Filter Medium and Production Method, Filter Element, Use of the Filter Element, and Water Injection System

Abstract

A filter medium is provided with a first layer as a support layer and a second layer as a filtration layer arranged downstream of the first layer. The first layer and the second layer both are provided with at least one active agent that is at least antibacterial. The active agent can be applied as a coating or as an impregnation. Examples of active agents are pyrithione, a metal salt of pyrithione, a pyrithione derivative, a metal salt of a pyrithione derivative, and a quaternary ammonium salt. A filter element is provided with such a filter medium in the form of a filter media pack. The filter medium and filter element can be used in a water injection system for internal combustion engines.

Claims

1. A filter medium comprising: a first layer as a support layer and a second layer as a filtration layer arranged downstream of the first layer; the first layer and the second layer both comprising at least one active agent that is at least antibacterial.

2. The filter medium according to claim 1, wherein the at least one active agent is selected from the group consisting of pyrithione, a metal salt of pyrithione, a pyrithione derivative, a metal salt of a pyrithione derivative, and a quaternary ammonium salt of the general formula NR.sub.4.sup.+X.sup. or RNR.sub.2.sup.+X.sup..

3. The filter medium according to claim 2, wherein the metal salt of pyrithione is an alkali metal salt, an alkaline earth metal salt, or a transition metal salt.

4. The filter medium according to claim 3, wherein the alkali metal salt is a sodium salt and wherein the transition metal of the transition metal salt is selected from the group consisting of zinc, manganese, copper, and iron.

5. The filter medium according to claim 2, wherein the metal salt of a pyrithione derivative is an alkali metal salt, an alkaline earth metal salt, or a transition metal salt.

6. The filter medium according to claim 5, wherein the alkali metal salt is a sodium salt and wherein the transition metal of the transition metal salt is selected from the group consisting of zinc, manganese, copper, and iron.

7. The filter medium according to claim 2, wherein, in the general formula NR.sub.4.sup.+X.sup. or RNR.sub.2.sup.+X.sup., R is an organic residue and is the same or different.

8. The filter medium according to claim 7, wherein R is selected from the group consisting of an alkoxy group of the general formula OCH.sub.3, a siloxy group of the general formula R.sub.3SiO, and an alkoxysilyl group of the general formula R.sup.1R.sup.2R.sup.3SiOR.sup.4.

9. The filter medium according to claim 8, wherein R.sup.1R.sup.2R.sup.3SiOR.sup.4 is a trialkoxysilylpropyl group.

10. The filter medium according to claim 9, wherein the quaternary ammonium salt is dimethyltetradecyl [3-(trimethoxsilyl)propyl] ammonium chloride or 3-(tri-methoxysilyl) propyldimethyl octadecyl ammonium chloride.

11. The filter medium according to claim 2, wherein the metal salt of pyrithione or the metal salt of a pyrithione derivative is a zinc salt.

12. The filter medium according to claim 2, wherein the metal salt of pyrithione is zinc pyrithione.

13. The filter medium according to claim 1, wherein the first layer and the second layer each are provided with an impregnation containing the at least one active agent and/or a coating containing the at least one active agent.

14. The filter medium according to claim 13, wherein the impregnation containing the at least one active agent and/or the coating containing the at least one active agent comprises a binding agent based on polyacrylate.

15. The filter medium according to claim 14, wherein the at least one active agent is zinc pyrithione.

16. The filter medium according to claim 15, wherein a ratio of a concentration of zinc pyrithione to a concentration of the binding agent in the impregnation containing the at least one active agent and/or the coating containing the at least one active agent is selected such that at least 0.1 wt.-% of zinc pyrithione is washed out of the coating containing the at least one active agent and/or of the impregnation containing the at least one active agent after 168 h in water at 65 C.

17. The filter medium according to claim 1, wherein the second layer is a nonwoven layer and comprises to at least 80 wt.-% synthetic fibers.

18. The filter medium according to claim 17, wherein the synthetic fibers are selected from one or more of the fibers of the group consisting of copolymer fibers, PET fibers, PBT fibers, PA fibers, PP fibers, and PE fibers.

19. The filter medium according to claim 18, wherein the synthetic fibers are meltblown fibers and/or staple fibers.

20. The filter medium according to claim 1, wherein an air permeability of the filter medium amounts to 100 to 850 l/m.sup.2s.

21. The filter medium according to claim 1, wherein the first layer comprises a mesh structure.

22. The filter medium according to claim 21, wherein the mesh structure has a thickness of less than 0.8 mm.

23. The filter medium according to claim 1, wherein the first layer comprises at least 80 wt.-% synthetic fibers.

24. The filter medium according to claim 23, wherein the synthetic fibers are selected from one or more of the fibers of the group consisting of copolymer fibers, PET fibers, PBT fibers, PA fibers, PP fibers, and PE fibers.

25. The filter medium according to claim 1, wherein the filter medium comprises a third layer arranged at an outflow side of the second layer, wherein the third layer is a support layer, wherein the first layer, the second layer, and the third layer each are provided with an impregnation containing the at least one active agent and/or a coating containing the at least one active agent.

26. The filter medium according to claim 1, wherein the first layer comprises a thickness that is reduced in comparison to a thickness of the second layer.

27. The filter medium according to claim 26, wherein the thickness of the first layer is reduced by at least 1.5 times compared to the thickness of the second layer.

28. The filter medium according to claim 1, wherein the first layer comprises a weight per surface area that is reduced in comparison to a weight per surface area of the second layer.

29. The filter medium according to claim 28, wherein the weight per surface area of the first layer is reduced by at least 1.2 times compared the weight per surface area of the second layer.

30. A filter element that comprises a filter media pack comprising a filter medium according to claim 1.

31. The filter element according to claim 30, wherein the filter media pack is a folded filter media pack and wherein the filter element is a round filter element or a flat filter element.

32. The filter element according to claim 30, further comprising at least one end disc connected by material fusion to the filter media pack.

33. The filter element according to claim 30 as a prefilter or a main filter in a fluid conduit of a water injection system of an internal combustion engine or of a gas turbine.

34. A method for producing a filter medium according to claim 1, comprising: providing individually the first layer, the second layer, and an optional third layer; individually coating or impregnating the first layer, the second layer, and the optional third layer with the at least one active agent; and subsequently joining the first layer, the second layer, and the optional third layer to the filter medium.

35. The method according to claim 34, selecting a zinc pyrithione solution as the at least one active agent.

36. The method according to claim 34, performing coating or impregnating by a padding process.

37. A water injection system for an internal combustion engine, the water injection system comprising a water tank, at least one injection device, a fluid conduit connecting in fluid communication the water tank to the at least one injection device, wherein in the fluid conduit between the water tank and the at least one injection device at least one filter element is arranged, wherein the at least one filter element comprises a filter media pack comprising a filter medium according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1 shows a schematic and simplified circuit diagram of the fluid conduit in a commercial vehicle.

[0042] FIG. 2 shows a schematic configuration of a first filter medium.

[0043] FIG. 3 shows a schematic configuration of a second filter medium.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0044] The Figures show only examples and are not to be understood as limiting.

[0045] FIG. 1 shows in a simplified manner the configuration of a medium conduit of a water injection system of an internal combustion engine with a fluid flow of water in flow direction 100. One can see a heated water tank 2 with a refill socket 1 and a sensor 3 for determining the water quality, the filling level, and/or the temperature.

[0046] The water tank 2 comprises a first supply line 11 to a pump module 5 arranged downstream of the water tank in flow direction 100. The pump module 5, as illustrated in FIG. 1, can be provided with a shut-off valve, an orifice plate, a check valve, a pressure sensor, and an optional heater.

[0047] In order to protect the pump module from contaminations from the water tank, the supply line 11 comprises a prefilter 4. It filters dirt particles of a magnitude of greater than 25 m from the fluid flow.

[0048] A second supply line 6 conducts the fluid further to a nozzle arrangement 9 which is arranged downstream of the pump module 5 in flow direction 100. Through the nozzles 10 of the nozzle arrangement 9, the injection of water into a piston engine or a gas turbine of the internal combustion engine can be performed. Optionally, the medium pressure upon supply of the medium into the nozzle arrangement 9 can be monitored by a pressure sensor 8.

[0049] The second supply line 6 comprises a main filter 7 which protects the nozzle arrangement 9 from clogging or soiling. The main filter 7 is also often described as a fine filter. It serves for filtration of particles with a particle size greater than 9 m from the fluid flow.

[0050] The maximum loading of the prefilter 4 and of the fine filter 7 amounts to preferably at least 10 grams, preferably at least 12 grams.

[0051] The pressure drop of the prefilter 4 in flow direction 100 amounts to preferably maximally 100 mbar at a flow rate of 110 l/h.

[0052] The pressure drop of the fine filter or main filter 7 amounts to preferably maximally 500 mbar at a flow rate of 80 l/h.

[0053] FIG. 2 shows the configuration of a filter medium 200 according to the invention for use in a prefilter 4 and/or main filter 7.

[0054] The filter medium 200 comprises at least a first layer 201 and at least a second layer 202.

[0055] The first layer 201 of the filter medium 200 is in this context the inflow-side layer, as can be seen in FIG. 2 based on the flow direction 100.

[0056] The first layer 201 is a support layer and can be embodied as a nonwoven layer or as a mesh layer. The predominant number of fibers of the first layer 201 are made of a synthetic plastic material. In case of a nonwoven layer, they can be, as an example and preferred, PBT fibers (polybutylene terephthalate fibers). Alternatively, the mesh can be embodied on the basis of PBT. The first layer 201 can comprise a weight per surface area of less than 130 g/m.sup.2, in particular between 70-110 g/m.sup.2. The average thickness of the second layer 202 can amount to in particular less than 0.7 mm, in particular between 0.4 to 0.6 mm.

[0057] The second layer 202 is a filtration layer and is embodied as a nonwoven layer. The predominant number of fibers of the second layer can be advantageously PET fibers in this context. The second layer 202 can have a weight per surface area of more than 140 g/m.sup.2, in particular between 160-180 g/m.sup.2. The average thickness of the second layer 202 can amount to more than 0.8 mm, in particular between 0.9 to 1.2 mm. The average fiber diameter amounts to 4 to 40 m. The data in regard to the thickness and the fiber diameter can be determined microscopically.

[0058] The filter medium 200 can be provided zigzag-folded in a filter element. The filter medium 200 can be arranged in the filter element as a hollow cylindrical folded bellows with star-shaped cross section. The folded bellows is delimited at each of its two terminal end faces by an end disc, respectively. A filter element of the afore described type is disclosed, for example, in DE 10 2016 008 502 A1 which is incorporated by reference in its entirety in the context of the present invention in particular with regard to the configuration of the filter element.

[0059] According to the invention, the first layer 201 as well as the second layer 202 comprise an at least antibacterial agent which is zinc pyrithione according to this exemplary embodiment.

[0060] The active agent, here zinc pyrithione, can be arranged in the form of a coating or impregnation 204 on the fibers of the first and second layers 201, 202 or penetrate the layers so that the layers are essentially impregnated with the active agent.

[0061] The exchange of the filter medium of the prefilter 4 in a water injection system can be performed every 15 years, for example.

[0062] FIG. 3 shows the configuration of a filter medium 300 for the main filter 7 which, of course, can be used also for the prefilter 4 in other applications.

[0063] The filter medium 300 is at least constructed of three layers with a first layer 301, a second layer 302, and a third layer 303.

[0064] The first layer 301 of the main filter 7 is an inflow-side layer. It can be embodied in analogy to the first layer 201 of the prefilter 4, in particular with respect to the weight per surface area and the thickness of the layer. It is embodied as a support layer and can be comprised of a mesh material and/or a nonwoven material. The fibers or the mesh structure of the first layer can be embodied to at least 80 wt.-% of PBT material.

[0065] The second layer 302 of the filter medium 300 is preferably embodied as a fine filter. It can be a nonwoven layer of meltblown fibers. The predominant number of meltblown fibers can be embodied in particular as PBT fibers. In comparison to cellulose fibers, PBT meltblown fibers have a dust storage capacity that is more than four times higher under analogous measuring conditions.

[0066] The second layer 302 can comprises a weight per surface area of more than 130 g/m.sup.2, in particular between 140-180 g/m.sup.2. The average thickness of the second layer 302 can amount to more than 0.8 mm, in particular between 0.9 to 1.1 mm. The average fiber diameter amounts to 0.1 to 10 m. The data with respect to the thickness and the fiber diameter can be determined microscopically.

[0067] The third outflow-side layer 303 can also be embodied as a support layer, namely as a nonwoven layer. This layer 303 can be embodied in particular as a spunbond layer. The spunbond layer comprises a reduced layer thickness, preferably a layer thickness that is at least reduced by 1.5 times compared to the first and second layers 301 and 302 arranged above. At least up to 80% PET fibers can be utilized as spunbond fiber material. The outflow-side layer 303 can be embodied also as a support layer in this context. The spunbond layer enables, on the one hand, drainage and imparts to the filter medium 300 overall a higher stiffness.

[0068] The zinc pyrithione coating or impregnation is schematically illustrated in FIG. 3 and identified by a reference character 304.

[0069] The entity of the filter medium 300 as a main filter 7 comprises an initial degree of separation, determined by particle count according to ISO 19438:2003-11, of more than 99.5% for particles of a particle size of greater than 10 m. The entity of the filter medium 300 of the main filter 7 comprises a dust storage capacity of 100 g/m.sup.2 at 300 mbar for loading with an air flow with 50 mg/l dust and at an inflow distribution of 0.16 l/cm.sup.2h according to ISO-19438:2003-11.

[0070] The high dust storage capacity enables exchange of the filter at an exchange interval of more than two years or more in a commercial vehicle.

[0071] The filter medium 300 of the main filter, in analogy to filter medium 200 of the prefilter, can be arranged in a filter element or alternatively arranged, folded or unfolded, in a planar frame structure in a flat filter element.

[0072] The air permeability of the filter medium 200 of the prefilter 4 according to ASTM D 737 is preferably at least three times as large as the air permeability of the filter medium 300 of the main filter 7.

[0073] In this context, the air permeability of the filter medium 200 of the prefilter 4 at 200 Pa can amount to between 150 to 250 l/m.sup.2/s, wherein the air permeability of the filter medium decreases minimally in comparison to a filter medium with analogous configuration and under analogous measuring conditions but with uncoated and/or non-impregnated layers.

[0074] The thickness of the filter medium 200 of the prefilter 4 amounts to preferably 0.25 to 0.4 mm at a pressure of 0.5 kPa.

[0075] In this context, the air permeability of the filter medium 300 of the main filter 7 at 200 Pa can amount to between 500 to 850 l/m.sup.2/s, wherein the air permeability of the filter medium increases minimally in comparison to a filter medium with analogous configuration and under analogous measuring conditions but with uncoated and/or non-impregnated layers.

[0076] The thickness of the filter medium 200 of the prefilter 4 amounts to preferably 0.8 to 2.0 mm at a pressure of 0.5 kPa.

[0077] In the following, a method for producing the filter media 200 and 300 according to the invention of the prefilter 4 and of the main filter 7 will be described in more detail.

[0078] The coating or impregnation is applied in the context of a padding method, also known as full bath impregnation, to the fibers of the layers.

[0079] In the context of a wet treatment, the layers are initially passed through a bath with impregnation or coating agent. In this bath, the so-called liquor which comprises the zinc pyrithione is arranged. The bath temperature can amount to preferably 40-60 C. and the exposure time approximately 20 to 30 min.

[0080] In a roll press, the filter medium can be squeezed.

[0081] Subsequently, a drying process or a condensation process of the filter medium 200, 300 can be performed.

[0082] The drying process can be performed at 120 C. and the condensation process at 140 C., for about 2 minutes, respectively.

[0083] The liquor comprises also water and a hydrophobic binding agent system, preferably based on polyacrylate, which binds the zinc pyrithione to the fibers of the respective layers.

[0084] The layers are preferably individually impregnated and/or coated during manufacture and then laid on top of each other for providing the filter medium according to the invention.

[0085] The concentration of the zinc pyrithione in the liquor can amount to preferably 5 g/l to 20 g/l. The concentration of the zinc pyrithione per kg of nonwoven material can amount to preferably at least 2 g, particularly preferred 4 g-20 g.

[0086] A storage in water at 65 C. for 168 h and a conductivity measurement showed that the conductivity of the water increased. This is an indication that some quantities of zinc pyrithione had been washed out. For long service lives, the slow washout of zinc pyrithione is advantageous because water in the water tank and in the conduits will be disinfected due to wash-out or the growth of germs will at least be reduced.

[0087] The electrical conductivity of the solution should be less than 200 S.

[0088] The antibacterial activity of the filter media 200 and 300 were determined according to the testing method AATCC 100:2012. In this context, the filter medium was exposed to bacteria at 37 C. for 20 h. Staphylococcus aureus (according to ATCC 6528) and Escherichia coli (according to ATCC 11 229) were used as testing germ. Filter media exclusively with PBT fibers showed an antibacterial activity of more than 99.4%, in particular of 99.4 to 99.99%, relative to both germs.

[0089] Furthermore, the fungicidal activity in the form of the so-called mildew resistance test (AATCC 30-III2013) was determined. Aspergillus niber (ATCC 6275) and Chaetomium globosum (ATCC 6205) were utilized as testing fungus. The incubation time was 7 days at 28 C. and more than 90% moisture. The impregnated filter media showed no growth in the test.

[0090] As a result, the antibacterial and the fungicidal test demonstrated excellent results for the action of the filter media 200 and 300.

[0091] The layers of the prefilter and of the main filter have been always described in the examples with PBT fibers or PET fibers. Alternatively, the layers can also comprise polyamide fibers or polypropylene fibers.

[0092] The filter media are resistant across a wide pH value range, in particular however in a pH value range between pH=0.6 to pH=9.