Automotive Panel

Abstract

Method for producing an automotive panel with the steps of (a) providing a first extrudate of polycarbonate and additives (mixture A), and providing endless filament glass rovings (Component C), (b) feeding mixture A, and component C into the main extruder, and forming a final extrudate, (d) compression moulding the final extrudate into an automotive panel whereby a second mixture of polycarbonate and a short length glass fibers (mixture B) is fed together with mixture A and component C.

Claims

1. A method for producing an automotive panel comprising: providing a first extrudate of polycarbonate and additives (mixture A), and providing endless filament glass rovings (component C); feeding mixture A, and component C into a main extruder, and forming a final extrudate; compression moulding the final extrudate into an automotive panel characterised in that a second mixture of polycarbonate and short length glass fibers (SGF) with an average fiber length of between 1-6 mm (mixture B) is fed together with mixture A and component C.

2. The method according to claim 1, whereby the endless glass rovings are cut just before feeding to the main extruder and/or broken in the main extruder such that the long glass fibers(LGF) have an average fiber length of between 10 and 15 mm for the bulk of the long glass fibers (LGF) in the final product.

3. The method according to claim 1, whereby the total glass content in the final product is between 20 and 35% by weight and the ratio between long glass fibers (LGF) and short glass fiber (SGF) is between 2:1 and 1:2.

4. The method according to claim 2, whereby the concentration of long glass fibers is at least 10% by weight of the final product.

5. The method according to claim 1, whereby mixture B comprises at least between 50 and 75% by weight of short glass fibers (SGF).

6. The method according to claim 1, whereby mixture A and/or B further comprises at least one of acrylonitrile butadiene styrene (ABS), or a polyester.

7. The method according to claim 1, whereby mixture B is not fully mixed into mixture A during the extrusion and forms discrete areas within extrudate A in the final product.

8. The method according to claim 1,-whereby the glass rovings and/or the short glass fibers contain a chemical sizing to increase the adhesion between the glass fibers and the polycarbonate.

9. The method according to claim 2, whereby the long and/or short glass fibers have an average fiber thickness of between 10 and 20 μm.

10. The method according to claim 1, whereby the short glass fibers have an average fiber length between 2 and 5 mm.

11. The method according to claim 1, whereby mixture B is supplied in the form of pellets and/or sticks.

12. The method according to claim 1, whereby the final extrudate is formed in slabs with predefined variable thickness and/or weight.

13. The method according to claim 1, whereby at least one of a glass fiber mat, veil or fabric is placed at least in one area of the mould before and/or after at least one slab of material is placed in the mould.

14. The method according to claim 1, including the step of treating at least one surface of the moulded trim part with an additional layer of resin, including a flame retarder, an intumescent layer, and/or laminating one or more layers to the final panel.

15. The method according to claim 1, whereby mixture A and/or B further comprises at least one flame retardant, which is a phosphorus compound selected from the groups of monomeric and oligomeric phosphates and phosphonates, phosphonate amines, phophazenes and phosphinates, a bromine-based, sulphur-based, and/or silicone-based flame retardant, wherein mixtures of several components selected from one or more of these groups can also be used as flame retardants.

16. The method according to claim 1, whereby at least part of the mould is put at a temperature below the glass transition temperature of the slab, while the mould surface is kept at a temperature above the glass transition of slab until the press is closed, the surface of the mould is heated using at least one of electric heating, induction heating, pulse-heating with a second tempering liquid or infrared heating.

17. The method according to claim 1, further comprising an additional step, whereby at least two panels produced according to one of the preceding claims are welded together forming one large panel.

18. A cover or lid for a traction-battery housing for a battery electric vehicle comprising at least one automotive moulded panel produced according to claim 1.

19. The cover or lid according to claim 18, whereby the panel comprises polycarbonate and glass fibers, and whereby the glass fibers consist of short glass fibers with a main average length of between 1 and 5 mm and long glass fibers with a main average length of between 10 and 15 mm.

20. The cover or lid according to one of the claim 18, whereby the glass fibers are between 20 and 35% by weight of the total weight of the panel.

21. The cover or lid according to one of the claim 18, whereby the long glass fibers are at least 15% of the weight of the plate.

22. The cover or lid according to one of the claim 18, whereby the panel comprises at least one additional layer laminated or coated to at least one surface being at least one of a decorative layer, electromagnetic shielding coating, an intumescent layer, a coating layer, or a metal layer.

23. The cover or lid according to claim 18, whereby the cover comprises more than one panel produced according to claim 1 thermally welded together.

24. A method of using the automotive panel produced according to claim 1, as an under battery cover for a battery electric vehicle, an under engine shield, an underbody panel, a door panel, a shell for an automotive seat, dash board panel or dash board, interior floor panel, parcel shelf, front or rear storage box and/or tire box, battery lid, or cover for a battery housing for a hybrid or battery electric vehicle.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0055] FIG. 1: Overview of the process steps

[0056] FIG. 2: Schematic drawing of a part of the production process.

[0057] FIG. 3: Cross section of the moulded material according to the invention.

[0058] FIG. 4: Schematic drawing of vehicle with battery

[0059] FIG. 5: Schematic drawing of a cover for a battery according to the invention

[0060] FIG. 1 is showing a schematic overview of the method of producing the automotive panel according to the invention.

[0061] In a first step mixture A (100) comprising the thermoplastic matrix polymer and optional additives, mixture B (200) comprising a thermoplastic matrix polymer, optionally additives, and short glass fibers (SGF) and component C (300), the endless filament rovings are prepared. Preferably, mixture A and/or B. are molten and mixed in a suitable device for instance an extruder. Depending on the mixture recipe used, a twin screw or mono-screw extruder is needed for eventually compounding and or melting, or a simple heating device like for instance infrared lamp might be enough. Where needed the mixtures might be dried before starting the production process.

[0062] In a main extruder (400) all ingredients come together and are mixed to form the final extrudate. The endless filaments might be broken by the action of the extruder or might be cut just before feeding into the extruder.

[0063] At the end of the extruder, the formed mass is portioned in slabs.

[0064] Preferably, the slabs are preformed in a thickness profile or shape that suits the moulding step.

[0065] The slabs are transferred for instance with a robotic arm to the mould for compression moulding the final part. A part can be made of multiple slabs with the same or variable weight and/or thickness profile.

[0066] In the compression moulding step, the slabs are laid in predefined order and the mould is closed to form the final part. As in most cases for battery covers the part might be large, preferably variable temperature management of the mould temperature and/or sequential closing of the mould might be used to further enhance the flowing of the material within the mould.

[0067] If the part is too big for the available press or for any other reason the part can not be made in one piece, introducing a welding seam to combine multiple part might be an option.

[0068] FIG. 2 is showing a possible production layout in more detail. A first twin-screw extruder (1) obtains mixture A and will heat and mix the mixture to form a first extrudate (2). This extrudate is fed into a second extruder (3). By the fluid action of the first extrudate coming from the first extruder, the endless glass filaments (4) provided as for instance as rovings on bobbins (5) are pulled into the second or main extruder (3). In the second or main extruder, the endless filaments (4) are broken into sections with an average size of between 10-15 mm of the bulk of the fibers formed and mixed into the extrudate (2). Alternatively, the rovings are cut or broken mechanically before feeding into the extrudate stream.

[0069] Either by a hopper (6) or via an additional extruder, mixture B. including short glass fibers is fed into the extrudate stream coming from the first extruder.

[0070] Mixture B can be supplied in the form of pellets, or sticks and directly fed into the extrudate stream in the form given, or preheated and fed in a molten form. Mixture B is preferably fed close to or together with the endless filament and/or cut glass rovings.

[0071] Mixture A will be a polycarbonate mixture, preferably without glass fiber content. This will ensure a good mixing of the polycarbonate and any additives used, while maintaining the energy needed for mixing and melting low just as well as it will reduce the content of destroyed short glass fiber in the final product.

[0072] Mixture B will be a polycarbonate mixture with a concentrated amount of glass fibers preferably 60 to 70%. This mixture should not necessary need a twin-screw extruder, a single screw system just for melting the mixture would be enough. Preferably, the mixture is already provided in premade pellets or sticks and only need melting and homogenisation and may be provided directly to the main extruder.

[0073] FIG. 3 is showing a cross section (8) of the material according to the invention forming a battery cover or lid after moulding in a preferred solution. Mixture A forms the continuous matrix throughout the part, while component C′ in the form of broken or cut glass rovings forming long glass fibers (LGF) are reinforcing the thermoplastic resin to enhance the mechanical features like impact resistance and bending stiffness. However due to the process and the moulding conditions the LGF will be orientated mainly in the direction of the flow of the extrudate during moulding, hence an anisotropy would exist with LGF alone. In a preferred solution, mixture A and mixture B are differing such that they are not 100% compatible. Hence, during the blending in the last extruder, mixture B forms discrete areas within mixture A, as these areas obtain a concentration of LGF and are formed randomly. Surprisingly, the overall mechanical performance of the part after moulding is further enhanced. This effect can also be observed when mixture A and mixture B are perfectly compatible in theory, but mixing is not carried out to full extend in the second extruder so local fluctuations in short glass fiber density are observed in the final product. While the viscosity of the final extrudate with a 30% GF concentration is lower for a combination of LGF and SGF, compared to only LGF ensuring a good compression moulding of larger parts and or a reduction in the press energy needed. Due to this surprising effect, it is possible to make the large parts needed for traction battery covers with a thickness distribution over the main area of between 2 and 4 mm. This results in a saving of energy, material and weight of part, while maintaining the mechanical properties needed for such a product.

[0074] Alternatively discrete pockets of mixture B within mixture A might be achieved with process conditions, like the starting temperature difference between mixture A and B and/or the blending conditions in the final extruder.

[0075] FIG. 4 is an example of the use of the automotive panel produced according to the invention in a battery box or housing 2 in a vehicle. The battery box or housing 2 comprises the power cell or cells (not shown) that may be needed for a battery electric vehicle (BEV) or a hybrid electric vehicle (HEV) for instance for electric cars and small people transporting units. The battery is used mainly as traction battery powering the main powertrain of the vehicle.

[0076] The battery box or housing (2) comprises an upper covering part forming a lid (3) made from the automotive panel according to the invention, and a lower part (4) containing the power cell or cells. Both fit together to form an enclosed space for the power cell or cells. Preferably the box is sealed with a sealing at the area of contact between the upper part and the lower part to prevent dirt and water from entering the box and get in contact with the content in particularly the power cells or the connections between the power cells. The lower part of the housing might be made of metal.

[0077] FIG. 5 is showing the upper covering part forming a lid for battery housing or box in more detail. The upper covering part comprises at least a thermoplastic carrier 6 according to the invention shaped to form the covering lid. The cover is shaped such that it is able to cover at least the open space in the lower part comprising the power cell or cells. Whereby also contours to cover other appliances might be given, for instance to cover additional cooling systems or connections. The battery cover might comprise any ribbing or beading to further increase the stiffness of the cover and/or to increase the impact durability.