Filter media comprising fibers comprising polyvinylidene fluoride and / or copolymers thereof and related methods

Abstract

Filter media comprising fibers comprising polyvinylidene fluoride (PVDF) and / or copolymers thereof are generally described.

Description

[0001] Related Applications

[0002] This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application No. 63 / 330,961, filed on April 14, 2022, and U.S. Patent Application No. 17 / 863,761, filed on July 13, 2022, which are hereby incorporated by reference in their entirety. Technical Field

[0003] Filter media comprising fibers comprising polyvinylidene fluoride (PVDF) and / or copolymers thereof are generally described. Background Art

[0004] Filter media is a product that can be used to remove pollutants in various applications. Some filter media include a layer comprising fibers, and the fiber includes polyvinylidene fluoride (PVDF) or its copolymer. However, these layers usually have a large average fiber diameter, a high surface nodule density and / or a high theoretical surface area to the ratio of the actual surface area, which may make them unsuitable for some filter applications. Therefore, it is necessary to improve the filter media and / or fine fiber layers comprising PVDF and / or its copolymers: it has a lower fiber diameter, a lower surface nodule density, and / or a lower theoretical surface area to the ratio of the actual surface area. Summary of the invention

[0005] Filter media comprising fibers comprising polyvinylidene fluoride (PVDF) and / or copolymers thereof are generally described.

[0006] In one aspect, a filter medium is provided. In some embodiments, the filter medium includes a fine fiber layer comprising a plurality of fine fibers; wherein the fine fibers comprise polyvinylidene fluoride (PVDF) and / or a copolymer thereof; wherein the average fiber diameter of the fine fibers is less than or equal to 150 nanometers; and wherein the surface node density of the fine fiber layer is less than or equal to 4 nodes / 100 square micrometers (um 2 ).

[0007] In some embodiments, the filter media includes a fine fiber layer comprising a plurality of fine fibers; wherein the fine fibers comprise polyvinylidene fluoride (PVDF) and / or a copolymer thereof; wherein the average fiber diameter of the fine fibers is less than or equal to 150 nanometers; and wherein the void volume of the fine fiber layer is greater than or equal to 70%.

[0008] In some embodiments, the filter medium includes a fine fiber layer comprising a plurality of fine fibers; wherein the fine fibers comprise polyvinylidene fluoride (PVDF) and / or its copolymers; wherein the average fiber diameter of the fine fibers is less than or equal to 150 nanometers; and wherein the ratio of the theoretical surface area of ​​the fine fiber layer to the actual surface area of ​​the fine fiber layer is greater than or equal to 1 and less than or equal to 15.

[0009] In some embodiments, the filter medium includes a fine fiber layer comprising a plurality of fine fibers; wherein the fine fibers comprise polyvinylidene fluoride (PVDF) and / or a copolymer thereof; wherein greater than or equal to 5% and less than or equal to 100% of the fine fibers have a diameter less than or equal to 100 nm; and wherein the surface nodule density of the fine fiber layer is less than or equal to 4 nodules / 100 square microns (um 2 ).

[0010] In some embodiments, the filter media includes a fine fiber layer comprising a plurality of fine fibers; wherein the fine fibers comprise polyvinylidene fluoride (PVDF) and / or a copolymer thereof; wherein greater than or equal to 5% and less than or equal to 100% of the fine fibers have a diameter less than or equal to 100 nm; and wherein the void volume of the fine fiber layer is greater than or equal to 70%.

[0011] In some embodiments, the filter medium includes a fine fiber layer comprising a plurality of fine fibers; wherein the fine fibers comprise polyvinylidene fluoride (PVDF) and / or its copolymers; wherein greater than or equal to 5% and less than or equal to 100% of the fine fibers have a diameter less than or equal to 100 nm; and wherein the ratio of the theoretical surface area of ​​the fine fiber layer to the actual surface area of ​​the fine fiber layer is greater than or equal to 1 and less than or equal to 15.

[0012] Other advantages and novel features of the present disclosure will become apparent from the following detailed description of several non-limiting embodiments of the present disclosure when considered in conjunction with the accompanying drawings. In the event that the present specification and documents incorporated by reference contain conflicting and / or inconsistent disclosures, the present specification shall prevail. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] 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 unless otherwise indicated. In the drawings, each identical or nearly identical component shown is generally represented by a single reference numeral. For purposes of clarity, not every component is labeled in 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:

[0014] Figure 1Ais a schematic diagram of a filter media including a fine fiber layer comprising fine fibers, according to certain embodiments.

[0015] Figure 1B is a schematic diagram of a thin fiber layer including thin fibers and nodules according to certain embodiments.

[0016] Figure 2 is a schematic diagram of a filter media including a fine fiber layer and a second layer according to certain embodiments.

[0017] Figure 3 is a schematic diagram of a filter media including a fine fiber layer, a second layer, and a third layer according to certain embodiments.

[0018] Figure 4A , Figure 4B , Figure 4C , Figure 4D and Figure 4E Each illustrates a non-limiting example of a design suitable for a liquid filter according to some embodiments.

[0019] Figure 5A , Figure 5B , Figure 5C , Figure 5D and Figure 5E Each illustrates a non-limiting example of a design suitable for a fuel filter according to some embodiments.

[0020] Fig. 6A , Figure 6B , Figure 6C and Fig.6D Each illustrates a non-limiting example of a design suitable for use in a hydraulic fluid filter according to some embodiments.

[0021] Fig. 7A and Figure 7B Each illustrates a non-limiting example of a design suitable for a HEPA filter according to some embodiments.

[0022] Figure 8 is a scanning electron microscopy (SEM) image at 5000 times magnification of a fine fiber layer including fine fibers and nodules according to certain embodiments. DETAILED DESCRIPTION

[0023] Disclosed herein are filter media comprising fibers containing polyvinylidene fluoride (PVDF) and / or its copolymers, and related methods. In some embodiments, the filter media includes a fine fiber layer, and the fine fiber layer includes fine fibers containing PVDF and / or its copolymers. In some embodiments, the layer comprising fibers containing PVDF and / or its copolymers has advantages over the layer comprising fibers containing other polymers, such as increased void volume, reduced compactness and / or increased air permeability. However, fibers containing PVDF and / or its copolymers typically have a larger average diameter than fibers containing other polymers, which may make them unsuitable for certain filter applications. Unexpectedly, in some embodiments, the filter media and / or fine fiber layers disclosed herein include PVDF and / or its copolymers, with a small average fiber diameter. In addition, while layers comprising fibers having a small average fiber diameter typically have lower void volume, higher solidity, higher surface nodule density, and / or higher theoretical surface area to actual surface area ratios than layers having larger average fiber diameters, surprisingly, in some embodiments, the fine fiber layers disclosed herein have small average fiber diameters while having high void volume, low solidity, low surface nodule density, and / or low theoretical surface area to actual surface area ratios. In fact, in some cases, the fine fiber layers disclosed herein have multiple advantages over other layers. For example, in some cases, the fine fiber layers disclosed herein have smaller average fiber diameters, lower surface nodule density, higher void volume, lower solidity, higher uniformity, lower mean flow pore size, lower maximum pore size, lower theoretical surface area to actual surface area ratios, higher air permeability, higher dust holding capacity, lower pressure drop, and / or higher efficiency at lower pressure drop compared to other layers.

[0024] Certain embodiments relate to filter media. Some such filter media are schematically shown in Figures 1A to 3 In some embodiments, the filter medium includes a fine fiber layer. For example, in Figure 1A In some cases, the filter medium 100 includes a fine fiber layer 110. In some embodiments, the fine fiber layer comprises fine fibers. For example, in Figure 1A In some cases, fine fiber layer 110 includes fine fibers.

[0025] The fine fibers may comprise one or more components. Examples of suitable components may include polyvinylidene fluoride (PVDF) and / or its copolymers, one or more salts and / or one or more additives. Examples of suitable PVDF copolymers include PVDF-HFP (hexafluoropropylene), PVDF-TFE (tetrafluoroethylene), PVDF-CTFE (chlorotrifluoroethylene) and / or PVDF-HFP-TFE.

[0026] The fine fibers can have any suitable average fiber diameter. In some embodiments, the fine fibers have an average fiber diameter 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 400 nm, greater than or equal to 500 nm, greater than or equal to 600 nm, greater than or equal to 750 nm, or greater than or equal to 900 nm. In certain embodiments, the fine fibers have an average fiber diameter of less than or equal to 1 micron, less than or equal to 900 nm, less than or equal to 750 nm, less than or equal to 600 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 175 nm, less than or equal to 150 nm, less than or equal to 140 nm, less than or equal to 130 nm, less than or equal to 120 nm, less than or equal to 110 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 1000 nm, greater than or equal to 10 nm and less than or equal to 500 nm, greater than or equal to 10 nm and less than or equal to 200 nm, greater than or equal to 50 nm and less than or equal to 200 nm, greater than or equal to 10 nm and less than or equal to 150 nm, greater than or equal to 10 nm and less than or equal to 100 nm, greater than or equal to 50 nm and less than or equal to 150 nm, or greater than or equal to 50 nm and less than or equal to 100 nm). Fiber diameters can be measured using scanning electron microscopy. Without wishing to be bound by any theory, it is believed that in some embodiments, having small fiber diameters (e.g., fiber diameters disclosed herein) in the fine fiber layer enables a smaller mean flow pore size, lower pressure drop, and / or higher efficiency at lower pressure drop.

[0027] In some embodiments, 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 25%, 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%, or all of the fine fibers have a diameter less than or equal to 100 nm (e.g., less than or equal to 95 nm, less than or equal to 90 nm, less than or equal to 85 nm, less than or equal to 80 nm, or less than or equal to 75 nm). In some embodiments, 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%, less than or equal to 50%, less than or equal to 40%, less than or equal to 30%, less than or equal to 20%, or less than or equal to 10% of the fine fibers have a diameter less than or equal to 100 nm (e.g., less than or equal to 95 nm, less than or equal to 90 nm, less than or equal to 85 nm, less than or equal to 80 nm, or less than or equal to 75 nm). Combinations of these ranges are also possible. For example, in some embodiments, greater than or equal to 5% and less than or equal to 100% (e.g., greater than or equal to 20% and less than or equal to 50%) of the fine fibers have a diameter less than or equal to 100 nm. As another example, in some embodiments, greater than or equal to 5% and less than or equal to 30% of the fine fibers have a diameter less than or equal to 75 nm. Without wishing to be bound by any theory, it is believed that in some embodiments, having small fiber diameters (e.g., fiber diameters disclosed herein) in the fine fiber layer enables smaller mean flow pore size, lower pressure drop, and / or higher efficiency at lower pressure drop.

[0028] In some cases, the fine fibers can be continuous fibers (e.g., electrospun fibers, meltblown fibers, melt-spun fibers, solvent-spun fibers, and / or centrifugal-spun fibers). Continuous fibers are made by a "continuous" fiber forming process (e.g., a meltblown process, a melt-spinning process, a melt electrospinning process, a solvent electrospinning process, a centrifugal spinning process, or a spunbond process), and generally have a longer length than discontinuous fibers. Discontinuous fibers can be cut (e.g., by filaments) into discontinuous discrete fibers having a specific length or length range as described in more detail herein, can be formed into discontinuous discrete fibers having a specific length or length range as described in more detail herein, or can naturally be discontinuous discrete fibers having a specific length or length range as described in more detail herein. A non-limiting example of a discontinuous fiber is a staple fiber.

[0029] The fine fibers can have any suitable length. For example, in some cases, the average length of the fine fibers is 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, or greater than or equal to 6 m. m, greater than or equal to 7.5 m, greater than or equal to 10 m, greater than or equal to 12.5 m, greater than or equal to 15 m, greater than or equal to 20 m, greater than or equal to 25 m, greater than or equal to 30 m, greater than or equal to 40 m, greater than or equal to 50 m, greater than or equal to 75 m, greater than or equal to 100 m, greater than or equal to 125 m, greater than or equal to 150 m, greater than or equal to 200 m, greater than or equal to 250 m, greater than or equal to 300 m, greater than or equal to 400 m, greater than or equal to 500 m, or greater than or equal to 750 m. In some embodiments, the average 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 m, less than or equal to 1 , less than or equal to 100mm, less than or equal to 100mm, less than or equal to 150mm, or less than or equal to 125mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 100mm and less than or equal to 1km, greater than or equal to 125mm and less than or equal to 25m, or greater than or equal to 125mm and less than or equal to 2m). Other ranges are also possible.

[0030] In embodiments where the fine fibers comprise electrospun fibers, the fine fibers can be electrospun using any suitable solvent (e.g., in combination with one or more polymers or copolymers disclosed herein). Suitable solvents may include dimethylacetamide (DMAc), dimethylformamide (DMF), N-methylpyrrolidone, tetramethylurea, tetrahydrofuran (THF), methyl ethyl ketone, acetone, ethyl acetate, 4-methoxy-4-methyl-2-pentanol, acetic acid, dichloromethane (DCM), 1,1,1,3,3,3-hexafluoro-2-propanol (HFP), dioxolane, water, and / or alcohols (e.g., ethanol, propanol, and / or isopropanol).

[0031] When adding polymer (and / or copolymer) to the solvent during electrospinning, any suitable relative humidity can be used. For example, in some embodiments, the relative humidity is greater than or equal to 18%, greater than or equal to 20%, greater than or equal to 22%, greater than or equal to 24%, greater than or equal to 26%, greater than or equal to 28%, greater than or equal to 30%, greater than or equal to 32%, greater than or equal to 34%, greater than or equal to 36%, greater than or equal to 38%, greater than or equal to 40%, or greater than or equal to 45%. In some embodiments, the relative humidity is less than or equal to 50%, less than or equal to 45%, less than or equal to 43%, less than or equal to 40%, less than or equal to 38%, less than or equal to 36%, less than or equal to 34%, less than or equal to 32%, less than or equal to 30%, less than or equal to 28%, less than or equal to 26%, less than or equal to 24%, or less than or equal to 22%. Combinations of the above ranges are also possible (e.g., greater than or equal to 18% and less than or equal to 50%, greater than or equal to 20% and less than or equal to 30%, greater than or equal to 34% and less than or equal to 50%, greater than or equal to 38% and less than or equal to 45%, or greater than or equal to 22% and less than or equal to 28%). The relative humidity can be determined using a relative humidity sensor. Without wishing to be bound by any theory, it is believed that in some embodiments, having a relative humidity within the above range during electrospinning achieves fibers with a smaller average diameter, fibers with a narrow diameter distribution, a fine fiber layer with higher uniformity, a fine fiber layer with a low surface node density, and / or a fine fiber layer with a low ratio of theoretical surface area to measured surface area.

[0032] When the polymer (and / or copolymer) is added to the solvent for electrospinning, the polymer solution can have any suitable conductivity. For example, in some cases, the conductivity of the polymer solution is 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 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 5,000 μS, less than or equal to 4,000 μS, less than or equal to 3,000 μS, less than or equal to 2,000 μS, less than or equal to 1,000 μS, less than or equal to 750 μS, less than or equal to 500 μS, less than or equal to 400 μS, less than or equal to 300 μS, less than or equal to 250 μS, less than or equal to 200 μS, less than or equal to 150 μS, less than or equal to 120 μS, or less than or equal to 100 μS. Combinations of these ranges are also possible (e.g., greater than or equal to 50 μS and less than or equal to 10,000 μS, greater than or equal to 100 μS and less than or equal to 500 μS, greater than or equal to 150 μS and less than or equal to 300 μS, greater than or equal to 400 μS and less than or equal to 1,000 μS, or greater than or equal to 750 μS and less than or equal to 1,000 μS). The conductivity can be determined using a conductivity meter. Without wishing to be bound by any theory, it is believed that in some embodiments, having a conductivity within the above range during electrospinning achieves fibers with a smaller average diameter, fibers with a narrow diameter distribution, a fine fiber layer with higher uniformity, a fine fiber layer with a low surface nodule density, and / or a fine fiber layer with a low ratio of theoretical surface area to measured surface area.

[0033] When the polymer (and / or copolymer) is added to the 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 mPascal-seconds, greater than or equal to 25 mPascal-seconds, greater than or equal to 50 mPascal-seconds, greater than or equal to 75 mPascal-seconds, greater than or equal to 100 mPascal-seconds, greater than or equal to 125 mPascal-seconds, greater than or equal to 150 mPascal-seconds, greater than or equal to 200 mPascal-seconds, greater than or equal to 250 mPascal-seconds, greater than or equal to 300 mPascal-seconds, or greater than or equal to 400 mPascal-seconds. 1000 mPascal-seconds, 1000 mPascal-seconds or more, 1500 mPascal-seconds or more, 1750 mPascal-seconds or more, 2000 mPascal-seconds or more, 2000 mPascal-seconds or more, 3000 mPascal-seconds or more, 400 mPascal-seconds or more, 500 mPascal-seconds or more, 600 mPascal-seconds or more, 750 mPascal-seconds or more, 900 mPascal-seconds or more, 1000 mPascal-seconds or more, 1250 mPascal-seconds or more, 1500 mPascal-seconds or more, 1750 mPascal-seconds or more, or 2000 mPascal-seconds or more. In some cases, the viscosity of the polymer solution is less than or equal to 6000 mPascal-seconds, less than or equal to 5000 mPascal-seconds, less than or equal to 4000 mPascal-seconds, less than or equal to 3000 mPascal-seconds, less than or equal to 2500 mPascal-seconds, less than or equal to 2250 mPascal-seconds, less than or equal to 2000 mPascal-seconds, less than or equal to 1750 mPascal-seconds, less than or equal to 1500 mPascal-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 these ranges are also possible (e.g., greater than or equal to 10 milliPascal-seconds and less than or equal to 6000 milliPascal-seconds, greater than or equal to 250 milliPascal-seconds and less than or equal to 6000 milliPascal-seconds, greater than or equal to 750 milliPascal-seconds and less than or equal to 3000 milliPascal-seconds, greater than or equal to 1000 milliPascal-seconds and less than or equal to 6000 milliPascal-seconds, 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). The viscosity of the fluid precursor can be measured using a rotational viscometer at 1.7 seconds -1The viscosity is determined at a shear rate of 100 and a temperature of 20°C. After the value displayed on the rotational viscometer stabilizes, the viscosity can be determined therefrom. An example of a suitable rotational viscometer is a Brookfield LVT viscometer with a No. 62 spindle. Without wishing to be bound by any theory, it is believed that having a viscosity within the above range during electrospinning can achieve fibers with a smaller average diameter, fibers with a narrow diameter distribution, a fine fiber layer with higher uniformity, a fine fiber layer with a low surface nodule density, and / or a fine fiber layer with a low ratio of theoretical surface area to measured surface area.

[0034] When the polymer (and / or copolymer) is added to the solvent for electrospinning, the polymer solution can have any suitable solid content. For example, in some embodiments, the polymer solution has greater than or equal to 12%, greater than or equal to 13%, greater than or equal to 14%, greater than or equal to 15%, greater than or equal to 16%, greater than or equal to 17%, greater than or equal to 18%, greater than or equal to 19%, greater than or equal to 20%, greater than or equal to 21%, greater than or equal to 22%, greater than or equal to 23%, greater than or equal to 24%, or greater than or equal to 25% solids. In some embodiments, the polymer solution has less than or equal to 30%, less than or equal to 29%, less than or equal to 28%, less than or equal to 27%, less than or equal to 26%, less than or equal to 25%, less than or equal to 24%, less than or equal to 23%, less than or equal to 22%, less than or equal to 21%, less than or equal to 20%, less than or equal to 19%, less than or equal to 18%, less than or equal to 17%, less than or equal to 16%, or less than or equal to 15% solids. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 12% and less than or equal to 30%, greater than or equal to 15% and less than or equal to 25%, greater than or equal to 20% and less than or equal to 30%, or greater than or equal to 25% and less than or equal to 30%). Without wishing to be bound by any theory, it is believed that having a solid content within the above range during electrospinning can achieve fibers with a smaller average diameter, fibers with a narrow diameter distribution, a fine fiber layer with higher uniformity, a fine fiber layer with a low surface nodule density and / or a fine fiber layer with a low ratio of theoretical surface area to measured surface area.

[0035] The fine fibers can have any suitable shape. In some embodiments, the fine fibers are cylindrical. In certain embodiments, the fine fibers are non-cylindrical (e.g., ribbon-shaped, flat, and / or fibril). In some cases, the fine fibers include core-sheath fibers (e.g., concentric core / sheath fibers and / or non-concentric core-sheath fibers), segmented pie-shaped fibers, side-by-side fibers, tip-trefoil fibers, split fibers, and "island-in-the-sea" fibers.

[0036] In some embodiments, the fine fibers include additives (e.g., the additives can be added during the manufacture of the fine fibers). Non-limiting examples of suitable additives include cationic surfactants, anionic surfactants, nonionic surfactants, ammonium salts (e.g., tetraethylammonium bromide (TEAB)), sulfonium salts, organic salts, inorganic salts, esters, ethers, and / or polymers (e.g., polymers derived from monomers such as 1-vinylpyrrolidin-2-one, N-alkyl-methacrylamide, vinyl acetate, 1-vinylimidazole, 1-vinyl[alkyl]imidazole, 1-vinyl-2-pyridine, 1-vinyl-4-pyridine, acrylamide, N-vinylformamide, and N-[alkyl]formamide). In some embodiments, the fine fiber layer and / or PVDF and / or its copolymer material include additives (e.g., TEAB).

[0037] In certain embodiments, the thin fibers include a salt. Examples of suitable salts may include ammonium salts (eg, tetraethylammonium bromide (TEAB)), sulfonium salts, organic salts (eg, pyridine), and / or inorganic salts.

[0038] In embodiments where the fine fibers include salt and / or additives, the fine fibers may include any suitable amount of salt and / or additives. For example, in some cases, the fine fibers include less than or equal to 10 wt%, less than or equal to 9 wt%, less than or equal to 8 wt%, less than or equal to 7 wt%, less than or equal to 6 wt%, less than or equal to 5 wt%, less than or equal to 4 wt%, less than or equal to 3 wt%, less than or equal to 2 wt%, or less than or equal to 1 wt% of salt and / or additives (alone or in combination). In some cases, the fine fibers include 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% of salt and / or additives (alone or in combination). Combinations of these ranges are also suitable (e.g., greater than or equal to 0.1 wt% and less than or equal to 10 wt%, 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%).

[0039] In certain embodiments, the fine fiber layer comprises fine fibers (e.g., any of the fine fibers disclosed herein). Figure 1A In the embodiment of the present invention, the fine fiber layer 110 includes fine fibers. The fine fiber layer may include 100% by weight of fine fibers.

[0040] In some embodiments, the thin fiber layer includes nodules. Figure 1BIn some cases, the fine fiber layer 110 includes fine fibers 111 and nodules 112. It should be understood that this figure is for illustration purposes only (e.g., in some embodiments, it may not be drawn to scale, the nodules may not be perfectly spherical, and the distribution of nodules may be more or less uniform than depicted).

[0041] In some embodiments, the fine fiber layer has a relatively low surface nodule density. For example, in some embodiments, the surface nodule density of the fine fiber layer is greater than or equal to 0.1 nodules / 100 μm. 2 , greater than or equal to 0.2 nodules / 100μm 2 , greater than or equal to 0.3 nodules / 100μm 2 , greater than or equal to 0.4 nodules / 100μm 2 , greater than or equal to 0.5 nodules / 100μm 2 , greater than or equal to 1 nodule / 100μm 2 , greater than or equal to 1.5 nodules / 100μm 2 , greater than or equal to 2 nodules / 100μm 2 , or greater than or equal to 3 nodules / 100 μm 2 In some embodiments, the surface nodule density of the fine fiber layer is less than or equal to 4 nodules / 100 μm 2 , less than or equal to 3.5 nodules / 100μm 2 , less than or equal to 3 nodules / 100μm 2 , less than or equal to 2.5 nodules / 100μm 2 , less than or equal to 2 nodules / 100μm 2 , less than or equal to 1.5 nodules / 100μm 2 , or less than or equal to 1 nodule / 100 μm 2 Combinations of these ranges are also possible (e.g., greater than or equal to 0.1 nodules / 100 μm 2 Less than or equal to 4 nodules / 100 μm 2 , greater than or equal to 0.1 nodules / 100μm 2 Less than or equal to 3 nodules / 100 μm 2 , or greater than or equal to 0.1 nodules / 100 μm 2 Less than or equal to 2 nodules / 100 μm 2 ).

[0042] As used herein, a node is a defective portion of a fiber formed during manufacturing that is different in size and / or shape from non-node portions of the fiber. As an example, Figure 8 is a SEM image in which some of the nodules are shown as circular circles.

[0043] In some embodiments, the nodules are spherical in shape, although it should be understood that in some cases they need not be perfect spheres and may be more similar to an oval. In some embodiments, the aspect ratio of the nodule is greater than or equal to 0.4 and less than or equal to 1, meaning that if all three dimensions (i.e., length, width, height) are compared and the ratios of all pairs of two dimensions (i.e., length to width, length to height, and width to height) are obtained, then when the smaller dimension is divided by the larger dimension, the ratio of each pair of two dimensions is greater than or equal to 0.4 and less than or equal to 1. To define the three dimensions, assume that the nodule is in a box, where the surface of the box is defined as the outermost point of the nodule on each of the three dimensions, so that the three dimensions of the box are considered to be the three dimensions of the nodule. As an example, the diameter of the non-nodular portion of the fiber is typically much smaller than the length of the non-nodular portion of the fiber, so that at least one of its aspect ratios does not fall within the range of greater than or equal to 0.4 and less than or equal to 1.

[0044] In some embodiments, the diameter of the nodule (e.g., the smallest diameter in the case of an imperfect sphere such as an ovoid) is greater than or equal to 300 nm (e.g., greater than or equal to 350 nm). In certain embodiments, the diameter of the nodule (e.g., the smallest diameter in the case of an imperfect sphere such as an ovoid) is at least 40% greater (e.g., at least 60% greater, at least 80% greater, at least 100% greater, at least 150% greater, at least 200% greater, at least 250% greater, at least 300% greater, at least 350% greater, or at least 400% greater) than the average diameter of the fiber (which should be understood as the average diameter of the non-nodular portion of the fiber).

[0045] As used herein, surface nodule density is the density of nodules observed when at least 2,500 μm 2 When determining the surface area of ​​a surface, the number of nodules detectable by scanning electron microscopy (SEM) is divided by the surface area of ​​the surface. For example, if nodules are present in the fine fiber layer at a depth that is no longer detectable from the viewing surface by SEM, they will not be counted when determining the surface nodule density of the surface. Although it should be understood that other areas (e.g., 100 microns by 100 microns or 50 microns by 50 microns) can also be evaluated, the magnification can be set to cover an area of ​​140 microns by 140 microns. The surface nodule density can be determined from the SEM images using any suitable software, or by manually counting the number of nodules in one or more SEM images where the total surface area is at least 2,500 μm 2) and divided by the surface area. Examples of software that can be used include ImageJ software. For example, SEM images can be converted into binary black and white images using ImageJ software (e.g., using the automatic "threshold" option in ImageJ software). Aspect ratios greater than or equal to 0.4 and less than or equal to 1 and greater than or equal to 0.05 μm can be used. 2 Surface area less than or equal to 100 μm 2 The nodule size was determined by performing the ImageJ "Analyze Particles" procedure.

[0046] Without wishing to be bound by any theory, it is believed that in some cases a lower surface nodule density (e.g., a surface nodule density disclosed herein) achieves higher uniformity (e.g., a lower mean flow pore size to maximum pore size ratio), which achieves improved filtration characteristics, such as a reduced pressure drop over time at a given filtration efficiency. Similarly, without wishing to be bound by any theory, it is believed that a lower surface nodule density (e.g., a surface nodule density disclosed herein) achieves low compactness and high void volume.

[0047] In some embodiments, the fine fiber layer has a relatively low ratio of theoretical surface area to measured surface area. For example, in some embodiments, the ratio of the theoretical surface area to the measured surface area of ​​the fine fiber layer is greater than or equal to 1, greater than or equal to 2, greater than or equal to 3, greater than or equal to 4, greater than or equal to 5, greater than or equal to 6, greater than or equal to 7, greater than or equal to 8, greater than or equal to 9, or greater than or equal to 10. In some embodiments, the ratio of the theoretical surface area to the measured surface area of ​​the fine fiber layer is less than or equal to 15, less than or equal to 14, less than or equal to 13, less than or equal to 12, less than or equal to 11, less than or equal to 10, less than or equal to 9, less than or equal to 8, less than or equal to 7, less than or equal to 6, less than or equal to 5, less than or equal to 4, less than or equal to 3, or less than or equal to 2. Combinations of these ranges are also possible (e.g., greater than or equal to 1 and less than or equal to 15, greater than or equal to 1 and less than or equal to 10, or greater than or equal to 1 and less than or equal to 5).

[0048] The measured surface area is measured by using a standard BET surface area measurement technique. The BET surface area is measured according to Section 10 of the Battery Council International Standard BCIS-03A (2009) "Recommended Battery Materials Specifications Valve Regulated Recombinant Batteries", which is "Standard Test Method for Surface Area of ​​Recombinant Battery Separator Mat". According to this technique, the BET surface area is measured by adsorption analysis with nitrogen using a BET surface analyzer (e.g., Micromeritics Gemini III 2375 surface area analyzer); the sample amount is 0.5 to 0.6 grams in, for example, a 3 / 4 inch tube; and the sample is degassed at 75°C for at least 3 hours.

[0049] As used herein, theoretical surface area is defined by the following equation:

[0050]

[0051] Among them, SA 理论 refers to the theoretical surface area, p refers to the density of the polymer forming the fibers, and mean (1 / D) refers to the reciprocal of the harmonic mean of the diameters of the fibers forming the web.

[0052] Without wishing to be bound by any theory, it is believed that in some cases a lower theoretical surface area to measured surface area ratio (e.g., the theoretical surface area to measured surface area ratio disclosed herein) results in higher uniformity (e.g., a lower mean flow pore size to maximum pore size ratio), which results in improved filtration characteristics, such as reduced pressure drop over time at a given filtration efficiency.

[0053] The fine fiber layer can have any suitable thickness. For example, in some cases, the thickness of the fine fiber layer is greater than the average fiber diameter of the fine fibers. In certain 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 3 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 these ranges are also possible (e.g., 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). The thickness can be determined by imaging a cross-section of the fine fiber layer using scanning electron microscopy (SEM).

[0054] The fine fiber layer can have any suitable weight per unit area. For example, in certain embodiments, the fine fiber layer has a weight per unit area of ​​greater than or equal to 0.001 gsm, greater than or equal to 0.01 gsm, greater than or equal to 0.1 gsm, greater than or equal to 1 gsm, greater than or equal to 2 gsm, greater than or equal to 3 gsm, greater than or equal to 4 gsm, greater than or equal to 5 gsm, greater than or equal to 7 gsm, greater than or equal to 10 gsm, greater than or equal to 12 gsm, or greater than or equal to 15 gsm. In 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 these 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). The basis weight may be measured according to ISO 536 (2012).

[0055] The fine fiber layer may have a relatively low solidity. For example, in some cases, the solidity of the fine fiber layer is greater than or equal to 1%, greater than or equal to 2%, greater than or equal to 3%, greater than or equal to 4%, greater than or equal to 5%, greater than or equal to 7.5%, 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%, or greater than or equal to 40%. In some embodiments, the solidity of the fine fiber layer is less than or equal to 50%, less than or equal to 45%, less than or equal to 40%, less than or equal to 35%, less than or equal to 30%, less than or equal to 25%, less than or equal to 20%, less than or equal to 15%, less than or equal to 10%, less than or equal to 7.5%, or less than or equal to 5%. Combinations of the above ranges are also possible (e.g., greater than or equal to 1% and less than or equal to 30%, greater than or equal to 4% and less than or equal to 25%, or greater than or equal to 5% and less than or equal to 20%). The solidity of a layer is equivalent to the percentage of the layer 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 and thickness per unit area of ​​the layer, and then applying the following formula: Solidity (%) = [weight per unit area / (fiber density*thickness)]*100%, where the weight per unit area and thickness can be determined as described elsewhere in this document. Fiber density is equivalent to the average density of one or more materials that form the fibers, which is usually given by the fiber manufacturer. The average density of the material that forms the fibers can be determined by: (1) determining the total volume of all fibers in the layer; and (2) dividing the total mass of all fibers in the layer by the total volume of all fibers in the layer. If the mass and density of each type of fiber in the layer are known, the volume of all fibers in the layer can be determined by: (1) for each type of fiber, dividing the total mass of fibers of that type in the layer by the density of fibers of that type; and (2) adding the volumes of each fiber type. If the mass and density of each type of fiber in a layer is unknown, the volume of all fibers in the layer can be determined based on Archimedes' principle. Without wishing to be bound by any theory, it is believed that in some embodiments, having a low solidity (e.g., the solidity disclosed herein) achieves improved filtration characteristics, such as higher air permeability, lower air resistance, higher dust holding capacity, lower pressure drop, and / or higher flux.

[0056] The fine fiber layer can have a relatively high void volume. For example, in some cases, the void volume of the fine fiber layer is greater than or equal to 70%, greater than or equal to 75%, greater than or equal to 80%, greater than or equal to 85%, greater than or equal to 90%, greater than or equal to 95%, or greater than or equal to 97%. In certain embodiments, the void volume of the fine fiber layer is less than or equal to 99%, less than or equal to 98%, less than or equal to 97%, less than or equal to 96%, less than or equal to 95%, less than or equal to 90%, less than or equal to 85%, less than or equal to 80%, or less than or equal to 75%. Combinations of these ranges are also possible (e.g., greater than or equal to 70% and less than or equal to 99%, greater than or equal to 75% and less than or equal to 96%, or greater than or equal to 80% and less than or equal to 95%). As used herein, void volume (%) is 100%-solidity (%). Without wishing to be bound by any theory, it is believed that in some embodiments, having a high void volume (e.g., the void volume disclosed herein) enables improved filtration characteristics, such as higher air permeability, lower air resistance, higher dust holding capacity, lower pressure drop, and / or higher flux.

[0057] The fine fiber layer can have any suitable mean flow pore size. For example, in some embodiments, the mean flow pore size of the fine fiber layer is greater than or equal to 0.001 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 0.2 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, or greater than or equal to 4 microns. In certain embodiments, the mean flow pore size of the fine fiber layer is 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, or less than or equal to 0.5 microns. Combinations of these ranges are also possible (e.g., greater than or equal to 0.001 micron and less than or equal to 5 microns, greater than or equal to 0.01 micron and less than or equal to 3 microns, or greater than or equal to 0.01 micron and less than or equal to 2 microns). The mean flow pore size can be measured using ASTM F316 (2003).

[0058] The fine fiber layer can have any suitable maximum pore diameter. For example, in certain embodiments, the maximum pore diameter of the fine fiber layer is 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, or greater than or equal to 4 microns. In some cases, the maximum pore diameter of the fine fiber layer is 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, or less than or equal to 1 micron. Combinations of these ranges are also possible (e.g., greater than or equal to 0.1 micron and less than or equal to 5 microns, greater than or equal to 0.1 micron and less than or equal to 4 microns, or greater than or equal to 0.1 micron and less than or equal to 2.5 microns). The maximum pore size can be measured using ASTM F316 (2003).

[0059] The fine fiber layer can have any suitable ratio of maximum pore size to mean flow pore size. In some embodiments, the ratio of maximum pore size to mean flow pore size of the fine fiber layer is greater than or equal to 1, greater than or equal to 1.1, greater than or equal to 1.2, greater than or equal to 1.3, greater than or equal to 1.5, greater than or equal to 1.75, greater than or equal to 2, greater than or equal to 2.5, greater than or equal to 3, greater than or equal to 3.5, or greater than or equal to 4. In some embodiments, the ratio of maximum pore size to mean flow pore size of the fine fiber layer is less than or equal to 5, less than or equal to 4.5, less than or equal to 4, less than or equal to 3.5, less than or equal to 3, less than or equal to 2.5, less than or equal to 2, less than or equal to 1.75, or less than or equal to 1.5. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 and less than or equal to 5, greater than or equal to 1.2 and less than or equal to 4, or greater than or equal to 1.2 and less than or equal to 3). Other ranges are also possible. The ratio of maximum pore size to mean flow pore size can be determined by obtaining the maximum pore size and mean flow pore size according to ASTM F316 (2003) and then dividing the maximum pore size by the mean flow pore size.

[0060] The fine fiber layer can have any suitable air permeability. For example, in some cases, the fine fiber layer has an air permeability greater than 0 CFM, greater than or equal to 0.1 CFM, greater than or equal to 0.5 CFM, greater than or equal to 1 CFM, greater than or equal to 2 CFM, 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 40 CFM, greater than or equal to 50 CFM, greater than or equal to 60 CFM, greater than or equal to 70 CFM, greater than or equal to 80 CFM, or greater than or equal to 90 CFM. In some cases, the air permeability of the fine fiber layer is 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 these 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). The air permeability can be measured according to ASTM D737-04 (2016) at a pressure of 125 Pa. Without wishing to be bound by any theory, it is believed that in some embodiments, higher air permeability reduces air resistance, reduces pressure drop, and / or increases dust loading.

[0061] The fine fiber layer can have any suitable elongation at break. For example, in some cases, 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 these 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%). The elongation at break can be measured according to T494 om-96.

[0062] The fine fiber layer can have any suitable tensile strength. For example, in some embodiments, the fine fiber layer has a tensile strength 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 130 gf / gsm, greater than or equal to 140 gf / gsm, greater than or equal to 150 gf / gsm, greater than or equal to 160 gf / gsm, greater than or equal to 170 gf / gsm, greater than or equal to 180 gf / gsm, greater than or equal to 190 gf / gsm, greater than or equal to 200 gf / gsm, greater than or equal to 210 gf / gsm, greater than or equal to 220 gf / gsm, greater than or equal to 230 gf / gsm, greater than or equal to 240 gf / gsm, greater than or equal to 250 gf / gsm, greater than or equal to 260 gf / gsm, greater than or equal to 270 gf / gsm, greater than or equal to 280 gf / gsm, greater than or equal to 290 gf / gsm, greater than or equal to 300 gf / gsm, greater than or equal to 310 gf / gsm, greater than or equal to 320 gf / gsm, greater than or equal to 330 gf / gsm, greater than or equal to 340 g 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, or greater than or equal to 900 gf / gsm. In certain embodiments, the tensile strength of the fine fiber layer 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 these 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).

[0063] As described herein, tensile strength can be determined by depositing fine fibers onto wax paper to have a unit area weight of 5 gsm. These independent fine fiber layers are then separated from the wax paper and the specimens are cut into a size of 1 inch by 7 inches to be measured on a Thwing-Albert tensile tester equipped with a 20N load cell. The gap between the jaws on the machine is 3.5 inches, and the stretching rate is 12 inches per minute. The tensile test data is then converted into a stress-strain curve (e.g., using Winwedge-12- software). The average tensile strength is determined by at least 10 individual measurements and calculated based on the stress-strain curve. The tensile strength is the average tensile strength normalized by dividing by the unit area weight.

[0064] In some embodiments, the fine fiber layer is treated. For example, in some cases, the fine fiber layer is heat laminated (e.g., with additional layers) (e.g., by passing the fine fiber layer, optionally with additional layers, through a hot air dryer).

[0065] In some embodiments, the filter media includes one or more additional layers (e.g., in addition to the fine fiber layer). Figure 2 In some cases, the filter medium 100 includes a fine fiber layer 110 and a second layer 120, wherein the second layer 120 is an additional layer. Figure 3 In some cases, the filter medium 100 includes a fine fiber layer 110, a second layer 120, and a third layer 130, wherein the second layer 120 and the third layer 130 are additional layers.

[0066] The filter media can have any suitable number of additional layers. For example, in certain embodiments, the filter media includes greater than 0, greater than or equal to 1, greater than or equal to 2, greater than or equal to 3, greater than or equal to 4, greater than or equal to 5, greater than or equal to 6, greater than or equal to 7, greater than or equal to 10, or greater than or equal to 15 additional layers. In some cases, the filter media includes less than or equal to 20, less than or equal to 18, less than or equal to 15, less than or equal to 13, less than or equal to 10, less than or equal to 8, less than or equal to 6, less than or equal to 5, less than or equal to 4, less than or equal to 3, or less than or equal to 2 additional layers. Combinations of these ranges are also possible (e.g., greater than 0 and less than or equal to 20 additional layers, greater than or equal to 1 and less than or equal to 10 additional layers, greater than or equal to 3 and less than or equal to 6 additional layers, or greater than or equal to 2 and less than or equal to 6 additional layers).

[0067] A plurality of suitable additional layers may be employed (e.g., in combination with at least one fine fiber layer to form a multilayer filter medium). For example, examples of suitable additional layers may include: a pre-filter layer, a backing, a scrim, a spacer, a meltblown layer, a meltspun layer, an electrospun layer (e.g., a melt electrospun layer and / or a solvent electrospun layer), a glass layer, a wet-laid layer, a dry-laid layer, an air-laid layer, a synthetic layer, a spunbond layer, a carded layer, a calendered layer, an oleophobic layer (e.g., a layer comprising an oleophobic additive or coating and / or a layer having an oil range greater than or equal to 1), an oleophilic layer, a charged (e.g., electrostatically charged, triboelectrically charged, and / or hydrocharged) layer, and / or a non-charged layer. The fine fiber layer may be deposited onto a backing layer, and then one or more additional layers may be laminated thereon (e.g., facing the backing layer, facing the fine fiber layer). Without wishing to be bound by any particular theory, it is believed that the meltblown layer may increase the capacity of the filter media and / or may provide intermediate stage filtration, the backing layer may increase the strength and / or pleatability of the filter media, the scrim may protect the filter media, and the pre-filter layer may increase the capacity of the filter media and / or protect the filter media.

[0068] In embodiments where one or more additional layers are oleophobic, one or more additional layers may include a coating (e.g., an oleophobic coating, an oleophobic component of an oleophobic coating) and / or contain a resin (e.g., an oleophobic resin, an oleophobic component of an oleophobic resin). The coating process may involve chemical deposition techniques and / or physical deposition techniques. For example, the coating process may include introducing a resin or material (e.g., an oleophobic component of a resin or material) dispersed in a solvent or solvent mixture into a preformed fiber layer (e.g., a preformed fiber web formed by a meltblowing process). As an example, the prefilter may be sprayed with a coating material (e.g., a water-based fluorinated acrylate such as AGE 550D). Non-limiting examples of coating methods include using vapor deposition (e.g., chemical vapor deposition, physical vapor deposition), layer-by-layer deposition, wax curing, self-assembly, sol-gel processing, slot die coater, gravure coating, screen coating, size press coating (e.g., double roll or metering blade type size press coater), film press coating, blade coating, roll blade coating, air knife coating, roll coating, foam application, reverse roll coating, rod coating, curtain coating, champlex coating, brush coating, Bill-blade coating, short dwell-blade coating, lip coating, gate roll coating, gate roll size press coating, laboratory size press coating, melt coating, dip coating, knife roll coating, spin coating, powder coating, spray coating (e.g., electrospray coating), gapped roll coating, roll transfer coating, padding saturant coating, saturated dipping, chemical bath deposition, and solution deposition. Other coating methods are also possible.

[0069] In some embodiments, the coating material can be applied to the fiber web using a non-compression coating technique. The non-compression coating technique can coat the fiber web without substantially reducing the thickness of the web. In other embodiments, the resin can be applied to the fiber web using a compression coating technique.

[0070] Other techniques include vapor deposition methods. Such methods include atmospheric pressure chemical vapor deposition (APCVD), low pressure chemical vapor deposition (LPCVD), metal organic chemical vapor deposition (MOCVD), plasma assisted chemical vapor deposition (PACVD) or plasma enhanced chemical vapor deposition (PECVD), laser chemical vapor deposition (LCVD), photochemical vapor deposition (PCVD), chemical vapor infiltration (CVI), chemical beam epitaxy (CBE), electron beam assisted radiation curing and atomic layer deposition. In physical vapor deposition (PVD), a film (e.g., a film comprising an oleophobic component) is deposited by condensing the desired film material in evaporated form onto a substrate. The method involves physical processes such as high temperature vacuum evaporation with subsequent condensation, plasma sputtering bombardment rather than chemical reaction, electron beam evaporation, molecular beam epitaxy and / or pulsed laser deposition.

[0071] In some embodiments, the surface of one or more layers (e.g., the surface of the first layer, the surface of the second layer, the surface of the third layer, the surface of the pre-filter layer, the surface of the main filter layer) can be modified using additives (e.g., oleophobic components as additives, such as oleophobic additives). In some embodiments, one or more layers (e.g., the first layer, the second layer, the third layer, the pre-filter layer, the main filter layer) can contain one or more additives (e.g., oleophobic components as additives, such as oleophobic additives). The additive can be a functional chemical substance added to the polymer / thermoplastic fiber during the meltblowing process, the electrospinning process, and / or the extrusion process, which can provide physical and chemical properties different from the physical and chemical properties of the polymer / thermoplastic itself at the surface after forming. In some embodiments, the additive can migrate to the surface of the fiber during or after the formation of the fiber material (polymer / thermoplastic) so that the surface of the fiber is modified by the additive, and the center of the fiber contains more polymer / thermoplastic material. In some embodiments, one or more additives are included to make the surface of the fiber oleophobic as described herein. For example, the additive can be an oleophobic material as described herein. Non-limiting examples of suitable additives include fluorinated acrylates, fluorinated surfactants, oleophobic silicones, fluorinated polymers, fluorinated monomers, fluorinated oligomers, and oleophobic polymers.

[0072] The additive (e.g., an oleophobic component in the form of an additive), if present, may be present in any suitable form before undergoing meltblowing, electrostatic spinning, or wet-laid web forming steps, or may be present in the fiber in any suitable form after fiber formation. For example, in some embodiments, the additive may be in the form of a liquid (e.g., melted) mixed with a thermoplastic material before or during fiber formation. In some cases, the additive may be in the form of particles before, during, or after fiber formation. In certain embodiments, particles of the melt additive may be present in fully formed fibers. In some embodiments, the additive may be a component of a binder, and / or may be added to one or more layers by spraying a layer with a composition comprising the additive. If it is a particle, the additive may have any suitable form (e.g., particles, flakes, ellipsoids, fibers of different shapes and sizes).

[0073] Any suitable size of additive particles (e.g., particles of an oleophobic component of the additive) can be included in the fiber-forming thermoplastic material to form the fibers and / or present in the fully formed fibers. For example, the average particle size (e.g., average diameter, or average cross-sectional dimension) of the particles can be greater than or equal to about 0.002 microns, greater than or equal to about 0.01 microns, greater than or equal to about 0.05 microns, greater than or equal to about 0.1 microns, greater than or equal to about 0.5 microns, greater than or equal to about 1 micron, greater than or equal to about 5 microns, greater than or equal to about 10 microns, greater than or equal to about 20 microns, greater than or equal to about 50 microns, greater than or equal to about 100 microns, or greater than or equal to about 200 microns. For example, the average particle size of the particles can be less than or equal to about 300 microns, less than or equal to about 200 microns, less than or equal to about 100 microns, less than or equal to about 50 microns, less than or equal to about 30 microns, less than or equal to about 15 microns, less than or equal to about 10 microns, less than or equal to about 5 microns, less than or equal to about 1 micron, less than or equal to about 0.1 micron, or less than or equal to about 0.01 micron. Combinations of the above ranges are also possible (e.g., greater than or equal to about 0.01 micron and less than or equal to about 10 microns). Other ranges are also possible. The average particle size as used herein is measured by dynamic light scattering.

[0074] In some embodiments, the material (e.g., oleophobic component, precursor that reacts to form the oleophobic component) can undergo a chemical reaction (e.g., polymerization) after being applied to a layer (e.g., a first layer, a second layer, a third layer, a pre-filter layer, a main filter layer). For example, the surface of a layer can be coated with one or more monomers that polymerize after coating. In another example, the surface of a layer can include monomers that polymerize after forming the fiber web due to a melt additive. In some such embodiments, in-line polymerization can be used. In-line polymerization (e.g., in-line UV polymerization) is a method of curing a monomer or liquid polymer solution onto a substrate under conditions sufficient to initiate polymerization (e.g., under UV irradiation).

[0075] The term "self-assembled monolayer" (SAM) refers to molecular assemblies that can be formed spontaneously by immersing a suitable substrate in a solution of an active surfactant in an organic solvent to produce an oleophobic surface.

[0076] In wax curing, the layer is immersed in molten alkyl ketene dimer (AKD) heated at 90°C and then cooled at room temperature in an atmosphere of dry N2 gas. AKD undergoes fractal growth as it solidifies and improves the oleophobicity of the substrate.

[0077] In some embodiments, the material used to form the surface modification layer (e.g., the surface modified first layer, the surface modified second layer, the surface modified third layer, the surface modified pre-filter layer, the surface modified main filter layer) or the material as a component of the surface modification layer (e.g., oleophobic component, a precursor that reacts to form an oleophobic component) can include small molecules, such as inorganic or organic oleophobic molecules. Non-limiting examples include hydrocarbons (e.g., CH4, C2H2, C2H4, C6H6), fluorocarbons (e.g., fluoroaliphatic compounds, fluoroaromatic compounds, fluoropolymers, fluorocarbon block copolymers, fluorocarbon acrylate polymers, fluorocarbon methacrylate polymers, fluoroelastomers, fluorosilanes, fluorosiloxanes, fluoropolyhedral oligomeric silsesquioxanes, fluorinated dendrimers, inorganic fluorine compounds, CF4, C2F4, C3F6, C3F8, C4H8, C5H6, etc.). 12 , C6F6, SF3, SiF4, BF3), silane (e.g., SiH4, Si2H6, Si3H8, Si4H 10), organosilanes (e.g., methylsilane, dimethylsilane, triethylsilane), siloxanes (e.g., dimethylsiloxane, hexamethyldisiloxane), ZnS, CuSe, InS, CdS, tungsten, silicon carbide, silicon nitride, silicon oxynitride, titanium nitride, carbon, silicon-germanium, and hydrophobic acrylic monomers terminated with alkyl groups and their halogenated derivatives (e.g., ethyl 2-ethylacrylate, methyl methacrylate; acrylonitrile). In certain embodiments, suitable hydrocarbon compounds for modifying the surface of the layer may have the formula C x H y , wherein x is an integer from 1 to 10, and y is an integer from 2 to 22. In certain embodiments, suitable silanes for modifying the surface of the layer may have the formula Si n H 2n+2 , wherein any hydrogen may be replaced by a halogen (e.g., Cl, F, Br, I), and wherein n is an integer from 1 to 10. In some embodiments, the material used to form the surface modification layer or the material that is a component of the surface modification layer may include one or more of wax, silicone, and corn-based polymers (e.g., zein). In some embodiments, the material used to form the surface modification layer or the material that is a component of the surface modification layer may include one or more nanoparticle materials. Other compositions are also possible.

[0078] As used herein, "small molecule" refers to a molecule with a relatively low molecular weight, whether naturally occurring or artificially produced (e.g., via chemical synthesis). Typically, a small molecule is an organic compound (i.e., it comprises carbon). Small organic molecules can comprise multiple carbon-carbon bonds, stereocenters, and other functional groups (e.g., amines, hydroxyls, carbonyls, and heterocycles, etc.). In certain embodiments, the molecular weight of a small molecule is at most about 1,000 g / mol, at most about 900 g / mol, at most about 800 g / mol, at most about 700 g / mol, at most about 600 g / mol, at most about 500 g / mol, at most about 400 g / mol, at most about 300 g / mol, at most about 200 g / mol, or at most about 100 g / mol. In certain embodiments, the molecular weight of the small molecule is at least about 100 g / mol, at least about 200 g / mol, at least about 300 g / mol, at least about 400 g / mol, at least about 500 g / mol, at least about 600 g / mol, at least about 700 g / mol, at least about 800 g / mol, or at least about 900 g / mol, or at least about 1,000 g / mol. Combinations of the above ranges (e.g., at least about 200 g / mol and up to about 500 g / mol) are also possible.

[0079] In some embodiments, the material used to form the surface modified layer (e.g., surface modified first layer, surface modified second layer, surface modified third layer, surface modified pre-filter layer, surface modified main filter layer) or the material that is a component of the surface modified layer (e.g., oleophobic component, precursor reacted to form oleophobic component) may include a crosslinking agent. Non-limiting examples of suitable crosslinking agents include materials having one or more acrylate groups, such as 1,6-hexanediol diacrylate and alkoxylated cyclohexanedimethanol diacrylate.

[0080] In some embodiments, the surface of the layer (e.g., the surface of the first layer, the surface of the second layer, the surface of the third layer, the surface of the pre-filter layer, the surface of the main filter layer) can be modified by roughening the surface of the layer or the material on the surface of the layer. In some such cases, the surface modification can be a roughened surface or material. The surface roughness of the surface of the layer or the material on the surface of the layer can be roughened microscopically and / or macroscopically. Non-limiting examples of methods for improving roughness include modifying the surface with certain fibers, mixing fibers with different diameters, and photolithography. In certain embodiments, fibers with different diameters (e.g., short fibers, continuous fibers) can be mixed or used to increase or reduce surface roughness. In some embodiments, electrospinning can be used alone or in combination with other methods (e.g., chemical vapor deposition) to produce an applied surface roughness. In some embodiments, photolithography can be used to roughen the surface. Photolithography includes many different types of surface treatments in which the design is transferred from a master to a surface.

[0081] In some embodiments, the roughness of a layer (e.g., the roughness of the first layer, the roughness of the second layer, the roughness of the third layer, the roughness of the pre-filter layer, the roughness of the main filter layer) can be used to modify the wettability of the layer with respect to a particular fluid. In some cases, the roughness can change or increase the wettability of the surface of the layer. In some cases, the roughness can be used to increase the oleophobicity of an essentially oleophobic surface. One of ordinary skill in the art will appreciate methods of modifying the roughness of the surface of a fiber web.

[0082] The filter media described herein can have an arrangement of multiple suitable layers. In some embodiments, the filter media includes a fine fiber layer as one of its outermost layers. In some embodiments, the filter media includes a fine fiber layer as an inner layer (i.e., a layer that is not the outermost layer). The filter media described herein incorporated in a filter element can be positioned so that the fine fiber layer is the upstream-most layer, the downstream-most layer, and / or the inner layer. Additional information about suitable features of the fine fiber layer and additional layers is provided below.

[0083] In certain embodiments, one or more additional layers include a gradient of one or more properties (e.g., fiber diameter). A filter medium comprising two or more layers may exhibit a gradual change in one or more properties at the interface between the layers. One or more properties may vary monotonically across the filter medium (e.g., monotonically increase, monotonically decrease) and / or one or more properties may vary in a manner other than monotonically across the filter medium. In some embodiments, air permeability, mean flow pore size, and / or penetration may decrease monotonically across the filter medium (e.g., from the upstream surface to the downstream surface) and / or decrease from the upstream surface of the filter medium to the fine fiber layer therein. In some embodiments, layers other than the outermost layer may have lower values ​​of air permeability, mean flow pore size, and / or penetration than other layers in the filter medium.

[0084] In some cases, one or more additional layers are fine fiber layers and can have any of the features disclosed herein for fine fiber layers or for additional layers.In embodiments including multiple fine fiber layers, the fine fiber layers can be the same or different.

[0085] In some embodiments, one or more additional layers may include one or more backing layers. The backing layer may support additional layers (e.g., fine fiber layers) present in the filter medium and / or may be layers on which additional layers are deposited during the manufacture of the filter medium. For example, in some embodiments, the filter medium may include a backing layer on which a fine fiber layer is deposited. The backing layer may provide structural support and / or improve the ease with which the filter medium can be manufactured without significantly increasing the resistance of the filter medium. In some embodiments, the backing layer does not significantly contribute to the filtering performance of the filter medium. In other embodiments, the backing layer may improve the performance of the filter medium in one or more ways (e.g., one or more backing layers may be positioned upstream of other layers and / or may be used as a pre-filter layer). In some embodiments, the filter medium includes two or more backing layers. For example, the filter medium may include two or more backing layers disposed on top of each other that form a composite backing layer together. In some embodiments, an adhesive may be disposed on the backing layer (e.g., positioned between the backing layer and the fine fiber layer).

[0086] In certain embodiments, the backing layer is flame retardant. For example, in some embodiments, the backing layer comprises flame retardant fibers. Flame retardant fibers (for example, synthetic fibers) may include flame retardants, for example some flame retardants based on phosphorus, which may have relatively low concentrations or may be substantially free of some undesirable and / or toxic components (for example, halogens). In certain embodiments, the backing layer may include a blend of fibers (for example, flame retardant fibers, non-flame retardant fibers). In some embodiments, the backing layer may be designed to have desired flame retardancy (for example, F1 grade, K1 grade).

[0087] It should be understood that any single backing layer (and / or composite backing layer) can independently have some or all of the properties described below with respect to the backing layer. It should also be understood that the filter medium can include two identical backing layers and / or can include two or more backing layers that differ in one or more aspects.

[0088] As described above, in some embodiments, the filter medium includes one or more additional layers in addition to the backing layer. Such additional layers are referred to herein as "additional layers". In addition to the fine fiber layer, additional layers (e.g., in combination with the backing layer) may also be provided. Non-limiting examples of suitable additional layers include pre-filter layers and protective layers. In some embodiments, the filter medium includes an additional layer that is a scrim (e.g., a pre-filter layer that is also a scrim, a protective layer that is also a scrim). The additional layer may be attached to another layer (e.g., a fine fiber layer, a backing layer, another additional layer) in the fiber web in various suitable ways (e.g., with an adhesive, by using a calender and / or by ultrasonic bonding).

[0089] When present, the additional layers can have a variety of properties. In some embodiments, the additional layers do not contribute significantly to the filtration performance of the filter medium. In other embodiments, the additional layers contribute to one or more properties of the filter medium. For example, the additional layers can be used as pre-filter layers. As another example, a relatively large percentage of the total pressure drop across the filter medium can occur across the additional layers. This may be beneficial when one or more other layers in the filter medium are relatively fragile and / or may not be able to withstand a large pressure drop.

[0090] It will be appreciated that any individual additional layer may independently have some or all of the properties described below with respect to the additional layers.It will also be appreciated that the filter medium may include two additional layers that are identical and / or may include two or more additional layers that differ in one or more aspects.

[0091] When present, additional layers (e.g., backing layers, additional layers) typically include a nonwoven web comprising a plurality of fibers. A variety of suitable types of nonwoven webs can be used as additional layers in the filter media described herein. For example, the filter media may include additional layers, the additional layers including wet-laid nonwoven webs, non-wet-laid nonwoven webs (e.g., melt-blown nonwoven webs, air-laid nonwoven webs, carded nonwoven webs, spunbonded nonwoven webs), electrostatically spun nonwoven webs, scrims, and / or other types of nonwoven webs. In some embodiments, the filter media includes an additional layer that is a paste-dot scrim. The paste-dot scrim may include a topological pattern formed by an adhesive (e.g., a topological pattern of points with a cylindrical cross section, a topological pattern of points with a non-cylindrical cross section). The adhesive may be polymeric (e.g., it may include poly (ester)) and / or may have a relatively high glass transition temperature (e.g., greater than 100°C).

[0092] In embodiments where more than one additional layer is present, each additional layer may independently be one or more of the types described above.

[0093] In some embodiments, additional layers (e.g., backing layers, additional layers) can be compressed. For example, the filter media can include additional layers that are calendered, such as a calendered meltblown layer, a calendered carded layer, a calendered spunbond layer, and / or a calendered wet-laid layer. Calendering can involve, for example, compressing one or more layers using calender rollers at a specific linear pressure, temperature, and line speed. For example, the linear pressure can be 50 psi to 400 psi (e.g., 200 psi to 400 psi, 50 psi to 200 psi, or 75 psi to 300 psi); the temperature can be 75°F to 400°F (e.g., 75°F to 300°F, 200°F to 350°F, or 275°F to 390°F); and the line speed can be 5 ft / min to 100 ft / min (e.g., 5 ft / min to 80 ft / min, 10 ft / min to 50 ft / min, 15 ft / min to 100 ft / min, or 20 ft / min to 90 ft / min). Other ranges of linear pressure, temperature, and line speed are also possible. In embodiments where there is more than one additional layer, each additional layer can be independently compressed at a linear pressure, temperature, and / or line speed in one or more of the above ranges.

[0094] When present, additional layers (e.g., backing layers, additional layers) can include a plurality of fibers containing a variety of suitable types of fibers. In some embodiments, additional layers include a plurality of fibers, and the plurality of fibers include natural fibers (e.g., hardwood fibers, softwood fibers, cellulose fibers) and / or regenerated cellulose fibers. For example, cellulose fibers can be hardwood fibers or softwood fibers. Cellulose fibers can be in addition to natural cellulose fibers. As an example, cellulose fibers can include regenerated and / or synthetic cellulose, such as rayon, lyocell and celluloid. As another example, cellulose fibers include natural cellulose derivatives, such as cellulose acetate and carboxymethyl cellulose. When present, cellulose fibers can include fibrillated cellulose fibers, and / or can include non-fibrillated cellulose fibers.

[0095] In some embodiments, the additional layer comprises a plurality of fibers comprising synthetic fibers and / or is made of synthetic fibers (in other words, it can be a synthetic layer). The synthetic fibers, if present, can include monocomponent synthetic fibers and / or multicomponent synthetic fibers (e.g., bicomponent synthetic fibers). The synthetic fibers, if present, can include coarse synthetic fibers and / or fine synthetic fibers. 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, 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(imide)), ... 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.

[0096] The synthetic fiber, if present, may include a binder fiber. The binder fiber, if present, may include a monocomponent binder fiber and / or a multicomponent binder fiber (e.g., a bicomponent binder fiber). Non-limiting examples of suitable materials that may be included in the binder fiber include: poly(olefins), such as poly(ethylene), poly(propylene), and poly(butylene); poly(esters) and co(esters), such as poly(ethylene terephthalate), co(ethylene terephthalate), poly(butylene terephthalate), and poly(ethylene isophthalate); poly(amides) and co(amides), such as nylon and aromatic polyamides; halogenated polymers, such as poly(tetrafluoroethylene); epoxy resins; phenolic resins; and melamine. Suitable co(ethylene terephthalate)s may include repeating units formed by polymerization of ethylene terephthalate monomers, and also include repeating units formed by polymerization of one or more comonomers. Such comonomers may include linear, cyclic and branched aliphatic dicarboxylic acids having 4 to 12 carbon atoms (e.g., succinic acid, glutaric acid, adipic acid, dodecanedioic acid and 1,4-cyclohexanedicarboxylic acid); aromatic dicarboxylic acids having 8 to 12 carbon atoms (e.g., isophthalic acid and 2,6-naphthalene dicarboxylic acid); linear, cyclic and branched aliphatic diols having 3 to 8 carbon atoms (e.g., 1,3-propylene glycol, 1,2-propylene glycol, 1,4-cyclohexanedicarboxylic acid); and / or aliphatic ether diols and aromatic / aliphatic ether diols having 4 to 10 carbon atoms (e.g., hydroquinone bis(2-hydroxyethyl) ether and poly(vinyl ether) glycols having a molecular weight of less than 460 g / mol, such as diethyleneether glycol).

[0097] In some embodiments, the additional layer comprises a plurality of fibers comprising glass fibers.

[0098] The additional layer may contain more than one type of fiber (e.g., both glass fibers and synthetic fibers) or may contain only one type of fiber (e.g., only subtypes of synthetic fibers, such as both fibers containing poly(olefins) and fibers containing poly(esters); or only fibers containing poly(propylene). In some embodiments, the plurality of fibers in the additional layer comprise fibers containing a blend of two or more of the polymers listed above (e.g., a blend of nylon and poly(esters)).

[0099] In embodiments where more than one additional layer is present, each additional layer may independently comprise fibers comprising one or more of the above-described fiber types.

[0100] When an additional layer (e.g., a backing layer, an additional layer) comprises a plurality of fibers comprising cellulose fibers (e.g., fibrillated cellulose fibers), the additional layer can have any suitable amount of cellulose fibers (e.g., fibrillated cellulose fibers). For example, in some embodiments, the cellulose fibers (e.g., fibrillated cellulose fibers) are present in the additional 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 5 wt%, greater than or equal to 10 wt%, greater than or equal to 20 wt%, greater than or equal to 30 wt%, greater than or equal to 40 wt%, greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 70 wt%, greater than or equal to 80 wt%, or greater than or equal to 90 wt%, relative to the total weight of the additional layer. In some embodiments, the cellulose fibers (e.g., fibrillated cellulose fibers) are present in the additional layer in an amount less than or equal to 100 wt%, less than or equal to 90 wt%, less than or equal to 80 wt%, less than or equal to 70 wt%, less than or equal to 60 wt%, less than or equal to 50 wt%, less than or equal to 40 wt%, less than or equal to 30 wt%, less than or equal to 20 wt%, less than or equal to 10 wt%, less than or equal to 5 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 100 wt%, greater than or equal to 1 wt% and less than or equal to 100 wt%, greater than or equal to 1 wt% and less than or equal to 50 wt%, greater than or equal to 1 wt% and less than or equal to 20 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 cellulosic fibers may be present in the additional layer in an amount of 100 wt. %, relative to the total weight of the additional layer and / or relative to the total weight of the fibers in the additional layer.

[0101] When an additional layer (e.g., a backing layer, an additional layer) comprises a plurality of fibers containing synthetic fibers (e.g., binder fibers and / or bicomponent fibers), the additional layer can have any suitable amount of synthetic fibers. For example, in some embodiments, the synthetic fibers (e.g., binder fibers and / or bicomponent fibers) are present in the additional 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 5 wt%, greater than or equal to 10 wt%, greater than or equal to 20 wt%, greater than or equal to 30 wt%, greater than or equal to 40 wt%, greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 70 wt%, greater than or equal to 80 wt%, or greater than or equal to 90 wt%, relative to the total weight of the additional layer. In some embodiments, synthetic fibers (e.g., binder fibers and / or bicomponent fibers) are present in the additional layer in an amount 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 10 weight percent, less than or equal to 5 weight percent, less than or equal to 2 weight percent, or less than or equal to 1 weight percent, relative to the total weight of the additional 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 1 wt % and less than or equal to 100 wt %, greater than or equal to 80 wt % and less than or equal to 100 wt %, greater than or equal to 1 wt % and less than or equal to 20 wt %, greater than or equal to 1 wt % and less than or equal to 10 wt %, greater than or equal to 10 wt % and less than or equal to 30 wt %, greater than or equal to 30 wt % and less than or equal to 80 wt %, or greater than or equal to 1 wt % and less than or equal to 50 wt %). Other ranges are also possible. In some embodiments, the synthetic fibers may be present in the additional layer in an amount of 100 wt %, relative to the total weight of the additional layer and / or relative to the total weight of the fibers in the additional layer.

[0102] When an additional layer (e.g., a backing layer, an additional layer) comprises a plurality of fibers comprising glass fibers, the additional layer can have any suitable amount of glass fibers. For example, in some embodiments, the glass fibers are present in the additional 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 5 wt%, greater than or equal to 10 wt%, greater than or equal to 20 wt%, greater than or equal to 30 wt%, greater than or equal to 40 wt%, greater than or equal to 50 wt%, greater than or equal to 60 wt%, greater than or equal to 70 wt%, greater than or equal to 80 wt%, or greater than or equal to 90 wt%, relative to the total weight of the additional layer. In some embodiments, the glass fibers are present in the additional layer in an amount of less than or equal to 100 wt%, less than or equal to 90 wt%, less than or equal to 80 wt%, less than or equal to 70 wt%, less than or equal to 60 wt%, less than or equal to 50 wt%, less than or equal to 40 wt%, less than or equal to 30 wt%, less than or equal to 20 wt%, less than or equal to 10 wt%, less than or equal to 5 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 100 wt%, greater than or equal to 1 wt% and less than or equal to 100 wt%, or greater than or equal to 1 wt% and less than or equal to 20 wt%). Other ranges are also possible. In some embodiments, the glass fibers may be present in the additional layer in an amount of 100 wt%, relative to the total weight of the additional layer and / or relative to the total weight of the fibers in the additional layer.

[0103] When present, additional layers (eg, backing layer, further layers) can have any suitable average fiber diameter, regardless of the type of fibers present. For example, in some embodiments, the average fiber diameter of the additional layer is greater than or equal to 0.1 micron, greater than or equal to 0.125 micron, greater than or equal to 0.15 micron, greater than or equal to 0.2 micron, greater than or equal to 0.25 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 0.75 micron, greater than or equal to 1 micron, greater than or equal to 1.25 micron, greater than or equal to 1.5 micron, 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 4 microns, greater than or equal to 5 microns, greater than or equal to 7.5 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 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 fiber diameter of the additional layer is less than or equal to 75 microns, less than or equal to 70 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 20 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 7.5 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 2.5 microns, less than or equal to 2 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 0.75 microns, less than or equal to 0.5 microns, less than or equal to 0.4 microns, less than or equal to 0.3 microns, or less than or equal to 0.25 microns. 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 75 micrometers, or greater than or equal to 0.5 micrometers and less than or equal to 25 micrometers). Other ranges are also possible. The average diameter can be determined by scanning electron microscopy.

[0104] When present, the ratio between the average fiber diameter of the fine fiber layer and the average fiber diameter of the additional layer (e.g., backing layer, additional layer) can have multiple values. For example, in some embodiments, the ratio between the average fiber diameter of the fine fiber layer and the average fiber diameter of the additional layer is greater than or equal to 0.001, greater than or equal to 0.005, greater than or equal to 0.01, greater than or equal to 0.05, greater than or equal to 0.1, greater than or equal to 0.15, greater than or equal to 0.2, greater than or equal to 0.3, greater than or equal to 0.4, greater than or equal to 0.5, greater than or equal to 0.6, greater than or equal to 0.7, greater than or equal to 0.8, or greater than or equal to 0.9. In some embodiments, the ratio between the average fiber diameter of the fine fiber layer and the average fiber diameter of the additional layer is less than or equal to 1, less than or equal to 0.95, less than or equal to 0.9, less than or equal to 0.85, less than or equal to 0.8, less than or equal to 0.75, less than or equal to 0.7, 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. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.001 and less than or equal to 1, greater than or equal to 0.01 and less than or equal to 1, or greater than or equal to 0.1 and less than or equal to 1).

[0105] In embodiments where the filter media includes two or more additional layers, each additional layer can independently include a ratio between the average fiber diameter of the fine fiber layer and the average fiber diameter of the additional layer within one or more of the ranges described above.

[0106] When an additional layer (e.g., a backing layer, an additional layer) comprises a plurality of fibers comprising cellulose fibers, the cellulose fibers therein can have any suitable average diameter. In some embodiments, the additional layer comprises cellulose fibers having an average diameter of 0.1 micron or more, 0.5 micron or more, 1 micron or more, 3 microns or more, 5 microns or more, 7 microns or more, 10 microns or more, 12.5 microns or more, 15 microns or more, 20 microns or more, 25 microns or more, 30 microns or more, 35 microns or more, 40 microns or more, or 45 microns or more. In some embodiments, the additional layer comprises cellulose fibers having an average diameter of less than or equal to 75 microns, less than or equal to 70 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 20 microns, less than or equal to 15 microns, less than or equal to 12.5 microns, less than or equal to 10 microns, or less than or equal to 7 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 75 microns, greater than or equal to 5 microns and less than or equal to 50 microns, or greater than or equal to 10 microns and less than or equal to 30 microns). Other ranges are also possible. The average diameter can be determined by scanning electron microscopy.

[0107] In embodiments where the filter media includes two or more additional layers comprising cellulosic fibers, each additional layer comprising cellulosic fibers can independently comprise cellulosic fibers having an average diameter within one or more of the above ranges.

[0108] When an additional layer (e.g., a backing layer, an additional layer) comprises a plurality of fibers comprising synthetic fibers, the synthetic fibers (e.g., binder fibers and / or bicomponent fibers) therein may have a variety of average diameters. In some embodiments, the additional layer comprises synthetic fibers (e.g., binder fibers and / or bicomponent fibers) having an average diameter of: greater than or equal to 0.01 microns, greater than or equal to 0.05 microns, greater than or equal to 0.075 microns, greater than or equal to 0.1 microns, greater than or equal to 0.125 microns, greater than or equal to 0.15 microns, greater than or equal to 0.2 microns, greater than or equal to 0.25 microns, greater than or equal to 0.3 microns, greater than or equal to 0.4 microns, greater than or equal to 0.5 microns, greater than or equal to 0.75 microns, greater than or equal to 0.8 microns, greater than or equal to 0.9 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, 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 100 microns, greater than or equal to 20 microns, greater than or equal to 30 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 80 microns, greater than or equal to 90 microns, greater than or equal to 100 microns, greater than or equal to 100 microns, greater than or equal to 100 microns, greater than or equal 1 micron, greater than or equal to 1.25 microns, 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 4 microns, greater than or equal to 5 microns, greater than or equal to 7.5 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 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 additional layer comprises synthetic fibers (e.g., binder fibers and / or bicomponent fibers) having an average diameter of 100 microns or less, 90 microns or less, 80 microns or less, 70 microns or less, 60 microns or less, 50 microns or less, 45 microns or less, 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, 1 ... 7.5 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 2.5 microns, less than or equal to 2 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 0.75 microns, less than or equal to 0.5 microns, less than or equal to 0.4 microns, less than or equal to 0.3 microns, less than or equal to 0.25 microns, less than or equal to 0.2 microns, less than or equal to 0.15 microns, less than or equal to 0.125 microns, less than or equal to 0.1 microns, or less than or equal to 0.075 microns. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.01 microns and less than or equal to 100 microns, greater than or equal to 0.01 microns and less than or equal to 50 microns, greater than or equal to 0.1 microns and less than or equal to 20 microns, greater than or equal to 1 micron and less than or equal to 20 microns, greater than or equal to 10 microns and less than or equal to 60 microns, or greater than or equal to 17 microns and less than or equal to 35 microns).Other ranges are also possible.The average diameter can be determined by scanning electron microscopy.

[0109] In embodiments where there is more than one additional layer comprising synthetic fibers, each additional layer comprising synthetic fibers can independently comprise synthetic fibers having an average fiber diameter within one or more of the above-noted ranges.

[0110] When an additional layer (e.g., a backing layer, an additional layer) comprises a plurality of fibers comprising glass fibers, the glass fibers therein may have a plurality of average diameters. In some embodiments, the additional layer comprises glass fibers having an average diameter of 0.1 micrometer or more, 0.15 micrometer or more, 0.2 micrometer or more, 0.25 micrometer or more, 0.3 micrometer or more, 0.4 micrometer or more, 0.5 micrometer or more, 0.75 micrometer or more, 1 micrometer or more, 1.25 micrometer or more, 1.5 micrometer or more, 2 micrometer or more, 2.5 micrometer or more, 3 micrometer or more, 4 micrometer or more, 5 micrometer or more, 7.5 micrometer or more, 10 micrometer or more, or 12.5 micrometer or more. In some embodiments, the additional layer comprises glass fibers having an average diameter of less than or equal to 40 microns, less than or equal to 35 microns, less than or equal to 30 microns, less than or equal to 25 microns, less than or equal to 20 microns, less than or equal to 15 microns, less than or equal to 12.5 microns, less than or equal to 10 microns, less than or equal to 7.5 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 2.5 microns, less than or equal to 2 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 0.75 microns, less than or equal to 0.5 microns, less than or equal to 0.4 microns, less than or equal to 0.3 microns, less than or equal to 0.25 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 40 microns, or greater than or equal to 0.4 microns and less than or equal to 20 microns). Other ranges are also possible. The average diameter can be determined by scanning electron microscopy.

[0111] In embodiments where there is more than one additional layer comprising glass fibers, each additional layer comprising glass fibers can independently comprise glass fibers having an average fiber diameter within one or more of the above ranges.

[0112] The fibers in the plurality of fibers in the additional layer (eg, backing layer, further layer), if present, can have any suitable average length. In some embodiments, the average length of the fibers (e.g., synthetic fibers, glass fibers, cellulosic fibers, and / or a combination of all fibers) in the additional layer is greater than or equal to 0.001 mm, greater than or equal to 0.01 mm, 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 0.75 mm, greater than or equal to 1 mm, greater than or equal to 1.25 mm, greater than or equal to 1.5 mm, greater than or equal to 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, greater than or equal to 7.5 mm, greater than or equal to 10 mm, greater than or equal to 12.5 mm, greater than or equal to 15 mm, greater than or equal to 20 mm, greater than or equal to 25 mm, greater than or equal to 30 mm, greater than or equal to 40 mm, greater than or equal to 50 mm, or greater than or equal to 75 mm. In some embodiments, the average length of the fibers (e.g., synthetic fibers, glass fibers, cellulose fibers, and / or a combination of all fibers) in the additional layer is less than or equal to 300 mm, less than or equal to 250 mm, less than or equal to 200 mm, less than or equal to 150 mm, less than or equal to 100 mm, less than or equal to 70 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 25 mm, less than or equal to 20 mm, less than or equal to 15 mm, less than or equal to 12.5 mm, less than or equal to 12 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 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 1.25 mm, less than or equal to 1 mm, less than or equal to 0.75 mm, less than or equal to 0.5 mm, or less than or equal to 0.4 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.01 mm and less than or equal to 300 mm, greater than or equal to 0.1 mm and less than or equal to 300 mm, greater than or equal to 0.1 mm and less than or equal to 12 mm, greater than or equal to 1 mm and less than or equal to 70 mm, greater than or equal to 3 mm and less than or equal to 300 mm, greater than or equal to 6 mm and less than or equal to 100 mm, greater than or equal to 1 mm and less than or equal to 10 mm, or greater than or equal to 0.1 mm and less than or equal to 25 mm). Other ranges are also possible.

[0113] In embodiments where more than one additional layer is present, each additional layer may independently comprise fibers having an average length within one or more of the above ranges.

[0114] In some embodiments, the additional layer (e.g., backing layer, additional layer) comprises continuous fibers, which can have a plurality of suitable lengths. For example, the average length of the fibers in the additional layer can be 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 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 length of the fibers in the additional layer 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 ... 100 mm, 100 mm, 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 400 mm, 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, 100 mm, 200 mm, 300 mm, 400 mm, 500 mm, 600 mm, 800 mm, 900 mm, 100 mm, 250 mm, 300 mm, 400 mm, 500 mm, 600 mm, 700 mm, 800 mm, 900 mm, 100 mm, 25 ...700 mm, 800 mm, 900 mm, 100 mm, 250 mm, 300 mm, 400 mm, 500 mm, 600 mm, 250 mm, 300 mm, 400 mm, 500 mm, 600 mm, 250 mm, 300 mm, 400 mm, 500 mm, 600 mm, 250 mm, 300 mm, 400 mm, 500 mm, 600 mm, 250 mm, 300 mm, 400 mm, 500 mm, 600 mm, 250 mm, 300 mm, 400 mm,

[0115] In embodiments where more than one additional layer is present, each additional layer may independently comprise fibers having an average length within one or more of the above ranges.

[0116] Some additional layers (e.g., backing layers, additional layers) contain components other than fibers. For example, the additional layer may contain a binder resin. The binder resin may comprise less than or equal to 90 wt %, less than or equal to 80 wt %, less than or equal to 70 wt %, less than or equal to 60 wt %, less than or equal to 50 wt %, less than or equal to 40 wt %, less than or equal to 30 wt %, less than or equal to 25 wt %, less than or equal to 20 wt %, less than or equal to 15 wt %, less than or equal to 12.5 wt %, less than or equal to 10 wt %, less than or equal to 7.5 wt %, less than or equal to 5 wt %, less than or equal to 4 ... or equal to 3 wt%, less than or equal to 2.5 wt%, less than or equal to 2 wt%, less than or equal to 1.5 wt%, less than or equal to 1.25 wt%, less than or equal to 1 wt%, less than or equal to 0.75 wt%, less than or equal to 0.5 wt%, less than or equal to 0.4 wt%, less than or equal to 0.3 wt%, less than or equal to 0.25 wt%, less than or equal to 0.2 wt%, less than or equal to 0.15 wt%, less than or equal to 0.125 wt%, or less than or equal to 0.1 wt%. The binder resin may comprise greater than or equal to 0 weight percent, greater than or equal to 0.1 weight percent, greater than or equal to 0.125 weight percent, greater than or equal to 0.15 weight percent, greater than or equal to 0.2 weight percent, greater than or equal to 0.25 weight percent, greater than or equal to 0.3 weight percent, greater than or equal to 0.4 weight percent, greater than or equal to 0.5 weight percent, greater than or equal to 0.75 weight percent, greater than or equal to 1 weight percent, greater than or equal to 1.25 weight percent, greater than or equal to 1.5 weight percent, greater than or equal to 2 weight percent, greater than or equal to 2.5 weight percent, greater than or equal to 3 weight percent, greater than or equal to 4 weight percent, greater than or equal to 5 weight percent, greater than or equal to 7.5 weight percent, greater than or equal to 10 weight percent, greater than or equal to 12.5 weight percent, greater than or equal to 15 weight percent, greater than or equal to 20 weight percent, or greater than or equal to 25 weight percent of the additional 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 90 wt %, less than or equal to 30 wt %, or greater than or equal to 10 wt % and less than or equal to 30 wt %) of the additional layer. Other ranges are also possible. In some embodiments, the additional layer is free of binder resin (i.e., binder resin comprises 0 wt % of the additional layer).

[0117] In embodiments where more than one additional layer is present, each additional layer may independently comprise a binder resin in an amount within one or more of the above ranges.

[0118] In some embodiments, the binder resin comprises a polymer. Non-limiting examples of suitable polymers used with the binder resin include thermoplastic polymers (e.g., acrylic resins, poly(vinyl acetate), poly(esters), poly(amides)), thermosetting polymers (e.g., epoxy resins, phenolic resins, melamine), vinyl acetate resins, epoxy resins, poly(ester) resins, copoly(ester) resins, poly(vinyl alcohol) resins, acrylic resins (e.g., 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), and poly(urethane), or combinations thereof.

[0119] When the additional layer (e.g., backing layer, additional layer) comprises a plurality of fibers comprising cellulose fibers, the cellulose fibers therein may have any suitable fibrillation level (i.e., the degree of branching in the fibers). The fibrillation level may be measured according to a number of suitable methods. For example, the fibrillation level of the fibrillated fibers may be measured according to the Canadian Standard Freeness (CSF) test specified by TAPPI Test Method T 227om09 Freeness of Pulp. The test may provide an average CSF value.

[0120] In certain embodiments, the average CSF value of cellulose fibers / regenerated cellulose fibers (when present) can be greater than, or equal to, 0.1 mL, greater than, or equal to, 0.5 mL, greater than, or equal to, 1 mL, greater than, or equal to, 10 mL, greater than, or equal to, 20 mL, greater than, or equal to, 35 mL, greater than, or equal to, 45 mL, greater than, or equal to, 50 mL, greater than, or equal to, 65 mL, greater than, or equal to, 70 mL, greater than, or equal to, 75 mL, greater than, or equal to, 80 mL, greater than, or equal to, 100 mL, greater than, or equal to, 110 mL, greater than, or equal to, 120 mL, greater than, or equal to, 130 mL, greater than, or equal to, 140 mL, greater than, or equal to, 150 mL, greater than, or equal to, 175 mL, greater than, or equal to, 200 mL, greater than, or equal to, 250 mL, greater than, or equal to, 300 mL, greater than, or equal to, 350 mL, greater than, or equal to, 400 mL, greater than, or equal to, 500 mL, greater than, or equal to, 600 mL, greater than, or equal to, 650 mL, greater than, or equal to, 700 mL, or greater than, or equal to, 750 mL. In some embodiments, the average CSF value of the cellulose fibers can be less than or equal to 800 mL, less than or equal to 750 mL, less than or equal to 700 mL, less than or equal to 650 mL, less than or equal to 600 mL, less than or equal to 550 mL, less than or equal to 500 mL, less than or equal to 450 mL, less than or equal to 400 mL, less than or equal to 350 mL, less than or equal to 300 mL, less than or equal to 250 mL, less than or equal to 225 mL, less than or equal to 200 mL, less than or equal to 150 mL, less than or equal to 140 mL, less than or equal to 130 mL, less than or equal to 120 mL, less than or equal to 110 mL, less than or equal to 100 mL, less than or equal to 90 mL, less than or equal to 85 mL, less than or equal to 70 mL, less than or equal to 50 mL, less than or equal to 40 mL, or less than or equal to 25 mL. Combinations of the above lower and upper limits are also possible (e.g., greater than or equal to 45 mL and less than or equal to 800 mL, greater than or equal to 120 mL and less than or equal to 500 mL, or greater than or equal to 0.1 mL and less than or equal to 800 mL). It should be understood that in certain embodiments, the fibers may have a fibrillation level outside of the above ranges. The average CSF value of the cellulose fibers used in the layer may be based on one type of cellulose fiber or more than one type of cellulose fiber.

[0121] The thickness of the additional layer (e.g., backing layer, additional layer) can be selected as desired. For example, in some embodiments, the thickness of the additional layer can be 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 0.02 mm, greater than or equal to 0.05 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 0.5 mm, greater than or equal to 0.8 mm, greater than or equal to 1.0 mm, greater than or equal to 2.0 mm, greater than or equal to 3.0 mm, or greater than or equal to 4.0 mm. In some cases, the thickness of the additional layer can be less than or equal to 10 mm, less than or equal to 9 mm, less than or equal to 8 mm, less than or equal to 7 mm, less than or equal to 6 mm, less than or equal to 5 mm, less than or equal to 3 mm, less than or equal to 2 mm, less than or equal to 1.2 mm, less than or equal to 1, less than or equal to 0.8 mm, less than or equal to 0.5 mm, less than or equal to 0.4 mm, or less than or equal to 0.2 mm. Combinations of the above ranges are also possible (for example, a thickness greater than or equal to 10 nm and less than or equal to 10 mm, greater than or equal to 0.02 mm and less than or equal to 10 mm, 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 5 mm, greater than or equal to 0.1 mm and less than or equal to 3 mm, or a thickness greater than or equal to 0.1 mm and less than or equal to 1 mm). Other values ​​of thickness are also possible. As determined herein, the thickness is determined according to standard ISO 534 (2011) at 2 N / cm 2 In embodiments where the additional layer is a fine fiber layer, the thickness may be determined by imaging a cross section of the fine fiber layer using scanning electron microscopy (SEM).

[0122] In embodiments where the filter media includes two or more additional layers, each additional layer can independently have a thickness within one or more of the ranges described above.

[0123] When present, the additional layer (e.g., backing layer, additional layer) can have a variety of suitable solidities. In some embodiments, the additional layer has a solidity greater than or equal to 0.001%, greater than or equal to 0.01%, greater than or equal to 0.1%, greater than or equal to 1%, greater than or equal to 2%, greater than or equal to 3%, greater than or equal to 4%, greater than or equal to 5%, greater than or equal to 7.5%, 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%, or greater than or equal to 40%. In some embodiments, the additional layer has a solidity less than or equal to 50%, less than or equal to 45%, less than or equal to 40%, less than or equal to 35%, less than or equal to 30%, less than or equal to 25%, less than or equal to 20%, less than or equal to 15%, less than or equal to 10%, less than or equal to 7.5%, or less than or equal to 5%. Combinations of the above-recited ranges are also possible (e.g., greater than or equal to 0.001% and less than or equal to 50%, or greater than or equal to 0.01% and less than or equal to 25%). Other ranges are also possible. Solidity can be measured as described elsewhere herein. In embodiments where there is more than one additional layer, each additional layer can independently have a solidity in one or more of the above-recited ranges.

[0124] When present, additional layers (eg, backing layer, additional layers) can have any suitable basis weight. In some embodiments, the additional layer has a weight per unit area of ​​greater than or equal to 0.001 gsm, greater than or equal to 0.01 gsm, greater than or equal to 0.1 gsm, greater than or equal to 1 gsm, greater than or equal to 2 gsm, greater than or equal to 5 gsm, greater than or equal to 7.5 gsm, greater than or equal to 10 gsm, greater than or equal to 12.5 gsm, greater than or equal to 15 gsm, greater than or equal to 17.5 gsm, greater than or equal to 20 gsm, greater than or equal to 25 gsm, greater than or equal to 30 gsm, greater than or equal to 40 gsm, greater than or equal to 50 gsm, greater than or equal to 75 gsm, greater than or equal to 100 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, or greater than or equal to 400 gsm. In some embodiments, the additional layer has a basis weight of 1000 gsm or less, 900 gsm or less, 800 gsm or less, 700 gsm or less, 600 gsm or less, 500 gsm or less, 400 gsm or less, 300 gsm or less, 250 gsm or less, 200 gsm or less, 150 gsm or less, 120 gsm or less, 100 gsm or less, 75 gsm or less, 50 gsm or less, 40 gsm or less, 30 gsm or less, 25 gsm or less, 20 gsm or less, 17.5 gsm or less, 15 gsm or less, 12.5 gsm or less, 10 gsm or less, or 7.5 gsm or less. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.001 gsm and less than or equal to 1000 gsm, greater than or equal to 2 gsm and less than or equal to 1000 gsm, greater than or equal to 5 gsm and less than or equal to 500 gsm, greater than or equal to 10 gsm and less than or equal to 300 gsm, greater than or equal to 15 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 20 gsm and less than or equal to 120 gsm, or greater than or equal to 30 gsm and less than or equal to 200 gsm). Other ranges of weight per unit area are also possible. The weight per unit area of ​​the additional layer can be determined according to ISO 536:2012.

[0125] In embodiments where more than one additional layer is present, each additional layer can independently have a weight per unit area in one or more of the ranges noted above.

[0126] When present, the additional layer (e.g., backing layer, additional layer) can have a variety of suitable elongation at break values. In some embodiments, the elongation at break of the additional layer (and / or the entire filter medium) is greater than or equal to 1%, greater than or equal to 2%, greater than or equal to 5%, greater than or equal to 7.5%, greater than or equal to 10%, greater than or equal to 15%, greater than or equal to 20%, greater than or equal to 25%, greater than or equal to 30%, or greater than or equal to 40%. In some embodiments, the elongation at break of the additional layer (and / or the entire filter medium) is less than or equal to 50%, less than or equal to 40%, less than or equal to 30%, less than or equal to 25%, less than or equal to 20%, less than or equal to 15%, less than or equal to 10%, less than or equal to 7.5%, less than or equal to 5%, 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%, greater than or equal to 1% and less than or equal to 10%, greater than or equal to 2% and less than or equal to 10%, or greater than or equal to 5% and less than or equal to 25%). Other ranges are also possible. The elongation at break of the additional layer (and / or the entire filter media) can be determined in accordance with T494 om-96 using a test span of 5 inches and a jaw separation speed of 12 inches / minute.

[0127] It should be understood that when two or more additional layers are present, each additional layer may independently have an elongation at break within one or more of the above ranges.

[0128] When present, the additional layer (e.g., backing layer, additional layer) can have a variety of suitable specific surface areas. In some embodiments, the specific surface area of ​​the additional layer is greater than or equal to 0.1 m 2 / g, greater than or equal to 0.2m 2 / g, greater than or equal to 0.5m 2 / g, greater than or equal to 1m 2 / g, greater than or equal to 2m 2 / g, greater than or equal to 5m 2 / g, greater than or equal to 10m 2 / g, greater than or equal to 15m 2 / g, greater than or equal to 20m 2 / g, greater than or equal to 25m 2 / g, greater than or equal to 30m 2 / g, greater than or equal to 35m 2 / g, greater than or equal to 40m 2 / g, or greater than or equal to 45m 2 In some embodiments, the specific surface area of ​​the additional layer is less than or equal to 50 m 2 / g, less than or equal to 45m 2 / g, less than or equal to 40m2 / g, less than or equal to 35m 2 / g, less than or equal to 30m 2 / g, less than or equal to 25m 2 / g, less than or equal to 20m 2 / g, less than or equal to 15m 2 / g, less than or equal to 10m 2 / g, less than or equal to 5m 2 / g, less than or equal to 2m 2 / g, less than or equal to 1m 2 / g, less than or equal to 0.5m 2 / g, less than or equal to 0.2m 2 / g, or less than or equal to 0.1m 2 / g. Combinations of the above ranges are also possible (e.g., greater than 0 m 2 / g and less than or equal to 50m 2 / g, greater than 0m 2 / g and less than or equal to 40m 2 / g, or greater than 0m 2 / g and less than or equal to 35m 2 / g). Other ranges are also possible. The specific surface area can be determined according to the Battery Council International Standard BCIS-03A (2009) "Recommended Battery Materials Specifications Valve Regulated Recombinant Batteries", Section 10, "Standard Test Method for Surface Area of ​​Recombinant Battery Separator Mat". According to this technique, the specific surface area is measured by adsorption analysis with nitrogen using a BET surface analyzer (e.g., Micromeritics Gemini III 2375 surface area analyzer); the sample amount is 0.5 to 0.6 grams in a 3 / 4 inch tube; and the sample is degassed at 100°C for a minimum of 3 hours.

[0129] In embodiments where more than one additional layer is present, each additional layer may independently have a specific surface area in one or more of the ranges recited above.

[0130] When present, the additional layer (e.g., backing layer, additional layer) can have a variety of suitable mean flow pore sizes. In some embodiments, the mean flow pore size of the additional layer is greater than or equal to 0.1 micron, greater than or equal to 0.125 micron, greater than or equal to 0.15 micron, greater than or equal to 0.2 micron, greater than or equal to 0.25 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 0.75 micron, greater than or equal to 1 micron, greater than or equal to 1.25 micron, greater than or equal to 1.5 micron, 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 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, greater than or equal to 12 microns, greater than or equal to 13 microns, greater than or equal to 14 microns, greater than or equal to 16 microns, greater than or equal to 17 microns, greater than or equal to 18 microns, greater than or equal to 19 microns, greater than or equal to 20 microns, greater than or equal to 21 microns, greater than or equal to 23 microns, greater than or equal to 24 microns, greater than or equal to 25 microns, greater than or equal to 26 microns, greater than or equal to 27 microns, greater than or equal to 28 microns, greater than or equal to 29 microns, greater than or equal to 30 microns, greater than or equal to 31 microns, greater than or equal to 4 microns or more, 5 microns or more, 7.5 microns or more, 10 microns or more, 12.5 microns or more, 15 microns or more, 20 microns or more, 25 microns or more, 30 microns or more, 35 microns or more, 40 microns or more, 45 microns or more, 50 microns or more, 75 microns or more, 100 microns or more, 125 microns or more, 150 microns or more, or 200 microns or more. In some embodiments, the mean flow pore size of the additional 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 125 microns, less than or equal to 100 microns, less than or equal to 75 microns, less than or equal to 50 microns, less than or equal to 45 microns, less than or equal to 40 microns, less than or equal to 35 microns, less than or equal to 30 microns, less than or equal to 25 microns, less than or equal to 20 microns, less than or equal to 15 microns, less than or equal to 10 microns, 12.5 microns, 10 microns or less, 7.5 microns or less, 5 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, 0.2 microns or less, 0.15 microns or less, or 0.125 microns or less. Combinations of the above ranges are also possible (e.g., 0.1 micron or less and 300 microns or less, 0.1 micron or less and 50 microns or less, 1 micron or less and 100 microns or less, 1 micron or less and 30 microns or less, or 2 microns or less and 30 microns or less). Other ranges are also possible. The mean flow pore size of the additional layer can be determined according to ASTM F316 (2003).

[0131] In embodiments where more than one additional layer is present, each additional layer may independently have a mean flow pore size in one or more of the ranges noted above.

[0132] When present, the additional layer (e.g., backing layer, additional layer) can have a plurality of suitable maximum pore sizes. In some embodiments, the maximum pore size of the additional layer is greater than or equal to 0.2 microns, greater than or equal to 0.25 microns, greater than or equal to 0.3 microns, greater than or equal to 0.4 microns, greater than or equal to 0.5 microns, greater than or equal to 0.75 microns, greater than or equal to 1 micron, greater than or equal to 1.25 microns, greater than or equal to 1.5 microns, greater than or equal to 2 microns, greater than or equal to 2.5 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 7.5 microns, greater than or equal to 10 ... equal to 12.5 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 75 microns, greater than or equal to 100 microns, greater than or equal to 125 microns, greater than or equal to 150 microns, greater than or equal to 200 microns, greater than or equal to 250 microns, greater than or equal to 300 microns, greater than or equal to 400 microns, or greater than or equal to 500 microns. In some embodiments, the additional layer has a maximum pore size of less than or equal to 750 microns, less than or equal to 500 microns, less than or equal to 400 microns, 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 125 microns, less than or equal to 100 microns, less than or equal to 75 microns, less than or equal to 50 microns, less than or equal to 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, or less than or equal to 10 microns. The maximum pore size can be determined according to ASTM F316 (2003).

[0133] In embodiments where more than one additional layer is present, each additional layer may independently have a maximum pore size in one or more of the ranges noted above.

[0134] When present, additional layers (e.g., backing layers, additional layers) can have a variety of suitable maximum pore size to mean flow pore size ratios. In some embodiments, the additional layers (and / or the entire filter media) have a maximum pore size to mean flow pore size ratio of greater than or equal to 1.1, greater than or equal to 1.2, greater than or equal to 1.3, greater than or equal to 1.5, greater than or equal to 1.75, greater than or equal to 2, greater than or equal to 2.5, greater than or equal to 3, greater than or equal to 4, greater than or equal to 5, greater than or equal to 7.5, greater than or equal to 10, greater than or equal to 12.5, greater than or equal to 15, greater than or equal to 20, or greater than or equal to 25. In some embodiments, the ratio of the maximum pore size of the additional layer (and / or the entire filter medium) to the mean flow pore size is less than or equal to 30, less than or equal to 25, less than or equal to 20, less than or equal to 15, less than or equal to 12.5, less than or equal to 10, less than or equal to 7.5, less than or equal to 5, less than or equal to 4, less than or equal to 3, less than or equal to 2.5, less than or equal to 2, less than or equal to 1.75, or less than or equal to 1.5. Combinations of the above ranges are also possible (e.g., greater than or equal to 1.1 and less than or equal to 30, greater than or equal to 1.3 and less than or equal to 30, greater than or equal to 1.3 and less than or equal to 25, or greater than or equal to 1.3 and less than or equal to 20). Other ranges are also possible. The ratio of the maximum pore size to the mean flow pore size can be determined by obtaining the maximum pore size and the mean flow pore size according to ASTM F316 (2003), and then dividing the maximum pore size by the mean flow pore size.

[0135] In embodiments where more than one additional layer is present, each additional layer can independently have a ratio of maximum pore size to mean flow pore size in one or more of the ranges noted above.

[0136] When present, the additional layer (e.g., backing layer, additional layer) can have any suitable surface average fiber diameter. For example, in some embodiments, the surface average fiber diameter of the additional layer can be greater than or equal to about 1 micron, greater than or equal to about 2 microns, greater than or equal to about 3 microns, greater than or equal to about 4 microns, greater than or equal to about 5 microns, greater than or equal to about 6 microns, greater than or equal to about 7 microns, greater than or equal to about 8 microns, greater than or equal to about 9 microns, greater than or equal to about 10 microns, greater than or equal to about 11 microns, greater than or equal to about 12 microns, greater than or equal to about 13 microns, greater than or equal to about 14 microns, greater than or equal to about 15 microns, greater than or equal to about 16 microns, greater than or equal to about 17 microns, greater than or equal to about 18 microns, greater than or equal to about 19 microns, or greater than or equal to about 20 microns. In some cases, the surface average fiber diameter of the additional layer can be less than or equal to about 25 microns, less than or equal to about 24 microns, less than or equal to about 23 microns, less than or equal to about 22 microns, less than or equal to about 21 microns, less than or equal to about 20 microns, less than or equal to about 19 microns, less than or equal to about 18 microns, less than or equal to about 18 microns, less than or equal to about 17 microns, less than or equal to about 16 microns, less than or equal to about 15 microns, less than or equal to about 14 microns, less than or equal to about 13 microns, or less than or equal to about 12 microns. All suitable combinations of the above ranges are also possible (e.g., greater than or equal to about 1 micron and less than or equal to about 25 microns, greater than or equal to about 10 microns and less than or equal to about 20 microns, greater than or equal to about 13 microns and less than or equal to about 17 microns, or greater than or equal to about 14 microns and less than or equal to about 16 microns).

[0137] It should be understood that when two or more additional layers are present, each additional layer can independently have a surface average diameter in one or more of the above ranges.

[0138] Typically, a layer may include multiple fibers having different average fiber diameters and / or fiber diameter distributions. In such cases, the average diameter of the fibers in the layer may be characterized using a weighted average such as a surface average fiber diameter. The surface average fiber diameter is defined as

[0139] d=Σ(m i / ρ i ) / Σ(m i / d i ρ i );

[0140] where d is the surface average fiber diameter in microns, and m i is the diameter d in micrometers i and g / cm 3 Density of the meter iThe equation assumes that the fibers are cylindrical, that the fibers have a circular cross-section, and that the fiber length is significantly greater than the fiber diameter. It should be understood that when the nonwoven web includes fibers that are substantially cylindrical and have a substantially circular cross-section, the equation also provides a meaningful value for the surface average fiber diameter.

[0141] The surface average fiber diameter can be calculated or measured using the above equation, as further described below.In embodiments where the diameter, density, and mass percentage of the fibers in a layer are known, the surface average fiber diameter can be calculated.

[0142] In other embodiments, the surface average fiber diameter of a layer can be determined by measuring the BET surface area (i.e., SSA) of the layer and the density p of the layer, as described in more detail below. In such cases, the surface average fiber diameter (SAFD) can be determined using the following modified formula:

[0143] SAFD [in μm] = 4 / (SSAρ [in g / cm3])

[0144] Where SSA is the BET surface area of ​​the layer, expressed in m 2 / g meter, and ρ is the density of the layer, in g / cm 3 count.

[0145] When present, the additional layer (e.g., backing layer, additional layer) can have a variety of suitable air permeabilities. In some embodiments, the air permeability of the additional layer is greater than or equal to 0.1 CFM, greater than or equal to 0.5 CFM, greater than or equal to 0.75 CFM, greater than or equal to 1 CFM, greater than or equal to 1.25 CFM, greater than or equal to 1.5 CFM, greater than or equal to 2 CFM, greater than or equal to 2.5 CFM, greater than or equal to 3 CFM, greater than or equal to 4 CFM, greater than or equal to 5 CFM, greater than or equal to 7.5 CFM, greater than or equal to 8 CFM, greater than or equal to 10 CFM, greater than or equal to 12.5 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 ...30 CFM, greater than or equal to 30 CFM, greater than or equal to 30 CFM, greater than or equal to 30 CFM, greater than or equal to 30 CFM, greater than or equal to 30 CFM, greater than or equal to 30 CFM, greater than or equal to 30 CFM, greater than or equal to 30 CFM, greater than or equal to 30 CFM, greater than or equal to 30 CFM, greater than or equal to 30 CFM, greater than or equal to 30 CFM, or equal to 40 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 125 CFM, greater than or equal to 150 CFM, greater than or equal to 200 CFM, greater than or equal to 250 CFM, greater than or equal to 300 CFM, greater than or equal to 400 CFM, greater than or equal to 500 CFM, greater than or equal to 750 CFM, greater than or equal to 1000 CFM, greater than or equal to 1250 CFM, greater than or equal to 1500 CFM, greater than or equal to 2000 CFM, greater than or equal to 2500 CFM, greater than or equal to 3000 CFM, or greater than or equal to 5000 CFM. In some embodiments, the additional layer has an air permeability of less than or equal to 8000 CFM, less than or equal to 5000 CFM, less than or equal to 3000 CFM, less than or equal to 2500 CFM, less than or equal to 2000 CFM, less than or equal to 1500 CFM, less than or equal to 1400 CFM, less than or equal to 1250 CFM, less than or equal to 1000 CFM, less than or equal to 800 CFM, less than or equal to 750 CFM, less than or equal to 500 CFM, less than or equal to 400 CFM, less than or equal to 300 CFM, less than or equal to 250 CFM, less than or equal to 200 CFM, less than or equal to 150 CFM, less than or equal to 125 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 40 CFM, less than or equal to 3 0CFM, less than or equal to 25CFM, less than or equal to 20CFM, less than or equal to 15CFM, less than or equal to 12.5CFM, less than or equal to 10CFM, less than or equal to 7.5CFM, less than or equal to 5CFM, less than or equal to 4CFM, less than or equal to 3CFM, less than or equal to 2.5CFM, less than or equal to 2CFM, less than or equal to 1.5CFM, less than or equal to 1.25CFM, less than or equal to 1CFM, or less than or equal to 0.75CFM.Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 CFM and less than or equal to 8000 CFM, greater than or equal to 0.5 CFM and less than or equal to 8000 CFM, greater than or equal to 0.5 CFM and less than or equal to 800 CFM, greater than or equal to 1 CFM and less than or equal to 1400 CFM, greater than or equal to 1 CFM and less than or equal to 500 CFM, greater than or equal to 5 CFM and less than or equal to 500 CFM, or greater than or equal to 8 CFM and less than or equal to 400 CFM). Other ranges are also possible. The air permeability can be determined according to ASTM test standard D737-04 (2016) at a pressure of 125 Pa.

[0146] It should be understood that when two or more additional layers are present, each additional layer may independently have an air permeability within one or more of the above ranges.

[0147] When present, the additional layers (e.g., backing layer, additional layers) can have a plurality of suitable dry tensile strengths. In some embodiments, the additional layers (and / or the entire filter media) have a dry tensile strength of greater than or equal to 1 lb / inch, greater than or equal to 2 lb / inch, greater than or equal to 5 lb / inch, greater than or equal to 10 lb / inch, greater than or equal to 15 lb / inch, greater than or equal to 20 lb / inch, greater than or equal to 25 lb / inch, greater than or equal to 30 lb / inch, greater than or equal to 35 lb / inch, greater than or equal to 40 lb / inch, greater than or equal to 50 lb / inch, greater than or equal to 60 lb / inch, greater than or equal to 70 lb / inch, greater than or equal to 80 lb / inch, greater than or equal to 90 lb / inch, greater than or equal to 100 lb / inch, greater than or equal to 125 lb / inch, greater than or equal to 150 lb / inch, or greater than or equal to 175 lb / inch. In some embodiments, the additional layer (and / or the entire filter media) has a dry tensile strength of less than or equal to 200 pounds / inch, less than or equal to 175 pounds / inch, less than or equal to 150 pounds / inch, less than or equal to 125 pounds / inch, less than or equal to 120 pounds / inch, less than or equal to 100 pounds / inch, less than or equal to 90 pounds / inch, less than or equal to 80 pounds / inch, less than or equal to 70 pounds / inch, less than or equal to 60 pounds / inch, less than or equal to 50 pounds / inch, less than or equal to 40 pounds / inch, less than or equal to 35 pounds / inch, less than or equal to 30 pounds / inch, less than or equal to 25 pounds / inch, less than or equal to 20 pounds / inch, less than or equal to 15 pounds / inch, less than or equal to 10 pounds / inch, or less than or equal to 5 pounds / inch. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 lb / inch and less than or equal to 200 lb / inch, greater than or equal to 2 lb / inch and less than or equal to 100 lb / inch, or greater than or equal to 5 lb / inch and less than or equal to 50 lb / inch). Other ranges are also possible. The dry tensile strength can be determined according to standard T494 om-96 using a 4 inch test span and a jaw separation speed of 1 inch / minute.

[0148] It should be understood that when two or more additional layers are present, each additional layer may independently have a tensile strength in one or more of the above ranges.

[0149] When present, the additional layers (e.g., backing layer, additional layers) can have a plurality of suitable dry Mullen bursting strengths. In some embodiments, the additional layers (and / or the entire filter media) can have a dry Mullen bursting strength of greater than or equal to 0.5 psi, greater than or equal to 1 psi, greater than or equal to 2 psi, greater than or equal to 5 psi, greater than or equal to 10 psi, greater than or equal to 20 psi, greater than or equal to 25 psi, greater than or equal to 30 psi, greater than or equal to 50 psi, greater than or equal to 75 psi, greater than or equal to 100 psi, greater than or equal to 125 psi, greater than or equal to 150 psi, greater than or equal to 175 psi, greater than or equal to 200 psi, greater than or equal to 225 psi, or greater than or equal to 240 psi. In some cases, the dry Mullen bursting strength of the additional layer (and / or the entire filter medium) can be less than or equal to 250 psi, less than or equal to 240 psi, less than or equal to 225 psi, less than or equal to 200 psi, less than or equal to 175 psi, less than or equal to 150 psi, less than or equal to 125 psi, less than or equal to 100 psi, less than or equal to 75 psi, less than or equal to 50 psi, less than or equal to 25 psi, less than or equal to 20 psi, less than or equal to 10 psi, less than or equal to 5 psi, less than or equal to 2 psi, less than or equal to 1 psi, less than or equal to 0.5 psi. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.5 psi and less than or equal to 250 psi, greater than or equal to 20 psi and less than or equal to 250 psi, or greater than or equal to 25 psi and less than or equal to 150 psi). Other values ​​of the dry Mullen bursting strength are also possible. The dry Mullen bursting strength can be determined according to standard T403om-91.

[0150] It should be understood that when two or more additional layers are present, each additional layer may independently have a dry Mullen burst strength in one or more of the above ranges.

[0151] When present, the additional layer (e.g., backing layer, additional layer) can have any suitable Gurley stiffness (e.g., in the cross direction and / or in the machine direction). In some embodiments, the additional layer has a Gurley stiffness (e.g., in the cross direction and / or in the machine direction) greater than or equal to about 1 mg, greater than or equal to about 2 mg, greater than or equal to about 5 mg, greater than or equal to about 10 mg, greater than or equal to about 50 mg, greater than or equal to about 100 mg, greater than or equal to about 200 mg, greater than or equal to about 300 mg, greater than or equal to about 500 mg, greater than or equal to about 800 mg, greater than or equal to about 1,000 mg, greater than or equal to about 1,200 mg, greater than or equal to about 1,400 mg, greater than or equal to 1,500 mg, greater than or equal to 2,000 mg, or greater than or equal to 3,000 mg. In some embodiments, the additional layer has a Gurley stiffness (e.g., in the cross direction and / or in the machine direction) of less than or equal to about 3,500 mg, less than or equal to about 3,000 mg, less than or equal to about 2,500 mg, less than or equal to about 2,000 mg, less than or equal to about 1,500 mg, less than or equal to about 1,400 mg, less than or equal to about 1,200 mg, less than or equal to about 1,000 mg, less than or equal to about 800 mg, less than or equal to about 500 mg, less than or equal to about 300 mg, less than or equal to about 200 mg, or less than or equal to about 100 mg. All suitable combinations of the above ranges are also possible (e.g., greater than or equal to about 1 mg and less than or equal to about 3,500 mg, greater than or equal to about 5 mg and less than or equal to about 2,500 mg, greater than or equal to about 10 mg and less than or equal to about 3,500 mg, greater than or equal to about 10 mg and less than or equal to about 1,000 mg, or greater than or equal to about 50 mg and less than or equal to about 2,000 mg). Stiffness can be determined according to TAPPI T543om-94 using Gurley stiffness (e.g., flexural resistance) reported in mm (equivalent to gu).

[0152] It should be understood that when two or more additional layers are present, each additional layer may independently have a Gurley Stiffness in one or more of the above ranges.

[0153] When present, the additional layer (e.g., backing layer, additional layer) can have any suitable dust holding capacity. In certain embodiments, the additional layer has a dust holding capacity of greater than or equal to 10 gsm, greater than or equal to 20 gsm, greater than or equal to 30 gsm, greater than or equal to 40 gsm, greater than or equal to 50 gsm, greater than or equal to 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, or greater than or equal to 400 gsm. In some embodiments, the dust holding capacity of the additional layer is less than or equal to 500 gsm, less than or equal to 450 gsm, less than or equal to 400 gsm, less than or equal to 350 gsm, less than or equal to 300 gsm, less than or equal to 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, or less than or equal to 50 gsm. Combinations of these ranges are also possible (e.g., greater than or equal to 10 gsm and less than or equal to 500 gsm, or greater than or equal to 20 gsm and less than or equal to 450 gsm). The dust holding capacity can be measured according to ISO 19438 (2003) using ISO medium test dust (A3).

[0154] It should be understood that when two or more additional layers are present, each additional layer may independently have a dust holding capacity within one or more of the above ranges.

[0155] When present, additional layers (e.g., backing layers, additional layers) can have any suitable pressure drop. In certain embodiments, the pressure drop of the additional layer is greater than or equal to 0.05 kPa, greater than or equal to 0.1 kPa, greater than or equal to 0.3 kPa, greater than or equal to 0.5 kPa, greater than or equal to 1 kPa, greater than or equal to 3 kPa, greater than or equal to 5 kPa, greater than or equal to 10 kPa, greater than or equal to 15 kPa, greater than or equal to 20 kPa, greater than or equal to 25 kPa, greater than or equal to 30 kPa, greater than or equal to 40 kPa, greater than or equal to 50 kPa, or greater than or equal to 60 kPa. In some embodiments, the pressure drop of the additional layer is less than or equal to 80 kPa, less than or equal to 75 kPa, less than or equal to 70 kPa, less than or equal to 65 kPa, less than or equal to 60 kPa, less than or equal to 55 kPa, less than or equal to 50 kPa, less than or equal to 45 kPa, less than or equal to 40 kPa, less than or equal to 35 kPa, less than or equal to 30 kPa, less than or equal to 25 kPa, less than or equal to 20 kPa, less than or equal to 15 kPa, less than or equal to 10 kPa, or less than or equal to 5 kPa. Combinations of these ranges are also possible (e.g., greater than or equal to 0.05 kPa and less than or equal to 80 kPa, or greater than or equal to 0.1 kPa and less than or equal to 50 kPa). The pressure drop can be measured according to ASTM D2986-91.

[0156] It should be understood that when two or more additional layers are present, each additional layer may independently have a pressure drop in one or more of the above ranges.

[0157] In some embodiments, two or more layers of the filter media (e.g., a fine fiber layer and an additional layer or two fine fiber layers) can be formed separately and combined by any suitable method (e.g., lamination, finishing) or by using an adhesive. Two or more layers can be formed using different processes or the same process. For example, each layer can be independently formed by an electrospinning process, a non-wet-laid process (e.g., a melt-blown process, a melt-spinning process, a centrifugal spinning process, an electrospinning process, a dry-laid process, an air-laid process), a wet-laid process, or any other suitable process.

[0158] The different layers can be attached together by any suitable method. For example, the layers can be attached to each other on either side by adhesives and / or melt-bonded to each other. Lamination and calendering methods can also be used. In some embodiments, the additional layer can be formed from any type of fiber or fiber blend via a wet-laid or non-wet-laid process and appropriately attached to another layer.

[0159] In some embodiments, the filter media includes an adhesive positioned between two or more layers (e.g., between a fine fiber layer and a second layer (e.g., a backing layer, an additional layer)). As also described above, some filter media described herein include an adhesive positioned between two or more pairs of layers (e.g., between a fine fiber layer and a second layer). It should be understood that the adhesive positioned between any particular pair of layers may have some or all of the properties described below with respect to the adhesive. It should also be understood that the filter media may include two locations where an adhesive is positioned where the adhesive has the same properties, and / or may include two or more locations where an adhesive is positioned where the adhesive differs in one or more aspects.

[0160] In some embodiments, filter medium includes the adhesive of the adhesive resin based on solvent.As used herein, the adhesive resin based on solvent is the adhesive that can experience liquid to solid transition when solvent evaporates from resin.The adhesive resin based on solvent can be applied when in liquid state.Subsequently, the solvent existing can be evaporated to produce solid adhesive.Therefore, the adhesive based on solvent can be considered to be different from hot melt adhesive, and the hot melt adhesive does not include volatile solvent (for example, the solvent evaporated under normal operating conditions) and usually experiences liquid to solid transition when adhesive is cooled.In the embodiment that adhesive is present in more than one position, each position that has adhesive can be independently included as the adhesive of the adhesive resin based on solvent.

[0161] The desired properties of adhesive can include enough viscosity and open time (that is, the amount of time that adhesive keeps viscosity after being exposed to ambient atmosphere).Do not wish to be bound by theory, the viscosity of adhesive can depend on the molecular weight of the glass transition temperature of adhesive and any polymer component of adhesive.Higher glass transition value and lower molecular weight value can promote the viscosity of enhancement, and higher molecular weight value can produce higher cohesive force and higher bond strength in adhesive.In some embodiments, the adhesive in one or more scopes of glass transition temperature and / or molecular weight described in this article can provide the suitable value of viscosity and open time.For example, adhesive can be configured to keep viscosity for a relatively long time (for example, adhesive can keep viscosity after any solvent that initially exists evaporates completely, and / or can be viscosity indefinitely when remaining at room temperature). In some embodiments, the open time of adhesive can be less than or equal to 24 hours, less than or equal to 12 hours, less than or equal to 6 hours, less than or equal to 1 hour, less than or equal to 30 minutes, less than or equal to 15 minutes, less than or equal to 10 minutes, less than or equal to 5 minutes, less than or equal to 3 minutes, less than or equal to 1 minute, less than or equal to 30 seconds or less than or equal to 10 seconds.In some embodiments, the open time of adhesive can be at least 1 second, at least 10 seconds, at least 15 seconds, at least 30 seconds, at least 1 minute, at least 3 minutes, at least 5 minutes, at least 10 minutes, at least 15 minutes, at least 30 minutes, at least 1 hour, at least 6 hours or at least 12 hours.The combination of the above-mentioned scope is also possible (for example, at least 1 second and less than or equal to 24 hours).Other values ​​are also possible.In the embodiment that adhesive is present in more than one position, each position that has adhesive can independently comprise the adhesive of open time in above-mentioned one or more scopes.

[0162] Non-limiting examples of suitable adhesives include adhesives comprising acrylates, acrylate copolymers, poly(urethanes), poly(esters), poly(vinyl alcohols), ethylene-vinyl acetate copolymers, silicone solvents, poly(olefins), synthetic and / or natural rubbers, synthetic elastomers, ethylene-acrylic acid copolymers, ethylene-methacrylate copolymers, ethylene-methyl methacrylate copolymers, poly(vinylidene chloride), poly(amides), epoxy resins, melamine resins, poly(isobutylene), styrene block copolymers, styrene-butadiene rubber, aliphatic urethane acrylates, and / or phenolic resins. In embodiments where an adhesive is present at more than one location, each location where an adhesive is present may independently comprise an adhesive comprising one or more of the above materials.

[0163] When present, adhesive can include crosslinking agent and / or can be crosslinked.In certain embodiments, crosslinking agent is less than or equal to 3000g / mol.In some embodiments, crosslinking agent is small molecule as described above and / or crosslinking is the reaction product of small molecule crosslinking agent as described above.In some embodiments, adhesive includes small molecule crosslinking agent (and / or its reaction product) of one or more of the following: carbodiimide, isocyanate, aziridine, zirconium compound (such as zirconium carbonate), metal acid ester, metal chelate, multifunctional propylene imine and amino resin.In some embodiments, adhesive includes at least one polymer and / or prepolymer with one or more reactive functional groups that can react with crosslinking agent and / or includes the reaction product of one or more reactive functional groups on polymer and / or prepolymer and crosslinking agent reaction.The non-limiting examples of suitable reactive functional groups include alcohol group, carboxylic acid group, epoxy group, amine group and amino group.In some embodiments, filter medium includes adhesive containing one or more polymers and / or prepolymers that can be self-crosslinked via the functional group attached thereto. In some embodiments, the filter media comprises a binder comprising a self-crosslinking reaction product of one or more polymers and / or prepolymers. In embodiments where the binder is present at more than one location, each location where the binder is present can independently comprise a binder comprising one or more of the above materials.

[0164] When present, the small molecule crosslinking agent and / or the crosslinks as the reaction products thereof may comprise any suitable amount of the adhesive. In some embodiments, the weight percent of the crosslinking agent and / or the crosslinks as the reaction products thereof relative to the total mass of the adhesive is greater than or equal to 0.1 weight percent, greater than or equal to 0.2 weight percent, greater than or equal to 0.5 weight percent, greater than or equal to 1 weight percent, greater than or equal to 2 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, or greater than or equal to 25 weight percent. In some embodiments, the weight percent of the small molecule crosslinking agent and / or the crosslinks as the reaction products thereof relative to the total mass of the adhesive is less than or equal to 30 weight percent, less than or equal to 25 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, less than or equal to 2 weight percent, less than or equal to 1 weight percent, less than or equal to 0.5 weight percent, or less than or equal to 0.2 weight percent. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.1 wt % and less than or equal to 30 wt %, or greater than or equal to 1 wt % and less than or equal to 20 wt %). Other ranges are also possible. In embodiments where adhesive is present at more than one location, each location where adhesive is present can independently contain an adhesive containing a small molecule crosslinking agent and / or a crosslinked adhesive as a reaction product thereof in one or more of the above-referenced amounts.

[0165] The adhesive and / or any small molecule cross-linking agent therein may be capable of undergoing a cross-linking reaction at any suitable temperature and / or may have undergone a cross-linking reaction at any suitable temperature. In some embodiments, the adhesive may be capable of undergoing a cross-linking reaction at a temperature of and / or may have undergone a cross-linking reaction at a temperature of greater than or equal to 24°C, greater than or equal to 40°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 110°C, greater than or equal to 120°C, greater than or equal to 130°C, or greater than or equal to 140°C. In some embodiments, the adhesive may be capable of undergoing a crosslinking reaction at a temperature of less than or equal to 150°C, less than or equal to 140°C, less than or equal to 130°C, less than or equal to 120°C, less than or equal to 110°C, less than or equal to 100°C, 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, or less than or equal to 40°C. Combinations of the above ranges are also possible (e.g., greater than or equal to 25°C and less than or equal to 150°C, or greater than or equal to 25°C and less than or equal to 130°C). Other ranges are also possible. In embodiments where the adhesive is present at more than one location, each location where the adhesive is present may independently contain an adhesive capable of undergoing a crosslinking reaction at a temperature in one or more of the above ranges and / or that has undergone a crosslinking reaction at a temperature in one or more of the above ranges.

[0166] When present, adhesive can comprise solvent and / or can be formed by the composition comprising solvent (for example, solvent has evaporated therefrom).For example, some embodiments relate to the adhesive applied to layer or filter medium when being dissolved or suspended in solvent.The limiting examples of suitable solvent include water, hydrocarbon solvent, ketone, aromatic solvent, fluorinated solvent, toluene, heptane, acetone, n-butyl acetate, methyl ethyl ketone, methylene chloride, naphtha and solvent oil.In the embodiment that adhesive is present in more than one position, each position that has adhesive can independently comprise one or more of the above-mentioned solvent and / or can be formed by the composition comprising one or more of the above-mentioned solvent.

[0167] When present, the adhesive may have a relatively low glass transition temperature. In some embodiments, the adhesive has a glass transition temperature of less than or equal to 60°C, less than or equal to 50°C, less than or equal to 45°C, less than or equal to 40°C, less than or equal to 35°C, less than or equal to 30°C, less than or equal to 25°C, less than or equal to 24°C, less than or equal to 20°C, 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 -5°C, less than or equal to -10°C, less than or equal to -20°C, less than or equal to -30°C, less than or equal to -40°C, less than or equal to -50°C, less than or equal to -60°C, less than or equal to -70°C, less than or equal to -80°C, less than or equal to -90°C, less than or equal to -100°C, or less than or equal to -110°C. In some embodiments, the glass transition temperature of the adhesive is greater than or equal to -125°C, greater than or equal to -110°C, greater than or equal to -100°C, greater than or equal to -90°C, greater than or equal to -80°C, greater than or equal to -70°C, greater than or equal to -60°C, 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, greater than or equal to 5°C, greater than or equal to 10°C, greater than or equal to 24°C, greater than or equal to 25°C, greater than or equal to 40°C, or greater than or equal to 50°C. Combinations of the above ranges are also possible (e.g., greater than or equal to -125°C and less than or equal to 60°C, or greater than or equal to -100°C and less than or equal to 25°C). Other ranges are also possible. The glass transition temperature values ​​of the adhesive can be measured by differential scanning calorimetry as described above. In embodiments where a binder is present at more than one location, each location where a binder is present can independently comprise a binder having a glass transition temperature in one or more of the above ranges.

[0168] When present, adhesive can have multiple suitable molecular weights.In some embodiments, the number average molecular weight of adhesive is greater than or equal to 10kDa, greater than or equal to 30kDa, greater than or equal to 50kDa, greater than or equal to 100kDa, greater than or equal to 300kDa, greater than or equal to 500kDa, greater than or equal to 1000kDa, greater than or equal to 2000kDa, or greater than or equal to 3000kDa.In some embodiments, the number average molecular weight of adhesive is less than or equal to 5000kDa, less than or equal to 4000kDa, less than or equal to 3000kDa, less than or equal to 1000kDa, less than or equal to 500kDa, less than or equal to 300kDa, less than or equal to 100kDa, less than or equal to 50kDa, or less than or equal to 30kDa.The combination of the above range is also possible (for example, greater than or equal to 10kDa and less than or equal to 5000kDa or greater than or equal to 30kDa and less than or equal to 3000kDa).Other scopes are also possible. The number average molecular weight can be measured by light scattering.In embodiments where a binder is present at more than one location, each location where a binder is present can independently comprise a binder having a molecular weight in one or more of the above ranges.

[0169] When present, adhesive can have a plurality of suitable weights per unit area.In some embodiments, the weight per unit area of ​​adhesive is greater than or equal to 0.05gsm, greater than or equal to 0.1gsm, greater than or equal to 0.2gsm, greater than or equal to 0.5gsm, greater than or equal to 1gsm, greater than or equal to 2gsm or greater than or equal to 5gsm.In some embodiments, the weight per unit area of ​​adhesive is less than or equal to 10gsm, less than or equal to 5gsm, less than or equal to 2gsm, less than or equal to 1gsm, less than or equal to 0.5gsm, less than or equal to 0.2gsm or less than or equal to 0.1gsm.The combination of the above-mentioned scope is also possible (for example, greater than or equal to 0.05gsm and less than or equal to 10gsm or greater than or equal to 0.1gsm and less than or equal to 5gsm).Other scopes are also possible.In the embodiment that adhesive is present in more than one position, each position that has adhesive can independently comprise the adhesive of weight per unit area in above-mentioned one or more scopes.

[0170] In embodiments where the filter media includes one or more adhesives, the total unit weight of the adhesives together in the filter media (i.e., the sum of the unit weights of the adhesives at each location) can be greater than or equal to 0.05 gsm, greater than or equal to 0.1 gsm, greater than or equal to 0.2 gsm, greater than or equal to 0.5 gsm, greater than or equal to 1 gsm, greater than or equal to 2 gsm, or greater than or equal to 5 gsm. In some embodiments, the total unit weight of the adhesives together in the filter media can be less than or equal to 10 gsm, less than or equal to 5 gsm, less than or equal to 2 gsm, less than or equal to 1 gsm, less than or equal to 0.5 gsm, less than or equal to 0.2 gsm, or less than or equal to 0.1 gsm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.05 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.

[0171] When present, the adhesive can attach two or more layers between which the adhesive is positioned. The bond strength between the two layers can be relatively high. For example, the adhesive can attach the two layers together with a bond strength of greater than or equal to 100 g / inch. 2 , greater than or equal to 150g / inch 2 , greater than or equal to 200g / inch 2 , greater than or equal to 500g / inch 2 , greater than or equal to 750g / inch 2 , greater than or equal to 1000g / inch 2 , greater than or equal to 1250g / inch 2 , greater than or equal to 1500g / inch 2 , greater than or equal to 1750g / inch 2 , greater than or equal to 2000g / inch 2 , greater than or equal to 2250g / inch 2 , greater than or equal to 2500g / inch 2 , greater than or equal to 2750g / inch 2 , greater than or equal to 3000g / inch 2 , greater than or equal to 3250g / inch 2 , greater than or equal to 3500g / inch 2 , greater than or equal to 3750g / inch 2 , greater than or equal to 4000g / inch 2 , greater than or equal to 4250g / inch 2 , greater than or equal to 4500g / inch 2 , or greater than or equal to 4750g / inch 2In some embodiments, the adhesive attaches the two layers together with a bond strength of less than or equal to 5000 g / inch 2 , less than or equal to 4750g / inch 2 , less than or equal to 4500g / inch 2 , less than or equal to 4250g / inch 2 , less than or equal to 4000g / inch 2 , less than or equal to 3750g / inch 2 , less than or equal to 3500g / inch 2 , less than or equal to 3250g / inch 2 , less than or equal to 3000g / inch 2 , less than or equal to 2750g / inch 2 , less than or equal to 2500g / inch 2 , less than or equal to 2250g / inch 2 , less than or equal to 2000g / inch 2 , less than or equal to 1750g / inch 2 , less than or equal to 1500g / inch 2 , less than or equal to 1250g / inch 2 , less than or equal to 1000g / inch 2 , less than or equal to 750g / inch 2 , less than or equal to 500g / inch 2 , less than or equal to 200g / inch 2 , or less than or equal to 150g / inch 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 100 g / inch 2 And less than or equal to 5000g / inch 2 , or greater than or equal to 150g / inch 2 And less than or equal to 3000g / inch 2 ). Other ranges are also possible. In embodiments where adhesive is present at more than one location, each location where adhesive is present can independently contain adhesive attaching two layers together with a bond strength in one or more of the above ranges. In some embodiments, the entire filter media as a whole has an internal bond strength in one or more of the above ranges. The bond strength of the entire filter media as a whole is equivalent to the weakest bond strength between the two layers of the media.

[0172] The bonding strength (e.g., internal bonding strength) between two layers (e.g., between two layers attached together by an adhesive) can be determined by using a z-direction peel strength test. In short, the bonding strength can be determined by the following steps. First, a 1 inch × 1 inch sample is mounted on a steel block measuring 1 inch × 1 inch × 0.5 inch using double-sided tape. The sample block is then mounted on the non-traverse head of the tensile tester with double-sided tape and another steel block of the same size is connected to the traverse head. The traverse head is lowered and bonded to the sample on the steel block of the non-traverse head. Sufficient pressure is applied so that the steel blocks are bonded together via the mounted samples. The traverse head is then moved at a traverse speed of 1 inch / minute, and the maximum load is obtained from the peak of the stress-strain curve. The bonding strength (e.g., internal bonding strength) between the two layers is considered to be equivalent to the maximum load measured by this step.

[0173] The filter medium has any suitable thickness. For example, in some embodiments, the filter medium has a thickness greater than or equal to 0.01 mm, greater than or equal to 0.1 mm, greater than or equal to 0.05 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, greater than or equal to 7 mm, greater than or equal to 8 mm, greater than or equal to 9 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 certain embodiments, the filter medium has a thickness of less than or equal to 30 mm, less than or equal to 28 mm, less than or equal to 25 mm, less than or equal to 23 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 13 mm, less than or equal to 10 mm, less than or equal to 9 mm, less than or equal to 8 mm, less than or equal to 7 mm, less than or equal to 6 mm, less than or equal to 5 mm, less than or equal to 4 mm, less than or equal to 3 mm, less than or equal to 2 mm, or less than or equal to 1 mm. Combinations of these ranges are also possible (e.g., greater than or equal to 0.01 mm and less than or equal to 30 mm, or greater than or equal to 0.1 mm and less than or equal to 20 mm). The thickness can be determined according to ISO 534 (2011) at 2 N / cm 2 Next measurement.

[0174] The filter media can have any suitable weight per unit area. For example, in certain embodiments, the filter media has a weight per unit area of ​​greater than or equal to 5 gsm, greater than or equal to 10 gsm, greater than or equal to 15 gsm, greater than or equal to 20 gsm, greater than or equal to 30 gsm, greater than or equal to 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, or greater than or equal to 400 gsm. In some cases, 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, or less than or equal to 50 gsm. Combinations of these ranges are also possible (e.g., greater than or equal to 5 gsm and less than or equal to 500 gsm, greater than or equal to 10 gsm and less than or equal to 300 gsm, or greater than or equal to 10 gsm and less than or equal to 200 gsm). The weight per unit area can be measured according to ISO 536:2012.

[0175] The filter media can have any suitable mean flow pore size. For example, in some cases, the filter media has a mean flow pore size of greater than or equal to 0.001 microns, greater than or equal to 0.01 microns, 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 0.7 microns, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 3 microns, greater than or equal to 5 microns, greater than or equal to 7 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, greater than or equal to 40 microns, 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, or greater than or equal to 90 microns. In some cases, the mean flow pore size of the filter media is less than or equal to 100 microns, less than or equal to 95 microns, less than or equal to 90 microns, less than or equal to 85 microns, less than or equal to 80 microns, less than or equal to 75 microns, less than or equal to 70 microns, less than or equal to 65 microns, less than or equal to 60 microns, less than or equal to 55 microns, less than or equal to 50 microns, less than or equal to 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 3 microns, less than or equal to 2 microns, or less than or equal to 1 micron. Combinations of these ranges are also possible (e.g., greater than or equal to 0.001 micron and less than or equal to 100 microns, greater than or equal to 0.01 micron and less than or equal to 50 microns, or greater than or equal to 0.01 micron and less than or equal to 20 microns). The mean flow pore size can be measured according to ASTM F-316 (2003).

[0176] The filter media can have any suitable maximum pore size. For example, in certain embodiments, the maximum pore size of the filter media is 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 0.7 micron, greater than or equal to 1 micron, greater than or equal to 3 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 30 microns, greater than or equal to 40 microns, 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 125 microns, greater than or equal to 150 microns, or greater than or equal to 175 microns. In some embodiments, the maximum pore size of the filter medium is less than or equal to 200 microns, less than or equal to 190 microns, less than or equal to 180 microns, less than or equal to 170 microns, less than or equal to 160 microns, less than or equal to 150 microns, less than or equal to 140 microns, less than or equal to 130 microns, less than or equal to 120 microns, less than or equal to 110 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, less than or equal to 60 microns, 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 10 microns, less than or equal to 5 microns, less than or equal to 3 microns, or less than or equal to 1 micron. Combinations of these ranges are also possible (e.g., greater than or equal to 0.1 micron and less than or equal to 200 microns, greater than or equal to 0.3 microns and less than or equal to 100 microns, or greater than or equal to 0.3 microns and less than or equal to 50 microns). The maximum pore size may be determined according to ASTM F316 (2003).

[0177] The filter media can have any suitable total Gurley bending stiffness (e.g., in the machine direction and / or in the cross direction). For example, in some cases, the filter media has a total Gurley bending stiffness (e.g., in the machine direction and / or in the cross direction) of greater than or equal to 1 mg, greater than or equal to 5 mg, greater than or equal to 10 mg, greater than or equal to 15 mg, greater than or equal to 20 mg, greater than or equal to 25 mg, greater than or equal to 50 mg, greater than or equal to 75 mg, greater than or equal to 100 mg, greater than or equal to 150 mg, greater than or equal to 200 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 750 mg, greater than or equal to 1000 mg, greater than or equal to 1500 mg, greater than or equal to 2000 mg, greater than or equal to 2500 mg, or greater than or equal to 3000 mg. In certain embodiments, the total Gurley bending stiffness of the filter media (e.g., in the machine direction and / or in the transverse direction) is less than or equal to 3500 mg, less than or equal to 3250 mg, less than or equal to 3000 mg, less than or equal to 2750 mg, less than or equal to 2500 mg, less than or equal to 2250 mg, less than or equal to 2000 mg, less than or equal to 1500 mg, less than or equal to 1000 mg, less than or equal to 750 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 200 mg, or less than or equal to 150 mg. Combinations of these ranges are also possible (e.g., greater than or equal to 1 mg and less than or equal to 3500 mg, greater than or equal to 10 mg and less than or equal to 3000 mg, or greater than or equal to 25 mg and less than or equal to 3000 mg). The total Gurley bending stiffness (e.g., in the machine direction and / or in the transverse direction) can be measured according to T543 om-94.

[0178] The filter media can have any suitable air permeability. For example, in some embodiments, the filter media has an air permeability of greater than or equal to 0.2 CFM, greater than or equal to 0.5 CFM, greater than or equal to 1 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 30 CFM, greater than or equal to 40 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 125 CFM, greater than or equal to 150 CFM, greater than or equal to 175 CFM, greater than or equal to 200 CFM, greater than or equal to 250 CFM, greater than or equal to 300 CFM, greater than or equal to 400 CFM, greater than or equal to 500 CFM, greater than or equal to 600 CFM, greater than or equal to 700 CFM, or greater than or equal to 800 CFM. In certain embodiments, the air permeability of the filter medium is 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 250 CFM, less than or equal to 200 CFM, less than or equal to 175 CFM, less than or equal to 150 CFM, less than or equal to 125 CFM, less than or equal to 100 CFM, less than or equal to 75 CFM, less than or equal to 50 CFM, less than or equal to 40 CFM, or less than or equal to 30 CFM. Combinations of these ranges are also possible (e.g., greater than or equal to 0.2 CFM and less than or equal to 1000 CFM, or greater than or equal to 0.5 CFM and less than or equal to 800 CFM). The air permeability can be measured according to ASTM D737-04 (2016) at a pressure of 125 Pa.

[0179] In some embodiments, the filter medium has a relatively high water permeability. For example, in some embodiments, the water permeability of the filter medium is greater than or equal to about 2 ml / min·cm 2 psi, greater than or equal to about 3 ml / min·cm 2 psi, greater than or equal to about 4 ml / min·cm 2 psi, greater than or equal to about 5 ml / min·cm 2 psi, greater than or equal to about 6 ml / min·cm 2 psi, greater than or equal to about 7 ml / min·cm 2 psi, or greater than or equal to about 8 ml / min·cm 2 ·psi. In some cases, the water permeability of the filter medium is less than or equal to about 9 ml / min·cm 2psi, less than or equal to about 8 ml / min·cm 2 psi, less than or equal to about 7 ml / min·cm 2 psi, less than or equal to about 6 ml / min·cm 2 psi, less than or equal to about 5 ml / min·cm 2 psi, less than or equal to about 4 ml / min·cm 2 psi, or less than or equal to about 3 ml / min·cm 2 It should be understood that all combinations of the above ranges are possible (e.g., greater than or equal to about 2 ml / min·cm 2 psi and less than or equal to about 9 ml / min·cm 2 ·psi, or greater than or equal to about 3 ml / min·cm·psi and less than or equal to about 6 ml / min·cm 2 psi). Other ranges are also possible.

[0180] Water permeability is the water flux divided by the pressure used to determine the water flow rate (e.g., 20 psi). The water flow rate is calculated by passing deionized water through an effective filtration area of ​​12.5 cm at a pressure of 20 psi. 2 The water flux is measured by measuring the time it takes for a filter medium or fiber web to collect 1,000 ml of water. The flow rate is determined by measuring the time until 1,000 ml of water is collected. The water flux is calculated by dividing the flow rate (ml / min) by the sample active area (cm 2 ) (i.e., the area exposed to the fluid flow) and is calculated as ml / min-cm 2 express.

[0181] The filter media can have any suitable dust holding capacity. For example, in some cases, the filter media has a dust holding capacity of greater than or equal to 1 gsm, greater than or equal to 2 gsm, greater than or equal to 3 gsm, greater than or equal to 4 gsm, greater than or equal to 5 gsm, greater than or equal to 6 gsm, greater than or equal to 7 gsm, greater than or equal to 8 gsm, greater than or equal to 9 gsm, greater than or equal to 10 gsm, greater than or equal to 15 gsm, greater than or equal to 20 gsm, greater than or equal to 30 gsm, greater than or equal to 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, or greater than or equal to 400 gsm. In some cases, the dust holding capacity of the filter media is less than or equal to 500 gsm, less than or equal to 475 gsm, less than or equal to 450 gsm, less than or equal to 425 gsm, less than or equal to 400 gsm, less than or equal to 375 gsm, less than or equal to 350 gsm, less than or equal to 325 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 100 gsm, less than or equal to 75 gsm, less than or equal to 50 gsm, less than or equal to 40 gsm, less than or equal to 30 gsm, or less than or equal to 20 gsm. Combinations of these ranges are also possible (e.g., greater than or equal to 1 gsm and less than or equal to 500 gsm, or greater than or equal to 10 gsm and less than or equal to 450 gsm). Dust holding capacity can be measured according to ISO 19438 2003) using ISO intermediate test dust (A3).

[0182] The filter media can have any suitable gamma (e.g., at most penetrating particle size (MPPS) or at 0.09 microns). For example, in some cases, the filter media has a gamma (e.g., at MPPS or at 0.09 microns) greater than or equal to 3, greater than or equal to 4, greater than or equal to 5, greater than or equal to 6, greater than or equal to 7, greater than or equal to 8, greater than or equal to 9, greater than or equal to 10, greater than or equal to 12, 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 40, greater than or equal to 50, greater than or equal to 75, greater than or equal to 100, greater than or equal to 125, greater than or equal to 150, greater than or equal to 200, or greater than or equal to 250. In some cases, the filter media has a gamma (e.g., at MPPS or at 0.09 microns) of 400 or less, 375 or less, 350 or less, 325 or less, 300 or less, 275 or less, 250 or less, 200 or less, 150 or less, 125 or less, 100 or less, 75 or less, 50 or less, 40 or less, 30 or less, or 25 or less. Combinations of these ranges are also possible (e.g., 3 or more and 400 or less, 4 or more and 300 or less).

[0183] γ is defined by the following formula: γ = (-log 10(% penetration / 100) / (average pressure drop, mm H2O)×100. The penetration (usually expressed as a percentage) is defined as follows: penetration (%) = (C / C0)*100, where C is the particle concentration after passing through the filter, and C0 is the particle concentration before passing through the filter. The penetration (and γ) can be measured at any desired particle size (e.g., MPPS or 0.09 microns). The MPPS penetration is the penetration of the most penetrating particle size; in other words, when the penetration is measured for a range of particle sizes, the MPPS penetration is the penetration value measured for the particle with the highest penetration. The penetration (e.g., MPPS penetration) and the average pressure drop can be measured for any particle size using the EN1822:2009 standard for air filtration described below. The penetration and average pressure drop can be measured by blowing dioctyl phthalate (DOP) particles through the filter medium and measuring the percentage of particles that pass through the filter medium and the pressure drop when the particles are blown through the filter medium. This can be accomplished 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. The TSI 3160 automated filter test unit is used to measure the DOP aerosol at 100 cm above the upstream surface of the filter media. 2 DOP particle groups with different average particle sizes are sequentially blown at the surface area. The particle groups can be blown at the upstream surface of the filter medium in the order of increasing average diameter, each with a geometric standard deviation of less than 1.3, and having 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 filter medium, the penetration rate and the average pressure drop are continuously and individually measured for each particle group. The upstream and downstream particle concentrations are measured by using a condensation particle counter. During the penetration measurement, 100 cm of the upstream surface of the filter medium is blown. 2 The surface area was subjected to a continuous load of DOP particles at an airflow of 12 L / min (producing a media face velocity of 2 cm / sec). Each particle population was blown at the upstream surface of the filter media for 120 seconds or so that at least 1000 particles were counted downstream of the filter media, whichever was longer.

[0184] To determine the MPPS penetration, the instrument measures the penetration value across the filter medium (or layer) by determining the DOP particle size at the highest penetration level measured for the test (i.e., the most penetrating particle size (MPPS)). The sample is sequentially exposed to particles of each size. The penetration of the particles is plotted as a function of the particle size, and a parabolic function is fitted to the data. Then, the maximum value of the parabolic function is found; the particle size at the maximum value is the most penetrating particle size (MPPS), and the penetration at the maximum value is the penetration at the MPPS.

[0185] The filter media can have any suitable efficiency (e.g., overall efficiency). For example, in some embodiments, the filter media has an efficiency (e.g., overall efficiency) greater than or equal to 10%, greater than or equal to 20%, greater than or equal to 30%, greater than or equal to 40%, greater than or equal to 50%, greater than or equal to 60%, greater than or equal to 70%, greater than or equal to 80%, greater than or equal to 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 99.9%, greater than or equal to 99.99%, greater than or equal to 99.999%, greater than or equal to 99.9999%, or greater than or equal to 99.99999%. In some embodiments, the efficiency (e.g., overall efficiency) of the filter media is less than 100%, less than or equal to 99.999999%, less than or equal to 99.999999%, less than or equal to 99.99999%, less than or equal to 99.99999%, less than or equal to 99.9999%, less than or equal to 99.999%, less than or equal to 99.99%, less than or equal to 99.9%, less than or equal to 99.5%, less than or equal to 99%, 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%, or less than or equal to 80%. Combinations of these ranges are also possible (e.g., greater than or equal to 10% and less than 100%, greater than or equal to 10% and less than or equal to 99.9999999%, greater than or equal to 30% and less than or equal to 99.9999999%, or greater than or equal to 40% and less than or equal to 99.9999999%). The efficiency can be determined by the following equation: Efficiency (%) = 100 - Penetration (%), where the penetration is determined as described above at any particle size (e.g., at 0.09 microns).

[0186] The filter media can have any suitable pressure drop. In certain embodiments, the filter media has a pressure drop of greater than or equal to 0.05 kPa, greater than or equal to 0.1 kPa, greater than or equal to 0.3 kPa, greater than or equal to 0.5 kPa, greater than or equal to 1 kPa, greater than or equal to 3 kPa, greater than or equal to 5 kPa, greater than or equal to 10 kPa, greater than or equal to 15 kPa, greater than or equal to 20 kPa, greater than or equal to 25 kPa, greater than or equal to 30 kPa, greater than or equal to 40 kPa, greater than or equal to 50 kPa, greater than or equal to 60 kPa, greater than or equal to 70 kPa, greater than or equal to 80 kPa, or greater than or equal to 90 kPa. In some embodiments, the pressure drop of the filter media is less than or equal to 100 kPa, less than or equal to 95 kPa, less than or equal to 90 kPa, less than or equal to 85 kPa, less than or equal to 80 kPa, less than or equal to 75 kPa, less than or equal to 70 kPa, less than or equal to 65 kPa, less than or equal to 60 kPa, less than or equal to 55 kPa, less than or equal to 50 kPa, less than or equal to 45 kPa, less than or equal to 40 kPa, less than or equal to 35 kPa, less than or equal to 30 kPa, less than or equal to 25 kPa, less than or equal to 20 kPa, less than or equal to 15 kPa, less than or equal to 10 kPa, or less than or equal to 5 kPa. Combinations of these ranges are also possible (e.g., greater than or equal to 0.05 kPa and less than or equal to 100 kPa, greater than or equal to 0.1 kPa and less than or equal to 95 kPa, or greater than or equal to 0.1 kPa and less than or equal to 90 kPa). The pressure drop can be measured according to ASTM D2 986-91.

[0187] The filter medium can have any suitable salt (e.g., NaCl) loading capacity. For example, in some cases, the filter medium has a salt (e.g., NaCl) loading capacity greater than or equal to 0.1 g / m 2 , greater than or equal to 0.3g / m 2 , greater than or equal to 0.5g / m 2 , greater than or equal to 0.7g / m 2 , greater than or equal to 1g / m 2 , greater than or equal to 2g / m 2 , greater than or equal to 3g / m 2 , greater than or equal to 4g / m 2 , greater than or equal to 5g / m 2 , greater than or equal to 6g / m 2 , greater than or equal to 7g / m 2 , greater than or equal to 8g / m 2 , greater than or equal to 9g / m 2 , greater than or equal to 10g / m 2, greater than or equal to 12g / m 2 , greater than or equal to 15g / 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 , or greater than or equal to 35g / m 2 In some cases, the salt (e.g., NaCl) loading capacity of the filter medium is less than or equal to 40 g / m 2 , less than or equal to 38g / m 2 , less than or equal to 35g / m 2 , less than or equal to 33g / m 2 , less than or equal to 30g / m 2 , less than or equal to 28g / m 2 , less than or equal to 25g / m 2 , less than or equal to 20g / m 2 , less than or equal to 15g / m 2 , less than or equal to 10g / m 2 , less than or equal to 5g / m 2 , less than or equal to 4g / m 2 , less than or equal to 3g / m 2 , less than or equal to 2g / m 2 , or less than or equal to 1g / m 2 Combinations of these ranges are also possible (e.g., greater than or equal to 0.1 g / m 2 And less than or equal to 40g / m 2 , or greater than or equal to 0.5g / m 2 And less than or equal to 30g / m 2 The salt (e.g., NaCl) loading capacity of the filter medium can be determined by dividing the nominal exposure area by 100 cm 2 The filter media was exposed to 15 mg / m 3 The concentration of salt (e.g., NaCl) particles with a median diameter of 0.26 micrometers at a face velocity of 5.3 cm / sec can be determined using an 8130 CertiTest equipped with a salt (e.g., NaCl) generator from TSI, Inc. TM The 8130 was operated in continuous mode with one pressure drop reading approximately every minute. A 100 cm 2 Filter media samples, containing 15mg / m 3The test was run at a flow rate of 32 liters per minute of salt (e.g., NaCl) (face velocity 5.3 cm / sec) until the pressure drop across the filter media increased by 250 Pa. The salt (e.g., NaCl) loading capacity was determined by weighing the filter media both before and after the test and dividing the measured mass increase by the area of ​​the filter media to obtain the salt (e.g., NaCl) loading capacity per unit area of ​​the filter media.

[0188] The filter media can have any suitable DOP oil loading capacity (e.g., while maintaining a pressure drop of less than or equal to 50 mm H2O). For example, in certain embodiments, the filter media has a DOP oil loading capacity (e.g., while maintaining a pressure drop of less than or equal to 50 mm H2O) greater than or equal to 1 g / m 2 , greater than or equal to 2g / m 2 , greater than or equal to 3g / m 2 , greater than or equal to 4g / m 2 , greater than or equal to 5g / m 2 , greater than or equal to 7g / m 2 , greater than or equal to 10g / m 2 , greater than or equal to 12g / m 2 , greater than or equal to 15g / m 2 , greater than or equal to 20g / m 2 , greater than or equal to 30g / m 2 , greater than or equal to 40g / m 2 , greater than or equal to 50g / m 2 , greater than or equal to 60g / m 2 , or greater than or equal to 70g / m 2 In some embodiments, the DOP oil loading capacity of the filter media (e.g., while maintaining a pressure drop of less than or equal to 50 mm H2O) is less than or equal to 80 g / 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 40g / m 2 , less than or equal to 30g / m 2 , less than or equal to 20g / m 2 , less than or equal to 15g / m 2 , less than or equal to 12g / m 2 , less than or equal to 10g / m 2 , less than or equal to 7g / m2 , or less than or equal to 6g / m 2 Combinations of these ranges are also possible (e.g., greater than or equal to 1 g / m 2 And less than or equal to 80g / m 2 , greater than or equal to 3g / m 2 And less than or equal to 70g / m 2 , or greater than or equal to 4g / m 2 And less than or equal to 70g / m 2 ).

[0189] Typically, the DOP oil loading process is performed by placing 100 cm of the filter media 2 The test area was exposed to a concentration of 80 mg / m 3 Up to 100 mg / m 3 , flow rate of 32L / min, and face velocity of 5.32cm / sec in an aerosol of DOP particles. The DOP particles are produced by a TDA 100P aerosol generator available from Air Techniques International and have a count median diameter of 0.18 microns, a mass mean diameter of 0.3 microns, and a geometric standard deviation of less than 1.6 microns. Depending on the specific test, the characteristics of different filter media can be determined continuously or by pausing the DOP oil load to perform one or more measurements during the DOP oil load. For example, the pressure drop across the filter media can be measured continuously as a function of the DOP oil load. The DOP oil load or DOP weight in the filter media per filter media area can be determined by measuring the pressure drop during the DOP oil load, stopping the oil load after the pressure drop doubles; and then weighing the filter media. Any increase in the filter media weight is attributed to the DOP oil, and therefore the DOP oil load is determined by taking the difference between the measured weight and the filter media that does not initially contain DOP. Other parameters (eg, penetration at MPPS, gamma) may also be determined during or after DOP oil loading by performing measurements as described herein.

[0190] In some embodiments, the filter media as a whole (e.g., a filter media including: one or more layers having oleophobic properties, such as one or more layers comprising an oleophobic component, one or more layers having an oil grade greater than or equal to 1, and / or one or more surface modified layers) can perform particularly well after undergoing a DOP oil loading process. Such performance characteristics can include: the filter media having a relatively low pressure drop after undergoing a DOP oil loading process; having a relatively low change in pressure drop after undergoing a DOP oil loading process compared to the same media before the DOP oil loading process; having a relatively low penetration rate at MPPS after undergoing a DOP oil loading process; having a relatively low change in penetration rate at MPPS after undergoing a DOP oil loading process compared to the same media before the DOP oil loading process; having a high gamma value after undergoing a DOP oil loading process; and / or having a relatively low change in gamma value after undergoing a DOP oil loading process compared to the same media before the DOP oil loading process.

[0191] In some embodiments, the filter media described herein can be designed for sterile filtration. In some such embodiments, the particle efficiency can be very high. In some embodiments, the particle efficiency of the filter media can be expressed in terms of log reduction value (i.e., LRV), which is a quantitative measure of the retention of microorganisms by the filter media. LRV is the permeability -1 The logarithm of and is expressed as follows:

[0192] LRV = Log{[CFU] 挑战物 / [CFU] 流出物 ]}

[0193] Where [CFU] 挑战物 is the total number of bacteria in colony forming units in the fluid before passing through the filter media and / or fiber mesh, and [CFU] 流出物 It is the total number of bacteria in colony forming units in the fluid after passing through the filter media and / or fiber web.

[0194] LRV can be determined using ASTM F838-05. When [CFU] 流出物 When [CFU] is zero, the filtered medium is considered sterile; however, if [CFU] 流出物 is zero, then one is used in the above equation to calculate the LRV. In short, for 76 cm 2 The sample area can be treated with a concentration of 10 7 CFU / 1cm 2 The sample area contains microorganisms (e.g., Brevundimonas diminuta) as the challenge. Therefore, [CFU] 挑战物 7.6×10 8An LRV of 8.88 or greater is considered sterile.

[0195] In some embodiments, the LRV of the filter medium for one or more microorganisms is greater than or equal to 4, greater than or equal to 5, greater than or equal to 6, greater than or equal to 7, greater than or equal to 8, greater than or equal to 8.88, greater than or equal to 9, or greater than or equal to 10. In some embodiments, the LRV of the filter medium for one or more microorganisms is less than or equal to 11, less than or equal to 10, or less than or equal to 9. Combinations of these ranges are also possible (e.g., greater than or equal to 4 and less than or equal to 11, greater than or equal to 8 and less than or equal to 11, greater than or equal to 8.88 and less than or equal to 11, or greater than or equal to 9 and less than or equal to 10). Examples of microorganisms include Serratia marcescens, Saccharomyces cerevisiae, Oenococcus oeni, Dekkera bruxellensis, and / or Bravimonus diminuta.

[0196] In some embodiments (when the article described herein is a filter medium), the filter medium can be incorporated into various filter elements for various filtering applications. Exemplary types of filters include biological treatment filters, chemical treatment filters, industrial treatment filters, medical filters (e.g., blood filters), ventilation filters, air filters, and water filters. The filter medium can be suitable for filtering gas or liquid. Water and / or air filters can be used to remove microorganisms, viral particles, and / or other pollutants. For example, the filter medium suitable for water filtration can be used to treat municipal water, wastewater, residential water, and / or industrial water (e.g., mining water, cooling tower / boiler water, nuclear water, semiconductor, and biopharmaceutical industry ultrapure water production). During use, when fluid (e.g., water) flows through the filter medium, the filter medium can mechanically trap pollutant particles on the filter medium.

[0197] The filter media described herein can be suitable for filtering a variety of fluids. For example, the filter media described herein can be a liquid filter and / or an air filter. The liquid can be water, fuel or another fluid. For example, the fluid can include diesel, hydraulic fluid, oil and / or other hydrocarbon liquids. Some methods can include using the filter media described herein to filter fluids, such as filtering liquids (e.g., water, fuel) or filtering air. The method can include passing the fluid (e.g., fluid to be filtered) through the filter media. When the fluid passes through the filter media, the components filtered from the fluid can be retained on the upstream side of the filter media and / or in the filter media. The filtrate can pass through the filter media.

[0198] In some embodiments, the filter medium is an air filter. For example, in some cases, the filter medium is a high efficiency particulate air (HEPA) filter or an ultra-low penetration air (ULPA) filter. These filters are required to remove particles at the efficiency level specified by EN1822:2009. In some embodiments, the filter medium removes particles with an efficiency greater than 99.95% (H 13), greater than 99.995% (H 14), greater than 99.9995% (U 15), greater than 99.99995% (U 16) or greater than 99.999995% (U 17). For example, in some embodiments, the ULPA U15 filter medium disclosed herein has an efficiency greater than 99.9995% at a particle size of 0.12 microns (or a particle size of 0.09 microns). As another example, in certain embodiments, the HEPA H14 filter media disclosed herein has an efficiency greater than 99.995% at a 0.2 micron particle size (e.g., or a 0.1 micron particle size or a 0.09 micron particle size). In some embodiments, the filter media may be suitable for HVAC applications. For HVAC applications, the efficiency may be measured at 0.3 microns according to ISO 16890 (2016). That is, the particle efficiency of the filter media may be greater than or equal to about 10% and less than or equal to about 90% or greater than or equal to about 35% and less than or equal to about 90%. In certain embodiments, the filter media is an air conditioning filter. According to some embodiments, the filter media is a gas turbine filter.

[0199] In some embodiments, the filter medium is post-processed. For example, in certain embodiments, the filter medium is corrugated (e.g., to increase surface area). In some embodiments, the filter medium is embossed. In some cases, the filter medium is waved. Examples of waved filter media are disclosed in International Patent Application No. PCT / US2008 / 055088 filed on February 27, 2008 (which is disclosed as WO 2008 / 106490) and International Patent Application No. PCT / US2018 / 023518 filed on March 21, 2018 (which is disclosed as WO 2018 / 175550), and are hereby incorporated by reference in their entirety.

[0200] In some embodiments, filter medium can be the component of filter element.That is, filter medium can be incorporated into the article suitable for end-user use.The limiting examples of suitable filter element include flat plate filter, bag filter, V-type filter (V-bank filters) (including, for example, 1 to 24 V), cartridge filter, cylindrical filter, conical filter and curved filter.Filter element can have any suitable height (for example, 2 inches to 124 inches for flat plate filter, 4 inches to 124 inches for V-type filter, 1 inch to 124 inches for cartridge filter medium and cylindrical filter medium).Filter element can also have any suitable width (2 inches to 124 inches for flat plate filter, 4 inches to 124 inches for V-type filter).Some filter media (for example, cartridge filter medium, cylindrical filter medium) can be characterized by diameter instead of width; These filter media can have the diameter (for example, 1 inch to 124 inches) of any suitable value. Filter elements typically include a frame that may be made from one or more materials such as cardboard, aluminum, steel, alloys, wood, and polymers.

[0201] In some embodiments, the filter media (e.g., in a filter element) can be pleated (e.g., rotary pleated and / or blade pleated). In some embodiments, the pleat height can be greater than or equal to 10 mm, greater than or equal to 15 mm, greater than or equal to 20 mm, greater than or equal to 25 mm, greater than or equal to 30 mm, greater than or equal to 35 mm, greater than or equal to 40 mm, greater than or equal to 45 mm, greater than or equal to 50 mm, greater than or equal to 53 mm, greater than or equal to 55 mm, greater than or equal to 60 mm, greater than or equal to 65 mm, greater than or equal to 70 mm, greater than or equal to 75 mm, greater than or equal to 80 mm, greater than or equal to 85 mm, greater than or equal to 90 mm, greater than or equal to 100 mm, greater than or equal to 110 mm, greater than or equal to 111 mm, greater than or equal to 112 mm, greater than or equal to 113 mm, greater than or equal to 114 mm, greater than or equal to 115 mm, greater than or equal to 116 mm, greater than or equal to 117 mm, greater than or equal to 118 mm, greater than or equal to 119 mm, greater than or equal to 120 mm, greater than or equal to 121 mm, greater than or equal to 122 mm, greater than or equal to 123 mm, greater than or equal to 124 mm, greater than or equal to 125 mm, greater than or equal to 126 mm, greater than or equal to 127 mm, greater than or equal to 128 mm, greater than or equal to 129 mm, greater than or equal to 130 mm, greater than or equal to 131 mm, greater than or equal to 132 mm, greater than or equal to 133 mm, or equal to 95mm, greater than or equal to 100mm, greater than or equal to 125mm, greater than or equal to 150mm, greater than or equal to 175mm, greater than or equal to 200mm, greater than or equal to 225mm, greater than or equal to 250mm, greater than or equal to 275mm, greater than or equal to 300mm, greater than or equal to 325mm, greater than or equal to 350mm, greater than or equal to 375mm, greater than or equal to 400mm, greater than or equal to 425mm, greater than or equal to 450mm, greater than or equal to 475mm, or greater than or equal to 500mm. In some embodiments, the pleat height can be less than or equal to 510 mm, less than or equal to 500 mm, less than or equal to 475 mm, less than or equal to 450 mm, less than or equal to 425 mm, less than or equal to 400 mm, less than or equal to 375 mm, less than or equal to 350 mm, less than or equal to 325 mm, less than or equal to 300 mm, less than or equal to 275 mm, less than or equal to 250 mm, less than or equal to 225 mm, less than or equal to 200 mm, less than or equal to 175 mm, less than or equal to 150 mm, less than or equal to 12 5mm, less than or equal to 100mm, less than or equal to 95mm, less than or equal to 90mm, less than or equal to 85mm, less than or equal to 80mm, less than or equal to 75mm, less than or equal to 70mm, less than or equal to 65mm, less than or equal to 60mm, less than or equal to 55mm, less than or equal to 53mm, less than or equal to 50mm, less than or equal to 45mm, less than or equal to 40mm, less than or equal to 35mm, less than or equal to 30mm, less than or equal to 25mm, less than or equal to 20mm, or less than or equal to 15mm. Combinations of the above ranges are also possible (for example, greater than or equal to 10mm and less than or equal to 510mm, or greater than or equal to 10mm and less than or equal to 100mm). Other ranges are also possible.

[0202] In some embodiments, the pleat density (the number of pleats per unit length of the medium) of the filter media (e.g., in a filter element) can be greater than or equal to 5 pleats per 100 mm, greater than or equal to 6 pleats per 100 mm, greater than or equal to 10 pleats per 100 mm, greater than or equal to 15 pleats per 100 mm, greater than or equal to 20 pleats per 100 mm, greater than or equal to 25 pleats per 100 mm, greater than or equal to 28 pleats per 100 mm, greater than or equal to 30 pleats per 100 mm, or greater than or equal to 35 pleats per 100 mm. In some embodiments, the filter media can have a pleat density of 40 or less pleats per 100 mm, 35 or less pleats per 100 mm, 30 or less pleats per 100 mm, 28 or less pleats per 100 mm, 25 or less pleats per 100 mm, 20 or less pleats per 100 mm, 15 or less pleats per 100 mm, 10 or less pleats per 100 mm, or 6 or less pleats per 100 mm. Combinations of the above-referenced ranges are also possible (e.g., 5 or more pleats per 100 mm and 100 or less pleats per 100 mm, 6 or more pleats per 100 mm and 100 or less pleats per 100 mm, 25 or more pleats per 100 mm and 28 or less pleats per 100 mm). Other ranges are also possible.

[0203] Other pleat heights and pleat densities are also possible. For example, the filter medium in a flat filter or a V-type filter can have a pleat height of 1 / 4 inch to 24 inches and / or a pleat density of 1 pleat / inch to 50 pleats / inch. As another example, the filter medium in a cartridge filter or a conical filter can have a pleat height of 1 / 4 inch to 24 inches and / or a pleat density of 1 / 2 pleat / inch to 100 pleats / inch. In some embodiments, the pleats can be separated by a pleat separator made of, for example, polymer, glass, aluminum and / or cotton. In other embodiments, the filter element can be free of a pleat separator. The filter medium can be a line backing, or it can be self-supporting.

[0204] In some cases, the filter element includes a housing that can be arranged around the filter medium. The housing can have various configurations, and the configuration varies based on the intended application. In some embodiments, the housing can be formed by a frame arranged to surround the filter medium periphery. For example, the frame can be thermally sealed around the periphery. In some cases, the frame has a generally rectangular configuration around all four sides of a generally rectangular filter medium. The frame can be formed by various materials, including any combination of, for example, cardboard, metal, polymer, or suitable material. The filter element can also include a variety of other features known in the art, such as stabilization features or any other suitable features for stabilizing the filter medium relative to the frame, spacers, etc.

[0205] In one group of embodiments, filter medium as herein described is incorporated into the filter element with cylindrical configuration, and it can be applicable to hydraulic applications and other applications.Cylindrical filter element can include a steel support net that can provide pleat support and interval and protect medium from damage during processing and / or installation.Steel support net can be positioned into upstream layer and / or downstream layer.Filter element can also include upstream support layer and / or downstream support layer that can protect filter medium during pressure fluctuation.These layers can be combined with filter medium 10, and it can include two or more layers as above.

[0206] In one group of embodiments, filter media as described herein is incorporated into a fuel filter element (e.g., a cylindrical fuel filter element). The fuel filter element can be of different types, e.g., a fuel filter element for removing particulates, a fuel-water separator for removing water from diesel fuel, and a fuel filter element for performing both particulate separation and water separation. The fuel filter element can be a single-stage element or a multi-stage element. In some cases, the medium can be pleated or wound, supported or unsupported, wound / pleated with a variety of media. In some designs, the medium is pleated, with a wound core at the center.

[0207] In some embodiments, filter media as described herein is incorporated into a fuel-water separator. The fuel-water separator can have a bowl-shaped design that collects water at the bottom. Depending on the water collection, water can be collected upstream, downstream, or on both sides of the collection bowl. The water can then be discharged by opening the valve at the bottom of the bowl and letting the water flow out until only fuel / diesel is contained in the bowl. In some embodiments, the fuel-water separator can include a water sensor so that if the water reaches a warning level, a signal is sent to the engine control unit, or a signal is sent directly to the driver. The fuel-water separator can also include a sensor that can alert the operator when the filter needs to be discharged. In some cases, a heater can be positioned near the filter to help avoid forming paraffin (under low temperature conditions) inside the filter that may prevent fuel from flowing to the engine.

[0208] The filter element can also have any suitable size. For example, the length of the filter element can be at least 15 inches, at least 20 inches, at least 25 inches, at least 30 inches, at least 40 inches, or at least 45 inches. The surface area of ​​the filter medium can be, for example, at least 220 square inches, at least 230 square inches, at least 250 square inches, at least 270 square inches, at least 290 square inches, at least 310 square inches, at least 330 square inches, at least 350 square inches, or at least 370 square inches.

[0209] The filter element may have the same property values ​​as those described above with respect to the filter media.

[0210] The filter media described herein can have a variety of suitable designs and a variety of suitable arrangements of layers therein. Non-limiting examples of designs suitable for liquid filtration are shown in FIG. 4A to FIG. 4E A non-limiting example of a design suitable for a fuel filter is shown in FIG. 5A to FIG. 5E A non-limiting example of a design suitable for a hydraulic fluid filter is shown in Figures 6A to 6D A non-limiting example of a design suitable for a HEPA filter is shown in FIG. 7A to FIG. 7B It should be noted that these designs can also be adapted for other purposes. For example, in some cases, FIG. 4A to FIG. 7B Any of the designs may be suitable as a liquid filter, fuel filter, hydraulic fluid filter and / or HEPA filter. FIG. 4A to FIG. 4E , FIG. 5A to FIG. 5E , FIG. 6A to FIG. 6D ,as well as FIG. 7A to FIG. 7B The arrows shown in indicate the direction in which fluid will flow through the filter media. Other configurations are also possible.

[0211] For example, in some cases, the filter medium includes a meltblown calender layer (e.g., as a backing layer) and a fine fiber layer. In some cases, the meltblown calender layer and the fine fiber layer are directly adjacent. In certain embodiments, in addition to the meltblown calender layer and the fine fiber layer, the filter medium also includes additional additional layers.

[0212] As another example, in some embodiments, the filter media includes a wet-laid synthetic layer (e.g., as a backing layer) and a fine fiber layer. In some cases, the wet-laid synthetic layer and the fine fiber layer are directly adjacent. In certain embodiments, in addition to the wet-laid synthetic layer and the fine fiber layer, the filter media also includes an additional additional layer.

[0213] As another example, in some embodiments, the filter medium includes a cellulose layer (e.g., as a backing layer) and a fine fiber layer. In some cases, the cellulose layer and the fine fiber layer are directly adjacent. In some embodiments, in addition to the cellulose layer and the fine fiber layer, the filter medium also includes another additional layer.

[0214] Properties of some exemplary layers that may be included in the filter media are described below in Table 1, and additional properties of some exemplary filter media including these layers are described below in Tables 2 through 5. The properties in Tables 2 through 5 may be measured generally as described elsewhere herein.

[0215] The initial efficiency at 1.5 microns can be determined according to ISO 19438 (2003) using ISO fine test dust (A2), where the initial efficiency at 1.5 microns is the efficiency at 1.5 microns measured when the pressure drop reaches 5 kPa (5% of the final value of 100 kPa).

[0216] The average fuel-water separation efficiency can be measured according to the SAEJ1488 (2010) test. The test involves passing a fuel (ultra-low sulfur diesel) sample with a controlled water content (2500ppm) through the medium at a face velocity of 0.069cm / second by a pump. Water is emulsified into small droplets by a centrifugal pump running at 3500rpm, and then challenged with the medium. The water is coalesced, flowed out, or both coalesced and flowed out, and collected at the bottom of the shell. The water content of the samples upstream and downstream of the medium is measured via Karl Fischer titration. The fuel-water separation efficiency is the amount of water removed from the fuel-water mixture, and is equal to (1-C / 2500)*100%, where C is the concentration of downstream water. The average efficiency is the average of the efficiencies measured during the 150-minute test. The first measurement of the samples upstream and downstream of the medium is performed 10 minutes from the start of the test. Then, the samples downstream of the medium are measured every 20 minutes until 150 minutes have passed since the start of the test. The pressure of the sample upstream and downstream of the filter media was also measured at these points in time.

[0217] The micron rating of the β200 efficiency can be determined by conducting a multi-pass filtration test according to the ISO 16889 (2008) procedure (modified by testing flat sheet samples) on a multi-pass filtration test stand manufactured by FTI. The measurement can be made by flowing a test fluid containing ISO A3 intermediate test dust manufactured by PTI, Inc. at an upstream weight dust level of 10 mg / liter in aviation hydraulic fluid AERO HFAMIL H-5606A manufactured by Mobil through the filter media at a flow rate of 1.7 L / minute until a terminal pressure drop of 172 kPa is reached.

[0218] Table 1. Exemplary layers

[0219]

[0220] Table 2. Exemplary Liquid Filtration Media

[0221]

[0222]

[0223] Table 3. Exemplary fuel filter media

[0224]

[0225]

[0226] Table 4. Exemplary Hydraulic Filter Media

[0227]

[0228] Table 5. Exemplary HEPA Filter Media

[0229]

[0230] The following examples are intended to illustrate certain embodiments of the invention, but are not intended to illustrate the full scope of the invention.

[0231] Example 1

[0232] This example illustrates the preparation of fine fibers comprising a PVDF copolymer.

[0233] Fiber A and fiber B, both containing PVDF copolymers, were formed using an electrospinning process that differed only in the relative humidity and conductivity used. Fiber A was formed at a lower relative humidity and higher conductivity than fiber B. Scanning electron microscopy was used to measure the resulting fiber diameter. The average diameter of fiber A was 80nm to 100nm, while the average diameter of fiber B was 200nm to 220nm.

[0234] This example shows that relative humidity and conductivity can be controlled during the electrospinning process to reduce the fiber diameter of fibers comprising PVDF copolymers. This is unexpected because it is generally difficult to form fibers comprising PVDF and / or its copolymers with small fiber diameters.

[0235] Example 2

[0236] This example analyzes the surface nodule density of a fine fiber layer comprising fibers A from Example 1.

[0237] A scanning electron microscopy (SEM) image of a thin fiber layer comprising fibers A from Example 1 (average diameter 80 nm to 100 nm) was taken (see Figure 8 , which has 5,000x magnification). Figure 8 The circles in show several examples of nodules.

[0238] The surface nodule density was determined using SEM images and ImageJ software, as discussed in more detail elsewhere in this article. The surface nodule density of the fine fiber layer was determined to be 3.7 nodules / 100 μm 2 .

[0239] This example shows that even with a small fiber diameter, a low surface nodule density is obtained. This is unexpected because the surface nodule density generally increases with decreasing fiber diameter, so that for PVDF copolymer fibers of this diameter, the surface nodule density would be expected to be much higher.

[0240] Example 3

[0241] This example characterizes the mean flow pore size and maximum pore size of a filter media configuration including a fine fiber layer comprising Fiber A and Fiber B from Example 1.

[0242] The following four filter media were tested:

[0243] ● Sample A had three layers: a polybutylene terephthalate (PBT) meltblown layer, a fine fiber layer comprising Fiber A, and a calendered PBT meltblown layer.

[0244] ● Sample B has five layers: a polypropylene scrim layer, a PVDF meltblown layer, a fine fiber layer comprising Fiber A, a PVDF meltblown layer, and a polypropylene scrim layer.

[0245] ● Sample C has three layers: a PBT meltblown layer, a fine fiber layer comprising fiber B, and a calendered PBT meltblown layer.

[0246] ● Sample D has five layers: a calendered PBT meltblown layer, a fine fiber layer comprising fiber B, a PBT meltblown layer, a fine fiber layer comprising fiber B, and a calendered PBT meltblown layer.

[0247] Sample A and Sample C are identical except that Sample A contains Fiber A and Sample C contains Fiber B.

[0248] The mean flow pore size and maximum pore size of Samples A to D were measured according to ASTM F316 (2003). As shown in Table 6, by comparing Sample A and Sample C, when Fiber A is used instead of Fiber B, a lower mean flow pore size and maximum pore size are achieved. As shown in Table 6, when Fiber A is used, the configuration with only one fine fiber layer (i.e., Samples A and B) achieves a mean flow pore size of about 0.2 microns. In contrast, when Fiber B is used, only one fine fiber layer (see Sample C) is insufficient to achieve a mean flow pore size of about 0.2 microns, and instead two fine fiber layers are required (see Sample D).

[0249] Table 6. Mean flow pore (MFP) diameter and maximum pore size (Max Pore Size) of samples A to D

[0250] sample MFP size (micrometers) Maximum pore size (micrometers) Sample A 0.21 0.50 Sample B 0.21 0.52 Sample C 0.42 0.74 Sample D 0.24 0.48

[0251] This example demonstrates that using PVDF copolymer fibers with smaller diameters reduces the mean flow pore size and the maximum pore size, such that only one fine fiber layer is required to obtain a mean flow pore size of about 0.2 microns, which improves ease and rate of manufacturing.

[0252] As shown in Table 6, even though the layer surrounding the fine fiber layer containing PVDF copolymer fibers contained PVDF in sample B and contained PBT in sample A, sample A and sample B had similar mean flow pore size and maximum pore size. In addition, it was determined that the use of PVDF in the layer surrounding the fine fiber layer in sample B improved the adhesion between the layers (i.e., the fine fiber layer containing PVDF copolymer fibers had better adhesion to the PVDF meltblown layer in sample B than the PBT meltblown layer in sample A).

[0253] A variation of Sample B without the top and bottom polypropylene scrim layers was also tested and found to have approximately the same mean flow pore size and maximum pore size as Sample B, as well as the improved bonding characteristics of Sample B. This suggests that a mono-material filter media can be formed with improved bonding while still maintaining the mean flow pore size and maximum pore size. Without wishing to be bound by any theory, it is believed that in some cases, simplifying the chemical composition of the materials in the filter media (e.g., by having multiple layers comprising the same polymer material, as in Sample B) reduces the number of sources of potential contaminants (e.g., extractables and leachables) from the filter media that could compromise the results of analytical characterization methods such as liquid chromatography mass spectrometry (LCMS).

[0254] Thus, this example demonstrates that filter media comprising PVDF and PVDF copolymers as the only polymeric materials achieves similar properties to filter media having PVDF copolymer and PBT layers, while having additional benefits such as improved adhesion and simplified chemical composition.

[0255] Example 4

[0256] This example characterizes the void volume achieved when using PVDF copolymers compared to polyamide-6.

[0257] The void volume of the fine fiber layer comprising fiber A from Examples 1 to 3 was compared to the void volume of the fine fiber layer comprising fiber C. The void volume was measured as described elsewhere herein. Like fiber A, fiber C also had an average fiber diameter of 80 nm to 100 nm. However, fiber C comprised polyamide 6 instead of a PVDF copolymer. The void volume of the fine fiber layer comprising fiber A was 85% to 95%, while the void volume of the fine fiber layer comprising fiber C was 70%.

[0258] This example shows that higher void volumes are achieved when the fine fiber layer comprises fibers comprising a PVDF copolymer rather than polyamide 6.

[0259] Example 5

[0260] This example characterizes the mean flow pore size, maximum pore size, and air permeability of different samples.

[0261] The following filter media were tested:

[0262] ● Sample A from Example 3

[0263] ● Sample E having four layers: a polyamide 6 meltblown layer, a fine fiber layer comprising fiber C, a polyamide 6 meltblown layer, and a polyamide 6 scrim layer

[0264] The mean flow pore size and maximum pore size of sample A and sample E were measured according to ASTM F316 (2003). The air permeability of sample A and sample E was measured at a pressure of 125 Pa according to ASTM D737-04 (2016). As shown in Table 7, although sample A and sample E have similar mean flow pore sizes, sample A has a higher air permeability.

[0265] Table 7. Mean flow pore (MFP) diameter and air permeability of sample A and sample E

[0266]

[0267] This example shows that higher air permeability is achieved when the fine fiber layer comprises fibers comprising a PVDF copolymer instead of polyamide 6.

[0268] Example 6

[0269] This example analyzes the retention of Serratia marcescens of Sample D according to ASTM F838-05. The filtrate count was less than 1 CFU. The LRV was 9.37. This example demonstrates that the filter media according to certain embodiments are sterile.

[0270] Although several embodiments of the present invention have been described and illustrated herein, a person of ordinary skill in the art will readily conceive of a variety of other means and / or structures for performing the functions described herein and / or obtaining the results and / or one or more advantages described herein, and each of such changes and / or modifications is considered to be within the scope of the present invention. More generally, it will be readily understood by those skilled in the art that all parameters, dimensions, materials, and configurations described herein are intended to be exemplary, and that the actual parameters, dimensions, materials, and / or configurations will depend on one or more specific applications using the teachings of the present invention. Those skilled in the art will recognize or be able to determine many equivalents of the specific embodiments of the present invention described herein using only routine experiments. Therefore, it should be understood that the aforementioned embodiments are presented only by way of example, and within the scope of the appended claims and their equivalents, the present invention can be implemented in a manner other than specifically described and claimed. The present invention relates to each individual feature, system, product, material, and / or method described herein. In addition, if such features, systems, products, materials, and / or methods are not mutually inconsistent, any combination of two or more such features, systems, products, materials, and / or methods is included within the scope of the present invention.

[0271] Unless explicitly stated to the contrary, as used herein in the specification and claims, unmodified nouns should be understood to mean "at least one".

[0272] The phrase "and / or" as used herein in the specification and claims should be understood to mean "one or both" of the elements so connected, i.e., in some cases the elements are present together, and in other cases the elements are present separately. Unless expressly indicated to the contrary, other elements may optionally be present in addition to the elements specifically indicated by the "and / or" clause, whether related or unrelated to those elements specifically indicated. Thus, as a non-limiting example, when used in conjunction with open language such as "comprising", a reference to "A and / or B" may refer to A without B (optionally including elements other than B) in one embodiment; to B without A (optionally including elements other than A) in another embodiment; to both A and B (optionally including other elements) in yet another embodiment; and so on.

[0273] As used herein in the specification and claims, "or" should be understood to have the same meaning as "and / or" as defined above. For example, when separating items in a list, "or" or "and / or" should be interpreted as inclusive, i.e., including at least one of many elements or lists of elements, but also including more than one, and optionally including additional unlisted items. Only terms that clearly indicate the opposite, such as "only one / kind" or "exactly one / kind", or when used in the claims, "consisting of..." refers to containing exactly one element in many elements or lists of elements. In general, when there is an exclusive term (such as "any", "one of", "only one of" or "exactly one of") before, the term "or" used in this article should only be interpreted as representing an exclusive alternative (i.e., "one or the other, not both"). "Substantially consisting of..." when used in the claims should have its ordinary meaning used in the field of patent law.

[0274] As used herein in the specification and claims, the phrase "at least one" when referring to a list of one or more elements should be understood to mean at least one element selected from any one or more elements in the list of elements, but does not necessarily include at least one of each element specifically listed in the list of elements, and does not exclude any combination of elements in the list of elements. This definition also allows that elements other than the elements specifically identified in the list of elements referred to by the phrase "at least one" may optionally be present, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, "at least one of A and B" (or equivalently, "at least one of A or B", or equivalently "at least one of A and / or B") may, in one embodiment, refer to at least one A, optionally including more than one A, without B being present (and optionally including elements other than B); in another embodiment, may refer to at least one B, optionally including more than one B, without A being present (and optionally including elements other than A); in yet another embodiment, may refer to at least one A, optionally including more than one A, and at least one B, optionally including more than one B (and optionally including other elements); and so on.

[0275] In the claims and the foregoing specification, all transitional phrases such as "comprising," "including," "with," "having," "containing," "involving," "having," etc. shall be understood as open-ended, i.e., meaning including but not limited to. Only the transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively, as set forth in Section 2111.03 of the U.S. Patent Office Manual of Patent Examining Procedures.

Claims

1. A filter medium comprising: a fine fiber layer comprising a plurality of fine fibers; wherein the fine fibers comprise polyvinylidene fluoride (PVDF) and / or a copolymer thereof; wherein the average fiber diameter of the fine fibers is less than or equal to 150 nanometers; and The surface nodule density of the fine fiber layer is less than or equal to 4 nodules / 100 square micrometers (um 2 ).

2. A filter medium comprising: a fine fiber layer comprising a plurality of fine fibers; wherein the fine fibers comprise polyvinylidene fluoride (PVDF) and / or a copolymer thereof; wherein the average fiber diameter of the fine fibers is less than or equal to 150 nanometers; and The void volume of the fine fiber layer is greater than or equal to 70%.

3. A filter medium comprising: a fine fiber layer comprising a plurality of fine fibers; wherein the fine fibers comprise polyvinylidene fluoride (PVDF) and / or a copolymer thereof; wherein the average fiber diameter of the fine fibers is less than or equal to 150 nanometers; and The ratio of the theoretical surface area of ​​the fine fiber layer to the actual surface area of ​​the fine fiber layer is greater than or equal to 1 and less than or equal to 15.

4. A filter medium comprising: a fine fiber layer comprising a plurality of fine fibers; wherein the fine fibers comprise polyvinylidene fluoride (PVDF) and / or a copolymer thereof; wherein greater than or equal to 5% and less than or equal to 100% of the fine fibers have a diameter less than or equal to 100 nm; and The surface nodule density of the fine fiber layer is less than or equal to 4 nodules / 100 square micrometers (um 2 ).

5. A filter medium comprising: a fine fiber layer comprising a plurality of fine fibers; wherein the fine fibers comprise polyvinylidene fluoride (PVDF) and / or a copolymer thereof; wherein greater than or equal to 5% and less than or equal to 100% of the fine fibers have a diameter less than or equal to 100 nm; and The void volume of the fine fiber layer is greater than or equal to 70%.

6. A filter medium comprising: a fine fiber layer comprising a plurality of fine fibers; wherein the fine fibers comprise polyvinylidene fluoride (PVDF) and / or a copolymer thereof; wherein greater than or equal to 5% and less than or equal to 100% of the fine fibers have a diameter less than or equal to 100 nm; and The ratio of the theoretical surface area of ​​the fine fiber layer to the actual surface area of ​​the fine fiber layer is greater than or equal to 1 and less than or equal to 15.

7. The filter media of any preceding claim, wherein the polyvinylidene fluoride (PVDF) and / or copolymer thereof comprises a PVDF copolymer.

8. The filter medium of any preceding claim, wherein the polyvinylidene fluoride (PVDF) and / or copolymers thereof comprise PVDF-hexafluoropropylene, PVDF-tetrafluoroethylene, PVDF-chlorotrifluoroethylene and / or PVDF-hexafluoropropylene-tetrafluoroethylene.

9. The filter medium of any preceding claim, wherein the fine fibers have an average fiber diameter greater than or equal to 10 nm and less than or equal to 1000 nm.

10. The filter medium of any preceding claim, wherein the fine fibers have an average fiber diameter greater than or equal to 10 nm and less than or equal to 150 nm.

11. The filter medium of any preceding claim, wherein greater than or equal to 5% and less than or equal to 100% of the fine fibers have a diameter less than or equal to 100 nm.

12. The filter media of any preceding claim, wherein greater than or equal to 5% of the fine fibers have a diameter less than or equal to 75 nm.

13. The filter medium of any preceding claim, wherein the fine fibers are electrospun fibers.

14. The filter medium of any preceding claim, wherein the fine fiber layer has a surface node density of less than or equal to 4 nodes / 100 square microns (um 2 ).

15. The filter media of any preceding claim, wherein the nodules have an aspect ratio greater than or equal to 0.4 and less than or equal to 1.

16. The filter media of any preceding claim, wherein the diameter of the nodules is at least 40% greater than the average fiber diameter.

17. The filter media of any preceding claim, wherein the diameter of the nodules is at least 200% greater than the average fiber diameter.

18. The filter medium of any preceding claim, wherein the nodules have a diameter greater than or equal to 300 nm.

19. The filter medium of any preceding claim, wherein the fine fiber layer has a surface nodule density greater than or equal to 0.1 nodules / 100 square microns (um 2 ).

20. The filter medium of any preceding claim, wherein the fine fiber layer has a surface nodule density of less than or equal to 2 nodules / 100 square microns (um 2 ).

21. The filter media of any preceding claim, wherein the fine fiber layer has a void volume greater than or equal to 70%.

22. The filter media of any preceding claim, wherein the fine fiber layer has a void volume greater than or equal to 80%.

23. The filter medium of any preceding claim, wherein a ratio of a theoretical surface area of ​​the fine fiber layer to an actual surface area of ​​the fine fiber layer is greater than or equal to 1 and less than or equal to 15.

24. The filter medium of any preceding claim, wherein a ratio of a theoretical surface area of ​​the fine fiber layer to an actual surface area of ​​the fine fiber layer is greater than or equal to 1 and less than or equal to 5.

25. The filter media of any preceding claim, wherein the fine fiber layer has a maximum pore size greater than or equal to 0.1 microns and less than or equal to 5 microns.

26. The filter media of any preceding claim, wherein the fine fiber layer has a maximum pore size greater than or equal to 0.1 microns and less than or equal to 2.5 microns.

27. The filter media of any preceding claim, wherein the fine fiber layer has a mean flow pore size greater than or equal to 0.001 microns and less than or equal to 5 microns.

28. The filter media of any preceding claim, wherein the fine fiber layer has a mean flow pore size greater than or equal to 0.01 microns and less than or equal to 2 microns.

29. The filter media of any preceding claim, wherein the fine fiber layer has a ratio of maximum pore size to mean flow pore size greater than or equal to 1 and less than or equal to 5.

30. The filter media of any preceding claim, wherein the fine fiber layer has a maximum pore size to mean flow pore size ratio greater than or equal to 1.2 and less than or equal to 3.

31. The filter media of any preceding claim, wherein the fine fiber layer has a thickness greater than or equal to 10 nanometers and less than or equal to 5 millimeters.

32. The filter media of any preceding claim, wherein the fine fiber layer has a basis weight greater than or equal to 0.001 gsm and less than or equal to 20 gsm.

33. The filter media of any preceding claim, wherein the fine fiber layer has an air permeability of less than or equal to 100 CFM.

34. The filter media of any preceding claim, wherein the fine fiber layer has an air permeability greater than or equal to 0.1 CFM.

35. The filter media of any preceding claim, wherein the fine fiber layer has an air permeability greater than or equal to 0.5 CFM and less than or equal to 30 CFM.

36. The filter media of any preceding claim, wherein the filter media has a basis weight greater than or equal to 5 gsm and less than or equal to 600.

37. The filter media of any preceding claim, wherein the filter media has a thickness greater than or equal to 0.01 mm and less than or equal to 30 mm.

38. The filter media of any preceding claim, wherein the filter media has an air permeability greater than or equal to 0.2 CFM and less than or equal to 1000 CFM.

39. The filter media of any preceding claim, wherein the filter media has an air permeability greater than or equal to 0.5 CFM and less than or equal to 800 CFM.

40. The filter media of any preceding claim, wherein the filter media has an overall efficiency greater than or equal to 10% and less than or equal to 99.9999999%.

41. The filter media of any preceding claim, wherein the filter media has a pressure drop greater than or equal to 0.05 kPA and less than or equal to 100 kPa.

42. The filter media of any preceding claim, wherein the filter media has a gamma greater than or equal to 3 and less than or equal to 400.

43. The filter media of any preceding claim, wherein the filter media is pleated.

44. The filter media of any preceding claim, wherein the filter media has a total Gurley bending stiffness in the machine direction and / or the cross direction of greater than or equal to 1 mg and less than or equal to 3500 mg.

45. The filter media of any preceding claim, wherein the filter media has a mean flow pore size greater than or equal to 0.001 microns and less than or equal to 100 microns.

46. ​​The filter media of any preceding claim, wherein the filter media has a maximum pore size greater than or equal to 0.1 microns and less than or equal to 200 microns.

47. The filter media of any preceding claim, wherein the filter media has a dust holding capacity greater than or equal to 1 gsm and less than or equal to 500 gsm.

48. The filter media of any preceding claim, wherein the filter media further comprises an additional layer.

49. The filter media of any preceding claim, wherein the ratio of the fiber diameter of the fine fiber layer to the fiber diameter of the additional layer is greater than or equal to 0.001 and less than or equal to 1.

50. The filter media of any preceding claim, wherein the additional layer is a backing layer.

51. The filter media of any preceding claim, wherein the additional layer comprises meltblown fibers, synthetic fibers, and / or cellulosic fibers.

52. The filter media of any preceding claim, wherein the additional layer is wet-laid and / or calendered.

53. The filter media of any preceding claim, wherein the additional layer is a meltblown calendered layer.

54. The filter media of any preceding claim, wherein the additional layer is a wet-laid synthetic layer.

55. The filter media of any preceding claim, wherein the additional layer comprises cellulose fibers.

56. A filter element comprising the filter media of any preceding claim.

57. A method of filtering a fluid using a filter medium according to any preceding claim.

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