Filter medium, filter media body, filter element and air filter

Abstract

Filter medium (10), in particular for an air filter, in particular a cabin air filter or for a fuel cell, comprising at least three active layers: - an outer catalytic active layer (12) comprising catalytic activated carbon particles (12a) for removing acidic (pH < 7) and / or hydrophilic gases, - a second, middle active layer (14) comprising phosphoric acid-impregnated activated carbon particles (14a) for the removal of ammonia, which is arranged downstream of the outer catalytic active layer (12), - a third, outer active layer (16) comprising activated carbon particles (16a) impregnated with ethylene urea and phosphoric acid for the removal of ammonia and formaldehyde, wherein the three active layers (12,14,16) are different from each other, and wherein the catalytic activated carbon particles (12a,14a) have an electronic structure of the carbon on the surface that has been altered by an activation process and wherein the impregnated activated carbon particles (14a,16a) have an impregnation applied to the activated carbon particles (14a,16a).

Description

Technical field

[0001] The invention relates to a filter medium according to the preamble of claim 1, a filter medium body according to claim 13, a filter element according to claim 14, an air filter according to claim 15, and a manufacturing method for a filter medium according to claim 16. State of the art

[0002] Filter media, especially for air filters, and particularly for cabin air filters, serve to supply a space, such as the passenger compartment of a motor vehicle or, for example, fuel cell cathode chambers, with purified air. Such filters are intended not only to remove coarse contaminants such as pollen or fine dust, but also odors, especially those from gaseous odorants, or harmful or reactive gaseous substances. The removal of gases and odorants is particularly challenging, as the different gases and odorants, due to their varying specific, especially chemical, properties, require different adsorption layers. However, the adsorption capacity of the filter medium decreases with the number of adsorption layers.For example, there is a risk of inhomogeneity in the adsorption layers, and the flow resistance of the filter medium generally increases, for instance in an air filter, thus increasing the energy consumption of an air conditioning system containing the air filter. Conventionally, filter media with multiple adsorption layers are used, designed to represent a compromise between the cleaning task and energy consumption. An air filter capable of removing both particulate contaminants (solid and / or liquid) and gaseous contaminants from the air is also known as a hybrid filter. Such hybrid filters are often specified via requirements specifications, which typically consider the following gases: n-butane, toluene, sulfur dioxide, nitrogen oxides, and ozone. These hybrid filters can also be specified, for example, according to ISO 11155 Part 2.Due to their age, these standards no longer reflect the gas and odor profiles that are now particularly prevalent in cities; in particular, odorous substances and harmful or reactive gaseous substances such as formaldehyde are not, or no longer sufficiently, taken into account in the standard specifications, so that the adsorption performance of conventional filters is often inadequate for specific odor profiles.

[0003] From US patent 7,758,674 B2, a filter device for filtering the air supplied to a fuel cell is known, wherein the filter device is intended to clean the air of both dirt particles and chemical contaminants. For this purpose, the filter device comprises a filter fleece on which the dirt particles are separated, as well as a chemical filter area comprising a layer of activated carbon, comprising a surface coating with an acidic or basic material or activated carbon impregnated with this material, and which serves as an adsorbent for adsorbing gaseous components in the air.

[0004] From DE 10 2013 011 511 A1 a filter device, in particular for the air to be supplied to a fuel cell, is known, comprising a carrier medium and activated carbon as an adsorbent, wherein the activated carbon is immobilized by the addition of adhesive.

[0005] From EP 1 468 718 A1 and DE 203 06 250 U1, an air filter unit with several filter elements is known, the elements containing activated carbon-based adsorbents as adsorption material. The filter unit includes at least a first filter element comprising granular, in particular spherical, activated carbon as adsorption material, and at least a second filter element comprising a combination of granular, in particular spherical, activated carbon and activated carbon fibers as adsorption material. The filter unit is particularly suitable for use in ventilation systems, air conditioning systems, and ventilation installations.

[0006] From WO 2004 / 033069 A2, filter media, particularly for water filtration in settling ponds, based on activated carbon are known, comprising three layers arranged one above the other, with an upper layer, a middle layer and a lower layer, wherein the middle layer consists of 80 to 95% of its dry weight of activated carbon, the difference being 100% organic and / or inorganic chemical fibers, the lower layer comprises 45 to 100% of its dry weight of organic chemical fibers with OH groups, optionally activated carbon and / or a material with a density of less than 0.9, wherein all or some of the OH groups have reacted with a grafting agent RX, wherein R is a hydrophobic group that is liquid at least 200 °C and atmospheric pressure and wherein RX is suitable to form a volatile leaving group HX during the reaction, the upper layer comprises 5 to 25% of its dry weight of activated carbon.The difference to 100% consists of organic and / or inorganic chemical fibers.

[0007] From DE10 2012 005 380 A1, a filter medium with biocidal effect for filtering air for the interior of a vehicle is known, consisting of at least one filter layer and at least one biocide layer, wherein the biocide layer comprises microcapsules which are formed from at least one polymer, wherein at least one biocide is stored on and / or in the microcapsules, and wherein the filter medium comprises a first filter layer designed as a carrier layer, a second filter layer designed as an activated carbon layer, a third filter layer designed as a fine dust filter, the biocide layer, a fourth filter layer designed as an activated carbon layer, and a fifth filter layer designed as a carrier fleece.

[0008] From WO 2012 / 100113 A1, a filter medium is known that comprises a first plurality of filter medium particles with a large substrate surface area, comprising at least one acidic impregnating agent; a second plurality of filter medium particles with a large substrate surface area, comprising at least one metal oxide; and a third plurality of filter medium particles with a large substrate surface area, comprising an amine impregnating agent, wherein activated carbon is disclosed for the adsorption bed of the filter, as well as a second plurality of filter medium particles comprising phosphoric acid-impregnated activated carbon and MgO / CaO-based nanocrystalline material. Several layers of impregnated activated carbon and nanocrystalline material embedded in an adsorbent bed are disclosed.For optimal performance, a two-layer filter medium is revealed, with an upper layer comprising a homogeneous mixture of an MgO / CaO based nanocrystalline material and Kureha activated carbon impregnated with phosphoric acid, and a lower, second layer consisting of a single layer of Calgon URC.

[0009] From DE 44 13 606 A1, a combination filter is known, consisting of a particle filter and an adsorption filter, in particular based on activated carbon, which is produced and impregnated in one step using a wet nonwoven process, wherein the particle filter layer and then the adsorption filter layer are successively produced from a mixture of adsorbent particles and (melt) fibers by suction into a sieve mold with dimensions corresponding to the final product, and wherein the aqueous dispersion of fibers and adsorbent particles also contains inorganic or organic substances for impregnating the adsorbents, in particular H3PO4.

[0010] From WO 02 / 085426 A2 a breathing air filter is known, with an air-permeable shell and at least one filter layer which is arranged in the shell and contains activated carbon.

[0011] From US2002 / 0088346 A1, a sheet-shaped filter mass for an air filter for an enclosed space, in particular a motor vehicle interior, is known, comprising standard type materials for forming filter masses and carbon elements activated for the adsorption of gaseous substances.

[0012] From GB 2 296 666 A a life-saving device is known, comprising a motor for driving a disc, a connecting rod whose upper end is arranged with the disc and whose lower end is arranged with the upper end of a compressible bellows, wherein the bellows is inflated and compressed by the connecting rod to draw outside air into a filter bottle, wherein the filter bottle has mesh filter layers and wherein a plurality of activated carbon filter layers are arranged one above the other in the filter bottle.

[0013] From DE 7 110 985 U, a filter for gas streams, in particular for gas streams containing radioactive or chemical particles, e.g. air, is known, comprising two or more layers of honeycomb material arranged slightly offset from one another such that the cells in one layer are not aligned with the cells of another "adjacent" layer, that the cells contain granules of activated carbon, and that the edges of the layers are covered with layers of foamed plastic which are sealed and connected to a surrounding shaped frame.

[0014] From DE 10 2012 007 503 A1, an adsorptive filter medium is known, in particular for the purification of gases and / or gas mixtures, preferably air, and / or in particular for the removal of chemical and / or biological toxins and / or pollutants from gases and / or gas mixtures, preferably air, wherein the filter medium comprises a plurality of a first filter element with a first adsorption material, in particular in the form of adsorbent particles, and a plurality of a second filter element different from the first filter element with a second adsorption material, in particular in the form of adsorbent particles, wherein the first filter element and the second filter element have different pressure losses and / or different flow resistances, and wherein the first adsorption material and / or the second adsorption material can be selected independently from the group consisting of activated carbon,in particular granular activated carbon, preferably spherical activated carbon and / or in particular shaped and / or extruded activated carbon and / or powdered activated carbon, wherein the first adsorption material and / or the second adsorption material, independently of each other, can be formed from in particular particulate activated carbon, in particular from granular, preferably spherical, activated carbon.

[0015] From WO 2010 / 127634 A1, a multilayer filter is known, comprising an upper layer and a lower layer, comprising a plurality of layers of a substrate medium and a plurality of layers of nanofibers, wherein the upper layer and the lower layer each have a layer of nanofibers and at least one unit comprising two layers of nanofibers is provided between the upper and the lower layer, comprising two layers of nanofibers between two substrate medium layers, and wherein a substrate medium layer may comprise activated carbon fibers.

[0016] From DE 10 2015 205 551 A1, a multi-layer filter material for an interior air conditioning filter element of a vehicle is known for the adsorption of, in particular, odorous substances, wherein the multi-layer filter material comprises an active layer having non-impregnated activated carbon particles, an impregnation layer having impregnated activated carbon particles, and an ion exchange layer having ion exchange particles.

[0017] From DE 10 2005 016 677 A1, a filter element with a multilayer filter material is known, in which an active layer with activated carbon fibers is arranged on the upstream side, to which an adsorbent layer with granular adsorbents is connected on the downstream side. A further active layer with activated carbon fibers can be connected to this adsorbent layer on the downstream side. The adsorbents used here can include activated carbon, zeolites, cyclodextrins, silicates, ion exchangers, and aluminosilicates.

[0018] From DE 10 2012 007 503 A1, another adsorptive filter medium is known, in which several first filter layers with a first adsorbent and several second filter layers with a second adsorbent different from the first filter layers are provided, which alternate and have different flow resistances or pressure losses.

[0019] From DE 10 2009 021 020 A1, another adsorptive filter material is known which contains an exchange resin loaded with metal cations.

[0020] From DE 10 2010 005 114 A1, a filter element is known, such as a cabin air filter for a motor vehicle. This filter element comprises a first layer with activated carbon particles for adsorbing pollutants and providing purified cabin air, a filter material layer, and a second layer with activated carbon particles and / or a catalyst material for ozone reduction. The filter element is, for example, enclosed by a filter assembly, which further comprises a filter element holder for retaining the filter element and an ozone generation device. The second layer of the filter element is arranged on the side facing the ozone generation device.

[0021] From EP 0 118 618 A1, a surface filter is known consisting of an air-permeable, flexible, in particular textile, carrier layer, which is only partially and uniformly covered with an adhesive to which adsorbent particles, in particular activated carbon spheres, are fixed. Furthermore, the use of such surface filters with activated carbon as an adsorbent for protective suits is disclosed.

[0022] From US 2015 / 0053080A1, an adsorptive filter medium (i.e., a filter unit or filter structure) is known that is suitable for purifying gases and / or gas mixtures, preferably air, and for removing chemical and / or biological toxins and / or pollutants from gases and / or gas mixtures, preferably air, and its use.

[0023] From EP 1 918 022 A1, high-performance adsorbents are known in the form of discrete activated carbon granules, preferably in spherical form, based on activated carbon with high microporosity, which are characterized by the following parameters: a total pore volume according to Gurvich of at least 0.7 cm³ / g, wherein at least 70% of this total pore volume is formed by micropores with pore diameters of s 20 Å, a mean pore diameter of at most 30 Å, and a BET surface area of ​​at least 1,500 m² / g. These high-performance adsorbents are particularly suitable for the adsorption of toxins, pollutants, and odors, especially from gas or air streams, for the purification or treatment of gases, such as air, for use in medicine and pharmaceuticals, and as sorption storage media for gases, especially hydrogen.

[0024] The invention is based on the objective of creating a filter medium that has a high and balanced adsorption capacity for a wide range of gases, and thus gas and odor profiles encompassing various properties, in particular gas and odor profiles encompassing n-butane, VOCs, NOx, SO2, H2S, NH3 and CH2O. Disclosure of the invention

[0025] This problem is solved according to the invention by a filter medium with the features of claim 1, a filter medium body with the features of claim 13, a filter element according to claim 14 and an air filter with the features of claim 15. The dependent claims specify advantageous and expedient further developments.

[0026] The filter medium according to the invention, in particular for an air filter, especially an interior air filter or for a fuel cell, comprises a catalytic active layer having catalytic activated carbon particles, in particular consisting of, a second active layer having impregnated or catalytic activated carbon particles, in particular consisting of, a third active layer having impregnated or catalytic activated carbon particles, in particular consisting of, wherein at least one active layer has impregnated activated carbon particles, wherein the three active layers are different from each other.

[0027] Catalytic activated carbon is an activated carbon in which the electronic structure of the surface carbon has been altered through an activation process. In one embodiment, 1 g of catalytic activated carbon is added to a mixture of 80 ml water and 30 ml 30 wt% H₂O₂ solution at a temperature of 23 °C and standard pressure, resulting in a temperature increase of >23 °C after 5 min and >33 °C after 10 min. The catalytic properties of the activated carbon can thus be demonstrated.

[0028] Impregnated activated carbon is used in this process, where the carbon has an impregnation applied to it. The gases and odors to be removed are chemically bound by the impregnation or converted by it into a form adsorbable by the next active layer. In other words, the impregnations applied to the activated carbon act chemisorptively with the respective gas or odor. The impregnated active layer thus has additional chemisorption properties that enhance adsorption or adapt it to a predetermined compound profile. The impregnation can be applied to activated carbon or to catalytic activated carbon as described in the invention.Suitable impregnations include, for example, potassium carbonate for the targeted removal of acidic gases (pH < 7 under standard conditions and measured in aqueous solution), hydrogen sulfide, sulfur dioxide or nitrogen oxides, phosphoric acid (H3PO4) and / or sulfuric acid (H2SO4) for the targeted removal of alkaline gases (pH >7 under standard conditions and measured in aqueous solution), ammonia and amines, and / or potassium iodide for the targeted removal of hydrogen sulfide, and / or sodium hydroxide (NaOH) for the targeted removal of acidic gases and hydrogen sulfide, and / or sulfur and / or silver.

[0029] In particular, the impregnated active layer can consist of multiply impregnated activated carbon treated with at least two of the aforementioned substances. The impregnated activated carbon is impregnated with phosphoric acid and ethylene urea. Furthermore, it is possible that the impregnated active layer consists of a mixture of at least two activated carbon particles impregnated with different substances.

[0030] The filter medium comprises an active layer containing catalytic activated carbon particles, a second active layer containing impregnated activated carbon particles, and a third active layer containing impregnated or catalytic activated carbon particles.

[0031] In a particularly preferred embodiment, the filter medium comprises an active layer having catalytic activated carbon particles, a second active layer having impregnated activated carbon particles, and a third active layer having impregnated activated carbon particles.

[0032] According to the invention, the order of the active layers is freely selectable and can be adapted to a specific gas and odor profile. The sequence of active layers is as follows: first, the second active layer, which contains impregnated activated carbon particles, is selected as the outermost active layer; second, the middle active layer, which contains catalytic activated carbon particles; and finally, the third, outer active layer, which contains impregnated activated carbon particles. Preferably, the first, outermost active layer in this sequence is a catalytic active layer. This has the advantage that the second active layer can be easily adapted to the moisture content and the still acidic environment (pH < 7) of the gas stream.

[0033] It is also conceivable that the filter medium consists of a first, outer active layer containing catalytic activated carbon particles, a second, middle active layer, which has catalytic activated carbon particles and provides for the third, outer active layer, which has impregnated activated carbon particles.

[0034] The filter medium according to the invention can thus be advantageously adapted to the specific requirements of a particular gas and odor profile. In particular, a gas and odor profile composed, for example, of acidic (pH < 7) and / or hydrophilic gases and odors and basic (pH > 7) and / or organic, especially hydrophobic, gases and odors, and in particular comprising n-butane, VOCs, NOx, SO2, H2S, NH3 and CH2O, can be filtered with good adsorption performance.

[0035] The catalytic active layer in the filter medium contains catalytic activated carbon particles for removing acidic (pH < 7 under standard conditions and measured in aqueous solution) and / or hydrophilic gases. This has the advantage of easily separating both hydrophilic and acidic (pH < 7) gases, as well as water present in the gas stream, from basic and / or organic, especially hydrophobic, gases and odorous substances, particularly harmful or reactive gaseous substances.

[0036] In one embodiment of the filter medium, the catalytic active layer comprises catalytically activated carbon particles with a mass distribution of 50 to 300 g / m². 2 , especially 150 to 300 g / m² 2 on.

[0037] In one embodiment of the filter medium, the catalytic activated carbon particles are bound, and in particular cross-linked, by the addition of an adhesive. This binding, and especially cross-linking, is advantageously achieved by the addition of an adhesive whose adhesive threads adhere to the surface of the activated carbon particles and connect different activated carbon particles to one another without impairing the adsorption capacity of the activated carbon. Suitable adhesives include, for example, reactive melt flow adhesives, e.g., based on polyurethane or silane. A thermoplastic adhesive, e.g., based on polyolefins, is also possible.

[0038] The second active layer in the filter medium contains impregnated activated carbon particles for removing ammonia.

[0039] The second active layer comprises phosphoric acid-impregnated activated carbon particles. Impregnation with phosphoric acid (H3PO4) has the advantage that ammonia (NH3) is bound to the adsorbent (substrate) by chemisorption, and thus, unlike physisorption, more strongly by chemical bonds, resulting in particularly reliable adsorption. In further embodiments, the impregnation consists of 2 to 15 wt.%, in particular 3.5 to 15 wt.%, and in particular 2 to 6 wt.% phosphoric acid.

[0040] In another embodiment, the second active layer comprises impregnated activated carbon particles with a mass coverage of 50 to 300 g / m². 2 , especially 50 to 150 g / m² 2 on.

[0041] In another embodiment, the first, outermost active layer in the sequence is a catalytic active layer comprising catalytic activated carbon particles. By combining the choice of sequence with an additional adjustment of the mass distribution, an even more favorable carbon-to-adhesive ratio can be achieved.

[0042] The active layers in embodiments can lie directly on top of each other.

[0043] In further embodiments, the impregnated activated carbon particles are bound, and in particular cross-linked, by the addition of an adhesive. This bonding, especially cross-linking, is advantageously achieved by the addition of an adhesive whose adhesive threads adhere to the surface of the activated carbon particles and connect different activated carbon particles to one another without impairing the adsorption capacity of the activated carbon. Suitable adhesives include, for example, reactive melt flow adhesives, e.g., based on polyurethane or silane. A thermoplastic adhesive, e.g., based on polyolefins, is also possible.

[0044] In another embodiment, the adhesive is a reactive melt flow adhesive.

[0045] The third active layer contains impregnated activated carbon particles for removing ammonia and formaldehyde. This has the advantage that residual ammonia is removed particularly thoroughly. Furthermore, this type of layer is also designed for the reliable adsorption of formaldehyde.

[0046] The third active layer comprises activated carbon particles impregnated with ethylene urea and phosphoric acid. This has the advantage that both ammonia and, for example, formaldehyde are chemically bound to the adsorption substrate by chemisorption. In further embodiments, the impregnation consists of 2 to 15 wt.%, in particular 3.5 to 15 wt.%, in particular 2 to 6 wt.% phosphoric acid and 10 to 20 wt.% ethylene urea.

[0047] In another embodiment, the third active layer comprises impregnated activated carbon particles with a mass coverage of 50 to 300 g / m². 2, especially from 50 to 150 g / m² 2 This has the additional advantage that formaldehyde, which has a small molecular size, and ammonia are adsorbed particularly effectively.

[0048] In another embodiment, the impregnated activated carbon particles are bound, and in particular cross-linked, by the addition of an adhesive. This binding, and especially cross-linking, is advantageously achieved by the addition of an adhesive whose adhesive threads adhere to the surface of the activated carbon particles and connect different activated carbon particles to one another without impairing the adsorption capacity of the activated carbon. Suitable adhesives include, for example, reactive melt flow adhesives, e.g., based on polyurethane or silane. A thermoplastic adhesive, e.g., based on polyolefins, is also possible.

[0049] In another embodiment, the adhesive is a reactive melt flow adhesive.

[0050] In another embodiment, the filter medium has at least one support layer. The support layer can, for example, be a textile support layer, particularly a nonwoven fabric. The support layer can carry the activated carbon particles or at least border the active layer. The support layer is, for example, designed as a support layer that optionally performs mechanical filtration of particulate contaminants from the gas stream to be purified. In this case, the support layer forms, for example, a support or filter nonwoven fabric on which dirt particles can be separated. The nonwoven fabric consists, for example, of polyester, polypropylene, polyamide, polyacrylonitrile, or polycarbonate.

[0051] In one embodiment, the activated carbon forms an active layer directly adjacent to the carrier layer, which is preferably bonded to the carrier layer via the adhesive. This can be achieved either by adhering the active layer to the carrier layer or by bonding it via uncured adhesive threads applied to the activated carbon particles. The carrier layer thus delimits the active layer at least on one side and is simultaneously bonded to it. This embodiment allows for the formation of open carrier-activated carbon layer layers with fixed activated carbon particles. Such carrier-activated carbon layer layers comprise at least one carrier layer and one activated carbon layer and can be easily stacked on top of each other, with the flow direction preferably being in the stacking direction, i.e., orthogonal to the plane of the layers.

[0052] In a further embodiment, at least two support layers are provided, wherein the filter medium is preferably designed without an additional filter layer. In this embodiment, the at least three active layers lie directly adjacent to one another within an upper and a lower support layer.

[0053] According to an alternative embodiment, at least one active layer can be bounded on both of its side surfaces by a support layer. Advantageously, the active layer is additionally bonded to both support layers.

[0054] In a further embodiment, the filter medium comprises a filter layer, in particular a particle filter layer. The filter layer is in particular designed as a textile particle filter layer, especially as a nonwoven fabric.

[0055] According to a further advantageous embodiment, at least one active layer can be sealed on its longitudinal and / or broad sides, so that, if necessary together with the support layers adjoining the side surfaces, an all-round boundary of the activated carbon layer can be achieved. The sealing on the longitudinal and / or broad sides increases the stability and improves the resistance to delamination and displacement in the respective active layer.

[0056] According to a further advantageous embodiment, at least one active layer can be provided with a seal on its end faces, i.e., its broad sides and longitudinal sides. Adjacent active layers are advantageously not bonded to each other; rather, bonding occurs only via the immediately adjacent carrier layer.

[0057] Suitable activated carbon types include those based on various raw materials such as coconut, bituminous coal, charcoal, or synthetic feedstocks, exhibiting different activation levels, catalytic properties, and impregnations. This allows for additional, advantageous customization to the target gas spectrum. Preferred raw materials are coconut, bituminous coal, and charcoal, with coconut-based activated carbon being particularly preferred.

[0058] The problem is also solved by a filter media body comprising a filter medium according to the invention and at least one side band.

[0059] In one embodiment, the filter media body is designed as a wound body, layered as a flat filter, or folded as a filter bellows.

[0060] The problem is further solved by a filter element comprising a filter media body or filter medium according to the invention, a frame, retaining elements, and at least one seal. In one embodiment, the filter element is an air filter element. In another embodiment, the filter element is an interior air filter element.

[0061] The problem is further solved by an air filter comprising a filter element or filter media body or filter medium according to the invention. In one embodiment, the air filter is an interior air filter.

[0062] The task is also accomplished by a fuel cell comprising an air filter according to the invention or a filter element according to the invention or a filter media body according to the invention or a filter medium according to the invention.

[0063] The task is also accomplished by an air conditioning system comprising an air filter or a filter element or a filter media body or a filter medium according to the invention.

[0064] The objective is also achieved by using the filter medium according to the invention in air conditioning systems, indoor air filters, filter elements, air filters, in particular room air filters, ventilation systems, fuel cells, in particular fuel cell air filters, in particular fuel cell cathode air filters.

[0065] A method for producing a filter medium according to the invention comprising the steps of applying a first catalytic active layer, comprising catalytic activated carbon particles, in particular consisting thereof, to a carrier layer; applying a second active layer, comprising impregnated or catalytic activated carbon particles, in particular consisting thereof, to the first active layer; and applying a third active layer, comprising impregnated or catalytic activated carbon particles, in particular consisting thereof, to the second active layer, wherein the sequence of the first, second, and third active layers is interchangeable and wherein a filter layer or a further carrier layer is additionally applied to the last applied activated carbon layer.

[0066] In a preferred embodiment, the at least one active layer comprises impregnated activated carbon particles.

[0067] In a preferred embodiment of the method according to the invention, a catalytic active layer comprising catalytic activated carbon particles is applied to a carrier layer, followed by an active layer comprising impregnated activated carbon particles, and subsequently an active layer comprising impregnated or catalytic activated carbon particles.

[0068] In another embodiment of the method, an adhesive is applied before the respective active layer is applied.

[0069] In further embodiments of the method, at least one further carrier layer is applied, in particular, for example, a further carrier layer is applied to the third active layer.

[0070] In further embodiments of the method, an additional filter layer is applied.

[0071] The invention also includes a filter medium produced according to the inventive method. Brief description of the drawings

[0072] It shows, schematically: Fig. 1 A highly simplified, sectional view of a filter medium according to one embodiment. embodiment(s) of the invention

[0073] In Fig. Figure 1 shows a filter medium 10, in particular for an air filter, especially a cabin air filter or for a fuel cell, wherein the filter medium comprises an outer catalytic active layer 12, which has catalytic activated carbon particles 12a, a second, middle active layer 14, which has impregnated activated carbon particles 14a, and a third, outer active layer 16, which has impregnated or catalytic activated carbon particles 16a, wherein at least one active layer, for example the third active layer 16, has impregnated activated carbon particles 16a. The catalytic activated carbon particles 12a of the catalytic, in the Fig. 1 outer active layer 12 of the filter medium 10 can, as in Fig. Figure 1 schematically shows that the components can also be bonded, and in particular cross-linked, by the addition of adhesive 18. The adhesive 18 can advantageously be a reactive melt flow adhesive, for example, based on polyurethane. The adhesive 18 can also advantageously bond a filter layer 20, in particular a particle filter layer 20, to the catalytic active layer 12. The catalytic activated carbon particles 12a of the catalytic active layer 12 can have a mass coverage of 50 to 300 g / m². 2 , especially 150 to 300 g / m² 2The catalytic active layer 12 features catalytic activated carbon particles 12a for removing acidic (pH < 7) and / or hydrophilic gases, thus removing hydrophilic gases and also adsorbing some of the water present in the gas stream. This allows the gas stream to be dried in a simple manner before passing through an active layer designed for basic and / or organic, especially hydrophobic, gases and odors, particularly harmful or reactive gaseous substances, for example, the second active layer 14. This further optimizes the adsorption capacity for basic and / or organic, especially hydrophobic, gases and odors, as well as harmful or reactive gaseous substances.

[0074] The impregnated activated carbon particles 14 a of the second active layer 14 of the filter medium 10 can be used as in Fig. Figure 1 schematically shows that the second active layer 14 can also be bonded, in particular cross-linked, by the addition of adhesive 18. The adhesive 18 can advantageously be a reactive melt flow adhesive, for example, based on polyurethane. Advantageously, the second active layer 14 comprises impregnated activated carbon particles 14a for ammonia removal, in particular phosphoric acid-impregnated activated carbon particles 14a. The phosphoric acid impregnation causes chemisorption of ammonia from the gas stream to be purified. For example, the impregnation can consist of 2 to 15 wt.%, in particular 3.5 to 15 wt.%, in particular 2 to 6 wt.% phosphoric acid.

[0075] Chemisorption enables stronger chemical bonds to the adsorbent compared to physisorption, resulting in particularly advantageous binding of ammonia. The impregnated activated carbon particles 14a of the second active layer 14 can be particularly advantageously treated with a mass covering of 50 to 300 g / m². 2, especially 50 to 150 g / m² 2 The mass distribution can be easily adjusted to the moisture content of the active layer and the gas stream environment, thereby requiring a smaller amount of adhesive to bind, and in particular crosslink, the impregnated activated carbon particles 14a. Adjusting the mass distribution also easily achieves a favorable carbon-to-adhesive ratio. The second active layer 14 is particularly advantageously arranged as an intermediate layer between the catalytic outer active layer 12 and the third outer active layer 16.

[0076] The impregnated activated carbon particles 16a of the second active layer 16 of the filter medium 10 can be used as in Fig.Figure 1 schematically shows that the components are also bonded, in particular cross-linked, by the addition of adhesive 18. The adhesive 18 can advantageously be a reactive melt flow adhesive, for example, based on polyurethane. The adhesive 18 can also advantageously bond a particle filter layer 20 to the first active layer 12. The third active layer 16 can, in particular, comprise impregnated activated carbon particles 16a for removing ammonia and formaldehyde. For example, the third active layer 16 can comprise activated carbon particles 16a impregnated with ethylene urea and phosphoric acid. The impregnated activated carbon particles 16a of the third active layer 16 can have a mass coverage of 50 to 300 g / m², in particular 50 to 150 g / m². 2 exhibit. For example, the impregnation can consist of 2 to 15 wt.%, in particular 3.5 to 15 wt.%, in particular 2 to 6 wt.% phosphoric acid and 10 to 20 wt.% ethylene urea.

[0077] The filter medium 10 can also have a carrier layer 22, in particular a textile carrier layer 22, in particular a carrier layer 22 designed as a nonwoven fabric.

[0078] The filter medium 10 can also have a filter layer 20, which can in particular be designed as a textile particle filter layer 20, in particular as a nonwoven fabric.

Claims

[1] Filter medium (10), in particular for an air filter, in particular a cabin air filter or for a fuel cell, comprising at least three active layers: - an outer catalytic active layer (12) comprising catalytic activated carbon particles (12a) for removing acidic (pH < 7) and / or hydrophilic gases, - a second, middle active layer (14) comprising phosphoric acid-impregnated activated carbon particles (14a) for the removal of ammonia, which is arranged downstream of the outer catalytic active layer (12), - a third, outer active layer (16) comprising activated carbon particles (16a) impregnated with ethylene urea and phosphoric acid for the removal of ammonia and formaldehyde, wherein the three active layers (12,14,16) are different from each other, and wherein the catalytic activated carbon particles (12a,14a) have an electronic structure of the carbon on the surface that has been altered by an activation process and wherein the impregnated activated carbon particles (14a,16a) have an impregnation applied to the activated carbon particles (14a,16a). [2] Filter medium (10) according to claim 1, characterized by , that the catalytic activated carbon particles (12a) are bound, in particular cross-linked, by the addition of adhesive (18). [3] Filter medium (10) according to any one of the preceding claims, characterized by , that the impregnated activated carbon particles (14a) are bound, in particular cross-linked, by the addition of adhesive (18). [4] Filter medium (10) according to any one of the preceding claims, characterized by , that the impregnated activated carbon particles (16a) are bound, in particular cross-linked, by the addition of adhesive (18). [5] Filter medium (10) according to any one of the preceding claims, characterized by that the filter medium (10) has at least one support layer (22). [6] Filter medium (10) according to any one of the preceding claims, characterized bythat the filter medium (10) has a filter layer (20). [7] Filter media body comprising a filter medium (10) according to any one of claims 1 to 6, and at least one side band and / or at least one head band. [8] Filter element comprising a filter media body according to claim 7, or a filter medium (10) according to any one of claims 1 to 6, a frame, at least one retaining element and / or at least one seal. [9] Air filter comprising a filter element according to claim 8, a filter media body according to claim 7 or a filter medium (10) according to any one of claims 1 to 6 and a housing.

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