Filter material having nanofiber layer and filter element made of such filter material

Abstract

The invention relates to a filter material having a nanofiber layer and a filter element made of such a filter material. The filter material (10) is equipped with a pre-filter layer (2) on the inflow side, an activated carbon layer (3) and a composite layer (1) which is designed as a fine filter layer having nanofibers. According to the invention, the layers are integrally bonded to one another. Since the pre-filter layer and the composite layer with nanofibers are combined in one filter material, a high dust storage capacity and a high mass coefficient are advantageously achieved at the same time.

Description

Technical Field

[0001] The invention relates to a filter material for filtering air in a filter element, comprising an inflow-side prefilter layer, an activated carbon layer, and a composite layer configured as a fine filter layer comprising nanofibers, and a filter element comprising such a filter material. Background Art

[0002] Known filters for filtering fluids, particularly air, are known from the prior art. For this reason, a filter element is usually inserted into a filter housing and is flowed through by air.

[0003] Different filter elements for filtering interior air are known from the prior art. For example, DE 10 2013 011 457 A1 describes an interior air filter element for the driver's cabin of agricultural and working machines.

[0004] The interior air filter element comprises an adsorption filter layer containing activated carbon, a fine filter layer (particularly for separating aerosols), and a surrounding seal for separating the unfiltered side from the clean side when installed in the filter housing. This multi-stage filter is also known as a multi-stage filter. The provision of a pleated pre-filter layer protects the adsorption layer and the fine filter layer from excessive dust loading and ensures their functionality for as long as possible. The disadvantage of this design is that the pre-filter layer requires additional installation space and the filter element is less compact. Summary of the Invention

[0005] The object of the present invention is to provide a filter material which, compared to known filter materials, has a more stable filtration efficiency over the service life, while the installation space requirement remains unchanged.

[0006] Technical Solutions

[0007] This object is achieved by the filter material described and claimed below.

[0008] According to the invention, it has been found to be advantageous to combine the prefilter layer, the activated carbon layer as adsorption layer, and the composite layer comprising nanofibers in one filter material.

[0009] The filter material according to the present invention is used for filtering air in a filter element. It comprises an inlet-side prefilter layer configured as a coarse dust filter layer, an activated carbon layer as an adsorption layer, and a composite layer as a mechanical filter medium. The composite layer is configured as a fine filter layer comprising nanofibers and can, for example, be configured to have EPA (High Efficiency Particulate Air) properties.

[0010] According to the present invention, the composite layer comprises a nanofiber layer on a carrier layer, which is provided with a cover layer on its other side. The layers are materially bonded to one another. The carrier layer can be composed of coarse fibers, while the cover layer can be composed of coarse fibers and / or microfibers.

[0011] According to the present invention, the pre-filter layer, the activated carbon layer, and the composite layer are also connected to one another in a materially bonded manner. Thus, the layers are not connected in a form-locking manner by co-pleating, i.e., not by folding the layers together, but rather in a materially bonded manner. This materially bonded connection is also referred to as "laminating to one another."

[0012] The material-locking connection can be achieved by any type of lamination or coating, by means of bonding (polymer threads, powders, M-webs, reactive or thermal adhesives such as thermoplastic hot melts, etc.), by hot pressing (calendering with or without fused fiber components), or by means of ultrasonic welding or calendering. The material-locking connection can be present over the entire surface or in spots on the layer surface. The advantage of a material-locking connection over the co-pleated connection of the individual layers is that the mechanical stability is significantly improved. Another advantage is the higher temperature stability: after heat storage in the filter material, a smaller increase in pressure loss is observed compared to a co-pleated filter material of otherwise identical construction. The filter material can also be pleated well as a whole with its material-locking layers. Without a material-locking connection, usually only two layers can be co-pleated together. The other layer must then be pleated separately, so that the filter element consists of two layers: the pleated layer and the co-pleated layer. However, such a multi-layered filter element requires more space. Due to the material-locking connection of all layers, a filter medium having three or more layers can be provided which requires less installation space during subsequent pleating than a co-pleated filter medium.

[0013] The combination of a pre-filter layer and a composite layer with nanofibers in one filter material allows for both a high dust storage capacity and a high quality factor. This material offers excellent value for money in terms of thickness: using this filter material in filters allows for good filtration efficiency without increasing pressure loss.

[0014] Compared to coarser fibers, nanofibers offer the advantage of a larger surface area, which in turn allows for improved filtration performance and a longer filter life. The higher barrier effect (interception effect) due to the smaller fiber diameter has a particularly positive effect here. Unlike electrostatic separation, the effects attributed to mechanical separation are largely maintained throughout the filter's operating life. Furthermore, filter media made from nanofibers exhibit lower pressure loss, resulting in lower energy requirements for the filter element.

[0015] The filter material according to the invention has an adsorption layer configured as an activated carbon layer, ie a layer having a certain proportion of activated carbon as an adsorbent. Filter elements made of such filter materials are referred to as combination filters.

[0016] In a particularly advantageous embodiment of the filter medium, the individual layers are connected by gluing using a polyolefin hotmelt adhesive as the thermoplastic fusion adhesive. This has the following advantages:

[0017] - good adhesion properties on the substrates to be bonded,

[0018] ->105℃ high thermal stability,

[0019] - stability with respect to oxidatively active degradation processes,

[0020] -High aging resistance, and

[0021] - Less noticeable in terms of fogging and odor.

[0022] Polyolefin hot melt adhesives may also be used to bond the layers of the composite to each other.

[0023] In a further development of the invention, the prefilter layer and / or the composite layer in the filter material is electrostatically charged, for example by corona or high-voltage technology, thereby further increasing the dust storage capacity.

[0024] In one possible design variant of the filter material, the activated carbon layer is equipped with a permanently adhesive adhesive mesh. This permanently adhesive adhesive mesh, also known as a mesh adhesive layer, is incorporated into the activated carbon layer. The adhesive layer can be created using a polyolefin hot-melt adhesive, which has filaments with a diameter of 5 to 20 microns that form the adhesive mesh. The permanently adhesive adhesive mesh advantageously separates particularly coarse dust particles, thereby protecting subsequent layers. Another function of the adhesive mesh is to attach and secure adsorbed particles to the activated carbon layer.

[0025] In an extension of the filter material, the filter material has an additional coarse filter layer, which can also be called a coarse dust filter layer. The function of the coarse dust filter layer is, on the one hand, to provide a support structure for the activated carbon layer or a support structure for the composite layer, and on the other hand to perform a filtering effect. Therefore, the advantages of this filter material are greater stability and a higher dust storage capacity. The higher dust storage capacity helps to keep the increase in pressure loss of the filter element as low as possible during the use period, especially in the presence of highly separating nanofibers. For this purpose, the coarse dust filter layer can be arranged upstream of the composite layer in the flow direction.

[0026] In one possible embodiment of the filter material, the prefilter layer or the (possibly present) coarse filter layer forms the carrier and thus the support structure for the activated carbon layer. The activated carbon layer can also consist, in particular, of activated carbon granules bonded to one another.

[0027] In the case of an activated carbon layer having a large number of individual activated carbon particles, in the prior art, a bulk accumulation of these particles is usually applied to a support structure and fixed by gluing. If, as described herein, a pre-filter layer or a (possibly present) coarse filter layer is used as a carrier, the pre-filter layer or the (possibly present) coarse filter layer can also perform a filtering function, which further improves the filter performance of the filter material.

[0028] Different variants of the filter material are conceivable, which differ in their structure. Here, the structure of the composite layer is uniform as follows when viewed in the flow direction: carrier layer, nanofiber layer, cover layer.

[0029] In a first variant, the filter material comprises an inflow-side prefilter layer, an outflow-side composite layer and an activated carbon layer situated therebetween.

[0030] The following sequence of layers is thus visible in the flow direction:

[0031] 1) Pre-filtration layer

[0032] 2) Activated carbon layer

[0033] 3) Composite layer

[0034] In a second variant, the filter material comprises an inflow-side prefilter layer, an outflow-side coarse filter layer with an activated carbon layer applied thereto, and a composite layer located therebetween. In particular, the prefilter layer and the composite layer are designed as a unit that is materially bonded to one another, for example by heat welding. Thus, the following sequence of layers is visible in the throughflow direction:

[0035] 1) Pre-filtration layer

[0036] 2) Composite layer

[0037] 3) Activated carbon layer

[0038] 4) Coarse filter layer

[0039] In a third variant, the filter material comprises a pre-filter layer on the inlet side with an activated carbon layer applied thereto (the activated carbon layer being located downstream of the pre-filter layer), a composite layer on the outlet side and a coarse filter layer situated therebetween, wherein in particular the coarse filter layer and the composite layer are constructed as units that are materially connected to each other and are bonded to each other, for example, using a thermoplastic hot melt adhesive.

[0040] The following sequence of layers is thus visible in the flow direction:

[0041] 1) Pre-filtration layer

[0042] 2) Activated carbon layer

[0043] 3) Coarse filter layer

[0044] 4) Composite layer

[0045] In a fourth variant, a pre-filter layer on the inlet side, a coarse filter layer with an activated carbon layer applied upstream, a further coarse filter layer, and a composite layer on the outlet side are provided. In particular, the further coarse filter layer and the composite layer are designed as a unit that is materially bonded to one another, for example, by heat welding.

[0046] The following sequence of layers is thus visible in the flow direction:

[0047] 1) Pre-filtration layer

[0048] 2) Activated carbon layer

[0049] 3) Coarse filter layer

[0050] 4) Coarse filter layer

[0051] 5) Composite layer.

[0052] In the second, third, and fourth variants, the unit being materially bonded to one another means that the pre-filter layer and the composite layer, or the coarse filter layer and the composite layer, have already been materially bonded to one another in a previous process and are then materially bonded to the other layer in a further process step. The materially bonded connection of the pre-filter layer or the coarse filter layer to the composite layer can be achieved thermally over the entire surface and / or by spot layer welding.

[0053] This allows the filter material to have a particularly high strength and good processability.

[0054] In one possible embodiment of the filter material, the filter material has a progressive structure, whereby the porosity of each layer—the pre-filter layer, the activated carbon layer, and the composite layer—decreases from the inflow side (raw gas side) to the outflow side (clean gas side) of the filter material. Porosity here refers to the ratio of the void volume of each nonwoven layer to the total volume. In other words, the progressive structure means that each layer becomes increasingly finer as viewed in the flow direction. This filter material provides particularly good dust filtration, and the pressure differential across the filter material is stable over time.

[0055] The present invention also relates to a filter element having the pleated filter material.

[0056] In one possible embodiment of the filter element, an edge band or a frame element can be attached to the pleated filter material, which edge band or frame element can stabilize the filter element and serve as a sealing element for a filter housing that accommodates the filter element.

[0057] The invention also relates to the use of the aforementioned filter element as an interior air filter for filtering and cleaning the cabin supply air in a vehicle, in particular a passenger car, commercial vehicle or bus.

[0058] The invention described and the advantageous developments of the invention described also constitute advantageous developments of the invention in combination with one another, insofar as this is technically advantageous.

[0059] With regard to further advantages and structurally and functionally advantageous embodiments of the invention, reference is made to the dependent claims and to the description of exemplary embodiments with reference to the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0060] The present invention will be described in detail with reference to the accompanying drawings. Corresponding elements and components are given the same reference numerals in the drawings. For greater clarity, the drawings are not drawn to scale.

[0061] In the schematic diagram

[0062] Figure 1 A sectional view showing a first embodiment variant of the filter material,

[0063] Figure 2 A sectional view showing a second embodiment variant of the filter material,

[0064] Figure 3 A sectional view showing a third embodiment variant of the filter material,

[0065] Figure 4 A sectional view showing a fourth embodiment variant of the filter material,

[0066] Figure 5 A view showing a portion of the pleated filter material,

[0067] Figure 6 A spatial schematic diagram of a filter element with filter material is shown. DETAILED DESCRIPTION

[0068] Figure 1A cross-sectional view of a first embodiment variant of the filter material 10 is shown. The throughflow direction of the air flow is indicated by an arrow L. The filter material 10 comprises a pre-filter layer 2 on the inflow side, an activated carbon layer 3 in the middle and a composite layer 1 on the outflow side, which is constructed as a fine filter layer with nanofibers. The composite layer 1 comprises a plurality of layers, namely a cover layer, a nanofiber layer and a carrier layer, which are connected to each other by material locking. Only the cover layer and the carrier layer are marked in the figure. The other embodiment variants described below also include this structure of the composite layer 1. The pre-filter layer 2, the activated carbon layer 3 and the composite layer 1 are connected to each other by material locking with a thermoplastic hot melt adhesive (not shown). The cover layer, the nanofiber layer and the carrier layer of the composite layer 1 can also be connected to each other with a thermoplastic hot melt adhesive or by thermal welding.

[0069] Figure 2 A cross-section is shown of a second embodiment variant of a filter material 10. An inlet-side prefilter layer 2, an outlet-side coarse filter layer 4 with an activated carbon layer 3 applied upstream thereof and a composite layer 1 situated therebetween are provided.

[0070] The pre-filter layer 2 and the composite layer 1 are connected to each other by heat welding. The composite layer 1, the activated carbon layer 3, and the coarse filter layer 4 are bonded to each other using a thermoplastic hot melt adhesive. The cover layer, the nanofiber layer, and the carrier layer of the composite layer 1 can be connected to each other using a thermoplastic hot melt adhesive or heat welding.

[0071] Figure 3 A cross-section through a third embodiment variant of a filter material 10 is shown. Here, a prefilter layer 2 on the inflow side, a composite layer 1 on the outflow side, and a coarse filter layer 4 located therebetween, with an activated carbon layer 3 applied thereto, the activated carbon layer 3 being arranged upstream of the coarse filter layer 4, are used.

[0072] The coarse filter layer 4 and the composite layer 1 are bonded to each other using a thermoplastic hot melt adhesive. The pre-filter layer 2, the activated carbon layer 3, and the coarse filter layer 4 are bonded to each other using a thermoplastic hot melt adhesive. The cover layer, the nanofiber layer, and the carrier layer of the composite layer 1 can be bonded to each other using a thermoplastic hot melt adhesive or by thermal welding.

[0073] Figure 4 A cross-sectional view of a fourth embodiment variant of the filter material 10 is shown. Figure 3 In contrast to the variant of , an additional filter layer, a coarse filter layer 4 , is used, which is positioned upstream of the composite layer 1 .

[0074] The coarse filter layer 4 and the composite layer 1 are connected to each other by heat welding. The pre-filter layer 2, the activated carbon layer 3, and the two coarse filter layers 4 are materially bonded to each other using a thermoplastic hot melt adhesive. The cover layer, the nanofiber layer, and the carrier layer of the composite layer 1 can be connected to each other using a thermoplastic hot melt adhesive or heat welding.

[0075] Figure 5The figure shows a portion of a filter material 10 after pleating (regardless of how many layers it is constructed from). The fold edge 11 is denoted by 11 as an example.

[0076] Figure 6 FIG. 1 shows a spatial schematic diagram of a filter element 100 having a filter material 10. The filter element 100 having a filter material 10 (which may be Figures 1 to 4 The structure shown and has been Figure 5 The pleats shown have edge strips 20 attached to the pleated filter material 10 , which contribute to stabilizing the filter element 100 and enable sealing relative to a filter receptacle (not shown here).

[0077] Reference Signs List

[0078] 1 Composite layer with nanofiber layer

[0079] 2 Pre-filter layer

[0080] 3 Activated carbon layer

[0081] 4 Coarse filter layer

[0082] 10 Filter material

[0083] 11 Folding edges

[0084] 20 Edge Band

[0085] 100 filter elements

[0086] L air flow direction

Claims

1. A filter material (10) for filtering air in a filter element (100), comprising an inflow-side prefilter layer (2), an activated carbon layer (3) and a composite layer (1) which is configured as a fine filter layer with nanofibers, characterized in that The pre-filter layer (2), the activated carbon layer (3) and the composite layer (1) are connected to each other in a material-locked manner, and The composite layer (1) comprises at least one cover layer, a nanofiber layer and a carrier layer.

2. The filter material according to claim 1, characterized in that The pre-filter layer (2) and / or the composite layer (1) are electrostatically charged.

3. The filter material according to claim 1, characterized in that The activated carbon layer (3) is provided with a permanently sticky adhesive mesh.

4. The filter material according to claim 1, characterized in that The filter material (10) has an additional coarse filter layer (4).

5. The filter material according to claim 4, characterized in that The pre-filter layer (2) or coarse filter layer (4) forms a support for the activated carbon layer (3).

6. Filter material according to one of the preceding claims, characterized in that The activated carbon layer (3) consists of activated carbon particles bonded to each other.

7. The filter material according to any one of claims 1 to 6, characterized in that The filter material (10) has the following structure: A pre-filter layer (2) on the inflow side, a composite layer (1) on the outflow side and an activated carbon layer (3) located therebetween.

8. The filter material according to any one of claims 1 to 6, characterized in that The filter material (10) has the following structure: A pre-filter layer (2) on the inflow side, a coarse filter layer (4) on the outflow side, together with an activated carbon layer (3) applied thereto, and a composite layer (1) located therebetween, wherein in particular the pre-filter layer (2) and the composite layer (1) are constructed as a unit that is materially connected to one another.

9. The filter material according to any one of claims 1 to 6, characterized in that The filter material (10) has the following structure: A prefilter layer (2) on the inflow side, a composite layer (1) on the outflow side, and at least one coarse filter layer (4) and an activated carbon layer (3) located therebetween, wherein in particular the activated carbon layer (3) is applied upstream to the first coarse filter layer (4), and optionally in addition, the second coarse filter layer (4) and the composite layer (1) are constructed as a unit connected to each other in a material-locked manner.

10. The filter material according to any one of claims 1 to 7, characterized in that The layers (1, 2, 3) of filter material have a progressive construction.

11. A filter element (100) comprising a filter material (10) according to one of the preceding claims, wherein: The filter material (10) is pleated, and the edge strip (20) or the frame element is attached to the pleated filter material (10).

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