Method and apparatus for processing polymeric materials

Abstract

The invention relates to a method and a device for processing or treating polymer materials, in particular thermoplastic waste plastics for the purpose of recovery, in which the polymer material to be processed is processed in a container (1) or a cutting compactor by means of at least one rotatable or rotatable tool (3a, 3b), wherein, if necessary, a plurality of rotatable or rotating tools (3a, 3b) are moved, mixed, heated and if necessary, and wherein the bulk or granular polymer material is subsequently discharged from the container (1) and fed into a conveyor (6), in particular an extruder (6), preferably a twin-screw or multi-screw extruder, in order to be compacted and melted or agglomerated, in particular there. According to the invention, the torque of the conveyor (6) is measured, and the rotational speed of the tool or of at least one of the plurality of tools (3a, 3b) is controlled or varied as a function of the torque of the conveyor (6).

Description

Field of the Invention

[0001] The present invention relates to a method and an apparatus for processing or treating polymeric materials as defined in the preambles of claims 1 and 16, in particular thermoplastic waste plastics for recycling purposes. Background Art

[0002] Methods and apparatuses for treating polymeric waste (in particular different thermoplastics) using a combination of a container or a pre-treatment unit (PCU) and a conveyor (in particular an extruder) connected thereto are well known.

[0003] Typically, a device for pre-treating the material to be processed is connected upstream of the extrusion system, such as a known cutting compactor or a pre-treatment unit (PCU), which is mostly a container directly connected to the extruder and having a rotary tool. Upstream of the extrusion process, the purpose of the treatment steps in the PCU is in particular to correspondingly change the shape and properties of the polymeric material. For this purpose, energy needs to be purposefully introduced into the material. Thermoplastic materials are in particular mixed, heated, softened, compacted, pre-degassed, dried, dehumidified, cut, crushed, crystallized and / or homogenized in the pre-treatment unit, and their bulk density is increased.

[0004] The polymer pre-treated in this way is then discharged into the extruder for compaction, in particular melting. Such a combined device has long been known, for example from EP2558263 or EP2689908.

[0005] The filling or loading process of the conveyor or extruder connected to the container is also assisted by the rotating mixing and crushing tools in the container or PCU. When the filling degree of the screw remains constant and high enough, the conveying process and the extrusion process are usually particularly effective. Therefore, the loading area of the conveyor or extruder is relatively sensitive and has a significant impact on the final result or the quality of the recycled material. In this regard, for example, the distance between the mixing and crushing tools and the screw of the conveyor or extruder, the shape and size of the loading opening, the rotation direction of the mixing tool relative to the conveying direction of the conveyor or extruder, etc. play a role. Of course, the profile of the screw teeth, the shape of the screw base and the free open surface of the screw groove on the side of the conveyor or extruder also play a role. If the feeding behavior of the conveyor or extruder is poor, for example, a pumping phenomenon of the volumetric output may occur, that is, the output changes over time, which is not conducive to reliable operation and the quality of the recycled material.

[0006] Therefore, in the prior art, there are many attempts to structurally adjust the sensitive areas of the loading or feeding of the conveyor or extruder or to design them in such a way as to assist the feeding behavior and feeding of the screw in the best possible way, and for example, to also improve the tolerance to material differences caused by operating conditions.

[0007] In particular, in order to obtain special material qualities and compound these materials, in addition to single-screw extruders, twin-screw or multi-screw extruders are also used. These extruder systems are likewise directly connected to the PCU. Here, the lowermost tool plane of the container feeds the pre-treated material into the extrusion device, and the lowermost tool plane is preferably formed by a disk on which tools can be mounted and is located in the region of the extruder opening.

[0008] The number of filling cycles of the tools in the lowermost tool plane in the conveyor opening or the extruder opening region generally has a special influence on the filling degree of the conveyor or the extruder. In addition, the average bulk density of the material in the PCU (especially in the lowermost region of the PCU), which corresponds to the average degree of compaction, also affects the filling degree together. Here, whether the conveyor or the extruder is filled from the side or in the region of the twin-screw gusset plate, or in which rotational direction of the tool the conveyor opening or the extruder opening is filled, is relatively immaterial.

[0009] The material fed into the conveyor or the extruder is immediately conveyed further, resulting in a filling-degree-related torque variation curve of the drive of the conveyor or the extruder. In principle, an attempt is made to keep the torque variation curve of the conveyor or the extruder or the filling degree of the conveyor or the extruder as constant as possible. This results in a high-quality melting of the polymer without shear peaks that could lead to too high a temperature of the polymer melt. If the conveyor or the extruder is fed too little, i.e., the filling degree is too low, it may lead to a loss of output and shear peaks, but may also lead to poor polymer homogenization. Therefore, keeping the filling degree of the conveyor or the extruder constant is advantageous for the quality and economy of the recyclate.

[0010] Figure 4 An unfavourable torque variation related to the tool speed of the extruder is illustrated by way of example. Here, for example, in order to try to meet the requirements regarding the humidity, degree of compaction and material temperature of the input material in the PCU, the tool speed is changed, which results in significant fluctuations in the extruder torque and the tool speed, which is especially unfavourable for the feeding behaviour and the material quality.

[0011] Mixing the material only in the PCU can buffer any fluctuations in the bulk density of the input material to a certain (small) extent. However, in some cases, mixing alone and the usually intensive pre-treatment of the material in the PCU are not sufficient, and it is not possible to keep the bulk density sufficiently constant for a long time in all cases. Instead, the bulk density of the treated material fluctuates around the average value over time. This is unfavourable and results in the aforementioned disadvantages. Summary of the Invention

[0012] Accordingly, the object of the present invention is to provide a method and a device for processing polymer materials of the type mentioned at the beginning, by means of which the filling level of a conveyor or an extruder can be kept as constant as possible.

[0013] According to the method, this object is achieved by the features of the characterizing part of claim 1. Accordingly, a method for processing or treating polymer materials, in particular thermoplastic waste plastics for recycling purposes, is provided, wherein the polymer material to be processed is moved, mixed, heated and, if necessary, comminuted in a container or a cutting compactor or a pretreatment unit (PCU) by means of at least one rotatable or revolving tool, and, if necessary, a plurality of rotatable or revolving tools, and subsequently the lumpy or granular polymer material is discharged from the container and fed into a conveyor or an extruder, in particular for further compaction and melting or agglomeration there.

[0014] According to the invention, the torque of the conveyor or the extruder is measured, and the rotational speed of at least one of the tools or the plurality of tools is controlled or changed as a function of the measured torque of the conveyor or the extruder.

[0015] According to the device, this object is achieved by the features of the characterizing part of claim 16. Accordingly, a device for processing or treating polymer materials (in particular thermoplastic waste plastics for recycling purposes) is provided, which is particularly suitable for carrying out the method described above, and which has at least one container or a cutting compactor or a pretreatment unit (PCU) for the material to be processed, wherein at least one tool, and, if necessary, a plurality of tools, which are rotatable or revolvable about a shaft, are arranged in the container for moving, mixing, heating and, if necessary, comminuting the material, and wherein a container opening is formed in the container through which the pretreated material can be discharged from the interior of the container. The container opening is in particular formed in the side wall of the container, in particular in the region or at the height of the lowermost or bottom-nearest tool. In addition, at least one conveyor or extruder is provided for receiving the material discharged from the container via the container opening.

[0016] According to the invention, a measuring device for measuring the torque of the conveyor or the extruder is provided and a control device which is communicatively connected or in data communication with the measuring device is provided, which control device is used to control the rotational speed of at least one of the tools or the plurality of tools, wherein the control device is configured and / or arranged to control the rotational speed of the tool as a function of the torque of the conveyor or the extruder. Accordingly, the control device controls the rotational speed of the tool as a function of the torque of the conveyor or the extruder measured by the measuring device.

[0017] Accordingly, according to the present invention, the torque of the conveyor or extruder directly affects, controls or changes the rotational speed of the tool or the plurality of tools rotating in the PCU or the container. By adjusting the rotational speed of the tool in this way, the filling cycle (Stopfzyklen) of the conveyor system or the extruder system will be directly affected, and accordingly the degree of filling of the screw thread grooves of the conveyor or the extruder will change, which in turn will change the torque of the conveyor or the extruder. In this way, the degree of filling of the conveyor or the extruder can be kept constant. The feeding behavior of the screw is improved and the output and output stability are also improved. As a result, the entire system composed of the cutting compactor and the conveyor or the extruder becomes more stable and has stronger performance. In addition, the quality of the obtained polymer material can be improved and the economy during operation can be increased.

[0018] In principle, the effects mentioned are relevant and present for all conveyors or extruders, that is, they apply not only to the compaction screws of extruders or granulators, but also to screws with mainly or only conveying functions, with no or low compaction.

[0019] The general term "conveyor" can be understood in this context both as a device with a non-compacting or decompacting screw and as a device with a compacting screw, that is, an extruder screw with an agglomerating or plasticizing effect.

[0020] The term "extruder" or "extruder screw" can be understood in this context both as a conveyor or conveying screw that can completely or partially melt the material, that is, a conventional extruder, and as a conveyor or conveying screw that can only agglomerate the softened material without melting it. Using such a screw for agglomeration or an agglomerating screw, the material is only compacted and sheared violently for a short time, but not plasticized. Therefore, the material provided by the agglomerating screw at its outlet is not completely melted, but consists of particles that are only melted on their surface and are bonded together like by sintering. But in both cases, the material is pressurized and compacted when being conveyed through the screw.

[0021] Systems for measuring the torque of a conveyor or an extruder are known. For example, in an extruder, a torque detection unit can be arranged in the connection area between the output shaft of the transmission and the extruder shaft for non-contact detection of the torque that can be transmitted to the extruder shaft through the output shaft of the transmission and the connection area. Other systems for continuously monitoring the torque of a conveyor or an extruder are also known, such as torque sensors based on the magnetostrictive principle. Such systems are mainly used to identify and eliminate possible overload situations, so that the extruder can operate, for example, closer to the load limit to increase the drive power or torque density.

[0022] Advantageously, the torque of the conveyor or extruder is measured continuously at defined, in particular regular, time intervals. The corresponding feature of an advantageous device is that the measuring device is configured and arranged to measure the torque of the conveyor or extruder continuously at defined, in particular regular, time intervals.

[0023] This means that during the duration of the method, the torque is measured either at predefined time points or at defined time intervals and the data is transmitted to the control device so that changes can be reacted to quickly and continuously and the rotational speed of the tool can be adjusted.

[0024] Advantageously, the conveyor or extruder runs at a fixed rotational speed. The corresponding feature of an advantageous device is that the control device is configured and arranged to run the conveyor or extruder at a fixed rotational speed.

[0025] If the conveyor or extruder runs at a fixed rotational speed nEx = constant [rpm], then in the case of a varying rotational speed nW [rpm] of the tool, each rotational speed nEx will result in a different filling cycle. This changes the degree of filling of the screw channels and thus the torque MEx [Nm] of the conveyor or extruder.

[0026] Advantageously, the rotational speed of the tool is reduced when the torque of the conveyor or extruder increases, or the rotational speed of the tool is increased when the torque of the conveyor or extruder decreases. The corresponding feature of an advantageous device is that the control device is configured and arranged to reduce the rotational speed of the tool when the torque of the conveyor or extruder increases, and / or to increase the rotational speed of the tool when the torque of the conveyor or extruder decreases.

[0027] The rotational speed nWE [rpm] of the tool in the PCU is defined as a function of the torque MEx [Nm] of the conveyor or extruder. Correspondingly, if the rotational speed of the tool is reduced as the torque of the conveyor or extruder increases, this will result in a reduced filling cycle, and thus a lower degree of filling of the conveyor or extruder or the screw channels of the conveyor or extruder. This in turn results in a decrease in the torque of the conveyor or extruder. This situation can be adjusted accordingly by a PID controller.

[0028] Advantageously, the rotational speed of the tool is controlled such that the torque of the conveyor or extruder remains constant or the torque fluctuations are less than + / - 5%, preferably less than + / - 3%. The corresponding feature of an advantageous device is that the control device is configured to adjust the rotational speed of the tool such that the torque of the conveyor or extruder remains constant or in a half-load state (halbbar), or the torque fluctuations are less than + / - 5%, preferably less than + / - 3%.

[0029] In this way, it can be achieved that the torque curve of the conveyor or extruder remains as constant as possible and peaks or large variations are avoided.

[0030] Advantageously, the rotational speed of the tool is controlled such that the degree of filling of the conveyor or extruder remains constant or the fluctuations in the degree of filling are small / less than + / - 10%, preferably less than + / - 5%. The corresponding feature of an advantageous device is that the control device is configured and arranged to adjust the rotational speed of the tool such that the degree of filling of the conveyor or extruder remains constant or at a semi-filled state, or the fluctuations in the degree of filling are small / less than + / - 10%, preferably less than + / - 5%.

[0031] As described at the beginning, it is also meaningful to keep the degree of filling (defined in kg / revolution) of the conveyor or extruder or the screw of the conveyor or extruder as constant as possible in terms of the quality and economy of the final product. The degree of filling of the conveyor or extruder can be determined or calculated in a practical way, or can be done, for example, by pressure measurement or ultrasonic measurement in the screw, as described in AT505618B1.

[0032] However, sometimes the material handling or pre-treatment follows different rules than the loading of the conveyor or extruder. For example, different parameters in the input material (such as widely varying humidity) may make it necessary to maintain a relatively high rotational speed of the tool in order to introduce sufficient energy into the material for a preset tool setting, for example to simultaneously maintain moisture evaporation and achieve compaction. Therefore, the degree of freedom of the rotational speed of the tool may be restricted.

[0033] Advantageously, the rotational speed of the tool is controlled such that the rotational speed of the tool is not lower than a determined minimum rotational speed. The corresponding feature of an advantageous device is that the control device is configured such that the rotational speed of the tool is not lower than a determined minimum rotational speed.

[0034] In this way, it is ensured that the torque of the conveyor or extruder remains as constant as possible, but at the same time sufficient energy can be introduced into the material to be processed. To compensate for different parameters in the input material and ensure good processing, it is advantageous that the rotational speed of the tool can also be adjusted independently of the torque of the conveyor or extruder, in particular increased. The corresponding feature of an advantageous device is that the rotational speed of the tool can also be adjusted independently of the torque of the conveyor or extruder, in particular increased.

[0035] Therefore, greater flexibility can be achieved in the processing, and for example, it can respond to the differences in the material to be processed. Especially under certain requirements, the rotational speed of the tool must be higher and cannot be reduced, because otherwise too little energy will be introduced into the material.

[0036] Advantageously, the tools in the container are arranged in at least two vertically stacked tool planes. A corresponding feature of an advantageous device is that a plurality (at least two) of the tools in the container are arranged in different tool planes, or at different distances from the bottom surface or in the lowermost region of the container, and the tools in the container are arranged in at least two vertically stacked tool planes.

[0037] Generally, the material to be processed is fed into the container from above, passes through the container from top to bottom within a certain residence time, and is heated, softened and mixed in the process, and then is discharged from below into a conveyor or an extruder. Arranging a plurality of tools at different heights or distances from the bottom surface facilitates advantageous processing and increases flexibility.

[0038] Advantageously, the lowermost tool plane is arranged in the region or at the height of the feed opening of the conveyor or the extruder. A corresponding feature of an advantageous device is that the lowermost tool plane is arranged in the region or at the height of the opening of the container or the feed opening of the conveyor or the extruder connected to the opening of the container.

[0039] This ensures effective filling of the conveyor or the extruder.

[0040] Advantageously, the tools in each tool plane can be rotated at different rotational speeds independently of each other, in particular by separate drives. A corresponding feature of an advantageous device is that the tools in each tool plane can be rotated at different rotational speeds independently of each other, in particular by separate drives.

[0041] This also increases the flexibility of processing. For this purpose, two or more different drives can be used, the rotational speeds of which can be correspondingly affected. Here, the tools can be driven from above, below or from the periphery.

[0042] Advantageously, the rotational speed of the tools in the lowermost tool plane is controlled according to the torque of the conveyor or the extruder. A corresponding feature of an advantageous device is that the rotational speed of the tools in the lowermost tool plane is controlled by a control device according to the torque of the conveyor or the extruder.

[0043] In this way, the rotational speed of the tools in the lowermost tool plane (i.e., in the region of the filling opening of the conveyor or the extruder) can be controlled according to the torque of the conveyor or the extruder. The rotational speeds of the tools in other higher tool planes can be controlled according to the torque of the conveyor or the extruder, but this is not necessary, that is to say, these tools can also be rotated at a defined or adjustable rotational speed that is independent of the torque of the conveyor or the extruder, or without torque control by a control device.

[0044] In this way, for example, the polymer material in the upper region of the container can be processed using a higher rotational speed and a correspondingly higher energy input (i.e., at a higher temperature). The rotational speed of the tool is correspondingly adjusted in the lower region of the PCU to keep the torque or filling level of the conveyor or extruder constant. This enables a degree of freedom or decoupling between the pre-treatment of the material in the container and the loading of the conveyor or extruder.

[0045] Advantageously, it can also be that only the rotational speed of the tools in the lowermost tool plane is controlled according to the torque of the conveyor or extruder, while the rotational speed of one or more tools in one or more other upper tool planes is controlled or adjusted independently of the torque of the conveyor or extruder. The corresponding feature of an advantageous device is that only the rotational speed of the tools in the lowermost tool plane is controlled according to the torque of the conveyor or extruder, while the rotational speed of one or more tools in one or more other upper tool planes is controlled or adjusted independently of the torque of the conveyor or extruder.

[0046] Here, the rotational speed of the tools in the other upper tool planes is not controlled according to the torque of the conveyor or extruder, but is controlled in other ways, which is not optional but mandatory. Advantageously, the rotational speed of all tools in each tool plane can also be separately controlled independently of each other according to the torque of the conveyor or extruder. The corresponding feature of an advantageous device is that the rotational speed of all tools in each tool plane is separately controlled independently of each other according to the torque of the conveyor or extruder.

[0047] Therefore, the rotational speed of all tools in all tool planes is controlled by torque, but can be adjusted separately independently of each other or individually.

[0048] Advantageously, the rotational speed of one or more tools in one or more other upper tool planes can also be adjusted such that a determined material temperature is reached in this region. Similarly advantageously, the temperature of the material is measured in this region, and the rotational speed of one or more tools in one or more other upper tool planes is controlled or changed according to the material temperature. The corresponding feature of an advantageous device is that the rotational speed of one or more tools in one or more other upper tool planes is adjusted such that a determined material temperature is reached in this region, and / or the rotational speed of one or more tools in one or more other upper tool planes is controlled or changed according to the material temperature.

[0049] These tools are advantageously disks, rods or beams, especially with cutting tools arranged thereon.

[0050] If these tools are arranged in multiple tool planes, especially with multiple disks stacked on top of each other, they can but do not have to be of the same size, so these tools can also have different sizes or diameters.

[0051] A favorable device is characterized in that the conveyor has at least one compaction screw and is configured as a single-screw extruder. Advantageously, the conveyor especially has a plurality of compaction screws. Particularly advantageously, the conveyor is a twin-screw extruder, especially a co-rotating twin-screw extruder. Therefore, in practice, it is particularly advantageous to achieve the effect of good filling degree, especially in a twin-screw extruder or a multi-screw extruder. In particular, for co-rotating, intermeshing twin-shaft or multi-shaft extruders (regardless of whether the screws are parallel or tapered in the feed area), the number of filling cycles in the lowest tool plane in the opening area of the extruder has a special influence on the filling degree of the extruder system, thus causing the torque curve of the extruder drive to depend on the filling degree.

[0052] For the feeding behavior, it is also particularly advantageous that the tools of the cutting compactor feed the pre-treated material into the feed opening of the conveyor or the extruder or assist in this process. This especially depends on the rotation direction of the screw and the rotation direction of the tool. It has proven advantageous in this regard that in the area in front of the container opening or in the area in front of the feed opening or the feeding opening of the conveyor or the extruder, the rotation direction of the tool in the lowest plane is substantially opposite or reverse to the conveying direction of the conveyor or the extruder. Such an arrangement is basically known, for example, from document EP2558263B1 or document EP2689908B1, and is hereby incorporated by reference into this disclosure document.

[0053] Particularly advantageously, the longitudinal axis of the conveyor or the screw or the longitudinal axis of the screw closest to the feed opening or the inner side of the inner wall of the housing or the screw housing is tangent to the inner side of the side wall of the container, wherein preferably, the screw is connected to the drive at its end face and transports to the discharge opening (especially the extrusion head) arranged at the end of the housing at its opposite end.

[0054] Furthermore, it is advantageous that the opening in the PCU is directly and indirectly connected to the feed opening without a long spacing or a transfer section (such as that of the conveying screw). Thus, an effective and gentle material transfer can be achieved.

[0055] A favorable device is further characterized in that the container is cylindrical or conical. However, the container does not necessarily have to have a cylindrical shape, although this shape is advantageous for practical and manufacturing technology reasons. For a container shape deviating from the cylindrical shape (such as a frustum-shaped container or a cylindrical container with an elliptical / oval bottom), assuming that the height of the virtual container is equal to its diameter, it can be converted into a cylindrical container with the same capture volume. In this case, if the container height (taking into account the safety spacing) significantly exceeds the formed mixing vortex, this container height is not considered because such an excessive container height is not utilized and thus no longer affects the material processing.

[0056] A favorable device is characterized in that the conveyor or extruder is tangentially connected to the container and / or the housing of the conveyor or extruder has a feed opening located in its end face or in its shell wall for the material to be captured by one or more screws of the conveyor or extruder, and this feed opening is connected to the container opening.

[0057] In another favorable design, the receiving container can be substantially cylindrical and have a flat bottom surface and a cylindrical shell-shaped side wall oriented perpendicular thereto. Additionally, if the axis of rotation of one or more tools coincides with the central axis of the receiving container, the structure can be simplified. In another favorable embodiment, the axis of rotation of one or more tools or the central axis of the container is oriented perpendicular to and / or orthogonal to the bottom surface. This also applies to conical containers. Through these special geometries, the feeding behavior can be optimized in a structurally stable and simply constructed device.

[0058] Also favorable in this regard is that the tool (or, if there are multiple tools stacked one above the other, the lowermost tool closest to the bottom surface) and the opening are at a relatively small distance from the bottom surface, especially arranged in the region of the lowermost quarter of the height of the receiving container. This distance is defined and measured as the distance from the lowermost edge of the opening or feed opening to the bottom of the container in the edge region of the container. Since the angular edges are usually designed to be rounded, this distance is measured from the lowermost edge of the opening along the imaginary extension of the side wall downward until the imaginary extension of the bottom of the container outward. A suitable distance is 10 to 400 mm.

[0059] Furthermore, it is favorable for processing if the radially outermost edge of the tool abuts against the side wall of the container.

[0060] Particularly favorable is a device having a cutting compactor or a pre-treatment unit (PCU), which has at least one mixing and crushing tool rotatable or revolving around a shaft and has a container opening formed in the side wall of the cutting compactor in the height region of the lowermost tool closest to the bottom surface. A twin-screw extruder is tangentially connected to this container opening and conveys the pre-treated material into it.

[0061] Other advantages and design aspects of the present invention can be derived from the description and the drawings. In the drawings, the present invention is schematically shown by non-limiting embodiments and will be described exemplarily below in conjunction with the drawings. Description of the Drawings

[0062] Figure 1 The first embodiment of the device according to the present invention is shown;

[0063] Figure 2 Another embodiment of the device according to the present invention is shown;

[0064] Figure 3 Shows yet another embodiment of the device according to the present invention;

[0065] Figure 4 Shows the results of a comparative test not according to the present invention;

[0066] Figure 5 Shows the results of the comparative test. Detailed implementation manner

[0067] Figure 1 Shows a first advantageous embodiment of a device for processing or treating polymeric materials according to the present invention, which polymeric materials are in particular thermoplastic waste plastics for recycling purposes. The basic structure and basic functions of such a cutting compactor - extruder combination are well known, for example from documents EP2558263 or EP2689908, and will be briefly described below. In addition, it should be noted that Figures 1 to 3 the illustrations are only schematic.

[0068] Figure 1 The device shown includes a cylindrical container or cutting compactor or pretreatment unit (PCU) 1 for receiving the polymeric material to be processed. Such a container 1 is well known, for example, from document EP123771. The container 1 is cylindrical and has a flat bottom surface and a cylindrical shell - shaped side wall 4 oriented perpendicular thereto.

[0069] Arranged in the container 1 is a rotatable or rotating tool 3a. Here, the tool 3a is a flat carrier disk arranged at a small distance from the bottom surface, rotating around a rotating shaft and oriented parallel to the bottom surface, with cutting tools 7 mounted on its upper side. The carrier disk is driven to rotate by a motor 300a via a shaft 2a, where the motor 300a is located below the container 1. Here, the rotating shaft or shaft 2a is arranged on the central longitudinal axis or central axis of the container 1. The tool 3a is mainly used to move, mix, heat and break up the material in the container 1. Correspondingly, the thermoplastic material in the container 1 is in particular mixed, heated, softened, compacted, pre - degassed, dried, dehumidified, cut, broken up, crystallized and / or homogenized, and its bulk density is increased. By the rotation of the tool 3a, a mixing vortex is formed in the material, and the material stays in the container 1 for a certain period of time and undergoes corresponding pretreatment there.

[0070] In the side wall 4 of the container 1, a container opening 5 is formed at the height of the only tool 3a in the current case or at the height of the lowest tool plane 30a. The housing or feed opening of a conveyor 6 (here a compacting twin - screw extruder 6) is tangentially connected to the container opening 5. Especially for multi - screw extruders, feeding is particularly sensitive, so a constant feed rate at as constant a level as possible is crucial.

[0071] The outer edge of the tool 3a is quite close to the side wall 4, about 5% of the radius. The screw of the extruder 6 close to the container is adapted to the contour of the inner wall 4 of the container 1 in the area of ​​the container opening 5 and is set back. No part of the extruder 6 protrudes into the interior space of the container 1. These tools 3a or knives 7 are located at approximately the same height or plane as the central longitudinal axis of the extruder 6.

[0072] In actual operation, the plastic material to be processed is usually fed into the container 1 in the form of plastic waste, bottles or films. The fed plastic material is especially crushed and mixed by the rotating tool 3a, and at the same time heated and softened by the introduced mechanical friction energy, but not melted. The softened but unmelted material is discharged from the container 1 through the container opening 5 after a certain residence time in the container 1 and is conveyed to the extruder 6 or fed to the extruder 6 in this way.

[0073] In the present embodiment, the extruder 6 is a known conventional co-rotating twin-screw extruder, in which the softened plastic material is melted in a first zone, followed by compaction, and then the polymer melt is discharged or pelletized at the opposite side.

[0074] According to the invention, a measuring device (not shown here) is provided for measuring the torque of the extruder 6 or of the two extruder screws. Such torque measuring devices for extruders are known. In addition, a control device (also not shown) is provided, which is connected in communication or data communication with the measuring device, for controlling the rotational speed of the tool 3a. The control device controls the rotational speed of the tool 3a as a function of the torque of the extruder 6 measured by the measuring device, wherein the torque of the extruder 6 is continuously measured at defined, appropriately reduced time intervals and the data are transmitted to the control device in order to be able to react quickly and continuously to changes and adjust the rotational speed of the tool 3a.

[0075] In this case, the rotational speed of the tool 3 a is controlled in such a way that the torque of the extruder 6 remains essentially constant and the torque fluctuations are less than + / −5%.

[0076] By adjusting the rotation speed of the tool 3a in the above-described manner, the filling cycle in the extruder 6 is directly influenced and the filling degree of the screw groove of the extruder 6 changes accordingly, and thus the torque of the extruder 6 changes accordingly. In this way, the filling degree of the extruder 6 can be kept very constant (see Example 1 below).

[0077] Figure 2 Devices and Figure 1 The device of is very similar in construction, except that two tools 3a, 3b are provided in the container 1, which are located in two tool planes 30a, 30b arranged one above the other, specifically, in two carrier plates arranged parallel to each other and carrying knives.

[0078] The lower tool 3a or the lowermost tool plane 30a is arranged in the region or at the height of the opening 5 of the container or the feed opening of the twin-screw extruder 6. The upper tool 3b or the upper tool plane 30b is arranged in the middle to upper region of the container 1.

[0079] The tools 3a, 3b in these two tool planes 30a, 30b can be rotated independently of each other and at different rotational speeds by two separate drives 300a, 300b arranged below and above the container 1.

[0080] According to the present invention, the rotational speed of the lower tool 3a in the lowermost tool plane 30a is controlled according to the torque of the extruder 6.

[0081] In order to compensate for different parameters in the input material and ensure good processing, advantageously, the rotational speed of the other tool 3b located above can be adjusted independently of the torque of the extruder 6. These tools 3b can be rotated, for example, at a fixed defined or freely adjustable rotational speed, or at a rotational speed depending on other parameters, which is independent of the torque of the conveyor or the extruder and is not torque-controlled by a control device.

[0082] This is reflected in the exemplary embodiment according to Figure 2 and the rotational speed of the upper tool 3b in the upper tool plane 30b located above is not controlled or adjusted according to or independently of the torque of the extruder 6. Here, the temperature of the material is measured in the region of the upper tool plane 30b, and the rotational speed of the upper tool 3b is controlled or changed according to the material temperature. However, this should only be understood as an exemplary option (see Example 2 below).

[0083] According to Figure 3 the device is similar to the device according to Figure 2 The only difference lies in Figure 3 both tools 3a and 3b in

[0084] Tests:

[0085] The following tests were all carried out on an exemplary test equipment according to the present invention. Here is a combination of a PCU (Preconditioning Unit) / twin-screw extruder, and a melt filter SW4 / 134 is equipped according to the equipment configuration shown below (PCU configuration 1 or 2).

[0086] High-density polyethylene (HD-PE) bottle shreds were used as test materials respectively. This material was obtained from waste containers in the sanitation field (such as shampoo bottles) or the cleaning field (such as household cleaner bottles). The material was first shredded and then pre-cleaned in a cleaning device. The basic characteristics or parameters of this material are good fluidity, but with different bulk densities and different moisture contents.

[0087] Each test device was equipped with a measuring device for measuring the torque of the extruder and a control device connected to the measuring device and used to control the rotational speed of the tool. The control device was programmed, trained, and set to control the rotational speed of the tool according to the torque of the conveyor or the extruder.

[0088] Example 1:

[0089] In PCU configuration 1 (similar to the device according to Figure 1 ), a pretreatment unit (PCU) or a container or a cutting compactor was used, which had a tool with a variable-speed drive. Only one (lower) tool plane was created here, and this tool plane was arranged in the container opening area or the extruder feeding area. According to the present invention, the rotational speed of the tool was controlled according to the torque of the extruder.

[0090] PCU configuration 1:

[0091]

[0092]

[0093] By adjusting the rotational speed of the tool in the above manner, the filling degree of the extruder in configuration 1 could be kept constant. The feeding behavior, output, and output stability of the extruder were also improved, and the quality of the obtained PE polymer material was very high.

[0094] Example 2:

[0095] In PCU configuration 2 (similar to the device according to Figure 2 or Figure 3 ), a PCU was used, which had two variable-speed drives.

[0096] The first lower tool plane (filling plane) was arranged in the feeding area of the extruder, and the rotational speed of the tool on this tool plane was affected and controlled by the torque of the extruder. Therefore, according to the present invention, the rotational speed of the tool was controlled according to the torque of the extruder.

[0097] Above the first tool plane or filling plane, there is a second tool plane arranged thereon. It is equipped with a second drive with variable rotational speed. The second tool plane (which can also consist of multiple tool planes stacked one above the other) is responsible for favorably preparing the input material. The rotational speeds of the tools on these tool planes are adjusted to input energy into the material to reach a determined material temperature. A measurement system that extends into the material or can detect the temperature from the side or above without contact is used to measure the material temperature. The temperature is basically determined by the polymer fed in. It should be ensured that the input material slices reach a determined temperature that is close to the softening temperature of the polymer. Thereby, a certain degree of pre-compaction is ensured, that is, the bulk density is made uniform. In addition, since the material is heated to near the softening point, the melting process in the extruder becomes easier. Since the softening temperature of the thermoplastic polymer used here is within the temperature range of water evaporation, the residual moisture in the input material can also be removed.

[0098] PCU configuration 2:

[0099]

[0100]

[0101] The results are as Figure 5 shown, where the torque of the extruder is shown as a function of the tool rotational speed.

[0102] It can be seen from Figure 5 that the change in the extruder torque depends on the rotational speed of the tools in the lowermost tool plane of the PCU. In this experiment, the rotational speed of the tools in the lowermost tool plane of the PCU was varied according to the extruder torque. There is no need to worry about the requirements of the input material here, such as humidity, compaction degree, and material temperature in the PCU, because these can all be handled by the upper tools in the upper tool plane through their own drives.

[0103] Figure 5 It can be clearly seen from that the favorable and uniform torque of the extruder is obtained, with little or very little fluctuation. In this way, the filling degree of the extruder can be kept extremely constant and high enough. The feeding behavior, output, and output stability of the twin-screw extruder are all improved. The quality of the HD-PE pellets obtained in this way is very satisfactory.

Claims

1. A method for processing or treating polymeric materials, in particular thermoplastic waste plastics for recycling purposes, Among them, the polymeric material to be processed is moved, mixed, heated and, if necessary, broken by at least one rotatable or revolving tool (3a, 3b), and if necessary a plurality of rotatable or revolving tools (3a, 3b) in a container (1) or a cutting compactor, and wherein the lumpy or granular polymeric material is then discharged from the container (1) and fed into a conveyor (6), in particular an extruder (6), preferably a twin-screw or multi-screw extruder, in order to effect in particular compaction and melting or agglomeration there, characterized in that the torque of the conveyor (6) is measured and the rotational speed of at least one of the tools or the plurality of tools (3a, 3b) is controlled or changed as a function of the torque of the conveyor (6).

2. The method according to claim 1, wherein The torque of the conveyor (6) is continuously measured at defined, in particular regular time intervals.

3. The method according to any one of claims 1 to 2, characterized in that The conveyor (6) is operated at a constant rotational speed.

4. The method according to any one of claims 1 to 3, characterized in that, The rotational speed of the tools (3a, 3b) is reduced when the torque of the conveyor (6) increases and / or the rotational speed of the tools (3a, 3b) is increased when the torque of the conveyor (6) decreases.

5. The method according to any one of claims 1 to 4, characterized in that The rotational speed of the tools (3a, 3b) is controlled such that the torque of the conveyor (6) remains constant or the fluctuations of the torque are less than + / - 5%.

6. The method according to any one of claims 1 to 5, characterized in that The rotational speed of the tools (3a, 3b) is controlled such that the degree of filling of the conveyor (6) remains constant or the fluctuations of the degree of filling are small / less than + / - 10%.

7. The method according to any one of claims 1 to 6, characterized in that The rotational speed of the tools (3a, 3b) is controlled such that the rotational speed of the tools (3a, 3b) is not lower than a determined minimum rotational speed.

8. The method according to any one of claims 1 to 7, characterized in that The rotational speed of the tools (3a, 3b) can also be adjusted independently of the torque of the conveyor (6), in particular increased.

9. The method according to any one of claims 1 to 8, characterized in that, The tools (3a, 3b) in the container are arranged in at least two tool planes (30a, 30b) stacked one above the other.

10. The method according to any one of claims 1 to 9, characterized in that, The tool (3a) or the lowermost tool plane (30a) is arranged in the region or at the height of the feed opening or container opening (5) of the conveyor (6).

11. The method according to any one of claims 9 to 10, characterized in that, The tools (3a, 3b) in each tool plane (30a, 30b) can rotate independently of one another and at different rotational speeds, in particular driven to rotate by separate drives (300a, 300b).

12. The method according to any one of claims 9 to 11, characterized in that The rotational speed of the tool (3a) in the lowermost tool plane (30a) is controlled as a function of the torque of the conveyor (6).

13. The method according to any one of claims 9 to 12, characterized in that The rotational speed of the tool (3a) in the lowermost tool plane (30a) is controlled as a function of the torque of the conveyor (6), while the rotational speed of one or more tools (3b) in one or more other tool planes (30b) located above is controlled or adjusted independently of the torque of the conveyor (6).

14. The method according to any one of claims 9 to 13, characterized in that As a function of the torque of the conveyor (6), the rotational speeds of all the tools (3a, 3b) in each tool plane (30a, 30b) are controlled separately and independently of one another.

15. The method according to any one of claims 9 to 14, characterized in that, Adjust the rotational speed of one or more tools (3b) in one or more other tool planes (30b) located above such that a defined material temperature is achieved in this area, and / or measure the temperature of the material in this area and control or change the rotational speed of one or more tools (3b) in one or more other tool planes (30b) located above based on the material temperature.

16. A device for processing or treating polymeric materials, in particular thermoplastic waste plastics for recycling purposes, the device being particularly adapted to perform the method according to claim 1. The device has at least one container (1) for the material to be processed or a cutting compactor, wherein, At least one tool (3a, 3b) that can rotate or revolve around a rotation axis (2) is arranged in the container (1), and if necessary, a plurality of tools (3a, 3b) that can rotate or revolve, for moving, mixing, heating, and if necessary, crushing the material. Wherein, in the container (1), in particular in the side wall (4) of the container (1), in particular in the area or height of the lowermost or bottom - closest tool (3a), a container opening (5) is formed through which the pre - treated material can be discharged from the interior of the container (1). Wherein, at least one conveyor (6), in particular an extruder (6), is provided for receiving the material discharged from the container (1). It is characterized in that a measuring device for measuring the torque of the conveyor (6) is provided, and a control device communicatively connected to the measuring device is provided, the control device being used to control the rotational speed of at least one tool in the tool (3a, 3b) or the plurality of tools (3a, 3b), wherein the control device is configured or arranged to control the rotational speed of the tool (3a, 3b) according to the torque of the conveyor (6).

17. The device according to claim 16, characterized in that, The measuring device is configured to continuously measure the torque of the conveyor (6) at defined, in particular regular, time intervals.

18. The device according to any one of claims 16 to 17, characterized in that, The control device is configured to operate the conveyor (6) at a fixed rotational speed.

19. The device according to any one of claims 16 to 18, characterized in that, The control device is configured to reduce the rotational speed of the tool (3a, 3b) when the torque of the conveyor (6) increases, and / or increase the rotational speed of the tool (3a, 3b) when the torque of the conveyor (6) decreases.

20. The device according to any one of claims 16 to 19, characterized in that, The control device is configured to adjust the rotational speed of the tool (3a, 3b) such that the torque of the conveyor (6) remains constant or at half - load, or the fluctuation of the torque is less than + / - 5%.

21. The device according to any one of claims 16 to 20, characterized in that, The control device is configured to adjust the rotational speed of the tool (3a, 3b) such that the filling degree of the conveyor (6) remains constant or at half - filling, or the fluctuation of the filling degree is small / less than + / - 10%.

22. The device according to any one of claims 16 to 21, characterized in that, The control device is configured to adjust the rotational speed of the tool (3a, 3b) such that the rotational speed of the tool (3a, 3b) is not lower than a defined minimum rotational speed.

23. The device according to any one of claims 16 to 22, characterized in that, The rotational speed of the tool (3a, 3b) can also be adjusted independently of the torque of the conveyor (6), in particular increased.

24. The device according to any one of claims 16 to 23, characterized in that, In the container (1), a plurality of, at least two tools (3a, 3b) are arranged in different tool planes (30a, 30b) or at different distances from the bottom surface or the lowermost region of the container (1), and the tools (3a, 3b) in the container (1) are arranged in at least two vertically stacked tool planes (30a, 30b).

25. The device according to any one of claims 16 to 24, characterized in that, The tool (3a) or the lowermost tool (3a) or the lowermost tool plane (30a) is arranged in the region or at the height of the container opening (5) or the feed opening of the conveyor (6) connected to the container opening (5).

26. The device according to any one of claims 24 to 25, characterized in that, The tools (3a, 3b) in each tool plane (30a, 30b) can be rotated at different speeds independently of each other, in particular driven to rotate by separate drives (300a, 300b).

27. The device according to any one of claims 24 to 26, characterized in that, The rotational speed of the tool (3a) in the lowermost tool plane (30a) can be controlled by the control device according to the torque of the conveyor (6).

28. The device according to any one of claims 24 to 27, characterized in that, The rotational speed of the tool (3a) in the lowermost tool plane (30a) can be controlled by the control device according to the torque of the conveyor (6), while the rotational speed of one or more tools (3b) in one or more other tool planes (30b) located above can be controlled or adjusted independently of the torque of the conveyor (6).

29. The device according to any one of claims 24 to 28, characterized in that, The rotational speed of all the tools (3a, 3b) in each tool plane (30a, 30b) can be separately and independently controlled by the control device according to the torque of the conveyor (6).

30. The device according to any one of claims 24 to 29, characterized in that, The rotational speed of one or more tools (3b) in one or more other tool planes (30b) located above is adjusted such that a determined material temperature is achieved in this region, and / or the rotational speed of one or more tools (3b) in one or more other tool planes (30b) located above can be controlled or changed according to the material temperature.

31. The device according to any one of claims 16 to 30, characterized in that The conveyor (6) is an extruder (6) having at least two screws, in particular a twin-screw extruder.

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