WO2024260961A1 - Spacer fabric, injection-molded composite, and method for producing an injection-molded composite - Google Patents

Abstract

The invention relates to a spacer fabric (1), in particular for forming an injection-molded composite, comprising: a first knitted-fabric layer (3) formed by at least a first thread system (F1) and a second thread system (F2) having a different pattern; a second knitted-fabric layer (4); and spacer threads (5) connecting the knitted-fabric layers (3, 4), wherein the first thread system (F1) has a loop-forming pattern. According to the invention, the ratio of the weights per unit area of the first knitted-fabric layer (3) and the second knitted-fabric layer (4) is at least 2:1, and the threads of the second thread system (F2) do not form loops and each extend as a partial weft over at least four wales.

Description

Müller Textil GmbH

Spacer fabric, injection-molded composite and method for producing an injection-molded composite

Description:

The invention relates to a spacer fabric, in particular for forming an injection-molded composite, with a first knitted fabric layer formed by at least a first thread system and a second thread system with a different lay, a second knitted fabric layer and spacer threads connecting the knitted fabric layers to one another, the first thread system having a stitch-forming lay. The invention also relates to an injection-molded composite with such a spacer fabric and a method for producing an injection-molded composite.

Spacer fabrics are characterized by a light, air-permeable structure, whereby spacer fabrics are elastic in the direction of their thickness due to the spacer threads running between the two layers of the fabric. Monofilament yarns are usually used as spacer threads, which have a comparatively high recovery effect due to their structure.

The basics of producing a spacer fabric are known to the expert, and additional reference is made to the specialist book “Wirkerei und Strickerei”, Markus Oliver Weber/Klaus-Peter Weber, 6th edition 2014 (ISBN 978-3-86641-299-6).

Due to their elastic properties, spacer fabrics can be used as soft, elastic layers that allow air circulation in mattresses, upholstered furniture, clothing or shoes. Spacer fabrics are also used as technical textiles in the automotive sector, for example for climate-controlled seats and seat covers, whereby Spacer fabrics enable good contour adaptation due to their cushioning properties and very good resilience.

In addition, spacer fabrics are particularly suitable for padding in the automotive sector and in other applications, such as furniture construction. For example, spacer fabrics are used in the automotive sector for interior paneling. Depending on the design, the spacer fabric can then form a visible surface itself or be combined with a covering layer, for example leather, artificial leather, another textile or a decorative film.

The pressure-elastic properties of the spacer fabric offer particular advantages in this case. In addition to a particularly pleasant and high-quality feel, tensions can also be reduced and stress on the material reduced. An additional covering layer in the form of leather, artificial leather, a textile or a film can work to a certain extent, which also significantly increases the durability.

Corresponding composite materials are then usually applied to a carrier and can be clamped, glued or otherwise attached.

In order to ensure efficient production and good recyclability, there is a need to reduce the amount of different materials used in many products. For example, adhesives contained in long-lasting plastic products may lose their function and/or be detrimental to recycling. Furthermore, reducing the amount of materials used can also result in benefits during the use of the corresponding products. It is known that volatile components can escape over a longer period of time from conventional adhesives used to bond plastic materials, which can be perceived as an odor, for example. The handling of adhesives during production can also lead to certain contaminations and/or increased safety requirements.

DE 10 2018 114 566 B3 describes that a spacer fabric intended as an interior trim part can be back-injected, with the back-injected plastic then forming a carrier.

DE 20 2013 005 923 U1 and WO 2014/202768 A1 describe an interior trim element, for example for a passenger compartment of a motor vehicle, which can have a foam or a spacer fabric as a cushioning layer. The cushioning layer can also be laminated with a thin film. Such a lamination on a rear side of the cushioning layer is provided in particular when, according to a variant, back-injection molding is provided.

It should be noted that when forming an injection molded composite, molten plastic is usually fed and/or pressed at high pressure. In principle, the expert can influence the viscosity and pressure to a certain extent in order to avoid excessive penetration of molten plastic into the spacer fabric if no separate film is to be used as a barrier. However, this limits the expert's options for variation in injection molding to a certain extent. The present invention is based on the object of increasing the variation options available to the person skilled in the art when forming an injection-molded composite with a spacer fabric. The spacer fabric should have good functional properties and good cushioning properties and should be particularly suitable for flexible injection molding, whereby the incorporation of additional materials in the form of a film or the like should also be avoided. Furthermore, an injection-molded composite and a method for producing an injection-molded composite should also be specified.

The subject matter of the invention and the solution to the problem are a spacer fabric according to patent claim 1, an injection-molded composite according to patent claim 13 and a method for producing an injection-molded composite according to patent claim 16.

Starting from a generic spacer fabric according to the preamble of patent claim 1, the invention therefore provides that the ratio of the area weight of the first knitted fabric layer to the second knitted fabric layer is at least 2:1 and that the threads of the second thread system do not form stitches and each extend as a partial weft over at least 4 stitch wales.

According to the invention, it is therefore provided that the first knitted fabric layer is formed heavier and thus denser than the first knitted fabric layer. With regard to the surface weights, the threads or thread system that directly form the first knitted fabric layer on the one hand and the second knitted fabric layer on the other hand must be taken into account. The spacer threads connecting the two knitted fabric layers are of course also to be included in the two Knitted fabric layers are incorporated, but are not taken into account when determining the basis weight. The basis weights can be determined very easily during production based on the thread consumption for the respective laying rails and/or calculated theoretically. Even in a sample of a spacer fabric to be examined, the spacer threads can be cut to separate the two knitted fabric layers and then the corresponding fragments can be removed from the knitted fabric layers. Under this condition, an experimental determination of the basis weights is also easily possible.

According to the invention, it is further provided that the first knitted fabric layer is formed by at least a first thread system and a second thread system of different lay. Using a warp knitting machine or a raschel machine, the different thread systems are preferably assigned to an associated laying rail. The movement of the corresponding laying rails and thus the formed lay is then described abstractly using corresponding lay images. Reference is also made to the specialist book "Wirkerei und Strickerei", Markus Oliver Weber/Klaus-Peter Weber, 6th edition 2014 (ISBN 978-3-86641-299-6), page 178 et seq. The terms "partial weft" (page 32), "twill" (page 134) and "even lay" (page 186) used below are also explained there in the sense of the present invention.

As a further aspect of the present invention, it is provided that the threads of the second thread system do not form stitches and each extend as a partial weft over at least 4 stitch wales. In terms of production, this corresponds to a weft placement under at least 4 needles. The second thread system itself does not form any stitches and runs diagonally in a zigzag pattern over at least 4 wales when viewed from above. This results in a relatively large surface coverage of the threads that are guided parallel to one another, whereby the corresponding laying rail is preferably provided with a full covering.

A simple geometrical analysis shows that the length of the thread used is directly correlated with the surface coverage. In terms of dimensional stability and the other mechanical properties, it is also important that the second thread system does not form any stitches, as this only has a comparatively minor effect on the integration of the spacer threads, also known as pile threads.

Against this background, the invention is also based on the finding that, with regard to a uniform, usually curved course of the spacer threads between the knitted layers and the pressure-elastic properties, it can be advantageous if the weight ratio of the stitch-forming threads in both knitted layers does not differ too much.

According to a preferred embodiment of the invention, the partial weft of the second thread system extends over more than 5 wales. The partial weft can extend over a maximum of 8 or a maximum of 7 wales. According to preliminary tests, it is particularly advantageous if the partial weft for the second thread system extends over 6 wales. Within the scope of the invention, it is achieved that the first knitted fabric layer is comparatively dense. It is understood that the spacer fabric should be injected behind the first knitted fabric layer.

The comparatively dense design with the diagonally zigzag threads of the second thread system and the overall higher surface weight compared to the second knitted layer means that molten plastic is retained more effectively during injection molding and/or pressing.

There is no need to laminate an additional barrier layer in the form of a film, fleece or the like. Instead, the molten plastic is preferably directly adjacent to the first knitted layer or even penetrates it to a certain extent. A certain degree of penetration can achieve a particularly reliable connection, but penetration or at least excessive penetration of the molten plastic through the first knitted layer can be avoided. The intimate connection of the molten plastic with the first knitted layer can, depending on the process, achieve a particularly high and long-term reliable bond, whereby additional materials such as adhesive or the like are not necessary and the associated disadvantages can be avoided.

According to a preferred embodiment of the invention, the first knitted fabric layer also comprises a third thread system, whereby the threads of the third thread system also do not form stitches and each extend as a partial weft over at least 4 stitch wales. In particular, the same laying as for the second thread system can be used for the third thread system. be provided, whereby here too it is particularly preferred that the corresponding laying rail is fully occupied.

The third thread system allows the first knitted layer to be made even denser. It goes without saying that the first knitted layer as a textile layer is not completely dense in the sense of a closed surface, but this is not necessary for back-injection molding. Rather, it is intended to ensure that during injection molding or back-injection molding, the remaining openings and pores are so small that molten plastic cannot pass through, even at low viscosity and high pressure.

In principle, the same or different threads can be used for the second thread system and the third thread system. If the same thread is used, the use of the second thread system and the third thread system ultimately results in a doubling of the number of threads in order to achieve a particularly dense surface.

As already explained above, the optionally provided third thread system can be designed to extend over 4 to 8, preferably 5 to 7 and for example 6 wales. In principle, it can be useful if the second thread system and the third thread system extend over the same number of wales, because then the individual threads can be arranged particularly evenly.

Against this background, it is particularly preferred if the second thread system and the third thread system are laid in the same way. The individual threads can then lay flat next to each other without crossing, which creates a particularly dense structure. It is important to note that that at intersections, due to the difference in height, certain gaps and spaces always remain, which is why a parallel and uniform arrangement of adjacent threads can be particularly advantageous, especially between the stitches formed.

According to the previously presented embodiments with the second and third thread systems, a particularly dense and thus particularly advantageous structure can be achieved within the scope of the invention. Depending on the requirements, however, it may be sufficient for the first knitted layer if only the first thread system and the second thread system are provided. Certain improvements can then be achieved by increasing the fineness. In principle, it is also possible to provide a double thread feed on a corresponding laying rail.

The threads of the first thread system form stitches and are therefore responsible for the structural strength of the first knitted layer. It can also be advantageous if the stitch-forming threads of the first thread system also extend over a large number of, for example, at least 4 wales.

The stitch-forming threads of the first thread system can also extend, for example, over 4 to 8, in particular 5 to 7 and preferably 6 wales.

It is also advantageous with regard to the threads of the first thread system if they extend over the same number of wales as the threads of the second thread system and, if applicable, the third thread system. This also allows for an improved parallel position of all Threads of the first thread system are used to achieve the densest possible structure essentially in one plane.

According to a preferred embodiment of the invention, a twill weave is provided for the threads of the first thread system. If the threads of the first thread system then extend over 6 wales, i.e. have an underlay length of 4 needles between the stitches during production, a twill velvet weave results according to a particularly preferred embodiment of the invention.

As already explained above, it is preferred if the threads of the first thread system, the threads of the second thread system and optionally the threads of the third thread system are arranged with a full thread feed or are processed in the laying rails with a full thread feed during production.

By using the three thread systems and the slanting of the threads of the first knitted layer, the ratio of the surface weights of the first knitted layer and the second knitted layer of at least 2:1 provided according to the invention can be significantly exceeded. According to a preferred embodiment of the invention, it is provided that the ratio of the surface weights of the first knitted layer and the second knitted layer is between 3:1 and 8:1, in particular between 4:1 and 7:1.

Multifilament yarns can be provided for the threads of the first thread system and/or the second thread system and/or the third thread system. Multifilament yarns consist of a large number of filaments, so that a particularly uniform and dense structure can be achieved. This is especially true if the threads are from different Thread systems run essentially flat, parallel to one another at least in sections. In a multifilament yarn, for example, between 12 and 72, in particular 36, filaments can be provided.

In particular, texturing of the multifilament yarns can also be provided, making them even softer and more voluminous.

The fineness of the threads can, for example, be in a range between 33 dtex and 400 dtex. In particular, it can also be provided that the threads of the second thread system, which do not form stitches, have a greater fineness than the threads of the first thread system.

Even if, within the scope of the invention, threads made of conventional polymers are preferred for the two knitted layers and the spacer threads, natural fibers or fibers made of natural raw materials can also be provided within the scope of the invention.

According to a particularly preferred embodiment of the invention, it is provided that the spacer fabric is formed entirely from a single polymer, so that only one polymer is used, which also makes recycling considerably easier.

For example, the entire spacer fabric can be made from a polyester and in particular polyethylene terephthalate, so that pure recycling is then possible. This is especially true if, when forming an injection-molded composite, a plastic body adjacent to the first fabric layer is also made from the same polymer. The term "single-type" refers in particular to the usual recycling classes, which differentiate between PET, PE and PP, for example. As a rule, it is not critical if different types of PET are used within a specific polymer class such as PET. In principle, however, it is of course also conceivable that the entire spacer fabric is made from just one type of polymer.

The present invention is particularly concerned with the design of the first knitted fabric layer in order to enable particularly flexible injection molding without impairing the desired pressure-elastic properties of the spacer fabric. Against this background, the thickness of the spacer fabric and the design of the second knitted fabric layer can be varied very freely. The preferred designs given below are of course to be regarded only as examples.

For example, the total thickness of the spacer fabric is between 2 mm and 10 mm, in particular between 3 mm and 7 mm. Such thicknesses are particularly suitable for forming an interior lining with a certain cushioning effect, for example.

As explained further below, the spacer fabric in an injection-molded composite can either form a visible surface and thus an external surface of the injection-molded composite or a functional part produced with it, or alternatively it can be combined with a decorative layer such as leather, artificial leather, another textile, a film or the like. Accordingly, the second layer of the fabric can also be designed differently against this background. The invention also relates to an injection-molded composite with the previously described spacer fabric on a plastic body, which is directly connected to the first fabric layer in a material-locking manner. The material-locking connection is preferably made directly between the first fabric layer and the preferably injection-molded plastic body without any additional material such as adhesive or the like.

In detail, various connection mechanisms come into consideration, which can also be combined with one another. With a material-to-material connection, the materials can adhere to one another, whereby during injection molding the molten polymer forming the plastic body can also intervene to a certain extent in the structure of the first knitted layer. However, there is also a certain degree of mechanical interlocking, whereby individual threads or filaments can also be enclosed by multifilament yarns, so that ultimately a connection is achieved that cannot be separated without causing damage. Depending on the process, a certain degree of fusion of the materials is also possible, especially if they consist of the same polymer or the same polymer class.

As already explained above, the second knitted layer can form a visible surface of the injection-molded composite. The second knitted layer can, for example, have an attractive structure, and openings, a hole pattern or the like can also be provided.

According to one variant, a decorative layer can also be applied to the second knitted fabric layer as described above. Such a decorative layer can be arranged in different ways. Depending on the material, welding, gluing, sewing or the like can be considered. Even if, depending on the application, undesirable adhesive is introduced as an additional material during bonding, the total amount of adhesive is reduced compared to a conventional interior trim part because the spacer fabric on the first fabric layer is directly bonded to the plastic body without any foreign material.

The invention also relates to a method for producing an injection-molded composite, wherein molten plastic is injected onto the first knitted fabric layer.

Within the scope of the invention, the method expressly includes different types of injection molding in the broad sense.

For example, the spacer fabric can be inserted into a mold, which is then closed at least at the first layer of the fabric. The molten plastic can then be injected into the closed mold to form the injection molded composite. It is also possible to use a type of injection molding. In this case, molten plastic is applied to the first layer of the fabric and only then pressed into the final shape. Depending on the type of finished product, the injection molded composite can also be created by depositing a molten strand.

If a decorative layer is arranged on the second knitted fabric layer, this can be arranged on the spacer fabric either when the molten plastic is applied or can be applied subsequently, depending on the manufacturing process. For example, it is also conceivable that a corresponding covering material for the decorative layer is first loosely placed in a mold and then connected to the second knitted layer in an integrated process during the formation of the injection molded composite. For this purpose, for example, a decorative layer made of leather, artificial leather or the like can be provided with a hot melt adhesive layer.

In contrast to the molding of the plastic body under high pressure, the amount of hot melt adhesive can be selected in such a way that it does not penetrate excessively into the spacer fabric even in the molten state and is essentially only intended for a connection with the second fabric layer.

The invention is explained below using exemplary figures. They show:

Fig. 1 an injection-molded composite with an injection-molded plastic body and a spacer fabric,

Fig. 2 a section of the injection molded composite according to Fig. 1 in a detailed view,

Fig. 3 shows an alternative embodiment of the injection-molded composite in a view corresponding to Fig. 2,

Fig. 4 is a laying pattern of a spacer fabric according to the invention,

Fig. 5 shows a laying pattern for an alternative embodiment of a spacer fabric according to the invention. Fig. 1 shows an injection-molded composite with a spacer fabric 1 and an injection-molded plastic body 2. The spacer fabric 1 has a first knitted fabric layer 3 adjacent to the plastic body 2, a second knitted fabric layer 4 forming the surface of the injection-molded composite, and spacer threads 5 connecting the knitted fabric layers 3, 4.

Fig. 2 shows a detailed view of a section of the injection-molded composite in a schematic representation. The first knitted layer 3 is directly bonded to the plastic body without any adhesive or other additional materials being provided in between. In particular, the material of the plastic body 2 can also penetrate into the first knitted layer 3 to a certain extent and also enclose individual threads or filaments of threads, thereby achieving a particularly intimate connection.

However, the first knitted layer 3, which is only shown in a highly schematic manner, is so dense that even in an injection molding process with a low viscosity of the molten plastic and a high pressure, no material can pass through the first knitted layer 3.

In the injection-molded composite formed, the spacer threads 5 support the outer second knitted fabric layer 4 in a pressure-elastic manner against the first knitted fabric layer 3, wherein the useful side formed by the second knitted fabric layer forms a visible surface in the embodiment according to Figs. 1 and 2.

The injection-molded composite shown in Figs. 1 and 2 can be provided, for example, as a panel part in a motor vehicle or the like. The plastic body 2 gives the injection-molded composite the desired shape and stability and can also be used in particular for connection to a Vehicle body or another type of sub-production. As described, spacer fabric 1 is connected directly without any additional material to the plastic body 2, which also determines the shape in detail.

The spacer fabric 1 is pressure-elastic in a known manner, with the second fabric layer 4 forming the visible and usually also haptically perceptible surface of the injection-molded composite. The second fabric layer 4 can be freely formed according to functional and aesthetic requirements and, for example, have a corresponding pattern and/or openings.

According to the invention, the ratio of the surface weights of the first knitted fabric layer 3 to the second knitted fabric layer 4 is at least 2:1, in particular between 3:1 and 8:1 and particularly preferably between 4:1 and 7:1. When determining the surface weight, the spacer threads 5 are not taken into account, even if they are integrated into the knitted fabric layers 3, 4 to a certain extent.

As explained below in connection with Figs. 4 and 5, a particularly dense design of the spacer fabric 1 on the first fabric layer 3 is achieved not only by the higher surface weight, but also by a particularly suitable laying of the corresponding threads.

Fig. 3 shows a variant based on Fig. 2 in which a separate decorative layer 6 is arranged on the second knitted layer 4. The decorative layer 6 can consist, for example, of leather, artificial leather, another textile, a film or the like.

Fig. 4 and 5 show concrete lay-ups for the spacer fabric 1. The first fabric layer 3 is made up of a first thread system F1, a second Thread system F2 and a third thread system F3. A full thread insertion is provided for all three thread systems F1, F2, F3 of the first knitted fabric layer 3. Fig. 4 and 5 each show the knitting pattern for the guide rails with which the spacer knitted fabric is made. For knitting technical reasons, the first thread system F1 is assigned to the guide rail L3, the second thread system F2 to the first guide rail L1 and the third thread system F3 to the second guide rail L2.

Only the threads of the first thread system F1 form stitches in a twill velvet weave. In the twill weave, double stitches are formed, with the threads running diagonally in between in a velvet lay. In the embodiment shown, the threads of the first thread system each extend over 6 wales. Textured multifilament yarns with 36 filaments and a fineness of 76 dtex can be provided as an example.

The threads of the second thread system F2 and the threads of the optionally provided third thread system F3 do not form stitches and are each provided as partial weft. In the specific embodiment, the partial weft for the second thread system F2 and the third thread system F3 also extends over 6 wales.

In addition, the threads of the thread systems F1, F2, F3 forming the first knitted layer 3 are of the same orientation. Accordingly, all of the threads of the first knitted layer 3 run largely parallel to one another and outside the formed stitches without any further crossing. This results in a particularly dense arrangement essentially in one plane, whereby the passage of molten plastic in an injection molding process can be particularly effectively avoided. The core of the present invention relates in particular to the design of the first knitted fabric layer 3, so that the design of the spacer threads 5 and the second knitted fabric layer 4 can be varied to a wide extent. In the exemplary embodiment shown, the spacer threads 5 are formed by a fourth thread system F4 and a fifth thread system F5, with the spacer threads 5 being fully threaded into the corresponding laying rails. The spacer threads 5 are made of monofilament yarn, which can have a fineness of 55 dtex, for example. The fourth thread system F4 is assigned to the laying rail L4 and the fifth thread system F5 to the laying rail L5.

By using the two thread systems F4 and F5 for the spacer threads 5 when the corresponding laying rail is fully occupied, a comparatively high density of spacer threads 5 is achieved in the embodiment.

It should also be noted that during injection molding the spacer fabric 1 itself can also be compressed and then returns to its elastic properties. Against this background, it is of course particularly important that no molten adhesive penetrates through the first fabric layer 3, which could possibly also impair the described elastic properties of the spacer fabric 1.

Fig. 4 relates to a spacer fabric 1 in which the second fabric layer 4 is provided as a visible surface according to Fig. 2. The second fabric layer 4 is made up of a sixth thread system F6 and a seventh thread system F7 formed. The sixth thread system F6 is assigned to the sixth guide rail L6 and the seventh thread system F7 is assigned to the seventh guide rail L7.

The sixth thread system F6 forms fringe stitches that run along a wale when fully drawn in. A multifilament yarn with 36 filaments and a fineness of 167 dtex is suitable, for example. The seventh thread system F7 creates a drawn-in weft with a 1 full / 1 empty assignment of the corresponding guide rail.

Accordingly, the seventh thread system F7 has a total of half the threads of the sixth thread system F6. The 1 full / 1 empty weft placement and the weft placement shown cause the fringe stitches formed by the sixth thread system L6 to be drawn, so that the corresponding wales run in a wave-like manner in a top view along the production direction and a certain hole look is achieved simply by drawing the fringe stitches. Multifilament yarns with a fineness of 167 dtex can also be provided for the seventh thread system F7 with the 1 full / 1 empty weft.

According to a preferred embodiment of the invention, the entire spacer fabric is made of a single polymer, for example polyethylene terephthalate (PET). The total thickness of the spacer fabric can be, for example, in a range between 2 mm and 10 mm, in particular between 3 mm and 7 mm. The specified ranges are particularly suitable for the formation of a pressure-elastic interior trim part.

Figure 5 relates to an alternative embodiment of a spacer fabric, in which essentially the second fabric layer 4 is connected to a sixth

Thread system F6 and a seventh thread system F7 are designed differently. The sixth thread system F6 is assigned to the sixth laying rail L6 and the seventh thread system F7 to the seventh laying rail L7. The sixth thread system F6 and the seventh thread system F7 each provide for the laying rails to be fully occupied. Both thread systems of the second knitted fabric layer 4 form stitches, with a satin lay (sixth thread system F6) and a jersey lay (seventh thread system F7) being provided on the one hand. A comparatively uniform surface is formed on which a decorative layer 6 can be arranged, in particular as shown in Fig. 3. For the second knitted fabric layer 4, for example, textured multifilament yarns with 36 filaments and a fineness of 76 dtex can be used.

Claims

Patent claims: 1. Knitted spacer fabric (1), in particular for forming an injection-molded composite, with a first knitted layer (3) formed by at least a first thread system (F1) and a second thread system (F2) of different laying, a second knitted layer (4) and spacer threads (5) connecting the knitted layers (3, 4), wherein the first thread system (F1) has a laying that forms stitches, characterized in that the ratio of the surface weights of the first knitted layer (3) and the second knitted layer (4) is at least 2:1 and that the threads of the second thread system (F2) do not form stitches and each extend as a partial weft over at least four wales. 2. Spacer fabric (1) according to claim 1, characterized in that the first knitted fabric layer (3) comprises a third thread system (F3), wherein the threads of the third thread system (F3) also do not form stitches and each extend as a partial weft over at least four stitch wales. 3. Spacer fabric (1) according to claim 2, characterized in that the threads of the second thread system (F2) and the third thread system (F3) are arranged in the same position. 4. Spacer fabric (1) according to one of claims 1 to 3, characterized in that the threads of the first thread system (F1) each extend over at least four wales. 5. Spacer fabric (1) according to claim 4, characterized in that the threads of the first thread system (F1) and the second thread system (F2) are arranged in the same position. 6. Spacer fabric (1) according to one of claims 1 to 5, characterized characterized in that the threads of the first thread system (F1) are arranged with a twill weave. 7. Spacer fabric (1) according to claim 6, characterized in that the threads of the first thread system (F1) are arranged in a twill velvet weave. 8. Spacer fabric (1) according to one of claims 1 to 7, characterized in that the threads of the first thread system (F1), the threads of the second thread system (F2) and optionally the threads of the third thread system (F3) are arranged with a full thread insertion. 9. Spacer fabric (1) according to one of claims 1 to 8, characterized in that the ratio of the surface weights of the first fabric layer (3) and the second fabric layer (4) is between 3:1 and 8:1. 10. Spacer fabric (1) according to one of claims 1 to 9, characterized in that the threads of the second thread system (F2) are textured multifilament yarns. 11. Knitted spacer fabric (1) according to one of claims 1 to 10, characterized in that the knitted spacer fabric (1) is formed from a single polymer, in particular from polyethylene terephthalate. 12. Spacer fabric (1) according to one of claims 1 to 11, characterized in that a total thickness is in a range between 2 mm and 10 mm. 13. Injection-moulded composite with a spacer fabric (1) according to one of the Claims 1 to 12 on an injection-molded plastic body (2), wherein the plastic body (2) is integrally connected to the first knitted layer (3) and wherein the second knitted layer (4) forms a pressure-elastic useful side with respect to the first knitted layer (3). 14. Injection-molded composite according to claim 13, wherein the second knitted fabric layer (4) forms a visible surface of the injection-molded composite. 15. Injection-molded composite according to claim 13, wherein a decorative layer is arranged on the second knitted fabric layer (4). 16. Method for producing an injection-molded composite, wherein a spacer fabric (1) according to one of claims 1 to 12 is provided and wherein molten plastic is injected and/or pressed onto the first fabric layer (3).