A method of extruding material using a multi-stage extruder.

Abstract

The present invention provides a method for removing volatile components and / or contained gases from plasticized materials. [Solution] A method of extruding a material (4) using a multi-stage extruder (1) having two extruder stages (2,3), wherein the material is plasticized in a first extruder stage of the multi-stage extruder, then transferred to another second extruder stage of the multi-stage extruder, fragmented in a splitting unit (5) of the multi-stage extruder, and volatile components and / or gases are removed at least partially from the material under negative pressure, preferably vacuum, in a negative pressure region (6) of the multi-stage extruder. In addition, at least in the normal mode of the multi-stage extruder, the negative pressure region is filled within the maximum amount of material allowed for component and / or gas removal, and / or the fragmented state of the material is maintained, such that at least one material flow and / or at least one melting pressure of the material passing through the first extruder stage and / or the other extruder stage is automatically adjusted.

Description

Technical Field

[0001] The present invention relates to a method of extruding a material by means of a multi-stage extruder having at least two extruder stages. For this purpose, the material is plasticized in a first extruder stage of the multi-stage extruder and then transferred to another extruder stage of the multi-stage extruder and additionally fragmented via a splitting unit of the multi-stage extruder, in which state it is subjected to a negative pressure in the negative pressure region of the multi-stage extruder, whereby volatile components and / or contained gases are at least partially removed from the material.

Background Art

[0002] The degassing of rubber compounds containing highly active carbon black is particularly important in the rubber industry, especially in the manufacture of tires and other industrial rubber products. These rubber compounds, often also called TBR Cab compounds, are widely applied in the manufacture of truck tires and bus tires. TBR means "Truck and Bus Radial" and excellent properties such as strength and abrasion resistance are evaluated. The term "Cab" refers to the use of highly active carbon black, i.e., the aforementioned highly active carbon black, which contributes to the improvement of the mechanical properties of the compound.

[0003] Based on the chemical properties of rubber compounds containing carbon black, an increase in porosity can be brought about in the extrudate after the extrusion process during general preheating treatment. This porosity is caused particularly by the release of the matrix and volatile components that can occur within the material during preheating. As a result, this porosity has an adverse effect on the properties of tires or other industrial rubber products by impairing the mechanical strength, durability, and impermeability of the final product. In addition, the non-uniform distribution of air bubbles can deteriorate the performance of the material in subsequent processing steps and final applications, which increases the risk of defects and shortens the lifespan of the product.

[0004] Solutions are already known from the prior art for degassing plasticized materials.

[0005] Swiss Patent No. 333283 describes a method and apparatus for the continuous mixing, plasticization, degassing, and extrusion of materials, particularly plastics, in a single working step. The material, mixed and plasticized in a kneader, is directly received by a discharge screw connected to the kneader, which continuously discharges the material through a nozzle. The plasticized material intermittently enters the discharge screw, which is flanged at a right angle from the kneader, and the intermittent inflows are offset, and the material is further conveyed while increasing the pressure. Degassing is performed at the discharge screw, located after the point where the material enters from the kneader. Here, the gas can either escape freely or be drawn out by vacuum. Since the material is processed intensively at the inlet of the discharge screw, volatile substances can escape in gaseous form.

[0006] German Patent Application Publication No. 2543328 similarly provides a method and apparatus for extruding plastics, rubber and other thermoplastics and elastomers, comprising two screw extruders, the first of which transfers the material to the second extruder. The downstream extruder is mechanically fixed to the upstream extruder and is equipped with a degasser in its inlet region. In addition, the supply point to the second extruder is located in the central region of this extruder. Between the supply point and the drive unit of the second extruder are both screw sections cut in the extrusion direction and screw sections cut in the opposite direction. An outlet for the material carried by the degasser is provided in the region of the counter-rotating screw section. This prevents material particles, which are generated by the bursting of bubbles during degassing and have a longer residence time in the extruder, from returning to the material flow. Instead, the material particles are guided to the outlet via the counter-rotating screw section.

[0007] European Patent Application Publication No. 0816048 describes an alternative method and another two-stage extrusion apparatus for extruding rubber compounds and plastics, with an exhaust device positioned between two stages. The first extrusion stage uses a gear extruder, while the second stage consists of a screw extruder. After the first extrusion stage, the extruded material is finely subdivided and / or divided via a dividing device located at or immediately after the end of this extrusion stage. Upon transition to the second extrusion stage, the subdivided extruded material reaches a space connected to a vacuum pump. The subdivided or divided material can either free-fall through this exhausted space, or be separated or peeled off by the extruder screw of the second stage of the dividing device, and in addition, can be taken from the dividing device and transferred to the deep screw flight region of the screw extruder, in which case this region is exhausted. The dividing device is formed in particular in the form of perforated plates in a perforated plate exchange device.

[0008] The above-mentioned solutions cannot always prevent porosity from occurring in tires or other industrial rubber products, because the degassing process is highly dependent on the amount of material in the space being degassed. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Swiss Patent No. 333283 [Patent Document 2] German Patent Application Publication No. 2543328 [Patent Document 3] European Patent Application Publication No. 0816048 [Overview of the project] [Problems that the invention aims to solve]

[0010] Against this backdrop, the fundamental problem underlying the present invention is to form a method of the type described at the beginning that can always ensure the removal of volatile components and / or contained gases from the plasticized material. [Means for solving the problem]

[0011] This problem is solved by the method according to the features of claim 1, according to the present invention. Further embodiments of the present invention are described in the dependent claims.

[0012] That is, the present invention envisions a method for extruding a material, such as a plastic, preferably a rubber compound, and more preferably a rubber compound mixed with highly active carbon black, such as TBR Cab compound, using a multistage extruder. Preferably, the multistage extruder is a two-stage extruder, for example, a tandem extruder. For extruding, the multistage extruder has at least two, preferably two, extruder stages, according to the present invention. The extruder stages are preferably connected to each other in a detachable manner and / or are movable apart when detached from each other, for example, are separable. This allows the extruder stages to be advantageously easily cleaned and / or maintained.

[0013] Furthermore, according to the present invention, the material is intended to be plasticized first in a first extruder stage of a multistage extruder for extrusion, and then transferred to another, preferably a second, extruder stage of the multistage extruder, so that the material is supplied to the first extruder stage accordingly. For example, preferably before, during, and / or after transfer to another extruder stage, the material is fragmented, i.e., divided and / or finely subdivided, through a dividing unit of the multistage extruder, according to the present invention, and in this state is exposed to a negative pressure region of the multistage extruder, particularly a negative pressure lowered compared to the ambient pressure, preferably a technical vacuum, thereby removing volatile components and / or contained gases from the material at least partially, preferably completely. Thus, the material is particularly degassed. The negative pressure region is preferably a transition section between the first extruder stage and another, particularly a second extruder stage. However, it is also conceivable that the negative pressure region is formed within a section of the first extruder stage, i.e., before the transition section, or within a section of another extruder stage, i.e., after the transition section. Furthermore, the transition section and the section of the first extruder stage before the transition section or the section of another extruder stage after the transition section can also be formed as a negative pressure region. Furthermore, the splitting unit can be formed as a sieve or a perforated disk, and can be formed to be detachably fixed and / or replaceable, for example, preferably within the housing of a replacement device. In this way, the splitting unit can be adapted to the material to be extruded, and by changing the geometric characteristics of the splitting unit, for example, the number of holes, the spacing between holes, and / or the hole diameter, process parameters such as the free surface of the material caused by fragmentation and / or the back pressure on the material being conveyed due to the splitting unit can be affected.

[0014] In addition, according to the present invention, in at least the normal mode, i.e., the manufacturing mode, of the multistage extruder, at least one material flow and / or at least one melting pressure of the material passing through the first extruder stage and / or another, particularly the second extruder stage, is automatically adapted, i.e., preferably controlled and / or adjusted, so that the negative pressure region is filled within a predetermined maximum amount of material permissible for removing components and / or gases, and / or the fragmented state of the material is maintained. This ensures that the negative pressure region of the multistage extruder is not over-supplied with material and that volatile components and / or contained gases are reliably removed from the plasticized material. This avoids porosity in products manufactured from the extruded material, such as tires or other industrial rubber products, which in turn ensures the mechanical strength and durability of the product.

[0015] In addition, in a particularly advantageous development of the present invention, at least in the normal mode of the multistage extruder, at least one sealing region of the multistage extruder, preferably indirectly or directly, leading to a negative pressure region in the conveying direction of another, particularly a second conveying stage, is preferably filled within the terminal section of the multistage extruder, thereby the material flow and / or melting pressure is adapted such that the material in the sealing region seals the negative pressure region with respect to at least the outlet opening of the multistage extruder, preferably the extrusion nozzle or mouthpiece. Preferably, the sealing region is completely filled with material. This also contributes to ensuring the removal of volatile components and / or contained gases from the material, because this can ensure a high negative pressure within the negative pressure range, particularly in combination with other sealing means.

[0016] Furthermore, in promising embodiments of the present invention, material flow adaptation is intended to be achieved at least, preferably when transitioning from the start mode to the normal mode of the multistage extruder, and especially when and / or as soon as a continuous material flow and / or melt pressure of material occupies the sealing region after the transition, by setting, preferably controlling and / or adjusting, the amount of material processed through another, particularly second, extruder stage to a target amount. Adherence to the target amount contributes to the stability of the entire extrusion process. The target amount minimizes the risk of process interruptions or failures in subsequent manufacturing steps, such as overfilling, material clogging, or undersupply. Setting the amount of material processed to the target amount is generally done, in particular, by changing the conveying capacity, for example, by changing the speed of the conveying unit of another, particularly second, extruder stage. Thus, exemplary, the target amount can be set by setting and / or approaching the speed of the conveying unit of another extruder stage to a target speed. Such a conveying unit or, as in the first extruder stage, could be, for example, an extruder screw or gear pump or at least one extruder gear. Therefore, the first extruder stage and / or the second extruder stage may be formed as a screw extruder or a gear extruder.

[0017] Generally, however preferably in relation to the embodiments described above, an advanced form of the present invention can be considered highly advantageous, in which the material flow is adapted by setting the -preferential-processing rate of material passing through the first extruder stage to a target processing rate that is reduced in particular to the -preferential-processing rate (i.e., the processing rate is reduced in particular to the target processing rate), at least when transitioning from the start mode to the normal mode of the multistage extruder, and particularly after the transition when a continuous material flow and / or melting pressure of material occupies the sealing region. This advantageously controls the transfer or supply of material to the second extruder stage. Setting the processing rate to the target processing rate can be done by changing the transport capacity, in particular by changing, preferably reducing, the speed of the transport unit of the first extruder stage. By appropriately reducing the processing rate in the first extruder stage to the target processing rate, the transfer or supply of material to the second extruder stage can be precisely controlled and / or adapted. For example, overfilling and / or overloading of a subsequent extruder stage can be prevented, and a stable material flow can be ensured. Therefore, it becomes possible to supply material to the second extruder stage uniformly and as needed. This contributes to the optimal utilization of the processing capacity of the second extruder stage, which in turn increases the overall efficiency of the extrusion process.

[0018] In preferred embodiments of the present invention, particularly in relation to the aforementioned advanced forms and / or embodiments, the target processing amount of material passing through the first extruder stage is set such that a continuous material flow and / or melting pressure occupies the sealing region, but a discontinuous material flow and / or melting pressure exists in a preferred conveying region of another, particularly a second extruder stage, upstream of the sealing region and / or downstream of the negative pressure region. This is very advantageous as it results in the conveying region not being completely filled with material, and the negative pressure region of the multistage extruder being filled with a predetermined maximum amount of material to be allowed to remove components and / or gases and / or maintaining a fragmented state of the material. That is, in this embodiment, the negative pressure region is not over-supplied with material.

[0019] In a promising embodiment of the present invention, to set and / or determine the target processing rate of material passing through the first extruder stage, the processing rate passing through the first extruder stage is reduced when a continuous material flow and / or continuous melting pressure of material is generated and / or occupied within the conveying area. Thus, by reducing the processing rate, the intended discontinuous material flow and / or melting pressure is initially achieved within the conveying area. However, the processing rate can be reduced to such an extent that it is no longer sufficiently high to set and / or maintain the intended continuous mass flow within the sealing area, thereby resulting in undesirable discontinuous material flow and / or melting pressure.

[0020] Furthermore, in an advanced form of the present invention, the target processing rate of the material passing through the first extruder stage is intended to be set and / or determined by reducing and then increasing the processing rate of the material passing through the first extruder stage when discontinuous material flow and / or melting pressure of material occurs and / or is present in the sealing region. In particular, when setting the target processing rate for discontinuous material flow and / or melting pressure in the conveying region, the processing rate, which has been reduced to the extent that continuous material flow and / or melting pressure of material occupying the sealing region transitions to discontinuous material flow and / or melting pressure of material, can be increased again, so that continuous material flow and / or melting pressure is generated again. Thus, advantageously, the target processing rate of the first extruder stage can be set to achieve discontinuous material flow and / or melting pressure in the conveying region and continuous material flow and / or melting pressure in the sealing region, in particular depending on the target processing rate of another extruder stage.

[0021] To set a target processing volume, the processing volume of material passing through the first extruder stage can be repeatedly reduced and increased. In particular, setting the target processing volume is preferably done by adjusting it via a control loop.

[0022] In particular, in connection with the above, the determined target throughput of the material through the first extruder stage is maintained for another normal mode following the new start-up mode, i.e., in particular for another manufacturing process, and / or is set as the throughput of the first extruder stage, at least tentatively, in another normal mode following the new start-up mode, i.e., in particular in another manufacturing process. Embodiments of the invention are advantageous in that the setting of the target throughput determined in the previous normal mode, i.e., in particular in the previous manufacturing process, allows for either a shorter setting time until the target throughput is set in another normal mode, especially when the same material is extruded again with the same process parameters and / or process conditions, or a complete elimination of such a setting time.

[0023] Furthermore, the setting and / or determination of the target throughput can be carried out by changing the conveying capacity, in particular by changing the speed of the conveying unit of the first extruder stage to the target speed, especially reducing it. Typically, the target speed is set by reducing the speed of the conveying unit of the first extruder stage until the continuous material flow and / or melt pressure of the material, which particularly occupies the sealing region, transitions to a discontinuous material flow and / or melt pressure of the material, at which point the discontinuous material flow and / or melt pressure occupies the conveying region and is increased again, thereby in particular causing a continuous material flow and / or melt pressure to occur again.

[0024] Furthermore, in a practical embodiment of the invention, at least in the start-up mode of a multi-stage extruder, in the negative pressure region, in particular immediately before and / or within the negative pressure region in the conveying direction, the material is conveyed through the first extruder stage until the material flow and / or melt pressure of the material at the nominal throughput occupies it. This advantageously results in a more efficient use of resources and reduces operating costs.

[0025] Furthermore, in one embodiment of the present invention, at least in the start-up mode of the multi-stage extruder, when the material flow and / or the melt pressure in the negative pressure region and / or within the negative pressure region occupy the nominal throughput, it is assumed that another, particularly the second extruder stage, is particularly shifted from the stationary state to the conveying state, and the throughput of another, particularly the second extruder stage, is set in a fixed relationship with respect to the nominal throughput of the first extruder stage. In this way, firstly, stable process conditions can be established and the extrusion of the material can be started with high quality. In addition, the amount of scrap material in the subsequent normal mode is reduced and the overall efficiency of the extrusion process is increased. In addition, the achievement of a stable material flow and / or melt pressure enables a flexible and controlled transition from the start-up mode to the normal mode.

[0026] The present invention allows for various embodiments. To clarify its basic principle further, some of them are illustrated in the drawings and will be described below.

Brief Description of the Drawings

[0027] [Figure 1] One embodiment of the method and the multi-stage extruder used therefor [Figure 2] Another embodiment of the multi-stage extruder having a vertical offset between the extruder stages

Embodiments for Carrying out the Invention

[0028] FIG. 1 shows one embodiment of the method according to the present invention, in which a material 4 is extruded by a multi-stage extruder 1, and the multi-stage extruder 1 has two extruder stages 2, 3. Accordingly, the multi-stage extruder 1 is particularly formed as a two-stage extruder or a tandem extruder.

[0029] For extrusion, the material 4 is first plasticized in the first extruder stage 2 of the multi-stage extruder 1 and then transferred to another, here the second extruder stage 3 of the multi-stage extruder 1.

[0030] In this configuration, to avoid the porosity of the extruded material 17, which consists of a highly active carbon black material 4, volatile components and / or gases are removed from the material 4 during its transfer from the first extruder stage 2 to the second extruder stage 3. For this purpose, the multistage extruder 1 includes a splitting device 5 fixed in a detachable manner in the transition section 11 between the first extruder stage 2 and the second extruder stage 3. Through the splitting device 5, via a perforated disk in this embodiment of the multistage extruder 1, the material 4 is fragmented by being pressurized in the transport direction 7 by the splitting device 5. In this fragmented state, the material 4 is subjected to a reduced negative pressure, preferably a technical vacuum, in a negative pressure region 6 of the multistage extruder 1 formed within the transition section 11 that directly follows the splitting device 5 in the transport direction 7. The negative pressure is provided via a negative pressure unit, not shown in detail, such as a negative pressure connection 18 connected to a vacuum pump.

[0031] In particular, to ensure optimal removal of volatile components and / or contained gases from the material 4 by avoiding oversupply of material 4 to the negative pressure region 6, the material flow and / or melting pressure of material 4 passing through the first extruder stage 2 and another extruder stage 3 are automatically adjusted in the normal mode of the multistage extruder 1 shown in Figure 1 so that the negative pressure region 6 is filled within a predetermined maximum amount of material 4 that is permissible for removing components and / or gases, and / or so that the fragmented state of material 4 is always maintained.

[0032] Furthermore, the material flow and / or melting pressure of the material 4 passing through the first extruder stage 2 and another extruder stage 3, in the normal mode of the multistage extruder 1, completely fills a sealing region 8 that indirectly follows a negative pressure region 6 in the transport direction 7 of the multistage extruder 1, thereby adapting the material 4 in the sealing region 8 to seal the negative pressure region 6 with respect to at least the outlet opening 9 of the multistage extruder 1. In this embodiment, the sealing region 8 is formed within the terminal section 12 of the second extruder stage 3. Furthermore, both the first extruder stage 2 and the second extruder stage 3 are pressure-tightly sealed at the respective drive-side bearings 13 of the transport units 14 and 15 of the extruder stages 2 and 3.

[0033] In a starting mode, not shown in detail, that precedes the normal mode of the multi-stage extruder 1, the material 4 is conveyed through the first extruder stage 2 until the material flow and / or melting pressure of the nominal processing amount of material 4 is occupied, particularly in the negative pressure region 6, here particularly just before the negative pressure region 6 in the conveying direction 7. This is done by transitioning the first extruder stage 2 from a stationary state to a conveying state and changing, in this case increasing, the conveying capacity of the conveying unit 14 of the first extruder stage 2, which is formed as an extruder screw. In particular, this is achieved by changing, in this case increasing, the speed of the conveying unit 14, which is formed as an extruder screw, to the nominal speed.

[0034] Next, in the starting mode of the multi-stage extruder 1, when the material flow and / or melting pressure occupies the nominal processing volume in the negative pressure region 6, another extruder stage 3 is transitioned from a stationary state to a conveying state, and the processing volume of the other extruder stage 3 is initially set to a fixed relationship with the nominal processing volume of the first extruder stage 2. Furthermore, this is done by changing, again increasing, the conveying capacity of the conveying unit 15 of the second extruder stage 3, which is similarly formed as an extruder screw, until the speed of the conveying unit 15 is fixed to the nominal speed of the conveying unit 14 of the first extruder stage 2.

[0035] Therefore, in this embodiment, the first extruder stage 2 and the second extruder stage 3 are each formed as screw extruders.

[0036] Automatic adjustment of the material flow and / or melting pressure of material 4 is performed by setting the processing amount of material 4 through another, in this case a second extruder stage 3, to a target processing amount when the continuous material flow and / or melting pressure of material 4 occupies the sealing area 8 after the multistage extruder 1 transitions from the start mode to the normal mode. Furthermore, the setting of the target processing amount is performed by setting the speed of the conveying unit 15 of another, in this case a second extruder stage 3, to a target speed and / or approaching this target speed.

[0037] Furthermore, automatic adjustment of the material flow and / or melting pressure of material 4 is also performed by setting the amount of material 4 passing through the first extruder stage 2 to a reduced target amount when a continuous material flow and / or melting pressure of material 4 occupies the sealing region 8 in normal mode.

[0038] The target processing amount of material 4 passing through the first extruder stage 2 is provisionally set such that, as shown in Figure 1, a continuous material flow and / or melting pressure of material 4 occupies the sealing region 8, but similarly, as can be seen from Figure 1, discontinuous material flow and / or melting pressure of material 4 exist in the transport region 10 of the multistage extruder 1, which is formed in the transport section 16 of the multistage extruder 1 upstream of the sealing region 8 and downstream of the negative pressure region 6 in the transport direction 7 of the multistage extruder 1. In particular, the transport section 16 is part of the second extruder stage 3.

[0039] To achieve this, the target processing rate of material 4 passing through the first extruder stage 2 is set and / or determined by reducing the processing rate passing through the first extruder stage 2 when a continuous material flow and / or continuous melting pressure of material 4 occurs and / or occupies the conveying area 10. In addition, the processing rate of material 4 passing through the first extruder stage 2 is increased again after being reduced when a discontinuous material flow and / or melting pressure of material 4 occurs and / or is present in the sealing area 8. In this way, the target processing rate can be set, in particular adjusted and determined, especially through multiple iterations of reducing and increasing the processing rate of material 4 passing through the first extruder stage 2.

[0040] The determined target processing amount of material 4 passing through the first extruder stage 2 is then maintained for another normal mode following a new start mode, and / or set at least provisionally as the processing amount of the first extruder stage 2 in another normal mode following a new start mode.

[0041] Furthermore, the target processing volume is set and / or determined by setting the speed of the conveying unit 14 of the first extruder stage 2 to the target speed, in particular by reducing and / or increasing it.

[0042] Furthermore, Figure 2 shows one embodiment of a multi-stage extruder 1 formed as a two-stage extruder having a first extruder stage 2 and a second extruder stage 3. A negative pressure region 6 is again formed in the transition section 11 between the first extruder stage 2 and the second extruder stage 3, which follows the dividing device 5 in the transport direction 7. In this embodiment, the material 4, which is not shown in detail, falls through the negative pressure region 6 at least due to gravity when transferred from the first extruder stage 2 to the second extruder stage 3, because there is a difference in distance, i.e., height, in the vertical axis direction between the cylinder 19 of the first extruder stage 2 and the cylinder 20 of the second extruder stage 3. Transfer is indicated by arrows. [Explanation of Symbols]

[0043] 1. Multistage extruder 2 Extruder Stages 3 Extruder Stages 4 Materials 5-part unit 6. Negative pressure region 7. Conveying direction 8 Sealing area 9 Exit opening 10 Transport Area 11 Transition Section 12 Terminal section 13 Bearings 14 Conveyor Unit 15 Conveyor Unit 16 Transport Sections 17 Extruded 18. Negative pressure connection 19 cylinders 20 cylinders

Claims

1. A method for extruding a material (4) by a multistage extruder (1) having at least two extruder stages (2, 3), wherein the material (4) is plasticized in a first extruder stage (2) of the multistage extruder (1), then transferred to another, preferably a second, extruder stage (3) of the multistage extruder (1), fragmented through a splitting unit (5) of the multistage extruder (1), and in this state subjected to negative pressure, preferably a technical vacuum, in a negative pressure region (6) of the multistage extruder (1), thereby removing volatile components and / or contained gases from the material (4), at least partially. A method characterized in that, in the normal mode of at least the multistage extruder (1), the negative pressure region (6) is filled within a predetermined maximum amount of material (4) to be permissible for removal of components and / or gases, and / or the fragmented state of the material (4) is maintained, such that at least one material flow and / or at least one melting pressure of the material (4) passing through the first extruder stage (2) and / or another extruder stage (3) is automatically adapted.

2. The method according to claim 1, characterized in that, in at least the normal mode of the multistage extruder (1), at least one sealing region (8) connected to the negative pressure region (6) in the conveying direction (7) of the multistage extruder (1) is particularly completely filled, and the material flow and / or melt pressure is adapted such that the material (4) in the sealing region (8) seals the negative pressure region (6) with respect to at least the outlet opening (9) of the multistage extruder (1) for the material (4).

3. The method according to claim 1 or 2, characterized in that the material flow and / or melt pressure adjustment is performed by setting the processing amount of material (4) passing through another extruder stage (3) to a target processing amount, at least when transitioning from the starting mode to the normal mode of the multistage extruder (1), and particularly after the transition when a continuous material flow and / or melt pressure of material (4) occupies the sealing region (8).

4. The method according to at least one of claims 1 to 3, characterized in that the material flow and / or melt pressure is adjusted by setting the processing rate of material (4) passing through the first extruder stage (2) to a reduced target processing rate, at least when the multistage extruder (1) is transitioning from a starting mode to a normal mode, and particularly after the transition when a continuous material flow and / or melt pressure of material (4) occupies the sealing region (8).

5. The method according to at least one of claims 1 to 4, characterized in that the target processing amount of material (4) passing through the first extruder stage (2) is set such that a continuous material flow and / or melt pressure of the material occupies the sealing region (8), but discontinuous material flow and / or melt pressure of the material (4) exists in the transport region (10) of the multistage extruder (1) upstream of the sealing region (8) and / or downstream of the negative pressure region (6) in the transport direction (7) of the multistage extruder (1).

6. The method according to at least one of claims 1 to 5, characterized in that the target processing amount of material (4) passing through the first extruder stage (2) is set and / or determined by reducing the processing amount passing through the first extruder stage (2) when a continuous material flow and / or continuous melting pressure of material (4) is generated and / or occupied within the conveying area (10).

7. The method according to at least one of claims 1 to 6, characterized in that the target processing amount of material (4) passing through the first extruder stage (2) is set and / or determined by increasing the processing amount of material (4) passing through the first extruder stage (2) particularly after it has been reduced, when discontinuous material flow and / or melt pressure of material (4) is generated and / or present within the sealing region (8).

8. The method according to at least one of claims 1 to 7, characterized in that a determined target processing amount of material (4) passing through a first extruder stage (2) is maintained for another normal mode following a new start mode, and / or is set at least provisionally as the processing amount of the first extruder stage (2) in another normal mode following a new start mode.

9. The method according to at least one of claims 1 to 8, characterized in that, at least in the starting mode of the multistage extruder (1), the material (4) is conveyed through the first extruder stage (2) to the point where the material flow and / or melting pressure of the nominal processing amount of material (4) occupies the negative pressure region (6), particularly in the conveying direction (7) immediately before and / or within the negative pressure region (6).

10. The method according to at least one of claims 1 to 9, characterized in that, at least in the starting mode of the multistage extruder (1), when the material flow and / or melt pressure occupies the negative pressure region (6) and / or the negative pressure region (6) at a nominal processing rate, another extruder stage (3) is transitioned, in particular, from a stationary state to a conveying state, and the processing rate of the other extruder stage (3) is set, at least initially, to a fixed relationship with respect to the nominal processing rate of the first extruder stage (2).

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