Filter material and filter containing the filter material

Abstract

The object of the present invention is to prevent or at least reduce the drawbacks of the prior art. [Solution] A filter material is provided, comprising at least a first material layer containing fibers and having a first surface and a second surface, a second material layer containing fibers and having a first surface and a second surface, the first surface of the second material layer being oriented parallel to the second surface of the first material layer, the first material layer comprising a mixture of meltblown filaments and fibers having individual lengths, the concentration of meltblown filaments increasing from the first surface to the second surface of the first material layer, the concentration of fibers having individual lengths increasing from the second surface to the first surface of the first material layer, and the second material layer comprising nanofibers forming the first surface of the second material layer.

Description

[Technical Field]

[0001] This application relates to a material for a filter material, a filter material containing the material for the filter material, and a filter element containing the filter material.

[0002] Fluid flows, such as airflow or other gas flows, may contain particulate matter, such as dust particles or soot particles. For example, intake airflow into the cabin of an electric vehicle, or intake airflow to heating, ventilation, and air conditioning systems, may contain particulate matter.

[0003] Removing some or almost all particulate matter from a fluid flow is desirable in many applications. Cabin air filters, for example, are used to remove particulate matter from incoming air to improve passenger comfort in a vehicle cabin.

[0004] Particulate matter contained in a fluid flow can also cause damage to internal components of certain processing equipment. It is desirable to remove some or (almost) all of the particulate matter from such fluid flows before they enter the processing equipment.

[0005] Fluid flows formed in industrial processes, such as gases, may also contain particulate matter. It is desirable to remove some or almost all of the particulate matter from such fluid flows before they are released into the atmosphere.

[0006] To obtain a clean flow of air, other gases, or other fluids, there is a need for filter media with higher efficiency and longer service life. A low pressure drop across the filter media is desirable, for example, to hardly restrict the fluid flow of air or other gases.

[0007] To reduce the maintenance and filter costs of filtration elements, a long service life for the filter material within the filtration element is desired, which is often a challenge for high-efficiency filter materials.

[0008] U.S. Patent No. 11,161,070 discloses a filter material comprising a surface-loaded filter layer containing fibers having an average diameter of less than 1 micron, a depth-loaded layer, and a support layer. The depth-loaded filter layer includes a glass-containing filter layer, a melt-blown filter layer, or a combination thereof. The surface-loaded filter layer containing fine fibers is positioned as the first layer encountered by the gas flow to be filtered, but can be readily blocked by particles.

[0009] U.S. Patent No. 8,679,218 discloses a filter comprising a first layer including a first phase comprising at least a plurality of first and second fibers, and a second phase comprising at least a plurality of third and fourth fibers, wherein the permeability of the first plurality of fibers is greater than that of the second plurality of fibers, the permeability of the third plurality of fibers is greater than that of the fourth plurality of fibers, and further comprising a second nanofiber layer. However, the interface between the first phase and the second phase can still be blocked by particles to be removed from the fluid being filtered.

[0010] U.S. Patent Application Publication No. 2004 / 0211160 discloses a multilayer fiber structure comprising a microfiber mat of a thermoplastic polymer produced by a meltblown process, comprising randomly oriented curled staple fibers including a first synthetic staple fiber having a first fiber fineness and at least one second synthetic staple fiber having a second fiber fineness, and a carded nonwoven fabric that is needle-processed on one side and thermoset, wherein the average fiber diameter of the meltblown microfibers decreases crosswise from the inlet side in the outflow direction. However, such a multilayer fiber structure may still not provide the desired high filtration efficiency, particularly for particles with small particle sizes.

[0011] However, there is still a need for a filter material that provides a desirable combination of filtration properties, including high filtration efficiency and high particle retention capacity, high air permeability of the filter material, low pressure drop on the filter material, and / or a long service life.

[0012] The object of the present invention is to prevent or at least reduce the drawbacks of the prior art.

[0013] This objective is achieved by the filter material described in claim 1.

[0014] A filter material comprising at least a first material layer containing fibers and having a first surface and a second surface, and a second material layer containing fibers and having a first surface and a second surface, wherein the first surface of the second material layer is oriented parallel to, preferably adjacent to, the second surface of the first material layer, and the first material layer containing fibers comprises meltblown filaments and fibers having individual lengths, wherein the concentration of meltblown filaments increases from the first surface to the second surface of the first material layer, and the concentration of fibers having individual lengths decreases from the first surface to the second surface of the first material layer, and the second material layer containing fibers comprises nanofibers forming the first surface of the second material layer, enables the collection of particles of different dimensions at different depths within the filter material without, or at least with reduced, blocking of the surface of the filter material by particles.

[0015] The term filament is understood to mean a fiber having a length greater than 200 mm, preferably greater than 500 mm, and more preferably greater than 1000 mm. A filament may be substantially endless if it is formed, for example, by continuously extruding the extruded filament through the spinning hole of a spinneret without cutting the extruded filament into individual fibers of different lengths.

[0016] The term "staple fiber" is understood to mean fibers with individual lengths ranging from at least 30 mm to 200 mm. The term "short cut fiber" is understood to mean fibers with individual lengths ranging from 2 mm to 30 mm.

[0017] The filtration element may include an inlet for the fluid to be filtered and an outlet for the fluid to be filtered, and may include a filter medium located between the inlet for the fluid to be filtered and the outlet for the fluid to be filtered Particularly, the filter medium may be disposed within a housing that includes an inlet for the fluid to be filtered and an outlet for the fluid to be filtered The fluid to be filtered passes through the filter medium within the filtration element in order to obtain a filtered fluid

[0018] Particularly, when the first surface of the first material layer containing fibers is oriented towards the inlet of the filtration element and the second surface of the second material layer containing fibers is oriented towards the outlet of the filtration element, the material for the filter medium may advantageously be included in a filter medium applicable to the filtration element Thus, the fluid to be filtered may enter the filter medium through the first surface of the first material layer containing fibers and may exit the filter medium through the second surface of the second material layer containing fibers

[0019] The filter medium can provide a desirable combination of filtration characteristics The first surface of the first material layer includes fibers having a higher concentration of individual lengths than the second surface of the first material layer, and the first surface of the first material layer includes a lower concentration of melt blown filaments than the second surface of the first material layer Since the average size of the openings between the fibers on the first surface of the first material layer is relatively large, it is possible to filter particles having a relatively large effective dimension by the first material layer without blocking the first material layer by particles having a relatively small effective dimension or at least reducing the risk thereof

[0020] Particles having relatively small dimensions can penetrate into the filter material through the first surface of the first material layer. However, as the concentration of fibers having individual lengths decreases from the first surface to the second surface of the first material layer and the concentration of melt-blown filaments increases from the first surface to the second surface of the first material layer, the average size of the openings between the fibers decreases from the first surface to the second surface of the first material layer. Thereby, particles of increasingly smaller dimensions are filtered out from the fluid and collected at different depths within the filter material from the first surface to the second surface of the first material layer.

[0021] The first material layer of the filter material includes a mixture of melt-blown filaments and fibers having individual lengths, the concentration of the melt-blown filaments increases from the first surface to the second surface of the first material layer, the concentration of the fibers having individual lengths increases from the second surface to the first surface of the first material layer, and preferably, the first material layer is configured to filter out particles having a maximum passing particle size of 200 nm or more, preferably 150 nm or more, or preferably 100 nm or more.

[0022] The second material layer including nanofibers forming the first surface of the second material layer preferably enables filtering out particles having even smaller effective dimensions from the fluid at the first surface of the second material layer. The average size of the openings between the fibers at the first surface of the second material layer is smaller than the average size of the openings between the fibers at the second surface of the first material layer.

[0023] The second material layer of the filter material includes nanofibers forming the first surface of the second material layer, and preferably, the second material layer is configured to filter out particles having a maximum passing particle size of 200 nm or less, preferably 150 nm or less, or preferably 100 nm or less.

[0024] In one embodiment, the first surface of the second material layer is oriented parallel to and directly adjacent to the second surface of the first material layer, meaning that the filter material does not contain any further material layer containing fibers between the first material layer containing fibers and the second material layer containing fibers.

[0025] The first material layer containing fibers within the filter material comprises a mixture of melt-blown filaments and fibers having individual lengths. The first material layer can be provided, for example, by a melt-blown process in which a polymer molten material is extruded into a high-speed flow of hot gas to produce melt-blown filaments, and by mixing fibers having individual lengths into a high-speed flow of hot gas.

[0026] The first material layer containing fibers in the filter material comprises a mixture of meltblown filaments and fibers having individual lengths. The fibers having individual lengths may constitute at least 50% by weight, preferably at least 60% by weight, preferably at least 70% by weight, or preferably at least 80% by weight, of the total weight of the mixture of meltblown filaments and fibers having individual lengths in the first material layer. The fibers having individual lengths may constitute up to 95% by weight, preferably up to 90% by weight, or preferably up to 85% by weight, of the total weight of the mixture of meltblown filaments and fibers having individual lengths in the first material layer.

[0027] Meltblown filaments may constitute at least 5% by weight, preferably at least 10% by weight, or preferably at least 15% by weight, of the total weight of the mixture of meltblown filaments and fibers having individual lengths in the first material layer. Meltblown filaments may constitute up to 50% by weight, preferably up to 40% by weight, or preferably up to 30% by weight, or preferably up to 40% by weight, of the total weight of the mixture of meltblown filaments and fibers having individual lengths in the first material layer.

[0028] The meltblown filaments contained in the first material layer comprising fibers of the material for the filter medium can comprise, or consist of, any suitable polymer including a polyolefin polymer such as polypropylene, polyethylene and / or a copolymer of polyolefins, a polyester polymer such as polyethylene terephthalate, polybutylene terephthalate and / or a copolymer or derivative of polyester, a polycarbonate and / or a copolymer or derivative of polycarbonate, a polylactic acid and / or a copolymer or derivative of polylactic acid, or any mixture or combination thereof.

[0029] The first material layer comprising fibers within the material for the filter medium includes a mixture of meltblown filaments and fibers having an individual length. The fibers having an individual length can have any cross-sectional shape including circular, oval, V-shaped, trilobal, multilobal or rectangular. The non-circular cross-sectional shapes enable improved filtration performance due to the higher surface area of the fibers.

[0030] The first material layer comprising fibers within the material for the filter medium includes a mixture of meltblown filaments and fibers having an individual length. The first material layer comprising fibers includes at least 30 g / m 2 or preferably at least 40 g / m 2 or preferably at least 50 g / m 2 or preferably at least 75 g / m 2 or preferably at least 100 g / m 2 or preferably at least 125 g / m 2 of fibers having an individual length. The first material layer comprising fibers includes up to 250 g / m 2 or preferably up to 200 g / m 2 or preferably up to 150 g / m 2 or preferably up to 125 g / m 2 or preferably at least 100 g / m 2 or preferably at least 80 g / m 2 of fibers having an individual length.

[0031] The individual length fibers contained in the first material layer containing the fibers of the filter material include, or may consist of, any suitable polymer, including polyolefin polymers, such as polypropylene, polyethylene and / or polyolefin copolymers; polyester polymers, such as polyethylene terephthalate, polybutylene terephthalate and / or polyester copolymers or derivatives; polylactic acid and / or polylactic acid copolymers or derivatives; or any mixture or combination thereof.

[0032] The first material layer containing fibers contains at least 5 g / m² 2 , or preferably at least 10 g / m² 2 , or preferably at least 15 g / m² 2 , or preferably at least 20 g / m² 2 It may contain meltblown filaments.

[0033] The weight of the first material layer containing fibers within the filter material is at least 30 g / m². 2 , or preferably at least 40 g / m² 2 , or preferably at least 50 g / m 2 , or preferably at least 75 g / m² 2 It is possible.

[0034] The weight of the first material layer containing fibers within the filter material is a maximum of 250 g / m². 2 , or preferably up to 200 g / m² 2 , or preferably up to 150 g / m² 2 , or preferably up to 125 g / m² 2 , or preferably up to 100 g / m² 2 It is possible.

[0035] The thickness of the filter material can vary, for example, depending on the application of the filter material. The thickness of the filter material can also be adjusted by the bonding technique used to integrate the filter material.

[0036] The thickness of the filter material may be at least 0.4 mm, or at least 0.6 mm, or at least 0.8 mm, or at least 1.0 mm, or at least 1.5 mm, or at least 2.0 mm. The thickness of the filter material is determined according to DIN EN ISO 9073-2 (1997). The thickness of the filter material may be up to 10.0 mm, or up to 8.0 mm, or up to 6.0 mm, or up to 5.0 mm, or up to 4.0 mm, or up to 3.0 mm.

[0037] In a filter material comprising a first material layer containing fibers comprising a mixture of meltblown filaments and fibers having individual lengths, the concentration of meltblown filaments increases from a first surface to a second surface of the first material layer. The concentration of meltblown filaments may, advantageously, increase progressively from a first surface to a second surface of the first material layer, meaning that the concentration of meltblown filaments increases gradually, i.e., not stepwise, from the first surface to the second surface of the first material layer. By progressively increasing the concentration of meltblown filaments, stepwise changes in the concentration of meltblown filaments between the first and second surfaces of the first material layer are prevented. Stepwise changes in the concentration of meltblown filaments create interfaces within the first material layer that can be blocked by particles.

[0038] The filter material comprises a first material layer containing fibers comprising a mixture of meltblown filaments and fibers having individual lengths, wherein the concentration of fibers having individual lengths increases from a second surface to a first surface of the first material layer. The concentration of fibers having individual lengths may, advantageously, increase progressively from a second surface to a first surface of the first material layer, meaning that the concentration of fibers having individual lengths increases gradually and / or continuously, i.e., not stepwise, from the second surface to the first surface of the first material layer. By progressively increasing the concentration of fibers having individual lengths, stepwise changes in the concentration of fibers having individual lengths between the first and second surfaces of the first material layer are prevented. Stepwise changes in the concentration of fibers having individual lengths create interfaces within the first material layer that can be blocked by particles.

[0039] The meltblown filaments contained in the first material layer containing fibers within the filter material may have an average diameter of 4 μm or less, preferably 1 μm or less, or preferably 750 nm or less. The meltblown filaments contained in the first material layer containing fibers within the filter material may have an average diameter of more than 500 nm.

[0040] The ratio of the average diameter of individual length fibers contained in the first material layer containing fibers in the filter material to the average diameter of meltblown filaments contained in the first material layer containing fibers in the filter material is at least 10, preferably at least 15, preferably at least 20, preferably at least 30, or preferably at least 40.

[0041] Individually lengthened fibers contained in the first material layer containing fibers within the filter material may have an average diameter of at least 5 μm, or preferably at least 10 μm. Individually lengthened fibers contained in the first material layer containing fibers within the filter material may have an average diameter of up to 75 μm, or preferably up to 50 μm, or preferably up to 40 μm.

[0042] The average diameter of a filament or fiber can be determined by averaging the diameters of 50 filaments or fibers using a scanning electron microscope (SEM).

[0043] The fibers having individual lengths contained in the first material layer, which includes fibers within the filter material, can advantageously have lengths of at least 6 mm and up to 40 mm. Processing of fibers having individual lengths less than 6 mm is difficult. For fibers having individual lengths greater than 40 mm, it has been found to be extremely difficult to consistently obtain a first material layer containing a mixture of meltblown filaments and fibers having individual lengths, in which the concentration of fibers having individual lengths gradually increases from the second surface to the first surface of the first material layer.

[0044] The individual length fibers contained in the first material layer containing fibers within the filter material may be crimped or straight. In one embodiment, the individual length fibers have a crimp of up to 15 fibers / cm, preferably up to 10 fibers / cm, or preferably up to 5 fibers / cm.

[0045] The individual fibers included in the first material layer containing fibers within the filter material may be staple fibers having a length in the range of at least 30 mm to 200 mm. In one embodiment, the staple fibers have a length in the range of 30 mm to 40 mm.

[0046] The fibers having individual lengths included in the first material layer containing fibers within the filter material may be short-cut fibers having lengths in the range of 2 mm to 30 mm. In one embodiment, the short-cut fibers have lengths of at least 6 mm and up to 24 mm, or preferably at least 6 mm and up to 18 mm, making it possible to consistently obtain a first material layer containing a mixture of melt-blown filaments and fibers having individual lengths in which the concentration of fibers having individual lengths gradually increases from the second surface to the first surface of the first material layer.

[0047] The nanofibers contained in the second material layer containing fibers within the filter material have an average diameter of 500 nm or less, preferably 400 nm or less, preferably 300 nm or less, or preferably 250 nm or less.

[0048] The nanofibers contained in the second material layer, which contains fibers of the filter material, may contain or consist of any suitable polymer, including polyurethane, polyvinylidene fluoride, polyamide, polyetherimide, polyimide, polyacrylonitrile, polyvinyl alcohol, polyethylene oxide, polyethersulfone, polycaprolactone, chitosan, polylactide, collagen, protein, and combinations and / or derivatives thereof.

[0049] In one embodiment, the nanofibers contained in the second material layer containing fibers of the filter material may contain, or consist of, a polymer that can be spun from a solvent.

[0050] In one embodiment, the filter material does not contain glass fibers, which is advantageous for recycling the filter material. During processing of a filter material containing glass fibers, small glass particles may detach from the glass fibers, which may be abrasive to the processing device and / or filter element. Furthermore, the detached glass particles may have a particle size that is suspected to be carcinogenic.

[0051] The first material layer containing fibers may contain a low-melting-point polymer having a melting temperature lower than the melting temperature of the melt-blown filaments contained in the first material layer containing fibers. The melting temperature of the polymer is determined by differential scanning calorimetry (DSC) according to ISO 11357-3. The low-melting-point polymer contained in the first material layer containing fibers may be advantageously used to bond melt-blown filaments and / or fibers of individual lengths together by raising the temperature to a temperature higher than the melting temperature of the low-melting-point polymer but lower than the melting temperature of the melt-blown filaments, providing sufficient time and / or pressure to allow the molten low-melting-point polymer to come into contact with and / or flow over the melt-blown filaments and / or fibers of individual lengths, and then lowering the temperature to solidify the low-melting-point polymer, thereby bonding the melt-blown filaments and / or fibers of individual lengths together.

[0052] The low-melting-point polymer that may be included in the first material layer containing fibers for the filter material may be any suitable polymer including polyolefin polymers, e.g., polypropylene, polyethylene and / or polyolefin copolymers, polyester polymers, e.g., polyethylene terephthalate, polybutylene terephthalate and / or polyester copolymers or derivatives, polylactic acid and / or polylactic acid copolymers or derivatives, or any mixture or combination thereof, provided that the low-melting-point polymer has a melting temperature lower than the melting temperature of the melt-blown filaments included in the first material layer containing fibers.

[0053] The low-melting-point polymer may, advantageously, be contained in powder particles included in a first material layer containing fibers. The powder particles may be mixed in a high-speed flow of high-temperature gas, for example, in a melt-blowing process, particularly together with fibers having individual lengths. The powder particles containing the low-melting-point polymer may also be added separately to the first material layer containing fibers.

[0054] The low-melting-point polymer may, instead or in addition, advantageously be included in the fibers, preferably multi-component fibers, particularly binary fibers, which may be selected from binary fibers having side-by-side, core-sheath, and / or island-in-the-sea configurations.

[0055] The filter material may include a first carrier layer having a first surface and a second surface, wherein the first surface of the first carrier layer is oriented parallel to, and preferably adjacent to, the second surface of the second material layer. The first carrier layer provides support for the second material layer containing nanofibers, thereby preventing or at least reducing damage to the nanofibers in the second material layer during handling and processing of the filter material or during use of the filter material containing the filter material.

[0056] In one embodiment, the first surface of the first carrier layer is oriented parallel to and directly adjacent to the second surface of the second material layer, meaning that the filter material does not contain any further material layer containing fibers between the second material layer containing fibers and the first carrier layer.

[0057] The first carrier layer included in the filter material may, in principle, be a nonwoven fabric containing fibers of individual lengths that can be produced by any type of nonwoven fabric, for example, by a well-known process such as a carding process, a wet-laid process, or an air-laid process, or any combination thereof.

[0058] The first carrier layer contained in the filter material may also be a nonwoven fabric containing filaments, which can be produced by a melt-blown process, or by spunbond, in which filaments are extruded from a spinneret and placed directly onto a conveyor belt as a web of filaments, and the web is then integrated (also known as bonded) to form a nonwoven fabric, or by a two-step process in which filaments are spun and preferably wound onto a bobbin in the form of a multifilament yarn, and the filaments or multifilament yarn is then unwound, the filaments are placed onto a conveyor belt as a web of filaments, and the web is integrated to form a nonwoven fabric, or by any combination thereof.

[0059] The first carrier layer included in the filter material may also include a combination of a nonwoven fabric containing fibers of individual lengths and a nonwoven fabric containing filaments.

[0060] The first carrier layer included in the filter material may preferably include a meltblown nonwoven fabric, a spunbond nonwoven fabric, or an assembly comprising a meltblown nonwoven fabric and a spunbond nonwoven fabric.

[0061] The first carrier layer contained in the filter material may consist of a third material layer containing fibers and having a first surface and a second surface, wherein the third material layer containing fibers contains a mixture of meltblown filaments and fibers having individual lengths, the concentration of meltblown filaments increasing from the first surface to the second surface of the third material layer, the concentration of fibers having individual lengths decreasing from the first surface to the second surface of the third material layer, and the second surface of the third material layer is oriented parallel to, preferably adjacent to, the second surface of the second material layer.

[0062] In one embodiment, the first surface of the third material layer is oriented parallel to and directly adjacent to the second surface of the second material layer, meaning that the filter material does not contain any further material layer containing fibers between the second material layer containing fibers and the third material layer.

[0063] The first carrier layer may include any suitable polymer comprising or consisting of individual lengths of fibers and / or filaments, including polyolefin polymers, such as polypropylene, polyethylene and / or polyolefin copolymers; polyester polymers, such as polyethylene terephthalate, polybutylene terephthalate and / or polyester copolymers or derivatives; polylactic acid and / or polylactic acid copolymers or derivatives; or any mixture or combination thereof.

[0064] The filter material may include a second carrier layer having a first surface and a second surface, the second surface of the second carrier layer oriented parallel to, preferably adjacent to, the first surface of the first material layer. The second carrier layer enables support for the first material layer, which includes a mixture of meltblown filaments and fibers having individual lengths, thereby preventing or at least reducing damage to the first material layer during handling and processing of the filter material or during use of a filter material containing the filter material.

[0065] In one embodiment, the second surface of the second carrier layer is oriented parallel to and directly adjacent to the first surface of the first material layer, meaning that the filter material does not contain any further material layer containing fibers between the second carrier layer and the first material layer containing fibers.

[0066] The second carrier layer included in the filter material may, in principle, be a nonwoven fabric containing fibers of individual lengths that can be produced by any type of nonwoven fabric, for example, by a well-known process such as a carding process, a wet-laid process, or an air-laid process, or any combination thereof.

[0067] The second carrier layer included in the filter material may also be a nonwoven fabric containing filaments, which can be produced by a melt-blown process, or by spunbond, in which filaments are extruded from a spinneret and placed directly onto a conveyor belt as a web of filaments, and the web is then integrated (also known as bonded) to form a nonwoven fabric, or by a two-step process in which filaments are spun and preferably wound onto a bobbin in the form of a multifilament yarn, and the filaments or multifilament yarn is then unwound, the filaments are placed onto a conveyor belt as a web of filaments, and the web is integrated to form a nonwoven fabric, or by any combination thereof.

[0068] The second carrier layer included in the filter material may also include a combination of a nonwoven fabric containing fibers of individual lengths and a nonwoven fabric containing filaments.

[0069] The second carrier layer included in the filter material may preferably include a meltblown nonwoven fabric, a spunbond nonwoven fabric, or an assembly comprising a meltblown nonwoven fabric and a spunbond nonwoven fabric.

[0070] The second carrier layer may include any suitable polymer, including or comprising polyolefin polymers, such as polypropylene, polyethylene and / or polyolefin copolymers; polyester polymers, such as polyethylene terephthalate, polybutylene terephthalate and / or polyester copolymers or derivatives; polylactic acid and / or polylactic acid copolymers or derivatives; or any mixture or combination thereof, and comprising individual fibers and / or filaments having distinct lengths.

[0071] The filter material may include a first carrier layer, but may exclude a second carrier layer oriented parallel to the first surface of the first material layer.

[0072] However, the filter material may, advantageously, include both a first carrier layer and a second carrier layer, as disclosed herein.

[0073] In one embodiment, the first surface of the first material layer containing fibers included in the filter material is made up of fibers having individual lengths.

[0074] In one embodiment, the second surface of the first material layer containing fibers included in the filter material is made of meltblown filaments.

[0075] In one embodiment, the second material layer is made of nanofibers.

[0076] The first and second material layers, each containing fibers in the filter material, may be bonded to each other by any suitable technique. The first and second material layers, each containing fibers in the filter material, may also be bonded to each other by applying an adhesive between the second surface of the first material layer and the first surface of the second material layer.

[0077] The first and second material layers containing fibers in the filter material may be bonded to each other by applying an ultrasonic bonding process. The ultrasonic bonding process can provide a filter material having a bonding area of ​​up to 20%, preferably up to 15%, or preferably up to 10%, or preferably up to 5%. The smaller the bonding area, the better the filtration performance.

[0078] The first and second material layers containing fibers in the filter material may be bonded to each other by applying a thermal bonding process, such as calendering, or by air bonding with a high-temperature fluid, particularly air. Thermal bonding processes are particularly advantageous when the first material layer containing fibers contains a low-melting-point polymer having a melting temperature lower than the melting temperature of the melt-blown filaments contained in the first material layer containing fibers. The calendering thermal bonding process can apply point bonding using a patterned calender roll to provide a filter material having a bonded area of ​​up to 20%, preferably up to 15%, or preferably up to 10%, or preferably up to 5%. A smaller bonded area improves filtration performance. The calendering thermal bonding process can apply surface bonding using a smooth calender roll.

[0079] The second material layer, which includes nanofibers forming the first surface of the second material layer, may be formed directly on the first carrier layer without requiring a separate bonding step.

[0080] Alternatively, the second material layer, which includes nanofibers forming the first surface of the second material layer, may be formed as a separate layer and bonded to the first carrier layer by any suitable technique for bonding the first material layer and the second material layer to each other, such as those disclosed above herein.

[0081] A first material layer comprising a mixture of meltblown filaments and fibers having individual lengths may be formed directly on a second carrier layer without requiring a separate bonding step.

[0082] Alternatively, the first material layer, comprising a mixture of meltblown filaments and fibers having individual lengths, may be formed as a separate layer and bonded to the second carrier layer by any suitable technique for bonding the first material layer and the second material layer to each other, such as those disclosed herein.

[0083] In one embodiment, a first intermediate product is provided, comprising a first carrier layer having a first surface and a second surface, wherein the first surface of the first carrier layer is oriented parallel to and preferably adjacent to the second surface of the second material layer; and a second intermediate product is provided, comprising a second carrier layer having a first surface and a second surface, wherein the second surface of the second carrier layer is oriented parallel to and preferably adjacent to the first surface of the first material layer, wherein the second surface of the first material layer and the first surface of the second material layer are then bonded to each other by any suitable technique.

[0084] The filter material may be electrostatically charged to further improve the filtration efficiency of the filter containing the filter material.

[0085] The filter material can be advantageously used in industrial filtration applications, such as filters for gas turbines, surface treatment, air pollution control or any other industrial filtration applications; filters for cleanroom applications, such as vehicle filters, such as buses, trains, subways or other passenger transport systems, but not limited to these; air purification applications, such as car cabin air filters or engine intake filters; filters for stationary air and / or climate control systems, such as air purifiers or heating, ventilation and air conditioning (HVAC) systems; vacuum cleaner filters; liquid filter systems; or other high-efficiency filter systems.

[0086] The filter material may also be advantageously used in combination with activated carbon or any other structure for adsorbing gases (combi-filter) in applications similar to those disclosed herein above.

[0087] A filter material containing the filter material described herein can be advantageously provided. In one embodiment, the filter material may consist of the filter material described herein.

[0088] A filter material containing the filter material described herein may be a pleated filter material. The pleats of the pleated filter material may have a height of at least 10 mm, preferably at least 20 mm, or preferably at least 30 mm, preferably at least 40 mm, or preferably at least 50 mm. The pleats of the pleated filter material may have a height of up to 300 mm, preferably at least 250 mm, or preferably at least 200 mm, or preferably at least 150 mm, or preferably at least 100 mm.

[0089] The filter material may have a filtration performance of at least 80%, preferably at least 90%, or preferably at least 99%, or preferably at least 99.995%, i.e., the percentage of all particles filtered out by the filter material, as tested with the maximum permeable particle size at typical test aerosols and rates for the various applications disclosed herein above.

[0090] Advantageously, a filtration element can be provided which includes an inlet for the fluid to be filtered and an outlet for the fluid to be filtered, and which includes a filter material as described herein. In particular, the filter material may be placed in a housing which includes an inlet for the fluid to be filtered and an outlet for the fluid to be filtered. The fluid to be filtered passes through the filter material in the filtration element to obtain the filtered fluid. The fluid to be filtered may be a gas, in particular air.

[0091] In one embodiment of the filtration element, the first surface of the first material layer containing fibers is preferably oriented toward the inlet of the filtration element, and the second surface of the second material layer containing fibers is preferably oriented toward the outlet of the filtration element. [Brief explanation of the drawing]

[0092] [Figure 1] A schematic representation of a filter material according to one embodiment of the present invention is shown. [Figure 2] A schematic diagram of a filter material according to another embodiment of the present invention is shown. [Figure 3]A schematic diagram of a filter material according to another embodiment of the present invention is shown. [Figure 4] A schematic diagram of a filter material according to another embodiment of the present invention is shown. [Figure 5] The increase in pressure drop during dust loading, the dust loading time, and the amount of dust stored in the filter material are summarized for Example 1 and Comparative Example 1. [Figure 6] For Example 1 and Comparative Example 1, the increase in pressure drop during dust loading relative to the amount of dust stored in the filter material is shown.

[0093] Figure 1 schematically shows a filter material according to one embodiment of the present invention. The filter material (100) includes a first material layer (110) containing fibers and having a first surface (111) and a second surface (112). The filter material (100) also includes a second material layer (120) containing fibers and having a first surface (121) and a second surface (122). The first surface (121) of the second material layer (120) is oriented parallel to and adjacent to the second surface (112) of the first material layer (110). The first material layer (110) comprises a mixture of meltblown filaments and fibers of individual lengths, the concentration of meltblown filaments increasing from the first surface (111) to the second surface (112) of the first material layer (110), and the concentration of fibers of individual lengths increasing from the second surface (112) to the first surface (111) of the first material layer (110). The second material layer (120) comprises nanofibers forming the first surface (121) of the second material layer (120).

[0094] Figure 2 schematically shows a filter material according to another embodiment of the present invention. The filter material (200) includes a first material layer (110) containing fibers and having a first surface (111) and a second surface (112). The filter material (100) also includes a second material layer (120) containing fibers and having a first surface (121) and a second surface (122). The first surface (121) of the second material layer (120) is oriented parallel to and adjacent to the second surface (112) of the first material layer (110). The first material layer (110) comprises a mixture of meltblown filaments and fibers of individual lengths, wherein the concentration of meltblown filaments increases from the first surface (111) to the second surface (112) of the first material layer (110), and the concentration of fibers of individual lengths increases from the second surface (112) to the first surface (111) of the first material layer (110). The second material layer (120) comprises nanofibers forming the first surface (121) of the second material layer (120). The filter material (200) further comprises a first carrier layer (130) having a first surface (131) and a second surface (132), wherein the first surface (131) of the first carrier layer (130) is oriented parallel to and adjacent to the second surface (122) of the second material layer (120).

[0095] Figure 3 schematically shows a filter material according to another embodiment of the present invention. The filter material (300) includes a first material layer (110) containing fibers and having a first surface (111) and a second surface (112). The filter material (100) also includes a second material layer (120) containing fibers and having a first surface (121) and a second surface (122). The first surface (121) of the second material layer (120) is oriented parallel to and adjacent to the second surface (112) of the first material layer (110). The first material layer (110) comprises a mixture of meltblown filaments and fibers of individual lengths, wherein the concentration of meltblown filaments increases from the first surface (111) to the second surface (112) of the first material layer (110), and the concentration of fibers of individual lengths increases from the second surface (112) to the first surface (111) of the first material layer (110). The second material layer (120) comprises nanofibers forming the first surface (121) of the second material layer (120). The filter material (200) further comprises a second carrier layer (140) having a first surface (141) and a second surface (142), wherein the second surface (142) of the second carrier layer (140) is oriented parallel to and adjacent to the first surface (111) of the first material layer (110).

[0096] Figure 4 schematically shows a filter material according to another embodiment of the present invention. The filter material (400) includes a first material layer (110) containing fibers and having a first surface (111) and a second surface (112). The filter material (100) also includes a second material layer (120) containing fibers and having a first surface (121) and a second surface (122). The first surface (121) of the second material layer (120) is oriented parallel to and adjacent to the second surface (112) of the first material layer (110). The first material layer (110) comprises a mixture of meltblown filaments and fibers of individual lengths, wherein the concentration of meltblown filaments increases from the first surface (111) to the second surface (112) of the first material layer (110), and the concentration of fibers of individual lengths increases from the second surface (112) to the first surface (111) of the first material layer (110). The second material layer (120) comprises nanofibers forming the first surface (121) of the second material layer (120). The filter material (200) further comprises a first carrier layer (130) having a first surface (131) and a second surface (132), wherein the first surface (131) of the first carrier layer (130) is oriented parallel to and adjacent to the second surface (122) of the second material layer (120). The filter material (200) further includes a second carrier layer (140) having a first surface (141) and a second surface (142), wherein the second surface (142) of the second carrier layer (140) is oriented parallel to and adjacent to the first surface (111) of the first material layer (110).

[0097] Example 1 A material comprising a first material layer containing fibers and having a first surface and a second surface, and a second material layer containing fibers and having a first surface and a second surface, 169 g / m² 2 A filter material having a weight of was prepared. The first surface of the second material layer is oriented parallel to and adjacent to the second surface of the first material layer.

[0098] The first material layer comprises a mixture of meltblown filaments and fibers of individual lengths, where the concentration of meltblown filaments increases from the first surface to the second surface of the first material layer, and the concentration of fibers of individual lengths increases from the second surface to the first surface of the first material layer. The first material layer has a density of 80 g / m². 2 It has the following weight.

[0099] The second material layer consists of nanofibers, with a density of 89 g / m². 2 It has the following weight.

[0100] Comparative Example 1 It consists of nanofibers and has the same 89 g / m² material density as the second material layer in Example 1. 2 A filter material with the following weight was prepared.

[0101] Comparative Example 2 80 g / m² containing fibers and material layers having a first surface and a second surface. 2 A filter material having a weight of was prepared. The material layer contained a mixture of meltblown filaments and fibers of individual lengths, the concentration of meltblown filaments increasing from the first surface to the second surface of the first material layer, and the concentration of fibers of individual lengths increasing from the second surface to the first surface of the first material layer (same as the first material layer in Example 1).

[0102] The filter material of the example was tested for filtering NaCl particles from an airflow. An air volume flow rate of 95 l / min was used, with a flow rate of 0.01 m³. 2 When applied to a filter material with a surface area, it provided an inflow air velocity of 15.83 cm / second.

[0103] The initial penetration rate of the filter material in Example 1 was 12%, while the initial penetration rate of the filter material in Comparative Example 1 was 41%, and the initial penetration rate of the filter material in Comparative Example 2 was 28%.

[0104] The table in Figure 5 summarizes the increase in pressure drop during dust loading, the dust loading time, and the amount of dust stored in the filter material for Example 1 and Comparative Example 1.

[0105] Figure 6 shows the increase in pressure drop during dust loading relative to the amount of dust stored in the filter material for Example 1 and Comparative Example 1.

[0106] The filter material according to the present invention enables a lower increase in pressure drop during dust loading compared to the comparative example. Furthermore, the dust loading time of the filter material according to the present invention can be increased compared to the comparative example. In addition, the amount of dust stored in the filter material according to the present invention is increased compared to the comparative example.

Claims

1. The material comprises at least a first material layer (110) containing fibers and having a first surface (111) and a second surface (112), and a second material layer (120) containing fibers and having a first surface (121) and a second surface (122), wherein the first surface (121) of the second material layer (120) is oriented parallel to, preferably adjacent to, the second surface (112) of the first material layer (110), and the first material layer (110) comprises meltblown filaments and fibers having individual lengths A filter material (100, 200) comprising a mixture of the above, wherein the concentration of the meltblown filaments increases from the first surface (111) to the second surface (112) of the first material layer (110), the concentration of the individual length fibers increases from the second surface (112) to the first surface (111) of the first material layer (110), and the second material layer (120) comprises nanofibers forming the first surface (121) of the second material layer (120).

2. The filter material (100, 200) according to claim 1, wherein the concentration of the meltblown filament increases gradually from the first surface (111) to the second surface (112) of the first material layer (110).

3. The filter material (100, 200) according to claim 1 or 2, wherein the concentration of the individual fibers of the specified length gradually increases from the second surface (112) to the first surface (111) of the first material layer (110).

4. The filter material (100, 200) according to any one of claims 1 to 3, wherein the meltblown filaments contained in the first material layer (110) have an average diameter of 4 μm or less, preferably 2 μm or less, more preferably 1 μm or less, and even more preferably 750 nm or less.

5. The filter material (100, 200) according to any one of claims 1 to 4, wherein the ratio of the average diameter of the individual length fibers contained in the first material layer (110) to the average diameter of the meltblown filaments contained in the first material layer (110) is at least 10, preferably at least 15, preferably at least 20, preferably at least 30, or preferably at least 40.

6. The filter material (100, 200) according to any one of claims 1 to 5, wherein the nanofibers contained in the second material layer (120) have an average diameter of 500 nm or less, preferably 400 nm or less, preferably 300 nm or less, or preferably 250 nm or less.

7. The filter material (100, 200) according to any one of claims 1 to 6, wherein the individual fibers having lengths included in the first material layer (110) have lengths of at least 6 mm and a maximum of 40 mm, preferably at least 6 mm and a maximum of 24 mm, or preferably at least 6 mm and a maximum of 18 mm.

8. The filter material (100, 200) according to any one of claims 1 to 7, wherein the first material layer (110) includes a low-melting-point polymer having a melting temperature lower than the melting temperature of the melt-blown filament.

9. The filter material (100, 200) according to claim 8, wherein the low-melting-point polymer is contained in powder particles and / or fibers, preferably two-component fibers.

10. The filter material (200) according to any one of claims 1 to 9, wherein the filter material (200) includes a carrier layer (130) having a first surface (131) and a second surface (132), and the first surface (131) of the carrier layer (130) is oriented parallel to and preferably adjacent to the second surface (122) of the second material layer (120).

11. The filter material (200) according to claim 10, wherein the first carrier layer (130) is composed of a third material layer (130) containing fibers and having a first surface (131) and a second surface (132), the third material layer (130) containing fibers containing a mixture of meltblown filaments and fibers having individual lengths, the concentration of the meltblown filaments increases from the first surface (131) to the second surface (132) of the third material layer (130), the concentration of the fibers having individual lengths decreases from the first surface (131) to the second surface (132) of the third material layer (130), and the second surface (132) of the third material layer (130) is oriented parallel to, preferably adjacent to, the second surface (122) of the second material layer (120).

12. The filter material (100, 200) according to any one of claims 1 to 11, wherein the first surface (111) of the first material layer (110) containing fibers is made of fibers having individual lengths.

13. The filter material (100, 200) according to any one of claims 1 to 12, wherein the second surface (112) of the first material layer (110) containing fibers is made of meltblown filaments.

14. A filter material comprising the filter material (100, 200) described in any one of claims 1 to 13.

15. A filter element comprising an inlet for a fluid to be filtered and an outlet for a fluid to be filtered, comprising the filter material according to claim 14 or the filter material according to any one of claims 1 to 13, wherein the first surface (111) of the first material layer (110) comprising fibers is preferably oriented toward the inlet of the filter element, and the second surface (122) of the second material layer (120) comprising fibers is oriented toward the outlet of the filter element.

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