Method for producing a composite component comprising at least one metal layer and a polymer layer

Abstract

The present invention relates to a method for producing a composite part comprising at least one metal layer and one polymer layer, the method comprising: (a) heating a metal sheet optionally comprising a surface treatment agent; (b) placing a polymer film on the metal sheet and optionally heating the polymer film; (c) applying a vacuum to bring the polymer film into contact with the entire surface of the metal sheet and removing air encapsulated between the metal sheet and the polymer film; (d) optionally maintaining the temperature of the metal sheet and the polymer film above a temperature that promotes the joining of the polymer film and the metal sheet to obtain the composite part.

Description

[0001] describe

[0002] The invention relates to a method for producing a composite component comprising at least one metal layer and one polymer layer.

[0003] Such laminates can be used, for example, in automotive engineering and electric vehicles to produce seat structures, underbody elements or battery housings or in electronic housings. The laminates can also be used for electromagnetic shielding, for example as a diffusion barrier against oils, fuels or cooling media.

[0004] The production of integral structures comprising metal and polymer is described, for example, in WO-A 02 / 068257. Here, fastening devices are used to fix plastic to metal, or metal to an injection-molded polymer.

[0005] WO-A 2016 / 083083 describes a plate-shaped or strip-shaped semi-finished product and a method for producing such a semi-finished product. The semi-finished product comprises at least one metal layer and at least one plastic layer, which are connected over the entire surface to form a composite material. The composite material is formed by a coil coating method.

[0006] Another method for producing a composite component comprising at least one metal and at least one polymer is known from WO-A 2021 / 063011. To produce the composite component, a metal component coated with an adhesion promoter or primer is brought into contact with a polymer component. The metal component and the polymer component are then joined by a physical process such as laser transmission welding, ultrasonic welding, friction welding and / or hot melt joining.

[0007] However, each of the known methods either requires complex machinery and a large number of method steps to produce a composite component comprising a metal layer and a polymer layer, or is used to connect functional elements to the metal instead of coating the metal with a polymer layer.

[0008] It is therefore an object of the present invention to provide a method for producing a composite component comprising at least one metal layer and one polymer layer, which method can be carried out without complex machines and a large number of method steps and which method also allows the production of composite components coated with polymers.

[0009] This object is achieved by a method for producing a composite component comprising at least one metal layer and one polymer layer, the method comprising:

[0010] (a) heating a metal sheet optionally comprising a surface treatment agent;

[0011] (b) placing a polymer film on the metal sheet and optionally heating the polymer film;

[0012] (c) applying a vacuum to bring the polymer film into contact with the entire surface of the metal sheet and remove air trapped between the metal sheet and the polymer film;

[0013] (d) optionally maintaining the temperature of the metal sheet and the polymer film above a temperature that promotes bonding of the polymer film and the metal sheet.

[0014] This method allows the polymer layer to be applied over the entire surface of the metal sheet, which is less labor-intensive than coil coating methods in which the metal sheet and the polymer are guided through a large number of rollers. In addition, with this method, smaller metal sheets can also be coated with a polymer layer. It is not necessary to coat the entire coil.

[0015] In order to achieve a stable connection between the metal sheet and the polymer film, it is preferred that the metal sheet at least comprises a surface treatment agent on the surface on which the polymer film is applied. The surface treatment agent is particularly an adhesion promoter or a primer to improve the connection between the polymer film and the metal sheet.

[0016] The adhesion promoter or primer is preferably based on polyacrylic acid; polymethacrylic acid; polyacrylate or polymethacrylate; polyvinylamine; phosphoric acid; polyphosphoric acid; vinylphosphonic acid copolymer; copolymer of maleic acid with at least one of acrylic acid, methacrylic acid and esters of acrylic acid or methacrylic acid; copolymer of maleic acid with styrene; copolymer of ethylene with maleic acid; copolymer of ethylene, polyvinylpyrrolidone with at least one of acrylic acid, methacrylic acid, esters of acrylic acid or methacrylic acid and maleic acid and modified polyethylene (phenol). Typically, the adhesion promoter or primer is applied in the form of an aqueous solution in combination with an inorganic component such as H2TiF6, an organosilane, zinc oxide by a coating method such as roller coating. The application of the adhesion promoter is not limited to roller coating, it can also be applied by brushing, dipping or spraying.

[0017] The metal of the metal sheet can be, for example, an aluminum alloy, steel, a magnesium alloy, copper or a galvanized steel material, such as galvanized steel. If the metal sheet is made of steel, the steel can be galvanized by hot-dip galvanizing or electro-galvanizing. The thickness of the metal sheet is preferably in the range of 0.01 mm to 3.0 mm, more preferably in the range of 0.1 mm to 2 mm, and in particular in the range of 0.5 mm to 2.0 mm. Particularly preferably, the metal of the metal sheet is a galvanized steel type, such as hot-dip galvanized steel or zinc-aluminum-magnesium alloy (ZM).

[0018] The polymer film is preferably made of a thermoplastic material. The advantage of using a thermoplastic material is that the material is ductile by heating and can be adapted to the shape of the metal sheet. In addition, the thermoplastic material can be melted without decomposition and is therefore weldable, whereby a good connection with the metal sheet can be achieved. The thermoplastic material is preferably selected from thermoplastic polyurethane, polybutylene terephthalate, polycarbonate and polyamide, and may also contain additives. Preferably, the thermoplastic material is selected from PA6, PA66, PA66 / 6, PA6.10, PA6.12, PA12, PA9T, PA6I / 6T, PA6T / 6I, PA6 / 6.36 or a combination thereof. Particularly preferably, the thermoplastic material comprises a polyether block polyamide, such as a polyether diamine with an aliphatic C4 to C 40 dicarboxylic acids and / or C6 to C 12 Lactams such as copolymers of caprolactam or laurolactam, aliphatic C4 to C 10 Diamine and aliphatic C4 to C 40 Copolymers of dicarboxylic acids, C6 to C 12 A condensation polymer of lactam, a copolymer of lactam and / or aliphatic dicarboxylic acid and aliphatic diamine, or a combination thereof.

[0019] The thermoplastic polymer may contain additional additives such as glass fibers, carbon fibers, aramid fibers, or combinations thereof. These fibers may be incorporated in the usual commercial form as rovings or cuttings. In addition, woven fabrics, scrims, flow mats, and short fibers made from the above-mentioned reinforcement materials may also be used.

[0020] Additionally, the thermoplastic material may further comprise an impact modifier such as maleic anhydride grafted copolymers of ethylene and at least one of an alpha-olefin, an acrylate and acrylic acid, copolymers of maleic anhydride and at least one of ethylene and an acrylate, styrene maleic anhydride or maleic anhydride grafted polypropylene.

[0021] Further additives which the thermoplastic material may comprise are any additives customarily used in thermoplastic materials, such as plasticizers, flame retardants, dyes or UV stabilizers.

[0022] To connect the metal sheet and the polymer layer, in a first step (a) the metal sheet is heated.

[0023] The heating of the metal sheet can be carried out by any heating method known to the person skilled in the art. The metal sheet can be heated, for example, by induction heating or near infrared radiation or by using an oven that can be operated electrically or heated by fuel. Furthermore, if the metal sheet is a planar metal sheet, the metal sheet can also be heated by direct heating, for example by passing the metal sheet between two heated rollers. However, preferably, the metal sheet is heated in an electrically operated oven or by induction heating.

[0024] In order to achieve a stable connection, the metal sheet is heated to a temperature that promotes the connection of the thermoplastic material to the metal sheet, in particular the chemical reaction of the thermoplastic material with the surface treatment agent. To this end, the metal sheet can be heated to a temperature above the melting temperature of the thermoplastic material. However, even lower temperatures may be sufficient if the reaction of the thermoplastic material and the metal sheet is promoted at a lower temperature. For example, in the case of a polyamide-based film, a suitable temperature to which the metal sheet can be heated is a temperature in the range of 150°C to 250°C, preferably 170°C to 220°C.

[0025] After heating the metal sheet, the metal sheet is placed in a device, preferably a thermoforming device, in which a polymer film can be placed on the metal sheet. As an alternative, the metal sheet can also be first placed in a device in which a polymer film can be placed on the metal sheet, and then the metal sheet is heated before the polymer film is placed on the metal sheet.

[0026] After the heated metal sheet is placed in the device or after the metal sheet is placed in the device and then heated, the polymer film is placed on the metal sheet and optionally heated. If the polymer film is heated, the heating of the polymer film is preferably carried out, for example, by infrared radiation. However, any other non-contact heating method that heats the polymer film after it is placed on the metal sheet can be used.

[0027] The temperature to which the polymer film 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 to a temperature above the melting temperature of the crystallites if the thermoplastic material is a semi-crystalline thermoplastic, but preferably below the melting temperature to avoid damage to the polymer film.

[0028] After placing the polymer film on the metal sheet and optionally heating the polymer film, a vacuum is applied to bring the polymer film into contact with the entire surface of the metal sheet and remove air trapped between the metal sheet and the polymer film.

[0029] By applying a vacuum, the polymer film adheres to the surface of the metal sheet and a strong connection can be achieved. Removing air that may be trapped between the metal sheet and the polymer film results in a smooth surface without air bubbles.

[0030] In order to apply the vacuum, the metal sheet may comprise openings through which the air can be evacuated. If the metal sheet should not have any openings, the air between the metal sheet and the polymer film can also be evacuated at the edge of the polymer film. If the air is evacuated at the edge of the polymer film, it is preferred that the air is evacuated at least on two opposite sides and preferably over the entire circumference of the polymer film.

[0031] For applying the vacuum, any suitable vacuum pump can be used. If the metal sheet comprises an opening for extracting the air between the metal sheet and the polymer film, the vacuum pump is connected to the space below the metal sheet. In particular, if the metal sheet comprises more than one opening, this space ensures that the pressure at all openings is the same and the polymer film is uniformly attracted to the metal sheet. If the metal sheet comprises only one opening for applying the vacuum, the vacuum pump can be connected directly to this opening.

[0032] If the air is evacuated at the edge of the polymer film, the polymer film is fixed in a device for applying a vacuum so that a gap is formed between the metal sheet and the edge of the polymer film and the vacuum is applied through this gap.

[0033] By applying a vacuum, the polymer film is brought into contact with the metal sheet uniformly over its entire surface, thereby forming a uniform polymer layer on the metal sheet.

[0034] After the polymer film is brought into contact with the entire surface of the metal sheet, the temperature of the metal sheet and the polymer film is maintained at a temperature that promotes the connection of the thermoplastic material and the metal sheet, preferably at a temperature higher than the melting temperature of the thermoplastic material of the polymer film. By maintaining this temperature, the thermoplastic material chemically reacts with the adhesion promoter or primer, thereby achieving a stable connection of the metal sheet and the polymer film and forming a composite component including a metal layer and a polymer layer.

[0035] Depending on the thickness of the metal sheet, the time required for the metal sheet to cool to a temperature below the melting temperature of the thermoplastic material is sufficient to achieve a stable connection of the metal sheet and the polymer film. Preferably, the temperature of the metal sheet and the polymer film is maintained above the melting temperature of the thermoplastic polymer for 1 s to 120 s, more preferably 1 s to 60 s, and in particular 5 s to 30 s.

[0036] If the time required for the metal sheet to cool to a temperature below the melting temperature of the thermoplastic material is not sufficient to allow the polymer film to be stably connected to the metal sheet, it may be necessary to heat the metal sheet to maintain this temperature. In addition to heating, it may also be sufficient to place the metal sheet on a thermally insulating material before applying the polymer film to the metal sheet, because due to the insulating material, the heat is dissipated especially on the side of the metal sheet to which the polymer film is applied.

[0037] The composite component produced by the method of the present invention can be a semi-finished product or a finished shaped component. If the composite component is a semi-finished product, the composite component can be a flat plate or a pre-shaped component. Regardless of whether the composite component is a flat plate or a pre-shaped component, in order to complete the component, the composite component can be further shaped, for example by a deep drawing method.

[0038] Other geometries onto which the film can be coated are also possible. The method of the invention is not limited to sheet-like geometries (such as coil-coated products). For example, thicker cable-like structures such as busbars can be coated with a film or a lead frame.

[0039] As an alternative or in addition to further shaping of the composite component, functional elements made of polymer material can be applied to the composite component. Such functional elements can be, for example, reinforcement elements, fixing elements for fixing another component to the composite component, such as clips or threads into which screws can be inserted. Furthermore, the functional elements can also be design elements applied to the composite component.

[0040] The functional element can be applied to the composite component by any suitable method known to the person skilled in the art, for example by gluing or welding. In particular, the functional element is applied to the composite component by welding.

[0041] If the functional element is applied to the composite component by welding, any welding method for welding two polymer components can be used. Suitable welding methods for applying the functional element to the polymer layer of the composite component are, for example, laser welding, ultrasonic welding, friction welding or heat fusion bonding.

[0042] In addition to applying the functional element by gluing or welding, the functional element can also be formed directly on the polymer layer of the composite component. In this case, the functional element is preferably formed by injection molding. To form the functional element, the composite component is inserted into an injection mold, the mold is closed, and the polymer melt is subsequently injected into the mold to form the functional element.

[0043] If the semi-finished product or the final formed part has a shape different from a flat sheet, it is preferred to preform the metal sheet and apply the polymer film to the preformed metal sheet.For preforming the metal sheet, any method for forming metal sheets can be used, such as deep drawing or pressing.

[0044] Regardless of whether the metal sheet is pre-formed or a flat metal sheet is used to create the composite part, it is preferred that the metal sheet is placed in a mould before the polymer film is placed on the metal sheet.

[0045] Since the vacuum is applied to bring the polymer film into contact with the entire surface of the metal sheet, the polymer film is pulled into every position on the surface of the metal sheet, and the polymer film makes uniform and complete contact with the metal sheet.

[0046] Instead of preforming the metal sheet before placing it in an apparatus for applying the polymer film to produce a preformed semifinished product or a final shaped part, it is also possible to use only one apparatus in which the metal sheet is formed and the polymer film is applied to the metal sheet.

[0047] In this case, a flat metal sheet is inserted into a mold in the device and then formed, for example, by a deep drawing method or a pressing method. After the metal sheet has been formed into the desired shape, the metal sheet is heated and then a polymer film is placed on the heated metal sheet. A vacuum is then applied to bring the polymer film into contact with the entire surface of the metal sheet, thereby producing a shaped composite component.

[0048] By means of the method according to the invention, composite parts can be produced without using complex methods for producing laminated materials. In particular, it is not necessary to provide a mold with a base body and a male mold for producing the composite part. Since the polymer film does not come into contact with the mold in the method according to the invention for applying a polymer film to a metal sheet, the composite part does not have to be completely cooled before being removed from the mold, so that the production capacity can be increased.

Claims

1. A method for producing a composite component comprising at least one metal layer and one polymer layer, the method comprising: (a) heating a metal sheet optionally comprising a surface treatment agent; (b) placing a polymer film on the metal sheet and optionally heating the polymer film; (c) applying a vacuum to bring the polymer film into contact with the entire surface of the metal sheet and remove air trapped between the metal sheet and the polymer film; (d) optionally maintaining the temperature of the metal sheet and the polymer film above a temperature that promotes joining of the polymer film and the metal sheet to obtain the composite part.

2. The method according to claim 1, wherein the polymer film is heated by infrared radiation.

3. The method according to claim 1 or 2, wherein the metal sheet is preformed.

4. The method according to any one of claims 1 to 3, wherein the metal sheet is placed in a mould before placing the polymer film on the metal sheet.

5. The method according to any one of claims 1 to 4, wherein the metal is steel, galvanized steel, an aluminum alloy, a magnesium alloy or copper.

6. The method of any one of claims 1 to 5, wherein the surface treatment agent comprises an adhesion promoter or a primer.

7. The method of claim 6, wherein the adhesion promoter or primer is based on polyacrylic acid; polymethacrylic acid; polyacrylates or polymethacrylates; polyvinylamines; vinylphosphonic acid copolymers; phosphoric acid; polyphosphoric acid; copolymers of maleic acid with at least one of acrylic acid, methacrylic acid and esters of acrylic acid or methacrylic acid; copolymers of maleic acid with styrene; copolymers of maleic acid with ethylene; copolymers of ethylene, polyvinylpyrrolidone with at least one of acrylic acid, methacrylic acid, esters of acrylic acid or methacrylic acid and maleic acid, and modified polyethylene (phenol).

8. The method according to any one of claims 1 to 7, wherein the polymer film is made of a thermoplastic material.

9. The method according to claim 8, wherein the thermoplastic material is selected from thermoplastic polyurethane, polybutylene terephthalate, polycarbonate and polyamide, and can further contain additives.

10. A method according to claim 8 or 9, wherein the metal sheet is heated to a temperature which promotes joining of the thermoplastic material and the metal sheet.

11. The method of claim 10, wherein the temperature to which the metal sheet is heated is above the melting temperature of the thermoplastic material. 12 . The method according to claim 1 , wherein a functional element made of a polymer material is applied to the polymer layer.