Filter media suitable for hydraulic applications

Abstract

Filter media suitable for hydraulic applications, as well as components, systems, and methods associated with the filter media, are provided. The filter media described herein comprise: a first layer having a first average diameter; a second layer adjacent to the first layer having a second average diameter, the first average diameter being greater than the second average diameter; and a third layer adjacent to the second layer having a third average diameter, the second average diameter being greater than the third average diameter, the third layer having a thickness of less than 200 microns. The filter media of the present application may have desirable characteristics of high dust holding capacity and low fluid flow resistance. The media can be incorporated into various filter element products, including hydraulic filters.

Description

[0001] This application is a divisional application of a Chinese patent application with an application date of October 5, 2011, a priority date of October 6, 2010, an application number of "201180047984.3", and an invention name of "Filter medium suitable for hydraulic applications". Technical Field

[0002] The present invention relates generally to filter media that can be used in hydraulic applications and, more particularly, to multi-layer filter media having desirable performance characteristics. Background Art

[0003] Filter media can be used to remove contaminants in a variety of applications. Depending on the application, the filter media can be designed to have different performance characteristics. For example, the filter media can be designed to have performance characteristics suitable for hydraulic applications that include filtering contaminants in pressurized fluids.

[0004] Generally, the filter medium can be formed by a fiber mesh. For example, the mesh may include other components such as ultrafine glass fibers. The fiber mesh provides a porous structure that allows a fluid (e.g., a hydraulic fluid) to flow through the filter medium. Contaminant particles contained in the fluid can be captured on the fiber mesh. The characteristics of the filter medium (e.g., fiber diameter and basis weight) have an impact on the filter performance, which includes filter efficiency, dirt holding capacity, and resistance to the fluid flowing through the filter.

[0005] There is a need for a filter media that can be used in hydraulic applications and that has a desirable balance of properties including high dust holding capacity and low resistance (high permeability) to fluid flow through the filter media. Summary of the invention

[0006] Filter media, including filter media suitable for hydraulic applications, and related components, systems, and methods related thereto are provided.

[0007] In one set of embodiments, a series of filter media is provided. In one embodiment, the filter media includes at least two layers. The first layer of the filter media includes at least 80% by weight glass fibers, wherein the fibers in the first layer have a first average diameter. The filter media also includes a second layer directly adjacent to the first layer, the second layer including glass fibers, wherein the fibers in the second layer have a second average diameter. The second average diameter is less than the first average diameter. The normalized resistance ratio of the second layer to the first layer is 1:1 to 5:1.

[0008] In another embodiment, the filter media includes at least three layers. The first layer of the filter media includes glass fibers, and the fibers in the first layer have a first average diameter. The second layer of the filter media includes glass fibers, and the fibers in the second layer have a second average diameter, wherein the second average diameter is less than the first average diameter. The third layer of the filter media includes glass fibers, and the fibers in the third layer have a third average diameter, wherein the third average diameter is less than the second average diameter. The second layer can be directly adjacent to the first filter layer and the third filter layer. The normalized resistance ratio of the second layer relative to the first layer is 1:1 to 15:1.

[0009] In another embodiment, the filter media comprises at least three layers. A first layer of the filter media comprises glass fibers, the fibers in the first layer having a first average diameter. A second layer of the filter media is adjacent to the first layer and comprises glass fibers, the fibers in the second layer having a second average diameter. A third layer of the filter media is adjacent to the second layer and comprises glass fibers, the fibers in the third layer having a third average diameter. The filter media has an absolute specific capacity at 10 microns greater than about 2.65.

[0010] In another embodiment, the filter media comprises at least three layers. The first layer of the filter media comprises glass fibers, the fibers in the first layer having a first average diameter. The second layer of the filter media is adjacent to the first layer comprising glass fibers, the fibers in the second layer having a second average diameter. The first and second layers have a thickness of less than 75 g / m 2 and a 10 micron absolute specific capacity of greater than about 3.4.

[0011] In another embodiment, the filter media comprises at least three layers. The first layer of the filter media comprises at least 90% by weight glass fibers, the basis weight of the first layer being greater than about 40 g / m 2 The second layer of the filter media is adjacent to the first layer and comprises at least 90% by weight glass fibers, the basis weight of the second layer being less than about 40 g / m 2 The third layer of the filter media is adjacent to the second layer and includes at least 90 weight percent glass fibers.

[0012] In another embodiment, the filter media includes a first layer comprising glass fibers, wherein the fibers in the first layer have a first average diameter. The filter media also includes a second layer adjacent to the first layer, wherein the second layer includes glass fibers. The fibers in the second layer have a second average diameter, and the first average diameter is greater than the second average diameter. The filter media also includes a third layer adjacent to the second layer, wherein the third layer includes synthetic polymer fibers. The fibers in the third layer have a third average diameter, wherein the second average diameter is greater than the third average diameter. The thickness of the third layer is less than about 200 microns.

[0013] In another embodiment, the filter media includes a first layer comprising glass fibers, wherein the fibers in the first layer have a first average diameter. The filter media also includes a second layer adjacent to the first layer, wherein the second layer includes glass fibers. The fibers in the second layer have a second average diameter, and the first average diameter is greater than the second average diameter. The filter media also includes a third layer adjacent to the second layer. The third layer includes synthetic polymer fibers. The fibers in the third layer have a third average diameter, wherein the second average diameter is greater than the third average diameter. The filter media has a viscosity of at least about 150 g / m 2 and a total dust holding capacity of greater than about 25 cfm / sf (cubic feet per minute per square foot).

[0014] In some embodiments, the filter media described above and in the present application may have the following characteristics: the normalized resistance ratio of the second layer relative to the first layer is 4:1 or greater, and the normalized resistance ratio of the third layer relative to the second layer is 4:1 or less. For example, in some cases, the normalized resistance ratio of the second layer relative to the first layer is 4:1 to 6:1, and the normalized resistance ratio of the third layer relative to the second layer is 2:1 to 4:1. The first layer may include less than about 20% by weight of synthetic fibers. In some cases, the first layer is a pre-filter layer and the unit weight of the first layer is greater than the unit weight of the second layer. At least one of the first layer and the second layer may include at least about 80% by weight of glass fibers. In other embodiments, at least one of the first layer and the second layer includes at least about 40% by weight or 60% by weight of ultrafine glass fibers. The average diameter of the ultrafine glass fibers may be 1 μm to 6 μm. The ratio of the first average diameter to the second average diameter may be less than 2:1. Optionally, the third average diameter may be less than about 1 micron. In some filter media, at least one of the first layer, the second layer, and the third layer may have a basis weight of less than about 40 g / m 2 .

[0015] In certain embodiments, the synthetic polymer fibers of the layer may include meltblown fibers. The synthetic polymer fibers may include materials selected from, for example, polyester, nylon, and polyphenylene sulfide. The thickness of the third layer may be less than about 180 microns. The third layer may have a median flow pore size of about 8 microns to about 12 microns and a beta retardant of at least 200. (10) In some cases, the basis weight of the third layer can be about 20 g / m 2 About 30g / m 2 .

[0016] The total dust holding capacity of the filter media described above and herein may be at least about 180 g / m 2 or at least about 230g / m 2 The total permeability of the filter media can be greater than about 35 cfm / sf or greater than about 40 cfm / sf. The filter media can have an efficiency of β(x) equal to at least 200 and a median flow pore size of x ± 2 microns. In some embodiments, the filter media can be used to form a hydraulic filter element. In some such embodiments, the third layer is downstream of the second layer, and the second layer is downstream of the first layer. Other configurations are also possible.

[0017] In one set of embodiments, a method is provided. A method of filtering a liquid includes passing a liquid containing particles through a filter medium. The filter medium may include one of the filter media described above and / or in the present application. For example, the filter medium may include at least three layers. In one embodiment, the first layer of the filter medium includes glass fibers, and the fibers in the first layer have a first average diameter. The second layer of the filter medium includes glass fibers, and the fibers in the second layer have a second average diameter, wherein the second average diameter is smaller than the first average diameter. In some embodiments, the third layer of the filter medium includes glass fibers, and the fibers in the third layer have a third average diameter, wherein the third average diameter is smaller than the second average diameter. In other embodiments, the third layer may include synthetic polymer fibers. The second layer may be directly adjacent to the first filter layer and the third filter layer. The normalized resistance ratio of the second layer relative to the first layer is 1:1 to 15:1.

[0018] Other aspects, embodiments, advantages and features of the invention will become apparent from the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, which are schematic and are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown is generally indicated by the same reference numeral. For clarity, not every component in every drawing is labeled, and not every component of every embodiment of the present invention is shown, where the description is not necessary for a person skilled in the art to understand the present invention. In the drawings:

[0020] Figure 1 An example of a filter medium having multiple layers according to one set of embodiments is shown;

[0021] Figure 2 showing a graph of 10 micron absolute specific capacity versus unit weight for filter media of various samples according to one set of embodiments; and

[0022] Figure 3A and Figure 3B is a table showing properties of a filter media having a first layer comprising glass fibers, a second layer comprising glass fibers, and a third layer comprising meltblown fibers, according to one set of embodiments. DETAILED DESCRIPTION

[0023] Filter media (including filter media suitable for hydraulic applications) and related components, systems and methods related to the filter media are provided. The filter media described in the present application may include two or more layers, at least one of the layers having a relatively high percentage of ultra-fine glass fibers. In addition, the filter media can be designed so that the ratio of average fiber diameters between the two layers is relatively small, which can make the interlayer resistance ratio relatively low. In some embodiments, at least one layer of the filter media includes synthetic polymer fibers. Certain filter media described in the present application can have the following desired characteristics: high dust holding capacity and low fluid flow resistance. The media can be incorporated into various filter element products including hydraulic filters.

[0024] like Figure 1 In the illustrated embodiment, the filter medium 10 includes a first layer 20 adjacent to a second layer 30. Optionally, the filter medium 10 can include a third layer 40 adjacent to the second layer. In some cases, additional layers, such as a fourth layer, a fifth layer, or a sixth layer, can also be included. The orientation of the filter medium 10 relative to the fluid flowing through the medium can generally be selected as desired. Figure 1 As shown, the first layer 20 is upstream of the second layer 30 in the direction of fluid flow indicated by arrow 50. However, in other embodiments, the first layer 20 is downstream of the second layer in the direction of fluid flow through the filter media.

[0025] As used herein, when a layer is referred to as being "adjacent" to another layer, it may be directly adjacent to the layer or intervening layers may also exist. A layer being "directly adjacent" or "contacting" another layer means that there are no intervening layers.

[0026] In some cases, each layer of the filter media has different features and filtering properties, such as when the different features and filtering properties are combined to obtain a desired total filtering performance compared to a filter media having a single layer structure. For example, in one set of embodiments, the first layer 20 is a pre-filter layer (also referred to as a "load layer") and the second layer 30 is a main filter layer (also referred to as an "effective layer"). Typically, the pre-filter layer is formed using fibers that are coarser than the fibers of the main filter layer, and therefore, the pre-filter layer has a lower fluid flow resistance than the main filter layer. Compared to the pre-filter layer, one or more main filter layers may include finer fibers and have a higher fluid flow resistance. Thus, compared to the pre-filter layer, the main filter layer can generally capture smaller sized particles. When a third layer 40 is present, the third layer can be an additional main filter layer having the same or different properties as the second layer 30. For example, the third layer can have even finer fibers and a higher fluid flow resistance than the second layer 30. In some embodiments, the third layer includes synthetic polymer fibers as described in more detail below.

[0027] The filter media may also have other configurations of a first layer, a second layer, and optionally a third layer or more layers. For example, in some cases, the filter media 10 does not include a pre-filter layer. In some such embodiments, the first layer 20 is an upstream main filter layer, and the second layer 30 is a main filter layer downstream of the first layer. Optionally, the filter media may include a third layer 40 (e.g., another main filter layer) located downstream of the second layer. The upstream layer may have coarser fibers than the layer downstream of the layer and therefore have a lower resistance to fluid flow than the layer. In some cases, the resistance of each layer increases from the most upstream layer to the most downstream layer.

[0028] In some embodiments, a layer having relatively coarse fibers may be located between two layers having relatively fine fibers. Other configurations are also possible. In addition, the filter media may include any suitable number of layers, for example, at least 2, 3, 4, 5, 6, 7, 8, or 9 layers, depending on the specific application and desired performance characteristics.

[0029] As described above, each layer of the filter media can have different properties. For example, the first layer and the second layer can include fibers having different characteristics (e.g., fiber diameter, fiber composition, and fiber length). The fibers having different characteristics can be made of one material (e.g., by using different process conditions) or different materials (e.g., glass fibers, synthetic fibers (e.g., organic polymer fibers), and combinations thereof). Without wishing to be limited by theory, it is believed that filter media having a multi-layer structure and the multi-layer structure having layers having different characteristics exhibit significantly improved performance characteristics, such as dust holding capacity and / or efficiency, compared to filter media having a single-layer structure.

[0030] In certain embodiments, one or more layers of the filter medium 10 include ultrafine glass fibers, chopped strand glass fibers, or a combination thereof. Ultrafine glass fibers and chopped strand glass fibers are known to those skilled in the art. Those skilled in the art can determine whether a glass fiber is an ultrafine glass fiber or a chopped strand glass fiber by observation (e.g., optical microscope, electron microscope). Ultrafine glass fibers and chopped strand glass fibers may also be chemically different. In some cases, although not required, chopped strand glass fibers may contain a higher content of calcium or sodium than ultrafine glass fibers. For example, chopped strand glass fibers may be nearly free of alkali, but have a high calcium oxide and aluminum oxide content. Ultrafine strand glass fibers may contain 10% to 15% of alkali (e.g., sodium oxide, magnesium oxide) and have a relatively low melting and processing temperature. These terms refer to the technology used to make glass fibers. Such technology imparts certain characteristics to glass fibers. Typically, chopped strand glass fibers are pulled out of a bushing tip and cut into fibers using a process similar to textile production. Chopped glass fibers are produced in a more controlled manner than ultra-fine glass fibers, and therefore, compared with ultra-fine glass fibers, chopped glass fibers are generally less variable in fiber diameter and length. Ultra-fine glass fibers are drawn from a bushing spinneret hole and further undergo a flame blowing or rotary spinning process. In some cases, a remelting process can be utilized to manufacture thin ultra-fine glass fibers. In this respect, ultra-fine glass fibers can be thin or thick. As used herein, the diameter of thin ultra-fine glass fibers is less than 1 micron, and the diameter of thick ultra-fine glass fibers is greater than or equal to 1 micron.

[0031] The ultra-fine glass fibers of one or more layers can have a small diameter, for example, less than 10.0 microns. For example, the average diameter of the ultra-fine glass fibers in the layer can be 0.1 microns to about 9.0 microns; and in some embodiments, about 0.3 microns to about 6.5 microns, or about 1.0 microns to 5.0 microns. In certain embodiments, the average fiber diameter of the ultra-fine glass fibers can be less than about 7.0 microns, less than about 5.0 microns, less than about 3.0 microns, or less than about 1.0 microns. The average diameter distribution of the ultra-fine glass fibers is usually log-normally distributed. However, it is understood that the ultra-fine glass fibers can be arranged with any other suitable average diameter distribution (e.g., Gaussian distribution).

[0032] The length of the microglass fibers can vary significantly due to process variations. The aspect ratio (ratio of length to diameter) of the microglass fibers in the layer can generally be in the range of about 100 to 10,000. In some embodiments, the aspect ratio of the microglass fibers in the layer is in the range of about 200 to 2500; or in the range of about 300 to 600. In some embodiments, the average aspect ratio of the microglass fibers in the layer can be about 1,000; or about 300. It should be understood that the above-mentioned dimensions are not limiting and the microglass fibers can also have other dimensions.

[0033] Thick ultra-fine glass fibers, thin ultra-fine glass fibers, or combinations thereof may be included in the layer. In some embodiments, the weight of the thick ultra-fine glass fibers accounts for about 20% to about 90% of the weight of the glass fibers. In some cases, for example, the weight of the thick ultra-fine glass fibers accounts for about 30% to about 60% of the weight of the glass fibers, or about 40% to about 60% of the weight of the glass fibers. For certain embodiments including thin ultra-fine glass fibers, the weight of the thin ultra-fine glass fibers accounts for about 0% to about 70% of the weight of the glass fibers. In some cases, for example, the weight of the thin ultra-fine glass fibers accounts for about 5% to about 60% of the weight of the glass fibers, or about 30% to about 50% of the weight of the glass fibers.

[0034] The average fiber diameter of the chopped glass fibers can be greater than the diameter of the ultra-fine glass fibers. In some embodiments, the diameter of the chopped glass fibers is greater than about 5 microns. For example, the diameter range can be up to about 30 microns. In some embodiments, the fiber diameter of the chopped glass fibers can be about 5 microns to about 12 microns. In certain embodiments, the average fiber diameter of the chopped fibers can be less than about 10.0 microns, less than about 8.0 microns, less than about 6.0 microns. The average diameter distribution of the chopped glass fibers is usually log-normally distributed. The chopped fiber diameter tends to follow a normal distribution. However, it is understood that the chopped glass fibers can be arranged with any suitable average diameter distribution (e.g., Gaussian distribution). In some embodiments, the length of the chopped glass fibers can be about 0.125 inches to about 1 inch (e.g., about 0.25 inches or about 0.5 inches).

[0035] It should be understood that the above mentioned dimensions are not limiting and the microglass fibers and / or chopped strands may have other dimensions as well.

[0036] In certain embodiments, the ratio of the weight percentage of ultrafine glass fibers to chopped glass fibers provides different characteristics of the filter media. Thus, in some embodiments, one or more layers of the filter media 10 (e.g., upstream layers, downstream layers, first layers, second layers, third layers, etc.) include a relatively large percentage of ultrafine glass fibers compared to chopped glass fibers. For example, at least 70% by weight, or at least 80% by weight, at least 90% by weight, at least 93% by weight, at least 95% by weight, at least 97% by weight, or at least 99% by weight of the fibers in the layer may be ultrafine glass fibers. In certain embodiments, all of the fibers in the layer are ultrafine glass fibers. However, in other embodiments, one or more layers of the filter media 10 (e.g., upstream layers, downstream layers, first layers, second layers, third layers, etc.) include a relatively high percentage of chopped fibers compared to ultrafine glass fibers. For example, at least 50%, at least 60%, at least 70%, or at least 80%, at least 90%, at least 93%, at least 95%, at least 97%, or at least 99% by weight of the fibers in the layer may be chopped fibers. Such percentages of chopped fibers may be in the range of 10 to 20%. (x) = 200 micron rating is particularly useful in certain embodiments greater than 15 microns. In certain embodiments, all fibers in a layer are chopped fibers.

[0037] In some embodiments, one or more layers of the filter medium 10 (e.g., upstream layer, downstream layer, first layer, second layer, third layer, etc.) include a relatively large percentage of ultra-fine glass fibers relative to all components used to form the layer. For example, one or more layers may include at least about 40% by weight, at least about 50% by weight, at least about 60% by weight, at least about 70% by weight, or at least about 80% by weight, at least about 90% by weight, at least about 93% by weight, at least about 95% by weight, at least about 97% by weight, or at least about 99% by weight of ultra-fine glass fibers. In a specific embodiment, one or more layers include ultra-fine glass fibers of about 90% by weight to about 99% by weight (e.g., about 90% by weight to about 95% by weight). In other embodiments, one or more layers include ultra-fine glass fibers of about 40% by weight to about 80% by weight or ultra-fine glass fibers of about 60% by weight to about 80% by weight. It should be understood that in certain embodiments, one or more layers of the filter medium do not include ultra-fine glass fibers within the above range or do not include ultra-fine glass fibers at all.

[0038] Any suitable amount of chopped fibers can be used in one or more layers of the filter media. In some cases, one or more layers include a relatively low percentage of chopped fibers. For example, one or more layers may include less than 30% by weight, or less than 20% by weight, or less than 10% by weight, or less than 5% by weight, or less than 2% by weight, or less than 1% by weight of chopped fibers. In some cases, one or more layers of the filter media do not include any chopped fibers. It should be understood that in certain embodiments, one or more layers of the filter media do not include chopped fibers within the above ranges.

[0039] One or more layers of the filter media 10 may also include microglass fibers having an average fiber diameter within a certain range and comprising a weight percentage of the layer within a certain range. For example, one or more layers of the filter media may include microglass fibers having an average fiber diameter of less than 5 microns and comprising less than about 50%, less than about 40%, less than about 30%, less than about 20%, less than about 10%, or less than about 5% of the microglass fibers in the layer. In some cases, the layer includes 0% of microglass fibers having an average fiber diameter of less than 5 microns. Additionally or alternatively, one or more layers of the filter media may include microglass fibers having an average fiber diameter greater than or equal to 5 microns and comprising greater than about 50%, greater than about 60%, greater than about 70%, greater than about 80%, greater than about 90%, greater than about 93%, or greater than about 97% of the microglass fibers in the layer. In some cases, more than one layer of the filter media includes such characteristics. It should be understood that in some cases one or more layers of the filter media include microglass fibers in a range different than that described above.

[0040] In other embodiments, one or more layers of the filter media include relatively fine fibers. For example, one or more layers of the filter media may include ultrafine glass fibers having an average fiber diameter of less than 5 microns, the ultrafine glass fibers accounting for greater than about 50%, greater than about 60%, greater than about 70%, greater than about 80%, greater than about 90%, greater than about 93%, or greater than about 97% of the ultrafine glass fibers in the layer. Additionally or alternatively, one or more layers of the filter media may include ultrafine glass fibers having an average fiber diameter greater than or equal to 5 microns, accounting for less than about 50%, less than about 40%, less than about 30%, less than about 20%, less than about 10%, or less than about 5% of the ultrafine glass fibers in the layer. In some cases, a layer includes 0% of ultrafine glass fibers having an average diameter greater than or equal to 5 microns. In some cases, more than one layer of the filter media includes this characteristic. It should be understood that in some cases, one or more layers of the filter media include ultrafine glass fibers in a range different from the above ranges.

[0041] In certain embodiments, one or more layers of the filter media 10 include a high percentage of glass fibers (e.g., ultrafine glass fibers and / or chopped glass fibers), regardless of whether the glass fibers in the layer are ultrafine glass fibers or chopped strands. For example, one or more layers (e.g., the first layer and / or the second layer) may contain at least about 40% by weight, at least about 50% by weight, at least about 60% by weight, at least about 70% by weight, at least about 80% by weight, at least about 90% by weight, or at least about 95% by weight of glass fibers. In some cases, all of the fibers in a layer (e.g., the first layer and / or the second layer) are formed of glass. It should be understood that in certain embodiments, one or more layers of the filter media do not include glass fibers within the above ranges or do not include glass fibers at all.

[0042] In some embodiments, regardless of whether the fibers in the layer are glass fibers (such as microglass fibers or chopped fibers) and / or synthetic fibers, the fibers having a fiber diameter of 7 microns or less account for greater than about 60%, greater than about 70%, or greater than about 80% by weight of the fibers in the layer. In some cases, the fibers having a fiber diameter of 5 microns or less account for greater than about 60%, greater than about 70%, or greater than about 80% by weight of the fibers in the layer. In some cases, the fibers having a fiber diameter of 3 microns or less account for greater than about 50%, greater than about 60%, or greater than about 70% by weight of the fibers in the layer.

[0043] In one set of specific embodiments, the filter medium includes a first layer (e.g., a pre-filter layer) having an average fiber diameter of about 1.0 microns to about 10.0 microns, such as about 1.0 microns to about 8.0 microns, whether the fibers in the layer are glass fibers (e.g., microfibers or chopped fibers) and / or synthetic fibers. The average fiber diameter of the second layer (e.g., a main filter layer) of the filter medium can be about 1.0 microns to about 9.0 microns, such as about 0.5 microns to about 5.5 microns. If the filter medium includes a third layer (e.g., downstream of the second layer), the average fiber diameter of the third layer can be about 0.1 microns to about 1.5 microns, or about 0.8 microns to about 5.0 microns, such as about 0.5 microns to about 2.5 microns, or about 0.1 microns to about 1.5 microns, as described below. Additional layers may also be present.

[0044] In some embodiments, the third layer can be composed of particles having an average diameter of less than about 1.5 microns (e.g., about 0.1 microns to about 1.5 microns, about 0.2 microns to about 1.5 microns, about 0.3 microns to about 1.5 microns, about 0.3 microns to about 1.4 microns, about 0.4 microns to about 1.3 microns, about 0.1 microns to about 0.5 microns, about 0.1 microns to about 0.2 microns, about 0.1 microns to about 0.3 microns, about 0.5 microns to about 1.5 microns, about 0.5 microns to about The invention also provides a method for forming fibers having a size of about 1.0 micron, about 0.7 micron to about 1.0 micron, about 0.2 micron to about 0.8 micron, about 0.2 micron to about 0.5 micron, about 0.3 micron to about 0.5 micron, about 0.4 micron to about 0.5 micron, about 0.4 micron to about 0.6 micron, about 0.4 micron to about 0.8 micron, about 0.6 micron to about 0.9 micron, about 0.2 micron to about 0.4 micron, about 0.2 micron to about 0.3 micron, and about 0.3 micron to about 0.4 micron).

[0045] In some embodiments, the third layer includes fibers formed by synthetic polymers. In certain embodiments, the third layer is manufactured according to a meltblown process, and the third layer can be formed by fibers having an average diameter less than about 1.5 microns (e.g., less than about 1.4 microns, less than about 1.3 microns, less than about 1.2 microns, less than about 1.1 microns, less than about 1 micron) and / or at least about 0.2 microns (e.g., at least about 0.3 microns, at least about 0.4 microns, at least about 0.5 microns) measured using a scanning electron microscope. As an example, in some embodiments, a synthetic polymer layer (e.g., a meltblown layer) is formed by fibers having an average diameter of about 0.2 microns to about 1.5 microns (e.g., about 0.3 microns to about 1.5 microns, about 0.3 microns to about 1.4 microns, about 0.4 microns to about 1.3 microns, about 0.7 microns to about 1.0 microns). As another example, in certain embodiments, the synthetic polymer layer (e.g., meltblown layer) is formed by fibers having an average diameter of about 0.2 microns to about 1.5 microns (e.g., about 0.5 microns to about 1.5 microns, about 0.5 microns to about 1.0 microns, about 0.2 microns to about 0.8 microns, about 0.2 microns to about 0.5 microns, about 0.3 microns to about 0.5 microns, about 0.4 microns to about 0.5 microns, about 0.4 microns to about 0.6 microns, about 0.4 microns to about 0.8 microns, about 0.2 microns to about 0.4 microns, about 0.2 microns to about 0.3 microns, about 0.3 microns to about 0.4 microns). In some cases, for example, if the fibers are meltblown, at least about 5% (e.g., at least about 10%, at least about 25%, at least about 50%, at least about 60%, at least about 75%) of the fibers in the synthetic material extend a distance of at least 0.3 microns in a direction substantially perpendicular to the surface of the third layer.

[0046] In some embodiments, the synthetic polymer fibers are formed according to processes such as meltblowing, meltspinning, melt electrospinning, and / or solvent electrospinning, and the fibers have one of the fiber diameter ranges listed above.

[0047] In some embodiments, the filter media 10 is designed such that the average fiber diameter of each layer is different. For example, the ratio of the average fiber diameter between two layers (e.g., between the first layer and the second layer, between the second layer and the third layer, between the first layer and the third layer, or between the upstream layer and the downstream layer, etc.) can be less than 10:1, less than 7:1, less than 5:1, less than 4:1, less than 3:1, less than 2:1, or less than 1:1. In some cases, a small difference in the average fiber diameter between two layers can result in a relatively low resistance ratio between the two layers. The relatively low resistance ratio between the two layers can, in turn, result in a filter media having advantageous properties, such as high dust holding capacity at a relatively low unit weight, as described in detail below.

[0048] Alternatively, the average fiber diameters of the two layers may have a greater difference. For example, the ratio of the average fiber diameters between the two layers (e.g., between the first layer and the second layer, between the second layer and the third layer, or between the first layer and the third layer) may be greater than 1:1, greater than 2:1, greater than 3:1, greater than 4:1, greater than 5:1, greater than 7:1, or greater than 10:1.

[0049] The third layer may be formed from fibers having a certain average length. For example, in some embodiments, the third layer may be formed from fibers having an average length of about 0.1 inches to about 1,000 inches or about 1 inch to about 100 inches.

[0050] The fibers in the third layer can have an average aspect ratio. For example, in some embodiments, the fibers in the third layer can have an average aspect ratio of about 5 to about 1,000,000 or about 10 to about 100,000.

[0051] The third layer can generally have any suitable thickness.In some embodiments, the thickness of the third layer is at least about 5 microns (for example, at least about 10 microns, at least about 20 microns, at least about 30 microns), and / or less than about 500 microns (for example, less than about 400 microns, less than about 200 microns, less than about 180 microns, less than about 150 microns).For example, the thickness of the third layer can be about 5 microns to about 500 microns (for example, about 5 microns to about 250 microns, about 10 microns to about 200 microns, about 20 microns to about 150 microns, about 30 microns to about 500 microns, about 50 microns to about 100 microns).According to TAPPI T411, use suitable calliper (for example, 200-A type electronic microcaliper manufactured by Emveco, tested under 1.5psi) to determine the thickness as indicated in the application.In some cases, if the thickness of the layer can not be determined using suitable calliper, then the visualization technology such as scanning electron microscope observed with cross section can be used.

[0052] The basis weight of the third layer can generally be selected as desired. In some embodiments, the basis weight of the third layer is at least about 1 g / m 2 (e.g., at least about 10 g / m 2 , at least about 25g / m 2 ) and / or less than about 100 g / m 2 (less than about 90g / m 2 , less than about 75g / m 2 , less than about 40g / m 2 , less than about 30g / m 2 , less than about 25g / m 2 or less than about 20g / m 2 For example, in certain embodiments, the basis weight of the third layer is about 1 g / m 2 About 100g / m 2 (For example, about 10 g / m 2 About 90g / m 2 , about 20g / m 2 About 30g / m 2 , about 15g / m 2 About 40g / m 2 , about 25g / m 2 About 75g / m 2 , about 2g / m 2 About 20g / m 2 , about 4g / m 2 About 12g / m 2 ).

[0053] The median flow pore size of the third layer can be changed as needed. For example, the median flow pore size of the third layer can be about 5 microns to about 50 microns, about 10 microns to about 30 microns, about 10 microns to about 20 microns, 5 microns to 15 microns, about 8 microns to about 12 microns, about 1 micron to about 5 microns, about 5 microns to about 9 microns, or about 13 microns to about 17 microns. As used in this application, the median flow pore size refers to the median flow pore size measured by using a capillary flow microporometer manufactured by Porous Materials, Inc. according to ASTM F316-03 standard.

[0054] The air permeability of the third layer can also be changed as needed. In some embodiments, the air permeability of the third layer is less than about 500 CFM (e.g., less than about 250 CFM, less than about 200 CFM) and / or at least about 20 CFM (e.g., at least about 50 CFM, at least about 100 CFM). For example, in some embodiments, the air permeability of the third layer can be about 20 CFM to about 500 CFM (e.g., about 50 CFM to about 250 CFM, about 100 CFM to about 200 CFM).

[0055] As described in the present application, in addition to or in place of glass fibers, one or more layers of the filter medium can include components such as synthetic fibers (e.g., synthetic polymer fibers). For example, one or more layers of the filter medium 10 can include a relatively high percentage of synthetic fibers, for example, at least about 50% by weight, at least about 60% by weight, at least about 70% by weight, at least about 80% by weight, at least about 90% by weight, at least about 95% by weight, at least about 97% by weight, at least about 99% by weight, or at least about 100% by weight of synthetic fibers (e.g., synthetic polymer fibers). In some cases, at least two layers of the filter medium or the entire filter medium include such percentages of synthetic fibers. Advantageously, synthetic fibers can be advantageous for moisture resistance, heat resistance, long-term aging resistance, and resistance to microbial degradation. In other embodiments, synthetic fibers account for a small percentage of the weight of the filter medium. For example, one or more layers of the filter medium can include less than or equal to about 25% by weight, less than or equal to about 15% by weight, less than or equal to about 5% by weight, or less than or equal to about 2% by weight of synthetic fibers. In some cases, one or more layers of the filter media do not include any synthetic fibers. It should be understood that synthetic fibers can be incorporated into filter media outside the disclosed range. Synthetic fibers can enhance the adhesion of glass fibers within the web during processing. Synthetic fibers can be, for example, binder fibers, bicomponent fibers (e.g., bicomponent binder fibers), and / or staple fibers.

[0056] In general, the synthetic fiber in any layer can have any suitable composition. In some cases, the synthetic fiber includes a thermoplastic material. The non-limiting examples of synthetic fibers include PVA (polyvinyl alcohol), polyester (e.g., polybutylene terephthalate, polybutylene naphthalate), polyethylene, polypropylene, acrylic polymers, polyolefins, polyamides (e.g., nylon), rayon, polycarbonate, polyphenylene sulfide, polystyrene, polybutylene terephthalate, polyurethane (e.g., thermoplastic polyurethane), regenerated cellulose and combinations thereof. Optionally, polymers can include fluorine atoms. Examples of such polymers include PVDF and PTFE. It should be understood that other suitable synthetic fibers may also be used. In some embodiments, the hydraulic fluid for hydraulic applications of synthetic fibers is chemically stable. Synthetic fibers may be formed by any suitable process (e.g., melt-blown, melt electrostatic spinning and / or solvent electrostatic spinning process).

[0057] In one group of embodiments, the synthetic fiber is a bicomponent fiber. Each component in the bicomponent fiber can have a different melting temperature. For example, the fiber can include a core and a sheath, wherein the activation temperature of the sheath is lower than the melting temperature of the core. This allows the sheath to melt before the core, so that the sheath is bonded to other fibers in the layer, while the core maintains its structural integrity. This is particularly conducive to forming a more adhesive layer for capturing filtrate. The core / sheath bonded fiber can be concentric or non-concentric, and exemplary core / sheath bonded fibers can include the following: polyester core / copolyester sheath, polyester core / polyethylene sheath, polyester core / polypropylene sheath, polypropylene core / polyethylene sheath and combinations thereof. Other exemplary bicomponent fibers can include split fiber fiber, side-by-side fiber and / or "island in the sea" fiber.

[0058] Alternatively, one or more layers of the filter media may include other types of fibers, such as cellulosic pulp fibers (eg, wood pulp fibers).

[0059] The filter medium can also include a binder. The binder usually accounts for a small weight percentage of the filter medium. For example, the binder can account for less than about 10 weight % or less than about 5 weight % (e.g., about 2% to about 5%) of the filter medium. In some embodiments, the binder can be about 4 weight % of the filter medium. As further described below, the binder can be added to the fiber in the wet fiber web state. In some embodiments, the binder coats the fiber and is used to make the fiber adhere to each other to promote attachment between the fibers.

[0060] In general, the binder can have any suitable composition. In some embodiments, the binder is resin-based. The binder can be in the form of one or more components, such as the binder can be in the form of a bicomponent fiber (e.g., the bicomponent fiber described above). However, it should be understood that not all embodiments include all of these components, but other suitable additives can be introduced.

[0061] In addition to the binders, glass components, and synthetic components described above, the filter media may include various other suitable additives (usually in small weight percentages), such as surfactants, coupling agents, cross-linking agents, and the like.

[0062] The fibrous media may have various desirable properties and characteristics that make it particularly suitable for hydraulic applications. However, it should be understood that the filter media described herein is not limited to hydraulic applications and the media may be used in other applications, such as air filtration or filtration of other liquids and gases.

[0063] Filter media 10, including one or more layers of filter media, may also have varying basis weights, pore sizes, thicknesses, permeabilities, dust holding capacities, efficiencies, and pressure drops, depending on the requirements of the desired application.

[0064] The overall basis weight of the filter media can vary with factors such as the strength requirements of a given filtration application, the number of layers in the filter media, the location of the layers (e.g., upstream, downstream, intermediate) and the materials used to form the layers, as well as the desired level of filtration efficiency and the level of resistance or pressure drop allowed. In certain embodiments described herein, enhanced performance (e.g., low resistance or pressure drop) is observed when the filter media includes multiple layers with different characteristics, each of which has a relatively low basis weight compared to certain single or multi-layer media. Therefore, some such filter media can also have a lower overall basis weight while achieving high performance characteristics. For example, the overall basis weight of the filter media (or two or more layers of the filter media) can range from about 20 to 200 g / m 2 , or about 90g / m 2 Up to 150g / m 2 In some embodiments, the total unit weight is less than about 200 g / m 2 , less than about 170g / m 2 , less than about 150g / m 2 , less than about 130g / m 2 , less than about 120g / m 2 , less than about 110g / m 2 , less than about 100g / m 2 , less than about 90g / m 2 , less than about 80g / m2 , less than about 70g / m 2 , less than about 70g / m 2 or less than about 60g / m 2 As determined herein, the total basis weight of the filter media is measured in accordance with Technical Association of the American Pulp and Paper Industry (TAPPI) standard T410. This value is expressed as grams per square meter or pounds per 3,000 square feet. The basis weight can generally be measured with a laboratory balance accurate to 0.1 gram.

[0065] In certain embodiments, one or more of the upstream layer, downstream layer, pre-filter layer, main filter layer, first layer, second layer, or third layer of the filter medium 10 can have a relatively low basis weight. In some embodiments, reducing the basis weight of one or more layers can allow the filter medium to have additional layers (e.g., at least three layers) while keeping the overall basis weight relatively low or within a certain range. For example, the basis weight of one or more such layers (or a combination of two or more layers) can range from about 10 to about 100 g / m 2 , about 20g / m 2 About 70g / m 2 or about 20g / m 2 About 50g / m 2 In some embodiments, one or more layers of the filter media, such as the first layer, the second layer, and / or the third layer (or a combination of two or more layers), have a basis weight of less than about 100 g / m 2 , less than about 90g / m 2 , less than about 80g / m 2 , less than about 70g / m 2 , less than about 60g / m 2 , less than about 50g / m 2 , less than about 40g / m 2 , less than about 30g / m 2 , less than about 20g / m 2 or less than about 10g / m 2 .

[0066] In one set of specific embodiments, the filter medium includes a first layer (e.g., a pre-filter layer) having a basis weight of about 5 g / m 2 About 70g / m 2 , for example about 40g / m 2 About 60g / m 2 The filter media may include a second layer (eg, a first main filter layer) adjacent to (eg, directly adjacent to) the first layer and having a basis weight of about 5 g / m 2 About 70g / m 2 , for example about 30g / m2 About 40g / m 2 In some cases, the filter media includes a third layer (e.g., a second main filter layer) adjacent to (e.g., directly adjacent to) the second layer, the third layer having a basis weight of about 5 g / m 2 About 70g / m 2 , for example about 30g / m 2 About 40g / m 2 Additional layers and alternative basis weight ranges are also possible.

[0067] In general, the ratio of unit weights between two different layers of the filter media (e.g., between the first layer and the second layer, between the second layer and the third layer, between the first layer and the third layer, etc.) can vary depending on the desired properties of the filter media. In some embodiments, the unit weight of the upstream layer (e.g., the pre-filter layer) of the filter media is greater than the unit weight of the downstream layer (e.g., the main filter layer). For example, the ratio of unit weights between the upstream layer and the downstream layer can be greater than 1:1, greater than 1.5:1, or greater than 2:1. However, in other embodiments, the unit weight of the upstream layer of the filter media is less than the unit weight of the downstream layer, for example, the ratio of unit weights between the upstream layer and the downstream layer can be less than 2:1, less than 1.5:1, or less than 1:1. In certain embodiments, the ratio of unit weights between the upstream layer and the downstream layer is 1:1.

[0068] The total thickness of the filter media can be from about 5 mils to 300 mils, such as from about 50 mils to about 200 mils. The thickness of the layer of the filter media can be from about 3 mils to about 100 mils, from about 3 mils to about 70 mils, from about 3 mils to about 60 mils, from about 3 mils to about 50 mils, from about 3 mils to about 40 mils, from about 3 mils to about 30 mils, from about 3 mils to about 20 mils, or from about 3 mils to about 10 mils. As described above, according to TAPPI T411, the thickness is determined using a suitable caliper (e.g., a 200-A electronic microcaliper manufactured by Emveco, tested at 1.5 psi).

[0069] In one set of specific embodiments, the filter medium includes a first layer (e.g., a pre-filter layer) having a thickness of about 3 mils to about 70 mils, such as about 15 mils to about 20 mils. The filter medium may include a second layer (e.g., a main filter layer) having a thickness of about 3 mils to about 60 mils, such as about 5 mils to about 10 mils. The filter medium may optionally include a third layer (e.g., downstream of the second layer) having a thickness of about 3 mils to about 60 mils, such as about 5 mils to about 10 mils. Additional layers are also possible.

[0070] The air permeability of the filter media 10 can generally be selected as desired. In some embodiments, the total permeability of the filter media can be about 2 cubic feet per minute per square foot (cfm / sf) to about 250 cfm / sf, about 7 cfm / sf to about 200 cfm / sf, about 15 cfm / sf to about 135 cfm / sf, about 15 cfm / sf to about 50 cfm / sf, about 2 cfm / sf to about 50 cfm / sf, or about 10 cfm / sf to about 40 cfm / sf. The total permeability of the filter media can be greater than about 10 cfm / sf, greater than about 20 cfm / sf, greater than about 25 cfm / sf, greater than about 30 cfm / sf, greater than about 35 cfm / sf, greater than about 40 cfm / sf, greater than about 45 cfm / sf, or greater than about 50 cfm / sf. As determined herein, the permeability of filter media is measured according to TAPPI Method T251. The permeability of filter media is an inverse function of flow resistance and can be measured using a Frazier permeability tester. The Frazier permeability tester measures the volume of air passing through a unit sample area per unit time at a fixed differential pressure across the sample. The permeability can be expressed as cubic feet per minute per square foot at a differential pressure of 0.5 inches of water.

[0071] The permeability of each layer of the filter media 10 may also vary. In some embodiments, one or more layers of the filter media (e.g., the upstream layer, the downstream layer, the first layer, the second layer, the third layer, etc.) have a permeability of about 3 cfm / sf to about 4000 cfm / sf, about 15 cfm / sf to about 700 cfm / sf, about 4 cfm / sf to about 400 cfm / sf, about 5 cfm / sf to about 250 cfm / sf, about 7 cfm / sf to about 200 cfm / sf, about 150 cfm / sf to about 250 cfm / sf, about 15 cfm / sf to about 150 cfm / sf, about 15 cfm / sf to about 50 cfm / sf, or about 4 cfm / sf to about 60 cfm / sf.

[0072] In one set of specific embodiments, the total permeability of the multilayer filter medium is about 2 cfm / sf to about 200 cfm / sf, such as about 3 cfm / sf to about 50 cfm / sf. The filter medium may include a first layer (e.g., a pre-filter layer) having a permeability of about 3 cfm / sf to about 4000 cfm / sf, such as about 15 cfm / sf to about 700 cfm / sf. The filter medium may include a second layer (e.g., adjacent to the pre-filter layer if the pre-filter layer is present) having a permeability of about 4 cfm / sf to about 800 cfm / sf, such as about 7 cfm / sf to about 400 cfm / sf. If the filter medium includes a third layer, the permeability of the layer may be about 2 cfm / sf to about 300 cfm / sf, such as about 4 cfm / sf to about 60 cfm / sf.

[0073] In certain embodiments, the permeability of one or more layers of the filter media is greater than or equal to about 20 cfm / sf, greater than or equal to about 50 cfm / sf, greater than or equal to about 80 cfm / sf, greater than or equal to about 100 cfm / sf, greater than or equal to about 130 cfm / sf, greater than or equal to about 160 cfm / sf, greater than or equal to about 190 cfm / sf, greater than or equal to about 210 cfm / sf, greater than or equal to about 230 cfm / sf, or greater than or equal to about 250 cfm / sf. In other embodiments, the permeability of one or more layers of the filter media is less than or equal to about 250 cfm / sf, less than or equal to about 220 cfm / sf, less than or equal to about 190 cfm / sf, less than or equal to about 160 cfm / sf, less than or equal to about 140 cfm / sf, less than or equal to about 120 cfm / sf, less than or equal to about 100 cfm / sf, less than or equal to about 80 cfm / sf, less than or equal to about 50 cfm / sf, or less than or equal to about 30 cfm / sf. Typically, the upstream layer has a greater permeability (lower resistance) and / or a lower pressure drop than the downstream layer, but other configurations are possible.

[0074] In certain embodiments, the permeability of the upstream layer of the filter medium (e.g., a pre-filter layer, or the top layer of the main filter layer) is greater than or equal to about 100 cfm / sf, greater than or equal to about 150 cfm / sf, or greater than or equal to about 200 cfm / sf, and the permeability of the downstream layer is less than or equal to about 200 cfm / sf, less than or equal to about 150 cfm / sf, less than or equal to about 100 cfm / sf, or less than or equal to about 50 cfm / sf.

[0075] Certain filter media can have a relatively low resistance ratio between two layers or a resistance ratio between two layers within a certain range, which provides advantageous filtration characteristics. For example, the resistance ratio between the second layer including fibers having a small average diameter and the first layer including fibers having a relatively large average diameter can be relatively low. In some cases, the second layer is downstream of the first layer, such as Figure 1 As shown. For example, in a specific embodiment, the second layer is the main filter layer and the first layer is the pre-filter layer. In another embodiment, the second layer is the downstream main filter layer and the first layer is the upstream filter layer. Other combinations are also possible. The resistance ratio between two layers (for example, between the second layer and the first layer, between the downstream layer and the upstream layer, between the main layer and the pre-filter layer, or between two main layers, etc.) is calculated as the ratio of the resistance of the layer with a relatively smaller average fiber diameter to the resistance of the layer with a relatively larger average fiber diameter, and the resistance ratio can be, for example, 0.5:1 to 15:1, 1:1 to 10:1, 1:1 to 7:1, 1:1 to 5:1, or 1:1 to 3.5:1. In some cases, the resistance ratio between the two layers is less than 15:1, less than 12:1, less than 10:1, less than 8:1, less than 6:1, less than 5:1, less than 4:1, less than 3:1, or less than 2:1, for example, while being above a certain value, such as greater than 0.01:1, greater than 0.1:1, or greater than 1:1. Advantageously, a range of resistance ratios (including low resistance ratios in some embodiments) can result in filter media having advantageous properties, such as high dust holding capacity and / or high efficiency, while maintaining a relatively low overall unit weight. Such features can allow filter media to be used in a variety of applications.

[0076] In one set of specific embodiments, the resistance ratio between the main filter layer of the filter medium and the pre-filter layer adjacent (e.g., directly adjacent) to the main filter layer is 0.5: 1 to 7: 1, 1: 1 to 5: 1, or 1: 1 to 3.5: 1. If the filter medium includes an additional main filter layer, the resistance ratio between the downstream main filter layer and the upstream main filter layer can be 1: 1 to 12: 1, 1: 1 to 8: 1, 1: 1 to 6: 1, or 1: 1 to 4: 1. Additional layers are also possible.

[0077] The resistance of a layer can be normalized relative to the unit weight of the layer to obtain a normalized resistance (e.g., the resistance of the layer divided by the unit weight of the layer). In some cases, the normalized resistance ratio between two layers (e.g., a second layer including fibers with a small average diameter and a first layer including fibers with a relatively large average diameter) is relatively low. For example, in a specific embodiment, the second layer is the main filter layer and the first layer is the pre-filter layer. In another embodiment, the second layer is the downstream main filter layer and the first layer is the upstream filter layer. Other combinations are also possible. The normalized resistance ratio between two layers (e.g., between the second layer and the first layer, between the downstream layer and the upstream layer, between the main layer and the pre-filter layer, or between two main layers, etc.) is calculated as the ratio of the normalized resistance of the layer with a relatively small average fiber diameter to the normalized resistance of the layer with a relatively large average fiber diameter, and the normalized resistance ratio can be, for example, 1:1 to 15:1, 1:1 to 10:1, 1:1 to 8:1, 1:1 to 5:1, or 1:1 to 3:1. In some cases, the normalized resistance ratio between the two layers is less than 15:1, less than 12:1, less than 10:1, less than 8:1, less than 6:1, less than 5:1, less than 4:1, less than 3:1 or less than 2:1, for example, while being above a certain value, such as greater than 0.01:1, greater than 0.1:1 or greater than 1:1.

[0078] In one set of specific embodiments, the normalized resistance ratio between the main filter layer of the filter medium and the pre-filter layer adjacent (e.g., directly adjacent) to the main filter layer is 1: 1 to 8: 1, 1: 1 to 5: 1, or 1: 1 to 3: 1. If the filter medium includes an additional main filter layer, the resistance ratio between the downstream main filter layer and the upstream main filter layer can be 1: 1 to 10: 1, 1: 1 to 8: 1, 1: 1 to 6: 1, 1: 1 to 4: 1, or 3: 1 to 4: 1. Additional layers are also possible.

[0079] In another set of specific embodiments, the filter media comprises: a normalized resistance ratio of the second layer to the first layer of 4:1 or greater; and a normalized resistance ratio of the third layer to the second layer of 4:1 or less. In some embodiments, the filter media comprises: a normalized resistance ratio of the second layer to the first layer of 4:1 to 6:1; and a normalized resistance ratio of the third layer to the second layer of 2:1 or 4:1. In some cases, the third layer in such embodiments comprises synthetic polymer fibers having one of the weight percentages described herein.

[0080] The filter medium 10 may also have good dust holding properties. For example, the total dust holding capacity (DHC) of the filter medium 10 is at least about 100 g / m 2 , at least about 120g / m 2 , at least about 140g / m 2 , at least about 150g / m2 , at least about 160g / m 2 , at least about 180g / m 2 , at least about 200g / m 2 , at least about 220g / m 2 , at least about 240g / m 2 , at least about 260g / m 2 , at least about 280g / m 2 Or at least about 300g / m 2 The dust holding capacity as referred to in this application was tested based on a multiple filter test according to the ISO 16889 procedure (modified by testing flat plate samples) on a multiple filter test stand manufactured by FTI. The test used an ISO A3 media test dust manufactured by PTI at an upstream gravity dust level of 10 mg / L. The test fluid was aviation hydraulic fluid AERO HFA MILH-5606A manufactured by Mobil. The test was conducted at a face velocity of 0.14 m / min until a final pressure of 172 kPa above the baseline filter pressure drop was obtained.

[0081] The dust holding capacity of the filter media can be normalized relative to the unit weight of the media to produce a specific capacity (e.g., the dust holding capacity of the media divided by the unit weight of the media). The specific capacity of the filter media described herein can be, for example, 1.5 to 3.0, 1.7 to 2.7, or 1.8 to 2.5. In certain embodiments, the specific capacity of the filter media is greater than or equal to 1.5, greater than or equal to 1.6, greater than or equal to 1.7, greater than or equal to 1.8, greater than or equal to 1.9, greater than or equal to 2.0, greater than or equal to 2.1, greater than or equal to 2.2, greater than or equal to 2.3, greater than or equal to 2.4, greater than or equal to 2.5, greater than or equal to 2.6, greater than or equal to 2.7, greater than or equal to 2.8, greater than or equal to 2.9, or greater than or equal to 3.0.

[0082] The dust holding capacity of a filter medium can also be measured relative to the total unit weight of the medium and the filtration ratio (β (x) ) to obtain a dimensionless value, i.e., "x micron absolute specific capacity". For example, for capturing particles of 10 microns or larger and having a specific β (10) For filter media with a dust holding capacity of 10 microns or larger, this can be calculated by multiplying the dust holding capacity of the media by the β (x) The square root of the log value of the value is taken and divided by the total unit weight of the media to calculate the "10 micron absolute specific capacity" of the media.

[0083] In certain embodiments, the filter media having two (or more) layers has an absolute specific capacity at 10 microns of greater than about 2.5, greater than about 2.65, greater than about 2.7, greater than about 2.75, greater than about 3.0, greater than about 3.4, greater than about 3.5, greater than about 3.6, greater than about 3.75, greater than about 4.0, greater than about 4.25, greater than about 4.5, greater than about 4.75, or greater than about 5.0. The total basis weight of the filter media can also be, for example, less than about 200 g / m 2 , less than about 150g / m 2 , less than about 100g / m 2 , less than about 90g / m 2 , less than about 80g / m 2 , less than about 75g / m 2 , less than about 70g / m 2 , less than about 68g / m 2 , less than about 65g / m 2 , less than about 60g / m 2 or less than about 50g / m 2 Other values ​​and ranges of absolute specific capacity and unit weight are possible.

[0084] In certain embodiments, the 10 micron absolute specific capacity of the filter media having three (or more) layers is greater than about 2.0, greater than about 2.25, greater than about 2.5, greater than about 2.6, greater than about 2.65, greater than about 2.75, greater than about 3.0, greater than about 3.5, greater than about 3.75, greater than about 4.0, greater than about 4.25, or greater than about 4.5. In addition, the total basis weight of the filter media can be, for example, less than about 200 g / m 2 , less than about 190g / m 2 , less than about 180g / m 2 , less than about 170g / m 2 , less than about 160g / m 2 , less than about 150g / m 2 , less than about 140g / m 2 , less than about 130g / m 2 , less than about 120g / m 2 , less than about 110g / m 2 , less than about 100g / m 2 , less than about 90g / m 2 , or less than about 80g / m 2 Other values ​​and ranges of absolute specific capacity and unit weight are possible.

[0085] In some embodiments, the filter media described herein include a relatively high total dust holding capacity (e.g., one of the above values) and a relatively high total permeability (e.g., one of the above values). For example, the filter media can have: at least about 150 g / m 2 (e.g., at least about 180 g / m 2 , at least about 200g / m 2 , at least about 230g / m 2 , at least about 250g / m 2 ) of total dust holding capacity; and a total permeability of greater than about 25 cfm / sf (e.g., greater than about 30 cfm / sf, greater than about 35 cfm / sf, greater than about 40 cfm / sf, greater than about 45 cfm / sf, or greater than about 50 cfm / sf). In certain embodiments, these performance characteristics are achieved using a filter media that includes a third layer comprising synthetic polymer fibers (e.g., a third layer comprising at least about 40 wt%, at least about 60 wt%, at least about 80 wt%, at least about 90 wt%, at least about 95 wt%, or about 100 wt% synthetic fibers).

[0086] The filter media described herein can be used to filter particles of various sizes, such as particles less than or equal to about 20 microns, less than or equal to about 15 microns, less than or equal to about 10 microns, less than or equal to about 5 microns, less than or equal to about 3 microns, or less than or equal to about 1 micron. The filtration efficiency of such particle sizes can be measured using multiple filtration tests. For example, the filtration efficiency values ​​are determined according to the ISO 16889 procedure (modified by testing flat plate samples) on a multiple filtration test bench manufactured by FTI. The test uses an ISO A3 media test dust manufactured by PTI at an upstream gravity dust level of 10 mg / L. The test fluid is an aviation hydraulic fluid AERO HFAMIL H-5606A manufactured by Mobil. The test is performed at a face velocity of 0.14 m / min until a final pressure of 172 kPa above the baseline filtration pressure drop is obtained. Particle counts (particles / ml) at selected particle sizes (e.g., 1, 3, 4, 5, 7, 10, 15, 20, 25, or 30 microns) upstream and downstream of the media can be taken at ten equally spaced points over the test time. The upstream and downstream particle counts for each selected particle size can be averaged. Based on the upstream average particle count (injected-C0) and the downstream average particle count (passed-C), the liquid filtration efficiency test value for each selected particle size can be determined by the relationship [(100-[C / C0])*100%].

[0087] Efficiency can also be expressed as a β value (or β ratio), where β (x)= y is the ratio of upstream counts (C0) to downstream counts (C), where x is the smallest particle size that yields an actual ratio of C0 / C equal to y. The penetration fraction of the medium is 1 divided by β (x) value (y), the efficiency fraction is 1-penetration fraction. Accordingly, the medium efficiency is 100 times the efficiency fraction, and 100*(1-1 / β (x) ) = efficiency percentage. For example, β (x) = 200 has an efficiency of [1-(1 / 200)]*100 or 99.5% for particles of x microns or larger. The filter media described in the present application can have a wide range of β values, such as β (x) =y, where x can be, for example, 1, 3, 5, 7, 10, 12, 15, 20, 25, 30, 50, 70, or 100, and where y can be, for example, at least 2, at least 10, at least 75, at least 100, at least 200, or at least 1000. It should also be understood that other values ​​of x and y are possible; for example, in some cases, y can be greater than 1000. It should be understood that for any value of x, y can be any number representing the actual ratio of CO / C (e.g., 10.2, 12.4). Similarly, for any value of y, x can be any number representing the minimum particle size that results in an actual ratio of CO / C equal to y.

[0088] In certain embodiments, the third layer of the filter media described herein has: a median flow pore size as described herein (e.g., from about 5 microns to about 50 microns, from about 10 microns to about 30 microns, from about 10 microns to about 20 microns, from 5 microns to 15 microns, from 8 microns to 12 microns, from about 1 micron to about 5 microns, from about 5 microns to about 9 microns, or from about 13 microns to about 17 microns); and a β (x) An efficiency equal to at least 200. In some cases, the third layer has a β (x) = an efficiency of at least 200 and a median flow pore size of x ± 2 microns. For example, if x = 10 and the third layer has β (10) If the efficiency is equal to at least 200, the median flow pore size of the third layer can be 10±2 microns (i.e., 8-12 microns). In other cases, the third layer has a β (x) Efficiency equal to at least 200 and median flow pore size of x ± 1 micron.

[0089] The filter medium can be produced using a process based on known technology. In some cases, a wet laid or dry laid process is used to produce the filter medium. Typically, the wet laid process includes mixing the fibers together; for example, glass fibers (e.g., chopped and / or ultrafine glass fibers) can be optionally mixed with any synthetic fibers to provide a glass fiber slurry. In some cases, the slurry is a water-based slurry. In certain embodiments, the ultrafine glass fibers and optionally any chopped fibers and / or synthetic fibers are stored in different storage tanks before being mixed together. Before being mixed together, the fibers can be processed by a pulping machine. In some embodiments, before being mixed together, the combination of chopped glass fibers, ultrafine glass fibers and / or synthetic fibers is processed by a pulping machine and / or a storage tank. As described above, the ultrafine glass fibers can include thin ultrafine glass fibers and thick ultrafine glass fibers.

[0090] It should be understood that any suitable method of forming the glass fiber slurry can be used. In some cases, additional additives are added to the slurry to facilitate processing. The temperature can also be adjusted to a suitable range, such as 33°F to 100°F (e.g., 50°F to 85°F). In some embodiments, the slurry temperature is maintained. In some cases, the temperature is not actively adjusted.

[0091] In some embodiments, the wet-laid web process uses equipment similar to conventional papermaking processes, including a hydraulic pulper, a former or headbox, a dryer, and an optional converter. For example, the slurry can be prepared in one or more pulpers. After the slurry in the pulper is properly mixed, the slurry can be pumped to the headbox, where the slurry may or may not be combined with other slurries, or additives may or may not be added. The slurry can also be diluted with additional water so that the final concentration of the fiber is within a suitable range, for example, about 0.1% to 0.5% by weight.

[0092] In some cases, the pH of the glass fiber slurry can be adjusted as desired. For example, the pH of the glass fiber slurry can be from about 1.5 to about 4.5, or from about 2.6 to about 3.2.

[0093] Before the slurry is sent to the headbox, the slurry can be passed through a centrifugal cleaner to remove unfiberized glass or shot. The slurry may or may not be passed through additional equipment such as a refiner or a high-frequency deflaker to further enhance fiber dispersion. The fibers can then be collected on a screen or wire at a suitable rate using any suitable machine such as a Fourdrinier, vacuum cylinder, drum, or inclined Fourdrinier.

[0094] In some embodiments, this process comprises that adhesive (and / or other components) is introduced into preformed glass fiber layer.In some embodiments, when glass fiber layer passes through along suitable screen or net, utilize applicable technology to can be the different components that are included in adhesive in separate emulsion form to add in glass fiber layer.In some cases, every kind of component of adhesive resin is mixed as emulsion before combining with other components and / or glass fiber layer.In some embodiments, the component included in adhesive can utilize for example gravity and / or vacuum to pass glass fiber layer.In some embodiments, one or more components included in adhesive can use softened water to dilute and be pumped in glass fiber layer.

[0095] As described above, different glass fiber layers can be combined to form a filter medium based on the desired properties. For example, in some embodiments, a relatively coarse pre-filter layer can be combined with a relatively fine fiber layer (i.e., a main filter layer) to form a multi-layer filter medium. Optionally, the filter medium can include one or more additional finer fiber layers as described above.

[0096] The multiphase filter medium can be formed in a suitable manner. For example, the filter medium or a portion thereof can be prepared by a wet-laid process, wherein a first glass fiber slurry (e.g., glass fibers in an aqueous solvent such as water) is applied to a mesh conveyor belt to form a first layer. Then, a second glass fiber slurry (e.g., glass fibers in an aqueous solvent such as water) is applied to the first layer. During the above process, a vacuum can be continuously applied to the first slurry and the second slurry to remove the solvent from the fibers so that the first layer and the second layer are simultaneously formed into a composite product. Then, the composite product is dried. Due to the manufacturing process, at least a portion of the fibers in the first layer can be interwoven with at least a portion of the fibers in the second layer (e.g., at the interface between the two layers). Additional layers can also be formed and added using similar processes or different processes such as lamination, co-pleating or finishing (i.e., placed directly adjacent to each other and held together by pressure). For example, in some cases, two layers (e.g., two fine fiber layers) are formed into a composite product by a wet-laid process, in which separate fiber slurries are stacked on top of each other while water is extracted from the slurries, and the composite product is then combined with a third layer (e.g., a pre-filter layer) by any suitable process (e.g., lamination, co-pleating, or finishing). It is understood that the filter media or composite products formed by the wet-laid process can be appropriately adjusted not only based on the composition of each fiber layer, but also based on the effect of using multiple fiber layers of different characteristics in appropriate combinations to form a filter medium having the characteristics described herein.

[0097] In one set of embodiments, at least two layers of the filter media (e.g., one layer and a composite article including more than one layer, or two composite articles including more than one layer) are laminated together. For example, a first layer (e.g., a pre-filter layer including relatively coarse fibers) can be laminated with a second layer (e.g., a main filter layer including relatively fine fibers), wherein the first layer and the second layer face each other to form a single multi-layer article (e.g., a composite article) that is integrally combined in a single production line assembly operation to form the filter media. If desired, the first layer and the second layer can be combined with an additional main filter layer (e.g., a third layer) using any suitable process before or after the lamination step. In other embodiments, two or more layers (e.g., a main filter layer) are laminated together to form a multi-layer article. After the two or more layers are laminated into a composite article, the composite article can be combined with additional layers by any suitable process.

[0098] In other embodiments, a dry-laid process is used. In a dry-laid process, glass fibers are chopped and dispersed in air and blown onto a conveyor belt before a binder is applied. Dry-laid processes are generally more suitable for producing highly porous media, including glass fiber bundles.

[0099] In some embodiments, one or more layers (e.g., the third layer) of the filter medium described in this application can be produced according to a meltblown process. For example, the meltblown process and manufacturing method described in U.S. Patent Publication No. 2009 / 0120048, which is called "Meltblown Filter Medium", can be used. For various purposes, the entire content of the patent is incorporated by reference into the present application, and the patent includes the lamination technology described in the present application. Electrostatic spinning technology can also be used to form one or more layers described in the present application. A synthetic polymer layer can be manufactured and adhered to a single-phase layer or a multi-phase layer in any suitable manner. In some embodiments, the layer comprising a synthetic polymer can be positioned downstream relative to a single-phase layer or a multi-phase layer, or vice versa.

[0100] During or after the formation of a layer, a composite product including two or more combined layers, or a final filter medium, the layer, composite product, or final filter medium can be further processed according to various known techniques. For example, the filter medium or a portion thereof can be pleated and used in a pleated filter element. For example, two layers can be combined by a co-pleating process. In some embodiments, the filter medium or its individual layers can be appropriately pleated by forming score lines at appropriate intervals from each other to allow the filter medium to be folded. It should be understood that any suitable pleating technology can be used. In some embodiments, the physical and mechanical qualities of the filter medium can be adjusted to set an increased number of pleats, which can be directly proportional to the increased surface area of ​​the filter medium. The increased surface area can allow the filter medium to have an increased filtration efficiency for particles from the fluid. For example, in some cases, the filter medium described in the present application includes 2 to 12 pleats / inch, 3 to 8 pleats / inch, or 2 to 5 pleats / inch. Other values ​​are also possible.

[0101] It should be understood that the filter medium may include other parts in addition to the two or more layers described herein. In some embodiments, further processing includes introducing one or more structural features and / or reinforcing elements. For example, the medium may be combined with additional structural features, such as polymers and / or metal mesh. In one embodiment, a screen backing may be provided on the filter medium to provide further rigidity. In some cases, the screen backing may help maintain the pleated configuration. For example, the screen backing may be an expanded metal screen or an extruded plastic screen.

[0102] As previously mentioned, the filter media disclosed in the present application can be incorporated into various filter elements for various applications including hydraulic and non-hydraulic filtration applications. Exemplary applications of hydraulic filters (e.g., high, medium, and low pressure filters) include mobile filters and industrial filters. Exemplary applications of non-hydraulic filters include fuel filters (e.g., automotive fuel filters), oil filters (e.g., lubricating oil filters or heavy-duty lubricating oil filters), chemical processing filters, industrial processing filters, medical filters (e.g., blood filters), air filters, and water filters. In some cases, the filter media disclosed in the present application can be used as a coalescer filter medium.

[0103] In some cases, filter element comprises a housing that can be arranged around the filter medium. The housing can have various configurations, wherein these configurations vary based on the intended application. In some embodiments, the housing can be formed by a frame arranged around the filter medium periphery. For example, the frame can be thermally sealed around the periphery. In some cases, the frame has a generally rectangular configuration around all four sides of a generally rectangular filter medium. The frame can be formed by various materials including any combination of, for example, cardboard, metal, polymer or suitable material. Filter element can also include various other features known in the art, such as stabilization features or any other suitable features that make the filter medium stable relative to the frame, the partition.

[0104] In one group of embodiments, filter medium described in the present application is incorporated into filter element with cylindrical structure, and this cylindrical filter element can be suitable for hydraulic application and other applications.Cylindrical filter element can include steel support net, and this steel support net can provide support and interval for pleat and prevent medium from being damaged during processing and / or installation.Steel support net can be positioned as upstream layer and / or downstream layer.Filter element can also include upstream support layer and / or downstream support layer that can protect filter medium during pressure fluctuation.These layers can be combined with filter medium 10 that can include two or more layers as described above.Filter element can also have any suitable size.For example, the length of filter element can be at least 15 inches, at least 20 inches, at least 25 inches, at least 30 inches, at least 40 inches or at least 45 inches.The surface area of ​​filter medium can be for example at least 220 square inches, at least 230 square inches, at least 250 square inches, at least 270 square inches, at least 290 square inches, at least 310 square inches, at least 330 square inches, at least 350 square inches or at least 370 square inches.

[0105] The filter element may have the same property values ​​as those described above in relation to the filter media. For example, the resistance ratio, unit weight ratio, dust holding capacity, efficiency, specific capacity and fiber diameter ratio between different layers of the filter media mentioned above may also be found in the filter element.

[0106] During use, when fluid flows through the filter medium, the filter medium mechanically captures particles on or in the layer. The filter medium does not need to be charged to enhance the capture of contaminants. Thus, in some embodiments, the filter medium is not charged. However, in some embodiments, the filter medium can be charged.

[0107] The following examples are intended to illustrate certain embodiments of the invention but should not be viewed as limiting the invention nor exemplifying the full scope of the invention.

[0108] Example 1

[0109] This example describes the formation of several multi-layer filter media and their characteristics according to various embodiments of the present invention.

[0110] Two-layer and three-layer filter media were prepared according to the specifications listed in Table 1. The two-layer filter media (Samples 2A, 2B, and 3) included a first main filter layer (denoted as the top phase main filter layer in Table 1) and a second main filter layer adjacent to the first layer (bottom phase main filter layer).

[0111] Two layers of media were formed by a wet papermaking process. Briefly, for one layer, 250 gallons of water were added to a hydropulper and sulfuric acid was then added to bring the pH to about 3.0. Fibers were added to the mixture and the fiber and water slurry was mixed for 4 minutes. The slurry was then pumped to a first tank with an additional 900 gallons of water. For the second layer, the process was repeated with the fibers required for the second layer and the slurry was pumped to a different tank.

[0112] The slurry from the first tank is pumped to the main stock box of the Fourdrinier paper machine along with additional water and additional sulfuric acid to reduce the pH to about 2.6. The slurry is allowed to flow onto the forming wire of the paper machine and drained by gravity and a series of vacuum slots, ultimately forming a loosely bound wet fiber web that is carried away by the moving forming wire. To make the second layer, the fibers in the second tank and the dilution water are pumped to a secondary headbox, also located in the Fourdrinier paper machine. The secondary headbox is positioned so that the forming wire carrying the drained fibers of the main stockbox passes below the secondary headbox. The second slurry is applied to the formed web from the main stockbox and then drained by the formed web. The water is then removed by another series of vacuum slots to obtain a combined single web comprising fibers from the main stockbox as a bottom layer and fibers from the secondary headbox as a top layer. This combined single web is then sprayed with a latex solution to add an organic binder. The web is then dried by passing through a series of steam-filled drying cans. Finally, the dryer fabric is wound into a roll on a reel.

[0113] The three-layer filter media (Samples 1, 4A, 4B, 5A, and 5B) included: a pre-filtration layer (pre-filtration single phase) as the first layer; a main filtration layer (top phase main filtration layer) as the second layer adjacent to the first layer; and an additional main filtration layer (bottom phase main filtration layer) adjacent to the second layer. Before being assembled with the first layer, the second layer and the third layer were simultaneously formed into a composite article using the same wet-laid process as used for the two-layer media. The first layer was then assembled with the composite article by finishing.

[0114] Table 1: Comparison of various two-layer and three-layer filter media

[0115]

[0116] Example 2

[0117] This example describes the formation of several single-layer and multi-layer filter media and their characteristics.

[0118] Table 2 includes ( x ) =1000, wherein x is about 4 to 4.5 microns. Comparative Sample 1A has a first (upstream) layer and a second (downstream) layer, the second layer having finer fibers than the first layer. The specific composition of the first layer and the second layer of Comparative Sample 1A is included in Table 4. The first layer and the second layer were formed using the hand sheeting protocol described below. Comparative Samples 2 to 10 are commercial grades from Hollingsworth and Vose Company. As shown in Table 2, all of the comparative samples have 10 μm absolute specific capacity values ​​of less than 2.7.

[0119] Table 2: Characteristics of various single-layer and multi-layer filter media

[0120]

[0121] Table 3 includes ( x ) =200, wherein x is about 6 to 7 microns. Comparative Sample 1B has the same composition as Comparative Sample 1A, except that the first and second layers are reversed. That is, Comparative Sample 1B has a first (upstream) layer and a second (downstream) layer, and the first layer has finer fibers than the second layer. The first and second layers were formed using the hand sheet protocol described below.

[0122] Comparative Samples 11 to 18 were commercial grades from Hollingsworth & Worth Ltd.

[0123] Samples 6 through 9 are two-layer filter media having various physical and performance characteristics according to certain embodiments of the present invention.

[0124] As shown in Table 2, the 10 μm absolute specific capacity values ​​of all comparative samples are less than 3.4, while the values ​​of samples 6 to 9 are greater than 3.4.

[0125] Table 3: Characteristics of various single-layer and multi-layer filter media

[0126]

[0127] The samples marked as "Handsheet" in Tables 2 and 3 were formed by a wet handsheet making process. The handsheet mold was prepared using standard procedures. To form the first layer, the entire volume of the handsheet mold was acidified to pH 3.0 using 5 mL of 25% sulfuric acid. From the prepared handsheet mold, 750 mL of acidified water was obtained and placed in a Waring 1 speed glass mixer. The stepless voltage regulator (Variac) was set to 60 for the pulping stage. 4.53 grams of Code 112 fiber and 0.5 grams of chopped fibers were added to the mixer and pulped until well dispersed (~60 seconds). The fiber and water slurry was then added to the top of the handsheet mold, the slurry was stirred and then drained through a forming wire. The wet paper was then vacuum dried on a light dryer.

[0128] The second layer required a modification to the handsheet process described above, i.e., the preformed first layer was used as the bottom paper, the first layer was placed on the handsheet mold and supported at the edges with blotter paper. The handsheet mold was clamped and water was added carefully to the sides of the mold so as not to disturb the now wet paper. The water was acidified again with 5 mL of 25% sulfuric acid and 750 mL was drawn off for the second layer mixture. A pre-weighed 2.42 grams of Code 104 fiber was mixed in a Waring 1 speed glass blender for ~60 seconds and then added to the top of the handsheet mold. The slurry was then carefully stirred so as not to disturb the wet bottom layer and then drained through the main layer and forming wire. The two-layer handsheet was then vacuum dried on a light dryer.

[0129] Samples 6 and 7 were formed using the method described in Example 1.

[0130] The commercial grade comparative samples shown in Tables 2 and 3 and samples 8 and 9 were formed using a papermaking process. Briefly, for one layer, about 1000 gallons of water were added to a hydropulper, and then 2 quarts of sulfuric acid were added to bring the pH to about 3.0. Fibers and 1000 gallons of water were added to the mixture, and the fiber and water slurry were mixed for 5 minutes. The slurry was then pumped to a first storage tank with an additional 4700 gallons of water.

[0131] For two layers of media, the process was repeated with the fibers needed for the second layer, except that 5,000 gallons of water were added instead of 4,700 gallons of water before being pumped into a different tank.

[0132] The slurry from the first storage tank is pumped to the main stock box of the Fourdrinier paper machine with additional water and additional sulfuric acid to reduce the pH to about 2.6. The slurry is allowed to flow onto the forming wire of the paper machine and drained by gravity and a series of vacuum slots, eventually forming a loosely bound wet fiber web, which is carried away by the moving forming wire. To make the second layer, the fibers from the second storage tank are pumped to the secondary headbox, which is also located in the Fourdrinier paper machine, together with the dilution water. The secondary headbox is positioned so that the forming wire carrying the drained fibers from the main stockbox passes below the secondary headbox. The second slurry is applied to the formed web from the main stockbox and then drained by the formed web. The water is then removed by another series of vacuum slots to obtain a combined single web including fibers from the main stockbox as the bottom layer and fibers from the secondary headbox as the top layer. The combined web is then dried by a series of steam-filled drying cans. Finally, the dry web is wound into a roll at a reel.

[0133] Table 4: Composition of Comparative Samples 1A and 1B

[0134]

[0135] Example 3

[0136] This example describes the features of several single layer and multi-layer filter media.

[0137] Figure 2 Shown is a graph of the absolute specific capacity at 10 microns for various filter media versus the total unit weight of the media. The unit weight is plotted on a log scale.

[0138] Comparative sample groups 19 and 20 are two-layer media and three-layer media, respectively.

[0139] Sample Group 10 is a two-layer media formed by the wet-laid process described in Example 1. Sample Group 11 is a three-layer media including a pre-filter layer, a first main filter layer, and a second main filter layer. The first main filter layer and the second main filter layer were made using the wet-laid process described in Example 1 to form a composite product, which was then finished with the pre-filter layer.

[0140] like Figure 2 As shown, Sample Group 10 (two-layer media) has a higher 10 μm absolute specific capacity and a lower basis weight than Comparative Sample Group 19 (two-layer media). For example, the filter media of Sample Group 10 has a 10 μm absolute specific capacity value greater than 3.4 and a unit weight less than 75 g / m 2 In contrast, the filter medium of comparative sample group 19 has a 10 μm absolute specific capacity value of less than 3.4 and at the same time has a specific capacity greater than 75 g / m 2 Unit weight.

[0141] In addition, Sample Group 11 (three-layer media) has a higher 10 μm absolute specific capacity and a lower basis weight than the filter media of Comparative Sample Group 20 (three-layer media). For example, the filter media of Sample Group 11 has a 10 μm absolute specific capacity value greater than 2.65. In contrast, the filter media of Comparative Sample Group 20 has a 10 μm absolute specific capacity value less than 2.65. The basis weight of the media of Sample Group 11 is less than the basis weight of the media of Comparative Sample Group 20.

[0142] Example 4

[0143] Figure 3A and Figure 3B is a table showing properties of a filter media having a first upstream layer comprising glass fibers, a second layer comprising glass fibers, and a third downstream layer comprising meltblown fibers. The first and second layers were formed using a process similar to that described in Example 1. The third layer was formed using a meltblowing process as described herein. Figure 3A and Figure 3B As shown, a relatively high total dust holding capacity is achieved while also maintaining a relatively high total permeability for a particular sample.

[0144] Thus, several aspects of at least one embodiment of the present invention have been described, and it should be understood that those skilled in the art are susceptible to various changes, modifications and improvements. Such changes, modifications and improvements are intended to be a part of the present disclosure, and are intended to be within the spirit and scope of the present invention. Therefore, the foregoing description and accompanying drawings are exemplary only.

[0145] This application also provides the following technical solutions:

[0146] 1. A filter medium comprising:

[0147] a first layer, the first layer comprising glass fibers, wherein the fibers in the first layer have a first average diameter;

[0148] a second layer adjacent to the first layer, the second layer comprising glass fibers, wherein the fibers in the second layer have a second average diameter, and wherein the first average diameter is greater than the second average diameter; and

[0149] A third layer adjacent to the second layer, the third layer comprising synthetic polymer fibers, wherein the fibers in the third layer have a third average diameter, wherein the second average diameter is greater than the third average diameter, and wherein the third layer has a thickness of less than about 200 microns.

[0150] 2. The filter medium of claim 1, wherein a normalized resistance ratio of the second layer to the first layer is 4:1 or greater, and a normalized resistance ratio of the third layer to the second layer is 4:1 or less.

[0151] 3. The filter medium of claim 1, wherein a normalized resistance ratio of the second layer to the first layer is 4:1 to 6:1, and a normalized resistance ratio of the third layer to the second layer is 2:1 to 4:1.

[0152] 4. The filter medium of clause 1, wherein the first layer comprises less than about 20% by weight synthetic fibers.

[0153] 5. The filter medium of clause 1, wherein the first layer is a pre-filtration layer, and the basis weight of the first layer is greater than the basis weight of the second layer.

[0154] 6. The filter media of item 1, wherein at least one of the first layer and the second layer comprises at least about 80% by weight glass fibers.

[0155] 7. The filter medium of clause 1, wherein at least one of the first layer and the second layer comprises at least about 40% by weight microglass fibers.

[0156] 8. The filter media of clause 1, wherein at least one of the first layer and the second layer comprises at least about 60% by weight microglass fibers.

[0157] 9. The filter medium according to item 7, wherein the average diameter of the ultrafine glass fibers is 1 μm to 6 μm.

[0158] 10. The filter medium of item 1, wherein the ratio of the first average diameter to the second average diameter is less than 2:1.

[0159] 11. The filter medium of clause 1, wherein the third average diameter is less than about 1 micron.

[0160] 12. The filter medium of clause 1, wherein at least one of the first layer, the second layer, and the third layer has a basis weight of less than about 40 g / m 2 .

[0161] 13. The filter media of clause 1, wherein the synthetic polymer fibers comprise meltblown fibers.

[0162] 14. The filter medium of clause 1, wherein the synthetic polymer fibers comprise a material selected from the group consisting of polyester, nylon, and polyphenylene sulfide.

[0163] 15. The filter medium of clause 1, wherein the third layer has a thickness of less than about 180 microns.

[0164] 16. The filter medium of claim 1, wherein the total dust holding capacity of the filter medium is at least about 180 g / m 2 .

[0165] 17. The filter medium of claim 1, wherein the total dust holding capacity of the filter medium is at least about 230 g / m 2 .

[0166] 18. The filter media of clause 1, wherein the filter media has a total permeability greater than about 35 cubic feet per minute per square foot.

[0167] 19. The filter media of clause 1, wherein the filter media has a total permeability greater than about 40 cubic feet per minute per square foot.

[0168] 20. The filter medium of clause 1, wherein the third layer has a median flow pore size of about 8 microns to about 12 microns and a beta (10) .

[0169] 21. The filter medium of claim 1, wherein the basis weight of the third layer is about 20 g / m 2 About 30g / m 2 .

[0170] 22. The filter medium of claim 1, wherein the filter medium has a β (x) Efficiency equal to at least 200 and median flow pore size of x ± 2 microns.

[0171] 23. A hydraulic filter element comprising the filter medium of clause 1.

[0172] 24. The hydraulic filter element of clause 23, wherein the third layer is downstream of the second layer, and the second layer is downstream of the first layer.

[0173] 25. A filter medium comprising:

[0174] a first layer, the first layer comprising glass fibers, wherein the fibers in the first layer have a first average diameter;

[0175] a second layer adjacent to the first layer, the second layer comprising glass fibers, wherein the fibers in the second layer have a second average diameter, and wherein the first average diameter is greater than the second average diameter; and

[0176] a third layer adjacent to the second layer, the third layer comprising synthetic polymer fibers, wherein the fibers in the third layer have a third average diameter, wherein the second average diameter is greater than the third average diameter, and

[0177] The filter medium has a thickness of at least about 150 g / m 2 and a total dust holding capacity of greater than about 25 cubic feet per minute per square foot.

[0178] 26. The filter medium of claim 25, wherein the normalized resistance ratio of the second layer to the first layer is 4:1 or greater, and the normalized resistance ratio of the third layer to the second layer is 4:1 or less.

[0179] 27. The filter medium of claim 25, wherein the normalized resistance ratio of the second layer to the first layer is 4:1 to 6:1, and the normalized resistance ratio of the third layer to the second layer is 2:1 to 4:1.

[0180] 28. The filter media of clause 25, wherein the first layer comprises less than about 20% by weight synthetic fibers.

[0181] 29. The filter media of clause 25, wherein the first layer is a pre-filter layer and the basis weight of the first layer is greater than the basis weight of the second layer.

[0182] 30. The filter media of clause 25, wherein at least one of the first layer and the second layer comprises at least about 80% by weight glass fibers.

[0183] 31. The filter media of clause 25, wherein at least one of the first layer and the second layer comprises at least about 40 weight percent microglass fibers.

[0184] 32. The filter media of clause 25, wherein at least one of the first layer and the second layer comprises at least about 60 weight percent microglass fibers.

[0185] 33. The filter medium of item 31, wherein the ultrafine glass fibers have an average diameter of 1 μm to 6 μm.

[0186] 34. The filter media of clause 25, wherein a ratio of the first average diameter to the second average diameter is less than 2:1.

[0187] 35. The filter media of clause 25, wherein the third average diameter is less than about 1 micron.

[0188] 36. The filter medium of clause 25, wherein at least one of the first layer, the second layer, and the third layer has a basis weight of less than about 40 g / m 2 .

[0189] 37. The filter media of clause 25, wherein the synthetic polymer fibers comprise meltblown fibers.

[0190] 38. The filter medium of clause 25, wherein the synthetic polymer fibers comprise a material selected from the group consisting of polyester, nylon, and polyphenylene sulfide.

[0191] 39. The filter medium of clause 25, wherein the third layer has a thickness of less than about 180 microns.

[0192] 40. The filter medium of clause 25, wherein the total dust holding capacity of the filter medium is at least about 180 g / m 2 .

[0193] 41. The filter medium of clause 25, wherein the total dust holding capacity of the filter medium is at least about 230 g / m 2 .

[0194] 42. The filter media of clause 25, wherein the filter media has a total permeability greater than about 35 cubic feet per minute per square foot.

[0195] 43. The filter media of clause 25, wherein the filter media has a total permeability greater than about 40 cubic feet per minute per square foot.

[0196] 44. The filter medium of clause 25, wherein the third layer has a median flow pore size of about 8 microns to about 12 microns and a beta retardation of at least 200. (10) .

[0197] 45. The filter medium of clause 25, wherein the basis weight of the third layer is about 20 g / m 2 About 30g / m 2 .

[0198] 46. ​​The filter medium of claim 25, wherein the filter medium has a β (x) Efficiency equal to at least 200 and median flow pore size of x ± 2 microns.

[0199] 47. A hydraulic filter element comprising the filter medium of clause 25.

[0200] 48. The hydraulic filter element of clause 47, wherein the third layer is downstream of the second layer, and the second layer is downstream of the first layer.

[0201] 49. The filter media of item 1 or 25, wherein the second layer is directly adjacent to the first layer.

[0202] 50. The filter media of item 1 or 25, wherein the third layer is directly adjacent to the second layer.

Claims

1. A filter medium for a hydraulic filter element, comprising: a first layer, the first layer comprising glass fibers, wherein the fibers in the first layer have a first average diameter; a second layer adjacent to the first layer, the second layer comprising glass fibers, wherein the fibers in the second layer have a second average diameter, and wherein the first average diameter is greater than the second average diameter; and a third layer adjacent to the second layer, the third layer comprising synthetic polymer fibers, wherein the synthetic polymer fibers comprise meltblown, meltspun, melt electrospun, and / or solvent electrospun fibers, wherein the fibers in the third layer have a third average diameter, wherein the second average diameter is greater than the third average diameter, and wherein the third layer has a thickness of less than 500 microns, wherein the filter medium has a thickness of 5 mils to 300 mils, The total permeability of the filter media is from 2 cfm / ft2 to 50 cfm / ft2. 2 . The filter medium according to claim 1 , wherein a normalized resistance ratio of the second layer to the first layer is 4:1 or greater, and a normalized resistance ratio of the third layer to the second layer is 4:1 or less.

3. The filter medium according to claim 1, wherein a normalized resistance ratio of the second layer to the first layer is 4:1 to 6:1, and a normalized resistance ratio of the third layer to the second layer is 2:1 to 4:

1.

4. The filter media of claim 1, wherein the first layer comprises less than 20% by weight synthetic fibers. 5 . The filter media of claim 1 , wherein the first layer is a pre-filter layer and a basis weight of the first layer is greater than a basis weight of the second layer.

6. The filter media of claim 1, wherein at least one of the first layer and the second layer comprises at least 80% by weight glass fibers.

7. The filter media of claim 1, wherein at least one of the first layer and the second layer comprises at least 40% by weight microglass fibers.

8. A hydraulic filter element comprising the filter medium of claim 1.

9. A filter medium for a hydraulic filter element, comprising: a first layer, the first layer comprising glass fibers, wherein the fibers in the first layer have a first average diameter; a second layer adjacent to the first layer, the second layer comprising glass fibers, wherein the fibers in the second layer have a second average diameter, and wherein the first average diameter is greater than the second average diameter; and a third layer adjacent to the second layer, the third layer comprising synthetic polymer fibers, wherein the synthetic polymer fibers comprise meltblown, meltspun, melt electrospun, and / or solvent electrospun fibers, wherein the fibers in the third layer have a third average diameter, wherein the second average diameter is greater than the third average diameter, and The filter medium has a thickness of at least 150 g / m 2 The total dust holding capacity, wherein the filter medium has a thickness of 5 mils to 300 mils, The total permeability of the filter media is from 2 cfm / ft2 to 50 cfm / ft2.

10. A hydraulic filter element comprising the filter medium of claim 9.

Images