Method and device for producing substrate for exhaust gas aftertreatment device

Abstract

The invention relates to a method for producing a substrate (1) for an exhaust gas aftertreatment device, comprising the following steps: 1. Applying (S1) a coating material (12) on an elastic substrate (11) mounted over a flexible liner (21); 2. Impregnating or pressing (S2) a surface of the substrate (1) into the coating material (12), in which surface inlet openings through the through-channels (2) of the substrate (1) are arranged; 3. Lifting the coated catalyst element (1); and 4. Post-treating the coating material (12) on the coated substrate (1), and in particular drying or calcining (S3).

Description

Technical Field

[0001] The present invention relates to a method for producing a substrate for an exhaust gas aftertreatment device as a catalyst element or filter element for an internal combustion engine, and in particular to measures for preventing clogging / occlusion (also called layer clogging) at a fluid flow inlet of the catalyst element. Background Art

[0002] Exhaust gas aftertreatment devices, in particular exhaust gas aftertreatment devices in the form of catalytic converters, i.e. catalytically coated flow substrates or filters (e.g. wall-flow filters), are generally used to purify combustion exhaust gases, for example from internal combustion engines. These devices enable chemical conversion of undesirable components of the combustion exhaust gases, such as carbon monoxide, nitrogen oxides, unburned hydrocarbons, soot, etc., or filtering of the combustion exhaust gases. Generally speaking, such exhaust gas aftertreatment devices have one or more substrate bodies. The substrate body generally includes a plurality of through-channels. The through-channels extend completely through the substrate body, or in the case of a wall-flow filter, largely through the substrate body, so that the filter is formed of a porous substrate material between adjacent filter channels. The inner wall of the through-channel may be coated with a catalyst material to form a catalytic surface, on which corresponding reactions and / or absorptions may be carried out to eliminate undesirable exhaust gas components.

[0003] The through-channels are approximately parallel in the substrate and are separated from one another by walls of substrate material, in particular ceramic material. The through-channels usually have an inlet opening which is arranged on a level of the substrate. This results in the level on which the inlet openings of the through-channels are arranged having a plurality of webs, on which components of the exhaust gas, such as particles, aerosols, droplets, etc., can be deposited during operation of the exhaust gas aftertreatment element and can form downward contamination. This process is known as blocking, occlusion or sooting and is often referred to as level blockage. Level blockage occurs in particular in operating conditions in which the exhaust gas contains many soot particles or aerosols.

[0004] The exhaust gas back pressure in the exhaust gas aftertreatment device increases due to layer blockage, which can impair the efficiency of the internal combustion engine. If the layer blockage is not removed, system failures may also occur.

[0005] One option for preventing clogging of the layer is to provide the layer of the substrate with a precious metal-containing coating having enhanced catalytic properties. Such a measure is known, for example, from document EP 2171232 B1. Thus, a device for aftertreatment of engine exhaust gases is known, which includes a substrate having a honeycomb structure defining a fluid path, the fluid path being designed so that a fluid can flow through the substrate, wherein the substrate has an inlet end surface positioned at one end of the substrate, wherein the substrate is coated with a chemical coating. The chemical coating on the inlet end surface has an increased load relative to any other chemical coating on the substrate in order to prevent and / or eliminate the surface on the substrate from entering occlusion, wherein the inlet end surface includes a three-dimensional topographic configuration so that the substrate is non-planar at the inlet end, and the chemical coating is arranged on the three-dimensional topographic design.

[0006] Due to the production process of such substrates for exhaust gas aftertreatment devices, the layer on which the inlet openings of the through-channels are arranged is not flat, except for the inlet openings of the through-channels, but can have an irregular, concave or convex design. This makes it difficult to apply a layer coating which should be arranged in particular uniformly on all the web structures between the through-channels.

[0007] In this regard, document EP 3195348 B1 provides a system for depositing a surface coating on a monolithic catalytic substrate. The system includes a coating liquid applicator arranged between an inflow system and a discharge system, wherein the coating liquid applicator has an inner core and an outer protrusion with a height, and a coating liquid tank is positioned below the coating liquid applicator for receiving the entire length of the coating liquid applicator in the coating liquid tank and maintaining the coating liquid. The coating liquid tank is vertically positioned so that the protrusion of the coating liquid applicator is at least partially immersed in the coating liquid. The coating liquid applicator is driven by a motor at a certain predetermined rotational speed during operation, wherein the operation is controlled according to a sensor signal from a light sensor. During operation, a substrate coating liquid is applied to the coating liquid applicator, so that the monolithic catalytic substrate moves through the coating liquid applicator at a predetermined speed, so that a certain amount of coating liquid is transferred from the coating liquid applicator to the surface of the monolithic catalytic substrate, wherein, according to the detection of whether the light beam is blocked by the coating liquid applicator, the height of the coating liquid applicator is set at the adjusted height.

[0008] In addition, document EP 3400108 B1 discloses a method for utilizing a terminal surface of a liquid coating substrate comprising a catalyst component, wherein the substrate is conveyed to a coating roller, and the liquid is applied to the terminal surface of the substrate by contacting the terminal surface with a coating roller loaded with the liquid. The substrate is conveyed to the coating roller and comprises contacting the terminal surface of the substrate with the rotating surface of the coating roller. In this case, the terminal surface is contacted with the rotating surface of the coating roller.

[0009] The disadvantage of the above-mentioned prior art is that it does not allow for a reproducible, uniform coating of non-planar layers of the substrate. The penetration depth of the coating material into the through-channels cannot be adjusted by known manufacturing processes either.

[0010] The object of the present invention is to provide a method for coating a layer surface of a substrate having inlet openings of through-channels with a coating material which reduces layer clogging, which method enables uniform coating even in the case of non-planar layers of the substrate and enables reproducible layer thicknesses and penetration depths deep into the through-channels. Summary of the invention

[0011] This object is achieved by a method for producing a substrate for an exhaust gas aftertreatment device according to claim 1 and by a corresponding device and substrate according to the independent claims.

[0012] Further embodiments are specified in the dependent claims.

[0013] According to a first aspect, a method for producing a substrate (1) for an exhaust gas aftertreatment device comprises the following steps:

[0014] - applying (S1) a coating material (12) on an elastic substrate (11);

[0015] - dipping or pressing (S2) the surface of the substrate (1) into the coating material (12),

[0016] An inlet opening of a through-channel (2) passing through the substrate (1) is arranged in the surface;

[0017] - lifting (S3) the coated substrate (1); and

[0018] - post-treating the coating material (12) on the coated substrate (1), and in particular drying or calcining,

[0019] - wherein the elastic substrate (11) extends over a flexible pad (21) and the pad absorbs the pressure of the substrate (1) on the elastic substrate (11) so that all inlet openings of the through-channels (2) through the substrate (1) can be filled with the coating material (12)

[0020] Moisturize.

[0021] The method according to the invention is advantageously used to prevent clogging of the layer and to achieve a uniform coating with reproducible layer thicknesses and penetration depths of the coating material into the through-channels even in the case of non-planar layers of the substrate. In this case, the coating material is preferably applied to a layer of the substrate in a separate production step independently of the actual catalytic coating of the substrate. This layer corresponds to the side of the substrate at which the openings of the through-channels and in particular the inlet openings terminate in the substrate. The coating is usually carried out with a material containing precious metals. The substrate produced in this way can advantageously be used in an exhaust gas aftertreatment device having one or more substrates.

[0022] Suitable substrates are embodiments known to the person skilled in the art in the field of automotive exhaust. The through-channels may penetrate the substrate completely (so-called flow-through substrates) or, in the case of wall-flow filters, may extend into the substrate to such an extent that the porous substrate material represents an exhaust gas filter between adjacent through-channels extending in parallel. A substrate which has been catalytically coated with a catalyst material is also referred to as a catalyst element.

[0023] The flow-through substrate is a conventional catalyst element in the prior art and can be composed of metal or glass fiber reinforced paper (corrugated carrier, for example, WO17153239A1, WO16057285A1, WO15121910A1 and the literature cited therein) or ceramic material. Refractory ceramics such as cordierite, silicon carbide or aluminum titanate are preferably used. The number of channels per unit area is characterized by the pore density, which generally ranges from 300 to 900 pores per square inch (cpsi). The wall thickness of the channel wall in the ceramic is between 0.5 mm and 0.05 mm.

[0024] All ceramic materials commonly used in the prior art can be used as wall-flow filters. Preferably, porous wall-flow filter substrates made of cordierite, silicon carbide or aluminum titanate are used. These wall-flow filter substrates have inflow channels and outflow channels, wherein the respective downstream ends of the inflow channels and the respective upstream ends of the outflow channels are alternately closed by airtight "plugs". As a result, the exhaust gas to be purified and flowing through the filter substrate is forced to pass through the porous wall between the inflow channel and the outflow channel, which provides an excellent particle filtration effect. The particle filtration performance can be designed by the porosity, the pore / radius distribution and the thickness of the wall. The porosity of the wall-flow filter is generally greater than 40%, generally from 40% to 75%, and in particular from 45% to 70% [as measured according to the latest version of DIN 66133 on the date of application]. The average pore size (diameter) is at least 3 μm, for example from 3 to 34 μm, preferably greater than 5 μm, and in particular from 5 to 28 μm or from 7 to 22 μm [measured according to DIN 66134, latest version at the date of application].

[0025] The surfaces in the through-channels of the substrate may be coated with a catalyst material. The process step of coating the through-channels with a catalyst material is optional and may be performed before, during or after the process step of coating the layer according to the invention with a coating material. Between these process steps, drying, reduction and calcination steps may be performed.

[0026] The coating material (12) may contain catalytically active components and in particular a solution containing a noble metal. The coating material may be identical to the catalyst material, different therefrom or may have a modified concentration of the catalytically active components. The coating material may be produced, for example, on the basis of a solution or suspension containing a noble metal with adsorptive or non-adsorptive properties; in particular, Rh-containing, Pt-containing and Pd-containing noble metal solutions or suspensions should be mentioned here. Such a coating material then has a catalyst for the oxidation of hydrocarbons to H2O and CO2, the oxidation of CO to CO2, or may also help reduce NOx.

[0027] Thus, the catalytic function of the coating material is substantially provided by metallic Rh, Pt and / or Pd and preferably Pt and / or Pd or Rh, or Rh and Pd, which coating material may be a thickened solution or in an alternative embodiment may be supported on a high surface area support oxide.

[0028] Suitable support oxides for these catalytically active metals are, for the person skilled in the art, high surface area, temperature-stable oxides. In general, these support oxides are aluminum oxide, silicon oxide, zirconium oxide or titanium oxide, or mixtures thereof. In this context, activated aluminum oxide is particularly known to the person skilled in the art. In particular, catalysts with 100 m 2 / g to 200m 2 / g of surface gamma alumina. Activated aluminas are frequently described in the literature and are commercially available. Activated aluminas usually contain silicon oxide or lanthanum oxide as stabilizer in an amount of up to 10% by weight, relative to the alumina.

[0029] In an alternative but preferred embodiment, the catalytic function is provided by Rh, and / or Pd, and / or Pt supported on high surface area alumina and a common oxygen storage material such as cerium oxide, cerium-zirconium mixed oxide, or a mixture of La, Y, Pr, Nd doped cerium oxide or cerium-zirconium mixed oxide.

[0030] The oxygen storage material is preferably those oxygen storage materials in which cerium / zirconium / rare earth metal mixed oxides are present. Lanthanum oxide, yttrium oxide, praseodymium oxide, neodymium oxide, samarium oxide and a mixture of one or more of these metal oxides can be, for example, considered as rare earth metal oxides. Lanthanum oxide, yttrium oxide, neodymium oxide and a mixture of one or more of these metal oxides are preferred. Particularly preferred are lanthanum oxide and yttrium oxide, and in this context, a mixture of lanthanum oxide and yttrium oxide is very particularly preferred. In a very preferred embodiment, the coating material in the final catalyst element has an oxidation function, particularly for hydrocarbons, CO and soot. In this case, in addition to the aforementioned carrier oxide, Pt and / or Pd are mainly or only present in the coating material as catalytically active species.

[0031] However, the above-mentioned noble metals for coating together with the coating material may also be present as a low-viscosity solution which may be thickened.

[0032] In the present context, noble metal solutions are those in which the noble metal is dissolved in a solvent, preferably water. The person skilled in the art knows which solutions can be used in this case. The noble metal compounds used to produce the solution are in particular the following:

[0033] The palladium compound is selected from the group consisting of tetraamminepalladium(II) chloride, palladium hydroxide, palladium chloride, palladium sulfate, palladium nitrate, dinitrosodiamminepalladium(II) chloride, dinitrosodiamminepalladium(II) sulfate, palladium glycine, tetraamminepalladium(II) sulfate, bis(ethylenediamino)palladium(II) carbonate, bis(ethylenediamino)palladium(II) sulfate, bis(acetylacetonate)palladium(II), diaminedichloropalladium(II), hydrated palladium oxide, tetraamminepalladium(II) hydrogen carbonate, bis(ethylenediamino)palladium(II) chloride and palladium acetate.

[0034] The rhodium compound is selected from rhodium (III) chloride, rhodium (III) iodide, hydrated rhodium (III) oxide, rhodium (III) nitrate and rhodium (III) sulfate.

[0035] The platinum compound is selected from platinum (II) chloride, tetrachloroplatinum (II) acid H2 (PtCl4), dinitrosodiammineplatinum (II) acid and their salts, dinitrosodiammineplatinum (II), tetraammineplatinum (II) salt, platinum (II) nitrate, hexachloroplatinum (IV) acid H2 (PtCl6), hexahydroxyplatinum (IV) acid, tetraammineplatinum (II) acetate, tetraethylammonium hexahydroxyplatinum (IV), diethanolammonium hexahydroxyplatinum (IV) and their salts.

[0036] In order to adjust the viscosity of the coating material, suitable auxiliary agents such as thickeners, surfactants, acids or bases, or shear-thinning substances can be added. Those skilled in the art know how to proceed here (see, for example, EP3131660B1). For example, auxiliary materials such as methylcellulose can be added to the solution for thickening.

[0037] In addition, for the configuration of the catalyst element produced according to the present invention, the substrate can be coated with different catalyst materials and thus form different catalyst technologies. There may be multiple components installed in the exhaust system in the form of substrates with one or different catalytic or pollutant absorption catalyst technologies. The end coating according to the present invention can be applied to any component where layer blockage is expected to occur. The application and operation mode of the end coating are independent of the component function or catalyst technology. The catalyst technology may be, for example, but not limited to, a DOC catalyst, a NSC catalyst, a DPF catalyst, a three-way catalyst (TWC), an SCR catalyst, an ASC catalyst, or a combination of these technologies.

[0038] Various catalyst materials are known from the prior art, for example, zeolites with Cu, Fe, V, W, Ce, Sb, Nb, Zr, Mo, Al, Pd can be used for SCR catalysts, such as, for example, from WO 2008 / 132452 A2, WO 2019 / 096785 A1, WO 2019 / 096786 A1, WO 2022 / 058404 A1, WO 2020 / 043662 A1, WO 2015 / 075083 A1, WO 2019 / 072527 A1, WO 2019 / 072527 A1, WO 2019 / 219629 A1, WO 2020 / 039074 A1, WO 2018 / 189177 A1, WO 2017 / 134001 A1, WO 2017 / 134005A1, WO 2017 / 134006 A1, WO 2017 / 134007 A1, WO2013 / 159825A1, WO 2017 / 178576 A1, WO 2018 / 054928 A1, WO 2018 / 029330A1 and WO 2022 / 128523 A1. Catalyst materials for TWC catalysts are known, for example, from WO2022223688A1, WO2021151876A1, WO2021140326A1, WO2008000449A2, WO2008113445A1 and WO2008113457A1. The person skilled in the art knows which catalyst material he uses for the purposes of the present invention (see also, for example, WO2019121994A1, WO2019121995A1, WO9535152A1, WO2008000449A2, EP0885650A2, EP1046423A2, EP1726359A1, EP1541220A1, EP1900416B1, EP3045226A1, WO2009012348A1 and EP1974809B1).

[0039] The three-way catalyst is basically composed of the following components: a noble metal, a high surface area carrier oxide and an oxygen storage material. In most cases, they contain platinum group metals such as Pt, Pd and Rh as catalytically active components, of which Pd and Rh are particularly preferred. The catalytically active metals are usually deposited so as to be highly dispersed on the high surface area oxide and the oxygen storage material. It is particularly preferred that the noble metal is pre-fixed on the oxygen storage material before it is mixed with the other components into the coating mixture. In the case of TWC, a partitioned or layered implementation scheme is now the normal situation. In a preferred embodiment, at least one TWC in the exhaust system having a catalyst element modified according to the present invention has a 2-layer structure with two different three-way coatings, preferably as described in EP3247493A1.

[0040] Oxygen storage materials are in particular those in which cerium / zirconium / rare earth metal mixed oxides are present. Lanthanum oxide, yttrium oxide, praseodymium oxide, neodymium oxide, samarium oxide and mixtures of one or more of these metal oxides can be considered, for example, as rare earth metal oxides. Lanthanum oxide, yttrium oxide, neodymium oxide and mixtures of one or more of these metal oxides are preferred. Particularly preferred are lanthanum oxide and yttrium oxide, and in this context, mixtures of lanthanum oxide and yttrium oxide are very particularly preferred.

[0041] As support oxides for the catalytically active metals, preferably high-surface-area, temperature-stable oxides are suitable for the person skilled in the art. Generally speaking, these support oxides are aluminum oxide, silicon oxide, zirconium oxide or titanium oxide, or mixtures thereof. In this context, activated aluminum oxide is particularly known to the person skilled in the art. In particular, catalysts with a surface area of ​​100 m 2 / g to 200m 2 / g of surface gamma alumina. Activated aluminas are frequently described in the literature and are commercially available. Activated aluminas usually contain silicon oxide or lanthanum oxide as stabilizer in an amount of up to 10% by weight, relative to the alumina.

[0042] According to the invention, the layer will be coated with the coating material in such a way that only the layer surface of the mesh between the through-channels is coated with the coating material and the inner surface of the through-channels is wetted with the coating material to a maximum depth of only 0 mm to 20 mm, preferably between 0 mm and 5 mm and particularly preferably between 0 mm and 2 mm.

[0043] As a result of production, the layers of the substrate to be coated according to the invention are generally not planar, but may have a convex or concave structure or some other irregularly shaped structure relative to its axial direction. This 3D structure of the layers may also vary within a batch of substrates.

[0044] In order to be uniformly coated with the coating material, the above method provides for pressing the layers of the catalyst element into the coating material applied flat on an elastic substrate, wherein a flexible pad is located below the elastic substrate. The coating material is provided in liquid form such as a dispersion, suspension, solution, gel, etc., which coating material can be provided together with the catalytically active material mentioned above.

[0045] Provision can be made for the liquid coating material to be applied evenly and in particular with a constant layer thickness onto an elastic substrate which is aligned in particular horizontally.

[0046] Subsequently, the layer of the substrate to be coated is pressed into the elastic base. The elastic base yields when the layer of the substrate is pressed in, and the flexible pad attached underneath provides a corresponding counterpressure of the elastic base on the layer of the substrate, so that the coating material on the elastic base comes into contact with the layer over the entire surface and the coating material is thereby applied to the inner surface of the through-channel with a constant layer thickness and a constant penetration depth, despite the inhomogeneities of the layer of the substrate.

[0047] The substrate is elastically formed with a closed surface to enable elasticity of shape when the layers of the base material are pressed. The closed surface of the substrate prevents the coating material from penetrating into the material of the elastic substrate and below, and thereby ensures minimal material loss of the coating material and a longer service life of the elastic substrate.

[0048] The elastic substrate can be an elastic plastic or rubber material, and in particular a foam rubber material and a smooth and / or closed surface. This substrate will be selected so that, for example, the elongation is 1% at an applied force of 5N / cm-25N / cm and preferably 6N / cm-15N / cm (ISO 2118), or the stiffness of the material width is 50kp / cm to 200kp / cm (Shore A hardness according to DIN 53505 is 60-95 and preferably 70-90). The substrate can, for example, consist of polyester with a coating made of PVC, PU or nitrile.

[0049] In particular, materials such as, for example, foam rubber materials with a closed surface can contact the substrate. For example, chloroprene rubber, foam rubber and silicone, Ceroma ("Werkstoffeigenschaften und Schwingungsisolation Technische Informationen", RRG INDUSTRIETECHNIK GMBH, www.rrg.de) and the like can be used. The elastic properties of the foam rubber material can be, for example, between 10 and 18 and in particular 12-14 Shore A hardness (according to DIN 53505) and / or between 0.1 g / cm 3 Up to 1g / cm 3 to describe the density between them.

[0050] However, in the case of extreme inhomogeneities in the level of the substrate, it is very advantageous according to the invention if there is a function below the elastic substrate which generates an appropriate counterpressure to the elastic substrate once the substrate is pressed onto it. According to the invention, the flexible pad acts as such a unit for generating counterpressure. In this case, the flexible pad is advantageously located in a recess of a harder but non-elastic unit relative to the flexible pad and the elastic substrate, which unit is preferably a substrate plate which itself cannot slip from the pressed substrate. This helps to sufficiently stabilize the flexible pad against slipping.

[0051] The flexible pad is characterized by a flexible upper side facing the lower side of the elastic substrate. The flexible pad consists of, for example, an optional sheath and a filler. The sheath and the filler may consist of the same material. For example, a simple foam pad or a silicone pad may be used. The flexible pad is preferably selected from a plastic material, such as a silicone pad or the like. Particularly preferably, a silicone pad with a thickness of up to 10 mm and preferably 2 mm and a Shore A hardness of 60 ± 5 (according to DIN 53505) is used. Other alternatives are known to those skilled in the art.

[0052] In order to fix the flexible pad to prevent slipping, the flexible pad is preferably placed in a recess that has been incorporated into a correspondingly sized, fixed and non-elastic unit (e.g., a base plate). Preferably, the flexible pad can also be formed by a recess in the base plate that is covered by a flexible, watertight and airtight material (e.g., similar to the above-mentioned shell). This creates a cavity between the base plate and the covering, which is referred to herein as the flexible pad. The fixing must be designed in such a way that leakage of the filler from the pad is prevented. Those skilled in the art are familiar with this design process.

[0053] The filler of the flexible pad is preferably a gas such as air, or a liquid such as water or silicone oil, or a gel such as a water mixture thickened with a thickener. For example, agar, guar gum, sodium sol and methylcellulose can be used as thickeners. It is particularly preferred to use a stable water mixture. In order to stabilize the water that is preferably used, additives such as glycerol, silicone oil or similar oils can be used. The person skilled in the art is familiar with the possibilities for stabilizing the water to prevent, for example, fungus formation.

[0054] The flexible pad or the substrate plate with the flexible pad is then positioned below the elastic substrate in such a way that when the substrate is pressed into the elastic substrate, the flexible pad can exert the counter pressure above the elastic substrate required to press the coating material into the substrate. Therefore, the substrate plate (if present) must be designed and positioned according to the requirements of a person skilled in the art.

[0055] Therefore, the base plate preferably has a recess for the flexible pad or forms a flexible pad. The recess also preferably corresponds to the size of the substrate to be pressed in. The recess should be designed so that the coating material on the elastic base is pressed onto the substrate and into the substrate as soon as the substrate is pressed into the elastic base and the flexible pad. In order to stabilize the recess, it can be advantageous if the recess is surrounded by a fastening ring. This promotes hardening of the edges of the recess and thus facilitates the fixing of the flexible pad in the recess. The corresponding flexible pad in the recess of the base plate is Figure 5 is shown in plan view and in Figure 6 1 is shown in a side view together with an associated elastic base. Furthermore, it can be advantageous if the recess has a passage through the base plate via which the liner can be connected to an inlet for the filling material of the liner. Thus, the amount of filling material in the flexible liner can be quickly adapted from the outside to the specifications of a new substrate or coating material without having to insert a new liner.

[0056] The shape of the flexible pad is adapted to the substrate to be coated with the coating material. A person skilled in the art knows how to proceed here. The diameter of the recess should correspond to the shape of the substrate to be coated and its size is at least the same as or larger than the size of the substrate used and preferably 10 mm to 30 mm larger than the diameter of the substrate. The depth of the recess is preferably 2 mm to 15 mm and more preferably 2 mm to 5 mm.

[0057] In principle, the elasticity or deformability of the elastic substrate and the flexible pad can be selected so that the unevenness of the layer of the substrate causes the substrate to abut against the entire surface of the layer when pressed into the substrate, and the coating material is thus applied to the entire layer. Any macroscopic unevenness of the surface of the layer side can be compensated by the interaction of the elasticity of the substrate and the forces acting on the substrate or the catalyst element.

[0058] The entire system consisting of elastic substrate and flexible pad applies an elasticity corresponding to the substrate to be coated. The elasticity can thus be controlled particularly advantageously by the filling level of the flexible pad. This elasticity can be selected, for example, so that, in the case of a macroscopic unevenness of the layer surface of, for example, + / -3 mm and preferably + / -1.5 mm and a contact pressure of the substrate on the elastic substrate and the flexible pad of, for example, between 5 N and 150 N, the pressed surface of the substrate lies against the full surface, so that a uniform application of the coating material on all areas of the layer surface is achieved. The maximum contact force should be limited only by the mechanical stability of the substrate.

[0059] Thus, the material of the elastic substrate and the flexible pad can be selected with respect to its elasticity or deformability so that, in case the layer of the substrate has a certain degree of unevenness, the material allows the surface of the substrate to lie against the surface of the entire layer. The unit for receiving the flexible pad in the recess is not elastic. Compared to the elastic substrate and the flexible pad, this unit has a much higher rigidity so that the pressure from the substrate on the elastic substrate and the flexible pad does not cause any deformation of this unit.

[0060] The layer of the substrate is accordingly pressed onto the elastic substrate to apply the coating material, with the result that the coating material is applied to the surface of the layer of the substrate and wherein the flexibility of the elastic substrate plus the flexible pad allows adaptation to unevenness in the layer of the substrate. For this purpose, it is advantageous if the liquid coating material is applied to the entire surface of the elastic substrate and in particular applied with a constant layer thickness. The layer thickness of the coating material applied to the elastic substrate is preferably 0.2 mm to 4 mm, preferably 0.2 mm to 2 mm and particularly preferably 0.2 mm to 1 mm.

[0061] In order to simplify the full-surface application of the coating material with a constant layer thickness to the elastic substrate, the coating material is preferably formed with an increased or suitable viscosity, in particular by using substances for adjusting the viscosity (e.g., gelling agents such as polysaccharides, cellulose, etc.). The viscosity is also selected with respect to the surface properties of the substrate so that shrinkage or droplet formation or island formation due to the surface tension of the coating material is avoided. The person skilled in the art knows how to proceed here.

[0062] Furthermore, the coating material should have shear-thinning properties, so that the application of the coating material does not lead to film ruptures etc. For example, viscosities of 0.5 Pa*s to 10 Pa*s and in particular 1 Pa*s to 6 Pa*s may be suitable here, with a shear rate between 12 l / s and 20 l / s and in particular between 14 l / s and 17 l / s or 16 l / s (according to DIN 53019 at 20° C., Anton Paar Rheolab QC rotational rheometer with CC39 system). Shear thinning allows the desired uniform distribution of the material in a stable film.

[0063] Prior to the press-in process, the application of a certain amount of coating material on the elastic substrate and the distribution on the surface in which the layers of the substrate can be accommodated can preferably be done by a doctor blade. Alternatively, the coating material can also be applied to the surface of the elastic substrate by means of a film applicator before the press-in process. In addition, before the press-in process, the coating material can be applied to the elastic substrate that moves relative to the slot die by means of a slot die. The moving elastic substrate can preferably be composed of a conveyor belt. This allows the elastic substrate to continue to move above the flexible pad. Therefore, the coating material can be applied to the moving elastic substrate, and then the substrate can be pressed into the coating material on the conveyor belt above the flexible pad ( Figure 6 ). Excess coating material can preferably be removed from the moving elastic substrate in the form of a conveyor belt and can be supplied for repeated use. Likewise, it is possible and preferred that residual coating material remaining from a previous coating operation before the application of the coating material is removed, in particular by scraping.

[0064] Then, the zone length of the coating material in the substrate can be determined via the viscosity of the coating material, the layer thickness applied to the elastic substrate, the contact duration and the intrusion pressure of the substrate. The zone length coated in this way can preferably be 0 mm to 20 mm, more preferably between 0 mm and 5 mm, and particularly preferably between 0 mm and 2 mm. These coating forms provide the possibility of a very accurately adjustable layer thickness of the coating material on the elastic substrate, which has a consistency of in particular less than ± 0.5 mm to ± 0.1 mm and in particular preferably as low as ± 0.05 mm or even ± 0.03 mm, and therefore in particular in conjunction with a closed surface provides a reproducible and defined transfer of the coating material to the substrate or catalyst element.

[0065] After the layer has been lifted from the coating material, the substrate may be heat treated to dry or calcine.

[0066] According to a further aspect, a device (10) for producing a substrate (1) for an exhaust gas aftertreatment device is provided, the device comprising:

[0067] - an elastic substrate (11) with a closed surface, in particular oriented horizontally;

[0068] - an application unit (13) configured to apply a liquid coating material (12) to the substrate (11);

[0069] a pressing unit (16) designed to dip or press the substrate (1) to be coated into the coating material (12) after the coating material (12) has been applied

[0070] In the embodiment of the present invention, the elastic substrate (11) extends over a flexible pad (21) and the pad absorbs the pressure of the substrate (1) on the elastic substrate (11) in such a way that all inlet openings of the through-channels (2) passing through the substrate (1) can be wetted by the coating material (12).

[0071] In a preferred embodiment, the device is characterized in that a non-elastically deformable base plate is arranged below the elastic base and the pad. A further preferred embodiment is one in which the base plate has a recess into which the flexible pad is enclosed to prevent slippage. Most preferably, the base plate provides laterally arranged passages for filling the flexible pad with a filling material (e.g., air or water or gel).

[0072] According to a further aspect, there is provided a substrate obtained according to one of the above methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0073] The following explains the embodiments in more detail with reference to the accompanying drawings. The following are shown:

[0074] Figure 1 is a perspective view of a layer of a substrate for an exhaust gas aftertreatment device;

[0075] Figure 2 is a cross-sectional view through a substrate to show non-uniform layers;

[0076] Figure 3 is a schematic diagram of an apparatus for applying a coating to a layer of a substrate without a flexible backing;

[0077] Figure 4 is a schematic diagram showing a flow chart of a method for producing a substrate having a topcoat layer without using a flexible backing;

[0078] Figure 5 is a plan view of a base plate having a recessed portion and a securing ring, a flexible pad being located in the recessed portion;

[0079] Figure 6 is an arrangement of a resilient substrate in the form of a conveyor belt according to the invention, wherein the flexible pads are located in recesses of the corresponding substrate plate. DETAILED DESCRIPTION

[0080] Figure 1 A perspective view of a substrate 1 such as a catalyst element used in a conventional exhaust gas after-treatment device is shown.

[0081] Figure 2 A cross-section through a substrate 1 is shown.

[0082] The substrate 1 is preferably formed of a porous substrate material and in particular a ceramic substrate material. The substrate 1 preferably has through-channels 2 extending parallel to one another, the inner walls 3 of which are optionally coated with a catalyst material in a manner known per se. The through-channels 2 may have a circular, hexagonal or square cross section, or a cross section shaped in some other way. The through-channels 2 terminate at a level 4 of the substrate 1, so that the level 4 of the substrate 1 has an inlet opening 5 of the through-channels 2.

[0083] like Figure 2As shown in the cross-sectional view through the substrate in FIG. 1 , the layer is not flat except for the inlet openings of the through-channels (i.e. over the entire extension of the layer), but can be deformed in the axial direction and can have a concave and / or convex and / or otherwise inhomogeneous structure. The through-channels 2 are separated from one another in the substrate material of the substrate 1 by intermediate walls 6, which in the layer result in a network structure between the inlet openings 5 ​​of the through-channels 2.

[0084] In the following, a device and a method are described by which a coating for avoiding clogging of the layer can be applied to the layer of the substrate 1. Suitable materials for such a coating are solutions containing precious metals, which can differ in composition and material from the layer material applied to the inner wall of the through-channel before or after the coating of the layer.

[0085] Figure 3 A basic and schematic illustration of an apparatus 10 for applying a coating to a layer of a substrate 1 is shown. Figure 4 Schematic illustration of a method for producing a substrate 1 having a coating for preventing layer clogging is described.

[0086] Figure 3 An apparatus 10 is shown having an elastic substrate 11 , to which a coating of a liquid coating material 12 can be applied by an application unit 13 .

[0087] The elastic substrate 11 has a closed surface. This closed surface prevents the coating material from penetrating into the material located below and thus ensures less material loss. In order to ensure that the pressure is applied as evenly as possible, the substrate 11 is supported by a fixed, non-elastically deformable substrate plate 14. A flexible pad 21 is not shown, which according to the invention will be positioned between the elastic substrate 11 and the substrate plate 14.

[0088] The coating material may be a material having a viscosity such that it can be applied with a layer thickness preferably between 0.2 mm and 3 mm on the flat surface of the elastic substrate 11 so that the flat surface forms a closed surface.

[0089] The coating material 12 may be applied by the applying unit 13. Specifically, the coating material 12 may be applied by placing the coating material on the elastic substrate 11 and distributing the coating material by means of a doctor blade or an applying device using a film applicator as the applying unit.

[0090] Alternatively, if Figure 4As shown, in step S1, the coating material 12 may be applied via a slot die 13 (as an application unit) which moves at a constant distance relative to the elastic substrate 11 in a translational manner and thereby releases the liquid coating material 12. The coating material 12 may have a solution containing a precious metal whose viscosity is increased by means of a gelling agent to such an extent that an adherent wet film of a constant thickness can be applied to the substrate 11.

[0091] The elastic substrate 11 moving relative to the slot die can be a conveyor belt, so that a layer thickness of the coating material 12 that can be adjusted very accurately can be applied to the entire surface of the moving elastic substrate 11 via the slot die 13, so as to ensure a reproducible and defined transfer of material to the substrate, in particular in combination with a closed surface.

[0092] After the coating material 12 is applied, in step S2, the layer of the substrate 1 to be coated is pressed into the coating material 12 by the pressing unit 16, in particular perpendicularly to the surface direction of the substrate 11. In doing so, the elastic substrate 11 is deformed due to its elasticity so that the mesh surface is in contact with the coating material 12 even in the case of an inhomogeneous layer. As a result, a complete coating of all surface portions of the layer of the substrate 1 formed by the mesh walls between the through channels 2 can be wetted with the coating material, so as to thereby reduce or eliminate layer clogging over the entire layer.

[0093] After pressing the substrate 1 into the coating material 12 on the elastic substrate 11, in step S3, the substrate 1 wetted by the coating material 12 is lifted off the substrate and then, if necessary, fed to a separate heat treatment to dry or calcine the applied coating material.

[0094] Subsequently, in step S4 , the coating material 12 is removed from the substrate 11 , for example by means of a doctor blade 15 , and the coating material is thus prepared again for the subsequent coating of the substrate 1 with a constant wet film thickness.

[0095] Figure 5 A base plate 14 is shown with a recess in which a flexible pad 21 is located. The recess is surrounded by a fastening ring 20. Via a passage 23 through the base plate 14, the pad 21 located in the recess can advantageously be filled with a filling material and thus adapt to changes in the quality of the substrate. According to the invention, the base plate 14 with the pad 21 is replaced by a Figure 3 and Figure 4 The base plate 14 in the.

[0096] Figure 6A substrate plate 14 having a recess and a flexible pad 21 located in the recess is shown below an elastic substrate 11. The substrate 1 having a concave surface is pressed into the coating material 12. The pressure generated on the elastic material 11 is substantially absorbed by the pad 21 in the recess of the non-elastic substrate plate 14. After the substrate 1 is lifted off the elastic substrate 11, the elastic substrate can act as a conveyor to place the subsequent coating material 12 over the pad, and a new substrate 1 can be coated accordingly.

[0097] Reference Numbers :

[0098] 1: Substrate to be coated

[0099] 2: Through the channel

[0100] 3: Middle wall

[0101] 4: Layer of substrate 1

[0102] 5: Entrance opening through channel 2

[0103] 6: Middle wall

[0104] 10: Device

[0105] 11: Elastic base

[0106] 12: Coating material

[0107] 13: Application unit

[0108] 14: Base plate

[0109] 15: Scraper

[0110] 16: Press-in unit

[0111] 20: Fastening ring

[0112] 21: Flexible pad

[0113] 23: Connector for filling flexible pad

Claims

1. A method for producing a substrate (1) for an exhaust gas aftertreatment device, the method comprising the following steps: - applying (S1) a coating material (12) on an elastic substrate (11); - dipping or pressing (S2) the surface of the substrate (1) in which the inlet opening of the through-channel (2) through the substrate (1) is arranged, into the coating material (12); - lifting (S3) the coated substrate (1); and - post-treating the coating material (12) on the coated substrate (1), and in particular drying or calcining, - wherein the elastic substrate (11) extends over a flexible pad (21) and the pad absorbs the pressure of the substrate (1) on the elastic substrate (11) so that all the inlet openings of the through-channels (2) through the substrate (1) can be wetted by the coating material (12). 2 . The method according to claim 1 , wherein the coating material ( 12 ) comprises a catalytically active component and is in particular a solution containing a noble metal.

3. A method according to claim 1 or 2, wherein the surface of the substrate (1) to be coated has a convex or concave or otherwise irregularly shaped structure relative to its axial direction.

4. The method according to one of claims 1 to 3, wherein the substrate (11) is an elastic plastic or rubber material, and in particular a foam rubber material, and has a smooth and / or closed surface.

5. Method according to one of claims 1 to 3, wherein the liquid coating material (12) is applied to the elastic substrate (11) in a planar manner and in particular with a constant layer thickness. The method according to claim 4 , wherein the coating material has a layer thickness of 0.2 mm to 4 mm.

7. The method according to one of claims 1 to 5, wherein the coating material is shear-thinning such that the application of the coating material does not result in film rupture, wherein the viscosity of the coating material at 20°C is selected from 0.5 Pa*s to 10 Pa*s.

8. A method according to one of claims 1 to 7, wherein the coating material (12) is applied to the substrate (11) by a doctor blade or by a film-drawing device on the substrate (11) or by a slot die on the substrate (11) that moves relative to a slot die (13).

9. Method according to one of claims 1 to 8, wherein residual coating material (12) remaining from a previous coating operation before said applying of said coating material (12) is removed, in particular by scraping.

10. A device (10) for manufacturing a substrate (1) for an exhaust gas aftertreatment device, the device comprising: - an elastic substrate (11) with a closed surface, in particular oriented horizontally; - an application unit (13) configured to apply the liquid coating material (12) applying to the substrate (11); - a pressing unit (16) designed to dip or press the substrate (1) to be coated into the coating material (12) after the coating material (12) has been applied, wherein the elastic base (11) extends over a flexible pad (21) and the pad absorbs the pressure of the substrate (1) on the elastic base (11) in such a way that all the inlet openings of the through-channels (2) through the substrate (1) can be wetted by the coating material (12).

11. The device according to claim 9, wherein a non-elastically deformable base plate (14) is arranged below the elastic base (11) and the pad (21).

12. A substrate (1) produced according to the method according to one of claims 1 to 9.

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