Glass fiber-free filter media comprising a densified layer made of synthetic fibers

Abstract

To provide a filter medium, and use and a method for manufacturing the same.SOLUTION: A multi-layer filter medium comprising a densified layer made of synthetic fibers, and methods of use and manufacture thereof.SELECTED DRAWING: None

Description

[Technical Field]

[0001] Technical field of the invention The present invention relates to a multi-layer filter medium comprising a densified layer made of synthetic fibers, and to methods of use and manufacture thereof. [Background technology]

[0002] prior art Filter media are used in a variety of systems to remove undesirable materials (ie, particles) from liquids or gases by passing the liquid or gas through the filter media.

[0003] In many areas of filtration, the demands on the purity of filtered liquids are increasing. This applies both to liquids used in industry, such as lubricating oils, hydraulic fluids, or fuels for internal combustion engines, and to liquids used in the food industry and for medical or pharmaceutical applications. For example, in the filtration of diesel fuel for internal combustion engines, the separation efficiency requirements for large particles of 4 μm according to ISO 19438:2003 have been constantly increasing over the past 15 years. For this reason, considerable efforts have been made to continuously increase the separation efficiency of the filter materials used while at the same time maintaining the dust retention capacity and thus at least preventing changes in the service life of the filters.

[0004] Filter media containing glass fibers are widely used filter materials for fuels. These filter media achieve very high particle removal efficiencies of ≥ 99.5%. However, the abrasive effect of glass fibers that can be washed out of the filter media can lead to damage to equipment located after the filter, such as the fine injection nozzles of fuel injection systems.

[0005] In fact, glass fibers can break into smaller pieces under mechanical stress during processing of the filter media. These small glass particles can also be present loosely in the filter media material and can be washed out of the media. Additionally, glass fibers that are loosely bound within the media can be washed out by fuel passing through the media.

[0006] Due to the abrasive nature of the glass fibers / particles, this so-called glass fiber shedding can damage working parts downstream of the filter element, which is why the use of glass fibers in high efficiency fuel media always presents a potential risk in the application.

[0007] EP 1 133 342 B1 and US Pat. No. 7,137,510 B1 disclose multi-layer filter media comprising a meltblown nonwoven fabric as the main filtration layer, the meltblown nonwoven fabric being made of PP (polypropylene) or PES (polyethersulfone).

[0008] US9,149,748B2 discloses a filter medium comprising a first layer, a second layer, and a third layer, wherein the second layer is disposed between the first and third layers and comprises a plurality of fibers formed by a meltblown process, and the air permeability and / or mean flow pore size of the first and third layers is higher than that of the second layer.

[0009] DE 10 2012 010 307 A1 discloses a multi-layer filter material comprising, in the direction of flow, a first layer comprising a wet-laid or dry-laid nonwoven, a second layer comprising a wet-laid nonwoven made of cellulose or synthetic fibers or a mixture thereof, and a third layer comprising a calendered meltblown nonwoven, which achieves an efficiency according to ISO 19348 of 99.3%. Summary of the Invention [Problem to be solved by the invention]

[0010] There remains a need to provide a filter media that does not contain glass fibers and yet provides very high removal efficiency for particle sizes ≧4 μm.

[0011] Summary of the Invention It is therefore an object of the present invention to provide a filter medium that has high separation efficiency (ie, ≧99.3% for 4 μm particles) without the use of glass fibers.

[0012] This object is solved by a filter medium comprising: a) a first layer; b) a second layer, and c) optionally a third layer.

[0013] In particular, this object is solved by a filter medium comprising: a) a first layer; b) a second layer having a large number of pores with a diameter of 4 to 13 μm; c) optionally a third layer. DETAILED DESCRIPTION OF THE INVENTION

[0014] In the context of the present invention, the diameter of a "multiple pores" is the diameter of a uniform distribution of pores within the layer. This characteristic can be determined according to the method defined below.

[0015] Preferably, the filter medium includes a third layer, and more preferably, the second layer is located between the first and third layers.

[0016] The first layer may be any layer selected from the group consisting of a wet-laid nonwoven, a dry-laid nonwoven, or a synthetic grid.

[0017] Within the meaning of the present invention, wet-laid nonwovens are all nonwovens that can be produced using the wet-laid process known to those skilled in the art for producing filter media.

[0018] The wet-laid nonwoven fabric of the first layer comprises natural fibers, synthetic fibers, or a mixture thereof. Examples of natural fibers include cellulose, cotton, wool, hemp, regenerated cellulose, and fibrillated cellulose. Preferably, the first layer comprises at least 70% natural fibers.

[0019] The average fiber diameter of the natural fibers may be 10 to 50 μm, preferably 15 to 40 μm, and more preferably 20 to 35 μm.

[0020] Synthetic fibers include polyester fibers, polypropylene fibers, multicomponent fibers in which the individual components have different melting points, polyamide fibers, and acrylic fibers.

[0021] Examples of polyester fibers are polybutylene terephthalate (PBT) fibers, polyethylene terephthalate (PET) fibers, and polylactic acid (PLA) fibers. An example of a preferred multicomponent fiber is a PET / CoPET bicomponent fiber having a core-sheath structure.

[0022] The average fiber diameter of the synthetic fibers is typically 3 to 30 μm, preferably 5 to 15 μm, and the cut length is typically 3 to 60 mm, preferably 4 to 12 mm.

[0023] The first layer may be made of 100% natural fibers or 100% synthetic fibers. Preferably, the first layer is made of 100% natural fibers.

[0024] The dry nonwoven fabric includes, for example, a spunlaid nonwoven fabric, which can be produced according to any production method.

[0025] Suitable polymers for spunlaid nonwovens include polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyolefins such as polypropylene, and polyurethanes, or mixtures thereof. In many applications, spunlaid nonwovens containing bicomponent fibers can be particularly advantageous. An example of a preferred multicomponent fiber is a PET / CoPET bicomponent fiber with a core-sheath structure. The typical average fiber diameter of spunlaid nonwovens is 5 to 30 μm, preferably 10 to 20 μm, and more preferably 12 to 17 μm.

[0026] For liquid applications such as fuel filtration, a first layer comprising at least 70% by weight natural fibers, based on the total weight of the fibers in the first layer, may be particularly suitable.

[0027] When the first layer comprises at least 70% natural fibers, the first layer is preferably saturated with a binder resin. Any known resinous binder composition can be used.

[0028] The thickness of the first layer can be selected as desired. Preferably, the first layer has a thickness of 0.15 mm or more, more preferably 0.20 mm or more, or most preferably 0.40 mm or more. The first layer can have a thickness of 2.00 mm or less, more preferably 1.60 mm or less, or most preferably 1.20 mm or less. Combinations of the above ranges are also possible, preferably 0.15 mm or more and about 1.00 mm or less. Thickness can be determined according to ISO Standard 534:2012-02 at a test plate pressure of 0.1 bar.

[0029] The porosity of the first filter layer is preferably 60 to 90%, and more preferably 70 to 80%.

[0030] The first layer may be a grid made of a thermoplastic polymer or a printed polymer pattern. The polymer of the printed polymer pattern is preferably a hot melt adhesive. The base material of the polymer of the printed polymer pattern or the hot melt adhesive may be selected from the group consisting of ethylene vinyl acetate (EVA) copolymer; polyolefin (PO), such as polyethylene (usually low-density polyethylene (LDPE) but also high-density polyethylene (HDPE); HDPE has a higher melting point and better heat resistance), polypropylene (PP), atactic polypropylene (APP), polybutene-1, polyethylene oxide, etc.; polyamide (PA) and copolyamide (CoPA); polyester (PES), copolyester (CoPES), such as polyethylene terephthalate (PET), PET copolymer (CoPET), polybutylene terephthalate (PBT), and PBT copolymer (CoPBT); thermoplastic polyurethane resin (TPU); styrene block copolymer (SBS); and mixtures thereof. If a printed polymer pattern is selected as the first layer, the polymer pattern is printed directly onto the second layer. The advantages and manufacturing method of the printed polymer pattern are described in patent application EP19166533.

[0031] The second layer includes a nonwoven fabric layer having a large number of pores with a diameter of 4 to 13 μm, preferably 5 to 11 μm.

[0032] Preferably, the maximum pore size (diameter) of the second layer is from 5 to 17 μm, preferably from 6 to 16 μm.

[0033] When the second layer has a large number of pores within the above range, a high initial efficiency can be achieved.

[0034] The second layer may be any layer selected from the group consisting of a spunbond nonwoven, a meltblown nonwoven, and a combination of a spunbond nonwoven and a meltblown nonwoven, provided that the diameter of the plurality of pores in the second layer falls within the ranges given above.

[0035] Suitable polymers for the second layer include, for example, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyolefins such as polypropylene, and polyurethanes, or mixtures thereof. In many applications, the use of bicomponent fibers can be particularly advantageous. An example of a preferred multicomponent fiber is a PET / CoPET bicomponent fiber having a core-sheath structure.

[0036] The second layer is preferably a meltblown layer. Preferably, the meltblown layer comprises polyester fibers. The second layer may comprise a meltblown layer and a spunbond layer. In this case, the meltblown layer and the spunbond layer constituting the second layer are densified together to obtain a second layer having the above-defined pore diameter.

[0037] The second layer is preferably a densified layer, more preferably a densified meltblown layer. The densification process ensures the desired diameter of the pores and uniformity of the layer, which results in superior performance.

[0038] The second layer can be made according to any known method for making spunbond or meltblown fabrics.

[0039] Preferably, the average fiber diameter (d1) of the fibers in the second layer (before calendering / densification) is 0.01 to 3 μm, more preferably 0.25 to 2.5 μm, and most preferably 0.5 to 2 μm.

[0040] Preferably, the fibers of the second layer (before being densified, i.e., before being calendered through a flat calender) have an average diameter (d1)≦1.8 μm, more preferably 0.6 μm≦d1≦1.8 μm, particularly preferably 0.60 μm≦d1≦1.75 μm, and at least 20%, preferably 30%, of the fibers of this layer have a diameter (d)≦1 μm, preferably 0.6 μm≦d≦1 μm, particularly preferably 0.60≦d≦0.95 μm. Preferably, at least 25%, particularly preferably at least 30%, of the fibers have a diameter of 0.60≦d≦0.90 μm. The proportion of fibers with a diameter of 0.6≦d≦0.85 μm is at least 25%, preferably at least 30%.

[0041] In the present invention, a distinction is made between "average fiber diameter" (d1) and "diameter" (d). This distinction is important because the average fiber diameter does not provide information about the amount of fine fibers with a diameter (d) of ≦1 μm.

[0042] When the second layer includes a spunbond layer and a meltblown layer, it is important that at least one layer (i.e., the spunbond layer alone, or the meltblown layer alone, or both) have a fiber diameter within the above ranges before calendering. For example, if the meltblown layer has a fiber diameter within the ranges indicated above, the additional spunbond layer of the second layer should have a thickness of 0.09 to 0.8 mm; a fiber diameter of 10 to 40 g / m 2 and 30~3500l / m 2 It may have an air permeability of .s.

[0043] The second layer is densified, i.e., calendered using a flat calender. The thickness of the calendered second layer can be selected as desired. Preferably, the second layer has a thickness of 0.09 mm or more, more preferably 0.10 mm or more, or most preferably 0.15 mm or more. The second layer may have a thickness of 1.00 mm or less, more preferably 0.70 mm or less, or most preferably 0.50 mm or less. Combinations of the above ranges are also possible, preferably 0.10 mm or more and about 0.50 mm or less. The thickness can be determined according to ISO Standard 534:2012-02 at a plate pressure of 0.1 bar.

[0044] The overall thickness of the filter media is preferably in the range of 0.20 mm or greater, more preferably 0.30 mm or greater, more preferably 0.50 mm or greater, and most preferably 0.80 mm or greater. The overall thickness of the filter media is preferably in the range of 2.00 mm or less, more preferably 1.5 mm or less, more preferably 1.20 mm or less, and more preferably 1.00 mm or less. Combinations of the above ranges are also possible, for example, preferably 0.50 mm or greater and about 1.00 mm or less. Thickness can be determined according to ISO Standard 534:2012-02 at a plate pressure of 0.1 bar.

[0045] The use of meltblown nonwovens as the second layer of filter media is highly advantageous because meltblown technology allows for the commercial production of nonwovens containing very fine fibers with very small diameters, as described above. The combination of such fine fiber-containing meltblown fibers and additional densification of the nonwoven web produces an initial filtration efficiency of ≥ 99.3% per ISO 19438:2003.

[0046] To achieve a high degree of separation due to the overall structure even at the initial stage of use of the filter medium, a layer containing cellulose can be advantageously used as the first layer (outlet layer). This material exhibits a very high degree of separation of the particles to be filtered even at the initial stage, but its storage capacity is lower than that of meltblown nonwoven fabrics.

[0047] Advantageously, in the filter layer according to the invention, the functions of foldability, support for other (synthetic) layers and very fine filtration are integrated in a cellulose layer as the first layer, preferably located on the outflow side.

[0048] Polyester fibers, such as PBT fibers, are preferably used for the second layer because they exhibit good heat resistance, making them well suited to processes involving calendering. This allows the temperature conditions during calendering to be adjusted as needed, resulting in a filter medium with the desired uniform pore size distribution and uniformity (i.e., a large number of pores). Furthermore, the use of fibers with good heat resistance avoids the problem of small fibers completely melting during the calendering process, resulting in undesirable foil-like properties of the second layer.

[0049] Because the filter media of the present invention does not contain glass fibers, damage to equipment located after the filter due to the abrasive effect of glass fibers that may be washed out of the filter media is avoided.

[0050] The filter media may include a third layer, which may be selected from the group consisting of a spunbond layer and a meltblown layer. Preferably, the third layer is a meltblown layer. Preferably, the third layer comprises polyester fibers, such as PBT, PET, or PET / CoPET bicomponent fibers.

[0051] More preferably, the polyester fibers contained in the second and third layers are polybutylene terephthalate (PBT) fibers.

[0052] The average fiber diameter of the fibers in the third layer, for example, polyester fibers, is 0.01 to 10 μm, more preferably 0.5 to 7 μm, and most preferably 1 to 5 μm.

[0053] The thickness of the third layer can be selected as desired. Preferably, the third layer has a thickness of 0.09 mm or more, more preferably 0.10 mm or more, or most preferably 0.15 mm or more. The third layer can have a thickness of 1.00 mm or less, more preferably 0.80 mm or less, or most preferably 0.50 mm or less. Combinations of the above ranges are also possible, for example, preferably 0.15 mm or more and about 0.50 mm or less. The thickness can be determined according to ISO Standard 534:2012-02 at a test plate pressure of 0.1 bar.

[0054] Preferably, the second layer is a densified meltblown nonwoven fabric, and the densification is preferably achieved by calendering.In the context of the present invention, the densified meltblown nonwoven fabric is produced by calendering using a flat roll, so that the entire surface of the meltblown nonwoven fabric, i.e., all the fibers on the surface, are partially melted, thereby achieving the desired diameter of the pores.This calendering process should be distinguished from the calendering process for bonding two or more layers, in which the calendering roll has a specific design (or pattern), usually in the form of dots, which protrudes across the surface of the roll, and causes the polymer fibers to melt by heat only in the protruding areas of the roll to achieve bonding.Such a calendering process for bonding two or more layers does not significantly affect the diameter of the pores of the filter layer. In contrast, during the calendering process using flat rolls to produce a densified meltblown nonwoven fabric, the meltblown nonwoven fabric is compressed to produce a specific pore size (i.e., the diameter of the majority of pores). In particular, the pore size distribution of the layer becomes uniform. Preferably, the second layer is composed exclusively of such a densified meltblown nonwoven fabric. Preferably, the second layer is composed of a meltblown layer and a spunbond layer that are both densified. More preferably, the second layer is composed of PBT (polybutylene terephthalate) fibers. Preferably, the second layer contains at least 50% by weight, more preferably at least 60% by weight, more preferably at least 70% by weight, more preferably at least 80% by weight, more preferably at least 90% by weight, and most preferably at least 95% by weight of PBT fibers, based on the total weight of the fibers in the second layer. The second layer can be densified (i.e., calendered) between two calender rolls at a high temperature of 40°C to 180°C, with a linear pressure of 5 N / mm to 450 N / mm. As a result, the separation efficiency of the filter material according to the present invention is significantly increased.

[0055] The individual layers of the filter media can be manufactured separately and then bonded together; or each layer can be formed directly on the surface of the underlying layer; or these two methods can be combined. The combination of the individual layers can be achieved by stacking and, optionally, bonding the layers together by, for example, gluing, sintering, or calendering. As explained above, if a calendering step is performed to achieve the bonding of the separate layers, this does not include the use of a flat calender.

[0056] Preferably, the first and second layers are bonded together by adhesive.

[0057] Preferably, the first and second layers, which have been previously bonded together, are adhesively bonded to the third layer.

[0058] Preferably, the basis weight increases from the second layer to the first layer, and optionally from the third layer to the first layer.

[0059] The basis weight of the first layer is preferably 100 to 350 g / m 2 and more preferably 125 to 300 g / m 2 and more preferably 175 to 250 g / m 2 is.

[0060] The basis weight of the second layer is preferably 10 to 200 g / m 2 and more preferably 25 to 150 g / m 2 and more preferably 50 to 100 g / m 2 is.

[0061] The basis weight of the third layer is preferably 10 to 175 g / m 2 and more preferably 15 to 150 g / m 2 and more preferably 20 to 90 g / m 2 is.

[0062] The overall basis weight of the filter media is preferably 150 to 700 g / m 2and more preferably 200 to 500 g / m 2 and more preferably 250 to 450 g / m 2 and most preferably 300 to 400 g / m 2 is.

[0063] Preferably, the basis weight increases from the second layer to the first layer, and optionally from the third layer to the first layer of filter media used.

[0064] Preferably, the air permeability increases from the first layer to the second layer, and optionally from the second layer to the third layer.

[0065] Preferably, the air permeability decreases from the third layer to the first layer.

[0066] The first layer may have an air permeability that is lower than the air permeability of any other layer in the filter media.

[0067] The first layer is preferably 1 L / m 2 sec or more, 2L / m 2 sec or more, or 3L / m 2 sec or more.

[0068] Preferably, the first layer has a density of 20 L / m 2 sec or less, 16L / m 2 sec or less, 12L / m 2 sec or less. Combinations of the above ranges are also possible. For example, the air permeability is preferably 1 L / m 2 sec or more and 20L / m 2 sec or less. The air permeability can be determined according to the standard EN / ISO 9237 (1995) (measurement area 20 cm at 2 mbar differential pressure). 2 (It is).

[0069] Preferably, the second layer is 5 L / m 2 sec or more, 10L / m 2 sec or more, 15L / m 2Preferably, the second layer has an air permeability of 70 L / m sec or more. 2 sec or less, 60L / m 2 sec or less, 40L / m 2 sec or less. Combinations of the above ranges are also possible. For example, the air permeability is preferably 5 L / m 2 sec or more and 70L / m 2 sec or less, more preferably 10 L / m 2 sec or more and 60L / m 2 sec or less, most preferably 15 L / m 2 sec or more and 40L / m 2 sec or less. The air permeability can be determined according to the standard EN / ISO 9237 (1995) (measurement area 20 cm at 2 mbar differential pressure). 2 (It is).

[0070] Preferably, the third layer has a density of 75 L / m 2 sec or more, 100L / m 2 sec or more, 125L / m 2 Preferably, the third layer has an air permeability of 400 L / m sec or more. 2 sec or less, 300L / m 2 sec or less, 200L / m 2 sec or less. Combinations of the above ranges are also possible. For example, the air permeability is preferably 75 L / m 2 sec or more and 250L / m 2 sec or less. The air permeability can be determined according to the standard EN / ISO 9237 (1995) (measurement area 20 cm at 2 mbar differential pressure). 2 (It is).

[0071] The overall air permeability of the filter medium is preferably 0.5 to 20 L / m 2 s, more preferably 0.5 to 15 L / m 2 s, most preferably 1 to 10 L / m 2 The range is s.

[0072] The present invention further relates to the use of a filter medium for liquid filtration comprising a) a first layer, b) a second layer, and c) optionally a third layer, wherein the direction of liquid flow during filtration is from the second layer to the first layer and optionally from the third layer to the first layer.

[0073] Preferably, the filter media of the present invention is used for liquid filtration.

[0074] The initial efficiency for particles ≧4.0 μm according to ISO 19438:2003 of the second layer is at least 99.3%, preferably 99.5% for particle sizes ≧4 μm (see method described below).

[0075] More preferably, the initial efficiency for particles >= 4.0 μm according to ISO 19438:2003 of the entire filter media is at least 99.7%.

[0076] Filter media manufacturing method The filter media of the present invention can be manufactured by any method known in the art. For example, the filter media of the present invention can be prepared by a method comprising the following steps: a) providing a first layer, a second layer, and optionally a third layer; b) bonding the second layer to the first layer by calendaring or gluing; and c) optionally bonding a third layer to the open surface of the second layer by calendaring or gluing;

[0077] Preferably, step a) comprises densifying the second layer by calendering. More preferably, step a) comprises densifying the second layer by calendering using flat calender rolls.

[0078] If the first layer is a printed polymer pattern, the second layer is first provided and densified. The first layer is then printed directly onto the densified second layer. Then, if a third layer is present, it is then adhered to the other side of the second layer.

[0079] Filter The filter media of the present invention can be included in a filter element. Preferably, the filter element comprises at least one filter medium described above, and optional additional layers.

[0080] The claimed filter media can be used in many applications, and filters made from the media of the present invention are particularly suitable for fuel filtration (e.g., gasoline or diesel), oil filtration (e.g., lubricating oil and hydraulic fluid), and liquid filtration such as water.

[0081] Preferred embodiments: 1. A filter medium comprising (or consisting of) a) a first layer, b) a second layer having a multitude of pores with diameters of 4 to 13 μm, and c) optionally a third layer. 2. The filter medium according to 1, wherein the second layer comprises a drylaid nonwoven. 3. The filter medium according to 1 or 2, wherein the second layer is one selected from the group consisting of a spunbond layer, a meltblown layer, and a combination of a spunbond layer and a meltblown layer. 4. The filter medium according to any one of 1 to 3, wherein the second layer comprises a meltblown layer. 5. The filter medium according to any one of 1 to 4, wherein the first layer comprises cellulose. 6. The filter medium according to any one of 1 to 5, wherein the filter medium comprises a third layer. 7. The filter medium according to any one of 1 to 6, wherein the second layer comprises a spunbond layer and a meltblown layer. 8. The filter medium according to any one of 1 to 7, wherein the second layer comprises a spunbond layer and a meltblown layer. 8. The filter medium according to any one of 1 to 7, wherein the second layer is densified. 9. The filter medium according to any one of 1 to 8, wherein the second layer comprises (or consists of) polyester fibers. 10. The filter medium according to any of 1 to 9, wherein the air permeability increases from the first layer to the second layer, and optionally from the second layer to the third layer. 11. The filter medium according to any of 1 to 10, wherein the basis weight increases from the second layer to the first layer, and optionally from the third layer to the first layer. 12. The filter medium according to any one of 1 to 4 and 6 to 11, wherein the first layer is a grid or a printed polymer pattern. 13. Use of a filter medium according to any one of 1 to 12 for filtering a liquid. 14. Use according to 13, wherein the direction of flow of the liquid during filtration is from the second layer to the first layer, and optionally from the third layer to the first layer. 15. Use according to 13 or 14, wherein the liquid is selected from the group consisting of fuel, oil, and water. 16. A method for producing a filter medium according to any one of 1 to 12, comprising the steps of: a) providing a first layer, a second layer, and optionally a third layer; b) densifying the second layer; c) bonding said first layer, said second layer, and optionally said third layer together. 17. A method for producing a filter medium according to any one of 1 to 12, comprising the steps of: a) providing a second layer and a third layer; b) densifying said second layer; c) printing a polymer pattern (i.e., the first layer) onto the second layer; d) combining said second layer of step c) with said third layer.

[0082] definition In this disclosure, the term "filter element" refers to any device that can be used in the process of filtration with the aid of an inserted filter media, i.e., a mechanical or physical process used to separate one substance from another, such as solids, liquids, and gases.

[0083] In this disclosure, the term "filter media" refers to materials used in filters to separate particles from their suspension in air or liquid.

[0084] As used in this disclosure, the term "inlet side" refers to the side of the filter media where the material to be filtered enters the filter media.

[0085] In this disclosure, the term "outlet side" refers to the side of the filter media where the material to be filtered exits the filter media.

[0086] In this disclosure, the term "flow direction" refers to the direction in which the material being filtered flows through the filter media, i.e., the flow direction is from the inlet side to the outlet side of the filter media.

[0087] In this disclosure, the term "layer" refers to any sheet of material used in a filter media.

[0088] In this disclosure, the term "surface" refers to any interface between a layer of filter media and its surroundings, or between the filter media and its surroundings.

[0089] In this disclosure, the term "liquid" refers to fuels, such as fuels for internal combustion engines, e.g., gasoline or diesel; oils, such as lubricating oils and hydraulic fluids; or water.

[0090] In this disclosure, the term "meltblown nonwoven" refers to any nonwoven fabric that can be produced using the meltblown process known to those skilled in the art of producing filter media, i.e., a process in which molten polymer is extruded into a high-velocity, hot gas stream to convert the molten polymer into fibers.

[0091] In this disclosure, the term "cellulose" refers to any material produced from plants that produce fibrous products based on polymers of cellulose molecules, as well as regenerated cellulose. Cotton plants produce separate cellulose fibers, while wood pulp is produced by mechanically and / or chemically separating wood fibers. Other sources of cellulose are fibers such as flax, manila, ramie, and jute. Regenerated cellulose (rayon) is produced by dissolving wood pulp in a solution and extruding the solution through a spinneret into a chemical bath that regenerates the fibers.

[0092] Test Method Fiber diameter is measured as follows: Device: Scanning Electron Microscope (SEM) "Phenom Fei" associated with the software Fibermetric V2 Sampling: Five different areas of the filter media are analyzed across the web width. Sample sputtering: Random recording of optical images; these areas are scanned at 1000x magnification.

[0093] Determination of fiber diameter by the "one-click" method, all fibers need to be recorded once; measurement points that detect fiber crossings and therefore do not represent fiber diameters are manually removed.

[0094] The average fiber diameter and the percentage of fibers with a particular fiber diameter are estimated using Excel and the data obtained from Fibermetric.

[0095] Therefore, at least five average fiber diameters are recorded for each sample, and these five averages are combined into a single average value, which is called the average fiber diameter for the sample.

[0096] A total of at least 500 fibers are evaluated.

[0097] The percentage of fibers with a constant diameter is also recorded.

[0098] The layer thicknesses of the first, second and third layers and the overall thickness of the filter medium are measured in accordance with DIN EN ISO 534 2012-02 at a plate pressure of 0.1 bar.

[0099] The air permeability is measured at 20 cm according to DIN EN ISO 9237 (1995). 2 A differential pressure of 200 Pa and 20 cm was used with a Textest FX3300 instrument with a test head of 2 It is measured with a sample size of

[0100] The basis weight is determined in accordance with DIN EN ISO 536(2012-11).

[0101] Efficiency: The initial separation degree and dust storage capacity are measured at 200 cm3 using A3 media test dust (ISO 12103-1, PTI Powder Technology Co., Ltd.) according to ISO 19438 (2003). 2 The test is performed on a flat sheet of (sample area), with an upstream concentration of 100 mg / l and a flow rate of 0.71 l / min. The test is terminated with a differential pressure increase of 0.7 bar.

[0102] The maximum pore size and the number of pores size are determined with reference to DIN ISO 4003:1990.

[0103] Pore ​​size is measured with reference to DIN ISO 4003:1990. The sample is placed between an airtight clamp on an orifice with an air supply and a connection to a pressure gauge (a U-tube with mm indicator). Each sample is tested with the top side facing up. Denatured ethanol (100% ethanol with 1% MEK (methyl-ethyl-ketone) as a denaturant) is poured against the edge of the upper sample holder (do not spray directly onto the sample; approximately 4 mm deep), applying slight excess air pressure to the liquid. The air pressure is slowly increased (approximately 5 mm water gauge per second) until the first bubbles are visible. The required air pressure level is to be read from the pressure gauge (in mm water gauge), and the surface tension of the ethanol (at 23 °C) can be used to calculate the diameter of the largest pore ("largest pore", "largest pore size", "largest pore diameter").

[0104] The air pressure was then increased until the air was blown over the entire surface (10 cm) with bubbles evenly distributed but not foaming. 2 ) passes through the sample, determining the "multiple pore" value. At this point the air pressure is read again and the relative pore size, i.e., "multiple pore" diameter, "multiple pore size," "multiple pore diameter," or "multiple pore diameter" is calculated.

[0105] The diameter of the "largest pore size" and "numerous pores" as described above can be calculated by using the following formulas:

number

[0106] The void volume is calculated from the actual density of the filter media and the average density of the fibers used according to the following formula: Porosity = (1 - filter media density [g / cm 3 ] / fiber density [g / cm 3 ])100% [Example]

[0107] example General example 1 In Table 1, three exemplary layer arrangements are disclosed. The first layer is a cellulose saturated base layer, followed by a densified meltblown layer based on PBT (polybutylene terephthalate). The densification process was carried out by a flat calender. Layer 3 is a meltblown layer based on PBT.

[0108] [Table 1]

[0109] Example 2 Compared to Example 1, the second layer includes the densified meltblown layer of Example 1 and an additional spunbond layer. The spunbond layer of the second layer includes PBT fibers with a fiber diameter of 15 μm and a basis weight of 20 g / m 2 and has a thickness of 0.09 mm. The meltblown and spunbond layers of the second layer are densified together in a flat calender.

[0110] Flow direction: Third layer (inlet side) - Second layer - First layer (outlet side)

[0111] Comparative Examples 1 and 2 First layer: Cellulose saturated base layer, wet Second layer: polyester meltblown fiber, densified by calendaring Third layer: Meltblown layer Flow direction: Third layer (inlet side) - Second layer - First layer (outlet side)

[0112] [Table 2]

[0113] Examples 1, 2, Comparative Example 1 and Comparative Example 2 all contain polyester meltblown fibers in the second layer.

[0114] As can be seen in Table 2, the filter media according to the present invention exhibits very good efficiency values ​​even though it does not contain glass fibers.

Claims

1. a) a first layer; b) a second layer having a large number of pores with a diameter of 4 to 13 μm; and c) optionally a third layer Filter media including.

2. 10. The filter media of claim 1, wherein the second layer comprises a drylaid nonwoven.

3. 3. The filter media of claim 1 or 2, wherein the second layer is one selected from the group consisting of a spunbond layer, a meltblown layer, and a combination of a spunbond layer and a meltblown layer.

4. The filter medium of any one of claims 1 to 3, wherein the first layer comprises cellulose.

5. The filter medium of any one of claims 1 to 4, wherein the filter medium comprises the third layer.

6. 6. The filter medium of claim 1, wherein the second layer is a densified layer.

7. The filter media of any one of claims 1 to 6, wherein the second layer comprises polyester fibers.

8. The filter media of any one of claims 1 to 7, wherein the second layer comprises a densified meltblown layer.

9. 9. The filter media of any one of claims 1 to 8, wherein air permeability increases from the first layer to the second layer, and optionally from the second layer to the third layer.

10. Basis weight increases from the second layer to the first layer, and optionally from the third layer to the first layer. The filter medium according to any one of claims 1 to 9.

11. 11. Use of a filter medium according to any one of claims 1 to 10, wherein the direction of liquid flow during filtration is from the second layer to the first layer, and optionally from the third layer to the first layer.

12. 12. Use of the filter medium of claim 11 for liquid filtration.

13. A method for producing a filter medium according to any one of claims 1 to 10, comprising the steps of: a) providing a first layer, a second layer, and optionally a third layer; b) densifying the second layer; c) bonding said first layer, said second layer, and optionally said third layer together.