Method of manufacturing composite component comprising core and skin region

Abstract

A method of manufacturing a composite part (2) comprising a core (4) and a skin region (6) formed from a skin polymer attached thereto, the method comprising the steps of: a) providing a core element (8) having a surface having at least one upper contact region having a plurality of anchoring sites (10); b) applying a layer (12) of a skin polymer in the form of granules on the contact area, whereby the skin polymer granules contact and embed the anchoring sites; c) applying a heating step, thereby melting the epidermal polymer particles to form a molten epidermal polymer matrix (18); d) applying a pressing and cooling step whereby the skin polymer matrix cures to form a skin region (6) mechanically joined into the anchoring site of the core element forming the core.

Description

Technical Field

[0001] The present invention relates to a novel method for manufacturing a composite component comprising a core and a skin region formed of a skin thermoplastic polymer attached thereto. Background Technology

[0002] One of the notorious challenges in the manufacture of plastic-containing composite parts is the proper bonding of adjacent layers of disparate materials. These adjacent layers can be either internal layers within the composite part, also known as the "core layer," or surface layers adjacent to the core layer, also known as the "skin layer." "Proper bonding" means that the layers involved should be reliably bonded, i.e., without a tendency for subsequent delamination and without adversely affecting the inherent properties of the materials involved. A further requirement for any such manufacturing process is that it should be as simple and energy-efficient as possible.

[0003] An important type of composite component is automotive interior components, which comprise a relatively rigid core serving as a rigid carrier, with a relatively flexible and / or soft outer skin. An example of this is vehicle trim panels, door panels, dashboards, instrument panels, etc., as discussed, for example, in WO 2017 / 046166 A1 and the references cited therein. These components are typically not planar, but rather have a rigid core with a three-dimensional shaped surface. For contact to be achieved across the entire surface, adjacent surface layers must have corresponding three-dimensional shapes.

[0004] A method and apparatus for manufacturing thin-walled hollow housings for components such as automotive door panels, controllers, and dashboards is slush molding. An alternative to slush molding involves deep drawing flexible foils or sheets into desired shapes.

[0005] A useful material for the skin of high-end soft-touch automotive interiors is polyvinyl chloride (PVC), which is available directly in powder form for slush molding. A possible alternative to PVC would be thermoplastic elastomers (TPE-S) based on styrene block copolymers; however, these must be ground into powder form at low temperatures.

[0006] An earlier patent relating to a method and apparatus for manufacturing thin-walled hollow shells by slush molding is US 4,562,025. As summarized in WO2017 / 046166 A1, the process begins with a box filled with a PVC compound in granular form, positioned below and locked onto a heated mold that supplies powder to the mold. The mold is repeatedly turned over to melt the powder onto the surface of the heated mold, and heating causes the granules to sinter. After the PVC granules have sintered together, a plasticized PVC sheet is formed, which is then cooled and removed from the mold.

[0007] Currently, the method for manufacturing internal components is based on a three-step process of post-foaming polyurethane (PU), which includes:

[0008] -Injection molding of the carrier (i.e., the core)

[0009] - PVC powder is slush molded (rotary molded) to form a skin.

[0010] -Use a PU foam layer to connect the skin and the carrier.

[0011] The three-step alternative method based on lamination involves

[0012] -Injection molding of the carrier (i.e., the core)

[0013] - Separate production as the skin of pre-formed foil

[0014] - The surface layer and the carrier are bonded together by gluing (i.e., by spraying adhesive).

[0015] Although the methods described above have proven effective, they have certain drawbacks.

[0016] In the case of post-foaming of PU, the used PU material cannot be recycled, posing health and safety issues and involving complex technologies. The slush molding process is very energy-intensive, as it involves temperature cycling from 50°C to 240°C. Necessary equipment includes:

[0017] - Injection molding machines and related tools

[0018] - Slush molding machine and related tools

[0019] - Polyurethane post-foaming machine and related tools

[0020] Furthermore, there is only limited adhesion between the PU foam and the outer layer. This could cause bulging during high-temperature airbag deployment.

[0021] In the case of lamination, the use of spray adhesives also brings health and safety issues related to VOCs and odor formation. Necessary equipment includes:

[0022] - Injection molding machines and related tools

[0023] -Lamination equipment used to apply adhesive and skin.

[0024] Therefore, it is desirable to provide an improved method for manufacturing composite parts, the composite parts comprising a core with good mechanical properties and at least one skin region made of a thermoplastic polymer attached thereto.

[0025] Specifically, what is expected is

[0026] - Eliminates the need for adhesive spraying or polyurethane foaming in the process.

[0027] - Reducing the number of production equipment parts and required tools, thus providing an investment advantage.

[0028] - Eliminates injection molding steps

[0029] - Eliminates the need for PU mixing unit, high-pressure mixing chamber and related tools

[0030] -Eliminates the slush molding process

[0031] Compared to slush molding, more favorable temperature cycling should be possible, essentially using a temperature cycle of 50-190-50°C instead of 50-240-50°C.

[0032] Ideally, components that combine structural rigidity with high-quality surface finish should be produced in a single processing step. Summary of the Invention

[0033] The present invention reduces the aforementioned disadvantages and provides the aforementioned desired advantages. It also provides further advantages as further mentioned below.

[0034] According to the present invention, a method for manufacturing a composite component is provided, the composite component comprising a core and at least one skin region formed of a skin polymer attached thereto, the method comprising the following steps:

[0035] a) Provide a core element having a surface having at least one upper contact area having a plurality of anchoring sites;

[0036] b) Apply a layer of skin polymer in granular form to the contact area, whereby the skin polymer granules contact and embed into the anchoring sites;

[0037] c) Apply a heating step, thereby melting the skin polymer particles to form a molten skin polymer matrix;

[0038] d) Applying a pressing and cooling step, whereby the skin polymer matrix solidifies to form a skin region that is mechanically bonded to the anchoring sites of the core element forming the core;

[0039] in

[0040] (i) The core element is provided as a preform of a thermoplastic fleece with reinforcing fibers oriented primarily in an orientation direction z perpendicular to the surface of the core element;

[0041] Or else

[0042] (ii) The core element is provided as a continuous sheet of thermoplastic pile fabric with reinforcing fibers, wherein the heating step c) and the pressing and cooling step d) are performed continuously in a double band press;

[0043] The thermoplastic pile fabric is composed of a core thermoplastic polymer, and the sponge-like surface structure of the thermoplastic pile fabric and / or the surface portion of the reinforcing fibers serve as the anchoring sites. The heating step c) also causes the core thermoplastic polymer to melt, thereby forming the core element as the core.

[0044] Another advantage of the above method is that it saves weight without sacrificing stiffness.

[0045] The method of the present invention can be advantageously implemented according to any one of the following three main embodiments.

[0046] According to the first embodiment (claim 2), the core element is provided as a blank of a thermoplastic pile fabric with reinforcing fibers oriented primarily in an orientation direction z perpendicular to the surface of the core element, and wherein the pressing and cooling steps are performed in a tool within a press. The term "blank" should be understood as a piece or section of the corresponding material, for example, a substantially rectangular plate. The heating step c) may be performed, for example, in an infrared heater, but preferably in a contact heater, wherein the aforementioned blank, covered with a layer of skin polymer in the form of granules, is placed on a heater plate. Thereafter, the heated blank is transferred to a press equipped with a pressing tool, in which step d) is performed. As will be understood, the tool may be configured with a planar surface for producing planar "2D" composite parts, or it may have a suitably configured surface for producing non-planar "3D" composite parts. The press equipped with the tool is configured such that a preselected thickness of the pressed composite part is obtained. The term "preselected thickness" refers to a constant thickness of the 2D composite part or a variable thickness of the 3D composite part.

[0047] The inventors have discovered that by using reinforcing fibers that are predominantly z-oriented, a favorable reaction force is applied by the core element to resist the compressive force applied during the pressing step, resulting in improved contact between the skin and the core.

[0048] According to the second embodiment (claim 3) and the third embodiment (claim 4), the core element is configured as a continuous sheet of thermoplastic fleece fabric with reinforcing fibers, wherein the heating step c) and the pressing and cooling steps d) are performed continuously in a double-belt press. A suitable double-belt press, for example, has been described in US 8540830 B2, having a first pressing stage with heating followed by a second pressing stage with cooling. In the present case, a layer of skin polymer in granular form is applied to the continuous sheet of thermoplastic fleece fabric with reinforcing fibers before entering the double-belt press.

[0049] According to the second embodiment, the composite component is then obtained by cutting sections of the continuously pressed sheet obtained in the pressing and cooling step d). In other words, the desired "final" composite component is obtained directly after the pressing and cooling steps performed in the dual-belt press. This embodiment has the advantages of simplicity and substantially uninterrupted operability. However, it will be understood that 2D composite components can only be formed in this way. By appropriately setting the distance between the pressing elements in the second stage of the dual-belt press, the degree of consolidation of the core element can be limited within a certain range.

[0050] In contrast, according to the third embodiment, the composite component is obtained through a series of steps performed after exiting the dual-belt press. Specifically, this includes:

[0051] (1) Cutting sections of the continuous pressed sheet obtained in the pressing and cooling step d),

[0052] (2) Optionally store the segment,

[0053] (3) subjecting the portion to a further heating step, thereby melting the outer skin polymer matrix and the core thermoplastic polymer.

[0054] (4) Further pressing and cooling steps are applied in the tool in the press to form the composite component.

[0055] As will be understood, this third embodiment combines some features of the first and second embodiments. In short, the dual-belt pressing method of the second embodiment is used to form segments of a pressed preform of the desired composite component. The preform is then subjected to further heating in the next immediate step or after temporary storage, followed by further pressing and cooling steps in the press's tooling. This subsequent step provides the aforementioned possibilities for 2D and 3D forming.

[0056] Advantageously (claim 5), in step b), a layer of skin polymer in the form of granules is applied with a predetermined particle size distribution, starting with relatively small-sized granules near the upper contact area of ​​the core element and ending with relatively large-sized granules or even a skin polymer foil away from the upper contact area. For example, the small-sized granules may have an average diameter of about 150 μm, and the large-sized granules may have an average diameter of about 300 μm.

[0057] According to another embodiment (claim 6), the method further includes an embossing step performed on the epidermal area.

[0058] The core thermoplastic polymer can be selected from a variety of known polymers, such as polyamide (PA), polypropylene (PP), polyphenylene sulfide (PPS), polyetherimide (PEI), and polyetheretherketone (PEEK), as well as acrylonitrile styrene acrylate (ASA) and acrylonitrile butadiene styrene (ABS). The melt temperature of the core thermoplastic polymer should be low enough that press heating at a temperature suitable for the skin polymer results in the melting of the core thermoplastic polymer.

[0059] For example, if PVC or TPE-S is used as the skin polymer, then a suitable core polymer would be PP, ASA, or ABS.

[0060] The actual choice of skin and core polymers will depend on the application. For aircraft interiors, PPS is the preferred core polymer, while for automotive interiors, PP can be used. For aerospace applications, a PEI-PEEK combination or a PPS-PEI combination is preferred.

[0061] In some embodiments where UHMWPE is used as the skin polymer, suitable core polymers include, in particular, PP.

[0062] According to one embodiment (claim 7), the core thermoplastic polymer is polypropylene, preferably polypropylene with a melt flow index (MFI) of 1 to 1000 (230°C, 2.16 kg), more preferably 10 to 300 g / 10 min.

[0063] As is also known in the field of fiber-reinforced thermoplastics, the reinforcing fibers can be selected from a variety of sources, including but not limited to glass fibers, carbon fibers, aramid fibers, and basalt fibers. Alternatively, the reinforcing fibers can be made from high-melting-point thermoplastics, i.e., from materials that do not melt at the processing temperature of the hot-pressing step. According to an advantageous embodiment (claim 8), the reinforcing fibers are glass fibers, carbon fibers, or recycled carbon fibers.

[0064] As also known from the field of fiber-reinforced thermoplastics, a core element formed from a thermoplastic pile fabric having reinforcing fibers may include structural reinforcement elements. Therefore, according to one embodiment, the core element further includes at least one reinforcing layer. In some embodiments, the reinforcing layer is selected from fabrics, multiaxial stitches, or unidirectional reinforcements.

[0065] The choice of skin polymer depends on the intended application.

[0066] According to one embodiment (claim 9), the skin polymer is ultra-high molecular weight polyethylene (UHMWPE). Due to its relatively rigid structure, UHMWPE as a skin polymer is mainly used in the manufacture of floor panels, panels for humid environments, and certain panels in recreational vehicles.

[0067] According to another embodiment (claim 10), the skin polymer is polyvinyl chloride (PVC). This material is readily available in powder or granule form for use in slush molding. In some embodiments, custom-made PVC granules with a diameter in the range of 50 to 250 μm are used, coated with one or more of a stabilizer packet, a release agent, a pigment, and a drying agent, and / or containing a plasticizer.

[0068] According to another embodiment (claim 11), the skin polymer is a thermoplastic elastomer (TPE-S) based on a styrene block copolymer. TPE-S is typically a soft elastomer material composed of an SBS / SEBS block copolymer, mineral oil, polyolefin, and stabilizers. The styrene blocks constitute the rigid domains providing the desired mechanical properties, while the ethylene-butadiene blocks constitute the elastomer core. They can be melt-processed under conditions similar to those of polyolefins. TPE-S materials generally exhibit rubbery properties, are resistant to both high and low temperatures, are easily colored, provide good adhesion to polyolefins, and are easily recyclable.

[0069] According to certain embodiments (claim 12), the skin polymer granules contain a blow expander. The use of blow expanders as tear accelerators in thermoplastic skin layers produced by slush molding is generally known, for example, from WO 2017 / 046166A1 and the references cited therein. In the context of this invention, including a blow expander in the skin polymer granules causes the skin to expand during the heating step, thereby reducing the skin density and providing a lightweight, soft-touch solution.

[0070] According to some embodiments (claim 13), the method further includes the step of forming a texture on an exposed surface area of ​​the epidermis. "Exposed surface area" refers to a surface area of ​​the epidermis away from the core.

[0071] According to yet another embodiment (claim 14), the composite component is a vehicle interior component, particularly a dashboard, instrument panel, trim panel, or door panel. Attached Figure Description

[0072] The above and other features and objects of the invention, as well as the ways in which they are realized, will become more apparent from the following description of various embodiments of the invention taken in conjunction with the accompanying drawings, and the invention itself will be better understood, wherein:

[0073] Figure 1 An apparatus for carrying out a first embodiment of the present invention is shown in a schematic perspective view;

[0074] Figure 2 A core element with a molten skin polymer matrix is ​​shown in an enlarged schematic perspective view after heating step c).

[0075] Figure 3 An apparatus for carrying out a second embodiment of the invention is shown in a schematic perspective view; and

[0076] Figure 4 An additional device for carrying out the third embodiment of the invention is shown in a schematic perspective view. Detailed Implementation

[0077] It should be understood that the accompanying drawings are not necessarily drawn to scale. In some cases, relative dimensions are substantially distorted for ease of visualization. Identical or corresponding features in the various drawings will generally be indicated by the same reference numerals.

[0078] Figure 1 and Figure 2 The first embodiment of the invention is illustrated herein. Production of a composite component 2, comprising a core 4 and a skin region 6 formed by a skin polymer attached thereto, begins with providing a core element 8 having a surface with an upper contact region having a plurality of anchoring sites 10. In the embodiment shown here, the core element 8 is a preform of a thermoplastic pile fabric with reinforcing fibers oriented primarily in an orientation direction z perpendicular to the surface of the core element. For simplicity, the anchoring sites are depicted as simple protrusions on the upper surface of the core element. A layer 12 of skin polymer in granular form is then applied to the contact region via a dispenser 14, whereby the skin polymer particles contact and embed into the anchoring sites 10.

[0079] The core element 8, loaded with the skin polymer, is then transferred to a heater assembly 16, which in this embodiment is a contact heater with a pair of hot plates. A heating step is then performed, thereby melting the skin polymer particles to form a molten skin polymer matrix 18.

[0080] The resulting composite object is transferred to a press 20 equipped with suitable tools 22. Here, pressing and cooling steps are performed, thereby solidifying the skin polymer matrix to form a skin region 6, which mechanically engages with the anchoring sites of the core element 8 now forming the core 4.

[0081] exist Figure 1 and Figure 2 In the embodiment shown, the core element 8 is a blank of a thermoplastic pile fabric f with reinforcing fibers r, which are mainly oriented in an orientation direction z perpendicular to the surface of the core element.

[0082] The second and third embodiments are in Figure 3 and Figure 4 As shown in the figure. In this case, the core element is provided as a continuous sheet 24 of thermoplastic fleece fabric with reinforcing fibers. The heating step, as well as the subsequent pressing and cooling steps, are carried out continuously in a twin-belt press 26. Before entering the twin-belt press, a layer 12 of skin polymer in the form of granules is applied to the sheet 24 by means of a distributor 14, whereby the skin polymer granules contact and embed into the anchoring sites 10.

[0083] According to the second embodiment, the composite component 2 is obtained by cutting sections 28 of a continuously pressed sheet 30, which is obtained by pressing and cooling using a dual-belt press.

[0084] exist Figure 3 In the embodiment shown, the embossing step can be applied to the sheet 30 exiting the dual-belt press 26 by the embossing roller 32.

[0085] According to a third embodiment, the composite component 2 is obtained through a series of steps performed after leaving the dual-belt press 26. As in the second embodiment, this includes cutting segments 28 of the continuously pressed sheet 30. After optional storage, the segments 28 are further heated in an oven 16, thereby melting the outer skin polymer matrix and the core thermoplastic polymer. Further pressing and cooling steps are then performed in the tooling 22 of the press 20, thereby forming the composite component 2.

[0086] In all the above embodiments, the thermoplastic pile fabric is composed of a core thermoplastic polymer, wherein the cavernous surface structure of the thermoplastic pile fabric and / or the surface portions of the reinforcing fibers serve as anchoring sites. The heating step also causes the core thermoplastic polymer to melt, thereby transforming the core element 8 into the core 4.

Claims

1. A method of manufacturing a composite component (2), said composite component (2) comprising a core (4) and a skin region (6) formed by a skin polymer attached thereto, said method comprising the steps of: a) Provide a core element (8) having a surface having at least one upper contact area having a plurality of anchoring sites (10); b) Apply a layer (12) of skin polymer in the form of granules to the contact area, whereby the skin polymer granules contact and embed into the anchoring sites; c) Apply a heating step, thereby melting the skin polymer particles to form a molten skin polymer matrix (18); d) Applying a pressing and cooling step, whereby the skin polymer matrix solidifies to form a skin region (6), which is mechanically bonded to the anchoring sites of the core element forming the core; in (i) The core element (8) is provided as a blank of a thermoplastic pile fabric (f) having reinforcing fibers (r) oriented primarily in an orientation direction (z) perpendicular to the surface of the core element; or (ii) The core element is provided as a continuous sheet (24) of thermoplastic pile fabric with reinforcing fibers, wherein the heating step (c) and the pressing and cooling step (d) are carried out continuously in a double-belt press (26); The thermoplastic pile fabric is composed of a core thermoplastic polymer, and the sponge-like surface structure of the thermoplastic pile fabric and / or the surface portion of the reinforcing fibers serve as the anchoring sites. The heating step c) also causes the core thermoplastic polymer to melt, thereby forming the core element as the core.

2. The method according to claim 1, wherein, The core element is provided as a blank of a thermoplastic pile fabric (f) with reinforcing fibers (r) oriented primarily in an orientation direction (z) perpendicular to the surface of the core element, and wherein the pressing and cooling steps are performed in a tool (22) within a press (20).

3. The method according to claim 1, wherein, The core element is provided as a continuous sheet (24) of thermoplastic pile fabric with reinforcing fibers, wherein the heating step c) and the pressing and cooling step d) are carried out continuously in the dual-belt press (26), wherein the composite component (2) is obtained by cutting a segment (28) of the continuous pressed sheet obtained in the pressing and cooling step d).

4. The method according to claim 1, wherein, The core element is provided as a continuous sheet (20) of thermoplastic pile fabric with reinforcing fibers, wherein the heating step c) and the pressing and cooling step d) are carried out continuously in the double-belt press (26), wherein the composite component is obtained by: (1) Cutting the continuous pressed sheet obtained in the pressing and cooling step d) into segments (28), (2) Optionally store the segment (28), (3) subjecting the segment (28) to a further heating step, thereby melting the outer skin polymer matrix and the core thermoplastic polymer. (4) Further pressing and cooling steps are applied in the tool (22) of the press (20) to form the composite component (2).

5. The method according to any one of claims 1 to 4, wherein, In step b), a layer (12) of skin polymer in the form of granules is applied with a predetermined particle size distribution, starting with relatively small-sized granules near the upper contact area and ending with relatively large-sized granules away from the upper contact area.

6. The method according to any one of claims 1 to 5, further comprising an embossing step performed on the epidermal region (6).

7. The method according to any one of claims 1 to 6, wherein, The core thermoplastic polymer is selected from polypropylene, PEI, and PPS.

8. The method according to any one of claims 1 to 7, wherein, The reinforcing fiber is glass fiber, carbon fiber, or recycled carbon fiber.

9. The method according to any one of claims 1 to 8, wherein, The skin polymer is ultra-high molecular weight polyethylene (UHMWPE).

10. The method according to any one of claims 1 to 8, wherein, The outer polymer is PVC.

11. The method according to any one of claims 1 to 8, wherein, The skin polymer is TPE-S.

12. The method according to claim 10 or 11, wherein, The surface polymer granules contain a blown agent.

13. The method according to any one of claims 10 to 12, further comprising the step of forming a texture onto an exposed surface area of ​​the epidermal surface.

14. The method according to any one of claims 1 to 13, wherein, The composite component is an interior component of the vehicle.

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