Filter insert for use in electrostatic separators

Abstract

The invention relates to a filter insert (10) for use in an electrostatic separator with a 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), the filter layer (16) comprising at least one dielectric layer, and ii) an electrical contact-making system (18) for connecting the filter insert (10) to a voltage source, comprising a first contact-making element (20), the electrical contact-making system (18) making contact with the first conductor layer (14) via the first contact-making element (20), the electrically conductive connection between the first contact-making element (20) and the first conductor layer (14) being established at least in part by an electrically conductive first plastics material (22), which integrally connects the first contact-making element (20) and the first conductor layer (14), and the first plastics material (22) at 20°C having a specific electrical resistance of 106 Ω*m or less.

Description

[0001] Filter insert for use in electrostatic precipitators

[0002] Description

[0003] The invention relates to a filter insert for use in an electrostatic precipitator with filter functionality and a corresponding electrostatic precipitator comprising such a filter insert as well as a method for producing a corresponding filter insert.

[0004] Modern filtration technology now offers numerous efficient alternatives and further developments to the well-known processes for separating unwanted components from fluid flows, which are mostly based on essentially mechanical separation, usually on a partially permeable filter element, which can, for example, consist of a porous material.

[0005] One of these developments, which is used particularly for gas purification, is so-called electrostatic precipitation, whereby the devices used are also known as electrostatic precipitators. In these electrostatic precipitators, the particles to be removed are first ionized by an electrode and then deposited on an oppositely charged collecting electrode. Such electrostatic precipitators are used primarily in industrial plants.

[0006] However, other requirements are placed on the performance characteristics of cabin air filters, particularly for use in vehicles, whereby, for example, the reliable separation of pollen and / or particulate matter and / or odors and / or exhaust gases is also desired.

[0007] To meet these requirements for cabin air filters, the concept of electrostatic separation, which in many cases is not strictly speaking filtration, was combined with mechanical separation processes to obtain high-performance filter elements. By combining conventional filter materials with an ionization device, the separation efficiency of filters can be significantly increased in many cases. For the purpose of clear identification, the corresponding filter elements are referred to as electrostatic precipitators with filter functionality within the scope of the present invention. However, it has been observed that the separation efficiency of such filter elements can decrease over the service life of the filter element, which is often attributed to a reduction in the electrostatic charge in the filter material over time.

[0008] To solve this problem, it has been proposed to design electrostatic precipitators with filter functionality in such a way that polarization of the filter material can be induced in the filter insert by applying a voltage to two polarization elements through the creation of an electric field. In combination with an ionization device, this polarization of the filter material can enable efficient separation, which can advantageously usually be maintained 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.

[0009] Particularly advantageous designs of these electrostatic precipitators with filter functionality can be achieved 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 multi-layer 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 or with a second electrically conductive conductor layer, determine the polarization of a dielectric filter material.By at least partially integrating the polarization elements into the filter medium and thus the filter insert, high-performance filter inserts are obtained which, in particular, have an advantageous weight and make it possible to reduce or even completely eliminate the requirements for the equipment 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.

[0010] However, the fundamentally advantageous design of filter media or filter inserts with integrated electrically conductive conductor layers also presents challenges, particularly in large-scale production. To ensure the desired functionality of the electrically conductive conductor layers, it is necessary to reliably electrically contact the electrically conductive conductor layers without adversely affecting the time and cost efficiency of production.

[0011] Precise and reliable contacting is made more difficult by the fact that the electrically conductive layer must be designed as a porous or permeable material in view of the required air permeability and can, for example, comprise a textile fabric, such as a fleece, whose reliable electrical contacting is not trivial, especially since this contacting must be adapted to high voltages.

[0012] In addition, the electrically conductive layer can consist at least partially of a layer of particulate material, such as activated carbon, or the necessary electrical conductivity can result from a coating, such as a coating with carbon black. In these cases, the electrically conductive layer is comparatively susceptible to strong mechanical stresses, which can lead to destruction of the layer or coating, especially during manufacturing.

[0013] In addition, the multi-layer filter media in corresponding filter inserts are usually used as pleated filter media, so that reliable contacting can also be made more difficult by the complex geometric shape of the folded conductive layer, which additionally hinders large-area contacting in particular.

[0014] 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 in most cases non-metallic or at least not exclusively metallic conductor layers can be problematic due to the different material properties, in particular with regard to durability, especially under different thermal loads, when different thermal expansion coefficients in the contact area have a detrimental effect.

[0015] From a manufacturing perspective, the typical nature of corresponding conductor layers and the physico-chemical properties of the materials give rise to the additional problem that there is a functional upper limit for the processing temperature during contacting to ensure that the conductor layers are not damaged during contacting. Furthermore, a further challenge from a manufacturing perspective is that the means and methods used to contact the conductor layer in the relatively thin and fluid-permeable multi-layer filter media must not lead to undesired contact between the conductor layer and the second polarization layer through the dielectric filter material. This is particularly challenging in designs in which polarization occurs via two conductor layers in the filter medium, i.e., without a vehicle-side polarization element.

[0016] The primary object of the present invention was to eliminate or at least mitigate the disadvantages of the prior art.

[0017] In particular, it was an object of the present invention to provide an advantageous filter insert with at least one conductor layer integrated into the filter medium, which is particularly efficient when used in an electrostatic precipitator with filter functionality and with which particularly good separation performance can be achieved, particularly in combination with an ionization device. Accordingly, it was also an object of the invention to provide an electrostatic precipitator based on this.

[0018] One object of the present invention was that the electrical contacting of the conductor layer of the filter medium in the filter insert should be particularly reliable and effective.

[0019] In this respect, a further object of the present invention was to ensure that the electrical contact in the specified filter insert was highly durable and that the electrical contact of the conductor layer was ensured even for high voltages under typical vehicle operating conditions, with particular emphasis on ensuring excellent resistance to typical mechanical stresses occurring during vehicle operation. Furthermore, the specified filter insert should ideally be designed so that even significant temperature changes do not lead to weak points in the contact area.

[0020] 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 carried out in a particularly time- and cost-efficient manner, so that the filter inserts to be specified can be produced particularly efficiently, in particular also in large quantities in an automated production process, wherein it was a supplementary object of the present invention to also specify a method for producing the filter inserts to be specified.

[0021] A further additional object of the present invention was that the manufacturing method to be specified should ensure efficient and reliable contacting of the conductor layers for a wide variety of conductor layers, in particular for those conductor layers that are more difficult to contact using conventional methods due to their physicochemical properties and / or their structure and / or their shape. In this respect, it was desirable that the manufacturing method to be specified should make it possible to avoid unwanted damage to the conductor layer and the formation of unwanted contacts between the polarization elements as far as possible.

[0022] The inventors of the present invention have found that the objects described above can be achieved in an advantageous manner if the contacting of the conductor layer and the contacting element provided for the contacting is carried out using an electrically conductive adhesive which, after curing, results in an electrically conductive plastic material and creates a material-to-material connection between the conductor layer and the contacting element, as defined in the claims.

[0023] This results in an advantageous manufacturing process which results in high-performance filter inserts in a particularly time- and cost-efficient manner, which have a reliable and resilient contact of the conductor layer, which has a high durability, especially under typical vehicle operating conditions and temperatures, especially at high polarization voltages.

[0024] The above-mentioned objects are accordingly achieved by the subject matter of the invention as defined in the claims. Preferred embodiments of the invention emerge from the subclaims and the following statements.

[0025] Such embodiments, which are referred to as preferred below, 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 as particularly preferred below are therefore very particularly preferred. Likewise preferred are embodiments in which a feature of an embodiment referred to as preferred to any extent is combined with one or more further features of other embodiments referred to as preferred to any extent. Features of preferred electrostatic precipitators and methods emerge 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 multi-layer filter medium comprising:

[0026] 1.1) an electrically conductive first conductor layer, and

[0027] 1.2) a filter layer, wherein the filter layer comprises at least one dielectric layer, and ii) 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 made by an electrically conductive first plastic material, which connects the first contacting element and the first conductor layer in a material-to-material manner, and wherein the first plastic material has a specific electrical resistance of 10 6 Q*m or less.

[0028] The invention relates to a filter insert intended for use in an electrostatic precipitator with filter functionality and combined therein with an ionization device for which the filter insert according to the invention can function as a collecting electrode. The term "filter insert" particularly expresses that it is an object that, with regard to its intended use, is intended to be arranged in a filter module, in particular a filter module of a vehicle, in a reversible and non-destructively replaceable manner.

[0029] The filter insert according to the invention comprises a multi-layer filter medium comprising at least one electrically conductive first conductor layer. This first conductor layer is intended to act as a polarization element in the polarization of the filter layer provided in the multi-layer filter medium. Those skilled in the art will understand that, in addition to the first conductor layer, a second polarization element is required for the polarization of the filter layer, in particular the electrical layer within the filter layer, so that a voltage difference can be applied between the first conductor layer and this second polarization element, thereby creating an electric field.

[0030] In a first embodiment, the second polarization element can be formed by an element separate from the filter insert, which, for example, is part of a vehicle filtration module and can be designed, for example, as a metallic plate. The advantage of this design is that the second polarization element is relocated outside the replaceable filter insert. This not only reduces the weight of the filter inserts according to the invention but also simplifies their construction. Furthermore, the amount of waste generated when replacing a used filter insert is reduced.

[0031] Even though it may be advantageous for certain embodiments to provide the second polarization element outside the filter insert according to the invention, the inventors consider it particularly advantageous in practice to integrate the second polarization element into the filter insert. While it would theoretically be conceivable to provide the second polarization element as a separate element from the multi-layer filter medium, for example again as a metallic plate, this is less preferred with regard to the overall weight. In this respect, the inventors consider it particularly advantageous for essentially all embodiments if the second polarization element for polarization is also integrated into the multi-layer filter medium, so that the multi-layer filter medium comprises a first conductor layer as well as a second conductor layer, and the filter layer can be arranged between this first conductor layer and the second conductor layer.A corresponding design of the multi-layer filter medium is associated with only a slight increase in weight and leads to a beneficial polarization effect on the filter layer arranged directly between the conductor layers. In addition, this makes it possible to integrate all the parts required for the polarization effect into the replaceable filter insert without high additional costs and without requiring additional installation space. This advantageously means that when the filter insert is replaced, all the components required for the proper functioning of the polarization are replaced, thus advantageously enabling simple maintenance of the entire system. Accordingly, a filter insert according to the invention is 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.

[0032] The electrical contacting of the second conductor layer can in particular also be effected via the electrical contacting system, so that the need for additional voltage sources for electrically connecting the second conductor layer is advantageously eliminated. Accordingly, a filter insert according to the invention is preferred, 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. Accordingly, this is 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.

[0033] In most applications, it is advantageous for cost- and time-efficient production to design the electrical connection between the second contacting element and the second conductor layer in the same way as the electrical connection between the first conductor layer and the first contacting 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 made by an electrically conductive second plastic material, wherein the second plastic material has a specific electrical resistance of 10 6 Q*m or less. A filter insert according to the invention is preferred, wherein the first plastic material and the second plastic material are of the same type.

[0034] In filter inserts according to the invention, the multilayer filter medium is preferably used in pleated form in order to maximize the inflow area available for fluid filtration. 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 lamination. A filter insert according to the invention is preferred, wherein the filter insert comprises the multilayer filter medium as a pleated filter medium. Additionally 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 long sides, and most particularly preferably all sides, are laminated with a lamination material, wherein the lamination material is preferably selected from the group consisting of textile fabrics, in particular nonwovens and felts.

[0035] 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 required for polarization, which is applied to the filter insert from the outside, to the polarization elements. In the context of the present invention, the corresponding structure is referred to as an electrical contacting system, which is designed to electrically connect the parts of the polarization system provided in the filter insert according to the invention, ie in particular the first conductor layer, 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.Additionally or alternatively, with regard to 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 by a material bond. Regardless of the specific design of the electrical contacting system, it will comprise a first contacting element, which is intended to establish an electrically conductive contact with the first conductor layer of the multi-layer filter medium.

[0036] According to the invention, the necessary contacting is achieved via an electrically conductive first plastic material, which creates a material bond between the first contacting element and the first conductor layer. The electrically conductive plastic of the filter insert according to the invention is obtained by bonding and can be understood as a cured electrically conductive adhesive. In the course of development, the inventors succeeded in identifying particularly suitable adhesive types with which the necessary electrical contacting via the electrically conductive plastic material can be advantageously realized.

[0037] According to the inventors, excellent results are achieved, in particular, with hot melt adhesives, also known as "hot melts." Such thermoplastics are liquefied at a temperature close to the melting point 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 for the first conductor layer, in particular plastic nonwovens, the inventors propose using hot melt adhesives whose melting point is not too high, so that the thermal stress on the first conductor layers used is not too high.Therefore, 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 thermoplastics, preferably from the group consisting of thermoplastics with 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 process.

[0038] The inventors have identified the use of curable adhesives as a powerful alternative to hot melt adhesives. Such curable adhesives have not yet reached their maximum degree of crosslinking in their applied state, but they also contain suitable initiators that can further crosslink the bonds provided in the adhesive. According to the inventors' findings, radiation-curable adhesives, in which further crosslinking can be triggered, 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 regard.In this respect, however, the inventors consider the use of radiation-curing adhesives to be preferred because they offer processing advantages, as no mixing of two or more components is required and the activation of the curing can be better controlled. The plastic materials obtained by curing curable adhesives are usually thermosetting plastics, which do not exhibit thermoplastic behavior. The advantage of using curable adhesives is that the connected conductor layers essentially do not have to experience any thermal stress and no devices for hot bonding need to be provided. 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-curable adhesive or a two-component adhesive. The electrically conductive connection between the first contacting element and the first conductor layer created by bonding during production is made at least partially by the electrically conductive first plastic material, which expresses that direct contact can sometimes occur between the first conductor layer and the contacting element, for example when these two components are fixed in contact with one another by the electrically conductive first plastic material.However, in the inventors' opinion, electrical contacts that rely on direct contact between the contacting element and the conductor layer are less preferred, particularly with regard to their resistance to mechanical stresses, such as those that occur during vehicle operation, and / or stresses that can result from thermal stresses on the different materials. Accordingly, it is preferred if the electrical contact between the contacting element and the conductor layer is made essentially entirely through the first plastic material.

[0039] Those skilled in the art understand that for electrical contact between the conductor layer and the contacting element, the plastic material must have a certain electrical conductivity. This functional minimum requirement for the electrical conductivity of the plastic material is characterized above by the specification of the material's resistivity. However, in the inventors' opinion, it is advantageous to select plastic materials that exhibit even better electrical conductivity and correspondingly lower resistivity, for example, through the addition of conductive components, particularly carbon black.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 a specific electrical resistance of 10 at 20 °C. 5 Q*m or less, preferably 10 4 Q*m or less. In their own experiments, the inventors have also identified advantageous parameters for the mechanical properties of the electrically conductive plastic material, which result in a high resistance of the bond, particularly under the loads occurring during typical vehicle operation. 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 1 N / mm 2or more. Also preferred is a filter insert according to the invention, 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.

[0040] The preferred shape of the plastic material in the filter insert according to the invention, and thus the preferred application pattern of the adhesive in the manufacturing process, results from process-related considerations that the inventors identified as particularly advantageous for the manufacturing process. The inventors recognized that there is a conflict of objectives between several aspects that cannot be perfectly resolved in the same way. On the one hand, it is desired to achieve reliable, large-area contact between the conductor layer via the plastic material, with a large bonding surface also advantageously usually providing high bond strength.On the other hand, the bonding surface also reduces the filtration area available for fluid filtration and disadvantageously increases the overall weight of the filter insert as well as the amount of adhesive required during production, which indirectly results in an increase in costs.

[0041] The inventors have found that the application of comparatively thin plastic strips or a grid structure comprising a plurality of overlapping such plastic strips advantageously results in very reliable and durable connections that 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 composed of a plurality of plastic strips, or a grid of a plurality of plastic dots, preferably a plastic strip, wherein the width of the plastic strip orthogonal to the longitudinal direction preferably corresponds to 30% or less, particularly preferably 20% or less, and most particularly preferably 10% or less, of the length of the plastic strip.

[0042] Furthermore, the inventors have found that when implementing the electrical contact via the plastic material to the conductor layer, it is advantageously possible to use relatively little material without adversely affecting the polarization capability. 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 that corresponds to 20% or less, preferably 10% or less, particularly preferably 5% or less, of the length of the filter insert.

[0043] The inventors have succeeded in identifying particularly advantageous orientations for the adhesive structure made of plastic material. In their experiments, particularly advantageous results were achieved when the adhesive was applied either along the folds, in particular along the back of the fold, or across the folds, so that it extends across multiple backs of the pleated material. While application along a filter fold enables a particularly advantageous continuous connection, bonding spanning the folds advantageously results in the conductor layer being contacted at multiple spaced-apart adhesive points, so that contact is made at multiple spaced-apart points relative to the surface of the unfolded conductor layer, which advantageously compensates for the occurrence of local defects.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 transverse to the pleat direction of the pleated filter element. Additionally 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 points spaced apart from one another along the conductor layer, wherein the spaced-apart adhesive points are preferably the bending points of the pleated multi-layer filter element.

[0044] At least theoretically, it would be conceivable to apply the adhesive used to form the plastic material directly between the conductor layer and the contact element to thereby create the desired bonded connection. However, the inventors have found that, particularly from a manufacturing perspective and with regard to the quality of the electronic contact, it is preferable to cover the contact element positioned on the conductor layer with the adhesive, so that the bonded connection is achieved through the material extending laterally beyond the contact 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 multi-layer filter medium.

[0045] The electrical contacting system to be provided according to the invention can be designed by a person skilled in the art in accordance with the respective application requirements and the design specifications of the filter module, in particular the vehicle filter module. For essentially 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 designs of the electrical contacting system are theoretically conceivable, which, for example, make use of cables, the inventors have designed a particularly advantageous electrical contacting system with a view to time- and cost-efficient production, which results in particularly synergistic advantages when the electrical contact is made by bonding using an electrically conductive plastic material.In the inventors' opinion, it is particularly advantageous if traditional electrical cabling is not used or is used only to a limited extent, but rather the contacting system is designed as largely as possible from components which themselves consist of an electrically conductive plastic. Accordingly, a filter insert according to the invention is preferred, wherein the electrically conductive components of the electrical contacting system are formed at least partially, preferably predominantly, particularly preferably substantially completely, from 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 of 10 at 20°C. 6 Q*m or less, preferably 10 5 Q*m or less, more preferably 10 4 Q*m or less.

[0046] According to the inventors' assessment, these electrically conductive components, which preferably consist of an electrically conductive plastic, should be arranged on a preferably thin substrate, which acts as a carrier and advantageously enables the electrically conductive components of the electrical contacting system to be assembled before attachment to the filter insert according to the invention and to be applied in a single step during the manufacturing process, for example, to the lateral lamination of the filter insert. Accordingly, a filter insert according to the invention is preferred, wherein the electrically conductive components of the electrical contacting system are conductive components arranged on a substrate and / or in a substrate.Additionally 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 pm, particularly preferably in the range from 80 to 150 pm.

[0047] The use of a thin substrate, in particular a film, in combination with conductive components made of plastic, advantageously allows the electrical contacting system to be designed not only in a particularly space-saving and lightweight manner, but also results in an electrical contacting system with a high degree of flexibility, in which the substrate and the conductive components lying thereon can be particularly easily adapted to the structural requirements of the filter insert according to the invention and whereby a low-stress bonding with the conductive plastic material can be realized in a synergistic manner.

[0048] The inventors' experiments have shown, in particular, that a corresponding electrical contact system can be advantageously printed onto the substrate, although, at least theoretically, other additive manufacturing processes could also be considered. Thus, a filter insert according to the invention is preferred, wherein the electrical contact system can be produced by printing the substrate with an electrically conductive material, preferably an electrically conductive plastic, wherein the printing is preferably a screen printing process.

[0049] In particular, additive manufacturing processes advantageously make it possible to obtain an electrical contacting system that is provided with the electrically conductive components only on one side and consequently has a bottom side whose properties are largely influenced by those of the substrate, which can advantageously be designed as an electrically insulating substrate. With regard to attachment, a filter insert according to the invention is therefore 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 whose central region essential elements of the electrical contacting system are arranged, for example, the contact points for the external voltage source or a potential voltage divider. The inventors propose that wing-like or tab-like projections can be formed on the sides, onto which the contacting elements intended for contacting the conductor layers are applied.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 then be glued with the electrically conductive adhesive in such a way that the material-to-material connection is established by the plastic material without this connection being made more difficult by excessive mechanical stresses.Accordingly, 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 arranged on laterally projecting projections of the substrate, wherein the laterally projecting projections preferably have a deformation region and a contact region, wherein the contact region is preferably wider than the deformation region transversely to the longitudinal direction of the filter insert. A filter insert according to the invention is particularly preferred, wherein the laterally projecting projections are L-shaped. Additionally or alternatively, a filter insert according to the invention is particularly preferred, wherein the laterally projecting projections are designed to be reversibly and non-destructively deformable, in particular bendable, in the deformation region.Additionally or alternatively, a filter insert according to the invention is also particularly preferred, 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.

[0050] In this embodiment, the conductor layer advantageously does not directly contact the contacting element, since the substrate lies between them. The electrically conductive contact is therefore essentially entirely realized by the electrically conductive plastic material, which can be glued over the contact area of ​​the laterally protruding projection.In this preferred embodiment, it is a filter insert according to the invention, 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 made substantially entirely by 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 made substantially entirely by the second plastic material.

[0051] The filter inserts according to the invention are intended to be combined with an ionization device for later use in an electrostatic precipitator with filter functionality. The voltage required for ionization will generally be significantly higher than the polarization voltage necessary or the maximum applicable polarization voltage, which is limited, particularly when both polarization elements are integrated into the multilayer filter medium, by the voltage at which undesirable breakdown occurs. 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 not possible in many cases or involves considerable equipment complexity, so that such a design is less preferred.For this purpose, it is proposed to design the electrical contacting system as a voltage divider, with which a voltage taken over from the ionization device can be adapted to the requirements of the filter insert. A filter insert according to the invention is therefore preferred, wherein the electrical contacting system is a voltage divider. For this purpose, the electrical contacting system can have contact points which are intended to be 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 resistance path applied to the first contacting element orThe voltage possibly omitted by the second contacting element can advantageously be 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 connected to the second contact point via a resistance path, wherein the first contacting element is electrically connected to the resistance path between the first contact point and the second contact point, and wherein the second contacting element is electrically connected to the second contact point.Additionally or alternatively, a filter insert according to the invention is also preferred, wherein the resistance path is of meandering design. Additionally or alternatively, a filter insert according to the invention is further 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 resistance path in such a way that the contact area between the resistance path and the contacting element is larger than the cross-section of the resistance path orthogonal to the longitudinal direction of the resistance path. Additionally or alternatively, a filter insert according to the invention is also preferred, wherein the second contacting element is not electrically conductively connected to the resistance path between the first contact point and the second contact point.

[0052] 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 side lamination of the filter insert, it is particularly easy to read from the outside. This makes it possible to provide the customer or the workshop with important information about the handling and / or installation of corresponding filter inserts according to the invention. Furthermore, it is possible to access the machine-readable information marking already during the production of the filter inserts according to the invention, for example if the information stored therein includes instructions on the control of the devices and / or the material selection.Within the scope of the present invention, the inventors consider it particularly advantageous if the stored information contains process instructions regarding which electrically conductive adhesive should be used and in which application pattern this adhesive is required for optimal fixation 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 work instructions regarding the application position of the electrical contacting system in the filter insert and / or the process parameters for connecting the contact elements to the corresponding conductor layers using the corresponding adhesive.

[0053] The inventors have succeeded in identifying preferred embodiments for the multi-layer filter medium to be used according to the invention and its individual layers, in particular the conductor layers, wherein particularly advantageous results could be achieved, in particular for the embodiments of the conductor layers referred to below as preferred, using electrically conductive adhesives.

[0054] Firstly, a filter insert according to the invention is preferred, wherein the first conductor layer comprises a first textile fabric, preferably a first textile fabric coated or impregnated at least in sections with an electrically conductive first material, and / or wherein the second conductor layer comprises a second textile fabric, preferably a second textile fabric coated or impregnated at least in sections with an electrically conductive second material. The term "textile fabric" is clear to the person skilled in the art and refers to two-dimensional textile products which may, for example, be woven, warp-knitted, needle-punched or knitted. In accordance with the understanding of the person skilled in the art, non-textile, fiber-containing fabrics, for example paper and cardboard, in which the fibers are held together, for example, primarily by binding agents, are not considered textile fabrics.Even though a wide range of textile fabrics could in principle be considered for the textile fabrics of the conductor layers, the inventors have been able to achieve the best performance characteristics with so-called "non-woven" materials, and in particular with spunbonded fabrics. A corresponding textile fabric made of a non-conductive material can advantageously be achieved by equipping the textile fabric with a conductive material, whereby, in the opinion of the inventors, a variety of possible methods are suitable in principle. Thus, a filter insert according to the invention is 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 fabric, preferably a spunbonded fabric.

[0055] In practice, the person skilled in the art readily distinguishes between an electrically conductive material and an electrically insulating material based on his or her expert and clear technical understanding of these terms. In this respect, a material is considered to be electrically conductive within the scope of the present invention in particular if its specific electrical resistance at 20 °C is 10 6 Q*m or less, preferably at 10 5 Q*m or less, particularly preferably 10 4 Q*m or less. Conversely, a material is considered to be an electrically insulating material within the scope of the present invention if its specific electrical resistance at 20 °C is 10 7 Q*m or more, preferably at 10 9 Q*m or more, particularly preferably at 10 11Q*m or more. Accordingly, metals and alloys, as well as carbon blacks, in particular conductive carbon black, and plastics made conductive by additives, are electrically conductive materials, whereas typical, unmodified plastics such as PET or PE are also electrically insulating materials, as are most glasses and ceramics. The specific electrical resistance of materials is a value that is well known to those skilled in the art and can be found in relevant tables for most materials. The measurement of the specific electrical resistance of other components is carried out in accordance with common 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 for high specific electrical resistances.The question of which of the two standards should be used depends on the requirements of the two regulations as well as the properties of the respective material being examined.

[0056] Those skilled in the art will understand that the electrical conductivity of conductor layers, for example, the first conductor layer, can in many cases, for example, when using composite materials, result from the presence of conductive material paths running through an otherwise largely insulating material. For example, a dielectric fleece whose fibers are coated with a thin layer of conductive carbon black can be an electrically conductive layer, even though the macroscopic resistivity of the composite material is relatively high due to the dielectric carrier material.

[0057] Furthermore, additionally or alternatively, a filter insert according to the invention is 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 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 textile fabric, 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, especially preferably polyethylene terephthalate.

[0058] Additionally 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, are produced or can be produced by equipping the respective textile fabric, in particular the nonwoven fabric, with the respective electrically conductive material using a process selected from the group consisting of impregnation, dip coating, in particular using a padding system, spray coating, application coating, in particular by means of a dispersion in the kiss-coat process, and print coating.

[0059] Additionally or alternatively, a filter insert according to the invention is also 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.

[0060] Additionally 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, are electrically conductive as a result of the coating of the respective textile fabric at least over 80% or more of the area, preferably over 90% or more, particularly preferably over 95% or more, very particularly preferably over 98% or more, particularly preferably substantially over the entire area.

[0061] Even though the conductor layers can contribute to the filtration performance of the filter media, particularly when designed as textile fabrics, the inventors consider it advantageous if the conductor layers are designed with sufficient open pores so that they primarily restrict the air flow through the filter medium as little as possible. With regard to the weight of the conductor layers, at least when using textile fabrics, there is a trade-off between the influence on the overall weight of the filter medium and a beneficial stabilizing effect of the conductor layers on the filter medium, thus improving the mechanical properties. In this respect, the inventors have succeeded in identifying suitable basis weights for the textile fabrics that advantageously resolve this trade-off.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 in the range of 500 to 30,000 L / (m) at 200 Pa. 2 s), preferably in the range of 2000 to 20000 L / (m 2 s). Additionally 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 of 5 to 200 g / m 2 , preferably in the range of 10 to 150 g / m 2 , particularly preferably in the range of 15 to 50 g / m 2 , have.

[0062] With regard to the general structure of the multi-layer 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.

[0063] Additionally 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 essentially 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, polytetrafluoroethylene-propylene, polypropylene, and polyethylene, polyesters, in particular polyethylene terephthalate, polycarbonates, polyamides, polyvinylidene fluoride, polyacrylonitrile, and polylactides.Additionally or alternatively, a filter insert according to the invention is particularly preferred, wherein the dielectric plastic material has a specific electrical resistance at 20 °C of 10. 7 Q*m or more, preferably at 10 9 Q*m or more, particularly preferably at 10 11 Q*m or more.

[0064] For the majority of embodiments, a filter insert according to the invention is preferred, wherein at least one of the dielectric layers is a particle filter layer comprising a third textile fabric. A filter insert according to the invention is particularly preferred, 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. Additionally or alternatively, a filter insert according to the invention is particularly preferred, wherein the particle filter layer has a basis weight in the range of 10 to 200 g / m2 , preferably in the range of 15 to 150 g / m 2 , particularly preferably in the range of 20 to 110 g / m 2 , has.

[0065] A filter insert according to the invention is preferred, in particular for multi-layer filter media containing activated carbon, wherein at least one of the dielectric layers is a protective layer which comprises a fourth textile fabric. A multi-layer filter medium according to the invention is particularly preferred, wherein the fourth textile fabric is a nonwoven fabric, preferably a spunbonded fabric.

[0066] Additionally or alternatively, a filter insert according to the invention is preferred, wherein the protective layer at 200 Pa has an air passage in the range of 500 to 30,000 L / (m 2 s), preferably in the range of 2000 to 20000 L / (m 2 s). Additionally or alternatively, a filter insert according to the invention is also preferred, wherein the protective layer has a basis weight in the range of 15 to 400 g / m2 , preferably in the range of 50 to 200 g / m 2 , is preferred. Additionally or alternatively, a filter insert according to the invention is again preferred, wherein the protective layer comprises one or more active ingredients selected from the group consisting of anti-allergenic active ingredients and biocidal active ingredients. Additionally or alternatively, a filter insert according to the invention is also particularly preferred, wherein the protective layer has a Gurley 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. In the opinion of the inventors, for the majority of the embodiments, additionally or alternatively, a filter insert according to the invention is also preferred, 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.

[0067] Activated carbon is known to those skilled in the art in the field of filtration technology as an important material and is commercially available from numerous manufacturers. It is preferred that the activated carbon layer be formed from a high mass fraction of activated carbon, so that, for example, the proportion of fibers or other carrier materials in the activated carbon layer should be kept as low as possible. Based on the inventors' experiments, this achieves a particularly good separation effect or cleaning performance while simultaneously minimizing thickness and weight. The inventors have found that particularly efficient filter inserts can be obtained with activated carbon layers that are as pure as possible, which preferably consist essentially exclusively of activated carbon apart from the binder.Accordingly, a filter insert according to the invention is preferred, wherein the activated carbon layer comprises activated carbon in a mass fraction of 80% or more, preferably 90% or more, particularly preferably 95% or more, based on the mass of the activated carbon layer. Additionally 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 succeeded in identifying particularly preferred ranges for the selection of the activated carbon and for the dimensioning of the activated carbon layer, with which excellent filter performances have been achieved in their own experiments. Namely, a filter insert according to the invention is preferred, wherein the activated carbon is particulate activated carbon, wherein the activated carbon preferably has an average diameter d50 in the range from 0.1 to 4 mm, preferably in the range from 0.2 to 2 mm.Additionally 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 1000 m 2 / g or more, particularly preferably 2000 m 2 / g or more. In addition or alternatively, a filter insert according to the invention is preferred, wherein the activated carbon layer has a basis weight in the range of 50 to 1000 g / m 2 , preferably in the range of 100 to 600 g / m 2 , has.

[0068] The invention also relates to an electrostatic precipitator with filter functionality, comprising:

[0069] I) a filter insert according to the invention, and

[0070] II) an ionization device for ionizing components of the fluid to be filtered.

[0071] In accordance with the expert understanding, it is preferably an electrostatic precipitator, wherein the electrostatic precipitator is designed to cause or promote the separation of electrically charged particles, in particular ionized particles, particularly preferably particles ionized by the ionization device, upon application of a voltage between the first contact point and the second contact point of the electrical contacting system as a result of a polarization of the multi-layer filter medium.

[0072] An electrostatic precipitator according to the invention is preferred, wherein the electrostatic precipitator is an air filter, preferably an interior air filter, particularly preferably an interior air filter for vehicles, in particular for land vehicles.

[0073] Additionally or alternatively, an electrostatic precipitator according to the invention is preferred, wherein the ionization device is an electrical 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. Thus, in contrast to alternative ionization devices known from the prior art, an electrostatic precipitator according to the invention is particularly preferred, wherein the ionization device does not comprise a radiation source for ionizing radiation.Finally, the invention also relates to a method for producing a filter insert according to the invention or an electrostatic precipitator according to the invention, comprising the method steps: a) producing or providing the multi-layer 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 to obtain the electrically conductive first plastic material and to produce an electrically conductive, material-to-material connection between the first contacting element and the first conductor layer.

[0074] The first adhesive serves to produce the first plastic material, whereby the term adhesive in the context of the present invention also includes hot melt adhesives, ie hot melts.

[0075] In 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 to connect 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, material-to-material connection between the second contacting element and the second conductor layer.

[0076] Additionally or alternatively, a method according to the invention is preferred, wherein the production of the multilayer filter medium comprises pleating the multilayer filter medium. Additionally or alternatively, preferably additionally, a method according to the invention is also preferred, wherein the production of the multilayer filter medium comprises laterally laminating the pleated multilayer filter medium.

[0077] 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 selected from the group consisting of hot melt adhesives, radiation-curable adhesives, and chemically curable adhesives, preferably hot melt adhesives. A method according to the invention is particularly preferred, wherein the first adhesive and the second adhesive are preferably of the same type.

[0078] 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, has a setting time according to DIN 16920-1981-06 (surface strength) of 30 s or less, preferably 20 s or less. Additionally or alternatively, 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 dynamic viscosity in the applied 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.

[0079] 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 stripes or a grid, preferably in stripes. Additionally 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 pleat direction of the pleated filter element.In addition or alternatively, 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 such that the respective adhesive contacts the respective conductor layer at two or more, preferably three or more, adhesive points spaced apart from one another along the conductor layer, wherein the spaced-apart adhesive points are preferably the bending points of the pleated multi-layer filter element. In addition or alternatively, 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 over 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 multi-layer filter medium and the corresponding conductor layer.

[0080] A method according to the invention is preferred, additionally comprising the method step: i) connecting the electrical contacting system to the lamination of the pleated multi-layer filter medium.

[0081] The invention and preferred embodiments of the invention are explained and described in more detail below with reference to the accompanying figures. Preferred embodiments of the method according to the invention serve to produce preferred filter inserts according to the invention. The figures show:

[0082] Fig. 1 is a perspective view of a filter insert according to the invention in a preferred embodiment;

[0083] Fig. 2 is a schematic representation of an exemplary electrical contacting system in a preferred embodiment;

[0084] Fig. 3 is a representation 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;

[0085] Fig. 4 shows a representation 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 view through a multi-layer filter medium in a preferred embodiment;

[0086] Fig. 1 shows a perspective view of a filter insert 10 according to the invention, which has a pleated, multi-layer filter medium 12 secured by a felt lamination 36 on both sides. On the side wall formed by the lateral lamination 36, an electrical contact system 18 is provided. This electrical contact system is designed as a voltage divider and comprises two contact points 38a, 38b (see Fig. 2), via which a voltage can be applied from an external voltage source, for example, indirectly via an ionization device.

[0087] The details of the electrical contact system 18 are visible in Fig. 2. In the example shown in Fig. 2, the electrically conductive components of the electrical contact system 18 are formed from a plastic that is highly electrically conductive due to its high carbon black content. The electrical contact system 18, designed as a voltage divider, comprises a resistance path 40 that connects the two contact points 38a, 38b and has a meandering course in some sections.

[0088] Laterally projecting projections 42a, 42b of the thin foil substrate 34 protrude from the resistance path 40 or the contact point 38a, 38b, respectively, onto which the first contacting element 20 and the second contacting element 26 are applied. One of the contacting elements contacts the resistance path 40 at a predetermined location to tap a desired voltage value. The contacting of the first conductor layer 14 by the electrical contacting system 18 via the first contacting element 20, which is to be provided according to the invention, is shown in more detail in Figs. 3 and 4.

[0089] 3 and 4 each show how a lateral projection 42a of the electronic contacting system 18 has been folded around the lamination 36 and contacts the first conductor layer 14 with the electrically poorly conductive underside of the substrate 34. Electrical contact is only established through the use of a comparatively short and narrow strip of adhesive, which cures when hardened 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 folded projection 42a of the electrical contacting system 18 and thus over the first contacting element 20, with the preferred course transverse to the pleat direction of the pleated multi-layer filter medium 12 being selected in each case.

[0090] In Figs. 2 to 4, the machine-readable information marking 44 is also visible, which in the example shown comprises process parameters for controlling precisely those devices which, in the process according to the invention, apply the adhesive from which the material-to-material connection is produced by means of the first plastic material 22.

[0091] 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 using the same adhesive. In the example shown in Figs. 3 and 4, this adhesive is a hot-melt adhesive having 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 2and an average shear force of more than 0.4 N / mm. Particularly in conjunction with the multi-layer filter medium 12, the structure of which is explained further below with reference to Fig. 5, an advantageous filter insert 10 according to the invention results, which is not only particularly time- and cost-efficient to manufacture, but also reliably meets the functional requirements over a wide range of ambient temperatures from -40 °C to +85 °C.

[0092] Fig. 5 shows a schematic cross-sectional view through a multi-layer filter medium 12 according to the invention, which comprises a multi-layer filter layer 16 arranged between the first conductor layer 14 and the second conductor layer 24 and bonded thereto via an adhesive. Both the first conductor layer 14 and the second conductor layer 24 are formed from a PET spunbonded fabric that has been made conductive by a coating of conductive carbon black and whose basis weight is approximately 30 g / m 2 amounts.

[0093] In the example shown, the filter layer 16 comprises an activated carbon layer 28, which comprises particulate activated carbon with an average diameter of approximately 0.25 to 0.6 mm and a specific surface area of ​​approximately 2000 m 2 / g. The activated carbon layer

[0094] 28 has a combined basis weight of approximately 215 g / m 2 , with about 15 g / m 2attributable to the binder. A protective layer 32 is arranged above the activated carbon layer 28, which in the example shown consists of a non-conductive polyester spunbonded fabric. Between the protective layer 32 and the first conductive layer 14, the particle filter layer 30 is also arranged, which in the example shown in Fig. 5 is designed as a needle-punched nonwoven fabric made entirely of a dielectric plastic.

[0095]

[0096] 10 filter inserts

[0097] 12 multi-layer filter medium

[0098] 14 first conductor layer

[0099] 16 filter layer

[0100] 18 electrical contact system

[0101] 20 first contact element

[0102] 22 first plastic material

[0103] 24 second conductor layer

[0104] 26 second contacting element

[0105] 28 activated carbon layer

[0106] 30 particle filter layer

[0107] 32 protective layer

[0108] 34 Substrat

[0109] 36 Laminating

[0110] 38a, 38b Contact points

[0111] 40 resistance section

[0112] 42a, 42b projections

[0113] 44 machine-readable information markings

Claims

Claims 1. Filter insert (10) for use in an electrostatic precipitator with filter functionality, comprising: i) a multi-layer filter medium (12) comprising: 1.1) an electrically conductive first conductor layer (14), and 1.2) 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 at least partially made by an electrically conductive first plastic material (22), which connects the first contacting element (20) and the first conductor layer (14) in a material-to-material manner, and wherein the first plastic material (22) has a specific electrical resistance of 10 6 Q*m or less.

2. Filter insert (10) according to claim 1, wherein the multi-layer filter medium (12) additionally comprises: 1.3) an electrically conductive second conductor layer (24), wherein the filter layer (16) is arranged between the first conductor layer (14) and the second conductor layer (24).

3. 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 at least partially made by an electrically conductive second plastic material, wherein the second plastic material has a specific electrical resistance of 10 6 Q*m or less.

4. 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 105 Q*m or less.

5. 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.

6. 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).

7. Filter insert (10) according to one of claims 1 to 6, wherein the electrically conductive components of the electrical contacting system (18) are at least partially formed by an electrically conductive plastic.

8. Filter insert (10) according to one of claims 6 or 7, wherein the substrate (34) is an electrically insulating substrate (34).

9. Filter insert (10) according to claim 8, wherein the substrate (34) is selected from the group consisting of electrically insulating films.

10. Filter insert (10) according to one of claims 6 to 9, wherein the average thickness of the substrate (34) is in the range of 20 to 500 pm.

11. Filter insert (10) according to one of claims 6 to 10, wherein the electrical contacting system (18) contacts the first conductor layer (14) with the side of the substrate (28) facing away from the first contacting element (20), wherein the electrically conductive connection between the first contacting element (20) and the first conductor layer (14) is made substantially completely by the first plastic material (22).

12. Filter insert (10) according to one of claims 6 to 11, wherein the first contacting element (20) and / or the second contacting element (26) are arranged on laterally projecting projections (42a, 42b) of the substrate (34), wherein the laterally projecting projections (42a, 42b) have a deformation region and a contact region, wherein the laterally projecting projections (42a, 42b) are designed to be reversibly and non-destructively deformable in the deformation region, wherein the electrical contacting system (18) contacts the first conductor layer (14) with the contact region of the first contacting element (20), and / or wherein the electrical contacting system (18) contacts the second conductor layer (24) with the contact region of the second contacting element (26).

13. Filter insert (10) according to one of claims 1 to 12, wherein the electrical contacting system (18) is a voltage divider.

14. Electrostatic precipitator comprising: I) a filter insert (10) according to one of claims 1 to 13, and II) an ionization device for ionizing components of the fluid to be filtered.

15. A method for producing a filter insert (10) according to one of claims 1 to 13 or an electrostatic precipitator according to claim 14, comprising the method steps: a) producing or providing the multi-layer filter medium (12), b) arranging the first contacting element (20) on the first conductor layer (14), c) applying a first adhesive to connect the first contacting element (20) and the first conductor layer (14), and d) curing the first adhesive to obtain the electrically conductive first plastic material (22) and to produce an electrically conductive, material-to-material connection between the first contacting element (20) and the first conductor layer (14).

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