Method of etching plastic substrate comprising spray and electrolytic regeneration

Abstract

The present invention relates to a method for etching a plastic substrate, said method comprising steps (A) to (C), where step (C) comprises the dip-free dispensing of an acidic etching composition comprising water and one or more manganese species. In addition, the dispensed acidic etching composition is treated in a regeneration compartment by applying a current for regeneration and return to the acidic etching composition.

Description

Technical Field

[0001] The present invention relates to a method for etching a plastic substrate, the method comprising steps (A) to (C), wherein step (C) comprises immersion-free dispensing of an acidic etching composition comprising water and one or more than one manganese species. In addition, the dispensed acidic etching composition is treated in a regeneration compartment by applying an electric current for regeneration and returned to the acidic etching composition. Background Art

[0002] Metallization of non-metallic substrates, such as plastic substrates, has a long history in modern technology. Typical applications are in the automotive industry and in hygiene articles.

[0003] However, making plastic substrates accept metal layers is critical. Typically, the corresponding methods basically first perform surface modification of the substrate surface, which is usually called etching. Typically, a delicate balance is required to ensure that the surface is sufficiently roughened without causing excessive etching.

[0004] Many methods and etching compositions are known, including compositions including chromium species, such as hexavalent chromium species (e.g., chromic acid), which may cause environmental problems. Although these compositions generally provide very strong and acceptable etching results, environmentally friendly alternatives are increasingly needed and have been provided in the art to some extent. In many cases, manganese-based etching compositions are instead utilized, which are becoming increasingly popular in the market, especially permanganate-based etching compositions.

[0005] EP 3 666 926 A1 mentions a method for producing manganese (III) ions from manganese (II) ions in a mixed acid aqueous solution of sulfuric acid and alkanesulfonic acid using ozone, wherein the efficiency of producing manganese (III) ions from manganese (II) ions with ozone is at least 60%. Electrolytic regeneration is considered a disadvantage.

[0006] JP 2003-013244 A mentions a method of depositing a catalyst for electroless plating onto the surface of a resin substrate. The method is characterized in that the surface of the resin substrate is etched with an etching solution containing a Pd compound.

[0007] US 8,603,352 B1 mentions applying a chromium-free composition of an acidic suspension of a manganese compound and manganese ions to an organic polymer surface in order to etch said surface.

[0008] EP 2 657 367 A1 mentions a pre-etching composition for treating a non-conductive substrate in an electroplating process to deposit a metal layer on the substrate surface.

[0009] Among the etching compositions based on permanganate, alkaline permanganate-based etching compositions in particular have been known to us for a long time. However, the etching potential of alkaline permanganate-based etching compositions is limited compared to acidic permanganate-based etching compositions, which generally provide stronger and more effective etching effects. However, on the downside, a serious disadvantage is that permanganate ions decompose rapidly in an acidic environment. This requires a continuous replenishment of fresh permanganate ions or a continuous recycling process of recombining permanganate ions chemically or electrolytically.

[0010] The aforementioned requirements typically require high energy consumption, resulting in an undesirably high CO2 footprint and / or elaborate wastewater treatment upon disposal.

[0011] In particular, the continuous electrolytic regeneration of manganese species, especially permanganate, constantly requires high energy consumption.

[0012] Therefore, there is an urgent need to provide further improved etching methods that utilize acidic, manganese-based etching compositions while reducing the costs required to maintain active manganese species, most preferably permanganate ions. In addition, there is a need to further reduce the impact of such etching compositions on the environment.

[0013] Objectives of the invention

[0014] It is therefore an object of the present invention to provide a method for etching plastic substrates which significantly reduces the costs, environmental impact and energy consumption required to maintain active manganese species without compromising the etching quality. Summary of the invention

[0015] The above object is achieved by a method for etching a plastic substrate (1), the method comprising the following steps:

[0016] (A) providing an etching compartment (10) and a regeneration compartment (30),

[0017] (B) providing the plastic substrate (1) in the etching chamber (10),

[0018] (C) contacting the plastic substrate (1) in the etching chamber (10) with an acidic etching composition, wherein the acidic etching composition comprises

[0019] (a) water, and

[0020] (b) one or more manganese species,

[0021] Thus, an etched plastic substrate is obtained.

[0022] Features

[0023] - the contacting in step (C) is to dispense the acidic etching composition onto the plastic substrate (1) without immersion, thereby obtaining a dispensed acidic etching composition, and

[0024] - At least a portion of the dispensed acidic etching composition is treated in the regeneration compartment (30) by applying an electric current for regeneration and returned to the acidic etching composition.

[0025] Method of the present invention combines two basic characteristics. First, the acidic etching composition is exempted from immersion distribution, rather than usually immersing / immersing / immersing the plastic substrate into the corresponding acidic etching composition. Second, at least a portion of the distributed acidic etching composition is processed (i.e., recycled and regenerated respectively) in a regeneration compartment and returned (i.e., supplemented) to the acidic etching composition. This combination usually makes it possible to maintain the active state of the acidic etching composition with significantly reduced costs (comprising less energy and resource consumption), thereby realizing extremely ideal and effective etching.

[0026] Therefore, in the method of the present invention, the plastic substrate (1) is not immersed, submerged and / or immersed in the acidic etching composition. Alternatively, in the method of the present invention, the acidic etching composition is actively contacted with the plastic substrate (i.e., by means of distribution), rather than the common immersion / immersion / immersion method in which the plastic substrate is actively contacted with the etching composition. Therefore, in the method of the present invention, the plastic substrate is static, wherein the acidic etching composition is in a movable state, wherein in the common immersion / immersion / immersion method, the etching composition in the form of an etching bath is in a static state (i.e., limited to the tank wall), and the plastic substrate is movable and is transported to the etching composition for etching. In addition, in the context of the present invention, it is most preferred that the etching performed is only the etching defined in step (C), i.e., the etching caused by distributing the acidic etching composition. Preferably, no other etching is performed on the plastic substrate. In other words, the method of the present invention is preferably single-step etching.

[0027] Those skilled in the art realize that no-immersion dispensing has several disadvantages. Therefore, those skilled in the art do not consider no-immersion dispensing as an etching method. The disadvantages of no-immersion dispensing are well known to those skilled in the art:

[0028] ● Aerosol formation due to finely dispersed droplets

[0029] ●Technology costs more than just immersion

[0030] ● Energy is required to transport and disperse the solution, and

[0031] ● Energy is required for heating to compensate for the cooling effect caused by evaporation of water due to the large specific surface area of ​​the droplets formed

[0032] ●Access to areas behind the substrate, such as holes, cavities and recesses

[0033] • A larger delivery is required for the same volume, and the solutions from the previous processing steps (ie water and organics) are introduced later.

[0034] The list of disadvantages is not exhaustive.

[0035] The inventors of the present invention have surprisingly found that the method of the present invention is superior to the prior art. Without wishing to be bound by a particular theory, it is assumed that the regeneration effect caused by the volume reduction can be achieved without incurring the disadvantages described above.

[0036] Specifically, experiments have shown that the number of finely dispersed etchant droplets formed by the selected applied pressure and nozzle type is unexpectedly small. Aerosol measurements near the etchant chamber show that there is no detectable aerosol. The results are below the detection limit. The acid emitted is typically 100 times lower than the limit or even lower, and the manganese emitted is typically 20 times lower than the limit or even lower.

[0037] Since the immersion-free dispensing significantly reduces the volume of acidic etching composition required compared to the common immersion / immersion / immersion method, the total volume of acidic etching composition that must be provided in the entire method is also significantly reduced. The main advantage of this is that the volume that must be handled in the corresponding regeneration compartment is also significantly reduced. This reduces the amount of current required for regeneration (and any other oxidation means) because the total amount of manganese species subjected to decomposition is also significantly reduced. Our examples have shown that in direct comparison, up to 80% of electrical energy can be saved compared to the immersion / immersion / immersion method also combined with electrolytic regeneration.

[0038] In addition, this significantly reduced overall volume requires less chemicals and thus reduces the environmental impact, for example upon disposal. Furthermore, our experiments have shown a number of other advantages:

[0039] Compared to the immersion / dipping method, the immersion-free dispensing used in the present invention allows selective contacting in terms of time and location. This means, for example, that the dispensing nozzle is preferably selectively activated and deactivated. Thus, for example, the front side of the plastic substrate can be significantly etched, while the back side is substantially not etched. This is advantageous, for example, in the following cases: (i) the front side of the plastic substrate comprises a relatively complex surface geometry, which requires more intensive etching, while the back side has a less complex surface geometry, which requires less intensive etching; or (ii) the two-component plastic substrate to be etched exhibits different materials on different sides, where one component requires more intensive etching than the other component. In addition, the dispensing nozzle can be activated for a certain time interval and then deactivated for a time interval. In other words, even if there is no means for at least partially covering the surface of the corresponding plastic substrate, the dispensing mode can be designed with regard to the requirements of the plastic substrate.

[0040] In addition, the immersion-free dispensing used in the present invention allows for significantly improved temperature management of the acidic etching composition compared to immersion / dipping methods. Since decomposition is closely related to temperature, the acidic etching composition can have a specific temperature that is ideally selected to achieve optimal etching, while the temperature during treatment in the regeneration compartment can be significantly reduced to minimize decomposition. Since the immersion-free dispensing allows for a reduction in total volume, the corresponding volumes for heating and cooling are also reduced compared to common immersion / dipping methods.

[0041] Surprisingly, it was found that the higher water evaporation of the immersion-free dispensing is advantageous. It was concluded that it compensates for the reduced water extraction by reducing the regeneration capacity. The electrolyte is then not diluted during operation and will be cooled by the evaporation effect. Therefore, due to this effect, the cooling capacity can be significantly reduced or even completely eliminated. This significantly reduces the technical costs of electrolytic regeneration, since integrated cooling devices are completely unnecessary or their size and energy can be reduced.

[0042] In addition, compared with the immersion / immersion method, the immersion-free distribution used in the present invention unexpectedly reduces etching defects and improves wettability. In fact, the immersion / immersion method usually requires strong mixing and movement of the etching composition, respectively. This usually leads to the formation of bubbles in the composition. In addition, side reactions, especially decomposition processes, can further form bubbles. If such bubbles are adsorbed on the surface of the plastic substrate, the etching on these spots is significantly weakened. Our experiments have shown that immersion-free distribution, especially spraying, significantly avoids such adverse effects. This phenomenon is even more obvious when the plastic substrate has a very complex surface geometry. The most preferred situation includes that the plastic substrate is not in contact with any surfactant in the step directly before the etching step or during the etching step. This completely avoids the introduction of undesirable surfactants into the etching composition. If there is a surfactant, it is assumed that the surfactant is oxidized and not removed from the etching composition. Therefore, the surfactant accumulates and the accumulation of surfactants and oxidized surfactants increases the capacity demand of the regeneration device. In addition, water will not be introduced into the etchant, which will cause undesirable dilution and require further measures and energy to separate the water. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 Schematic diagram representing the method of the present invention, which illustrates the principle of the method of the present invention. The figure does not necessarily represent the actual size and ratio of the compartments and other equipment involved.

[0044] Reference Symbols

[0045] 1 are plastic substrates and multiple plastic substrates respectively

[0046] 2 racks

[0047] 3 Vertical airflow

[0048] 10 Etching compartment

[0049] 11 Openings with doors

[0050] 12+ dispensing nozzles

[0051] 13 Distribution pipeline

[0052] 14 Supply lines

[0053] 15 Ventilation ducts

[0054] 16 Liquid separator

[0055] 17 Pump

[0056] 20 Storage Tanks

[0057] 21 Inlet regeneration line

[0058] 22 Outlet regeneration line

[0059] 30 regeneration compartments DETAILED DESCRIPTION

[0060] Step (A):

[0061] In step (A), an etching compartment (10) and a regeneration compartment (30) are provided.

[0062] Preferably, in the method of the present invention, the etching compartment (10) and the regeneration compartment (30) are distinct and separate compartments, which are preferably spatially separated.

[0063] The etching compartment is the location where etching is performed, and the regeneration compartment is the location where regeneration occurs. The two compartments are preferably connected by a transmission pipeline fluid that transmits the acidic etching composition and distributes the acidic etching composition respectively. Further details are provided below in conjunction with the more detailed description of the drawings.

[0064] Preferably, in the method of the present invention, the etching compartment is made of or at least comprises a material resistant to acidic etching compositions. Preferred materials are fluoropolymer plastics, most preferably one or more selected from the group consisting of polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) and polychlorotrifluoroethylene (PCTFE), most preferably polyvinylidene fluoride (PVDF).

[0065] During step (C), the etching compartment comprises a plastic substrate. In order to avoid the release of the distributed acidic etching composition, the etching compartment is closed during step (C). This also includes that the etching compartment is sufficiently tight. Therefore, preferably, in the method of the present invention, the etching compartment comprises an opening equipped with a door.

[0066] Typically, the plastic substrate preferably comprises a plurality of plastic substrates. In order to properly etch this plurality of plastic substrates, they are fixed on a frame (meaning temporarily attached to a frame). Therefore, preferably, in the method of the present invention, during step (C), the etching compartment comprises a frame and the plastic substrate is fixed on the frame.

[0067] Preferably, in the method of the present invention, the etching chamber (10) comprises one or more than one dispensing nozzle (12) for immersion-free dispensing in step (C), preferably a plurality of dispensing nozzles, most preferably a plurality of spray nozzles.

[0068] More preferably, in the method of the present invention, the etching compartment (10) has a 2The total spray window area comprises 0.1 to 2, preferably 0.3 to 1.8, more preferably 0.5 to 1.6, even more preferably 0.7 to 1.4, most preferably 0.9 to 1.3 dispensing nozzles. This is most preferably applicable to the spray nozzles.

[0069] Typically, the plastic substrate and the plurality of plastic substrates each occupy a specific space in the etching compartment, and preferably, one or more dispensing nozzles are located around it, most preferably, at the side relative to the plastic substrate and the plurality of plastic substrates, respectively. This space is usually characterized by a certain side length in three dimensions (height, depth, width), and thus usually defines a cube. In the context of the present invention, the term "total spray window area" means the sum of the side surface areas of this cube. The total spray window area is sometimes also simply referred to as "spray window" or "maximum processing size (Warenfenster)".

[0070] In some cases, it is highly preferred that, in the method of the present invention, the etching compartment (10) comprises 5 to 1000 dispensing nozzles, more preferably 10 to 600 dispensing nozzles, even more preferably 30 to 400 dispensing nozzles, even more preferably 50 to 200 dispensing nozzles, most preferably 70 to 150 dispensing nozzles. This preference refers to a single etching compartment (if more than one is used).

[0071] In some cases, it is even more preferred that, in the method of the present invention, the etching compartment (10) comprises 10 to 700 spray nozzles, preferably 25 to 600 spray nozzles, more preferably 40 to 500 spray nozzles, even more preferably 50 to 400 spray nozzles, even more preferably 60 to 300 spray nozzles, most preferably 80 to 200 spray nozzles. This preferably refers to a single etching compartment (if more than one is used).

[0072] In this particular case, the one or more dispensing nozzles are preferably one or more spraying nozzles.

[0073] Preferably, in the method of the present invention, in the etching compartment (10), one or more dispensing nozzles (12) are inert to the acidic etching composition.

[0074] More preferably, in the method of the present invention, in the etching chamber (10), one or more dispensing nozzles (12) at least partially comprise or completely consist of fluoropolymer plastic, titanium, stainless steel, combinations and / or composites thereof. Preferred fluoropolymer plastics are one or more selected from the group consisting of: polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) and polychlorotrifluoroethylene (PCTFE), most preferably polyvinylidene fluoride (PVDF).

[0075] Our experiments have shown that the etching compartment does not need to be airtight to prevent any mist of the acidic etching composition from escaping (i.e., meaning leaking). Alternatively, an internal airflow is sufficient in most cases to avoid this. Therefore, preferably, in the method of the present invention, in the etching compartment (10), a vertical airflow (3) is applied, preferably from top to bottom, to convey at least a portion of the distributed acidic etching composition. This is very effective in preventing leaking. Therefore, the vertical airflow preferably comprises at least a portion of the distributed acidic etching composition.

[0076] Preferably, in the method of the present invention, the vertical gas flow comprises ambient air, most preferably ambient air and at least a portion of the dispensed acidic etching composition. In some cases, it is preferred that the vertical gas flow alternatively or additionally comprises an inert protective gas, preferably nitrogen or a noble gas.

[0077] More preferably, in the method of the present invention, vertical airflow is applied at intervals. Generally, it is preferred that in the method of the present invention, vertical airflow is applied after the contact in step (C) is completed, preferably until no dispensed acidic etching composition can escape when the door at the opening is opened to remove the plastic substrate, most preferably until substantially all dispensed acidic etching compositions are removed from the etching compartment. This also preferably means that vertical airflow is applied during step (B) of the subsequent operation of the method of the present invention. Compared to the flow rate applied during step (B) and / or after the contact in step (C) is completed, vertical airflow is not applied (i.e. stopped) during step (C) or is applied at a reduced flow rate.

[0078] The use of vertical airflow is an important safety feature. Thus, a mixture of gas and the distributed acid etching composition is obtained. Preferably, in the method of the invention, the etching compartment comprises a ventilation duct (15) for sucking the vertical airflow, which is connected to a liquid separator (16) to separate the liquid from the airflow. This results in a separated liquid containing the distributed acid etching composition in liquid form and most preferably transferred to a storage tank (20).

[0079] Preferably, in the method of the present invention, the ventilation duct is located at or near the bottom of the etching compartment.

[0080] In step (A), a regeneration compartment is also provided for regeneration. Regeneration is carried out by applying an electric current. Typically, the electric current oxidizes at least a portion of one or more than one manganese species in the distributed acidic etching composition, thereby regenerating (i.e., recycling) it, causing the formation of an acidic etching composition, ready for contacting again in step (C). Most preferably, permanganate ions, i.e., manganese species with an oxidation number of +VII, are formed in the regeneration compartment. This procedure is generally referred to as electrolytic reoxidation. In the context of the present invention, the great benefit of electrolytic reoxidation is that the total concentration of all manganese species remains relatively stable. In fact, in addition to supplementing the manganese species removed, it is generally not necessary to add manganese species to maintain the operation of the method. This contributes to relatively high process stability.

[0081] Preferably, in the method of the present invention, the regeneration is not a regeneration without applying an electric current.

[0082] More preferably, in the process of the present invention, the regeneration does not involve ozone. This means that preferably no ozone (most preferably as a gas) is intentionally added for the regeneration.

[0083] Preferably, in the method of the present invention, the current is direct current (DC), preferably with a current density of 0.1 A / dm 2 Up to 10A / dm 2 , preferably 0.2A / dm 2 Up to 7.5A / dm 2 , more preferably 0.3A / dm 2 Up to 5A / dm 2 , even more preferably 0.4A / dm 2 Up to 2.5A / dm 2 , the most preferred is 0.5A / dm 2 Up to 1A / dm 2 Preferably, the current density is within 0.1A / dm 2 Up to 2A / dm 2 , more preferably 0.2A / dm 2 Up to 1A / dm 2 , the most preferred is 0.3A / dm 2 Up to 0.8A / dm 2 The current density is the anode current density.

[0084] Generally, it is preferred that, in the method of the present invention, the current is applied continuously while the method of the present invention is being carried out; most preferably, it is applied while there is a pause between the first step and the second step (C).

[0085] Preferably, the electric current (most preferably the continuously applied electric current) prevents the presence of manganese species having an oxidation number of +II.

[0086] Preferably, in the method of the present invention, the regeneration in the regeneration compartment is carried out at a temperature in the range of 20°C to 65°C, preferably 25°C to 60°C, more preferably 30°C to 55°C, most preferably 35°C to 50°C, even most preferably 37°C to 43°C.

[0087] In order to apply an electric current, a cathode and an anode are generally required.It is generally preferred that in the method of the invention at least one anode and at least one cathode are included in the production compartment.

[0088] It is generally preferred that in the method of the present invention, the distance between the at least one anode and the at least one cathode is in the range of 0.5 mm to 100 mm, preferably 1 mm to 90 mm, more preferably 2 mm to 80 mm, even more preferably 3 mm to 70 mm, even more preferably 4 mm to 60 mm, most preferably 5 mm to 50 mm.

[0089] More preferably, in the process of the present invention, the regeneration compartment (20) comprises a stack of a plurality of anodes and at least one cathode.

[0090] Even more preferably, in the method of the present invention, the stack of the plurality of anodes is at a distance from the at least one cathode in the range of 0.5 mm to 100 mm, preferably 1 mm to 90 mm, more preferably 2 mm to 80 mm, even more preferably 3 mm to 70 mm, even more preferably 4 mm to 60 mm, most preferably 5 mm to 50 mm. Most preferably, in the method of the present invention, the distance is in the range of 9 mm to 70 mm, preferably 10 mm to 60 mm, more preferably 11 mm to 50 mm, even more preferably 12 mm to 30 mm, most preferably 13 mm to 20 mm. The distance is defined as the shortest distance between the at least one anode and the at least one cathode.

[0091] Preferably, in the method of the present invention, the regeneration compartment comprises at least one permeable barrier, preferably an ion-selective permeable barrier, most preferably an ion-selective permeable membrane.

[0092] Preferably, in the method of the present invention, the at least one permeable barrier is not inorganic. Preferably, in the method of the present invention, the at least one permeable barrier substantially does not contain, preferably does not contain, ceramics. In some cases, it is preferred that in the method of the present invention, the regeneration compartment does not comprise a permeable barrier.

[0093] More preferably, in the method of the present invention, the at least one permeable barrier is organic. More preferably, in the method of the present invention, the at least one permeable barrier is organic and comprises fluorine (preferably fluorinated), most preferably organic and perfluorinated. Most preferably, the at least one permeable barrier is a Nafion type membrane, but the at least one membrane is not particularly limited to this specific brand.

[0094] Such barriers typically result in an anolyte sub-compartment comprising an anolyte and a catholyte sub-compartment comprising a catholyte.Preferably, the anolyte comprises, most preferably is, a dispensed acidic etching composition for regeneration.

[0095] Preferably, in the method for the present invention, the stacking of a plurality of anodes comprises an anode layer, preferably 3 or more than 3 anode layers, more preferably 3 to 300 anode layers, even more preferably 4 to 200 anode layers, even more preferably 6 to 100 anode layers, most preferably 8 to 60 anode layers, even most preferably 9 to 30 anode layers. This anode layer stacking unexpectedly shows extremely effective electrolytic regeneration without too unfavorable shielding. This also makes the design of the regeneration compartment extremely compact.

[0096] Preferably, in the method of the present invention, in the stack, the distance between the anode layers is in the range of 0.5 mm to 20 mm, preferably 1 mm to 15 mm, more preferably 2 mm to 12 mm, even more preferably 3 mm to 10 mm, most preferably 4 mm to 9 mm. In some cases, the best distance is in the range of 1 mm to 6 mm, preferably 1.5 mm to 4 mm.

[0097] Preferably, in the process of the present invention, at least one anode, preferably a stack of a plurality of anodes, most preferably an anode layer comprises a sheet, a mesh, a woven mesh and / or an expanded metal (ie a metal mesh).

[0098] Preferably, in the process of the present invention, at least one anode, preferably a stack of a plurality of anodes, most preferably an anode layer, has a surface factor of 1 or more, preferably 1.4 or more, even more preferably 1.7 or more, even more preferably 2 or more, most preferably 2.1 or more, even most preferably 2.2 or more. In the context of the present invention, the surface factor denotes a parameter defining the total effective surface area per geometric area. For example, a geometric area of ​​1 m 2 The surface factor of the plate (i.e., surface) is usually 2 (for simplicity, the area of ​​the cut edges is neglected), giving a total effective surface area of ​​2m 2(including the front and back sides). The surface factor therefore does not have any size / unit. If, for example, the holes in the plate and the openings in the mesh have a determined number and a determined size, respectively, a surface factor lower than or even higher than 2 is usually obtained. However, the surface factor of commercially available meshes today usually does not exceed 2.5. In the context of the present invention, the surface factor as defined above is most preferably applicable to the individual anode layers in the stack.

[0099] Preferably, in the method of the present invention, at least one anode, preferably a stack of multiple anodes, comprises platinum, titanium, niobium, lead, gold, an alloy comprising at least one of them, an oxide thereof and / or a combination thereof; preferably at least one of platinum, titanium and gold.

[0100] In fact, not all anode materials are suitable for the purpose achieved by the method of the present invention. Because the etching composition is acidic and because of the strong oxidation characteristics of manganese species, the anode material must be carefully selected. The minimum requirement is that the corresponding material is (electro)chemically inert to the acidic etching composition. It is very preferred that, in the method of the present invention, the stack of at least one anode and multiple anodes respectively includes a platinized anode and / or a platinum anode, preferably a platinized titanium anode and / or a platinized niobium anode.

[0101] Generally, it is preferred that in the method of the present invention, at least one cathode comprises stainless steel, zirconium, titanium, platinum, niobium, lead, an alloy comprising at least one thereof, an oxide thereof and / or a combination thereof, preferably stainless steel, platinized titanium, niobium and / or zirconium.

[0102] Preferably, in the process according to the invention, at least one cathode and at least one anode (corresponding to a stack of a plurality of anodes) are oriented vertically, preferably vertically and parallel to each other.

[0103] Preferably, in the method of the present invention, at least one anode (corresponding to a stack of multiple anodes) provides a total effective anode surface area A1 and at least one cathode provides a total effective cathode surface area A2, wherein A1 is greater than A2. In the context of the present invention, "total effective surface area" refers to the area available for regeneration.

[0104] Preferably, in the method of the present invention, A1:A2 is in the range of 5: 1 to 100: 1, preferably 10: 1 to 85: 1, more preferably 15: 1 to 70: 1, even more preferably 20: 1 to 60: 1, most preferably 30: 1 to 50: 1. In some cases, A1:A2 is preferably in the range of 5: 1 to 30: 1, preferably 6: 1 to 25: 1, more preferably 7: 1 to 20: 1.

[0105] Step (B):

[0106] In step (B), a plastic substrate is provided in an etching chamber.

[0107] The substrate is a plastic substrate, also referred to as a polymer resin substrate (also an organic polymer substrate). Most preferably, the plastic substrate is a thermoplastic resin substrate.

[0108] Generally, it is preferred to process the plastic substrate vertically in the method of the present invention. Preferably, in the method of the present invention, the providing in step (B) comprises vertically moving (e.g. placing) the plastic substrate into the etching chamber. Preferably, the etched plastic substrate is vertically moved out (e.g. removed) from the etching chamber after step (C).

[0109] Preferably, in the process of the present invention, the plastic substrate comprises a butadiene moiety, preferably polybutadiene.

[0110] It is also preferred that in the method of the present invention, the plastic substrate comprises a nitrile moiety.

[0111] It is also preferred that in the method of the present invention, the plastic substrate comprises acryl moieties.

[0112] It is also preferred that in the process of the present invention the plastic substrate comprises a styrene moiety.

[0113] More preferably, in the method of the present invention, in step (B), the plastic substrate comprises acrylonitrile butadiene styrene (ABS), acrylonitrile butadiene styrene-polycarbonate (ABS-PC), polypropylene (PP), polyamide (PA), polyetherimide (PEI), polyetherketone (PEK), epoxy resin, or a mixture or composite thereof.

[0114] Preferably, in the method of the present invention, polyetherketone (PEK) includes polyaryletherketone (PAEK), polyetheretherketone (PEEK), polyetheretheretherketone (PEEEK), polyetheretherketoneketone (PEEKK), polyetherketoneetherketoneketone (PEKEKK), polyetherketoneketone (PEKK) and / or mixtures thereof, preferably includes polyetheretherketone (PEEK), polyaryletherketone (PAEK) and / or mixtures thereof.

[0115] In some cases, it is highly preferred that, in the method of the present invention, the plastic substrate comprises a 2-component (2K) plastic substrate, preferably including polycarbonate (PC) as one component. Preferably, the 2K plastic substrate comprises polycarbonate / acrylonitrile butadiene styrene-polycarbonate (PC / ABS-PC) and / or polycarbonate / acrylonitrile butadiene styrene (PC / ABS). The etching composition used in the method of the present invention selectively etches ABS and ABS-PC without etching the PC component.

[0116] Preferably, in the method of the present invention, the plastic substrate comprises a plurality of plastic substrates, preferably a plurality of plastic substrates are fixed on at least one support. From the treatment of the etched plastic substrate described throughout this document until the subsequent metallization step, the use of a metallization rack is common in decorative chrome electroplating. This is particularly advantageous for decorative automotive parts, sanitary products and packaging / storage materials.

[0117] Preferably, in the process of the present invention, the plastic substrate is used for decorative articles. Most preferably, the plastic substrate is a decorative automotive pre-component, a decorative sanitary pre-product or a decorative packaging / storage pre-material. In the context of the present invention, the term "pre-" in combination with the plastic substrate means that the final plastic substrate having the desired functionality is obtained by subjecting the etched plastic substrate to a subsequent metallization step.

[0118] Step (C):

[0119] In step (C) of the method of the present invention, the plastic substrate (1) is contacted with an acidic etching composition in an etching chamber to obtain an etched plastic substrate. The acidic etching composition comprises

[0120] (a) water, and

[0121] (b) one or more manganese species.

[0122] As mentioned, the acidic etching composition comprises water, preferably an aqueous acidic etching composition, most preferably, water is the only solvent in the acidic etching composition. Preferably, the concentration of water is in the range of 10.8 mol / L to 27.5 mol / L, preferably 12 mol / L to 26 mol / L, more preferably 13.1 mol / L to 24.5 mol / L, even more preferably 13.9 mol / L to 23.3 mol / L, most preferably 14.7 mol / L to 22.6 mol / L.

[0123] As also mentioned, the etching composition is acidic. Preferably, in the method of the present invention, the acidic etching composition is strongly acidic, preferably with a pH of 2 or less, more preferably 1 or less, even more preferably 0.5 or less, most preferably zero or less.

[0124] Preferably, in the method of the present invention, the total concentration of all one or more than one manganese species is in the range of 0.005 mol / L to 0.3 mol / L, preferably 0.01 mol / L to 0.25 mol / L, more preferably 0.015 mol / L to 0.2 mol / L, even more preferably 0.02 mol / L to 0.15 mol / L, even more preferably 0.025 mol / L to 0.11 mol / L, most preferably 0.03 mol / L to 0.09 mol / L, based on the total volume of the acidic etching composition.

[0125] Preferably, in the method of the present invention, in the acidic etching composition, one or more than one manganese species comprises permanganate ions, preferably the acidic etching composition is an acidic permanganate-based etching composition. This preferably means that in the acidic etching composition, the permanganate ion is an active etching species, most preferably an active etching species, and even most preferably the most active etching species. More preferably, in the method of the present invention, in the acidic etching composition, 5 mol% to 35 mol%, preferably 8 mol% to 30 mol%, more preferably 10 mol% to 27 mol%, most preferably 12 mol% to 21 mol% of all manganese species are permanganate ions.

[0126] Preferably, in the method of the present invention, the concentration of permanganate ions is in the range of 0.002 mol / L to 0.09 mol / L, preferably 0.003 mol / L to 0.075 mol / L, more preferably 0.004 mol / L to 0.06 mol / L, even more preferably 0.005 mol / L to 0.045 mol / L, even more preferably 0.006 mol / L to 0.03 mol / L, most preferably 0.007 mol / L to 0.016 mol / L based on the total volume of the acidic etching composition. This mainly refers to the concentration before contacting.

[0127] Preferably, in the method of the present invention, the acidic etching composition further comprises

[0128] (c) one or more than one, preferably one, inorganic acid.

[0129] Preferably, in the method of the present invention, the one or more than one inorganic acid comprises sulfuric acid and / or phosphoric acid, more preferably phosphoric acid, most preferably phosphoric acid is the only inorganic acid in the acidic etching composition, even more preferably phosphoric acid is the only acid in the acidic etching composition. This alternatively means that in some cases, it is preferred that in the method of the present invention, the acidic etching composition is substantially free of, preferably free of, sulfuric acid.

[0130] Preferably, in the method of the present invention, the total concentration of the one or more than one inorganic acid is in the range of 7 mol / L to 12 mol / L, preferably 8 mol / L to 11 mol / L, based on the total volume of the acidic etching composition.

[0131] Even more preferably, in the method of the present invention, in the acidic etching composition, the concentration of phosphoric acid is in the range of 7.4 mol / L to 11.8 mol / L, preferably 7.8 mol / L to 11.5 mol / L, more preferably 8.2 mol / L to 11.2 mol / L, even more preferably 8.5 mol / L to 11 mol / L, most preferably 8.7 mol / L to 10.8 L, even most preferably 9.2 mol / L to 10.5 L, based on the total volume of the acidic etching composition.

[0132] Preferably, in the method of the present invention, the acidic etching composition further comprises

[0133] (d) one or more ions selected from the group consisting of silver, bismuth, cerium and lead.

[0134] Ions as defined in (d) are generally used for electrolytic regeneration, most preferably silver ions.

[0135] Preferably, the silver ions include silver (I) and / or silver (II) ions, and most preferably include at least silver (I) ions.

[0136] Preferably, the bismuth ions include bismuth (III) and / or (IV) ions.

[0137] Preferably, the lead ions comprise lead (II) ions.

[0138] Most preferably, the one or more ions selected from (d) comprise silver ions, preferably silver (I) and / or silver (II) ions, most preferably at least silver (I) ions.

[0139] Preferably, in the method of the present invention, the total concentration of the ions defined in (d) is in the range of 0.0001 mol / L to 0.2 mol / L, preferably 0.0005 mol / L to 0.15 mol / L, most preferably 0.001 mol / L to 0.1 mol / L, based on the total volume of the acidic etching composition.

[0140] More preferably, in the method of the present invention, the total concentration of silver ions is in the range of 0.0001 mol / L to 0.2 mol / L, preferably 0.0003 mol / L to 0.15 mol / L, most preferably 0.0005 mol / L to 0.1 mol / L, based on the total volume of the acidic etching composition. This is most applicable when silver ions are the only ions defined according to (d).

[0141] More preferably, in the method of the present invention, in the etching composition, the concentration of silver (I) ions is in the range of 0.0001 mol / L to 0.09 mol / L, preferably 0.0002 mol / L to 0.07 mol / L, more preferably 0.0005 mol / L to 0.05 mol / L, even more preferably 0.0007 mol / L to 0.03 mol / L, most preferably 0.001 mol / L to 0.01 mol / L, even most preferably 0.0015 mol / L to 0.005 mol / L. This is most applicable when silver ions are the only ions defined according to (d).

[0142] In some cases, it is preferred that in the method of the present invention, the acidic etching composition includes alkaline ions, most preferably sodium ions, and preferably the total amount of alkaline ions is in the range of 0.002 mol / L to 0.5 mol / L, preferably in the range of 0.004 mol / L to 0.3 mol / L, based on the total volume of the acidic etching composition.

[0143] Preferably, in the method of the present invention, (a), (b), (c) and (d) account for 90 wt% or more, preferably 92 wt% or more, more preferably 94 wt% or more, even more preferably 96 wt% or more, most preferably 98 wt% or more, even most preferably 99 wt% or more of the total weight of the acidic etching composition.

[0144] Preferably, in the method of the present invention, in step (C), with reference to a temperature of 25° C., the density of the etching composition is between 1.15 g / cm 3 Up to 1.51g / cm 3 , preferably 1.22g / cm 3 Up to 1.41g / cm 3 , more preferably 1.24 g / cm 3 Up to 1.39g / cm 3 , most preferably 1.26g / cm 3 Up to 1.38g / cm 3 This also generally means that the acidic etching composition has a relatively low vapor pressure.

[0145] Preferably, in the method of the present invention, the acidic etching composition substantially contains no, preferably no, methane sulfonic acid and its salts; preferably, substantially contains no, preferably no, C1 to C4 alkyl sulfonic acid and its salts; most preferably, substantially contains no, preferably no, C1 to C4 sulfonic acid and its salts.

[0146] Preferably, in the method of the present invention, the acidic etching composition is substantially free of, preferably free of, bromide and iodide anions; preferably, substantially free of, preferably free of, chloride, bromide and iodide anions; most preferably, substantially free of, preferably free of, halide anions.

[0147] Preferably, in the method of the present invention, the acidic etching composition is substantially free of, preferably free of, trivalent chromium ions and hexavalent chromium compounds; preferably, is substantially free of, preferably free of, any compounds and ions comprising chromium.

[0148] Preferably, in the method of the present invention, the acidic etching composition contains substantially no, preferably no, palladium and / or copper ions; more preferably, contains substantially no, preferably no, palladium and / or copper compounds; most preferably, contains substantially no, preferably no, any activator for subsequent metallization. In other words, preferably, the acidic etching composition is not also an activating composition. Very preferably, the activation is performed in a subsequent separate step, most preferably using palladium.

[0149] Preferably, in the method of the present invention, the acidic etching composition contains substantially no, preferably no, manganese (II) ions.

[0150] Without wishing to be bound by a particular theory, it is postulated that in the most preferred permanganate-based acidic etching compositions, manganese species with oxidation numbers (III) and / or (IV) are present in addition to the permanganate ion.

[0151] In the method according to the invention, the contacting in step (C) is an immersion-free contacting, i.e. the acidic etching composition is dispensed onto the plastic substrate without immersion (see also above for more information). This dispensing also or alternatively indicates that the liquid is distributed (meaning dispersed) onto the plastic substrate without immersion, immersion and impregnation. This means that the acidic etching composition is most preferably actively dispensed, dispersed and distributed onto the plastic substrate, respectively, by pressure.

[0152] Preferably, in the method of the present invention, the non-immersion dispensing comprises, is preferably (most preferably alternatively represents) spraying, flushing and / or rinsing, most preferably spraying.

[0153] In the context of the present invention, spraying in step (C) causes a spray of the acidic etching composition to contact the plastic substrate. This preferably comprises (additionally or alternatively) spraying, aerosol and mist dispersion. The spray preferably comprises (at least in part) very fine spray droplets (e.g., from about 100 nm diameter) up to even medium and larger droplets (e.g., 10 μm, 100 μm, 500 μm, 1000 μm). This also comprises sprays with extremely uniform droplet sizes and sprays with large variations in droplet sizes. However, it is extremely preferred to have substantially uniform spraying and spraying of fine to medium-sized droplets, respectively.

[0154] In the context of the present invention, flushing causes flushing of the acidic etching composition. This preferably comprises spraying, purging and ejecting the acidic etching composition, preferably directly towards the plastic substrate. Typically, this type of distribution has a very strong directionality when transferring the acidic etching composition to the plastic substrate.

[0155] In the context of the present invention, rinsing includes screen rinsing (including laminar flow, waterfall flushing, etc.), trickling, dripping and spraying of the acidic etching composition on the plastic substrate. This is preferably carried out without applying additional pressure.

[0156] It is generally preferred that, in the method of the present invention, the contacting in step (C) comprises a flow rate of 50 L / m2 based on the total spray window area. 2 / min to 250L / m 2 / min, preferably 75L / m 2 / min to 225L / m 2 / min, more preferably 100L / m 2 / min to 200L / m 2 / min, most preferably 125L / m 2 / min to 175L / m 2 The acidic etching composition is dispensed in an amount in the range of 100 Å / min. In the context of the present invention, this parameter is also referred to as specific volume flow rate.

[0157] Preferably, in the method of the present invention, in step (C), the distance between the plastic substrate and the one or more dispensing nozzles is in the range of 5 cm to 30 cm, preferably 8 cm to 26 cm, more preferably 10 cm to 22 cm.

[0158] Preferably, in the method of the present invention, in step (C), the non-immersion dispensing is performed using a dispensing pressure. The dispensing pressure refers to the force with which the acidic etching composition is dispensed (ie pressed) onto the plastic substrate. The pressure is most preferably combined with spraying.

[0159] More preferably, in the method of the present invention, in step (C), the non-immersion dispensing is carried out at a dispensing pressure in the range of 0.3 bar to 5 bar, more preferably 0.5 bar to 4 bar, even more preferably 0.7 bar to 3 bar, most preferably 1 bar to 2 bar.

[0160] Most preferred are the use of spraying and misting, respectively, since, of the various dispensings described above, spraying requires a relatively smaller volume of the acidic etching composition compared to rinsing and rinsing while providing excellent wetting.

[0161] Most preferably, in the method of the present invention, in step (C), the non-immersion dispensing comprises spraying at a spray pressure in the range of 0.3 bar to 5 bar, more preferably 0.5 bar to 4 bar, even more preferably 0.7 bar to 3 bar, most preferably 1 bar to 2 bar.

[0162] Typically, the temperature of the acidic etching composition has a significant effect on the etching results, especially over time.

[0163] Preferably, in the method of the present invention, during the contacting in step (C), the temperature of the acidic etching composition is 25°C or higher, preferably 28°C or higher, more preferably 30°C or higher, even more preferably 33°C or higher, most preferably 35°C or higher, even most preferably 39°C or higher. This is also often referred to as the etching temperature. In general, the higher the temperature, the stronger the etching action. However, if the temperature is too high, unfavorable decomposition is observed. In this context, unfavorable means that the decomposition is too fast and too strong to be regenerated reasonably. Therefore, the temperature most preferably does not exceed 60°C.

[0164] Therefore, it is more preferred that, in the method of the present invention, during the contacting in step (C), the temperature of the acidic etching composition is in the range of 25°C to 60°C, preferably 28°C to 55°C, more preferably 30°C to 50°C, even more preferably 33°C to 47°C, most preferably 35°C to 44°C, even most preferably 39°C to 42°C.

[0165] As already indicated above, the method of the invention allows for temperature management. The most preferred goal for this is to provide a relatively high temperature during the contacting period, while, by contrast, lowering the temperature during the regeneration period in order to prevent or reduce undesired decomposition. Therefore, in certain situations, it is preferred that, in the method of the invention, in the etching compartment (10), the temperature of the acidic etching composition during the contacting period is higher than the acidic etching composition dispensed during the treatment in the regeneration compartment (30).

[0166] More preferably, in the method of the present invention, in the etching compartment (10), the temperature of the acidic etching composition during contact is 39°C or higher, wherein the temperature of the dispensed acidic etching composition treated in the regeneration compartment (30) is below 39°C.

[0167] Most preferably, the temperature management comprises and utilizes a heat exchanger, respectively.

[0168] However, in other cases, it is preferred that, in the method of the present invention, the temperature of the acidic etching composition and the acidic etching composition being dispensed is substantially the same. This means that the temperature is maintained near the desired temperature with only very small temperature variations, most preferably maintained at a temperature of 40°C ± 1°C. In this case, it is most preferred that no additional energy and equipment for cooling is required.

[0169] The duration of contact with the acidic etching composition is generally referred to as the etching time. Preferably, in the method of the present invention, the duration of contact in step (C) is in the range of 1 minute to 120 minutes, preferably 2 minutes to 90 minutes, more preferably 3 minutes to 70 minutes, even more preferably 4 minutes to 50 minutes, and most preferably 5 minutes to 30 minutes. In some cases, 5 minutes to 15 minutes is excellent.

[0170] Preferably, in the method of the present invention, during step (C), substantially no, preferably no, manganese dioxide (MnO2) is deposited on the etched plastic substrate. Therefore, in the method of the present invention, a step for reducing the manganese dioxide on the etched plastic substrate is not required (and therefore not applied); i.e., dissolving MnO2 by chemical reduction using a reducing agent. Therefore, preferably, the etched plastic substrate obtained after step (C) is not contacted with a corresponding composition comprising a reducing agent. General rinsing with water is sufficient. Therefore, preferably, the method of the present invention further comprises rinsing with water after step (C), more preferably rinsing with water that does not contain a reducing agent capable of chemically reducing manganese dioxide.

[0171] In addition, in step (C) of the method of the present invention, the acidic etching composition distributed is obtained by the step. In the case of the present invention, this mainly includes most of the acidic etching composition that is ultimately used for etching, which also means that in this part, the oxidation number of one or more than one manganese species is generally lower than the oxidation number before contact. This means that it is in a state with a higher degree of reduction after contact, which is mainly due to etching and also due to decomposition. However, the acidic etching composition distributed may additionally include a part of the acidic etching composition that has not yet contacted the plastic substrate or completely missed the plastic substrate (and therefore will no longer contact the plastic substrate). This part is generally smaller than the part involved in etching. In fact, compared to the acidic etching composition, in the acidic etching composition distributed, the average oxidation number of one or more than one manganese species is lower. Therefore, at least a portion of the acidic etching composition distributed is treated in the regeneration compartment by applying an electric current for regeneration. Preferably, all the acidic etching compositions distributed are processed in the regeneration compartment.

[0172] Preferably, in the method of the present invention, the partially distributed acidic etching composition is supplied via a delivery line (e.g. an inlet regeneration line, see Figure 1 ) is transported to the regeneration compartment, most preferably supported by a pump. In the regeneration compartment, the acidic etching composition is formed and reformed respectively. Preferably, in the method of the present invention, the part treated in the regeneration compartment is at least temporarily absent from the etching compartment. Therefore, it is preferred that etching and regeneration are carried out in separate locations and different devices, respectively.

[0173] After regeneration, the treated portion is conveyed back to the acidic etching composition. Thus, the method of the invention involves an annular flow. Preferably, in the method of the invention, the treated and returned portions of the distributed acidic etching composition represent replenishment of and replenishment of the acidic etching composition used in another step (c) within the method of the invention, respectively.

[0174] Preferably, in the process according to the invention, the process is carried out repeatedly. This means that the process according to the invention comprises a first, second, third step (C), etc. The same preferably applies to step (B), and preferably therefore a new (meaning another) plastic substrate is included in each step (C). Therefore, the process according to the invention is preferably carried out in a loop. This also comprises, most preferably repeatedly, most preferably continuously, treating a portion in the regeneration compartment and returning it to the acidic etching composition.

[0175] Other steps:

[0176] After step (C), ie after etching of the plastic substrate, metallization is usually carried out.

[0177] Preferably, the method of the present invention further comprises the following steps after step (C):

[0178] (D) contacting the etched plastic substrate with an activating composition to obtain an activated plastic substrate;

[0179] and / or (preferably and)

[0180] (E) contacting the etched plastic substrate or the activated plastic substrate (preferably the activated plastic substrate) with a first metallization composition such that a first metal or metal alloy layer is deposited thereon, thereby producing a first metallized plastic substrate.

[0181] In this context, the method according to the invention is preferably also a method for activating plastic substrates, a method for metallizing plastic substrates, respectively.

[0182] In the method of the present invention, preferably step (D) is a separate and independent step from step (C). In other words, the acidic etching composition used in step (C) is preferably not the activating composition used in step (D).

[0183] In step (D) of the process of the invention, the etched plastic substrate is contacted with an activating composition.

[0184] Preferably, in the method of the present invention, in step (D), the activating composition comprises palladium, preferably dissolved palladium ions or colloidal palladium, most preferably colloidal palladium. Preferably, the colloidal palladium comprises tin.

[0185] Preferably, in the method of the present invention, in step (D), the activation composition comprises palladium in a total concentration ranging from 20 mg / L to 200 mg / L, preferably from 40 mg / L to 150 mg / L, even more preferably from 50 mg / L to 110 mg / L, most preferably from 55 mg / L to 80 mg / L, based on the total volume of the activation composition. Preferably, this total concentration includes both dissolved palladium ions and colloidal palladium. The above concentrations are based on elemental palladium.

[0186] Preferably, in the method of the present invention, in step (D), the temperature of the activation composition is in the range of 25°C to 70°C, preferably 30°C to 60°C, even more preferably 36°C to 50°C, most preferably 39°C to 46°C.

[0187] Preferably, in the process of the present invention, in step (D), the contacting is carried out for a duration ranging from 1 minute to 15 minutes, preferably from 2 minutes to 12 minutes, even more preferably from 3 minutes to 9 minutes, most preferably from 4 minutes to 7 minutes.

[0188] Preferably, in the method of the present invention, step (D) comprises the following steps

[0189] (D-1) contacting the activated plastic substrate with an accelerator composition to modify the activated plastic substrate, wherein the accelerator composition:

[0190] - in case the activation composition in step (D) comprises colloidal palladium, no reducing agent is included but at least one complexing agent for the tin ions is included, or

[0191] - In case the activation composition in step (D) comprises palladium ions instead of colloidal palladium, a reducing agent for reducing the palladium ions to metallic palladium.

[0192] Preferably, in the method of the present invention, in step (D-1), the accelerator composition does not include a reducing agent but includes at least one complexing agent for tin ions and is acidic, preferably further includes sulfuric acid.

[0193] In the context of the present invention, step (D-1) as defined above is carried out after contacting the etched plastic substrate with an activating composition in order to obtain an activated plastic substrate.

[0194] After step (D1), a completely activated plastic substrate is generally obtained.

[0195] In step (E) of the method of the present invention, the fully etched plastic substrate or the activated plastic substrate is contacted with a first metallization composition so that a first metal or metal alloy layer is deposited thereon, thereby producing a first metallized plastic substrate.

[0196] Thus, step (E) is performed after the activation in step (D) or is applied in a direct metallization manner to the etched plastic substrate without activation. In the latter case, step (D) is not required. However, it is preferred that, in the process of the present invention, steps (D) and (E) are performed.

[0197] Preferably, in the method of the present invention, in step (E), the first metallization composition comprises nickel ions, preferably nickel ions and a reducing agent for reducing the nickel ions, so that the first metal or metal alloy layer is a nickel or nickel alloy layer, respectively. Therefore, the first metallized plastic substrate is preferably a first nickel or nickel alloy metallized plastic substrate.

[0198] Preferably, in the process of the present invention, in step (E), the first metallization composition is alkaline, preferably having a pH in the range of 8.0 to 11.0, preferably 8.2 to 10.2, more preferably 8.4 to 9.3, most preferably 8.6 to 9.0. However, in some rare cases, it is preferred that in the process of the present invention, in step (E), the first metallization composition is instead acidic, preferably weakly acidic, most preferably having a pH in the range of 6 to 6.9.

[0199] Preferably, in the process of the present invention, in step (E), the temperature of the first metallization composition is in the range of 18°C ​​to 60°C, preferably 20°C to 55°C, even more preferably 23°C to 50°C, most preferably 26°C to 45°C.

[0200] Preferably, the first metallized plastic substrate is subsequently further metallized.

[0201] Preferably, the method of the present invention further comprises the following steps after step (D) or (E):

[0202] (F) contacting the activated plastic substrate or the first metallized plastic substrate with a second metallization composition such that a second metal or metal alloy layer is deposited thereon, thereby producing a second metallized plastic substrate.

[0203] If step (F) is performed after step (D), then step (E) is preferably omitted and the second metallization composition corresponds substantially to the first metallization composition. However, this is not preferred. More preferably, steps (E) and (F) are performed consecutively. This does not exclude a rinsing step.

[0204] Step (F) preferably allows for at least two alternatives.

[0205] In a first alternative, it is preferred that in the process of the present invention, in step (F), the second metallization composition comprises copper ions, the concentration of which is preferably in the range of 0.002 mol / L to 0.4 mol / L, more preferably 0.004 mol / L to 0.25 mol / L, even more preferably 0.005 mol / L to 0.1 mol / L, most preferably 0.007 mol / L to 0.04 mol / L, based on the total volume of the second metallization composition. Most preferably, the copper ions are copper (II) ions.

[0206] More preferably, in the process of the present invention, in the first alternative the second metallization composition is acidic, preferably having a pH of 2 or less, preferably 1 or less. In some cases, it is alternatively preferred that the second metallization composition in the process is alkaline and comprises copper ions.

[0207] In some cases, it is preferred that in the methods of the present invention, the second metallization composition comprises a pyrophosphate salt, and most preferably comprises a pyrophosphate salt and is alkaline.

[0208] More preferably, in the method of the present invention, in the first alternative, the second metallization composition comprises at least one acid (and most preferably acidic, preferably as defined above), preferably comprises at least one inorganic acid, more preferably comprises at least one sulfuric acid. Preferably, the total concentration of the at least one acid (more preferably at least one inorganic acid, most preferably at least sulfuric acid) is in the range of 0.001 mol / L to 0.5 mol / L, preferably in the range of 0.003 mol / L to 0.3 mol / L, more preferably in the range of 0.005 mol / L to 0.1 mol / L, most preferably in the range of 0.007 mol / L to 0.07 mol / L, based on the total volume of the second metallization composition.

[0209] More preferably, in the process of the present invention, the temperature of the second metallization composition in the first alternative is in the range of 20°C to 80°C, preferably in the range of 21°C to 60°C, more preferably in the range of 22°C to 45°C, even more preferably in the range of 23°C to 40°C, most preferably in the range of 24°C to 35°C.

[0210] More preferably, in the process of the present invention, in the first alternative the second metallization composition is substantially free of, preferably comprises no, reducing agent for copper ions.

[0211] Most preferably, in the method of the present invention, in the first alternative the second metallization composition is a copper immersion composition. Thus, the copper ions are not reduced to metallic copper with the aid of a reducing agent. This is also referred to as alternative electroplating.

[0212] In a second alternative, it is preferred that in the process of the present invention, in step (F), the second metallization composition comprises nickel ions.

[0213] More preferably, in the process of the present invention, in the second alternative the second metallization composition is substantially free of, preferably comprises no, reducing agent for nickel ions.

[0214] More preferably, in the process of the present invention, in the second alternative the second metallization composition is acidic, preferably having a pH in the range of 1.0 to 5.0, preferably 2.0 to 4.5, more preferably 2.8 to 4.0, most preferably 3.3 to 3.7.

[0215] More preferably, in the process of the invention, the temperature of the second metallization composition in the second alternative is in the range of 25 to 70°C, preferably 35 to 65°C, even more preferably 45 to 61°C, most preferably 52 to 58°C.

[0216] More preferably, in the process of the present invention, the contacting in the second alternative is carried out for a duration ranging from 1 minute to 10 minutes, preferably from 2 minutes to 8 minutes, most preferably from 2.5 minutes to 5.5 minutes.

[0217] More preferably, in the method of the present invention, in the second alternative, a current is applied, the current preferably being 0.3 A / dm 2 Up to 10.0A / dm 2 Within the range, preferably 0.5A / dm 2 Up to 8.0A / dm 2 In the range, more preferably 0.8A / dm 2 Up to 6.0A / dm 2 In the range of 1.0A / dm 2 Up to 4.0A / dm 2 Range, most preferably 1.3A / dm 2 Up to 2.5A / dm 2 Therefore, the second alternative is preferably electrolytic nickel deposition.

[0218] More preferably, in the process of the invention, in the second alternative the second metallization composition comprises chloride ions and / or (preferably and) boric acid.

[0219] More preferably, in the method of the present invention, in the second alternative the second metallization composition is a Watts Nickel composition. Thus, preferably, in the method of the present invention, in the second alternative the second metallization composition comprises chloride ions, sulfate ions and boric acid.

[0220] After step (F), the second metallized plastic substrate is preferably further metallized.

[0221] Preferably, the method of the present invention further comprises the following steps after step (F):

[0222] (G) contacting the second metallized plastic substrate with a third metallization composition to electrolytically deposit a third metal or metal alloy layer thereon, thereby producing a third metallized plastic substrate.

[0223] Preferably, in the method of the present invention, the third metallization composition comprises copper ions, and the concentration of the copper ions is preferably in the range of 0.05 mol / L to 3 mol / L, more preferably in the range of 0.1 mol / L to 2 mol / L, even more preferably in the range of 0.2 mol / L to 1.5 mol / L, and most preferably in the range of 0.3 mol / L to 1 mol / L, based on the total volume of the third metallization composition.

[0224] Preferably, in the method of the present invention, an electric current, preferably a direct current, is applied in step (G).

[0225] More preferably, in the method of the present invention, the third metallization composition is acidic or basic. In this case, the acidic third metallization composition represents the first alternative; the basic third metallization composition represents the second alternative, wherein the first alternative is more preferred.

[0226] More preferably, in the process of the present invention, the pH of the third metallization composition according to the first alternative is 2 or less, preferably 1 or less.

[0227] More preferably, in the method of the present invention, the third metallization composition according to the first alternative comprises at least one acid, preferably at least one inorganic acid, more preferably at least sulfuric acid. Preferably, the total concentration of the at least one acid (more preferably at least one inorganic acid, most preferably at least sulfuric acid) is in the range of 0.1 mol / L to 5 mol / L, preferably in the range of 0.2 mol / L to 3 mol / L, more preferably in the range of 0.3 mol / L to 2 mol / L, most preferably in the range of 0.4 mol / L to 1.5 mol / L, based on the total volume of the second metallization composition.

[0228] More preferably, in the method of the present invention, the third metallization composition according to the first alternative comprises chloride ions, preferably, the total concentration of chloride ions is 500 mg / L or less, preferably 300 mg / L or less, most preferably 150 mg / L or less.

[0229] More preferably, in the process of the present invention, the temperature of the third metallization composition according to the first alternative is in the range of 20°C to 49°C, preferably in the range of 22°C to 43°C, more preferably in the range of 24°C to 39°C, most preferably in the range of 26°C to 35°C.

[0230] More preferably, in the process of the present invention, the pH of the third metallization composition according to the second alternative is in the range of 7.1 to 12, preferably in the range of 7.4 to 11, most preferably in the range of 7.6 to 10.

[0231] More preferably, in the method of the present invention, the third metallization composition according to the second alternative comprises cyanide ions or pyrophosphate ions, preferably pyrophosphate ions.

[0232] More preferably, in the method of the invention, the temperature of the third metallization composition according to the second alternative is in the range of 50°C to 70°C.

[0233] In the context of the present invention, the terms first, second and third metallized plastic substrates denote the number of non-metallized plastic substrates corresponding to the respective steps as defined above.

[0234] Preferably, in the process of the present invention, after step (G) the third metallized plastic substrate is contacted with one or more other metallizing compositions, wherein at least one of the one or more other metallizing compositions comprises trivalent chromium ions so as to deposit a chromium or chromium alloy metal layer, respectively.

[0235] Most preferably, the chromium or chromium alloy metal layer is the outermost metal layer, respectively.Thus, most preferably, the method of the present invention is used for metallizing a plastic substrate, wherein the metallization comprises chromium deposition, preferably decorative chromium deposition.

[0236] In the context of the present invention, a sequence of steps, in particular a metallization step, is preferably defined. Preferably, this does not exclude intermediate steps between these steps, such as a rinsing step. Thus, preferably, in the process of the present invention, an intermediate step, most preferably a rinsing step, is carried out between at least one of steps (B), (C) and preferably (D) to (G).

[0237] The present invention will now be further described with reference to the drawings and the following examples.

[0238] In the storage tank (20), an acidic etching composition used in the method of the present invention is provided. The acidic etching composition is a permanganate-based acidic etching composition comprising 9 mol / L to 11 mol / L phosphoric acid.

[0239] The acidic etching composition is transferred from a reservoir (20) through a supply line (14) to the etching compartment (10) with the support of a pump (17).

[0240] In the etching compartment (10), a distribution line (13) distributes the acidic etching composition to a plurality of distribution nozzles (12), which are preferably spray nozzles. Figure 1 , the distribution line (13) is shown twice. For simplicity only, it is not shown that the second distribution line (13) is also connected to the supply line (14).

[0241] A rack (2) with a plurality of plastic substrates (1) is placed between two dispensing lines (13) with a corresponding plurality of dispensing nozzles (12). The rack (2) with a corresponding plurality of plastic substrates (1) is moved vertically into an etching compartment (10) through an opening (11) equipped with a door. After the rack (2) is correctly placed, the door is closed and the etching compartment (10) is closed, but not completely sealed.

[0242] In order to etch a plurality of plastic substrates (1) on a rack (2), the etching process is initiated by dispensing, preferably spraying (dispensing pressure, spraying pressure in the range of 1 to 2 bar, respectively) an acidic etching composition onto the plurality of plastic substrates (1). Thus, uniform etching is achieved on all plastic substrates (1).

[0243] During etching, an acidic etching composition is dispensed onto a plurality of plastic substrates (1) on a rack (2) to produce a dispensed acidic etching composition. The dispensed acidic etching composition is collected in a reservoir (20). In some cases, the reservoir (20) is spatially separated from the etching compartment (10) but fluidly connected via a pipe or a transfer line.

[0244] In order to avoid that the acidic etching composition escapes during step (C) and is contaminated outside the etching compartment (10), a moderate air flow, preferably a laminar air flow, is applied to form a vertical air flow (3) from top to bottom. The vertical air flow (3) is applied at least when the door of the opening (11) is open. The ventilation duct (15) absorbs the vertical air flow (3) and the acidic etching composition distributed therewith, which is mainly mist-like. In the liquid separator (16), the gas (i.e., air in this article) is separated from any liquid, wherein the liquid is replenished in the storage tank (20) through a transfer line.

[0245] exist Figure 1 In the embodiment of the present invention, the temperature of the acidic etching composition in the storage tank (20) is roughly the same as the acidic etching composition distributed by a plurality of distribution nozzles (12). Therefore, a heating unit (not shown) applies heat to the storage tank (20), and thus maintains a relatively constant temperature during the whole method. However, in some cases, the distributed acidic etching composition is cooled and regenerated in the regeneration compartment (30) at a lower temperature. In this case, the acidic etching composition is brought to a certain temperature by the heating unit before being in contact with the plastic substrate.

[0246] For regeneration, the dispensed acidic etching composition is treated in a regeneration compartment (30) and conveyed through an inlet regeneration line (21). In the regeneration compartment (30), an electric current is preferably applied continuously. Since permanganate ions are active etching species, permanganate ions are continuously formed (i.e., reoxidized) in the regeneration compartment (30) at least at repeated time intervals, most preferably continuously. The regenerated (i.e., reoxidized) dispensed acidic etching composition is returned to the storage tank (20) through an outlet regeneration line (22).

[0247] Examples

[0248] The invention will now be illustrated with reference to the following non-limiting examples.

[0249] Example (A), spraying + electrolytic regeneration; according to the present invention:

[0250] In step (A), the etching chamber is provided in the form of a box (dimensions 1.4 m x 0.9 m x 0.7 m) made of polyvinylidene fluoride (PVDF). The box has an opening on the top that can be closed and opened by a door. The total spray window area is about 100 dm 2 .

[0251] In the etching compartment, 112 spray nozzles (40 on each longer part and 16 on each shorter part (ie, transverse part)) as distribution nozzles are distributed on 14 distribution lines, corresponding to each dm 2 The total spray window area is about 1.1 distribution nozzles. Subsequent larger-scale tests have shown that these lateral nozzles can be omitted without any negative impact on the etching results. Each spray nozzle is made of polyvinylidene fluoride (PVDF).

[0252] The etching chamber is not airtight during etching. A vertical air flow of ambient air is applied from top to bottom to prevent the escape of hazardous spray. The flow rate of the vertical air flow is about 500 m 3 / h, while the etching compartment is open for placing and removing racks with multiple plastic substrates. In order to draw vertical airflow, two ventilation ducts are installed near the bottom of the etching compartment. A liquid separator is used to separate ambient air from the spray.

[0253] A separate storage tank connected to the etching compartment fluid by a pipeline forms a storage tank. In this example, a total volume of 200L of acidic etching composition (and placed in the storage tank) is utilized, which is significantly less than a common immersion / dipping process. Before the acidic etching composition is actively pumped to a plurality of plastic substrates in the etching compartment through a supply line and a distribution line, the storage tank is heated to a temperature of about 40°C to 41°C for the acidic etching composition.

[0254] The regeneration compartment 30 for regenerating the acid etching composition distributed comprises 6 subunits, each of which comprises a single cathode and a stack of 9 anode layers (each anode layer is an expanded metal, with a distance of 1mm to 5mm from the next anode layer, and a surface factor of about 2). The cathode is made of stainless steel and each anode layer is made of platinum-plated niobium. The anode current technically applicable to each subunit is in the range of 40 to 300A, wherein the current actually applied and required is relatively low (see Table 1 below). The current is applied continuously. The distance between the cathode and the stack of the anode layer is about 5mm to 30mm. The total effective anode surface area A1 of each stack of the anode layer is about 300dm 2 , where the total effective cathode surface area A2 is about 30 dm 2 , so that the A1:A2 ratio is about 10. The stack of cathode and anode layers is separated by a Nafion type membrane, thereby producing an anolyte (which is the distributed acidic etching composition to be regenerated) and a catholyte comprising phosphoric acid. The direction of the stack of cathode and anode layers is vertical.

[0255] In step (B) of the method of the present invention, a plurality of circular or strip-shaped plastic substrates (ABS and ABS-PC, each with a surface size of 0.1 dm 2 Up to 10dm 2 The plastic substrate is mounted on the frame. The frame is placed vertically into the etching chamber and positioned accordingly.

[0256] Before contacting the plastic substrate with the acidic etching composition, the plastic substrate was pretreated by contacting it with a cleaning solution (Uniclean 151, a product of Atotech) for 10 minutes and then rinsed. No swelling or swelling composition, respectively, was used and required. Therefore, no contact with an organic solvent was involved. Thus, a cleaned plastic substrate was obtained.

[0257] After cleaning, the cleaned plastic substrate was contacted with an aqueous surfactant solution for 1 minute to improve wettability. No rinsing was applied between this step and the subsequent step (C). It should be mentioned that the use of a surfactant is not mandatory.

[0258] In step (C), a permanganate-based etching composition is used, which includes about 10 mol / L phosphoric acid, about 10 mmol / L permanganate ions (about 60 mmol / L total manganese species concentration), and about 1 to 2 mmol / L silver (I) ions.

[0259] In step (C), the acidic etching composition is sprayed onto the plastic substrate at a spray pressure of 2 bar for forming a spray. Etching is carried out at a temperature of about 40° C. and for ABS plastic substrates, the time length is 8 minutes, and for ABS-PC plastic substrates, the time length is 15 minutes. During etching, the distributed acidic etching composition is collected in a storage tank and transported from the storage tank portion to a regeneration compartment, and then returned to the storage tank.

[0260] The etch quality was evaluated and is summarized in Table 1 below.

[0261] After step (C), rinsing is performed with water.

[0262] In step (D), the etched plastic substrate is contacted with an activation composition comprising colloidal palladium (approximately: 50 mg / LPd, temperature 40° C., contact time 5 minutes) to obtain an activated plastic substrate.

[0263] In a subsequent step (D-1), the activated plastic substrate is contacted with an accelerator composition comprising no reducing agent but a complexing agent for tin ions at 45° C. for 3 minutes. Thus, a completely activated plastic substrate is obtained.

[0264] Prior to step (E), rinsing is performed with water.

[0265] In step (E), the activated and rinsed plastic substrate is contacted with a first metallization composition to obtain a first metallized plastic substrate. The fully activated plastic substrate is contacted with an alkaline (pH of about 8.6 to 9.0) first metallization composition (temperature of about 40° C.; contact time of about 10 minutes) for electroless nickel plating. The first metallization composition includes about 3.5 g / L nickel ions and about 15 g / L hypophosphite ions as a reducing agent for nickel ions to obtain a nickel alloy metallized plastic substrate.

[0266] In step (F), the nickel alloy metallized plastic substrate is contacted with an acidic second metallization composition comprising copper (II) ions for about 0.5 minutes (copper immersion, ie, copper electroplating; pH < 1; temperature about 25°C, no reducing agent).

[0267] The second metallized plastic substrate having the second metal layer (ie, copper) is then rinsed with water.

[0268] In step (G), after rinsing, the respective plastic substrate is contacted with a third metallization composition (acidic pH) in order to obtain a third metallized plastic substrate having a layer thickness of the copper layer of more than 30 μm (contact time of about 70 minutes, 25° C., 40 g / L copper ions; at about 4 A / dm 2 Electrolytic copper plating).

[0269] Subsequently, a further metallization step is carried out, finally depositing a chromium layer. Metallized plastic substrates with a layer thickness of the copper layer greater than 30 μm are subjected to at least one further nickel plating.

[0270] In a final metallization step, the respective plastic substrate is contacted with another metallization composition comprising 15 g / L to 30 g / L of trivalent chromium and boric acid (acidic pH, 25° C. to 60° C.) in order to obtain a metallized plastic substrate with a chromium layer.

[0271] Finally, the optical quality of the chrome layer was evaluated by analyzing the coverage and optical defects (especially bubbles). Thus, no turbidity and other optical defects were observed, especially no bubbles or other physical defects were observed. Specifically, the chrome layer showed a very uniform optical distribution. Although this result was also obtained in all other examples (see below), it was observed that examples (A) and (B) had fewer plating defects. It was observed that the immersion-free distribution avoids the adhesion of bubbles to plastic substrates, especially with complex surface geometries (e.g., grooves, grooves, inner edges, etc. on the surface). Such geometries usually lead to etching defects and subsequently to plating defects, respectively.

[0272] Furthermore, the plastic substrate with the final chrome layer also passed the PV1200 thermal cycle test (96 hours, including 8 cycles up to +80°C and -40°C).

[0273] For the adhesion test, the corresponding plastic substrates obtained after step (G) (ie, copper plated) were tested together. The adhesion values ​​of ABS and ABS-PC are summarized in Table 1 below.

[0274] Compared to the following examples, only Example (A) simultaneously demonstrates fewer plating defects on plastic substrates with complex surface geometries and less consumption of energy and chemicals.

[0275] Example (B), Spray + Feed and Discharge; Comparative:

[0276] Example (B) is carried out as in Example (A), but with the following changes:

[0277] No regeneration compartment is provided, and therefore no electrolytic regeneration is performed. Instead, a certain portion of the volume of the dispensed acidic etching composition is removed at a certain removal rate at intervals and an equal volume is replenished with freshly prepared acidic etching composition to maintain the concentration of permanganate ions. The removal rate is about 1.5 vol% per hour based on the total volume of the acidic etching composition.

[0278] In this method, although no electric current is required, a large amount of waste acidic etching composition is obtained over time instead, which is extremely undesirable in terms of environment and economy. Similar to Example (A), Example (B) is maintained at a total volume of 200 L to provide sufficient acidic etching composition for spraying. However, during step (C) in Example (B), removal and the same replenishment are carried out at 3 L / h to maintain the volume and etching quality reported as above Example (A).

[0279] In Example (B), the acidic etching composition does not include silver ions.

[0280] Example (C), Immersion + Feed and Drain; Comparative:

[0281] Example (C) follows Example (B) with the following additional changes:

[0282] In step (C), conventional immersion / submersion / immersion is performed instead of non-immersion dispensing. The total volume of the corresponding etching tank is 525L, which is much more than twice the total volume used in Examples (A) and (B).

[0283] From an environmental and economic point of view, example (C) represents a worst case setup, which contains even greater amounts of waste etching composition. To maintain 525 L, a removal rate of about 1.5 vol% is applied as in example (B), which results in removal and replenishment of about 8 L / h.

[0284] Example (D), immersion + electrolytic regeneration; comparative:

[0285] Example (D) is carried out as in Example (A), but with the following changes:

[0286] In this example, the usual immersion / immersion / dipping was performed instead of the non-immersion distribution. The corresponding etching tank also had a total volume of 525 L as used in Example (C). However, compared with Example (A), the current required for each subunit during electrolytic regeneration was much higher (see Table 1 below)

[0287] This comparative example clearly shows that combining leaching-free dispensing and electrolytic regeneration as described above in Example (A) has great advantages.

[0288] Table 1. Some etching parameters and results of ABS and ABS / PC

[0289]

[0290]

[0291] Table 1 generally shows that ABS and ABS-PC plastic substrates can be effectively and successfully etched in substantially all different examples. In other words, the method of the present invention does not compromise the good results that have been achieved in general applications. Generally speaking, a small difference of about 0.1 N / mm in adhesion is not significant.

[0292] The above examples (A) to (D) clearly show that only example (A) avoids the generation of significant waste volumes and at the same time the energy and chemical consumption is the lowest. Although the pure etching results are very similar, example (A) provides the best economic and ecological results and is very suitable for replacing the common immersion / dipping process.

[0293] Furthermore, it was unexpectedly observed that due to the immersion-free dispensing, fewer bubbles were attached to the plastic substrate in Examples (A) and (B). This in turn resulted in fewer etching defects and subsequently fewer plating defects. Such bubble defects are typical for immersion etching processes.

[0294] Besides, the results show that in Examples (A) and (B), the previous step of wetting the plastic substrate surface can be omitted without any negative impact on the etching quality.

[0295] In summary, Example (A) is the only example that simultaneously achieves fewer bubble defects and the greatest reduction in energy and chemical consumption without compromising etching quality.

Claims

1. A method for etching a plastic substrate (1), the method comprising the following steps (A) providing an etching compartment (10) and a regeneration compartment (30), (B) providing the plastic substrate (1) in the etching chamber (10), (C) contacting the plastic substrate (1) in the etching chamber (10) with an acidic etching composition, wherein the acidic etching composition comprises (a) water, and (b) one or more manganese species, Thus, an etched plastic substrate is obtained. Features - the contacting in step (C) is to dispense the acidic etching composition onto the plastic substrate (1) without immersion, thereby obtaining a dispensed acidic etching composition, and - At least a portion of the dispensed acidic etching composition is treated in the regeneration compartment (30) by applying an electric current for regeneration and returned to the acidic etching composition.

2. The method according to claim 1, wherein the etching chamber (10) comprises one or more dispensing nozzles (12) for immersion-free dispensing in step (C), preferably a plurality of dispensing nozzles, most preferably a plurality of spray nozzles.

3. A method according to claim 1 or 2, wherein in the etching chamber (10), the one or more dispensing nozzles (12) at least partially include fluoropolymer plastic, titanium, stainless steel, their combinations and / or composites or completely consist of fluoropolymer plastic, titanium, stainless steel, their combinations and / or composites.

4. The method according to any one of claims 1 to 3, wherein in the etching compartment (10) a vertical gas flow (3) is applied, preferably from top to bottom, to transport at least a portion of the dispensed acidic etching composition.

5. The method according to claim 4, wherein the etching chamber comprises a ventilation duct (15) for sucking the vertical air flow, the ventilation duct being connected to a liquid separator (16) for separating liquid from the air flow.

6. The method according to any one of claims 1 to 5, wherein the regeneration compartment (20) comprises a stack of a plurality of anodes and at least one cathode.

7. The method according to any one of claims 1 to 6, wherein the distance between the stack of the plurality of anodes and the at least one cathode is in the range of 0.5 mm to 100 mm, preferably 1 mm to 90 mm, more preferably 2 mm to 80 mm, even more preferably 3 mm to 70 mm, even more preferably 4 mm to 60 mm, most preferably 5 mm to 50 mm.

8. The method according to any one of claims 1 to 7, wherein in the acidic etching composition, the one or more than one manganese species comprises permanganate ions, preferably, the acidic etching composition is a permanganate-based acidic etching composition.

9. The method according to claim 8, wherein the concentration of the permanganate ion is in the range of 0.002 mol / L to 0.09 mol / L, preferably 0.003 mol / L to 0.075 mol / L, more preferably 0.004 mol / L to 0.06 mol / L, even more preferably 0.005 mol / L to 0.045 mol / L, even more preferably 0.006 mol / L to 0.03 mol / L, most preferably 0.007 mol / L to 0.016 mol / L, based on the total volume of the acidic etching composition.

10. The method according to any one of claims 1 to 9, wherein the non-immersion dispensing comprises, preferably spraying, flushing and / or rinsing, most preferably spraying.

11. The method according to any one of claims 1 to 10, wherein the contacting in step (C) comprises a spraying rate of 50 L / m based on the total spraying window area. 2 / min to 250L / m 2 / min, preferably 75L / m 2 / min to 225L / m 2 / min, more preferably 100L / m 2 / min to 200L / m 2 / min, most preferably 125L / m 2 / min to 175L / m 2 The acidic etching composition is dispensed in an amount within the range of 1:1 / min.

12. The method according to any one of claims 1 to 11, wherein in step (C), the non-immersion dispensing is performed under a dispensing pressure.

13. The method according to any one of claims 1 to 12, wherein in step (C), the non-immersion dispensing comprises, preferably spraying at a spraying pressure in the range of 0.3 bar to 5 bar, more preferably 0.5 bar to 4 bar, even more preferably 0.7 bar to 3 bar, most preferably 1 bar to 2 bar.

14. The method according to any one of claims 1 to 13, wherein during the contacting in step (C), the temperature of the acidic etching composition is 25°C or higher, preferably 28°C or higher, more preferably 30°C or higher, even more preferably 33°C or higher, most preferably 35°C or higher, even most preferably 39°C or higher.

15. The method according to any one of claims 1 to 14, wherein in the etching compartment (10) the temperature of the acidic etching composition during the contacting is higher than the dispensed acidic etching composition processed in the regeneration compartment (30).

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