CN115397539A

CN115397539A - Filter media with irregular structure and/or reversibly stretchable layer

Info

Publication number: CN115397539A
Application number: CN202180028800.2A
Authority: CN
Inventors: 布鲁斯·史密斯; 穆罕默德·A·哈桑; 马克西姆·西林; 素德海尔·金卡; 格雷格·瓦格纳·法雷尔; 大卫·T·希利
Original assignee: Hollingsworth and Vose Co
Current assignee: Hollingsworth and Vose Co
Priority date: 2020-05-04
Filing date: 2021-05-04
Publication date: 2022-11-25
Also published as: WO2021226049A1; EP4146369A1; WO2021226049A8

Abstract

The present disclosure generally provides articles and methods relating to filter media. In some embodiments, the filter media has an irregular surface structure. For example, the filter media may include a plurality of peaks that are irregular in one or more ways. The ratio of the standard deviation of peak height to the average peak height may be greater than or equal to 0.05 and/or the ratio of the standard deviation of peak spacing to the average peak spacing may be greater than or equal to 0.08. In some embodiments, the filter media comprises a nonwoven web having a layer thickness greater than 0.3mm and/or a stiffness of 100mg or less.

Description

Filter media with irregular structure and/or reversibly stretchable layer

Technical Field

The present invention relates generally to filter media, and more particularly to filter media having an irregular structure.

Background

The filter media may be formed from one or more fiber webs. The fiber web provides a porous structure that allows fluid (e.g., gas, air) to flow through the filter media. Contaminant particles contained within the fluid may be trapped on or within the fibrous web. Filter media characteristics such as surface area and basis weight (basis weight) affect 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 result in a higher fluid flow resistance, and thus a higher pressure drop.

There is a need for a filter media that can be used in a variety of applications that has a desirable balance of properties including high efficiency and low resistance to fluid flow through the filter media, resulting in high gamma values.

Disclosure of Invention

A filter media, related components, and related methods are generally described.

In some embodiments, a filter media is provided. The filter media includes a nonwoven web having a stiffness of less than or equal to 100mg and an average surface height of greater than 0.3 mm.

In some embodiments, a filter media is provided. The filter media 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 a corrugated configuration by the second layer. The second layer is formed of a reversibly stretchable material.

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

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

In some embodiments, a filter media is provided. The filter media includes a nonwoven 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 pitch to the average peak pitch is greater than or equal to 0.08. The nonwoven web has an average surface height of greater than 0.3 mm.

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

In some embodiments, a method of making a filter media is provided. The method comprises the following steps: the nonwoven web is deposited onto the reversibly stretchable layer and the reversibly stretchable layer is at least partially recovered. The nonwoven web forms a plurality of peaks during recovery of the reversibly stretched layer.

In some embodiments, a method of making a filter media is provided. The method comprises the following steps: the layer is deposited onto the reversibly stretchable layer and the reversibly stretchable layer is at least partially recovered. The layer forms a plurality of peaks during recovery of the reversibly stretched layer.

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

Drawings

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

FIG. 1 is a schematic illustration of a filter media according to some embodiments;

FIG. 2 is an example of measured relative surface topography according to some embodiments;

FIG. 3A is an example of a set of line data obtained during measurement of relative surface topography in accordance with some embodiments;

FIG. 3B is an example of a set of line data in which a local maximum (shown as a larger point) has been identified and employed to determine a peak height (Hi) and a spacing (Di) between two adjacent peaks;

fig. 4A-4C are schematic illustrations of filter media according to some embodiments;

FIG. 5A is a schematic illustration of a filter media including two layers according to some embodiments;

FIG. 5B is a schematic illustration of a filter media including three layers according to some embodiments;

6A-6C and 6D-6F are schematic diagrams of methods of making filter media according to some embodiments;

fig. 7A-7B are schematic diagrams of fibers coated with an adhesive, according to some embodiments;

FIG. 8 is a schematic illustration of a filter media including two layers according to some embodiments;

FIGS. 9A-9C are schematic illustrations of a wave filter media according to some embodiments;

10-11 are photographs of an apparatus that may be used to fabricate a filter media according to some embodiments;

FIG. 12 is a graph illustrating the percent increase in γ and γ as a function of stretch according to some embodiments;

FIG. 13 is a graph illustrating thickness and percent increase in thickness as a function of stretch according to some embodiments;

FIG. 14 is a graph illustrating surface height as a function of stretch according to some embodiments;

FIG. 15 is a graph illustrating basis weight as a function of stretch according to some embodiments;

FIG. 16 is a graph illustrating γ as a function of surface height according to some embodiments;

FIG. 17 is a graph showing the ratio of the standard deviation of peak pitch to the average peak pitch at different degrees of stretch according to some embodiments;

FIG. 18 is a graph illustrating a ratio of peak height standard deviation to average peak height according to some embodiments;

FIG. 19 is a graph illustrating the ratio of the standard deviation of peak pitch to the average peak pitch according to some embodiments; and

FIG. 20 is a graph illustrating a ratio of peak height standard deviation to average peak height according to some embodiments.

Detailed Description

Articles and methods relating to filter media are generally provided. Some embodiments relate to filter media that include an irregular structure. The irregularities may be present on an outer surface of the filter media, in an interior of the filter media, and/or throughout the filter media. In some embodiments, the irregular structure comprises an irregular configuration (e.g., spatial configuration, surface configuration) of at least a portion of one or more layers in the filter media. For example, the filter media may include one or more layers having surfaces and/or three-dimensional shapes that create irregular structures. In some embodiments, the irregular structure may 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 may be formed by undulations in the layer and/or the surface of the layer. Advantageously, the irregular structure may be used to increase the gamma of the filter media by, for example, increasing the relative amount of filter media per unit area. By way of example, filter media including certain irregular peaks may have a greater surface area per unit area of filter media and/or a greater basis weight per unit area than certain conventional filter media.

The filter media described herein may also have one or more desired physical properties. For example, the filter media may be relatively thin and/or have a relatively low stiffness. In some embodiments, the filter media may have a thinness and/or stiffness that is not achievable by other methods. Such lightweight, thin, and/or low stiffness media may be desirable for a variety of applications, including bag filters and face masks. Some filter media may be thick and/or rigid, but still have the structure described herein.

Some embodiments relate to methods of forming filter media including irregular structures. As will be described in further detail below, one method of forming such a filter media includes: one or more layers are deposited onto the reversibly stretchable layer, and then the reversibly stretchable layer is at least partially recovered. During recovery, the reversibly stretchable layer may shorten along the direction in which the reversibly stretchable layer is stretched, possibly to the pre-stretched dimension of the reversibly stretchable layer. Upon recovery of the reversibly stretchable layer, the recovering reversibly stretchable layer can pull any layer deposited on the reversibly stretchable layer through recovery. The restoration process may cause the filter media and/or one or more portions of the filter media to include an irregular structure, such as a plurality of peaks having one or more irregular characteristics. Without wishing to be bound by any particular theory, it is believed that forming the peaks in this manner may be particularly easy and/or may result in the peaks being formed with a particularly desirable irregular morphology. However, it should also be understood that other methods of forming the structures described herein are also possible.

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 suitable for use in acoustic applications, articles configured for and/or suitable for use in acoustic insulation applications, articles configured for and/or suitable for use in thermal insulation applications, articles of clothing, and/or articles suitable for use in clothing. Such articles may have one or more features described elsewhere herein with respect to the filter media and/or may differ from the filter media described elsewhere herein in one or more ways.

One non-limiting example of a filter media comprising an irregular structure is shown in FIG. 1. In fig. 1, the irregular structure is present at least at the surface of the filter medium; thus, fig. 1 shows a filter medium comprising an irregular structure at the surface. The filter media 1000 shown in fig. 1 includes a plurality of peaks 100. The plurality of peaks 100 includes

peaks

10, 20, 30, 40, and 50 separated by

valleys

60, 70, 80, and 90. Each peak has a height and a width. Peaks that are not on the outer edge of the filter media (i.e., peaks 20, 30, and 40) have two nearest neighbor spacings; the peaks (i.e., peaks 10 and 50) on the outer edge of the filter media have a nearest neighbor spacing. By way of example, peak 40 has a height 40H, a width 40W, and two

nearest neighbor spacings

40A and 40B. These characteristics of the peaks can be determined by means of scanning optical microscopy, such as the Keyence VR-3000G2, measurement Unit Model VR3200 Wide-Area 3D Measurement system. The surface topography of the filter media can be measured with a scanning optical microscope at a resolution of at least 25 microns in each of the x-axis and y-axis and at least 0.5 microns in the z-axis according to the standard described in ISO 25178 (2006). This measurement produces a matrix of values representing the height of the surface measured at a set of points on the sample, where the x-position and y-position of each measured surface height are given by the columns and rows of the matrix, respectively. Then, the following z-value can be defined as the reference height (as shown by the dashed line 2 in fig. 1): the points constituting 95% of the measured surface topography are above the z-value and the points constituting 5% of the measured surface topography are below the z-value. The reference height can be subtracted from the height of each point in the measured surface topography to produce a relative height of each point in the measured surface topography and a relative surface topography comprised of relative height values.

The final product may then be prepared according to ISO 16610-21:2011 further computational processing is performed on the relative surface topography to determine the height of each peak. The calculation process may include the following sequence of steps: (1) Removing the outer 10% of the dots from each edge to reduce edge effects; (2) Applying a gaussian filter with kernel size of 30 pixels to smooth the resulting data; (3) Converting the resulting data into a set of line data by selecting every 10 rows; 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. Fig. 2 shows one example of the relative surface topography measured after step (2) according to the process, and fig. 3A shows one example of a set of line data measured after step (3) according to the process. Fig. 3B shows an example of a set of line data at which local maxima have been identified (shown as larger points) and employed to determine peak height (Hi) and spacing (Di) between two adjacent peaks.

In some embodiments, like that shown in fig. 1-3B, the peaks within the plurality of peaks may differ from one another in one or more ways. For example, the plurality of peaks may include two or more peaks having different heights, different spacings from nearest neighbors of the plurality of peaks, and/or different shapes. By way of example, referring to fig. 1, the height 40H of peak 40 is different from the height 20H of peak 20. As another example, the spacing 40A between

peaks

30 and 40 and the spacing 40B between

peaks

40 and 50 are different. In some embodiments, the plurality of peaks does not include two peaks having the same height, does not include two groups of peaks having the same spacing, and/or does not include two peaks having the same width. For example, the irregular structure and/or filter media may not include a peak having the same height, spacing, and/or width as another peak.

In some embodiments, the plurality of peaks includes two or more peaks that are similar in one or more ways. 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 fig. 1, the height 20H of the peak 20 has the same value as the height 50H of the peak 50. In some embodiments, the plurality of peaks includes two or more peaks that are similar in one or more ways (e.g., peaks having the same height, the same spacing from nearest neighbors, and/or the same width) and two or more peaks that are different in one or more ways (e.g., peaks having different heights, different spacings from nearest neighbors of the two or more peaks, and/or different widths). Referring again to fig. 1, the plurality of peaks 100 includes

peaks

20 and 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.

It should be understood that the irregular structure may be present at any location within the filter media, but need not be present at all locations. For example, like the filter media shown in fig. 1, some filter media may include a first surface having an irregular structure (e.g., a plurality of peaks) and include a second surface opposite the first surface that is relatively regular (e.g., flat) or completely free of the irregular structure (e.g., peaks) by comparison. Unlike the filter media shown in fig. 1, some filter media may include two opposing surfaces, each of which includes an irregular structure. For example, some filter media may include two opposing surfaces, each of the two opposing surfaces including a plurality of peaks, and/or each of the two opposing surfaces including a plurality of peaks that are irregular in one or more ways. In some embodiments, as will be described in more detail below, a filter media comprises: a first surface comprising a first plurality of peaks that are irregular in one or more ways; and a second surface comprising a second plurality of peaks similar in all respects other than amplitude to a plurality of valleys positioned between peaks in the first plurality of peaks. The second plurality of peaks may 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 may have a small height.

If one or more portions of the filter media described herein (e.g., one or more layers in the filter media, one or more surfaces of the filter media) include an irregular structure, the filter media described herein should be understood to include an irregular structure. The irregularities (e.g., peaks) may be located at one or more surfaces of the filter media, in the interior of the filter media, and/or throughout the filter media. By way of example, a filter media comprising an irregular structure may comprise: a plurality of peaks present at one or more surfaces of the filter media that are irregular in one or more ways; a plurality of peaks extending through one or more layers of the filter media; and/or a plurality of peaks present at one or more surfaces of a layer of the filter media.

It should also be understood that in embodiments where the irregular structure is not present at the outer surface of the filter media, the characteristics of the irregular structure may be measured by: the portion of the filter media that impedes the measurement of the irregularities is removed and the irregularities are measured as described above. For example, in some embodiments, the filter media includes two opposing layers that are free of irregularities, but includes a layer positioned between the two opposing layers that are free of irregularities that includes irregularities (e.g., a plurality of peaks that are irregular in one or more ways). For such filter media, a layer comprising one of the surfaces that is free of irregularities can be removed such that the irregularities are exposed, and the features of interest of the exposed irregularities can be measured by optical microscopy as described above.

In some embodiments, the filter media comprises one or more layers. As used herein, a layer may have a common topography, may have a common chemical composition, may be positioned between two other layers, may separate two other layers, and/or may provide a common function in a filter media, among other features. Some tiers may be topologically connected across the tiers, and some tiers may include two or more portions that are topologically disconnected from each other. For example, fig. 4A shows one example of a filter media 1002A that includes: a first layer 202, the first layer 202 being topologically connected across the layers; and a second layer 302, the second layer 302 including portions (e.g., portion 602 and portion 702) that are topologically disconnected from each other. Fig. 4B shows a perspective view of this same filter media. Although not shown in fig. 4A-4B, other types of layers may also include irregular structures. Additionally, some layers may be free of portions that may be removed from the layer without the use of special tools and/or without breaking apart the layer, and some layers may include such portions.

In some embodiments, a layer in a filter media first takes the form of a layer when incorporated into the filter media. In other words, a collection of articles that were not a layer prior to incorporation into a filter media can be considered to form a layer of the filter media after incorporation into the filter media. A specific example of such a layer is a plurality of elastically extensible fibers. The plurality of fibers may be separate, mechanically decoupled fibers prior to incorporation into the filter media. When incorporated into a filter media, the elastically extensible fibers may have a common function (e.g., act as a scrim) and/or may separate two layers (e.g., an efficiency layer and a support layer). Fig. 4C shows one example of a plurality of elastically extensible fibers forming layer 302 positioned between layer 202 and layer 402. Non-limiting examples of suitable layers include nonwoven webs, meshes, a plurality of fibers that are not in direct contact with each other and/or are not mechanically coupled to each other, and an adhesive that adheres two layers together, the adhesive being positioned between the two layers.

For example, with reference to fig. 1, the filter media 1000 may be a single layer filter media. As another example, also with reference to fig. 1, the filter media 1000 may be a filter media comprising two or more layers. FIG. 5A illustrates one non-limiting embodiment of a filter media 1001 including a first layer 201 and a second layer 301. In some embodiments, the filter media may include one or more layers having an irregular structure. The irregular structure may include an irregular spatial configuration of the layers. For example, a layer or a portion of a layer 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 a case, 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 the following structure: the structure is such that each peak on the first side of the layer has a corresponding valley on the opposite side of the layer, and each valley on the first side of the layer has a corresponding peak on the opposite side of the layer. The plurality of valleys may be similar in one or more ways to their corresponding plurality of peaks, and/or the plurality of peaks may be similar in one or more ways to their corresponding plurality of valleys. For example, a pair of corresponding valleys and peaks may be located in approximately the same location, may have approximately the same peak height, may have approximately the same peak width, may have approximately the same peak shape, and/or may have approximately the same nearest neighbor spacing. A layer arranged such that its entire thickness is arranged in three-dimensional peaks and valleys may be referred to as a layer comprising a plurality of peaks extending through the entire thickness of the layer and/or may be referred to as a relief layer.

One example of a relief layer is layer 201 in fig. 5A. Layer 201 in fig. 5A includes a plurality of peaks 101, the plurality of peaks 101 including

peaks

11, 21, 31, 41, and 51 separated by

valleys

61, 71, 81, and 91. The

valleys

61, 71, 81, and 91 together form a plurality of valleys 101T (not shown). These peaks and valleys are present at the upper side of the layer 201 (and at the upper side of the filter medium 301). The plurality of peaks 101 have a corresponding plurality of valleys 101O (not shown), including valleys 11O, 21O, 31O, 41O, and 51O on the bottom side of layer 201, and the plurality of valleys 101T (not shown) have a corresponding plurality of peaks 101TO (not shown), including peaks 61O, 71O, 81O, and 91O. In some embodiments, the profile of the top surface of the relief layer (e.g., layer 201) may be substantially the same as the profile of the bottom surface of the relief layer when viewed in cross-section.

In some embodiments, a relief layer has a structure that indicates a layer that has not been relieved at a certain point in time and has undergone a process of relieving it. The undulating layer may include portions that are in tension (e.g., upper surfaces of the peaks, lower surfaces of the valleys positioned between the peaks) and/or portions that are in compression (e.g., lower surfaces of the peaks, upper surfaces of the valleys positioned between the peaks). The layers may be undulated by various suitable processes, such as folding, crimping, creasing, and the like. In some embodiments, heat shrinking may be performed to undulate one or more layers. For example, one or more layers may be disposed on a layer having a high thermal shrinkage, and the layer having a high thermal shrinkage may be heated to shrink it and cause the one or more layers disposed on the layer having a high thermal shrinkage to undulate.

In some embodiments, the filter media includes a layer that does not include irregularities. A layer that does not contain irregular structures may not include any peaks (e.g., the layer may be relatively flat), or the layer may include a plurality of regular peaks. For example, like the filter media shown in fig. 5A, the filter media can include one layer that includes irregularities (e.g., peaks) and one layer that does not include irregularities (e.g., peaks). For example, the filter media 1001 shown in fig. 5A includes a layer 201 having a plurality of peaks (e.g., 11, 21, 31, 41, and 51), and also includes a layer 301 that does not have any peaks. In embodiments where a layer, such as layer 201 shown in fig. 5A, includes a plurality of peaks, the peaks may have one or more irregular features as described herein.

In some embodiments, the filter media comprises two or more layers comprising irregular structures (e.g., two or more layers comprising a plurality of peaks that are irregular in one or more ways) and two or more layers that do not comprise irregular structures (e.g., two or more layers that do not comprise peaks or comprise a plurality of peaks having a regular structure). For such embodiments, the layers may be arranged relative to each other in a variety of suitable ways. For example, two layers each comprising a plurality of peaks that are irregular in one or more ways are positioned on opposite sides of a layer that does not comprise a plurality of peaks that are irregular in one or more ways. A filter media having this structure may be manufactured by pleating two layers on opposite sides of a reversibly stretched layer. As another example, two layers each free of one or more irregular peaks may be positioned on opposite sides of a layer comprising one or more irregular peaks. For example, one or more layers comprising a plurality of peaks can be positioned between two outer layers that are completely free of peaks and/or relatively flat.

In some embodiments, the filter media includes only layers having a plurality of peaks that are irregular in one or more ways.

As shown in fig. 5A, some filter media include a single layer having multiple peaks. Some filter media include two or more layers each having a plurality of peaks. FIG. 5B illustrates one non-limiting embodiment of a filter media comprising two layers each having a plurality of peaks. In fig. 5B, the filter media 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 includes a plurality of peaks separated by a plurality of valleys. The surface of each of the layers opposite the first surface includes a plurality of valleys corresponding to peaks present in the first surface of the layer and a plurality of peaks corresponding to valleys present in the first surface of the layer.

In some embodiments, the filter media includes two or more layers that undulate together. For example, in fig. 5B, both the first layer and the third layer are also undulating layers that undulate together. In other words, both the first layer and the third layer are undulating, and the first layer includes a first plurality of peaks that is substantially similar to a second plurality of peaks present in the third layer. Referring to fig. 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 about the same as 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 undulating on opposite sides of a layer that is not undulating. As another example, the filter media may include first and second layers as follows: both the first and second layers are undulating and include undulations that are substantially similar in location, but have substantially different amplitudes (e.g., substantially different average peak heights). Some filter media may include layers that undulate together and layers that undulate separately.

Various suitable types of layers may 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 of any type of layer (e.g., filter media including a scrim and an efficiency layer; filter media including a scrim, an efficiency layer, and a nanofiber layer; filter media including a scrim, an efficiency layer, a nanofiber layer, and a carrier layer). Some filter media include two or more layers of a single kind (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. may refer to any type of layer, and it should be understood that the layers described herein may be combined with each other in a variety of different combinations and in a variety of different orders. It should also be understood that reference to a nonwoven web may refer to any type of nonwoven web layer, such as an efficiency layer as a nonwoven web, a nanofiber layer as a nonwoven web, a scrim as a nonwoven web, a carrier layer as a nonwoven web, and/or a support layer as a nonwoven web. The characteristics of the different types of layers that may be included in the filter media are described in further detail below.

The filter media described herein can be manufactured in a variety of suitable ways. One method that may be particularly advantageous for making filter media is illustrated in fig. 6A-6C. In this method, a layer having a relatively low stiffness is corrugated using a layer capable of undergoing reversible stretching to form a corrugated layer. A layer capable of undergoing reversible stretch is stretched, and a layer having a relatively low stiffness is deposited on the layer capable of undergoing reversible stretch when the layer capable of undergoing reversible stretch is in a stretched state (i.e., when the layer capable of undergoing reversible stretch is in the form of a reversibly stretched layer). Then, when the reversible stretching layer recovers, the reversible stretching layer pulls back the layer having the relatively low rigidity by the recovery, thereby wrinkling the layer having the relatively low rigidity. The reversibly stretchable layer may be fully restored (i.e., to the original dimensions of the reversibly stretchable layer prior to stretching) or partially restored (i.e., to dimensions between the original dimensions of the reversibly stretchable layer prior to stretching and the dimensions of the reversibly stretchable layer when in a stretched state). In other words, a layer capable of undergoing reversible stretching may be stretched in a fully reversible manner or in a partially reversible and partially irreversible manner. Fig. 6A shows a possible first step of reversibly stretching a layer capable of undergoing reversible stretching, such as a scrim, to a stretched state. Fig. 6B shows a possible second step of depositing a layer, such as an efficiency layer, on the reversibly tensile layer. Fig. 6C shows the recovery of the reversibly stretched layer. During the recovery process, the layer having a relatively low stiffness wrinkles and forms a plurality of peaks that are irregular in height, spacing, width, and/or shape. The reversibly stretchable layer may hold the peaks in place.

In some embodiments, like the embodiments shown in fig. 6A-6C, the reversibly tensile layer may be a layer that is topologically connected across the entire layer. Similarly, and also like the embodiments shown in fig. 6A-6C, the reversibly tensile layer may take the form of a layer before any layer is deposited thereon. The reversibly tensile layer may also include portions that are topologically disconnected from each other, and/or may not be a layer until one or more other layers are deposited on the reversibly tensile layer (e.g., as with layer 302 depicted in fig. 4A-4C). As one example, in some embodiments, the reversibly stretchable layer includes a plurality of elastically extensible fibers that initially do not form a layer. The elastically extensible fiber may be reversibly stretchable (e.g., reversibly stretchable along the axis of the elastically extensible fiber). Depositing one or more layers on the elastically extensible fibers may allow 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 to layers in the filter media. Fig. 6D to 6F show schematic diagrams of such a process.

In general, any suitable number of layers may be undulating using layers capable of undergoing reversible stretching (e.g., undulating any suitable number of layers by crimping). In some embodiments not shown in fig. 6A-6C, after the layer having the relatively low stiffness is deposited on the reversibly tensile layer, one or more other layers may be deposited on the reversibly tensile layer. In some embodiments, one or more other layers may be deposited onto the reversibly stretchable layer along with a layer having a relatively low stiffness. One or more other layers may be deposited prior to recovery of the reversibly stretched layer. For example, a second efficiency layer may be deposited onto the first efficiency layer deposited onto the reversibly stretched scrim, a deposited nanofiber layer may be deposited onto the efficiency layer deposited onto the reversibly stretched scrim, or both efficiency layers may be deposited together onto the reversibly stretched scrim. The reversibly stretched layer may then be recovered as shown in fig. 6C. During this step, the layer deposited on the reversibly stretchable layer (e.g., deposited on and/or with the layer having the relatively low stiffness) may become undulating (e.g., may become undulating by wrinkling). In some embodiments, like the embodiment shown in fig. 5B, the layers may undulate together and/or wrinkle together. After becoming undulating and/or wrinkled, the layer may be maintained in an undulating and/or wrinkled configuration by reversibly stretching the layer. In addition to layers having a relatively low stiffness, one or more other layers deposited onto the reversibly stretchable layer may also have a relatively low stiffness, which may promote such favorable wrinkling. In some embodiments, one or more other layers may be deposited onto the reversibly tensile layer after the reversibly tensile layer is restored. In some embodiments, such a layer may prevent the reversibly stretchable layer from undergoing further reversible stretching.

In some embodiments, like the embodiments shown in fig. 6A-6C, the layer to be wrinkled is deposited directly onto the reversibly stretchable layer, and the resulting wrinkled and recovered layers are 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 the layer, or intervening layers or materials may also be present. A layer "directly on," directly adjacent "or" in contact with "another layer means that there are no intervening layers or materials present.

In some embodiments, the layer to be wrinkled is deposited on the layer or material deposited onto the reversibly stretchable layer, and the resulting wrinkled layer and recovery layer are adjacent but not directly adjacent. For example, the layer to be creped may be deposited on the adhesive deposited onto the reversibly stretchable layer such that the adhesive is positioned between the resulting creped layer and the recovery layer. In some embodiments in which the adhesive is positioned between the layer to be wrinkled and the reversibly stretchable layer, the adhesive may be deposited on the reversibly stretchable layer before and/or after stretching.

For example, the adhesive may be deposited onto a scrim, the scrim may be stretched, and then the efficiency layer may be deposited onto the stretched scrim. In this case, the adhesive and the scrim are stretched together in the direction in which the scrim is stretched. The efficiency layer may be poorly bonded to the scrim in the direction in which the scrim is stretched, and thus the efficiency layer may detach from the scrim in the opposite direction at some locations when the scrim is restored. In this case, the efficiency layer may be pleated, and the scrim may include undulations (or become undulating) that follow the undulations in the efficiency layer. The undulations in the scrim may be much smaller than the undulations in the efficiency layer (i.e., they may have much smaller average peak heights), and thus the scrim may be considered relatively flat but not completely flat compared to the efficiency layer.

In one particular embodiment, the above process may 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. The case of full coating may 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 shown in fig. 7A, where adhesive 804A coats the entire circumference of the elastically extensible fibers 904). The case of partial coating may include depositing adhesive onto the elastically extensible fibers such that the adhesive coats portions of the elastically extensible fibers, such as closer to the adhesive source and/or portions for other layers to be subsequently deposited onto (e.g., as shown in fig. 7B, where adhesive 804B coats some, but not all, of the circumference of the elastically extensible fibers 904).

The reversibly stretchable layer may also be bonded to another layer by ultrasonic bonding. The reversibly stretchable layer may be reversibly stretched, optionally the reversibly stretchable layer may be recovered, and then the reversibly stretchable layer is laminated to another layer deposited on the reversibly stretchable layer. This process may be formed in conjunction with or in place of the process described in the preceding paragraph to adhere the reversibly stretchable layer and the layer deposited on the reversibly stretchable layer together 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.

The process described in the previous paragraph may be performed in a roll-to-roll manner. As an example, in some embodiments, the reversibly stretchable layer (or a plurality of elastically extensible fibers that form the reversibly stretchable layer when incorporated into a filter media) is supplied from a roll, a plurality of spools, or an instrument (e.g., a yarn or filament bundle) that provides a plurality of ends of a yarn or filament. Then, when incorporated into a filter media, the reversibly stretchable layer or the plurality of elastically extensible fibers forming the reversibly stretchable layer may be passed under a station that applies an adhesive to the reversibly stretchable layer or the plurality of elastically extensible fibers forming the reversibly stretchable layer, stretched, and then used as a substrate upon which another layer (e.g., an efficiency layer) is deposited. The other layer may be a pre-existing layer wound around and deposited from a roll, or may be a layer formed on the reversibly stretchable layer (e.g., a layer formed on the reversibly stretchable layer from a solution or melt). Two layers joined together by adhesive may be joined with other layers (which may themselves be provided from other rolls). These other layers may be deposited while the reversibly stretchable layer is in a reversibly stretched state and/or while the reversibly stretchable layer is in a recovered state. The two layers joined together by the adhesive may also pass through a station where other processes are performed. These treatments may include bonding (e.g., via ultrasonic horn and/or calender), laminating (e.g., thermal, chemical, and/or mechanical), pleating, and/or charging. One or more of these treatments may cause the reversibly stretched layer to become bonded to another layer and/or mechanically coupled to another layer (e.g., a scrim, such as a second scrim) such that the reversibly stretched layer cannot undergo further reversible stretching. After manufacture, the final filter media may be wound around a final roll.

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

A layer deposited on a reversibly stretched layer in a reversibly stretched state may undergo a decrease in length as the reversibly stretched layer returns to a recovered length. The reduction in length may be equivalent to a corresponding reduction in length experienced by the reversibly stretchable layer upon recovery. When the reversibly stretchable layer exhibits substantially complete recovery, the reduction in length of the layer may fall within one or more ranges that can be derived from the above ranges by the following equation:

percent length reduction = (1-100/(100 + percent stretch)). 100%.

For example, a fully recovered layer deposited on a reversibly stretched layer stretched to 50% of its original length would have a corresponding length reduction of 33% of the original length of the layer. As another example, a fully recovered layer deposited on a reversibly stretched layer stretched to 1000% of its original length would have a corresponding reduction in length of 91% of the original length of the layer.

In some embodiments, a filter media including an irregular structure may further include one or more additional structures. The additional structures may include 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 ways). In general, the additional structures, whether regular or irregular, may be on a different length scale than the irregular structures. For example, the additional structure may include one or more features (e.g., peaks, valleys) having a size that is greater in magnitude than features (e.g., peaks, valleys) of the irregular structure. A non-limiting example of a filter media including an irregular structure and an additional structure is shown in fig. 8. As shown in fig. 8, the filter media 1005 may include both irregular structures and additional structures 500. The irregularities may be present on an outer surface of the filter media, in an interior of the filter media, and/or throughout the filter media. In some cases, as shown in fig. 8, the irregular structure may be present on an outer surface of the filter media and/or may extend through the entire thickness of one or more layers of the filter media. In some cases, a relief layer in a filter media, such as relief layer 305 in fig. 8, can include an irregular structure as described herein. In the case of irregular structures, the presence of additional structures including regular undulations and/or irregular undulations (e.g., multiple peaks) can increase the relative amount of filter media per unit area, which can desirably increase the gamma of the filter media.

In some embodiments, one or more layers in the filter media may include both irregular structures and additional structures. As an example, in some embodiments, a filter media includes a layer having a plurality of peaks that are irregular in one or more ways and having additional structure. The plurality of peaks that are irregular in one or more ways typically, but not always, have a smaller length scale than the additional structure. In some embodiments, one or more layers in the filter media are undulating in two length scales. For example, the layers in the filter media may undulate in an irregular manner, and then further undulate on a larger length scale to form additional layers. The plurality of peaks constituting the irregular undulations may at least partially have a different orientation and/or a different average peak height than the undulations forming the additional structures.

In some embodiments, the one or more additional structures are formed by an additional step of imparting additional structure to the filter media (e.g., pleating, corrugating). For example, a filter media comprising an irregular structure having a plurality of peaks may be pleated to impart regular peaks to the filter media. The pleat peak height, peak spacing and/or peak size may be significantly greater than the same features of the irregular structure. In some such cases, pleating may be used to impart relatively macroscopic structure to the filter media as a whole, while irregular structures impart relatively microscopic structure to the filter media. In some embodiments, the additional structures may be relatively macroscopic as compared to the irregular structures and may be formed by: a filter media, such as filter media 1001 in fig. 1, is subjected to a process of forming undulations, such as pleating and/or corrugating, to form a filter media, such as filter media 1005, that includes irregular structures and additional structures.

Various techniques may be employed to form additional structures in the layer including the irregular structure. Some such techniques include: a layer comprising a first plurality of peaks making up an irregular structure, such as a layer comprising a plurality of peaks irregular in one or more ways, is undulating to form a second plurality of peaks making up an additional structure. As an example, a layer comprising a first plurality of peaks and any other layers that undulate with a layer comprising a plurality of peaks may be pleated and/or corrugated. Pleating and/or corrugating the layer may cause the formation of a relatively regular second plurality of peaks. As another example, a layer comprising a first plurality of peaks and any other layers undulating with a layer comprising a plurality of peaks may be subjected to one or more of the above-described treatments to form a second plurality of peaks that are irregular in one or more ways. In other words, the additional structure may be an irregular structure and/or may be formed by one of the methods employed to form the first plurality of peaks. For example, the layer including the first plurality of peaks and any other layers that undulate with the layer including the first plurality of peaks may be folded, curled, wrinkled on and/or may be disposed on the layer undergoing heat shrinkage.

In some embodiments, a filter media including one or more layers having a lofted layer further includes one or more additional support layers (e.g., one or more fibrous support layers) that hold the one or more lofted layers in a lofted configuration. The support layer may not have a plurality of irregular peaks and/or may be relatively flat prior to undulation. Fig. 9A illustrates an exemplary embodiment of a filter media in which the layers undulate by being corrugated and are held in a corrugated configuration by two support layers. Fig. 9A depicts the following filter media 1006: the filter media 1006 has at least one corrugated layer and at least one support layer that maintains the corrugated layer in a corrugated configuration to maintain separation of peaks and valleys of adjacent waves of the corrugated layer. In the illustrated embodiment, the filter media 1006 includes an efficiency layer 12, a first downstream support layer 14 and a second upstream support layer 16 disposed on opposite sides of the efficiency layer 12. Although not shown, the efficiency layer 12 may include an irregular structure, such as a plurality of peaks that are irregular in one or more ways. The first and second support layers 14, 16 may not have a plurality of peaks prior to being corrugated with the efficiency layer 12. The support layers 14, 16 may help to retain the efficiency layer 12, and optionally any additional layers described elsewhere herein, in the corrugated configuration. The additional layer may have one or more structural features described elsewhere herein with respect to the layer including the plurality of peaks that are irregular in one or more ways. For example, each additional layer may or may not be independently: including a plurality of peaks, being a corrugated layer prior to being corrugated, being corrugated with one or more other layers, and/or being corrugated with one or more other layers.

With further reference to fig. 9A, in some embodiments, a scrim is positioned between the support layer 14 and the efficiency layer 12 and/or between the support layer 16 and the efficiency layer 12. In some embodiments, a nanofiber layer is positioned between the support layer 14 and the efficiency layer 12 and/or between the support layer 16 and the efficiency layer 12. Although two

support layers

14, 16 are shown, the filter media 10 need not include two support layers. In case only one support layer is provided, this support layer may be arranged upstream or downstream of the filter layer.

The filter media 1006 may also optionally include one or more outer layers or blankets on the most upstream and/or most downstream sides of the filter media 1006. Fig. 9A illustrates a top layer 18 disposed on the upstream side of the filter media 1006 to serve as, for example, an upstream dust holding layer. The top layer 18 may also serve as an aesthetic layer. The layers in the illustrated embodiment are arranged such that the top layer 18 is disposed on the air inlet side, labeled I, the second support layer 16 is immediately downstream of the top layer 18, the efficiency layer 12 is disposed immediately downstream of the second support layer 16, and the first support layer 14 is disposed downstream of the efficiency layer 12 on the air outlet side, labeled O. The direction of the air flow, i.e. from the air inlet I to the air outlet O, is indicated by the arrow marked with reference a.

The outer or cover layer may alternatively or additionally be a base layer disposed on the downstream side of the filter media 1006 to serve as a stiffening member that provides structural integrity to the filter media 1006 to help maintain the undulating configuration. The outer layer or covering may also be used to provide abrasion resistance. FIG. 9B illustrates another embodiment of a filter media 1006B similar to the filter media 1006 of FIG. 9A. In this embodiment, the filter media 1006B does not include a top layer, but rather has an efficiency layer 12B, a first support layer 14B disposed immediately downstream of the efficiency layer 12B, a second support layer 16B disposed immediately upstream of the efficiency layer 12B on the air intake side I, and a bottom layer 18B disposed immediately downstream of the first support layer 14B on the air outflow side O. Additional layers, such as scrim layers and/or nanofiber layers, may be positioned between the efficiency layer and the support layer shown in fig. 9B. Further, as shown in the exemplary embodiments of fig. 9A and 9B, the outer or cover layer may have a topography that is different from the topography of the efficiency layer and/or any support layers. For example, in a pleated or non-pleated configuration, the outer or cover layer may be non-corrugated (e.g., substantially flat, without undulations, and/or without peaks that are irregular in one or more ways), while the efficiency layer, any support layer, and/or any layer positioned between the efficiency layer and the support layer may have a corrugated configuration. One skilled in the art will appreciate that a variety of other configurations are possible, and that the filter media may include any number of layers in various arrangements.

It should be understood that while some embodiments relate to corrugated filter media, like those shown in fig. 9A and/or 9B, some filter media that are not corrugated may have one or more of the features shown in fig. 9A and/or 9B. As an example, a layer comprising a first plurality of peaks, such as a layer comprising a plurality of peaks that are irregular in one or more ways, may be further undulated by methods other than in a wave form to form a second plurality of peaks, and may be positioned in a filter media comprising one or more support layers and/or one or more outer or cover layers. The method other than being corrugated may be any of those described herein, such as pleating, folding, crimping, pleating, and/or heat shrinking.

Filter media including irregular and additional structures, such as filter media including one or more layers, may be manufactured in a variety of suitable ways. In an exemplary embodiment, the layer is corrugated (e.g., a layer comprising a plurality of peaks that are irregular in one or more ways, an efficiency layer, a scrim, a nanofiber layer, and/or a support layer). The layers to be corrugated may be positioned adjacent to each other from the air entry side to the air exit side in a desired arrangement, and the combined layers may be transferred between first and second moving surfaces traveling at different speeds, such as where the second surface travels at a lower speed than the first surface. A suction force, such as a vacuum force, may be used to pull the layer toward the first moving surface and then toward the second moving surface as the layer travels from the first moving surface to the second moving surface. The difference in velocity may cause the layer to form z-direction waves as the layer passes onto the second moving surface, thereby forming peaks and valleys in the layer. The speed of each surface can be varied to achieve 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 peaks and waves may have amplitudes between 0.1 inches and 4.0 inches, such as between 0.1 inches and 1.0 inches, between 0.1 inches and 2.0 inches, or between 3.0 inches and 4.0 inches. For some applications, the peaks and waves may have amplitudes between 0.1 and 1.0 inches, between 0.1 and 0.5 inches, or between 0.1 and 0.3 inches. The properties of the different layers may also be varied to achieve a desired filter media construction. In an exemplary embodiment, the filter media has 2 to 6 waves per inch with a height (total thickness) in the range between 0.025 inch and 2 inch, although this may vary significantly depending on the intended application. For example, in other embodiments, the filter media may have 2 to 4 waves per inch, such as 3 waves per inch. The total thickness of the media may be between 0.025 inches and 4.0 inches, such as between 0.1 inches and 1.0 inches, between 0.1 inches and 2.0 inches, or between 3.0 inches and 4.0 inches. For some applications, the total thickness of the media may be between 0.1 and 0.5 inches, or between 0.1 and 0.3 inches. As shown in fig. 9A, 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 corrugated filter media may be determined according to Edana WSP 120.1 standard (2005) with a presser foot selected to have a load of 2 ounces and an area of 1 square inch.

In the embodiment shown in fig. 9A, 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 entrance side I and the air exit side O), as shown in fig. 9C. The support layers 14, 16 will extend across the peaks P and into the valleys T such that the support layers 14, 16 also have a wave configuration. Those skilled in the art will appreciate that the peaks P on the air entry side I of the efficiency layer 12 will have corresponding valleys T on the air exit side O. Thus, the downstream support layer 14 extends into a valley T, and, just conversely, the same valley T is a peak P across which the upstream support layer 16 extends. Since the downstream support layer 14 extends into the valleys T on the air outflow side O of the efficiency layer 12, the downstream rough layer 14 maintains adjacent peaks P on the air outflow side O at a distance from each other and adjacent valleys T on the air outflow side O at a distance from each other. The upstream support layer 16, if provided, may also keep adjacent peaks P at a distance from each other on the air entry side I of the efficiency layer 12, and may keep adjacent valleys T at a distance from each other on the air entry side I of the efficiency layer 12. Thus, the efficiency layer 12 has a significantly increased surface area compared to the surface area of a fibrous filtration layer in a planar configuration. In certain exemplary embodiments, the surface area in the wavy configuration is increased by at least 50%, and in some cases by up to 120%, as compared to the surface area of the same layer in the planar configuration. In other words, the corrugated construction may include at least 50% more filter media area per filter media track, or at least 120% more filter media area per filter media track, as compared to other equivalent non-corrugated filter media.

In embodiments where the upstream support layer and/or the downstream support layer hold one or more other layers in a corrugated 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 may be occupied by support layers to give structural support to other layers. For example, at least 95% or substantially all of the available volume in the valleys may be filled with the support layer. The support layer may have a solidity (solid) of 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 ranges are also possible (e.g., 1% or more and 30% or less, 4% or more and 20% or less, or 5% or more and 15% or less). Other ranges are also possible.

The solidity of the support layer can be determined by using the following formula: solidity = [ basis weight/(fiber density thickness) ] + 100%. Basis weight and thickness may be determined as described elsewhere herein. The fiber density is equivalent to the average density of the material or materials forming the fiber, which is typically given by the fiber manufacturer. The average density of the material forming the fibers may 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 medium by the total volume of all fibers in the filter medium. If the mass and density of each type of fiber in the filter media is known, the volume of all the fibers in the filter media can be determined by: (1) Dividing, for each type of fiber, the total mass of the type of fiber in the filter media by the density of the type of fiber; and (2) adding the volumes of each fiber type. If the mass and density of each type of fiber in the filter media is unknown, the volume of all fibers in the filter media can be determined according to Archimedes' principle.

Additionally, as shown in the exemplary embodiment of fig. 9A, the support layer extending across the peaks and into the valleys may be such that the surface area of the support layer contacting the top layer 18A across the peaks is similar to the surface area of the support layer across the valleys. Similarly, the surface area of the support layer in contact with the bottom layer 18B (fig. 9B) across the peaks may 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 may 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%.

In certain exemplary embodiments, the downstream support layer 14 and/or the upstream support layer 16 may have a fiber density at the peaks that is greater than its fiber density in the valleys; and in some embodiments, the mass of the fiber at the peaks is less than its mass in the valleys. This may be caused by the roughness of the downstream support layer 14 and/or the upstream support layer 16 relative to the efficiency layer 12. In particular, the relatively thin nature of the efficiency layer 12 will allow the downstream support layer 14 and/or the upstream support layer 16 to conform around the waves formed in the efficiency layer 12 as the layer passes from the first moving surface to the second moving surface. Since the support layers 14, 16 extend across the peak P, the distance traveled will be less than the distance traveled by the

layers

14, 16 to fill the valleys. Thus, the support layers 14, 16 will compact at the peaks, and thus have an increased fiber density at the peaks as compared to the valleys through which the layers will travel to form the annular configuration.

Once the layers are formed in a corrugated configuration, the corrugated shape can be maintained by activating the binder fibers (e.g., binder fibers in one or both support layers) to effect bonding of the fibers. A variety of techniques may be used to activate the binder fibers. For example, if a multicomponent fiber is used, such as a bicomponent binder fiber having a core and a sheath, the binder fiber may be activated upon application of heat. If monocomponent binder fibers are used, the binder fibers may be activated upon application of heat, steam, and/or some other form of warm moisture. It is also possible to position the top layer 18 (fig. 9A) and/or the bottom layer 18B (fig. 9B) on top of the upstream support layer 16 (fig. 9A) or on the bottom of the downstream support layer 14B (fig. 9B), respectively, and simultaneously or sequentially mate with the upstream support layer 16 or the downstream support layer 14B, such as by bonding. Those skilled in the art will also appreciate that various techniques other than the use of adhesive fibers may alternatively be used to couple the layers to one another. The layers may also be separate adhesive layers and/or the layers may be coupled to each other, including adhesive, prior to being corrugated.

The filter media described herein may be suitable for use in a variety of filtration applications. For example, the filter media described herein may be suitable for HVAC bag filters, HVAC panel filters, respiratory protection equipment, medical filters, vacuum cleaner filters, indoor 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., filters) and/or liquid filters (e.g., water filters, fuel filters). In some embodiments, the filtration 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 need to remove particles at efficiency levels greater than 99.95% and 99.9995%, respectively. In some embodiments, the filter media can remove particles with an efficiency of greater than 95%, greater than 99.995%, greater than 99.99995%, or up to 99.999995%. In some embodiments, the filter media may be suitable for HVAC applications. That is, the filter media can have a particulate efficiency of 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 may be a HEPA filter, ULPA filter, or HVAC filter, and may be one component of a filter element as described in more detail below.

In some embodiments, the filter media described herein may be a component of a filter element. That is, the filter media may be incorporated into an article suitable for use by an end user. Non-limiting examples of suitable filter elements include flat panel filters, V-bank filters (including, for example, 1V-bank to 24V-banks), cartridge filters, cylindrical filters, conical filters, and curvilinear filters. The filter element can have any suitable height (e.g., between 2 inches and 124 inches for flat filters, between 4 inches and 124 inches for V-bank filters, between 1 inch and 124 inches for cartridge filters and cylindrical filters). The filter element can also have any suitable width (between 2 inches and 124 inches for flat filters and between 4 inches and 124 inches for V-bank filters). Some filter elements (e.g., cartridge filters, cylindrical filters) can be characterized by a diameter instead of a width; the filter elements may have any suitable value of diameter (e.g., between 1 inch and 124 inches). The filter element typically comprises a frame, which may be made of one or more materials such as cardboard, aluminium, steel, alloys, wood and polymers.

The filter media described herein may advantageously operate in one or more ways. In some embodiments, the filter media has a desired high value of γ, which is the rating applied to the filter media based on the relationship between the rate of penetration and the pressure drop across the media, or the particulate efficiency as a function of the pressure drop across the media or web. In general, a higher gamma value indicates better filtration performance, i.e.High particle efficiency as a function of pressure drop. As noted above, and without wishing to be bound by any particular theory, increasing the surface area of the filter media will generally increase the gamma of the filter media. Accordingly, filter media having relatively high surface areas, such as filter media comprising a plurality of peaks that are irregularly structured and/or irregular in one or more ways, as described herein, can also have relatively high gamma values. γ is defined by the following equation: gamma = (-log) ₁₀ (initial penetration%/100)/initial pressure drop, mm H ₂ O). Times.100. The penetration, usually expressed as a percentage, is defined as follows: penetration (%) = (C/C) ₀ ) 100, wherein C is the concentration of particles after passing through the filter, and C ₀ Is the concentration of particles before passing through the filter. The initial penetration is the penetration measured when the filter media is first exposed to the particles, and the initial pressure drop is the pressure drop measured when the filter media 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 employing a TSI 8130 automatic filter tester for penetration values in excess of 0.001% (8130 CertiTest from TSI ^TM Filter tester) and a TSI 3160 automated filter tester for penetration values less than or equal to 0.001%. The two instruments have an area of 100cm ² For analysis of flat sheet filter media.

In measuring γ, an aerosol of NaCl composed of NaCl particles with an average diameter of 0.26 microns was blown at the filter medium using a TSI 8130 automatic filter tester or a TSI 3160 automatic filter tester. The NaCl particles may be produced from a 2 wt% aqueous NaCl solution through which an NaCl aerosol is formed by blowing dilution air at a pressure of 30psi at a flow rate of 70L/min. The aerosol was then blown through the filter media at a pressure of 30psi and a flow rate of 32L/min, which corresponds to a face velocity of 5.3 cm/s. While the TSI 8130 or TSI 3160 automatic filter tester blows the NaCl aerosol, both the pressure drop and the penetration rate of the NaCl aerosol through the filter media are measured simultaneously by two condensed nuclear particle counters, one of which is upstream of the filter media and one of which is downstream of the filter media. The particle collection efficiency is reported at the start of the test and is the percentage of upstream challenge particles collected by the filter at the start of the test. The initial pressure drop was also measured at the beginning of the test.

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

As noted above, some filter media described herein include an irregular structure that yields one or more resulting advantages. The irregular structure may be in the form of an irregular surface structure. As an example, the irregular surface structure may take the form of a plurality of peaks that are irregular in one or more ways in the surface. As another example, the irregular surface structure may take the form of a plurality of peaks: the plurality of peaks are present at the surface of and/or extend through one or more layers (e.g. in the case of a relief layer), the plurality of peaks being irregular in one or more ways. For example, the filter media may include a plurality of peaks present on the surface of and/or extending through 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 media includes a plurality of peaks extending through the entire filter media. In other words, the filter media may comprise only layers that undulate together and wherein the undulation takes the form of a plurality of peaks that are irregular in one or more ways. Several characteristics of multiple peaks that are irregular in one or more ways are described below. It should be understood that the description may refer to a plurality of peaks present at a surface of the filter media, at a surface of one or more layers in the filter media, extending through a thickness of the filter media, and/or extending through one or more layers in the filter media. These features may be characteristic of multiple peaks in one or more undulating layers and/or not characteristic of multiple peaks of an undulating layer.

When the filter media includes a plurality of peaks, such as a plurality of peaks that are irregular in one or more ways, 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 0.3mm, greater than or equal to 0.5mm, greater than or equal to 0.75mm, greater than or equal to 1mm, greater than or equal to 1.5mm, greater than or equal to 2mm, greater than or equal to 2.5mm, greater than or equal to 3mm, greater than or equal to 4mm, greater than or equal to 5mm, greater than or equal to 6mm, greater than or equal to 7mm, greater than or equal to 8mm, greater than or equal to 9mm, greater than or equal to 10mm, greater than or equal to 11mm, or greater than or equal to 13mm. In some embodiments, the filter media comprises a plurality of peaks having the following average peak heights: the average peak height is less than or equal to 15mm, less than or equal to 13mm, less than or equal to 11mm, less than or equal to 10mm, less than or equal to 9mm, less than or equal to 8mm, less than or equal to 7mm, less than or equal to 6mm, less than or equal to 5mm, less than or equal to 4mm, less than or equal to 3mm, less than or equal to 2.5mm, less than or equal to 2mm, less than or equal to 1.5mm, less than or equal to 1mm, less than or equal to 0.75mm, or less than or equal to 0.5mm. Combinations of the above ranges are also possible (e.g., 0.3mm or more and 15mm or less, 0.3mm or more and 10mm or less, 1mm or more and 8mm or less, or 3mm or more and 7mm or less). Other ranges are also possible. The average peak height may be determined by: as described above, the peak heights of the peaks constituting the plurality of peaks are found by using a scanning optical microscope, and then these peak heights are averaged to obtain an average peak height.

When the filter media includes a plurality of peaks, such as a plurality of peaks that are irregular in one or more ways, the plurality of peaks can have a particularly advantageous standard deviation of peak heights. For example, the standard deviation of the peak heights of the plurality of peaks can be greater than or equal to 0.1mm, 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 0.4mm, greater than or equal to 0.5mm, greater than or equal to 0.75mm, greater than or equal to 1mm, greater than or equal to 1.25mm, greater than or equal to 1.5mm, greater than or equal to 1.75mm, greater than or equal to 2mm, greater than or equal to 2.25mm, greater than or equal to 2.5mm, or greater than or equal to 2.75mm. In some embodiments, the filter media comprises a plurality of peaks having the following peak height standard deviations: the standard deviation of the peak heights is less than or equal to 3mm, less than or equal to 2.75mm, less than or equal to 2.5mm, less than or equal to 2.25mm, less than or equal to 2mm, less than or equal to 1.75mm, less than or equal to 1.5mm, less than or equal to 1.25mm, less than or equal to 1mm, less than or equal to 0.75mm, less than or equal to 0.5mm, less than or equal to 0.4mm, less than or equal to 0.3mm, less than or equal to 0.25mm, less than or equal to 0.2mm, or less than or equal to 0.15mm. Combinations of the above ranges are also possible (e.g., 0.1mm or more and 3mm or less, 0.15mm or more and 1.5mm or less, or 0.2mm or more and 1mm or less). Other ranges are also possible. The standard deviation of peak heights can be determined by: as described above, the peak height standard deviation is obtained by finding the peak height of the peaks constituting the plurality of peaks using a scanning optical microscope, and then using a standard statistical technique to determine the standard deviation of the peak height.

When the filter media includes a plurality of peaks, such as a plurality of peaks that are irregular in one or more ways, the plurality of peaks can have a particularly advantageous ratio of peak height standard deviation to average peak height. For example, the plurality of peaks can have the following ratio of peak height standard deviation to average peak height: a ratio of the standard deviation of peak height to the average peak height of 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, or 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: a ratio of the standard deviation of the peak heights to the 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., 0.03 or more and 0.8 or less, 0.05 or more and 0.6 or less, or 0.07 or more and 0.5 or less). Other ranges are also possible. The ratio of the standard deviation of peak height to the average peak height can be determined by: as described above, the standard deviation of peak heights and the average peak height are found, and then their ratio is taken.

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

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

When the filter media includes a plurality of peaks, such as a plurality of peaks that are irregular in one or more ways, the plurality of peaks can have a particularly advantageous ratio of standard deviation of peak spacing to average peak spacing. For example, the ratio of the standard deviation of the peak pitch to the average peak pitch of the plurality of peaks may 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 peak spacing to the average peak spacing of: the ratio of the standard deviation of the peak pitch to the average peak pitch is 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 ranges are also possible (e.g., 0.08 or more and 1 or less, 0.15 or more and 0.8 or less, or 0.15 or more and 0.5 or less). Other ranges are also possible. The ratio of the standard deviation of the peak pitch to the average peak pitch may be determined by: as described above, the peak-to-peak standard deviation and the average peak-to-peak distance are found, and then their ratio is taken.

The filter media described herein can have an advantageous average surface height. In some embodiments, the filter media includes a layer having a plurality of peaks that are irregular in one or more ways, the layer having a favorable average surface height. In some embodiments, the filter media (and/or the layer comprising the plurality of irregular peaks in the filter media) has an average surface height of: the average surface height is greater than or equal to 0.3mm, greater than or equal to 0.5mm, greater than or equal to 0.75mm, greater than or equal to 1mm, greater than or equal to 1.5mm, greater than or equal to 2mm, greater than or equal to 2.5mm, greater than or equal to 3mm, greater than or equal to 4mm, greater than or equal to 5mm, greater than or equal to 6mm, greater than or equal to 7mm, greater than or equal to 8mm, or greater than or equal to 9mm. In some embodiments, the filter media (and/or the layer comprising the plurality of irregular peaks in the filter media) has an average surface height of: the average surface height is less than or equal to 10mm, less than or equal to 9mm, less than or equal to 8mm, less than or equal to 7mm, less than or equal to 6mm, less than or equal to 5mm, less than or equal to 4mm, less than or equal to 3mm, less than or equal to 2.5mm, less than or equal to 2mm, less than or equal to 1.5mm, less than or equal to 1mm, less than or equal to 0.75mm, or less than or equal to 0.5mm. Combinations of the above ranges are also possible (e.g., 0.3mm or more and 10mm or less, 1mm or more and 8mm or less, or 3mm or more and 7mm or less). Other ranges are also possible. As used herein, the average surface height of the filter media and/or layers in the filter media is: after a selected amount of computational processing, the average of the relative heights of each point in the relative surface topography of the filter media and/or layers in the filter media. The relative surface topography of the filter media and/or layers in the filter media can be determined using a scanning optical microscope as described above. The resulting data can then be processed by performing steps (1) and (2) of the process described above for determining peak height. Finally, the processed data may 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 media (e.g., if the layer is covered by a relatively flat outer or cover layer), one or more layers positioned outside of the associated layer can be removed such that the associated layer is exposed, and the average surface height of the exposed associated layer can be measured by optical microscopy as described above.

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 the filter media is undulating or not and the size of the undulations. For example, filter media that includes undulations over a single length scale (e.g., filter media that includes layers that have been pleated such as by the process shown in fig. 6A-6C, but that does not include additional structure formed by, for example, pleating or corrugating) typically have lower basis weights than filter media that includes undulations over two or more length scales (e.g., filter media that includes layers that have been pleated such as by the process shown in fig. 6A-6C, and that also includes additional structure formed by, for example, pleating or corrugating).

In some embodiments, the filter media comprising undulations over a single length scale has the following basis weight: the basis weight is greater than or equal to 20g/m ² Greater than or equal to 25g/m ² Greater than or equal to 30g/m ² And not less than 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 70g/m or more ² 80g/m or more ² Greater than or equal to 90g/m ² 95g/m or more 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 130g/m or more ² 140g/m or more ² Greater than or equal to 200g/m ² 225g/m or more 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 700g/m or more ² Greater than or equal to 800g/m ² Or greater than or equal to 900g/m ² . In some embodiments, the filter media comprising undulations over a single length scale has the following basis weight: the basis weight is less than or equal to 1000g/m ² Less than or equal to 900g/m ² Less than or equal to 800g/m ² 700g/m or less 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 225g/m or less ² Less than or equal to 150g/m ² Less than or equal to 140g/m ² 130g/m or less 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 95g/m or less 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., 20g/m or more) ² And 1000g/m or less ² 60g/m or more ² And 150g/m or less ² 70g/m or more ² And is not more than 140g/m ² Or 95g/m or more ² And is not more than 140g/m ² ). Other ranges are also possible. The basis weight of the filter media may be determined by weighing a known area of filter media and then dividing the measured weight by the known area.

As described above, a filter media including undulations over two or more length scales may be provided. The ratio of the basis weight of the filter media after forming undulations (e.g., by corrugating or pleating) on the larger of the two length scales 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 structure undulation ratio (which is equivalent to, for example, the wave ratio of the corrugated media or the pleat ratio for pleated media). Filter media including undulations over two or more length scales may have the following additional structural undulation ratios: the additional structure undulation ratio is 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. A filter media including undulations over two or more length scales can have the following additional structural undulation ratios: the additional structure relief ratio is 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 ranges are also possible (e.g., 1.5 or more and 24 or more and 3 or less). Other ranges are also possible.

The filter media described herein can have a variety of suitable thicknesses. The thickness of the filter media will generally depend on whether the filter media is undulating or not and the size of the undulations. For example, filter media that includes undulations over a single length scale (e.g., filter media that includes layers that have been pleated such as by the process shown in fig. 6A-6C, but that does not include additional structures formed by, for example, pleating or corrugating) typically have a thickness that is less than filter media that includes undulations over two or more length scales (e.g., filter media that includes layers that have been pleated such as by the process shown in fig. 6A-6C, and that also includes additional structures formed by pleating or corrugating).

In some embodiments, a filter media comprising undulations over a single length scale has the following thicknesses: the thickness is greater than or equal to 2mm, greater than or equal to 3mm, greater than or equal to 4mm, greater than or equal to 5mm, greater than or equal to 6mm, greater than or equal to 7mm, greater than or equal to 8mm, greater than or equal to 10mm, greater than or equal to 12.5mm, greater than or equal to 15mm, or greater than or equal to 17.5mm. In some embodiments, a filter media comprising undulations over a single length scale has the following thicknesses: the thickness is less than or equal to 20mm, less than or equal to 17.5mm, less than or equal to 15mm, less than or equal to 12.5mm, less than or equal to 10mm, less than or equal to 8mm, less than or equal to 7mm, less than or equal to 6mm, less than or equal to 5mm, less than or equal to 4mm, or less than or equal to 3mm. Combinations of the above ranges are also possible (e.g., 2mm or more and 20mm or less, 2mm or more and 15mm or less, 2mm or more and 10mm or less, or 3mm or more and 7mm or less). Other ranges are also possible. The thickness of the filter media may be determined by Edana WSP 120.1 standard (2005) with a presser foot selected to have a load of 2 ounces and an area of 1 square inch. It should be understood that the above values may also refer to the thickness of filter media including undulations over two or more length scales that have been extended to form filter media including undulations over a single length scale. In some embodiments, the value of the above thickness may be the thickness of the corrugated or pleated filter media prior to being corrugated or pleated.

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

The filter media described herein can have a plurality of combined mean flow pore sizes. In some embodiments, the filter media has the following average flow pore size: the mean flow pore size is 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 equal to 75 microns. In some embodiments, the filter media has the following average flow pore size: the mean flow pore size is less than or equal to 100 micrometers, less than or equal to 75 micrometers, less than or equal to 60 micrometers, less than or equal to 50 micrometers, less than or equal to 40 micrometers, less than or equal to 35 micrometers, less than or equal to 30 micrometers, less than or equal to 25 micrometers, less than or equal to 22 micrometers, less than or equal to 20 micrometers, less than or equal to 18 micrometers, less than or equal to 16 micrometers, less than or equal to 14 micrometers, less than or equal to 12 micrometers, less than or equal to 10 micrometers, less than or equal to 8 micrometers, less than or equal to 7 micrometers, less than or equal to 6 micrometers, less than or equal to 5 micrometers, less than or equal to 4 micrometers, less than or equal to 3 micrometers, less than or equal to 2 micrometers, less than or equal to 1.5 micrometers, less than or equal to 1 micrometer, less than or equal to 0.75 micrometers, or less than or equal to 0.5 micrometers. Combinations of the above ranges are also possible (e.g., 0.2 to 100 micrometers, 0.2 to 75 micrometers, 4 to 25 micrometers, 6 to 16 micrometers, or 7 to 12 micrometers). Other ranges are also possible. The mean flow pore size of the filter media may be determined according to ASTM F316 (2011).

The filter media described herein can have a variety of suitable pressure drops. In some embodiments, the filter media has the following pressure drop: the pressure drop is greater than or equal to 0.2mm H ₂ O, 0.4mm H or more ₂ O, 0.6mm H or more ₂ O, 0.8mm H or more ₂ O, 1mm H or more ₂ O, 1.2mm H or more ₂ O, 1.4mm H or more ₂ O, 1.6mm H or more ₂ O, 1.8mm H or more ₂ O, 2mm H or more ₂ O, 2.5mm H or more ₂ O, 3mm H or more ₂ O, 3.5mm H or more ₂ O, 4mm H or more ₂ O, 5mm H or more ₂ O, 6mm H or more ₂ O, greater than or equal to 8mm H ₂ O, 10mm H or more ₂ O, 15mm H or more ₂ O, 20mm H or more ₂ O, greater than or equal to 30mm H ₂ O, 40mm H or more ₂ O, 50mm H or more ₂ O, 60mm H or more ₂ O, or greater than or equal to 80mm H ₂ And (O). In some embodiments, the filter media has the following pressure drop: the pressure drop is less than or equal to 100mm H ₂ O, less than or equal to 80mm H ₂ O, less than or equal to 60mm H ₂ O, less than or equal to 50mm H ₂ O, less than or equal to 40mm H ₂ O, less than or equal to 30mm H ₂ O, less than or equal to 20mm H ₂ O, less than or equal to 15mm H ₂ O, less than or equal to 10mm H ₂ O, less than or equal to 8mm H ₂ O, less than or equal to 6mm H ₂ O, less than or equal to 5mm H ₂ O, less than or equal to 4mm H ₂ O, less than or equal to 3.5mm H ₂ O, less than or equal to 3mm H ₂ O, less than or equal to 2.5mm H ₂ O, less than or equal to 2mm H ₂ O, less than or equal to 1.8mm H ₂ O, less than or equal to 1.6mm H ₂ O, 1.4mm H or less ₂ O, less than or equal to 1.2mm H ₂ O, less than or equal to 1mm H ₂ O, less than or equal to 0.8mm H ₂ O, less than or equal to 0.6mm H ₂ O, or 0.4mm H or less ₂ And (O). Combinations of the above ranges are also possible (e.g., 0.2mm H or greater) ₂ O is not more than 100mm H ₂ O, 0.2mm H or more ₂ O is not more than 10mm H ₂ O, 0.4mm H or more ₂ O is less than or equal to 6mm H ₂ O, 0.8mm H or more ₂ O is less than or equal toAt 4mm H ₂ O, or 1.2mm H or more ₂ O is not more than 1.8mm H ₂ O). Other ranges are also possible. The pressure drop of the filter media can be determined by measurement of γ using an automatic filter tester TSI 8130 or an automatic filter tester TSI 3160 as described above.

The filter media described herein can have multiple initial permeabilities. In some embodiments, the filter media has the following initial permeabilities: the initial penetration rate is 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 the following initial penetration rates: the initial penetration is 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 ranges are also possible (e.g., 0.00005% or more and 80% or less). Other ranges are also possible. The initial penetration rate of the filter media can be determined by measurement of γ using the TSI 8130 automatic filter tester or the TSI 3160 automatic filter tester as described above.

The filter media described herein can have a variety of suitable air permeabilities. In some embodiments, the filter media has the following air permeabilities: the air permeability is greater than or equal to 1CFM, greater than or equal to 2CFM, greater than or equal to 3CFM, greater than or equal to 5CFM, greater than or equal to 7.5CFM, greater than or equal to 10CFM, greater than or equal to 15CFM, greater than or equal to 20CFM, greater than or equal to 25CFM, greater than or equal to 30CFM, greater than or equal to 35CFM, greater than or equal to 40CFM, greater than or equal to 50CFM, greater than or equal to 60CFM, greater than or equal to 75CFM, greater than or equal to 100CFM, greater than or equal to 120CFM, greater than or equal to 150CFM, greater than or equal to 170CFM, greater than or equal to 200CFM, greater than or equal to 225CFM, greater than or equal to 250CFM, greater than or equal to 275CFM, greater than or equal to 300CFM, greater than or equal to 325CFM, greater than or equal to 350CFM, greater than or equal to 400CFM, greater than or equal to 500CFM, greater than or equal to 600CFM, or equal to 800CFM. In some embodiments, the filter media has the following air permeabilities: the air permeability is less than or equal to 1000CFM, less than or equal to 800CFM, less than or equal to 600CFM, less than or equal to 500CFM, less than or equal to 400CFM, less than or equal to 350CFM, less than or equal to 325CFM, less than or equal to 300CFM, less than or equal to 275CFM, less than or equal to 250CFM, less than or equal to 225CFM, less than or equal to 200CFM, less than or equal to 170CFM, less than or equal to 150CFM, less than or equal to 120CFM, less than or equal to 100CFM, less than or equal to 75CFM, less than or equal to 60CFM, less than or equal to 50CFM, less than or equal to 40CFM, less than or equal to 35CFM, less than or equal to 30CFM, less than or equal to 25CFM, less than or equal to 20CFM, less than or equal to 15CFM, less than or equal to 10CFM, less than or equal to 7.5CFM, less than or equal to 5CFM, less than or equal to 3CFM, or less than or equal to 2CFM. Combinations of the above ranges are also possible (e.g., 1CFM or more and 1000CFM or less, 20CFM or more and 350CFM or less, 35CFM or more and 170CFM or less, or 20CFM or more and 350CFM or less). Other ranges are also possible. The air permeability of the filter media can be measured according to ASTM test standard D737 (1996) at a pressure drop of 125Pa at a test area of 38cm ² Is determined on the sample of (1). As is common in the artAs known to those, a unit CFM is equivalent to a unit CFM/sf or ft/min.

In some embodiments, the filter media described herein have a relatively high efficiency for one or more particle sizes. The efficiency can be expressed in terms of a beta value (or beta ratio), where beta is _(x) = y upstream count (C) ₀ ) To downstream count (C), and wherein x is the minimum particle size that will achieve C ₀ The actual ratio to C is equal to y. Medium at beta _(x) The penetration fraction at the particle value of (a) is 1 divided by y. The efficiency fraction was 1-penetration fraction. Thus, the percent efficiency of the media is 100% multiplied by the efficiency fraction, and 100% ((1-1/β)) _(x) ) = percentage efficiency. For example, for particles of x microns or larger, have a beta _(x) Filter media of =200 having [1- (1/200)]*100% or 99.5% efficiency. The filter media described herein can have a wide range of beta values, e.g., beta _(x) = y, wherein x may be, for example, 1, 3, 5, 7, 10, 12, 15, 20, 25, 30, 50, 70, or 100, and wherein y may be, for example, at least 2, at least 10, at least 75, at least 100, at least 200, or at least 1000. It should be understood that other values of x and y are possible; for example, in some cases, y may be greater than 1000. It should also be understood that for any value of x, y can be the value representing C ₀ Any number of actual ratios to C (e.g., 10.2, 12.4). Likewise, for any value of y, x can be any number representing the minimum particle size that will achieve C ₀ The actual ratio to C equals y.

In some embodiments, the filter media described herein has a relatively high hydraulic pressure γ. The hydraulic pressure γ of the filter medium is given by the following formula: hydraulic pressure gamma = (10 x (air permeability) ^0.77 /(. Beta.200)). As described in the preceding paragraph, the β 200 of the filter media is equivalent to the following minimum particle size: the filter media exhibits an efficiency of at least 99.5% for this minimum particle size. The air permeability of the filter media may be determined as described elsewhere herein. The micron rating for beta 200 efficiency can be passed through a multi-pass filter test stand made by FTIDetermined by performing a multipass filtration test as per ISO 16889 (2008) procedure (modified by testing flat sheet samples). The measurement may be performed by: flowing a fluid comprising ISO A3 media test dust manufactured by PTI, inc. at an upstream weight dust level of 10 mg/liter in aviation hydraulic fluid AERO HFAMILL-5606A manufactured by Mobil at a face velocity of 24.55cm/min through a filter having a flow velocity of 110 cm/min ² Until a terminal pressure drop of 200kPa is reached. The hydraulic pressure γ of the filter medium may 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 filter media has a hydraulic pressure γ of 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 ranges are also possible (e.g., 15 or more and 50 or less, 20 or more and 45 or less, 25 or more and 40 or less, or 30 or more and 35 or less). Other ranges are also possible.

In some embodiments, the average flow pore size and air permeability of the filter media may 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 ) 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 media (([ mean flow pore size in microns ]) ]/[ air permeability in CFM]) ^1/2 ) 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 to0.8 or greater, 0.9 or greater, 1 or greater, 1.25 or greater, 1.5 or greater, 1.75 or greater, 2 or greater, 2.25 or greater, 2.5 or greater, or 2.75 or greater. Combinations of the above ranges are also possible (e.g., 0.1 or more and 3 or less, 0.1 or more and 0.5 or less, 0.2 or more and 0.8 or less, 0.5 or more and 0.5 or less and 1 or less, 0.7 or more and 1.5 or less, 1 or more and 2 or less, or 1.5 or more and 3 or less). Other ranges are also possible.

The filter media described herein can have a variety of suitable dust holding capacities as measured by a variety of suitable techniques. One method of determining the dust holding capacity of the filter media is to employ the process described in modified ASHRAE52.1 (1992) as discussed in the following paragraphs. In some embodiments, the filter media has the following dust holding capacity as determined by the modified ASHRAE52.1 (1992) process described in the following paragraphs: the dust holding capacity is greater than or equal to 22g/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 70g/m or more ² 80g/m or more 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 135g/m or more ² Greater than or equal to 150g/m ² 162g/m or more ² Greater than or equal to 180g/m ² 200g/m or more ² Greater than or equal to 250g/m ² Greater than or equal to 300g/m ² 400g/m or more ² And 500g/m or more 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 the following dust holding capacity as determined by the modified ASHRAE 52.1 (1992) process described in the following paragraphs: the dust holding capacity is 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 200g/m ² Less than or equal to 180g/m ² 162g/m or less ² Less than or equal to 150g/m ² 135g/m or less 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., 22g/m or greater) ² And 200g/m or less ² And 60g/m or more ² And not more than 200g/m ² 80g/m or more ² And is not more than 162g/m ² Or 90g/m or more ² And 135g/m or less ² ). Other ranges are also possible.

The dust holding capacity of the filter media can be determined by the process described in ASHRAE 52.1 (1992) modified such that: (1) Weighing the filter media before the process begins and at the end of the process, and (2) determining a mass of dust retained by the filter media by subtracting the measured mass of the filter media before the process begins from the measured mass of the filter media at the end of the process. The process may be carried out by dividing the area by 1ft ² Is exposed to a gas flow at 2g/100ft ³ Is carried out with air containing ASHRAE 52.1 synthesis test dust. Air containing test dust can be fed to the filter media at a face velocity of 15ft/min until the filter media reaches a pressure drop of 1.5 inches H ₂ And O. At this point, the process is complete and the mass of the filter media at the end of the process can be determined by weighing.

Another method of determining the dust holding capacity of a filter media is to perform a multi-pass filtration test based on ISO 16889 (2008) as described elsewhere herein. In some embodiments, the filter media has the following dust holding capacity as determined by the ISO 16889 (2008) based multipass filtration test described elsewhere herein: the containerThe dust amount is greater than or equal to 50g/m ² Greater than or equal to 75g/m ² Greater than or equal to 100g/m ² 125g/m or more ² Greater than or equal to 150g/m ² 175g/m or more ² Greater than or equal to 200g/m ² 225g/m or more ² Greater than or equal to 250g/m ² 275g/m or more ² Greater than or equal to 300g/m ² 325g/m or more ² 350g/m or more ² And is greater than or equal to 375g/m ² Greater than or equal to 400g/m ² 425g/m or more ² Greater than or equal to 450g/m ² 475g/m or more ² And 500g/m or more ² And is not less than 525g/m ² 550g/m or more ² Or greater than or equal to 575g/m ² . In some embodiments, the filter media has the following dust holding capacity as determined by the ISO 16889 (2008) based multipass filtration test described elsewhere herein: the dust holding capacity is less than or equal to 600g/m ² 575g/m or less 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 325g/m or less ² Less than or equal to 300g/m ² 275g/m or less 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 175g/m or less ² Less than or equal to 150g/m ² 125g/m or less 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., 50g/m or greater) ² And 600g/m or less ² Or 225g/m or more ² And 600g/m or less ² ). Other ranges are also possible.

Determining dust holding capacity of filter mediaA third method is to perform an ISO 19438 (2013) based multi-pass filtering test as described in the following paragraphs. In some embodiments, the filter media has the following dust holding capacity as determined by the ISO 19438 (2013) based multipass filtration test described in the following paragraphs: the dust holding capacity is greater than or equal to 50g/m ² Greater than or equal to 60g/m ² 70g/m or more ² 80g/m or more ² Greater than or equal to 90g/m ² Greater than or equal to 100g/m ² 125g/m or more ² Greater than or equal to 150g/m ² 175g/m or more ² Greater than or equal to 200g/m ² 225g/m or more ² Greater than or equal to 250g/m ² 275g/m or more ² Greater than or equal to 300g/m ² 325g/m or more ² 350g/m or more ² And is greater than or equal to 375g/m ² Greater than or equal to 400g/m ² 425g/m or more ² Greater than or equal to 450g/m ² 475g/m or more ² Greater than or equal to 500g/m ² And 525g/m or more ² 550g/m or more ² Or greater than or equal to 575g/m ² . In some embodiments, the filter media has the following dust holding capacity: the dust holding capacity is less than or equal to 600g/m ² Less than or equal to 575g/m ² 550g/m or less 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 325g/m or less ² Less than or equal to 300g/m ² 275g/m or less ² Less than or equal to 250g/m ² 225g/m or less ² Less than or equal to 200g/m ² 175g/m or less ² Less than or equal to 150g/m ² 125g/m or less 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., 50g/m or greater) ² And 600g/m or less ² Or 90g/m or more ² And 600g/m or less ² ). Other ranges are also possible.

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

As noted above, some filter media described herein include more than one layer. In some embodiments, the filter media comprises an efficiency layer. The efficiency layer may increase the efficiency of the filter media. When present, the efficiency layer may be positioned in a number of suitable locations in the filter media, such as the most upstream layer, the most downstream layer, or a layer having both one or more layers positioned upstream and one or more layers positioned downstream. In other words, the efficiency layer may be a first layer, a second layer, a third layer, a fourth layer, or other layers. In some embodiments, the filter media includes more than one efficiency layer. For example, the filter media may include first and second layers as efficiency layers, first and third layers as efficiency layers, or any other combination of layers as efficiency layers.

The efficiency layers described herein can be independent and/or can be supported by another layer (e.g., by needling).

Some of the efficiency layers described herein are fibrous. For example, the efficiency layer may be a nonwoven web. The nonwoven web may be a wet laid web, an air laid web, a meltblown web, a meltspun web, a melt fibrillated web, an electrospun web, a solution spun web, a solution blown web, a centrifugally spun web, a carded web, a spunbond web, a spunmelt web, a carded nonwoven web, a spunlaced web (e.g., a hydroentangled and hydroentangled web), or a composite web (e.g., a nonwoven web formed by two or more processes, such as by an air laid process and a meltblown process, or a nonwoven web formed by a spunbond process and a meltblown process).

In some embodiments, the efficiency layer comprises a fiber web (e.g., of the type described in the preceding paragraph) that has been subjected to one or more processes after formation to reduce the diameter of the fibers in the efficiency layer. By way of example, in some embodiments, the efficiency layer is formed (e.g., by one of the processes in the preceding paragraph) to include multicomponent fibers (e.g., bicomponent fibers, "islands-in-the-sea" fibers). One or more components of the multicomponent fiber may then be removed, leaving a fiber with a smaller diameter. The components may be removed, for example, by water spraying. Another example of a process that may be employed to reduce the fiber diameter of the fibers is fibrillation.

The efficiency layer may also be free of fibers. For example, porous, perforated, and/or fibrillated films may be suitable for use as the efficiency layer. A filtration layer comprising two or more efficiency layers may comprise efficiency layers that are all the same type of layer and/or web (e.g., the filtration media may comprise two efficiency layers that are meltblown webs), efficiency layers that are respective different types of layers and/or webs (e.g., the filtration media may comprise a first efficiency layer that is a meltblown web and a second efficiency layer that is an electrospun web), or may comprise 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 (e.g., a second type of web) that is different from the first type (e.g., the filtration media may comprise two efficiency layers that are meltblown webs and one efficiency layer that is an electrospun web).

The efficiency layer may include a variety of suitable types of fibers. As described above, the efficiency layer can include wet laid fibers, air laid fibers, carded fibers, meltblown fibers, melt spun fibers, melt fibrillated fibers, centrifugally spun fibers, electrospun fibers, solution spun fibers, spunmelt fibers, spunbond fibers, and/or fibrillated fibers. In some embodiments, the filter media includes an efficiency layer having non-natural fibers (e.g., synthetic fibers, non-synthetic fibers) and/or natural fibers.

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 (ether sulfone) 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.

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

In some embodiments, the efficiency layer includes two or more types of fibers. For example, the efficiency layer may include two types of fibers having different dielectric constants. One example of a pair of such fibers are poly (propylene) fibers and acrylic fibers (e.g., dry-spun acrylic fibers). Another example of a pair of such fibers are poly (propylene) fibers and polyester fibers. The relative amounts of poly (propylene) fibers, acrylic fibers, and/or polyester fibers 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. 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. Combinations of the above ranges are also possible (for example, 5 or more and 95 or less and 5 or 30 or more. Other ranges are also possible.

When present, the efficiency layer can include synthetic fibers having a variety of suitable average diameters. Each efficiency layer in the filter media may independently comprise synthetic fibers having the following average diameters: the average diameter is greater than or equal to 0.05 microns, greater than or equal to 0.1 microns, greater than or equal to 0.2 microns, greater than or equal to 0.5 microns, greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 3 microns, greater than or equal to 5 microns, greater than or equal to 10 microns, greater than or equal to 12 microns, greater than or equal to 20 microns, greater than or equal to 25 microns, greater than or equal to 30 microns, or greater than or equal to 40 microns. Each efficiency layer in the filter media may independently comprise synthetic fibers having the following average diameters: the average diameter is 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 20 microns, less than or equal to 12 microns, less than or equal to 10 microns, less than or equal to 5 microns, less than or equal to 3 microns, less than or equal to 2 microns, less than or equal to 1 micron, less than or equal to 0.5 microns, less than or equal to 0.2 microns, or less than or equal to 0.1 microns. Combinations of the above ranges are also possible (e.g., 0.05 to 50 microns, 0.05 to 12 microns, 0.2 to 3 microns, or 0.2 to 2 microns). Other ranges are also possible.

It should also be noted that the efficiency layer may 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 may be fibers of the same chemical composition, or may have different chemical compositions. Non-limiting examples of suitable cross-sections include circular, oval, Y-shaped, I-shaped (e.g., dog bone shaped), closed C-shaped, multi-lobed (e.g., tri-lobed, 4-lobed, 5-lobed, 6-lobed, including more than 6 lobes, X-shaped, crenulated).

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

When present, the efficiency layer can have a variety of suitable basis weights. The basis weight of the efficiency layer in which the undulations have not yet been formed is often lower than the basis weight of an efficiency layer comprising one or more sets of undulations. Creating undulations in the efficiency layer tends to increase the amount of efficiency layer per filter media footprint and, therefore, tends to increase the basis weight of the efficiency layer. As described above, the manufacture of the filter media may include forming undulations in an efficiency layer that is initially not undulating, and then undergoing one or more processes to form one or more sets of undulations. For this reason, it may be easier to refer to the basis weight of the efficiency layer before it is undulating. These basis weights are equivalent to the basis weight of the efficiency layer if extended to remove all undulations in the efficiency layer.

Each efficiency layer in the filter media, prior to undulation, may independently have a basis weight of: the basis weight is greater than or equal to 0.02g/m ² 0.05g/m or more ² Greater than or equal to 0.1g/m ² 0.2g/m or more 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 75g/m or more ² Greater than or equal to 100g/m ² 125g/m or more ² Greater than or equal to 150g/m ² 175g/m or more ² Greater than or equal to 200g/m ² 225g/m or more ² Greater than or equal to 250g/m ² 275g/m or more ² Greater than or equal to 300g/m ² Greater than or equal to 350g/m ² 400g/m or more ² Or greater than or equal to 450g/m ² . Each efficiency layer in the filter media, prior to being undulated, may independently have a basis weight of: the basis weight is less than or equal to 500g/m 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 275g/m or less ² Less than or equal to 250g/m ² 225g/m or less ² Less than or equal to 200g/m ² 175g/m or less ² Less than or equal to 150g/m ² 125g/m or less 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., 0.02g/m or greater) ² And 500g/m or less ² 0.02g/m or more ² And 300g/m or less ² And not less than 0.02g/m ² And 100g/m or less ² 0.05g/m or more ² And 50g/m or less ² Or 0.2g/m or more ² And is less than or equal to 30g/m ² ). Other ranges are also possible.

As described above, an efficiency layer comprising undulations over a single length scale may be provided. In some embodiments, the efficiency layer comprising undulations over a single length scale has the following basis weight: theA basis weight of 0.05g/m or more ² 0.08g/m or more ² 0.1g/m or more ² 0.125g/m or more ² Greater than or equal to 0.15g/m ² Greater than or equal to 0.2g/m ² 0.25g/m or more ² 0.3g/m or more ² Greater than or equal to 0.4g/m ² 0.5g/m or more ² 0.75g/m or more 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 75g/m or more ² Greater than or equal to 100g/m ² 125g/m or more 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 1250g/m or more ² . In some embodiments, the efficiency layer comprising undulations over a single length scale has the following basis weight: the basis weight is less than or equal to 1500g/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 125g/m or less ² Is less than or equal toEqual 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/m ² 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., 0.05g/m or greater) ² And is less than or equal to 1500g/m ² 0.08g/m or more ² And is less than or equal to 1500g/m ² 0.08g/m or more ² And 1000g/m or less ² And at most 0.08g/m ² And 500g/m or less ² And not less than 0.2g/m ² And 250g/m or less ² Or 0.8g/m or more ² And 150g/m or less ² ). Other ranges are also possible. If the filter media includes two or more efficiency layers having undulations over a single length scale, each efficiency layer can independently have a basis weight within one or more of the ranges listed above.

When present, the efficiency layer can have a variety of suitable thicknesses. As described above with respect to the basis weight of the efficiency layer, the thickness of the efficiency layer in which the undulations have not yet been formed is often lower than the thickness of an efficiency layer that includes one or more sets of undulations. As described above, the manufacture of the filter media may include forming undulations in an efficiency layer that is not initially undulating, and then undergoing 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 undulation. These thicknesses are equivalent to the thickness of the efficiency layer if extended to remove all the undulations in the efficiency layer.

Each efficiency layer in the filter media may independently have the following thickness prior to undulation: the thickness is greater than or equal to 0.001mm, greater than or equal to 0.002mm, greater than or equal to 0.005mm, greater than or equal to 0.01mm, greater than or equal to 0.02mm, greater than or equal to 0.05mm, greater than or equal to 0.075mm, greater than or equal to 0.1mm, greater than or equal to 0.13mm, greater than or equal to 0.2mm, greater than or equal to 0.3mm, greater than or equal to 0.4mm, greater than or equal to 0.5mm, greater than or equal to 0.7mm, greater than or equal to 1mm, greater than or equal to 1.25mm, greater than or equal to 1.5mm, greater than or equal to 1.75mm, greater than or equal to 2mm, greater than or equal to 2.25mm, greater than or equal to 2.5mm, greater than or equal to 2.75mm, greater than or equal to 3mm, greater than or equal to 3.5mm, greater than or equal to 4mm, or greater than or equal to 4.5mm. Each efficiency layer in the filter media may independently have the following thickness prior to undulation: the thickness is less than or equal to 5mm, less than or equal to 4.5mm, less than or equal to 4mm, less than or equal to 3.5mm, less than or equal to 3mm, less than or equal to 2.75mm, less than or equal to 2.5mm, less than or equal to 2.25mm, less than or equal to 2mm, less than or equal to 1.75mm, less than or equal to 1.5mm, less than or equal to 1.25mm, less than or equal to 1mm, less than or equal to 0.7mm, less than or equal to 0.5mm, less than or equal to 0.4mm, less than or equal to 0.3mm, less than or equal to 0.2mm, less than or equal to 0.13mm, less than or equal to 0.1mm, less than or equal to 0.075mm, less than or equal to 0.05mm, less than or equal to 0.02mm, less than or equal to 0.01mm, less than or equal to 0.005mm, or less than or equal to 0.002mm. Combinations of the above ranges are also possible (e.g., 0.001mm or more and 5mm or less, 0.001mm or more and 3mm or less, 0.001mm or more and 2.5mm or less, 0.01mm or more and 2.5mm or less, 0.1mm or more and 0.7mm or less, or 0.13mm or more and 0.3mm or less). Other ranges are also possible.

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

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

When present, the efficiency layer can have a variety of suitable mean flow pore sizes. Each efficiency layer in the filter media may independently have the following average flow pore size: the mean flow pore size is greater than or equal to 0.1 micron, greater than or equal to 0.2 micron, greater than or equal to 0.3 micron, greater than or equal to 0.4 micron, greater than or equal to 0.5 micron, greater than or equal to 0.6 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 microns, greater than or equal to 5 microns, greater than or equal to 6 microns, greater than or equal to 7 microns, greater than or equal to 8 microns, greater than or equal to 9 microns, greater than or equal to 10 microns, greater than or equal to 11 microns, greater than or equal to 12 microns, greater than or equal to 13 microns, greater than or equal to 14 microns, greater than or equal to 15 microns, greater than or equal to 17.5 microns, greater than or equal to 20 microns, greater than or equal to 22.5 microns, greater than or equal to 25 microns, greater than or equal to 30 microns, greater than or equal to 40 microns, greater than or equal to 50 microns, or equal to 75 microns. Each efficiency layer in the filter media may independently have the following average flow pore size: the mean flow pore size is 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 ranges are also possible (e.g., 0.1 to 100 micrometers greater than or equal to, 0.2 to 25 micrometers greater than or equal to, 0.5 to 1 micrometer greater than or equal to, 2 to 25 micrometers greater than or equal to, 5 to 15 micrometers greater than or equal to, or 7 to 12 micrometers greater than or equal to). Other ranges are also possible. The average flow pore size of the efficiency layer may be determined according to ASTM F316 (2011).

When present, the efficiency layer can have a variety of suitable solidities. Each efficiency layer in the filter media may independently have the following solidity: the degree of truth is 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%. Each efficiency layer in the filter media may independently have the following solidity: the degree of solidity is 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 ranges are also possible (e.g., 0.5% or more and 40% or less, 0.5% or more and 12% or less, 2% or more and 8% or less, or 2.5% or more and 6% or less). Other ranges are also possible.

The solidity of the efficiency layer can be determined by using the following formula: solidity = [ basis weight/(fiber density thickness) ] + 100%. Basis weight and thickness may be determined as described elsewhere herein. The fiber density is equivalent to the average density of the material or materials forming the fiber, which is typically given by the fiber manufacturer. The average density of the material forming the fibers may 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 medium by the total volume of all fibers in the filter medium. If the mass and density of each type of fiber in the filter media is known, the volume of all the fibers in the filter media can be determined by: (1) For each type of fiber, dividing the total mass of the type of fiber in the filter media by the density of the type of fiber; and (2) adding the volumes of each type of fiber. If the mass and density of each type of fiber in the filter media is unknown, the volume of all fibers in the filter media can be determined according to Archimedes' principle.

When present, the efficiency layer can have a variety of suitable stiffnesses. In some embodiments, the efficiency layer is a layer having a relatively low stiffness. Some efficiency layers may also have a relatively high stiffness. If undulating by the method described herein, such an efficiency layer can be manufactured by: an efficiency layer having a relatively low stiffness is initially deposited onto the reversibly tensile layer, and the efficiency layer is then corrugated to form a relief layer (e.g., by a process similar to that shown in fig. 6A-6C). This efficiency layer may then be impregnated with an adhesive that increases the stiffness of the efficiency layer. The adhesive may also improve the structural integrity and/or compression resistance of the efficiency layer. For this purpose, thermoplastic adhesives and/or thermosetting adhesives may be employed. One example of a suitable thermoplastic adhesive is a hot melt adhesive (e.g., a hot melt adhesive comprising poly (olefin), poly (ester), poly (amide), poly (urethane), and/or ethylene vinyl acetate). Non-limiting examples of suitable thermosetting adhesives include: acrylic adhesives, adhesives comprising (and/or the reaction product of) vinyl esters, phenolic adhesives, thermosetting poly (urethane), epoxy resins, and unsaturated poly (ethylene terephthalate). In some embodiments, the adhesive may comprise an adhesive as described elsewhere herein.

Each efficiency layer in the filter media may independently have the following stiffness: the stiffness is greater than or equal to 1mg, greater than or equal to 2mg, greater than or equal to 3mg, greater than or equal to 4mg, greater than or equal to 5mg, greater than or equal to 6mg, greater than or equal to 8mg, greater than or equal to 10mg, greater than or equal to 15mg, greater than or equal to 20mg, greater than or equal to 25mg, greater than or equal to 30mg, greater than or equal to 40mg, greater than or equal to 50mg, greater than or equal to 75mg, greater than or equal to 100mg, greater than or equal to 125mg, greater than or equal to 150mg, greater than or equal to 175mg, greater than or equal to 200mg, greater than or equal to 225mg, greater than or equal to 250mg, greater than or equal to 300mg, greater than or equal to 500mg, greater than or equal to 750mg, greater than or equal to 1000mg, greater than or equal to 2000mg, greater than or equal to 5000mg, greater than or equal to 7500mg, greater than or equal to 10000mg, or equal to 12500mg. Each efficiency layer in the filter media may independently have the following stiffness: the stiffness is less than or equal to 15000mg, less than or equal to 12500mg, less than or equal to 10000mg, less than or equal to 7500mg, less than or equal to 5000mg, less than or equal to 2000mg, less than or equal to 1000mg, less than or equal to 750mg, less than or equal to 500mg, less than or equal to 300mg, less than or equal to 250mg, less than or equal to 225mg, less than or equal to 200mg, less than or equal to 175mg, less than or equal to 150mg, less than or equal to 125mg, less than or equal to 100mg, less than or equal to 75mg, less than or equal to 50mg, less than or equal to 40mg, less than or equal to 30mg, less than or equal to 25mg, less than or equal to 20mg, less than or equal to 15mg, less than or equal to 10mg, less than or equal to 8mg, less than or equal to 6mg, less than or equal to 5mg, less than or equal to 4mg, less than or equal to 3mg, or less than or equal to 2mg. Combinations of the above-described ranges are also possible (e.g., 1mg or more and 12500mg or less, 1mg or more and 200mg or less, 1mg or more and 100mg or less, 1mg or more and 50mg or less, 3mg or more and 30mg or less, or 5mg or more and 10mg or less). Other ranges are also possible. The stiffness of the efficiency layer can be determined from WSP 90.2 (2015).

When present, the efficiency layer can have a variety of suitable pressure drops. Each efficiency layer in the filter media may independently have the following pressure drop: the pressure drop is greater than or equal to 0.1mm H ₂ O, 0.2mm H or more ₂ O, 0.3mm H or more ₂ O, 0.4mm H or more ₂ O, 0.5mm H or more ₂ O, 0.75mm H or more ₂ O, 1mm H or more ₂ O, 1.2mm H or more ₂ O, 1.5mm H or more ₂ O, 2mm H or more ₂ O, 2.5mm H or more ₂ O, 3mm H or more ₂ O, 3.5mm H or more ₂ O, 4mm H or more ₂ O, 5mm H or more ₂ O, 6mm H or more ₂ O, greater than or equal to 7mm H ₂ O, greater than or equal to 8mm H ₂ O, 10mm H or more ₂ O, 12mm H or more ₂ O, is greater than or equal toAt 15mm H ₂ O, 20mm H or more ₂ O, greater than or equal to 30mm H ₂ O, 40mm H or more ₂ O, 50mm H or more ₂ O, or 75mm H or more ₂ And O. Each efficiency layer in the filter media may independently have the following pressure drop: the pressure drop is less than or equal to 100mm H ₂ O, 75mm H or less ₂ O, less than or equal to 50mm H ₂ O, less than or equal to 40mm H ₂ O, less than or equal to 30mm H ₂ O, 20mm H or less ₂ O, less than or equal to 15mm H ₂ O, less than or equal to 12mm H ₂ O, less than or equal to 10mm H ₂ O, less than or equal to 8mm H ₂ O, less than or equal to 7mm H ₂ O, less than or equal to 6mm H ₂ O, less than or equal to 5mm H ₂ O, 4mm H or less ₂ O, less than or equal to 3.5mm H ₂ O, less than or equal to 3mm H ₂ O, less than or equal to 2.5mm H ₂ O, less than or equal to 2mm H ₂ O, less than or equal to 1.5mm H ₂ O, less than or equal to 1.2mm H ₂ O, less than or equal to 1mm H ₂ O, or 0.75mm H or less ₂ And O. Combinations of the above ranges are also possible (e.g., 0.1mm H or greater) ₂ O is not more than 100mm H ₂ O, 0.5mm H or more ₂ O is not more than 12mm H ₂ O, 1mm H or more ₂ O is less than or equal to 7mm H ₂ O, or 1.2mm H or more ₂ O is less than or equal to 3.5mm H ₂ O). The pressure drop of the efficiency layer can be determined by measurement of γ using an automatic filter tester TSI 8130 or an automatic filter tester TSI 3160 as described above.

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

When present, the efficiency layer may be charged or may be uncharged. In some embodiments, the filter media includes at least one charged efficiency layer and at least one uncharged efficiency layer. In some embodiments, the filter media includes an efficiency layer that is an electrically charged meltblown fiber web. The filter media may also include an efficiency layer that is a charged carded web, such as a charged carded web comprising poly (propylene) fibers and/or acrylic (e.g., dry-spun acrylic) fibers. The electrical charge may be generated on the efficiency layer by a variety of suitable charging processes, non-limiting examples of which include electrostatic charging processes, triboelectric charging processes, and hydrodynamic charging processes. In some embodiments, the filter media includes a charged electrospinning efficiency layer that acquires its charge during electrospinning. As one particular example, some filter media include a triboelectrically charged carded web comprising poly (propylene) fibers and/or acrylic (e.g., dry-spun acrylic) fibers.

The hydrodynamic charging process may include impinging jets and/or streams of water droplets onto an initially uncharged efficiency layer to cause the efficiency layer to become electrostatically charged. At the end of the hydrodynamic charging process, the efficiency layer may have an electret charge. The jets and/or streams of water droplets may impinge on the efficiency layer at a variety of suitable pressures, such as pressures between 10psi and 50psi, and may be provided by a variety of suitable sources, such as a sprayer. In some embodiments, the efficiency layer is hydraulically charged by using an apparatus that can be used for hydroentanglement of fibers, which operates at a lower pressure than is typically used for the hydroentanglement process. The water impinging on the efficiency layer may be relatively pure; for example, the water may be distilled and/or deionized water. After being electrostatically charged in this manner, the efficiency layer may be dried, such as with an air dryer.

In some embodiments, the efficiency layer is hydraulically charged while moving laterally. The efficiency layer may be transported on a porous belt, such as a screen or mesh-type conveyor belt. When the efficiency layer is transported on a porous belt, the efficiency layer may be exposed to a spray and/or jet of water pressurized by a pump. The water jets and/or sprays can impinge on the efficiency layer and/or penetrate into the efficiency layer. In some embodiments, a vacuum is provided below the porous conveyor belt, which may aid in the passage of water through the efficiency layer and/or reduce the amount of time and energy required to dry the efficiency layer at the end of the hydrocharging process.

As noted above, some filter media herein include a layer that is a scrim. Some filter media include two or more layers as a scrim. The scrim may be a fairly open layer. For example, the scrim may have a relatively high air permeability (e.g., in excess of 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 may include the following scrims: the scrim 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 may be layers that are capable of undergoing reversible stretch and/or may be formed of reversibly stretchable materials. In some embodiments, also as described above, the filter media comprises the following scrim: the scrim holds one or more other layers (e.g., one or more efficiency layers and/or one or more nanofiber layers) such that the filter media includes a plurality of peaks that are irregular in one or more ways. For example, the scrim may hold one or more other layers such that the one or more other layers are undulating, and the undulations are irregular in one or more ways. Some filter media may include the following scrims: the scrim protects one or more layers of the filter media, such as one or more layers of the filter media that are held by additional scrims such that the filter media includes peaks that are irregular in one or more ways. Some scrims may be positioned adjacent to the efficiency layer and/or may be adhered to the efficiency layer by an adhesive.

A variety of suitable scrims may be employed in the filter media described herein. In some embodiments, the filter media comprises a fibrous scrim. For example, the filter media may include the scrim as a nonwoven web, such as a spunbond web. As another example, the filter media may include a scrim that is a mesh, such as an extruded mesh. As a third example, the filter media may include a scrim that is a woven material. As a fourth and fifth example, the filter media may include a scrim that is a perforated film and/or a fibrillated film. In some embodiments, the scrim may include elastically extensible fibers that are not in direct contact with each other. One or more scrims may be cut from hundreds of yards of material wound around a roll and/or from a creel.

When the filter media includes a spunbond scrim, the spunbond scrim can include a variety of suitable types of spunbond fibers. The spunbond scrim may include fibers that are synthetic fibers such as polyolefin fibers (e.g., poly (propylene) fibers), polyester fibers, and/or nylon fibers.

When the filter media includes a spunbond scrim, the spunbond scrim can include fibers having a variety of suitable average diameters. The spunbond scrim may include fibers having the following average diameters: the average diameter is greater than or equal to 1 micron, greater than or equal to 2 microns, greater than or equal to 5 microns, greater than or equal to 7.5 microns, greater than or equal to 10 microns, greater than or equal to 12.5 microns, greater than or equal to 15 microns, greater than or equal to 20 microns, greater than or equal to 25 microns, greater than or equal to 30 microns, greater than or equal to 35 microns, greater than or equal to 40 microns, or greater than or equal to 45 microns. The spunbond scrim may include fibers having the following average diameters: the average diameter is less than or equal to 50 microns, less than or equal to 45 microns, less than or equal to 40 microns, less than or equal to 35 microns, less than or equal to 30 microns, less than or equal to 25 microns, less than or equal to 20 microns, less than or equal to 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, or less than or equal to 2 microns. Combinations of the above ranges are also possible (e.g., 1 micron or more and 50 microns or less, or 15 microns or more and 35 microns or less). Other ranges are also possible.

It should also be noted that the spunbond scrim may 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 may be fibers of the same chemical composition, or may 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., tri-lobed, 4-lobed, 5-lobed, 6-lobed, including more than 6 lobes, X-shaped, crenulated). When the filter media includes a spunbond scrim, the fibers in the filter media may be continuous. In some embodiments, the scrim (e.g., a mesh scrim, a nonwoven scrim, a woven scrim, a scrim comprising elastically elongatable fibers that are not in direct contact with each other) comprises elastically elongatable fibers. In other words, the scrim may comprise the following fibers: the fiber can be drawn to a relatively high elongation without breaking and then allowed to recover to a length that is close to or the same as the length of the fiber before it was drawn. This may be advantageous for scrims that are capable of undergoing reversible stretching, such as for scrims on which one or more other layers are deposited when the scrim is in a reversibly stretched state.

As noted above, some filter media include a scrim in the form of a plurality of elastically elongatable fibers. The elastically extensible fibers may be disconnected from each other and/or initially capable of being separated from each other. In other words, in some embodiments, the scrim may have a non-conventional topography that includes fibers that do not collectively form a web. For example, the scrim may have a topography similar to that of layer 302 shown in fig. 4A and 4B. In some embodiments, the elastically elongatable fibers and the disconnected fibers in the scrim may be oriented substantially parallel to each other. The elastically extensible fibers may be oriented generally at any suitable angle relative to the filter media (e.g., in the machine direction, in the cross direction, or in a direction between the machine direction and the cross direction).

In some embodiments, the disconnected elastically extensible fibers may together form a reversibly stretchable layer when incorporated into a filter media. As also described above, such elastically extensible fibers may be adhered to additional layers (e.g., efficiency layers) and/or may be used to create undulations in one or more other layers upon recovery from a reversibly stretched layer.

Some elastically extensible fibers are capable of being stretched up to 1.5 times their original length without breaking, and then may recover to a length that is close to or the same as their length prior to being stretched. In some embodiments, the scrim comprises the following elastically extensible fibers: the elastically extensible fiber is capable of being stretched up 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 original length without breaking, and then the elastically extensible fiber can be restored to a length that is close to or the same as its length before being stretched. Combinations of the above ranges are also possible (e.g., 1 or more and 10 or less). Other ranges are also possible.

Non-limiting examples of suitable elastically extensible fibers include: fibers comprising elastomeric materials, such as fibers comprising block copolymers (e.g., styrene-containing block copolymers, such as Kraton), fibers comprising polyurethanes (e.g., spandex fibers), fibers comprising polyester ethers, fibers comprising polyesters, olefin-based fibers (e.g., crosslinked poly (olefin) fibers), stiff 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).

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

When present, the scrim may comprise elastically extensible fibers having a variety of suitable average lengths. The scrim may comprise elastically extensible fibers having the following average lengths: the average length is greater than or equal to 5mm, greater than or equal to 10mm, greater than or equal to 20mm, greater than or equal to 50mm, greater than or equal to 100mm, greater than or equal to 200mm, greater than or equal to 500mm, greater than or equal to 1m, greater than or equal to 2m, greater than or equal to 5m, greater than or equal to 10m, greater than or equal to 20m, greater than or equal to 50m, or greater than or equal to 100m. In some embodiments, the elastically extensible fibers may be continuous fibers. The scrim may comprise elastically extensible fibers having the following average lengths: the average length is less than or equal to 200m, less than or equal to 100m, less than or equal to 50m, less than or equal to 20m, less than or equal to 10m, less than or equal to 5m, less than or equal to 2m, less than or equal to 1m, less than or equal to 750mm, less than or equal to 500mm, less than or equal to 400mm, less than or equal to 300mm, less than or equal to 250mm, less than or equal to 200mm, less than or equal to 100mm, less than or equal to 90mm, less than or equal to 50mm, less than or equal to 20mm, or less than or equal to 10mm. Combinations of the above ranges are also possible (e.g., 5mm or more and 100m or less). Other ranges are also possible. The elastically extensible fibers may extend throughout the source of the scrim, such as throughout the entire material wound around a roll or formed into a creel.

When present, the scrim may comprise elastically extensible fibers having a variety of suitable deniers. In some embodiments, the elastically extensible fibers have the following denier: the denier is greater than or equal to 20, greater than or equal to 30, greater than or equal to 50, greater than or equal to 75, greater than or equal to 100, greater than or equal to 150, greater than or equal to 200, greater than or equal to 300, greater than or equal to 500, greater than or equal to 750, greater than or equal to 1000, or greater than or equal to 1500. In some embodiments, the elastically extensible fibers have the following denier: the denier is less than or equal to 2000, less than or equal to 1500, less than or equal to 1000, less than or equal to 750, less than or equal to 500, less than or equal to 300, less than or equal to 200, less than or equal to 150, less than or equal to 100, less than or equal to 75, less than or equal to 50, or less than or equal to 30. Combinations of the above ranges are also possible (e.g., 20 or more and 2000 or less). Other ranges are also possible.

As noted above, some scrims may 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 may be allowed to recover to a length that is close to or the same as the length of the scrim before it was stretched. The scrim may also be formed of a reversibly stretchable material, but cannot be reversibly stretched by itself. As one example, the scrim may be formed of a reversibly stretchable material, and may then be laminated to a layer that cannot be reversibly stretched. This layer may prevent the scrim from being subjected to reversible stretching (e.g., the reversible stretching that the scrim would be able to withstand without lamination).

In some embodiments, the scrim is capable of (and/or is formed of) being capable of being subjected to (and/or being formed of) the following reversible stretch: the reversible stretch is 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 is capable of (and/or is formed of) being capable of being subjected to (and/or being formed of) the following reversible stretch: the reversible stretch is 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 ranges are also possible (e.g., 50% or more and 1000% or less, 100% or more and 400% or less, or 200% or more and 300% or less). Other ranges are also possible.

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

When present, the scrim can have a variety of suitable basis weights. The basis weight of the scrim in which the undulations have not yet been formed is often lower than the basis weight of a scrim comprising one or more sets of undulations. Creating undulations in the scrim tends to increase the amount of scrim per filter media footprint and, therefore, tends to increase the basis weight of the scrim. As described above, the manufacture of the filter media may include: the undulations are formed in an initially non-undulating scrim and 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 basis weight of the scrim before it is undulated. These basis weights are equivalent to the basis weight of the scrim if extended to remove all the undulations in the scrim.

The scrim, prior to being laid up, may have the following basis weight: the basis weight is greater than or equal to 0.1g/m ² 0.2g/m or more ² Greater than or equal to 0.3g/m ² 0.5g/m or more ² 0.75g/m or more 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 50g/m or more ² Greater than or equal to 60g/m ² 70g/m or more ² 80g/m or more ² Or greater than or equal to 100g/m ² . The scrim, prior to being laid up, may have the following basis weight: the basis weight is less than or equal to 120g/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 (0.1 g/m or more) ² And 120g/m or less ² And 1g/m or more ² And 120g/m or less ² And 5g/m or more ² And 120g/m or less ² And not less than 20g/m ² And 80g/m or less ² Or 40g/m or more ² And 60g/m or less ² ). Other ranges are also possible. The basis weight of the scrim may be determined by weighing a known area of scrim and then dividing the measured weight by the known area.

When present, the scrim may have a variety of suitable thicknesses. The thickness of the scrim in which the undulations have not yet been formed tends to be lower than the thickness of a scrim comprising one or more sets of undulations. As described above, the manufacture of the filter media may include forming undulations in an initially non-undulating scrim, and then undergoing 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 it is undulated. These thicknesses are equivalent to the thickness of the scrim if extended to remove all the undulations in the scrim.

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

As noted above, some scrims may be relatively open. When present, the scrim may include the following openings: the opening may be parameterized by the longest line having an end point on the outer boundary of the opening and passing through the opening. The line will be equivalent to the diameter of a circular opening or equivalent to the diagonal of a rectangular opening. In some embodiments, the scrim comprises openings having end points on the outer boundaries of the openings and the longest line through the opening that 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 inch, greater than or equal to 1.5 inch, greater than or equal to 1.75 inch, 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 may include openings having endpoints on the outer boundaries of the openings and the longest line 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 ranges are also possible (e.g., 0.1 inch or more and 5 inches or less, 0.1 inch or more and 1 inch or less, or 0.1 inch or more and 0.5 inch or less). Other ranges are also possible. The openings can have a variety of shapes (e.g., square, rectangular, etc.).

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

As described above, some filter media include a nanofiber layer. The nanofiber layer may improve the filtration performance of the filter media. In some embodiments, the nanofiber layer serves as an efficiency layer. In such cases, the nanofiber layer may have one or more properties described herein with respect to the efficiency layer and/or may have one or more properties described herein with respect to the nanofiber layer. When present, the nanofiber layer may be positioned in a number of suitable locations in the filter media, such as the most upstream layer, the most downstream layer, or a layer having both one or more layers positioned upstream and one or more layers positioned downstream. In other words, the nanofiber layer may be a first layer, a second layer, a third layer, a fourth layer, or other layers. In some embodiments, the filter media comprises more than one nanofiber layer. For example, the filter media may include first and second layers that are nanofiber layers, second and third layers that are nanofiber layers, first and third layers that are nanofiber layers, or any other combination of layers that are 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).

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

In some embodiments, the nanofiber layer comprises a web (e.g., a web of the type described in the preceding paragraph) that has been subjected to 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 preceding paragraph) to include a multicomponent fiber (e.g., a bicomponent fiber, an "islands-in-the-sea" fiber). One or more components of the multicomponent fiber may then be removed, leaving a fiber with a smaller diameter. The components may be removed, for example, by water spraying. Another example of a process that may be employed to reduce the fiber diameter of the fibers is fibrillation.

The nanofiber layer may include 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 (ether sulfone) fibers, polyester fibers, polycarbonate fibers, and/or poly (lactic acid) fibers. An example of a natural fiber is chitosan fiber.

When present, the nanofiber layer may comprise synthetic fibers having a variety of suitable average diameters. Each nanofiber layer in the filter media may independently comprise synthetic fibers having the following average diameters: the average diameter is greater than or equal to 20nm, greater than or equal to 50nm, greater than or equal to 75nm, greater than or equal to 100nm, greater than or equal to 200nm, greater than or equal to 500nm, or greater than or equal to 750nm. Each nanofiber layer in the filter media may independently comprise synthetic fibers having the following average diameters: the average diameter is less than or equal to 1 micron, less than or equal to 750nm, less than or equal to 500nm, less than or equal to 200nm, less than or equal to 100nm, less than or equal to 75nm, or less than or equal to 50nm. Combinations of the above ranges are also possible (e.g., 20nm or more and 1 μm or less). Other ranges are also possible.

It should also be noted that the nanofiber layer may 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 may be fibers of the same chemical composition, or may have different chemical compositions. Non-limiting examples of suitable cross-sections include circular, oval, Y-shaped, I-shaped (e.g., dog bone shaped), closed C-shaped, multi-lobed (e.g., tri-lobed, 4-lobed, 5-lobed, 6-lobed, comprising more than 6 lobes, X-shaped, crenulated).

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

When present, the nanofiber layer may have a variety of suitable basis weights. The basis weight of the nanofiber layer in which the undulations have not yet been formed is often lower than the basis weight of a nanofiber layer comprising one or more sets of undulations. Creating undulations in the nanofiber layer tends to increase the amount of nanofiber layer per area of filter media footprint, and thus tends to increase the basis weight of the nanofiber layer. As described above, the manufacture of the filter media may include forming undulations in an initial, non-undulating nanofiber layer, and then undergoing one or more processes to form one or more sets of undulations. For this reason, it may be easier to refer to the basis weight of the nanofiber layer before undulation. These basis weights are equivalent to the basis weight of the nanofiber layer if extended to remove all undulations in the nanofiber layer.

Each nanofiber layer in the filter media, prior to undulation, may independently have a basis weight of: the basis weight is greater than or equal to 0.02g/m ² 0.03g/m or more ² 0.04g/m or more ² 0.05g/m or more ² 0.075g/m or more ² 0.1g/m or more ² Greater than or equal to 0.2g/m ² 0.5g/m or more 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 thanOr equal to 4g/m ² . Each nanofiber layer in the filter media, prior to undulation, may independently have a basis weight of: the basis weight is less than or equal to 5g/m ² Less than or equal to 4g/m ² Less than or equal to 3g/m ² Less than or equal to 2g/m ² 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/m ² . Combinations of the above ranges are also possible (e.g., 0.02g/m or greater) ² And is not more than 5g/m ² 0.05g/m or more ² And is less than or equal to 3g/m ² Or 0.1g/m or more ² And is less than or equal to 2g/m ² ). Other ranges are also possible.

In some embodiments, the nanofiber layer is provided with a carrier layer. The nanofiber layer may be directly adjacent to the carrier layer, or there may be one or more layers positioned between the carrier layer and the nanofiber layer. In some embodiments, the filter media includes a nanofiber layer and a carrier layer with an adhesive positioned therebetween. The nanofiber layer may be deposited onto the carrier layer during formation (e.g., during an electrospinning 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 may also serve as a backing, which is described in more detail elsewhere herein.

Some carrier layers are fibrous. For example, the carrier layer may be a nonwoven web, such as a meltblown web, a spunbond web, 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 media may also include a non-fibrous support layer. Non-limiting examples of suitable non-fibrous carrier layers include perforated films and fibrillated films.

When present, the carrier layer may comprise synthetic fibers having a variety of suitable average diameters. Each carrier layer in the filter media may independently comprise synthetic fibers having the following average diameters: the average diameter is greater than or equal to 0.5 micrometers, greater than or equal to 0.75 micrometers, greater than or equal to 1 micrometer, greater than or equal to 1.25 micrometers, greater than or equal to 1.5 micrometers, greater than or equal to 1.75 micrometers, greater than or equal to 2 micrometers, greater than or equal to 2.25 micrometers, greater than or equal to 2.5 micrometers, greater than or equal to 2.75 micrometers, greater than or equal to 3 micrometers, greater than or equal to 4 micrometers, greater than or equal to 5 micrometers, greater than or equal to 7.5 micrometers, greater than or equal to 10 micrometers, greater than or equal to 12.5 micrometers, greater than or equal to 15 micrometers, greater than or equal to 20 micrometers, greater than or equal to 30 micrometers, or greater than or equal to 40 micrometers. Each carrier layer in the filter media may independently comprise synthetic fibers having the following average diameters: the average diameter is 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 microns. Combinations of the above ranges are also possible (e.g., 0.5 to 50 microns, 0.5 to 20 microns, or 1 to 3 microns). Other ranges are also possible.

It should also be noted that the carrier layer may comprise 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 may be fibers of the same chemical composition, or may have different chemical compositions. Non-limiting examples of suitable cross-sections include circular, oval, Y-shaped, I-shaped (e.g., dog bone shaped), closed C-shaped, multi-lobed (e.g., tri-lobed, 4-lobed, 5-lobed, 6-lobed, comprising more than 6 lobes, X-shaped, crenulated).

When present, the carrier layer can have a variety of suitable basis weights. The basis weight of the carrier layer in which the undulations have not yet been formed tends to be lower than the basis weight of the carrier layer comprising one or more sets of undulations. Forming undulations in the carrier layer tends to increase the amount of carrier layer per filter media footprint and thus tends to increase the basis weight of the carrier layer. As described above, the fabrication of the filter media may include forming undulations in an initially non-undulating carrier layer, and then undergoing one or more processes to form one or more sets of undulations. For this reason, it may be easier to refer to the basis weight of the carrier layer before undulation. These basis weights are equivalent to the basis weight of the carrier layer if extended to remove all undulations in the carrier layer.

Each carrier layer in the filter media may independently have the following basis weight prior to undulation: the basis weight is 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 17.5g/m or more ² Greater than or equal to 20g/m ² 22.5g/m or more ² Greater than or equal to 25g/m ² 27.5g/m or more 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 media may independently have the following basis weight prior to undulation: the basis weight is less than or equal to 100g/m 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., 5g/m or more) ² And 100g/m or less ² Or 5g/m or more ² And is less than or equal to 30g/m ² ). Other ranges are also possible. The basis weight of the carrier layer may be determined by weighing a carrier layer of known area and then dividing the measured weight by the known area.

As described above, some filter media, such as corrugated filter media, include one or more support layers. The support layer may support one or more other layers of the wave form of the filter media. In some embodiments, one or more support layers may be used as a pre-filter and/or backing. When used as a pre-filter, the support layer may be positioned upstream of the efficiency layer, and may help filter larger particles from the fluid prior to exposure to the efficiency layer. This may improve the capacity of the filter media and/or protect the efficiency layer. The support layer used as a backing may be relatively open (e.g., the support layer may contribute little to the air resistance of the filter) and/or may 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 pleatable backing.

In an exemplary embodiment, the filter media includes the following downstream support layers: the downstream support layer is disposed on the air outflow side of the corrugated layer and effectively retains the corrugated layer in a corrugated configuration. The filter media may also include an upstream support layer disposed on an air entrance side of the corrugated layer opposite the downstream support layer. The upstream support layer may also help to maintain the corrugated layer in a corrugated configuration. As discussed above, one skilled in the art will appreciate that the filter media may include any number of layers, and the filter media need not include two support layers or top layers. In certain exemplary embodiments, the filter media may include a single support layer positioned upstream or downstream of other corrugated layers. In other embodiments, the filter media 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 media.

The support layers described herein may be formed using a variety of techniques known in the art, including melt blowing, air laying techniques, carding, spunbonding, and extrusion. In an exemplary embodiment, the filter media comprises one or more support layers that are carded or air-laid webs. In some embodiments, the filter media comprises one or more support layers that are extruded webs. The filter media may also include one or more support layers that are perforated films and/or fibrillated films.

A variety of materials, including synthetic and non-synthetic materials, can also be used to form the fibers of any support layer included in the filter media described herein. The one or more support layers may include meltblown fibers, staple fibers, and/or spunbond fibers. In one exemplary embodiment, the one or more support layers are formed from staple fibers, and in particular from a combination of binder and non-binder fibers. One suitable fiber composition is a blend of at least 20% binder fiber and the balance non-binder fiber. Various types of binder fibers and non-binder fibers can be used to form the media of the present invention. The binder fibers may be formed of any material effective to promote thermal bonding between the layers, and thus will have an activation temperature lower than the melting temperature of the non-binder fibers. The binder fibers may be monocomponent fibers or any of a number of multicomponent (e.g., bicomponent) binder fibers. In one embodiment, the binder fibers may be bicomponent fibers, and each component may have a different melting temperature. For example, the binder fiber may include a core and a sheath, wherein the sheath has an activation temperature that is less than the melting temperature of the core. This allows the sheath to melt before the core, allowing the sheath to bond with other fibers in the layer while the core maintains its structural integrity. This may be particularly advantageous as it results in a more adhesive layer for capturing the filtrate. The core/sheath binder fibers may be concentric or non-concentric, and exemplary core/sheath binder fibers may 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 may include split fiber fibers, side-by-side fibers, and/or "islands-in-the-sea" fibers.

The non-binding fibers, if present in one or more support layers, may be synthetic and/or non-synthetic, and in exemplary embodiments, the non-binding fibers may 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-binding fibers may include polyester, polyacrylic, polyolefin, nylon, rayon, and combinations thereof.

When present, the support layer may comprise a suitable percentage of synthetic fibers. For example, in some embodiments, the weight percentage of the synthetic fibers in each support layer is independently between 80wt% and 100wt% of all the fibers in the support layer. In some embodiments, the weight percentage of the synthetic fibers in each support layer is independently greater than or equal to 80wt%, greater than or equal to 90wt%, or greater than or equal to 95wt%. In some embodiments, the weight percentage of the synthetic fibers in each support layer is independently less than or equal to 100wt%, less than or equal to 95wt%, less than or equal to 90wt%, or less than or equal to 85wt%. Combinations of the above ranges are also possible (e.g., 80wt% or more and 100wt% or less). Other ranges are also possible. In some embodiments, one or more support layers comprise 100wt% synthetic fibers. In some embodiments, one or more support layers comprise synthetic fibers in the ranges described above relative to the total weight of the support layer (e.g., comprising any resin).

When present, the support layer may be formed from a variety of fiber types and sizes. In exemplary embodiments where the filter media 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 other layers present in the filter media. In some cases where the filter media includes both an upstream support layer and a downstream support layer, the upstream support layer is formed from fibers having the following average diameters: the average diameter is less than or equal to the average diameter of the downstream support layer, but greater than the average diameter of the other layers present in the filter media. In certain exemplary embodiments, the filter media includes a downstream support layer and/or an upstream support layer formed from fibers having an average diameter in a 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 may be in the range of 18 microns to 22 microns. In some cases, the downstream support layer and/or the upstream support layer may include relatively fine fibers. For example, in some embodiments, the finer downstream support layer and/or the finer upstream support layer may 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.

When present, the support layer may comprise fibers having a variety of suitable average lengths. The fibers may include staple fibers and/or continuous fibers. Each support layer in the filter media may independently comprise synthetic fibers having the following average length: the average length is greater than or equal to 20mm, greater than or equal to 50mm, greater than or equal to 75mm, greater than or equal to 100mm, greater than or equal to 200mm, greater than or equal to 250mm, greater than or equal to 300mm, greater than or equal to 400mm, greater than or equal to 500mm, greater than or equal to 750mm, greater than or equal to 1m, greater than or equal to 2m, greater than or equal to 5m, greater than or equal to 10m, greater than or equal to 20m, greater than or equal to 50m, or greater than or equal to 100m. Each support layer in the filter media may independently comprise synthetic fibers having the following average lengths: the average length is less than or equal to 200m, less than or equal to 100m, less than or equal to 50m, less than or equal to 20m, less than or equal to 10m, less than or equal to 5m, less than or equal to 2m, less than or equal to 1m, less than or equal to 750mm, less than or equal to 500mm, less than or equal to 400mm, less than or equal to 300mm, less than or equal to 250mm, less than or equal to 200mm, less than or equal to 100mm, less than or equal to 75mm, or less than or equal to 50mm. Combinations of the above ranges are also possible (e.g., 20m or more and 200m or less, 20mm or more and 100mm or less, or 20mm or more and 75mm or less). Other ranges are also possible.

It should also be noted that the support layer may comprise 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 may be fibers of the same chemical composition, or may have different chemical compositions. Non-limiting examples of suitable cross-sections include circular, oval, Y-shaped, I-shaped (e.g., dog bone shaped), closed C-shaped, multi-lobed (e.g., tri-lobed, 4-lobed, 5-lobed, 6-lobed, including more than 6 lobes, X-shaped, crenulated).

When present, the support layer can have a variety of suitable basis weights. The basis weight of the support layer in which the undulations have not yet been formed is often lower than the basis weight of a support layer comprising one or more sets of undulations. Forming undulations in the support layer tends to increase the amount of support layer per filter media footprint and therefore tends to increase the basis weight of the support layer. As described above, the manufacture of the filter media may include forming undulations in a support layer that is not initially undulating, and then undergoing one or more processes to form one or more sets of undulations. For this reason, it may be easier to refer to the basis weight of the support layer before undulation. These basis weights are equivalent to the basis weight of the support layer if extended to remove all undulations in the support layer.

Each support layer may independently have the following basis weight prior to undulation: the basis weight is greater than or equal to 10g/m ² Greater than or equal to 20g/m ² 22g/m or more ² 33g/m or more ² Greater than or equal to 50g/m ² Greater than or equal to 60g/m ² 70g/m or more ² 80g/m or more ² Or greater than or equal to 90g/m ² . Each support layer may independently have the following basis weight prior to undulation: the basis weight is less than or equal to 99g/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 Is less than or equal to22g/m ² Or less than or equal to 20g/m ² . Combinations of the above ranges are also possible (e.g., 10g/m or greater) ² And not more than 99g/m ² Or 33g/m or more ² And 70g/m or less ² ). Other ranges are also possible. The basis weight of a support layer may be measured by weighing a known area of the support layer and then dividing the measured weight by the known area.

When present, the support layer can have a variety of suitable thicknesses. Each support layer in the filter media may independently have the following thickness: the thickness is greater than or equal to 3 mils (mil), 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. Each support layer in the filter media may independently have the following thickness: the thickness is 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 ranges are also possible (e.g., 4 mils to 200 mils, 4 mils to 100 mils, 8 mils to 30 mils, 15 mils to 60 mils, or 12 mils to 20 mils). Other ranges are also possible. The thickness of the support layer may be determined by Edana WSP 120.1 standard (2005) with a presser foot selected to have a load of 2 ounces and an area of 1 square inch.

When present, the support layer may have a variety of suitable mean flow pore sizes. Each support layer in the filter media may independently have the following average flow pore size: the mean flow pore size is greater than or equal to 30 micrometers, greater than or equal to 40 micrometers, greater than or equal to 50 micrometers, greater than or equal to 75 micrometers, greater than or equal to 100 micrometers, or greater than or equal to 120 micrometers. Each support layer in the filter media may independently have the following average flow pore size: the mean flow pore size is 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., 30 microns or more and 150 microns or less, or 50 microns or more and 120 microns or less). Other ranges are also possible. The mean flow pore size of the support layer may be determined according to ASTM F316 (2011).

When present, the support layer may have a variety of suitable stiffnesses. Each support layer in the filter media may independently have the following stiffness: the stiffness is greater than or equal to 200mg, greater than or equal to 300mg, greater than or equal to 500mg, greater than or equal to 750mg, greater than or equal to 1000mg, greater than or equal to 2000mg, greater than or equal to 5000mg, or greater than or equal to 7500mg. Each support layer in the filter media may independently have the following stiffness: the stiffness is less than or equal to 10000mg, less than or equal to 7500mg, less than or equal to 5000mg, less than or equal to 2000mg, less than or equal to 1000mg, less than or equal to 750mg, less than or equal to 500mg, or less than or equal to 300mg. Combinations of the above-described ranges are also possible (e.g., 200mg or more and 10000mg or less). Other ranges are also possible. The stiffness of the support layer can be determined from WSP 90.2 (2015).

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 greater than or equal to 8 mils and less than or equal to 30 mils (e.g., greater than or equal to 12 mils), as measured in a planar configurationEar and 20 mils or less), 10g/m or more ² And not more than 99g/m ² (e.g., 22g/m or more) ² And not more than 99g/m ² Or 33g/m or more ² And 70g/m or less ² ) And a mean flow pore size of 30 microns or more and 150 microns or less (e.g., 50 microns or more and 120 microns or less).

As described above, some filter media, such as corrugated filter media, include one or more cover layers disposed on the air intake side I and/or the air outflow side O. As an example, fig. 9A illustrates the top layer 18 as a cover layer disposed on the air intake side I of the filter media 1006. In some embodiments, the filter media comprises an outermost layer that is a wire backing. In some embodiments, the filter media includes a cover layer that can serve as a dust-laden layer and/or can serve as an aesthetic layer. In an exemplary embodiment, the cover layer is a planar layer that mates with the remainder of the filter media after assembly and/or corrugating. The overlay may provide an aesthetically pleasing top surface. The cover layer may 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 present. In certain exemplary embodiments, the cover layer is formed of fibers having an average fiber diameter of 5 microns or more and 20 microns or less. Thus, the cover layer can act as a dust holding layer without affecting the gamma value of the filter medium.

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

In some embodiments (e.g., the embodiment shown in fig. 9B), the filter media includes a bottom layer disposed on the air outflow side. The bottom layer may serve as a reinforcing component, providing structural integrity to the filter media to help maintain the waved configuration if the filter media includes one or more layers of corrugations. The bottom layer may also function to provide abrasion resistance. This may be particularly desirable in ASHRAE bag type applications where the outermost layer is subject to wear during use. As discussed above, the bottom layer may have a similar construction to the cover layer. In some embodiments, the filter media includes both a base layer and a cover layer. In an exemplary embodiment, the bottom layer is the roughest layer, i.e., the bottom layer is formed of fibers having an average diameter greater than the average diameter of the fibers forming all other layers of the filter media. One exemplary base layer is a spunbond layer, however a variety of other layers having a variety of configurations may be used.

When present, any outer layer, such as a cover layer and/or a base layer, can also be formed using a variety of techniques known in the art, including melt blowing, wet-laid techniques, air-laid techniques, carding, spunbonding, and extrusion. In an exemplary embodiment, the cover layer is an airlaid layer and the base layer is a spunbond layer. In some embodiments, the filter media includes a cover layer that is an extruded mesh and/or netting. The resulting layer may also have a variety of thicknesses, air permeabilities, and basis weights as required by the desired application.

When present, the cover layer and/or the base layer may include a variety of suitable types of fibers including synthetic and non-synthetic materials. In an exemplary embodiment, the filter media includes a cover layer and/or a base layer formed from staple fibers, and particularly a cover layer and/or a base layer formed from a combination of binder fibers and non-binder fibers. One suitable fiber composition is a blend of at least 20% binder fiber and the balance non-binder fiber. Various types of binder fibers 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.

In one exemplary embodiment, the filter media includes a cover layer and/or a bottom layer, each of the cover layer and/or bottom layer independently having a thickness of 2 mils or greater and 50 mils or less, an air permeability of 100CFM or greater and 1200CFM or less, and 10g/m or greater as measured in a planar configuration ² And 50g/m or less ² Basis weight of (c). The cover layer may also have an air permeability greater than 1200CFM, such asAn air permeability in excess of 1500CFM (e.g., a thickness and/or air permeability outside of the above ranges in addition to a thickness and/or air permeability within the above ranges). The thickness of the cover layer may be determined by Edana WSP 120.1 standard (2005) with a presser foot selected to have a load of 2 ounces and an area of 1 square inch. The air permeability of the cover layer may be measured according to ASTM test standard D737 (1996) at a test area of 38cm ² At a pressure drop of 125 Pa. The basis weight of the cover layer may be determined by weighing a known area of the support layer and then dividing the measured weight by the known area.

As noted above, some of the filter media described herein include a binder. An adhesive may be positioned between the two layers to adhere the two layers together. When present, the adhesive may be positioned in a variety of suitable locations 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, the adhesive may be positioned between the first layer and the second layer, between the second layer and the third layer, between the third layer and the fourth layer, and/or between any other two layers. In some embodiments, the filter media includes an adhesive positioned between two separate pairs of layers (e.g., between the first layer and the second layer, and between the second layer and the third layer; between the first layer and the second layer, and between the third layer and the fourth layer). One or more layers of the filter media (e.g., first layer, second layer, third layer, fourth layer, efficiency layer, scrim) may also be impregnated with an adhesive (e.g., by dip coating and/or sandwiching (nip) techniques). The properties of some of the adhesives are described in further detail below.

A variety of binders may be employed in the filter media described herein. Non-limiting examples of suitable adhesives include pressure sensitive adhesives and/or high tack adhesives (high tack adhesives) (e.g., carbobond 1995), hot melt adhesives (e.g., bostik HM4105, bostik 2751). The binder may comprise one or more polymers, such as one or more thermoset polymers and/or one or more thermoplastic polymers. Non-limiting examples of thermosetting adhesives include acrylic resins, vinyl ester resins, phenolic resins, thermosetting polyurethane resins, epoxy resins, and unsaturated polyethylene terephthalate resins. Non-limiting examples of thermoplastic adhesives include hot melt adhesives, such as polyolefin adhesives, polyester adhesives, polyamide adhesives, thermoplastic polyurethane adhesives, and ethylene vinyl acetate adhesives. In some embodiments, the filter media comprises a water-based adhesive. In some embodiments, the adhesive is applied in the form of an emulsion. The solid dispersed in the emulsion may comprise an acrylic copolymer.

When present, the adhesive may have a variety of suitable basis weights. The amount of adhesive between any two layers can be greater than or equal to 0.1g/m ² 0.15g/m or more ² Greater than or equal to 0.2g/m ² 0.25g/m or more ² Greater than or equal to 0.3g/m ² 0.35g/m or more ² Greater than or equal to 0.4g/m ² 0.45g/m or more ² 0.5g/m or more ² 0.6g/m or more 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 1.75g/m or more 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 And not less than 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 50g/m ² Less than or equal to 45g/m ² Less than or equal to 40g/m ² Less than or equal to 35g/m ² Less than or equal to 30g/m ² Less than or equal to 25g/m ² Less than or equal to 20g/m ² Less than or equal to 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., 0.1g/m or greater) ² And 50g/m or less ² And not less than 0.1g/m ² And 20g/m or less ² 0.1g/m or more ² And is not more than 5g/m ² And not less than 0.3g/m ² And is less than or equal to 1g/m ² 0.3g/m or more ² And 0.5g/m or less ² Or 10g/m or more ² And is less than or equal to 20g/m ² ). Other ranges are also possible.

The basis weight may be one or more of the following basis weights: (1) basis weight of binder relative to the final filter media; (2) basis weight of adhesive relative to the following filter media: the filter media has been expanded to remove one set of undulations in the filter media but not other undulations (e.g., expanded to remove undulations formed by a corrugating process but not remove undulations formed by a pleating process); and (3) a basis weight that has been extended to remove all undulations therein.

In some embodiments, the filter media includes a pair of layers with no adhesive positioned therebetween. Some filter media are completely free of binder. In some embodiments, other methods may be employed to bond the layers of the filter media together in addition to or in lieu of using an adhesive. For example, ultrasonic welding, calendaring, and/or laminating (e.g., thermal, chemical, and/or mechanical laminating) may be employed to bond two or more layers of the filter media together.

When present, the adhesive may be applied to the layer in a variety of suitable ways. As one example, the adhesive may be applied to the layer by spraying. As another example, the adhesive may 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 may pass through a volume of adhesive and thereby be coated by the adhesive.

The filter media may also include a layer having 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. One example of a functional ingredient is an adsorbent ingredient. The adsorbent composition may adsorb one or more substances to which the filter media is exposed, such as one or more harmful substances (e.g., harmful gases) that may be present in the fluid to which the filter media is exposed. Non-limiting examples of suitable adsorbent compositions include activated carbon and ion exchange resins.

Example 1

This example describes the manufacture and testing of filter media that includes irregularities present at the surface of the filter media and extending through the uppermost layer in the filter media.

Each filter media was manufactured by: the meltblown efficiency layer is adhered to the stretched mesh scrim, and the stretched mesh scrim is then recovered. First, a mesh scrim and a meltblown efficiency layer were prepared. Cutting the mesh scrim and meltblown efficiency layer to desired sizes: the mesh scrim was cut to form a 15 inch by 16 inch rectangle, and the meltblown efficiency layer was cut to form a rectangle having a width of 15 inches and a length equal to the stretched length of the mesh to which the meltblown efficiency layer was to be applied. The mesh scrim was then placed on a blotter (Paper blotter) and an adhesive was applied to the mesh scrim with a medium-fine-haired paint roller. The binder was 50wt% of water and carbon 1955 (55 wt% of solid acrylic copolymer emulsion) to 50wt% of a mixture. After coating with the adhesive, the mesh scrim was hung and air dried for at least 10 minutes.

After the mesh scrim and the meltblown efficiency layer are prepared, they are assembled together to form a filter media. The mesh scrim was clamped to a piece of parchment paper placed over the wood board by battens secured to the board by locating pins. FIG. 10 illustrates a wood board, wood strips, and locating pins. The distal wood strip is then moved away from the proximal wood strip to stretch the filter media until the desired degree of stretch is obtained. At this point, the melt blown efficiency layer was lightly pressed against the adhesive coated web using a lightweight roller device. Fig. 11 shows a photograph of an exemplary meltblown efficiency layer adhered to an adhesive coated web stretched to 300% of its original length. Finally, the meltblown efficiency layer is removed from the parchment paper and the wood strands along with the mesh scrim to recover the mesh scrim and cut away the excess portion of the mesh scrim not covered by the meltblown efficiency layer. The mesh scrim was recovered by removing the locating pins from the distal wood strands and manually reducing the tension on the stretched mesh scrim. During this process, the meltblown efficiency layer becomes wrinkled.

Two sets of filter media were made, both of which included a polypropylene meltblown efficiency layer with fibers having diameters from 1 to 3 microns and a SWM X30014 styrene block copolymer mesh scrim. For the first type of filter media (type A), the polypropylene melt-blown efficiency layer had 7.7g/m ² And is uncharged. For the second type of filter media (type B), the polypropylene meltblown efficiency layer has 32g/m ² And is hydraulically charged.

For both types of filter media, the degree of stretch of the mesh scrim is increased up to a 300% stretch level prior to bonding the meltblown efficiency layer to the mesh scrim, thereby increasing the gamma, average surface height, thickness, and basis weight of the resulting filter media. Stretching the mesh scrim to a stretch level of 400% did not result in further increases in these values. Tables 1 and 2 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.

TABLE 1 characteristics of Filter media of type A

TABLE 2 characteristics of Filter media of type B

Fig. 12 and 13 show gamma and thickness, respectively, of a type a filter media as a function of the degree of stretch of the mesh scrim prior to bonding the bonded meltblown efficiency layer to the mesh scrim. In fig. 12 and 13, the x-axis is the degree of stretch, which is equivalent to the difference between the stretched length of the mesh scrim and the original length of the mesh scrim when the meltblown efficiency layer is applied, divided by the original length of the mesh scrim, and then multiplied by 100%. FIGS. 14 and 15 show the average surface height (S) of the two types of filter media, respectively _a ) And basis weight as a function of the degree of stretch of the mesh scrim prior to bonding the bonded meltblown efficiency layer to the mesh scrim. In fig. 14 and 15, the x-axis is the ratio of the stretched length of the mesh scrim when the meltblown efficiency layer is applied to the original length of the mesh scrim. Fig. 16 shows gamma as a function of the average surface height of the two types of filter media to show that gamma increases with the average surface height.

For type B filter media, increasing the degree of stretch of the mesh scrim before adhering the meltblown efficiency layer thereto also increases the surface irregularities of the filter media. Fig. 17 and 18 show a comparison between simulations of type B filter media and pleated filter media. The y-axis of fig. 17 shows the ratio of the standard deviation of peak pitch to the mean peak pitch across each sample, which is determined by: step (4) is performed on each row, following steps (1) to (2) of the flow described above with respect to ISO 16610-21, 2011, and then the peak to peak spacing standard deviation is determined using standard statistical techniques. The y-axis of fig. 18 shows the ratio of the standard deviation of peak height to the average peak height across each sample, which is determined by: step (4) is performed on each row, following steps (1) to (2) of the flow described above in relation to ISO 16610-21, 2011, and then using standard statistical techniques to determine the height standard deviation. The x-axis of fig. 17 and 18 shows the position in the sample at the row where the relevant ratio is measured. The data from the stretched sample are the data measured from the above sample. The data from the simulated pleats is data obtained based on a simulation of pleated media including 10mm high minor pleats at a pitch of 2.5 mm; variations in pleat height and spacing, which are typically found during the manufacture of pleated media, are included in the simulations.

As shown in fig. 17, the ratio of the standard deviation of peak spacing to the average peak spacing increases with the degree of stretching of the mesh scrim before the meltblown efficiency layer is adhered thereto. As also shown in fig. 17, the ratio of the standard deviation of the peak pitch to the average peak pitch for each filter media of type B is much greater than the ratio of the standard deviation of the peak pitch to the average peak pitch for the simulated pleated filter media. As shown in fig. 18, the ratio of the standard deviation of peak height to the average peak height decreases with the degree of stretching of the mesh scrim before the meltblown efficiency layer is adhered thereto. This is because the average peak height increases with the degree of stretching of the mesh scrim before the meltblown efficiency layer is adhered thereto to a greater degree than the standard deviation of peak heights. However, as shown in fig. 18, the ratio of the standard deviation of peak height to the average peak height of the filter media described in this example greatly exceeded the ratio of the standard deviation of peak height to the average peak height of the simulated filter media with pleats for all cases.

Example 2

This example describes the manufacture and testing of filter media comprising a reversibly stretchable layer and manufactured in a continuous manner.

Two filter media were manufactured by: the first and second layers (or combination of layers) are deposited onto opposite sides of the reversibly stretchable layer, and the reversibly stretchable layer is then recovered. The layer deposited onto the reversibly stretchable layer is unwound from the roll and then the layer is adhered to the reversibly stretchable layer. Subsequently, the reversibly stretched layer is restored, thereby causing the layer deposited on the reversibly stretched layer to become undulating. Finally, the resulting filter media is wound around another roll. Table 3 shows selected characteristics of the filter media.

TABLE 3 characteristics of the Filter media

Fig. 19 and 20 show the contrast data from these filter media. The y-axis of fig. 19 shows the ratio of the standard deviation of peak pitch to the mean peak pitch across each sample, which is determined by: according to the above with respect to ISO 16610-21:2011, step (4) is performed on each row, and then the peak-to-peak standard deviation is determined using standard statistical techniques. The y-axis of fig. 20 shows the ratio of the standard deviation of peak height to the mean peak height across each sample, which is determined by: according to the above with respect to ISO 16610-21:2011, step (4) is performed on each row, and then standard statistical techniques are used to determine the height standard deviation. The x-axis of fig. 19 and 20 shows the position in the sample at the row where the relevant ratio is measured. Fig. 19 and 20 illustrate that a continuous roll-to-roll process can be employed to make filter media having an irregular structure, and also demonstrate the advantages described with respect to filter media having an irregular structure but made using a laboratory scale process.

Example 3

This example describes the manufacture and testing of filter media including a reversibly stretchable layer and suitable for use in hydraulic applications.

The process described in example 2 was employed to form two filter media suitable for hydraulic applications. Additional control filter media were made. The filter media includes glass fibers. Table 4 below summarizes the properties of the three filter media.

TABLE 3 characteristics of the Filter media

As can be seen from table 4, the filter media manufactured by using the reversible stretching layer has a higher hydraulic pressure γ and a higher dust holding amount than the control filter media.

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

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

The indefinite articles "a" and "an" as used herein in the specification and claims should be understood to mean "at least one" unless explicitly stated to the contrary.

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., the 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 way, i.e., "one or more" of the elements so combined. In addition to the elements specifically identified by the "and/or" clause, other elements may optionally be present, whether related or unrelated to those elements specifically identified. Thus, as a non-limiting example, when used in conjunction with open language such as "including," references to "a and/or B" may refer in one embodiment to a alone (optionally including elements other than B); in another embodiment, reference may be made to B alone (optionally including elements other than a); in yet another embodiment, reference may be made to both a and B (optionally including other elements); and so on.

As used herein in the specification and claims, "or" should be understood to have the same meaning as "and/or" as defined above. For example, when separating items in a list, "or" and/or "should be understood as being 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 additional unrecited items. Terms such as "only one" or "exactly one" or "consisting of 8230, when used in the claims, mean including exactly one of a plurality or list of elements. In general, the term "or" as used herein, when preceded by an exclusive term such as "either," "one," "only one," or "exactly one," should only be construed as indicating an exclusive alternative (i.e., "one or the other, but not both"). When used in the claims, "consisting essentially of" \8230; \8230 ";" consists of "shall have its ordinary meaning as used in the patent law field.

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 or every element specifically listed within the list of elements, and does not exclude any combination of elements in the list of elements. The definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase "at least one" refers, 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 refer, in one embodiment, to the presence of at least one a, optionally including more than one a, and the absence of B (and optionally including elements other than B); in another embodiment may refer to the presence of at least one B, optionally including more than one B, and the absence of a (and optionally including elements other than a); in yet another embodiment may refer to at least one a, optionally including more than one a and at least one B, optionally including more than one B (and optionally including other elements); and so on.

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

In the claims as well as in the foregoing specification, all transitional phrases such as "comprising," "including," "carrying," "having," "containing," "involving," "holding," "consisting of 8230 \8230, constituting," and the like are to be understood to be open-ended, i.e., to mean including but not limited to. As described in the patent examination program Manual of the U.S. patent office, section 2111.03, only the transition phrases "consisting of 8230; \8230, composition" and "consisting essentially of 8230; \8230, composition" should be closed or semi-closed transition phrases, respectively.

Claims

1. A filter media, comprising:

a first layer and a second layer, wherein:

the first layer has an average surface height greater than 0.3 mm;

the first layer is held in a relief configuration by the second layer; and is

The second layer is formed of a reversibly stretchable material.

2. The filter media of claim 1, wherein the first layer comprises a plurality of peaks having an average peak height and a peak height standard deviation, and wherein a ratio of the peak height standard deviation to the average peak height is greater than or equal to 0.05.

3. The filter media of claim 2, wherein a ratio of the standard deviation of peak height to the average peak height is greater than or equal to 0.15 and less than or equal to 0.5.

4. The filter media of any of claims 1-3, wherein the first layer comprises a plurality of peaks having an average peak pitch and a peak pitch standard deviation, and wherein a ratio of the peak pitch standard deviation to the average peak pitch is greater than or equal to 0.08.

5. The filter media of claim 4, wherein a ratio of the standard deviation of peak pitch to the average peak pitch is greater than or equal to 0.15 and less than or equal to 0.5.

6. A filter media, comprising:

a layer, wherein:

the layer comprises a plurality of peaks having an average peak height and a standard deviation of peak height;

a ratio of the standard deviation of the peak heights to the average peak height is greater than or equal to 0.05; and is

The layer has an average surface height greater than 0.3 mm.

7. The filter media of claim 6, wherein a ratio of the standard deviation of the peak heights to the average peak height is greater than or equal to 0.15 and less than or equal to 0.5.

8. The filter media of any of claims 6 to 7, wherein the layer comprises a plurality of peaks having an average peak pitch and a peak pitch standard deviation, and wherein a ratio of the peak pitch standard deviation to the average peak pitch is greater than or equal to 0.08.

9. The filter media of claim 8, wherein a ratio of the standard deviation of the peak pitch to the average peak pitch is greater than or equal to 0.15 and less than or equal to 0.5.

10. A filter media, comprising:

a layer, wherein:

the layer comprises a plurality of peaks having an average peak pitch and a standard deviation of the peak pitch;

a ratio of the standard deviation of peak pitch to the average peak pitch is greater than or equal to 0.08; and is

The layer has an average surface height greater than 0.3 mm.

11. The filter media of claim 10, wherein a ratio of the standard deviation of peak pitch to the average peak pitch is greater than or equal to 0.15 and less than or equal to 0.5.

12. The filter media of any of claims 10 to 11, wherein the layer comprises a plurality of peaks having an average peak height and a peak height standard deviation, and wherein a ratio of the peak height standard deviation to the average peak height is greater than or equal to 0.05.

13. The filter media of claim 12, wherein a ratio of the standard deviation of the peak heights to the average peak height is greater than or equal to 0.15 and less than or equal to 0.5.

14. The filter media of any of claims 6 to 13, wherein the layer has a stiffness of less than or equal to 15000 mg.

15. The filter media of any preceding claim, wherein the layer or first layer is a meltblown fiber web.

16. A filter media as in any preceding claim, wherein the or a first layer is electrically charged.

17. The filter media of any one of claims 1 to 15, wherein the layer or first layer is uncharged.

18. The filter media of any preceding claim, wherein the filter media further comprises a scrim, or the second layer is a scrim.

19. The filter media of claim 18, wherein the scrim is a mesh and/or a membrane.

20. The filter media of claim 18, wherein the scrim is a spunbond web.

21. The filter media of any of claims 18-20, wherein the scrim is capable of undergoing at least 50% reversible stretch along at least one axis.

22. The filter media of any of claims 18 to 21, wherein the layer is adhered to the scrim by an adhesive.

23. The filter media of any preceding claim, wherein the filter media further comprises a third layer.

24. The filter media of claim 23, wherein the third layer is an electrospun fiber web.

25. The filter media of claim 24, wherein the electrospun fiber web and the scrim are positioned on opposite sides of the meltblown fiber web.

26. The filter media of any preceding claim, wherein the filter media comprises a support layer.

27. The filter media of claim 26, wherein the support layer maintains the layers in the corrugated configuration and maintains separation of peaks and valleys of adjacent waves of the layers.

28. The filter media of any preceding claim, wherein the filter media has a γ of greater than or equal to 10.

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

30. The filter media of any preceding claim, wherein the plurality of peaks extend through the layer.

31. The filter media of any preceding claim, wherein the layer is a corrugated layer.

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

33. The filter element of claim 32, wherein the filter element is of a type selected from the group consisting of: flat filters, V-bank filters, cartridge filters, cylindrical filters, conical filters, and curvilinear filters.

34. A method of making a filter media, comprising:

depositing a layer onto the reversibly stretchable layer; and

at least partially recovering the reversibly stretched layer, wherein the layer forms a plurality of peaks during recovery of the reversibly stretched layer.

35. The method of claim 34, wherein the layer has a stiffness of less than or equal to 15000 mg.

36. The method of any of claims 34-35, wherein the layer comprises a plurality of peaks having an average peak height and a peak height standard deviation, and wherein a ratio of the peak height standard deviation to the average peak height is greater than or equal to 0.05.

37. The method of claim 36, wherein a ratio of the standard deviation of peak height to the average peak height is greater than or equal to 0.15 and less than or equal to 0.5.

38. The method of any of claims 34-37, wherein the layer comprises a plurality of peaks having an average peak pitch and a peak pitch standard deviation, and wherein a ratio of the peak pitch standard deviation to the average peak pitch is greater than or equal to 0.08.

39. The method of claim 38, wherein a ratio of the standard deviation of peak pitch to the average peak pitch is greater than or equal to 0.15 and less than or equal to 0.5.

40. The method of any of claims 34 to 39, wherein the layer is a meltblown web.

41. The method of any one of claims 34 to 40, wherein the layer is electrically charged.

42. The method of any one of claims 34 to 40, wherein the layer is uncharged.

43. The method of any one of claims 34 to 42, wherein the reversibly stretchable layer is a scrim.

44. The method of claim 43, wherein the scrim is a mesh and/or film.

45. The method of claim 43, wherein the scrim is a spunbond web.

46. The method of any of claims 44-45, wherein the scrim is capable of undergoing at least 50% reversible stretch along at least one axis.

47. The method of any one of claims 34 to 46, wherein the layer is adhered to the reversibly stretchable layer by an adhesive.

48. The method of any of claims 34-47, wherein the filter media further comprises a second layer.

49. The method of claim 48, wherein the second layer is an electrospun fiber web.

50. The method of claim 49, wherein the electrospun fiber web and the scrim are positioned on opposite sides of the meltblown fiber web.

51. The method of any one of claims 34 to 50, wherein the filter media comprises a support layer.

52. The method of claim 51, wherein the support layer maintains the layer in a waved configuration and maintains separation of peaks and valleys of adjacent waves of the layer.

53. The method of any of claims 34-52, wherein the filter media has a γ of greater than or equal to 10.

54. The method of any of claims 34-53, wherein the filter media has an air permeability greater than or equal to 0.1 CFM.

55. The method of any one of claims 34 to 54, wherein the plurality of peaks extend through the layer.

56. The method of any one of claims 34 to 55, wherein the layer is a relief layer.

57. The method of any one of claims 34 to 56, wherein the reversibly stretchable layer comprises fibers and/or strands.

58. The method of claim 57, wherein the fibers and/or strands comprise an elastomer.

59. The method of claim 58, wherein the elastomer comprises a poly (urethane), a poly (ester-ether), a poly (ester), a poly (olefin), and/or a two-component elastomer.

60. The method of any one of claims 34 to 59, wherein the reversibly stretchable layer is a nonwoven web.

61. The method of any one of claims 57 to 59, wherein the strands are not in direct contact with each other.

62. The method of any of claims 57-61, wherein the strands are spaced apart between nearest neighbors by an average spacing of greater than or equal to 2 mm.

63. The filter media or method of any preceding claim, wherein the layer is carded.

64. The filter media or method of any preceding claim, wherein the layer comprises poly (olefin) fibers, poly (ester) fibers, and/or poly (amide) fibers.

65. The filter media or method of any preceding claim, wherein the layer comprises acrylic fibers.

66. The filter media or method of claim 65, wherein the acrylic fibers are dry-spun acrylic fibers.

67. The filter media of any preceding claim, wherein the filter media comprises poly (propylene) fibers.

68. The filter media of any preceding claim, wherein the filter media comprises acrylic fibers and poly (propylene) fibers, and wherein the weight ratio of the acrylic fibers to the poly (propylene) fibers is greater than or equal to 30.

69. The filter media or method of any preceding claim, wherein the layer is triboelectrically charged.

70. The filter media or method of any preceding claim, wherein the layer is laminated to the reversibly stretchable layer by mechanical, thermal, and/or chemical lamination.

71. The filter media or method of any preceding claim, wherein the layer is bonded to the reversibly tensile layer by ultrasonic bonding.

72. The filter media or method of any preceding claim, wherein the filter media comprises two or more layers of the same type.

73. The filter media or method of claim 70, wherein the two or more layers are efficiency layers.

74. The filter media or method of any preceding claim, wherein the filter media has a hydraulic pressure γ of greater than or equal to 15.

75. The filter media or method of any preceding claim, wherein the filter media has greater than or equal to 50g/m as determined by an ISO 16889 (2008) based multipass filtration test ² The dust holding amount of (2).

76. The filter media or method of any preceding claim, wherein the filter media has greater than or equal to 50g/m as determined by an ISO 19438 (2013) -based multipass filtration test ² The dust holding amount of (2).

77. The filter media or method of any preceding claim, wherein the square root of the ratio of the average flow pore size of the filter media to the air permeability is less than or equal to 3.

78. The filter media or method of any preceding claim, wherein the layer or first layer is impregnated with an adhesive.

79. The filter media or method of any preceding claim, wherein the second layer is laminated to a third layer.

80. The filter media of claim 79, wherein the third layer prevents the second layer from being able to withstand reversible stretching.