lifespan, collection capacity (e.g., dust holding capacity), pressure drop, or airflow through the filter media. As used herein, the term or phrase "pressure drop" of a filter, media, or material thereof may refer to the drop in pressure from the upstream side to the downstream side of the filter, media, or material thereof.

[0044] The PLA fibers and / or the second fibers can be continuous or discontinuous (e.g., staple fibers). In some embodiments, the PLA fibers can have a diameter of about 0.1 μm to about 200 μm, or about 5 μm to about 50 μm. The PLA fibers can have a linear density of about 0.5 denier to about 50 denier. The PLA fiber and / or the second fiber may include one or more nucleating agents that promote the formation of polymer crystals in the fiber. Suitable nucleating agents may be or may include, but are not limited to, inorganic additives, organic additives, polymers, etc., or any combination thereof.

[0045] The filter media and / or one or more fibers of the filter media may include one or more charging additives or charge control agents (CCAs). For example, the filter media, its first plurality of fibers, and / or its second plurality of fibers may include one or more charging additives or charge control agents. The one or more charging additives may be capable of, or may be configured to, modify (e.g., increase or decrease) the triboelectric charge of the filter media and / or its one or more fibers. The one or more charging additives may also be capable of, or may be configured to increase, the stability and / or duration of the triboelectric charge of the filter media and / or its one or more fibers. The one or more charging additives may be capable of, or may be configured to modify, improve the stability, and / or increase the duration of the triboelectric charge without compromising other characteristics or properties of the filter media, including the lifetime, collection capacity, and / or pressure drop. In at least one embodiment, the first plurality of fibers, which may include PLA fibers, and / or the second plurality of fibers may include one or more charging additives or charge control agents (CCAs). In another example, the first plurality of fibers, which may include non-PLA fibers, and / or the second plurality of fibers, may include one or more charging additives or charge control agents (CCAs). In yet another example, the first plurality of fibers, which may include a combination of PLA and non-PLA fibers, and / or the second plurality of fibers, may include one or more charging additives or charge control agents (CCAs). The charging additive may be present in one or more fibers of the filter media in an amount of about 0.02% to 33% by weight of the total weight of the filter media or one or more fibers thereof.

[0046] The charge additive may be or may include, but is not limited to, triphenylmethane, ammonium compounds, immonium compounds, fluorinated ammonium compounds, fluorinated immonium compounds, biscationic acid amides, polymeric ammonium compounds, diallylammonium compounds, aryl sulfide derivatives, phenol derivatives, phosphonium compounds, fluorinated phosphonium compounds, calix(n)arene, metal complex compounds, benzimidazolone, azine, thiazine, oxazine, etc., or any combination thereof. Exemplary charge additives may include, but are not limited to, one or more nucleating agents having a surface charge opposite to the partial charge of the polymer, such as magnesium stearate (MgSt), phosphonium salts (e.g., triphenylphosphine, tributylphosphine, trimethylphosphine, dimethylphenylphosphine, methyldiphenylphosphine, tris(2-ethylhexyl)phosphine, tetrabutyl-phosphonium hexafluorophosphate, tetrabutyl-phosphonium hydrogen sulfate, and tetrabutylammonium-phenylphosphonate), pyridinium salts (e.g., tritylpyridinium tetrafluoroborate), pyrrolidinium salts (e.g., 1-butyl-1-methylpyrrolidinium bromide), sulfonium (e.g., triphenylsulfonium tetrafluoroborate), sulfonates (e.g., sodium octyl sulfonate), phosphonates (e.g., phosphonic acids, esters, and salts; phosphinic acids, esters, and salts; phosphonamides; phosphinamides), phosphonates (e.g., tetrabutylammonium-phenylphosphonate), and the like, or any combination thereof. Exemplary charging additives may include, but are not limited to, one or more high dielectric constant articles, such as CaCuTiO, BaTiO, and TiO; articles that are more electronegative than PP, such as PTFE and silicon; articles with ultra-low dielectric loss tangent properties, such as silicon nitride, alumina, ceramics, high density polyethylene, and the like; or any combination thereof.Exemplary charge additives include metal salts of aluminum or magnesium, lead zirconate titanate, potassium niobate, lithium niobate, lithium tantalate, sodium tungstate, unsaturated carboxylic acids or derivatives thereof, unsaturated epoxy or silane monomers, maleic anhydride, monoazo metal compounds, alkyl acrylate monomers, alkyl methacrylate monomers, polytetrafluoroethylene, alkylenes, arylenes, arylene dialkylenes, alkylenediarylenes, oxydialkylenes or oxydiarylenes, polyacrylic and polymethacrylic acid compounds, organic titanates, quaternary phosphonium trihalozinc salts, organic silicone complex compounds, dicarboxylic acid compounds, cyclic or acyclic polyethers and cyclodextrins, and amine derivatives. complex salt compounds of di-tert-butylsalicylic acid, potassium tetraphenylborate, potassium bisborate, sulfonamides and metal salts, cycloalkyl and dimethyl silicone compounds, azo dyes, phthalate esters, quaternary ammonium salts, carbazole, diammonium and triammonium, hydrophobic silica and iron oxide, phenyl, substituted phenyl, naphthyl, substituted naphthyl, thienyl, alkenyl and alkyl ammonium complex salt compounds, dioctyl sodium sulfosuccinate and sodium benzoate, zinc complex compounds, alumina particles treated with silane coupling from the group consisting of mica, monoalkyl and dialkyl tin oxides, and urethane compounds, metal complexes of salicylic acid compounds, oxazolidinone, piperazine or perfluoroalkane, Lecigran MT (Lecigran The additives may be or may include, but are not limited to, methyl methacrylate (MT), nigrosine, fumed silica, carbon black, paratrifluoromethylbenzoic acid and orthofluorobenzoic acid, poly(styrene-co-vinylpyridinium toluenesulfonate), methyl or butyltriphenyl heteroaromatic amines, triphenylamine dyes and azine dyes, alkyldimethylbenzyl ammonium salts, and the like, or any combination thereof.In an exemplary embodiment, the charging additive may include an electret additive under the trade name FWM02™, commercially available from Keimei Plastifizierung Technik (Yantai) Co., Ltd., Shandong Province, China. FWM02™ increases the charge density on the fiber surface, thereby extending its charge retention period. FWM02™ may increase the melt strength of the fiber compared to fibers without the charging additive. The increased melt strength of fibers containing the charging additive FWM02™ may reduce the relative amount of defects (e.g., melt shot, broken fibers, etc.), thereby improving the fiber's ability to retain and / or generate a charge. FWM02™ has a bulk density of about 0.50 g / cm. 3 ~about 0.55g / cm 3, a particle weight of about 60 ea / g to about 65 ea / g, a filter pressure value (FPV) of 0.5 bar / g or less, a pressure rise value (PRV) of about 0.5 Pa / g or less, and / or a melt flow index of about 650 to 655 g / 10 min. In another embodiment, the charging additive can include an electret additive under the trade name CON-CHARGE01585, which is commercially available from CONSTAB Polyolefin Additives GmbH of Luthen, Germany. Exemplary charge control agents include one or more metal salts of aluminum or magnesium, lead zirconate titanate, potassium niobate, lithium niobate, lithium tantalate, sodium tungstate, unsaturated carboxylic acids or derivatives thereof, unsaturated epoxy or silane monomers, maleic anhydride, monoazo metal compounds, alkyl acrylate monomers, alkyl methacrylate monomers, polytetrafluoroethylene, alkylene, alkylene-based CCA, arylene, arylene-based CCA, arylene dialkylene, alkylenediarylene, silicon nitride, PTFE, tourmaline, acid anhydride, maleic anhydride, alkylene glycol, polyethylene glycol, PDLA, Polyvel's CTL-01 and CN-L01, talc (Imerys' Jetfine or Liaoniing Jinghua New Materials' SK-9900), N'1,N'6-dibenzoyladipohydrazide (Shanxi Chemical The surfactant may be or may include, but is not limited to, aromatic sulfonic acid derivatives (TMC-306 from Research), aromatic sulfonic acid derivatives (LAK-301 from Takemoto Oil Co., Ltd.), sorbitol (SORB from Euro OTC Pharma GmbH), polyethylene glycol, NA S516 from Sukano, NC PL830 from KRITILEN, MAXITHEN® BIOL from Gabriel-Chemie, dioctyl adipate, ethylene bisstearamide, zinc phenylphosphonate (PPZn), ECOPROMOTE® from Nissan Chemical Industries, Ltd., etc., or any combination thereof.One or more charging additives may be or may include, but are not limited to, electret additives under the trade name MagIQ™, available from Avient, Avon Lake, Ohio, USA. Other CCAs that can be used may be described in U.S. Patent No. 10,571,137, the contents of which are incorporated herein by reference to the extent that they do not conflict with the present disclosure. The charging additive may include any combination of the foregoing.

[0047] The filter media, its first plurality of fibers, and / or its second plurality of fibers may include a charge control agent in an amount of about 0.02% to about 33% by weight of the total weight of the filter media, its first plurality of fibers, and / or its second plurality of fibers. For example, the filter media, its first plurality of fibers, and / or its second plurality of fibers may include a charge control agent in an amount of about 0.2%, about 1%, about 5%, about 10%, or about 15% to about 20%, about 25%, about 30%, or about 33% by weight of the total weight of the filter media, its first plurality of fibers, and / or its second plurality of fibers.

[0048] The first plurality of fibers and / or the second plurality of fibers may comprise one or more waxes. Exemplary waxes may be or may include, but are not limited to, one or more of polyolefins, polyethylene, functionalized waxes such as amines, amides, fluorinated waxes, mixed fluorinated and amide waxes such as esters, quaternary amines, carboxylic acid or acrylic polymer emulsions, chlorinated polyethylene, natural or synthetic ester waxes, carnauba wax, paraffins, etc., or any combination thereof. The one or more waxes may be fractionated or distilled to obtain specific fractions meeting specific viscosity and / or temperature criteria.

[0049] The filter media, its first plurality of fibers, its second plurality of fibers, and / or its substrate may include one or more additives. Exemplary additives may be or include, but are not limited to, one or more antibacterial agents or compositions, one or more antiviral agents or compositions, or combinations thereof. Exemplary antibacterial and antiviral agents or compositions may be or include, but are not limited to, silver, zinc, copper, organosilicon, tributyltin, compounds thereof, complexes thereof, one or more organic compounds, such as organic compounds containing one or more of chlorine, bromine, and fluorine, or any combination thereof.

[0050] The PLA fibers can be poly-L-lactic acid (PLLA), poly-D-lactide (PLDA), or a combination thereof. In at least one embodiment, the second fibers can be or include a friction-negative material. In at least one embodiment, the second fibers can include polypropylene (PP) and / or acrylic fibers. In at least one embodiment, the weight ratio of the first fibers to the second fibers is about 1: 1. In at least one embodiment, the first fibers and / or the second fibers contain no more than about 2% spin finish, and preferably are free or substantially free of spin finish. Contemplated fibers may have one or more cross-sectional shapes, including, without limitation, round, kidney bean, dogbone, trilobal, barbell, bowtie, star, Y-shaped, etc. It should be understood that the cross-sectional shape of the fiber may be selected and / or may depend at least in part on one or more performance characteristics of the filter media and / or one or more fibers thereof.

[0051] The filter media and / or its fibers may be or have a gradient density. For example, the filter media and / or its fibers may be prepared or configured as a filter media and / or fiber sheet having a gradient density, in which one or more properties are altered (e.g., increased or decreased) from one side or surface thereof to the opposing side or surface thereof. For example, the filter media and / or its fibers may have pore sizes that increase or decrease from the upper surface (e.g., upstream side) to the lower surface (e.g., downstream side). In an exemplary embodiment, the filter media and / or its fiber sheet has pore sizes that decrease from the upper surface (e.g., upstream side) to the lower surface (e.g., downstream side). It should be understood that by varying the gradient density of one or more properties of the filter media and / or its fibers, the collection capacity, effectiveness, and / or efficiency of the fibrous filter media may be altered (e.g., increased). Other properties of the filter media and / or its fibers that may be varied according to the gradient may be or may include, but are not limited to, the length of the fibers, the thickness or diameter of the fibers, the relative composition of each fiber in the mixture, the charge density of the fibers, etc., or any combination thereof.

[0052] The filter media and / or fibers thereof may include one or more bicomponent fibers. As used herein, the term or phrase "bicomponent fiber" refers to a fiber comprising at least two materials bonded or otherwise bonded to one another. For example, the filter media and / or fibers thereof may be or include one or more bicomponent fibers. Bicomponent fibers may be prepared by extruding two materials (e.g., polymers) through the same spinneret. Exemplary material combinations for bicomponent fibers may be or include, but are not limited to, polypropylene (PP) / polyethylene (PE), polyethylene terephthalate (PET) / polypropylene (PP), etc., or any combination thereof. As further described herein, one or more fibers of the filter media and / or fibers thereof (e.g., multiple fibers) may be bonded to one another by thermal bonding, chemical bonding, and / or mechanical bonding (e.g., entanglement). A method of manufacturing a filter media can include providing or preparing a plurality of polylactic acid (PLA) fibers and triboelectrically charging the PLA fibers. The method can also include triboelectrically charging the PLA fibers with a plurality of second fibers or with a second fiber.

[0053] The fibers may be made or prepared by any method including, but not limited to, airlaid, wet-laid, extruded, co-formed, needlepunched, stitched, hydroentangled, meltblown, spunbonded, spunlaced, heat-bonded, carded, spinneret, gel-spun, melt-spun, wet-spun, dry-spun, islands-in-the-sea staple or spunbonded, segmented pie staple or spunbonded, electrospinning, and the like, or any combination thereof. The foregoing and / or additional methods of preparing or manufacturing fibers are described in U.S. Pat. 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 Application Publication No. 2009 / 266,759, the disclosures of which are incorporated herein by reference for all purposes to the extent not inconsistent with this disclosure. In exemplary embodiments, the system, filter media, and / or fibers thereof may comprise spunbond lines or fibers. Spunbond fibers or filaments may be prepared or formed by spinning molten polymer into fibers or filaments and drawing the molten fibers. The fibers may be prepared as fiber bundles that can be separated, spread, and / or layered on a net to form a web. The fibers may also be bonded into a sheet or film form by thermal bonding and embossing. In another exemplary embodiment, the system, filter media, and / or fibers thereof may include fibers prepared using or formed from a meltblowing die. Examples of suitable meltblowing dies that may be utilized are described in detail in U.S. Patent Nos. 6,972,104, 8,017,534, 7,772,456, and U.S. Patent Application Publication No. 2020 / 0216979, the entire disclosures of which are incorporated herein by reference in their entireties for all purposes to the extent not inconsistent with this disclosure.

[0054] In exemplary embodiments, a system for preparing a filter medium and / or fibers thereof may include one or more carders. For example, a system may include two carders arranged in series with one another. Short length fibers may be processed into a continuous fiber web by opening, blending, and / or consolidation. The fiber web prepared from carding may be subjected to one or more additional processes. For example, the fiber web may be subjected to a secondary process of bonding to improve or enhance the integrity and / or strength of the fiber web. It should be understood that the bonding process may be achieved using chemical, thermal, and / or mechanical methods. In at least one embodiment, the electrostatic or electret substrate prepared from the fibers can be a high-loft triboelectric filter media prepared by carding and needling. In at least one embodiment, the method can include needling the fibers. The method can further include carding the fibers. In other embodiments, the method can include spunbonding the fibers. In yet other embodiments, the method can include meltblowing the fibers.

[0055] In at least one embodiment, the method can include contacting the first fibers and / or the second fibers with one or more nucleating agents, charge additives, charge control agents, or combinations thereof. For example, the method can include adding or otherwise contacting one or more nucleating agents to the first fibers and / or the second fibers. In another example, the method can include adding or otherwise contacting one or more charge additives to the first fibers and / or the second fibers. In yet another example, the method can also include adding or otherwise contacting one or more charge control agents to the first fibers and / or the second fibers.

[0056] In at least one embodiment, the filter media, the first plurality of fibers (e.g., PLA fibers), and / or the second plurality of fibers can be made or prepared using a dual beam meltblowing system. The dual beam meltblowing system can be oriented at an angle such that the two fiber streams of the dual beam meltblowing system intermingle or otherwise contact each other, thereby triboelectrically charging one or more of the fibers. For example, the two fiber streams of the dual beam meltblowing system can intermingle or otherwise contact each other, thereby triboelectrically charging one or more of the fibers. It should be understood that the fibers (e.g., the first plurality of fibers and / or the second plurality of fibers) can be triboelectrically charged by needling, vibration generation, or hydroentanglement. In this embodiment, the triboelectric charging method can be needling, vibration generation, or hydroentanglement.

[0057] In at least one embodiment, the filter media, first plurality of fibers (e.g., PLA fibers), and / or second plurality of fibers can be produced by meltblowing and then triboelectrically charged. For example, a low-viscosity PLA resin can be extruded using a meltblowing die to produce PLA fibers. The meltblown PLA fibers can be triboelectrically charged by a hydroentanglement (i.e., hydrocharging) process in which clean water functions or acts as a second component that generates friction on the PLA fibers or their surfaces.

[0058] In at least one embodiment, the filter media and / or fibers thereof may comprise bicomponent fibers comprising two or more materials. The bicomponent fibers may be spunbonded or meltblown. In an exemplary embodiment, the first material of the bicomponent fiber comprises PLA. The second material of the bicomponent fiber may be selected from one or more of the materials disclosed herein. It should be understood that the bicomponent fibers may have various cross sections, such as side-by-side, segmented pie, hollow segmented pie, segmented ribbon, etc., or any combination thereof. The bicomponent fibers may be triboelectrically charged by vibration, needling, hydroentanglement, etc., or any combination thereof. In at least one embodiment, the filter media and / or its fibers can be contacted or otherwise rubbed against any suitable material to triboelectrically charge the filter media and / or its fibers. For example, a PLA article, such as a fiber, film, or fabric, can be rubbed against any suitable material disclosed herein to convert frictional (e.g., mechanical) energy into electrical energy. This system, commonly known as a triboelectric nanogenerator (TENG), converts mechanical energy harvested from the environment into electricity to power small devices such as sensors and air filtration, or to charge consumer electronics. Because PLA has a high charge density for triboelectric charging, triboelectrically charged PLA surfaces can be excellent materials for TENG systems.

[0059] The first and / or second fibers may comprise one or more polymers, which may include one or more charge additives, charge enhancers, and / or charge control agents. The charge additives, charge enhancers, and / or charge control agents may be capable of or configured to maintain or enhance triboelectric charging in the filter or its fibers. The charge additives may be added to the fibers by any suitable conventional method. For example, the charge additive may be added to polypropylene fibers by mixing, combining, adding, or otherwise contacting a particulate (e.g., powder and / or granule) charge additive with a polymer melt just before extruding and thoroughly mixing the melt. Thus, the charge additive particles, suspended and well-dispersed in the melt, are found to some extent on the fiber surface after extrusion. The second fibers can comprise polypropylene (PP), an acrylic polymer, or a combination thereof. In at least one embodiment, the second fibers can comprise a blend of polypropylene (PP) and acrylic fibers. In another embodiment, the second fibers can comprise a blend of PP and an additional polymer. In yet another embodiment, the second fibers can comprise a blend of an acrylic polymer and an additional polymer. The additional polymer can be or can include any polymer disclosed herein, including those disclosed with respect to the second fibers.

[0060] One or more fibers of the filter media may comprise heterofilaments, which are homopolymers or copolymers, or bicomponent fibers in which one of the components is an electret. In one embodiment, one or more fibers of the filter media may comprise a homopolymer of PP. In another embodiment, one or more fibers of the filter media may be PP fibers. In another embodiment, one or more fibers of the filter media may be bicomponent fibers comprising PP and an additional polymer and / or electret. For example, one or more fibers of the filter media may be bicomponent fibers comprising PP and an electret. The one or more fibers of the filter media may comprise melt-spun or non-melt-spun fibers in the form of continuous fibers, staple fibers, bicomponent fibers, etc. In an exemplary embodiment, the one or more fibers of the filter media are staple fibers and contain 2% or less of a spin finish, preferably free or substantially free of a spin finish (e.g., bare staple fibers).

[0061] In exemplary embodiments, at least a portion of the fibers may comprise one or more polymers, which may include charge additives, charge enhancers, or charge control agents, as described above, and at least a portion of the fibers may comprise PLA. PLA fibers may comprise, for example, racemic PLLA (poly-L-lactic acid), regular PLLA, poly-D-lactide (PLDA), poly-DL-lactic acid (PDLLA), or combinations thereof. Furthermore, a PLA-based surface herein refers to the surface of a fiber, fabric, or film that is at least 50% PLA-based resin. The remainder or remaining portion of the composition may contain other resins, such as polyhydroxybutyrate (PHB), or other biodegradable materials, nucleating agents, antioxidants, charge enhancers, etc., or any combination thereof. In at least one embodiment, the fibers may comprise 100% PLA resin. In at least one embodiment, the PLA fibers can include one or more charging additives. In another embodiment, the filter media can include first fibers that can include PLA and second fibers that can include a charging additive. The second fibers can include any of the fibers described above. In yet another embodiment, both the PLA fibers and the second fibers can include a charging additive.

[0062] In at least one embodiment, the filter media and / or its fibers can include one or more nanoparticles. For example, one or more nanoparticles can be incorporated into the substrate, the filter media, and / or its fibers. The nanoparticles have at least one dimension less than 1 μm or less than 100 nm. The one or more nanoparticles can increase, or can be configured to increase, the overall surface area of ​​the filter media, thereby improving its filtration efficiency and allowing it to capture submicron contaminants without significantly compromising other factors, such as pressure drop (i.e., airflow) through the filter. The nanoparticles can enable the filter media to remain relatively efficient even after the electrostatic charge begins to decay over time. Furthermore, adhesion between the fibers and the nanoparticles can be promoted by the electrostatic charge, allowing the nanoparticles to be deeply dispersed throughout the filter media. In at least one embodiment, the nanoparticles are "deeply" dispersed within the substrate or its fibers. As used herein, the term "deeply" means that the nanoparticles are dispersed beyond the 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 and second opposing surfaces. In at least one embodiment, the nanoparticles are dispersed substantially throughout the medium from the first surface to the second opposing surface. In at least one embodiment, the nanoparticles are dispersed throughout a portion of the medium from the first surface to a location between the first and second surfaces.

[0063] The nanoparticles can be selected to have different triboelectric properties relative to the first and / or second fibers to further enhance particle removal using the triboelectric effect. In this manner, the generated nanoparticles can be formed in an electric field and may be less susceptible to chemical contamination that can reduce the triboelectric effect. Nanoparticles can be used that have different adsorption or surface charge characteristics than the first and / or second fibers (e.g., in oil or water filtration). This difference can be used to enhance or create local electric field gradients within the filter media to enhance particle removal. The nanoparticles and / or fibers can have different wetting properties.

[0064] The nanoparticles may be or may include any suitable material such as, but not limited to, glass, biosoluble glass, ceramic material, acrylic, carbon, metal, alumina, one or more polymers (e.g., nylon, polyethylene terephthalate, etc.), polyvinyl chloride (PVC), polyolefin, polyacetal, polyester, cellulose ether, polyalkylene sulfide, poly(arylene oxide), polysulfone, modified polysulfone polymers, polyvinyl alcohol, polyamide, polystyrene (PS), polyacrylonitrile, polyvinylidene chloride, polymethyl methacrylate, polyvinylidene fluoride, etc., or any combination thereof.

[0065] In at least one embodiment, the nanoparticles can be bonded or adhered to the fibers through mechanical entanglement. This mechanical adhesion can be supplemented with an adhesive or binder. In at least one embodiment, the nanoparticles can be non-crimped (i.e., they do not contain the significant wavy, bent, curved, coiled, sawtooth, or similar shapes associated with nanoparticles in their relaxed state). In at least one embodiment, the nanoparticles can have a crimped structure of varying lengths. For example, when these crimped nanofibers of varying lengths are attached to the fibers, they firmly attach and entangle with each other and with, on, and around the fibers to form the modified fibers. In at least one embodiment, the attachment of the nanofibers to the fibers can be achieved by electrostatic attraction and / or van der Waals forces between the fibers and the nanoparticles. A more complete description of nanoparticle-incorporated filter media can be found in commonly assigned, co-pending U.S. Provisional Patent Application No. 63 / 328,970, filed April 8, 2022, the complete disclosure of which is incorporated herein by reference in its entirety for all purposes.

[0066] The following numbered paragraphs disclose one or more exemplary variations of the subject matter of the present application. 1. A filter media comprising a first plurality of fibers, the first plurality of fibers comprising polylactic acid (PLA) fibers or acrylic fibers, the first plurality of fibers being triboelectrically charged. 2. The filter media of paragraph 1, further comprising a second plurality of fibers, wherein the first plurality of fibers are triboelectrically charged by the second plurality of fibers. 3. The filter media of paragraph 2, wherein at least a portion of the second plurality of fibers comprises a friction-negative material. 4. The filter media of paragraphs 2 or 3, wherein at least a portion of the second plurality of fibers comprises a tribopositive material, the tribopositive material comprising a relatively lower positive charge than the first plurality of fibers. 5. The filter media of any one of paragraphs 2-4, wherein at least a portion of the second plurality of fibers comprises polypropylene (PP) fibers. 6. The filter media of paragraph 5, wherein the polypropylene fibers comprise an elongation of about 25% to about 100%, a tensile strength of about 25 cN / tex to about 100 cN / tex, or a combination thereof. 7. The filter media of any one of paragraphs 1-5, wherein the first plurality of fibers comprises acrylic fibers. 8. The filter media of any one of paragraphs 2-6, wherein the first plurality of fibers comprises PLA fibers and at least a portion of the second plurality of fibers comprises acrylic fibers. 9. The filter media of any one of paragraphs 1-8, wherein the first plurality of fibers further comprises polyhydroxyalkanoate (PHBV).

[0067] 10. The filter media of any one of paragraphs 2-9, wherein the weight ratio of the first plurality of fibers to the second plurality of fibers is about 1:1. 11. The filter media of any one of paragraphs 2-10, wherein the first plurality of fibers and the second plurality of fibers are nonwoven fibers. 12. The filter media of any one of paragraphs 1-11, wherein the first plurality of fibers is present in an amount of at least 10 wt.% of the total weight of the filter media. 13. The filter media of any one of paragraphs 1 to 12, wherein the PLA fibers comprise poly-L-lactic acid (PLLA). 14. The filter media of any one of paragraphs 1-13, wherein the first plurality of fibers, the second plurality of fibers, or a combination thereof, comprises about 2% or less of a spin finish. 15. The filter media of any one of paragraphs 1-14, wherein the first plurality of fibers comprises continuous fibers. 16. The filter media of any one of paragraphs 1-14, wherein the first plurality of fibers comprises non-continuous fibers. 17. The filter media of any one of paragraphs 1-16, wherein the first plurality of fibers have a diameter of from about 0.1 μm to about 200 μm. 18. The filter media of any one of paragraphs 1-17, wherein the first plurality of fibers has a linear density of from about 0.5 denier to about 50 denier. 19. The filter media of any one of paragraphs 1-18, wherein the first plurality of fibers, the second plurality of fibers, or a combination thereof, comprises one or more nucleating agents. 20. The filter media of any one of paragraphs 1-19, wherein the first plurality of fibers, the second plurality of fibers, or a combination thereof, comprises one or more charge additives or a combination thereof configured to modify the charge of the first plurality of fibers and increase the stability of the charge of the first plurality of fibers.

[0068] 21. The filter media of paragraph 20, wherein the one or more charging additives comprise one or more of triphenylmethane, ammonium compounds, immonium compounds, fluorinated ammonium compounds, fluorinated immonium compounds, biscationic acid amides, polymeric ammonium compounds, diallylammonium compounds, arylsulfide derivatives, phenol derivatives, phosphonium compounds, fluorinated phosphonium compounds, calix(n)arene, metal complex compounds, benzimidazolone, azine, thiazine, oxazine, or any combination thereof. 22. The filter media of paragraph 20 or 21, wherein the one or more charge additives include a nucleating agent. 23. The filter media of any one of paragraphs 19-22, wherein the one or more charge additives comprise a relatively higher electronegative charge than the first plurality of fibers or the second plurality of fibers. 24. The filter media of any one of paragraphs 19-23, wherein the one or more charging additives comprise a relatively higher dielectric constant than the first plurality of fibers or the second plurality of fibers. 25. The filter media of any one of paragraphs 1-24, wherein the first plurality of fibers comprises one or more charge control agents. 26. The filter media of any one of paragraphs 1 to 25, wherein the filter media is formed by carding and needling. 27. The filter media of any one of paragraphs 2-26, wherein the first plurality of fibers and the second plurality of fibers comprise a spunbond charged media. 28. The filter media of any one of paragraphs 2-27, wherein the first plurality of fibers and the second plurality of fibers comprise a meltblown electrostatically charged media. 29. The filter media of any one of paragraphs 1-27, wherein the first plurality of fibers is triboelectrically charged by rubbing the first plurality of fibers with one or more machines, the one or more machines including one or more of a carding machine, a needling machine, or a combination thereof. 30. The filter media of any one of paragraphs 1-28, wherein the first plurality of fibers comprises PLA fibers, and wherein the first plurality of fibers is triboelectrically charged by hydrocharging.

[0069] 31. The filter media of any one of paragraphs 2-30, wherein the second plurality of fibers comprises one or more biodegradable fibers. 32. The filter media of paragraph 31, wherein the one or more biodegradable fibers comprise one or more of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), polyhydroxybutyrate (PHB), polybutylene succinate (PBS), poly(butylene adipate-co-terephthalate) (PBAT), poly(3-hydroxybutyrate-co-e-hydroxyvalerate) (PHBV), polyhydroxyalkanoate (PHA), polycaprolactone (PCL), or any combination thereof. 33. The filter media of paragraph 31 or 32, wherein the one or more biodegradable fibers are selected from the group consisting of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), polyhydroxybutyrate (PHB), polybutylene succinate (PBS), poly(butylene adipate-co-terephthalate) (PBAT), poly(3-hydroxybutyrate-co-e-hydroxyvalerate) (PHBV), polyhydroxyalkanoates (PHA), polycaprolactone (PCL), and combinations thereof. 34. The filter media of any one of paragraphs 31 to 33, wherein the one or more biodegradable fibers comprise PHBH. 35. An air filter product comprising a filter media according to any one of paragraphs 1 to 34.

[0070] 36. A method of manufacturing a filter media, the method comprising contacting a first plurality of fibers comprising polylactic acid (PLA) fibers or acrylic fibers with a second plurality of fibers, wherein contacting the first plurality of fibers with the second plurality of fibers triboelectrically charges the first plurality of fibers. 37. The method of paragraph 36, wherein the second plurality of fibers comprises a friction-negative material. 38. The method of paragraph 36, wherein the second plurality of fibers comprises a tribopositive material, the tribopositive material comprising a relatively lower positive charge than the first plurality of fibers. 39. The method of paragraph 36, wherein the second plurality of fibers comprises polypropylene (PP). 40. The method of paragraph 39, wherein the first plurality of fibers comprises acrylic fibers. 41. The method of paragraph 36, wherein the first plurality of fibers comprises PLA fibers and the second plurality of fibers comprises acrylic fibers. 42. The method of any one of paragraphs 36 to 41, wherein the first plurality of fibers further comprises polyhydroxyalkanoate (PHBV). 43. The method of any one of paragraphs 36-42, wherein the weight ratio of the first plurality of fibers to the second plurality of fibers is about 1:1. 44. The method of any one of paragraphs 36-43, wherein the first plurality of fibers and the second plurality of fibers are nonwoven fibers.

[0071] 45. The method of any one of paragraphs 36 to 44, wherein the filter media comprises PLA fibers in an amount of at least 50% by weight. 46. ​​The method of any one of paragraphs 36 to 45, wherein the PLA fibers comprise poly-L-lactic acid (PLLA). 47. The method of any one of paragraphs 36-46, further comprising carding the first plurality of fibers and the second plurality of fibers. 48. The method of any one of paragraphs 36-47, further comprising spunbonding the first plurality of fibers and the second plurality of fibers. 49. The method of any one of paragraphs 36-47, further comprising meltblowing the first plurality of fibers and the second plurality of fibers. 50. The method of any one of paragraphs 36 to 49, further comprising contacting one or more nucleating agents with the first plurality of fibers, the second plurality of fibers, or a combination thereof. 51. The method of any one of paragraphs 36 to 50, further comprising contacting one or more charging additives with the first plurality of fibers, the second plurality of fibers, or a combination thereof. 52. The method of any one of paragraphs 36 to 51, further comprising contacting one or more charge control agents with the first plurality of fibers, the second plurality of fibers, or a combination thereof. 53. An air filter product prepared according to the method of any one of paragraphs 36 to 52.

[0072] The examples and other embodiments described herein are illustrative and not intended to be limiting in describing the full scope of the compositions and methods of the present disclosure. Equivalent changes, modifications, and variations of specific embodiments, materials, compositions, and methods may be made within the scope of the present disclosure with substantially similar results. [Example]

[0073] Exemplary fiber mixtures (1)-(3) comprising a mixture of a first plurality of fibers and a second plurality of fibers were prepared and evaluated for their respective effectiveness in filtering particles from air passing therethrough. In particular, each of the fiber mixtures (1)-(3) was evaluated to determine the average particle penetration rate therethrough. It should be understood that a relative improvement or increase in particle penetration through the filter media and / or the fiber mixture indicates a relative decrease in the effectiveness of the filter media and / or fiber mixture. Each of the fiber mixtures (1)-(3) contained a first plurality of fibers and a second plurality of fibers in a 1:1 weight ratio (50% by 50% by weight). All fibers were conditioned at approximately 30% relative humidity (RH) for at least three days prior to carding. The fibers were pre-weighed and hand-mixed prior to carding and needling to prepare the fiber mixtures. The dimensions of the fiber mixtures (1)-(3) were approximately 10 inches by 10 inches (approximately 25.4 cm by approximately 25.4 cm).

[0074] The first fiber mixture (1) contained a mixture of acrylic and polypropylene (PP) fibers. The second fiber mixture (2) contained a mixture of PLA and acrylic fibers. The third fiber mixture (3) contained a mixture of PLA and PP fibers. The PLA fibers did not contain a spin finish (i.e., no finish).

[0075] Particle penetration was evaluated or measured with an ATI 100S instrument using 0.3 μm particles at least three days after needling. Fiber mixtures (1)-(3) were evaluated using an ATI 100S instrument at 85 liters per minute (lpm) and 32 lpm. The average resistivity of each of fiber mixtures (1)-(3) was also evaluated / measured. It should be understood that triboelectric charging of the fibers occurred during the carding and / or needling process. The basis weight of each of fiber mixtures (1)-(3) was measured in grams per square foot (gsf), grams per square meter (gsm), and ounces per square yard (ozy). It should be understood that the measurements were normalized to 134 gsm for comparison purposes. Fiber mixtures (1)-(3) were each evaluated twice, and the results are summarized in Tables 1 and 2, respectively. JPEG2025534357000001.jpg42170 JPEG2025534357000002.jpg41170

[0076] As shown in Table 1, particles permeated fiber mixture (1) containing acrylic and PP fibers by approximately 19.7% at approximately 85 lpm and approximately 7.2% at approximately 32 lpm. The particle permeation rate for fiber mixture (2) containing acrylic and PLA fibers was approximately 8.3% at approximately 85 lpm and approximately 2.4% at approximately 32 lpm. Furthermore, particles permeated fiber mixture (3) containing PP and PLA fibers by approximately 7.6% at approximately 85 lpm and approximately 1.9% at approximately 32 lpm. The average resistivity of fiber mixture (1) was substantially identical to that of the remaining fiber mixtures (2) and (3). It should be understood that average resistivity is directly proportional to pressure drop and inversely proportional to air permeability. Similar results were observed when evaluated twice, as shown in Table 2. Thus, it was surprisingly and unexpectedly found that the PLA-incorporated fiber mixtures (2) and (3) exhibited relatively superior filtration efficiency compared to the PLA-free fiber mixture (1) without compromising air permeability and / or pressure drop. [Example]

[0077] The exemplary fiber mixtures (1)-(3) of Example 1 and another exemplary fiber mixture (4) were evaluated for their respective effectiveness in filtering particles from air passing therethrough. Fiber mixture (4) was prepared by adding a charging additive, i.e., FWM02, to fiber mixture (3). Specifically, the charging additive was added to PP fiber and mixed with PLA fiber in a 1:1 weight ratio to prepare fiber mixture (4). The effectiveness was evaluated as described above with respect to Example 1. It should be understood that the measurements were normalized to 126 gsm for comparison purposes. The results are summarized in Table 3. JPEG2025534357000003.jpg47170

[0078] As shown in Table 3, the particle permeability of fiber mixture (4) containing the charging additive was similar to that observed for fiber mixtures (2) and (3). Furthermore, although fiber mixtures (2) to (4) had significantly lower particle permeability compared to fiber mixture (1), the average resistance was essentially the same for each of fiber mixtures (1) to (4). Thus, it was surprisingly and unexpectedly discovered that fiber mixtures (2) to (4) incorporating PLA exhibited relatively superior filtration efficiency compared to fiber mixture (1) without sacrificing air permeability and / or pressure drop. [Example]

[0079] The effects of the fiber mixtures (1) to (3) of Example 1 were evaluated after aging for one week and two weeks. The results are summarized in Tables 4, 5, and 6. JPEG2025534357000004.jpg41170 JPEG2025534357000005.jpg43170 JPEG2025534357000006.jpg42170

[0080] As shown in Tables 4-6, the effectiveness and efficiency of fiber mixtures (1)-(3) were essentially identical after one week and two weeks. For example, after one week, particles penetrated fiber mixture (1) by approximately 21.8% at approximately 85 lpm and approximately 7.6% at 32 lpm (normalized values), fiber mixture (2) by approximately 12.7% at approximately 85 lpm and approximately 3.4% at 32 lpm, and fiber mixture (3) by approximately 8.7% at approximately 85 lpm and approximately 1.7% at 32 lpm. Similar results were observed after two weeks, as shown in Table 6. [Example]

[0081] Flat sheet filters (4) to (7) were prepared using triboelectrically charged media or triboelectrically charged fiber blends and evaluated for filtration effectiveness. The fiber blends were prepared in a 1:1 weight ratio, carded, and needle-punched with various scrims or supports. The PLA fibers were unfinished or unspin-finished. Basis weights and net fiber weights were essentially identical. Flat sheet filter (4) contained a blend of PP and acrylic fibers plus a PP scrim. Flat sheet filter (5) contained PLA and acrylic fibers plus a PP scrim. Flat sheet filter (6) contained PLA and acrylic fibers with antimicrobial and gas-absorbing additives. Flat sheet filter (7) contained PLA and acrylic fibers plus a PP scrim with a gas-absorbing additive. The results are shown below. JPEG2025534357000007.jpg54170

[0082] As shown in Table 7, PLA-incorporated filters (5)–(7) demonstrated improved filtration efficiency compared with filter (4) containing a PP blend. This improvement was observed across all three particle sizes (E1 = 0.3–1 μm, E2 = 1–3 μm, and E3 = 3–10 μm). Surprisingly and unexpectedly, it was found that the improved filtration efficiency was accompanied by a reduction in pressure drop. In particular, PLA-incorporated filters (5)–(7) demonstrated significant improvements in particle size groups E1 and E2. For example, filter (5), which contained PLA and acrylic fibers plus a PP scrim, demonstrated an improvement in filtration efficiency of over 13 points in group E1 (i.e., 53.1 vs. 66.5) and over 4 points in group E2 (i.e., 86.6 vs. 90.9), while also reducing pressure drop by nearly 15% (i.e., 0.202 vs. 0.171). Filters (7) containing PLA and acrylic fibers plus a PP scrim with a gas-absorbing additive improved filtration efficiency by over 16 points in group E1 (i.e., 53.1 vs. 69.7) and almost 3 points in group E2 (i.e., 94.7 vs. 97.2), while reducing pressure drop by almost 5% (i.e., 0.202 vs. 0.1911). [Example]

[0083] Exemplary fiber blends (8) and (9) containing a first plurality of fibers and a second plurality of fibers were prepared and evaluated. Fiber blend (8) contained acrylic fibers and PP fibers without a spin finish, while fiber blend (9) contained PP fibers and acrylic fibers with a charging additive (i.e., FWM02) without a spin finish. The basis weights and net fiber weights of fiber blends (8) and (9) were substantially identical. The weight ratio of acrylic fibers to PP fibers in fiber blends (8) and (9) was approximately 1:1. The linear densities of fiber blends (8) and (9) were substantially identical, ranging from approximately 1.7 decitex (dtex) to approximately 3.6 dtex. The charging additive was added to fiber blend (9) during spinning. The fiber blend was processed by needle punching to reinforce the fibers. The properties of the PP fibers with and without the charging additive are summarized in Table 8. JPEG2025534357000008.jpg43157

[0084] As shown in Table 8, the PP fibers used in fiber blend (9) containing the charging additive exhibited a relatively lower elongation rate compared to the PP fibers used in fiber blend (8). Similarly, the PP fibers used in fiber blend (9) containing the charging additive exhibited a relatively higher tensile strength compared to the PP fibers used in fiber blend (8). Without being bound by theory, it is believed that the relatively higher tensile strength and relatively lower elongation rate allowed the fibers to be stretched more than the PP fibers without the charging additive. A relative increase in fiber stretch is believed to affect crystallization. Specifically, a relative increase in fiber stretch is believed to increase the amount or rate of crystallization, thereby improving the order or orientation of the crystals, which in turn enhances the fiber's effectiveness in generating and / or retaining triboelectric charge. Naturally, PP fibers with and without the charging additive were evaluated by scanning electron microscopy (SEM) to observe their physical attributes and morphology. SEM micrographs showed that the PP fibers treated with the charging additive exhibited significantly greater surface roughness compared to the PP fibers without the charging additive. Without being bound by theory, it is believed that the increased surface roughness contributes, at least in part, to the effectiveness of the PP fibers in generating and retaining or maintaining triboelectric charges. SEM micrographs also showed that the PP fibers treated with the charging additive had relatively less alignment between fibers and more curvature, bending, and twisting compared to PP fibers without the charging additive, in which the fibers were significantly aligned or parallel to each other.

[0085] Fiber blends (8) and (9) were aged for 3 days. Ten handsheets of each of fiber blends (8) and (9) were evaluated using an ATI 100S instrument at 85 lpm and 32 lpm. Average permeability and resistance to 0.3 μm NaCl salt particles were evaluated. The results are summarized in Table 9. JPEG2025534357000009.jpg30158

[0086] As shown in Table 9, fiber blend (9) exhibited relatively improved filtration performance compared to fiber blend (8) without the charging additive. Surprisingly and unexpectedly, the improved filtration did not come at the expense of resistance and pressure drop, which remained essentially the same. Specifically, particles penetrated approximately 14.9% of fiber blend (8) and only approximately 8.6% of fiber blend (9). At 32 lpm, particles penetrated approximately 4.1% of fiber blend (8) and only approximately 1.9% of fiber blend (9). The resistance (mmH2O) of fiber blend (9) was essentially the same as fiber blend (8) at 32 lpm and only slightly higher at 85 lpm. Thus, fiber blend (9) exhibited improved filtration efficiency at essentially the same pressure drop as fiber blend (8).

[0087] Handsheets prepared from fiber blends (8) and (9) were aged under controlled temperature and humidity conditions. Specifically, fiber blends (8) and (9) were aged at about 70°C and about 80% RH for about 24 hours, followed by aging at about -20°C for about 24 hours. The aged fiber blends (8) and (9) were then evaluated for their filtration effectiveness. The results are summarized in Table 10. JPEG2025534357000010.jpg35142As shown in Table 10, fiber mixture (9) had a lower particle transmittance than fiber mixture (8) after aging, but maintained essentially the same resistance. In particular, the average transmittance of fiber mixture (9) was approximately 9.6%, while the average transmittance of fiber mixture (8) was approximately 13.3%. [Example]

[0088] Flat sheet filters (10) and (11) were prepared from fiber mixtures (8) and (9), respectively, and the partial filtration effect was evaluated. Specifically, filter sheets (10) and (11) were prepared from fiber mixtures (8) and (9), and measurements were performed at an air surface velocity of approximately 180 fpm. The particles were KCl salt particles (0.3 μm to 10 μm in diameter). The results are summarized in Table 11. JPEG2025534357000011.jpg37141

[0089] As shown in Table 11, sheet filter (11) demonstrated improved filtration efficiency over sheet filter (10) for all three particle sizes. Although the pressure drop of sheet filter (11) was relatively higher than that of sheet filter (10), this increase in pressure drop reflected the reduced thickness of sheet filter (11) (i.e., approximately 111.7 mm for sheet filter (10) versus approximately 104.2 mm for sheet filter (11). In particular, sheet filter (11) demonstrated substantial improvement in particle size group E1 (approximately 57.9 vs. approximately 68.3). Particle group E1 is typically associated with charge density. [Example]

[0090] Exemplary fiber blends (12) and (13) were prepared, each comprising a blend of a first plurality of fibers including PLA fibers and a second plurality of fibers including poly(hydroxybutyrate-co-3-hexanoate) (PHBH) fibers, and evaluated for their effectiveness in filtering particles from air passing therethrough. Specifically, fiber blends (12) and (13) were each evaluated to determine the average particle penetration rate therethrough. The PLA and PHBH fibers did not contain a spin finish. Fiber blend (12) contained approximately 50% PLA fiber by weight and approximately 50% PHBH fiber by weight. Fiber blend (13) contained approximately 60% PLA fiber by weight and approximately 40% PHBH fiber by weight. All fibers were conditioned at approximately 30% relative humidity (RH) for at least three days prior to carding. The fibers were pre-weighed and hand mixed, then carded and needled to prepare fiber mixtures (12) and (13), which measured approximately 10 inches by 10 inches (approximately 25.4 cm by approximately 25.4 cm).

[0091] Fiber mixtures (12) and (13) were evaluated using an ATI 100S machine at 85 liters per minute (lpm) and 32 lpm. The average resistivity of each of fiber mixtures (12) and (13) was also evaluated / measured. It should be understood that triboelectric charging of the fibers occurred during the carding and / or needling process. The basis weight of each of fiber mixtures (12) and (13) was measured in grams per square foot (gsf), grams per square meter (gsm), and ounces per square yard (ozy). It should be understood that the measurements were normalized for comparison. Fiber mixtures (12) and (13) were evaluated approximately four days after the date of manufacture. The results are summarized in Table 12. JPEG2025534357000012.jpg44141

[0092] As shown in Table 12, the difference in average permeability between the 85 lpm and 32 lpm flow rates supports the belief that the PLA fibers in fiber blends (12) and (13) were triboelectrically charged. In particular, the average permeability at the low flow rate of approximately 32 lpm was lower than the average permeability at the high flow rate, supporting the belief that the PLA fibers in fiber blends (12) and (13) were triboelectrically charged. After aging for four days, the average permeability remained virtually the same, further demonstrating that the PLA fibers retained their charge even after aging.

[0093] While the devices, systems, and methods have been described in detail herein in accordance with certain preferred embodiments thereof, many modifications and variations thereon may be made by those skilled in the art. Accordingly, the foregoing description should not be construed as limited thereto, but should be construed as including such obvious variations as may be set forth above, and should be construed as being limited only by the spirit and scope of the following claims.

Claims

1. 1. A filter media comprising: a first plurality of fibers, the first plurality of fibers comprising polylactic acid (PLA) fibers or acrylic fibers, the first plurality of fibers being triboelectrically charged.

2. 10. The filter media of claim 1, further comprising a second plurality of fibers, said first plurality of fibers being triboelectrically charged by said second plurality of fibers.

3. The filter media of claim 2 , wherein at least a portion of the second plurality of fibers comprises a friction-negative material.

4. 4. The filter media of claim 2 or claim 3, wherein at least a portion of the second plurality of fibers comprises a tribopositive material, the tribopositive material comprising a relatively lower positive charge than the first plurality of fibers.

5. The filter media of any one of claims 2 to 4, wherein at least a portion of the second plurality of fibers comprises polypropylene (PP) fibers.

6. 6. The filter media of claim 5, wherein the polypropylene fibers comprise an elongation of about 25% to about 100%, a tensile strength of about 25 cN / tex to about 100 cN / tex, or a combination thereof.

7. The filter media of any one of claims 1 to 5, wherein the first plurality of fibers comprises acrylic fibers.

8. The filter media of any one of claims 2-6, wherein the first plurality of fibers comprises PLA fibers and at least a portion of the second plurality of fibers comprises acrylic fibers.

9. The filter media of any one of claims 1 to 8, wherein the first plurality of fibers further comprises polyhydroxyalkanoate (PHBV).

10. The filter media of any one of claims 2 to 9, wherein the weight ratio of the first plurality of fibers to the second plurality of fibers is about 1:

1.

11. The filter media of any one of claims 2 to 10, wherein the first plurality of fibers and the second plurality of fibers are nonwoven fibers.

12. The filter media of any one of claims 1 to 11, wherein the first plurality of fibers is present in an amount of at least 10 wt% of the total weight of the filter media.

13. The filter medium of any one of claims 1 to 12, wherein the PLA fibers comprise poly-L-lactic acid (PLLA).

14. The filter media of any one of claims 1 to 13, wherein the first plurality of fibers, the second plurality of fibers, or a combination thereof comprises a spin finish of about 2% or less.

15. The filter media of any one of claims 1 to 14, wherein the first plurality of fibers comprises continuous fibers.

16. The filter media of any one of claims 1 to 14, wherein the first plurality of fibers comprises non-continuous fibers.

17. The filter media of any one of claims 1 to 16, wherein the first plurality of fibers have a diameter of from about 0.1 μm to about 200 μm.

18. The filter media of any one of claims 1-17, wherein the first plurality of fibers has a linear density of from about 0.5 denier to about 50 denier.

19. The filter media of any one of claims 1 to 18, wherein the first plurality of fibers, the second plurality of fibers, or a combination thereof comprises one or more nucleating agents.

20. 20. The filter media of any one of claims 1-19, wherein the first plurality of fibers, the second plurality of fibers, or a combination thereof comprises one or more charge additives or a combination thereof configured to modify a charge of the first plurality of fibers and increase the stability of a charge of the first plurality of fibers.

21. 21. The filter media of claim 20, wherein the one or more charging additives comprise one or more of triphenylmethane, ammonium compounds, immonium compounds, fluorinated ammonium compounds, fluorinated immonium compounds, biscationic acid amides, polymeric ammonium compounds, diallylammonium compounds, arylsulfide derivatives, phenol derivatives, phosphonium compounds, fluorinated phosphonium compounds, calix(n)arenes, metal complex compounds, benzimidazolones, azines, thiazines, oxazines, or any combination thereof.

22. 22. The filter media of claim 20 or 21, wherein the one or more charging additives comprises a nucleating agent.

23. 23. The filter media of any one of claims 19-22, wherein the one or more charging additives comprise a relatively higher electronegative charge than the first plurality of fibers or the second plurality of fibers.

24. 24. The filter media of any one of claims 19-23, wherein the one or more charging additives comprise a relatively higher dielectric constant than the first plurality of fibers or the second plurality of fibers.

25. The filter media of any one of claims 1 to 24, wherein the first plurality of fibers comprises one or more charge control agents.

26. The filter medium of any one of claims 1 to 25, wherein the filter medium is formed by carding and needling.

27. The filter media of any one of claims 2 to 26, wherein the first plurality of fibers and the second plurality of fibers comprise a spunbond charged media.

28. 28. The filter media of any one of claims 2-27, wherein the first plurality of fibers and the second plurality of fibers comprise meltblown electrostatic media.

29. 28. The filter media of any one of claims 1-27, wherein the first plurality of fibers are triboelectrically charged by rubbing the first plurality of fibers with one or more machines, the one or more machines comprising one or more of a carding machine, a needling machine, or a combination thereof.

30. 29. The filter media of any one of claims 1-28, wherein the first plurality of fibers comprises PLA fibers, and the first plurality of fibers are triboelectrically charged by hydrocharging.

31. The filter media of any one of claims 2 to 30, wherein the second plurality of fibers comprises one or more biodegradable fibers.

32. 32. The filter media of claim 31, wherein the one or more biodegradable fibers comprise one or more of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), polyhydroxybutyrate (PHB), polybutylene succinate (PBS), poly(butylene adipate-co-terephthalate) (PBAT), poly(3-hydroxybutyrate-co-e-hydroxyvalerate) (PHBV), polyhydroxyalkanoate (PHA), polycaprolactone (PCL), or any combination thereof.

33. 33. The filter media of claims 31 or 32, wherein the one or more biodegradable fibers are selected from the group consisting of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (PHBH), polyhydroxybutyrate (PHB), polybutylene succinate (PBS), poly(butylene adipate-co-terephthalate) (PBAT), poly(3-hydroxybutyrate-co-e-hydroxyvalerate) (PHBV), polyhydroxyalkanoates (PHA), polycaprolactone (PCL), and combinations thereof.

34. 34. The filter medium of any one of claims 31 to 33, wherein the one or more biodegradable fibers comprise PHBH.

35. An air filter product comprising the filter media of any one of claims 1 to 34.

36. 1. A method of manufacturing a filter media, the method comprising contacting a first plurality of fibers comprising polylactic acid (PLA) fibers or acrylic fibers with a second plurality of fibers, wherein contacting the first plurality of fibers with the second plurality of fibers triboelectrically charges the first plurality of fibers.

37. 37. The method of claim 36, wherein the second plurality of fibers comprises a friction-negative material.

38. 37. The method of claim 36, wherein said second plurality of fibers comprises a tribopositive material, said tribopositive material comprising a relatively lower positive charge than said first plurality of fibers.

39. 37. The method of claim 36, wherein the second plurality of fibers is polypropylene (PP).

40. 40. The method of claim 39, wherein the first plurality of fibers comprises acrylic fibers.

41. 37. The method of claim 36, wherein the first plurality of fibers comprises PLA fibers and the second plurality of fibers comprises acrylic fibers.

42. 42. The method of any one of claims 36-41, wherein the first plurality of fibers further comprises polyhydroxyalkanoate (PHBV).

43. 43. The method of any one of claims 36 to 42, wherein the weight ratio of the first plurality of fibers to the second plurality of fibers is about 1:

1.

44. 44. The method of any one of claims 36 to 43, wherein the first plurality of fibers and the second plurality of fibers are nonwoven fibers.

45. 45. The method of any one of claims 36 to 44, wherein the filter medium comprises PLA fibers in an amount of at least 50% by weight.

46. The method of any one of claims 36 to 45, wherein the PLA fibers comprise poly-L-lactic acid (PLLA).

47. 47. The method of any one of claims 36 to 46, further comprising carding the first plurality of fibers and the second plurality of fibers.

48. 48. The method of any one of claims 36 to 47, further comprising spunbonding the first plurality of fibers and the second plurality of fibers.

49. 48. The method of any one of claims 36-47, further comprising meltblowing the first plurality of fibers and the second plurality of fibers.

50. 50. The method of any one of claims 36-49, further comprising contacting one or more nucleating agents with the first plurality of fibers, the second plurality of fibers, or a combination thereof.

51. 51. The method of any one of claims 36-50, further comprising contacting one or more charging additives with the first plurality of fibers, the second plurality of fibers, or a combination thereof.

52. 52. The method of any one of claims 36-51, further comprising contacting one or more charge control agents with the first plurality of fibers, the second plurality of fibers, or a combination thereof.

53. An air filter product prepared according to the method of any one of claims 36 to 52.

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