Method and apparatus for producing a substrate for an exhaust gas aftertreatment system

Abstract

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

Description

Technical area

[0001] The invention relates to a method for producing substrates for exhaust gas aftertreatment devices as catalyst elements or filter elements for internal combustion engines, and in particular to measures for preventing the occurrence of sooting / blocking phenomena, also known as face plugging, at a fluid flow inlet of the catalyst element. Technical background

[0002] For the purification of combustion exhaust gases, e.g. from internal combustion engines, exhaust gas aftertreatment devices are generally used, particularly in the form of catalysts, i.e. catalytically coated flow-through substrates or filters, e.g. wall-flow filters. These enable the chemical conversion of undesirable components of the combustion exhaust gas, such as carbon monoxide, nitrogen oxides, unburned hydrocarbons, soot and the like, or a filtering of combustion exhaust gas. Such exhaust gas aftertreatment devices generally have one or more substrate bodies. A substrate body generally comprises a plurality of through-channels. The through-channels extend completely through the substrate body or, in the case of a wall-flow filter, mostly through the substrate body, so that a filter is formed by the porous substrate material between adjacent filter channels.The inner walls of the passageways may be coated with a catalyst material to form a catalytic surface on which appropriate reactions and / or adsorptions can take place to eliminate the undesirable exhaust gas components.

[0003] The through-channels generally run parallel in the substrate and are separated from one another by walls of the substrate material, in particular a ceramic material. The through-channels generally have inlet openings arranged on an end face of the substrate. This means that the end face on which the inlet openings of the through-channels are arranged has a large number of webs on which components of the exhaust gas, such as particles, aerosols, droplets and the like, can deposit during operation of the exhaust gas aftertreatment element and form a fuzz of contamination. This process is known as sooting, blockage, or sooting and is generally referred to as face plugging. Face plugging occurs particularly in operating conditions in which the exhaust gas contains a high concentration of soot particles or aerosols.

[0004] Face plugging increases exhaust backpressure in the exhaust aftertreatment system, which can impair the efficiency of the internal combustion engine. Failure to remove the face plug can also lead to system failure.

[0005] One way to prevent face plugging is to provide the end face of a substrate with a noble metal-containing coating that has enhanced catalytic properties. Such a measure is known, for example, from document EP 2171232 B1. This discloses a device for the aftertreatment of engine exhaust gases, comprising a substrate having a cellular structure defining fluid passages configured to allow fluid flow through the substrate, the substrate having an inlet end face positioned at one end of the substrate, the substrate being coated with a chemical coating.The chemical coating on the inlet end face has an increased loading relative to any other chemical coating on the substrate to prevent and / or eliminate face entry clogging on the substrate; wherein the inlet end face comprises a three-dimensional topographical feature such that the substrate at the inlet end is non-planar and the chemical coating is disposed on the three-dimensional topographical feature.

[0006] Due to the manufacturing process of such substrates for exhaust aftertreatment systems, the end face where the inlet openings of the through-channels are located is not flat, except for the inlet openings of the through-channels, but can have an irregular, concave, or convex configuration. This complicates the application of a front-side coating, which should be uniformly applied, in particular, to all web-like structures between the through-channels.

[0007] In this regard, EP 3195348 B1 provides a system for depositing a surface coating on a monolithic catalytic substrate. The system comprises a coating liquid applicator arranged between a supply and discharge system, the coating liquid applicator having an inner core and an outer nub with a height, a coating liquid trough positioned below the coating liquid applicator to accommodate the full length of the coating liquid applicator within the coating liquid trough and retain a coating liquid. The coating liquid trough is positioned vertically such that the nub of the coating liquid applicator is at least partially immersed in the coating liquid.During operation, a motor drives the coating liquid applicator at a specific predetermined speed, with operation being controlled based on a sensor signal from a light sensor. During operation, a substrate coating liquid is applied to the coating liquid applicator, a monolithic catalytic substrate is moved through the coating liquid applicator at the predetermined speed, so that a quantity of the coating liquid is transferred from the coating liquid applicator to a surface of the monolithic catalytic substrate. Depending on whether a light beam is blocked by the coating liquid applicator, the height of the coating liquid applicator is adjusted to an appropriate height.

[0008] Furthermore, EP 3400108 B1 discloses a method for coating a terminal surface of a substrate with a liquid comprising a catalyst component, wherein a substrate is conveyed to a coating roller, and the liquid is applied to a terminal surface of the substrate by bringing the terminal surface into contact with the coating roller, which is loaded with the liquid. Conveying the substrate to the coating roller comprises bringing the terminal surface of the substrate into contact with a rotating surface of the coating roller. The terminal surface is thereby brought into contact with the rotating surface of the coating roller.

[0009] The above-mentioned prior art has the disadvantage that it does not allow for a reproducible, uniform coating on non-flat substrate faces. Furthermore, the penetration depth of the coating material into the through-channels cannot be adjusted using the known manufacturing processes.

[0010] It is an object of the present invention to provide a method for coating an end face of a substrate having inlet openings of through-channels with a face plugging reducing coating material, which enables a uniform coating even with non-planar end faces of the substrate and enables a reproducible layer thickness and penetration depth into the through-channels. Disclosure of the invention

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

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

[0013] According to a first aspect, there is provided a method for producing a substrate (1) for an exhaust gas aftertreatment device, comprising the following steps: - applying (S1) a coating material (12) to an elastic base (11); - immersing or pressing (S2) a surface of the substrate (1), on which inlet openings of through-channels (2) through the substrate (1) are arranged, into the coating material (12); - lifting (S3) the coated substrate (1); and - post-treatment, in particular drying or calcining of the coating material (12) on the coated substrate (1), - wherein the elastic base (11) extends over a flexible cushion (21) and this cushion absorbs the pressure of the substrate (1) on the elastic base (11) in such a way that all inlet openings of through-channels (2) through the substrate (1) can be wetted with the coating material (12).

[0014] The method according to the invention is advantageously used to prevent face plugging and to enable a uniform coating even on non-flat end faces of the substrate with a reproducible layer thickness and penetration depth of the coating material into the through-channels. The coating material is preferably applied to the end face of the substrate in a separate manufacturing step independent of the actual catalytic coating of the substrate. The end face corresponds to a side of the substrate at which openings, in particular the inlet openings, of the through-channels end in the substrate. The coating is generally applied with a material containing precious metals. The substrate produced in this way can advantageously be used in an exhaust gas aftertreatment system comprising one or more substrates.

[0015] Suitable substrates include the embodiments known to those skilled in the art for automotive exhaust gases. The through-channels can completely penetrate the substrate—so-called flow-through substrates—or, in the case of a wall-flow filter, extend so far into the substrate that the porous substrate material forms a filter for the exhaust gas between parallel adjacent through-channels. Substrates that have been catalytically coated with a catalyst material are also called catalyst elements.

[0016] Flow-through substrates are conventional catalyst elements in the prior art, which can be made of metal or glass fiber-reinforced paper (corrugated carrier, e.g., WO17153239A1, WO16057285A1, WO15121910A1 and literature cited therein) or ceramic materials. Refractory ceramics such as cordierite, silicon carbide, or aluminum titanate, etc., are preferred. The number of channels per unit area is characterized by the cell density, which is typically between 300 and 900 cells per square inch (cpsi). The wall thickness of the channel walls for ceramics is between 0.5 and 0.05 mm.

[0017] All conventional ceramic materials can be used as wall-flow filters. Porous wall-flow filter substrates made of cordierite, silicon carbide, or aluminum titanate are preferred. These wall-flow filter substrates have inflow and outflow channels, with the downstream ends of the inflow channels and the upstream ends of the outflow channels sealed with gas-tight plugs, offset from one another. This forces the exhaust gas to be cleaned, which flows through the filter substrate, to pass through the porous wall between the inflow and outflow channels, resulting in excellent particle filtration efficiency. The porosity, pore / radius distribution, and wall thickness can be tailored to the particle filtration properties. The porosity of wall-flow filters is typically more than 40%, generally from 40% to 75%, particularly from 45% to 70% [measured according to DIN 66133 - latest version on the date of filing].The average pore size (diameter) is at least 3 µm, e.g. from 3 µm to 34 µm, preferably more than 5 µm, in particular from 5 µm to 28 µm or from 7 µm to 22 µm [measured according to DIN 66134 latest version on the date of filing].

[0018] The surfaces in the through-channels of the substrate can be coated with a catalyst material. The process step of coating the through-channels with a catalyst material is optional and can be performed before, during, or after the process step of coating the end faces with the coating material according to the invention. Drying, reduction, and calcination steps can be performed between these process steps.

[0019] The coating material (12) can comprise a catalytically active component, in particular a noble metal-containing solution. The coating material can be identical to the catalyst material, different from it, or have a different concentration of catalytically active components. The coating material can be produced, for example, from noble metal-containing solutions or suspensions with adsorbing or non-adsorbing properties; in particular, noble metal solutions or suspensions containing Rh, Pt, and Pd are mentioned here. Such coating materials then have catalysts for the oxidation of hydrocarbons to H2O and CO2, of CO to CO2, or can also help reduce NOx.

[0020] The catalytic function of the coating material is therefore essentially provided by the metals Rh, Pt and / or Pd, preferably Pt and / or Pd or Rh or Rh and Pd, which can be supported as a possibly thickened solution or, in an alternative embodiment, on high-surface area carrier oxides.

[0021] High-surface-area, temperature-stable oxides are considered by those skilled in the art as support oxides for these catalytically active metals. These are generally aluminum oxides, silicon oxides, zirconium oxides, or titanium oxides, or mixtures thereof. Active aluminum oxide, in particular, is known to those skilled in the art in this context. It refers in particular to γ-aluminum oxide with a surface area of ​​100 to 200 m². 2 / g. Active alumina is widely described in the literature and is commercially available. It typically contains silicon oxide or lanthanum oxide as a stabilizer in an amount of up to 10 wt.% based on the alumina.

[0022] In an alternative but preferred embodiment, the catalytic function is provided by Rh and / or Pd and / or Pt supported on a mixture of high-surface-area aluminum oxide and common oxygen storage materials such as cerium oxides, cerium-zirconium mixed oxides or cerium or cerium-zirconium mixed oxides doped with La, Y, Pr, Nd.

[0023] The oxygen storage materials are preferably those containing cerium / zirconium / rare earth metal mixed oxides. Examples of rare earth metal oxides that can be considered are lanthanum oxide, yttrium oxide, praseodymium oxide, neodymium oxide, samarium oxide, and mixtures of one or more of these metal oxides. Lanthanum oxide, yttrium oxide, neodymium oxide, and mixtures of one or more of these metal oxides are preferred. Particular preference is given to lanthanum oxide, yttrium oxide, and a mixture of lanthanum oxide and yttrium oxide is particularly preferred in this context. In a highly preferred embodiment, the coating material in the final catalyst element has an oxidative function, particularly with respect to hydrocarbons, CO, and soot. In this case, in addition to the above-mentioned carrier oxides, Pt and / or Pd are predominantly or exclusively present as catalytically active species in the coating material.

[0024] However, the precious metals mentioned above for coating with the coating material can also be present as a thickened, low-viscosity solution.

[0025] Precious metal solutions in this context are those containing the precious metals dissolved in a solvent, preferably water. Those skilled in the art will know which solutions can be used in this case. Precious metal compounds for preparing the solution include, in particular, the following: The palladium compound is selected from tetraaminepalladium(II) chloride, palladium hydroxide, palladium chloride, palladium sulfate, palladium nitrate, diaminedinitritopalladium(II) chloride, diaminedinitritopalladium(II) sulfate, palladium glycinate, tetraaminepalladium(II) sulfate, bis(ethylenediamino)palladium(II) carbonate, bis(ethylenediamino)palladium(II) sulfate, bis(acetylacetonato)palladium(II), diaminedichloropalladium(II), palladium oxide hydrate, tetraaminepalladium(II) hydrogencarbonate, bis(ethylenediamino)palladium(II) chloride, palladium acetate.

[0026] The rhodium compounds are selected from rhodium(III) chloride, rhodium(III) iodide, rhodium(III) oxide hydrate, rhodium(III) nitrate, and rhodium(III) sulfate.

[0027] The platinum compound is selected from platinum(II) chloride, tetrachloroplatinic(II) acid H2(PtCl4), dinitrosulfatoplatinic(II) acid and its salts, diamminodinitritoplatinic(II), tetraammineplatinic(II) salts, platinum(II) nitrate, hexachloroplatinic(IV) acid H2(PtCl6), hexahydroxoplatinic(IV) acid, tetraammineplatinic(II) acetate, tetraethylammonium hexahydroxyplatinate(IV), bis(ethanolammonium) hexahydroxyplatinate(IV) and its salts. To adjust the viscosity of the coating materials, appropriate auxiliaries such as thickeners, surface-active substances, acids or bases, or shear-thinning substances can be added. Those skilled in the art will know how to proceed (see, for example, EP3131660B1). For example, auxiliaries such as methylcellulose can be added to the solution for thickening.

[0028] In addition, the substrates for constructing catalyst elements produced according to the invention can be coated with different catalyst materials, thus forming different catalyst technologies. Several components in the form of substrates with one or different catalytic or pollutant-adsorbing catalyst technologies can be installed in an exhaust system. The face-side coating according to the invention can be applied to any component in which face plugging is expected to occur. The application and functionality of the face-side coating is independent of the component function or the catalyst technology. The catalyst technologies can include, but are not limited to, DOC catalysts, NSC catalysts, DPF catalysts, 3-way catalysts (TWC), SCR catalysts, ASC catalysts, or combinations of the technologies.

[0029] A wide variety of catalyst materials are known from the prior art. For example, zeolites containing Cu, Fe, V, W, Ce, Sb, Nb, Zr, Mo, Al, Pd can be used for SCR catalysts, as described, for example, in the publications 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 / 134005 A1, WO 2017 / 134006 A1, WO 2017 / 134007 A1, WO 2013 / 159825 A1, WO 2017 / 178576 A1, WO 2018 / 054928 A1, WO 2018 / 029330 A1, and WO 2022 / 128523 A1. Catalyst materials used for TWC catalysts are known, for example, from WO2022223688A1, WO2021151876A1, WO2021140326A1, WO2008000449A2, WO2008113445A1, and WO2008113457A1. The expert knows which one he would use for the purpose at hand (see e.g.also WO2019121994A1, WO2019121995A1, WO9535152A1, WO2008000449A2, EP0885650A2, EP1046423A2, EP1726359A1, EP1541220A1, EP1900416B1, EP3045226A1, WO2009012348A1 and EP1974809B1).

[0030] Three-way catalysts essentially consist of the components noble metal, high-surface-area carrier oxide, and oxygen storage material. The catalytically active components are usually platinum group metals, such as Pt, Pd, and Rh, with Pd and Rh being particularly preferred. The catalytically active metals are often deposited in highly dispersed form on the high-surface-area oxides and the oxygen storage materials. It is particularly preferred if the noble metals are pre-fixed to the oxygen storage material before it is mixed with the other components in the coating mixture. Zoned or layered designs are now the norm for TWCs. In a preferred embodiment, at least one TWC in the exhaust system comprising the catalyst element modified according to the invention has a two-layer structure with two different three-way coatings, preferably as described in EP3247493A1.

[0031] The oxygen storage materials are, in particular, those containing cerium / zirconium / rare earth metal mixed oxides. Examples of suitable rare earth metal oxides include lanthanum oxide, yttrium oxide, praseodymium oxide, neodymium oxide, samarium oxide, and mixtures of one or more of these metal oxides. Lanthanum oxide, yttrium oxide, neodymium oxide, and mixtures of one or more of these metal oxides are preferred. Particular preference is given to lanthanum oxide, yttrium oxide, and a mixture of lanthanum oxide and yttrium oxide is particularly preferred in this context. High-surface-area, temperature-stable oxides are preferred as support oxides for catalytically active metals. These are generally aluminum oxides, silicon oxides, zirconium oxides, or titanium oxides, or mixtures thereof. Active aluminum oxide, in particular, is known to those skilled in the art in this context. It refers, in particular, to γ-aluminum oxide with a surface area of ​​100 to 200 m². 2 / g. Active alumina is widely described in the literature and is commercially available. It typically contains silicon oxide or lanthanum oxide as a stabilizer in an amount of up to 10 wt.% based on the alumina.

[0032] According to the invention, the end-face coating with the coating material should be carried out in such a way that only the end-face surfaces of the webs between the through-channels are coated and the inner surfaces of the through-channels are wetted with the coating material, for example, only up to a maximum depth of 0 to 20 mm, preferably between 0 and 5 mm, particularly preferably between 0 and 2 mm.

[0033] Due to manufacturing processes, the end faces of a substrate to be coated according to the invention are often not flat, but may have a convex or concave or otherwise irregularly shaped structure with respect to their axial direction. This 3D structure of the end faces can also vary within a batch of substrates.

[0034] For uniform coating with the coating material, the above method involves pressing the end face of the catalyst element into a coating material applied flatly to an elastic substrate, with the flexible cushion located beneath the elastic substrate. The coating material is provided in liquid form as a dispersion, suspension, solution, gel, or the like, which can be provided with the aforementioned catalytically active materials.

[0035] It can be provided that the liquid coating material is applied over a large area on the elastic base, which is in particular horizontally oriented, in particular with a constant layer thickness.

[0036] The end face of the substrate to be coated is then pressed into the elastic base. The elastic base yields when the end face of the substrate is pressed into the base, and the flexible cushion underneath ensures appropriate counterpressure from the elastic base against the end face of the substrate, ensuring that the coating material on the elastic base comes into full contact with the end face. This ensures that the coating material is applied to the inner surfaces of the through-channels with a constant layer thickness and constant penetration depth, despite any unevenness in the end face of the substrate.

[0037] The underlay is designed to be elastic with a closed surface to allow for shape elasticity when the end face of the substrate is pressed onto it. The closed surface of the underlay prevents the coating material from penetrating the material of the elastic underlay and the underlying layer, thus minimizing coating material loss and extending the usability of the elastic underlay.

[0038] The elastic base can be made of an elastic plastic or a rubber material, particularly a foamed rubber material, and have a smooth and / or closed surface. This base should be selected so that, for example, an elongation of 1% can be achieved with a force application of 5–25 N / cm, preferably 6–15 N / cm (ISO 2118) or a strength of 50 to 200 kp / cm of material width is ensured (Shore A hardness according to DIN 53505 of 60–95, preferably 70–90). The base can be made of polyester with a PVC, PU, ​​or nitrile coating, for example.

[0039] In particular, the base can be coated with a material such as a foamed rubber material with a closed surface. Examples include neoprene, foamed rubber and silicone, Sylomer (“Material Properties and Vibration Isolation Technical Information”, RRG INDUSTRIETECHNIK GMBH, www.rrg.de), and the like. The elastic properties of the foamed rubber material can, for example, be achieved with a Shore A hardness (according to DIN 53505) of between 10 and 18, in particular between 12 and 14, and / or a density between 0.1 g / cm 3 up to 1 g / cm 3 be described.

[0040] For substrates with extremely pronounced unevenness on their end faces, it is particularly advantageous according to the invention if a function exists beneath the elastic base that generates appropriate counterpressure on the elastic base as soon as the substrate is pressed onto the elastic base. According to the invention, a flexible cushion acts as such a counterpressure-generating unit. The flexible cushion is advantageously located in a recess in a unit that is harder than the flexible cushion and the elastic base but is not elastic, preferably a base plate that cannot itself be displaced by the substrate being pressed into it. This helps to sufficiently stabilize the flexible cushion against slipping.

[0041] The flexible cushion is characterized by a flexible upper side facing the underside of the elastic base. The flexible cushion consists, for example, of a covering (if present) and a filling. The covering and filling can be made of the same material. For example, a simple foam cushion or silicone cushion can be used. The flexible cushion is preferably selected from a plastic material such as a silicone mat and the like. A silicone mat with a thickness of up to 10 mm, preferably around 2 mm, with a Shore A hardness (according to DIN 53505) of 60±5 is particularly preferred. Those skilled in the art will know of other alternatives. To secure the flexible cushion against slipping, it preferably rests in a recess which has been incorporated into a correspondingly dimensioned, rigid and non-elastic unit, e.g. a base plate.Preferably, the flexible cushion can also be formed by a recess in a base plate, which is covered by a flexible, water- and airtight material, e.g., similar to the casing described above.

[0042] This creates a cavity between the base plate and the cover, referred to here as a flexible cushion. The fixation must be designed to prevent the filling from escaping from the cushion. The design procedures are familiar to those skilled in the art.

[0043] The filling of the flexible cushion 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. Examples of thickeners that can be used are agar agar, guar gum, natrosol, or methylcellulose. A stabilized water mixture is particularly preferred. To stabilize the preferably used water, glycerin, silicone oil, or similar oils can be added, for example. Those skilled in the art are familiar with the possibilities for stabilizing the water, for example, against fungal growth.

[0044] The flexible cushion or the base plate comprising the flexible cushion is then positioned beneath the elastic base such that, when the substrate is pressed into the elastic base, the flexible cushion can exert the counterpressure necessary to press the coating material into the substrate via the elastic base. The base plate, if present, must therefore be designed and positioned in accordance with the expert's requirements.

[0045] The base plate therefore preferably has a recess for the flexible cushion or forms one. The recess preferably corresponds to the dimensions of the substrate to be pressed in. The recess should be designed in such a way that a coating material located on the elastic base is pressed onto and into the substrate as soon as the substrate is pressed into the elastic base and the flexible cushion. To stabilize the recess, it can be advantageous if the recess is enclosed by a fastening ring. This promotes the stiffening of the end of the recess, which facilitates the fixation of the flexible cushion in the recess. A corresponding flexible cushion in a recess of a base plate is Fig. 5 as supervision and in Fig. 6 with the corresponding elastic base shown as a side view. Furthermore, it can be advantageous if the recess has an access through the base plate, through which the cushion can be connected to an inlet for the cushion's filling material. This allows the amount of filling material in the flexible cushion to be adjusted relatively quickly from the outside to suit the requirements of new substrates or coating materials, without having to insert a new cushion.

[0046] The shape of the flexible pad is adapted to the substrate to be coated with the coating material. Those skilled in the art know how to proceed here. The diameter of the recess should correspond to the shape of the substrates to be coated and be at least the same size as or larger than the substrate sizes used, preferably 10-30 mm larger than the substrate diameter. The depth of the recess is preferably 2-15 mm, more preferably 2-5 mm.

[0047] In principle, the elasticity or deformability of the elastic base and the flexible cushion can be selected such that the unevenness of the substrate's face when pressed into the base results in the base being in full contact with the face, thus ensuring that the coating material is applied over the entire face. Macroscopic unevenness of any kind on the face can be compensated for by the interaction of the elasticity of the base and the force acting on the substrate or the catalyst element.

[0048] The entire system consisting of the elastic base and flexible cushion therefore exerts an elasticity adapted to the substrates to be coated. This elasticity can be controlled particularly advantageously by the fill level of the flexible cushion. This elasticity can, for example, be selected such that with a macroscopic unevenness of the end surface of, for example, + / - 3 mm, preferably + / - 1.5 mm and a contact force of the substrate on the elastic base and the flexible cushion of, for example, between 5 and 150 N, the pressed surface of the substrate rests completely on the end surface in order to achieve uniform application of the coating material to all areas of the end surface. The maximum contact force should only be limited by the mechanical stability of the substrate.

[0049] Thus, the material of the elastic base and the flexible cushion can be selected in terms of its elasticity or deformability so that, even with a substrate with a certain unevenness on the front side, the surface of the base can be pressed against the entire front surface. The unit for accommodating the flexible cushion in the recess is not elastic. It has a much higher strength than the elastic base and the flexible cushion, so that the pressure exerted by the substrate on the elastic base and the flexible cushion does not cause this unit to deform.

[0050] To apply the coating material, the end face of the substrate is pressed onto the elastic base, whereby the coating material is applied to the end faces of the substrate. The flexibility of the elastic base plus the flexible cushion allows for adaptation to unevenness on the end face of the substrate. For this purpose, it is advantageous if the liquid coating material is applied evenly to the elastic base, particularly with a constant layer thickness. The layer thickness of the coating material applied to the elastic base is preferably 0.2 to 4 mm, preferably 0.2 to 2 mm, and particularly preferably 0.2 to 1 mm.

[0051] To facilitate the flat application of the coating material to the elastic substrate with a constant layer thickness, the coating material is preferably designed with an increased or suitable viscosity, in particular by using substances to adjust the viscosity, such as gelling agents such as polysucroses, celluloses, and the like. Furthermore, the viscosity is selected in conjunction with the surface properties of the substrate to prevent shrinkage or the formation of droplets or islands due to the surface tension of the coating material. Those skilled in the art know how to proceed in this regard.

[0052] Furthermore, the coating material should exhibit shear-thinning properties to prevent film tears or similar phenomena when applied. For example, a viscosity of 0.5 to 10 Pa*s, especially 1 to 6 Pa*s, at a shear rate between 12 and 20 1 / s, especially between 14 and 17 1 / s, or at 16 1 / s may be suitable (Anton Paar Rheolab QC with CC39, at 20 °C, according to DIN 53019). Shear thinning enables the required uniform distribution of the material into a stable film.

[0053] The application of a quantity of coating material to the elastic base prior to the pressing process and its distribution over a surface in which the front surface of the substrate can be accommodated can preferably be carried out using a doctor blade. Alternatively, the coating material can also be applied to the surface of the elastic base prior to the pressing process using a film applicator. Furthermore, the coating material can be applied to the elastic base, which is moved relative to the slot die, prior to the pressing process using a slot die. The moving elastic base can preferably be represented by a conveyor belt. This allows the elastic base to move further over the flexible cushion. Coating material can thus be applied to the moving elastic base, and the substrate can then be pressed over the flexible cushion into the coating material on the conveyor belt. Fig. 6). Excess coating material can preferably be removed from the moving elastic support in the form of a conveyor belt and recycled. It is also possible and preferred that the residues of coating material from a previous coating process remaining before the application of the coating material be removed, in particular by peeling off.

[0054] The zone length of the coating material in the substrate can then be determined via the viscosity of the coating material, the layer thickness applied to the elastic substrate, the contact time, and the pressing pressure of the substrate. The zone length coated in this way can preferably be 0 to 20 mm, more preferably between 0 and 5 mm, particularly preferably between 0 and 2 mm. These coating forms offer the possibility of very precisely adjustable layer thickness of the coating material on the elastic substrate, in particular with a constancy of less than ± 0.5 mm to ± 0.1 mm, particularly preferably up to ± 0.05 mm or even ± 0.03 mm, and thus, especially in conjunction with the closed surface, a reproducible and defined transfer of coating material to the substrate or catalyst element.

[0055] After the end face is removed from the coating material, the substrate can be thermally treated for drying or calcination.

[0056] According to a further aspect, a device (10) for producing a substrate (1) for an exhaust gas aftertreatment device is specified, comprising: - a particularly horizontally oriented elastic base (11) with a closed surface; - an application unit (13) designed to apply a liquid coating material (12) to the substrate (11); - a press-in unit (16) which is designed to immerse or press a substrate (1) to be coated into the coating material (12) after the coating material (12) has been applied, wherein the elastic base (11) runs over a flexible cushion (21) and this cushion absorbs the pressure of the substrate (1) on the elastic base (11) in such a way that all inlet openings of through-channels (2) through the substrate (1) can be wetted with the coating material (12).

[0057] In a preferred embodiment, the device is characterized in that a non-elastically deformable base plate is arranged beneath the elastic support and the cushion. A further preferred embodiment is one in which the base plate has a recess into which the flexible cushion is securely enclosed. Most preferably, the base plate provides a laterally arranged access for filling the flexible cushion with filling material (e.g., air, water, or gel).

[0058] According to a further aspect, a substrate is provided produced by one of the above methods. Brief description of the drawings

[0059] Embodiments are explained in more detail below with reference to the attached drawings. They show: Fig. 1 a perspective view of an end face of a substrate for an exhaust gas aftertreatment device; Fig. 2 a cross-sectional view through a substrate to illustrate an uneven end face; Fig. 3 a schematic diagram of a device without a flexible pad for applying a coating to an end face of a substrate; Fig. 4 a schematic diagram of a flow chart illustrating the method for producing a substrate with a frontal coating without using a flexible pad. Fig. 5 a top view of a base plate with a recess and fastening ring in which a flexible cushion lies. Fig. 6 an inventive arrangement of an elastic base in the form of a conveyor belt with a flexible cushion in a recess of a corresponding base plate. Description of embodiments

[0060] Fig. 1 shows a perspective view of a substrate 1 as used in conventional exhaust gas aftertreatment devices, e.g. as a catalyst element.

[0061] Fig. 2 shows a cross-sectional view through the substrate 1. The substrate 1 is preferably formed from a porous, in particular ceramic, substrate material. The substrate 1 preferably has through-channels 2 running parallel to one another, the inner walls 3 of which are optionally coated with a catalyst material in a conventional manner. The through-channels 2 can have a round, hexagonal, square cross-section, or a cross-section shaped in some other way. The through-channels 2 end at an end face 4 of the substrate 1, so that the end face 4 of the substrate 1 has inlet openings 5 ​​for the through-channels 2.

[0062] Due to the manufacturing process, as shown in the sectional view through the substrate in Fig. 2, the front side, apart from the inlet openings of the through-channels (i.e., over the entire frontal extension), is not flat, but may be deformed in the axial direction and have a concave and / or convex and / or otherwise uneven structure. The through-channels 2 are separated from one another in the substrate material of the substrate 1 by partition walls 6, which lead to web-like structures on the front side between the inlet openings 5 ​​of the through-channels 2.

[0063] The following describes a device and a method for applying a coating to the end face of the substrate 1, which serves to prevent face plugging. A suitable material for such a coating is a noble metal-containing solution, which may differ in composition and materials from the layer material applied to the inner walls of the through-channels before or after the end faces are coated.

[0064] In Fig. 3 shows a basic and schematic representation of a device 10 for applying a coating to the front side of a substrate 1. In conjunction with the schematic sketches of the Fig. 4 describes a basic process sequence for producing the substrate 1 with a coating to prevent face plugging.

[0065] Fig. 3 shows a device 10 with an elastic base 11, onto which a coating of a liquid coating material 12 can be applied by means of a coating unit 13.

[0066] The elastic base 11 has a closed surface. This closed surface prevents the coating material from penetrating the underlying material, thus reducing material loss. To ensure the most even pressure application possible, the base 11 is supported by a rigid, non-elastically deformable base plate 14. Not shown is the flexible cushion 21, which, according to the invention, would be positioned between the elastic base 11 and the base plate 14.

[0067] The coating material may be a material having a viscosity such that it can be applied to a flat surface of the elastic base 11 with a layer thickness of preferably between 0.2 and 3 mm, so that it forms a closed surface.

[0068] The coating material 12 can be applied using an application unit 13. In particular, the coating material 12 can be applied by placing the coating material on the elastic substrate 11 and spreading it using a doctor blade or by applying it using a film-pulling device (as an application unit).

[0069] Alternatively, as in Fig. As outlined in Figure 4, in step S1, the coating material 12 can be applied via a slotted nozzle 13 (as an application unit), which moves translationally relative to the elastic substrate 11 at a constant distance, thereby dispensing the liquid coating material 12. The coating material 12 can comprise a precious metal-containing solution whose viscosity is increased by means of a gelling agent to such an extent that a continuous wet film of constant thickness can be applied to the substrate 11.

[0070] The elastic base 11 moved relative to the slot nozzle can be a conveyor belt, so that a very precisely adjustable layer thickness of the coating material 12 can be applied flatly onto the moving elastic base 11 via a slot nozzle 13 in order to ensure a reproducible and defined material transfer to the substrate, particularly in connection with the closed surface.

[0071] After the application of the coating material 12, in step S2, the end face of the substrate 1 to be coated is pressed into the coating material 12 using a press-in unit 16, in particular perpendicular to the surface direction of the base 11. The elastic base 11 deforms due to its elasticity, so that even with an uneven end face, the web-shaped surfaces come into contact with the coating material 12. This makes it possible to completely coat all surface sections of the end face of the substrate 1, which are formed by the web-like walls between the through-channels 2, with the coating material, in order to reduce or prevent face plugging across the entire end face.

[0072] After pressing the substrate 1 into the coating material 12 on the elastic base 11, in step S3 the substrate 1 wetted with the coating material 12 is lifted off the base and can then, if necessary, be subjected to a separate thermal treatment in order to dry or calcine the applied coating material.

[0073] Subsequently, in step S4, the coating material 12 is removed from the base 11, e.g. using a stripper 15, and the base 11 is thus prepared again for a subsequent coating of a substrate 1 with a constant wet film thickness.

[0074] In Fig. 5 shows a base plate 14 which has a recess with the flexible cushion 21 located therein. The recess is enclosed by a fastening ring 20. Via an access 23 through the base plate 14, the cushion 21 located in the recess can advantageously be filled with filling material and thus adapted to changed circumstances with regard to the substrate quality. The base plate 14 with the cushion 21 replaces, according to the invention, in the Fig. 3 and Fig. 4 the base plate 14 there.

[0075] Fig.6 shows the base plate 14 with the recess and the flexible cushion 21 located therein beneath the elastic support 11. A substrate 1 with a concave end face is pressed into the coating material 12. The pressure generated on the elastic material 11 is essentially absorbed by the cushion 21 in the recess of the non-elastic base plate 14. After the substrate 1 is lifted from the elastic support 11, the latter can act as a conveyor belt to place the next coating material 12 over the cushion, and a new substrate 1 can be coated accordingly. Numbering of the figures: 1 substrate to be coated 2 through channels 3 partition walls 4 Front surface of the substrate 1 5 inlet openings of the through channels 2 6 partition walls 10 Device 11 elastic pad 12 Coating material 13 Coating unit 14 Base plate 15 pullers 16 Press-in unit 20 mounting ring 21 Flexible Pillow 23 Connection to the filling of the flexible cushion QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 2171232 B1

[0005] EP 3195348 B1

[0007] EP 3400108 B1

[0008] WO 17153239A1

[0016] WO 16057285A1

[0016] WO 15121910A1

[0016] EP 3131660B1

[0027] WO 2008 / 132452 A2

[0029] WO 2019 / 096785 A1

[0029] WO 2019 / 096786 A1

[0029] WO 2022 / 058404 A1

[0029] WO 2020 / 043662 A1

[0029] WO 2015 / 075083 A1

[0029] WO 2019 / 072527 A1

[0029] WO 2019 / 219629 A1

[0029] WO 2020 / 039074 A1

[0029] WO 2018 / 189177 A1

[0029] WO 2017 / 134001 A1

[0029] WO 2017 / 134005 A1

[0029] WO 2017 / 134006 A1

[0029] WO 2017 / 134007 A1

[0029] WO 2013 / 159825 A1

[0029] WO 2017 / 178576 A1

[0029] WO 2018 / 054928 A1

[0029] WO 2018 / 029330 A1

[0029] WO 2022 / 128523 A1

[0029] WO 2022223688A1

[0029] WO 2021151876A1

[0029] WO 2021140326A1

[0029] WO 2008000449A2

[0029] WO 2008113445A1

[0029] WO 2008113457A1

[0029] WO 2019121994A1

[0029] WO 2019121995A1

[0029] WO 9535152A1

[0029] EP 0885650A2

[0029] EP 1046423A2

[0029] EP 1726359A1

[0029] EP 1541220A1

[0029] EP 1900416B1

[0029] EP 3045226A1

[0029] WO 2009012348A1

[0029] EP 1974809B1

[0029] EP 3247493A1

[0030] Cited non-patent literature

[0000] DIN 53505 [0038, 0039, 0041] www.rrg.de

[0039]

Claims

[1] Method for producing a substrate (1) for an exhaust gas aftertreatment device, comprising the following steps: - applying (S1) a coating material (12) to an elastic base (11); - immersing or pressing (S2) a surface of the substrate (1), on which inlet openings of through-channels (2) through the substrate (1) are arranged, into the coating material (12); - lifting (S3) the coated substrate (1); and - post-treatment, in particular drying or calcining of the coating material (12) on the coated substrate (1), - wherein the elastic base (11) extends over a flexible cushion (21) and this cushion absorbs the pressure of the substrate (1) on the elastic base (11) in such a way that all inlet openings of through-channels (2) through the substrate (1) can be wetted with the coating material (12). [2] Method according to claim 1, wherein the coating material (12) comprises a catalytically active component, in particular a noble metal-containing solution. [3] 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 with respect to its axial direction. [4] Method according to one of claims 1 to 3, wherein the base (11) comprises an elastic plastic or a rubber material, in particular a foamed 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 base (11) in a planar manner, in particular with a constant layer thickness. [6] Method according to claim 4, wherein the coating material has a layer thickness of 0.2 to 4 mm. [7] Method according to one of claims 1 to 5, wherein the coating material is shear-thinning, so that the application of the coating material does not lead to film tears, wherein a viscosity of the coating material at 20 °C of 0.5 to 10 Pa*s is selected. [8] Method according to one of claims 1 to 7, wherein the coating material (12) is applied to the substrate (11) by means of a doctor blade or by means of a film drawing device on the substrate (11) or by means of a slot nozzle (13) on the substrate (11) moved relative to the slot nozzle. [9] Method according to one of claims 1 to 8, wherein the residues of coating material (12) of a previous coating process remaining before the application of the coating material (12) are removed, in particular by peeling off. [10] Device (10) for producing a substrate (1) for an exhaust gas aftertreatment device, comprising: - a particularly horizontally oriented elastic base (11) with a closed surface; - an application unit (13) designed to apply a liquid coating material (12) to the substrate (11); - a press-in unit (16) which is designed to immerse or press a substrate (1) to be coated into the coating material (12) after the application of the coating material (12), wherein the elastic base (11) runs over a flexible cushion (21) and this cushion absorbs the pressure of the substrate (1) on the elastic base (11) in such a way that all inlet openings of through-channels (2) through the substrate (1) can be wetted with the coating material (12). [11] Device according to claim 9, wherein a non-elastically deformable base plate (14) is arranged under the elastic base (11) and the cushion (21). [12] Substrate (1) produced by the method according to one of claims 1 to 9.

Images