Method and device for producing cushioning material, and cushioning material

Abstract

The invention relates in particular to a process for producing a cushioning material (29) for producing a seat cushion, comprising the following measures: a) extruding a material comprising at least one thermoplastic polymer in an extrusion device (12) so as to produce a curtain (18) of molten endless fibres (19), the curtain (18) falling down due to gravity, the extrusion device (12) comprises a plurality of extrusion nozzles (17) distributed in the longitudinal direction (X) and the transverse direction (Y) of the extrusion device (12) and a pressure regulating device (13) for regulating the extrusion pressure; b) receiving a curtain (18) made of molten endless fibres (19) and falling due to gravity between two rollers (20) rotating in opposite directions, thereby producing a 3D entanglement of irregularly distributed endless fibres (19) wound into loops and fused to each other, c) solidifying the 3D entanglement by immersion in a cooling liquid, the process further comprises at least one of the following measures during the continuous extrusion: d) temporally and / or locally varying the extrusion pressure; e) changing the conveying speed at which the curtain (18) is conveyed by the roller (20).

Description

Field of the Invention

[0001] The present invention relates to a method and an apparatus for producing a cushioning material and a cushioning material. Specifically, the cushioning material can be configured for manufacturing a seat cushion and can be intended, for example, for vehicle seats, in particular for seats of motor vehicles and / or aircraft and / or trains. Background Art

[0002] Generally, vehicle seats have a frame, a plurality of cushioning elements, and a covering material. Specifically, the cushioning elements are used to provide support and comfort for vehicle occupants. The cushioning elements are usually composed of foam materials, for example, composed of injection-molded polyethylene or polyurethane polymer foam molded in a special mold.

[0003] In particular, in order to locally change the support or comfort characteristics of a vehicle seat, it is interesting to arrange cushioning elements with different hardnesses in the vehicle seat. So far, this usually requires separately producing and installing cushioning elements with appropriate individual hardnesses. This increases the complexity of vehicle seat production. Summary of the Invention

[0004] Therefore, the present invention is based on the task of reducing the production cost of vehicle seats.

[0005] This is achieved by the subject matter of the independent claims of the present disclosure. Further embodiments follow from the dependent claims, the description, and the drawings.

[0006] Therefore, a method for producing a cushioning material for manufacturing a seat cushion is proposed, the method comprising the following measures:

[0007] a) Extruding a material comprising at least one thermoplastic polymer in an extrusion device to form a gravity-fed curtain of molten endless fibres, wherein the extrusion device comprises a plurality of extrusion nozzles distributed longitudinally and transversely in the extrusion device and a pressure regulating device for regulating the extrusion pressure;

[0008] b) Receiving the curtain made of molten endless fibres and falling due to gravity between two counter-rotating rollers, thereby producing a three-dimensional (3D) entanglement of randomly distributed endless fibres, and the randomly distributed endless fibres are wound into loops together and fused together,

[0009] c) Curing the 3D entanglement by immersion in a coolant,

[0010] The method further comprises at least one of the following measures during continuous and / or continuous extrusion, or in other words, during extrusion:

[0011] d) changing the extrusion pressure temporally and / or locally;

[0012] e) changing the conveying speed at which the curtain is conveyed through the rollers.

[0013] The endless fibers can be hollow fibers and / or solid fibers. Their diameter can be, for example, between 0.2 mm and 2 mm, preferably between 0.3 mm and 1.5 mm. The composition of the endless fibers can include, for example, at least 95 wt% polyester. Generally, the composition of the continuous fibers can include various different thermoplastic polymers, but is preferably only thermoplastic polymers.

[0014] The density of the resulting 3D entanglement can be, for example, between 20 kg / m 3 and 70 kg / m 3 In particular, to improve air circulation and / or moisture absorption, the 3D entanglement can have gaps between the endless fibers, especially between the fused or welded loops of the endless fibers, and these loops remain at least partially or completely free.

[0015] In the term "endless fiber", "endless" can mean that the length of the fiber is much greater than the diameter of the fiber, for example, in a ratio of at least 100 or even 1,000 or even 5,000.

[0016] The loops or entanglements can specifically include continuous fibers that cross themselves or are fused to adjacent endless fibers, or are formed thereby.

[0017] The rollers can be included in a calendering device or form a calendering device and / or can be calendering machine parts.

[0018] The rollers can each rotate about a rotation axis extending parallel to each other. Additionally or alternatively, these rotation axes can extend parallel to the longitudinal direction of the extrusion device. The falling direction, or in other words, the direction in which the curtain extends in the direction of the rollers, can extend orthogonally to the longitudinal and / or transverse direction of the extrusion device. The transverse and longitudinal directions of the extrusion device can extend orthogonally to each other.

[0019] Here, terms such as direction, axis, extension, and dimension can be used interchangeably, especially for a common spatial orientation.

[0020] The 3D entanglement and specifically the cushioning material formed thereby can be made into an elongated web, also referred to herein as a cushioning material web or material web. This can be specifically achieved by the continuous execution of the method disclosed herein, which is generally possible according to the embodiments.

[0021] The longitudinal dimension of the 3D entanglement and / or the material web can correspond to the guiding direction, or in other words, to the conveying direction of the material being extruded through the counter-rotating rollers.

[0022] The thickness dimension of the 3D entanglement and / or the material web can be determined by the separation of the rotational axes of the counter-rotating rollers. The lateral direction of the extrusion device can correspond to the thickness dimension of the 3D entanglement and / or the material web, and / or cause material extrusion in the direction of or along this thickness dimension.

[0023] The lateral dimension of the 3D entanglement and / or the cushioning material can be determined by the longitudinal dimension of the extrusion device, and in particular by the distribution of its extrusion nozzles in the longitudinal direction. Generally, the lateral direction of the extrusion device can correspond to the thickness dimension of the 3D entanglement and / or the material web, and / or cause material extrusion in the direction of or along this thickness dimension.

[0024] The extrusion nozzles can be particularly evenly distributed in the longitudinal and / or lateral direction of the extrusion device. Optional temporal and / or local variations in the extrusion pressure can be accomplished by appropriate control of the extrusion device and in particular its pressure regulating equipment.

[0025] Even when optionally changing the conveying speed of the curtain through the rollers, this conveying speed can be lower than the falling speed of the endless fiber curtain to cause an increase in the formation of additional loops.

[0026] The conveying speed can generally be adjusted by changing the rotational speed of at least one roller. Alternatively or additionally, other rollers and / or calendering equipment for receiving and conveying the cured 3D entanglement can be provided, and their rotational speeds can affect the conveying speed of the curtain picked up by the rollers. To change this conveying speed, the rotational speeds of these optional other rollers can be changed.

[0027] The curing of the 3D entanglement preferably occurs within a very short time after the formation of the 3D entanglement (e.g., within less than 5 seconds), and in particular immediately after the formation of the 3D entanglement. For this purpose, specifically, the roller receiving the curtain can be at least partially immersed in a coolant, for example up to half of its diameter.

[0028] The extrusion temperature at which the extrusion device extrudes the material can be, for example, between 180 °C and 260 °C. The material to be extruded can be sent to the extrusion device in the form of polymer granules to be melted, in particular.

[0029] Changing the extrusion pressure can particularly locally and / or temporally change the throughput of the material being extruded through the extrusion device. This can correspondingly change the density of the resulting 3D entanglement and / or cushioning material. The varying density is accompanied by correspondingly varying hardness characteristics.

[0030] Specifically, an at least temporal and / or local increase in the inflation pressure can increase the density temporally and / or locally. Conversely, a decrease in the inflation pressure can correspondingly decrease the density. Compared to the lowest extrusion pressure and / or the immediately preceding extrusion pressure in the method, increasing the extrusion pressure can include an increase of at least 10%, at least 20%, or at least 50%. Compared to the highest extrusion pressure and / or the immediately preceding extrusion pressure in the method, decreasing the extrusion pressure can include a decrease of at least 10%, at least 20%, or at least 50%.

[0031] Similarly, the conveying speed of the curtain through the rollers can affect the density of the resulting 3D entanglement and / or cushioning material. Specifically, since metaphorically speaking, the material being extruded is carried away and / or not carried away as quickly, a decrease in the conveying speed can increase the density. Conversely, an increase in the conveying speed can correspondingly decrease the density.

[0032] Thus, the method presented herein can directly form regions with density variations and thus hardness variations in the 3D entanglement and / or cushioning material, especially during continuous production. Subsequently, portions can be separated from the 3D entanglement and / or cushioning material to be used as and / or further processed into seat cushions. These portions can have both regions with a correspondingly increased density and regions with a correspondingly decreased density. Separating out these portions by cutting, for example, can be a separate measure of the method disclosed herein. The portions can be further processed into the desired final installation shape.

[0033] According to one embodiment, the change in the conveying speed and the possible temporal change in the extrusion pressure are periodic. Such changes can generally include increasing and decreasing the conveying speed and / or the extrusion pressure, especially alternately and / or at least temporarily. Compared to the maximum value and / or the minimum value and / or the immediately preceding value of the method, the change in the conveying speed or the extrusion pressure can represent a deviation of at least 10%, at least 20%, or at least 50%.

[0034] The periodic changes can produce regions of increased and / or decreased density at correspondingly uniform intervals, especially in the longitudinal direction of the produced 3D entanglement and / or cushioning material. This simplifies the subsequent separation of the individual portions to be used as seat cushions or for manufacturing seat cushions. This can also reduce material waste.

[0035] The regions of correspondingly increased and / or decreased density produced by changing the conveying speed can extend across the entire width of the produced 3D entanglement and / or cushioning material. Within each of these regions, the density can be substantially uniform.

[0036] According to one embodiment, the local variation of the extrusion pressure includes generating a non-uniform distribution of the extrusion pressure along the longitudinal direction of the extrusion device. In other words, the extrusion pressure is non-uniform and non-constant in this longitudinal direction. The non-uniform distribution of the extrusion pressure along the longitudinal direction of the extrusion device can correspond to generating a corresponding non-uniform throughput of the material through the extrusion nozzles in the longitudinal direction. Specifically, the intermediate region along the longitudinal direction of the extrusion device (or the transverse direction of the 3D entanglement and / or cushioning material generated) can have a pressure different from that of at least one outer region observed in the longitudinal direction of the extrusion device, specifically a lower pressure than it. For example, the distribution of the extrusion pressure in the longitudinal direction can be symmetric about the intermediate region of the extrusion device.

[0037] The corresponding distribution of the extrusion pressure can achieve a corresponding distribution of the density along the longitudinal direction of the extrusion device (or in the transverse direction of the 3D entanglement) in the curtain of endless fibers and / or the 3D entanglement.

[0038] Specifically, the non-uniform distribution of the extrusion pressure can be continuously maintained. In this way, an elongated material web can be produced, which is elongated when observed in its longitudinal direction and specifically has continuous regions with a density deviated from that of adjacent regions.

[0039] According to one embodiment, the method at least has measure e), and the degree to which the extrusion pressure is kept constant or less than the conveying speed varies over time. The varying degree can be related to, for example, the relative difference of the corresponding value of the extrusion pressure or the conveying speed before the currently observed time point, or can be defined accordingly. The fact that the conveying speed varies (relatively) to a greater extent than the extrusion pressure means that the targeted influence on the density by changing the conveying speed may not be affected, or only slightly affected.

[0040] According to one embodiment, the method at least has measure d) regarding the temporal variation of the extrusion pressure, while the conveying speed is kept constant or varies over time to a lesser extent. The corresponding degree of variation can be defined as described above. The result of similar advantages is a description of how to change the conveying speed while the extrusion pressure does not change so strongly.

[0041] According to one embodiment, the method includes both measures d) and e), and these measures are at least temporarily executed simultaneously. As described above, measure d) can produce a density change specifically in the transverse direction of the 3D entanglement or the cushioning material, while measure e) can allow a density change specifically in the transverse direction of the 3D entanglement or the cushioning material.

[0042] If measures d) and e) are carried out successively, which can also be alternatively or additionally provided according to the embodiment, it becomes possible to create spatially separated regions with correspondingly arranged density variations in the width and longitudinal direction of the 3D entanglement or cushioning material. If these measures are carried out simultaneously, the density variations in the transverse and longitudinal directions of the 3D entanglement or cushioning material can be at least partially overlapped. This makes it possible to create even curved shapes in multiple regions, or metaphorically speaking, in regions that "turn" when viewed from above and / or in L-shaped, C-shaped or U-shaped regions, for example, where the density of these regions deviates from that of adjacent regions. This increases the degree of freedom in creating regions of different hardness in the 3D entanglement or cushioning material.

[0043] The pressure regulation herein can be understood as regulating the pressure, in particular by generating a corresponding pressure, for example by applying such pressure to a material volume. Similarly, it can be understood that, for example, local pressure regulation is carried out by distributing and / or supplying a material that has had a corresponding pressure applied at another location.

[0044] According to another embodiment, the pressure regulation device includes a plurality of extrusion pumps or other pressure regulation devices specifically for directly applying pressure to a material volume, and the other pressure regulation devices particularly include valves whose pressure application can be individually adjusted. The extrusion pumps and / or pressure regulation devices can be distributed particularly in the longitudinal direction of the extrusion device. They can transfer the correspondingly generated and / or regulated pressure to at least part of the extrusion nozzles. The correspondingly formed pressure regulation device can precisely regulate the pressure variations provided according to the embodiment.

[0045] The present invention also relates to a cushioning material. The cushioning material can have any material properties explained herein, particularly the material properties of endless fibers and / or 3D entanglement. In addition, the cushioning material can be produced by or using methods and / or devices according to any variant described herein and can have all the features resulting therefrom.

[0046] Specifically, the cushioning material can have: an elongated material web, the material web including a 3D entanglement of randomly distributed endless fibers, the randomly distributed endless fibers forming loops fused to each other (i.e., loops with other endless fibers), and the material web having a non-uniform density in the longitudinal direction. In contrast, the density can be constant in the width direction. However, it can depend on the position in the longitudinal direction. Specifically, in the longitudinal direction, regions of increasing and decreasing density can follow each other, for example, alternatingly.

[0047] In addition, for example, if the sizes of the respective successive regions of increasing and decreasing density in the longitudinal direction are uniform, in particular, the non-uniform density in the longitudinal direction can vary periodically.

[0048] According to one embodiment, there are a plurality of first regions with increasing density in the longitudinal direction, each of the first regions being separated from each other by a second region, the density of the second region being lower than the density of the first region.

[0049] - Each of the first regions has a longitudinal extension of at least 1 cm, and / or

[0050] - The longitudinal extension of the first region is less than the corresponding spacing between adjacent first regions in the longitudinal direction.

[0051] Additionally or alternatively, the longitudinal extension of the first region or the region with generally increasing density can be less than the corresponding transverse extension of these regions. This emphasizes the creative possibility of locally and restrictively increasing only the density and hardness of the cushioning material.

[0052] The present invention also relates to a device for producing a cushioning material for manufacturing a seat cushion, the device comprising:

[0053] - An extrusion device having a plurality of extrusion nozzles and a pressure setting device for adjusting the extrusion pressure, the plurality of extrusion nozzles being distributed in the longitudinal and transverse directions of the extrusion device;

[0054] - At least two counter-rotating rollers,

[0055] - A coolant reservoir,

[0056] The extrusion device is designed to extrude a material comprising at least one thermoplastic polymer, thereby producing a gravity-drop curtain of molten endless fibers,

[0057] and the rollers are designed to receive the gravity-drop curtain of molten endless fibers between the plurality of rollers to produce a three-dimensional (3D) entanglement of randomly distributed endless fibers, the randomly distributed endless fibers forming loops fused to each other, i.e., specifically loops fused to another loop of another endless fiber, and the rollers send the produced 3D entanglement to the coolant reservoir for curing.

[0058] The device is configured to implement at least one of the following measures during extrusion:

[0059] a) Changing the extrusion pressure temporally and / or locally;

[0060] b) Changing the conveying speed of the curtain through the rollers, or in other words, changing the conveying speed at which the curtain is conveyed through the rollers.

[0061] Generally, the device can be configured to perform a method according to any variant described herein, specifically, to produce a cushioning material according to any variant described herein. Description of the Drawings

[0062] Example embodiments of the present invention are explained below with reference to the accompanying drawings. In all the drawings, the same reference numerals may be used for like features. Not all instances of the features shown in the drawings may always be provided with the corresponding dedicated reference numerals of the feature.

[0063] Figure 1 A device according to an embodiment of the present invention is shown, which device performs a method according to an embodiment of the present invention to produce a cushioning material according to an embodiment of the present invention.

[0064] Figure 2 A device according to another embodiment of the present invention is shown, which device performs a method according to another embodiment of the present invention to produce a cushioning material according to another embodiment of the present invention.

[0065] Figure 3 A device according to yet another embodiment of the present invention is shown, which device performs a method according to yet another embodiment of the present invention to produce a cushioning material according to yet another embodiment of the present invention. Detailed Description

[0066] Figure 1 A device 10 according to an embodiment of the present invention is shown. The device 10 includes an extrusion device 12 having a pressure regulating device 13. The pressure regulating device 13 includes a plurality of pressure regulating means, each pressure regulating means being in the form of an extrusion pump 14.

[0067] The extrusion pumps 14 are distributed along the longitudinal X of the extrusion device 12 and, specifically, are evenly spaced from each other. The longitudinal X is orthogonal to the transverse Y of the extrusion device 12 and extends orthogonally to the direction Z, and the material to be extruded is taken out of the extrusion device 12 along the direction Z.

[0068] The distribution plate 16 can in principle be designed according to the prior art and has a plurality of invisible extrusion nozzles 17. The extrusion nozzles 17 are distributed in the longitudinal X and the transverse Y and form openings at the bottom of the distribution plate 16.

[0069] The extrusion device 12 is supplied with a solid, specifically a granular polymer material, specifically a polymer material mixture. The polymer material mixture is melted by the extrusion device 12, and the extrusion pumps 14 apply an extrusion pressure thereto. Specifically, each extrusion pump 14 has a volume of molten material supplied thereto, and a separately adjustable pressure is applied to this volume of molten material. The volume of material with the corresponding pressure applied thereto is sent by each extrusion pump 14 to a set of associated extrusion nozzles 17 and is extruded through the extrusion nozzles 17. Preferably, the distribution plate 16 is designed and has specifically separate regions such that each extrusion nozzle 17 has material sent to it only from one of the extrusion pumps 14.

[0070] The extrusion nozzles 17 each extrude endless fibers 19 in molten form, i.e., molten endless fibers 19, having any of the characteristics described herein. These molten continuous fibers fall vertically downward in the Z direction and relative to the extrusion device 12 due to gravity. During this process, the endless fibers 19 form a curtain 18 shown only schematically.

[0071] The curtain 18 of endless fibers 19 is received in a first calendering device 21 comprising two counter-rotating rollers 20, more precisely, between these rollers 20. Each roller 20 rotates about a rotation axis R which, in the example shown, extends parallel to the longitudinal X of the extrusion device 12.

[0072] Each roller 20 is at least partially immersed in a coolant stored in a coolant reservoir 24. In the example shown, the roller 20 is not heated. The roller 20 rotates specifically at a speed lower than the falling speed of the curtain 18. More precisely, the conveying speed at which the material is fed through between the rollers 20 is lower than the falling speed of the curtain 18. This causes the endless fibers 19 themselves to form loops and possibly form loops with each other. During this process, the endless fibers 19 and specifically their loops are fused, or in other words, welded to each other. Specifically, the loops of the endless fibers are welded to the loops of other endless fibers. In addition to loops, in principle, it can also be said to be arcs or lassos.

[0073] Thus, no later than after the curtain 18 passes through the rollers 20, there is a 3D entanglement of the endless fibers 19 with loops distributed irregularly (i.e., randomly), and these loops are at least partially fused to each other (i.e., specifically to the loops of other endless fibers 19). This 3D entanglement is cured by being immersed in the coolant in the coolant reservoir 24, resulting in a cushioning material 29.

[0074] The cured 3D entanglement is taken out of the coolant reservoir 24 in the form of a cushioning material web 28 (also simply referred to as the material web 28). The position of a deflection roller 22 (not shown) for this purpose is indicated. The material web 28 is generally formed elongated along a longitudinal axis or in a longitudinal direction L. Its transverse dimension B extends orthogonally to its longitudinal dimension L. The thickness dimension D defines the distance between the surfaces of the material web 28 facing each other, and each of these surfaces has, for example, a transverse dimension B.

[0075] In a subsequent step not shown separately, individual parts 33 are separated from the material web 28 by optional device components not shown separately (or by using components of a separate device). The parts 33 form, for example, a cushion for a seat surface of a vehicle seat or can be further processed into such a cushion. The seat surfaces are schematically represented or outlined. An intermediate seat surface area 34 and a seat surface area 36 are enclosed between them.

[0076] Figure 1 The illustration shows that the transverse dimension B of the produced material web 28 corresponds to the longitudinal X or the longitudinal dimension of the extrusion device 12. Conversely, the Z-direction 12 of the extrusion device or the falling direction of the curtain 18 corresponds to the longitudinal dimension L of the material web 28.

[0077] Finally, the device 10 also includes a second calendering device 23, which includes two counter-rotating rollers 26. The axes of rotation of these other rollers 26 are not shown separately, but they extend parallel to the axis of rotation R of the rollers 20 of the first calendering device 21.

[0078] The presented embodiment generally provides that the conveying speed of the curtain 18 through the rollers 20 of the first calendering device 21 varies over time, specifically periodically. In this example, this is achieved by temporarily increasing or decreasing the rotational speed of the rollers 22 in the coolant reservoir 24 accordingly, such that the curtain 18 is guided through the first calendering device 21 faster or slower accordingly.

[0079] Thus, the material density within the material web 28 changes locally according to the varying conveying speed. If the conveying speed increases, the material density decreases in the corresponding segments guided through the rollers 20, while if the conveying speed decreases, the material density increases accordingly.

[0080] Thus, the material web 28 has regions 32 with relatively reduced density and regions 30 with increased density that are alternately arranged along its longitudinal dimension L. Accordingly, the hardness of the material web 28 alternates along its longitudinal dimension L.

[0081] Each of the regions 30, 32 extends over the entire width B and the entire thickness D of the material web 28. These regions 30, 32 are arranged uniformly, or in other words, are periodically spaced along the longitudinal L, which is caused by the corresponding periodic variation of the conveying speed. Thus, the regions 30 with increased density each have a uniform size and the same density. The regions 32 with reduced density also each have a uniform size among themselves and the same density.

[0082] In addition, it is also shown above that the regions 30 with increased density always include components with two protrusions 33; their sides 36 are shown in the example. This helps to reduce material waste.

[0083] Figure 2 and Figure 3 each show solutions according to other embodiments of the present invention. Features with the same reference numerals as in Figure 1 have the same reference numerals, even if they are not explained separately again in each case in the context of Figure 2 and Figure 3 the context.

[0084] Figure 2The embodiments of Figure 1 differ from the variants in

[0085] that the spatial position and / or orientation of the regions 30 with increased density within the produced material web 28, and the operation of the operating device 10 to achieve this. Figure 2 More precisely, in this case, an uneven extrusion pressure distribution is generated along the longitudinal X of the extrusion device 12. In the example shown, this is achieved by the fact that, compared to the other extrusion pumps 14,

[0086] the extrusion pump 14 located on the far right in

[0087] generates a higher extrusion pressure. During continuous material production, the calender devices 21, 23 preferably operate at a constant rotational speed. Figure 2 As a result, due to the increased material throughput of the extrusion nozzle 17 associated with the extrusion pump 14 located on the far right, the density of the region 30 of the material web 28 produced by the extruded fibers 19 of this extrusion nozzle 17 increases, and thus the hardness increases. This region 30 extends continuously in a strip along the longitudinal axis L of the material web 28.

[0088] Figure 3 illustrates another variant combining Figure 1 and Figure 2 variants. Thus, an uneven extrusion pressure distribution is generated along the longitudinal X of the extrusion device 12, and as a result, a preferably periodically varying conveying speed of the curtain 18 through the rollers 20 of the first calender device 21 is also generated.

[0089] The latter in turn causes regions 30, 32 with increased or decreased density to alternate in sequence along the longitudinal axis L. Conversely, a locally increased extrusion pressure produces a strip-shaped region 31 with increased density, as Figure 3 shown, which region 31 extends along the longitudinal axis L.

[0090] Since the above measures for generating increased density in the regions within the material web 28 are at least partially carried out simultaneously, this means that each region 30, 31 with increased density t is produced to overlap in the overlapping region 41. If this is to be prevented or at least restricted, it is possible, for example, by Figure 3 the extrusion pump 14 located on the far right in

[0091] In the example shown, the material web 28 has regions 30, 31 of increased density which extend at an angle towards one another such that the seat surfaces shown schematically can be separated out, in each of which the sides 36 and the rear parts 35 extending at an angle thereto have an increased density. Thus, in plan view, each of the separated parts has a C-shaped or (rotated) U-shaped region of increased density formed by the regions 30, 31.

Claims

1. A process for producing a cushioning material (29) for manufacturing a seat cushion, the process comprising the following measures: a) extruding a material comprising at least one thermoplastic polymer in an extrusion device (12) to produce a curtain (18) of molten endless fibers (19), said curtain (18) falling due to gravity, said extrusion device (12) comprising a plurality of extrusion nozzles (17) distributed in the longitudinal direction (X) and the transverse direction (Y) of said extrusion device (12) and a pressure regulating device (13) for regulating the extrusion pressure; b) receiving said curtain (18) made of molten endless fibers (19) falling due to gravity between two counter-rotating rollers (20) so as to produce a 3D entanglement of irregularly distributed endless fibers (19) forming loops fused together, c) solidifying the 3D entanglement by immersing it in a cooling liquid, The process also includes at least one of the following measures during extrusion: d) varying the extrusion pressure temporally and / or locally; e) varying the transport speed at which the curtain (18) is transported by means of the rollers (20).

2. The process according to claim 1, in, The variation of the conveying speed and / or the temporal variation of the extrusion pressure are periodic.

3. The process according to claim 1 or 2 with measure d), in, The local variation of the extrusion pressure comprises generating an uneven distribution of the extrusion pressure along the longitudinal direction (X) of the extrusion device (12).

4. The process according to claim 3, in, The uneven distribution of the extrusion pressure is constantly maintained.

5. The process according to any one of the preceding claims, in, The process comprises at least measure e), and the pressing pressure is kept constant or varies over time to a degree less than the conveying speed.

6. The process according to any one of the preceding claims, in, The process comprises both measures d) and e), and these measures are at least temporarily carried out simultaneously.

7. The process according to any one of the preceding claims, in, The pressure regulating device (13) comprises a plurality of displacement pumps (14) or other pressure regulating devices, wherein the displacement pressures of the displacement pumps (14) and the other pressure regulating devices are individually adjustable.

8. A cushioning material (29), The invention relates to an elongated material web (28) comprising a 3D entanglement of randomly distributed endless fibers (19) forming loops fused to each other, the material web (28) having a non-uniform density in the longitudinal direction (L).

9. The cushioning material (29) according to claim 8 with variant a), in, The density in the longitudinal direction (L) is not uniform but changes periodically.

10. A cushioning material (29) according to claim 8 or according to claim 9 with variant a), in, In the longitudinal direction, there are a plurality of first regions (30) with increasing density, each of the first regions (30) being separated from each other by a second region (32), the density of the second region (32) being lower than that of the first region (30), - said first regions (30) each have a longitudinal extension of at least 1 cm, and / or - the longitudinal extension of the first regions (30) is smaller than the corresponding spacing between adjacent first regions (30) in the longitudinal direction.

11. A device (10) for producing a cushioning material (29) for manufacturing a seat cushion, the device comprising: - an extrusion device (12), the extrusion device (12) having a plurality of extrusion nozzles (17) and a pressure setting device (13) for adjusting the extrusion pressure, the plurality of extrusion nozzles (17) being distributed in the longitudinal direction (X) and the transverse direction (Y) of the extrusion device (12), - at least two counter-rotating rollers (20), - a coolant reservoir (24), The extrusion device (12) is configured to extrude a material comprising at least one thermoplastic polymer to produce a gravity-falling curtain (18) of molten endless fibers (19), The roller (20) is configured to receive the curtain (18) of molten endless fibers (19) falling due to gravity between a plurality of the rollers (20) to produce a 3D tangle (1) of irregularly distributed endless fibers (19), the irregularly distributed endless fibers (19) being wound into a loop and fused to each other, and the roller is also configured to send the produced 3D tangle to the cooling liquid reservoir (24) for solidification, The device (10) is configured to implement at least one of the following measures during extrusion: a) varying the extrusion pressure temporally and / or locally; b) varying the transport speed at which the curtain (18) is transported by means of the rollers (20).

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