Applicator for applying coating medium to substrates

Abstract

The invention relates to an applicator (1) for coating a substrate (2) with a coating medium (3), wherein the applicator (1) has at least one supply line (4) for the coating medium, an end plate (9) with at least one nozzle (5) for applying the coating medium onto the substrate (2), and a cavity (6) in which the coating medium can be distributed prior to application onto the substrate (2), wherein at least one nozzle (5) is laterally inclined. The invention also relates to applicator systems, devices, methods and uses related to the applicator.

Description

[0001] Applicator for applying coating medium to substrates

[0002] The present invention relates to an applicator as well as systems, devices, and methods for applying a coating medium to a substrate. The substrates themselves are used, for example, in catalytic exhaust gas aftertreatment, particularly in the automotive sector.

[0003] State of the art

[0004] Substrates or substrate monoliths are used in the chemical industry as catalyst supports. They also play an important role in the treatment of automotive exhaust gases. A variety of catalytic exhaust gas purification technologies have been developed to remove emissions from motor vehicle exhaust gases that are harmful to the environment and health. Their basic principle is usually based on passing the exhaust gas to be purified over a substrate, e.g., a flow-through or wall-flow honeycomb or monolith, with a catalytically active coating applied to it. The catalyst promotes the chemical reaction of various exhaust gas components, forming harmless products such as carbon dioxide and water.

[0005] The flow-through or wall-flow monoliths described above are also referred to as catalyst supports, carriers, or even substrate monoliths, as they carry the catalytically active coating on their surface or in the pores of the wall that form this surface. The catalytically active coating is generally applied to the catalyst support in a coating process in the form of a suspension (often referred to as a "washcoat" in the case of catalysts for exhaust gas purification). Many such processes have been published in the past by automotive catalyst manufacturers (WO9947260A1, EP2521618B1, EP1136462B1, EP1900442A1).

[0006] Despite these state-of-the-art processes, it remains a challenge to uniformly coat substrate monoliths. Varying coating amounts should be avoided whenever possible, for example, due to the high costs of precious metals and rare earths. Uniform coatings are also preferable from a catalytic perspective. The dripping of the coating medium after its application to the substrate also poses a challenge for substrate production.

[0007] An important aspect of such processes is the precise and uniform coating of the inner surfaces of the channels of such catalyst supports with the coating medium (washcoat), particularly with regard to, for example, coating length in the openings of the substrate, the applied coating quantity, the uniformity of the coating thickness, the uniformity of the coating length or of coating gradients along the longitudinal axis of the catalyst support, as well as in the production of layered or zoned coating designs.

[0008] Producing a precise and uniform coating is particularly challenging because the channels of the catalyst supports, into which the coating is uniformly applied, are very narrow. Typical catalyst supports for exhaust aftertreatment systems have approximately 31 to 140 cells / cm 2(200 to 900 cells per square inch, cpsi), so that the openings of the catalyst channels are generally in the tenth of a millimeter range. Uniform coating is made even more difficult because the coating media are suspensions of inorganic particles, which generally have a relatively high viscosity. Therefore, there is a fundamental risk, especially with minor process variations, that the individual channels will be unevenly loaded with coating medium. As a result, the penetration depth of the coating medium into the catalyst support can vary considerably in local areas. Uneven distribution of the catalytic coating can lead to impaired properties of the coated catalyst during intended use. However, since such coating processes are carried out on an industrial scale with a variety of substrates, a high level of uniformity and precision is required.Since the coatings contain precious metals such as platinum and palladium and rare earths, efficient use is also necessary for cost reasons.

[0009] EP2415522A1 describes such a coating process for catalyst supports, in which the coating medium is applied to a substrate from above. The coating medium is fed into a cavity via a plunger through a feed line and then applied to the substrate through the nozzles of a cover plate. The entire amount of coating medium for the catalyst support is first introduced into an area above the substrate and then sucked into the channels by applying a negative pressure. The area above the catalyst support can be delimited laterally by a jacket. In order to obtain a large number of evenly coated substrates in industrial production, it is necessary that exactly the same amount of coating medium is always applied evenly in the area above the substrate.

[0010] A further difficulty with such processes is that the coating medium is discharged from the cover plate under positive pressure. This allows a precisely defined amount of the relatively viscous coating medium to be evenly applied and distributed in the area above the substrate. Too little pressure would result in undesirable variations in the amount and distribution, for example, because some of the coating medium could remain in the nozzles of the cover plate, drip undesirably, or accumulate beneath the cover plate. If the coating medium is discharged under positive pressure, however, a precisely defined amount can be metered and evenly distributed.However, discharge at overpressure can have the undesirable effect that irregularities can arise when the coating medium impacts the substrate and when the area above the substrate is subsequently filled, resulting in uneven coatings.

[0011] Such undesirable effects are particularly problematic on an industrial scale, where a catalyst support is coated within a short period of time. In practice, such an automated coating process generally takes less than 20 seconds, and often only about 4 to 10 seconds.

[0012] If the exact same amount of coating medium is not always used in industrial processes, if it is not evenly sucked into the channels, or if it does not flow evenly down the channels, coated substrates can vary from one another and exhibit significant irregularities in the thickness, uniformity, and depth of the coating in the channels. In practice, it has been shown that even with precise control of the dosage of the coating medium, uniform suction, and drying, coated substrates with significant variations in the coating in the channels are obtained. Figure 7 of the present application shows, by way of example, a cross-section of a catalyst support coated using a typical prior art process.Although the coating medium was evenly applied from the end plate and sucked into the channels of the substrate, the channels were not evenly coated. The darker coating medium penetrated deeply into the channels in some areas, but only slightly in others, where the light, uncoated areas are much larger. Overall, an irregular zigzag pattern can be seen. Too much coating medium was generally applied to the channels and areas that were coated too deeply. This also results in the coating thickness in such channels being greater than intended. As a result, the catalyst channels are tapered, reducing the flow velocities of exhaust gases. Such local variations in catalyst performance and flow lead to reduced catalyst performance during intended use.The exhaust gases are not sufficiently cleaned in areas where the coating depth is too shallow, while in areas where the penetration depth is too deep, the flow is reduced and coating medium is wasted, which generally contains rare and expensive metals.

[0013] A further challenge is that many products require zone coating on both sides of the substrate. For technical reasons, zones with different catalytic coatings must be as close to each other as possible, yet must not overlap. Therefore, flat and straight zone profiles are particularly important for such multiple coatings.

[0014] There is therefore a need for improved devices and methods for coating catalyst supports which overcome the described disadvantages.

[0015] Object of the invention

[0016] The invention is based on the object of providing devices and methods with which a precise and uniform coating of substrates with coating media can be achieved. In particular, a uniform application of coating media into the parallel channels of catalyst supports for exhaust gas purification devices is to be achieved, so that the channels can be coated over a length that is as uniform and defined as possible. The methods should be efficient, rapid, and feasible on an industrial scale with high throughput.

[0017] Subject of the invention The object underlying the invention is achieved by an applicator, method, and uses according to the patent claims. The subject of the invention is an applicator for coating a substrate with a coating medium, wherein the applicator has at least one supply line for the coating medium, a cover plate with at least one nozzle for applying the coating medium to the substrate, and a cavity in which the coating medium can be distributed before application to the substrate, characterized in that at least one nozzle is laterally inclined.

[0018] The coating medium is first introduced into the applicator cavity through a feed line and then forced out of the cavity through the nozzles of the cover plate under pressure. The applicator allows the precise dosing of the coating medium onto a substrate, such as a substrate monolith for automotive exhaust aftertreatment. The applicator applies a defined amount of the coating medium to be applied to a substrate in an area above the substrate. The area above the substrate can, for example, be limited at the bottom by the end face of the substrate (with the openings of the channels) and at the sides by a collar. The coating medium remains in the area above the substrate during dispensing from the applicator, without a vacuum being created and the coating medium being sucked in.Only when the entire amount of coating medium with which the substrate is to be coated has been introduced into the area is it sucked from the area into the substrate by applying a negative pressure.

[0019] It has proven advantageous if the applicator is designed to approximately match the diameter and / or shape of the end face of the substrate to be coated. Larger diameter substrates require larger applicators than smaller ones. Typically, the applicator has a diameter in the range of 50-400 mm, more preferably 75-350 mm.

[0020] Preferably, the cross-section of the area corresponds to the cross-section of the substrate and that of the cover plate. This allows for uniform filling of the area, followed by uniform suction of the coating medium into the substrate.

[0021] The end plate preferably has a symmetrical cross-section, specifically when viewed from the direction in which the coating medium is discharged. The end plate can, for example, have a circular, oval, trapezoidal, square, rectangular, or polygonal, such as a hexagonal, cross-section. The shape of the connecting plate is preferably adapted to the cross-section of the catalyst support.

[0022] The cross-section of the cover plate is preferably circular or oval. This is advantageous, on the one hand, because catalyst supports often have a circular or oval cross-section. Furthermore, it has been found that a round cover plate with laterally inclined nozzles enables a particularly uniform application of the coating medium to the catalyst support. In particular, a particularly uniform circular application pattern can be obtained with a plurality of laterally inclined nozzles.

[0023] It is preferred that the geometry of the nozzle arrangement essentially corresponds to the cross-section of the plate. For example, the nozzles are preferably arranged in a circular pattern on a circular end plate. This is advantageous for maximizing the space in the applicator and preventing the coating medium from being applied unevenly or not at all to certain areas of the catalyst support.

[0024] The cover plate preferably has a thickness of 2-10 mm, more preferably 4-5 mm. The cover plate is preferably shaped like a disc. The cross-section of the cover plate is preferably circular, with the shape preferably being cylindrical. Such round configurations enable a particularly uniform or symmetrical arrangement of the nozzles, and thus a uniform application of the coating medium to the substrate.

[0025] The coating medium is discharged from the applicator through the nozzles of the cover plate. The cover plate preferably has a plurality of nozzles. The term "nozzle" refers to the component of the cover plate from which the coating solution is applied to the substrate. The nozzles comprise flow channels with openings on the inlet and outlet sides of the cover plate. At the inlet side, the coating solution can be forced from the cavity in the applicator into the channels of the nozzles. At the outlet side, the coating medium is discharged and applied to the substrate. According to the invention, at least one nozzle is inclined. "Inclined" means that the nozzle is not arranged at a right angle to the cover plate, as with conventional plates, but is inclined relative to the cover plate.If the plate is not flat, the nozzle is inclined compared to the view of the end plate from the bottom side, i.e. the discharge side.

[0026] According to the invention, the nozzle is inclined laterally. "Laterally" means that the nozzle, when viewed from below, is not exclusively inclined toward the center of the end plate or away from the center of the end plate (outward). The lateral direction is therefore the direction that is at right angles to the direction toward the center. The lateral inclination of the nozzle causes the coating medium to be discharged from the nozzle at an angle to the side, at least partially in a direction that is neither toward nor away from the center.

[0027] If the end plate has a circular or oval cross-section, "sideways" tilted means that the nozzle, viewed from below, is tilted exclusively or partly in a tangential direction. The tangential direction is perpendicular to the radial direction of the round or oval end plate.

[0028] In a preferred embodiment, the at least one nozzle is substantially laterally inclined. This means that the nozzle is either only laterally (tangentially) inclined or that the inclination deviates only slightly from the purely lateral direction (in the case of round or oval plates: the tangential direction), for example by less than 10°, in particular by less than 5°. Thus, the nozzle is not inclined, or is only slightly inclined, towards the center of the plate or outwards (in the radial direction). In these embodiments, the coating medium is discharged substantially or only slightly to the side, but not towards the center or edges of the coating plate. This has the advantage that the coating solution does not accumulate at any point on the substrate, in particular when a large proportion of the nozzles are aligned in the same way. If, on the other hand, the nozzles are inclined towards the center, more coating medium is applied towards the center.If the nozzles are tilted outwards, more coating medium is applied towards the outside, while less is discharged towards the center. For even application, a slight inclination of the laterally tilted nozzles towards the center can also be advantageous, so that each nozzle is tilted slightly towards the neighboring nozzle. The lateral inclination of the nozzle means that the coating medium is not discharged from the end plate in a vertical jet, but rather at an angle to the side. Surprisingly, it has been found that a particularly even coating can be achieved if the nozzles of the end plate are tilted laterally. It is assumed that in this embodiment it is particularly advantageous that the coating medium impacts the substrate from the side. This reduces the force of the impact.Applying the coating medium in the form of oblique jets also appears to result in a more even distribution of the coating medium across the substrate. A further advantage appears to be that the coating medium does not penetrate, or only slightly, into the channels of the substrate before being drawn into them under vacuum. The laterally inclined nozzles may also cause the coating medium to spread quickly laterally on the substrate after impact, thereby further reducing the impact force of the jets during the subsequent application process. Overall, the applicator according to the invention allows the individual channels of the substrate to be coated particularly evenly, with a particularly uniform penetration depth being achieved.

[0029] It is not necessary for the nozzle to be laterally inclined along its entire length. It is only necessary that the lower section be inclined toward the outlet. For example, a laterally inclined nozzle can consist of a straight hole in the end plate and a laterally inclined nozzle on the outlet side.

[0030] In a preferred embodiment, the angle of inclination of the at least one nozzle is between 2 and 50°, preferably between 10 and 40°, and particularly preferably between 15 and 30°. The inclination is defined relative to a view of the plate from below. It has been found that the advantages regarding the uniformity of the coated products can be particularly pronounced at such angles of inclination.

[0031] Preferably, the majority of the nozzles in the end plate have a lateral inclination. According to the invention, it is preferred that at least 80%, in particular at least 90% or at least 95%, of the nozzles in the end plate are laterally inclined. In a preferred embodiment, the nozzles are not inclined, or only slightly inclined, toward the center or outward (in the radial direction).

[0032] The end plate according to the invention preferably has a plurality of nozzles.

[0033] The cover plate preferably has 10 to 500 nozzles, in particular 60 to 320 nozzles, or particularly preferably 95 to 225 nozzles. Such a high number of nozzles enables uniform application of the coating medium and can reduce local variations in the coating.

[0034] Preferably, the nozzles are arranged as uniformly as possible and at as equal a distance from each other as possible. In a preferred embodiment, all nozzles are equally spaced from their neighboring nozzles. Such arrangements are advantageous for achieving the most uniform application of the coating medium and the most uniform coating of the substrate.

[0035] In a preferred embodiment, the cover plate has laterally inclined nozzles and optionally a central nozzle. The central nozzle can be tilted or not tilted. Preferably, all nozzles are laterally inclined, with the central nozzle not tilted. With such an arrangement, the coating medium can be applied particularly evenly to the substrate because all nozzles, possibly except for a central nozzle, discharge the coating medium in the form of oblique jets. With this arrangement, particularly evenly coated substrates can be obtained.

[0036] In another embodiment, the cover plate does not have a central nozzle, but rather at least one inclined nozzle that directs the jet obliquely toward the center of the catalyst support (as viewed from above). This allows the coating medium to be applied evenly, even without a central nozzle in the cover plate, and also to the center of the catalyst support.

[0037] In a preferred embodiment, all nozzles of the end plate are arranged symmetrically, in particular rotationally symmetrically. Preferably, the laterally inclined nozzles are arranged in concentric circles around the central, non-inclined nozzle. The plate preferably comprises a central nozzle and 2 to 9 hole circles, each with 6 to 54 nozzles, in the periphery. The nozzles are spaced as evenly as possible from one another. The arrangement in concentric circles is particularly advantageous because it allows for a uniform distribution of the nozzles in a simple design. In a preferred embodiment, the nozzles in a concentric circle are aligned equally. Each nozzle can be inclined tangentially or towards an adjacent nozzle in the same way. This achieves a particularly uniform distribution of the coating medium on the substrate. In a preferred embodiment, the nozzles are arranged in a spiral.The nozzles are arranged in a spiral pattern from the center of the plate outward. Even with this arrangement, a uniform application of the coating medium to the substrate can be achieved.

[0038] In a preferred embodiment, the distance between the nozzles is between

[0039] 4 to 20 mm, preferably between 6 and 10 mm, each relative to the center of the discharge openings. Preferably, all spacings between adjacent nozzles in the end plate, in each concentric circle and / or in a spiral arrangement, are identical.

[0040] The diameter of the discharge opening of the nozzles is preferably between 0.5 and 5 mm, particularly preferably between 1.6 and 3 mm. Preferably, all nozzles in the plate have discharge openings of the same diameter. This enables particularly uniform application and coating of the substrate. Such nozzles allow coating media to be applied particularly efficiently to substrates that are catalyst supports for exhaust gas purification devices with fine parallel channels.

[0041] Alternatively, the coating medium can be applied unevenly to the substrate. This can result in a coating with a gradient. For specific applications, it may be advantageous to set a higher concentration of the catalytic coating in the inner or outer channels. A gradient can be achieved, for example, if the nozzle outlet openings differ from one another in certain areas of the plate and / or if the nozzle inclination is varied so that more coating solution is discharged in some areas than in others.

[0042] It is preferred that the nozzles are designed in the shape of a nozzle. This means that they protrude from the end plate towards the discharge side. The nozzle design is advantageous because a lateral inclination can be adjusted in a relatively simple and stable manner and gluing the plate from below is made more difficult. The nozzles preferably have a length of 5 mm - 15 mm, more preferably a length of 6 - 8 mm. The height of the elevation above the edge of the end plate is around 0.5 - 2.9 mm, more preferably 1.5 - 2.5 mm. In a preferred embodiment, the nozzles have a concave or countersunk nozzle towards the outlet. The distance between the nozzles is preferably in the range of

[0043] 5-20 mm and most preferably 8-14 mm. In another embodiment, the nozzles can be channels that do not protrude from the plate, for example, in the form of holes.

[0044] The nozzles in the cover plate, which are preferably nozzle-shaped, can have any shape and cross-section (e.g., channels, slots, circles, spirals, etc.). In the simplest case, the nozzles are channels with a round cross-section. The nozzles and / or outlet openings in the cover plate are preferably of the same size.

[0045] The cavity, the end plate with its nozzles are preferably coordinated in their dimensions and design to ensure a homogeneous distribution of the coating medium on the substrate to be coated.

[0046] The entire applicator is preferably made of plastic. However, it can also be constructed entirely of metal. The materials are selected to be compatible with the catalytically active coating for automotive exhaust aftertreatment. PE-HD 1000 is the preferred plastic material. Metal parts are preferably made of a stainless steel equivalent to or similar to material number 1.4571 (X6CrNiMoTi17-12-2).

[0047] In a preferred embodiment, a baffle plate is arranged in the cavity, blocking the flow of the coating medium from the supply line to at least one opening. The coating medium is preferably metered into the applicator by a pump. The baffle plate can be arranged statically. Alternatively, the baffle plate can be reversibly movable. In this case, it preferably blocks the flow of the coating medium in the unpressurized state, while when pressure is exerted on the baffle plate by the coating medium, the flow of the coating medium from the supply line to at least one opening is permitted. The pressure built up via the coating medium serves to displace the baffle plate of the applicator such that the path to the end plate opens. The coating suspension can then be pressed into the cavity of the applicator, for example, through nozzles in the baffle plate.The baffle plate inside the applicator, which closes when depressurized, prevents the coating medium from dripping onto the front side of the substrate. With such a movable baffle plate, the accuracy of dosing the coating medium onto the substrate can be further increased. The applicator and the methods can be used to coat a variety of substrates. It is preferred that the interior of the substrate is coated. The substrate preferably has a plurality of channels, which are in particular parallel to one another and which are specifically loaded with the coating medium from one side, in particular by suction. The substrate is particularly preferably a catalyst support for exhaust gas aftertreatment.The channels are preferably filled in such a way that their inner surfaces are coated but not completely filled, so that they are still permeable to fluids such as exhaust gases after the coating has dried.

[0048] The applicator is advantageously used to produce a substrate monolith with a catalytically active coating for automotive exhaust aftertreatment. The coating medium used here is generally a suspension (slurry, washcoat), which may have acidic or basic properties, but at least has a very abrasive effect (see below). This must be taken into account in the advantageous design of the applicator according to the invention. The coating media to be used are well known to those skilled in the art.

[0049] The substrate is preferably a catalyst support of the wall-flow type (wall-flow filter) or of the flow-through type, in particular in the form of a monolith. Flow-through monoliths are catalyst supports commonly used in the prior art, which can be made of metal (corrugated carrier, e.g. WO17153239A1, WO16057285A1, WO15121910A1 and literature cited therein) or ceramic materials. Refractory ceramics such as corderite, silicon carbide or aluminum titanate, etc., are preferably used. The number of nozzles per area is characterized by the cell density, which is usually between approximately 1,300 and 5,800 cells / cm 2 (200 to 900 cells per square inch, cpsi). The wall thickness of the ceramic nozzle walls is between 0.5 and 0.05 mm.

[0050] Any conventional ceramic material can be used as wall-flow monoliths or wall-flow filters. Porous wall-flow filter substrates made of corderite, silicon carbide, or aluminum titanate are preferred. These wall-flow filter substrates have inlet and outlet openings, with the downstream ends of the inlet openings and the upstream ends of the outlet openings sealed with gas-tight plugs offset from one another. The exhaust gas to be cleaned, which flows through the filter substrate, is forced to pass through the porous wall between the inlet and outlet openings, resulting in an excellent particle filtration effect. The filtration properties for particles can be tailored to the porosity, pore / radius distribution, and wall thickness.The porosity of the uncoated wall-flow filters is generally more than 40%, generally from 40% to 75%, particularly from 50% to 70% (measured according to DIN 66133 - latest version on the filing date). The average pore size (diameter) of the uncoated filters is at least 7 μm, e.g., from 7 μm to 34 μm, preferably more than 10 μm, particularly more preferably from 10 μm to 25 μm, or very preferably from 15 μm to 20 μm (measured according to DIN 66134 - latest version on the filing date).

[0051] The coating medium is preferably a suspension. The solvent is preferably water. Such coating media are referred to in the technical field as washcoats. The coating medium is preferably pseudoplastic (https: / / de.wikipedia.org / wiki / Strukturviskosit%C3%A4t). The viscosity is preferably from 1.0087 to 1000 mPas, preferably 100 to 780 mPas, at a shear rate of 100 l / s. The viscosity can be measured, for example, with a viscometer according to EN ISO 3219. The coating media, particularly in the form of washcoats, have solids and contain the catalytically active components or their precursors as well as inorganic oxides such as aluminum oxide, titanium dioxide, zirconium oxide, cerium oxide, or combinations thereof, where the oxides can be doped with, for example, silicon or lanthanum.Oxides of vanadium, chromium, manganese, iron, cobalt, copper, zinc, nickel, or rare earth metals such as lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, or combinations thereof can be used as catalytically active components. Precious metals such as platinum, palladium, gold, rhodium, iridium, osmium, ruthenium, and combinations thereof can also be used as catalytically active components. These metals can also be present as alloys with each other or with other metals, or as oxides. In the liquid coating medium, the metals can also be present as precursors, such as nitrates, sulfites or organyls of the precious metals mentioned as well as their mixtures, in particular palladium nitrate, palladium sulfite, platinum nitrate, platinum sulfite or Pt(NH3)4(NOs)2 can be used.The catalytically active component can then be obtained from the precursor by calcination at about 400°C to about 700°C.

[0052] Metal ions from the platinum group metals, in particular platinum, palladium, and rhodium, have proven suitable for the oxidation of hydrocarbons, while the SCR reaction, for example, has been shown to be most effective with zeolites or zeotypes (molecular sieves with other or additional elements as cations in the framework compared to zeolites) that are exchanged with iron and / or copper ions. The material that determines the catalytic activity (washcoat) can therefore also contain zeolites or zeotypes. In principle, all types or mixtures thereof that are suitable for the respective application area can be used as zeolites or zeotypes. These include naturally occurring, but preferably synthetically produced zeolites. These can have framework types, for example, from the group consisting of beta, ferrierite, Y, USY, ZSM-5, ITQ.Examples of synthetically produced small-pore zeolites and zeotypes in question here are those that have the structural types ABW, AGO, AEI, AEN, AFN, AFT, AFX, ANA, APC, APD, ATN, ATT, ATV, AWO, AWW, BIK, BRE, CAS, ODO, CHA, DDR, DFT, EAB, EDI, EPI, ERI, ESV, GIS, GOO, IHW, ITE, ITW, JBW, KFI, LEV, LTA, LTJ, MER, MON, MTF, NSI, OWE, PAU, PHI, RHO, RTE, RTH, SAS, SAT, SAV, SIV, THO, TSC, UEI, UFI, VNI, YUG and ZON. Preference is given to using small-pore zeolites derived from a structural type from the group consisting of CHA, LEV, AFT, AEI, AFI, AFX, KFI, ERI, and DDR. Particularly preferred are those derived from the CHA, LEV, AEI, AFX, AFI, or KFI framework. Zeolites of the AEI or CHA type are particularly preferred in this context. Mixtures of the aforementioned species are also possible. The SAR value of the zeolite or the corresponding value for the zeotype (e.g.,SAPO -> (Al+P) / 2Si) should be in the range of 5 to 50, preferably 10 to 45, and very preferably 20 to 40. For correspondingly good activity, e.g. in the SCR reaction, it is necessary that the zeolites or zeotypes, and in particular the small-pore type, are exchanged with metal ions, especially transition metal ions. Here, the person skilled in the art can use the metal ions preferably used for the corresponding reaction, especially copper ions. The person skilled in the art knows how such an ion exchange can be carried out (e.g. W02008 / 106519A1). The degree of exchange (number of ions at exchange sites / total number of exchange sites) should be between 0.3 and 0.5. Exchange sites here are those where the positive ions compensate for negative charges of the lattice. Preferably, other non-exchanged metal ions, in particular Fe and / or Cu ions, can also be present in the final SCR catalyst.The ratio of exchanged to non-exchanged ions is >50:50, preferably 60:40 - 95:5, and most preferably 70:30 - 90:10. The ions occupying exchange sites are visible in electron paramagnetic resonance analysis and can be quantitatively determined (Quantitative EPR, Gareth R. Eaton, Sandra S. Eaton, David P. Barr, Ralph T. Weber, Springer Science & Business Media, 2010). All non-ion-exchanged cations are located elsewhere within or outside the zeolite / zeotype. The latter do not compensate for any negative charge of the zeolite / zeole type framework. They are invisible in EPR and can thus be calculated from the difference between the total metal loading (e.g., determined by ICP) and the value determined in EPR. The addition of the corresponding ions to the coating mixture is controlled so that the total amount of metal ions, in particular Fe and / or Cu ions in the final catalyst is 0.5 - 10 wt.%, preferably 1 - 5 wt.-% of the coating quantity.

[0053] In addition to the components just discussed, the coating medium can also contain other constituents. These components can further support the catalytic function of the catalytically active material, but do not themselves actively intervene in the reaction. Materials used here include so-called binders. The latter ensure, among other things, that the materials and components involved in the reaction can adhere sufficiently firmly to the corresponding substrate. Binders selected from the group consisting of aluminum oxide, titanium dioxide, zirconium dioxide, silicon dioxide or their oxide hydroxides (e.g. boehmite) or mixtures thereof have proven advantageous components in this context. High-surface-area aluminum oxides are advantageously used in this case. The binder is used in a specific amount in the coating.Based on the solid material used in the coating suspension, the further component, e.g. the binder, is used in an amount of max. 25 wt.%, preferably max. 20 wt.% and very particularly preferably in an amount of 5 wt.% - 15 wt.%.

[0054] The substrate monoliths produced in this way, which are catalytically active in exhaust gas aftertreatment, can in principle be used in all exhaust gas aftertreatment systems known to those skilled in the art in the automotive exhaust gas sector. The catalytic coating of the substrate monolith can preferably be selected from the group consisting of three-way catalysts, SCR catalysts, nitrogen oxide storage catalysts, oxidation catalysts, and soot ignition coatings. Regarding the individual catalytic activities in question and their explanation, reference is made to the statements in WO2011151711 A1. The invention also relates to a method for coating a substrate with a coating medium using an applicator according to the invention, comprising the steps:

[0055] (a) Applying the coating medium through the nozzles of the end plate onto the substrate, and

[0056] (b) Suction of the coating medium into the substrate.

[0057] The coating medium is applied in step (a) in an area above the substrate. Due to the at least partially oblique arrangement of the nozzles, the coating medium is applied to the substrate in an oblique jet, which leads to a particularly uniform coating. Only when the complete amount of coating medium for the substrate has been fed into the area is the coating medium sucked into the substrate in step (b). The sucking in takes place by applying a negative pressure, in particular a vacuum. In step (a), the coating medium is preferably applied using pressure, for example between 0.3 and 10 bar, in particular between 1.5 and 3.5 bar. In step b), the sucking in preferably takes place with a negative pressure, for example between 10 and 500 mbar, in particular between 50 and 200 mbar. With such settings, a particularly efficient and rapid production of the coated substrate can be achieved.

[0058] The process is preferably automated and carried out at high throughput, preferably in a continuous process for a defined number of pieces. In automated processes, the coating medium is applied in step (a) at high speed, for example, within a time period of 200 ps to 6 s, in particular between 500 ps and 3 s. Preferably, the suction in step (b) takes place within a time period of 10 ps to 10 s, in particular between 20 ps and 2.5 s.

[0059] The process according to the invention is advantageous in that it allows for a particularly uniform coating of the fine channels of a catalyst support. Since the penetration depth of the coating medium into the catalyst substrate is particularly uniform, the process is particularly suitable for automated production, in which a large number of substrates are coated in rapid succession.

[0060] In a preferred embodiment, the process applies two or more coatings to the same substrate, typically in defined subregions (zones) with different catalytic effects. In the prior art, it is particularly complex to apply multiple coatings to a catalyst substrate in specific regions. Particular care must be taken to ensure that the zones are relatively clearly localized. Since the process according to the invention allows precise control of the penetration depth, the process is particularly suitable for applying and combining zones.For example, a catalyst substrate can be coated on one side with a zone of a first coating medium at a penetration depth of, for example, 10 to 90% of the channel length. A second coating medium is then applied from the other side of the catalyst substrate in a second zone, also at a penetration depth of, for example, 10 to 90% of the channel length. Such zones can be applied in different areas of the substrate and / or on top of each other to optimize specific catalytic reactions.

[0061] The invention also relates to an applicator system for coating a substrate with a coating medium, comprising an applicator according to the invention and a control unit by means of which a defined amount of coating medium can be dispensed from the applicator. The control unit can preferably be set to repeatedly dispense the same defined amount of coating medium. The system preferably comprises dosing means, such as a tank, supply lines, and valves. This allows a series of similar substrates to be coated in the same way in an automated process. The defined amount of coating medium is selected and set, for example, with regard to the dimensions of the substrate and the channels as well as the desired coating. It is, for example, between 20 ml and 5000 ml, in particular between 60 ml and 1500 ml, particularly preferably between 120 ml and 800 ml.The applicator system may include other common means such as a tank for coating medium, a positive displacement pump, valves and a control unit to monitor the process.

[0062] The invention also relates to a device for coating a substrate with a coating medium, comprising

[0063] (i) an applicator and / or an applicator system according to the invention,

[0064] (ii) means for fixing the substrate beneath the applicator,

[0065] (iii) an area above the fixed substrate for introducing the coating medium from the applicator, and (iv) means for sucking the coating medium into the substrate.

[0066] The device can be used to carry out the coating process described above. The means for securing the substrate is preferably a holder into which the substrate can be received, secured, and removed again after coating, preferably in an automated process. The region (iii) can be temporarily formed after the substrate has been secured, for example by attaching a jacket to the upper edge of the substrate to prevent the coating medium from flowing out to the sides. The means for suction can be a vacuum pump that is connected to the substrate from below via a pipeline. The device can preferably coat a plurality of substrates one after the other in an automated manner, without external intervention in the process.

[0067] The invention also relates to the use of an applicator, applicator system and / or device according to the invention for producing a substrate monolith with a catalytically active coating for automotive exhaust gas aftertreatment.

[0068] The invention also relates to the use of the applicator, applicator system and / or device according to the invention for increasing the uniformity of the coating in a substrate monolith.

[0069] In the methods and uses mentioned, the applicator of the invention, as described above, is preferably used.

[0070] Figures 1 to 8 show schematically and by way of example embodiments of the invention and, for comparison, objects according to the prior art.

[0071] Fig. 1 shows schematically and by way of example a device for coating substrates with an applicator according to the invention in cross section.

[0072] Fig. 2 shows, by way of example and schematically, the lateral lower view of the end plate of an applicator according to the invention.

[0073] Fig. 3 shows the cross-section through a cover plate with a laterally inclined nozzle.

[0074] Fig. 4 shows the top view of the discharge side of the end plate according to Fig. 2.

[0075] Fig. 5 shows the top view according to Fig. 4, in which the concentric circles of the nozzles and the radial direction of the plate are indicated. Fig. 6 shows a section of the cross-section of a cover plate with a laterally inclined and a vertical nozzle and jets of coating medium impinging on a substrate.

[0076] Fig. 7 is a photograph of the cross-section of a catalyst support coated in a conventional manner with a cover plate with vertical nozzles.

[0077] Fig. 8 is a photograph of a catalyst support coated according to the invention with a cover plate with inclined nozzles. The photograph shows a direct comparison to Fig. 7 from the same test series.

[0078] In the following, embodiments of the invention and, for comparison, according to the prior art are explained with reference to the figures.

[0079] Figure 1 shows, by way of example and schematically, the cross-section of a device for coating a substrate 2 with an applicator 1 according to the invention. The substrate 2 to be coated is fixed for a coating process by means 15, such as a holder. The coating medium is metered onto the end face of a substrate 2, which is a catalyst carrier with a plurality of fine parallel channels 14. A type of collar 11 is placed / inserted around this end face, preventing the coating medium from running down the end face and the sides of the substrate 2. The end face of the substrate 2 and the collar 11 delimit an area 10 into which the coating medium is introduced before the substrate 2 is coated. The coating medium is first fed via the feed line 4 into a cavity 6 above the end plate 9. The end plate 9 has a plurality of laterally inclined nozzles 5.The coating medium is introduced through the nozzles from the cavity 6 into the area 10 above the substrate 2. In doing so, the exact amount of coating medium required to coat the specific substrate is introduced. After the coating medium has been introduced, a vacuum is created below the substrate 2 using means 13, such as a pump, whereby the coating medium is sucked from above into the parallel channels 14. The amount, thickness, and penetration depth of the coating medium can be controlled, among other things, by the amount and viscosity of the coating medium, the structure of the substrate 2, and the vacuum. The process can be adjusted so that the coating penetrates into the channels 14 up to a zone boundary 16. The coating medium can be introduced up to a zone boundary 16.This means that the process is conducted in such a way that the coating medium is applied only above the zone boundary 16, so that the catalyst support 1 is coated on only one side. The zone boundary 16 is shown as a line and thus represents an ideal profile. In practice, the zone boundary is irregular. The uniformity can be significantly improved with the applicator 1 according to the invention (see Figures 7 and 8).

[0080] 2, 3 and 5 show schematically and by way of example an applicator 1 according to the invention with an end plate 9 which has a plurality of laterally inclined nozzles 5. Fig. 2 shows a lateral bottom view of the applicator 1, Fig. 4 a bottom plan view and Fig. 5 a plan view according to Fig. 4 with concentric circles of the nozzles and the radial direction from the center of the plate outwards. The end plate 9 is round, which enables an arrangement of the nozzles 5 in concentric circles with equal spacing. The inclination of the nozzles 5 in the concentric circles is exclusively lateral and tangential, as can also be seen in Fig. 5 with the concentric circular patterns. This means that the nozzles 5 in the concentric circles are not inclined inwards or outwards in the indicated radial direction. This enables a uniform application of the coating medium.The nozzles 5 are regularly arranged and equally spaced from one another. This enables uniform discharge of the coating medium into an area 10 above the substrate. The nozzles 5 in each concentric circle are essentially inclined towards the adjacent nozzle. This achieves a regular discharge pattern. Furthermore, this prevents the jets of coating medium from the nozzles 5 from impinging perpendicularly onto the substrate and preventing coating medium from undesirably penetrating channels before the vacuum is applied. The nozzles in Figs. 2 to 5 have nozzles 12 that protrude from the end plate. Fig. 3 shows a cross-section of the end plate 9 with a laterally inclined nozzle 5 with a nozzle 12.

[0081] Fig. 6 shows, by way of example and schematically, how coating medium 3 is discharged from a laterally inclined nozzle 7 and, for comparison, from a vertical nozzle 8 into the region 10 above the substrate 2. An oblique jet is generated from the laterally inclined nozzle 7, whereby the effect of the impact on the upwardly open, fine channels 14 of the substrate 2 is weakened. In this way, unwanted penetration of the coating medium 3 into the channels 14 before suction can be prevented or at least significantly reduced, which leads to a more homogeneous coating. Figs. 7 and 8 show photographs of cross sections of coated catalyst supports and illustrate the advantages of the invention. Fig. 7 shows the cross section of a coated catalyst support according to the prior art, which was produced using an applicator with an outlet plate with vertical nozzles. The upper coated zone is dark and the lower uncoated zone is lighter.The coating has penetrated the channels irregularly. Significant and random fluctuations can be seen over larger domains. Particularly noticeable are smaller areas in which the coating medium has penetrated relatively deeply into the channels in an undesirable manner. Fig. 8 shows the cross-section of a catalyst support coated according to the invention. The support and the resolution correspond to Fig. 7, so the products are comparable. In Fig. 8 it can be seen that the zone boundary between the dark coated zone and the light uncoated zone is uniform and straight. Significant irregularities, as in Fig. 7, are not present. It should be noted that the somewhat darker tint of some sections below the zone boundary is not caused by penetrated coating medium, but by shadows. The loose components, which are only visible in Fig.8 are caused by the splitting process and are also not relevant for the comparison of the coatings. A comparison of Figures 7 and 8 shows that a significant improvement in the uniformity of the coating can be achieved with the applicator according to the invention with laterally inclined nozzles.

[0082] The applicator, applicator system, device, methods, and uses according to the invention solve the problem underlying the invention. According to the invention, it is possible to coat substrates, such as catalyst supports for exhaust gas purification devices, with high precision. This is made possible by a simple design measure, so that the process can be carried out efficiently, quickly, and on an industrial scale with high throughput. In particular, it is possible to coat the fine channels of catalyst supports for exhaust gas purification devices with high precision, whereby clearly defined zones can be obtained. This enables significant savings in expensive catalytic materials, especially precious metals or rare earths, and the provision of particularly high-performance exhaust gas purification devices and other catalytic devices. List of reference symbols:

[0083] 1 applicator

[0084] 2 Substrate to be coated 3 Coating medium

[0085] 4 Supply area inside the applicator (1)

[0086] 5 Nozzle in the end plate (9)

[0087] 6 Cavity inside the applicator (1)

[0088] 7 inclined nozzle 8 straight nozzle

[0089] 9 End plate

[0090] 10 Area above the substrate

[0091] 11 Collar that delimits the area (10)

[0092] 12 Nozzle 13 Means for sucking in the coating medium

[0093] 14 parallel channels in the substrate (2)

[0094] 15 means for fixing the substrate

[0095] 16 Zone boundary

Claims

Patent claims 1 . Applicator (1) for coating a substrate (2) with a coating medium (3), wherein the applicator (1) has at least one feed line (4) for the coating medium, an end plate (9) with at least one nozzle (5) for applying the coating medium to the substrate (2), and a cavity (6) in which the coating medium can be distributed before application to the substrate (2), characterized in that at least one nozzle (5) is laterally inclined.

2. Applicator (1) according to claim 1, characterized in that the angle of inclination of the laterally inclined nozzle is 2 to 50°, preferably 15 to 30°.

3. Applicator (1) according to at least one of the preceding claims, characterized in that the end plate (9) has a circular or oval cross-section.

4. Applicator (1) according to claim 3, characterized in that the at least one nozzle (5) is not substantially inclined inwards or outwards in the radial direction.

5. Applicator (1) according to at least one of the preceding claims, characterized in that the nozzles are arranged at equal distances from one another.

6. Applicator (1) according to at least one of the preceding claims, characterized in that the end plate (9) has a plurality of laterally inclined nozzles and a central nozzle.

7. Applicator (1) according to at least one of the preceding claims, characterized in that laterally inclined nozzles (5) are arranged in concentric circles around a central nozzle.

8. Applicator (1) according to claim 7, characterized in that the nozzles (5) in each concentric circle are aligned and / or inclined in the same way.

9. Applicator (1) according to at least one of the preceding claims, characterized in that the nozzles (5) are arranged spirally.

10. Applicator (1) according to at least one of the preceding claims, characterized in that a baffle plate in the cavity (6) blocks the flow of the coating medium (3) from the feed line (4) to the at least one nozzle (5) in the unpressurized state and allows the flow of the coating medium (3) from the feed line (4) to the at least one nozzle (5) when pressure is exerted by the coating medium (3) on the baffle plate.

11. Applicator system for coating a substrate (2) with a coating medium (3), comprising an applicator (1) according to at least one of the preceding claims and a control unit which is adjustable to discharge a defined amount of coating medium (3) from the applicator (1).

12. Device for coating a substrate (2) with a coating medium (3), comprising (i) an applicator (1) and / or an applicator system according to at least one of the preceding claims, (ii) means for fixing the substrate (2) beneath the applicator (1), (iii) an area (10) above the fixed substrate (2) for introducing the coating medium (3) from the applicator (1), and (iv) means for sucking the coating medium (3) into the substrate (2).

13. A method for coating a substrate with coating medium using an applicator (1), an applicator system and / or a device according to at least one of the preceding claims, comprising the steps: (a) applying the coating medium (3) through the nozzles (5) of the end plate (9) onto the substrate (2), and (b) Suction of the coating medium (3) into the substrate (2).

14. Use of an applicator (1), an applicator system and / or a device according to one of claims 1 to 12 for producing a substrate monolith with a catalytically active coating for automotive exhaust gas aftertreatment.

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