Method for powder coating components

Abstract

The invention relates to a method for powder coating a component, comprising: a providing step in which the component and a coating powder having polymer particles and an additive are provided; an electrical loading step in which the coating powder particles are provided with an electrical charge; a dispersion step in which the electrically loaded polymer particles are mixed with a dispersion liquid to form a dispersion; an application step in which the dispersion is in contact with a surface of the component, with evaporation of the dispersion liquid and deposition of polymer particles on the surface, the surface being electrically loaded and / or negatively charged and / or grounded in contrast to the electrically loaded polymer particles, and wherein the surface has a surface temperature higher than the boiling point of the dispersion liquid; and a fusion step in which the component and / or the polymer particles deposited on the surface are heated by means of a heat source such that the polymer particles are fused and / or foamed and / or expanded with each other, forming a polymer coating arranged on the surface of the component.

Description

Technical Field

[0001] The present invention relates to a method for powder coating a component according to claim 1. Background Technology

[0002] In an exemplary method for conventional powder coating of a component, the component and coating powder having polymer particles are first provided in a providing step. Immediately following, in an electroloading step, the coating powder is electroloaded using a loading unit. In a subsequent application step, the electroloaded coating powder comes into contact with a surface of the component that is electroloaded or grounded in contrast to the electroloaded coating powder particles, causing the electroloaded polymer particles to be electrostatically attracted by the surface or electrostatically unloaded through the component surface, thus depositing on the surface. In a subsequent fusion step, the component and / or the polymer particles deposited on the surface of the component are heated using a heat source, causing the coating particles to fuse together in the formation of a polymer coating disposed on the surface of the component. Particularly in the case of components with enclosed narrow cavities or narrow access portions leading to such cavities, conventional powder coating methods can only reliably apply the polymer coating process to the cavity-facing areas of the component's surface.

[0003] An apparatus and spray booth for powder coating by means of triboelectric loading are known from DE 10 2019 125 162 B3. An apparatus and facility for electrostatic powder coating of an object are disclosed in EP 3 727 703 B1. A spray gun for powder coating by means of electrostatic triboelectric loading is known from DE 20 2011051 418 U1. Summary of the Invention

[0004] The object of the present invention is to provide a method for powder coating a component, which enables the application of a polymer coating to the entire surface of the component reliably and with low facility costs.

[0005] This task is solved by the present invention. Preferred improvements of the present invention are disclosed herein.

[0006] According to the present invention, a method for powder coating a component is provided, comprising: a providing step, wherein a component and a coating powder having polymer particles and additives are provided; an electroloading step, wherein the coating powder particles are charged; a dispersing step, wherein the electroloaded particles of the coating powder are mixed with a dispersing liquid while forming a dispersion; an applying step, wherein the dispersion is brought into contact with a surface while the dispersing liquid evaporates and the coating particles are deposited on the surface of the component, wherein the surface is electroloaded and / or grounded in contrast to the electroloaded coating particles, and wherein the surface has a surface temperature higher than the boiling point of the dispersing liquid; and a fusion step, wherein the component and / or the coating particles deposited on the surface are heated by means of a heat source, such that the polymer particles fuse and / or foam and / or expand with each other while forming a polymer coating disposed on the surface of the component. The dispersing liquid, which has evaporated at a low temperature, acts as a carrier medium for the coating particles, such that the coating particles are uniformly distributed by the dispersing liquid, for example, in cavities enclosed by the component, and then uniformly deposited on the inner side of the hard-to-reach cavities of the component while the dispersing liquid evaporates. Compared to known methods for conventional powder coating of components, this proposed method enables a reliable and cost-effective polymer coating process to be applied to the entire surface of the component, even in hard-to-reach areas. Further advantages are derived from mixing the electrically loaded coating particles with the dispersion liquid: for example, it prevents the unloading of the coating particles before actual powder coating. The charge on the coating particles is effectively retained in the dispersion liquid. Furthermore, it prevents the coating particles from repelling each other as strongly as before due to their like charges. Therefore, this method can be used, for example, to powder coat hard-to-reach slots of all types of electric motors to apply an electrically insulating layer to the slots.

[0007] For example, the polymer particles of the powder coating are configured such that each particle has the same material, preferably a thermosetting or thermoplastic material, or a mixture of at least one thermosetting material and at least one thermoplastic material. Particularly preferably, the material is polyphenylene sulfide (PPS), polyetherimide (PEI), polyether ketone ketone (PEKK), polyether ether ketone (PEEK), or epoxy resin. Alternatively, the polymer particles may have different materials, selected from the group consisting of thermosetting or thermoplastic materials, or a mixture of at least one thermosetting material and at least one thermoplastic material. Furthermore, in addition to the polymer particles, the powder coating may also contain conventional additives, such as additives for improving thermal conductivity.

[0008] In order to perform heating of the component to be coated particularly efficiently, the heat source is configured, by way of an induction heater or an infrared radiator.

[0009] Additionally, the particles contained in the coating powder are configured, by way of example, to have D 10 : 1-200μm, D 50 : 10-500μm and D 90 Percentile in the range of 15-1000 μm.

[0010] For the purpose of electrically loading the coating powder, it is exemplary that the coating powder is applied using a nozzle with a flat nozzle. The system is loading. For this purpose, the following parameters are set as an example:

[0011] -Powder ejection: at 4.5m 3 25% of the total airflow per hour

[0012] - Applying a high voltage of -60KV at a maximum current of 10μA.

[0013] -0.2m 3 / h electrode free purge air

[0014] -0.8m 3 Fluidized air flow rate / h.

[0015] To efficiently mix the coating powder particles from the electrically loaded unit with the dispersion liquid immediately thereafter, it is exemplary that a container, preferably an insulated container and / or a Dewar flask, is provided in the providing step, which externally restricts the internal space of the container and the internal space of the container is filled with the dispersion liquid, and in the dispersion step, at least the electrically loaded polymer, additive, or coating particles are blown into the dispersion liquid, more specifically preferably below the level of the dispersion liquid located in the internal space of the container.

[0016] In order to specifically influence the behavior of the dispersion and the properties of the resulting polymer coating, the dispersion is preferably configured to have at least one additive component, wherein the at least one additive component is configured to be mixed with the polymer particles that are initially neutralized, either prior to the electroloading step, or prior to the dispersion step, with the dispersion liquid and the electroloaded polymer particles, more preferably in the internal space of the container.

[0017] An exemplary configuration is made whereby additives are also added to the polymer particles. Preferably, these can be chemical foaming agents and / or WLF (thermal conductivity) additives to improve thermal conductivity. Preferably, hexagonal boron nitride and / or alumina can be used as WLF additives. Physical foaming agents are preferred, particularly expanded microspheres, which can be used as foaming agents. In the case of additives, especially in the case of WLF additives, the electroloading process can also be meaningful. Therefore, the additives can also be added to the polymer powder before the electroloading process, and then mixed with the dispersion liquid as a coating particle stream.

[0018] Expandable microspheres can, for example, have Company model More precisely, preferred model 951DU 120, or model number 950DU 80, or model number 930DU 120, or model number 920DU 120 or model 093DU 120. In particular, the WLF additive improves the thermal conductivity of polymer particles deposited on the surface, thereby allowing the polymer particles to fuse together more quickly during the fusion step and to form a polymer coating more rapidly. A foaming agent is used to form a foamed and / or expanded polymer coating during the fusion step.

[0019] In order to draw out the dispersion from the internal space of the container and supply it to the components, the container is exemplaryly configured to have a syringe-like and / or nozzle-like application unit on its lower side opposite to the level of the dispersion liquid, the application unit restricting the application outlet outward, the application outlet being in flow connection with the internal space of the container.

[0020] In order to enable coating of the component even in areas of cavities enclosed by the component, it is exemplary that, in the application step, the dispersion is introduced by means of an application unit and through an application outlet into the cavity confined outward by the component, and / or applied to a region of the surface of the component, preferably facing the cavity confined outward by the component.

[0021] If the component is, for example, made of a tube, and in order to reliably coat the component even in the area of ​​the inner circumferential surface, it is preferably arranged such that, in the application step, the dispersion is introduced by means of an application unit and through an application outlet into a cavity restricted outward by the component, such that the dispersion rises in the cavity against the direction of gravity, wherein, preferably, the evaporated dispersion liquid is arranged such that it flows out of the cavity through an opening restricted outward by the component, preferably into the surrounding environment.

[0022] The component is configured, for example, to consist of a tube open on both sides or a tube open on one side.

[0023] In order to enable seamless coating of the entire surface of the component during operation, it is exemplary that the component is preferably completely submerged in the dispersion during the application step.

[0024] Purely optional and for cases where the coating particles blown into the dispersion are not sufficiently mixed with the dispersion, in order to improve mixing, the container is preferably provided with a stirrer arranged in the internal space of the container and constructed and / or adapted to mix the dispersion at least with the polymer particles blown into the dispersion, or with the polymer particles and at least one additive component in the case of forming a dispersion.

[0025] In order to enable the dispersed liquid to evaporate quickly and without residue from the dispersion, it is preferably configured such that the boiling point of the dispersed liquid is equal to or less than -50°C, preferably less than -100°C, and / or the dispersed liquid is liquid nitrogen or liquid inert gas or liquid carbon dioxide, and / or the surface temperature is in the range of 10°C to 50°C, preferably in the range of 15°C to 25°C.

[0026] To obtain a closed and seamless polymer coating, it is exemplary that, during the fusion step, polymer particles deposited on the surface are fused together with a first additive component and / or a second additive component in the formation of the polymer coating.

[0027] For illustrative and / or exemplary purposes only, the dispersion is configured to have 80 wt% liquid nitrogen and 20 wt% polymer particles. However, in principle, the dispersion may also have 1 wt% to 50 wt% polymer particles in the liquid nitrogen. Alternatively, the dispersion may have 70 wt% liquid nitrogen, 20 wt% polymer particles, and 10 wt% WLF additive. However, in principle, the dispersion may also have 1 wt% to 30 wt% polymer particles in the liquid nitrogen and 1 wt% to 20 wt% WLF additive. Alternatively, the dispersion may have 70 wt% liquid nitrogen, 20 wt% polymer particles, and 10 wt% expanded microspheres. However, in principle, the dispersion may also have 1 wt% to 30 wt% polymer particles in the liquid nitrogen and 1 wt% to 20 wt% expanded microspheres. Alternatively, the dispersion may have 60 wt% liquid nitrogen, 20 wt% polymer particles, 10 wt% WLF additive, and 10 wt% expanded microspheres. However, in principle, the dispersion may also have 1% to 30% by weight of polymer particles in liquid nitrogen, 1% to 20% by weight of WLF additives, and 1% to 20% by weight of expanded microspheres. Attached Figure Description

[0028] Embodiments of the present invention will now be described with reference to the accompanying drawings.

[0029] in:

[0030] Figure 1 A container with dispersed liquid inside its container space is shown in a side cross-sectional view;

[0031] Figure 2 A side sectional view shows a tube open on both sides as an example of a component, in which the dispersed body rises against the direction of gravity in its tube passage;

[0032] Figure 3 The component with a closed cavity is shown in a side sectional view, in which the dispersion is introduced into the cavity;

[0033] Figure 4 The side sectional view shows the results based on Figure 3 The component, wherein the dispersed liquid of the dispersion evaporated in the cavity flows out through an opening associated with the component;

[0034] Figure 5 A side-section view illustrates, as an example of a component, a tube closed on one side, wherein a dispersion is introduced through an opening associated with the tube into a cavity confined outward by the tube; and

[0035] Figure 6 The side cross-sectional view shows a tube closed on one side, with the dispersed liquid of the dispersion evaporating in the cavity flowing out through the opening associated with the tube. Detailed Implementation

[0036] The following is based on Figures 1 to 6 A method for powder coating a component is described. The method includes a providing step, an electrical loading step, a dispersing step, an applying step, and a fusing step.

[0037] In the provision step, components (such as, for example) are provided. Figures 2 to 6 (As shown in different embodiments) and a coating powder having polymer particles, which may also contain additives. Furthermore, in the providing step, an insulated container 1 is provided, which externally restricts the internal space of the container and is, here only exemplarily, filled with liquid nitrogen. The container 1 has a syringe-like and / or nozzle-like application unit 2 on its lower side opposite the liquid nitrogen level, which externally restricts an application outlet. This application outlet is in flow connection to the internal space of the container.

[0038] The coating powder comprises polymer particles and may also contain additional additives. The polymer particles can be made of plastic, more specifically, thermosetting or thermoplastic plastics. In particular, the polymer particles can be made of, for example, polyphenylene sulfide (PPS), polyetherimide (PEI), polyether ketone ketone (PEKK), polyether ether ketone (PEEK), or epoxy resin.

[0039] Immediately following the step is the electrical loading step. In the electrical loading step, the coating powder is fluidized using a fluidizing device (not shown), in which powder particles are mixed with air, and the mixture of coating powder particles and air exits the fluidizing device as a coating powder particle gas flow and is supplied to the loading device (not shown). The fluidizing device can be designed in different ways depending on the application of the method. During the loading step, the coating powder particle gas flow is guided through the loading device, where the coating powder particles are electrically loaded. In the loading device, the coating powder particles can be electrically loaded, for example, by friction, by means of corona discharge, by means of a strong electric field, or by means of the gate electrode of the loading device.

[0040] The dispersion step is performed immediately following the loading step. In the dispersion step, the coated particles, which were electrically loaded after the electrical loading step, are blown into liquid nitrogen, more specifically, below the level of liquid nitrogen in the internal space of the container. Figure 1 Arrow 3 indicates the blowing of the coating particle airflow. Subsequently, the coating particles are mixed with liquid nitrogen to form a dispersion consisting of electrically loaded coating particles and liquid nitrogen. Alternatively, and for optimal mixing of the coating particles blown into the liquid nitrogen with the liquid nitrogen in the formation of the dispersion, container 1 has a stirrer 4 arranged within the container's internal space, which mixes the liquid nitrogen with the coating particles blown into the dispersion liquid in the formation of the dispersion.

[0041] The application step follows the dispersion step in time. In the application step, the dispersion comes into contact with at least a portion of the surface of the component. The surface of the component is electrically grounded via a grounding wire 5, allowing the charge on the polymer particles to flow away upon contact with the grounded surface. Furthermore, the surface of the component has a temperature higher than the boiling point of liquid nitrogen. Depending on the design of the component, the dispersion can contact the surface in different ways.

[0042] like Figure 2 As shown, the component can be, for example, constructed from a tube 11. The tube 11 outwardly restricts the tube channel. The tube channel is open on both sides; more precisely, it extends downward relative to the direction of gravity through a lower opening and upward relative to the direction of gravity through an upper opening. During the application step, the dispersion can be introduced into the tube channel via the application unit and through the lower opening of the application outlet. Figure 2 Arrow 13 indicates the introduction of the dispersion. The dispersion rises against gravity in the tube channel, where nitrogen evaporates and coating particles are deposited on the inner circumferential surface, becoming part of the surface of tube 11. Subsequently, the evaporated nitrogen exits the tube channel through the opening located above. Figure 2 Arrow 15 indicates the departure of evaporated nitrogen.

[0043] like Figure 3 and Figure 4The component, as presented, can also be constructed, for example, from an elliptical or oval hollow body 21. The hollow body 21 confines a cavity outward, which opens outward through an opening 23 confined by the hollow body 21. During the application step, the dispersion can be introduced into the cavity against gravity by means of an application unit and through the application outlet via the opening 23. Figure 3 Arrow 25 indicates the introduction of the dispersion. Nitrogen evaporates in the cavity, and coating particles are deposited on the inner circumferential surface, becoming part of the surface of the hollow body 21. Subsequently, the evaporated nitrogen exits the cavity against gravity through opening 23. Figure 4 Arrow 27 indicates the departure of nitrogen.

[0044] like Figure 5 and Figure 6 As shown, the component can also be, for example, a tube 31 with a tube bottom 33 that outwardly restricts the tube channel, which is opened only through an opening 35 located upward relative to the direction of gravity. The tube channel is closed along the direction of gravity by means of the tube bottom 33. In the application step, the dispersion can be introduced into the tube channel through the opening 35 via an application unit and an application outlet. Figure 5 Arrow 37 indicates the introduction of the dispersion. Nitrogen evaporates in the tube channel, and coating particles are deposited on the inner circumferential surface, becoming part of the surface of tube 31. Subsequently, the evaporated nitrogen exits the tube channel against gravity through opening 35. Figure 6 Arrow 39 indicates the departure of nitrogen.

[0045] Alternatively, the component can be completely submerged in the dispersion, more precisely, regardless of the component's specific geometry. Here, nitrogen evaporates, and polymer particles are deposited on the entire surface of the component.

[0046] Immediately following the application step, a fusion step is performed. In the fusion step, the surface of the component is heated, at least in the area on which the coating powder particles were deposited during the application step, by means of a heat source. Thus, the coating powder particles fuse together to form a polymer layer disposed on the surface of the component.

[0047] Prior to or during the dispersion step, the polymer particles may optionally be mixed with one or more additive components, such that the additive components are part of the dispersion and are deposited together with the polymer particles onto the surface of the component during the application step. The additive components may, for example, have chemical blowing agents or hexagonal boron nitride as thermal conductors or alumina as thermal conductors, or physical blowing agents (e.g., expanded microspheres). The additive components are deposited together with the polymer particles onto the surface of the component and are part of the polymer coating after the fusion step.

[0048] Reference Symbol List

[0049] 1 Container

[0050] 2. Application Unit

[0051] 3 arrows

[0052] 4. Stirrer

[0053] 5. Grounding wire

[0054] 11 tubes

[0055] 13 arrows

[0056] 15 arrows

[0057] 21 Hollow body

[0058] 23 Opening

[0059] 25 arrows

[0060] 27 arrows

[0061] 31 tubes

[0062] 33 tube bottom

[0063] 35 Opening

[0064] 37 arrows

[0065] 39 arrows

Claims

1. A method for powder coating a component, comprising: The step involves providing the component and a coating powder having polymer particles and additive particles; An electrical loading step, wherein the coated powder particles are charged; The dispersion step involves mixing electrically coated powder particles with a dispersion liquid while forming a dispersion. An application step in which the dispersion is brought into contact with the surface while evaporating the dispersion liquid and depositing the coating powder particles on the surface of the component, wherein the surface is electrically loaded and / or grounded in contrast to electrically loaded coating powder particles, and wherein the surface has a surface temperature higher than the boiling point of the dispersion liquid. The fusion step involves heating the component and / or coating powder particles deposited on the surface by means of a heat source, such that the coating powder particles fuse together and / or foam and / or expand in the process of forming a polymer coating disposed on the surface of the component.

2. The method according to claim 1, characterized in that, In the providing step, a container (1), preferably an insulated container and / or a Dewar flask, is provided, which externally restricts the internal space of the container and the internal space of the container is filled with the dispersion liquid, and in the dispersion step, at least electrically loaded polymer particles are blown into the dispersion liquid, more specifically preferably below the level of the dispersion liquid in the internal space of the container.

3. The method according to claim 1 or 2, characterized in that, The dispersion has at least one additive component, wherein the at least one additive component is configured to be mixed with the dispersion liquid and the electrically loaded polymer particles prior to the dispersion step, or wherein the at least one additive component is configured to be mixed with the dispersion liquid and the polymer particles during the dispersion step, more precisely, in the internal space of the container.

4. The method according to claim 2 or 3, characterized in that, The container (1) has an injection-shaped and / or nozzle-shaped application unit (2) on its lower side opposite to the free surface of the dispersed liquid. The application unit restricts the application outlet outward, which is in flow connection with the internal space of the container.

5. The method according to claim 4, characterized in that, In the application step, the dispersion is introduced by means of the application unit (2) and through the application outlet into a cavity defined outward by the component, and / or applied to a region of the surface of the component, which preferably faces the cavity defined outward by the component.

6. The method according to claim 4, characterized in that, In the application step, the dispersion is introduced into a cavity restricted outward by the member by means of the application unit (2) and through the application outlet, such that the dispersion rises against gravity in the cavity, wherein preferably, the evaporated dispersion liquid flows out of the cavity through the opening restricted outward by the member, preferably into the surrounding environment.

7. The method according to any one of the preceding claims, characterized in that, In the application step, the component is preferably completely submerged in the dispersion.

8. The method according to any one of claims 2 to 7, characterized in that, The container (1) has a stirrer (4) arranged in the internal space of the container and configured to and / or suitable for mixing the dispersion liquid with at least the coating powder particles blown into the dispersion liquid or with the polymer particles and the at least one additive component in the case of forming the dispersion.

9. The method according to any one of the preceding claims, characterized in that, The boiling point of the dispersed liquid is equal to or less than -50°C, preferably less than -100°C, and / or the dispersed liquid is liquid nitrogen, liquid inert gas, or liquid carbon dioxide, and / or the surface temperature of the surface is in the range of 10°C to 50°C, preferably in the range of 15°C to 25°C.

10. The method according to any one of claims 3 to 9, characterized in that, In the fusion step, the coating powder particles and / or additional additive components deposited on the surface are fused together to form the polymer coating.

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