Single-material sandwich composite

Abstract

The invention relates to a single-material sandwich composite (10) made of polyethylene terephthalate and a method for producing a single-material sandwich composite (10) made of polyethylene terephthalate, comprising: a first needle-punched nonwoven (12) made of polyethylene terephthalate fibers; a second needle-punched nonwoven (14) made of polyethylene terephthalate fibers; a sandwich core (16) made of polyethylene terephthalate granules, wherein the sandwich core (16) is arranged between the first needle-punched nonwoven (12) and the second needle-punched nonwoven (14) on a first side (18) of the second needle-punched nonwoven (14); and a decorative layer (20) made of polyethylene terephthalate, wherein the decorative layer (20) is arranged on the second needle-punched nonwoven (14), and wherein the decorative layer (20) is arranged on a second side (22) of the second needle-punched nonwoven (14) opposite the first side (18).

Description

[0001] The following invention relates to a single-material sandwich composite made of polyethylene terephthalate, according to the applicable claim 1.

[0002] Composite materials in automotive engineering are an important component for lightweight construction. The combination of different materials, such as plastics and metals, makes it possible to utilize their positive properties in a targeted manner. However, a permanent bond between different materials negatively impacts recycling at the end of the product life cycle, as separating the materials is often impossible or only possible with considerable effort. For the further use of plastics, maintaining a high degree of purity is of particular importance.

[0003] DE 19520294 A1 describes an open-cell plastic foam film arrangement, wherein smooth, closed surfaces are deep-drawn and heat-fixed after extrusion in a thermoforming plant using a double-sided vacuum.

[0004] DE 10 2014 005 008 A1 relates to a method for manufacturing a sandwich component, in particular for a motor vehicle, comprising the steps of: providing a sandwich semi-finished product comprising a honeycomb core with a plurality of honeycomb webs and two thermoplastic face sheets; arranging the sandwich semi-finished product in a heating tool in which it is subsequently heated to a predetermined temperature; arranging the heated sandwich semi-finished product in a forming tool in which it is subsequently formed; wherein one of the two face sheets is provided with a predetermined number of through-holes.

[0005] DE 19520293 A1 describes an open-cell plastic foam film with smooth, closed surfaces, wherein, after leaving a thermoforming plant, it is perforated in a device or perforating station by means of needles present in a needle plate.

[0006] European patent application EP 1 815 977 A1 discloses a reusable panel for motor vehicles and a method and apparatus for its production. It discloses a single-material sandwich composite made in particular of polyethylene terephthalate (= PET), comprising: (a) a first needle-punched nonwoven 3 of PET fibers, (b) a second needle-punched nonwoven 3 of PET fibers, (c) a foamed sandwich core 4 of PET granules, wherein the sandwich core 4 is arranged between the first needle-punched nonwoven 3 and the second needle-punched nonwoven 3 on a first side of the second needle-punched nonwoven 3, and (d) a decorative layer 6 of PET, wherein the decorative layer 6 is arranged on the second needle-punched nonwoven 3, and wherein the decorative layer 6 is arranged on a second side of the second needle-punched nonwoven 3 opposite the first side, such that the sandwich composite in particular has the layer sequence 3 / 4 / 3 / 6.

[0007] DE 10 2023 002 270 A1 discloses a method for producing a single-material sandwich composite made of polyethylene terephthalate using a production plant, comprising the steps of: - producing a sandwich core by foam extrusion from polyethylene terephthalate granules; - producing a needle-punched nonwoven fabric from polyethylene terephthalate fibers; - perforating the sandwich core; and - forming the sandwich composite from the perforated sandwich core and the needle-punched nonwoven fabric. The invention further relates to a single-material composite and a production plant.

[0008] The object of the present invention is to create a single-material sandwich composite by means of which a single-material sandwich composite that is easy to recycle can be produced simply and cost-effectively.

[0009] This problem is solved by a single-material sandwich composite according to the independent claims. Advantageous embodiments are specified in the dependent claims.

[0010] One aspect of the invention relates to a single-material sandwich composite made of polyethylene terephthalate, comprising a first needle-punched nonwoven fabric made of polyethylene terephthalate fibers, a second needle-punched nonwoven fabric made of polyethylene terephthalate fibers, and a sandwich core made of polyethylene terephthalate granules, wherein the sandwich core is arranged between the first needle-punched nonwoven fabric and the second needle-punched nonwoven fabric on a first side of the second needle-punched nonwoven fabric.

[0011] Furthermore, a decorative layer made of polyethylene terephthalate is provided, wherein the decorative layer is arranged on the second needle-punched nonwoven fabric, and wherein the decorative layer is arranged on a second side of the second needle-punched nonwoven fabric opposite the first side.

[0012] In particular, this enables the later, and especially more cost-effective, material recycling of vehicle components by ensuring the material composition of all layers—substrates, decorative layers, binders, and the like—is coordinated. Established composite materials do not achieve this, as they are characterized by a combination of different materials to combine their specific, application-specific positive properties. The presented single-material sandwich composite comprises the components decorative layer, face layer, and core layer. While some offcuts may be generated during the manufacturing process, these become valuable secondary material due to the mono-material construction.

[0013] A monomaterial needle-punched nonwoven fabric, consisting of a combination of low-melting-point PET fibers or CoPES fibers with a melting point of approximately 140° to 180° Celsius and PET fibers with a melting point of approximately 255° Celsius, forms the surface layer of the composite. Through heating and subsequent shaping during the manufacturing process, a fiber composite is formed in the surface layers, containing, for example, PET reinforcing fibers and a matrix of low-melting-point PET, which also creates a material-bonded connection to the foam core.

[0014] The nonwoven fabric is produced after calendering by mechanical needling and by adhesion as a result of thermal action and is used with a basis weight of 200 grams per square meter to 800 grams per square meter.

[0015] According to an advantageous embodiment, the single-material sandwich composite is needle-punched to create a bond between the layers. Needle-punching is a process in which two or more layers are joined by inserting needles through the layers and then removing them. This leaves small holes or channels in the layers, which can be used to bond them. Needle-punching is frequently used to join different materials, particularly composites, as in this case. By inserting the needle into the layers, they can be precisely aligned and positioned, resulting in high accuracy and stability of the bond. The advantages of needle-punching lie particularly in its high accuracy, low deformation, high load-bearing capacity, and ease of use.

[0016] According to the invention, at least one of the needle-punched nonwovens is made of bicomponent fibers. Bicomponent fibers are fibers that consist, for example, of different materials which are bonded together during a spinning process. They are frequently used in needle-punched nonwovens to improve their properties and performance. In the production of bicomponent fibers, two different polymers or polymer mixtures are simultaneously extruded through a spinneret and intertwined to form a single fiber. The two components can be present in different proportions and mixing ratios, which influences the properties of the resulting fiber. Examples include segmented bicomponent fibers, concentric bicomponent fibers, and asymmetric bicomponent fibers. Bicomponent fibers are used in many applications.These enable improved performance, durability and functionality of needle-punched nonwovens compared to conventional single-fiber fabrics.

[0017] Another advantageous embodiment involves producing the sandwich core by foam extrusion. Specifically, the single-material core layer of the single-material sandwich panel is made of PET foam. This is continuously produced by thermoplastic foam extrusion with, for example, a density between 80 kg / m² and 300 kg / m². The foam can be in the form of a foam sheet or a block foam.

[0018] It has also proven advantageous to incorporate an adhesive between at least one of the layers, particularly by sintering. To improve application between the individual layers, the adhesive can be made of, for example, PES and / or CoPES and / or PET, particularly by sintering.

[0019] In a further advantageous embodiment, the single-material sandwich composite is designed for installation in a motor vehicle. For example, component applications such as parcel shelves, door panels, or parts thereof, such as trunk and frunk linings, seat backrest tensioning elements, and headliners, can be manufactured or produced using the described single-material sandwich composite.

[0020] Further advantages, features, and details of the invention will become apparent from the following description of a preferred embodiment and from the drawings. The features and combinations of features mentioned above in the description, as well as those mentioned below in the figure description and / or shown in the figures alone, can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention.

[0021] This shows: Fig. 1 a schematic sectional view of an embodiment of a single-material sandwich composite material; Fig. 2 a schematic perspective view of an embodiment of a polyethylene terephthalate fiber; Fig. 3 a schematic sectional view of the embodiment Fig. 2; Fig. 4 A schematic flowchart for the production of a single-material sandwich composite.

[0022] In the figures, identical or functionally equivalent elements are provided with the same reference symbols.

[0023] Fig. Figure 1 shows a schematic sectional view of an embodiment of a single-material sandwich composite 10 according to one embodiment. The single-material sandwich composite 10 is made of polyethylene terephthalate. The single-material sandwich composite 10 has at least one first needle-punched nonwoven 12 made of polyethylene terephthalate fibers. A second needle-punched nonwoven 14 made of polyethylene terephthalate fibers is also shown. Furthermore, the single-material sandwich composite 10 has a sandwich core 16 made of polyethylene terephthalate granules, wherein the sandwich core 16 is arranged between the first needle-punched nonwoven 12 and the second needle-punched nonwoven 14 at a first side 18 of the second needle-punched nonwoven 14. Furthermore, a decorative layer 20 made of polyethylene terephthalate is provided, wherein the decorative layer 20 is arranged on the second needle-punched nonwoven fabric 14, and wherein the decorative layer 20 is arranged on a second side 22 opposite the first side 18.

[0024] In particular, it may be provided that the single-material sandwich composite 10 is needle-punched to create a bond between the layers. Alternatively, the single-material sandwich composite 10 may be bonded to create a bond between the layers.

[0025] Furthermore, it may be provided that the single-material sandwich composite 10 is produced using a one-shot process.

[0026] It is also possible that at least one of the needle-punched nonwovens 12, 14 has PET reinforcing fibers. Alternatively and additionally, at least one of the needle-punched nonwovens 12, 14 can be made of bicomponent fibers.

[0027] Furthermore, it may be provided that the sandwich core 16 is produced by foam extrusion. It may also be provided that an adhesive agent is introduced, in particular sintered, between at least one of the layers.

[0028] Furthermore, it may be provided that the single-material sandwich composite 10 is designed for arrangement in a motor vehicle.

[0029] In particular, this shows that Fig. 1. The layers are bonded by mechanical interlocking, in particular pinning, and / or chemical bonding, in particular adhesion. The cost-effective one-shot process combines all layers of the composite into a finished component in a single step. Thanks to the mono-material construction, the resulting offcuts become valuable secondary material.

[0030] To enable cost-effective material recycling of, for example, vehicle components later on, it is necessary to coordinate the material composition of all layers, especially the substrate, decorative layer, and binder. Established composite materials do not meet this requirement, as they are characterized by a combination of different materials to combine their specific, application-specific positive properties.

[0031] The presented single-material sandwich composite 10 is composed in particular of the components decoration, face layer and core layer. The layers are bonded by mechanical needling and / or chemical bonding.

[0032] Fig. Figure 2 shows a schematic perspective view of an embodiment of polyethylene terephthalate fibers. A monomaterial needle-punched nonwoven fabric, with a combination of low-melting-point PET fibers or CoPES fibers with a melting point of approximately 140°C to 180°C and with PET fibers, particularly with a melting point of approximately 255°C, forms the surface layers of the composite. Heating and subsequent shaping during the manufacturing process create a fiber composite in the surface layers, consisting of PET reinforcing fibers and a matrix of low-melting-point PET, which also forms a material-bonded connection for foam sweeping. The PET fibers used can be a mixture of low-melting-point fibers and reinforcing fibers, or partially or completely as bicomponent fibers. In the case of bicomponent fibers, the low-melting-point PET encapsulates the PET reinforcing fibers, as, for example, in the Fig. 2 is shown. Thus, the Fig. 2 in particular the so-called PET core 24 of a fiber and the PET sheath 26 of a fiber.

[0033] The Fig. Figure 3 shows a schematic sectional view of the Fig. 2.

[0034] The nonwoven fabric is consolidated after calendering by mechanical needling or by adhesion as a result of thermal action and is used with a basis weight of approximately 200 g per square meter to 800 g per square meter.

[0035] The core layer of the sandwich composite 10 is made of PET foam. This is continuously produced by thermoplastic foam extrusion with a density between 80 kg / m² and 300 kg / m². The foam can be in the form of a foam sheet or a block foam.

[0036] The decorative layer, adapted to the material of the substrate, can be made of textile or synthetic leather, and can also be made of polyester. It may contain small amounts of additives, pigments, or co-polyesters that do not negatively affect the recycling process.

[0037] The individual layers of the composite can be joined mechanically, for example by needling, chemically, for example by melting due to thermal action, or during component manufacturing by heating to the processing temperature. If required, an adhesive made of PES and / or CoPES and / or PET can be applied, for example by sintering, to increase the bond between the layers.

[0038] Fig.Figure 4 shows a schematic flowchart according to an embodiment of a manufacturing process for producing a single-material sandwich composite 10. The following steps are not necessarily to be regarded as a chronological sequence, but can be carried out partly in parallel or in a different order.

[0039] In a first step (S1), the PET fiber, a low-melting-point PET fiber, a PET bicomponent fiber, or a CoPS fiber is prepared. In a second step (S2), the two needle-punched nonwovens 12 and 14 are produced. In a third step (S3), a decision is made as to whether needling is required. If so, a fourth step (S4) can be carried out, in which the needling is performed.

[0040] In a fifth step, S5, PET granules are prepared. In a sixth step, S6, the foam is then extruded. In a seventh step, S7, a decision is made as to whether needling should be performed. If not, the process proceeds to an eighth step, S8, in which the needle-punched nonwovens 12 and 14 are joined with the foam core 16. If needling is still not performed, the process proceeds to a ninth step, S9, in which thermal bonding is carried out between the foam core 16 from the sixth step, S6, and the produced needle-punched nonwovens 12 and 14.

[0041] Starting from the third step S3, the ninth step S9 can also be carried out, as already mentioned. If needling is performed, the process can proceed from the seventh step S7 to the fourth step S4. Starting from the fourth step S4, a semi-finished roll can then be produced in a tenth step S10. This can also be provided from the ninth step S9. In an eleventh step S11, it can be decided whether the semi-finished roll is to be cut to size. If so, a twelfth step S12 is carried out and the semi-finished roll is cut to size. From this, a semi-finished sheet is then produced, particularly in a thirteenth step S13. If no cutting is carried out, the process can proceed to a fourteenth step S14, in which heating takes place.Starting from the thirteenth step S13 and the eighth step S8, the heating can also be carried out in the fourteenth step S14.

[0042] In a fifteenth step, S15, the decorative layer 20 may be provided. In a sixteenth step, S16, it may be checked whether needing to be applied. If needing to be applied is required, then the fourth step, S4, may be carried out. If needing to be applied is not required, then in a seventeenth step, S17, it may be checked whether an adhesive should be added. If so, then in an eighteenth step, S18, the adhesive is applied. The adhesive may, for example, be provided as PET and / or PES in a nineteenth step, S19.

[0043] If no adhesive is required, step nine, S9, can be performed starting from step seventeen, S17. Starting from step fourteen, S14 (heating), step twenty, S20, corresponding to shaping, can be performed. This step can also be performed starting from step seventeen, S17, as well as from step eighteen, S18. After shaping, the process concludes with step twenty-first, S21.

[0044] The single-material sandwich composite 10 is heated from room temperature (RT) to T0. If the decorative layer was not processed onto the substrate of the semi-finished product, it must be heated above the temperature of the binder T0. b They are processed to guarantee a bond. Furthermore, the temperature at the beginning of the forming process is above T u , in order to enable a network structuring of the connection points of the fibers of the cover layers.

[0045] The temperature T0 and T u These result from the permissible processing windows of the selected materials in the substrate and decoration. The lower limit T u is determined by the melting temperature T v The melt or bicomponent fibers of the sandwich composite's face layer must only harden after forming. The upper limit of the temperature range is determined by the melting temperature of the components, but especially by the temperature T. d , beyond which the decorative material is damaged, is limited.

Claims

[1] Single-grade sandwich composite (10) made of polyethylene terephthalate, comprising: - a first needle-punched nonwoven (12) made of polyethylene terephthalate fibers; - a second needle-punched nonwoven (14) made of polyethylene terephthalate fibers; - a sandwich core (16) made of polyethylene terephthalate granules, wherein the sandwich core (16) is arranged between the first needle-punched nonwoven (12) and the second needle-punched nonwoven (14) on a first side (18) of the second needle-punched nonwoven (14); and - a decorative layer (20) made of polyethylene terephthalate, wherein the decorative layer (20) is arranged on the second needle-punched nonwoven fabric (14), and wherein the decorative layer (20) is arranged on a second side (22) of the second needle-punched nonwoven fabric (14) opposite the first side (18), characterized by , that the needle-punched nonwovens (12, 14) and the sandwich core (16) of the single-material sandwich composite (10) are needle-punched to create a bond between the layers and at least one of the needle-punched nonwovens (12, 14) has bicomponent fibers, wherein the low-melting PET encapsulates the PET reinforcing fibers in the bicomponent fibers. [2] Single-material sandwich composite (10) according to the preceding claim, characterized by , that the sandwich core (16) is produced by foam extrusion. [3] Single-material sandwich composite (10) according to any one of the preceding claims, characterized by that an adhesive agent is introduced, in particular sintered, between at least one of the layers. [4] Single-material sandwich composite (10) according to any one of the preceding claims, characterized by , that the single-material sandwich composite (10) is designed for arrangement in a motor vehicle.

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