High efficiency filter media

Abstract

Articles and methods related to filter media are generally provided. In certain embodiments, the filter media has a certain design and / or includes one or more layers that improve its efficiency and / or performance. The filter media includes a first layer and a second layer. The first layer has an average diameter of less than 1 micron.

Description

Technical Field

[0001] High efficiency filter media is generally described. Background Art

[0002] Filter media is a product that can be used to remove pollutants in various applications. Depending on the application, filter media can be designed to have different performance characteristics. For example, filter media can be designed to have performance characteristics that are suitable for HEPA and / or ULPA applications. Although there are many types of filter media for filtering particles from the air, the improvement in the physics and / or performance characteristics (for example, efficiency, hot PAO loading capacity, mechanical HEPA efficiency) of filter media will be useful. Summary of the invention

[0003] Filter media, related components, and related methods are generally described.

[0004] In some aspects, a filter medium is provided. The filter medium includes a first layer and a second layer disposed on the first layer, wherein the first layer includes a plurality of fine fibers having an average diameter of less than 1 micron. The porosity of the first layer is greater than 80%. The normalized surface area of ​​the second layer is greater than 15 m 2 / m 2 The efficiency measure of the second layer is greater than 2.5.

[0005] Other advantages and new features of the present disclosure become apparent from the following detailed description of a plurality of non-limiting embodiments of the present disclosure when considered in conjunction with the accompanying drawings. In the case where this specification and the documents incorporated by reference comprise conflicting and / or inconsistent disclosures, this specification shall prevail. If two or more documents incorporated by reference comprise conflicting and / or inconsistent disclosures relative to each other, then the documents with a later effective date shall prevail. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Non-limiting embodiments of the present disclosure will be described by way of example with reference to the accompanying drawings, which are schematic and are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown is generally represented by a single numeral. For purposes of clarity, not every component is labeled in every drawing, nor is every component of every embodiment of the disclosure shown, where an illustration is not necessary to enable one of ordinary skill in the art to understand the present disclosure. In the drawings:

[0007] Figure 1 is a schematic diagram of a cross-section of a filter medium according to one set of embodiments;

[0008] Figure 2 is a schematic diagram of a cross-section of a filter medium including two layers according to one set of embodiments;

[0009] Figure 3A is a schematic diagram of a cross-section of a fine fiber layer comprising an impact modifier according to one set of embodiments;

[0010] Figure 3B is a schematic diagram of a cross-section of a fine fiber layer without an impact modifier according to one set of embodiments;

[0011] Figure 4 is a schematic diagram of a cross-section of a filter medium including three layers according to one set of embodiments;

[0012] Figure 5 is a schematic diagram of a cross-section of a filter medium including four layers according to one set of embodiments;

[0013] Figure 6 is a schematic diagram of a cross-section of a filter medium including a spacer layer according to one set of embodiments;

[0014] Figure 7 is a schematic diagram of a cross-section of a filter medium including a meltblown layer according to one set of embodiments;

[0015] Figure 8 is a graph of air resistance as a function of time according to one set of embodiments;

[0016] Figures 9 to 11 is a graph of air resistance as a function of cycle number according to one set of embodiments;

[0017] Figure 12 to Figure 13 is a graph of air resistance at different stages of a DOP interval load test according to one set of embodiments; and

[0018] Fig.14 is a graph of penetration of a DOP aerosol as a function of DOP loading time, according to one set of embodiments. DETAILED DESCRIPTION

[0019] Articles and methods generally are provided that relate to filter media.In certain embodiments, the filter media has a design and / or includes one or more layers that enhance its efficiency and / or performance.

[0020] In some embodiments, the filter medium includes a main filter layer with one or more advantageous features. For example, the filter medium may include a main filter layer comprising a plurality of nanofibers. Nanofibers may be particularly suitable for retaining small particles and / or retaining particles with high efficiency. As another example, in some embodiments, the filter medium includes a main filter layer, and the main filter layer includes fine fibers containing an impact modifier. The impact modifier may enhance the impact resistance of the fibers in the main filter layer and / or the impact resistance of the main filter layer as a whole. The impact modifier may also improve the porosity of the main filter layer, increase the efficiency of the main filter layer, increase the oil loading capacity of the main filter layer, improve one or more mechanical properties (e.g., elongation at break, tensile strength, toughness, puncture strength) of the main filter layer, and / or increase the durability of the main filter during pleating. In some cases, one or more of these advantages are achieved without sacrificing filtering properties.

[0021] In some embodiments, the filter media includes a pre-filter layer having one or more beneficial properties. As an example, the filter media can include a pre-filter layer having one or more features that enhance its ability to repel and / or capture particles. Such features can include having a relatively high normalized surface area, being charged (e.g., hydrocharged), being oleophobic, and / or containing an oleophobic additive.

[0022] For example, in one group of embodiments, the filter medium includes a pre-filter layer with a relatively high normalized surface area. The high normalized surface area may be related to a high weight per unit area, a high fiber density, and / or the presence of fibers with a relatively small diameter. In some cases, the high normalized surface area can be converted into an increased amount of fiber area that can be used to filter particles and / or absorb fluids (e.g., oil). In some cases, a pre-filter layer with a relatively high normalized surface area can impart improved initial efficiency and / or improved oil loading to the pre-filter layer and / or the filter medium.

[0023] As another example, in some embodiments, the filter medium includes a pre-filter layer with a charge. All other factors being the same, the pre-filter layer with a charge can exhibit one or more advantages compared to the pre-filter layer without a charge. For example, the pre-filter layer with a charge can exhibit improved oil loading characteristics and / or improved initial efficiency. In some cases, the filter medium includes a pre-filter layer with a large amount of charge, such as by water electret charging. The pre-filter layer with a large amount of charge can have a relatively high total charge, charge density and / or a relatively uniform charge distribution. This can improve the oil loading capacity and / or initial efficiency of the pre-filter layer.

[0024] As a third example, in some embodiments, the filter medium includes a pre-filter layer comprising an oleophobic additive. The presence of the oleophobic additive can achieve low pressure drop at high oil loads, high gamma at high oil loads, and / or low penetration at high oil loads. Such properties can be beneficial in applications where the filter medium is in an environment with medium or high ambient oil levels. For example, in clean rooms (e.g., pharmaceutical clean rooms, electronic clean rooms, clean rooms for integrated circuit manufacturing), in gas turbines (e.g., offshore gas turbines), in indoor air purifiers, in masks, in vacuum cleaners, in spray booths, and / or for filtering filter media used in oily aerosols.

[0025] The filter medium described herein may also include additional layers in addition to the main filter layer and the pre-filter layer. Such layers may also have one or more advantageous properties. As an example, in some embodiments, the filter medium includes an oleophobic spacer layer, which improves the oleophobicity of the filter medium as a whole, thereby improving the filtration efficiency. As another example, in some embodiments, the filter medium includes one or more layers that improve the load capacity and / or life of the filter medium. Such layers may include a wet-laid layer and / or a coarse melt-blown layer. In some embodiments, such layers have the ability to capture a relatively large amount of particles. Such layers may also be further used as a support layer and / or backing layer of one or more additional layers (e.g., main filter layer, pre-filter layer) present in the filter medium. Additionally or alternatively, such layers (e.g., coarse melt-blown layers) may be oleophobic and / or may be charged via one or more methods described elsewhere herein.

[0026] In some embodiments, the filter media described herein have a specific combination and / or order of layers that produces desired filter media properties. In some embodiments, the filter media described herein exhibit increased efficiency, increased oil loading capacity, and / or increased mechanical HEPA efficiency.

[0027] Figure 1 One non-limiting embodiment of a filter medium 100 is shown. In some embodiments, the filter medium includes two or more layers. For example, the filter medium can include a first layer and a second layer. Figure 2 A shows a filter medium (e.g., such as Figure 1 100) is a non-limiting embodiment of a filter medium. For example, in Figure 2 , filter media 100 includes a first layer 102 and a second layer 104 positioned adjacent to the first layer 102 .

[0028] In some embodiments, and as described in more detail below, one of the layers (e.g., the first layer) in a filter medium comprising two or more layers is a main filter layer. The main filter layer can, for example, have a higher efficiency than one or more other layers of the medium. In some embodiments, the main filter layer has a relatively small average fiber diameter and / or comprises fibers (e.g., fine fibers) having a relatively small average fiber diameter. For example, in some embodiments, the main filter layer is a fine fiber layer.

[0029] When the filter media includes a fine fiber layer and / or a main filter layer containing fine fibers, the fine fibers may include one or more components. Examples of suitable components include matrix polymers, impact modifiers, and salts. Figure 3A An example of a fine fiber is schematically shown in FIG. Figure 3A As shown, in some cases, the fine fiber 101 includes a matrix polymer 103 and a plurality of impact modifier domains 105. The impact modifier domains present in the fine fiber can have a structure such as Figure 3A The morphology and / or distribution shown may be different from Figure 3A As an example, some fine fibers may contain impact modifier microdomains that are not uniformly shaped or uniformly distributed. Fine fibers may also be formed from a continuous phase that does not include any impact modifier microdomains dispersed in the matrix polymer. An example of such a fine fiber is shown in Figure 3B middle.

[0030] In some embodiments, the filter medium includes a pre-filter layer (for example, a second layer of the pre-filter layer). The pre-filter layer can be used, for example, to filter out larger particles from the fluid before the fine fiber layer is exposed to the fluid. This can prevent the substance to be filtered (for example, oil) from penetrating into the main filter layer and / or reduce the degree of penetration of the substance to be filtered (for example, oil) into the main filter layer. This filtration can also protect (for example, mechanically) the main filter layer, which can be desirable when the main filter layer is a relatively fragile fine fiber layer. The pre-filter used in the filter medium described herein can have a variety of suitable designs. In some embodiments, the filter medium includes a pre-filter layer that is a meltblown layer. In some cases, the pre-filter layer includes an oleophobic additive (for example, a fluorocarbon additive). In some embodiments, the pre-filter layer is charged. In such an embodiment, a charge can be caused on the pre-filter layer by a charging process (for example, an electrostatic charging process, a friction charging process, or a water electret charging process).

[0031] In some embodiments, the filter medium may include one or more additional layers. It should be noted that one or more additional layers may be provided on the filter medium (e.g., Figure 2In some cases, the filter medium may include two or more layers, three or more layers, four or more layers, or even more layers, for example, Figures 4 to 7 shown.

[0032] Figure 4 A non-limiting embodiment of a filter medium 110 comprising three layers is shown. Figure 4 , the filter medium 110 includes a first layer 102 , a second layer 104 , and a third layer 106 . Figure 4 The third layer 106 is shown positioned adjacent to the first layer 102 on an opposite side from the second layer 104 . Figure 4 The first and second layers in Figure 2 The first and second layers in the filter medium 100 shown are the same, or may be different. In some embodiments, and as described in more detail below, the filter medium may include a third layer that is a backing layer or support layer. In some embodiments, the filter medium includes a backing layer or support layer positioned on the side of the main filter layer opposite to the pre-filter layer. In some cases, the backing layer or support layer may be a wet-laid nonwoven fibrous web.

[0033] In some embodiments, the filter media includes four layers. Figure 5 As shown, filter media 120 includes a first layer 102 , a second layer 104 , a third layer 108 positioned adjacent to the first layer 102 on an opposite side from the second layer 104 , and a fourth layer 112 positioned adjacent to the second layer 104 on an opposite side from the first layer 102 . Figure 5 The first and second layers of the filter medium 120 may be Figure 2 The first and second layers in the filter medium 110 shown are the same, or may be different. In some embodiments, the filter medium comprising four layers includes a backing layer or support layer as the outermost layer (e.g., Figure 5 In some embodiments, the filter medium may include a third layer and a fourth layer that are backing layers or support layers, a first layer that is a main filter layer, and a second layer that is a pre-filter layer). In some embodiments where the filter medium includes two or more support layers, each (or at least one) of the two or more support layers is a wet-laid nonwoven web. In embodiments where two or more support layers are included, the two or more support layers may differ from each other in one or more aspects (even if both support layers are wet-laid nonwoven webs). In some embodiments, a support layer positioned adjacent to a pre-filter layer may have a higher efficiency than a support layer positioned adjacent to a main filter layer. The characteristics of the various support layers are described in further detail below.

[0034] In some embodiments, the filter media may include one or more additional layers. Figure 6 One non-limiting embodiment of a filter medium 130 including additional layers is shown. Figure 6 As shown, filter media 130 may include a first layer 102 , a second layer 104 , a third layer 106 , and an additional layer 114 positioned between the first layer 102 and the second layer 104 . Figure 6 The first layer, the second layer and the third layer of the filter medium 130 may be Figure 4 The first, second, and third layers in the illustrated filter media 110 are identical, or may differ in one or more aspects. In some embodiments, additional layers are positioned between the main filter layer and the pre-filter layer and / or downstream of the pre-filter layer.

[0035] The filter medium may also include a Figure 6 The positions shown are different for additional layers. As an example, Figure 7 A non-limiting embodiment of a filter medium including an additional layer positioned on the outermost surface of the filter medium is shown. As shown therein, the filter medium 140 includes a first layer 102, a second layer 104, a third layer 106, and an additional layer 116 positioned upstream of the second layer 104 on the opposite side from the first layer 102. Figure 7 The first, second, and third layers of the filter medium 140 shown may be Figure 4 The first, second, and third layers of the filter media 110 shown are identical or may differ in one or more aspects. The filter media may also be Figure 6 to Figure 7 Additional layers are included in the locations of those shown. As an example, in some embodiments, the filter media includes an additional layer between the support layer and the main filter layer.

[0036] An example of an additional layer is an oleophobic spacer. The oleophobic spacer can be positioned between the main filter layer and the pre-filter layer. In some embodiments, the oleophobic spacer is oleophobic, contains an oleophobic additive, includes an oleophobic coating, and / or has an oil rating greater than or equal to 1. In applications where the filter medium is in an environment with medium or high ambient oil levels, the presence of an oleophobic spacer is beneficial. For example, the presence of an oleophobic spacer can prevent oil from migrating into adjacent layers (e.g., into the main filter layer) and / or improve the life of the filter medium. Non-limiting examples of suitable types of oleophobic spacers include membrane layers, scrim layers, and meltblown layers. In some cases, more than one oleophobic spacer can be present in the filter medium.

[0037] Another example of additional layer is coarse meltblown layer. Coarse meltblown layer can be positioned upstream of pre-filter layer and / or at the outermost surface of filter medium. As described in more detail below, coarse meltblown layer can have one or more characteristics different from one or more other meltblown layers (e.g., meltblown pre-filter layer) also positioned in filter medium. As two examples, in some cases, coarse meltblown layer can have average fiber diameter larger than other meltblown layers also positioned in filter medium, higher porosity and / or larger average pore size. In some embodiments, coarse meltblown layer can be used as additional protective layer for adjacent layers (e.g., pre-filter layer, main layer), and / or further increase the oil load capacity of filter medium. Coarse meltblown can also be coated with oleophobic additive.

[0038] In some embodiments, the filter media includes one or more additional layers (eg, oleophobic layer, coarse meltblown layer) that are charged. The charge may be induced on the additional layer by a charging process (eg, an electrostatic charging process, a friction charging process, or a hydro-electret charging process).

[0039] In some embodiments, a binder resin is present between two or more layers in the filter media. As an example, in some embodiments, a binder resin is present between the main filter layer and the pre-filter layer, between the main filter layer and the support layer, between the main filter layer and the backing, between the main filter layer and the additional layer, between the pre-filter layer and the support layer, between the pre-filter layer and the backing, between the pre-filter layer and the additional layer, between the support layer and the backing, between the support layer and the additional layer, and / or between the backing and the additional layer. When present, the binder resin can be used to bind the two layers it is positioned between to each other.

[0040] As used herein, when a layer is referred to as being "on" or "adjacent" another layer, it can be directly on or directly adjacent to the layer, or intervening layers may also be present. A layer being directly "on," "directly adjacent to," or "in contact with" another layer means that there are no intervening layers.

[0041] In addition, it should be understood that although the discussion herein may refer to layers as "first layer," "second layer," "third layer," and / or "fourth layer," such references are merely for convenience, and the layers described herein may be claimed as any appropriately numbered layers, and the numbered layers claimed may have the characteristics described elsewhere herein for one or more types of layers that may be present in the filter medium. For example, the "first layer" claimed may be a pre-filter layer, a main filter layer, a support layer, a backing, and / or an additional layer. Similarly, the "first layer" may have one or more characteristics described elsewhere herein for a pre-filter layer, a main filter layer, a support layer, a backing, and / or an additional layer. Similarly, the "second layer" claimed may be any of the above-mentioned types of layers and / or include one or more characteristics described elsewhere herein for any of the above-mentioned types of layers. The same applies to the "third layer," "fourth layer," "fifth layer," and additional layers claimed.

[0042] In some embodiments, one or more of the layers of the filter media can be a main filter layer (i.e., an efficiency layer). For example, in some embodiments, the filter media includes a first layer that is a main filter layer. In some embodiments, the filter media includes a main filter layer that is a fine fiber layer. The characteristics of the fine fiber layer are further described in detail herein.

[0043] The fine fiber layer described herein can include fine fibers having any of a variety of suitable average fiber diameters. In some embodiments, the fine fiber layer includes fine fibers having an average fiber diameter of 10 nm or more, 25 nm or more, 50 nm or more, 75 nm or more, 100 nm or more, 150 nm or more, 200 nm or more, 250 nm or more, 300 nm or more, 400 nm or more, 500 nm or more, 750 nm or more, 1 micron or more, 2 microns or more, 3 microns or more, 4 microns or more, or 5 microns or more. In certain embodiments, the fine fiber layer comprises fine fibers having an average fiber diameter of less than or equal to 6 microns, less than or equal to 5 microns, less than or equal to 4 microns, less than or equal to 3 microns, less than or equal to 2 microns, less than or equal to 1 micron, less than or equal to 750 nm, less than or equal to 500 nm, less than or equal to 400 nm, less than or equal to 300 nm, less than or equal to 250 nm, less than or equal to 200 nm, less than or equal to 150 nm, or less than or equal to 100 nm. Combinations of these ranges are also possible (e.g., greater than or equal to 10 nm and less than or equal to 6 microns, greater than or equal to 25 nm and less than or equal to 1 micron, or greater than or equal to 50 nm and less than or equal to 300 nm). In certain embodiments, the fine fibers include nanofibers. As used herein, nanofibers are fibers having an average fiber diameter less than or equal to 1 micron (e.g., any of the above diameters less than or equal to 1 micron or a combination thereof).

[0044] When the fine fiber layer comprises two or more types of fine fibers, each type of fine fibers can independently have an average fiber diameter in one or more of the above ranges, and / or all of the fine fibers in the fine fiber layer together can have an average fiber diameter in one or more of the above ranges. When the filter media comprises two or more fine fiber layers, each fine fiber layer can independently comprise fine fibers having an average fiber diameter in one or more of the above ranges. In embodiments where the filter media comprises two or more fine fiber layers, the average fiber diameters of the two or more fine fiber layers can be the same or different.

[0045] In some cases, the fine fiber layer comprises fine fibers that are continuous fibers (e.g., electrospun fibers, melt-blown fibers, solvent-spun fibers, and / or centrifugal-spun fibers). Continuous fibers are made by a "continuous" fiber forming process (e.g., a melt-blown process, a melt-spinning process, a melt electrospinning process, a solvent electrospinning process, a centrifugal spinning process, or a spunbond process) and typically have a longer length than non-continuous fibers. In some embodiments, the fine fiber layer comprises a nonwoven web comprising continuous fibers.

[0046] The fine fiber layers described herein may include fine fibers having any of a variety of suitable average fiber lengths. For example, in some cases, the fine fibers have an average fiber length of 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 200 mm, greater than or equal to 250 mm, greater than or equal to 300 mm, greater than or equal to 400 mm, greater than or equal to 500 mm, greater than or equal to 750 mm, greater than or equal to 1 m, greater than or equal to 1.25 m, greater than or equal to 1.5 m, greater than or equal to 2 m, greater than or equal to 2.5 m, greater than or equal to 3 m, greater than or equal to 4 m, greater than or equal to 5 m, greater than or equal to 6 m, greater than or equal to 7 m, greater than or equal to 8 m, greater than or equal to 9 m, greater than or equal to 10 m, greater than or equal to 11 m, greater than or equal to 125 m, greater than or equal to 15 m, greater than or equal to 16 m, greater than or equal to 17 m, greater than or equal to 18 m, greater than or equal to 19 m, greater than or equal to 20 m, greater than or equal to 21 m, greater than or equal to 23 m, greater than or equal to 24 m, greater than or equal to 25 m, greater than or equal to 26 m, greater than or equal to 27 m, greater than or equal to 28 m, greater than or equal to 29 m, greater than or equal to 30 m, greater than or equal to 40 m, greater than or equal to 500 mm, greater than or equal to 500 mm, greater than or equal to 650 mm, greater than or equal to 750 mm, greater than or equal to 1 m, greater than or equal to 1.25 m, greater than or 5m, greater than or equal to 7.5m, greater than or equal to 10m, greater than or equal to 12.5m, greater than or equal to 15m, greater than or equal to 20m, greater than or equal to 25m, greater than or equal to 30m, greater than or equal to 40m, greater than or equal to 50m, greater than or equal to 75m, greater than or equal to 100m, greater than or equal to 125m, greater than or equal to 150m, greater than or equal to 200m, greater than or equal to 250m, greater than or equal to 300m, greater than or equal to 400m, greater than or equal to 500m, or greater than or equal to 750m. In some embodiments, the average fiber length of the fine fibers is less than or equal to 1 km, less than or equal to 750 m, less than or equal to 500 m, less than or equal to 400 m, less than or equal to 300 m, less than or equal to 250 m, less than or equal to 200 m, less than or equal to 150 m, less than or equal to 125 m, less than or equal to 100 m, less than or equal to 75 m, less than or equal to 50 m, less than or equal to 40 m, less than or equal to 30 m, less than or equal to 25 m, less than or equal to 20 m, less than or equal to 15 ...25 m, less than or equal to 125 m, less than or equal to 125 m, less than or equal to 125 m, less than or equal to 125 m, less than or equal to 125 m, less than or equal to 125 m, less than or equal to 125 m, less than or equal to 125 m, less than or equal to 125 m, less than or equal to 125 m, less than or equal 100 mm, 100 mm, 150 mm, 200 mm, 300 mm, 400 mm, 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, 10 ...500 mm, 500 mm, 500 mm, 500 mm, 500 mm, 500 mm, 500 mm, 500 mm, 500 mm, 500 mm, 500 mm, 500 mm, 500 mm, 500 mm, 500 mm,

[0047] When the fine fiber layer comprises two or more types of fine fibers, each type of fine fibers can independently have an average fiber length in one or more of the above ranges, and / or all of the fine fibers in the fine fiber layer together can have an average fiber length in one or more of the above ranges. When the filter media comprises two or more fine fiber layers, each fine fiber layer can independently comprise fine fibers having an average fiber length in one or more of the above ranges. In embodiments where the filter media comprises two or more fine fiber layers, the average fiber lengths of the two or more fine fiber layers can be the same or different.

[0048] When present, the fine fibers can have any suitable shape. In some embodiments, the fine fiber layer includes fine fibers that are cylindrical. In certain embodiments, the fine fiber layer includes fine fibers that are non-cylindrical (e.g., ribbon-shaped, flat, and / or fibrils). In some cases, the fine fiber layer includes such fine fibers, which include core-sheath fibers (e.g., concentric core / sheath fibers and / or non-concentric core-sheath fibers), segmented pie-shaped fibers, parallel fibers, tip-trilobal fibers, split fibers, and "island" fibers.

[0049] According to some embodiments, the fine fiber layer comprises fine fibers comprising a matrix polymer. Figure 3A As shown, in some cases, the fine fibers include a matrix polymer (composed of Figure 3A The matrix polymer may be a polymer in which different components (e.g., impact modifier) ​​are dispersed. Figure 3A As shown, in some cases, a component (e.g., Figure 3A The impact modifier 105) is shown dispersed in the matrix polymer. When present, the matrix polymer can form a continuous phase.

[0050] In some embodiments, the matrix polymer comprises a homopolymer. Without wishing to be bound by theory, it is believed that having a matrix polymer comprising a homopolymer increases compatibility with the impact modifier. In some cases, one or more homopolymers account for greater than or equal to 50% by weight, greater than or equal to 55% by weight, greater than or equal to 60% by weight, greater than or equal to 65% by weight, greater than or equal to 70% by weight, greater than or equal to 75% by weight, greater than or equal to 80% by weight, greater than or equal to 85% by weight, greater than or equal to 90% by weight, greater than or equal to 95% by weight, greater than or equal to 97% by weight, greater than or equal to 98% by weight, or greater than or equal to 99% by weight of the matrix polymer. In certain embodiments, one or more homopolymers account for less than or equal to 100 weight %, less than or equal to 99 weight %, less than or equal to 98 weight %, less than or equal to 97 weight %, less than or equal to 95 weight %, less than or equal to 90 weight %, less than or equal to 85 weight %, less than or equal to 80 weight %, less than or equal to 75 weight %, less than or equal to 70 weight %, less than or equal to 65 weight %, or less than or equal to 60 weight %. Combinations of the above ranges are also possible (e.g., greater than or equal to 50 weight % and less than or equal to 100 weight %, greater than or equal to 80 weight % and less than or equal to 100 weight %, or greater than or equal to 90 weight % and less than or equal to 100 weight %). Other ranges are also possible. In some embodiments, one or more homopolymers account for 100 weight % of the matrix polymer.

[0051] When the matrix polymer comprises two or more types of homopolymers, each type of homopolymer can independently account for one or more amounts of the matrix polymer in the above ranges, and / or all homopolymers in the matrix polymer together can account for one or more amounts of the matrix polymer in the above ranges.

[0052] Homopolymers can contain a relatively high percentage of identical repeating units. In some embodiments, at least 90% (e.g., at least 93%, at least 95%, at least 97%, at least 99%, or 100%) of the repeating units (e.g., monomers) in a homopolymer are identical.

[0053] In some embodiments, the matrix polymer is a type of polymer other than a thermosetting plastic. Thermosetting polymers may undergo one or more reactions (e.g., one or more crosslinking reactions) when heated. Thermosetting polymers typically do not flow when heat is applied, but instead become less viscous. Thermosetting polymers may include one or more types of polymers (e.g., paired polymers) and / or one or more chemicals (e.g., paired chemicals).

[0054] In certain embodiments, the matrix polymer includes a thermoplastic polymer. Without wishing to be bound by theory, it is believed that the matrix polymer comprising a thermoplastic polymer shows an increased solubility in an organic solvent and / or an increased viscoelastic behavior. It is believed that this makes it easier to form fine fibers. In some cases, one or more thermoplastic polymers account for more than or equal to 50% by weight, more than or equal to 55% by weight, more than or equal to 60% by weight, more than or equal to 65% by weight, more than or equal to 70% by weight, more than or equal to 75% by weight, more than or equal to 80% by weight, more than or equal to 85% by weight, more than or equal to 90% by weight, more than or equal to 95% by weight, more than or equal to 97% by weight, more than or equal to 98% by weight, or more than or equal to 99% by weight of the matrix polymer. In certain embodiments, one or more thermoplastic polymers account for less than or equal to 100 weight %, less than or equal to 99 weight %, less than or equal to 98 weight %, less than or equal to 97 weight %, less than or equal to 95 weight %, less than or equal to 90 weight %, less than or equal to 85 weight %, less than or equal to 80 weight %, less than or equal to 75 weight %, less than or equal to 70 weight %, less than or equal to 65 weight %, or less than or equal to 60 weight %. Combinations of the above ranges are also possible (e.g., greater than or equal to 50 weight % and less than or equal to 100 weight %, greater than or equal to 80 weight % and less than or equal to 100 weight %, or greater than or equal to 90 weight % and less than or equal to 100 weight %). Other ranges are also possible. In some embodiments, the thermoplastic polymer accounts for 100 weight % of the matrix polymer.

[0055] When the matrix polymer comprises two or more types of thermoplastic polymers, each type of thermoplastic polymer can independently account for one or more amounts of the matrix polymer in the above ranges, and / or all thermoplastic polymers in the matrix polymer together can account for one or more amounts of the matrix polymer in the above ranges.

[0056] In certain embodiments, the matrix polymer comprises a linear polymer. Without wishing to be bound by theory, it is believed that a matrix polymer comprising a linear polymer exhibits increased solubility in an organic solvent and / or increased viscoelastic behavior. It is believed that this makes it easier to form fine fibers. In some cases, the linear polymer accounts for more than or equal to 50% by weight, more than or equal to 55% by weight, more than or equal to 60% by weight, more than or equal to 65% by weight, more than or equal to 70% by weight, more than or equal to 75% by weight, more than or equal to 80% by weight, more than or equal to 85% by weight, more than or equal to 90% by weight, more than or equal to 95% by weight, more than or equal to 97% by weight, more than or equal to 98% by weight, or more than or equal to 99% by weight of the matrix polymer. In certain embodiments, the linear polymer accounts for less than or equal to 100 weight %, less than or equal to 99 weight %, less than or equal to 98 weight %, less than or equal to 97 weight %, less than or equal to 95 weight %, less than or equal to 90 weight %, less than or equal to 85 weight %, less than or equal to 80 weight %, less than or equal to 75 weight %, less than or equal to 70 weight %, less than or equal to 65 weight %, or less than or equal to 60 weight %. Combinations of the above ranges are also possible (e.g., greater than or equal to 50 weight % and less than or equal to 100 weight %, greater than or equal to 80 weight % and less than or equal to 100 weight %, or greater than or equal to 90 weight % and less than or equal to 100 weight %). Other ranges are also possible. In some embodiments, the linear polymer accounts for 100 weight % of the matrix polymer.

[0057] When the matrix polymer comprises two or more types of linear polymers, each type of linear polymer can independently account for one or more amounts of the matrix polymer in the above ranges, and / or all linear polymers in the matrix polymer together can account for one or more amounts of the matrix polymer in the above ranges.

[0058] Examples of suitable base polymers can include synthetic polymers such as polyamides (e.g., nylons, such as nylon 6 (also known as polyamide 6)), polyesters (e.g., poly(caprolactone), poly(butylene terephthalate)), polyurethanes, polyureas, acrylic resins, polymers containing side chains containing carbonyl functional groups (e.g., poly(vinyl acetate), poly(acrylamide)), poly(ether sulfones), polyacrylics (e.g., poly(acrylonitrile), poly(acrylic acid)), polystyrenes, polycarbonates, polyvinyl chlorides, Polysulfones, poly(amic acids), fluorinated polymers (e.g., poly(vinylidene fluoride)), polyols (e.g., poly(vinyl alcohol)), polyethers (e.g., poly(ethylene oxide)), poly(vinyl pyrrolidone), poly(allylamine), butyl rubber, polyethylene, polymers containing silane functional groups, polymers containing thiol functional groups, polymers containing methylol functional groups (e.g., phenolic polymers, melamine polymers, melamine-formaldehyde polymers, crosslinkable polymers containing pendant methylol groups), and / or combinations thereof. In some embodiments, the matrix polymer comprises a copolymer of two or more of the above-listed polymers and / or a blend of two or more of the above-listed polymers (e.g., a blend of polyamide and polyester). In certain embodiments, the matrix polymer is a glassy polymer and / or a semi-crystalline polymer.

[0059] In some embodiments, the matrix polymer comprises a homopolymer.Examples of suitable homopolymers include synthetic polymers, such as those described in the previous paragraph that contain a relatively high percentage of repeating units that are identical.

[0060] In some embodiments, the matrix polymer comprises a thermoplastic polymer.Examples of suitable thermoplastic polymers include the synthetic polymers described above that lack functional groups that react upon application of heat.

[0061] In some embodiments, the matrix polymer comprises a linear polymer. Examples of suitable linear polymers include the above-mentioned synthetic polymers with a linear structure. Such polymers may not be branched and / or cross-linked, or may contain branched and / or cross-linked in relatively small amounts.

[0062] In embodiments where the fine fibers comprise a matrix polymer, the matrix polymer may have any suitable average molecular weight (e.g., number average molecular weight (M)). n ) and / or weight average molecular weight (M w In some embodiments, the average molecular weight of the matrix polymer (e.g., M n and / or M w) is greater than 3 kDa, greater than or equal to 5 kDa, greater than or equal to 7 kDa, greater than or equal to 10 kDa, greater than or equal to 15 kDa, greater than or equal to 20 kDa, greater than or equal to 25 kDa, greater than or equal to 30 kDa, greater than or equal to 35 kDa, greater than or equal to 40 kDa, greater than or equal to 45 kDa, or greater than or equal to 50 kDa. In certain embodiments, the average molecular weight (e.g., M) of the matrix polymer is greater than or equal to 3 kDa, greater than or equal to 5 kDa, greater than or equal to 7 kDa, greater than or equal to 10 kDa, greater than or equal to 15 kDa, greater than or equal to 20 kDa, greater than or equal to 25 kDa, greater than or equal to 30 kDa, greater than or equal to 35 kDa, greater than or equal to 40 n and / or M w ) is less than or equal to 100kDa, less than or equal to 90kDa, less than or equal to 80kDa, less than or equal to 70kDa, less than or equal to 60kDa, less than or equal to 50kDa, less than or equal to 45kDa, less than or equal to 40kDa, less than or equal to 35kDa, less than or equal to 30kDa, or less than or equal to 25kDa. Combinations of the above ranges are also possible (e.g., greater than 3kDa and less than or equal to 100kDa, greater than or equal to 7kDa and less than or equal to 100kDa, or greater than or equal to 15kDa and less than or equal to 50kDa). Other ranges are also possible. Molecular weight (e.g., mean molecular weight) can be determined using gel permeation chromatography (GPC), and can be determined using the formula disclosed elsewhere herein.

[0063] When the matrix polymer comprises two or more types of polymers, each type of polymer may independently have a molecular weight in one or more of the above ranges, and / or all polymers in the matrix polymer together may have a molecular weight in one or more of the above ranges.

[0064] In embodiments where the fine fibers comprise a matrix polymer (and / or a matrix polymer and an impact modifier), the matrix polymer may comprise only polymers of a specific molecular weight. That is, in certain embodiments, the fine fibers comprise a matrix polymer that comprises only polymers of a specific molecular weight and does not comprise any other polymers or components. For example, in some embodiments, the matrix polymer comprises only polymers having a molecular weight greater than 3 kDa, greater than or equal to 5 kDa, greater than or equal to 7 kDa, greater than or equal to 10 kDa, greater than or equal to 15 kDa, greater than or equal to 20 kDa, greater than or equal to 25 kDa, greater than or equal to 30 kDa, greater than or equal to 35 kDa, greater than or equal to 40 kDa, greater than or equal to 45 kDa, or greater than or equal to 50 kDa. In certain embodiments, the matrix polymer comprises only polymers having a molecular weight of less than or equal to 100 kDa, less than or equal to 90 kDa, less than or equal to 80 kDa, less than or equal to 70 kDa, less than or equal to 60 kDa, less than or equal to 50 kDa, less than or equal to 45 kDa, less than or equal to 40 kDa, less than or equal to 35 kDa, less than or equal to 30 kDa, or less than or equal to 25 kDa. Combinations of the above ranges are also possible (e.g., greater than 3 kDa and less than or equal to 100 kDa, greater than or equal to 7 kDa and less than or equal to 100 kDa, or greater than or equal to 15 kDa and less than or equal to 50 kDa). Other ranges are also possible.

[0065] The matrix polymer described herein can have any suitable glass transition temperature. For example, in some embodiments, the glass transition temperature of the matrix polymer is greater than or equal to 20°C, greater than or equal to 25°C, greater than or equal to 30°C, greater than or equal to 40°C, greater than or equal to 45°C, greater than or equal to 50°C, greater than or equal to 60°C, greater than or equal to 70°C, 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 125°C, greater than or equal to 150°C, greater than or equal to 175°C, or greater than or equal to 200°C. In certain embodiments, the glass transition temperature of the matrix polymer is less than or equal to 250°C, less than or equal to 225°C, less than or equal to 200°C, less than or equal to 175°C, less than or equal to 150°C, less than or equal to 125°C, less than or equal to 100°C, less than or equal to 90°C, less than or equal to 80°C, less than or equal to 70°C, less than or equal to 60°C, less than or equal to 50°C, less than or equal to 40°C, less than or equal to 30°C, or less than or equal to 25°C. Combinations of the above ranges are possible (e.g., greater than or equal to 20°C and less than or equal to 250°C or greater than or equal to 45°C and less than or equal to 225°C). Other ranges are also possible. The value of the glass transition temperature can be measured by differential scanning calorimetry (DSC).

[0066] When the matrix polymer comprises two or more types of polymers, each type of polymer may independently have a glass transition temperature of one or more in the above ranges, and / or all polymers in the matrix polymer together may have a glass transition temperature of one or more in the above ranges.

[0067] In embodiments where the fine fibers include a matrix polymer (and / or a matrix polymer and an impact modifier), the fine fibers (and / or the combination of the matrix polymer and the impact modifier in the fine fibers) can include any suitable amount of the matrix polymer. In certain embodiments, the matrix polymer comprises greater than or equal to 75% by weight, greater than or equal to 80% by weight, greater than or equal to 85% by weight, greater than or equal to 90% by weight, greater than or equal to 95% by weight, or greater than or equal to 97% by weight of the fine fibers (and / or the combination of the matrix polymer and the impact modifier in the fine fibers). In some embodiments, the matrix polymer comprises less than or equal to 99% by weight, less than or equal to 97% by weight, less than or equal to 95% by weight, less than or equal to 90% by weight, less than or equal to 85% by weight, or less than or equal to 80% by weight of the fine fibers (and / or the combination of the matrix polymer and the impact modifier in the fine fibers). Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 75 wt % and less than or equal to 99 wt %, greater than or equal to 80 wt % and less than or equal to 97 wt %, or greater than or equal to 85 wt % and less than or equal to 95 wt %). Other ranges are also possible.

[0068] When the fine fibers contain two or more types of matrix polymers, each type of matrix polymer can independently account for one or more amounts of the fine fibers within the above ranges, and / or all of the matrix polymers in the fine fibers together can account for one or more amounts of the fine fibers within the above ranges.

[0069] According to some embodiments, the fine fiber layer may comprise a plurality of fine fibers comprising an impact modifier dispersed in a matrix polymer. As described above, this is schematically shown in Figure 3B , which depicts fine fibers 101 comprising an impact modifier 105 dispersed in the form of microdomains in a matrix polymer 103. When present, the impact modifier can have any of a variety of properties, which are described in further detail below.

[0070] In embodiments where the fine fibers include an impact modifier (and / or a matrix polymer and an impact modifier), the fine fibers (and / or a combination of a matrix polymer and an impact modifier in the fine fibers) may include any suitable amount of the impact modifier. In certain embodiments, the impact modifier comprises greater than or equal to 1 wt %, greater than or equal to 3 wt %, greater than or equal to 5 wt %, greater than or equal to 10 wt %, greater than or equal to 15 wt %, or greater than or equal to 20 wt % of the fine fibers (and / or a combination of a matrix polymer and an impact modifier in the fine fibers). In some embodiments, the impact modifier comprises 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 5 wt %, or less than or equal to 3 wt % of the fine fibers (and / or a combination of a matrix polymer and an impact modifier in the fine fibers). Combinations of the above-referenced ranges are also possible (eg, greater than or equal to 1 wt % and less than or equal to 25 wt %, greater than or equal to 3 wt % and less than or equal to 20 wt %, or greater than or equal to 5 wt % and less than or equal to 15 wt %). Other ranges are also possible.

[0071] When the fine fibers contain two or more types of impact modifiers, each type of impact modifier can independently account for one or more amounts of the fine fibers within the above ranges, and / or all impact modifiers in the fine fibers together can account for one or more amounts of the fine fibers within the above ranges.

[0072] In some embodiments, impact modifiers can make brittle materials (e.g., matrix polymers) more impact resistant. Without wishing to be bound by any theory, it is believed that in some cases, impact modifiers make brittle materials more impact resistant by: (1) preventing crack propagation in brittle materials by widening the crack tip so that the mechanical energy is distributed over a larger radius of curvature, and / or (2) creating areas where strain can occur without cracking, such as areas where the impact modifier expands and / or cavitates.

[0073] In certain embodiments, the impact modifier comprises a copolymer comprising at least two different types of repeating units. One type of repeating unit may have an affinity for the matrix polymer, while the other type of repeating unit may not have an affinity for the matrix polymer.

[0074] In certain embodiments, the impact modifier for a copolymer comprises greater than or equal to 2, greater than or equal to 3, greater than or equal to 4, or greater than or equal to 5 different types of repeating units. According to some embodiments, the impact modifier for a copolymer comprises less than or equal to 6, less than or equal to 5, less than or equal to 4, less than or equal to 3, or less than or equal to 2 different types of repeating units. Combinations of the above ranges are also possible (e.g., greater than or equal to 2 and less than or equal to 6, greater than or equal to 2 and less than or equal to 5, or greater than or equal to 2 and less than or equal to 4). Other ranges are also possible. In some cases, copolymers include terpolymers. In some cases, copolymers include random copolymers, block copolymers, and / or graft copolymers.

[0075] When the fine fibers include two or more types of impact modifiers, each type of impact modifier may independently include repeating units in amounts of one or more of the types in the above ranges and / or have one or more of the above structures.

[0076] The repeating unit having affinity for the matrix polymer may be a repeating unit of the same type as the repeating unit in the matrix polymer, may be miscible with the matrix polymer, may contain one or more reactive sites capable of covalently bonding to the matrix polymer and / or configured to covalently bond to the matrix polymer, may be capable of and / or configured to have an ionic interaction with the matrix polymer, and / or may have an overall solubility parameter similar to that of the repeating unit of the matrix polymer. Whether a covalent bond is formed and whether an ionic interaction is present may be determined by spectroscopic techniques such as FTIR.

[0077] When the Flory-Huggins parameter (χ) is less than or equal to 0.75 (e.g., 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, less than or equal to 0.2, or less than or equal to 0.1), the two repeating units can have similar total solubility parameters. The total solubility parameter of each monomer can be known or can be determined using the Hansen solubility parameters. For example, the Hansen solubility parameters for dipole-dipole interactions, dispersion forces, and hydrogen bonding of exemplary repeating units are shown in Table 1 below. These can be converted to total solubility parameters by the following equation:

[0078]

[0079] The Flory-Huggins parameter (χ) can be determined from the overall solubility parameter using the following equation:

[0080]

[0081] where δ 2is the total solubility parameter of the repeating units of the matrix polymer, δ 1 is the total solubility parameter of the repeating unit of the impact modifier, V 2 is the molar volume of the repeating unit of the base polymer (which can be determined by dividing the density of the repeating unit by the molecular weight of the repeating unit), R is the gas constant (equal to 8.31 J / mol / K), and T is the absolute temperature in Kelvin.

[0082] Table 1. Examples of solubility parameters for exemplary repeating units.

[0083]

[0084] For example, for various combinations of repeating units, by using the overall solubility parameter (δ T ) to solve Equation 2 and the obtained Flory-Huggins parameters are shown in Table 2 below, where X (along the diagonal) indicates that the Flory-Huggins parameter is 0.

[0085] Table 2. Examples of Flory-Huggins parameters for various combinations of repeating units

[0086]

[0087] As an example of a repeating unit in an impact modifier having an affinity for a matrix polymer, a repeating unit in an impact modifier having the same type as a repeating unit present in the matrix polymer will have an affinity for the matrix polymer. The Flory-Huggins parameter for this pair of repeating units is 0.

[0088] As another example, if the repeating units in the impact modifier are miscible with the matrix polymer, it can have an affinity for the matrix polymer. Miscibility can occur when a homopolymer comprising the relevant repeating units forms a homogeneous solution with the matrix polymer in a solid glass phase. This can be determined, for example, by DSC, where a homogeneous solution will show a single glass transition. For each sample, two heating and cooling cycles can be performed, and the miscibility can be determined during the second heating. The heating and cooling can be performed at a ramp rate of 5°C per minute. Each sample can be heated to an upper temperature greater than the melting temperature of the polymer as observed by DSC, and then cooled to -60°C.

[0089] In certain embodiments, the repeating units present in the impact modifier do not have an affinity for the matrix polymer. In such embodiments, they may be of a different type than all repeating units present in the matrix polymer, may be immiscible with the matrix polymer, may lack reactive sites configured to and / or capable of covalently bonding to the matrix polymer, may not be capable of and / or not configured to have ionic interactions with the matrix polymer, and / or they may have an overall solubility parameter that is different than the overall solubility parameter of any repeating unit present in the matrix polymer (e.g., for each repeating unit present in the matrix polymer, its Flory-Huggins parameter may be greater than 0.75).

[0090] According to some embodiments, the impact modifier and / or its repeating units include polyamide (e.g., polyamide 6, polyamide 11, and / or polyamide 6,6), polystyrene, polyether, polypropylene, polycarbonate, polyethylene, polyester, ABS (acrylonitrile butadiene styrene), and / or PVC (polyvinyl chloride). Examples of suitable impact modifiers include the impact modifiers in Table 3.

[0091] Table 3. Non-limiting examples of suitable impact modifiers, matrix polymers, and combinations thereof

[0092]

[0093]

[0094] The impact modifier can have any suitable average molecular weight (e.g., M n and / or M w For example, in some cases, the average molecular weight of the impact modifier (e.g., M n and / or M w ) is greater than or equal to 1 kDa, greater than or equal to 3 kDa, greater than or equal to 5 kDa, greater than or equal to 7 kDa, greater than or equal to 10 kDa, greater than or equal to 15 kDa, greater than or equal to 20 kDa, greater than or equal to 25 kDa, greater than or equal to 30 kDa, greater than or equal to 35 kDa, greater than or equal to 40 kDa, greater than or equal to 45 kDa, greater than or equal to 50 kDa, greater than or equal to 55 kDa, or greater than or equal to 60 kDa. In some embodiments, the average molecular weight (e.g., M) of the impact modifier is greater than or equal to 1 kDa, greater than or equal to 3 kDa, greater than or equal to 5 kDa, greater than or equal to 60 kDa, greater than or equal to 70 kDa, greater than or equal to 80 kDa, greater than or equal to 90 kDa, greater than or equal to 10 kDa, greater than or equal to 15 kDa, greater than or equal to 20 kDa, greater than or equal to 25 kDa, greater than or equal to 30 kDa, greater than or equal to 35 kDa, greater than or equal to 40 kDa, greater than or equal to 45 kDa, greater than or equal to 50 kDa, greater than or equal to 55 kDa, or greater than or equal to 60 kDa. n and / or M w) is less than or equal to 100kDa, less than or equal to 90kDa, less than or equal to 80kDa, less than or equal to 70kDa, less than or equal to 60kDa, less than or equal to 50kDa, less than or equal to 45kDa, less than or equal to 40kDa, less than or equal to 35kDa, less than or equal to 30kDa, or less than or equal to 25kDa. Combinations of the above ranges are also possible (e.g., greater than or equal to 1kDa and less than or equal to 100kDa, greater than or equal to 3kDa and less than or equal to 100kDa, greater than or equal to 7kDa and less than or equal to 100kDa, greater than or equal to 20kDa and less than or equal to 70kDa). Other ranges are also possible. The average molecular weight can be determined using gel permeation chromatography (GPC), and can be determined using the formula disclosed elsewhere herein.

[0095] When the fine fibers contain two or more types of impact modifiers, each type of impact modifier may independently have a molecular weight in one or more of the above ranges, and / or all of the impact modifiers together may have a molecular weight in one or more of the above ranges.

[0096] The ratio of the average molecular weight of the impact modifier to the average molecular weight of the matrix polymer present in the same fine fiber can have any suitable value. For example, in certain embodiments, the ratio of the average molecular weight of the impact modifier to the average molecular weight of the matrix polymer is greater than or equal to 1:30, greater than or equal to 1:20, greater than or equal to 1:10, greater than or equal to 2:10, greater than or equal to 3:10, greater than or equal to 4:10, greater than or equal to 5:10, greater than or equal to 6:10, greater than or equal to 7:10, greater than or equal to 8:10, greater than or equal to 9:10, greater than or equal to 1:1, greater than or equal to 1.25:1, greater than or equal to 1.5:1, or greater than or equal to 1.75:1. In some cases, the ratio of the average molecular weight of the impact modifier to the average molecular weight of the base polymer is less than or equal to 2: 1, less than or equal to 1.9: 1, less than or equal to 1.8: 1, less than or equal to 1.7: 1, less than or equal to 1.6: 1, less than or equal to 1.5: 1, less than or equal to 1.4: 1, less than or equal to 1.3: 1, less than or equal to 1.2: 1, less than or equal to 1.1: 1, less than or equal to 1: 1, less than or equal to 8: 10, less than or equal to 6: 10, less than or equal to 4: 10, less than or equal to 2: 10, or less than or equal to 1: 10. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 1:30 and less than or equal to 2: 1, or greater than or equal to 1: 10 and less than or equal to 2: 1). Other ranges are also possible.

[0097] When the fine fibers contain two or more types of impact modifiers and / or matrix polymers, the ratio of the average molecular weight of each type of impact modifier to each type of matrix polymer can be in one or more of the above ranges. In some embodiments, the ratio of the average molecular weight of all impact modifiers together to all matrix polymers together is in one or more of the above ranges.

[0098] The impact modifiers described herein can have any suitable polydispersity index (PDI). For example, in some cases, the PDI of the impact modifier is 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, or less than or equal to 2. In some cases, the PDI of the impact modifier 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, or greater than or equal to 2.5. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 and less than or equal to 3 or greater than or equal to 1 and less than or equal to 2). Other ranges are also possible.

[0099] When the fine fibers contain two or more types of impact modifiers, each type of impact modifier may independently have a PDI in one or more of the above ranges, and / or all of the impact modifiers together may have a PDI in one or more of the above ranges.

[0100] PDI can be determined from the following equation:

[0101] PDI=M w / M n (Equation 3),

[0102] Among them, M w is the weight average molecular weight and M n is the number average molecular weight, and M w and M n It can be calculated from the parameters measured using gel permeation chromatography according to ASTM D 3536 (1991).

[0103] M w It can be determined or measured according to the following equation:

[0104]

[0105] where w i is the total weight (mass) of polymer chains of a specific length or molecular weight, M i is the molecular weight of an individual polymer chain of a specific length or molecular weight, N iM is the number of polymer chains of approximately the same specific length or molecular weight, and N is the number of unique polymer chains of specific length or molecular weight within the sample. w The same equation is used to determine other variables (e.g., w i and M i ) value.

[0106] M n It can be determined according to the following equation:

[0107]

[0108] Among them, M i 、N i and N are as described above.

[0109] In some embodiments, the fine fibers include an impact modifier that is substantially non-chemically reactive with a matrix polymer that is also present in the fine fibers. For example, in some cases, less than or equal to 10% (e.g., less than or equal to 5%, less than or equal to 3%, less than or equal to 1%, or none) of the repeating units present in the impact modifier have a functional group that is capable of reacting with and / or is configured to react with the matrix polymer. This can be determined by chemical analysis utilizing FTIR (Fourier transform infrared) spectroscopy, NMR (nuclear magnetic resonance) spectroscopy, and / or titration. As another example, in some cases, during a calorimetry process, there is no observable heat flow (e.g., due to a chemical reaction) in the fine fibers comprising the impact modifier and the matrix polymer.

[0110] According to some embodiments, the fine fibers include an impact modifier and a matrix polymer, and the impact modifier does not substantially affect one or more thermal transitions of the matrix polymer. For example, in some cases, the glass transition temperature of the matrix polymer is substantially unaffected by the addition of the impact modifier (e.g., it can remain within 25%, within 20%, within 15%, within 10%, or within 5% of the glass transition temperature it has in the absence of the impact modifier, and / or can have the same glass transition temperature as it has in the absence of the impact modifier). As another example, in some cases, one or more thermal transitions (e.g., melting and / or crystallization) of the matrix polymer are reversible even in the presence of the impact modifier. The thermal transition and its reversibility can be determined by DSC.

[0111] In certain embodiments, the impact modifier exhibits an independent thermal transition relative to the matrix polymer, as determined by DSC, even when both are present in the same fibril.

[0112] In some embodiments, the impact modifier may be capable of being separated from the matrix polymer present in the fine fibers by physical methods (eg, extraction).

[0113] In some cases, the impact modifier is dispersed in the matrix polymer. For example, in some cases, the impact modifier is uniformly dispersed throughout the matrix polymer. In certain embodiments, the impact modifier is present in a microdomain in a continuous phase (e.g., a continuous phase that is a matrix polymer and / or comprises a matrix polymer). Whether the impact modifier is dispersed in the matrix polymer and the morphological characteristics of the dispersion (if present) can be determined by transmission electron microscopy (TEM) using staining for comparison.

[0114] According to certain embodiments, the fine fibers include one or more impact modifiers in the form of discrete microdomains. The impact modifier discrete microdomains can have any suitable average maximum cross-sectional diameter. For example, in some cases, the average maximum cross-sectional diameter of the impact modifier discrete microdomains is greater than or equal to 1 / 100, greater than or equal to 1 / 90, greater than or equal to 1 / 80, greater than or equal to 1 / 70, greater than or equal to 1 / 60, greater than or equal to 1 / 50, greater than or equal to 1 / 40, greater than or equal to 1 / 30, greater than or equal to 1 / 20, greater than or equal to 1 / 10, greater than or equal to 1 / 7, greater than or equal to 1 / 5, greater than or equal to 1 / 4, greater than or equal to 1 / 3, or greater than or equal to 1 / 2 of the average diameter of the fine fibers. In certain embodiments, the average maximum cross-sectional diameter of the discrete microdomains of the impact modifier is less than or equal to 3 / 4, less than or equal to 2 / 3, less than or equal to 1 / 2, less than or equal to 1 / 3, less than or equal to 1 / 4, less than or equal to 1 / 5, less than or equal to 1 / 7, less than or equal to 1 / 10, less than or equal to 1 / 20, less than or equal to 1 / 30, less than or equal to 1 / 40, less than or equal to 1 / 50, less than or equal to 1 / 60, less than or equal to 1 / 70, less than or equal to 1 / 80, or less than or equal to 1 / 90 of the average maximum cross-sectional diameter of the fine fibers. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 / 100 and less than or equal to 3 / 4 or greater than or equal to 1 / 100 and less than or equal to 1 / 4). Other ranges are also possible.

[0115] When the fine fibers contain two or more types of impact modifier discrete microdomains, each type of impact modifier discrete microdomains can independently have an average maximum cross-sectional diameter in one or more of the above ranges, and / or all of the impact modifier discrete microdomains together can have an average maximum cross-sectional diameter in one or more of the above ranges.

[0116] In some embodiments, the fine fibers comprise discrete microdomains of impact modifier, and the average diameter of the discrete microdomains of impact modifier is greater than or equal to 10 nm, greater than or equal to 25 nm, greater than or equal to 50 nm, greater than or equal to 75 nm, greater than or equal to 100 nm, greater than or equal to 150 nm, greater than or equal to 200 nm, greater than or equal to 250 nm, greater than or equal to 300 nm, greater than or equal to 350 nm, greater than or equal to 400 nm, or greater than or equal to 450 nm. In certain embodiments, the average diameter of the discrete microdomains of impact modifier is less than or equal to 500 nm, less than or equal to 450 nm, less than or equal to 400 nm, less than or equal to 350 nm, less than or equal to 300 nm, less than or equal to 250 nm, less than or equal to 200 nm, less than or equal to 150 nm, less than or equal to 100 nm, less than or equal to 75 nm, less than or equal to 50 nm, or less than or equal to 25 nm. Combinations of the above-referenced ranges are also possible (eg, greater than or equal to 10 nm and less than or equal to 500 nm). Other ranges are also possible. The average diameter of discrete microdomains of the impact modifier can be determined by transmission electron microscopy (TEM).

[0117] When the fine fibers contain two or more types of impact modifier discrete microdomains, each type of impact modifier discrete microdomains can independently have an average maximum cross-sectional diameter in one or more of the above ranges, and / or all of the impact modifier discrete microdomains together can have an average maximum cross-sectional diameter in one or more of the above ranges.

[0118] The impact modifier can have any suitable glass transition temperature related to the temperature at which the filter media will be used. For example, in some embodiments, the glass transition temperature of the impact modifier is lower (e.g., at least 1°C, at least 3°C, at least 5°C, at least 10°C, at least 15°C, or at least 20°C lower) than the temperature at which the filter media will be used (e.g., greater than or equal to 20°C, greater than or equal to 40°C, greater than or equal to 60°C, or greater than or equal to 80°C; less than or equal to 100°C, less than or equal to 80°C, less than or equal to 60°C, or less than or equal to 40°C use temperature; combinations of the above ranges are also possible, such as greater than or equal to 20°C and less than or equal to 100°C, or greater than or equal to 20°C and less than or equal to 60°C). Without wishing to be bound by any theory, it is believed that using an impact modifier having a glass transition temperature lower than the use temperature (e.g., the range specified herein) allows the impact modifier to absorb energy at about the speed / frequency of crack propagation in the matrix polymer.

[0119] The impact modifiers described herein may have any suitable absolute glass transition temperature. Without wishing to be bound by theory, it is believed that a low glass transition temperature imparts rubber properties to the impact modifier, which may allow it to make brittle materials more impact-resistant. In some cases, the glass transition temperature of the impact modifier is greater than or equal to -50°C, greater than or equal to -40°C, greater than or equal to -30°C, greater than or equal to -20°C, greater than or equal to -10°C, greater than or equal to 0°C, or greater than or equal to 10°C. In some cases, the glass transition temperature of the impact modifier is less than or equal to 15°C, less than or equal to 10°C, less than or equal to 5°C, less than or equal to 0°C, less than or equal to -10°C, less than or equal to -20°C, less than or equal to -30°C, or less than or equal to -40°C. Combinations of the above ranges are also possible (e.g., greater than or equal to -50°C and less than or equal to 15°C). Other ranges are also possible. The value of the glass transition temperature can be measured by DSC.

[0120] When the fine fibers contain two or more types of impact modifiers, each type of impact modifier can independently have a glass transition temperature in one or more of the above ranges, and / or all of the impact modifiers together can have a glass transition temperature in one or more of the above ranges.

[0121] In certain embodiments, the fine fibers present in the fine fiber layer comprise a salt. Examples of suitable salts include ammonium salts (e.g., tetraethylammonium bromide (TEAB)), sulfonium salts, organic salts (e.g., pyridine), and / or inorganic salts.

[0122] In embodiments where the fine fibers include salt, the fine fibers may include any suitable amount of salt. For example, in some cases, the amount of salt in the fine fibers in the fine fiber layer is 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%, or less than or equal to 1 wt%. In some cases, the amount of salt in the fine fibers in the fine fiber layer is greater than or equal to 0.1 wt%, greater than or equal to 0.5 wt%, greater than or equal to 1 wt%, greater than or equal to 2 wt%, greater than or equal to 3 wt%, or greater than or equal to 4 wt%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 wt% and less than or equal to 5 wt% or greater than or equal to 1 wt% and less than or equal to 5 wt%). Other ranges are also possible.

[0123] In some embodiments, the filter media includes a fine fiber layer in which at least some (or all) of the fine fibers do not contain an impact modifier. An example of such a fine fiber layer is schematically shown in Figure 3B For example, in one set of embodiments, the fine fiber layers described herein do not comprise fine fibers comprising an impact modifier dispersed in a matrix polymer.

[0124] In embodiments where the fine fiber layer does not comprise an impact modifier dispersed in a matrix polymer, the fine fibers may comprise any of a variety of suitable materials, such as those described elsewhere herein as suitable for use as a matrix polymer.

[0125] The fine fiber layers described herein can have any of a variety of suitable porosities (i.e., void volumes). In some embodiments, the fine fiber layer has a porosity 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 80%, greater than or equal to 85%, greater than or equal to 90%, greater than or equal to 95%, or greater than or equal to 97%. In some embodiments, the fine fiber layer has a porosity less than or equal to 99%, less than or equal to 98%, less than or equal to 97%, 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 80%, or less than or equal to 75%. Combinations of the above ranges are also possible (e.g., greater than or equal to 65% and less than or equal to 99%, greater than or equal to 70% and less than or equal to 97%, greater than or equal to 80% and less than or equal to 97%, or greater than 80% and less than or equal to 99%). Other ranges are also possible.

[0126] When the filter media includes two or more fine fiber layers, each fine fiber layer can independently have a porosity in one or more of the above ranges. In embodiments where the filter media includes two or more fine fiber layers, the porosity of the two or more fine fiber layers can be the same or different.

[0127] The porosity of a layer is equal to 100% - [the solidity of the layer]. The solidity of a layer is equal to the percentage of the interior of the layer that is occupied by solid material. A non-limiting way of determining the solidity of a layer is described in this paragraph, but other methods are possible. The method described in this paragraph includes determining the weight per unit area and the thickness of the layer, and then applying the following formula: Solidity = [weight per unit area of ​​the layer / (density of the components forming the layer·thickness of the layer)]·100%. The density of the components forming the layer is equal to the average density of one or more materials (e.g., fibers therein, any other components therein) that form the components of the layer, which is typically specified by the manufacturer of each material. The average density of the materials that form the components of the layer can be determined by: (1) determining the total volume of all components in the layer; and (2) dividing the total mass of all components in the layer by the total volume of all components in the first type of layer. If the mass and density of each component of the layer are known, the volume of all components in the layer can be determined by: (1) for each type of component, dividing the total mass of the components in the first type of layer by the density of the component; and (2) summing the volumes of each component. If the mass and density of each component of a layer are unknown, the volume of all components in the layer can be determined based on Archimedean principle.

[0128] The fine fiber layer described herein can have any of a variety of suitable average pore sizes. In some embodiments, the average pore size of the fine fiber layer is greater than or equal to 0.001 microns, greater than or equal to 0.01 microns, greater than or equal to 0.05 microns, greater than or equal to 0.1 microns, greater than or equal to 0.2 microns, greater than or equal to 0.5 microns, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 3 microns, greater than or equal to 4 microns, greater than or equal to 5 microns, greater than or equal to 6 microns, greater than or equal to 7 microns, greater than or equal to 8 microns, or greater than or equal to 9 microns. In some embodiments, the average pore size of the fine fiber layer is 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 microns, less than or equal to 3 microns, less than or equal to 2 microns, less than or equal to 1 micron, less than or equal to 0.5 microns, less than or equal to 0.2 microns, less than or equal to 0.1 micron, less than or equal to 0.05 microns, or less than or equal to 0.01 microns. Combinations of the above-referenced ranges are also possible (eg, greater than or equal to 0.001 microns and less than or equal to 10 microns, greater than or equal to 0.01 microns and less than or equal to 8 microns, or greater than or equal to 0.01 microns and less than or equal to 5 microns). Other ranges are also possible.

[0129] When the filter media includes two or more fine fiber layers, each fine fiber layer can independently have an average pore size in one or more of the above ranges. In embodiments where the filter media includes two or more fine fiber layers, the porosity of the two or more fine fiber layers can be the same or different.

[0130] The average pore size can be measured using ASTM F316 (2003).

[0131] The fine fiber layers described herein may have any suitable maximum pore diameter. In some embodiments, the fine fiber layer has a maximum pore diameter greater than or equal to 0.1 micron, greater than or equal to 0.2 micron, greater than or equal to 0.3 micron, greater than or equal to 0.4 micron, greater than or equal to 0.5 micron, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 3 microns, greater than or equal to 4 microns, greater than or equal to 5 microns, greater than or equal to 6 microns, greater than or equal to 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, or greater than or equal to 12 microns. In some embodiments, the fine fiber layer has a maximum pore diameter 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 microns, less than or equal to 3 microns, less than or equal to 2 microns, or less than or equal to 1 micron. Combinations of the above-referenced ranges are also possible (eg, greater than or equal to 0.1 microns and less than or equal to 15 microns, greater than or equal to 0.3 microns and less than or equal to 12 microns, or greater than or equal to 0.3 microns and less than or equal to 12 microns). Other ranges are also possible.

[0132] When the filter media includes two or more fine fiber layers, each fine fiber layer can independently have a maximum pore diameter in one or more of the above ranges. In embodiments where the filter media includes two or more fine fiber layers, the maximum pore diameters of the two or more fine fiber layers can be the same or different.

[0133] The maximum pore size can be measured using ASTM F316 (2003).

[0134] The fine fiber layer described herein can have any of a variety of suitable thicknesses. For example, in some embodiments, the thickness of the fine fiber layer is greater than the average fiber diameter of the fine fibers in the layer. For example, in some embodiments, the thickness of the fine fiber layer is greater than or equal to 10 nm, greater than or equal to 20 nm, greater than or equal to 30 nm, greater than or equal to 40 nm, greater than or equal to 50 nm, greater than or equal to 100 nm, greater than or equal to 500 nm, greater than or equal to 1 micron, greater than or equal to 10 microns, greater than or equal to 0.1 mm, greater than or equal to 1 mm, greater than or equal to 3 mm, or greater than or equal to 4 mm. In some embodiments, the thickness of the fine fiber layer is less than or equal to 5 mm, less than or equal to 4 mm, less than or equal to 3 mm, less than or equal to 2 mm, less than or equal to 1 mm, less than or equal to 0.5 mm, less than or equal to 0.2 mm, less than or equal to 0.1 mm, less than or equal to 10 microns, less than or equal to 1 micron, less than or equal to 500 nm, or less than or equal to 100 nm. Combinations of the above-referenced ranges are also possible (eg, greater than or equal to 10 nm and less than or equal to 5 mm, greater than or equal to 20 nm and less than or equal to 1 mm, or greater than or equal to 50 nm and less than or equal to 0.2 mm). Other ranges are also possible.

[0135] When the filter media includes two or more fine fiber layers, each fine fiber layer can independently have a thickness in one or more of the above ranges. In embodiments where the filter media includes two or more fine fiber layers, the thickness of the two or more fine fiber layers can be the same or different.

[0136] The thickness can be determined by imaging a cross section of the fine fiber layer using a scanning electron microscope (SEM).

[0137] The fine fiber layer described herein can have any of a variety of suitable weights per unit area. For example, in some embodiments, the fine fiber layer has a weight per unit area of ​​greater than or equal to 0.001 g / m 2In some embodiments, the fine fiber layer has a weight per unit area of ​​less than or equal to 20 gsm, less than or equal to 18 gsm, less than or equal to 15 gsm, less than or equal to 13 gsm, less than or equal to 10 gsm, less than or equal to 8 gsm, less than or equal to 5 gsm, less than or equal to 4 gsm, less than or equal to 3 gsm, less than or equal to 2 gsm, or less than or equal to 1 gsm. Combinations of the above-referenced ranges are also possible (eg, greater than or equal to 0.001 gsm and less than or equal to 20 gsm, greater than or equal to 0.01 gsm and less than or equal to 10 gsm, or greater than or equal to 0.1 gsm and less than or equal to 5 gsm). Other ranges are also possible.

[0138] When the filter media includes two or more fine fiber layers, each fine fiber layer can independently have a basis weight in one or more of the above ranges. In embodiments where the filter media includes two or more fine fiber layers, the basis weights of the two or more fine fiber layers can be the same or different.

[0139] The weight per unit area may be measured according to ASTM D3776-20 (2020).

[0140] The fine fiber layer described herein can have any of a variety of suitable air permeabilities. For example, in some embodiments, the air permeability of the fine fiber layer is greater than 0 ft 3 / (minute ft 2)(CFM), greater than or equal to 0.1CFM, greater than or equal to 0.5CFM, greater than or equal to 1CFM, greater than or equal to 2CFM, greater than or equal to 5CFM, greater than or equal to 7CFM, greater than or equal to 10CFM, greater than or equal to 12CFM, greater than or equal to 15CFM, greater than or equal to 20CFM, greater than or equal to 25CFM, greater than or equal to 30CFM, greater than or equal to 40CFM, greater than or equal to 50CFM, greater than or equal to 60CFM, greater than or equal to 70CFM, greater than or equal to 80CFM, or greater than or equal to 90CFM. In some cases, the fine fiber layer has an air permeability of less than or equal to 100 CFM, less than or equal to 90 CFM, less than or equal to 80 CFM, less than or equal to 70 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, less than or equal to 25 CFM, less than or equal to 20 CFM, less than or equal to 15 CFM, less than or equal to 12 CFM, less than or equal to 10 CFM, less than or equal to 7 CFM, or less than or equal to 5 CFM. Combinations of the above-referenced ranges are also possible (e.g., greater than 0 CFM and less than or equal to 100 CFM, greater than or equal to 0.1 CFM and less than or equal to 50 CFM, or greater than or equal to 0.5 CFM and less than or equal to 30 CFM). Other ranges are also possible.

[0141] When the filter media includes two or more fine fiber layers, each fine fiber layer can independently have an air permeability in one or more of the above ranges. In embodiments where the filter media includes two or more fine fiber layers, the air permeabilities of the two or more fine fiber layers can be the same or different.

[0142] The air permeability may be measured at a pressure of 125 Pa according to ASTM D737-04 (2016).

[0143] The fine fiber layers described herein can have any suitable elongation at break. In some embodiments, the fine fiber layer has an elongation at break of greater than or equal to 5%, greater than or equal to 10%, greater than or equal to 15%, greater than or equal to 20%, greater than or equal to 30%, greater than or equal to 40%, greater than or equal to 50%, greater than or equal to 60%, greater than or equal to 70%, greater than or equal to 80%, greater than or equal to 90%, greater than or equal to 100%, greater than or equal to 125%, greater than or equal to 150%, greater than or equal to 175%, or greater than or equal to 200%. In some embodiments, the elongation at break of the fine fiber layer is 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%, less than or equal to 90%, less than or equal to 80%, less than or equal to 70%, less than or equal to 60%, or less than or equal to 50%. Combinations of the above ranges are also possible (e.g., greater than or equal to 5% and less than or equal to 300%, greater than or equal to 20% and less than or equal to 300%, greater than or equal to 40% and less than or equal to 300%, greater than or equal to 30% and less than or equal to 200%, or greater than or equal to 40% and less than or equal to 80%). Other ranges are also possible.

[0144] When the filter media includes two or more fine fiber layers, each fine fiber layer can independently have an elongation at break of one or more of the above ranges. In embodiments where the filter media includes two or more fine fiber layers, the elongation at break of the two or more fine fiber layers can be the same or different.

[0145] Elongation at break may be determined according to the standard T494 om-96 (1996) test using a test span of 3.5 inches and a jaw separation speed of 12 inches / minute.

[0146] The fine fiber layer described herein can have any suitable tensile strength. In some embodiments, the fine fiber layer has a tensile strength (normalized by weight per unit area) greater than or equal to 15 gf / gsm, greater than or equal to 30 gf / gsm, greater than or equal to 50 gf / gsm, greater than or equal to 60 gf / gsm, greater than or equal to 70 gf / gsm, greater than or equal to 75 gf / gsm, greater than or equal to 80 gf / gsm, greater than or equal to 100 gf / gsm, greater than or equal to 125 gf / gsm, greater than or equal to 150 gf / gsm, greater than or equal to 200 gf / gsm, greater than or equal to 250 gf / gsm, greater than or equal to 300 gf / gsm, greater than or equal to 400 gf / gsm, greater than or equal to 500 gf / gsm, greater than or equal to 600 gf / gsm, greater than or equal to 700 gf / gsm, greater than or equal to 800 gf / gsm, greater than or equal to 100 gf / gsm, greater than or equal to 125 gf / gsm, greater than or equal to 150 gf / gsm, greater than or equal to 200 gf / gsm, greater than or equal to 250 gf / gsm, greater than or equal to 300 gf / gsm, greater than or equal to 400 gf / gsm, greater than or equal to 5 ... gf / gsm, greater than or equal to 600 gf / gsm, greater than or equal to 700 gf / gsm, greater than or equal to 800 gf / gsm, or greater than or equal to 900 gf / gsm. In certain embodiments, the tensile strength of the fine fiber layer (normalized by weight per unit area) is less than or equal to 1000 gf / gsm, less than or equal to 900 gf / gsm, less than or equal to 800 gf / gsm, less than or equal to 700 gf / gsm, less than or equal to 600 gf / gsm, less than or equal to 500 gf / gsm, less than or equal to 400 gf / gsm, less than or equal to 300 gf / gsm, less than or equal to 250 gf / gsm, less than or equal to 200 gf / gsm, less than or equal to 150 gf / gsm, less than or equal to 125 gf / gsm, less than or equal to 100 gf / gsm, less than or equal to 80 gf / gsm, less than or equal to 70 gf / gsm, or less than or equal to 60 gf / gsm. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 15 gf / gsm and less than or equal to 1000 gf / gsm, greater than or equal to 30 gf / gsm and less than or equal to 1000 gf / gsm, greater than or equal to 50 gf / gsm and less than or equal to 1000 gf / gsm, greater than or equal to 75 gf / gsm and less than or equal to 1000 gf / gsm, or greater than or equal to 80 gf / gsm and less than or equal to 150 gf / gsm). Other ranges are also possible.

[0147] When the filter media includes two or more fine fiber layers, each fine fiber layer can independently have a tensile strength in one or more of the above ranges. In embodiments where the filter media includes two or more fine fiber layers, the tensile strengths of the two or more fine fiber layers can be the same or different.

[0148] The tensile strength of the fine fiber layer can be determined according to the following steps. First, the fine fibers can be deposited on wax paper to form a fine fiber layer with a weight per unit area of ​​5 gsm. The fine fiber layer can then be removed from the wax paper and cut to form a free-standing specimen with a size of 1 inch by 7 inches. The tensile strength of these specimens can be determined on a Thwing-Albert tensile testing machine equipped with a 20N load cell. The gap between the jaws on the machine can be set to 3.5 inches, and the stretching rate used can be 12 inches / minute. The tensile test data obtained under these conditions can then be converted into a stress-strain curve (for example, using Winwedge-12-software). The average tensile strength can be calculated from the stress-strain curve based on the measurement results of at least 10 different specimens.

[0149] The fine fiber layers described herein can have any suitable tenacity (i.e., the amount of tensile energy absorbed by the fine fiber layer before breaking). In some embodiments, the fine fiber layer has a tenacity 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 35 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 90 gsm, or greater than or equal to 100 gsm. In some embodiments, the fine fiber layer has a tenacity less than or equal to 120 gsm, less than or equal to 110 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, or less than or equal to 35 gsm. Combinations of the above-referenced ranges are also possible (eg, greater than or equal to 20 gsm and less than or equal to 120 gsm, greater than or equal to 25 gsm and less than or equal to 110 gsm, or greater than or equal to 40 gsm and less than or equal to 100 gsm). Other ranges are also possible.

[0150] When the filter media includes two or more fine fiber layers, each fine fiber layer can independently have a tenacity in one or more of the above ranges. In embodiments where the filter media includes two or more fine fiber layers, the tenacities of the two or more fine fiber layers can be the same or different.

[0151] Toughness can be measured according to T494 om-96, where toughness is the total area under the stress-strain curve.

[0152] In some embodiments, the fine fiber layer includes fine fibers that are electrospun fibers. In such embodiments, the fine fibers can be electrospun from a solution comprising any suitable solvent (e.g., to further include a solution of one or more polymers disclosed herein). Suitable solvents may include formic acid (FA), acetic acid, trifluoroacetic acid (TFAA), dichloromethane (DCM), 1,1,1,3,3,3-hexafluoro-2-propanol (HFP), pentafluoropentanoic acid (PFPA), tetrahydrofuran (THF), dimethylacetamide, dimethylformamide, dioxolane, acetone, ethyl acetate, water, and / or alcohol (e.g., ethanol, propanol, and / or isopropanol).

[0153] The solution (e.g., comprising at least a solvent and a polymer from which the electrospun fibers are formed) from which the fine fiber layer is electrospun can have any suitable conductivity. For example, in some cases, the conductivity of the polymer solution is greater than or equal to 10 μS, greater than or equal to 25 μS, greater than or equal to 50 μS, greater than or equal to 75 μS, greater than or equal to 100 μS, greater than or equal to 120 μS, greater than or equal to 150 μS, greater than or equal to 200 μS, greater than or equal to 250 μS, greater than or equal to 300 μS, greater than or equal to 400 μS, greater than or equal to 500 μS, greater than or equal to 750 μS, greater than or equal to 1,000 μS, greater than or equal to 2,000 μS, greater than or equal to 3,000 μS, greater than or equal to 4,000 μS, or greater than or equal to 5,000 μS. In certain embodiments, the conductivity of the polymer solution is less than or equal to 15,000 μS, less than or equal to 14,000 μS, less than or equal to 13,000 μS, less than or equal to 12,000 μS, less than or equal to 11,000 μS, less than or equal to 10,000 μS, less than or equal to 9,000 μS, less than or equal to 8,000 μS, less than or equal to 7,000 μS, less than or equal to 6,000 μS, less than or equal to 5 ,000μS, less than or equal to 4,000μS, less than or equal to 3,000μS, less than or equal to 2,000μS, less than or equal to 1,000μS, less than or equal to 750μS, less than or equal to 500μS, less than or equal to 400μS, less than or equal to 300μS, less than or equal to 250μS, less than or equal to 200μS, less than or equal to 150μS, less than or equal to 120μS, or less than or equal to 100μS. Combinations of the above ranges are also possible (e.g., greater than or equal to 10μS and less than or equal to 10,000μS, greater than or equal to 100μS and less than or equal to 500μS, or greater than or equal to 120μS and less than or equal to 300μS). The conductivity can be determined using a conductivity meter.

[0154] When one or more polymers are added to a solvent for electrospinning, the polymer solution can have any suitable viscosity. For example, in some cases, the viscosity of the polymer solution is greater than or equal to 10 millipascal-seconds, greater than or equal to 25 millipascal-seconds, greater than or equal to 50 millipascal-seconds, greater than or equal to 75 millipascal-seconds, greater than or equal to 100 millipascal-seconds, greater than or equal to 125 millipascal-seconds, greater than or equal to 150 millipascal-seconds, greater than or equal to 200 millipascal-seconds, greater than or equal to 250 millipascal-seconds, greater than or equal to 300 millipascal-seconds, greater than or equal to 400 millipascal-seconds, greater than or equal to 500 millipascal-seconds, greater than or equal to 750 millipascal-seconds, greater than or equal to 1000 millipascal-seconds, greater than or equal to 1250 millipascal-seconds, greater than or equal to 1500 millipascal-seconds, greater than or equal to 1750 millipascal-seconds, or greater than or equal to 2000 millipascal-seconds. In some cases, the viscosity of the polymer solution is less than or equal to 2500 milliPascal-seconds, less than or equal to 2250 milliPascal-seconds, less than or equal to 2000 milliPascal-seconds, less than or equal to 1750 milliPascal-seconds, less than or equal to 1500 milliPascal-seconds, less than or equal to 1250 milliPascal-seconds, less than or equal to 1000 milliPascal-seconds, less than or equal to 750 milliPascal-seconds, less than or equal to 500 milliPascal-seconds, less than or equal to 400 milliPascal-seconds, less than or equal to 300 milliPascal-seconds, less than or equal to 250 milliPascal-seconds, less than or equal to 200 milliPascal-seconds, less than or equal to 150 milliPascal-seconds, less than or equal to 125 milliPascal-seconds, or less than or equal to 100 milliPascal-seconds. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 10 milliPascal-seconds and less than or equal to 2500 milliPascal-seconds, greater than or equal to 75 milliPascal-seconds and less than or equal to 500 milliPascal-seconds, or greater than or equal to 100 milliPascal-seconds and less than or equal to 300 milliPascal-seconds). Other ranges are also possible.

[0155] The viscosity of the polymer solution can be measured by using a rotational viscometer at 1.7 s -1 The viscosity is determined at a shear rate of 1000 Å and a temperature of 20° C. After the value displayed thereon has stabilized, the viscosity can be determined by a rotational viscometer. An example of a suitable rotational viscometer is a Brookfield LVT viscometer with a No. 62 spindle.

[0156] In some embodiments, one or more of the layers of the filter medium can be a pre-filter layer. In some embodiments, the filter medium includes a pre-filter layer, which is a nonwoven fiber web, such as a meltblown layer. That is, in some embodiments, the filter medium includes a pre-filter layer formed by a meltblown process. The filter medium can also include a pre-filter layer that is a non-meltblown layer. That is, in some embodiments, the pre-filter layer can be formed by a process other than the meltblown process (e.g., electrostatic spinning, solvent spinning, centrifugal spinning, etc.). The characteristics of the pre-filter layer will be further described in detail below.

[0157] The pre-filter layer described herein can include fibers having various suitable average fiber diameters. In some embodiments, the average fiber diameter of the fibers in the pre-filter layer is greater than or equal to 0.5 microns, greater than or equal to 0.6 microns, greater than or equal to 0.8 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 2.25 microns, greater than or equal to 2.5 microns, greater than or equal to 2.75 microns, greater than or equal to 3 microns, greater than or equal to 3.25 microns, greater than or equal to 3.5 microns, or greater than or equal to 3.75 microns. In some embodiments, the average fiber diameter of the fibers in the pre-filter layer is less than or equal to 4 microns, less than or equal to 3.75 microns, less than or equal to 3.5 microns, less than or equal to 3.25 microns, less than or equal to 3 microns, less than or equal to 2.75 microns, less than or equal to 2.5 microns, less than or equal to 2.25 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, less than or equal to 0.8 microns, or less than or equal to 0.6 microns. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.5 microns and less than or equal to 4 microns, greater than or equal to 1 micron and less than or equal to 3 microns, or greater than or equal to 1 micron and less than or equal to 2.5 microns). Other ranges are also possible.

[0158] When the pre-filter layer comprises two or more types of fibers, each type of fiber can independently have an average fiber diameter in one or more of the above ranges, and / or all of the fibers in the pre-filter layer together can have an average fiber diameter in one or more of the above ranges. When the filter media comprises two or more pre-filter layers, the preceding sentence can apply independently for each pre-filter layer. In embodiments where the filter media comprises two or more pre-filter layers, the average fiber diameters of the two or more pre-filter layers can be the same or different.

[0159] In some embodiments, the pre-filter layer comprises synthetic fibers. For example, the synthetic fibers can comprise greater than or equal to 60 weight percent, greater than or equal to 65 weight percent, greater than or equal to 70 weight percent, greater than or equal to 75 weight percent, greater than or equal to 80 weight percent, greater than or equal to 85 weight percent, greater than or equal to 90 weight percent, greater than or equal to 92 weight percent, greater than or equal to 95 weight percent, greater than or equal to 98 weight percent, greater than or equal to 98.5 weight percent, greater than or equal to 99 weight percent, or greater than or equal to 99.5 weight percent of the pre-filter layer. In some embodiments, synthetic fibers can account for less than or equal to 100 weight percent, less than or equal to 99.5 weight percent, less than or equal to 99 weight percent, less than or equal to 98.5 weight percent, less than or equal to 98 weight percent, less than or equal to 95 weight percent, less than or equal to 92 weight percent, less than or equal to 90 weight percent, less than or equal to 85 weight percent, less than or equal to 80 weight percent, less than or equal to 75 weight percent, less than or equal to 70 weight percent, or less than or equal to 65 weight percent of the pre-filter layer. Combinations of the above ranges are also possible (e.g., greater than or equal to 60 weight percent and less than or equal to 100 weight percent, greater than or equal to 70 weight percent and less than or equal to 99 weight percent, or greater than or equal to 80 weight percent and less than or equal to 98 weight percent). Other ranges are also possible. In some embodiments, synthetic fibers account for 100 weight percent of all fibers in the pre-filter layer (e.g., in a meltblown pre-filter layer).

[0160] When the pre-filter layer comprises two or more types of synthetic fibers, each type of synthetic fiber can independently account for an amount of the pre-filter in one or more of the above ranges, and / or all of the synthetic fibers in the pre-filter layer together can account for an amount of the pre-filter layer in one or more of the above ranges. When the filter media comprises two or more pre-filter layers, the preceding sentence can apply independently for each pre-filter layer. In embodiments where the filter media comprises two or more pre-filter layers, the amount of synthetic fibers present in the two or more pre-filter layers can be the same or different.

[0161] The synthetic fibers present in the pre-filter layer can have any of a variety of suitable average fiber diameters. In some embodiments, the average fiber diameter of the synthetic fibers in the pre-filter layer is greater than or equal to 0.5 microns, greater than or equal to 0.6 microns, greater than or equal to 0.8 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 2.25 microns, greater than or equal to 2.5 microns, greater than or equal to 2.75 microns, greater than or equal to 3 microns, greater than or equal to 3.25 microns, greater than or equal to 3.5 microns, or greater than or equal to 3.75 microns. In some embodiments, the average fiber diameter of the synthetic fibers in the pre-filter layer is less than or equal to 4 microns, less than or equal to 3.75 microns, less than or equal to 3.5 microns, less than or equal to 3.25 microns, less than or equal to 3 microns, less than or equal to 2.75 microns, less than or equal to 2.5 microns, less than or equal to 2.25 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, less than or equal to 0.8 microns, or less than or equal to 0.6 microns. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.5 microns and less than or equal to 4 microns, greater than or equal to 1 micron and less than or equal to 3 microns, or greater than or equal to 1 micron and less than or equal to 2.5 microns). Other ranges are also possible.

[0162] When the pre-filter layer comprises two or more types of synthetic fibers, each type of synthetic fiber can independently have an average fiber diameter in one or more of the above ranges, and / or all of the synthetic fibers in the pre-filter layer together can have an average fiber diameter in one or more of the above ranges. When the filter media comprises two or more pre-filter layers, the preceding sentence can apply independently for each pre-filter layer. In embodiments where the filter media comprises two or more pre-filter layers, the average fiber diameters of the synthetic fibers in the two or more pre-filter layers can be the same or different.

[0163] In some cases, the synthetic fibers present in the pre-filter layer may be continuous fibers, such as the types of continuous fibers described elsewhere herein as suitable for inclusion in a fine fiber layer.

[0164] Non-limiting examples of suitable synthetic fibers include fibers comprising one or more of the following materials: poly(olefins) (e.g., poly(propylene)), poly(esters) (e.g., poly(butylene terephthalate), poly(ethylene terephthalate)), nylon, poly(aramid) (para and / or meta), poly(vinyl alcohol), poly(ether sulfone), poly(acrylic) (e.g., poly(acrylonitrile)), fluorinated polymers (e.g., poly(vinylidene fluoride)), cellulose acetate, acrylic resins (dry spun acrylic, modified acrylic, wet spun acrylic), polyvinyl chloride, polytetrafluoroethylene, polystyrene, polysulfone, polycarbonate, polyamide, polyurethane, phenolic resin polymers, polyvinylidene fluoride, polyethylene, polyimide, Kevlar, Nomex, halogenated polymers, polyphenylene oxide, polyphenylene sulfide, polymethylpentene, polyetheretherketone, PET, liquid crystal polymers (e.g., poly(p-phenylene-2,6-benzobis(difluoromethane)), ... oxadiazole (PBO), polyester-based liquid crystal polymers such as polyesters produced by the condensation polymerization of 4-hydroxybenzoic acid and 6-hydroxynaphthalene-2-carboxylic acid), and combinations thereof.

[0165] Synthetic fibers can include monocomponent and / or multicomponent fibers (i.e., fibers having multiple compositions, such as bicomponent fibers). In some cases, synthetic fibers can include meltblown fibers, meltspun fibers, electrospun (e.g., melt, solvent) fibers, or centrifugal spun fibers. Synthetic fibers can also include staple fibers.

[0166] In some embodiments, the pre-filter layer comprises glass fibers (e.g., microglass fibers, chopped strand fibers, and / or combinations thereof). The glass fibers, if present, can be present in the pre-filter layer (e.g., non-meltblown pre-filter layer) in any suitable amount. In some embodiments, the weight percent of glass fibers in the pre-filter layer can be greater than or equal to 0 weight percent, greater than or equal to 10 weight percent, greater than or equal to 20 weight percent, greater than or equal to 30 weight percent, greater than or equal to 40 weight percent, greater than or equal to 50 weight percent, greater than or equal to 60 weight percent, greater than or equal to 70 weight percent, greater than or equal to 80 weight percent, greater than or equal to 90 weight percent, or greater than or equal to 95 weight percent. In some embodiments, the weight percent of glass fibers in the pre-filter layer can be less than or equal to 100 weight percent, less than or equal to 95 weight percent, less than or equal to 90 weight percent, less than or equal to 80 weight percent, less than or equal to 70 weight percent, less than or equal to 60 weight percent, less than or equal to 50 weight percent, less than or equal to 40 weight percent, less than or equal to 30 weight percent, less than or equal to 20 weight percent, or less than or equal to 10 weight percent. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 weight percent and less than or equal to 100 weight percent, or greater than or equal to 0 weight percent and less than or equal to 95 weight percent). Other ranges are also possible. In some embodiments where the pre-filter layer is a meltblown layer, the pre-filter layer does not contain glass fibers (e.g., glass fibers account for 0 weight percent of the pre-filter layer).

[0167] When the pre-filter layer comprises two or more types of glass fibers, each type of glass fiber may independently account for an amount of the pre-filter layer in one or more of the above ranges, and / or all of the glass fibers in the pre-filter layer together may account for an amount of the pre-filter layer in one or more of the above ranges. When the filter media comprises two or more pre-filter layers, the preceding sentence may apply independently for each pre-filter layer.

[0168] In some embodiments, the pre-filter layer comprises glass fibers having an average diameter of 0.1 microns or greater, 0.15 microns or greater, 0.2 microns or greater, 0.25 microns or greater, 0.3 microns or greater, 0.4 microns or greater, 0.5 microns or greater, 0.75 microns or greater, 1 micron or greater, 1.25 microns or greater, 1.5 microns or greater, 2 microns or greater, 2.5 microns or greater, 3 microns or greater, 4 microns or greater, 5 microns or greater, 7.5 microns or greater, 10 microns or greater, or 12.5 microns or greater. In some embodiments, the pre-filter layer comprises glass fibers having an average diameter of 40 microns or less, 35 microns or less, 30 microns or less, 25 microns or less, 20 microns or less, 15 microns or less, 12.5 microns or less, 10 microns or less, 7.5 microns or less, 5 microns or less, 4 microns or less, 3 microns or less, 2.5 microns or less, 2 microns or less, 1.5 microns or less, 1.25 microns or less, 1 micron or less, 0.75 microns or less, 0.5 microns or less, 0.4 microns or less, 0.3 microns or less, 0.25 microns or less, or 0.2 microns or less. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.1 micrometers and less than or equal to 40 micrometers, greater than or equal to 0.4 micrometers and less than or equal to 20 micrometers, greater than or equal to 0.15 micrometers and less than or equal to 15 micrometers, greater than or equal to 0.15 micrometers and less than or equal to 3 micrometers, greater than or equal to 0.25 micrometers and less than or equal to 3 micrometers, or greater than or equal to 0.25 micrometers and less than or equal to 2 micrometers). Other ranges are also possible.

[0169] When the pre-filter layer comprises two or more types of glass fibers, each type of glass fiber can independently have an average diameter in one or more of the above ranges, and / or all of the glass fibers in the pre-filter layer can have an average diameter in one or more of the above ranges. In embodiments where the filter media comprises two or more pre-filter layers, the average fiber diameters of the glass fibers in the two or more pre-filter layers can be the same or different.

[0170] In some embodiments, the pre-filter includes additives, such as charge stabilizing additives. An example of a suitable class of charge stabilizing additives is a hindered amine light stabilizer. Without wishing to be bound by any particular theory, it is believed that the hindered amine light stabilizer can accept and stabilize charged substances (e.g., positively charged substances, such as protons from water; negatively charged substances) thereon. An example of a suitable hindered amine light stabilizer is CHIMASSORB 944FL. Other 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, triamides), stearates / salts (e.g., magnesium stearate, calcium stearate) and stearamide (e.g., ethylene bis stearamide). The charge stabilizing additive can be incorporated into the fiber and / or can be incorporated into the pre-filter in another manner (e.g., as particles, as a coating on the fiber). An example of the way in which the charge stabilizing additive can be incorporated into the fiber is by forming a continuous fiber from a composition containing a charge stabilizing additive.

[0171] In some embodiments, the surface of the pre-filter layer can be modified using additives (e.g., oleophobic additives). In some embodiments, the pre-filter layer includes one or more additives (e.g., oleophobic additives). For example, in some embodiments, the pre-filter layer can be subjected to one or more surface treatments. For example, chemical vapor deposition (CVD) (e.g., plasma enhanced CVD, audio and / or radio frequency plasma enhanced CVD, microwave discharge CVD, atmospheric plasma discharge CVD, DC plasma discharge CVD) can be used to functionalize its surface. As an example, the pre-filter layer can be exposed to oxygen plasma. Such treatment can cause surface oxidation of the pre-filter layer, can produce functional groups such as alcohols and carboxylic acids at the surface of the pre-filter layer, and / or can increase the hydrophilicity of the pre-filter layer. As another example, CVD can be used to modify one or more monomers (e.g., acrylic monomers such as hydroxyethyl methacrylate, fluorocarbon additives (e.g., fluorinated and / or perfluorinated monomers such as hexafluorobutyric acid, CF 4 , CHF 3 , C 2 F 6 , C 3 F 8 , C 4 F 8 , C 2 F 4 , C 3 F 6 , C 4 F 10 , C 5 F 10 , C 5F 12 , C 6 F 12 , C 6 F 14 , Perfluorohexylethyl acrylate (C 11 H 7 F 13 O 2 ), perfluorohexylethyl methacrylate (C 12 H 9 F 13 O 2 ), allyl pentafluorobenzene (C 9 H 5 F 5 ), pentafluorostyrene (C 8 H 3 F 5 ) etc.) are deposited onto the pre-filter layer. In some embodiments, the monomers may be deposited in the presence of a carrier gas (e.g., an inert gas such as helium or argon). Depositing these monomers may affect the hydrophobicity of the surface of the pre-filter layer (e.g., acrylic monomers may make the surface more hydrophilic, fluorinated monomers may make the surface more hydrophobic). In some embodiments, the CVD treatment may include exposing the pre-filter layer to ammonia optionally accompanied by one or more inert gases (e.g., helium, argon). Additional surface treatments (e.g., additional CVD treatments) are also possible.

[0172] The pre-filter layer described herein can have any suitable normalized surface area. In some embodiments, the normalized surface area of ​​the pre-filter layer is greater than or equal to 7 m 2 / m 2 , greater than or equal to 8m 2 / m 2 , greater than or equal to 9m 2 / m 2 , greater than or equal to 10m 2 / m 2 , greater than or equal to 12m 2 / m 2 , greater than or equal to 14m 2 / m 2 , greater than or equal to 15m 2 / m 2 , greater than or equal to 16m 2 / m 2 , greater than or equal to 18m 2 / m 2 , greater than or equal to 20m 2 / m 2 , greater than or equal to 22m 2 / m 2 , greater than or equal to 25m 2 / m 2 , greater than or equal to 30m 2 / m 2 , greater than or equal to 35m 2 / m 2 , greater than or equal to 40m 2 / m 2 , greater than or equal to 45m 2 / m 2 , greater than or equal to 50m 2 / m 2 , greater than or equal to 55m 2 / m 2 , greater than or equal to 60m 2 / m 2 , greater than or equal to 65m 2 / m 2 , greater than or equal to 70m 2 / m 2 , greater than or equal to 80m 2 / m 2 , greater than or equal to 90m 2 / m 2 , or greater than or equal to 100m 2 / m 2 In some embodiments, the normalized surface area of ​​the pre-filter layer is less than or equal to 130 m 2 / m 2 , less than or equal to 100m 2 / m 2 , less than or equal to 90m 2 / m 2 , less than or equal to 80m 2 / m 2 , less than or equal to 70m 2 / m 2 , less than or equal to 65m 2 / m 2 , less than or equal to 60m 2 / m 2 , less than or equal to 55m 2 / m 2 , less than or equal to 50m 2 / m 2 , less than or equal to 45m 2 / m 2 , less than or equal to 40m 2 / m 2 , less than or equal to 35m 2 / m 2 , less than or equal to 30m 2 / m 2 , less than or equal to 25m 2 / m 2, less than or equal to 22m 2 / m 2 , less than or equal to 20m 2 / m 2 , less than or equal to 18m 2 / m 2 , less than or equal to 16m 2 / m 2 , less than or equal to 15m 2 / m 2 , less than or equal to 14m 2 / m 2 , less than or equal to 12m 2 / m 2 , less than or equal to 10m 2 / m 2 , less than or equal to 9m 2 / m 2 , or less than or equal to 8m 2 / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 7 m 2 / m 2 And less than or equal to 130m 2 / m 2 , greater than or equal to 10m 2 / m 2 And less than or equal to 100m 2 / m 2 , greater than 10m 2 / m 2 And less than or equal to 100m 2 / m 2 , greater than or equal to 15m 2 / m 2 And less than or equal to 70m 2 / m 2 , greater than 15m 2 / m 2 And less than or equal to 70m 2 / m 2 , or greater than or equal to 20m 2 / m 2 And less than or equal to 60m 2 / m 2 ). Other ranges are also possible.

[0173] When the filter media includes two or more pre-filter layers, each pre-filter layer can independently have a normalized surface area in one or more of the above ranges. In embodiments where the filter media includes two or more pre-filter layers, the normalized surface areas of the two or more pre-filter layers can be the same or different.

[0174] As used herein, normalized surface area refers to the ratio of the total fiber surface area associated with a plurality of fibers within a layer to the surface area of ​​the layer (i.e., the area that the layer would spatially cover if disposed on a substrate, such substrate positioned beneath the layer). The total fiber surface area associated with a plurality of fibers includes the fiber surface area within the layer, e.g., the surface area of ​​fibers present in the interior of the layer. Figure 2 can be used to illustrate the concept of normalized surface area. Figure 2 As shown, second layer 104 may include a plurality of fibers disposed therein and a surface 104A. The normalized surface area of ​​second layer 104 may correspond to the ratio of the total fiber surface area associated with the plurality of fibers within second layer 104 to the surface area physically overlaid on first layer 102 by layer surface 104A.

[0175] The normalized surface area of ​​a layer can be determined by determining the average fiber diameter, determining the density of the material forming the fibers in the layer, determining the weight per unit area of ​​the layer, and then applying the following formula: Normalized surface area = [weight per unit area / (polymer density·fiber diameter·π / 4)]. The density of the material forming the fibers in the layer can be determined as described elsewhere in this document regarding the method for determining the porosity of the layer. The weight per unit area can be measured according to ASTM D3776M-20 (2020). It should be noted that the above method is a non-limiting example of a method for determining the normalized surface area of ​​a layer, and other methods can also be used to determine the normalized surface area of ​​a layer.

[0176] The pre-filter layer described herein can have any of a variety of suitable porosities (i.e., void volumes). In some embodiments, the porosity of the pre-filter layer is greater than or equal to 80%, greater than or equal to 82%, greater than or equal to 84%, greater than or equal to 85%, greater than or equal to 86%, greater than or equal to 88%, greater than or equal to 90%, greater than or equal to 92%, greater than or equal to 94%, greater than or equal to 95%, or greater than or equal to 96%. In some embodiments, the porosity of the pre-filter layer is less than or equal to 99%, less than or equal to 96%, less than or equal to 95%, less than or equal to 94%, less than or equal to 92%, less than or equal to 90%, less than or equal to 88%, less than or equal to 86%, less than or equal to 85%, less than or equal to 84%, or less than or equal to 82%. Combinations of the above ranges are also possible (e.g., greater than or equal to 80% and less than or equal to 99%, greater than or equal to 85% and less than or equal to 96%, or greater than or equal to 90% and less than or equal to 95%). Other ranges are possible.

[0177] When the filter media includes two or more pre-filter layers, each pre-filter layer can independently have a porosity in one or more of the above ranges. In embodiments where the filter media includes two or more pre-filter layers, the porosity of the two or more pre-filter layers can be the same or different.

[0178] The porosity of the pre-filter layer can be determined as described elsewhere herein with respect to the determination of the porosity of the main filter layer (eg, fine fiber layer).

[0179] The pre-filter layer described herein can have any of a variety of suitable average pore sizes. In some embodiments, the average pore size of the pre-filter layer 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 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 25 microns, greater than or equal to 30 microns, greater than or equal to 35 microns, greater than or equal to 40 microns, or greater than or equal to 45 microns. In some embodiments, the average pore size of the pre-filter layer is less than or equal to 50 microns, less than or equal to 45 microns, less than or equal to 40 microns, less than or equal to 35 microns, less than or equal to 30 microns, less than or equal to 25 microns, less than or equal to 20 microns, less than or equal to 17.5 microns, less than or equal to 15 microns, less than or equal to 12.5 microns, less than or equal to 10 microns, less than or equal to 7 microns, less than or equal to 5 microns, less than or equal to 3 microns, or less than or equal to 2 microns. Combinations of the above-referenced ranges are also possible (eg, greater than or equal to 1 micron and less than or equal to 50 microns, greater than or equal to 2 microns and less than or equal to 30 microns, or greater than or equal to 5 microns and less than or equal to 20 microns). Other ranges are also possible.

[0180] When the filter media includes two or more pre-filter layers, each pre-filter layer can independently have an average pore size in one or more of the above ranges. In embodiments where the filter media includes two or more pre-filter layers, the average pore sizes of the two or more pre-filter layers can be the same or different.

[0181] The average pore size can be measured using ASTM F316 (2003).

[0182] The pre-filter layer described herein can have any of a variety of suitable thicknesses. In some embodiments, the thickness of the pre-filter layer is greater than or equal to 0.1 mm, greater than or equal to 0.2 mm, greater than or equal to 0.3 mm, greater than or equal to 0.4 mm, greater than or equal to 0.5 mm, greater than or equal to 0.6 mm, greater than or equal to 0.8 mm, greater than or equal to 1 mm, greater than or equal to 1.2 mm, greater than or equal to 1.4 mm, greater than or equal to 1.6 mm, or greater than or equal to 1.8 mm. In some embodiments, the thickness of the pre-filter layer is less than or equal to 2 mm, less than or equal to 1.8 mm, less than or equal to 1.6 mm, less than or equal to 1.4 mm, less than or equal to 1.2 mm, less than or equal to 1 mm, less than or equal to 0.8 mm, less than or equal to 0.6 mm, less than or equal to 0.5 mm, less than or equal to 0.4 mm, less than or equal to 0.3 mm, or less than or equal to 0.2 mm. Combinations of the above ranges are also possible (eg, greater than or equal to 0.1 mm and less than or equal to 2 mm, greater than or equal to 0.3 mm and less than or equal to 1.6 mm, or greater than or equal to 0.5 mm and less than or equal to 1.4 mm). Other ranges are also possible.

[0183] When the filter media includes two or more pre-filter layers, each pre-filter layer can independently have a thickness in one or more of the above ranges. In embodiments where the filter media includes two or more pre-filter layers, the thickness of the two or more pre-filter layers can be the same or different.

[0184] The thickness of the pre-filter layer may be determined according to ASTM D1777 (2015) at an applied pressure of 0.8 kPa.

[0185] The pre-filter layer described herein can have any of a variety of suitable basis weights. For example, in some embodiments, the pre-filter layer has a basis weight of 5 gsm or more, 7.5 gsm or more, 10 gsm or more, 12.5 gsm or more, 15 gsm or more, 17.5 gsm or more, 20 gsm or more, 25 gsm or more, 30 gsm or more, 40 gsm or more, 50 gsm or more, 60 gsm or more, 70 gsm or more, 80 gsm or more, or 90 gsm or more. In some embodiments, the pre-filter layer has a weight per unit area of ​​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, 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 100 gsm, greater than or equal to 15 gsm and less than or equal to 80 gsm, or greater than or equal to 20 gsm and less than or equal to 70 gsm). Other ranges are also possible.

[0186] When the filter media includes two or more pre-filter layers, each pre-filter layer can independently have a basis weight in one or more of the above ranges. In embodiments where the filter media includes two or more pre-filter layers, the basis weights of the two or more pre-filter layers can be the same or different.

[0187] The weight per unit area may be measured according to ASTM D3776M-20 (2020).

[0188] The pre-filter layer described herein can have any of a variety of suitable air permeabilities. In some embodiments, the air permeability of the pre-filter layer is greater than or equal to 5 CFM, greater than or equal to 7 CFM, greater than or equal to 10 CFM, greater than or equal to 12 CFM, greater than or equal to 15 CFM, greater than or equal to 20 CFM, greater than or equal to 25 CFM, greater than or equal to 30 CFM, greater than or equal to 35 CFM, greater than or equal to 40 CFM, greater than or equal to 45 CFM, greater than or equal to 50 CFM, greater than or equal to 55 CFM, greater than or equal to 60 CFM, or greater than or equal to 65 CFM. In some embodiments, the air permeability of the pre-filter layer is less than or equal to 70 CFM, less than or equal to 65 CFM, less than or equal to 60 CFM, less than or equal to 55 CFM, less than or equal to 50 CFM, less than or equal to 45 CFM, less than or equal to 40 CFM, less than or equal to 35 CFM, less than or equal to 30 CFM, less than or equal to 25 CFM, less than or equal to 20 CFM, less than or equal to 15 CFM, less than or equal to 12 CFM, less than or equal to 10 CFM, or less than or equal to 7 CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 5 CFM and less than or equal to 70 CFM, greater than or equal to 5 CFM and less than or equal to 50 CFM, or greater than or equal to 10 CFM and less than or equal to 40 CFM). Other ranges are also possible.

[0189] When the filter media includes two or more pre-filter layers, each pre-filter layer can independently have an air permeability of one or more of the above ranges. In embodiments where the filter media includes two or more pre-filter layers, the air permeabilities of the two or more pre-filter layers can be the same or different.

[0190] The air permeability may be measured at a pressure of 125 Pa according to ASTM D737-04 (2016).

[0191] The pre-filter layer described herein can have any suitable efficiency (e.g., efficiency before exposure to isopropyl alcohol (IPA) vapor). In some embodiments, the efficiency of the pre-filter layer (e.g., efficiency before exposure to IPA vapor) is greater than or equal to 95%, greater than or equal to 96%, greater than or equal to 97%, greater than or equal to 98%, greater than or equal to 98.5%, greater than or equal to 99%, greater than or equal to 99.5%, greater than or equal to 99.7%, greater than or equal to 99.9%, greater than or equal to 99.95%, greater than or equal to 99.99%, greater than or equal to 99.995%, greater than or equal to 99.999%, greater than or equal to 99.9995%, greater than or equal to 99.9999%, or greater than or equal to 99.99995%. In some embodiments, the efficiency of the pre-filter layer (e.g., efficiency before IPA vapor exposure) is less than 100%, less than or equal to 99.99995%, less than or equal to 99.9999%, less than or equal to 99.9995%, less than or equal to 99.9999%, less than or equal to 99.9995%, less than or equal to 99.999%, less than or equal to 99.995%, less than or equal to 99.999%, less than or equal to 99.995%, less than or equal to 99.99%, less than or equal to 99.95%, less than or equal to 99.9%, less than or equal to 99.7%, less than or equal to 99.5%, less than or equal to 99%, less than or equal to 98.5%, less than or equal to 98%, less than or equal to 97%, or less than or equal to 96%. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 95% and less than 99.99995%, greater than or equal to 98% and less than or equal to 99.9995%, or greater than or equal to 99% and less than or equal to 99.995%). Other ranges are also possible.

[0192] When the filter medium includes two or more pre-filter layers, each pre-filter layer can independently have an efficiency of one or more of the above ranges (e.g., efficiency before IPA vapor exposure). In embodiments where the filter medium includes two or more pre-filter layers, the efficiencies of the two or more pre-filter layers can be the same or different. In some embodiments, the efficiency described in the preceding paragraphs is the efficiency at the most penetrating particle size (MPPS). The efficiency at MPPS is the value of the efficiency measured for particles with the highest penetration rate. In some embodiments, the efficiency described in the preceding paragraphs is the efficiency at 0.09 microns. The efficiency at 0.09 microns is the value of the efficiency measured for particles with an average diameter of 0.09 microns. In some embodiments, the efficiency in the preceding paragraphs is the efficiency at 0.3 microns. The efficiency at 0.3 microns is the value of the efficiency measured for particles with an average diameter of 0.3 microns.

[0193] The efficiency of a layer can be determined by the following equation: Efficiency (%) = 100 - Penetration (%). The penetration of a layer can be determined as follows: % Penetration = C / C 0 *100, where C is the concentration of particles measured after passing through the layer, and C 0 is the concentration of particles measured before passing through the layer. Penetration can be measured at the relevant particle size (e.g., MPPS, 0.09 micron or 0.3 micron) of the described efficiency type. Penetration can be measured for any particle size using the EN1822:2009 standard for air filtration described below.

[0194] Penetration can be measured by blowing dioctyl phthalate (DOP) particles through the layer and measuring the percentage of particles that pass through and the pressure drop as the particles are blown through the layer.

[0195] This can be achieved based on the EN 1822:2009 standard for MPPS DOP particles by using a TSI 3160 automated filter test unit from TSI, Inc. equipped with a dioctyl phthalate generator for DOP aerosol testing. When determining efficiency under MPPS, the TSI 3160 automated filter test unit is used at 100 cm upstream of the layer surface. 2 DOP particle groups with different average particle sizes are sequentially blown at the surface area. The particle groups are blown at the upstream surface of the layer (or filter medium) in the order of increasing average diameter, wherein each particle group has a geometric standard deviation of less than 1.3, and the particle group has the following set of average diameters: 0.04 microns, 0.08 microns, 0.12 microns, 0.16 microns, 0.2 microns, 0.26 microns and 0.3 microns. During the time period during which the particle group is blown at the upstream surface of the layer, the penetration rate can be continuously and individually measured for each particle group.

[0196] When determining efficiency at 0.09 microns, a TSI 3160 automated filter test unit is used to blow DOP particles having a particle size of 0.09 microns across 100 cm of the upstream surface of the layer. 2 Surface area.

[0197] During both types of penetration measurements, the particle concentrations upstream and downstream can be measured by using a condensation particle counter. During both types of penetration measurements, 100 cm of the upstream surface of the layer can be measured. 2 The surface area was subjected to a continuous load of DOP particles under an airflow of 12 L / min, resulting in a media face velocity of 2 cm / sec. Each particle population was blown at the upstream surface of the layer for a maximum of 480 seconds, or until at least 1000 particles were counted downstream of the layer, whichever was shorter.

[0198] The efficiency at 0.3 microns can be determined in the same manner as the efficiency at MPPS and the efficiency at 0.09 microns, except that it can be done at a face velocity of 5.3 cm / sec and can be measured using a TSI 8130.

[0199] The pre-filter layers described herein can have any suitable efficiency metric (e.g., an efficiency metric prior to IPA vapor exposure). In some embodiments, the pre-filter layer has an efficiency metric (e.g., an efficiency metric prior to IPA vapor exposure) greater than or equal to 2.5, greater than or equal to 2.6, greater than or equal to 2.8, greater than or equal to 3, greater than or equal to 3.2, greater than or equal to 3.4, greater than or equal to 3.5, greater than or equal to 3.6, greater than or equal to 3.8, greater than or equal to 4, greater than or equal to 4.2, greater than or equal to 4.5, greater than or equal to 4.7, greater than or equal to 5, greater than or equal to 5.2, greater than or equal to 5.5, or greater than or equal to 5.7. In some embodiments, the efficiency metric of the pre-filter layer (e.g., the efficiency metric prior to IPA vapor exposure) is less than or equal to 6, less than or equal to 5.7, less than or equal to 5.5, less than or equal to 5.2, less than or equal to 5, less than or equal to 4.7, less than or equal to 4.5, less than or equal to 4.2, less than or equal to 4, less than or equal to 3.8, less than or equal to 3.6, less than or equal to 3.5, less than or equal to 3.4, less than or equal to 3.2, less than or equal to 3, less than or equal to 2.8, or less than or equal to 2.6. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 2.5 and less than or equal to 6, greater than or equal to 2.5 and less than or equal to 6, greater than or equal to 3 and less than or equal to 5.5, or greater than or equal to 3.5 and less than or equal to 5). Other ranges are also possible.

[0200] When the filter media includes two or more pre-filter layers, each pre-filter layer can independently have an efficiency metric (e.g., an efficiency metric prior to IPA vapor exposure) in one or more of the above ranges. In embodiments where the filter media includes two or more pre-filter layers, the efficiency metrics of the two or more pre-filter layers can be the same or different.

[0201] The efficiency metric (e.g., the efficiency metric before IPA vapor exposure) can be determined by the following equation: efficiency metric (EM) = -log (% penetration (DOP) / 100). The penetration (%) can be determined as described elsewhere herein with respect to determining the efficiency of the pre-filter layer using DOP particles having an average diameter of 0.09 microns. The penetration can be determined before IPA vapor exposure.

[0202] The pre-filter layers described herein can have any suitable pressure drop (e.g., an average pressure drop). In some cases, the pre-filter layers described herein can have a relatively low pressure drop. In some embodiments, the pressure drop of the pre-filter layer is greater than or equal to 0.001 kPa, greater than or equal to 0.002 kPa, greater than or equal to 0.003 kPa, greater than or equal to 0.005 kPa, greater than or equal to 0.007 kPa, greater than or equal to 0.01 kPa, greater than or equal to 0.02 kPa, greater than or equal to 0.03 kPa, greater than or equal to 0.035 kPa, greater than or equal to 0.04 kPa, greater than or equal to 0.05 kPa, greater than or equal to 0.06 kPa, or greater than or equal to 0.07 kPa. In some embodiments, the pressure drop of the pre-filter layer is less than or equal to 0.08 kPa, less than or equal to 0.07 kPa, less than or equal to 0.06 kPa, less than or equal to 0.05 kPa, less than or equal to 0.04 kPa, less than or equal to 0.035 kPa, less than or equal to 0.03 kPa, less than or equal to 0.02 kPa, less than or equal to 0.01 kPa, less than or equal to 0.007 kPa, less than or equal to 0.005 kPa, less than or equal to 0.003 kPa, or less than or equal to 0.002 kPa. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.001 kPa and less than or equal to 0.08 kPa, greater than or equal to 0.005 kPa and less than or equal to 0.04 kPa, or greater than or equal to 0.01 kPa and less than or equal to 0.03 kPa). Other ranges are also possible.

[0203] When the filter media includes two or more pre-filter layers, each pre-filter layer can independently have a pressure drop in one or more of the above ranges. In embodiments where the filter media includes two or more pre-filter layers, the pressure drops of the two or more pre-filter layers can be the same or different.

[0204] The pressure drop of the pre-filter layer and the efficiency of the pre-filter layer can be determined simultaneously by the method for determining the efficiency of the pre-filter layer using DOP particles having an average diameter of 0.09 microns as described elsewhere herein. In some embodiments, the pressure drop is the average pressure drop measured over the same time period as the efficiency of the pre-filter layer using DOP particles having an average diameter of 0.09 microns as described elsewhere herein. Specifically, when determining the pressure drop at 0.09 microns, a TSI 3160 automated filter test unit is used to blow DOP particles having a particle size of 0.09 microns across 100 cm of the upstream surface of the layer. 2The particles may be blown at the upstream surface of the layer for a maximum of 480 seconds, or until at least 1000 particles are counted downstream of the layer, whichever is shorter. The pressure drop may be continuously measured for the particle group over the period of time that the particle group blows through the pre-filter layer, and an average value of the pressure drop over the period of time may be calculated.

[0205] The pre-filter layers described herein can have any suitable ratio of the initial efficiency metric (before IPA vapor exposure) to the mechanical (discharge) efficiency metric. In some embodiments, the ratio of the initial efficiency metric to the mechanical (discharge) efficiency metric of the pre-filter layer is greater than or equal to 2, greater than or equal to 2.2, greater than or equal to 2.4, greater than or equal to 2.6, greater than or equal to 2.8, greater than or equal to 3, greater than or equal to 3.2, greater than or equal to 3.5, greater than or equal to 3.7, greater than or equal to 4, greater than or equal to 4.2, greater than or equal to 4.5, or greater than or equal to 4.7. In some embodiments, the ratio of the initial efficiency metric to the mechanical (discharge) efficiency metric of the pre-filter layer is less than or equal to 5, less than or equal to 4.7, less than or equal to 4.5, less than or equal to 4.2, less than or equal to 4, less than or equal to 3.7, less than or equal to 3.5, less than or equal to 3.2, less than or equal to 3, less than or equal to 2.8, less than or equal to 2.6, less than or equal to 2.4, or less than or equal to 2.2. Combinations of the above-referenced ranges are also possible (eg, greater than or equal to 2 and less than or equal to 5, greater than or equal to 2 and less than or equal to 4, or greater than or equal to 2 and less than or equal to 3). Other ranges are also possible.

[0206] When the filter media includes two or more pre-filter layers, each pre-filter layer can independently have a ratio of the initial efficiency metric to the mechanical (discharge) efficiency metric in one or more of the above ranges. In embodiments where the filter media includes two or more pre-filter layers, the ratio of the initial efficiency metric to the mechanical (discharge) efficiency metric of the two or more pre-filter layers can be the same or different.

[0207] The efficiency metric (e.g., initial efficiency metric) of the pre-filter layer can be determined as described elsewhere herein. The mechanical (discharge) efficiency metric can be characterized as the efficiency metric (EM) measured after the layer is subjected to IPA vapor discharge treatment. The efficiency metric can be determined by the same equation described elsewhere herein for determining the efficiency of the pre-filter layer (i.e., -log (% penetration (DOP) / 100), where penetration is determined as described elsewhere herein for determining the efficiency of the pre-filter layer using DOP particles having an average diameter of 0.09 microns).

[0208] The pre-filter layer can be exposed to isopropyl alcohol vapor with a 6 inch × 6 inch sample according to the ISO 16890-4 (2016) standard. The layer to be tested can be cut into 6 inch × 6 inch squares and placed on the shelf of the metal rack. The metal rack and the layer can then be placed on top of a container containing at least 250 mL of 99.9 wt % isopropyl alcohol. After this step, the metal rack, the layer and the container can be placed in a 24 inch × 18 inch × 11 inch chamber. A second container containing 250 mL of 99.9 wt % isopropyl alcohol can then be placed in the container above the top shelf of the metal rack, and the lid of the chamber can be closed and tightly sealed. The device can be kept at 70 ° F and 50% relative humidity for at least 14 hours, after which the layer can be removed and allowed to dry at room temperature for one hour. Then, those characterized as the layer properties after undergoing the isopropyl alcohol vapor discharge process, including the efficiency metric (EM) of the layer, can be measured as described elsewhere herein.

[0209] As described above, in some embodiments, the surface of the pre-filter layer can be modified using additives described elsewhere herein (e.g., oleophobic additives, fluorocarbon additives). Such a pre-filter layer can be oleophobic and / or can have an oil grade greater than or equal to 1. In some embodiments, the oil grade of the pre-filter layer is greater than or equal to 1, greater than 1, greater than or equal to 1.5, 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 grade of the pre-filter layer 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, less than or equal to 2, or less than or equal to 1.5. Combinations of the above-referenced ranges are also possible (eg, 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 5, or greater than or equal to 1 and less than or equal to 4). Other ranges are also possible.

[0210] When the filter media includes two or more pre-filter layers, each pre-filter layer can independently have an oil grade in one or more of the above ranges. In embodiments where the filter media includes two or more pre-filter layers, the oil grades of the two or more pre-filter layers can be the same or different.

[0211] The oil grade of the layer can be determined by measuring according to AATCC TM 118 (2020) at 23°C and 50% relative humidity (RH). Briefly, 5 drops of each test oil (average droplet diameter of about 2 mm) can be placed on five different locations on the surface of the layer. After contacting the layer at 23°C and 50% RH for 30 seconds, the test oil with the maximum oil surface tension that does not wet the surface of the layer (e.g., the contact angle with the surface is greater than or equal to 90°) corresponds to the oil grade (listed in Table 4). For example, if a test oil with a surface tension of 26.6 mN / m does not wet the surface of the layer after 30 seconds (i.e., the contact angle with the surface is greater than or equal to 90 degrees), and a test oil with a surface tension of 25.4 mN / m wets the surface of the layer within thirty seconds, the oil grade of the layer is 4. As another example, if a test oil having a surface tension of 25.4 mN / m does not wet the surface of the layer after 30 seconds, while a test oil having a surface tension of 23.8 mN / m wets the surface of the layer within thirty seconds, the oil level of the layer is 5. As yet another example, if a test oil having a surface tension of 23.8 mN / m does not wet the surface of the layer after 30 seconds, while a test oil having a surface tension of 21.6 mN / m wets the surface of the layer within thirty seconds, the oil level of the layer is 6. In some embodiments, if three or more of the five droplets partially wet the surface in a given test (e.g., droplets are formed on the surface, but not as round droplets), the oil level is expressed as the nearest 0.5 value determined by subtracting 0.5 from the number of the test liquids. As an example, if a test oil with a surface tension of 25.4 mN / m does not wet the surface of the layer after 30 seconds, while a test oil with a surface tension of 23.8 mN / m only partially wets the surface of the layer within thirty seconds after 30 seconds (for example, three or more of the test droplets form droplets on the surface of the layer that are not rounded droplets), the oil grade of the layer is 5.5.

[0212] Table 4.

[0213] Oil grade Test oil Surface tension (mN / m) 1 Kaydol (mineral oil) 31 2 65 / 35Kaydol / 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

[0214] In some embodiments, the filter media described herein include a charged pre-filter layer. In some embodiments, the charged pre-filter layer can be a charged meltblown layer. When present, the charged meltblown layer can include synthetic fibers, such as synthetic fibers having an average fiber diameter in one or more of the ranges described elsewhere herein for such fibers (e.g., greater than or equal to 0.5 microns and less than or equal to 4 microns, greater than or equal to 1 micron and less than or equal to 3 microns, or greater than or equal to 1 micron and less than or equal to 2.5 microns). The charged pre-filter layer can be formed via any of the various suitable methods and / or steps described herein, such as electrostatic charging, tribocharging, and / or hydro-electret charging.

[0215] In some such embodiments, one or more charge additives may be present in the pre-filter layer when the pre-filter layer undergoes a charging process. The presence of the charge additive during the charging process may be beneficial. As an example, the presence of such a charge additive during the hydro-electret charging process may advantageously promote hydroentanglement of the fibers and / or result in a more efficient hydro-electret charging process. In some embodiments, hydroentanglement of the fibers may advantageously impart a relatively low pressure drop to the pre-filter layer.

[0216] In some embodiments, the pre-filter layer can be subjected to one or more surface treatments prior to charging. Any of a variety of surface treatment methods (e.g., chemical vapor deposition) can be used, and / or any of a variety of surface modifiers (e.g., fluorinated monomers, fluorocarbon additives) can be introduced into the pre-filter layer prior to charging. For example, in one set of embodiments, the pre-filter can be treated with a fluorocarbon coating. Such a fluorocarbon coating can advantageously impart an oil grade greater than 1 to the pre-filter layer and / or render the pre-filter layer oleophobic.

[0217] In some embodiments, the pre-filter layer is charged by a hydro-electret charging process. The hydro-electret charging process may include impinging a jet and / or stream of water droplets onto an initially uncharged layer to electrostatically charge it. At the end of the hydro-electret charging process, the layer may have an electret charge. The jet and / or stream of water droplets may impinge on the layer at various suitable pressures (e.g., pressures of 10 psi to 1000 psi) and may be provided by various suitable sources, such as a sprayer.

[0218] In some embodiments, the following pressures may be used during the hydro-electret 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 may be used during the hydro-electret 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-referenced ranges are also possible (eg, 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.

[0219] In some embodiments, the layer is hydro-electret charged by using an apparatus that can be used for hydroentanglement of fibers, which operates at a lower pressure than is normally used for hydroentanglement processes. The water impinging on the layer can be relatively pure; for example, it can be distilled water and / or deionized water. After being electrostatically charged in this manner, the layer can be dried, for example with an air dryer.

[0220] In some embodiments, the layer is hydro-electret charged while being moved laterally. The layer may be transported on a porous belt, such as a screen or mesh type conveyor belt. While it is being transported on the porous belt, it may be exposed to a spray and / or jet of water pressurized by a pump. The water jet and / or spray may impinge on the layer and / or penetrate into it. In some embodiments, a vacuum is provided below the porous conveyor belt, which may help the water pass through the layer and / or reduce the amount of time and energy required to dry the layer at the end of the hydro-electret charging process.

[0221] In some embodiments, the hydro-electret charging device may include a plurality of nozzles configured to spray jets of pressurized water at the layers described herein. The nozzles may be present in the device at any suitable number density and / or have any suitable diameter. In some embodiments, the nozzles may be present in the hydro-electret charging device at the following nozzle number density: greater than or equal to 10 nozzles / inch, greater than or equal to 15 nozzles / inch, greater than or equal to 20 nozzles / inch, greater than or equal to 25 nozzles / inch, greater than or equal to 30 nozzles / inch, greater than or equal to 35 nozzles / inch, greater than or equal to 40 nozzles / inch, greater than or equal to 45 nozzles / inch, greater than or equal to 50 nozzles / inch, greater than or equal to 55 nozzles / inch, greater than or equal to 60 ... Equal to 70 nozzles / inch, greater than or equal to 80 nozzles / inch, greater than or equal to 90 nozzles / inch, greater than or equal to 100 nozzles / inch, greater than or equal to 110 nozzles / inch, greater than or equal to 120 nozzles / inch, greater than or equal to 130 nozzles / inch, greater than or equal to 140 nozzles / inch, greater than or equal to 150 nozzles / inch, greater than or equal to 160 nozzles / inch, greater than or equal to 170 nozzles / inch, greater than or equal to 180 nozzles / inch, or greater than or equal to 190 nozzles / inch. In some embodiments, the nozzles may be present in the hydro-electret charging device at a nozzle number density of less than or equal to 200 nozzles / inch, less than or equal to 190 nozzles / inch, less than or equal to 180 nozzles / inch, less than or equal to 170 nozzles / inch, less than or equal to 160 nozzles / inch, less than or equal to 150 nozzles / inch, less than or equal to 140 nozzles / inch, less than or equal to 130 nozzles / inch, less than or equal to 120 nozzles / inch, less than or equal to 110 nozzles / inch, less than or equal to 10 inch, less than or equal to 0 nozzles / inch, less than or equal to 90 nozzles / inch, less than or equal to 80 nozzles / inch, less than or equal to 70 nozzles / inch, less than or equal to 60 nozzles / inch, less than or equal to 55 nozzles / inch, less than or equal to 50 nozzles / inch, less than or equal to 45 nozzles / inch, less than or equal to 40 nozzles / inch, less than or equal to 35 nozzles / inch, less than or equal to 30 nozzles / inch, less than or equal to 25 nozzles / inch, less than or equal to 20 nozzles / inch, or less than or equal to 15 nozzles / inch. Combinations of the above ranges are also possible (e.g., greater than or equal to 10 nozzles / inch and less than or equal to 200 nozzles / inch). Other ranges are also possible.

[0222] 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.

[0223] In some embodiments, each of the plurality of nozzles in the hydro-electret charging device may independently have a diameter in one or more of the above ranges. In some embodiments, the diameters of two or more of the plurality of nozzles may be the same or different.

[0224] In some embodiments, the pre-filter layer is charged via a triboelectric charging process. The triboelectric charging process can include contacting and then separating two surfaces, at least one of which is the surface on which the fibers to be charged are located. The process can result in charge transfer between the two surfaces and associated charge accumulation on the two surfaces. The surfaces can be selected so that they have sufficiently different positions in the triboelectric series to produce a desired level of charge transfer therebetween when in contact.

[0225] As described above, in some embodiments, one or more of the layers of the filter media described herein can be a support layer. The support layer can be used to support one or more other layers of the filter media, such as the main filter layer and / or the pre-filter layer. In some cases, the support layer can be used to protect and / or cover one or more other layers of the medium, such as the main filter layer and / or the pre-filter layer. As described above, in some embodiments, the filter media can include a single support layer (e.g., a single support layer adjacent to the main filter layer on the opposite side of the pre-filter layer). In some embodiments, the filter media can include more than one support layer, such as the first support layer and the second support layer. One such support layer can be positioned adjacent to the main filter layer on the opposite side of the pre-filter layer, and another such support layer can be positioned adjacent to the pre-filter layer on the opposite side of the main filter layer. The characteristics of the support layer will be described in further detail below.

[0226] References herein to one or more support layers should be understood to refer independently to each support layer in the filter media (if any support layer is present at all). That is, each support layer present may independently have some, all, or none of the following characteristics. In some embodiments, two or more support layers in the filter media may have similar compositions and / or characteristics. In other embodiments, each support layer in the filter media may have different compositions and / or characteristics.

[0227] In some embodiments, one or more support layers described herein can be one or more nonwoven webs, such as one or more wet-laid layers. The wet-laid layer can be formed by a wet-laid process. For example, in the embodiment in which the filter medium includes a single support layer, the support layer can be a wet-laid nonwoven web. In the embodiment in which the filter medium includes two or more support layers, each of the two or more support layers can be independently a wet-laid nonwoven web. In some embodiments, the filter medium includes one or more support layers that are non-wet-laid layers. That is, in some embodiments, the filter medium includes one or more support layers formed by a non-wet-laid process (e.g., air-laid process, carding process, spinning process (e.g., spunbond process)). In some embodiments, the filter medium includes one or more support layers, and the one or more support layers are spunbond layers, or are layers formed by a spunbond process.

[0228] In some embodiments, one or more support layers comprise synthetic fibers. In some embodiments, synthetic fibers comprise greater than or equal to 0 weight percent, greater than or equal to 10 weight percent, greater than or equal to 20 weight percent, greater than or equal to 30 weight percent, greater than or equal to 40 weight percent, greater than or equal to 50 weight percent, greater than or equal to 60 weight percent, greater than or equal to 70 weight percent, greater than or equal to 75 weight percent, greater than or equal to 80 weight percent, greater than or equal to 85 weight percent, greater than or equal to 90 weight percent, greater than or equal to 92 weight percent, greater than or equal to 95 weight percent, or greater than or equal to 98 weight percent of the support layer. In some embodiments, synthetic fibers may comprise less than or equal to 100 wt %, less than or equal to 98 wt %, less than or equal to 95 wt %, less than or equal to 92 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 75 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 20 wt %, or less than or equal to 10 wt % of the support layer. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0 wt % and less than or equal to 100 wt %, greater than or equal to 40 wt % and less than or equal to 95 wt %, greater than or equal to 75 wt % and less than or equal to 95 wt %, or greater than or equal to 75 wt % and less than or equal to 90 wt %). Other ranges are also possible.

[0229] When the support layer comprises two or more types of synthetic fibers, each type of synthetic fiber can independently account for an amount of the support layer in one or more of the above ranges, and / or all synthetic fibers in the support layer together can account for an amount of the support layer in one or more of the above ranges. Similarly, when the filter media comprises two or more support layers, each layer can independently include any particular type of synthetic fiber in an amount in one or more of the above ranges, and / or can include a total amount of synthetic fibers in one or more of the above ranges. In embodiments where the filter media comprises two or more support layers, the amount of synthetic fibers in the two or more support layers can be the same or different.

[0230] One or more support layers described herein may include any of a variety of suitable synthetic fibers as described elsewhere herein with respect to the pre-filter layer. The synthetic fibers may have any of a variety of suitable average fiber diameters described below relative to the average fiber diameter of the fibers within the support layer.

[0231] In some embodiments, the support layer comprises glass fibers (e.g., microglass fibers, chopped strand glass fibers, or combinations thereof). In some embodiments, the glass fibers account for greater than or equal to 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%, greater than or equal to 35 wt%, greater than or equal to 40 wt%, or greater than or equal to 45 wt% of the support layer. In some embodiments, the glass fibers account for less than or equal to 50 wt%, less than or equal to 45 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%, less than or equal to 15 wt%, or less than or equal to 10 wt% of the support layer. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 wt% and less than or equal to 50 wt%, or greater than or equal to 5 wt% and less than or equal to 25 wt%). Other ranges are also possible.

[0232] The average diameter of the glass fibers (if present) can be, for example, less than or equal to 20 microns, less than or equal to 15 microns, less than or equal to 12 microns, less than or equal to 10 microns, less than or equal to 9 microns, less than or equal to 7 microns, less than or equal to 5 microns, less than or equal to 3 microns, less than or equal to 1 micron, less than or equal to 0.5 microns, or less than or equal to 0.3 microns. In some cases, the average fiber diameter of the glass fibers can be greater than or equal to 0.1 microns, greater than or equal to 0.3 microns, greater than or equal to 0.5 microns, greater than or equal to 1 micron, greater than or equal to 3 microns, greater than or equal to 7 microns, greater than or equal to 9 microns, greater than or equal to 11 microns, or greater than or equal to 20 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 micron and less than or equal to 20 microns, greater than or equal to 0.1 micron and less than or equal to 10 microns, or greater than or equal to 5 microns and less than or equal to 15 microns). Other ranges are also possible.

[0233] In embodiments where the support layer comprises microglass fibers, the average diameter of the microglass fibers can be in one or more of the above ranges for glass fibers (e.g., greater than or equal to 0.1 micrometers and less than or equal to 10 micrometers). In some embodiments, the average length of the microglass fibers, if present, 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 50 mm, less than or equal to 40 mm, less than or equal to 30 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 3 mm, less than or equal to 2 mm, less than or equal to 1 mm, less than or equal to 0.5 mm, less than or equal to 0.25 mm, less than or equal to 0.1 mm, less than or equal to 0.05 mm, or less than or equal to 0.025 mm. In certain embodiments, the average length of the microglass fibers can be greater than or equal to 0.01 mm, greater than or equal to 0.025 mm, greater than or equal to 0.05 mm, greater than or equal to 0.1 mm, greater than or equal to 0.25 mm, greater than or equal to 0.5 mm, greater than or equal to 1 mm, greater than or equal to 2 mm, 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 20 mm, greater than or equal to 30 mm, greater than or equal to 40 mm, greater than or equal to 50 mm, greater than or equal to 60 mm, or greater than or equal to 80 mm. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.01 mm and less than 100 mm). Other ranges are also possible.

[0234] In the embodiment where the support layer includes chopped strand fibers, the average diameter of the chopped strand fibers may be in one or more of the above ranges for glass fibers (e.g., greater than or equal to 5 microns and less than or equal to 15 microns). Typically, the average fiber diameter of chopped strand glass fibers (if present) may be greater than the diameter of microglass fibers. In some embodiments, the average length of chopped strand glass fibers (if present) may be less than or equal to 18 mm, less than or equal to 15 mm, less than or equal to 10 mm, less than or equal to 8 mm, less than or equal to 6 mm, less than or equal to 5 mm, less than or equal to 4 mm, or less than or equal to 3 mm. In certain embodiments, the average length of chopped strand glass fibers may be greater than or equal to 3 mm, greater than or equal to 4 mm, greater than or equal to 6 mm, greater than or equal to 7 mm, greater than or equal to 8 mm, greater than or equal to 10 mm, or greater than or equal to 15 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 3 mm and less than 18 mm). Other ranges are also possible. When the support layer comprises two or more types of glass fibers, each type of glass fiber can independently account for an amount of the support layer in one or more of the above ranges, and / or all of the glass fibers in the support layer together can account for an amount of the support layer in one or more of the above ranges. Similarly, when the filter media comprises two or more support layers, each layer can independently include any particular type of glass fiber in an amount in one or more of the above ranges, and / or can include a total amount of glass fibers in one or more of the above ranges. In embodiments where the filter media comprises two or more support layers, the amount of glass fibers in the two or more support layers can be the same or different.

[0235] In some embodiments, the support layer comprises cellulose fibers. In some embodiments, the cellulose fibers account for greater than or equal to 0 weight percent, greater than or equal to 1 weight percent, greater than or equal to 5 weight percent, greater than or equal to 10 weight percent, greater than or equal to 15 weight percent, greater than or equal to 20 weight percent, greater than or equal to 30 weight percent, greater than or equal to 40 weight percent, greater than or equal to 50 weight percent, greater than or equal to 60 weight percent, greater than or equal to 70 weight percent, greater than or equal to 80 weight percent, or greater than or equal to 90 weight percent of the support layer. In some embodiments, the cellulose fibers account for less than or equal to 100 weight percent, less than or equal to 90 weight percent, less than or equal to 80 weight percent, less than or equal to 70 weight percent, less than or equal to 60 weight percent, less than or equal to 50 weight percent, less than or equal to 40 weight percent, less than or equal to 30 weight percent, less than or equal to 20 weight percent, less than or equal to 15 weight percent, less than or equal to 10 weight percent, less than or equal to 5 weight percent, or less than or equal to 1 weight percent of the support layer. Combinations of the above-referenced ranges are also possible (eg, greater than or equal to 0 wt % and less than or equal to 100 wt %, greater than or equal to 0 wt % and less than or equal to 80 wt %, or greater than or equal to 0 wt % and less than or equal to 50 wt %). Other ranges are also possible.

[0236] When the support layer comprises two or more types of cellulose fibers, each type of cellulose fibers can independently account for an amount of the support layer in one or more of the above ranges, and / or all of the cellulose fibers in the support layer together can account for an amount of the support layer in one or more of the above ranges. Similarly, when the filter media comprises two or more support layers, each layer can independently include any particular type of cellulose fibers in an amount in one or more of the above ranges, and / or can include a total amount of cellulose fibers in one or more of the above ranges. In embodiments where the filter media comprises two or more support layers, the amount of cellulose fibers in the two or more support layers can be the same or different.

[0237] Non-limiting examples of cellulosic fibers include softwood fibers, hardwood fibers, mixtures of hardwood and softwood fibers, regenerated cellulose fibers, and / or mechanical pulp fibers (eg, groundwood pulp, chemically treated mechanical pulp, and thermomechanical pulp).

[0238] The average diameter of the cellulose fibers in the pre-filter layer (if present) can be, for example, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 3 microns, greater than or equal to 4 microns, greater than or equal to 5 microns, greater than or equal to 8 microns, greater than or equal to 10 microns, greater than or equal to 15 microns, greater than or equal to 20 microns, greater than or equal to 30 microns, or greater than or equal to 40 microns. In some cases, the average diameter of the cellulose fibers can be less than or equal to 50 microns, less than or equal to 40 microns, less than or equal to 30 microns, less than or equal to 20 microns, less than or equal to 15 microns, less than or equal to 10 microns, less than or equal to 7 microns, less than or equal to 5 microns, less than or equal to 4 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 5 microns). Other values ​​of the average fiber diameter are also possible.

[0239] The cellulose fibers in the pre-filter layer, if present, can have any suitable average length. For example, in some embodiments, the average length of the cellulose fibers can be greater than or equal to 0.5 mm, greater than or equal to 1 mm, greater than or equal to 2 mm, greater than or equal to 3 mm, greater than or equal to 4 mm, greater than or equal to 5 mm, greater than or equal to 6 mm, or greater than or equal to 8 mm. In some cases, the average length of the cellulose fibers can be less than or equal to 10 mm, less than or equal to 8 mm, less than or equal to 6 mm, less than or equal to 4 mm, less than or equal to 2 mm, or less than or equal to 1 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 mm and less than or equal to 3 mm). Other values ​​of average fiber length are also possible.

[0240] When present, the cellulosic fibers may include fibrillated cellulosic fibers, and / or may include non-fibrillated cellulosic fibers.

[0241] In some embodiments, the pre-filter layer may include fibrillated fibers. As known to those of ordinary skill in the art, fibrillated fibers include parent fibers that branch into fibrils of smaller diameter, which in some cases can further branch into fibrils of even smaller diameter, wherein further branching is also possible. The branching nature of the fibrils results in a layer and / or fiber web with a high surface area, and can increase the number of contact points between the fibrillated fibers in the web and other fibers. Such an increase in contact points between the fibrillated fibers of the web and other fibers and / or components can help improve the mechanical properties (e.g., flexibility, strength) and / or filtration performance characteristics of the layer and / or fiber web.

[0242] In some embodiments, the parent fiber (if present) can have an average diameter in the micron or submicron range. For example, the average diameter of the parent fiber can be greater than or equal to 0.5 micron, greater than or equal to 1 micron, greater than or equal to 5 microns, greater than or equal to 10 microns, greater than or equal to 20 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 60 microns, or greater than or equal to 70 microns. In some embodiments, the average diameter of the parent fiber can be less than or equal to 75 microns, less than or equal to 55 microns, less than or equal to 35 microns, less than or equal to 25 microns, less than or equal to 15 microns, less than or equal to 10 microns, less than or equal to 5 microns, less than or equal to 2 microns, or less than or equal to 0.5 micron. Combinations of the above ranges are also possible (for example, the average diameter of the parent fiber is greater than or equal to 1 micron and less than or equal to 25 microns). Other ranges are also possible.

[0243] The average diameter of protofibrils (if present) is usually less than the average diameter of parent fibers.Depending on the average diameter of parent fibers, in some embodiments, the average diameter of protofibrils can be less than or equal to 25 microns, less than or equal to 20 microns, less than or equal to 10 microns, less than or equal to 5 microns, less than or equal to 1 micron, less than or equal to 0.5 micron, less than or equal to 0.1 micron, less than or equal to 0.05 micron, or less than or equal to 0.01 micron.In some embodiments, the average diameter of protofibrils can be greater than or equal to 0.003 micron, greater than or equal to 0.01 micron, greater than or equal to 0.05 micron, greater than or equal to 0.1 micron, greater than or equal to 0.5 micron, greater than or equal to 1 micron, greater than or equal to 5 microns, greater than or equal to 10 microns, or greater than or equal to 20 microns.The combination of the above ranges is also possible (for example, the average diameter of protofibrils is greater than or equal to 0.01 micron and less than or equal to 20 microns).Other ranges are also possible.

[0244] In some embodiments, the average length of fibrillated fibers (if present) can be less than or equal to 10 mm, less than or equal to 8 mm, less than or equal to 6 mm, less than or equal to 5 mm, less than or equal to 4 mm, less than or equal to 3 mm, or less than or equal to 2 mm. In certain embodiments, the average length of fibrillated fibers can be greater than or equal to 1 mm, greater than or equal to 2 mm, greater than or equal to 4 mm, greater than or equal to 5 mm, greater than or equal to 6 mm, or greater than or equal to 8 mm. Combinations of the above ranges are also possible (e.g., the average length of fibrils is greater than or equal to 4 mm and less than 6 mm). Other ranges are also possible.

[0245] The average length of fibrillated fibers refers to the average length of the parent fibers from one end of the parent fibers to the opposite end. In some embodiments, the maximum average length of the fibrillated fibers falls within the above range. The maximum average length refers to the mean value of the maximum size along an axis of the fibrillated fibers (including parent fibers and fibrils). It should be understood that in certain embodiments, fibers and fibrils can have sizes outside the above range.

[0246] The fibrillation level of fibrillated fibers (if present) can be measured according to many suitable methods.For example, the fibrillation level can be measured according to the Canadian Standard Freeness (CSF) test specified by the freeness of TAPPI test method T 227om 09 pulp.The test can provide an average CSF value.In some embodiments, the average CSF value of fibrillated fibers can vary between 10mL and 750mL.In certain embodiments, the average CSF value of the fibrillated fibers used in one or more pre-filter layers can be greater than or equal to 10mL, greater than or equal to 50mL, greater than or equal to 100mL, greater than or equal to 200mL, greater than or equal to 400mL, greater than or equal to 600mL, or greater than or equal to 700mL.In some embodiments, the average CSF value of fibrillated fibers can be less than or equal to 800mL, less than or equal to 600mL, less than or equal to 400mL, less than or equal to 200mL, less than or equal to 100mL, or less than or equal to 50mL. Combinations of the above ranges are also possible (e.g., the average CSF value of the fibrillated fibers is greater than or equal to 10 mL and less than or equal to 300 mL). Other ranges are also possible. The average CSF value of the fibrillated fibers can be based on one type of fibrillated fibers or more than one type of fibrillated fibers.

[0247] One or more support layers described herein may include components other than fibers. For example, the support layer may include a binder resin. Typically, the binder resin may be used to connect the fibers in the layer. The binder resin may account for less than or equal to 60% by weight, less than or equal to 50% by weight, less than or equal to 40% by weight, less than or equal to 30% by weight, less than or equal to 25% by weight, less than or equal to 20% by weight, less than or equal to 15% by weight, less than or equal to 10% by weight, less than or equal to 7.5% by weight, less than or equal to 5% by weight, less than or equal to 4% by weight, less than or equal to 3% by weight, less than or equal to 2% by weight, less than or equal to 1.5% by weight, less than or equal to 1% by weight, less than or equal to 0.75% by weight, less than or equal to 0.5% by weight, less than or equal to 0.4% by weight, less than or equal to 0.2% by weight, or less than or equal to 0.1% by weight of the support layer. The binder resin may account for greater than or equal to 0 wt %, greater than or equal to 0.1 wt %, greater than or equal to 0.2 wt %, greater than or equal to 0.4 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 3 wt %, greater than or equal to 4 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 %, greater than or equal to 40 wt %, or greater than or equal to 50 wt % of the support layer. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt % and less than or equal to 50 wt %, greater than or equal to 5 wt % and less than or equal to 50 wt %, or greater than or equal to 10 wt % and less than or equal to 30 wt %). Other ranges are also possible. In some embodiments, the support layer is free of binder resin (ie, the binder resin comprises 0 wt % of the support layer).

[0248] When the support layer comprises two or more types of binder resins, each type of binder resin can independently account for one or more amounts of the support layer in the above ranges, and / or all binder resins in the support layer together can account for one or more amounts of the support layer in the above ranges. Similarly, when the filter medium comprises two or more support layers, each layer can independently contain any particular type of binder resin in an amount in one or more of the above ranges, and / or can contain a total amount of binder resin in one or more of the above ranges. In embodiments where the filter medium comprises two or more support layers, the amounts of binder resins in the two or more support layers can be the same or different.

[0249] In some embodiments, the binder resin comprises a polymer. In order to be used in the non-limiting examples of suitable polymers on the binder resin, include thermoplastic polymers (for example, acrylic resins, poly (vinyl acetate), poly (ester), poly (amide)), thermosetting polymers (for example, epoxy resins, phenolic resins, melamine), vinyl acetate resins, epoxy resins, poly (ester) resins, copoly (ester) resins, poly (vinyl alcohol) resins, acrylic resins (for example, styrene acrylic resins), styrene acrylate, styrene butyl acrylate, styrene butadiene, poly (methyl methacrylate), copolymers of styrene and methyl methacrylate, phenolic resins, acrylonitrile rubber, poly (ethylene), poly (urethane), and combinations thereof. Alternatively or additionally, the binder resin may include fluorocarbons, fluorine-free chemicals and / or chemicals containing minimum fluorine atoms. In some cases, the presence of acrylic resins in the support layer may contribute to improving the stiffness of the support layer. In some embodiments, the support layer includes a flame retardant resin containing halogen and / or phosphorus. The support layer may also include a flame retardant resin that does not contain halogen and / or phosphorus.

[0250] In some embodiments, the filter medium comprises a water-repellent additive with minimum fluorine atoms or without fluorine atoms. In some embodiments, the water-repellent additive comprises one or more water-repellent functional groups. Each water-repellent functional group can independently be an alkyl group comprising more than or equal to 3 carbon atoms, an alkenyl group comprising more than or equal to 3 carbon atoms, and / or an alkynyl group comprising more than or equal to 3 carbon atoms. In some embodiments, each water-repellent functional group independently comprises less than or equal to 30 carbon atoms. The water-repellent functional group can be substituted or unsubstituted. In some cases, one or more of the water-repellent functional groups are substituted with aryl. In some embodiments, one or more water-repellent functional groups are straight chain functional groups, branched functional groups or hyperbranched functional groups.

[0251] In one group of embodiments, each water-repellent functional group can be independently a side chain of a repeating unit of a polymer and / or bonded to a silicon atom and / or a metal atom. Non-limiting examples of suitable metals include titanium, zirconium and / or aluminum. Non-limiting examples of suitable polymers include poly(siloxanes), poly(silazanes), poly(acrylates), poly(urethanes), poly(ethers), poly(ureas), poly(esters), poly(carbodiimides) and the like. In some cases, the water-repellent functional group is a hydrolyzate of a substance comprising a metal atom, a hydrolyzable functional group and a water-repellent functional group bonded thereto by a side chain and / or the polymer. In some embodiments, the water-repellent additive includes an oligomer.

[0252] In some embodiments, water repellent additive comprises two or more water repellent functional groups bonded to common atoms.Non-limiting examples of common atoms include carbon atoms, silicon atoms, titanium atoms, zirconium atoms and / or aluminum atoms.In some embodiments, water repellent additive is the reaction product of silane, titanate, zirconate and / or aluminate.In some embodiments, water repellent additive includes silanol, silicon alkoxide (siloxide), siloxane and / or silane ether.In some embodiments, two or more functional groups can include identical or different two or more functional groups.

[0253] In addition, in some embodiments, the water repellent additive comprises one or more polar non-hydrolyzable groups. In some such embodiments, one or more polar non-hydrolyzable groups can be bonded to carbon atoms, metal atoms and / or silicon atoms independently of each other. Non-limiting examples of suitable metal atoms include titanium atoms, zirconium atoms and aluminum atoms. In some embodiments, one or more polar non-hydrolyzable groups are each independently the side chains of the repeating units of the polymer described above for the water repellent functional group. In some embodiments, one or more polar non-hydrolyzable groups include amino, acetoxy and / or acetamido. In some embodiments, the ratio of the number of water repellent functional groups to the number of one or more polar non-hydrolyzable groups is greater than or equal to 0.1 and less than or equal to 10.

[0254] Additionally or alternatively, in some embodiments, the filter medium comprises a fluorinated water repellent additive comprising a fluorinated polymer, a fluorinated oligomer, or a fluorinated monomer that can be and / or configured to undergo a polymerization reaction to form a fluorinated polymer and / or a fluorinated oligomer. For example, non-limiting examples of fluorinated polymers include perfluoropoly(ethers), fluorinated poly(urethanes), and the like. In some embodiments, the fluorinated polymer includes a plurality of fluorinated side chains. In some cases, the fluorinated side chains include the structure -C n F m R y , wherein n is 3 to 4, m is ≥ 1, R is an atom or a group of atoms, and y ≥ 0. Optionally, in some embodiments, m = 2n + 1. In some embodiments, the fluorinated side chain includes the structure -(CF 2 ) n CF 3 , wherein n is 2 to 3. In some embodiments, the fluorinated side chain comprises the structure -(C n F m O) x -, where n and m are integers appropriately selected to form an effective structure, and x is from 1 to 10. Other ranges are also possible.

[0255] In some embodiments, the molecular weight of the fluorinated polymer is greater than or equal to 169 g / mol and less than or equal to 200 kg / mol. In some embodiments, the fluorinated polymer is a homopolymer, a copolymer, a random copolymer, a block copolymer, or a block-like copolymer. In some embodiments, all repeating units of the fluorinated polymer are fluorinated. In some embodiments, the fluorinated polymer comprises non-fluorinated repeating units.

[0256] Non-limiting examples of fluorinated water repellent additives include fluorinated poly(ethers) (e.g., perfluoropoly(ethers), oligofluorinated ethers, fluorinated poly(urethanes), oligofluorinated polyurethanes, and polymers and oligomers containing side chains containing structural motifs having the above structures.

[0257] In some embodiments, the filter media may include a water repellent additive having minimal or no fluorine atoms as described above and a fluorinated water repellent additive comprising a fluorinated polymer, fluorinated oligomer, or fluorinated monomer as described herein.

[0258] In addition, further details regarding some types of additives are provided in U.S. Application No. 17 / 101,707 (filed on November 23, 2020 and entitled “Filter Media Comprising Non-Fluorinated Water Repellent Additives”), U.S. Application No. 17 / 534,186 (filed on November 23, 2021 and entitled “Filter Media Comprising Fluorinated and Non-Fluorinated Water Repellent Additives”), and International Application No. PCT / US21 / 60626 (filed on November 23, 2021 and entitled “Filter Media Comprising Fluorinated and Non-Fluorinated Water Repellent Additives”), each of which is incorporated herein by reference in its entirety for all purposes.

[0259] In some embodiments, the support layer comprises an oleophobic additive as described elsewhere herein with respect to the pre-filter layer. For example, in some cases, the support layer comprises an additive that is a fluorocarbon additive (e.g., a fluorinated monomer such as hexafluorobutyric acid, CF 4 , CHF 3 , C 2 F 6 , C 3 F 8 , C 4 F 8, C 2 F 4 , C 3 F 6 , C 4 F 10 , C 5 F 10 , C 5 F 12 , C 6 F 12 , C 6 F 14 , perfluorohexylethyl acrylate (C 11 H 7 F 13 O 2 ), perfluorohexylethyl methacrylate (C 12 H 9 F 13 O 2 ), allyl pentafluorobenzene (C 9 H 5 F 5 ), pentafluorostyrene (C 8 H 3 F 5 ) etc.; reaction products of such monomers), as described elsewhere herein. When present, such additives may be introduced into the support layer by one or more of the methods described for introducing oleophobic additives into the pre-filter layer.

[0260] The support layer may include an oleophobic additive in any suitable amount. In some embodiments, the oleophobic additive may be present in the support layer in an amount 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 3 wt%, greater than or equal to 5 wt%, greater than or equal to 7 wt%, or greater than or equal to 9 wt%. In some embodiments, the oleophobic additive may be present in the support layer in an amount less than or equal to 10 wt%, less than or equal to 9 wt%, less than or equal to 7 wt%, less than or equal to 5 wt%, less than or equal to 3 wt%, less than or equal to 2 wt%, or less than or equal to 1 wt%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 10 wt%). Other ranges are also possible.

[0261] When the support layer comprises two or more types of oleophobic additives, each type of oleophobic additive can independently account for an amount of the support layer in one or more of the above ranges, and / or all oleophobic additives in the support layer together can account for an amount of the support layer in one or more of the above ranges. Similarly, when the filter media comprises two or more support layers, each layer can independently include any particular type of oleophobic additive in an amount in one or more of the above ranges, and / or can include a total amount of oleophobic additive in one or more of the above ranges. In embodiments where the filter media comprises two or more support layers, the amount of oleophobic additive in the two or more support layers can be the same or different.

[0262] In some embodiments, one or more support layers described herein may include one or more crosslinking agents and / or reaction products of crosslinking agents. The reaction product of a crosslinking agent may include a portion of a crosslinking agent chemically bonded to a portion of a crosslinking agent that undergoes a crosslinking reaction to form a reaction product (e.g., an unreacted core initially present in a crosslinking agent comprising two or more functional groups that undergo a crosslinking reaction). Such a portion may be referred to as a "reacted crosslinking agent". Non-limiting examples of suitable crosslinking agents include crosslinking agents suitable for inclusion in acrylic resins and / or flame retardant resins.

[0263] The filter media described herein may include a crosslinking agent and / or a reacted crosslinking agent in any suitable amount. In some embodiments, the crosslinking agent and / or the reacted crosslinking agent may be present in the support layer in an amount greater than or equal to 0 wt%, greater than or equal to 0.5 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 10 wt%, or greater than or equal to 15 wt%. In some embodiments, the crosslinking agent and / or the reacted crosslinking agent may be present in the support layer in an amount 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 5 wt%, less than or equal to 2 wt%, less than or equal to 1 wt%, or less than or equal to 0.5 wt%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 20 wt%). Other ranges are also possible.

[0264] When the support layer comprises two or more types of cross-linking agents and / or reacted cross-linking agents, each type of cross-linking agent and / or reacted cross-linking agent can independently account for one or more amounts of the support layer in the above ranges, and / or all cross-linking agents and / or reacted cross-linking agents in the support layer can together account for one or more amounts of the support layer in the above ranges. Similarly, when the filter medium comprises two or more support layers, each layer can independently contain any particular type of cross-linking agent and / or reacted cross-linking agent in an amount in one or more of the above ranges, and / or can contain a total amount of cross-linking agent and / or reacted cross-linking agent in one or more of the above ranges. In embodiments where the filter medium comprises two or more support layers, the amounts of cross-linking agents and / or reacted cross-linking agents in the two or more support layers can be the same or different.

[0265] The support layer described herein may include fibers having any of a variety of suitable average fiber diameters. In some embodiments, the average fiber diameter of the fibers in the support layer is greater than or equal to 1 micron, greater than or equal to 1.5 microns, greater than or equal to 2 microns, greater than or equal to 3 microns, greater than or equal to 4 microns, greater than or equal to 5 microns, greater than or equal to 6 microns, greater than or equal to 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 12 microns, greater than or equal to 15 microns, greater than or equal to 16 microns, or greater than or equal to 18 microns. In some embodiments, the average fiber diameter of the fibers in the support layer is less than or equal to 20 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 12 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 microns, less than or equal to 3 microns, less than or equal to 2 microns, or less than or equal to 1.5 microns. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 1 micron and less than or equal to 20 microns, greater than or equal to 5 microns and less than or equal to 16 microns, greater than or equal to 8 microns and less than or equal to 15 microns, greater than or equal to 2 microns and less than or equal to 8 microns, or greater than or equal to 2 microns and less than or equal to 5 microns). Other ranges are also possible.

[0266] When the support layer comprises two or more types of fibers, each type of fiber can independently have an average fiber diameter in one or more of the above ranges, and / or all of the fibers in the support layer together can have an average fiber diameter in one or more of the above ranges. Similarly, when the filter media comprises two or more support layers, each support layer can independently comprise one or more types of fibers having an average fiber diameter in one or more of the above ranges, and / or can comprise fibers that have an average fiber diameter in one or more of the above ranges in general. In embodiments where the filter media comprises two or more support layers, the average fiber diameters of the fibers in the two or more support layers can be the same or different.

[0267] In embodiments where the filter media includes two or more support layers, the average fiber diameters of the fibers in the two or more support layers can be the same or different. For example, the filter media can include a first support layer having an average fiber diameter within one or more of the above ranges (e.g., greater than or equal to 1 micron and less than or equal to 20 microns, greater than or equal to 5 microns and less than or equal to 16 microns, or greater than or equal to 8 microns and less than or equal to 15 microns) and a second support layer having an average fiber diameter within one or more of the above ranges (e.g., greater than or equal to 1 micron and less than or equal to 20 microns, greater than or equal to 2 microns and less than or equal to 8 microns, or greater than or equal to 2 microns and less than or equal to 5 microns). In some cases, the support layer positioned adjacent to the pre-filter layer on the opposite side from the main filter layer can include fibers having an average fiber diameter that is less than the average fiber diameter of the fibers in the support layer positioned adjacent to the main filter layer on the opposite side from the pre-filter layer. In other cases, the support layer positioned adjacent to the pre-filter layer on the opposite side from the main filter layer may contain fibers having an average fiber diameter greater than the average fiber diameter of the fibers in the support layer positioned adjacent to the main filter layer on the opposite side from the pre-filter layer, and / or both support layers may be present and contain fibers having the same average fiber diameter.

[0268] The support layer described herein can include fibers having various suitable average fiber lengths. In some embodiments, the average fiber length of the fibers in the support layer is greater than or equal to 1 mm, greater than or equal to 1.5 mm, greater than or equal to 2 mm, greater than or equal to 2.5 mm, greater than or equal to 3 mm, greater than or equal to 5 mm, greater than or equal to 7 mm, greater than or equal to 10 mm, greater than or equal to 12 mm, greater than or equal to 15 mm, greater than or equal to 18 mm, greater than or equal to 20 mm, greater than or equal to 30 mm, greater than or equal to 50 mm, greater than or equal to 75 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, or greater than or equal to 275 mm. In some embodiments, the average fiber length of the fibers in the support layer is 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 75 mm, less than or equal to 50 mm, less than or equal to 30 mm, less than or equal to 20 mm, less than or equal to 18 mm, less than or equal to 15 mm, less than or equal to 12 mm, less than or equal to 10 mm, less than or equal to 7 mm, less than or equal to 5 mm, less than or equal to 3 mm, less than or equal to 2.5 mm, less than or equal to 2 mm, or less than or equal to 1.5 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 mm and less than or equal to 300 mm, greater than or equal to 2 mm and less than or equal to 100 mm, greater than or equal to 3 mm and less than or equal to 18 mm, or greater than or equal to 2 mm and less than or equal to 12 mm). Other ranges are possible.

[0269] When the support layer comprises two or more types of fibers, each type of fiber can independently have an average fiber length in one or more of the above ranges, and / or all of the fibers in the support layer together can have an average fiber length in one or more of the above ranges. Similarly, when the filter media comprises two or more support layers, each support layer can independently comprise one or more types of fibers having an average fiber length in one or more of the above ranges, and / or can comprise fibers that collectively have an average fiber length in one or more of the above ranges. In embodiments where the filter media comprises two or more support layers, the average fiber lengths of the fibers in the two or more support layers can be the same or different.

[0270] In embodiments where the filter media includes two or more support layers, the average fiber lengths of the fibers in the two or more support layers can be the same or different. For example, the filter media can include a first support layer having an average fiber length within one or more of the above ranges (e.g., greater than or equal to 1 mm and less than or equal to 300 mm, greater than or equal to 2 mm and less than or equal to 100 mm, or greater than or equal to 3 mm and less than or equal to 18 mm) and a second support layer having an average fiber diameter within one or more of the above ranges (e.g., greater than or equal to 1 mm and less than or equal to 300 mm, greater than or equal to 2 mm and less than or equal to 100 mm, or greater than or equal to 2 mm and less than or equal to 12 mm). In some cases, a support layer positioned adjacent to a pre-filter layer on the opposite side from the main filter layer can include fibers having an average fiber length less than the average fiber length of fibers in a support layer positioned adjacent to the main filter layer on the opposite side from the pre-filter layer. In other cases, the support layer positioned adjacent to the pre-filter layer on the opposite side from the main filter layer may contain fibers having an average fiber length greater than the average fiber length of fibers in the support layer positioned adjacent to the main filter layer on the opposite side from the pre-filter layer, and / or both support layers may be present and contain fibers having the same average fiber length.

[0271] The support layer can have any of a variety of suitable thicknesses. In some embodiments, the thickness of the support layer is greater than or equal to 0.05 mm, greater than or equal to 0.07 mm, greater than or equal to 0.1 mm, greater than or equal to 0.2 mm, greater than or equal to 0.4 mm, greater than or equal to 0.6 mm, greater than or equal to 0.8 mm, greater than or equal to 1 mm, greater than or equal to 1.2 mm, greater than or equal to 1.5 mm, greater than or equal to 2 mm, greater than or equal to 2.5 mm, greater than or equal to 3 mm, greater than or equal to 3.5 mm, greater than or equal to 4 mm, or greater than or equal to 4.5 mm. In some embodiments, the thickness of the support layer is 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 3.5 mm, less than or equal to 2.5 mm, less than or equal to 2 mm, less than or equal to 1.5 mm, less than or equal to 1.2 mm, less than or equal to 1 mm, less than or equal to 0.8 mm, less than or equal to 0.6 mm, less than or equal to 0.4 mm, less than or equal to 0.2 mm, less than or equal to 0.1 mm, or less than or equal to 0.07 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.05 mm and less than or equal to 5 mm, greater than or equal to 0.1 mm and less than or equal to 1 mm, or greater than or equal to 0.1 mm and less than or equal to 1 mm). Other ranges are also possible.

[0272] When the filter media includes two or more support layers, each support layer can independently have a thickness in one or more of the above ranges. In embodiments where the filter media includes two or more support layers, the thickness of the two or more support layers can be the same or different.

[0273] The thickness of the support layer may be determined according to ASTM D1777 (2015) under an applied pressure of 0.8 kPa.

[0274] The support layer may have any suitable normalized surface area. In some embodiments, the normalized surface area of ​​the support layer is greater than or equal to 0.01 m 2 / m 2 , greater than or equal to 0.05m 2 / m 2 , greater than or equal to 0.1m 2 / m 2 , greater than or equal to 0.5m 2 / m 2 , greater than or equal to 1m 2 / m 2 , greater than or equal to 3 m 2 / m 2 , greater than or equal to 5 m 2 / m 2 , greater than or equal to 10 m 2 / m 2 , greater than or equal to 25m 2 / m 2 , greater than or equal to 50 m 2 / m 2 , greater than or equal to 100 m 2 / m 2 , greater than or equal to 150m 2 / m 2 , greater than or equal to 200 m 2 / m 2 , greater than or equal to 250 m 2 / m 2 , greater than or equal to 300m 2 / m 2 , or greater than or equal to 350m 2 / m 2 In some embodiments, the normalized surface area of ​​the support layer is less than or equal to 400 m 2 / m 2 , less than or equal to 350 m 2 / m 2 , less than or equal to 300m 2 / m 2 , less than or equal to 250 m 2 / m2 , less than or equal to 200 m 2 / m 2 , less than or equal to 150m 2 / m 2 , less than or equal to 100m 2 / m 2 , less than or equal to 50m 2 / m 2 , less than or equal to 25m 2 / m 2 , less than or equal to 10m 2 / m 2 , less than or equal to 5m 2 / m 2 , less than or equal to 3m 2 / m 2 , less than or equal to 1m 2 / m 2 , less than or equal to 0.5m 2 / m 2 , less than or equal to 0.1m 2 / m 2 , or less than or equal to 0.05m 2 / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 0.01 m 2 / m 2 And less than or equal to 400m 2 / m 2 , or greater than or equal to 0.1m 2 / m 2 And less than or equal to 3m 2 / m 2 ). Other ranges are also possible.

[0275] When the filter media includes two or more support layers, each support layer can independently have a normalized surface area in one or more of the above ranges. In embodiments where the filter media includes two or more support layers, the normalized surface areas of the two or more support layers can be the same or different.

[0276] The normalized surface area of ​​the support layer may be determined as described elsewhere herein with respect to the determination of the normalized surface area of ​​the pre-filter layer.

[0277] As described above, in some embodiments, the filter media can include exactly one support layer. In other embodiments, the filter media can include two or more support layers. Various support layer characteristics will be described below for each of these configurations.

[0278] In embodiments where the filter media includes a single support layer, the support layer can have a basis weight of 25 gsm or more, 30 gsm or more, 35 gsm or more, 40 gsm or more, 50 gsm or more, 60 gsm or more, 70 gsm or more, 80 gsm or more, 90 gsm or more, 100 gsm or more, 110 gsm or more, 120 gsm or more, 130 gsm or more, 150 gsm or more, 175 gsm or more, 200 gsm or more, 225 gsm or more, 250 gsm or more, or 275 gsm or more. In embodiments where the filter media includes a single support layer, the support layer can have a basis weight of 300 gsm or less, 275 gsm or less, 250 gsm or less, 225 gsm or less, 200 gsm or less, 175 gsm or less, 150 gsm or less, 130 gsm or less, 120 gsm or less, 110 gsm or less, 100 gsm or less, 90 gsm or less, 80 gsm or less, 70 gsm or less, 60 gsm or less, 50 gsm or less, 40 gsm or less, 35 gsm or less, 30 gsm or less, or 25 gsm or less. Combinations of the above-referenced ranges are also possible (eg, greater than or equal to 25 gsm and less than or equal to 300 gsm, or greater than or equal to 25 gsm and less than or equal to 120 gsm). Other ranges are also possible.

[0279] The weight per unit area may be measured according to ASTM D3776M-20 (2020).

[0280] In embodiments where the filter media comprises a single support layer, the support layer can have an average pore size of greater than or equal to 0.1 microns, greater than or equal to 0.2 microns, greater than or equal to 0.4 microns, greater than or equal to 0.6 microns, greater than or equal to 0.8 microns, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 5 microns, greater than or equal to 10 microns, greater than or equal to 15 microns, greater than or equal to 20 microns, greater than or equal to 25 microns, greater than or equal to 30 microns, greater than or equal to 35 microns, greater than or equal to 40 microns, greater than or equal to 45 microns, greater than or equal to 50 microns, greater than or equal to 60 microns, greater than or equal to 80 microns, greater than or equal to 100 microns, greater than or equal to 150 microns, greater than or equal to 200 microns, or greater than or equal to 250 microns. In some embodiments, the average pore size of the support layer as the only support layer in the filter medium is less than or equal to 300 microns, less than or equal to 250 microns, less than or equal to 200 microns, less than or equal to 150 microns, less than or equal to 100 microns, less than or equal to 80 microns, less than or equal to 60 microns, less than or equal to 50 microns, less than or equal to 45 microns, less than or equal to 40 microns, less than or equal to 35 microns, less than or equal to 30 microns, less than or equal to 25 microns, less than or equal to 15 microns, less than or equal to 10 microns, less than or equal to 5 microns, less than or equal to 2 microns, less than or equal to 1 micron, less than or equal to 0.6 microns, less than or equal to 0.4 microns, or less than or equal to 0.2 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 micron and less than or equal to 300 microns, greater than or equal to 1 micron and less than or equal to 100 microns). Other ranges are also possible.

[0281] The average pore size can be measured using ASTM F316 (2003).

[0282] In embodiments where the filter media includes a single support layer, the efficiency of the support layer (e.g., before exposure to IPA vapor) can be greater than or equal to 1%, greater than or equal to 2%, greater than or equal to 5%, greater than or equal to 7%, greater than or equal to 10%, greater than or equal to 15%, 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%, or greater than or equal to 45%. In embodiments where the filter media includes a single support layer, the efficiency of the support layer (e.g., before exposure to IPA vapor) can be less than or equal to 50%, less than or equal to 45%, less than or equal to 40%, less than or equal to 5%, less than or equal to 35%, less than or equal to 30%, less than or equal to 25%, less than or equal to 10%, less than or equal to 5%, less than or equal to 3%, or less than or equal to 2%. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 1% and less than or equal to 50%, or greater than or equal to 1% and less than 35%). Other ranges are also possible. In some embodiments, the efficiencies described in the preceding paragraphs are efficiencies at MPPS. In some embodiments, the efficiencies described in the preceding paragraphs are efficiencies at 0.09 microns. In some embodiments, the efficiencies described in the preceding paragraphs are efficiencies at 0.3 microns. The efficiencies of the support layer at MPPS, at 0.09 microns, and at 0.3 microns can be determined as described elsewhere herein for determining the efficiency of the pre-filter layer.

[0283] In embodiments where the filter media comprises a single support layer, the support layer can have an air permeability greater than or equal to 0.5 CFM, greater than or equal to 1 CFM, greater than or equal to 5 CFM, greater than or equal to 10 CFM, greater than or equal to 25 CFM, greater than or equal to 50 CFM, greater than or equal to 75 CFM, greater than or equal to 100 CFM, greater than or equal to 200 CFM, greater than or equal to 300 CFM, greater than or equal to 400 CFM, greater than or equal to 500 CFM, greater than or equal to 600 CFM, or greater than or equal to 700 CFM. In embodiments where the filter media includes a single support layer, the air permeability of the support layer can be less than or equal to 800 CFM, less than or equal to 700 CFM, less than or equal to 600 CFM, less than or equal to 500 CFM, less than or equal to 400 CFM, less than or equal to 300 CFM, less than or equal to 200 CFM, less than or equal to 100 CFM, less than or equal to 75 CFM, less than or equal to 50 CFM, less than or equal to 25 CFM, less than or equal to 10 CFM, less than or equal to 5 CFM, or less than or equal to 1 CFM. Combinations of these ranges are also possible (e.g., greater than or equal to 0.5 CFM and less than or equal to 800 CFM, or greater than or equal to 1 CFM and less than or equal to 500 CFM). Other ranges are also possible.

[0284] The air permeability may be measured at a pressure of 125 Pa according to ASTM D737-04 (2016).

[0285] In embodiments where the filter media includes two or more support layers, the basis weight of each support layer can independently be 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 20 gsm, greater than or equal to 25 gsm, greater than or equal to 30 gsm, greater than or equal to 35 gsm, greater than or equal to 40 gsm, or greater than or equal to 45 gsm. In some embodiments, the basis weight of each support layer can independently be less than or equal to 50 gsm, less than or equal to 45 gsm, less than or equal to 40 gsm, less than or equal to 35 gsm, less than or equal to 30 gsm, less than or equal to 25 gsm, less than or equal to 20 gsm, less than or equal to 15 gsm, or less than or equal to 12.5 gsm. Combinations of the above ranges are also possible (e.g., greater than or equal to 10 gsm and less than or equal to 50 gsm, or greater than or equal to 15 gsm and less than or equal to 15 gsm). Other ranges are also possible. The weight per unit area of ​​two or more support layers can be the same or different.

[0286] The weight per unit area may be measured according to ASTM D3776M-20 (2020).

[0287] In embodiments where the filter media includes two or more support layers, the air permeabilities of the two or more support layers may be the same or different.

[0288] In embodiments where the filter media comprises two or more support layers, the air permeability of the support layer adjacent to the main filter layer on the opposite side of the pre-filter layer may be greater than or equal to 1 CFM, greater than or equal to 5 CFM, greater than or equal to 10 CFM, greater than or equal to 25 CFM, greater than or equal to 50 CFM, greater than or equal to 75 CFM, greater than or equal to 100 CFM, greater than or equal to 200 CFM, greater than or equal to 300 CFM, greater than or equal to 400 CFM, greater than or equal to 500 CFM, greater than or equal to 600 CFM, or greater than or equal to 700 CFM. In embodiments where the filter media includes two or more support layers, the air permeability of the support layer adjacent to the main filter layer on the opposite side of the pre-filter layer is less than or equal to 800 CFM, less than or equal to 700 CFM, less than or equal to 600 CFM, less than or equal to 500 CFM, less than or equal to 400 CFM, less than or equal to 300 CFM, less than or equal to 200 CFM, less than or equal to 100 CFM, less than or equal to 75 CFM, less than or equal to 50 CFM, less than or equal to 25 CFM, less than or equal to 10 CFM, or less than or equal to 5 CFM. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 1 CFM and less than or equal to 800 CFM, greater than or equal to 1 CFM and less than or equal to 500 CFM). Other ranges are also possible.

[0289] In embodiments where the filter media includes two or more support layers, the support layer adjacent to the pre-filter layer on the opposite side from the main filter layer may have an air permeability of greater than or equal to 1 CFM, greater than or equal to 5 CFM, greater than or equal to 10 CFM, greater than or equal to 25 CFM, greater than or equal to 50 CFM, greater than or equal to 75 CFM, greater than or equal to 100 CFM, greater than or equal to 200 CFM, greater than or equal to 300 CFM, greater than or equal to 400 CFM, or greater than or equal to 450 CFM. Figure 5 In embodiments where a filter medium similar to the filter medium shown in ) includes two or more support layers (e.g., a third layer, a fourth layer), the air permeability of the support layer adjacent to the pre-filter layer on the opposite side of the main filter layer can be less than or equal to 500 CFM, less than or equal to 500 CFM, less than or equal to 450 CFM, less than or equal to 300 CFM, less than or equal to 200 CFM, less than or equal to 100 CFM, less than or equal to 75 CFM, less than or equal to 50 CFM, less than or equal to 25 CFM, less than or equal to 10 CFM, or less than or equal to 5 CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 CFM and less than or equal to 500 CFM). Other ranges are also possible.

[0290] The air permeability may be measured at a pressure of 125 Pa according to ASTM D737-04 (2016).

[0291] In embodiments where the filter media includes two or more support layers, the efficiency of the support layer adjacent to the main filter layer on the side opposite the pre-filter layer (e.g., efficiency before IPA vapor exposure) can be greater than or equal to 1%, greater than or equal to 2%, greater than or equal to 5%, greater than or equal to 7%, greater than or equal to 10%, greater than or equal to 15%, 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%, or greater than or equal to 45%. In embodiments where the filter media includes two or more support layers, the efficiency of the support layer adjacent to the main filter layer on the side opposite the pre-filter layer (e.g., efficiency before IPA vapor exposure) can be 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 10%, less than or equal to 5%, 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 50%). Other ranges are possible.

[0292] In some embodiments, the efficiencies described in the preceding paragraphs are efficiencies at MPPS. In some embodiments, the efficiencies described in the preceding paragraphs are efficiencies at 0.09 microns. In some embodiments, the efficiencies described in the preceding paragraphs are efficiencies at 0.3 microns. The efficiencies of one or more support layers at MPPS, at 0.09 microns, and at 0.3 microns can be determined as described elsewhere herein with respect to determination of pre-filter layer efficiencies.

[0293] In embodiments where the filter media comprises two or more support layers, the efficiency of the support layer adjacent to the pre-filter layer on the opposite side from the main filter layer (e.g., efficiency prior to IPA vapor exposure) can be greater than or equal to 5%, greater than or equal to 7%, greater than or equal to 10%, greater than or equal to 15%, greater than or equal to 20%, greater than or equal to 30%, greater than or equal to 40%, greater than or equal to 50%, greater than or equal to 60%, greater than or equal to 70%, greater than or equal to 80%, greater than or equal to 85%, greater than or equal to 90%, greater than or equal to 95%, greater than or equal to 97%, greater than or equal to 98%, or greater than or equal to 98.5%. In embodiments where the filter media includes two or more support layers, the efficiency of the support layer adjacent to the pre-filter layer on the opposite side from the main filter layer (e.g., efficiency prior to IPA vapor exposure) can be less than or equal to 99%, less than or equal to 98.5%, less than or equal to 98%, less than or equal to 97%, 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 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%, less than or equal to 15%, less than or equal to 10%, or less than or equal to 7%. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 5% and less than or equal to 99%). Other ranges are also possible.

[0294] In some embodiments, the efficiencies described in the preceding paragraphs are efficiencies at MPPS. In some embodiments, the efficiencies described in the preceding paragraphs are efficiencies at 0.09 microns. In some embodiments, the efficiencies described in the preceding paragraphs are efficiencies at 0.3 microns. The efficiencies of one or more support layers at MPPS, at 0.09 microns, and at 0.3 microns can be determined as described elsewhere herein with respect to determination of pre-filter layer efficiencies.

[0295] In embodiments where the filter media includes two or more support layers, the ratio of the efficiency (e.g., efficiency before exposure to IPA vapor) of a first support layer (e.g., a support layer adjacent to the main filter layer on the side opposite the pre-filter layer) to the efficiency (e.g., efficiency before exposure to IPA vapor) of a second support layer (e.g., a support layer adjacent to the pre-filter layer on the side opposite the main filter layer) can be less than or equal to 1:1.1, less than or equal to 1:1.3, less than or equal to 1:1.5, less than or equal to 1:2, less than or equal to 1:3, less than or equal to 1:4, less than or equal to 1:5, less than or equal to 1:10, less than or equal to 1:20, less than or equal to 1:30, less than or equal to 1:40, less than or equal to 1:50, less than or equal to 1:60, less than or equal to 1:70, less than or equal to 1:80, less than or equal to 1:90, less than or equal to 1:95, or less than or equal to 1:98. In embodiments where the filter media includes two or more support layers, the ratio of the efficiency of the first support layer (e.g., the efficiency before exposure to IPA vapor) to the efficiency of the second support layer (e.g., the efficiency before exposure to IPA vapor) can be greater than or equal to 1:99, greater than or equal to 1:98, greater than or equal to 1:95, greater than or equal to 1:90, greater than or equal to 1:80, greater than or equal to 1:70, greater than or equal to 1:60, greater than or equal to 1:50, greater than or equal to 1:40, greater than or equal to 1:30, greater than or equal to 1:20, greater than or equal to 1:10, greater than or equal to 1:5, greater than or equal to 1:4, greater than or equal to 1:3, greater than or equal to 1:2, greater than or equal to 1:1.5, or greater than or equal to 1:1.3. Combinations of these ranges are also possible (e.g., less than or equal to 1:1.1 and greater than or equal to 1:99, less than or equal to 1:1.1 and greater than or equal to 1:50). Other ranges are also possible.

[0296] In some embodiments, the ratios described in the preceding paragraphs are ratios of efficiencies at MPPS. In some embodiments, the ratios described in the preceding paragraphs are ratios of efficiencies at 0.09 microns. In some embodiments, the ratios described in the preceding paragraphs are ratios of efficiencies at 0.3 microns. The efficiencies of one or more support layers at MPPS, at 0.09 microns, and at 0.3 microns can be determined as described elsewhere herein for determining the efficiency of a pre-filter layer.

[0297] In embodiments where the filter media comprises two or more support layers, the average pore size of the support layer adjacent to the main filter layer on the opposite side from the pre-filter layer can be greater than or equal to 0.1 microns, greater than or equal to 0.2 microns, greater than or equal to 0.4 microns, greater than or equal to 0.6 microns, greater than or equal to 0.8 microns, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 5 microns, greater than or equal to 10 microns, greater than or equal to 15 microns, greater than or equal to 20 microns, greater than or equal to 25 microns, greater than or equal to 30 microns, greater than or equal to 35 microns, greater than or equal to 40 microns, greater than or equal to 45 microns, greater than or equal to 50 microns, greater than or equal to 60 microns, greater than or equal to 80 microns, greater than or equal to 100 microns, greater than or equal to 150 microns, greater than or equal to 200 microns, or greater than or equal to 250 microns. In some embodiments, the average pore size of the support layer adjacent to the main filter layer on the opposite side of the pre-filter layer is less than or equal to 300 microns, less than or equal to 250 microns, less than or equal to 200 microns, less than or equal to 150 microns, less than or equal to 100 microns, less than or equal to 80 microns, less than or equal to 60 microns, less than or equal to 50 microns, less than or equal to 45 microns, less than or equal to 40 microns, less than or equal to 35 microns, less than or equal to 30 microns, less than or equal to 25 microns, less than or equal to 15 microns, less than or equal to 10 microns, less than or equal to 5 microns, less than or equal to 2 microns, less than or equal to 1 micron, less than or equal to 0.6 microns, less than or equal to 0.4 microns, or less than or equal to 0.2 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 micron and less than or equal to 300 microns, greater than or equal to 1 micron and less than or equal to 100 microns, or greater than or equal to 1 micron and less than or equal to 50 microns). Other ranges are also possible.

[0298] In embodiments where the filter media comprises two or more support layers, the average pore size of the support layer adjacent to the pre-filter layer on the opposite side from the main filter layer can be greater than or equal to 0.1 microns, greater than or equal to 0.2 microns, greater than or equal to 0.4 microns, greater than or equal to 0.6 microns, greater than or equal to 0.8 microns, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 5 microns, greater than or equal to 10 microns, greater than or equal to 15 microns, greater than or equal to 20 microns, greater than or equal to 25 microns, greater than or equal to 30 microns, greater than or equal to 35 microns, greater than or equal to 40 microns, greater than or equal to 45 microns, greater than or equal to 50 microns, greater than or equal to 60 microns, greater than or equal to 80 microns, greater than or equal to 100 microns, greater than or equal to 150 microns, greater than or equal to 200 microns, or greater than or equal to 250 microns. In embodiments where the filter media includes two or more support layers, the average pore size of the support layer adjacent to the pre-filter layer on the opposite side from the main filter layer can be less than or equal to 300 microns, less than or equal to 250 microns, less than or equal to 200 microns, less than or equal to 150 microns, less than or equal to 100 microns, less than or equal to 80 microns, less than or equal to 60 microns, less than or equal to 50 microns, less than or equal to 45 microns, less than or equal to 40 microns, less than or equal to 35 microns, less than or equal to 30 microns, less than or equal to 25 microns, less than or equal to 15 microns, less than or equal to 10 microns, less than or equal to 5 microns, less than or equal to 2 microns, less than or equal to 1 micron, less than or equal to 0.6 microns, less than or equal to 0.4 microns, or less than or equal to 0.2 microns. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.1 micron and less than or equal to 300 microns, greater than or equal to 1 micron and less than or equal to 100 microns, or greater than or equal to 1 micron and less than or equal to 30 microns). Other ranges are also possible.

[0299] The average pore size can be measured using ASTM F316 (2003).

[0300] In embodiments where the filter media includes two or more support layers, the ratio of the average pore size of the first support layer (e.g., the support layer adjacent to the main filter layer on the side opposite the pre-filter layer) to the average pore size of the second support layer (e.g., the support layer adjacent to the pre-filter layer on the side opposite the main filter layer) can be less than or equal to 1:1.1, less than or equal to 1:1.3, less than or equal to 1:1.5, less than or equal to 1:2, less than or equal to 1:3, less than or equal to 1:4, less than or equal to 1:5, less than or equal to 1:7, less than or equal to 1:10, less than or equal to 1:15, less than or equal to 1:20, less than or equal to 1:25, less than or equal to 1:30, less than or equal to 1:35, less than or equal to 1:40, or less than or equal to 1:45. In embodiments where the filter media includes two or more support layers, the ratio of the average pore size of the first support layer to the average pore size of the second support layer can be greater than or equal to 1:50, greater than or equal to 1:45, greater than or equal to 1:40, greater than or equal to 1:30, greater than or equal to 1:25, greater than or equal to 1:20, greater than or equal to 1:15, greater than or equal to 1:10, greater than or equal to 1:7, greater than or equal to 1:5, greater than or equal to 1:3, greater than or equal to 1:2, greater than or equal to 1:1.5, or greater than or equal to 1:1.3. Combinations of the above-referenced ranges are also possible (e.g., less than or equal to 1:1.1 and greater than or equal to 1:50). Other ranges are also possible.

[0301] In embodiments where the filter media comprises two or more support layers, the ratio of the normalized surface area of ​​a first support layer (e.g., a support layer adjacent to the main filter layer on the side opposite the pre-filter layer) to the normalized surface area of ​​a second support layer (e.g., a support layer adjacent to the pre-filter layer on the side opposite the main filter layer) can be less than or equal to 15:1, less than or equal to 14:1, less than or equal to 13:1, less than or equal to 12:1, less than or equal to 11:1, less than or equal to 10:1, less than or equal to 9:1, less than or equal to 8:1, less than or equal to 7:1, less than or equal to 6:1, or less than or equal to 5.5:1. In embodiments where the filter media comprises two or more support layers, the ratio of the normalized surface area of ​​the first support layer to the normalized surface area of ​​the second support layer can be greater than or equal to 5: 1, greater than or equal to 5.5: 1, greater than or equal to 6: 1, greater than or equal to 7: 1, greater than or equal to 8: 1, greater than or equal to 9: 1, greater than or equal to 10: 1, greater than or equal to 11: 1, greater than or equal to 12: 1, greater than or equal to 13: 1, or greater than or equal to 14: 1. Combinations of the above-referenced ranges are also possible (e.g., less than or equal to 15: 1 and greater than or equal to 5: 1). Other ranges are also possible.

[0302] In embodiments where the filter media comprises two or more support layers, the ratio of the average pore size of the pre-filter layer to the average pore size of the support layer adjacent to the pre-filter layer on the opposite side from the main filter layer may be less than or equal to 1:1.3, less than or equal to 1:1.5, less than or equal to 1:2, less than or equal to 1:3, less than or equal to 1:4, less than or equal to 1:5, less than or equal to 1:7, less than or equal to 1:10, less than or equal to 1:15, less than or equal to 1:20, less than or equal to 1:25, less than or equal to 1:30, less than or equal to 1:35, less than or equal to 1:40, or less than or equal to 1:45. In embodiments where the filter media includes two or more support layers, the ratio of the average pore size of the pre-filter layer to the average pore size of the support layer adjacent to the pre-filter layer on the opposite side from the main filter layer can be greater than or equal to 1:50, greater than or equal to 1:45, greater than or equal to 1:40, greater than or equal to 1:30, greater than or equal to 1:25, greater than or equal to 1:20, greater than or equal to 1:15, greater than or equal to 1:10, greater than or equal to 1:7, greater than or equal to 1:5, greater than or equal to 1:3, greater than or equal to 1:2, greater than or equal to 1:1.5. Combinations of the above-referenced ranges are also possible (e.g., less than or equal to 1:1.3 and greater than or equal to 1:50). Other ranges are also possible.

[0303] As mentioned above, the filter media described herein may include one or more additional layers, e.g. Figure 6 to Figure 7 As shown. For example, the filter medium may include an additional layer as an oleophobic spacer layer and / or an additional layer as a coarse meltblown layer. In some cases, the filter medium includes an oleophobic layer, which is a nonwoven fiber web (e.g., a meltblown layer), a film layer, and / or a scrim layer. In some embodiments, one or more additional layers (e.g., an oleophobic spacer layer, a coarse meltblown layer) present in the filter medium can be charged via a charging process described elsewhere herein (e.g., an electrostatic charging process, a friction charging process, and / or a hydro-electret charging process).

[0304] When present, the additional layers (e.g., oleophobic spacer layer, coarse meltblown layer) can include fibers having any of a variety of suitable average fiber diameters. In some embodiments, the average fiber diameter of the fibers in the additional layers is greater than or equal to 0.4 microns, greater than or equal to 0.5 microns, greater than or equal to 0.6 microns, greater than or equal to 0.8 microns, greater than or equal to 1 micron, greater than or equal to 1.5 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, or greater than or equal to 8 microns. In some embodiments, the average fiber diameter of the fibers in the additional layer is less than or equal to 10 microns, less than or equal to 8 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 1.5 microns, less than or equal to 1 micron, less than or equal to 0.8 microns, less than or equal to 0.6 microns, or less than or equal to 0.5 microns. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.4 microns and less than or equal to 10 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 3 microns). Other ranges are also possible.

[0305] When the additional layer comprises two or more types of fibers, each type of fiber can independently have an average fiber diameter in one or more of the above ranges, and / or all of the fibers in the additional layer together can have an average fiber diameter in one or more of the above ranges. Similarly, when the filter media includes two or more additional layers, each additional layer can independently comprise one or more types of fibers having an average fiber diameter in one or more of the above ranges, and / or can comprise fibers that collectively have an average fiber diameter in one or more of the above ranges. In embodiments where the filter media includes two or more additional layers, the average fiber diameters of the two or more additional layers can be the same or different.

[0306] In some embodiments, the fibers in the additional layers are continuous fibers, such as those described elsewhere herein as suitable for inclusion in a fine fiber layer. In one set of embodiments, one or more additional layers comprise meltblown fibers.

[0307] When present, additional layers (e.g., oleophobic spacer, coarse meltblown layer) may include synthetic fibers.Synthetic fibers may include any suitable type of synthetic polymer.The example of suitable synthetic fibers includes polyester (e.g., polyethylene terephthalate, polybutylene terephthalate), polycarbonate, polyamide (e.g., various nylon polymers), polyaramid, polyimide, polyethylene, polypropylene, polyetheretherketone, polyolefin, acrylic, polyvinyl alcohol, regenerated cellulose (e.g., synthetic cellulose such as lyocell, rayon), polyacrylonitrile, polyvinylidene fluoride (PVDF), copolymers of polyethylene and PVDF, polyethersulfone and combinations thereof. In some embodiments, synthetic fibers are organic polymer fibers.Synthetic fibers may also include multicomponent fibers (i.e., fibers such as bicomponent fibers with a variety of compositions). In some cases, synthetic fibers may include meltblown fibers, melt-spun fibers, electrostatic spinning (e.g., melt electrostatic spinning, solvent electrostatic spinning) fibers or centrifugal spinning fibers, which may be formed by polymers described herein (e.g., polyester, polypropylene). In some embodiments, synthetic fibers may be electrostatic spinning fibers. When present, the additional layers may also include a combination of more than one type of synthetic fibers. It will be appreciated that other types of synthetic fibers may also be used.

[0308] In some embodiments, the synthetic fibers comprise greater than or equal to 80 weight percent, greater than or equal to 82.5 weight percent, greater than or equal to 85 weight percent, greater than or equal to 87.5 weight percent, greater than or equal to 90 weight percent, greater than or equal to 92 weight percent, greater than or equal to 94 weight percent, greater than or equal to 95 weight percent, greater than or equal to 96 weight percent, greater than or equal to 97 weight percent, greater than or equal to 98 weight percent, or greater than or equal to 99 weight percent of the additional layer. In some embodiments, the synthetic fibers comprise less than or equal to 100 weight percent, less than or equal to 99 weight percent, less than or equal to 98 weight percent, less than or equal to 97 weight percent, less than or equal to 96 weight percent, less than or equal to 95 weight percent, less than or equal to 94 weight percent, less than or equal to 92 weight percent, less than or equal to 90 weight percent, less than or equal to 87.5 weight percent, or less than or equal to 85 weight percent of the additional layer. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 80 wt % and less than or equal to 100 wt %, greater than or equal to 80 wt % and less than or equal to 99 wt %, greater than or equal to 85 wt % and less than or equal to 96 wt %, or greater than or equal to 90 wt % and less than or equal to 95 wt %). Other ranges are also possible. In some embodiments, the synthetic fibers comprise exactly 100 wt % of the additional layer.

[0309] When the additional layer comprises two or more types of synthetic fibers, each type of synthetic fiber can independently account for an amount of the additional layer that is one or more of the above ranges, and / or all of the synthetic fibers in the additional layer together can account for an amount of the additional layer that is one or more of the above ranges. Similarly, when the filter media comprises two or more additional layers, each additional layer can independently include one or more types of synthetic fibers in one or more of the above ranges, and / or can include synthetic fibers that collectively account for an amount of the additional layer that is one or more of the above ranges. In embodiments where the filter media comprises two or more additional layers, the amounts of synthetic fibers in the two or more additional layers can be the same or different.

[0310] When present, the additional layer (e.g., oleophobic spacer layer, coarse meltblown layer) may include one or more additives. In some embodiments, such as embodiments in which the additional layer is a meltblown layer, the additional layer may include wax. For example, the wax may account for more than or equal to 1% by weight of the additional layer, more than or equal to 1.5% by weight, more than or equal to 2% by weight, more than or equal to 2.5% by weight, more than or equal to 3% by weight, or more than or equal to 3.5% by weight. For example, the wax may account for less than or equal to 4% by weight of the additional layer, less than or equal to 3.5% by weight, less than or equal to 3% by weight, less than or equal to 2.5% by weight, less than or equal to 2% by weight, or less than or equal to 1.5% by weight. Combinations of the above ranges are also possible (e.g., greater than or equal to 1% by weight and less than or equal to 4% by weight). Other ranges are also possible.

[0311] When the filter media includes two or more additional layers, each additional layer can independently contain a wax in one or more of the above ranges. In embodiments where the filter media includes two or more additional layers, the amount of wax in the two or more additional layers can be the same or different.

[0312] In some embodiments, the additional layers may include charge additives and / or oleophobic additives (eg, fluorocarbon additives), such as those described elsewhere herein with respect to the pre-filter layer.

[0313] The additional layers described herein (e.g., oleophobic spacer layer, coarse meltblown layer) can have any of a variety of suitable porosities (i.e., void volume). In some embodiments, each of the one or more additional layers can independently have a porosity of one or more of the ranges described elsewhere herein for the pre-filter layer (e.g., greater than or equal to 80% and less than or equal to 99%, greater than or equal to 85% and less than or equal to 96%, or greater than or equal to 90% and less than or equal to 95%).

[0314] When the filter media includes two or more additional layers, each additional layer can independently have a porosity in one or more of the above ranges. In embodiments where the filter media includes two or more additional layers, the porosity of the two or more additional layers can be the same or different.

[0315] The porosity of the additional layer may be determined as described elsewhere herein with respect to the pre-filter layer.

[0316] The additional layers described herein (e.g., oleophobic spacer layer, coarse meltblown layer) can have any suitable normalized surface area. In some embodiments, the normalized surface area of ​​the additional layer is greater than or equal to 1 m 2 / m 2 , greater than or equal to 2m 2 / m 2 , greater than or equal to 3m 2 / m 2 , greater than or equal to 5m 2 / m 2 , greater than or equal to 10m 2 / m 2 , greater than or equal to 15m 2 / m 2 , greater than or equal to 20m 2 / m 2 , greater than or equal to 25m 2 / m 2 , greater than or equal to 30m 2 / m 2 , greater than or equal to 35m 2 / m 2 , greater than or equal to 40m 2 / m 2 , or greater than or equal to 45m 2 / m 2 In some embodiments, the normalized surface area of ​​the additional layer is less than or equal to 50 m 2 / m 2 , less than or equal to 45m 2 / m 2 , less than or equal to 40m 2 / m 2 , less than or equal to 35m 2 / m 2 , less than or equal to 30m 2 / m 2 , less than or equal to 25m 2 / m 2 , less than or equal to 20m 2 / m 2 , less than or equal to 15m 2 / m 2 , less than or equal to 10m2 / m 2 , less than or equal to 5m 2 / m 2 , less than or equal to 3m 2 / m 2 , or less than or equal to 2m 2 / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 1 m 2 / m 2 And less than or equal to 50m 2 / m 2 , greater than or equal to 1 m 2 / m 2 and less than or equal to 40 m 2 / m 2 , or greater than or equal to 1m 2 / m 2 And less than or equal to 30m 2 / m 2 ). Other ranges are also possible.

[0317] When the filter media includes two or more additional layers, each additional layer can independently have a normalized surface area in one or more of the above ranges. In embodiments where the filter media includes two or more additional layers, the normalized surface areas of the two or more additional layers can be the same or different.

[0318] The normalized surface area of ​​the additional layer can be determined as described elsewhere herein with respect to the pre-filter layer.

[0319] The additional layers described herein (e.g., oleophobic spacer layer, coarse meltblown layer) can have any of a variety of suitable thicknesses. In some embodiments, the thickness of the additional layer is less than the thickness of the pre-filter layer also present in the filter medium. In some embodiments, the thickness of the additional layer is greater than or equal to 0.05 mm, greater than or equal to 0.06 mm, greater than or equal to 0.07 mm, greater than or equal to 0.08 mm, greater than or equal to 0.1 mm, greater than or equal to 0.13 mm, greater than or equal to 0.15 mm, greater than or equal to 0.2 mm, greater than or equal to 0.25 mm, greater than or equal to 0.3 mm, greater than or equal to 0.35 mm, greater than or equal to 0.38 mm, greater than or equal to 0.4 mm, greater than or equal to 0.5 mm, greater than or equal to 0.6 mm, or greater than or equal to 0.8 mm. In some embodiments, the thickness of the additional layer is less than or equal to 1 mm, less than or equal to 0.8 mm, less than or equal to 0.6 mm, less than or equal to 0.4 mm, less than or equal to 0.38 mm, less than or equal to 0.35 mm, less than or equal to 0.3 mm, less than or equal to 0.25 mm, less than or equal to 0.2 mm, less than or equal to 0.15 mm, less than or equal to 0.13 mm, less than or equal to 0.1 mm, less than or equal to 0.08 mm, less than or equal to 0.07 mm, or less than or equal to 0.06 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.05 mm and less than or equal to 1 mm, greater than or equal to 0.07 mm and less than or equal to 0.6 mm, or greater than or equal to 0.13 mm and less than or equal to 0.38 mm). Other ranges are also possible.

[0320] When the filter media includes two or more additional layers, each additional layer can independently have a thickness in one or more of the above ranges. In embodiments where the filter media includes two or more additional layers, the thickness of the two or more additional layers can be the same or different.

[0321] The thickness of the additional layer may be determined according to ASTM D1777 (2015) at an applied pressure of 0.8 kPa.

[0322] The additional layers described herein (e.g., oleophobic spacer layer, coarse meltblown layer) can have any of a variety of suitable weights per unit area. In some embodiments, the weight per unit area of ​​the additional layer is less than the weight per unit area of ​​the pre-filter layer also present in the filter media. In some embodiments, the weight per unit area of ​​the additional layer is greater than or equal to 0.5 gsm, greater than or equal to 1 gsm, greater than or equal to 3 gsm, greater than or equal to 5 gsm, greater than or equal to 7 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 25 gsm, greater than or equal to 30 gsm, greater than or equal to 35 gsm, greater than or equal to 40 gsm, or greater than or equal to 45 gsm. In some embodiments, the additional layer has a weight per unit area of ​​less than or equal to 50 gsm, less than or equal to 45 gsm, less than or equal to 40 gsm, less than or equal to 35 gsm, less than or equal to 30 gsm, less than or equal to 25 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 7 gsm, less than or equal to 5 gsm, less than or equal to 3 gsm, or less than or equal to 1 gsm. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.5 gsm and less than or equal to 50 gsm, greater than or equal to 5 gsm and less than or equal to 35 gsm, or greater than or equal to 10 gsm and less than or equal to 25 gsm). Other ranges are also possible.

[0323] When the filter media includes two or more additional layers, each additional layer can independently have a basis weight in one or more of the above ranges. In embodiments where the filter media includes two or more additional layers, the basis weights of the two or more additional layers can be the same or different.

[0324] The weight per unit area can be measured according to ASTM D3776M-20.

[0325] The additional layers described herein (e.g., oleophobic spacer layer, coarse meltblown layer) can have any of a variety of suitable air permeabilities. In some embodiments, the air permeability of the additional layer is greater than or equal to 1 CFM, greater than or equal to 2.5 CFM, greater than or equal to 5 CFM, greater than or equal to 7.5 CFM, 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 100 CFM, greater than or equal to 150 CFM, greater than or equal to 200 CFM, greater than or equal to 300 CFM, greater than or equal to 400 CFM, greater than or equal to 500 CFM, greater than or equal to 600 CFM, greater than or equal to 700 CFM, greater than or equal to 800 CFM, greater than or equal to 900 CFM, greater than or equal to 1000 CFM, greater than or equal to 1100 CFM, greater than or equal to 1200 CFM, greater than or equal to 1300 CFM, or greater than or equal to 1400 CFM. In some embodiments, the additional layer has an air permeability of less than or equal to 1500 CFM, less than or equal to 1400 CFM, less than or equal to 1300 CFM, less than or equal to 1200 CFM, less than or equal to 1100 CFM, less than or equal to 1000 CFM, less than or equal to 900 CFM, less than or equal to 800 CFM, less than or equal to 700 CFM, less than or equal to 600 CFM, less than or equal to 500 CFM, less than or equal to 400 CFM, less than or equal to 300 CFM, less than or equal to 200 CFM, less than or equal to 150 CFM, less than or equal to 100 CFM, less than or equal to 50 CFM, less than or equal to 25 CFM, less than or equal to 10 CFM, less than or equal to 7.5 CFM, less than or equal to 5 CFM, or less than or equal to 2.5 CFM. Combinations of the above ranges are also possible (eg, greater than or equal to 1 CFM and less than or equal to 1500 CFM, greater than or equal to 5 CFM and less than or equal to 1000 CFM, or greater than or equal to 10 CFM and less than or equal to 600 CFM). Other ranges are also possible.

[0326] When the filter media includes two or more additional layers, each additional layer can independently have an air permeability in one or more of the above ranges. In embodiments where the filter media includes two or more additional layers, the air permeabilities of the two or more additional layers can be the same or different.

[0327] The air permeability may be measured at a pressure of 125 Pa according to ASTM D737-04 (2016).

[0328] The additional layers described herein (e.g., oleophobic spacer layer, coarse meltblown layer) can have any of a variety of suitable average pore sizes. In some embodiments, the average pore size of the additional layer 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 8 microns, 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 25 microns, greater than or equal to 30 microns, greater than or equal to 35 microns, greater than or equal to 40 microns, or greater than or equal to 45 microns. In some embodiments, the average pore size of the additional layer is less than or equal to 50 microns, less than or equal to 45 microns, less than or equal to 40 microns, less than or equal to 35 microns, less than or equal to 30 microns, less than or equal to 25 microns, less than or equal to 20 microns, less than or equal to 17.5 microns, less than or equal to 15 microns, less than or equal to 12.5 microns, less than or equal to 10 microns, less than or equal to 8 microns, less than or equal to 5 microns, less than or equal to 3 microns, 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 50 microns, greater than or equal to 2 microns and less than or equal to 30 microns, greater than or equal to 5 microns and less than or equal to 20 microns, greater than or equal to 4 microns and less than or equal to 25 microns, or greater than or equal to 8 microns and less than or equal to 15 microns). Other ranges are also possible.

[0329] When the filter media includes two or more additional layers, each additional layer can independently have an average pore size in one or more of the above ranges. In embodiments where the filter media includes two or more additional layers, the average pore sizes of the two or more additional layers can be the same or different.

[0330] The average pore size can be measured using ASTM F316 (2003).

[0331] In embodiments where the filter medium includes an additional layer as an oleophobic spacer layer, the average pore size of the oleophobic spacer layer can be in one or more of the above ranges (e.g., greater than or equal to 1 micron and less than or equal to 50 microns, greater than or equal to 4 microns and less than or equal to 25 microns, or greater than or equal to 8 microns and less than or equal to 15 microns). In embodiments where the filter medium includes an additional layer as a coarse meltblown layer, the average pore size of the coarse meltblown layer can be in one or more of the above ranges (e.g., greater than or equal to 1 micron and less than or equal to 50 microns, greater than or equal to 2 microns and less than or equal to 30 microns, or greater than or equal to 5 microns and less than or equal to 20 microns).

[0332] The additional layers described herein (e.g., oleophobic spacer layer, coarse meltblown layer) can have any suitable efficiency (e.g., efficiency before exposure to IPA vapor). In some embodiments, the efficiency of the additional layer (e.g., efficiency before exposure to IPA vapor) is greater than or equal to 1%, greater than or equal to 3%, greater than or equal to 5%, greater than or equal to 7%, greater than or equal to 10%, greater than or equal to 25%, greater than or equal to 50%, greater than or equal to 75%, greater than or equal to 80%, greater than or equal to 85%, greater than or equal to 90%, greater than or equal to 95%, greater than or equal to 99%, greater than or equal to 99.9%, greater than or equal to 99.95%, greater than or equal to 99.99%, greater than or equal to 99.995%, or greater than or equal to 99.999%. In some embodiments, the efficiency of the additional layer (e.g., efficiency before exposure to IPA vapor) is less than or equal to 99.9995%, less than or equal to 99.999%, less than or equal to 99.995%, less than or equal to 99.99%, less than or equal to 99.95%, less than or equal to 99.9%, less than or equal to 99.95%, less than or equal to 99.9%, less than or equal to 99%, 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 50%, less than or equal to 25%, less than or equal to 10%, less than or equal to 7%, less than or equal to 5%, or less than or equal to 3%. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 1% and less than or equal to 99.9995%, greater than or equal to 5% and less than or equal to 99.995%, or greater than or equal to 5% and less than or equal to 99.95%). Other ranges are also possible.

[0333] In some embodiments, the efficiency described in the preceding paragraph is the efficiency at MPPS. In some embodiments, the efficiency described in the preceding paragraph is the efficiency at 0.09 microns. In some embodiments, the efficiency described in the preceding paragraph is the efficiency at 0.3 microns.

[0334] When the filter media includes two or more additional layers, each additional layer may independently have an efficiency in one or more of the above ranges. In embodiments where the filter media includes two or more additional layers, the efficiencies of the two or more additional layers may be the same or different.

[0335] The efficiency of one or more additional layers at MPPS, at 0.09 microns, and at 0.3 microns can be determined as described elsewhere herein with respect to the determination of the efficiency of the pre-filter layer.

[0336] The additional layers described herein (e.g., oleophobic spacer layer, coarse meltblown layer) can have any suitable efficiency metric (e.g., efficiency metric before exposure to IPA vapor). In some embodiments, the efficiency metric of the additional layer (e.g., efficiency metric before exposure to IPA vapor) is greater than or equal to 0.1, greater than or equal to 0.3, greater than or equal to 0.5, greater than or equal to 0.7, greater than or equal to 1, greater than or equal to 2, greater than or equal to 3, greater than or equal to 4, greater than or equal to 5, or greater than or equal to 6. In some embodiments, the efficiency metric of the additional layer (e.g., efficiency metric before exposure to IPA vapor) is 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, less than or equal to 0.7, less than or equal to 0.5, or less than or equal to 0.3. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 and less than or equal to 7, greater than or equal to 0.5 and less than or equal to 5, or greater than or equal to 1 and less than or equal to 5). Other ranges are also possible.

[0337] When the filter media includes two or more additional layers, each additional layer may independently have an efficiency metric in one or more of the above ranges. In embodiments where the filter media includes two or more additional layers, the efficiency metrics of the two or more additional layers may be the same or different.

[0338] The efficiency metric of the one or more additional layers can be determined as described elsewhere herein with respect to the determination of the efficiency metric of the pre-filter layer. This involves using the same equation described elsewhere herein for determining the efficiency metric of the pre-filter layer (i.e., -log(% penetration (DOP) / 100), where penetration is determined as described elsewhere herein with respect to determining the efficiency of the pre-filter layer using DOP particles having an average diameter of 0.09 microns.

[0339] The additional layers described herein (e.g., oleophobic spacer layer, coarse meltblown layer) have any suitable pressure drop (e.g., average pressure drop). In some embodiments, the pressure drop of the additional layer is greater than or equal to 0.0001 kPa, greater than or equal to 0.0005 kPa, greater than or equal to 0.001 kPa, greater than or equal to 0.005 kPa, greater than or equal to 0.01 kPa, greater than or equal to 0.02 kPa, greater than or equal to 0.025 kPa, greater than or equal to 0.03 kPa, or greater than or equal to 0.035 kPa. In some embodiments, the pressure drop of the additional layer is less than or equal to 0.04 kPa, less than or equal to 0.035 kPa, less than or equal to 0.03 kPa, less than or equal to 0.025 kPa, less than or equal to 0.02 kPa, less than or equal to 0.01 kPa, less than or equal to 0.005 kPa, less than or equal to 0.001 kPa, or less than or equal to 0.0005 kPa. Combinations of the above-referenced ranges are also possible (eg, greater than or equal to 0.0001 kPa and less than or equal to 0.04 kPa, greater than or equal to 0.001 kPa and less than or equal to 0.03 kPa, or greater than or equal to 0.001 kPa and less than or equal to 0.025 kPa). Other ranges are also possible.

[0340] When the filter media includes two or more additional layers, each additional layer may independently have a pressure drop in one or more of the above ranges. In embodiments where the filter media includes two or more additional layers, the pressure drops of the two or more additional layers may be the same or different.

[0341] The pressure drop of the additional layers may be determined as described elsewhere herein with respect to the determination of the pressure drop of the pre-filter layer.

[0342] The additional layers described herein (e.g., oleophobic spacer layer, coarse meltblown layer) may have any suitable ratio of initial efficiency metric to mechanical (discharge) efficiency metric. In some embodiments, the ratio of the initial efficiency metric of the additional layer to the mechanical (discharge) efficiency metric is greater than or equal to 0.1, greater than or equal to 0.5, greater than or equal to 1, greater than or equal to 1.5, greater than or equal to 2, or greater than or equal to 2.5. In some embodiments, the ratio of the initial efficiency metric of the additional layer to the mechanical (discharge) efficiency metric is less than or equal to 3, less than or equal to 2.5, less than or equal to 2, less than or equal to 1.5, less than or equal to 1, or less than or equal to 0.5. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 and less than or equal to 3). Other ranges are also possible.

[0343] When the filter media includes two or more additional layers, each additional layer can independently have a ratio of the initial efficiency metric to the mechanical (discharge) efficiency metric in one or more of the above ranges. In embodiments where the filter media includes two or more additional layers, the ratio can be the same for the two or more additional layers, or the two or more additional layers can have different values ​​thereof.

[0344] The ratio of the initial efficiency metric to the mechanical (discharge) efficiency metric of the additional layer may be determined as described elsewhere herein with respect to the determination of the ratio of the initial efficiency metric to the mechanical (discharge) efficiency metric of the pre-filter layer.

[0345] As described above, the filter medium may include an additional layer that is a coarse meltblown layer. The coarse meltblown layer may be positioned at various suitable locations, such as downstream of a pre-filter layer (e.g., a meltblown pre-filter layer). In addition, the coarse meltblown layer may have one or more characteristics (e.g., average fiber diameter, porosity, average pore size, etc.) that are different from one or more other meltblown layers (e.g., a pre-filter layer) that are also positioned in the filter medium. In some embodiments, the coarse meltblown layer includes fibers having an average diameter greater than that of the fibers in the pre-filter layer (e.g., a meltblown pre-filter layer). For example, the coarse meltblown layer may include fibers having any suitable average fiber average diameter described elsewhere herein for the additional layer (e.g., greater than or equal to 0.4 microns and less than or equal to 10 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 3 microns).

[0346] In the embodiment that the filter medium includes a coarse meltblown layer and a pre-filter layer (for example, a meltblown pre-filter layer), the coarse meltblown layer can be formed by a first type of polymer resin, and the pre-filter layer can be formed by a second type of polymer resin. In some cases, the first type of polymer resin can have a lower melt flow index (melt flow index, MFI) than the second type of polymer resin. For example, the difference in melt flow index between such two types of polymer resins may lead to differences in fiber structure and / or porosity of the resulting meltblown layer. For example, compared with the meltblown pre-filter layer, the coarse meltblown layer may have a higher porosity, higher mechanical strength and / or better fiber tie-down. In some cases, compared with a layer with poor fiber tie-down, a layer with better fiber tie-down may have a lower amount of loose fibers and / or a smoother surface present on its surface. In some embodiments, the first type of polymer resin may have a relatively low melt flow index (MFI) (for example, 1MFI to 500MFI). In some embodiments, the second type of polymer resin may have a relatively high melt flow index (MFI) (for example, greater than 1000MFI).

[0347] The filter media described herein can have any of a variety of suitable thicknesses. In some embodiments, the filter media has a thickness greater than or equal to 0.1 mm, greater than or equal to 0.2 mm, greater than or equal to 0.3 mm, greater than or equal to 0.4 mm, greater than or equal to 0.5 mm, greater than or equal to 0.6 mm, greater than or equal to 0.8 mm, greater than or equal to 1 mm, greater than or equal to 1.5 mm, greater than or equal to 2 mm, greater than or equal to 2.5 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 7.5 mm, greater than or equal to 10 mm, greater than or equal to 15 mm, greater than or equal to 20 mm, or greater than or equal to 25 mm. In some embodiments, the filter media has a thickness of 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, less than or equal to 7.5 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 2.5 mm, less than or equal to 2 mm, less than or equal to 1.5 mm, less than or equal to 1 mm, less than or equal to 0.8 mm, less than or equal to 0.6 mm, greater than or equal to 0.5 mm, less than or equal to 0.4 mm, less than or equal to 0.3 mm, or less than or equal to 0.2 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 mm and less than or equal to 30 mm, greater than or equal to 0.1 mm and less than or equal to 5 mm, greater than or equal to 0.2 mm and less than or equal to 3 mm, or greater than or equal to 0.3 mm and less than or equal to 1 mm). Other ranges are also possible.

[0348] The thickness of the filter medium may be determined according to ASTM D1777 (2015) under an applied pressure of 0.8 kPa.

[0349] The filter media described herein can have any of a variety of suitable weights per unit area. For example, in some embodiments, the filter media has a weight per unit area of ​​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 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 200 gsm, greater than or equal to 250 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 filter media has a weight per unit area of ​​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 250 gsm, less than or equal to 200 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 40 gsm, or less than or equal to 30 gsm. Combinations of the above ranges are also possible (e.g., greater than or equal to 20 gsm and less than or equal to 500 gsm, greater than or equal to 20 gsm and less than or equal to 300 gsm, greater than or equal to 30 gsm and less than or equal to 250 gsm, or greater than or equal to 40 gsm and less than or equal to 150 gsm). Other ranges are also possible.

[0350] The weight per unit area of ​​the filter medium may be measured according to ISO 536 (2012).

[0351] The filter media described herein can have any of a variety of suitable air permeabilities. In some embodiments, the filter media has an air permeability greater than or equal to 1 CFM, greater than or equal to 1.5 CFM, greater than or equal to 1.75 CFM, greater than or equal to 2 CFM, greater than or equal to 5 CFM, greater than or equal to 10 CFM, greater than or equal to 20 CFM, greater than or equal to 40 CFM, greater than or equal to 60 CFM, greater than or equal to 80 CFM, greater than or equal to 100 CFM, greater than or equal to 250 CFM, greater than or equal to 500 CFM, or greater than or equal to 750 CFM. In some embodiments, the air permeability of the filter media is 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 250 CFM, less than or equal to 100 CFM, less than or equal to 80 CFM, less than or equal to 60 CFM, less than or equal to 40 CFM, less than or equal to 20 CFM, less than or equal to 10 CFM, less than or equal to 5 CFM, less than or equal to 2 CFM, or less than or equal to 1.5 CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 CFM and less than or equal to 1000 CFM, greater than or equal to 1.5 CFM and less than or equal to 500 CFM, or greater than or equal to 2 CFM and less than or equal to 100 CFM). Other ranges are also possible.

[0352] The air permeability may be measured at a pressure of 125 Pa according to ASTM D737-04 (2016).

[0353] The filter media described herein can have any suitable pressure drop (e.g., an average pressure drop). In some cases, the filter media described herein can have a relatively low pressure drop. In some embodiments, the pressure drop of the filter media is greater than or equal to 0.02 kPa, greater than or equal to 0.03 kPa, greater than or equal to 0.04 kPa, greater than or equal to 0.05 kPa, greater than or equal to 0.06 kPa, greater than or equal to 0.08 kPa, greater than or equal to 0.1 kPa, greater than or equal to 0.11 kPa, greater than or equal to 0.13 kPa, greater than or equal to 0.15 kPa, greater than or equal to 0.17 kPa, greater than or equal to 0.2 kPa, greater than or equal to 0.25 kPa, greater than or equal to 0.3 kPa, or greater than or equal to 0.35 kPa. In some embodiments, the pressure drop of the filter media is less than or equal to 0.4 kPa, less than or equal to 0.35 kPa, less than or equal to 0.3 kPa, less than or equal to 0.25 kPa, less than or equal to 0.2 kPa, less than or equal to 0.15 kPa, less than or equal to 0.13 kPa, less than or equal to 0.11 kPa, less than or equal to 0.1 kPa, less than or equal to 0.08 kPa, less than or equal to 0.06 kPa, less than or equal to 0.05 kPa, less than or equal to 0.04 kPa, or less than or equal to 0.03 kPa. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.02 kPa and less than or equal to 0.4 kPa, greater than or equal to 0.04 kPa and less than or equal to 0.15 kPa, or greater than or equal to 0.06 kPa and less than or equal to 0.11 kPa). Other ranges are also possible.

[0354] The pressure drop of the filter media layer can be determined as described elsewhere herein with respect to the pressure drop of the pre-filter layer.

[0355] The filter media described herein can have any suitable efficiency (e.g., efficiency prior to exposure to IPA vapor). In some embodiments, the filter media has an efficiency (e.g., efficiency prior to exposure to IPA vapor) greater than or equal to 85%, greater than or equal to 90%, greater than or equal to 95%, greater than or equal to 97%, greater than or equal to 98%, greater than or equal to 99%, greater than or equal to 99.5%, greater than or equal to 99.9%, greater than or equal to 99.95%, greater than or equal to 99.99%, greater than or equal to 99.995%, greater than or equal to 99.999%, greater than or equal to 99.9995%, greater than or equal to 99.9999%, or greater than or equal to 99.99995%. In some embodiments, the efficiency of the filter media (e.g., efficiency prior to exposure to IPA vapor) is less than 100%, less than or equal to 99.99995%, less than or equal to 99.9999%, less than or equal to 99.9995%, less than or equal to 99.9999%, less than or equal to 99.9995%, less than or equal to 99.999%, less than or equal to 99.995%, less than or equal to 99.99%, less than or equal to 99.95%, less than or equal to 99.9%, less than or equal to 99.5%, less than or equal to 99%, less than or equal to 98%, less than or equal to 97%, less than or equal to 95%, or less than or equal to 90%. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 85% and less than 99.99995%, greater than or equal to 95% and less than 99.99995%, or greater than or equal to 99.5% and less than or equal to 99.99995%). Other ranges are also possible.

[0356] In some embodiments, the efficiency described in the preceding paragraphs is the efficiency at MPPS. In some embodiments, the efficiency described in the preceding paragraphs is the efficiency at 0.09 microns. In some embodiments, the efficiency described in the preceding paragraphs is the efficiency at 0.3 microns. The efficiency of the filter media at MPPS, at 0.09 microns, and at 0.3 microns (e.g., the efficiency before exposure to IPA vapor) can be determined as described elsewhere herein for the efficiency of the pre-filter layer.

[0357] In some embodiments, the filter medium is a HEPA filter. The filter medium described herein can have any suitable mechanical (discharge) HEPA efficiency. In some embodiments, the mechanical (discharge) efficiency of the filter medium is greater than or equal to 99.95%, greater than or equal to 99.99%, greater than or equal to 99.995%, greater than or equal to 99.999%, greater than or equal to 99.9995%, greater than or equal to 99.9999%, greater than or equal to 99.99995%. In some embodiments, the mechanical (discharge) HEPA efficiency of the filter medium is less than 100%, less than or equal to 99.99995%, less than or equal to 99.9999%, less than or equal to 99.9995%, less than or equal to 99.9999%, less than or equal to 99.9995%, less than or equal to 99.9999%, less than or equal to 99.995%, or less than or equal to 99.999%. Combinations of these ranges are also possible (eg, greater than or equal to 99.95% and less than 99.99995%, greater than or equal to 99.95% and less than 99.995%, or greater than or equal to 99.9995% and less than or equal to 99.99995%). Other ranges are also possible.

[0358] In some embodiments, the mechanical (discharge) efficiency described in the preceding paragraph is the mechanical (discharge) efficiency at MPPS. In some embodiments, the mechanical (discharge) efficiency described in the preceding paragraph is the efficiency at 0.09 microns. In some embodiments, the mechanical (discharge) efficiency described in the preceding paragraph is the efficiency at 0.3 microns.

[0359] The mechanical (discharge) efficiency of the filter media may be determined as described elsewhere herein with respect to the mechanical (discharge) efficiency of the pre-filter layer.

[0360] The filter media layers described herein can have any suitable ratio of an efficiency metric (e.g., an efficiency metric prior to IPA vapor exposure) to a mechanical (discharge) efficiency metric. In some embodiments, the filter media has an efficiency metric (e.g., an initial efficiency metric) to a mechanical (discharge) efficiency metric greater than or equal to 1, greater than or equal to 1.1, greater than or equal to 1.25, greater than or equal to 1.5, greater than or equal to 2, greater than or equal to 2.5, greater than or equal to 3, greater than or equal to 3.5, greater than or equal to 4, greater than or equal to 4.5, greater than or equal to 5, greater than or equal to 5.5, greater than or equal to 6, or greater than or equal to 6.5. In some embodiments, the ratio of the efficiency metric (e.g., the efficiency metric prior to IPA vapor exposure) to the mechanical (discharge) efficiency metric of the filter media is 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 3.5, less than or equal to 3, less than or equal to 2.5, less than or equal to 2, less than or equal to 1.5, less than or equal to 1.25, or less than or equal to 1.1. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 1 and less than or equal to 7, greater than or equal to and 2 less than or equal to 6, or greater than or equal to 3 and less than or equal to 5). Other ranges are also possible.

[0361] In some embodiments, the ratios described in the preceding paragraphs are ratios of efficiencies at MPPS. In some embodiments, the ratios described in the preceding paragraphs are ratios of efficiencies at 0.09 microns. In some embodiments, the ratios described in the preceding paragraphs are ratios of efficiencies at 0.3 microns. The efficiencies of the filter media at MPPS, at 0.09 microns, and at 0.3 microns can be determined as described elsewhere herein with respect to determination of pre-filter layer efficiencies.

[0362] The filter media layers described herein can have any suitable hot PAO loading capacity. In some embodiments, the hot PAO loading capacity of the filter media is greater than or equal to 10 g / m 2 , greater than or equal to 11g / m 2 , greater than or equal to 12g / m 2 , greater than or equal to 13g / m 2 , greater than or equal to 15g / m 2 , greater than or equal to 17g / m 2 , greater than or equal to 20g / m 2 , greater than or equal to 25g / m 2 , greater than or equal to 30g / m 2 , greater than or equal to 35g / m 2 , greater than or equal to 40g / m 2 , greater than or equal to 45g / m2 , greater than or equal to 50g / m 2 , greater than or equal to 55g / m 2 , greater than or equal to 60g / m 2 , greater than or equal to 65g / m 2 , greater than or equal to 70g / m 2 , greater than or equal to 75g / m 2 , greater than or equal to 80g / m 2 , greater than or equal to 85g / m 2 , greater than or equal to 90g / m 2 , or greater than or equal to 95g / m 2 In some embodiments, the hot PAO loading capacity of the filter media is less than or equal to 100 g / m 2 , less than or equal to 95g / m 2 , less than or equal to 90g / m 2 , less than or equal to 85g / m 2 , less than or equal to 80g / m 2 , less than or equal to 75g / m 2 , less than or equal to 70g / m 2 , less than or equal to 65g / m 2 , less than or equal to 60g / m 2 , less than or equal to 55g / m 2 , less than or equal to 50g / m 2 , less than or equal to 45g / m 2 , less than or equal to 40g / m 2 , less than or equal to 35g / m 2 , less than or equal to 30g / m 2 , less than or equal to 25g / m 2 , less than or equal to 20g / m 2 , less than or equal to 17g / m 2 , less than or equal to 15g / m 2 , less than or equal to 13g / m 2 , less than or equal to 12g / m 2 , or less than or equal to 11g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 10 g / m 2 And less than or equal to 100g / m 2 , greater than or equal to 20g / m 2 And less than or equal to 100g / m 2 , greater than or equal to 12g / m 2 And less than or equal to 70g / m 2 , greater than or equal to 15g / m 2And less than or equal to 40g / m 2 ). Other ranges are also possible.

[0363] The hot PAO loading capacity of the filter media can be determined as described in the publication IEST RP CC001.6 (2016) HEPA and ULPA Filters-Modified for Interval Loading, which includes the use of a hot oil photometer. The test can be performed using a continuous loading step or an interval loading step. In other words, the filter media can have a PAO loading capacity of one or more of the ranges provided above determined by the continuous loading step and / or a PAO loading capacity of one or more of the ranges provided above determined by the interval loading step. In the continuous loading step, the nominal exposure area is 45 cm 2 The continuous loading concentration of the filter medium is 100 mg / cm 3 and a media face velocity of 1.75 cm / sec (flow rate of 11 L / min) of hot PAO aerosol (i.e., thermally generated polyalphaolefin (PAO) oil particles) until the pressure drop across the filter media doubles. The PAO aerosol can be thermally generated and can have a mass mean diameter of 0.3 microns. The PAO loading capacity can be determined by weighing the filter media before and after the test and dividing the measured mass increase by the area of ​​the filter media to obtain the PAO loading capacity per unit area of ​​the filter media.

[0364] Additionally or alternatively, various PAO interval loading steps can also be used for hot PAO loading. In other words, the filter media can have a PAO loading capacity within one or more of the ranges provided above as determined by one of the PAO interval loading steps provided below.

[0365] In the first type of interval PAO load test, the nominal exposure area was 45 cm 2 The filter medium was loaded with PAO aerosol at a media face velocity of 1.75 cm / sec (flow rate of 11 liters per minute) for 10 minutes, after which loading was suspended for 24 hours. The test was stopped after repeating the interval loading 10 times or until the air resistance across the filter medium increased by a factor of two (whichever occurred first). The PAO aerosol used in the first type of interval loading step had a mass mean diameter of 0.3 microns and a mass of 100 mg / m 3 The air resistance across the filter media can be determined simultaneously with the hot PAO loading capacity of the filter media by the method described above for determining the hot PAO loading capacity of the filter media.

[0366] In the second type of interval PAO loading test, in addition to using a concentration of 30 mg / m 3A similar protocol to the first type of interval PAO loading test can be used with the exception of the PAO aerosol.

[0367] In the third type of interval PAO load test, the nominal exposure area is 45cm 2 The filter media was preloaded with hot PAO aerosol at a media face velocity of 1.75 cm / sec (flow rate of 11 liters per minute) for 30 minutes and then placed at room temperature and sealed in a resealable container. After 10 days, the filter media was tested again by loading the PAO aerosol at a media face velocity of 1.75 cm / sec (flow rate of 11 liters per minute) for 30 minutes. The PAO aerosol used in the third interval loading step had a mass mean diameter of 0.3 microns and a mass mean diameter of 30 mg / m 3 The PAO loading capacity can then be calculated as described above.

[0368] In some embodiments, after being subjected to one or more of the interval oil loading tests described herein (e.g., the PAO interval loading test described above), the filter media described herein can exhibit a relatively small increase in air resistance. In some embodiments, the final air resistance of the filter media described herein (after the interval oil loading test) can be less than or equal to 2 times, less than or equal to 1.99 times, less than or equal to 1.9 times, less than or equal to 1.8 times, less than or equal to 1.7 times, less than or equal to 1.6 times, less than or equal to 1.5 times, less than or equal to 1.4 times, less than or equal to 1.3 times, less than or equal to 1.2 times, less than or equal to 1.1 times, or less than or equal to 1.05 times the initial air resistance (before the interval oil loading test). In some embodiments, the final air resistance of the filter media described herein (after the interval oil load test) can be greater than or equal to 1 times, greater than or equal to 1.05 times, greater than or equal to 1.1 times, greater than or equal to 1.2 times, greater than or equal to 1.3 times, greater than or equal to 1.4 times, greater than or equal to 1.5 times, greater than or equal to 1.6 times, greater than or equal to 1.7 times, greater than or equal to 1.8 times, greater than or equal to 1.9 times, or greater than or equal to 1.99 times the initial air resistance (before the oil load test). Combinations of the above ranges are also possible (e.g., greater than or equal to 1 times and less than 2 times, or greater than or equal to 1 times and less than or equal to 1.99 times). Other ranges are also possible.

[0369] In some embodiments, the filter media described herein can exhibit efficiencies in one or more of the above-noted HEPA efficiency ranges both before and after being subjected to one or more of the spacer oil loading tests (e.g., the PAO spacer loading test) described elsewhere herein.

[0370] The filter media described herein can have any suitable continuous hot PAO loading time. In some embodiments, the filter media has a continuous hot PAO loading time of greater than or equal to 20 minutes, greater than or equal to 25 minutes, greater than or equal to 30 minutes, greater than or equal to 35 minutes, greater than or equal to 40 minutes, greater than or equal to 60 minutes, greater than or equal to 80 minutes, greater than or equal to 100 minutes, greater than or equal to 125 minutes, greater than or equal to 150 minutes, greater than or equal to 175 minutes, greater than or equal to 200 minutes, greater than or equal to 250 minutes, greater than or equal to 300 minutes, greater than or equal to 350 minutes, greater than or equal to 400 minutes, or greater than or equal to 450 minutes. In some embodiments, the continuous hot PAO loading time of the filter media is less than or equal to 500 minutes, less than or equal to 450 minutes, less than or equal to 400 minutes, less than or equal to 350 minutes, less than or equal to 300 minutes, less than or equal to 250 minutes, less than or equal to 225 minutes, less than or equal to 200 minutes, less than or equal to 175 minutes, less than or equal to 150 minutes, less than or equal to 125 minutes, less than or equal to 100 minutes, less than or equal to 80 minutes, less than or equal to 60 minutes, less than or equal to 40 minutes, less than or equal to 35 minutes, less than or equal to 30 minutes, or less than or equal to 25 minutes. Combinations of the above ranges are also possible (e.g., greater than or equal to 20 minutes and less than or equal to 500 minutes, greater than or equal to 25 minutes and less than or equal to 300 minutes, or greater than or equal to 30 minutes and less than or equal to 200 minutes). Other ranges are also possible.

[0371] The continuous hot PAO loading time of the filter media can be determined as described in the publication IEST RP CC001.6 (2016) HEPA and ULPA Filters-Modified for Continuous Loading by using a hot oil photometer and adopting the continuous oil loading procedure described above for the measurement of hot PAO loading capacity. Specifically, the continuous hot PAO loading time of the filter media can be determined as the time it takes for the pressure drop across the filter media to double.

[0372] The filter media described herein can have any suitable continuous DOP loading time. In some embodiments, the filter media has a continuous DOP loading time of greater than or equal to 20 minutes, greater than or equal to 25 minutes, greater than or equal to 30 minutes, greater than or equal to 35 minutes, greater than or equal to 40 minutes, greater than or equal to 60 minutes, greater than or equal to 80 minutes, greater than or equal to 100 minutes, greater than or equal to 125 minutes, greater than or equal to 150 minutes, greater than or equal to 175 minutes, greater than or equal to 200 minutes, greater than or equal to 250 minutes, greater than or equal to 300 minutes, greater than or equal to 350 minutes, greater than or equal to 400 minutes, or greater than or equal to 450 minutes. In some embodiments, the continuous DOP load time of the filter media is less than or equal to 500 minutes, less than or equal to 450 minutes, less than or equal to 400 minutes, less than or equal to 350 minutes, less than or equal to 300 minutes, less than or equal to 250 minutes, less than or equal to 225 minutes, less than or equal to 200 minutes, less than or equal to 175 minutes, less than or equal to 150 minutes, less than or equal to 125 minutes, less than or equal to 100 minutes, less than or equal to 80 minutes, less than or equal to 60 minutes, less than or equal to 40 minutes, less than or equal to 35 minutes, less than or equal to 30 minutes, or less than or equal to 25 minutes. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 20 minutes and less than or equal to 500 minutes, greater than or equal to 75 minutes and less than or equal to 500 minutes, greater than or equal to 25 minutes and less than or equal to 300 minutes, or greater than or equal to 30 minutes and less than or equal to 200 minutes). Other ranges are also possible.

[0373] The continuous DOP loading time of the filter media can be determined with the help of the TSI 8130 instrument. Using a continuous loading step, 100 cm 2 The filter medium with a surface area of ​​1.577 square meters can be continuously loaded with DOP aerosol at a face velocity of 5.3 cm / sec (32 liters per minute) until the pressure drop across the filter medium doubles. The DOP aerosol can have a mass weighted mean diameter of 0.3 microns and a mass of 100 mg / m 3 The continuous DOP loading time of the filter media is determined as the time it takes for the pressure drop to reach twice its initial value.

[0374] In some embodiments, a pre-screening DOP interval load test may be performed to determine if the filter media has sufficient oil loading capacity. The test may be performed with the aid of a TSI 8130 instrument. In the pre-screening DOP interval load test, a nominal exposure area of ​​100 cm2 may be first pre-loaded with a dioctyl phthalate (DOP) aerosol at a media face velocity of 5.3 cm2 / sec (flow rate of 32 liters / min). 2The filter media may be loaded for 30 minutes and then placed at room temperature and sealed in a resealable container. After 10 days, the filter media may be retested by loading with a DOP aerosol at a media face velocity of 2.0 cm / sec (flow rate of 12 L / min) for 1 hour. The DOP aerosol used in the interval loading test may have a mass mean diameter of 0.3 microns and a mass average diameter of 100 mg / m 3 The air resistance of the filter media can be monitored at multiple stages of the pre-screening DOP interval load test, including before pre-loading (AR t＝0 ), after 30 minutes of preload, after 10 days of pause and after final load (AR t＝10天 ). This can be done using the same instrument used to load the DOP aerosol. In some cases, the air resistance is the average of the air resistances measured over a period of 1 minute to 1.4 minutes. For example, before preloading (AR t＝0 ) and after final load (AR t＝10天 The air resistance of the filter medium can be determined as the average of the air resistances measured during the time period. AR can then be determined for each filter medium. t＝0 / AR t＝10天 ratio.

[0375] In some embodiments, the AR of the filter media described herein is t＝0 / AR t＝10天 The ratio can be greater than or equal to 1, greater than or equal to 1.01, greater than or equal to 1.05, greater than or equal to 1.1, greater than or equal to 1.15, greater than or equal to 1.2, greater than or equal to 1.25, greater than or equal to 1.29, 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 1.6, greater than or equal to 1.7, greater than or equal to 1.8, or greater than or equal to 1.9. In some embodiments, the AR of the filter media described herein is greater than or equal to 1. t＝0 / AR t＝10天 The ratio can be less than or equal to 2, less than or equal to 1.9, less than or equal to 1.8, less than or equal to 1.7, less than or equal to 1.6, less than or equal to 1.5, less than or equal to 1.4, less than or equal to 1.3, less than or equal to 1.29, less than or equal to 1.25, less than or equal to 1.2, less than or equal to 1.15, less than or equal to 1.1, less than or equal to 1.05, or less than or equal to 1.01. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 and less than or equal to 2, greater than or equal to 1 and less than or equal to 1.3, or greater than or equal to 1 and less than or equal to 1.29). Other ranges are also possible. In some embodiments, AR t＝0 / AR t＝10天 Filter media with a value less than 1.3 may be associated with a particularly advantageous group of oil loading capacities.

[0376] In some embodiments, the filter media described herein can exhibit efficiencies in one or more of the above-noted HEPA efficiency ranges both before and after being subjected to the above-noted DOP Interval Loading Test.

[0377] In some embodiments, the filter medium as a whole can have a Gurley stiffness in the machine direction of greater than or equal to 100 mg, greater than or equal to 125 mg, greater than or equal to 150 mg, greater than or equal to 200 mg, greater than or equal to 250 mg, greater than or equal to 300 mg, greater than or equal to 400 mg, greater than or equal to 500 mg, greater than or equal to 600 mg, greater than or equal to 700 mg, greater than or equal to 800 mg, greater than or equal to 900 mg, greater than or equal to 1000 mg, greater than or equal to 1200 mg, greater than or equal to 1400 mg, greater than or equal to 1600 mg, or greater than or equal to 1800 mg. In some embodiments, the Gurley stiffness of the filter media in the machine direction can be less than or equal to 2000 mg, less than or equal to 1800 mg, less than or equal to 1600 mg, less than or equal to 1400 mg, less than or equal to 1200 mg, less than or equal to 1000 mg, less than or equal to 900 mg, less than or equal to 800 mg, less than or equal to 700 mg, less than or equal to 600 mg, less than or equal to 500 mg, less than or equal to 400 mg, less than or equal to 300 mg, less than or equal to 250 mg, less than or equal to 200 mg, less than or equal to 150 mg, or less than or equal to 125 mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 100 mg and less than or equal to 2000 mg, greater than or equal to 200 mg and less than or equal to 1800 mg, greater than or equal to 300 mg and less than or equal to 1600 mg, greater than or equal to 100 mg and less than or equal to 1000 mg, greater than or e...

Claims

1. A filter medium comprising: a first layer comprising a plurality of fine fibers having an average diameter of less than 1 micron; and a second layer disposed on the first layer, wherein: The porosity of the first layer is greater than 80%; The normalized surface area of ​​the second layer is greater than 15m 2 / m 2 ,as well as The efficiency metric of the second layer is greater than 2.

5.

2. The filter media of any preceding claim, wherein the first layer has a porosity of less than or equal to 99%.

3. The filter media of any preceding claim, wherein the plurality of fine fibers have an average diameter greater than or equal to 0.01 microns.

4. The filter media of any preceding claim, wherein the fine fibers comprise greater than or equal to 1 wt% and less than or equal to 25 wt% impact modifier, and wherein the impact modifier is dispersed in a matrix polymer.

5. The filter medium of any preceding claim, wherein the impact modifier comprises a copolymer comprising 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.

6. The filter media of any preceding claim, wherein the matrix polymer comprises greater than or equal to 50 weight percent and less than or equal to 100 weight percent thermoplastic polymer.

7. The filter media of any preceding claim, wherein the second layer has an efficiency metric less than or equal to 6.

8. The filter medium of any preceding claim, wherein the normalized surface area of ​​the second layer is less than or equal to 100 m 2 / m 2 .

9. The filter media of any preceding claim, wherein the second layer is a meltblown layer.

10. The filter media of any preceding claim, wherein the second layer has a basis weight greater than, or equal to, 5 gsm and less than, or equal to, 100 gsm.

11. The filter media of any preceding claim, wherein the second layer has an average fiber diameter greater than or equal to 0.5 microns and less than 4 microns.

12. The filter media of any preceding claim, wherein the second layer has an oil grade greater than 1 and less than or equal to 8.

13. The filter media of any preceding claim, wherein the second layer has an initial efficiency greater than 95% and less than or equal to 99.99995%.

14. The filter media of any preceding claim, wherein the second layer is hydroelectret charged.

15. The filter media of any preceding claim, wherein the second layer comprises a fluorocarbon coating.

16. The filter media of any preceding claim, wherein the second layer comprises a plurality of synthetic fibers.

17. The filter media of any preceding claim, wherein the second layer has a pressure drop greater than or equal to 0.001 kPa and less than or equal to 0.08 kPa.

18. The filter media of any preceding claim, further comprising a first wet-laid nonwoven fibrous web positioned adjacent to the first layer on an opposite side from the second layer.

19. The filter media of any preceding claim, further comprising a second wet-laid nonwoven fibrous web positioned adjacent to the second layer on an opposite side from the first layer.

20. The filter media of any preceding claim, wherein the ratio of the specific surface area of ​​the second layer to the specific surface area of ​​the second wet-laid nonwoven fibrous web is greater than or equal to 5:1 and less than or equal to 15:

1.

21. The filter media of any preceding claim, wherein the first wet-laid nonwoven fibrous web and / or the second wet-laid nonwoven fibrous web comprises a binder resin in an amount from 5% to 50% by weight.

22. The filter media of any preceding claim, wherein a ratio of the efficiency of the first wet-laid nonwoven web to the efficiency of the second wet-laid nonwoven web is greater than or equal to 1:1.1 and less than or equal to 1:

99.

23. The filter media of any preceding claim, wherein the ratio of the average pore size of the first wet-laid nonwoven fibrous web to the average pore size of the second wet-laid nonwoven fibrous web is greater than or equal to 1:1.3 and less than or equal to 1:

50.

24. The filter media of any preceding claim, wherein the filter media has a hot PAO loading capacity greater than or equal to 10 g / m 2 And less than or equal to 100g / m 2 .

25. The filter media of any preceding claim, wherein the filter media has a hot PAO loading capacity greater than or equal to 12 g / m 2 And less than or equal to 70g / m 2 .

26. The filter media of any preceding claim, wherein the filter media has a hot PAO loading capacity greater than or equal to 15 g / m 2 And less than or equal to 40g / m 2 .

27. The filter media of any preceding claim, wherein the filter media has a continuous DOP loading greater than or equal to 20 minutes and less than or equal to 500 minutes.

28. The filter media of any preceding claim, wherein the filter media has a continuous DOP loading greater than or equal to 25 minutes and less than or equal to 300 minutes.

29. The filter media of any preceding claim, wherein the filter media has a continuous DOP loading greater than or equal to 30 minutes and less than or equal to 200 minutes.

30. The filter media of any preceding claim, wherein the filter media after being subjected to a PAO spacer load test has a final air resistance after oil loading that is less than 2 times the initial air resistance of the filter media before the PAO spacer oil load test.

31. The filter media of any preceding claim, wherein the filter media has an efficiency in the HEPA range both before and after being subjected to a PAO interval loading test.

32. The filter medium of any preceding claim, wherein the filter medium has an AR t＝0 / AR t＝10天 The ratio is less than or equal to 2.

33. The filter media of any preceding claim, wherein the filter media has an efficiency in the HEPA range both before and after being subjected to a DOP interval load test.

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