CN117982986A

CN117982986A - Filter media comprising adhesive and/or oleophobic properties

Info

Publication number: CN117982986A
Application number: CN202410179825.8A
Authority: CN
Inventors: 苏达卡尔·贾加纳坦; 道格拉斯·M·吉蒙; 嘉利·刘
Original assignee: Hollingsworth and Vose Co
Current assignee: Hollingsworth and Vose Co
Priority date: 2017-03-28
Filing date: 2018-03-28
Publication date: 2024-05-07
Also published as: CN110621386A; EP3600601A4; CN114470971A; CN110621386B; CN114470971B; EP3600601A1; WO2018183481A1

Abstract

The present application relates to filter media comprising adhesive and/or oleophobic properties. Articles and methods relating to filter media are generally provided. In certain embodiments, the filter media includes at least a first layer, a second layer, and a binder resin disposed between the first layer and the second layer. 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 binder 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 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 IPA vapor discharge. The filter medium may be, for example, a HEPA filter and/or a ULPA filter.

Description

Filter media comprising adhesive and/or oleophobic properties

The present application is a divisional application of chinese patent application entitled "filter media comprising adhesive and/or oleophobic properties", application No. 201880030782.X, patent application 201880030782.X is a national application entering the national stage of china according to international application filed under the cooperation of patent about 28 days 3 in 2018 (PCT/US 2018/024820), the priority date of which is 28 days 3 in 2017.

Technical Field

The present invention relates generally to filter media and, more particularly, to filter media that include a binder and/or have oleophobic properties.

Background

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

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

While there are many types of filter media for filtering particulates from air, improvements in the physical and/or performance characteristics (e.g., strength, air resistance, efficiency, and high dust holding capacity) of the filter media would be beneficial.

Disclosure of Invention

Filter media and related components and methods related thereto are provided.

In one set of embodiments, a filter medium is provided. In some embodiments, the filter media comprises a first layer; a second layer, wherein the second layer is formed from fibers having an average fiber diameter of less than 1 micron; 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 filter media has a stiffness (stick) of greater than or equal to 200mg. The bond strength between the first layer and the second layer is greater than or equal to 150 g/inch ². The filter media exhibits a gamma value greater than or equal to 18 at the most penetrating particle size.

In some embodiments, the filter media comprises a first layer; a second layer, wherein the second layer is formed from fibers having an average fiber diameter of less than 1 micron; and an adhesive between the first layer and the second layer. The first layer is bonded to the second layer by an adhesive. The adhesive comprises a solvent-based resin comprising a polymer having a glass transition temperature of less than or equal to 24 ℃.

In some embodiments, the filter media comprises a first layer; a second layer, wherein the second layer is formed from fibers having an average fiber diameter of less than 1 micron; and an 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. The first layer is bonded to the second layer by an adhesive. The bond strength between the first layer and the second layer is greater than or equal to 150 g/inch ². The filter media exhibits less than a 50% increase in air resistance after subjecting the filter media to IPA vapor discharge compared to the filter media prior to IPA vapor discharge.

In some embodiments, the filter media includes a first layer and a second layer, and an adhesive between the first layer and the second layer. The first layer is bonded to the second layer by an adhesive. The second layer is formed from fibers having an average fiber diameter of less than 1 micron. The oil level of at least one of the first layer and the second layer is greater than or equal to 1. The bond strength between the first layer and the second layer is greater than or equal to 150 g/inch ². The filter media has a stiffness greater than or equal to 200mg, wherein the stiffness is measured in the machine or cross direction.

In some embodiments, the filter media includes a first layer and a second layer, and an adhesive between the first layer and the second layer. The first layer is bonded to the second layer by an adhesive. The first layer comprises fibers. The second layer is a film layer. The oil level of at least one of the first layer and the second layer is greater than or equal to 1. The bond strength between the first layer and the second layer is greater than or equal to 150 g/inch ². The filter media has a stiffness greater than or equal to 200mg, wherein the stiffness is measured in the machine or cross direction.

In some embodiments, the filter media includes a first layer and a second layer. The second layer is formed from fibers having an average fiber diameter of less than 1 micron. The oil level of at least one of the first layer and the second layer is greater than or equal to 1. The filter media has a stiffness greater than or equal to 200mg, wherein the stiffness is measured in the machine or cross direction. The filter media has a pressure drop of less than or equal to 50mm H ₂ O at a DOP oil loading of greater than or equal to 4.5g/m ².

In some embodiments, the filter media includes a first layer and a second layer. The first layer comprises fibers. The second layer is a film layer. The oil level of at least one of the first layer and the second layer is greater than or equal to 1. The filter media has a stiffness greater than or equal to 200mg, wherein the stiffness is measured in the machine or cross direction. The filter media has a pressure drop of less than or equal to 50mm H ₂ O at a DOP oil loading of greater than or equal to 4.5g/m ².

In some embodiments, the filter media includes a first layer and a second layer. The second layer is formed from fibers having an average fiber diameter of less than 1 micron. The oil level of at least one of the first layer and the second layer is greater than or equal to 1. The filter media has a stiffness greater than or equal to 200mg, wherein the stiffness is measured in the machine or cross direction. The filter media has a gamma value greater than or equal to 10 at DOP oil loadings greater than or equal to 4.5g/m ².

In some embodiments, the filter media includes a first layer and a second layer. The first layer comprises fibers. The second layer is a film layer. The oil level of at least one of the first layer and the second layer is greater than or equal to 1. The filter media has a stiffness greater than or equal to 200mg, wherein the stiffness is measured in the machine or cross direction. The filter media has a gamma value greater than or equal to 10 at DOP oil loadings greater than or equal to 4.5g/m ².

In another set of embodiments, a method is provided. In some embodiments, a method of making a filter media includes spraying a composition comprising a solvent-based binder resin and a cross-linking agent onto a first layer to form a binder coated first layer, performing a solvent-based spinning process to deposit fibers on the binder coated first layer, wherein the fibers have an average fiber diameter of less than 1 micron and form a second layer; and laminating the second layer to the third layer such that the third layer is disposed on an opposite side of the second layer from the first layer.

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

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

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%.

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%.

In some embodiments as described above and/or herein, the efficiency of the filter media according to standard EN1822:2009 is greater than 99.99995%.

In some embodiments as described above and/or herein, the efficiency of the filter media according to standard EN1822:2009 is greater than 99.999995%.

In some embodiments as described above and/or herein, the efficiency of the filter media according to standard EN1822:2009 is greater than 99.9999995%.

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

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

In some embodiments as described above and herein, the second layer is a main filtration layer.

In some embodiments, the filter media further comprises a third layer, as described above and herein.

In some embodiments as above and described herein, the first layer is a wet laid layer.

In some embodiments as above and described herein, the first layer is a meltblown layer.

In some embodiments as above and described herein, the first layer is a charged meltblown layer.

In some embodiments as above and described herein, the first layer is a support layer.

In some embodiments as above and described herein, the first layer is a pre-filter layer.

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

In some embodiments as above and described herein, the third layer is a wet laid layer.

In some embodiments as above and described herein, the third layer is a pre-filter layer.

In some embodiments as above and described herein, the third layer is a support layer.

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

In some embodiments as above and described herein, the third layer is added online.

In some embodiments as above and described herein, the adhesive comprises water.

In some embodiments as above and described herein, the adhesive comprises a cross-linking agent.

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

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

In some embodiments as above and described herein, the filter media further comprises a fourth layer.

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

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

In some embodiments as above and described herein, the fourth layer is a main filtration layer.

In some embodiments as above and described herein, the filter media further comprises a fifth layer.

In some embodiments as above and described herein, the fifth layer is a meltblown layer.

In some embodiments as above and described herein, the fifth layer is a pre-filter layer.

In some embodiments as above and described herein, the gamma value at MPPS after exposure to IPA vapor is greater than or equal to 14.

In some embodiments as above and described herein, the first layer is a surface modified layer.

In some embodiments as above and described herein, the second layer is a surface modified layer.

In some embodiments as above and described herein, the third layer is a surface modified layer.

In some embodiments as above and described herein, the surface modification of at least one of the first layer, the second layer, and the third layer is performed by a chemical deposition technique.

In some embodiments as above and described herein, the surface modification of at least one of the first layer, the second layer, and the third layer is performed by plasma enhanced chemical vapor deposition.

In some embodiments as above and described herein, the surface modification of at least one of the first layer, the second layer, and the third layer is performed by electron beam assisted radiation curing.

In some embodiments as above and described herein, the surface modification of at least one of the first layer, the second layer, and the third layer is performed by a physical deposition technique.

In some embodiments as above and described herein, the surface modification of at least one of the first layer, the second layer, and the third layer is performed by powder coating.

In some embodiments as above and described herein, the first layer further comprises an oleophobic component.

In some embodiments as above and described herein, the second layer further comprises an oleophobic component.

In some embodiments as above and described herein, the third layer further comprises an oleophobic component.

In some embodiments as above and described herein, the oleophobic component of at least one of the first layer, the second layer, and the third layer is a layer deposited by a chemical deposition technique.

In some embodiments as above and described herein, the oleophobic component of at least one of the first layer, the second layer, and the third layer is a layer deposited by plasma enhanced chemical vapor deposition.

In some embodiments as above and described herein, the oleophobic component of at least one of the first layer, the second layer, and the third layer is a layer deposited by electron beam assisted radiation curing.

In some embodiments as above and described herein, the oleophobic component of at least one of the first layer, the second layer, and the third layer is a layer deposited by a physical deposition technique.

In some embodiments as above and described herein, the oleophobic component of at least one of the first layer, the second layer, and the third layer is a layer deposited by powder coating.

In some embodiments as above and described herein, the oleophobic component comprises an oleophobic resin.

In some embodiments as described above and herein, the oleophobic ingredient includes an oleophobic additive.

In some embodiments as above and described herein, the first layer has an oil grade greater than or equal to 1.

In some embodiments as above and described herein, the second layer has an oil grade greater than or equal to 1.

In some embodiments as above and described herein, the oil grade of the upstream most distant layer is greater than or equal to 1.

In some embodiments as above and described herein, the filtration media has a DOP penetration at MPPS of less than or equal to 0.5%, less than or equal to 0.05%, less than or equal to 0.005%, less than or equal to 0.0005%, less than or equal to 0.00005%, or less than or equal to 0.000005% at a DOP oil loading of greater than or equal to 4.5g/m ².

In some embodiments as above and described herein, the oleophobic ingredient comprises a polymer.

In some embodiments as above and described herein, the oleophobic ingredient includes an organofluorine.

In some embodiments as above and described herein, the oleophobic ingredient includes one or more of waxes, silicones, corn-based polymers, and nanoparticle materials.

In some embodiments as above and described herein, the first layer comprises fibers and an oleophobic component, and the oleophobic component is in the form of a coating disposed on one or more fibers within the first layer.

In some embodiments as above and described herein, the coating at least partially surrounds one or more fibers within the first layer.

In some embodiments as above and described herein, the filter media has a stiffness in the machine direction of greater than or equal to 300mg.

In some embodiments as above and described herein, the filter media has a basis weight of less than or equal to 150g/m ².

In some embodiments as above and described herein, the filter media is pleated and the pleat height is greater than or equal to 10mm and less than or equal to 510mm.

In some embodiments as above and described herein, the filter media is pleated and has a pleat density of greater than or equal to 6 pleats per 100mm and less than or equal to 100 pleats per 100 mm.

In some embodiments as above and described herein, the stiffness is measured in the cross machine direction.

In some embodiments as above and described herein, the stiffness is measured in the machine direction.

Other advantages and novel features of the invention will become apparent from the following detailed description of various non-limiting embodiments of the invention when considered in conjunction with the drawings. In the event that this specification contains conflicting and/or inconsistent disclosure from a document incorporated by reference, the specification shall control. If two or more documents incorporated by reference contain conflicting and/or inconsistent disclosure with respect to each other, the documents following the effective date should prevail.

Drawings

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

FIG. 1A illustrates a filter media comprising two layers according to some embodiments;

FIG. 1B illustrates a filter medium comprising an oleophobic component in accordance with some embodiments;

FIG. 1C illustrates a filter media including a coating layer;

FIG. 1D illustrates a filter media including three layers according to some embodiments;

FIG. 1E illustrates a filter media including five layers according to some embodiments;

FIGS. 2A-2C illustrate a method of forming a tri-layer medium according to some embodiments;

FIG. 3 illustrates a lamination process for forming a filter media according to some embodiments;

FIGS. 4A-4C illustrate filter media that may be formed using the process illustrated in FIG. 3, according to some embodiments;

FIG. 5 illustrates MPPS penetration of a filter medium as a function of oil loading according to some embodiments;

FIG. 6 illustrates pressure drop as a function of oil loading for a filter medium according to some embodiments; and

Fig. 7 shows gamma of a filter medium as a function of oil loading according to some embodiments.

Detailed Description

Articles and methods relating to filter media are generally provided. In certain embodiments, the filter media includes at least a first layer, a second layer, and a binder resin disposed between the first layer and the second layer. 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 binder 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 one or more of high stiffness, high bond strength between the first and second layers, high gamma value, and/or low air resistance increase after being subjected to IPA vapor discharge. The filter media may be, for example, HEPA filter media and/or ULPA filter media.

In some embodiments, the filter media may include one or more layers having oleophobic properties. For example, one or more layers may comprise an oleophobic component as described herein, such as an oleophobic additive or oleophobic coating and/or may have an oil grade of greater than or equal to 1. In some embodiments, a layer or layers having oleophobic properties (e.g., a layer or layers comprising an oleophobic component, a layer or layers having an oil grade greater than or equal to 1) may impart one or more benefits to the filter medium as a whole, such as a low pressure drop at high oil loadings, a high gamma at high oil loadings, and/or a low penetration at high oil loadings. One or more of these characteristics may be beneficial in applications where the filter media is disposed in an environment having medium or high ambient oil levels. For example, the filter media may be used in a clean room (e.g., pharmaceutical clean room, electronic clean room, clean room for integrated circuit manufacturing), gas turbine (e.g., offshore gas turbine), indoor air cleaner, mask, vacuum cleaner, paint spray booth, and/or for filtering oily aerosols. In some embodiments, the filter medium having a layer or layers with oleophobic properties (e.g., a layer or layers comprising an oleophobic component, a layer or layers with an oil grade greater than or equal to 1) can be a HEPA filter, ULPA filter, and/or HVAC filter. Other types of filter media are also possible.

Methods for making the filter media described herein are also provided. In some embodiments, the manufacture of the filter media may include spraying a composition comprising a binder resin onto the first layer to form a binder coated first layer, and performing a solvent-based spinning process to deposit fibers forming the second layer onto the binder 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 the third layer such that the third layer is disposed on an opposite side of the second layer from the first layer. Other configurations and methods of bonding or forming the first, second, and third layers are also possible.

Fig. 1A depicts a filter medium 100 according to some embodiments of the invention. The filter media 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 main filtration layer. The main filtration layer may, for example, have a higher efficiency than one or more other layers of media. For example, in some cases, the main filtration layer is a fine fiber layer, such as a layer formed by a solvent-based spinning process. In some embodiments, a binder resin is present between the first layer and the second layer. An adhesive resin may be used to bond the first layer to the second layer. In some embodiments, the binder resin may be present in relatively small amounts between the first and second layers, 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 the adhesive are described in more detail below.

As described herein, in some embodiments, one or more layers of the filter media can have oleophobic properties, such as comprising an oleophobic component and/or having an oil grade greater than or equal to 1 (e.g., one or more of the first, second, third, and fourth layers can comprise an oleophobic component and/or have an oil grade greater than or equal to 1). For example, the layer may comprise an oleophobic component as described herein. In some embodiments, the oleophobic ingredient can be present within the layer, for example, in the form of an additive dispersed throughout the layer and/or in the form of a coating disposed on one or more fibers within the layer (e.g., a conformal coating of one or more fibers within the layer, a coating at least partially surrounding one or more fibers within the layer). In some embodiments, the oleophobic component can be present as a component of a coating layer disposed on a surface of a layer of the filter media. In some cases, the layer or layers may be a surface modified layer, e.g., a layer in which at least a portion of the surface of the layer has been modified. For example, the surface of the layer or layers may undergo one or more processes to modify the surface, such as roughening the surface of the layer or layers and/or depositing an oleophobic component on the surface of the layer or layers. In some embodiments, the surface modifying layer may have a higher oil grade than an otherwise equivalent layer that is not a surface modifying layer.

Fig. 1B shows one non-limiting example of a filter media 101, wherein a first layer 110 comprises an oleophobic component 115. In fig. 1B, the oleophobic ingredient is present within the first layer, and the oleophobic ingredient and the first layer together comprise a single layer.

In some embodiments, one or more layers of the filter media may include a coating layer comprising an oleophobic component. The coating layer may be disposed on a surface of a layer of the filter media. Fig. 1C shows one non-limiting example of a filter media 102, wherein a first layer 110 comprises an oleophobic component 115 in the form of a coating layer 116 disposed on a surface 112 of the first layer. In some embodiments, the layer of filter media may include both an oleophobic component within the layer (e.g., in the form of an additive, in the form of a coating on one or more fibers within the layer) and a coating layer comprising an oleophobic component (the same or different oleophobic component as the oleophobic component within the layer). One non-limiting example of a filter medium having this configuration is a filter medium that includes an oleophobic coating and a fluorocarbon melt additive.

In some embodiments including a filter element comprising a filter medium having at least one layer having oleophobic properties, the layer having oleophobic properties may be disposed upstream of one or more other layers of the filter medium (e.g., it may be disposed near an inlet of the filter element). In some embodiments, the layer may include a coating layer including an oleophobic component, and the coating layer may be disposed on an upstream side of the layer. For example, for a filter media as in fig. 1C, the first layer 110 may be disposed upstream of the second layer 120 in the filter element, and the coating layer 116 may be disposed on the upstream surface 112 of the first layer. Other configurations are also described in more detail below.

In some embodiments, a single layer within the filter media may comprise an oleophobic component (e.g., one of the first layer, the second layer, the pre-filter layer, or the main filter layer may comprise an oleophobic component). In some embodiments, two or more layers of the filter media may include an oleophobic component (e.g., at least two of the first layer, the second layer, the pre-filter layer, and the main filter layer may include an oleophobic component). In some embodiments, each layer of the filter media may comprise an oleophobic component.

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

In some embodiments, the layer having oleophobic properties (e.g., layer comprising an oleophobic component, layer having an oil grade greater than or equal to 1, surface modifying layer) can be the furthest upstream layer of the filter element or a layer disposed on the inlet side of the filter element. In other embodiments, the layer having oleophobic properties (e.g., layer comprising an oleophobic component, layer having an oil grade greater than or equal to 1, surface modifying layer) can be one or more layers downstream of the furthest upstream layer or layers disposed downstream of the inlet side in the filter element.

In some embodiments, the filter media may include at least three layers, as exemplarily shown in fig. 1D. The 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 layer and the third layer. An adhesive resin may be used to bond the second layer to the third layer. In some embodiments, the binder resin may be present in relatively small amounts between the second layer and the third layer, but the bond between the second layer and the third layer may be relatively strong (e.g., a bond strength greater than or equal to 150 g/inch ²).

In some cases, each layer of filter media has different characteristics and filtration characteristics that when combined, produce a desired overall filtration performance, for example, as compared to filter media having a single layer structure. For example, in one set of embodiments, the third layer 130 is a pre-filter layer and the second layer 120 is a main filter layer. In some embodiments, as described further below, the pre-filter layer may be formed using coarser fibers and, thus, may have a lower fluid flow resistance than the main filter layer. The main filter layer may contain finer fibers and have a higher resistance to fluid flow than the pre-filter layer. Thus, the main filter layer may generally capture particles of a smaller size than the pre-filter layer.

As noted above, each layer of filter media may have different characteristics. For example, the first and second layers may comprise fibers having different characteristics (e.g., fiber diameter, fiber composition, and fiber length). Fibers having different characteristics may be made of one material (e.g., by using different process conditions) or a different material (e.g., different types of fibers).

In some embodiments, the filter media may include more than one layer of the same type. For example, the filter may include two pre-filter layers, two support layers, and/or two main filter layers. FIG. 1E depicts one non-limiting example of an embodiment in which the filter media includes at least one pre-filter layer, at least one support layer, and two main filter layers. As shown, the filter media 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 layer and the fourth layer 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 example, when the fifth layer is disposed downstream of other layers in the filter element, the fifth layer 150 is a support layer that acts as a cover or protective layer. In some cases, the fifth layer may also function as an efficiency layer. In some embodiments, both the third layer and the fifth layer are support layers. It should be understood that this figure is not limiting and that the filter media may include other numbers and types of layers, the layers may be positioned in a different order (e.g., two layers of the same type may be directly adjacent to each other, each layer of the filter media may be different, the filter media may not have a symmetrical configuration, and/or the filter media may include six, seven, or more layers.

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

Certain embodiments relate to methods for manufacturing filter media. An exemplary method for manufacturing the filter media is shown in fig. 2A-2C. In fig. 2A, an adhesive 290 is deposited (e.g., sprayed) on the first layer 210. The first layer may be a pre-filter layer or a support layer. In some embodiments, the binder may have a glass transition temperature of less than or equal to 25 ℃ and greater than or equal to-150 ℃ and/or may be a solvent-based resin, as described in more detail below. In some embodiments, the adhesive may include a solvent that is at least partially evaporated from the adhesive-based resin during or after depositing the adhesive on the first layer. In some embodiments, the solvent may be water or another solvent.

In some embodiments, the adhesive resin may undergo crosslinking after the adhesive is deposited on the first layer. Such a process may allow the adhesive to be deposited using a method suitable for applying a liquid (e.g., spraying) while also having good properties consistent with solids (e.g., lack of flow upon exposure to isopropyl alcohol vapor) after the deposition process is complete.

In some embodiments, spraying the adhesive may allow a relatively small amount of adhesive to be deposited on the first layer, as compared to other methods 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 spray parameters (e.g., distance between the nozzle and the first layer, air pressure applied to the adhesive during spraying, size of the nozzle, etc.) may be selected as desired to control the amount of adhesive deposited on the first layer and other parameters.

After spraying the adhesive onto the first layer, a second layer 220 (e.g., a fine fiber layer) may be formed on the layer 210 by performing a solvent-based spinning process, as exemplarily shown in fig. 2B. Non-limiting examples of solvent spinning processes include electrospinning processes (e.g., solvent electrospinning) or centrifugal spinning processes. In some embodiments, the solvent-based spinning process may result in the formation of fibers having an average fiber diameter of less than 1 micron. In some embodiments, the second layer may be a main filtration layer.

In some embodiments, the use of a solvent-based resin may reduce the conductivity of the substrate (e.g., first layer) on which the resin is deposited and/or may facilitate adhesion and/or uniform deposition of the second layer (e.g., by a solvent spinning process).

In some embodiments, a third layer may be laminated to the second layer. For example, an adhesive may be deposited (e.g., sprayed) on the second layer 220, and then the second layer and the third layer may be joined. The adhesive may increase the bonding strength between the second layer and the third layer. Optionally, an adhesive may be deposited (e.g., sprayed) on the third layer prior to laminating the third layer to the second layer. The resulting media is illustratively shown in fig. 2C, wherein a third layer 230 is laminated to the second layer 220 and is directly adjacent to the second layer 220. In some embodiments, the third layer is a pre-filter layer or a support layer. For example, in some embodiments in which the first layer is a pre-filter layer and the second layer is a main filter layer, the third layer may be a support layer. In embodiments where the first layer is a support layer and the second layer is a main filtration layer, the third layer may be a pre-filtration layer.

In some embodiments, after laminating two or more layers together, the filter media may be subjected to one or more processing steps. For example, the filter media may be subjected to a step in which increased heat is applied, such as by a felt dryer cartridge, by an air dryer, by calender rolls, and/or by a flat bed laminator. In some embodiments, the filter media may be subjected to two or more such steps in sequence (e.g., the filter media may be passed through a felt dryer cartridge and then through an air dryer). The increased heat may help evaporate any solvent that remains in the filter media prior to this step.

In some embodiments, applying heat to the filter media may include exposing the filter media to an environment (e.g., interior of a dryer cartridge, interior of an air dryer, interior of a calender roll, interior of a flat bed laminator) having a temperature greater than or equal to 40 ℃, greater than or equal to 60 ℃, greater than or equal to 80 ℃, or greater than or equal to 100 ℃. In some embodiments, applying heat to the filter media may include exposing the filter media to an environment (e.g., interior of a dryer cartridge, interior of an air dryer, interior of a calender roll, interior of a flat bed laminator) having a temperature of less than or equal to 120 ℃, less than or equal to 100 ℃, less than or equal to 80 ℃, or less than or equal to 60 ℃. Combinations of the above ranges are also possible (e.g., greater than or equal to 40 ℃ and less than or equal to 120 ℃). Other ranges are also possible.

In some embodiments, applying heat to the filter media may include passing the filter media through a heated environment (e.g., inside a dryer cartridge, inside an air dryer, inside a calender roll, inside a flat bed laminator) at a rate of 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 10 m/min, or greater than or equal to 20 m/min. In some embodiments, applying heat to the filter media may include passing the filter media through a heated environment (e.g., inside a dryer cartridge, inside an air dryer, inside a calender roll, inside a flat bed laminator) at a rate of less than or equal to 40 m/min, less than or equal to 20 m/min, less than or equal to 10 m/min, less 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.

In some embodiments, one or more of the steps depicted in fig. 2A-2C may be repeated in forming the filter media. For example, the 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 an electrospinning process or a centrifugal spinning process. 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 occur sequentially (e.g., the steps depicted in fig. 2A-2C may be performed on one side of the first layer, then on the opposite side of the first layer) or simultaneously (the first layer may be coated with adhesive on both the top and bottom sides, then the steps depicted in fig. 2B-2C may be performed on both sides of the first layer). In some embodiments, five, nine, thirteen or more layers of filter media may be constructed in this manner.

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

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

References herein to a pre-filter layer or pre-filter layers should be understood to refer to each pre-filter layer in the filter medium independently (if any pre-filter layer is indeed present). That is, each pre-filter layer present may independently have any of the features described herein or may not have the features described herein. In some embodiments, two or more pre-filter layers in a filter media may have similar compositions and/or characteristics. In other embodiments, each pre-filter layer in the filter media may have a different composition and/or characteristics.

In embodiments where the filter media includes at least one pre-filter layer (e.g., first layer, third layer), the fibers in the pre-filter layer or layers may have any suitable average diameter. In some embodiments, the fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) have an average diameter greater than or equal to 0.1 microns, greater than or equal to 0.2 microns, greater than or equal to 0.5 microns, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 5 microns, greater than or equal to 10 microns, greater than or equal to 20 microns, greater than or equal to 40 microns, or greater than or equal to 60 microns. In some embodiments, the fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) have an average diameter of less than or equal to 75 microns, less than or equal to 60 microns, less than or equal to 40 microns, less than or equal to 20 microns, less than or equal to 10 microns, less than or equal to 5 microns, less than or equal to 2 microns, less than or equal to 1 micron, less than or equal to 0.5 microns, or less than or equal to 0.2 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 microns and less than or equal to 75 microns, greater than or equal to 0.5 microns and less than or equal to 40 microns, or greater than or equal to 0.5 microns and less than or equal to 2 microns). Other ranges are also possible.

In some embodiments in which the filter media includes at least one pre-filter layer (e.g., first layer, third layer, fifth layer), the pre-filter layer may comprise 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 layers (e.g., first layer, third layer, 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 layers (e.g., first layer, third layer, 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.

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

In some embodiments of filter media that include at least one pre-filter layer (e.g., first layer, third layer, fifth layer), the pre-filter layer or layers may include fiber types such as synthetic fibers, glass fibers, and/or cellulose fibers. In some cases, the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may contain a relatively high weight percentage of synthetic fibers (e.g., 100 weight%). For example, the pre-filter layer or layers (e.g., first, third, fifth) may comprise synthetic fibers formed from a melt-blowing process, a melt-spinning process, a centrifugal spinning process, electrospinning, wet-laid, dry-laid, or air-laid process. In some cases, the synthetic fibers may be continuous, as described further below. In some embodiments, the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may contain relatively little or no glass fibers. In other embodiments, the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may comprise a relatively high weight percentage of glass fibers (e.g., 100 wt%).

In some embodiments, the filter media may include at least one pre-filter layer (e.g., first layer, third layer, fifth layer), and at least one of the pre-filter layers present may comprise synthetic fibers. The synthetic fibers may have a relatively small average fiber diameter (e.g., less than or equal to about 2 microns). For example, the average diameter of the synthetic fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to about 2 microns (e.g., about 0.5 microns to about 1.0 microns). In some embodiments, the synthetic fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be continuous fibers formed by any suitable process (e.g., melt-blowing, melt-spinning, electrospinning (e.g., melt-electrospinning, solvent-electrospinning), centrifugal spinning, wet-laid, dry-laid, or air-laid processes). In certain embodiments, the synthetic fibers may be formed by an electrospinning process. In other embodiments, the synthetic fibers may be discontinuous. In some embodiments, all of the fibers in the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) are 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), polycarbonates, 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, polyethersulfones, and combinations thereof. In some embodiments, the synthetic fibers are organic polymer fibers. Synthetic fibers may also include multicomponent fibers (i.e., fibers having multiple components such as bicomponent fibers). In some cases, the synthetic fibers can include melt blown fibers, melt spun fibers, electrospun (e.g., melt electrospun, solvent electrospun) fibers, or spun fibers, which can be formed from the polymers described herein (e.g., polyesters, polypropylene). In some embodiments, the synthetic fibers may be electrospun fibers. When present, the pre-filter layer or layers (e.g., first, third, fifth) may also comprise a combination of more than one type of synthetic fibers. It should be understood that other types of synthetic fiber types may also be used.

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

In some cases, the synthetic fibers (if present) can be continuous (e.g., meltblown fibers, spunbond fibers, electrospun fibers, centrifugal spun fibers, etc.). The length of the continuous fibers is provided above. In other embodiments, the synthetic fibers (if present) are not continuous (e.g., staple fibers). The length of the staple fibers is provided above. Continuous fibers are made by a "continuous" fiber forming process (e.g., a melt blowing process, a spunbond process, an electrospinning process, or a centrifugal spinning process) and generally have a longer length than discontinuous fibers. Discontinuous fibers are short fibers that are typically cut (e.g., from filaments) or formed into discrete fibers that are discontinuous to have a particular length or range of lengths.

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

In some embodiments, the filter media may include at least one pre-filter layer (e.g., first layer, third layer, fifth layer), and at least one of the pre-filter layers present may comprise bicomponent fibers. The bicomponent fibers may comprise a thermoplastic polymer. The components of the 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 below the melting temperature of the core. This melts the sheath before the core so that the sheath bonds to the other fibers in the layer while the core maintains its structural integrity. The core/sheath binder fibers may be coaxial or non-coaxial. Other exemplary bicomponent fibers may include split fibers, side-by-side fibers, and/or "islands-in-the-sea" fibers.

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

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

In some embodiments, the filter media may include at least one pre-filter layer (e.g., first layer, third layer, fifth layer), and at least one of the pre-filter layers present may comprise one or more cellulosic fibers, such as softwood fibers, hardwood fibers, a mixture of hardwood and softwood fibers, regenerated cellulosic fibers, and/or mechanical pulp fibers (e.g., groundwood pulp, chemically treated mechanical pulp, and thermomechanical pulp).

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

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

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

In some embodiments, the filter media may include one or more pre-filter layers (e.g., first layer, third layer, fifth layer), and at least one of the pre-filter layers may comprise fibrillated fibers. As known to those of ordinary skill in the art, fibrillated fibers include parent fibers that branch into smaller diameter fibrils, which in some cases may further branch into even smaller diameter fibrils, with further branching also being possible. The branching nature of the fibrils results in a layer and/or web having a high surface area and may increase the number of points of contact between fibrillated fibers and other fibers in the web. Such an increase in contact points between fibrillated fibers of the web and other fibers and/or components may contribute to the mechanical properties (e.g., flexibility, strength) and/or filtration performance characteristics of the reinforcing layer and/or web.

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

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 fiber, in some embodiments, the average diameter of the fibrils may be less than or equal to about 25 microns, less than or equal to about 20 microns, less than or equal to about 10 microns, less than or equal to about 5 microns, less than or equal to about 1 micron, less than or equal to about 0.5 microns, less than or equal to about 0.1 microns, less than or equal to about 0.05 microns, or less than or equal to about 0.01 microns. In some embodiments, the average diameter of the fibrils may be greater than or equal to about 0.003 microns, greater than or equal to about 0.01 microns, greater than or equal to about 0.05 microns, greater than or equal to about 0.1 microns, greater than or equal to about 0.5 microns, greater than or equal to about 1 micron, greater than or equal to about 5 microns, greater than or equal to about 10 microns, or greater than or equal to about 20 microns. Combinations of the above ranges are also possible (e.g., fibrils having an average diameter greater than or equal to about 0.01 microns and less than or equal to about 20 microns). Other ranges are also possible.

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

The level of fibrillation of fibrillated fibers (if present) may be measured according to any number of suitable methods. For example, the level of fibrillation may be measured according to the canadian standard freeness (CANADIAN STANDARD FREENESS, CSF) test, specified by TAPPI test method T227Om 09 freeness of pulp. This test may provide an average CSF value. In some embodiments, the average CSF value of the fibrillated fibers may vary from about 10mL to about 750 mL. In certain embodiments, the fibrillated fibers used in the pre-filter layer or layers may have an average CSF value of greater than or equal to about 10mL, greater than or equal to about 50mL, greater than or equal to about 100mL, greater than or equal to about 200mL, greater than or equal to about 400mL, greater than or equal to about 600mL, or greater than or equal to about 700mL. In some embodiments, the fibrillated fibers can have an average CSF value of less than or equal to about 800mL, less than or equal to about 600mL, less than or equal to about 400mL, less than or equal to about 200mL, less than or equal to about 100mL, or less than or equal to about 50mL. Combinations of the above ranges are also possible (e.g., fibrillated fibers having an average CSF value of greater than or equal to about 10mL 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 fibers or more than one type of fibrillated fibers.

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

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) comprising glass fibers (e.g., micro-glass fibers, chopped glass fibers, or a combination thereof).

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

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

In general, the chopped glass fibers (if present) may have an average fiber diameter that is greater than the diameter of the microglass fibers. In some embodiments, the length of the chopped glass fibers may be in the range of about 0.125 inches to about 1 inch (e.g., about 0.25 inches or about 0.5 inches). In some embodiments, the chopped glass fibers may have an average length of less than or equal to about 1 inch, less than or equal to about 0.8 inch, less than or equal to about 0.6 inch, less than or equal to about 0.5 inch, less than or equal to about 0.4 inch, less than or equal to about 0.3 inch, or less than or equal to about 0.2 inch. In certain embodiments, the chopped glass fibers may have an average length of 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., chopped glass fibers having an average length of greater than or equal to about 0.125 inches and less than about 1 inch). Other ranges are also possible.

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

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

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

In embodiments where the filter media includes at least one pre-filter layer (e.g., first layer, third layer, fifth layer), the pre-filter layer or layers may have any suitable basis weight. In some embodiments, the basis weight of the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be greater than or equal to 0.2g/m ², greater than or equal to 0.5g/m ², greater than or equal to 1g/m ², greater than or equal to 2g/m ², greater than or equal to 3g/m ², greater than or equal to 5g/m ², greater than or equal to 10g/m ², greater than or equal to 20g/m ², greater than or equal to 40g/m ², or greater than or equal to 100g/m ². In some embodiments, the basis weight of the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 150g/m 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 0.5g/m ². Combinations of the above ranges are also possible (e.g., greater than or equal to 0.2g/m ² and less than or equal to 150g/m ², greater than or equal to 0.5g/m ² and less than or equal to 40g/m ², or greater than or equal to 3g/m ² and less than or equal to 40g/m ²). Other ranges are also possible. The basis weight may be determined according to standard ISO 536.

In some embodiments in which the filter media includes at least one pre-filter layer (e.g., first layer, third layer, fifth layer), the thickness of the pre-filter layer or layers may be greater than or equal to 0.02mm, greater than or equal to 0.05mm, greater than or equal to 0.1mm, greater than or equal to 0.2mm, greater than or equal to 0.5mm, greater than or equal to 1mm, or greater than or equal to 2mm. In some embodiments, the thickness of the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 5mm, less than or equal to 2mm, less than or equal to 1mm, less than or equal to 0.5mm, less than or equal to 0.2mm, less than or equal to 0.1mm, or less than or equal to 0.05mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.02mm and less than or equal to 5mm, or greater than or equal to 0.1mm and less than or equal to 1 mm). Other ranges are also possible. The thickness of the pre-filter layer or layers may be determined according to standard ISO 534 at 50 kPa.

In some embodiments in which the filter media includes at least one pre-filter layer (e.g., first layer, third layer, fifth layer), the pre-filter layer or layers may have an average flow pore size of greater than or equal to 0.5 microns, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 4 microns, greater than or equal to 10 microns, greater than or equal to 20 microns, greater than or equal to 50 microns, or greater than or equal to 70 microns. In some embodiments, the average flow pore size of the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 100 microns, less than or equal to 70 microns, less than or equal to 50 microns, less than or equal to 20 microns, less than or equal to 10 microns, less than or equal to 4 microns, less than or equal to 2 microns, or less than or equal to 1 micron. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.5 microns and less than or equal to 100 microns, greater than or equal to 1 micron and less than or equal to 70 microns, or greater than or equal to 0.5 microns and less than or equal to 4 microns). Other ranges are also possible. The average flow pore size may be determined according to standard ASTM F316-03.

In some embodiments, the filter media may include one or more pre-filter layers (e.g., first layer, third layer, fifth layer), and the pressure drop across the pre-filter layer or layers may be greater than or equal to 0.1mm H ₂ O, greater than or equal to 0.2mm H ₂ O, greater than or equal to 0.6mm H ₂ O, greater than or equal to 1mm H ₂ O, greater than or equal to 2mm H ₂ O, greater than or equal to 5mm H ₂ O, greater than or equal to 10mm H ₂ O, or greater than or equal to 25mm H ₂ O. In some embodiments, the pressure drop across the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 50mm H ₂ O, less than or equal to 25mm H ₂ O, less than or equal to 10mm H ₂ O, less than or equal to 5mm H ₂ O, less than or equal to 2mm H ₂ O, less than or equal to 1mm H ₂ O, less than or equal to 0.6mm H ₂ O, or less than or equal to 0.2mm H ₂ O. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1mm H ₂ O and less than or equal to 50mm H ₂ O, or greater than or equal to 0.6mm H ₂ O and less than or equal to 25mm H ₂ O). Other ranges are also possible. Pressure drop can be determined using ASTM D2 986-91.

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

In some embodiments, the filter media may include one or more pre-filter layers, and the solidity of the pre-filter layer or 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 embodiments, the solidity of the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) 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 solidity can be determined by using the following formula: solidity= [ basis weight/(fiber density x thickness) ]x100. The basis weight and thickness may be determined as described herein. The porosity can be derived from the solidity based on the following equation: solidity (%) =100-porosity (%). The fiber density is equal to the average density of the material or materials forming the fibers, which is typically specified by the fiber manufacturer. The average density is obtained by dividing the total mass of fibers within the filter by the total volume of fibers within the prefilter, where the total volume of fibers within the prefilter is the sum of the ratio of the mass of each fiber type to the density of each fiber type.

In some embodiments, the filter media may include one or more pre-filter layers, and the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may have a dioctyl phthalate (DOP) particle efficiency of 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 DOP particle efficiency of the pre-filter layer or layers (e.g., first layer, third layer, fifth layer) may 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. DOP particle efficiency may be measured by blowing DOP particles through a pre-filter layer or layers (e.g., first layer, third layer, fifth layer) and measuring the percentage of particles that penetrate the layers. The percentage can be determined as follows: based on the EN1822:2009 standard for Most Penetrating Particle Size (MPPS) DOP particles, TSI 3160 automated filter test unit from TSI, inc. Equipped with a DOP generator for DOP aerosol testing was used, and particles with an average diameter varying from 0.02 to 0.3 microns produced by the particle generator were used. The penetration was measured at a face velocity of 2.0 cm/sec under continuous loading of DOP particles.

In some embodiments, the pre-filter layer (e.g., first layer, third layer, fifth layer) is charged. Charge may be induced on the pre-filter layer by a charging process (e.g., an electrostatic charging process, a triboelectric charging process, or a hydrocharging process). In other embodiments, the pre-filter layer (e.g., first layer, third layer, fifth layer) is not charged.

In some embodiments, the pre-filter layer (e.g., first layer, third layer, fifth layer) is flame retardant or comprises one or more flame retardant components. For example, the pre-filter layer may include flame retardant fibers, flame retardant binders, flame retardant coatings, and/or flame retardant additives (e.g., flame retardant particles, flame retardant flakes). The flame retardant component may be introduced during manufacture (e.g., during a melt blowing process, melt spinning process, electrospinning process, centrifugal spinning process, wet-laid process, dry-laid process, or air-laid process), or may be added to the binder.

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

References herein to a main filtration layer or layers should be understood to refer to each main filtration layer in the filter medium independently (if any is indeed present). That is, each main filtration layer that is present may independently have any of the characteristics described below or may not have the characteristics described below. In some embodiments, two or more main filtration layers in a filter media may have similar compositions and/or characteristics. In other embodiments, each main filtration layer in the filter media may have a different composition and/or characteristics.

In some embodiments including at least one main filtration layer (e.g., second layer, fourth layer), the main filtration layer or layers (e.g., second layer, fourth layer) may be a solvent spun layer or layers, such as an electrospun (e.g., solvent-electrospun) layer or layers, or a centrifugal spun layer or layers. As used herein, a layer is a solvent spun layer if the layer is formed during a solvent spinning process, or if the layer comprises solvent spun fibers.

In some embodiments, the filter media may include at least one main filtration layer, and the main filtration layer or layers (e.g., second layer, 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 media may comprise a blend of: wherein one or more components of the blend are synthetic fibers (e.g., a blend comprising at least one type of synthetic fiber, a blend comprising at least two types of synthetic fibers, or a blend comprising three or more types of synthetic fibers). In some embodiments, the main filtration layer or layers (e.g., second layer, fourth layer, if present) may contain a relatively high amount of nylon fibers (e.g., up to 100 wt.% nylon fibers). In some embodiments, one or more of the synthetic fibers may be continuous fibers. For example, in some embodiments, the main filtration layer (e.g., second layer, fourth layer) comprises 100% continuous synthetic fibers (e.g., 100% solvent spun fibers such as 100% electrospun fibers).

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

In some embodiments where the filter media includes at least one main filtration layer, the fibers within the main filtration layer (e.g., second layer, fourth layer) may have any suitable average length. In some embodiments, the average length of the fibers in the main filtration layer or layers (e.g., second layer, fourth 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 fibers in the main filtration layer or layers (e.g., second layer, fourth 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. In some embodiments, the fibers within the main filtration layer (e.g., second layer, fourth layer) may be or may comprise continuous fibers.

In some embodiments, the filter media may include at least one main filtration layer, and the main filtration layer or layers (e.g., second layer, fourth layer) may include one or more additives. In some embodiments, the additive may include a charge additive, such as sodium chloride. In some embodiments, the weight% of sodium chloride of the main filtration layer or layers (e.g., second layer, fourth layer) may be greater than or equal to 0 weight%, greater than or equal to 2 weight%, greater than or equal to 4 weight%, greater than or equal to 6 weight%, or greater than or equal to 8 weight%. In some embodiments, the weight percent of sodium chloride of the main filtration layer or layers (e.g., second layer, fourth layer) may be less than or equal to 10 weight percent, less than or equal to 8 weight percent, less than or equal to 6 weight percent, less than or equal to 4 weight percent, or less than or equal to 2 weight percent. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 10 wt%). Other ranges are also possible.

In some embodiments, the additive may include a UV protectant. In some embodiments, the weight% of the UV protectant of the main filtration layer or layers (e.g., second layer, fourth layer) may be greater than or equal to 0 weight%, greater than or equal to 2 weight%, greater than or equal to 4 weight%, greater than or equal to 6 weight%, or greater than or equal to 8 weight%. In some embodiments, the weight% of the UV protectant of the main filtration layer or layers (e.g., second layer, fourth layer) may be less than or equal to 10 weight%, less than or equal to 8 weight%, less than or equal to 6 weight%, less than or equal to 4 weight%, or less than or equal to 2 weight%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 10 wt%). Other ranges are also possible.

In some embodiments, the additive may include an antioxidant. In some embodiments, the weight% of the antioxidant of the main filtration layer or layers (e.g., second layer, fourth layer) may be greater than or equal to 0 weight%, greater than or equal to 2 weight%, greater than or equal to 4 weight%, greater than or equal to 6 weight%, or greater than or equal to 8 weight%. In some embodiments, the weight% of the antioxidant of the main filtration layer or layers (e.g., second layer, fourth layer) may be less than or equal to 10 weight%, less than or equal to 8 weight%, less than or equal to 6 weight%, less than or equal to 4 weight%, or less than or equal to 2 weight%. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 10 wt%). Other ranges are also possible.

In embodiments where the filter media includes at least one main filtration layer, the main filtration layer or layers (e.g., second layer, fourth layer) may have any suitable basis weight. In some embodiments, the basis weight of the main filtration layer (e.g., second layer, fourth layer) may be greater than or equal to 0.01g/m ², greater than or equal to 0.03g/m ², greater than or equal to 0.05g/m ², greater than or equal to 0.1g/m ², greater than or equal to 0.3g/m ², greater than or equal to 0.5g/m ², greater than or equal to 1g/m ², greater than or equal to 3g/m ², greater than or equal to 5g/m ², greater than or equal to 10g/m ², or greater than or equal to 30g/m ². In some embodiments, the basis weight of the main filtration layer (e.g., second layer, fourth layer) may be less than or equal to 40g/m ², less than or equal to 30g/m ², 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 0.5g/m ², less than or equal to 0.3g/m ², less than or equal to 0.1g/m ², less than or equal to 0.05g/m ², or less than or equal to 0.03g/m ². Combinations of the above ranges are also possible (e.g., greater than or equal to 0.01g/m ² and less than or equal to 40g/m ², greater than or equal to 0.03g/m ² and less than or equal to 30g/m ², or greater than or equal to 0.01g/m ² and less than or equal to 5g/m ²). Other ranges are also possible. The basis weight may be determined according to standard ISO 536.

In some embodiments in which the filter media includes at least one main filtration layer, the thickness of the main filtration layer or layers (e.g., second layer, fourth layer) may be greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 5 microns, greater than or equal to 10 microns, greater than or equal to 20 microns, greater than or equal to 50 microns, greater than or equal to 100 microns, greater than or equal to 200 microns, greater than or equal to 500 microns, greater than or equal to 1000 microns, greater than or equal to 2000 microns, greater than or equal to 3000 microns, or greater than or equal to 4000 microns. In some embodiments, the thickness may be less than or equal to 5000 microns, less than or equal to 4000 microns, less than or equal to 3000 microns, less than or equal to 2000 microns, less than or equal to 1000 microns, less than or equal to 500 microns, less than or equal to 200 microns, less than or equal to 100 microns, less than or equal to 50 microns, less than or equal to 20 microns, less than or equal to 10 microns, less than or equal to 5 microns, or less than or equal to 2 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 micron and less than or equal to 5000 microns, greater than or equal to 5 microns and less than or equal to 1000 microns, or greater than or equal to 10 microns and less than or equal to 500 microns). Other ranges are also possible. The thickness of the main filter layer or layers may be determined by using SEM cross-sectional imaging.

In some embodiments, the filter media may include one or more main filtration layers, and the solidity of the main filtration layer or 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 embodiments, the solidity of the main filtration layer or layers (e.g., second layer, fourth layer) 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.

In some embodiments, the filter media may include one or more main filtration layers, and the pressure drop across the main filtration layer or layers (e.g., second layer, fourth layer) may be greater than or equal to 0.5mm H ₂ O, greater than or equal to 0.75mm H ₂ O, greater than or equal to 1mm H ₂ O, greater than or equal to 2.5mm H ₂ O, greater than or equal to 5mm H ₂ O, greater than or equal to 7.5mm H ₂ O, greater than or equal to 10mm H ₂ O, greater than or equal to 25mm H ₂ O, or greater than or equal to 50mm H ₂ O. In some embodiments, the pressure drop across the main filtration layer or layers (e.g., second layer, fourth layer) may be less than or equal to 100mm H ₂ O, less than or equal to 75mm H ₂ O, less than or equal to 50mm H ₂ O, less than or equal to 25mm H ₂ O, less than or equal to 10mm H ₂ O, less than or equal to 7.5mm H ₂ O, less than or equal to 5mm H ₂ O, less than or equal to 2.5mm H ₂ O, less than or equal to 1mm H ₂ O, or less than or equal to 0.75mm H ₂ O. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.5mm H ₂ O and less than or equal to 100mm H ₂ O, or greater than or equal to 1mm H ₂ O and less than or equal to 75mm H ₂ O). Other ranges are also possible. Pressure drop can be determined using ASTM D2 986-91.

In some embodiments, one or more layers may be a film layer (e.g., an extruded film layer, a molded film layer, a non-fibrous film layer, a synthetic film layer). In these embodiments, the membrane layer may act as a main filtration layer. It should be appreciated that while the description herein generally focuses on filter media that include a fibrous layer (e.g., fibrous main filtration layer), the description above and herein also applies to filter media that include one or more membrane main filtration layers. In some embodiments, the film layer does not comprise fibers (e.g., it is non-fibrous). The membrane layer may be disposed at any suitable location in the filter media. For example, in some embodiments, the second layer and/or the fourth layer is a film layer. The properties of the film layer will be described in more detail below.

References herein to a membrane layer or layers should be understood to refer to each membrane layer in the filter medium independently (if any membrane layer is indeed present). That is, each film layer present may independently have any or none of the characteristics described below. In some embodiments, two or more membrane layers in the filter media may have similar compositions and/or properties. In other embodiments, each membrane layer in the filter media may have a different composition and/or characteristics.

In general, any suitable material may be used to form the film layers (e.g., second layer, fourth layer). Suitable materials include synthetic materials such as Polytetrafluoroethylene (PTFE) (e.g., expanded or unexpanded polytetrafluoroethylene), polyvinylidene fluoride (PVDF), polyethylene (e.g., linear low density polyethylene, ultra high molecular weight polyethylene), polypropylene, polycarbonate, polyester, nitrocellulose mixed esters, polyethersulfone, cellulose acetate, polyimide, polyvinylidene fluoride, polyacrylonitrile, polysulfone, polyethersulfone, polyamide (e.g., nylon), and the like. In some embodiments, the membrane layer may comprise a fluorinated polymer, such as PVDF or PTFE.

When present, the film layers (e.g., second layer, fourth layer) may be a single layer film or a multilayer film. In embodiments using a multilayer film, the different layers may have different compositions. In general, the film layer may be formed by suitable methods known in the art.

When present, the film layers (e.g., second layer, fourth layer) have a plurality of holes. The pores allow the fluid to pass through while contaminating particles are trapped on the membrane layer. In some embodiments, the average flow pore size of the membrane layer may be greater than or equal to about 0.1 microns, greater than or equal to about 0.15 microns, greater than or equal to about 0.2 microns, greater than or equal to about 0.5 microns, greater than or equal to about 1 micron, greater than or equal to about 10 microns, greater than or equal to about 20 microns, greater than or equal to about 30 microns, or greater than or equal to about 40 microns. In some cases, the average flow pore size of the membrane layer may be less than or equal to about 50 microns, less than or equal to about 40 microns, less than or equal to about 30 microns, less than or equal to about 20 microns, less than or equal to about 15 microns, less than or equal to about 10 microns, less than or equal to about 5 microns, less than or equal to about 2 microns, or less than or equal to about 1 micron. Combinations of the above ranges are also possible (e.g., greater than or equal to about 0.1 microns and less than or equal to about 50 microns, greater than or equal to about 0.5 microns and less than or equal to about 40 microns). Other values of the average pore size are also possible. The average flow pore size may be determined according to standard ASTM F316-08 method B, BS 6140.

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

References herein to a support layer or layers should be understood to refer to each support layer in the filter medium independently (if any support layer is indeed present). That is, each support layer present 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 media may have similar compositions and/or properties. In other embodiments, each support layer in the filter media may have a different composition and/or characteristics.

In some embodiments including at least one support layer, the support layer or layers (e.g., first layer, third layer, fifth layer) may be a wet laid layer. That is, in some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) may be formed by a wet-laid process. In other embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) may be a non-wet laid layer. That is, in some embodiments, the support layer or layers (e.g., first layer, third layer, 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 layers may be spunbond layers, or layers formed by a spunbond process.

In some embodiments, the filter media may include one or more support layers, and the support layer or layers (e.g., first, third, fifth) 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), polycarbonates, 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, polyethersulfones, and combinations thereof. In some embodiments, the synthetic fibers are organic polymer fibers. Synthetic fibers may also include multicomponent fibers (i.e., fibers having multiple components such as bicomponent fibers). In some cases, the synthetic fibers can include melt blown fibers, melt spun fibers, electrospun (e.g., melt electrospun, solvent electrospun) fibers, or spun fibers, which can be formed from the polymers described herein (e.g., polyesters, polypropylene). In some embodiments, the synthetic fibers may be staple fibers. In some embodiments, the synthetic fibers may be fibers that include a flame retardant. The filter media and each layer within the filter media may also include a combination of more than one type of synthetic fibers. It should be understood that other types of synthetic fibers may also be used.

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

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

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

In some embodiments where the filter media includes a support layer or layers (e.g., first layer, third layer, fifth layer) having coarse synthetic fibers, the wt% of coarse synthetic fibers in the support layer (e.g., first layer, third layer, fifth layer) may be greater than or equal to 1 wt%, greater than or equal to 2 wt%, greater than or equal to 5wt%, greater than or equal to 10wt%, 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 percent of the coarse synthetic fibers in the support layer (e.g., first layer, third layer, fifth layer) may be less than or equal to 100 weight percent, less than or equal to 90 weight percent, less than or equal to 70 weight percent, less than or equal to 50 weight percent, less than or equal to 30 weight percent, less than or equal to 20 weight percent, less than or equal to 10 weight percent, less than or equal to 5 weight percent, or less than or equal to 2 weight percent. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 wt% and less than or equal to 100 wt%, greater than or equal to 10wt% and less than or equal to 100 wt%, or greater than or equal to 30 wt% and less than or equal to 100 wt%). Other ranges are also possible. In some embodiments, the weight% of the coarse synthetic fibers in the support layer (e.g., first layer, third layer, fifth layer) may be 100 weight%.

In some embodiments, the filter media may include a support layer or layers (e.g., first, third, fifth layers), and the support layer or layers may comprise fine synthetic fibers. In such embodiments, the average diameter of the fine synthetic fibers may be any suitable value. In embodiments comprising both fine synthetic fibers 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 layers. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) may comprise fine synthetic fibers having an average diameter greater than or equal to 1 micron, greater than or equal to 1.5 microns, greater than or equal to 2.5 microns, greater than or equal to 5 microns, greater than or equal to 7.5 microns, greater than or equal to 10 microns, greater than or equal to 12.5 microns, greater than or equal to 15 microns, or greater than or equal to 17.5 microns. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) may comprise fine synthetic fibers having an average diameter of less than or equal to 20 microns, less than or equal to 17.5 microns, less than or equal to 15 microns, less than or equal to 12.5 microns, less than or equal to 10 microns, less than or equal to 7.5 microns, less than or equal to 5 microns, less than or equal to 2.5 microns, or less than or equal to 1.5 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 micron and less than or equal to 20 microns, or greater than or equal to 1.5 microns and less than or equal to 10 microns). Other ranges are also possible.

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

In some embodiments, the filter media may include a support layer or layers (e.g., first, third, fifth layers), and the support layer or layers may include binder fibers. Typically, binder fibers (if present) may be used to join the fibers in the layers. In some embodiments, the binder fibers comprise a polymer having a lower melting point than one or more of the major components in the layer (e.g., certain fibers). The binder fibers may be monocomponent (e.g., polyethylene fibers, copolyester fibers) or multicomponent (e.g., bicomponent fibers). For example, the binder fibers may be bicomponent fibers. The bicomponent fibers may comprise a thermoplastic polymer. The components of the 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 below the melting temperature of the core. This melts the sheath before the core so that the sheath bonds to the other fibers in the layer while the core maintains its structural integrity. The core/sheath binder fibers may be coaxial or non-coaxial. Other exemplary bicomponent fibers may include split fibers, side-by-side fibers, and/or "islands-in-the-sea" fibers. In general, the total weight percent of the coarse and/or fine diameter fibers may include binder fibers.

In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) may comprise binder fibers having an average diameter greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 5 microns, greater than or equal to 10 microns, greater than or equal to 15 microns, greater than or equal to 20 microns, or greater than or equal to 25 microns. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) may comprise binder fibers having an average diameter of less than or equal to 30 microns, less than or equal to 25 microns, less than or equal to 20 microns, less than or equal to 15 microns, less than or equal to 10 microns, less than or equal to 5 microns, or less than or equal to 2 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 micron and less than or equal to 30 microns, or greater than or equal to 2 microns and less than or equal to 20 microns). Other ranges are also possible.

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

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

In some embodiments, the filter media may include one or more support layers (e.g., first, third, fifth layers), and the support layer or layers may include one or more binder resins. In general, a binder resin may be used for the fibers in the tie layer. In general, the binder resin may have any suitable composition. For example, the binder resin may include a thermoplastic resin (e.g., acrylic, polyvinyl acetate, polyester, polyamide), a thermosetting resin (e.g., epoxy, phenolic), or a combination thereof. In some cases, the binder resin includes one or more of a vinyl acetate resin, an epoxy resin, a polyester resin, a copolyester resin, a polyvinyl alcohol resin, an acrylic resin (e.g., a styrene acrylic resin), and a phenol resin. Other resins are also possible. In some such embodiments, the resin may include a polymeric resin comprising a covalently attached flame retardant.

The resin (if present) may 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 adhesion between the fibers. The fibers may be coated using any suitable method and apparatus, for example, curtain coating, gravure coating, melt coating, dip coating, knife roll coating, spin coating, or the like. In some embodiments, the binder precipitates upon addition to the fiber blend. Where appropriate, the fibers may be provided with any suitable precipitant (e.g., epichlorohydrin), for example, by injection into the blend. In some embodiments, the resin is added in a manner such that one or more layers or the entire filter media is impregnated with resin (e.g., resin infiltrated monolith) when added to the fibers. In the multilayer net, the resin may be added to each layer separately before combining the layers, or the resin may be added to the layers after combining the layers. 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 above methods. In other embodiments, the resin is added to the wet layer.

In certain embodiments, a binder may be present in the layer, and the binder may include both binder fibers and a binder resin.

In some embodiments, the filter media may include one or more support layers (e.g., first layer, third layer, fifth layer), and the weight% of the binder resin in the support layer or layers (e.g., first layer, third layer, fifth layer) may be greater than or equal to 0 weight%, greater than or equal to 5 weight%, greater than or equal to 10 weight%, greater than or equal to 15 weight%, greater than or equal to 20 weight%, greater than or equal to 25 weight%, greater than or equal to 30 weight%, greater than or equal to 40 weight%, greater than or equal to 50 weight%, greater than or equal to 60 weight%, greater than or equal to 70 weight%, or greater than or equal to 80 weight%. In some embodiments, the weight% of the binder resin in the support layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 90 weight%, less than or equal to 80 weight%, less than or equal to 70 weight%, less than or equal to 60 weight%, less than or equal to 50 weight%, less than or equal to 40 weight%, less than or equal to 30 weight%, less than or equal to 25 weight%, less than or equal to 20 weight%, less than or equal to 15 weight%, less than or equal to 10 weight%, or less than or equal to 5 weight%. 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.

In some embodiments, the filter media may include at least one support layer, and the support layer or layers (e.g., first layer, third layer, fifth layer) may include 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 percent of the additive of the support layer or layers (e.g., first layer, third layer, fifth layer) may be greater than or equal to 0 weight percent, greater than or equal to 2 weight percent, greater than or equal to 4 weight percent, greater than or equal to 6 weight percent, or greater than or equal to 8 weight percent. In some embodiments, the weight percent of the additive of the support layer or layers (e.g., first layer, third layer, fifth layer) may be less than or equal to 10 weight percent, less than or equal to 8 weight percent, less than or equal to 6 weight percent, less than or equal to 4 weight percent, or less than or equal to 2 weight percent. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 wt% and less than or equal to 10 wt%). Other ranges are also possible. Each additive may be added independently in one or more of the above ranges.

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

In embodiments where the filter media includes at least one support layer (e.g., first, third, fifth layer), the support layer or layers may have any suitable basis weight. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) may have a basis weight of greater than or equal to 10g/m ², greater than or equal to 20g/m ², greater than or equal to 35g/m ², greater than or equal to 40g/m ², greater than or equal to 80g/m ², greater than or equal to 120g/m ², greater than or equal to 150g/m ², greater than or equal to 200g/m ², or greater than or equal to 250g/m ². In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) may have a basis weight of less than or equal to 300g/m 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/m ², or less than or equal to 20g/m ². Combinations of the above ranges are also possible (e.g., greater than or equal to 10g/m 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, greater than or equal to 20g/m ² and less than or equal to 200g/m ², greater than or equal to 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 basis weight may be determined according to standard ISO 536.

In some embodiments in which the filter media includes at least one support layer (e.g., first layer, third layer, fifth layer), the support layer or layers (e.g., first layer, third layer, fifth layer) can have an average flow pore size of greater than or equal to 20 microns, greater than or equal to 50 microns, greater than or equal to 70 microns, greater than or equal to 100 microns, greater than or equal to 150 microns, greater than or equal to 200 microns, or greater than or equal to 250 microns. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) can have an average flow pore size of less than or equal to 300 microns, less than or equal to 250 microns, less than or equal to 200 microns, less than or equal to 150 microns, less than or equal to 100 microns, less than or equal to 70 microns, or less than or equal to 50 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 20 microns and less than or equal to 300 microns, or greater than or equal to 50 microns and less than or equal to 150 microns). Other ranges are also possible. The average flow pore size may be determined according to standard ASTM F316-03.

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

In some embodiments in which the filter media includes a support layer or layers (e.g., first, third, fifth layers), the support layer or layers may be capable of removing particulates 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 support layer or layers (e.g., first layer, third layer, fifth layer) may have an efficiency of 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 filtration layer are present in the filter media, the main filtration layer may have a higher efficiency than the support layer.

In some embodiments, the support layer (e.g., first layer, third layer, fifth layer) is flame retardant or comprises one or more flame retardant components. For example, the support layer may include flame retardant fibers, flame retardant binders, flame retardant coatings, and/or flame retardant additives (e.g., flame retardant particles, flame retardant flakes). The flame retardant component may be introduced during manufacture (e.g., during a melt blowing process, melt spinning process, electrospinning process, centrifugal spinning process, wet-laid process, dry-laid process, or air-laid process), or may be added to the binder.

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

In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) have a dry tensile strength in the machine direction of greater than or equal to 2 lbs/inch, greater than or equal to 5 lbs/inch, greater than or equal to 10 lbs/inch, greater than or equal to 15 lbs/inch, greater than or equal to 20 lbs/inch, greater than or equal to 25 lbs/inch, greater than or equal to 30 lbs/inch, greater than or equal to 35 lbs/inch, greater than or equal to 40 lbs/inch, greater than or equal to 45 lbs/inch, greater than or equal to 50 lbs/inch, or greater than or equal to 55 lbs/inch. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) have a dry tensile strength in the machine direction of less than or equal to 60 lbs/inch, less than or equal to 55 lbs/inch, less than or equal to 50 lbs/inch, less than or equal to 45 lbs/inch, less than or equal to 40 lbs/inch, less than or equal to 35 lbs/inch, less than or equal to 30 lbs/inch, less than or equal to 25 lbs/inch, less than or equal to 20 lbs/inch, less than or equal to 15 lbs/inch, less than or equal to 10 lbs/inch, or less than or equal to 5 lbs/inch. Combinations of the above ranges are also possible (e.g., greater than or equal to 2 lbs/inch and less than or equal to 60 lbs/inch, or greater than or equal to 10 lbs/inch and less than or equal to 40 lbs/inch). 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 jaw separation speed of 1 inch/minute.

In some embodiments in which the filter media includes at least one support layer (e.g., first layer, third layer, fifth layer), the support layer or layers (e.g., first layer, third layer, fifth layer) can have a dry-maren burst strength of greater than or equal to 20psi, greater than or equal to 30psi, greater than or equal to 50psi, greater than or equal to 75psi, greater than or equal to 100psi, greater than or equal to 125psi, greater than or equal to 150psi, greater than or equal to 175psi, greater than or equal to 200psi, or greater than or equal to 225psi. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) have a dry Marlen burst strength of less than or equal to 250psi, less than or equal to 225psi, less than or equal to 200psi, less than or equal to 175psi, less than or equal to 150psi, less than or equal to 125psi, less than or equal to 100psi, less than or equal to 75psi, less than or equal to 50psi, or less than or equal to 30psi. Combinations of the above ranges are also possible (e.g., greater than or equal to 20psi and less than or equal to 250psi, or greater than or equal to 30psi and less than or equal to 150 psi). Other ranges are also possible. The dry trendent burst strength may be determined according to standard T403 om-91.

In embodiments where the filter media includes at least one support layer (e.g., first, third, fifth layers), the support layer or layers may have any suitable Gurley stiffness. The stiffness may be measured in the machine direction or it may be measured in the cross direction. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) have a Gurley stiffness in the cross-machine direction of greater than or equal to 10mg, greater than or equal to 20mg, greater than or equal to 50mg, greater than or equal to 100mg, greater than or equal to 200mg, greater than or equal to 500mg, greater than or equal to 1000mg, or greater than or equal to 2000mg. In some embodiments, the support layer or layers (e.g., first layer, third layer, fifth layer) have a Gurley stiffness in the cross-machine direction of less than or equal to 3500mg, less than or equal to 2000mg, less than or equal to 1000mg, less than or equal to 500mg, less than or equal to 200mg, less than or equal to 100mg, less than or equal to 50mg, or less than or equal to 20mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 10mg and less than or equal to 3500mg, or greater than or equal to 200mg and less than or equal to 1000 mg). Other ranges are also possible. Stiffness can be determined from TAPPI T543 om-94 using Gurley stiffness (bending resistance) reported in mm (equivalent to gu).

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

As described above, in some embodiments, an adhesive may be present in one or more locations in the filter media (e.g., between the first layer and the second layer, and/or between the second layer and the third layer, etc.). References herein to an adhesive without specifying the location of the adhesive should be understood to refer to the adhesive being present at each location in the filter medium independently (if the adhesive is actually present at any location). That is, at each location where an adhesive is present, the adhesive present there may independently have any or none of the following characteristics. In some embodiments, two or more locations in the filter media where the binder is present may comprise binders having similar compositions and/or properties. In other embodiments, each binder present in the filter media may have a different composition and/or characteristics.

In some embodiments, the adhesive or adhesives may be solvent-based adhesive resins. As used herein, a solvent-based binder resin is a binder capable of undergoing a liquid-to-solid transition upon evaporation of the solvent from the resin. The solvent-based binder resin may be applied while in a liquid state. Subsequently, the solvent present may be evaporated to produce a solid adhesive. Thus, solvent-based adhesives may be considered to be different from hot melt adhesives that 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.

Desirable properties of the adhesive may include sufficient tack and open time (i.e., the amount of time the adhesive remains tacky after exposure to ambient atmosphere). Without wishing to be bound by theory, the tackiness of the adhesive may depend on both the glass transition temperature of the adhesive and the molecular weight of any polymer components of the adhesive. Higher glass transition values and lower molecular weight values may promote enhanced tack, and higher molecular weight values may result in higher cohesion and higher bond strength in the adhesive. In some embodiments, adhesives having glass transition temperatures and/or molecular weights within one or more of the ranges described herein may provide suitable values for both tack and open time. For example, the adhesive may be adapted and arranged to remain tacky for a relatively long period of time (e.g., the adhesive may remain tacky after complete evaporation of any solvent initially present, and/or may have an indefinite tack when held at room temperature). In some embodiments, the open time of the adhesive may 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 may 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.

It is also believed that exposure to isopropyl alcohol (IPA) vapor may result in a filter comprising the binder resin having a high pressure drop due to dissolution of the binder by the IPA vapor, and the presence of a cross-linking agent in the binder may reduce such dissolution and pressure drop in some embodiments.

As described above, in some embodiments, an adhesive may be present between the first layer and the second layer and/or between other layers of the medium (e.g., between the second layer and the third layer). The adhesive may be used to coat one or more layers using the solvent spraying methods described herein or using any other suitable method. Non-limiting examples of suitable binders include acrylates, acrylate copolymers, polyurethanes, polyesters, poly (vinyl alcohol), ethylene-vinyl acetate copolymers, silicone solvents, polyolefins, synthetic and/or natural rubber, 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.

In embodiments in which there are three or more layers (e.g., a first layer, a second layer, and a third layer), each interface may comprise an adhesive independently selected from the adhesives described herein. In some embodiments, the adhesive at the first interface (e.g., between the first layer and the second layer) is different than the adhesive at the second interface (e.g., between the second adhesive and the third adhesive). In other embodiments, the adhesive at different interfaces is the same.

In some embodiments, when present, the adhesive may comprise a cross-linking agent. In some embodiments, the cross-linking agent is a small molecule (i.e., the cross-linking agent is not a polymer). In some embodiments, the small molecule crosslinker is one or more of the following: carbodiimides, isocyanates, aziridines, zirconium compounds (e.g., zirconium carbonate), metal esters, metal chelates, multifunctional propenimides, and amino resins. In some embodiments, the binder comprises 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, amine groups, and amino groups.

In some embodiments, the adhesive does not include a small molecule crosslinker, but the polymer molecules forming the adhesive may undergo self-crosslinking via functional groups attached to the polymer.

In some embodiments, a temperature may be applied to the adhesive to aid in solvent removal and/or to accelerate the rate of crosslinking. In some embodiments, the temperature may be greater than or equal to 24 ℃, greater than or equal to 40 ℃, greater than or equal to 50 ℃, greater than or equal to 60 ℃, greater than or equal to 70 ℃, greater than or equal to 80 ℃, greater than or equal to 90 ℃, greater than or equal to 100 ℃, greater than or equal to 110 ℃, greater than or equal to 120 ℃, greater than or equal to 130 ℃, or greater than or equal to 140 ℃. In some embodiments, the temperature may be less than or equal to 150 ℃, less than or equal to 140 ℃, less than or equal to 130 ℃, less than or equal to 120 ℃, less than or equal to 110 ℃, less than or equal to 100 ℃, less than or equal to 90 ℃, less than or equal to 80 ℃, less than or equal to 70 ℃, less than or equal to 60 ℃, less than or equal to 50 ℃, or less than or equal to 40 ℃. Combinations of the above ranges are also possible (e.g., greater than or equal to 24 ℃ and less than or equal to 150 ℃, or greater than or equal to 24 ℃ and less than or equal to 130 ℃). Other ranges are also possible.

When present, the small molecule cross-linking agent may constitute any suitable amount of binder. In some embodiments, the weight% of the total mass of binder and crosslinker present in a specified location (e.g., between two layers, such as between a first layer and a second layer, or between a second layer and a third layer) of the crosslinker relative to the filter media can be greater than or equal to 0.1 weight%, greater than or equal to 0.2 weight%, greater than or equal to 0.5 weight%, greater than or equal to 1 weight%, greater than or equal to 2 weight%, greater than or equal to 5 weight%, greater than or equal to 10 weight%, greater than or equal to 15 weight%, greater than or equal to 20 weight%, or greater than or equal to 25 weight%. In some embodiments, the weight% of the small molecule crosslinker relative to the total mass of binder and crosslinker present in a designated location (e.g., between two layers, such as between a first layer and a second layer, or between a second layer and a third layer) may be less than or equal to 30 weight%, less than or equal to 25 weight%, less than or equal to 20 weight%, less than or equal to 15 weight%, less than or equal to 10 weight%, less than or equal to 5 weight%, less than or equal to 2 weight%, less than or equal to 1 weight%, less than or equal to 0.5 weight%, or less than or equal to 0.2 weight%. 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.

The binder and/or any small molecule cross-linking agent(s) the binder comprises, if present, may be capable of undergoing a cross-linking reaction at any suitable temperature. In some embodiments, the crosslinking agent may be capable of undergoing a crosslinking reaction at a temperature greater than or equal to 24 ℃, greater than or equal to 40 ℃, greater than or equal to 50 ℃, greater than or equal to 60 ℃, greater than or equal to 70 ℃, greater than or equal to 80 ℃, greater than or equal to 90 ℃, greater than or equal to 100 ℃, greater than or equal to 110 ℃, greater than or equal to 120 ℃, greater than or equal to 130 ℃, or greater than or equal to 140 ℃. In some embodiments, the adhesive and/or any small molecule cross-linking agent comprised by the adhesive may be capable of undergoing a cross-linking reaction at a temperature of less than or equal to 150 ℃, less than or equal to 140 ℃, less than or equal to 130 ℃, less than or equal to 120 ℃, less than or equal to 110 ℃, less than or equal to 100 ℃, less than or equal to 90 ℃, less than or equal to 80 ℃, less than or equal to 70 ℃, less than or equal to 60 ℃, less than or equal to 50 ℃, or less than or equal to 40 ℃. Combinations of the above ranges are also possible (e.g., greater than or equal to 25 ℃ and less than or equal to 150 ℃, or greater than or equal to 25 ℃ and less than or equal to 130 ℃). Other ranges are also possible.

In some embodiments in which an adhesive is present in at least one location in the filter media (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 adhesives may comprise a solvent prior to application of the adhesive to the layers. In some embodiments, the adhesive or adhesives may be applied to the layer or filter media 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, methylene chloride, naphtha, and mineral spirits (MINERAL SPIRITS).

In some embodiments, the glass transition temperature of the adhesive may be relatively low. In some embodiments, the glass transition temperature of the adhesive may be less than or equal to 60 ℃, less than or equal to 50 ℃, less than or equal to 45 ℃, less than or equal to 40 ℃, less than or equal to 35 ℃, less than or equal to 30 ℃, less than or equal to 24 ℃, less than or equal to 25 ℃, less than or equal to 20 ℃, less than or equal to 15 ℃, less than or equal to 10 ℃, less than or equal to 5 ℃, less than or equal to 0 ℃, less than or equal to-5 ℃, less than or equal to-10 ℃, less than or equal to-20 ℃, less than or equal to-30 ℃, less than or equal to-40 ℃, less than or equal to-50 ℃, less than or equal to-60 ℃, less than or equal to-70 ℃, less than or equal to-80 ℃, less than or equal to-90 ℃, less than or equal to-100 ℃, or less than or equal to-110 ℃. In some embodiments, the glass transition temperature of the adhesive may be greater than or equal to-125 ℃, greater than or equal to-110 ℃, greater than or equal to-100 ℃, greater than or equal to-90 ℃, greater than or equal to-80 ℃, greater than or equal to-70 ℃, greater than or equal to-60 ℃, greater than or equal to-50 ℃, greater than or equal to-40 ℃, greater than or equal to-30 ℃, greater than or equal to-20 ℃, greater than or equal to-10 ℃, greater than or equal to 0 ℃, greater than or equal to 5 ℃, greater than or equal to 10 ℃, greater than or equal to 24 ℃, greater than or equal to 25 ℃, 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-125 ℃ and less than or equal to 60 ℃, or greater than or equal to-100 ℃ and less than or equal to 25 ℃). Other ranges are also possible. The glass transition temperature value of the adhesive can be measured by differential scanning calorimetry.

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

In embodiments where the filter media comprises an adhesive at any single location (e.g., between two layers, such as between a first layer and a second layer, and/or between a second layer and a third layer), the adhesive or adhesives may have any suitable basis weight at that location. In some embodiments, the adhesive or adhesives may have a basis weight at any single location of greater than or equal to 0.05g/m ², greater than or equal to 0.1g/m ², greater than or equal to 0.2g/m ², greater than or equal to 0.5g/m ², greater than or equal to 1g/m ², greater than or equal to 2g/m ², or greater than or equal to 5g/m ². In some embodiments, the adhesive or adhesives may have a basis weight at any single location of 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, less than or equal to 0.5g/m ², less than or equal to 0.2g/m ², or less than or equal to 0.1g/m ². Combinations of the above ranges are also possible (e.g., greater than or equal to 0.05g/m ² and less than or equal to 10g/m ², or greater than or equal to 0.1g/m ² and less than or equal to 5g/m ²). Other ranges are also possible. The basis weight of the adhesive at any single location may be determined in accordance with standard ISO 536, wherein the basis weight of the filter media measured prior to the application of the adhesive to that location is subtracted from the basis weight measured after the application of the adhesive to that location to obtain the basis weight of the adhesive at that location.

In embodiments in which the filter media comprises one or more binders, the total basis weight of the total amount of binders in the filter media (i.e., the sum of the basis weights of the binders at each location) may be greater than or equal to 0.05g/m ², greater than or equal to 0.1g/m ², greater than or equal to 0.2g/m ², greater than or equal to 0.5g/m ², greater than or equal to 1g/m ², greater than or equal to 2g/m ², or greater than or equal to 5g/m ². In some embodiments, the total basis weight of the adhesive or adhesives may be 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, less than or equal to 0.5g/m ², less than or equal to 0.2g/m ², or less than or equal to 0.1g/m ². Combinations of the above ranges are also possible (e.g., greater than or equal to 0.05g/m ² and less than or equal to 10g/m ², or greater than or equal to 0.1g/m ² and less than or equal to 5g/m ²). Other ranges are also possible.

In some embodiments, the filter media may include an adhesive in at least one location, and the adhesive may be capable of adhering one layer to another layer (e.g., adhering a first layer to a second layer, and/or adhering a second layer to a third layer) with a relatively large bond strength. In some embodiments, the adhesive or adhesives may adhere the two layers together with the following bond strengths: greater than or equal to 100 g/inch ², greater than or equal to 150 g/inch ², greater than or equal to 200 g/inch ², greater than or equal to 500 g/inch ², greater than or equal to 750 g/inch ², greater than or equal to 1000 g/inch ², greater than or equal to 1250 g/inch ², greater than or equal to 1500 g/inch ², greater than or equal to 1750 g/inch ², greater than or equal to 2000 g/inch ², greater than or equal to 2250 g/inch ², greater than or equal to 2500 g/inch ², greater than or equal to 2750 g/inch ², greater than or equal to 3000 g/inch ², greater than or equal to 3250 g/inch ², greater than or equal to 3500 g/inch ², greater than or equal to 3750 g/inch ², greater than or equal to 4000 g/inch ², greater than or equal to 1500 g/inch ², greater than or equal to 4500 g/inch ², or greater than or equal to 3650 g/inch 4732. In some embodiments, the adhesive or adhesives may adhere the two layers together with the following bond strengths: less than or equal to 5000 g/inch ², less than or equal to 4750 g/inch ², less than or equal to 4500 g/inch ², less than or equal to 4250 g/inch ², less than or equal to 4000 g/inch ², less than or equal to 3750 g/inch ², less than or equal to 3500 g/inch ², less than or equal to 3250 g/inch ², less than or equal to 3000 g/inch ², less than or equal to 2750 g/inch ², less than or equal to 2500 g/inch ², less than or equal to 2250 g/inch ², less than or equal to 2000 g/inch ², less than or equal to 1750 g/inch ², less than or equal to 1500 g/inch ², less than or equal to 1250 g/inch ², less than or equal to 1000 g/inch ², less than or equal to 750 g/inch ², less than or equal to 500 g/inch ², less than or equal to 200 g/inch ², or less than or equal to 150 g/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 5000 g/inch ², or greater than or equal to 150 g/inch ² and less than or equal to 3000 g/inch ²). Other ranges are also possible. In some embodiments, the entire filter media generally has an internal bond strength within one or more of the ranges described above. The bond strength of the entire filter media is generally equal to the weakest bond strength between the two layers of the media.

The bond strength (e.g., internal bond strength) between two layers (e.g., between a first layer and a second layer, between a second layer and a third layer) can be determined using a z-direction peel strength test. In short, the bonding strength was determined by mounting 1 "x 1" samples on steel blocks having a size of 1 "x 0.5" using double-sided adhesive tape. The sample block was mounted on a non-traversing head of the tensile tester with double-sided tape and another steel block of the same size was attached to the traversing head. The traversing head moves downward and engages the sample on the steel block of the non-traversing head. Sufficient pressure is applied so that the steel blocks are bonded together via the installed sample. The traversing head was moved at a traversing speed of 1 "/min and the maximum load was derived from the peak of the stress-strain curve. The bond strength (e.g., internal bond strength) between the two layers is considered equal to the maximum load.

As described herein, in certain embodiments, one or more layers (e.g., first layer, second layer, third layer, pre-filter layer, main filter layer) may include oleophobic properties, may include an oleophobic component, and/or may be a surface-modified layer. In some embodiments, one or more layers may include a coating (e.g., an oleophobic coating, an oleophobic component that is an oleophobic coating) and/or include a resin (e.g., an oleophobic resin, an oleophobic component that is an oleophobic resin). The coating process may involve chemical deposition techniques and/or physical deposition techniques. For example, the coating process may include introducing a resin or material (e.g., an oleophobic component that is a resin or material) dispersed in a solvent or solvent mixture into a preformed fibrous layer (e.g., a preformed fibrous web formed by a melt-blown process). As one example, the pre-filter layer may be sprayed with a coating material (e.g., a water-based fluorinated acrylate, such as AGE 550D). Non-limiting examples of coating methods include the use of vapor deposition (e.g., chemical vapor deposition, physical vapor deposition), layer-by-layer deposition, wax curing, self-assembly, sol-gel processing, slot die coating, gravure coating, screen coating, size press coating (e.g., twin roll or metering doctor blade size press coating), film press coating, doctor blade coating, roll doctor blade coating, air knife coating, roll coating, foam application, reverse roll coating, bar coating, curtain coating, composite coating (champlex coating), brush coating, beer doctor blade coating (Bill-blade coating), short dwell doctor blade coating, lip coating, gate roll size press coating, laboratory size press coating, melt coating, dip coating, knife roll coating, spin coating, powder coating, spray coating (e.g., electrospray), notched roll coating, roll transfer coating, filler saturation coating, saturation dip coating, chemical bath deposition, and solution deposition. Other coating methods are also possible. The layer having oleophobic properties and/or being a surface-modifying layer may be charged or uncharged, and it is understood that any of the techniques described herein may be used to form a charged or uncharged layer.

In some embodiments, the coating material may be applied to the web using a non-compressive coating technique. The non-compressive coating technique may coat the web without substantially reducing the thickness of the web. In other embodiments, the resin may be applied to the web using a compression coating technique.

Other techniques include vapor deposition methods. Such methods include Atmospheric Pressure Chemical Vapor Deposition (APCVD), low Pressure Chemical Vapor Deposition (LPCVD), metal Organic Chemical Vapor Deposition (MOCVD), plasma Assisted Chemical Vapor Deposition (PACVD) or Plasma Enhanced Chemical Vapor Deposition (PECVD), laser Chemical Vapor Deposition (LCVD), photochemical vapor deposition (PCVD), chemical Vapor Infiltration (CVI), chemical Beam Epitaxy (CBE), electron beam assisted radiation curing, and atomic layer deposition. In Physical Vapor Deposition (PVD), a thin film (e.g., a thin film comprising an oleophobic component) is deposited by condensing a desired film material in vaporized form onto a substrate. The method involves physical processes such as high temperature vacuum evaporation followed by condensation, plasma sputter bombardment rather than chemical reaction, electron beam evaporation, molecular beam epitaxy and/or pulsed laser deposition.

In some embodiments, the surface of one or more layers (e.g., the surface of the first layer, the surface of the second layer, the surface of the third layer, the surface of the pre-filter layer, the surface of the main filter layer) may be modified with an additive (e.g., an oleophobic component that is an additive such as an oleophobic additive). In some embodiments, one or more layers (e.g., first layer, second layer, third layer, pre-filter layer, main filter layer) may contain an additive or additives (e.g., an oleophobic component that is an additive such as an oleophobic additive). The additives may be functional chemicals added to the polymer/thermoplastic fiber during the melt blowing process, the electrospinning process, and/or the extrusion process, which may cause the physical and chemical properties on the surface to differ from the physical and chemical properties of the polymer/thermoplastic fiber itself after formation. For example, additives may be added to the electrospinning solution used to form one or more of the second layer, the fourth layer, and the main filtration layer. In some embodiments, the additives may migrate to the surface of the fiber during or after formation of the fiber material (polymer/thermoplastic material) such that the surface of the fiber is modified with the additives, wherein the center of the fiber contains more polymer/thermoplastic material. In some embodiments, one or more additives are included to render the surface of the fiber oleophobic as described herein. For example, the additive may be an oleophobic material as described herein. Non-limiting examples of suitable additives include fluorinated acrylates, fluorosurfactants, oleophobic silicones, fluoropolymers, fluoromonomers, fluorooligomers, and oleophobic polymers.

The additives (e.g., oleophobic component in the form of an additive), if present, may be present in the fibers in any suitable form prior to undergoing the melt blowing, electrospinning, or wet-laid procedure or after fiber formation. For example, in some embodiments, the additive may be in a liquid (e.g., melted) form that is mixed with the thermoplastic material prior to or during fiber formation. In some cases, the additives may be in particulate form before, during, or after fiber formation. In certain embodiments, particles of the melt additive may be present in the fully formed fibers. In some embodiments, the additive may be a component of the binder, and/or may be added to one or more layers by spraying the layers with a composition comprising the additive. If particulate, the additive may have any suitable morphology (e.g., particles, flakes, ellipsoids, fibers of different shapes and sizes).

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

In some embodiments, the material (e.g., oleophobic component, precursor that reacts to form the oleophobic component) may undergo a chemical reaction (e.g., polymerization) after application to the layers (e.g., first layer, second layer, third layer, pre-filter layer, main filter layer). For example, the surface of the layer may be coated with one or more monomers that polymerize after coating. In another example, the surface of the layer may comprise monomers that polymerize after formation of the web due to the melt additives. In some such embodiments, in-line polymerization may be used. In-line polymerization (e.g., in-line ultraviolet polymerization) is a process of curing a monomer or liquid polymer solution on a substrate under conditions sufficient to induce polymerization (e.g., under UV irradiation).

The term "self-assembled monolayer" (self-assembled monolayer, SAM) refers to a molecular assembly that can spontaneously form by immersing a suitable substrate in a solution of active surfactant in an organic solvent to create an oleophobic surface.

In wax solidification, the layer is immersed in molten Alkyl Ketene Dimer (AKD) heated at 90 ℃ and then cooled at room temperature in an atmosphere of dry N ₂ gas. AKD undergoes fractal growth as it solidifies and improves oleophobicity of the substrate.

In some embodiments, the substance used to form the surface-modified layer (e.g., surface-modified first layer, surface-modified second layer, surface-modified third layer, surface-modified pre-filter layer, surface-modified main filter layer) or the substance that is a component of the surface-modified layer (e.g., oleophobic component, precursor that reacts to form the oleophobic component) may comprise a small molecule, such as an inorganic or organic oleophobic molecule. Non-limiting examples include hydrocarbons (e.g., CH ₄、C₂H₂、C₂H₄、C₆H₆), fluorocarbons (e.g., fluoroaliphatic compounds, fluoroaromatic compounds, fluoropolymers, fluorocarbon block copolymers, fluorocarbon acrylate polymers, fluorocarbon methacrylate polymers, fluoroelastomers, fluorosilanes, fluorosilicones, fluoropolyhedral oligomeric silsesquioxanes, fluorinated dendrimers, inorganic fluoro 、CF₄、C₂F₄、C₃F₆、C₃F₈、C₄H₈、C₅H₁₂、C₆F₆、SF₃、SiF₄、BF₃), silanes (e.g., siH ₄、Si₂H₆、Si₃H₈、Si₄H₁₀), organosilanes (e.g., methylsilane, dimethylsilane, triethylsilane), siloxanes (e.g., dimethylsiloxane, hexamethyldisiloxane), znS, cuSe, inS, cdS, tungsten, silicon carbide, silicon nitride, silicon oxynitride, titanium nitride, carbon, silicon-germanium, and hydrophobic acrylic monomers capped with alkyl groups and halogenated derivatives thereof (e.g., 2-ethyl acrylate, methyl methacrylate, acrylonitrile). In certain embodiments, suitable hydrocarbons for modifying the surface of the layer may have the formula C _xH_y, wherein x is an integer from 1 to 10, y is an integer from 2 to 22, in certain embodiments, suitable silanes for modifying the surface of the layer may have the formula Si _nH_2n+2, wherein any hydrogen may be substituted with a halogen (e.g., cl, F, br, I), and wherein n is an integer from 1 to 10, in certain embodiments, the material used to form the surface modified layer or a material that is a component of the surface modified layer may comprise one or more of waxes, silicones, and corn-based polymers (e.g., zein), the substance used to form the surface-modified layer or the substance that is a component of the surface-modified layer may comprise one or more nanoparticulate materials. Other compositions are also possible.

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

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

In some embodiments, the surface of the layer (e.g., the surface of the first layer, the surface of the second layer, the surface of the third layer, the surface of the pre-filter layer, the surface of the main filter layer) may be modified by roughening the surface or the material on the surface of the layer. In some such cases, the surface modification may be a roughened surface or material. The surface roughness of the layer or of the material on the surface of the layer may be microscopically and/or macroscopically roughened. Non-limiting examples of methods for increasing roughness include modifying surfaces with certain fibers, mixing fibers having different diameters, and photolithography. In certain embodiments, fibers having different diameters (e.g., staple fibers, continuous fibers) may be mixed or used to increase or decrease surface roughness. In some embodiments, electrospinning may be used to create applied surface roughness alone or in combination with other methods (e.g., chemical vapor deposition). In some embodiments, photolithography may be used to roughen the surface. Photolithography includes many different types of surface treatments in which designs are transferred from a master onto a surface.

In some embodiments, the roughness of the layers (e.g., the roughness of the first layer, the roughness of the second layer, the roughness of the third layer, the roughness of the pre-filter layer, the roughness of the main filter layer) may be used to alter the wettability of the layers with respect to a particular fluid. In some cases, the roughness may alter or enhance the wettability of the surface of the layer. In some cases, roughness may be used to enhance oleophobicity of a surface that is essentially oleophobic. One of ordinary skill in the art will appreciate methods of altering the roughness of the surface of the web.

As described above, in some embodiments, the filter media may include one or more layers having an oil grade greater than or equal to 1 (e.g., a first layer having an oil grade greater than or equal to 1, a second layer having an oil grade greater than or equal to 1, a third layer having an oil grade greater than or equal to 1, a pre-filter layer having an oil grade greater than or equal to 1, a main filter layer having an oil grade greater than or equal to 1, a most upstream layer having an oil grade greater than or equal to 1). The oil grade may be due to fibers within a layer having an oil grade of greater than or equal to 1 in nature (e.g., poly (tetrafluoroethylene) fibers), may be due to surface modification that increases the oil grade of fibers within a layer having an initially lower oil grade, and/or may be due to oleophobic components that increase the oil grade of the layer. Layers having a relatively high oil grade may or may not be charged. In some embodiments, one or more layers within the filter media have an oil grade of greater than or equal to 1, greater than or equal to 2, greater than or equal to 3, greater than or equal to 4, greater than or equal to 4.5, greater than or equal to 5, greater than or equal to 5.5, greater than or equal to 6, greater than or equal to 6.5, greater than or equal to 7, or greater than or equal to 7.5. In some embodiments, one or more layers within the filter media have an oil grade of less than or equal to 8, less than or equal to 7.5, less than or equal to 7, less than or equal to 6.5, less than or equal to 6, less than or equal to 5.5, less than or equal to 5, less than or equal to 4.5, less than or equal to 4, less than or equal to 3, or less than or equal to 2. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 and less than or equal to 8, greater than or equal to 1 and less than or equal to 6, or greater than or equal to 5 and less than or equal to 6). Other ranges are also possible.

The oil grade as described herein is determined according to AATCC TM 118 (1997) measured at 23 ℃ and 50% Relative Humidity (RH). Briefly, 5 drops of each test oil (average drop diameter of about 2 mm) were placed at five different locations on the surface of the web. After 30 seconds of contact with the web at 23 ℃ and 50% rh, the test oil with the greatest oil surface tension that does not wet the surface of the web (e.g., contact angle greater than or equal to 90 degrees with the surface) corresponds to the oil grade (listed in table 1). For example, if a test oil having a surface tension of 26.6mN/m does not wet (i.e., has a contact angle with the surface of greater than or equal to 90 degrees) the surface of the web after 30 seconds, but a test oil having a surface tension of 25.4mN/m wets the surface of the web within 30 seconds, the oil rating of the web is 4. As another example, if a test oil having a surface tension of 25.4mN/m does not wet the surface of the web after 30 seconds, but a test oil having a surface tension of 23.8mN/m wets the surface of the web within 30 seconds, the oil grade of the web is 5. As yet another example, if a test oil having a surface tension of 23.8mN/m does not wet the surface of the web after 30 seconds, but a test oil having a surface tension of 21.6mN/m wets the surface of the web within 30 seconds, the oil grade of the web is 6. In some embodiments, if three or more of the five droplets partially wet the surface in a given test (e.g., form droplets on the surface, but not rounded droplets), the oil grade is expressed as the closest 0.5 value determined by subtracting 0.5 from the number of test liquids. As an example, if a test oil having a surface tension of 25.4mN/m does not wet the surface of the web after 30 seconds, but a test oil having a surface tension of 23.8mN/m only partially wets the surface of the web within 30 seconds after 30 seconds (e.g., three or more test droplets form droplets that are not round droplets on the surface of the web), the oil grade of the web is 5.5.

TABLE 1

In some embodiments, the filter media as a whole may have one or more desired characteristics. For example, the filter medium may be a High Energy Particulate Air (HEPA) or Ultra Low Penetration Air (ULPA) filter. According to EN1822:2009, these filters require particulate removal at efficiency levels greater than 99.95% and 99.9995%, respectively. In some embodiments, the filter media may remove particulates at an efficiency of greater than 95%, greater than 99.995%, or greater than 99.99995%, or as high as 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%. The 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 embodiments, a HEPA, ULPA, or HVAC filter may include a meltblown prefilter layer (e.g., a meltblown polypropylene prefilter layer having a basis weight of, for example, 3g/m ² to 40g/m ²), an electrospun main filter layer (e.g., a nylon electrospun main filter layer having a basis weight of, for example, 0.01g/m ² to 5g/m ², including, for example, an average fiber diameter of 40nm to 300 nm), and a support layer (e.g., a wet laid synthetic support layer having a basis weight of, for example, 35g/m ² to 80g/m ²). Other types of filter media and efficiencies are also possible. In some embodiments, the filter media may be a HEPA, ULPA or HVAC filter and may be a component of a filter element as described in more detail below.

The filter medium as a whole may have any suitable stiffness. The stiffness may be measured in the machine direction or it may be measured in the cross direction. In some embodiments, the filter media has a Gurley stiffness in the cross-machine direction of greater than or equal to 50mg, greater than or equal to 100mg, greater than or equal to 150mg, greater than or equal to 200mg, greater than or equal to 250mg, greater than or equal to 300mg, greater than or equal to 350mg, greater than or equal to 400mg, greater than or equal to 450mg, greater than or equal to 500mg, greater than or equal to 1000mg, greater than or equal to 1500mg, greater than or equal to 2000mg, or greater than or equal to 3000mg. In some embodiments, the filter media has a Gurley stiffness in the cross-machine direction of less than or equal to 3500mg, less than or equal to 3000mg, less than or equal to 2000mg, less than or equal to 1500mg, less than or equal to 1000mg, less than or equal to 500mg, less than or equal to 450mg, less than or equal to 400mg, less than or equal to 350mg, less than or equal to 300mg, less than or equal to 250mg, less than or equal to 200mg, less than or equal to 150mg, or less than or equal to 100mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 50mg and less than or equal to 3000mg, or greater than or equal to 100mg and less than or equal to 1500 mg). Other ranges are also possible. Stiffness can be determined from TAPPI T543 om-94 using Gurley stiffness (bending resistance) reported in mm (equivalent to gu).

In some embodiments, the filter media has a Gurley stiffness in the machine direction of greater than or equal to 100mg, greater than or equal to 150mg, greater than or equal to 200mg, greater than or equal to 250mg, greater than or equal to 300mg, greater than or equal to 350mg, greater than or equal to 400mg, greater than or equal to 450mg, greater than or equal to 350mg, greater than or equal to 500mg, greater than or equal to 1000mg, greater than or equal to 1500mg, greater than or equal to 2000mg, greater than or equal to 2500mg, or greater than or equal to 3000mg. In some embodiments, the support layer or layers have a Gurley stiffness in the machine direction of less than or equal to 3500mg, less than or equal to 3000mg, less than or equal to 2500mg, less than or equal to 2000mg, less than or equal to 1500mg, less than or equal to 1000mg, less than or equal to 500mg, less than or equal to 350mg, less than or equal to 450mg, less than or equal to 400mg, less than or equal to 350mg, less than or equal to 300mg, less than or equal to 250mg, less than or equal to 200mg, or less than or equal to 150mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 100mg and less than or equal to 3000mg, or greater than or equal to 150mg and less than or equal to 3000 mg). Other ranges are also possible. Stiffness can be determined from TAPPI T543 om-94 using Gurley stiffness (bending resistance) reported in mm (equivalent to gu).

Because it may be desirable to rate a filter medium or layer based on the relationship between penetration and pressure drop across the medium, or particle efficiency as a function of pressure drop across the medium or web, the filter medium may be rated according to a value known as the gamma value. In general, higher gamma values indicate better filtration performance, i.e. high particulate efficiency as a function of pressure drop. The gamma value is expressed according to the following formula: gamma= (-log ₁₀ (MPPS penetration%/100)/pressure drop, mm H ₂ O) ×100, where MPPS penetration equals MPPS penetration as described below and can be measured using EN1822:2009 standard as described below. As described below, γ can be measured before or after exposure to IPA vapor. The MPPS penetration for any given gamma value is the penetration at MPPS measured at the time the gamma value was measured. Unless otherwise indicated, references to gamma should be considered to refer to gamma values measured before the filter media is subjected to IPA vapor and DOP oil loading. In this case, the relevant MPPS is the MPPS value prior to exposure to the IPA vapor discharge and the DOP oil load, and the relevant MPPS penetration value is the MPPS penetration prior to exposure to the IPA vapor discharge and the DOP oil load.

The transmission, often expressed as a percentage, is defined as follows: penetration (%) = (C/C ₀) ×100, where C is the particle concentration after passing through the filter and C ₀ is the particle concentration before passing through the filter. Typical tests for penetration include blowing dioctyl phthalate (DOP) particles through the filter medium or layer and measuring the percentage of particles penetrating the filter medium or layer. The penetration values described herein were determined based on the EN1822:2009 standard for MPPSDOP particles using a TSI 3160 automated filter test unit from TSI, inc. In this test, a set of particles varying in average diameter from 0.04 microns to 0.3 microns were produced by a particle generator. The instrument measures the penetration value across the filter medium (or layer) by determining the DOP particle size (i.e., the Most Penetrating Particle Size (MPPS)) at the highest penetration level of the measurement test. Thus, all gamma values described herein refer to gamma values at the most penetrating particle size. All penetration values, and thus gamma values as described herein, were determined as follows: the continuous loading of DOP particles was used and the upstream face of the layer was subjected to a gas flow of 12 liters/min over a 100cm ² surface area of the web, resulting in a media face velocity of 2 cm/sec. Particles of sizes 0.04 microns, 0.08 microns, 0.12 microns, 0.16 microns, 0.2 microns, 0.26 microns and 0.3 microns with geometric standard deviations less than 1.3 are produced and the filter media is sequentially exposed to the particles of each size. The penetration of the particles as a function of particle size was plotted and the data fitted with a parabolic function. Then, obtaining the maximum value of the parabolic function; the particle size at the maximum is the Most Penetrating Particle Size (MPPS), and the penetration at the maximum is the penetration at MPPS.

The pressure drop value (e.g., for determining γ) is determined by an air resistance test based on EN1822:2009 standard using a TSI 3160 automated filter test unit from TSI, inc. The instrument measures the pressure drop across the filter medium (or layer) while subjecting the filter medium or layer to a face velocity of 5.3 cm/sec.

The filter media as a whole may have a relatively high gamma value at MPPS (e.g., prior to exposure to IPA vapor discharge). In some embodiments, the filter media has a gamma value at MPPS of 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 gamma value at MPPS of 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.

The filter medium as a whole may have any suitable basis weight. In some embodiments, the filter media may have a basis weight of greater than or equal to 20g/m ², greater than or equal to 40g/m ², greater than or equal to 50g/m ², greater than or equal to 75g/m ², greater than or equal to 100g/m ², greater than or equal to 125g/m ², greater than or equal to 150g/m ², greater than or equal to 175g/m ², greater than or equal to 200g/m ², greater than or equal to 225g/m ², greater than or equal to 250g/m ², or greater than or equal to 275g/m ². In some embodiments, the filter media may have a basis weight of less than or equal to 300g/m 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 20g/m 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 basis weight may be determined according to standard ISO 536.

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

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

The pressure drop across the filter medium may be of any suitable value. In some embodiments, the pressure drop across the filter medium may be greater than or equal to 0.5mm H ₂ O, greater than or equal to 1mm H ₂ O, greater than or equal to 2mm H ₂ O, greater than or equal to 5mm H ₂ O, greater than or equal to 10mm H ₂ O, greater than or equal to 20mm H ₂ O, greater than or equal to 50mm H ₂ O, or greater than or equal to 100mm H ₂ O. In some embodiments, the pressure drop across the filter medium may be less than or equal to 200mm H ₂ O, less than or equal to 100mm H ₂ O, less than or equal to 50mm H ₂ O, less than or equal to 20mm H ₂ O, less than or equal to 10mm H ₂ O, less than or equal to 5mm H ₂ O, less than or equal to 2mm H ₂ O, or less than or equal to 1mm H ₂ O. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.5mm H ₂ O and less than or equal to 200mm H ₂ O, or greater than or equal to 2mm H ₂ O and less than or equal to 100mm H ₂ O). Other ranges are also possible. Pressure drop can be determined using ASTM D2 986-91.

In some embodiments, the filter media as a whole may perform particularly well after exposure to isopropyl alcohol (IPA) vapor (and, in some cases, prior to exposure to IPA vapor or oil loading). Such performance characteristics may include: the filter media has a relatively low pressure drop after exposure to IPA vapor, a relatively low pressure drop change after IPA vapor exposure compared to the same media prior to IPA vapor exposure, a high gamma value at MPPS after exposure to IPA vapor, and/or a relatively low gamma value change after IPA vapor exposure compared to the same media prior to IPA vapor exposure.

Typically, IPA vapor exposure is performed in accordance with ISO 16880-4 standard. The filter media to be tested was cut into 6 inch by 6 inch squares and placed on a rack of metal racks. The metal rack and media were then placed over a container containing at least 250ml 99.9 wt% IPA. After this step, the metal rack, media and container were placed in a 24 inch x 18 inch x 11 inch chamber. A second container containing 250ml of 99.9 wt.% IPA was then placed in the container above the top shelf of the metal shelf and the lid of the chamber was closed and tightly sealed. The device was maintained at 70°f and 50% relative humidity for at least 14 hours, after which the filter media was removed and allowed to dry at room temperature for 1 hour. The filter media properties after IPA exposure were then measured.

In some embodiments, the maximum pressure drop of the filter media as a whole after IPA exposure may be greater than or equal to 1mm H ₂ O, greater than or equal to 3mm H ₂ O, greater than or equal to 5mm H ₂ O, greater than or equal to 7.5mm H ₂ O, greater than or equal to 10mm H ₂ O, greater than or equal to 25mm H ₂ O, greater than or equal to 50mm H ₂ O, or greater than or equal to 75mm H ₂ O. In some embodiments, the maximum pressure drop of the filter media after IPA exposure may be less than or equal to 100mm H ₂ O, less than or equal to 75mm H ₂ O, less than or equal to 50mm H ₂ O, less than or equal to 25mm H ₂ O, less than or equal to 10mm H ₂ O, less than or equal to 7.5mm H ₂ O, less than or equal to 5mm H ₂ O, or less than or equal to 3mm H ₂ O. Combinations of the above ranges are also possible (e.g., greater than or equal to 1mm H ₂ O and less than or equal to 100mm H ₂ O, or greater than or equal to 3mm H ₂ O and less than or equal to 75mm H ₂ O). Other ranges are also possible. Pressure drop can be determined using ASTM D2986-91.

In some embodiments, the maximum pressure drop of a filter medium after IPA exposure may be quite similar to the maximum pressure drop of the same filter medium before IPA exposure. In some embodiments, the percent change in the maximum pressure drop of the filter media after IPA exposure may 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 percent change in the maximum pressure drop of the filter media after IPA exposure may 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. Pressure drop can be determined using ASTM D2 986-91. The percent change in value (e.g., pressure drop) is defined by the following equation: percentage change = -final value) - (initial value)/-initial value) ×100.

In some embodiments, the filter media may have a relatively high gamma value at MPPS after exposure to IPA vapor. In some embodiments, the filter media may have a gamma value at MPPS after exposure to IPA vapor of 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 filter media may have a gamma value at MPPS of 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 after exposure to IPA vapor. 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.

In some embodiments, the gamma value of the filter media as a whole after IPA exposure may be quite similar to the gamma value of the same filter media prior to IPA exposure. In some embodiments, the percent change in 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 percent change in 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 percent change in value (e.g., gamma value) is defined by the following equation: percentage change = -final value) - (initial value)/-initial value) ×100.

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

Typically, the DOP oil loading process is performed by exposing a 100cm ² test area of the filter media to an aerosol of DOP particles at a concentration of 80mg/m ³ to 100mg/m ³, a flow rate of 32L/min, and a face velocity of 5.32 cm/sec. The DOP particles were produced by a TDA 100P aerosol generator available from Air Techniques International and had a median count diameter of 0.18 microns, a mass average diameter of 0.3 microns, and a geometric standard deviation of less than 1.6 microns. Depending on the particular test, different filter media characteristics may be determined continuously during the DOP oil load or by suspending the DOP oil load for one or more measurements. For example, the pressure drop across the filter media as a function of DOP oil loading may be measured continuously. As another example, the DOP oil loading or the weight of DOP in the filter medium per filter medium area at any given pressure drop can be determined by: the pressure drop during DOP oil loading was measured continuously, the oil loading was stopped once the relevant pressure drop was reached, and the filter media was then weighed. Any increase in filter media weight is due to DOP oil, so DOP oil loading can be determined by taking the difference between the measured weight and the original DOP-free filter media. Other parameters (e.g., penetration at MPPS, γ) may also be determined during or after DOP oil loading by taking measurements as described herein.

In some embodiments, the filter medium may have a pressure drop at a DOP oil loading of greater than or equal to 4.5g/m ², greater than or equal to 5g/m ², greater than or equal to 6g/m ², greater than or equal to 7g/m ², greater than or equal to 8g/m ², greater than or equal to 9g/m ², greater than or equal to 10g/m ², greater than or equal to 11g/m ², greater than or equal to 20g/m ², greater than or equal to 30g/m ², greater than or equal to 40g/m ², greater than or equal to 50g/m ², greater than or equal to 60g/m ², or greater than or equal to 70g/m ² of H ₂ O. In some embodiments, the filter medium may have a pressure drop of less than or equal to 50mm H ₂ O at a DOP oil loading of less than or equal to 80g/m ², less than or equal to 70g/m ², less than or equal to 60g/m ², less than or equal to 50g/m ², less than or equal to 40g/m ², less than or equal to 30g/m ², less than or equal to 20g/m ², less than or equal to 11g/m ², less than or equal to 10g/m ², less than or equal to 9g/m ², less than or equal to 8g/m ², less than or equal to 7g/m ², or less than or equal to 6g/m ². Combinations of the above ranges are also possible (e.g., a pressure drop of less than or equal to 50mm H ₂ O at DOP oil loadings of greater than or equal to 5g/m ² and less than or equal to 80g/m ² or greater than or equal to 5g/m ² and less than or equal to 11g/m ²). Other ranges are also possible.

In some embodiments, the filter media is permeable to oil at a loading of greater than or equal to 4.5g/m ², greater than or equal to 5g/m ², greater than or equal to 6g/m ², greater than or equal to 7g/m ², greater than or equal to 8g/m ², greater than or equal to 9g/m ², greater than or equal to 10g/m ², greater than or equal to 11g/m ², greater than or equal to 15g/m ², greater than or equal to 20g/m ², greater than or equal to 25g/m ², greater than or equal to 30g/m ², greater than or equal to 35g/m ², greater than or equal to 40g/m ², greater than or equal to 45g/m ², greater than or equal to 50g/m ², greater than or equal to 55g/m ², greater than or equal to 60g/m ², greater than or equal to 65g/m ², greater than or equal to 70g/m ², greater than or equal to 60g/m DOE 32 at a loading of MPP of greater than or equal to 35g/m ², such as at a loading of 5.12% at or less than or equal to 3.12. In some embodiments, the filter medium may have a penetration rate of 35g/m ², 30g/m ², 25g/m ², 20g/m ², 15g/m ², 12g/m ², 11g/m ², 10g/m ², 9g/m ², 8g/m ², 7g/m ², 536 g/m 5326, 35g/m ², 35g/m 5336, 35g/m 5369, 35g/m ², 15g/m ², 35g/m ², 35g/m ², 10g/m ², and 35g/m ². Combinations of the above ranges are also possible (e.g., a penetration rate of less than or equal to 0.5% at MPPS at DOP oil loadings of greater than or equal to 4.5g/m ² and less than or equal to 80g/m ² or greater than or equal to 4.5g/m ² and less than or equal to 12g/m ²). Other ranges are also possible. The penetration at MPPS can be measured by using a TSI 3160 automated filter test unit from TSI, inc. equipped with a dioctyl phthalate generator for DOP aerosol testing based on the EN1822:2009 standard for MPPSDOP particles as described above.

In some embodiments, the filter medium may have a filtration rate of at least 4.5g/m ², at least 5g/m ², at least 6g/m ², at least 7g/m ², at least 8g/m ², at least 9g/m ², at least 10g/m ², at least 11g/m ², at least 15g/m ², at least 20g/m ², at least 25g/m ², at least 30g/m ², at least 35g/m ², at least 40g/m ², at least 45g/m ², at least 50g/m ², at least 55g/m ², at least 60g/m ², at least 65g/m ², at least 70g/m ², at least 60g/m ², at least 32% MPPS 32, and at least 35g/m 3705% oil penetration (e.g/g/m 3605) at least 0.g/m 3613. In some embodiments, the filter medium may have a penetration rate of 35g/m ², 30g/m ², 25g/m ², 20g/m ², 15g/m ², 12g/m ², 11g/m ², 10g/m ², 9g/m ², 8g/m ², 7g/m ², 536 g/m 5326, 35g/m ², 35g/m 6252, 35g/m 5395, 35g/m 5305% or less at 35g/m 35.05% or less of oil at 80g/m ², 75g/m ², 70g/m ², 65g/m ², 60g/m ², 55g/m ², 50g/m ², 45g/m 8642, 52 g/m ², 35g/m ² g/m, 20g/m ², 15g/m ², 12g/m ², 11g/m ², 10g/m ², 35g/m or less than 9g/m 363. Combinations of the above ranges are also possible (e.g., a penetration rate of less than or equal to 0.05% at MPPS at DOP oil loadings of greater than or equal to 4.5g/m ² and less than or equal to 80g/m ² or greater than or equal to 4.5g/m ² and less than or equal to 12g/m ²). Other ranges are also possible.

In some embodiments, the filtration media can have a filtration rate of oil penetration of greater than or equal to 4.5g/m ², greater than or equal to 5g/m ², greater than or equal to 6g/m ², greater than or equal to 7g/m ², greater than or equal to 8g/m ², greater than or equal to 9g/m ², greater than or equal to 10g/m ², greater than or equal to 11g/m ², greater than or equal to 15g/m ², greater than or equal to 20g/m ², greater than or equal to 25g/m ², greater than or equal to 30g/m ², greater than or equal to 35g/m ², greater than or equal to 40g/m ², greater than or equal to 45g/m ², greater than or equal to 50g/m ², greater than or equal to 55g/m ², greater than or equal to 60g/m ², greater than or equal to 65g/m ², greater than or equal to 70g/m ², greater than or equal to 60g/m DOS 32 at a loading of greater than or equal to 35g/m ², such as at 0.005H. In some embodiments, the filter medium can have a penetration rate of 35g/m ², 30g/m ², 25g/m ², 20g/m ², 15g/m ², 12g/m ², 11g/m ², 10g/m ², 9g/m ², 8g/m ², 7g/m ², 536 g/m 5326, 35g/m ², 35g/m 5336, 35g/m 5369, 35g/m ², 15g/m ², 35g/m ², 35g/m ², 10g/m ², and 35g/m ². Combinations of the above ranges are also possible (e.g., a penetration rate of less than or equal to 0.005% at MPPS at DOP oil loadings of greater than or equal to 4.5g/m ² and less than or equal to 80g/m ² or greater than or equal to 4.5g/m ² and less than or equal to 12g/m ²). Other ranges are also possible.

In some embodiments of the present invention, in some embodiments, the filter media can have a penetration rate of greater than or equal to 3.5g/m ², greater than or equal to 4g/m ², greater than or equal to 4.5g/m ², greater than or equal to 5g/m ², greater than or equal to 6g/m ², greater than or equal to 7g/m ², greater than or equal to 8g/m ², greater than or equal to 9g/m ², greater than or equal to 10g/m ², greater than or equal to 11g/m ², greater than or equal to 15g/m ², greater than or equal to 20g/m ², greater than or equal to 25g/m ², greater than or equal to 30g/m ², greater than or equal to 35g/m ², greater than or equal to 40g/m ², greater than or equal to 45g/m ², greater than or equal to 50g/m ², greater than or equal to 55g/m ², greater than or equal to 60g/m ², greater than or equal to 10g/m 5295 g/m, greater than or equal to 60g/m 3665, greater than or equal to 20g/m 0005 g/m ², or equal to 43, at a load of No. 438 g/m or equal to 0005 g/m U15 filter media). In some embodiments, the filter medium is permeable to oil at a loading of less than or equal to 80g/m ², less than or equal to 75g/m ², less than or equal to 70g/m ², less than or equal to 65g/m ², less than or equal to 60g/m ², less than or equal to 55g/m ², less than or equal to 50g/m ², less than or equal to 45g/m ², less than or equal to 40g/m ², less than or equal to 35g/m ², less than or equal to 30g/m ², less than or equal to 25g/m ², less than or equal to 20g/m ², less than or equal to 15g/m ², less than or equal to 12g/m ², less than or equal to 11g/m ², less than or equal to 10g/m ², less than or equal to 9g/m ², less than or equal to 8g/m ², less than or equal to 7g/m 658 g/m, less than or equal to 8g/m 976 g/m 7248, less than or equal to 0005 g/m 0005 g/3.5, and less than or equal to 48 g/3.5.p 57 at a load of No. 3248. Combinations of the above ranges are also possible (e.g., a penetration rate of less than or equal to 0.0005% at MPPS at DOP oil loadings of greater than or equal to 3.5g/m ² and less than or equal to 80g/m ² or greater than or equal to 3.5g/m ² and less than or equal to 12g/m ²). Other ranges are also possible.

In some embodiments of the present invention, in some embodiments, the filter media is in a range of greater than or equal to 3.5g/m ², greater than or equal to 4g/m ², greater than or equal to 4.5g/m ², greater than or equal to 5g/m ², greater than or equal to 6g/m ², greater than or equal to 7g/m ², greater than or equal to 8g/m ², greater than or equal to 9g/m ², greater than or equal to 10g/m ², greater than or equal to 11g/m ², greater than or equal to 15g/m ², greater than or equal to 20g/m ², greater than or equal to 25g/m ² the penetration at MPPS at DOP oil loadings of greater than or equal to 30g/m ², greater than or equal to 35g/m ², greater than or equal to 40g/m ², greater than or equal to 45g/m ², greater than or equal to 50g/m ², greater than or equal to 55g/m ², greater than or equal to 60g/m ², greater than or equal to 65g/m ², greater than or equal to 70g/m ², or greater than or equal to 75g/m ² may be less than or equal to 0.00005% (e.g., U16 filter media). In some embodiments, the filter media can have a penetration rate of no greater than 80g/m ², no greater than 75g/m ², no greater than 70g/m ², no greater than 65g/m ², no greater than 60g/m ², no greater than 55g/m ², no greater than 50g/m ², no greater than 45g/m ², no greater than 40g/m ², no greater than 35g/m ², no greater than 30g/m ², no greater than 25g/m ², no greater than 20g/m ², no greater than 15g/m ², no greater than 12g/m ², no greater than 11g/m ², no greater than 10g/m ², no greater than 9g/m ², no greater than 8g/m ², no greater than 7g/m 8g/m ², no greater than 35g/m ², no greater than 30g/m ², no greater than 25g/m ², no greater than 20g/m ², no greater than 15g/m ², no greater than 12g/m ², no greater than 11g/m ², no greater than 10g/m 6533, no greater than 8g/m 6535, no greater than 3g/m 7248, no greater than 3g/m or no greater than 3 at load. Combinations of the above ranges are also possible (e.g., a penetration rate of less than or equal to 0.00005% at MPPS at DOP oil loadings of greater than or equal to 3.5g/m ² and less than or equal to 80g/m ² or greater than or equal to 3.5g/m ² and less than or equal to 12g/m ²). Other ranges are also possible.

In some embodiments of the present invention, in some embodiments, the filter media is in a range of greater than or equal to 3.5g/m ², greater than or equal to 4g/m ², greater than or equal to 4.5g/m ², greater than or equal to 5g/m ², greater than or equal to 6g/m ², greater than or equal to 7g/m ², greater than or equal to 8g/m ², greater than or equal to 9g/m ², greater than or equal to 10g/m ², greater than or equal to 11g/m ², greater than or equal to 15g/m ², greater than or equal to 20g/m ², greater than or equal to 25g/m ² the penetration at MPPS at DOP oil loadings of greater than or equal to 30g/m ², greater than or equal to 35g/m ², greater than or equal to 40g/m ², greater than or equal to 45g/m ², greater than or equal to 50g/m ², greater than or equal to 55g/m ², greater than or equal to 60g/m ², greater than or equal to 65g/m ², greater than or equal to 70g/m ², or greater than or equal to 75g/m ² may be less than or equal to 0.000005% (e.g., U17 filter media). In some embodiments, the filter media is permeable to oil at a loading of less than or equal to 80g/m ², less than or equal to 75g/m ², less than or equal to 70g/m ², less than or equal to 65g/m ², less than or equal to 60g/m ², less than or equal to 55g/m ², less than or equal to 50g/m ², less than or equal to 45g/m ², less than or equal to 40g/m ², less than or equal to 35g/m ², less than or equal to 30g/m ², less than or equal to 25g/m ², less than or equal to 20g/m ², less than or equal to 15g/m ², less than or equal to 12g/m ², less than or equal to 11g/m ², less than or equal to 10g/m ², less than or equal to 9g/m ², less than or equal to 8g/m ², less than or equal to 7g/m 658 g/m, less than or equal to 8g/m 976, less than or equal to 35g/m ², less than or equal to 30g/m 3452, less than or equal to 15g/m 6535, less than or equal to 35g/m 6535, less than or equal to 6535 g/3, and No. 7248, at a load of No. ². Combinations of the above ranges are also possible (e.g., a penetration rate of less than or equal to 0.000005% at MPPS at DOP oil loadings of greater than or equal to 3.5g/m ² and less than or equal to 80g/m ² or greater than or equal to 3.5g/m ² and less than or equal to 12g/m ²). Other ranges are also possible.

In some embodiments, the filter medium may have a gamma value of greater than or equal to 8 at a DOP oil loading of greater than or equal to 4.5g/m ², greater than or equal to 5g/m ², greater than or equal to 6g/m ², greater than or equal to 7g/m ², greater than or equal to 8g/m ², greater than or equal to 9g/m ², or greater than or equal to 10g/m ². In some embodiments, the filter medium may have a gamma value of greater than or equal to 8 at a DOP oil loading of less than or equal to 11g/m ², less than or equal to 10g/m ², less than or equal to 9g/m ², less than or equal to 8g/m ², less than or equal to 7g/m ², less than or equal to 6g/m ², or less than or equal to 5g/m ². Combinations of the above ranges are also possible (e.g., a gamma value greater than or equal to 8 at DOP oil loadings greater than or equal to 4.5g/m ² and less than or equal to 11g/m ²). Other ranges are also possible. Gamma may be determined based on MPPS penetration of the DOP particles as described above.

In some embodiments, the filter medium may have a gamma value of greater than or equal to 10 at a DOP oil loading of greater than or equal to 4.5g/m ², greater than or equal to 5g/m ², greater than or equal to 6g/m ², greater than or equal to 7g/m ², greater than or equal to 8g/m ², greater than or equal to 9g/m ², or greater than or equal to 10g/m ². In some embodiments, the filter medium may have a gamma value of greater than or equal to 10 at a DOP oil loading of less than or equal to 11g/m ², less than or equal to 10g/m ², less than or equal to 9g/m ², less than or equal to 8g/m ², less than or equal to 7g/m ², less than or equal to 6g/m ², or less than or equal to 5g/m ². Combinations of the above ranges are also possible (e.g., a gamma value greater than or equal to 10 at DOP oil loadings greater than or equal to 4.5g/m ² and less than or equal to 11g/m ²). Other ranges are also possible. Gamma may be determined based on MPPS penetration of the DOP particles as described above.

In some embodiments, the PAO loading capacity of the filter media as a whole may be greater than or equal to 3g/m ², greater than or equal to 5g/m ², greater than or equal to 10g/m ², greater than or equal to 20g/m ², greater than or equal to 50g/m ², greater than or equal to 75g/m ², greater than or equal to 100g/m ², or greater than or equal to 150g/m ². In some embodiments, the PAO loading capacity of the filter media may be less than or equal to 200g/m 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 3g/m 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 may be determined by: the 491cm ² filter media was loaded with PAO oil at a loading rate of 120mg/m ³ and media face velocity of 5.3 cm/sec until the pressure drop across the filter media increased by 250Pa. The PAO particles may be produced by Laskin nozzles and may have a median diameter of 0.25 microns. The PAO load capacity is determined by: the filter media was weighed before and after testing and the measured mass increase was divided by the area of the filter media to obtain the PAO loading capacity per unit area of the filter media.

In some embodiments, the filter media as a whole may have a NaCl loading capacity greater than or equal to 0.1g/m ², greater than or equal to 0.3g/m ², greater than or equal to 0.5g/m ², greater than or equal to 1g/m ², greater than or equal to 2g/m ², greater than or equal to 5g/m ², greater than or equal to 7.5g/m ², greater than or equal to 10g/m ², greater than or equal to 12.5g/m ², greater than or equal to 15g/m ², greater than or equal to 17.5g/m ², greater than or equal to 20g/m ², greater than or equal to 22.5g/m ², greater than or equal to 25g/m ², or greater than or equal to 27.5g/m ². In some embodiments, the filter media can have a NaCl loading capacity of less than or equal to 30g/m ², less than or equal to 27.5g/m ², less than or equal to 25g/m ², less than or equal to 22.5g/m ², less than or equal to 20g/m ², less than or equal to 17.5g/m ², less than or equal to 15g/m ², less than or equal to 12.5g/m ², less than or equal to 10g/m ², less than or equal to 7.5g/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 0.5g/m ², or less than or equal to 0.3g/m ². Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1g/m ² and less than or equal to 30g/m ², or greater than or equal to 0.3g/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 determined by exposing a filter media having a nominal exposure area of 100cm ² to NaCl particles having a median diameter of 0.26 microns at a concentration of 15mg/m ³ and a face velocity of 5.3 cm/sec. NaCl loading was determined using an automated filter test unit 8130CERTITEST ^TM equipped with a sodium chloride generator from TSI, inc. The average particle size produced by the salt particle generator was 0.26 microns mass average diameter. 8130 operates in a continuous mode, with about one pressure drop reading per minute. A 100cm ² sample of filter media containing 15mg/m ³ of NaCl was used for testing at a flow rate of 32 liters/min (face velocity of 5.3 cm/sec) until the pressure drop across the filter media increased by 250Pa. The NaCl loading capacity was determined as follows: the filter media was weighed before and after testing and the measured mass increase was divided by the area of the filter media to obtain the NaCl loading capacity per unit area of the filter media. In some embodiments, the air permeability of the filter medium as a whole may be greater than or equal to 0.6CFM, greater than or equal to 1CFM, greater than or equal to 1.4CFM, greater than or equal to 5CFM, greater than or equal to 10CFM, greater than or equal to 20CFM, greater than or equal to 67CFM, greater than or equal to 100CFM, or greater than or equal to 200CFM. In some embodiments, the air permeability of the filter media can be less than or equal to 260CFM, less than or equal to 200CFM, less than or equal to 100CFM, less than or equal to 67CFM, less than or equal to 20CFM, less than or equal to 10CFM, less than or equal to 5CFM, less than or equal to 1.4CFM, or less than or equal to 1CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.6CFM and less than or equal to 260CFM, or greater than or equal to 1.4CFM and less than or equal to 67 CFM). Other ranges are also possible. Air permeability may be determined using TAPPI method T251.

The solidity of the filter medium as a whole may be any suitable value. In some embodiments, the filter media has a solidity of 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 embodiments, the filter media has a solidity of 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, less than or equal to 0.002, less than or equal to 0.001, less than or equal to 0.0005, or less than or equal to 0.0002. 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. The solidity can be determined by using the following formula: the solidity% = [ basis weight/(fiber density x thickness) ]x100. The basis weight and thickness may be determined as described herein. The porosity can be derived from the solidity based on the following equation: solidity (%) =100-porosity (%).

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

In some embodiments, the dry tensile strength of the filter media as a whole in the machine direction may be greater than or equal to 6 lbs/inch, greater than or equal to 10 lbs/inch, greater than or equal to 20 lbs/inch, greater than or equal to 30 lbs/inch, greater than or equal to 40 lbs/inch, greater than or equal to 50 lbs/inch, greater than or equal to 60 lbs/inch, greater than or equal to 70 lbs/inch, greater than or equal to 80 lbs/inch, greater than or equal to 90 lbs/inch, greater than or equal to 100 lbs/inch, greater than or equal to 110 lbs/inch, greater than or equal to 120 lbs/inch, greater than or equal to 130 lbs/inch, or greater than or equal to 140 lbs/inch. In some embodiments, the filter media can have a dry tensile strength in the machine direction of less than or equal to 150 lbs/inch, less than or equal to 140 lbs/inch, less than or equal to 130 lbs/inch, less than or equal to 120 lbs/inch, less than or equal to 110 lbs/inch, less than or equal to 100 lbs/inch, less than or equal to 90 lbs/inch, less than or equal to 80 lbs/inch, less than or equal to 70 lbs/inch, less than or equal to 60 lbs/inch, less than or equal to 50 lbs/inch, less than or equal to 40 lbs/inch, less than or equal to 30 lbs/inch, less than or equal to 20 lbs/inch, or less than or equal to 10 lbs/inch. Combinations of the above ranges are also possible (e.g., greater than or equal to 6 lbs/inch and less than or equal to 150 lbs/inch, or greater than or equal to 10 lbs/inch and less than or equal to 100 lbs/inch). Other ranges are also possible. The 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 jaw separation speed of 1 inch/minute.

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

In some embodiments, the filter media as a whole may have a wet tensile strength in the machine direction of greater than or equal to 6 lbs/inch, greater than or equal to 10 lbs/inch, greater than or equal to 20 lbs/inch, greater than or equal to 30 lbs/inch, greater than or equal to 40 lbs/inch, greater than or equal to 50 lbs/inch, greater than or equal to 60 lbs/inch, greater than or equal to 70 lbs/inch, greater than or equal to 80 lbs/inch, greater than or equal to 90 lbs/inch, greater than or equal to 100 lbs/inch, greater than or equal to 110 lbs/inch, greater than or equal to 120 lbs/inch, greater than or equal to 130 lbs/inch, or greater than or equal to 140 lbs/inch. In some embodiments, the filter media can have a wet tensile strength in the machine direction of less than or equal to 150 lbs/inch, less than or equal to 140 lbs/inch, less than or equal to 130 lbs/inch, less than or equal to 120 lbs/inch, less than or equal to 110 lbs/inch, less than or equal to 100 lbs/inch, less than or equal to 90 lbs/inch, less than or equal to 80 lbs/inch, less than or equal to 70 lbs/inch, less than or equal to 60 lbs/inch, less than or equal to 50 lbs/inch, less than or equal to 40 lbs/inch, less than or equal to 30 lbs/inch, less than or equal to 20 lbs/inch, or less than or equal to 10 lbs/inch. Combinations of the above ranges are also possible (e.g., greater than or equal to 6 lbs/inch and less than or equal to 150 lbs/inch, or greater than or equal to 10 lbs/inch and less than or equal to 100 lbs/inch). Other ranges are also possible. The 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 jaw separation speed of 1 inch/minute.

The dry trendent burst strength of the filter medium as a whole can be any suitable value. In some embodiments, the filter media can have a dry Marlen burst strength of greater than or equal to 10psi, greater than or equal to 20psi, greater than or equal to 50psi, greater than or equal to 75psi, greater than or equal to 100psi, greater than or equal to 125psi, greater than or equal to 150psi, greater than or equal to 175psi, greater than or equal to 200psi, greater than or equal to 225psi, greater than or equal to 250psi, or greater than or equal to 275psi. In some embodiments, the filter media can have a dry Marlen burst strength of less than or equal to 300psi, less than or equal to 275psi, less than or equal to 250psi, less than or equal to 225psi, less than or equal to 200psi, less than or equal to 175psi, less than or equal to 150psi, less than or equal to 125psi, less than or equal to 100psi, less than or equal to 75psi, less than or equal to 50psi, or less than or equal to 20psi. Combinations of the above ranges are also possible (e.g., greater than or equal to 10psi and less than or equal to 300psi, or greater than or equal to 20psi and less than or equal to 200 psi). Other ranges are also possible. The dry trendent burst strength may be determined according to standard T403 om-91.

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

In some embodiments, the filter media as a whole may have a Gurley stiffness in the cross-machine direction of greater than or equal to 50mg, greater than or equal to 100mg, greater than or equal to 150mg, greater than or equal to 200mg, greater than or equal to 300mg, greater than or equal to 350mg, greater than or equal to 400mg, greater than or equal to 450mg, greater than or equal to 500mg, greater than or equal to 1000mg, greater than or equal to 1500mg, or greater than or equal to 2000mg. In some embodiments, the filter media can have a Gurley stiffness in the cross-machine direction of less than or equal to 3000mg, less than or equal to 2000mg, less than or equal to 1500mg, less than or equal to 1000mg, less than or equal to 500mg, less than or equal to 450mg, less than or equal to 400mg, less than or equal to 350mg, less than or equal to 300mg, less than or equal to 250mg, less than or equal to 200mg, or less than or equal to 100mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 50mg and less than or equal to 3000mg, or greater than or equal to 100mg and less than or equal to 3000 mg). Other ranges are also possible. Stiffness can be determined from TAPPI T543 om-94 using Gurley stiffness (bending resistance) reported in mm (equivalent to gu).

In some embodiments, the filter media as a whole may have a Gurley stiffness in the machine direction of greater than or equal to 100mg, greater than or equal to 150mg, greater than or equal to 200mg, greater than or equal to 250mg, greater than or equal to 300mg, greater than or equal to 350mg, greater than or equal to 400mg, greater than or equal to 450mg, greater than or equal to 500mg, greater than or equal to 1000mg, or greater than or equal to 2000mg. In some embodiments, the filter media can have a Gurley stiffness in the machine direction of less than or equal to 3000mg, less than or equal to 2000mg, less than or equal to 1000mg, less than or equal to 500mg, less than or equal to 450mg, less than or equal to 400mg, less than or equal to 350mg, less than or equal to 300mg, less than or equal to 250mg, less than or equal to 200mg, or less than or equal to 150mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 100mg and less than or equal to 300mg, or greater than or equal to 150mg and less than or equal to 2000 mg). Other ranges are also possible. Stiffness can be determined from TAPPI T543om-94 using Gurley stiffness (bending resistance) reported in mm (equivalent to gu).

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

In some embodiments, the filter media comprises a first layer and a second layer, and the second layer is formed from fibers having an average fiber diameter of less than 1 micron. An adhesive may be present between the first layer and the second layer, and the first layer may be bonded to the second layer by the adhesive. The filter media can have a stiffness greater than or equal to 200mg and a bond strength between the first layer and the second layer of greater than or equal to 150 g/inch ². The filter media may also exhibit a gamma value of greater than or equal to 18 at the easiest penetration particle size when tested for penetration using 0.02 microns to 0.3 microns particles traveling at a face velocity of about 2.0 cm/sec and when tested for air resistance at a face velocity of about 5.3 cm/sec.

In some embodiments, the filter media includes a first layer, a second layer formed from fibers having an average fiber diameter of less than 1 micron, and an adhesive between the first layer and the second layer. The first layer may be bonded to the second layer by an adhesive. The binder may comprise a solvent-based resin comprising a polymer having a glass transition temperature of less than or equal to 25 ℃.

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

In some embodiments, the filter media includes a first layer, a second layer formed from fibers having an average fiber diameter of less than 1 micron, and an adhesive between the first layer and the second layer. The adhesive between the first layer and the second layer may be present in an amount of less than 10 gsm. The first layer may be bonded to the second layer by an adhesive, and the bond strength between the first layer and the second layer may be greater than or equal to 150 g/inch ². The filter media may exhibit less than 50% increase in air resistance after subjecting the filter media to IPA vapor discharge compared to the filter media prior to IPA vapor discharge.

In some embodiments, a filter media comprising one or more layers (e.g., a two-layer filter media, a three-layer filter media, a five-layer filter media, which may include, for example, a HEPA filter, a ULPA filter, or an HVAC filter) may be a component of the filter element. That is, the filter media may be incorporated into an article 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 curvilinear filters. The filter element can have any suitable height (e.g., 2 inches to 124 inches for flat panel filters, 4 inches to 124 inches for V-bank filters, 1 inch to 124 inches for cartridge filter media and cylindrical filter media). The filter element may also have any suitable width (2 inches to 124 inches for flat panel filters and 4 inches to 124 inches for V-type filters). Some filter media (e.g., cartridge filter media, cylindrical filter media) may be characterized by a diameter rather than a width; the diameter of these filter media may be any suitable value (e.g., 1 inch to 124 inches). The filter element typically includes a frame, which may be made of one or more materials (e.g., cardboard, aluminum, steel, alloys, wood, and polymers).

In some embodiments, the filter media described herein can be a component of a filter element and can be pleated. The pleat height and pleat density (pleats per unit length of media) may be selected as desired. In some embodiments of the present invention, in some embodiments, the pleating height may be greater than or equal to 10mm, greater than or equal to 15mm, greater than or equal to 20mm, greater than or equal to 25mm, greater than or equal to 30mm, greater than or equal to 35mm, greater than or equal to 40mm, greater than or equal to 45mm, greater than or equal to 50mm, greater than or equal to 53mm, greater than or equal to 55mm, greater than or equal to 60mm, greater than or equal to 65mm, greater than or equal to 70mm, greater than or equal to 75mm, greater than or equal to 80mm, greater than or equal to 85mm, greater than or equal to 90mm, greater than or equal to 95mm, greater than or equal to 100mm, greater than or equal to 125mm, greater than or equal to 150mm, greater than or equal to 175mm, greater than or equal to 200mm, greater than or equal to 225mm, greater than or equal to 250mm, greater than or equal to 275mm, greater than or equal to 300mm, greater than or equal to 325mm, greater than or equal to 350mm, greater than or equal to 375mm, greater than or equal to 400mm, greater than or equal to 425mm, greater than or equal to 450mm, greater than or equal to 475mm, or greater than or equal to 500mm. In some embodiments, the pleat height may be less than or equal to 510mm, less than or equal to 500mm, less than or equal to 475mm, less than or equal to 450mm, less than or equal to 425mm, less than or equal to 400mm, less than or equal to 375mm, less than or equal to 350mm, less than or equal to 325mm, less than or equal to 300mm, less than or equal to 275mm, less than or equal to 250mm, less than or equal to 225mm, less than or equal to 200mm, less than or equal to 175mm, less than or equal to 150mm, less than or equal to 125mm, less than or equal to 100mm, less than or equal to 95mm, less than or equal to 90mm, less than or equal to 85mm, less than or equal to 80mm, less than or equal to 75mm, less than or equal to 70mm, less than or equal to 65mm, less than or equal to 60mm, less than or equal to 55mm, less than or equal to 53mm, less than or equal to 50mm, less than or equal to 45mm, less than or equal to 40mm, less than or equal to 35mm, less than or equal to 25mm, less than or equal to 15mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 10mm and less than or equal to 510mm, or greater than or equal to 10mm and less than or equal to 100 mm). Other ranges are also possible.

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

Other pleat heights and pleat densities may also be possible. For example, the filter media within a flat filter or V-filter may have a pleat height of 1/4 inch to 24 inches, and/or a pleat density of 1 pleat/inch to 50 pleats/inch. As another example, the filter media within a cartridge filter or conical filter may have a pleat height of 1/4 inch to 24 inches and/or a pleat density of 1/2 pleats/inch to 100 pleats/inch. In some embodiments, the pleats may be separated by pleat separators 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 it may be self-supporting.

Example 1

In this example, a five-layer filter media was produced in which layers were laminated together using a solvent-based adhesive.

Fig. 3 illustrates a schematic diagram of a system 300 for forming a filter medium described herein. Solvent-based adhesive 310 (Super 77, synthetic elastomer dissolved in acetone, cyclohexane, dimethyl glutarate and other petroleum distillates; available from 3M company) was sprayed onto the first layer (support layer) having a basis weight of 50g/M ². The adhesive coating has a basis weight of less than 10g/m ² (e.g., less than 1g/m ²). The support layer coated with the adhesive then enters a spinning unit 320 (e.g., an electrospinning chamber) where a second layer (nylon main filtration layer) is added near the adhesive. Next, a third layer (spunbond pre-filter layer; trade name reemy 2250) sprayed with an adhesive having a basis weight of less than 10g/m ² (e.g., less than 1g/m ²) is added by lamination via the winding unit 330 to form a three-layer filter media. The resulting filter media formed during this first pass is shown in fig. 4A and includes a first layer 410, a second layer 420, a third layer 430, and an adhesive 490. Referring back to fig. 3, adhesive 340 is then applied to the third layer (pre-filter layer) at a basis weight of less than 10g/m ² (e.g., less than 1g/m ²), and the three-layer filter media is again passed through the spinning unit to add a fourth layer (nylon main filter layer) near the opposite side of the third layer. The fifth layer (support layer) was sprayed with adhesive and laminated such that its adhesive coated side was adjacent to the fourth layer to form a five-layer filter media. Fig. 4A-4C illustrate the resulting structure formed using the systems and methods described above. The filter medium 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 medium 1).

For comparison purposes, a four-layer filter media (filter media 2) was made by hand finishing together two adhesive-free filter media, each of which was made by electrospinning a second layer (main filtration layer) onto a first layer (support layer). Manual finishing is performed after each filter media is wound once. The electrospun main filtration layer of filter medium 2 is similar in structure (e.g., fiber diameter, material, and basis weight) to the main filtration layer of filter medium 1, and the support layer of filter medium 2 is similar in structure (e.g., fiber diameter, material, and basis weight) to the support layer of filter medium 2. The spunbond pre-filter layer present in filter medium 1 but not in filter medium 2 does not contribute significantly to the gamma value of filter medium 1 due to its relatively low air resistance and high penetration rate compared to the other layers in the medium.

Filter media 1 had a higher gamma value (59.1) than filter media 2 (45.1), indicating that filter media formed by the method described in this example that included a solvent-based binder was superior to filter media that did not include a binder.

Example 2

This example describes the use of an adhesive comprising a small molecule cross-linker.

Two-layer filter media were prepared by electrospinning a second layer (main filtration layer) having a basis weight of 0.2g/m ² onto the first layer (support layer).

The adhesive composition was prepared by adding carbodiimide crosslinking agent (Carbodilite E-02; available from Nisshinbo Chemicals) in varying amounts (e.g. 0 wt%, 3 wt% or 7 wt% crosslinking agent relative to the total weight of the layer) to an aqueous acrylate copolymer adhesive (Carbobond 1995; available from Lubrizol Corporation) having a glass transition temperature of-30 ℃.

The adhesive composition (comprising Carbobond and cross-linker both) was sprayed onto the third layer (polyester spunbond protective layer; trade name reemy 2250) at 1g/m ². The adhesive coated third layer was laminated to two layers of filter media at 80 ℃ and the air resistance of the resulting three layers of filter media was measured. Then, as described above, the three-layer filter medium was exposed to IPA vapor, after which the air resistance of the three-layer filter medium was measured again. The filter media comprising the adhesive composition containing 0 wt% crosslinker or 3 wt% crosslinker had a significant increase in air resistance after exposure to IPA vapor (3.7 mm H ₂ O to 18.8mm H ₂ O for 0 wt% crosslinker, 3.7mm H ₂ O to 9.4mm H ₂ O for 3 wt% crosslinker). The filter media comprising the adhesive composition containing 7 wt% crosslinker exhibited a negligible increase in air resistance after IPA vapor exposure (3.3 mm H ₂ O to 4.1mm H ₂ O).

Example 3

This example describes the manufacture of a filter media.

An in-line nozzle system is customized that is capable of applying adhesive to a filter media layer in-line at several points during the manufacturing process. A wet laid synthetic medium having a basis weight of 50g/m ² was used as the first layer (support layer) and passed through the system and sprayed with adhesive. The adhesive-covered layer was then passed into an electrospinning line to deposit a second layer (nylon electrospun main filtration layer) adjacent to the adhesive. The main filtration layer had a basis weight of 0.25g/m ² and an average fiber diameter of 100 nm. These two layers were then finished with a third layer (20 g/m ² polypropylene meltblown web prefilter layer) coated with adhesive so that the adhesive on the meltblown prefilter layer was adjacent to the main filter layer. The multilayer media is passed through a felt dryer that can be maintained at a surface temperature of 120 ℃. The laminated media was wound into a roll and characterized.

The adhesive used above was Carbobond in combination with a Carbodilite crosslinker. Carbobond 1995 was prepared at 15% by weight solids and blended with 10% wet weight Carbodilite E02 crosslinker. The pH of the blend was adjusted to 7 to 8 using potassium hydroxide. There was 1.03g/m ² of adhesive at each interface in the final filter media (i.e., 1.03g/m ² of adhesive at the interface between the wet laid layer and the main filtration layer, and 1.03g/m ² of adhesive at the interface between the main filtration layer and the meltblown layer.)

The three-layer main filter manufactured as described above has an average internal bond strength of 343 g/inch ² and good bonding of the three layers. These filter media also exhibit other positive characteristics after exposure to IPA vapor, such as a negligible increase in air resistance (17.1 mm H ₂ O to 17.8mm H ₂ O), a negligible increase in penetration under MPPS (0.0044% to 0.01373%), and a relatively high gamma value (22.7).

Example 4

This example describes the manufacture of a filter medium as in example 3.

Three layers of filter media were made by employing similar steps as used in example 3.

The first layer (support layer) was a 60g/m ² synthetic wet laid backing with 380mg stiffness, 25.7 lbs/inch machine direction tensile strength, 0.016 inch thickness and 70psi dry Maren strength.

The second layer (main filtration layer) was made of nylon fibers (electrospun fibers) having an average fiber diameter of about 120 nm.

The third layer (pre-filter layer) was a meltblown polypropylene layer having a basis weight of 22g/m ² and an average fiber diameter of 1.5 microns. The pre-filter layer was also corona charged so that its initial efficiency for 0.3 micron DOP particles measured at a face velocity of 5.32 cm/sec was 8.5% and IPA vapor discharge efficiency was 65%.

The adhesive formulation was also similar to that employed in example 3, except that it had 12.5 wt% solids. Between each pair of layers (i.e., between the support layer and the main filtration layer, and between the main filtration layer and the pre-filtration layer) was added 0.8g/m ² of adhesive, for a total of 1.6g/m ² of adhesive for the entire filter media.

The filter media showed a 9% increase in air resistance after IPA vapor discharge and a gamma value of 18.89 after IPA vapor discharge. The average internal bond strength of the filter media was 189.4 g/inch ².

Example 5

This example shows a comparison of several properties of a filter medium having oleophobic properties (oleophobic coating) with two filter media lacking oleophobic properties (oleophobic coating).

Filter media 1 was a three-layer filter media comprising a 20g/m ² melt blown polypropylene pre-filter layer, a 0.25g/m ² electrospun nylon main filter layer, and a 60g/m ² wet laid polyester and acrylate support layer. The pre-filter layer was charged by corona discharge to form an electret with a NaCl penetration of 2.5% for 0.3 micron particles and a pressure drop of 2mm H ₂ O at a face velocity of 5.32 cm/sec. The average fiber diameter of the main filtration layer was 100nm. The filter medium 1 is prepared by: the adhesive is sprayed onto the support layer, the support layer coated with the adhesive is passed through an electrospinning unit to form a main filtration layer disposed on the support layer, and then the pre-filtration layer coated with the sprayed adhesive is laminated to the support layer coated with the main filtration layer. These steps are performed in-line and do not require an external lamination step.

Filter media 2 is a three-layer filter media that includes 30g/m ² of the meltblown pre-filter layer and the main filter layer and support layer described above for filter media 1.

Filter medium 3 is similar to filter medium 1 except that it includes an oleophobic coating with an oil grade of 5 to 6 on the pre-filter layer. The oleophobic coating is formed on the pre-filter layer prior to lamination of the pre-filter layer to the support layer coated with the main filter layer. The oleophobic coating is formed by passing the pre-filter layer through a vacuum plasma chamber containing a C6 fluorinated acrylate monomer. During this step, the C6 fluorinated acrylate monomers polymerize on the surface of the pre-filter layer fibers to form a thin coating (e.g., film). Then, the pre-filter layer was charged with corona discharge, sprayed with an adhesive, and laminated to the support layer coated with the main filter layer as described above for filter medium 1.

Table 2 below shows several characteristics of the formed filter media 1,2, and 3.

TABLE 2

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For each filter media, the following procedure was performed. The 100cm ² test area was exposed to aerosols of DOP particles at concentrations of 80mg/m ³ to 100mg/m ³. The DOP particles were produced by a TDA100P aerosol generator available from Air Techniques International and had a median count diameter of 0.18 microns, a mass average diameter of 0.3 microns, and a geometric standard deviation of less than 1.6 microns. During this process, the pressure drop across the filter medium is measured continuously. When the pressure drop increased to a value of 4mm H ₂ O greater than that of the formed filter media (which was not exposed to DOP particles), the filter media was weighed to determine the oil loading and the MPPS penetration of the filter media was measured using a TSI 3160 instrument at a face velocity of 2 cm/sec. The process was repeated with MPPS penetration measurements and oil loading measurements at each 4mm H ₂ O increase in pressure drop until an endpoint pressure drop of 55mm H ₂ O was reached.

Fig. 5 shows MPPS penetration as a function of oil loading for filter media 1-3, fig. 6 shows pressure drop as a function of oil loading for filter media 1-3, and fig. 7 shows gamma as a function of oil loading for filter media 1-3. For each of these characteristics, filter media 3 exhibits better performance than either filter media 1 or filter media 2 at higher oil loading levels. For example, as shown in fig. 5, the filter medium 3 has a penetration rate of less than or equal to 0.004 at MPPS at DOP oil loadings of greater than or equal to 4.5g/m ². FIG. 6 shows that filter medium 3 has a pressure drop of less than or equal to 50mm H ₂ O at DOP oil loadings of greater than or equal to 4.5g/m ². FIG. 7 shows that filter medium 3 has a gamma value greater than or equal to 10 at DOP oil loadings greater than or equal to 4.5g/m ².

Although various embodiments of the invention have been described and illustrated herein, a person of ordinary skill in the art will readily envision a variety of other means and/or structures for performing the functions and/or obtaining the results and/or one or more of the advantages described herein, and each of such variations and/or modifications is deemed to be within the scope of the present invention. More generally, those skilled in the art will readily appreciate that all parameters, dimensions, materials, and configurations described herein are meant to be exemplary and that the actual parameters, dimensions, materials, and/or configurations will depend upon the specific application or applications for which the teachings of the present invention are used. Those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the invention described herein. It is, therefore, to be understood that the foregoing embodiments are presented by way of example only and that, within the scope of the appended claims and equivalents thereto, the invention may be practiced otherwise than as specifically described and claimed. The present invention is directed to each individual feature, system, article, material, kit, and/or method described herein. Furthermore, if two or more such features, systems, articles, materials, kits, and/or methods are not mutually inconsistent, any combination of two or more such features, systems, articles, materials, kits, and/or methods is included within the scope of the present invention.

All definitions as defined and used herein should be understood to have precedence over dictionary definitions, definitions in documents incorporated by reference, and/or general meanings of the defined terms.

Objects without quantitative word modifications as used herein in the specification and claims should be understood to mean "at least one" unless explicitly stated to the contrary.

The phrase "and/or" as used herein in the specification and claims should be understood to mean "either or both" of the elements so combined, i.e., elements that in some cases coexist and in other cases separately. The various elements listed with "and/or" should be interpreted in the same manner, i.e. "one or more" of the elements so combined. In addition to the elements specifically identified by the "and/or" clause, other elements may optionally be present, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, reference to "a and/or B" when used in conjunction with an open language such as "comprising" may refer in one embodiment to a alone (optionally including elements other than B); may refer to B alone (optionally including elements other than a) in another embodiment; in yet another embodiment may refer to both a and B (optionally including other elements); etc.

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 in a list are separated, "or" and/or "should be understood to include, i.e., include at least one of the plurality of elements or lists of elements, but also include more than one, and optionally include additional unlisted items. Only the opposite terms, such as "only one of them" or "exactly one of them", or "consisting of" when used in the claims, are explicitly indicated to mean that exactly one element of the plurality or list of elements is included. Generally, when an exclusive term (e.g., "either," "one," "only one," or "exactly one") is present, the term "or" as used herein should be understood to mean only an exclusive alternative (i.e., "one or the other but not both"). "consisting essentially of" when used in the claims shall have the general meaning of what is used in the patent laws.

As used herein in the specification and claims, the phrase "at least one" when referring to a list of one or more elements is understood to mean at least one element selected from any one or more elements in the list of elements, but does not necessarily include at least one of each element specifically listed in the list of elements nor exclude any combination of elements in the list of elements. The definition also allows that elements may optionally be present other than the elements specifically identified in the list of elements referred to by the phrase "at least one," whether related or unrelated to those elements specifically identified. Thus, as one non-limiting example, "at least one of a and B" (or equivalently "at least one of a or B," or equivalently "at least one of a and/or B") may refer in one embodiment to at least one a, optionally including more than one a, without the presence of 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 being present (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); etc.

It should also be understood that in any method claimed herein that includes more than one step or act, the order of the steps or acts of the method is not necessarily limited to the order in which the steps or acts of the method are recited, unless clearly indicated to the contrary.

In the claims and in the above specification, all transitional phrases such as "comprising," "including," "carrying," "having," "containing," "involving," "holding," "including," and the like are to be construed as open-ended, i.e., to mean including but not limited to. Only transitional phrases "consisting of" and "consisting essentially of" shall be closed or semi-closed transitional phrases, respectively, as set forth in section 2111.03 of the U.S. patent office patent review program manual.

The invention also provides the following technical scheme:

Appendix 1. A filter medium comprising:

A first layer;

a second layer, wherein the second layer is formed from fibers having an average fiber diameter of less than 1 micron; and

An adhesive between the first layer and the second layer, wherein the first layer is bonded to the second layer by the adhesive,

Wherein at least one of the first layer and the second layer has an oil grade greater than or equal to 1,

Wherein the bond strength between the first layer and the second layer is greater than or equal to 150 g/inch ², and

Wherein the filter media has a stiffness greater than or equal to 200mg, wherein the stiffness is measured in the machine or cross direction.

Appendix 2. A filter medium comprising:

A first layer, wherein the first layer comprises fibers;

A second layer, wherein the second layer is a film layer; and

Appendix 3. A filter medium comprising:

a first layer; and

A second layer, wherein the second layer is formed from fibers having an average fiber diameter of less than 1 micron,

Wherein the filter medium has a stiffness of greater than or equal to 200mg, wherein the stiffness is measured in the machine or cross direction, and

Wherein the filter medium has a pressure drop of less than or equal to 50mm H ₂ O at a DOP oil loading of greater than or equal to 4.5g/m ².

Appendix 4. A filter medium comprising:

a first layer, wherein the first layer comprises fibers; and

A second layer, wherein the second layer is a film layer,

Appendix 5. A filter medium comprising:

a first layer; and

Wherein the filter medium has a gamma value of greater than or equal to 10 at a DOP oil loading of greater than or equal to 4.5g/m ².

Appendix 6. A filter medium comprising:

a first layer, wherein the first layer comprises fibers; and

A second layer, wherein the second layer is a film layer,

Appendix 7 the filter media of any preceding appendix, wherein the efficiency of the filter media according to standard EN1822:2009 is greater than 95%.

Appendix 8 the filter media of any preceding appendix, wherein the efficiency of the filter media according to standard EN1822:2009 is greater than 99.95%.

Appendix 9 the filter media of any preceding appendix, wherein the efficiency of the filter media according to standard EN1822:2009 is greater than 99.995%.

Appendix 10 the filter media of any preceding appendix, wherein the efficiency of the filter media according to standard EN1822:2009 is greater than 99.9995%.

Appendix 11 the filter media of any preceding appendix, wherein the efficiency of the filter media according to standard EN1822:2009 is greater than 99.99995%.

Appendix 12 the filter media of any preceding appendix, wherein the efficiency of the filter media according to standard EN1822:2009 is greater than 99.999995%.

Appendix 13 the filter media of any preceding appendix, wherein the efficiency of the filter media according to standard EN1822:2009 is greater than 99.9999995%.

Appendix 14. The filter media of any preceding appendix, wherein the fibers of the second layer are solvent spun fibers.

Appendix 15. The filter media of any preceding appendix, wherein the fibers of the second layer are electrospun fibers or spun fibers.

Appendix 16. The filter media of any preceding appendix, wherein the second layer is a main filtration layer.

Appendix 17 the filter media of any preceding appendix, wherein the first layer is a wet-laid layer.

Appendix 18. The filter media of any preceding appendix, wherein the first layer is a meltblown layer.

Appendix 19 the filter media of any preceding appendix, wherein the first layer is a charged meltblown layer.

Appendix 20. The filter media of any preceding appendix, wherein the first layer is a support layer.

Appendix 21 the filter media of any preceding appendix, wherein the first layer is a pre-filter layer.

Appendix 22. The filter media of any preceding appendix, wherein the filter media comprises a third layer.

Appendix 23. The filter media of any preceding appendix, wherein the third layer is a meltblown layer.

Appendix 24. The filter media of any preceding appendix, wherein the third layer is a wet-laid layer.

A filter media according to any preceding appendix, wherein the third layer is a pre-filter layer.

A filter media according to any preceding appendix, wherein the third layer is a support layer.

Appendix 27. The filter media of any preceding appendix, wherein the third layer is a charged meltblown layer.

Appendix 28. The filter media of any preceding appendix, wherein the first layer is a surface-modified layer.

Appendix 29. The filter media of any preceding appendix, wherein the second layer is a surface-modified layer.

Appendix 30. The filter media of any preceding appendix, wherein the third layer is a surface-modified layer.

Appendix 31. The filter media of any preceding appendix, wherein the surface modification of at least one of the first layer, the second layer and the third layer has been performed by a chemical deposition technique.

Appendix 32. The filter media of any preceding appendix, wherein the surface modification of at least one of the first layer, the second layer and the third layer has been performed by plasma enhanced chemical vapor deposition.

Appendix 33. The filter media of any preceding appendix, wherein the surface modification of at least one of the first layer, the second layer and the third layer has been performed by electron beam assisted radiation curing.

Appendix 34. The filter media of any preceding appendix, wherein the surface modification of at least one of the first layer, the second layer and the third layer has been performed by a physical deposition technique.

Appendix 35. The filter media of any preceding appendix, wherein the surface modification of at least one of the first layer, the second layer and the third layer has been performed by powder coating.

Appendix 36 the filter media of any preceding appendix, wherein the first layer further comprises an oleophobic component.

Appendix 37 the filter media of any preceding appendix, wherein the second layer further comprises an oleophobic component.

A filtration medium according to any preceding appendix, wherein the third layer further comprises an oleophobic component.

Appendix 39 the filter media of any preceding appendix, wherein the oleophobic component of at least one of the first layer, the second layer and the third layer is a layer that has been deposited by a chemical deposition technique.

A appendix 40. The filter media of any preceding appendix, wherein the oleophobic component of at least one of the first layer, the second layer and the third layer is a layer that has been deposited by plasma enhanced chemical vapor deposition.

Appendix 41. The filter media of any preceding appendix, wherein the oleophobic component of at least one of the first layer, the second layer and the third layer is a layer that has been deposited by electron beam assisted radiation curing.

Appendix 42. The filter media of any preceding appendix, wherein the oleophobic component of at least one of the first layer, the second layer and the third layer is a layer that has been deposited by a physical deposition technique.

Appendix 43 the filter media of any preceding appendix, wherein the oleophobic component of at least one of the first layer, the second layer and the third layer is a layer that has been deposited by powder coating.

Appendix 44. The filter media of any preceding appendix, wherein the oleophobic component comprises an oleophobic resin.

Appendix 45 the filter media of any preceding appendix, wherein the oleophobic component comprises an oleophobic additive.

Appendix 46. The filter media of any preceding appendix, wherein the first layer has an oil grade greater than or equal to 1.

Appendix 47 the filter media of any preceding appendix, wherein the second layer has an oil grade greater than or equal to 1.

Appendix 48. The filter media of any preceding appendix, wherein the oil grade of the layer furthest upstream is greater than or equal to 1.

The filter medium of any preceding appendix 49, wherein the filter medium has a DOP penetration at MPPS of less than or equal to 0.5%, less than or equal to 0.05%, less than or equal to 0.005%, less than or equal to 0.0005%, less than or equal to 0.00005%, or less than 0.000005% at a DOP oil loading of greater than or equal to 4.5g/m ².

Appendix 50. The filter media of any preceding appendix, wherein the oleophobic component comprises a polymer.

Appendix 51 the filter media of any preceding appendix, wherein the oleophobic component comprises organofluorine.

The filter medium of any preceding appendix, wherein the oleophobic component comprises one or more of a wax, a silicone, a corn-based polymer, and a nanoparticle material.

Appendix 53. The filter media of any preceding appendix, wherein the first layer comprises fibers and an oleophobic component, and wherein the oleophobic component is in the form of a coating disposed on one or more fibers within the first layer.

Appendix 54. The filter media of any appendix 50, wherein the coating at least partially surrounds one or more fibers within the first layer.

Appendix 55. The filter media of any preceding appendix, wherein the filter media has a gamma value of greater than or equal to 18.

Appendix 56 the filter media of any preceding appendix, wherein the filter media has a stiffness of greater than or equal to 300mg.

Appendix 57 the filter media of any preceding appendix, wherein the filter media has a basis weight of less than or equal to 150g/m ².

Appendix 58 the filter media of any preceding appendix, wherein the thickness of the filter media is less than or equal to 1mm.

Appendix 59 the filter media of any preceding appendix, wherein the filter media is pleated and the pleat height is greater than or equal to 10mm and less than or equal to 510mm.

A filter media according to any preceding appendix, wherein the filter media is pleated and has a pleat density of greater than or equal to 6 pleats per 100mm and less than or equal to 100 pleats per 100 mm.

Appendix 61. The filter media of any preceding appendix, wherein the stiffness is measured in the cross-machine direction.

Appendix 62. The filter media of any preceding appendix, wherein the stiffness is measured in the machine direction.

Appendix 63. A method comprising filtering a fluid through a filter medium according to any of the foregoing appendix.

Claims

1. A filter media, comprising:

A first layer;

Wherein the air permeability of the first layer is greater than or equal to 2CFM,

Wherein the first layer has an average flow pore size of greater than or equal to 0.5 microns and less than or equal to 100 microns, and

Wherein the filter media has a stiffness greater than or equal to 50mg, wherein the stiffness is measured in the cross machine direction.

2.A filter media, comprising:

A first layer, wherein the first layer comprises fibers;

A second layer, wherein the second layer is a film layer; and

3. The filter media of claim 1, wherein the filter media has an efficiency according to standard EN1822:2009 of greater than 95%.

4. The filter media of claim 1, wherein the fibers of the second layer are solvent spun fibers, electrospun fibers, or spun fibers.

5. The filter media of claim 1, wherein the first layer is a wet laid layer, a meltblown layer, a charged meltblown layer, a support layer, or a pre-filter layer.

6. The filter media of claim 1, wherein the filter media comprises a third layer.

7. The filter media of claim 6, wherein the third layer is a meltblown layer, a wet-laid layer, a pre-filter layer, or a support layer.

8. The filter media of claim 6, wherein the third layer is a charged meltblown layer.

9. The filter media of claim 1, wherein the first layer or the second layer is a surface modified layer.

10. The filter medium of claim 9, wherein surface modification of at least one of the first layer and the second layer has been performed by a chemical deposition technique, by plasma enhanced chemical vapor deposition, by electron beam assisted radiation curing, by a physical deposition technique, or by powder coating.

11. The filter medium of claim 1, wherein the filter medium has a DOP penetration at MPPS of less than or equal to 0.5% at a DOP oil loading of greater than or equal to 4.5g/m ².

12. The filter media of claim 1, wherein the filter media has a gamma value greater than or equal to 18.

13. The filter media of claim 1, wherein the filter media has a basis weight of less than or equal to 150g/m ².

14. The filter media of claim 1, wherein the filter media has a thickness of less than or equal to 1mm.

15. The filter media of claim 1, wherein the filter media is pleated and has a pleat height of greater than or equal to 10mm and less than or equal to 510mm.

16. The filter media of claim 1, wherein the filter media is pleated and has a pleat density of greater than or equal to 6 pleats per 100mm and less than or equal to 100 pleats per 100 mm.

17. The filter media of claim 1, wherein the filter media is a component of a filter element.

18. The filter media of claim 1, wherein the first layer comprises multicomponent fibers.

19. The filter media of claim 1, wherein the filter media has a stiffness greater than or equal to 200mg, wherein the stiffness is measured in a machine direction or a cross-machine direction.

20. The filter media of claim 1, wherein the first layer is a pre-filter layer.

21. The filter media of claim 1, wherein the first layer is an upstream-most layer.