Filter media comprising a binder

Abstract

Generally provided are filtration media comprising a binder, articles and methods relating to filtration media. In certain embodiments, the filtration media includes at least a first layer, a second layer, and a binder resin disposed between the first and second layers. In some embodiments, the first layer can be a prefilter layer or a support layer. The second layer may, for example, include fibers formed by a solution spinning process and / or can include fine fibers. In some embodiments, the binder resin can be present in a relatively low amount and / or can have a low glass transition temperature. The filtration media as a whole can have one or more advantageous properties, including one or more of high stiffness, high bond strength between the first and second layers, high gamma, and / or low air resistance increase after being subjected to an IPA vapor discharge. The filtration media can be, for example, a HEPA filter and / or a ULPA filter.

Description

[0001] This application is a divisional application of Chinese patent application No. 201780077261.5 entitled "Filter Media Containing Adhesive". Patent application No. 201780077261.5 is a national application that entered the Chinese national phase under the Patent Cooperation Treaty (PCT / US2017 / 066667) filed on December 15, 2017, with a priority date of December 15, 2016. Technical Field

[0002] The present invention generally relates to filter media, and more particularly to filter media comprising adhesives. Background Technology

[0003] Filter media can be used to remove contaminants in a variety of applications. Depending on the application, filter media can be designed with different performance characteristics. For example, filter media can be designed with performance characteristics suitable for HEPA and / or ULPA applications.

[0004] Typically, filter media can be formed from a fiber web. For example, the web can contain components such as synthetic fibers. The fiber web provides a porous structure that allows fluids (e.g., air) to flow through the filter media. Contaminant particles contained within the fluid can be trapped on the fiber web. Filter media characteristics (e.g., fiber diameter and basis weight) affect filter performance, including filtration efficiency, dust holding capacity, and resistance to fluid flow through the filter.

[0005] Although many types of filter media exist for filtering particulate matter from the air, improvements in the physical and / or performance characteristics of filter media (e.g., strength, air resistance, efficiency, and high dust holding capacity) would be beneficial. Summary of the Invention

[0006] The filter media, as well as related components and methods, are provided.

[0007] In one set of embodiments, a filter medium is provided. In some embodiments, the filter medium includes a first layer; a second layer, wherein the second layer is formed of fibers with an average fiber diameter of less than 1 micrometer; and an adhesive between the first layer and the second layer, wherein the first layer is bonded to the second layer by the adhesive. The stiffness of the filter medium is greater than or equal to 200 mg. The bonding strength between the first layer and the second layer is greater than or equal to 150 g / inch. 2 The filter media exhibits a γ value greater than or equal to 18 at the most easily penetrating particle size.

[0008] In some embodiments, the filter media includes a first layer; a second layer, wherein the second layer is formed of fibers with an average fiber diameter of less than 1 micrometer; and an adhesive between the first layer and the second layer. The first layer is bonded to the second layer by the adhesive. The adhesive comprises a solvent-based resin containing a polymer with a glass transition temperature of less than or equal to 24°C.

[0009] In some embodiments, the filter media includes a first layer; a second layer, wherein the second layer is formed of fibers with an average fiber diameter of less than 1 micrometer; and an adhesive between the first and second layers. The adhesive between the first and second layers is present in an amount of less than 10 gsm. The first layer is bonded to the second layer by the adhesive. The bond strength between the first and second layers is greater than or equal to 150 g / in. 2 Compared to the filter media before IPA vapor discharge, the filter media exhibited less than 50% increase in air resistance after being subjected to IPA vapor discharge.

[0010] In another set of embodiments, a method is provided. In some embodiments, the method of manufacturing a filter medium includes spraying a composition comprising a solvent-based adhesive resin and a crosslinking agent onto a first layer to form an adhesive-coated first layer; performing a solvent-based spinning process to deposit fibers onto the adhesive-coated first layer, wherein the fibers have an average fiber diameter of less than 1 micrometer and forming a second layer; and laminating the second layer onto a third layer such that the third layer is disposed on the side of the second layer opposite to the first layer.

[0011] Other advantages and novel features of the invention will become apparent from the following detailed description of several non-limiting embodiments of the invention when considered in conjunction with the accompanying drawings. In the event of conflicting and / or inconsistent disclosures between this specification and any documents incorporated by reference, this specification shall prevail. If two or more documents incorporated by reference contain disclosures that conflict and / or are inconsistent with each other, the document with the later effective date shall prevail. Attached Figure Description

[0012] Non-limiting embodiments of the invention will be described by way of example with reference to the accompanying drawings, which are schematic and not intended to be drawn to scale. In the drawings, each identical or substantially identical component shown is generally denoted by a single reference numeral. For clarity, not every component is labeled in each figure, nor are every component of each embodiment of the invention shown, where illustration would be unnecessary for those skilled in the art to understand the invention. In the drawings:

[0013] Figure 1A A filter medium comprising two layers is shown according to some embodiments;

[0014] Figure 1B A filter medium comprising three layers is shown according to some embodiments;

[0015] Figure 1C A filter media comprising five layers is shown according to some embodiments;

[0016] Figures 2A to 2C A method for forming a three-layer medium according to some embodiments is shown;

[0017] Figure 3 The lamination process for forming filter media according to some embodiments is shown; and

[0018] Figures 4A to 4C The following are examples of uses based on some implementation schemes. Figure 3 The filter media formed by the process shown. Detailed Implementation

[0019] Articles and methods relating to filter media are generally provided. In some embodiments, the filter media comprises at least a first layer, a second layer, and an adhesive resin disposed between the first and second layers. In some embodiments, the first layer may be a pre-filter layer or a support layer. The second layer may, for example, comprise fibers formed by a solution spinning process and / or may comprise fine fibers. In some embodiments, the adhesive resin may be present in a relatively low amount and / or may have a low glass transition temperature. The filter media as a whole may have one or more advantageous properties, including high stiffness, high bonding strength between the first and second layers, a high gamma value, and / or a low increase in air resistance after being subjected to IPA vapor discharge. The filter media may be, for example, a HEPA filter and / or a ULPA filter.

[0020] Methods for manufacturing the filter media described herein are also provided. In some embodiments, manufacturing the filter media may include spraying a composition comprising an adhesive resin onto a first layer to form an adhesive-coated first layer, and performing a solvent-based spinning process to deposit fibers forming a second layer onto the adhesive-coated first layer. The second layer may be a solvent-spun layer, such as an electrospun layer. In some embodiments, the second layer may be laminated to a third layer such that the third layer is disposed on the side of the second layer opposite to the first layer. Other configurations and methods of joining or forming the first, second, and third layers are also possible.

[0021] Figure 1AA filter medium 100 according to certain embodiments of the present invention is depicted. The filter medium 100 includes a first layer 110 and a second layer 120. In some embodiments, and as described in more detail below, the first layer is a support layer or a pre-filter layer. The second layer may be a primary filter layer. The primary filter layer may, for example, have a higher efficiency than one or more other layers of the medium. For example, in some cases, the primary filter layer is a layer of fine fibers, such as a layer formed by a solvent-based spinning process. In some embodiments, an adhesive resin is present between the first and second layers. The adhesive resin may be used to bond the first layer to the second layer. In some embodiments, the adhesive resin may be present between the first and second layers in a relatively small amount, but the bond between the first and second layers may be relatively strong (e.g., a bond strength greater than or equal to 150 g / inch). 2 The properties of the layers (e.g., pre-filter layer, support layer, and main filter layer) and adhesives are described in more detail below.

[0022] It should be understood that, optionally, the filter media may also include additional layers, such as a third, fourth, and / or fifth layer. In some embodiments, one or more layers (e.g., first, second, third, fourth, and fifth layers) may be added using an in-line process. It should also be understood that the orientation of filter media 100 (and other filter media described herein) relative to the fluid flowing through the filter media or within the filter element can generally be selected as needed. In some embodiments, the first layer 110 is downstream of the second layer 120 (e.g., within the filter element). In other embodiments, the first layer 110 is upstream of the second layer 120 (e.g., within the filter element).

[0023] In some implementations, the filter media may include at least three layers, such as Figure 1B As exemplarily illustrated, filter media 102 includes a first layer 110, a second layer 120, and a third layer 130. In some embodiments, the third layer may be a support layer or a pre-filter layer. For example, in one set of embodiments, the first layer may be a support layer and the third layer may be a pre-filter layer. In another set of embodiments, the first layer may be a pre-filter layer and the third layer may be a support layer. In some embodiments, an adhesive resin is present between the second and third layers. The adhesive resin may be used to bond the second layer to the third layer. In some embodiments, the adhesive resin may be present between the second and third layers in a relatively small amount, but the bond between the second and third layers may be relatively strong (e.g., a bond strength greater than or equal to 150 g / inch). 2 ).

[0024] In some cases, each layer of a filter medium has different characteristics and filtration properties, and when combined, for example, compared to a filter medium with a single-layer structure, produces the desired overall filtration performance. For example, in one set of embodiments, the third layer 130 is a pre-filter layer, and the second layer 120 is the main filter layer. In some embodiments, as further described below, the pre-filter layer can be formed using coarser fibers and therefore can have lower fluid flow resistance than the main filter layer. The main filter layer can contain finer fibers and have higher fluid flow resistance than the pre-filter layer. Therefore, the main filter layer can typically capture smaller particles compared to the pre-filter layer.

[0025] As described above, each layer of the filter media can have different properties. For example, the first and second layers can contain fibers with different characteristics (e.g., fiber diameter, fiber composition, and / or fiber length). Fibers with different characteristics can be made of one material (e.g., by using different process conditions) or different materials (e.g., different types of fibers).

[0026] In some implementations, the filter media may include more than one layer of the same type. For example, a filter may include two pre-filter layers, two support layers, and / or two main filter layers. Figure 1C A non-limiting example of an embodiment in which the filter medium includes at least one pre-filter layer, at least one support layer, and two main filter layers is depicted. As shown in the figure, filter medium 104 includes a first layer 110, a second layer 120, a third layer 130, a fourth layer 140, and a fifth layer 150. In some embodiments, the third layer is a pre-filter layer, and both the second and fourth layers are main filter layers. In some embodiments, one, but not both, of the third and fifth layers is a support layer and the other is a pre-filter layer. For example, in one embodiment, for instance, when the fifth layer is disposed downstream of other layers in the filter element, the fifth layer 150 serves as a support layer, acting as a cover or protective layer. In some cases, the fifth layer may also serve as an efficiency layer. In some embodiments, both the third and fifth layers are support layers. It should be understood that this figure is non-limiting, and the filter medium may include other numbers and types of layers, and the layers may be positioned in different orders (e.g., two layers of the same type may be directly adjacent to each other, each layer of the filter medium may be different, the filter medium may not have a symmetrical configuration, and / or the filter medium may include six, seven, or more layers).

[0027] As used herein, when a layer is described as being "on" or "adjacent" to another layer, it can be directly on or directly adjacent to that layer, or there can be intermediate layers. A layer that is "on" another layer, "directly adjacent" to another layer, or "in contact" with another layer means that there are no intermediate layers.

[0028] Some embodiments relate to methods for manufacturing filter media. Exemplary methods for manufacturing filter media are shown in... Figures 2A to 2C In. Figure 2A In this process, adhesive 290 is deposited (e.g., sprayed) onto a first layer 210. The first layer may be a pre-filtered layer or a support layer. In some embodiments, the adhesive may have a glass transition temperature of less than or equal to 25°C and greater than or equal to -150°C and / or may be a solvent-based resin, as described in more detail below. In some embodiments, the adhesive may contain a solvent that at least partially evaporates from the adhesive-based resin during or after the adhesive is deposited onto the first layer. In some embodiments, the solvent may be water or another solvent.

[0029] In some embodiments, the adhesive resin may undergo crosslinking after the adhesive is deposited on the first layer. Such a process allows the adhesive to be deposited using methods suitable for applying liquids (e.g., spraying), while retaining good properties consistent with solids after the deposition process is complete (e.g., lack of flow when exposed to isopropanol vapor).

[0030] In some implementations, spraying the adhesive allows a relatively small amount of adhesive to be deposited on the first layer compared to other methods used for depositing adhesives. Spraying may include passing the adhesive through any suitable nozzle (e.g., an air atomizing nozzle, an ultrasonic nozzle, a piezoelectric nozzle, etc.). Other spraying parameters (e.g., the distance between the nozzle and the first layer, the air pressure applied to the adhesive during spraying, the size of the nozzle, etc.) can be selected as needed to control the amount of adhesive deposited on the first layer and other parameters.

[0031] After the adhesive is sprayed onto the first layer, a second layer 220 (e.g., a fine fiber layer) can be formed on layer 210 by a solvent-based spinning process, such as... Figure 2B As exemplified in the example. Non-limiting examples of solvent spinning processes include electrospinning processes (e.g., solvent electrospinning) or centrifugal spinning processes. In some embodiments, solvent-based spinning processes can result in the formation of fibers with an average fiber diameter of less than 1 micrometer. In some embodiments, the second layer can be the main filter layer.

[0032] In some implementations, using a solvent-based resin can reduce the conductivity of the substrate on which the resin is deposited (e.g., the first layer) and / or can facilitate the adhesion and / or uniform deposition of the second layer (e.g., by a solvent spinning process).

[0033] In some embodiments, a third layer can be laminated onto the second layer. For example, an adhesive can be deposited (e.g., sprayed) onto the second layer 220, and then the second and third layers can be bonded. The adhesive can increase the bond strength between the second and third layers. Optionally, the adhesive can be deposited (e.g., sprayed) onto the third layer before the third layer is laminated to the second layer. The resulting medium is exemplarily shown in... Figure 2C In this configuration, the third layer 230 is laminated to and directly adjacent to the second layer 220. In some embodiments, the third layer is a pre-filtering layer or a support layer. For example, in some embodiments where the first layer is a pre-filtering layer and the second layer is the main filtering layer, the third layer can be a support layer. In embodiments where the first layer is a support layer and the second layer is the main filtering layer, the third layer can be a pre-filtering layer.

[0034] In some embodiments, after two or more layers are laminated together, the filter media may be subjected to one or more processing steps. For example, the filter media may be subjected to steps in which increased heat is applied, such as through a felt drying drum, through an air dryer, through calendering rolls, and / or through a flatbed laminator. In some embodiments, the filter media may be subjected to two or more such steps sequentially (e.g., the filter media may be passed through a felt drying drum and then through an air dryer). The increased heat may help evaporate any solvent remaining in the filter media prior to this step.

[0035] In some embodiments, applying heat to the filter medium can include exposing the filter medium to an environment with a temperature greater than or equal to 40°C, greater than or equal to 60°C, greater than or equal to 80°C, or greater than or equal to 100°C (e.g., inside a drying drum, inside an air dryer, inside a calendering roll, or inside a flatbed laminator). In some embodiments, applying heat to the filter medium can include exposing the filter medium to an environment with a temperature less than or equal to 120°C, less than or equal to 100°C, less than or equal to 80°C, or less than or equal to 60°C (e.g., inside a drying drum, inside an air dryer, inside a calendering roll, or inside a flatbed laminator). Combinations of the above ranges are also possible (e.g., greater than or equal to 40°C and less than or equal to 120°C). Other ranges are also possible.

[0036] In some embodiments, applying heat to the filter medium can include passing the filter medium through a heated environment (e.g., the interior of a drying drum, an air dryer, a calender roll, or a flatbed laminator) at a rate greater than or equal to 0.1 m / min, greater than or equal to 0.2 m / min, greater than or equal to 0.5 m / min, greater than or equal to 1 m / min, greater than or equal to 2 m / min, greater than or equal to 5 m / min, greater than or equal to 1 m / min, greater than or equal to 5 m / min, less than or equal to 2 m / min, less than or equal to 1 m / min, less than or equal to 0.5 m / min, or less than or equal to 0.2 m / min. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 m / min and less than or equal to 40 m / min). Other ranges are also possible.

[0037] In some implementations, the process of forming the filter media can be repeated. Figures 2A to 2C One or more steps are described in the text. For example, an adhesive may be deposited (e.g., sprayed) on both sides of the first layer and / or a layer may be formed on each side of the first layer by a solvent spinning process such as electrospinning or centrifugal spinning. In some embodiments, layers may be laminated to both the top and bottom of the filter media. It should be understood that these steps may be sequential (e.g., Figures 2A to 2C The steps described can be performed on one side of the first layer and then on the opposite side of the first layer, or simultaneously (the first layer can be applied with adhesive to both the top and bottom sides simultaneously, and then simultaneously on both sides of the first layer). Figures 2B to 2C The steps described in the text occur. In some implementations, filter media with five, nine, thirteen, or more layers can be constructed in this manner.

[0038] In embodiments where one or more layers are added to a filter medium, the process for adding the layers can be an online process or an offline process. For example, in some embodiments, a method can be used with... Figure 3 The system described herein involves online processes for adding one or more layers (e.g., first, second, third, fourth, and fifth layers). That is, the filter media can be manufactured on a production line, and the two or more processes described herein can occur on the same production line. Suitable processes that can be performed online include lamination, spraying adhesive onto the layers, and gravure printing processes (e.g., hot melt gravure printing). In some embodiments, online processes may include fewer unwinding and rewinding processes compared to offline processes.

[0039] As described above, in some embodiments, one or more layers may be pre-filtering layers. For example, in some embodiments, the first layer is a pre-filtering layer. In some embodiments, the third layer is a pre-filtering layer. In some embodiments, both the third and fifth layers are pre-filtering layers. The characteristics of the pre-filtering layers will be described in more detail below.

[0040] The reference to "pre-filter layer or multiple pre-filter layers" herein should be understood as referring independently to each pre-filter layer in the filter medium (if any pre-filter layers are present). That is, each existing pre-filter layer may independently possess any of the characteristics described herein or may not possess the characteristics described herein. In some embodiments, two or more pre-filter layers in the filter medium may have similar composition and / or characteristics. In other embodiments, each pre-filter layer in the filter medium may have different composition and / or characteristics.

[0041] In embodiments where the filter medium includes at least one pre-filter layer (e.g., a first layer, a third layer), the fibers in the pre-filter layer or multiple pre-filter layers can have any suitable average diameter. In some embodiments, the average diameter of the fibers in the pre-filter layer or multiple pre-filter layers (e.g., a first layer, a third layer, a fifth layer) is greater than or equal to 0.1 micrometers, greater than or equal to 0.2 micrometers, greater than or equal to 0.5 micrometers, greater than or equal to 1 micrometer, greater than or equal to 2 micrometers, greater than or equal to 5 micrometers, greater than or equal to 10 micrometers, greater than or equal to 20 micrometers, greater than or equal to 40 micrometers, or greater than or equal to 60 micrometers. In some embodiments, the average diameter of the fibers in the pre-filter layer or multiple pre-filter layers (e.g., a first layer, a third layer, a fifth layer) is less than or equal to 75 micrometers, less than or equal to 60 micrometers, less than or equal to 40 micrometers, less than or equal to 20 micrometers, less than or equal to 10 micrometers, less than or equal to 5 micrometers, less than or equal to 2 micrometers, less than or equal to 1 micrometer, less than or equal to 0.5 micrometers, or less than or equal to 0.2 micrometers. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 micrometers and less than or equal to 75 micrometers, greater than or equal to 0.5 micrometers and less than or equal to 75 micrometers, greater than or equal to 0.5 micrometers and less than or equal to 40 micrometers, or greater than or equal to 0.5 micrometers and less than or equal to 2 micrometers). Other ranges are also possible.

[0042] In some embodiments where the filter media includes at least one pre-filter layer (e.g., a first, third, or fifth layer), the pre-filter layer may contain continuous fibers. The continuous fibers may have any suitable average length. In some embodiments, the average length of the continuous fibers in the pre-filter layer or multiple pre-filter layers (e.g., a first, third, or fifth layer) may be greater than or equal to 1 inch, greater than or equal to 2 inches, greater than or equal to 5 inches, greater than or equal to 10 inches, greater than or equal to 20 inches, greater than or equal to 50 inches, greater than or equal to 100 inches, greater than or equal to 200 inches, or greater than or equal to 500 inches. In some embodiments, the average length of the continuous fibers in the pre-filter layer or multiple pre-filter layers (e.g., a first, third, or fifth layer) may be less than or equal to 1000 inches, less than or equal to 500 inches, less than or equal to 200 inches, less than or equal to 100 inches, less than or equal to 50 inches, less than or equal to 20 inches, less than or equal to 10 inches, or less than or equal to 5 inches. Combinations of the above characteristics are also possible (e.g., greater than or equal to 5 inches and less than or equal to 1000 inches). Other ranges are also possible.

[0043] In some embodiments where the filter media includes at least one pre-filter layer (e.g., a first, third, or fifth layer), the pre-filter layer may contain short fibers. The short fibers may have any suitable average length. In some embodiments, the average length of the short fibers in the pre-filter layer or multiple pre-filter layers (e.g., a first, third, or fifth layer) may be greater than or equal to 0.3 mm, greater than or equal to 0.5 mm, greater than or equal to 1 mm, greater than or equal to 2 mm, greater than or equal to 5 mm, greater than or equal to 10 mm, greater than or equal to 20 mm, or greater than or equal to 50 mm. In some embodiments, the average length of the short fibers in the pre-filter layer or multiple pre-filter layers (e.g., a first, third, or fifth layer) may be less than or equal to 100 mm, less than or equal to 50 mm, less than or equal to 20 mm, less than or equal to 10 mm, less than or equal to 5 mm, less than or equal to 2 mm, less than or equal to 1 mm, or less than or equal to 0.5 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.3 mm and less than or equal to 100 mm, or greater than or equal to 1 mm and less than or equal to 50 mm). Other ranges are also possible.

[0044] In some embodiments of a filter media comprising at least one pre-filter layer (e.g., a first, third, or fifth layer), the pre-filter layer or multiple pre-filter layers may contain fiber types such as synthetic fibers, glass fibers, and / or cellulose fibers. In some cases, the pre-filter layer or multiple pre-filter layers (e.g., a first, third, or fifth layer) may contain a relatively high weight percentage of synthetic fibers (e.g., 100% by weight). For example, the pre-filter layer or multiple pre-filter layers (e.g., a first, third, or fifth layer) contain synthetic fibers formed by meltblowing, melt spinning, centrifugal spinning, electrospinning, wet web forming, dry web forming, or air-laid web forming processes. In some cases, the synthetic fibers may be continuous, as further described below. In some embodiments, the pre-filter layer or multiple pre-filter layers (e.g., a first, third, or fifth layer) may contain relatively few glass fibers or no glass fibers. In other embodiments, the pre-filter layer or multiple pre-filter layers (e.g., a first, third, or fifth layer) may contain a relatively high weight percentage of glass fibers (e.g., 100% by weight).

[0045] In some embodiments, the filter medium may include at least one pre-filter layer (e.g., a first, third, or fifth layer), and at least one of the pre-filter layers may contain synthetic fibers. The synthetic fibers may have a relatively small average fiber diameter (e.g., less than or equal to about 2 micrometers). For example, the average diameter of the synthetic fibers in the pre-filter layer or multiple pre-filter layers (e.g., a first, third, or fifth layer) may be less than or equal to about 2 micrometers (e.g., about 0.5 micrometers to about 1.0 micrometer). In some embodiments, the synthetic fibers in the pre-filter layer or multiple pre-filter layers (e.g., a first, third, or fifth layer) may be continuous fibers formed by any suitable process (e.g., meltblowing, melt spinning, electrospinning (e.g., melt electrospinning, solvent electrospinning), centrifugal spinning, wet web forming, dry web forming, or air-jet web forming). In some embodiments, the synthetic fibers may be formed by an electrospinning process. In other embodiments, the synthetic fibers may be discontinuous. In some embodiments, all fibers in the pre-filter layer or multiple pre-filter layers (e.g., a first, third, or fifth layer) are synthetic fibers.

[0046] Synthetic fibers can comprise any suitable type of synthetic polymer. Examples of suitable synthetic fibers include polyesters (e.g., polyethylene terephthalate, polybutylene terephthalate), polycarbonates, polyamides (e.g., various nylon polymers), polyaramids, polyimides, polyethylene, polypropylene, polyetheretherketones, polyolefins, acrylics, polyvinyl alcohol, regenerated cellulose (e.g., synthetic cellulose such as lyocell, rayon), polyacrylonitrile, polyvinylidene fluoride (PVDF), copolymers of polyethylene and PVDF, polyethersulfone, and combinations thereof. In some embodiments, the synthetic fibers are organic polymer fibers. Synthetic fibers can also comprise multicomponent fibers (i.e., fibers having multiple compositions, such as bicomponent fibers). In some cases, synthetic fibers can comprise meltblown fibers, melt-spun fibers, electrospun fibers (e.g., melt electrospun, solvent electrospun) fibers, or centrifugally spun fibers, which can be formed from the polymers described herein (e.g., polyester, polypropylene). In some embodiments, the synthetic fibers can be electrospun fibers. When present, a pre-filter layer or multiple pre-filter layers (e.g., first layer, third layer, fifth layer) may also contain a combination of more than one type of synthetic fiber. It should be understood that other types of synthetic fibers may also be used.

[0047] In some implementations, the average diameter of the synthetic fibers in one or more pre-filter layers (if present, e.g., first, third, and fifth layers) can be, for example, greater than or equal to about 0.1 micrometers, greater than or equal to about 0.3 micrometers, greater than or equal to about 0.5 micrometers, greater than or equal to about 1 micrometer, greater than or equal to about 2 micrometers, greater than or equal to about 3 micrometers, greater than or equal to about 4 micrometers, greater than or equal to about 5 micrometers, greater than or equal to about 8 micrometers, greater than or equal to about 10 micrometers, greater than or equal to about 12 micrometers, greater than or equal to about 15 micrometers, or greater than or equal to about 20 micrometers. In some cases, the average diameter of the synthetic fibers can be less than or equal to about 30 micrometers, less than or equal to about 20 micrometers, less than or equal to about 15 micrometers, less than or equal to about 10 micrometers, less than or equal to about 7 micrometers, less than or equal to about 5 micrometers, less than or equal to about 4 micrometers, less than or equal to about 1.5 micrometers, less than or equal to about 1 micrometer, less than or equal to about 0.8 micrometers, or less than or equal to about 0.5 micrometers. Combinations of the above ranges are also possible (e.g., greater than or equal to about 1 micrometer and less than or equal to about 5 micrometers). Other values ​​for the average fiber diameter are also possible. The average fiber diameter can be determined, for example, by scanning electron microscopy.

[0048] In some cases, synthetic fibers (if present) can be continuous (e.g., meltblown fibers, spunbond fibers, electrospun fibers, centrifugally spun fibers, etc.). The length of continuous fibers has been provided above. In other embodiments, synthetic fibers (if present) are not continuous (e.g., short fibers). The length of short fibers has been provided above. Continuous fibers are produced by a “continuous” fiber forming process (e.g., meltblown, spunbond, electrospun, or centrifugally spun) and generally have a longer length than discontinuous fibers. Discontinuous fibers are short fibers that are typically cut (e.g., from filaments) or formed as discontinuous discrete fibers to have a specific length or length range.

[0049] In embodiments where the filter media includes at least one pre-filter layer (e.g., a first, third, or fifth layer) comprising synthetic fibers, the synthetic fibers may constitute any suitable portion of that layer. In some embodiments, the percentage by weight of synthetic fibers in the pre-filter layer (e.g., the first, third, or fifth layer) may be greater than or equal to 0% by weight, greater than or equal to 10% by weight, greater than or equal to 20% by weight, greater than or equal to 30% by weight, greater than or equal to 40% by weight, greater than or equal to 50% by weight, greater than or equal to 60% by weight, greater than or equal to 70% by weight, greater than or equal to 80% by weight, or greater than or equal to 90% by weight. In some embodiments, the weight percentage of synthetic fibers in the pre-filter layers (e.g., the first, third, and fifth layers) can be less than or equal to 100% by weight, less than or equal to 90% by weight, less than or equal to 80% by weight, less than or equal to 70% by weight, less than or equal to 60% by weight, less than or equal to 50% by weight, less than or equal to 40% by weight, less than or equal to 30% by weight, less than or equal to 20% by weight, or less than or equal to 10% by weight. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% by weight and less than or equal to 100% by weight, or greater than or equal to 10% by weight and less than or equal to 100% by weight). Other ranges are also possible. In some embodiments, the weight percentage of synthetic fibers in the pre-filter layers (e.g., the first, third, and fifth layers) can be 100% by weight.

[0050] In some embodiments, the filter medium may include at least one pre-filter layer (e.g., a first layer, a third layer, a fifth layer), and at least one of the pre-filter layers may contain bicomponent fibers. The bicomponent fibers may contain thermoplastic polymers. The components of the bicomponent fibers may have different melt temperatures. For example, the fiber may comprise a core and a sheath, wherein the activation temperature of the sheath is lower than the melt temperature of the core. This causes the sheath to melt before the core, allowing the sheath to bond to the other fibers in the layer, while the core maintains its structural integrity. The core / sheath bonded fibers may be coaxial or non-coaxial. Other exemplary bicomponent fibers may include split-film fibers, side-by-side fibers, and / or "island-type" fibers.

[0051] In some embodiments, the average length of the bicomponent fibers (if present) can be at least about 0.1 mm, at least about 0.5 mm, at least about 1.0 mm, at least about 1.5 mm, at least about 2.0 mm, at least about 3.0 mm, at least about 4.0 mm, at least about 5.0 mm, at least about 6.0 mm, at least about 7.0 mm, at least about 8.0 mm, at least about 9.0 mm, at least about 10.0 mm, at least about 12.0 mm, at least about 15.0 mm; and / or less than or equal to about 15.0 mm, less than or equal to about 12.0 mm, less than or equal to about 10.0 mm, less than or equal to about 5.0 mm, less than or equal to about 4.0 mm, less than or equal to about 1.0 mm, less than or equal to about 0.5 mm, or less than or equal to about 0.1 mm. Combinations of the above ranges are also possible (e.g., at least about 1.0 mm and less than or equal to about 4.0 mm). Other values ​​for the average fiber length are also possible.

[0052] In embodiments where the filter media includes at least one pre-filter layer comprising bicomponent fibers (e.g., a first layer, a third layer, a fifth layer), the bicomponent fibers can constitute any suitable portion of that layer. In some embodiments, the weight percentage of the bicomponent fibers in the pre-filter layer or multiple pre-filter layers can be greater than or equal to 0% by weight, greater than or equal to 2.5% by weight, greater than or equal to 5% by weight, greater than or equal to 7.5% by weight, greater than or equal to 10% by weight, greater than or equal to 15% by weight, greater than or equal to 20% by weight, greater than or equal to 25% by weight, greater than or equal to 30% by weight, greater than or equal to 35% by weight, greater than or equal to 40% by weight, or greater than or equal to 45% by weight. In some embodiments, the weight percentage of the bicomponent fibers in the pre-filter layer or multiple pre-filter layers may be less than or equal to 50% by weight, less than or equal to 45% by weight, less than or equal to 40% by weight, less than or equal to 35% by weight, less than or equal to 30% by weight, less than or equal to 25% by weight, less than or equal to 20% by weight, less than or equal to 15% by weight, less than or equal to 10% by weight, less than or equal to 7.5% by weight, less than or equal to 5% by weight, or less than or equal to 2.5% by weight. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% by weight and less than or equal to 50% by weight, or greater than or equal to 0% by weight and less than or equal to 10% by weight). Other ranges are also possible.

[0053] In some embodiments, the filter medium may include at least one pre-filter layer (e.g., a first layer, a third layer, a fifth layer), and at least one of the pre-filter layers may contain one or more cellulose fibers, such as cork fiber, hardwood fiber, a mixture of hardwood fiber and cork fiber, regenerated cellulose fiber and / or mechanical pulp fiber (e.g., groundwood pulp, chemically treated mechanical pulp and thermomechanical pulp).

[0054] The average diameter of the cellulose fibers in one or more pre-filter layers (i.e., in embodiments including at least one pre-filter layer (e.g., a first layer, a third layer, a fifth layer)) can be, for example, greater than or equal to about 1 micrometer, greater than or equal to about 2 micrometers, greater than or equal to about 3 micrometers, greater than or equal to about 4 micrometers, greater than or equal to about 5 micrometers, greater than or equal to about 8 micrometers, greater than or equal to about 10 micrometers, greater than or equal to about 15 micrometers, greater than or equal to about 20 micrometers, greater than or equal to about 30 micrometers, or greater than or equal to about 40 micrometers. In some cases, the average diameter of the cellulose fibers can be less than or equal to about 50 micrometers, less than or equal to about 40 micrometers, less than or equal to about 30 micrometers, less than or equal to about 20 micrometers, less than or equal to about 15 micrometers, less than or equal to about 10 micrometers, less than or equal to about 7 micrometers, less than or equal to about 5 micrometers, less than or equal to about 4 micrometers, or less than or equal to about 2 micrometers. Combinations of the above ranges are also possible (e.g., greater than or equal to about 1 micrometer and less than or equal to about 5 micrometers). Other values ​​for the average fiber diameter are also possible.

[0055] In some embodiments, the cellulose fibers (if present) may have an average length. For example, in some embodiments, the average length of the cellulose fibers may be greater than or equal to about 0.5 mm, greater than or equal to about 1 mm, greater than or equal to about 2 mm, greater than or equal to about 3 mm, greater than or equal to about 4 mm, greater than or equal to about 5 mm, greater than or equal to about 6 mm, or greater than or equal to about 8 mm. In some cases, the average length of the cellulose fibers may be less than or equal to about 10 mm, less than or equal to about 8 mm, less than or equal to about 6 mm, less than or equal to about 4 mm, less than or equal to about 2 mm, or less than or equal to about 1 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to about 1 mm and less than or equal to about 3 mm). Other values ​​for the average fiber length are also possible.

[0056] In embodiments where the filter media includes at least one pre-filter layer comprising cellulose fibers (e.g., a first layer, a third layer, a fifth layer), the cellulose fibers may constitute any suitable portion of that layer. In some embodiments, the weight percentage of cellulose fibers in the pre-filter layer or multiple pre-filter layers (e.g., a first layer, a third layer, a fifth layer) may be greater than or equal to 0% by weight, greater than or equal to 10% by weight, greater than or equal to 20% by weight, greater than or equal to 30% by weight, greater than or equal to 40% by weight, greater than or equal to 50% by weight, greater than or equal to 60% by weight, greater than or equal to 70% by weight, greater than or equal to 80% by weight, or greater than or equal to 90% by weight. In some embodiments, the weight percentage of cellulose fibers in the pre-filter layer or multiple pre-filter layers (e.g., the first, third, and fifth layers) can be less than or equal to 100% by weight, less than or equal to 90% by weight, less than or equal to 80% by weight, less than or equal to 70% by weight, less than or equal to 60% by weight, less than or equal to 50% by weight, less than or equal to 40% by weight, less than or equal to 30% by weight, less than or equal to 20% by weight, or less than or equal to 10% by weight. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% by weight and less than or equal to 100% by weight, or greater than or equal to 0% by weight and less than or equal to 80% by weight). Other ranges are also possible. In some embodiments, the weight percentage of cellulose fibers in the pre-filter layer (e.g., the first, third, and fifth layers) can be 100% by weight.

[0057] In some embodiments, the filter medium may include one or more pre-filter layers (e.g., a first layer, a third layer, a fifth layer), and at least one pre-filter layer may contain fibrillated fibers. As known to those skilled in the art, fibrillated fibers comprise parent fibers branching into smaller diameter fibrils, and in some cases, these smaller diameter fibrils may further branch into even smaller diameter fibrils, where further branching is also possible. The branching nature of the fibrils results in layers and / or fiber webs with high surface areas and can increase the number of contact points between the fibrillated fibers and other fibers in the web. This increase in contact points between the fibrillated fibers and other fibers and / or components of the web can help enhance the mechanical properties (e.g., flexibility, strength) and / or filtration performance characteristics of the layers and / or fiber webs.

[0058] In some embodiments, the parent fiber (if present) may have an average diameter in the range of micrometers or submicrometers. For example, the average diameter of the parent fiber may be greater than or equal to about 0.5 micrometers, greater than or equal to about 1 micrometer, greater than or equal to about 5 micrometers, greater than or equal to about 10 micrometers, greater than or equal to about 20 micrometers, greater than or equal to about 30 micrometers, greater than or equal to about 40 micrometers, greater than or equal to about 50 micrometers, greater than or equal to about 60 micrometers, or greater than or equal to about 70 micrometers. In some embodiments, the average diameter of the parent fiber may be less than or equal to about 75 micrometers, less than or equal to about 55 micrometers, less than or equal to about 35 micrometers, less than or equal to about 25 micrometers, less than or equal to about 15 micrometers, less than or equal to about 10 micrometers, less than or equal to about 5 micrometers, less than or equal to about 2 micrometers, or less than or equal to about 0.5 micrometers. Combinations of the above ranges are also possible (e.g., the average diameter of the parent fiber is greater than or equal to about 1 micrometer and less than or equal to about 25 micrometers). Other ranges are also possible.

[0059] The average diameter of the fibrils (if present) is typically smaller than the average diameter of the parent fibers. Depending on the average diameter of the parent fibers, in some embodiments, the average diameter of the fibrils may be less than or equal to about 25 micrometers, less than or equal to about 20 micrometers, less than or equal to about 10 micrometers, less than or equal to about 5 micrometers, less than or equal to about 1 micrometer, less than or equal to about 0.5 micrometers, less than or equal to about 0.1 micrometers, less than or equal to about 0.05 micrometers, or less than or equal to about 0.01 micrometers. In some embodiments, the average diameter of the fibrils may be greater than or equal to about 0.003 micrometers, greater than or equal to about 0.01 micrometers, greater than or equal to about 0.05 micrometers, greater than or equal to about 0.1 micrometers, greater than or equal to about 0.5 micrometers, greater than or equal to about 1 micrometer, greater than or equal to about 5 micrometers, greater than or equal to about 10 micrometers, or greater than or equal to about 20 micrometers. Combinations of the above ranges are also possible (e.g., the average diameter of the fibrils is greater than or equal to about 0.01 micrometers and less than or equal to about 20 micrometers). Other ranges are also possible.

[0060] In some embodiments, the average length of the fibrillated fibers (if present) may be less than or equal to about 10 mm, less than or equal to about 8 mm, less than or equal to about 6 mm, less than or equal to about 5 mm, less than or equal to about 4 mm, less than or equal to about 3 mm, or less than or equal to about 2 mm. In some embodiments, the average length of the fibrillated fibers may be greater than or equal to about 1 mm, greater than or equal to about 2 mm, greater than or equal to about 4 mm, greater than or equal to about 5 mm, greater than or equal to about 6 mm, or greater than or equal to about 8 mm. Combinations of the above ranges are also possible (e.g., the average length of the fibrillated fibers is greater than or equal to about 4 mm and less than about 6 mm). Other ranges are also possible. The average length of the fibrillated fibers refers to the average length of the parent fiber from one end to the opposite end. In some embodiments, the maximum average length of the fibrillated fibers falls within the above ranges. The maximum average length refers to the average of the maximum dimensions along one axis of the fibrillated fibers (including the parent fiber and the fibrillated fibers). It should be understood that in some embodiments, the fibers and fibrillated fibers may have dimensions outside the above ranges.

[0061] The fibrillation level of fibrillated fibers (if present) can be measured using any number of suitable methods. For example, the fibrillation level can be measured using the Canadian Standard Freeness (CSF) test, specified by the TAPPI test method T227Om 09 for pulp. This test provides an average CSF value. In some embodiments, the average CSF value of the fibrillated fibers can vary between about 10 mL and about 750 mL. In some embodiments, the average CSF value of the fibrillated fibers used in the pre-filter layer or multiple pre-filter layers can be greater than or equal to about 10 mL, greater than or equal to about 50 mL, greater than or equal to about 100 mL, greater than or equal to about 200 mL, greater than or equal to about 400 mL, greater than or equal to about 600 mL, or greater than or equal to about 700 mL. In some embodiments, the average CSF value of the fibrillated fibers may be less than or equal to about 800 mL, less than or equal to about 600 mL, less than or equal to about 400 mL, less than or equal to about 200 mL, less than or equal to about 100 mL, or less than or equal to about 50 mL. Combinations of the above ranges are also possible (e.g., the average CSF value of the fibrillated fibers is greater than or equal to about 10 mL and less than or equal to about 300 mL). Other ranges are also possible. The average CSF value of the fibrillated fibers may be based on one type of fibrillated fiber or more than one type of fibrillated fiber.

[0062] In embodiments where the filter media includes at least one pre-filter layer (e.g., a first, third, or fifth layer) comprising fibrillated fibers, the fibrillated fibers may constitute any suitable portion of that layer. In some embodiments, the weight percentage of fibrillated fibers in the pre-filter layer or multiple pre-filter layers (e.g., a first, third, or fifth layer) may be greater than or equal to 0% by weight, greater than or equal to 10% by weight, greater than or equal to 25% by weight, greater than or equal to 50% by weight, greater than or equal to 75% by weight, or greater than or equal to 90% by weight. In some embodiments, the weight percentage of fibrillated fibers in the pre-filter layer or multiple pre-filter layers (e.g., a first, third, or fifth layer) may be less than or equal to 100% by weight, less than or equal to 90% by weight, less than or equal to 75% by weight, less than or equal to 50% by weight, less than or equal to 25% by weight, or less than or equal to 10% by weight. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% by weight and less than or equal to 100% by weight, or greater than or equal to 0% by weight and less than or equal to 75% by weight). Other ranges are also possible. In some embodiments, the fibrillated fibers in the pre-filter layers (e.g., the first, third, and fifth layers) can be 100% by weight.

[0063] In some embodiments, the filter medium may include at least one pre-filter layer (e.g., a first layer, a third layer, a fifth layer) comprising glass fibers (e.g., microglass fibers, chopped glass fibers, or combinations thereof).

[0064] The average diameter of the glass fibers (if present) can be, for example, less than or equal to about 30 micrometers, less than or equal to about 25 micrometers, less than or equal to about 15 micrometers, less than or equal to about 12 micrometers, less than or equal to about 10 micrometers, less than or equal to about 9 micrometers, less than or equal to about 7 micrometers, less than or equal to about 5 micrometers, less than or equal to about 3 micrometers, or less than or equal to about 1 micrometer. In some cases, the average fiber diameter of the glass fibers can be greater than or equal to about 0.1 micrometers, greater than or equal to about 0.3 micrometers, greater than or equal to about 1 micrometer, greater than or equal to about 3 micrometers, or greater than or equal to about 7 micrometers, greater than or equal to about 9 micrometers, greater than or equal to about 11 micrometers, or greater than or equal to about 20 micrometers. Combinations of the above ranges are also possible (e.g., greater than or equal to about 0.1 micrometers and less than or equal to about 9 micrometers). Other values ​​for the average fiber diameter are also possible.

[0065] In some embodiments, the average length of the microglass fibers (if present) may be less than or equal to about 10 mm, less than or equal to about 8 mm, less than or equal to about 6 mm, less than or equal to about 5 mm, less than or equal to about 4 mm, less than or equal to about 3 mm, or less than or equal to about 2 mm. In some embodiments, the average length of the microglass fibers may be greater than or equal to about 1 mm, greater than or equal to about 2 mm, greater than or equal to about 4 mm, greater than or equal to about 5 mm, greater than or equal to about 6 mm, or greater than or equal to about 8 mm. Combinations of the above ranges are also possible (e.g., the average length of the microglass fibers is greater than or equal to about 4 mm and less than about 6 mm). Other ranges are also possible.

[0066] Typically, chopped glass fibers (if present) can have an average fiber diameter greater than that of microfibers. In some embodiments, the length of the chopped glass fibers can range from about 0.125 inches to about 1 inch (e.g., about 0.25 inches or about 0.5 inches). In some embodiments, the average length of the chopped glass fibers can be less than or equal to about 1 inch, less than or equal to about 0.8 inches, less than or equal to about 0.6 inches, less than or equal to about 0.5 inches, less than or equal to about 0.4 inches, less than or equal to about 0.3 inches, or less than or equal to about 0.2 inches. In some embodiments, the average length of the chopped glass fibers can be greater than or equal to about 0.125 inches, greater than or equal to about 0.2 inches, greater than or equal to about 0.4 inches, greater than or equal to about 0.5 inches, greater than or equal to about 0.6 inches, or greater than or equal to about 0.8 inches. Combinations of the above ranges are also possible (e.g., the average length of the chopped glass fibers is greater than or equal to about 0.125 inches and less than about 1 inch). Other ranges are also possible.

[0067] In some embodiments, the filter media may include at least one pre-filter layer (e.g., a first layer, a third layer, a fifth layer), and this layer may contain any suitable amount of glass fiber. In some embodiments, the weight percentage of fiber in the pre-filter layer or multiple pre-filter layers (e.g., a first layer, a third layer, a fifth layer) may be greater than or equal to 0% by weight, greater than or equal to 10% by weight, greater than or equal to 20% by weight, greater than or equal to 30% by weight, greater than or equal to 40% by weight, greater than or equal to 50% by weight, greater than or equal to 60% by weight, greater than or equal to 70% by weight, greater than or equal to 80% by weight, greater than or equal to 90% by weight, or greater than or equal to 95% by weight. In some embodiments, the weight percentage of fibers in the pre-filter layer or multiple pre-filter layers (e.g., the first, third, and fifth layers) can be less than or equal to 100% by weight, less than or equal to 95% by weight, less than or equal to 90% by weight, less than or equal to 80% by weight, less than or equal to 70% by weight, less than or equal to 60% by weight, less than or equal to 50% by weight, less than or equal to 40% by weight, less than or equal to 30% by weight, less than or equal to 20% by weight, or less than or equal to 10% by weight. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% by weight and less than or equal to 100% by weight, or greater than or equal to 0% by weight and less than or equal to 95% by weight). Other ranges are also possible. In some embodiments, the weight percentage of glass fibers in the pre-filter layer (e.g., the first, third, and fifth layers) can be 100% by weight.

[0068] In some embodiments, the filter media may include at least one pre-filter layer (e.g., a first layer, a third layer, a fifth layer), and the pre-filter layer or multiple pre-filter layers may contain one or more additives. In some embodiments, the additives may include waxes, such as acrawax. In some embodiments, the weight percentage of wax in the pre-filter layer or multiple pre-filter layers may be greater than or equal to 0% by weight, greater than or equal to 0.1% by weight, greater than or equal to 0.2% by weight, greater than or equal to 0.5% by weight, greater than or equal to 1% by weight, or greater than or equal to 2% by weight. In some embodiments, the weight percentage of wax in the pre-filter layer or multiple pre-filter layers (e.g., a first layer, a third layer, a fifth layer) may be less than or equal to 4% by weight, less than or equal to 2% by weight, less than or equal to 1% by weight, less than or equal to 0.5% by weight, less than or equal to 0.2% by weight, or less than or equal to 0.1% by weight. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% by weight and less than or equal to 10% by weight, or greater than or equal to 0.5% by weight and less than or equal to 4% by weight). Other ranges are also possible.

[0069] In some embodiments, the additive (if present) may include stearates (e.g., magnesium stearate, calcium stearate). In some embodiments, the weight percentage of magnesium stearate in the pre-filter layers (e.g., the first, third, and fifth layers) may be greater than or equal to 0% by weight, greater than or equal to 0.1% by weight, greater than or equal to 0.2% by weight, greater than or equal to 0.5% by weight, greater than or equal to 1% by weight, or greater than or equal to 2% by weight. In some embodiments, the weight percentage of magnesium stearate in the pre-filter layers or multiple pre-filter layers (e.g., the first, third, and fifth layers) may be less than or equal to 4% by weight, less than or equal to 2% by weight, less than or equal to 1% by weight, less than or equal to 0.5% by weight, less than or equal to 0.2% by weight, or less than or equal to 0.1% by weight. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% by weight and less than or equal to 10% by weight, or greater than or equal to 0.5% by weight and less than or equal to 4% by weight). Other ranges are also possible.

[0070] In embodiments where the filter media includes at least one pre-filter layer (e.g., a first, third, or fifth layer), the pre-filter layer or multiple pre-filter layers can have any suitable weight. In some embodiments, the weight of the pre-filter layer or multiple pre-filter layers (e.g., a first, third, or fifth layer) can be greater than or equal to 0.2 g / m³. 2 ≥0.5g / m 2 ≥1g / m 2 ≥2g / m 2 ≥3g / m 2 ≥5g / m 2 ≥10g / m 2 ≥20g / m 2 ≥40g / m 2 or greater than or equal to 100g / m 2 In some implementations, the weight of the pre-filter layer or multiple pre-filter layers (e.g., first layer, third layer, fifth layer) can be less than or equal to 150 g / m³. 2 Less than or equal to 100g / m 2 Less than or equal to 40g / m 2 Less than or equal to 20g / m 2 Less than or equal to 10g / m 2 Less than or equal to 5g / m 2 Less than or equal to 2g / m 2 Less than or equal to 1g / m 2 or less than or equal to 0.5 g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 0.2 g / m³).2 And less than or equal to 150g / m 2 ≥0.5g / m 2 And less than or equal to 40 g / m2, or greater than or equal to 3 g / m2 2 And less than or equal to 40g / m 2 Other ranges are also possible. The fixed weight can be determined according to standard ISO 536.

[0071] In some embodiments where the filter media includes at least one pre-filter layer (e.g., a first, third, or fifth layer), the thickness of the pre-filter layer or multiple pre-filter layers may be 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 0.5 mm, greater than or equal to 1 mm, or greater than or equal to 2 mm. In some embodiments, the thickness of the pre-filter layer or multiple pre-filter layers (e.g., a first, third, or fifth layer) may be less than or equal to 5 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, or less than or equal to 0.05 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.02 mm and less than or equal to 5 mm, or greater than or equal to 0.1 mm and less than or equal to 1 mm). Other ranges are also possible. The thickness of the pre-filter layer or multiple pre-filter layers can be determined according to standard ISO 534 at 50 kPa.

[0072] In some embodiments where the filter medium includes at least one pre-filter layer (e.g., a first layer, a third layer, a fifth layer), the average flow pore size of the pre-filter layer or multiple pre-filter layers can be greater than or equal to 0.5 micrometers, greater than or equal to 1 micrometer, greater than or equal to 2 micrometers, greater than or equal to 4 micrometers, greater than or equal to 10 micrometers, greater than or equal to 20 micrometers, greater than or equal to 50 micrometers, or greater than or equal to 70 micrometers. In some embodiments, the average flow pore size of the pre-filter layer or multiple pre-filter layers (e.g., a first layer, a third layer, a fifth layer) can be less than or equal to 100 micrometers, less than or equal to 70 micrometers, less than or equal to 20 micrometers, less than or equal to 10 micrometers, less than or equal to 4 micrometers, less than or equal to 2 micrometers, or less than or equal to 1 micrometer. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.5 micrometers and less than or equal to 100 micrometers, greater than or equal to 1 micrometer and less than or equal to 70 micrometers, or greater than or equal to 0.5 micrometers and less than or equal to 4 micrometers). Other ranges are also possible. The average flow orifice diameter can be determined according to the standard ASTM F316-03.

[0073] In some embodiments, the filter medium may include one or more pre-filter layers (e.g., a first layer, a third layer, a fifth layer), and the pressure drop across the pre-filter layers or multiple pre-filter layers may be greater than or equal to 0.1 mm H2O, greater than or equal to 0.2 mm H2O, greater than or equal to 0.6 mm H2O, greater than or equal to 1 mm H2O, greater than or equal to 2 mm H2O, greater than or equal to 5 mm H2O, greater than or equal to 10 mm H2O, or greater than or equal to 25 mm H2O. In some embodiments, the pressure drop across the pre-filter layers or multiple pre-filter layers (e.g., a first layer, a third layer, a fifth layer) may be less than or equal to 50 mm H2O, less than or equal to 25 mm H2O, less than or equal to 10 mm H2O, less than or equal to 5 mm H2O, less than or equal to 2 mm H2O, less than or equal to 1 mm H2O, less than or equal to 0.6 mm H2O, or less than or equal to 0.2 mm H2O. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 mm H2O and less than or equal to 50 mm H2O, or greater than or equal to 0.6 mm H2O and less than or equal to 25 mm H2O). Other ranges are also possible. Pressure drop can be determined using ASTM D2986-91.

[0074] In some implementations, the filter media may include one or more pre-filter layers, and the air permeability of the pre-filter layers or multiple pre-filter layers (e.g., first layer, third layer, fifth layer) may be greater than or equal to 2 feet. 3 / minutes / feet 2 (CFM), greater than or equal to 4 CFM, greater than or equal to 8 CFM, greater than or equal to 10 CFM, greater than or equal to 20 CFM, greater than or equal to 50 CFM, greater than or equal to 100 CFM, greater than or equal to 300 CFM, greater than or equal to 500 CFM, or greater than or equal to 1000 CFM. In some embodiments, the permeability of the pre-filter layer or multiple pre-filter layers (e.g., the first layer, the third layer, the fifth layer) may be less than or equal to 1400 CFM, less than or equal to 1000 CFM, less than or equal to 500 CFM, less than or equal to 300 CFM, less than or equal to 300 CFM, less than or equal to 100 CFM, less than or equal to 50 CFM, less than or equal to 20 CFM, less than or equal to 10 CFM, less than or equal to 8 CFM, or less than or equal to 4 CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 2 CFM and less than or equal to 1400 CFM, or greater than or equal to 8 CFM and less than or equal to 300 CFM). Other ranges are also possible. Air permeability can be determined using the TAPPI method T251.

[0075] In some embodiments, the filter medium may include one or more pre-filter layers, and the density of the pre-filter layer or multiple pre-filter layers (e.g., first layer, third layer, fifth layer) may be greater than or equal to 0.001, greater than or equal to 0.0025, greater than or equal to 0.005, greater than or equal to 0.01, greater than or equal to 0.025, greater than or equal to 0.05, greater than or equal to 0.1, greater than or equal to 0.25, greater than or equal to 0.5, greater than or equal to 1, greater than or equal to 2.5, greater than or equal to 5, greater than or equal to 10, or greater than or equal to 25. In some implementations, the density of the pre-filter layer or multiple pre-filter layers (e.g., first, third, and fifth layers) may be less than or equal to 50, less than or equal to 25, less than or equal to 10, less than or equal to 5, less than or equal to 2.5, less than or equal to 1, less than or equal to 0.5, less than or equal to 0.25, less than or equal to 0.1, less than or equal to 0.05, less than or equal to 0.025, less than or equal to 0.01, less than or equal to 0.005, or less than or equal to 0.0025. Combinations of the above 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. The density can be determined using the following formula: Density = [Weight / (Fiber Density * Thickness)] * 100. The weight and thickness can be determined as described herein. Porosity can be derived from density based on the following equation: Density (%) = 100 - Porosity (%). Fiber density is equal to the average density of the material forming the fiber or a combination of materials, which is typically specified by the fiber manufacturer. Average density is obtained by dividing the total mass of fibers within the filter by the total volume of fibers within the pre-filter, where the total volume of fibers within the pre-filter is the sum of the ratios of the mass of each fiber type to the density of each fiber type.

[0076] In some embodiments, the filter media may include one or more pre-filter layers, and the dioctyl phthalate (DOP) particle efficiency of the pre-filter layer or multiple pre-filter layers (e.g., first layer, third layer, fifth layer) may be greater than or equal to 20%, greater than or equal to 25%, greater than or equal to 30%, greater than or equal to 35%, greater than or equal to 40%, greater than or equal to 45%, greater than or equal to 50%, greater than or equal to 55%, greater than or equal to 60%, greater than or equal to 65%, greater than or equal to 70%, greater than or equal to 75%, greater than or equal to 80%, greater than or equal to 85%, greater than or equal to 90%, greater than or equal to 95%, greater than or equal to 97%, greater than or equal to 99%, or greater than or equal to 99.5%. In some implementations, the DOP particle efficiency of the pre-filter layer or multiple pre-filter layers (e.g., first, third, and fifth layers) can be less than or equal to 99.5%, less than or equal to 99%, less than or equal to 97%, less than or equal to 95%, less than or equal to 90%, less than or equal to 85%, less than or equal to 80%, less than or equal to 70%, less than or equal to 60%, less than or equal to 50%, less than or equal to 40%, or less than or equal to 30%. Combinations of the above ranges are also possible (e.g., greater than or equal to 20% and less than or equal to 80%). Other ranges are also possible. The DOP particle efficiency can be measured by blowing DOP particles through the pre-filter layer or multiple pre-filter layers (e.g., first, third, and fifth layers) and measuring the percentage of particles that penetrate the layers. This percentage can be determined as follows: Based on the EN 1822:2009 standard for most penetrating particle size (MPPS) DOP particles, a TSI 3160 automated filter test unit from TSI, Inc., equipped with a DOP generator for DOP aerosol testing, was used, with particles generated by the particle generator having an average diameter varying from 0.02 μm to 0.3 μm. Penetration was measured under a continuous load of DOP particles at a surface velocity of 2.0 cm / s.

[0077] In some embodiments, the pre-filter layers (e.g., the first, third, and fifth layers) are charged. Charge can be induced on the pre-filter layers through a charging process (e.g., electrostatic charging, triboelectric charging, or hydraulic charging). In other embodiments, the pre-filter layers (e.g., the first, third, and fifth layers) are not charged.

[0078] In some embodiments, the pre-filter layer (e.g., the first, third, or fifth layer) is flame-retardant or contains one or more flame-retardant components. For example, the pre-filter layer may contain flame-retardant fibers, flame-retardant binders, flame-retardant coatings, and / or flame-retardant additives (e.g., flame-retardant particles, flame-retardant sheets). The flame-retardant components may be introduced during manufacturing (e.g., during meltblowing, melt spinning, electrospinning, centrifugal spinning, wet web forming, dry web forming, or air-laid web forming processes) or may be added to the binder.

[0079] As described above, in some embodiments, one or more layers of the filter media may be the main filter layer. For example, in some embodiments, the second layer may be a pre-filter layer. In other embodiments, both the second and fourth layers are main filter layers. The main filter layer may, for example, have a higher efficiency than one or more other layers of the media. The characteristics of the main filter layer will be described in more detail here.

[0080] The reference to "primary filter layer" or "multiple primary filter layers" herein should be understood as referring independently to each primary filter layer in the filter medium (if any primary filter layers do exist). That is, each existing primary filter layer may independently possess any of the characteristics described below or may not possess the characteristics described below. In some embodiments, two or more primary filter layers in the filter medium may have similar composition and / or characteristics. In other embodiments, each primary filter layer in the filter medium may have different composition and / or characteristics.

[0081] In some embodiments that include at least one primary filter layer (e.g., a second layer, a fourth layer), the primary filter layer or multiple primary filter layers (e.g., a second layer, a fourth layer) can be solvent-spun layers or multiple solvent-spun layers, such as electrospun (e.g., solvent-electrospun) layers or multiple electrospun layers, or centrifugally spun layers or multiple centrifugally spun layers. As used herein, a layer is a solvent-spun layer if it is formed during a solvent spinning process, or if it contains solvent-spun fibers.

[0082] In some embodiments, the filter medium may include at least one primary filter layer, and the primary filter layer or multiple primary filter layers (e.g., a second layer, a fourth layer) may comprise synthetic fibers. Non-limiting examples of suitable synthetic fibers include nylon, poly(vinylidene fluoride), poly(acrylonitrile), poly(ether sulfone), and polyurea. In some embodiments, the filter medium may comprise blends in which one or more components are synthetic fibers (e.g., blends comprising at least one type of synthetic fiber, blends comprising at least two types of synthetic fibers, or blends comprising three or more types of synthetic fibers). In some embodiments, the primary filter layer or multiple primary filter layers (if present, e.g., a second layer, a fourth layer) may comprise a relatively high amount of nylon fibers (e.g., up to 100% by weight of nylon fibers). In some embodiments, one or more synthetic fibers may be continuous fibers. For example, in some embodiments, the primary filter layer (e.g., a second layer, a fourth layer) comprises 100% continuous synthetic fibers (e.g., 100% solvent-spun fibers such as 100% electrospun fibers).

[0083] In embodiments where the filter media includes at least one primary filter layer, the fibers in the primary filter layer or multiple primary filter layers (e.g., a second layer, a fourth layer) can have any suitable average diameter. In some embodiments, the average diameter of the fibers in the primary filter layer (e.g., a second layer, a fourth layer) is greater than or equal to 20 nm, greater than or equal to 40 nm, greater than or equal to 100 nm, greater than or equal to 200 nm, greater than or equal to 300 nm, or greater than or equal to 500 nm. In some embodiments, the average diameter of the fibers in the primary filter layer or multiple primary filter layers (e.g., a second layer, a fourth layer) is less than or equal to 1000 nm, less than or equal to 500 nm, less than or equal to 300 nm, less than or equal to 200 nm, less than or equal to 100 nm, or less than or equal to 40 nm. Combinations of the above ranges are also possible (e.g., greater than or equal to 20 nm and less than or equal to 1000 nm, greater than or equal to 40 nm and less than or equal to 500 nm, or greater than or equal to 40 nm and less than or equal to 300 nm). Other ranges are also possible.

[0084] In some embodiments where the filter media includes at least one primary filter layer, the fibers within the primary filter layer (e.g., a second, fourth layer) can have any suitable average length. In some embodiments, the average length of the fibers in the primary filter layer or multiple primary filter layers (e.g., a second, fourth layer) can be greater than or equal to 1 inch, greater than or equal to 2 inches, greater than or equal to 5 inches, greater than or equal to 10 inches, greater than or equal to 20 inches, greater than or equal to 50 inches, greater than or equal to 100 inches, greater than or equal to 200 inches, or greater than or equal to 500 inches. In some embodiments, the average length of the fibers in the primary filter layer or multiple primary filter layers (e.g., a second, fourth layer) can be less than or equal to 1000 inches, less than or equal to 500 inches, less than or equal to 200 inches, less than or equal to 100 inches, less than or equal to 50 inches, less than or equal to 20 inches, less than or equal to 10 inches, or less than or equal to 5 inches. Combinations of the above characteristics are also possible (e.g., greater than or equal to 5 inches and less than or equal to 1000 inches). Other ranges are also possible. In some implementations, the fibers within the main filter layer (e.g., the second or fourth layer) may be continuous fibers or may contain continuous fibers.

[0085] In some embodiments, the filter media may include at least one primary filter layer, and the primary filter layer or multiple primary filter layers (e.g., a second layer, a fourth layer) may contain one or more additives. In some embodiments, the additives may include charge additives, such as sodium chloride. In some embodiments, the weight percentage of sodium chloride in the primary filter layer or multiple primary filter layers (e.g., a second layer, a fourth layer) may be greater than or equal to 0% by weight, greater than or equal to 2% by weight, greater than or equal to 4% by weight, greater than or equal to 6% by weight, or greater than or equal to 8% by weight. In some embodiments, the weight percentage of sodium chloride in the primary filter layer or multiple primary filter layers (e.g., a second layer, a fourth layer) may be less than or equal to 10% by weight, less than or equal to 8% by weight, less than or equal to 6% by weight, less than or equal to 4% by weight, or less than or equal to 2% by weight. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% by weight and less than or equal to 10% by weight). Other ranges are also possible.

[0086] In some embodiments, the additive may include a UV protectant. In some embodiments, the weight percentage of the UV protectant in the primary filter layer or multiple primary filter layers (e.g., the second layer, the fourth layer) may be greater than or equal to 0% by weight, greater than or equal to 2% by weight, greater than or equal to 4% by weight, greater than or equal to 6% by weight, or greater than or equal to 8% by weight. In some embodiments, the weight percentage of the UV protectant in the primary filter layer or multiple primary filter layers (e.g., the second layer, the fourth layer) may be less than or equal to 10% by weight, less than or equal to 8% by weight, less than or equal to 6% by weight, less than or equal to 4% by weight, or less than or equal to 2% by weight. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% by weight and less than or equal to 10% by weight). Other ranges are also possible.

[0087] In some embodiments, the additive may include an antioxidant. In some embodiments, the weight percentage of the antioxidant in the primary filter layer or multiple primary filter layers (e.g., the second layer, the fourth layer) may be greater than or equal to 0% by weight, greater than or equal to 2% by weight, greater than or equal to 4% by weight, greater than or equal to 6% by weight, or greater than or equal to 8% by weight. In some embodiments, the weight percentage of the antioxidant in the primary filter layer or multiple primary filter layers (e.g., the second layer, the fourth layer) may be less than or equal to 10% by weight, less than or equal to 8% by weight, less than or equal to 6% by weight, less than or equal to 4% by weight, or less than or equal to 2% by weight. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% by weight and less than or equal to 10% by weight). Other ranges are also possible.

[0088] In embodiments where the filter media includes at least one primary filter layer, the primary filter layer or multiple primary filter layers (e.g., second layer, fourth layer) can have any suitable weight. In some embodiments, the weight of the primary filter layer (e.g., second layer, fourth layer) can be greater than or equal to 0.01 g / m³. 2 ≥0.03g / m 2 ≥0.05g / m 2 ≥0.1g / m 2 ≥0.3g / m 2 ≥0.5g / m 2 ≥1g / m 2 ≥3g / m 2 ≥5g / m 2 ≥10g / m 2 or greater than or equal to 30g / m 2 In some implementations, the weight of the primary filter layer (e.g., the second or fourth layer) can be less than or equal to 40 g / m³. 2 Less than or equal to 30g / m2 Less than or equal to 10g / m 2 Less than or equal to 5g / m 2 Less than or equal to 3g / m 2 Less than or equal to 1g / m 2 Less than or equal to 0.5 g / m 2 Less than or equal to 0.3 g / m 2 Less than or equal to 0.1 g / m 2 Less than or equal to 0.05 g / m 2 Or less than or equal to 0.03 g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 0.01 g / m³). 2 And less than or equal to 40g / m 2 ≥0.03g / m 2 And less than or equal to 30g / m 2 Or greater than or equal to 0.01 g / m 2 And less than or equal to 5g / m 2 Other ranges are also possible. The fixed weight can be determined according to standard ISO 536.

[0089] In some embodiments where the filter medium includes at least one primary filter layer, the thickness of the primary filter layer or multiple primary filter layers (e.g., a second layer, a fourth layer) may be greater than or equal to 1 micrometer, greater than or equal to 2 micrometers, greater than or equal to 5 micrometers, greater than or equal to 10 micrometers, greater than or equal to 20 micrometers, greater than or equal to 50 micrometers, greater than or equal to 100 micrometers, greater than or equal to 200 micrometers, greater than or equal to 500 micrometers, greater than or equal to 1000 micrometers, greater than or equal to 2000 micrometers, greater than or equal to 3000 micrometers, or greater than or equal to 4000 micrometers. In some embodiments, the thickness may be less than or equal to 5000 micrometers, less than or equal to 4000 micrometers, less than or equal to 3000 micrometers, less than or equal to 2000 micrometers, less than or equal to 1000 micrometers, less than or equal to 500 micrometers, less than or equal to 200 micrometers, less than or equal to 1 ... Combinations of the above ranges are also possible (e.g., greater than or equal to 1 micrometer and less than or equal to 5000 micrometers, greater than or equal to 5 micrometers and less than or equal to 1000 micrometers, or greater than or equal to 10 micrometers and less than or equal to 500 micrometers). Other ranges are also possible. The thickness of the main filter layer or multiple main filter layers can be determined using SEM cross-sectional imaging.

[0090] In some implementations, the filter medium may include one or more primary filter layers, and the density of the primary filter layer or multiple primary filter layers (e.g., second layer, fourth layer) may be greater than or equal to 0.001, greater than or equal to 0.0025, greater than or equal to 0.005, greater than or equal to 0.01, greater than or equal to 0.025, greater than or equal to 0.05, greater than or equal to 0.1, greater than or equal to 0.25, greater than or equal to 0.5, greater than or equal to 1, greater than or equal to 2.5, greater than or equal to 5, greater than or equal to 10, or greater than or equal to 25. In some implementations, the density of the primary filter layer or multiple primary filter layers (e.g., second, fourth layers) can be less than or equal to 50, less than or equal to 25, less than or equal to 10, less than or equal to 5, less than or equal to 2.5, less than or equal to 1, less than or equal to 0.5, less than or equal to 0.25, less than or equal to 0.1, less than or equal to 0.05, less than or equal to 0.025, less than or equal to 0.01, less than or equal to 0.005, or less than or equal to 0.0025. Combinations of the above 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.

[0091] In some implementations, the filter medium may include one or more main filter layers, and the pressure drop across the main filter layer or multiple main filter layers (e.g., the second layer, the fourth layer) may be greater than or equal to 0.5 mm H2O, greater than or equal to 0.75 mm H2O, greater than or equal to 1 mm H2O, greater than or equal to 2.5 mm H2O, greater than or equal to 5 mm H2O, greater than or equal to 7.5 mm H2O, greater than or equal to 10 mm H2O, greater than or equal to 25 mm H2O, or greater than or equal to 50 mm H2O. In some implementations, the pressure drop across the primary filter layer or multiple primary filter layers (e.g., the second, fourth layer) can be less than or equal to 100 mmH2O, less than or equal to 75 mmH2O, less than or equal to 50 mmH2O, less than or equal to 25 mmH2O, less than or equal to 10 mmH2O, less than or equal to 7.5 mmH2O, less than or equal to 5 mmH2O, less than or equal to 2.5 mmH2O, less than or equal to 1 mmH2O, or less than or equal to 0.75 mmH2O. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.5 mmH2O and less than or equal to 100 mmH2O, or greater than or equal to 1 mmH2O and less than or equal to 75 mmH2O). Other ranges are also possible. The pressure drop can be determined using ASTM D2986-91.

[0092] As described above, in some embodiments, one or more layers may be support layers. Support layers may be used to support one or more other layers of the medium, such as a main filter layer. In some cases, support layers may be used to protect and / or cover one or more other layers of the medium, such as a main filter layer. For example, in some embodiments, the third layer is a support layer. In some embodiments, the first layer is a support layer. In some embodiments, the fifth layer is a support layer. The characteristics of the support layers will be described in more detail below.

[0093] The reference to "support layer or multiple support layers" in this document should be understood as referring independently to each support layer in the filter medium (if any support layers are present). That is, each existing support layer may independently have any of the characteristics described below or may not have the characteristics described below. In some embodiments, two or more support layers in the filter medium may have similar composition and / or characteristics. In other embodiments, each support layer in the filter medium may have different composition and / or characteristics.

[0094] In some embodiments that include at least one support layer, the support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer) may be wet-laid layers. That is, in some embodiments, the support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer) may be formed by a wet-laid process. In other embodiments, the support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer) may be non-wet-laid layers. That is, in some embodiments, the support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer) may be formed by a non-wet-laid process (e.g., air-laid process, carding process, spinning process (e.g., spunbond process)). In some embodiments, the support layer or multiple support layers may be spunbond layers, or layers formed by a spunbond process.

[0095] In some embodiments, the filter media may include one or more support layers, and the support layers (e.g., first, third, and fifth layers) may comprise synthetic fibers. The synthetic fibers may comprise any suitable type of synthetic polymer. Examples of suitable synthetic fibers include polyesters (e.g., polyethylene terephthalate, polybutylene terephthalate), polycarbonate, polyamides (e.g., various nylon polymers), polyaramids, polyimides, polyethylene, polypropylene, polyetheretherketone, polyolefins, acrylics, polyvinyl alcohol, regenerated cellulose (e.g., synthetic cellulose such as lyocell, rayon), polyacrylonitrile, polyvinylidene fluoride (PVDF), copolymers of polyethylene and PVDF, polyethersulfone, and combinations thereof. In some embodiments, the synthetic fibers are organic polymer fibers. The synthetic fibers may also comprise multicomponent fibers (i.e., fibers with multiple components, such as bicomponent fibers). In some cases, synthetic fibers may include meltblown fibers, melt-spun fibers, electrospun (e.g., melt electrospun, solvent electrospun) fibers, or centrifugally spun fibers, which may be formed from polymers described herein (e.g., polyester, polypropylene). In some embodiments, the synthetic fibers may be short fibers. In some embodiments, the synthetic fibers may be fibers containing flame retardants. The filter media and each layer within the filter media may also include combinations of more than one type of synthetic fiber. It should be understood that other types of synthetic fibers may also be used.

[0096] In some embodiments, the filter media may include a support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer), and the support layer or multiple support layers may contain flame-retardant fibers and / or fibers containing flame retardants. In some embodiments, the fibers containing flame retardants may be synthetic fibers. Typically, the total weight percentage of coarse-diameter fibers and / or fine-diameter fibers as described below may include fibers containing flame retardants (e.g., flame-retardant fibers).

[0097] In some embodiments, the filter media may include at least one support layer, and the support layer or multiple support layers may comprise coarse synthetic fibers. In some embodiments, the support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer) may comprise coarse synthetic fibers with an average diameter greater than or equal to 4 micrometers, greater than or equal to 7 micrometers, greater than or equal to 10 micrometers, greater than or equal to 15 micrometers, greater than or equal to 17 micrometers, greater than or equal to 20 micrometers, greater than or equal to 25 micrometers, greater than or equal to 30 micrometers, greater than or equal to 35 micrometers, greater than or equal to 40 micrometers, greater than or equal to 45 micrometers, greater than or equal to 50 micrometers, or greater than or equal to 55 micrometers. In some embodiments, the support layer or multiple support layers (e.g., the first layer, the third layer, the fifth layer) may comprise coarse synthetic fibers with an average diameter less than or equal to 60 micrometers, less than or equal to 55 micrometers, less than or equal to 50 micrometers, less than or equal to 45 micrometers, less than or equal to 40 micrometers, less than or equal to 35 micrometers, less than or equal to 30 micrometers, less than or equal to 25 micrometers, less than or equal to 20 micrometers, less than or equal to 17 micrometers, less than or equal to 15 micrometers, less than or equal to 10 micrometers, or less than or equal to 7 micrometers. Combinations of the above ranges are also possible (e.g., greater than or equal to 4 micrometers and less than or equal to 60 micrometers, greater than or equal to 7 micrometers and less than or equal to 40 micrometers, greater than or equal to 10 micrometers and less than or equal to 60 micrometers, or greater than or equal to 17 micrometers and less than or equal to 35 micrometers). Other ranges are also possible.

[0098] In embodiments where the filter media includes at least one support layer (e.g., a first, third, or fifth layer) and the support layer or multiple support layers contain coarse synthetic fibers, the average length of the coarse synthetic fibers in the support layer or multiple support layers can be any suitable value. In some embodiments, the average length of the coarse synthetic fibers in the support layer or multiple support layers (e.g., a first, third, or fifth layer) is greater than or equal to 3 mm, greater than or equal to 6 mm, greater than or equal to 10 mm, greater than or equal to 20 mm, greater than or equal to 50 mm, greater than or equal to 100 mm, greater than or equal to 200 mm, greater than or equal to 5000 mm, greater than or equal to 10000 mm, or greater than or equal to 20000 mm. In some embodiments, the average length of the coarse synthetic fibers in the support layer or multiple support layers (e.g., the first, third, and fifth layers) is less than or equal to 25400 mm, less than or equal to 20000 mm, less than or equal to 10000 mm, less than or equal to 5000 mm, less than or equal to 2000 mm, less than or equal to 1000 mm, less than or equal to 500 mm, less than or equal to 200 mm, less than or equal to 100 mm, less than or equal to 50 mm, less than or equal to 20 mm, or less than or equal to 10 mm or 6 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 3 mm and less than or equal to 25400 mm, or greater than or equal to 6 mm and less than or equal to 25400 mm). Other ranges are also possible. In some embodiments, the coarse synthetic fibers are continuous fibers. In other embodiments, the coarse synthetic fibers are discontinuous fibers (e.g., short fibers).

[0099] In some embodiments where the filter media includes a support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer) having coarse synthetic fibers, the weight percentage of coarse synthetic fibers in the support layer (e.g., the first layer, the third layer, the fifth layer) can be 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 50 wt%, greater than or equal to 70 wt%, or greater than or equal to 90 wt%. In some embodiments, the weight percentage of coarse synthetic fibers in the support layer (e.g., the first layer, the third layer, the fifth layer) can be less than or equal to 100 wt%, less than or equal to 90 wt%, less than or equal to 70 wt%, less than or equal to 50 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%, or less than or equal to 2 wt%. Combinations of the above ranges are also possible (e.g., greater than or equal to 1% by weight and less than or equal to 100% by weight, greater than or equal to 10% by weight and less than or equal to 100% by weight, or greater than or equal to 30% by weight and less than or equal to 100% by weight). Other ranges are also possible. In some embodiments, the weight percentage of coarse synthetic fibers in the support layers (e.g., the first layer, the third layer, the fifth layer) can be 100% by weight.

[0100] In some embodiments, the filter media may include a support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer), and the support layer or multiple support layers may contain fine synthetic fibers. In such embodiments, the average diameter of the fine synthetic fibers can be any suitable value. In embodiments containing both fine and coarse synthetic fibers, the average diameter of the fine synthetic fibers may be smaller than the average diameter of the coarse synthetic fibers present in the support layer or multiple support layers. In some embodiments, the support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer) may contain fine synthetic fibers with an average diameter greater than or equal to 1 micrometer, greater than or equal to 1.5 micrometers, greater than or equal to 2.5 micrometers, greater than or equal to 5 micrometers, greater than or equal to 7.5 micrometers, greater than or equal to 10 micrometers, greater than or equal to 12.5 micrometers, greater than or equal to 15 micrometers, or greater than or equal to 17.5 micrometers. In some embodiments, the support layer or multiple support layers (e.g., the first layer, the third layer, the fifth layer) may comprise fine synthetic fibers with an average diameter of less than or equal to 20 micrometers, less than or equal to 17.5 micrometers, less than or equal to 15 micrometers, less than or equal to 12.5 micrometers, less than or equal to 10 micrometers, less than or equal to 7.5 micrometers, less than or equal to 5 micrometers, less than or equal to 2.5 micrometers, or less than or equal to 1.5 micrometers. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 micrometer and less than or equal to 20 micrometers, or greater than or equal to 1.5 micrometers and less than or equal to 10 micrometers). Other ranges are also possible.

[0101] In embodiments where the filter media includes at least one support layer (e.g., a first, third, or fifth layer) and the support layer or multiple support layers comprise fine synthetic fibers, the average length of the fine synthetic fibers in the support layer or multiple support layers can be any suitable value. In some embodiments, the average length of the fine synthetic fibers in the support layer or multiple support layers (e.g., a first, third, or fifth layer) is greater than or equal to 3 mm, greater than or equal to 6 mm, greater than or equal to 9 mm, greater than or equal to 12 mm, greater than or equal to 15 mm, greater than or equal to 18 mm, greater than or equal to 21 mm, greater than or equal to 24 mm, greater than or equal to 27 mm, greater than or equal to 50 mm, greater than or equal to 100 mm, greater than or equal to 200 mm, greater than or equal to 500 mm, greater than or equal to 10000 mm, or greater than or equal to 20000 mm. In some embodiments, the average length of the fine synthetic fibers in the support layer or multiple support layers is less than or equal to 25400 mm, less than or equal to 20000 mm, less than or equal to 10000 mm, less than or equal to 5000 mm, less than or equal to 2000 mm, less than or equal to 1000 mm, less than or equal to 500 mm, less than or equal to 200 mm, less than or equal to 100 mm, less than or equal to 50 mm, less than or equal to 30 mm, less than or equal to 27 mm, less than or equal to 24 mm, less than or equal to 21 mm, less than or equal to 18 mm, less than or equal to 15 mm, less than or equal to 12 mm, less than or equal to 9 mm, or less than or equal to 6 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 3 mm and less than or equal to 25400 mm, greater than or equal to 6 mm and less than or equal to 25400 mm, greater than or equal to 3 mm and less than or equal to 30 mm, or greater than or equal to 6 mm and less than or equal to 12 mm). Other ranges are also possible. In some embodiments, the fine synthetic fibers are continuous fibers (e.g., fibers formed by meltblowing or spunbonding processes). In other embodiments, the fine synthetic fibers are discontinuous fibers (e.g., short fibers). In some embodiments where the filter media includes a support layer or multiple support layers having fine synthetic fibers, the weight percentage of the fine synthetic fibers in the support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer) can be greater than or equal to 0 wt%, greater than or equal to 5 wt%, greater than or equal to 10 wt%, greater than or equal to 15 wt%, greater than or equal to 20 wt%, greater than or equal to 25 wt%, greater than or equal to 30 wt%, greater than or equal to 35 wt%, or greater than or equal to 40 wt%, greater than or equal to 45 wt%.In some embodiments, the weight percentage of fine synthetic fibers in the support layer or multiple support layers (e.g., the first layer, the third layer, the fifth layer) may be less than or equal to 50% by weight, less than or equal to 45% by weight, less than or equal to 40% by weight, less than or equal to 35% by weight, less than or equal to 30% by weight, less than or equal to 25% by weight, less than or equal to 20% by weight, less than or equal to 15% by weight, less than or equal to 10% by weight, or less than or equal to 5% by weight. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% by weight and less than or equal to 50% by weight, or greater than or equal to 1% by weight and less than or equal to 30% by weight). Other ranges are also possible.

[0102] In some embodiments, the filter media may include a support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer), and the support layer or multiple support layers may contain bonding fibers. Typically, bonding fibers (if present) can be used to bond the fibers in the layers. In some embodiments, the bonding fibers comprise a polymer having a lower melting point than one or more of the main components (e.g., certain fibers) in the layer. The bonding fibers may be single-component (e.g., polyethylene fibers, copolyester fibers) or multi-component (e.g., bicomponent fibers). For example, the bonding fibers may be bicomponent fibers. Bicomponent fibers may include thermoplastic polymers. The components of a bicomponent fiber may have different melting temperatures. For example, the fiber may comprise a core and a sheath, wherein the activation temperature of the sheath is lower than the melting temperature of the core. This causes the sheath to melt before the core, such that the sheath bonds to the other fibers in the layer, while the core maintains its structural integrity. The core / sheath bonding fibers may be coaxial or non-coaxial. Other exemplary bicomponent fibers may include split-film fibers, side-by-side fibers, and / or "island-type" fibers. Typically, the total weight percentage of coarse-diameter fibers and / or fine-diameter fibers may include bonding fibers.

[0103] In some embodiments, the support layer or multiple support layers (e.g., the first, third, and fifth layers) may contain bonding fibers with an average diameter greater than or equal to 1 micrometer, greater than or equal to 2 micrometers, greater than or equal to 5 micrometers, greater than or equal to 10 micrometers, greater than or equal to 15 micrometers, greater than or equal to 20 micrometers, or greater than or equal to 25 micrometers. In some embodiments, the support layer or multiple support layers (e.g., the first, third, and fifth layers) may contain bonding fibers with an average diameter less than or equal to 30 micrometers, less than or equal to 25 micrometers, less than or equal to 20 micrometers, less than or equal to 15 micrometers, less than or equal to 10 micrometers, less than or equal to 5 micrometers, or less than or equal to 2 micrometers. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 micrometer and less than or equal to 30 micrometers, or greater than or equal to 2 micrometers and less than or equal to 20 micrometers). Other ranges are also possible.

[0104] In embodiments where the filter media includes at least one support layer (e.g., a first, third, or fifth layer) and the support layer or multiple support layers contain bonding fibers, the average length of the bonding fibers in the support layer or multiple support layers can be any suitable value. In some embodiments, the average length of the bonding fibers in the support layer or multiple support layers (e.g., a first, third, or fifth layer) is greater than or equal to 3 mm, greater than or equal to 6 mm, greater than or equal to 9 mm, greater than or equal to 12 mm, greater than or equal to 15 mm, greater than or equal to 18 mm, greater than or equal to 21 mm, greater than or equal to 24 mm, or greater than or equal to 27 mm. In some embodiments, the average length of the bonding fibers in the support layer or multiple support layers (e.g., a first, third, or fifth layer) is less than or equal to 30 mm, less than or equal to 27 mm, less than or equal to 24 mm, less than or equal to 21 mm, less than or equal to 18 mm, less than or equal to 15 mm, less than or equal to 12 mm, less than or equal to 9 mm, or less than or equal to 6 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 3 mm and less than or equal to 30 mm, or greater than or equal to 6 mm and less than or equal to 12 mm). Other ranges are also possible.

[0105] In some embodiments where the filter media includes a support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer) having bonded fibers, the weight percentage of the bonded fibers in the support layer or multiple support layers may be greater than or equal to 0% by weight, greater than or equal to 5% by weight, greater than or equal to 10% by weight, greater than or equal to 15% by weight, greater than or equal to 20% by weight, greater than or equal to 25% by weight, greater than or equal to 30% by weight, greater than or equal to 40% by weight, greater than or equal to 50% by weight, greater than or equal to 60% by weight, greater than or equal to 70% by weight, or greater than or equal to 80% by weight. In some embodiments, the weight percentage of the bonding fibers in the support layer or multiple support layers (e.g., the first layer, the third layer, the fifth layer) may be 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 10 wt%, or less than or equal to 5 wt%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 90 wt%, or greater than or equal to 10 wt% and less than or equal to 30 wt%). Other ranges are also possible.

[0106] In some embodiments, the filter media may include one or more support layers (e.g., a first layer, a third layer, a fifth layer), and the support layers or multiple support layers may contain one or more binder resins. Typically, the binder resin can be used to bond fibers in the layers. Typically, the binder resin can have any suitable composition. For example, the binder resin may include thermoplastic resins (e.g., acrylics, polyvinyl acetate, polyesters, polyamides), thermosetting resins (e.g., epoxy resins, phenolic resins), or combinations thereof. In some cases, the binder resin includes one or more of vinyl acetate resins, epoxy resins, polyester resins, copolyester resins, polyvinyl alcohol resins, acrylic resins (e.g., styrene-acrylic resins), and phenolic resins. Other resins are also possible. In some such embodiments, the resin may include a polymeric resin containing a covalently attached flame retardant.

[0107] Resin (if present) can be added to the fibers in any suitable manner, including, for example, in a wet state. In some embodiments, the resin coats the fibers and is used to adhere the fibers to each other to promote fiber adhesion. Any suitable method and equipment can be used to coat the fibers, such as using curtain coating, gravure coating, melt coating, dip coating, roller coating, or spin coating. In some embodiments, the binder precipitates when added to the fiber blend. Where appropriate, any suitable precipitant (e.g., epichlorohydrin) can be provided to the fibers, for example, by injection into the blend. In some embodiments, when added to the fibers, the resin is added in such a way that one or more layers or the entire filter medium is impregnated with resin (e.g., resin permeates the whole). In multilayer meshes, the resin can be added to each layer separately before layer assembly, or the resin can be added to the layers after layer assembly. In some embodiments, the resin is added to the fibers in a dry state, for example, by spraying or saturation impregnation, or any of the methods described above. In other embodiments, the resin is added to a wet layer.

[0108] In some embodiments, the adhesive may be present in the layer, and the adhesive may include both adhesive fibers and adhesive resin.

[0109] In some embodiments, the filter medium may include one or more support layers (e.g., a first layer, a third layer, a fifth layer), and the weight percentage of the binder resin in the support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer) may be greater than or equal to 0% by weight, greater than or equal to 5% by weight, greater than or equal to 10% by weight, greater than or equal to 15% by weight, greater than or equal to 20% by weight, greater than or equal to 25% by weight, greater than or equal to 30% by weight, greater than or equal to 40% by weight, greater than or equal to 50% by weight, greater than or equal to 60% by weight, greater than or equal to 70% by weight, or greater than or equal to 80% by weight. In some embodiments, the weight percentage of the binder resin in the support layer or multiple support layers (e.g., the first layer, the third layer, the fifth layer) may be less than or equal to 90% by weight, less than or equal to 80% by weight, less than or equal to 70% by weight, less than or equal to 60% by weight, less than or equal to 50% by weight, less than or equal to 40% by weight, less than or equal to 30% by weight, less than or equal to 25% by weight, less than or equal to 20% by weight, less than or equal to 15% by weight, less than or equal to 10% by weight, or less than or equal to 5% by weight. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% by weight and less than or equal to 90% by weight, or greater than or equal to 10% by weight and less than or equal to 30% by weight). Other ranges are also possible.

[0110] In some embodiments, the filter media may include at least one support layer, and the support layer or multiple support layers (e.g., first layer, third layer, fifth layer) may contain one or more additives. In some embodiments, the additives may include, for example, one or more of antimicrobial additives, antifungal additives, UV protectants, antioxidants, or other components. In some embodiments, the weight percentage of the additives in the support layer or multiple support layers (e.g., first layer, third layer, fifth layer) may be greater than or equal to 0% by weight, greater than or equal to 2% by weight, greater than or equal to 4% by weight, greater than or equal to 6% by weight, or greater than or equal to 8% by weight. In some embodiments, the weight percentage of the additives in the support layer or multiple support layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 10% by weight, less than or equal to 8% by weight, less than or equal to 6% by weight, less than or equal to 4% by weight, or less than or equal to 2% by weight. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% by weight and less than or equal to 10% by weight). Other ranges are also possible. Each additive may be added independently in one or more of the above ranges.

[0111] In some embodiments where the filter media includes at least one support layer (e.g., a first layer, a third layer, a fifth layer), the thickness of the support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer) may be greater than or equal to 0.05 mm, greater than or equal to 0.1 mm, greater than or equal to 0.25 mm, greater than or equal to 0.38 mm, greater than or equal to 0.5 mm, greater than or equal to 1 mm, greater than or equal to 2 mm, or greater than or equal to 3 mm. In some embodiments, the thickness of the support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer) may be less than or equal to 5 mm, less than or equal to 3 mm, less than or equal to 2 mm, less than or equal to 1 mm, less than or equal to 0.5 mm, less than or equal to 0.38 mm, less than or equal to 0.25 mm, or less than or equal to 0.1 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.25 mm and less than or equal to 2 mm, greater than or equal to 0.38 mm and less than or equal to 1 mm, greater than or equal to 0.05 mm and less than or equal to 5 mm, or greater than or equal to 0.1 mm and less than or equal to 3 mm). Other ranges are also possible. The thickness of the support layer or multiple support layers can be determined according to standard ISO 534 at 50 kPa.

[0112] In embodiments where the filter media includes at least one support layer (e.g., a first layer, a third layer, a fifth layer), the support layer or multiple support layers can have any suitable weight. In some embodiments, the weight of the support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer) can be greater than or equal to 10 g / m³. 2 ≥20g / m 2 ≥35g / m 2 ≥40g / m 2 ≥80g / m 2 ≥120g / m 2 ≥150g / m 2 ≥200g / m 2 or greater than or equal to 250g / m 2 In some implementations, the weight of the support layer or multiple support layers (e.g., the first layer, the third layer, the fifth layer) can be less than or equal to 300 g / m². 2 Less than or equal to 250g / m 2 Less than or equal to 200g / m 2 Less than or equal to 150g / m 2 Less than or equal to 120g / m 2 Less than or equal to 80g / m 2 Less than or equal to 40g / m 2 Less than or equal to 35g / m2 Or less than or equal to 20g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 10 g / m³). 2 And less than or equal to 300g / m 2 Greater than or equal to 10g / m 2 And less than or equal to 150g / m 2 ≥20g / m 2 And less than or equal to 200g / m 2 ≥40g / m 2 And less than or equal to 120g / m 2 or greater than or equal to 35g / m 2 And less than or equal to 80g / m 2 Other ranges are also possible. The fixed weight can be determined according to standard ISO 536.

[0113] In some embodiments where the filter media includes at least one support layer (e.g., a first, third, or fifth layer), the average flow orifice diameter of the support layer or multiple support layers (e.g., a first, third, or fifth layer) can be greater than or equal to 20 micrometers, greater than or equal to 50 micrometers, greater than or equal to 70 micrometers, greater than or equal to 100 micrometers, greater than or equal to 150 micrometers, greater than or equal to 200 micrometers, or greater than or equal to 250 micrometers. In some embodiments, the average flow orifice diameter of the support layer or multiple support layers (e.g., a first, third, or fifth layer) can be less than or equal to 300 micrometers, less than or equal to 250 micrometers, less than or equal to 200 micrometers, less than or equal to 150 micrometers, less than or equal to 100 micrometers, less than or equal to 70 micrometers, or less than or equal to 50 micrometers. Combinations of the above ranges are also possible (e.g., greater than or equal to 20 micrometers and less than or equal to 300 micrometers, or greater than or equal to 50 micrometers and less than or equal to 150 micrometers). Other ranges are also possible. The average flow orifice diameter can be determined according to the standard ASTM F316-03.

[0114] In some embodiments, the filter medium may include one or more support layers (e.g., a first layer, a third layer, a fifth layer), and the air permeability of the support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer) may be greater than or equal to 10 CFM, greater than or equal to 20 CFM, greater than or equal to 50 CFM, greater than or equal to 75 CFM, greater than or equal to 100 CFM, greater than or equal to 200 CFM, greater than or equal to 500 CFM, greater than or equal to 800 CFM, or greater than or equal to 1000 CFM. In some embodiments, the air permeability of the support layer or multiple support layers may be less than or equal to 1400 CFM, less than or equal to 1000 CFM, less than or equal to 800 CFM, less than or equal to 500 CFM, less than or equal to 20 CFM, less than or equal to 20 CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 10 CFM and less than or equal to 1400 CFM, greater than or equal to 20 CFM and less than or equal to 500 CFM, greater than or equal to 50 CFM and less than or equal to 800 CFM, or greater than or equal to 200 CFM and less than or equal to 500 CFM). Other ranges are also possible. Air permeability can be determined using the TAPPI method T251.

[0115] In some embodiments where the filter media includes a support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer), the support layer or multiple support layers may be able to remove particles at certain efficiency levels as measured by the EN1822:2009 standard as described herein. In some embodiments, the efficiency of the support layer may be greater than or equal to 20%, greater than or equal to 25%, greater than or equal to 30%, greater than or equal to 35%, greater than or equal to 40%, greater than or equal to 45%, greater than or equal to 50%, greater than or equal to 55%, greater than or equal to 60%, greater than or equal to 65%, greater than or equal to 70%, greater than or equal to 75%, greater than or equal to 80%, greater than or equal to 85%, greater than or equal to 90%, greater than or equal to 95%, greater than or equal to 97%, greater than or equal to 99%, or greater than or equal to 99.5%. In some embodiments, the efficiency of the support layer or multiple support layers (e.g., first layer, third layer, fifth layer) can be less than or equal to 99.5%, less than or equal to 99%, less than or equal to 97%, less than or equal to 95%, less than or equal to 90%, less than or equal to 85%, less than or equal to 80%, less than or equal to 70%, less than or equal to 60%, less than or equal to 50%, less than or equal to 40%, or less than or equal to 30%. Combinations of the above ranges are also possible (e.g., greater than or equal to 20% and less than or equal to 80%). In embodiments where both a support layer and a main filter layer are present in the filter medium, the main filter layer can have a higher efficiency than the support layer.

[0116] In some embodiments, the support layer (e.g., the first, third, or fifth layer) is flame-retardant or contains one or more flame-retardant components. For example, the support layer may contain flame-retardant fibers, flame-retardant binders, flame-retardant coatings, and / or flame-retardant additives (e.g., flame-retardant particles, flame-retardant sheets). The flame-retardant components may be introduced during manufacturing (e.g., during meltblowing, melt spinning, electrospinning, centrifugal spinning, wet web forming, dry web forming, or air-laid web forming processes) or may be added to the binder.

[0117] In embodiments where the filter media includes a support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer), the support layer or multiple support layers may have any suitable dry tensile strength in the transverse direction. In some embodiments, the dry tensile strength of the support layer or multiple support layers (e.g., a first layer, a third layer, a fifth layer) in the transverse direction is greater than or equal to 1 psi, greater than or equal to 2 psi, greater than or equal to 4 psi, greater than or equal to 6 psi, greater than or equal to 8 psi, greater than or equal to 10 psi, greater than or equal to 12 psi, greater than or equal to 15 psi, or greater than or equal to 17 psi. In some implementations, the dry tensile strength in the transverse direction of the support layer or multiple support layers (e.g., the first, third, and fifth layers) is less than or equal to 20 psi, less than or equal to 17 psi, less than or equal to 15 psi, less than or equal to 12 psi, less than or equal to 10 psi, less than or equal to 8 psi, less than or equal to 6 psi, less than or equal to 4 psi, or less than or equal to 2 psi. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 psi and less than or equal to 20 psi, or greater than or equal to 6 psi and less than or equal to 15 psi). Other ranges are also possible. The dry tensile strength in the transverse direction can be determined according to standard T494 om-96 using a test span of 4 inches and a gripper separation speed of 1 inch / minute.

[0118] In some implementations, the dry tensile strength of the support layer or multiple support layers (e.g., the first layer, the third layer, the fifth layer) in the machine direction is 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 15 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 35 psi, greater than or equal to 40 psi, greater than or equal to 45 psi, greater than or equal to 50 psi, or greater than or equal to 55 psi. In some implementations, the dry tensile strength in the machine direction of the support layer or multiple support layers (e.g., first, third, and fifth layers) is less than or equal to 60 psi, less than or equal to 55 psi, less than or equal to 50 psi, less than or equal to 45 psi, less than or equal to 40 psi, less than or equal to 35 psi, less than or equal to 30 psi, less than or equal to 25 psi, less than or equal to 20 psi, less than or equal to 15 psi, less than or equal to 10 psi, or less than or equal to 5 psi. Combinations of the above ranges are also possible (e.g., greater than or equal to 2 psi and less than or equal to 60 psi, or greater than or equal to 10 psi and less than or equal to 40 psi). Other ranges are also possible. The dry tensile strength in the machine direction can be determined according to standard T494om-96 using a test span of 4 inches and a gripper separation speed of 1 inch / minute.

[0119] In some embodiments where the filter media includes at least one support layer (e.g., a first, third, or fifth layer), the dry malan burst strength of the support layer or multiple support layers (e.g., a first, third, or fifth layer) can be greater than or equal to 20 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, or greater than or equal to 225 psi. In some embodiments, the dry malan burst strength of the support layer or multiple support layers (e.g., a first, third, or fifth layer) is less than or equal to 250 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, or less than or equal to 30 psi. Combinations of the above ranges are also possible (e.g., greater than or equal to 20 psi and less than or equal to 250 psi, or greater than or equal to 30 psi and less than or equal to 150 psi). Other ranges are also possible. The bursting strength of dry malenome can be determined according to standard T403 om-91.

[0120] In embodiments where the filter media includes at least one support layer (e.g., a first, third, or fifth layer), the support layer or multiple support layers can have any suitable Gurley stiffness. In some embodiments, the support layer or multiple support layers (e.g., a first, third, or fifth layer) has a Gurley stiffness in the transverse direction greater than or equal to 10 mg, greater than or equal to 20 mg, greater than or equal to 50 mg, greater than or equal to 100 mg, greater than or equal to 200 mg, greater than or equal to 500 mg, greater than or equal to 1000 mg, or greater than or equal to 2000 mg. In some embodiments, the support layer or multiple support layers (e.g., a first, third, or fifth layer) has a Gurley stiffness in the transverse direction less than or equal to 3500 mg, less than or equal to 2000 mg, less than or equal to 1000 mg, less than or equal to 50 mg, less than or equal to 20 mg, less than or equal to 20 mg, less than or equal to 100 mg, less than or equal to 50 mg, or less than or equal to 20 mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 10 mg and less than or equal to 3500 mg, or greater than or equal to 200 mg and less than or equal to 1000 mg). Other ranges are also possible. Stiffness can be determined according to TAPPI T543om-94 using Gurley stiffness (bending strength) recorded in mm (equivalent to gu).

[0121] In some embodiments, the Gurley stiffness of the support layer or multiple support layers (e.g., the first, third, and fifth layers) in the machine direction is greater than or equal to 150 mg, greater than or equal to 200 mg, greater than or equal to 350 mg, greater than or equal to 500 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 some embodiments, the Gurley stiffness of the support layer or multiple support layers (e.g., the first, third, and fifth layers) in the machine direction is less than or equal to 3500 mg, less than or equal to 3000 mg, less than or equal to 2500 mg, less than or equal to 200 mg, less than or equal to 1500 mg, less than or equal to 1000 mg, less than or equal to 500 mg, less than or equal to 350 mg, or less than or equal to 200 mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 150 mg and less than or equal to 3500 mg, greater than or equal to 200 mg and less than or equal to 3500 mg, greater than or equal to 2000 mg and less than or equal to 2000 mg, or greater than or equal to 350 mg and less than or equal to 2000 mg). Other ranges are also possible. Stiffness can be determined according to TAPPI T543 om-94 using Gurley stiffness (bending strength) recorded in mm (equivalent to gu).

[0122] As described above, in some embodiments, an adhesive may be present in one or more locations within the filter medium (e.g., between the first and second layers, and / or between the second and third layers, etc.). Reference to the adhesive without specifying its location should be understood as referring to the adhesive present independently at each location within the filter medium (if the adhesive is indeed present at any location). That is, at each location where the adhesive is present, the adhesive present therein may independently have any of the following characteristics or not have the following characteristics. In some embodiments, two or more locations within the filter medium where the adhesive is present may contain adhesives having similar composition and / or properties. In other embodiments, the adhesives present in the filter medium may have different compositions and / or properties.

[0123] In some embodiments, the adhesive or multiple adhesives may be solvent-based adhesive resins. As used herein, a solvent-based adhesive resin is an adhesive that undergoes a liquid-to-solid transition when the solvent evaporates from the resin. A solvent-based adhesive resin may be applied in a liquid state. Subsequently, the solvent present may evaporate to produce a solid adhesive. Therefore, solvent-based adhesives can be considered different from hot-melt adhesives, which do not contain volatile solvents (e.g., solvents that evaporate under normal operating conditions) and typically undergo a liquid-to-solid transition when the adhesive cools.

[0124] Desired properties of an adhesive may include sufficient tackiness and open time (i.e., the amount of time the adhesive remains tacky after exposure to the ambient atmosphere). Not wishing to be bound by theory, the tackiness of an adhesive can depend on both the glass transition temperature of the adhesive and the molecular weight of any polymeric component of the adhesive. Higher glass transition values ​​and lower molecular weight values ​​can promote enhanced tackiness, and higher molecular weight values ​​can result in higher cohesive forces and higher bond strength in the adhesive. In some embodiments, adhesives having glass transition temperatures and / or molecular weights within one or more ranges described herein can provide suitable values ​​for both tackiness and open time. For example, adhesives can be tuned and arranged to remain tacky for a relatively long period of time (e.g., the adhesive can remain tacky after any initially present solvent has completely evaporated, and / or can remain tacky indefinitely when held at room temperature). In some embodiments, the open time of the 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 the 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. Combinations of the above ranges are also possible (e.g., at least 1 second and less than or equal to 24 hours). Other values ​​are also possible.

[0125] It is also believed that exposure to isopropyl alcohol (IPA) vapors may cause filters containing adhesive resins to have a high pressure drop due to the dissolution of the adhesive by the IPA vapors. In some embodiments, the presence of a crosslinking agent in the adhesive can reduce this dissolution and pressure drop.

[0126] As described above, in some embodiments, an adhesive may be present between the first and second layers and / or between other layers of the medium (e.g., between the second and third layers). The adhesive can be used to coat one or more layers using the solvent spraying method described herein or any other suitable method. Non-limiting examples of suitable adhesives include acrylates, acrylate copolymers, polyurethanes, polyesters, poly(vinyl alcohol), ethylene-vinyl acetate copolymers, silicone solvents, polyolefins, synthetic rubbers and / or natural rubbers, synthetic elastomers, ethylene-acrylic acid copolymers, ethylene-methacrylate copolymers, ethylene-methyl methacrylate copolymers, poly(vinylidene chloride), polyamides, epoxy resins, melamine resins, poly(isobutylene), styrene block copolymers, styrene-butadiene rubber, aliphatic urethane acrylates, and phenolic resins.

[0127] In embodiments comprising three or more layers (e.g., a first, second, and third layer), each interface may contain an adhesive independently selected from the adhesives described herein. In some embodiments, the adhesive at the first interface (e.g., between the first and second layers) differs from the adhesive at the second interface (e.g., between the second and third adhesives). In other embodiments, the adhesives at the different interfaces are the same.

[0128] In some embodiments, when an adhesive is present, the adhesive may contain a crosslinking agent. In some embodiments, the crosslinking agent is a small molecule (i.e., the crosslinking agent is not a polymer). In some embodiments, the small molecule crosslinking agent is one or more of the following: carbodiimide, isocyanate, aziridine, zirconium compounds (e.g., zirconium carbonate), metal esters, metal chelates, polyfunctional acrylimide, and amino resins. In some embodiments, the adhesive contains at least one polymer having one or more active sites capable of reacting with the crosslinking agent. Non-limiting examples of suitable reactive sites include alcohol groups, carboxylic acid groups, epoxy groups, amino groups, and amino groups.

[0129] In some implementations, the adhesive does not contain small molecule crosslinking agents, but the polymer molecules that form the adhesive can undergo self-crosslinking via functional groups attached to the polymer.

[0130] In some embodiments, temperature may be applied to the adhesive to aid solvent removal and / or to accelerate the rate of crosslinking. In some embodiments, the temperature may be 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 temperature may be 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 24°C and less than or equal to 150°C, or greater than or equal to 24°C and less than or equal to 130°C). Other ranges are also possible.

[0131] When present, small molecule crosslinking agents can constitute any suitable amount of adhesive. In some embodiments, the weight percentage of the total mass of adhesive and crosslinking agent present at a designated location of the filter media (e.g., between two layers, such as between the first and second layers, or between the second and third layers) can be greater than or equal to 0.1 wt%, greater than or equal to 0.2 wt%, greater than or equal to 0.5 wt%, greater than or equal to 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 15 wt%, greater than or equal to 20 wt%, or greater than or equal to 25 wt%. In some embodiments, the weight percentage of the small molecule crosslinker relative to the total mass of the adhesive and crosslinker present at a specified location (e.g., between two layers, such as between the first and second layers, or between the second and third layers) can be less than or equal to 30 wt%, less than or equal to 25 wt%, less than or equal to 20 wt%, less than or equal to 15 wt%, less than or equal to 10 wt%, less than or equal to 5 wt%, less than or equal to 2 wt%, less than or equal to 1 wt%, less than or equal to 0.5 wt%, or less than or equal to 0.2 wt%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 wt% and less than or equal to 30 wt%, or greater than or equal to 1 wt% and less than or equal to 20 wt%). Other ranges are also possible.

[0132] The adhesive and / or any small molecule crosslinking agent contained in the adhesive (if present) can undergo a crosslinking reaction at any suitable temperature. In some embodiments, the crosslinking agent can undergo a crosslinking reaction at temperatures 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 and / or any small molecule crosslinking agent contained in the adhesive can undergo a crosslinking reaction at temperatures 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.

[0133] In some embodiments where an adhesive is present at at least one location in the filter medium (e.g., between two layers, such as between a first layer and a second layer, or between a second layer and a third layer), the adhesive or multiple adhesives may contain a solvent before the adhesive is applied to the layers. In some embodiments, the adhesive or multiple adhesives may be applied to the layers or filter medium while dissolved or suspended in a solvent. Non-limiting examples of suitable solvents include water, hydrocarbon solvents, ketones, aromatic solvents, fluorinated solvents, toluene, heptane, acetone, n-butyl acetate, methyl ethyl ketone, dichloromethane, naphtha, and mineral spirits.

[0134] In some embodiments, the glass transition temperature of the adhesive can be relatively low. In some embodiments, the glass transition temperature of the adhesive can be 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 24°C, less than or equal to 25°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 can be 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 of the adhesive can be measured by differential scanning calorimetry.

[0135] The molecular weight of the adhesive can be selected as needed. In some embodiments, the number average molecular weight of the adhesive can be greater than or equal to 10 kDa, greater than or equal to 30 kDa, greater than or equal to 50 kDa, greater than or equal to 100 kDa, greater than or equal to 300 kDa, greater than or equal to 500 kDa, greater than or equal to 1000 kDa, greater than or equal to 2000 kDa, or greater than or equal to 3000 kDa. In some embodiments, the number average molecular weight of the adhesive can be less than or equal to 5000 kDa, less than or equal to 4000 kDa, less than or equal to 3000 kDa, less than or equal to 1000 kDa, less than or equal to 5000 kDa, less than or equal to 300 kDa, less than or equal to 100 kDa, less than or equal to 50 kDa, or less than or equal to 30 kDa. Combinations of the above ranges are also possible (e.g., greater than or equal to 10 kDa and less than or equal to 5000 kDa, or greater than or equal to 30 kDa and less than or equal to 3000 kDa). Other ranges are also possible. Number-average molecular weight can be measured by light scattering.

[0136] In embodiments where the filter media contains an adhesive at any single location (e.g., between two layers, such as between the first and second layers, and / or between the second and third layers), the adhesive or multiple adhesives may have any suitable weight at that location. In some embodiments, the weight of the adhesive or multiple adhesives at any single location may be greater than or equal to 0.05 g / m³. 2 ≥0.1g / m 2 ≥0.2g / m 2 ≥0.5g / m 2 ≥1g / m 2 ≥2g / m 2 or greater than or equal to 5g / m 2 In some embodiments, the weight of the adhesive or multiple adhesives at any single location can be less than or equal to 10 g / m³. 2 Less than or equal to 5g / m 2 Less than or equal to 2g / m 2 Less than or equal to 1g / m 2 Less than or equal to 0.5 g / m 2 Less than or equal to 0.2 g / m 2 or less than or equal to 0.1 g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 0.05 g / m³). 2 And less than or equal to 10g / m 2 or greater than or equal to 0.1 g / m 2 And less than or equal to 5g / m 2 Other ranges are also possible. The weight of the adhesive at any single location can be determined according to standard ISO 536, whereby the weight of the filter media measured before the adhesive is applied to the location is subtracted from the weight measured after the adhesive is applied to the location to obtain the weight of the adhesive at that location.

[0137] In embodiments where the filter media comprises one or more adhesives, the total weight of the adhesives in the filter media (i.e., the sum of the weights of the adhesives at each location) can be greater than or equal to 0.05 g / m³. 2 ≥0.1g / m 2 Greater than or equal to 0.2 g / m 2 ≥0.5g / m 2 ≥1g / m 2 ≥2g / m 2 or greater than or equal to 5g / m 2In some embodiments, the total weight of the adhesive or a combination of adhesives may be less than or equal to 10 g / m³. 2 Less than or equal to 5g / m 2 Less than or equal to 2g / m 2 Less than or equal to 1g / m 2 Less than or equal to 0.5 g / m 2 Less than or equal to 0.2 g / m 2 or less than or equal to 0.1 g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 0.05 g / m³). 2 And less than or equal to 10g / m 2 or greater than or equal to 0.1 g / m 2 And less than or equal to 5g / m 2 Other ranges are also possible.

[0138] In some embodiments, the filter media may contain an adhesive at at least one location, and the adhesive may be able to adhere one layer to another with relatively high bonding strength (e.g., adhering the first layer to the second layer, and / or adhering the second layer to the third layer). In some embodiments, the adhesive or multiple adhesives may adhere the two layers together with a bonding strength greater than or equal to 100 g / inch. 2 ≥150g / inch 2 ≥200g / inch 2 ≥500g / inch 2 ≥750g / inch 2 ≥1000g / inch 2 ≥1250g / inch 2 ≥1500g / inch 2 ≥1750g / inch 2 ≥2000g / inch 2 ≥2250g / inch 2 ≥2500g / inch 2 ≥2750g / inch 2 ≥3000g / inch 2 ≥3250g / inch 2 ≥3500g / inch 2 ≥3750g / inch 2 ≥4000g / inch 2 ≥4250g / inch 2 ≥4500g / inch2 or greater than or equal to 4750g / inch 2 In some implementations, an adhesive or multiple adhesives can bond 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 some embodiments, the entire filter media generally has an internal bonding strength within one or more of the ranges mentioned above. The overall bonding strength of the filter media is equal to the weakest bonding strength between the two layers of the media.

[0139] The bond strength (e.g., internal bond strength) between two layers (e.g., between the first and second layers, or between the second and third layers) can be determined using a z-axis peel strength test. In short, the bond strength is determined by mounting a 1”×1” sample onto a 1”×1”×0.5” steel block using double-sided tape. The sample block is mounted on the non-transverse head of a tensile testing machine with double-sided tape, and another steel block of the same size is attached to the transverse head. The transverse head moves downwards and bonds to the sample on the steel block on the non-transverse head. Sufficient pressure is applied so that the steel blocks bond together via the mounted sample. The transverse head moves at a transverse speed of 1” / min, and the maximum load is obtained from the peak of the stress-strain curve. The bond strength between the two layers (e.g., internal bond strength) is considered equal to the maximum load.

[0140] In some embodiments, the filter media as a whole may have one or more desired properties. For example, the filter media may be a high-energy particulate air (HEPA) or ultra-low-penetration air (ULPA) filter. According to EN1822:2009, these filters are required to remove particulates at efficiency levels greater than 99.95% and 99.9995%, respectively. In some embodiments, the filter media may remove particulates with an efficiency greater than 95%, greater than 99.995%, or greater than 99.99995%, or up to 99.999995%. In some embodiments, the filter media may be suitable for HVAC applications. That is, the particulate 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%. HEPA, ULPA, or HVAC filter media may include, for example, a pre-filter layer disposed upstream of the main filter layer and a support layer disposed downstream of the main filter layer. In some implementations, HEPA, ULPA, or HVAC filters may include a meltblown pre-filter layer (e.g., with a specific weight of, for example, 3 g / m³). 2 Up to 40g / m 2 The meltblown polypropylene pre-filter layer and the electrospun main filter layer (e.g., with a weight of, for example, 0.01 g / m³) 2 Up to 5g / m 2 It includes, for example, a nylon electrospun main filter layer with an average fiber diameter of 40 nm to 300 nm and a support layer (e.g., with a fixed weight of, for example, 35 g / m³). 2 Up to 80g / m 2 (Wet-laid web-forming support layer). Other types of filter media and efficiencies are also possible. In some embodiments, the filter media can be a HEPA, ULPA, or HVAC filter and can be a component of a filter element as described in more detail below.

[0141] The filter media as a whole can have any suitable stiffness. In some embodiments, the filter media has a Gurley stiffness in the transverse direction greater than or equal to 50 mg, greater than or equal to 100 mg, greater than or equal to 200 mg, greater than or equal to 500 mg, greater than or equal to 1000 mg, greater than or equal to 1500 mg, greater than or equal to 2000 mg, or greater than or equal to 3000 mg. In some embodiments, the filter media has a Gurley stiffness in the transverse direction less than or equal to 3500 mg, less than or equal to 3000 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 500 mg, less than or equal to 200 mg, or less than or equal to 100 mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 50 mg and less than or equal to 3000 mg, or greater than or equal to 100 mg and less than or equal to 1500 mg). Other ranges are also possible. Stiffness can be determined according to the Gurley stiffness (bending strength) recorded in mm (equivalent to gu) according to TAPPI T543om-94.

[0142] In some embodiments, the Gurley stiffness of the filter media in the machine direction is 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 350 mg, greater than or equal to 500 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 the machine direction. In some embodiments, the Gurley stiffness of the support layer or multiple support layers in the machine direction is less than or equal to 3500 mg, less than or equal to 3000 mg, less than or equal to 2500 mg, less than or equal to 2000 mg, less than or equal to 150 mg, less than or equal to 1000 mg, less than or equal to 500 mg, less than or equal to 350 mg, less than or equal to 200 mg, or less than or equal to 150 mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 100 mg and less than or equal to 3000 mg, or greater than or equal to 150 mg and less than or equal to 3000 mg). Other ranges are also possible. Stiffness can be determined according to TAPPI T543 om-94 using Gurley stiffness (bending strength) recorded in mm (equivalent to gu).

[0143] Because it may be desirable to rate filter media or layers based on the relationship between penetration rate and pressure drop across the medium, or as a function of the pressure drop across the medium or mesh, filter media can be rated using a value known as the γ value. Generally, a higher γ value indicates better filtration performance, i.e., higher particle efficiency as a function of pressure drop. The γ value is expressed by the following formula: γ = (-log 10 (MPPS penetration % / 100) / pressure drop, mm H2O)×100, where the MPPS penetration is equal to the MPPS penetration as described below and can be measured using the EN1822:2009 standard as described below. As described below, γ can be measured before or after exposure to IPA vapors. For any given γ value, the MPPS penetration is the penetration at MPPS measured at that γ value. Unless otherwise stated, reference to γ ​​should be considered as referring to the γ value measured before the filter media is exposed to IPA vapors. In this case, the relevant MPPS is the MPPS value before exposure to IPA vapor discharge, and the relevant MPPS penetration is the MPPS penetration value before exposure to IPA vapor discharge.

[0144] Transmission rate, often expressed as a percentage, is defined as follows: Transmission rate (%) = (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. A typical test for transmission rate involves blowing dioctyl phthalate (DOP) particles through a filter medium or layer and measuring the percentage of particles that penetrate the filter medium or layer. The transmission rate values ​​described herein are determined based on the EN1822:2009 standard for MPPS DOP particles using a TSI 3160 automated filter test unit from TSI, Inc., equipped with a dioctyl phthalate generator for DOP aerosol testing. In this test, a set of particles with an average diameter varying from 0.04 micrometers to 0.3 micrometers is generated by the particle generator. The instrument measures the transmission rate across the filter medium (or layer) by determining the DOP particle size at the highest transmission rate level measured in the test (i.e., the most penetrating particle size (MPPS)). Therefore, all γ values ​​described herein refer to the γ values ​​at the most penetrating particle size. All transmittance values ​​were determined as follows, and thus the γ value described herein was determined: using a continuous load of DOP particles and making the upstream face of the layer 100 cm from the fiber web. 2The filter media is subjected to an airflow of 12 liters per minute, resulting in a surface velocity of 2 cm / s. Particles with geometric standard deviations less than 1.3, ranging in size from 0.04 μm to 0.3 μm (0.04 μm, 0.08 μm, 0.12 μm, 0.16 μm, 0.2 μm, 0.26 μm, and 0.3 μm), are generated, and the filter media is sequentially exposed to these particles. The particle penetration as a function of particle size is plotted, and the data are fitted with a parabolic function. The maximum value of the parabolic function is then obtained; the particle size at the maximum value is the most easily penetrated particle size (MPPS), and the penetration rate at the maximum value is the penetration rate at the MPPS.

[0145] The pressure drop value (e.g., used to determine γ) is determined based on EN1822:2009 standard by air resistance testing using the TSI 3160 automated filter test unit from TSI, Inc. The instrument measures the pressure drop across the filter media (or layer) when the filter media or layer is subjected to a surface velocity of 5.3 cm / s.

[0146] The filter media as a whole can have a relatively high γ value under MPPS (e.g., before exposure to IPA vapor discharge). In some embodiments, the filter media has a γ value under MPPS greater than or equal to 16, greater than or equal to 18, greater than or equal to 20, greater than or equal to 25, greater than or equal to 50, greater than or equal to 75, greater than or equal to 100, greater than or equal to 125, greater than or equal to 150, greater than or equal to 175, greater than or equal to 200, or greater than or equal to 225. In some embodiments, the filter media has a γ value under MPPS less than or equal to 250, less than or equal to 225, less than or equal to 200, less than or equal to 175, less than or equal to 150, less than or equal to 125, less than or equal to 100, less than or equal to 75, less than or equal to 50, less than or equal to 25, less than or equal to 20, or less than or equal to 18. Combinations of the above ranges are also possible (e.g., greater than or equal to 16 and less than or equal to 250, or greater than or equal to 18 and less than or equal to 150). Other ranges are also possible.

[0147] The filter media as a whole can have any suitable weight. In some embodiments, the weight of the filter media can be greater than or equal to 20 g / m³. 2 ≥40g / m 2 ≥50g / m 2 ≥75g / m 2 ≥100g / m 2 ≥125g / m 2 ≥150g / m 2 ≥175g / m 2 ≥200g / m2 ≥225g / m 2 ≥250g / m 2 or greater than or equal to 275g / m 2 In some implementations, the weight of the filter media can be less than or equal to 300 g / m³. 2 Less than or equal to 275g / m 2 Less than or equal to 250g / m 2 Less than or equal to 225g / m 2 Less than or equal to 200g / m 2 Less than or equal to 175g / m 2 Less than or equal to 150g / m 2 Less than or equal to 125g / m 2 Less than or equal to 100g / m 2 Less than or equal to 75g / m 2 Less than or equal to 50g / m 2 or less than or equal to 40g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 20 g / m³). 2 And less than or equal to 300g / m 2 or greater than or equal to 40g / m 2 And less than or equal to 200g / m 2 Other ranges are also possible. The fixed weight can be determined according to standard ISO 536.

[0148] In some embodiments, the thickness of the filter media as a whole is greater than or equal to 0.075 mm, greater than or equal to 0.1 mm, greater than or equal to 0.25 mm, greater than or equal to 0.5 mm, greater than or equal to 0.75 mm, greater than or equal to 1 mm, or greater than or equal to 2.5 mm. In some embodiments, the thickness of the filter media is less than or equal to 5 mm, less than or equal to 2.5 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 0.25 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.075 mm and less than or equal to 5 mm, or greater than or equal to 0.1 mm and less than or equal to 1 mm). Other ranges are also possible. The thickness of the filter media can be determined according to standard ISO 534 at 50 kPa.

[0149] In some embodiments, the average flow pore size of the filter media as a whole can be greater than or equal to 0.1 micrometers, greater than or equal to 0.2 micrometers, greater than or equal to 0.5 micrometers, greater than or equal to 1 micrometer, greater than or equal to 2 micrometers, greater than or equal to 5 micrometers, greater than or equal to 10 micrometers, greater than or equal to 20 micrometers, or greater than or equal to 40 micrometers. In some embodiments, the average flow pore size of the filter media can be less than or equal to 60 micrometers, less than or equal to 40 micrometers, less than or equal to 20 micrometers, less than or equal to 10 micrometers, less than or equal to 5 micrometers, less than or equal to 2 micrometers, less than or equal to 1 micrometer, less than or equal to 0.5 micrometers, or less than or equal to 0.2 micrometers. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 micrometers and less than or equal to 60 micrometers, or greater than or equal to 0.5 micrometers and less than or equal to 40 micrometers). Other ranges are also possible. The average flow pore size can be determined according to the standard ASTM F316-03.

[0150] The pressure drop across the entire filter medium can be any suitable value. In some embodiments, the pressure drop across the filter medium can be greater than or equal to 0.5 mm H2O, greater than or equal to 1 mm H2O, greater than or equal to 2 mm H2O, greater than or equal to 5 mm H2O, greater than or equal to 10 mm H2O, greater than or equal to 20 mm H2O, greater than or equal to 50 mm H2O, or greater than or equal to 100 mm H2O. In some embodiments, the pressure drop across the filter medium can be less than or equal to 200 mm H2O, less than or equal to 100 mm H2O, less than or equal to 50 mm H2O, less than or equal to 20 mm H2O, less than or equal to 10 mm H2O, less than or equal to 5 mm H2O, less than or equal to 2 mm H2O, or less than or equal to 1 mm H2O. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.5 mm H2O and less than or equal to 200 mm H2O, or greater than or equal to 2 mm H2O and less than or equal to 100 mm H2O). Other ranges are also possible. Pressure drop can be determined using ASTM D2986-91.

[0151] In some implementations, the filter media as a whole can perform particularly well after exposure to isopropanol (IPA) vapor. Such performance characteristics may include: a relatively low pressure drop after exposure to IPA vapor, a relatively low change in pressure drop after exposure to IPA vapor compared to the same media before IPA vapor exposure, a high γ value at MPPS after exposure to IPA vapor, and / or a relatively low change in γ value after exposure to IPA vapor compared to the same media before IPA vapor exposure.

[0152] Typically, IPA vapor exposure is performed according to ISO 16890-4. The filter media to be tested is cut into 6-inch x 6-inch squares and placed on a metal rack. The metal rack and media are then placed on top of a container containing at least 250 mL of 99.9% by weight IPA. Following this step, the metal rack, media, and container are placed in a 24-inch x 18-inch x 11-inch chamber. A second container containing 250 mL of 99.9% by weight IPA is then placed in the container on top of the metal rack, and the chamber lid is closed and tightly sealed. The apparatus is maintained at 70°F and 50% relative humidity for at least 14 hours, after which the filter media is removed and allowed to dry at room temperature for 1 hour. The properties of the filter media after IPA exposure are then measured.

[0153] In some embodiments, the maximum pressure drop of the filter media as a whole after IPA exposure can be greater than or equal to 1 mm H2O, greater than or equal to 3 mm H2O, greater than or equal to 5 mm H2O, greater than or equal to 7.5 mm H2O, greater than or equal to 10 mm H2O, greater than or equal to 25 mm H2O, greater than or equal to 50 mm H2O, or greater than or equal to 75 mm H2O. In some embodiments, the maximum pressure drop of the filter media after IPA exposure can be less than or equal to 100 mm H2O, less than or equal to 75 mm H2O, less than or equal to 50 mm H2O, less than or equal to 25 mm H2O, less than or equal to 10 mm H2O, less than or equal to 7.5 mm H2O, less than or equal to 5 mm H2O, or less than or equal to 3 mm H2O. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 mm H2O and less than or equal to 100 mm H2O, or greater than or equal to 3 mm H2O and less than or equal to 75 mm H2O). Other ranges are also possible. Pressure drop can be determined using ASTM D2 986-91.

[0154] In some embodiments, the maximum pressure drop of the filter media after IPA exposure can be comparable to the maximum pressure drop of the same filter media before IPA exposure. In some embodiments, the percentage change in the maximum pressure drop of the filter media after IPA exposure can be 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%, or less than or equal to 5%. In some embodiments, the percentage change in the maximum pressure drop of the filter media after IPA exposure can be greater than or equal to 0%, greater than or equal to 10%, greater than or equal to 20%, greater than or equal to 30%, or greater than or equal to 40%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% and less than or equal to 50%, or greater than or equal to 0% and less than or equal to 20%). Other ranges are also possible. The pressure drop can be determined using ASTM D2 986-91. The percentage change of a value (e.g., pressure drop) is defined by the following equation: Percentage change = |(final value) - (initial value)| / (initial value) * 100.

[0155] In some embodiments, the filter media may have a relatively high γ value under MPPS after exposure to IPA vapor. In some embodiments, the γ value of the filter media under MPPS after exposure to IPA vapor may be greater than or equal to 14, greater than or equal to 18, greater than or equal to 20, greater than or equal to 40, greater than or equal to 60, or greater than or equal to 80. In some embodiments, the γ value of the filter media under MPPS after exposure to IPA vapor may be less than or equal to 100, less than or equal to 80, less than or equal to 60, less than or equal to 40, less than or equal to 20, or less than or equal to 18. Combinations of the above ranges are also possible (e.g., greater than or equal to 14 and less than or equal to 100, or greater than or equal to 18 and less than or equal to 60). Other values ​​are also possible.

[0156] In some embodiments, the gamma value of the filter media as a whole after IPA exposure can be quite similar to the gamma value of the same filter media before IPA exposure. In some embodiments, the percentage change in the gamma value of the filter media after IPA exposure can be 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 25%, less than or equal to 20%, less than or equal to 15%, less than or equal to 10%, or less than or equal to 5%. In some embodiments, the percentage change in the gamma value of the filter media after IPA exposure can be greater than or equal to 0%, greater than or equal to 10%, greater than or equal to 20%, greater than or equal to 30%, greater than or equal to 40%, or greater than or equal to 50%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0% and less than or equal to 60%, or greater than or equal to 0% and less than or equal to 40%). Other ranges are also possible. The percentage change of a value (e.g., the value of γ) is defined by the following equation: Percentage change = |(final value) - (initial value)| / (initial value) * 100.

[0157] In some implementations, the PAO loading capacity of the filter media as a whole can be greater than or equal to 3 g / m³. 2 ≥5g / m 2 ≥10g / m 2 ≥20g / m 2 ≥50g / m 2 ≥75g / m 2 ≥100g / m 2 or greater than or equal to 150g / m 2 In some implementations, the PAO loading capacity of the filter media can be less than or equal to 200 g / m³. 2 Less than or equal to 150g / m 2 Less than or equal to 100g / m 2 Less than or equal to 75g / m 2 Less than or equal to 50g / m 2 Less than or equal to 20g / m 2 Less than or equal to 10g / m 2 or less than or equal to 5g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 3 g / m³). 2 And less than or equal to 200g / m 2 or greater than or equal to 5g / m 2 And less than or equal to 150g / m 2 Other ranges are also possible. The PAO loading capacity of the filter media can be determined as follows: at 120 mg / m³3 The loading rate and the medium surface velocity at 5.3 cm / s were achieved by loading 491 cm with PAO oil. 2 The filter media is subjected to pressure increases of 250 Pa across the filter media. PAO particles can be generated by a Laskin nozzle and can have a median diameter of 0.25 micrometers. The PAO loading capacity is determined by weighing the filter media before and after testing and increasing the measured mass by dividing by the area of ​​the filter media to obtain the PAO loading capacity per unit area of ​​the filter media.

[0158] In some implementations, the overall NaCl loading capacity of the filter media can be greater than or equal to 0.1 g / m³. 2 ≥0.3g / m 2 ≥0.5g / m 2 ≥1g / m 2 ≥2g / m 2 ≥5g / m 2 ≥7.5g / m 2 ≥10g / m 2 ≥12.5g / m 2 ≥15g / m 2 ≥17.5g / m 2 ≥20g / m 2 ≥22.5g / m 2 ≥25g / m 2 or greater than or equal to 27.5 g / m 2 In some implementations, the NaCl loading capacity of the filter media can be less than or equal to 30 g / m³. 2 Less than or equal to 27.5 g / m 2 Less than or equal to 25g / m 2 Less than or equal to 22.5 g / m 2 Less than or equal to 20g / m 2 Less than or equal to 17.5 g / m 2 Less than or equal to 15g / m 2 Less than or equal to 12.5 g / m 2 Less than or equal to 10g / m 2 Less than or equal to 7.5 g / m 2 Less than or equal to 5g / m 2 Less than or equal to 2g / m 2 Less than or equal to 1g / m 2 Less than or equal to 0.5 g / m 2 or less than or equal to 0.3 g / m2 Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 g / m³). 2 And less than or equal to 30g / m 2 or greater than or equal to 0.3 g / m 2 And less than or equal to 20g / m 2 Other ranges are also possible. The NaCl loading capacity of the filter media can be achieved by making the nominal exposure area 100 cm². 2 The filter media was exposed to 15 mg / m³ 3 The concentration and median diameter of NaCl particles of 0.26 μm at a surface velocity of 5.3 cm / s were used to determine the NaCl loading. The NaCl loading was determined using an 8130 CertiTest from TSI, Inc. equipped with a sodium chloride generator. TM The automated filter testing unit determined the average particle size to be 0.26 micrometers mass-average diameter, produced by the salt particle generator. The 8130 operated in continuous mode, with approximately one pressure drop reading per minute. A concentration of 15 mg / m³ was used. 3 100cm of NaCl 2 The filter media samples were tested at a flow rate of 32 liters / minute (surface velocity of 5.3 cm / second) until the pressure drop across the filter media increased by 250 Pa. The NaCl loading capacity was determined as follows: the filter media was weighed before and after the test, and the measured mass was increased and divided by the area of ​​the filter media to obtain the NaCl loading capacity per unit area of ​​the filter media.

[0159] In some embodiments, the overall air permeability of the filter media can be greater than or equal to 0.6 CFM, greater than or equal to 1 CFM, greater than or equal to 1.4 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 67 CFM, greater than or equal to 100 CFM, or greater than or equal to 200 CFM. In some embodiments, the overall air permeability of the filter media can be less than or equal to 260 CFM, less than or equal to 200 CFM, less than or equal to 100 CFM, less than or equal to 67 CFM, less than or equal to 20 CFM, less than or equal to 10 CFM, less than or equal to 5 CFM, less than or equal to 1.4 CFM, or less than or equal to 1 CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.6 CFM and less than or equal to 260 CFM, or greater than or equal to 1.4 CFM and less than or equal to 67 CFM). Other ranges are also possible. The air permeability can be determined using the TAPPI method T251.

[0160] The density of the filter media as a whole can be any suitable value. In some embodiments, the density of the filter media is greater than or equal to 0.0001, greater than or equal to 0.0002, greater than or equal to 0.0005, greater than or equal to 0.001, greater than or equal to 0.002, greater than or equal to 0.005, greater than or equal to 0.01, greater than or equal to 0.02, greater than or equal to 0.05, greater than or equal to 1, greater than or equal to 2, greater than or equal to 5, greater than or equal to 10, or greater than or equal to 25. In some implementations, the density of the filter media is less than or equal to 50, less than or equal to 25, less than or equal to 10, less than or equal to 5, less than or equal to 2, less than or equal to 1, less than or equal to 0.5, less than or equal to 0.2, less than or equal to 0.1, less than or equal to 0.05, less than or equal to 0.02, less than or equal to 0.01, less than or equal to 0.005, or less than or equal to 0.002. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.0001 and less than or equal to 50, or greater than or equal to 0.001 and less than or equal to 25). Other ranges are also possible. Density can be determined using the following formula: Density % = [Weight / (Fiber Density * Thickness)] * 100. Weight and thickness can be determined as described herein. Porosity can be obtained from density based on the following equation: Density (%) = 100 - Porosity (%).

[0161] In some implementations, the dry tensile strength of the filter media as a whole in the transverse direction may be greater than or equal to 3 psi, greater than or equal to 4 psi, greater than or equal to 5 psi, greater than or equal to 10 psi, greater than or equal to 15 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 35 psi, greater than or equal to 40 psi, greater than or equal to 45 psi, greater than or equal to 50 psi, greater than or equal to 55 psi, greater than or equal to 60 psi, greater than or equal to 65 psi, or greater than or equal to 70 psi. In some implementations, the dry tensile strength of the filter media in the transverse direction can be less than or equal to 75 psi, less than or equal to 70 psi, less than or equal to 65 psi, less than or equal to 60 psi, less than or equal to 55 psi, less than or equal to 50 psi, less than or equal to 45 psi, less than or equal to 40 psi, less than or equal to 35 psi, less than or equal to 30 psi, less than or equal to 25 psi, less than or equal to 20 psi, less than or equal to 15 psi, less than or equal to 10 psi, less than or equal to 5 psi, or less than or equal to 4 psi. Combinations of the above ranges are also possible (e.g., greater than or equal to 3 psi and less than or equal to 75 psi, or greater than or equal to 4 psi and less than or equal to 50 psi). Other ranges are also possible. The dry tensile strength in the transverse direction can be determined according to standard T494 om-96 using a test span of 4 inches and a gripper separation speed of 1 inch / minute.

[0162] In some implementations, the dry tensile strength of the filter media as a whole in the machine direction may be greater than or equal to 6 psi, greater than or equal to 10 psi, greater than or equal to 20 psi, greater than or equal to 30 psi, greater than or equal to 40 psi, greater than or equal to 50 psi, greater than or equal to 60 psi, greater than or equal to 70 psi, greater than or equal to 80 psi, greater than or equal to 90 psi, greater than or equal to 100 psi, greater than or equal to 110 psi, greater than or equal to 120 psi, greater than or equal to 130 psi, or greater than or equal to 140 psi. In some implementations, the dry tensile strength of the filter media in the machine direction can be less than or equal to 150 psi, 140 psi, 130 psi, 120 psi, 110 psi, 100 psi, 90 psi, 80 psi, 70 psi, 60 psi, 50 psi, 40 psi, 30 psi, 20 psi, or 10 psi. Combinations of the above ranges are also possible (e.g., greater than or equal to 6 psi and less than or equal to 150 psi, or greater than or equal to 10 psi and less than or equal to 100 psi). Other ranges are also possible. The dry tensile strength in the machine direction can be determined according to standard T494om-96 using a test span of 4 inches and a gripper separation speed of 1 inch / minute.

[0163] In some implementations, the wet tensile strength of the filter media as a whole in the transverse direction may be greater than or equal to 3 psi, greater than or equal to 4 psi, greater than or equal to 5 psi, greater than or equal to 10 psi, greater than or equal to 15 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 35 psi, greater than or equal to 40 psi, greater than or equal to 45 psi, greater than or equal to 50 psi, greater than or equal to 55 psi, greater than or equal to 60 psi, greater than or equal to 65 psi, or greater than or equal to 70 psi. In some implementations, the wet tensile strength of the filter media in the transverse direction can be less than or equal to 75 psi, less than or equal to 70 psi, less than or equal to 65 psi, less than or equal to 60 psi, less than or equal to 55 psi, less than or equal to 50 psi, less than or equal to 45 psi, less than or equal to 40 psi, less than or equal to 35 psi, less than or equal to 30 psi, less than or equal to 25 psi, less than or equal to 20 psi, less than or equal to 15 psi, less than or equal to 10 psi, less than or equal to 5 psi, or less than or equal to 4 psi. Combinations of the above ranges are also possible (e.g., greater than or equal to 3 psi and less than or equal to 75 psi, or greater than or equal to 4 psi and less than or equal to 50 psi). Other ranges are also possible. The wet tensile strength in the transverse direction can be determined according to standard T494 om-96 using a test span of 4 inches and a gripper separation speed of 1 inch / minute.

[0164] In some implementations, the wet tensile strength of the filter media as a whole in the machine direction may be greater than or equal to 6 psi, greater than or equal to 10 psi, greater than or equal to 20 psi, greater than or equal to 30 psi, greater than or equal to 40 psi, greater than or equal to 50 psi, greater than or equal to 60 psi, greater than or equal to 70 psi, greater than or equal to 80 psi, greater than or equal to 90 psi, greater than or equal to 100 psi, greater than or equal to 110 psi, greater than or equal to 120 psi, greater than or equal to 130 psi, or greater than or equal to 140 psi. In some implementations, the wet tensile strength of the filter media in the machine direction may be less than or equal to 150 psi, less than or equal to 140 psi, less than or equal to 130 psi, less than or equal to 120 psi, less than or equal to 110 psi, less than or equal to 100 psi, less than or equal to 90 psi, less than or equal to 80 psi, less than or equal to 70 psi, less than or equal to 60 psi, less than or equal to 50 psi, less than or equal to 40 psi, less than or equal to 30 psi, less than or equal to 20 psi, or less than or equal to 10 psi. Combinations of the above ranges are also possible (e.g., greater than or equal to 6 psi and less than or equal to 150 psi, or greater than or equal to 10 psi and less than or equal to 100 psi). Other ranges are also possible. Dry tensile strength in the machine direction can be determined according to standard T494 om-96 using a test span of 4 inches and a gripper separation speed of 1 inch / minute.

[0165] The burst strength of the filter media as a whole can be any suitable value. In some embodiments, the burst strength of the filter media can be greater than or equal to 10 psi, greater than or equal to 20 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, greater than or equal to 250 psi, or greater than or equal to 275 psi. In some embodiments, the burst strength of the filter media can be less than or equal to 300 psi, less than or equal to 275 psi, less than or equal to 250 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, or less than or equal to 20 psi. Combinations of the above ranges are also possible (e.g., greater than or equal to 10 psi and less than or equal to 300 psi, or greater than or equal to 20 psi and less than or equal to 200 psi). Other ranges are also possible. The bursting strength of dry martensite can be determined according to standard T403 om-91.

[0166] The wet rupture strength of the filter media as a whole can be any suitable value. In some implementations, the wet rupture strength of the filter media can be 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 30 psi, greater than or equal to 40 psi, greater than or equal to 50 psi, greater than or equal to 60 psi, greater than or equal to 70 psi, greater than or equal to 80 psi, greater than or equal to 90 psi, greater than or equal to 100 psi, greater than or equal to 110 psi, greater than or equal to 120 psi, greater than or equal to 130 psi, greater than or equal to 140 psi, greater than or equal to 150 psi, greater than or equal to 160 psi, greater than or equal to 170 psi, greater than or equal to 180 psi, or greater than or equal to 190 psi. In some implementations, the wet buoyancy burst strength of the filter media can be less than or equal to 200 psi, less than or equal to 190 psi, less than or equal to 180 psi, less than or equal to 170 psi, less than or equal to 160 psi, less than or equal to 150 psi, less than or equal to 140 psi, less than or equal to 130 psi, less than or equal to 120 psi, less than or equal to 110 psi, less than or equal to 100 psi, less than or equal to 90 psi, less than or equal to 80 psi, less than or equal to 70 psi, less than or equal to 60 psi, less than or equal to 50 psi, less than or equal to 40 psi, less than or equal to 30 psi, less than or equal to 20 psi, or less than or equal to 10 psi. Combinations of the above ranges are also possible (e.g., greater than or equal to 5 psi and less than or equal to 200 psi, or greater than or equal to 10 psi and less than or equal to 150 psi). Other ranges are also possible. The dry buoyancy burst strength can be determined according to standard T403 om-91.

[0167] In some embodiments, the Gurley stiffness of the filter media as a whole in the transverse direction can be greater than or equal to 50 mg, greater than or equal to 100 mg, greater than or equal to 200 mg, greater than or equal to 500 mg, greater than or equal to 1000 mg, greater than or equal to 1500 mg, or greater than or equal to 2000 mg. In some embodiments, the Gurley stiffness of the filter media in the transverse direction can be less than or equal to 3000 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 500 mg, less than or equal to 200 mg, or less than or equal to 100 mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 50 mg and less than or equal to 3000 mg, or greater than or equal to 100 mg and less than or equal to 3000 mg). Other ranges are also possible. Stiffness can be determined according to TAPPI T543 om-94 using Gurley stiffness (bending resistance) recorded in mm (equivalent to gu).

[0168] In some embodiments, the Gurley stiffness of the filter media as a whole in the machine direction can be 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 500 mg, greater than or equal to 1000 mg, or greater than or equal to 2000 mg. In some embodiments, the Gurley stiffness of the filter media in the machine direction can be less than or equal to 3000 mg, less than or equal to 2000 mg, less than or equal to 1000 mg, less than or equal to 500 mg, less than or equal to 200 mg, or less than or equal to 150 mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 100 mg and less than or equal to 300 mg, or greater than or equal to 150 mg and less than or equal to 2000 mg). Other ranges are also possible. The stiffness can be determined according to TAPPI T543om-94 using Gurley stiffness (bending resistance) recorded in mm (equivalent to gu).

[0169] In some embodiments, the filter media is flame-retardant as a whole and / or contains one or more flame retardants described herein in one or more layers. For example, according to DIN 4102-1, the filter media may have a B2 rating.

[0170] In some embodiments, the filter media comprises a first layer and a second layer, wherein the second layer is formed of fibers with an average fiber diameter of less than 1 micrometer. An adhesive may be present between the first and second layers, and the first layer may be bonded to the second layer by the adhesive. The filter media may have a stiffness greater than or equal to 200 mg and a strength greater than or equal to 150 g / in. 2The bonding strength between the first and second layers. When the penetration rate was tested using particles ranging from 0.02 to 0.3 micrometers traveling at a surface velocity of approximately 2.0 cm / s and when the air resistance was tested at a surface velocity of approximately 5.3 cm / s, the filter media also exhibited a γ value greater than or equal to 18 at the most penetrating particle size.

[0171] In some embodiments, the filter media includes a first layer, a second layer formed of fibers with an average fiber diameter of less than 1 micrometer, and an adhesive between the first and second layers. The first layer can be bonded to the second layer by the adhesive. The adhesive may comprise a solvent-based resin containing a polymer with a glass transition temperature of less than or equal to 25°C.

[0172] In some embodiments, a method for manufacturing a filter medium includes spraying a composition comprising a solvent-based adhesive resin and a crosslinking agent onto a first layer to form an adhesive-coated first layer, performing a solvent-based spinning process to deposit fibers onto the adhesive-coated first layer, and laminating a second layer onto a third layer such that the third layer is disposed on the opposite side of the second layer to the first layer. The fibers in the second layer may have an average fiber diameter of less than 1 micrometer and form the second layer.

[0173] In some embodiments, the filter media includes a first layer, a second layer formed of fibers with an average fiber diameter of less than 1 micrometer, and an adhesive between the first and second layers. The adhesive between the first and second layers may be present in an amount of less than 10 gsm. The first layer can be bonded to the second layer by the adhesive, and the bond strength between the first and second layers may be greater than or equal to 150 g / inch. 2 Compared to the filter media before IPA vapor discharge, the filter media can exhibit an increase in air resistance of less than 50% after being subjected to IPA vapor discharge.

[0174] In some of the embodiments described above and / or herein, the efficiency of the filter media according to standard EN1822:2009 is greater than 95%.

[0175] In some of the embodiments described above and herein, the efficiency of the filter media according to standard EN1822:2009 can be greater than 99.95%.

[0176] In some embodiments as described above and / or herein, the efficiency of the filter media according to standard EN1822:2009 is greater than 99.995%.

[0177] In some embodiments as described above and / or herein, the efficiency of the filter media according to standard EN1822:2009 is greater than 99.9995%.

[0178] In some embodiments as described above and herein, the fibers of the second layer are solvent-spun fibers.

[0179] In some embodiments as described above and herein, the fibers of the second layer are electrospun fibers or centrifugally spun fibers.

[0180] In some implementations as described above and herein, the second layer is the primary filtering layer.

[0181] In some implementations, as described above and herein, the filter medium also includes a third layer.

[0182] In some of the embodiments described above and in this document, the first layer is a wet-laid web layer.

[0183] In some of the implementation schemes described above and herein, the first layer is a support layer.

[0184] In some embodiments as described above and herein, the third layer is a meltblown layer.

[0185] In some implementations as described above and herein, the third layer is a pre-filtering layer.

[0186] In some embodiments as described above and herein, the third layer is an electrically charged meltblown layer.

[0187] In some implementation schemes as described above and in this document, the third layer is added online.

[0188] In some embodiments as described above and herein, the adhesive contains water.

[0189] In some embodiments as described above and herein, the adhesive comprises a crosslinking agent.

[0190] In some embodiments as described above and herein, the glass transition temperature of the adhesive is greater than or equal to -150°C.

[0191] In some embodiments as described above and herein, the adhesive between the second and third layers is present in an amount of less than 10 gsm.

[0192] In some embodiments as described above and herein, the filter medium further includes a fourth layer.

[0193] In some embodiments as described above and herein, the fibers of the fourth layer are solvent-spun fibers.

[0194] In some embodiments as described above and herein, the fibers of the fourth layer are electrospun fibers or centrifugally spun fibers.

[0195] In some implementations as described above and in this document, the fourth layer is the primary filtering layer.

[0196] In some embodiments as described above and herein, the filter medium further includes a fifth layer.

[0197] In some of the embodiments described above and herein, the fifth layer is a meltblown layer.

[0198] In some implementations as described above and herein, the fifth layer is a pre-filtering layer.

[0199] In some embodiments as described above and herein, the γ value under MPPS after exposure to IPA vapor is greater than or equal to 14.

[0200] In some implementations, filter media comprising one or more layers (e.g., two-layer, three-layer, or five-layer filter media, which may include, for example, HEPA, ULPA, or HVAC filters) may be components of a filter element. That is, the filter media may be incorporated into an article of manufacture suitable for end-user use. Non-limiting examples of suitable filter elements include flat-plate filters, V-type filters (including, for example, 1V to 24V), cartridge filters, cylindrical filters, conical filters, and kinetic filters. Filter elements may have any suitable height (e.g., 2 inches to 24 inches for flat-plate filters, 4 inches to 124 inches for V-type filters, and 1 inch to 124 inches for cartridge and cylindrical filter media). Filter elements may also have any suitable width (2 inches to 24 inches for flat-plate filters, and 4 inches to 124 inches for V-type filters). Some filter media (e.g., cartridge and cylindrical filter media) may be characterized by their diameter rather than their width; the diameter of these filter media may be any suitable value (e.g., 1 inch to 124 inches). Filter elements typically include a frame, which can be made of one or more materials, such as cardboard, aluminum, steel, alloys, wood, and polymers.

[0201] In some embodiments, the filter media described herein may be a component of a filter element and may be pleated. The pleat depth and pleat density can be selected as needed. For example, the filter media in a flat panel filter or V-filter may have a pleat depth 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 media in a cartridge filter or cone filter may have a pleat depth 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 may be separated by a pleat separator made of, for example, polymer, glass, aluminum, and / or cotton. In other embodiments, the filter element may lack a pleat separator. The filter media may be wire-backed or self-supporting.

[0202] Example 1

[0203] In this embodiment, a five-layer filter medium was manufactured, wherein a solvent-based adhesive was used to bond the layers together.

[0204] Figure 3 A schematic diagram of a system 300 for forming the filter media described herein is shown. A solvent-based binder 310 (Super 77, a synthetic elastomer dissolved in acetone, cyclohexane, dimethyl glutarate, and other petroleum distillates; available from 3M) is sprayed onto a substrate with a weight of 50 g / m³. 2 On the first layer (support layer). The adhesive coating has a weight of less than 10 g / m³. 2 (For example, less than 1g / m 2 The support layer coated with adhesive then enters the spinning unit 320 (e.g., an electrospinning chamber), where a second layer (a nylon main filter layer) is added near the adhesive. Next, a sprayed solution with a weight of less than 10 g / m³ is added via lamination through the winding unit 330. 2 (For example, less than 1g / m 2 The third layer of the adhesive (spunbond pre-filter layer; trade name Reemay 2250) is applied to form a three-layer filter media. The resulting filter media formed during this first pass is shown in... Figure 4A It includes a first layer 410, a second layer 420, a third layer 430, and an adhesive 490. (Refer to previous section) Figure 3 Then at less than 10g / m 2 (For example, less than 1g / m 2 Adhesive 340 is applied to the third layer (pre-filter layer) at a fixed weight, and the three layers of filter media are passed through the spinning unit again to add a fourth layer (nylon main filter layer) near the opposite side of the third layer. The fifth layer (support layer) is sprayed with adhesive and laminated so that its adhesive-coated side is adjacent to the fourth layer to form a five-layer filter media. Figures 4A to 4C The resulting structure formed using the above-described system and method is shown. The filter media includes a first layer 410, a second layer 420, a third layer 430, a fourth layer 440, a fifth layer 440, and an adhesive 490 (filter media 1).

[0205] For comparative purposes, a four-layer filter medium (filter medium 2) was manufactured by manually combining two adhesive-free filter media. Each adhesive-free filter medium was manufactured by electrospinning a second layer (main filter layer) onto a first layer (support layer). Manual finishing was performed after each filter medium was wound once. The electrospun main filter layer of filter medium 2 is structurally similar to the main filter layer of filter medium 1 (e.g., fiber diameter, material, and weight), and the support layer of filter medium 2 is structurally similar to the support layer of filter medium 2 (e.g., fiber diameter, material, and weight). Compared to other layers in the medium, the spunbond pre-filter layer, present in filter medium 1 but absent in filter medium 2, did not significantly contribute to the γ value of filter medium 1 due to its relatively low air resistance and high permeability.

[0206] Filter medium 1 has a higher γ value (59.1) than filter medium 2 (45.1), indicating that the filter medium containing a solvent-based binder formed by the method described in this embodiment is superior to the filter medium without a binder.

[0207] Example 2

[0208] This embodiment describes the use of an adhesive containing a small molecule crosslinking agent.

[0209] By setting the weight to 0.2 g / m 2 The second layer (main filter layer) is electrospun onto the first layer (support layer) to prepare two layers of filter media.

[0210] Adhesive compositions were prepared by adding a carbodiimide crosslinker (Carbodilite E-02; available from Nisshinbo Chemicals) in different amounts (e.g., 0 wt%, 3 wt%, or 7 wt% of the crosslinker relative to the total weight of the layers) to an aqueous acrylate copolymer adhesive (Carbobond 1995; available from Lubrizol Corporation) with a glass transition temperature of -30°C.

[0211] The adhesive composition (containing both Carbobond 1995 and a crosslinking agent) was applied at a concentration of 1 g / m³. 2The adhesive was sprayed onto the third layer (polyester spunbond protective layer; trade name Reemay 2250). The adhesive-coated third layer was laminated to the two filter media at 80°C, and the air resistance of the resulting three-layer filter media was measured. Then, as described above, the three-layer filter media was exposed to IPA vapor, and the air resistance of the three-layer filter media was measured again. Filter media containing adhesive compositions with 0% or 3% crosslinking agent exhibited a significant increase in air resistance after exposure to IPA vapor (3.7 mm H2O to 18.8 mm H2O for 0% crosslinking agent, and 3.7 mm H2O to 9.4 mm H2O for 3% crosslinking agent). Filter media containing adhesive compositions with 7% crosslinking agent showed a negligible increase in air resistance after IPA vapor exposure (3.3 mm H2O to 4.1 mm H2O).

[0212] Example 3

[0213] This embodiment describes the manufacture of the filter media.

[0214] A customized in-line nozzle system capable of applying adhesive to the filter media layer at several points during the manufacturing process. Using a nozzle with 50 g / m³... 2 A fixed-weight wet-laid synthetic medium is used as the first layer (support layer) and passed through the system, then sprayed with an adhesive. The adhesive-coated layer is then fed into an electrospinning production line to deposit a second layer (nylon electrospinning main filter layer) near the adhesive. The main filter layer has a density of 0.25 g / m³. 2 The weight and average fiber diameter of 100 nm were determined. These two layers were then combined with a third layer coated with an adhesive (20 g / m²). 2 The polypropylene meltblown pre-filter layer is prepared so that the adhesive on the meltblown pre-filter layer is adjacent to the main filter layer. This multilayer media is then passed through a felt dryer that can maintain a surface temperature of 120°C. The laminated media is then wound into rolls and characterized.

[0215] The adhesive used above was Carbobond 1995 in combination with Carbodilite crosslinking agent. Carbobond 1995 was prepared as 15% by weight solids and blended with 10% by weight wet Carbodilite E02 crosslinking agent. The pH of the blend was adjusted to 7 to 8 using potassium hydroxide. 1.03 g / m³ was present at each interface in the final filter media. 2 The adhesive (i.e., 1.03 g / m²) is present at the interface between the wet-laid web layer and the main filter layer. 2 The adhesive has a concentration of 1.03 g / m at the interface between the main filter layer and the meltblown layer. 2 (Adhesive.)

[0216] The three-layer main filter manufactured as described above has a strength of 343 g / in. 2 The average internal bonding strength and good bonding of the three layers. These filter media also exhibited other positive properties after exposure to IPA vapor, such as negligible increase in air resistance (17.1 mm H2O to 17.8 mm H2O), negligible increase in penetration at MPPS (0.0044% to 0.01373%), and a relatively high γ value (22.7).

[0217] Example 4

[0218] This embodiment describes the manufacture of the filter media as in Example 3.

[0219] The three-layer filter media is manufactured using similar steps to those used in Example 3.

[0220] The first layer (support layer) is 60g / m² steel with a stiffness of 380mg, a machine direction tensile strength of 25.7 psi, a thickness of 0.016 inches, and a dry malon strength of 70psi. 2 Synthetic wet-laid web backing.

[0221] The second layer (main filter layer) is made of nylon fibers (electrospun fibers) with an average fiber diameter of about 120 nm.

[0222] The third layer (pre-filter layer) has a fixed weight of 22g / m³. 2 The meltblown polypropylene layer has an average fiber diameter of 1.5 micrometers. The pre-filter layer was also corona charged so that its initial efficiency for 0.3 micrometer DOP particles, measured at a surface velocity of 5.32 cm / s, was 8.5%, and its IPA vapor discharge efficiency was 65%.

[0223] The adhesive formulation is similar to that used in Example 3, except that it has 12.5% ​​by weight solids. 0.8 g / m² is added between each pair of layers (i.e., between the support layer and the main filter layer, and between the main filter layer and the pre-filter layer). 2 The adhesive content is 1.6 g / m³ for the entire filter media. 2 Adhesive.

[0224] The filter media exhibited a 9% increase in air resistance after IPA vapor discharge and a γ value of 18.89 after IPA vapor discharge. The average internal bonding strength of the filter media was 189.4 g / in. 2 .

[0225] Although various embodiments of the invention have been described and illustrated herein, those skilled in the art will readily conceive of various 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 such variation and / or modification is considered to be within the scope of the invention. More generally, those skilled in the art will readily understand that all parameters, dimensions, materials, and configurations described herein are intended to be exemplary, and actual parameters, dimensions, materials, and / or configurations will depend on one or more specific applications using the teachings of the invention. Those skilled in the art will recognize or be able to determine many equivalents of the specific embodiments of the invention described herein using only conventional experimentation. Therefore, it should be understood that the foregoing embodiments are shown by way of example only, and that the invention can be practiced in ways other than those specifically described and claimed within the scope of the appended claims and their equivalents. The invention relates to the various individual features, systems, articles, materials, kits, and / or methods described herein. Furthermore, any combination of two or more such features, systems, articles, materials, kits, and / or methods is included within the scope of the invention if two or more such features, systems, articles, materials, kits, and / or methods do not contradict each other.

[0226] All definitions defined and used herein should be understood to take precedence over dictionary definitions, definitions in referenced literature, and / or the general meaning of the defined terms.

[0227] Unless otherwise expressly stated, objects without quantifiers as used herein in the specification and claims shall be understood to mean “at least one / one”.

[0228] The phrase “and / or” as used herein in the specification and claims should be understood to mean “any one or both” of the elements in such a combination, i.e., elements that coexist in some cases and exist separately in others. Multiple elements listed with “and / or” should be interpreted in the same way, i.e., “one or more” of the elements in such a combination. Other elements may optionally be present, whether related to or unrelated to those specifically indicated by the “and / or” clause. Thus, as a non-limiting example, when used in conjunction with open-ended language such as “comprising,” reference to “A and / or B” may refer only to A in one embodiment (optionally including elements other than B); in another embodiment only to B (optionally including elements other than A); in yet another embodiment to both A and B (optionally including other elements); and so on.

[0229] 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 items are listed separately, “or” or “and / or” should be understood to include, i.e., include multiple elements or at least one of the elements in the list, but also include more than one, and optionally include additional unlisted items. Only explicitly indicating the opposite terms, such as “only one” or “exactly one”, or when used in claims, “consisting of” means including multiple elements or exactly one of the elements in the list. Generally, when preceded by an exclusive term (e.g., “any,” “one,” “only one,” or “exactly one”), the term “or” as used herein should only be understood to indicate an exclusive alternative (i.e., “one or the other but not both”). “Substantially consisting of” should have its general meaning as used in the field of patent law when used in claims.

[0230] 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, but does not necessarily include at least one of each element specifically listed in the list, nor exclude any combination of elements in the list. This definition also allows for the optional presence of elements other than those specifically indicated in the list of elements referred to by the phrase “at least one,” whether related to or unrelated to those specifically indicated elements. 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”) in one embodiment may refer to at least one A, optionally including more than one A, without B (and optionally including elements other than B); in another embodiment, it may refer to at least one B, optionally including more than one B, without A (and optionally including elements other than A); in yet another embodiment, it 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.

[0231] It should also be understood that, unless explicitly stated otherwise, in any method claimed herein that includes more than one step or action, the order of the steps or actions of the method is not necessarily limited to the order in which the steps or actions of the method are described.

[0232] In the claims and in the above description, all transitional phrases such as “comprising,” “including,” “with,” “having,” “containing,” “involving,” “holding,” “including,” etc., shall be understood as open-ended, that is, meaning including but not limited to. Only the transitional phrases “consisting of” and “consisting substantially of” shall be closed or semi-closed transitional phrases, respectively, as set forth in Section 2111.03 of the U.S. Patent Examination Procedure Manual.

[0233] The present invention also provides the following technical solutions:

[0234] Note 1. A filter medium comprising:

[0235] First layer;

[0236] The second layer, wherein the second layer is formed of fibers with an average fiber diameter of less than 1 micrometer; and

[0237] The adhesive between the first layer and the second layer, wherein the first layer is bonded to the second layer by the adhesive,

[0238] The stiffness of the filter medium is greater than or equal to 200 mg.

[0239] The bonding strength between the first layer and the second layer is greater than or equal to 150 g / inch. 2 ,

[0240] The filter medium exhibits a γ value greater than or equal to 18 at the most easily penetrating particle size.

[0241] Note 2. A filter medium comprising:

[0242] First layer;

[0243] The second layer, wherein the second layer is formed of fibers with an average fiber diameter of less than 1 micrometer; and

[0244] The adhesive between the first layer and the second layer, wherein the first layer is bonded to the second layer by the adhesive,

[0245] The adhesive comprises a solvent-based resin containing a polymer with a glass transition temperature of less than or equal to 24°C.

[0246] Note 3. A method for manufacturing a filter medium, comprising:

[0247] A composition comprising a solvent-based adhesive resin and a crosslinking agent is sprayed onto a first layer to form a first layer coated with the adhesive;

[0248] A solvent-based spinning process is performed to deposit fibers onto the first layer coated with an adhesive, wherein the fibers have an average fiber diameter of less than 1 micrometer and form a second layer; and

[0249] The second layer is laminated to the third layer, such that the third layer is positioned on the side of the second layer opposite to the first layer.

[0250] Note 4. A filter medium comprising:

[0251] First layer;

[0252] The second layer, wherein the second layer is formed of fibers with an average fiber diameter of less than 1 micrometer; and

[0253] The adhesive between the first layer and the second layer,

[0254] The adhesive between the first layer and the second layer is present in an amount of less than 10 gsm, wherein the first layer is bonded to the second layer by the adhesive, and wherein the bond strength between the first layer and the second layer is greater than or equal to 150 g / inch. 2 ,as well as

[0255] Compared to the filter medium before IPA vapor discharge, the filter medium exhibits an increase in air resistance of less than 50% after being subjected to IPA vapor discharge.

[0256] Note 5. The filter medium or method according to any of the preceding notes, wherein the efficiency of the filter medium according to standard EN1822:2009 is greater than 95%.

[0257] Note 6. The filter medium or method according to any of the preceding notes, wherein the efficiency of the filter medium according to standard EN1822:2009 is greater than 99.95%.

[0258] Note 7. The filter medium or method according to any of the preceding notes, wherein the efficiency of the filter medium according to standard EN1822:2009 is greater than 99.995%.

[0259] Note 8. The filter medium or method according to any of the preceding notes, wherein the efficiency of the filter medium according to standard EN1822:2009 is greater than 99.9995%.

[0260] Note 9. According to any of the preceding notes, the filter medium or method, wherein the fibers of the second layer are solvent-spun fibers.

[0261] Note 10. According to any of the preceding notes, the filter medium or method, wherein the fibers of the second layer are electrospun fibers or centrifugally spun fibers.

[0262] Note 11. The filter medium or method according to any of the foregoing notes, wherein the second layer is the primary filter layer.

[0263] Note 12. The filter medium or method according to any of the preceding notes, wherein the first layer is a wet-laid web layer.

[0264] Note 13. The filter medium or method according to any of the foregoing notes, wherein the first layer is a support layer.

[0265] Note 14. The filter medium or method according to any of the foregoing notes, wherein the filter medium includes a third layer.

[0266] Note 15. The filter medium or method according to any of the preceding notes, wherein the third layer is a meltblown layer.

[0267] Note 16. The filter medium or method according to any of the preceding notes, wherein the third layer is a pre-filter layer.

[0268] Note 17. The filter medium according to any of the preceding notes, wherein the third layer is an electrically charged meltblown layer.

[0269] Note 18. The filter medium according to any of the foregoing notes, wherein the third layer is added online.

[0270] Note 19. The filter medium or method according to any of the foregoing notes, wherein the adhesive comprises water.

[0271] Note 20. The filter medium or method according to any of the foregoing notes, wherein the adhesive comprises a crosslinking agent.

[0272] Note 21. According to any of the preceding notes, the filter medium or method wherein the glass transition temperature of the adhesive is greater than or equal to -150°C.

[0273] Note 22. In any of the filter media or methods described in the foregoing notes, the adhesive between the second layer and the third layer is present in an amount of less than 10 gsm.

[0274] Note 23. The filter medium or method according to any of the foregoing notes further includes a fourth layer.

[0275] Note 24. The filter medium or method according to Note 23, wherein the fibers of the fourth layer are solvent-spun fibers.

[0276] Note 25. The filter medium or method according to any one of Notes 23 to 24, wherein the fibers of the fourth layer are electrospun fibers or centrifugally spun fibers.

[0277] Note 26. The filter medium or method according to any one of Notes 23 to 25, wherein the fourth layer is the main filter layer.

[0278] Note 27. The filter medium or method according to any one of Notes 23 to 26 further includes a fifth layer.

[0279] Note 28. The filter medium or method according to any one of Notes 23 to 27, wherein the fifth layer is a meltblown layer.

[0280] Note 29. The filter medium or method according to any one of Notes 23 to 28, wherein the fifth layer is a pre-filter layer.

[0281] Note 30. The filter media according to any of the foregoing notes, wherein the γ value at MPPS after exposure to IPA vapor is greater than or equal to 14.

[0282] Note 31. According to any of the preceding notes, the filter medium, wherein the adhesive is capable of undergoing a crosslinking reaction at a temperature greater than or equal to 24°C and less than or equal to 150°C, wherein the glass transition temperature of the adhesive is less than or equal to 24°C.

Claims

1. A filter medium, comprising: The first layer, wherein the first layer is a pre-filtering layer or a support layer; The second layer, wherein the second layer is formed of fibers with an average fiber diameter of less than 1 micrometer; and The adhesive between the first layer and the second layer, wherein the first layer is bonded to the second layer by the adhesive, The adhesive is cross-linked by a cross-linking agent. The adhesive is: an adhesive containing acrylates, and / or an adhesive containing acrylate copolymers, and / or an adhesive containing a reaction product of a carboxylic acid group and the crosslinking agent; and / or an adhesive crosslinked by a reaction between the adhesive and carbodiimide functional groups present in the adhesive. The stiffness of the filter medium is greater than or equal to 200 mg, and the stiffness is determined according to the Gurley stiffness recorded in mg according to TAPPI T543 om-94. The bonding strength between the first layer and the second layer is greater than or equal to 150 g / inch. 2 The bonding strength is determined using a z-direction peel strength test. The filter medium exhibits a γ value greater than or equal to 18 at the most easily penetrating particle size, and the γ value is determined by γ = (-log 10 The value is determined by (MPPS transmittance % / 100) / pressure drop, mm H2O)×100, where MPPS transmittance is measured using the EN1822:2009 standard. Compared to the filter media before isopropanol vapor discharge, the filter media exhibited less than 50% increase in air resistance after being subjected to isopropanol vapor discharge. This increase in air resistance was determined based on EN1822:2009 standard by air resistance testing using a TSI 3160 automated filter test unit from TSI, Inc.

2. A filter medium, comprising: The first layer, wherein the first layer is a pre-filtering layer or a support layer; The second layer, wherein the second layer is formed of fibers with an average fiber diameter of less than 1 micrometer; and The adhesive between the first layer and the second layer, wherein the first layer is bonded to the second layer by the adhesive, The adhesive comprises a solvent-based resin containing a polymer with a glass transition temperature less than or equal to 24°C, the glass transition temperature being determined by differential scanning calorimetry. The adhesive is cross-linked by a cross-linking agent, and The adhesive is: an adhesive containing acrylates, and / or an adhesive containing acrylate copolymers, and / or an adhesive containing a reaction product of carboxylic acid groups and the crosslinking agent; and / or an adhesive crosslinked by a reaction between the adhesive and carbodiimide functional groups present in the adhesive. Compared to the filter media before isopropanol vapor discharge, the filter media exhibited less than 50% increase in air resistance after being subjected to isopropanol vapor discharge. This increase in air resistance was determined based on EN1822:2009 standard by air resistance testing using a TSI 3160 automated filter test unit from TSI, Inc.

3. A filter medium, comprising: The first layer, wherein the first layer is a pre-filtering layer or a support layer; The second layer, wherein the second layer is formed of fibers with an average fiber diameter of less than 1 micrometer; and The adhesive between the first layer and the second layer, The adhesive between the first layer and the second layer is present in an amount of less than 10 gsm, wherein the first layer is bonded to the second layer by the adhesive, and wherein the bond strength between the first layer and the second layer is greater than or equal to 150 g / inch. 2 The bonding strength is determined using a z-direction peel strength test. The adhesive is cross-linked by a cross-linking agent. The adhesive is: an adhesive containing acrylates, and / or an adhesive containing acrylate copolymers, and / or an adhesive containing a reaction product of a carboxylic acid group and the crosslinking agent; and / or an adhesive crosslinked by a reaction between the adhesive and carbodiimide functional groups present in the adhesive, and Compared to the filter media before isopropyl alcohol (IPA) vapor discharge, the filter media exhibited less than 50% increase in air resistance after being subjected to IPA vapor discharge. This increase in air resistance was determined based on EN1822:2009 standard through air resistance testing using a TSI 3160 automated filter test unit from TSI, Inc.

4. A filter medium, comprising: The first layer, wherein the first layer is a pre-filtering layer or a support layer; The second layer, wherein the second layer is formed of fibers with an average fiber diameter of less than 1 micrometer; and The adhesive between the first layer and the second layer, wherein the first layer is bonded to the second layer by the adhesive, The adhesive is cross-linked by a cross-linking agent. The crosslinking agent comprises a weight percentage of the adhesive that is greater than or equal to 0.1% by weight and less than or equal to 30% by weight. Where the γ value under MPPS after exposure to IPA vapor is greater than or equal to 14, the γ value is determined by γ = (-log 10 (MPPS penetration % / 100) / pressure drop, mm H2O)×100 is determined, where MPPS penetration is measured using the EN1822:2009 standard.

5. A filter medium, comprising: The first layer, wherein the first layer is a pre-filtering layer or a support layer; The second layer, wherein the second layer is formed of fibers with an average fiber diameter of less than 1 micrometer; and The adhesive between the first layer and the second layer, wherein the first layer is bonded to the second layer by the adhesive, The adhesive is cross-linked by a cross-linking agent. The adhesive is: an adhesive containing acrylates, and / or an adhesive containing acrylate copolymers, and / or an adhesive containing a reaction product of a carboxylic acid group and the crosslinking agent; and / or an adhesive crosslinked by a reaction between the adhesive and carbodiimide functional groups present in the adhesive. Compared to the filter media before isopropanol vapor discharge, the filter media exhibited less than 50% increase in air resistance after being subjected to isopropanol vapor discharge. This increase in air resistance was determined based on EN1822:2009 standard by air resistance testing using a TSI 3160 automated filter test unit from TSI, Inc.

6. The filter medium according to any of the preceding claims, wherein the filter medium has an efficiency greater than 95% according to standard EN1822:2009.

7. The filter medium according to any one of claims 1 to 5, wherein the filter medium has an efficiency greater than 99.95% according to standard EN1822:2009.

8. The filter medium according to any one of claims 1 to 5, wherein the filter medium has an efficiency greater than 99.995% according to standard EN1822:2009.

9. The filter medium according to any one of claims 1 to 5, wherein the filter medium has an efficiency greater than 99.9995% according to standard EN1822:2009.

10. The filter medium according to any one of claims 1 to 5, wherein the fibers of the second layer are solvent-spun fibers.

11. The filter medium according to any one of claims 1 to 5, wherein the fibers of the second layer are electrospun fibers or centrifugally spun fibers.

12. The filter medium according to any one of claims 1 to 5, wherein the second layer is the main filter layer.

13. The filter medium according to any one of claims 1 to 5, wherein the first layer is a wet-laid web layer.

14. The filter medium according to any one of claims 1 to 5, wherein the first layer is a support layer.

15. The filter medium according to any one of claims 1 to 5, wherein the filter medium comprises a third layer, wherein the third layer is a pre-filter layer or a support layer.

16. The filter medium according to claim 15, wherein the third layer is a melt-blown layer.

17. The filter medium according to claim 15, wherein the third layer is a pre-filter layer.

18. The filter medium according to claim 15, wherein the third layer is an electrically charged melt-blown layer.

19. The filter medium according to claim 15, wherein the third layer is added online.

20. The filter medium according to any one of claims 1 to 5, wherein the adhesive comprises water.

21. The filter medium according to any one of claims 1 to 5, wherein the adhesive comprises a crosslinking agent.

22. The filter medium according to any one of claims 1 to 5, wherein the glass transition temperature of the adhesive is greater than or equal to -150°C.

23. The filter medium of claim 15, wherein the adhesive between the second layer and the third layer is present in an amount of less than 10 gsm.

24. The filter medium of claim 15, further comprising a fourth layer, wherein the fourth layer is a primary filter layer.

25. The filter medium according to claim 24, wherein the fibers of the fourth layer are solvent-spun fibers.

26. The filter medium according to any one of claims 24 to 25, wherein the fibers of the fourth layer are electrospun fibers or centrifugally spun fibers.

27. The filter medium according to any one of claims 24 to 25 further comprises a fifth layer, wherein the fifth layer is a pre-filter layer or a support layer.

28. The filter medium according to claim 27, wherein the fifth layer is a meltblown layer.

29. The filter medium according to claim 27, wherein the fifth layer is a pre-filter layer.

30. The filter medium according to any one of claims 1 to 3 and 5, wherein the γ value at MPPS after exposure to IPA vapor is greater than or equal to 14.

31. The filter medium according to any one of claims 1 to 5, wherein the adhesive is capable of undergoing a crosslinking reaction at a temperature greater than or equal to 24°C and less than or equal to 150°C, wherein the glass transition temperature of the adhesive is less than or equal to 24°C.

32. The filter medium according to any one of claims 1 to 3 and 5, wherein the crosslinking agent accounts for more than or equal to 0.1% by weight and less than or equal to 30% by weight of the adhesive.

33. The filter medium according to any one of claims 1 to 5, wherein the adhesive comprises acrylate and / or acrylate copolymer.

34. The filter medium according to any one of claims 1 to 5, wherein the adhesive comprises a reaction product of a carboxylic acid group and the crosslinking agent.

35. The filter medium according to any one of claims 1 to 5, wherein the adhesive comprises a crosslinking agent, wherein the crosslinking agent crosslinks the adhesive by a reaction between the carbodiimide functional groups thereon and the adhesive.

36. The filter medium according to any one of claims 1 to 5, wherein the crosslinking agent accounts for more than or equal to 5% by weight and less than or equal to 30% by weight of the adhesive.

37. The filter medium according to any one of claims 1 to 5, wherein the second layer comprises synthetic fibers.

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