Filter insert for use in electrostatic precipitators

Abstract

The invention relates to a filter insert (10) for use in an electrostatic precipitator with filter functionality, comprising: i) a multilayer filter medium (12), comprising: i.1) ​​an electrically conductive first conductor layer (14), and i.2) a filter layer (16), wherein the filter layer (16) comprises at least one dielectric layer, and ii) an electrical contacting system (18) for connecting the filter element (10) to a voltage source, comprising a first contacting element (20), wherein the electrical contacting system (18) contacts the first conductor layer (14) via the first contacting element (20), wherein the electrically conductive connection between the first contacting element (20) and the first conductor layer (14) is at least partially provided by an electrically conductive first plastic material (22) which connects the first contacting element (20) and the first conductor layer (14) in a metallurgical bond, and wherein the first plastic material (22) has a specific electrical resistance of 106 Ω·m or less at 20 °C.

Description

The invention relates to a filter insert for use in an electrostatic separator having filter functionality and to a corresponding electrostatic separator comprising such a filter insert and to a method for producing a corresponding filter insert.Modern filtration technology today knows numerous powerful alternatives and further developments to the well-known methods for separating undesired components from fluid streams, which are mostly based on a substantially mechanical separation, mostly on a merely partially permeable filter element, which can consist for example of a porous material.One of these further developments, which is used in particular for gas cleaning, is the so-called electrostatic separation, the devices used also being referred to as electrostatic precipitators. In these electrostatic precipitators, the particles to be removed are ionized by an electrode in a first step and are subsequently deposited on an oppositely charged precipitation electrode. Corresponding electrostatic precipitators are used in particular in industrial plants.However, other requirements are placed on the performance characteristics of interior air filters, in particular for use in vehicles, wherein, for example, reliable separation of pollen and / or particulate matter and / or odors and / or exhaust gases is also desired.In order to meet these requirements for indoor air filters, the concept of electrostatic separation, which in many cases is strictly not filtration, has been combined with mechanical separation methods to obtain efficient filter elements. The combination of classic filter materials with an ionization device makes it possible in many cases to already significantly increase the separation performance of filters, wherein the corresponding filter elements are referred to as electrostatic separators with filter functionality for the purposes of clear identification within the scope of the present invention. However, in the case of corresponding filter elements, it is observed that the separation performance can decrease over the service life of the filter element, which is frequently attributed to an electrostatic charge in the filter material that is reduced over time.To solve this problem, it has been proposed to design electrostatic separators with filter functionality such that a polarization of the filter material can be caused in the filter insert by the application of a voltage to two polarization elements via the build-up of an electric field. In combination with an ionization device, this polarization of the filter material can enable efficient separation, which can advantageously be preserved for the most part over the entire service life of the filter element. Background information on the basic technology is disclosed, for example, in WO 2007 / 135232 A1 or EP 3 448 540 B1.Particularly advantageous configurations of these electrostatic separators with filter functionality can be obtained if the polarization elements are at least partially integrated into the filter medium installed in the filter insert. For this purpose, individual layers of a multilayer filter medium can be designed as electrically conductive layers. Such an electrically conductive conductor layer of the filter medium can, for example, together with a second polarization element arranged on the vehicle side or together with a second electrically conductive conductor layer, cause the polarization of a dielectric filter material. Due to the at least partial integration of the polarization elements into the filter medium and thus the filter insert, efficient filter inserts are obtained which in particular have an advantageous weight and make it possible to reduce or even completely eliminate the requirements imposed on the devices required on the vehicle side if no vehicle-side polarization elements have to be provided in order to realize the polarization of the dielectric layer.The basically advantageous configuration of the filter media or of the filter inserts with integrated electrically conductive conductor layers is, however, also associated with challenges, in particular in industrial production. In order to ensure the desired functionality of the electrically conductive conductor layers, it is namely necessary to make reliable electrical contact with the electrically conductive conductor layers without the time and cost efficiency of the production being adversely affected.The precise and reliable contacting is made more difficult by the fact that the electrically conductive conductor layer must be designed as a porous or permeable material with a view to the required air permeability, and can comprise, for example, a textile planar structure, for example a nonwoven, the reliable electrical contacting of which is not trivial, in particular since this contacting must be matched to high voltages.In addition, the electrically conductive conductor layer can consist at least partially of a layer of particulate material, for example activated carbon, or the necessary electrical conductivity can result from a coating, for example a coating with carbon black. In these cases, the electrically conductive conductor layer is comparatively susceptible to strong mechanical loads, which can lead to destruction of the layer or coating, in particular during production.In addition, the multilayer filter media are mostly used in corresponding filter inserts as pleated filter media, so that reliable contacting can also be made more difficult by the demanding geometric shape of the folded conductive conductor layer, which in particular additionally prevent contacting over a large area.A further problem arises from the fact that the electrically conductive connection between the regularly metallic contact points of a high-voltage source, which can be provided on the vehicle side, for example, and the conductor layers which are non-metallic or at least not exclusively metallic in most cases can be problematic as a result of the different material properties, in particular also with regard to durability, in particular also in the case of different thermal loads, if different coefficients of thermal expansion in the contact region have a disadvantageous effect.From the manufacturing point of view, the typical nature of corresponding conductor layers and the physicochemical properties of the materials result in the additional problem that during the contacting there is a functional upper limit for the processing temperature so that the conductor layers are not damaged during the contacting. In addition, from the manufacturing standpoint, there is a further challenge in that the means and methods used for contacting the conductor layer in the relatively thin and fluid-permeable multilayer filter media should not lead to undesired contacting of the conductor layer with the second polarization layer through the dielectric filter material, which is particularly challenging in particular in configurations in which the polarization takes place via two conductor layers in the filter medium, i.e. without a vehicle-side polarization element.The primary object of the present invention was to eliminate or at least alleviate the disadvantages of the prior art.In particular, it was an object of the present invention to specify an advantageous filter insert having at least one conductor layer integrated into the filter medium, which filter insert is particularly efficient when used in an electrostatic separator having filter functionality and with which particularly good separation performances can be achieved, in particular in combination with an ionization device. Accordingly, it was an object of the invention to also provide an electrostatic precipitator built thereon.In this case, it was an object of the present invention that the electrical contacting of the conductor layer of the filter medium in the filter insert should be particularly reliable and effective.In this respect, it was a further object of the present invention that the electrical contacting in the filter insert to be specified should have a high durability and the electrical contacting of the conductor layer should also ensure high voltages under typical vehicle operating conditions, wherein in particular an excellent resistance to typical mechanical loads occurring during vehicle operation should be ensured. In addition, the filter insert to be specified should ideally be designed such that even relatively severe temperature changes do not lead to weak points in the region of the contacting.It was a further object of the present invention that the production of the filter inserts to be specified, in particular the contacting of the conductor layer of the installed filter media, can be effected in a particularly time- and cost-effective manner, such that the filter inserts to be specified can be produced particularly efficiently, in particular also in large numbers in an automated production method, wherein it was a supplementary object of the present invention to also specify a method for producing the filter inserts to be specified.It was a further supplementary object of the present invention that the production method to be specified should ensure the efficient and reliable contacting of the conductor layers for a large number of conductor layers, in particular also for those conductor layers which, because of their physicochemical properties and / or their structure and / or their shape, are more difficult to contact with conventional methods. In this respect, it was desirable that the production method to be specified should make it possible to avoid undesired damage to the conductor layer and the formation of undesired contactings between the polarization elements as far as possible.The inventors of the present invention have found that the objects described above can be advantageously achieved if the contacting of the conductor layer and of the contacting element provided for the contacting is effected using an electrically conductive adhesive, which results after curing in an electrically conductive plastic material and generates a cohesive connection between the conductor layer and the contacting element, as defined in the claims.This achieves an advantageous production method which results in a particularly time- and cost-effective manner in efficient filter inserts which have reliable and loadable contacting of the conductor layer, which has a high durability, in particular even at high polarization voltages, in particular under typical vehicle use conditions and temperatures.The above objects are achieved, accordingly, by the subject matter of the invention as defined in the claims. Preferred embodiments according to the invention are evident from the dependent claims and the following explanations.Such embodiments, which are referred to below as preferred, are combined in particularly preferred embodiments with features of other embodiments referred to as preferred. Combinations of two or more of the embodiments referred to below as particularly preferred are thus very particularly preferred. Also preferred are embodiments in which a feature of one embodiment designated as preferred to any extent is combined with one or more further features of other embodiments designated as preferred to any extent. Features of preferred electrostatic precipitators and methods result from the features of preferred filter inserts.The invention relates in particular to a filter insert for use in an electrostatic precipitator with filter functionality, comprising:i) a multilayer filter medium comprising:i.1) an electrically conductive first conductor layer, andi.2) a filter layer, wherein the filter layer comprises at least one dielectric layer, andii) an electrical contacting system for connecting the filter insert to a voltage source, comprising a first contacting element,wherein the electrical contacting system contacts the first conductor layer via the first contacting element, wherein the electrically conductive connection between the first contacting element and the first conductor layer is at least partially effected by an electrically conductive first plastic material which connects the first contacting element and the first conductor layer in a materially bonded manner, and wherein the first plastic material has a specific electrical resistance of 10 6 Ω*m or less at 20° C.The invention relates to a filter insert which is provided for use in an electrostatic precipitator with filter functionality and in which it is combined with an ionization device for which the filter insert according to the invention can function as a precipitation electrode. The term "filter insert" expresses in particular that it is an object which, with regard to its intended use, is intended to be arranged in a filter module, in particular a filter module of a vehicle, such that it can be exchanged reversibly and non-destructively.The filter insert according to the invention comprises a multilayer filter medium which comprises at least one electrically conductive first conductor layer. This first conductor layer is provided to cooperate as a polarization element during the polarization of the filter layer provided in the multilayer filter medium.The skilled person understands that for the polarization of the filter layer, in particular of the electrical layer within the filter layer, a second polarization element is required next to the first conductor layer, so that a voltage difference can be applied between the first conductor layer and this second polarization element, so that an electric field is formed.In a first embodiment, the second polarization element can be formed by an element separate from the filter insert, which element is, for example, a component of a vehicle filtration module and can be formed, for example, as a metallic plate. The advantage of this embodiment can be seen in the fact that the second polarization element is displaced out of the replaceable filter insert. This not only allows the weight of the filter inserts according to the invention to be reduced, but also allows the construction thereof to be simplified. In addition, the amount of waste which arises during the replacement of a used filter insert is reduced.Even if it can be advantageous for certain embodiments to introduce the second polarization element outside the filter insert according to the invention, the inventors find it particularly advantageous for practice to integrate the second polarization element into the filter insert. Although it would theoretically be conceivable in this case to provide the second polarization element as an element separate from the multilayer filter medium, for example again as a metallic plate, this is less preferred with regard to the total weight. In this respect, the inventors find it particularly advantageous for substantially all embodiments if the second polarization element for the polarization is likewise integrated into the multilayer filter medium, such that the multilayer filter medium comprises, in addition to a first conductor layer, also a second conductor layer and the filter layer can be arranged between this first conductor layer and the second conductor layer. A corresponding configuration of the multilayer filter medium is associated only with a slight increase in weight and leads to an advantageous polarization effect on the filter layer arranged directly between the conductor layers. In addition, it is hereby possible, without high additional costs and the need for installation space, to integrate all the parts necessary for the polarization effect into the replaceable filter insert, whereby all the components required for the proper functioning of the polarization are advantageously replaced when replacing the filter insert, so that simple maintenance of the overall system is advantageously possible. A filter insert according to the invention is accordingly preferred, wherein the multi-layer filter medium additionally comprises:i.3) an electrically conductive second conductor layer,wherein the filter layer is arranged between the first conductor layer and the second conductor layer.The electrical contacting of the second conductor layer can in particular also take place via the electrical contacting system, so that the need for further voltage sources for the electrical connection of the second conductor layer is advantageously dispensed with. A filter insert according to the invention is preferred accordingly, wherein the electrical contacting system comprises a second contacting element, wherein the electrical contacting system contacts the second conductor layer via the second contacting element. This is accordingly a filter insert according to the invention, wherein the electrical contacting system is configured such that a voltage difference can be applied between the first conductor layer and the second conductor layer.In most applications, in the course of cost- and time-efficient production, it is advantageous to implement the electrical connection between the second contact-making element and the second conductor layer in the same way as the electrical connection between the first conductor layer and the first contact-making element. Accordingly, a filter insert according to the invention is preferred, wherein the electrically conductive connection between the second contacting element and the second conductor layer is at least partially effected by an electrically conductive second plastic material, wherein the second plastic material has a specific electrical resistance of 10 6 Ω*m or less at 20° C. A filter insert according to the invention is preferred, wherein the first plastic material and the second plastic material are of the same type.In filter inserts according to the invention, the multi-layer filter medium is preferably used in pleated form in order to maximize the inflow surface available for fluid filtration. In order to impart advantageous stability to the filter medium in this form, a pleated filter medium folded in this way can advantageously be provided with a side lining. A filter insert according to the invention is preferred, wherein the filter insert comprises the multi-layer filter medium as pleated filter medium. In addition or alternatively, a filter insert according to the invention is preferred, wherein at least one of the sides of the pleated multilayer filter medium, preferably at least two sides, particularly preferably at least the longitudinal sides, very particularly preferably all sides, are laminated with a laminating material, wherein the laminating material is preferably selected from the group consisting of textile planar structures, in particular nonwovens and felts.Regardless of whether only one conductor layer is integrated into the filter insert as part of the polarization system, or whether both polarization elements are integrated into the filter insert, in particular in the form of two conductor layers, a structure is required which distributes the voltage necessary for the polarization, which is applied to the filter insert from the outside, to the polarization elements. Within the scope of the present invention, the corresponding structure is referred to as an electrical contacting system, which is configured to connect the parts of the polarization system provided in the filter insert according to the invention, i.e. in particular the first conductor layer, in an electrically conductive manner to an external voltage source, which can be part of a vehicle, for example. A filter insert according to the invention is preferred, wherein the voltage source is a high voltage source. In addition or alternatively, with regard to the positioning, a filter insert according to the invention is preferred, wherein the electrical contacting system is connected to the lamination of the pleated filter medium, preferably in a materially bonded manner.Regardless of the specific configuration of the electrical contacting system, the latter will comprise a first contacting element, which is provided to produce an electrically conductive contacting with the first conductor layer of the multilayer filter medium.According to the invention, the contacting necessary for this is effected via an electrically conductive first plastic material, which causes a cohesive connection between the first contacting element and the first conductor layer. The electrically conductive plastic of the filter insert according to the invention is obtained as a result of adhesion and can be understood as a cured electrically conductive adhesive. In the course of development, the inventors have succeeded in identifying particularly suitable types of adhesive with which the necessary electrical contacting via the electrically conductive plastic material can be advantageously realized.According to the inventors' judgment, excellent results are achieved in particular with hot melt adhesives, which are also referred to as "hotmelt". Such thermoplastic materials are liquefied at a temperature in the range of the melting temperature and applied to the contacting element and the first conductor layer, where they solidify after cooling and form the electrically conductive first plastic material. With regard to the preferred materials of the first conductor layer, in particular nonwoven plastics materials, the inventors propose that those hot-melt adhesives should be used whose melting temperature is not too high, so that the thermal load on the first conductor layers used is not too high. A filter insert according to the invention is therefore preferred, wherein the first plastic material and / or the second plastic material, preferably the first plastic material and the second plastic material, are selected from the group consisting of thermoplastic materials, preferably from the group consisting of thermoplastic materials having a melting temperature of 300° C. or less, particularly preferably 220° C. or less. Alternatively or additionally, a filter insert according to the invention is preferred, wherein the first plastic material and / or the second plastic material, preferably the first plastic material and the second plastic material, can be produced by softening and subsequent cooling of a thermoplastic, preferably in a hot-melt bonding method.As a powerful alternative to the use of hot melt adhesives, the inventors have identified the use of curable adhesives. Curable adhesives of this kind have not yet reached the maximum degree of crosslinking in their application state, but additionally comprise suitable initiators with which further crosslinking of the compounds provided in the adhesive can be achieved. According to the inventors' knowledge, radiation-curable adhesives in which the further crosslinking can be initiated, for example, by the application of UV radiation, or chemically-curable adhesives which are available, for example, as two-component adhesives, are suitable in this respect. To this extent, however, the inventors contemplate the use of radiation-curing adhesives as preferred, since these are associated with processing advantages, since no mixing of two or more components has to take place and the activation of the curing can be controlled better. The plastic materials obtained by curing curable adhesives are usually thermosetting plastics which do not exhibit thermoplastic behavior. The advantage of using curable adhesive compositions is that the conductor layers connected thereto have to be subjected essentially to no thermal stress and no devices have to be provided for the heat bonding. A filter insert according to the invention is preferred, wherein the first plastic material and / or the second plastic material, preferably the first plastic material and the second plastic material, are selected from the group consisting of thermosetting plastics. Alternatively or additionally, a filter insert according to the invention is preferred, wherein the first plastic material and / or the second plastic material, preferably the first plastic material and the second plastic material, can be produced by curing a curable adhesive, preferably a radiation-curable or chemically-curable adhesive, particularly preferably a UV-radiation-curable adhesive or a two-component adhesive.The electrically conductive connection between the first contacting element and the first conductor layer produced during the production by adhesion is effected at least partially by the electrically conductive first plastic material, which expresses that a direct contact may partially occur between the first conductor layer and the contacting element, for example if these two components are fixed in contact with one another by the electrically conductive first plastic material. According to the inventors' judgment, such electrical contactings that put on the direct contact between the contacting element and the conductor layer are less preferred, however, in particular with regard to their resistance to mechanical loads, such as occur, for example, during the driving operation of a vehicle and / or stresses that may result from thermal loads of the different materials. It is preferred accordingly if the electrical contacting between the contacting element and the conductor layer takes place substantially completely through the first plastic material.The skilled person understands that for the electrical contacting between the conductor layer and the contacting element it is necessary that the plastic material has a certain electrical conductivity. This minimum functional requirement for the electrical conductivity of the plastic material is characterized above by the specification of the specific resistance of the material. According to the inventors' judgment, however, it is advantageous to select for good electrical contacting those plastic materials which, for example, have an even better electrical conductivity and correspondingly a lower specific resistance due to the admixture of conductive constituents, in particular carbon black. A filter insert according to the invention is preferred accordingly, wherein the first plastic material and / or the second plastic material, preferably the first plastic material and the second plastic material, have a specific electrical resistance at 20° C. of 10 5 Ω*m or less, preferably 10 4 Ω*m or less.In his own experiments, the inventors have additionally identified advantageous characteristic variables for the mechanical properties of the electrically conductive plastic material, with which a high resistance of the bond results, in particular in the case of the loads occurring during typical operation of a vehicle. A filter insert according to the invention is preferred, wherein the first plastic material and / or the second plastic material, preferably the first plastic material and the second plastic material, have a tensile shear strength according to DIN EN 1465-2009-07 of 0.1 N / mm 2 or more, preferably of 1 N / mm 2 or more. A filter insert according to the invention is likewise preferred, wherein the first plastic material and / or the second plastic material, preferably the first plastic material and the second plastic material, have an average peel force according to DIN EN 1464-2010-06 of 0.4 N / mm or more, preferably of 1 N / mm or more, in the roller peel test.The preferred shape of the plastic material in the filter insert according to the invention, and thus the preferred application scheme of the adhesive in the production method, results from process engineering considerations which have been identified by the inventors as being particularly advantageous for the production method. Namely, the inventors have recognized that there is a conflict of goals between several aspects that cannot be solved perfectly in the same way. On the one hand, it is desired that there is reliable large-area contacting of the conductor layer via the plastic material, wherein a large bond area additionally advantageously mostly provides a high bond strength. On the other hand, however, the bond area also reduces the filtration area available for fluid filtration and disadvantageously increases the overall weight of the filter insert and the adhesive insert required during production, which indirectly results in an increase in costs.The inventors have found to this extent that the application of comparatively thin plastic strips or a lattice structure which comprises a plurality of overlapping such plastic strips advantageously results in very reliable and durable connections which block comparatively little filter surface. A filter insert according to the invention is preferred, wherein the first plastic material and / or the second plastic material, preferably the first plastic material and the second plastic material, form a plastic strip, a grid structure of a plurality of plastic strips or a grid of a plurality of plastic points, preferably a plastic strip, wherein the width of the plastic strip perpendicular to the longitudinal direction preferably corresponds to 30% or less, particularly preferably 20% or less, very particularly preferably 10% or less, of the length of the plastic strip.In addition, the inventors have found that, when the electrical contacting via the plastic material is implemented on the conductor layer, it is advantageously possible to use relatively little material without the polarizing ability adversely suffering therefrom. A filter insert according to the invention is preferred, wherein the first plastic material and / or the second plastic material, preferably the first plastic material and the second plastic material, have a maximum length which corresponds to 20% or less, preferably 10% or less, particularly preferably 5% or less, of the length of the filter insert.The inventors have succeeded in identifying particularly advantageous alignments of the adhesive structure made of plastic material. In the experiments of the inventors, it was possible to achieve particularly advantageous results if the adhesive is applied either along the fold folds, in particular along the fold spine, or is applied transversely to the fold folds, such that it extends over a plurality of fold spines of the pleated material. While the application along a filter fold allows a particularly advantageous continuous connection, the adhesive bonding spanning the folds advantageously results in the conductor layer being contacted at a plurality of adhesive sites spaced apart from one another, so that the contacting takes place at a plurality of sites spaced apart from one another with respect to the surface of the unfolded conductor layer, whereby the occurrence of local defects can be advantageously compensated. Accordingly, a filter insert according to the invention is preferred, wherein the first plastic material and / or the second plastic material, preferably the first plastic material and the second plastic material, have their greatest longitudinal extent substantially parallel or transversely to the fold direction of the pleated filter element. In addition or alternatively, a filter insert according to the invention is also preferred, wherein the first plastic material and / or the second plastic material, preferably the first plastic material and the second plastic material, contact the respective conductor layer at two or more, preferably three or more, adhesive sites spaced apart from one another along the conductor layer, wherein the adhesive sites spaced apart from one another are preferably the bending points of the pleated multilayer filter element.At least theoretically, it would be conceivable to bring the adhesive used to form the plastic material directly between the conductor layer and the contacting element, in order thereby to produce the desired material-to-material connection. However, the inventors have found that, in particular from the standpoint of production technology, it is also preferred with regard to the quality of the electronic contacting if the contacting element positioned on the conductor layer is stuck over with the adhesive, so that the cohesive connection takes place through the material protruding laterally beyond the contacting element. In this respect, a filter insert according to the invention is preferred, wherein the first plastic material and / or the second plastic material, preferably the first plastic material and the second plastic material, are arranged at least partially, preferably substantially completely, on the side of the respective contacting element and the corresponding conductor layer facing away from the multilayer filter medium.The electrical contacting system to be provided according to the invention can be designed by the person skilled in the art according to the respective application requirements and the design requirements of the filter module, in particular of the vehicle filter module. For substantially all embodiments, a filter insert according to the invention is preferred, wherein the electrical contacting system comprises a first contact point and a second contact point for contacting the voltage source.Even if very simple embodiments of the electrical contacting system are theoretically conceivable, which for example rely on the use of cables, the inventors have designed a particularly advantageous electrical contacting system with a view to a time- and cost-effective production, which produces particularly synergistic advantages in particular with the execution of the electrical contacting via the adhesive bonding by means of an electrically conductive plastic material. According to the inventors' judgment, it is especially advantageous if classical electrical wiring is not used or if it is used only to a small extent, but rather the contacting system is designed as largely as possible from components which themselves consist of an electrically conductive plastic. A filter insert according to the invention is accordingly preferred, wherein the electrically conductive components of the electrical contacting system are formed at least partially, preferably predominantly, particularly preferably substantially completely, by an electrically conductive plastic. A filter insert according to the invention is particularly preferred, wherein the electrically conductive plastic of the electrical contacting system has a specific electrical resistance at 20° C. of 10 6 Ω*m or less, preferably 10 5 Ω*m or less, particularly preferably 10 4 Ω*m or less.According to the inventors' judgment, these electrically conductive components, which preferably consist of an electrically conductive plastic, should be arranged on a preferably thin substrate, which functions as a carrier and advantageously makes it possible to assemble the electrically conductive components of the electrical contacting system before attachment to the filter insert according to the invention and to apply them during the production method in only a single step, for example to the lateral lamination of the filter insert. A filter insert according to the invention is therefore preferred, wherein the electrically conductive components of the electrical contacting system are conductive components arranged on a substrate and / or in a substrate. In addition or alternatively, a filter insert according to the invention is preferred, wherein the substrate is selected from the group consisting of electrically insulating films, preferably plastic films, wherein the average thickness of the substrate is preferably in the range from 20 to 500 μm, particularly preferably in the range from 80 to 150 μm.The use of a thin substrate, in particular a film, in combination with conductive components formed from plastic advantageously allows the electrical contacting system to be configured not only in a particularly space-saving and low-weight manner, but results in an electrical contacting system with high flexibility, in which the substrate and the conductive components lying thereon can be adapted particularly easily to the structural requirements of the filter insert according to the invention and as a result of which a low-stress adhesion to the conductive plastic material can be realized in a synergistic manner.The experiments of the inventors have shown in particular that a corresponding electrical contact-making system can be advantageously printed on the substrate, wherein other additive manufacturing methods could also be considered at least theoretically. A filter insert according to the invention is thus preferred, wherein the electrical contacting system can be produced by printing on the substrate with an electrically conductive material, preferably an electrically conductive plastic, wherein the printing is preferably a screen printing method.In particular, additive manufacturing methods advantageously make it possible to obtain an electrical contacting system which is provided with the electrically conductive components only on one side and consequently has an underside, the properties of which are largely influenced by that of the substrate, which can advantageously be embodied as an electrically insulating substrate. With regard to the attachment, a filter insert according to the invention is thus preferred, wherein the electrical contacting system comprises the electrically conductive components of the electrical contacting system at least partially, preferably predominantly, particularly preferably substantially completely, preferably at least the contact points and the contacting elements, on the same side of the substrate.In a particularly preferred embodiment, the substrate is designed as a comparatively thin film, in the central region of which essential elements of the electrical contacting system are arranged, for example the contact points for the external voltage source or also a possible voltage divider. The inventors propose that lateral wing-like or tab-like projections can be formed, on which the contacting elements are applied, which are provided for contacting the conductor layers. When such a contacting system is applied to the lateral lamination of a filter insert according to the invention, the wing-like tabs can be folded over particularly easily, so that they each contact the conductor layer and can subsequently be glued with the electrically conductive adhesive in such a way that the cohesive connection is produced by the plastic material without this connection being made more difficult by excessively strong mechanical stresses. A filter insert according to the invention is preferred accordingly, wherein the first contacting element and / or the second contacting element, preferably the first contacting element and the second contacting element, are arranged on laterally protruding projections of the substrate, wherein the laterally protruding projections preferably have a deformation region and a contact region, wherein the contact region transversely to the longitudinal direction of the filter insert is preferably wider than the deformation region. A filter insert according to the invention is particularly preferred, wherein the laterally protruding projections are L-shaped. Particularly preferred in this case is additionally or alternatively a filter insert according to the invention, wherein the laterally protruding projections are embodied in the deformation region to be reversibly and non-destructively deformable, in particular bendable. Particularly preferred is additionally or alternatively also a filter insert according to the invention, wherein the electrical contacting system contacts the first conductor layer with the contact region of the first contacting element, and / or wherein the electrical contacting system contacts the second conductor layer with the contact region of the second contacting element.In this embodiment, the conductor layer advantageously does not make direct contact with the contacting element, since the substrate lies between them. The electrically conductive contacting is accordingly realized substantially completely by the electrically conductive plastic material, with which the contact region of the laterally protruding protrusion can be glued over. In this preferred embodiment, the filter insert according to the invention is concerned, wherein the electrical contacting system contacts the first conductor layer with the side of the substrate facing away from the first contacting element, wherein the electrically conductive connection between the first contacting element and the first conductor layer is effected substantially completely through the first plastic material, and / or wherein the electrical contacting system contacts the second conductor layer with the side of the substrate facing away from the second contacting element, wherein the electrically conductive connection between the second contacting element and the second conductor layer is effected substantially completely through the second plastic material.The filter inserts according to the invention are intended to be combined with an ionization device in a later use in an electrostatic precipitator with filter functionality. The voltage required for ionization will generally be significantly higher than the polarization voltage necessary for polarization or that can be applied to the maximum extent, which is limited by the voltage at which undesired breakdown occurs, in particular when the two polarization elements are integrated into the multilayer filter medium. One conceivable solution would be to provide different voltage sources for the ionization device and the filter insert. However, the inventors have recognized that such a provision of separate high-voltage sources is in many cases not possible or is associated with a high outlay on apparatus, and therefore a corresponding configuration is less preferred. For this purpose, it is proposed to design the electrical contact-making system as a voltage divider, by means of which a voltage taken over by the ionization device can be matched to the requirements of the filter insert. A filter insert according to the invention is thus preferred, wherein the electrical contacting system is a voltage divider. For this purpose, the electrical contacting system can have contact points which are provided for being contacted directly or indirectly via the ionization device with an electrical potential difference which is designed for the ionization device. Between these contact points, a resistance path is provided, which preferably has a meandering contour. The voltage that is dropped across the first contacting element or, if applicable, the second contacting element can be advantageously adjusted by positioning the contacting element along this resistance path, so that, for example, only a reduced voltage is present between the two contacted conductor layers compared to the ionization device. Against this background, a filter insert according to the invention is preferred, wherein in the electrical contacting system the first contact point is electrically conductively connected to the second contact point via a resistance path, wherein the first contacting element is electrically conductively connected to the resistance path between the first contact point and the second contact point, and wherein the second contacting element is electrically conductively connected to the second contact point. In addition or alternatively, a filter insert according to the invention is also preferred, wherein the resistance path is formed in a meandering manner. In addition or alternatively, a filter insert according to the invention is preferred, wherein the first contacting element and / or the second contacting element, preferably the first contacting element and the second contacting element, are connected to the resistor section in such a way that the contact area between the resistor section and the contacting element is larger than the cross section of the resistor section orthogonal to the longitudinal direction of the resistor section. In addition or alternatively, a filter insert according to the invention is preferred, wherein the second contact element is not electrically conductively connected to the resistance path between the first contact point and the second contact point.In particularly preferred embodiments, in addition to the electrically conductive components of the contacting system, machine-readable information, for example in the form of a QR code, can also be provided on the substrate. In particular, if the electrical contacting system is applied to the lateral lining of the filter insert, this is particularly easy to read from the outside. This makes it possible to provide the customer or the workshop operation with important information about the handling and / or the installation of corresponding filter inserts according to the invention. In addition, it is possible to utilize the machine-readable information marking already during the production of the filter inserts according to the invention, for example if the information stored therein comprises instructions about the control of the devices and / or the selection of materials. Within the scope of the present invention, the inventors find it particularly advantageous if the stored information contains method instructions on which electrically conductive adhesive is to be used and in which application pattern this is required for optimum fixing of the contacting elements on the conductor layer. A filter insert according to the invention is preferred, wherein the electrical contacting system comprises a machine-readable information marking, preferably a matrix code or a QR code, wherein the machine-readable information marking comprises information and / or operating instructions about the application position of the electrical contacting system in the filter insert and / or the method parameters for connecting the contact elements to the corresponding conductor layers by means of the corresponding adhesive.The inventors succeeded in identifying preferred embodiments for the multilayer filter medium to be used according to the invention and for the individual layers thereof, in particular the conductor layers, it being possible to achieve particularly advantageous results, in particular with respect to the embodiments of the conductor layers referred to as preferred below, using electrically conductive adhesives.A filter insert according to the invention is preferred first, wherein the first conductor layer comprises a first textile planar structure, preferably a first textile planar structure coated or impregnated at least in sections with an electrically conductive first material, and / or wherein the second conductor layer comprises a second textile planar structure, preferably second textile planar structure coated or impregnated at least in sections with an electrically conductive second material.The term "textile fabric" is clear to the skilled person and denotes two-dimensional textile products which can be woven, knitted, needled or knitted, for example. In accordance with the expert's understanding, non-textile fibrous fabrics, for example paper and cardboard, in which the fibers are held together, for example, primarily by binding agents, do not belong to the textile fabrics. Even if a wide range of textile fabrics were in principle possible for the textile fabrics of the conductor layers, the inventors have been able to achieve the best performance characteristics, in particular with so-called "nonwovens" and in this case in particular with spunbonded nonwovens. A corresponding textile fabric made of a non-conductive material can be advantageously achieved by equipping the textile fabric with a conductive material, wherein, according to the inventors' judgment, in principle a multiplicity of possible methods are suitable. A filter insert according to the invention is thus preferred, wherein the first textile fabric and / or the second textile fabric, preferably the first textile fabric and the second textile fabric, are a nonwoven, preferably a spunbonded nonwoven.The distinction between an electrically conductive material as distinct from an electrically insulating material is without any constraint for those skilled in the art and based on their skilled and clear technical understanding of these terms. In this respect, a material in the context of the present invention is particularly considered to be an electrically conductive material when its specific electrical resistance at 20° C. is 10 6 Ω*m or less, preferably 10 5 Ω*m or less, particularly preferably 10 4 Ω*m or less. Conversely, a material in the context of the present invention is particularly applicable as an electrically insulating material when its specific electrical resistance at 20° C. is 10 7 Ω*m or more, preferably 10 9 Ω*m or more, particularly preferably 10 11 Ω*m or more. Accordingly, metals and alloys, however, are also carbon blacks, such as, in particular, conductive carbon black, and plastics made conductive by additives, are electrically conductive materials, whereas typical unmodified plastics such as PET or PE likewise belong to the electrically insulating materials, such as, for example, most glasses and ceramics. The electrical resistivity of materials is a value well known to the skilled person, which can be found in reference tables relevant for most materials. The measurement of the specific electrical resistance in other components takes place in accordance with the usual practice either according to DIN EN ISO 3915 from 1999, which is used in particular for particularly conductive materials, or according to IEC 60093 from 1993, which is used in the case of high specific electrical resistances. The question as to which of the two standards is to be used is directed to the specifications of the two regulations and the properties of the respective material investigated.The skilled person understands that the electrical conductivity of conductor layers, for example of the first conductor layer, can in many cases, for example when using composite materials, result from the presence of conductive material paths which run in an otherwise largely insulating material. Thus, for example, a dielectric fleece whose fibers are provided with a thin layer of conductive carbon black can be an electrically conductive layer, although the macroscopic specific resistance of the composite material is relatively high as a result of the dielectric carrier material.Furthermore, a filter insert according to the invention is additionally or alternatively preferred, wherein the first textile fabric and / or the second textile fabric, preferably the first textile fabric and the second textile fabric, consist of a plastic, based on the mass of the textile fabric, to a mass fraction of 80% or more, preferably 90% or more, particularly preferably 95% or more, very particularly preferably substantially 100%, wherein the plastic is preferably selected from the group consisting of polyacrylonitriles, polyolefins, polyesters and mixtures of these plastics, particularly preferably polyacrylonitriles, polypropylene, polyethylene terephthalate and mixtures of these plastics, particularly preferably polyethylene terephthalate.In addition or alternatively, a filter insert according to the invention is also preferred, wherein the first conductor layer and / or the second conductor layer, preferably the first conductor layer and the second conductor layer, can be produced or produced by equipping the respective textile planar structure, in particular the nonwoven, with the respective electrically conductive material by a method selected from the group consisting of impregnation, dip coating, in particular with a pad system, spray coating, application coating, in particular by means of a dispersion in the kiss-coat method, and pressure coating.In addition or as an alternative, a filter insert according to the invention is preferred, wherein the electrically conductive first material and / or the electrically conductive second material, preferably the electrically conductive first material and the electrically conductive second material, are selected from the group consisting of metals, conductive plastics and carbon, preferably carbon, in particular carbon black or graphene, wherein the electrically conductive material is particularly preferably identical for the first conductor layer and the second conductor layer.Additionally or alternatively, a filter insert according to the invention is preferred, wherein the first conductor layer and / or the second conductor layer, preferably the first conductor layer and the second conductor layer, are electrically conductive due to the coating of the respective textile fabric at least over 80% or more of the surface area, preferably over 90% or more, particularly preferably over 95% or more, very particularly preferably over 98% or more, in particular preferably substantially over the entire surface.Even if the conductor layers can contribute to the filtration performance of the filter media, in particular if they are designed as textile fabrics, the inventors find it advantageous if the conductor layers are designed with sufficient open pores, so that they primarily restrict the passage of air through the filter medium as little as possible. With regard to the weight of the conductor layers, at least when textile fabrics are used, there is in this respect a conflict of goals between the influence on the total weight of the filter medium and an advantageous stabilizing effect of the conductor layers on the filter medium and thus an improvement in the mechanical properties. In this respect, the inventors have succeeded in identifying suitable weights per unit area for the textile fabrics, with which this conflict of goals can be solved in an advantageous manner. Against this background, a filter insert according to the invention is preferred, wherein the first conductor layer and / or the second conductor layer, preferably the first conductor layer and the second conductor layer, have an air passage at 200 Pa in the range from 500 to 30000 L / (m 2 s), preferably in the range from 2000 to 20000 L / (m 2 s). In addition or alternatively, a filter insert according to the invention is also preferred, wherein the first textile fabric and / or the second textile fabric, preferably the first textile fabric and the second textile fabric, have a basis weight in the range from 5 to 200 g / m 2, preferably in the range from 10 to 150 g / m 2, particularly preferably in the range from 15 to 50 g / m 2.With regard to the general structure of the multilayer filter medium, a filter insert according to the invention is preferred, wherein the filter layer comprises one or more further layers, preferably further layers arranged between the first conductor layer and the second conductor layer, wherein the filter layer preferably comprises two or more dielectric layers, particularly preferably three or more dielectric layers.In addition or alternatively, a filter insert according to the invention is also preferred, wherein at least one of the dielectric layers, preferably all of the dielectric layers, consists of a dielectric plastic material to a mass fraction of 80% or more, preferably 90% or more, particularly preferably 95% or more, very particularly preferably substantially 100%, based on the mass of the dielectric layer. A filter insert according to the invention is particularly preferred, wherein the dielectric plastic material is selected from the group consisting of polyolefins, in particular polytetrafluoroethylene, polytetrafluoroethylenepropylene, polypropylene, and polyethylene, polyesters, in particular polyethylene terephthalate, polycarbonates, polyamides, polyvinylidene fluoride, polyacrylonitrile, and polylactides. Particularly preferred is additionally or alternatively a filter insert according to the invention, wherein the dielectric plastic material has a specific electrical resistance at 20° C. of 10 7 Ω*m or more, preferably at 10 9 Ω*m or more, particularly preferably at 10 11 Ω*m or more.A filter insert according to the invention is preferred for the predominant number of embodiments, wherein at least one of the dielectric layers is a particle filter layer which comprises a third textile planar structure. Particularly preferred is a filter insert according to the invention, wherein the third textile fabric is a nonwoven fabric, wherein the third textile fabric is preferably selected from the group consisting of needle-punched nonwovens and meltblown nonwovens. Particularly preferred is additionally or alternatively a filter insert according to the invention, wherein the particle filter layer has a weight per unit area in the range from 10 to 200 g / m 2, preferably in the range from 15 to 150 g / m 2, particularly preferably in the range from 20 to 110 g / m 2.A filter insert according to the invention is preferred for multilayer filter media containing activated carbon in particular, wherein at least one of the dielectric layers is a protective layer which comprises a fourth textile planar structure. a multilayer filter medium according to the invention is particularly preferred in this case, wherein the fourth textile planar structure is a nonwoven fabric, preferably a spunbonded nonwoven fabric.In addition or alternatively, a filter insert according to the invention is preferred, wherein the protective layer has an air passage at 200 Pa in the range from 500 to 30000 L / (m 2 s), preferably in the range from 2000 to 20000 L / (m 2 s). In addition or alternatively, a filter insert according to the invention is also preferred, wherein the protective layer has a weight per unit area in the range from 15 to 400 g / m 2, preferably in the range from 50 to 200 g / m 2. In addition or alternatively, a filter insert according to the invention is preferred in turn, wherein the protective layer comprises one or more active substances selected from the group consisting of antiallergic active substances and biocidal active substances. Particularly preferred is additionally or alternatively also a filter insert according to the invention, wherein the protective layer has a Cucumbery flexural rigidity, determined according to ASTM D6125-97, in the range from 0.4 to 40 mN, preferably in the range from 0.5 to 20 mN, particularly preferably in the range from 0.6 to 10 mN.For the predominant number of embodiments, according to the inventors' judgment, a filter insert according to the invention is also preferred additionally or alternatively, wherein the filter layer comprises an activated carbon layer, wherein the activated carbon layer comprises activated carbon in a mass fraction of 70% or more, based on the mass of the activated carbon layer.Activated carbon is known as an important material to the skilled person in the field of filtration technology and is commercially available from numerous manufacturers. It is preferred that the activated carbon layer is formed from activated carbon to a high mass fraction, so that, for example, the fraction of fibers or other carrier materials in the activated carbon layer should be kept as low as possible. As a result, starting from the experiments of the inventors, a particularly good separation effect or cleaning performance is achieved with a simultaneous minimization of the thickness or the weight. The inventors have found that particularly efficient filter inserts can be obtained with activated carbon layers which are as pure as possible and which preferably consist essentially exclusively of activated carbon apart from the binder. A filter insert according to the invention is accordingly preferred, wherein the activated carbon layer comprises activated carbon in a mass proportion of 80% or more, preferably 90% or more, particularly preferably 95% or more, based on the mass of the activated carbon layer. In addition or alternatively, a filter insert according to the invention is preferred, wherein the activated carbon is fixed in the activated carbon layer by a binder. The inventors have thus succeeded in identifying, for the selection of activated carbon and for the dimensioning of the activated carbon layer, particularly preferred regions with which excellent filter performance has been obtained in separate experiments. A filter insert according to the invention is namely preferred, wherein the activated carbon is particulate activated carbon, wherein the activated carbon preferably has an average diameter d50in the range from 0.1 to 4 mm, preferably in the range from 0.2 to 2 mm. In addition or alternatively, a filter insert according to the invention is also preferred, wherein the activated carbon has a specific surface area of 500 m 2 / g or more, preferably of 1000 m 2 / g or more, particularly preferably of 2000 m 2 / g or more. In turn, a filter insert according to the invention is preferred additionally or alternatively, wherein the activated carbon layer has a weight per unit area in the range from 50 to 1000 g / m 2, preferably in the range from 100 to 600 g / m 2.The invention also relates to an electrostatic precipitator with filter functionality comprising:I) a filter insert according to the invention, andII) An ionization device for ionizing constituents of the fluid to be filtered.In accordance with the expert's understanding, it is preferably an electrostatic separator, wherein the electrostatic separator is configured to cause or to transport the separation of electrically charged particles, in particular of ionized particles, particularly preferably particles ionized by the ionization device, when a voltage is applied between the first contact point and the second contact point of the electrical contacting system as a result of a polarization of the multilayer filter medium.An electrostatic separator according to the invention is preferred, wherein the electrostatic separator is an air filter, preferably an interior air filter, particularly preferably an interior air filter for vehicles, in particular for land vehicles.In addition or alternatively, an electrostatic separator according to the invention is preferred, wherein the ionization device is an electric ionization device, wherein the ionization device is preferably configured to effect the ionization of components of the fluid to be filtered at least partially, preferably substantially completely, by means of corona discharge. In contrast to alternative ionization devices known from the prior art, an electrostatic separator according to the invention is thus preferred, wherein the ionization device does not comprise a radiation source for ionizing radiation.The invention finally also relates to a method for producing a filter insert according to the invention or an electrostatic separator according to the invention, comprising the method steps: a) producing or providing the multilayer filter medium, b) arranging the first contacting element on the first conductor layer, c) applying a first adhesive for connecting the first contacting element and the first conductor layer, and d) curing the first adhesive for obtaining the electrically conductive first plastic material and for producing an electrically conductive, materially bonded connection between the first contacting element and the first conductor layer.The first adhesive is used to produce the first plastic material, wherein the term adhesive also includes hot melt adhesives, i.e. hotmelts, in the context of the present invention.In the light of the above disclosure, a method according to the invention is preferred, additionally comprising the method steps:e) arranging the second contacting element on the second conductor layer,f) applying a second adhesive for connecting the second contacting element and the second conductor layer,g) curing the second adhesive to obtain the electrically conductive second plastic material and to produce an electrically conductive, materially bonded connection between the second contacting element and the second conductor layer.In addition or alternatively, a method according to the invention is preferred, wherein the production of the multi-layer filter medium comprises the pleated structure of the multi-layer filter medium. In addition or alternatively, preferably additionally, a method according to the invention is also preferred, wherein the production of the multilayer filter medium comprises the lateral lamination of the pleated multilayer filter medium.Preference is given to a method according to the invention, wherein the first adhesive and / or the second adhesive, preferably the first adhesive and the second adhesive, are selected from the group consisting of hotmelt adhesives, radiation-curable adhesives and chemically-curable adhesives, preferably hotmelt adhesives. A method according to the invention is particularly preferred, wherein the first adhesive and the second adhesive are preferably of the same type.Preference is given to a method according to the invention, wherein the first adhesive and / or the second adhesive, preferably the first adhesive and the second adhesive, have a setting time according to DIN 16920-1981-06 (surface strength) of 30 s or less, preferably 20 s or less. In addition or alternatively, a method according to the invention is preferred, wherein the first adhesive and / or the second adhesive, preferably the first adhesive and the second adhesive, have a dynamic viscosity in the application state, measured according to Brookfield HBTD, in the range from 3 to 100 Pa s, preferably in the range from 6 to 60 Pa s, particularly preferably in the range from 12 to 40 Pa s.With regard to the application scheme, a method according to the invention is preferred, wherein the first adhesive and / or the second adhesive, preferably the first adhesive and the second adhesive, are applied in strip form or in grid form, preferably in strip form. In addition or alternatively, a method according to the invention is preferred, wherein the first adhesive and / or the second adhesive, preferably the first adhesive and the second adhesive, are applied parallel or transversely to the fold direction of the pleated filter element. In turn, a method according to the invention is preferred additionally or alternatively, wherein the first adhesive and / or the second adhesive, preferably the first adhesive and the second adhesive, are applied in such a way that the respective adhesive contacts the respective conductor layer at two or more, preferably three or more, adhesive sites spaced apart from one another along the conductor layer, wherein the adhesive sites spaced apart from one another are preferably the break points of the pleated multilayer filter element. In addition or as an alternative, a method according to the invention is again preferred, wherein the first adhesive and / or the second adhesive, preferably the first adhesive and the second adhesive, are applied in a length which corresponds to 20% or less, preferably 10% or less, particularly preferably 5% or less, of the length of the filter insert. Also preferred additionally or alternatively is a method according to the invention, wherein the first adhesive and / or the second adhesive, preferably the first adhesive and the second adhesive, are applied at least partially, preferably substantially completely, to the side of the respective contacting element facing away from the multilayer filter medium and the corresponding conductor layer.Preference is given to a method according to the invention, additionally comprising the method step: i) connecting the electrical contacting system to the lamination of the pleated multilayer filter medium.The invention and preferred embodiments of the invention are explained and described in more detail below with reference to the attached figures. Preferred embodiments of the method according to the invention serve for the production of preferred filter inserts according to the invention. In the figures, the following are shown: FIG. 1 shows a perspective illustration of a filter insert according to the invention in a preferred embodiment; FIG. 2 shows a schematic illustration of an exemplary electrical contacting system in a preferred embodiment; FIG. 3 shows an illustration of the contacting of a first conductor layer of a filter insert according to the invention with the electrical contacting system of FIG. 2 in a first embodiment; FIG. 4 shows an illustration of the contacting of a first conductor layer of a filter insert according to the invention with the electrical contacting system of FIG. 2 in a second embodiment. FIG. 5 shows a schematic cross-sectional representation through a multi-layer filter medium in a preferred embodiment;FIG. 1 shows a perspective illustration of a filter insert 10 according to the invention, which filter insert has a pleated multilayer filter medium 12 which is fixed by a lamination 36 on both sides with a felt material. On the side wall formed by the lateral lamination 36, an electrical contacting system 18 is provided, which is designed as a voltage divider and comprises two contact points 38 a, 38 b(cf. FIG. 2 ), via which a voltage can be applied by an external voltage source, for example indirectly via an ionization device.The details of the electrical contacting system 18 are visible in FIG. 2. In the example shown in FIG. 2, the electrically conductive components of the electrical contacting system 18 are formed by a plastic that is electrically highly conductive due to a high carbon black content. The electrical contacting system 18 embodied as a voltage divider comprises a resistor section 40 which connects the two contact points 38 a, 38 bto one another and has a meandering course in sections.Laterally protruding projections 42 a, 42 bof the thin substrate 34 designed as a film protrude from the resistor section 40 or the contact point 38 a, 38 b, on which the first contacting element 20 and the second contacting element 26 are applied, wherein one of the contacting elements contacts the resistor section 40 at a predetermined point in order to pick up a desired voltage value. The contacting of the first conductor layer 14 by the electrical contacting system 18 via the first contacting element 20 to be provided according to the invention is shown in more detail in FIGS. 3 and 4.FIGS. 3 and 4 each show how a lateral protrusion 42 aof the electronic contacting system 18 has been bent around the lamination 36 and contacts the first conductor layer 14 with the low-electrical-conductivity underside of the substrate 34. The electrical contacting is effected only by the use of a comparatively short and narrow strip of adhesive, which cures in the cured state to form an electrically conductive first plastic material 22. FIGS. 3 and 4 differ in how the elongated first plastic material 22 is laid over the bent-over projection 42 aof the electrical contacting system 18 and thus over the first contacting element 20, wherein the preferred course is selected transversely to the direction of folding of the pleated multi-layer filter medium 12.In addition, the machine-readable information marking 44 is visible in FIGS. 2 to 4, which in the example shown comprises method parameters for controlling precisely those devices which apply the adhesive in the method according to the invention, from which the cohesive connection is produced by means of the first plastic material 22.In the example shown in FIGS. 3 and 4, the filter insert 10 according to the invention has a first conductor layer 14 and a second conductor layer 24, wherein the first contacting element 20 and the second contacting element 26 are each contacted by means of the same adhesive. In the example shown in FIGS. 3 and 4, this adhesive is a hot-melt adhesive which has a specific electrical resistance of 500 Ω*m or less. The corresponding first plastic material 22 has a tensile shear strength of more than 1 N / mm 2 and an average shear force of more than 0.4 N / mm. In particular in conjunction with the multilayer filter medium 12, the structure of which is explained further below with reference to FIG. 5, this yields an advantageous filter insert 10 according to the invention, which is not only to be produced in a particularly time- and cost-effective manner, but which reliably fulfills the functional requirements in a broad range of ambient temperatures of -40° C. to +85 ° C.FIG. 5 shows a schematic cross-sectional illustration through a multilayer filter medium 12 according to the invention, which comprises a multilayer filter layer 16 which is arranged between the first conductor layer 14 and the second conductor layer 24 and is bonded thereto by means of an adhesive. Both the first conductor layer 14 and the second conductor layer 24 are formed by a PET spunbonded nonwoven which has been rendered conductive by a coating with conductive carbon black and whose weight per unit area is approximately 30 g / m 2.In the example shown, the filter layer 16 comprises an activated carbon layer 28 which comprises particulate activated carbon having an average diameter of about 0.25 to 0.6 mm and a specific surface area of about 2000 m 2 / g. The activated carbon layer 28 has a combined weight per unit area of about 215 g / m 2, wherein about 15 g / m 2 are dispensed with as the binder. Above the activated carbon layer 28 a protective layer 32 is arranged which in the example shown consists of a non-conductive polyester spunbonded nonwoven. Between the protective layer 32 and the first conductor layer 14 there is also arranged the particle filter layer 30, which in the example shown in FIG. 5 is designed as a needle-punched fleece, which consists entirely of a dielectric plastic.Reference numerals denote reference numerals10 Filter insert 12 multilayer filter medium 14 first conductor layer 16 filter layer 18 electrical contact-making system 20 first contact-making element 22 first plastic material 24 second conductor layer 26 second contact-making element 28 activated carbon layer 30 particle filter layer 32 protective layer 34 substrate 36 lamination 38a, 38b contact points 40 resistance path 42a, 42b projections 44 machine-readable information markingReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedWO 2007 / 135232 A1

[0006] EP 3 448 540 B1

[0006] Cited Non-Patent LiteratureDIN EN ISO 3915

[0059]

Claims

Filter insert (10) for use in an electrostatic separator with filter functionality, comprising: i) a multilayer filter medium (12) comprising: i.1) an electrically conductive first conductor layer (14), and i.2) a filter layer (16), wherein the filter layer (16) comprises at least one dielectric layer, and ii) an electrical contacting system (18) for connecting the filter insert (10) to a voltage source, comprising a first contacting element (20), wherein the electrical contacting system (18) contacts the first conductor layer (14) via the first contacting element (20), wherein the electrically conductive connection between the first contacting element (20) and the first conductor layer (14) is effected at least partially by an electrically conductive first plastic material (22), which connects the first contacting element (20) and the first conductor layer (14) in a materially integral manner, and wherein the first plastic material (22) has a specific electrical resistance of 10 6 Ω*m or less at 20° C.The filter cartridge (10) of claim 1, wherein the multi-layer filter media (12) additionally comprises: i.3) an electrically conductive second conductor layer (24), wherein the filter layer (16) is disposed between the first conductor layer (14) and the second conductor layer (24).Filter insert (10) according to claim 2, wherein the electrical contacting system (18) comprises a second contacting element (26), wherein the electrical contacting system (18) contacts the second conductor layer (24) via the second contacting element (26), wherein the electrically conductive connection between the second contacting element (26) and the second conductor layer (24) is effected at least partially by an electrically conductive second plastic material, wherein the second plastic material has a specific electrical resistance of 10 6 Ω*m or less at 20°C.Filter insert (10) according to one of claims 1 to 3, wherein the first plastic material (22) and / or the second plastic material has a specific electrical resistance of 10 5 Ω*m or less at 20°C.Filter insert (10) according to one of claims 1 to 4, wherein the first plastic material (22) and / or the second plastic material forms a plastic strip or a grid structure.Filter insert (10) according to one of Claims 1 to 5, wherein the electrically conductive components of the electrical contacting system (18) are conductive components arranged on a substrate (34) and / or in a substrate (34).Filter insert (10) according to one of Claims 1 to 6, wherein the electrically conductive components of the electrical contacting system (18) are formed at least partially by an electrically conductive plastic.Filter insert (10) according to one of Claims 1 to 7, wherein the electrical contact-making system (18) contacts the first conductor layer (14) with the side of the substrate (28) facing away from the first contact-making element (20), wherein the electrically conductive connection between the first contact-making element (20) and the first conductor layer (14) is effected substantially completely through the first plastic material (22).Filter insert (10) according to one of Claims 1 to 8, wherein the electrical contact-making system (18) is a voltage divider.Electrostatic precipitator comprising: I) a filter insert (10) according to any one of claims 1 to 9, and II) an ionization device for ionizing components of the fluid to be filtered.Method for producing a filter insert (10) according to one of Claims 1 to 9 or an electrostatic separator according to Claim 10, comprising the method steps: a) producing or providing the multilayer filter medium (12), b) arranging the first contacting element (20) on the first conductor layer (14), c) applying a first adhesive for connecting the first contacting element (20) and the first conductor layer (14), and d) curing the first adhesive for obtaining the electrically conductive first plastic material (22) and for producing an electrically conductive, materially bonded connection between the first contacting element (20) and the first conductor layer (14).

Images