Metal-plastic hybrid material having aluminum and / or alloys thereof as metal components

Abstract

The invention relates to: a method for preparing a metal-plastic hybrid material, in particular by using an acidic aqueous composition, said material comprising at least one substrate having at least one metal surface at least partially made of aluminum and / or an alloy thereof, and at least one thermoplastic material applied to said metal surface of the substrate; a metal-plastic hybrid material obtainable by such a process; the use of the acidic aqueous composition for adhering the substrate to the plastic; the metal-plastic hybrid material itself; and the use of the metal-plastic hybrid material as a component in the automotive, building or electronics industry.

Description

[0001] The invention relates to: a method for producing a metal-plastic hybrid material, in particular by using an acidic aqueous composition, the material comprising at least one substrate having at least one metal surface at least partially made of aluminum and / or its alloys and at least one thermoplastic material applied to the metal surface of the substrate; the metal-plastic hybrid material obtainable by this method; the use of the acidic aqueous composition for adhering the substrate to the plastic; the metal-plastic hybrid material itself; and the use of the metal-plastic hybrid material as a component in the automotive, construction or electronics industry. Background Art

[0002] Metal-plastic hybrids are one of the solutions proposed to reduce the weight of parts used in the automotive industry, such as in structural parts or in other components such as covers of battery materials, elements of powertrains, control panels, etc. In order to obtain such parts and components, plastics and metals can be joined together in several ways to develop a bonding material with an ideal combination of the properties of both materials (metal and plastic). However, joining dissimilar materials such as metal and plastic is very challenging, not only because of the different chemical properties of the two materials and therefore their surfaces, but also due to the shrinkage of the plastic material (such as thermoplastic materials) resulting from the dissimilarity of the two materials, as observed, for example, during molding.

[0003] Conventionally, metals are bonded to thermoplastic materials using adhesives. However, the production of such products using adhesives not only increases the number of production steps, but also the adhesion strength may decrease over time or may not exhibit integration strength at high temperatures. Therefore, the application of such methods in technical fields such as the automotive industry is unsuitable - not taking into account the economic and ecological disadvantages associated therewith - because here a significant heat resistance is often required due to electrodeposition and painting processes.

[0004] Nowadays, aluminum is often used as the metal component material of choice for building metal-plastic hybrid materials, especially for electric vehicle applications or electronic devices, such as smart phones, mobile devices, etc. Various methods have been reported describing the joining of aluminum to thermoplastic materials, especially in the electronics industry, where the aluminum surface is typically anodized, treated with plasma, or etched in a controlled manner to produce surface roughness before injection molding (for example by using nanomolding technology (NMT)).

[0005] Plastic-metal hybrid materials are generally often formed by injection molding a thermoplastic material onto the surface of a metal part, such as an aluminum part, which has nano-sized pores, micron-sized pores, or both. For example, WO 2020 / 003208 A1 discloses such a plastic-metal hybrid material, in which the plastic contains polyketone. These pores are usually formed by the aforementioned controlled chemical etching or anodizing process. The adhesion mechanism is based on mechanical interlocking, in which the plastic material in a molten state is directly injected into the pores of the metal surface.

[0006] Both controlled chemical etching and anodizing processes (also called flash anodizing) require special equipment and have the disadvantage that an additional etching or anodizing step must be used to produce surface roughness when preparing plastic-metal hybrid materials. Such controlled chemical etching and anodizing processes are disclosed, for example, in EP 2 894 240 A1 and EP 3 854 909 A1 and JP 2021-186993 A: EP 2 894 240 A1 relates to a metal-resin composite structure obtained by bonding a metal component and a resin component formed by a thermoplastic resin composition to each other. In order to achieve sufficient adhesion between the metal component and the resin, the surface of the metal component must be roughened. EP 3 854 909 A1 relates to a metal / resin composite structure comprising a metal component and a resin component, which is integrated into the metal component and is formed by a resin composition containing a thermoplastic resin. The metal component has a fine uneven shape, i.e., a surface roughness, at least on the surface of the integrated part with the resin component, which is the result of the surface roughening step performed. In addition, an inorganic particle layer must be present between the metal and the resin component. JP 2021-186993 A discloses a metal / resin composite material comprising a metal component and a cured resin bonded to the metal component. The metal component has a fine concave-convex structure on the surface of the bonding part with the cured resin, and therefore has roughness, and the cured resin is prepared from a thermosetting polyurethane elastic material.

[0007] However, the lifetime of the resulting roughened, in particular etched or anodized surface of metallic materials (such as aluminum-based materials) is very limited. Taking anodization as an example, the application window or processing of plastic materials is only a few hours, otherwise the pores close naturally and adhesion cannot be obtained. In addition, the aforementioned nanomolding technology (NMT) can only be applied to very clearly defined nanopores and very small parts, thereby limiting the application to very small electronic devices. The engineering plastics suitable for this application are also limited: for example, polybutylene terephthalate and polyethylene terephthalate (PBT and PET) each discolor during further processing of the part due to their weak acid resistance. Nylon-based materials like polyamide (PA) and polyphthalamide (PPA) both also have only poor acid resistance.

[0008] Therefore, there is a need to provide metal-plastic hybrid materials and methods for their preparation, which contain aluminum and / or its alloys as metal component and have excellent and permanent or at least long-lasting adhesion properties as far as the adhesion between the metal and the plastic is concerned, but at the same time these materials can be prepared without the need to use conventional adhesives and further and in particular without having to carry out a separate surface roughening step such as an anodizing step or chemical etching of the surface, which materials further allow the use of a wider range of thermoplastic polymer materials (including PBT and PET) than in conventional methods for preparing metal-plastic hybrid materials containing aluminum and / or its alloys, and which can further be prepared in a flexible, convenient and ecologically and economically advantageous manner.

[0009] question

[0010] The object of the present invention is therefore to provide metal-plastic hybrid materials and methods for their preparation, which contain aluminum and / or its alloys as metal component and have excellent and permanent or at least long-lasting adhesion properties with regard to the adhesion between the metal and the plastic in question, but at the same time these materials can be prepared without the need to use conventional adhesives and further, in particular, without having to carry out a separate surface roughening step such as an anodizing step or chemical etching of the surface, which materials further allow the use of a wider range of thermoplastic polymer materials (including PBT and PET) than in conventional methods for preparing metal-plastic hybrid materials containing aluminum and / or its alloys and which can further be prepared in a flexible, convenient and ecologically and economically advantageous manner.

[0011] Solution

[0012] This object has been solved by the subject matter of the claims of the present application and by its preferred embodiments disclosed in the present description, ie by the subject matter described herein.

[0013] The first subject of the present invention is a method for preparing a metal-plastic hybrid material, the material comprising a substrate S1 having at least one metal surface and at least one thermoplastic material applied to the metal surface of the substrate S1, the method comprising at least steps 1) and 2) and optionally step 3a) or 3b), namely

[0014] 1) applying an aqueous acidic composition at least partially to at least one metal surface of a substrate S1 to at least partially form a film on said surface,

[0015] wherein the metal surface is at least partially made of aluminum and / or at least one aluminum alloy, and

[0016] wherein the acidic aqueous composition comprises, in addition to water, at least one water-soluble polymer having at least one functional group selected from the group consisting of acid groups, hydroxyl groups, amino groups, and mixtures thereof, as at least one component a1), and at least one metal cation selected from the group consisting of titanium ions, zirconium ions and hafnium ions, and mixtures thereof as at least one component a2), and preferably free fluoride anions as at least one component a3), and

[0017] and optionally drying or curing the film to form a dried or cured layer,

[0018] 2) applying at least one thermoplastic polymer material TM1 at least partially to the film or to the dried or cured layer obtained after step 1),

[0019] wherein the at least one thermoplastic polymer material TM1 is i) applied in the form of a foil or ii) applied by injection in the molten state onto the film obtained after step 1) or onto the dried or solidified layer to form a metal-plastic hybrid material, and

[0020] 3a) optionally injecting at least one thermoplastic polymer material TM2, which is identical or different to the thermoplastic material TM1 applied in step 2) and is present in a molten state, at least partially onto the surface of the foil of the metal-plastic hybrid material obtained after steps 2) and i), or

[0021] 3b) Optionally, a further substrate S2 having at least one metallic surface, which is at least partially made of aluminum and / or at least one aluminum alloy and has been subjected to the treatment according to method step 1), is applied to the surface of the foil of the metal-plastic hybrid material obtained after steps 2) and i), or vice versa.

[0022] A further subject matter of the invention is a metal-plastic hybrid material obtainable by this method.

[0023] A further subject of the present invention is the use of an acidic aqueous composition as defined in conjunction with step 1) of the aforementioned process according to the invention for adhering a metal surface of a substrate at least partially made of aluminum and / or at least one aluminum alloy to a thermoplastic material, such as a thermoplastic material TM1, which is present on the surface in the form of a foil or applied to the surface by injection molding.

[0024] A further subject of the invention is a metal-plastic hybrid material itself, i.e. a metal-plastic hybrid material comprising:

[0025] a substrate S1 having at least one metallic surface, the at least one metallic surface being at least partially made of at least one aluminum and / or at least one aluminum alloy,

[0026] a film or a dried or cured layer at least partially applied to said metal surface, obtainable by at least partially applying to said metal surface an aqueous acidic composition as defined in connection with step 1) of the method of the invention as described above, and

[0027] at least one thermoplastic polymer material TM1 in the form of a foil or in a form obtainable by injection moulding, in each case at least partially applied to a film or a dried or cured layer, preferably as defined in step 2) of the process according to the invention, and,

[0028] Optionally, further, at least one thermoplastic polymer material TM2, the at least one thermoplastic polymer material TM2 being identical to or different from the thermoplastic polymer material TM1, is at least partially applied on the at least one thermoplastic polymer material TM1 in a form obtainable by injection molding, with the proviso that the thermoplastic polymer material TM1 has been applied in the form of a foil,

[0029] or

[0030] Optionally, further, a substrate S2 having at least one metal surface, said surface being at least partially made of aluminum and / or at least one aluminum alloy, said substrate having a film or a dried or cured layer at least partially applied on said metal surface, said film or a dried or cured layer being obtainable by applying an aqueous acidic composition as defined in combination with step 1) of the aforementioned method of the present invention, wherein said film or a dried or cured layer at least partially present on said metal surface of substrate S2 is in a position adjacent to at least one thermoplastic polymer material TM1, provided that the thermoplastic polymer material TM1 has been applied in the form of a foil.

[0031] Preferably, when the metal-plastic hybrid material comprises an additional substrate S2, it can be considered as a sandwich structure comprising two substrates S1 and S2, wherein each of these substrates is adhered to one surface of the thermoplastic material TM1 in the form of a foil by means of an adhesive film or a dried or cured layer obtained by applying an aqueous acidic composition as defined in conjunction with step 1) of the aforementioned method of the present invention. Preferably, each of the substrates S1 and S2 is a sheet or coil made of aluminum and / or its alloys.

[0032] A further subject matter of the present invention is the use of the metal-plastic hybrid material or the metal-plastic hybrid material obtainable by the process according to the invention as a component in the automotive, construction or electronics industry.

[0033] It has been found that the acidic aqueous composition used in the present invention is capable of providing a conversion coating on the metal surface of the substrate and at the same time providing good adhesion between the metal surface and the thermoplastic material TM1 applied on the metal surface due to the adhesion promoting properties of the formed conversion coating film or layer. It has been found that sufficient adhesion cannot be obtained without applying the acidic aqueous composition. It has been further found that the water-soluble polymer present in the acidic aqueous composition acts as an adhesion promoter in this regard. Achieving excellent adhesion is particularly relevant because it has been found that the strength of the adhesion layer between the metal surface and the thermoplastic material used has a significant impact on the life of the metal-plastic hybrid material. In addition, it has been found that all kinds of substrates with different shapes can be used, especially sheets, coils and / or other shapes of substrates containing metal aluminum and / or aluminum alloys.

[0034] Furthermore, it has been found that the application of the acidic aqueous composition used according to the invention to the metal surface according to step 1) represents a surface treatment of said metal surface which not only provides a microstructuring of the surface by a pickling passivation treatment, in particular when there is at least one metal cation selected from the group of titanium ions, zirconium ions and hafnium ions, and mixtures thereof, preferably in combination with molybdenum cations (which is important for the mechanical interlocking of the thermoplastic polymer material TM1), but also provides a real chemical bonding by the functional groups of the water-soluble polymer used. Since the surface roughness has already been generated by applying the acidic aqueous composition used according to the invention to the metal surface according to step 1), it is not necessary to apply any conventional surface treatment to the metal surface, such as plasma treatment, chemical etching and / or anodizing, let alone to carry out a surface treatment in a separate process step.

[0035] Furthermore, it has been found, particularly surprisingly, that adhesion problems and problems known in the prior art when combining two different materials, namely, a thermoplastic polymer TM1 on the one hand and aluminum and / or its alloys on the other hand, can be overcome by the method of the invention for preparing a metal-plastic hybrid material, in particular by using an acidic aqueous composition for chemical pretreatment of the metal surface as shown in step 1) of the method of the invention before carrying out step 2). It has been found that the method for preparing a metal-plastic hybrid material in particular allows even the use of thermoplastic polymers with relatively high melting temperatures, such as TM1, such as polyamides, in particular polyamide 6, applied directly by injection molding according to step 2) of the method of the invention, and furthermore, the use of thermoplastic polyesters such as PET and PBT, despite their poor acid resistance. Injecting a thermoplastic material directly onto a metal surface according to step 2) offers many advantages, among which simplicity, robustness and a wide application window. The flexibility of the method can be achieved, for example, because step 1) of the method can be used in a coil production line by a roller coater or can be sprayed at a job coater, which makes the method highly flexible.

[0036] It has also been found that by applying the acidic aqueous composition used according to the invention, not only excellent adhesion but also very good corrosion protection is achieved.

[0037] It has been found, surprisingly, that the process according to the invention allows direct thermoplastic injection of the thermoplastic polymer TM1 onto the aluminum-containing metal surface according to step 2), despite only a very short contact time between TM1 and the metal surface and despite a significant temperature difference between the molten thermoplastic polymer material TM2 (which may exceed 200°C) and the substrate temperature of the surface (which is typically room temperature, i.e. in the range of 18°C ​​to 25°C, but can also be heated if necessary, e.g. up to 60°C). It has been found that, in particular, the presence of functional groups of a water-soluble polymer in the acidic aqueous composition used allows very rapid bonding before cooling of the thermoplastic material after application / injection.

[0038] Furthermore, it has been found that chemical pretreatment of the metal surface using an acidic aqueous composition as shown in step 1) of the method of the invention before carrying out step 2) also provides strong adhesion to the thermoplastic material TM1 (when applied as a foil compound to the treated metal surface). It has also been found that the foil formed by applying TM1 can then be further used as an adhesion layer or interface layer, onto which a further thermoplastic material TM2, which is the same or different from TM1, can be applied by injection in optional step 3a) of the method (when carried out), in particular when the foil formed from TM1 in step 2) is chemically compatible with the material TM2 applied in optional step 3a). Similarly, when the metal surface of a further substrate has also been subjected to a chemical pretreatment as defined in step 1) of the process according to the invention by using the acidic aqueous composition used according to the invention, in an optional step 3b), the product obtained after step 2) (in particular when TM1 has been applied as a foil to the metal surface) can also be applied to the metal surface of the further substrate, said surface also being made at least partially of aluminum and / or its alloys, to form a sandwich structure in which the foil made by using TM1 flanks the two metal surfaces of the two substrates. DETAILED DESCRIPTION

[0039] In the sense of the present invention, the term "comprising", for example in connection with an acidic aqueous composition, preferably has the meaning of "consisting of". For example, with respect to the acidic aqueous composition, in addition to all mandatory components present therein, one or more further optional components as identified below may also be included therein. In each case, all components may be present in their preferred embodiments, as identified below.

[0040] The proportions and amounts given below in wt.-% (weight %) of any components present in the acidic aqueous composition add up to 100 wt.-%, based in each case on the total weight of the acidic aqueous composition.

[0041] Method of the present invention

[0042] The first subject of the present invention is a method for preparing a metal-plastic hybrid material, which comprises a substrate S1 having at least one metal surface and at least one thermoplastic material applied to the metal surface of the substrate S1, the method comprising at least steps 1) and 2) and optionally step 3a) or 3b).

[0043] In addition to steps 1) and 2) and optional step 3a) or 3b), the method may also include further steps. For example, a cleaning step of the metal surface may be performed before step 1), for example by an acidic, alkaline or pH-neutral, preferably alkaline cleaning composition, wherein in the case of an acidic cleaning composition, the composition is different from the acidic aqueous composition used in step 1).

[0044] More specifically, before step 1), one or more of the following optional steps may be performed in the following order:

[0045] Step A-1): preferably alkaline or acidic cleaning of the surface of the substrate and optionally subsequent rinsing,

[0046] step B-1): subjecting the surface of the substrate to pickling, ie etching, and subsequently rinsing the surface of the substrate,

[0047] step C-1): contacting the surface of the substrate with an aqueous composition comprising at least one inorganic acid, said aqueous composition being different from the acidic aqueous composition used in step 1), or alternatively with an aqueous alkaline composition or a pH-neutral aqueous composition, and

[0048] Step D-1): rinsing the surface of the substrate obtained after contacting according to steps C-1) and / or B-1).

[0049] Alternatively, steps A-1) and B-1) can be performed in one step, which is preferred. Preferably, both steps A-1) and B-1) are performed.

[0050] Optional step C-1) is used to remove aluminum oxide, undesirable alloy components, surface layers, brushing dust, etc. from the surface of the substrate, and thereby activate the surface for subsequent treatment in step 1). This step represents a chemical etching step. Preferably, at least one inorganic acid of the composition in step C-1) is sulfuric acid and / or nitric acid and / or phosphoric acid, more preferably sulfuric acid. The content of at least one inorganic acid is preferably in the range of 1.5 to 75 g / l, more preferably 2 to 60 g / l and most preferably 3 to 55 g / l. The composition used in step C-1) preferably further comprises one or more metal ions selected from the group of titanium ions, zirconium ions, hafnium ions and mixtures thereof, and optionally further comprises molybdenum ions. In the treatment of the parts, the duration of the treatment with the composition in step C-1) is preferably in the range of 30 seconds to 10 minutes, more preferably 40 seconds to 6 minutes and most preferably 45 seconds to 4 minutes. The treatment temperature is preferably in the range of 20°C to 55°C, more preferably 25°C to 50°C and most preferably 30°C to 45°C. In the treatment of the coil, the duration of the treatment is preferably in the range of 3 seconds to 1 minute, most preferably 5 to 20 seconds. Preferably, however, the optional step C-1) is not carried out.

[0051] Preferably, the method does not comprise any step of surface treatment of the metal surface S1 chosen from plasma treatment, chemical etching and / or anodization, in particular not before carrying out step 1). Neither optional steps B-1) nor C-1) represent a chemical etching step, by which any surface roughness of the substrate can be produced, as disclosed in the prior art. Optional steps B-1) and / or C-1) are instead merely preparation steps for the subsequent deposition of the film obtained by applying the aqueous acidic composition in step 1).

[0052] The rinsing step D-1) and the optional rinsing as part of step A-1) are preferably performed by using deionized water or tap water. Preferably, step D-1) is performed by using deionized water.

[0053] Preferably, the process does not comprise any step involving any treatment with chromium ions, such as Cr(III) and / or Cr(VI) ions.

[0054] Substrate

[0055] The metal surface of the substrate S1 is at least partially made of aluminum and / or at least one aluminum alloy. Preferably, the entire metal surface is at least partially made of aluminum and / or at least one aluminum alloy. More preferably, the substrate S1 itself is a metal substrate at least partially made of aluminum and / or at least one aluminum alloy. Preferably, the metal surface does not contain any amount of steel and / or steel alloy that exceeds the amount of aluminum and / or its alloys present therein. Examples of aluminum alloys are aluminum-magnesium alloys, aluminum-magnesium-silicon alloys, aluminum-copper alloys, aluminum-zinc alloys, and aluminum-zinc-copper alloys.

[0056] In the case of an aluminium alloy, the alloy preferably contains more than 50 wt.-% aluminium, based on the total weight of the alloy. The method is particularly suitable for all aluminium alloys containing more than 50 wt.-% aluminium, in particular for aluminium-magnesium alloys, including but not limited to AA5005, and for aluminium-magnesium-silicon alloys, including but not limited to AA6014, AA6060 and AA6063, for casting alloys - for example AlSi7Mg, AlSi9Mg, AlSi10Mg, AlSi11Mg, AlSi12Mg - and for wrought alloys - for example AlSiMg. Aluminium-magnesium alloys (including AA5005) and aluminium-magnesium-silicon alloys (including AA6060 and AA6063) are typically used, for example, in the field of aluminium finishing and / or for the processing of wheels and / or in other vehicle parts (such as electric vehicle parts, for example battery housings). The method is further suitable for all alloys of the so-called AA1000, AA2000, AA3000, AA4000, AA5000, AA6000, AA7000 and AA8000 series. A preferred example of the AA2000 series is AA2024. A preferred example of the AA7000 series is AA7075. AA2024 and AA7075 are often used in the aerospace industry. Other examples are and

[0057] All kinds of substrates with different shapes and geometries can be used.Preferably, the substrate is selected from sheets and coils and parts, in particular parts suitable for the automotive industry, and mixtures thereof.

[0058] Steps of the method 1)

[0059] In step 1), an aqueous acidic composition is at least partially applied to at least one metal surface of the substrate S1 to at least partially form a film on said surface. Optional drying or curing of the film may be performed in step 1) to form a dried or cured layer. Preferably, such drying or curing is performed. Drying is preferably performed, for example, at a temperature in the range of 15°C to 100°C, more preferably at a temperature in the range of 18°C ​​to 95°C, in particular at a temperature in the range of 20°C to 90°C.

[0060] Step 1) is preferably a contacting step, wherein the metal surface is contacted with the aqueous acidic composition. "Contacting" includes spraying, dipping, waterfall or roller coating procedures. "Contacting" can also be flooding of the surface or even manual wiping or brushing.

[0061] The treatment time, i.e. the period of time during which the surface is in contact with the acidic aqueous composition used in step 1), is preferably from 15 seconds to 20 minutes, more preferably from 30 seconds to 10 minutes, and most preferably from 45 seconds to 5 minutes, such as for example from 1 to 3 minutes, preferably in each case when parts, in particular parts suitable for the automotive industry, are used as substrates. In the case where the substrate is a coil, the treatment time is preferably less than 1 minute, more preferably less than 30 or 15 seconds, even more preferably less than 10 seconds, yet more preferably in the range of 1 to 5 seconds.

[0062] The temperature of the acidic aqueous composition used in step 1) is preferably 5 to 50°C, more preferably 15 to 45°C and most preferably 25 to 40°C.

[0063] By carrying out step 1), preferably, a conversion coating film is formed on the metal surface. Preferably, a coating is formed after drying or curing, preferably drying, and the coating has the following coating weight determined by XRF (X-ray fluorescence spectroscopy): due to the presence of component a2) in the acidic aqueous composition of 0.1 to 50 mg / m 2 , more preferably 0.2 to 30 mg / m 2 , even more preferably 0.5 to 20 mg / m 2 , still more preferably 1.0 to 15 mg / m 2 , and more preferably 1.5 to 10 mg / m 2 , especially 2.0 to 8 mg / m 2 zirconium and / or titanium and / or hafnium, preferably zirconium and / or titanium, more preferably zirconium, in each case calculated as metal. Preferably, in the presence of optional component a4) as defined below, the coating has the following coating weight determined by XRF (X-ray fluorescence spectroscopy): 0.1 to 40 mg / m 2 , more preferably 0.2 to 30 mg / m 2 , even more preferably 0.5 to 20 mg / m 2 , still more preferably 1.0 to 15 mg / m 2 , and more preferably 1.5 to 10 mg / m 2 , especially 2.0 to 8 mg / m 2 of molybdenum, calculated as metal.

[0064] Acidic aqueous composition

[0065] The acidic aqueous composition comprises, in addition to water, at least one water-soluble polymer having at least one functional group selected from the group consisting of acid groups, hydroxyl groups, amino groups, and mixtures thereof, as at least one component a1), and at least one metal cation selected from the group consisting of titanium ions, zirconium ions and hafnium ions, and mixtures thereof, as at least one component a2). All components present in the composition are different from one another.

[0066] Preferably, the acidic aqueous composition used in step 1) has a pH value in the range of 0.1 to <7.0, more preferably 0.5 to 6.5, still more preferably 1.0 to 6.0, even more preferably 1.5 to 5.5, still more preferably 2.0 to 5.0, yet more preferably 2.5 to 4.5, still more preferably 3.0 to 4.0, most preferably >3.0 to <3.7. Preferably, the pH value is measured at room temperature (23° C.). If necessary, the pH can preferably be adjusted by using nitric acid, aqueous ammonia and / or sodium carbonate.

[0067] In the sense of the present invention, the term "aqueous" with respect to the acidic aqueous composition used in step 1) preferably means that the composition is a composition which contains at least 50 wt.-%, preferably at least 60 wt.-%, more preferably at least 70 wt.-%, in particular at least 80 wt.-%, most preferably at least 90 wt.-% of water, based on its total content of organic and inorganic solvents including water. Thus, the composition may contain at least one organic solvent other than water, however, in an amount lower than the amount of water present.

[0068] Preferably, the acidic aqueous composition used in step 1) contains at least 50 wt.-%, preferably at least 60 wt.-%, more preferably at least 70 wt.-%, in particular at least 80 wt.-%, most preferably at least 90 wt.-% of water, in each case based on its total weight.

[0069] The acidic aqueous composition can be used as a dipping bath. However, it can also be applied by almost any conventional coating procedure as outlined above in connection with step 1), like for example spraying, rolling, brushing, wiping, etc. Spraying, dipping, waterfall coating or rolling coating are preferred.

[0070] The acidic aqueous composition used in step 1) is preferably a solution.

[0071] Preferably, the acidic aqueous composition used in step 1) has a temperature in the range of 18 to 35°C, more preferably 20 to 35°C, especially 20 to 30°C.

[0072] Water-soluble polymer (component a1)

[0073] The acidic aqueous composition comprises, as at least one component a1), at least one water-soluble polymer having at least one functional group selected from the group consisting of an acid group, a hydroxyl group, an amino group, and mixtures thereof.

[0074] The solubility is determined at a temperature of 20° C. and atmospheric pressure (1.013 bar).

[0075] Preferably, the at least one water-soluble polymer used as component a1) is present in the acidic aqueous composition in an amount ranging from 0.05 to 2.0 g / L or 0.05 to 5.0 g / L, more preferably from 0.10 to 1.8 g / L, even more preferably from 0.12 to 1.6 g / L, still more preferably from 0.14 to 1.5 g / L, yet more preferably from 0.16 to 1.4 g / L, still more preferably from 0.18 to 1.2 g / L, most preferably from 0.20 to 1.0 g / L. Alternatively, the at least one water-soluble polymer used as component a1) is present in the acidic aqueous composition in an amount ranging from 0.1 to 15.0 g / L, more preferably from 0.3 to 12.0 g / L, even more preferably from 0.5 to 11.0 g / L, still more preferably from 0.7 to 10.0 g / L.

[0076] Preferably, at least one water-soluble polymer used as component a1) has at least one functional group selected from carboxylic acid groups, phosphonic acid groups, sulfonic acid groups, hydroxyl groups, amino groups, and mixtures thereof, more preferably selected from carboxylic acid groups, hydroxyl groups, amino groups, and mixtures thereof, even more preferably selected from carboxylic acid groups.

[0077] Preferably, the at least one water-soluble polymer used as component a1) is a homopolymer or copolymer obtainable by polymerization of at least one ethylenically unsaturated monomer, at least one part of which carries at least one functional group selected from acid groups, hydroxyl groups, amino groups, and mixtures thereof; more preferably a homopolymer or copolymer obtainable by polymerization of at least one vinyl monomer and / or (meth)acrylic monomer, at least one part of which carries at least one functional group selected from acid groups, hydroxyl groups, amino groups, and mixtures thereof. In particular, in the case of homopolymers and copolymers of vinylphenol, these polymers can be modified with compounds carrying amino groups, such as ethanolamine and / or N-methylglucamine, via a condensation reaction, in particular a Mannich reaction.

[0078] Examples of monomers that contain acid groups are acrylic acid and methacrylic acid and maleic acid. Examples of monomers that contain hydroxyl groups are 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, (meth) 3-phenoxy-2-hydroxypropyl acrylate, mono(meth) glyceryl acrylate, N-(2-hydroxypropyl) (meth) acrylamide, allyl alcohol, hydroxystyrene, hydroxyalkyl vinyl ethers such as hydroxybutyl vinyl ether and vinyl benzyl alcohol, vinyl phenol and vinyl alcohol. Examples of other non-functional monomers that can be used additionally and that do not particularly have acid groups, hydroxyl groups, and mixtures thereof are ethylene, propylene, butylene and aliphatic C 1 -C 30- (Meth)acrylic esters of monohydric alcohols, for example methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate, lauryl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 3-propylheptyl (meth)acrylate, stearyl (meth)acrylate, behenyl (meth)acrylate, benzyl (meth)acrylate, cyclohexyl (meth)acrylate and isobornyl (meth)acrylate. However, non-functional vinyl monomers are preferred, in particular over aliphatic C 1 -C 30 - Non-functional (meth)acrylates of monohydric alcohols.

[0079] If the polymer a1) is a homopolymer, it is preferably a poly(meth)acrylic acid. If the polymer a1) is a copolymer and carries at least acid groups as functional groups, it is preferably a (meth)acrylic copolymer, which preferably comprises a polymer backbone and at least one side chain attached to the polymer backbone, which side chains carry acid groups, such as carboxylic acid groups.

[0080] The term "(meth)acryloyl" means "acryloyl" and / or "methacryloyl". Similarly, "(meth)acrylate" means acrylate and / or methacrylate, and "(meth)acrylic" means acrylic and methacrylic. "(Meth)acrylic polymers" are at least partly formed from "acrylic monomers" and / or "methacrylic monomers", but in case the polymer a1) is a copolymer, it may additionally contain non-acryloyl and non-methacryloyl monomer units if other ethylenically unsaturated monomers such as vinyl monomers are additionally used. Preferably, the main chain of such a (meth)acrylic copolymer is formed from more than 50 mol-%, even more preferably more than 75 mol-% of (meth)acrylic monomers.

[0081] Preferably, the at least one water-soluble polymer used as component a1) is selected from

[0082] (Meth)acrylic acid homopolymers, in particular acrylic acid homopolymers,

[0083] copolymers of (meth)acrylic acid and at least one ethylenically unsaturated monomer different from (meth)acrylic acid, in particular copolymers of (meth)acrylic acid and maleic acid,

[0084] copolymers of maleic acid and at least one ethylenically unsaturated monomer different from maleic acid, in particular copolymers of maleic acid and ethylene and / or propylene and / or at least one alkyl vinyl ether such as methyl vinyl ether,

[0085] copolymers of vinylphosphonic acid and at least one ethylenically unsaturated monomer different from vinylphosphonic acid, in particular copolymers of (meth)acrylic acid and vinylphosphonic acid and copolymers of (meth)acrylic acid and vinylphosphonic acid and maleic acid,

[0086] Vinyl alcohol homopolymer,

[0087] a copolymer of vinyl alcohol and at least one ethylenically unsaturated monomer different from vinyl alcohol, such as vinyl acetate,

[0088] Vinylphenol homopolymer,

[0089] a copolymer of vinylphenol and at least one ethylenically unsaturated monomer different from vinylphenol,

[0090] a copolymer of vinylmercaptoethanol and at least one ethylenically unsaturated monomer different from vinylmercaptoethanol, and

[0091] Homopolymers and copolymers of vinylphenol which have been modified with at least one amine, preferably at least one primary amine such as N-ethanolamine and / or N-methylglucamine, and mixtures thereof. The modification is preferably carried out via a Mannich base reaction based on the condensation of formaldehyde with primary or secondary amines.

[0092] More preferably, the at least one water-soluble polymer used as component a1) is selected from (meth)acrylic acid homopolymers, in particular acrylic acid homopolymers; copolymers of (meth)acrylic acid and at least one ethylenically unsaturated monomer different from (meth)acrylic acid, in particular copolymers of (meth)acrylic acid and maleic acid; copolymers of maleic acid and at least one ethylenically unsaturated monomer different from maleic acid, in particular copolymers of maleic acid and ethylene and / or propylene and / or at least one alkyl vinyl ether such as methyl vinyl ether; homopolymers of vinyl alcohol; copolymers of vinyl alcohol and at least one ethylenically unsaturated monomer different from vinyl alcohol; homopolymers and copolymers of vinylphenol which have been modified with at least one amine, preferably at least one primary or secondary amine, such as N-ethanolamine and / or N-methylglucamine; and mixtures thereof. Particularly preferred polymers are N-methylglucamine modified poly(vinylphenol), N-ethanolamine modified poly(vinylphenol), poly(maleic acid-co-vinyl methyl ether), poly(maleic acid-co-acrylic acid), polyacrylic acid, poly(vinyl-phosphonic acid-co-acrylic acid), poly(acrylic acid-co-maleic acid-co-vinylphosphonic acid), poly(acrylic acid-co-vinyl mercaptoethanol), poly(acrylic acid-co-maleic acid-co-vinyl mercaptoethanol) and mixtures thereof.

[0093] Preferably, the at least one water-soluble polymer has a weight average molecular weight (M) in the range of 1 000 to 350 000 g / mol, preferably 2 000 to 325 000 g / mol, more preferably 3 000 to 300 000 g / mol, still more preferably 4 000 to 375 000 g / mol. w ). The weight average molecular weight was determined by the method described below in the "Methods" section.

[0094] If a polymer a1) is used, this polymer a1) is a poly(meth)acrylic acid, in particular polyacrylic acid, which preferably has a weight average molecular weight (M) in the range of 10 000 to 350 000 g / mol, preferably 50 000 to 325 000 g / mol, more preferably 100 000 to 300 000 g / mol, still more preferably 150 000 or 200 000 to 375 000 g / mol. w If a polymer a1) is used which is a copolymer prepared at least partly from maleic acid, it preferably has a weight average molecular weight (M) in the range of 10 000 to 200 000 g / mol, preferably 15 000 to 150 000 g / mol, more preferably 20 000 to 100 000 g / mol, still more preferably 30 000 to 80 000 g / mol. w If a polymer a1) is used which is a homopolymer or copolymer prepared at least partly from vinyl alcohol and / or vinyl phenol, it preferably has a weight average molecular weight (M) in the range of 500 to 100 000 g / mol, preferably 750 to 50 000 g / mol, more preferably 1 000 to 25 000 g / mol, even more preferably 1 000 to 10 000 g / mol. w ).

[0095] Component a2)

[0096] The acidic aqueous composition used in step 1) further comprises as at least one component a2) at least one metal cation selected from the group consisting of titanium ions, zirconium ions and hafnium ions, and mixtures thereof.

[0097] Preferably, the aqueous acidic composition used in step 1) comprises at least one component a2) in an amount in the range of 0.1 to 10 g / L, calculated as metal in each case, wherein component a2) is preferably selected from titanium ions and zirconium ions and mixtures thereof, most preferably selected from zirconium ions. The content of component a2) can be monitored and determined by ICP-OES (inductively coupled plasma optical emission spectroscopy). The method is described in detail hereinafter. Preferably, when the aqueous acidic composition used in step 1) is applied by spraying, it comprises at least one component a2) in an amount in the range of 0.1 to 1.0 g / L, more preferably 0.2 to 0.6 g / L, even more preferably 0.2 to 0.4 g / L, calculated as metal in each case. Preferably, when the aqueous acidic composition used in step 1) is applied by roller coating, it comprises at least one component a2) in an amount in the range of 0.2 to 8.0 g / L, more preferably 0.5 to 7.5 g / L, even more preferably 0.7 to 5.0 g / L, yet more preferably 1.0 to 3.0 or 2.0 g / L, calculated in each case as metal.

[0098] Preferably, a precursor metal compound is used to generate the metal cation present as component a2) in the composition. Preferably, the precursor metal compound is water-soluble. The solubility is determined at a temperature of 20° C. and atmospheric pressure (1.013 bar).

[0099] Particularly preferred zirconium compounds, titanium compounds and / or hafnium compounds are complex fluorides of these metals. The term "complex fluoride" includes monoprotonated and multiprotonated forms as well as deprotonated forms. Mixtures of such complex fluorides can also be used. In the sense of the present invention, complex fluorides are complexes formed by zirconium, titanium and / or hafnium with fluoride ions in the composition (for example, by coordinating fluoride anions to zirconium, titanium and / or hafnium cations in the presence of water). In addition, it is also possible to use carbonates and / or complex carbonates and / or lactates and / or in particular nitrates of zirconium, titanium and / or hafnium. However, preferably, these cations are incorporated into the composition in the form of their complex fluorides.

[0100] Further optional components (components a3), a4) and / or a5))

[0101] The aqueous acidic composition may comprise additional components as listed hereinafter. In view of the ingredients of the aqueous composition, as used herein throughout the specification, the term "further comprises" means "in addition to the mandatory components". Thus, such "additional" components include ions other than the metal ions mentioned above.

[0102] Optionally and preferably, the acidic aqueous composition used in step 1) further comprises at least one component a3), i.e. free fluoride anions as at least one component a3). If free fluoride anions are present, they are preferably present in an amount in the range of 1 to 50 mg / L, more preferably 2 to 40 mg / L, even more preferably 3 to 30 mg / L, yet more preferably 5 to 25 mg / L, calculated in each case as fluorine.

[0103] The acidic aqueous composition used in step 1) optionally and preferably contains free fluoride anions as component a3). These can result from the presence of component a2), i.e., in particular when complex fluorides of Ti, Zr and / or Hf are present in the composition, but can also or alternatively result from the presence of other optional components as described below, such as by incorporating at least one water-soluble fluorine compound. Examples of such water-soluble fluorine compounds are fluorides (except complex fluorides of Ti, Zr and / or Hf) and hydrofluoric acid. The free fluoride content is determined by a fluoride-sensitive electrode according to the method disclosed in the "Methods" section.

[0104] Optionally and preferably, the acidic aqueous composition used in step 1) further comprises

[0105] Platinum cations as at least one component a4) are preferably present in an amount in the range of 0.01 to 8.0 g / L, calculated as metal.

[0106] Preferably, in particular when the aqueous acidic composition used in step 1) is applied by spraying, it comprises at least one component a4) in an amount in the range of 0.01 to 0.2 g / L, more preferably 0.01 to 0.1 g / L, even more preferably 0.01 to 0.05 or to 0.03 g / L, in each case calculated as metal. Preferably, in particular when the aqueous acidic composition used in step 1) is applied by roller coating, it comprises at least one component a4) in an amount in the range of 0.2 to 8.0 g / L, more preferably 0.4 to 7.5 g / L, even more preferably 0.5 to 6.0 g / L, in each case calculated as metal.

[0107] Preferably, the amount of component a4) is lower than the amount of component a2).

[0108] For the preparation of the aqueous acidic composition, preferably, in case the composition contains a4), a water-soluble (at a temperature of 20° C. and atmospheric pressure (1.013 bar)) molybdenum salt is used. Preferably, the molybdenum ions are incorporated in the form of at least one molybdate, preferably at least one ammonium molybdate.

[0109] Optionally, the acidic aqueous composition used in step 1) further comprises at least one organosilane as optional component a5), preferably in an amount ranging from 10 to 500 ppm, more preferably from 20 to 100 ppm.

[0110] Examples are, for example, (3-aminopropyl)trimethoxysilane, (3-aminopropyl)triethoxysilane, N-2-aminoethyl-3-aminopropyltrimethoxysilane, (3-mercaptopropyl)trimethoxysilane, (3-mercaptopropyl)triethoxysilane, (3-glycidoxypropyl)trimethoxysilane and / or (3-glycidoxypropyl)triethoxysilane, and / or vinyltrimethoxysilane.

[0111] Additional optional components

[0112] Optionally, the aqueous acidic composition further comprises at least one metal cation selected from the following group: cations of metals of the 1st to 3rd subgroups (copper, zinc and scandium) and the 5th to 8th subgroups (vanadium, chromium, manganese, iron, cobalt and nickel) of the periodic table (including lanthanides) and the 2nd main group (alkaline earth metal group) of the periodic table, lithium, bismuth and tin. However, preferably, metal cations of the chromium, cobalt and nickel families are not used. The above-mentioned metal cations are usually introduced in the form of their water-soluble compounds, preferably as their water-soluble salts. Preferred cations are selected from the group consisting of cations of cerium and other lanthanides, iron, calcium, copper, magnesium, manganese, niobium, tantalum, yttrium, vanadium, lithium, bismuth, zinc and tin.

[0113] Optionally, the aqueous acidic composition further comprises at least one pH adjusting substance, which is preferably selected from the group consisting of nitric acid, sulfuric acid, methanesulfonic acid, acetic acid, aqueous ammonia, sodium hydroxide and sodium carbonate, wherein nitric acid, aqueous ammonia and sodium carbonate are preferred. Depending on the pH of the acidic aqueous composition, the above compounds can be in their fully or partially deprotonated form or in a protonated form.

[0114] Optionally, the aqueous acidic composition further comprises at least one complexing agent. An example is 1-hydroxyethane-1,1-diphosphonic acid (HEDP).

[0115] Optionally, the aqueous acidic composition further comprises at least one corrosion inhibitor. Examples are L-cysteine ​​and other amino acids, benzotriazole and mixtures thereof. Preferably, the at least one corrosion inhibitor does not contain any kind of metal ions.

[0116] Optionally, the aqueous composition further comprises at least one organic acid, preferably at least one organic acid having at least two carboxylic acid groups and / or at least one organic acid having at least one carboxylic acid group and at least one further functional group having at least one donor atom (such as an OH-group) (e.g. lactic acid), in particular when the aqueous composition is alkaline. The presence of such compounds can contribute to the stabilization of at least one metal ion (such as a Zr cation) in the composition.

[0117] Optionally, the aqueous acidic composition further comprises phosphate anions, which may preferably be added in the form of phosphoric acid. Preferably, the phosphate anions are present in an amount in the range of 0.5 to 90 g / L, as P 2 O 5 calculate.

[0118] The aqueous composition may further comprise at least one of the following components: one or more waxes, one or more wetting agents, and one or more defoaming agents.

[0119] Optional step 1a)

[0120] After step 1), the surface of the substrate obtained after the contacting according to step 1) may optionally be rinsed, preferably with deionized water or tap water (optional step 1a)). If this step is performed, it is preferably done before any drying or curing performed in step 1).

[0121] Step 2 of the method

[0122] In step 2), at least one thermoplastic polymer material TM1 is at least partially applied to the film obtained after step 1) or to the dried or solidified layer, wherein the at least one thermoplastic polymer material TM1 is applied i) in the form of a foil (option i)) or ii) by injection in the molten state (option (ii)) to the film obtained after step 1) or to the dried or solidified layer to form a metal-plastic hybrid material. Preferably, step 2), i.e. option i), is not performed by injection molding.

[0123] The formed foil obtained from the use of the thermoplastic polymer material TM1 in step 2), ie the first option i), is preferably used as a compatibilizer material for the thermoplastic polymer material TM2 optionally subsequently injected in optional step 3a).

[0124] Step 2), i.e. the second option ii), and optional step 3a) each represent an injection molding step, wherein the thermoplastic polymer material TM1 (or TM2 in the case of step 3a)) is injected directly onto the metal surface of the substrate, to which the acidic aqueous composition has previously been applied in step 1).

[0125] Step 2) can be performed in a continuous or discontinuous manner.

[0126] The substrate obtained after step 1) or after optional step 1a) is preferably heated before carrying out step 2), preferably to a temperature above the melting temperature of the thermoplastic material TM1 used.

[0127] Preferably, the thermoplastic polymer material TM1 used in step 2) and / or the thermoplastic polymer material TM2 used in optional step 3a) is applied in such a way that a vacuum is applied to bring the corresponding thermoplastic polymer material into contact with at least a portion of the substrate, but preferably with the entire surface (which surface has been in contact with the acidic aqueous composition in step 1)), and remove the air enclosed between the surface of the substrate and the corresponding thermoplastic polymer material. Preferably, the temperature of the substrate and the corresponding thermoplastic polymer material applied thereto is kept above a temperature that promotes the connection of the applied thermoplastic polymer material to the metal substrate. After the aforementioned heating, the substrate is preferably placed in a device, preferably a thermoforming device, in which the corresponding thermoplastic polymer material can be placed on the surface of the substrate: for example, wherein the thermoplastic polymer material TM1 can be applied as a foil. As an alternative, it is also possible to first place the substrate into a device in which the corresponding thermoplastic polymer material is applied and then heat the substrate before the thermoplastic polymer material is placed thereon. Preferably, after the heated substrate is placed in the device or after the substrate is placed in the device and then heated, the corresponding thermoplastic polymer material is placed on the substrate and optionally heated, as in the case of step 2) in which the material is injected in the molten state, i.e. option ii). If the thermoplastic polymer material is heated, the heating can be performed, for example, by infrared radiation.

[0128] The temperature to which the thermoplastic polymer material is heated is preferably selected such that the thermoplastic material is rubber-elastic. For this purpose, the thermoplastic material is preferably heated to a temperature above the glass transition temperature of the thermoplastic material (if the thermoplastic material is an amorphous thermoplastic), or above the crystallite melting temperature (if the thermoplastic material is a semi-crystalline thermoplastic), but preferably below the melting temperature to avoid any damage. After placing the respective thermoplastic polymer material on the surface of the substrate and optionally after having heated the material, a vacuum is preferably applied as described above.

[0129] By applying vacuum, the thermoplastic polymer material is preferably attached to the surface of the substrate and a strong connection can be achieved. Removing the air that may be enclosed between the surface of the substrate and the thermoplastic polymer material preferably produces a smooth surface without bubbles. In order to apply vacuum, the substrate may include openings through which air can be extracted. If the substrate should not have any openings, the air between the substrate and the thermoplastic polymer material can also be extracted at the edge of the thermoplastic polymer material. If air is extracted at the edge, it is preferred that air is extracted at least on two opposite sides and preferably on the entire periphery of the corresponding thermoplastic polymer material. In order to apply vacuum, any suitable vacuum pump can be used. If air is extracted at the edge of the thermoplastic polymer material, the corresponding thermoplastic polymer material is preferably fixed in a device for applying vacuum so that a gap is formed between the substrate and the edge of the thermoplastic polymer material and a vacuum is applied through the gap. By applying vacuum, the thermoplastic polymer material preferably contacts the substrate uniformly over the entire surface of the substrate, and therefore forms a uniform layer on the surface of the substrate.

[0130] After the thermoplastic polymer material is preferably brought into contact with the entire surface of the substrate, the temperature of the substrate and the corresponding thermoplastic polymer material is preferably maintained at a temperature that promotes the connection of the thermoplastic material to the substrate, preferably at a temperature above the melting temperature of the thermoplastic material. By maintaining this temperature, the thermoplastic material preferably chemically reacts at least with the functional groups of the water-soluble polymer initially present in the acidic aqueous composition, thereby achieving a stable connection between the surface of the substrate and the corresponding thermoplastic polymer material and forming a composite part comprising a "metal layer" (metal surface of the substrate) and a "polymer layer" (applied thermoplastic material).

[0131] Preferably, at least before carrying out step 2), option ii), the substrate obtained after step 1), optionally 1a), is placed in a mold before carrying out step 3).

[0132] Optional step 3a)

[0133] In optional step 3a), at least one thermoplastic polymer material TM2, which is identical or different to the thermoplastic material TM1 applied in step 2) and is present in a molten state, is at least partially injected onto the surface of the foil of the metal-plastic hybrid material obtained after steps 2) and i).

[0134] If optional step 3a) is performed, the thermoplastic polymer material TM2 is preferably different from the thermoplastic polymer material TM1.

[0135] Optional step 3b)

[0136] In optional step 3b), a further substrate S2 having at least one metallic surface (which surface is at least partially made of aluminum and / or at least one aluminum alloy and has been subjected to the treatment of method step 1), i.e. by using an acidic aqueous composition) is applied to the surface of the foil of the metal-plastic hybrid material obtained after steps 2) and i), or vice versa.

[0137] Thermoplastic polymer materials TM1 and TM2

[0138] The thermoplastic polymer material TM1 may be the same as or different from the thermoplastic material TM2, preferably different therefrom.

[0139] Preferably, the thermoplastic polymer material TM1 is capable of chemically bonding to the functional groups of the water-soluble polymer initially present in the acidic aqueous composition used in step 1).

[0140] Preferably, the thermoplastic polymer material TM1 is selected from polyamides, polyesters such as PET and / or PBT, polyurethanes, polycarbonates, polyolefins such as polypropylene and polyethylene, and mixtures thereof. Recycled thermoplastic polymer materials such as recycled polyamides can be used. Preferably, the polyamide is selected from PA6, PA66, PA66 / 6, PA6.10, PA6.12, PA12, PA9T, PA6I / 6T, PA6T / 6I, PA6 / 6.36 and combinations thereof. Most preferred are polyesters such as PET and / or PBT, and polyamides. Preferably, at least one polyester is applied as at least one thermoplastic polymer material TM1 via step 2) (i) or (ii).

[0141] Thermoplastic polymer material TM1 such as polyamide in a form in which it has been compounded with at least one additive such as at least one rubber such as EPDM (ethylene propylene diene monomer) rubber may be used, in particular to improve the properties of the thermoplastic polymer material, such as to reduce its water absorption. Alternatively or additionally, the thermoplastic polymer material TM1 and / or TM2, preferably TM2, may optionally comprise (i) at least one fiber such as glass fiber, carbon fiber, aramid fiber and combinations thereof, and / or may optionally comprise (ii) a polyether block polyamide such as a polyether diamine and an aliphatic C 4 To C 40 Dicarboxylic acids and / or C 6 To C 12 Copolymers of lactams such as caprolactam or lauryl lactam, aliphatic C 4 To C 10 Diamine and aliphatic C 4 To C 40 Copolymers of dicarboxylic acids, C 6 To C 12Polycondensation products of lactams, copolymerization products of lactams and / or aliphatic dicarboxylic acids with aliphatic diamines, and combinations thereof, and / or may optionally contain (iii) at least one impact modifier, such as maleic anhydride grafted copolymers of ethylene with at least one of an α-olefin, a (meth)acrylate and (meth)acrylic acid, copolymers of maleic anhydride with at least one of ethylene and (meth)acrylate, styrene maleic anhydride or maleic anhydride grafted polypropylene.

[0142] Preferably, the thermoplastic polymer material TM2 is selected from polyamide, polyester such as PET and / or PBT, polyolefin such as polypropylene and polyethylene, and mixtures thereof. Preferably, the polyamide is selected from PA6, PA66, PA66 / 6, PA6.10, PA6.12, PA12, PA9T, PA6I / 6T, PA6T / 6I, PA6 / 6.36 and combinations thereof. Recycled thermoplastic polymer materials, such as recycled polyamide, can be used.

[0143] Preferably, the thermoplastic polymer material TM1 has a melting temperature in the range of 80 to 280° C. For example, a polyolefin may have a melting temperature of 80° C., whereas a polyamide has a significantly higher melting temperature of, for example, 280° C.

[0144] Preferably, the thermoplastic polymer material TM2 has a melting temperature in the range as defined for the thermoplastic polymer material TM1.

[0145] Metal-plastic hybrid material obtainable by the method of the present invention

[0146] A further subject matter of the present invention is a metal-plastic hybrid material obtainable by the process according to the invention.

[0147] All preferred embodiments described above in conjunction with the method according to the invention and its preferred embodiments are also preferred embodiments of the metal-plastic hybrid material according to the invention obtainable by said method.

[0148] Preferably, the dry layer thickness of the layer obtained by drying or curing the film obtainable by at least partially applying the aqueous acidic composition as defined in conjunction with step 1) of the aforementioned inventive method to the metal surface is in the range of 100 to 1000 nm, more preferably 150 to 750 nm, in particular 250 to 550 nm.

[0149] Use of acidic aqueous compositions

[0150] A further subject of the present invention is the use of an acidic aqueous composition as defined in conjunction with step 1) of the aforementioned inventive method for adhering a metal surface of a substrate at least partially made of aluminum and / or at least one aluminum alloy to a thermoplastic polymer material (such as thermoplastic material TM1) present on said surface in the form of a foil or applied to said surface by injection molding, preferably by using the inventive method.

[0151] All preferred embodiments described above in conjunction with the inventive method, the inventive metal-plastic hybrid material obtainable by said method, and preferred embodiments thereof are also preferred embodiments of the inventive use.

[0152] Metal-Plastic Hybrid Materials

[0153] A further subject of the invention is a metal-plastic hybrid material itself, i.e. a metal-plastic hybrid material comprising:

[0154] a substrate S1 having at least one metallic surface, the at least one metallic surface being at least partially made of at least one aluminum and / or at least one aluminum alloy,

[0155] a film or a dried or cured layer at least partially applied to said metal surface, obtainable by at least partially applying to said metal surface an aqueous acidic composition as defined in connection with step 1) of the method of the invention as described above, and

[0156] at least one thermoplastic polymer material TM1 in the form of a foil or in a form obtainable by injection moulding, in each case at least partially applied to a film or a dried or cured layer, preferably as defined in step 2) of the process according to the invention, and,

[0157] Optionally, further, at least one thermoplastic polymer material TM2, the at least one thermoplastic polymer material TM2 being identical to or different from the thermoplastic polymer material TM1, is at least partially applied on the at least one thermoplastic polymer material TM1 in a form obtainable by injection molding, with the proviso that the thermoplastic polymer material TM1 has been applied in the form of a foil,

[0158] or

[0159] Optionally, further, a substrate S2 having at least one metal surface, said surface being at least partially made of aluminum and / or at least one aluminum alloy, said substrate having a film or a dried or cured layer at least partially applied on said metal surface, said film or a dried or cured layer being obtainable by applying an aqueous acidic composition as defined in combination with step 1) of the aforementioned method of the present invention, wherein said film or a dried or cured layer at least partially present on said metal surface of substrate S2 is in a position adjacent to at least one thermoplastic polymer material TM1, provided that the thermoplastic polymer material TM1 has been applied in the form of a foil.

[0160] Preferably, a metal-plastic hybrid material is obtainable by the process of the present invention.

[0161] Preferably, the thermoplastic polymer material TM1 in the form of a laminate or in a form obtainable by injection moulding has a total thickness in the range of 200 to 800 μm.

[0162] All preferred embodiments described above in conjunction with the inventive method, the inventive metal-plastic hybrid material obtainable by said method, the inventive use, and preferred embodiments thereof are also preferred embodiments of the inventive metal-plastic hybrid material itself.

[0163] Preferably, the film or the dried or cured layer, preferably the dried or cured, preferably the dried layer, applied at least partially on the metal surface of the metal-plastic hybrid material has the following coating weight determined by XRF (X-ray fluorescence spectroscopy):

[0164] Since the component a2) is present in the acidic aqueous composition used in an amount of 0.1 to 40 mg / m 2 , more preferably 0.2 to 30 mg / m 2 , even more preferably 0.5 to 20 mg / m 2 , still more preferably 1.0 to 15 mg / m 2 , and more preferably 1.5 to 10 mg / m 2 , especially 2.0 to 8 mg / m 2 of zirconium and / or titanium and / or hafnium, preferably zirconium and / or titanium, more preferably zirconium, in each case calculated as metal,

[0165] 0 or 0.1 to 40 mg / m 2 , more preferably 0 or 0.2 to 30 mg / m 2 , even more preferably 0 or 0.5 to 20 mg / m 2 , still more preferably 0 or 1.0 to 15 mg / m 2 , and more preferably 0 or 1.5 to 10 mg / m 2 , especially 2.0 to 8 mg / m2 of molybdenum, calculated as metal.

[0166] If at least one thermoplastic polymer material TM2 is present in the metal-plastic hybrid material, preferably, optional step 3a) of the inventive method is performed. In this case, the thermoplastic polymer material TM1 has been applied in the form of a foil in step 2) and in step 3a), the thermoplastic polymer material TM2 is applied on top via injection molding.

[0167] If within the metal-plastic hybrid material there is a further substrate S2 which also has at least one metallic surface at least partially made of aluminium and / or at least one aluminium alloy, then preferably, the optional step 3b) of the method according to the invention has already been carried out. In this case, the thermoplastic polymer material TM1 has already been applied in the form of a foil in step 2) and in step 3b), after at least one metallic surface of the substrate S2 has likewise been treated with an acidic aqueous composition according to step 1), the substrate S2 is applied with its treated surface in a position adjacent to the foil formed of the thermoplastic polymer material TM1, resulting in the overall formation of a sandwich structure, wherein the foil made of TM1 flanks the two metallic surfaces of the two substrates S1 and S2, each of which carries the coating obtained by the treatment step 1). Preferably, when the metal-plastic hybrid material comprises a further substrate S2, it can be considered as a sandwich structure comprising two substrates S1 and S2, wherein each of these substrates is adhered to one surface of the thermoplastic material TM1 present in the form of a foil by means of an adhesive film or a dried or cured layer obtainable by applying an aqueous acidic composition as defined in conjunction with step 1) of the method according to the invention described above. Preferably, substrates S1 and S2 are each a sheet or coil made of aluminum and / or its alloys. Depending on the desired application, the total thickness of each coil or sheet may be in the range of 0.2 mm to 3 mm.

[0168] Uses of Metal-Plastic Hybrid Materials

[0169] A further subject matter of the present invention is the use of the metal-plastic hybrid material or the metal-plastic hybrid material obtainable by the process according to the invention as a component in the automotive, construction or electronics industry.

[0170] All preferred embodiments described above in conjunction with the method of the invention, the metal-plastic hybrid material of the invention obtainable by said method, the aforementioned use of the invention, the metal-plastic hybrid material of the invention itself, and preferred embodiments thereof are also preferred embodiments of the use of the metal-plastic hybrid material of the invention.

[0171] In particular, metal-plastic hybrid materials in which the substrate S1 and optionally the substrate S2 are foils can be used for electric mobility (E-mobility) applications, the manufacture of parts for the electronics industry, and / or for the manufacture of automotive parts, especially where weight reduction is desired. Further possible uses include LiDAR and EMI shielding applications, the manufacture of panel controls in cars, the manufacture of battery housings and protective panels for batteries.

[0172] method

[0173] 1. Cross-cut test according to DIN EN ISO 2409 (06-2013)

[0174] According to DIN EN ISO 2409 (06-2013), the cross-cut test is used to determine the adhesion strength. The cutter spacing is 3 mm. Based on the characteristic cross-cut value in the range of 0 (very good adhesion) to 5 (very poor adhesion), the evaluation is carried out. Each sample is tested three times and the average value is determined.

[0175] 2. Average molecular weight M w and M n Determination

[0176] The number average molecular weight and weight average molecular weight (M) were measured according to the following schemes: n and M w ): The samples were analyzed by SEC (size exclusion chromatography) equipped with a MALS detector. The absolute molar mass was obtained, where the dn / dC value was chosen to be equal to 0.1875 mL / g in order to obtain a recovery mass of about 90%. The polymer sample was dissolved in the mobile phase and the resulting solution was filtered with a 0.45 μm Millipore filter. The elution conditions were those of the following. Mobile phase: H 2 O 100% vol.0.1M NaCl, 25mM NaH 2 PO 4 , 25 mM Na 2 HPO 4 ; 100ppm NaN 3 ; Flow rate: 1 mL / min; Column: Varian Aquagel OHmixed H, 8 μm, 3*30 cm; Detection: RI (concentration detector Agilent) + MALLS (multi-angle laser light scattering) Mini DawnTristar + UV at 290 nm; Sample concentration: about 0.5 wt% in mobile phase; Injection loop: 100 μL. The polydispersity P can be obtained from the M n and M w Value calculation.

[0177] 3. Determination of free fluoride content

[0178] The free fluoride content is determined by means of a fluoride ion selective electrode. The electrode is calibrated using at least three stock solutions with known fluoride concentrations. The calibration process results in the establishment of a calibration curve. The fluoride content is then determined by using this curve.

[0179] 4. ICP-OES

[0180] According to DIN EN ISO 11885 (date: September 1, 2009), inductively coupled plasma atomic emission spectrometry (ICP-OES) is used to determine the amount of certain elements (such as zirconium, titanium, hafnium, etc.) in the sample analyzed. The sample is subjected to thermal excitation in an argon plasma generated by a high-frequency field, and the light emitted due to the electron transition becomes visible as spectral lines of the corresponding wavelength and is analyzed using an optical system. There is a linear relationship between the intensity of the emitted light and the concentration of the element in question. Prior to implementation, calibration measurements are performed according to the specific sample analyzed using known element standards (reference standards). These calibrations can be used to determine the concentration of unknown solutions, such as the concentration of the amount of titanium, zirconium and hafnium.

[0181] 5. Tensile Strength

[0182] Tensile strength was measured according to ISO 527-1:2012.

[0183] Examples

[0184] The following examples further illustrate the present invention but should not be construed as limiting its scope.

[0185] 1. Preparation of acidic aqueous coating compositions

[0186] 1.1 A number of acidic aqueous compositions A1 to A3 (1 L each) were prepared. All aqueous compositions contained H in an amount corresponding to the ppm value of zirconium. 2 ZF 6 , calculated as metal, as shown in Table 1a below. All aqueous compositions further contained ammonium heptamolybdate in an amount corresponding to the ppm value of molybdenum, calculated as metal, as shown in Table 1 below. All compositions were free of chromium and contained free fluoride anions. Each of these compositions further contained one of the following water-soluble polymers P1 to P3:

[0187] P1: with M > 150,000 g / mol w of commercially available polyacrylic acid,

[0188] P2: Copolymer of maleic acid and vinyl methyl ether,

[0189] P3: Copolymer of maleic acid and ethylene.

[0190] Table 1a:

[0191]

[0192] 1.2 A number of further acidic aqueous compositions A4 to A6 (1 L each) were prepared. All aqueous compositions contained H in an amount corresponding to the ppm value of zirconium. 2 ZF 6 , calculated as metal, as shown in Table 1b below. All aqueous compositions further contain ammonium heptamolybdate in an amount corresponding to the ppm value of molybdenum, calculated as metal, as shown in Table 1b below. All compositions are free of chromium and contain free fluoride anions. Each of these compositions further contains one of the water-soluble polymers P1 to P3 as already determined above.

[0193] Table 1b:

[0194]

[0195] 2. Preprocessing

[0196] 2.1 An aluminum alloy substrate in coil form (substrate T1; 5754AlMg3) was used as the substrate. 5754AlMg3 is an aluminum-magnesium alloy substrate.

[0197] By using commercial alkaline products The substrate was cleaned with S 5160 (at 60°C to 70°C). Then, it was rinsed twice with tap water (each time for 30 seconds). Next, the substrate was cleaned with a commercial product S 5240 / 2 was subjected to an acid cleaning step. Then, it was rinsed with tap water (30 seconds) and subsequently with deionized water (30 seconds).

[0198] A contacting step is then carried out, i.e. the surface of the substrate is contacted with one of the acidic aqueous compositions A1 to A3 described above in item 1.1, in order to form a conversion coating with adhesion-promoting properties on the surface of the substrate. The contacting step is carried out by spraying one of the acidic aqueous compositions onto the surface of the substrate for 60 seconds in each case. Prior to spraying, the acidic aqueous composition is heated to 25° C.

[0199] After the contacting step, a drying step is carried out after a period of blowing air (15 minutes at 60° C. to 70° C.). The resulting dry layer thickness is in the range of 50 to 200 nm.

[0200] 2.2 An aluminum alloy substrate (substrate T2; AA 6060) was used as the substrate.

[0201] By using commercial alkaline products The substrate was cleaned with T 5281A (at 55°C). Then, it was rinsed twice with tap water (each time for 30 seconds). Next, the substrate was cleaned with commercial product P 4432 was subjected to an acid cleaning step. Then, it was rinsed three times with tap water (each time for 60 seconds).

[0202] A contacting step is then carried out, i.e. the surface of the substrate is contacted with one of the acidic aqueous compositions A4 to A6 described above in item 1.2, in order to form a conversion coating with adhesion-promoting properties on the surface of the substrate. The contacting step is carried out by spraying one of the acidic aqueous compositions onto the surface of the substrate for 60 seconds in each case. Prior to spraying, the acidic aqueous composition is heated to 30° C.

[0203] After the contacting step, three rinses with tap water were performed (each lasting 60 seconds).

[0204] Then, a drying step (8 minutes at 100° C.) was performed after blowing air for a while.

[0205] 3. Preparation of Metal-Plastic Hybrid Materials

[0206] 3.1 Polybutylene terephthalate (PBT) and glass fiber (commercially available product PBT-GF30) is applied by injection molding directly to the surface of the substrate obtained after the pretreatment as described in item 2.1 at a temperature between 180 and 240° C. The resulting laminate produced by injection molding has a thickness (of the plastic layer) in the range of 400 μm to 2 cm, depending on the desired application.

[0207] 3.2 A sandwich structure is also produced in the same manner as described in item 3.1, however, wherein PBT-GF30 was injected between the two surfaces of two substrates, each surface being obtained after the pretreatment as described in item 2.1.

[0208] 3.3 Polybutylene terephthalate (PBT) and glass fiber (commercially available product A mixture of PBT-GF30) is applied by injection molding directly onto the surface of the substrate obtained after the pretreatment as described in item 2.2 at a temperature between 180 and 240° C. The resulting laminate produced by injection molding has a thickness (of the plastic layer) in the range of 400 μm to 2 cm, depending on the desired application.

[0209] 4. Properties of the obtained metal-plastic hybrid materials

[0210] 4.1 A number of properties of the products obtained by the methods described above in items 3.1 and 3.2 were investigated. These properties were determined according to the test methods described above. The results are shown in Tables 2 and 3. In particular, the adhesion strength was investigated.

[0211] Table 2:

[0212] Aqueous compositions for chemical pretreatment Cross-cut A1 0 A2 0 A3 0

[0213] As is evident from Table 2, excellent adhesion of the PBT to the metal substrate was achieved in all cases.

[0214] Table 3:

[0215] Aqueous compositions for chemical pretreatment Tensile strength [MPa] A1 23.7 A2 20.8 A3 15.0

[0216] For the sandwich structure, a peel test was performed. The results showed that no peeling could be obtained.

[0217] 4.2 A number of properties of the product obtained by the method described above in item 3.3 were investigated. These properties were determined according to the test methods described above. The results are shown in Table 4. In particular, the adhesion strength was investigated.

[0218] Table 4:

[0219] Aqueous compositions for chemical pretreatment Cross-cut A4 0 A5 0 A6 0

[0220] As is evident from Table 4, excellent adhesion of PBT to the metal substrate was achieved in all cases.

Claims

1. A method for preparing a metal-plastic hybrid material, the material comprising a substrate S1 having at least one metal surface and at least one thermoplastic material applied to the metal surface of the substrate S1, the method comprising at least steps 1) and 2) and optionally step 3a) or 3b), namely 1) applying an aqueous acidic composition at least partially to the at least one metal surface of the substrate S1 to at least partially form a film on the surface, wherein the metal surface is at least partially made of aluminum and / or at least one aluminum alloy, and wherein the acidic aqueous composition comprises, in addition to water, at least one water-soluble polymer having at least one functional group selected from the group consisting of acid groups, hydroxyl groups, amino groups, and mixtures thereof, as at least one component a1), at least one metal cation selected from the group consisting of titanium ions, zirconium ions and hafnium ions, and mixtures thereof as at least one component a2), and free fluoride anions as at least one component a3), and and optionally drying or curing the film to form a dried or cured layer, 2) applying at least one thermoplastic polymer material TM1 at least partially to the film or to the dried or cured layer obtained after step 1), wherein the at least one thermoplastic polymer material TM1 is i) applied in the form of a foil or ii) applied by injection in the molten state onto the film obtained after step 1) or onto the dried or solidified layer to form the metal-plastic hybrid material, and 3a) optionally injecting at least one thermoplastic polymer material TM2, which is identical or different to the thermoplastic material TM1 applied in step 2) and is present in a molten state, at least partially onto the surface of the foil of the metal-plastic hybrid material obtained after steps 2) and i), or 3b) Optionally, a further substrate S2 having at least one metallic surface, which is at least partially made of aluminum and / or at least one aluminum alloy and has been subjected to the treatment of method step 1), is applied to the surface of the foil of the metal-plastic hybrid material obtained after steps 2) and i), or vice versa.

2. The method according to claim 1, characterized in that The acidic aqueous composition used in step 1) has a pH value in the range of 0.1 to <7.0, preferably 0.5 to 6.5, more preferably 1.0 to 6.0, even more preferably 1.5 to 5.5, still more preferably 2.0 to 5.0, yet more preferably 2.5 to 4.5, yet more preferably 3.0 to 4.0, most preferably >3.0 to <3.

7.

3. The method according to claim 1 or 2, characterized in that: The at least one water-soluble polymer used as component a1) is present in the acidic aqueous composition in an amount ranging from 0.05 to 2.0 g / L, preferably from 0.10 to 1.8 g / L, more preferably from 0.12 to 1.6 g / L, still more preferably from 0.14 to 1.5 g / L, yet more preferably from 0.16 to 1.4 g / L, still more preferably from 0.18 to 1.2 g / L, most preferably from 0.20 to 1.0 g / L.

4. The method according to one or more of the preceding claims, characterized in that The at least one water-soluble polymer used as component a1) has at least one functional group selected from carboxylic acid groups, phosphonic acid groups, sulfonic acid groups, hydroxyl groups, amino groups, and mixtures thereof, more preferably selected from carboxylic acid groups, hydroxyl groups, amino groups, and mixtures thereof, even more preferably selected from carboxylic acid groups.

5. Method according to one or more of the preceding claims, characterized in that The at least one water-soluble polymer used as component a1) is a homopolymer or copolymer obtainable by polymerization of at least one ethylenically unsaturated monomer, at least a portion of which carries at least one functional group as defined in claims 1 and 4; preferably a homopolymer or copolymer obtainable by polymerization of at least one vinyl monomer and / or (meth)acrylic monomer, at least a portion of which carries at least one functional group as defined in claims 1 and 4.

6. Method according to one or more of the preceding claims, characterized in that The at least one water-soluble polymer used as component a1) is selected from (meth)acrylic acid homopolymers, in particular acrylic acid homopolymers; copolymers of (meth)acrylic acid and at least one ethylenically unsaturated monomer different from (meth)acrylic acid, in particular copolymers of (meth)acrylic acid and maleic acid; copolymers of maleic acid and at least one ethylenically unsaturated monomer different from maleic acid, in particular copolymers of maleic acid and ethylene and / or propylene and / or at least one alkyl vinyl ether such as methyl vinyl ether; copolymers of vinylphosphonic acid and at least one ethylenically unsaturated monomer different from vinylphosphonic ...propylene and maleic acid; copolymers of vinyl phenol and at least one ethylenically unsaturated monomer different from vinyl phenol; copolymers of vinyl mercaptoethanol and at least one ethylenically unsaturated monomer different from vinyl mercaptoethanol; homopolymers and copolymers of vinyl phenol which have been modified with at least one amine, preferably at least one primary amine such as N-ethanolamine and / or N-methylglucamine; and mixtures thereof.

7. Method according to one or more of the preceding claims, characterized in that The at least one water-soluble polymer used as component a1) is selected from (meth)acrylic acid homopolymers, in particular acrylic acid homopolymers; copolymers of (meth)acrylic acid and at least one ethylenically unsaturated monomer different from (meth)acrylic acid, in particular copolymers of (meth)acrylic acid and maleic acid; copolymers of maleic acid and at least one ethylenically unsaturated monomer different from maleic acid, in particular copolymers of maleic acid and ethylene and / or propylene and / or at least one alkyl vinyl ether, such as methyl vinyl ether; homopolymers of vinyl alcohol; copolymers of vinyl alcohol and at least one ethylenically unsaturated monomer different from vinyl alcohol; homopolymers and copolymers of vinylphenol, which have been modified with at least one amine, preferably at least one primary amine, such as N-ethanolamine and / or N-methylglucamine; and mixtures thereof, Preferably selected from N-methylglucamine-modified poly(vinylphenol), N-ethanolamine-modified poly(vinylphenol), poly(maleic acid-co-vinyl methyl ether), poly(maleic acid-co-acrylic acid), polyacrylic acid, poly(vinyl-phosphonic acid-co-acrylic acid), poly(acrylic acid-co-maleic acid-co-vinylphosphonic acid), poly(acrylic acid-co-maleic acid-co-vinylmercaptoethanol) and mixtures thereof.

8. Method according to one or more of the preceding claims, characterized in that The aqueous acidic composition used in step 1) comprises the at least one component a2) in an amount in the range of 0.1 to 10.0 g / L, calculated in each case as metal, wherein component a2) is preferably selected from titanium ions and zirconium ions and mixtures thereof, most preferably selected from zirconium ions, wherein, when the aqueous acidic composition used in step 1) is applied by spraying, the aqueous acidic composition preferably comprises the at least one component a2) in an amount in the range of 0.1 to 1.0 g / L, more preferably 0.2 to 0.6 g / L, even more preferably 0.2 to 0.4 g / L, calculated in each case as metal, and wherein, when the aqueous acidic composition used in step 1) is applied by roller coating, the aqueous acidic composition comprises the at least one component a2) in an amount in the range of 0.2 to 8.0 g / L, more preferably 0.5 to 7.5 g / L, even more preferably 0.7 to 5.0 g / L, yet more preferably 1.0 to 3.0 or 2.0 g / L, calculated in each case as metal.

9. Method according to one or more of the preceding claims, characterized in that The aqueous acidic composition used in step 1) further comprises platinum cations as at least one component a4), preferably in an amount in the range of 0.01 to 8.0 g / L, wherein when the aqueous acidic composition used in step 1) is applied by spraying, the aqueous acidic composition preferably comprises the at least one component a4) in an amount in the range of 0.01 to 0.2 g / L, more preferably 0.01 to 0.1 g / L, even more preferably 0.01 to 0.05 or to 0.03 g / L, in each case calculated as metal, and wherein, when the aqueous acidic composition used in step 1) is applied by roller coating, the aqueous acidic composition preferably comprises the at least one component a4) in an amount in the range of 0.2 to 8.0 g / L, more preferably 0.4 to 7.5 g / L, even more preferably 0.5 to 6.0 g / L, in each case calculated as metal.

10. Method according to one or more of the preceding claims, characterized in that The at least one thermoplastic polymer material TM1 and the at least one thermoplastic polymer material TM2 are independently selected from polyamide; polyester, in particular PET and / or PBT; polyurethane; polycarbonate; polyolefin, in particular polypropylene and / or polyethylene; and mixtures thereof, wherein preferably, the at least one thermoplastic polymer material TM1 is selected from polyester, in particular PET and / or PBT.

11. A metal-plastic hybrid material obtainable by a process according to one or more of claims 1 to 10.

12. Use of an acidic aqueous composition as defined in one or more of claims 1 to 9 for adhering a metal surface of a substrate at least partially made of aluminum and / or at least one aluminum alloy to a thermoplastic polymer material present on said surface in the form of a foil or applied to said surface by injection molding.

13. A metal-plastic hybrid material comprising a substrate S1 having at least one metallic surface, the at least one metallic surface being at least partially made of at least one aluminum and / or at least one aluminum alloy, a film or a dried or cured layer at least partially applied to said metal surface, obtainable by applying at least partially to said metal surface an aqueous acidic composition as defined in conjunction with step 1) in one or more of the preceding claims 1 to 9, and at least one thermoplastic polymer material TM1 in the form of a foil or in a form obtainable by injection moulding, in each case at least partially applied to the film or the dried or cured layer, preferably as defined in step 2) in one or more of claims 1 to 9, and, Optionally, further, at least one thermoplastic polymer material TM2, the at least one thermoplastic polymer material TM2 being identical to or different from the thermoplastic polymer material TM1, is at least partially applied on the at least one thermoplastic polymer material TM1 in a form obtainable by injection molding, with the proviso that the thermoplastic polymer material TM1 has been applied in the form of a foil, or Optionally, further, a substrate S2 having at least one metal surface, said surface being at least partially made of aluminum and / or at least one aluminum alloy, said substrate having a film or a dried or cured layer at least partially applied on said metal surface, said film or a dried or cured layer being obtainable by applying an aqueous acidic composition as defined in step 1) in combination with one or more of the preceding claims 1 to 9, wherein said film or a dried or cured layer at least partially present on said metal surface of said substrate S2 is in a position adjacent to said at least one thermoplastic polymer material TM1, provided that said thermoplastic polymer material TM1 has been applied in the form of a foil.

14. The metal-plastic hybrid material according to claim 11 or 13, characterized in that: At least the film or the dried or cured layer, preferably the dried or cured layer, obtainable by applying the aqueous acidic composition to the metal surface of the substrate S1 has a dry layer thickness in the range of 100 to 1000 nm, and / or is characterized in that the film or the dried or cured layer, preferably the dried or cured layer, obtainable by applying the aqueous acidic composition to the metal surface of the substrate S1 has the following coating weight determined by XRF (X-ray fluorescence spectroscopy): Since the component a2) is present in the acidic aqueous composition used in an amount of 0.1 to 50 mg / m 2 , more preferably 0.2 to 30 mg / m 2 , even more preferably 0.5 to 20 mg / m 2 , still more preferably 1.0 to 15 mg / m 2 , and more preferably 1.5 to 10 mg / m 2 , especially 2.0 to 8 mg / m 2 of zirconium and / or titanium and / or hafnium, preferably zirconium and / or titanium, more preferably zirconium, in each case calculated as metal, 0 or 0.1 to 40 mg / m 2 , more preferably 0 or 0.2 to 30 mg / m 2 , even more preferably 0 or 0.5 to 20 mg / m 2 , still more preferably 0 or 1.0 to 15 mg / m 2 , and more preferably 0 or 1.5 to 10 mg / m 2 , especially 2.0 to 8 mg / m 2 of molybdenum, calculated as metal.

15. Use of the metal-plastic hybrid material according to one or more of claims 11, 13 or 14 as a component in the automotive, construction or electronics industry.

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