FILTER MEDIUM FOR ENGINE AIR FILTER

Description

[0001] The present invention relates to a filter medium for engine air filters, wherein the filter medium comprises a carrier layer and a meltblown layer, and a filter element with such a filter medium. State of the art

[0002] Key quality criteria for air filter media include high filtration efficiency, meaning the removal of both large and small particles, and a sufficiently high dust holding capacity. For engine air filter media, it's important to note that under full load, the engine draws in between 200 m³ and 500 m³ of air per hour, depending on its displacement. This air is laden with dirt and dust particles. If the filter element doesn't allow enough air to pass through, the engine cannot reach its full performance potential. US2015013285A1 discloses a filter medium, primarily for engine air filters, with a substrate and a fine fiber layer that can be produced by meltblowing.

[0003] Engine air filter elements are responsible for supplying the engine with clean air, which is necessary for a proper combustion process. The engine air filter medium also performs the following functions with regard to air management in the vehicle: filtering the engine intake air; improving airflow for optimal combustion and engine acoustics, such as dampening intake noise; and protecting downstream engine components, such as a turbocharger, from particle contamination.

[0004] To increase filtration efficiency, nanofiber layers are used (i.e., with a fiber diameter of less than 1.5 µm), but these require complex manufacturing processes and are therefore expensive. Another disadvantage is the low mechanical stability of the nanofiber layer.

[0005] Additionally, the engine air filters must be replaced at the intervals specified by the vehicle manufacturer. This is done as part of the inspection work. If there is a high dust content in the air (or a certain mileage), it is advisable to replace the filter sooner. Therefore, ideally, the filter medium (or the filter itself) should be as inexpensive as possible.

[0006] The invention is therefore based on the objective of creating a filter medium and a filter element that is particularly suitable for air filters of engines, has very good efficiency and dust storage capacity, and is easy to produce using standard manufacturing processes and is therefore correspondingly cost-effective to manufacture. Detailed description of the invention

[0007] The present invention relates to a filter medium for engine air filters, comprising a carrier layer and a meltblown layer containing polyester fibers, wherein the filter medium is electrically charged, wherein the filter medium has a maximum pore diameter of 35 to 110 µm, determined according to DIN ISO 4003 (1990-10), and wherein the diameters of many pores of the filter medium are 25-65 µm, determined according to DIN ISO 4003 (1990-10).

[0008] The filter medium is particularly suitable for engine air filters. Previously, engine air filter media were not charged because rapid discharge occurred under high dust loads, resulting in no discernible difference in filtration efficiency compared to an uncharged medium. Surprisingly, it was found that the charged filter medium of the present invention exhibits better efficiency and dust holding capacity compared to uncharged media. Therefore, the meltblown layer can be produced with larger fiber diameters. This enables more cost-effective manufacturing as well as higher efficiency and dust holding capacity of the filter medium at the same pressure drop.

[0009] Preferably, the polyester fibers contain polybutylene terephthalate or consist of polybutylene terephthalate fibers.

[0010] The mean diameter of these meltblown fibers is particularly 2 to 8 µm, preferably 2 to 5 µm, and most preferably 3 to 4 µm. The mean diameter is measured using the method described herein.

[0011] The meltblown layer according to the invention has a thickness of, in particular, 0.05 to 0.90 mm at a contact pressure of 0.005 bar, preferably 0.10 to 0.80 mm and particularly preferably 0.15 to 0.70 mm.

[0012] The basis weight of the meltblown layer is in particular 5 to 90 g / m², preferably 10-60 g / m², particularly preferably 15-25 g / m².

[0013] The air permeability of the meltblown layer according to the invention is in particular 50-3000 l / m 2< s, preferably 300 to 2000 l / m 2< s and particularly preferably 800 to 1300 l / m 2< s.

[0014] The meltblown nonwoven fabric according to the invention is produced using the meltblown process known in the industry. Suitable polymers (especially polyesters) include, for example, polyethylene terephthalate or polybutylene terephthalate. Preferably, the meltblown layer comprises polybutylene terephthalate fibers. Particularly preferably, the meltblown layer consists of polybutylene terephthalate fibers. Depending on the requirements, additives such as hydrophilizing agents, hydrophobizing agents, crystallization accelerators, or colorants can be added to the polymers. The meltblown layer can be electrically charged during production or charged together with the carrier layer. All known charging methods, such as corona charging, are suitable.

[0015] To increase charge stability, additives known in the scientific community can be added, such as bis-stearoyl-ethylenediamide.

[0016] The support layer can be a wet layer or a dry layer.

[0017] Wet-laid layers or paper layers within the meaning of the invention are all layers that can be produced using wet-laying processes known in the trade for the manufacture of filter papers. The wet-laid layer can contain natural fibers, synthetic fibers, or mixtures thereof. Examples of natural fibers are cellulose, cotton, wool, and hemp, wherein the cellulose material used can include wood-free and / or wood-containing cellulose from coniferous and / or deciduous trees, regenerated cellulose, and fibrillated cellulose.

[0018] Suitable synthetic fibers include, for example, polyester fibers (e.g., polyethylene terephthalate, polybutylene terephthalate and PLA fibers), polyolefin fibers, polyamide fibers, polyacrylonitrile fibers and multi-component fibers with different melting points of the individual components.

[0019] The synthetic fibers in the wet-laid layer have a mean fiber diameter of particularly 3 µm (0.1 dtex) to 30 µm (10 dtex), preferably 7 to 20 µm, and the cut length is preferably 3 mm - 20 mm, particularly preferably 4 mm - 12 mm.

[0020] The backing layer can comprise 100 wt.% natural fibers (based on the total amount of fibers). The backing layer can comprise 30-45 wt.% synthetic fibers and 70-55 wt.% natural fibers, or 100 wt.% synthetic fibers. Preferably, the backing layer comprises 100 wt.% natural fibers.

[0021] The wet-laid support layer has a thickness at a contact pressure of 0.005 bar of in particular 0.1 mm to 1.2 mm, preferably 0.2 mm to 0.9 mm, particularly preferably 0.3 mm to 0.8 mm.

[0022] The dried support layer is a layer that can be produced using known drying processes for manufacturing nonwoven layers. Preferably, the nonwoven layer is a spunbond or carded nonwoven comprising only synthetic fibers. Preferably, the dried support layer consists of a spunbond nonwoven layer. The dried support layer preferably has a thickness of 1 mm to 3.0 mm at a contact pressure of 0.005 bar. Particularly preferably, the thickness of the dried support layer is 1.2 mm to 2.5 mm, and especially 1.3 mm to 2.1 mm.

[0023] The dried support layer comprises mono- and / or bicomponent synthetic fibers. Preferably, the dried support layer comprises (or consists of) monocomponent polyester fibers and, particularly preferably, polyethylene terephthalate fibers. Suitable synthetic fibers include, for example, polyester fibers (e.g., polyethylene terephthalate, polybutylene terephthalate, and PLA fibers), polyolefin fibers, polyamide fibers, polyacrylonitrile fibers, and multicomponent fibers with different melting points of the individual components.

[0024] Bicomponent fibers consist of a thermoplastic material with at least one fiber component having a higher melting point and a second fiber component having a lower melting point. The physical configuration of these fibers is known to those skilled in the art and typically consists of a side-by-side or sheath-core structure.

[0025] The bicomponent fibers can be produced from a variety of thermoplastic materials, including polyolefins (such as polyethylenes and polypropylenes), polyesters (such as polyethylene terephthalate (PET), polybutylene terephthalate (PBT)), and polyamides, including nylon 6, nylon 6.6, nylon 6.12, etc.). Preferably, the bicomponent fibers are made from polyesters. Particularly preferably, the bicomponent fibers consist of PET / coPET.

[0026] The mono- and bicomponent fibers of the dried support layer have in particular a mean diameter of 10 to 50 µm, preferably of 12 to 40 µm and particularly preferably of 14 to 35 µm.

[0027] The substrate layer can be impregnated, the type of impregnating agent being selected by a person skilled in the art depending on the intended use of the filter material according to the invention. The proportion of the dry impregnating agent to the total weight of the paper is typically 0.5 wt.% - 50 wt.%, preferably 5 wt.% - 40 wt.%. Substances known for filter papers are used as impregnating agents, such as phenolic resins or epoxy resins from alcoholic solutions, but also aqueous dispersions of, for example, acrylates, phenolic resins, polyvinyl chloride, and polyvinyl acetates. Another possible class of impregnating agents are aqueous solutions of, for example, polyvinyl alcohol, melamine resin, and urea resin. To improve wettability and thus increase the flow rate, the impregnation can be made hydrophilic or oleophilic by suitable additives such as surfactants or fluorocarbon resins.

[0028] The mass per unit area of ​​the support layer (i.e., wet or dry layer) is in particular 50-350 g / m², preferably 70-250 g / m² and particularly preferably 80-200 g / m².

[0029] The support layer (i.e., wet or dry layer) has an air permeability of particularly 50-4000 l / m 2< s, preferably 100-3000 l / m 2< s and particularly preferably 200 to 2800 l / m 2< s.

[0030] The filter medium can either consist solely of the combination of the carrier layer and meltblown layer described here, or it can include one or more other layers.

[0031] To produce the filter medium, the meltblown layer can be bonded to the carrier layer. Any method known to those skilled in the art can be used for this purpose, such as needling, waterjet needling, thermal processes (i.e., calendering and ultrasonic bonding), and chemical processes (i.e., bonding with adhesives). Preferably, the meltblown layer is bonded to the carrier layer using spot calendering or adhesives. The amount of adhesive applied is 2–10 g / m², preferably 4–8 g / m².

[0032] The filter medium according to the invention has a surface mass of preferably 55 g / m² to 440 g / m², preferably 80 to 300 g / m², and particularly preferably 90 to 200 g / m². The air permeability of the filter medium is preferably 50 to 1200 l / m² s, preferably 100 to 1000 l / m² s, and particularly preferably 200 to 900 l / m² s.

[0033] Preferably, the thickness of the filter medium at a contact pressure of 0.005 bar is 0.4 to 2.5 mm, particularly preferably 0.45 to 2 mm and even more preferably 0.45 to 1 mm.

[0034] The maximum pore diameter (or largest pore size) of the filter medium according to the invention is 35-110 µm. The diameters of many pores of the filter medium according to the invention are 25-65 µm.

[0035] The filter medium has an H-value of, in particular, 1.00 to 2.50, preferably 1.00 to 2.00, and especially preferably 1.00 to 1.80. The H-value is calculated from:

[0036] If the H-value is within the range described above, very good homogeneity is evident, so that the filter medium can guarantee very high efficiency and dust storage capacity for a longer period of time.

[0037] The filter medium according to the invention has an efficiency of at least 99.00%, preferably at least 99.70%, and particularly preferably at least 99.90%. The efficiency specified here corresponds to the overall efficiency after a pressure increase to 2000 Pa. This is to be distinguished from an initial efficiency.

[0038] The filter medium according to the invention has a dust storage capacity of in particular 70 to 350 g / m 2< , preferably 100 to 300 g / m 2< and particularly preferably 125 to 300 g / m 2< .

[0039] Since the filter medium according to the invention has excellent breaking strength, it only needs to be renewed after longer time intervals.

[0040] Filter media containing natural fibers have a breaking strength in the machine direction (MD) of, in particular, 60-200 N, preferably 70-180 N and particularly preferably 75-100 N. Filter media containing only synthetic fibers (and no natural fibers) have a breaking strength in the machine direction (MD) of 250-600 N, preferably 350-600 N and particularly preferably 400-600 N.

[0041] The flow direction is preferably from the side of the carrier layer, but can also be from the side of the meltblown layer.

[0042] The present invention also relates to a filter element comprising the filter medium. The filter element can additionally comprise another filter medium that differs from the filter medium according to the invention, i.e., has different properties.

[0043] One particularly advantageous application area for the filter medium according to the invention is engine air filters. Testing methods

[0044] Area measure according to DIN EN ISO 536:2012-11.

[0045] thickness according to DIN EN ISO 9073-2 (1997-02) at 0.5 kPa contact pressure with 2500 mm² test area (56.42 mm diameter).

[0046] Air permeability according to DIN EN ISO 9237 (1995-12) at a pressure difference of 200 Pa.

[0047] pore size According to DIN ISO 4003 (1990-10), based on flat sample measurements. Reagents: Denatured ethanol (= 100 L ethanol with 1 L MEK (methyl ethyl ketone) as denaturant). The fleece is clamped airtight over a cavity equipped with an air supply line and a connection to a manometer (U-tube with mm markings).

[0048] Denatured ethanol is added over the edge of the upper sample holder (do not spray directly onto the sample / approx. 4 mm height) and a slight overpressure is simultaneously created. The overpressure is slowly increased (approx. 5 mm water column / sec) until the first air bubble becomes visible.

[0049] The necessary pressure is read from the manometer (mm WS), and the largest pore diameter, or "largest pore," is calculated using the surface tension of the ethanol (23°C). If the overpressure is increased until air passes through the entire test area (10 cm²) (with an almost uniform distribution of air bubbles, but no foaming), the value for the number of pores is obtained. For this, the overpressure of the "many pores" is again determined, and the corresponding pore diameter is calculated. Breaking force

[0050] For the entire filter medium (carrier + meltblown; where the filter medium includes natural fibers) in accordance with DIN EN ISO 1924-2 (2009-05) (measuring strip with a length of 100 mm, a width of 15 mm; pull-off speed 15 mm / min). For the entire filter medium (carrier + meltblown; where the filter medium does not include natural fibers) in accordance with DIN EN ISO 29073 Part 3 (1992-08) (measuring strip with a length of 100 mm, a width of 50 mm; pull-off speed 100 mm / min). Efficiency and dust storage capacity

[0051] The stated efficiency values ​​were measured based on flat sample measurements according to ISO 5011:2014. Test conditions: Test dust ISO 12103-A2 (ISO Fine) Mass concentration: 1 g / m³ < Flow velocity 11.1 cm / s Filter area: 100 cm² <

[0052] The overall efficiency and dust storage capacity are measured when a final pressure of 2000 Pa is reached. Fiber diameter

[0053] Measurement principle: Images are acquired at a defined magnification using a scanning electron microscope. These images are then measured using automated software. Measurement points that capture fiber intersections and therefore do not represent the fiber diameter are manually removed. Fiber bundles are generally treated as a single fiber. Devices:

[0054] Scanning electron microscope Phenom Fei with associated software Fibermetric V2.1 Conducting the test:

[0055] Sampling: Nonwoven fabric at 5 points across the width of the roll (at 1.8m) Recordings:

[0056] a. Sputter the sample; b. Randomly scan the optical image; the identified location is then imaged at 1000x magnification using SEM. c. Determine the fiber diameter using the "one-click" method, requiring each fiber to be scanned once; d. Evaluate the average value and fiber diameter distribution using the data obtained from Fibermetric in Excel. Thus, the mean fiber diameter is recorded at at least five locations per nonwoven fabric. The five average values ​​are then combined into a single mean value. This value is designated as the mean fiber diameter of the nonwoven fabric. At least 500 fibers are evaluated. Examples Example 1

[0057] A 20 g / m² PBT (polybutylene terephthalate) meltblown with a thickness of 0.22 mm, an air permeability of 650 l / m² / s, and a mean fiber diameter of 3.5 µm was bonded to a 135 g / m² wet-laid paper layer with a thickness of 0.68 mm using a spot calender and loaded with a corona charge. The paper layer used here consists of wood pulp and was previously impregnated with resin.

[0058] The resulting filter material has a thickness of 0.75 mm, an air permeability of 365 l / m²s, and a surface mass of 155 g / m². The largest pore diameter of the filter medium is 39 µm, and the diameter of many pores is 27 µm. Example 2

[0059] A 60 g / m² PBT meltblown with a thickness of 0.66 mm, an air permeability of 1200 l / m² s and a mean fiber diameter of 4 µm was bonded to a 130 g / m² PET / CoPET spunbond nonwoven with a thickness of 1.47 mm using a dot calender and charged with corona charge.

[0060] The resulting filter material has a thickness of 2.00 mm, an air permeability of 900 l / m²s, and a surface mass of 190 g / m². The largest pore diameter of the filter medium is 100 µm, and the diameter of many pores is 58 µm. Comparative example 1

[0061] It uses the same filter medium as example 1, but was not charged with corona charge. Comparative example 2

[0062] It is the same filter medium as in example 2, but was not charged with corona charge.

[0063] Some advantages of the filter medium according to the invention are listed in Table 1. Table 1 Example 1 Comparative example 1 Example 2 Comparative example 2 Efficiency (%) 99,98 99,84 99,90 99,29 Dust storage capacity (g / m²< ) 127 123 272 220

Claims

1. A filter medium for engine air filters, comprising a carrier layer and a meltblown layer, which contains polyester fibers, wherein the filter medium is electrically charged, wherein the filter medium has a maximum pore diameter of 35-110 µm, determined according to DIN ISO 4003 (1990-10), and wherein the diameters of many pores of the filter medium are 25-65 µm, determined according to DIN ISO 4003 (1990-10).

2. The filter medium according to claim 1, characterized in that the polyester fibers contain polybutylene terephthalate.

3. The filter medium according to any of the preceding claims, characterized in that the polyester fibers have a mean diameter of 2-8 µm.

4. The filter medium according to any of the preceding claims, characterized in that the meltblown layer has a basis weight of 5-90 g / m2.

5. The filter medium according to any of the preceding claims, characterized in that the filter medium has an overall efficiency of at least 99.00%.

6. The filter medium according to any of the preceding claims, characterized in that the carrier layer contains a paper layer or a spunbond layer.

7. The filter medium according to claim 6, characterized in that the spunbond layer contains monocomponent or bicomponent polyester fibers.

8. The filter medium according to claim 7, characterized in that the bicomponent fibers contain PET / CoPET.

9. The filter medium according to any of the preceding claims, characterized in that the filter medium consists of the carrier layer and the meltblown layer.

10. A filter element comprising a filter medium according to any of the preceding claims.