EP3519076A1 - Support filtrant comprenant des fibres ignifuges - Google Patents

Support filtrant comprenant des fibres ignifuges

Info

Publication number
EP3519076A1
EP3519076A1 EP17857510.6A EP17857510A EP3519076A1 EP 3519076 A1 EP3519076 A1 EP 3519076A1 EP 17857510 A EP17857510 A EP 17857510A EP 3519076 A1 EP3519076 A1 EP 3519076A1
Authority
EP
European Patent Office
Prior art keywords
equal
less
filter media
fibers
flame retardant
Prior art date
Legal status (The legal status 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 status listed.)
Pending
Application number
EP17857510.6A
Other languages
German (de)
English (en)
Other versions
EP3519076A4 (fr
Inventor
Xiaodan ZHANG
Douglas M. Guimond
Carrie Liu
Nagendra Anantharamaiah
Sudhakar Jaganathan
Gerald Gadbois
Maxim Silin
Mark A. GALLIMORE
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Hollingsworth and Vose Co
Original Assignee
Hollingsworth and Vose Co
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 US15/283,014 external-priority patent/US11014030B2/en
Application filed by Hollingsworth and Vose Co filed Critical Hollingsworth and Vose Co
Publication of EP3519076A1 publication Critical patent/EP3519076A1/fr
Publication of EP3519076A4 publication Critical patent/EP3519076A4/fr
Pending legal-status Critical Current

Links

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
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B21/00—Layered products comprising a layer of wood, e.g. wood board, veneer, wood particle board
    • B32B21/10—Next to a fibrous or filamentary layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B23/00—Layered products comprising a layer of cellulosic plastic substances, i.e. substances obtained by chemical modification of cellulose, e.g. cellulose ethers, cellulose esters, viscose
    • B32B23/10—Layered products comprising a layer of cellulosic plastic substances, i.e. substances obtained by chemical modification of cellulose, e.g. cellulose ethers, cellulose esters, viscose next to a fibrous or filamentary layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
    • B32B5/022—Non-woven fabric
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
    • B32B5/028—Net structure, e.g. spaced apart filaments bonded at the crossing points
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
    • B32B5/06—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer characterised by a fibrous or filamentary layer mechanically connected, e.g. by needling to another layer, e.g. of fibres, of paper
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/22—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed
    • B32B5/24—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer
    • B32B5/26—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by the presence of two or more layers which are next to each other and are fibrous, filamentary, formed of particles or foamed one layer being a fibrous or filamentary layer another layer next to it also being fibrous or filamentary
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B7/00—Layered products characterised by the relation between layers; Layered products characterised by the relative orientation of features between layers, or by the relative values of a measurable parameter between layers, i.e. products comprising layers having different physical, chemical or physicochemical properties; Layered products characterised by the interconnection of layers
    • B32B7/04—Interconnection of layers
    • B32B7/12—Interconnection of layers using interposed adhesives or interposed materials with bonding properties
    • D—TEXTILES; PAPER
    • D04—BRAIDING; LACE-MAKING; KNITTING; TRIMMINGS; NON-WOVEN FABRICS
    • D04H—MAKING TEXTILE FABRICS, e.g. FROM FIBRES OR FILAMENTARY MATERIAL; FABRICS MADE BY SUCH PROCESSES OR APPARATUS, e.g. FELTS, NON-WOVEN FABRICS; COTTON-WOOL; WADDING ; NON-WOVEN FABRICS FROM STAPLE FIBRES, FILAMENTS OR YARNS, BONDED WITH AT LEAST ONE WEB-LIKE MATERIAL DURING THEIR CONSOLIDATION
    • D04H1/00—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres
    • D04H1/70—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres
    • D04H1/72—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres the fibres being randomly arranged
    • D04H1/728—Non-woven fabrics formed wholly or mainly of staple fibres or like relatively short fibres characterised by the method of forming fleeces or layers, e.g. reorientation of fibres the fibres being randomly arranged by electro-spinning
    • 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
    • B01D2239/0457—Specific fire retardant or heat resistant properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/02—2 layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/03—3 layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/04—4 layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/05—5 or more layers
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2250/00—Layers arrangement
    • B32B2250/20—All layers being fibrous or filamentary
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2260/00—Layered product comprising an impregnated, embedded, or bonded layer wherein the layer comprises an impregnation, embedding, or binder material
    • B32B2260/02—Composition of the impregnated, bonded or embedded layer
    • B32B2260/021—Fibrous or filamentary layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2260/00—Layered product comprising an impregnated, embedded, or bonded layer wherein the layer comprises an impregnation, embedding, or binder material
    • B32B2260/04—Impregnation, embedding, or binder material
    • B32B2260/046—Synthetic resin
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
    • B32B2262/02—Synthetic macromolecular fibres
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B32B2262/00—Composition or structural features of fibres which form a fibrous or filamentary layer or are present as additives
    • B32B2262/02—Synthetic macromolecular fibres
    • B32B2262/0223—Vinyl resin fibres
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    • B32B2262/02—Synthetic macromolecular fibres
    • B32B2262/0223—Vinyl resin fibres
    • B32B2262/0238—Vinyl halide, e.g. PVC, PVDC, PVF, PVDF
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    • B32B2262/02—Synthetic macromolecular fibres
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    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F1/00—General methods for the manufacture of artificial filaments or the like
    • D01F1/02—Addition of substances to the spinning solution or to the melt
    • D01F1/07—Addition of substances to the spinning solution or to the melt for making fire- or flame-proof filaments
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
    • D01F6/58—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products
    • D01F6/62—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from homopolycondensation products from polyesters
    • D—TEXTILES; PAPER
    • D01—NATURAL OR MAN-MADE THREADS OR FIBRES; SPINNING
    • D01F—CHEMICAL FEATURES IN THE MANUFACTURE OF ARTIFICIAL FILAMENTS, THREADS, FIBRES, BRISTLES OR RIBBONS; APPARATUS SPECIALLY ADAPTED FOR THE MANUFACTURE OF CARBON FILAMENTS
    • D01F6/00—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof
    • D01F6/78—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolycondensation products
    • D01F6/84—Monocomponent artificial filaments or the like of synthetic polymers; Manufacture thereof from copolycondensation products from copolyesters

Definitions

  • the present embodiments relate generally to filter media including a flame retardant filtration layer, and specifically, to filter media having enhanced filtration properties.
  • Filter media can be used to remove contamination in a number of applications.
  • Filter media may be designed to have different performance characteristics, depending on their desired use. For example, relatively lower efficiency filter media may be used for heating, ventilating, refrigerating, air conditioning applications. For applications that demand different performance characteristics (e.g., very high efficiency), such as for clean rooms or biomedical applications, high efficiency particulate air (HEP A) or ultra-low penetration air (ULPA) filters may be used.
  • HEP A high efficiency particulate air
  • ULPA ultra-low penetration air
  • Filter media can be used to remove contamination in a variety of applications.
  • filter media include one or more fiber webs.
  • the fiber web provides a porous structure that permits fluid (e.g., air) to flow through the web. Contaminant particles contained within the fluid may be trapped on the fiber web.
  • Fiber web characteristics e.g., pore size, fiber dimensions, fiber composition, basis weight, amongst others
  • pore size e.g., pore size, fiber dimensions, fiber composition, basis weight, amongst others
  • Filter media including a flame retardant filtration layer (e.g., backer layer), and related components, systems, and methods associated therewith are provided.
  • a flame retardant filtration layer e.g., backer layer
  • 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.
  • a filter media comprises a flame retardant wet-laid nonwoven web comprising fibers comprising a phosphorus-based flame retardant.
  • a filter media comprises a wet-laid nonwoven web comprising flame retardant fibers, wherein the wet-laid nonwoven web comprises less than or equal to about 1500 ppm of total halogens.
  • a filter media comprises a flame retardant nonwoven web comprising fibers comprising a phosphorus-based flame retardant having a length of less than or equal to about 30 mm, wherein the fibers comprise a phosphorus-based flame retardant, and wherein the nonwoven web has a thickness of less than or equal to about 1 mm and the nonwoven web has an air permeability of greater than or equal to about 20 CFM and less than or equal to about 800 CFM.
  • a filter media comprises a nonwoven web comprising flame retardant fibers having a length of less than or equal to about 30 mm, wherein the nonwoven web comprises less than or equal to about 1500 ppm of total halogens, the nonwoven web has a thickness of less than or equal to about 1 mm, and the nonwoven web has an air permeability of greater than or equal to about 20 CFM and less than or equal to about 800
  • a filter media comprises a flame retardant non-woven web comprising first synthetic fibers having an average fiber diameter of greater than or equal to about 15 microns, wherein the weight percentage of first synthetic fibers of all fibers in the flame retardant non- woven web is greater than or equal to about 40 wt.%, and second synthetic fibers having an average fiber diameter of greater than or equal to about 0.5 microns and less than about 15 microns.
  • the weight percentage of second synthetic fibers of all fibers in the flame retardant non-woven web is less than or equal to about 50 wt.%, the first and/or second synthetic fibers comprise a phosphorus-based flame retardant, and the surface average fiber diameter of the non- woven web is greater than or equal to about 13 microns and less than or e using the formula:
  • the filter media may also comprise an efficiency layer, wherein the filter media has a dust holding capacity of greater than or equal to about 20 g/m 2 .
  • a filter media comprises a flame retardant non-woven web comprising first synthetic fibers having an average fiber diameter of greater than or equal to about 15 microns, wherein the weight percentage of first synthetic fibers of all fibers in the flame retardant non- woven web is greater than or equal to about 40 wt.%, and second synthetic fibers having an average fiber diameter of greater than or equal to about 0.5 microns and less than about 15 microns.
  • the weight percentage of second synthetic fibers of all fibers in the flame retardant non-woven web is less than or equal to about 50 wt.%, the first and/or second synthetic fibers comprise a phosphorus-based flame retardant, the surface average fiber diameter of the flame retardant non- woven web is greater than or equal to about 13 microns and less than or equal to about 17 microns and is measured using the formula:
  • SSA is the BET surface of the flame retardant non-woven web in m /g and p is the density of the layer in g/cm , and the basis weight of the flame retardant non-woven web is less than or equal to about 110 g/m .
  • the filer media may also comprise an efficiency layer.
  • a flame retardant wetlaid non-woven web comprises first synthetic fibers having an average fiber diameter of greater than or equal to about 15 microns, wherein the weight percentage of first synthetic fibers of all fibers in the flame retardant wetlaid non- woven web is greater than or equal to about 40 wt.%, and second synthetic fibers having an average fiber diameter of greater than or equal to about 0.5 microns and less than about 15 microns.
  • the weight percentage of second synthetic fibers of all fibers in the flame retardant wetlaid non-woven web is less than or equal to about 50 wt.%, the first and/or second synthetic fibers comprise a phosphorus-based flame retardant, and the surface average fiber diameter of the flame retardant wetlaid non-woven web is greater than or equal to about 13 microns and less than or equal to about 17 microns and is measured using the formula: wherein SSA is the BET surface of the flame retardant wetlaid non- woven web in m 2 /g and p is the density of the layer in g/cm 3.
  • a method of manufacturing a non- woven web comprises providing fibers comprising a phosphorus- based flame retardant and forming a non-woven web using a wetlaid process.
  • FIG. 1A shows a cross-section of filter media according to certain embodiments
  • FIG. IB shows a cross-section of filter media according to certain embodiments
  • FIG. 1C shows a cross-section of filter media according to certain embodiments
  • FIG. ID shows a cross-section of filter media according to certain embodiments
  • FIG. IE shows a cross-section of filter media according to certain embodiments
  • FIG. IF shows a cross-section of filter media according to certain embodiments
  • FIG. 1G shows a cross-section of filter media according to certain embodiments
  • FIG.2 shows a graph of dust holding capacity versus surface average fiber diameter for various filter media.
  • a filtration layer may include a nonwoven web (e.g., wet-laid nonwoven web) comprising certain fibers (e.g., flame retardant fibers).
  • the fibers e.g., synthetic fibers
  • the fibers may comprise a flame retardant, such as certain phosphorus-based flame retardants, that has a relatively low concentration of or is substantially free of certain undesirable and/or toxic components (e.g., halogens).
  • the nonwoven web may comprise a blend of fibers (e.g., flame retardant fibers, non-flame retardant fibers).
  • the nonwoven web may also comprise a blend of coarse and fine diameter synthetic fibers that impart beneficial performance properties to the filtration layer.
  • the filtration layer may be designed to have a desirable flame retardancy (e.g., Fl rating, Kl rating) and performance properties without compromising certain mechanical properties (e.g., pleatability of the media) and/or environmental attributes (e.g., relatively low toxicity).
  • Filter media described herein may be particularly well-suited for applications that involve filtering air, though the media may also be used in other applications.
  • flame retardancy is achieved using certain traditional flame retardants that have been found to be toxic upon direct exposure, produce toxic degradation products, and/or produce corrosive and/or toxic fire emissions.
  • Some existing filter media have tried to address this problem by using non-traditional flame retardants in a resin.
  • these flame retardant resins may impart limited flame retardancy even at relatively high weight percentages.
  • the amount of resin comprising a flame retardant (e.g., flame retardant resin) necessary to impart some flame retardancy may adversely affect one or more filtration and/or mechanical properties.
  • a filter media comprising a filtration layer that does not suffer from one or more limitations of existing and/or conventional filter media is described.
  • a filtration layer comprising a suitable blend of fibers (e.g., synthetic fibers) comprising a flame retardant and fibers not comprising a flame retardant (e.g., to produce high flame retardancy) may have beneficial flame retardancy (e.g., Fl rating, Kl rating), performance properties (e.g., dust holding capacity), environmental attributes (e.g., low total halogens), and mechanical properties (e.g., stiffness, durability).
  • beneficial flame retardancy e.g., Fl rating, Kl rating
  • performance properties e.g., dust holding capacity
  • environmental attributes e.g., low total halogens
  • mechanical properties e.g., stiffness, durability
  • fiber characteristics e.g., composition, diameters
  • beneficial properties such as flame retardancy and high dust holding capacity.
  • the filtration layer may comprise a relatively high weight percentage of synthetic fibers (e.g., flame retardant fibers) and/or be substantially free of glass fibers to impart durability, impart suitability for certain applications, and/or enhance flame retardancy.
  • the filtration layer may comprise a binder (e.g., resin, fibers) that imparts stiffness and/or enhances flame retardancy.
  • a filter media described herein, may comprise the filtration layer and an efficiency layer (e.g., electrospun layer, meltblown layer).
  • a filter media 10 may include a filtration layer 15 including a nonwoven web comprising fibers (e.g., synthetic fibers) comprising a flame retardant. These fibers (e.g., flame retardant fibers) may be selected to impart high flame retardancy without adversely affecting one or more important properties for a given application.
  • fibers e.g., flame retardant fibers
  • the fibers comprising a flame retardant and filtration layer 15 may comprise a relatively low amount of or be substantially free of certain components that are undesirable for given application, such as halogens, antimony trioxide, and/or metal hydrates.
  • the fibers comprising a flame retardant and/or the nonwoven web may comprise less than or equal to about 1500 ppm total halogens, less than 900 ppm of chlorine, and/or less than 900 ppm of bromine.
  • the fibers comprising a flame retardant may be synthetic fibers.
  • the fibers e.g., flame retardant fibers
  • Filtration layer 15, as described herein, may have an Fl and/or Kl rating as measured according to DIN 53438 (June 1984).
  • the structural features of the filtration layer including nonwoven web 15 e.g., pleatable backer layer
  • filtration layer 15 may have beneficial performance and mechanical properties, such as relatively low thickness (e.g., greater than or equal to about 0.25 mm and less than or equal to about 2.0 mm, or less than or equal to about 1.0 mm), high air permeability (e.g., greater than or equal to about 20 CFM and less than or equal to about 800 CFM), high dust holding capacity, and/or pleatability.
  • the filtration layer may have a blend of coarse and fine diameter fibers that produces a surface average fiber diameter that imparts sufficient dust holding capacity and/or air permeability at a relatively low basis weight.
  • surface average fiber diameter is described in more detail below.
  • the blend of coarse and fine diameter fibers may comprise coarse diameter fibers comprising a flame retardant, fine diameter fibers comprising a flame retardant, coarse diameter fibers not comprising a flame retardant (e.g., coarse diameter non-flame retardant fibers), and fine diameter fibers not comprising a flame retardant.
  • the filtration layer 15 may serve as a depth filtration backer layer in filter media 10 (e.g., pleatable filter media).
  • filter media 10 may include filtration layer 15 comprising fibers comprising a flame retardant (also referred to herein as "flame retardant filtration layer”) and a second layer 20 as shown in FIGs. 1B-1G.
  • second layer 20 may be an efficiency layer (e.g., meltblown efficiency layer, electrospun efficiency layer).
  • filtration layer 15 and the second layer 20 may be directly adjacent.
  • layers 15 and 20 may be adjacent to one another, and one or more intervening layers (e.g., pre-filter layer) may separate the layers.
  • filter media 10 may comprise one or more optional layers (e.g., scrim layer, a backer layer, pre-filter layer, efficiency layer) positioned upstream and/or downstream of layers 15 and 20 as illustrated in FIGs. 1C-G.
  • filter media 10 may comprise one or more layers upstream of layer 15 and/or layer 20.
  • the filter media may comprise a third layer 25 (e.g., scrim layer, second efficiency layer, capacity layer) upstream of the flame retardant filtration layer (e.g., pleatable backer layer) and the second layer.
  • a filter media may comprise a capacity layer, such as a pre-filter layer (e.g., meltblown layer), upstream of layer 20 (e.g., electrospun layer), which is upstream of layer 15.
  • a capacity layer such as a pre-filter layer (e.g., meltblown layer), upstream of layer 20 (e.g., electrospun layer), which is upstream of layer 15.
  • the capacity layer may be directly adjacent to layer 20 and layer 20 may be directly adjacent to layer 15.
  • the filter media may comprise a third layer 25 (e.g., scrim layer, second efficiency layer, pre-filter layer) downstream of the flame retardant filtration layer (e.g., pleatable backer layer) and the second layer.
  • a filter media 10 e.g., HVAC filter media
  • the third layer may be directly adjacent to the second layer (e.g., efficiency layer).
  • layers 20 and 25 may be indirectly adjacent to one another, and one or more intervening layers may separate the layers.
  • the filter media may comprise a third layer 25 (e.g., electrospun layer) and fourth layer 30 (e.g., second filtration layer) upstream of layers 15 and 20 as shown in FIG. ID.
  • layer 25 may be directly adjacent to layer 20 and/or layer 30 may be directly adjacent to layer 25.
  • the filter media may comprise a third layer 25 (e.g., scrim layer, second filtration layer), fourth layer 30 (e.g., electrospun layer), and a fifth layer 35 (e.g., scrim layer, pre-filter layer) upstream of layers 15 and 20 as shown in FIG. IE.
  • layer 25 may be directly adjacent to layer 20, layer 30 may be directly adjacent to layer 25, and/or layer 35 may be directly adjacent to layer 30.
  • the filter media 10 may comprise one or more layers downstream of layer 15 and/or layer 20.
  • filter media 10 may comprise a layer 40 downstream of the second layer.
  • layer 40 may be directly adjacent to filtration layer 15.
  • one or more intervening layers may separate the layers 15 and 40.
  • filter media 10 may include a filtration layer 15, a second layer 20 (e.g., efficiency layer), a third layer 25 (e.g., meltblown layer), and a fourth layer 40 (e.g., electrospun layer), as shown illustratively in FIG. IF.
  • layer 15 may be directly adjacent to layers 20 and/or 40
  • layer 25 may be directly adjacent to layers 20 and/or 30, and/or layer 20 may be directly adjacent to layers 15 and/or 25.
  • filter media may also comprise a fifth layer 45 (e.g., scrim layer), as shown in FIG. 1G, downstream of layer 40.
  • layer 45 may be directly adjacent to layer 40.
  • filter media 10 may include a filtration layer 15, a second layer 20, and either a third layer 25 or a fourth layer 30.
  • the one or more optional layers may be any suitable layer (e.g., a scrim layer, a substrate layer, an efficiency layer, a capacity layer, a spacer layer, a support layer).
  • a scrim layer e.g., a scrim layer, a substrate layer, an efficiency layer, a capacity layer, a spacer layer, a support layer.
  • a layer when referred to as being "adjacent" another layer, it can be directly adjacent the layer, or an intervening layer also may be present.
  • a layer that is "directly adjacent" another layer means that no intervening layer is present.
  • one or more layers in the filter media may be designed to be discrete from another layer. That is, the fibers from one layer do not substantially intermingle (e.g., do not intermingle at all) with fibers from another layer.
  • fibers from the flame retardant filtration layer do not substantially intermingle with fibers of the second layer (e.g., efficiency layer).
  • Discrete layers may be joined by any suitable process including, for example, lamination, thermo-dot bonding, calendering, ultrasonic processes, or by adhesives, as described in more detail below. It should be appreciated, however, that certain embodiments may include one or more layers that are not discrete with respect to one another.
  • the configurations of the layers shown in the figures are by way of example only, and that in other embodiments, filter media including other configurations of layers may be possible.
  • the filter media may comprise filtration layer 15 and may not comprise second layer 20 (e.g., efficiency layer).
  • an article e.g., filter media
  • the article may consist essentially of filtration layer 15 (e.g., pleatable backer layer).
  • the article may comprise filtration layer 15.
  • second, third, “fourth”, and “fifth” layers refer to different layers within the media, and are not meant to be limiting with respect to the location of that layer.
  • additional layers e.g., “sixth”, or “seventh” layers
  • not all layers shown in the figures need be present in some embodiments.
  • filtration layer 15 may be flame retardant.
  • flame retardant filtration layer e.g., flame retardant nonwoven web
  • the filtration layer comprises flame retardant fibers.
  • flame retardant fiber has its ordinary meaning in the art and may refer to a fiber having a flame retardant distributed within and/or throughout the fiber. In general, the fiber may comprise any suitable flame retardant that has sufficient flame retardant properties.
  • 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 flame retardant fibers may comprise a phosphorus-based flame retardant and/or a nitrogen-based flame retardant.
  • the flame retardant may be covalently attached to one or more components in the fiber.
  • a polymer in the fiber may comprise the flame retardant.
  • the flame retardant may be in the backbone of the polymer and/or be pendant groups in the polymer.
  • a polymer comprising a flame retardant may be formed by reacting one or more functional groups on the polymer with the flame retardant.
  • the polymer may be a copolymer comprising a flame retardant as a repeat unit. In some such cases, the polymer may be formed by reacting a monomer with the flame retardant as a co-monomer.
  • a PET/flame retardant copolymer may be formed by adding a phosphorus-based flame retardant in the reaction mixture with terephthalic acid and ethylene glycol during the esterification reaction or with the ethylene glycol and dimethyl terephthalate during the transesterification reaction. After covalent attachment of the flame retardant to the component of the fiber, the component may be used to make the fibers comprising a flame retardant.
  • Non-limiting examples of suitable monomers that may be copolymerized with a flame retardant 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 flame retardants include polyesters, polyolefins, polystyrenes, styrene copolymers, vinyl chloride polymers, vinyl polymers, polyamides, polycarbonates, polyurethanes, polyepoxides, lyocell, and rayon.
  • the flame retardant may not be covalently attached to a component of the fiber. In some embodiments, the flame retardant may be added to the material used to form the fiber prior to fiber formation.
  • the fibers comprising a flame retardant may comprise a relatively low amount of or be substantially free of certain undesirable components (e.g., halogens, bromine, chlorine, antimony trioxide, metal hydrates).
  • the fibers and/or filtration layer may comprise less than or equal to about 1500 ppm, less than or equal to about 1200 ppm, less than or equal to about 1000 ppm, less than or equal to about 900 ppm, less than or equal to about 750 ppm, less than or equal to about 500 ppm, less than or equal to about 350 ppm, less than or equal to about 200 ppm, or less than or equal to about 100 ppm of total halogens as determined according to EPA SW-846 5050/9056.
  • the fibers comprising a flame retardant and/or filtration layer may be substantially free of total halogens (e.g., 0 ppm of total halogens).
  • the fibers comprising a flame retardant (also referred to herein as "flame retardant fibers") and/or filtration layer may comprise less than or equal to about 900 ppm, less than or equal to about 800 ppm, less than or equal to about 700 ppm, less than or equal to about 600 ppm, less than or equal to about 500 ppm, less than or equal to about 400 ppm, less than or equal to about 300 ppm, less than or equal to about 200 ppm, or less than or equal to about 100 ppm of chlorine and/or bromine as determined according to EPA SW-846 5050/9056 or DIN EN 14582 (method A).
  • the fibers comprising a flame retardant and/or filtration layer may be substantially free of chlorine and/or bromine (e.g., 0 ppm of chlorine, 0 ppm of bromine).
  • the fibers comprising a flame retardant (e.g., flame retardant fibers) and/or filtration layer may comprise a relatively low amount or be substantially free of antimony trioxide.
  • a flame retardant e.g., flame retardant fibers
  • filtration layer may comprise a relatively low amount or be substantially free of antimony trioxide.
  • less than or equal to about 0.5 mg/m 3 , less than or equal to about 0.4 mg/m 3 , less than or equal to about 0.3 mg/m 3 , less than or equal to about 0.2 mg/m 3 , less than or equal to about 0.1 mg/m 3 , less than or equal to about 0.05 mg/m 3 , less than or equal to about 0.025 mg/m 3 , or less than or equal to about 0.01 mg/m 3 may be released as measured according to "Method for the Determination of Antimony Trioxide [Air Monitoring Methods, Vol. 7 (2003)]," The MAK Collection for Occupational Health and Safety (2012).
  • the fibers comprising a flame retardant may impart a relatively high flame retardancy to the filtration layer.
  • the filtration layer may have a Fl and/or Kl rating as measured according to DIN 53438 (June 1984).
  • the flame retardant filtration layer may comprise a relatively high weight percentage of flame retardant fibers (e.g., greater than or equal to about 60 wt.% and less than or equal to about 80 wt.%).
  • the total weight percentage of flame retardant fibers in the flame retardant filtration layer and/or in the total weight percentage of flame retardant fibers of all fibers in the filtration layer may be greater than or equal to about 10 wt.%, greater than or equal to about 20 wt.%, greater than or equal to about 30 wt.%, greater than or equal to about 40 wt.%, greater than or equal to about 50 wt.%, greater than or equal to about 60 wt.%, greater than or equal to about 70 wt.%, greater than or equal to about 80 wt.%, greater than or equal to about 85 wt.%, or greater than or equal to about 90 wt.%.
  • the total weight percentage of flame retardant fibers in the flame retardant filtration layer and/or in the total weight percentage of flame retardant fibers of all fibers in the filtration layer may be less than or equal to about 97 wt.%, less than or equal to about 90 wt.%, less than or equal to about 80 wt.%, less than or equal to about 70 wt.%, less than or equal to about 60 wt.%, less than or equal to about 50 wt.%, less than or equal to about 40 wt.%, less than or equal to about 30 wt.%, or less than or equal to about 25 wt.%.
  • the weight percentage of fibers comprising a flame retardant may vary based on the other fibers in the filtration layer and/or filter media.
  • the total weight percentage of flame retardant fibers in the filtration layer and/or the total weight percentage of flame retardant fibers of all fibers in the filtration layer may comprise greater than or equal to about 80 wt.% and less than or equal to about 95 wt.% when glass fibers are present. In some embodiments, the total weight percentage of flame retardant fibers in the filtration layer and/or the total weight percentage of flame retardant fibers of all fibers in the filtration layer may comprise greater than or equal to about 40 wt.% and less than or equal to about 60 wt.% when cellulose fibers are present.
  • the total weight percentage of flame retardant fibers in the filtration layer and/or the total weight percentage of flame retardant fibers of all fibers in the filtration layer may comprise greater than or equal to about 20 wt.% and less than or equal to about 60 wt.% when synthetic fibers are present.
  • the filtration layer may comprise uncrimped fibers.
  • the fibers comprising a flame retardant may be uncrimped fiber.
  • the filtration layer may consist essentially of uncrimped fibers.
  • the fibers comprising a flame retardant used in the filtration layer may have an average fiber diameter of greater than or equal to about 0.5 microns, greater than or equal to about 1 micron, greater than or equal to about 2 microns, greater than or equal to about 5 microns, greater than or equal to about 10 microns, greater than or equal to about 15 microns, greater than or equal to about 20 microns, greater than or equal to about 25 microns, greater than or equal to about 30 micron, greater than or equal to about 35 microns, greater than or equal to about 40 microns, greater than or equal to about 45 microns, greater than or equal to about 50 microns, greater than or equal to about 75 microns, or greater than or equal to about 100 microns.
  • the average fiber diameter may be less than or equal to about 100 microns, less than or equal to about 75 microns, less than or equal to about 60 microns, less than or equal to about 55 microns, less than or equal to about 50 microns, less than or equal to about 45 microns, less than or equal to about 40 microns, less than or equal to about 35 microns, less than or equal to about 30 microns, less than or equal to about 25 microns, less than or equal to about 20 microns, less than or equal to about 15 microns, less than or equal to about 10 microns, or less than or equal to about 5 microns.
  • the fibers in filtration layer 15 may be relatively short.
  • the average length of the fibers may be less than or equal to about 30 mm, less than or equal to about 27 mm, less than or equal to about 25 mm, less than or equal to about 22 mm, less than or equal to about 20 mm, less than or equal to about 18 mm, less than or equal to about 15 mm, less than or equal to about 12 mm, less than or equal to about 9 mm, or less than or equal to about 6 mm.
  • the average length may be greater than or equal to about 3 mm, greater than or equal about 6 mm, greater than or equal about 9 mm, greater than or equal about 12 mm, greater than or equal about 15 mm, greater than or equal about 18 mm, greater than or equal about 20 mm, greater than or equal about 22 mm, or greater than or equal about 25 mm. All suitable combinations of the above-referenced ranges are also possible (e.g., greater than or equal about 3 mm and less than or equal to about 30 mm, greater than or equal about 3 mm and less than or equal to about 20 mm, greater than or equal about 6 mm and less than or equal to about 12 mm).
  • the fiber characteristic of filtration layer 15 may also be selected to impart desirable performance properties to the filter media.
  • such a filtration layer may be a nonwoven web comprising coarse and fine diameter fibers (e.g., synthetic fibers).
  • the fiber diameters and relative weight percentages of the fibers may be selected such that the nonwoven web has a certain surface average fiber diameter, as described in more detail below.
  • the filtration layer may comprise greater than or equal to about 40 wt.% of one or more coarse diameter fibers (e.g., greater than or equal to about 15 microns) and less than or equal to about 50 wt.% of one or more fine diameter fibers (e.g., less than about 15 microns) to produce a surface average fiber diameter within a desired range, e.g., greater than or equal to about 13 microns and less than or equal to about 17 microns.
  • the filter media may have a dust holding capacity of greater than or equal to about 20 g/m and/or a Gurley stiffness of, e.g., greater than or equal to about 50 mg and less than or equal to about 1,500 mg in the cross direction.
  • the flame retardant filtration layer may have a higher dust holding capacity and/or air permeability than a filtration layer having the same surface average fiber diameter, but different fiber characteristics (e.g., relative weight percentage, diameter).
  • filtration layer 15 may serve as a depth filtration layer that trap particles within the layer.
  • suitable ranges for surface average fiber diameter, weight percentage of coarse diameter fibers, and weight percentage of fine diameter are needed to allow for depth filtration. For example, if the surface average fiber diameter is above the suitable range, the ability of the filtration layer to trap particles may be substantially diminished. If the surface average fiber diameter is below the suitable range, the filtration mechanism of the layer may change to surface filtration in which many particles are trapped on the upstream surface of the layer and, as a result, the layer may have a higher pressure drop. In some embodiments, a high pressure drop can reduce the service life of the filter media. Without being bound by theory, it is believed that the surface average fiber diameter may serve as a parameter that is predictive of the efficiency and filtration mechanism of the layer (e.g. depth filtration, surface filtration).
  • a weight percentage of fine diameter fibers above the suitable range may result in a reduction in air permeability and dust holding capacity, due at least in part to webbing and/or bundling of the fine diameter fibers in the presence of certain binders and/or during the web
  • the webbing and/or bundling of the fine diameter fibers may result in blockage of a significant percentage of the pores in a layer.
  • a weight percentage of coarse diameter fibers above the suitable range may result in a layer having a reduced capacity to trap particles.
  • a blend of coarse and fine diameter fibers may be needed to achieve a suitable surface average fiber diameter.
  • a filtration layer may comprise multiple fibers having different average fiber diameters and/or fiber diameter distributions.
  • the average diameter of the fibers in a layer may be characterized using a weighted average, such as the surface average fiber diameter.
  • the surface average fiber diameter is defined as wherein d is the surface average fiber diameter in microns and is m, the number fraction of the fibers with diameter d, in microns and density p 5 in g/cm in the filtration layer.
  • the equation assumes that the fibers are cylindrical, the fibers have a circular cross-section, and that the fiber length is significantly greater than the diameter of the fibers. It should be understood that the equation also provides meaningful surface average fiber diameter values when a nonwoven web includes fibers that are substantially cylindrical and have a substantially circular cross-section.
  • the surface average fiber diameter may be computed using the equation above or measured, as described further below. In embodiments in which the diameters, densities, and mass percentages of the fibers in the filtration layer are known, the surface average fiber diameter may be computed.
  • the surface average fiber diameter of the filtration layer may be determined by measuring the BET surface average of the filtration layer (i.e., SSA) and the density p of the layer, as described in more detail below.
  • the surface average fiber diameter SAFD may be determined using the modified formula below:
  • SSA is the BET surface of the filtration layer in m /g and p is the density of the layer in g/cm .
  • the BET surface area is measured through use of a standard BET surface area measurement technique.
  • 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
  • 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, e.g., 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 density of a layer may be determined by accurately measuring the mass and volume of the layer (e.g., excluding the void volume) and then calculating the density of the layer.
  • the mass of the layer may be determined by weighing the layer.
  • the volume of the layer may be determined using any known method of accurately measuring volume. For example, the volume may be determined using pycnometry.
  • the volume of the layer may be determined using an Archimedes method provided that an accurate measurement of volume is produced.
  • the volume may be determined by fully submerging the layer in a wetting fluid and measuring the volume displacement of the wetting liquid as a result of fully submerging the layer.
  • the flame retardant filtration layer may have a surface average fiber diameter of greater than or equal to about 1 micron, greater than or equal to about 2 microns, greater than or equal to about 4 microns, greater than or equal to about 6 microns, greater than or equal to about 8 microns, greater than or equal to about 10 microns, greater than or equal to about 11 microns, greater than or equal to about 12 microns, greater than or equal to about 13 microns, greater than or equal to about 14 microns, greater than or equal to about 15 microns, greater than or equal to about 16 micron, greater than or equal to about 17 microns, greater than or equal to about 18 microns, greater than or equal to about 19 microns, greater than or equal to about 20 microns, greater than or equal to about 25 microns, greater than or equal to about 30 microns, or greater than or equal to about 35 microns.
  • the surface average fiber diameter may be less than or equal to about 40 microns, less than or equal to about 35 microns, less than or equal to about 30 microns, less than or equal to about 25 microns, less than or equal to about 20 microns, less than or equal to about 19 microns, less than or equal to about 18 microns, less than or equal to about 18 microns, less than or equal to about 17 microns, less than or equal to about 16 microns, less than or equal to about 15 microns, less than or equal to about 14 microns, less than or equal to about 13 microns, less than or equal to about 12 microns, less than or equal to about 10 microns, or less than or equal to about 5 microns.
  • a surface average fiber diameter of greater than or equal to about 13 microns and less than or equal to about 17 microns may be preferred.
  • filtration layer 15 may comprise a blend of coarse and fine diameter fibers that produces a suitable surface average fiber diameter.
  • the filtration layer may comprise a relatively high weight percentage of coarse diameter fibers (e.g., greater than or equal to about 40 wt.%).
  • the total weight percentage of coarse diameter fibers in the filtration layer and/or in the total weight percentage of coarse diameter fibers of all fibers in the filtration layer may be greater than or equal to about 10 wt.%, greater than or equal to about 20 wt.%, greater than or equal to about 30 wt.%, greater than or equal to about 40 wt.%, greater than or equal to about 50 wt.%, greater than or equal to about 60 wt.%, greater than or equal to about 70 wt.%, greater than or equal to about 80 wt.%, or greater than or equal to about 85 wt.%.
  • the total weight percentage of coarse diameter fibers in the filtration layer and/or in the total weight percentage of coarse diameter fibers of all fibers in the filtration layer may be less than or equal to about 90 wt.%, less than or equal to about 80 wt.%, less than or equal to about 70 wt.%, less than or equal to about 60 wt.%, less than or equal to about 50 wt.%, less than or equal to about 40 wt.%, less than or equal to about 30 wt.%, less than or equal to about 20 wt.%, or less than or equal to about 15 wt.%.
  • the total weight percentage of coarse diameter fibers in the flame retardant filtration layer and/or in the total weight percentage of coarse diameter fibers of all fibers in the filtration layer may include two or more populations of coarse diameter fibers having a different average fiber diameter.
  • a flame retardant filtration layer having a total weight percentage of coarse diameter fibers of greater than or equal to about 40 wt.% and less than or equal to about 80 wt.% may comprise a first population of coarse diameter fibers having an average fiber diameter of greater than or equal to about 15 microns and less than or equal to about 25 microns at a weight percentage of greater than or equal to about 5 wt.% and less than or equal to about 95 wt.% (e.g., greater than or equal to about 10 wt.% and less than or equal to about 60 wt.%) and a second population of coarse diameter fibers having an average fiber diameter of greater than or equal to about 25 microns and less than or equal to about 50 microns at a weight percentage of greater
  • a blend of coarse diameter fibers may be used to help achieve the desired surface average fiber diameter.
  • any suitable number of coarse diameter fiber populations having different average fiber diameters may be used.
  • the total weight percentage of coarse diameter fibers is composed of one population of coarse diameter fibers. That is, the layer does not comprise two or more populations of coarse diameter fibers having a different average fiber diameter.
  • coarse diameter fibers used in the flame retardant filtration layer may have an average fiber of diameter greater than or equal to about 15 microns, greater than or equal to about 17 microns, greater than or equal to about 20 microns, greater than or equal to about 25 microns, greater than or equal to about 30 microns, greater than or equal to about 35 microns, greater than or equal to about 40 micron, greater than or equal to about 45 microns, greater than or equal to about 50 microns, or greater than or equal to about 55 microns.
  • the average fiber diameter may be less than or equal to about 60 microns, less than or equal to about 55 microns, less than or equal to about 50 microns, less than or equal to about 45 microns, less than or equal to about 40 microns, less than or equal to about 35 microns, less than or equal to about 30 microns, less than or equal to about 25 microns, less than or equal to about 20 microns, or less than or equal to about 17 microns. All suitable combinations of the above-referenced ranges are also possible (e.g., greater than or equal to about 10 microns and less than or equal to about 60 microns, greater than or equal to about 17 microns and less than or equal to about 35 microns).
  • the coarse diameter fibers in the filtration layer may have an average length of greater than or equal to about 3 mm, greater than or equal about 6 mm, greater than or equal about 9 mm, greater than or equal about 12 mm, greater than or equal about 15 mm, greater than or equal about 18 mm, greater than or equal about 20 mm, greater than or equal about 22 mm, or greater than or equal about 25 mm.
  • the average length of the coarse diameter fibers may be less than or equal to about 30 mm, less than or equal to about 27 mm, less than or equal to about 25 mm, less than or equal to about 22 mm, less than or equal to about 20 mm, less than or equal to about 18 mm, less than or equal to about 15 mm, less than or equal to about 12 mm, less than or equal to about 9 mm, or less than or equal to about 6 mm. All suitable combinations of the above-referenced ranges are also possible (e.g., greater than or equal about 3 mm and less than or equal to about 30 mm, greater than or equal about 6 mm and less than or equal to about 12 mm).
  • filtration layer 15 may comprise a blend of coarse diameter fibers and fine diameter fibers to produce a suitable surface average fiber diameter.
  • the total weight percentage of fine diameter fibers in the filtration layer and/or in the total weight percentage of fine diameter fibers of all fibers in the filtration layer may be less than or equal to about 50 wt.%, less than or equal to about 45 wt.%, less than or equal to about 40 wt.%, less than or equal to about 35 wt.%, less than or equal to about 30 wt.%, less than or equal to about 25 wt.%, less than or equal to about 20 wt.%, or less than or equal to about 15 wt.%.
  • the total weight percentage of fine diameter fibers in the filtration layer and/or in the total weight percentage of fine diameter fibers of all fibers in the filtration layer may be greater than or equal to about 0.5 wt.%, greater than or equal to about 5 wt.%, greater than or equal to about 10 wt.%, greater than or equal to about 15 wt.%, greater than or equal to about 20 wt.%, greater than or equal to about 25 wt.%, greater than or equal to about 30 wt.%, greater than or equal to about 35 wt.%, greater than or equal to about 40 wt.%, or greater than or equal to about 45 wt.%.
  • the total weight percentage of fine diameter fibers in the flame retardant filtration layer and/or in the total weight percentage of fine diameter fibers of all fibers in the filtration layer may include two or more populations of fine diameter fibers having a different average fiber diameter.
  • a filtration layer comprising flame retardant fibers having a total weight percentage of fine diameter fibers of greater than or equal to about 10 wt.% and less than or equal to about 30 wt.% may comprise a first population of fine diameter fibers having an average fiber diameter of greater than or equal to about 0.1 microns and less than or equal to about 10 microns at a weight percentage of greater than or equal to about 5 wt.% and less than or equal to about 95 wt.% (e.g., greater than or equal to about 10 wt.% and less than or equal to about 60 wt.%) and a second population of fine diameter fibers having an average fiber diameter of greater than or equal to about 10 microns and less than about 15 microns at a weight percentage
  • the blend of fine diameter fibers may be used to help achieve the desired surface average fiber diameter.
  • any suitable number of fine fiber populations having different average fiber diameters may be used.
  • the total weight percentage of fine diameter fibers is composed of one population of fine diameter fibers. That is, the layer does not comprise two or more populations of fine diameter fibers having a different average fiber diameter.
  • fine diameter fibers used in the filtration layer may have an average fiber diameter of less than about 15 microns, less than or equal to about 12 microns, less than or equal to about 10 microns, less than or equal to about 8 microns, less than or equal to about 6 microns, less than or equal to about 5 microns, less than or equal to about 4 microns, less than or equal to about 3 microns, less than or equal to about 2 microns, or less than or equal to about 1 micron.
  • the average fiber diameter may be greater than or equal to about 0.5 microns, greater than or equal to about 1 micron, greater than or equal to about 2 microns, greater than or equal to about 3 microns, greater than or equal to about 4 microns, greater than or equal to about 5 microns, greater than or equal to about 6 microns, greater than or equal to about 8 microns, greater than or equal to about 10 microns, or greater than or equal to about 12 microns. All suitable combinations of the above-referenced ranges are also possible (e.g., greater than or equal to about 0.5 microns and less than about 15 microns, greater than or equal to about 2 microns and less than or equal to about 10 microns).
  • the fine diameter fibers in the filtration layer may have an average length of greater than or equal to about 0.1 mm, greater than or equal to about 0.3 mm, greater than or equal to about 0.5 mm, greater than or equal to about 0.8 mm, greater than or equal to about 1 mm, greater than or equal to about 3 mm, greater than or equal about 6 mm, greater than or equal about 9 mm, greater than or equal about 12 mm, greater than or equal about 15 mm, greater than or equal about 18 mm, greater than or equal about 20 mm, greater than or equal about 22 mm, or greater than or equal about 25 mm.
  • the average length of the fine diameter fibers may be less than or equal to about 30 mm, less than or equal to about 27 mm, less than or equal to about 25 mm, less than or equal to about 22 mm, less than or equal to about 20 mm, less than or equal to about 18 mm, less than or equal to about 15 mm, less than or equal to about 12 mm, less than or equal to about 9 mm, less than or equal to about 6 mm, less than or equal to about 3 mm, or less than or equal to about 1 mm. All suitable combinations of the above-referenced ranges are also possible (e.g., greater than or equal about 0.1 mm and less than or equal to about 30 mm, greater than or equal about 0.3 mm and less than or equal to about 12 mm).
  • the coarse and/or fine diameter fibers are not glass fibers.
  • a relatively high weight percentage of the total coarse and/or fine diameter fibers in the flame retardant filtration layer may be synthetic fibers.
  • the weight percentage of synthetic fibers of all fibers in the filtration layer may be greater than or equal to about 80 wt.%, greater than or equal to about 85 wt.%, greater than or equal to about 88 wt.%, greater than or equal to about 90 wt.%, greater than or equal to about 92 wt.%, greater than or equal to about 95 wt.%, greater than or equal to about 97 wt.%, or greater than or equal to about 99 wt.%.
  • the flame retardant filtration layer may include 100 wt.% synthetic fibers.
  • the filtration layer may be substantially free of glass fibers.
  • the weight percentage of coarse synthetic fibers of all coarse diameter fibers in the filtration layer may be greater than or equal to about 80 wt.%, greater than or equal to about 85 wt.%, greater than or equal to about 88 wt.%, greater than or equal to about 90 wt.%, greater than or equal to about 92 wt.%, greater than or equal to about 95 wt.%, greater than or equal to about 97 wt.%, or greater than or equal to about 99 wt.%.
  • the weight percentage of coarse synthetic fibers of all coarse diameter fibers in the filtration layer may be 100 wt.%.
  • the weight percentage of synthetic fibers of all fine diameter fibers in the filtration layer may be greater than or equal to about 80 wt.%, greater than or equal to about 85 wt.%, greater than or equal to about 88%, greater than or equal to about 90 wt.%, greater than or equal to about 92 wt.%, greater than or equal to about 95 wt.%, greater than or equal to about 97 wt.%, or greater than or equal to about 99 wt.%. In some embodiments, the weight percentage of synthetic fibers of all fine diameter fibers in the filtration layer may be 100 wt.%.
  • synthetic fibers 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, polyvinyl alcohol, regenerated cellulose (e.g., synthetic cellulose such lyocell, rayon), polyacrylonitriles, polyvinylidene fluoride (PVDF), copolymers of polyethylene and PVDF, polyether sulfones, and combinations thereof.
  • the synthetic fibers are organic polymer fibers.
  • Synthetic fibers may also include multi-component fibers (i.e., fibers having multiple compositions such as bicomponent fibers).
  • synthetic fibers may include meltblown, meltspun, electrospun (e.g., melt, solvent), or centrifugal spun fibers, which may be formed of polymers described herein (e.g., polyester, polypropylene).
  • synthetic fibers may be staple fibers.
  • the synthetic fibers may be fibers comprising a flame retardant.
  • the filter media, as well as each of the layers within the filter media, may also include combinations of more than one type of synthetic fiber. It should be understood that other types of synthetic fibers may also be used.
  • the fibers comprising a flame retardant may be synthetic fibers.
  • the total weight percentage of coarse and/or fine diameter fibers may include fibers comprising a flame retardant (e.g., flame retardant fibers).
  • one or more layers (e.g second layer) in the filter media may include one or more cellulose fibers, such as softwood fibers, hardwood fibers, a mixture of hardwood and softwood fibers, regenerated cellulose fibers (e.g., rayon, fibrillated synthetic cellulose fibers such as Lyocell fibers), microfibrillated cellulose, and mechanical pulp fibers (e.g., groundwood, chemically treated mechanical pulps, and thermomechanical pulps).
  • cellulose fibers such as softwood fibers, hardwood fibers, a mixture of hardwood and softwood fibers, regenerated cellulose fibers (e.g., rayon, fibrillated synthetic cellulose fibers such as Lyocell fibers), microfibrillated cellulose, and mechanical pulp fibers (e.g., groundwood, chemically treated mechanical pulps, and thermomechanical pulps).
  • Exemplary softwood fibers include fibers obtained from mercerized southern pine (e.g., mercerized southern pine fibers or "HPZ fibers”), northern bleached softwood kraft (e.g., fibers obtained from Robur Flash (“Robur Flash fibers”)), southern bleached softwood kraft (e.g., fibers obtained from Brunswick pine (“Brunswick pine fibers”)), or chemically treated mechanical pulps ("CTMP fibers”).
  • HPZ fibers can be obtained from Buckeye Technologies, Inc., Memphis, TN
  • Robur Flash fibers can be obtained from
  • Exemplary hardwood fibers include fibers obtained from Eucalyptus (“Eucalyptus fibers”). Eucalyptus fibers are commercially available from, e.g., (1) Suzano Group, Suzano, Brazil (“Suzano fibers”), (2) Group Portucel Soporcel, Cacia, Portugal (“Cacia fibers”), (3) Tembec, Inc., Temiscaming, QC, Canada (“Tarascon fibers”), (4) Kartonimex Intercell, Duesseldorf, Germany, (“Acacia fibers”), (5) Mead-Westvaco, Stamford, CT (“Westvaco fibers”), and (6) Georgia-Pacific, Atlanta, GA ("Leaf River fibers”).
  • Eucalyptus fibers are commercially available from, e.g., (1) Suzano Group, Suzano, Brazil (“Suzano fibers”), (2) Group Portucel Soporcel, Cacia, Portugal (“Cacia fibers”), (3) Tembec, Inc.,
  • the average diameter of the cellulose fibers in one or more layers may be, for example, greater than or equal to about 1 micron, greater than or equal to about 2 microns, greater than or equal to about 3 microns, greater than or equal to about 4 microns, greater than or equal to about 5 microns, greater than or equal to about 8 microns, greater than or equal to about 10 microns, greater than or equal to about 15 microns, greater than or equal to about 20 microns, greater than or equal to about 30 microns, or greater than or equal to about 40 microns.
  • the cellulose fibers may have an average diameter of less than or equal to about 50 microns, less than or equal to about 40 microns, less than or equal to about 30 microns, less than or equal to about 20 microns, less than or equal to about 15 microns, less than or equal to about 10 microns, less than or equal to about 7 microns, less than or equal to about 5 microns, less than or equal to about 4 microns, or less than or equal to about 2 microns. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to about 1 micron and less than or equal to about 5 microns). Other values of average fiber diameter are also possible.
  • the cellulose fibers may have an average length.
  • cellulose fibers may have an average length of greater than or equal to about 0.5 mm, greater than or equal to about 1 mm, greater than or equal to about 2 mm, greater than or equal to about 3 mm, greater than or equal to about 4 mm, greater than or equal to about 5 mm, greater than or equal to about 6 mm, or greater than or equal to about 8 mm.
  • cellulose fibers may have an average length of less than or equal to about 10 mm, less than or equal to about 8 mm, less than or equal to about 6 mm, less than or equal to about 4 mm, less than or equal to about 2 mm, or less than or equal to about 1 mm. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to about 1 mm and less than or equal to about 3 mm). Other values of average fiber length are also possible.
  • the weight percentage of cellulose fibers in one or more layers may be greater than or equal to about 0 wt.%, greater than or equal to about 5 wt.%, greater than or equal to about 10 wt.%, greater than or equal to about 15 wt.%, greater than or equal to about 45 wt.%, greater than or equal to about 65 wt.%, or greater than or equal to about 90 wt.%.
  • the weight percentage of the cellulose fibers in one or more layers may be less than or equal to about 100 wt.%, less than or equal to about 85 wt.%, less than or equal to about 55 wt.%, less than or equal to about 20 wt.%, less than or equal to about 10 wt.%, or less than or equal to about 2 wt.%.
  • a layer includes the above-noted ranges of cellulose fibers with respect to the total weight of fibers in the layer.
  • one or more layers e.g., flame retardant filtration layer, second layer
  • the entire filter media is substantially free of glass fibers (e.g., less than 1 wt.% glass fibers, between about 0 wt.% and about 1 wt.% glass fibers).
  • the flame retardant filtration layer may include 0 wt.% glass fibers.
  • one or more layers in the filter media may include glass fibers (e.g., microglass fibers, chopped strand glass fibers, or a combination thereof).
  • the average diameter of glass fibers may be, for example, less than or equal to about 30 microns, less than or equal to about 25 microns, less than or equal to about 15 microns, less than or equal to about 12 microns, less than or equal to about 10 microns, less than or equal to about 9 microns, less than or equal to about 7 microns, less than or equal to about 5 microns, less than or equal to about 3 microns, or less than or equal to about 1 micron.
  • the glass fibers may have an average fiber diameter of greater than or equal to about 0.1 microns, greater than or equal to about 0.3 microns, greater than or equal to about 1 micron, greater than or equal to about 3 microns, or greater than equal to about 7 microns greater than or equal to about 9 microns, greater than or equal to about 11 microns, or greater than or equal to about 20 microns. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to about 0.1 microns and less than or equal to about 9 microns). Other values of average fiber diameter are also possible.
  • the weight percentage of the glass fibers may be greater than or equal to about 0 wt.%, greater than or equal to about 5 wt.%, greater than or equal to about 10 wt.%, greater than or equal to about 15 wt.%, greater than or equal to about 45 wt.%, greater than or equal to about 65 wt.%, or greater than or equal to about 90 wt.%.
  • the weight percentage of the glass fibers in one or more layers may be less than or equal to about 100 wt.%, less than or equal to about 85 wt.%, less than or equal to about 55 wt.%, less than or equal to about 20 wt.%, less than or equal to about 10 wt.%, or less than or equal to about 2 wt.% . Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to about 0 wt.% and less than or equal to about 100 wt.%).
  • a layer includes the above-noted ranges of glass fibers with respect to the total weight of fibers in the layer.
  • filtration layer 15 may comprise one or more binders (e.g., binder resin, binder fiber) that serve to impart structural integrity to the filtration layer, as well as provide important mechanical properties, such as Gurley stiffness, Mullen burst, and/or tensile strength, to the media.
  • the binder may comprise a flame retardant.
  • the filtration layer may comprise a relatively low weight percentage of a flame retardant resin.
  • at least some of the binder fibers may be fibers comprising a flame retardant.
  • the binder may be one or more binder fibers.
  • binder fibers may be used to join fibers within the layer.
  • binder fibers comprise polymers with a lower melting point than one or more major component in the layer, such as certain fibers.
  • Binder fibers may be monocomponent (e.g., polyethylene fibers, copolyester fibers) or multicomponent (e.g., bicomponent fibers).
  • a binder fiber may be a bicomponent fiber.
  • the bicomponent fibers may comprise a thermoplastic polymer. Each component of the bicomponent fiber can have a different melting temperature.
  • the fibers can include a core and a sheath where the activation temperature of the sheath is lower than the melting temperature of the core. This allows the sheath to melt prior to the core, such that the sheath binds to other fibers in the layer, while the core maintains its structural integrity.
  • the core/sheath binder fibers can be concentric or non-concentric.
  • Other exemplary bicomponent fibers can include split fiber fibers, side-by-side fibers, and/or "island in the sea" fibers. In general, the total weight percentage of coarse and/or fine diameter fibers may include binder fibers.
  • the binder may be one or more binder resins.
  • binder resin may be used to join fibers within the layer.
  • the binder resin may have any suitable composition.
  • the binder resin may comprise a thermoplastic (e.g., acrylic, polyvinylacetate, polyester, polyamide), a thermoset (e.g., epoxy, phenolic resin), or a combination thereof.
  • a binder resin includes one or more of a vinyl acetate resin, an epoxy resin, a polyester resin, a copolyester resin, a polyvinyl alcohol resin, an acrylic resin such as a styrene acrylic resin, and a phenolic resin.
  • the resin may comprise a polymeric resin comprising a covalently attached flame retardant.
  • the resin may be added to the fibers in any suitable manner including, for example, in the wet state.
  • the resin coats the fibers and is used to adhere fibers to each other to facilitate adhesion between the fibers. Any suitable method and equipment may be used to coat the fibers, for example, using curtain coating, gravure coating, melt coating, dip coating, knife roll coating, or spin coating, amongst others.
  • the binder is precipitated when added to the fiber blend.
  • any suitable precipitating agent e.g., Epichlorohydrin, fluorocarbon
  • the resin upon addition to the fibers, is added in a manner such that one or more layer or the entire filter media is impregnated with the resin (e.g., the resin permeates throughout).
  • a resin may be added to each of the layers separately prior to combining the layers, or the resin may be added to the layer after combining the layers.
  • resin is added to the fibers while in a dry state, for example, by spraying or saturation impregnation, or any of the above methods. In other embodiments, a resin is added to a wet layer.
  • the binder may comprise both binder fibers and binder resin. Regardless of whether the binder is a binder fiber, binder resin, or both, the total weight percentage of binder in the filtration layer may be greater than or equal to about 0.5 wt. %, greater than or equal to about 1 wt.%, greater than or equal to about 5 wt.%, greater than or equal to about 10 wt.%, greater than or equal to about 20 wt.%, greater than or equal to about 30 wt.%, greater than or equal to about 40 wt.
  • total weight percentage may be less than or equal to about 90 wt.%, less than or equal to about 80 wt.%, less than or equal to about 70 wt.%, less than or equal to about 60 wt.%, less than or equal to about 50 wt.%, less than or equal to about 40 wt.%, less than or equal to about 30 wt.%, less than or equal to about 20 wt.%, less than or equal to about 15 wt.%, less than or equal to about 10 wt.%, or less than or equal to about 5 wt.%.
  • the total weight percentage of binder fiber (e.g., bicomponent fiber) in the filtration layer may be greater than or equal to about 0.5 wt. %, greater than or equal to about 1 wt.%, greater than or equal to about 3 wt.%, greater than or equal to about 5 wt.%, greater than or equal to about 8 wt.%, greater than or equal to about 10 wt.%, greater than or equal to about 20 wt.%, greater than or equal to about 25 wt.%, greater than or equal to about 30 wt.%, greater than or equal to about 40 wt.
  • binder fiber e.g., bicomponent fiber
  • total weight percentage of binder fiber e.g.,
  • bicomponent fiber may be less than or equal to about 90 wt.%, less than or equal to about 80 wt.%, less than or equal to about 70 wt.%, less than or equal to about 60 wt.%, less than or equal to about 50 wt.%, less than or equal to about 40 wt.%, less than or equal to about 30 wt.%, less than or equal to about 25 wt.%, less than or equal to about 20 wt.%, less than or equal to about 18 wt.%, less than or equal to about 15 wt.%, less than or equal to about 12 wt.%, less than or equal to about 10 wt.%, less than or equal to about 8 wt.%, less than or equal to about 5 wt.%, less than or equal to about 3 wt.%, or less than or equal to about 1 wt.%.
  • one or more layers e.g., filtration layer, second layer
  • the entire filter media may include a relatively low percentage (e.g., less than or equal to about 10 wt.%, less than or equal to about 5 wt. %, less than or equal to about 1 wt. %, 0 wt.%) of binder fibers (e.g.,
  • the total weight percentage of binder resin in the flame retardant filtration layer may be greater than or equal to about 0 wt. %, greater than or equal to about 1 wt.%, greater than or equal to about 3 wt.%, greater than or equal to about 5 wt.%, greater than or equal to about 8 wt.%, greater than or equal to about 10 wt.%, greater than or equal to about 20 wt.%, greater than or equal to about 25 wt.%, greater than or equal to about 30 wt.%, greater than or equal to about 40 wt.
  • total weight percentage of binder resin may be less than or equal to about 90 wt.%, less than or equal to about 80 wt.%, less than or equal to about 70 wt.%, less than or equal to about 60 wt.%, less than or equal to about 50 wt.%, less than or equal to about 40 wt.%, less than or equal to about 30 wt.%, less than or equal to about 25 wt.%, less than or equal to about 20 wt.%, less than or equal to about 18 wt.%, less than or equal to about 15 wt.%, less than or equal to about 12 wt.%, less than or equal to about 10 wt.%, less than or equal to about 8 wt.%, less than or equal to about 90 wt.%, less than or equal to about 80 wt.%, less than or equal to about 70 wt.%, less than or equal to about 60 wt.%, less than or equal to about 50 wt.
  • the weight percentage of binder resin may be less than or equal to 30 wt.%.
  • the filtration layer may comprise 0 wt.% of binder resin.
  • binder fibers used in the flame retardant filtration layer may have a fiber diameter greater than or equal to about 1 micron, greater than or equal to about 2 microns, greater than or equal to about 5 microns, greater than or equal to about 8 microns, greater than or equal to about 10 microns, greater than or equal to about 12 microns, greater than or equal to about 15 micron, greater than or equal to about 18 microns, greater than or equal to about 20 microns, greater than or equal to about 22 microns, or greater than or equal to about 25 microns.
  • the fiber diameter may be less than or equal to about 30 microns, less than or equal to about 28 microns, less than or equal to about 25 microns, less than or equal to about 22 microns, less than or equal to about 20 microns, less than or equal to about 18 microns, less than or equal to about 15 microns, less than or equal to about 12 microns, less than or equal to about 10 microns, less than or equal to about 5 microns, or less than or equal to about 2 microns.
  • the binder fibers in the flame retardant filtration layer may have an average length of greater than or equal to about 3 mm, greater than or equal about 6 mm, greater than or equal about 9 mm, greater than or equal about 12 mm, greater than or equal about 15 mm, greater than or equal about 18 mm, greater than or equal about 20 mm, greater than or equal about 22 mm, or greater than or equal about 25 mm.
  • the average length of the binder fibers may be less than or equal to about 30 mm, less than or equal to about 27 mm, less than or equal to about 25 mm, less than or equal to about 22 mm, less than or equal to about 20 mm, less than or equal to about 18 mm, less than or equal to about 15 mm, less than or equal to about 12 mm, less than or equal to about 9 mm, or less than or equal to about 6 mm. All suitable combinations of the above- referenced ranges are also possible (e.g., greater than or equal about 3 mm and less than or equal to about 30 mm, greater than or equal about 6 mm and less than or equal to about 12 mm).
  • filter media 10 may include a flame retardant filtration layer.
  • the flame retardant filtration layer may have certain enhanced mechanical properties, such as Gurley stiffness, tensile strength, and/or Mullen Burst strength.
  • the flame retardant filtration layer may provide sufficient Gurley stiffness such that the filter media can be pleated to include sharp, well-defined peaks which can be maintained in a stable configuration during use.
  • the flame retardant filtration layer may have a relatively high Gurley stiffness.
  • the filtration layer may have a Gurley stiffness in the cross direction of greater than or equal to about 10 mg, greater than or equal to about 50 mg, greater than or equal to about 100 mg, greater than or equal to about 200 mg, greater than or equal to about 300 mg, greater than or equal to about 500 mg, greater than or equal to about 800 mg, greater than or equal to about 1,000 mg, greater than or equal to about 1,200 mg, or greater than or equal to about 1,400 mg.
  • the filtration layer may have a Gurley stiffness in the cross direction of less than or equal to about 1,500 mg, less than or equal to about 1,400 mg, less than or equal to about 1,200 mg, less than or equal to about 1,000 mg, less than or equal to about 800 mg, less than or equal to about 500 mg, less than or equal to about 300 mg, less than or equal to about 200 mg, or less than or equal to about 100 mg. All suitable combinations of the above-referenced ranges are also possible (e.g., greater than or equal to about 10 mg and less than or equal to about 3,500 mg, greater than or equal to about 50 mg and less than or equal to about 1,500 mg, greater than or equal to about 200 mg and less than or equal to about 1,000 mg).
  • the stiffness may be determined using the Gurley stiffness (bending resistance) recorded in units of mm (equivalent to gu) in accordance with TAPPI T543 om-94.
  • the flame retardant filtration layer may have a Gurley stiffness in the machine direction of greater than or equal to about 200 mg, greater than or equal to about 350 mg, greater than or equal to about 500 mg, greater than or equal to about 750 mg, greater than or equal to about 1,000 mg, greater than or equal to about 1,500 mg, greater than or equal to about 2,000 mg, greater than or equal to about 2,500 mg, or greater than or equal to about 3,000 mg.
  • the flame retardant filtration layer may have a Gurley stiffness in the machine direction of less than or equal to about 3,500 mg, less than or equal to about 3,000 mg, less than or equal to about 2,500 mg, less than or equal to about 2,000 mg, less than or equal to about 1,500 mg, less than or equal to about 1,000 mg, less than or equal to about 750 mg, or less than or equal to about 500 mg. All suitable combinations of the above-referenced ranges are also possible (e.g., greater than or equal to about 200 mg and less than or equal to about 3,500 mg, greater than or equal to about 350 mg and less than or equal to about 2,000 mg).
  • the flame retardant filtration layer may have a dry tensile strength in the machine direction (MD) of greater than or equal to about 2 lb/in, greater than or equal to about 4 lb/in, greater than or equal to about 5 lb/in, greater than or equal to about 10 lb/in, greater than or equal to about 15 lb/in, greater than or equal to about 20 lb/in, greater than or equal to about 30 lb/in, greater than or equal to about 40 lb/in, greater than or equal to about 50 lb/in, or greater than or equal to about 55 lb/in.
  • MD machine direction
  • the dry tensile strength in the machine direction may be less than or equal to about 60 lb/in, less than or equal to about 50 lb/in, less than or equal to about 40 lb/in, less than or equal to about 30 lb/in, less than or equal to about 20 lb/in, less than or equal to about 10 lb/in, or less than or equal to about 5 lb/in. All suitable combinations of the above-referenced ranges are also possible (e.g., greater than or equal to about 2 lb/in and less than or equal to about 60 lb/in, greater than or equal to about 10 lb/in and less than or equal to about 40 lb/in). Other values of dry tensile strength in the machine direction are also possible.
  • the dry tensile strength in the machine direction may be determined according to the standard T494 om-96 using a test span of 4 in and a jaw separation speed of 1 in/min.
  • the flame retardant filtration layer may have a dry tensile strength in the cross direction (CD) of greater than or equal to about 1 lb/in, greater than or equal to about 2 lb/in, greater than or equal to about 5 lb/in, greater than or equal to about 6 lb/in, greater than or equal to about 8 lb/in, greater than or equal to about 10 lb/in, greater than or equal to about 12 lb/in, greater than or equal to about 15 lb/in, or greater than or equal to about 18 lb/in.
  • CD dry tensile strength in the cross direction
  • the dry tensile strength in the cross direction may be less than or equal to about 20 lb/in, less than or equal to about 18 lb/in, less than or equal to about 15 lb/in, less than or equal to about 12 lb/in, less than or equal to about 10 lb/in, less than or equal to about 8 lb/in, less than or equal to about 6 lb/in, or less than or equal to about 5 lb/in.
  • dry tensile strength in the cross direction may be determined according to the standard T494 om-96 using a test span of 4 in and a jaw separation speed of 1 in/min.
  • the flame retardant filtration layer may have a dry Mullen Burst strength of greater than or equal to about 5 psi, greater than or equal to about 20 psi, greater than or equal to about 25 psi, greater than or equal to about 30 psi, greater than or equal to about 50 psi, greater than or equal to about 75 psi, greater than or equal to about 100 psi, greater than or equal to about 125 psi, greater than or equal to about 150 psi, greater than or equal to about 175 psi, greater than or equal to about 200 psi, greater than or equal to about 225 psi, or greater than or equal to about 240 psi.
  • the dry Mullen Burst strength may be less than or equal to about 250 psi, less than or equal to about 240 psi, less than or equal to about 225 psi, less than or equal to about 200 psi, less than or equal to about 175 psi, less than or equal to about 150 psi, less than or equal to about 125 psi, less than or equal to about 100 psi, less than or equal to about 75 psi, less than or equal to about 50 psi, or less than or equal to about 25 psi.
  • filtration layer 15 may have a relatively high air permeability.
  • the air permeability of the flame retardant filtration layer may be greater than or equal to about 20 ft 3 /min/ft 2 (CFM), greater than or equal to about 50 ft 3 /min/ft 2 (CFM), greater than or equal to about 75 CFM, greater than or equal to about 100 CFM, greater than or equal to about 150 CFM, greater than or equal to about 200 CFM, greater than or equal to about 250 CFM, greater than or equal to about 300 CFM, greater than or equal to 350 CFM, greater than or equal to about 400 CFM, greater than or equal to about 450 CFM, greater than or equal to about 500 CFM, greater than or equal to 550 CFM, greater than or equal to about 600 CFM, greater than or equal to about 650 CFM, greater than or equal to about 700 CFM, or greater than or equal to about 750 CFM.
  • the air permeability of the flame retardant filtration layer may be less than or equal to about 800 CFM, less than or equal to about 750 CFM, less than or equal to about 700 CFM, less than or equal to about 650 CFM, less than or equal to about 600 CFM, less than or equal to about 550 CFM, less than or equal to about 500 CFM, less than or equal to about 450 CFM, less than or equal to about 400 CFM, less than or equal to about 350 CFM, less than or equal to about 300 CFM, less than or equal to about 250 CFM, less than or equal to about 200 CFM, less than or equal to about 150 CFM, or less than or equal to about 100 CFM.
  • air permeability is measured according to the standard ASTM D737- 75.
  • the sample is clamped on to a test head which provides a circular test area of 38.3 cm referred to as nozzle, at a force of at least 50+/- 5 N without distorting the sample and with minimum edge leakage.
  • a steady flow of air perpendicular to the sample test area is then supplied providing a pressure differential of 12.5 mm H 2 0 across the material being tested. This pressure differential is recorded from the pressure gauge or manometer connected to the test head.
  • the air permeability through the test area is measured in ft 3 /min/ft 2 using a flow meter or volumetric counter.
  • a Frazier air permeability tester is an example apparatus for such a measurement.
  • the flame retardant filtration layer may have a relatively small basis weight.
  • the filtration layer may have a basis weight of less than or equal to about 200 g/m 2 , less than or equal to about 175 g/m 2 , less than or equal to about 150 g/m 2 , less than or equal to about 120 g/m 2 , less than or equal to about
  • the flame retardant filtration layer may have a basis weight of greater than or equal to about 20 g/m , greater than or equal to about 30 g/m 2 , greater than or equal to about 40 g/m 2 , greater than or equal to about 50 g/m 2 , greater than or equal to about 60 g/m 2 , greater than or equal to about 70 g/m 2 , greater than or equal to about 80 g/m 2 , greater than or equal to about 90 g/m 2 , greater than or equal to about 100 g/m 2 , greater than or equal to about 120 g/m 2 , greater than or equal to about 140 g/m 2 , greater than or equal to about 160 g/m 2 , or greater than or equal to about 180 g/m .
  • the flame retardant filtration layer may be relatively thin.
  • the flame retardant filtration layer may have a thickness of less than or equal to about 2.0 mm, less than or equal to about 1.8 mm, less than or equal to about 1.5 mm, less than or equal to about 1.2 mm, less than or equal to about 1.0 mm, less than or equal to about 0.8 mm, less than or equal to about 0.7 mm, less than or equal to about 0.6 mm, or less than or equal to about 0.5 mm, or less than or equal to about 0.4 mm.
  • the flame retardant filtration layer may have a thickness of greater than or equal to about 0.25 mm, greater than or equal to about 0.3 mm, greater than or equal to about 0.4 mm, greater than or equal to about 0.5 mm, greater than or equal to about 0.6 mm, greater than or equal to about 0.8 mm, greater than or equal to about 1.0 mm, greater than or equal to about 1.2 mm, greater than or equal to about 1.5 mm, or greater than or equal to about 1.8 mm.
  • the mean flow pore size may be selected as desired.
  • the flame retardant filtration layer may have a mean flow pore size of greater than or equal to about 20 microns, greater than or equal to about 40 microns, greater than or equal to about 50 microns, greater than or equal to about 75 microns, greater than or equal to about 100 microns, greater than or equal to about 125 micron, greater than or equal to about 150 microns, greater than or equal to about 175 microns, greater than or equal to about 200 microns, greater than or equal to about 225 microns, greater than or equal to about 250 microns, or greater than or equal to about 275 microns.
  • the flame retardant filtration layer may have a mean flow pore size of less than or equal to about 300 microns, less than or equal to about 275 microns, less than or equal to about 250 microns, less than or equal to about 225 microns, less than or equal to about 200 microns, less than or equal to about 175 microns, less than or equal to about 150 microns, less than or equal to about 125 microns, less than or equal to about 100 microns, less than or equal to about 75 microns, or less than or equal to about 50 micron.
  • Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to about 20 microns and less than or equal to about 300 microns, greater than or equal to about 50 microns and less than or equal to about 150 microns).
  • Other values of mean flow pore size are also possible.
  • the mean flow pore size may be determined according to the standard ASTM F316 (2003).
  • the filter media may include a second layer.
  • the second layer functions to enhance particle capture efficiency of the filter media, and may be referred to as an efficiency layer.
  • the efficiency layer does not include a spacer layer (e.g., spun-bond layer) when referring to the structural and performance characteristics of the efficiency layer, and/or the number of layers within the efficiency layer.
  • the average efficiency of the second layer and/or the entire filter media may vary based on the application.
  • the second layer and/or the entire filter media may have DEHS average efficiency at 0.4 microns of greater than or equal to about 10%, greater than or equal to about 20%, greater than or equal to about 35%, greater than or equal to about 50%, greater than or equal to about 60%, greater than or equal to about 70%, greater than or equal to about 80%, greater than or equal to about 90%, greater than or equal to about 95%, greater than or equal to about 97%, greater than or equal to about 99%, greater than or equal to about 99.5%, greater than or equal to about 99.9%, greater than or equal to about 99.95%, greater than or equal to about 99.99%, greater than or equal to about 99.995%, greater than or equal to 99.999%, greater than or equal to
  • the second layer and/or the entire filter media may have DEHS average efficiency at 0.4 microns of less than or equal to 99.99999%, less than or equal to 99.9999%, less than or equal to about 99.999%, less than or equal to about 99.99%, less than or equal to about 99.997%, less than or equal to about 99.995%, less than or equal to about 99.9%, less than or equal to about 99.5%, less than or equal to about 99%, less than or equal to about 98%, less than or equal to about 97%, less than or equal to about 95%, less than or equal to about 90%, less than or equal to about 85%, less than or equal to about 75%, less than or equal to about 60%, less than or equal to about 50%, less than or equal to about 40%, less than or equal to about 30%, less than or equal to about 20%, or less than or equal to about 10%.
  • the DEHS average efficiency may be measured according to EN 1822, and for efficiencies ⁇ 90%, may be measured according to EN779:2012. In some embodiments, the average efficiency of a layer (e.g., second layer) and/or a filter media may be tested following the EN779-2012 standard.
  • the testing uses an air flow of 0.944 m 3 /s (3400 m 3 /h) and a maximum final test pressure drop of 250 Pa (e.g., for Coarse or G filter media) or a maximum final test pressure drop of 450 Pa (e.g., for Medium, or M, or Fine, or F, filter media).
  • the second layer may comprise synthetic fibers, amongst other fiber types.
  • the second, third layer, fourth layer, and/or fifth layer may comprise a relatively high weight percentage of synthetic fibers (e.g., 100 wt.%).
  • the second, third layer, fourth layer, and/or fifth layer may comprise synthetic fibers formed from a meltblown process, melt spinning process, centrifugal spinning process, or electro spinning process.
  • the synthetic fibers may be continuous as described further below.
  • the second layer may comprise synthetic staple fibers.
  • the second, third layer, fourth layer, and/or fifth layer may comprise relatively little (e.g., less than or equal to about 10 wt.%, less than or equal to about 5 wt.%, less than or equal to about 3 wt.%, less than or equal to about 1 wt.%) or no glass fibers.
  • the second, third layer, fourth layer, and/or fifth layer may comprise glass fibers.
  • the second layer may comprise a relatively high weight percentage of glass fibers.
  • the second layer may comprise greater than or equal to about 5 wt.% and less than or equal to about 100 wt.% (e.g., greater than or equal to about 10 wt.% and less than or equal to about 97 wt.%) of total fibers in the filter media of glass fibers.
  • one or more layers e.g., second, third layer, fourth layer, fifth layer
  • one or more layers may consist essentially of uncrimped fibers.
  • the second layer e.g., efficiency layer
  • third layer e.g., fourth layer, and/or fifth layer
  • the average fiber diameter may be greater than or equal to about 0.05 microns, greater than or equal to about 0.06 microns, greater than or equal to about 0.07 microns, greater than or equal to about 0.08 microns, greater than or equal to about 0.09 microns, greater than or equal to about 0.1 micron, 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 0.8 microns, greater than or equal to about 1 micron, greater than or equal to about 2 microns, greater than or equal to about 3 microns, or greater than or equal to about 4 microns. All suitable combinations of the above-referenced ranges are also possible (e.g., greater than or equal to about 0.05 micron and less than or equal to about 5 microns).
  • the fibers in the second, third layer, fourth layer, and/or fifth layer may have an average length which may depend on the method of formation of the fibers.
  • the synthetic fibers may be continuous (e.g., meltblown fibers, spunbond fibers, electrospun fibers, centrifugal spun fibers, etc.).
  • continuous synthetic fibers may have an average length of at least about 5 cm, at least about 10 cm, at least about 15 cm, at least about 20 cm, at least about 50 cm, at least about 100 cm, at least about 200 cm, at least about 500 cm, at least about 700 cm, at least about 1000 cm, at least about 1500 cm, at least about 2000 cm, at least about 2500 cm, at least about 5000 cm, at least about 10000 cm; and/or less than or equal to about 10000 cm, less than or equal to about 5000 cm, less than or equal to about 2500 cm, less than or equal to about 2000 cm, less than or equal to about 1000 cm, less than or equal to about 500 cm, or less than or equal to about 200 cm.
  • the synthetic fibers are not continuous (e.g., staple fibers). In general, synthetic non-continuous fibers may be characterized as being shorter than continuous synthetic fibers.
  • the fibers in the second, third layer, fourth layer, and/or fifth layer may have an average length of greater than or equal to about 0.1 mm, greater than or equal to about 0.3 mm, greater than or equal to about 0.5 mm, greater than or equal to about 0.8 mm, greater than or equal to about 1 mm, greater than or equal to about 3 mm, greater than or equal about 6 mm, greater than or equal about 9 mm, greater than or equal about 12 mm, greater than or equal about 15 mm, greater than or equal about 18 mm, greater than or equal about 20 mm, greater than or equal about 22 mm, greater than or equal about 25 mm, greater than or equal about 28 mm, greater than or equal about 30 mm, greater than or equal about 32 mm, greater than or equal about 35 mm, greater than or equal about 38 mm, greater than or equal about 40 mm, greater than or equal about 42 mm, or greater than or equal about 45 mm.
  • the average length of the fibers in the second, third layer, fourth layer, and/or fifth layer may be less than or equal to about 50 mm, less than or equal to about 48 mm, less than or equal to about 45 mm, less than or equal to about 42 mm, less than or equal to about 40 mm, less than or equal to about 38 mm, less than or equal to about 35 mm, less than or equal to about 32 mm, less than or equal to about 30 mm, less than or equal to about 27 mm, less than or equal to about 25 mm, less than or equal to about 22 mm, less than or equal to about 20 mm, less than or equal to about 18 mm, less than or equal to about 15 mm, less than or equal to about 12 mm, less than or equal to about 9 mm, less than or equal to about 6 mm, less than or equal to about 3 mm, or less than or equal to about 1 mm. All suitable combinations of the above-referenced ranges are also possible (e.g., greater than or equal about
  • the weight percentage of synthetic fibers in the second, third layer, fourth layer, and/or fifth layer and/or in the weight percentage of synthetic fibers of all fibers in the second layer may be greater than or equal to about 1%, greater than or equal to about 20%, greater than or equal to about 40%, greater than or equal to about 60%, greater than or equal to about 80%, greater than or equal to about 90%, or greater than or equal to about 95%.
  • the weight percentage of synthetic fibers and/or in the weight percentage of synthetic fibers of all fibers in the second layer in the second layer may be less than or equal to about 100%, less than or equal to about 98%, less than or equal to about 85%, less than or equal to about 75%, less than or equal to about 50%, less than or equal to about 25%, or less than or equal to about 10%. All suitable combinations of the above-referenced ranges are also possible (e.g., greater than or equal to about 80% and less than or equal to about 100%). Other values of weight percentage of synthetic fibers in the second layer are also possible.
  • the second layer includes 100% synthetic fibers.
  • the second layer (e.g., efficiency layer), third layer, fourth layer, and/or fifth layer may have a basis weight of less than or equal to about 120 g/m , less than or equal to about 100 g/m 2 , less than or equal to about 75 g/m 2 , less than or equal to about 50 g/m 2 , less than or equal to about 35 g/m 2 , less than or equal to about 25 g/m 2 , less than or equal to about 20 g/m 2 , less than or equal to about 15 g/m 2 , less than or equal to about 10 g/m 2 , less than or equal to about 5 g/m 2 , less than or equal to about 1 g/m 2 , less than or equal to about 0.8 g/m 2 , less than or equal to about 0.5 g/m 2 , less than or equal to about 0.1 g/m 2 , less than or equal to about 0.08 g/m 2 , or less than or equal to about
  • the second, third layer, fourth layer, and/or fifth layer may have a basis weight of greater than or equal to about 0.05 g/m , greater than or equal to about 0.06 g/m 2 , greater than or equal to about 0.08 g/m 2 , greater than or equal to about 0.1 g/m 2 , greater than or equal to about 0.2 g/m 2 , greater than or equal to about 0.5 g/m 2 , greater than or equal to about 0.8 g/m 2 , greater than or equal to about 1 g/m 2 , greater than or equal to about 5 g/m 2 , greater than or equal to about 10 g/m 2 , greater than or equal to about 15 g/m 2 , greater than or equal to about 20 g/m 2 , greater than or equal to about 30 g/m 2 , greater than or equal to about 40 g/m 2 , greater than or equal to about 50 g/m 2 , greater than or equal to about 60 g/m 2 ,
  • the second, third layer, fourth layer, and/or fifth layer may have a thickness of less than or equal to about 5 mm, less than or equal to about 4.5 mm, less than or equal to about 4 mm, less than or equal to about 3.5 mm, less than or equal to about 3 mm, less than or equal to about 2.5 mm, less than or equal to about 2 mm, less than or equal to about 1.5 mm, less than or equal to about 1 mm, less than or equal to about 0.5 mm, less than or equal to about 0.1 mm, less than or equal to about 0.05 mm, or less than or equal to about 0.01 mm.
  • the second, third layer, fourth layer, and/or fifth layer may have a thickness of greater than or equal to about 0.001 mm, greater than or equal to about 0.005 mm, greater than or equal to about 0.01 mm, greater than or equal to about 0.05 mm, greater than or equal to about 0.08 mm, greater than or equal to about 0.1 mm, greater than or equal to about 0.5 mm, greater than or equal to about 1 mm, greater than or equal to about 1.5 mm, greater than or equal to about 2 mm, greater than or equal to about 2.5 mm, greater than or equal to about 3 mm, greater than or equal to about 3.5 mm, or greater than or equal to about 4 mm.
  • the second layer (e.g., an efficiency layer), third layer, fourth layer, and/or fifth layer may include a single layer. In other embodiments, however, the second layer may include more than one layer (i.e., sub-layers) to form a multi-layered structure.
  • the plurality of sub-layers may differ based on certain features such as air permeability, basis weight, fiber type, and/or particulate efficiency. In certain cases, the plurality of sub-layers may be discrete and combined by any suitable method, such as lamination, point bonding, or collating.
  • the sub-layers are substantially joined to one another (e.g., by lamination, point bonding, thermo-dot bonding, ultrasonic bonding, calendering, use of adhesives (e.g., glue-web), and/or co-pleating).
  • sub-layers may be formed as a composite layer (e.g., by a wet laid process).
  • the efficiency layer may be electrostatically charged.
  • Electrostatic charge may be imparted to the second efficiency layer or the filter media using methods known to those of ordinary skill in the art including, but not limited to, corona charging, charge bars, hydroentangling charging, triboelectric charging, hydrocharging, or use of additives. In other embodiments, the efficiency layer may not be charged.
  • a filter media having the flame retardant filtration layer described herein may exhibit advantageous and enhanced filtration performance characteristics, such as dust holding capacity (DHC) and efficiency.
  • DHC dust holding capacity
  • Filter media described herein may have a relatively high dust holding capacity.
  • the dust holding capacity is the difference in the weight of the filter media before exposure to a certain amount of fine dust and the weight of the filter media after the exposure to the fine dust, upon reaching a particular pressure drop across the filter media, divided by the area of the fiber web. Dust holding capacity may be determined according to the weight (mg) of dust captured per square cm of the media (e.g., through a 100 cm test area). As determined herein, dust holding capacity is measured using aerosol of atomized salt (e.g., KC1) particles using an ASHRAE 52.2 flat sheet test rig tested at 15 fpm velocity where the final pressure drop when the dust holding capacity is measured is 1.5 inches of H 2 0 on a column. The dust holding capacity may be determined using the ASHRAE 52.2 standard.
  • the filter media may have a dust holding capacity of greater than or equal to about 10 g/m 2 , greater than or equal to about 20 g/m 2 , greater than or equal to about 25 g/m 2 , greater than or equal to about 50 g/m 2 , greater than or equal to about 75 g/m 2 , greater than or equal to about 100 g/m 2 , greater than or equal to about 125 g/m 2 , greater than or equal to about 150 g/m 2 , greater than or equal to about 175 g/m 2 , greater than or equal to about 200 g/m 2 , greater than or equal to about 225 g/m 2 , greater than or equal to about 250 g/m 2 , or greater than or equal to about 275 g/m 2.
  • the dust holding capacity may be less than or equal to about 300 g/m , less than or equal to about 275 g/m 2 , less than or equal to about 250 g/m 2 , less than or equal to about 225 g/m 2 , less than or equal to about 200 g/m 2 , less than or equal to about 175 g/m 2 , less than or equal to about 150 g/m 2 , less than or equal to about 125 g/m 2 , less than or equal to about 100 g/m 2 , less than or equal to about 80 g/m 2 , less than or equal to about 60 g/m 2 , or less than or equal to about 50 g/m .
  • the average efficiency of a layer (e.g., second layer) and/or filter media increases as a function of particle size.
  • the average efficiency may be greater than or equal to about 20% and less than or equal to about 100% (e.g., greater than or equal to about 40% and less than or equal to about 100%) for 0.3-1.0 micron-sized particles, for 1.0-3.0 micron-sized particles, or 3.0-10.0 micron-sized particles.
  • the average efficiency of a filtration layer (e.g., second layer) and/or filter media may be greater than or equal to about 10%, greater than or equal to about 20%, greater than or equal to about 35%, greater than or equal to about 50%, greater than or equal to about 60%, greater than or equal to about 70%, greater than or equal to about 80%, greater than or equal to about 90%, greater than or equal to about 95%, greater than or equal to about 97%, greater than or equal to about 99%, greater than or equal to about 99.5%, greater than or equal to about 99.9%, greater than or equal to about 99.95%, greater than or equal to about 99.99%, or greater than or equal to about 99.995% for 0.3-1.0 micron-sized particles, for 1.0-3.0 micron-sized particles, or 3.0-10.0 micron-sized particles.
  • the average efficiency may be less than or equal to about 100%, less than or equal to about 99.999%, less than or equal to about 99.99%, less than or equal to about 99.997%, less than or equal to about 99.995%, less than or equal to about 99.9%, less than or equal to about 99.5%, less than or equal to about 99%, less than or equal to about 98%, less than or equal to about 97%, less than or equal to about 95%, less than or equal to about 90%, less than or equal to about 85%, less than or equal to about 75%, less than or equal to about 60%, less than or equal to about 50%, less than or equal to about 40%, less than or equal to about 30%, less than or equal to about 20%, or less than or equal to about 10% for 0.3-1.0 micron-sized particles, for 1.0-3.0 micron-sized particles, or 3.0-10.0 micron- sized particles.
  • the average efficiency as a function of particle size may be determined according to EN 1822.
  • the average efficiency of a mechanical efficiency layer and/or filter media may be tested using EN 1822.
  • the average efficiency of the second layer or filter media may be tested following the ASHRAE 52.2 standard.
  • the average efficiency of a charged efficiency layer and/or filter media may be tested using ASHRAE 52.2 standard.
  • the testing uses a test air flow rate of 25 FPM. The test is run at an air temperature of 69°F, a relative humidity of 25%, and a barometric pressure of 29.30 in Hg.
  • the testing also uses a challenge aerosol of atomized salt (e.g., KC1) particles having a range of particle sizes between 0.3-1.0 microns, 1.0-3.0 microns, or 3.0-10.0 microns.
  • atomized salt e.g., KC1
  • the second layer (e.g., efficiency layer) and/or filter media described herein may be classified by a MERV (Minimum Efficiency Reporting Value) rating based on the results of the ASHRAE 52.2 efficiency.
  • MERV ratings are generally used by the HVAC (Heating, Ventilating, and Air Conditioning) industry to describe a filter's ability to remove particulates from the air. A higher MERV rating means better filtration and greater performance.
  • the second layer or filter media described herein has a MERV rating that is in the range of about 5 to 12 (e.g., between about 8 and 12, between about 6 and 9), however the rating can vary based on the intended use.
  • a filtration layer or filter media described herein has a MERV rating of greater than or equal to about 5, greater than or equal to about 6, greater than or equal to about 7, greater than or equal to about 8, greater than or equal to about 9, greater than or equal to about 10, greater than or equal to about 11, or greater than or equal to about 12.
  • the MERV rating may be, for example, less than or equal to 15, less than or equal to 14, less than or equal to 13, less than or equal to 12, less than or equal to 11, or less than or equal to 10. It should be understood that all suitable combinations of the above-referenced ranges are possible (e.g., greater than or equal to about 5 and less than or equal to about 15).
  • the air permeability of the filter media may be greater than or equal to about 1 CFM, greater than or equal to about 5 CFM, greater than or equal to about 10 CFM, greater than or equal to about 25 CFM, greater than or equal to about 50 CFM, greater than or equal to about 75 CFM, greater than or equal to about 100 CFM, greater than or equal to 125 CFM, greater than or equal to about 150 CFM, greater than or equal to about 175 CFM, greater than or equal to about 200 CFM, greater than or equal to 225 CFM, greater than or equal to about 250 CFM, or greater than or equal to about 275 CFM.
  • the air permeability of the filter media may be less than or equal to about 300 CFM, less than or equal to about 275 CFM, less than or equal to about 250 CFM, less than or equal to about 225 CFM, less than or equal to about 200 CFM, less than or equal to about 175 CFM, less than or equal to about 150 CFM, less than or equal to about 125 CFM, less than or equal to about 100 CFM, less than or equal to about 75 CFM, less than or equal to about 50 CFM, or less than or equal to about 25 CFM.
  • the filter media may have a relatively low pressure drop.
  • the filter media may have a pressure drop of less than or equal to about 1,300 Pa, less than or equal to about 1,200 Pa, less than or equal to about 1,000 Pa, less than or equal to about 750 Pa, less than or equal to about 500 Pa, less than or equal to about 250 Pa, less than or equal to about 150 Pa, less than or equal to about 130 Pa, less than or equal to about 100 Pa, less than or equal to about 80 Pa, less than or equal to about 60 Pa, less than or equal to about 40 Pa, less than or equal to about 20 Pa, or less than or equal to about 10 Pa.
  • the filter media may have a pressure drop of greater than or equal to about 4 Pa, greater than or equal to about 6 Pa, greater than or equal to about 10 Pa, greater than or equal to about 20 Pa, greater than or equal to about 40 Pa, greater than or equal to about 60 Pa, greater than or equal to about 80 Pa, greater than or equal to about 100 Pa, greater than or equal to about 150 Pa, greater than or equal to about 250 Pa, greater than or equal to about 500 Pa, greater than or equal to about 750 Pa, greater than or equal to about 1,000 Pa, or greater than or equal to about 1,250 Pa.
  • the pressure drop as described herein, can be determined at 10.5 FPM face velocity using a TSI 8130 filtration tester, according to ISO 3968.
  • the filter media may have a basis weight of greater than or equal to about 20 g/m 2 , greater than or equal to about 25 g/m 2 , greater than or equal to about
  • the filter media may have a basis weight of less than or equal to about 200 g/m 2 , less than or equal to about 175 g/m 2 , less than or equal to about 150 g/m 2 , less than or equal to about 125 g/m 2 , less than or equal to about 100 g/m 2 , less than or equal to about 75 g/m 2 , less than or equal to about 50 g/m 2 , less than or equal to about 40 g/m 2 , or less than or equal to about 30 g/m 2.
  • the filter media may have a thickness of greater than or equal to about 0.25 mm, greater than or equal to about 0.3 mm, greater than or equal to about 0.4 mm, greater than or equal to about 0.5 mm, greater than or equal to about 0.6 mm, greater than or equal to about 0.8 mm, greater than or equal to about 1.0 mm, greater than or equal to about 1.2 mm, greater than or equal to about 1.5 mm, greater than or equal to about 1.8 mm, greater than or equal to about 2.0 mm, or greater than or equal to about 2.2 mm.
  • the filter media may have a thickness of less than or equal to about 2.5 mm, less than or equal to about 2.2 mm, less than or equal to about 2.0 mm, less than or equal to about 1.8 mm, less than or equal to about 1.5 mm, less than or equal to about 1.2 mm, less than or equal to about 1.0 mm, less than or equal to about 0.8 mm, less than or equal to about 0.6 mm, less than or equal to about 0.5 mm, or less than or equal to about 0.4 mm.
  • the flame retardant filtration layer may comprise a relatively high weight percentage of the filter media (e.g., greater than or equal to about 65 wt.%).
  • the weight percentage of the flame retardant filtration layer in the filter media may be greater than or equal to about 65 wt.%, greater than or equal to about 70 wt.%, greater than or equal to about 75 wt.%, greater than or equal to about 80 wt.%, greater than or equal to about 85 wt.%, greater than or equal to about 90 wt.%, greater than or equal to about 92 wt.%, greater than or equal to about 95 wt.%, greater than or equal to about 97 wt.%, or greater than or equal to about 99 wt.%.
  • the weight percentage of the flame retardant filtration layer in the filter media may be less than or equal to about
  • the filter media may comprise a relatively high weight percentage of flame retardant fibers.
  • the total weight percentage of flame retardant fibers in the filter media and/or in the total weight percentage of flame retardant fibers of all fibers in the filter media may be greater than or equal to about 20 wt.%, greater than or equal to about 30 wt.%, greater than or equal to about 40 wt.%, greater than or equal to about 50 wt.%, greater than or equal to about 60 wt.%, greater than or equal to about 70 wt.%, or greater than or equal to about 80 wt.%.
  • the total weight percentage of flame retardant fibers in the filter media and/or in the total weight percentage of flame retardant fibers of all fibers in the filter media may be less than or equal to about 90 wt.%, less than or equal to about 85 wt.%, less than or equal to about 80 wt.%, less than or equal to about 70 wt.%, less than or equal to about 60 wt.%, less than or equal to about 50 wt.%, less than or equal to about 40 wt.%, less than or equal to about 30 wt.%, less than or equal to about 20 wt.%, or less than or equal to about 15 wt.%.
  • the filter media may comprise a relatively high weight percentage of coarse diameter fibers.
  • the total weight percentage of coarse diameter fibers in the filter media and/or in the total weight percentage of coarse diameter fibers of all fibers in the filter media may be greater than or equal to about 20 wt.%, greater than or equal to about 30 wt.%, greater than or equal to about 40 wt.%, greater than or equal to about 50 wt.%, greater than or equal to about 60 wt.%, greater than or equal to about 70 wt.%, or greater than or equal to about 80 wt.%.
  • the total weight percentage of coarse diameter fibers in the filter media and/or in the total weight percentage of coarse diameter fibers of all fibers in the filter media may be less than or equal to about 85 wt.%, less than or equal to about 80 wt.%, less than or equal to about 70 wt.%, less than or equal to about 60 wt.%, less than or equal to about 50 wt.%, less than or equal to about 40 wt.%, less than or equal to about 30 wt.%, less than or equal to about 20 wt.%, or less than or equal to about 15 wt.%.
  • the total weight percentage of fine diameter fibers in the filter media and/or in the total weight percentage of fine diameter fibers of all fibers in the filter media may be less than or equal to about 40 wt.%, less than or equal to about 35 wt.%, less than or equal to about 30 wt.%, less than or equal to about 25 wt.%, less than or equal to about 20 wt.%, less than or equal to about 15 wt.%, or less than or equal to about 10 wt.%.
  • the total weight percentage of fine diameter fibers in the flame retardant filtration layer and/or in the total weight percentage of fine diameter fibers of all fibers in the filter media may be greater than or equal to about 5 wt.%, greater than or equal to about 10 wt.%, greater than or equal to about 15 wt.%, greater than or equal to about 20 wt.%, greater than or equal to about 25 wt.%, greater than or equal to about 30 wt.%, or greater than or equal to about 35 wt.%.
  • the filter media may contain a relatively high weight percentage of synthetic fibers.
  • the weight percentage of synthetic fibers in the filter media and/or in the weight percentage of synthetic fibers of all fibers in the filter media may be greater than or equal to about 1%, greater than or equal to about 20%, greater than or equal to about 40%, greater than or equal to about 60%, greater than or equal to about 80%, greater than or equal to about 90%, or greater than or equal to about 95%.
  • the weight percentage of synthetic fibers in the filter media and/or in the weight percentage of synthetic fibers of all fibers in the filter media may be less than or equal to about 100%, less than or equal to about 98%, less than or equal to about
  • the filter media includes 100% synthetic fibers.
  • one or more layers e.g., filtration layer comprising flame retardant fibers, second layer
  • the entire filter media is substantially free of glass fibers (e.g., less than 1 wt.% glass fibers, between about 0 wt.% and about 1 wt.% glass fibers).
  • the flame retardant filtration layer, second layer, and/or the entire filter media may include 0 wt.% glass fibers.
  • Filter media described herein may be produced using suitable processes, such a wet laid or a non-wet laid process.
  • the flame retardant filtration layer and/or the filter media described herein may be produced using a wet laid process.
  • a wet laid process involves mixing together of fibers of one or more type; for example, coarse synthetic fibers of one diameter may be mixed together with coarse synthetic fibers of another diameter, and/or with fine diameter fibers, to provide a fiber slurry.
  • the slurry may be, for example, an aqueous-based slurry.
  • fibers are optionally stored separately, or in combination, in various holding tanks prior to being mixed together (e.g., to achieve a greater degree of uniformity in the mixture).
  • a first fiber may be mixed and pulped together in one container and a second fiber may be mixed and pulped in a separate container.
  • the first fibers and the second fibers may subsequently be combined together into a single fibrous mixture.
  • Appropriate fibers may be processed through a pulper before and/or after being mixed together.
  • combinations of fibers are processed through a pulper and/or a holding tank prior to being mixed together. It can be appreciated that other components may also be introduced into the mixture.
  • other combinations of fibers types may be used in fiber mixtures, such as the fiber types described herein.
  • a media including two or more layers such as a filtration layer comprising flame retardant fibers and a second layer is formed by a wet laid process.
  • a first dispersion e.g., a pulp
  • a solvent e.g., an aqueous solvent such as water
  • a second dispersion e.g., another pulp
  • a solvent e.g., an aqueous solvent such as water
  • Vacuum is continuously applied to the first and second dispersions of fibers during the above process to remove the solvent from the fibers, thereby resulting in an article containing first and second layers.
  • the article thus formed is then dried and, if necessary, further processed (e.g., calendered) by using known methods to form multi-layered filter media.
  • any suitable method for creating a fiber slurry may be used.
  • further additives are added to the slurry to facilitate processing.
  • the temperature may also be adjusted to a suitable range, for example, between 33 °F and 100 °F (e.g., between 50 °F and 85 °F). In some cases, the temperature of the slurry is maintained. In some instances, the temperature is not actively adjusted.
  • the wet laid process uses similar equipment as in a conventional papermaking process, for example, a hydropulper, a former or a headbox, a dryer, and an optional converter.
  • the slurry may be pumped into a headbox where the slurry may or may not be combined with other slurries. Other additives may or may not be added.
  • the slurry may also be diluted with additional water such that the final concentration of fiber is in a suitable range, such as for example, between about 0.1% and 0.5% by weight.
  • the pH of the fiber slurry may be adjusted as desired.
  • fibers of the slurry may be dispersed under generally neutral conditions.
  • the slurry Before the slurry is sent to a headbox, the slurry may optionally be passed through centrifugal cleaners and/or pressure screens for removing unfiberized material.
  • the slurry may or may not be passed through additional equipment such as refiners or deflakers to further enhance the dispersion of the fibers.
  • deflakers may be useful to smooth out or remove lumps or protrusions that may arise at any point during formation of the fiber slurry.
  • Fibers may then be collected on to a screen or wire at an appropriate rate using any suitable equipment, e.g., a fourdrinier, a rotoformer, a cylinder, or an inclined wire fourdrinier.
  • a resin is added to a layer (e.g., a pre-formed layer formed by a wet-laid process).
  • a layer e.g., a pre-formed layer formed by a wet-laid process.
  • different components included in the resin e.g., polymeric binder and/or other components
  • each component of the resin is mixed as an emulsion prior to being combined with the other components and/or layer.
  • the components included in the resin may be pulled through the layer using, for example, gravity and/or vacuum.
  • one or more of the components included in the resin may be diluted with softened water and pumped into the layer.
  • a resin may be applied to a fiber slurry prior to introducing the slurry into a headbox.
  • the resin may be introduced (e.g., injected) into the fiber slurry and impregnated with and/or precipitated on to the fibers.
  • a resin may be added to a layer by a solvent saturation process.
  • the second layer described herein may be produced using a non-wet laid process, such as blowing or spinning process.
  • the second layer may be formed by an electro spinning process.
  • the second layer may be formed by a meltblowing system, such as the meltblown system described in U.S. Publication No. 2009/0120048, filed November 07, 2008, and entitled “Meltblown Filter Medium", and U.S. Publication No. 2012-0152824, filed December 17, 2010, and entitled, "Fine Fiber Filter Media and Processes", each of which is incorporated herein by reference in its entirety for all purposes.
  • the second layer may be formed by a meltspinning or a centrifugal spinning process.
  • a non-wet laid process such as an air laid or carding process, may be used to form the second layer.
  • synthetic 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.
  • forming the layers through a non-wet laid process may be more suitable for the production of a highly porous media.
  • the layer may be impregnated (e.g., via saturation, spraying, etc.) with any suitable resin, as discussed above.
  • a non-wet laid process (e.g., meltblown, electrospun) may be used to form the second layer and a wet laid process may be used to form the flame retardant filtration layer.
  • the second layer e.g., efficiency layer
  • the flame retardant filtration layer may be combined using any suitable process (e.g., adhesives, lamination, co-pleating, or collation).
  • the filter media may be further processed according to a variety of known techniques. For instance, a coating method may be used to include a resin in the filter media.
  • additional layers can be formed and/or added to a filter media using processes such as adhesives, lamination, co-pleating, or collation.
  • two layers are formed into a composite article by a wet laid process as described above, and the composite article is then combined with a third layer by any suitable process (e.g., adhesives, lamination, co-pleating, or collation).
  • a filter media or a composite article formed by the processes described herein may be suitably tailored not only based on the components of each layer, but also according to the effect of using multiple layers of varying properties in appropriate combination to form filter media having the characteristics described herein.
  • two or more layers of the filter media may be formed separately and combined by any suitable method such as lamination, collation, or by use of adhesives.
  • the two or more layers may be formed using different processes, or the same process.
  • each of the layers may be independently formed by a non-wet laid process (e.g., meltblown process, melt spinning process, centrifugal spinning process, electro spinning process, dry laid process, air laid process), a wet laid process, or any other suitable process.
  • layers may be adhered together by any suitable method. For instance, layers may be adhered by an adhesive and/or melt-bonded to one another on either side. Lamination and calendering processes may also be used. In some embodiments, an additional layer may be formed from any type of fiber or blend of fibers via an added headbox or a coater and appropriately adhered to another layer.
  • further processing may involve pleating the filter media.
  • two layers may be joined by a co-pleating process.
  • the filter media, or various layers thereof may be suitably pleated by forming score lines at appropriately spaced distances apart from one another, allowing the filter media to be folded.
  • one layer can be wrapped around a pleated layer. It should be appreciated that any suitable pleating technique may be used.
  • a filter media can be post-processed such as subjected to a corrugation process to increase surface area within the web.
  • a filter media may be embossed.
  • the filter media may include any suitable number of layers, e.g., one layer, at least 2, at least 3, at least 4, at least 5, at least 6, at least 7 layers. In some embodiments, the filter media may include up to 20 layers.
  • Filter media described herein may be used in an overall filtration arrangement or filter element.
  • one or more additional layers or components are included with the filter media.
  • additional layers e.g., a third layer, a fourth layer
  • additional layers include a meltblown layer, a wet laid layer, a spunbond layer, a carded layer, an air-laid layer, a spunlace layer, a forcespun layer or an electrospun layer.
  • the filter media may include other parts in addition to the one or more layers described herein.
  • further processing includes incorporation of one or more structural features and/or stiffening elements.
  • the filter media may be combined with additional structural features such as polymeric and/or metallic meshes.
  • a screen backing may be disposed on the filter media, providing for further Gurley stiffness.
  • a screen backing may aid in retaining the pleated configuration.
  • a screen backing may be an expanded metal wire or an extruded plastic mesh.
  • a layer described herein may be a nonwoven web.
  • a nonwoven web may include non-oriented fibers (e.g., a random arrangement of fibers within the web). Examples of nonwoven webs include webs made by wet-laid or non-wet laid processes as described herein.
  • the filter media may be incorporated into a variety of suitable filter elements for use in various applications including gas and liquid filtration.
  • Filter media suitable for gas filtration may be used for HVAC, HEPA, face mask, and ULPA filtration applications.
  • the filter media may be used in heating and air conditioning ducts.
  • the filter media may be used for respirator and face mask applications (e.g., surgical face masks, industrial face masks, and industrial respirators).
  • the filter media can be incorporated into a variety of filter elements for use in hydraulic filtration applications. Exemplary uses of hydraulic filters (e.g., high-, medium-, and low-pressure specialty filters) include mobile and industrial filters.
  • 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. 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, vacuum bag filter elements, fuel filter elements, and oil filter elements (e.g., lube oil filter elements or heavy duty lube oil 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, vacuum bag filter systems, fuel filter systems, and oil 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 meshes in a cylindrical shape. During use, fluids can flow from the outside through the pleated media to the inside of the radial element.
  • 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.
  • 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.
  • a substrate may be added to the filter media.
  • the filter elements may have the same property values as those noted above in connection with the filter media.
  • the above-noted pressure drop, thicknesses, and/or basis weight may also be found in filter elements.
  • the filter media mechanically trap contaminant particles on the filter media as fluid (e.g., air) flows through the filter media.
  • the filter media need not be electrically charged to enhance trapping of contamination.
  • the filter media are not electrically charged.
  • the filter media may be electrically charged.
  • the flame retardant filtration layer (e.g., pleatable backer layer) and/or the filter media may be used for non-filtration application.
  • the flame retardant filtration layer (e.g., pleatable backer layer) and/or the filter media may be used in window shade applications.
  • This example describes the dust holding capacity for five filter media including a meltblown efficiency layer adhesively bound to a filtration layer comprising synthetic fibers
  • the filtration layer comprising synthetic fibers was a pleatable backer layer.
  • the surface average fiber diameter of the pleatable backer layer varied in each filter media.
  • Optimal dust holding capacity was observed when the surface average fiber diameter (SAFD) was in the range of 13 microns to 17 microns.
  • SAFD surface average fiber diameter
  • Filter media containing a metblown efficiency layer and a pleatable backer layer were formed.
  • the pleatable backer layer was upstream and directly adjacent to the meltblown efficiency layer.
  • the efficiency layer was a meltblown polypropylene fiber web having an average fiber diameter of 0.6 microns.
  • the efficiency layer was a mechanical efficiency layer with an F9 efficiency rating according to the EN779 standard.
  • the pleatable backer layer contained a blend of a first population of coarse polyester fibers having an average diameter of 25 microns, a second population of coarse polyester fibers having an average diameter of 15 microns, a first population of fine polyester fibers having an average fiber diameter of 9 microns, and a second population of fine polyester fibers having an average fiber diameter of 13 microns, and an acrylic binder.
  • the pleatable backer layers were formed via a wetlaid process and had a basis weight between about 80 g/m and 85 g/m . Table 1 shows the weight percentage of total fibers for each fiber type in the pleatable backer layer as well as the surface average fiber diameter and air permeability. The surface average fiber diameter was calculated as described herein. Unless otherwise indicated, the structural and performance properties of the layers and entire filter were measured as described herein.
  • the pleatable backer layers differed in the weight percentage of fine and coarse diameter fibers that were used and the surface average fiber diameter.
  • the dust holding capacity was the highest for filter media having a surface average fiber diameter of between 13 microns and 17 microns.
  • Figure 2 shows the dust holding capacity versus surface average fiber diameter for the filter media in Example 1.
  • This example describes the flame retardancy of two filter media including a filtration layer including fibers comprising a flame retardant and a filter media lacking fibers comprising a flame retardant.
  • the filter media including fibers comprising a flame retardant achieved a higher flame retardant rating than the filter media lacking such fibers.
  • Two filter media i.e., filter media 1 and filter media 2 containing fibers comprising a flame retardant were formed using a wet-laid process.
  • the filter media contained a blend of polyester fibers comprising a phosphorus-based flame retardant and non-flame retardant fibers that did not comprise a flame retardant.
  • the composition of the two filter media are provided in Table 1.
  • One filter media not containing fibers comprising a flame retardant i.e., filter media 3
  • the composition of filter media 3 is also provided in Table 2. All fibers in the filter media had an average length of less than or equal to about 6 mm. All of the filter media had a basis weight between about
  • Filter media 1 and 3 were essentially identical, except filter media 1 contained 69 wt.% of polyester fibers having an average diameter of 13 microns that contained a phosphorus-based flame retardant whereas filter media 3 contained 69 wt.% of polyester fibers having an average diameter of 13 microns that did not contain a flame retardant. Filter media 1 and 2 differed in the composition of non-flame retardant fibers.
  • the flame retardancy of the filter media was determined according to DIN53438 surface ignition (F tests) and edge ignition tests (K tests) as described herein.
  • Filter media 1 and 2 were flame retardant with a Fl and Kl rating.
  • Filter media 3 was not flame retardant and received a F2 and K3 rating.
  • the flame retardancy test data and ratings are shown in Tables 3-8.
  • This example describes the flame retardancy of a filter media including a flame retardant filtration layer including fibers comprising a phosphorous-based flame retardant and a glass efficiency layer and a filter media including a filtration layer lacking fibers comprising a phosphorous-based flame retardant and a glass efficiency layer.
  • the filter media including the flame retardant filtration layer achieved a higher flame retardant rating than the filter media lacking the fibers comprising a phosphorous-based flame retardant.
  • a filter media i.e., filter media 4 containing a flame retardant filtration layer was formed using a wet-laid process.
  • the flame retardant filtration layer was formed as described in Example 2 with respect to filter media 1 and 2.
  • the glass efficiency layer was formed on the flame retardant filtration layer.
  • the glass efficiency layer contained 92 wt.% Johns Manville 106 glass fibers and 8 wt.% bicomponent fibers.
  • the glass efficiency layer had a basis weight of 30 g/m .
  • Filter media 5 contained a filtration layer formed as described in Example 1 with respect to filter media 3 and a glass efficiency layer.
  • the glass efficiency layer contained 92 wt.% Johns Manville 106 glass fibers and 8 wt.% bicomponent fibers.
  • the glass efficiency layer had a basis weight of 30 g/m .
  • Filter media 4 and 5 were essentially identical, except filter media 4 contained 69 wt.% of polyester fibers having an average diameter of 13 microns that contained a phosphorus-based flame retardant in the filtration layer whereas filter media 5 contained 69 wt.% of polyester fibers having an average diameter of 13 microns that did not contain a flame retardant in the filtration layer.
  • the flame retardancy of the filter media was determined according to DIN53438 surface ignition (F tests) and edge ignition tests (K tests) as described herein.
  • Filter media 4 was flame retardant with a Fl and Kl rating as shown in Tables 9 and 10.
  • Filter media 5 was not flame retardant and received a F3 and K3 rating as shown in Tables 11 and 12.

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Abstract

La présente invention concerne un support filtrant comprenant une couche de filtration composée de fibres (par exemple des fibres synthétiques) renfermant des composants ignifuges ; l'invention concerne également des composants, des systèmes et des procédés associés. Dans certains modes de réalisation, la couche de filtration peut comporter une bande non tissée (par exemple une bande non tissée appliquée par voie humide) comprenant des fibres comportant un agent ignifuge spécifique contenant une concentration relativement faible ou sensiblement nulle de certains composants indésirables et/ou toxiques (par exemple des halogènes). Dans certains modes de réalisation, la bande non tissée peut également comprendre un mélange de fibres. Par exemple, dans certains modes de réalisation, la bande non tissée peut également comprendre un mélange de fibres synthétiques de diamètre grossier et de diamètre fin qui confèrent à la couche de filtration des propriétés avantageuses en termes de performances. Dans certains modes de réalisation, la couche de filtration peut être conçue pour avoir des propriétés ignifuges souhaitables (classe F1, classe K1 par exemple) et présenter certaines performances sans compromettre certaines propriétés mécaniques (par exemple l'aptitude au plissage du support) et/ou certains critères environnementaux (par exemple une toxicité relativement faible). Le support filtrant selon la présente invention peut être particulièrement approprié pour des applications impliquant la filtration d'air, mais peut aussi être utilisé dans d'autres applications.
EP17857510.6A 2016-09-30 2017-09-29 Support filtrant comprenant des fibres ignifuges Pending EP3519076A4 (fr)

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US15/283,014 US11014030B2 (en) 2016-02-17 2016-09-30 Filter media including flame retardant fibers
PCT/US2017/054340 WO2018064500A1 (fr) 2016-09-30 2017-09-29 Support filtrant comprenant des fibres ignifuges

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DE102012220546A1 (de) * 2012-11-12 2014-05-15 Neenah Gessner Gmbh Flammhemmend ausgerüstetes Gasfiltermaterial mit hoher Staubspeicherfähigkeit

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