CN110446538B

CN110446538B - Filter media including a corrugated filter layer

Info

Publication number: CN110446538B
Application number: CN201880019489.3A
Authority: CN
Inventors: 布鲁斯·史密斯; 大卫·T·希利; 英格丽德·吕克特; 朱司强
Original assignee: Hollingsworth and Vose Co
Current assignee: Hollingsworth and Vose Co
Priority date: 2017-03-22
Filing date: 2018-03-21
Publication date: 2022-10-14
Anticipated expiration: 2038-03-21
Also published as: EP3600598A4; WO2018175556A1; EP3600598A1; CN110446538A

Abstract

Described herein are filter media comprising a corrugated filtration layer. The filter layer may be held in a corrugated configuration by the support layer. In some cases, the filtration layer may have a combination of properties (e.g., mean flow pore size, basis weight, etc.) that may result in enhanced filtration performance (e.g., reduced air permeability), particularly in high humidity environments. The filter media may be used to form a variety of filter elements for a variety of applications. In some embodiments, at least one surface of the filtration layer is hydrophilic.

Description

Filter media including a corrugated filter layer

Technical Field

The present invention relates to filtration, and more particularly to filter media including a wave filter layer.

Background

Filter media can be used to remove contaminants in a variety of applications. Typically, the filter media includes one or more fiber webs. The fibrous web provides a porous structure that allows fluid (e.g., air) to flow through the web. Contaminant particles contained in the fluid may be trapped on the web. Web properties (e.g., pore size, fiber composition, basis weight, etc.) affect the filtration performance of the media. Although different types of filter media are available, improvements are needed.

Disclosure of Invention

In one aspect, a filter media is provided. In some embodiments, the filter media comprises a fibrous filtration layer and a support layer that holds the fibrous filtration layer in a waved configuration and maintains separation of peaks and valleys of adjacent waves of the fibrous filtration layer, wherein at least one surface of the fibrous filtration layer is hydrophilic.

In some embodiments, the filter media comprises a fiber filtration layer and a support layer that holds the fiber filtration layer in a waved configuration and maintains separation of peaks and valleys of adjacent waves of the fiber filtration layer, wherein at least one surface of the fiber filtration layer is hydrophilic, and wherein the air permeability of the filter media decreases by less than or equal to 20% after being loaded with moisture at 95%.

In some embodiments, the filter media includes a fiber filtration layer and a support layer that holds the fiber filtration layer in a waved configuration and maintains separation of peaks and valleys of adjacent waves of the fiber filtration layer. The fibrous filtration layer has a mean flow pore size of at least about 11.5 microns. The filter media has a minimum DEHS particulate filtration efficiency of at least about 25%.

In some embodiments, the filter media includes a fiber filtration layer and a support layer that holds the fiber filtration layer in a waved configuration and maintains separation of peaks and valleys of adjacent waves of the fiber filtration layer. The fibrous filtration layer in a corrugated configuration is formed from fibrous layers having a planar configuration and a transition salt loading (transition salt load) of at least about 2.0 gsm. The filter media has a minimum DEHS particulate filtration efficiency of at least about 25%.

Other aspects 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 mutually contradictory and/or inconsistent disclosures, the document with the later effective date shall control.

Drawings

FIG. 1A is a side view of one embodiment of a filter media;

FIG. 1B is a side view of another embodiment of a filter media;

FIG. 1C is a side view of one layer of the filter media of FIG. 1A;

FIG. 2A is a graph showing resistance pressure (resistance pressure) versus salt loading for multiple fiber filtration layers;

FIG. 2B is a graph showing transition salt loading versus mean flow pore size for a plurality of fibrous filtration layers;

FIG. 2C is a graph showing cake pressure slope versus mean flow pore size for multiple fiber filtration layers;

FIG. 3A is a plot of the natural logarithm of specific penetration (i.e., the natural logarithm of penetration divided by the basis weight) versus the mean flow pore size for a plurality of fibrous filtration layers;

FIG. 3B is a graph showing basis weight versus mean flow pore size for a plurality of fibrous filtration layers;

FIG. 4 is a graph showing the percentage of the difference in maximum air permeability minus the minimum air permeability value expressed as a percentage of the maximum value versus the mean flow pore size for a plurality of filter media in a humid environment; and

fig. 5 is a graph showing percent reduction in air permeability after loading with moisture versus type of hydrophilic treatment for a plurality of filter media.

Detailed Description

Filter media including a corrugated filter layer are described herein. The filter layer may be held in a corrugated configuration by the support layer. As described further below, the filtration layer can have a combination of properties (e.g., mean flow pore size and/or basis weight and/or hydrophilic surface, etc.) that can result in enhanced filtration performance (e.g., efficiency), particularly in high humidity environments. The filter media may be used to form a variety of filter elements for a variety of applications.

Medium

Generally, various filter media are provided having at least one filtration (e.g., fibrous) layer that is maintained in a waved or curvilinear configuration by one or more additional support layers (e.g., fibrous). As a result of the undulating configuration, the filter media has an increased surface area, which may result in improved filtration characteristics. The filter media may include a plurality of layers, and only some or all of the layers may be corrugated.

FIG. 1A illustrates an exemplary embodiment of a filter media 10 having at least one filtration layer 10 and at least one support layer that holds the filtration layer in a waved configuration to maintain separation of peaks and valleys of adjacent waves of the filtration layer. In the illustrated embodiment, the filter media 10 includes a fibrous filtration layer (e.g., a fine fiber filtration layer) 12, a first downstream support layer 14 and a second upstream support layer 16 disposed on opposite sides of the fibrous filtration layer 12. The

support layers

14, 16 may help maintain the fibrous filtration layer 12 and optionally any additional filtration layers in a corrugated configuration. 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, the support layer may be arranged upstream or downstream of the filter layer.

The filter media 10 may also optionally include one or more outer layers or blankets positioned at the most upstream and/or most downstream sides of the filter media 10. FIG. 1A shows a top layer 18 disposed on the upstream side of the filter media 10 to, for example, function as an upstream dust holding layer. The top layer 18 may also function as an aesthetic layer, as will be discussed in more detail below. The layers in the illustrated embodiment are arranged such that the top layer 18 is disposed on the air entry side, labeled I, the second support layer 16 is immediately downstream of the top layer 18, the fibrous filtration layer 12 is immediately downstream of the second support layer 16, and the first support layer 14 is disposed downstream of the first layer 12 on the air outflow 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 bottom layer disposed on the downstream side of the filter media 10 to function as a stiffening component that provides structural integrity to the filter media 10 to help maintain the corrugated configuration. The outer layer or covering may also serve to provide abrasion resistance. FIG. 1B shows another embodiment of a filter media 10B similar to filter media 10 of FIG. 1B. In this embodiment, the filter media 10B does not include a top layer, but rather has a fibrous filtration layer 12B, a first support layer 14B disposed just downstream of the fibrous filtration layer 12B, a second support layer 16B disposed just upstream of the fibrous filtration layer 12B on the air entry side I, and a bottom layer 18B disposed just downstream of the first support layer 14B on the air exit side O. Further, as shown in the exemplary embodiment of fig. 1A and 1B, the outer or cover layer may have a topography that is different from the topography of the fibrous filtration 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 planar), whereas the fibrous filtration layer and/or any support layer may have a corrugated configuration. Those 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 a variety of arrangements.

Fiber filter layer

As indicated above, in one exemplary embodiment, the filter media 10 includes at least one fibrous filtration layer 12, which may optionally be hydrophobic or hydrophilic. In an exemplary embodiment, a single filter layer 12 formed from fine fibers is used, however the filter media 10 may include any number of additional filter layers disposed between the downstream and upstream support layers, adjacent the fiber filter layer 12, or elsewhere within the filter media. Although not shown, the additional filter layer may maintain the corrugated configuration as the fibrous filter layer 12. In certain exemplary embodiments, the filter media 10 may include one or more additional filtration layers disposed upstream of the fibrous filtration layer 12. The additional filter layer may be formed of fine fibers or may be formed of fibers having an average fiber diameter greater than the average fiber diameter of the fibers forming the fibrous filter layer 12.

The fibrous filtration layer may be designed to have a particular mean flow pore size. Advantageously, in some embodiments, a fibrous filtration layer having a mean flow pore size of 11.5 microns or greater may have an increased NaCl loading, improved high humidity performance, and/or a smaller reduction in air permeability after NaCl loading as compared to a fibrous filtration layer having a smaller mean flow pore size. However, the mean flow pore size of 11.5 microns or greater is not intended to be limiting, and other embodiments may include other ranges (e.g., about 5 microns to about 45 microns).

In some embodiments, the fibrous filtration layer has a mean flow pore size of at least about 5 microns, at least about 6 microns, at least about 8 microns, at least about 10 microns, at least about 11 microns, at least about 11.5 microns, at least about 13 microns, at least about 15 microns, at least about 16 microns, at least about 20 microns, at least about 25 microns, at least about 30 microns, at least about 35 microns, or at least about 40 microns. In certain embodiments, the fibrous filtration layer has a mean flow pore size of less than or equal to about 45 microns, less than or equal to about 40 microns, less than or equal to about 35 microns, less than or equal to about 30 microns, less than or equal to about 25 microns, less than or equal to about 20 microns, less than or equal to about 16 microns, less than or equal to about 15 microns, less than or equal to about 13 microns, less than or equal to 11.5 microns, less than or equal to 11 microns, less than or equal to 10 microns, less than or equal to 8 microns, or less than or equal to 6 microns. Combinations of the above ranges are also possible (e.g., about 5 microns to about 45 microns, about 11.5 microns to about 25 microns, about 11.5 microns to about 16 microns). In some embodiments, other ranges are possible, including less than 11.5 microns (e.g., about 5 microns to about 11 microns).

As used herein, mean flow pore diameter refers to the mean flow pore diameter as measured by a capillary flow porosimeter (e.g., model CFP-34RTF 8A-X-6 manufactured by port Materials, inc.) using a1,1,2,3,3,3-hexafluoropropylene low surface tension fluid, according to the ASTM F316-03 standard. The mean flow pore size of the fibrous filtration layer can be designed by selecting the average fiber diameter, basis weight, and/or thickness of the layer, as known to one of ordinary skill in the art. In some cases, the mean flow pore size may be designed by adjusting process parameters (e.g., air flow and/or temperature) during the manufacture of the fibrous filtration layer (e.g., using melt-blowing techniques). In some embodiments, the combined mean flow pore size of the filtration layers may be in one or more of the ranges described above. Further, in embodiments where more than one filter layer is present in the media, the mean flow pore size of each filter layer can be one or more of the ranges described above.

The basis weight of the fibrous filtration layer can be designed by adjusting process parameters such as the number of fibers contained in the filtration layer. In some embodiments, the basis weight of the fibrous filtration layer may be greater than or equal to about 3g/m ² Greater than or equal to about 5g/m ² Greater than or equal to about 8g/m ² Greater than or equal to about 10g/m ² Greater than or equal to about 12g/m ² Greater than or equal to about 14g/m ² Greater than or equal to about 15g/m ² Greater than or equal to about 16g/m ² Greater than or equal to about 18g/m ² Greater than or equal to about 20g/m ² Greater than or equal to about 25g/m ² Greater than or equal to about 30g/m ² Greater than or equal to about 35g/m ² Greater than or equal to about 40g/m ² Or greater than or equal to about 45g/m ² . In some cases, the basis weight of the fibrous filtration layer may be less than or equal to about 50g/m ² (e.g., less than or equal to about 50g/m ² Less than or equal to about 45g/m ² Less than or equal to 40g/m ² Less than or equal to about 35g/m ² Less than or equal to about 30g/m ² Less than or equal to about 25g/m ² Less than or equal to about 20g/m ² Less than or equal to about 18g/m ² Less than or equal to about 16g/m ² Less than or equal to about 15g/m ² Less than or equal to about 14g/m ² Less than or equal to about 12g/m ² Less than or equal to 10g/m ² Is less than or equal to8g/m ² Or less than or equal to 5g/m ² ). Combinations of the above-described ranges are also possible (e.g., greater than or equal to about 3 g/m) ² And less than or equal to about 50g/m ² Greater than or equal to about 10g/m ² And less than or equal to about 40g/m ² Or greater than or equal to about 14g/m ² And less than or equal to about 20g/m ² Basis weight of (d). Other ranges are also possible. In some embodiments, the combined basis weight of the combination of filtration layers may be in one or more of the ranges described above. As determined herein, the basis weight of the filter layer is measured according to the Edana WSP 130.1 standard. Further, in embodiments where more than one filter layer is present in the media, the basis weight of each filter layer can be one or more of the ranges described above.

In some embodiments, the basis weight and/or mean flow pore size may be adjusted such that the fibrous filtration layer has a desired minimum DEHS (diethyl-hexyl-sebacate) particulate filtration efficiency. In some cases, the basis weight of the fiber filtration layer and/or the mean flow pore size of the fiber filtration layer may be increased or decreased such that the fiber filtration layer has a particular minimum DEHS particle filtration efficiency (e.g., a minimum DEHS particle filtration efficiency of at least about 25%). For example, in some embodiments, for a fiber filtration layer having a mean flow pore size of at least about 11.5 microns, the basis weight can be adjusted (e.g., increased) such that the fiber filtration layer has a minimum DEHS particle filtration efficiency of at least about 25%. In some embodiments and as further described in example 1, the relationship between basis weight, mean flow pore size, and efficiency of the fibrous filtration layer can be expressed as:

where BW is the basis weight of the fiber filtration layer (in grams per square meter), MP is the average pore size of the fiber filtration layer (in microns), a and b are coefficients, and E is the minimum DEHS particle filtration efficiency (expressed as a fraction) of the fiber filtration layer. In some embodiments, a is 2,b is 6.5. In some embodiments, a is greater than or equal to 2 and less than or equal to 2.3, b is a number greater than or equal to 6.5 and less than or equal to about 8. For example, in other embodiments, a is 2, 2.1, 2.25, or 2.28 and b is 6.5, 7, 7.5, or 8. In some cases, for a given mean flow pore size, a parameter (e.g., a fixed weight) may be selected to achieve a particular minimum DEHS particle filtration efficiency (e.g., a minimum DEHS particle filtration efficiency of at least about 0.25 (i.e., 25%) or at least about 0.35 (i.e., 35%). For example, in some cases, when a is 2 and b is 6.5, the fibrous filtration layer has a particular minimum DEHS particulate filtration efficiency (e.g., at least about 25% or at least about 35%) and a particular mean flow pore size (e.g., at least about 11.5 microns), and the basis weight can be designed to be at least about 8.76g/m ² . Without wishing to be bound by theory, the above equation demonstrates the relationship between basis weight, mean flow pore size, and efficiency of a fibrous filtration layer, which can be used to design a fibrous filtration layer that provides desirable properties under wet conditions, including a smaller reduction in air permeability in a wet environment as compared to certain conventional fibrous filtration layers. The air permeability in a humid environment is described in more detail below.

The fibrous filtration layers and/or media described herein (e.g., having a mean flow pore size of at least about 11.5 microns) can have a wide range of minimum DEHS particulate filtration efficiencies. In some embodiments, the minimum DEHS particle filtration efficiency of the fibrous filtration layer and/or filter media is from about 25% to about 75%, from about 30% to 75%, or from about 35% to about 55%. In some embodiments, the fiber filtration layer and/or filter media has a minimum DEHS particle filtration efficiency of greater than or equal to about 25%, greater than or equal to about 30%, greater than or equal to about 35%, greater than or equal to about 45%, greater than or equal to about 55%, or greater than or equal to about 65%. Other minimum DEHS particle filtration efficiencies are possible. In some embodiments, the minimum DEHS particle filtration efficiency of the fibrous filtration layer and/or media is less than or equal to 75%, less than or equal to 65%, less than or equal to 55%, or less than or equal to 45%. In some embodiments, the combined minimum DEHS particle filtration efficiency of the fibrous filtration layers may be in one or more of the ranges described above. In some embodiments, the minimum DEHS particle efficiency of the filter media may be greater than that of the fibrous filtration layer, as additional layers (e.g., outer or cover layers) added to the media may help trap particles, thereby increasing the minimum DEHS particles throughout the filter media.

In some embodiments, the fibrous filtration layer and/or filter media described herein (e.g., having a mean flow pore size of at least about 11.5 microns) can have a wide range of average DEHS particle filtration efficiencies. In some embodiments, the average DEHS efficiency of the fibrous filtration layer and/or media is greater than or equal to about 25%, greater than or equal to about 30%, greater than or equal to about 35%, greater than or equal to about 40%, greater than or equal to about 45%, greater than or equal to about 50%, greater than or equal to about 55%, greater than or equal to about 60%, greater than or equal to about 65%, greater than or equal to about 70%, greater than or equal to about 75%, or greater than or equal to about 80%. Other efficiencies are also possible. In some embodiments, the average DEHS efficiency of the fibrous filtration layer and/or media is less than or equal to 99.9%, less than or equal to 99.8%, less than or equal to 99.7%, less than or equal to 99.5%, less than or equal to 99%, less than or equal to 98%, less than or equal to 95%, less than or equal to 90%, less than or equal to 85%, less than or equal to 80%, less than or equal to 70%, less than or equal to 60%, or less than or equal to 50%. In some embodiments, the average DEHS particle efficiency of the filter media may be greater than that of the fibrous filtration layer, as additional layers (e.g., outer or cover layers) added to the media may help to trap particles, thereby increasing the average DEHS particle efficiency of the overall filter media.

As mentioned herein, the minimum DEHS particle filtration efficiency and average DEHS particle filtration efficiency of a filtration layer or media is tested according to EN779-2012 standard and using 0.4 microns or greater. The test uses 0.944m ³ Air flow rate per second. The test begins by initially measuring the pressure drop and DEHS particle efficiency of the sample. The test then included gradual loading of the sample with standard test dust (ANSI/ASHRAE 52.2) in 30g increments, and measuring the pressure drop and DEHS particulate efficiency after each load increment until a pressure drop of 450Pa or greater was reachedAnd the test is completed. As used herein, minimum DEHS particle filtration efficiency refers to the lowest DEHS particle efficiency obtained throughout the test. As used herein, the average DEHS particulate filtration efficiency is determined as the average of the DEHS particulate efficiencies obtained throughout the test (including the DEHS particulate efficiency initially measured prior to standard test dust loading and the DEHS particulate efficiency at all loading levels, including the particulate DEHS efficiency at a maximum test pressure of 450Pa or greater).

As described herein, fibrous filtration layers (e.g., having a mean flow pore size greater than about 11.5 microns) and/or filtration media can advantageously have improved performance (e.g., reduced air permeability reduction) in high humidity environments as compared to certain conventional fibrous filtration layers (e.g., having a mean flow pore size less than about 11.5 microns). Without wishing to be bound by theory, improved humidity performance may generally be associated with increased transition salt loading of the fibrous filtration layer. In some cases, the transition salt loading may be measured using a NaCl (sodium chloride) challenge (or NaCl loading) with an automated filter test unit equipped with a sodium chloride generator (e.g., 8130CertiTest from TSI, inc ^TM ). The average particle size produced by the salt particle generator was about 0.3 micron mass mean diameter. The instrument measures the pressure drop across the filtration layer and/or media and the resulting penetration value on-the-fly. The test unit may be run in a continuous mode, approximately one pressure drop/penetration reading per minute. 23mg NaCl/m ³ NaCl particles of air concentration were continuously loaded to 100cm at a flow rate of 5.3 cm/sec ² On the sample. The sample was continuously loaded until a penetration of 1% (or less) was reached. The penetration (often expressed as a percentage) is defined as follows:

penetration = C/C ₀

Wherein C is the concentration of particles after passing through the filter, C ₀ Is the concentration of particles before passing through the filter.

In some embodiments, the fibrous filtration layer and/or filter media has a transition salt loading of at least about 2.0gsm (grams per square meter). The conversion salt loading may be by way of a flat fibrous filter layer or on the filter media as a wholeThe NaCl load as described above was followed and the resistance pressure (in mm H) was plotted as a function of NaCl load (gsm (i.e., grams per square meter)) ₂ O meter). Referring now to fig. 2A, an initial depth loading line is calculated by fitting a simple linear regression line to the initial ten minute region (i.e., the initial ten consecutive data points) of the NaCl load curve (i.e., resistance pressure versus NaCl load) that begins with the first reading taken one minute after the test began. A cake loading line (see fig. 2A) is calculated by fitting a simple linear regression line to ten consecutive data points of the NaCl loading curve, wherein the first to tenth data points are selected such that the fiber filtration layer and/or media has a penetration of less than 1%, and the eleventh data point (not included in the simple linear regression fit) has a penetration of greater than or equal to 1% (e.g., plotted by the ten data points before and including the point at which the measured penetration drops below 1%). The transition salt loading described herein is defined as the value of NaCl loading (in grams) per unit area (in square meters) of the fiber filtration layer at the intersection of the initial depth load line and the filter cake load line.

In some embodiments, the transition salt loading of the planar fibrous filter media is at least about 2.0gsm, at least about 2.5gsm, at least about 3.0gsm, at least about 3.5gsm, at least about 4.0gsm, or at least about 5.0gsm. In some embodiments, the transition salt loading is less than or equal to about 10.0gsm, less than or equal to about 5.0gsm, less than or equal to about 4.0gsm, less than or equal to about 3.5gsm, less than or equal to about 3.0gsm, or less than or equal to about 2.5gsm. Combinations of the above ranges are also possible (e.g., about 2.0gsm to about 10.0 gsm). The fibrous filtration layers and media described herein generally have an increased transition salt loading, which generally corresponds to a lower resistance pressure for an equivalent NaCl loading, as compared to conventional filtration layers and media.

The slope of the filter cake load line described herein may have a particular value. In some embodiments, the slope of the cake load line of the fibrous filtration layer can be less than or equal to about 7.5mm H ₂ O/gsm salt loading, less than or equal to about 7mm H ₂ O/gsm salt loading, less than or equal to about 6mm H ₂ O/gsm salt loading, less than or equal to about 5.5mm H ₂ O/gsm salt loading, less than or equal to about 5mm H ₂ O/gsm salt loading, less than or equal to about 4.5mm H ₂ O/gsm salt loading, less than or equal to about 4mm H ₂ O/gsm salt loading, or less than or equal to about 3.5mm H ₂ O/gsm salt loading. In some embodiments, the slope of the cake load line of the fiber filtration layer can be greater than or equal to 0mm H ₂ O/gsm salt loading of greater than or equal to about 1mm H ₂ O/gsm salt loading, greater than or equal to about 2mm H ₂ O/gsm salt loading of greater than or equal to about 3mm H ₂ O/gsm salt loading, greater than or equal to about 4mm H ₂ O/gsm salt loading, greater than or equal to about 4.5mm H ₂ O/gsm salt loading of greater than or equal to about 5mm H ₂ O/gsm salt loading, greater than or equal to about 5.5mm H ₂ O/gsm salt loading, or greater than or equal to about 6mm H ₂ O/gsm salt loading, or greater than or equal to about 7mm H ₂ O/gsm salt loading. Combinations of the above ranges are also possible (e.g., 0mm H ₂ O/gsm salt loading to about 7mm H ₂ O/gsm salt loading, 1mm H ₂ O/gsm salt loading to about 7mm H ₂ O/gsm salt loading, about 3mm H ₂ O/gsm salt loading to about 6mm H ₂ O/gsm salt loading, about 5mm H ₂ O/gsm salt loading to about 6mm H ₂ O/gsm salt loading). Other ranges are also possible.

Advantageously, in some embodiments, the fibrous filtration layers (e.g., having a mean flow pore size of greater than about 11.5 microns) and/or filter media described herein may have a relatively lower reduction in air permeability in a humid environment as compared to certain conventional fibrous filtration layers (e.g., having a mean flow pore size of less than about 11.5 microns) and/or filter media. In some embodiments, the percent reduction in air permeability after moisture loading is less than or equal to about 50%, less than or equal to about 45%, less than or equal to about 44%, less than or equal to about 42%, less than or equal to about 40%, less than or equal to about 35%, less than or equal to about 30%, or less than or equal to about 25%. In certain embodiments, the percent reduction in air permeability after moisture loading is at least about 25%, at least about 35%, at least about 40%, at least about 42%, at least about 44%, or at least about 45%. Combinations of the above ranges are also possible (e.g., a reduction in air permeability after loading with moisture of about 35% to 50%, about 42% to about 45%, about 42% to about 50%). Other ranges are also possible.

As mentioned herein, air permeability after loading with moisture is determined by using an automated filter test unit equipped with a sodium chloride generator (e.g., TSI 8130CertiTest from TSI, inc ^TM ) With NaCl aerosol of about 0.3 micron particles (23 mg NaCl/m) ³ Air) to 100cm ² The samples were loaded for 30 minutes before the humidity challenge was determined. The sample (e.g., a filter media comprising a fibrous filtration layer and a support layer in a wave configuration) was loaded at a face velocity of 14.1 cm/sec for 30 minutes. Once loaded with NaCl, the samples were placed in sample holders connected to a Frazier air permeability machine and enclosed in a chamber that included a steam generator to generate humidity. A hygrometer probe is inserted into the cassette to measure the temperature and humidity inside the chamber. At the start of the test, the relative humidity in the chamber was 50% and the test was performed by taking an initial air permeability reading at a pressure drop of 0.5 "water column, followed by turning on the steam generator and taking air permeability and humidity readings every 30 seconds. Once the humidity reaches 90% (or, in some cases, 95%), the reading continues for about 12 minutes, after which the steam generator is turned off. The readings are continued until the relative humidity in the chamber returns to its level at the beginning of the test (i.e., 50%), at which point the air permeability has stabilized. The percent reduction in air permeability after moisture loading is the difference between the maximum air permeability value (which is the air permeability value measured when the relative humidity returns to its level at the start of the test (i.e., 50%) minus the minimum air permeability value (at 90% or 95%, as the case may be)) expressed as a percentage of the maximum air permeability value.

In some cases, the fibrous filtration layer may have a particular solidity. As used herein, "solidity" generally refers to the removal of the basis weight of a fibrous filtration layer (i.e., BW/(ρ × t)) by multiplying the average density of the fibers by the uncompressed thickness of the fibrous filtration layer, where BW is the basis weight, ρ is the density, and t is the uncompressed thickness. Uncompressed thickness as used herein refers to the thickness of the fibrous filtration layer as determined by measuring the thickness of the fibrous filtration layer with a micrometer at a series of different loadings and extrapolating to determine the thickness at zero loading. In some embodiments, the fibrous filtration layer has a solidity of at least about 1%, at least about 2%, at least about 2.5%, at least about 5%, at least about 10%, at least about 13%, or at least about 15%. In certain embodiments, the fibrous filtration layer has a solidity of less than or equal to about 20%, less than or equal to about 15%, less than or equal to about 13%, less than or equal to about 10%, less than or equal to about 5%, less than or equal to about 4%, less than or equal to about 3.5%, less than or equal to 3%, less than or equal to about 2.5%, or less than or equal to about 2%. Combinations of the above ranges are also possible (e.g., about 1% to about 20%, about 2.5% to about 13%, about 5% to about 20%). Other ranges are also possible.

In some embodiments, the fibrous filtration layer may have a particular surface area. In some cases, the surface area of the fibrous filtration layer may be from about 0.8 square meters per gram to about 2.5 square meters per gram. For example, the surface area may be about 1.2 square meters per gram to about 1.6 square meters per gram. The surface area may be determined by any suitable method known in the art, including, for example, BET gas adsorption.

The fibrous filtration layer 12 may be formed from a variety of fibers, but in an exemplary embodiment, the fibrous filtration layer 12 is formed from fibers having an average fiber diameter of less than or equal to about 10 microns, less than or equal to about 8 microns, less than about 5 microns, less than about 4 microns, less than about 3 microns, less than about 2 microns, less than about 1.6 microns, less than about 1.2 microns, less than about 1 micron, less than about 0.8 microns, less than about 0.5 microns, less than about 0.4 microns, or less than about 0.3 microns. In certain embodiments, the fibrous filtration layer has an average fiber diameter of at least 0.2 microns, at least 0.3 microns, at least 0.4 microns, at least about 0.5 microns, at least about 0.8 microns, at least about 1 micron, at least about 1.2 microns, at least about 1.6 microns, at least about 2 microns, at least about 3 microns, at least about 4 microns, at least about 5 microns, or at least about 8 microns. Combinations of the above ranges are also possible (e.g., about 0.5 microns to about 10 microns, about 1 micron to about 5 microns, about 1.6 microns to about 3 microns, about 0.2 microns to about 10 microns). Other ranges are also possible. The average diameter of the fibers can be determined, for example, by scanning electron microscopy.

A variety of materials may also be used to form the fibers, including synthetic and non-synthetic materials. In an exemplary embodiment, the fibrous filtration layer 12 and any additional filtration layers are formed from meltblown fibers. Certain suitable melt blowing processes have been described in commonly owned U.S. patent No. 8,608,817, which is incorporated herein by reference in its entirety. In some embodiments, the fibrous filtration layer may be formed by wet-laid techniques, air-laid techniques, electrospinning, spunbond, centrifugal spinning, or carding. By way of non-limiting example, exemplary materials include polyolefins, such as polypropylene and polyethylene; polyesters such as polybutylene terephthalate and polyethylene terephthalate; polyamides, such as nylon; a polycarbonate; polyphenylene sulfide; polystyrene; and polyurethanes.

The fibrous filtration layer may contain a suitable percentage of synthetic fibers. For example, in some embodiments, the weight percentage of synthetic fibers in the filtration layer may be from about 50 wt% to about 100 wt% of all fibers in the filtration layer. In some embodiments, the weight percentage of synthetic fibers in the filtration layer may be greater than or equal to about 50 weight percent, greater than or equal to about 60 weight percent, greater than or equal to about 70 weight percent, greater than or equal to about 80 weight percent, greater than or equal to about 90 weight percent, or greater than or equal to about 95 weight percent. In some embodiments, the weight percentage of synthetic fibers in the filtration layer may be less than or equal to about 100 weight%, less than or equal to about 95 weight%, less than or equal to about 90 weight%, less than or equal to about 80 weight%, less than or equal to about 70 weight%, or less than or equal to about 50 weight%. Combinations of the above ranges are also possible (e.g., a weight percentage of greater than or equal to about 90 wt% and less than or equal to about 100 wt%). Other ranges are also possible. In some embodiments, the filtration layer comprises 100% synthetic fibers by weight. In some embodiments, the filtration layer comprises synthetic fibers in the ranges described above relative to the total weight of the filtration layer (e.g., including any resin). In some embodiments, the percentage of the combined synthetic fibers of the filtration layer may be in one or more of the ranges described above. Further, in embodiments where more than one filter layer is present in the media, the percentage of synthetic fibers of each filter layer may be one or more of the ranges described above. In another embodiment, the above ranges of fibers may be applied to the entire filter media (which may include multiple filtration layers). The remaining fibers of the filtration layer and/or the filter media may be non-synthetic fibers such as glass fibers, glass wool fibers, and/or cellulose pulp fibers (e.g., wood pulp fibers).

In some embodiments, the fiber filtration layer 12 may include glass fibers (e.g., microglass fibers, chopped glass fibers, or a combination thereof). The type and size of the glass fibers may also vary, but in one exemplary embodiment the fibers are microglass fibers, such as type a or type E glass fibers manufactured using a spinning or flame attenuation (attenuation) process and having an average fiber diameter in the range of about 0.2 μm to 5 μm. Microglass fibers and chopped strand glass fibers are known to those of ordinary skill in the art. One of ordinary skill in the art can determine by observation (e.g., optical microscopy, electron microscopy) whether the glass fibers are microglass or chopped. Microglass fibers may also be chemically different from chopped strand glass fibers. In some cases, although not required, the chopped glass fibers may contain a greater content of calcium or sodium than the microglass fibers. For example, the chopped glass fibers may be nearly alkali-free, having a high calcium oxide and alumina content. Microglass fibers may contain 10% to 15% alkali (e.g., sodium, magnesium oxide) and have relatively low melting and processing temperatures. These terms refer to the techniques used to make the glass fibers. Such techniques impart certain characteristics to the glass fibers. Typically, chopped glass fibers are drawn from the tip of the cannula and cut into fibers in a manner similar to textile production. Chopped strand glass fibers are produced in a more controlled manner than microglass fibers, with the result that chopped strand glass fibers generally have less variation in fiber diameter and length than microglass fibers. The microglass fibers are pulled from the cannula tip and further subjected to a flame blowing or rotational spinning process. In some cases, fine microglass fibers may be made using a remelting process. In this regard, the microglass fibers may be fine or coarse. As used herein, fine microglass fibers have a diameter of less than or equal to 1 micron and coarse microglass fibers have a diameter of greater than or equal to 1 micron.

The microglass fibers may have a small diameter. For example, in some embodiments, the microglass fibers may have an average diameter of less than or equal to about 10 microns, less than or equal to about 9 microns, less than or equal to about 7 microns, less than or equal to about 5 microns, less than or equal to about 3 microns, or less than or equal to about 1 micron. In some cases, the microglass fibers may have an average fiber diameter of greater than or equal to about 0.1 microns, greater than or equal to about 0.3 microns, greater than or equal to about 1 micron, greater than or equal to about 3 microns, or greater than or equal to about 7 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to about 0.1 microns and less than or equal to about 10 microns, greater than or equal to about 0.1 microns and less than or equal to about 5 microns, greater than or equal to about 0.3 microns and less than or equal to about 3 microns). Other values of average fiber diameter are also possible. The average diameter distribution of the microglass fibers is generally lognormal. However, it is understood that the microglass fibers may be provided in any other suitable average diameter distribution (e.g., gaussian distribution).

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

In general, the average fiber diameter of the chopped glass fibers may be greater than the diameter of the microglass fibers. For example, in some embodiments, the chopped glass fibers may have an average diameter of greater than or equal to about 5 microns, greater than or equal to about 7 microns, greater than or equal to about 9 microns, greater than or equal to about 11 microns, or greater than or equal to about 20 microns. In some cases, the chopped glass fibers may have an average fiber diameter of less than or equal to about 30 microns, less than or equal to about 25 microns, less than or equal to about 15 microns, less than or equal to about 12 microns, or less than or equal to about 10 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to about 5 microns and less than or equal to about 12 microns). Other values of average fiber diameter are also possible. The chopped diameters tend to follow a normal distribution. Although, it is understood that the chopped glass fibers may be provided in any suitable average diameter distribution (e.g., a gaussian distribution).

In some embodiments, the chopped glass fibers may have a length in the range of about 3mm to about 25mm (e.g., about 6mm, or about 12 mm). In some embodiments, the chopped glass fibers may have an average length of less than or equal to about 25mm, less than or equal to about 20mm, less than or equal to about 15mm, less than or equal to about 12mm, less than or equal to about 10mm, less than or equal to about 7mm, or less than or equal to about 5mm. In certain embodiments, the chopped glass fibers may have an average length of greater than or equal to about 3mm, greater than or equal to about 5mm, greater than or equal to about 10mm, greater than or equal to about 12mm, greater than or equal to about 15mm, or greater than or equal to about 20mm. Combinations of the above ranges are also possible (e.g., the chopped glass fibers have an average length of greater than or equal to about 3mm and less than about 25 mm). Other ranges are also possible.

It is to be understood that the above dimensions are not limiting and that the microglass fibers and/or chopped fibers, as well as the other fibers described herein, may also have other dimensions.

In some embodiments, the average diameter of the glass fibers in the fiber filtration layer (e.g., whether the glass fibers are microglass, chopped, or another type) may be greater than or equal to about 1.5 microns, greater than or equal to about 2 microns, greater than or equal to about 2.5 microns, greater than or equal to about 3 microns, greater than or equal to about 4.5 microns, greater than or equal to about 5 microns, greater than or equal to about 6 microns, greater than or equal to about 7 microns, or greater than or equal to about 9 microns. In some cases, the average diameter of the glass fibers in the fibrous filtration layer can have an average fiber diameter of less than or equal to about 10 microns, less than or equal to about 9 microns, less than or equal to about 7 microns, less than or equal to about 6 microns, less than or equal to about 5 microns, less than or equal to about 4.5 microns, less than or equal to about 3 microns, less than or equal to about 2.5 microns, or less than or equal to about 2 microns. Combinations of the above ranges are also possible (e.g., greater than or equal to about 1.5 microns and less than or equal to about 10 microns, greater than or equal to about 2 microns and less than or equal to about 9 microns, greater than or equal to about 2 microns and less than or equal to about 5 microns, greater than or equal to about 2.5 microns and less than or equal to about 4.5 microns).

In some embodiments, the average length of the glass fibers in the fiber filtration layer (e.g., whether the glass fibers are microglass, chopped, or another type) may be less than or equal to about 25mm, less than or equal to about 20mm, less than or equal to about 15mm, less than or equal to about 12mm, less than or equal to about 10mm, less than or equal to about 8mm, less than or equal to about 5mm, less than or equal to about 3mm, or less than or equal to about 1mm. In certain embodiments, the average length of the glass fibers in the fibrous filtration layer may be greater than or equal to about 0.05mm, greater than or equal to about 0.1mm, greater than or equal to about 0.3mm, greater than or equal to about 0.5mm, greater than or equal to about 1mm, greater than or equal to about 5mm, greater than or equal to about 10mm, greater than or equal to about 15mm, greater than or equal to about 20mm, greater than or equal to about 30mm, or greater than or equal to about 40mm. Combinations of the above ranges are also possible (e.g., greater than or equal to about 1mm and less than about 25mm, greater than or equal to about 0.3mm and less than about 20mm, greater than or equal to about 0.1mm and less than about 12mm, greater than or equal to about 0.2mm and less than about 6mm, greater than or equal to about 0.5mm and less than about 3 mm). Other ranges are also possible.

The resulting fibrous filtration layer 12, as well as any additional filtration layers, may also have a variety of thicknesses, air permeabilities, basis weights, and filtration efficiencies as required by the desired application.

In one exemplary embodiment, the thickness of the fibrous filtration layer 12 is in the range of about 6 mils to 22 mils, as measured in a planar configuration; for example, from about 10 mils to about 18 mils, or from about 12 mils to 16 mils. As referred to herein, thickness is determined according to Edana WSP 120.1 standard at about 1 ounce load per square foot on a flat layer. Further, in embodiments where more than one filter layer is present in the media, the thickness of each filter layer can be one or more of the ranges described above.

The air permeability of the fibrous filtration layer may be in the range of about 30CFM to 150 CFM. For example, the air permeability may be at least about 30CFM, at least about 50CFM, at least about 65CFM, at least about 75CFM, at least about 100CFM, or at least about 125CFM. In some embodiments, the air permeability of the fibrous filtration layer may be less than or equal to about 150CFM, less than or equal to about 125CFM, less than or equal to about 100CFM, less than or equal to about 75CFM, less than or equal to about 65CFM, or less than or equal to about 50CFM. Combinations of the above ranges are also possible (e.g., about 30CFM to 150CFM, about 65CFM to 100 CFM). Other ranges are also possible. As determined herein, air permeability is measured according to ASTM D737-04 (2012). The air permeability of a filter layer or media is an inverse function of flow resistance and can be measured with a Frazier permeability tester. The Frazier permeability tester measures the volume of air passing over a sample per unit area of sample per unit time at a fixed pressure differential across the sample. Permeability can be expressed as cubic feet per minute per square foot at a water differential of 0.5 inches.

Supporting layer

Also as indicated above, the filter media 10 may include at least one support layer. In an exemplary embodiment, the filter media 10 includes a downstream support layer 14 that is disposed on the air outflow side O of the fiber filtration layer 12 and is effective to maintain the fiber filtration layer 12 in a corrugated configuration. The filter media 10 may also include an upstream support layer 16 disposed on the air intake side I of the fiber filtration layer 12 opposite the downstream support layer 14. The upstream support layer 16 may also help maintain the fibrous filtration layer 12 in a corrugated configuration. As indicated above, those skilled in the art will appreciate that filter media 10 may include any number of layers, and it need not include two support layers or top layers. In certain exemplary embodiments, the filter media 10 may be formed from a fibrous filtration layer 12 and a single

adjacent support layer

14 or 16. 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 14, 16 may be formed from a variety of fiber types and sizes. In one exemplary embodiment, the downstream support layer 14 is formed from fibers having an average fiber diameter that is greater than or equal to the average fiber diameter of the fibrous filtration layer 12, the upstream support layer 16, and the top layer 18 (if provided). In some cases, the upstream support layer 16 is formed from fibers having an average fiber diameter that is less than or equal to the average fiber diameter of the downstream support layer 14, but greater than the average fiber diameter of the fibrous filtration layer 12 and the top layer 18. In certain exemplary embodiments, the downstream support layer 14 and/or the upstream support layer 16 may be formed from fibers having an average fiber diameter in the range of about 10 μm to 32 μm, or 12 μm to 32 μm. For example, the average fiber diameter of the downstream support layer and/or the upstream support layer may be in the range of about 18 μm to 22 μm. In some cases, the downstream support layer and/or the upstream support layer may comprise relatively finer fibers than conventional support layers. 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 fiber diameter in the range of about 9 μm to 18 μm. For example, the average fiber diameter of the finer downstream support layer and/or the finer upstream support layer may be in the range of about 12 μm to 15 μm.

The average fiber length of the fibers of the support layer (e.g., downstream support layer, upstream support layer) may be, for example, about 1.0 inch to about 3.0 inches (e.g., about 1.5 inches to about 2 inches). In some embodiments, the average fiber length of the fibers of the support layer may be less than or equal to about 3 inches, less than or equal to about 2.5 inches, less than or equal to about 2 inches, less than or equal to about 1.5 inches, or less than or equal to about 1.1 inches. In some embodiments, the fibers of the support layer may have an average fiber length of greater than or equal to about 1 inch, greater than or equal to about 1.5 inches, greater than or equal to about 2.0 inches, or greater than or equal to about 2.5 inches. Combinations of the above ranges are also possible (e.g., the average fiber length of the fibers is greater than or equal to about 1.5 inches and less than about 2 inches). Other ranges are also possible.

A variety of materials may also be used to form the fibers of the support layers 14, 16, including synthetic and non-synthetic materials. In one exemplary embodiment, the support layers 14, 16 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 about 20% binder fibers and the balance non-binder fibers. Various types of binder fibers and non-binder fibers can be used to form the media of the present invention. The binder fibers may be formed of any material that is effective to promote thermal bonding between the layers and, thus, has an activation temperature that is lower than the melting temperature of the non-binder fibers. The binder fibers may be monocomponent fibers or any of a number of 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 comprise a core and a sheath, wherein the sheath has an activation temperature that is lower 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 trapping the filtrate. The core/sheath binder fibers may be coaxial or non-coaxial, 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, side-by-side fiber, and/or "islands-in-the-sea" fiber.

The non-binding fibers may be synthetic and/or non-synthetic, and in one exemplary embodiment, the non-binding fibers may be about 100% synthetic. Generally, synthetic fibers are preferred over non-synthetic fibers for resistance to moisture, heat, long term aging, and microbial degradation. Exemplary synthetic non-binding fibers may include polyester, acrylic, polyolefin, nylon, rayon, and combinations thereof. Alternatively, the non-binding fibers used to form the media can include non-synthetic fibers, such as glass fibers, glass wool fibers, cellulose pulp fibers (e.g., wood pulp fibers), and combinations thereof.

The support layer may comprise a suitable percentage of synthetic fibers. For example, in some embodiments, the weight percentage of the synthetic fibers in the support layer may be from about 80 weight percent to about 100 weight percent of all the fibers in the support layer. In some embodiments, the weight percentage of synthetic fibers in the support layer may be greater than or equal to about 80 weight percent, greater than or equal to about 90 weight percent, or greater than or equal to about 95 weight percent. In some embodiments, the weight percentage of synthetic fibers in the support layer may be less than or equal to about 100 weight percent, less than or equal to about 95 weight percent, less than or equal to about 90 weight percent, or less than or equal to about 85 weight percent. Combinations of the above ranges are also possible (e.g., a weight percentage of greater than or equal to about 80 weight percent and less than or equal to about 100 weight percent). Other ranges are also possible. In some embodiments, the support layer comprises 100% by weight of synthetic fibers. In some embodiments, the support layer comprises synthetic fibers in the above-described ranges relative to the total weight of the support layer (e.g., including any resin). Further, in embodiments where more than one filter layer is present in the media, the percentage of synthetic fibers of each filter layer and/or support layer may be one or more of the ranges described above. In other embodiments, the above ranges of fibers may be applied to the entire filter media (which may include multiple filtration layers). The remaining fibers of the filtration layer and/or the filter media may be non-synthetic fibers such as glass fibers, glass wool fibers, and/or cellulose pulp fibers (e.g., wood pulp fibers).

The support layers 14, 16 may also be formed using various techniques known in the art, including melt blowing, wet-laid techniques, air-laid techniques, carding, electrospinning and spunbonding. However, in one exemplary embodiment, the support layers 14, 16 are carded or air-laid. The resulting layers 14, 16 may also have a variety of thicknesses, air permeabilities, and basis weights as required by the desired application. In one exemplary embodiment, the downstream support layer 14 and the upstream support layer 16 each have a thickness in the range of about 8 mils to 30 mils (e.g., about 12 mils to 20 mils), a basis weight in the range of about 10gsm to 99gsm (e.g., about 22gsm to about 99gsm, about 33gsm to 70 gsm), and a mean flow pore size in the range of about 30 microns to 150 microns (e.g., about 50 microns to about 120 microns), as measured in a planar configuration.

For example, in some embodiments, the support layers each have a thickness of at least about 8 mils, at least about 10 mils, at least about 12 mils, at least about 15 mils, at least about 20 mils, or at least about 25 mils. In certain embodiments, the support layer may have a thickness of less than or equal to about 30 mils, less than or equal to about 25 mils, less than or equal to about 20 mils, less than or equal to about 15 mils, less than or equal to about 12 mils, or less than or equal to about 10 mils. Combinations of the above ranges are also possible (e.g., about 8 mils to about 30 mils, about 12 mils to about 20 mils). Other ranges are also possible. The thickness of the support layer is determined as described herein under a load of about 1 ounce per square foot on a planar layer according to the Edana WSP 120.1 standard.

In certain embodiments, the support layers each have a basis weight of at least about 10gsm, at least about 20gsm, at least about 22gsm, at least about 33gsm, at least about 50gsm, at least about 60gsm, at least about 70gsm, at least about 80gsm, or at least about 90gsm. In some embodiments, the support layers each have a basis weight of less than or equal to about 99gsm, less than or equal to about 90gsm, less than or equal to about 80gsm, less than or equal to about 70gsm, less than or equal to about 60gsm, less than or equal to about 50gsm, less than or equal to about 33gsm, less than or equal to about 22gsm, or less than or equal to about 22gsm. Combinations of the above ranges are also possible (e.g., about 10gsm to about 99gsm, about 33gsm to about 70 gsm). Other ranges are also possible. As described herein, the basis weight of a support layer is measured according to the Edana WSP 130.1 standard.

In some embodiments, the support layer has a mean flow pore size of at least about 30 microns, at least about 40 microns, at least about 50 microns, at least about 75 microns, at least about 100 microns, or at least about 120 microns. In certain embodiments, the support layer has a mean flow pore size of less than or equal to about 150 microns, less than or equal to about 120 microns, less than or equal to about 100 microns, less than or equal to about 75 microns, less than or equal to about 50 microns, or less than or equal to about 40 microns. Combinations of the above ranges are also possible (e.g., about 30 to 150 microns, about 50 to about 120 microns). Other ranges are also possible. The mean flow pore size may be determined by capillary flow porosimetry, as described above.

Outer or covering layers

As previously indicated, the filter media 10 may also optionally include one or more outer layers or coverings disposed on the air intake side I and/or the air outflow side O. Fig. 1A shows a top layer 18 disposed on the air intake side I of the filter media 10. The top layer 18 may function as a dust-carrying layer and/or it may function as an aesthetic layer. In an exemplary embodiment, the top layer 18 is a planar layer that mates with the filter media 10 after corrugating the fibrous filtration layer 12 and support layers 14, 16. The top layer 18 thus provides an aesthetically pleasing top surface. The top layer 18 may be formed from a variety of fiber types and sizes, but in an exemplary embodiment, the top layer 18 is formed from fibers having an average fiber diameter that is less than the average fiber diameter of the upstream support layer 16 disposed immediately downstream of the top layer 18, but greater than the average fiber diameter of the fibrous filtration layer 12. In certain exemplary embodiments, the top layer 18 is formed from fibers having an average fiber diameter in the range of about 5 μm to 20 μm. Thus, the top layer 18 can function as a dust-holding layer without affecting the alpha value of the filter media 10, as will be discussed in more detail below.

As shown in FIG. 1B, the filter media 10B may alternatively or additionally include a bottom layer 18B disposed on the air outflow side O of the filter media 10B. The bottom layer 18B may function as a reinforcement component that provides structural integrity to the filter media 10B to help maintain the corrugated configuration. The bottom layer 18B may also function to provide abrasion resistance. This may be particularly desirable in ASHRAE bag applications where the outermost layer is subject to wear during use. The bottom layer 18B may have a similar configuration as the top layer 18, as discussed above. However, in one exemplary embodiment, the bottom layer 18B is the coarsest layer, i.e., it is formed from fibers having an average fiber diameter greater than the average fiber 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.

A variety of materials may also be used to form the fibers of the outer or cover layer, including synthetic and non-synthetic materials. In one exemplary embodiment, the outer or cover layer (e.g., top layer 18 and/or bottom layer 18B) is formed from staple fibers, particularly a combination of binder and non-binder fibers. One suitable fiber composition is a blend of at least about 20% binder fibers and the balance non-binder fibers. Various types of bonded and unbonded fibers may be used to form the media of the present invention, including those previously discussed above with respect to the support layers 14, 16.

Outer or cover layers, such as the top layer 18 and/or any bottom layer, may also be formed using a variety of techniques known in the art, including melt blowing, wet-laid techniques, air-laid techniques, carding, electrospinning, and spunbonding. However, in one exemplary embodiment, the top layer 18 is an airlaid layer and the bottom layer 18B is a spunbond layer. The resulting layer may also have a variety of thicknesses, air permeabilities, and basis weights as desired for the desired application. In an exemplary embodiment, the outer or cover layer has a thickness in the range of about 2 mils to 50 mils, an air permeability in the range of about 100CFM to 1200CFM, and a basis weight in the range of about 10gsm to 50gsm, as measured in a planar configuration.

Those skilled in the art will appreciate that although FIG. 1A illustrates a four layer filter media, the media may include any number of layers in a variety of configurations. Various layers may be added to enhance filtration, provide support, alter structure, or for a variety of other purposes. By way of non-limiting example, the filter media may include a variety of spunbond layers, wet-laid cellulose layers, dry-laid synthetic nonwoven layers, wet-laid synthetic layers, and wet-laid microglass layers.

Manufacturing method

Some or all of the layers may be formed into a corrugated configuration using a variety of manufacturing techniques, but in one exemplary embodiment at least one of the filtration layer 12 (e.g., fine fibers), any additional filtration layers, and support layers 14, 16 are disposed adjacent to each other in a desired arrangement from the air entry side to the air exit side, and the combined layers are conveyed between first and second moving surfaces that travel at different speeds (e.g., the second surface travels at a slower speed than the first surface). As the layer travels from the first moving surface to the second moving surface, a suction force (e.g., a vacuum force) may be used to pull the layer toward the first moving surface and then toward the second moving surface. The difference in velocity causes the layer to form z-direction waves as it passes over the second moving surface, thereby forming peaks and valleys in the layer. The speed of each surface can be varied to achieve the desired wavenumber 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 to 0.025 "to 4". For example, the peaks and valleys may have an amplitude of about 0.1 "to 4.0", such as about 0.1 "to 1.0", about 0.1 "to 2.0", or about 3.0 "to 4.0". For some applications, the amplitude of the peaks and valleys may be about 0.1 "to 1.0", about 0.1 "to 0.5", or about 0.1 "to 0.3". The characteristics of the different layers may also be varied to achieve a desired filter media configuration. In one exemplary embodiment, the filter media has about 2 to 6 waves per inch and a height (overall thickness) in the range of about 0.025 "to 2", although this may vary significantly depending on the intended application, for example, in other embodiments the filter media may have about 2 to 4 waves per inch, such as about 3 waves per inch. The overall thickness of the media can be about 0.025 "to 4.0", such as about 0.1 "to 1.0", about 0.1 "to 2.0", or about 3.0 "to 4.0". For some applications, the overall thickness of the media may be about 0.1 "to 0.5", or about 0.1 "to 0.3". As shown in fig. 1A, 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 as described above under the Edana WSP 120.1 standard at about 1 ounce load per 1 square inch presser foot.

In the embodiment shown in FIG. 1A, when the fiber filtration layer 12 and the support layers 14, 16 are corrugated, the resulting fiber filtration layer 12 has a plurality of peaks P and valleys T on each surface thereof (i.e., the air entrance side I and the air outflow side O), as shown in FIG. 1C. The support layers 14, 16 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 fibrous filtration layer 12 have corresponding valleys T on the air exit side O. Thus, the downstream support layer 14 extends into a trough T, and, just conversely, the same trough T is a peak P through which the upstream support layer 16 extends. Because the downstream support layer 14 extends into the valleys T on the air outflow side O of the fibrous filtration layer 12, the downstream coarse layer 14 maintains adjacent peaks P on the air outflow side O at a distance from one another and adjacent valleys T on the air outflow side O at a distance from one another. The upstream support layer 16, if provided, may also maintain adjacent peaks P on the air-entry side I of the fiber filtration layer 12 at a distance from one another, and may maintain adjacent valleys T on the air-entry side I of the fiber filtration layer 12 at a distance from one another. As a result, the fibrous filtration layer 12 has a significantly increased surface area compared to the surface area of a planar configuration of fibrous filtration layers. In certain exemplary embodiments, the surface area of the undulating configuration is increased by at least about 50%, and in some cases, up to 120%, as compared to the surface area of the same layer in a planar configuration.

In embodiments in which the upstream support layer and/or the downstream support layer maintain the fiber filtration layer in a waved 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 the fibrous layer. For example, at least 95% or substantially all of the available volume in the valleys may be filled with the support layer, and the solidity of the support layer may be about 1% to 90%, about 1% to 50%, about 10% to 50%, or about 20% to 50%. Further, as shown in the exemplary embodiment of FIG. 1A, the support layer extending across the peaks and to the valleys may be such that the surface area of the support layer that contacts the topsheet 18A across the peaks is similar to its surface area across the valleys. Similarly, the surface area of the support layer that contacts the bottom layer 18B across the peaks (FIG. 1B) may be similar to that across the valleys. For example, the surface area of the support layer that is in contact with the top or bottom layer through the peaks may differ from the surface area of the support layer that is in contact with the top or bottom layer through the valleys by less than about 70%, less than about 50%, less than about 30%, less than about 20%, less than about 10%, or less than about 5%.

In certain exemplary embodiments, the fiber density of the downstream and/or upstream support layers 14, 16 may be greater at the peaks than it is in the valleys; in some embodiments, the fiber mass is less at the peaks than it is in the valleys. This may be caused by the roughness of the downstream and/or upstream support layers 14, 16 relative to the fibrous filter layer 12. In particular, the relatively fine nature of the fibrous filtration layer 12 will conform to the waves formed in the downstream and/or upstream support layers 14, 16 around the fibrous filtration layer 12 as the layers move from the first moving surface to the second moving surface. When the support layers 14, 16 extend across the peaks P, the distance traveled is less than the distance traveled by the

layers

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

Once the layers are formed into the corrugated configuration, the corrugated shape can be maintained by activating the bonding fibers to produce fiber bonding. A variety of techniques may be used to activate the binder fibers. For example, if bicomponent binder fibers having a core and a sheath are used, the binder fibers may be activated upon the 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 hot moisture. The top layer 18 (fig. 1A) and/or the bottom layer 18B (fig. 1B) may also be disposed on the top of the upstream support layer 16 (fig. 1A) or the bottom of the downstream support layer 14B (fig. 1B), respectively, and simultaneously or subsequently mated with the upstream support layer 16 or the downstream support layer 14B, such as by bonding. One skilled in the art will also appreciate that a variety of techniques may optionally be used to mate the layers to one another in addition to the use of binder fibers. The layers may also be separately bonded layers, and/or they may be mated to each other, including bonding, prior to corrugating.

A saturant (saturant) may also optionally be applied to the material prior to drying the material. Various saturants can be used with the media of the present invention to facilitate formation of the layer at temperatures below the melting temperature of the fibers. Exemplary saturants can include phenolic resins, melamine resins, urea-formaldehyde resins, epoxy resins, polyacrylates, polystyrene/acrylates, polyvinyl chloride, polyethylene/vinyl chloride, polyvinyl acetate, polyvinyl alcohol, and combinations and copolymers thereof in aqueous or organic solvents.

In some embodiments, the resulting media may also have a gradient in at least one and optionally all of the following characteristics: bonded and unbonded fiber compositions, fiber diameter, solidity, basis weight, and saturant content. For example, in one embodiment, the media may have a lightweight, lofty, coarse fiber, lightly bonded and lightly saturated sheet upstream and a heavier, denser, fine fiber, strongly bonded and strongly saturated sheet downstream. This allows coarser particles to be captured in the upstream layers, preventing premature saturation of the bottom layer. In other embodiments, the most upstream layer may be lighter and/or more lofty than the most downstream layer. That is, the upstream layer may have a lower solidity (e.g., solid volume fraction of fibers in the layer) and basis weight than the downstream layer. Further, in embodiments where the filtration media comprises a saturant, the media can have a gradient with respect to the amount of saturant in the most upstream and most downstream layers. One skilled in the art will appreciate the various characteristics that a layer of media may have.

Electrostatic charge may also optionally be imparted to the filter media or to multiple layers of the media to form a layer of electret fibers. For example, an electrical charge may be imparted to the fibrous filtration layer prior to engagement with one or more support layers. In another embodiment, an electrical charge is imparted to a filter media comprising more than one layer (e.g., a fibrous filtration layer and one or more support layers). Depending on the material, amount of charge, and charging method used to form each layer, the charge may remain in one or more layers or dissipate after a short time (e.g., within hours). Various techniques are known for imparting permanent dipoles to polymer webs in order to form electret filter media. Charging may be produced by using AC and/or DC corona discharge units and combinations thereof. The specific characteristics of the discharge are determined by the electrode shape, polarity, gap size and gas or gas mixture. Charging may also be accomplished using other techniques, including friction-based charging techniques.

In some embodiments, the fibrous filtration layer may be made hydrophobic or hydrophilic. As described further below, in some cases, the hydrophilicity of the filter layer can alter the magnitude of the reduction in air permeability of the NaCl-loaded media compared to the unloaded media in a humid environment. In certain embodiments, the NaCl loaded media including the hydrophilic fibrous filtration layer may have a relatively low reduction in air permeability after exposure to a humid environment.

As mentioned herein, air permeability after loading with moisture is tested by using an automated filter test unit equipped with a sodium chloride generator (e.g., TSI 8130CertiTest from TSI, inc ^TM ) With NaCl aerosol of about 0.3 micron particles (23 mg NaCl/m) ³ Air) to 100cm ² The humidity challenge was performed to determine 30 minutes after the sample was loaded. The sample (e.g., a filter media comprising a fibrous filtration layer and a support layer in a waved configuration) was loaded at a face velocity of 14.1 cm/sec for 30 minutes. Once loaded with NaCl, the samples were placed in sample holders attached to a Frazier air permeability machine and enclosed in a chamber that included a steam generator to generate humidity. A hygrometer probe is inserted into the cassette to measure the temperature and humidity inside the chamber. At the start of the test, the relative humidity in the chamber was 50% and the test was performed by taking an initial air permeability reading at a pressure drop of 0.5 "water column, after which the steam generator was turned on and air permeability and humidity readings were taken every 30 seconds. Once the humidity reaches 90% (or, in some cases, 95%), the reading continues for about 12 minutes, after which the steam generator is turned off. Relay (S)The reading was continued until the relative humidity in the chamber returned to its level at the beginning of the test (i.e., 50%), at which time the air permeability had stabilized. The percent reduction in air permeability after moisture loading is the difference between the maximum air permeability value (which is the air permeability value measured when the relative humidity has returned to its level at the start of the test, i.e. 50%) minus the minimum air permeability value (which may be at 90% or 95% as the case may be).

In some embodiments, the fibrous filtration layer is hydrophilic and may have a reduction in air permeability after loading with moisture of less than or equal to 20%, less than or equal to 19%, less than or equal to 18%, less than or equal to 17%, less than or equal to 16%, less than or equal to 15%, less than or equal to 14%, less than or equal to 13%, less than or equal to 12%, less than or equal to 11%, less than or equal to 10%, less than or equal to 9%, less than or equal to 8%, less than or equal to 7%, or less than or equal to 6%. In certain embodiments, the reduction in air permeability after moisture loading is greater than or equal to 5%, greater than or equal to 6%, greater than or equal to 7%, greater than or equal to 8%, greater than or equal to 9%, greater than or equal to 10%, greater than or equal to 11%, greater than or equal to 12%, greater than or equal to 13%, greater than or equal to 14%, greater than or equal to 15%, greater than or equal to 16%, greater than or equal to 17%, greater than or equal to 18%, or greater than or equal to 19%. Combinations of the above ranges are also possible (e.g., less than or equal to 20% and greater than or equal to 5%, less than or equal to 15%, and greater than or equal to 10%). Other ranges are also possible.

In some cases, the fibrous filtration layer may be hydrophobic. In certain embodiments, the fibrous filtration layer may be hydrophilic. One skilled in the art can select suitable methods for rendering the fibrous filtration layer hydrophobic or hydrophilic, including but not limited to adding a hydrophobic or hydrophilic coating containing additives (e.g., during extrusion of the fibers) and/or selecting a hydrophobic or hydrophilic fibrous material. In some cases, the fibers of the support layer may also be selectively made hydrophobic or hydrophilic. For example, such support layers may be carded or air-laid in which a topical finish (topical finishes) is applied to the fibers prior to treatment, and/or the fibers may be selected based on their hydrophobic or hydrophilic properties.

The decrease in air permeability after moisture loading of a filter media including a hydrophilic fibrous filtration layer may be less than the decrease in air permeability after moisture loading of a filter media including a hydrophobic fibrous filtration layer.

In some embodiments, a layer of the filter media (e.g., a fibrous filtration layer, a support layer) (and/or at least a portion of the fibers of the layer) may be modified such that at least a portion of the surface of the layer (and/or at least a portion of the surface of the fibers of the layer) is hydrophilic. In certain embodiments, one or both of the upstream and downstream surfaces of a layer (e.g., fibrous filtration layer, support layer) are modified. In other embodiments, the layers (e.g., fibrous filtration layer, support layer) are modified to a depth below the surface, and in some cases, throughout the thickness of the layer. In certain embodiments, the layer is modified using chemical vapor deposition, topical application of a coating (e.g., by spray, dip, flexographic, or reverse roll application), incorporation of a hydrophilic melt additive, incorporation of hydrophilic fibers, or combinations thereof. Other (surface) modification techniques may also be used. For example, the layers (e.g., fibrous filter layer, support layer) may include a chemical vapor deposition coating.

In some embodiments, the filter Media and/or one or more layers of filter Media (e.g., a fiber filtration layer) to be modified (e.g., such that at least one surface of the fiber filtration layer is hydrophilic) can include one or more of the features, materials, components, and/or methods described in commonly owned U.S. patent No. 7,883,562 entitled "wave filter Media and Elements," issued 2/8/2011, which is incorporated herein by reference in its entirety.

In some embodiments, the hydrophilic modification of the layer can be performed at any suitable time. For example, at least one surface of a layer (e.g., fibrous filtration layer, support layer) can be modified to be hydrophilic after and/or during formation of the layer (e.g., during a melt blowing process, an electrospinning process, etc., as described herein). In certain embodiments, at least one surface of the layer may be modified to be hydrophilic during and/or after formation of the wave configuration of the layer.

In some embodiments, at least one surface of a layer (e.g., fibrous filtration layer, support layer) may be modified to make the surface hydrophilic or to increase the hydrophilicity of the surface. For example, a hydrophilic surface with a water contact angle of about 60 ° may be modified to have a water contact angle of about 15 °. In another example, a hydrophobic surface having a water contact angle of about 100 ° may be modified to have a water contact angle of less than 90 ° (e.g., a water contact angle of less than 60 °).

As used herein, the term "hydrophilic" refers to materials having a water contact angle of less than 90 degrees. As the water contact angle decreases, the material generally becomes more hydrophilic. Thus, "hydrophilic surface" may refer to a surface having a water contact angle of less than 90 degrees. In some embodiments, the surface can be modified to be hydrophilic such that the water contact angle is less than 90 degrees, less than or equal to about 80 degrees, less than or equal to about 75 degrees, less than or equal to about 70 degrees, less than or equal to about 65 degrees, less than or equal to about 60 degrees, less than or equal to about 55 degrees, less than or equal to about 50 degrees, less than or equal to about 45 degrees, less than or equal to about 40 degrees, less than or equal to about 35 degrees, less than or equal to about 30 degrees, less than or equal to about 25 degrees, less than or equal to about 20 degrees, or less than or equal to about 15 degrees. In some embodiments, the water contact angle is greater than or equal to about 0 degrees, greater than or equal to about 5 degrees, greater than or equal to about 10 degrees, greater than or equal to about 15 degrees, greater than or equal to about 20 degrees, greater than or equal to about 25 degrees, greater than or equal to about 35 degrees, greater than or equal to about 45 degrees, or greater than about 60 degrees. Combinations of the above ranges are also possible (e.g., greater than or equal to about 0 degrees and less than about 90 degrees, greater than or equal to about 0 degrees and less than about 60 degrees). In an exemplary embodiment, the contact angle of the surface (e.g., after modification) is less than or equal to 60 degrees. Water contact angles can be measured using ASTM D5946-04. The water contact angle is the angle between a surface (e.g., the surface of a fibrous filtration layer) and a tangent line drawn to the surface of a water droplet at a triple point when the droplet lands on a planar solid surface. The measurement may be performed using a contact angle meter or a goniometer. In some embodiments, the hydrophilicity of the surface can be such that a water droplet located on the surface completely wets the surface (e.g., the water droplet is fully absorbed into the material such that the water contact angle is 0).

In some embodiments, the reduction in water contact angle of at least one surface of the layer after modification as described herein is greater than or equal to about 0 degrees, greater than or equal to 1 degree, greater than or equal to about 2 degrees, greater than or equal to about 5 degrees, greater than or equal to about 10 degrees, greater than or equal to about 15 degrees, greater than or equal to about 20 degrees, greater than or equal to about 25 degrees, greater than or equal to about 35 degrees, greater than or equal to about 45 degrees, greater than or equal to about 60 degrees, greater than or equal to about 75 degrees, greater than or equal to about 80 degrees, or greater than or equal to about 90 degrees, as compared to the water contact angle of the at least one surface prior to modification. In certain embodiments, the at least one surface of the layer after modification has a reduction in water contact angle of less than or equal to about 100 degrees, less than or equal to about 90 degrees, less than or equal to about 80 degrees, less than or equal to about 75 degrees, less than or equal to about 70 degrees, less than or equal to about 65 degrees, less than about 60 degrees, less than or equal to about 55 degrees, less than or equal to about 50 degrees, less than or equal to about 45 degrees, less than or equal to about 40 degrees, less than or equal to about 35 degrees, less than or equal to about 30 degrees, less than or equal to about 25 degrees, less than or equal to about 20 degrees, less than or equal to about 15 degrees, less than or equal to about 10 degrees, less than or equal to about 5 degrees, or less than or equal to about 2 degrees compared to the water contact angle of the at least one surface prior to modification. Combinations of the above ranges are also possible (e.g., greater than or equal to 0 degrees and less than or equal to 100 degrees). Other ranges are also possible.

In some embodiments, the fibrous filtration layer may comprise fibers that may be modified such that at least one surface of the fibrous filtration layer comprising the fibers is hydrophilic. In some cases, the fibers may be hydrophilic. In some embodiments, the fibers may be hydrophobic and may be modified to be hydrophilic. Non-limiting examples of fibers that can be modified (e.g., to enhance or impart hydrophilicity) can include polymers such as polyolefins (e.g., polypropylene, polyethylene, polybutylene, copolymers of olefin monomers such as ethylene or propylene), polyesters (e.g., polybutylene terephthalate (PBT), polyethylene terephthalate (PET), coPET, polylactic acid (PLA)), polyamides (e.g., nylons such as polyamide 6 (PA 6), polyamide 11 (PA 11), aramids), polycarbonates, and combinations thereof (e.g., polylactic acid/polystyrene, PEN/PET polyesters, copolyamides). In cases where the fibers are hydrophilic (e.g., polylactic acid, PA 6), the fibers may be modified to enhance the hydrophilicity of the fibers. In one exemplary embodiment, the fibers may have a water contact angle greater than 60 degrees (e.g., greater than 60 degrees and less than 90 degrees) and the fibers are modified such that the water contact angle is less than or equal to 60 degrees (e.g., greater than or equal to 0 degrees and less than or equal to 60 degrees).

In some embodiments, a gas may be used to modify the hydrophilicity of at least one surface of a layer (e.g., a filtration layer, a support layer). For example, after the layer is formed, the layer may be exposed to a gaseous environment. In some such cases, molecules in the gas may react with materials (e.g., fibers, resins, additives) on the surface of the layer to form functional groups, e.g., charged moieties, and/or to increase the oxygen content on the surface of the layer. Non-limiting examples of functional groups include hydroxyl groups, carbonyl groups, ether groups, ketone groups, aldehyde groups, acid groups, amide groups, acetate groups, phosphate groups, sulfite groups, sulfate groups, amine groups, nitrile groups, and nitro groups. Non-limiting examples of gases that may react with at least one surface of a layer include CO ₂ 、SO ₂ 、SO ₃ 、NH ₃ 、N ₂ H ₄ 、N ₂ 、O ₂ 、H ₂ He, ar, NO, air, and combinations thereof.

In certain embodiments, a coating (e.g., a polymeric coating) may be used to modify the hydrophilicity of at least one surface of a layer (e.g., a fibrous filtration layer, a support layer). For example, after the layer is formed, a coating may be applied to at least one surface of the layer. In certain embodiments, the coating comprises acrylates (e.g., acrylamide, (hydroxyethyl) methacrylate), carboxylic acids (e.g., acrylic acid, citric acid), sulfonates (e.g., 1,3-propanesultone, N-hydroxysulfosuccinimide, methyl triflate), polyols (e.g., glycerol, pentanesulfonate, and mixtures thereof)Tetrols, glycols, propyleneglycols, saccharoses), amines (e.g. allylamine, ethyleneimine,

Oxazolines), silicon-containing compounds (e.g., tetraethyl orthosilicate, hexamethyldisiloxane, silane), and combinations thereof. In some embodiments, the coatings may be applied independently, as a mixture of two or more coatings, or sequentially (e.g., coating a first coating with a second coating).

In some embodiments, a wetting agent (e.g., a surfactant) may be used to modify the hydrophilicity of at least one surface of the layer. For example, after forming the layer, a wetting agent may be applied to at least one surface of the layer. Non-limiting examples of suitable wetting agents include anionic surfactants (e.g., sodium dioctyl sulfosuccinate, disodium salt of alkyl polyglucoside ester), nonionic surfactants (e.g., alkylphenol ethoxylates, alcohol ethoxylates, polyglycerol esters, polyglucosides), cationic surfactants (e.g., of the formula R) ¹ R ² R ³ R ⁴ N ⁺ X ^- Wherein R is ¹ 、R ² R3 and R4 each represent the same or different alkyl groups, X ^- Is a halogen such as a chloride ion), an amphoteric surfactant (e.g., a surfactant comprising a cationic group and an anionic group such as an N-alkyl betaine), and combinations thereof.

In some embodiments, the layer may be immersed in a material (e.g., a coating, a surfactant). In certain embodiments, the material may be sprayed onto the layer. The weight percentage of the material (e.g., coating, surfactant, functional group) used to modify at least one surface of a layer (e.g., fibrous filtration layer, support layer) can be greater than or equal to about 0.0001 weight%, greater than or equal to about 0.0005 weight%, greater than or equal to about 0.001 weight%, greater than or equal to about 0.005 weight%, greater than or equal to about 0.01 weight%, greater than or equal to about 0.05 weight%, greater than or equal to about 0.1 weight%, greater than or equal to about 0.5 weight%, greater than or equal to about 1 weight%, greater than or equal to about 2 weight%, or greater than or equal to about 4 weight%, relative to the total weight of the layer. In some cases, the weight percentage of the material used to modify at least one surface of a layer relative to the total weight of the layer may be less than or equal to about 5 weight%, less than or equal to about 3 weight%, less than or equal to about 1 weight%, less than or equal to about 0.5 weight%, less than or equal to about 0.1 weight%, less than or equal to about 0.05 weight%, less than or equal to about 0.01 weight%, or less than or equal to about 0.005 weight%. Combinations of the above ranges are also possible (e.g., the weight percent of the material is greater than or equal to about 0.0001 weight percent and less than about 5 weight percent). Other ranges are also possible. The weight percent of material in a layer is based on the dry solids of the layer, and can be determined by weighing the layer before and after surface modification as described herein.

In some cases, melt additives may be incorporated into the fibers and/or layers to enhance the hydrophilicity of the layers. For example, in certain embodiments, melt additives may be used to modify the hydrophilicity of at least one surface of a layer (e.g., fibrous filtration layer, support layer). In some cases, a melt additive (e.g., a hydrophilic melt additive) may be blended with one or more fibers of a layer (e.g., during formation of the fibers and/or formation of the layer). Non-limiting examples of suitable (hydrophilic) melt additives include monoglycerides, mixed glycerides, fatty acid di-esters of polyethylene oxide, ethoxylated castor oil, blends of glyceryl oleate and alkylphenol ethoxylates, and polyethylene glycol esters of fatty acids. Other hydrophilic melt additives are also possible.

In some cases, the melt additive may comprise a pre-blended masterbatch melt additive. Pre-blended masterbatch melt additives are known in the art, and based on the teachings of the present specification, one of ordinary skill in the art can incorporate the pre-blended masterbatch melt additives into the fibrous filtration layer such that at least one surface of the fibrous filtration layer is hydrophilic.

The weight percent of the melt additive (or pre-blended masterbatch melt additive) used to modify at least one surface of a layer may be greater than or equal to about 0.0001 weight percent, greater than or equal to about 0.0005 weight percent, greater than or equal to about 0.001 weight percent, greater than or equal to about 0.005 weight percent, greater than or equal to about 0.01 weight percent, greater than or equal to about 0.05 weight percent, greater than or equal to about 0.1 weight percent, greater than or equal to about 0.5 weight percent, greater than or equal to about 1 weight percent, greater than or equal to about 2 weight percent, greater than or equal to about 4 weight percent, greater than or equal to about 6 weight percent, or greater than or equal to about 8 weight percent, relative to the total weight of the layer. In some cases, the weight percent of the melt additive used to modify at least one surface of a layer may be less than or equal to about 10 weight percent, less than or equal to about 8 weight percent, less than or equal to about 5 weight percent, less than or equal to about 3 weight percent, less than or equal to about 1 weight percent, less than or equal to about 0.5 weight percent, less than or equal to about 0.1 weight percent, less than or equal to about 0.05 weight percent, less than or equal to about 0.01 weight percent, or less than or equal to about 0.005 weight percent relative to the total weight of the layer. Combinations of the above ranges are also possible (e.g., a weight percentage of material is greater than or equal to about 0.0001 wt% and less than about 10 wt%, or greater than or equal to about 0.0001 wt% and less than about 5 wt%). Other ranges are also possible. The weight percent of material in a layer is based on the dry solids of the layer and can be determined by thermogravimetric analysis.

The filter media may also be pleated after it is formed into a corrugated configuration, various exemplary configurations being discussed in more detail below. Those skilled in the art will appreciate that the corrugated filter media may be pleated using virtually any pleating technique known in the art. Typically, filtration media is pleated by forming a plurality of parallel score lines in the media and forming a fold along each score line.

Filter media characteristics

As noted above, the characteristics of the resulting filter media can vary depending on the intended use. In some embodiments, the mean flow pore size of the fibrous filtration layer is effective to improve the performance (e.g., reduced air permeability reduction) of the filtration media in relatively high humidity environments.

In some embodiments, the filter media described herein is classified as a G1, G2, G3, G4, M5, M6, F7, F8, or F9 filter media. The average and minimum efficiency ranges for these categories for DEHS particles of 0.4 microns or greater are listed in table 1. The test was carried out as described below, according to the standard EN779-2012 above, until the maximum final pressure drop was 250Pa or 450Pa.

TABLE 1

The resulting media may also have a variety of thicknesses, air permeabilities, basis weights, and initial efficiencies as desired for the desired application. As referred to herein, the thickness is determined using a suitable caliper according to the Edana WSP 120.1 standard. As referred to herein, the basis weight is determined according to the Edana WSP 130.1 standard.

For example, in one embodiment, as shown in FIG. 1A, the thickness t of the resulting media _m May range from about 0.025 "to 4", peaks and valleys have an amplitude of about 0.025 "to 4" (e.g., about 0.1 "to 1.0", about 0.1 "to 2.0", or about 3.0 "to 4.0" in some applications, about 0.1 "to 0.5", or about 0.1 "to 0.3" in other applications), and an air permeability in a range of about 30CFM to 400CFM (e.g., about 50CFM to 120CFM, or about 70CFM to 90 CFM). The resulting media may also have a basis weight in the range of about 125gsm to 250gsm (e.g., about 150gsm to 250gsm, or about 135gsm to 160 gsm), and/or a loading of about 60mg/100cm at a face velocity of 5.3 cm/sec ² Has a NaCl loading of less than about 25mm H after about 0.3 μm particles ₂ O (e.g., less than about 20mm H) ₂ O)。

Filter element

As previously mentioned, the filter media disclosed herein may be incorporated into a variety of filter elements for a variety of applications, including both liquid and air filtration applications. Exemplary uses include ASHRAE bag filters, pleatable HVAC filters, gas turbine bag filters, liquid bag filter media (liquid bag filter media), dust bag house filters (dust bag house filters), residential house filters, paint spray booth filters, face masks (e.g., surgical and industrial face masks), cabin air filters, commercial ASHRAE filters, respirator filters, automotive air intake filters, automotive fuel filters, automotive lube filters, indoor air purifier filters, and vacuum cleaner exhaust filters. The filter element can have a variety of configurations, some exemplary filter element configurations are discussed in more detail below. Other exemplary filter elements include, by way of non-limiting example, radial filter elements including cylindrical filter media disposed therein, micron-tube bag filters (also known as sock filters) for liquid filtration, face masks, and the like.

Plate type filter

In one exemplary embodiment, the filter media may be used in a panel filter. In particular, the filter media may include a housing disposed thereabout. The housing may have a variety of configurations, and the specific configuration may vary based on the intended application. The housing may be in the form of a frame disposed about the perimeter of the filter media. The frame may have a generally rectangular configuration such that it surrounds all four sides of the generally rectangular filter media 10, although the specific shape may vary. The frame may be formed from a variety of materials, including cardboard, metal, polymers, and the like. In certain exemplary embodiments, the frame may have a thickness of about 12 "or less, or about 2" or less. In another embodiment, the frame may be formed by an edge of the filter media. In particular, the perimeter of the filter media 10' may be heat sealed to form a frame therearound. The panel filter may also include a number of other features known in the art, such as stabilizing features for stabilizing the filter media relative to a frame, spacer, or the like.

In use, the panel filter element can be used in a variety of applications, including commercial and residential HVAC filters (e.g., furnace filters); an automobile cabin air filter; an automotive air intake filter; and a paint spray booth filter. The particular characteristics of the filter element can vary based on the intended use, but in certain examplesIn embodiments, the filtration element has a MERV rating in the range of 7 to 20, and may be, for example, greater than about 13, greater than about 15, greater than about 17, or greater than about 19. The pressure drop of the filter element may be about 0.1 ″ -H ₂ O to 5"H ₂ In the range of O, e.g. about 0.1H ₂ O to 1"H ₂ O。

Folding filter (folded filter)

The corrugated filter media may also be pleated and used in pleated filters. As previously discussed, the corrugated media or multiple layers thereof may be pleated by forming score lines spaced a predetermined distance from each other and folding the media. However, those skilled in the art will appreciate that other pleating techniques may be used. Once the media is pleated, the media may be incorporated into a housing. The media may have any number of pleats depending on the frame size and intended use. In certain exemplary embodiments, the filter media has 1 to 2 pleats per inch, and the pleat height is in the range of about 0.75 "to 2". However, some applications utilize peaks up to a height of 12".

To facilitate pleating, the filter media may be self-supporting, i.e., it may have a stiffness that allows pleating. In certain exemplary embodiments, the filter media has a minimum stiffness of about 200mg to achieve pleating according to the Gurley stiffness tester. Alternatively or additionally, the filter media may include various reinforcing elements (e.g., stabilizing straps, screen backings, etc.).

In use, the pleated corrugated filter element may be used in a variety of applications, including pleatable HVAC filters, residential furnace filters, cabin air filters, commercial ASHRAE filters, automotive air intake filters, automotive fuel filters, automotive lube filters, indoor air cleaner filters, and vacuum cleaner exhaust filters. The specific characteristics of the filter element may vary based on the intended use, but in certain exemplary embodiments, the filter element has a MERV rating in the range of 7 to 20. For example, the MERV rating may be greater than about 13, greater than about 15, greater than about 17, or greater than about 19. The pressure drop of the filter element may be about 0.1 ″ -H ₂ O to 5"H ₂ In the range of OE.g. about 0.1H ₂ O to 1"H ₂ And (O). The filter media may also have a thickness of less than about 0.5 "prior to pleating and a thickness of about 2" or less after pleating. However, in some applications, the thickness after pleating may be up to 12".

Bag filter/bag filter

In yet another embodiment, the filter media may incorporate bag filters or bag filters for heating, air conditioning, ventilation, gas turbine filtration, and/or refrigeration; and a micron-sized liquid filter bag. The bag filter or bag house filter may be formed as follows: a pocket is formed inside the filter by placing two filter media together (or folding a single filter media in half) and mating the three sides (or two if folded) to each other so that only one side remains open. In some embodiments, a plurality of filter bags may be attached to a frame to form a filter element. Each pocket may be positioned such that the open end is in the frame, thereby allowing air to flow into each pocket. The frame may include a rectangular ring extending to and holding each pocket. Those skilled in the art will appreciate that the frame may have virtually any configuration and that a variety of mating techniques known in the art may be used to couple the bag to the frame. Further, the frame may comprise any number of bags, but bag filters typically comprise 6 to 10 bags.

The specific characteristics of the filter element may vary based on the intended use, but in certain exemplary embodiments, the MERV rating of the filter element is in the range of about 7 to 20 (e.g., 13 to 20). For example, the MERV rating may be greater than about 13, greater than about 15, greater than about 17, or greater than about 19. The pressure drop of the filter element may be about 0.1 ″ -H ₂ O to 5"H ₂ In the range of O, e.g. about 0.1H ₂ O to 1"H ₂ And O. The thickness of the filter media can also be about 2 "or less, or about 0.5" or less, however, the thickness can vary depending on the intended application.

By way of non-limiting example, a standard 8-bag ASHRAE bag filter typically has 30 "deep bags in a 24" x24 "frame and produces 80 square feet of media. An ASHRAE bag filter of the same size but using a corrugated filter media according to the invention will produce 176 square feet of media.

Face mask

In yet another embodiment, the filter media may be incorporated into a personal protection filter device, such as a face mask designed to remove contaminants from breathable air. In one embodiment, the filter media is used to form an industrial face mask designed for use in a workplace. The mask may include, for example, an outer structural support layer, a filtration layer, and an inner structural support layer, although any suitable combination of layers may be used. Each layer may be charged or uncharged. Each layer may be hydrophobic or hydrophilic. The structural support layer may be a nonwoven layer that is thermally moldable under suitable conditions (e.g., 6 to 8 seconds at a temperature of about 105 to 110 ℃). The filter layer may be formed from a meltblown material or a fiberglass material. In one set of embodiments, the mask has a filter area of about 170cm ² This is standard in the United states, or about 150cm in area ² This may be standard in other parts of the world.

In another embodiment, the filter media is used in a surgical mask. Surgical masks include personal protective filtering devices that are typically worn by medical personnel, primarily for two reasons: preventing the transfer of germs from the medical personnel to the patient (and vice versa), and protecting the medical personnel from harmful bodily fluid attacks. The surgical mask may include, for example, an outer structural support layer, a filtration layer, and an inner structural support layer, although any suitable combination of layers may be used. Each layer may be charged or uncharged. In some embodiments, the structural support layer is polypropylene spunbond and the filter layer is formed from a meltblown material or a fiberglass material. The filter media may be folded for greater coverage area and may include, for example, 200cm ² To 1000cm ² The filtration area of (a).

The following non-limiting examples serve to further illustrate the invention:

example 1

This example illustrates the importance of mean flow pore size to filtration performance according to some embodiments described herein.

Samples a through G are meltblown fiber filtration layer samples designed to have a minimum DEHS efficiency of at least 25% (planar configuration without a support layer). A number of properties of the samples were measured and the results are shown in table 2.

TABLE 2

Samples were tested for transition salt loading according to the protocol described above.

FIG. 2A shows the resistance (mm H) of samples A and B obtained from the conversion salt loading test ₂ O) versus NaCl loading (gsm). The figure also shows the cake load line and the initial depth load line for samples a and B. As noted above, the transition salt loading is defined as the value of NaCl loading per unit area (gsm) at the intersection of the initial depth load line and the filter cake load line. The transition salt loading for sample a (having a mean flow pore size of 10.43 microns) was about 1.2 and for sample B (having a mean flow pore size of 16.38 microns) was about 3.6.

Figure 2B shows a plot of the transition salt loading of samples a-G as a function of mean flow pore size. As shown, samples with mean flow pore sizes greater than 11.5 microns had significantly higher transition salt loadings than samples with mean flow pore sizes less than 11.5 microns. Higher conversion salt loadings are generally associated with improved filtration performance under high humidity conditions as well as standard conditions.

Fig. 2C shows a plot of the slope of the cake load line versus the mean flow pore size for samples a through G. As shown, samples with mean flow pore sizes greater than 11.5 microns had a lower slope of the filter cake load line than samples with mean flow pore sizes less than 11.5 microns. Lower slopes can result in higher conversion salt loadings, which are generally associated with improved high humidity filtration performance.

Fig. 2B-2C demonstrate that a fibrous filtration layer having a minimum DEHS efficiency of at least 25% and a mean flow pore size of at least about 11.5 microns has a significantly increased conversion salt loading as compared to a fibrous filtration layer having a mean flow pore size of less than 11.5 microns at that efficiency. Since high transition salt loadings are generally associated with improved high humidity performance, fibrous filtration layers having a mean flow pore size of at least about 11.5 microns are expected to have improved filtration performance in high humidity environments.

Fig. 3A is a plot of the natural log specific penetration (i.e., the natural log of penetration divided by constant weight) versus the mean flow pore size for samples a through G. The regression curves shown on the graph demonstrate the relationship between the mean flow pore size of the fiber filtration layer, the basis weight of the fiber filtration layer, and the permeability. Thus, there is also a relationship between the mean flow pore size of the fibrous filtration layer, the basis weight of the fibrous filtration layer, and the efficiency. For example, with the latter relationship in part, the following equations have been developed to determine the appropriate average pore size and weighting values needed to achieve the target minimum DEHS efficiency.

Where BW is the basis weight of the fiber filtration layer, MP is the mean flow pore size, and E is the minimum DEHS efficiency of the fiber filtration layer as a target.

FIG. 3B is a plot of basis weight (gsm) versus mean flow pore size for samples A through G. The above relationship is used to define a curve that is the boundary of the constant weight and mean flow pore size values that satisfy the minimum DEHS efficiency of 35% (to satisfy the F7 category). The minimum DEHS efficiency of a fibrous filtration layer having a combination of basis weight and mean flow pore size at or above the boundary is 35% or greater. Fibrous filtration layers having a mean flow pore size greater than 11.5 microns and at or above the boundary also have improved high humidity performance, as described above.

Example 2

This example demonstrates the correlation between filter media performance and mean flow pore size under wet conditions.

Samples of filter media including a range of average pore sizes (about 10 microns to 16.5 microns) were tested in a humid environment. The filter media samples included a fibrous filtration layer between two support layers, with the combined layers being in a corrugated configuration. The test followed the protocol described above to measure the percent reduction in air permeability after loading with moisture.

As described in the above protocol, the percent reduction in air permeability after moisture loading is the difference between the maximum air permeability (as measured during the test) minus the minimum air permeability (as measured at 90% humidity during the test) expressed as a percentage of the maximum air permeability value. Fig. 4 shows a plot of the difference versus mean flow pore size. As shown, for mean flow pore diameters greater than about 11.5 microns, the mean difference is about 44% or less. For mean flow pore diameters of less than 11.5 microns, the mean difference is 46% or greater.

The data shows that filter media including mean flow pore sizes greater than 11.5 microns have a smaller difference between maximum and minimum air permeability than filter media including mean flow pore sizes less than 11.5 microns.

Example 3

This example demonstrates that modification of the filter media enhances the hydrophilicity of at least one surface of a layer of the filter media. The filter media samples were tested in a humid environment. The filter media samples included a fibrous filtration layer between two support layers, with the combined layers being in a corrugated configuration. The test followed the protocol described above to measure the reduction in air permeability after loading with moisture (at 95% humidity).

Two samples were treated with surfactant (e.g., one using topical dip, one using topical spray) prior to loading and moisture, while the third sample was not treated, as shown in fig. 5. The percent reduction in air permeability after loading with moisture (at 95% humidity) is plotted in figure 5. The local immersion and local spraying of the hydrophilically treated waveform samples containing surfactant showed lower pressure drop reduction compared to the untreated waveform samples.

Those skilled in the art will further appreciate the features and advantages of the invention based on the above-described embodiments. Accordingly, the invention is not to be limited by what has been particularly shown and described, except as indicated by the appended claims. All publications and references cited herein are expressly incorporated by reference in their entirety.

Claims

1. A filter media, comprising:

a fiber filtration layer and a support layer that holds the fiber filtration layer in a waved configuration and maintains separation of peaks and valleys of adjacent waves of the fiber filtration layer,

wherein at least one surface of the fibrous filtration layer is hydrophilic, the water contact angle is less than or equal to 60 degrees, an

Wherein the filter media has a reduction in air permeability after being loaded with 95% moisture of less than or equal to 20%.

2. The filter media of claim 1, wherein the fibrous filtration layer comprises hydrophilic fibers.

3. The filter media of claim 1 or 2, wherein the fibrous filtration layer has a mean flow pore size of at least 5 microns.

4. The filter media of claim 1 or 2, wherein the support layer has a density at the peaks that is greater than a density at the valleys.

5. The filter media of claim 1 or 2, wherein the filter media has a minimum DEHS particulate filtration efficiency of at least 25%.

6. The filter media of claim 1 or 2, wherein the fibrous filter media comprises a coating.

7. The filter media of claim 6, wherein the coating comprises a polymeric coating selected from the group consisting of acrylates, carboxylic acids, sulfonates, polyols, amines, silicon-containing compounds, and combinations thereof.

8. The filter media of claim 1 or 2, wherein the fibrous filtration layer comprises a wetting agent.

9. The filter media of claim 8, wherein the wetting agent is a surfactant.

10. The filter media of claim 9, wherein the surfactant is selected from the group consisting of anionic surfactants, nonionic surfactants, cationic surfactants, amphoteric surfactants, and combinations thereof.

11. The filter media of claim 6, wherein the coating is present in the fibrous filtration layer in an amount greater than or equal to 0.0001 wt% and less than 5 wt% relative to the total weight of the layer.

12. The filter media of claim 1 or 2, wherein the fibrous filtration layer comprises a melt additive.

13. The filter media of claim 12, wherein the melt additive is selected from the group consisting of monoglycerides, mixed glycerides, di-fatty acid esters of polyethylene oxide, ethoxylated castor oil, blends of glyceryl oleate and alkylphenol ethoxylates, polyethylene glycol esters of fatty acids, and pre-blended masterbatch melt additives.

14. The filter media of claim 13, wherein the weight percentage of the melt additive used to modify the at least one surface of the layer is greater than or equal to 0.0001 weight% and less than 10 weight% relative to the total weight of the layer.

15. The filter media of claim 1 or 2, wherein the support layer is formed of fibers having an average fiber diameter greater than or equal to an average fiber diameter of the fibrous filtration layer.

16. A filter media as in claim 1 or 2, wherein the basis weight of the fibrous filtration layer is selected such that:

wherein:

BW is the basis weight of the fiber filter layer;

MP is the average pore size of the fiber filtration layer;

e is the minimum DEHS efficiency, expressed as a fraction, of the fibrous filtration layer;

a is equal to 2; and

b equals 6.5.

17. The filter media of claim 1 or 2, wherein the support layer comprises fibers having an average fiber diameter of 10 to 32 microns.

18. The filter media of claim 1 or 2, wherein the filter media comprises a second support layer having an average fiber diameter of 10 to 32 microns.

19. The filter media of claim 1 or 2, wherein the filter media further comprises at least one cover layer disposed on the support layer.

20. The filter media of claim 1 or 2, wherein the fibrous filtration layer comprises fibers having an average fiber diameter of 0.2 microns to 10 microns.

21. The filter media of claim 1 or 2, wherein the fibrous filtration layer has a mean flow pore size of at least 11.5 microns.

22. The filter media of claim 1 or 2, wherein the basis weight of the fibrous filtration layer is greater than or equal to 10g/m ² And less than or equal to 40g/m ² 。

23. The filter media of claim 1 or 2, wherein the fiber filtration layer has a basis weight of greater than or equal to 13g/m ² And less than or equal to 20g/m ² 。

24. The filter media of claim 1 or 2, wherein the filter cake load line of the fibrous filtration layer has a slope of 1mm H ₂ O/gsm salt loading to 7mm H per sample ₂ O/gsm salt loading per sample.

25. The filter media of claim 1 or 2, wherein the fibrous filtration layer has a thickness in the range of 6 mils to 22 mils.

26. The filter media of claim 1 or 2, wherein the fibrous filtration layer has an air permeability in the range of 30 to 150CFM as measured according to ASTM F778-88.

27. The filter media of claim 1 or 2, wherein the fibrous filtration layer has a surface area of at least 0.8 grams per square meter.

28. The filter media of claim 1 or 2, wherein the peaks and valleys of the fibrous filtration layer have an amplitude of 0.1 "to 4.0".

29. The filter media of claim 1 or 2, wherein the fiber filtration layer is from 1% to 20% dense.

30. The filter media of claim 1 or 2, wherein the filter media has a minimum DEHS particulate filtration efficiency of at least 35%.

31. The filter media of claim 1 or 2, wherein the fiber filtration layer in the waved configuration is formed from a fiber layer having a planar configuration and a transition salt loading of at least 3.5 gsm.

32. A method for forming a filter media, comprising:

modifying the hydrophilicity of at least one surface of a fibrous filtration layer of the filtration media such that the filtration media has a permeability wherein the filtration media has a reduction in air permeability after being 95% loaded with moisture of less than or equal to 20%,

wherein at least one surface of the fiber filtration layer is hydrophilic, and wherein the filter media comprises a support layer that holds the fiber filtration layer in a waved configuration and maintains separation of peaks and valleys of adjacent waves of the fiber filtration layer.