Method for coating the metal surface of a component with a plastic and a component made of a first and a different second metal

Abstract

A method for coating the metal surface of a component with a plastic, wherein the method comprises: Providing a component (10, 20) consisting of a first metal and a second metal different from it, with a metal surface; Providing a plastic with at least one maleic anhydride grafted base plastic component and / or of a plastic with at least one functional group from a silane compound, whereby a self-adhesive plastic (30) is produced; Injection molding or extrusion of the material-bonding and self-adhesive plastic (30) onto the preheated component (10, 20), wherein the application of the material-bonding and self-adhesive plastic (30) is applied to the metal surface preheated to a temperature of 120 to 220°C, so that it is applied directly to the metal surface and the metal surface is at least partially coated.

Description

Technical area

[0001] The invention relates to a method for coating a metal surface with a plastic and to a component having a metal surface coated with a plastic. Background of the invention

[0002] When coating or encasing metal profiles with plastic, a bonding agent is commonly used to bond the two materials, as described, for example, in EP 1 024 244 B2. This approach results in disadvantages, particularly in automotive applications, which are outlined below: As part of the increasing effort to reduce weight, aluminum components are being used in vehicle construction, including in power supply components. Copper components are generally used for the transition points to the consumers. Due to the different potentials in the electrochemical series, corrosion occurs between copper and aluminum in the presence of moisture and oxygen. To prevent corrosion, the transition area between the materials must be hermetically sealed. In particular, the functionality of the transition area must be guaranteed over the service life of the vehicle. Due to the low material costs, low processing temperatures, and short process times, polypropylene or, in general, polyolefins, as well as copolymers or blends from this plastic group, are suitable for insulation, i.e. for encasing the current-carrying metal components.

[0003] In the above-mentioned material bond between dissimilar metals (such as copper and aluminum), there are often gaps, gaps, or other openings due to the manufacturing process, into which air can penetrate and water deposits can form. Furthermore, moisture accumulation can occur due to capillary action. This leads to electrochemical corrosion of the metals.

[0004] For this reason, optimal adhesion between the metal component and the applied plastic is desirable. In the prior art, this was achieved by applying an adhesion promoter or primer to the metal surface to be coated or encased, for example by spraying or rolling, painting, printing, etc. This does result in the plastic adhering well to the sections of the metal where the adhesive has been applied, but gap penetration, i.e. the ability of the plastic to fill gaps, capillary spaces or non-adherent areas and to form a strong bond with the metal, is greatly reduced. Adhesion of the plastic in the gap and thus a sealed, filled space is very difficult to achieve. In particular, this non-adherent plastic mass can create a capillary space into which moisture can penetrate (delamination effect).If this area is at the dew point of a component or vehicle, moisture will be deposited over a longer period of time, which can lead to field failures after years.

[0005] EP 1 024 244 A2 relates to a composite profile. DE 10 2008 052 619 A1 relates to a material-to-material bonding of individual wire-shaped elements. EP 0 721 831 A1 relates to a method and apparatus for producing plastic / metal composite bodies. WO 2004 / 050 351 A1 relates to a plastic-metal composite component. DE 11 2008 001 402 T5 relates to a method for producing a flame-retardant silane-crosslinked olefin resin and an insulated wire. DE 11 2010 004 666 T5 relates to a composition for a wire coating material, an insulated wire, and a cable harness. DE 11 2005 003 235 T5 refers to a flame-retardant resin composition. DE 44 40 394 A1 refers to a fire-retardant resin composition. Description of the invention

[0006] An object of the invention is to provide a method for coating a metal surface with a plastic and a component with a metal surface coated with a plastic, whereby the service life of the coated component can be increased, in particular when it has a connecting region of different metals, gaps, cut edges and / or other openings.

[0007] The object is achieved by a method according to claim 1 and by a component according to claim 7. Advantageous further developments follow from the subclaims, the following general description of the invention and the description of preferred embodiments.

[0008] When reference is made below to a coating or sheathing of a metal surface, this does not mean that the entire metal surface or the entire component bearing the metal surface - such as a flat conductor, a contact tab or a contact plug - has to be completely coated or sheathed. Rather, it is important that the plastic is at least partially applied directly to the metal surface, i.e. without an intermediate layer of an adhesion promoter (also referred to as a "primer" or simply "adhesive"). The metal surface and the plastic therefore form at least a partial direct bond. This is achieved by providing the plastic with at least one functional group from an acid compound and / or a plastic with at least one functional group from a silane compound, thereby producing a self-adhesive plastic.

[0009] This eliminates the need to apply a bonding agent to the metal surface, which not only simplifies the coating process, specifically the injection molding or extrusion process, but also has a number of other advantageous effects: Instead of priming the metal surface with a mask, using an additional, cost-intensive material, preheating, the actual coating process, and the process infrastructure (e.g., with an exhaust ventilation system, etc.), the metal surface can be insulated and sealed in a single process (injection molding, extrusion). This results in time and cost savings due to the reduced process effort. Furthermore, free spaces, gaps, openings, and the like can be produced without cavities and with excellent durability, as they are simply filled during the injection molding or extrusion process.The plastic does not come off due to its self-adhesive properties.

[0010] According to the invention, the component to be coated comprises a first metal and a different second metal, which are bonded to one another. The two metal components can be designed, for example, as roll-clad bimetal or as metal plates welded together in an overlapping manner. In the automotive sector, copper or copper alloys and aluminum or aluminum alloys are particularly used for this purpose. The coating or sheathing with the self-adhesive plastic encloses the connection area between the two metals. "Enclosure" here, of course, is not to be understood as a completely hermetically sealed enclosure, but rather such that the transition area or contact area between the two metal components is coated with the self-adhesive plastic.Injection molding or extrusion ensures that the self-adhesive plastic completely penetrates, fills, seals, insulates, and connects any corners, edges, surfaces, cavities, gaps, and openings that may be present in the joining area between the two metals. This ensures that no air or moisture can reach the sensitive areas of the metal transitions, thus preventing or at least minimizing corrosion.

[0011] In one embodiment, the component to be coated comprises a first metal and a different second metal, which are separated from each other. A bond between the two components is created using the self-adhesive plastic.

[0012] The process described above is particularly used for sheathing flat conductors with lateral outlets. The flat conductor can then consist of the first metal, e.g., aluminum or an aluminum alloy, and the lateral outlets can be made of the second metal, e.g., copper or a copper alloy. In this case, all the lateral outlets, which are implemented using contact tabs, for example, can be sealed and insulated in a simple yet extremely reliable manner. Of course, the application of the concept presented here is more extensive, including contact plugs, multilayer flat conductors, so-called B+ lines, and other current-carrying metal components. In particular, a connection made of metals with different electrochemical potentials can be effectively protected against corrosion in this way.

[0013] An improvement in the surface adhesion of the self-adhesive plastic to the metal surface can be achieved by anodizing (e.g. 'flash anodizing') at least part of the metal surface.

[0014] Furthermore, at least part of the metal surface can be completely or partially tinned, nickel-plated, silver-plated, gold-plated or chrome-plated.

[0015] Polypropylene or polyethylene copolymers with incorporated functional groups from acid compounds or silane compounds are preferably used as self-adhesive plastics. Maleic anhydride has proven to be a suitable acid compound. The use of a thermoplastic elastomer, polyvinyl chloride (PVC), styrene polymers or blends with styrene polymers, a polyamide (PA) or a polyamide blend, and silicone is also possible.

[0016] By applying a standard process pressure during injection molding (including holding pressure) or extrusion, excellent adhesion is achieved. The melt temperature of the plastic during injection molding or extrusion is preferably within the standard range. The viscosity, i.e., the gap-permeability of the self-adhesive plastic, can be further increased by modifying the polymer's molecular weight or molecular chain length, or by using additives. Preheating the metals to be bonded to the plastic mass between 120°C and 220°C, according to the invention, is preferred for optimal chemical bonding during the injection molding or extrusion process.

[0017] The present invention is particularly suitable for coating or encasing current-carrying components in automotive engineering. This is because, given the fierce competition in the automotive industry, extremely efficient manufacturing processes are essential, while still maintaining excellent quality and durability. The coating technology presented here is suitable for achieving these goals, as it increases the service life of the coated components while simplifying production. Nevertheless, the invention is also applicable and useful in other sectors. Examples include: the transport sector in general, i.e., in addition to the automotive sector, aviation, aerospace, shipping, and rail transport; mechanical engineering, furniture manufacturing, the electrical and electronics sectors, particularly entertainment electronics; medical technology, building services engineering; structural engineering and drywall construction; and civil and road engineering.Furthermore, further advantages and features of the present invention will become apparent from the following description of preferred embodiments. The features described therein can be implemented alone or in combination with one or more of the above-mentioned features, provided the features do not contradict each other. The following description of the preferred embodiments is made with reference to the accompanying drawings. Short description of the drawings The Fig. 1a to 1h show cross-sections of elongated wrapped profiles. The Fig. 2a and Fig. 2b show cross sections through a connecting area of ​​two different metals, which were welded using a welding process ( Fig. 2a) and once using roll cladding ( Fig. 2b) are connected. The Fig. 3a to 3d show locally overmolded or extruded connection areas of two metal components. Fig. 4a to 4d show modifications of the cross sections of the Fig. 3a to 3d, where the metal components are already partially coated. The Fig. 5a and Fig. 5b shows cross sections of a locally overmolded flat metal and a welded stranded conductor. The Fig. 6 shows an example of a locally overmolded or extrusion-coated component attached to an insulated flat conductor, the contact side being coated with a metallization. The Fig. Figure 7 shows schematically and exemplarily a manufacturing process with an extrusion tool and other stations. Ways to implement the invention

[0018] The Fig. 1a to 1h show cross sections through various exemplary profiles with continuous and / or discontinuous branches. Here and in all other figures, reference numeral 10 denotes a profile main body, which Fig. 1a to 1h is elongated perpendicular to the plane of the paper. The profile main bodies are electrically conductive components, for example, made of aluminum. Outlets provided on the profile main body 10 are generally designated by the reference numeral 20. The outlets 20 are made of the same or a different material as the profile main body 10. Different outlets 20 can also be made of different materials. The outlets 20 are usually provided laterally on the profile main body 10; they can be provided continuously or discontinuously on multiple sides of the profile main body 10.

[0019] The profile main bodies 10 shown here are particularly suitable for use as single-layer or multi-layer flat conductors for installation in automotive construction. The profile main body 10 and the lateral branches 20, which together form a "component" in general terms, are therefore preferably current-carrying. The profiles in the Fig. 1a to 1h, however, show that other design variants are possible; the cross-sections shown here exemplify the wide range of applications of the wrapped profiles across many industries. Fig. 1d, for example, shows a sheathed profile that not only has two main bodies 10 designed as flat conductors with associated lateral outlets 20, but also has another extruded or sheathed material 100, which may be, for example, an optical fiber or stranded wire. Generally speaking, the profile main body 10 and the lateral outlets 20 can be current-conducting, light-conducting, fluid-conducting, mechanically stabilizing, for fastening, or for another purpose. In the case of electrical conduction, the profile main body 10 and / or the lateral outlets 20 are preferably made entirely of metal, in particular aluminum or copper. The profile main body 10 and / or the lateral outlets 20 can comprise glass fibers and / or consist of a transparent plastic, such as polycarbonate or PMMA, provided they have a metal surface.The lateral outlets 20 can also be constructed from several interconnected metals, in particular aluminum and copper. In principle, the profile main body 10 and / or the lateral outlet 20 can be made of conductive or non-conductive materials or components.

[0020] The fastening function mentioned above as a possible embodiment of the outlets is in the Fig. 1f, in which a partially covered fastening element 20, which may be a metal clip, is provided on the profile main body 10. Such a fastening element 20 with respect to a tubular profile main body 10 is shown in Fig. 1h shown.

[0021] From the Fig. Figure 1g shows a profile with a partially enclosed notch punched out of the profile body 10. This can be a contact lug for electrical contact or a fastening element.

[0022] In all figures, reference numeral 30 denotes a plastic component (or "plastic"), which is integrally connected to the profile main body 10 as a casing. The plastic component 30 partially or completely encloses the profile main body 10, without, however, completely enclosing the outlets 20, wherein the Fig. 1g represents an exception to this. It should be mentioned at this point that the plastic component 30 does not have to completely enclose the lateral outlets 20, but is present at least in the area of ​​the transitions between the lateral outlets 20 and the profiles 10. The material-to-material connection of the plastic component 30 to the profile main body 10 is achieved at least partially by the fact that the plastic component 30 is a self-adhesive plastic. In addition to a base plastic component - such as polypropylene, polyethylene, or polyolefin in general - the self-adhesive plastic has one or more built-in functional groups made of acid compounds and / or silane compounds.

[0023] In the Fig. 1g shows an embodiment in which, in addition to the integral sheathing with the plastic component 30, another plastic component 31 is attached to the main body or to the plastic component 30 and / or integrally connected thereto. This can be designed, for example, as a sealing lip.

[0024] The Fig. 2a and Fig. 2b each show a connection area of ​​two different metal elements, where here a connection lug 20, for example made of copper, is connected to a profile main body 10, for example made of aluminum, in the connection area 50. In the Fig. 2a, the two parts 10 and 20 were welded together. In the Fig. 2b, the connection was made by roll bonding. In both cases, gaps or generally free spaces S may remain, which are filled watertight and airtight by injection molding or extrusion of the self-adhesive plastic component 30. In the previously common use of an adhesion promoter to achieve the connection between the plastic component 30 and the profile main body 10 or the outlets 20, a sufficient material bond between the metal and the plastic was often not established in the gap areas S, making these areas susceptible to corrosion.

[0025] In the Fig. 3a to 3d show locally overmolded or coated profiles or elements with outlets 20. In the connection area 50 of the two metal parts, the self-adhesive plastic component 30 was extruded or injected. Fig. 3a and Fig. 3b correspond to the Fig. 2a and Fig. 2b, where the coating or sheathing is shown in the connection area 50. Further profiles are shown in the Fig. 3c and Fig. 3d shown. From the Fig. 3c shows that openings 40, which serve as areas of “claws,” can be filled with the self-adhesive plastic 30. Such a claw is effectively enabled by the self-adhesive plastic 30 used here. A different geometry is evident from the Fig. 3d.

[0026] The profiles of the Fig. 4a to 4d correspond to the profiles of Fig. 3a to 3d, showing cases in which the profile main body 10 already has an existing sheath 31 and / or the outlets 20 already have a plastic sheath 32. The self-adhesive plastic 30 and the previously applied plastic sheaths 31 and 32 partially overlap and form a tight and secure connection, thereby providing even greater protection for the sheathed component, in particular the connection area 50 between the two metal parts 10 and 20.

[0027] The Fig. 5a and Fig. 5b shows further embodiments in which a stranded conductor 60 is welded to the profile main body 10 or the outlet 20. The welded stranded conductor 60 is also at least partially coated with a plastic component 33. The strands of the stranded conductor 60 are designated by reference numeral 61.

[0028] Due to the direct material-to-material connection of the self-adhesive plastic 30, complete sealing is possible even in the connection area 50 with a stranded conductor, which was previously extremely difficult with the aid of an adhesion promoter.

[0029] The Fig. 6 shows an example of a component attached to a flat conductor 11, comprising a profile main body 10 and an outlet 20, wherein the contact area of ​​the outlet 20 is coated with a metallization 70. The metallization 70 can be at least partially tinned, nickel-plated, silver-plated, gold-plated, or chrome-plated. The flat conductor 11 is already coated with a plastic sheath 31 as an insulating material. The self-adhesive plastic component 30 overlaps or adheres to the plastic sheath 31 of the flat conductor 11, the flat conductor 11, the profile main body 10, the outlet 20, and the metallized surface 70 of the outlet 20. The self-adhesive plastic component 30 thus insulates another plastic, three different metal surfaces, and a metallized surface from the outside, thus preventing, for example, the penetration of moisture into the critical transition areas 50.

[0030] The Fig.Figure 7 schematically shows an extrusion process with an extrusion die and additional stations. The extrusion die is designated by the reference numeral 200, and the extruder by 201. Before extrusion in the extrusion die 200, which has an extruder 201, the component to be coated, i.e., for example, the main profile body 10 with outlets 20, is preheated to a temperature preferably between 150°C and 220°C. Preheating to 180°C has proven suitable for applying a polypropylene to aluminum. This preheating takes place at station 210. By preheating the component to be coated, the material-to-material bond with the self-adhesive plastic 30 is significantly improved or, in some cases, depending on the materials used, even made possible.At the station designated "coil" 220, the component to be coated is prepared, which here is provided as an aluminum strip for producing a flat conductor as the profile main body 10. This is of course purely exemplary, and whether an aluminum strip is unwound from a roll and subsequently fed to the heating device 210 and then to the extrusion tool 200, or whether the component to be coated is fed in another way, is not critical here. After extrusion (or alternatively, injection molding), calibration may take place in a calibration device 230, whereby the product is brought to the final product dimensions, followed by cooling in a water bath 240 at approximately 10°C. Finally, the coated component is cut to size in a cutting device 250 using a knife or saw 251 and packaged at station 260.For the process described here, a transport or belt speed of approximately 4 to 5 m per minute is considered.

[0031] The following plastics, for example, are suitable for the described embodiments: - Self-adhesive polyolefins, especially self-adhesive polypropylene and polyethylene; ethylene / ethyl acrylate copolymers; - Maleic anhydride grafted EPM or EPDM (ethylene / propylene / diene copolymers); ethylene / butene copolymer; - Thermoplastic elastomers (TPE), ie blends such as TPE-V thermoplastic / elastomer blends cross-linked (PTV) or TPE-O thermoplastic / elastomer blends uncross-linked (TPO) or copolymers such as TPE-U thermoplastic polyurethanes (TPU), TPE-E thermoplastic copolyesters (TPC), TPE-A polyether block amides (TPA) or TPE-S styrene block copolymers (TPS); which are polar or metal-adherent; surface activation via plasma treatment can be advantageous; - Polyvinyl chloride (PVC) as a polar polymer material; for example, wires, profiles, etc. can be coated with PVC during the extrusion process; - Styrene polymers such as polystyrene (PS), its homopolymers and copolymers, acrylonitrile / butadiene / styrene graft polymers (ABS), styrene / acrylonitrile copolymers (SAN), styrene / butadiene / styrene block polymers (SBS) can also be grafted with an adhesion promoter such as MAH (maleic anhydride); - Polyamides (PA) and their copolymers or blends; - Silicones, especially LSR variants (Liquid Silicone Resins).

Claims

[1] A method for coating the metal surface of a component with a plastic, the method comprising: Providing a component (10, 20) made of a first and a different second metal having a metal surface; Providing a plastic with at least one maleic anhydride grafted Base plastic component and / or a plastic having at least one functional group consisting of a silane compound, whereby a self-adhesive plastic (30) is produced; Injection molding or extruding the cohesively bonding and self-adhesive plastic (30) onto the preheated component (10, 20), wherein the application of the cohesively bonding and self-adhesive plastic (30) is applied to the metal surface preheated to a temperature of 120 to 220°C, so that it is applied directly to the metal surface and the metal surface is at least partially coated. [2] Method according to claim 1, characterized by that the first and second metals are bonded together and the coating encloses the bonding region (50) of the two metals. [3] Method according to claim 1, characterized by that the first and second metal are separated from each other and a connection of the two metals with the self-adhesive plastic (30) is created. [4] Method according to one of claims 1 to 3, characterized by that the first metal is aluminum or an aluminum alloy and the second metal is copper or a copper alloy. [5] Method according to one of the preceding claims, characterized bythat the component to be coated (10, 20) has a flat conductor and / or one or more contact lugs or contact plugs or current-carrying metal components. [6] Method according to one of the preceding claims, characterized by that the component (10, 20) has a gap (S), a cut edge or an opening (40) which is filled with the self-adhesive plastic (30) during injection molding or extrusion. [7] Component (10, 20) made of a first and a different second metal, produced by a method according to one of claims 1 to 6, with a metal surface coated with a plastic (30) in a material-to-material bonding manner, wherein the material-to-material bonding and self-adhesive plastic (30) comprises a base plastic component grafted with at least one maleic anhydride and / or a plastic with at least one functional group of a silane compound. [8] Component (10, 20) according to claim 7, characterized by that the first and second metals are bonded together, wherein the coating encloses the bonding region (50) of the two metals. [9] Component (10, 20) according to claim 7, characterized by that the first and second metal are separated from each other, wherein a connection of the two metal surfaces consists of the cohesively bonding and self-adhesive plastic (30). [10] Component (10, 20) according to one of claims 7 to 9, characterized by that the first metal is aluminum or an aluminum alloy and the second metal is copper or a copper alloy. [11] Component (10, 20) according to one of claims 7 to 10, characterized by that the coated component (10, 20) has a flat conductor and / or one or more contact lugs or contact plugs or current-carrying metal components. [12] Component (10, 20) according to one of claims 7 to 11, characterized by that it has a gap (S), a cut edge or an opening (50) which is filled with the materially bonding plastic (30). [13] Component (10, 20) according to any one of claims 7-12, characterized by that the self-adhesive plastic (30) has a base plastic component grafted with maleic anhydride and / or one or more incorporated functional groups of a silane compound, wherein the self-adhesive plastic has at least one of the following substances: • Polypropylene copolymer or polyethylene copolymer • thermoplastic elastomer, • Polyvinyl chloride (PVC) • Styrene polymers or blends with styrene polymers, • a polyamide (PA), PA copolymer or a polyamide blend • Silicone. [14] Component (10, 20) according to one of claims 7-13, wherein the metal surface is at least partially tinned, nickel-plated, silver-plated, gold-plated or chrome-plated.

Images