WO2018156561A1 - Electret-containing filter media - Google Patents

Electret-containing filter media Download PDF

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Publication number
WO2018156561A1
WO2018156561A1 PCT/US2018/018924 US2018018924W WO2018156561A1 WO 2018156561 A1 WO2018156561 A1 WO 2018156561A1 US 2018018924 W US2018018924 W US 2018018924W WO 2018156561 A1 WO2018156561 A1 WO 2018156561A1
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WO
WIPO (PCT)
Prior art keywords
equal
filter media
less
layer
cfm
Prior art date
Application number
PCT/US2018/018924
Other languages
English (en)
French (fr)
Inventor
Sudheer Jinka
Original Assignee
Hollingsworth & Vose Company
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from US15/438,042 external-priority patent/US11077394B2/en
Priority claimed from US15/438,028 external-priority patent/US10814261B2/en
Priority claimed from US15/790,651 external-priority patent/US20180236385A1/en
Application filed by Hollingsworth & Vose Company filed Critical Hollingsworth & Vose Company
Priority to CN202211237409.6A priority Critical patent/CN115646068A/zh
Priority to EP18757748.1A priority patent/EP3585499A4/en
Priority to CN201880025705.5A priority patent/CN110545894B/zh
Publication of WO2018156561A1 publication Critical patent/WO2018156561A1/en

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D39/00—Filtering material for liquid or gaseous fluids
    • B01D39/14—Other self-supporting filtering material ; Other filtering material
    • B01D39/16—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres
    • B01D39/1607—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres the material being fibrous
    • B01D39/1623—Other self-supporting filtering material ; Other filtering material of organic material, e.g. synthetic fibres the material being fibrous of synthetic origin
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/04—Additives and treatments of the filtering material
    • B01D2239/0435—Electret
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/06—Filter cloth, e.g. knitted, woven non-woven; self-supported material
    • B01D2239/0604—Arrangement of the fibres in the filtering material
    • B01D2239/064—The fibres being mixed
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/06—Filter cloth, e.g. knitted, woven non-woven; self-supported material
    • B01D2239/065—More than one layer present in the filtering material
    • B01D2239/0654—Support layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01D—SEPARATION
    • B01D2239/00—Aspects relating to filtering material for liquid or gaseous fluids
    • B01D2239/12—Special parameters characterising the filtering material
    • B01D2239/1258—Permeability

Definitions

  • the present embodiments relate generally to filter media and electret-containing media specifically, to filter media including open support layers.
  • Filter elements can be used to remove contamination in a variety of applications.
  • Such elements can include a filter media which may be formed of a web of fibers.
  • the filter media provides a porous structure that permits fluid (e.g., air) to flow through the media.
  • Contaminant particles e.g., dust particles, soot particles
  • the filter media may be designed to have different performance characteristics.
  • filter media for filtering particulates from air
  • improvements in the physical and/or performance characteristics of the filter media e.g., strength, air resistance, efficiency, and high dust holding capacity
  • Filter media are generally provided.
  • the subject matter of this application involves, in some cases, interrelated products, alternative solutions to a particular problem, and/or a plurality of different uses of structures and compositions.
  • filter media are provided.
  • the filter media comprises an open support layer and a charged fiber layer mechanically attached to the open support layer, wherein the charged fiber layer comprises a first plurality of fibers comprising a first polymer and a second plurality of fibers comprising a second polymer, wherein the first polymer is acrylic, and wherein the open support layer is a mesh having an air permeability of greater than 1100 CFM and less than or equal to 20000 CFM.
  • the filter media comprises an open support layer and a charged fiber layer mechanically attached to the open support layer, wherein the charged fiber layer comprises a plurality of fibers having an average fiber diameter of less than 15 microns and greater than or equal to 1 micron, and wherein the open support layer is a mesh having an air permeability of greater than 1100 CFM and less than or equal to 20000 CFM.
  • the filter media comprises an open support layer and a charged fiber layer mechanically attached to the support layer, wherein the open support layer has an air permeability of greater than 1100 CFM and less than or equal to 20000 CFM, wherein the filter media has an overall basis weight of greater than or equal to 12 g/m 2 and less than or equal to 700 g/m 2 ,wherein the filter media has a gamma greater than or equal to 90 and less than or equal to 250, and wherein the filter media has an overall air permeability of greater than or equal to 30 CFM and less than or equal to 1100 CFM.
  • the filter media comprises a charged fiber layer, an open support layer mechanically attached to the charged fiber layer, and a coarse support layer that holds the charged fiber layer in a waved configuration and maintains separation of peaks and troughs of adjacent waves of the charged fiber layer, wherein the charged fiber layer has a basis weight of less than or equal to 12 g/m and greater than or equal to 250 g/m , wherein the open support layer has an air permeability of greater than 1100 CFM and less than or equal to 20000 CFM, and wherein the filter media has an overall air permeability of greater than or equal to 10 CFM and less than or equal to 1000 CFM.
  • the filter media comprises an open support layer having an air permeability of greater than 1100 CFM and less than or equal to 20000 CFM, a charged fiber layer adjacent the open support layer and comprising a first plurality of fibers comprising a first polymer and a second plurality of fibers comprising a second polymer, an additional layer associated with the open support layer and the charged fiber layer, and a fine fiber layer associated with the additional layer, wherein the fine fiber layer comprises a plurality of electrospun fibers and wherein the open support layer and the additional layer have a combined air permeability of greater than 45 CFM and less than 1100 CFM.
  • the filter media comprises an open support layer having an air permeability of greater than 1100 CFM and less than or equal to 20000 CFM, a charged fiber layer adjacent the open support layer and comprising a first plurality of fibers comprising a first polymer and a second plurality of fibers comprising a second polymer, an additional layer associated with the open support layer and the charged fiber layer, wherein the additional layer comprises a plurality of meltblown fibers, and a coarse support layer that holds at least the charged fiber layer in a waved configuration and maintains separation of peaks and troughs of adjacent waves of the charged fiber layer, wherein the open support layer and the additional layer have a combined air permeability of greater than 45 CFM and less than 1100 CFM.
  • the filter media comprises an open support layer, a charged fiber layer mechanically attached to the open support layer, wherein the charged fiber layer comprises a first plurality of fibers comprising a first polymer and a second plurality of fibers comprising a second polymer, an additional layer associated with the open support layer and the charged fiber layer, and a coarse support layer that holds at least the charged fiber layer in a waved configuration and maintains separation of peaks and troughs of adjacent waves of the charged fiber layer, wherein the open support layer and the additional layer have a combined air permeability of greater than or equal to 45 CFM and less than 1100 CFM.
  • the filter media comprises a charged fiber layer comprising a first plurality of fibers comprising a first polymer and a second plurality of fibers comprising a second polymer, wherein the charged fiber layer has a BET surface area of greater than or equal to 0.35 m /g and less than or equal to 125,000 fibers per gram of the charged fiber layer.
  • the filter media comprises an open support layer having an air permeability of greater than or equal to 500 CFM adjacent the charged fiber layer.
  • the first plurality of fibers and/or the second plurality of fibers have a cross-sectional shape selected from the group consisting of round, elliptical, dogbone, kidney bean, ribbon, irregular, and multi-lobal.
  • the first plurality of fibers and/or the second plurality of fibers have an average largest cross-sectional dimension of greater than or equal to 2 microns and less than or equal to 15 microns.
  • an open support layer is mechanically attached to the charged fiber layer.
  • the filter media is anti-microbial. In certain embodiments, the filter media is anti-microbial. In certain embodiments, the filter media is anti-microbial. In certain
  • the charged fiber layer is anti-microbial.
  • the open support layer is anti-microbial.
  • the first plurality of fibers and/or the second plurality of fibers are anti-microbial.
  • the filter media has a bacterial filtration efficiency of greater than or equal to 99.999%. In certain embodiments, the filter media has a viral filtration efficiency of greater than or equal to 99.999%.
  • the first plurality of fibers and/or the second plurality of fibers comprise a bacteriostatic, fungistatic, and/or virostatic additive. In certain embodiments, the first plurality of fibers and/or the second plurality of fibers comprise a bacteriostatic, fungistatic, and/or virostatic additive. In certain embodiments, the second plurality of fibers comprise acrylic.
  • the charged fiber layer has a BET surface area of greater than or equal to 0.33 m 2 /g and less than or equal to 1.5 m 2 /g. In certain embodiments, the charged fiber layer has a BET surface area of greater than or equal to 0.35 m /g and less than or equal to 1 m /g.
  • the charged fiber layer has less than or equal to 125,000 fibers per gram and greater than or equal to 50,000 fibers per gram. In certain embodiments, the charged fiber layer has less than or equal to 105,000 fibers and greater than or equal to 75,000 fibers per gram.
  • the filter media is fire resistant.
  • the charged fiber layer is configured to remain charged after direct contact with an ignition source.
  • the first plurality of fibers and/or the second plurality of fibers are fire resistant.
  • the additional layer is a meltblown layer, a spunbond layer, or a carded web layer.
  • the charged fiber layer comprises a first plurality of fibers comprising a first polymer and a second plurality of fibers comprising a second polymer.
  • the first polymer and the second polymer have different dielectric constants.
  • a difference in dielectric constants between the first polymer and the second polymer is greater than or equal to 0.8 and less than or equal to 8.
  • a difference in dielectric constants between the first polymer and the second polymer is greater than or equal to 1.5 and less than or equal to 5.
  • the second polymer comprises a synthetic material selected from the group consisting of polypropylene, dry-spun acrylic, polyvinyl chloride, mod-acrylic, wet spun acrylic, polytetrafluoroethylene, polypropylene, polystyrene, polysulfone, polyethersulfone, polycarbonate, nylon, polyurethane, phenolic, polyvinylidene fluoride, polyester, polyaramid, polyimide, polyolefin, Kevlar, Nomex, halogenated polymers, polyacrylics, polyphenylene oxide, polyphenylene sulfide, polymethyl pentene, and combinations thereof.
  • the second polymer is polypropylene.
  • the second polymer is present in the charged fiber layer in an amount greater than or equal to 10 wt% and less than or equal to 90 wt% versus the total weight of the charged fiber layer. In certain embodiments, the second polymer is present in the charged fiber layer in an amount greater than or equal to 25 wt% and less than or equal to 75 wt% versus the total weight of the charged fiber layer. In certain embodiments, the second polymer is present in the charged fiber layer in an amount greater than or equal to 35 wt% and less than or equal to 65 wt% versus the total weight of the charged fiber layer.
  • the first polymer comprises a synthetic material selected from the group consisting of polypropylene, dry-spun acrylic, polyvinyl chloride, mod- acrylic, wet spun acrylic, polytetrafluoroethylene, polypropylene, polystyrene, polysulfone, polyethersulfone, polycarbonate, nylon, polyurethane, phenolic, polyvinylidene fluoride, polyester, polyaramid, polyimide, polyolefin, Kevlar, Nomex, halogenated polymers, polyacrylics, polyphenylene oxide, polyphenylene sulfide, polymethyl pentene, and combinations thereof.
  • the first polymer is dry- spun acrylic.
  • the first polymer is present in the charged fiber layer in an amount greater than or equal to 10 wt% and less than or equal to 90 wt% versus the total weight of the charged fiber layer. In certain embodiments, the first polymer is present in the charged fiber layer in an amount greater than or equal to 25 wt% and less than or equal to 75 wt% versus the total weight of the charged fiber layer. In certain embodiments, the first polymer is present in the charged fiber layer in an amount greater than or equal to 35 wt% and less than or equal to 65 wt% versus the total weight of the charged fiber layer.
  • the first plurality of fibers have an average fiber diameter of less than 15 microns and greater than or equal to 1 micron.
  • the second plurality of fibers have an average fiber diameter of less than 15 microns and greater than or equal to 1 micron.
  • the open support layer has a solidity of less than or equal to 10% and greater than or equal to 0.1%. In certain embodiments, the open support layer has a solidity of less than or equal to 2% and greater than or equal to 0.1%.
  • the charged fiber layer is needled to the support layer. In certain embodiments, the charged fiber layer is needled to the support layer at a punch density of greater than or equal to 15 punches per square centimeter and less than or equal to 60 punches per square centimeter. In certain embodiments, the charged fiber layer is needled to the support layer at a penetration depth of needling of greater than or equal to 8 mm and less than or equal to 20 mm.
  • the charged fiber layer has a basis weight of greater than or equal to 10 g/m 2 and less than or equal to 600 g/m 2. In certain embodiments, the open support layer has a basis weight of less than or equal to 200 g/m and greater than or equal to 2 g/m In certain embodiments, the open support layer has a basis weight of less than or equal to 50 g/m 2 and greater than or equal to 5 g/m 2.
  • the open support layer has a strand count along a first axis of greater than or equal to 2 threads per inch and less than or equal to 27 threads per inch. In certain embodiments, the open support layer has a strand count along a first axis of greater than or equal to 3 strands per inch and less than or equal to 20 strands per inch.
  • the open support layer comprises a plurality of fibers or strands having an average fiber diameter of greater than or equal to 0.5 microns and less than or equal to 2 mm. In certain embodiments, the open support layer comprises a plurality of fibers or strands having an average fiber diameter of greater than or equal to 0.5 microns and less than or equal to 10 microns. In certain embodiments, the open support layer comprises a plurality of fibers or strands having an average fiber diameter of greater than or equal to 10 microns and less than or equal 20 microns. In certain embodiments, the open support layer comprises a plurality of fibers or strands having an average fiber diameter of greater than or equal to 500 microns and less than or equal to 2 mm.
  • the open support layer is formed by a spunbond process and comprises a plurality of fibers having an average fiber diameter of greater than or equal to 10 microns and less than or equal to 20 microns. In certain embodiments, the open support layer is formed by a meltblown process and comprises a plurality of fibers having an average fiber diameter of greater than or equal to 0.5 microns and less than or equal to 10 microns. In certain embodiments, the open support layer is a mesh and comprises a plurality of strands having an average strand diameter of greater than or equal to 500 microns and less than or equal to 2 mm.
  • the charged fiber layer has an uncompressed thickness of greater than or equal to 5 mils and less than or equal to 600 mils, or greater than or equal to 30 mils and less than or equal to 350 mils.
  • the charged fiber layer has an air permeability of greater than or equal to 10 CFM and less than or equal to 1200 CFM. In certain embodiments, the charged fiber layer has an air permeability of greater than or equal to 80 CFM and less than or equal to 1200 CFM. In certain embodiments, the charged fiber layer has an air permeability of greater than or equal to 50 CFM and less than or equal to 650 CFM.
  • the filter media has an overall basis weight of greater than or equal to 12 g/m 2 and less than or equal to 700 g/m 2. In certain embodiments, the filter media has an overall basis weight of greater than or equal to 25 g/m and less than or equal to 650 g/m .
  • the filter media has an overall basis weight of greater than or equal to 30 g/m 2 and less than or equal to 800 g/m 2. In certain embodiments, the filter media has an overall basis weight of greater than or equal to 100 g/m and less than or equal to 450 g/m .
  • the filter media has an overall thickness of greater than or equal to 5 mils and less than or equal to 600 mils. In certain embodiments, the filter media has an overall thickness of greater than or equal to 30 mils and less than or equal to 350 mils.
  • the filter media has an overall thickness of greater than or equal to 100 mil and less than or equal to 4000 mil. In certain embodiments, the filter media has an overall thickness of greater than 150 mil and less than or equal to 1000 mil.
  • the filter media has an overall air permeability of greater than or equal to 30 CFM and less than or equal to 1100 CFM. In certain embodiments, the filter media has an overall air permeability of greater than or equal to 100 CFM and less than or equal to 700 CFM. In certain embodiments, the filter media has an overall air permeability of greater than or equal to 10 CFM and less than or equal to 1000 CFM.
  • the filter media has a normalized efficiency of greater than or equal to 1 and less than or equal to 3.5. In certain embodiments, the filter media has a dust holding capacity of greater than or equal to about 1 g/m 2 and less than or equal to about 140 g/m 2. In certain embodiments, the filter media has a dust holding capacity of greater than or equal to about 80 g/m 2 and less than or equal to about 140 g/m 2.
  • the filter media has a dust holding capacity of greater than or equal to 5 g/m 2 and less than or equal to 600 g/m 2. In certain embodiments, the filter media has a dust holding capacity of greater than or equal to 200 g/m and less than or equal to 350 g/m .
  • the filter media has a gamma of greater than or equal to 30 and less than or equal to 250. In certain embodiments, the filter media has a gamma of greater than or equal to 75 and less than or equal to 150. In certain embodiments, the filter media has a normalized gamma of greater than or equal to 1 and less than or equal to 10.9. In certain embodiments, the filter media has a normalized gamma of greater than or equal to 1 and less than or equal to 5.6.
  • the filter media has a gamma of greater than or equal to
  • the filter media has a gamma of greater than or equal to 20 and less than or equal to 250.
  • the filter media has an initial efficiency of greater than or equal to 50% and less than or equal to 99.999%. In certain embodiments, the filter media has an initial efficiency of greater than or equal to 90% and less than or equal to
  • the charged fiber layer has a periodicity of greater than or equal to 10 and less than or equal to 40 waves per 6 inches. In certain embodiments, the charged fiber layer has a periodicity of greater than or equal to 5 and less than or equal to 9 waves per 6 inches. In certain embodiments, the charged fiber layer has a periodicity of greater than or equal to 3 and less than or equal to 15 waves per 6 inches.
  • the filter media comprises a coarse support layer.
  • the coarse support layer comprises a plurality of fibers having an average fiber diameter of greater than or equal to 8 micron and less than or equal to 85 microns.
  • the coarse support layer comprises a plurality of fibers having an average fiber diameter of greater than or equal to 12 microns and less than or equal to 60 microns.
  • the coarse support layer has a basis weight of less than or equal to 100 g/m 2 and greater than or equal to 5 g/m 2. In certain 2 embodiments, the coarse support layer has a basis weight of less than or equal to 40 g/m and greater than or equal to 12 g/m .
  • the filter media comprises an outer layer.
  • FIG. 1A is a schematic diagram showing a cross-section of a filter media according to one set of embodiments
  • FIG. IB is a schematic diagram showing a cross-section of a filter media according to one set of embodiments
  • FIG. 1C is a schematic diagram showing a cross-section of a filter media according to one set of embodiments
  • FIG. 2A is a schematic diagram showing a cross-section of a filter media according to one set of embodiments
  • FIG. 2B is a schematic diagram showing a cross-section of a filter media according to one set of embodiments
  • FIG. 2C is a schematic diagram showing a cross-section of a filter media according to one set of embodiments
  • FIG. 2D is a schematic diagram showing a cross-section of a filter media according to one set of embodiments
  • FIG. 3 is a plot of normalized gamma of exemplary filter media versus basis weight of a charged fiber layer of the filter media, with or without an open support layer, according to one set of embodiments;
  • FIG. 4 is a plot of normalized efficiency of exemplary filter media versus basis weight of a charged fiber layer of the filter media, with or without an open support layer, according to one set of embodiments;
  • FIG. 5 is a plot of pressure drop (Pa) of exemplary filter media, versus basis weight of a charged fiber layer, with or without an open support layer, according to one set of embodiments.
  • FIG. 6 is a plot of air resistance versus dust holding capacity of exemplary filter media having a basis weight of 70 g/m , each filter media comprising a charged fiber with or without an open support layer, according to one set of embodiments.
  • Filter media such as electret-containing filtration media for filtering gas streams (e.g., air), are described herein.
  • the filter media may be designed to have desirable properties such as stable filtration efficiency over the lifetime of the filter media, increased normalized gamma, relatively low pressure drop (i.e. resistance), and/or relatively low basis weight.
  • the filter media may be a composite of two or more types of fiber layers where each layer may be designed to enhance its function without substantially negatively impacting the performance of another layer of the media.
  • one layer of the media may be designed to have a relatively low basis weight and/or a relatively high air permeability, and another layer of the media may be designed to have stable filtration efficiency and/or a relatively high efficiency throughout the filter media's lifetime.
  • the filter media described herein may be particularly well-suited for applications that involve filtering gas streams (e.g., face masks, cabin air filtration, vacuum filtration, room filtration, furnace filtration, respirator equipment, residential or industrial HVAC filtration, high-efficiency particulate arrestance (HEPA) filters, ultra-low particular air (ULPA) filters, medical equipment), though the media may also be used in other applications.
  • filtering gas streams e.g., face masks, cabin air filtration, vacuum filtration, room filtration, furnace filtration, respirator equipment, residential or industrial HVAC filtration, high-efficiency particulate arrestance (HEPA) filters, ultra-low particular air (ULPA) filters, medical equipment
  • the filter media described herein may include an open support layer and a second layer that is charged (e.g., a charged fiber layer).
  • the open support layer is mechanically attached (e.g., needled) to the second layer.
  • the open support layer and/or the second layer may be in a waved configuration.
  • the filter media may comprise one or more coarse support layers.
  • the second layer is in a waved configuration and the one or more coarse support layers holds the second layer in the waved configuration and maintains separation of peaks and troughs of adjacent waves of the second layer.
  • one or more additional layers such as a meltblown layer may be associated with the open support layer.
  • a filter media comprising one or more additional layers associated with the open support layer may be in a waved configuration.
  • the incorporation of one or more additional layers such as a meltblown layer into the filter media described herein may, in some cases, increase the efficiency (e.g., initial efficiency) of the filter media as compared to similar filter media without such additional layer(s).
  • the open support layer may be positioned upstream of the charged fiber layer (e.g., in a filter element) with respect to the direction of gas/fluid flow.
  • the second layer may be positioned upstream of the first layer (e.g., in a filter element) with respect to the direction of gas/fluid flow.
  • Such a configuration of layers may also stabilize the filtration efficiency of the filter media throughout its lifetime.
  • the presence of charges in the second layer may improve the efficiency of the media relative to a filter media without charges in the second layer.
  • the open support layer may have a relatively high air
  • permeability a relatively low basis weight, and/or a relatively high open area, thereby providing mechanical reinforcement while adding a relatively small amount of basis weight to the overall filter media (e.g., as compared to filter media including other support layers such as coarse support layers).
  • the second layer (e.g., the charged fiber layer) may have a relatively low number of fibers per gram of the second layer (e.g., less than or equal to 125,000 fibers per gram) and a relatively high surface area per unit mass (e.g., greater than 0.33 m /g).
  • such layers may exhibit increased initial efficiency, increased charge generation, and/or decreased charge dissipation (e.g., during use of the layer and/or a filter media comprising the layer) as compared to layers with lower surface areas per unit mass and/or relatively higher numbers of fibers per gram of the layer.
  • FIG. 1A An example of a filter media including two or more layers is shown in FIG. 1A.
  • a filter media 100 may include a first layer 110 (e.g., an open support layer) and a second layer 120 adjacent first layer 110.
  • first layer 110 may be directly adjacent (i.e., in direct contact with at least a portion of) second layer 120.
  • second layer 120 may be positioned upstream or downstream of, but not in contact with, first layer 110.
  • the first layer is an open support layer, for example, having a relatively high air permeability and the second layer is a charged fiber layer (e.g., an electret layer).
  • the filter media includes one or more coarse support layers as described in more detail below.
  • the open support layer may be positioned between two layers.
  • a filter media 102 shown in cross section, may include a first layer 110 (e.g., the open support layer), a second layer 120 adjacent first layer 110, and a third layer 122 adjacent first layer 110.
  • first layer 110 may be directly adjacent (i.e., in direct contact with at least a portion of) second layer 120 and/or third layer 122 (e.g., such that first layer 110 is disposed between the second layer and the third layer).
  • second layer 120 may be positioned upstream of, but not in contact with, first layer 110, and third layer 122 may be position downstream of, but not in contact with, first layer 110.
  • second layer 120 may be positioned downstream of, but not in contact with, first layer 110, and third layer 122 may be position upstream of, but not in contact with, first layer 110.
  • the first layer is an open support layer, for example, having a relatively high air permeability and the second layer and the third layer may each be a charged fiber layer.
  • the second layer and the third layer may be different.
  • the first layer is an open support layer
  • the second layer is a charged fiber layer
  • the third layer is a coarse support layer.
  • the coarse support layer e.g., the third layer
  • the coarse support layer is illustrated as being adjacent the first layer in FIG. IB
  • those skilled in the art would understand, based upon the teachings of this specification, that the coarse support layer may be adjacent the second layer or disposed between the first layer and the second layer.
  • first layer and second layer generally refer to different layers of a filter media and do not necessarily denote a particular order of the layers (e.g., within a filter element).
  • a first layer e.g., an open support layer
  • the first layer may be positioned downstream of the second layer with respect to the direction of fluid flow.
  • a layer when referred to as being "adjacent" another layer, it can be directly adjacent to the layer, or one or more intervening layers also may be present.
  • a layer that is "directly adjacent" another layer means that no intervening layer is present.
  • the filter media may comprise one or more additional layers (e.g., a meltblown layer, a spunbond layer) associated with the first layer (e.g., the open support layer).
  • additional layers e.g., a meltblown layer, a spunbond layer
  • an additional layer 130 e.g., a meltblown layer
  • second layer 120 is adjacent (e.g., directly adjacent) additional layer 130.
  • associated with means generally held in close proximity, for example, an additional layer associated with an open support layer may be adjacent the surface.
  • a (additional) layer when referred to as being associated with another layer, it can be directly adjacent to (e.g., in contact with) the surface, coated onto at least a portion of the layer, or one or more intervening components (e.g., fibers, layers) also may be present.
  • An additional layer that is associated with another layer may have no intervening component(s)/layer(s) present.
  • the additional layer is deposited on the open support layer e.g., such that the material(s) of the additional layer are coated on and/or interspersed between the fibers of the open support layer.
  • the additional layer is a separate layer, directly adjacent the open support layer.
  • the filter media may comprise an open support layer, a first additional layer (e.g., a meltblown layer, a spunbond layer) associated with the open support layer, a second additional layer (e.g., a fine fiber layer such as an electrospun layer) associated with the first additional layer, and, a second layer associated with the first and/or second additional layer.
  • the filter media may be an electret-containing media. For instance, a layer (e.g., a second layer) of the media may be charged.
  • the net charge of the layer may be negative or positive.
  • at least a surface of the second layer may comprise a negatively charged material and/or a positively charged material.
  • the polymers in the second layer e.g., the first polymer and the second polymer
  • the second layer is formed via a carding process (e.g., where the fibers are manipulated by rollers and extensions (e.g., hooks, needles)).
  • the polymer fibers within the second layer with a significant difference in dielectric constant and/or that are relatively far apart on the triboelectric series may undergo contact electrification as a result of the carding process to produce a charged non-woven web.
  • Charged non-woven webs may have enhanced performance properties, including an increased efficiency, compared to a similar non-woven web that is uncharged, all other factors being equal.
  • a layer may be neutral (e.g., have no net charge).
  • the filter media comprises an open support layer having a relatively high air permeability and/or a relatively low basis weight.
  • suitable open support layers include meshes, scrims, and netting.
  • the open support layer is a mesh (e.g., a mesh having an air permeability greater than 1100 CFM).
  • the open support layer is a scrim (e.g., a scrim having an air permeability greater than 1100 CFM).
  • the scrim is formed via a meltblown process or a spunbond process.
  • the open support layer may have certain desirable characteristics, such as basis weight, solidity, and/or air permeability.
  • the open support layer may have a basis weight of less than or equal to 200 g/m 2 , less than or equal to 100 g/m 2 , less than or equal to 90 g/m 2 , less than or equal to 85 g/m 2 , less than or equal to 80 g/m 2 , less than or equal to 70 g/m 2 , less than or equal to 60 g/m 2 , less than or equal to 50 g/m 2 , less than or equal to 40 g/m 2 , less than or equal to 30 g/m 2 , less than or equal to 25 g/m 2 , less than or equal to 10 g/m 2 , or less than or 2
  • the open support layer (e.g., a mesh) may have a basis weight of greater than or equal to 2 g/m 2 , greater than or equal to 3 g/m 2 , greater than or equal to 10 g/m 2 , greater than or equal to 25 g/m 2 , greater than or equal to 30 g/m 2 , greater than or equal to 40 g/m 2 , greater than or equal to 50 g/m 2 , greater than or equal to 60 g/m 2 , greater than or equal to 70 g/m 2 , greater than or equal to 80 g/m 2 , greater than 85 g/m 2 , greater than or equal to 90 g/m 2 , greater than or equal to 100 g/m 2 , or greater than or equal to 200 g/m .
  • a basis weight of less than or equal to 200 g/m and greater than or equal to 2 g/m 2 a basis weight of less than or equal to 50 g/m 2 and greater than or equal to 5 g/m .
  • Other values of basis weight are also possible.
  • the basis weight may be determined according to test standard ASTM D-846.
  • the open support layer has a relatively high air permeability.
  • the open support layer e.g., a mesh
  • the open support layer has an air permeability of greater than 1,100 CFM, greater than or equal to 1,250 CFM, greater than or equal to 1,500 CFM, greater than or equal to 1,750 CFM, greater than or equal to 2,000 CFM, greater than or equal to 2,500 CFM, greater than or equal to 3,000 CFM, greater than or equal to 5,000 CFM, greater than or equal to 7,500 CFM, greater than or equal to 10,000 CFM, greater than or equal to 12,500 CFM, greater than or equal to 15,000 CFM, or greater than or equal to 17,500 CFM.
  • the open support layer has an air permeability of less than or equal to 20,000 CFM, less than or equal to 17,500 CFM, less than or equal to 15,000 CFM, less than or equal to 12,500 CFM, less than or equal to 10,000 CFM, less than or equal to 7,500 CFM, less than or equal to 5,000 CFM, less than or equal to 3,000 CFM, less than or equal to 2,500 CFM, less than or equal to 2,000 CFM, less than or equal to 1,750 CFM, less than or equal to 1,500 CFM, or less than or equal to 1,250 CFM. Combinations of the above-referenced ranges are also possible (e.g., an air permeability of greater than 1,100 CFM and less than or equal to 20,000 CFM). Other values of air permeability are also possible. Air permeability of the open support layer, as determined herein, is measured according to the test standard ASTM D737 over 38 cm surface area of the media and using a pressure of 125 Pa.
  • the open support layer may be formed by a spunbond process and have an air permeability of greater than 500 CFM, greater than or equal to 600 CFM, greater than or equal to 700 CFM, greater than or equal to 800 CFM, greater than or equal to 900 CFM, greater than or equal to 1000 CFM, greater than or equal to 1100 CFM, greater than or equal to 1200 CFM, or greater than or equal to 1300 CFM.
  • the open support layer may have an air permeability of less than or equal to 1400 CFM, less than or equal to 1300 CFM, less than or equal to 1200 CFM, less than or equal to 1100 CFM, less than or equal to 1000 CFM, less than or equal to 900 CFM, less than or equal to 800 CFM, less than or equal to 700 CFM, or less than or equal to 600 CFM. Combinations of the above-referenced ranges are also possible (e.g., greater than 500 CFM and less than or equal to 1400 CFM). Other ranges are also possible.
  • the open support layer may have a solidity of less than or equal to 10%, less than or equal to 8%, less than or equal to 6%, less than or equal to 5%, less than or equal to 4%, less than or equal to 3%, less than or equal to 2%, less than or equal to 1%, or less than or equal to 0.5%. In some embodiments, the open support layer may have a solidity of greater than or equal to 0.1%, greater than or equal to 0.5%, greater than or equal to 1%, greater than or equal to 2%, greater than or equal to 3%, greater than or equal to 4%, greater than or equal to 5%, greater than or equal to 6%, or greater than or equal to 8%.
  • Solidity generally refers to the percentage of volume of solids with respect to the total volume of the layer.
  • the open support layer may have, in some cases, a particular strand count.
  • the strand count may be greater than or equal to 2 strands per inch, greater than or equal to 3 strands per inch, greater than or equal to 5 strands per inch, greater than or equal to 7 strands per inch, greater than or equal to 10 strands per inch, greater than or equal to 12 strands per inch, greater than or equal to 15 strands per inch, greater than or equal to 17 strands per inch, greater than or equal to 20 strands per inch, greater than or equal to 22 strands per inch, or greater than or equal to 25 strands per inch.
  • the strand count may be less than or equal to 27 strands per inch, less than or equal to 25 strands per inch, less than or equal to 22 strands per inch, less than or equal to 20 strands per inch, less than or equal to 17 strands per inch, less than or equal to 15 strands per inch, less than or equal to 12 strands per inch, less than or equal to 10 strands per inch, less than or equal to 7 strands per inch, less than or equal to 5 strands per inch, or less than or equal to 3 strands per inch.
  • Other ranges of strand count are also possible.
  • Strand count is measured along a first axis of the open support layer.
  • the open support layer e.g., a mesh
  • the open support layer may have a first strand count in a first axis of the open support layer, and a second strand count, different than the first strand count, in a second axis of the open support layer orthogonal to the first axis.
  • the second strand count measured along a second axis of the open support layer may range as noted above in the context of the strand count measured along a first axis of the open support layer (e.g., a second strand count of greater than or equal to 2 strands per inch and less than or equal to 27 strands per inch, greater than or equal to 3 strands per inch and less than or equal to 20 strands per inch).
  • the term axis generally refers to a reference direction of the layer parallel to one or more strands in the layer.
  • strand count may be determined by counting the number of strands per inch laying substantially perpendicular to the particular axis (e.g., the number of strands/fibers intersecting the strand parallel to the axis).
  • the open support layer comprises a plurality of fibers or strands.
  • the fibers or strands of the open support layer may be continuous or non- continuous.
  • Continuous fibers e.g., strands
  • Non-continuous fibers are, for example, staple fibers that are generally cut (e.g., from a filament) or formed as non- continuous discrete fibers to have a particular length or a range of lengths as described in more detail below.
  • the plurality of fibers or strands of the open support layer include synthetic fibers or strands (e.g., synthetic polymer fibers or strands).
  • the synthetic fibers or strands of the open support layer may be continuous fibers.
  • suitable synthetic fibers/strands include polyester, polyaramid, polyimide, polyolefin (e.g., polyethylene such as high density polyethylene, low density polyethylene, and/or linear low density polyethylene), ethylene- vinyl acetate, polyacrylamide, polylactic acid, polypropylene, Kevlar, Nomex, halogenated polymers (e.g., polyethylene terephthalate), acrylics, polyphenylene oxide, polyphenylene sulfide, thermoplastic elastomers (e.g., thermoplastic polyurethane), polymethyl pentene, and combinations thereof.
  • the open support layer is a fibrous layer, an extruded layer, an oriented layer, a woven layer, or a non-woven layer.
  • an adhesive is co-extruded with one or more
  • fibers/strands of the open support layer e.g., for joining the open support layer to a second layer.
  • the plurality of fibers (or strands) in the open support layer may have an average fiber (or strand) diameter of greater than or equal to 0.5 microns, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 3 microns, greater than or equal to 4 microns, greater than or equal to 5 microns, greater than or equal to 6 microns, greater than or equal to 8 microns, greater than or equal to 10 microns, greater than or equal to 15 microns, greater than or equal to 20 microns, greater than or equal to 50 microns, greater than or equal to 75 microns, greater than or equal to 100 microns, greater than or equal to 250 microns, greater than or equal to 500 microns, greater than or equal to 750 microns, greater than or equal to 1 mm, greater than or equal to 1.25 mm, greater than or equal to 1.5 mm, or greater than or equal to 1.75 mm.
  • the plurality of fibers in the open support layer may have an average fiber (or strand) diameter of less than or equal to 2 mm, less than or equal to 1.75 mm, less than or equal to 1.5 mm, less than or equal to 1.25 mm, less than or equal to 1 mm, less than or equal to 750 microns, less than or equal to 500 microns, less than or equal to 250 microns, less than or equal to 100 microns, less than or equal to 75 microns, less than or equal to 50 microns, less than or equal to 20 microns, less than or equal to 15 microns, less than or equal to 10 microns, less than or equal to 8 microns, less than or equal to 7 microns, less than or equal to 6 microns, less than or equal to 5 microns, less than or equal to 4 microns, less than or equal to 3 microns, less than or equal to 2 microns, or less than or equal to 1 micron.
  • Combinations of the above- referenced ranges are also possible (e.g., greater than or equal to 0.5 microns and less than or equal to 2 mm, greater than or equal to 0.5 microns and less than or equal to 10 microns, greater than or equal to 10 microns and less than or equal 20 microns, greater than or equal to 500 microns and less than or equal to 2 mm).
  • Other values of average fiber (or strand) diameter for the open support layer are also possible.
  • Individual fiber/strand diameters within the open support layer may be measured by microscopy, for example scanning electron microscopy (SEM), and statistics regarding fiber/strand diameter such as average fiber/strand diameter, median fiber/strand diameter, and fiber/strand diameter standard deviation may be determined by performing appropriate statistical techniques on the measured fiber/strand diameters.
  • SEM scanning electron microscopy
  • the open support layer is formed by a spunbond process and comprises a plurality of fibers having an average fiber diameter of greater than or equal to 10 microns and less than or equal to 20 microns
  • the open support layer is formed by a meltblown process and comprises a plurality of fibers having an average fiber diameter of greater than or equal to 0.5 microns and less than or equal to 10 microns.
  • the open support layer is a mesh and comprises a plurality of strands having an average strand diameter of greater than or equal to 500 microns and less than or equal to 2 mm.
  • the open support layer comprises a plurality of fibers (e.g., synthetic fibers, continuous fibers) (or strands) having a continuous length.
  • the plurality of fibers (or strands) in the open support layer may have an average length of greater than about 5 inches, greater than or equal to 10 inches, greater than or equal to 25 inches, greater than or equal to 50 inches, greater than or equal to 100 inches, greater than or equal to 300 inches, greater than or equal to 500 inches, greater than or equal to 700 inches, or greater than or equal to 900 inches.
  • the fibers may have an average length of less than or equal to 1000 inches, less than or equal to 800 inches, less than or equal to 600 inches, less than or equal to 400 inches, or less than or equal to 100 inches. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 50 inches and less than or equal to 1000 inches). Other ranges are also possible.
  • the open support layer comprises a plurality of fibers (e.g., synthetic fibers, staple fibers) (or strands) having an average length of less than about 5 inches (127 mm).
  • the plurality of fibers (or strands)in the open support layer may have an average length of, for example, less than or equal to 100 mm, less than or equal to 80 mm, less than or equal to 60 mm, less than or equal to 40 mm, less than or equal to 20 mm, less than or equal to 10 mm, less than or equal to 5 mm, less than or equal to 1 mm, less than or equal to 0.5 mm, or less than or equal to 0.1 mm.
  • plurality of fibers (or strands) in the open support layer may have an average length of greater than or equal to 0.02 mm, greater than or equal to 0.1 mm, greater than or equal to 0.5 mm, greater than or equal to 1 mm, greater than or equal to 5 mm, greater than or equal to 10 mm, greater than or equal to 20 mm, greater than or equal to 40 mm, greater than or equal to 60 mm. Combinations of the above-referenced ranges are possible (e.g., greater than or equal to 0.02 mm and less than or equal to 80 mm, greater than or equal to 0.03 mm and less than or equal to 40 mm). Other ranges are also possible.
  • the open support layer has a dry tensile strength of greater than or equal 4 lbs/in, greater than or equal to 5 lbs/in, greater than or equal to 7 lbs/in, greater than or equal to 10 lbs/in, greater than or equal to 15 lbs/in, greater than or equal to 20 lbs/in, greater than or equal to 25 lbs/in, greater than or equal to 30 lbs/in, greater than or equal to 35 lbs/in, greater than or equal to 40 lbs/in, greater than or equal to 45 lbs/in, greater than or equal to 50 lbs/in, or greater than or equal to 55 lbs/in.
  • the open support layer has a dry tensile strength of less than or equal to 60 lbs/in, less than or equal to 55 lbs/in, less than or equal to 50 lbs/in, less than or equal to 45 lbs/in, less than or equal to 40 lbs/in, less than or equal to 35 lbs/in, less than or equal to 30 lbs/in, less than or equal to 25 lbs/in, less than or equal to 20 lbs/in, less than or equal to 15 lbs/in, less than or equal to 10 lbs/in, less than or equal to 7 lbs/in, or less than or equal to 5 lbs/in.
  • a dry tensile strength of greater than or equal to 4 lbs/in and less than or equal to 60 lbs/in, greater than or equal to 10 lbs/in and less than or equal to 30 lbs/in.
  • Other ranges are also possible.
  • the dry tensile strength is measured according to the standard EN/ISO 1924-4 using a jaw separation speed of 10 mm/min and a sample size of 3 inches by 6 inches.
  • the open support layer may have a particular thickness.
  • the thickness is greater than or equal to 10 microns, greater than or equal to 15 microns, greater than or equal to 20 microns, greater than or equal to 50 microns, greater than or equal to 75 microns, greater than or equal to 100 microns, greater than or equal to 250 microns, greater than or equal to 500 microns, greater than or equal to 750 microns, greater than or equal to 1 mm, greater than or equal to 1.25 mm, greater than or equal to 1.5 mm, or greater than or equal to 1.75 mm.
  • the thickness of the the open support layer may be less than or equal to 2 mm, less than or equal to 1.75 mm, less than or equal to 1.5 mm, less than or equal to 1.25 mm, less than or equal to 1 mm, less than or equal to 750 microns, less than or equal to 500 microns, less than or equal to 250 microns, less than or equal to 100 microns, less than or equal to 75 microns, less than or equal to 50 microns, less than or equal to 20 microns, or less than or equal to 15 microns,.
  • Thickness as determined herein, may be measured according to ASTM standard D-1777 at 0.3 psi.
  • the open support layer may have a dry tensile elongation at break of greater than or equal to 5%.
  • the open support layer may have a dry tensile elongation at break of greater than or equal to 5%, greater than or equal to 10%, greater than or equal to 20%, greater than or equal to 30%, greater than or equal to 40%, greater than or equal to 50%, greater than or equal to 60%, greater than or equal to 70%, greater than or equal to 80%, greater than or equal to 90%, greater than or equal to 100%, greater than or equal to 110%, greater than or equal to 120%, greater than equal to 130%, or greater than or equal to 140%.
  • the open support layer may have a dry tensile elongation at break of less than or equal to 150%, less than or equal to 140%, less than or equal to 130%, less than or equal to 120%, less than or equal to 110%, less than or equal to 100%, less than or equal to 90%, less than or 80%, less than or equal to 70%, less than or equal to 60%, less than or equal to 50%, less than or equal to 40%, less than or equal to 30%, less than or equal to 20%, or less than or equal to 10%. Combinations of the above reference ranges are also possible (e.g., greater than or equal to 5% and less than or equal to 150%, greater than or equal to 10% and less than or equal to 60%). Other ranges are also possible. As determined herein, the dry tensile elongation at break is measured according to the standard EN/ISO 1924-4 using a jaw separation speed of 10 mm/min.
  • the first layer e.g., an open support layer such as a mesh
  • the second layer e.g., a charged fiber layer
  • the first layer e.g., an open support layer such as a mesh
  • the second layer e.g., a charged fiber layer
  • adhesives e.g., glue-web
  • the first layer (e.g., the open support layer) and the second layer may be mechanically attached.
  • suitable means for mechanical attachment include needling, stitching, and hydroentangling.
  • the first layer is needled to the second layer.
  • the first layer and the second layer may be mechanically attached to one another such that the filter media comprising the first layer and the second layer is substantially free of adhesives.
  • an open support layer is mechanically attached to the second layer (e.g., a charged fiber layer) and are joined to one another without an adhesive.
  • the open support layer and the second layer may be joined to one another by mechanical attachment and an adhesive.
  • the needling may have a particular punch density.
  • the punch density of needling is greater than or equal to 1 punch per square centimeter, greater than or equal to 2 punches per square centimeter, greater than or equal to 3 punches per square centimeter, greater than or equal to 5 punches per square centimeter, greater than or equal to 7 punches per square centimeter, greater than or equal to 10 punches per square centimeter, greater than or equal to 15 punches per square centimeter, greater than or equal to 20 punches per square centimeter, greater than or equal to 25 punches per square centimeter, greater than or equal to 30 punches per square centimeter, greater than or equal to 35 punches per square centimeter, greater than or equal to 40 punches per square centimeter, greater than or equal to 45 punches
  • the needling punch density is less than or equal to 60 punches per square centimeter, less than or equal to 55 punches per square centimeter, less than or equal to 50 punches per square centimeter, less than or equal to 45 punches per square centimeter, less than or equal to 40 punches per square centimeter, less than or equal to 35 punches per square centimeter, less than or equal to 30 punches per square centimeter, less than or equal to 25 punches per square centimeter, less than or equal to 20 punches per square centimeter, less than or equal to 15 punches per square centimeter, less than or equal to 10 punches per square centimeter, less than or equal to 7 punches per square centimeter, less than or equal to 5 punches per square centimeter, less than or equal to 3 punches per square centimeter, or less than or equal to 2 punches per square centimeter.
  • Combinations of the above referenced ranges are also possible (e.g., greater than or equal to 1 punches per square centimeter and less than or equal to 60 punches per square centimeter, greater than or equal to 1 punches per square centimeter and less than or equal to 10 punches per square centimeter, greater than or equal to 15 punches per square centimeter and less than or equal to 60 punches per square centimeter, greater than or equal to 25 punches per square centimeter and less than or equal to 45 punches per square centimeter). Other ranges are also possible.
  • the open support layer may be needled to the charged fiber layer using a particular penetration depth of needling across at least the two layers.
  • the penetration depth of needling across two or more layers of the filter media is greater than or equal to 8 mm, greater than or equal to 10 mm, greater than or equal to 12 mm, greater than or equal to 14 mm, greater than or equal to 16 mm, or greater than or equal to 18 mm.
  • the penetration depth of needling across two or more layers of the filter media is less than or equal to 20 mm, less than or equal to 18 mm, less than or equal to 16 mm, less than or equal to 14 mm, less than or equal to 12 mm, or less than or equal to 10 mm. Combinations of the above referenced ranges are also possible (e.g., a penetration depth of needling of greater than or equal to 8 mm and less than or equal to 20 mm, greater than or equal to 12 mm and less than or equal to 16 mm). Other ranges are also possible.
  • the second layer is a charged fiber layer.
  • the charged fiber layer comprises a plurality of fibers.
  • the fibers of the second layer may be non-continuous (e.g., staple fibers).
  • the charged fiber layer may have certain structural characteristics, such as basis weight and/or fiber diameter.
  • the charged fiber layer may have a basis weight of greater than or equal to
  • the charged fiber layer may have a basis weight of less than or equal to 700 g/m 2 , less than or equal to 600 g/m 2 , less than or equal to 500 g/m 2 , or greater than or equal to 600 g/m 2.
  • 400 g/m 2 less than or equal to 300 g/m 2 , less than or equal to 200 g/m 2 , less than or equal to 100 g/m 2 , less than or equal to 90 g/m 2 , less than or equal to 80 g/m 2 , less than or equal to 70 g/m 2 , less than or equal to 60 g/m 2 , less than or equal to 50 g/m 2 , less than or equal to 40 g/m 2 , less than or equal to 30 g/m 2 , less than or equal to 25 g/m 2 , less than or equal to 20 g/m 2 , or less than or equal to 15 g/m 2.
  • a basis weight of greater than or equal to 12 g/m 2 and less than or equal to 700 g/m 2 a basis weight of greater than or equal to 12 g/m 2 and less than or equal to 250 g/m 2 , a basis weight of greater than or equal to 15 g/m 2 and less than or equal to 100 g/m 2 ).
  • Other values of basis weight are also possible.
  • the basis weight may be determined as described above.
  • the charged fiber layer may comprise a plurality of fibers having a particular average fiber diameter.
  • the plurality of fibers of the second layer have an average fiber diameter of greater than or equal tol micron, greater than or equal to 2 microns, greater than or equal to 3 microns, greater than or equal to 5 microns, greater than or equal to 7 microns, greater than or equal to 9 microns, greater than or equal to 10 microns, greater than or equal to 12 microns, greater than or equal to 14 microns, greater than or equal to 15 microns, greater than or equal to 16 microns, greater than or equal to 18 microns, greater than or equal to 19 microns, greater than or equal to 20 microns, or greater than or equal to 21 microns.
  • the plurality of fibers of the second layer have an average fiber diameter of greater than or equal tol micron, greater than or equal to 2 microns, greater than or equal to 3 microns, greater than or equal to 5 microns, greater than or equal to 7 micron
  • the plurality of fibers of the second layer have an average fiber diameter of less than or equal to 22 microns, less than or equal to 21 microns, less than or equal to 20 microns, less than or equal to 19 microns, less than or equal to 18 microns, less than or equal to 16 microns, less than or equal to 15 microns, less than or equal to 14 microns, less than or equal to 12 microns, less than or equal to 10 microns, less than or equal to 9 microns, less than or equal to 7 microns, less than or equal to 5 microns, less than or equal to 4 microns, less than or equal to 3 microns, or less than or equal to 2 microns.
  • the charged fiber layer may comprise a plurality of fibers that are relatively fine (e.g., having an average fiber diameter less than 15 microns).
  • the second layer comprises a plurality of fibers having an average fiber diameter less than 15 microns, less than or equal to 14 microns, less than or equal to 12 microns, less than or equal to 10 microns, less than or equal to 9 microns, less than or equal to 7 microns, less than or equal to 5 microns, less than or equal to 4 microns, less than or equal to 3 microns, or less than or equal to 2 microns.
  • the second layer comprises a plurality of fibers having an average fiber diameter of greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 3 microns, greater than or equal to 5 microns, greater than or equal to 7 microns, greater than or equal to 9 microns, greater than or equal to 10 microns, greater than or equal to 12 microns, or greater than or equal to 14 microns.
  • the filter media comprises an open support layer (i.e. a first layer) and a charged fiber layer (i.e. a second layer) adjacent the open support layer, the charged fiber layer comprising a plurality of fibers having an average fiber diameter less than 15 microns.
  • the charged fiber layer may comprise a one or more plurality of fibers.
  • the charged fiber layer comprises a first plurality of fibers (e.g., comprising a first polymer) and a second plurality of fibers (e.g., comprising a second polymer, different than the first polymer).
  • each of the plurality of fibers e.g., the first plurality of fibers, the second plurality of fibers
  • the charged fiber layer comprises a first plurality of fibers and a second plurality of fibers, the first plurality of fibers and/or the second plurality of fibers having an average fiber diameter of less than 15 microns and greater than or equal to 1 micron.
  • the charged fiber layer comprises a first plurality of fibers and a second plurality of fibers, the first plurality of fibers and/or the second plurality of fibers having an average fiber diameter of greater than or equal to 1 micron and less than or equal to 22 microns.
  • the plurality of fibers of the charged fiber layer include synthetic fibers (synthetic polymer fibers).
  • the synthetic fibers of the second layer may be staple fibers.
  • suitable synthetic fibers include polypropylene, dry-spun acrylic (e.g., produced from a dry-spinning process), polyvinyl chloride, mod-acrylic, wet spun acrylic, polytetrafluoroethylene, polypropylene, polystyrene, polysulfone, polyethersulfone, polycarbonate, nylon (e.g., nylon 6/6), polyurethane, phenolic, polyvinylidene fluoride, polyester, polyaramid, polyimide, polyolefin (e.g., polyethylene), Kevlar, Nomex, halogenated polymers (e.g., polyethylene terephthalate), polyacrylics, polyphenylene oxide, polyphenylene sulfide, polymethyl pentene, and combinations thereof.
  • the synthetic fibers are halogen-free such that significant dioxins are not detectable when incinerated.
  • the fibers may be halogen-free acrylic fibers formed by dry spinning.
  • the second layer and/or the entire filter media is halogen-free such that significant dioxins are not detectable when incinerated.
  • the charged fiber layer comprises a mixture of two or more polymeric fibers.
  • the charged fiber layer may comprise at least a first plurality of fibers comprising a first polymer and a second plurality of fibers comprising a second polymer.
  • the charged fiber layer comprises a first plurality of fibers comprising a first polymer where the first polymer is acrylic (e.g., dry-spun acrylic).
  • the charged fiber layer comprises a second plurality of fibers comprising a second type of polymer fiber, different than the first type of polymer fiber.
  • the second type of polymer fiber is polypropylene.
  • the first polymer and the second polymer are selected such that the first polymer and the second polymer have different dielectric constants.
  • the two polymers having different dielectric constants may facilitate charging of the layer (e.g., triboelectric charging).
  • two polymers with different dielectric constants in the layer may come into frictional contact during manufacture of the layer such that one polymer will lose electrons and give them away to the other polymer and, as a result, the polymer losing electrons is net positively charged, the other polymer receiving electrons is net negatively charged.
  • the second layer of the filter media is a charged fiber layer
  • the charged layer may have one or more characteristics described in commonly-owned U.S. Patent No. 6,623,548, entitled “Filter materials and methods for the production thereof, issued September 23, 2003, which is incorporated herein by reference in its entirety for all purposes.
  • the second layer is an electrostatically charged layer formed by blending together polypropylene fibers with halogen free acrylic fibers, polypropylene with polyvinyl chloride (PVC) fibers, or a mixture of halogen free acrylic fibers and PVC fibers and, optionally, carding the blended fibers so as to form a non- woven fabric.
  • the difference in dielectric constants between the first polymer and the second polymer may be selected to be greater than or equal to 0.8, greater than or equal to 1, greater than or equal to 1.2, greater than or equal to 1.5, greater than or equal to 2, greater than or equal to 3, greater than or equal to 5, or greater than or equal to 7.
  • the difference in dielectric constants between the first polymer and the second polymer may be selected to be less than or equal to 8, less than or equal to 7, less than or equal to 5, less than or equal to 3, less than or equal to 2, less than or equal to 1.5, less than or equal to 1.2, or less than or equal to 1.
  • Table 1 shows representative dielectric constants for several exemplary polymers.
  • the first polymer and the second polymer may be present in the second layer in any suitable amount.
  • the first polymer is present in the second layer in an amount of greater than or equal to 10 wt%, greater than or equal to 15 wt%, greater than or equal to 20 wt%, greater than or equal to 25 wt%, greater than or equal to 30 wt%, greater than or equal to 35 wt%, greater than or equal to 40 wt%, greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 65 wt%, greater than or equal to 70 wt%, greater than or equal to 75 wt%, greater than or equal to 80 wt%, or greater than or equal to 85 wt% with respect to the total amount of fibers in the layer and/or the total weight of the layer.
  • the first polymer is present in the second layer in an amount of less than or equal to 90 wt%, less than or equal to 85 wt%, less than or equal to 80 wt%, less than or equal to 75 wt%, less than or equal to 70 wt%, less than or equal to 65 wt%, less than or equal to 60 wt%, less than or equal to 50 wt%, less than or equal to 40 wt%, less than or equal to 35 wt%, less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, or less than or equal to 15 wt% with respect to the total amount of fibers in the layer and/or the total weight of the layer.
  • the second polymer is present in the second layer in an amount of less than or equal to 90 wt%, less than or equal to 85 wt%, less than or equal to 80 wt%, less than or equal to 75 wt%, less than or equal to 70 wt%, less than or equal to 65 wt%, less than or equal to 60 wt%, less than or equal to 50 wt%, less than or equal to 40 wt%, less than or equal to 35 wt%, less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, or less than or equal to 15 wt% with respect to the total amount of fibers in the layer and/or the total weight of the layer.
  • the second polymer is present in the second layer in an amount of greater than or equal to 10 wt%, greater than or equal to 15 wt%, greater than or equal to 20 wt%, greater than or equal to 25 wt%, greater than or equal to 30 wt%, greater than or equal to 35 wt%, greater than or equal to 40 wt%, greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 65 wt%, greater than or equal to 70 wt%, greater than or equal to 75 wt%, greater than or equal to 80 wt%, or greater than or equal to 85 wt% with respect to the total amount of fibers in the layer and/or the total weight of the layer.
  • the second layer comprises the first polymer in an amount of greater than or equal to 10 wt% and less than or equal to 90 wt% and the second polymer in an amount of less than or equal to 90 wt% and greater than or equal to 10 wt% with respect to the total amount of fibers in the layer.
  • the second layer comprises the first polymer in an amount of greater than or equal to 25 wt% and less than or equal to 75 wt% and the second polymer in an amount of less than or equal to 75 wt% and greater than or equal to 25 wt% with respect to the total amount of fibers in the layer.
  • the second layer may comprise the first polymer in an amount of greater than or equal to 35 wt% and less than or equal to 65 wt%, and the second polymer in an amount of less than or equal to 65 wt% and greater than or equal to 35 wt%, with respect to the total amount of fibers in the layer.
  • the second layer comprises each of the first polymer and the second polymer in an amount of about 50 wt% with respect to the total amount of fibers in the layer.
  • the charged fiber layer comprises a plurality of fibers (e.g., synthetic fibers, staple fibers) having an average length of less than 5 inches (127 mm).
  • the plurality of fibers in the charged fiber layer may have an average length of, for example, less than or equal to 100 mm, less than or equal to 80 mm, less than or equal to 60 mm, less than or equal to 40 mm, less than or equal to 20 mm, less than or equal to 10 mm, less than or equal to 5 mm, less than or equal to 1 mm, less than or equal to 0.5 mm, or less than or equal to 0.1 mm.
  • plurality of fibers in the charged fiber layer may have an average length of greater than or equal to 0.02 mm, greater than or equal to 0.1 mm, greater than or equal to 0.5 mm, greater than or equal to 1 mm, greater than or equal to 5 mm, greater than or equal to 10 mm, greater than or equal to 20 mm, greater than or equal to 40 mm, greater than or equal to 60 mm. Combinations of the above-referenced ranges are possible (e.g., greater than or equal to 1 mm and less than or equal to 80 mm, greater than or equal to 1 mm and less than or equal to 60 mm). Other ranges are also possible.
  • the charged fiber layer may be designed to have a relatively high surface area and/or a relatively low number of fibers per gram (of the layer).
  • a charged fiber layer having a relatively high surface area per gram (of the layer) and a relatively low number of fibers per gram (of the layer) may exhibit an increased initial efficiency, increased charge generation (e.g., triboelectric charge), and/or decreased charge dissipation (e.g., during use of the layer and/or a filter media comprising the layer), as compared to layers having a relatively low surface areas per unit mass and/or relatively higher numbers of fibers per gram of the layer.
  • increased charge generation e.g., triboelectric charge
  • charge dissipation e.g., during use of the layer and/or a filter media comprising the layer
  • the BET surface area of the charged fiber layer is greater than or equal to 0.33 m 2 /g, greater than or equal to 0.35 m 2 /g, greater than or equal to
  • 0.37 m 2 /g greater than or equal to 0.4 m 2 /g, greater than or equal to 0.5 m 2 /g, greater than or equal to 0.6 m 2 /g, greater than or equal to 0.7 m 2 /g, greater than or equal to 0.8 m 2 /g, greater than or equal to 0.9 m 2 /g, greater than or equal to 1 m 2 /g, or greater than or equal to 1.2 m /g.
  • the BET surface area of the charged fiber layer is less than or equal to 1.5 m 2 /g, less than or equal to 1.2 m 2 /g, less than or equal to 1 m 2 /g, less than or equal to 0.9 m 2 /g, less than or equal to 0.8 m 2 /g, less than or equal to 0.75 m 2 /g, less than or equal to 0.7 m 2 /g, less than or equal to 0.6 m 2 /g, less than or equal to 0.5 m 2 /g, less than or equal to 0.4 m 2 /g, less than or equal to 0.37 m 2 /g, or less than or equal to 0.35 m /g.
  • Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.33 m 2 /g and less than or equal to 1.5 m 2 /g, greater than or equal to 0.35 m 2 /g and less than or equal to 1 m 2 /g). Other ranges are also possible.
  • BET surface area is measured through use of a standard
  • the BET surface area is measured according to section 10 of Battery Council International Standard BCIS-03A, "Recommended Battery Materials Specifications Valve Regulated Recombinant Batteries", section 10 being "Standard Test Method for Surface Area of Recombinant Battery Separator Mat”. Following this technique, the BET surface area is measured via adsorption analysis using a BET surface analyzer (e.g., Micromeritics Gemini III 2375 Surface Area Analyzer) with nitrogen gas; the sample amount is between 0.5 and 0.6 grams in a 3/4" tube; and, the sample is allowed to degas at 75 degrees C for a minimum of 3 hours.
  • a BET surface analyzer e.g., Micromeritics Gemini III 2375 Surface Area Analyzer
  • the charged fiber layer has a particular number of fibers per gram (of fiber layer). In some embodiments, the charged fiber layer has less than or equal to 125,000 fibers, less than or equal to 120,000 fibers, less than or equal to 110,000 fibers, less than or equal to 105,000 fibers, less than or equal to 103,000 fibers, less than or equal to 100,000 fibers, less than or equal to 95,000 fibers, less than or equal to 90,000 fibers, less than or equal to 80,000 fibers, less than or equal to 75,000 fibers, less than or equal to 70,000 fibers, or less than or equal to 60,000 fibers per gram (of fiber layer).
  • the charged fiber layer has greater than or equal to 50,000 fibers, greater than or equal to 60,000 fibers, greater than or equal to 70,000 fibers, greater than or equal to 75,000 fibers, greater than or equal to 80,000 fibers, greater than or equal to 90,000 fibers, greater than or equal to 95,000 fibers, greater than or equal to 100,000 fibers, greater than or equal to 103,000 fibers, greater than or equal to 105,000 fibers, greater than or equal to 110,000 fibers, or greater than or equal to 120,000 fibers per gram (of fiber layer).
  • the number of fibers per gram (of fiber layer) may be determined by dividing the average BET surface area of the fiber layer (e.g., the charged fiber layer) by the average geometric surface area of the fibers in the (charged) fiber layer.
  • Average geometric surface area of the fibers in the (charged) fiber layer may be determined, in some cases, by measuring the average cross-sectional perimeter of the fibers (e.g., by Scanning Electron Microscopy) and multiplying by the average fiber length.
  • the charged fiber layer has a BET surface area greater than or equal to 0.33 m 2 /g (e.g., greater than or equal to 0.33 m 2 /g and less than or equal to 1.5 m /g) and less than or equal to 125,000 fibers (e.g., less than or equal to 125,000 fibers and greater than or equal to 50,000 fibers per gram) per gram (of charged fiber layer).
  • the first plurality of fibers and/or the second plurality of fibers of the charged fiber layer have a particular average largest cross-sectional dimension, for example, of greater than or equal to 2 microns, greater than or equal to 2.5 microns, greater than or equal to 3 microns, greater than or equal to 5 microns, greater than or equal to 7 microns, greater than or equal to 9 microns, greater than or equal to 10 microns, greater than or equal to 12 microns, or greater than or equal to 14 microns.
  • the first plurality of fibers and/or the second plurality of fibers of the charged fiber have an average largest cross-sectional dimension of less than or equal to 15 microns, less than or equal to 14 microns, less than or equal to 12 microns, less than or equal to 10 microns, less than or equal to 9 microns, less than or equal to 7 microns, less than or equal to 5 microns, or less than or equal to 3 microns.
  • the first plurality of fibers and/or the second plurality of fibers of the charged fiber layer may be designed to have a particular cross- sectional shape.
  • the cross-sectional shape of the first plurality of fibers and/or second plurality of fibers is selected from the group consisting of round, elliptical, dogbone, kidney bean, ribbon, irregular, and multi-lobal.
  • the first plurality of fibers and/or the second plurality of fibers have a multi-lobal shape (e.g., dilobal, trilobal, quadralobal, pentalobal, polylobal).
  • a multilobal shaped fiber generally refers to a fiber having, at a cross- section of the fiber, two or more (e.g., three or more, four or more, five or more) lobes extending from a core of the fiber.
  • the lobes may be, in some cases, the same or different material as the core.
  • the lobes and the core of the fiber are the same material.
  • the fiber is a bicomponent or multi- component fiber (e.g., the lobe(s) and the core comprise different materials).
  • the charged fiber layer may be designed to have a particular uncompressed thickness.
  • the uncompressed thickness of the charged fiber layer may be greater than or equal to greater than or equal to 5 mils, greater than or equal to 10 mils, greater than or equal to 25 mils, greater than or equal to 30 mils, greater than or equal to 50 mils, greater than or equal to 100 mils, greater than or equal to 200 mils, greater than or equal to 250 mils, greater than or equal to 300 mils, greater than or equal to 350 mils, greater than or equal to 400 mils, greater than or equal to 450 mils, or greater than or equal to 500 mils.
  • the uncompressed thickness of the charged fiber layer may be greater than or equal to 5 mils, greater than or equal to 10 mils, greater than or equal to 25 mils, greater than or equal to 30 mils, greater than or equal to 50 mils, greater than or equal to 100 mils, greater than or equal to 200 mils, greater than or equal to 250 mils, greater than or equal to 300 mils, greater than or equal
  • uncompressed thickness of the charged fiber layer may be less than or equal to 600 mils, less than or equal to 500 mils, less than or equal to 450 mils, less than or equal to 400 mils, less than or equal to 350 mils, less than or equal to 300 mils, less than or equal to 250 mils, less than or equal to 200 mils, less than or equal to 100 mils, less than or equal to 50 mils, less than or equal to 25 mils, or less than or equal to 10 mils. Combinations of the above referenced ranges are also possible (e.g., greater than or equal to 5 mils and less than or equal to 600 mils, greater than or equal to 30 mils and less than or equal to 350 mils). Other ranges are also possible.
  • Uncompressed thickness is determined using a Mitutoyo thickness gauge. Briefly, the fiber layer is compressed using a circular probe having a diameter of 1 mm under at least three different weights (e.g., 10 grams, 5 grams, 2 grams). The ordinary least squares linear regression is determined for each weight and corresponding thickness, and is used to calculated the thickness of the fiber layer corresponding to 0 grams of applied weight (i.e. The uncompressed thickness for that layer).
  • the charged fiber layer may have a particular air permeability.
  • the air permeability of the charged fiber layer is greater than or equal to 10 CFM, greater than or equal to 25 CFM, greater than or equal to 50 CFM, greater than or equal to 80 CFM, greater than or equal to 100 CFM, greater than or equal to 200 CFM, greater than or equal to 250 CFM, greater than or equal to 300 CFM, greater than or equal to 350 CFM, greater than or equal to 400 CFM, greater than or equal to 450 CFM, greater than or equal to 500 CFM, greater than or equal to 550 CFM, greater than or equal to 600 CFM, greater than or equal to 650 CFM, greater than or equal to 700 CFM, greater than or equal to 750 CFM, greater than or equal to 800 CFM, greater than or equal to 850 CFM, greater than or equal to 900 CFM, greater than or equal to 950 CFM, greater than or equal to 1000 CFM, greater than or equal to 1050 CFM, greater than or equal to
  • the air permeability of the charged fiber layer is less than or equal to 1200 CFM, less than or equal to 1150 CFM, less than or equal to 1100 CFM, less than or equal to 1050 CFM, less than or equal to 1000 CFM, less than or equal to 950 CFM, less than or equal to 900 CFM, less than or equal to 850 CFM, less than or equal to 800 CFM, less than or equal to 750 CFM, less than or equal to 700 CFM, less than or equal to 650 CFM, less than or equal to 600 CFM, less than or equal to 550 CFM, less than or equal to 500 CFM, less than or equal to 450 CFM, less than or equal to 400 CFM, less than or equal to 350 CFM, less than or equal to 300 CFM, less than or equal to 250 CFM, less than or equal to 200 CFM, less than or equal to 150 CFM, less than or equal to 100 CFM, less than or equal to 80 CFM, less than or equal to 50 CFM, or less than
  • Air permeability of the second layer is measured according to the test standard ASTM D737 over 38 cm surface area of the media and using a pressure of 125 Pa.
  • the filter media comprises a first layer and a second layer as described above and herein.
  • the filter media comprises an open support layer (i.e. The first layer) and a charged fiber layer (i.e. The second layer) mechanically attached to the open support layer.
  • filter media 100 comprises an open support layer (i.e. first layer 110) mechanically attached to a charged fiber layer (i.e. second layer 120).
  • the open support layer has an air permeability of greater than 1100 CFM and less than or equal to 20000 CFM and/or a solidity of less than or equal to 10%.
  • the open support layer may be a mesh.
  • the filter media includes an open support layer (e.g., a mesh) mechanically attached (e.g., needled) to a charged fiber layer comprising a plurality of fibers having a relatively low fiber diameter.
  • an open support layer e.g., a mesh
  • the incorporation of fibers having relatively low fiber diameters increases the surface area of the fiber layer and generally increases filtration performance and/or provides a relatively low pressure drop across the fiber layer.
  • the filter media may comprise one or more additional layers associated with the first layer (e.g., the open support layer).
  • the one or more additional layers may be selected from a meltblown layer, a spunbond layer, or a carded web layer.
  • At least one layer of the one or more additional layers is a meltblown layer.
  • the additional layer may be formed by, and/or comprises fibers formed by, a meltblown process. Meltblown processes are described in more detail, below.
  • at least one layer of the one or more additional layers is a spunbond layer.
  • the spubbond layer may be formed by, and/or comprise fibers formed by, a spunbond process.
  • At least one layer of the one or more additional layers may be a carded fiber layer.
  • the first layer e.g., an open support layer such as a mesh
  • the one or more additional layer(s) e.g., a meltblown layer
  • the open support layer and the additional layer(s) may be mechanically attached e.g., to the charged fiber layer.
  • the open support layer and/or additional layer is laminated to the charged support layer.
  • the open support layer and/or additional layer is needled to the charged support layer.
  • the open support layer, the additional layer(s), and/or the charged fiber layer may be mechanically attached to one another such that the filter media comprising the open support layer, the additional layer(s), and the charged fiber layer is substantially free of adhesives.
  • an open support layer is mechanically attached to the additional layer(s) and/or charged fiber layer and are joined to one another without an adhesive.
  • the open support layer, the additional layer(s), and/or the charged fiber layer may be joined to one another by mechanical attachment and an adhesive.
  • the open support layer, the additional layer(s), and/or the charged fiber layer may be maintained in a waved configuration.
  • the filter media comprises a coarse support layer that holds the open support layer, additional layer(s), and/or the charged fiber layer in a waved configuration to maintain separation of peaks and troughs of adjacent waves of the layer(s).
  • the open support layer, the additional layer(s), and/or the charged fiber layer may be non-waved (e.g., substantially planar).
  • each of) the additional layer(s) may have a particular basis weight that is greater than or equal to 2 g/m 2 , greater than or equal to 3 g/m 2 , greater than or equal to 5 g/m 2 , greater than or equal to 7 g/m 2 , greater than or equal to
  • the basis weight of (each of) the additional layer(s) is less than or equal to
  • 100 g/m 2 less than or equal to 95 g/m 2 , less than or equal to 90 g/m 2 , less than or equal to 85 g/m 2 , less than or equal to 80 g/m 2 , less than or equal to 75 g/m 2 , less than or equal to 70 g/m 2 , less than or equal to 65 g/m 2 , less than or equal to 60 g/m 2 , less than or equal to 55 g/m 2 , less than or equal to 50 g/m 2 , less than or equal to 45 g/m 2 , less than or equal to 40 g/m 2 , less than or equal to 35 g/m 2 , less than or equal to 30 g/m 2 , less than or equal to 25 g/m 2 , less than or equal to 20 g/m 2 , less than or equal to 15 g/m 2 , less than or equal to 12 g/m 2 , less than or equal to 10 g/m 2 ,
  • At least one of the one or more additional layers is a meltblown layer having a basis weight of greater than or equal to 2 g/m and less than or equal to 100 g/m 2 .
  • the additional layer(s) may have a particular thickness that is greater than or equal to 4 mils, greater than or equal to 5 mils, greater than or equal to 6 mils, greater than or equal to 8 mils, greater than or equal to 10 mils, greater than or equal to 12 mils, greater than or equal to 15 mils, greater than or equal to 18 mils, greater than or equal to 20 mils, or greater than or equal to 22 mils.
  • 4 mils greater than or equal to 5 mils, greater than or equal to 6 mils, greater than or equal to 8 mils, greater than or equal to 10 mils, greater than or equal to 12 mils, greater than or equal to 15 mils, greater than or equal to 18 mils, greater than or equal to 20 mils, or greater than or equal to 22 mils.
  • the thickness of each additional layer is less than or equal to 25 mils, less than or equal to 22 mils, less than or equal to 20 mils, less than or equal to 18 mils, less than or equal to 15 mils, less than or equal to 12 mils, less than or equal to 10 mils, less than or equal to 8 mils, less than or equal to 6 mils, or less than or equal to 5 mils.
  • the total basis weight of an additional layer and the open support layer may be greater than or equal to 10 g/m 2 , greater than or equal to 15 g/m 2 , greater than or equal to 20 g/m 2 , greater than or equal to 25 g/m 2 , greater than or equal to
  • 70 g/m 2 greater than or equal to 75 g/m 2 , greater than or equal to 80 g/m 2 , greater than or equal to 85 g/m 2 , greater than or equal to 90 g/m 2 , greater than or equal to 95 g/m 2 , greater than or equal to 100 g/m 2 , greater than or equal to 110 g/m 2 , greater than or equal to 120 g/m 2 , or greater than or equal to 130 g/m 2.
  • the total basis weight of the additional layer and the open support layer is less than or equal to 140 g/m 2 , less than or equal to 130 g/m 2 , less than or equal to 120 g/m 2 , less than or equal to 110 g/m 2 , less than or equal to 100 g/m 2 , less than or equal to 95 g/m 2 , less than or equal to 90 g/m 2 , less than or equal to 85 g/m 2 , less than or equal to 80 g/m 2 , less than or equal to 75 g/m 2 , less than or equal to 70 g/m 2 , less than or equal to 65 g/m 2 , less than or equal to 60 g/m 2 , less than or equal to 55 g/m 2 , less than or equal to 50 g/m 2 , less than or equal to 45 g/m 2 , less than or equal to 40 g/m 2 , less than or equal to 35 g/m 2 , less than
  • each additional layer may have a particular average fiber diameter.
  • the average fiber diameter of an additional layer may be greater than or equal to 0.5 microns, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 3 microns, greater than or equal to 5 microns, greater than or equal to 8 microns, greater than or equal to 10 microns, greater than or equal to 12 microns, greater than or equal to 15 microns, or greater than or equal to 17 microns.
  • the average fiber diameter of the additional layer may be less than or equal to 20 microns, less than or equal to 17 microns, less than or equal to 15 microns, less than or equal to 12 microns, less than or equal to 10 microns, less than or equal to 8 microns, less than or equal to 5 microns, less than or equal to 3 microns, less than or equal to 2 microns, or less than or equal to 1 micron. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 1 micron and less than or equal to 20 microns).
  • Each additional layer may be selected to have a particular air permeability.
  • the air permeability of the additional layer(s) is greater than or equal to 45 CFM, greater than or equal to 50 CFM, greater than or equal to 75 CFM, greater than or equal to 100 CFM, greater than or equal to 200 CFM, greater than or equal to 300 CFM, greater than or equal to 400 CFM, greater than or equal to 500 CFM, greater than or equal to 600 CFM, greater than or equal to 700 CFM, greater than or equal to 800 CFM, greater than or equal to 900 CFM, or greater than or equal to 1000 CFM.
  • the air permeability of the additional layer(s) is less than 1100 CFM, less than or equal to 1000 CFM, less than or equal to 900 CFM, less than or equal to 800 CFM, less than or equal to 700 CFM, less than or equal to 600 CFM, less than or equal to 500 CFM, less than or equal to 400 CFM, less than or equal to 300 CFM, less than or equal to 200 CFM, less than or equal to 100 CFM, less than or equal to 75 CFM, or less than or equal to 50 CFM. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 45 CFM and less than 1100 CFM). Other ranges are also possible.
  • the open support layer and additional layer(s) may have a particular combined air permeability.
  • the combined air permeability of the open support layer and the addition layer(s) is greater than or equal to 45 CFM, greater than or equal to 50 CFM, greater than or equal to 75 CFM, greater than or equal to 100 CFM, greater than or equal to 200 CFM, greater than or equal to 300 CFM, greater than or equal to 400 CFM, greater than or equal to 500 CFM, greater than or equal to 600 CFM, greater than or equal to 700 CFM, greater than or equal to 800 CFM, greater than or equal to 900 CFM, or greater than or equal to 1000 CFM.
  • the combined air permeability of the open support layer and the addition layer(s) is less than 1100 CFM, less than or equal to 1000 CFM, less than or equal to 900 CFM, less than or equal to 800 CFM, less than or equal to 700 CFM, less than or equal to 600 CFM, less than or equal to 500 CFM, less than or equal to 400 CFM, less than or equal to 300 CFM, less than or equal to 200 CFM, less than or equal to 100 CFM, less than or equal to 75 CFM, or less than or equal to 50 CFM. Combinations of the above- referenced ranges are also possible (e.g., greater than or equal to 45 CFM and less than 1100 CFM, greater than or equal to 45 CFM and less than or equal to 700 CFM). Other ranges are also possible.
  • one or more additional layers are charged.
  • any of a variety of techniques can be used to charge the one or more additional layers.
  • Examples include AC and/or DC corona discharge, charge bars, triboelectric charging, hydrocharging, or use of additives.
  • a layer of a filter media e.g., one or more additional layers of the filter media
  • a hydrocharging process carried out by impinging jets and/or a stream of droplets of a polar fluid (e.g., water) onto the layer at a pressure sufficient to impart electret charge, followed by drying.
  • the jets or stream of polar fluid can be provided by any suitable spray method.
  • the layer may be transported e.g., on a porous support such as a belt, mesh screen, or fabric, during the hydrocharging process.
  • a vacuum may be placed proximate the porous support e.g., to aid in the passage of the polar fluid through the layer.
  • the layer may be dried (e.g., via a through- air drying process).
  • the one or more additional layers may be uncharged.
  • meltblown layers charged by hydrocharging as described herein may be associated with an open support layer and laminated to a charged fiber layer and have a relatively high combined value of gamma as compared to uncharged meltblown layers. Combined values of gamma are described in more detail, below.
  • one or more additional layers is a fine fiber layer.
  • the fine fiber layer is formed by a solvent-based spinning process (e.g., an electro spinning process).
  • the fine fiber layer or layers may comprise synthetic fibers, glass fibers, and/or cellulose fibers, amongst other fiber types.
  • the fine fiber layer may comprise a relatively high weight percentage of synthetic fibers (e.g., 100 weight percent).
  • the fine fiber layer or layers may comprise synthetic fibers formed from a meltblown process, melt spinning process, centrifugal spinning process, electrospinning, wet laid, dry laid, or air laid process.
  • the synthetic fibers may be continuous, as described further below.
  • the fine fiber layer is formed by an electrospinning process (e.g., comprising electrospun fibers).
  • the filter media comprises an open support layer, a meltblown layer associated with (e.g., directly adjacent) the open support layer, and a fine fiber layer associated with (e.g., directly adjacent) the meltblown layer.
  • the filter media may comprise a fine fiber layer comprising synthetic fibers.
  • the synthetic fibers may have a relatively small average fiber diameter (e.g., less than or equal to about 2 microns).
  • the synthetic fibers in a fine fiber layer may have an average cross-sectional dimension (e.g., diameter) of less than or equal to about 2 microns (e.g., between about 0.08 microns and about 2.0 microns).
  • the synthetic fibers in a fine fiber layer or layers may be continuous fibers formed by any suitable process (e.g., a melt-blown, a meltspun, an electrospinning (e.g., melt electrospinning, solvent electrospinning), centrifugal spinning).
  • the synthetic fibers may be formed by an electrospinning (e.g., melt electrospinning, solvent electrospinning), centrifugal spinning).
  • the synthetic fibers may be formed by an electrospinning (e.g., melt electrospinning, solvent electrospinning), centrifug
  • the synthetic fibers may be non- continuous. In some embodiments, all of the fibers in a fine fiber layer or layers are synthetic fibers.
  • the synthetic fibers in a fine fiber layer(s) may include any suitable type of synthetic polymer.
  • suitable synthetic fibers include polyesters (e.g., polyethylene terephthalate, polybutylene terephthalate), polycarbonate, polyamides (e.g., various nylon polymers), polyaramid, polyimide, polyethylene, polypropylene, polyether ether ketone, polyolefin, acrylics (e.g., polyacrylic acid), polylactic acid, polyvinyl alcohol, polyvinyl chloride, regenerated cellulose (e.g., synthetic cellulose such lyocell, rayon), polyacrylonitriles, polyvinylidene fluoride (PVDF), copolymers of polyethylene and PVDF, polyether sulfones, polycarbonate, and combinations thereof.
  • polyesters e.g., polyethylene terephthalate, polybutylene terephthalate
  • polycarbonate e.g., various nylon polymers
  • polyamides e
  • the average diameter of the synthetic fibers of one or more fine fiber layers may be, for example, greater than or equal to about 0.08 microns, greater than or equal to about 0.1 microns, greater than or equal to about 0.2 microns, greater than or equal to about 0.3 microns, greater than or equal to about 0.4 microns, greater than or equal to about 0.5 microns, greater than or equal to about 0.6 microns, greater than or equal to about 0.8 microns, greater than or equal to about 1 microns, greater than or equal to about 1.2 microns, greater than or equal to about 1.4 microns, greater than or equal to about 1.6 microns, or greater than or equal to about 1.8 microns.
  • the synthetic fibers of one or more fine fiber layers may have an average diameter of less than or equal to about 2 microns, less than or equal to about 1.8 microns, less than or equal to about 1.6 microns, less than or equal to about 1.4 microns, less than or equal to about 1.2 microns, less than or equal to about 1 micron, less than or equal to about 0.8 microns, less than or equal to about 0.6 microns, less than or equal to about 0.5 microns, less than or equal to about 0.4 microns, less than or equal to about 0.3 microns, less than or equal to about 0.2 microns, or less than or equal to about 0.1 microns.
  • the synthetic fibers (if present) may be continuous (e.g., meltblown fibers, spunbond fibers, electrospun fibers, centrifugal spun fibers, etc.). Lengths of continuous fibers are provided above. In other embodiments, the synthetic fibers (if present) are not continuous (e.g., staple fibers).
  • Continuous fibers are made by a "continuous" fiber-forming process, such as a meltblown process, a spunbond process, an electro spinning process, or a centrifugal spinning process, and typically have longer lengths than non-continuous fibers.
  • Non-continuous fibers are staple fibers that are generally cut (e.g., from a filament) or formed as non-continuous discrete fibers to have a particular length or a range of lengths.
  • the fine fiber layer may have any suitable basis weight.
  • the fine fiber layer may have a basis weight of greater than or equal to 0.01 g/m , greater than or equal to
  • 0.03 g/m 2 greater than or equal to 0.05 g/m 2 , greater than or equal to 0.1 g/m 2 , greater than or equal to 0.3 g/m 2 , greater than or equal to 0.5 g/m 2 , greater than or equal to 1 g/m 2 , greater than or equal to 3 g/m 2 , greater than or equal to 5 g/m 2 , greater than or equal to 6 g/m 2 , or greater than or equal to 8 g/m 2.
  • the fine fiber layer may have a basis weight of less than or equal to 10 g/m , less than or equal to 8 g/m 2 , less than or equal to 6 g/m 2 , less than or equal to 5 g/m 2 , less than or equal to 3 g/m 2 , less than or equal to 1 g/m 2 , less than or equal to 0.5 g/m 2 , less than or equal to 0.3 g/m 2 , less than or equal to 0.1 g/m 2 , less than or equal to 0.05 g/m 2 , or less than or equal to 0.03 g/m .
  • Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.01 g/m 2 and less than or equal to 10 g/m 2 , greater than or equal to 0.03 g/m 2 and less than or equal to 10 g/m 2 , or greater than or equal to 0.01 g/m 2 and less than or equal to 5 g/m ). Other ranges are also possible.
  • the basis weight may be determined according to test standard ASTM D-846.
  • the fine fiber layer may have a particular air
  • the air permeability of the fine fiber layer is greater than or equal to 10 CFM, greater than or equal to 25 CFM, greater than or equal to 50 CFM, greater than or equal to 80 CFM, greater than or equal to 100 CFM, greater than or equal to 200 CFM, greater than or equal to 250 CFM, greater than or equal to 300 CFM, greater than or equal to 350 CFM, greater than or equal to 400 CFM, or greater than or equal to 450 CFM.
  • the air permeability of the fine fiber layer is less than or equal to 500 CFM, less than or equal to 450 CFM, less than or equal to 400 CFM, less than or equal to 350 CFM, less than or equal to 300 CFM, less than or equal to 250 CFM, less than or equal to 200 CFM, less than or equal to 150 CFM, less than or equal to 100 CFM, less than or equal to 80 CFM, less than or equal to 50 CFM, or less than or equal to 25 CFM. Combinations of the above referenced ranges are also possible (e.g., greater than or equal to 10 CFM and less than or equal to 500 CFM). Other ranges are also possible.
  • Air permeability of the second layer, as used herein, is measured according to the test standard ASTM D737 over 38 cm surface area of the media and using a pressure of 125 Pa.
  • a filter media comprises an open support layer, an additional layer such as a meltblown layer or spunbond layer associated with the open support layer, and a charged fiber layer adjacent the additional layer.
  • a filter media comprises an open support layer, an additional layer such as a meltblown layer or spunbond layer associated with the open support layer, and a fine fiber layer adjacent (e.g., directly adjacent) the additional layer.
  • a charged fiber layer may be adjacent (e.g., directly adjacent) the fine fiber layer.
  • the combined air permeability of the open support layer, additional layer (e.g., meltblown layer), and fine fiber layer may be greater than or equal to 10 CFM, greater than or equal to 20 CFM, greater than or equal to 40 CFM, greater than or equal to 60 CFM, greater than or equal to 80 CFM, greater than or equal to 100 CFM, greater than or equal to 150 CFM, greater than or equal to 200 CFM, greater than or equal to 250 CFM, greater than or equal to 300 CFM, greater than or equal to 350 CFM, greater than or equal to 400 CFM, or greater than or equal to 450 CFM.
  • the combined air permeability of the open support layer, additional layer (e.g., meltblown layer), and fine fiber layer is less than or equal to 500 CFM, less than or equal to 450 CFM, less than or equal to 400 CFM, less than or equal to 350 CFM, less than or equal to 300 CFM, less than or equal to 250 CFM, less than or equal to 200 CFM, less than or equal to 150 CFM, less than or equal to 100 CFM, less than or equal to 80 CFM, less than or equal to 60 CFM, less than or equal to 40 CFM, or less than or equal to 20 CFM. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 10 CFM and less than or equal to 500 CFM).
  • the filter media may comprise any suitable number of open support layers, additional layers, and/or charged fiber layers, each of which may or may not be mechanically attached to one another.
  • the filter media may comprise a charged fiber layer disposed between two open support layers (e.g., a first open support layer upstream and mechanically attached to the charged fiber layer, and a second open support layer downstream and mechanically attached to the charged fiber layer).
  • the filter media may comprise an open support layer disposed between two charged fiber layers (e.g., a first charged fiber layer upstream and mechanically attached to the open support layer and a second charged fiber layer downstream and mechanically attached to the open support layer).
  • filter media 102 may comprise an open support layer (i.e. first layer 110) disposed between a first charged layer (i.e. second layer 120) and a second charged layer (i.e. Third layer 122).
  • the filter media may comprise one or more, two or more, three or more, or four or more charged fibers layers, one or more of which is mechanically attached to an open support layer. In certain embodiments, the filter media may comprise five or fewer, four or fewer, three or fewer, or two fewer charged fiber layers, one or more of which is mechanically attached to an open support layer. Combinations of the above-referenced ranges are also possible (e.g., 1-5 charged fiber layers). Other ranges are also possible.
  • the filter media may comprise one or more, two or more, three or more, or four or more open support layers, one or more of which is mechanically attached to a charged fiber layer.
  • the filter media may comprise five or fewer, four or fewer, three or fewer, or two fewer open support layers, one or more of which is mechanically attached to an charged fiber layer. Combinations of the above-referenced ranges are also possible (e.g., , 1-5 open support layers). Other ranges are also possible.
  • Filter media having a charged fiber layer mechanically attached to an open support layer as described herein may have desirable structural properties such as overall basis weight and/or overall thickness.
  • the filter media may have an overall basis weight of greater than or equal to 12 g/m , greater than or equal to 20 g/m 2 , greater than or equal to 25 g/m 2 , greater than or equal to 30 g/m 2 , greater than or equal to 40 g/m 2 , greater than or equal to 50 g/m 2 , greater than or equal to 60 g/m 2 , greater than or equal to 70 g/m 2 , greater than or equal to 80 g/m 2 , greater than 85 g/m 2 , greater than or equal to 90 g/m 2 , greater than or equal to 100 g/m 2 , greater than or equal to 150 g/m 2 , greater than or equal to 200 g/m 2 g/m 2 , greater than or equal to 250 g/m 2 , greater than or equal to 300
  • the filter media may have an overall basis weight of less than or equal to 750 g/m , less than or equal to 700 g/m 2 , less than or equal to 650 g/m 2 , less than or equal to 600 g/m 2 , less than or equal to
  • 550 g/m 2 less than or equal to 500 g/m 2 , less than or equal to 450 g/m 2 , less than or equal to 400 g/m 2 , less than or equal to 350 g/m 2 , less than or equal to 300 g/m 2 , less than or equal to 250 g/m 2 , less than or equal to 200 g/m 2 , less than or equal to 150 g/m 2 , less than or equal to 100 g/m 2 , less than or equal to 90 g/m 2 , less than or equal to 85 g/m 2 , less than or equal to 80 g/m 2 , less than or equal to 70 g/m 2 , less than or equal to 60 g/m 2 , less than or equal to 50 g/m 2 , less than or equal to 40 g/m 2 , less than or equal to 30 g/m 2 , less than or equal to 25 g/m 2 , or less than or equal to 20 g/m
  • the overall basis weight may be determined according to test standard ASTM D-846.
  • the filter media may have an overall thickness of greater than or equal to 5 mils, greater than or equal to 10 mils, greater than or equal to 15 mils, greater than or equal to 20 mils, greater than or equal to 30 mils, greater than or equal to 40 mils, greater than or equal to 50 mils, greater than or equal to 100 mils, greater than or equal to 150 mils, greater than or equal to 200 mils, greater than or equal to 250 mils, greater than or equal to 300 mils, greater than or equal to 350 mils, greater than or equal to 400 mils, greater than or equal to 450 mils, greater than or equal to 500 mils, greater than or equal to 550 mils, greater than or equal to 600 mils, greater than or equal to 700 mils, greater than or equal to 800 mils, greater than or equal to 900 mils, greater than or equal to 1000 mils,
  • the filter media has an overall thickness of less than or equal to 2000 mils, less than or equal to 1800 mils, less than or equal to 1600 mils, less than or equal to 1400 mils, less than or equal to 1200 mils, less than or equal to 1000 mils, less than or equal to 900 mils, less than or equal to 800 mils, less than or equal to 700 mils, less than or equal to 600 mils, less than or equal to 550 mils, less than or equal to 500 mils, less than or equal to 450 mils, less than or equal to 400 mils, less than or equal to 350 mils, less than or equal to 300 mils, less than or equal to 250 mils, less than or equal to 200 mils, less than or equal to 150 mils, less than or equal to 100 mils, less than or equal to 50 mils, less than or equal to 40 mils, less than or equal to 30 mils, less than or equal to 20 mils, less than or equal to 15 mils, or less than or equal to 10 mils.
  • Other values of overall thickness are also possible.
  • the overall thickness may be determined according to test standard ASTM D-1777.
  • Filter media having a charged fiber layer mechanically attached to an open support layer as described herein may have desirable filtration properties such as gamma, normalized gamma, pressure drop, and/or overall air permeability.
  • the filter media may exhibit suitable overall air permeability characteristics.
  • the overall air permeability of a filter media may range from between about 30 CFM and about 1100 CFM.
  • the overall air permeability of the filter media may be greater than or equal to 30 CFM, greater than or equal to 50 CFM, greater than or equal to 75 CFM, greater than or equal to 100 CFM, greater than or equal to 150 CFM, greater than or equal to 200 CFM, greater than or equal to 300 CFM, greater than or equal to 400 CFM, greater than or equal to 500 CFM, greater than or equal to 600 CFM, greater than or equal to 700 CFM, greater than or equal to 800 CFM, greater than or equal to 900 CFM, or greater than or equal to 1000 CFM.
  • the filter media has an overall air permeability of less than or equal to 1100 CFM, less than or equal to 1000 CFM, less than or equal to 900 CFM, less than or equal to 800 CFM, less than or equal to 700 CFM, less than or equal to 600 CFM, less than or equal to 500 CFM, less than or equal to 400 CFM, less than or equal to 300 CFM, less than or equal to 200 CFM, less than or equal to 100 CFM, less than or equal to 75 CFM, or less than or equal to 50 CFM. Combinations of the above-referenced ranges are also possible (e.g., an air permeability of greater than or equal to 30 CFM and less than or equal to 1100 CFM). Other ranges are also possible. Overall air permeability of the filter media, as determined herein, is measured according to the test standard ASTM D737 over 38 cm surface area of the media and using a pressure of 125 Pa.
  • the pressure drop across the filter media may vary depending on the particular application of the filter media.
  • the pressure drop across the filter media may range from between 1 Pa and 120 Pa, or between 1 Pa and 100 Pa.
  • the pressure drop across the filter media may be greater than or equal to 1 Pa, greater than or equal to 2 Pa, greater than or equal to 5 Pa, greater than or equal to 10 Pa, greater than or equal to 20 Pa, greater than or equal to 30 Pa, greater than or equal to 40 Pa, greater than or equal to 50 Pa, greater than or equal to 60 Pa, greater than or equal to 70 Pa, greater than or equal to 80 Pa, greater than or equal to 90 Pa, greater than or equal to 100 Pa, or greater than or equal to 110 Pa.
  • the pressure drop across the filter media may be less than or equal to 120 Pa, less than or equal to 110 Pa, less than or equal to 100 Pa, less than or equal to90 Pa, less than or equal to 80 Pa, less than or equal to 70 Pa, less than or equal to 60 Pa, less than or equal to 50 Pa, less than or equal to 40 Pa, less than or equal to 30 Pa, less than or equal to 20 Pa, less than or equal to 10 Pa, less than or equal to 5 Pa, or less than or equal to 2 Pa. Combinations of the above-referenced ranges are also possible (e.g., a pressure drop of greater than or equal 1 Pa and less than or equal to 120 Pa, greater than or equal to 1 Pa and less than or equal to 100 Pa). Other ranges are also possible.
  • the pressure drop is measured as the differential pressure across the filter media or fiber layer when exposed to NaCl aerosol at a face velocity of 95 liters per minute.
  • the face velocity is the velocity of air as it hits the upstream side of the filter media or layer(s).
  • Values of pressure drop are typically recorded as millimeters of water or Pascals.
  • the values of pressure drop described herein were determined according to EN13274-7 standard.
  • the pressure drop value is measured with NaCl aerosol of particle size 0.65 micron with a face velocity of 95 liters/min over an area of 100 cm .
  • the filter media may have a desirable normalized efficiency.
  • the normalized efficiency of the filter media may be greater than or equal to 1, greater than or equal to 1.25, greater than or equal to 1.5, greater than or equal to 2, greater than or equal to 2.5, or greater than or equal to 3.
  • the filter media may have a normalized efficiency of less than or equal to 3.5, less than or equal to 3, less than or equal to 2.5, less than or equal to 2, or less than or equal to 1.5. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 1 and less than or equal to 3.5). Other values of the normalized efficiency of the filter media are also possible.
  • Normalized efficiency is provided without units and refers to the ratio of the initial efficiency percentage of the filter media to the total basis weight (measured in g/m ) of the one or more charged fiber layers within the filter media (i.e. not including any open support layers or coarse support layers).
  • Initial efficiency was determined according to EN 13274-7 standard using NaCl aerosol of particle size 0.65 micron with a face velocity of 95 liters/min over an area of 100 cm .
  • filter media comprising an open support layer (e.g., having an air permeability greater than 1100 CFM) mechanically attached (e.g., needled) to a charged fiber layer may exhibit a decreased pressure drop and/or increased dust holding capacity as compared to a filter media with a support layer having an air permeability less than or equal to 1100 CFM adjacent to the charged fiber layer.
  • the filter media may have a certain dust holding capacity.
  • the filter media may have a dust holding capacity of
  • the 2 dust holding capacity of the filter media may be less than or equal to 140 g/m , less than or equal to 130 g/m 2 , less than or equal to 120 g/m 2 , less than or equal to 110 g/m 2 , less than or equal to 100 g/m 2 , less than or equal to 90 g/m 2 , less than or equal to 80 g/m 2 , less than or equal to 70 g/m 2 , less than or equal to 60 g/m 2 , less than or equal to 50 g/m 2 , less than or equal to 40 g/m 2 , less than or equal to 30 g/m 2 , less than or equal to 20 g/m 2 , less than or equal to 10 g/m 2 .
  • Combinations of the above- referenced ranges are also possible (e.g., greater than or equal to about 1 g/m and less than or equal to about 140 g/m 2 , greater than or equal to about 80 g/m 2 and less than or equal to about 140 g/m ).
  • Other values of dust holding capacity are also possible.
  • the dust holding capacity of a filter media comprising an open support layer mechanically attached to a charged fiber layer, not in a waved configuration is tested based upon standard ISO/TS 11155-1. The testing uses ISO 12103-1, A2 fine test dust at a base upstream gravimetric dust level of 75 mg/m . The test is run at a face velocity of 20 cm/sec over a filter area of 100 cm until filter media reaches an air resistance of 82 Pa.
  • filters may be rated according to a value termed gamma value. Generally, higher gamma values are indicative of better filter performance, i.e., a high particulate efficiency as a function of pressure drop.
  • the NaCl penetration percentage is based on the percentage of particles that penetrate through the filter media or layer. With decreased NaCl penetration percentage (i.e., increased particulate efficiency) where particles are less able to penetrate through the filter media or layer, gamma increases. With decreased pressure drop (i.e., low resistance to fluid flow across the filter), gamma increases.
  • Penetration often expressed as a percentage, is defined as follows: Pen
  • the initial penetration is the first taken at the beginning of the test and can be used to determine the initial efficiency of the filter media.
  • Pressure drop values e.g., for determining gamma
  • the instrument measures a pressure drop across the filter media (or layer) when the filter media or layer is subjected to a 95 liters/min face velocity over an area of 100 cm .
  • the filter media (e.g., the filter media comprising an open support layer mechanically attached to a charged fiber layer, the filter media comprising an open support layer and one or more additional layers) as a whole may have a relatively high value of gamma.
  • the value of gamma for the filter is greater than or equal to 30, greater than or equal to 50, greater than or equal to 75, greater than or equal to 100, greater than or equal to 125, greater than or equal to 150, greater than or equal to 175, greater than or equal to 200, or greater than or equal to 225.
  • the value of gamma for the filter media is less than or equal to 250, less than or equal to 225, less than or equal to 200, less than or equal to 175, less than or equal to 150, less than or equal to 125, less than or equal to 100, less than or equal to 75, or less than or equal to 50. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 30 and less than or equal to 250, or greater than or equal to 75 and less than or equal to 150). Other ranges are also possible.
  • the open support layer, one or more additional layers (e.g., meltblown layer), and charged fiber layer may have a relatively high combined value of gamma.
  • the combined value of gamma for the open support layer,one or more additional layers, and charged fiber layer is greater than or equal to 1, greater than or equal to 5, greater than or equal to 10, greater than or equal to 20, greater than or equal to 30, greater than or equal to 50, greater than or equal to 75, greater than or equal to 90, greater than or equal to 100, greater than or equal to 125, greater than or equal to 150, greater than or equal to 175, greater than or equal to 180, greater than or equal to 200, or greater than or equal to 225 .
  • the combined value of gamma for the open support, one or more additional layers, and charged fiber layer is less than or equal to 250, less than or equal to 225, less than or equal to 200, less than or equal to 180, less than or equal to 175, less than or equal to 150, less than or equal to 125, less than or equal to 100, less than or equal to 90, less than or equal to 75, less than or equal to 50, less than or equal to 30, less than or equal to 20, less than or equal to 10, or less than or equal to 5.
  • Combinations of the above referenced ranges are also possible (e.g., greater than or equal to 1 and less than or equal to 180, or greater than or equal to 90 and less than or equal to 180). Other ranges are also possible.
  • the open support layer, additional layer such as a meltblown layer, and charged fiber layer are laminated together and have a combined value of gamma of greater than or equal to 90 and less than or equal to 180.
  • the meltblown layer may be hydrocharged as described herein.
  • the open support layer, additional layer(s), and/or charged fiber layer are maintained in a waved configuration and have a combined value of gamma of greater than or equal to 90 and less than or equal to 250.
  • the open support layer, additional layer(s), and/or charged fiber layer are non-waved and have a combined value of gamma of greater than or equal to 90 and less than or equal to 250.
  • the filter media may have a desirable normalized gamma.
  • Normalized gamma is a unitless parameter and refers to the ratio of the gamma of the filter media to the total basis weight (measured in g/m ) of the one or more charged fiber layers within the filter media (i.e. not including any open support layers or coarse support layers).
  • the normalized gamma of the filter media may be greater than or equal to 1, greater than or equal to 1.5, greater than or equal to 2, greater than or equal to 2.5, greater than or equal to 3, greater than or equal to 3.5, greater than or equal to 4, greater than or equal to 4.5, greater than or equal to 5, greater than or equal to 5.5, greater than or equal to 5.6, greater than or equal to 6, greater than or equal to, greater than or equal to 6.5, greater than or equal to 7, greater than or equal to 7.5, greater than or equal to 8, greater than or equal to 8.5, greater than or equal to 9, greater than or equal to 9.5, greater than or equal to 10, or greater than or equal to 10.5.
  • the normalized gamma of the filter media may be less than or equal to 10.9, less than or equal to 10.5, less than or equal to 10, less than or equal to 9.5, less than or equal to 9, less than or equal to 8.5, less than or equal to 8, less than or equal to 7.5, less than or equal to 7, less than or equal to 6.5, less than or equal to 6, less than or equal to 5.6, less than or equal to 5.5, less than or equal to 5, less than or equal to 4.5, less than or equal to 4, less than or equal to 3.5, less than or equal to 3, less than or equal to 2.5, less than or equal to 2, or less than or equal to 1.5.
  • the filter media comprises a charged fiber layer comprising a plurality of fibers and the filter media has a normalized gamma of greater than or equal to 1 and less than or equal to 5.6.
  • the filter media comprises a plurality of fibers a charged fiber layer comprising a plurality of fibers that are relatively fine (e.g., having an average fiber diameter less than 15 microns) and the filter media has a normalized gamma of greater than or equal to 1 and less than or equal to 10.9.
  • a filter media and/or a layer may be designed to have a penetration or efficiency (e.g., initial efficiency).
  • the initial efficiency of the filter media is greater than or equal to 50% greater than or equal to 55% greater than or equal to 60% greater than or equal to 65% greater than or equal to 70% greater than or equal to 75% greater than or equal to 80% greater than or equal to 85% greater than or equal to 90%, greater than or equal to 92%, greater than or equal to 95%, greater than or equal to 96%, greater than or equal to 97%, greater than or equal to 98%, greater than or equal to 99%, greater than or equal to 99.5%, greater than or equal to 99.8%, greater than or equal to 99.9%, or greater than or equal to 99.99%.
  • the initial efficiency of the filter media is less than or equal to 99.999%, less than or equal to 99.99%, less than or equal to 99.9%, less than or equal to 99.8%, less than or equal to 99.5%, less than or equal to 99%, less than or equal to 98%, less than or equal to 97%, less than or equal to 96%, less than or equal to 95%, less than or equal to 92%, less than or equal to 90%, less than or equal to 85%, less than or equal to 80%, less than or equal to 75%, less than or equal to 70%, less than or equal to 65%, less than or equal to 60%, or less than or equal to 55%.
  • the filter media may comprise an open support layer and a charged fiber layer mechanically attached to the open support layer, wherein the open support layer has an air permeability of greater than 1100 CFM and less than or equal to 20000 CFM and is a mesh. In some embodiments, the open support layer has a solidity of less than or equal to 10%.
  • the filter media may comprise an open support layer and a charged fiber layer mechanically attached to the open support layer, wherein the open support layer has an air permeability of greater than 1100 CFM and less than or equal to 20000 CFM.
  • the filter media has an overall basis weight of greater than or equal to 12 g/m 2 and less than or equal to 700 g/m 2 , a gamma greater than or equal to 90 and less than or equal to 250, and/or an overall air permeability of greater than or equal to 30 CFM and less than or equal to 1100 CFM.
  • the charged fiber layer may be needled to the open support layer.
  • the filter media may comprise at least one layer (e.g., a charged fiber layer) that is held in a waved or curvilinear configuration.
  • the filter media (and/or one or more open support layers of the filter media) are held in a waved or curvilinear configuration by one or more additional support layers (e.g., one or more coarse support layers).
  • additional support layers e.g., one or more coarse support layers.
  • the filter media may have an increased surface area which can result in improved filtration properties.
  • the filter media may include various layers (e.g., an open support layer, one or more fiber layers such as charged fiber layers, a coarse support layer, a top and/or bottom layer), and only some or all of the layers may be waved.
  • the filter media having at least one layer that is held in a waved or curvilinear configuration as described herein may comprise a relatively charged fiber layer having a relatively low basis weight.
  • an open support layer such as a mesh may provide additional mechanical reinforcement and/or structural stability (e.g., to a filter media having a waved configuration) while having a relatively high air permeability.
  • FIG. 2A illustrates one exemplary embodiment of the filter media 200 having a first layer 210 (e.g., an open support layer such as a mesh) and a second layer 220 (e.g., a charged fiber layer) adjacent first layer 210.
  • first layer 210 and second layer 220 are in a waved configuration comprising peaks and troughs of adjacent waves of the filter media.
  • filter media 202 comprises first layer 210 (e.g. open support layer such as a mesh) disposed between second layer 220 (e.g., a first charged fiber layer) and third layer 222 (e.g., a second charged fiber layer).
  • the filter media comprises a coarse support layer that holds one or more layers (e.g., the open support layer, one or more additional layer(s), and/or the charged fiber layer) in a waved configuration to maintain separation of peaks and troughs of adjacent waves of the one or more layers.
  • filter media 204 includes a first layer 210 (e.g., an open support layer such as a mesh) disposed between second layer 220 (e.g., a first charged fiber layer) and third layer 230 (e.g., a second charged fiber layer).
  • filter media 204 comprises a first coarse support layer 230 adjacent second layer 220 and a second coarse support layer 232 adjacent third layer 222.
  • Coarse support layers 230 and 232 can help maintain the second layer 220 and third layer 230, and optionally any additional layers (e.g., the open support layer), in the waved configuration. While two coarse support layers 230, 232 are shown, the filter media 204 need not include both coarse support layers. Where only one support layer is provided, the support layer can be disposed upstream or downstream of the layer(s).
  • the filter media 204 can also optionally include one or more outer or cover layers located on the upstream-most and/or downstream-most sides of the filter media 204.
  • FIG. 2C illustrates a top layer 240 disposed on the upstream side of the filter media 204 to function, for example, as an upstream dust holding layer and/or a support layer.
  • the top layer 240 can also function as an aesthetic layer, which will be discussed in more detail below.
  • the layers in the illustrated embodiment are arranged so that the top layer 240 is disposed on the air entering side, labeled I, the first coarse support layer 230 is just downstream of the top layer 240, the second fiber layer 220 is disposed just downstream of the first coarse support layer 230, the open support layer 210 is disposed downstream of the second fiber layer 220, the third fiber layer 222 is disposed downstream of the open support layer 210, and the second coarse support layer 232 is disposed downstream of the third fiber layer 222 on the air outflow side, labeled O.
  • the direction of air flow i.e., from air entering I to air outflow O, is indicated by the arrows marked with reference A.
  • the outer or cover layer can alternatively or additionally be a bottom layer disposed on the downstream side of the filter media 204 to function as a strengthening component that provides structural integrity to the filter media 204 to help maintain the waved configuration.
  • the outer or cover layer(s) can also function to offer abrasion resistance.
  • one or more additional layers (e.g., meltblown layer) and associated open support layer and/or charged fiber layer are in a waved configuration.
  • one or more coarse support layers holds the one or more additional layers (e.g., meltblown layer) and associated open support layer and/or charged fiber layer in the waved configuration and maintains separation of peaks and troughs of adjacent waves of the layer(s).
  • a filter media comprises an open support layer, an additional layer (e.g., a meltblown layer) associated with the open support layer, and a charged fiber layer, wherein the additional layer, open support layer, and charged fiber layer are in a waved configuration.
  • the filter media comprises a fine fiber layer which may, in some cases, be in a waved configured (e.g., the open support layer, additional layer(s), fine fiber layer, and charged fiber layer are in a waved configuration).
  • the outer or cover layer(s) can have a topography different from the topographies of the fiber layer and/or any support layers.
  • the outer or cover layer(s) may be non-waved (e.g., substantially planar), whereas the fiber layer(s) and/or any open support layers may have a waved
  • the filter media can include any number of layers in various arrangements.
  • the fiber layers and/or support layers may have waved configuration including a plurality of peaks P and troughs T with respect to each surface thereof.
  • a peak P on one side of the fiber layer may have a corresponding trough T on the opposite side.
  • second layer 220 may extend into a trough T, and exactly opposite that same trough T is a peak P, across which upstream third layer 222 may extend.
  • Peaks and troughs may also be present in a single fiber layer as shown illustratively in FIG. 2D.
  • the troughs may be partially or substantially filled with fibers (e.g., partially or substantially filled with the coarse support layer).
  • the fiber layers, and/or some or all of the support layers can be formed into a waved configuration using various manufacturing techniques, but in an exemplary embodiment involving a single fiber layer, the fiber layer is positioned on a first moving surface adjacent to a second moving surface, and the fiber layer is conveyed between the first and second moving surfaces that are traveling at different speeds.
  • the fiber layers are positioned adjacent to one another in a desired arrangement from air entering side to air outflow side, and the combined layers are conveyed between first and second moving surfaces that are traveling at different speeds.
  • the second surface may be traveling at a speed that is slower than the speed of the first surface.
  • a suction force such as a vacuum force
  • a suction force can be used to pull the layer(s) toward the first moving surface, and then toward the second moving surface as the layer(s) travel from the first to the second moving surfaces.
  • the speed difference causes the layer(s) to form Z-direction waves as they pass onto the second moving surface, thus forming peaks and troughs in the layer(s).
  • the speed of each surface as well as the ratio of speeds between the two surfaces can be altered to obtain a percentage of fiber orientations as described herein. Generally, a higher ratio of speeds results in a higher percentage of fibers having a more angled orientation with respect to the horizontal, or with respect to a surface (e.g., a planar surface) of the fiber layer or an outer or cover layer.
  • one or more fiber layers, or a filter media is formed using a ratio of speeds of at least 1.5, at least 2.5, at least 3.5, at least 4.0, at least 4.5, at least 5.0, at least 5.5, or at least 6.0.
  • the ratio of speeds is less than or equal to 10.0, less than or equal to 9.0, less than or equal to 8.0, less than or equal to 7.0, less than or equal to 6.0, less than or equal to 5.0, or less than or equal to 4.0, less than or equal to 3.5, less than or equal to 3.0, or less than or equal to 2.5. Combinations of the above-referenced ranges are also possible. Other ratios are also possible.
  • the speed of each surface can be also altered to obtain the desired number of waves per inch.
  • the distance between the surfaces can also be altered to determine the amplitude of the peaks and troughs, and in an exemplary embodiment the distance is adjusted between 0 to 2".
  • the properties of the different layers can also be altered to obtain a desired filter media configuration.
  • the periodicity (e.g., the number of waves per inch) of the second layer (e.g., the charged fiber layer) may range between 3 and 40 waves per 6 inches (e.g., between 3 and 15 waves per 6 inches, between 5 and 9 waves per 6 inches, between 10 and 40 waves per 6 inches).
  • the periodicity of the fiber layer may be greater than or equal to 3 waves, greater than or equal to 4 waves, greater than or equal to 5 waves, greater than or equal to 6 waves, greater than or equal to 7 waves, greater than or equal to 8 waves, greater than or equal to 9 waves, greater than or equal to 10 waves, greater than or equal to 11 waves, greater than or equal to 12 waves, greater than or equal to 13 waves, greater than or equal to 14 waves, greater than or equal to 15 waves, greater than or equal to 17 waves, greater than or equal to 20 waves, greater than or equal to 25 waves, greater than or equal to 30 waves, or greater than or equal to 35 waves per 6 inches.
  • the periodicity of the second layer may be less than or equal to 40 waves, less than or equal to 35 waves, less than or equal to 30 waves, less than or equal to 25 waves, less than or equal to 20 waves, less than or equal to 17 waves, less than or equal to 15 waves, less than or equal to 14 waves, less than or equal to 13 waves, less than or equal to 12 waves, less than or equal to 11 waves, less than or equal to 10 waves, less than or equal to 9 waves, less than or equal to 8 waves, less than or equal to 7 waves, less than or equal to 6 waves, less than or equal to 5 waves, or less than or equal to 4 waves per 6 inches.
  • each layer may have a periodicity having one or more of the above-referenced ranges.
  • any suitable number of charged fiber layers may be present in the filter media (e.g., the filter media comprising an open support layer and one or more charged fiber layers, where at least one charged fiber layer is held in a waved or curvilinear
  • the filter media may comprise one or more, two or more, three or more, or four or more charged fibers layers, one or more of which is mechanically attached to an open support layer. In certain embodiments, the filter media may comprise five or fewer, four or fewer, three or fewer, or two fewer charged fiber layers, one or more of which is mechanically attached to an open support layer.
  • the filter media may comprise one or more, two or more, three or more, or four or more open support layers, one or more of which is mechanically attached to a charged fiber layer.
  • the filter media may comprise five or fewer, four or fewer, three or fewer, or two fewer open support layers, one or more of which is mechanically attached to an charged fiber layer. Combinations of the above-referenced ranges are also possible (e.g., 1-5 charged fiber layers). Other ranges are also possible.
  • Filter media having an open support layer, a coarse support layer, and a charged fiber layer, where at least the charged fiber layer is held in a waved or curvilinear configuration as described herein may have desirable structural properties such as overall basis weight.
  • the filter media may have an overall basis weight of greater than or equal to 30 g/m 2 , greater than or equal to 40 g/m 2 , greater than or equal to
  • the filter media may have an overall basis weight of less than or equal to 800 g/m 2 , less than or equal to 750 g/m 2 , less than or equal to 700 g/m 2 , less than or equal to 650 g/m 2 , less than or equal to 600 g/m 2 , less than or equal to 550 g/m 2 , less than or equal to 500 g/m 2 , less than or equal to 450 g/m 2 , less than or equal to 400 g/m 2 , less than or equal to 350 g/m 2 , less than or equal to 300 g/m 2 , less than or equal to 250 g/m 2 , less than or equal to 200 g/m 2 , less than or equal to 150 g/m 2 , less than or equal to 100 g/m 2 , less than or equal to 90 g/m 2 , less than or equal to 85 g/m 2 , less than or equal to 80 g/m 2 , less than
  • Other values of overall basis weight are also possible.
  • the overall basis weight may be determined according to test standard ASTM D-846.
  • the filter media (e.g., the filter media comprising an open support layer, a coarse support layer, and one or more charged fiber layers, where at least one charged fiber layer is held in a waved or curvilinear configuration) has a particular thickness.
  • the thickness of the overall filter media is greater than or equal to 100 mil, greater than or equal to 150 mil, greater than or equal to 200 mil, greater than or equal to 250 mil, greater than or equal to 300 mil, greater than or equal to 400 mil, greater than or equal to 500 mil, greater than or equal to 600 mil, greater than or equal to 700 mil, greater than or equal to 800 mil, greater than or equal to 900 mil, greater than or equal to 1000 mil, greater than or equal to 1500 mil, greater than or equal to 2000 mil, greater than or equal to 2500 mil, greater than or equal to 3000 mil, or greater than or equal to 3500 mil.
  • the thickness of the overall filter media is less than or equal to 4000 mil, less than or equal to 3500 mil, less than or equal to 3000 mil, less than or equal to 2500 mil, less than or equal to 2000 mil, less than or equal to 1500 mil, less than or equal to 1000 mil, less than or equal to 900 mil, less than or equal to 800 mil, less than or equal to 700 mil, less than or equal to 600 mil, less than or equal to 500 mil, less than or equal to 400 mil, less than or equal to 300 mil, less than or equal to 250 mil, less than or equal to 200 mil, or less than or equal to 150 mil.
  • Filter media having an open support layer, a coarse support layer, and one or more charged fiber layers, where at least one charged fiber layer is held in a waved or curvilinear configuration as described herein may have desirable filtration properties such as dust holding capacity, gamma, pressure drop, and/or overall air permeability.
  • the filter media may exhibit suitable overall air permeability characteristics.
  • the overall air permeability of a filter media may range from between about 10 CFM and about 1000 CFM.
  • the overall air permeability of the filter media may be greater than or equal to 10 CFM, greater than or equal to 25 CFM, greater than or equal to 50 CFM, greater than or equal to 75 CFM, greater than or equal to 100 CFM, greater than or equal to 150 CFM, greater than or equal to 200 CFM, greater than or equal to 300 CFM, greater than or equal to 400 CFM, greater than or equal to 500 CFM, greater than or equal to 600 CFM, greater than or equal to 700 CFM, greater than or equal to 800 CFM, or greater than or equal to 900 CFM.
  • the filter media has an overall air permeability of less than or equal to 1000 CFM, less than or equal to 900 CFM, less than or equal to 800 CFM, less than or equal to 700 CFM, less than or equal to 600 CFM, less than or equal to 500 CFM, less than or equal to 400 CFM, less than or equal to 300 CFM, less than or equal to 200 CFM, less than or equal to 100 CFM, less than or equal to 75 CFM, less than or equal to 50 CFM, or less than or equal to 25 CFM.
  • Other ranges are also possible.
  • Overall air permeability of the filter media, as determined herein, is measured according to the test standard ASTM D737 over 38 cm surface area of the media and using a pressure of 125 Pa.
  • the pressure drop across the filter media e.g., the filter media comprising an open support layer, a coarse support layer, and one or more charged fiber layers, where at least one charged fiber layer is held in a waved or curvilinear configuration
  • the pressure drop across the filter media may range from between 2 Pa and 200 Pa, or between 3 Pa and 25 Pa. In some embodiments, the pressure drop across the filter media may be greater than or equal to 2 Pa, greater than or equal to 3 Pa, greater than or equal to 5 Pa, greater than or equal to 10 Pa, greater than or equal to 20 Pa, greater than or equal to 25 Pa, greater than or equal to 50 Pa, greater than or equal to 75 Pa, greater than or equal to 100 Pa, greater than or equal to 125 Pa, greater than or equal to 150 Pa, or greater than or equal to 175 Pa.
  • the pressure drop across the filter media may be less than or equal to 200 Pa, less than or equal to 175 Pa, less than or equal to 150 Pa, less than or equal to 125 Pa, less than or equal to 100 Pa, less than or equal to 75 Pa, less than or equal to 50 Pa, less than or equal to 25 Pa, less than or equal to 20 Pa, less than or equal to 10 Pa, less than or equal to 5 Pa, or less than or equal to 3 Pa. Combinations of the above-referenced ranges are also possible (e.g., a pressure drop of greater than or equal 2 Pa and less than or equal to 200 Pa, greater than or equal to 3 Pa and less than or equal to 25 Pa). Other ranges are also possible.
  • the filter media described herein can have beneficial dust holding properties.
  • the filter media e.g., the filter media comprising an open support layer, a coarse support layer, and one or more charged fiber layers, where at least one charged fiber layer is held in a waved or curvilinear configuration
  • DHC dust holding capacity
  • the filter media may have a dust holding capacity (DHC) of greater than or equal to 5 g/m , greater than or equal to 10 g/m 2 , greater than or equal to 25 g/m 2 , greater than or equal to 50 g/m 2 , greater than or equal to 75 g/m 2 , greater than or equal to 100 g/m 2 , greater than or equal to 150 g/m 2 , greater than or equal to 200 g/m 2 , greater than or equal to 250 g/m 2 , greater than or equal to 300 g/m 2 , greater than or equal to 350 g/m 2 , greater than or equal to 400 g/m 2 , greater than or equal to 450
  • the DHC of the filter media may be less than or equal to 600 g/m 2 , less than or equal to 550 g/m 2 , less than or equal to 500 g/m 2 , less than or equal to 450 g/m 2 , less than or equal to 400 g/m 2 , less than or equal to 350 g/m 2 , less than or equal to 300 g/m 2 , less than or equal to 250 g/m 2 , less than or equal to 200 g/m 2 , less than or equal to 150 g/m 2 , less than or equal to 100 g/m 2 , less than or equal to 75 g/m 2 , less than or equal to 50 g/m 2 , less than or equal to 25 g/m 2 , or less than or equal to 10 g/m . Combinations of the above-referenced ranges are also possible (e.g., a DHC of greater than or equal to 5 g/m 2 and less than or equal to 600 g/m 2
  • the dust holding capacity of a filter media comprising an open support layer, a coarse support layer, and one or more charged fiber layers, where at least one charged fiber layer is held in a waved or curvilinear configuration is tested based on the
  • ASHRAE 52.2 standard The testing uses ASHRAE test dust at a base upstream gravimetric dust level of 70 mg/m 2. The test is run at a face velocity of 0.944 m 3 /s (3400 m /h) until a terminal pressure of 450 Pa.
  • the filter media (e.g., the filter media comprising an open support layer and one or more charged fiber layers, where at least one charged fiber layer is held in a waved or curvilinear configuration) as a whole may have a relatively high value of gamma.
  • the value of gamma for the filter is greater than or equal to 20, greater than or equal to 30, greater than or equal to 50, greater than or equal to 75, greater than or equal to 100, greater than or equal to 125, greater than or equal to 150, greater than or equal to 175, greater than or equal to 200, or greater than or equal to 225.
  • the value of gamma for the filter media is less than or equal to 250, less than or equal to 225, less than or equal to 200, less than or equal to 175, less than or equal to 150, less than or equal to 125, less than or equal to 100, less than or equal to 75, less than or equal to 50, or less than or equal to 30. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 20 and less than or equal to 250, or greater than or equal to 75 and less than or equal to 150). Other ranges are also possible.
  • Gamma is determined as described above.
  • the filter media (e.g., the filter media comprising an open support layer, a coarse support layer, and one or more charged fiber layers, where at least one charged fiber layer is held in a waved or curvilinear configuration) may be designed to have a particular initial efficiency (e.g., initial efficiency).
  • the initial efficiency of the filter media is greater than or equal to 50% greater than or equal to 55% greater than or equal to 60% greater than or equal to 65% greater than or equal to 70% greater than or equal to 75% greater than or equal to 80% greater than or equal to 85% greater than or equal to 90%, greater than or equal to 92%, greater than or equal to 95%, greater than or equal to 96%, greater than or equal to 97%, greater than or equal to 98%, greater than or equal to 99%, greater than or equal to 99.5%, greater than or equal to 99.8%, greater than or equal to 99.9%, or greater than or equal to 99.99%.
  • the initial efficiency of the filter media is less than or equal to 99.999%, less than or equal to 99.99%, less than or equal to 99.9%, less than or equal to 99.8%, less than or equal to 99.5%, less than or equal to 99%, less than or equal to 98%, less than or equal to 97%, less than or equal to 96%, less than or equal to 95%, less than or equal to 92%, less than or equal to 90%, less than or equal to 85%, less than or equal to 80%, less than or equal to 75%, less than or equal to 70%, less than or equal to 65%, less than or equal to 60%, or less than or equal to 55%. Combinations of the above-referenced ranges are also possible (e.g., an initial efficiency of greater than or equal to 50% and less than or equal to 99.999%, greater than or equal to 90% and less than or equal to 99.999%). Other ranges are also possible.
  • the filter media comprises a charged fiber layer, an open support layer mechanically attached to the charged fiber layer and a coarse support layer that holds the charged fiber layer in a waved configuration and maintains separation of peaks and troughs of adjacent waves of the charged fiber layer.
  • the charged fiber layer has a basis weight of less than or equal to 12 g/m and greater than or equal to 700 g/m .
  • the open support layer has an air permeability of greater than 1100 CFM and less than or equal to 20000 CFM.
  • the filter media has an overall air permeability of greater than or equal to 10 CFM and less than or equal to 1000 CFM.
  • the filter media comprises one or more coarse support layers (e.g., that holds the charged fiber layer in a waved configuration and maintains separation of peaks and troughs of adjacent waves of the charged fiber layer).
  • coarse support layers e.g., that holds the charged fiber layer in a waved configuration and maintains separation of peaks and troughs of adjacent waves of the charged fiber layer.
  • the coarse support layers 230, 232 can be formed from a variety of fibers types and sizes.
  • the downstream coarse support layer 232 is formed from fibers having an average fiber diameter that is greater than or equal to an average fiber diameter of the second layer 220 and/or third layer 222, the upstream coarse support layer 230, and the top layer 240, if provided.
  • the upstream support layer 230 is formed from fibers having an average fiber diameter that is less than or equal to an average fiber diameter of the downstream support layer 232, but that is greater than an average fiber diameter of the second layer 220 and/or third layer 222.
  • the fibers of the coarse support layer(s) may have an average fiber length of, for example, between about 0.5 inches and 6.0 inches (e.g., between 1.5 inches and 3 inches).
  • the fibers of the coarse support layer may have an average fiber length of less than or equal to 6 inches, less than or equal to 5.5 inches, less than or equal to 5 inches, less than or equal to 4.5 inches, less than or equal to 4 inches, less than or equal to 3.5 inches, less than or equal to 3 inches, less than or equal to 2.5 inches, less than or equal to 2 inches, or less than or equal to 1 inch.
  • the fibers of the coarse support layer may have an average fiber length of greater than or equal to 0.5 inches, greater than or equal to 1 inch, greater than or equal to 1.5 inches, greater than or equal to 2 inches, greater than or equal to 2.5 inches, greater than or equal to 3 inches, greater than or equal to 3.5 inches, greater than or equal to 4 inches, greater than or equal to 4.5 inches, greater than or equal to 5 inches, or greater than or equal to 5.5 inches. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.5 inches and less than or equal to 6 inches, greater than or equal to 1.5 inches and less than or equal to 3 inches). Other ranges are also possible.
  • the plurality of fibers in the coarse support layer(s) may have an average fiber diameter of greater than or equal to 8 microns, greater than or equal to 10 microns, greater than or equal to 12 microns, greater than or equal to 15 microns, greater than or equal to 20 microns, greater than or equal to 25 microns, greater than or equal to 30 microns, greater than or equal to 35 microns, greater than or equal to 40 microns, greater than or equal to 45 microns, greater than or equal to 50 microns, greater than or equal to 55 microns, greater than or equal to 60 microns, greater than or equal to 65 microns, greater than or equal to 70 microns, greater than or equal to 75 microns, or greater than or equal to 80 microns.
  • the plurality of fibers in the coarse support layer(s) may have an average fiber diameter of less than or equal to 85 microns, less than or equal to 80 microns, less than or equal to 75 microns, less than or equal to 70 microns, less than or equal to 65 microns, less than or equal to 60 microns, less than or equal to 55 microns, less than or equal to 50 microns, less than or equal to 45 microns, less than or equal to 40 microns, less than or equal to 35 microns, less than or equal to 30 microns, less than or equal to 25 microns, less than or equal to 20 microns, less than or equal to 15 microns, less than or equal to 12 microns, or less than or equal to 10 microns.
  • Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 8 micron and less than or equal to 85 microns, greater than or equal to 12 microns and less than or equal to 60 microns). Other values of average fiber diameter for the coarse support layer(s) are also possible.
  • the coarse support layer(s) are formed from staple fibers, and in particular from a
  • the binder fibers can be formed from any material that is effective to facilitate thermal bonding between the layers, and will thus have an activation temperature that is lower than the melting temperature of the non-binder fibers.
  • the binder fibers can be monocomponent fibers or any one of a number of bicomponent binder fibers.
  • the binder fibers can be bicomponent fibers, and each component can have a different melting temperature.
  • the binder fibers can include a core and a sheath where the activation temperature of the sheath is lower than the melting temperature of the core.
  • the core/sheath binder fibers can be concentric or non-concentric, and exemplary core/sheath binder fibers can include the following: a polyester core/copolyester sheath, a polyester core/polyethylene sheath, a polyester core/polypropylene sheath, a polypropylene core/polyethylene sheath, a polyamide core/polyethylene sheath, and combinations thereof.
  • Other exemplary bicomponent binder fibers can include split fiber fibers, side-by-side fibers, and/or "island in the sea" fibers.
  • the non-binder fibers can be synthetic and/or non-synthetic, and in an exemplary embodiment the non-binder fibers can be about 100 percent synthetic.
  • synthetic fibers are preferred over non- synthetic fibers for resistance to moisture, heat, long-term aging, and microbiological degradation.
  • Exemplary synthetic non-binder fibers can include polyesters, acrylics, polyolefins, nylons, rayons, and combinations thereof.
  • the non-binder fibers used to form the coarse support layer(s) can include non-synthetic fibers such as glass fibers, glass wool fibers, cellulose pulp fibers, such as wood pulp fibers, and combinations thereof.
  • Non-limiting examples of suitable synthetic fibers include polyester, polyaramid, polyimide, polyolefin (e.g., polyethylene), polypropylene, Kevlar, Nomex, halogenated polymers (e.g., polyethylene terephthalate), acrylics, polyphenylene oxide,
  • the coarse support layer(s) can also be formed using various techniques known in the art, including meltblowing, wet laid techniques, air laid techniques, carding, and spunbonding. In an exemplary embodiment, however, the coarse support layers are carded or airlaid webs.
  • the resulting layers can also have a variety of thicknesses, air permeabilities, and basis weights depending upon the requirements of a desired application.
  • the downstream coarse support layer and the upstream coarse support layer each have a thickness in the range of 2 mil to 1000 mil (e.g., between 12 mil to 100 mil) and a basis weight in the range of 5 g/m to 100 g/m 2 (e.g., between 12 g/m 2 and 40 g/m 2 ).
  • the thickness of one or more coarse support layer(s) is greater than or equal to 2 mil, greater than or equal to 3 mil, greater than or equal to 5 mil, greater than or equal to 10 mil, greater than or equal to 12 mil, greater than or equal to 15 mil, greater than or equal to 25 mil, greater than or equal to 50 mil, greater than or equal to 75 mil, greater than or equal to 100 mil, greater than or equal to 150 mil, greater than or equal to 200 mil, greater than or equal to 250 mil, greater than or equal to 300 mil, greater than or equal to 400 mil, greater than or equal to 500 mil, greater than or equal to 600 mil, greater than or equal to 700 mil, greater than or equal to 800 mil, or greater than or equal to 900 mil.
  • the thickness of one or more coarse support layer(s) is less than or equal to 1000 mil, less than or equal to 900 mil, less than or equal to 800 mil, less than or equal to 700 mil, less than or equal to 600 mil, less than or equal to 500 mil, less than or equal to 400 mil, less than or equal to 300 mil, less than or equal to 250 mil, less than or equal to 200 mil, less than or equal to 150 mil, less than or equal to 100 mil, less than or equal to 75 mil, less than or equal to 50 mil, less than or equal to 25 mil, less than or equal to 15 mil, less than or equal to 12 mil, less than or equal to 10 mil, less than or equal to 5 mil, or less than or equal to 3 mil. Combinations of the above referenced ranges are also possible (e.g., a thickness of greater than or equal to 2 mil and less than or equal to 1000 mil, greater than or equal to 12 mil and less than or equal to 100 mil). Other ranges are also possible.
  • the coarse support layer(s) may each have a basis weight of less than or equal to 100 g/m 2 , less than or equal to 90 g/m 2 , less than or equal to 85 g/m 2 , less than or equal to 80 g/m 2 , less than or equal to 70 g/m 2 , less than or equal to 60 g/m 2 , less than or equal to 50 g/m 2 , less than or equal to 40 g/m 2 , less than or equal to 30 g/m 2 , less than or equal to 25 g/m 2 , less than or equal to 12 g/m 2 , or less than or equal to 10 g/m".
  • the coarse support layer may have a basis weight of greater than or equal to 5 g/m 2 , greater than or equal to 10 g/m 2 , greater than or equal to 12 g/m 2 , greater than or equal to 25 g/m 2 , greater than or equal to 30 g/m 2 , greater than or equal to 40 g/m 2 , greater than or equal to 50 g/m 2 , greater than or equal to 60 g/m 2 , greater than or equal to 70 g/m 2 , greater than or equal to 80 g/m 2 , greater than 85 g/m 2 , or greater than or equal to 90 g/m .
  • the filter media can also optionally include one or more outer or cover layers (e.g., a top layer, a bottom layer) disposed on the air entering side I and/or the air outflow side O (as illustrated in FIG. 2C).
  • the cover layer can function as a dust loading layer and/or it can function as an aesthetic layer and/or a support layer.
  • the cover layer is a planar layer that is mated to the filter media after the charged fiber layer(s) and, optionally, other layer(s) are waved. The cover layer thus provides a top surface that is aesthetically pleasing.
  • the cover layer can be formed from a variety of fiber types and sizes, but in an exemplary embodiment the cover layer is formed from fibers having an average fiber diameter that is less than an average fiber diameter of the coarse support layer(s) directly adjacent the cover layer, but that is greater than an average fiber diameter of the charged fiber layer(s) (e.g., the second layer). In certain exemplary embodiments, the cover layer is formed from fibers having an average fiber diameter in the range of about 5 ⁇ to 20 ⁇ .
  • the filter media described herein may be, in some cases, antimicrobial.
  • the filter media (or any given layer) may comprise a plurality of fibers that are antimicrobial.
  • Such filter media may be useful for, for example, the prevention of microbial (e.g., bacterial, fungal, viral) growth on one or more components (e.g., fibers, layers) or the filter media.
  • the filter media described herein may be, in some cases, oleophobic.
  • the filter media (or any given layer) may be tailored to have a particular oil repellency level.
  • Such filter media may be used, for example, to remove or coalesce oil, lubricants, and/or cooling agents from a gas stream that passes through the filter media.
  • the oil repellency level of the filter media or layer is between 1 and 7 (e.g., 1-4, 2-5, 3-6, 4-7). In some embodiments, the oil repellency level of the filter media or layer is greater than or equal to 1.
  • the oil repellency level of the filter media or layer or sublayer is 1, 2, 3, 4, 5, 6, or 7.
  • Oil repellency level as described herein is determined according to AATCC TM 118 (1997) measured at 23 °C and 50% relative humidity (RH). Briefly, 5 drops of each test oil (having an average droplet diameter of about 2 mm) are placed on five different locations on the surface of the filter media or layer or sublayer. The test oil with the greatest oil surface tension that does not wet (i.e. has a contact angle greater than or equal to 90 degrees with the surface) the surface of the filter media or layer or sublayer after 30 seconds of contact with the filter media at 23 °C and 50% RH, corresponds to the oil repellency level (listed in Table 2).
  • the filter media or layer or sublayer has an oil repellency level of 4.
  • the filter media or layer or sublayer has an oil repellency level of 5.
  • the filter media or layer or sublayer has an oil repellency level of 6.
  • the oil repellency level is expressed to the nearest 0.5 value determined by subtracting 0.5 from the number of the test liquid.
  • the filter media or layer or sublayer has an oil repellency level of 5.5.
  • At least one surface of a layer (e.g., open support layer, additional layer) and/or at least one surface of the filter media may be modified such that the filter media has an oil repellency level of greater than or equal to 1.
  • the filter media may have at least one modified surface.
  • the filter media comprises a plurality of fibers wherein at least a portion of the fibers comprise a modified surface.
  • the material used to modify at least one surface of the filter media and/or fibers may be applied on any suitable portion of the filter media.
  • the material may be applied such that one or more surfaces of the filter media are modified without substantially modifying the interior of the filter media.
  • a single surface of the filter media may be modified.
  • the upstream surface of the filter media may be coated.
  • more than one surface of the filter media may be coated (e.g., the upstream and downstream surfaces).
  • at least a portion of the interior of the filter media may be modified along with at least one surface of the filter media.
  • the entire filter media is modified with the material.
  • any suitable method for modifying the surface chemistry of at least one surface of the filter media and/or the plurality of fibers may be used (e.g., to modify the oil repellency level of the filter media (or one or more layers of the filter media)).
  • the surface chemistry of the filter media and/or the plurality of fibers may be modified by coating at least a portion of the surface, using melt-additives, and/or altering the roughness of the surface.
  • the surface modification may be a coating.
  • Such coating(s) may be used to modify the oil repellency level of the filter media (or one or more layers of the filter media).
  • a coating process involves introducing resin or a material (e.g., hydrophobic material, hydrophilic material, lipophilic material, lipophobic material) dispersed in a solvent or solvent mixture into a pre-formed fiber layer (e.g., a pre-formed filter media formed by a meltblown process).
  • Non-limiting examples of coating methods include the use of chemical vapor deposition, a slot die coater, gravure coating, screen coating, size press coating (e.g., a two roll-type or a metering blade type size press coater), film press coating, blade coating, roll-blade coating, air knife coating, roll coating, foam application, reverse roll coating, bar coating, curtain coating, champlex coating, brush coating, Bill-blade coating, short dwell-blade coating, lip coating, gate roll coating, gate roll size press coating, laboratory size press coating, melt coating, dip coating, knife roll coating, spin coating, spray coating, gapped roll coating, roll transfer coating, padding saturant coating, and saturation impregnation. Other coating methods are also possible.
  • the hydrophilic, hydrophobic, lipophilic, and/or lipophobic material may be applied to the filter media using a non-compressive coating technique.
  • the non-compressive coating technique may coat the filter media, while not substantially decreasing the thickness of the web.
  • the resin may be applied to the filter media using a compressive coating technique.
  • a surface described herein is modified using chemical vapor deposition (e.g. , to modify the oil repellency level of the filter media (or one or more layers of the filter media)).
  • chemical vapor deposition the filter media is exposed to gaseous reactants from gas or liquid vapor that are deposited onto the filter media under high energy level excitation such as thermal, microwave, UV, electron beam or plasma.
  • a carrier gas such as oxygen, helium, argon and/or nitrogen may be used.
  • vapor deposition methods include atmospheric pressure chemical vapor deposition (APCVD), low pressure chemical vapor deposition (LPCVD), metal-organic chemical vapor deposition (MOCVD), plasma assisted chemical vapor deposition (PACVD) or plasma enhanced chemical vapor deposition (PECVD), laser chemical vapor deposition (LCVD), photochemical vapor deposition (PCVD), chemical vapor infiltration (CVI) and chemical beam epitaxy (CBE).
  • APCVD atmospheric pressure chemical vapor deposition
  • LPCVD low pressure chemical vapor deposition
  • MOCVD metal-organic chemical vapor deposition
  • PCVD plasma assisted chemical vapor deposition
  • PECVD plasma enhanced chemical vapor deposition
  • LCVD laser chemical vapor deposition
  • PCVD photochemical vapor deposition
  • CVI chemical vapor infiltration
  • CBE chemical beam epitaxy
  • PVD physical vapor deposition
  • the coating may be dried by any suitable method.
  • drying methods include the use of a photo dryer, infrared dryer, hot air oven steam-heated cylinder, or any suitable type of dryer familiar to those of ordinary skill in the art.
  • the fibers of the filter media may be coated without substantially blocking the pores of the filter media. In some instances, substantially all of the fibers may be coated without substantially blocking the pores. In some embodiments, the filter media may be coated with a relatively high weight percentage of resin or material without blocking the pores of the filter media using the methods described herein (e.g., by dissolving and/or suspending one or more material in a solvent to form the resin).
  • the surface may be modified using melt additives (e.g., to modify the oil repellency level of the filter media (or one or more layers of the filter media)).
  • melt additives are functional chemicals that are added to thermoplastics fibers during an extrusion process that may render different physical and chemical properties at the surface from those of the thermoplastic itself after formation.
  • the material may undergo a chemical reaction (e.g., polymerization) after being applied to the filter media.
  • a surface of the filter media may be coated with one or more monomers that can be polymerized after coating.
  • a surface of the filter media may include monomers, as a result of the melt additive, that are polymerized after formation of the filter media.
  • an in-line polymerization may be used. In-line polymerization (e.g., in -line ultraviolet polymerization) is a process to cure a monomer or liquid polymer solution onto a substrate under conditions sufficient to induce polymerization (e.g., under UV irradiation).
  • any suitable material may be used to alter the surface chemistry, and accordingly the oleophobicity, of the filter media.
  • the material may be charged.
  • the surface charge of the filter media may further facilitate coalescence and/or increase the oil carry over.
  • a filter media having a lipophilic modified surface may have a decreased oil carry over and/or produce larger coalesced droplets than a filter media having a non-modified surface.
  • the net charge of the modified surface may be negative, positive, or neutral.
  • the modified surface may comprise a negatively charged material and/or a positively charged material.
  • the surface may be modified with an electrostatically neutral material.
  • materials that may be used to modify the surface include polyelectrolytes (e.g., anionic, cationic), oligomers, polymers (e.g., fluorinated polymers, perfluoroalkyl ethyl methacrylate, polycaprolactone, poly
  • [bis(trifluoroethoxy)phosphazene] small molecules (e.g., carboxylate containing monomers, amine containing monomers, polyol), ionic liquids, monomer precursors, and gases, and combinations thereof.
  • the polymer may include a species having the formula -C n F2 n+ i or -C n F m , where n is an integer greater than 1, and m is an integer greater than 1 (e.g., -C 6 F 13 ).
  • anionic polyelectrolytes may be used to modify the surface of the filter media.
  • one or more anionic polyelectrolytes may be spray or dip coated onto at least one surface of the filter media.
  • cationic polyelectrolytes may be used to modify the surface of the filter media.
  • silicone or derivatives thereof
  • At least a surface of the filter media may be treated or coated with polydimethylsiloxane.
  • the surface of the filter media may be silylated (e.g., a substituted silyl group may be incorporated onto at least a surface of the filter media).
  • a filler material e.g., an organic filler material, and inorganic filler material
  • a filler material may be added to the filter media to modify the surface and/or oil repellency level of the filter media (or one or more layers of the filter media).
  • small molecules as defined further below e.g., monomers, polyol
  • small molecules may be used to modify the oil repellency level of the filter media.
  • small molecules may be used as melt- additives.
  • small molecules may be deposited on at least one surface of the filter media via coating (e.g., chemical vapor deposition). Regardless of the modification method, the small molecules on a surface of the filter media may be polymerized after deposition in some
  • the small molecules such as monobasic carboxylic acids and/or unsaturated dicarboxylic (dibasic) acids, may be used to modify at least one surface of the filter media.
  • the small molecules may be amine containing small molecules.
  • the amine containing small molecules may be primary, secondary, or tertiary amines. In some such cases, the amine containing small molecule may be a monomer.
  • the small molecule may be an inorganic or organic hydrophobic molecule.
  • Non-limiting examples include hydrocarbons (e.g., CH 4 , C 2 H 2 , C 2 H 4 , C 6 H 6 ), fluorocarbons (e.g., CF 4 , C 2 F 4 , C 3 F 6 , C 3 F 8 , C 4 H 8 , C 5 Hi 2 , C 6 F 6 , C 6 Fi 3 , or other fluorocarbons having the formula -C n F 2n+ i or -C n F m , where n is an integer greater than 1, and m is an integer greater than 1), silanes (e.g., SiH 4 , Si 2 H 6 , Si 3 H 8 ,
  • suitable hydrocarbons for modifying a surface of the filter media may have the formula C x H y , where x is an integer from 1 to 10 and y is an integer from 2 to 22.
  • suitable silanes for modifying a surface of the filter media may have the formula Si n H 2n+2 where any hydrogen may be substituted for a halogen (e.g., CI , F, Br, I), where n is an integer from 1 to 10.
  • a halogen e.g., CI , F, Br, I
  • small molecules refers to molecules, whether naturally- occurring or artificially created (e.g., via chemical synthesis) that have a relatively low molecular weight.
  • a small molecule is an organic compound (i.e., it contains carbon).
  • the small organic molecule may contain multiple carbon-carbon bonds, stereocenters, and other functional groups (e.g., amines, hydroxyl, carbonyls, and heterocyclic rings, etc.).
  • the molecular weight of a small molecule is at most about 1,000 g/mol, at most about 900 g/mol, at most about 800 g/mol, at most about 700 g/mol, at most about 600 g/mol, at most about 500 g/mol, at most about 400 g/mol, at most about 300 g/mol, at most about 200 g/mol, or at most about 100 g/mol.
  • the molecular weight of a small molecule is at least about 100 g/mol, at least about 200 g/mol, at least about 300 g/mol, at least about 400 g/mol, at least about 500 g/mol, at least about 600 g/mol, at least about 700 g/mol, at least about 800 g/mol, or at least about 900 g/mol, or at least about 1,000 g/mol.
  • polymers may be used to modify the oil repellency level of the filter media (or one or more layers of the filter media). For example, one or more polymer may be applied to at least a portion of a surface of the filter media via a coating technique.
  • the polymer may be formed from monobasic carboxylic acids and/or unsaturated dicarboxylic (dibasic) acids.
  • the polymer may be a graft copolymer and may be formed by grafting polymers or oligomers to polymers in the fibers and/or filter media (e.g., resin polymer).
  • the graft polymer or oligomer may comprise carboxyl moieties that can be used to form a chemical bond between the graft and polymers in the fibers and/or filter media.
  • Non- limiting examples of polymers in the fibers and/or filter media that can be used to form a graft copolymer include polyethylene, polypropylene, polycarbonate, polyvinyl chloride, polytetrafluoroethylene, polystyrene, cellulose, polyethylene terephthalate, polybutylene terephthalate, and nylon, and combinations thereof. Graft polymerization can be initiated through chemical and/or radiochemical (e.g., electron beam, plasma, corona discharge, UV-irradiation) methods.
  • the polymer may be a polymer having a repeat unit that comprises an amine (e.g., polyallylamine, polyethyleneimine, polyoxazoline).
  • the polymer may be a polyol.
  • a gas may be used to modify the oil repellency level of the filter media (or one or more layers of the filter media).
  • the molecules in the gas may react with material (e.g., fibers, resin, additives) on the surface of the filter media to form functional groups, such as charged moieties, and/or to increase the oxygen content on the surface of the filter media.
  • the weight percent of the material used to modify at least one surface of the filter media may be greater than or equal to about 0.0001 wt%, greater than or equal to about 0.0005 wt%, greater than or equal to about 0.001 wt%, greater than or equal to about 0.005 wt%, greater than or equal to about 0.01 wt%, greater than or equal to about 0.05 wt%, greater than or equal to about 0.1 wt%, greater than or equal to about 0.5 wt%, greater than or equal to about 1 wt%, greater than or equal to about 2 wt%, or greater than or equal to about 3 wt% of the filter media.
  • the weight percentage of the material used to modify at least one surface of the filter media may be less than or equal to about 4 wt%, less than or equal to about 3 wt%, less than or equal to about 1 wt%, less than or equal to about 0.5 wt%, less than or equal to about 0.1 wt%, less than or equal to about 0.05 wt%, less than or equal to about 0.01 wt%, or less than or equal to about 0.005 wt% of the filter media.
  • a weight percentage of material of greater than or equal to about 0.0001 wt% and less than about 4 wt%, or greater than or equal to about 0.01 wt% and less than about 0.5 wt%).
  • Other ranges are also possible.
  • the weight percentage of material in the filter media is based on the dry solids of the filter media and can be determined by weighing the filter media before and after the material is applied.
  • the outer or cover layer is formed from staple fibers, and in particular from a combination of binder fibers and non-binder fibers.
  • One suitable fiber composition is a blend of at least about 20% binder fiber and a balance of non-binder fiber.
  • a variety of types of binder and non-binder fibers can be used to form the media of the present invention, including those previously discussed above with respect to the open support layer(s) and/or the coarse support layer(s).
  • the outer or cover layer can also be formed using various techniques known in the art, including meltblowing, wet laid techniques, air laid techniques, carding, and spunbonding.
  • a top layer is an airlaid layer and a bottom layer is a spunbond layer.
  • the resulting layer can also have a variety of thicknesses, air permeabilities, and basis weights depending upon the requirements of a desired application.
  • a layer of the filter media may be a non-wet laid layer formed using a non-wet laid process (e.g., an air laid process, a carding process, a meltblown process).
  • a non-wet laid process e.g., an air laid process, a carding process, a meltblown process.
  • an air laid process or a carding process may be used.
  • fibers may be mixed while air is blown onto a conveyor.
  • the fibers are manipulated by rollers and extensions (e.g., hooks, needles) associated with the rollers.
  • a layer of the filter media may include fibers formed from a meltblown process.
  • the meltblown layer may have one or more characteristics described in commonly-owned U.S. Patent No. 8,608,817, entitled “Meltblown Filter Medium", issued on December 17, 2013, which is based on U.S. Patent Application Serial No. 12/266,892 filed on May 14, 2009, commonly-owned U.S. Patent
  • the filter media comprises a charged fiber layer comprising a plurality of fibers, wherein at least a portion of the plurality of fibers are formed from a meltblown process.
  • the filter media may be used for a number of applications, such as respirator and face mask applications, cabin air filtration, military garments, HVAC systems (e.g., for industrial areas and buildings), clean rooms, vacuum filtration, furnace filtration, room air cleaning, high-efficiency particulate arrestance (HEPA) filters, ultra-low particular air (ULPA) filters, and respirator protection equipment (e.g., industrial respirators).
  • applications such as respirator and face mask applications, cabin air filtration, military garments, HVAC systems (e.g., for industrial areas and buildings), clean rooms, vacuum filtration, furnace filtration, room air cleaning, high-efficiency particulate arrestance (HEPA) filters, ultra-low particular air (ULPA) filters, and respirator protection equipment (e.g., industrial respirators).
  • HVAC systems e.g., for industrial areas and buildings
  • HEPA high-efficiency particulate arrestance
  • ULPA ultra-low particular air
  • respirator protection equipment e.g., industrial respirators.
  • the filter media may be incorporated into a face mask.
  • the filter media can be, for example, folded, edge sealed, collated, or molded, with or without a supporting structure, within the face mask.
  • the face mask may be a full face piece or a half face piece, and may be disposable or reusable.
  • face masks are used to protect the respiratory system when the air contains hazardous amounts of particulate contaminants in the form of solid particles or liquid droplets that can cause impairment through inhalation. Accordingly, a face mask generally needs to provide adequate protection with good breathability (e.g., low resistance).
  • the face mask may be designed to filter dust, fog, fumes, vapors, smoke, sprays or mists.
  • face masks may be worn in areas where activities such as grinding, welding, road paving (e.g., where hot asphalt fumes are present), coal mining, transferring diesel fuel, or pesticide spraying are performed.
  • the face mask may also be designed for wearing in hospitals (e.g., performing surgery), distillers and refineries in chemical industries, painting facilities, or oil fields.
  • the face mask may be a surgical face mask or an industrial face mask.
  • the filter media may be incorporated into a variety of other suitable filter elements for use in various applications including gas filtration.
  • the filter media may be used in heating and air conditioning ducts.
  • Filter elements may have any suitable configuration as known in the art including bag filters and panel filters.
  • Filter assemblies for filtration applications can include any of a variety of filter media and/or filter elements.
  • the filter elements can include the above-described filter media and/or layers (e.g., first layer, second layer). Examples of filter elements include gas turbine filter elements, dust collector elements, heavy duty air filter elements, automotive air filter elements, air filter elements for large displacement gasoline engines (e.g., SUVs, pickup trucks, trucks), HVAC air filter elements, HEPA filter elements, ULPA filter elements, and vacuum bag filter elements.
  • Filter elements can be incorporated into corresponding filter systems (gas turbine filter systems, heavy duty air filter systems, automotive air filter systems, HVAC air filter systems, HEPA filter systems, ULPA filter system, and vacuum bag filter systems).
  • the filter media can optionally be pleated into any of a variety of configurations (e.g., panel, cylindrical).
  • Filter elements can also be in any suitable form, such as radial filter elements, panel filter elements, or channel flow elements.
  • a radial filter element can include pleated filter media that are constrained within two open wire support materials in a cylindrical shape.
  • the filter element includes a housing that may be disposed around the filter media.
  • the housing can have various configurations, with the configurations varying based on the intended application.
  • the housing may be formed of a frame that is disposed around the perimeter of the filter media.
  • the frame may be thermally sealed around the perimeter.
  • the frame has a generally rectangular configuration surrounding all four sides of a generally rectangular filter media.
  • the frame may be formed from various materials, including for example, cardboard, metal, polymers, or any combination of suitable materials.
  • the filter elements may also include a variety of other features known in the art, such as stabilizing features for stabilizing the filter media relative to the frame, spacers, or any other appropriate feature.
  • the filter media can be incorporated into a bag (or pocket) filter element.
  • a bag filter element may be formed by any suitable method, e.g., by placing two filter media together (or folding a single filter media in half), and mating three sides (or two if folded) to one another such that only one side remains open, thereby forming a pocket inside the filter.
  • multiple filter pockets may be attached to a frame to form a filter element. It should be understood that the filter media and filter elements may have a variety of different constructions and the particular construction depends on the application in which the filter media and elements are used.
  • the filter elements may have the same property values as those noted above in connection with the filter media and/or layers. For example, the above-noted
  • filter media mechanically trap contaminant particles on the filter media as fluid (e.g., air) flows through the filter media.
  • the filter media comprises an open support layer, a charged fiber layer associated with the open support layer, and an additional layer associated with the charged fiber layer and the open support layer.
  • the filter media comprises an open support layer, a charged fiber layer associated with the open support layer, an additional layer associated with the charged fiber layer and the open support layer, and a fine fiber layer associated with the additional layer.
  • the filter media comprises an open support layer, a charged fiber layer associated with the open support layer, an additional layer associated with the charged fiber layer and the open support layer, and a coarse support layer that holds at least the charged fiber layer in a waved configuration and maintains separation of peaks and troughs of adjacent waves of the charged fiber layer,
  • the open support layer, charged fiber layer, additional layer, and/or fine fiber layer, if present, may be mechanically attached (e.g., needled) to one another.
  • the open support layer has an air permeability of greater than 1100 CFM and less than or equal to 20000 CFM. In certain embodiments, the open support layer and the additional layer have a combined air permeability of greater than 45 CFM and less than 1100 CFM. In a particular set of embodiments, the open support layer comprises a mesh.
  • the additional layer is a meltblown layer, a spunbond layer, or a carded web layer. In a particular set of embodiments, the additional layer is a meltblown layer. In certain embodiments, the additional layer is a meltblown layer assiocated with the open support layer and may be laminated to a charged fiber layer. In some cases, the combined value of gamma of the meltblown layer, the open support layer, and the charged fiber layer may be greater than or equal to 90 and less than or equal to 250. In some embodiments, the metlblown layer may be charged e.g., by hydrocharging.
  • the filter media comprises a fine fiber layer associated with the additional layer.
  • the fine fiber layer comprises a plurality of electrospun fibers.
  • the fine fiber layer may comprise a plurality of fibers having an average fiber diameter of greater than or equal to 0.1 microns and less than or equal to 2 microns.
  • the charged fiber layer comprises a first plurality of fibers comprising a first polymer and a second plurality of fibers comprising a second polymer.
  • the total number of fibers in the charged fiber layer (e.g., the total number of fibers in the first plurality of fibers and second plurality of fibers) per gram of charged fiber layer is greater than or equal to 50,000 fibers and less than or equal to 125,000 fibers per gram of charged fiber layer.
  • the charged fiber layer has a BET surface area of greater than or equal to 0.33 m /g and less than or equal to 1.5 m /g.
  • first plurality of fibers and/or the second plurality of fibers may have an average length of greater than or equal to 30 mm.
  • first plurality of fibers and/or the second plurality of fibers are multi- lobal (e.g., trilobal).
  • the filter media (and/one or more layers of the filter media e.g., the charged fiber layer) may be antimicrobial.
  • antimicrobial as used herein is given its ordinary meaning in the art and generally refers to a material (e.g., a polymer) which destroys or inhibits the growth of microorganisms (e.g., bacteria, viruses, fungi) and, in some cases, pathogenic microorganisms.
  • the charged fiber layer and/or the open support layer of the filter media may be antimicrobial.
  • one or more layers of the filter media comprise a plurality of antimicrobial fibers.
  • a charged fiber layer comprises a first plurality of fibers and a second plurality of fibers, where the first plurality of fibers (and/or the second plurality of fibers) comprises a plurality of antimicrobial fibers (e.g., comprising an antimicrobial polymer).
  • the open support layer e.g., a mesh, a scrim, a netting, a spunbond layer
  • the plurality of (antimicrobial) fibers comprise a bacteriostatic, fungistatic, and/or virostatic polymer.
  • the plurality of (antimicrobial) fibers comprise a polymer such as polypropylene and are bacteriostatic, fungistatic, and/or virostatic.
  • suitable polymers for use in antimicrobial fibers include polyethylene, polypropylene, polystyrene, ethylene/vinyl acetate copolymer, ethylene- vinyl alcohol copolymer, poly amide (e.g., nylon), polyacrylonitrile, acrylic, and polyethylene terephthalate.
  • amide e.g., nylon
  • the plurality of fibers (e.g., the first plurality of fibers, the second plurality of fibers) of one or more layers of the filter media comprise an antimicrobial additive such as a bacteriostatic, fungistatic, and/or virostatic additive.
  • Non-limiting examples of suitable antimicrobial additives include silver and derivatives thereof (e.g., silver particles, silver ions), zinc and derivatives thereof (e.g., zinc pyrithione), metal oxides (silver oxide, iron oxide, titanium oxide, copper oxide, and zinc oxide), triclosan, quarternary ammonium compounds, chitosan, poly(hexamethylene biguanide), terpinoids, flavonoids, quinones, lectins, and n-halamines.
  • the plurality of fibers comprise a polymer such as polypropylene and an antimicrobial additive such as triclosan.
  • the plurality of fibers comprise a polymer such as polyamide or acrylic and an antimicrobial additive such as quartenary ammonium compound, chitosan, and/or n-halamines.
  • an antimicrobial additive such as quartenary ammonium compound, chitosan, and/or n-halamines.
  • Other combinations of polymers and antimicrobial additives are also possible.
  • the filter media (and/or one or more layers of the filter media) may be designed to have a particular bacterial filtration efficiency.
  • the bacterial filtration efficiency of the filter media (and/or one or more layers of the filter media) may be greater than or equal to 95%, greater than or equal to 98%, greater than or equal to 99%, greater than or equal to 99.5%, greater than or equal to 99.9%, greater than or equal to 99.99%, greater than or equal to 99.999%, greater than or equal to 99.999%, or greater than or equal to 99.9999%.
  • the bacterial filtration efficiency of the filter media is less than or equal to 99.99995%, less than or equal to 99.9999%, less than or equal to 99.999%, less than or equal to 99.99%, less than or equal to 99.9%, less than or equal to 99.5%, less than or equal to 99%, or less than or equal to 98%. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 95% and less than or equal to 99.99995%). Other ranges are also possible.
  • the bacterial filtration efficiency is measured according to ASTM F2101 as the percent of bacteria ⁇ staphylococcus aureus) collected downstream of a filter media versus the bacteria provided upstream of the filter media in an aerosol initially comprising 1 million bacterial units at a face velocity of 12.5 cm/s and a flow rate of 30 liters per minute over an area of 40 cm .
  • the filter media (and/or one or more layers of the filter media) may be designed to have a particular viral filtration efficiency.
  • the viral filtration efficiency of the filter media (and/or one or more layers of the filter media) may be greater than or equal to 95%, greater than or equal to 98%, greater than or equal to 99%, greater than or equal to 99.5%, greater than or equal to 99.9%, greater than or equal to 99.99%, greater than or equal to 99.999%, greater than or equal to 99.999%, or greater than or equal to 99.9999%.
  • the viral filtration efficiency of the filter media is less than or equal to 99.99995%, less than or equal to 99.9999%, less than or equal to 99.999%, less than or equal to 99.99%, less than or equal to 99.9%, less than or equal to 99.5%, less than or equal to 99%, or less than or equal to 98%. Combinations of the above- referenced ranges are also possible (e.g., greater than or equal to 95% and less than or equal to 99.99995%). Other ranges are also possible.
  • the viral filtration efficiency is measured according to ASTM F2101 as the percent of viruses (Phi X174 bacteriophase) collected downstream of a filter media versus the viruses provided upstream of the filter media in an aerosol initially comprising 10 plaque-forming units of the virus at a flow rate of 30 liters per minute and face velocity of 12.5 cm/s over an area of 40cm .
  • the filter media may be designed to have a desirable fire resistance (e.g., Fl rating, Kl rating) and performance properties without e.g., compromising certain mechanical and/or filtration properties (e.g., pleatability of the media).
  • the filter media is fire resistant (e.g., passes a glow wire test according to IEC60695-2-11 (2010)).
  • the charged fiber layer of the filter media is configured to remain charged after direct contact with an ignition source (e.g., a flame, a "glow" wire at 850 °C).
  • the first plurality of fibers and/or the second plurality of fibers are fire resistant.
  • the filter media (and/or one or more layers of the filter media e.g., the charged fiber layer) may be fire resistant.
  • the charged fiber layer (or other layer) comprises a plurality of fibers (e.g., a first plurality of fibers, a second plurality of fibers), wherein at least a portion of the plurality of fibers are fire resistant.
  • the plurality of fibers may comprise a polymer and/or fire resistant additive.
  • the plurality of fibers do not comprise a fire resistant coating (e.g., a coating different than the material(s) from which the fiber is formed).
  • Non-limiting examples of polymers for use in fire resistant fibers include polypropylene and polyester.
  • the fire resistant fibers comprise a fire resistant additive.
  • the fiber may also comprise a relatively low amount of or be substantially free of (e.g., does not comprise) certain undesirable components (e.g., halogens, bromine, chlorine, antimony trioxide, metal hydrates).
  • the fire resistant additive fibers may comprise a phosphorus-based fire resistant additive and/or a nitrogen-based fire resistant additive.
  • Non-limiting examples of fire resistant additives include phosphorous-based additives (e.g., propionylmethylphosphinate),
  • phosphoramidate and derivates thereof allyl-functionalized polyphosphazene, and non-halogenated compounds such as hydroxymethylphosphonium salts and N-methylol phosphonopropionamide and derivatives thereof.
  • the fibers comprising a fire resistant additive may impart a relatively high fire resistance to the filter media.
  • the filter media may have a Fl and/or Kl rating as measured according to DIN 53438 (June 1984).
  • the term "fire resistant filter media" (e.g., comprising a charged fiber layer) has its ordinary meaning in the art and may refer to a filter media which passes a glow wire test according to IEC60695-2-11 (2010).
  • the filter media may be configured to pass a glow wire test according to IEC60695-2-11 (2010) conducted at 850 °C.
  • a glow wire element is heated to 850 °C and contacted at 1 N of force with a surface of the filter media for 30 seconds, and then removed from the filter media.
  • the filter media has generally passed the glow wire test if, within 30 seconds of the removal of the glow wire, the filter media has not burned (or, any flame has self-extinguished within the 30 seconds after removal of the glow wire element).
  • a charged fiber layer of the filter media remains substantially charged after the glow wire test.
  • fire resistant fiber has its ordinary meaning in the art and may refer to a fiber having a fire resistant additive distributed within and/or throughout the fiber.
  • the fiber may comprise any suitable fire resistant additive that has sufficient fire resistance properties.
  • the fire resistant additive may be covalently attached to one or more components in the fiber.
  • a polymer in the fiber may comprise the fire resistant additive.
  • the fire resistant additive may be in the backbone of the polymer and/or be pendant groups in the polymer.
  • a polymer comprising a fire resistant additive may be formed by reacting one or more functional groups on the polymer with the fire resistant additive.
  • the polymer may be a copolymer comprising a fire resistant additive as a repeat unit. In some such cases, the polymer may be formed by reacting a monomer with the fire resistant additive as a co-monomer.
  • a PET/ fire resistant additive copolymer may be formed by adding a phosphorus-based fire resistant additive in the reaction mixture with terephthalic acid and ethylene glycol during the esterification reaction or with the ethylene glycol and dimethyl terephthalate during the
  • the component may be used to make the fibers comprising a fire resistant additive.
  • Non-limiting examples of suitable monomers that may be copolymerized with a fire resistant additive includes esters, olefins, styrenes, vinyl chlorides, vinyl monomers, amine monomers, monomers comprising one or more carboxylic acid, bisphenols, phosgene, epoxy, isocyanate, polyols, and combinations thereof.
  • Non-limiting examples of polymers that may be modified with fire resistant additive include polypropylene, polyesters, polyolefins, polystyrenes, styrene copolymers, vinyl chloride polymers, vinyl polymers, polyamides, polycarbonates, polyurethanes, polyepoxides, polyacrylonitrile, acrylics, polytetrafluoroethylene, polyimides, and polyimidazoles.
  • the fire resistant additive may not be covalently attached to a component of the fiber. In some embodiments, the fire resistant additive may be added to the material used to form the fiber prior to fiber formation.
  • the following example demonstrates the formation of a filter media comprising an open support layer and a charged fiber layer, according to some embodiments.
  • Sample 1 included several filter media of varying basis weight comprising: a charged filter media having a basis weight between 20 g/m and 85 g/m , comprising a plurality of charged fibers having an average fiber diameter of greater than or equal to 15 microns; and
  • a support layer comprising a scrim and having an air permeability of less than or equal to 1100 CFM, needled to the charged filter media.
  • Sample 2 included several filter media of varying basis weight comprising: a charged filter media having a basis weight between 20 g/m and 85 g/m , comprising a plurality of charged fibers having an average fiber diameter of less than 15 microns; and
  • an open support layer (a mesh) having an air permeability of greater than 1100 CFM, needled to the charged filter media.
  • the mesh of sample 2 comprised polypropylene strands having a strand count of 5 per inch along a first axis and 6 per inch in along a second axis.
  • FIG. 3 shows a plot of the normalized gamma versus the basis weight of the charged fiber layer.
  • FIG. 4 shows a plot of the normalized efficiency versus the basis weight of the charged fiber layer.
  • Sample 2 filter media demonstrated an increase in normalized gamma and normalized efficiency, even at relatively low basis weights of the charged fiber layer, as compared to Sample 1.
  • FIG. 5 is a plot of pressure drop (Pa) versus basis weight of the charged fiber layer. Sample 2 filter media demonstrated a decrease in resistance as compared to Sample 1.
  • FIG. 6 is a plot of dust holding capacity for Sample 1 having a basis weight of 70 g/m 2 versus Sample 2 having a basis weight of 70 g/m 2.
  • Sample 2 filter media demonstrated a significant increase in dust holding capacity for a given air resistance of the filter media, as compared to Sample 1.
  • a reference to "A and/or B,” when used in conjunction with open-ended language such as “comprising” can refer, in some embodiments, to A without B (optionally including elements other than B); in another embodiment, to B without A (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); etc.
  • the phrase "at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements.
  • This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase "at least one" refers, whether related or unrelated to those elements specifically identified.
  • At least one of A and B can refer, in some embodiments, to at least one, optionally including more than one, A, with no B present (and optionally including elements other than B); in another embodiment, to at least one, optionally including more than one, B, with no A present (and optionally including elements other than A); in yet another embodiment, to at least one, optionally including more than one, A, and at least one, optionally including more than one, B (and optionally including other elements); etc.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
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PCT/US2018/018924 2017-02-21 2018-02-21 Electret-containing filter media WO2018156561A1 (en)

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EP18757748.1A EP3585499A4 (en) 2017-02-21 2018-02-21 ELECTRIC FILTER MEDIA
CN201880025705.5A CN110545894B (zh) 2017-02-21 2018-02-21 含驻极体的过滤介质

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US15/438,042 US11077394B2 (en) 2017-02-21 2017-02-21 Electret-containing filter media
US15/438,028 US10814261B2 (en) 2017-02-21 2017-02-21 Electret-containing filter media
US15/438,042 2017-02-21
US15/438,028 2017-02-21
US15/790,651 US20180236385A1 (en) 2017-02-21 2017-10-23 Electret-containing filter media
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CN110545894A (zh) 2019-12-06
CN115646068A (zh) 2023-01-31

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