Articles including filter media having irregular structures and / or reversible stretch layers

Abstract

Filter articles and filter elements including a reversible stretch layer filter media are generally provided. The filtration articles and filtration elements described herein can be used in a variety of applications, applications, including as respirators or respiratory protection devices, medical filters, indoor air filtration articles for HVAC and HEPA applications, cabin air filters for vehicles, indoor air purifier filters, vacuum cleaner filters, heavy air filters, hydraulic fluid filters, and process liquid filter filters.

Description

Technical Field

[0001] The present invention relates generally to filter media, and more particularly to filter media having an irregular structure. Background Art

[0002] The filter medium can be formed by one or more fiber meshes. The fiber mesh provides a porous structure that allows fluid (e.g., gas, air) to flow through the filter medium. Pollutant particles contained in the fluid can be captured on or within the fibrous mesh. Filter medium characteristics such as surface area and weight per unit area affect the filtration performance including filtration efficiency, pressure drop, and resistance to fluid flow through the filter. Generally, for a given flow rate through the filter, a higher filtration efficiency may cause a higher fluid flow resistance, thereby causing a higher pressure drop.

[0003] A need exists for a filter media that can be used in a variety of applications and that has a desirable balance of properties including high efficiency and low resistance to fluid flow through the filter media, resulting in a high gamma value. Summary of the Invention

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

[0005] In some embodiments, a filter medium is provided that includes a nonwoven fibrous web having a stiffness less than or equal to 100 mg and an average surface height greater than 0.3 mm.

[0006] In some embodiments, a filter medium is provided. The filter medium includes a first layer and a second layer. The first layer has an average surface height greater than 0.3 mm. The first layer is held in an undulating configuration by the second layer. The second layer is formed of a reversibly stretchable material.

[0007] In some embodiments, a filter medium is provided. The filter medium comprises a nonwoven fibrous web comprising a plurality of peaks having an average peak height and a peak height standard deviation. The ratio of the peak height standard deviation to the average peak height is greater than or equal to 0.05. The nonwoven fibrous web has an average surface height greater than 0.3 mm.

[0008] In some embodiments, a filter medium is provided. The filter medium includes a layer comprising a plurality of peaks, the plurality of peaks having an average peak height and a peak height standard deviation. The ratio of the peak height standard deviation to the average peak height is greater than or equal to 0.05. The average surface height of the layer is greater than 0.3 mm.

[0009] In some embodiments, a filter medium is provided. The filter medium includes a nonwoven fibrous web comprising a plurality of peaks having an average peak-to-peak spacing and a standard deviation of the peak-to-peak spacing. The ratio of the standard deviation of the peak-to-peak spacing to the average peak-to-peak spacing is greater than or equal to 0.08. The nonwoven fibrous web has an average surface height greater than 0.3 mm.

[0010] In some embodiments, a filter medium is provided. The filter medium includes a layer comprising a plurality of peaks having an average peak spacing and a peak spacing standard deviation. The ratio of the peak spacing standard deviation to the average peak spacing is greater than or equal to 0.08. The layer has an average surface height greater than 0.3 mm.

[0011] In some embodiments, a method of making a filter medium is provided. The method includes depositing a nonwoven fibrous web onto a reversibly stretchable layer and at least partially recovering the reversibly stretchable layer. The nonwoven fibrous web forms a plurality of peaks during recovery of the reversibly stretchable layer.

[0012] In some embodiments, a method of making a filter medium is provided. The method includes depositing a layer onto a reversibly stretchable layer and at least partially recovering the reversibly stretchable layer. The layer forms a plurality of peaks during recovery of the reversibly stretchable layer.

[0013] In some embodiments, a filter article is provided. The filter article includes a filter medium comprising a nonwoven web. The air permeability of the nonwoven web is greater than or equal to 2 CFM. The nonwoven web comprises a plurality of peaks having an average peak height and a standard deviation of the peak height. The ratio of the standard deviation of the peak height to the average peak height is greater than or equal to 0.15 and less than or equal to 0.5. The average surface height of the nonwoven web is greater than 0.3 mm. In some such embodiments, the filter article includes a medical filter (e.g., a surgical drape, gown, cap, hood, mask, operating room shoes or shoe covers). In some such embodiments, the filter article includes a scarf, headscarf, stroller cover, protective shield, sheet, curtain or clothing (e.g., for body covering). In some such cases, the filter article can provide protection when personnel (e.g., first responders and NGO personnel) enter an environment with harmful particles in the air, such as a war zone. In some such embodiments, the filter article includes geotextiles and / or materials used in construction projects for reinforcement, filtration, drainage and erosion prevention. In some such embodiments, the filtration article comprises a respirator or respiratory protection device (e.g., an elastomeric half-mask respirator, an elastomeric full-face respirator, a filtering facepiece respirator, or a powered air-purifying respirator (PAPR)). The respirator or respiratory protection device may include a particulate filtering respirator (e.g., an N95 respirator, an N99 respirator, an N100 respirator, an R95 respirator, an R99 respirator, an R100 respirator, a P95 respirator, a P99 respirator, a P100 respirator, and a HE (High Efficiency Particulate Air) respirator). In some such embodiments, the filtration article comprises an indoor air filtration article for HVAC and HEPA applications (e.g., a cut-and-frame fan coiling unit filter, a cut-and-frame panel filter, an HVAC panel filter, an HVAC box filter, or an HVAC V-bank filter). Indoor air filtration products can be configured for residential or commercial use. Filter products can include cabin air filters for vehicles. Filter products can include indoor air purifier filters. Filter products can include vacuum cleaner filters. Filter products include heavy-duty air filters, hydraulic fluid filters, and process liquid filtration filters.

[0014] In some embodiments, a method of making a filtration article is provided. The method includes depositing a layer onto a reversibly stretchable layer; and at least partially recovering the reversibly stretchable layer, wherein the layer forms a plurality of peaks during recovery of the reversibly stretchable layer.

[0015] In some embodiments, a filter element is provided. The filter element includes a filter medium comprising a nonwoven fiber web. The nonwoven fiber web has an air permeability greater than or equal to 2 CFM. The nonwoven fiber web comprises a plurality of peaks having an average peak height and a peak height standard deviation. The ratio of the peak height standard deviation to the average peak height is greater than or equal to 0.15 and less than or equal to 0.5. The nonwoven fiber web has an average surface height greater than 0.3 mm.

[0016] Other advantages and novel features of the present invention will become apparent from the following detailed description of various non-limiting embodiments of the present invention when considered in conjunction with the accompanying drawings. In the event that this specification and the documents incorporated by reference include conflicting and / or inconsistent disclosures, this specification shall prevail. If two or more documents incorporated by reference include conflicting and / or inconsistent disclosures relative to each other, the document with the later effective date shall prevail. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, which are schematic and not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown is generally represented by a single numeral. For purposes of clarity, not every component is labeled in every figure, nor is every component of every embodiment of the invention shown, where an illustration is not necessary to allow one of ordinary skill in the art to understand the invention. In the drawings:

[0018] Figure 1 is a schematic diagram of a filter medium according to some embodiments;

[0019] Figure 2 is an example of measured relative surface topography according to some embodiments;

[0020] Figure 3A is an example of a set of line data obtained during measurement of relative surface topography according to some embodiments;

[0021] Figure 3B is an example of a set of line data where a local maximum (shown as a larger point) has been identified and used to determine the peak height (Hi) and the spacing (Di) between two adjacent peaks;

[0022] Figures 4A to 4C is a schematic diagram of a filter medium according to some embodiments;

[0023] Figure 5A is a schematic diagram of a filter medium including two layers according to some embodiments;

[0024] Figure 5B is a schematic diagram of a filter medium including three layers according to some embodiments;

[0025] Figures 6A to 6C and Figures 6D to 6F is a schematic diagram of a method of manufacturing a filter medium according to some embodiments;

[0026] 7A to 7B is a schematic diagram of a binder-coated fiber according to some embodiments;

[0027] Figure 8 is a schematic diagram of a filter medium including two layers according to some embodiments;

[0028] Figures 9A to 9C is a schematic diagram of a corrugated filter medium according to some embodiments;

[0029] Figures 10 and 11 is a photograph of an apparatus that can be used to manufacture filter media according to some embodiments;

[0030] Figure 12 is a graph showing gamma and percent gamma increase as a function of stretch according to some embodiments;

[0031] Figure 13 is a graph showing thickness and percent increase in thickness as a function of stretching according to some embodiments;

[0032] Figure 14 is a graph showing surface height as a function of stretch according to some embodiments;

[0033] Figure 15 is a graph showing basis weight as a function of stretching according to some embodiments;

[0034] Figure 16 is a graph showing γ as a function of surface height according to some embodiments;

[0035] Figure 17 is a graph showing the ratio of the standard deviation of the peak spacing to the average peak spacing at different stretching levels according to some embodiments;

[0036] Figure 18 is a graph showing the ratio of peak height standard deviation to average peak height according to some embodiments;

[0037] Figure 19is a graph illustrating the ratio of the standard deviation of the peak separation to the average peak separation according to some embodiments; and

[0038] Figure 20 is a graph showing the ratio of peak height standard deviation to average peak height according to some embodiments.

[0039] Figure 21 FIG45 is a graph showing the pressure drop performance of Sample No. 45 relative to Control Sample A and Control Sample B during the DOP oil loading process. Specific implementation plan

[0040] Generally, products and methods related to filter media are provided. Some embodiments relate to filter media containing irregular structures. The irregular structures can be present on the outer surface of the filter media, in the interior of the filter media and / or throughout the entire filter media. In some embodiments, the irregular structure includes an irregular conformation (e.g., spatial conformation, surface conformation) of at least a portion of one or more layers in the filter media. For example, the filter media can include one or more layers having a surface and / or three-dimensional shape that produces the irregular structure. In some embodiments, the irregular structure can be a plurality of peaks having one or more irregular features. For example, the plurality of peaks can have irregular sizes, spacings and / or shapes. In some such cases, the plurality of peaks can be formed by undulations in the surface of the layer and / or layer. Advantageously, the irregular structure can be used to improve the gamma of the filter media by, for example, increasing the relative amount of filter media per unit area. As an example, compared with certain conventional filter media, a filter media containing certain irregular peaks can have a larger surface area per unit area of ​​filter media and / or a larger unit area weight per unit area.

[0041] The filter media described herein can also have one or more desirable physical properties. For example, the filter media can be relatively thin and / or have a relatively low stiffness. In some embodiments, the filter media can have a thinness and / or stiffness that is not otherwise achievable. Such a lightweight, thin, and / or low stiffness media can be desirable for a variety of applications, including face mask filters and face masks. Some filter media can be thick and / or rigid, but still have the structures described herein.

[0042] Some embodiments relate to methods of forming a filter medium comprising an irregular structure. As will be described in further detail below, one method of forming such a filter medium includes depositing one or more layers onto a reversibly stretchable layer and then at least partially recovering the reversibly stretchable layer. During recovery, the reversibly stretchable layer can shorten along the direction in which it was stretched, possibly to its pre-stretched size. As the reversibly stretchable layer recovers, the recovering reversibly stretchable layer can pull any layers deposited thereon with it. The recovery process can cause the filter medium and / or one or more portions thereof to comprise an irregular structure, such as a plurality of peaks having one or more irregular features. Without wishing to be bound by any particular theory, it is believed that forming peaks in this manner can be particularly easy and / or can result in the formation of peaks having particularly desirable irregular morphologies. However, it should also be understood that other methods of forming the structures described herein are also possible.

[0043] Some embodiments relate to articles other than filter media, and / or methods of forming articles other than filter media. Such articles may include articles configured for and / or adapted for use in acoustic applications, articles configured for and / or adapted for use in sound insulation applications, articles configured for and / or adapted for use in thermal insulation applications, articles of clothing, and / or articles adapted for use in clothing. Such articles may have one or more of the features described elsewhere herein with respect to filter media, and / or may differ from the filter media described elsewhere herein in one or more respects.

[0044] Figure 1 A non-limiting example of a filter medium comprising an irregular structure is shown in FIG. Figure 1 In the embodiment, the irregular structure exists at least at the surface of the filter medium; therefore, Figure 1 A filter medium comprising irregular structures at the surface is shown. Figure 1Filter media 1000 shown in FIG. includes a plurality of peaks 100. Peaks 100 include peaks 10, 20, 30, 40, and 50 separated by valleys 60, 70, 80, and 90. Each peak has a height and a width. Peaks not on the outer edge of the filter media (i.e., peaks 20, 30, and 40) have two nearest-neighbor spacings; peaks on the outer edge of the filter media (i.e., peaks 10 and 50) have one nearest-neighbor spacing. As an example, peak 40 has a height 40H, a width 40W, and two nearest-neighbor spacings 40A and 40B. These peak characteristics can be determined using a scanning optical microscope, such as a Keyence VR-3000G2, Measurement Unit Model VR3200 Wide-Area 3D Measurement System. The surface topography of the filter media can be measured using a scanning optical microscope with a resolution of at least 25 microns in each of the x- and y-axes and at least 0.5 microns in the z-axis, according to the standards described in ISO 25178 (2006). This measurement produces a matrix of values ​​representing the surface heights measured at a set of points on the sample, where the x and y positions of each measured surface height are given by the columns and rows of the matrix, respectively. Such z values ​​can then be defined as reference heights (e.g. Figure 1 2): 95% of the points constituting the measured surface topography are above this z-value, and 5% of the points constituting the measured surface topography are below this z-value. This reference height can be subtracted from the height of each point in the measured surface topography to generate a relative height for each point in the measured surface topography and a relative surface topography composed of the relative height values.

[0045] The relative surface topography can then be further processed in accordance with ISO 16610-21:2011 to determine the height of each peak. The calculation process may include the following steps in sequence: (1) removing the outer 10% of points from each edge to reduce edge effects; (2) applying a Gaussian filter with a kernel size of 30 pixels to smooth the resulting data; (3) converting the resulting data into a set of line data by selecting every 10th line; and (4) identifying local maxima. The local maximum identified in step (4) is the peak height. The spacing between two peaks can be determined by finding the difference between the positions of the points where these local maxima occur. Figure 2 shows an example of the relative surface topography measured after step (2) according to the process, and Figure 3A An example of a set of line data measured after step (3) according to the process is shown. Figure 3B An example of a set of line data is shown where a local maximum (shown as a larger dot) has been identified and used to determine the peak height (Hi) and the spacing (Di) between two adjacent peaks.

[0046] In some embodiments, Figures 1 to 3B As shown in FIG, peaks within a plurality of peaks may differ from one another in one or more respects. For example, a plurality of peaks may include two or more peaks having different heights, different spacings from their nearest neighbors, and / or different shapes. As an example, referring to FIG. Figure 1 , height 40H of peak 40 is different from height 20H of peak 20. As another example, spacing 40A between peak 30 and peak 40 is different from spacing 40B between peak 40 and peak 50. In some embodiments, the plurality of peaks does not include two peaks with the same height, does not include two sets of peaks with the same spacing, and / or does not include two peaks with the same width. For example, the irregular structure and / or filter medium may not include a peak with the same height, spacing, and / or width as another peak.

[0047] In some embodiments, the plurality of peaks includes two or more peaks that are similar in one or more aspects. For example, the plurality of peaks may include two peaks having the same height, two sets of peaks having the same spacing, and / or two peaks having the same width. As an example, referring to Figure 1 , the height 20H of peak 20 has the same value as the height 50H of peak 50. In some embodiments, the plurality of peaks includes two or more peaks that are similar in one or more respects (e.g., peaks having the same height, the same spacing from their nearest neighbors, and / or the same width) and two or more peaks that are different in one or more respects (e.g., peaks having different heights, different spacing from their nearest neighbors, and / or different widths). Referring again to Figure 1 , the plurality of peaks 100 includes a peak 20 and a peak 50 having heights 20H and 50H of the same value, and also includes a peak 40 having a height 40H of a different value from 20H and 50H.

[0048] It should be understood that the irregular structure can be present at any location within the filter medium, but need not be present at all locations. For example, some filter media may be like Figure 1 , as shown in FIG, includes a first surface having an irregular structure (e.g., a plurality of peaks), and includes a second surface opposite the first surface that is relatively regular (e.g., flat) or completely lacks irregular structures (e.g., peaks). Figure 1Unlike the filter media shown in , some filter media can include two opposing surfaces, each of which includes an irregular structure. For example, some filter media can include two opposing surfaces, each of which includes a plurality of peaks, and / or each of which includes a plurality of peaks that are irregular in one or more aspects. In some embodiments, as will be described in more detail below, the filter media includes: a first surface, the first surface including a first plurality of peaks that are irregular in one or more aspects; and a second surface, the second surface including a second plurality of peaks that are similar in all aspects except amplitude to a plurality of valleys positioned between peaks in the first plurality of peaks. The second plurality of peaks can have the same (or substantially similar) position, shape, spacing, and / or width as the plurality of valleys positioned between peaks in the first plurality of peaks, but can have a smaller height.

[0049] If one or more portions of the filter media described herein (e.g., one or more layers thereof, one or more surfaces thereof) contain irregular structures, then it should be understood to contain irregular structures. The irregular structures (e.g., a plurality of peaks) can be located at one or more surfaces of the filter media, within the interior of the filter media, and / or throughout the filter media. As an example, a filter media containing irregular structures can include: a plurality of peaks that are irregular in one or more aspects and are present at one or more surfaces of the filter media; a plurality of peaks that extend through one or more layers of the filter media; and / or a plurality of peaks that are present at one or more surfaces of a layer of the filter media.

[0050] It should also be understood that in embodiments where irregularities are not present at the outer surface of the filter media, the characteristics of the irregularities can be measured by removing a portion of the filter media that obstructs measurement of the irregularities and measuring the irregularities as described above. For example, in some embodiments, the filter media includes two opposing layers that do not contain irregularities, but includes a layer that contains irregularities (e.g., a plurality of peaks that are irregular in one or more aspects) positioned between the two opposing layers that do not contain irregularities. For such a filter media, the layer that includes one of the surfaces that do not contain irregularities can be removed, exposing the irregularities, and the characteristics of interest of the exposed irregularities can be measured by optical microscopy as described above.

[0051] In some embodiments, the filter media includes one or more layers. As used herein, a layer may have a common morphology, may have a common chemical composition, may be positioned between two other layers, may separate two other layers, and / or may serve a common function in the filter media, among other characteristics. Some layers may be topologically connected throughout the layer, and some layers may include two or more portions that are topologically disconnected from one another. For example, Figure 4A An example of a filter medium 1002A is shown that includes a first layer 202 that is topologically connected throughout the layer and a second layer 302 that includes portions (e.g., portion 602 and portion 702) that are topologically disconnected from each other. Figure 4B A perspective view of this same filter medium is shown. Figures 4A to 4B Not shown in , but any type of layer may contain irregular structures. In addition, some layers may not contain parts that can be removed from the layer without using specialized tools and / or without splitting the layer, and some layers may contain such parts.

[0052] In some embodiments, a layer in a filter medium first takes the form of a layer when incorporated into the filter medium. In other words, a collection of articles that were not layers prior to incorporation into the filter medium can be considered to form a layer of the filter medium after incorporation into the filter medium. A specific example of such a layer is a plurality of elastically extensible fibers. Prior to incorporation into the filter medium, the plurality of fibers can be separate, mechanically disconnected fibers. Upon incorporation into the filter medium, the elastically extensible fibers can have a common function (e.g., serve as a scrim) and / or can separate two layers (e.g., an efficiency layer and a support layer). Figure 4C One example of a plurality of elastically extensible fibers forming layer 302 is shown positioned between layer 202 and layer 402. Non-limiting examples of suitable layers include a nonwoven web, a mesh, a plurality of fibers that are not in direct contact with each other and / or mechanically coupled to each other, and an adhesive adhering two layers together, the adhesive being positioned between the two layers.

[0053] For example, by referring to Figure 1 In another embodiment, the filter medium 1000 can be a single-layer filter medium. Figure 1 In another embodiment, the filter medium 1000 may be a filter medium including two or more layers. Figure 5AA non-limiting embodiment of a filter medium 1001 is shown, comprising a first layer 201 and a second layer 301. In some embodiments, the filter medium may include one or more layers comprising an irregular structure. The irregular structure may include an irregular spatial configuration of the layer. For example, a layer or portion thereof may have a non-planar spatial configuration with one or more irregular features. In some embodiments, the entire thickness of a layer, or the entire thickness of a portion of a layer, may be arranged into three-dimensional peaks and valleys. In such cases, each non-terminal peak is adjacent to a valley, and each non-terminal valley is adjacent to a peak. In other words, the layer may have a structure such that each peak on a first side of the layer has a corresponding valley on the opposite side of the layer, and each valley on a first side of the layer has a corresponding peak on the opposite side of the layer. Multiple valleys may be similar in one or more respects to their corresponding multiple peaks, and / or multiple peaks may be similar in one or more respects to their corresponding multiple valleys. For example, a pair of corresponding valleys and peaks may be located at substantially the same location, have substantially the same peak height, have substantially the same peak width, have substantially the same peak shape, and / or have substantially the same nearest-neighbor spacing. A layer arranged such that its entire thickness is arranged into three-dimensional peaks and valleys may be referred to as a layer containing a plurality of peaks extending through the entire thickness of the layer and / or as an undulating layer.

[0054] An example of an undulating layer is Figure 5A Layer 201 in. Figure 5A Layer 201 in FIG. 2 includes a plurality of peaks 101, including peaks 11, 21, 31, 41, and 51 separated by valleys 61, 71, 81, and 91. Valleys 61, 71, 81, and 91 together form a plurality of valleys 101T (not shown). These peaks and valleys are present on the upper side of layer 201 (and on the upper side of filter medium 301). Peaks 101 have corresponding valleys 1010 (not shown), including valleys 110, 210, 310, 410, and 510 on the bottom side of layer 201, and valleys 101T (not shown) have corresponding peaks 101TO (not shown), including peaks 61O, 71O, 81O, and 91O. In some embodiments, the profile of the top surface of the contoured layer (eg, layer 201 ) can be substantially the same as the profile of the bottom surface of the contoured layer when viewed in cross-section.

[0055] In some embodiments, the undulating layer has a structure indicating that the layer had no undulation at a certain point in time and has undergone a process that causes it to undulate. The undulating layer may include portions that are in tension (e.g., the upper surface of the peaks, the lower surface of the valleys positioned between the peaks) and / or portions that are in compression (e.g., the lower surface of the peaks, the upper surface of the valleys positioned between the peaks). The layer may be made undulating by various suitable processes such as folding, curling, gathering, etc. In some embodiments, heat shrinkage may be performed to cause one or more layers to undulate. For example, one or more layers may be disposed on a layer having high heat shrinkage, and the layer having high heat shrinkage may be heated to cause it to shrink and cause the one or more layers disposed thereon to become undulating.

[0056] In some embodiments, the filter medium includes a layer that does not contain irregular structures. The layer that does not contain irregular structures may not contain any peaks (e.g., it may be relatively flat), or it may contain a plurality of regular peaks. For example, Figure 5A As with the filter medium shown in FIG, the filter medium may include a layer containing an irregular structure (e.g., a plurality of peaks) and a layer not containing an irregular structure (e.g., peaks). Figure 5A The filter medium 1001 shown in FIG includes a layer 201 containing a plurality of peaks (e.g., 11, 21, 31, 41, and 51), and also includes a layer 301 that does not contain any peaks. Figure 5A In embodiments where layer 201 shown in comprises a plurality of peaks, the peaks may have one or more irregular features as described herein.

[0057] In some embodiments, the filter medium includes two or more layers that include an irregular structure (e.g., two or more layers that include a plurality of peaks that are irregular in one or more aspects) and two or more layers that do not include an irregular structure (e.g., two or more layers that do not contain peaks or that include a plurality of peaks that have a regular structure). For such embodiments, the layers can be arranged relative to each other in various suitable ways. For example, two layers that each include a plurality of peaks that are irregular in one or more aspects are positioned on opposite sides of a layer that does not include a plurality of peaks that are irregular in one or more aspects. A filter medium having such a structure can be manufactured by pleating the two layers on opposite sides of a reversibly stretchable layer. As another example, two layers that each do not include a plurality of peaks that are irregular in one or more aspects can be positioned on opposite sides of a layer that includes a plurality of peaks that are irregular in one or more aspects. For example, one or more layers that include a plurality of peaks can be positioned between two outer layers that are completely free of peaks and / or are relatively flat.

[0058] In some embodiments, the filter media includes only layers comprising a plurality of peaks that are irregular in one or more respects.

[0059] Some filter media (like Figure 5A ) include a single layer comprising a plurality of peaks. Some filter media include two or more layers, each comprising a plurality of peaks. Figure 5B One non-limiting embodiment of a filter medium comprising two layers, each comprising a plurality of peaks, is shown. Figure 5B In the embodiment, filter medium 1003 includes a first layer 203, a second layer 303, and a third layer 403. The first layer 203 and the third layer 403 each include two opposing surfaces. In both the first layer 203 and the third layer 403, the first surface comprises a plurality of peaks separated by a plurality of valleys. The surface opposite the first surface in each of these layers comprises a plurality of valleys and a plurality of peaks, the plurality of valleys corresponding to the peaks present in the first surface of the layer, and the plurality of peaks corresponding to the valleys present in the first surface of the layer.

[0060] In some embodiments, the filter media comprises two or more layers that are undulated together. Figure 5B In the embodiment of the present invention, the first layer and the third layer are also both undulating layers that undulate together. In other words, both the first layer and the third layer are undulating, and the first layer contains a first plurality of peaks that are substantially similar to the second plurality of peaks present in the third layer. Figure 5B , the plurality of peaks present in the upper surface of layer 203 are substantially similar to the plurality of peaks present in the upper surface of layer 403. In some cases where the first layer and the third layer undulate together, the plurality of peaks and the plurality of valleys in the first layer are substantially the same as those in the third layer. In some embodiments, the filter media includes two or more layers that undulate but do not undulate together. For example, the filter media may include two layers that undulate on opposite sides of a layer that does not undulate. As another example, the filter media may include a first layer and a second layer, both of which undulate and include undulations that are substantially similar in position, but the undulations have substantially different amplitudes (e.g., substantially different average peak heights). Some filter media may include some layers that undulate together and some layers that undulate separately.

[0061] Various suitable types of layers can be included in the filter media described herein, such as efficiency layers, scrims, nanofiber layers, carrier layers, and support layers. Some filter media include at most one layer of any type (e.g., filter media including one scrim and one efficiency layer; filter media including one scrim, one efficiency layer, and one nanofiber layer; filter media including one scrim, one efficiency layer, one nanofiber layer, and one carrier layer). Some filter media include two or more layers of a single type (e.g., filter media including one scrim and two efficiency layers; filter media including one scrim, two efficiency layers, and one nanofiber layer). It should be understood that references to a first layer, a second layer, a third layer, etc. can refer to any type of layer, and it should be understood that the layers described herein can be combined with each other in various different combinations and in various different orders. It should also be understood that reference to a nonwoven web can refer to any type of nonwoven web layer, such as an efficiency layer that is a nonwoven web, a nanofiber layer that is a nonwoven web, a scrim that is a nonwoven web, a carrier layer that is a nonwoven web, and / or a support layer that is a nonwoven web. The characteristics of the different types of layers that can be included in the filter media are described in further detail below.

[0062] The filter media described herein can be manufactured in a variety of suitable ways. Figures 6A to 6C A method for manufacturing a filter medium that can be particularly advantageous is shown in . In this method, a layer having a relatively low stiffness is wrinkled using a layer capable of undergoing reversible stretching to form an undulating layer. The layer capable of undergoing reversible stretching is stretched, and while it is in a stretched state (i.e., when it is in the form of a reversibly stretched layer), a layer having a relatively low stiffness is deposited onto the layer capable of undergoing reversible stretching. Then, when the reversibly stretched layer recovers, the reversibly stretched layer wrinkles the layer having a relatively low stiffness as it pulls the layer having a relatively low stiffness back. The reversibly stretched layer can fully recover (i.e., recover to its original size before being stretched) or partially recover (i.e., recover to a size between its original size before being stretched and its size when in the stretched state). In other words, the layer capable of undergoing reversible stretching can be stretched in a fully reversible manner or in a partially reversible and partially irreversible manner. Figure 6A A possible first step of reversibly stretching a layer capable of undergoing reversible stretching, such as a scrim, to a stretched state is shown. Figure 6B A possible second step of depositing a layer, such as an efficiency layer, onto the reversibly stretchable layer is shown. Figure 6C The recovery of the reversibly stretched layer is shown. During the recovery process, the layer with relatively low stiffness wrinkles and forms a plurality of peaks that are irregular in height, spacing, width and / or shape. The reversibly stretched layer can hold the peaks in place.

[0063] In some embodiments, Figures 6A to 6CAs in the embodiment shown in FIG, the reversibly stretchable layer may be a layer topologically connected throughout the layer. Figures 6A to 6C As in the embodiment shown in FIG, the reversibly stretchable layer may be in the form of a layer before any layer is deposited thereon. The reversibly stretchable layer may also include portions that are topologically disconnected from one another and / or not be a layer until one or more additional layers are deposited thereon (e.g., as in FIG. Figures 4A to 4C As an example, in some embodiments, the reversibly stretchable layer comprises a plurality of elastically extensible fibers that are not initially formed into a layer. The elastically extensible fibers can be reversibly stretched (e.g., along their axis). Depositing one or more layers thereon can cause the elastically extensible fibers to take the form of a scrim that holds the layers deposited thereon in an undulating configuration, thereby converting the elastically extensible fibers into layers in the filter media. Figures 6D to 6F A schematic diagram of such a process is shown.

[0064] In general, any suitable number of layers can be undulated (e.g., by wrinkling) using layers capable of undergoing reversible stretching. Figures 6A to 6C In some embodiments shown in , after depositing a layer having a relatively low stiffness on the reversibly stretchable layer, one or more additional layers may be deposited onto the reversibly stretchable layer. In some embodiments, one or more additional layers may be deposited onto the reversibly stretchable layer along with the layer having a relatively low stiffness. The one or more additional layers may be deposited before the reversibly stretchable layer recovers. For example, a second efficiency layer may be deposited onto a first efficiency layer deposited onto the reversibly stretchable scrim, a nanofiber layer may be deposited onto an efficiency layer deposited onto the reversibly stretchable scrim, or both efficiency layers may be deposited together onto the reversibly stretchable scrim. Then, as Figure 6C As shown, the reversibly stretchable layer may be allowed to recover. During this step, a layer deposited on the reversibly stretchable layer (e.g., on and / or with a layer having relatively low stiffness) may become undulating (e.g., by wrinkling). In some embodiments, as Figure 5B As in the embodiment shown in FIG, the layers can undulate and / or wrinkle together. After becoming undulated and / or wrinkled, the layers can be maintained in the undulated and / or wrinkled configuration by the reversibly stretch layer. In addition to the layer with relatively low stiffness, one or more additional layers deposited on the reversibly stretch layer can also have relatively low stiffness, which can promote such favorable wrinkling. In some embodiments, one or more additional layers can be deposited on the reversibly stretch layer after the reversibly stretch layer has recovered. In some embodiments, such a layer can prevent the reversibly stretch layer from undergoing further reversible stretching.

[0065] In some embodiments, Figures 6A to 6CAs in the embodiment shown in FIG, the layer to be wrinkled is deposited directly onto the reversibly stretchable layer, with the resulting wrinkled layer and recovery layer being directly adjacent. As used herein, when a layer is referred to as being "on" or "adjacent" another layer, it can be directly on or adjacent to that layer, or intervening layers or materials may also be present. A layer being "directly on," "directly adjacent," or "in contact with" another layer means that there are no intervening layers or materials.

[0066] In some embodiments, the layer to be wrinkled is deposited on the layer or material deposited onto the reversibly stretchable layer, with the resulting wrinkled layer and the recovery layer being adjacent but not directly adjacent. For example, the layer to be wrinkled can be deposited on the adhesive deposited onto the reversibly stretchable layer, such that the adhesive is positioned between the resulting wrinkled layer and the recovery layer. In some embodiments where the adhesive is positioned between the layer to be wrinkled and the reversibly stretchable layer, the adhesive can be deposited onto the reversibly stretchable layer before and / or after stretching.

[0067] For example, an adhesive can be deposited onto the scrim, the scrim can be stretched, and then the efficiency layer can be deposited onto the stretched scrim. In this case, the adhesive is stretched along with the scrim in the direction in which the scrim was stretched. The efficiency layer may bond poorly to the scrim in the direction in which the scrim was stretched, and thus, when the scrim is allowed to recover, the efficiency layer may separate from the scrim in the opposite direction at certain locations. In such a case, the efficiency layer may be wrinkled, and the scrim may contain undulations that follow the undulations in the efficiency layer (or become undulated). The undulations in the scrim may be much smaller than those in the efficiency layer (i.e., they may have a much smaller average peak height), and thus, the scrim may be considered relatively flat, but not completely flat, compared to the efficiency layer.

[0068] In one particular embodiment, the above process can be performed using a scrim in the form of a plurality of elastically extensible fibers. As an example, in some embodiments, the adhesive is deposited onto the plurality of elastically extensible fibers such that the adhesive completely coats or partially coats the elastically extensible fibers. Complete coating can include depositing the adhesive onto the elastically extensible fibers such that the adhesive coats the entire circumference of the elastically extensible fibers along at least a portion of the length of the elastically extensible fibers (e.g., as in Figure 7A , where adhesive 804A coats the entire circumference of elastically extensible fibers 904). Partial coating can include depositing adhesive onto the elastically extensible fibers such that the adhesive coats portions of the elastically extensible fibers, such as portions closer to the adhesive source and / or to which additional layers will subsequently be deposited (e.g., Figure 7B, where adhesive 804B coats some, but not all, of the circumference of elastically extensible fibers 904).

[0069] The reversibly stretchable layer can also be bonded to another layer by ultrasonic bonding. The reversibly stretchable layer can be reversibly stretched, optionally allowed to recover, and then laminated to another layer deposited thereon. This process can be combined with or instead of the process described in the previous paragraph to adhere the reversibly stretchable layer and the layer deposited thereon with an adhesive. In some embodiments, the layer to which the reversibly stretchable layer is bonded via ultrasonic bonding prevents the reversibly stretchable layer from undergoing further reversible stretching after recovery.

[0070] The process described in the previous paragraph can be performed in a roll-to-roll manner. As an example, in some embodiments, the reversible stretch layer (or the multiple elastically elongated fibers that form the reversible stretch layer when incorporated into the filter medium) are supplied by rollers, a plurality of spools or instruments (e.g., yarn or filament bundles) that supply multiple yarns or filament ends. Then, when incorporated into the filter medium, the reversible stretch layer or the multiple elastically elongated fibers that form the reversible stretch layer can be passed through, stretched, and then used as a substrate for another layer (e.g., an efficiency layer) to be deposited thereon below the station to which an adhesive is applied. The other layer can be a pre-existing layer wound around a roller and deposited from a roller, or can be a layer (e.g., formed from a solution or melt) formed on the reversible stretch layer. The two layers bonded together by an adhesive can be bonded with another layer (the other layer itself can be supplied from another roller). These other layers can be deposited when the reversible stretch layer is in a reversible stretch state and / or when the reversible stretch layer is in a recovered state. The two layers bonded together by an adhesive can also pass through the other stations that perform other processes. Such processes may include bonding (e.g., via an ultrasonic horn and / or a calender), laminating (e.g., thermal lamination, chemical lamination, and / or mechanical lamination), pleating, and / or charging. One or more of these processes may cause the reversibly stretchable layer to become bonded to another layer and / or mechanically coupled to another layer (e.g., a scrim, such as a second scrim), rendering the reversibly stretchable layer incapable of further reversible stretching. Following fabrication, the final filter media may be wound around a final roll.

[0071] When the reversibly stretch layer is stretched, the direction of stretching can generally be selected as desired. In some embodiments, the reversibly stretch layer can be stretched in the machine direction. In some embodiments, the reversibly stretch layer can be stretched in the transverse direction. When stretched, the reversibly stretch layer can be stretched to various suitable lengths. The reversibly stretch layer can be stretched to a length of greater than or equal to 50%, greater than or equal to 75%, greater than or equal to 100%, greater than or equal to 125%, greater than or equal to 150%, greater than or equal to 175%, greater than or equal to 200%, greater than or equal to 225%, greater than or equal to 250%, greater than or equal to 275%, greater than or equal to 300%, greater than or equal to 325%, greater than or equal to 350%, greater than or equal to 375%, greater than or equal to 400%, greater than or equal to 450%, greater than or equal to 500%, greater than or equal to 600%, or greater than or equal to 800% of its initial length. In some embodiments, the reversibly stretchable layer is stretched to a length of less than or equal to 1000%, less than or equal to 800%, less than or equal to 600%, less than or equal to 500%, less than or equal to 450%, less than or equal to 400%, less than or equal to 375%, less than or equal to 350%, less than or equal to 325%, less than or equal to 300%, less than or equal to 275%, less than or equal to 250%, less than or equal to 225%, less than or equal to 200%, less than or equal to 175%, less than or equal to 150%, less than or equal to 125%, less than or equal to 100%, or less than or equal to 75% of its initial length. Combinations of the above ranges are also possible (e.g., greater than or equal to 50% and less than or equal to 1000%, greater than or equal to 100% and less than or equal to 400%, or greater than or equal to 200% and less than or equal to 300%). Other ranges are also possible.

[0072] A layer deposited on a reversibly stretched layer in a reversibly stretched state may experience a decrease in length as the reversibly stretched layer recovers to its recovered length. The decrease in length may be equivalent to a corresponding decrease in length experienced by the reversibly stretched layer upon recovery. When the reversibly stretched layer exhibits substantially complete recovery, the decrease in length of the layer may fall within one or more ranges derivable from the above ranges by the following formula: Percentage of Length Reduction = (1-100 / (100+Percentage of Stretch))*100%.

[0073] For example, a fully recovered layer deposited on a reversibly stretchable layer stretched to 50% of its original length will have a corresponding length reduction of 33% of its original length. As another example, a fully recovered layer deposited on a reversibly stretchable layer stretched to 1000% of its original length will have a corresponding length reduction of 91% of its original length.

[0074] In some embodiments, the filter medium comprising an irregular structure may further comprise one or more additional structures. The additional structures may comprise peaks, valleys, undulations and / or other features. The one or more additional structures may be regular (e.g., a plurality of regular peaks) or irregular (e.g., a plurality of peaks that are irregular in one or more aspects). Generally, whether regular or irregular, the additional structures may be on a different length scale than the irregular structures. For example, the additional structures may comprise one or more features (e.g., peaks, valleys) that are larger in magnitude than the features (e.g., peaks, valleys) of the irregular structure. Figure 8 A non-limiting example of a filter medium comprising an irregular structure and an additional structure is shown in FIG. Figure 8 As shown in , filter media 1005 can contain both irregular structures and additional structures 500. The irregular structures can be present on the exterior surface of the filter media, within the interior of the filter media, and / or throughout the filter media. In some cases, as Figure 8 As shown, the irregular structure can be present on the outer surface of the filter media and / or can extend through the entire thickness of one or more layers of the filter media. In some cases, the undulating layers in the filter media, such as Figure 8 The undulating layer 305 in the filter medium can include an irregular structure as described herein. With respect to the irregular structure, the presence of additional structure including regular undulations and / or irregular undulations (e.g., a plurality of peaks) can increase the relative amount of filter media per unit area, which can desirably increase the gamma of the filter media.

[0075] In some embodiments, one or more layers in the filter medium may contain both irregular structures and additional structures. As an example, in some embodiments, the filter medium includes a layer that contains a plurality of peaks that are irregular in one or more aspects and contains additional structures. The plurality of peaks that are irregular in one or more aspects typically, but not always, have a length scale that is smaller than the additional structures. In some embodiments, one or more layers in the filter medium are undulating on two length scales. For example, a layer in the filter medium may undulate in an irregular manner and then further undulate on a larger length scale to form additional structures. The plurality of peaks that constitute the irregular undulations may, at least in part, have an orientation that is different from the undulations that form the additional structures and / or an average peak height that is different from the undulations that form the additional structures.

[0076] In some embodiments, one or more additional structures are formed by additional steps that impart additional structure to the filter medium (e.g., pleating, corrugating). For example, a filter medium comprising an irregular structure including a plurality of peaks can be pleated to impart regular peaks to the filter medium. The peak height, peak spacing, and / or peak size of the pleats can be significantly greater than the same features of the irregular structure. In some such cases, pleating can be used to impart a relatively macroscopic structure to the filter medium as a whole, while the irregular structure imparts a relatively microscopic structure to the filter medium. In some embodiments, the additional structure can be relatively macroscopic compared to the irregular structure and can be formed by making the filter medium, for example, Figure 1 Filter media 1001 in FIG. 1 is subjected to a relief forming process, such as pleating and / or corrugating, to form a filter media, such as filter media 1005 , that includes irregular structures and additional structures.

[0077] Various techniques can be employed to form additional structure in a layer comprising an irregular structure. Some such techniques include undulating a layer comprising a first plurality of peaks constituting the irregular structure, e.g., a layer comprising a plurality of peaks that are irregular in one or more aspects, to form a second plurality of peaks constituting the additional structure. As an example, the layer comprising the first plurality of peaks and any other layers that undulate with the layer comprising the plurality of peaks can be pleated and / or corrugated. Pleating and / or corrugating the layer can result in the formation of a relatively regular second plurality of peaks. As another example, the layer comprising the first plurality of peaks and any other layers that undulate with the layer comprising the plurality of peaks can undergo one or more of the above-described processes to form a second plurality of peaks that are irregular in one or more aspects. In other words, the additional structure can be an irregular structure and / or can be formed by one of the methods employed to form the first plurality of peaks. For example, the layer comprising the first plurality of peaks and any other layers that undulate with the layer comprising the first plurality of peaks may be folded, curled, pleated, and / or may be disposed over the layer undergoing heat shrinkage.

[0078] In some embodiments, a filter medium comprising one or more layers having an undulating layer further comprises one or more additional support layers (e.g., one or more fibrous support layers) that hold the one or more undulating layers in an undulating configuration. The support layer may not have a plurality of irregular peaks and / or may be relatively flat prior to undulation. Figure 9A An exemplary embodiment of a filter media is shown in which a layer is undulated by corrugation and is held in the corrugated configuration by two support layers. Figure 9AA filter medium 1006 is depicted having at least one corrugated layer and at least one support layer that holds the corrugated layer in a corrugated configuration, thereby keeping the peaks and valleys of adjacent waves of the corrugated layer separated. In the illustrated embodiment, filter medium 1006 includes an efficiency layer 12, a first downstream support layer 14 disposed on opposite sides of efficiency layer 12, and a second upstream support layer 16. Although not shown, efficiency layer 12 may include an irregular structure, such as a plurality of peaks that are irregular in one or more aspects. First support layer 14 and second support layer 16 may not have a plurality of peaks prior to being corrugated with efficiency layer 12. Support layers 14, 16 may help hold efficiency layer 12, as well as any optional additional layers described elsewhere herein, in a corrugated configuration. The additional layers may have one or more structural features described elsewhere herein with respect to layers that include a plurality of peaks that are irregular in one or more aspects. For example, each additional layer may, independently or not, contain a plurality of peaks, be an undulating layer prior to corrugation, be a corrugated layer prior to corrugation, undulate with one or more other layers, and / or be corrugated with one or more other layers.

[0079] Further references Figure 9A In some embodiments, a scrim is positioned between support layer 14 and efficiency layer 12 and / or between support layer 16 and efficiency layer 12. In some embodiments, a nanofiber layer is positioned between support layer 14 and efficiency layer 12 and / or between support layer 16 and efficiency layer 12. Although two support layers 14, 16 are shown, filter media 10 need not include two support layers. Where only one support layer is provided, the support layer can be positioned upstream or downstream of the filter layer.

[0080] Filter media 1006 may also optionally include one or more outer layers or cover layers located on the upstream-most side and / or the downstream-most side of filter media 1006 . Figure 9A A top layer 18 is shown disposed on the upstream side of filter media 1006 to serve as, for example, an upstream dust-holding layer. Top layer 18 can also serve as an aesthetic layer. The layers in the illustrated embodiment are arranged such that top layer 18 is disposed on the air inlet side, designated I, second support layer 16 is immediately downstream of top layer 18, efficiency layer 12 is disposed immediately downstream of second support layer 16, and first support layer 14 is disposed downstream of efficiency layer 12 on the air outlet side, designated O. The direction of air flow, from air inlet I to air outlet O, is indicated by the arrows labeled A.

[0081] The outer layer or cover layer may alternatively or additionally be a bottom layer disposed on the downstream side of the filter media 1006 to serve as a reinforcement component that provides structural integrity to the filter media 1006, thereby helping to maintain the corrugated configuration. The outer layer or cover layer may also serve to provide wear resistance. Figure 9B Shown with Figure 9A Another embodiment of filter medium 1006B is similar to filter medium 1006. In this embodiment, filter medium 1006B does not include a top layer, but rather has an efficiency layer 12B, a first support layer 14B disposed immediately downstream of efficiency layer 12B, a second support layer 16B disposed immediately upstream of efficiency layer 12B on the air inlet side I, and a bottom layer 18B disposed immediately downstream of first support layer 14B on the air outlet side O. Figure 9B Between the efficiency layer and the support layer shown in , additional layers, such as a scrim layer and / or a nanofiber layer, are positioned. Figure 9A and Figure 9B In the exemplary embodiment shown in FIG, the outer layer or cover layer can have a different topography than the topography of the efficiency layer and / or any support layer. For example, in either a pleated or non-pleated configuration, the outer layer or cover layer can be non-corrugated (e.g., generally flat, lacking undulations, and / or lacking a plurality of peaks that are irregular in one or more aspects), while the efficiency layer, any support layer, and / or any layer positioned between the efficiency layer and the support layer can have a corrugated configuration. Those skilled in the art will appreciate that a variety of other configurations are possible, and that the filter media can include any number of layers in various arrangements.

[0082] It should be understood that while some embodiments involve waved filter media, Figure 9A and Figure 9B Some filter media may have Figure 9A and / or Figure 9B As an example, a layer comprising a first plurality of peaks, such as a layer comprising a plurality of peaks that is irregular in one or more aspects, can be further undulated to form a second plurality of peaks by methods other than corrugation and can be positioned in a filter medium comprising one or more support layers and / or one or more outer or cover layers. Methods other than corrugation can be any of those described herein, such as pleating, folding, crimping, wrinkling, and / or heat shrinking.

[0083] Filter media comprising irregular structures and other structures, for example, filter media comprising one or more layers can be manufactured in various suitable ways. In an exemplary embodiment, the layer is corrugated (for example, a layer, an efficiency layer, a scrim, a nanofiber layer and / or a support layer comprising a plurality of peaks that are irregular in one or more aspects). The layer to be corrugated can be positioned adjacent to each other from the air inlet side to the air outlet side in a desired arrangement, and the combined layer can be transferred between a first moving surface and a second moving surface traveling at different speeds, for example, when the second surface travels at a speed lower than the speed of the first surface, between the first moving surface and the second moving surface. Suction force, for example, a vacuum force can be used to pull the layer toward the first moving surface, and then pull the layer toward the second moving surface when the layer travels from the first moving surface to the second moving surface. When the layer is transferred to the second moving surface, the speed difference can cause the layer to form a z-direction wave, thereby forming peaks and valleys in the layer. The speed of each surface can be changed to obtain the desired number of waves per inch. The distance between the surfaces can also be varied to determine the amplitude of the peaks and valleys, and in one exemplary embodiment, the distance is adjusted between 0.025 inches and 4 inches. For example, the amplitude of the peaks and waves can be between 0.1 inches and 4.0 inches, such as 0.1 inches to 1.0 inches, 0.1 inches to 2.0 inches, or 3.0 inches to 4.0 inches. For certain applications, the amplitude of the peaks and waves can be between 0.1 inches and 1.0 inches, 0.1 inches to 0.5 inches, or 0.1 inches to 0.3 inches. The characteristics of the different layers can also be varied to obtain the desired filter media construction. In one exemplary embodiment, the filter media has 2 to 6 waves per inch, wherein the height (total thickness) is within the range of between 0.025 inches and 2 inches, however this can vary significantly depending on the intended application. For example, in other embodiments, the filter media can have 2 to 4 waves per inch, such as 3 waves per inch. The total thickness of the media can be from 0.025 inches to 4.0 inches, such as from 0.1 inches to 1.0 inches, from 0.1 inches to 2.0 inches, or from 3.0 inches to 4.0 inches. For some applications, the total thickness of the media can be from 0.1 inches to 0.5 inches, or from 0.1 inches to 0.3 inches. Figure 9A As shown in , in some embodiments, a single wave W extends from the middle of one peak to the middle of an adjacent peak. The thickness of the waved filter media can be determined according to the Edana WSP 120.1 standard (2005) using a presser foot selected to have a 2 ounce load and a 1 square inch area.

[0084] exist Figure 9A In the embodiment shown, when the efficiency layer 12 and the support layers 14, 16 are corrugated, the resulting efficiency layer 12 will have a plurality of peaks P and a plurality of valleys T on each surface thereof (i.e., the air inlet side I and the air outlet side O), as shown in FIG. Figure 9C As shown in . Support layers 14 and 16 extend across peaks P and into valleys T, giving support layers 14 and 16 a wavy configuration. Those skilled in the art will understand that peaks P on the air inlet side I of efficiency layer 12 will have corresponding valleys T on the air outlet side O. Therefore, downstream support layer 14 will extend into valley T, and conversely, upstream support layer 16 will extend across the same valley T as peaks P. Because downstream support layer 14 extends into valley T on the air outlet side O of efficiency layer 12, downstream roughness layer 14 will maintain adjacent peaks P on the air outlet side O at a distance from each other, and adjacent valleys T on the air outlet side O at a distance from each other. Upstream support layer 16, if provided, will similarly maintain adjacent peaks P on the air inlet side I of efficiency layer 12 at a distance from each other, and adjacent valleys T on the air outlet side I of efficiency layer 12 at a distance from each other. Thus, the efficiency layer 12 has a significantly increased surface area compared to the surface area of ​​a fibrous filter layer in a flat configuration. In certain exemplary embodiments, the surface area in the corrugated configuration is increased by at least 50%, and in some cases as much as 120%, compared to the surface area of ​​the same layer in a flat configuration. In other words, the corrugated configuration can include at least 50%, or at least 120%, more filter media area per filter media footprint than an otherwise equivalent non-corrugated filter media.

[0085] In embodiments where the upstream support layer and / or downstream support layer holds one or more other layers in a wavy configuration, it may be desirable to reduce the amount of free volume (e.g., volume not occupied by any fibers) in the valleys. That is, a relatively high percentage of the volume in the valleys can be occupied by the support layer to provide structural support for the other layers. For example, at least 95% or substantially all of the available volume in the valleys can be filled with the support layer. The solidity of the support layer can be greater than or equal to 1%, greater than or equal to 1.25%, greater than or equal to 1.5%, greater than or equal to 2%, greater than or equal to 2.5%, greater than or equal to 3%, greater than or equal to 4%, greater than or equal to 5%, greater than or equal to 7.5%, greater than or equal to 10%, greater than or equal to 12.5%, greater than or equal to 15%, greater than or equal to 20%, or greater than or equal to 25%. The solidity of the support layer can be less than or equal to 30%, less than or equal to 25%, less than or equal to 20%, less than or equal to 15%, less than or equal to 12.5%, less than or equal to 10%, less than or equal to 7.5%, less than or equal to 5%, less than or equal to 4%, less than or equal to 3%, less than or equal to 2.5%, less than or equal to 2%, less than or equal to 1.5%, or less than or equal to 1.25%. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 1% and less than or equal to 30%, greater than or equal to 4% and less than or equal to 20%, or greater than or equal to 5% and less than or equal to 15%). Other ranges are also possible.

[0086] The solidity of the support layer can be determined by using the following formula: Solidity = [weight per unit area / (fiber density * thickness)] * 100%. The weight per unit area and thickness can be determined as described elsewhere in this document. Fiber density is equivalent to the average density of the one or more materials that form the fibers, which is typically given by the fiber manufacturer. The average density of the material that forms the fibers can be determined by: (1) determining the total volume of all fibers in the filter media; and (2) dividing the total mass of all fibers in the filter media by the total volume of all fibers in the filter media. If the mass and density of each type of fiber in the filter media are known, the volume of all fibers in the filter media can be determined by: (1) for each type of fiber, dividing the total mass of fibers of that type in the filter media by the density of fibers of that type; and (2) adding the volumes of each fiber type. If the mass and density of each type of fiber in the filter media are unknown, the volume of all fibers in the filter media can be determined according to Archimedes' principle.

[0087] In addition, if Figure 9A As shown in the exemplary embodiment of FIG, the support layer extends across the peaks and into the valleys so that the surface area of ​​the support layer in contact with the top layer 18A across the peaks is similar to the surface area of ​​the support layer in contact with the bottom layer 18B across the valleys. Figure 9B ) can be similar to the surface area of ​​the support layer across the valleys. For example, the surface area of ​​the support layer in contact with the top or bottom layer across the peaks can differ from the surface area of ​​the support layer in contact with the top or bottom layer across the valleys by less than 70%, less than 50%, less than 30%, less than 20%, less than 10%, or less than 5%.

[0088] In certain exemplary embodiments, downstream support layer 14 and / or upstream support layer 16 may have a greater fiber density at peaks than in valleys; and in some embodiments, the fiber mass at peaks is less than in valleys. This may be due to the roughness of downstream support layer 14 and / or upstream support layer 16 relative to efficiency layer 12. Specifically, the relatively fine nature of efficiency layer 12 causes downstream support layer 14 and / or upstream support layer 16 to conform around the waves formed in efficiency layer 12 as the layers transfer from the first moving surface to the second moving surface. Because support layers 14, 16 extend across peaks P, the distance they travel will be less than the distance each layer 14, 16 travels to fill the valleys. Consequently, support layers 14, 16 will compact at the peaks, thus having an increased fiber density at the peaks compared to the valleys through which the layers travel to form an annular configuration.

[0089] Once the layer is formed into a wavy configuration, the wavy shape can be maintained by activating the binder fibers (e.g., binder fibers in one or both support layers) to achieve bonding of the fibers. Various techniques can be used to activate the binder fibers. For example, if multicomponent fibers are used, such as bicomponent binder fibers having a core and a sheath, the binder fibers can be activated upon application of heat. If monocomponent binder fibers are used, the binder fibers can be activated upon application of heat, steam, and / or some other form of warm moisture. The top layer 18 ( Figure 9A ) and / or bottom layer 18B( Figure 9B ) are positioned on the upstream support layer 16 ( Figure 9A ) on top or downstream support layer 14B ( Figure 9B ) and are simultaneously or sequentially coupled to the upstream support layer 16 or the downstream support layer 14B, for example, by bonding. Those skilled in the art will also appreciate that various techniques other than using binder fibers may be used to optionally couple the layers to one another. The layers may also be separate adhesive layers, and / or the layers may be coupled to one another, including bonding, prior to corrugation.

[0090] The filter media described herein can be suitable for a variety of filtration applications. For example, the filter media described herein can be suitable for HVAC bag filters, HVAC panel filters, respiratory protection equipment, medical filters, vacuum cleaner filters, room air purifier filters, cabin air filters, heavy-duty air filters (e.g., air filters suitable for use in tractors and / or trucks), and hydraulic fluid filters. Some of the filter media described herein can be fluid filters, such as gas filters (e.g., air filters) and / or liquid filters (e.g., water filters, fuel filters).

[0091] In some embodiments, the filter media described herein is a high energy particulate air (HEPA) filter or an ultra-low penetration air (ULPA) filter. According to EN1822:2009, these filters are required to remove particles at efficiency levels greater than 99.95% and 99.9995%, respectively. In some embodiments, the filter media can remove particles at an efficiency greater than 95%, greater than 99.995%, greater than 99.99995%, or up to 99.999995%. In some embodiments, the filter media can be suitable for HVAC applications. That is, the filter media can have a particle efficiency 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%. Other types of filter media and efficiencies are also possible. In some embodiments, the filter media can be a HEPA filter, an ULPA filter, or an HVAC filter, and can be a component of a filter element as described in more detail below.

[0092] In some embodiments, filter medium described herein can be the component of filter element.That is to say, filter medium can be incorporated into the goods being suitable for being used by end-user.The limiting examples of suitable filter element comprises flat plate filter, V-type filter (V-bank filters) (comprising for example 1 to 24 V-shaped portions), cartridge filter, cylindrical filter, cone filter and curve filter.Filter element can have any suitable height (for example, for flat plate filter between 2 inches and 124 inches, for V-type filter between 4 inches and 124 inches, for cartridge filter and cylindrical filter between 1 inch and 124 inches).Filter element can also have any suitable width (for flat plate filter between 2 inches and 124 inches, for V-type filter between 4 inches and 124 inches).Some filter elements (for example, cartridge filter, cylindrical filter) can be characterized by diameter rather than width; These filter elements can have the diameter (for example, between 1 inch and 124 inches) of any suitable value. Filter elements typically include a frame that may be made from one or more materials such as cardboard, aluminum, steel, alloys, wood, and polymers.

[0093] In one embodiment, an article comprising a filter medium described herein may comprise a filter for indoor air filtration. Indoor air filtration may comprise industrial or commercial indoor air filtration. Indoor air filtration may comprise residential indoor air filtration.

[0094] In one embodiment, a filter for indoor air filtration can include a fan coil unit (FCU) filter element. In one embodiment, the FCU filter element includes the filter media described herein and is frameless.

[0095] In one embodiment, the filter for indoor air filtration may include an HVAC filter. The HVAC filter may include an HVAC bag filter or bag filter. The HVAC filter may include an HVAC panel filter.

[0096] HVAC panel filters using the filter media described herein allow for sustained efficiency. Typical MERV 13 panel filter efficiency drops from 90% to 50% over the life of the panel filter. In contrast, panel filters including the filter media described herein provide consistent efficiency over their life while meeting the restriction requirements.

[0097] In one embodiment, an article comprising the filter media described herein may comprise a respirator or respiratory protective device. Respirators using the filter media described herein are highly breathable. Respirators using the filter media described herein provide 50% lower breathing resistance while providing greater than 95% efficiency against viruses and particles.

[0098] In one embodiment, the respirator can be an elastomeric half-mask respirator. The elastomeric half-mask respirator can include a replaceable cartridge or filter and can be reusable. The elastomeric half-mask respirator can be configured to cover the nose and mouth and provide protection against gases, vapors, or particles when equipped with an appropriate cartridge or filter.

[0099] In one embodiment, the respirator can be an elastomeric full-face respirator. The elastomeric full-face respirator can include a replaceable canister, cartridge, or filter and can be reusable. The elastomeric full-face respirator can be configured to cover the face and eyes and provide protection against gases, vapors, or particles when equipped with an appropriate canister, cartridge, or filter.

[0100] In one embodiment, the respirator can be a filtering facepiece respirator. A filtering facepiece respirator can be disposable and configured to cover the nose and mouth. A filtering facepiece respirator can filter out particles such as dust, mist, and smoke. A filtering facepiece respirator does not provide protection against gases or vapors.

[0101] In one embodiment, the respirator can be a powered air-purifying respirator (PAPR). A PAPR can include a hood or helmet that covers the nose, mouth, and eyes and a battery-powered blower to draw air through an attached filter, canister, or cartridge. When equipped with appropriate filters, canisters, or cartridges, a PAPR can provide protection against gases, vapors, or particles.

[0102] In one embodiment, the filter media described herein can be used in a particulate filter respirator. The particulate filter respirator can include a specific filter respirator that falls within one of the ten categories of NIOSH-approved particulate filter respirators. In one embodiment, the particulate filter respirator can be selected from the group consisting of N95, N99, N100, R95, R99, R100, P95, P99, P100, and HE (High Efficiency Particulate Air). N95 particulate filter respirators filter at least 95% of airborne particles and are not resistant to oil. N99 particulate filter respirators filter at least 99% of airborne particles and are not resistant to oil. N100 particulate filter respirators filter at least 99.97% of airborne particles and are not resistant to oil. R95 particulate filter respirators filter at least 95% of airborne particles and are slightly resistant to oil. R99 particulate filter respirators filter at least 99% of airborne particles and are slightly resistant to oil. R100 particulate filter respirators filter at least 99.97% of airborne particles and are slightly resistant to oil. P95 particulate filter respirators filter at least 95% of airborne particles and are highly resistant to oil. P99 particulate filter respirators filter at least 99% of airborne particles and are highly resistant to oil. P100 particulate filter respirators filter at least 99.97% of airborne particles and are highly resistant to oil. HE particulate filter respirators filter at least 99.97% of airborne particles and are intended for use only with PAPRs, and PAPRs use only HE filters.

[0103] The filter media described herein may also be suitable for use in medical surgical gowns where it can provide protection against pathogens as well as high breathability and comfort. Due to the innovative higher surface area design of the media described herein, it is stretchable after lamination with a reversible stretch layer and other scrims. Such stretchability provides great comfort to the wearer around the elbows and knees in addition to providing a good seal around the cuffs of the gown. Another medical application suitable for the filter media described herein is a powered air-purifying respirator (PAPR) "surgical hood filter," where such media can deliver excellent filtration efficiency at a lower pressure drop, thereby reducing the PAPR's blower size and lowering its power consumption.

[0104] In another example, the filter media described herein can also be suitable for use in respiratory applications such as filtering facepiece respirators (FFR), elastomeric half mask respirators (EHMR), elastomeric full facepiece respirators, and powered air filtering respirators (PAPR). Under the NIOSH-42CFR84 standard, NIOSH-approved particulate filtering respirators are classified as follows: N95, N99, N100, R95, R99, R100, P84, P99, and P100. Comparable European classifications for such respirators can be found in EN149:2001 (FFP1, FFP2, and FFP3), EN140-half and quarter masks, and EN136-full masks. Other comparable classifications for such masks can be found in Australia / New Zealand AS / NZA1716:2012, China GB2626-2006, South Korea KMOEL-2017-64, and Japan JMHLW-Notification 214, 2018.

[0105] For the P series, the respirator devices must be strongly resistant to oil, and for this reason, some respirator manufacturers utilize a special surface coating technology called chemical vapor deposition of polyfluoroalkyl substances (PFAS) to improve the oleophobicity of the filter media used in such applications. Such a treatment utilizes compounds based on C3 or C6 fluorinated chemicals, which reduce the media's affinity for oil particles and significantly improve the paraffin oil loading curve of the P100 mask. This in turn helps media manufacturers achieve the strict efficiency performance requirements of P100 respirators without exceeding the pressure drop limit. In 2019, Germany proposed new regulations to the European Union to restrict the entry of perfluorohexanoic acid (PFHxA) into the market. The use of fluorocarbon-based "C6" water / oil repellents in European non-woven goods may end in time, and it is believed that in the future, all fluorocarbon-based water / oil repellents will be banned. In some embodiments of the present invention, the filter media comprises two or more meltblown layers that are undulated together, and without applying a CVD surface treatment for polyfluoroalkyl substances (PFAS), it achieves P-100 efficiency performance at a pressure drop 65% lower than the permitted limit. Such performance (PFAS-free P-series masks) is achieved by the media of the present invention having a lower pressure drop and a higher oil loading capacity due to the presence of surface undulation, without the need to apply harmful environmental chemicals such as PFAS. In addition, such masks will be highly breathable with a breathing resistance 40% to 60% lower than competitive media, and will better fit the wearer because they are inherently stretchable due to the presence of a reversible stretch layer.

[0106] In one embodiment, an article comprising the filter media described herein can include a medical filter. Surgical gowns and hoods using the filter media described herein provide stretchable fit and protection. In one embodiment, the stretchable protective garment can be a unitary component with suitable holes or openings for placement over various body parts of the user (e.g., ears in the case of a face mask respirator). The stretchable high-efficiency filter media described herein provides surgeons with high fit and comfort as well as N95 protection against particles, germs, and viruses.

[0107] In one embodiment, the medical filter may include a medical gown. The medical gown may include a surgical gown and / or a hood. According to the American National Standards Institute / Association of the Advancement of Medical Instrumentation (ANSI / AAMI) PB70, medical gowns may include Class 1, Class 2, Class 3, or Class 4 classifications. The ANSI / AAMI PB70 standard establishes a system for classifying protective clothing and sheets used in healthcare facilities based on their liquid barrier properties, and specifies relevant marking requirements and standardized test methods for determining compliance. Class 1 classification involves minimal risk use, such as during basic care, standard isolation, covering visitors with gowns, or in standard medical units. Class 2 classification involves low-risk use, such as during blood draws, suturing, use in intensive care units (ICUs) or pathology laboratories. Class 3 classification involves medium-risk use, such as during arterial blood draws, insertion of intravenous (IV) lines, in emergency rooms, or use for trauma cases. Level 4 classification involves high-risk use, such as during prolonged, fluid-intensive procedures, surgery, when pathogen resistance is required, or when infectious disease (non-airborne) is suspected.

[0108] In one embodiment, protective clothing materials and related methods and clothing are provided. In some embodiments, the protective clothing material can include a reversible stretch layer that acts as a barrier (e.g., an impermeable barrier) against certain fluids (e.g., body fluids, water) and microorganisms (e.g., bacteria, fungi, viruses). The barrier properties of the reversible stretch layer can be at least partially due to the structural uniformity (e.g., pore size uniformity, air permeability uniformity) of the reversible stretch layer, a suitable unit area weight and / or a relatively small pore size (e.g., mean flow pore size, maximum pore size) of the reversible stretch layer. In some embodiments, the reversible stretch layer can have a relatively high air permeability that imparts beneficial properties (e.g., relatively high airflow, breathability) to the protective clothing material without adversely affecting its protection rating (e.g., ANSI / AAMI level 4). In certain embodiments, the protective clothing material can also include one or more coarse fiber layers (e.g., spunbond webs) that impart beneficial properties (e.g., splash resistance) to the protective clothing material. The protective apparel materials described herein may be particularly useful in a variety of applications, including forming ANSI / AAMI Level 4 protective garments (eg, surgical gowns, surgical drapes, surgical gowns, surgical hoods).

[0109] In some embodiments, the reversible stretch layer can have a relatively small mean flow pore size (e.g., greater than or equal to about 2 microns and less than or equal to about 5 microns) and / or a maximum pore size (e.g., greater than or equal to about 6 microns and less than or equal to about 9 microns). The reversible stretch layer can also have a suitable unit area weight (e.g., greater than or equal to about 20 g / m2 and less than or equal to about 40 g / m2). In some embodiments, the reversible stretch layer can be relatively lightweight, breathable and / or air permeable. For example, the reversible stretch layer can have a relatively high air permeability (e.g., greater than or equal to about 4 CFM and less than or equal to about 10 CFM), and / or a relatively high water vapor transmission rate (e.g., greater than or equal to about 1,000 g / m2 / day). In certain embodiments, the reversible stretch layer can be relatively thin (e.g., greater than or equal to about 1 mil and less than or equal to about 6 mils).

[0110] In some embodiments, the reversible stretch layer can be relatively structurally uniform so that when measured over the entire reversible stretch layer, the variation or range of one or more structural characteristics is relatively small. For example, in some embodiments, when measured over the entire reversible stretch layer, the standard deviation of the mean flow pore size can be less than 1 micron. The difference between the maximum pore size and the mean flow pore size can be relatively small (e.g., greater than or equal to about 0 micron and less than or equal to about 10 microns). In some such embodiments, the ratio of the mean flow pore size to the maximum pore size can be greater than or equal to about 0.35 and less than or equal to about 0.55. In certain embodiments, when measured over the entire reversible stretch layer, the standard deviation of the air permeability can be less than 1 CFM.

[0111] In some embodiments, the protective clothing material can include one or more nonwoven webs or layers having a portion (e.g., surface, interior, entirety) that repels a fluid (e.g., hydrophilic fluid, aqueous fluid, body fluid). In such cases, the nonwoven web or layer can substantially block the transmission of fluid droplets through the protective clothing material. For example, a coarse fiber layer can repel fluid droplets (e.g., aqueous fluid, body fluid, hydrophilic fluid). As another example, a coarse fiber layer can repel droplets of a specific size, and the fiber layer can repel fluid droplets that are not repelled and / or removed by the coarse fiber layer. For example, the fiber layer can be designed to repel smaller droplets that bypass the coarse fiber layer. In certain embodiments, the protective clothing material includes one or more nonwoven webs or layers (e.g., coarse fiber layer, fiber layer) having a portion (e.g., surface, interior, entirety) that repels a hydrophilic fluid (e.g., aqueous fluid, body fluid). In some such embodiments, at least a portion of a nonwoven web or layer can be hydrophobic. For example, the nonwoven web may include fibers formed from a hydrophobic material (eg, polypropylene) and / or may be modified with a hydrophobic material.

[0112] In some embodiments, as described in more detail below, the protective clothing material may include one or more modified nonwoven webs or layers (e.g., a surface-modified fiber layer, a surface-modified rough layer, a surface-modified nonwoven web). In some such embodiments, at least a portion (e.g., the surface, the interior, substantially all, the entirety) of the nonwoven web or layer may be modified to repel fluids (e.g., aqueous fluids, body fluids). For example, the nonwoven web or layer may be modified to change and / or reduce the wettability of at least a portion (e.g., at least one surface of the layer) of the nonwoven web or layer relative to a specific fluid (e.g., to make the layer or nonwoven web more hydrophobic). For example, a hydrophobic surface with a water contact angle of 100° can be modified to have a water contact angle greater than 100°, such as 130° or greater. In another example, a hydrophobic surface with a water contact angle of 100° can be modified to have a water contact angle of 150° or greater. In some embodiments, a surface with a contact angle greater than or equal to 150° may be referred to as a "superhydrophobic surface." Superhydrophobic surfaces can also have low contact angle hysteresis.

[0113] As used herein, the terms "repel" and "repelling" may refer to the ability of a fluid to interact with a nonwoven web or layer such that the fluid has a contact angle of greater than or equal to 90 degrees relative to at least a portion (e.g., a surface) of the nonwoven web or layer. As used herein, the term "wettability" may refer to the ability of a fluid to interact with a nonwoven web or layer such that the fluid has a contact angle of less than 90 degrees relative to at least a portion (e.g., a surface) of the nonwoven web or layer.

[0114] In some embodiments, the reversible stretch layer can be splash resistant. As used herein, the terms "splash resistant" (also referred to as spray impact resistant) and "splash resistance" (also referred to as spray impact resistant) have their common meanings in the art and can refer to the ability of a layer to resist the penetration of a spray fluid. In some embodiments, the splash resistance of a layer and / or protective clothing material can be determined using AATCC 42, which measures resistance to water penetration by impact. In brief, 500 mL of deionized water was sprayed against the taut surface of a test specimen backed by pre-weighed blotting paper using a 2-inch diameter nozzle with 25 holes at a height of 0.6 m. The test specimen backed by pre-weighed blotting paper was angled at 45 degrees. The blotting paper was then reweighed to determine water permeability and the specimen was classified accordingly. If the weight difference was less than 1.0 g, the specimen was splash resistant. In some embodiments, the weight difference of the reversible stretch layer and / or protective garment material according to this test can be less than 1.0 g (e.g., less than 0.8 g, less than 0.6 g, less than 0.3 g).

[0115] As described herein, protective clothing materials comprising one or more reversibly stretch fiber layers can be particularly useful in a variety of applications, including forming ANSI / AAMI Level 4 protective garments (e.g., surgical gowns, surgical hoods). In some embodiments, the protective clothing material can have the required protection rating and good wearability (e.g., comfort). For example, in some embodiments, the protective clothing material and / or the reversible stretch layer can pass the ASTM F1671-13 Method B (i.e., viral penetration) and ASTM F1670-08 (2014) e1 Method (i.e., synthetic blood penetration) tests required for ANSI / AAMI Level 4 certification.

[0116] In one group of embodiments, chemical vapor deposition is used to modify the surface and / or interior of a nonwoven web, layer, or protective clothing material, such as a surface, interior, and / or at least a portion of the entirety of a nonwoven web, layer, or protective clothing material. In chemical vapor deposition, the nonwoven web is exposed to a gaseous reactant from a gas or liquid vapor, which is deposited onto the nonwoven web under high energy level excitation (e.g., heat, microwaves, UV, electron beams, or plasma). Optionally, a carrier gas such as oxygen, helium, argon, and / or nitrogen may be used.

[0117] Other vapor deposition 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), and chemical beam epitaxy (CBE).

[0118] In physical vapor deposition (PVD), thin films are deposited by condensing the desired film material in vaporized form onto a substrate. This method involves a physical process such as high-temperature vacuum evaporation followed by condensation or plasma sputtering bombardment rather than a chemical reaction.

[0119] After the coating is applied to the nonwoven web, layer or protective clothing material, the coating can be dried by any suitable method. Non-limiting examples of drying methods include using a light dryer, an infrared dryer, a hot air oven steam heating drum or any suitable type of dryer familiar to those of ordinary skill in the art.

[0120] In some embodiments, at least a portion of a nonwoven web, layer, or protective garment material can be modified (e.g., coated) without substantially blocking the pores of the nonwoven web. In some cases, substantially all of the fibers can be coated without substantially blocking the pores. In some embodiments, a nonwoven web, layer, or protective garment material can be coated with a relatively high weight percentage of a resin or material using the methods described herein (e.g., by dissolving and / or suspending one or more materials in a solvent to form a resin) without blocking the pores of the nonwoven web, layer, or protective garment material.

[0121] Protective clothing materials can be incorporated into various protective clothing for various environments including operating rooms or any other place where ANSI / AAMI level 4 protective clothing is required. Protective clothing materials can be used to form surgical gowns (e.g., surgical hoods, surgical gowns). The term "surgical gown" has its ordinary meaning in the art and can comply with 21C.FR§878.4040(a)(2012). For example, surgical gowns can be devices intended to be worn by operating room personnel during surgical procedures to protect both surgical patients and operating room personnel from the effects of transfer of microorganisms, body fluids, and particulate matter. Non-limiting examples include surgical caps, hoods, face masks, gowns, operating room shoes and shoe covers, and isolation masks and gowns. In certain embodiments, protective clothing materials can be used to form surgical sheets. The term "surgical sheets" has its ordinary meaning in the art and can comply with 21C.FR§878.4370(a)(2012). For example, a surgical sheet can be a device made of natural or synthetic materials that is intended to be used as a protective patient cover to isolate the site of the surgical incision from microorganisms and other contaminants. In certain embodiments, the device can include a plastic wound protector that can be adhered to the skin around the surgical incision or placed in the wound to cover its exposed edges. In some cases, the device can include a self-retaining finger cuff that is intended to allow the surgeon's finger to be repeatedly inserted into the rectum during the execution of transurethral prostatectomy. Those of ordinary skill in the art will appreciate the method for forming surgical garments from protective clothing materials. Typically, protective clothing materials are cut and sewn together as in traditional clothing manufacturing, except that heat sealing and / or ultrasonic seams are used to replace traditional suture techniques involving lines. Heat sealing or ultrasonic seams are used to form a good seal (e.g., an impermeable seal) while maintaining the integrity and barrier protection of the garment.

[0122] During use, the protective clothing material mechanically captures contaminants (e.g., body fluids, microorganisms) and prevents penetration. The protective clothing material does not need to be charged to enhance the capture of contaminants. Therefore, in some embodiments, the protective clothing material is not charged. However, in some embodiments, the protective clothing material can be charged.

[0123] In one embodiment, an article comprising the filter media described herein can comprise a vacuum cleaner filter. In one embodiment, the vacuum cleaner filter can comprise a vacuum bag filter. For example, the bag in a vacuum cleaner can comprise a primary or initial filter, and in the case of cartridge and bag upright vacuum cleaners, the bag filter can act as a central system for filtration. A vacuum bag filter can comprise the filter media described herein. As air travels through the vacuum to the bag, it can escape through tiny pores, with any dust or dirt larger than these pores being captured in the vacuum bag.

[0124] In one embodiment, the vacuum cleaner filter can include a vacuum cartridge filter. Such a vacuum cartridge filter in a vacuum cleaner can be disposable. The cartridge filter can also be equipped with a rubber housing that can be gently slid into an enclosed area within the vacuum machine. In some embodiments, the vacuum cartridge filter includes a HEPA filter or an ULPA filter. High-efficiency particulate air (HEPA) vacuum cartridge filters can capture 99.97% of matter that is 0.3 microns or larger. Ultra-low penetration air (ULPA) vacuum cartridge filters can capture 99.99% of dust, dirt, mold, bacteria, or any other airborne particles with a diameter of 0.12 microns.

[0125] The filter media described herein can be suitable for a variety of filtration applications. For example, the filter media described herein can be suitable for HVAC bag filters. Bag filters or bag filters are used in HVAC applications as high-efficiency final filters in medical, commercial, industrial and institutional applications, and as pre-filters in HEPA devices. A full-size standard bag filter is typically 24 inches by 24 inches (W×H), and its depth can vary between 12 inches and 36 inches. The frame (manifold frame) material is typically recycled plastic or galvanized steel. The number of filter bags / elements can vary between 1 and 12 bags, and the filter media can be synthetic or glass fiber combined with activated carbon for removing gaseous pollutants in addition to particulate pollutants.

[0126] Such filters are typically rated according to the Ashrae 52.2 test standard or the ISO-16890 test standard. ASHRAE 52.2 tests a variety of particles (0.3 microns to 10 microns). MERV (Minimum Efficiency Reporting Value) ratings from 1 to 16 are meant to be performance-related—the higher the number, the more effective the filter. Filters are loaded with Ashrae dust until they reach the manufacturer's recommended final pressure drop to measure the dust holding capacity (DHC) associated with the filter's service life. According to Table 1 below, fractional efficiency at different intervals during the dust load using potassium chloride (KCl) as an aerosol challenge is measured to calculate the MERV rating. For critical applications where stable efficiency throughout the life of the filter is crucial, it is preferred to rate the filter according to Ashrae 52.2 (Appendix-J). Appendix J was added to the ASHRAE 52.2 standard in 2008 as a non-ANSI-approved optional adjustment step to provide a method for identifying efficiency drops. The reported value according to Appendix J is referred to as MERV 'A'. Filters tested in accordance with Standard 52.2 with the Appendix J option have both MERV and MERV 'A'.

[0127] Table 1. Ashrae MERV ratings and their efficiency ranges

[0128]

[0129] Under the ISO 16890 standard, air filters are classified based on their particulate matter efficiency, which can be summarized in Table 2 below. Air filters classified under the three PM classes must achieve a minimum particle removal efficiency of 50%. Like ASHRAE 52.2 with Appendix J, the ISO 16890 test protocol incorporates a step to account for any electrostatic charge. In the case of ISO 16890, the final efficiency value is calculated based on the average efficiency of the filter with and without a charge. The filter is then assigned a percentage that correlates to the PM group into which the filter can be classified. Percentages are rounded down to the nearest multiple of 5%.

[0130] Table 2: Filter classification according to ISO 16890.

[0131]

[0132] For another situation, the filter media described herein can be applicable to HVAC V-design filters. V-type filters are compact and are used as high-efficiency final filters in medical, commercial, industrial and institutional applications in HVAC applications, as well as as pre-filters in HEPA devices. These V-type filters in air supply are typically used in the second filter stage or as pre-filters for clean room process applications. Full-size standard elements are typically 24 inches by 24 inches (W×H), and their depth can be as high as 12 inches. The number of V-shaped portions / elements can vary between 1 and 8 V-shaped portions, and they are constructed with small pleated sheets of filter media, which can be synthetic or glass fiber combined with activated carbon. Such filters are typically rated according to the Ashrae 52.2 test standard or the ISO-16890 test standard as previously described.

[0133] For another application, the filter media described herein can be suitable for HVAC box filter design. Box filters are compact and used as high-efficiency final filters in medical, commercial, industrial and institutional applications in HVAC applications, as well as pre-filters in HEPA devices. These compact box filters in air supply are typically used in the second filter stage or as pre-filters for clean room process applications. Full-size standard elements are typically 24 inches by 24 inches (W×H), and their depth can be as high as 12 inches. The number of pleats per inch in such element designs can vary between 0.25 PPI and 12 PPI, and they are constructed with small pleated panels of filter media or support media to counteract varying airflows, or they can be constructed with deep pleats in which the pleats are separated by aluminum media separators to ensure uniform airflow and durable filter assemblies. Typical filter media in such filter designs can be synthetic or glass fiber combined with activated carbon. Such filters are typically rated according to the Ashrae 52.2 test standard or the ISO-16890 test standard as previously described.

[0134] For another case, the filter media described herein can be applicable to HVAC panel filter designs. Panel filters are used as primary filters in medical, commercial, industrial and institutional applications in HVAC applications, as well as as pre-filters to protect and extend the life of valuable downstream filters. They typically capture larger particles of 10 microns and above in ventilation intake or recirculated air. Full-size standard panel filter elements are typically 24 inches by 24 inches (W×H), and their depth can be as high as 6 inches. The number of pleats per inch in such element designs can vary between 0.25 PPI and 6 PPI, and they are constructed with pleated wire mesh backing media for higher strength and durability. Typical filter media in such filter designs can be synthetic or cotton / polyester blends or combined with activated carbon. Such filters are typically rated according to the Ashrae 52.2 test standard or the ISO-16890 test standard as previously described.

[0135] The filter media described herein can also be adapted for use in cut-frame panel filter designs that do not require media pleating. This technological advancement is due to the innovative design of the media described herein, which has an expanded surface area in an undulating pattern. Such filters are typically rated according to the Ashrae 52.2 test standard or the ISO-16890 test standard, as previously described.

[0136] In another embodiment, the filter media described herein can also be used in cut-frame fan-coil unit filters for hospitals and offices. This technological advancement is due to the innovative design of the media described herein, which has an extended surface area in an undulating pattern, thereby providing low pressure drop and high dust holding capacity. Such filters are generally rated according to the Ashrae 52.2 test standard or the ISO-16890 test standard, as previously described.

[0137] In one embodiment, an article comprising the filter media described herein may comprise an indoor air purifier filter. Dust, pollen, pet dander, mold spores, and dust mite feces may act as allergens that trigger allergies in allergy-sensitive people. Smoke particles, viruses, bacteria, mold, and volatile organic compounds (VOCs) may also pose health risks. An indoor air purifier or air cleaner is a device that includes a filter and removes such pollutants from indoor air to improve indoor air quality.

[0138] In one embodiment, an article including the filter media described herein can include a cabin air filter. Cabin air filters in vehicles help remove harmful pollutants, including pollen and dust, from the air breathed by occupants of the vehicle.

[0139] In one embodiment, an article comprising the filter media described herein can include a heavy-duty air filter. The heavy-duty air filter can be used for heavy-duty engine air filtration and can be suitable for use in large and / or heavy equipment such as tractors and trucks.

[0140] In one embodiment, an article comprising the filter media described herein may include a hydraulic fluid filter. Hydraulic applications of ESA filter media, such as those for wind turbines, provide high dirt holding capacity. ESA hydraulic media offers up to 100% higher dirt holding capacity, which doubles service life and reduces maintenance costs.

[0141] The filter media described herein can operate advantageously in one or more ways. In some embodiments, the filter media has a desirably high gamma value, where gamma is a rating applied to filter media based on the relationship between penetration and pressure drop across the media, or is the particle efficiency as a function of pressure drop across the media or web. Generally, higher gamma values ​​indicate better filtration performance, i.e., high particle efficiency as a function of pressure drop. As described above, and without wishing to be bound by any particular theory, increasing the surface area of ​​a filter media will generally increase its gamma. Thus, filter media described herein having a relatively high surface area, such as filter media comprising an irregular structure and / or a plurality of peaks that are irregular in one or more respects, can also have a relatively high gamma value. γ is defined by the formula: γ = (-log 10(initial penetration % / 100) / initial pressure drop, mmH2O)×100. Penetration, which is usually expressed as a percentage, is defined as follows: Penetration (%)=(C / C0)*100, where C is the concentration of particles after passing through the filter, and C0 is the concentration of particles before passing through the filter. The initial penetration is the penetration measured when the filter medium is first exposed to the particles, and the initial pressure drop is the pressure drop measured when the filter medium is first exposed to the particles. The penetration and γ described herein are the penetration and γ measured using NaCl particles with an average diameter of 0.26 microns. Both penetration and pressure drop can be measured by using a TSI 8130 Automatic Filter Tester (8130 CertiTest from TSI) for penetration values ​​exceeding 0.001%. TM Filter Tester) and the TSI 3160 Automatic Filter Tester for penetration values ​​less than or equal to 0.001%. Both instruments have an area of ​​100 cm 2 The circular opening is used to analyze flat-sheet filter media.

[0142] When measuring γ, a TSI 8130 automatic filter tester or a TSI 3160 automatic filter tester is used to blow a NaCl aerosol consisting of NaCl particles with an average diameter of 0.26 microns at the filter medium. The NaCl particles can be generated from a 2% by weight NaCl aqueous solution by blowing dilution air through the NaCl aqueous solution at a pressure of 30 psi at a flow rate of 70 L / min to cause the solution to form a NaCl aerosol. The aerosol is then blown through the filter medium at a pressure of 30 psi and a flow rate of 32 L / min (which corresponds to a face velocity of 5.3 cm / sec). While the NaCl aerosol is blown by the TSI 8130 automatic filter tester or the TSI 3160 automatic filter tester, the pressure drop across the filter medium and the penetration rate of the NaCl aerosol are measured simultaneously by two condensation particle counters (one upstream of the filter medium and one downstream of the filter medium). The particle collection efficiency is reported at the start of the test and is the percentage of upstream challenge particles that are collected by the filter at the start of the test. The initial pressure drop is also measured at the start of the test.

[0143] In some embodiments, the filter media has a gamma greater than or equal to 8, greater than or equal to 10, greater than or equal to 15, greater than or equal to 20, greater than or equal to 25, greater than or equal to 30, greater than or equal to 40, greater than or equal to 50, greater than or equal to 75, greater than or equal to 100, greater than or equal to 125, greater than or equal to 150, greater than or equal to 175, greater than or equal to 200, greater than or equal to 225, greater than or equal to 250, greater than or equal to 275, greater than or equal to 300, greater than or equal to 330, greater than or equal to 350, greater than or equal to 375, greater than or equal to 400, greater than or equal to 450, greater than or equal to 500, greater than or equal to 600, greater than or equal to 700, greater than or equal to 800, greater than or equal to 900, or greater than or equal to 1000. In some embodiments, the filter media has a gamma of 1200 or less, 1000 or less, 900 or less, 800 or less, 700 or less, 600 or less, 500 or less, 450 or less, 400 or less, 375 or less, 350 or less, 330 or less, 300 or less, 275 or less, 250 or less, 225 or less, 200 or less, 175 or less, 150 or less, 125 or less, 100 or less, 75 or less, 50 or less, 40 or less, 30 or less, 25 or less, 20 or less, 15 or less, or 10 or less. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 8 and less than or equal to 1200, greater than or equal to 8 and less than or equal to 400, greater than or equal to 25 and less than or equal to 330, greater than or equal to 30 and less than or equal to 330, or greater than or equal to 600 and less than or equal to 1200). Other ranges are also possible.

[0144] As described above, some filter media described herein include irregular structures that produce one or more resulting advantages. The irregular structure can be in the form of an irregular surface structure. As an example, it can take the form of a plurality of peaks that are irregular in one or more aspects in the surface. As another example, it can take the form of a plurality of peaks that are irregular in one or more aspects and / or extend through one or more layers (e.g., in the case of an undulating layer). For example, the filter medium can include a surface that is present in one or more of the following types of layers and / or extend through a plurality of peaks in one or more of the following types of layers: an efficiency layer, a nanofiber layer, a carrier layer, and a scrim. In some embodiments, the filter medium includes a plurality of peaks that extend through the entire filter medium. In other words, the filter medium can only include layers that undulate together and wherein the undulations take the form of a plurality of peaks that are irregular in one or more aspects. Several features of a plurality of peaks that are irregular in one or more aspects are described below. It should be understood that this description may refer to peaks that are present at the surface of the filter media, at the surface of one or more layers thereof, extend through the thickness of the filter media, and / or extend through one or more layers thereof. These features may be characteristics of peaks in one or more contoured layers and / or may not be characteristics of peaks in contoured layers.

[0145] When the filter media includes a plurality of peaks, such as a plurality of peaks that are irregular in one or more aspects, the plurality of peaks can have a particularly advantageous average peak height. For example, the average peak height of the plurality of peaks can be greater than or equal to 0.3 mm, greater than or equal to 0.5 mm, greater than or equal to 0.75 mm, greater than or equal to 1 mm, greater than or equal to 1.5 mm, greater than or equal to 2 mm, greater than or equal to 2.5 mm, greater than or equal to 3 mm, greater than or equal to 4 mm, greater than or equal to 5 mm, greater than or equal to 6 mm, greater than or equal to 7 mm, greater than or equal to 8 mm, greater than or equal to 9 mm, greater than or equal to 10 mm, greater than or equal to 11 mm, or greater than or equal to 13 mm. In some embodiments, the filter media comprises a plurality of peaks having an average peak height of less than or equal to 15 mm, less than or equal to 13 mm, less than or equal to 11 mm, less than or equal to 10 mm, less than or equal to 9 mm, less than or equal to 8 mm, less than or equal to 7 mm, less than or equal to 6 mm, less than or equal to 5 mm, less than or equal to 4 mm, less than or equal to 3 mm, less than or equal to 2.5 mm, less than or equal to 2 mm, less than or equal to 1.5 mm, less than or equal to 1 mm, less than or equal to 0.75 mm, or less than or equal to 0.5 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.3 mm and less than or equal to 15 mm, greater than or equal to 0.3 mm and less than or equal to 10 mm, greater than or equal to 1 mm and less than or equal to 8 mm, or greater than or equal to 3 mm and less than or equal to 7 mm). Other ranges are also possible. The average peak height can be determined by finding the peak heights of the peaks that make up the plurality of peaks using a scanning optical microscope, as described above, and then averaging these peak heights to obtain the average peak height.

[0146] When the filter media comprises a plurality of peaks, for example, a plurality of peaks that are irregular in one or more aspects, the plurality of peaks can have a particularly advantageous peak height standard deviation. For example, the peak height standard deviation of the plurality of peaks can be greater than or equal to 0.1 mm, greater than or equal to 0.15 mm, greater than or equal to 0.2 mm, greater than or equal to 0.25 mm, greater than or equal to 0.3 mm, greater than or equal to 0.4 mm, greater than or equal to 0.5 mm, greater than or equal to 0.75 mm, greater than or equal to 1 mm, greater than or equal to 1.25 mm, greater than or equal to 1.5 mm, greater than or equal to 1.75 mm, greater than or equal to 2 mm, greater than or equal to 2.25 mm, greater than or equal to 2.5 mm, or greater than or equal to 2.75 mm. In some embodiments, the filter media comprises a plurality of peaks having a peak height standard deviation of less than or equal to 3 mm, less than or equal to 2.75 mm, less than or equal to 2.5 mm, less than or equal to 2.25 mm, less than or equal to 2 mm, less than or equal to 1.75 mm, less than or equal to 1.5 mm, less than or equal to 1.25 mm, less than or equal to 1 mm, less than or equal to 0.75 mm, less than or equal to 0.5 mm, less than or equal to 0.4 mm, less than or equal to 0.3 mm, less than or equal to 0.25 mm, less than or equal to 0.2 mm, or less than or equal to 0.15 mm. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.1 mm and less than or equal to 3 mm, greater than or equal to 0.15 mm and less than or equal to 1.5 mm, or greater than or equal to 0.2 mm and less than or equal to 1 mm). Other ranges are also possible. The peak height standard deviation can be determined by finding the peak heights of the peaks that make up the plurality of peaks using a scanning optical microscope as described above, and then determining the standard deviation of the peak heights using standard statistical techniques to obtain the peak height standard deviation.

[0147] When the filter media comprises a plurality of peaks, such as a plurality of peaks that are irregular in one or more respects, the plurality of peaks can have a particularly favorable ratio of peak height standard deviation to average peak height. For example, the ratio of the standard deviation of the peak heights to the average peak height for the plurality of peaks can be greater than or equal to 0.03, greater than or equal to 0.035, greater than or equal to 0.04, greater than or equal to 0.045, greater than or equal to 0.05, greater than or equal to 0.055, greater than or equal to 0.06, greater than or equal to 0.065, greater than or equal to 0.07, greater than or equal to 0.075, greater than or equal to 0.08, greater than or equal to 0.09, greater than or equal to 0.1, greater than or equal to 0.15, greater than or equal to 0.2, greater than or equal to 0.25, greater than or equal to 0.3, greater than or equal to 0.35, greater than or equal to 0.4, greater than or equal to 0.45, greater than or equal to 0.5, greater than or equal to 0.55, greater than or equal to 0.6, greater than or equal to 0.65, greater than or equal to 0.7, or greater than or equal to 0.75. In some embodiments, the filter media comprises a plurality of peaks having a ratio of peak height standard deviation to average peak height of less than or equal to 0.8, less than or equal to 0.75, less than or equal to 0.7, less than or equal to 0.65, less than or equal to 0.6, less than or equal to 0.55, less than or equal to 0.5, less than or equal to 0.45, less than or equal to 0.4, less than or equal to 0.35, less than or equal to 0.3, less than or equal to 0.25, less than or equal to 0.2, less than or equal to 0.15, less than or equal to 0.1, less than or equal to 0.09, less than or equal to 0.08, less than or equal to 0.075, less than or equal to 0.07, less than or equal to 0.065, less than or equal to 0.06, less than or equal to 0.055, less than or equal to 0.05, less than or equal to 0.045, less than or equal to 0.04, or less than or equal to 0.035. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.03 and less than or equal to 0.8, greater than or equal to 0.05 and less than or equal to 0.6, or greater than or equal to 0.07 and less than or equal to 0.5). Other ranges are also possible. The ratio of the peak height standard deviation to the average peak height can be determined by finding the peak height standard deviation and the average peak height as described above, and then taking their ratio.

[0148] When the filter media comprises a plurality of peaks, such as a plurality of peaks that are irregular in one or more aspects, the plurality of peaks can have a particularly advantageous average peak spacing. For example, the average peak spacing of the plurality of peaks can be greater than or equal to 1 mm, greater than or equal to 1.5 mm, greater than or equal to 2 mm, greater than or equal to 2.5 mm, greater than or equal to 3 mm, greater than or equal to 3.5 mm, greater than or equal to 4 mm, greater than or equal to 5 mm, greater than or equal to 6 mm, greater than or equal to 7 mm, greater than or equal to 8 mm, greater than or equal to 9 mm, greater than or equal to 10 mm, greater than or equal to 12 mm, greater than or equal to 14 mm, greater than or equal to 16 mm, or greater than or equal to 18 mm. In some embodiments, the filter media comprises a plurality of peaks having an average peak-to-peak spacing of less than or equal to 20 mm, less than or equal to 18 mm, less than or equal to 16 mm, less than or equal to 14 mm, less than or equal to 12 mm, less than or equal to 10 mm, less than or equal to 9 mm, less than or equal to 8 mm, less than or equal to 7 mm, less than or equal to 6 mm, less than or equal to 5 mm, less than or equal to 4 mm, less than or equal to 3.5 mm, less than or equal to 3 mm, less than or equal to 2.5 mm, less than or equal to 2 mm, or less than or equal to 1.5 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 mm and less than or equal to 20 mm, greater than or equal to 2 mm and less than or equal to 14 mm, or greater than or equal to 3 mm and less than or equal to 10 mm). Other ranges are also possible. The average peak-to-peak spacing can be determined by finding the spacing between each peak and its two nearest neighbors using a scanning optical microscope as described above, and then averaging these spacings to obtain the average peak-to-peak spacing.

[0149] When the filter media comprises a plurality of peaks, for example, a plurality of peaks that are irregular in one or more aspects, the plurality of peaks can have a particularly advantageous standard deviation of the peak spacing. For example, the standard deviation of the peak spacing of the plurality of peaks can be greater than or equal to 0.2 mm, greater than or equal to 0.25 mm, greater than or equal to 0.3 mm, greater than or equal to 0.35 mm, greater than or equal to 0.4 mm, greater than or equal to 0.45 mm, greater than or equal to 0.5 mm, greater than or equal to 0.6 mm, greater than or equal to 0.8 mm, greater than or equal to 1 mm, greater than or equal to 2 mm, greater than or equal to 3 mm, greater than or equal to 4 mm, greater than or equal to 5 mm, greater than or equal to 6 mm, greater than or equal to 7 mm, greater than or equal to 8 mm, or greater than or equal to 9 mm. In some embodiments, the filter media comprises a plurality of peaks having a peak spacing standard deviation of less than or equal to 10 mm, less than or equal to 9 mm, less than or equal to 8 mm, less than or equal to 7 mm, less than or equal to 6 mm, less than or equal to 5 mm, less than or equal to 4 mm, less than or equal to 3 mm, less than or equal to 2 mm, less than or equal to 1 mm, less than or equal to 0.8 mm, less than or equal to 0.6 mm, less than or equal to 0.5 mm, less than or equal to 0.45 mm, less than or equal to 0.4 mm, less than or equal to 0.35 mm, less than or equal to 0.3 mm, or less than or equal to 0.25 mm. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.2 mm and less than or equal to 10 mm, greater than or equal to 0.3 mm and less than or equal to 7 mm, or greater than or equal to 0.4 mm and less than or equal to 4 mm). Other ranges are also possible. The peak spacing standard deviation can be determined by finding the spacing between each peak and its two nearest neighbors using a scanning optical microscope as described above, and then using standard statistical techniques to determine the standard deviation of the nearest neighbor peak spacings.

[0150] When the filter media comprises a plurality of peaks, for example, a plurality of peaks that are irregular in one or more aspects, the plurality of peaks can have a particularly advantageous ratio of the standard deviation of the peak spacing to the average peak spacing. For example, the ratio of the standard deviation of the peak spacing to the average peak spacing for the plurality of peaks can be greater than or equal to 0.08, greater than or equal to 0.085, greater than or equal to 0.09, greater than or equal to 0.095, greater than or equal to 0.1, greater than or equal to 0.125, greater than or equal to 0.15, greater than or equal to 0.2, greater than or equal to 0.25, greater than or equal to 0.3, greater than or equal to 0.35, greater than or equal to 0.4, greater than or equal to 0.45, greater than or equal to 0.5, greater than or equal to 0.6, greater than or equal to 0.7, greater than or equal to 0.8, or greater than or equal to 0.9. In some embodiments, the filter media comprises a plurality of peaks having a ratio of the standard deviation of the peak spacing to the average peak spacing of less than or equal to 1, less than or equal to 0.9, less than or equal to 0.8, less than or equal to 0.7, less than or equal to 0.6, less than or equal to 0.5, less than or equal to 0.45, less than or equal to 0.4, less than or equal to 0.35, less than or equal to 0.3, less than or equal to 0.25, less than or equal to 0.2, less than or equal to 0.15, less than or equal to 0.1, less than or equal to 0.125, less than or equal to 0.1, less than or equal to 0.095, less than or equal to 0.09, or less than or equal to 0.085. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.08 and less than or equal to 1, greater than or equal to 0.15 and less than or equal to 0.8, or greater than or equal to 0.15 and less than or equal to 0.5). Other ranges are also possible. The ratio of the peak spacing standard deviation to the average peak spacing can be determined by finding the peak spacing standard deviation and the average peak spacing as described above and then taking their ratio.

[0151] The filter media described herein can have a favorable average surface height. In some embodiments, the filter media includes a layer having a favorable average surface height that includes a plurality of peaks that are irregular in one or more aspects. In some embodiments, the average surface height of the filter media (and / or the layer containing a plurality of irregular peaks therein) is greater than or equal to 0.3 mm, greater than or equal to 0.5 mm, greater than or equal to 0.75 mm, greater than or equal to 1 mm, greater than or equal to 1.5 mm, greater than or equal to 2 mm, greater than or equal to 2.5 mm, greater than or equal to 3 mm, greater than or equal to 4 mm, greater than or equal to 5 mm, greater than or equal to 6 mm, greater than or equal to 7 mm, greater than or equal to 8 mm, or greater than or equal to 9 mm. In some embodiments, the average surface height of the filter medium (and / or a layer thereof comprising a plurality of irregular peaks) is less than or equal to 10 mm, less than or equal to 9 mm, less than or equal to 8 mm, less than or equal to 7 mm, less than or equal to 6 mm, less than or equal to 5 mm, less than or equal to 4 mm, less than or equal to 3 mm, less than or equal to 2.5 mm, less than or equal to 2 mm, less than or equal to 1.5 mm, less than or equal to 1 mm, less than or equal to 0.75 mm, or less than or equal to 0.5 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.3 mm and less than or equal to 10 mm, greater than or equal to 1 mm and less than or equal to 8 mm, or greater than or equal to 3 mm and less than or equal to 7 mm). Other ranges are also possible. As used herein, the average surface height of the filter medium and / or a layer thereof is the average of the relative heights of each point in the relative surface topography of the filter medium and / or a layer thereof after a selected amount of computational processing. The relative surface topography of the filter medium and / or a layer thereof can be determined using scanning optical microscopy as described above. Then, steps (1) and (2) of the process for determining peak heights described above can be performed to process the resulting data. Finally, the processed data can be averaged to obtain an average surface height. If a layer having an average surface height within one or more of the ranges listed above is not on the outer surface of the filter medium (e.g., if it is covered by a relatively flat outer layer or cover layer), one or more layers positioned outside of the relevant layer can be removed so that the relevant layer is exposed, and the average surface height of the exposed relevant layer can be measured by optical microscopy as described above.

[0152] The filter media described herein can have a variety of suitable basis weights. The basis weight of the filter media will generally depend on whether it is undulating and the size of the undulations. For example, a filter media that includes undulations on a single length scale (e.g., including a filter media that has been, for example, Figures 6A to 6Cpleated layers, but not including additional structure formed by, for example, pleating or corrugating) generally have a greater dimensional consistency than filter media that includes undulations on two or more length scales (e.g., including layers that have been, for example, formed by Figures 6A to 6C The process shown in FIG. 5 shows a pleated layer and also includes a filter medium with additional structure formed by, for example, pleating or corrugating) with a lower basis weight.

[0153] In some embodiments, the filter media comprising undulations in a single length dimension has a basis weight greater than or equal to 20 g / 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 50g / m 2 , greater than or equal to 60g / m 2 , greater than or equal to 70g / m 2 , greater than or equal to 80g / m 2 , greater than or equal to 90g / m 2 , greater than or equal to 95g / m 2 , greater than or equal to 100g / m 2 , greater than or equal to 110g / m 2 , greater than or equal to 120g / m 2 , greater than or equal to 130g / m 2 , greater than or equal to 140g / 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 , greater than or equal to 300g / m 2 , greater than or equal to 350g / m 2 , greater than or equal to 400g / m 2 , greater than or equal to 500g / m 2 , greater than or equal to 600g / m 2 , greater than or equal to 700g / m 2 , greater than or equal to 800g / m 2 , or greater than or equal to 900g / m 2 In some embodiments, the filter medium comprising undulations in a single length dimension has a basis weight of less than or equal to 1000 g / m 2 , less than or equal to 900g / m 2 , less than or equal to 800g / m 2 , less than or equal to 700g / m 2, less than or equal to 600g / m 2 , less than or equal to 500g / m 2 , less than or equal to 400g / m 2 , less than or equal to 350g / m 2 , less than or equal to 300g / m 2 , less than or equal to 250g / m 2 , less than or equal to 225g / m 2 , less than or equal to 150g / m 2 , less than or equal to 140g / m 2 , less than or equal to 130g / m 2 , less than or equal to 120g / m 2 , less than or equal to 110g / m 2 , less than or equal to 100g / m 2 , less than or equal to 95g / m 2 , less than or equal to 90g / m 2 , 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 35g / m 2 , less than or equal to 30g / m 2 , or less than or equal to 25g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 20 g / m 2 And less than or equal to 1000g / m 2 , greater than or equal to 60g / m 2 And less than or equal to 150g / m 2 , greater than or equal to 70g / m 2 and less than or equal to 140g / m 2 , or greater than or equal to 95g / m 2 and less than or equal to 140g / m 2 Other ranges are possible. The weight per unit area of ​​the filter media can be determined by weighing a filter media of known area and then dividing the measured weight by the known area.

[0154] As described above, filter media including undulations on two or more length scales can be provided. The ratio of the basis weight of the filter media after forming undulations on the larger of the two length scales (e.g., by corrugation or pleating) to the basis weight of the filter media before forming undulations on the larger of the two length scales can be referred to as an additional structural undulation ratio (which is equivalent to, for example, the wave ratio of corrugated media or the pleat ratio of pleated media). The additional structural undulation ratio of the filter media including undulations on two or more length scales can be greater than or equal to 1.5, greater than or equal to 1.75, greater than or equal to 2, greater than or equal to 2.25, greater than or equal to 2.5, greater than or equal to 2.75, greater than or equal to 3, greater than or equal to 3.5, greater than or equal to 4, greater than or equal to 4.5, greater than or equal to 5, greater than or equal to 6, greater than or equal to 7, greater than or equal to 8, greater than or equal to 10, greater than or equal to 12.5, greater than or equal to 15, greater than or equal to 17.5, or greater than or equal to 20. Additional structural relief ratios for filter media comprising relief on two or more length scales can be less than or equal to 24, less than or equal to 20, less than or equal to 17.5, less than or equal to 15, less than or equal to 12.5, less than or equal to 10, less than or equal to 8, less than or equal to 7, less than or equal to 6, less than or equal to 5, less than or equal to 4.5, less than or equal to 4, less than or equal to 3.5, less than or equal to 3, less than or equal to 2.75, less than or equal to 2.5, less than or equal to 2.25, less than or equal to 2, or less than or equal to 1.75. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 1.5 and less than or equal to 24, or greater than or equal to 1.5 and less than or equal to 3). Other ranges are also possible.

[0155] The filter media described herein can have a variety of suitable thicknesses. The thickness of the filter media will generally depend on whether it is undulating and the size of the undulations. For example, a filter media that includes undulations on a single length scale (e.g., including undulations that have been, for example, Figures 6A to 6C pleated layers, but not including additional structure formed by, for example, pleating or corrugating) generally have a greater dimensional consistency than filter media that includes undulations on two or more length scales (e.g., including layers that have been, for example, formed by Figures 6A to 6C The process shown in FIG. 5 is a pleated layer and also includes a filter media of lower thickness with additional structure formed by pleating or corrugating.

[0156] In some embodiments, the filter medium comprising undulations in a single length dimension has a thickness greater than or equal to 2 mm, greater than or equal to 3 mm, greater than or equal to 4 mm, greater than or equal to 5 mm, greater than or equal to 6 mm, greater than or equal to 7 mm, greater than or equal to 8 mm, greater than or equal to 10 mm, greater than or equal to 12.5 mm, greater than or equal to 15 mm, or greater than or equal to 17.5 mm. In some embodiments, the filter medium comprising undulations in a single length dimension has a thickness less than or equal to 20 mm, less than or equal to 17.5 mm, less than or equal to 15 mm, less than or equal to 12.5 mm, less than or equal to 10 mm, less than or equal to 8 mm, less than or equal to 7 mm, less than or equal to 6 mm, less than or equal to 5 mm, less than or equal to 4 mm, or less than or equal to 3 mm. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 2 mm and less than or equal to 20 mm, greater than or equal to 2 mm and less than or equal to 15 mm, greater than or equal to 2 mm and less than or equal to 10 mm, or greater than or equal to 3 mm and less than or equal to 7 mm). Other ranges are also possible. The thickness of the filter media can be determined using the Edana WSP 120.1 standard (2005) with a presser foot selected to have a 2 ounce load and an area of ​​1 square inch. It should be understood that the above values ​​may also refer to the thickness of a filter media that includes undulations on two or more length scales, where the undulations have been extended to form a filter media that includes undulations on a single length scale. In some embodiments, the above thickness values ​​may be the thickness of the corrugated or pleated filter media prior to corrugation or pleating.

[0157] As described above, filter media comprising undulations on two or more length scales can be provided. These filter media can have a thickness defined by the undulations on a second length scale (e.g., wave height or pleat height). In some embodiments, the thickness of the filter media comprising undulations on two or more length scales is greater than or equal to 8 mm, greater than or equal to 10 mm, greater than or equal to 12.5 mm, greater than or equal to 15 mm, greater than or equal to 20 mm, greater than or equal to 25 mm, greater than or equal to 30 mm, greater than or equal to 40 mm, greater than or equal to 50 mm, greater than or equal to 60 mm, greater than or equal to 80 mm, or greater than or equal to 100 mm. In some embodiments, the filter medium comprising undulations on two or more length scales has a thickness of less than or equal to 120 mm, less than or equal to 100 mm, less than or equal to 80 mm, less than or equal to 60 mm, less than or equal to 50 mm, less than or equal to 40 mm, less than or equal to 30 mm, less than or equal to 25 mm, less than or equal to 20 mm, less than or equal to 15 mm, less than or equal to 12.5 mm, or less than or equal to 10 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 8 mm and less than or equal to 120 mm, or greater than or equal to 8 mm and less than or equal to 50 mm). Other ranges are also possible. The thickness of the filter medium can be determined using the Edana WSP 120.1 standard (2005) with a presser foot selected to have a 2 ounce load and an area of ​​1 square inch.

[0158] The filter media described herein can have a variety of suitable mean flow pore sizes. In some embodiments, the filter media has a mean flow pore size greater than or equal to 0.2 microns, greater than or equal to 0.5 microns, greater than or equal to 0.75 microns, greater than or equal to 1 micron, greater than or equal to 1.5 microns, greater than or equal to 2 microns, greater than or equal to 3 microns, greater than or equal to 4 microns, greater than or equal to 5 microns, greater than or equal to 6 microns, greater than or equal to 7 microns, greater than or equal to 8 microns, greater than or equal to 10 microns, greater than or equal to 12 microns, greater than or equal to 14 microns, greater than or equal to 16 microns, greater than or equal to 18 microns, greater than or equal to 20 microns, greater than or equal to 22 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 50 microns, greater than or equal to 60 microns, or greater than or equal to 75 microns. In some embodiments, the filter media has a mean flow pore size of 100 microns or less, 75 microns or less, 60 microns or less, 50 microns or less, 40 microns or less, 35 microns or less, 30 microns or less, 25 microns or less, 22 microns or less, 20 microns or less, 18 microns or less, 16 microns or less, 14 microns or less, 12 microns or less, 10 microns or less, 8 microns or less, 7 microns or less, 6 microns or less, 5 microns or less, 4 microns or less, 3 microns or less, 2 microns or less, 1.5 microns or less, 1 micron or less, 0.75 microns or less, or 0.5 microns or less. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.2 microns and less than or equal to 100 microns, greater than or equal to 0.2 microns and less than or equal to 75 microns, greater than or equal to 4 microns and less than or equal to 25 microns, greater than or equal to 6 microns and less than or equal to 16 microns, or greater than or equal to 7 microns and less than or equal to 12 microns). Other ranges are also possible. The mean flow pore size of the filter media can be determined according to ASTM F316 (2011).

[0159] The filter media described herein can have various suitable pressure drops. In some embodiments, the pressure drop of the filter medium is greater than or equal to 0.2 mm H2O, greater than or equal to 0.4 mm H2O, greater than or equal to 0.6 mm H2O, greater than or equal to 0.8 mm H2O, greater than or equal to 1 mm H2O, greater than or equal to 1.2 mm H2O, greater than or equal to 1.4 mm H2O, greater than or equal to 1.6 mm H2O, greater than or equal to 1.8 mm H2O, greater than or equal to 2 mm H2O, greater than or equal to 2.5 mm H2O, greater than or equal to 3 mm H2O, greater than or equal to 3.5 mm H2O, greater than or equal to 4 mm H2O, greater than or equal to 5 mm H2O, greater than or equal to 6 mm H2O, greater than or equal to 8 mm H2O, greater than or equal to 10 mm H2O, greater than or equal to 15 mm H2O, greater than or equal to 20 mm H2O, greater than or equal to 30 mm H2O, greater than or equal to 40 mm H2O, greater than or equal to 50 mm H2O, greater than or equal to 60 mm H2O, or greater than or equal to 80 mm H2O. In some embodiments, the pressure drop of the filter medium is less than or equal to 100 mm HO, less than or equal to 80 mm HO, less than or equal to 60 mm HO, less than or equal to 50 mm HO, less than or equal to 40 mm HO, less than or equal to 30 mm HO, less than or equal to 20 mm HO, less than or equal to 15 mm HO, less than or equal to 10 mm HO, less than or equal to 8 mm HO, less than or equal to 6 mm HO, less than or equal to 5 mm HO, less than or equal to 4 mm HO, less than or equal to 3.5 mm HO, less than or equal to 3 mm HO, less than or equal to 2.5 mm HO, less than or equal to 2 mm HO, less than or equal to 1.8 mm HO, less than or equal to 1.6 mm HO, less than or equal to 1.4 mm HO, less than or equal to 1.2 mm HO, less than or equal to 1 mm HO, less than or equal to 0.8 mm HO, less than or equal to 0.6 mm HO, or less than or equal to 0.4 mm HO. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.2 mm HO and less than or equal to 100 mm HO, greater than or equal to 0.2 mm HO and less than or equal to 10 mm HO, greater than or equal to 0.4 mm HO and less than or equal to 6 mm HO, greater than or equal to 0.8 mm HO and less than or equal to 4 mm HO, or greater than or equal to 1.2 mm HO and less than or equal to 1.8 mm HO). Other ranges are also possible. The pressure drop of the filter media can be determined by measuring gamma using the TSI 8130 Automatic Filter Tester or the TSI 3160 Automatic Filter Tester as described above.

[0160] The filter media described herein can have various initial penetration rates. In some embodiments, the filter media has an initial penetration rate of less than or equal to 80%, less than or equal to 70%, less than or equal to 60%, less than or equal to 50%, less than or equal to 40%, less than or equal to 30%, less than or equal to 20%, less than or equal to 15%, less than or equal to 10%, 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%, less than or equal to 0.0002%, or less than or equal to 0.0001%. In some embodiments, the filter media has an initial penetration greater than or equal to 0.00005%, 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 0.1%, greater than or equal to 0.2%, greater than or equal to 0.5%, greater than or equal to 1%, greater than or equal to 2%, greater than or equal to 5%, greater than or equal to 10%, greater than or equal to 15%, greater than or equal to 20%, greater than or equal to 30%, greater than or equal to 40%, greater than or equal to 50%, greater than or equal to 60%, or greater than or equal to 70%. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.00005% and less than or equal to 80%). Other ranges are also possible. The initial penetration of the filter media can be determined by gamma measurement using the TSI 8130 Automatic Filter Tester or the TSI 3160 Automatic Filter Tester as described above.

[0161] The filter media described herein can have a variety of suitable air permeabilities. In some embodiments, the filter media has an air permeability greater than or equal to 1 CFM, greater than or equal to 2 CFM, greater than or equal to 3 CFM, greater than or equal to 5 CFM, greater than or equal to 7.5 CFM, greater than or equal to 10 CFM, greater than or equal to 15 CFM, greater than or equal to 20 CFM, greater than or equal to 25 CFM, greater than or equal to 30 CFM, greater than or equal to 35 CFM, greater than or equal to 40 CFM, greater than or equal to 50 CFM, greater than or equal to 60 CFM, greater than or equal to 75 CFM, greater than or equal to 80 CFM, greater than or equal to 90 CFM, greater than or equal to 100 CFM, greater than or equal to 150 CFM, greater than or equal to 20 CFM, greater than or equal to 25 CFM, greater than or equal to 30 CFM, greater than or equal to 35 CFM, greater than or equal to 40 CFM, greater than or equal to 50 CFM, greater than or equal to 60 CFM, greater than or equal to 75 CFM, greater than or equal to 80 CFM, greater than or equal to 8 ... greater than or equal to 100 CFM, greater than or equal to 120 CFM, greater than or equal to 150 CFM, greater than or equal to 170 CFM, greater than or equal to 200 CFM, greater than or equal to 225 CFM, greater than or equal to 250 CFM, greater than or equal to 275 CFM, greater than or equal to 300 CFM, greater than or equal to 325 CFM, greater than or equal to 350 CFM, greater than or equal to 400 CFM, greater than or equal to 500 CFM, greater than or equal to 600 CFM, or greater than or equal to 800 CFM. In some embodiments, the filter media has an air permeability of less than or equal to 1000 CFM, less than or equal to 800 CFM, less than or equal to 600 CFM, less than or equal to 500 CFM, less than or equal to 400 CFM, less than or equal to 350 CFM, less than or equal to 325 CFM, less than or equal to 300 CFM, less than or equal to 275 CFM, less than or equal to 250 CFM, less than or equal to 225 CFM, less than or equal to 200 CFM, less than or equal to 170 CFM, less than or equal to 150 CFM, less than or equal to 120 CFM, less than or equal to 100 CFM, less than or equal to 75 CFM, less than or equal to 60 CFM, less than or equal to 50 CFM, less than or equal to 40 CFM, less than or equal to 35 CFM, less than or equal to 30 CFM, less than or equal to 25 CFM, less than or equal to 20 CFM, less than or equal to 15 CFM, less than or equal to 10 CFM, less than or equal to 7.5 CFM, less than or equal to 5 CFM, less than or equal to 3 CFM, or less than or equal to 2 CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 CFM and less than or equal to 1000 CFM, greater than or equal to 20 CFM and less than or equal to 350 CFM, greater than or equal to 35 CFM and less than or equal to 170 CFM, or greater than or equal to 20 CFM and less than or equal to 350 CFM). Other ranges are also possible. The air permeability of the filter medium can be determined according to ASTM test standard D737 (1996) at a pressure drop of 125 Pa over a test area of ​​38 cm 2 As will be known to those of ordinary skill in the art, the unit CFM is equivalent to the unit cfm / sf or feet / minute.

[0162] In some embodiments, the filter media described herein have a relatively high efficiency for one or more particle sizes. This efficiency can be expressed using a beta value (or beta ratio), where β (x) = y is the ratio of upstream counts (C0) to downstream counts (C), and where x is the minimum particle size that will achieve an actual ratio of C0 to C equal to y. (x) The penetration score at the value is 1 divided by y. The efficiency score is 1-penetration score. Therefore, the efficiency percentage of the medium is 100% multiplied by the efficiency score, and 100%*(1-1 / β (x) ) = efficiency percentage. For example, for particles of x microns or larger, with β (x) = 200, the percent efficiency of the filter media is [1-(1 / 200)]*100% or 99.5%. The filter media described herein can have a wide range of β values, such as β (x) =y, where x can be, for example, 1, 3, 5, 7, 10, 12, 15, 20, 25, 30, 50, 70, or 100, and where y can be, for example, at least 2, at least 10, at least 75, at least 100, at least 200, or at least 1000. It will be appreciated that other values ​​of x and y are possible; for example, in some cases, y can be greater than 1000. It will also be appreciated that for any value of x, y can be any number that represents the actual ratio of CO to C (e.g., 10.2, 12.4). Similarly, for any value of y, x can be any number that represents the minimum particle size that will achieve an actual ratio of CO to C equal to y.

[0163] In some embodiments, the filter media described herein have a relatively high hydraulic gamma. The hydraulic gamma of the filter media is given by the following formula: Hydraulic gamma = (10*(air permeability) 0.77 / (β200)). As described in the preceding paragraph, the β200 of a filter medium is equivalent to the minimum particle size for which the filter medium exhibits at least 99.5% efficiency. The air permeability of the filter medium can be determined as described elsewhere herein. The micron rating for β200 efficiency can be determined by conducting a multi-pass filtration test in accordance with the ISO 16889 (2008) procedure (modified by testing flat sheet samples) on a multi-pass filtration test bench manufactured by FTI. The measurement can be made by causing a test fluid containing ISO A3 media test dust manufactured by PTI, Inc. in aviation hydraulic fluid AERO HFA MIL H-5606A manufactured by Mobil at an upstream weight dust level of 10 mg / liter to flow through a cross-sectional area of ​​110 cm at a face velocity of 24.55 cm / minute. 2The filter medium is subjected to a pressure drop of 200 kPa until a terminal pressure drop of 200 kPa is achieved. The hydraulic gamma of the filter medium can be greater than or equal to 15, greater than or equal to 20, greater than or equal to 25, greater than or equal to 30, greater than or equal to 35, greater than or equal to 40, or greater than or equal to 45. In some embodiments, the hydraulic gamma of the filter medium is less than or equal to 50, less than or equal to 45, less than or equal to 40, less than or equal to 35, less than or equal to 30, less than or equal to 25, or less than or equal to 20. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 15 and less than or equal to 50, greater than or equal to 20 and less than or equal to 45, greater than or equal to 25 and less than or equal to 40, or greater than or equal to 30 and less than or equal to 35). Other ranges are also possible.

[0164] In some embodiments, the mean flow pore size and air permeability of the filter media can be related to each other in an advantageous manner. For example, in some embodiments, the square root of the ratio of the mean flow pore size to the air permeability of the filter media (([mean flow pore size in microns] / [air permeability in CFM]) 1 / 2 ) is less than or equal to 3, less than or equal to 2.75, less than or equal to 2.5, less than or equal to 2.25, less than or equal to 2, less than or equal to 1.75, less than or equal to 1.5, less than or equal to 1.25, less than or equal to 1, less than or equal to 0.9, less than or equal to 0.8, less than or equal to 0.7, less than or equal to 0.6, less than or equal to 0.5, less than or equal to 0.4, less than or equal to 0.3, or less than or equal to 0.2. In some embodiments, the square root of the ratio of the mean flow pore size to the air permeability of the filter medium (([mean flow pore size in microns] / [air permeability in CFM]) 1 / 2 ) is greater than or equal to 0.1, greater than or equal to 0.2, greater than or equal to 0.3, greater than or equal to 0.4, greater than or equal to 0.5, greater than or equal to 0.6, greater than or equal to 0.7, greater than or equal to 0.8, greater than or equal to 0.9, greater than or equal to 1, greater than or equal to 1.25, greater than or equal to 1.5, greater than or equal to 1.75, greater than or equal to 2, greater than or equal to 2.25, greater than or equal to 2.5, or greater than or equal to 2.75. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 and less than or equal to 3, greater than or equal to 0.1 and less than or equal to 0.5, greater than or equal to 0.2 and less than or equal to 0.8, greater than or equal to 0.5 and less than or equal to 0.5 and less than or equal to 1, greater than or equal to 0.7 and less than or equal to 1.5, greater than or equal to 1 and less than or equal to 2, or greater than or equal to 1.5 and less than or equal to 3). Other ranges are also possible.

[0165] The filter media described herein can have various suitable dust holding capacities as measured by various suitable techniques. One method of determining the dust holding capacity of a filter media is to employ the procedure described in the modified ASHRAE 52.1 (1992) as discussed in the following paragraphs. In some embodiments, the dust holding capacity of the filter media as determined by the modified ASHRAE 52.1 (1992) procedure as described in the following paragraphs is greater than or equal to 22 g / 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 , greater than or equal to 70g / m 2 , greater than or equal to 80g / m 2 , greater than or equal to 90g / m 2 , greater than or equal to 100g / m 2 , greater than or equal to 110g / m 2 , greater than or equal to 135g / m 2 , greater than or equal to 150g / m 2 , greater than or equal to 162g / m 2 , greater than or equal to 180g / m 2 , greater than or equal to 200g / m 2 , greater than or equal to 250g / m 2 , greater than or equal to 300g / m 2 , greater than or equal to 400g / m 2 , greater than or equal to 500g / m 2 , greater than or equal to 600g / m 2 , or greater than or equal to 800g / m 2 In some embodiments, the filter media has a dust holding capacity of less than or equal to 1000 g / m 2 as determined by the modified ASHRAE 52.1 (1992) procedure described in the following paragraphs. 2 , less than or equal to 800g / m 2 , less than or equal to 600g / m 2 , less than or equal to 500g / m 2 , less than or equal to 400g / m 2 , less than or equal to 300g / m 2 , less than or equal to 200g / m 2 , less than or equal to 180g / m 2 , less than or equal to 162g / m 2 , less than or equal to 150g / m 2 , less than or equal to 135g / m 2, less than or equal to 110g / m 2 , less than or equal to 100g / m 2 , less than or equal to 90g / m 2 , 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 , or less than or equal to 30g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 22 g / m 2 And less than or equal to 200g / m 2 , greater than or equal to 60g / m 2 And less than or equal to 200g / m 2 , greater than or equal to 80g / m 2 and less than or equal to 162g / m 2 , or greater than or equal to 90g / m 2 and less than or equal to 135g / m 2 ). Other ranges are also possible.

[0166] The dust holding capacity of a filter medium can be determined by the procedure described in ASHRAE 52.1 (1992) modified so that: (1) the filter medium is weighed before the start of the procedure and at the end of the procedure, and (2) the mass of dust held by the filter medium is determined by subtracting the measured mass of the filter medium before the start of the procedure from the measured mass of the filter medium at the end of the procedure. This procedure can be performed by subtracting the measured mass of the filter medium at the end of the procedure from the measured mass of the filter medium at the end of the procedure. 2 The filter media is exposed to 2g / 100ft 3 The test is performed using air containing an ASHRAE 52.1 synthetic test dust at a concentration of 1.5 psi. The air containing the test dust may be supplied to the filter media at a face velocity of 15 ft / min until the pressure drop across the filter media reaches 1.5 inches of H2O. At this point, the procedure is complete and the mass of the filter media at the end of the procedure may be determined by weighing.

[0167] Another method of determining the dust holding capacity of a filter medium is to perform a multi-pass filtration test based on ISO 16889 (2008) as described elsewhere herein. In some embodiments, the dust holding capacity of the filter medium is greater than or equal to 50 g / m 2 as determined by the multi-pass filtration test based on ISO 16889 (2008) as described elsewhere herein. 2 , greater than or equal to 75g / m 2 , greater than or equal to 100g / m 2 , greater than or equal to 125g / m2 , 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 , greater than or equal to 275g / m 2 , greater than or equal to 300g / m 2 , greater than or equal to 325g / m 2 , greater than or equal to 350g / m 2 , greater than or equal to 375g / m 2 , greater than or equal to 400g / m 2 , greater than or equal to 425g / m 2 , greater than or equal to 450g / m 2 , greater than or equal to 475g / m 2 , greater than or equal to 500g / m 2 , greater than or equal to 525g / m 2 , greater than or equal to 550g / m 2 , or greater than or equal to 575g / m 2 In some embodiments, the filter media has a dust holding capacity of less than or equal to 600 g / m 2 as determined by the multi-pass filtration test based on ISO 16889 (2008) described elsewhere herein. 2 , less than or equal to 575g / m 2 , less than or equal to 550g / m 2 , less than or equal to 525g / m 2 , less than or equal to 500g / m 2 , less than or equal to 475g / m 2 , less than or equal to 450g / m 2 , less than or equal to 425g / m 2 , less than or equal to 400g / m 2 , less than or equal to 375g / m 2 , less than or equal to 350g / m 2 , less than or equal to 325g / m 2 , 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 , or less than or equal to 75g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 50 g / m 2 And less than or equal to 600g / m 2 , or greater than or equal to 225g / m 2 And less than or equal to 600g / m 2 ). Other ranges are also possible.

[0168] A third method for determining the dust holding capacity of a filter medium is to perform a multi-pass filtration test based on ISO 19438 (2013) as described in the following paragraphs. In some embodiments, the dust holding capacity of the filter medium is greater than or equal to 50 g / m 2 as determined by the multi-pass filtration test based on ISO 19438 (2013) as described in the following paragraphs. 2 , greater than or equal to 60g / m 2 , greater than or equal to 70g / m 2 , greater than or equal to 80g / m 2 , greater than or equal to 90g / 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 , greater than or equal to 275g / m 2 , greater than or equal to 300g / m 2 , greater than or equal to 325g / m 2 , greater than or equal to 350g / m 2 , greater than or equal to 375g / m 2 , greater than or equal to 400g / m 2 , greater than or equal to 425g / m 2 , greater than or equal to 450g / m 2 , greater than or equal to 475g / m 2 , greater than or equal to 500g / m 2 , greater than or equal to 525g / m 2 , greater than or equal to 550g / m 2 , or greater than or equal to 575g / m 2 In some embodiments, the dust holding capacity of the filter medium is less than or equal to 600 g / m 2, less than or equal to 575g / m 2 , less than or equal to 550g / m 2 , less than or equal to 525g / m 2 , less than or equal to 500g / m 2 , less than or equal to 475g / m 2 , less than or equal to 450g / m 2 , less than or equal to 425g / m 2 , less than or equal to 400g / m 2 , less than or equal to 375g / m 2 , less than or equal to 350g / m 2 , less than or equal to 325g / m 2 , 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 90g / m 2 , less than or equal to 80g / m 2 , less than or equal to 70g / m 2 , or less than or equal to 60g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 50 g / m 2 And less than or equal to 600g / m 2 , or greater than or equal to 90g / m 2 And less than or equal to 600g / m 2 ). Other ranges are also possible.

[0169] The dust holding capacity of the filter media can be determined by conducting a multi-pass filtration test according to the ISO 19438 (2013) procedure (modified by testing flat sheet samples) on a multi-pass filtration test stand manufactured by FTI. The procedure is similar to the procedure for ISO 16889 (2008) described elsewhere herein, but uses an upstream weight dust level of 25 mg / L (instead of 10 mg / L) and includes running the test at a face velocity of 3.6 cm / min until a terminal pressure drop of 100 kPa is reached (instead of using a face velocity of 24.55 cm / min until a terminal pressure drop of 200 kPa is reached).

[0170] As described above, some filter media described herein include more than one layer. In some embodiments, the filter media includes an efficiency layer. The efficiency layer can improve the efficiency of the filter media. When present, the efficiency layer can be positioned in a variety of suitable locations in the filter media, such as the most upstream layer, the most downstream layer, or a layer where there is both one or more layers positioned upstream and one or more layers positioned downstream. In other words, the efficiency layer can be the first layer, the second layer, the third layer, the fourth layer, or another layer. In some embodiments, the filter media includes more than one efficiency layer. For example, the filter media can include the first and second layers as efficiency layers, the first and second layers as efficiency layers, the first and third layers as efficiency layers, or any other combination of layers as efficiency layers.

[0171] The efficiency layers described herein may be capable of being freestanding, and / or may be supported by additional layers (eg, by needling).

[0172] Some efficiency layers described herein are fibrous. For example, the efficiency layer can be a nonwoven web. The nonwoven web can be a wet-laid web, an air-laid web, a melt-blown web, a melt-spun web, a melt-fibrillated web, an electrostatically spun web, a solution-spun web, a solution-blown web, a centrifugal-spun web, a carded web, a spunbond web, a spunmelt web, a carded nonwoven web, a spunlace web (e.g., a spunlace and entangled web), or a composite web (e.g., a nonwoven web formed by two or more processes, such as a nonwoven web formed by an air-laid process and a melt-blown process or a nonwoven web formed by a spunbond process and a melt-blown process).

[0173] In some embodiments, the efficiency layer comprises a fiber web (e.g., a fiber web of the type described in the previous paragraph) that has been subjected to one or more processes after formation to reduce the diameter of the fibers therein. As an example, in some embodiments, the efficiency layer is formed (e.g., by one of the processes in the previous paragraph) to include multi-component fibers (e.g., bicomponent fibers, "island-in-the-sea" fibers). One or more components of the multi-component fibers are then removed, leaving fibers with smaller diameters. The components can be removed by, for example, a water jet. Another example of a process that can be employed to reduce the fiber diameter of the fibers is fibrillation.

[0174] The efficiency layer may also be fiber-free. For example, a porous membrane, a perforated membrane, and / or a fibrillated membrane may be suitable for use as an efficiency layer. A filter layer comprising two or more efficiency layers may include efficiency layers that are all the same type of layer and / or web (e.g., a filter medium may include two efficiency layers that are meltblown webs), efficiency layers that are layers and / or webs of different types (e.g., a filter medium may include a first efficiency layer that is a meltblown web and a second efficiency layer that is an electrospun web), or may include two or more efficiency layers of a first type (e.g., a first type of web) and one or more efficiency layers of a second type different from the first type (e.g., a second type of web) (e.g., a filter medium may include two efficiency layers that are meltblown webs and one efficiency layer that is an electrospun web).

[0175] The efficiency layer can comprise various suitable types of fibers. As described above, the efficiency layer can comprise wet-laid fibers, air-laid fibers, carded fibers, melt-blown fibers, melt-spun fibers, melt-fibrillated fibers, centrifugal-spun fibers, electrospun fibers, solution-spun fibers, solution-spun fibers, spunmelt fibers, spunbond fibers, and / or fibrillated fibers. In some embodiments, the filter media includes an efficiency layer comprising non-natural fibers (e.g., synthetic fibers, non-synthetic fibers) and / or natural fibers.

[0176] Non-limiting examples of synthetic fibers include polyolefin fibers (e.g., poly(propylene) fibers, poly(ethylene) fibers), polyester fibers (e.g., poly(butylene terephthalate) fibers, poly(ethylene terephthalate) fibers), poly(amide fibers) (e.g., nylon 6 fibers, nylon 11 fibers), polycarbonate fibers, acrylic fibers (e.g., dry-spun acrylic fibers, wet-spun acrylic fibers), poly(4-methyl-1-pentene) fibers, polystyrene fibers, fluoropolymer fibers (e.g., poly(vinylidene fluoride) fibers), poly(ethersulfone) fibers, ethylene vinyl acetate fibers, ethylene vinyl alcohol fibers, poly(vinyl alcohol) fibers, poly(phenylene sulfide) fibers, poly(lactic acid) fibers, and regenerated cellulose fibers (e.g., rayon, viscose, cellulose acetate). Non-limiting examples of non-synthetic, non-natural fibers include glass fibers and rock wool fibers.

[0177] Non-limiting examples of natural fibers include chitosan fibers, cotton fibers, wood pulp fibers, jute fibers, flax fibers, hemp fibers, and wool fibers.

[0178] In some embodiments, the efficiency layer comprises two or more types of fibers. For example, the efficiency layer may comprise two types of fibers having different dielectric constants. One example of such a fiber pair is poly(propylene) fiber and acrylic fiber (e.g., dry-spun acrylic fiber). Another example of such a fiber pair is poly(propylene) fiber and polyester fiber. The relative amounts of poly(propylene) fiber, acrylic fiber, and / or polyester fiber can generally be selected as desired. In some embodiments, the weight ratio of poly(propylene) fiber to acrylic fiber (e.g., dry spun acrylic fiber) and / or polyester fiber is greater than, or equal to, 5:95, greater than, or equal to, 10:90, greater than, or equal to, 15:85, greater than, or equal to, 20:80, greater than, or equal to, 25:75, greater than, or equal to, 30:70, greater than, or equal to, 35:65, greater than, or equal to, 40:60, greater than, or equal to, 45:55, greater than, or equal to, 50:50, greater than, or equal to, 55:45, greater than, or equal to, 60:40, greater than, or equal to, 65:45, greater than, or equal to, 70:30, greater than, or equal to, 75:25, greater than, or equal to, 80:20, greater than, or equal to, 85:15, or greater than, or equal to, 90:10. In some embodiments, the weight ratio of poly(propylene) fiber to acrylic fiber (e.g., dry-spun acrylic fiber) and / or polyester fiber is less than or equal to 95:5, less than or equal to 90:10, less than or equal to 85:15, less than or equal to 80:20, less than or equal to 75:25, less than or equal to 70:30, less than or equal to 65:35, less than or equal to 60:40, less than or equal to 55:45, less than or equal to 50:50, less than or equal to 45:55, less than or equal to 35:65, less than or equal to 30:70, less than or equal to 25:75, less than or equal to 20:80, less than or equal to 15:85, or less than or equal to 10:90. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 5:95 and less than or equal to 95:5, or greater than or equal to 30:70 and less than or equal to 70:30). Other ranges are also possible.

[0179] When present, the efficiency layer can comprise synthetic fibers having various suitable average diameters. Each efficiency layer in the filter media can independently comprise synthetic fibers having an average diameter of 0.05 microns or greater, 0.1 microns or greater, 0.2 microns or greater, 0.5 microns or greater, 1 micron or greater, 2 microns or greater, 3 microns or greater, 5 microns or greater, 10 microns or greater, 12 microns or greater, 20 microns or greater, 25 microns or greater, 30 microns or greater, or 40 microns or greater. Each efficiency layer in the filter media can independently comprise synthetic fibers having an average diameter of 50 microns or less, 40 microns or less, 30 microns or less, 25 microns or less, 20 microns or less, 12 microns or less, 10 microns or less, 5 microns or less, 3 microns or less, 2 microns or less, 1 micron or less, 0.5 microns or less, 0.2 microns or less, or 0.1 microns or less. Combinations of the above-referenced ranges are also possible (e.g., 0.05 microns or greater and 50 microns or less, 0.05 microns or greater and 12 microns or less, 0.2 microns or greater and 3 microns or less, or 0.2 microns or greater and 2 microns or less). Other ranges are also possible.

[0180] It should also be noted that the efficiency layer can contain fibers having two or more different diameters and / or two or more different types of cross-sections. Such fibers having different cross-sections and / or diameters can have the same chemical composition or can have different chemical compositions. Non-limiting embodiments of suitable cross-sections include circular, oval, Y-shaped, I-shaped (e.g., dog-bone), closed C-shaped, multi-lobed (e.g., trilobed, quadrilobed, pentalobed, hexalobed, including more than six lobes, X-shaped, crenulated).

[0181] When present, the efficiency layer may comprise synthetic fibers having various suitable average lengths. The fibers may include staple fibers and / or continuous fibers. Each efficiency layer in the filter media can independently comprise synthetic fibers having an average length of 0.01 mm or greater, 0.02 mm or greater, 0.05 mm or greater, 0.1 mm or greater, 0.2 mm or greater, 0.5 mm or greater, 1 mm or greater, 2 mm or greater, 5 mm or greater, 10 mm or greater, 20 mm or greater, 50 mm or greater, 90 mm or greater, 100 mm or greater, 200 mm or greater, 250 mm or greater, 300 mm or greater, 400 mm or greater, 500 mm or greater, 750 mm or greater, 1 m or greater, 2 m or greater, 5 m or greater, 10 m or greater, 20 m or greater, 50 m or greater, or 100 m or greater. Each efficiency layer in the filter media can independently comprise synthetic fibers having an average length of 200 m or less, 100 m or less, 50 m or less, 20 m or less, 10 m or less, 5 m or less, 2 m or less, 1 m or less, 750 mm or less, 500 mm or less, 400 mm or less, 300 mm or less, 250 mm or less, 200 mm or less, 100 mm or less, 90 mm or less, 50 mm or less, 20 mm or less, 10 mm or less, 5 mm or less, 2 mm or less, 1 mm or less, 0.5 mm or less, or 0.2 mm or less. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.01 mm and less than or equal to 200 mm, greater than or equal to 0.01 mm and less than or equal to 500 mm, greater than or equal to 50 mm and less than or equal to 300 mm, or greater than or equal to 90 mm and less than or equal to 250 mm). Other ranges are also possible.

[0182] When present, the efficiency layer can have a variety of suitable weights per unit area. The weight per unit area of ​​an efficiency layer in which undulations have not yet been formed tends to be lower than the weight per unit area of ​​an efficiency layer that includes one or more sets of undulations. Forming undulations in the efficiency layer tends to increase the amount of efficiency layer per filter media track area and, therefore, tends to increase the weight per unit area of ​​the efficiency layer. As described above, the manufacture of the filter media can include forming undulations in an initially non-undulating efficiency layer, which then undergoes one or more processes to form one or more sets of undulations. For this reason, it may be easier to refer to the weight per unit area of ​​the efficiency layer before the undulations. These weights per unit area are equivalent to the weight per unit area of ​​the efficiency layer if expanded to remove all undulations in the efficiency layer.

[0183] Each efficiency layer in the filter media may independently have a basis weight before undulation greater than or equal to 0.02 g / 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 0.2g / 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 5g / m 2 , greater than or equal to 10g / 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 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 , greater than or equal to 275g / m 2 , greater than or equal to 300g / m 2 , greater than or equal to 350g / m 2 , greater than or equal to 400g / m 2 , or greater than or equal to 450g / m 2 Each efficiency layer in the filter medium may independently have a weight per unit area of ​​less than or equal to 500 g / m2 before undulation. 2, less than or equal to 450g / m 2 , less than or equal to 400g / m 2 , less than or equal to 350g / m 2 , 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 , 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 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 , less than or equal to 0.1g / m 2 , or less than or equal to 0.05g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 0.02 g / m 2 And less than or equal to 500g / m 2 , greater than or equal to 0.02g / m 2 And less than or equal to 300g / m 2 , greater than or equal to 0.02g / m 2 And less than or equal to 100g / m 2 , greater than or equal to 0.05g / m 2 And less than or equal to 50g / m 2 , or greater than or equal to 0.2g / m 2 And less than or equal to 30g / m 2 ). Other ranges are also possible.

[0184] As described above, an efficiency layer comprising undulations on a single length scale may be provided. In some embodiments, the efficiency layer comprising undulations on a single length scale has a weight per unit area greater than or equal to 0.05 g / m2 , greater than or equal to 0.08g / m 2 , greater than or equal to 0.1g / m 2 , greater than or equal to 0.125g / m 2 , greater than or equal to 0.15g / m 2 , greater than or equal to 0.2g / m 2 , greater than or equal to 0.25g / m 2 , greater than or equal to 0.3g / m 2 , greater than or equal to 0.4g / m 2 , greater than or equal to 0.5g / m 2 , greater than or equal to 0.75g / m 2 , greater than or equal to 1g / m 2 , greater than or equal to 1.25g / m 2 , greater than or equal to 1.5g / m 2 , greater than or equal to 2g / m 2 , greater than or equal to 2.5g / m 2 , greater than or equal to 3g / m 2 , greater than or equal to 4g / m 2 , greater than or equal to 5g / m 2 , greater than or equal to 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 20g / m 2 , greater than or equal to 25g / 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 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 200g / m 2 , greater than or equal to 250g / m 2 , greater than or equal to 300g / m 2 , greater than or equal to 400g / m 2 , greater than or equal to 500g / m 2 , greater than or equal to 600g / m 2 , greater than or equal to 800g / m 2 , greater than or equal to 1000g / m 2 , or greater than or equal to 1250g / m2 In some embodiments, the efficiency layer comprising undulations on a single length scale has a weight per unit area of ​​less than or equal to 1500 g / m 2 , less than or equal to 1250g / m 2 , less than or equal to 1000g / m 2 , less than or equal to 800g / m 2 , less than or equal to 600g / m 2 , less than or equal to 500g / m 2 , less than or equal to 400g / m 2 , 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 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 , less than or equal to 40g / 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 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 4g / m 2 , less than or equal to 3g / m 2 , less than or equal to 2.5g / m 2 , less than or equal to 2g / m 2 , less than or equal to 1.5g / m 2 , less than or equal to 1.25g / m 2 , less than or equal to 1g / m 2 , less than or equal to 0.75g / m 2 , less than or equal to 0.5g / m 2 , less than or equal to 0.4g / m 2 , less than or equal to 0.3g / m 2 , less than or equal to 0.25g / m 2 , less than or equal to 0.2g / m 2 , less than or equal to 0.15g / m 2 , less than or equal to 0.125g / m2 , less than or equal to 0.1g / m 2 , or less than or equal to 0.08g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 0.05 g / m 2 And less than or equal to 1500g / m 2 , greater than or equal to 0.08g / m 2 And less than or equal to 1500g / m 2 , greater than or equal to 0.08g / m 2 And less than or equal to 1000g / m 2 , greater than or equal to 0.08g / m 2 And less than or equal to 500g / m 2 , greater than or equal to 0.2g / m 2 And less than or equal to 250g / m 2 , or greater than or equal to 0.8g / m 2 And less than or equal to 150g / m 2 Other ranges are also possible. If the filter media includes two or more efficiency layers having undulations on a single length scale, each efficiency layer can independently have a basis weight within one or more of the above-listed ranges.

[0185] When present, the efficiency layer can have a variety of suitable thicknesses. As described above with respect to the weight per unit area of ​​the efficiency layer, the thickness of an efficiency layer without undulations tends to be lower than the thickness of an efficiency layer including one or more sets of undulations. As described above, the manufacture of the filter media can include forming undulations in an initially non-undulating efficiency layer, which is then subjected to one or more processes to form one or more sets of undulations. For this reason, it may be easier to refer to the thickness of the efficiency layer before the undulations. If expanded to remove all undulations in the efficiency layer, these thicknesses are equivalent to the thickness of the efficiency layer. The thickness of each efficiency layer in the filter media before undulation can independently be greater than or equal to 0.001 mm, greater than or equal to 0.002 mm, greater than or equal to 0.005 mm, greater than or equal to 0.01 mm, greater than or equal to 0.02 mm, greater than or equal to 0.05 mm, greater than or equal to 0.075 mm, greater than or equal to 0.1 mm, greater than or equal to 0.13 mm, greater than or equal to 0.2 mm, greater than or equal to 0.3 mm, greater than or equal to 0.4 mm, greater than or equal to 0.5 mm, greater than or equal to 0.7 mm, greater than or equal to 1 mm, greater than or equal to 1.25 mm, greater than or equal to 1.5 mm, greater than or equal to 1.75 mm, greater than or equal to 2 mm, greater than or equal to 2.25 mm, greater than or equal to 2.5 mm, greater than or equal to 2.75 mm, greater than or equal to 3 mm, greater than or equal to 3.5 mm, greater than or equal to 4 mm, or greater than or equal to 4.5 mm. The thickness of each efficiency layer in the filter media before corrugation can independently be less than or equal to 5 mm, less than or equal to 4.5 mm, less than or equal to 4 mm, less than or equal to 3.5 mm, less than or equal to 3 mm, less than or equal to 2.75 mm, less than or equal to 2.5 mm, less than or equal to 2.25 mm, less than or equal to 2 mm, less than or equal to 1.75 mm, less than or equal to 1.5 mm, less than or equal to 1.25 mm, less than or equal to 1 mm, less than or equal to 0.7 mm, less than or equal to 0.5 mm, less than or equal to 0.4 mm, less than or equal to 0.3 mm, less than or equal to 0.2 mm, less than or equal to 0.13 mm, less than or equal to 0.1 mm, less than or equal to 0.075 mm, less than or equal to 0.05 mm, less than or equal to 0.02 mm, less than or equal to 0.01 mm, less than or equal to 0.005 mm, or less than or equal to 0.002 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.001 mm and less than or equal to 5 mm, greater than or equal to 0.001 mm and less than or equal to 3 mm, greater than or equal to 0.001 mm and less than or equal to 2.5 mm, greater than or equal to 0.01 mm and less than or equal to 2.5 mm, greater than or equal to 0.1 mm and less than or equal to 0.7 mm, or greater than or equal to 0.13 mm and less than or equal to 0.3 mm).Other ranges are also possible.

[0186] As described above, an efficiency layer comprising undulations on a single length scale can be provided. In some embodiments, the thickness of the efficiency layer comprising undulations on a single length scale is greater than or equal to 1.5 mm, greater than or equal to 2 mm, greater than or equal to 2.5 mm, greater than or equal to 3 mm, greater than or equal to 4 mm, greater than or equal to 5 mm, greater than or equal to 7.5 mm, greater than or equal to 10 mm, or greater than or equal to 12.5 mm. In some embodiments, the thickness of the efficiency layer comprising undulations on a single length scale is less than or equal to 15 mm, less than or equal to 12.5 mm, less than or equal to 10 mm, less than or equal to 7.5 mm, less than or equal to 5 mm, less than or equal to 4 mm, less than or equal to 3 mm, less than or equal to 2.5 mm, or less than or equal to 2 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 1.5 mm and less than or equal to 15 mm, or greater than or equal to 2 mm and less than or equal to 15 mm). Other ranges are also possible. If the filter media includes two or more efficiency layers having undulations on a single length scale, each efficiency layer can independently have a thickness within one or more of the ranges listed above.

[0187] The thickness of the efficiency layer having a thickness less than or equal to 0.025 mm can be determined by cross-sectional SEM. The thickness of the efficiency layer having a thickness greater than 0.025 mm can be determined by the Edana WSP 120.1 standard (2005) with a presser foot selected to have a 2 ounce load and a 1 square inch area.

[0188] When present, the efficiency layer can have various suitable mean flow pore sizes. The mean flow pore size of each efficiency layer in the filter media can independently be greater than or equal to 0.1 micron, greater than or equal to 0.2 micron, greater than or equal to 0.3 micron, greater than or equal to 0.4 micron, greater than or equal to 0.5 micron, greater than or equal to 0.6 micron, greater than or equal to 0.8 micron, greater than or equal to 1 micron, greater than or equal to 1.25 micron, greater than or equal to 1.5 micron, greater than or equal to 1.75 micron, greater than or equal to 2 micron, greater than or equal to 5 micron, greater than or equal to 6 micron, greater than or equal to 7 micron, greater than or equal to 8 micron, greater than or equal to 9 micron, greater than or equal to 10 micron, greater than or equal to 11 micron, greater than or equal to 12 micron, greater than or equal to 13 micron, greater than or equal to 14 micron, greater than or equal to 15 micron, greater than or equal to 17.5 micron, greater than or equal to 20 micron, greater than or equal to 22.5 micron, greater than or equal to 25 micron, greater than or equal to 30 micron, greater than or equal to 40 micron, greater than or equal to 50 micron, or greater than or equal to 75 micron. The mean flow pore size of each efficiency layer in the filter media can independently be less than or equal to 100 microns, less than or equal to 75 microns, less than or equal to 50 microns, less than or equal to 40 microns, less than or equal to 30 microns, less than or equal to 25 microns, less than or equal to 22.5 microns, less than or equal to 20 microns, less than or equal to 17.5 microns, less than or equal to 15 microns, less than or equal to 14 microns, less than or equal to 13 microns, less than or equal to 12 microns, less than or equal to 11 microns, less than or equal to 10 microns, less than or equal to 9 microns, less than or equal to 8 microns, less than or equal to 7 microns, less than or equal to 6 microns, less than or equal to 5 microns, less than or equal to 2 microns, less than or equal to 1.75 microns, less than or equal to 1.5 microns, less than or equal to 1.25 microns, less than or equal to 1 micron, less than or equal to 0.8 microns, less than or equal to 0.6 microns, less than or equal to 0.5 microns, less than or equal to 0.4 microns, or less than or equal to 0.3 microns. Combinations of the above-referenced ranges are also possible (e.g., 0.1 μm or greater and 100 μm or less, 0.2 μm or greater and 25 μm or less, 0.5 μm or greater and 1 μm or less, 2 μm or greater and 25 μm or less, 5 μm or greater and 15 μm or less, or 7 μm or greater and 12 μm or less). Other ranges are also possible. The mean flow pore size of the efficiency layer can be determined according to ASTM F316 (2011).

[0189] When present, the efficiency layer can have various suitable solidities. The solidity of each efficiency layer in the filter media can independently be greater than or equal to 0.5%, greater than or equal to 1%, greater than or equal to 1.5%, greater than or equal to 2%, greater than or equal to 2.5%, greater than or equal to 3%, greater than or equal to 3.5%, greater than or equal to 4%, greater than or equal to 5%, greater than or equal to 6%, greater than or equal to 7%, greater than or equal to 8%, greater than or equal to 10%, greater than or equal to 12%, greater than or equal to 15%, greater than or equal to 20%, greater than or equal to 25%, greater than or equal to 30%, or greater than or equal to 35%. The solidity of each efficiency layer in the filter media can independently be less than or equal to 40%, less than or equal to 35%, less than or equal to 30%, less than or equal to 25%, less than or equal to 20%, less than or equal to 15%, less than or equal to 12%, less than or equal to 10%, less than or equal to 8%, less than or equal to 7%, less than or equal to 6%, less than or equal to 5%, less than or equal to 4%, less than or equal to 3.5%, less than or equal to 3%, less than or equal to 2.5%, less than or equal to 2%, less than or equal to 1.5%, or less than or equal to 1%. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.5% and less than or equal to 40%, greater than or equal to 0.5% and less than or equal to 12%, greater than or equal to 2% and less than or equal to 8%, or greater than or equal to 2.5% and less than or equal to 6%). Other ranges are also possible.

[0190] The solidity of the efficiency layer can be determined by using the following formula: Solidity = [weight per unit area / (fiber density * thickness)] * 100%. The weight per unit area and thickness can be determined as described elsewhere in this document. Fiber density is equivalent to the average density of the material or materials that form the fibers, which is typically specified by the fiber manufacturer. The average density of the material that forms the fibers can be determined by: (1) determining the total volume of all fibers in the filter media; and (2) dividing the total mass of all fibers in the filter media by the total volume of all fibers in the filter media. If the mass and density of each type of fiber in the filter media are known, the volume of all fibers in the filter media can be determined by: (1) for each type of fiber, dividing the total mass of fibers of that type in the filter media by the density of fibers of that type; and (2) adding the volumes of each fiber type. If the mass and density of each type of fiber in the filter media are unknown, the volume of all fibers in the filter media can be determined according to Archimedes' principle.

[0191] When present, the efficiency layer can have various suitable stiffnesses. In some embodiments, the efficiency layer is a layer having a relatively low stiffness. Some efficiency layers can also have a relatively high stiffness. If undulated by the methods described herein, such an efficiency layer can be made by initially depositing an efficiency layer having a relatively low stiffness onto the reversibly stretchable layer, and then corrugating the efficiency layer to form an undulated layer (e.g., by corrugating the efficiency layer with a relatively high stiffness). Figures 6A to 6C ). Such an efficiency layer can then be impregnated with a binder that increases the stiffness of the efficiency layer. The binder can also enhance the structural integrity and / or compression resistance of the efficiency layer. For this purpose, thermoplastic binders and / or thermosetting binders can be used. An example of a suitable thermoplastic binder is a hot melt adhesive (e.g., a hot melt adhesive comprising poly(olefins), poly(esters), poly(amides), poly(urethanes), and / or ethylene vinyl acetate). Non-limiting examples of suitable thermosetting binders include: acrylic binders, binders comprising vinyl esters (and / or their reaction products), phenolic binders, thermosetting poly(urethanes), epoxy resins, and unsaturated poly(ethylene terephthalate). In some embodiments, the binder may include the binders described elsewhere herein.

[0192] The stiffness of each efficiency layer in the filter media can independently be greater than or equal to 1 mg, greater than or equal to 2 mg, greater than or equal to 3 mg, greater than or equal to 4 mg, greater than or equal to 5 mg, greater than or equal to 6 mg, greater than or equal to 8 mg, greater than or equal to 10 mg, greater than or equal to 15 mg, greater than or equal to 20 mg, greater than or equal to 25 mg, greater than or equal to 30 mg, greater than or equal to 40 mg, greater than or equal to 50 mg, greater than or equal to 75 mg, greater than or equal to 100 mg, greater than or equal to 150 ... greater than or equal to 125 mg, greater than or equal to 150 mg, greater than or equal to 175 mg, greater than or equal to 200 mg, greater than or equal to 225 mg, greater than or equal to 250 mg, greater than or equal to 300 mg, greater than or equal to 500 mg, greater than or equal to 750 mg, greater than or equal to 1000 mg, greater than or equal to 2000 mg, greater than or equal to 5000 mg, greater than or equal to 7500 mg, greater than or equal to 10000 mg, or greater than or equal to 12500 mg. The stiffness of each efficiency layer in the filter media can independently be less than or equal to 15,000 mg, less than or equal to 12,500 mg, less than or equal to 10,000 mg, less than or equal to 7,500 mg, less than or equal to 5,000 mg, less than or equal to 2,000 mg, less than or equal to 1,000 mg, less than or equal to 750 mg, less than or equal to 500 mg, less than or equal to 300 mg, less than or equal to 250 mg, less than or equal to 225 mg, less than or equal to 200 mg, less than or equal to 2000 mg, less than or equal to 1000 mg, less than or equal to 750 mg, less than or equal to 500 mg, less than or equal to 300 mg, less than or equal to 250 mg, less than or equal to 225 mg, less than or equal to 20 ...1000 mg, less than or equal to 750 mg, less than or equal to 500 mg, less than or equal to 300 mg, less than or equal to 250 mg, less than or equal to 225 mg, less than or equal to 2000 mg, less than or equal to 2000 mg, less than or equal to 2000 mg, less than or equal to 2000 mg, less than or equal to 2000 mg, less than or equal to 1000 mg, less than or equal to 750 mg, less than or equal to 500 mg, less than 175 mg, less than or equal to 150 mg, less than or equal to 125 mg, less than or equal to 100 mg, less than or equal to 75 mg, less than or equal to 50 mg, less than or equal to 40 mg, less than or equal to 30 mg, less than or equal to 25 mg, less than or equal to 20 mg, less than or equal to 15 mg, less than or equal to 10 mg, less than or equal to 8 mg, less than or equal to 6 mg, less than or equal to 5 mg, less than or equal to 4 mg, less than or equal to 3 mg, or less than or equal to 2 mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 1 mg and less than or equal to 12500 mg, greater than or equal to 1 mg and less than or equal to 200 mg, greater than or equal to 1 mg and less than or equal to 100 mg, greater than or equal to 1 mg and less than or equal to 50 mg, greater than or equal to 3 mg and less than or equal to 30 mg, or greater than or equal to 5 mg and less than or equal to 10 mg). Other ranges are also possible. The stiffness of the efficiency layer can be determined according to WSP 90.2 (2015).

[0193] When present, the efficiency layer can have various suitable pressure drops. The pressure drop of each efficiency layer in the filter media can independently be greater than or equal to 0.1 mm H2O, greater than or equal to 0.2 mm H2O, greater than or equal to 0.3 mm H2O, greater than or equal to 0.4 mm H2O, greater than or equal to 0.5 mm H2O, greater than or equal to 0.75 mm H2O, greater than or equal to 1 mm H2O, greater than or equal to 1.2 mm H2O, greater than or equal to 1.5 mm H2O, greater than or equal to 2 mm H2O, greater than or equal to 2.5 mm H2O, greater than or equal to 3 mm H2O, greater than or equal to 3.5 mm H2O, greater than or equal to 4 mm H2O, greater than or equal to 5 mm H2O, greater than or equal to 6 mm H2O, greater than or equal to 7 mm H2O, greater than or equal to 8 mm H2O, greater than or equal to 10 mm H2O, greater than or equal to 12 mm H2O, greater than or equal to 15 mm H2O, greater than or equal to 20 mm H2O, greater than or equal to 30 mm H2O. H2O, greater than or equal to 40 mmH2O, greater than or equal to 50 mmH2O, or greater than or equal to 75 mmH2O. The pressure drop of each efficiency layer in the filter media can independently be less than or equal to 100 mm HO, less than or equal to 75 mm HO, less than or equal to 50 mm HO, less than or equal to 40 mm HO, less than or equal to 30 mm HO, less than or equal to 20 mm HO, less than or equal to 15 mm HO, less than or equal to 12 mm HO, less than or equal to 10 mm HO, less than or equal to 8 mm HO, less than or equal to 7 mm HO, less than or equal to 6 mm HO, less than or equal to 5 mm HO, less than or equal to 4 mm HO, less than or equal to 3.5 mm HO, less than or equal to 3 mm HO, less than or equal to 2.5 mm HO, less than or equal to 2 mm HO, less than or equal to 1.5 mm HO, less than or equal to 1.2 mm HO, less than or equal to 1 mm HO, or less than or equal to 0.75 mm HO. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.1 mm H2O and less than or equal to 100 mm H2O, greater than or equal to 0.5 mm H2O and less than or equal to 12 mm H2O, greater than or equal to 1 mm H2O and less than or equal to 7 mm H2O, or greater than or equal to 1.2 mm H2O and less than or equal to 3.5 mm H2O). The pressure drop of the efficiency layer can be determined by gamma measurement using the TSI 8130 Automatic Filter Tester or the TSI 3160 Automatic Filter Tester as described above.

[0194] When present, the efficiency layer can have various suitable air permeabilities. The air permeability of each efficiency layer in the filter media can independently be greater than or equal to 0.1 CFM, greater than or equal to 0.2 CFM, greater than or equal to 0.5 CFM, greater than or equal to 0.75 CFM, greater than or equal to 1 CFM, greater than or equal to 1.5 CFM, greater than or equal to 2 CFM, greater than or equal to 5 CFM, greater than or equal to 10 CFM, greater than or equal to 15 CFM, greater than or equal to 20 CFM, greater than or equal to 30 CFM, greater than or equal to 40 CFM, greater than or equal to 50 CFM, greater than or equal to 70 CFM, or greater than or equal to 80 CFM. FM, greater than or equal to 90 CFM, greater than or equal to 100 CFM, greater than or equal to 120 CFM, greater than or equal to 150 CFM, greater than or equal to 175 CFM, greater than or equal to 200 CFM, greater than or equal to 225 CFM, greater than or equal to 250 CFM, greater than or equal to 275 CFM, greater than or equal to 300 CFM, greater than or equal to 350 CFM, greater than or equal to 400 CFM, greater than or equal to 500 CFM, greater than or equal to 600 CFM, or greater than or equal to 800 CFM. The air permeability of each efficiency layer in the filter media can independently be less than or equal to 1000 CFM, less than or equal to 800 CFM, less than or equal to 600 CFM, less than or equal to 500 CFM, less than or equal to 400 CFM, less than or equal to 350 CFM, less than or equal to 300 CFM, less than or equal to 275 CFM, less than or equal to 250 CFM, less than or equal to 225 CFM, less than or equal to 200 CFM, less than or equal to 175 CFM, less than or equal to 150 CFM, less than or equal to 120 CFM, less than or equal to 100 CFM, less than or equal to 90 CFM, less than or equal to 70 CFM, less than or equal to 50 CFM, less than or equal to 40 CFM, less than or equal to 30 CFM, less than or equal to 20 CFM, less than or equal to 15 CFM, less than or equal to 10 CFM, less than or equal to 5 CFM, less than or equal to 2 CFM, less than or equal to 1.5 CFM, less than or equal to 1 CFM, less than or equal to 0.75 CFM, less than or equal to 0.5 CFM, or less than or equal to 0.2 CFM. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 CFM and less than or equal to 1000 CFM, greater than or equal to 2 CFM and less than or equal to 250 CFM, greater than or equal to 20 CFM and less than or equal to 120 CFM, or greater than or equal to 40 CFM and less than or equal to 90 CFM). Other ranges are also possible. The air permeability of the efficiency layer can be measured according to ASTM test standard D737 (1996) at a pressure drop of 125 Pa over a test area of ​​38 cm 2 Determined on the sample.

[0195] When present, the efficiency layer can be charged or can be uncharged. In some embodiments, the filter medium includes at least one charged efficiency layer and at least one uncharged efficiency layer. In some embodiments, the filter medium includes an efficiency layer that is a charged meltblown fiber web. The filter medium can also include an efficiency layer that is a charged carded fiber web (e.g., a charged carded web comprising poly(propylene) fibers and / or acrylic (e.g., dry-spun acrylic) fibers). The charge can be generated on the efficiency layer by various suitable charging processes, non-limiting examples of which include electrostatic charging processes, friction charging processes, and hydrocharging processes. In some embodiments, the filter medium includes a charged electrospun efficiency layer that obtains its charge during electrospinning. As a specific example, some filter media include a friction-charged carded web comprising poly(propylene) fibers and / or acrylic (e.g., dry-spun acrylic) fibers.

[0196] The hydrocharging process can include impinging a jet and / or stream of water droplets onto an initially uncharged efficiency layer to cause it to become electrostatically charged. At the end of the hydrocharging process, the efficiency layer can have an electret charge. The jet and / or stream of water droplets can impinge on the efficiency layer at various suitable pressures (e.g., a pressure of 10 psi to 50 psi) and can be provided by various suitable sources (e.g., a sprayer). In some embodiments, the efficiency layer is hydrocharged using equipment that can be used for hydroentanglement of fibers, the equipment operating at a pressure lower than that typically used for hydroentanglement processes. The water impinging on the efficiency layer can be relatively pure; for example, it can be distilled water and / or deionized water. After being electrostatically charged in this manner, the efficiency layer can be dried, for example, using an air dryer.

[0197] In some embodiments, the efficiency layer is hydrodynamically charged while being moved laterally. The efficiency layer can be transported on a porous belt (e.g., a screen or mesh conveyor belt). While being transported on the porous belt, the efficiency layer can be exposed to sprays and / or jets of water pressurized by a pump. The water jets and / or sprays can impinge on and / or penetrate the efficiency layer. In some embodiments, a vacuum is provided beneath the porous conveyor belt, which can facilitate the passage of water through the efficiency layer and / or reduce the time and energy required to dry the efficiency layer at the end of the hydrocharging process.

[0198] As described above, some filter media herein include a layer that is a scrim. Some filter media include two or more layers that are scrims. The scrim can be a fairly open layer. For example, the scrim can have a relatively high air permeability (e.g., greater than 1000 CFM) and / or a relatively low pressure drop (e.g., a pressure drop that does not significantly contribute to the pressure drop of the filter media as a whole). The filter media can include such a scrim: it supports one or more other layers (e.g., one or more efficiency layers and / or one or more nanofiber layers) without significantly increasing the pressure drop of the filter media. Some scrims can be layers that can undergo reversible stretching and / or can be formed from reversibly stretchable materials. In some embodiments, also as described above, the filter media includes such a scrim: it holds one or more other layers (e.g., one or more efficiency layers and / or one or more nanofiber layers) in a manner that causes the filter media to include a plurality of peaks that are irregular in one or more aspects. For example, a scrim can hold one or more other layers such that the one or more other layers are undulating, and the undulation is irregular in one or more aspects. Some filter media can include a scrim that protects one or more layers of filter media, such as one or more layers of filter media held by another scrim such that the filter media includes a plurality of peaks that are irregular in one or more aspects. Some scrims can be positioned adjacent to an efficiency layer and / or can be adhered to the efficiency layer by an adhesive.

[0199] Various suitable scrims can be adopted in the filter media described in this article. In some embodiments, the filter medium includes a fibrous scrim. For example, the filter medium can include a scrim as a nonwoven web (for example, a spunbond web). As another example, the filter medium can include a scrim as a mesh (for example, an extruded mesh). As a third example, the filter medium can include a scrim as a woven material. As the fourth and fifth examples, the filter medium can include a scrim as a perforated membrane and / or a fibrillated membrane. In some embodiments, the scrim can include elastically extensible fibers that are not in direct contact with each other. One or more scrims can be cut from material wound around a roller and / or from hundreds of yards of length from a creel.

[0200] When the filter media includes a spunbond scrim, the spunbond scrim can include various suitable types of spunbond fibers. The spunbond scrim can include fibers that are synthetic fibers, such as polyolefin fibers (eg, poly(propylene) fibers), polyester fibers, and / or nylon fibers.

[0201] When the filter media comprises a spunbond scrim, the spunbond scrim can comprise fibers having various suitable average diameters. The spunbond scrim can comprise fibers having an average diameter of 1 micron or greater, 2 microns or greater, 5 microns or greater, 7.5 microns or greater, 10 microns or greater, 12.5 microns or greater, 15 microns or greater, 20 microns or greater, 25 microns or greater, 30 microns or greater, 35 microns or greater, 40 microns or greater, or 45 microns or greater. The spunbond scrim can comprise fibers having an average diameter of 50 microns or less, 45 microns or less, 40 microns or less, 35 microns or less, 30 microns or less, 25 microns or less, 20 microns or less, 15 microns or less, 12.5 microns or less, 10 microns or less, 7.5 microns or less, 5 microns or less, or 2 microns or less. Combinations of the above-referenced ranges are also possible (eg, greater than or equal to 1 micrometer and less than or equal to 50 micrometers, or greater than or equal to 15 micrometers and less than or equal to 35 micrometers). Other ranges are also possible.

[0202] It should also be noted that the spunbond scrim can include fibers with two or more different diameters and / or two or more different types of cross-sections. Such fibers with different cross-sections and / or diameters can have the same chemical composition or can have different chemical compositions. Non-limiting embodiments of suitable cross-sections include: circular, oval, Y-shaped, I-shaped (e.g., dog-bone shaped), closed C-shaped, multi-lobed (e.g., trilobal, 4-lobal, 5-lobal, 6-lobal, including more than 6 leaves, X-shaped, crenulate). When the filter medium includes a spunbond scrim, the fibers in the filter medium can be continuous. In some embodiments, the scrim (e.g., mesh scrim, nonwoven scrim, woven scrim, a scrim comprising elastically extensible fibers that are not in direct contact with each other) includes elastically extensible fibers. In other words, the scrim can include such fibers: it can be stretched to a relatively high elongation without breaking, then allowed to recover to a length close to or identical to its length before being stretched. This may be advantageous for scrims that are capable of undergoing reversible stretching, such as for scrims that have one or more other layers deposited thereon while the scrim is in a reversibly stretched state.

[0203] As described above, some filter media include a scrim in the form of a plurality of elastically extensible fibers. The elastically extensible fibers may be disconnected from one another and / or may initially separate from one another. In other words, in some embodiments, the scrim may have an unconventional topography comprising fibers that do not together form a web. For example, the scrim may have a Figure 4A and Figure 4B302 shown in FIG. 304. In some embodiments, the elastically extensible fibers and the disconnected fibers in the scrim can be oriented substantially parallel to each other. The elastically extensible fibers can be oriented at any suitable angle relative to the filter media as a whole (e.g., in the machine direction, in the cross direction, or in a direction between the machine direction and the cross direction).

[0204] In some embodiments, disconnected elastically stretchable fibers can together form a reversibly stretchable layer when incorporated into a filter media. Also as described above, such elastically stretchable fibers can be adhered to additional layers (e.g., an efficiency layer) and / or can be used to create relief in one or more other layers upon recovery from the reversibly stretchable layer.

[0205] In some embodiments, the scrim comprises a fiber that can be stretched to 1.75 times, 2 times, 2.25 times, 2.5 times, 2.75 times, 3 times, 3.25 times, 3.5 times, 3.75 times, 4 times, 4.5 times, 5 times, 5.5 times, 6 times, 6.5 times, 7 times, 7.5 times, 8 times, 8.5 times, 9 times, 9.5 times, or 10 times its initial length without breaking, and can then be recovered to an elastically stretchable fiber that is close to or identical to its length before being stretched. The combination of the above ranges is also possible (e.g., greater than or equal to 1 and less than or equal to 10). Other ranges are also possible.

[0206] Non-limiting examples of suitable elastically stretchable fibers include: fibers comprising an elastomeric material, such as fibers comprising block copolymers (e.g., block copolymers containing styrene, such as Kraton), fibers comprising a polyurethane elastomer (e.g., spandex fibers), fibers comprising polyester-ethers, fibers comprising polyesters; olefin-based fibers (e.g., cross-linked poly(olefin) fibers); hard elastic fibers (e.g., elastic fibers comprising semi-crystalline polymers such as poly(formaldehyde), poly(propylene), poly(r-methyl-1-pentene), and / or poly(ethylene)); and multicomponent (e.g., bicomponent) elastic fibers (e.g., poly(ether-ester) elastic fibers).

[0207] When present, the scrim can comprise elastically extensible fibers having various suitable average diameters. The scrim can comprise elastically extensible fibers having an average diameter of 0.01 mm or greater, 0.02 mm or greater, 0.025 mm or greater, 0.03 mm or greater, 0.035 mm or greater, 0.04 mm or greater, 0.05 mm or greater, 0.06 mm or greater, 0.07 mm or greater, 0.08 mm or greater, 0.1 mm or greater, 0.15 mm or greater, 0.2 mm or greater, 0.25 mm or greater, 0.3 mm or greater, 0.35 mm or greater, 0.4 mm or greater, 0.5 mm or greater, 0.6 mm or greater, 0.7 mm or greater, 0.8 mm or greater, 1 mm or greater, or 1.5 mm or greater. The scrim may comprise elastically extensible fibers having an average diameter of 2 mm or less, 1.5 mm or less, 1 mm or less, 0.8 mm or less, 0.7 mm or less, 0.6 mm or less, 0.5 mm or less, 0.4 mm or less, 0.35 mm or less, 0.3 mm or less, 0.25 mm or less, 0.2 mm or less, 0.15 mm or less, 0.1 mm or less, 0.08 mm or less, 0.07 mm or less, 0.06 mm or less, 0.05 mm or less, 0.04 mm or less, 0.035 mm or less, 0.03 mm or less, 0.025 mm or less, or 0.02 mm or less. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.01 mm and less than or equal to 2 mm, greater than or equal to 0.1 mm and less than or equal to 2 mm, greater than or equal to 0.2 mm and less than or equal to 2 mm, greater than or equal to 0.3 mm and less than or equal to 2 mm, or greater than or equal to 0.3 mm and less than 0.8 mm). Other ranges are also possible.

[0208] When present, the scrim can comprise elastically extensible fibers having various suitable average lengths. The scrim can comprise elastically extensible fibers having an average length of 5 mm or greater, 10 mm or greater, 20 mm or greater, 50 mm or greater, 100 mm or greater, 200 mm or greater, 500 mm or greater, 1 m or greater, 2 m or greater, 5 m or greater, 10 m or greater, 20 m or greater, 50 m or greater, or 100 m or greater. In some embodiments, the elastically extensible fibers can be continuous fibers. The scrim can comprise elastically extensible fibers having an average length of less than or equal to 200 m, less than or equal to 100 m, less than or equal to 50 m, less than or equal to 20 m, less than or equal to 10 m, less than or equal to 5 m, less than or equal to 2 m, less than or equal to 1 m, less than or equal to 750 mm, less than or equal to 500 mm, less than or equal to 400 mm, less than or equal to 300 mm, less than or equal to 250 mm, less than or equal to 200 mm, less than or equal to 100 mm, less than or equal to 90 mm, less than or equal to 50 mm, less than or equal to 20 mm, or less than or equal to 10 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 5 mm and less than or equal to 100 m). Other ranges are also possible. The elastically extensible fibers can extend throughout the source of the scrim, such as throughout the entire material wound around a roller or forming a creel.

[0209] When present, the scrim can comprise elastically extensible fibers having various suitable deniers. In some embodiments, the elastically extensible fibers have a denier of 20 or more, 30 or more, 50 or more, 75 or more, 100 or more, 150 or more, 200 or more, 300 or more, 500 or more, 750 or more, 1000 or more, or 1500 or more. In some embodiments, the elastically extensible fibers have a denier of 2000 or less, 1500 or less, 1000 or less, 750 or less, 500 or less, 300 or less, 200 or less, 150 or less, 100 or less, 75 or less, 50 or less, or 30 or less. Combinations of the above-recited ranges are also possible (e.g., 20 or more and 2000 or less). Other ranges are also possible.

[0210] As mentioned above, some scrims can be relatively extensible and / or reversibly stretchable. When present, the scrim as a whole can be stretched to a relatively high elongation without breaking, and then allowed to recover to a length close to or the same as its length before being stretched. The scrim can also be formed from a reversibly stretchable material, but cannot itself be reversibly stretched. As an example, the scrim can be formed from a reversibly stretchable material and then laminated to a layer that cannot be reversibly stretched. The layer can prevent the scrim from undergoing reversible stretching (e.g., the reversible stretching that the scrim would be able to undergo if not laminated).

[0211] In some embodiments, the scrim may be capable of undergoing (and / or be formed from a material capable of undergoing) a reversible stretch of greater than or equal to 50%, greater than or equal to 75%, greater than or equal to 100%, greater than or equal to 125%, greater than or equal to 150%, greater than or equal to 175%, greater than or equal to 200%, greater than or equal to 225%, greater than or equal to 250%, greater than or equal to 275%, greater than or equal to 300%, greater than or equal to 325%, greater than or equal to 350%, greater than or equal to 375%, greater than or equal to 400%, greater than or equal to 450%, greater than or equal to 500%, greater than or equal to 600%, or greater than or equal to 800%. In some embodiments, the scrim can be capable of undergoing (and / or be formed from a material capable of undergoing) a reversible stretch of less than or equal to 1000%, less than or equal to 800%, less than or equal to 600%, less than or equal to 500%, less than or equal to 450%, less than or equal to 400%, less than or equal to 375%, less than or equal to 350%, less than or equal to 325%, less than or equal to 300%, less than or equal to 275%, less than or equal to 250%, less than or equal to 225%, less than or equal to 200%, less than or equal to 175%, less than or equal to 150%, less than or equal to 125%, less than or equal to 100%, or less than or equal to 75%. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 50% and less than or equal to 1000%, greater than or equal to 100% and less than or equal to 400%, or greater than or equal to 200% and less than or equal to 300%). Other ranges are also possible.

[0212] In some embodiments, the filter media includes a scrim having a relatively low stiffness. The stiffness of the scrim can be less than or equal to 500 mg, less than or equal to 400 mg, less than or equal to 350 mg, less than or equal to 300 mg, less than or equal to 275 mg, less than or equal to 250 mg, less than or equal to 225 mg, less than or equal to 200 mg, less than or equal to 175 mg, less than or equal to 150 mg, less than or equal to 125 mg, less than or equal to 100 mg, less than or equal to 80 mg, less than or equal to 60 mg, less than or equal to 50 mg, less than or equal to 40 mg, less than or equal to 30 mg, less than or equal to 25 mg, less than or equal to 20 mg, or less than or equal to 15 mg. The stiffness of the scrim can be greater than or equal to 10 mg, greater than or equal to 15 mg, greater than or equal to 20 mg, greater than or equal to 25 mg, greater than or equal to 30 mg, greater than or equal to 40 mg, greater than or equal to 50 mg, greater than or equal to 60 mg, greater than or equal to 80 mg, greater than or equal to 100 mg, greater than or equal to 125 mg, greater than or equal to 150 mg, greater than or equal to 175 mg, greater than or equal to 200 mg, greater than or equal to 225 mg, greater than or equal to 250 mg, greater than or equal to 275 mg, greater than or equal to 300 mg, greater than or equal to 350 mg, or greater than or equal to 400 mg. Combinations of the above ranges are also possible (e.g., less than or equal to 500 mg and greater than or equal to 10 mg, or less than or equal to 350 mg and greater than or equal to 10 mg). Other ranges are also possible. The stiffness of the scrim can be determined according to WSP 90.2 (2015).

[0213] When present, the scrim can have a variety of suitable weights per unit area. The weight per unit area of ​​a scrim in which undulations have not yet been formed tends to be lower than the weight per unit area of ​​a scrim that includes one or more sets of undulations. Forming undulations in the scrim tends to increase the amount of scrim per filter media track area and, therefore, tends to increase the weight per unit area of ​​the scrim. As described above, the manufacture of the filter media can include forming undulations in an initially non-undulating scrim that is then subjected to one or more processes to form one or more sets of undulations. For this reason, it may be easier to refer to the weight per unit area of ​​the scrim before the undulations. If expanded to remove all undulations from the scrim, these weights per unit area are equivalent to the weight per unit area of ​​the scrim.

[0214] The weight per unit area of ​​the scrim before undulation can be greater than or equal to 0.1 g / m 2 , greater than or equal to 0.2g / m 2 , greater than or equal to 0.3g / m 2 , greater than or equal to 0.5g / m 2, greater than or equal to 0.75g / m 2 , 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 7.5g / m 2 , greater than or equal to 10g / 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 40g / m 2 , greater than or equal to 50g / m 2 , greater than or equal to 60g / m 2 , greater than or equal to 70g / m 2 , greater than or equal to 80g / m 2 , or greater than or equal to 100g / m 2 The weight per unit area of ​​the scrim before undulation can be less than or equal to 120 g / m 2 , less than or equal to 100g / m 2 , 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 25g / m 2 , less than or equal to 20g / m 2 , less than or equal to 15g / m 2 , less than or equal to 10g / m 2 , less than or equal to 7.5g / m 2 , less than or equal to 5g / m 2 , less than or equal to 3g / m 2 , less than or equal to 2g / m 2 , less than or equal to 1g / m 2 , less than or equal to 0.75g / m 2 , less than or equal to 0.5g / m 2 , less than or equal to 0.3g / m 2 , or less than or equal to 0.2g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 g / m 2 And less than or equal to 120g / m 2, greater than or equal to 1g / m 2 And less than or equal to 120g / m 2 , greater than or equal to 5g / m 2 And less than or equal to 120g / m 2 , greater than or equal to 20g / m 2 And less than or equal to 80g / m 2 , or greater than or equal to 40g / m 2 and less than or equal to 60g / m 2 ). Other ranges are also possible. The weight per unit area of ​​the scrim can be determined by weighing a scrim of known area and then dividing the measured weight by the known area.

[0215] When present, the scrim can have a variety of suitable thicknesses. The thickness of a scrim in which undulations have not yet been formed tends to be lower than the thickness of a scrim that includes one or more sets of undulations. As described above, the manufacture of filter media can include forming undulations in an initially non-undulating scrim that is then subjected to one or more processes to form one or more sets of undulations. For this reason, it may be easier to refer to the thickness of the scrim before undulations. If expanded to remove all undulations from the scrim, these thicknesses are equivalent to the thickness of the scrim.

[0216] The scrim may have a thickness before undulation of 0.01 mm or greater, 0.015 mm or greater, 0.02 mm or greater, 0.025 mm or greater, 0.03 mm or greater, 0.035 mm or greater, 0.04 mm or greater, 0.045 mm or greater, 0.05 mm or greater, 0.055 mm or greater, 0.06 mm or greater, 0.065 mm or greater, 0.07 mm or greater, 0.08 mm or greater, 0.09 mm or greater, 0.1 mm or greater , greater than or equal to 0.15mm, greater than or equal to 0.2mm, greater than or equal to 0.25mm, greater than or equal to 0.3mm, greater than or equal to 0.35mm, greater than or equal to 0.4mm, greater than or equal to 0.45mm, greater than or equal to 0.5mm, greater than or equal to 0.55mm, greater than or equal to 0.6mm, greater than or equal to 0.65mm, greater than or equal to 0.7mm, greater than or equal to 0.8mm, greater than or equal to 0.9mm, greater than or equal to 1mm, greater than or equal to 1.5mm, greater than or equal to 2mm, greater than or equal to 3mm, or greater than or equal to 4mm. The scrim may have a thickness before undulation of 5 mm or less, 4 mm or less, 3 mm or less, 2 mm or less, 1.5 mm or less, 1 mm or less, 0.9 mm or less, 0.8 mm or less, 0.7 mm or less, 0.65 mm or less, 0.6 mm or less, 0.55 mm or less, 0.5 mm or less, 0.45 mm or less, 0.4 mm or less, 0.35 mm or less, 0.3 mm or less, 0.25 mm or less, or 0.65 mm or less. 0.2 mm, 0.15 mm, 0.1 mm, 0.09 mm, 0.08 mm, 0.07 mm, 0.065 mm, 0.06 mm, 0.055 mm, 0.05 mm, 0.045 mm, 0.04 mm, 0.035 mm, 0.03 mm, 0.025 mm, 0.02 mm, or 0.015 mm. Combinations of the above ranges are also possible (e.g., 0.01 mm or greater and 5 mm, 0.01 mm or greater and 2.5 mm, 0.1 mm or greater and 5 mm, 0.3 mm or greater and 1 mm or greater, or 0.4 mm or greater and 0.6 mm or less).The thickness of the scrim can be determined by the Edana WSP 120.1 standard (2005) with a presser foot selected to have a 2 ounce load and a 1 square inch area.

[0217] As mentioned above, some scrims can be relatively open.When existing, scrim can comprise such opening, and it can parameterize by having endpoint and passing the longest line of opening on the outer boundary of opening.This line will be equal to the diameter of circular opening or be equal to the diagonal line of rectangular opening.In some embodiments, scrim comprises such opening, the longest line that has endpoint and passes opening on the outer boundary of opening of described opening is greater than or equal to 0.1 inch, greater than or equal to 0.15 inch, greater than or equal to 0.2 inch, greater than or equal to 0.25 inch, greater than or equal to 0.3 inch, greater than or equal to 0.35 inch, greater than or equal to 0.4 inch, greater than or equal to 0.45 inch, greater than or equal to 0.5 inch, greater than or equal to 0.6 inch, greater than or equal to 0.8 inch, greater than or equal to 1 inch, greater than or equal to 1.25 inches, greater than or equal to 1.5 inches, greater than or equal to 1.75 inches, greater than or equal to 2 inches, greater than or equal to 2.5 inches, greater than or equal to 3 inches or greater than or equal to 4 inches. The scrim can include openings having a longest line having endpoints on an outer boundary of the opening and passing through the opening that is less than or equal to 5 inches, less than or equal to 4 inches, less than or equal to 3 inches, less than or equal to 2.5 inches, less than or equal to 2 inches, less than or equal to 1.75 inches, less than or equal to 1.5 inches, less than or equal to 1.25 inches, less than or equal to 1 inch, less than or equal to 0.9 inches, less than or equal to 0.6 inches, less than or equal to 0.5 inches, less than or equal to 0.45 inches, less than or equal to 0.4 inches, less than or equal to 0.35 inches, less than or equal to 0.3 inches, less than or equal to 0.25 inches, less than or equal to 0.2 inches, or less than or equal to 0.15 inches. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.1 inches and less than or equal to 5 inches, greater than or equal to 0.1 inches and less than or equal to 1 inch, or greater than or equal to 0.1 inches and less than or equal to 0.5 inches). Other ranges are also possible. The opening can have a variety of shapes (eg, square, rectangular, etc.).

[0218] The fibers in the plurality of elastically extensible fibers (e.g., in a scrim comprising the plurality of elastically extensible fibers) can be spaced apart from one another at various suitable distances. In some embodiments, the average spacing between each elastically extensible fiber in the plurality of elastically extensible fibers and its nearest neighbor is greater than or equal to 2 mm, greater than or equal to 3 mm, greater than or equal to 5 mm, greater than or equal to 7.5 mm, greater than or equal to 10 mm, greater than or equal to 15 mm, greater than or equal to 20 mm, greater than or equal to 30 mm, greater than or equal to 50 mm, or greater than or equal to 75 mm. In some embodiments, the average spacing between each elastically extensible fiber in the plurality of elastically extensible fibers and its nearest neighbor is less than or equal to 100 mm, less than or equal to 75 mm, less than or equal to 50 mm, less than or equal to 30 mm, less than or equal to 20 mm, less than or equal to 15 mm, less than or equal to 10 mm, less than or equal to 7.5 mm, less than or equal to 5 mm, or less than or equal to 3 mm. Combinations of the above ranges are also possible (e.g., greater than or equal to 2 mm and less than or equal to 100 mm). Other ranges are also possible. It should be understood that the above ranges refer to average values, and the plurality of elastically extensible fibers may include evenly spaced elastically extensible fibers or non-evenly spaced elastically extensible fibers.

[0219] As described above, some filter media include a nanofiber layer. The nanofiber layer can improve the filtration performance of the filter media. In some embodiments, the nanofiber layer acts as an efficiency layer. In such a case, the nanofiber layer can have one or more characteristics described herein for the efficiency layer and / or can have one or more characteristics described herein for the nanofiber layer. When present, the nanofiber layer can be positioned in a plurality of suitable positions in the filter media, such as the upstreammost layer, the downstreammost layer, or a layer having one or more layers positioned upstream and one or more layers positioned downstream. In other words, the nanofiber layer can be the first layer, the second layer, the third layer, the fourth layer, or another layer. In some embodiments, the filter media includes more than one nanofiber layer. For example, the filter media can include the first and second layers as nanofiber layers, the second and third layers as nanofiber layers, the first and third layers as nanofiber layers, or any other combination of layers as nanofiber layers. In some embodiments, the filter media includes a nanofiber layer and a scrim layer positioned on opposite sides of another efficiency layer (e.g., a meltblown efficiency layer, another nanofiber efficiency layer).

[0220] Some nanofiber layers described herein are fibrous. For example, the nanofiber layer can be a nonwoven web. In some embodiments, the nonwoven web is an electrospun web, a meltblown web, or a centrifugally spun web, and / or includes electrospun fibers, meltblown fibers, and / or centrifugally spun fibers.

[0221] In some embodiments, the nanofiber layer comprises a fiber web (e.g., a fiber web of the type described in the previous paragraph) that has undergone one or more processes after formation to reduce the diameter of the fibers in the nanofiber layer. As an example, in some embodiments, the nanofiber layer is formed (e.g., by one of the processes in the previous paragraph) to include multicomponent fibers (e.g., bicomponent fibers, "island-in-the-sea" fibers). One or more components of the multicomponent fibers are then removed, leaving fibers with smaller diameters. The components can be removed by, for example, a water jet. Another example of a process that can be employed to reduce the fiber diameter of the fibers is fibrillation.

[0222] The nanofiber layer can comprise synthetic fibers and / or natural fibers. Non-limiting examples of synthetic fibers include nylon fibers (e.g., nylon 6 fibers), poly(vinylidene fluoride) fibers, poly(ethersulfone) fibers, polyester fibers, polycarbonate fibers, and / or poly(lactic acid) fibers. An example of a natural fiber is chitosan fiber.

[0223] When present, the nanofiber layer can comprise synthetic fibers having various suitable average diameters. Each nanofiber layer in the filter media can independently comprise synthetic fibers having an average diameter of 20 nm or greater, 50 nm or greater, 75 nm or greater, 100 nm or greater, 200 nm or greater, 500 nm or greater, or 750 nm or greater. Each nanofiber layer in the filter media can independently comprise synthetic fibers having an average diameter of 1 micron or less, 750 nm or less, 500 nm or less, 200 nm or less, 100 nm or less, 75 nm or less, or 50 nm or less. Combinations of the above-referenced ranges are also possible (e.g., 20 nm or greater and 1 micron or less). Other ranges are also possible.

[0224] It should also be noted that the nanofiber layer can include fibers having two or more different diameters and / or two or more different types of cross-sections. Such fibers having different cross-sections and / or diameters can have the same chemical composition, or can have different chemical compositions. Non-limiting embodiments of suitable cross-sections include circular, oval, Y-shaped, I-shaped (e.g., dog-bone), closed C-shaped, multi-lobed (e.g., trilobed, 4-lobed, 5-lobed, 6-lobed, including more than 6 lobes, X-shaped, crenulated).

[0225] When present, the nanofiber layer may comprise synthetic fibers having various suitable average lengths. The fibers may include staple fibers and / or continuous fibers. Each nanofiber layer in the filter media can independently comprise synthetic fibers having an average length of 0.2 mm or greater, 0.5 mm or greater, 1 mm or greater, 2 mm or greater, 5 mm or greater, 10 mm or greater, 15 mm or greater, 20 mm or greater, 25 mm or greater, 30 mm or greater, 40 mm or greater, 50 mm or greater, 75 mm or greater, 100 mm or greater, 150 mm or greater, 200 mm or greater, 250 mm or greater, 300 mm or greater, 350 mm or greater, 400 mm or greater, 450 mm or greater, 500 mm or greater, 750 mm or greater, 1 m or greater, 2 m or greater, 5 m or greater, 10 m or greater, 20 m or greater, 50 m or greater, or 100 m or greater. Each nanofiber layer in the filter media can independently comprise synthetic fibers having an average length of 200 m or less, 100 m or less, 50 m or less, 20 m or less, 10 m or less, 5 m or less, 2 m or less, 1 m or less, 750 mm or less, 500 mm or less, 450 mm or less, 400 mm or less, 350 mm or less, 300 mm or less, 250 mm or less, 200 mm or less, 150 mm or less, 100 mm or less, 75 mm or less, 50 mm or less, 40 mm or less, 30 mm or less, 25 mm or less, 20 mm or less, 15 mm or less, 10 mm or less, 5 mm or less, 2 mm or less, 1 mm or less, or 0.5 mm or less. Combinations of the above ranges are also possible (e.g., greater than or equal to 0.2 mm and less than or equal to 100 mm, greater than or equal to 0.2 mm and less than or equal to 500 mm, greater than or equal to 20 mm and less than or equal to 500 mm, or greater than or equal to 100 mm and less than or equal to 350 mm). Other ranges are also possible.

[0226] When present, the nanofiber layer can have a variety of suitable weights per unit area. The weight per unit area of ​​a nanofiber layer in which undulations have not yet been formed tends to be lower than the weight per unit area of ​​a nanofiber layer that includes one or more sets of undulations. The formation of undulations in the nanofiber layer tends to increase the amount of nanofiber layer per filter medium track area, and therefore tends to increase the weight per unit area of ​​the nanofiber layer. As described above, the manufacture of the filter medium can include forming undulations in an initially non-undulating nanofiber layer, which is then subjected to one or more processes to form one or more sets of undulations. For this reason, it may be easier to refer to the weight per unit area of ​​the nanofiber layer before the undulations. These weights per unit area are equivalent to the weight per unit area of ​​the nanofiber layer if expanded to remove all undulations in the nanofiber layer.

[0227] Each nanofiber layer in the filter medium may independently have a basis weight before undulation greater than or equal to 0.02 g / m 2 , greater than or equal to 0.03g / m 2 , greater than or equal to 0.04g / m 2 , greater than or equal to 0.05g / m 2 , greater than or equal to 0.075g / 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 1.5g / m 2 , greater than or equal to 2g / m 2 , greater than or equal to 3g / m 2 , or greater than or equal to 4g / m 2 Each nanofiber layer in the filter medium may independently have a basis weight of less than or equal to 5 g / m2 before undulation. 2 , less than or equal to 4g / m 2 , less than or equal to 3g / m 2 , less than or equal to 2g / m 2 , less than or equal to 1.5g / 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 , less than or equal to 0.1g / m 2 , less than or equal to 0.075g / m 2 , less than or equal to 0.05g / m 2 , less than or equal to 0.04g / m 2 , or less than or equal to 0.03g / m2 Combinations of the above ranges are also possible (e.g., greater than or equal to 0.02 g / m 2 and less than or equal to 5g / m 2 , greater than or equal to 0.05g / m 2 and less than or equal to 3g / m 2 , or greater than or equal to 0.1g / m 2 and less than or equal to 2g / m 2 ). Other ranges are also possible.

[0228] In some embodiments, the nanofiber layer is provided with a carrier layer. The nanofibers can be directly adjacent to the carrier layer, or one or more layers can be positioned between the carrier layer and the nanofiber layer. In some embodiments, the filter medium comprises a nanofiber layer and a carrier layer with an adhesive positioned therebetween. The nanofiber layer can be deposited onto the carrier layer during formation (e.g., during an electrostatic spinning process). In some embodiments, the carrier layer supports the nanofiber layer and / or allows the nanofiber layer to be handled in an easy manner without experiencing damage. Some carrier layers can also serve as backings, which are described in more detail elsewhere in this article.

[0229] Some carrier layers are fibrous. For example, the carrier layer can be a nonwoven web, such as a meltblown web, a spunbond web, a mesh, a net, and / or a carded web. In some embodiments, the carrier layer comprises synthetic fibers, non-limiting examples of which include polypropylene fibers, polyester fibers, and nylon fibers. The filter medium can also include a non-fibrous carrier layer. Non-limiting examples of suitable non-fibrous carrier layers include perforated membranes and fibrillated membranes.

[0230] When present, the support layer can comprise synthetic fibers having various suitable average diameters. Each support layer in the filter media can independently comprise synthetic fibers having an average diameter of 0.5 microns or greater, 0.75 microns or greater, 1 micron or greater, 1.25 microns or greater, 1.5 microns or greater, 1.75 microns or greater, 2 microns or greater, 2.25 microns or greater, 2.5 microns or greater, 2.75 microns or greater, 3 microns or greater, 4 microns or greater, 5 microns or greater, 7.5 microns or greater, 10 microns or greater, 12.5 microns or greater, 15 microns or greater, 20 microns or greater, 30 microns or greater, or 40 microns or greater. Each carrier layer in the filter media can independently comprise synthetic fibers having an average diameter of less than or equal to 50 microns, less than or equal to 40 microns, less than or equal to 30 microns, less than or equal to 20 microns, less than or equal to 15 microns, less than or equal to 12.5 microns, less than or equal to 10 microns, less than or equal to 7.5 microns, less than or equal to 5 microns, less than or equal to 4 microns, less than or equal to 3 microns, less than or equal to 2.75 microns, less than or equal to 2.5 microns, less than or equal to 2.25 microns, less than or equal to 2 microns, less than or equal to 1.75 microns, less than or equal to 1.5 microns, less than or equal to 1.25 microns, less than or equal to 1 micron, or less than or equal to 0.75 micron. Combinations of the above-referenced ranges are also possible (e.g., greater than or equal to 0.5 microns and less than or equal to 50 microns, greater than or equal to 0.5 microns and less than or equal to 20 microns, or greater than or equal to 1 micron and less than or equal to 3 microns). Other ranges are also possible.

[0231] It should also be noted that the carrier layer can contain fibers having two or more different diameters and / or two or more different types of cross-sections. Such fibers having different cross-sections and / or diameters can have the same chemical composition, or can have different chemical compositions. Non-limiting embodiments of suitable cross-sections include circular, oval, Y-shaped, I-shaped (e.g., dog-bone), closed C-shaped, multi-lobed (e.g., trilobed, 4-lobed, 5-lobed, 6-lobed, including more than 6 lobes, X-shaped, crenulated).

[0232] When present, the carrier layer can have a variety of suitable weights per unit area. The weight per unit area of ​​a carrier layer in which undulations have not yet been formed tends to be lower than the weight per unit area of ​​a carrier layer that includes one or more sets of undulations. The formation of undulations in the carrier layer tends to increase the amount of carrier layer per filter medium track area and therefore tends to increase the weight per unit area of ​​the carrier layer. As described above, the manufacture of the filter medium may include forming undulations in an initially non-undulating carrier layer, which then undergoes one or more processes to form one or more sets of undulations. For this reason, it may be easier to refer to the weight per unit area of ​​the carrier layer before the undulations. These weights per unit area are equivalent to the weight per unit area of ​​the carrier layer if expanded to remove all undulations in the carrier layer.

[0233] Each carrier layer in the filter medium may independently have a basis weight before undulation greater than or equal to 5 g / 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 , greater than or equal to 27.5g / 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 50g / m 2 , greater than or equal to 60g / m 2 , or greater than or equal to 80g / m 2 Each carrier layer in the filter medium may independently have a weight per unit area of ​​less than or equal to 100 g / m2 before undulation. 2 , less than or equal to 80g / 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 35g / m 2 , 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 , or less than or equal to 7.5g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 5 g / m 2 And less than or equal to 100g / m 2 , or greater than or equal to 5g / m 2 And less than or equal to 30g / m 2 ). Other ranges are also possible. The weight per unit area of ​​the carrier layer can be determined by weighing a carrier layer of known area and then dividing the measured weight by the known area.

[0234] As described above, some filter media (e.g., corrugated filter media) include one or more support layers. The support layer can support one or more other layers of the corrugated filter media. In some embodiments, one or more support layers can serve as a pre-filter and / or backing. When serving as a pre-filter, the support layer can be positioned upstream of the efficiency layer and can help filter out large particles from the fluid before being exposed to the efficiency layer. This can enhance the capacity of the filter media and / or protect the efficiency layer. The support layer serving as a backing can be relatively open (e.g., it may only minimally contribute to the air resistance of the filter media) and / or can provide structural support for the filter media. In some embodiments, the filter media includes a support layer that also serves as a relatively rigid and / or pleated backing layer.

[0235] In one exemplary embodiment, the filter medium includes a downstream support layer disposed on the air outflow side of the corrugated layer and effectively maintaining the corrugated layer in a corrugated configuration. The filter medium may also include an upstream support layer disposed on the air inlet side of the corrugated layer opposite the downstream support layer. The upstream support layer may also help maintain the corrugated layer in a corrugated configuration. As described above, those skilled in the art will understand that the filter medium may include any number of layers and it does not necessarily have to include two support layers or a top layer. In certain exemplary embodiments, the filter medium may include a single support layer positioned upstream or downstream of other corrugated layers. In other embodiments, the filter medium may include any number of additional layers arranged in a variety of configurations. The specific number and type of layers will depend on the intended use of the filter medium.

[0236] The support layers described herein can be formed using a variety of techniques known in the art, including meltblowing, air-laid technology, carding, spunbonding, and extrusion. In an exemplary embodiment, the filter medium includes one or more support layers that are carded or air-laid webs. In some embodiments, the filter medium includes one or more support layers that are extruded webs. The filter medium may also include one or more support layers that are perforated membranes and / or fibrillated membranes.

[0237] A variety of materials can also be used to form the fibers of any support layer included in the filter media described herein, including synthetic materials and non-synthetic materials. One or more support layers can include meltblown fibers, staple fibers, and / or spunbond fibers. In an exemplary embodiment, one or more support layers are formed from staple fibers, and in particular from a combination of binder fibers and non-binder fibers. A suitable fiber composition is a blend of at least 20% binder fibers and the remainder non-binder fibers. Various types of binder fibers and non-binder fibers can be used to form the media of the present invention. The binder fibers can be formed from any material that effectively promotes thermal bonding between layers and will therefore have an activation temperature lower than the melting temperature of the non-binder fibers. The binder fibers can be either a single-component fiber or a plurality of multi-component (e.g., bicomponent) binder fibers. In one embodiment, the binder fibers can be bicomponent fibers, and each component can have a different melting temperature. For example, the binder fibers can include a core and a sheath, wherein the activation temperature of the sheath is lower than the melting temperature of the core. This allows the sheath to melt before the core, so that the sheath bonds to the other fibers in the layer while the core maintains its structural integrity. This can be particularly advantageous because it creates a more cohesive layer for capturing the filtrate. The core / sheath binder fibers can be concentric or non-concentric, and exemplary core / sheath binder fibers can include the following: polyester core / copolyester sheath, polyester core / polyethylene sheath, polyester core / polypropylene sheath, polypropylene core / polyethylene sheath, polyamide core / polyethylene sheath, and combinations thereof. Other exemplary bicomponent binder fibers can include split-fiber fibers, side-by-side fibers, and / or "islands-in-the-sea" fibers.

[0238] If present in one or more support layers, the non-binder fibers can be synthetic and / or non-synthetic, and in an exemplary embodiment, the non-binder fibers can be 100% synthetic. Synthetic fibers can have advantageous properties with respect to resistance to moisture, heat, long-term aging, and / or microbial degradation. Exemplary synthetic non-binder fibers can include polyester, acrylic, polyolefin, nylon, rayon, and combinations thereof.

[0239] When present, support layer can comprise the synthetic fiber of suitable percentage.For example, in some embodiments, the weight percent of the synthetic fiber in each support layer is independently 80 wt % to 100 wt % of all fibers in the support layer.In some embodiments, the weight percent of the synthetic fiber in each support layer is independently greater than or equal to 80 wt %, greater than or equal to 90 wt % or greater than or equal to 95 wt %.In some embodiments, the weight percent of the synthetic fiber in each support layer is independently less than or equal to 100 wt %, less than or equal to 95 wt %, less than or equal to 90 wt % or less than or equal to 85 wt %.The combination of above-mentioned scope is also possible (for example, greater than or equal to 80 wt % and less than or equal to 100 wt %).Other scopes are also possible.In some embodiments, one or more support layers comprise the synthetic fiber of 100 wt %.In some embodiments, relative to the gross weight of (for example, comprising any resin) support layer, one or more support layers comprise the synthetic fiber of above-mentioned scope.

[0240] When present, the support layer can be formed from a variety of fiber types and sizes. In an exemplary embodiment in which the filter medium includes a downstream support layer, the downstream support layer is formed from fibers having an average diameter greater than or equal to the average diameter of the fibers in the other layers present in the filter medium. In some cases in which the filter medium includes both an upstream support layer and a downstream support layer, the upstream support layer is formed from fibers having an average diameter less than or equal to the average diameter of the fibers in the downstream support layer, but greater than the average diameter of the other fibers in the other layers present in the filter medium. In certain exemplary embodiments, the filter medium includes a downstream support layer and / or an upstream support layer formed from fibers having an average diameter in the range of 10 microns to 32 microns, or 12 microns to 32 microns. For example, the average diameter of the downstream support layer and / or the upstream support layer can be in the range of 18 microns to 22 microns. In some cases, the downstream support layer and / or the upstream support layer can include relatively fine fibers. For example, in some embodiments, the finer downstream support layer and / or the finer upstream support layer can be formed from fibers having an average diameter in the range of 9 microns to 18 microns. For example, the average diameter of the finer downstream support layer and / or the finer upstream support layer may be in the range of 12 microns to 15 microns.

[0241] When present, the support layer can comprise fibers having various suitable average lengths. The fibers can include staple fibers and / or continuous fibers. Each support layer in the filter media can independently comprise fibers having an average length of 20 mm or greater, 50 mm or greater, 75 mm or greater, 100 mm or greater, 200 mm or greater, 250 mm or greater, 300 mm or greater, 400 mm or greater, 500 mm or greater, 750 mm or greater, 1 m or greater, 2 m or greater, 5 m or greater, 10 m or greater, 20 m or greater, 50 m or greater, or 100 m or greater. Each support layer in the filter media can independently comprise fibers having an average length of 200 m or less, 100 m or less, 50 m or less, 20 m or less, 10 m or less, 5 m or less, 2 m or less, 1 m or less, 750 mm or less, 500 mm or less, 400 mm or less, 300 mm or less, 250 mm or less, 200 mm or less, 100 mm or less, 75 mm or less, or 50 mm or less. Combinations of the above-referenced ranges are also possible (e.g., 20 m or more and 200 m or less, 20 mm or more and 100 mm or less, or 20 mm or more and 75 mm or less). Other ranges are also possible.

[0242] It should also be noted that the support layer can include fibers having two or more different diameters and / or two or more different types of cross-sections. Such fibers having different cross-sections and / or diameters can have the same chemical composition, or can have different chemical compositions. Non-limiting embodiments of suitable cross-sections include circular, oval, Y-shaped, I-shaped (e.g., dog-bone), closed C-shaped, multi-lobed (e.g., trilobed, 4-lobed, 5-lobed, 6-lobed, including more than 6 lobes, X-shaped, crenulated).

[0243] When present, the support layer can have a variety of suitable weights per unit area. The weight per unit area of ​​a support layer in which undulations have not yet been formed tends to be lower than the weight per unit area of ​​a support layer that includes one or more sets of undulations. Forming undulations in the support layer tends to increase the amount of support layer per filter media track area, and therefore tends to increase the weight per unit area of ​​the support layer. As described above, the manufacture of the filter media can include forming undulations in an initially non-undulating support layer, which is then subjected to one or more processes to form one or more sets of undulations. For this reason, it may be easier to refer to the weight per unit area of ​​the support layer before the undulations. These weights per unit area are equivalent to the weight per unit area of ​​the support layer if all undulations in the support layer are removed.

[0244] Each support layer may independently have a weight per unit area greater than or equal to 10 g / m 2 , greater than or equal to 20g / m 2 , greater than or equal to 22g / m 2 , greater than or equal to 33g / m 2 , greater than or equal to 50g / m 2 , greater than or equal to 60g / m 2 , greater than or equal to 70g / m 2 , greater than or equal to 80g / m 2 , or greater than or equal to 90g / m 2 The weight per unit area of ​​each support layer before undulation can independently be less than or equal to 99 g / m 2 , less than or equal to 90g / m 2 , 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 33g / m 2 , less than or equal to 22g / 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 10 g / m 2 and less than or equal to 99g / m 2 , or greater than or equal to 33g / m 2 and less than or equal to 70g / m 2 ). Other ranges are also possible. The weight per unit area of ​​the support layer can be measured by weighing a support layer of known area and then dividing the measured weight by the known area.

[0245] When present, the support layer can have various suitable thicknesses. The thickness of each support layer in the filter media can independently be greater than or equal to 3 mils, greater than or equal to 4 mils, greater than or equal to 5 mils, greater than or equal to 6 mils, greater than or equal to 8 mils, greater than or equal to 10 mils, greater than or equal to 12 mils, greater than or equal to 15 mils, greater than or equal to 20 mils, greater than or equal to 25 mils, greater than or equal to 30 mils, greater than or equal to 40 mils, greater than or equal to 50 mils, greater than or equal to 60 mils, greater than or equal to 75 mils, greater than or equal to 100 mils, greater than or equal to 125 mils, greater than or equal to 150 mils, or greater than or equal to 175 mils. The thickness of each support layer in the filter media can independently be less than or equal to 200 mils, less than or equal to 175 mils, less than or equal to 150 mils, less than or equal to 125 mils, less than or equal to 100 mils, less than or equal to 75 mils, less than or equal to 60 mils, less than or equal to 50 mils, less than or equal to 40 mils, less than or equal to 30 mils, less than or equal to 25 mils, less than or equal to 20 mils, less than or equal to 15 mils, less than or equal to 12 mils, less than or equal to 10 mils, less than or equal to 8 mils, less than or equal to 6 mils, less than or equal to 5 mils, or less than or equal to 4 mils. Combinations of the above-referenced ranges are also possible (e.g., 4 mils or more and 200 mils or less, 4 mils or more and 100 mils or less, 8 mils or more and 30 mils or less, 15 mils or more and 60 mils or less, or 12 mils or more and 20 mils or less). Other ranges are also possible. The thickness of the support layer can be determined using the Edana WSP 120.1 standard (2005) with a presser foot selected to have a 2 ounce load and a 1 square inch area.

[0246] When present, the support layer can have various suitable mean flow pore sizes. The mean flow pore size of each support layer in the filter medium can independently be greater than or equal to 30 microns, greater than or equal to 40 microns, greater than or equal to 50 microns, greater than or equal to 75 microns, greater than or equal to 100 microns, or greater than or equal to 120 microns. The mean flow pore size of each support layer in the filter medium can independently be less than or equal to 150 microns, less than or equal to 120 microns, less than or equal to 100 microns, less than or equal to 75 microns, less than or equal to 50 microns, or less than or equal to 40 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to 30 microns and less than or equal to 150 microns, or greater than or equal to 50 microns and less than or equal to 120 microns). Other ranges are also possible. The mean flow pore size of the support layer can be determined according to ASTM F316 (2011).

[0247] When present, the support layer can have various suitable stiffnesses. The stiffness of each support layer in the filter medium can independently be greater than or equal to 200 mg, greater than or equal to 300 mg, greater than or equal to 500 mg, greater than or equal to 750 mg, greater than or equal to 1000 mg, greater than or equal to 2000 mg, greater than or equal to 5000 mg, or greater than or equal to 7500 mg. The stiffness of each support layer in the filter medium can independently be less than or equal to 10,000 mg, less than or equal to 7500 mg, less than or equal to 5000 mg, less than or equal to 2000 mg, less than or equal to 1000 mg, less than or equal to 750 mg, less than or equal to 500 mg, or less than or equal to 300 mg. Combinations of the above ranges are also possible (e.g., greater than or equal to 200 mg and less than or equal to 10,000 mg). Other ranges are also possible. The stiffness of the support layer can be determined in accordance with WSP 90.2 (2015).

[0248] In one exemplary embodiment, the filter media includes a downstream support layer and an upstream support layer, each of the downstream support layer and the upstream support layer having a thickness greater than or equal to 8 mils and less than or equal to 30 mils (e.g., greater than or equal to 12 mils and less than or equal to 20 mils), a density greater than or equal to 10 g / m 2 and less than or equal to 99g / m 2 (For example, greater than or equal to 22g / m 2 and less than or equal to 99g / m 2 , or greater than or equal to 33g / m 2 and less than or equal to 70g / m 2 ) and a mean flow pore size greater than or equal to 30 microns and less than or equal to 150 microns (e.g., greater than or equal to 50 microns and less than or equal to 120 microns).

[0249] As described above, some filter media (e.g., corrugated filter media) include one or more outer layers or cover layers disposed on the air inlet side I and / or the air outlet side O. As an example, Figure 9AThe top layer 18 is shown as a cover layer disposed on the air inlet side 1 of the filter medium 1006. In some embodiments, the filter medium includes an outermost layer as a wire backing. In some embodiments, the filter medium includes a cover layer that can serve as a dust-bearing layer and / or can serve as an aesthetic layer. In an exemplary embodiment, the cover layer is a planar layer that fits with the rest of the filter medium after assembly and / or corrugation. The cover layer can provide an aesthetically pleasing top surface. The cover layer can be formed from a variety of fiber types and sizes. In an exemplary embodiment, the cover layer is formed from fibers having an average fiber diameter that is different from the average fiber diameter of the fibers in the upstream support layer (if an upstream support layer is present). In certain exemplary embodiments, the cover layer is formed from fibers having an average fiber diameter greater than or equal to 5 microns and less than or equal to 20 microns. As a result, the cover layer can serve as a dust-holding layer without affecting the gamma value of the filter medium.

[0250] The filter media may also include a non-fibrous cover layer. Non-limiting examples of suitable non-fibrous cover layers include perforated membranes and fibrillated membranes.

[0251] In some embodiments (e.g., Figure 9B ), the filter medium includes a bottom layer disposed on the air outflow side. The bottom layer can act as a reinforcing component, and if the filter medium includes one or more corrugated layers, the bottom layer provides structural integrity to the filter medium to help maintain the corrugated structure. The bottom layer can also serve to provide wear resistance. This may be particularly desirable in ASHRAE bag applications where the outermost layer is subject to wear during use. As discussed above, the bottom layer can have a similar construction to the cover layer. In some embodiments, the filter medium includes both a bottom layer and a cover layer. In an exemplary embodiment, the bottom layer is the coarsest layer, i.e., it is formed of fibers having an average diameter greater than the average diameter of the fibers of all other layers forming the filter medium. An exemplary bottom layer is a spunbond layer, however, a variety of other layers having a variety of constructions can be used.

[0252] When present, any outer layer (e.g., cover layer and / or bottom layer) can also be formed using a variety of techniques known in the art, including meltblowing, wet-laid technology, air-laid technology, carding, spunbond, and extrusion. In an exemplary embodiment, the cover layer is an air-laid layer, and the bottom layer is a spunbond layer. In some embodiments, the filter medium includes a cover layer that is an extruded web and / or mesh. The resulting layer can also have a variety of thicknesses, air permeabilities, and unit area weights, depending on the requirements of the desired application.

[0253] When present, the cover layer and / or base layer can comprise various suitable types of fibers, including synthetic and non-synthetic materials. In an exemplary embodiment, the filter media includes a cover layer and / or base layer formed from staple fibers, and in particular, a combination of binder fibers and non-binder fibers. One suitable fiber composition is a blend of at least 20% binder fibers and the balance non-binder fibers. A variety of types of binder and non-binder fibers can be used to form the media of the present invention, including those previously discussed above with respect to the support layer.

[0254] In one exemplary embodiment, the filter media includes a cover layer and / or a bottom layer, each of the cover layer and / or the bottom layer independently having a thickness greater than or equal to 2 mils and less than or equal to 50 mils, an air permeability greater than or equal to 100 CFM and less than or equal to 1200 CFM, and a density greater than or equal to 10 g / m 2 And less than or equal to 50g / m 2 The cover layer may also have an air permeability greater than 1200 CFM, such as an air permeability greater than 1500 CFM (e.g., having a thickness and / or air permeability not within the above ranges in addition to having a thickness and / or air permeability within the above ranges). The thickness of the cover layer may be determined using the Edana WSP 120.1 standard (2005) with a presser foot selected to have a 2 ounce load and an area of ​​1 square inch. The air permeability of the cover layer may be determined using the ASTM test standard D737 (1996) over a test area of ​​38 cm 2 The weight per unit area of ​​the cover layer can be determined by weighing a support layer of known area and dividing the measured weight by the known area.

[0255] As mentioned above, some filter media described herein include adhesives. Adhesives can be positioned between two layers to adhere them together. When present, adhesives can be positioned in multiple suitable positions in the filter media, such as between the efficiency layer and the scrim, between the efficiency layer and the nanofiber layer, between the nanofiber layer and the support layer, and / or between any other two layers in the filter media. In other words, adhesives can be positioned between the first and second layers, between the second and third layers, between the third and fourth layers, and / or between any other two layers. In some embodiments, the filter media includes adhesives positioned between two pairs of layers (for example, between the first and second layers, and between the second and third layers; between the first and second layers, and between the third and fourth layers). One or more layers (for example, the first, second, third, fourth layers, efficiency layers, scrims) of the filter media can also be impregnated with adhesive (for example, by dip coating and / or clamping (nip) technology). The characteristics of some adhesives are described in further detail below.

[0256] In the filter medium described herein, can adopt multiple adhesives.The limiting examples of suitable adhesives include pressure-sensitive adhesives and / or high-viscosity adhesives (for example, Carbobond 1995), hot melt adhesives (for example, Bostik HM4105, Bostik 2751).Adhesives can include one or more polymers, for example one or more thermosetting polymers and / or one or more thermoplastic polymers.The limiting examples of thermosetting adhesives include acrylic resins, vinyl ester resins, phenolic resins, thermosetting polyurethane resins, epoxy resins and unsaturated polyethylene terephthalate resins.The limiting examples of thermoplastic adhesives include hot melt adhesives, for example polyolefin adhesives, polyester adhesives, polyamide adhesives, thermoplastic polyurethane adhesives and ethylene vinyl acetate adhesives.In some embodiments, filter medium includes water-based adhesives.In some embodiments, adhesives are used in emulsion form.The solids dispersed in the emulsion can include acrylic copolymers.

[0257] When present, the adhesive may have any suitable basis weight. The amount of adhesive between any two layers may be greater than or equal to 0.1 g / m 2 , greater than or equal to 0.15g / m 2 , greater than or equal to 0.2g / m 2 , greater than or equal to 0.25g / m 2 , greater than or equal to 0.3g / m 2 , greater than or equal to 0.35g / m 2 , greater than or equal to 0.4g / m 2 , greater than or equal to 0.45g / m 2 , greater than or equal to 0.5g / m2 , greater than or equal to 0.6g / m 2 , greater than or equal to 0.8g / m 2 , greater than or equal to 1g / m 2 , greater than or equal to 1.25g / m 2 , greater than or equal to 1.5g / m 2 , greater than or equal to 1.75g / m 2 , greater than or equal to 2g / m 2 , greater than or equal to 2.5g / m 2 , greater than or equal to 3g / m 2 , greater than or equal to 4g / m 2 , greater than or equal to 5g / m 2 , greater than or equal to 6g / m 2 , greater than or equal to 8g / 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 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 , or greater than or equal to 45g / m 2 The amount of adhesive between any two layers can be less than or equal to 50 g / 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 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 8g / m 2 , less than or equal to 6g / m 2 , less than or equal to 5g / m 2 , less than or equal to 4g / m 2 , less than or equal to 3g / m 2 , less than or equal to 2.5g / m 2, less than or equal to 2g / m 2 , less than or equal to 1.75g / m 2 , less than or equal to 1.5g / m 2 , less than or equal to 1.25g / m 2 , less than or equal to 1g / m 2 , less than or equal to 0.8g / m 2 , less than or equal to 0.6g / m 2 , less than or equal to 0.5g / m 2 , less than or equal to 0.45g / m 2 , less than or equal to 0.4g / m 2 , less than or equal to 0.35g / m 2 , less than or equal to 0.3g / m 2 , less than or equal to 0.25g / m 2 , less than or equal to 0.2g / m 2 , or less than or equal to 0.15g / m 2 Combinations of the above ranges are also possible (e.g., greater than or equal to 0.1 g / m 2 And less than or equal to 50g / m 2 , greater than or equal to 0.1g / m 2 and less than or equal to 20g / m 2 , greater than or equal to 0.1g / m 2 and less than or equal to 5g / m 2 , greater than or equal to 0.3g / m 2 and less than or equal to 1g / m 2 , greater than or equal to 0.3g / m 2 And less than or equal to 0.5g / m 2 , or greater than or equal to 10g / m 2 and less than or equal to 20g / m 2 ). Other ranges are also possible.

[0258] The weight per unit area may be one or more of the following weights per unit area: (1) the weight per unit area of ​​the adhesive relative to the final filter medium; (2) the weight per unit area of ​​the adhesive relative to the filter medium that has been expanded to remove one set of undulations but not other undulations (e.g., expanded to remove undulations formed by the corrugation process but not by the pleating process); and (3) the weight per unit area of ​​the adhesive that has been expanded to remove all undulations therein.

[0259] In some embodiments, the filter media includes pairs of layers without adhesive positioned therebetween. Some filter media lack adhesives at all. In some embodiments, other methods are used in addition to or in lieu of methods using adhesives to bond the layers of the filter media together. For example, ultrasonic welding, calendaring, and / or lamination (e.g., thermal lamination, chemical lamination, and / or mechanical lamination) can be used to bond two or more layers of the filter media together.

[0260] When present, the adhesive can be applied to the layer in a variety of suitable ways. As an example, the adhesive can be applied to the layer by spraying. As another example, the adhesive can be applied to the layer by passing the layer through a volume of adhesive. For example, in the case of a layer comprising elastically extensible fibers (e.g., a scrim comprising such fibers), the elastically extensible fibers can be passed through a volume of adhesive and thereby become coated with the adhesive.

[0261] The filter medium may also include a layer comprising a functional component. The layer may be a layer as described herein, or may be a layer that differs from one or more of the layers described herein in one or more ways. An example of a functional component is an adsorbent component. The adsorbent component may adsorb one or more substances to which the filter medium is exposed, such as one or more harmful substances (e.g., harmful gases) that may be present in the fluid to which the filter medium is exposed. Non-limiting examples of suitable adsorbent components include activated carbon and ion exchange resins.

[0262] Example 1

[0263] This example describes the fabrication and testing of a filter media including an uppermost layer of irregular structures present at its surface and extending therethrough.

[0264] Each filter medium is manufactured by adhering the meltblown efficiency layer to a stretched mesh scrim, and then restoring the stretched mesh scrim. First, prepare the mesh scrim and the meltblown efficiency layer. The mesh scrim and the meltblown efficiency layer are cut into desired sizes: the mesh scrim is cut to form a 15-inch by 16-inch rectangle, and the meltblown efficiency layer is cut to form a rectangle with a width of 15 inches and a length equal to the stretched length of the mesh to which the meltblown efficiency layer will be applied. Then, the mesh scrim is placed on blotting paper and an adhesive is applied thereto with a medium fine-haired paint roller. The adhesive is a 50% by weight: 50% by weight mixture of water and Carbobond 1955 (55% by weight solid acrylic copolymer emulsion). After coating with the adhesive, the mesh scrim is hung and air-dried for at least 10 minutes.

[0265] After the mesh scrim and meltblown efficiency layer are prepared, they are assembled together to form the filter media. The mesh scrim is clamped to a piece of parchment paper, which is set on a wooden board by wooden strips fixed to the board by dowel pins. Figure 10 The planks, strips, and dowel pins are shown. The distal strip is then moved away from the proximal strip to stretch the filter media until the desired stretch is achieved. At this point, a lightweight roller device is used to gently press the meltblown efficiency layer onto the adhesive-coated web. Figure 11 A photograph of an exemplary meltblown efficiency layer adhered to an adhesive-coated mesh stretched to 300% of its original length is shown. Finally, the meltblown efficiency layer and mesh scrim are removed from the parchment and wood strips, the mesh scrim is allowed to recover, and the excess portion of the mesh scrim not covered by the meltblown efficiency layer is cut away. The mesh scrim is recovered by removing the dowel pins from the distal wood strips and manually reducing the tension on the stretched mesh scrim. During this process, the meltblown efficiency layer becomes wrinkled.

[0266] Two sets of filter media were made, both of which included a polypropylene meltblown efficiency layer having fibers with diameters ranging from 1 to 3 microns and a SWM X30014 styrenic block copolymer mesh scrim. For the first type of filter media (Type A), the polypropylene meltblown efficiency layer had a 7.7 g / m 2 For the second type of filter media (Type B), the polypropylene meltblown efficiency layer has a weight per unit area of ​​32 g / m 2 The weight per unit area is hydraulically charged.

[0267] For both types of filter media, increasing the degree of stretching of the mesh scrim up to 300% stretching before adhering the meltblown efficiency layer to the mesh scrim increased the gamma, average surface height, thickness, and basis weight of the resulting filter media. Stretching the mesh scrim to 400% stretching did not result in further increases in these values. Tables 3 and 4 below show the effect of initial mesh scrim stretching on several properties of the resulting filter media for Type A and Type B filter media, respectively.

[0268] Table 3. Characteristics of Type A Filter Media

[0269]

[0270]

[0271] Table 4. Characteristics of Type B Filter Media

[0272]

[0273] Figure 12 and Figure 13 Gamma and thickness of Type A filter media are shown, respectively, as a function of the degree of stretching of the mesh scrim prior to adhering the meltblown efficiency layer to the mesh scrim. Figure 12 and Figure 13 , the x-axis is the degree of stretch, which is equivalent to the difference between the stretched length of the mesh scrim when the meltblown efficiency layer is applied and the original length of the mesh scrim, divided by the original length of the mesh scrim, and then multiplied by 100%. Figure 14 and Figure 15 The average surface height (Sa) and basis weight of the two types of filter media are shown as a function of the degree of stretching of the mesh scrim before the meltblown efficiency layer is adhered to the mesh scrim. Figure 14 and Figure 15 , the x-axis is the ratio of the stretched length of the mesh scrim when the meltblown efficiency layer is applied to the initial length of the mesh scrim. Figure 16 Gamma is shown as a function of mean surface height for both types of filter media, indicating that gamma increases with mean surface height.

[0274] For Type B filter media, increasing the degree to which the mesh scrim is stretched prior to adhering the meltblown efficiency layer thereto also increases the irregularities of the surface of the filter media. Figure 17 and Figure 18 A comparison between filter media of Type B and a simulation of pleated filter media is shown. Figure 17 The y-axis shows the ratio of the standard deviation of the peak spacing across each sample to the average peak spacing, which is determined by following steps (1) to (2) of the procedure described above for ISO 16610-21:2011, performing step (4) on each row, and then using standard statistical techniques to determine the standard deviation of the peak spacing. Figure 18 The y-axis shows the ratio of the peak height standard deviation to the mean peak height across each sample, which is determined by following steps (1) to (2) of the procedure described above for ISO 16610-21:2011, performing step (4) on each row, and then using standard statistical techniques to determine the height standard deviation. Figure 17 and Figure 18 The x-axis shows the position of the row in the sample where the relevant ratio was measured. The data from the stretched sample is the data measured from the above sample. The data from the simulated pleats is data obtained based on a simulation of pleated media, which includes small 10 mm high pleats with a spacing of 2.5 mm. Variations in pleat height and spacing commonly found during the manufacture of pleated media were included in the simulation.

[0275] like Figure 17 As shown in , the ratio of the peak spacing standard deviation to the average peak spacing increases with the degree of stretching of the mesh scrim prior to adhering the meltblown efficiency layer thereto. Figure 17As shown in , the ratio of the standard deviation of the peak spacing to the average peak spacing of each filter medium of type B is much greater than the ratio of the standard deviation of the peak spacing to the average peak spacing of the simulated pleated filter medium. Figure 18 As shown in , the ratio of the peak height standard deviation to the average peak height decreases with the degree to which the mesh scrim is stretched prior to adhering the meltblown efficiency layer thereto. This is because the average peak height increases to a greater extent than the peak height standard deviation with the degree to which the mesh scrim is stretched prior to adhering the meltblown efficiency layer thereto. However, as Figure 18 As shown in , for all cases, the ratio of the peak height standard deviation to the average peak height for the filter media described in this example greatly exceeds the ratio of the peak height standard deviation to the average peak height for the simulated filter media having pleats.

[0276] Example 2

[0277] This example describes the fabrication and testing of a filter media including a reversibly stretchable layer and produced in a continuous manner.

[0278] Two filter media were manufactured by depositing a first layer and a second layer (or combination of layers) onto opposite sides of a reversibly stretched layer, then allowing the reversibly stretched layer to recover. The layer deposited onto the reversibly stretched layer was unwound from a roll and then bonded to the reversibly stretched layer. Subsequently, the reversibly stretched layer was recovered, causing the layer deposited thereon to become undulating. Finally, the resulting filter media was wound around another roll. Table 5 shows selected properties of the filter media.

[0279] Table 5. Characteristics of filter media.

[0280]

[0281]

[0282] Figure 19 and Figure 20 Comparative data from these filter media are shown. Figure 19 The y-axis shows the ratio of the standard deviation of the peak spacing across each sample to the average peak spacing, which is determined by following steps (1) to (2) of the procedure described above for ISO 16610-21:2011, performing step (4) on each row, and then using standard statistical techniques to determine the standard deviation of the peak spacing. Figure 20 The y-axis shows the ratio of the peak height standard deviation across each sample to the mean peak height, which is determined by following steps (1) to (2) of the procedure described above for ISO 16610-21:2011, performing step (4) on each row, and then using standard statistical techniques to determine the height standard deviation. Figure 19 and Figure 20 The x-axis shows the position in the sample at the row where the correlation ratio was measured. Figure 19 and Figure 20 It is shown that filter media having irregular structures can be manufactured using a continuous roll-to-roll process, and the advantages described with respect to filter media having irregular structures but manufactured using a laboratory-scale process are also demonstrated.

[0283] Example 3

[0284] This example describes the fabrication and testing of a filter media including a reversibly stretchable layer and suitable for hydraulic applications.

[0285] The procedure described in Example 2 was used to form two filter media suitable for hydraulic applications. An additional control filter media was produced. This filter media contained glass fibers. Table 6 below summarizes the properties of the three filter media.

[0286] Table 6. Characteristics of filter media.

[0287]

[0288]

[0289] As can be seen from Table 6, the filter media made by using the reversibly stretchable layer had higher hydraulic gamma and higher dust holding capacity compared to the control filter media.

[0290] Example 4

[0291] This example describes the fabrication and testing of a filter media including a reversibly stretchable layer and suitable for HVAC panel applications.

[0292] The procedure described in Example 2 was followed, except for the final step of locking the structure onto another scrim to form a filter media suitable for HVAC panel applications. Another control filter media was produced. This control filter media contained electret carded fibers typically used in MERV 13 panel filters, but its efficiency dropped dramatically during operation due to electret charge decay. When tested according to the Ashrae 52.2 (Appendix J) test standard, it achieved a MERV-A of 9. Table 7 below summarizes the properties of the three filter media.

[0293] Table 7. Characteristics of filter media.

[0294]

[0295] As can be seen from Table 7, the filter media manufactured by using the reversible stretch layer has a good MERV-A rating of MERV 13 or above during operation, while the control media can only provide MERV-9 A. In addition, when compared with the control media, the reversible stretch filter media described herein can achieve a comparable or lower pressure drop.

[0296] Example 5

[0297] This example describes the fabrication and testing of a filter media including a reversibly stretchable layer suitable for P100 pancake respiratory applications.

[0298] The procedure described in Example 2 was followed, except for the final step of locking the structure onto another scrim to form a filter medium suitable for respiratory applications. Two additional control filter media, typically used in the manufacture of P100 respirators, were manufactured or obtained. These control filter media comprised electret meltblown fibers surface-treated with a fluoropolymer using chemical vapor deposition techniques. The developed reversibly stretchable filter media described herein and the control samples were tested under standard testing conditions for respirators having a dual-filter "pancake." The test conditions are listed below in Table 8.

[0299] Table 8. Test conditions for P100 respirator filter media

[0300]

[0301] Table 9. Characteristics of P100 respirator filter media

[0302]

[0303] As can be seen in Table 9, the filter media manufactured using the reversible stretch layer met all requirements of the NIOSH 42CFR84 standard for the P100 respiratory test. Furthermore, the reversibly stretchable filter media described herein achieved these stringent requirements at a pressure drop 50% to 60% lower than the control sample. This lower pressure drop reduces air permeability resistance and increases oil loading capacity, which in turn increases wearer comfort and respirator life. Figure 21 The pressure drop performance of Sample No. 45 relative to Control Sample A and Control Sample B during the DOP oil loading process is shown.

[0304] Example 6

[0305] This example describes the fabrication and testing of a filter media including a reversibly stretchable layer suitable for use in a bag filter element.

[0306] The procedure described in Example 2 was followed, except for the final step of locking the structure onto another scrim to form a filter media suitable for face mask applications. Another control filter media was used as a benchmark. The control sample was a commercial-grade media typically used to manufacture ePM 1-60% bag filters when tested according to the ISO 16890 test standard. The developed filter elements described herein and the control filter elements were tested according to the ISO 16890 test standard at air flow rates expected for short-bag applications. The test conditions are listed below in Table 10.

[0307] Table 10. Test conditions for P100 respirator filter media

[0308] Test parameters Test conditions <![CDATA[Test air flow rate, (m 3 / h)]]> 3400 <![CDATA[Filter medium surface area under test, (m 2 )]]> 3.33 Number of bags 8 Bag depth (m) 0.35 Bag length (m) 0.61 Bag width (m) 0.61 Pressure drop required for the application, (mm) 8 Required ISO 16890 efficiency ePM1-60%

[0309] Table 11. Characteristics of ePM1-60 bag filter

[0310]

[0311] As can be seen from Table 11, filter bag elements made with reversibly stretchable layers meet the ePM 1-60% efficiency requirement at an initial pressure drop 25% lower than the competitive control media. This lower pressure drop reduces the energy consumption to operate such filters and makes it easy for facility managers to replace high-field dielectric filter elements with short bag filter elements without having to change any installed HVAC hardware such as fan size or filter housing size.

[0312] Although several embodiments of the present invention are described and illustrated herein, it will be readily apparent to those skilled in the art that various other methods and / or structures for performing the functions and / or obtaining the results and / or one or more advantages described herein may be employed, and each of such variations and / or modifications is considered to be within the scope of the present invention. More generally, it will be readily understood by those skilled in the art that all parameters, dimensions, materials, and configurations described herein are intended to be exemplary, and that actual parameters, dimensions, materials, and / or configurations will depend on one or more specific applications for which the teachings of the present invention are used. Those skilled in the art will recognize or be able to determine many equivalents of the specific embodiments of the present invention described herein using only routine experimentation. Therefore, it will be understood that the aforementioned embodiments are provided only as examples, and within the scope of the appended claims and their equivalents, the present invention may be implemented in a manner different from that specifically described and claimed. The present invention relates to each individual feature, system, product, material, kit, and / or method described herein. In addition, if two or more such features, systems, products, materials, kits, and / or methods are not mutually inconsistent, any combination of such features, systems, products, materials, kits, and / or methods is included within the scope of the present invention.

[0313] All definitions, as defined and used herein, should be understood to control over dictionary definitions, definitions in documents incorporated by reference, and / or ordinary meanings of the defined terms.

[0314] Unless explicitly stated to the contrary, as used herein in the specification and claims, nouns without quantifiers should be understood to mean "at least one."

[0315] As used herein in the specification and claims, the phrase "and / or" should be understood to mean "either or both" of the elements so combined (i.e., elements that are present in combination in some cases and separately in other cases). Multiple elements listed with "and / or" should be understood in the same manner, i.e., "one or more" of the elements so combined. In addition to the elements specifically indicated by the "and / or" clause, other elements may optionally be present, whether related or unrelated to those specifically indicated. Thus, as a non-limiting example, when used in conjunction with open language such as "comprising", a reference to "A and / or B" may refer to only A (optionally including elements other than B) in one embodiment; to only B (optionally including elements other than A) in another embodiment; to both A and B (optionally including other elements) in yet another embodiment; and so on.

[0316] As used herein in the specification and claims, "or" should be understood to have the same meaning as "and / or" as defined above. For example, when separating the items in a list, "or" or "and / or" should be understood to be inclusive, i.e., including at least one of a plurality of elements or a list of elements, but also including more than one, and optionally including items not listed in addition. Only terms that are clearly indicated to the contrary, such as "only one" or "exactly one" or (when used in the claims) "consisting of ... ", will refer to exactly one element in a plurality of elements or a list of elements. Usually, when in front of an exclusive term such as "either one", "one", "only one" or "exactly one", the term "or" as used herein should only be interpreted to indicate an exclusive alternative (i.e., "one or the other, but not both"). When used in the claims, "substantially consisting of ... " should have its ordinary meaning used in the field of patent law.

[0317] As used herein in the specification and claims, the phrase "at least one" in reference to a list of one or more elements should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but does not necessarily include at least one of each and every element specifically listed in the list of elements, and does not exclude any combination of elements in the list of elements. This definition also allows that elements other than the elements specifically identified in the list of elements to which the phrase "at least one" refers may optionally be present, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, "at least one of A and B" (or equivalently, "at least one of A or B," or equivalently, "at least one of A and / or B") may, in one embodiment, refer to the presence of at least one A, optionally including more than one A, and the absence of B (and optionally including elements in addition to B); in another embodiment, refer to the presence of at least one B, optionally including more than one B, and the absence of A (and optionally including elements in addition to A); in yet another embodiment, refer to at least one A, optionally including more than one A, and at least one B, optionally including more than one B (and optionally including other elements); and so on. It will also be understood that, unless expressly stated to the contrary, in any method claimed herein that includes more than one step or action, the order of the method steps or actions is not necessarily limited to the order in which the method steps or actions are enumerated.

[0318] In the claims and throughout the foregoing description, all transitional phrases such as "comprising," "including," "with," "having," "containing," "involving," "maintaining," "consisting of," and the like are to be construed as open-ended, i.e., meaning including, but not limited to, including. Only the transitional phrases "consisting of" and "consisting essentially of" are to be closed or semi-closed transitional phrases, respectively, as set forth in the United States Patent Office Manual of Patent Examining Procedures, Section 2111.03.

Claims

1. A filter product comprising: A filter medium comprising: a nonwoven fiber web, wherein: the air permeability of the nonwoven fiber web is greater than or equal to 2 CFM; the nonwoven fiber web comprises a plurality of peaks having an average peak height and a peak height standard deviation; the ratio of the peak height standard deviation to the average peak height is greater than or equal to 0.15 and less than or equal to 0.5; and the average surface height of the nonwoven fiber web is greater than 0.3 mm.

2. A filtration article according to any preceding claim, wherein the filtration article comprises a medical filter.

3. The filtration article of any preceding claim, wherein the medical filter comprises a surgical drape, a gown, a cap, a hood, a mask, an operating room shoe, or shoe covers.

4. The filtration article of any preceding claim, wherein the filtration article comprises a respirator or respiratory protection device.

5. The filtering article of any preceding claim, wherein the respirator or respiratory protection device comprises an elastomeric half-mask respirator, an elastomeric full-face respirator, a filtering facepiece respirator, or a powered air-purifying respirator (PAPR).

6. The filtration article of any preceding claim, wherein the respirator or respiratory protection device comprises a particulate filtering respirator.

7. The filtration article according to any preceding claim, wherein the particulate filtering respirator is selected from the group consisting of an N95 respirator, an N99 respirator, an N100 respirator, an R95 respirator, an R99 respirator, an R100 respirator, a P95 respirator, a P99 respirator, a P100 respirator, and an HE (high efficiency particulate air) respirator.

8. The filtration article of any preceding claim, wherein the filtration article comprises an indoor air filtration article for HVAC and HEPA applications.

9. The filtration article of any preceding claim, wherein the indoor air filtration article comprises a cut frame fan coil unit filter, a cut frame panel filter, an HVAC panel filter, an HVAC box filter, or an HVAC V-filter.

10. The filtration article of any preceding claim, wherein the indoor air filtration article is configured for residential use.

11. The filtration article of any preceding claim, wherein the indoor air filtration article is configured for commercial use.

12. The filtration article of any preceding claim, wherein the filtration article comprises a cabin air filter for a vehicle.

13. The filtration article of any preceding claim, wherein the filtration article comprises a room air purifier filter.

14. The filtration article of any preceding claim, wherein the filtration article comprises a vacuum cleaner filter.

15. The filtration article of any preceding claim 1, wherein the filtration article comprises a heavy duty air filter.

16. The filtration article of any preceding claim, wherein the filtration article comprises a hydraulic fluid filter.

17. A filtration article according to any preceding claim, wherein the filtration article comprises a process liquid filtration filter.

18. The filtering article of any preceding claim, wherein the filtering article comprises a scarf, a stroller cover, a protective shield, a sheet, a curtain, or a garment.

19. A filtration article according to any preceding claim, wherein the filtration article comprises a geotextile and / or a material used in construction.

20. A method of making a filter article, comprising: depositing a layer onto the reversibly stretchable layer; as well as The reversibly stretchable layer is at least partially recovered, wherein the layer forms a plurality of peaks during the recovery of the reversibly stretchable layer.

21. A filter element comprising: A filter medium comprising: a nonwoven fiber web, wherein: the air permeability of the nonwoven fiber web is greater than or equal to 2 CFM; the nonwoven fiber web comprises a plurality of peaks having an average peak height and a peak height standard deviation; the ratio of the peak height standard deviation to the average peak height is greater than or equal to 0.15 and less than or equal to 0.5; and the average surface height of the nonwoven fiber web is greater than 0.3 mm.

Images