High performance filter media

Abstract

Filter media including a nonwoven web having high performance are generally described. For example, in some embodiments, the nonwoven webs described herein have a relatively high gamma value and / or a relatively high ratio of dust holding capacity to weight per unit area. As further examples, in some embodiments, the nonwoven webs described herein are capable of relatively uniformly loading dust across its depth. The latter characteristic may help increase the ratio of [gamma] and / or dust holding capacity to weight per unit area.

Description

Technical Field

[0001] The present invention generally relates to filter media, and more particularly, to filter media that comprise polypropylene fibers, have a high gamma, have a high dust holding capacity, and / or are configured to capture dust across the entire thickness of one or more layers therein. Background Art

[0002] Filter media can be used in various applications. For example, filter media can be used to remove contaminants from fluids. Some filter media may exhibit undesirable characteristics such as low dust holding capacity and / or low gamma values.

[0003] Accordingly, there is a need for improved filter media designs. Summary of the Invention

[0004] Filter media, related components, and related methods are generally described.

[0005] In some embodiments, a filter media is provided. The filter media includes a nonwoven fibrous web containing fibers. Polypropylene comprises at least 75 wt% of the polymers in the nonwoven fibrous web. The average diameter of the fibers in the nonwoven fibrous web is less than or equal to 15 microns. The gamma of the nonwoven fibrous web is greater than or equal to 200. The ratio of the dust holding capacity of the filter media to the basis weight of the filter media is greater than or equal to 1 gsm / gsm. The thickness of the nonwoven fibrous web is greater than 6 mils.

[0006] In some embodiments, the filter media includes a nonwoven fibrous web containing fibers. Polypropylene comprises at least 75 wt% of the polymers in the nonwoven fibrous web. The average diameter of the fibers in the nonwoven fibrous web is less than or equal to 15 microns. The gamma of the nonwoven fibrous web is greater than or equal to 200. The nonwoven fibrous web is configured such that after undergoing an NaCl loading process, the NaCl density at the downstream surface of the nonwoven fibrous web is greater than or equal to 50% of the NaCl density at the upstream surface of the nonwoven fibrous web.

[0007] When considered in conjunction with the accompanying drawings, other advantages and novel features of the present invention will become apparent from the following detailed description of the invention's various non-limiting embodiments. In the event that the present specification and the documents incorporated by reference contain conflicting and / or inconsistent disclosures, the present specification shall prevail. If two or more documents incorporated by reference contain conflicting and / or inconsistent disclosures relative to each other, then the document with the later effective date shall prevail. Brief Description of the Drawings

[0008] Non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, which are schematic and not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown is generally represented by a single reference numeral. For purposes of clarity, not every component is labeled in each drawing, nor is every component of every embodiment of the present invention shown where illustration is not necessary to enable one of ordinary skill in the art to understand the present invention. In the drawings:

[0009] Figure 1 A non-limiting example of a nonwoven fibrous web according to some embodiments is shown;

[0010] Figure 2 A non-limiting example of a filter medium including a nonwoven fibrous web and an additional layer according to some embodiments is shown;

[0011] Figure 3 A non-limiting example of a layer containing an adsorbent material according to some embodiments is shown;

[0012] Figure 4A A non-limiting example of a corrugated configuration of a filter medium according to some embodiments is shown;

[0013] Figure 4B A filter medium including a cover layer according to some embodiments is shown;

[0014] Figure 5 A non-limiting example of a corrugated configuration of a filter medium according to some embodiments is shown;

[0015] Figure 6 A non-limiting example of a filter medium including an irregular structure according to some embodiments is shown;

[0016] Figure 7 An example of a relative surface topography according to some embodiments is shown;

[0017] Figures 8A to 8B An example of multiple sets of line data according to some embodiments is shown;

[0018] Figures 9A to 9B An example of a filter medium including a first layer that is topologically connected throughout the layer and a second layer that includes portions that are topologically unconnected to each other according to some embodiments is shown;

[0019] Figure 10 An example of a plurality of resiliently extensible fibers forming a layer according to some embodiments is shown;

[0020] Figure 11AShows an example of a filter medium including a layer having a plurality of peaks according to some embodiments;

[0021] Figure 11B Shows a non - limiting embodiment of a filter medium including two layers each having a plurality of peaks according to some embodiments;

[0022] Figures 12A to 12C Shows a method of manufacturing a filter medium according to some embodiments;

[0023] Figures 12D to 12F Shows a schematic diagram of a process of manufacturing a filter medium according to some embodiments;

[0024] Figures 13 to 16 Is a SEM image of a non - woven web according to some embodiments; and

[0025] Figure 17 Is a graph showing the NaCl density as a function of the thickness of two non - woven webs according to some embodiments. Detailed Description

[0026] Generally describes a filter medium including a non - woven web having high performance. For example, in some embodiments, the non - woven webs described herein have a relatively high γ value and / or a relatively high ratio of dust - holding capacity to basis weight. As another example, in some embodiments, the non - woven webs described herein are capable of loading dust relatively uniformly throughout their depth. The latter property can contribute to increasing γ and / or the ratio of dust - holding capacity to basis weight.

[0027] In some embodiments, a non - woven web having high performance contains a relatively large amount of polypropylene. Polypropylene can be advantageously melt - blown to form fibers that can be charged. After being charged, compared to an uncharged non - woven web, a non - woven web containing polypropylene can exhibit enhanced performance in one or more aspects, such as reduced penetration and / or enhanced capture of charged substances. In some embodiments, the polypropylene present in the non - woven web can have one or more characteristics that enhance performance. As an example, the polypropylene present in the non - woven web can have a particularly beneficial melt flow rate. The melt flow rate of the polypropylene can be relatively similar to the melt flow rate of other components (e.g., any additives) in the non - woven web, which can enhance their mixing. In some embodiments, the melt flow rate of the polypropylene can promote the formation of fibers having a favorable average fiber diameter, such as an average fiber diameter large enough to retain a desired amount of static charge and / or support relatively high resistance to compaction. The latter property can be desirable for non - woven webs provided in rolls (which exert forces that may cause compaction).

[0028] Figure 1 shows a nonwoven web having high performance, such as a non-limiting example of a nonwoven web having one or more of the features described herein. Figure 1 Depicts a nonwoven web 100 having high performance.

[0029] In some embodiments, a nonwoven web having high performance is provided as a component of a filtration medium. The filtration medium may also include other components, such as additional layers (some or all of which may be other nonwoven webs). In such embodiments, the nonwoven web having high performance may be an outer layer (e.g., the most upstream layer, the most downstream layer) or an inner layer (e.g., positioned between at least one upstream layer and one downstream layer). For example, Figure 2 shows a non-limiting example of a filtration medium 202 including a nonwoven web 200 and a layer 204. The total number of layers provided may vary (e.g., the filtration medium may include two or more, three or more, four or more, five or more, or even more layers), and some or all of the layers may be of the same type (e.g., the filtration medium may include two or more nonwoven webs having high performance and / or two or more other layers of the same type).

[0030] Non-limiting examples of exemplary combinations of layers include the following: an adsorption layer / a charged layer containing discontinuous fibers / a nonwoven web having high performance / a nonwoven web containing nanofibers / a spunbond layer; a charged layer containing discontinuous fibers / a nonwoven web having high performance / a nonwoven web containing nanofibers / a spunbond layer / an adsorption layer; an adsorption layer / a nonwoven web having high performance / a nonwoven web containing nanofibers / a spunbond layer; a nonwoven web having high performance / a nonwoven web containing nanofibers / a spunbond layer / an adsorption layer; a nonwoven web having high performance / a nonwoven web having high performance with different average fiber diameters / a backing; a nonwoven web having high performance / a backing; an adsorption layer / a nonwoven web having high performance; a nonwoven web having high performance / a spunbond layer; a nonwoven web having high performance / a grid; a nonwoven web having high performance / a nonwoven web containing nanofibers / a spunbond layer / a backing; and a nonwoven web having high performance / a nonwoven web containing nanofibers / a carded layer / a spunbond layer / a grid.

[0031] The nonwoven webs described herein may also be provided alone or as the sole layer in a filtration medium.

[0032] Further details regarding the individual layers that may be included in the filtration medium are provided in further detail below.

[0033] As described above, in some embodiments, a nonwoven web with high performance is provided. Such a nonwoven web can be a main filter or can be used as a pre-filter for the main filter. The filter medium can also include two or more nonwoven webs with high performance. Such nonwoven webs can be the same or can be different in one or more aspects.

[0034] The nonwoven web with high performance can have various different designs. In some embodiments, the filter medium includes a nonwoven web with high performance that is a meltblown layer. Such a meltblown layer can have various fiber designs. For example, the nonwoven web with high performance can include split meltblown fibers (e.g., manufactured with the help of a high-pressure water jet) and / or multi-component meltblown fibers (e.g., bicomponent meltblown fibers, multi-component meltblown fibers formed by extrusion). The nonwoven web with high performance can also include cylindrical fibers, irregularly shaped fibers, fibers with an elliptical cross-section, fibers with a dogbone cross-section, ribbon fibers, and / or multi-lobed fibers (e.g., bilobed, trilobed, tetralobed, and / or pentalobed fibers).

[0035] The nonwoven web with high performance can have a relatively high polypropylene content. In some embodiments, the polypropylene accounts for greater than or equal to 75 wt%, greater than or equal to 77.5 wt%, greater than or equal to 80 wt%, greater than or equal to 82.5 wt%, greater than or equal to 85 wt%, greater than or equal to 87.5 wt%, greater than or equal to 90 wt%, greater than or equal to 92.5 wt%, greater than or equal to 95 wt%, greater than or equal to 97.5 wt%, greater than or equal to 99 wt%, greater than or equal to 99.25 wt%, greater than or equal to 99.5 wt%, or greater than or equal to 99.75 wt% of all the polymers in the nonwoven web (including those present in the fibers, any additives present, and any other components present). In some embodiments, the polypropylene accounts for less than or equal to 99.9 wt%, less than or equal to 99.75 wt%, less than or equal to 99.5 wt%, less than or equal to 99.25 wt%, less than or equal to 99 wt%, less than or equal to 97.5 wt%, less than or equal to 95 wt%, less than or equal to 92.5 wt%, less than or equal to 90 wt%, less than or equal to 87.5 wt%, less than or equal to 85 wt%, less than or equal to 82.5 wt%, less than or equal to 80 wt%, or less than or equal to 77.5 wt% of all the polymers in the nonwoven web. Combinations of the above ranges are also possible (e.g., greater than or equal to 75 wt% and less than or equal to 99.9 wt%, greater than or equal to 80 wt% and less than or equal to 99.5 wt%, or greater than or equal to 85 wt% and less than or equal to 99 wt%). Other ranges are also possible.

[0036] When a high-performance nonwoven web contains two or more types of polypropylene, each type of polypropylene can independently be present as one or more of the above ranges, and / or all of the polypropylene in the high-performance nonwoven web can together be present as one or more of the above ranges. When the filter medium includes two or more high-performance nonwoven webs, the foregoing can apply independently for each such nonwoven web.

[0037] Among the fibers present in the high-performance nonwoven web, various suitable types of polypropylene can be employed, including polypropylene resins supplied by: ExxonMobil (e.g., those having a melt flow rate of 500, 925, or 1550), LyondellBasel (e.g., those having a melt flow rate of 450, 500, 800, 1100, 1200, 1500, or 1800), Total Energies (e.g., those having a melt flow rate of 100 or 1300); and / or Borealis (e.g., those having a melt flow rate of 450, 800, 1200, or 2000).

[0038] The polypropylene contained in the high-performance nonwoven fiber web can have a melt flow rate within a range that enhances performance. For example, in some embodiments, the melt flow rate of the polypropylene contained in such a nonwoven fiber web is greater than or equal to 10, greater than or equal to 20, greater than or equal to 30, greater than or equal to 40, greater than or equal to 50, greater than or equal to 75, greater than or equal to 100, greater than or equal to 150, greater than or equal to 200, greater than or equal to 300, greater than or equal to 500, greater than or equal to 600, greater than or equal to 800, greater than or equal to 1000, greater than or equal to 1200, greater than or equal to 1400, greater than or equal to 1600, greater than or equal to 1800, or greater than or equal to 2000. In some embodiments, the melt flow rate of the polypropylene present in the high-performance nonwoven fiber web is less than or equal to 2200, less than or equal to 2000, less than or equal to 1800, less than or equal to 1600, less than or equal to 1400, less than or equal to 1200, less than or equal to 1000, less than or equal to 800, less than or equal to 600, less than or equal to 500, less than or equal to 300, less than or equal to 200, less than or equal to 150, less than or equal to 100, less than or equal to 75, less than or equal to 50, less than or equal to 40, less than or equal to 30, or less than or equal to 20. Combinations of the above ranges are also possible (e.g., greater than or equal to 10 and less than or equal to 2200, greater than or equal to 10 and less than or equal to 2000, greater than or equal to 30 and less than or equal to 1600, or greater than or equal to 100 and less than or equal to 1200). Other ranges are also possible.

[0039] The melt flow rate of the polypropylene can be determined by ASTM D1238-20, during which a load of 2.16 kg is applied to the die maintained at a temperature of 230 °C. The flow of the polypropylene can be measured over a 10-minute period under these conditions.

[0040] When the high-performance nonwoven fiber web contains two or more types of polypropylene, each type of polypropylene can independently have a melt flow rate within one or more of the above ranges, and / or all of the polypropylene in the high-performance nonwoven fiber web can together have a melt flow rate within one or more of the above ranges. When the filter medium includes two or more high-performance nonwoven fiber webs, the foregoing can apply independently to each such nonwoven fiber web.

[0041] In some embodiments, the high-performance nonwoven web comprises one or more polymers other than polypropylene (e.g., which are also present in the fibers containing polypropylene and which are present in other fibers). As an example, in some embodiments, the high-performance nonwoven web further comprises other types of polyolefins (e.g., polyethylene, poly-4-methyl-1-pentene, polybutene, olefin copolymers).

[0042] In some embodiments, the high-performance nonwoven web comprises additives, such as charge stabilizing additives. In some embodiments, the charge stabilizing additive comprises greater than or equal to 0.1 wt%, greater than or equal to 0.2 wt%, greater than or equal to 0.3 wt%, greater than or equal to 0.4 wt%, greater than or equal to 0.5 wt%, greater than or equal to 0.6 wt%, greater than or equal to 0.8 wt%, greater than or equal to 1 wt%, greater than or equal to 1.25 wt%, greater than or equal to 1.5 wt%, greater than or equal to 1.75 wt%, greater than or equal to 2 wt%, greater than or equal to 2.5 wt%, greater than or equal to 3 wt%, or greater than or equal to 3.5 wt% of the high-performance nonwoven web. In some embodiments, the charge stabilizing additive comprises less than or equal to 4 wt%, less than or equal to 3.5 wt%, less than or equal to 3 wt%, less than or equal to 2.5 wt%, less than or equal to 2 wt%, less than or equal to 1.75 wt%, less than or equal to 1.5 wt%, less than or equal to 1.25 wt%, less than or equal to 1 wt%, less than or equal to 0.8 wt%, less than or equal to 0.6 wt%, less than or equal to 0.5 wt%, less than or equal to 0.4 wt%, less than or equal to 0.3 wt%, or less than or equal to 0.2 wt% of the high-performance nonwoven web. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 wt% and less than or equal to 4 wt%, greater than or equal to 0.1 wt% and less than or equal to 3 wt%, greater than or equal to 0.2 wt% and less than or equal to 4 wt%, greater than or equal to 0.5 wt% and less than or equal to 3 wt%, or greater than or equal to 0.8 wt% and less than or equal to 2 wt%). Other ranges are also possible.

[0043] When a nonwoven fibrous web having high performance contains two or more types of charge stabilizing additives, each type of charge stabilizing additive can independently be present in one or more of the above ranges, and / or all of the charge stabilizing additives in the nonwoven fibrous web having high performance can together be present in one or more of the above ranges. When the nonwoven fibrous web contains one or more components (e.g., one or more resins) containing a charge stabilizing additive, each such component can individually be present in one or more of the above ranges, and / or all such components can together be present in one or more of the above ranges. When the filter medium includes two or more nonwoven fibrous webs having high performance, the foregoing can apply independently for each such nonwoven fibrous web.

[0044] An example of a suitable class of charge stabilizing additives is hindered amine light stabilizers. Without wishing to be bound by any particular theory, it is believed that hindered amine light stabilizers are capable of accepting and stabilizing charged species thereon (e.g., positively charged species such as protons from water; negatively charged species). An example of a suitable hindered amine light stabilizer is CHIMASSORB 944 FL. Further non-limiting examples of suitable charge stabilizing additives include fused aromatic thioureas, organic triazines, UV stabilizers, phosphites / salts, additives containing two or more amide groups (e.g., bisamides, trisamides), stearates / salts (e.g., magnesium stearate, calcium stearate), and stearamides (e.g., ethylenebisstearamide). The charge stabilizing additives can be incorporated into the fibers present in the nonwoven fibrous web having high performance, and / or can be incorporated into such a nonwoven fibrous web in another manner (e.g., as particles, as a coating on the fibers). An example of a way to incorporate the charge stabilizing additives into the fibers is by forming (e.g., by meltblowing) continuous fibers from a composition containing the charge stabilizing additive.

[0045] In some embodiments, the charge stabilizing additive is supplied as a component of the resin present in a high performance nonwoven web. In such embodiments, the melt flow rate of the resin can be relatively close to the melt flow rate of the polypropylene also present in the high performance nonwoven web. The melt flow rate of the charge stabilizing additive can be greater than or equal to 10, greater than or equal to 20, greater than or equal to 30, greater than or equal to 40, greater than or equal to 50, greater than or equal to 75, greater than or equal to 100, greater than or equal to 150, greater than or equal to 200, greater than or equal to 300, greater than or equal to 500, greater than or equal to 600, greater than or equal to 800, greater than or equal to 1000, greater than or equal to 1200, greater than or equal to 1400, greater than or equal to 1600, or greater than or equal to 1800. In some embodiments, the melt flow rate of the charge stabilizing additive is less than or equal to 2000, less than or equal to 1800, less than or equal to 1600, less than or equal to 1400, less than or equal to 1200, less than or equal to 1000, less than or equal to 800, less than or equal to 600, less than or equal to 500, less than or equal to 300, less than or equal to 200, less than or equal to 150, less than or equal to 100, less than or equal to 75, less than or equal to 50, less than or equal to 40, less than or equal to 30, or less than or equal to 20. Combinations of the above ranges are also possible (e.g., greater than or equal to 10 and less than or equal to 2000, greater than or equal to 30 and less than or equal to 1800, or greater than or equal to 50 and less than or equal to 1600). Other ranges are also possible.

[0046] The melt flow rate of the charge stabilizing additive can be determined by the same methods described elsewhere herein for determining the melt flow rate of polypropylene.

[0047] When the high performance nonwoven web contains two or more types of resins containing a charge stabilizing additive, each type of resin can independently have a melt flow rate within one or more of the above ranges, and / or all of the resins in the high performance nonwoven web can together have a melt flow rate within one or more of the above ranges. When the filter medium includes two or more high performance nonwoven webs, the foregoing can apply independently for each such nonwoven web.

[0048] In some embodiments, the difference in melt flow rate between the resin containing a charge stabilizing additive and polypropylene (e.g., polypropylene present in the fibers), both of which are present in a nonwoven fibrous web having high performance, is relatively small. The absolute value of this difference can be less than or equal to 1200, less than or equal to 1000, less than or equal to 750, less than or equal to 500, less than or equal to 300, less than or equal to 200, less than or equal to 100, less than or equal to 75, less than or equal to 50, less than or equal to 30, less than or equal to 20, or less than or equal to 10. The absolute value of this difference can be greater than or equal to 0, greater than or equal to 10, greater than or equal to 20, greater than or equal to 30, greater than or equal to 50, greater than or equal to 75, greater than or equal to 100, greater than or equal to 200, greater than or equal to 300, greater than or equal to 500, greater than or equal to 750, or greater than or equal to 1000. Combinations of the above ranges are also possible (e.g., less than or equal to 1200 and greater than or equal to 0). Other ranges are also possible. In some embodiments, the difference is constantly equal to 0.

[0049] When a nonwoven fibrous web having high performance contains two or more types of resins containing a charge stabilizing additive and / or two or more types of polypropylene, each pair of resin and polypropylene types can independently have a melt flow rate difference with an absolute value within one or more of the above ranges, and / or the absolute value of the melt flow rate difference between all of the resins in the nonwoven fibrous web as a whole and all of the other polypropylene in the nonwoven fibrous web as a whole can be within one or more of the above ranges. When the filter medium includes two or more nonwoven fibrous webs having high performance, the foregoing can apply independently to each such nonwoven fibrous web.

[0050] In some embodiments, the nonwoven fibrous web having high performance is flame retardant and / or contains a flame retardant substance. The flame retardant nonwoven fibrous web can pass the glow wire test according to IEC60695-2-11(2010). The flame retardant substance can include flame retardant fibers and / or flame retardant additives. The former can include fibers having flame retardant additives distributed within and / or throughout the fibers. Such fibers can be manufactured by the methods for incorporating charge stabilizing additives into fibers described elsewhere herein. The flame retardant nonwoven fibrous web can also include flame retardant additives located at positions other than within the fibers therein.

[0051] The amount of the flame retardant substance in the high-performance nonwoven fiber web can be selected as desired. In some embodiments, the flame retardant substance accounts for greater than or equal to 0.1 wt%, greater than or equal to 0.2 wt%, greater than or equal to 0.3 wt%, greater than or equal to 0.5 wt%, greater than or equal to 0.75 wt%, greater than or equal to 1 wt%, greater than or equal to 2 wt%, greater than or equal to 5 wt%, greater than or equal to 7.5 wt%, greater than or equal to 10 wt%, greater than or equal to 15 wt%, greater than or equal to 20 wt%, greater than or equal to 25 wt%, greater than or equal to 30 wt%, or greater than or equal to 35 wt% of the high-performance nonwoven fiber web. In some embodiments, the flame retardant substance accounts for less than or equal to 40 wt%, less than or equal to 35 wt%, less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, less than or equal to 15 wt%, less than or equal to 10 wt%, less than or equal to 7.5 wt%, less than or equal to 5 wt%, less than or equal to 2 wt%, less than or equal to 1 wt%, less than or equal to 0.75 wt%, less than or equal to 0.5 wt%, less than or equal to 0.3 wt%, or less than or equal to 0.2 wt% of the relatively high-performance nonwoven fiber web. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 wt% and less than or equal to 40 wt%, greater than or equal to 0.2 wt% and less than or equal to 20 wt%, or greater than or equal to 0.3 wt% and less than or equal to 10 wt%). Other ranges are also possible.

[0052] When the high-performance nonwoven fiber web contains two or more types of flame retardant substances, each type of flame retardant substance can independently be present in one or more of the above ranges, and / or all of the flame retardant substances in the high-performance nonwoven fiber web can be present in one or more of the above ranges. When the filter medium includes two or more high-performance nonwoven fiber webs, the foregoing can apply independently to each such nonwoven fiber web.

[0053] Various suitable flame retardant additives can be included in the high-performance nonwoven fiber webs described herein (e.g., in the flame retardant fibers and / or elsewhere). For example, such nonwoven fiber webs can include phosphorus-based flame retardant additives and / or nitrogen-based flame retardant additives. Non-limiting examples of flame retardant additives include phosphorus-based additives, nitrogen-based additives, mineral additives, carbon-based additives, and bio-based additives. Such additives can include propionylmethylphosphinic acid ester / salt, dioxaphosphorinanes and their derivatives, triazine-based compounds, aminophosphates and their derivatives, allyl-functionalized polyphosphazenes, and non-halogenated compounds such as hydroxymethyl Salts and N-hydroxymethylphosphonyl propionamide and its derivatives. The flame retardant additive may also include one or more of those described in: Seidi F, Movahedifar E, Naderi G, Akbari V, Ducos F, Shamsi R, Vahabi H, Saeb MR. Flame Retardant Polypropylenes: A Review. Polymers (Basel). July 29, 2020; 12(8):1701. doi:10.3390 / polym12081701. PMID:32751298; PMCID:PMC7464193.

[0054] In some embodiments, the high-performance nonwoven web is antimicrobial. Such nonwoven webs can disrupt and / or inhibit the growth of microorganisms (e.g., bacteria, viruses, fungi), and in some cases, can disrupt and / or inhibit the growth of pathogenic microorganisms. In some embodiments, the high-performance nonwoven web contains antimicrobial substances. The antimicrobial substances can include antimicrobial fibers and / or antimicrobial additives. The former can include fibers having antimicrobial additives distributed within and / or throughout the fiber. Such fibers can be manufactured by the methods described elsewhere herein for incorporating charge stabilizing additives into fibers. The antimicrobial nonwoven web can also contain antimicrobial additives located in positions other than within the fibers therein.

[0055] The amount of antimicrobial substance in the high-performance nonwoven fiber web can be selected according to the expectation. In some embodiments, the amount is greater than or equal to 0.01 wt%, greater than or equal to 0.015 wt%, greater than or equal to 0.02 wt%, greater than or equal to 0.025 wt%, greater than or equal to 0.03 wt%, greater than or equal to 0.04 wt%, greater than or equal to 0.05 wt%, greater than or equal to 0.075 wt%, greater than or equal to 0.1 wt%, greater than or equal to 0.2 wt%, greater than or equal to 0.5 wt%, greater than or equal to 0.75 wt%, greater than or equal to 1 wt%, greater than or equal to 1.5 wt%, greater than or equal to 2 wt%, greater than or equal to 2.5 wt%, greater than or equal to 3 wt%, greater than or equal to 4 wt%, greater than or equal to 5 wt%, greater than or equal to 6 wt%, greater than or equal to 8 wt%, greater than or equal to 10 wt%, greater than or equal to 12.5 wt%, greater than or equal to 15 wt%, or greater than or equal to 17.5 wt% of the high-performance nonwoven fiber web. The amount can be less than or equal to 20 wt%, less than or equal to 17.5 wt%, less than or equal to 15 wt%, less than or equal to 12.5 wt%, less than or equal to 10 wt%, less than or equal to 8 wt%, less than or equal to 6 wt%, less than or equal to 5 wt%, less than or equal to 4 wt%, less than or equal to 3 wt%, less than or equal to 2.5 wt%, less than or equal to 2 wt%, less than or equal to 1.5 wt%, less than or equal to 1 wt%, less than or equal to 0.75 wt%, less than or equal to 0.5 wt%, less than or equal to 0.2 wt%, less than or equal to 0.1 wt%, less than or equal to 0.075 wt%, less than or equal to 0.05 wt%, less than or equal to 0.04 wt%, less than or equal to 0.03 wt%, less than or equal to 0.025 wt%, less than or equal to 0.02 wt%, or less than or equal to 0.015 wt% of the high-performance nonwoven fiber web. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.01 wt% and less than or equal to 20 wt%, greater than or equal to 0.02 wt% and less than or equal to 10 wt%, or greater than or equal to 0.03 wt% and less than or equal to 3 wt%). Other ranges are also possible.

[0056] When the high-performance nonwoven fiber web contains two or more types of antimicrobial substances, each type of antimicrobial substance can independently be present in one or more of the above ranges, and / or all of the antimicrobial substances in the high-performance nonwoven fiber web can be present in one or more of the above ranges. When the filter medium includes two or more high-performance nonwoven fiber webs, the foregoing can apply independently for each such nonwoven fiber web.

[0057] Antimicrobial additives can include bacteriostatic, fungistatic, and / or virustatic additives. Non-limiting examples of suitable antimicrobial additives include silver and its derivatives (e.g., silver particles, silver ions), zinc and its derivatives (e.g., zinc pyrithione), copper, metal oxides (e.g., silver oxide, iron oxide, titanium oxide, copper oxide, zinc oxide), triclosan, quaternary ammonium compounds, chitosan, poly(hexamethylene biguanide), terpinoids, flavonoids, quinones, lectins, n-haloamines, and citric acid.

[0058] Antimicrobial fibers can include bacteriostatic, fungistatic, and / or virustatic polymers. Non-limiting examples of suitable polymers for antimicrobial fibers include polyethylene, polypropylene, polystyrene, ethylene / vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyamide (e.g., nylon), polyacrylonitrile, acrylics, and polyethylene terephthalate.

[0059] In some embodiments, a nonwoven fibrous web having high performance contains antiallergenic substances. Antiallergenic substances can include antiallergenic fibers and / or antiallergenic additives. The former can include fibers having antiallergenic additives distributed within and / or throughout the fibers. Such fibers can be manufactured by the methods described elsewhere herein for incorporating charge stabilizing additives into fibers. The nonwoven fibrous web can also contain antiallergenic additives located at positions other than within the fibers therein. For example, the nonwoven fibrous web can contain such antiallergenic additives that are separate from the fibers and are introduced into the nonwoven fibrous web by treating the nonwoven fibrous web with a solution containing the antiallergenic additive (e.g., an aqueous solution, an acid solution, a base solution).

[0060] The amount of the anti - allergen substance in the non - woven fiber web with high performance can be selected according to the expectation. In some embodiments, the anti - allergen substance accounts for greater than or equal to 0.001 wt%, greater than or equal to 0.002 wt%, greater than or equal to 0.005 wt%, greater than or equal to 0.0075 wt%, greater than or equal to 0.01 wt%, greater than or equal to 0.02 wt%, greater than or equal to 0.05 wt%, greater than or equal to 0.075 wt%, greater than or equal to 0.1 wt%, greater than or equal to 0.2 wt%, greater than or equal to 0.5 wt%, greater than or equal to 0.75 wt%, greater than or equal to 1 wt%, greater than or equal to 1.25 wt%, greater than or equal to 1.5 wt%, greater than or equal to 1.75 wt%, greater than or equal to 2 wt%, greater than or equal to 3 wt%, greater than or equal to 4 wt%, greater than or equal to 5 wt%, greater than or equal to 6 wt%, or greater than or equal to 8 wt% of the non - woven fiber web with relatively high performance. In some embodiments, the anti - allergen substance accounts for less than or equal to 10 wt%, less than or equal to 8 wt%, less than or equal to 6 wt%, less than or equal to 5 wt%, less than or equal to 4 wt%, less than or equal to 3 wt%, less than or equal to 2 wt%, less than or equal to 1.75 wt%, less than or equal to 1.5 wt%, less than or equal to 1.25 wt%, less than or equal to 1 wt%, less than or equal to 0.75 wt%, less than or equal to 0.5 wt%, less than or equal to 0.2 wt%, less than or equal to 0.1 wt%, less than or equal to 0.075 wt%, less than or equal to 0.05 wt%, less than or equal to 0.02 wt%, less than or equal to 0.01 wt%, less than or equal to 0.0075 wt%, less than or equal to 0.005 wt%, or less than or equal to 0.002 wt% of the non - woven fiber web with relatively high performance. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.001 wt% and less than or equal to 10 wt%, greater than or equal to 0.01 wt% and less than or equal to 5 wt%, or greater than or equal to 0.1 wt% and less than or equal to 2 wt%). Other ranges are also possible.

[0061] When the non - woven fiber web with high performance contains two or more types of anti - allergen substances, each type of anti - allergen substance can independently be present in one or more of the above ranges, and / or all of the anti - allergen substances in the non - woven fiber web with high performance can be present in one or more of the above ranges. When the filter medium includes two or more non - woven fiber webs with high performance, the foregoing can apply independently to each such non - woven fiber web.

[0062] The anti-allergen additive can include silver and / or one or more drugs. Non-limiting examples of suitable drugs include antihistamines (e.g., diphenhydramine, chlorpheniramine, cetirizine, levocetirizine, fexofenadine, loratadine, doxylamine), ketotifen, naphazoline, fluticasone, budesonide, triamcinolone acetonide, hydrocortisone, desloratadine, azelastine, acrivastine, betotastine, olopatadine, epinephrine, pseudoephedrine, and oxymetazoline.

[0063] The fibers in the nonwoven fiber web having high performance can have various suitable average fiber diameters. In some embodiments, the average fiber diameter of the fibers in the nonwoven fiber web is greater than or equal to 0.5 microns, greater than or equal to 0.75 microns, greater than or equal to 1 micron, greater than or equal to 1.25 microns, greater than or equal to 1.5 microns, greater than or equal to 1.75 microns, greater than or equal to 2 microns, greater than or equal to 2.5 microns, greater than or equal to 3 microns, greater than or equal to 3.5 microns, greater than or equal to 4 microns, greater than or equal to 4.5 microns, greater than or equal to 5 microns, greater than or equal to 6 microns, greater than or equal to 7 microns, greater than or equal to 8 microns, greater than or equal to 9 microns, greater than or equal to 10 microns, greater than or equal to 11 microns, greater than or equal to 12 microns, greater than or equal to 13 microns, or greater than or equal to 14 microns. In some embodiments, the average fiber diameter of the fibers in the nonwoven fiber web is less than or equal to 15 microns, less than or equal to 14 microns, less than or equal to 13 microns, less than or equal to 12 microns, less than or equal to 11 microns, less than or equal to 10 microns, less than or equal to 9 microns, less than or equal to 8 microns, less than or equal to 7 microns, less than or equal to 6 microns, less than or equal to 5 microns, less than or equal to 4.5 microns, less than or equal to 4 microns, less than or equal to 3.5 microns, less than or equal to 3 microns, less than or equal to 2.5 microns, less than or equal to 2 microns, less than or equal to 1.75 microns, less than or equal to 1.5 microns, less than or equal to 1.25 microns, less than or equal to 1 micron, or less than or equal to 0.75 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.5 microns and less than or equal to 15 microns, greater than or equal to 0.5 microns and less than or equal to 5 microns, greater than or equal to 1 micron and less than or equal to 4.5 microns, greater than or equal to 2 microns and less than or equal to 4 microns, greater than or equal to 3 microns and less than or equal to 15 microns, greater than or equal to 3 microns and less than or equal to 12 microns, or greater than or equal to 3 microns and less than or equal to 10 microns). Other ranges are also possible.

[0064] When a high-performance nonwoven fibrous web contains two or more types of fibers, each type of fiber can independently have an average fiber diameter within one or more of the above ranges, and / or all of the fibers in the high-performance nonwoven fibrous web can together have an average fiber diameter within one or more of the above ranges. When the filter medium includes two or more high-performance nonwoven fibrous webs, the foregoing can apply independently to each such nonwoven fibrous web.

[0065] In some embodiments, the filter medium includes two or more high-performance nonwoven fibrous webs having different average fiber diameters. As an example, the filter medium can include a high-performance nonwoven fibrous web having a relatively large average fiber diameter (e.g., greater than or equal to 3 microns) and a high-performance nonwoven fibrous web having a relatively small average fiber diameter (e.g., less than or equal to 5 microns, less than or equal to 4.5 microns, or less than or equal to 4 microns).

[0066] The high-performance nonwoven fibrous web can have various suitable densifications. In some embodiments, the high-performance nonwoven fibrous web has a relatively low densification. Without wishing to be bound by any particular theory, it is believed that a low densification can beneficially make the nonwoven fibrous web more porous, which can reduce the pressure drop and also allow contaminants to be collected throughout the thickness of the nonwoven fibrous web. This can desirably increase γ and / or the ratio of dust holding capacity to basis weight. In some embodiments, the densification of the high-performance nonwoven fibrous web is less than or equal to 15%, less than or equal to 13%, less than or equal to 11%, less than or equal to 10%, less than or equal to 9%, less than or equal to 8%, less than or equal to 7%, less than or equal to 6%, less than or equal to 5%, less than or equal to 4%, less than or equal to 3%, less than or equal to 2.75%, less than or equal to 2.5%, less than or equal to 2.25%, less than or equal to 2%, less than or equal to 1.75%, less than or equal to 1.5%, or less than or equal to 1.25%. In some embodiments, the densification of the high-performance nonwoven fibrous web is greater than or equal to 1%, greater than or equal to 1.25%, greater than or equal to 1.5%, greater than or equal to 1.75%, greater than or equal to 2%, greater than or equal to 2.25%, greater than or equal to 2.5%, greater than or equal to 2.75%, greater than or equal to 3%, greater than or equal to 4%, greater than or equal to 5%, greater than or equal to 6%, greater than or equal to 7%, greater than or equal to 8%, greater than or equal to 9%, greater than or equal to 10%, greater than or equal to 11%, or greater than or equal to 13%. Combinations of the above ranges are also possible (e.g., greater than or equal to 1% and less than or equal to 15%, greater than or equal to 2% and less than or equal to 10%, or greater than or equal to 2.5% and less than or equal to 6%). Other ranges are also possible.

[0067] The density of a nonwoven fibrous web having high performance is equal to the percentage of the interior of the nonwoven fibrous web occupied by solid material. A non-limiting way of determining the density of such a nonwoven fibrous web is described in this paragraph, but other methods are possible. The method described in this paragraph involves determining the basis weight and thickness of the nonwoven fibrous web and then applying the following formula: density = [basis weight of the nonwoven fibrous web / (density of the components forming the nonwoven fibrous web × thickness of the nonwoven fibrous web)] × 100%. The density of the components forming the nonwoven fibrous web is equal to the average density of one or more materials of the components forming the nonwoven fibrous web (such as the fibers therein, any other components therein), which is typically specified by the manufacturer of each material. The average density of the materials of the components forming the nonwoven fibrous web can be determined by: (1) determining the total volume of all components in the nonwoven fibrous web; and (2) dividing the total mass of all components in the nonwoven fibrous web by the total volume of all components in the nonwoven fibrous web. If the mass and density of each component in the nonwoven fibrous web are known, the volume of all components in the nonwoven fibrous web can be determined by: (1) for each type of component, dividing the total mass of the component in the nonwoven fibrous web by the density of the component; and (2) summing the volumes of each component. If the mass and density of each component in the nonwoven fibrous web are unknown, the volume of all components in the nonwoven fibrous web can be determined according to Archimedes' principle.

[0068] When the filter medium comprises two or more nonwoven fibrous webs having high performance, each such nonwoven fibrous web can independently have a density within one or more of the above ranges.

[0069] A high-performance nonwoven web can have a variety of suitable thicknesses. In some embodiments, the thickness of the high-performance nonwoven web is greater than or equal to 6 mils, greater than or equal to 10 mils, greater than or equal to 25 mils, greater than or equal to 50 mils, greater than or equal to 75 mils, greater than or equal to 100 mils, greater than or equal to 150 mils, greater than or equal to 200 mils, greater than or equal to 250 mils, greater than or equal to 300 mils, greater than or equal to 350 mils, greater than or equal to 400 mils, or greater than or equal to 450 mils. In some embodiments, the thickness of the high-performance nonwoven web is less than or equal to 500 mils, less than or equal to 450 mils, less than or equal to 400 mils, less than or equal to 350 mils, less than or equal to 300 mils, less than or equal to 250 mils, less than or equal to 200 mils, less than or equal to 150 mils, less than or equal to 100 mils, less than or equal to 75 mils, less than or equal to 50 mils, less than or equal to 25 mils, or less than or equal to 10 mils. Combinations of the above ranges are also possible (e.g., greater than or equal to 6 mils and less than or equal to 500 mils). Other ranges are also possible.

[0070] The thickness of the high-performance nonwoven web can be determined under a pressure of 2.65 psi applied by a 1-foot 2 foot pressure foot in accordance with ASTM D1777 (2019).

[0071] When the filter medium includes two or more high-performance nonwoven webs, each such nonwoven web can independently have a thickness within one or more of the above ranges.

[0072] A high-performance nonwoven web can have a variety of suitable basis weights. In some embodiments, the basis weight of the high-performance nonwoven web is greater than or equal to 2 g / m 2(gsm), greater than or equal to 3 gsm, greater than or equal to 4 gsm, greater than or equal to 5 gsm, greater than or equal to 6 gsm, greater than or equal to 8 gsm, greater than or equal to 10 gsm, greater than or equal to 15 gsm, greater than or equal to 20 gsm, greater than or equal to 30 gsm, greater than or equal to 50 gsm, greater than or equal to 75 gsm, greater than or equal to 100 gsm, greater than or equal to 125 gsm, greater than or equal to 150 gsm, greater than or equal to 175 gsm, greater than or equal to 200 gsm, greater than or equal to 225 gsm, greater than or equal to 250 gsm, greater than or equal to 275 gsm, greater than or equal to 300 gsm, greater than or equal to 350 gsm, greater than or equal to 400 gsm, or greater than or equal to 450 gsm. In some embodiments, the basis weight of the high-performance nonwoven web is less than or equal to 500 gsm, less than or equal to 450 gsm, less than or equal to 400 gsm, less than or equal to 350 gsm, less than or equal to 300 gsm, less than or equal to 275 gsm, less than or equal to 250 gsm, less than or equal to 225 gsm, less than or equal to 200 gsm, less than or equal to 175 gsm, less than or equal to 150 gsm, less than or equal to 125 gsm, less than or equal to 100 gsm, less than or equal to 75 gsm, less than or equal to 50 gsm, less than or equal to 30 gsm, less than or equal to 20 gsm, less than or equal to 15 gsm, less than or equal to 10 gsm, less than or equal to 8 gsm, less than or equal to 6 gsm, less than or equal to 5 gsm, less than or equal to 4 gsm, or less than or equal to 3 gsm. Combinations of the above ranges are also possible (e.g., greater than or equal to 2 gsm and less than or equal to 500 gsm, greater than or equal to 5 gsm and less than or equal to 300 gsm, or greater than or equal to 10 gsm and less than or equal to 200 gsm). Other ranges are also possible.

[0073] The basis weight of the high-performance nonwoven web can be determined in accordance with ASTM D3776-20 (2020).

[0074] When the filter medium includes two or more high-performance nonwoven webs, each such nonwoven web can independently have a basis weight within one or more of the above ranges.

[0075] A high-performance nonwoven fibrous web can have various suitable average flow pore sizes. In some embodiments, the average flow pore size of the high-performance nonwoven fibrous web is greater than or equal to 20 microns, greater than or equal to 25 microns, greater than or equal to 30 microns, greater than or equal to 40 microns, greater than or equal to 50 microns, greater than or equal to 75 microns, greater than or equal to 100 microns, greater than or equal to 125 microns, greater than or equal to 150 microns, or greater than or equal to 175 microns. In some embodiments, the average flow pore size of the high-performance nonwoven fibrous web is less than or equal to 200 microns, less than or equal to 175 microns, less than or equal to 150 microns, less than or equal to 125 microns, less than or equal to 100 microns, less than or equal to 75 microns, less than or equal to 50 microns, less than or equal to 40 microns, less than or equal to 30 microns, or less than or equal to 25 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 20 microns and less than or equal to 200 microns, greater than or equal to 20 microns and less than or equal to 150 microns, or greater than or equal to 20 microns and less than or equal to 100 microns). Other ranges are also possible.

[0076] The average flow pore size of the high-performance nonwoven fibrous web can be determined in accordance with ASTM F316 (2003).

[0077] When the filter medium includes two or more high-performance nonwoven fibrous webs, each such nonwoven fibrous web can independently have an average flow pore size within one or more of the above ranges.

[0078] A high-performance nonwoven fibrous web can have various suitable air permeabilities. In some embodiments, the air permeability of the high-performance nonwoven fibrous web is greater than or equal to 20 ft 3 / min / ft 2 (CFM), greater than or equal to 50 CFM, greater than or equal to 75 CFM, greater than or equal to 100 CFM, greater than or equal to 200 CFM, greater than or equal to 500 CFM, greater than or equal to 750 CFM, or greater than or equal to 1000 CFM. In some embodiments, the air permeability of the high-performance nonwoven fibrous web is less than or equal to 1300 CFM, less than or equal to 1000 CFM, less than or equal to 750 CFM, less than or equal to 500 CFM, less than or equal to 200 CFM, less than or equal to 100 CFM, less than or equal to 75 CFM, or less than or equal to 50 CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 20 CFM and less than or equal to 1300 CFM). Other ranges are also possible.

[0079] The air permeability of the high-performance nonwoven fiber web can be determined at a pressure of 125 Pa according to ASTM D737-04 (2016).

[0080] When the filter medium comprises two or more high-performance nonwoven fiber webs, each such nonwoven fiber web can independently have an air permeability within one or more of the above ranges.

[0081] The high-performance nonwoven fiber web can have a relatively high γ value. γ is defined by the following formula: γ = (-log 10 (Initial penetration rate, % / 100%) / (Initial air resistance, mm H2O)) · 100. The penetration rate (usually expressed as a percentage) is defined as follows: Penetration rate (%) = (C / C0) · 100%, where C is the particle concentration after passing through the high-performance nonwoven fiber web, and C0 is the particle concentration before passing through the high-performance nonwoven fiber web.

[0082] The initial penetration rate can be measured by blowing NaCl particles through the high-performance nonwoven fiber web and measuring the percentage of particles that penetrate through it. This can be achieved by using a TSI 8130 automated filter test unit from TSI, Inc. equipped with a generator for performing NaCl aerosol tests on NaCl particles with a particle size of 0.26 microns. The TSI 8130 automated filter test unit can be used to perform an automated program named "filter test" for 0.26-micron particles at a face velocity of 5.3 cm / sec encoded by the software therein. Briefly, the test involves blowing NaCl particles with an average particle diameter of 0.26 microns at a 100 cm 2 surface area on the upstream surface of the nonwoven fiber web. The upstream and downstream particle concentrations can be measured using a condensation particle counter. During the penetration rate measurement, the 100 cm 2 surface area of the upstream surface of the nonwoven fiber web can be subjected to a continuous flow of NaCl particles at a media face velocity of 5.3 cm / sec until the penetration rate reading determined by the TSI 8130 automated filter test unit is stable.

[0083] While following the same procedure, the initial air resistance of the high-performance nonwoven fiber web can also be measured simultaneously with the initial NaCl penetration rate at 0.26 microns.

[0084] In some embodiments, for a nonwoven fibrous web having high performance, γ is greater than or equal to 200, greater than or equal to 250, greater than or equal to 300, greater than or equal to 350, greater than or equal to 400, greater than or equal to 450, greater than or equal to 500, greater than or equal to 550, greater than or equal to 600, greater than or equal to 650, greater than or equal to 700, greater than or equal to 750, greater than or equal to 800, or greater than or equal to 850. In some embodiments, for a nonwoven fibrous web having high performance, γ is less than or equal to 900, less than or equal to 850, less than or equal to 800, less than or equal to 750, less than or equal to 700, less than or equal to 650, less than or equal to 600, less than or equal to 550, less than or equal to 500, less than or equal to 450, less than or equal to 400, less than or equal to 350, less than or equal to 300, or less than or equal to 250. Combinations of the above ranges are also possible (e.g., greater than or equal to 200 and less than or equal to 900, greater than or equal to 200 and less than or equal to 750, or greater than or equal to 200 and less than or equal to 600). Other ranges are also possible.

[0085] When the filter medium comprises two or more nonwoven fibrous webs having high performance, each such nonwoven fibrous web can independently have a γ within one or more of the above ranges.

[0086] In some embodiments, a nonwoven fibrous web having high performance has a relatively low air resistance after NaCl loading and / or a relatively low increase in air resistance after NaCl loading. The NaCl loading can be carried out by blowing NaCl particles through the nonwoven fibrous web for 30 minutes. This can be achieved by using a TSI-8130 automated filter test unit having the above-described characteristics regarding γ. A 2 wt% NaCl solution in distilled water can be used as the source for NaCl aerosol generation. The loading can be achieved by blowing the aerosol at a face velocity of 14.2 cm / sec for 30 minutes over a 100 cm 2 surface area at the upstream surface of the nonwoven fibrous web. During this process, the air resistance and the penetration rate can be measured every minute. The air resistance after NaCl loading can be the last measured air resistance (i.e., after 30 minutes of NaCl loading).

[0087] The air resistance of the nonwoven fibrous web with high performance after NaCl loading can be greater than or equal to 0.1 mmH2O, greater than or equal to 0.2 mmH2O, greater than or equal to 0.3 mmH2O, greater than or equal to 0.4 mmH2O, greater than or equal to 0.5 mmH2O, greater than or equal to 0.6 mmH2O, greater than or equal to 0.8 mmH2O, greater than or equal to 1 mmH2O, greater than or equal to 2 mmH2O, greater than or equal to 5 mmH2O, greater than or equal to 7.5 mmH2O, greater than or equal to 10 mmH2O, greater than or equal to 12.5 mmH2O, greater than or equal to 15 mmH2O, greater than or equal to 17.5 mmH2O, greater than or equal to 20 mmH2O, greater than or equal to 22 mmH2O, greater than or equal to 23 mmH2O, or greater than or equal to 24 mmH2O. The air resistance of the nonwoven fibrous web with high performance after NaCl loading can be less than or equal to 25 mmH2O, less than or equal to 24 mmH2O, less than or equal to 23 mmH2O, less than or equal to 22 mmH2O, less than or equal to 20 mmH2O, less than or equal to 17.5 mmH2O, less than or equal to 15 mmH2O, less than or equal to 12.5 mmH2O, less than or equal to 10 mmH2O, less than or equal to 7.5 mmH2O, less than or equal to 5 mmH2O, less than or equal to 2 mmH2O, less than or equal to 1 mmH2O, less than or equal to 0.8 mmH2O, less than or equal to 0.6 mmH2O, less than or equal to 0.5 mmH2O, less than or equal to 0.4 mmH2O, less than or equal to 0.3 mmH2O, or less than or equal to 0.2 mmH2O. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 mmH2O and less than or equal to 25 mmH2O, greater than or equal to 0.5 mmH2O and less than or equal to 24 mmH2O, or greater than or equal to 1 mmH2O and less than or equal to 23 mmH2O). Other ranges are also possible.

[0088] When the filter medium comprises two or more nonwoven fibrous webs with high performance, each such nonwoven fibrous web can independently have an air resistance after NaCl loading within one or more of the above ranges.

[0089] In some embodiments, a nonwoven web having high performance has a relatively low ratio of air resistance after NaCl loading to air resistance before NaCl loading (i.e., the ratio of the final air resistance measured during the above NaCl loading process to the first air resistance measured during the process). This ratio can be 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, less than or equal to 10, less than or equal to 9, less than or equal to 8, less than or equal to 7, less than or equal to 6, less than or equal to 5, less than or equal to 4, less than or equal to 3, less than or equal to 2, less than or equal to 1.75, less than or equal to 1.5, less than or equal to 1.4, less than or equal to 1.3, or less than or equal to 1.2. This ratio can be greater than or equal to 1.1, greater than or equal to 1.2, greater than or equal to 1.3, greater than or equal to 1.4, greater than or equal to 1.5, greater than or equal to 1.75, greater than or equal to 2, greater than or equal to 3, greater than or equal to 4, greater than or equal to 5, greater than or equal to 6, greater than or equal to 7, greater than or equal to 8, greater than or equal to 9, greater than or equal to 10, greater than or equal to 11, greater than or equal to 12, greater than or equal to 13, or greater than or equal to 14. Combinations of the above ranges are also possible (e.g., greater than or equal to 1.1 and less than or equal to 15, greater than or equal to 1.2 and less than or equal to 12, or greater than or equal to 1.3 and less than or equal to 10). Other ranges are also possible.

[0090] When the filter medium includes two or more nonwoven webs having high performance, each such nonwoven web can independently have a ratio of air resistance after NaCl loading to air resistance before NaCl loading within one or more of the above ranges.

[0091] Some high-performance nonwoven webs are configured such that during NaCl loading, the captured NaCl particles are relatively evenly distributed throughout the nonwoven web. This can be parameterized by the NaCl density at the downstream surface being relatively high compared to the NaCl density at the upstream surface when measuring the NaCl density at the downstream surface and the NaCl density at the upstream surface after undergoing the NaCl loading process. After undergoing the NaCl loading process, the NaCl density at the downstream surface of the nonwoven web can be greater than or equal to 50%, greater than or equal to 55%, greater than or equal to 60%, greater than or equal to 65%, greater than or equal to 70%, greater than or equal to 75%, greater than or equal to 80%, greater than or equal to 85%, or greater than or equal to 90% of the NaCl density at the upstream surface. After undergoing the NaCl loading process, the NaCl density at the downstream surface of the nonwoven web can be less than or equal to 95%, less than or equal to 90%, less than or equal to 85%, less than or equal to 80%, less than or equal to 75%, less than or equal to 70%, less than or equal to 65%, or less than or equal to 60% of the NaCl density at the upstream surface. Combinations of the above ranges are also possible (e.g., greater than or equal to 50% and less than or equal to 95%). Other ranges are also possible.

[0092] The NaCl density at the upstream surface and the NaCl density at the downstream surface of the high-performance nonwoven web can be determined by various suitable techniques. One such technique involves determining the density of the upstream surface and the downstream surface of the nonwoven web before the NaCl loading process and after the NaCl loading process. The increase in density during NaCl loading may be attributed solely to NaCl. The density at these locations and time points can be determined using a QTRS Tree ring scanner and a data analyzer model QTRS-01X (Quintek Measurement Systems, Knoxville, TN). The QTRS Tree ring scanner can be used to pass an X-ray beam through the upstream surface and the downstream surface of the high-performance nonwoven web. Then, the transmitted intensity observed at each location can be compared with the transmitted intensity of a sample with a known density. Finally, the density at each location can be determined using the Lambert-Beer law.

[0093] When the filter medium includes two or more high-performance nonwoven webs, each such nonwoven web can be independently configured such that the NaCl density at the downstream surface after undergoing the NaCl loading process is within one or more of the above ranges as a percentage of the NaCl density at the upstream surface.

[0094] Some high-performance nonwoven webs have a relatively high dust holding capacity. In some embodiments, the dust holding capacity of the high-performance nonwoven web is greater than or equal to 5 gsm, greater than or equal to 7.5 gsm, greater than or equal to 10 gsm, greater than or equal to 12.5 gsm, greater than or equal to 15 gsm, greater than or equal to 17.5 gsm, greater than or equal to 20 gsm, greater than or equal to 30 gsm, greater than or equal to 40 gsm, greater than or equal to 50 gsm, greater than or equal to 60 gsm, greater than or equal to 80 gsm, greater than or equal to 100 gsm, greater than or equal to 120 gsm, greater than or equal to 150 gsm, or greater than or equal to 180 gsm. In some embodiments, the dust holding capacity of the high-performance nonwoven web is less than or equal to 200 gsm, less than or equal to 180 gsm, less than or equal to 150 gsm, less than or equal to 120 gsm, less than or equal to 100 gsm, less than or equal to 80 gsm, less than or equal to 60 gsm, less than or equal to 50 gsm, less than or equal to 40 gsm, less than or equal to 30 gsm, less than or equal to 20 gsm, less than or equal to 17.5 gsm, less than or equal to 15 gsm, less than or equal to 12.5 gsm, less than or equal to 10 gsm, or less than or equal to 7.5 gsm. Combinations of the above ranges are also possible (e.g., greater than or equal to 5 gsm and less than or equal to 200 gsm, greater than or equal to 10 gsm and less than or equal to 180 gsm, or greater than or equal to 15 gsm and less than or equal to 150 gsm). Other ranges are also possible.

[0095] The dust holding capacity can be determined by blowing ISO 12103-1 A2 fine test dust at the high-performance nonwoven web until the air resistance increases by 50 Pa, and then measuring the mass increase during the process. This process can be accomplished by using a Palas MFP 3000 instrument and applying it to blow A2 test dust at a media face velocity of 20 cm / second at a 100 cm 2 surface area on the upstream surface of the nonwoven web.

[0096] When the filter medium includes two or more high-performance nonwoven webs, each such nonwoven web can independently have a dust holding capacity within one or more of the above ranges.

[0097] Some high-performance nonwoven webs have a relatively high ratio of dust holding capacity to basis weight. In some embodiments, the ratio of dust holding capacity to basis weight of a high-performance nonwoven web is greater than or equal to 0.4 gsm / gsm, greater than or equal to 0.5 gsm / gsm, greater than or equal to 0.6 gsm / gsm, greater than or equal to 0.7 gsm / gsm, greater than or equal to 0.8 gsm / gsm, greater than or equal to 0.9 gsm / gsm, greater than or equal to 1 gsm / gsm, greater than or equal to 1.25 gsm / gsm, greater than or equal to 1.5 gsm / gsm, greater than or equal to 2 gsm / gsm, greater than or equal to 3 gsm / gsm, greater than or equal to 4 gsm / gsm, greater than or equal to 5 gsm / gsm, greater than or equal to 6 gsm / gsm, greater than or equal to 7 gsm / gsm, greater than or equal to 8 gsm / gsm, or greater than or equal to 9 gsm / gsm. In some embodiments, the ratio of dust holding capacity to basis weight of a high-performance nonwoven web is less than or equal to 10 gsm / gsm, less than or equal to 9 gsm / gsm, less than or equal to 8 gsm / gsm, less than or equal to 7 gsm / gsm, less than or equal to 6 gsm / gsm, less than or equal to 5 gsm / gsm, less than or equal to 4 gsm / gsm, less than or equal to 3 gsm / gsm, less than or equal to 2 gsm / gsm, less than or equal to 1.5 gsm / gsm, less than or equal to 1.25 gsm / gsm, less than or equal to 1 gsm / gsm, less than or equal to 0.9 gsm / gsm, less than or equal to 0.8 gsm / gsm, less than or equal to 0.7 gsm / gsm, or less than or equal to 0.6 gsm / gsm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.4 gsm / gsm and less than or equal to 10 gsm / gsm, greater than or equal to 0.6 gsm / gsm and less than or equal to 8 gsm / gsm, or greater than or equal to 0.8 gsm / gsm and less than or equal to 5 gsm / gsm). Other ranges are also possible.

[0098] When the filter medium comprises two or more high-performance nonwoven webs, each such nonwoven web can independently have a ratio of dust holding capacity to basis weight within one or more of the above ranges.

[0099] Some high-performance nonwoven webs have a relatively high ratio of dust holding capacity to initial air resistance. In some embodiments, the ratio of dust holding capacity to initial air resistance of the high-performance nonwoven fiber web is greater than or equal to 175 gsm / mm H2O, greater than or equal to 200 gsm / mm H2O, greater than or equal to 300 gsm / mm H2O, greater than or equal to 500 gsm / mm H2O, greater than or equal to 750 gsm / mm H2O, greater than or equal to 1000 gsm / mm H2O, greater than or equal to 1250 gsm / mm H2O, greater than or equal to 1500 gsm / mm H2O, or greater than or equal to 1750 gsm / mm H2O. In some embodiments, the ratio of dust holding capacity to initial air resistance of the high-performance nonwoven fiber web is less than or equal to 2000 gsm / mm H2O, less than or equal to 1750 gsm / mm H2O, less than or equal to 1500 gsm / mm H2O, less than or equal to 1250 gsm / mm H2O, less than or equal to 1000 gsm / mm H2O, less than or equal to 750 gsm / mm H2O, less than or equal to 500 gsm / mm H2O, less than or equal to 300 gsm / mm H2O, or less than or equal to 200 gsm / mm H2O. Combinations of the above ranges are also possible (e.g., greater than or equal to 175 gsm / mm H2O and less than or equal to 2000 gsm / mm H2O). Other ranges are also possible.

[0100] When the filter medium includes two or more high-performance nonwoven fiber webs, each such nonwoven fiber web can independently have a ratio of dust holding capacity to initial air resistance within one or more of the above ranges.

[0101] In some embodiments, the high-performance nonwoven web is tested by the MERV 13A Appendix J described in ANSI / ASHRAE Standard 52.2-2017.

[0102] In some embodiments, the high-performance nonwoven fiber web is charged. For example, it can be a charged meltblown layer. The charged nonwoven fiber web can be formed via any of the various suitable methods and / or steps described herein such as electrostatic charging, triboelectric charging, and / or hydroelectret charging.

[0103] In some such embodiments, when the nonwoven web undergoes a charging process, one or more charge additives (e.g., one or more of those described elsewhere herein) may be present in the high-performance nonwoven web. The presence of the charge additive(s) during the charging process can be beneficial. As an example, the presence of such a charge additive during a hydroelectret charging process can advantageously promote the hydroentanglement of the fibers and / or enable a more efficient hydroelectret charging process. In some embodiments, the hydroentanglement of the fibers can advantageously impart a relatively low air resistance to the nonwoven web.

[0104] In some embodiments, the high-performance nonwoven web is charged by a hydroelectret charging process. The hydroelectret charging process can include impinging a jet and / or stream of water droplets onto an initially uncharged nonwoven web to electrostatically charge it. At the end of the hydroelectret charging process, the nonwoven web can have an electret charge. The jet and / or stream of water droplets can impinge on the nonwoven web at various suitable pressures (e.g., pressures from 10 psi to 1000 psi) and can be provided by various suitable sources such as an injector.

[0105] In some embodiments, the following pressures can be used during the hydroelectret charging process: greater than or equal to 10 psi, greater than or equal to 50 psi, greater than or equal to 100 psi, greater than or equal to 200 psi, greater than or equal to 300 psi, greater than or equal to 400 psi, greater than or equal to 500 psi, greater than or equal to 600 psi, greater than or equal to 700 psi, greater than or equal to 800 psi, or greater than or equal to 900 psi. In some embodiments, the following pressures can be used during the hydroelectret charging process: less than or equal to 1000 psi, less than or equal to 900 psi, less than or equal to 800 psi, less than or equal to 700 psi, less than or equal to 600 psi, less than or equal to 500 psi, less than or equal to 400 psi, less than or equal to 300 psi, less than or equal to 200 psi, less than or equal to 100 psi, or less than or equal to 50 psi. Combinations of the above ranges are also possible (e.g., greater than or equal to 10 psi and less than or equal to 1000 psi, greater than or equal to 100 psi and less than or equal to 500 psi, or greater than or equal to 200 psi and less than or equal to 400 psi). Other ranges are also possible.

[0106] When the filter medium includes two or more high-performance nonwoven webs, during the hydroelectret charging process, each such nonwoven web can independently be subjected to a pressure within one or more of the above ranges.

[0107] In some embodiments, a high-performance nonwoven web is water electrocharged using a device that can be used for hydroentangling of fibers, which operates at a lower pressure than is typically used for the hydroentangling process. The water impinging on the nonwoven web can be relatively pure; for example, it can be distilled water and / or deionized water. After electrostatic charging in this manner, the nonwoven web can be dried, for example, with an air dryer.

[0108] In some embodiments, a high-performance nonwoven web is water electrocharged while being transported laterally. The nonwoven web can be transported on a porous belt such as a screen or a mesh-type conveyor belt. While it is being transported on the porous belt, it can be exposed to jets and / or sprays of water pressurized by a pump. The water jets and / or sprays can impinge on and / or penetrate the nonwoven web. In some embodiments, a vacuum is provided below the porous conveyor belt, which can assist in the passage of water through the nonwoven web and / or reduce the amount of time and energy required to dry the nonwoven web at the end of the water electrocharging process.

[0109] In some embodiments, the hydroelectret charging device can include a plurality of nozzles configured to jet streams of pressurized water at the nonwoven web described herein. The nozzles can be present in the device at any suitable number density and / or have any suitable diameter. In some embodiments, the nozzles can be present in the hydroelectret charging device at a nozzle number density of: greater than or equal to 10 nozzles per inch, greater than or equal to 15 nozzles per inch, greater than or equal to 20 nozzles per inch, greater than or equal to 25 nozzles per inch, greater than or equal to 30 nozzles per inch, greater than or equal to 35 nozzles per inch, greater than or equal to 40 nozzles per inch, greater than or equal to 45 nozzles per inch, greater than or equal to 50 nozzles per inch, greater than or equal to 55 nozzles per inch, greater than or equal to 60 nozzles per inch, greater than or equal to 70 nozzles per inch, greater than or equal to 80 nozzles per inch, greater than or equal to 90 nozzles per inch, greater than or equal to 100 nozzles per inch, greater than or equal to 110 nozzles per inch, greater than or equal to 120 nozzles per inch, greater than or equal to 130 nozzles per inch, greater than or equal to 140 nozzles per inch, greater than or equal to 150 nozzles per inch, greater than or equal to 160 nozzles per inch, greater than or equal to 170 nozzles per inch, greater than or equal to 180 nozzles per inch, or greater than or equal to 190 nozzles per inch. In some embodiments, the nozzles can be present in the hydroelectret charging device at a nozzle number density of: less than or equal to 200 nozzles per inch, less than or equal to 190 nozzles per inch, less than or equal to 180 nozzles per inch, less than or equal to 170 nozzles per inch, less than or equal to 160 nozzles per inch, less than or equal to 150 nozzles per inch, less than or equal to 140 nozzles per inch, less than or equal to 130 nozzles per inch, less than or equal to 120 nozzles per inch, less than or equal to 110 nozzles per inch, less than or equal to 100 nozzles per inch, less than or equal to 90 nozzles per inch, less than or equal to 80 nozzles per inch, less than or equal to 70 nozzles per inch, less than or equal to 60 nozzles per inch, less than or equal to 55 nozzles per inch, less than or equal to 50 nozzles per inch, less than or equal to 45 nozzles per inch, less than or equal to 40 nozzles per inch, less than or equal to 35 nozzles per inch, less than or equal to 30 nozzles per inch, less than or equal to 25 nozzles per inch, less than or equal to 20 nozzles per inch, or less than or equal to 15 nozzles per inch. Combinations of the above ranges are also possible (e.g., greater than or equal to 10 nozzles per inch and less than or equal to 200 nozzles per inch). Other ranges are also possible.

[0110] In some embodiments, the nozzle diameter of the nozzle can be greater than or equal to 50 microns, greater than or equal to 60 microns, greater than or equal to 70 microns, greater than or equal to 80 microns, greater than or equal to 90 microns, greater than or equal to 100 microns, greater than or equal to 120 microns, greater than or equal to 140 microns, greater than or equal to 160 microns, greater than or equal to 180 microns, greater than or equal to 200 microns, greater than or equal to 220 microns, greater than or equal to 240 microns, greater than or equal to 260 microns, or greater than or equal to 280 microns. In some embodiments, the nozzle diameter of the nozzle can be less than or equal to 300 microns, less than or equal to 280 microns, less than or equal to 260 microns, less than or equal to 240 microns, less than or equal to 220 microns, less than or equal to 200 microns, less than or equal to 180 microns, less than or equal to 160 microns, less than or equal to 140 microns, less than or equal to 120 microns, less than or equal to 100 microns, less than or equal to 90 microns, less than or equal to 80 microns, less than or equal to 70 microns, or less than or equal to 60 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 50 microns and less than or equal to 300 microns). Other ranges are also possible.

[0111] In some embodiments, each of the plurality of nozzles in the water electret charging device can independently have a diameter within one or more of the above ranges. In some embodiments, the diameters of two or more of the plurality of nozzles can be the same or different.

[0112] In some embodiments, a high-performance nonwoven web is charged via a triboelectric charging process. The triboelectric charging process can include bringing two surfaces into contact and then separating them, at least one of which is the surface on which the fibers to be charged are located. This process can cause charge transfer between the two surfaces and the accumulation of associated charges on the two surfaces. The surfaces can be selected such that they have sufficiently different positions in the triboelectric series to produce a desired level of charge transfer therebetween upon contact.

[0113] A high-performance nonwoven web can also be charged via an electrostatic charging process, such as via a corona discharge process.

[0114] As described elsewhere herein, in some embodiments, the filter medium includes an adsorption layer. Such a layer can also contain an adsorbent material, which can be particulate. The adsorption layer can be capable of and / or configured to remove contaminants from the fluid. Adsorption can include physical adsorption (e.g., via weak interactions such as van der Waals forces and / or hydrogen bonds) and / or can include chemical adsorption (e.g., via stronger interactions such as covalent bonds and / or ionic bonds). The filter medium can also include two or more adsorption layers. Such adsorption layers can be the same or can differ in one or more respects.

[0115] The adsorbent material can be present in the adsorption layer in various suitable amounts. In some embodiments, the adsorbent material is greater than or equal to 1 wt%, greater than or equal to 2 wt%, greater than or equal to 5 wt%, greater than or equal to 7.5 wt%, greater than or equal to 10 wt%, greater than or equal to 12.5 wt%, greater than or equal to 15 wt%, greater than or equal to 17.5 wt%, greater than or equal to 20 wt%, greater than or equal to 25 wt%, greater than or equal to 30 wt%, greater than or equal to 40 wt%, greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 70 wt%, greater than or equal to 80 wt%, greater than or equal to 85 wt%, greater than or equal to 90 wt%, greater than or equal to 92.5 wt%, greater than or equal to 95 wt%, or greater than or equal to 97.5 wt% of the adsorption layer. In some embodiments, the adsorbent material is less than or equal to 99 wt%, less than or equal to 97.5 wt%, less than or equal to 95 wt%, less than or equal to 92.5 wt%, less than or equal to 90 wt%, less than or equal to 85 wt%, less than or equal to 80 wt%, less than or equal to 70 wt%, less than or equal to 60 wt%, less than or equal to 50 wt%, less than or equal to 40 wt%, less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, less than or equal to 17.5 wt%, less than or equal to 15 wt%, less than or equal to 12.5 wt%, less than or equal to 10 wt%, less than or equal to 7.5 wt%, less than or equal to 5 wt%, or less than or equal to 2 wt% of the adsorption layer. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 wt% and less than or equal to 99 wt%, greater than or equal to 15 wt% and less than or equal to 95 wt%, or greater than or equal to 30 wt% and less than or equal to 90 wt%). Other ranges are also possible.

[0116] When the adsorption layer contains two or more types of adsorbent materials, each type of adsorbent material can independently be present in one or more of the above ranges, and / or all of the adsorbent materials in the adsorption layer can together be present in one or more of the above ranges. When the filter medium includes two or more adsorption layers, the foregoing can apply independently to each such layer.

[0117] The adsorption layer described herein may contain various types of adsorbing substances. An example of a suitable type of adsorbing substance is activated carbon. Without wishing to be bound by any particular theory, it is believed that activated carbon can physically adsorb one or more pollutants. Activated carbon can be derived from coconut shells or from wood. In some embodiments, the activated carbon is also surface-treated. Non-limiting examples of surface treatment include treatment that converts activated carbon to chemically activated carbon, treatment with calcium carbonate, treatment with potassium iodide, treatment with tris(hydroxymethyl)aminomethane, treatment with phosphoric acid, treatment with metals (such as transition metals, such as copper, silver, zinc, and / or molybdenum), and treatment with triethylenediamine.

[0118] In some embodiments, the surface-treated activated carbon includes impregnating the activated carbon with a substance for surface treatment thereof to cause a chemical reaction at the surface of the activated carbon. During this process, the substance for surface treatment of the activated carbon is present in an amount of 0.5% to 30% (e.g., 2% to 10% of the weight of the activated carbon) of the weight of the activated carbon. After surface treatment, the activated carbon may contain nitrogen-containing functional groups (such as amine groups), polar functional groups, and / or sulfur-containing functional groups (such as sulfur bonded to the activated carbon matrix). Surface treatment can also increase the surface area of the activated carbon.

[0119] Chemically activated carbon can be formed by treating activated carbon with metal chlorides (such as ZnCl2, FeCl3, MgCl2) in the presence of heat. Such treatment can cause the activated carbon to exhibit an increase in surface area (e.g., increased to 500 m 2 / g to 1000 m 2 / g) and / or an increase in porosity, and / or can cause a change in the pore size distribution in the activated carbon. Such treatment can also cause phenolic functional groups, lactone acid functional groups, and / or carboxylic acid functional groups to form on the activated carbon.

[0120] Other suitable types of adsorbing substances include ion exchange resins (such as cation exchange resins and anion exchange resins), polymers, activated alumina, alloys (such as copper-zinc alloys), molecular sieves, metal oxides (such as copper oxide, titanium dioxide), zeolites, salts (such as metal chloride salts, metal bicarbonates including sodium bicarbonate, sulfates), and MOF.

[0121] Non-limiting examples of suitable cation exchange resins include substances containing negatively charged functional groups and / or acidic functional groups (such as sulfuric acid functional groups, sulfonic acid functional groups, and / or acrylic acid functional groups). For example, some cation exchange resins may include poly(styrenesulfonic acid) and / or poly(acrylic acid).

[0122] Non-limiting examples of suitable anion exchange resins include materials containing positively charged functional groups and / or basic functional groups such as amine functional groups (e.g., primary amine functional groups, secondary amine functional groups, tertiary amine functional groups, quaternary amine functional groups). For example, some anion exchange resins may include poly(ethyleneimine), poly(diallyldimethylammonium chloride), and / or poly(4-vinylpyridine ).

[0123] Suitable superabsorbent polymers may be capable of absorbing one or more liquids (e.g., water) in an amount exceeding their weight. Non-limiting examples of suitable superabsorbent polymers include poly(acrylates), poly(acrylamides), carboxymethylcellulose, copolymers thereof, and crosslinked networks formed therefrom.

[0124] In some embodiments, the activated alumina suitable for inclusion in the filter media described herein is surface-treated with permanganate (e.g., sodium permanganate, potassium permanganate, both). The permanganate may be at least 12 wt%, at least 15 wt%, or at least 17.5 wt% of the resulting material. In some embodiments, the permanganate is at most 20 wt%, at most 17.5 wt%, or at most 15 wt% of the resulting material. Combinations of the above ranges are also possible (e.g., at least 12 wt% and at most 20 wt%). Other ranges are also possible.

[0125] Non-limiting examples of substances that the adsorbent material may be capable of and / or configured to remove (e.g., types of contaminants) include volatile organic compounds (e.g., toluene, n-butane, SO2, NO x ), benzene, aldehydes (e.g., acetaldehyde, formaldehyde), acidic gases (e.g., H2S, HCl, HF, HCN), basic gases (e.g., ammonia, amines such as trimethylamine and / or triethylamine), H2, CO, N2, sulfur, hydrocarbons, alcohols, O3, water, and gaseous chemical weapons (e.g., nerve agents, mustard gas). Such substances may be gaseous or may be liquid. Some of these contaminants may have unpleasant odors and some may be toxic. Contaminants may originate from various sources (e.g., microorganisms, sewage, swamps, farm animals, power generation, fuel processing, plastic manufacturing, steel blast furnaces, chemical and / or semiconductor industries, automotive combustion, food processing, office buildings, tobacco smoke).

[0126] Table 1 below shows various adsorbing substances and example substances to which they may be particularly suitable for adsorption. It should be understood that Table 1 is non-limiting, and the adsorbing substances listed in Table 1 may be configured to be used for and / or capable of adsorbing other types of substances other than those listed in Table 1, and the substances listed in Table 1 may be configured to be adsorbed by other types of adsorbing substances other than those listed in Table 1 and / or capable of being adsorbed by other types of adsorbing substances other than those listed in Table 1.

[0127] Table 1.

[0128]

[0129] It should be understood that some, all of the adsorbing substances listed in Table 1 and described elsewhere herein may be present in the adsorption layer described herein or any of the adsorbing substances listed in Table 1 and described elsewhere herein may not be present in the adsorption layer described herein, and the adsorption layer described herein may be suitable for adsorbing some, all of the substances listed in Table 1 and described elsewhere herein or the adsorption layer described herein may not be suitable for adsorbing the substances listed in Table 1 and described elsewhere herein. In some embodiments, the adsorption layer comprises one type of adsorbing substance, two types of adsorbing substances, three types of adsorbing substances, four types of adsorbing substances, or even more types of adsorbing substances.

[0130] The adsorbent material may have a relatively high weight per unit area. In some embodiments, the weight per unit area of the adsorbent material is greater than or equal to 70 gsm, greater than or equal to 80 gsm, greater than or equal to 90 gsm, greater than or equal to 100 gsm, greater than or equal to 125 gsm, greater than or equal to 150 gsm, greater than or equal to 175 gsm, greater than or equal to 200 gsm, greater than or equal to 250 gsm, greater than or equal to 300 gsm, greater than or equal to 400 gsm, greater than or equal to 500 gsm, greater than or equal to 750 gsm, greater than or equal to 1000 gsm, greater than or equal to 1250 gsm, greater than or equal to 1500 gsm, or greater than or equal to 1750 gsm. In some embodiments, the weight per unit area of the adsorbent material is less than or equal to 2000 gsm, less than or equal to 1750 gsm, less than or equal to 1500 gsm, less than or equal to 1250 gsm, less than or equal to 1000 gsm, less than or equal to 750 gsm, less than or equal to 500 gsm, less than or equal to 400 gsm, less than or equal to 300 gsm, less than or equal to 250 gsm, less than or equal to 200 gsm, less than or equal to 175 gsm, less than or equal to 150 gsm, less than or equal to 125 gsm, less than or equal to 100 gsm, less than or equal to 90 gsm, or less than or equal to 80 gsm. Combinations of the above ranges are also possible (e.g., greater than or equal to 70 gsm and less than or equal to 2000 gsm, greater than or equal to 90 gsm and less than or equal to 1000 gsm, or greater than or equal to 90 gsm and less than or equal to 250 gsm). Other ranges are also possible.

[0131] The weight per unit area of the adsorbent material can be determined in accordance with ISO 536:2012.

[0132] When the adsorption layer comprises two or more types of adsorbent materials, each type of adsorbent material can independently have a weight per unit area within one or more of the above ranges, and / or all of the adsorbent materials in the adsorption layer can together have a weight per unit area within one or more of the above ranges. When the filter medium includes two or more adsorption layers, the foregoing can apply independently for each such layer.

[0133] The adsorbent material can take the form of particles that can have various suitable average diameters. In some embodiments, the average diameter of the adsorption particles is greater than or equal to 250 microns, greater than or equal to 300 microns, greater than or equal to 350 microns, greater than or equal to 400 microns, greater than or equal to 450 microns, greater than or equal to 500 microns, greater than or equal to 550 microns, greater than or equal to 600 microns, greater than or equal to 650 microns, greater than or equal to 700 microns, greater than or equal to 750 microns, greater than or equal to 800 microns, greater than or equal to 850 microns, greater than or equal to 900 microns, greater than or equal to 950 microns, greater than or equal to 1 mm, greater than or equal to 1.05 mm, greater than or equal to 1.1 mm, or greater than or equal to 1.15 mm. In some embodiments, the average diameter of the adsorption particles is less than or equal to 1.2 mm, less than or equal to 1.15 mm, less than or equal to 1.05 mm, less than or equal to 1 mm, less than or equal to 950 microns, less than or equal to 900 microns, less than or equal to 850 microns, less than or equal to 800 microns, less than or equal to 750 microns, less than or equal to 700 microns, less than or equal to 650 microns, less than or equal to 600 microns, less than or equal to 550 microns, less than or equal to 500 microns, less than or equal to 450 microns, less than or equal to 400 microns, less than or equal to 350 microns, or less than or equal to 300 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 250 microns and less than or equal to 1.2 mm, or greater than or equal to 250 microns and less than or equal to 850 microns). Other ranges are also possible.

[0134] The average diameter of the adsorption particles can be determined in accordance with ASTM D2862 (2016).

[0135] When the adsorption layer comprises two or more types of adsorption particles, each type of adsorption particle can independently have an average diameter within one or more of the above ranges, and / or all of the adsorption particles in the adsorption layer can together have an average diameter within one or more of the above ranges. When the filter medium includes two or more adsorption layers, the foregoing can apply independently for each such layer.

[0136] Some filter media can include two adsorption layers containing an adsorption material in particulate form, each adsorption layer containing adsorption particles having an average diameter within one or more of the above ranges and containing adsorption particles having an average diameter different from the average diameter of the adsorption particles in the other layer. For example, in some embodiments, the filter medium includes a first layer containing adsorption particles and a second adsorption layer, and the average diameter of the adsorption particles in the first adsorption layer is greater than or equal to 150%, greater than or equal to 200%, greater than or equal to 250%, greater than or equal to 300%, greater than or equal to 350%, greater than or equal to 400%, or greater than or equal to 450% of the average diameter of the adsorption particles in the second adsorption layer. In some embodiments, the filter medium includes a first layer containing adsorption particles and a second layer, and the average diameter of the adsorption particles in the first adsorption layer is less than or equal to 500%, less than or equal to 450%, less than or equal to 400%, less than or equal to 350%, less than or equal to 300%, less than or equal to 250%, or less than or equal to 200% of the average diameter of the adsorption particles in the second adsorption layer. Combinations of the above ranges are also possible (e.g., greater than or equal to 150% and less than or equal to 500%). Other ranges are also possible.

[0137] The adsorption particles can have various suitable specific surface areas. In some embodiments, the adsorption layer contains adsorption particles having a specific surface area of: greater than or equal to 1 m 2 / g, greater than or equal to 2 m 2 / g, greater than or equal to 5 m 2 / g, greater than or equal to 7.5 m 2 / g, greater than or equal to 10 m 2 / g, greater than or equal to 12.5 m 2 / g, greater than or equal to 15 m 2 / g, greater than or equal to 17.5 m 2 / g, greater than or equal to 20 m 2 / g, greater than or equal to 25 m 2 / g, greater than or equal to 30 m 2 / g, greater than or equal to 40 m 2 / g, greater than or equal to 50 m 2 / g, greater than or equal to 75 m 2 / g, greater than or equal to 100 m 2 / g, greater than or equal to 200 m 2 / g, greater than or equal to 500 m 2 / g, greater than or equal to 750 m 2 / g, greater than or equal to 1000 m 2 / g, greater than or equal to 1500 m 2 / g, greater than or equal to 2000 m 2 / g, greater than or equal to 2500 m 2 / g, greater than or equal to 3000 m 2 / g, greater than or equal to 3500 m 2 / g, greater than or equal to 4000 m 2 / g, greater than or equal to 4500 m 2 / g, or greater than or equal to 5000 m 2 / g. In some embodiments, the adsorption layer comprises adsorption particles having a specific surface area of the following: less than or equal to 5500 m 2 / g, less than or equal to 5000 m 2 / g, less than or equal to 4500 m 2 / g, less than or equal to 4000 m 2 / g, less than or equal to 3500 m 2 / g, less than or equal to 3000 m 2 / g, less than or equal to 2500 m 2 / g, less than or equal to 2000 m 2 / g, less than or equal to 1500 m 2 / g, less than or equal to 1000 m 2 / g, less than or equal to 750 m 2 / g, less than or equal to 500 m 2 / g, less than or equal to 200 m 2 / g, less than or equal to 100 m 2 / g, less than or equal to 75 m 2 / g, less than or equal to 50 m 2 / g, less than or equal to 40 m 2 / g, less than or equal to 30 m 2 / g, less than or equal to 25 m 2 / g, less than or equal to 20 m 2 / g, less than or equal to 17.5 m 2 / g, less than or equal to 15 m 2 / g, less than or equal to 12.5 m 2 / g, less than or equal to 10 m 2 / g, less than or equal to 7.5 m 2 / g, less than or equal to 5 m 2 / g, or less than or equal to 2 m 2 / g. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 m 2 / g and less than or equal to 5500 m 2 / g, greater than or equal to 20 m 2 / g and less than or equal to 3000 m 2 / g, or greater than or equal to 20 m 2 / g and less than or equal to 40 m 2 / g). Other ranges are possible.

[0138] The specific surface area of the adsorbed particles can be measured according to ASTM D5742 (2016).

[0139] When the adsorption layer contains two or more types of adsorbed particles, each type of adsorbed particle can independently have a specific surface area within one or more of the above ranges, and / or all of the adsorbed substances in the adsorption layer can together have a specific surface area within one or more of the above ranges. When the filter medium includes two or more adsorption layers, the foregoing can apply independently to each such layer.

[0140] In some embodiments, the layer containing the adsorbed substance further contains multicomponent fibers. The multicomponent fibers can include bicomponent fibers (i.e., fibers containing two components), and / or can include fibers containing three or more components. The multicomponent fibers can have various suitable structures. For example, the layer containing the adsorbed substance can contain one or more of the following types of bicomponent fibers: core / sheath fibers (e.g., concentric core / sheath fibers, non-concentric core-sheath fibers), segmented pie-shaped fibers, side-by-side fibers, tip-lobed fibers, and "island-in-the-sea" fibers. The core-sheath bicomponent fibers can contain a sheath having a melting temperature lower than that of the core. When heated (e.g., during a bonding step), the sheath can melt before the core, thereby binding the adsorbed substances together while the core remains solid. In such embodiments, the multicomponent fibers can serve as a binder for the layer.

[0141] When present, the multicomponent fibers can be included in the adsorption layer in various suitable amounts. In some embodiments, the multicomponent fibers account for greater than or equal to 6 wt%, greater than or equal to 7 wt%, greater than or equal to 8 wt%, greater than or equal to 10 wt%, greater than or equal to 12.5 wt%, greater than or equal to 15 wt%, or greater than or equal to 17.5 wt% of the adsorption layer. In some embodiments, the multicomponent fibers account for less than or equal to 20 wt%, less than or equal to 17.5 wt%, less than or equal to 15 wt%, less than or equal to 12.5 wt%, less than or equal to 10 wt%, less than or equal to 8 wt%, or less than or equal to 7 wt% of the adsorption layer. Combinations of the above ranges are also possible (e.g., greater than or equal to 6 wt% and less than or equal to 20 wt%). Other ranges are possible.

[0142] When the adsorption layer comprises two or more types of multicomponent fibers, each type of multicomponent fiber may independently be present in one or more of the above ranges, and / or all of the multicomponent fibers in the adsorption layer may together be present in one or more of the above ranges. When the filter medium comprises two or more adsorption layers, the foregoing may apply independently for each such layer.

[0143] Non-limiting examples of suitable materials that may be included in the multicomponent fibers include polyolefins such as polyethylene, polypropylene, and polybutene; polyesters and copolyesters such as poly(ethylene terephthalate), copoly(ethylene terephthalate), poly(butylene terephthalate), and poly(ethylene isophthalate); polyamides and copolyamides such as nylon and aromatic polyamides; and halogenated polymers such as polytetrafluoroethylene. Suitable copoly(ethylene terephthalate) may comprise repeating units formed by polymerization of ethylene terephthalate monomers and also comprise repeating units formed by polymerization of one or more comonomers. Such comonomers may include linear, cyclic, and branched aliphatic dicarboxylic acids having 4 to 12 carbon atoms (e.g., succinic acid, glutaric acid, adipic acid, dodecanedioic acid, and 1,4-cyclohexanedicarboxylic acid); aromatic dicarboxylic acids having 8 to 12 carbon atoms (e.g., isophthalic acid and 2,6-naphthalenedicarboxylic acid); linear, cyclic, and branched aliphatic diols having 3 to 8 carbon atoms (e.g., 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol, 2-methyl-1,3-propanediol, and 1,4-cyclohexanediol); and / or aliphatic and aromatic / aliphatic ether diols having 4 to 10 carbon atoms (e.g., hydroquinone bis(2-hydroxyethyl) ether and poly(ethylene ether) glycol having a molecular weight below 460 g / mol such as diethylene ether glycol).

[0144] Copoly(ethylene terephthalate) can contain repeating units formed by the polymerization of comonomers (e.g., monomers other than ethylene glycol and terephthalic acid) in various suitable amounts. For example, copoly(ethylene terephthalate) can be formed from a mixture of monomers, where the comonomer can account for greater than or equal to 0.5 mol%, greater than or equal to 0.75 mol%, greater than or equal to 1 mol%, greater than or equal to 1.5 mol%, greater than or equal to 2 mol%, greater than or equal to 3 mol%, greater than or equal to 5 mol%, greater than or equal to 7.5 mol%, greater than or equal to 10 mol%, or greater than or equal to 12.5 mol% of the total amount of monomers. Copoly(ethylene terephthalate) can be formed from a mixture of monomers, where the comonomer accounts for less than or equal to 15 mol%, less than or equal to 12.5 mol%, less than or equal to 10 mol%, less than or equal to 7.5 mol%, less than or equal to 5 mol%, less than or equal to 3 mol%, less than or equal to 2 mol%, less than or equal to 1.5 mol%, less than or equal to 1 mol%, or less than or equal to 0.75 mol% of the total amount of monomers. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.5 mol% and less than or equal to 15 mol%). Other ranges are also possible.

[0145] In embodiments where the copoly(ethylene terephthalate) contains two or more types of repeating units formed by the polymerization of comonomers, each type of repeating unit can independently account for mol% within one or more of the above ranges of the total amount of monomers from which the copoly(ethylene terephthalate) is formed, and / or all of the comonomers together can account for mol% within one or more of the above ranges of the total amount of monomers from which the copoly(ethylene terephthalate) is formed.

[0146] Non-limiting examples of suitable pairs of materials that can be included in the bicomponent fibers include polyethylene / poly(ethylene terephthalate), polypropylene / poly(ethylene terephthalate), copoly(ethylene terephthalate) / poly(ethylene terephthalate), poly(butylene terephthalate) / poly(ethylene terephthalate), copolyamide / polyamide, and polyethylene / polypropylene. In the foregoing list, the material with the lower melting temperature is listed first, and the material with the higher melting temperature is listed second. A core-sheath bicomponent fiber containing one of the above pairs can have a sheath containing the first material and a core containing the second material.

[0147] In embodiments where the layer contains two or more types of bicomponent fibers, each type of bicomponent fiber can independently contain one of the above pairs of materials.

[0148] The multicomponent fibers described herein can include components having various suitable melting points. In some embodiments, the multicomponent fibers include components having a melting point of: greater than or equal to 80 °C, greater than or equal to 90 °C, greater than or equal to 100 °C, greater than or equal to 110 °C, greater than or equal to 120 °C, greater than or equal to 130 °C, greater than or equal to 140 °C, greater than or equal to 150 °C, greater than or equal to 160 °C, greater than or equal to 170 °C, greater than or equal to 180 °C, greater than or equal to 190 °C, greater than or equal to 200 °C, greater than or equal to 210 °C, or greater than or equal to 220 °C. In some embodiments, the multicomponent fibers include components having a melting point of: less than or equal to 230 °C, less than or equal to 220 °C, less than or equal to 210 °C, less than or equal to 200 °C, less than or equal to 190 °C, less than or equal to 180 °C, less than or equal to 170 °C, less than or equal to 160 °C, less than or equal to 150 °C, less than or equal to 140 °C, less than or equal to 130 °C, less than or equal to 120 °C, less than or equal to 110 °C, less than or equal to 100 °C, or less than or equal to 90 °C. Combinations of the above ranges are also possible (e.g., greater than or equal to 80 °C and less than or equal to 230 °C, or greater than or equal to 110 °C and less than or equal to 230 °C). Other ranges are also possible. In some embodiments, the multicomponent fibers include components having a melting point less than or equal to 100 °C.

[0149] The melting point of the components of the multicomponent fibers can be determined by performing differential scanning calorimetry. The differential scanning calorimetry measurement can be performed by: heating the multicomponent fibers to 300 °C at 20 °C / minute, cooling the multicomponent fibers to room temperature, and then determining the melting point during reheating to 300 °C at 20 °C / minute.

[0150] When present, the multicomponent fibers can have various suitable average diameters. In some embodiments, the adsorption layer includes multicomponent fibers having an average diameter of: greater than or equal to 10 microns, greater than or equal to 12.5 microns, greater than or equal to 15 microns, greater than or equal to 17.5 microns, greater than or equal to 20 microns, greater than or equal to 22.5 microns, greater than or equal to 25 microns, greater than or equal to 27.5 microns, or greater than or equal to 30 microns. In some embodiments, the adsorption layer includes multicomponent fibers having an average diameter of: less than or equal to 32.5 microns, less than or equal to 30 microns, less than or equal to 27.5 microns, less than or equal to 25 microns, less than or equal to 22.5 microns, less than or equal to 20 microns, less than or equal to 17.5 microns, less than or equal to 15 microns, or less than or equal to 12.5 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 10 microns and less than or equal to 32.5 microns). Other ranges are also possible.

[0151] When the adsorption layer comprises two or more types of multicomponent fibers, each type of multicomponent fiber may independently have an average fiber diameter within one or more of the above ranges, and / or all of the multicomponent fibers in the adsorption layer may together have an average fiber diameter within one or more of the above ranges. When the filter medium includes two or more adsorption layers, the foregoing may apply independently to each such layer.

[0152] When present, the multicomponent fibers may have various suitable deniers. In some embodiments, the adsorption layer comprises multicomponent fibers having a denier of: greater than or equal to 0.9, greater than or equal to 1, greater than or equal to 1.25, greater than or equal to 1.5, greater than or equal to 1.75, greater than or equal to 2, greater than or equal to 2.5, greater than or equal to 3, greater than or equal to 3.5, greater than or equal to 4, greater than or equal to 4.5, greater than or equal to 5, or greater than or equal to 5.5. In some embodiments, the adsorption layer comprises multicomponent fibers having a denier of: less than or equal to 6, less than or equal to 5.5, less than or equal to 5, less than or equal to 4.5, less than or equal to 4, less than or equal to 3.5, less than or equal to 3, less than or equal to 2.5, less than or equal to 2, less than or equal to 1.75, less than or equal to 1.5, less than or equal to 1.25, or less than or equal to 1. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.9 and less than or equal to 6). Other ranges are also possible.

[0153] When the adsorption layer comprises two or more types of multicomponent fibers, each type of multicomponent fiber may independently have a denier within one or more of the above ranges, and / or all of the multicomponent fibers in the adsorption layer may together have a denier within one or more of the above ranges. When the filter medium includes two or more adsorption layers, the foregoing may apply independently to each such layer.

[0154] In some embodiments, the adsorption layer comprises an adhesive. The adhesive may bond the adsorbent materials together. In other words, it may act as a binder for the layer. An example of a suitable adhesive is a polyurethane hot melt adhesive. The adhesive may initially be provided as an uncrosslinked material that crosslinks upon exposure to moisture (e.g., water vapor). The final adsorption layer may comprise the adhesive in a crosslinked form. Prior to crosslinking, the viscosity of the adhesive may be greater than or equal to 3500 Pa·s and less than or equal to 8000 Pa·s. This viscosity may be measured using a Brookfield viscometer with a 27 rotor at 120 °C and for 20 minutes -1Determined at a shear rate of. Additional non-limiting examples of suitable adhesives include acrylics, polyurethanes, polyolefins, polyesters, polyamides, polyureas, and copolymers thereof. Such adhesives can also be hot melt adhesives and / or can be crosslinkable. Such adhesives can also be supplied as a dispersion, and after the dispersion is applied, the solvent evaporates from the dispersion to produce the final solid adhesive.

[0155] When present, the adhesive can be included in the adsorption layer in various suitable amounts. In some embodiments, the adhesive is greater than or equal to 5 wt%, greater than or equal to 6 wt%, greater than or equal to 7 wt%, greater than or equal to 8 wt%, greater than or equal to 10 wt%, greater than or equal to 12.5 wt%, greater than or equal to 15 wt%, greater than or equal to 17.5 wt%, greater than or equal to 20 wt%, greater than or equal to 22.5 wt%, greater than or equal to 25 wt%, greater than or equal to 30 wt%, or greater than or equal to 35 wt% of the adsorption layer. In some embodiments, the adhesive is less than or equal to 40 wt%, less than or equal to 35 wt%, less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 22.5 wt%, less than or equal to 20 wt%, less than or equal to 17.5 wt%, less than or equal to 15 wt%, less than or equal to 12.5 wt%, less than or equal to 10 wt%, less than or equal to 8 wt%, less than or equal to 7 wt%, or less than or equal to 6 wt% of the adsorption layer. Combinations of the above ranges are also possible (e.g., greater than or equal to 5 wt% and less than or equal to 40 wt%, or greater than or equal to 7 wt% and less than or equal to 20 wt%). Other ranges are also possible.

[0156] When the adsorption layer comprises two or more types of adhesives, each type of adhesive can independently be present in one or more of the above ranges, and / or all of the adhesives in the adsorption layer can together be present in one or more of the above ranges. When the filter medium comprises two or more adsorption layers, the foregoing can apply independently for each such layer.

[0157] In some embodiments, the adsorption layer is non-fibrous. In other words, it can be free of fibers and / or contain fibers in a relatively small amount. In such embodiments, the adsorbent material can be bound together and / or retained in the layer by components other than fibers. For example, the adsorbent material can be bound together and / or retained in the layer by an adhesive and / or the molten components of a multi-component fiber. The components that bind the adsorbent material together and / or retain it in the layer can also similarly adhere it to an adjacent layer (e.g., the support layer).

[0158] As used herein, when a layer is referred to as being "on" or "adjacent" to another layer, it can be directly on or adjacent to that layer, or there can also be intermediate layers or materials therebetween. A layer that is directly "on" another layer, "directly adjacent" to another layer, or "in contact" with another layer means that there are no intermediate layers or materials therebetween.

[0159] Figure 3 A non - limiting example of a layer that contains an adsorbent material (in the form of adsorbent particles) and no fibers and is positioned between two other layers is shown. In Figure 3 layer 306 contains a plurality of adsorbent particles 308 and a binder 310. The binder layer can also have a morphology similar to that of Figure 3 but in which the molten components of the multicomponent fibers rather than the Figure 3 binder shown in Figure 3 bind the adsorbent material (e.g., particles) together. In either case, it is apparent that in some embodiments, the material that binds the adsorbent material together is not fibrous. Instead, such material can have other morphologies (e.g., it can include small spheres as shown in Figure 3 or it can have other suitable non - fibrous morphologies).

[0160] When present, the material that binds the adsorbent particles together can have one or more similarities to the Figure 3 binder shown in Figure 3 and / or can be different from the Figure 3 binder shown in Figure 3 in one or more aspects. For example, the material that binds the adsorbent material together can have a relatively uniform morphology throughout the layer (e.g., it can contain particles of relatively uniform size), or can contain different components throughout the layer (e.g., it can contain particles of different sizes). As another example, the material that binds the adsorbent material together can have a relatively uniform density throughout the layer, or can be distributed throughout the layer such that some regions of the layer are more enriched in the material compared to other regions of the layer. As a third example, the relative size of the material that binds the adsorbent material together relative to the adsorbent material can be similar to the relative size of the Figure 3 binder relative to the adsorbent particles shown in Figure 3 or can be different from the relative size of the Figure 3 binder relative to the adsorbent particles shown in

[0161] Similarly, the adsorbent layer can contain adsorbent materials that are similar to the Figure 3 adsorbent particles shown in Figure 3 in one or more aspects and / or adsorbent materials that are different from the Figure 3 adsorbent particles shown in Figure 3 For example, the adsorbent layer can contain particles having a morphology similar to those shown in Figure 3 or can be different from Figure 3Those shown differ in shape or may be non-particulate. As another example, the adsorbent material may have a size and / or shape uniformity similar to that of the Figure 3 adsorbent particles shown, or may be more or less uniform than the Figure 3 adsorbent particles shown. As a third example, the adsorbent material may have a relatively uniform density throughout the layer or may be distributed throughout the layer such that some regions of the layer are more enriched in the adsorbent material than other regions of the layer.

[0162] In some embodiments, the fibers comprise less than or equal to 20 wt%, less than or equal to 17.5 wt%, less than or equal to 15 wt%, less than or equal to 12.5 wt%, less than or equal to 10 wt%, less than or equal to 8 wt%, less than or equal to 6 wt%, less than or equal to 4 wt%, less than or equal to 2 wt%, or less than or equal to 1 wt% of the adsorption layer. In some embodiments, the fibers comprise greater than or equal to 0 wt%, greater than or equal to 1 wt%, greater than or equal to 2 wt%, greater than or equal to 4 wt%, greater than or equal to 6 wt%, greater than or equal to 8 wt%, greater than or equal to 10 wt%, greater than or equal to 12.5 wt%, greater than or equal to 15 wt%, or greater than or equal to 17.5 wt% of the adsorption layer. Combinations of the above ranges are also possible (e.g., less than or equal to 20 wt% and greater than or equal to 0 wt%, or less than or equal to 20 wt% and greater than or equal to 6 wt%). Other ranges are also possible. In some embodiments, the fibers comprise 0 wt% of the adsorption layer (i.e., the adsorption layer is non-fibrous).

[0163] When the adsorption layer comprises two or more types of fibers, each type of fiber may independently be present in one or more of the above ranges, and / or all of the fibers in the adsorption layer may together be present in one or more of the above ranges. When the filter medium comprises two or more adsorption layers, the foregoing may apply independently for each such layer.

[0164] The adsorption layer can have a relatively high adsorption efficiency. In some embodiments, the adsorption efficiency of the adsorption layer is greater than or equal to 0%, greater than or equal to 1%, greater than or equal to 2%, greater than or equal to 5%, greater than or equal to 7.5%, greater than or equal to 10%, greater than or equal to 12.5%, greater than or equal to 15%, greater than or equal to 17.5%, greater than or equal to 20%, greater than or equal to 25%, greater than or equal to 30%, greater than or equal to 35%, greater than or equal to 40%, greater than or equal to 45%, greater than or equal to 50%, greater than or equal to 60%, or greater than or equal to 80%. In some embodiments, the adsorption efficiency of the adsorption layer is less than or equal to 100%, less than or equal to 80%, less than or equal to 60%, less than or equal to 50%, less than or equal to 45%, less than or equal to 40%, less than or equal to 35%, less than or equal to 30%, less than or equal to 25%, less than or equal to 20%, less than or equal to 17.5%, less than or equal to 15%, less than or equal to 12.5%, less than or equal to 10%, less than or equal to 7.5%, less than or equal to 5%, less than or equal to 2%, or less than or equal to 1%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% and less than or equal to 30%, greater than or equal to 0% and less than or equal to 50%, or greater than or equal to 0% and less than or equal to 100%). Other ranges are also possible.

[0165] The adsorption efficiency of the adsorption layer can be measured according to ISO 11155-2 (2009).

[0166] In embodiments where the layer contains two or more types of adsorption substances, each type of adsorption substance can independently have an adsorption efficiency for one or more substances (e.g., volatile organic compounds (e.g., toluene, n-butane, SO2, NO x ), benzene, aldehydes (e.g., acetaldehyde, formaldehyde), acidic gases (e.g., H2S, HCl, HF, HCN), basic gases (e.g., ammonia, amines such as trimethylamine and / or triethylamine), H2, CO, N2, sulfur, hydrocarbons, alcohols, O3, water, and gaseous chemical weapons (e.g., nerve agents, mustard gas)) within one or more of the above ranges. In some embodiments, all the adsorption substances in the layer together have an adsorption efficiency for one or more substances (e.g., volatile organic compounds (e.g., toluene, n-butane, SO2, NO x) The adsorption efficiency of benzene, aldehydes (e.g., acetaldehyde, formaldehyde), acidic gases (e.g., H2S, HCl, HF, HCN), basic gases (e.g., ammonia, amines such as trimethylamine and / or triethylamine), H2, CO, N2, sulfur, hydrocarbons, alcohols, O3, water, and gaseous chemical weapons (e.g., nerve agents, mustard gas). When the filter medium includes two or more adsorption layers, the foregoing can be applied independently for each such layer.

[0167] The adsorption layer can exhibit a relatively low penetration rate for one or more substances. In some embodiments, the penetration rate for one or more substances is less than or equal to 90%, less than or equal to 80%, less than or equal to 70%, less than or equal to 60%, less than or equal to 50%, less than or equal to 40%, less than or equal to 30%, or less than or equal to 20%. In some embodiments, the penetration rate for one or more substances is greater than or equal to 10%, greater than or equal to 20%, greater than or equal to 30%, greater than or equal to 40%, greater than or equal to 50%, greater than or equal to 60%, greater than or equal to 70%, or greater than or equal to 80%. Combinations of the above ranges are also possible (e.g., less than or equal to 90% and greater than or equal to 10%). Other ranges are also possible.

[0168] The penetration rate of the adsorption layer for any particular substance is the percentage of the substance that passes through the adsorption layer. This can be determined on a flat sample of the layer according to ISO11155-2 (2009). Briefly, the method includes: (1) drying the flat in a drying chamber at 60 °C until the filter mass is observed to have stabilized within ±2% of the mass; (2) conditioning the flat in a climatic chamber at 23 °C and 50% relative humidity for 14 hours; (3) placing the flat on a test bench and exposing it to clean air for 15 minutes; (4) exposing the flat to an air stream having 40% relative humidity and containing the relevant substance (i.e., the substance whose penetration rate is being evaluated), and then measuring the amount of the relevant substance in the air stream after passing through the flat by using a gas analyzer. The air stream can have a face velocity of 20 cm / sec and a temperature of 23 °C. The measurement can be carried out until the concentration of the relevant substance in the air after passing through the flat is 95% of the concentration of the relevant substance in the air before passing through the flat, or it can be carried out for a predetermined time. Unless otherwise specified, the measurement is carried out for 0 minutes (i.e., the time point when the flow through the flat has reached a steady state), and the concentration of the relevant substance in the air stream before passing through the flat is 80 ppm. Specifically, for the above ranges, the measurement time is 0 minutes, and the concentration of the relevant substance in the air stream before passing through the flat is 80 ppm. The penetration rate is equal to 100% multiplied by the ratio of the amount of the relevant substance in the air passing through the flat (in ppm) to the initial amount of the relevant substance in the air before passing through the flat (in ppm).

[0169] The adsorption layer may have a penetration rate within one or more of the ranges in the preceding paragraph for one or more of the following substances: volatile organic compounds (e.g., toluene, n-butane, SO2, NO x ), benzene, aldehydes (e.g., acetaldehyde, formaldehyde), acidic gases (e.g., H2S, HCl, HF, HCN), basic gases (e.g., ammonia, amines such as trimethylamine and / or triethylamine), H2, CO, N2, sulfur, hydrocarbons, alcohols, O3, water, and gaseous chemical weapons (e.g., nerve agents, mustard gas). When the filter medium includes two or more adsorption layers, the foregoing may apply independently to each such layer.

[0170] The adsorption layer may be capable of providing a relatively high cumulative purification quantity value for a fluid initially containing formaldehyde. For example, the adsorption layer may have the following grades: F1 (i.e., it may be capable of providing a cumulative purification quantity of greater than or equal to 300 mg per weight of the adsorption layer and less than 600 mg per weight of the adsorption layer in mg), F2 (i.e., it may be capable of providing a cumulative purification quantity of greater than or equal to 600 mg per weight of the adsorption layer and less than 1 g per weight of the adsorption layer in mg), F3 (i.e., it may be capable of providing a cumulative purification quantity of greater than or equal to 1 g per weight of the adsorption layer and less than 1.5 g per weight of the adsorption layer in mg), or F4 (i.e., it may be capable of providing a cumulative purification quantity of greater than or equal to 1.5 g per weight of the adsorption layer in mg).

[0171] The grading of the adsorption layer may be determined according to GB / T 18801-2015. Briefly, the process includes injecting formaldehyde gas at 20 mg / hour into a 3 m 3 chamber including the adsorption layer, recording the formaldehyde concentration in the chamber every five minutes until one hour has passed, and then multiplying the formaldehyde adsorption rate by the formaldehyde flow rate.

[0172] When the filter medium includes two or more adsorption layers, each such adsorption layer may independently have one or more of the above grades.

[0173] The adsorption layer can be capable of providing a relatively high cumulative purification amount value for a fluid initially containing benzene. For example, the adsorption layer can have the following grades: B1 (i.e., it can be capable of providing a cumulative purification amount greater than or equal to 300 mg per weight of the adsorption layer in mg and less than 600 mg per weight of the adsorption layer in mg), B2 (i.e., it can be capable of providing a cumulative purification amount greater than or equal to 600 mg per weight of the adsorption layer in mg and less than 1 g per weight of the adsorption layer in mg), B3 (i.e., it can be capable of providing a cumulative purification amount greater than or equal to 1 g per weight of the adsorption layer in mg and less than 1.5 g per weight of the adsorption layer in mg), or B4 (i.e., it can be capable of providing a cumulative purification amount greater than or equal to 1.5 g per weight of the adsorption layer in mg).

[0174] The grading of the adsorption layer can be determined according to GB / T 18801-2015. Briefly, the process includes injecting benzene gas at 20 mg / hour into a 3 m chamber including the layer, recording the concentration of benzene in the chamber every five minutes until one hour has passed, and then multiplying the benzene adsorption rate by the benzene flow rate. 3 When the filter medium includes two or more adsorption layers, each such adsorption layer can independently have one or more of the above grades.

[0175] When the filter medium includes two or more adsorption layers, each such adsorption layer can independently have one or more of the above grades.

[0176] The adsorption layer can have a relatively high clean air delivery rate for a fluid initially containing formaldehyde. The clean air delivery rate for a fluid initially containing formaldehyde can be greater than or equal to 10 m 3 / hour, greater than or equal to 20 m 3 / hour, greater than or equal to 50 m 3 / hour, greater than or equal to 75 m 3 / hour, greater than or equal to 100 m 3 / hour, greater than or equal to 150 m 3 / hour, greater than or equal to 200 m 3 / hour, greater than or equal to 250 m 3 / hour, greater than or equal to 300 m 3 / hour, greater than or equal to 400 m 3 / hour, greater than or equal to 500 m 3 / hour, or greater than or equal to 600 m 3 / hour. The clean air delivery rate for a fluid initially containing formaldehyde can be less than or equal to 700 m 3 / hour, less than or equal to 600 m 3 / hour, less than or equal to 500 m 3 / hour, less than or equal to 400 m 3 / hour, less than or equal to 300m 3 / hour, less than or equal to 250m 3 / hour, less than or equal to 200m 3 / hour, less than or equal to 150m 3 / hour, less than or equal to 100m 3 / hour, less than or equal to 75m 3 / hour, less than or equal to 50m 3 / hour, or less than or equal to 20m 3 / hour. Combinations of the above ranges are also possible (e.g., greater than or equal to 10m 3 / hour and less than or equal to 700m 3 / hour). Other ranges are also possible.

[0177] The clean air delivery rate of the adsorption layer for a fluid initially containing formaldehyde can be determined in accordance with GB / T 18801-2015. Briefly, the process includes: (1) pumping 1 mg / m 3 of formaldehyde into a 1 m 3 sealed chamber containing the adsorption layer, and then measuring the concentration of formaldehyde every 5 minutes for 60 minutes; (2) pumping 1 mg / m 3 of formaldehyde into a 1 m 3 sealed chamber without the adsorption layer, and then measuring the concentration of formaldehyde every 5 minutes for 60 minutes; (3) determining the difference between the formaldehyde removed from the chamber containing the adsorption layer and the formaldehyde removed from the chamber without the adsorption layer as the volume of formaldehyde removed; and (4) dividing the volume of formaldehyde removed by 60 minutes to obtain the clean air delivery rate.

[0178] When the filter medium includes two or more adsorption layers, each adsorption layer can independently have a clean air delivery rate within one or more of the above ranges for a fluid initially containing formaldehyde.

[0179] The adsorption layer can have a relatively high clean air delivery rate for a fluid initially containing benzene. The clean air delivery rate for a fluid initially containing benzene can be greater than or equal to 10m 3 / hour, greater than or equal to 20m 3 / hour, greater than or equal to 50m 3 / hour, greater than or equal to 75m 3 / hour, greater than or equal to 100m 3 / hour, greater than or equal to 150m 3 / hour, greater than or equal to 200m 3 / hour, greater than or equal to 250m 3 / hour, greater than or equal to 300m 3 / hour, greater than or equal to 400 m 3 / hour, greater than or equal to 500 m 3 / hour, or greater than or equal to 600 m 3 / hour. The clean air delivery rate for a fluid initially containing benzene can be less than or equal to 700 m 3 / hour, less than or equal to 600 m 3 / hour, less than or equal to 500 m 3 / hour, less than or equal to 400 m 3 / hour, less than or equal to 300 m 3 / hour, less than or equal to 250 m 3 / hour, less than or equal to 200 m 3 / hour, less than or equal to 150 m 3 / hour, less than or equal to 100 m 3 / hour, less than or equal to 75 m 3 / hour, less than or equal to 50 m 3 / hour, or less than or equal to 20 m 3 / hour. Combinations of the above ranges are also possible (e.g., greater than or equal to 10 m 3 / hour and less than or equal to 700 m 3 / hour). Other ranges are also possible.

[0180] The clean air delivery rate of the adsorption layer for a fluid initially containing benzene can be determined according to GB / T 18801-2015. Briefly, the process includes: (1) pumping 1 mg / m 3 of benzene into a 1 m 3 sealed chamber containing the adsorption layer, and then measuring the concentration of benzene every 5 minutes for 60 minutes; (2) pumping 1 mg / m 3 of benzene into a 1 m 3 sealed chamber without the adsorption layer, and then measuring the concentration of benzene every 5 minutes for 60 minutes; (3) determining the difference between the benzene removed from the chamber containing the adsorption layer and the benzene removed from the chamber without the adsorption layer as the volume of benzene removed; and (4) dividing the volume of benzene removed by 60 minutes to obtain the clean air delivery rate.

[0181] When the filter medium includes two or more adsorption layers, each adsorption layer can independently have a clean air delivery rate for a fluid initially containing benzene within one or more of the above ranges.

[0182] The adsorption layer can have various suitable basis weights. In some embodiments, the basis weight of the adsorption layer is greater than or equal to 120 gsm, greater than or equal to 150 gsm, greater than or equal to 175 gsm, greater than or equal to 200 gsm, greater than or equal to 225 gsm, greater than or equal to 250 gsm, greater than or equal to 300 gsm, greater than or equal to 400 gsm, greater than or equal to 500 gsm, greater than or equal to 600 gsm, greater than or equal to 700 gsm, greater than or equal to 800 gsm, greater than or equal to 900 gsm, greater than or equal to 1000 gsm, greater than or equal to 1100 gsm, greater than or equal to 1200 gsm, greater than or equal to 1500 gsm, or greater than or equal to 1750 gsm. In some embodiments, the basis weight of the adsorption layer is less than or equal to 2000 gsm, less than or equal to 1750 gsm, less than or equal to 1500 gsm, less than or equal to 1200 gsm, less than or equal to 1100 gsm, less than or equal to 1000 gsm, less than or equal to 900 gsm, less than or equal to 800 gsm, less than or equal to 700 gsm, less than or equal to 600 gsm, less than or equal to 500 gsm, less than or equal to 400 gsm, less than or equal to 300 gsm, less than or equal to 250 gsm, less than or equal to 225 gsm, less than or equal to 200 gsm, less than or equal to 175 gsm, or less than or equal to 150 gsm. Combinations of the above ranges are also possible (e.g., greater than or equal to 120 gsm and less than or equal to 2000 gsm, or greater than or equal to 120 gsm and less than or equal to 1100 gsm). Other ranges are also possible.

[0183] The basis weight of the adsorption layer can be determined in the same manner as the basis weight of the nonwoven web for high performance described above.

[0184] When the filter medium includes two or more adsorption layers, each adsorption layer can independently have a basis weight within one or more of the above ranges.

[0185] The adsorption layer can have various suitable thicknesses. In some embodiments, the thickness of the adsorption layer is greater than or equal to 0.5 mm, greater than or equal to 0.75 mm, greater than or equal to 1 mm, greater than or equal to 1.25 mm, greater than or equal to 1.5 mm, greater than or equal to 1.75 mm, greater than or equal to 2 mm, greater than or equal to 2.25 mm, greater than or equal to 2.5 mm, greater than or equal to 2.75 mm, greater than or equal to 3 mm, greater than or equal to 3.5 mm, greater than or equal to 4 mm, greater than or equal to 4.5 mm, greater than or equal to 5 mm, greater than or equal to 6 mm, or greater than or equal to 7 mm. In some embodiments, the thickness of the adsorption layer is less than or equal to 8 mm, less than or equal to 7 mm, less than or equal to 6 mm, less than or equal to 5 mm, less than or equal to 4.5 mm, less than or equal to 4 mm, less than or equal to 3.5 mm, less than or equal to 3 mm, less than or equal to 2.75 mm, less than or equal to 2.5 mm, less than or equal to 2.25 mm, less than or equal to 2 mm, less than or equal to 1.75 mm, less than or equal to 1.5 mm, less than or equal to 1.25 mm, less than or equal to 1 mm, or less than or equal to 0.75 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.5 mm and less than or equal to 8 mm, greater than or equal to 0.5 mm and less than or equal to 5 mm, or greater than or equal to 0.5 mm and less than or equal to 2.5 mm). Other ranges are also possible.

[0186] The thickness of the adsorption layer can be determined according to ASTM D1777 (2015) at an applied pressure of 0.8 kPa.

[0187] In some embodiments, the adsorption layer and the support layer on which the adsorption layer is disposed together have a thickness within one or more of the ranges of the preceding paragraphs. In some embodiments, the adsorption layer has a thickness within one or more of the ranges of the preceding paragraphs and is disposed on the support layer. When the filter medium includes two or more adsorption layers, the foregoing can apply independently for each such layer.

[0188] In some embodiments, the filter medium includes a nonwoven fibrous web containing nanofibers. The nonwoven fibrous web containing nanofibers can improve the filtration performance of the filter medium and / or can be used as an efficiency layer. The filter medium can also include two or more nonwoven fibrous webs containing nanofibers. Such nonwoven fibrous webs can be the same or can differ in one or more respects.

[0189] When present, the nonwoven fibrous web containing nanofibers can have various suitable morphologies. For example, the nonwoven fibrous web containing nanofibers can be an electrospun nonwoven fibrous web, a meltblown nonwoven fibrous web, a centrifugally spun nonwoven fibrous web, an electrosprayed nonwoven fibrous web, or a fibrillated spun nonwoven fibrous web. In some embodiments, the nonwoven fibrous web is disposed (e.g., directly or indirectly) on a carrier. Non-limiting examples of suitable carriers include a spunbond layer, a wet-laid backing, a carded backing, a meltblown nonwoven fibrous web, a meltblown nonwoven fibrous web disposed on a spunbond layer, and a calendered meltblown layer.

[0190] The fibers present in the nonwoven fibrous web containing nanofibers can have various suitable types. In some embodiments, the nonwoven fibrous web containing nanofibers contains fibers including one or more of the following: polyether-b-polyamide, polysulfone, polyamide (e.g., nylon such as nylon 6), polyester (e.g., polycaprolactone, poly(butylene terephthalate)), polyurethane, polyurea, acrylics, polymers containing side chains with carbonyl functional groups (e.g., poly(vinyl acetate), cellulose esters, polyacrylamide), poly(ethersulfone), polyacrylic acids (e.g., polyacrylonitrile, poly(acrylic acid)), fluorinated polymers (e.g., poly(vinylidene fluoride)), polyols (e.g., poly(vinyl alcohol)), polyethers (e.g., poly(ethylene oxide)), poly(vinylpyrrolidone), polyallylamine, butyl rubber, polyethylene, polymers containing silane functional groups, polymers containing thiol functional groups, and polymers containing hydroxymethyl functional groups (e.g., phenolic polymers, melamine polymers, melamine-formaldehyde polymers, crosslinkable polymers containing side group hydroxymethyl).

[0191] In some embodiments, the nonwoven fibrous web containing nanofibers contains fibers containing a matrix polymer and an impact modifier. The presence of the matrix polymer and the impact modifier can enhance one or more mechanical properties (e.g., elongation at break, tensile strength, toughness, puncture strength, durability during pleating) of the nonwoven fibrous web containing nanofibers.

[0192] Non-limiting examples of suitable matrix polymers include synthetic polymers such as polyamides (e.g., nylons such as nylon 6 (also known as polyamide 6)), polyesters (e.g., polycaprolactone, poly(butylene terephthalate)), polyurethanes, polyureas, acrylates, polymers containing side chains with carbonyl functional groups (e.g., poly(vinyl acetate)), cellulose, cellulose esters, polyacrylamides, poly(ethersulfone), polyacrylic acids (e.g., polyacrylonitrile, poly(acrylic acid)), polystyrene, polycarbonates, polyvinyl chloride, polysulfones, poly(amic acids), fluorinated polymers (e.g., poly(vinylidene fluoride)), polyols (e.g., poly(vinyl alcohol)), polyethers (e.g., poly(ethylene oxide)), poly(vinylpyrrolidone), polyallylamine, butyl rubber, polyethylene, polymers containing silane functional groups, polymers containing thiol functional groups, polymers containing hydroxymethyl functional groups (e.g., phenolic polymers, melamine polymers, melamine-formaldehyde polymers, crosslinkable polymers containing side group hydroxymethyl), and / or combinations thereof. In some embodiments, the matrix polymer includes copolymers of two or more of the polymers listed above and / or blends of two or more of the polymers listed above (e.g., a blend of a polyamide and a polyester). In certain embodiments, the matrix polymer is a glassy polymer and / or a semi-crystalline polymer.

[0193] In certain embodiments, the impact modifier comprises a copolymer containing at least two different monomers, wherein at least one monomer has an affinity for the matrix polymer and wherein at least one monomer has no affinity for the matrix polymer. As used herein, a copolymer is a polymer derived from at least two different types of monomers.

[0194] In some embodiments, a monomer has an affinity for the matrix polymer when the monomer is the same as the monomer of the matrix polymer, when the monomer is miscible with the matrix polymer, when the monomer contains a reaction site that will covalently bond with the matrix polymer, when the monomer undergoes ionic interactions with the matrix polymer, and / or when the total solubility parameter of the monomer is similar to the total solubility parameter of the monomer of the matrix polymer. Whether a covalent bond is formed and whether ionic interactions exist can be determined by spectroscopic techniques such as FTIR.

[0195] According to some embodiments, the impact modifier and / or its monomers include polyamides (e.g., polyamide 6, polyamide 11, and / or polyamide 6,6), polystyrene, polyethers, polypropylenes, polycarbonates, polyethylene, polyesters, ABS (acrylonitrile butadiene styrene), and / or PVC (polyvinyl chloride). Examples of suitable impact modifiers include the impact modifiers in Table 2.

[0196] Table 2.

[0197]

[0198] A nonwoven fibrous web containing nanofibers can contain fibers having various suitable average fiber diameters. In some embodiments, the average fiber diameter of the fibers in the nonwoven fibrous web containing nanofibers is greater than or equal to 50 nm, greater than or equal to 55 nm, greater than or equal to 60 nm, greater than or equal to 65 nm, greater than or equal to 70 nm, greater than or equal to 75 nm, greater than or equal to 80 nm, greater than or equal to 85 nm, greater than or equal to 90 nm, greater than or equal to 95 nm, greater than or equal to 100 nm, greater than or equal to 105 nm, greater than or equal to 110 nm, greater than or equal to 115 nm, greater than or equal to 120 nm, greater than or equal to 125 nm, greater than or equal to 130 nm, greater than or equal to 140 nm, greater than or equal to 150 nm, greater than or equal to 175 nm, greater than or equal to 200 nm, greater than or equal to 225 nm, greater than or equal to 250 nm, or greater than or equal to 275 nm. In some embodiments, the average fiber diameter of the fibers in the nonwoven fibrous web containing nanofibers is less than or equal to 300 nm, less than or equal to 275 nm, less than or equal to 250 nm, less than or equal to 225 nm, less than or equal to 200 nm, less than or equal to 175 nm, less than or equal to 150 nm, less than or equal to 140 nm, less than or equal to 130 nm, less than or equal to 125 nm, less than or equal to 120 nm, less than or equal to 115 nm, less than or equal to 110 nm, less than or equal to 105 nm, less than or equal to 100 nm, less than or equal to 95 nm, less than or equal to 90 nm, less than or equal to 85 nm, less than or equal to 80 nm, less than or equal to 75 nm, less than or equal to 70 nm, less than or equal to 65 nm, less than or equal to 60 nm, or less than or equal to 55 nm. Combinations of the above ranges are also possible (e.g., greater than or equal to 50 nm and less than or equal to 300 nm, greater than or equal to 60 nm and less than or equal to 200 nm, or greater than or equal to 80 nm and less than or equal to 120 nm). Other ranges are also possible.

[0199] When the nonwoven fibrous web containing nanofibers contains two or more types of fibers, each type of fiber can independently have an average fiber diameter within one or more of the above ranges, and / or all of the fibers in the nonwoven fibrous web containing nanofibers can together have an average fiber diameter within one or more of the above ranges. When the filter medium includes two or more nonwoven fibrous webs containing nanofibers, the foregoing can independently apply to each such nonwoven fibrous web.

[0200] Nonwoven fiber webs containing nanofibers can have a variety of suitable basis weights. In some embodiments, the basis weight of the nonwoven fiber web containing nanofibers is greater than or equal to 0.01 gsm, greater than or equal to 0.02 gsm, greater than or equal to 0.03 gsm, greater than or equal to 0.04 gsm, greater than or equal to 0.05 gsm, greater than or equal to 0.06 gsm, greater than or equal to 0.08 gsm, greater than or equal to 0.1 gsm, greater than or equal to 0.2 gsm, greater than or equal to 0.5 gsm, greater than or equal to 0.75 gsm, greater than or equal to 1 gsm, greater than or equal to 1.25 gsm, greater than or equal to 1.5 gsm, greater than or equal to 1.75 gsm, greater than or equal to 2 gsm, greater than or equal to 2.5 gsm, greater than or equal to 3 gsm, greater than or equal to 3.5 gsm, greater than or equal to 4 gsm, or greater than or equal to 4.5 gsm. In some embodiments, the basis weight of the nonwoven fiber web containing nanofibers is less than or equal to 5 gsm, less than or equal to 4.5 gsm, less than or equal to 4 gsm, less than or equal to 3.5 gsm, less than or equal to 3 gsm, less than or equal to 2.5 gsm, less than or equal to 2 gsm, less than or equal to 1.75 gsm, less than or equal to 1.5 gsm, less than or equal to 1.25 gsm, less than or equal to 1 gsm, less than or equal to 0.75 gsm, less than or equal to 0.5 gsm, less than or equal to 0.2 gsm, less than or equal to 0.1 gsm, less than or equal to 0.08 gsm, less than or equal to 0.06 gsm, less than or equal to 0.05 gsm, less than or equal to 0.04 gsm, less than or equal to 0.03 gsm, or less than or equal to 0.02 gsm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.01 gsm and less than or equal to 5 gsm, greater than or equal to 0.03 gsm and less than or equal to 4 gsm, or greater than or equal to 0.05 gsm and less than or equal to 2 gsm). Other ranges are also possible.

[0201] The basis weight of the nonwoven fiber web containing nanofibers can be determined in the same manner as the basis weight of nonwoven fiber webs for high performance described above.

[0202] When the filter medium includes two or more nonwoven fiber webs containing nanofibers, each nonwoven fiber web containing nanofibers can independently have a basis weight within one or more of the above ranges.

[0203] A nonwoven fibrous web containing nanowires can have various suitable thicknesses. In some embodiments, the thickness of the nonwoven fibrous web containing nanofibers is greater than or equal to 0.1 micrometer, greater than or equal to 0.15 micrometer, greater than or equal to 0.2 micrometer, greater than or equal to 0.25 micrometer, greater than or equal to 0.3 micrometer, greater than or equal to 0.4 micrometer, greater than or equal to 0.5 micrometer, greater than or equal to 0.6 micrometer, greater than or equal to 0.8 micrometer, greater than or equal to 1 micrometer, greater than or equal to 2 micrometers, greater than or equal to 5 micrometers, greater than or equal to 7.5 micrometers, greater than or equal to 10 micrometers, greater than or equal to 15 micrometers, greater than or equal to 20 micrometers, greater than or equal to 25 micrometers, greater than or equal to 30 micrometers, greater than or equal to 40 micrometers, greater than or equal to 50 micrometers, greater than or equal to 60 micrometers, or greater than or equal to 80 micrometers. In some embodiments, the thickness of the nonwoven fibrous web containing nanofibers is less than or equal to 100 micrometers, less than or equal to 80 micrometers, less than or equal to 60 micrometers, less than or equal to 50 micrometers, less than or equal to 40 micrometers, less than or equal to 30 micrometers, less than or equal to 25 micrometers, less than or equal to 20 micrometers, less than or equal to 15 micrometers, less than or equal to 10 micrometers, less than or equal to 7.5 micrometers, less than or equal to 5 micrometers, less than or equal to 2 micrometers, less than or equal to 1 micrometer, less than or equal to 0.8 micrometer, less than or equal to 0.6 micrometer, less than or equal to 0.5 micrometer, less than or equal to 0.4 micrometer, less than or equal to 0.3 micrometer, less than or equal to 0.25 micrometer, less than or equal to 0.2 micrometer, less than or equal to 0.15 micrometer, or less than or equal to 0.1 micrometer. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 micrometer and less than or equal to 100 micrometers, greater than or equal to 0.2 micrometer and less than or equal to 50 micrometers, or greater than or equal to 0.5 micrometer and less than or equal to 10 micrometers). Other ranges are also possible.

[0204] The thickness of the nanofiber layer can be determined by cross-sectional scanning electron microscopy.

[0205] When the filter medium includes two or more nonwoven fibrous webs containing nanofibers, each nonwoven fibrous web containing nanofibers can independently have a thickness within one or more of the above ranges.

[0206] Nonwoven fiber webs containing nanofibers can have various suitable densifications. In some embodiments, the densification of the nonwoven fiber web containing nanofibers is greater than or equal to 0.1%, greater than or equal to 0.2%, greater than or equal to 0.3%, greater than or equal to 0.4%, greater than or equal to 0.5%, greater than or equal to 0.6%, greater than or equal to 0.8%, greater than or equal to 1%, greater than or equal to 2%, greater than or equal to 5%, greater than or equal to 7.5%, greater than or equal to 10%, greater than or equal to 12.5%, greater than or equal to 15%, greater than or equal to 20%, or greater than or equal to 25%. In some embodiments, the densification of the nonwoven fiber web containing nanofibers is less than or equal to 30%, less than or equal to 25%, less than or equal to 20%, less than or equal to 15%, less than or equal to 12.5%, less than or equal to 10%, less than or equal to 7.5%, less than or equal to 5%, less than or equal to 2%, less than or equal to 1%, less than or equal to 0.8%, less than or equal to 0.6%, less than or equal to 0.5%, less than or equal to 0.4%, less than or equal to 0.3%, or less than or equal to 0.2%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1% and less than or equal to 30%, greater than or equal to 0.5% and less than or equal to 20%, or greater than or equal to 1% and less than or equal to 10%). Other ranges are also possible.

[0207] The densification of the nonwoven fiber web containing nanofibers can be determined in the same manner as the densification of the nonwoven fiber web having high performance described above.

[0208] When the filter medium includes two or more nonwoven fiber webs containing nanofibers, each nonwoven fiber web containing nanofibers can independently have a densification within one or more of the above ranges.

[0209] Nonwoven fiber webs containing nanofibers can have various suitable air permeabilities. In some embodiments, the air permeability of the nonwoven fiber web containing nanofibers is greater than or equal to 10 (CFM), greater than or equal to 20 CFM, greater than or equal to 30 CFM, greater than or equal to 40 CFM, greater than or equal to 50 CFM, greater than or equal to 60 CFM, greater than or equal to 70 CFM, greater than or equal to 80 CFM, greater than or equal to 100 CFM, greater than or equal to 125 CFM, or greater than or equal to 150 CFM. In some embodiments, the air permeability of the nonwoven fiber web containing nanofibers is less than or equal to 170 CFM, less than or equal to 150 CFM, less than or equal to 125 CFM, less than or equal to 100 CFM, less than or equal to 80 CFM, less than or equal to 60 CFM, less than or equal to 50 CFM, less than or equal to 40 CFM, less than or equal to 30 CFM, or less than or equal to 20 CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 10 CFM and less than or equal to 170 CFM, greater than or equal to 30 CFM and less than or equal to 80 CFM, or greater than or equal to 40 CFM and less than or equal to 70 CFM). Other ranges are also possible.

[0210] The air permeability of the nonwoven fiber web containing nanofibers can be determined in the same manner as described above for determining the air permeability of nonwoven fiber webs with high performance.

[0211] When the filter medium includes two or more nonwoven fiber webs containing nanofibers, each nonwoven fiber web containing nanofibers can independently have an air permeability within one or more of the above ranges.

[0212] In some embodiments, the nonwoven fibrous web comprising nanofibers comprises fibers having oleophobic properties, comprises oleophobic components, and / or is surface-modified. In some embodiments, the nonwoven fibrous web comprising nanofibers includes a coating (e.g., an oleophobic coating, an oleophobic component that is an oleophobic coating) and / or comprises a resin (e.g., an oleophobic resin, an oleophobic component that is an oleophobic resin). The coating process can involve chemical deposition techniques and / or physical deposition techniques. For example, the coating process can include introducing a resin or material (e.g., an oleophobic component that is a resin or material) dispersed in a solvent or solvent mixture into a pre-formed fiber layer (e.g., a pre-formed fibrous web formed by an electrospinning process). As an example, a pre-filter can be sprayed with a coating material (e.g., water-based fluorinated acrylate such as AGE 550D). Non-limiting examples of coating methods include using vapor deposition (e.g., chemical vapor deposition, physical vapor deposition), layer-by-layer deposition, wax curing, self-assembly, sol-gel processing, using a slot die coater, gravure coating, screen coating, size press coating (e.g., using a two-roll type or a metering knife type size press coater), film press coating, knife coating, roll knife coating, air knife coating, roll coating, foam application, reverse roll coating, bar coating, curtain coating, champlex coating, brush coating, Bill-blade coating, short dwell-blade coating, lip coating, gate roll coating, gate roll size press coating, laboratory size press coating, melt coating, dip coating, knife roll coating, spin coating, powder coating, spray coating (e.g., electrospray coating), notched roll coating, roll transfer coating, padding saturant coating, saturation dipping, chemical bath deposition, and solution deposition. Other coating methods are possible. As further described elsewhere herein, the nonwoven fibrous web comprising nanofibers can be charged or uncharged, and it should be understood that any of the techniques described herein can be used to form a charged or uncharged layer.

[0213] In some embodiments, a non-compressive coating technique can be used to apply a coating material to the nonwoven fibrous web comprising nanofibers. The non-compressive coating technique can coat the nonwoven fibrous web comprising nanofibers while substantially not reducing its thickness. In other embodiments, a compressive coating technique can be used to apply a resin to the nonwoven fibrous web comprising nanofibers.

[0214] Other techniques include vapor deposition methods. Such methods include atmospheric pressure chemical vapor deposition (APCVD), low pressure chemical vapor deposition (LPCVD), metal-organic chemical vapor deposition (MOCVD), plasma assisted chemical vapor deposition (PACVD) or plasma enhanced chemical vapor deposition (PECVD), laser chemical vapor deposition (LCVD), photochemical vapor deposition (PCVD), chemical vapor infiltration (CVI), chemical beam epitaxy (CBE), electron beam assisted radiation curing, and atomic layer deposition. In physical vapor deposition (PVD), a thin film (e.g., a thin film comprising an oleophobic component) is deposited by condensing a desired film material in vaporized form onto a substrate. The method involves physical processes such as high temperature vacuum evaporation followed by condensation, plasma sputter bombardment rather than chemical reactions, electron beam evaporation, molecular beam epitaxy, and / or pulsed laser deposition.

[0215] In some embodiments, the surface of the nonwoven fibrous web comprising nanofibers can be modified using an additive (e.g., the oleophobic component of an additive such as an oleophobic additive). In some embodiments, the nonwoven fibrous web comprising nanofibers comprises one or more additives (e.g., the oleophobic component of an additive such as an oleophobic additive). The additive can be a functional chemical added to the polymeric fiber / thermoplastic fiber during the electrospinning process, which can result in physical and chemical properties at the surface after formation that are different from the physical and chemical properties of the polymer / thermoplastic itself. For example, the additive can be added to the electrospinning solution used to form the nonwoven fibrous web comprising nanofibers. In some embodiments, the additive can migrate towards the surface of the fiber during and / or after fiber formation such that the surface of the fiber is modified by the additive, wherein the center of the fiber contains more polymer / thermoplastic material. In some embodiments, one or more additives are included to make the surface of the fiber oleophobic as described herein. For example, the additive can be an oleophobic material as described herein. Non-limiting examples of suitable additives include fluorinated acrylates, fluorosurfactants, oleophobic silicones, fluoropolymers, fluorinated monomers, fluorinated oligomers, and oleophobic polymers.

[0216] If present, the additive (e.g., the oleophobic component in the form of an additive) can be present in any suitable form before undergoing the electrospinning procedure and / or in the fiber after fiber formation. For example, in some embodiments, the additive can be in the form of a liquid (e.g., molten) mixed with the thermoplastic material before and / or during fiber formation. In some cases, the additive can be in particulate form before, during, and / or after fiber formation. In certain embodiments, particles of the melt additive can be present in the fully formed fiber. In some embodiments, the additive can be a component of a binder and / or can be added to one or more layers by spraying the layer with a composition comprising the additive. If particulate, the additive can have any suitable morphology (e.g., particles, flakes, ellipsoids, fibers of different shapes and sizes).

[0217] In some embodiments, materials (e.g., oleophobic components, precursors that react to form oleophobic components) undergo a chemical reaction (e.g., polymerization) after being applied to a nonwoven fibrous web comprising nanofibers. For example, the surface of a nonwoven fibrous web comprising nanofibers can be coated with one or more monomers that polymerize after coating. In another example, the surface of a nonwoven fibrous web comprising nanofibers can comprise monomers that polymerize after formation of the nanofiber layer due to a melt additive. In some such embodiments, in-line polymerization can be used. In-line polymerization (e.g., in-line UV polymerization) is a process of curing a monomer or liquid polymer solution onto a substrate under conditions sufficient to initiate polymerization (e.g., under UV irradiation).

[0218] The term "self-assembled monolayer" (SAM) refers to a molecular assembly that can be spontaneously formed by immersing a suitable substrate into a solution of an active surfactant in an organic solvent to produce an oleophobic surface. In some embodiments, the surface modification includes a SAM formed on one or more fiber surfaces in a nonwoven fibrous web comprising nanofibers.

[0219] In wax curing, a nonwoven fibrous web comprising nanofibers is immersed in molten alkylketene dimer (AKD) heated at 90 °C and then cooled at room temperature in an atmosphere of dry N2 gas. AKD undergoes fractal growth upon its solidification and improves the oleophobicity of the nonwoven fibrous web comprising nanofibers. In some embodiments, the surface modification includes a layer formed by wax curing.

[0220] In some embodiments, the materials used to form a surface-modified nonwoven fibrous web comprising nanofibers or the components of such a layer include small molecules, such as inorganic or organic oleophobic molecules. Non-limiting examples include hydrocarbons (e.g., CH4, C2H2, C2H4, C6H6), fluorocarbons (e.g., fluorinated aliphatic compounds, fluorinated aromatic compounds, fluoropolymers, fluorocarbon block copolymers, fluorocarbon acrylate polymers, fluorocarbon methacrylate polymers, fluorinated elastomers, fluorosilanes, fluorosiloxanes, fluoropolyhedral oligomeric silsesquioxanes, fluorinated dendrimers, inorganic fluorine compounds, CF4, C2F4, C3F6, C3F8, C4H8, C5H 12 、C6F6、SF3、SiF4、BF3), silanes (e.g., SiH4, Si2H6, Si3H8, Si4H 10) silanes (e.g., methylsilane, dimethylsilane, triethylsilane), siloxanes (e.g., dimethylsiloxane, hexamethyldisiloxane), ZnS, CuSe, InS, CdS, tungsten, silicon carbide, silicon nitride, silicon oxynitride, titanium nitride, carbon, silicon-germanium, and alkyl-capped hydrophobic acrylic monomers and their halogenated derivatives (e.g., ethyl acrylate, methyl methacrylate; acrylonitrile). In certain embodiments, suitable hydrocarbons for modifying the surface of a nonwoven web comprising nanofibers have the formula C x H y , where x is an integer from 1 to 10, and y is an integer from 2 to 22. In certain embodiments, suitable silanes for modifying the surface of a nonwoven web comprising nanofibers have the formula Si n H 2n+2 , where any hydrogen may be replaced by a halogen (e.g., Cl, F, Br, I), and where n is an integer from 1 to 10. In some embodiments, the substance used to form the surface-modified nonwoven web comprising nanofibers or the substance that is a component of the surface-modified nonwoven web comprising nanofibers comprises one or more of wax, silicone, and corn-based polymers (e.g., zein). In some embodiments, the substance used to form the surface-modified nonwoven web comprising nanofibers or the substance that is a component of the surface-modified nonwoven web comprising nanofibers may comprise one or more nanoparticulate materials. Other compositions are possible.

[0221] As used herein, "small molecule" refers to a molecule having a relatively low molecular weight, whether naturally occurring or artificially produced (e.g., via chemical synthesis). Generally, small molecules are organic compounds (i.e., they contain carbon). Small organic molecules may contain multiple carbon-carbon bonds, stereocenters, and / or other functional groups (e.g., amines, hydroxyls, carbonyls, and heterocycles, etc.). In certain embodiments, the molecular weight of the small molecule is at most 1,000 g / mol, at most 900 g / mol, at most 800 g / mol, at most 700 g / mol, at most 600 g / mol, at most 500 g / mol, at most 400 g / mol, at most 300 g / mol, at most 200 g / mol, or at most 100 g / mol. In certain embodiments, the molecular weight of the small molecule is at least 100 g / mol, at least 200 g / mol, at least 300 g / mol, at least 400 g / mol, at least 500 g / mol, at least 600 g / mol, at least 700 g / mol, at least 800 g / mol, at least 900 g / mol, or at least 1,000 g / mol. Combinations of the above ranges are also possible (e.g., at least 200 g / mol and at most 500 g / mol). Other ranges are also possible.

[0222] In some embodiments, the material used to form the surface-modified nanofiber-containing nonwoven web or the material that is a component of the nanofiber-containing nonwoven web (e.g., an oleophobic component, a precursor that reacts to form an oleophobic component) includes a crosslinking agent. Non-limiting examples of suitable crosslinking agents include materials having one or more acrylate groups, such as 1,6-hexanediol diacrylate and alkoxylated cyclohexanedimethanol diacrylate.

[0223] In some embodiments, the surface of the nanofiber-containing nonwoven web is modified by roughening the surface of the nanofiber-containing nonwoven web or the material on the surface. In some such cases, the surface modification can be the roughened surface or material. The surface roughness of the surface of the nanofiber-containing nonwoven web or the material on the surface of the nanofiber-containing nonwoven web can be roughened microscopically and / or macroscopically. Non-limiting examples of methods for increasing roughness include modifying the surface with certain fibers, mixing fibers of different diameters, and lithography. In certain embodiments, fibers of different diameters (e.g., short fibers, continuous fibers) can be mixed or used to increase or decrease surface roughness. In some embodiments, electrospinning can be used alone or in combination with other methods (e.g., chemical vapor deposition) to produce an applied surface roughness. In some embodiments, lithography can be used to roughen the surface. Lithography encompasses many different types of surface preparation in which a design is transferred from a master to a surface.

[0224] In some embodiments, the roughness of the nanofiber-containing nonwoven web can be used to modify the wettability of the nanofiber-containing nonwoven web with respect to a particular fluid. In some cases, the roughness can change or increase the wettability of the surface of the nanofiber-containing nonwoven web. In some cases, the roughness can be used to increase the oleophobicity of an inherently oleophobic surface.

[0225] The oil rating of some oleophobic nonwoven fiber webs containing nanofibers can be greater than or equal to 1. The oil rating can be due to fibers (e.g., polytetrafluoroethylene fibers) within the nonwoven fiber web that inherently have an oil rating greater than or equal to 1, can be due to surface modification that increases the oil rating of fibers within a layer that initially had a lower oil rating, and / or can be due to oleophobic components that increase the oil rating of the layer. In some embodiments, the oil rating of the nonwoven fiber web containing nanofibers is greater than or equal to 1, greater than or equal to 2, greater than or equal to 3, greater than or equal to 4, greater than or equal to 4.5, greater than or equal to 5, greater than or equal to 5.5, greater than or equal to 6, greater than or equal to 6.5, greater than or equal to 7, or greater than or equal to 7.5. In some embodiments, the oil rating of the nonwoven fiber web containing nanofibers is less than or equal to 8, less than or equal to 7.5, less than or equal to 7, less than or equal to 6.5, less than or equal to 6, less than or equal to 5.5, less than or equal to 5, less than or equal to 4.5, less than or equal to 4, less than or equal to 3, or less than or equal to 2. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 and less than or equal to 8, greater than or equal to 1 and less than or equal to 8, greater than or equal to 1 and less than or equal to 6, or greater than or equal to 5 and less than or equal to 6). Other ranges are also possible.

[0226] The oil grade can be determined by measurement at 23 °C and 50% relative humidity (RH) according to AATCC TM 118 (1997). Briefly, five drops of each test oil (average droplet diameter of about 2 mm) are placed at five different positions on the surface of a nonwoven web containing nanofibers. After 30 seconds of contact with the web at 23 °C and 50% RH, the test oil with the maximum oil surface tension that does not wet the surface of the web (e.g., contact angle with the surface greater than or equal to 90 degrees) corresponds to the oil grade (listed in Table 3). For example, if the test oil with a surface tension of 26.6 mN / m does not wet (i.e., contact angle with the surface greater than or equal to 90 degrees) the surface of the nonwoven web containing nanofibers after 30 seconds, but the test oil with a surface tension of 25.4 mN / m wets the surface of the nonwoven web containing nanofibers within thirty seconds, then the oil grade of the nonwoven web containing nanofibers is 4. As another example, if the test oil with a surface tension of 25.4 mN / m does not wet the surface of the nonwoven web containing nanofibers after 30 seconds, but the test oil with a surface tension of 23.8 mN / m wets the surface of the nonwoven web containing nanofibers within thirty seconds, then the oil grade of the nonwoven web containing nanofibers is 5. As yet another example, if the test oil with a surface tension of 23.8 mN / m does not wet the surface of the nonwoven web containing nanofibers after 30 seconds, but the test oil with a surface tension of 21.6 mN / m wets the surface of the nonwoven web containing nanofibers within thirty seconds, then the oil grade of the nanofiber layer is 6. In some embodiments, if three or more of the five droplets partially wet the surface in a given test (e.g., form droplets on the surface, but not rounded droplets), the oil grade is expressed as the closest 0.5 value determined by subtracting 0.5 from the number of the test liquid. As an example, if the test oil with a surface tension of 25.4 mN / m does not wet the surface of the nonwoven web containing nanofibers after 30 seconds, but the test oil with a surface tension of 23.8 mN / m only partially wets (e.g., three or more of the test droplets form droplets that are not rounded droplets on the surface of the web) the surface of the nonwoven web containing nanofibers within thirty seconds after 30 seconds, then the oil grade of the nonwoven web containing nanofibers is 5.5.

[0227] Table 3.

[0228] Oil grade Test oil Surface tension (mN / m) 1 Kaydol (mineral oil) 31 2 65 / 35 Kaydol / n - hexadecane 28 3 n - hexadecane 27.5 4 n - tetradecane 26.6 5 n - dodecane 25.4 6 n - decane 23.8 7 n - octane 21.6 8 n - heptane 20.1

[0229] When the filter medium includes two or more nonwoven webs containing nanofibers, each nonwoven web containing nanofibers can independently have an oil grade within one or more of the above ranges.

[0230] The nonwoven fibrous web containing nanofibers may also contain fibers having hydrophobic properties, contain hydrophobic components (e.g., hydrophobic additives), and / or be surface-modified to be hydrophobic. In some embodiments, the nonwoven fibrous web containing nanofibers includes a hydrophobic coating and / or contains a hydrophobic resin. For example, in some embodiments, the nonwoven fibrous web containing nanofibers contains hydrophobic fibers. Non-limiting examples of such fibers include polypropylene fibers and polyvinylidene fluoride fibers. In some embodiments, one or more of the above techniques for increasing the oleophobicity of the nonwoven fibrous web containing nanofibers may also increase its hydrophobicity. For example, the presence of fluorine-containing substances (e.g., fluoropolymers) and / or non-polar substances (e.g., polyolefins, waxes, silicon-based materials) in the nonwoven fibrous web containing nanofibers will increase both its oleophobicity and hydrophobicity.

[0231] The water contact angle of the hydrophobic nonwoven fibrous web containing nanofibers can be greater than or equal to 90°, greater than or equal to 100°, greater than or equal to 110°, greater than or equal to 120°, greater than or equal to 130°, greater than or equal to 140°, or greater than or equal to 150°. The water contact angle of the hydrophobic nonwoven fibrous web containing nanofibers can be less than or equal to 160°, less than or equal to 150°, less than or equal to 140°, less than or equal to 130°, less than or equal to 120°, less than or equal to 110°, or less than or equal to 100°. Combinations of the above ranges are also possible (e.g., greater than or equal to 90° and less than or equal to 160°). Other ranges are also possible.

[0232] The water contact angle can be determined by following the procedure described in ASTM D5946 (2009) and measuring the contact angle within 15 seconds of water application.

[0233] When the filter medium includes two or more nonwoven fibrous webs containing nanofibers, each nonwoven fibrous web containing nanofibers can independently have a water contact angle within one or more of the above ranges.

[0234] In some embodiments, the nonwoven fibrous web comprising nanofibers comprises fibers having hydrophilic properties, comprises hydrophilic components (e.g., hydrophilic additives), and / or is surface-modified to be hydrophilic. For example, in some embodiments, the nonwoven fibrous web comprising nanofibers comprises hydrophilic fibers. Non-limiting examples of such fibers include poly(amide) fibers (e.g., nylon fibers) and poly(ester) fibers. As another example, the nonwoven fibrous web comprising nanofibers can be surface-treated with a hydrophilic surfactant. Non-limiting examples of suitable such surfactants include alkylbenzene sulfonates (e.g., 4-(5-dodecyl)benzenesulfonate), fatty acids and their salts (e.g., sodium stearate), lauryl sulfate, dialkyl sulfosuccinates (e.g., sodium dioctyl sulfosuccinate), lignosulfonates, alkyl ether phosphates, benzalkonium chloride, and perfluorooctane sulfonates.

[0235] The water contact angle of the hydrophilic nonwoven fibrous web comprising nanofibers can be less than 90°, less than or equal to 80°, less than or equal to 70°, less than or equal to 60°, less than or equal to 50°, less than or equal to 40°, less than or equal to 30°, less than or equal to 20°, or less than or equal to 10°. The water contact angle of the hydrophilic nonwoven fibrous web comprising nanofibers can be greater than or equal to 0°, greater than or equal to 10°, greater than or equal to 20°, greater than or equal to 30°, greater than or equal to 40°, greater than or equal to 50°, greater than or equal to 60°, greater than or equal to 70°, or greater than or equal to 80°. Combinations of the above ranges are also possible (e.g., less than 90° and greater than or equal to 0°). Other ranges are also possible. The nonwoven fibrous web comprising nanofibers can also be so hydrophilic that water applied to it is drawn into the layer, and thus no droplet that can be used to measure the contact angle can be formed. When such behavior is observed, the contact angle of the specified layer is 0°.

[0236] The water contact angle can be determined in accordance with ASTM D5946 (2009) as described elsewhere herein for the water contact angle of the hydrophobic nonwoven fibrous web comprising nanofibers.

[0237] When the filter medium comprises two or more nonwoven fibrous webs comprising nanofibers, each nonwoven fibrous web comprising nanofibers can independently have a water contact angle within one or more of the above ranges.

[0238] In some embodiments, the nonwoven fibrous web comprising nanofibers is charged. Such charging can be performed in the manner described above for the charging of nonwoven fibrous webs having high performance.

[0239] In some embodiments, the filter medium includes a charged layer and includes discontinuous fibers (e.g., short fibers). This layer can help provide charge to the filter medium, which can be beneficial for reasons discussed elsewhere herein regarding nonwoven webs with high performance due to being charged. The filter medium can also include two or more charged layers and include discontinuous fibers. Such layers can be the same or can differ in one or more respects.

[0240] In some embodiments, as described herein, a charged layer that includes discontinuous fibers can include one or more plural-root fibers. For example, in certain embodiments, a charged layer that includes discontinuous fibers includes a first plural-root fiber (e.g., including a first polymer) and a second plural-root fiber (e.g., including a second polymer different from the first polymer). In some such embodiments, each plural-root fiber (e.g., the first plural-root fiber, the second plural-root fiber) can have an average fiber diameter as described above. For example, in an exemplary embodiment, the charged fiber layer includes a first plural-root fiber and a second plural-root fiber, and the average fiber diameter of the first plural-root fiber and / or the second plural-root fiber is less than 15 micrometers and greater than or equal to 1 micrometer. In another exemplary embodiment, the charged fiber layer includes a first plural-root fiber and a second plural-root fiber, and the average fiber diameter of the first plural-root fiber and / or the second plural-root fiber is greater than or equal to 1 micrometer and less than or equal to 22 micrometers.

[0241] In certain embodiments, the fibers present in a charged layer that includes discontinuous fibers include synthetic fibers (synthetic polymer fibers). The synthetic fibers can be short fibers. Non-limiting examples of suitable synthetic fibers include polypropylene, dry-spun acrylics (e.g., produced by a dry-spinning process), polyvinyl chloride, modified acrylics, wet-spun acrylics, polytetrafluoroethylene, polypropylene, polystyrene, polysulfone, polyethersulfone, polycarbonate, nylon (e.g., nylon 6 / 6), polyurethane, phenolics, polyvinylidene fluoride, polyester, polyaramide, polyimide, polyolefins (e.g., polyethylene), Kevlar, Nomex, halogenated polymers (e.g., polyethylene terephthalate), polyacrylics, polyphenylene ether, polyphenylene sulfide, polymethylpentene, and combinations thereof. In some embodiments, the synthetic fibers are halogen-free such that when incinerated, no significant dioxins are detectable. For example, the fibers can be halogen-free acrylic fibers formed by dry-spinning. In some embodiments, the second layer and / or the entire filter medium is halogen-free such that when incinerated, no significant dioxins are detectable.

[0242] In some embodiments, the charged layer comprising discontinuous fibers comprises a mixture of two or more polymer fibers. For example, the charged layer comprising discontinuous fibers can at least comprise a first plurality of fibers containing a first polymer and a second plurality of fibers containing a second polymer. For example, in an exemplary embodiment, the charged layer comprising discontinuous fibers comprises a first plurality of fibers containing a first polymer, wherein the first polymer is acrylic (e.g., dry-spun acrylic). In certain embodiments, the charged layer comprising discontinuous fibers comprises a second plurality of fibers containing a second type of polymer fiber different from the first type of polymer fiber. In certain embodiments, the second type of polymer fiber is polypropylene.

[0243] In certain embodiments, the first polymer and the second polymer are selected such that the first polymer and the second polymer have different dielectric constants. Two polymers having different dielectric constants can facilitate charging of the layer (e.g., triboelectrification). Without wishing to be bound by theory, the two polymers having different dielectric constants in the layer can be in frictional contact during manufacture of the layer such that one polymer will lose electrons and transfer them to the other polymer, and as a result, the polymer losing electrons has a net positive charge and the other polymer receiving the electrons has a net negative charge. In some embodiments, the charged layer comprising discontinuous fibers can have one or more of the features described in co-owned U.S. Patent No. 6,623,548, entitled "Filter materials and methods for the production thereof," issued September 23, 2003, which is incorporated herein by reference in its entirety for all purposes. For example, in some embodiments, the charged layer comprising discontinuous fibers is an electrostatically charged layer formed by blending together: polypropylene fibers with halogen-free acrylic fibers, polypropylene fibers with polyvinyl chloride (PVC) fibers, or a mixture of halogen-free acrylic fibers and PVC fibers, and optionally, carding the blended fibers to form a nonwoven fabric.

[0244] In some embodiments, the difference in dielectric constant between a first polymer and a second polymer positioned in a charged layer comprising discontinuous fibers can be greater than or equal to 0.8, greater than or equal to 1, greater than or equal to 1.2, greater than or equal to 1.5, greater than or equal to 2, greater than or equal to 3, greater than or equal to 5, or greater than or equal to 7. In certain embodiments, the difference in dielectric constant between the first polymer and the second polymer can be less than or equal to 8, less than or equal to 7, less than or equal to 5, less than or equal to 3, less than or equal to 2, less than or equal to 1.5, less than or equal to 1.2, or less than or equal to 1. Combinations of these ranges are also possible (e.g., the difference in dielectric constant between the first polymer and the second polymer is greater than or equal to 0.8 and less than or equal to 8, greater than or equal to 1.5 and less than or equal to 5). Other ranges are also possible.

[0245] Table 4 shows the representative dielectric constants of several exemplary polymers.

[0246] Table 4.

[0247] Polymer Dielectric constant Polytetrafluoroethylene 2.10 Polypropylene 2.2–2.36 Polyethylene 2.25–2.35 Polystyrene 2.45–2.65 Polyvinyl chloride 2.8–3.1 Polysulfone 3.07 Polyethersulfone 3.10 Polyethylene terephthalate 3.1 Polycarbonate 3.17 Acrylic 3.5–4.5 Nylon 6 / 6 4.0-4.6 Polyurethane 6.3 Phenolic 6.5 Polyvinylidene fluoride 8.4

[0248] The first polymer and the second polymer can be present in the charged layer comprising discontinuous fibers in various suitable amounts. For example, in some embodiments, the first polymer comprises greater than or equal to 10 wt%, greater than or equal to 15 wt%, greater than or equal to 20 wt%, greater than or equal to 25 wt%, greater than or equal to 30 wt%, greater than or equal to 35 wt%, greater than or equal to 40 wt%, greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 65 wt%, greater than or equal to 70 wt%, greater than or equal to 75 wt%, greater than or equal to 80 wt%, or greater than or equal to 85 wt% of the fibers in the charged layer comprising discontinuous fibers. In certain embodiments, the first polymer comprises less than or equal to 90 wt%, less than or equal to 85 wt%, less than or equal to 80 wt%, less than or equal to 75 wt%, less than or equal to 70 wt%, less than or equal to 65 wt%, less than or equal to 60 wt%, less than or equal to 50 wt%, less than or equal to 40 wt%, less than or equal to 35 wt%, less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, or less than or equal to 15 wt% of the fibers in the charged layer comprising discontinuous fibers. Combinations of these ranges are also possible (e.g., greater than or equal to 10 wt% and less than or equal to 90 wt%, greater than or equal to 25 wt% and less than or equal to 75 wt%, greater than or equal to 35 wt% and less than or equal to 65 wt%). Other ranges are also possible.

[0249] In some embodiments, the second polymer is less than or equal to 90 wt%, less than or equal to 85 wt%, less than or equal to 80 wt%, less than or equal to 75 wt%, less than or equal to 70 wt%, less than or equal to 65 wt%, less than or equal to 60 wt%, less than or equal to 50 wt%, less than or equal to 40 wt%, less than or equal to 35 wt%, less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, or less than or equal to 15 wt% of the fibers in the charge-bearing layer comprising the discontinuous fibers. In certain embodiments, the second polymer is greater than or equal to 10 wt%, greater than or equal to 15 wt%, greater than or equal to 20 wt%, greater than or equal to 25 wt%, greater than or equal to 30 wt%, greater than or equal to 35 wt%, greater than or equal to 40 wt%, greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 65 wt%, greater than or equal to 70 wt%, greater than or equal to 75 wt%, greater than or equal to 80 wt%, or greater than or equal to 85 wt% of the fibers in the charge-bearing layer comprising the discontinuous fibers. Combinations of the above ranges are also possible (e.g., greater than or equal to 10 wt% and less than or equal to 90 wt%, greater than or equal to 25 wt% and less than or equal to 75 wt%, greater than or equal to 35 wt% and less than or equal to 65 wt%). Other ranges are also possible.

[0250] In some embodiments, relative to the total amount of fibers in the layer, the charge-bearing layer comprising the discontinuous fibers comprises a first polymer in an amount greater than or equal to 10 wt% and less than or equal to 90 wt% and a second polymer in an amount less than or equal to 90 wt% and greater than or equal to 10 wt%. For example, in some embodiments, relative to the total amount of fibers in the layer, the charge-bearing layer comprising the discontinuous fibers comprises a first polymer in an amount greater than or equal to 25 wt% and less than or equal to 75 wt% and a second polymer in an amount less than or equal to 75 wt% and greater than or equal to 25 wt%. In certain embodiments, relative to the total amount of fibers in the layer, the charge-bearing layer comprising the discontinuous fibers can comprise a first polymer in an amount greater than or equal to 35 wt% and less than or equal to 65 wt% and a second polymer in an amount less than or equal to 65 wt% and greater than or equal to 35 wt%. In certain embodiments, relative to the total amount of fibers in the layer, the charge-bearing layer comprising the discontinuous fibers comprises each of the first polymer and the second polymer in an amount of about 50 wt%.

[0251] In some embodiments, a charge-bearing layer that includes discontinuous fibers can include a plurality of fibers having a specific average fiber diameter. In some embodiments, the average fiber diameter of the plurality of fibers positioned in the charge-bearing layer that includes discontinuous fibers is greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 3 microns, greater than or equal to 5 microns, greater than or equal to 7 microns, greater than or equal to 9 microns, greater than or equal to 10 microns, greater than or equal to 12 microns, greater than or equal to 14 microns, greater than or equal to 15 microns, greater than or equal to 16 microns, greater than or equal to 18 microns, greater than or equal to 19 microns, greater than or equal to 20 microns, or greater than or equal to 21 microns. In certain embodiments, the average fiber diameter of the plurality of fibers positioned in the charge-bearing layer that includes discontinuous fibers is less than or equal to 22 microns, less than or equal to 21 microns, less than or equal to 20 microns, less than or equal to 19 microns, less than or equal to 18 microns, less than or equal to 16 microns, less than or equal to 15 microns, less than or equal to 14 microns, less than or equal to 12 microns, less than or equal to 10 microns, less than or equal to 9 microns, less than or equal to 7 microns, less than or equal to 5 microns, less than or equal to 4 microns, less than or equal to 3 microns, or less than or equal to 2 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 micron and less than or equal to 22 microns, greater than or equal to 1 micron and less than or equal to 15 microns, or greater than or equal to 15 microns and less than or equal to 22 microns). Other ranges are also possible.

[0252] When a charge-bearing layer that includes discontinuous fibers includes two or more types of fibers, each type of fiber can independently have an average fiber diameter within one or more of the above ranges, and / or all of the fibers in the charge-bearing layer that includes discontinuous fibers can be present within one or more of the above ranges. When the filter medium includes two or more charge-bearing layers that include discontinuous fibers, the foregoing can independently apply to each such layer.

[0253] In some embodiments, the charged layer comprising discontinuous fibers can comprise a plurality of relatively thin fibers (e.g., having an average fiber diameter less than 15 microns). For example, in certain embodiments, the plurality of relatively thin fibers have an average fiber diameter less than 15 microns, less than or equal to 14 microns, less than or equal to 12 microns, less than or equal to 10 microns, less than or equal to 9 microns, less than or equal to 7 microns, less than or equal to 5 microns, less than or equal to 4 microns, less than or equal to 3 microns, or less than or equal to 2 microns. In some embodiments, the plurality of relatively thin fibers have an average fiber diameter greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 3 microns, greater than or equal to 5 microns, greater than or equal to 7 microns, greater than or equal to 9 microns, greater than or equal to 10 microns, greater than or equal to 12 microns, or greater than or equal to 14 microns. Combinations of the above ranges are also possible (e.g., less than 15 microns and greater than or equal to 1 micron, less than 15 microns and greater than or equal to 3 microns, less than or equal to 12 microns and greater than or equal to 3 microns). Other ranges are also possible.

[0254] When the charged layer comprising discontinuous fibers comprises two or more types of fibers, each type of fiber can independently have an average fiber diameter within one or more of the above ranges, and / or all of the fibers in the charged layer comprising discontinuous fibers can together have an average fiber diameter within one or more of the above ranges. When the filter medium includes two or more charged layers comprising discontinuous fibers, the foregoing can independently apply to each such layer.

[0255] In some embodiments, the first plurality of fibers and / or the second plurality of fibers present in the charged layer comprising discontinuous fibers have a specific average maximum cross-sectional size, e.g., an average maximum cross-sectional size greater than or equal to 2 microns, greater than or equal to 2.5 microns, greater than or equal to 3 microns, greater than or equal to 5 microns, greater than or equal to 7 microns, greater than or equal to 9 microns, greater than or equal to 10 microns, greater than or equal to 12 microns, or greater than or equal to 14 microns. In some embodiments, the average maximum cross-sectional size of the first plurality of fibers and / or the second plurality of fibers in the charged layer comprising discontinuous fibers is less than or equal to 15 microns, less than or equal to 14 microns, less than or equal to 12 microns, less than or equal to 10 microns, less than or equal to 9 microns, less than or equal to 7 microns, less than or equal to 5 microns, or less than or equal to 3 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 2 microns and less than or equal to 15 microns). Other ranges are also possible.

[0256] The average maximum cross-sectional size of the fibers can be determined in accordance with test standard ASTM D2130-22.

[0257] In certain embodiments, the cross-sectional shape of the first plurality of fibers and / or the second plurality of fibers positioned within the charged layer comprising discontinuous fibers can be selected as desired. In some embodiments, the cross-sectional shape of the first plurality of fibers and / or the second plurality of fibers is selected from circular, oval, dogbone, kidney bean, ribbon, irregular, and multi-lobed. In a particular set of embodiments, the first plurality of fibers and / or the second plurality of fibers have a multi-lobed shape (e.g., bilobed, trilobed, quadrilobed, pentalobed, multi-lobed). As used herein, multi-lobed shaped fibers generally refer to fibers having two or more (e.g., three or more, four or more, five or more) lobes extending from the core of the fiber at the cross-section of the fiber. In some cases, the lobes can be of the same or different material as the core. In some embodiments, the lobes and the core of the fiber are of the same material. In certain embodiments, the fiber is a bicomponent or multicomponent fiber (e.g., the lobes and the core comprise different materials).

[0258] In some embodiments, the charged layer comprising discontinuous fibers comprises fibers (e.g., synthetic fibers, staple fibers) having an average length of less than 5 inches (127 mm). For example, the average length of the fibers in the charged layer comprising discontinuous fibers can be less than or equal to 100 mm, less than or equal to 80 mm, less than or equal to 60 mm, less than or equal to 40 mm, less than or equal to 20 mm, less than or equal to 10 mm, less than or equal to 5 mm, less than or equal to 1 mm, less than or equal to 0.5 mm, or less than or equal to 0.1 mm. In some cases, the average length of the fibers in the charged layer comprising discontinuous fibers can be greater than or equal to 0.02 mm, greater than or equal to 0.1 mm, greater than or equal to 0.5 mm, greater than or equal to 1 mm, greater than or equal to 5 mm, greater than or equal to 10 mm, greater than or equal to 20 mm, greater than or equal to 40 mm, greater than or equal to 60 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 mm and less than or equal to 80 mm, greater than or equal to 1 mm and less than or equal to 60 mm). Other ranges are also possible.

[0259] When the charged layer comprising discontinuous fibers comprises two or more types of fibers, each type of fiber can independently have an average fiber length within one or more of the above ranges, and / or all of the fibers in the charged layer comprising discontinuous fibers can together have an average fiber length within one or more of the above ranges. When the filter medium includes two or more charged layers comprising discontinuous fibers, the foregoing can apply independently to each such layer.

[0260] The basis weight of the charged layer containing discontinuous fibers can be selected as needed. For example, in some embodiments, the basis weight of the charged layer containing discontinuous fibers can be greater than or equal to 12 gsm, greater than or equal to 15 gsm, greater than or equal to 20 gsm, greater than or equal to 25 gsm, greater than or equal to 30 gsm, greater than or equal to 40 gsm, greater than or equal to 50 gsm, greater than or equal to 60 gsm, greater than or equal to 70 gsm, greater than or equal to 80 gsm, greater than or equal to 100 gsm, greater than or equal to 200 gsm, greater than or equal to 300 gsm, greater than or equal to 400 gsm, greater than or equal to 500 gsm, or greater than or equal to 600 gsm. In some cases, the basis weight of the charged layer containing discontinuous fibers can be less than or equal to 700 gsm, less than or equal to 600 gsm, less than or equal to 500 gsm, less than or equal to 400 gsm, less than or equal to 300 gsm, less than or equal to 200 gsm, less than or equal to 100 gsm, less than or equal to 90 gsm, less than or equal to 80 gsm, less than or equal to 70 gsm, less than or equal to 60 gsm, less than or equal to 50 gsm, less than or equal to 40 gsm, less than or equal to 30 gsm, less than or equal to 25 gsm, less than or equal to 20 gsm, or less than or equal to 15 gsm. Combinations of the above ranges are also possible (e.g., greater than or equal to 12 gsm and less than or equal to 700 gsm, greater than or equal to 12 gsm and less than or equal to 250 gsm, or greater than or equal to 15 gsm and less than or equal to 100 gsm). Other ranges are also possible.

[0261] The basis weight of the charged layer containing discontinuous fibers can be determined as described above for the basis weight of the nonwoven fibrous web with high performance.

[0262] When the filter medium includes two or more charged layers containing discontinuous fibers, each charged layer containing discontinuous fibers can independently have a basis weight within one or more of the above ranges.

[0263] In some cases, the charged layer containing discontinuous fibers can be designed to have a relatively high surface area and / or a relatively low number of fibers per gram (of the layer). Advantageously and without wishing to be bound by theory, compared to a layer having a relatively low surface area per unit mass and / or a relatively high number of fibers per gram of the layer, the charged layer containing discontinuous fibers having a relatively high surface area per gram (of the layer) and a relatively low number of fibers per gram (of the layer) can exhibit increased initial efficiency, increased charge generation (e.g., frictional charge), and / or reduced charge dissipation (e.g., during use of the layer and / or the filter medium including the layer).

[0264] In some embodiments, the BET surface area of the charged layer comprising discontinuous fibers is greater than or equal to 0.33 m 2 / g, greater than or equal to 0.35 m 2 / g, greater than or equal to 0.37 m 2 / g, greater than or equal to 0.4 m 2 / g, greater than or equal to 0.5 m 2 / g, greater than or equal to 0.6 m 2 / g, greater than or equal to 0.7 m 2 / g, greater than or equal to 0.8 m 2 / g, greater than or equal to 0.9 m 2 / g, greater than or equal to 1 m 2 / g, or greater than or equal to 1.2 m 2 / g. In some embodiments, the BET surface area of the charged layer comprising discontinuous fibers is less than or equal to 1.5 m 2 / g, less than or equal to 1.2 m 2 / g, less than or equal to 1 m 2 / g, less than or equal to 0.9 m 2 / g, less than or equal to 0.8 m 2 / g, less than or equal to 0.75 m 2 / g, less than or equal to 0.7 m 2 / g, less than or equal to 0.6 m 2 / g, less than or equal to 0.5 m 2 / g, less than or equal to 0.4 m 2 / g, less than or equal to 0.37 m 2 / g, or less than or equal to 0.35 m 2 / g. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.33 m 2 / g and less than or equal to 1.5 m 2 / g, greater than or equal to 0.35 m 2 / g and less than or equal to 1 m 2 / g). Other ranges are also possible.

[0265] The BET surface area of the layer can be measured by using standard BET surface area measurement techniques, for example, in accordance with Section 10 of the International Battery Commission Standard BCIS-03A, "Recommended Battery Materials Specifications Valve Regulated Recombinant Batteries", which is "Standard Test Method for Surface Area of Recombinant Battery Separator Mat". After this technique, the BET surface area can be measured using a BET surface analyzer (e.g., Micromeritics GeminiIII 2375 surface area analyzer) by adsorption analysis with nitrogen; in a 3 / 4-inch tube, the sample amount can be from 0.5 grams to 0.6 grams; and the sample can be degassed at 75 °C for at least 3 hours.

[0266] When the filter medium comprises two or more charged layers comprising discontinuous fibers, each charged layer comprising discontinuous fibers can independently have a BET surface area within one or more of the above ranges.

[0267] In certain embodiments, the charged layer comprising discontinuous fibers has a specific number of fibers per gram (of the fiber layer). In some embodiments, the charged layer comprising discontinuous fibers has less than or equal to 125,000 fibers per gram (of the layer), less than or equal to 120,000 fibers per gram, less than or equal to 110,000 fibers per gram, less than or equal to 105,000 fibers per gram, less than or equal to 103,000 fibers per gram, less than or equal to 100,000 fibers per gram, less than or equal to 95,000 fibers per gram, less than or equal to 90,000 fibers per gram, less than or equal to 80,000 fibers per gram, less than or equal to 75,000 fibers per gram, less than or equal to 70,000 fibers per gram, or less than or equal to 60,000 fibers per gram. In certain embodiments, the charged layer comprising discontinuous fibers has greater than or equal to 50,000 fibers per gram (of the layer), greater than or equal to 60,000 fibers per gram, greater than or equal to 70,000 fibers per gram, greater than or equal to 75,000 fibers per gram, greater than or equal to 80,000 fibers per gram, greater than or equal to 90,000 fibers per gram, greater than or equal to 95,000 fibers per gram, greater than or equal to 100,000 fibers per gram, greater than or equal to 103,000 fibers per gram, greater than or equal to 105,000 fibers per gram, greater than or equal to 110,000 fibers per gram, or greater than or equal to 120,000 fibers per gram. Combinations of the above ranges are also possible (e.g., less than or equal to 125,000 fibers per gram and greater than or equal to 50,000 fibers per gram, less than or equal to 105,000 fibers per gram and greater than or equal to 75,000 fibers per gram). Other ranges are also possible.

[0268] The number of fibers per gram can be determined by dividing the average BET surface area of the layer by the average geometric surface area of the fibers in the (charged) fiber layer. The average geometric surface area of the fibers in the layer can be determined by measuring the average cross-sectional perimeter of the fibers (e.g., by scanning electron microscopy) and multiplying by the average fiber length.

[0269] When the charged layer comprising discontinuous fibers comprises two or more types of fibers, each type of fiber can independently have a number of fibers per gram within one or more of the above ranges, and / or all of the fibers in the charged layer comprising discontinuous fibers can together have a number of fibers per gram within one or more of the above ranges. When the filter medium includes two or more charged layers comprising discontinuous fibers, the foregoing can apply independently to each such layer.

[0270] In one exemplary embodiment, the charged layer comprising discontinuous fibers has greater than or equal to 0.33 m 2 / g (e.g., greater than or equal to 0.33 m 2 / g and less than or equal to 1.5 m 2The BET surface area of ( / g) and less than or equal to 125,000 fibers per gram (e.g., less than or equal to 125,000 fibers per gram and greater than or equal to 50,000 fibers) for the (charged fiber layer).

[0271] The charged layer containing discontinuous fibers can have various suitable uncompressed thicknesses. In some embodiments, the uncompressed thickness of the charged layer containing discontinuous fibers can be greater than or equal to greater than or equal to 5 mils, greater than or equal to 10 mils, greater than or equal to 25 mils, greater than or equal to 30 mils, greater than or equal to 50 mils, greater than or equal to 100 mils, greater than or equal to 200 mils, greater than or equal to 250 mils, greater than or equal to 300 mils, greater than or equal to 350 mils, greater than or equal to 400 mils, greater than or equal to 450 mils, or greater than or equal to 500 mils. In certain embodiments, the uncompressed thickness of the charged layer containing discontinuous fibers can be less than or equal to 600 mils, less than or equal to 500 mils, less than or equal to 450 mils, less than or equal to 400 mils, less than or equal to 350 mils, less than or equal to 300 mils, less than or equal to 250 mils, less than or equal to 200 mils, less than or equal to 100 mils, less than or equal to 50 mils, less than or equal to 25 mils, or less than or equal to 10 mils. Combinations of the above ranges are also possible (e.g., greater than or equal to 5 mils and less than or equal to 600 mils, greater than or equal to 30 mils and less than or equal to 350 mils). Other ranges are also possible.

[0272] The uncompressed thickness of the charged layer containing discontinuous fibers can be determined using a Mitutoyo thickness gauge. Briefly, the layer can be compressed with a circular probe having a diameter of 1 mm at at least three different weights (e.g., 10 grams, 5 grams, 2 grams). Ordinary least squares linear regression can be determined for each weight and the corresponding thickness, which can be used to calculate the thickness of the layer corresponding to an applied weight of 0 grams (i.e., the uncompressed thickness of the layer).

[0273] When the filter medium includes two or more charged layers containing discontinuous fibers, each charged layer containing discontinuous fibers can independently have an uncompressed thickness within one or more of the above ranges.

[0274] The air permeability of the charged layer comprising discontinuous fibers can have various suitable air permeabilities. In some embodiments, the air permeability of the charged layer comprising discontinuous fibers is greater than or equal to 10 CFM, greater than or equal to 25 CFM, greater than or equal to 50 CFM, greater than or equal to 80 CFM, greater than or equal to 100 CFM, greater than or equal to 200 CFM, greater than or equal to 250 CFM, greater than or equal to 300 CFM, greater than or equal to 350 CFM, greater than or equal to 400 CFM, greater than or equal to 450 CFM, greater than or equal to 500 CFM, greater than or equal to 550 CFM, greater than or equal to 600 CFM, greater than or equal to 650 CFM, greater than or equal to 700 CFM, greater than or equal to 750 CFM, greater than or equal to 800 CFM, greater than or equal to 850 CFM, greater than or equal to 900 CFM, greater than or equal to 950 CFM, greater than or equal to 1000 CFM, greater than or equal to 1050 CFM, greater than or equal to 1100 CFM, or greater than or equal to 1150 CFM. In certain embodiments, the air permeability of the charged layer comprising discontinuous fibers is less than or equal to 1200 CFM, less than or equal to 1150 CFM, less than or equal to 1100 CFM, less than or equal to 1050 CFM, less than or equal to 1000 CFM, less than or equal to 950 CFM, less than or equal to 900 CFM, less than or equal to 850 CFM, less than or equal to 800 CFM, less than or equal to 750 CFM, less than or equal to 700 CFM, less than or equal to 650 CFM, less than or equal to 600 CFM, less than or equal to 550 CFM, less than or equal to 500 CFM, less than or equal to 450 CFM, less than or equal to 400 CFM, less than or equal to 350 CFM, less than or equal to 300 CFM, less than or equal to 250 CFM, less than or equal to 200 CFM, less than or equal to 150 CFM, less than or equal to 100 CFM, less than or equal to 80 CFM, less than or equal to 50 CFM, or less than or equal to 25 CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 10 CFM and less than or equal to 1200 CFM, greater than or equal to 80 CFM and less than or equal to 1200 CFM, greater than or equal to 50 CFM and less than or equal to 650 CFM). Other ranges are also possible.

[0275] The air permeability of the charged layer comprising discontinuous fibers can be determined in the manner described above for determining the air permeability of a nonwoven web having high performance.

[0276] In some embodiments, the filter medium includes a backing. The backing can be a relatively porous layer that provides structural support for one or more other layers in the filter medium (e.g., a high-performance nonwoven web, a nonwoven web containing nanofibers) and / or for the filter medium as a whole. The backing can also contribute to pleatability. In some embodiments, the presence of the backing may not significantly affect the air permeability of the filter medium.

[0277] The air permeability of the backing can be selected as needed. In some embodiments, the air permeability of the backing is greater than or equal to 200 CFM, greater than or equal to 225 CFM, greater than or equal to 250 CFM, greater than or equal to 275 CFM, greater than or equal to 300 CFM, greater than or equal to 350 CFM, greater than or equal to 400 CFM, greater than or equal to 500 CFM, greater than or equal to 750 CFM, greater than or equal to 1000 CFM, or greater than or equal to 1250 CFM. In some embodiments, the air permeability of the backing is less than or equal to 1500 CFM, less than or equal to 1000 CFM, less than or equal to 750 CFM, less than or equal to 500 CFM, less than or equal to 400 CFM, less than or equal to 350 CFM, less than or equal to 300 CFM, less than or equal to 275 CFM, less than or equal to 250 CFM, or less than or equal to 225 CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 200 CFM and less than or equal to 1500 CFM, greater than or equal to 250 CFM and less than or equal to 1250 CFM, or greater than or equal to 300 CFM and less than or equal to 1000 CFM). Other ranges are also possible.

[0278] The air permeability of the backing can be measured in the same manner as the air permeability of the high-performance nonwoven webs described elsewhere herein.

[0279] When the filter medium includes two or more backings, each backing can independently have an air permeability within one or more of the above ranges.

[0280] The stiffness of the backing can be selected as needed. In some embodiments, the stiffness of the backing is greater than or equal to 300 mg, greater than or equal to 350 mg, greater than or equal to 400 mg, greater than or equal to 450 mg, greater than or equal to 500 mg, greater than or equal to 600 mg, greater than or equal to 750 mg, greater than or equal to 1000 mg, greater than or equal to 1250 mg, greater than or equal to 1500 mg, greater than or equal to 1750 mg, greater than or equal to 2000 mg, greater than or equal to 2250 mg, greater than or equal to 2500 mg, or greater than or equal to 2750 mg. In some embodiments, the stiffness of the backing is less than or equal to 3000 mg, less than or equal to 2750 mg, less than or equal to 2500 mg, less than or equal to 2250 mg, less than or equal to 2000 mg, less than or equal to 1750 mg, less than or equal to 1500 mg, less than or equal to 1250 mg, less than or equal to 1000 mg, less than or equal to 750 mg, less than or equal to 600 mg, less than or equal to 500 mg, less than or equal to 450 mg, less than or equal to 400 mg, or less than or equal to 350 mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 300 mg and less than or equal to 3000 mg, greater than or equal to 400 mg and less than or equal to 2500 mg, or greater than or equal to 500 mg and less than or equal to 2000 mg). Other ranges are also possible.

[0281] The stiffness of the backing can be determined according to TAPPI T543 om-94.

[0282] When the filter medium includes two or more backings, each backing can independently have a stiffness within one or more of the above ranges.

[0283] In some embodiments, the filter medium includes a grid. The grid can comprise a plurality of strands (e.g., connected to each other in one or more locations). The strands can comprise metal, synthetic material, and / or natural material. The strands can be flexible and / or ductile.

[0284] In some embodiments, the grid has a relatively high air permeability. In other words, it can be a relatively porous layer. In some embodiments, the air permeability of the grid is greater than or equal to 500 CFM, greater than or equal to 750 CFM, greater than or equal to 1000 CFM, or greater than or equal to 1250 CFM. In some embodiments, the air permeability of the backing is less than or equal to 1500 CFM, less than or equal to 1000 CFM, or less than or equal to 750 CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 500 CFM and less than or equal to 1500 CFM). Other ranges are also possible.

[0285] The air permeability of the grid can be measured in the same manner as the air permeability of the high-performance nonwoven webs described elsewhere herein.

[0286] When the filter medium includes two or more grids, each grid can independently have an air permeability within one or more of the above ranges.

[0287] In some embodiments, the filter medium includes one or more layers (e.g., a high-performance nonwoven web, an adsorption layer, a nonwoven web including nanofibers, a charged layer including discontinuous fibers) held in a corrugated or curved configuration by one or more support layers. Such layers may be referred to herein as "corrugated layers." In some embodiments, the corrugated configuration of the corrugated layer can increase the surface area of the layer relative to a planar layer of similar length, thereby resulting in improved filtration characteristics such as efficiency and air resistance. In addition to the corrugated layer, the filter media described herein can include one or more non-corrugated layers.

[0288] Figure 4A A non-limiting example of the corrugated configuration of the filter medium is shown, which includes a corrugated layer and a support layer that holds the corrugated layer in a corrugated configuration to keep the peaks and valleys of adjacent corrugations of the filter layer separated. As Figure 4A shown, the filter medium 10 can include a corrugated layer 12 positioned between a first support layer 16 and an optional second support layer 14. Although two support layers (e.g., 14 and 16) are shown, it should be understood that the filter medium 10 does not need to include two support layers. In the case where only one support layer is provided, the support layer can be disposed on the top or bottom surface of the corrugated layer (e.g., upstream or downstream). One or more support layers (e.g., 14, 16) can help hold the corrugated layer 12 and any optional additional layers or webs in a corrugated configuration, as further described below.

[0289] As described herein, in some embodiments, the filter medium 10 can also include one or more optional layers. For example, the filter medium 10 can optionally include one or more cover layers located on the top (e.g., most upstream) and / or bottom (e.g., most downstream) sides of the filter medium 10. As Figure 4A shown, the filter medium 10 can include a cover layer 18 positioned on the top (e.g., most upstream) side of the filter medium. In certain embodiments, the cover layer 18 can serve as an aesthetic layer or an abrasion-resistant layer. In some such embodiments, as Figure 4AAs shown, the filter medium can be configured such that the cover layer 18 is positioned on the fluid (e.g., air) inlet side (labeled I) of the filter medium, the support layer 16 is positioned directly or indirectly adjacent to the cover layer 18 (e.g., downstream of the cover layer 18), the filter layer 12 is positioned directly or indirectly adjacent to the support layer 16 (e.g., downstream of the support layer 16), and an optional second support layer 14 is positioned directly or indirectly adjacent to the filter layer 12 (e.g., downstream of the filter layer 12) on the fluid (e.g., air) outlet side (labeled O). The direction of fluid (e.g., air) flow (i.e., from fluid inlet I to fluid outlet O) is indicated by the arrow labeled A.

[0290] In some embodiments, as Figure 4B shown, in addition to Figure 4A the optional cover layer 18 in Figure 4A or as an alternative to the optional cover layer 18 in

[0291] In some embodiments, as Figure 4A and Figure 4B shown, the optional cover layer can have a different topography from that of the corrugated layer and / or the support layer. For example, whether the filter medium is in a pleated or non-pleated configuration, the cover layer can be non-corrugated (e.g., substantially planar), while the corrugated layer and / or the support layer can have a corrugated configuration.

[0292] Some or all of the layers may be formed into a corrugated configuration using various manufacturing techniques, but in one exemplary embodiment, the corrugated layer, at least one support layer, and any additional fibrous webs or layers are positioned adjacent to one another from the air inlet side to the air outlet side in a desired arrangement, and the combined layers are conveyed between a first moving surface and a second moving surface traveling at different speeds (e.g., where the second surface travels at a slower speed than the first surface). As the layers travel from the first moving surface to the second moving surface, a suction force (e.g., a vacuum force) may be used to pull the layers toward the first moving surface and then toward the second moving surface. The speed differential causes the layers to form z-direction corrugations as they are transferred onto the second moving surface, thereby forming peaks and valleys in the layers. The speed of each surface may be varied to obtain a desired number of corrugations per inch. The distance between the surfaces may also be varied to determine the amplitude of the peaks and valleys, and in one exemplary embodiment, the distance is adjusted to be between 0.025 inches and 4 inches. For example, the amplitude of the peaks and valleys may be from about 0.1 inches to 2.0 inches, such as from about 0.1 inches to 1.0 inches or from about 0.1 inches to 2.0. For certain applications, the amplitude of the peaks and valleys may be from about 0.1 inches to 1.0 inches, from about 0.1 inches to 0.5 inches, or from about 0.1 inches to 0.3 inches. The properties of the different layers may also be varied to obtain a desired filter media configuration. In one exemplary embodiment, the filter media has from about 2 to 6 corrugations per inch, where the height (total thickness) is in the range of about 0.025 inches to 2 inches, although this may vary significantly depending on the intended application. For example, in some other embodiments, the filter media may have from about 2 to 4 corrugations per inch, such as about 3 corrugations per inch. As Figure 4A shown, a single corrugation W extends from the middle of one peak to the middle of an adjacent peak.

[0293] In Figure 4A the embodiment shown, when the corrugated layer 12 and the support layer are corrugated, as Figure 5As shown, the resulting corrugated layer 12 will have a plurality of peaks P and valleys T on each of its surfaces (i.e., the air inlet side I and the air outlet side O). The support layer will extend across the peaks P and into the valleys T such that the support layer also has a corrugated configuration. Those skilled in the art will understand that the peaks P on the air inlet side I of the filter layer will have corresponding valleys T on the air outlet side O. Thus, the downstream support layer will extend into the valleys T, and directly opposite the same valley T is the peak P across which the upstream support layer will extend. Since the downstream support layer extends into the valleys T on the air outlet side O of the filter layer, the downstream support layer (if provided) will keep the adjacent peaks P on the air outlet side O spaced apart from each other, and will keep the adjacent valleys T on the air outlet side O spaced apart from each other. The upstream support layer (if provided) can similarly keep the adjacent peaks P on the air inlet side I of the filter layer spaced apart from each other, and can keep the adjacent valleys T on the air inlet side I of the filter layer spaced apart from each other. As a result, the corrugated layer has a significantly increased surface area compared to the surface area it would have in a planar configuration. In some exemplary embodiments, the surface area of the corrugated configuration is increased by at least about 50% compared to the surface area of the same layer in a planar configuration, and in some cases up to 120%.

[0294] In embodiments where one or more support layers hold the corrugated layer in a corrugated configuration, it may be desirable to reduce the amount of free volume (e.g., the volume not occupied by any fibers) in the valleys. That is, a relatively high percentage of the volume in the valleys can be occupied by the support layer to give structural support to the corrugated layer. For example, at least 95% or substantially all of the available volume in the valleys can be filled with the support layer, and the support layer can have a density in the range of about 1% to 90%, about 1% to 50%, about 10% to 50%, or about 20% to 50%. Additionally, as Figure 4A shown in the exemplary embodiment of, the support layer extending across the peaks and into the valleys can result in the surface area of the support layer in contact with the cover layer 18 being similar across the peaks and across the valleys. Similarly, Figure 4B the surface area of the support layer in contact with the cover layer 18B shown in can be similar across the peaks and across the valleys. For example, the surface area of the support layer in contact with the top or bottom layer across the peaks can differ from the surface area of the support layer in contact with the cover layer across the valleys by less than about 70%, less than about 50%, less than about 30%, less than about 20%, less than about 10%, or less than about 5%.

[0295] In certain exemplary embodiments, one or more support layers may have a greater fiber density at the peaks than in the valleys; and in some embodiments, a smaller fiber mass at the peaks than in the valleys. In some embodiments, this may be caused by the roughness of the support layer relative to the corrugated layer. In particular, when the layer is transferred from a first moving surface to a second moving surface, the relatively delicate nature of the corrugated layer may allow the support layer to conform to the waves formed in the corrugated layer. When the support layer extends across a peak P, the distance traveled will be less than the distance each support layer travels to fill a valley. As a result, the support layer may be compacted at the peaks, and thus have an increased fiber density at the peaks compared to the valleys through which the layer travels to form the annular structure.

[0296] After the layer is formed into a corrugated structure, the corrugated shape may be maintained by activating binder fibers to affect the bonding of the fibers. Various techniques may be used to activate the binder fibers. For example, if bicomponent binder fibers having a core and a sheath are used, the binder fibers may be activated by applying heat. If single-component binder fibers are used, the binder fibers may be activated by applying heat, steam, and / or some other form of warm moisture. Those skilled in the art will also understand that various techniques other than using binder fibers may optionally be used to connect the layers to each other. The layers may also be separate binder layers, and / or they may be connected (including bonded) to each other before being corrugated.

[0297] In some embodiments, the filter media described herein and / or one or more layers positioned therein (e.g., high-performance nonwoven webs, adsorption layers, nonwoven webs comprising nanofibers, charged layers comprising discontinuous fibers) include irregular structures. The irregular structures may be used to increase the surface area of the filter media per unit volume of the filter media, which may increase the γ and / or dust holding capacity of the filter media.

[0298] Figure 6 A non-limiting example of a filter media including an irregular structure is shown in Figure 6 In, the irregular structure is present at least at the surface of the filter media; thus, Figure 6 shows a filter media 602 including an irregular structure at the surface. Figure 6The filter medium shown in includes a plurality of peaks 612. The plurality of peaks 612 includes peaks 612A, 612B, 612C, 612D, and 612E separated by valleys 614A, 614B, 614C, and 614D. Each peak has a height and a width. Peaks that are not on the outer edge of the filter medium (i.e., peaks 612B, 612C, and 612D) have two nearest neighbor spacings; those on the outer edge of the filter medium (i.e., peaks 612A and 612E) have one nearest neighbor spacing. As an example, peak 612D has a height 612DH, a width 612DW, and two nearest neighbor spacings 612DA and 612DB. These features of the peaks can be determined by means of a scanning optical microscope such as a Keyence VR-3000G2, Measurement Unit Model VR3200 Wide-Area 3D Measurement system. The surface topography of the filter medium can be measured using a scanning optical microscope at a resolution of at least 25 microns in each of the x-axis and y-axis and at least 0.5 microns in the z-axis according to the standards described in ISO 25178 (2006). This measurement produces a numerical matrix representing the surface height measured at a set of points on the sample, where the x-position and y-position of each measured surface height are given by the columns and rows of the matrix, respectively. Then, such a z-value can be defined as the reference height (as shown by the dashed line 616 in Figure 6 ): 95% of the points constituting the measured surface topography are higher than the z-value and 5% of the points constituting the measured surface topography are lower than the z-value. This reference height can be subtracted from the heights of the points in the measured surface topography to produce the relative height of the points in the measured surface topography and the relative surface topography composed of the relative height values.

[0299] The relative surface topography can then undergo further computational processing according to ISO 16610-21:2011 to determine the height of each peak. The computational process can include the following steps in sequence: (1) removing the outer 10% of the points from each edge to reduce edge effects; (2) applying a Gaussian filter with a kernel size of 30 pixels to smooth the resulting data; (3) converting the resulting data into a set of line data by selecting every 10th row; and (4) identifying local maxima. The local maxima identified in step (4) are the peak heights. The spacing between two peaks can be determined by finding the difference between the positions of the points at which these local maxima occur. Figure 7 An example of the relative surface topography measured after step (2) according to this procedure is shown, and Figure 8A An example of a set of line data measured after step (3) according to this procedure is shown. Figure 8B ​An example of a set of line data is shown that identifies local maxima (shown as larger points) and is used to determine the peak height (Hi) and the spacing (Di) between two adjacent peaks.

[0300] In some embodiments, as Figures 6 to 8B shown in, the peaks within a plurality of peaks can differ from each other in one or more respects. For example, the plurality of peaks can include two or more peaks having different heights, different spacings from their nearest neighbors, and / or different shapes. As an example, referring to Figure 6 , the height 612DH of peak 612D is different from the height 612BH of peak 612B. As another example, the spacing 612DA between peak 612C and peak 612D is different from the spacing 612DB between peak 612D and peak 612E. In some embodiments, the plurality of peaks do not include two peaks having the same height, do not include two sets of peaks having the same spacing, and / or do not include two peaks having the same width. For example, an irregular structure and / or a filter medium may not include peaks having the same height, spacing, and / or width as another peak.

[0301] In some embodiments, the plurality of peaks include two or more peaks that are similar to each other in one or more respects. For example, the plurality of peaks can include two peaks having the same height, two sets of peaks having the same spacing, and / or two peaks having the same width. As an example, referring to Figure 6 , the height 612BH of peak 612B has the same value as the height 612DH of peak 612D. In some embodiments, the plurality of peaks include two or more peaks that are similar to each other in one or more respects (e.g., having the same height, the same spacing from the nearest neighbor, and / or the same width) and two or more peaks that are different from each other in one or more respects (e.g., having different heights, different spacings from their nearest neighbors, and / or different widths). Referring again to Figure 6 , the plurality of peaks 612 include peak 612B and peak 612E having heights 612BH and 612EH that have the same value, and also include peak 612D having a height 612DH that has a value different from 612DH and 12BH.

[0302] It should be understood that an irregular structure can be present at any location within the filter medium, but need not be present at all locations. For example, some filter media can include a first surface having an irregular structure (e.g., a plurality of peaks) like the filter medium shown in Figure 6 , and include a second surface opposite the first surface, which is relatively regular (e.g., flat) or completely free of irregular structures (e.g., peaks) in comparison. As compared with Figure 6The filtration media shown are different. Some filtration media can include two opposing surfaces, each of which includes an irregular structure. For example, some filtration media can include two opposing surfaces, each of which includes a plurality of peaks and / or each of which includes a plurality of peaks that are irregular in one or more respects. In some embodiments, as will be described in more detail below, the filtration media includes a first surface and a second surface. The first surface includes a first plurality of peaks that are irregular in one or more respects. The second surface includes a second plurality of peaks that are similar to the plurality of valleys between the peaks located in the first plurality of peaks in all respects except amplitude. The second plurality of peaks can have the same (or substantially similar) position, shape, spacing, and / or width as the plurality of valleys between the peaks located in the first plurality of peaks, but may have a smaller height.

[0303] If one or more portions of the filtration media described herein (e.g., one or more layers thereof, one or more surfaces thereof) include an irregular structure, it should be understood to include the irregular structure. The irregular structure (e.g., a plurality of peaks) can be located at one or more surfaces of the filtration media, within the interior of the filtration media, and / or throughout the filtration media. As an example, a filtration media including an irregular structure can include: a plurality of peaks that are irregular in one or more respects and are present at one or more surfaces of the filtration media; a plurality of peaks that extend through one or more layers of the filtration media; and / or a plurality of peaks that are present at one or more surfaces of the layers of the filtration media.

[0304] It should also be understood that in embodiments where the irregular structure is not present at the outer surface of the filtration media, the characteristics of the irregular structure can be measured by removing the portion of the filtration media that blocks the irregular structure from the measurement and measuring the irregular structure as described above. For example, in some embodiments, the filtration media includes two opposing layers that do not include an irregular structure, but includes a layer that includes an irregular structure (e.g., a plurality of peaks that are irregular in one or more respects) located between the two opposing layers that do not include an irregular structure. For such a filtration media, the layer including one of the surfaces that does not include an irregular structure can be removed so that the irregular structure is exposed, and the characteristics of the exposed irregular structure can be measured by optical microscopy as described above.

[0305] Some layers can be topologically connected throughout the layer, and some layers can include two or more portions that are topologically unconnected to each other. For example, Figure 9A An example of a filtration media 902 is shown. The filtration media 902 includes a first layer 900 that is topologically connected throughout the layer and a second layer 904 that includes portions (e.g., portions 916A and 916B) that are topologically unconnected to each other.Figure 9B A perspective view of the same filter medium is shown. Although not shown in Figures 9A to 9B , either type of layer may include an irregular structure. In addition, some layers may not have portions that can be removed from the layer without using a dedicated tool and / or without breaking the layer, and some layers may include such portions.

[0306] In some embodiments, the layers in the filter medium adopt the form of a layer for the first time when incorporated into the filter medium. In other words, a collection of articles that are not layers before being incorporated into the filter medium can be considered to form a layer of the filter medium after being incorporated therein. A specific example of such a layer is a plurality of elastically extensible fibers. Before being incorporated into the filter medium, the plurality of fibers can be independent and mechanically unconnected fibers. After being incorporated into the filter medium, the elastically extensible fibers can have a common function (e.g., serving as a scrim) and / or can separate two layers (e.g., an efficiency layer and a support layer). Figure 10 An example of a plurality of elastically extensible fibers forming layer 1004 positioned between layers 1000 and 1018 is shown. Non-limiting examples of suitable layers include nonwoven fiber webs, grids, a plurality of fibers that do not directly contact each other and / or are not mechanically connected to each other, and an adhesive that adheres two layers together (the adhesive being positioned between the two layers).

[0307] For example, by referring to Figure 6 , the filter medium 602 can be a single-layer filter medium. As another example, also by referring to Figure 6 , the filter medium 602 can be a filter medium including two or more layers. Figure 11AFIG. 0 shows a non-limiting embodiment of a filter medium 1102 including a first layer 1100 and a second layer 1104. In some embodiments, the filter medium can include one or more layers including an irregular structure. The irregular structure can include an irregular spatial conformation of the layer. For example, the layer or a portion thereof can have a non-planar spatial conformation having one or more irregular features. In some embodiments, the entire thickness of the layer or a portion of its entire thickness can be arranged as three-dimensional peaks and valleys. In such a case, each non-terminal peak is adjacent to a valley, and each non-terminal valley is adjacent to a peak. In other words, the layer can have a structure such that each peak on one side of the layer has a corresponding valley on the opposite side of the layer, and each valley on one side of the layer has a corresponding peak on the opposite side of the layer. The plurality of valleys can be similar to their corresponding plurality of peaks in one or more respects, and / or the plurality of peaks can be similar to their corresponding plurality of valleys in one or more respects. For example, a pair of corresponding valleys and peaks can be located at substantially the same position, can have substantially the same peak height, can have substantially the same peak width, can have substantially the same peak shape, and / or can have substantially the same nearest neighbor spacing. A layer arranged such that its entire thickness is arranged as three-dimensional peaks and valleys can be referred to as a layer including a plurality of peaks extending through the entire thickness of the layer and / or a undulating layer.

[0308] An example of an undulating layer is Figure 11A layer 1100 in Figure 11A Layer 1100 in includes a plurality of peaks 1112, the plurality of peaks 1112 including peaks 1112A, 1112B, 1112C, 1112D, and 1112E separated by valleys 1114A, 1114B, 1114C, and 1114C. Valleys 1114A, 1114B, 1114C, and 1114C together form a plurality of valleys 1114 (not shown). These peaks and valleys are present at the upper side of layer 1100 (and of filter medium 1102). The plurality of peaks 1112 have corresponding plurality of valleys 1112O (not shown), the plurality of valleys 1112O including valleys 1112AO, 1112BO, 1112CO, 1112DO, and 1112EO on the bottom side of layer 1110, and the plurality of valleys 1114T (not shown) have corresponding plurality of peaks 1114TO (not shown), the plurality of peaks 1114TO including peaks 1114AO, 1114BO, 1114CO, and 1114DO. In some embodiments, when viewed in cross-section, the profile of the top surface of the undulating layer (e.g., layer 1100) can be substantially the same as the profile of the bottom surface of the undulating layer.

[0309] In some embodiments, the undulating layer has a structure indicative of a layer that has no undulations at some time points and has undergone a process to make it undulate. The undulating layer can include portions in tension (e.g., the upper surface of a peak, the lower surface of a valley positioned between peaks) and / or portions in compression (e.g., the lower surface of a peak, the upper surface of a valley positioned between peaks). The layer can be made to undulate by various suitable processes such as folding, curling, pleating, etc. In some embodiments, heat shrinkage can be performed to make one or more layers undulate. For example, one or more layers can be disposed on a layer having high heat shrinkage, and the layer having high heat shrinkage can be heated, thereby causing it to shrink and causing the one or more layers disposed thereon to become undulated.

[0310] In some embodiments, the filter medium includes a layer that does not include an irregular structure. The layer that does not include an irregular structure can not include any peaks (e.g., it can be relatively flat), or it can include a regular plurality of peaks. For example, like Figure 11A the filter medium shown in, the filter medium can include a layer that includes an irregular structure (e.g., a plurality of peaks) and a layer that does not include an irregular structure (e.g., peaks). For example, Figure 11A the filter medium 1102 shown in includes a layer 1100 that contains a plurality of peaks (e.g., 1112A, 1112B, 1112C, 1112D, and 1112E), and also includes a layer 1104 that does not contain any peaks. In embodiments where the layer such as Figure 11A the layer 1100 shown in includes a plurality of peaks, the peaks can have one or more irregular features as described herein.

[0311] In some embodiments, the filter medium includes two or more layers that include an irregular structure (e.g., two or more layers that include a plurality of peaks that are irregular in one or more respects) and two or more layers that do not include an irregular structure (e.g., two or more layers that have no peaks or include a regular plurality of peaks). For such embodiments, the layers can be arranged relative to each other in various suitable ways. For example, two layers each including a plurality of peaks that are irregular in one or more respects are positioned on opposite sides of a layer that does not have a plurality of peaks that are irregular in one or more respects. A filter medium having this structure can be manufactured by pleating two layers on opposite sides of a reversibly stretchable layer. As another example, two layers that each do not have a plurality of peaks that are irregular in one or more respects can be positioned on opposite sides of a layer that includes a plurality of peaks that are irregular in one or more respects. For example, one or more layers that include a plurality of peaks can be positioned between two outer layers that are completely without peaks and / or are relatively flat.

[0312] In some embodiments, the filter medium comprises only a layer having a plurality of peaks that are irregular in one or more respects.

[0313] Some filter media (such as Figure 11A as shown therein) comprise a single layer having a plurality of peaks. Some filter media comprise two or more layers each comprising a plurality of peaks. Figure 11B A non-limiting embodiment of a filter medium comprising two layers each comprising a plurality of peaks is shown. In Figure 11B therein, the filter medium 1102 comprises a first layer 1100, a second layer 1104, and a third layer 1118. The first layer 1100 and the third layer 1118 each comprise two opposite surfaces. In both the first layer 1100 and the third layer 1118, the first surface comprises a plurality of peaks separated by a plurality of valleys. The surface opposite the first surface in each of these layers comprises a plurality of valleys corresponding to the peaks present in the first surface of the layer and a plurality of peaks corresponding to the valleys present in the first surface of the layer.

[0314] In some embodiments, the filter medium comprises two or more layers that co-undulate. For example, in Figure 11B therein, the first layer and the third layer are also two undulating layers that co-undulate. In other words, both the first layer and the third layer are undulating, and the first layer comprises a first plurality of peaks that are substantially similar to a second plurality of peaks present in the third layer. Referring to Figure 11B therein, the plurality of peaks present in the upper surface of the layer 1100 are substantially similar to the plurality of peaks present in the upper surface of the layer 1118. In some cases where the first layer and the third layer co-undulate, the plurality of peaks and valleys in the first layer are substantially the same as the third layer. In some embodiments, the filter medium comprises two or more layers that are undulating but not co-undulating. For example, the filter medium can comprise two layers that undulate on opposite sides of a non-undulating layer. As another example, the filter medium can comprise a first layer and a second layer that are both undulating and comprise undulations that are substantially similar in position, but have substantially different amplitudes for their undulations (e.g., substantially different average peak heights). Some filter media can comprise some layers that co-undulate and some layers that undulate individually.

[0315] The filter media described herein can be manufactured in a variety of suitable ways. Figures 12A to 12CShown is a method of manufacturing a filter medium that can be particularly advantageous. In this method, a layer capable of undergoing reversible stretching is used to pleat a layer having a relatively low stiffness to form a undulating layer. The layer capable of undergoing reversible stretching is stretched, and while it is in the stretched state (i.e., while it is in the form of the reversibly stretchable layer), the layer having a relatively low stiffness is deposited onto the layer capable of undergoing reversible stretching. Then, when the reversibly stretchable layer recovers, it pulls back the layer having a relatively low stiffness with it, thereby pleating the layer having a relatively low stiffness. The reversibly stretchable layer can recover completely (i.e., return to its initial dimensions before being stretched) or partially (i.e., return to a dimension between its initial dimensions before being stretched and its dimensions while in the stretched state). In other words, the layer capable of undergoing reversible stretching can be stretched in a fully reversible manner or in a partially reversible and partially irreversible manner. Figure 12A Shown is a possible first step of reversibly stretching a layer capable of undergoing reversible stretching, such as a scrim, to a stretched state. Figure 12B Shown is a possible second step of depositing a layer, such as an efficiency layer, onto the reversibly stretchable layer. Figure 6 C shows the recovery of the reversibly stretchable layer. During the recovery process, the layer having a relatively low stiffness pleats and forms a plurality of peaks that are irregular in height, spacing, width, and / or shape. The reversibly stretchable layer can hold the peaks in place.

[0316] In some embodiments, like Figures 12A to 12C the embodiment shown in Figures 12A to 12C the reversibly stretchable layer can be a layer that is topologically connected throughout the layer. Similarly, and also like Figures 9A to 9B the embodiment shown in Figures 12D to 12F Shown is a schematic description of such a process.

[0317] Generally, any suitable number of layers can be undulated (e.g., by pleating) using a layer capable of undergoing reversible stretching. In some embodiments, in Figures 12A to 12CNot shown in the figure, after depositing a layer with relatively low stiffness on the reversibly stretchable layer, one or more additional layers can be deposited on the reversibly stretchable layer. In some embodiments, one or more additional layers can be deposited on the reversibly stretchable layer together with the layer with relatively low stiffness. One or more additional layers can be deposited before the reversibly stretchable layer recovers. For example, a nonwoven web containing nanofibers can be deposited on a high-performance nonwoven web deposited on a reversibly stretchable scrim. Then, as Figure 12C shown, the reversibly stretchable layer can be allowed to recover. During this step, the layers deposited on the reversibly stretchable layer (e.g., deposited on the layer with relatively low stiffness and / or deposited together with the layer with relatively low stiffness) can become undulated (e.g., by pleating). In some embodiments, like Figure 11B the embodiment shown, the layers can undulate and / or pleat together. After undulating and / or pleating, the layers can be held in the undulated and / or pleated configuration by the reversibly stretchable layer. One or more additional layers deposited on the reversibly stretchable layer other than the layer with relatively low stiffness can also have relatively low stiffness, which can facilitate this favorable pleating. In some embodiments, one or more additional layers can be deposited on the reversibly stretchable layer (e.g., a high-performance nonwoven web) after the recovery of the reversibly stretchable layer. In some embodiments, such layers can prevent the reversibly stretchable layer from undergoing further reversible stretching.

[0318] In some embodiments, like Figures 12A to 12C the embodiment shown, the layer to be pleated is deposited directly on the reversibly stretchable layer, and the resulting pleated layer and the recovered layer are directly adjacent.

[0319] In some embodiments, the layer to be pleated is deposited on a layer or material deposited on the reversibly stretchable layer, and the resulting pleated layer and the recovered layer are adjacent but not directly adjacent. For example, the layer to be pleated can be deposited on an adhesive deposited on the reversibly stretchable layer such that the adhesive is positioned between the resulting pleated layer and the recovered layer. In some embodiments where the adhesive is positioned between the layer to be pleated and the reversibly stretchable layer, the adhesive can be deposited on the reversibly stretchable layer before and / or after stretching.

[0320] For example, an adhesive can be deposited onto a scrim, the scrim can be stretched, and then additional layers can be deposited onto the stretched scrim. In such a case, the adhesive along with the scrim is stretched in the direction in which the scrim is stretched. The additional layers may not bond well to the scrim in the direction in which the scrim is stretched, such that when the scrim is allowed to return to its original state, the additional layers can separate from the scrim in some locations in the opposite direction. In such a case, the additional layers can be pleated, and the scrim can include undulations (or be undulated) that follow the undulations in the additional layers. The undulations in the scrim can be much smaller than the undulations in the additional layers (i.e., they can have a much smaller average peak height), such that the scrim can be considered relatively flat but not completely flat compared to the additional layers.

[0321] In one specific embodiment, the above process can be carried out with a scrim in the form of a plurality of elastically extensible fibers. As an example, in some embodiments, an adhesive is deposited onto a plurality of elastically extensible fibers such that it completely or partially coats the elastically extensible fibers. The former case can include depositing the adhesive onto the elastically extensible fibers such that the adhesive coats the entire outer periphery of the elastically extensible fibers along at least a portion of the length of the elastically extensible fibers. The latter case can include depositing the adhesive onto the elastically extensible fibers such that some portions of the elastically extensible fibers, such as portions closer to the adhesive source and / or portions onto which additional layers will subsequently be deposited.

[0322] The reversibly stretchable layer can also be bonded to another layer by ultrasonic bonding. The reversibly stretchable layer can be reversibly stretched, optionally allowed to return to its original state, and then laminated to another layer deposited thereon. This process can be combined with or replace the process described in the foregoing paragraph for using an adhesive to adhere the reversibly stretchable layer and the layer deposited thereon. In some embodiments, the layer to which the reversibly stretchable layer is bonded via ultrasonic bonding prevents the reversibly stretchable layer from undergoing further reversible stretching after it returns to its original state.

[0323] The processes described in the foregoing paragraphs can be carried out in a roll-to-roll manner. As an example, in some embodiments, the reversibly stretchable layer (or the plurality of elastically extensible fibers that form the reversibly stretchable layer when incorporated into a filter medium) is supplied by a roll, a plurality of spools, or an apparatus (e.g., a yarn or filament beam) that supplies a plurality of yarn or filament ends. The reversibly stretchable layer or the plurality of elastically extensible fibers that form the reversibly stretchable layer when incorporated into a filter medium can then pass under an operating table where an adhesive is applied thereto, be stretched, and then used as a substrate on which additional layers (e.g., a nonwoven fibrous web having high performance) are deposited. The additional layer can be a pre-existing layer wound around and deposited from a roll, or can be a layer formed (e.g., from a solution or a melt) on the reversibly stretchable layer. The two layers joined together by the adhesive can be joined to an additional layer (which itself can be supplied by an additional roll). These additional layers can be deposited when the reversibly stretchable layer is in the reversibly stretched state and / or when the reversibly stretchable layer is in the relaxed state. The two layers joined together by the adhesive can also pass through additional operating tables where additional processes are carried out. Such processes can include bonding (e.g., via an ultrasonic horn and / or a calender), laminating (e.g., thermally, chemically, and / or mechanically), pleating, and / or charging. One or more of these processes can cause the reversibly stretchable layer to become bonded and / or mechanically coupled to another layer (e.g., a scrim such as a second scrim) such that it cannot undergo further reversible stretching. After manufacture, the final filter medium can be wound around a final roll.

[0324] When the reversible stretching layer is stretched, the direction of stretching can generally be selected as needed. In some embodiments, the reversible stretching layer can be stretched in the machine direction. In some embodiments, the reversible stretching layer can be stretched in the cross direction. When stretched, the reversible stretching layer can be stretched to various suitable lengths. The reversible stretching layer can be stretched to a length that is greater than or equal to 50%, greater than or equal to 75%, greater than or equal to 100%, greater than or equal to 125%, greater than or equal to 150%, greater than or equal to 175%, greater than or equal to 200%, greater than or equal to 225%, greater than or equal to 250%, greater than or equal to 275%, greater than or equal to 300%, greater than or equal to 325%, greater than or equal to 350%, greater than or equal to 375%, greater than or equal to 400%, greater than or equal to 450%, greater than or equal to 500%, greater than or equal to 600%, or greater than or equal to 800% of its initial length. In some embodiments, the reversible stretching layer is stretched to a length that is less than or equal to 1000%, less than or equal to 800%, less than or equal to 600%, less than or equal to 500%, less than or equal to 450%, less than or equal to 400%, less than or equal to 375%, less than or equal to 350%, less than or equal to 325%, less than or equal to 300%, less than or equal to 275%, less than or equal to 250%, less than or equal to 225%, less than or equal to 200%, less than or equal to 175%, less than or equal to 150%, less than or equal to 125%, less than or equal to 100%, or less than or equal to 75% of its initial length. Combinations of the above ranges are also possible (e.g., greater than or equal to 50% and less than or equal to 1000%, greater than or equal to 100% and less than or equal to 400%, or greater than or equal to 200% and less than or equal to 300%). Other ranges are also possible.

[0325] A layer deposited on a reversible stretching layer in a reversibly stretched state can recover as the reversible stretching layer returns to its original length, thereby experiencing a reduction in length. The reduction in length can be equivalent to the corresponding reduction in length experienced by the reversible stretching layer upon recovery. When the reversible stretching layer exhibits substantially complete recovery, the reduction in length of the layer can fall within one or more ranges that can be derived from the above ranges using the following formula:

[0326] Percentage reduction in length = (1 - 100 / (100 + percentage of stretching)) * 100%.

[0327] For example, a layer that is completely recovered and deposited on a reversible stretching layer stretched to 50% of its initial length will have a corresponding 33% reduction in length of the initial length of the layer. As another example, a layer that is completely recovered and deposited on a reversible stretching layer stretched to 1000% of its initial length will have a corresponding 91% reduction in length of the initial length of the layer.

[0328] The filter media described herein can be used in a variety of suitable applications. In some embodiments, the filter media described herein are used in air filters, non-limiting examples of which include indoor air filters, cabin air filters, air filters for medical applications, fan coil unit filters, ULPA filters, HEPA filters, cabin air filters, and HVAC filters.

[0329] In some embodiments, the filter media described herein are components of a filter element. That is, the filter media can be incorporated into an article suitable for end-user use.

[0330] Non-limiting examples of suitable filter elements include flat panel filters, wire-backed filters, cartridge filters, pleated panel filters, bag filters, mini-pleat filters, V-type filters (including, for example, from 1 to 24 Vs), thermoformed filters, cylindrical filters, conical filters, channel flow filters, and radial seal filters. Channel flow filters can include alternating rows of flat filter media and corrugated filter media. In some embodiments, these alternating rows can surround a honeycomb network of channels. In some embodiments, channel flow filters can include some channels sealed with an adhesive (e.g., channel flow filters can include alternating sealed and unsealed channels). In use, air can flow into the open channels in the channel flow filter, pass through the filter element, and then flow out of adjacent open channels.

[0331] The filter element can have a variety of suitable shapes, such as circular, oval, cubic, and / or prismatic. The filter element can have any suitable height (e.g., from 2 inches to 124 inches for flat panel filters, from 4 inches to 124 inches for V-type filters, and from 1 inch to 124 inches for cartridge and cylindrical filter media). The filter element can also have any suitable width (from 2 inches to 124 inches for flat panel filters, from 4 inches to 124 inches for V-type filters). Some filter media (e.g., cartridge and cylindrical filter media) can be characterized by a diameter rather than a width; these filter media can have any suitable value of diameter (e.g., from 1 inch to 124 inches). The filter element generally includes a frame, which can be made of one or more materials such as cardboard, aluminum, steel, alloys, wood, and polymers.

[0332] In some embodiments, the filter media described herein is a component of a filter element and is pleated. As described above, in some embodiments, the filter media described herein can be a component of a filter element and can be pleated. Without wishing to be bound by any particular theory, it is believed that pleating the filter media advantageously increases its surface area in a manner proportional to the number of pleats present. This increased surface area can improve the filtration efficiency of the filter media. Some pleated filter media can include two or more layers joined by a co-pleating process. Pleating can be achieved by forming score lines at appropriate spaced distances from each other, thereby allowing the filter media to be folded.

[0333] The pleat height and pleat density (number of pleats per unit length of the filter medium) can be selected as needed. In some embodiments, the pleat height is greater than or equal to 3 mm, greater than or equal to 5 mm, greater than or equal to 10 mm, greater than or equal to 15 mm, greater than or equal to 20 mm, greater than or equal to 25 mm, greater than or equal to 30 mm, greater than or equal to 35 mm, greater than or equal to 40 mm, greater than or equal to 45 mm, greater than or equal to 50 mm, greater than or equal to 53 mm, greater than or equal to 55 mm, greater than or equal to 60 mm, greater than or equal to 65 mm, greater than or equal to 70 mm, greater than or equal to 75 mm, greater than or equal to 80 mm, greater than or equal to 85 mm, greater than or equal to 90 mm, greater than or equal to 95 mm, greater than or equal to 100 mm, greater than or equal to 125 mm, greater than or equal to 150 mm, greater than or equal to 175 mm, greater than or equal to 200 mm, greater than or equal to 225 mm, greater than or equal to 250 mm, greater than or equal to 275 mm, greater than or equal to 300 mm, greater than or equal to 325 mm, greater than or equal to 350 mm, greater than or equal to 375 mm, greater than or equal to 400 mm, greater than or equal to 425 mm, greater than or equal to 450 mm, greater than or equal to 475 mm, or greater than or equal to 500 mm. In some embodiments, the pleat height is less than or equal to 510 mm, less than or equal to 500 mm, less than or equal to 475 mm, less than or equal to 450 mm, less than or equal to 425 mm, less than or equal to 400 mm, less than or equal to 375 mm, less than or equal to 350 mm, less than or equal to 325 mm, less than or equal to 300 mm, less than or equal to 275 mm, less than or equal to 250 mm, less than or equal to 225 mm, less than or equal to 200 mm, less than or equal to 175 mm, less than or equal to 150 mm, less than or equal to 125 mm, less than or equal to 100 mm, less than or equal to 95 mm, less than or equal to 90 mm, less than or equal to 85 mm, less than or equal to 80 mm, less than or equal to 75 mm, less than or equal to 70 mm, less than or equal to 65 mm, less than or equal to 60 mm, less than or equal to 55 mm, less than or equal to 53 mm, less than or equal to 50 mm, less than or equal to 45 mm, less than or equal to 40 mm, less than or equal to 35 mm, less than or equal to 30 mm, less than or equal to 25 mm, less than or equal to 20 mm, less than or equal to 15 mm, less than or equal to 10 mm, or less than or equal to 5 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 3 mm and less than or equal to 510 mm, greater than or equal to 10 mm and less than or equal to 510 mm, or greater than or equal to 10 mm and less than or equal to 100 mm). Other ranges are also possible.

[0334] In some embodiments, the pleat density of the filter medium is greater than or equal to 5 pleats per 100 mm, greater than or equal to 6 pleats per 100 mm, greater than or equal to 10 pleats per 100 mm, greater than or equal to 15 pleats per 100 mm, greater than or equal to 20 pleats per 100 mm, greater than or equal to 25 pleats per 100 mm, greater than or equal to 28 pleats per 100 mm, greater than or equal to 30 pleats per 100 mm, or greater than or equal to 35 pleats per 100 mm. In some embodiments, the pleat density of the filter medium is less than or equal to 40 pleats per 100 mm, less than or equal to 35 pleats per 100 mm, less than or equal to 30 pleats per 100 mm, less than or equal to 28 pleats per 100 mm, less than or equal to 25 pleats per 100 mm, less than or equal to 20 pleats per 100 mm, less than or equal to 15 pleats per 100 mm, less than or equal to 10 pleats per 100 mm, or less than or equal to 6 pleats per 100 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 5 pleats per 100 mm and less than or equal to 100 pleats per 100 mm, greater than or equal to 6 pleats per 100 mm and less than or equal to 100 pleats per 100 mm, or greater than or equal to 25 pleats per 100 mm and less than or equal to 28 pleats per 100 mm). Other ranges are also possible.

[0335] Other pleat heights and pleat densities may also be possible. For example, the filter medium within a flat filter or a V - filter may have 1 a pleat height of 1 / 4 inch to 24 inches and / or a pleat density of 1 pleat per inch to 50 pleats per inch. As another example, the filter medium within a cartridge filter or a cone filter may have 1 a pleat height of 1 / 4 inch to 24 inches and / or 1 a pleat density of 1 / 2 pleat per inch to 100 pleats per inch.

[0336] In some embodiments, the pleats are separated by pleat separators made of, for example, polymers, glass, aluminum, and / or cotton. In other embodiments, the filter element does not have pleat separators. When present, the pleat separators may be positioned on the upstream surface of the filter medium and / or may be positioned on the downstream surface of the filter medium. The pleat separators may include portions that separate the pleats and have the following width (i.e., in the direction separating the pleats): greater than or equal to 1 / 2 inches, greater than or equal to 1 inch, greater than or equal to 1.5 inches, greater than or equal to 2 inches, greater than or equal to 2.5 inches, greater than or equal to 3 inches, greater than or equal to 3.5 inches, or greater than or equal to 4 inches. In some embodiments, the pleat separator includes portions that separate the pleats and have the following widths: less than or equal to 5 inches, less than or equal to 4 inches, less than or equal to 3.5 inches, less than or equal to 3 inches, less than or equal to 2.5 inches, less than or equal to 2 inches, less than or equal to 1.5 inches, or less than or equal to 1 inch. Combinations of the above ranges are also possible (e.g., greater than or equal to 3 inches and less than or equal to 2 inches, greater than or equal to 2 inches and less than or equal to 1 inch).

[0337] In some embodiments, the filter medium includes one or more additional structural elements. For example, the filter medium may further include reinforcement elements such as polymeric grids and / or metallic grids. As another example, the filter medium may further include a screen backing, which may help to hold the filter medium in a pleated configuration. Such a filter medium may be wire-backed (e.g., by expanded wire) and / or include an extruded plastic grid. The filter medium may also be self-supporting.

[0338] Example 1

[0339] This example compared various properties of several charged meltblown nonwoven fiber webs containing polypropylene fibers. Selected characteristics of these nonwoven fiber webs are listed in Tables 5 through 8 below. As can be seen from these tables, many nonwoven fiber webs exhibit a desirable ratio of dust holding capacity to basis weight, ratio of dust holding capacity to initial air resistance, and / or γ.

[0340] Table 5.

[0341]

[0342] Table 6.

[0343]

[0344] Table 7.

[0345]

[0346] Table 8.

[0347]

[0348] Example 2

[0349] This example compared the NaCl distribution in sample numbers 5 and 12 described in Example 1.

[0350] Two nonwoven fiber webs were imaged using SEM, subjected to the NaCl loading process as described above, and then imaged again using SEM. Figure 13 Shows sample number 5 before NaCl loading, and Figure 14 shows the same nonwoven fiber web after NaCl loading. As can be understood from these figures, NaCl was captured throughout the thickness of the web. Figure 15 And Figure 16 show SEM images of sample number 12 before and after NaCl loading, respectively. These figures show that most of the NaCl was captured in the upstream portion of sample number 12 and very little NaCl was captured in the downstream portion.

[0351] Figure 17 Is a graph showing the NaCl density in each of these two nonwoven fiber webs after NaCl loading. As can be seen from Figure 17 The NaCl density is much more uniform in sample number 5 compared to sample number 12.

[0352] Example 3

[0353] This example compares the anti-compaction properties of an exemplary nonwoven fiber web with high performance with those of a control nonwoven fiber web having a dust holding capacity per unit area weight ratio of less than 1 gsm / gsm.

[0354] Test samples were obtained from three different locations in the final rolls of sample numbers 6, 7, 10, and 11 and compared with each other. The final rolls had been wound around a 3-inch diameter core and had an outer diameter of at least 12 inches. The test samples were obtained from the outer surface of the final roll, the middle portion of the final roll between its outer surface and the core, and the portion of the final roll directly adjacent to the core. The test samples inside the final roll were subjected to some compressive stress during roll formation and storage, and all samples were allowed to expand until they reached an equilibrium thickness before measurement. Tables 9 and 10 below show the air permeability, air resistance, penetration rate, γ, and the decrease in air permeability after compaction for the two types of nonwoven fiber webs. As can be seen from Tables 9 and 10, the nonwoven fiber web with high performance exhibits higher air permeability, lower resistance, higher γ values, and lower decrease in air permeability compared to the control nonwoven fiber web.

[0355] Table 9.

[0356]

[0357] Table 10.

[0358]

[0359] Although several embodiments of the present invention have been described and illustrated herein, those of ordinary skill in the art will readily conceive of various other means and / or structures for performing the functions and / or obtaining the results and / or one or more of the advantages described herein, and each such variation and / or modification is considered to be within the scope of the present invention. More generally, those skilled in the art will readily understand that all parameters, dimensions, materials, and configurations described herein are intended to be exemplary, and the actual parameters, dimensions, materials, and / or configurations will depend upon one or more specific applications of the teachings of the present invention. Those skilled in the art will recognize or be able to ascertain using no more than routine experimentation many equivalents to the specific embodiments of the invention described herein. Accordingly, it is to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and their equivalents, the invention may be practiced otherwise than as specifically described and claimed. The present invention relates to each and every distinct feature, system, article, material, kit, and / or method described herein. Moreover, if such features, systems, articles, materials, kits, and / or methods are not mutually inconsistent, any combination of two or more of such features, systems, articles, materials, kits, and / or methods is included within the scope of the present invention.

[0360] All definitions, as defined and used herein, shall be understood to prevail over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.

[0361] Unless the context clearly dictates otherwise, as used in the specification and claims herein, singular nouns without an article shall be understood to mean "at least one."

[0362] As used in the specification and claims herein, the phrase "and / or" shall be understood to mean "either or both" of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with "and / or" shall be construed in the same manner, i.e., "one or more" of the elements so conjoined. Other elements may optionally exist aside from the elements specifically identified by the "and / or" clause, whether related or unrelated to those specifically identified. Thus, as a non-limiting example, when used in conjunction with open-ended language such as "comprising," reference to "A and / or B" may in one embodiment refer to only A (optionally including elements other than B); in another embodiment, only B (optionally including elements other than A); in yet another embodiment, to both A and B (optionally including other elements); and so on.

[0363] As used herein in the specification and claims, "or" shall be understood to have the same meaning as "and / or" as defined above. For example, when separating items in a list, "or" or "and / or" shall be understood to be inclusive, i.e., including at least one of a plurality of elements or of a list of elements, but also including more than one of a plurality of elements or of a list of elements, and optionally including additional unrecited items. Only terms explicitly stating the contrary, such as "only one of" or "exactly one of", or when used in claims "consisting of", will refer to including exactly one element of a plurality of elements or of a list of elements. In general, when preceded by an exclusive term (such as "any", "one of", "only one of" or "exactly one of"), the term "or" as used herein shall only be understood to represent exclusive alternatives (i.e., "one or the other, but not both"). "Consisting essentially of" when used in the context of a claim shall have its ordinary meaning as used in the field of patent law.

[0364] As used herein in the specification and claims, the phrase "at least one" when referring to a list of one or more elements shall be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically recited within the list of elements, and not excluding any combinations of elements in the list of elements. This definition also allows that there may optionally be additional elements other than those specifically recited within the list of elements referred to in the phrase "at least one", whether related or unrelated to those specifically recited. Thus, as a non-limiting example, "at least one of A and B" (or equivalently, "at least one of A or B", or equivalently, "at least one of A and / or B") may in one embodiment refer to at least one A, optionally including more than one A, without B (and optionally including elements other than B); in another embodiment, to at least one B, optionally including more than one B, without A (and optionally including elements other than A); in yet another embodiment, to at least one A, optionally including more than one A, and at least one B, optionally including more than one B (and optionally including other elements); and so forth.

[0365] It should also be understood that, unless explicitly stated to the contrary, in any method claimed herein that includes more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order of the steps or acts recited in the method.

[0366] In the claims and in the specification above, all transitional phrases such as "comprising", "including", "carrying", "having", "containing", "involving", "holding", "consisting of", etc. shall be construed to be open-ended, i.e., meaning including but not limited to. As set forth in section 2111.03 of the United States Patent and Trademark Office's Manual of Patent Examining Procedure, only the transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively.

Claims

1. A filter medium, comprising: A nonwoven fibrous web containing fibers, wherein: Polypropylene accounts for at least 75% by weight of the polymers in the nonwoven fibrous web; The average diameter of the fibers in the nonwoven fibrous web is less than or equal to 15 micrometers; The γ of the nonwoven fibrous web is greater than or equal to 200; The ratio of the dust holding capacity of the filter medium to the basis weight per unit area of the filter medium is greater than or equal to 1 gsm / gsm, and The thickness of the nonwoven fibrous web is greater than 6 mils.

2. A filter medium, comprising: A nonwoven fibrous web containing fibers, wherein: Polypropylene accounts for at least 75% by weight of the polymers in the nonwoven fibrous web; The average diameter of the fibers in the nonwoven fibrous web is less than or equal to 15 micrometers; The γ of the nonwoven fibrous web is greater than or equal to 200; and The nonwoven fibrous web is configured such that after undergoing a NaCl loading process, the NaCl density at the downstream surface of the nonwoven fibrous web is greater than or equal to 50% of the NaCl density at the upstream surface of the nonwoven fibrous web.

3. The filter medium according to any one of the preceding claims, wherein the filter medium further comprises a charged layer containing discontinuous fibers.

4. The filter medium according to any one of the preceding claims, wherein the filter medium is a nonwoven fibrous web held in a corrugated configuration by a support layer.

5. The filter medium according to any one of the preceding claims, wherein the filter medium comprises a plurality of irregular peaks.

6. The filter medium according to any one of the preceding claims, wherein the resistance of the nonwoven fibrous web after NaCl loading is less than or equal to 25 mm H2O.

7. The filter medium according to any one of the preceding claims, wherein the filter medium further comprises an adsorption layer.

8. The filter medium according to any one of the preceding claims, wherein the adsorption layer contains an adsorbent.

9. The filter medium according to any one of the preceding claims, wherein the adsorbent comprises an ion exchange resin, activated carbon, MOF, and / or zeolite.

10. The filter medium according to any one of the preceding claims, wherein the filter medium further comprises a nonwoven fibrous web containing nanofibers.

11. The filter medium according to any one of the preceding claims, wherein the average diameter of the nanofibers is less than or equal to 300 nm.

12. The filter medium according to any one of the preceding claims, wherein the filter medium further comprises a second nonwoven fibrous web, and the second nonwoven fibrous web also contains fibers containing polypropylene.

13. The filter medium according to any one of the preceding claims, wherein the average diameter of the fibers in the second nonwoven fibrous web is less than the average diameter of the fibers in the nonwoven fibrous web.

14. The filter medium according to any one of the preceding claims, wherein the average diameter of the fibers in the second nonwoven fibrous web is less than or equal to 5 micrometers.

15. The filter medium according to any one of the preceding claims, wherein the nonwoven fibrous web is a meltblown one.

16. The filter medium according to any one of the preceding claims, wherein the second nonwoven fibrous web is a meltblown one.

17. The filter medium according to any one of the preceding claims, wherein the filter medium further comprises a backing.

18. The filter medium according to any one of the preceding claims, wherein the air permeability of the backing is greater than or equal to 200 CFM.

19. The filter medium according to any one of the preceding claims, wherein the stiffness of the backing is greater than or equal to 300 mg.

20. The filter medium according to any one of the preceding claims, wherein the nonwoven fiber web contains a flame retardant.

21. The filter medium according to any one of the preceding claims, wherein the nonwoven fiber web contains an antimicrobial substance and / or an anti-allergen substance.

22. The filter medium according to any one of the preceding claims, wherein the antimicrobial substance is antibacterial, antifungal and / or antiviral.

23. The filter medium according to any one of the preceding claims, wherein the nonwoven fiber web contains citric acid, zinc, copper and / or silver.

24. The filter medium according to any one of the preceding claims, wherein the average flow pore size of the nonwoven fiber web is greater than or equal to 20 microns.

25. The filter medium according to any one of the preceding claims, wherein the air permeability of the nonwoven fiber web is greater than or equal to 20 CFM and less than or equal to 1300 CFM.

26. The filter medium according to any one of the preceding claims, wherein the nonwoven fiber web has passed the MERV13 Appendix J test.

27. The filter medium according to any one of the preceding claims, wherein the melt flow rate of the polypropylene is less than or equal to 2000.

28. The filter medium according to any one of the preceding claims, wherein the nonwoven fiber web is charged by hydrostatic electret.

29. The filter medium according to any one of the preceding claims, wherein the average diameter of the fibers in the nonwoven fiber web is greater than or equal to 3 microns.

30. The filter medium according to any one of the preceding claims, wherein the density of the nonwoven fiber web is less than or equal to 6%.

31. The filter medium according to any one of the preceding claims, wherein the dust holding capacity of the nonwoven fiber web is greater than or equal to 20 gsm.

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