Device for applying a coating

Abstract

The invention relates to a device (1) for applying a coating (B) with at least one slot (2) extending over a length (L) and a storage chamber (3) for the coating material. The device according to the invention is characterized in that several discrete and individually controllable heating elements (5) are provided along the length (L).

Description

[0001] The invention relates to a device for applying a coating, comprising at least one slit extending over a length and a reservoir for a coating material. The invention also relates to a method for applying a coating with such a device, as well as the use of the device and / or the method.

[0002] Such devices are also known as slot nozzles. Slot nozzles for applying coatings, for example, for applying a dispersion of solids and a binder to a surface moving relative to the slot nozzle, are known from the prior art. The coating material fed to the slot nozzle is often referred to as a suspension or, more commonly, by the English term slurry.

[0003] An exemplary slot nozzle coating device is known from EP 4 169 623 A1. This document shows that, to achieve a more uniform coating application, the design of the slot nozzle, such as the shape of the reservoir, can be adapted with considerable effort. This is extremely complex and, in practice, typically only works for a single, consistently identical mixture of the coating material, which represents a significant disadvantage.

[0004] The object of the present invention is to create an improved device for applying a coating material using a slot nozzle, which is able to provide a desired, for example uniform, layer thickness of the coating simply, efficiently and for various coating materials.

[0005] According to the invention, this problem is solved by a device having the features in claim 1, and in particular in the characterizing part of claim 1.

[0006] The device according to the invention for applying a coating comprises, similar to the structure described in the prior art, a slot extending over a certain length, which is connected along its entire length to a reservoir for the coating material. The special feature of the invention lies in the fact that several discrete and individually controllable heating elements are provided distributed along the length of the slot. These heating elements allow the coating material to be heated. The heating can be implemented such that, along the length of the slot, certain sections are heated more intensely than others. The viscosity of the coating material can be influenced by the heating.Typically, the viscosity of the coating material decreases with increasing temperature, allowing the material to flow more easily. In the area of ​​the slot where the material has the lower viscosity, the coating becomes correspondingly thicker. Therefore, if irregularities in the coating thickness are observed after a short coating run, the temperature can be easily and efficiently increased in those areas where the coating is thinner than desired, thus reducing the viscosity of the coating material. More coating material will then be extruded, resulting in the desired layer thickness.

[0007] Besides achieving a uniform coating thickness, which is usually desirable, it is of course also possible to achieve deliberately irregular coating thicknesses in this way, if this should be desired.

[0008] According to a particularly advantageous embodiment of the device according to the invention, the heating elements are electrical resistance heating elements which can be controlled very simply and efficiently independently of one another via an electronic control system. In principle, a control system is also conceivable which adjusts the temperature accordingly based on measured values ​​of the layer thickness in order to achieve a uniform or desired non-uniform layer thickness.

[0009] According to a particularly advantageous embodiment, the heating elements are in thermally conductive contact with the transition zone between the reservoir and the respective longitudinal section of the slot in the device or slot nozzle, thus ensuring heating occurs precisely in the area where the change in viscosity is most beneficial. Naturally, other areas of the reservoir can also be heated, so that the device, for example, has a multitude of electrical resistance heating elements extending over a large portion of the device's height and positioned side-by-side along the length of the slot, either within the device or adhered to its surface. Since the device itself is typically made of a highly thermally conductive material such as a metal, this is sufficient to achieve the desired effect.

[0010] A further highly advantageous embodiment can provide that the heating elements are arranged unevenly along the length of the slot nozzle. This allows design areas where the uniform dispensing of the coating material is critical to be equipped with more and / or more closely spaced heating elements, or with heating elements with a higher heating capacity, than other areas. It is particularly preferred that, in the longitudinal direction, the spacing of the heating elements is greater in the center of the slot than at the outer edges.

[0011] As mentioned above, this device allows for the very uniform or desired uneven coating of a substrate by adjusting the viscosity of the coating material along the length of the slot, depending on the desired layer thickness, through an increase or decrease in the temperature in the respective area. The device and / or the process can, in principle, be used for any type of coating. It is particularly suitable for coating a carrier film with an active material for an electrode, provided it is supplied as a slurry, in order to produce, for example, anodes and / or cathodes for lithium-ion batteries.

[0012] Further advantageous embodiments and developments of the device according to the invention also result from the exemplary embodiment, which is described in more detail below with reference to the figures.

[0013] This shows: Fig. 1 a schematic view of a device for slot nozzle coating in a design according to the prior art; Fig. 2 a sectional view of the device made of Fig. 1 according to line II - II; and Fig. 3 a view analogous to the one in Fig. 1 in a device according to the invention for slot nozzle coating.

[0014] In the presentation of the Fig. Figure 1 and, directly adjacent to it in a sectional side view, each device labeled 1 for applying a coating by means of at least one slot 2 extending over a length L can be seen. Such devices 1 are often also referred to as slot nozzles, and the coating process carried out with them as slot nozzle coating.

[0015] The slot nozzle 1 includes an internal storage chamber designated 3, the shape of which has been chosen here purely as an example. This chamber could just as easily be located in only one half of the slot nozzle 1 or have any other shape than shown here.

[0016] In practice, a coating material, for example in the form of a so-called slurry, is always supplied to this slot nozzle 1 or its storage chamber 3. In the illustration of the Fig. Figure 1 indicates the supply of the coating material into the reservoir 3 via the thick arrow labeled 4. In this way, the reservoir 3 is supplied with pressurized coating material, which then exits the slot 2 along its length L and, in a manner known per se, is deposited onto a substrate movable relative to the slot 2, as shown in the illustration. Fig. The substrate S, as indicated by the feed direction V, is applied to the slot 2. This substrate S moves relative to the slot 2 in the direction of feed V, so that the coating designated B is applied.

[0017] The substrate S can be positioned below the slot 2 in the direction of gravity, or above it, or at an angle to it, so that the feed direction V, e.g. at an angle of 90°, runs in the direction of gravity. This is not essential for the device shown here.

[0018] In practice, it is often the case that the coating B applied using such a slot nozzle 1 results in uneven layer thicknesses along the length L, which typically corresponds to the width of the substrate S to be coated. This is shown in the illustration of the Fig. Figure 1 is symbolized by the arrows of varying thickness, which represent the exit of the coating material from slot 2. In this example, less material is discharged from slot 2 at the outer edge than in the center. This can typically be counteracted by the shape of the reservoir 3, which is already achieved here by the upwardly curved edge.

[0019] Nevertheless, a uniform coating thickness cannot be achieved with such a device 1, or at best only with a design tailored to exactly one slurry of a specific composition and viscosity. Flexibility in using the device 1 for different mixtures is then no longer possible; instead, a very complex custom design is required for each individual mixture. Limited flexibility is possible with conventional slot nozzles, where very limited measures can be taken to compensate for non-homogeneous loading by placing shims of varying thicknesses between the nozzle plates. This alters the pressure conditions in the nozzle, which can lead to profile changes. However, not every slurry can be applied uniformly using this complex method.

[0020] To efficiently counteract this and to achieve a device 1 with high flexibility regarding the coating material used and the possibility of simple and efficient adjustment of the dispensed coating quantity with respect to the length L of the slot 2, the device 1 is additionally equipped with heating elements 5. These heating elements 5, which are shown in the illustration of the Fig. The heating elements 5, which can be identified as 3, are arranged as several discrete heating elements 5 along the length L. In the embodiment shown here, nine heating elements 5 are used, only of which are designated with the reference numeral 5. These discrete heating elements 5 can be implemented, for example, as electrical resistance heating elements, such as heating mats. The heating elements 5 can be individually controlled, which allows for different heating levels in the individual areas of the device 1, and thus of the coating material located in the storage chamber 3, relative to the length L.If, for example, a coating material is used which has a lower viscosity at a higher temperature, i.e., flows more easily, then the amount of coating material applied to the area of ​​the respective heating element 5 can be increased by raising the temperature in order to achieve the most uniform coating possible.

[0021] Based on the one in Fig. In the case shown in 1, where the laterally outer areas in the direction of length L have a smaller layer thickness, the heating would therefore decrease, for example, from the outside towards the center, in order to reduce the heat output in the Fig. The uniform coating shown in Figure 3 is achieved by a uniform exit of the coating material from slot 2. To counteract, in particular, such a systematically reduced discharge of the coating material in the outer edge regions, it can be, as shown in the illustration of the Fig.As shown in Figure 3, the distances between the heating elements 5 vary in the direction of the length L, in particular that they are smaller in the outer areas than in the middle, so that there are more heating elements 5 per unit length in the outer areas of the slot 2 than in the middle.

[0022] By selectively controlling these heating elements 5, a uniform coating can now be achieved across the entire length L of the slot 2 and thus typically across the entire width of the substrate S. The values ​​required for this can be easily and efficiently determined experimentally and saved. They can then be reused later, so that a coating B with a homogeneous layer thickness can be achieved reproducibly for the respective slurry. If different values ​​are required for a different type of slurry, for example with different binders and / or additives, these can also be determined and saved for reuse of the same slurry, and then adjusted accordingly.

[0023] In addition, it would also be conceivable in principle to regulate the temperature depending on the layer thickness measured in different areas across the width of the substrate S. QUOTES INCLUDED IN THE DESCRIPTION

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

[0000] EP 4 169 623 A1

[0003]

Claims

[1] Device (1) for applying a coating (B) having at least one slot (2) extending over a length (L) and a storage chamber (3) for the coating material, characterized by , that several discrete and individually controllable heating elements (5) are provided along the length (L). [2] Device (1) according to claim 1, characterized by , that the heating elements (5) are designed as electrical resistance heating elements. [3] Device according to claim 1 or 2, characterized by , that the heating elements (5) are in thermally conductive contact at least with the transition area between the storage chamber (3) and the slot (2). [4] Device (1) according to claim 1, 2 or 3, characterized by , that the heating elements (5) are unevenly distributed along the length (L) of the slot (2). [5] Device (1) according to claim 4, characterized by, that the sections of the heating elements (5) are larger relative to each other in the direction of length (L) in the middle of the slot (2) than on the outside. [6] Method for coating a substrate (S) using a device (1) according to any one of claims 1 to 5, characterized by , that depending on the desired thickness of the coating (B) along the length (L) of the slot (2) the viscosity of the coating material is adjusted by increasing or decreasing the heating power of the respective heating element (5) in the respective area. [7] Use of the device (1) according to any one of claims 1 to 5 and / or the method according to claim 6 for coating a carrier film with an active material stored as a slurry for a battery electrode.

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