Composite filtration media for liquid filtration

Abstract

A composite filtration medium for use in filtering liquids includes an upper layer made of a polymeric material of polymer fibers. A middle layer is disposed below the upper layer and is made of a polymeric material of polymer fibers, the middle layer having a weight per unit area. A lower layer is disposed below the middle layer and is made of a polymeric material of polymer fibers, the lower layer having a basis weight. A polymeric support layer is disposed on the lower surface of the lower layer and has a basis weight.

Description

[Technical Field]

[0001] This application is a non-provisional application that claims the benefit of U.S. Provisional Application No. 63 / 445,176, filed February 13, 2023, the contents of which are incorporated herein by reference in their entirety.

[0002] The present invention relates to a composite filtration medium and a method for preparing the same. [Background technology]

[0003] As engine exhaust emission standards become increasingly stringent, engine design must be optimized to improve efficiency and reduce emissions. Advances in engine technology are also increasing the demands for the cleanliness of liquids, such as fuel and engine oil. Modern engines operate at high pressures, so even tiny particles can wear or damage sensitive components in the engine system, such as nozzles. Changes in fuel also affect filtration standards. Key changes include the use of ultra-low sulfur diesel and environmentally friendly biodiesel. While sulfur and sulfur compounds in traditional fuels can help lubricate engine parts and reduce wear, current biodiesel and other alternative fuels typically have a higher water content than traditional diesel. In addition to these changes, impurities and water can be introduced into fuel during normal transportation, causing contamination. Furthermore, during vehicle use, solid impurities in fuel can cause wear and nozzle clogging in the engine system, while water in fuel can cause combustion instability and corrosion of parts. Consequently, fuel filtration requirements have become more stringent, leading to correspondingly higher standards for filter media.

[0004] To improve filtration efficiency, most fuel filter media currently on the market are glass fiber. However, glass fiber is brittle and prone to breakage during processing and use, easily causing secondary pollution and damaging the engine. Therefore, the development of synthetic materials for liquid filtration that are durable, have high filtration efficiency, and have a long service life is extremely important. Most synthetic materials have excellent toughness and are resistant to breakage, which can extend the service life of the filter and engine. Furthermore, high filtration efficiency can be achieved by rationally selecting polymer materials with high filtration efficiency and separation performance.

[0005] Therefore, there is a need for an improved filtration media, which is made from a synthetic polymeric material that is resistant to shedding, and which has higher filtration efficiency and greater contaminant holding capacity while maintaining high filtration performance, low flow resistance, and low thickness. The media and techniques disclosed in this invention provide devices and methods that meet this need.

[0006] The prior art referred to and / or described herein is not intended as an admission that any patent, publication, or other information referred to herein is "prior art" with respect to the present invention. Furthermore, this section should not be construed to imply that a search has been conducted or that other relevant information does not exist as defined in 37 CFR 1.56(a).

[0007] All US patents and applications and all other published documents mentioned anywhere in this specification are incorporated herein by reference in their entirety.

[0008] Without limiting the scope of the invention, a brief summary of some of the claimed embodiments of the invention is provided below. Further details of the summarized embodiments of the invention and / or other embodiments of the invention can be found in the detailed description of the invention below.

[0009] A brief abstract of the technical disclosure herein is also provided solely for purposes of complying with 37 CFR 1.72. The abstract is not intended to be used to interpret the scope of the claims. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view of an embodiment of a composite filtration media. [Figure 2] FIG. 2 is a cross-sectional view of an embodiment using a composite filtration media with two layers of filtration media in the top and middle layers. [Figure 3] FIG. 3 is a cross-sectional view of an embodiment using a composite filtration media with two underlying layers of filtration media. [Figure 4] FIG. 4 is a cross-sectional view of an embodiment using a composite filtration media with an optional protective layer. [Figure 5] FIG. 5 is a cross-sectional view of an embodiment using a composite filtration media with a protective layer and a bicomponent fiber composite top layer. [Figure 6] FIG. 6 is a cross-sectional view of an embodiment using a composite filtration media with three layers of filtration media in the protective and intermediate layers. [Figure 7] FIG. 7 is a diagram of a filter element using a composite filtration medium. DETAILED DESCRIPTION OF THE INVENTION

[0011] The following description and drawings sufficiently illustrate particular embodiments to enable those skilled in the art to practice them. Other embodiments may include structural, logical, electrical, process, and other changes. Portions and features of some embodiments may be included in, or substituted for, other embodiments. Embodiments set forth in the claims encompass all available equivalents of those claims.

[0012] The synthetic composite filter media used for liquid filtration has the characteristics of high filtration and separation efficiency, large dust holding capacity, long service life, and low liquid flow resistance. All materials used for the filter media are synthetic polymer fiber materials. The total thickness of this composite filter media does not exceed 2mm, and the weight per unit area is 180g / m. 2 ~400g / m 2 For a particle size of 4 μm, the filtration efficiency of particulate matter reaches 70% to 99.95%, and the dust retention capacity is 150 g / m 2 Exceeds.

[0013] This composite filtration medium consists of multiple micron fiber layers with fiber diameters ranging from 0.5 to 10 μm. These micron fiber layers form a structure that gradually changes from top to bottom, with fiber diameter, pore size, and air permeability gradually decreasing. This filtration medium also includes one support layer and has a weight per unit area of ​​70 to 250 g / m. 2 This ensures the overall strength and rigidity of the filtration medium. It may also contain one additional protective layer, and its weight per unit area is 10-30g / m 2 The support layer and optional protective layer can be made of PET, PA or other polymeric materials.

[0014] Figure 1 shows a cross-sectional view of one embodiment of a composite filtration medium. This composite filtration medium 1 comprises four layers, from upstream to downstream: an upper layer 2, a middle layer 3, a lower layer 4, and a support layer 5, each of which serves as a functional filtration layer. A protective layer can be optionally added above the upper layer. The average fiber diameters of the upper, middle, and lower functional layers gradually decrease from top to bottom.

[0015] The upper layer is made of polymer materials such as meltblown materials, bicomponent materials, drylaid nonwovens, spunlaced nonwovens, and blended materials. The blended materials can include nonwovens formed by blending thick staple fibers with fine meltblown fibers. The thick staple fibers can be polyethylene terephthalate (PET) or polyamide (PA), and the meltblown fibers can be polybutylene terephthalate (PBT), polyethylene terephthalate (PET), or polyamide (PA). The upper layer can be a single-layer filtration medium or a combination of multiple filtration media. Multilayer filtration media can have different performance characteristics and use different polymer fibers. The average fiber diameter of the upper layer is 4 μm to 25 μm. When combining multiple layers, the difference in average fiber diameter between adjacent layers must not exceed 10 μm. The weight per unit area of ​​the upper layer is 20 g / m. 2 ~100g / m 2 is.

[0016] The intermediate layer can be made of a polymer material, typically a meltblown nonwoven and / or a bicomponent material. The meltblown nonwoven material can be polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyamide (PA), or polylactic acid (PLA). The average fiber diameter of the intermediate layer can be 1 μm to 5 μm. The intermediate layer can include a single filtration media layer or a combination of multiple filtration media layers. The multiple filtration media layers can have different properties and use different polymer fibers. When multiple filtration media layers are used, the difference in average fiber diameter between two adjacent layers should not exceed 5 μm. The weight per unit area of ​​the intermediate layer should be 20 g / m. 2 ~90g / m 2 is.

[0017] The lower layer is made of a polymer material and can be made of nanofibers produced by meltblown or electrospun methods. The average fiber diameter of the lower layer is 0.05 μm to 2 μm. The lower layer can be a single filtration medium layer or a combination of multiple filtration medium layers. When multiple filtration medium layers are combined, the difference in average fiber diameter between adjacent layers must not exceed 2 μm. The multiple filtration medium layers can have different properties and can use different polymer fibers. The nanofibers can be made of one or a mixture of multiple materials, with commonly used materials including polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), polyamide (PA), etc. Meltblown materials include polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polyamide (PA), polylactic acid (PLA), etc. The weight per unit area of ​​the lower layer is 1 g / m. 2 ~80g / m 2 is.

[0018] The support layer can be a rigid nonwoven. Materials used as the support layer include spunbond nonwovens, wetlaid nonwovens, carded or spunbond nonwovens, or combinations thereof. Synthetic nonwovens include polyester nonwovens, nylon nonwovens, polyolefin (e.g., polypropylene) nonwovens, polycarbonate nonwovens, or blends or composite nonwovens thereof. Other suitable support layer materials include polyester fibers or bicomponent polyester fibers, polypropylene / polyethylene terephthalate, or polyethylene / polyethylene terephthalate bicomponent fibers, which are typically used in spunbond processes.

[0019] In some embodiments, the weight per unit area of ​​the support layer is at least 70 g / m 2 , 100g / m 2 , 125g / m 2 or 180 g / m 2 In other embodiments, the weight per unit area of ​​the support layer is at most 150 g / m 2 , 200g / m 2 or 250 g / m 2In one exemplary embodiment, the weight per unit area of ​​the support layer is 100 g / m 2 ~150g / m 2 In another embodiment, the weight per unit area of ​​the support layer is 120 g / m 2 ~145g / m 2 The weight per unit area of ​​the support layer can be measured according to the TAPPI T410 om-08 standard.

[0020] In some embodiments, the average mean flow pore size of the support layer is at least 35 μm, 10 μm, 15 μm, 20 μm, or 25 μm. In other embodiments, the average pore size of the support layer can reach 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, or 90 μm. For example, in one exemplary embodiment, the average pore size of the support layer ranges from 25 μm to 50 μm. In some embodiments, the average pore size is preferably measured using capillary flow porometry.

[0021] The upper, middle, and lower layers may each include multiple layers of filtration media. The polymer composition and physical properties of each filtration media layer used in the upper, middle, and lower layers may be selected depending on the filtration performance.

[0022] Meltblown fibers can be used in the top, middle, and bottom filtration media layers of composite filtration media. In one embodiment, polymers used in meltblown fibers can include polybutylene terephthalate (PBT) and polyester. Suitable thermoplastic polymers for forming meltblown fibers include, but are not limited to, polyolefins, condensates (e.g., polyamides (PA), polyesters, polycarbonates (PC), and polyarylates), vinyl polymers, polyols, polydienes, polyurethanes (PU), polyethers, polyacrylates, polycarbonates (PC), and polystyrenes (PS). Suitable polyolefins include polypropylene (PP), polyethylene (PE), polybutene (PB), and copolymers and / or blends thereof. By way of example, the fibers can include ethylene polymers and copolymers thereof, specifically copolymers of ethylene and α-olefins. Other examples of polymers suitable for producing media fibers further include poly(1-pentene), poly(2-pentene), poly(3-methyl-1-pentene), poly(4-methyl-1-pentene), nylon, polybutene (PB), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), and the like.

[0023] The support layer and optional protective layer can comprise spunbond, dry-laid, or wet-laid filtration media. The support layer can be a monocomponent or bicomponent polymer. Polymers that can be used for the support and protective layers include condensation polymers such as polyesters (polyethylene terephthalate (PET) and polybutylene terephthalate (PBT)), polyacetal (POM) and polyamide (PA), and addition polymers such as polyethylene (PE), polytetrafluoroethylene, and polypropylene (PP). Commonly used polymers for filtration material construction include polypropylene (PP), polyester, and nylon. Other polymers suitable for nonwoven filtration media include polycyclohexylene dimethylene terephthalate (PCT) and polyphenylene sulfide (PPS), which contain staple fibers with higher melting points.

[0024] In some embodiments, staple fibers can be used in one or more layers to provide support, spacing, and other filtration performance advantages to composite filtration media. Staple fibers can include monocomponent and bicomponent materials. Staple fibers are typically short-cut fibers with an average diameter of 10-30 μm and a length typically between 6 mm and 30 mm. Suitable polymers include condensation polymers such as polyesters (polyethylene terephthalate (PET) and polybutylene terephthalate (PBT)), polyacetal (POM) and polyamide (PA), and addition polymers such as polyethylene (PE), polytetrafluoroethylene (PTFE) and polypropylene (PP). Polymers used in the construction of such laminated filters include polypropylene (PP), polyester, and nylon. Other polymers suitable for nonwoven filtration media include higher melting point staple fibers such as polycyclohexylene dimethylene terephthalate (PCT) and polyphenylene sulfide (PPS).

[0025] Bicomponent fibers can be made of any suitable material, including multiple thermoplastic materials, such as polyolefins (e.g., polypropylene (PE), polypropylene (PP), etc.), polyesters (e.g., polyethylene terephthalate (PET) and polybutylene terephthalate (PBT)), and nylons (e.g., nylon 6, nylon 6.6, nylon 6.12, etc.). Any thermoplastic with an appropriate melting point can be used in bicomponent fibers, with higher melting point polymers being used for the higher melting point portion of the fiber. The bicomponent structure can have a polyethylene terephthalate (PET) / polyethylene terephthalate (PET) or nylon 6 / nylon 6.6 structure, with the polyethylene terephthalate (PET) component and nylon component having different melting points.

[0026] The polymer other than the fibers used in each layer of the composite filtration medium can be one or a combination of two or more of the following, and the polymer can be selected from, but is not limited to, thermoplastic polyurethane (TPU), polyvinylidene fluoride (PVDF), nylon, polylactic acid (PLA), polyacrylonitrile (PAN), polyetherimide (PEI), polyurethane, polystyrene, polyimide, polyethylene glycol terephthalate, polybutylene terephthalate, nylon (nylon 6, nylon 66, nylon 56, nylon 1010), polyacrylonitrile, polyvinylidene fluoride, polyvinyl fluoride, polytetrafluoroethylene, chlorotrifluoroethylene, polyethylene oxide, polymethyl methacrylate, poly(m-phenylene isophthalamide), polysulfone, polyphenylene sulfone resin, polyethersulfone, polyphenylene sulfide, polyetherimide, polylactic acid, poly-L-lactic acid, poly-D-lactic acid, polycaprolactone, polyvinyl alcohol, and polyvinylpyrrolidone.

[0027] In the embodiment, the weight per unit area of ​​each upper layer of filtration media is 20 to 60 g / m 2 In an embodiment, the fibers constituting the upper media layer may have an average fiber diameter of 4 μm to 25 μm. In an embodiment, the mean flow pore size of each filtration media layer is 35 μm or greater. In another embodiment, the mean flow pore size of each filtration media layer may be 35 to 70 μm. In an embodiment, the total weight per unit area of ​​the upper layers is 20 to 100 g / m. 2 is.

[0028] In some embodiments, the weight per unit area of ​​the top layer is at least 20 g / m 2 , min.40g / m 2 , min.60g / m 2 or a minimum of 70 g / m 2 In some embodiments, the weight per unit area of ​​the top layer is at most 30 g / m 2 , up to 50g / m 2 or up to 70 g / m 2In one exemplary embodiment, the weight per unit area of ​​the top layer is 30 g / m 2 ~60g / m 2 In another exemplary embodiment, the weight per unit area of ​​the top layer is 25 g / m 2 ~55g / m 2 The weight per unit area of ​​the top layer can be measured according to the TAPPI T410 om-08 standard.

[0029] In some embodiments, the mean flow pore size of the upper layer is at least 35 μm, at least 45 μm, at least 50 μm, at least 55 μm, or at least 65 μm. In some embodiments, the mean flow pore size of the upper layer is at most 40 μm, at most 45 μm, at most 50 μm, at most 60 μm, or at most 70 μm. In one exemplary embodiment, the mean flow pore size of the upper layer is between 40 μm and 55 μm. In some embodiments, the mean flow pore size is preferably determined based on capillary flow porometry.

[0030] In an embodiment, the weight per unit area of ​​each filtration medium layer in the intermediate layer is 20 to 60 g / m 2 In an embodiment, the average fiber diameter of the fibers making up the intermediate media layers may be 1 μm to 5 μm. In an embodiment, the mean flow pore size of each filtration media layer does not exceed 30 μm. In another embodiment, the mean flow pore size of each filtration media layer may be 10 to 30 μm. In an embodiment, the total weight per unit area of ​​the intermediate layers is 20 g / m. 2 ~90g / m 2 is.

[0031] In some embodiments, the weight per unit area of ​​the intermediate layer is at least 20 g / m 2 , min.40g / m 2 , min.60g / m 2 or a minimum of 70 g / m 2 In some embodiments, the weight per unit area of ​​the intermediate layer is at most 30 g / m 2 , up to 50g / m 2 or up to 90g / m 2 In one exemplary embodiment, the weight per unit area of ​​the intermediate layer is 50 g / m 2 ~90g / m2 In another exemplary embodiment, the weight per unit area of ​​the intermediate layer is 35 g / m 2 ~65g / m 2 The weight per unit area of ​​the interlayer can be measured according to the TAPPI T410 om-08 standard.

[0032] In some embodiments, the mean flow pore size of the intermediate layer is at least 10 μm, at least 15 μm, at least 20 μm, or at least 25 μm. In some embodiments, the mean flow pore size of the intermediate layer is at most 15 μm, at most 20 μm, at most 25 μm, or at most 30 μm. In one exemplary embodiment, the mean flow pore size of the intermediate layer is between 10 μm and 25 μm. In some embodiments, the mean flow pore size is preferably determined based on capillary flow porometry.

[0033] In an embodiment, the weight per unit area of ​​each lower layer of filtration medium is 5 to 50 g / m 2 In an embodiment, the fibers comprising the lower media layer may have an average fiber diameter of 0.05 μm to 2 μm. In an embodiment, the mean flow pore size of each filtration media layer does not exceed 15 μm. In another embodiment, the mean flow pore size of each filtration media layer may be 2 μm to 20 μm. In an embodiment, the total weight per unit area of ​​the lower layers is 1 g / m. 2 ~80g / m 2 is.

[0034] In some embodiments, the weight per unit area of ​​the underlayer is at least 5 g / m 2 , min.15g / m 2 , min.25g / m 2 , min.40g / m 2 , min.55g / m 2 or minimum 60g / m 2 In some embodiments, the weight per unit area of ​​the underlayer is at most 10 g / m 2 , up to 15g / m 2 , up to 30g / m 2 , up to 50g / m 2 or up to 70 g / m 2 In one exemplary embodiment, the weight per unit area of ​​the lower layer is 5 g / m2 ~10g / m 2 In another exemplary embodiment, the weight per unit area of ​​the bottom layer is 20 g / m 2 ~60g / m 2 The weight per unit area of ​​the lower layer can be measured according to the TAPPI T410 om-08 standard.

[0035] In some embodiments, the mean flow pore size of the lower layer is at least 2 μm, at least 10 μm, or at least 15 μm. In some embodiments, the mean flow pore size of the lower layer is at most 5 μm, at most 10 μm, at most 15 μm, or at most 20 μm. In one exemplary embodiment, the mean flow pore size of the lower layer is between 10 μm and 15 μm. In some embodiments, the mean flow pore size is preferably determined based on capillary flow porometry.

[0036] In some embodiments, the average fiber diameter of the middle layer fibers is smaller than the average fiber diameter of the top layer fibers. In some embodiments, the average fiber diameter of the bottom layer fibers is smaller than the average fiber diameter of the middle layer fibers. In some embodiments, the average fiber diameter of the middle layer fibers is smaller than the average fiber diameter of the top layer fibers, and the average fiber diameter of the bottom layer fibers is smaller than the average fiber diameter of the middle layer fibers.

[0037] In some embodiments, the mean flow pore size of the intermediate layer is smaller than the mean flow pore size of the top filtration media layer, and the mean flow pore size of the bottom filtration media layer is smaller than the mean flow pore size of the intermediate layer. In some embodiments, the mean flow pore size of the intermediate layer is smaller than the mean flow pore size of the top filtration media layer. In some embodiments, the mean flow pore size of the bottom filtration media layer is smaller than the mean flow pore size of the intermediate layer.

[0038] In some embodiments, the weight per unit area of ​​the support layer is at least 70 g / m 2 , min.100g / m 2 , min. 125g / m 2 or a minimum of 180 g / m 2 In some embodiments, the weight per unit area of ​​the support layer is at most 100 g / m 2 , up to 150g / m 2 or up to 250 g / m 2In one exemplary embodiment, the weight per unit area of ​​the support layer is 150 g / m 2 ~180g / m 2 In another exemplary embodiment, the weight per unit area of ​​the support layer is 120 g / m 2 ~145g / m 2 The weight per unit area of ​​the support layer can be measured according to the TAPPI T410 om-08 standard.

[0039] In some embodiments, the support layer has a mean flow pore size of at least 35 μm, at least 10 μm, at least 15 μm, at least 20 μm, or at least 25 μm. In some embodiments, the support layer has a mean flow pore size of at most 10 μm, at most 15 μm, at most 20 μm, at most 25 μm, at most 30 μm, at most 35 μm, at most 40 μm, at most 50 μm, at most 60 μm, at most 70 μm, at most 80 μm, or at most 90 μm. In one exemplary embodiment, the support layer has a mean flow pore size of between 25 μm and 50 μm. In some embodiments, the mean flow pore size is preferably determined based on capillary flow porometry.

[0040] FIG. 2 shows a cross-sectional schematic of a composite filtration media 15, including a top layer 16, a middle layer 17, a bottom layer 18, and a support layer 19. The top layer 16 utilizes two filtration media layers 20 and 21. The middle layer may also include two separate filtration media layers 22 and 23. The filtration media layers may be selected according to their material properties, including polymer type, mean flow pore size, fiber diameter, weight per unit area, thickness, and air permeability. The top filtration media layers 20 and 21 and the middle filtration media layers 22 and 23 may have the same or different properties, depending on the filtration performance required of the composite filtration media.

[0041] FIG. 3 shows a cross-sectional schematic of a composite filtration media 30, which includes an upper layer 31, a middle layer 32, a lower layer 33, and a support layer 34. The lower layer uses two filtration media layers 35 and 36. The filtration media layers can be selected according to their material properties, including polymer type, mean flow pore size, fiber diameter, weight per unit area, thickness, and air permeability. The lower filtration media layers 35 and 36 can have the same or different properties, depending on the filtration performance required of the composite filtration media.

[0042] FIG. 4 shows a cross-sectional schematic of a composite filtration media 40, with a protective layer 41 disposed over an upper layer 42, a middle layer 43, a lower layer 44, and a support layer 45. Filtration media layers can be selected according to their material properties, including polymer type, mean flow pore size, fiber diameter, weight per unit area, thickness, and air permeability.

[0043] FIG. 5 shows a cross-sectional schematic of a composite filtration media 50, with a protective layer 51 disposed over a top layer 52, a middle layer 53, a bottom layer 54, and a support layer 55. The filtration media layers can be selected according to their material properties, including polymer type, mean flow pore size, fiber diameter, weight per unit area, thickness, and air permeability. The top layer can include a blend of two different fiber types, which can include relatively large, stiff staple fibers 56 and smaller, finer fibers (e.g., meltblown fibers) 57.

[0044] FIG. 6 shows a cross-sectional schematic of a composite filtration media 60, with a protective layer 61 positioned above an upper layer 62, a middle layer 63, a lower layer 64, and a support layer 65. The filtration media layers can be selected according to their material properties, including polymer type, mean flow pore size, fiber diameter, weight per unit area, thickness, and air permeability. The middle layer is made up of three separate filtration media layers 66, 67, and 68. Media layers 66, 67, and 68 can have the same or different properties, depending on the filtration performance required for the composite filtration media. The lower layer 64 can include a nanofiber layer to achieve higher filtration efficiency.

[0045] The composite liquid filtration media can include a nanofiber layer in either the top, middle, or bottom layer. In at least one embodiment, the nanofibers comprise any one of the following polymers: polyurethane (PU), polystyrene, polyimide (PI), polyethylene terephthalate (PET), polyethylene glycol terephthalate, polybutylene terephthalate (PBT), polyethersulfone (PES), polylactic acid (PLA), thermoplastic polyurethane (TPU), nylon (nylon 6, nylon 66, nylon 56, nylon 1010), polyacrylonitrile (PAN), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), and / or any combination thereof.

[0046] In at least one embodiment, the nanofibers include fibers selected from the group consisting of nanofibers produced by needle electrospinning, nanofibers produced by nozzle-free electrospinning, nanofibers produced by centrifugal spinning, nanofibers produced by electroblowing spinning, and / or any combination thereof.

[0047] In at least one embodiment, the nanofibers have an average diameter of less than 5 μm. In at least one embodiment, the nanofibers have a diameter of less than 1 μm. In at least one embodiment, the nanofibers have a diameter of less than 0.5 μm. In at least one embodiment, the nanofibers may have a diameter of between 0.15 μm and 0.3 μm.

[0048] The nanofiber layer can include a blend or mixture of multicomponent nanofibers. The multicomponent nanofibers can include nanofibers of different diameters in the nanofiber layer. That is, a mixture of thick and fine nanofibers can be used to increase the void volume of the nanofiber layer and form a lofty structure. This structure can achieve a higher dust holding capacity while maintaining high filtration efficiency. For a description and examples of nanofiber layers containing multicomponent nanofibers that can be used in the present invention, see U.S. Application No. 63 / 445,294, filed February 13, 2023 ("Multicomponent Composite Structure Filtration Media"), the entire contents of which are incorporated herein by reference.

[0049] The nanofiber layer can include multi-layered nanofibers. The multi-layered nanofibers can include a nanofiber layer containing one or more groups of electrospun nanofibers, with an inner support layer containing thicker fibers. The inner support layer increases the void volume of the nanofiber layer, forming a loftier structure. This structure can achieve higher dust holding capacity while maintaining high filtration efficiency. For a description and examples of nanofiber layers containing multi-layered nanofibers that can be used in the present invention, see U.S. Application No. 63 / 445,293, filed February 13, 2023 (Composite Filtration Media and Methods for Preparing the Same), the entire contents of which are incorporated herein by reference.

[0050] In one embodiment, the upper layer, middle layer or lower layer may include multi-layered nanofibers, the multi-layered nanofiber layer including a nanofiber layer and an inner support layer, the nanofiber layer including a first fiber distribution, the average fiber diameter of which is 10 nm to 200 nm, the inner support layer including a second fiber distribution, the average fiber diameter of which is 0.3 to 25 μm, and among the plurality of multi-layered nanofibers, the inner support layer is disposed between at least two nanofiber layers.

[0051] In one embodiment, the nanofiber layer can include multi-component nanofibers, where the thick nanofibers have a diameter of 300 nm to 5 μm and the fine nanofibers have a diameter of 50 nm to 300 nm, and in another embodiment, the thick nanofibers have a diameter of greater than 0.1 μm, preferably greater than 0.3 μm, more preferably greater than 0.5 μm, and the fine nanofibers have a diameter of less than 0.3 μm, less than 0.2 μm, or less than 100 nm.

[0052] In some embodiments, the nanofiber layer has a weight per unit area of ​​at most 1.5 g / m 2 , up to 2g / m 2 , up to 2.5g / m 2 , up to 3g / m 2 , up to 3.5g / m 2 , up to 4g / m 2 , up to 4.5g / m2 , up to 5g / m 2 , up to 10g / m 2 , up to 20g / m 2 In some embodiments, the nanofiber layer has a weight per unit area of ​​at least 0.1 g / m 2 , up to 20g / m 2 In one exemplary embodiment, the nanofiber layer has a weight per unit area of ​​at least 2 g / m 2 , up to 10g / m 2 is.

[0053] In some embodiments, the materials and processes used to manufacture the composite filtration media can avoid significant compression of the individual layers of material that make up the media. Limiting compression of each layer can maintain the pore size and thickness range designed for each layer to ensure optimal filtration performance. The top, middle, bottom, and support layers (including any individual filtration media layers and any optional protective layers that make up the top, middle, and bottom layers) can be adhered to form the composite filtration media using ultrasonic bonding, spray adhesives, and / or other bonding methods that do not significantly compress the individual layers. In some embodiments, the total thickness of the composite filtration media is no less than 70% of the sum of the individual thicknesses of the individual materials. In some embodiments, the total thickness of the composite filtration media is no less than 80% of the sum of the individual thicknesses of the individual materials. In some embodiments, the total thickness of the composite filtration media is no less than 90% of the sum of the individual thicknesses of the individual materials.

[0054] The composite filtration media produced by the materials and methods of the present invention have several valuable properties: they can be relatively thin yet maintain a high contaminant holding capacity, they have high filtration efficiency, and they exhibit low flow resistance.

[0055] In the composite filtration media, the upper, middle, and lower layers form a gradient structure from top to bottom, with the average fiber diameter, mean flow pore size, and air permeability gradually decreasing from the upper layer to the lower layer. In an embodiment, each of the upper, middle, and lower layers can include one or more individual filtration media layers, which form an overall gradient structure from the upper layer to the lower layer, with the average fiber diameter, mean flow pore size, and air permeability all decreasing from the upper layer to the lower layer. In an embodiment, each of the upper, middle, and lower layers can include one or more individual filtration media layers, which form a gradient structure from top to bottom within each layer, with the average fiber diameter, mean flow pore size, and air permeability all decreasing from the upper layer to the lower layer. In an embodiment, each of the upper, middle, and lower layers can include one or more individual filtration media layers, which form a gradient structure within each layer from top to bottom within each layer, with the average fiber diameter, mean flow pore size, and air permeability all decreasing from top to bottom. The gradient structure (pore size, fiber diameter, thickness, air permeability, weight per unit area, etc.) of each layer of the composite filtration media layer can be designed to maximize the filtration performance required for the filtration application.

[0056] The liquid filtration performance of composite filtration media can be evaluated using a multi-channel test bench conforming to ISO 19438. This test measures the filtration efficiency of the filtration media and the dust holding capacity at a specified terminal pressure differential. This test can be performed using a specific concentration of test dust in a specific liquid (e.g., lubricating oil, hydraulic fluid, fuel, etc.). In one example, the test liquid can be No. 15 aviation hydraulic fluid. In one example, the liquid can contain a contaminant concentration of 100 mg / L, and the contaminant can be the A3 test dust specified in ISO 12103. In one example, the flow rate on the test bench is 0.7 L / min. The terminal pressure drop of the test can vary from 50 to 150 kPa. In one example, the dust holding capacity and efficiency are measured when the terminal pressure drop of the test bench reaches 100 kPa.

[0057] In one embodiment, the weight per unit area is 200 to 350 g / m 2The composite fuel filter media, with a thickness of 1.0 to 1.3 mm, has a filtration efficiency of 95% or more for particulate matter 4 μm or larger, and a dust holding capacity of 200 g / m 2 The composite media may have a middle layer of one or more meltblown fiber layers, each layer having a thickness of less than 0.4 mm, and a bottom layer of meltblown fiber layers having a thickness of less than 0.2 mm. The composite media layers may be ultrasonically bonded together.

[0058] In one embodiment, the weight per unit area is 180 to 330 g / m 2 The composite fuel filter media, not exceeding 1.2 mm in thickness, has a filtration efficiency of 99% or more for particulate matter 4 μm or larger, and a dust holding capacity of 200 g / m 2 The lower layer of the composite filtration medium may include two or more layers of meltblown fiber filtration medium, each layer having a thickness of less than 0.3 mm. The layers of the composite filtration medium may be bonded together by ultrasonic waves.

[0059] In one embodiment, the weight per unit area is 250 to 350 g / m 2 The composite fuel filter media, with a thickness of 1.0 to 1.4 mm, has a filtration efficiency of over 90% for particulate matter 4 μm or larger, and a dust holding capacity of 240 g / m 2 In one embodiment, the weight per unit area is 250 to 350 g / m 2 The composite fuel filter media, with a thickness of 1.0 to 1.4 mm, has a filtration efficiency of 80% or more for particulate matter 4 μm or larger, and a dust holding capacity of 240 g / m 2 The composite filtration medium may have a protective layer disposed over the upper layer. The composite filtration medium may include a meltblown upper layer having a thickness of less than 0.5 mm and a meltblown middle layer having a thickness of less than 0.3 mm. Each layer of the composite filtration medium may be bonded together using ultrasonic waves.

[0060] In one embodiment, the weight per unit area is 200 to 300 g / m 2The composite fuel filter media, with a thickness of 1.0 to 1.5 mm, has a filtration efficiency of over 90% for particulate matter 4 μm or larger, and a dust holding capacity of 240 g / m 2 In one embodiment, the weight per unit area is 200 to 300 g / m 2 The composite fuel filter media, with a thickness of 1.0 to 1.5 mm, has a filtration efficiency of 80% or more for particulate matter 4 μm or larger, and a dust holding capacity of 240 g / m 2 The composite filtration medium may include an upper layer comprising a mixture of short fibers and meltblown fibers. The upper layer may have a thickness of less than 0.5 mm. Each layer of the composite filtration medium may be ultrasonically bonded.

[0061] In one embodiment, the weight per unit area is 250 to 350 g / m 2 The composite fuel filter media, with a thickness of 1.0 to 1.4 mm, has a filtration efficiency of 99.5% or more for particulate matter 4 μm or larger, and a dust holding capacity of 180 g / m 2 The bottom layer of the composite filtration medium can include a nanofiber layer. The thickness of the bottom layer can be less than 0.3 mm. The layers of the composite filtration medium can be bonded together using ultrasonic waves.

[0062] In one embodiment, the weight per unit area is 200 to 350 g / m 2 The composite fuel filter media, with a thickness of 1.0 to 1.5 mm, has a filtration efficiency of 80% or more for particulate matter 4 μm or larger, and a dust holding capacity of 240 g / m 2 In one embodiment, the weight per unit area is 200 to 350 g / m 2 The composite fuel filter media, with a thickness of 1.0 to 1.5 mm, has a filtration efficiency of over 90% for particulate matter 4 μm or larger, and a dust holding capacity of 240 g / m 2 In one embodiment, the weight per unit area is 200 to 350 g / m 2 The composite fuel filter media, with a thickness of 1.0 to 1.5 mm, has a filtration efficiency of 95% or more for particulate matter 4 μm or larger, and a dust holding capacity of 200 g / m 2 In one embodiment, the weight per unit area is 200 to 350 g / m 2The composite fuel filter media, with a thickness of 1.0 to 1.5 mm, has a filtration efficiency of 99% or more for particulate matter 4 μm or larger, and a dust holding capacity of 200 g / m 2 In one embodiment, the weight per unit area is 200 to 350 g / m 2 The composite fuel filter media, with a thickness of 1.0 to 1.5 mm, has a filtration efficiency of 99.5% or more for particulate matter 4 μm or larger, and a dust holding capacity of 180 g / m 2 In one embodiment, the weight per unit area is 200 to 350 g / m 2 The composite fuel filter media, with a thickness of 1.0 to 1.5 mm, has a filtration efficiency of 99.9% or more for particulate matter 4 μm or larger, and a dust holding capacity of 180 g / m 2 The composite filtration medium may have a lower layer containing nanofibers. The composite filtration medium may have a protective layer disposed over the upper layer. The composite filtration medium may have a middle layer containing two or more independent meltblown media layers, each layer having a thickness of less than 0.5 mm. The composite filtration medium may have layers that are bonded together by ultrasonic waves.

[0063] In some embodiments, a wire mesh support can be positioned downstream of the support layer. In some embodiments, the filtration media (e.g., the filtration media in a filter element) can be pleated. The filtration media of the present invention can be manufactured into other filter elements, including plate filters, cylindrical filters, or other filtration members.

[0064] Figure 7 shows one embodiment of a cylindrical filter element in which the composite filtration media can be used. Filter element 70 has a top 71, a bottom 72, an exterior surface 73, and a fluid inlet or outlet 74 (depending on the filter's flow design). The composite filtration media is placed in the filter element with the top layer of media facing upstream and the bottom layer facing downstream. If the fluid is being filtered as it flows from the exterior to the interior of the filter element, the top layer faces the exterior surface of the filter element. If the fluid is being filtered as it flows from the interior to the exterior of the filter element, the bottom layer faces the exterior surface of the filter element.

[0065] As used herein, a fiber having an "average" diameter means that the average fiber diameter of the fibers in a sample of fibers is that value.

[0066] Fiber diameter can be measured using planar scanning electron microscope (SEM) images. The sample can be sputter-coated. A suitable sputter-coating material is a 60:40 mixture of gold (Au):palladium (Pd). Measuring the fiber diameter at at least 30 locations on the sample allows for more accurate measurements.

[0067] As used herein, "nanofibers" can include fibers with a diameter of 5 μm. In some embodiments, fine nanofibers have a diameter of at least 10 nm or at least 100 nm.

[0068] The term "diameter" refers to the diameter of a circular cross-section of a fiber or the largest cross-sectional dimension of a non-circular cross-section of a fiber.

[0069] As used herein, the term "particle size" refers to the diameter of a particle as determined according to the method described in ISO 11171:2016.

[0070] Unless otherwise specified, pore size measurements are based on capillary flow porometry. Capillary flow testing can be performed using a continuous pressure scan mode. It is useful to use silicone oil, with a surface tension of 20.1 dynes / cm and a wetting contact angle of 0, as the wetting liquid. The test is first performed in the dry state of the sample, with pressures applied from low to high, and then again in the wet state, with pressures applied from low to high. This test is typically performed at ambient temperature (e.g., 20°C to 25°C). Up to 256 data points can be collected across the entire pressure scan range for the dry and wet curves. Generally, bending and / or shape factors are not used (i.e., factors equal to 1 can be used for comparison with other test methods that use adjustment factors).

[0071] In the capillary flow porometry measurement procedure, the mean flow pore size of a filtration medium is defined as the pore size at which 50% of the total flow through the layer under test flows through pores of size equal to or smaller than the size under test.

[0072] As used herein, "pressure drop" (also referred to herein as "dP" or "ΔP") means the pressure (applied by a pump) required to force a fluid through a filter or filtration medium at a specific fluid velocity. Unless otherwise specified, pressure drop is measured according to the method described in ISO 3968:2017.

[0073] The term "comprises" and variations thereof, when used in the specification and claims, are not limiting. Such terms are understood to imply the inclusion of the recited steps or elements, or combinations of steps and elements, but not the exclusion of other steps or elements, or combinations of steps and elements. "Consisting of" means consisting of what is included in, and limited to, the recited elements. Thus, "consisting of" means that the recited elements are necessary or mandatory, and that no other elements may be present. "Consisting essentially of" means including all elements recited in the recited elements, and is limited to other elements that do not interfere with or contribute to the activity or function specified by the recited elements herein. Thus, "consisting of" means that the recited elements are necessary or mandatory, and that other elements are optional and may or may not be present, specifically whether they have a substantial effect on the activity or function of the recited elements.

[0074] The terms "preferred" and "preferably" refer to embodiments of the invention that may provide certain advantages in some cases. However, other embodiments may also be preferred, in other cases, either the same or different. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are unnecessary, nor is it intended to exclude other embodiments from the scope of the invention.

[0075] Unless otherwise stated, the terms "a," "an," "the," and "at least one" are used interchangeably and mean one or more. At least one of and "comprised at least one of" refer to any one or any combination of two or more of the listed items.

[0076] As used herein, unless otherwise stated, "or" and "and / or" are used in their ordinary sense. "And / or" refers to one or all of the listed elements, or a combination of any two or more of the listed elements.

[0077] Similarly, herein, the recitation of numerical ranges includes all numbers subsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, 5, etc.). As used herein, references to a number "up to" (e.g., up to 50) include the number in question (e.g., 50).

[0078] For any method disclosed herein including discrete steps, those steps may be performed in any practicable order, and, where appropriate, any combination of two or more steps may be performed simultaneously.

[0079] References herein to "one embodiment," "an embodiment," "certain embodiments," or "some embodiments" mean that the particular feature, structure, composition, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of such phrases herein do not necessarily refer to the same embodiment of the present invention. Furthermore, the particular features, structures, compositions, or characteristics may be combined in any suitable manner in one or more embodiments.

[0080] Any standard methods (eg, ASTM, ISO, etc.) cited herein are the most recent editions of the methods available at the time of filing of the present invention, unless otherwise stated.

[0081] Unless otherwise specified, all numbers expressing component numbers, molecular weights, and the like used in the specification and claims are understood to be modified in all instances by the term "about." As used herein, when referring to a measured quantity, the term "about" refers to expected variations in the measured quantity when a skilled artisan makes a measurement, using caution depending on the target measurement and the precision of the measuring device being used. Thus, unless indicated to the contrary, the numerical values ​​and parameters set forth in the specification and claims are approximations that may vary depending on the properties sought by the present invention. Furthermore, and without any attempt to limit the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed in light of the number of reported significant digits and using ordinary rounding techniques.

[0082] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible, however, all numerical values ​​inherently contain ranges necessarily resulting from the standard deviation found in their respective testing measurements.

[0083] All titles should not be used to limit the meaning of the text unless otherwise stated. [Example]

[0084] [Example 1]

[0085] The weight per unit area is 140g / m 2 A polyethylene terephthalate (PET) spunbond nonwoven fabric with a density of 35 g / m is prepared as a support layer. 2 Polybutylene terephthalate (PBT) meltblown nonwoven fabric with a density of 25 g / m 2 The average fiber diameters are 6.25 μm and 5.53 μm, respectively. The middle layer is 45 g / m 2 Polybutylene terephthalate (PBT) meltblown nonwoven fabric with a density of 30 g / m 2 The lower layer is made of a 30g / m2 polybutylene terephthalate (PBT) meltblown nonwoven fabric with average fiber diameters of 2.2μm and 1.43μm, respectively. 2 The polyamide (PA) meltblown nonwoven fabric has an average fiber diameter of 1.56 μm. The properties and performance of each layer are shown in Table 1. The upper layer, middle layer, lower layer and support layer are stacked from top to bottom as shown in Figure 2. After ultrasonic bonding, a synthetic composite fuel filtration medium is obtained, with a weight per unit area of ​​300 g / m. 2 , and the thickness is 1.25mm.

[0086] Tested according to ISO 9237, synthetic composite filtration media has an air permeability of 30 l / m 2 / s. Filtration efficiency and dust holding capacity are tested using a multi-channel test stand in accordance with ISO 19438. The test medium is No. 15 aviation hydraulic fluid, and the test dust is A3 dust as specified in ISO 12103. The test conditions are a flow rate of 0.7 l / min, △P of 100 kPa, and a contaminant (dust) concentration of 100 mg / l. The test results show that the filtration efficiency for particulate matter 4 μm or larger is 95%, and the dust holding capacity is 220 g / m 2 is. [Table 1] [Example 2]

[0087] The weight per unit area is 120g / m 2 A polyethylene terephthalate (PET) spunbond nonwoven fabric of 40 g / m is prepared as a support layer. 2 The middle layer is made of two layers of polybutylene terephthalate (PBT) meltblown nonwoven fabric, with an average fiber diameter of 7.35 μm. The weight per unit area of ​​each layer is 30 g / m. 2 The average fiber diameters are 1.78 μm and 1 μm, respectively. The lower layer is 30 g / m 2 The polyamide (PA) meltblown nonwoven fabric has an average fiber diameter of 1.3 μm. The properties and performance of each layer are shown in Table 2. The upper layer, middle layer, lower layer, and support layer obtained above are stacked from top to bottom as shown in Figure 3. After ultrasonic bonding, a synthetic composite fuel filtration medium is obtained, with a weight per unit area of ​​250 g / m. 2 , and the thickness is 1.05mm.

[0088] Tested according to ISO 9237, synthetic composite filtration media has an air permeability of 30 l / m 2 / s. Filtration efficiency and dust holding capacity are tested using a multi-channel test stand in accordance with ISO 19438. The test medium is No. 15 aviation hydraulic fluid, and the test dust is A3 dust as specified in ISO 12103. The test conditions are a flow rate of 0.7 l / min, △P of 100 kPa, and a contaminant (dust) concentration of 100 mg / l. The test results show that the filtration efficiency for particulate matter 4 μm or larger is 99%, and the dust holding capacity is 210 g / m 2 is. [Table 2] [Example 3]

[0089] The weight per unit area is 20g / m 2A polyethylene terephthalate (PET) spunbond nonwoven fabric with a weight per unit area of ​​54.2 g / m is prepared as a protective layer. The upper layer is a polyethylene terephthalate (PET) spunlace nonwoven fabric with a weight per unit area of ​​54.2 g / m. 2 The average fiber diameter is approximately 8 μm. The middle layer is a polybutylene terephthalate (PBT) meltblown nonwoven fabric with a weight per unit area of ​​28.6 g / m. 2 The average fiber diameter is 2.89 μm. The lower layer is a polybutylene terephthalate (PBT) meltblown nonwoven fabric with a weight per unit area of ​​40 g / m. 2 The average fiber diameter is 1.68 μm. The weight per unit area is 120 g / m 2 The support layer is a polyethylene terephthalate (PET) spunbond nonwoven fabric. The properties and performance of each layer are shown in Table 3. The protective layer, upper layer, middle layer and support layer are arranged from top to bottom as shown in Figure 4. After bonding with ultrasound, the weight per unit area is 260 g / m 2 , to obtain a synthetic fuel filtration media that is 1.3mm thick.

[0090] Tested according to ISO 9237, synthetic composite filtration media has an air permeability of 30 l / m 2 / s. Filtration efficiency and dust holding capacity are tested using a multi-channel test stand in accordance with ISO 19438. The test medium is No. 15 aviation hydraulic fluid, and the test dust is A3 dust as specified in ISO 12103. The test conditions are a flow rate of 0.7 l / min, △P of 100 kPa, and a contaminant (dust) concentration of 100 mg / l. The test results show that the filtration efficiency for particulate matter 4 μm or larger is 90%, and the dust holding capacity is 250 g / m 2 is. [Table 3] [Example 4]

[0091] The weight per unit area is 20g / m 2A polyethylene terephthalate (PET) spunbond nonwoven fabric is prepared as a protective layer. The upper layer is a polybutylene terephthalate (PBT) meltblown nonwoven fabric with a weight per unit area of ​​38 g / m. 2 The average fiber diameter is 6.25 μm. The middle layer is a polybutylene terephthalate (PBT) meltblown nonwoven fabric with a weight per unit area of ​​28 g / m. 2 The average fiber diameter is 2.89 μm. The lower layer is a polybutylene terephthalate (PBT) meltblown nonwoven fabric with a weight per unit area of ​​40 g / m. 2 The average fiber diameter is 1.68 μm. The weight per unit area is 120 g / m 2 A polyethylene terephthalate (PET) spunbond nonwoven fabric is prepared as the support layer. The properties and performance of each layer are shown in Table 4. The protective layer, upper layer, middle layer and support layer are arranged from top to bottom as shown in Figure 4. After bonding with ultrasound, the weight per unit area is 250 g / m 2 , to obtain a synthetic fuel filtration media that is 1.2mm thick.

[0092] Tested according to ISO 9237, synthetic composite filtration media has an air permeability of 80 l / m 2 / s. Filtration efficiency and dust holding capacity are tested using a multi-channel test stand in accordance with ISO 19438. The test medium is No. 15 aviation hydraulic fluid, and the test dust is A3 dust as specified in ISO 12103. The test conditions are a flow rate of 0.7 l / min, △P of 100 kPa, and a contaminant (dust) concentration of 100 mg / l. The test results show that the filtration efficiency for particulate matter 4 μm or larger is 90%, and the dust holding capacity is 240 g / m 2 is. [Table 4] [Example 5]

[0093] The weight per unit area is 20g / m 2 A polyethylene terephthalate (PET) spunbond nonwoven fabric is prepared as a protective layer. The upper layer is a bicomponent material with a weight per unit area of ​​42.5 g / m.2 It is made by mixing thick polyethylene terephthalate (PET) staple fibers and fine polybutylene terephthalate (PBT) meltblown fibers. The middle layer is 28.6 g / m 2 The polybutylene terephthalate (PBT) meltblown nonwoven fabric has an average fiber diameter of 2.89 μm. The lower layer is 40 g / m 2 It is a polybutylene terephthalate (PBT) meltblown nonwoven fabric with an average fiber diameter of 1.68 μm and a weight per unit area of ​​120 g / m 2 A polyethylene terephthalate (PET) spunbond nonwoven fabric is prepared as the support layer. The properties and performance of each layer are shown in Table 5. The protective layer, upper layer, middle layer and support layer are arranged from top to bottom as shown in Figure 5. After bonding with ultrasound, the weight per unit area is 250 g / m 2 , to obtain a synthetic fuel filtration media that is 1.2mm thick.

[0094] Tested according to ISO 9237, the synthetic composite filtration media has an air permeability of 70 l / m 2 / s. Filtration efficiency and dust holding capacity are tested using a multi-channel test stand in accordance with ISO 19438. The test medium is No. 15 aviation hydraulic fluid, and the test dust is A3 dust as specified in ISO 12103. The test conditions are a flow rate of 0.7 l / min, △P of 100 kPa, and a contaminant (dust) concentration of 100 mg / l. The test results show that the filtration efficiency for particulate matter 4 μm or larger is 90%, and the dust holding capacity is 250 g / m 2 is. [Table 5] [Example 6]

[0095] The weight per unit area is 20g / m 2 A polyethylene terephthalate (PET) spunbond nonwoven fabric is prepared as a protective layer. The upper layer is a polybutylene terephthalate (PBT) meltblown nonwoven fabric with a weight per unit area of ​​25 g / m. 2The average fiber diameter is 5.90 μm. The middle layer is made of three layers of meltblown nonwoven fabric, each of which is 30 g / m 2 Polybutylene terephthalate (PBT) meltblown nonwoven fabric with an average fiber diameter of 1.7 μm and a weight of 30 g / m 2 Polybutylene terephthalate (PBT) meltblown nonwoven fabric with an average fiber diameter of 0.88 μm and a weight of 30 g / m 2 The fabric is a polybutylene terephthalate (PBT) meltblown nonwoven fabric with an average fiber diameter of 1.3 μm. The lower layer is a nanofiber layer fabricated by electrospinning, with an average nanofiber diameter of 0.5 μm. The performance of each layer is shown in Table 6. The weight per unit area is 120 g / m. 2 A polyethylene terephthalate (PET) spunbond nonwoven fabric is prepared as a support layer.

[0096] The protective layer, upper layer, middle layer, lower layer and supporting layer are arranged from top to bottom, and then subjected to ultrasonic compounding treatment, so that the final weight per unit area is 250g / m 2 , to obtain a synthetic oil filtration media with a thickness of 1.1 mm.

[0097] Tested according to ISO 9237, synthetic composite filtration media has an air permeability of 10 l / m 2 / s. Filtration efficiency and dust holding capacity are tested using a multi-channel test stand in accordance with ISO 19438. The test medium is No. 15 aviation hydraulic fluid, and the test dust is A3 dust as specified in ISO 12103. The test conditions are a flow rate of 0.7 l / min, △P of 100 kPa, and a contaminant (dust) concentration of 100 mg / l. The test results show that the filtration efficiency for particulate matter 4 μm or larger is 99.9%, and the dust holding capacity is 200 g / m 2 is. [Table 6]

[0098] Other embodiments of the composite filtration media are as follows. [Embodiment 1]

[0099] 1. A composite filtration medium for use in filtering liquids, comprising: a. An upper layer, comprising a polymeric material of polymeric fibers, the material having a mean flow pore size greater than 35 μm and the polymeric fibers having an average fiber diameter of 4-25 μm. b. A middle layer disposed below the upper layer, comprising a polymer material of polymer fibers, the material having a mean flow pore size not exceeding 35 μm, and the polymer fibers having an average fiber diameter of 1 μm to 5 μm. c. A lower layer disposed below the intermediate layer, comprising a polymer material of polymer fibers, the material having a mean flow pore size not exceeding 15 μm, and the polymer fibers having an average fiber diameter of 0.05 μm to 2 μm. d. A support layer provided below the lower layer, the weight per unit area of ​​which is 70 g / m 2 The support layer comprises a polymer material of polymer fibers having an average fiber diameter of 15 μm or more. wherein the composite filtration medium is substantially free of glass fibers, has a total thickness of not more than 2 mm, and has a total weight per unit area of ​​not more than 200 g / m 2 That's all. [Embodiment 2]

[0100] 2. The composite filtration media of embodiment 1, wherein the middle layer polymeric fibers have an average fiber diameter smaller than the average fiber diameter of the top layer fibers, and the bottom layer polymeric fibers have an average fiber diameter smaller than the average fiber diameter of the middle layer fibers. [Embodiment 3]

[0101] The intermediate layer includes a meltblown polymer layer, and its weight per unit area is 25 to 35 g / m 2 2. The composite filtration medium of embodiment 1, wherein the thickness is 0.15 to 0.2 mm. [Embodiment 4]

[0102] The intermediate layer comprises a plurality of meltblown polymer layers, and each meltblown layer has a weight per unit area of ​​25 to 35 g / m 2 2. The composite filtration medium of embodiment 1, wherein the thickness is 0.1 to 0.3 mm. [Embodiment 5]

[0103] 2. The composite filtration medium of embodiment 1, wherein the lower layer comprises a meltblown polymer layer, the thickness of which is 0.2-0.4 mm and the average fiber diameter of which is greater than 1 μm. [Embodiment 6]

[0104] 2. The composite filtration medium of embodiment 1, wherein the lower layer comprises a nanofiber layer, and the nanofiber layer has an average fiber diameter of 0.3-0.7 μm. [Embodiment 7]

[0105] 2. The composite filtration medium of claim 1, wherein the top layer comprises a meltblown polymer layer having an average fiber diameter of less than 10 μm. [Embodiment 8]

[0106] 2. The composite filtration media of embodiment 1, wherein the top layer comprises a mixture of staple fibers and meltblown fibers, and the average fiber diameter of the staple fibers is at least twice the average fiber diameter of the meltblown fibers. [Embodiment 9]

[0107] When tested in accordance with ISO 19438, the composite filter media has a filtration efficiency of 90% or more for particulate matter 4 μm or larger and a dust holding capacity of 200 g / m 2 The composite filtration medium of embodiment 1, as described above. [Embodiment 10]

[0108] When tested in accordance with ISO 19438, the composite filter media has a filtration efficiency of 99% or more for particulate matter 4 μm or larger and a dust holding capacity of 200 g / m 2 The composite filtration medium of embodiment 1, as described above. [Embodiment 11]

[0109] 1. A composite filtration medium for use in filtering liquids, comprising: a. Upper layer: Contains polymer fiber polymer material, and the weight per unit area of ​​the upper layer is 20~100g / m 2 and the average fiber diameter of the polymer fibers is 4 μm to 20 μm. b. An intermediate layer provided below the upper layer, comprising a polymer material of polymer fiber, and having a weight per unit area of ​​20 to 90 g / m 2 and the average fiber diameter of the polymer fibers is smaller than the average diameter of the upper layer polymer fibers. c. A lower layer provided below the intermediate layer, comprising a polymer material of polymer fiber, and having a weight per unit area of ​​20 to 60 g / m 2 and the average fiber diameter of the polymer fibers is smaller than the average fiber diameter of the intermediate layer polymer fibers. d. A support layer provided below the lower layer, the weight per unit area of ​​which is 70 g / m 2 or more, and the average fiber diameter is 15 μm or more. wherein the composite filtration medium is substantially free of glass fibers, has a total thickness of not more than 2 mm, and has a total weight per unit area of ​​not more than 200 g / m 2 That's all. [Embodiment 12]

[0110] 12. The composite filtration media of claim 11, wherein the middle layer comprises a polymeric material having a mean flow pore size of less than 35 μm and the bottom layer comprises a polymeric material having a mean flow pore size of less than 15 μm, and the bottom layer polymeric material has a mean flow pore size that is less than the mean flow pore size of the middle layer polymeric material. [Embodiment 13]

[0111] 12. The composite filtration medium of embodiment 11, wherein the intermediate layer comprises a meltblown polymer layer, the average fiber diameter of which is 1-5 μm and the thickness of which is 0.15-0.2 mm. [Embodiment 14]

[0112] 12. The composite filtration medium of embodiment 11, wherein the intermediate layer comprises a plurality of meltblown polymer layers, each meltblown layer having an average fiber diameter of 0.8-5 μm and a thickness of 0.1-0.3 mm. [Embodiment 15]

[0113] 12. The composite filtration media of embodiment 11, wherein the bottom layer comprises a plurality of meltblown polymer layers, the thickness of which is 0.2-0.4 mm and the average fiber diameter of which is greater than 1 μm. [Embodiment 16]

[0114] 12. The composite filtration medium of embodiment 11, wherein the lower layer comprises a nanofiber layer, and the nanofiber layer has an average fiber diameter of 0.3 to 0.7 μm. [Embodiment 17]

[0115] 12. The composite filtration media of claim 11, wherein the top layer comprises a meltblown polymer layer having an average fiber diameter of less than 10 μm. [Embodiment 18]

[0116] 12. The composite filtration media of embodiment 11, wherein the top layer comprises a mixture of short polymeric fibers and polymeric meltblown fibers, and the average fiber diameter of the short fibers is at least twice the average fiber diameter of the meltblown fibers. [Embodiment 19]

[0117] When tested in accordance with ISO 19438, the composite filtration media has a filtration efficiency of 90% or more for particulate matter 0.4 μm and larger, and a dust holding capacity of 200 g / m 2 12. The composite filtration medium of embodiment 11. [Embodiment 20]

[0118] When tested in accordance with ISO 19438, the composite filtration media has a filtration efficiency of 99% or greater for particulate matter 0.4 μm and larger, and a dust holding capacity of 200 g / m 2 12. The composite filtration medium of embodiment 11. [Embodiment 21]

[0119] 1. A composite filtration medium for use in filtering liquids, comprising: a. An upper layer, comprising a polymeric material of polymeric fibers, the material having a mean flow pore size greater than 35 μm and the polymeric fibers having an average fiber diameter of 5-20 μm. b. A middle layer disposed below the upper layer, comprising a polymer material of polymer fibers, the material having a mean flow pore size not exceeding 35 μm, and the polymer fibers having an average fiber diameter of 1 μm to 5 μm. c. A lower layer disposed below the intermediate layer, comprising a polymer material of polymer fibers, the material having a mean flow pore size not exceeding 15 μm, and the polymer fibers having an average fiber diameter of 0.1 μm to 2 μm. d. A support layer provided below the lower layer, the weight per unit area of ​​which is 70 g / m 2 The support layer comprises a polymer material of polymer fibers having an average fiber diameter of 15 μm or more. wherein the composite filtration medium is substantially free of glass fibers, has a total thickness of no more than 2 mm, and has a total weight per unit area of ​​180 g / m 2 That's all. [Embodiment 22]

[0120] 22. The composite filtration media of embodiment 21, wherein the average diameter of the polymeric fibers of the middle layer is smaller than the average fiber diameter of the top layer fibers, and the average fiber diameter of the polymeric fibers of the bottom layer is smaller than the average fiber diameter of the middle layer fibers. [Embodiment 23]

[0121] The intermediate layer includes a meltblown polymer layer, and its weight per unit area is 25 to 35 g / m 2 22. The composite filtration medium of embodiment 21, wherein the thickness is 0.15 to 0.2 mm. [Embodiment 24]

[0122] The intermediate layer comprises a plurality of meltblown polymer layers, and each meltblown layer has a weight per unit area of ​​25 to 35 g / m 2 22. The composite filtration medium of embodiment 21, wherein the thickness is 0.1 to 0.3 mm. [Embodiment 25]

[0123] 22. The composite filtration medium of embodiment 21, wherein the bottom layer comprises a meltblown polymer layer having a thickness of 0.1 to 0.3 mm and an average fiber diameter greater than 0.5 μm. [Embodiment 26]

[0124] 22. The composite filtration medium of embodiment 21, wherein the lower layer comprises a nanofiber layer, the nanofiber layer comprising multi-component nanofibers of thick nanofibers and fine nanofibers, the thick nanofibers having an average fiber diameter of 0.4-3 μm, and the fine nanofibers having an average fiber diameter of 0.1-0.3 μm. [Embodiment 27]

[0125] 22. The composite filtration media of claim 21, wherein the top layer comprises a meltblown polymer layer having an average fiber diameter of less than 10 μm. [Embodiment 28]

[0126] 22. The composite filtration media of embodiment 21, wherein the top layer comprises a mixture of staple fibers and meltblown fibers, and the average fiber diameter of the staple fibers is at least twice the average fiber diameter of the meltblown fibers. [Embodiment 29]

[0127] When tested in accordance with ISO 19438, the composite filter media has a filtration efficiency of at least 70% for particulate matter 4 μm and larger, and a dust holding capacity of 200 g / m 2 22. The composite filtration medium of embodiment 21. [Embodiment 30]

[0128] When tested in accordance with ISO 19438, the composite filter media has a filtration efficiency of 80% or more for particulate matter 4 μm or larger and a dust holding capacity of 200 g / m 2 22. The composite filtration medium of embodiment 21. [Embodiment 31]

[0129] 1. A composite filtration medium for use in filtering liquids, comprising: a. Upper layer: Contains polymer fiber polymer material, and the weight per unit area of ​​the upper layer is 20~100g / m 2 and the average fiber diameter of the polymer fibers is 5 to 20 μm. b. An intermediate layer provided below the upper layer, comprising a polymer material of polymer fiber, and having a weight per unit area of ​​20 to 80 g / m 2 and the average fiber diameter of the polymer fibers is smaller than the average diameter of the upper layer polymer fibers. c. A lower layer provided below the intermediate layer, comprising a polymer material of polymer fiber, and having a weight per unit area of ​​20 to 60 g / m 2 and the average fiber diameter of the polymer fibers is less than the average fiber diameter of the intermediate layer polymer fibers; and d. A support layer provided below the lower layer, the weight per unit area of ​​which is 70 g / m 2 or more, and the average fiber diameter is 15 μm or more. wherein the composite filtration medium is substantially free of glass fibers, has a total thickness of no more than 2 mm, and has a total weight per unit area of ​​180 g / m 2 That's all. [Embodiment 32]

[0130] 32. The composite filtration medium of claim 31, wherein the middle layer comprises a polymeric material having a mean flow pore size of less than 35 μm and the bottom layer comprises a polymeric material having a mean flow pore size of less than 15 μm, and the bottom layer polymeric material has a mean flow pore size that is less than the mean flow pore size of the middle layer polymeric material. [Embodiment 33]

[0131] The intermediate layer includes a meltblown polymer layer, and its weight per unit area is 30 to 60 g / m 2 32. The composite filtration medium of embodiment 31, wherein the average fiber diameter is 1-5 μm and the thickness is 0.15-0.2 mm. [Embodiment 34]

[0132] 32. The composite filtration medium of embodiment 31, wherein the intermediate layer comprises a plurality of meltblown polymer layers, each meltblown layer having an average fiber diameter of 0.8-5 μm and a thickness of 0.1-0.3 mm. [Embodiment 35]

[0133] 32. The composite filtration medium of embodiment 31, wherein the bottom layer comprises a meltblown polymer layer having a thickness of 0.10 to 0.3 mm and an average fiber diameter greater than 0.5 μm. [Embodiment 36]

[0134] 32. The composite filtration medium of embodiment 31, wherein the lower layer comprises a nanofiber layer, the nanofibers comprising multicomponent nanofibers of thick nanofibers and fine nanofibers, the thick nanofibers having an average fiber diameter of 0.4 to 3 μm, and the fine nanofibers having an average fiber diameter of 0.1 to 0.3 μm. [Embodiment 37]

[0135] 32. The composite filtration media of embodiment 31, wherein the top layer comprises a meltblown polymer layer having an average fiber diameter of less than 10 μm. [Embodiment 38]

[0136] 32. The composite filtration media of embodiment 31, wherein the top layer comprises a mixture of short polymeric fibers and polymeric meltblown fibers, and the average fiber diameter of the short fibers is at least twice the average fiber diameter of the meltblown fibers. [Embodiment 39]

[0137] When tested in accordance with ISO 19438, the composite filter media has a filtration efficiency of 90% or more for particulate matter 4 μm or larger and a dust holding capacity of 200 g / m 2 32. The composite filtration medium of embodiment 31. [Embodiment 40]

[0138] When tested in accordance with ISO 19438, the composite filter media has a filtration efficiency of 99% or more for particulate matter 4 μm or larger and a dust holding capacity of 200 g / m 2 32. The composite filtration medium of embodiment 31. [Embodiment 41]

[0139] The composite filtration medium of any preceding embodiment, wherein the lower layer comprises a plurality of multi-layered nanofibers, the multi-layered nanofibers comprising a nanofiber layer and an inner support layer, the nanofiber layer comprising a first fiber distribution having an average fiber diameter of 10 nm to 300 nm, and the inner support layer comprising a second fiber distribution having an average fiber diameter of 0.3 to 25 μm, and wherein, in the plurality of multi-layered nanofibers, the inner support layer is disposed between at least two nanofiber layers.

[0140] The above description is for the purpose of illustrating the present invention, not for the purpose of limiting it. For example, the above examples (one or more aspects thereof) can be combined with each other. Those skilled in the art can adopt other embodiments after reading the above description. In accordance with the provisions of Title 37, U.S. Code, Section 1.72(b), the Abstract is provided to enable readers to quickly understand the substance of the technical solution, and it is expressly stated that it is not intended to be used to interpret or limit the scope or meaning of the claims when submitted. Furthermore, in specific embodiments, various features may be combined to simplify the disclosure. This should not be construed as implying that features not claimed for protection are essential to the claims. The substance of the invention may be embodied in some technical features of a particular embodiment. Therefore, the following claims are incorporated by reference into the specific embodiments, with each claim existing as an independent embodiment, and these embodiments can be combined with each other in various combinations or arrangements. The scope of the present invention shall be determined by reference to the appended claims, along with the full scope of their legal equivalents.

[0141] Although the inventive concepts have been described with reference to specific exemplary embodiments, various modifications and changes can be made to these embodiments without departing from the broader scope of each embodiment of the invention. Embodiments based on the inventive concepts may be referred to herein, singly or collectively, as the "invention," but this is for convenience only and is not intended to limit the scope of this application to any single disclosure or inventive concept (if multiple embodiments are actually disclosed).

[0142] All embodiments have been described in detail herein to enable those skilled in the art to practice the disclosed embodiments. Other embodiments may be adopted and based on them to create other embodiments. Accordingly, structure and logic may be interchanged and modified without departing from the scope of the disclosure. The above detailed description does not limit the invention, and the scope of each embodiment is defined by the appended claims and all claims with legal equivalents.

[0143] In this specification, the term "or" may be interpreted as either inclusive or exclusive. Furthermore, multiple instances of a resource, operation, or structure described herein may be provided for a single instance. Furthermore, the boundaries between each resource, operation, module, engine, and data store may be freely defined within certain boundaries, and specific operations are described in specific descriptive paragraphs. Other distributions of functionality are contemplated and may fall within the scope of the embodiments of the present disclosure. In general, structures and functions described in the examples as a single resource may also be implemented as a combined structure or resource. Similarly, structures and functions described as a single resource may also be implemented as a single resource. This means that all other variations, modifications, additions, and improvements are intended to be within the scope of the embodiments of the present disclosure, as defined in the appended claims. Accordingly, the specification and drawings are illustrative of the present invention, not limiting.

[0144] For purposes of explaining the present invention, the foregoing description has been given with reference to specific exemplary embodiments. However, the foregoing illustrative discussion is not intended to be exhaustive of possible exemplary embodiments or to limit the present invention to the precise form disclosed. As noted above, various modifications and variations can be made to the present invention. The exemplary embodiments have been selected or described to better explain the principles involved and their practical applications, and to enable those skilled in the art to better utilize various modified embodiments suited to the particular uses envisioned.

[0145] In this specification, the terms "first" and "second" may be used to describe various elements, but these elements should not be understood to be limited by these terms. These terms are used to distinguish one element from another. For example, a first contact member may be referred to as a second contact member, and similarly, a second contact member may be referred to as a first contact member, without departing from the scope of the exemplary embodiments. The first contact member and the second contact member are both contact members, but are not the same contact member.

[0146] The terms used herein when describing exemplary embodiments are used only to describe the particular exemplary embodiment and are not limiting. As used in the description of exemplary embodiments and the accompanying examples, the singular forms "a," "an," and "the" include the plural, unless otherwise stated. Also, the term "and / or" means the inclusion of any and all possible combinations of one or more of the associated items. Furthermore, as used herein, the terms "comprises" and / or "comprises" indicate the presence of features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0147] As used herein, the term "if" may be understood as "upon" or "when" or "responsive to determining" or "responsive to detecting," depending on the context. Similarly, the phrase "if determined" or "if [said condition or event] is detected" may be understood as "when determining" or "responsive to determining" or "when [said condition or event] is detected" or "responsive to detected [said condition or event]," depending on the context.

Claims

1. 1. A composite filtration medium for use in filtering liquids, comprising: a. an upper layer, comprising a polymeric material of polymer fibers, said material having a mean flow pore size greater than 35 μm and a mean fiber diameter of the polymeric fibers between 4 and 25 μm; b. a middle layer disposed below the upper layer, the middle layer comprising a polymeric material of polymeric fibers, the mean flow pore size of the material not exceeding 35 μm, and the polymeric fibers having an average fiber diameter of 1 μm to 5 μm; c. a lower layer disposed below the intermediate layer, the lower layer comprising a polymeric material of polymeric fibers, the material having a mean flow pore size not exceeding 15 μm, and the polymeric fibers having a mean fiber diameter of 0.05 μm to 2 μm; d. a support layer provided below the lower layer, the weight per unit area of ​​which is 70 g / m2 or more, the support layer comprising a polymer material containing polymer fibers with an average fiber diameter of 15 μm or more; Here, the composite filtration medium is substantially free of glass fibers, has a total thickness of not more than 2 mm, and has a total weight per unit area of ​​180 g / m2 or more.

2. the average fiber diameter of the middle layer polymer fibers is smaller than the average fiber diameter of the top layer fibers; and 10. The composite filtration media of claim 1, wherein the bottom layer polymeric fibers have an average fiber diameter that is smaller than the average fiber diameter of the middle layer fibers.

3. The intermediate layer comprises a meltblown polymer layer, and its weight per unit area is 20 to 90 g / m ２ 2. The composite filtration medium of claim 1, wherein the thickness is 0.10 to 0.40 mm.

4. The intermediate layer comprises a plurality of meltblown polymer layers, each of which has a weight per unit area of ​​1 to 80 g / m ２ 2. The composite filtration medium of claim 1, wherein the thickness is 0.10 to 0.35 mm.

5. 2. The composite filtration medium of claim 1, wherein the lower layer comprises a meltblown polymer layer having a thickness of 0.1-0.3 mm and an average fiber diameter greater than 0.5 μm.

6. 2. The composite filtration medium of claim 1, wherein the lower layer comprises a nanofiber layer, the nanofiber layer comprising multi-component nanofibers of thick nanofibers and fine nanofibers, the thick nanofibers having an average fiber diameter of 0.4 to 3 μm, and the fine nanofibers having an average fiber diameter of 0.1 to 0.3 μm.

7. 10. The composite filtration media of claim 1, wherein the top layer comprises a meltblown polymer layer having an average fiber diameter of less than 10 microns.

8. 10. The composite filtration media of claim 1, wherein the top layer comprises a mixture of staple fibers and meltblown fibers, and the average fiber diameter of the staple fibers is at least twice the average fiber diameter of the meltblown fibers.

9. When tested in accordance with ISO 19438, the composite filter media has a filtration efficiency of 70% or more for particulate matter 4 μm or larger and a dust retention capacity of 150 g / m. ２ 2. The composite filtration medium of claim 1, wherein:

10. When tested in accordance with ISO 19438, the composite filter media has a filtration efficiency of 80% or more for particulate matter 4 μm or larger and a dust retention capacity of 150 g / m ２ 2. The composite filtration medium of claim 1, wherein:

11. 1. A composite filtration medium for use in filtering liquids, comprising: a. Upper layer, comprising a polymer material of polymer fiber, the weight per unit area of ​​the upper layer being 20-100 g / m ２ and the polymer fibers have an average fiber diameter of 4 to 25 μm; b. An intermediate layer provided below the upper layer, comprising a polymer material of polymer fibers, and having a weight per unit area of ​​20 to 90 g / m ２ and the average fiber diameter of the polymer fibers is smaller than the average fiber diameter of the upper layer polymer fibers; c. A lower layer provided below the intermediate layer, comprising a polymer material of polymer fibers, and having a weight per unit area of ​​1 to 80 g / m ２ and the average fiber diameter of the polymer fibers is less than the average fiber diameter of the intermediate layer polymer fibers; and d. A polymer support layer provided below the lower layer, the weight per unit area of ​​which is 70 g / m ２ or more, and the average fiber diameter is 15 μm or more, wherein the composite filtration medium is substantially free of glass fibers, has a total thickness of no more than 2 mm, and has a total weight per unit area of ​​180 g / m ２ A composite filtration medium for use in filtering liquids, characterized in that:

12. the intermediate layer comprises a polymeric material having a mean flow pore size of less than 35 μm; 12. The composite filtration media of claim 11, wherein the bottom layer comprises a polymeric material having a mean flow pore size of less than 15 μm, and the mean flow pore size of the bottom layer polymeric material is less than the mean flow pore size of the middle layer polymeric material.

13. The intermediate layer comprises a meltblown polymer layer, the average fiber diameter of which is 1 to 5 μm, and the weight per unit area is up to 40 g / m ２ 12. The composite filtration medium of claim 11, wherein the thickness is 0.10 to 0.40 mm.

14. 12. The composite filtration media of claim 11, wherein the intermediate layer comprises a plurality of meltblown polymer layers, each of which has an average fiber diameter of 1-5 μm and a thickness of 0.1-0.35 mm.

15. 12. The composite filtration medium of claim 11, wherein the bottom layer comprises a meltblown polymer layer having a thickness of 0.1-0.3 mm and an average fiber diameter greater than 0.5 μm.

16. 12. The composite filtration medium of claim 11, wherein the lower layer comprises a nanofiber layer, and the nanofiber layer has an average fiber diameter of 0.1 to 0.7 μm.

17. 12. The composite filtration medium of claim 11, wherein the lower layer comprises a nanofiber layer, and the nanofiber layer comprises multi-component nanofibers of thick nanofibers and fine nanofibers, the thick nanofibers having an average fiber diameter of 0.4 to 3 μm, and the fine nanofibers having an average fiber diameter of 0.1 to 0.3 μm.

18. 12. The composite filtration media of claim 11, wherein the bottom layer comprises a plurality of multi-layered nanofibers, the multi-layered nanofibers comprising a nanofiber layer and an inner support layer, the nanofiber layer comprising a first fiber distribution having an average fiber diameter of 10 nm to 300 nm, the inner support layer comprising a second fiber distribution having an average fiber diameter of 0.3 μm to 25 μm, and wherein, in the plurality of multi-layered nanofibers, a support layer is disposed between at least two nanofiber layers.

19. 12. The composite filtration media of claim 11, wherein the top layer comprises a meltblown polymer layer having an average fiber diameter of less than 10 microns.

20. 12. The composite filtration media of claim 11, wherein the top layer comprises a mixture of short polymeric fibers and polymeric meltblown fibers, and the short fibers have an average fiber diameter that is at least twice the average fiber diameter of the meltblown fibers.

21. When tested in accordance with ISO 19438, the composite filter media has a filtration efficiency of 70% or more for particulate matter 4 μm or larger and a dust retention capacity of 150 g / m. ２ 12. The composite filtration medium of claim 11, wherein:

22. When tested in accordance with ISO 19438, the composite filter media has a filtration efficiency of 80% or more for particulate matter 4 μm or larger and a dust retention capacity of 150 g / m ２ 12. The composite filtration medium of claim 11, wherein:

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