Multi-layer filter media

Description

[0001] The invention relates to a filter medium according to the preamble of claim 1. State of the art

[0002] From EP 1 932 576 A1, a filter element for cleaning an airflow is known, comprising a filter medium consisting of multiple layers of nonwoven fabric and adsorbent layers, wherein the filter medium is folded multiple times and the nonwoven layers and adsorbent layers are arranged parallel to each other. The filter medium has two or three layers overlapping each other, each layer consisting of an adsorbent layer with nonwoven fabric layers applied to both sides. Document US 2017 / 320001 A1 also discloses a filter medium for cleaning an airflow comprising multiple layers of nonwoven fabric and adsorbent layers, wherein the nonwoven layers and adsorbent layers are arranged parallel to each other.

[0003] The disadvantage is that two layers of nonwoven fabric always lie on top of each other inside the filter medium, resulting in an unnecessary doubling of the inner nonwoven fabric layers for the function of the filter element, a greater thickness of the filter medium and a corresponding increase in material consumption. Task

[0004] The object of the present invention is to create a filter medium in which the use of material is optimized and which, with corresponding functionality, has a lower thickness compared to filter media known from the prior art. Technical solution

[0005] This problem is solved by a filter medium having the features of claim 1.

[0006] According to the invention, it was found to be advantageous to construct the filter medium such that nonwoven layers and adsorbent layers alternate continuously: The filter medium according to the invention serves to purify an airflow and has a plurality of nonwoven layers and adsorbent layers, wherein the nonwoven layers and the adsorbent layers are arranged parallel to each other. A nonwoven fabric is understood here to be, in particular, a nonwoven fabric as defined in ISO 9092:2019 (Nonwovens). Accordingly, composites ("nonwoven composites") comprising several nonwovens, as well as nonwovens combined with further material layers, are also considered nonwovens. Nonwoven layers are layers of nonwoven fabric, and adsorbent layers are layers comprising adsorbents.Advantageously, the filter medium has at least two superimposed layers, a first layer consisting of a nonwoven fabric layer bonded to an adsorbent layer, and a second layer consisting of an adsorbent layer with nonwoven fabric layers applied to both sides. Such a filter medium thus has at least two layers and five layers (two layers of the first layer plus three layers of the second layer). Each nonwoven fabric layer can contain one or more sublayers. In the case of multiple sublayers, these together form the nonwoven fabric layer as a composite. A filter medium constructed in this way has the advantage that there is no doubling of nonwoven fabric layers. Compared to filter media with doubling of nonwoven fabric layers, the filter medium according to the invention is thinner and more material-efficient.This results in a lower pressure loss and therefore a higher filtration performance of the filter medium.

[0007] In the filter medium according to the invention, the inner nonwoven layers of the filter medium have a smaller thickness and a higher separation efficiency than the outer nonwoven layers of the filter medium. Inner nonwoven layers are defined as those layers to which further layers are attached on both sides. An outer nonwoven layer is defined as a layer that borders the filter medium and to which another layer is attached only on one side. The thickness of the inner nonwoven layers can be less than one millimeter, and the thickness is to be determined according to DIN EN ISO 9073-2:1997-02. The separation efficiency of the inner nonwoven layers can be comparable to that of at least EPA filters (Efficient Particulate Air Filters) according to EN 1822-1:2009, i.e., have a separation efficiency of over 85%.This inner nonwoven layer can preferably be a nanofiber nonwoven layer or a membrane layer. Such membrane layers can, for example, be formed from a carrier nonwoven and a laminated film.

[0008] In an advantageous embodiment of the filter medium according to the invention, it additionally comprises a third layer, wherein the third layer consists of an adsorbent layer bonded to a nonwoven layer. In this filter medium, the second layer is arranged between the first and third layers. This ensures that the nonwoven layers and adsorbent layers are always arranged alternately parallel to each other.

[0009] In a particularly advantageous and therefore preferred embodiment of the filter medium according to the invention, the filter medium is folded multiple times, in particular pleated, such that a plurality of fold edges and fold surfaces lying between the fold edges are formed. The layers of the filter medium are positively connected to one another, i.e., the layers lie on top of each other by means of the fold surfaces and fold edges of the different layers touching each other, and the layers therefore cannot slip relative to each other.

[0010] In a further development of the filter medium according to the invention, the layers are bonded together by means of a material connection, in particular by welding or bonding. In the case of welding, the material connection is made at points or along a line. In the case of bonding, a so-called laminating adhesive can be applied over the entire surface of the layers, thus bonding the layers over their entire surface.

[0011] In one possible configuration of the filter medium, it has a progressive structure such that the porosity of the nonwoven layers, or at least of the inner nonwoven layers, gradually decreases from one layer to the next, from the inflow side (raw gas side) to the outflow side (clean gas side) of the filter medium. Here, porosity is understood as the ratio of void volume to total volume of a given nonwoven layer. Such a filter medium offers particularly good dust filtration.

[0012] Activated carbon, zeolites, mixed oxide catalysts, silica gel, or similar materials can be used as adsorbents in the adsorbent layers of the filter medium. In a particularly advantageous embodiment of the filter medium, the adsorbent layers contain granules or powder of activated carbon. In addition to pure activated carbon, mixtures containing activated carbon, impregnating agents, fillers, and / or binders, can also be used in the adsorbent layers.

[0013] The filter medium can be used in a filter element, which is used in the air filtration of the interior of a motor vehicle.

[0014] The described invention and the described advantageous further developments of the invention also represent advantageous further developments of the invention when combined with each other - insofar as this is technically sensible.

[0015] Regarding further advantages and structurally and functionally advantageous embodiments of the invention, reference is made to the dependent claims and the description of exemplary embodiments with reference to the accompanying figures. Example of implementation

[0016] The invention will be explained in more detail with reference to the attached figures. Corresponding elements and components are identified by the same reference numerals in the figures. For the sake of clarity, the figures are not drawn to scale.

[0017] They show in schematic representation Fig. 1: One embodiment of a filter medium with two layers. Fig. 2: Another embodiment of a filter medium with two layers. Fig. 3: One embodiment of a filter medium with three layers. Fig. 4: Another embodiment of a filter medium with three layers. Fig. 5: Another embodiment of a filter medium with three layers.

[0018] Fig. 1 Figure 1 shows a filter medium 10 through which an airflow L flows from an inlet side 7, the raw gas side, towards the outlet side 8, the clean gas side, thereby cleaning the airflow L. This direction of airflow L through the filter medium 10 also applies to the following figures.

[0019] The filter medium 10 made of Fig. 1It has two layers, a first layer 1 and a second layer 2. The first layer 1 consists of a nonwoven layer 4 and an adsorbent layer 5. The second layer 2 consists of a nonwoven layer 4, an adsorbent layer 5, and another nonwoven layer 4. The adsorbent layer 5 is covered on both sides by the nonwoven layers 4.

[0020] All layers 4 and 5 of layers 1 and 2 are arranged parallel to each other, and layers 1 and 2 lie on top of each other. The filter medium 10 is pleated and has numerous fold edges and fold surfaces located between the fold edges. The pleating creates a positive connection between layers 1 and 2. Additionally, layers 1 and 2 can also be bonded together by a material bond (not shown here). Such a material bond can be achieved by welding or gluing.

[0021] The in Fig. 2The illustrated filter medium 10 also has a structure with a first layer 1 and a second layer 2. In contrast to the filter element 10 made of Fig. 1 However, the filter medium 10 has a progressive structure. This progressive structure is achieved by decreasing the porosity of the nonwoven layers 4, specifically the particle filter layers 4.2, from the upstream side 7 to the downstream side 8. Each subsequent particle filter layer 4.2 is more densely packed than each preceding one.

[0022] Fig. 3Figure 1 shows a filter medium 10 with a first layer 1, a second layer 2, and a third layer 3. The first layer 1 consists of a nonwoven layer 4 bonded to an adsorbent layer 5. The nonwoven layer 4 is designed as a support layer 4.1. The support layer 4.1 is an outer nonwoven layer 4 of the filter medium 10, which can exhibit higher stiffness and stability than the inner nonwoven layers 4. The inner nonwoven layers 4 can be designed as particle filter layers 4.2 and are thus unstable and optimized for particle filtration. The second layer 2 consists of such particle filter layers 4.2, which are attached to both sides of an adsorbent layer 5. The third layer 3 consists of an adsorbent layer 5 and a support layer 4.1.The second layer 2 is arranged between the first layer 1 and the third layer 3, so that nonwoven layers 4 and adsorbent layers 5 always alternate.

[0023] The example of Fig. 4 shows a filter medium 10 with three layers 1, 2, 3. In contrast to the filter medium 10 made of Fig. 3 All nonwoven layers 4 are designed as particle filter layers 4.2. The filter medium 10, like the filter medium 10 made of Fig. 2 , a progressive structure, i.e. the porosity of the particle filter layers 4.2 decreases from the upstream side 7 to the downstream side 8 of the filter medium 10.

[0024] The filter medium 10 also consists of Fig. 5 It has a progressive structure with three layers 1, 2, 3. In contrast to the design of the filter medium 10 made of Fig. 4The outer nonwoven layers 4, however, were designed as support layers 4.1. Only the inner particle filter layers 4.2 create the progressive structure of the filter medium 10, by decreasing the porosity of the particle filter layers 4.2 from the upstream side 7 to the downstream side 8 of the filter medium 10. In other words, the particle filter layer 4.2 that flows through first has a higher porosity than the particle filter layer 4.2 that flows through later.

[0025] To better bond layers 1, 2, and 3 of the filter medium 10 and to create a filter element with good overall stability, an edge band 6 can be attached, in particular glued, to the ends of the folded edges. Such an edge band 6 is shown with a dashed line in Fig. 5 hinted at. Reference symbol list

[0026] 1 First layer 2 Second layer 3 Third layer 4 Nonwoven layer 4.1 4.2 Carrier layer Particle filter layer 5 Adsorber layer 6 Edge tape 7 Inlet side (raw gas side) 8 Outlet side (clean gas side) 10 Filter medium Airflow

Claims

1. Filter medium (10) for cleaning an air stream (L), comprising a plurality of nonwoven plies (4) and adsorber plies (5), wherein the nonwoven plies (4) and the adsorber plies (5) are arranged parallel to one another, wherein the filter medium (10) has at least two layers (1, 2) which lie one on top of the other and which comprise a first layer (1), consisting of a nonwoven ply (4) which is connected to an adsorber ply (5), and a second layer (2), consisting of an adsorber ply (5) to which nonwoven plies (4) are attached on both sides, characterized in that the inner nonwoven plies (4) of the filter medium (10) have a smaller thickness and greater separation efficiency than the outer nonwoven plies (4) of the filter medium (10).

2. Filter medium according to Claim 1, which has a third layer (3) consisting of an adsorber ply (5) which is connected to a nonwoven ply (4), wherein the second layer (2) is arranged between the first layer (1) and the third layer (3), with the result that nonwoven plies 4 and adsorber plies 5 continually alternate.

3. Filter medium according to one of the preceding claims, characterized in that the filter medium (10) is folded multiple times, and the layers (1, 2, 3) are connected to one another in a form-fitting manner.

4. Filter medium according to one of the preceding claims, characterized in that the layers (1, 2, 3) are connected to one another in a cohesively bonded manner, in particular by welding or adhesive bonding.

5. Filter medium according to one of the preceding claims, characterized in that the inner nonwoven plies (4) of the filter medium (10) are in the form of a nonwoven-nanofabric ply or membrane ply.

6. Filter medium according to one of the preceding claims, characterized in that the filter medium (10) has a progressive structure such that the porosity of the nonwoven plies (4) decreases from an inflow side (7) to an outflow side (8) of the filter medium (10).

7. Filter medium according to one of the preceding claims, characterized in that the adsorber plies (5) contain granules or powder composed of activated carbon.