DE102014004430B4 - Method for coating the metal surface of a component with a plastic and component made of a first and a different second metal - Google Patents

Abstract

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 with 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 of a silane compound, thereby producing a self-adhesive plastic (30);
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.

Description

technical field

The invention relates to a method for coating a metal surface with a plastic and to a component with a metal surface coated with a plastic.

Background of the invention

• Im Rahmen der zunehmenden Gewichtsreduzierung finden beim Fahrzeugbau Aluminiumkomponenten Verwendung, auch bei Bestandteilen der Stromversorgung. Für die Übergangsstellen zu den Verbrauchern werden in der Regel Kupferkomponenten verwendet. Aufgrund der unterschiedlichen Potentiale in der elektrochemischen Spannungsreihe findet eine Korrosion zwischen Kupfer und Aluminium bei Anwesenheit von Feuchtigkeit und Sauerstoff statt. Um die Korrosion zu unterbinden, muss der Übergangsbereich zwischen den Materialien hermetisch abgedichtet sein. Insbesondere soll die Funktionalität des Übergangsbereichs über die Fahrzeuglebensdauer garantiert werden. Aufgrund der niedrigen Materialkosten, der geringen Verarbeitungstemperatur und der geringen Prozesszeit bieten sich zur Isolation, d.h. zur Ummantelung der stromführenden Metallkomponenten, Polypropylen bzw. allgemein Polyolefine sowie Copolymere oder Blends aus dieser Kunststoffgruppe an.

When coating or encasing metal profiles with a plastic, an adhesion promoter is usually used to bond the two materials, as is the case, for example, in EP 1 024 244 B2 This approach results in disadvantages, particularly in vehicle applications, which are explained below:

• As part of the increasing weight reduction, aluminum components are 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 vehicle's service life. Due to the low material costs, the low processing temperature and the short process time, polypropylene or generally polyolefins as well as copolymers or blends from this plastic group are suitable for insulation, i.e. for sheathing the current-carrying metal components.

In the material connection between different metals (such as copper and aluminum) mentioned above, there are often gaps, gaps or other openings due to the manufacturing process, into which air can penetrate and water deposits can form. In addition, moisture can accumulate due to capillary action. This leads to electrochemical corrosion of the metals.

For this reason, optimal adhesion between the metal component and the applied plastic is desirable. In the prior art, an adhesion promoter or primer was applied to the metal surface to be coated or encased, for example by spraying or rolling, painting, printing, etc. This means that the plastic adheres well to the sections of the metal where an 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 firm bond with the metal in these areas, is greatly reduced. It is very difficult to achieve adhesion of the plastic in the gap and thus a sealed, filled space. In particular, this non-adherent plastic mass can in turn 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 after a long time, which can lead to field failures after years.

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

Description of the Invention

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 if it has a connecting region made of different metals, gaps, cut edges and/or other openings.

The object is achieved with a method according to claim 1 and with 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.

When we refer to a coating or sheathing of a metal surface below, this does not mean that the entire metal surface or the entire component carrying the metal surface - such as a flat conductor, a contact tab or a contact plug - must be completely coated or encased. What is more important is that the plastic is at least partially applied directly to the metal surface, i.e. without an intermediate layer of an adhesion promoter (also known as a "primer" or simply "adhesive"). The metal surface and the plastic thus form a direct, at least partially, material 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.

This means that there is no need to apply an adhesion promoter 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 masking, an additional, costly material, preheating, the actual coating process and the process infrastructure (for example with a ventilation system, etc.), the metal surface can be insulated and sealed in one process (injection molding, extrusion). This saves time and money due to the lower process effort. In addition, free spaces, gaps, openings and the like can be produced without the formation of cavities and with excellent durability, as they are simply filled in the injection molding process or in the extrusion process. The plastic does not detach due to its self-adhesive properties.

According to the invention, the component to be coated has a first and a different second metal, which are connected to one another. The two metal components can be designed, for example, as roll-plated bimetal or as metal plates welded to one another in an overlapping manner. In the automotive sector, copper or copper alloys and aluminum or aluminum alloys are used in particular. The coating or sheathing with the self-adhesive plastic encloses the connection area of the two metals. "Enclosure" here is of course not to be understood as an all-round, hermetically sealed enclosure, but rather in such a way that the transition area or contact area of the two metal components is coated with the self-adhesive plastic. The injection molding or extrusion now ensures that the self-adhesive plastic completely penetrates into corners, edges, surfaces, cavities, gaps, openings that may be present in the connection area of the two metals, fills them, seals them, insulates them and connects them. This ensures that no air or moisture reaches the sensitive areas of the metal transitions, thus preventing corrosion or at least reducing it to a minimum.

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

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

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.

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

Polypropylene or polyethylene copolymers with built-in 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 here. The use of a thermoplastic elastomer, polyvinyl chloride (PVC), styrene polymers or blends with styrene polymers, a polyamide (PA) or a polyamide blend, as well as silicone is also possible.

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 in the usual range. The viscosity, ie the gap-permeability of the self-adhesive plastic, can be increased further by modifying the molecular weight or molecular chain length of the polymer 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 an optimal chemical bond in the injection molding process or extrusion.

The present invention is particularly suitable for coating or sheathing current-carrying components in automobile construction. In automobile construction in particular, with the prevailing competition, extremely efficient manufacturing processes are important, while still ensuring excellent quality and durability. The coating technology presented here is suitable with regard to these goals, since an increase in the service life of the coated components can be achieved with simplified production. Nevertheless, the invention can also be implemented and is useful in other areas. Examples include: the transport sector in general, i.e. in addition to the automotive sector, aviation, aerospace, shipping, rail transport; mechanical engineering, furniture construction, electrical and electronics sectors, in particular entertainment electronics, medical technology, building technology, the structural engineering or drywall sector and the civil and road construction sector. In addition, further advantages and features of the present invention can be seen from the following description of preferred embodiments. The features described there can be implemented alone or in combination with one or more of the features mentioned above, provided that 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 1a to 1h show cross-sections of elongated coated profiles.
• The 2a and 2b show cross-sections through a connection area of two different metals, which were welded once using a welding process ( 2a) and once using roll cladding ( 2b) are connected.
• The 3a to 3d show locally overmolded or extruded connection areas between two metal components.
• 4a to 4d show variations of the cross sections of the 3a to 3d , whereby the metal components are already partially coated.
• The 5a and 5b show cross-sections of a locally overmolded flat metal and a welded stranded conductor.
• The 6 shows an example of a locally overmolded or extruded component attached to an insulated flat conductor, with the contact side coated with a metallization.
• The 7 shows schematically and exemplarily a manufacturing process with an extrusion tool and other stations.

Ways to carry out the invention

The 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 designates a profile main body, which is 1a to 1h is elongated perpendicular to the plane of the paper. The profile main bodies are current-conducting components, for example made of aluminum. Outlets provided on the profile main body 10 are generally designated with the reference numeral 20. The outlets 20 consist of the same or a different material than the profile main body 10. Various outlets 20 can also be provided from different materials. The outlets 20 are usually provided on the side of the profile main body 10, they can be provided on several sides of the profile main body 10, continuously or discontinuously.

The profile main bodies 10 shown here are particularly suitable for use as single-layer or multi-layer flat conductors for installation in automobile construction. The profile main body 10 and the lateral outlets 20, which together form a "component" in general terms, are therefore preferably current-carrying. The profiles in the 1a to 1h However, show that other design variants are possible; the cross-sections shown here illustrate the wide range of applications of the coated profiles across many industries. 1d For example, a sheathed profile is shown which 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 can be a light guide or stranded conductor. In general, 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 side 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 side outlets 20 can also be constructed from several metals connected to one another, in particular aluminum and copper. In principle, the profile main body 10 and/or the side outlet 20 can consist of conductive or non-conductive materials or components.

The fastening function mentioned above as a possible embodiment of the outlets is in the 1f in which a partially encased fastening element 20, which may be a metal clip, is provided on the profile main body 10. Such a fastening element 20 with reference to a tubular profile main body 10 is shown in the 1 hour shown.

From the 1g A profile is produced in which a partially encased outlet (notch) is punched out of the profile main body 10. This can be a contact lug for electrical contact or a fastening element.

In all figures, the reference numeral 30 designates 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 encases the profile main body 10, but without completely encasing the outlets 20, whereby the 1g is an exception to this. It should be mentioned at this point that the plastic component 30 does not have to completely encase the lateral outlets 20, but is at least present in the area of the transitions between the lateral outlets 20 and the profiles 10. The material connection of the plastic component 30 to the profile main body 10 is at least partially achieved by the fact that the plastic component 30 is a self-adhesive plastic. The self-adhesive plastic has a base plastic component - such as polypropylene, polyethylene or polyolefin in general - and one or more built-in functional groups made of acid compounds and/or silane compounds.

In the 1g an embodiment is shown in which, in addition to the material-locking sheath with the plastic component 30, a further plastic component 31 is attached to the main body or to the plastic component 30 and/or is materially connected thereto. This can be designed as a sealing lip, for example.

The 2a and 2b each show a connection area of two different metal elements, whereby 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 2a The two parts 10 and 20 were welded together. In the 2b the connection was made by means of roll cladding. In both cases, gaps or generally free spaces S can remain, which are filled in a watertight and airtight manner by injection molding or extruding the self-adhesive plastic component 30. In the case of the previously common use of an adhesion promoter to achieve the connection between the plastic component 30 and the main profile body 10 or the outlets 20, there was often not enough material connection between the metal and the plastic in the gap areas S, so that these areas were susceptible to corrosion.

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

The profiles of the 4a to 4d correspond to the profiles of the 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.

The 5a and 5b show 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 the reference numeral 61.

Due to the direct material bond 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.

The 6 shows an example of a component attached to a flat conductor 11 with 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 coats or adheres in an overlapping manner 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 and thus prevents, for example, moisture from penetrating the critical transition areas 50.

The 7 shows a schematic of an extrusion process with an extrusion tool and other stations. The extrusion tool is designated with the reference number 200 and the extruder with 201. Before extrusion in the extrusion tool 200, which has an extruder 201, the component to be coated, ie 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 to be suitable for applying polypropylene to aluminum. This preheating takes place at station 210. By preheating the component to be coated, the 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 as "coil" 220, the component to be coated is provided, 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 then 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 decisive here. After extrusion (or alternatively injection molding), calibration may take place in a calibration device 230, whereby the product is brought to the later product size, followed by cooling in a water bath 240 at about 10°C, and finally the coated component is cut to size in a cutting device 250 using a knife or a saw 251 and packaged at station 260. In the process shown here, a transport or belt speed of about 4 to 5 m per minute comes into consideration.

• - Selbsthaftende Polyolefine, besonders selbsthaftendes Polypropylen und Polyethylen; Ethylen/Ethylacrylat-Copolymere;
• - Maleinsäureanhydrid gepfropftes EPM oder EPDM (Ethylen/Propylen/Dien-Copolymere); Ethylen/Buten-Copolymer;
• - Thermoplastische Elastomere (TPE), d.h. Blends wie z.B. TPE-V Thermoplast/Elastomerblends vernetzt(PTV) oder TPE-O Thermoplast/Elastomerblends unvernetzt (TPO) bzw. Copolymere wie z.B. TPE-U thermoplastische Polyurethane (TPU), TPE-E thermoplastische Copolyester (TPC), TPE-A Polyether-Blockamide (TPA) oder TPE-S Styrol-Blockcopolymere (TPS); die polar bzw. Metall-anhaftend sind; eine Oberflächenaktivierung über Plasmabehandlung kann von Vorteil sein;
  • - Polyvinylchlorid (PVC) als ein polares Polymermaterial; so können beispielsweise Drähte, Profile usw. mit PVC im Extrusionsprozess ummantelt werden;
  • - Styrolpolymerisate, wie etwa Polystyrol (PS), deren Homopolymere und Copolymere, Acrylnitril/Butadien/Styrolpfropfpolymere(ABS), Styrol/Acrylnitrilcopolymere (SAN), Styrol/Butadien/Styrol-Blockpolymere (SBS) können ebenfalls mit einem Haftvermittler, wie z.B. MAH (Maleinsäure Anhydrid) gepfropft werden;
  • - Polyamide (PA) und deren Copolymerisate oder Blends (Mischungen);
  • - Silikone, insbesondere LSR-Varianten (Liquid Silicone Resins).

The following plastics, for example, are suitable for the described embodiments:

• - Self-adhesive polyolefins, in particular 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 in 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 (14)

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 with a metal surface; providing a plastic with at least one maleic anhydride-grafted base plastic component and/or a plastic with at least one functional group from a silane compound, thereby producing a self-adhesive plastic (30); Injection molding or extruding the cohesively binding and self-adhesive plastic (30) onto the preheated component (10, 20), wherein the cohesively binding 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. procedure according to claim 1 , characterized in that the first and second metal are bonded to each other and the coating encloses the connection region (50) of the two metals. procedure according to claim 1 , characterized in 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. Method according to one of the Claims 1 until 3 , characterized in that the first metal is aluminium or an aluminium alloy and the second metal is copper or a copper alloy. Method according to one of the preceding claims, characterized in that 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. Method according to one of the preceding claims, characterized in that the component (10, 20) has a gap (S), a cutting edge or an opening (40) which is filled with the self-adhesive plastic (30) during injection molding or extrusion. Component (10, 20) made of a first and a different second metal, produced by a method according to one of the Claims 1 until 6 with a metal surface cohesively coated with a plastic (30), wherein the cohesively binding and self-adhesive plastic (30) has a base plastic component grafted with at least one maleic anhydride and/or a plastic with at least one functional group consisting of a silane compound. Component (10, 20) after claim 7 , characterized in that the first and second metals are bonded together, wherein the coating encloses the bonding region (50) of the two metals. Component (10, 20) after claim 7 , characterized in that the first and second metal are separated from each other, wherein a connection of the two metal surfaces consists of the cohesively binding and self-adhesive plastic (30). Component (10, 20) according to one of the Claims 7 until 9 , characterized in that the first metal is aluminium or an aluminium alloy and the second metal is copper or a copper alloy. Component (10, 20) according to one of the Claims 7 until 10 , characterized in 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. Component (10, 20) according to one of the Claims 7 until 11 , characterized in that it has a gap (S), a cutting edge or an opening (50) which is filled with the cohesively binding plastic (30). Component (10, 20) according to one of the Claims 7 - 12 , characterized in that the self-adhesive plastic (30) has a base plastic component grafted with maleic anhydride and/or one or more built-in functional groups made 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. Component (10, 20) according to one of the Claims 7 - 13 , wherein the metal surface is at least partially tinned, nickel-plated, silver-plated, gold-plated or chrome-plated.

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