Filter Medium, Method for Producing Same, and Use of the Filter Medium in a Filter Element

Abstract

A filter medium for filtration of a gaseous medium is provided with a carded nonwoven layer and a filter paper layer arranged as a neighboring filter layer at an outflow side of the carded nonwoven layer. The carded nonwoven layer has a first air permeability and the filter paper layer has a second air permeability, wherein the first air permeability of the carded nonwoven layer is higher than the second air permeability of the filter paper layer. In a filter element with such a filter medium, the filter medium is folded to a folded filter medium with folds with a fold spacing of more than 3.5 mm and a fold height of between 10 mm to 60 mm.

Claims

1. A filter medium for filtration of a gaseous medium, the filter medium comprising: a carded nonwoven layer; a filter paper layer arranged as a neighboring filter layer at an outflow side of the carded nonwoven layer; the carded nonwoven layer comprising a first air permeability and the filter paper layer comprising a second air permeability, wherein the first air permeability of the carded nonwoven layer is higher than the second air permeability of the filter paper layer.

2. The filter medium according to claim 1, wherein the first air permeability of the carded nonwoven layer, measured according to DIN EN ISO 9237 at a differential pressure of 200 Pa, amounts to more than 800 l/m.sup.2/s.

3. The filter medium according to claim 2, wherein the first air permeability of the carded nonwoven layer amounts to 1,600l/m.sup.2/s to 6,000l/m.sup.2/s.

4. The filter medium according to claim 1, wherein the second air permeability of the filter paper layer, measured according to DIN EN ISO 9237 at a differential pressure of 200 Pa, is less than 800 l/m.sup.2/s.

5. The filter medium according to claim 1, wherein the carded nonwoven layer comprises fibers of an average fineness in a range of 1 decitex to 30 decitex.

6. The filter medium according to claim 1, wherein the average weight per surface area of the carded nonwoven layer, measured according to DIN EN 29073-1, amounts to between 10 g/m.sup.2 to 120 g/m.sup.2.

7. The filter medium according to claim 1, wherein the filter paper layer comprises a wet-laid cellulose fiber layer.

8. The filter medium according to claim 7, wherein the wet-laid cellulose fiber layer comprises up to 30 percent by weight of synthetic fibers.

9. The filter medium according to claim 1, wherein the filter paper layer and/or the carded nonwoven layer comprises an impregnation.

10. The filter medium according to claim 9, wherein the filter paper layer comprises cellulose fibers and wherein the impregnation strengthens and bonds the cellulose fibers.

11. The filter medium according to claim 9, wherein the impregnation is a flame-retardant impregnation.

12. The filter medium according to claim 11, wherein the flame-retardant impregnation comprises a flame retardant agent.

13. The filter medium according to claim 12, wherein the flame retardant agent is a phosphorus-based flame retardant agent.

14. The filter medium according to claim 12, wherein the flame retardant agent and a concentration of the flame retardant agent are selected such that the filter paper layer and/or the carded nonwoven layer comprises flame-retardant properties according to the flammability rating F1 according to DIN 53 438-3.

15. The filter medium according to claim 12, wherein the flame retardant agent and a concentration of the flame retardant agent are selected such that the filter medium comprises flame-retardant properties according to the flammability rating F1 according to DIN 53 438-3.

16. The filter medium according to claim 1, wherein at least 80 percent by weight of fibers of the carded nonwoven layer contain polyester.

17. The filter medium according to claim 1, wherein the filter paper layer and the carded nonwoven layer are laminated to each other.

18. The filter medium according to claim 17, wherein the filter paper layer and the carded nonwoven layer are laminated to each other by pressure and heat.

19. The filter medium according to claim 18, wherein the filter paper layer and the carded nonwoven layer are laminated to each other by pressure and heat applied by thermo/pressure calandering.

20. The filter medium according to claim 1, wherein the filter paper layer and the carded nonwoven layer are connected to each other.

21. The filter medium according to claim 20, wherein the filter paper layer and the carded nonwoven layer are connected to each other by an adhesive middle layer.

22. A filter element comprising: a filter medium comprising a carded nonwoven layer; a filter paper layer arranged as a neighboring filter layer at an outflow side of the carded nonwoven layer; the carded nonwoven layer comprising a first air permeability and the filter paper layer comprising a second air permeability, wherein the first air permeability of the carded nonwoven layer is higher than the second air permeability of the filter paper layer; wherein the filter medium is folded to a folded filter medium comprising folds with a fold spacing of more than 3.5 mm and a fold height of between 10 mm to 60 mm.

23. The filter element according to claim 22, wherein the fold spacing is 4 mm to 8 mm.

24. The filter element according to claim 22, wherein the folds of the folded filter medium comprise end face edges, wherein the carded nonwoven layer and the filter paper layer of the folded filter medium are glued to each other along the end face edges.

25. The filter element according to claim 24, wherein the carded nonwoven layer and the filter paper layer of the folded filter medium are glued to each other by continuous adhesive traces.

26. The filter element according to claim 24, wherein the continuous adhesive traces are comprised of hot melt adhesive.

27. The filter element according to claim 22 configured as an intake air filter of an internal combustion engine.

28. A method for producing a filter element according claim 22, the method comprising: providing the carded nonwoven layer; arranging the filter paper layer at the outflow side relative to the carded nonwoven layer as a neighboring filter layer; connecting the carded nonwoven layer and the filter paper layer to form the filter medium; and folding the filter medium to the folded filter medium of the filter element.

29. The method according to claim 28, further comprising applying adhesive traces prior to folding the filter medium and connecting folds of the folded filter medium by the adhesive traces during folding to connect the filter paper layer and the carded nonwoven layer to each other.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In the following, the invention will be explained in more detail with the aid of embodiments and with the aid of Figures. The embodiments are only to be understood in an exemplary fashion and are in no way limiting in regard to the subject matter of the invention.

[0035] FIG. 1 is a schematic illustration of a filter medium according to the invention, comprised of a carded nonwoven layer and a filter paper layer.

[0036] FIG. 2 is a lateral view of a folded filter medium according to the invention.

[0037] FIGS. 3a to 3c are schematic illustrations of a filter medium according to the invention, comprised of a carded nonwoven layer and a filter paper layer which are connected to each other by different lamination types.

[0038] FIG. 4 is a graphic illustration of the pressure drop relative to the dust intake capacity of the filter medium in comparison to a comparative filter medium.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0039] FIGS. 1 and 2 show an embodiment of a filter medium 1 according to the invention with a nonwoven layer of synthetic fibers, formed in the form of a carded nonwoven layer 2, arranged at the inflow side and a filter paper layer 3 arranged at the outflow side, for example, an impregnated filter paper layer.

[0040] The fibers of the filter paper layer 3 are arranged more closely to each other and thus have a higher degree of separation than the fibers of the carded nonwoven layer 2.

[0041] The filter paper layer 3 arranged at the outflow side is water-resistant (measured based on the water absorption capacity according to DIN EN ISO 535 wherein water-resistant in the meaning of this application is a water absorption capacity according to Cobb60 of DIN EN ISO 535 below 20 g/m5 at 20 C. and standard pressure) and preferably furnished to be flame-retardant. The flow direction 8 is illustrated in FIGS. 1 and 3a to 3c by arrows.

[0042] The cellulose fibers are preferably wet-laid when producing the filter paper layer 3.

[0043] The carded nonwoven layer 2 can be formed to at least 80 percent by weight (wt. %) of polyester. This fiber type has been found to be in particular heat-resistant and is therefore preferred. The remaining 20 wt. % of such fiber types can be, for example, bi-component fibers with a polyester core and a co-polyester sheath.

[0044] The fineness of the fibers of the carded nonwoven layer 2 amounts to between 1 decitex to 30 decitex, preferably 3 decitex to 15 decitex.

[0045] The average fiber diameter of the fibers of the carded nonwoven layer can preferably be greater than 10 Om. The air permeability of the carded nonwoven layer 2 amounts to preferably 1,600 l/(m.sup.2*s) to 6,000 l/(m.sup.2*s) at a pressure difference of 200 Pa in accordance with EN ISO 9237. The employed measuring device must correspond to the specifications of the above-mentioned standard.

[0046] In a particularly preferred variant, the carded nonwoven layer 2 can be comprised of fibers of a polyester or comprise more than 80 percent by weight of such fibers. In a further preferred variant, at least 10 percent by weight of the fibers of the carded nonwoven layer 2 can be comprised of bi-component fibers or so-called core-sheath fibers which contain proportions of a polyester copolymer. In this context, preferably the core material can be comprised of a pure polyester material and the sheath fibers of a polyester copolymer, in particular of a co-polyester with reduced melting temperature compared to polyester.

[0047] Alternatively or in addition to a polyester material, also polypropylene as a fiber material can be used for the fibers of the carded nonwoven layer 2. The average fiber length of the fibers of the carded nonwoven layer 2 can amount to between, for example, 20 mm to 100 mm, preferably between 50 mm and 60 mm.

[0048] For use in a filter element, not illustrated in detail, the filter medium is folded to a so-called folded bellows which is illustrated in sections in FIG. 2. A corresponding filter element with a filter medium embodied as a folded bellows is disclosed, for example, in DE 10 2012 25 019 862 A1.

[0049] The fold spacing (a) of the folded filter medium 1 can amount to preferably more than 3.5 mm, particularly preferred between 4 mm to 8 mm.

[0050] The fold height (b) of the folded filter medium 1 can be preferably between 10 mm to 60 mm.

[0051] In accordance with FIGS. 3a to 3c, the layers of the filter medium can be connected to each other by lamination. In this context, the connection between the layers 2 and 3 is produced by an adhesive 5, for example. The latter can be provided preferably in the form of an adhesive layer (nonwoven) or an adhesive powder or can be embodied as a spray-on application as an interrupted film. The connection by means of adhesive is illustrated in FIG. 3c.

[0052] Alternative types of lamination are provided by thermofusion or thermo-calandering, i.e., a connection of the layers by means of heat and/or by increased pressure. This is illustrated in FIG. 3b. A further optional possibility resides in a local (interrupted) connection of the layers by ultrasound welding. This is illustrated in FIG. 3a in which the filter medium comprises weld spots 4 which are introduced, for example, by ultrasound welding or thermo-calandering into the filter material. Of course, individual methods or method steps, which are illustrated in FIGS. 3a to 3c, can also be combined with each other.

[0053] A further optional connection possibility is available in the production of folded bellows from the filter medium. For this purpose, the layers 2 and 3 are supplied separately to a folding machine. The connection of the layers can then be preferably realized by the end face edge gluing of the folded bellows, i.e., an adhesive trace which is applied along the end face edges and holds together the folds and effects a separation between raw and clean side in the region of the fold pockets or of the end faces that are formed by the end face edges extending in a zigzag shape. In addition, in case of the loose layers in the process, adhesive traces but also adhesive beads applied prior to the folding process can ensure the cohesion of the layers.

[0054] The filter medium 1 comprises preferably maximally three filter layers, i.e., a further filter layer in addition to the carded nonwoven layer 2 and the filter paper layer 3. One or two optional adhesive layers which connect the three filter layers to each other can also be provided. The arrangement of maximally three filter layers promotes an inexpensive manufacture by means of a process-reliable stable foldability of the filter medium. In this context, the filter paper layer 3 is always a filter layer neighboring the carded nonwoven layer 2.

[0055] However, in the context of the present invention, it is possible that two carded nonwoven layers of different fineness are provided wherein a first one of these two layers is the carded nonwoven layer 2 and the second carded nonwoven layer arranged above is arranged at the inflow side relative to the carded nonwoven layer 2. It is also possible in the context of the present invention that the filter paper layer 3 comprises a gradient in regard to the fiber density and/or the average fiber diameter in flow-through direction, which is indicated in FIG. 1 by an arrow. Preferably, in this context the outflow side of the filter medium is more strongly compacted and is comprised on average of finer fibers than the inflow side.

[0056] For additional increase of the mechanical strength and stiffness, individual filter layers can be needled, impregnated or thermally bonded.

[0057] The filter medium 1 according to the invention is used preferably in air filter elements. A particularly preferred application in this context is the filtration of intake air of internal combustion engines required for combustion, for example, of motor vehicles and motorcycles.

[0058] The diagram illustrated in FIG. 4 illustrates the increase of the dust intake capacity or dust storage capacity of a filter element comprised of folded filter medium of the filter medium 1 according to the invention in comparison to a conventional paper element (single-layer cellulose paper) whose folds are produced only of filter paper. This was contrasted with an increasing pressure drop.

[0059] Relative to this comparative medium, the use of a filter medium in the meaning of the invention provides significant performance improvement. The dust intake capacity of the filter element 1 according to the invention for the same degree of separation relative to the dust capacity of the single-layer cellulose paper is significantly increased (see Table 1). By connecting the two aforementioned layers, an optimization of the filtration performance (dust intake capacity and/or separation degree) is realized. The increase of the dust intake capacity materializes over the course of a continuous dust addition and the thus induced pressure loss increase of the respective filter element 1 or 10. This is determined in accordance with the method of ISO 5011 described in the version at the time of first filing of the present invention. A test dust according to ISO 12103-A2 in the version at the time of first filing of the present invention was used. The mass flow of the dust-laden test flow amounted to 750 kg/h. By use of the filter medium according to the invention, material can be saved in comparison to a filter paper of comparable thickness or a combination of filter paper and a spunbond layer. Also, the pressure loss by use of the filter medium according to the invention is significantly reduced, which has further advantages in certain fields of application.

TABLE-US-00001 TABLE 1 ISO 5011 dust test air mass flow 750 kg/h test dust ISO 12103-1 A2 final pressure loss increase 20 mbar initial final degree of degree of dust separation separation capacity Filter material [%] [%] [g] Single-layer paper medium 99.2 99.6 150 (single-layer cellulose paper) Filter medium 1 according to 99.2 99.6 197 the invention (carded nonwoven layer 2 and filter paper layer 3 arranged at the outflow side thereof)