Method for the production of construction panels made of plastic

Abstract

The invention relates to a method in which, as a starting product, a material layer (1) made of thermoplastic material is heated to the softening point of said material and arranged on a substrate (2). A mould (3), which has an end face (4) facing the material layer (1) and slots (5) arranged in the end face (4) and oriented at a right angle to the material layer (1), is moved towards the material layer (1) and pressed against it so that a partial volume of the material layer (1) flows into the slots (5) of the mould (3). After retracting the mould (3), ribs (9) remain on the material layer (1) and project therefrom at right angles. In order to be able to more easily remove the material layer thus formed from the mould, the mould (3) is divided into a plurality of mould segments (3.1, 3.2) which are retracted one after the other.

Description

[0001] Process for producing plastic building panels

[0002] The invention relates to a method for producing building panels according to the preamble of patent claim 1.

[0003] Plastic building panels with ribs are well known. Compared to panels without a rib structure, they possess similar flexural rigidity and are significantly lighter at the same thickness. They are used primarily in construction and transportation, but also in aerospace and wind turbine construction. The rib structure is often manufactured separately, for example in the form of a honeycomb structure, and then bonded to at least one cover layer. Producing a rib structure, particularly a honeycomb structure, from reused plastic is difficult, especially if the plastic contains fibers. Consequently, in building panels of this type, the rib structure and the cover layer are typically made of plastics of different quality and composition, which in turn severely limits their later reuse.In this context, reuse refers to the production of shredded plastics with fiber content as granules for extrusion or injection molding. If the cover layer is bonded to the rib structure, this problem is further exacerbated by the adhesive used.

[0004] The document DE69716802T2 shows a method for producing a honeycomb structure from ceramic material according to the principle of backward extrusion.

[0005] Document WO0181267A2 describes a method for producing honeycomb panels with closed honeycombs. Hydraulically binding materials, i.e., cement-based materials, are described. There is no mention of composite panels made of different materials or of plastics.

[0006] The document WQ2009097836A1 D3 concerns a lightweight plastic panel produced by deep drawing a plastic film.

[0007] Document US2015 / 298368A1 describes a method for creating a rib structure in a layer of a composite material made of metal and plastic. Patent EP3292754B1 describes a method and device for producing honeycombs for beekeeping.

[0008] Based on this prior art, the object of the invention is to provide a manufacturing method for building panels in which the building panels consist of a single material and which can be carried out with comparatively little effort.

[0009] This problem is solved by the measures specified in the characterising part of patent claim 1.

[0010] The inventive solution has the particular advantage that the starting product can contain natural or synthetic fibers of virtually any fiber length. The sequential retraction of the tool after the pressing process allows the building board to be demolded without additional retention measures. Furthermore, the board produced using the method consists entirely of the same material, unlike conventional boards, in which the core, consisting of a ribbed structure, and the cover layer are composed of different materials. This allows building battens produced using the inventive method to be shredded and reused when no longer needed. Alternatively, if the building boards are made of a biodegradable material, they can be disposed of after use, for example, by composting, if necessary after being shredded.

[0011] Particular embodiments of the method according to the invention are defined in the dependent patent claims.

[0012] Embodiments of the invention are explained below with reference to the attached drawings.

[0013] Figure 1 shows a layer of material and a tool arranged at a distance therefrom;

[0014] Figure 2 shows the arrangement according to Figure 1 with the tool lowered;

[0015] Figure 3 shows the sequential removal of the tool segments;

[0016] Figure 4 shows the build plate after complete removal of the tool; Figure 5 shows an alternative tool with a different method of separating the individual tool segments;

[0017] Figure 6 shows a first possible combination of a building board produced according to the method according to the invention with a cover plate;

[0018] Figure 7 shows a second possible combination of two mirror-imaged building panels;

[0019] Figure 8 shows another possible combination with two building plates and one

[0020] cover plate, and

[0021] Figure 9 is a schematic representation of the production of a building board in

[0022] Continuous process.

[0023] Figure 1 shows the initial situation of the process, in which a material layer 1 made of a thermoplastic, for example polypropylene or a biodegradable thermoplastic, rests on a base 2 as the starting product. The material layer 1 can contain a proportion of natural or artificial fibers. A tool 3 is arranged above the material layer 1. The base 2 and / or the tool 3 can be heated. The tool 3 has an end face 4 interrupted by slits 5. Preferably, the material layer 1 comes directly from a wide-slot extrusion line and is applied to the base 2 while still soft, thereby saving energy for heating the material layer 1.

[0024] In the illustration in Figure 2, the tool 3 is pressed onto the material layer 1 in the direction of arrow 6, whereby sheet material is pressed into the slots 5 of the tool 3, according to the principle of reverse extrusion, i.e., the plastic material flows in a direction opposite to the direction of movement 6 of the tool 3. If the tool 3 were then retracted as a whole, it would be almost impossible to avoid the deformed material layer 1 sticking to the tool 3, especially if the slots 5 have little or no tightening. Either a retaining device would have to be provided to hold the material layer 1 on the base 2, for example a vacuum device, and / or the tool 3 would have to be equipped with ejectors, as is known, for example, in the injection molding process.The process step shown in Figure 3 eliminates the need for the previously mentioned additional devices for removing the tool. For this purpose, the tool 3 is divided into tool segments 3.1 and 3.2, with the individual segments being movable independently of one another towards and away from the material layer 1. The arrows 7 illustrate how the individual tool segments 3.1 and 3.2 are retracted one after the other, while adjacent tool segments continue to press the process product against the base 2 and hold it there. In the illustrations in Figures 1 to 3, the parting planes between the individual tool segments 3.1, 3.2 are perpendicular to the plane of the drawing, so that the tool segments 3.1, 3.2 are rod-shaped. In addition, however, the tool segments 3.1, 3.2 may also be divided into planes parallel to the drawing plane, whereby these additional separation planes are preferably adapted to the arrangement of the slots 5 or the later ribs 9.

[0025] The sequential movement of the tool segments is not only advantageous during demoulding, but also during the pressing process, because it allows the same pressure to be generated in the material layer 1 with less force as if the tool 3 were lowered as a whole.

[0026] Figure 4 shows the product of the process, a building board 8 with a rib structure 9 and a residual layer 10 remaining after the pressing process. The rib structure 9 preferably consists of connected ribs, which can be arranged, for example, triangular, square, or hexagonal in plan view, i.e., honeycomb-shaped. The material 10 of the starting product remaining between the ribs 9 can be kept very thin, depending on the intended application of the building board 8.

[0027] Figure 5 shows an alternative embodiment of the tool 3, in which individual tool segments 3.3 are identically formed and separated between the ribs. However, the embodiment shown in Figures 1 to 3 has the advantage that the rib structure 9 is easier to demold.

[0028] Figure 6 shows one possible way of further processing the construction panel 8 by applying a cover panel 11, which preferably consists of the same material as the construction panel 8, in order to take advantage of the material's recyclability. The cover panel 11 is preferably applied immediately after removing the tool 3, while the material of the construction panel 8 is still soft. The cover panel 11 can also be heated for this purpose, resulting in a welded composite panel. This preferably results in closed cells, so that the composite panel can also be used in humid or wet environments.

[0029] It is also possible to construct the material layer 1 forming the starting product from two layers with different softening temperatures and to subject the composite plate thus formed to the pressing process.

[0030] If, as shown in Figure 7, two building panels 8 are arranged in a mirror image and connected to one another in the manner described in connection with Figure 6, a composite panel with twice the thickness compared to Figure 6 is obtained.

[0031] Figure 8 shows, for example, how two building panels 8 can be stacked together to form a composite panel and supplemented by a cover panel 11. In this way, laminated bodies with low weight and high flexural rigidity can be produced in virtually any thickness. Both the building panel 8 and the composite panels produced with it can be covered with additional layers on one or both sides, for example, to give the respective composite panel a special appearance or to make it printable.

[0032] With the method described so far, structured building panels 8 can be produced in a continuous process and thus theoretically endlessly, as shown schematically in Figure 9, for example. The material layer 1, preferably coming directly from a wide-slot extrusion die, is transferred to a base 2, which in this example is designed as a circulating conveyor belt and preferably moves continuously in a transport direction 12. The tool segments 3.1 and 3.2 on the left in the figure are lowered one after the other in the direction of arrow 6 and held in the lowered position by hold-down means 14 while they move synchronously with the base 2. After the pressing process, the tool segments 3.1, 3.2 are raised one after the other in the direction of arrow 7 and transported back to the starting position in the direction of arrows 13. The tool segments 3.1, 3.2 can be moved up and down by pneumatic, hydraulic, or mechanical means and, for example, guided in a revolving manner by a chain. On the return path indicated by arrows 13, the tool segments 3.1, 3.2 can be automatically inspected and freed of any adhering plastic or fiber residue. Reference number 13 designates optional suction devices that can be used to assist demolding. The system according to Figure 9 can also be operated intermittently, for example by pressing the tool 3 as a whole against the material layer 1 and then demolding by withdrawing the tool segments 3.1, 3.2 one after the other.

[0033] The described principle of independently movable tool segments can also be used to cool the build plate 8 after the pressing process, thereby minimizing potential warpage. While the tool segments used for the pressing process are either heated or still warm from the plastic tool layer, a second set of tool segments can be provided, which are cold or additionally cooled and used after demolding the first set of tool segments to hold down and cool the build plate.

[0034] List of reference symbols

[0035] 1 material layer

[0036] 2 base

[0037] 3 tools

[0038] 3.1 Tool segment

[0039] 3.2 Tool segment

[0040] 3.3 Tool segment

[0041] 4 Frontal surface

[0042] 5 slots

[0043] 6 Pressing direction

[0044] 7 arrows

[0045] 8 building board

[0046] 9 Rib structure

[0047] 10 remaining layer

[0048] 11 Cover plate

[0049] 12 Transport direction

[0050] 13 Return transport direction

[0051] 14 hold-down devices

[0052] 15 Absorbents

Claims

Patent claims 1. A method for producing a building board (8), in which a plastically deformable material layer (1) made of thermoplastic material is arranged on a base (2) as the starting product and a tool (3) with an end face (4) facing the material layer (1) and slots (5) arranged in the end face (4) and oriented at right angles to the material layer (1) is moved towards the material layer (1) and pressed against it, so that a partial volume of the material layer (1) flows into the slots (5) of the tool (3), after which the tool (3) is withdrawn so that ribs (9) oriented at right angles to the plane of the material layer (1) protrude from the material layer (1), characterized in that the tool (3) is divided into tool segments (3.1, 3.2) and these tool segments (3.1, 3.2) are withdrawn one after the other.

2. Method according to claim 1, characterized in that the tool segments (3.1, 3.2) are pressed successively against the material layer (1).

3. Method according to one of the preceding claims, characterized in that at least some of the slots (5) are connected to one another in such a way that they form a pattern of triangles, squares, hexagons, circles or ovals in the end face (4) of the tool (3).

4. Method according to one of the preceding claims, characterized in that the plastic is polypropylene.

5. Method according to one of the preceding claims, characterized in that the plastic is a biodegradable plastic.

6. Method according to one of the preceding claims, characterized in that the plastic contains fibers.

7. Method according to one of the preceding claims, characterized in that at least part of the plastic is recycled plastic.

8. Method according to one of the preceding claims, characterized in that the material layer (1) is a composite layer of at least two plastics with different softening temperatures and the plastic layer with the lower softening point is facing the tool (3).

9. Method according to one of the preceding claims, characterized in that two building panels (8) and / or one building panel (8) and one cover panel (11) are connected to one another.

10. Method according to claim 9, characterized in that the joining process takes place before the plastic hardens.

11. Method according to one of claims 2 to 10, characterized in that the material layer (1) is moved in the direction of its plane and that the tool segments (3.1, 3.2) are moved in the same direction at the same speed while they are successively pressed onto the material layer (1) and then successively lifted off therefrom.

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