Method for producing a flat component

Abstract

The invention relates, among other things, to a method for producing a planar component (10) in sandwich lightweight construction with a high-quality surface (26).

Description

[0001] The invention relates to a method for manufacturing a planar structural element in sandwich lightweight construction with a high-quality surface.

[0002] Such procedures have been developed and implemented on a large scale by the applicant for decades.

[0003] The following German patent applications of the applicant are provided as examples only: DE 10 2018 117 337, DE 10 2017 109 953, DE 10 2016 112 290 A1, DE 10 2013 018 694 A1, DE 10 2013 008 592 A1, DE 10 2013 005 523 A1, DE 10 2013 008 364 A1, DE 10 2015 111 052 A1 and DE 10 2012 017 698 A1, the contents of which are hereby incorporated into the content of the present patent application to avoid repetition.

[0004] The methods predominantly used by the applicant to date for the production of such a planar component include in particular combinations of thermoplastic deep-drawn films with polyurethane foams.

[0005] Based on this, the invention aims to provide a method for manufacturing a planar component that meets the requirements for low weight and high stiffness and can be manufactured cost-effectively.

[0006] The invention solves this problem with the features of claim 1.

[0007] The principle of the invention consists, firstly, in using an expandable particle foam instead of the polyurethane two-component foams used so far.

[0008] Suitable expandable particle foams include, for example, EPS, EPE, and EPP. These are particle foams that, when fully expanded and cured, can typically exhibit densities ranging from 15 kg / m³ to 80 kg / m³.

[0009] According to the invention, a film-like substrate is first provided. This can be, for example, a thermoformable film, e.g., made of ABS or PMMA. This film can, for example, have a wall thickness between 0.2 and 13 mm. The film can, for example, be thermoformed in a first tool. However, the substrate used can also be a thin skin, a thin film, or another sheet-like material. The substrate does not necessarily have to be thermoformed.

[0010] According to the invention, the substrate is arranged in a lower tool. The lower tool has, in particular, a receiving chamber for particles, which will be explained in more detail later.

[0011] The inventive method provides that granular starting material is supplied in the form of loose particles of an expandable particle foam. Suitable materials are those known as expandable particle foams. In particular, this includes expandable particle foams made of EPS, EPE, or EPP, or also expandable PEEK. A further definition follows below.

[0012] The granular starting material can be supplied in the form of small spheres or beads, or in the form of granular particles of other regular or irregular shapes and geometries. The starting material is particularly suitable for pouring.

[0013] The particles are loosely present in the granular starting material, i.e., not yet firmly bonded together.

[0014] According to the invention, the next step involves partial foaming of the particles. Partial foaming means that the particles are not yet fully foamed. For example, according to the invention, it can be provided that, with respect to a foaming or expansion process from 0 to 100%, starting from the volume of the particles of the starting material up to the volume of the particles in the final foamed state, partial foaming of between 30 and 95% takes place. The term "partial foaming" particularly includes embodiments of the invention in which at least the step of additional foaming of the particles can still be carried out, leading to a final foamed state of the particles.

[0015] The partial foaming step is carried out, in particular but not necessarily, at a location remote from the lower tool in which the substrate is arranged. Furthermore, the partial foaming of the particles can advantageously be carried out in an oven, especially an infrared oven.

[0016] According to a further step of the inventive method, the partially foamed particles can be transferred to the lower tool. This transfer can, for example, take place immediately after the partial foaming step. However, it can also take place significantly later after the partial foaming step.

[0017] The transfer and / or arrangement or positioning of the partially foamed particles into the lower tool can be done mechanically, automatically, or manually.

[0018] According to the invention, the tool is now closed, in particular. For this purpose, for example, an upper tool can move against the lower tool and close off a receiving or storage space for the partially foamed particles – as well as for the substrate located in the lower tool.

[0019] According to the invention, the tool is further heated. The invention also encompasses keeping the tool constantly at a constant temperature or at a temperature within a predetermined temperature range.

[0020] According to the invention, the partially foamed particles are then subjected to a final foaming process to form a fully foamed particle foam. The particles expand to their maximum size or volume and essentially fuse or sinter together. The particle foam mass simultaneously bonds with the substrate. The final foaming process is activated by the mold temperature. The invention also encompasses the use of additional or alternative activating agents for the activation and execution of the final foaming process of the particles, i.e., for the foaming of the partially foamed particles to a fully foamed state.

[0021] According to the invention, the particle foam mass is then allowed to harden. As a result of this hardening process, the particle foam mass forms a permanent, strong bond with the substrate.

[0022] The invention also includes providing the substrate on its inner side facing the particle foam mass with a suitable chemical, e.g., in the form of an adhesion promoter, before the partially foamed particles are placed in the lower tool, in order to optimize the bond between the substrate and the particle foam mass or the formation of the bond between the substrate and the particle foam mass.

[0023] After the particle foam has hardened, the tool can be opened and the resulting molded part removed. This molded part represents the component to be manufactured according to the invention, or can be further processed into such a component through subsequent machining steps. Definition of expandable particle foam:

[0024] For the purposes of this patent application, expandable particle foams include, for example, the following materials: Expandable polystyrene is abbreviated as EPS. This is known, for example, under the brand name Styropor and can be obtained, for example, from the company Metz EPS-Hartschaumzuschnitte in 74376 Gemmrigheim.

[0025] Expandable polyethylenes (EPE) are also considered particle foams within the meaning of the present patent application. Finally, expandable polypropylenes (EPP) are also considered well suited for the purposes of the invention.

[0026] In particular, the term particle foam as used in this patent application includes thermoplastic particle foams. These can have granules as a starting material, especially microgranules, for example with particle diameters on the order of between 0.1 and 5 mm, and more preferably particles with a diameter of approximately 1 mm.

[0027] Blowing agents are preferably arranged within the granular starting material particles of the particle foam. These can be activated thermally and / or by chemicals, for example also by the action of water vapor, to trigger the pre-expansion process.

[0028] The process of residual foaming, i.e., the final foaming of already pre-foamed particles to form fully foamed particles, is also referred to as sintering in the context of the present patent application.

[0029] For polystyrene particle foam particles, pentane, which is polymerized into the granular particles, is one example of a suitable blowing agent. As soon as the particles are exposed to temperatures above 100°C, the blowing agent can evaporate, causing the thermoplastic base material to expand into polystyrene foam particles.

[0030] According to the invention, the second foaming stage can take place in the lower tool, wherein the tool temperature is selected so that the blowing agent can evaporate completely and the particles can be foamed completely.

[0031] Besides EPS (extrudable polystyrene), XPS is also a viable option for the invention.

[0032] For example, Schaumaplast GmbH & Co. KG in 68799 Reilingen is a possible source of expandable polypropylene EPP or XPS.

[0033] Particle foams for use with the invention can also be provided by expandable copolymers. Such materials are available, for example, under the trade name Grupor from Kunststoffwerk Katzbach GmbH & Co. KG in 93413 Cham, Germany.

[0034] Expandable PEEK (polyetheretherketone) can also be used as a starting material for the particle foam that can be used within the scope of the invention. This is available, for example, under the trade names Gatone or Victrex.

[0035] The method according to the invention serves to produce a component with a high-quality surface. A high-quality surface can, for example, be particularly durable, e.g., exceptionally impact-resistant, and furthermore, be particularly suitable for outdoor applications. In particular, a high-quality surface can exhibit properties as required for so-called Class A surfaces.

[0036] The invention relates to a method for manufacturing a planar component. The term "planar" means that the component extends considerably further along a surface in the x and y directions than in a z direction perpendicular to it. The surface can be flat or curved in space, even multiply curved, and can assume any desired spatial shape.

[0037] According to an advantageous embodiment of the invention, the substrate is provided by a deep-drawn film. This allows the use of conventional components of a building element that have already been extensively tested and, in particular, enables the provision of a high-quality surface for the component.

[0038] According to a further advantageous embodiment of the invention, step k) is carried out by applying a cover layer to the side of the particle foam mass facing away from the substrate. Such a cover layer can, for example, be an interior decorative layer, such as wall paneling, and in particular a plastic layer. If the manufactured component forms, for example, a wall or a wall section of a caravan or caravan trailer, the decorative layer can, for example, be a typical interior finish of such a caravan, manufactured in the conventional manner.

[0039] According to a further advantageous embodiment of the invention, the method according to the invention comprises the following step: l) Machining the forming part into a component.

[0040] Various processing methods are possible as processing steps. These include, for example, separating or detaching parts or areas of the molded part, and possibly also separating or detaching sections of the substrate. This also includes, for example, a cleaning step and / or a surface treatment step, especially on the outside of the substrate, such as roughening, polishing, or smoothing the surface, and possibly also the application of an additional layer or film, for example, an additional functional layer.

[0041] The invention also includes processing the side of the cured particle foam facing away from the substrate, for example by combining or applying an additional skin or material or film, e.g. by spraying, gluing, painting, riveting, screwing or bonding to another element.

[0042] According to a further advantageous embodiment of the invention, the film has a wall thickness between 0.2 mm and 13 mm. This embodiment of the invention also allows the use of conventional films that have been tested on numerous composite materials and whose deep-drawing and surface properties are well known and researched.

[0043] According to a further advantageous embodiment of the invention, the cured particle foam mass comprises a wall thickness of between 1 cm and 30 cm. The wall thickness of the cured particle foam mass is calculated and designed based on the required strength of the manufactured component. Despite the relatively large wall thicknesses, the finished component can have a very low weight.

[0044] According to a further advantageous embodiment of the invention, the component is designed as a vehicle part for a motor vehicle, or for a commercial vehicle, or for a caravan vehicle, and is, for example, an interior fitting part, or a cargo area cover, or a trim part, or a hood, or a roof element, or a roof segment, or a vehicle wall, or a vehicle wall element.

[0045] According to a further advantageous embodiment of the invention, the granular starting material comprises expandable EPS, expandable EPP, or expandable PEEK. These are all materials that are foamable, i.e., expandable, and which, according to the invention, are suitable for being initially only partially foamed or expanded in order to subsequently undergo a final foaming or expansion step in a tool.

[0046] According to a further advantageous embodiment of the invention, the method comprises step m), which is carried out before step h): m) Positioning reinforcing elements, in particular of the type of tie rods, for example of the type of tapes, in the lower tool, wherein after the partially foamed particles have been introduced into the lower tool the particles envelop the reinforcing elements.

[0047] According to this advantageous embodiment of the invention, the end-foamed, expanded particle foam mass is reinforced or stiffened by reinforcing elements. These are designed, in particular, to transmit tensile forces in a direction transverse to the planar extent of the component. This increases the stiffness of the component. The invention also encompasses situations where the reinforcing elements extend along the direction of the planar component. For example, planar structures such as mats, nonwovens, knitted fabrics, etc., made of reinforcing fibers, such as glass fibers, carbon fibers, aramid fibers, basalt fibers, or other suitable reinforcing fibers, can be placed in the lower mold before being filled with partially foamed particles.

[0048] According to a further aspect, the invention relates to a planar component according to claim 10.

[0049] The invention is based on the objective of providing a component which has high strength and load-bearing capacity at low weight and can be manufactured inexpensively.

[0050] The invention solves this problem with the features of claim 10.

[0051] To avoid repetition, reference is made to the preceding statements relating to claims 1 to 9 in an analogous manner with regard to the explanation and elucidation of the features of claim 10 and the explanation of the invention according to claim 10.

[0052] Further advantages of the invention will become apparent from the uncited dependent claims, as well as from the following description of the exemplary embodiments illustrated in the drawings. These show: Fig. 1 in a partially cutaway schematic view of an embodiment of an oven into which granular starting material in the form of particles of a particle foam is filled, wherein the granular starting material is unfoamed, Fig. 2 the oven of Fig. 1 with an additional infrared radiant heater shown, wherein the previously filled particles have been brought into a partially foamed state, Fig. 3 a first tool with lower tool and upper tool and a film designed as a substrate in a web-like, flat state, Fig. 4 the closed tool of Fig. 3 with deep-drawn film, Fig. 5 a further tool in which the deep-drawn film of Fig. 4 is positioned, wherein the partially foamed particles of the particle foam according to Fig. 2 are filled into the lower tool, Fig. 6 the tool of Fig. 5 with additionally shown upper tool shortly before the tool is completely closed, Fig. 7 the tool of Fig.6 in a completely closed state, with an additional heating device for the tool shown, Fig. 8 the tool of Fig. 7 in an open state with end-foamed, cured particle foam mass, Fig. 9 the molded part removed from the tool of Fig. 8, indicating parting lines along which protruding areas of the substrate are separated, Fig. 10 a further embodiment of a molded part or of a component according to the inventive method formed with an additional layer on the side of the cured particle foam mass facing away from the substrate, and Fig. 11 a further embodiment of a component according to the inventive in a representation according to Fig. 10, wherein, for illustrative purposes only, the pore structure of the cured particle foam is shown in a manner modified compared to Fig. 10.

[0053] Exemplary embodiments of the invention are described in the following description of the figures, also with reference to the drawings. For the sake of clarity, identical or comparable parts, elements, or areas are designated with the same reference numerals, sometimes with the addition of lowercase letters, even where different embodiments are concerned.

[0054] Features that are described, illustrated, or disclosed only in relation to one embodiment may also be provided in any other embodiment of the invention. Such modified embodiments are included in the invention, even if they are not shown in the drawings.

[0055] All disclosed features are essential to the invention. The disclosure of this application hereby fully incorporates the content of the disclosures in the associated priority documents (copy of the prior application), as well as in the cited publications and the described devices of the prior art, also for the purpose of including one or more features of the items disclosed therein in one or more claims of the present application. Such modified embodiments are also encompassed by the invention, even if they are not shown in the drawings.

[0056] Exemplary embodiments of components manufactured according to the inventive method are collectively designated by 10 in Figures 8, 9, 10 and 11.

[0057] The following describes the method for manufacturing such a component 10, starting with Fig. 1: As shown in Fig. 1, a container 12 is depicted into which a particle foam granulate 11 is filled. The individual granule particles, designated by reference numerals 30a, 30b, and 30c, are unfoamed and constitute the starting material for manufacturing a particle foam. The individual materials that can be used according to the inventive method will be discussed in detail later.

[0058] As shown in Fig. 2, the container 12 is part of an oven 13 in which the granular particles 30a, 30b, 30c can be partially foamed. For this purpose, a heater 14, in particular an infrared heater 14, is provided, which introduces a predetermined radiant power into the oven 13 using infrared rays 15 (indicated) in order to reach a specific temperature or temperature range. The granular particles 30a, 30b, 30c are exposed to the heat in the oven 13 for a predetermined time and partially foam up. It can be seen that the individual particles 30a, 30b, 30c of Fig. 1 increase considerably in volume and, according to Fig. 2, transform into partially foamed particles 31a, 31b, 31c.

[0059] It should be noted that the figures are of course not to scale, but are only intended to illustrate the process of foaming and the increase in volume.

[0060] The partially foamed particles 31a, 31b, 31c are still loose, and in particular not yet bonded together. During the partial foaming process according to Fig. 2, additional measures, such as vibrating the container 12, stirring, using chemicals, or introducing chemicals into the container 12, etc., can be taken to ensure that the particles 31a, 31b, 31c do not bond together, or do not bond predominantly together, but remain transportable as a loose, pourable, or at least pourable mass. This mass is filled into a lower mold 23 of a mold 17b, as shown in Fig. 5.

[0061] First, the production of the substrate 21 will be explained with reference to Figures 3 and 4: As shown in Fig. 3, a first tool 17 is provided, which comprises an upper tool 18 and a lower tool 19. The relevant tool parts can be designed in the manner of a die and a male die. In Fig. 3, a film 20 can be seen in a flat, web-like state, i.e., an initial state. Fig. 3 shows the tool in its open state.

[0062] As a result of the tool closing, the film 20 is deep-drawn from its flat state. The deep-drawing process allows any desired three-dimensional contour to be applied to the film. The deep-drawing process can be assisted by heat in the conventional manner (not shown in the figures). As an alternative to the embossing / die-forming process of the tool 17 in Fig. 3, blow molding or other forming processes are also suitable for the deep-drawing process, in which the film is heated and drawn into its final shape by suction.

[0063] After opening the tool 17 from the state shown in Fig. 4, the deep-drawn film 21 can be removed and fed to another tool. Such a second tool 17b is shown in Figures 5 to 8.

[0064] The invention also encompasses situations where the film 21 remains in the lower tool 19 after the deep-drawing process, and only the upper tool is replaced. In the following, it is assumed that, starting from Fig. 5, the deep-drawn film 21 has been transferred to another, second lower tool 23 of a different tool 17b.

[0065] As shown in Fig. 5, the pourable or pourable mass of partially foamed particles 31a, 31b, 31c is transferred into the lower tool 23 into a storage chamber 22, which serves to receive the partially foamed particles 31a, 31b, 31c and which faces the rear side 35 of the deep-drawn film 21. Filling the second lower tool 23, or the storage chamber 22 provided for this purpose, can be carried out manually, mechanically, or with machine assistance until a predetermined volume or mass of partially foamed particles 31a, 31b, 31c is positioned and, in particular, distributed within the storage chamber 22.

[0066] In this case, a discharge or dispensing device, not shown in the figures, may be provided which distributes the particles evenly along the accommodation space 22 in the manner of a feed head.

[0067] The tool 17b is then closed. For this purpose, an upper tool 24 is moved from a state as shown in Fig. 6, in which the tool 17b is still partially open, into a closed state. The housing space 22 is now completely closed.

[0068] Fig. 7 shows a heater 25 that heats the tool 17b, preferably both the lower tool 23 and the upper tool 24. The tool temperature is selected according to the materials used for the particle foam.

[0069] As a result of the temperature effect, the partially foamed particles 31a, 31b, 31c become completely foamed. A honeycomb structure can be seen – only indicated by way of example in Fig. 8. This is also only to be understood schematically: in reality, the structure of the completely foamed particles will be irregular. Another comparable structure is shown in Fig. 11: Here, instead of the frame structure of Fig. 8, an irregular, polygonal structure is shown in the schematic cross-sectional view.

[0070] Fig. 8 clearly shows that the partially foamed particles 31a, 31b, 31c according to Fig. 7 mutate into fully foamed particles 32a, 32b, 32c, whereby no free spaces remain between individual foamed particles 32a, 32b, 32c. Fig. 7, by contrast, still indicates such free spaces, exemplified by 36.

[0071] It should be noted that the designation "fully foamed particles 32a, 32b, 32c" is misleading: In fact, the multitude of fully foamed particles 32a, 32b, 32c together form a fully foamed particle foam mass 33 or a fully foamed particle foam. As shown in Fig. 8, this can also harden within a short time, so that – as Fig. 8 indicates – the tool can be opened and the upper tool 24 lifted off the lower tool 23. The resulting molded part 10 can then be removed from the mold.

[0072] As a result of the final foaming process – with the tool closed – the particle foam bonds permanently and firmly to the inner surface 35 of the deep-drawn film 21. This provides a lightweight, rigid and load-bearing composite component that is nevertheless inexpensive to manufacture.

[0073] As shown in Fig. 9, if necessary, excess areas 34a, 34b of the film 21 can be cut off along the dividing lines 29a, 29b.

[0074] The embodiment shown in Fig. 10 shows the back side 27 of the component 10, which can be provided with an additional layer 28, e.g. made of plastic.

[0075] The invention also includes components in which, instead of a deep-drawn film 21 made of ABS or PMMA, a thin film made of polyethylene or polypropylene, or in particular so-called slush skins, is used as substrate 21.

[0076] The side 26 of the deep-drawn film 21, which faces away from the cured particle foam 33, can form a high-quality surface. Since conventional, well-known, and proven materials can be used to produce the deep-drawn film 21, the corresponding surface properties of these materials can be utilized.

[0077] The invention also encompasses situations where the surface 26 of the substrate 21 is subjected to separate processing to provide a high-quality surface. This could include, for example, processing steps such as polishing, painting, vapor deposition, roughening, wetting, etc.

[0078] Figure 8 shows, by way of example, the wall thicknesses W1 of the deep-drawn film 21 or the substrate and W2, namely the wall thickness of the cured particle foam 33. The wall thickness W1 can be between 0.2 mm and 13 mm, and the wall thickness W2 between 1 cm and 30 cm.

[0079] The invention particularly encompasses components designed as caravan wall elements. For example, wall sections of a caravan trailer or caravan, or complete wall elements of a caravan, can be used in vehicle construction using the method according to the invention.

[0080] The invention further comprises embodiments which provide that reinforcing elements are placed in the accommodation space 22 before the accommodation space 22 is filled with partially foamed particles 31a, 31b, 31c.

[0081] The reinforcing elements, not shown in the figures, can, for example, include reinforcing fibers. As a result of filling the housing 22 with partially foamed particles 31a, 31b, 31c, the particles are evenly distributed and encase the reinforcing elements on multiple sides, preferably on all sides. The finished component 10 comprises a cured particle foam compound that securely encloses the reinforcing elements. By positioning the reinforcing elements, tensile forces, in particular, can be transmitted and absorbed.

Claims

1. Method for producing a planar structural element (10) in sandwich lightweight construction with a high-quality surface (26), comprising the following steps: a) Providing a foil-like substrate (21) b) Arranging the substrate (21) in a sub-tool (23) of a tool (17b), c) Providing granular starting material in the form of loose particles (30a, 30b, 30c) of an expandable particle foam, such as EPS, EPE or PEEK, d) partial foaming of the particles (30a, 30b, 30c), especially in an infrared oven, e) in particular transferring the partially foamed particles (31a, 31b, 31c) into the lower tool (23), and arranging the partially foamed particles (31a, 31b, 31c) into a storage space (22) in the lower tool (23), f) in particular closing the tool (17b), g) in particular heating the tool (17b), h) Final foaming of the partially foamed particles (31a, 31b, 31c) to a fully foamed particle foam (33), wherein the particle foam bonds with the substrate, i) Allowing the particle foam to harden (33), j) in particular opening the tool (17b) and removing the resulting mold (10).

2. Method according to claim 1, characterized in that the substrate is provided by a deep-drawn film (21).

3. Method according to claim 1 or 2, characterized by the step: k) applying a cover layer (28) to the side (27) of the particle foam (33) facing away from the substrate (21).

4. Method according to one of the preceding claims, characterized by the step: I) Machining the forming part into a component (10).

5. Method according to claim 2, characterized in that the film (21) has a wall thickness (W1) between 0.2 mm and 13 mm.

6. Method according to one of the preceding claims, characterized in that the cured particle foam (33) has a wall thickness (W2) between 1 cm and 30 cm.

7. Method according to one of the preceding claims, characterized in that the component (10) is designed as a vehicle part for a motor vehicle or for a commercial vehicle or for a caravan vehicle, such as an interior fitting part, load compartment cover, trim part, engine hood, roof element or roof segment, vehicle wall, or vehicle wall element.

8. Method according to one of the preceding claims, characterized in that the starting material is provided as expandable EPS, PP, or PEEK.

9. Method according to one of the preceding claims, characterized in that before carrying out step h), the following step is carried out: m) Positioning reinforcement elements, in particular of the type of tie rods, for example of the type of tapes, in the lower tool, wherein after the partially foamed particles (31a, 31b, 31c) have been introduced into the lower tool (23) these envelop the reinforcement elements.

10. Planar component (10) with a high-quality surface (26), in particular manufactured according to one of the preceding claims, comprising a substrate (21), in particular a deep-drawn film, with which a cured particle foam (33) is bonded.

11. Component according to claim 10, characterized in that the foil (21) has a wall thickness (W1) between 0.2 mm and 13 mm.

12. Component according to claim 10 or 11, characterized in that the cured particle foam (33) has a wall thickness (W2) between 1 and 30 cm.

13. Component according to one of claims 10 to 12, characterized in that the particle foam (33) is foamed against the substrate (21).