Method and device for processing polymer materials

Abstract

The invention relates to a method and a device for processing or treating polymer materials, in particular thermoplastic waste plastic for recycling purposes, wherein, in a container or cutter-compactor (1), the polymer materials to be processed are, by means of at least one rotatable or rotating tool (3a, 3b), optionally a plurality of rotatable or rotating tools (3a, 3b), moved, mixed, heated and optionally comminuted, and wherein the polymer materials, which are in the form of pieces or particles, are subsequently discharged from the container (1) and introduced into a conveyor (6), in particular an extruder (6), preferably a twin-screw or multiple-screw extruder, in particular in order to be compacted and melted or agglomerated therein. 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 tools (3a, 3b) is controlled or changed according to the torque of the conveyor (6).

Description

[0001] Method and device for processing polymer materials

[0002] The invention relates to a method and a device for processing or preparing polymer materials, in particular thermoplastic waste plastic for recycling purposes, according to the preambles of claim 1 and claim 16, respectively.

[0003] Methods and devices in which a combination of a container or a preconditioning unit (PCU) and a conveyor connected to it, in particular an extruder, are used for the processing of polymer waste, in particular of different thermoplastics, are well known.

[0004] Often, devices for pretreating the materials to be processed are installed upstream of an extrusion system, for example, well-known cutter-compactors or preconditioning units (PCUs). These are usually containers with rotating tools directly coupled to an extruder. This pretreatment step in the PCU, which precedes the extrusion process, has the task, among other things, of modifying the shape and properties of the polymer materials. It is advantageous to introduce energy into the material. In the pretreatment unit, the thermoplastic materials are mixed, heated, softened, compacted, pre-degassed, dried, dehumidified, cut, crushed, crystallized, and / or homogenized, and their bulk density is increased.

[0005] The polymers pretreated in this way are then fed into an extruder to be compacted, in particular melted. Such combination devices have long been known, for example, from EP 2 558 263 or EP 2 689 908.

[0006] The mixing and shredding tools circulating in the container or PCU also support the filling or feeding process of the conveyor or extruder connected to the container. Both the conveying process and the extrusion process are generally particularly efficient when the screw fill level is consistent and sufficiently high. The area of ​​feeding of the conveyor or extruder is therefore sensitive and has a significant influence on the end result and the quality of the recyclates. In this context, factors such as the distance between the mixing and shredding tools and the conveyor or extruder screw, the shape and size of the feed opening, and the direction of rotation of the mixing tools in relation to the conveying direction of the conveyor or extruder all play a certain role. However, on the conveyor or extruder side, the profile of the screw flight, the shape of the screw base and the screw outlet also play a role.the free open area of ​​the screw flight. For example, unfavorable feed behavior of the conveyor or extruder can lead to surge in the volumetric throughput, i.e., a change in throughput over time, which is detrimental to reliable operation and the quality of the recyclates.

[0007] There has therefore been no lack of attempts in the state of the art to either adapt the construction of the sensitive area of ​​the feeding or intake of a conveyor or extruder or to design it in such a way that the intake behavior and feeding of the screw are supported in the best possible way and, for example, also become more tolerant to operational material differences.

[0008] In particular, to achieve special material qualities and also to compound these materials, twin-screw or multi-screw extruders are used alongside single-screw extruders. These extruder systems are also directly coupled to the PCU. The lowest tool level of the container, which preferably consists of a disc onto which tools can be mounted and is located near the extruder opening, feeds the pretreated materials into the extrusion device.

[0009] The number of stuffing cycles of the tools in the lowest tool level near the conveyor opening or extruder opening generally has a significant influence on the fill level of the conveyor or extruder. Furthermore, the average bulk density of the materials in the PCU, particularly in the lowest area of ​​the PCU, corresponding to the average compaction, is partly responsible for the fill level. It is relatively unimportant whether the conveyor or extruder is filled from the side or in the area of ​​the twin-screw gusset, or the direction of rotation of the tools used to fill the conveyor opening or extruder opening.

[0010] The material drawn into the conveyor or extruder is immediately transported onwards, resulting in a torque curve of the conveyor or extruder drive that depends on the fill level. Basically, the aim is to keep the torque curve of the conveyor or extruder, or the fill level of the conveyor or extruder, as constant as possible. This results in high-quality melting of the polymers without shear peaks that can lead to excessive temperature buildup in the polymer melt. Overfeeding the conveyor or extruder, i.e., an insufficient fill level, can lead to throughput losses and shear peaks, but can also result in poorly homogenized polymers. Accordingly, keeping the fill level of the conveyor or extruder constant is beneficial for the quality of the recyclates and for cost-effectiveness.

[0011] Fig. 4 illustrates an example of an unfavorable change in extruder torque as a function of the tool speed. Here, for example, the tool speed was varied in an attempt to meet the moisture, compaction, and temperature requirements of the incoming material in the PCU. This resulted in significant fluctuations in extruder torque and tool speed, which were detrimental to, among other things, the feeding behavior and material quality.

[0012] Even the mere mixing of the materials in the PCU has a certain (minor) dampening effect on any bulk density fluctuations of the input materials. However, mixing alone, and often also intensive pretreatment of the materials in the PCU, is not sufficient in some cases, and it is not always possible to maintain the bulk density sufficiently constant over an extended period. Rather, the bulk density of the processed materials fluctuates upwards and downwards from an average value over time. This is already detrimental and causes the disadvantages described above.

[0013] It is therefore an object of the present invention to provide a method and a device of the type mentioned at the outset with which the filling level of the conveyor or the extruder can be kept as constant as possible.

[0014] This object is achieved according to the method by the characterizing features of claim 1. Accordingly, a method for processing or conditioning polymer materials, in particular thermoplastic waste plastic for recycling purposes, is provided, wherein the polymer materials to be processed are moved, mixed, heated and optionally comminuted in a container or cutter-compactor or a preconditioning unit (PCU) by at least one rotatable or rotating tool, optionally several rotatable or rotating tools, and wherein the polymer materials in lumpy or particulate form are then discharged from the container and introduced into a conveyor or extruder, in particular in order to be further compacted and melted or agglomerated there.

[0015] According to the invention, it is provided that the torque of the conveyor or extruder is measured, and the speed of the tool or at least one of the tools is controlled or changed depending on the measured torque of the conveyor or extruder.

[0016] This object is achieved according to the device analogously by the characterizing features of claim 16. Accordingly, a device for processing or conditioning polymer materials, in particular thermoplastic waste plastic for recycling purposes, is provided, which is particularly suitable for carrying out the above method, with at least one container or cutter-compactor or a preconditioning unit (PCU) for the material to be processed, wherein at least one tool which can be rotated or rotated about an axis of rotation, optionally several rotatable or rotating tools, is or are arranged in the container for moving, mixing, heating and optionally comminuting the material, 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 formed in particular in a side wall of the container, in particular in the region of the orthe height of the lowest or ground-level tool. Furthermore, at least one conveyor or extruder is provided to receive the material discharged from the container through the container opening.

[0017] According to the invention, a measuring device is provided for measuring the torque of the conveyor or extruder, and a control device is provided that is in communication connection or data communication with the measuring device for controlling the rotational speed of the tool or at least one of the tools. The control device is designed and / or configured to control the rotational speed of the tool as a function of the torque of the conveyor or extruder. The control device thus controls the rotational speed of the tool as a function of the torque of the conveyor or extruder measured by the measuring device.

[0018] The invention therefore proposes directly influencing, controlling, or changing the speed at which the tool(s) rotate in the PCU or in the container via the torque of the conveyor or extruder. By adjusting the speed of the tools in this way, the stuffing cycles in the conveyor or extruder system are directly influenced, and the fill level of the screw flights of the conveyor or extruder changes accordingly, and subsequently, the torque of the conveyor or extruder, in turn, changes. In this way, the fill level of the conveyor or extruder can be kept constant. The feeding behavior of the screw is improved, and the throughput and throughput consistency are also improved. The overall system consisting of cutter-compactor and conveyor or extruder is thus more stable and efficient. Furthermore, the quality of the resulting polymer materials can be improved, and operating efficiency can be increased.

[0019] In principle, the effects mentioned are relevant and present in all conveyors or extruders, i.e. not only in compressing screws for extruders or agglomerators, but also in non- or less compressing screws with predominantly or purely conveying function.

[0020] The general term “conveyor” refers to systems with non-compressing or decompressing screws as well as systems with compressing screws, i.e. extruder screws with an agglomerating or plasticizing effect.

[0021] In this text, the terms "extruder" and "extruder screw" refer to conveyors or conveyor screws with which the material is completely or partially melted, i.e. classic extruders, but also conveyors or conveyor screws with which the softened material is only agglomerated but not melted. With such agglomerating screws or agglomerating screws, the material is only briefly compressed and sheared, but not plasticized. The agglomerating screw therefore delivers material at its output that is not completely melted, but consists of particles that are only partially melted on their surface and are caked together in a kind of sintering. In both cases, however, pressure is exerted on the material via the screw during conveying, causing it to be compacted.

[0022] Systems for measuring the torque of conveyors or extruders are well known. For example, in extruders, a torque detection unit can be installed in the connection area between the gearbox output shaft and the extruder shaft to measure the torque transmitted to the extruder shaft via the gearbox output shaft and the connection area without contact. Other systems for continuously monitoring the torque of conveyors or extruders are also known, for example, torque sensors based on the principle of magnetostriction. Such systems are primarily used to detect and prevent potential overload situations, for example, to operate the extruder closer to its load limits, to increase drive power or torque density.

[0023] Advantageously, the torque of the conveyor or extruder is continuously measured at defined, in particular regular, intervals. An advantageous device is accordingly characterized in that the measuring device is designed and configured to continuously measure the torque of the conveyor or extruder at defined, in particular regular, intervals.

[0024] This means that the torque is measured during the process either at predefined times or at defined time intervals or distances and the data is transmitted to the control device in order to be able to react quickly and continuously to changes and to adjust the speed of the tools.

[0025] Advantageously, the conveyor or extruder is operated at a fixed speed. An advantageous device is accordingly characterized in that the control device is designed and configured to operate the conveyor or extruder at a fixed speed.

[0026] If the conveyor or extruder runs at a fixed speed nEx = const [rpm], then with a variable tool speed nW [rpm], different stuffing cycles result per speed nEx. This changes the filling level of the screw flights and, subsequently, the torque of the conveyor or extruder MEx [Nm].

[0027] Advantageously, the tool speed is reduced as the torque of the conveyor or extruder increases, and the tool speed is increased as the torque of the conveyor or extruder decreases. An advantageous device is accordingly characterized in that the control device is designed and configured to reduce the tool speed as the torque of the conveyor or extruder increases and / or to increase the tool speed as the torque of the conveyor or extruder decreases.

[0028] The tool speed nWE [rpm] in the PCU is defined as a function of the conveyor or extruder torque MEx [Nm]. Accordingly, if the tool speed is reduced when the conveyor or extruder torque increases, this leads to fewer stuffing cycles and thus to a lower filling level of the conveyor or extruder, or of the conveyor or extruder's screw flights. This, in turn, leads to a decrease in the conveyor or extruder torque. This can be appropriately mapped using a PID controller.

[0029] Advantageously, the 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%. An advantageous device is accordingly characterized in that the control device is designed to adjust the speed of the tool such that the torque of the conveyor or extruder remains constant or is half constant or the torque fluctuations are less than + / - 5%, preferably less than + / - 3%.

[0030] In this way, it can be ensured that the torque curve of the conveyor or extruder is kept as constant as possible and peaks or major changes are avoided.

[0031] Advantageously, the speed of the tool is controlled such that the fill level of the conveyor or extruder remains constant or the fluctuations in the fill level are small / less than + / - 10%, preferably less than + / - 5%. An advantageous device is accordingly characterized in that the control device is designed to adjust the speed of the tool such that the fill level of the conveyor or extruder remains constant or is half constant or the fluctuations in the fill level are small / less than + / - 10%, preferably less than + / - 5%.

[0032] As mentioned in the introduction, it is also advisable, with regard to the quality of the end product and cost-effectiveness, to keep the fill level of the conveyor or extruder, or of the screw(s) of the conveyor or extruder, as constant as possible, e.g., defined in kg / revolution. The fill level of the conveyor or extruder can be determined or calculated in a practical manner, or can be measured, for example, by measuring the pressure in the screw or by ultrasonic measurement, as described, for example, in AT 505618 B1.

[0033] However, material preparation sometimes follows different rules than feeding the conveyor or extruder. For example, different parameters in the input material, such as highly variable moisture levels, may require the tool speed to be kept relatively high in order to inject sufficient energy into the material with a given tool setup, e.g., to maintain moisture evaporation and achieve compaction. This can limit the degree of freedom of the tool speed.

[0034] Advantageously, the speed of the tool is controlled in such a way that the speed of the tool does not fall below a certain minimum speed. An advantageous device is accordingly characterized in that the control device is designed to adjust the speed of the tool in such a way that the speed of the tool does not fall below a certain minimum speed.

[0035] This ensures that the torque of the conveyor or extruder is kept as constant as possible, while at the same time ensuring that sufficient energy can always be introduced into the material being processed. To compensate for different parameters in the input material and ensure good processing, it can be advantageous if the speed of the tool can also be adjusted, in particular increased, independently of the torque of the conveyor or extruder. An advantageous device is accordingly characterized in that the speed of the tool can also be adjusted, in particular increased, independently of the torque of the conveyor or extruder.

[0036] This allows for greater flexibility in processing and allows for adaptation to differences in the materials being processed, for example. Above all, for certain requirements, the tool speed must be higher and cannot be reduced, as otherwise too little energy would be transferred into the material.

[0037] Advantageously, the tools in the container are arranged in at least two superimposed tool levels. An advantageous device is accordingly characterized in that several, at least two, tools are arranged in the container in different tool levels or at different distances from the bottom surface or lowest region of the container, and in that the tools in the container are arranged in at least two superimposed tool levels.

[0038] Often, the material to be processed is fed into the container at the top, passes through the container from top to bottom, and is heated, softened, and mixed during a certain dwell time. It is then discharged into the conveyor or extruder at the bottom. Tools at different heights or distances from the floor facilitate advantageous processing and increase flexibility.

[0039] Advantageously, the lowest tool level is arranged in the area or at the height of the feed opening of the conveyor or extruder. An advantageous device is accordingly characterized in that the lowest tool level is arranged in the area or at the height of the container opening or the feed opening of the conveyor or extruder connected to the container opening.

[0040] This ensures effective filling of the conveyor or extruder.

[0041] Advantageously, the tools in the individual tool levels can be rotated independently of one another and at different speeds, in particular via separate drives. An advantageous device is accordingly characterized in that the tools in the individual tool levels can be rotated independently of one another and at different speeds, in particular via separate drives.

[0042] This also increases machining flexibility. For this purpose, two or more different drives can be used, each of which can be adjusted accordingly. It is possible to drive the tools from above, below, or from the periphery.

[0043] Advantageously, the rotational speed of the tool in the lowest tool level is controlled as a function of the torque of the conveyor or extruder. An advantageous device is accordingly characterized in that the rotational speed of the tool in the lowest tool level can be controlled by the control device as a function of the torque of the conveyor or extruder.

[0044] In this way, the speed of the tools at the lowest tool level, i.e., in the area of ​​the filling opening of the conveyor or extruder, is controlled depending on the torque of the conveyor or extruder. The speed of the tools at the other, higher tool levels can be controlled depending on the torque of the conveyor or extruder, but this is not required. These tools can also rotate at a defined or adjustable speed that is not dependent on the torque of the conveyor or extruder, or is not torque-controlled via the control device.

[0045] In this way, for example, the polymer material in the upper section of the container can be processed at higher speeds and correspondingly higher energy input, i.e., at higher temperatures. In the lower section of the PCU, the tool speed is then adjusted accordingly to keep the torque of the conveyor or extruder, or the fill level, constant. This achieves a degree of freedom, or decoupling, of the material preparation in the container from the feed of the conveyor or extruder.

[0046] Advantageously, it can also be provided that the speed of the tool is controlled only in the lowest tool level as a function of the torque of the conveyor or extruder, and the speed of the tool(s) in the other tool level(s) above is controlled or adjusted independently of the torque of the conveyor or extruder. An advantageous device is accordingly characterized in that the speed of the tool is controllable only in the lowest tool level by the control device as a function of the torque of the conveyor or extruder, and the speed of the tool(s) in the other tool level(s) above is controlled or adjusted independently of the torque of the conveyor or extruder.

[0047] Here, it is therefore not optional, but mandatory, that the speed of the tools on the other, higher tool levels is not controlled based on the torque of the conveyor or extruder, but rather differently. Advantageously, it can also be provided that the speeds of all tools in each tool level are controlled independently of one another, depending on the torque of the conveyor or extruder. An advantageous device is accordingly characterized in that the speeds of all tools in each tool level can be controlled independently of one another by the control device, depending on the torque of the conveyor or extruder.

[0048] Accordingly, the speeds of all tools in all tool levels are torque-controlled, but can be adjusted independently or individually.

[0049] Advantageously, it can also be provided that the speed of the tool or tools in the other tool level(s) above is controlled such that a specific material temperature is reached in this area. It is also advantageous if the temperature of the material in this area is measured and the speed of the tool or tools in the other tool level(s) above is controlled or changed depending on this material temperature. An advantageous device is accordingly characterized in that the speed of the tool or tools in the other tool level(s) above is controlled such that a specific material temperature is reached in this area and / or that the speed of the tool or tools in the other tool level(s) above is controllable or changeable depending on this material temperature.

[0050] The tools are advantageously discs, bars or beams, in particular with knives arranged thereon.

[0051] If tools are arranged in several tool levels, in particular several disks on top of each other, they can, but do not have to, be the same size, and can therefore also have different dimensions or diameters.

[0052] An advantageous device is characterized in that the conveyor has at least one compressing screw and is designed as a single-screw extruder. Conveyors with multiple compressing screws are also particularly advantageous. It is particularly advantageous if the conveyor is a twin-screw extruder, in particular a co-rotating twin-screw extruder. In practice, the effects for achieving a good fill level are particularly advantageous with twin-screw extruders or multi-screw extruders. Especially with co-rotating, intermeshing twin-screw or multi-screw extruders – regardless of whether the screws are parallel or conical, especially in the feed area – the number of stuffing cycles of the lowest tool level in the area of ​​the extruder opening has a particular influence on the fill level of the extruder system, resulting in a torque curve of the extruder drive that depends on the fill level.

[0053] The feed behavior is also advantageous, among other things, depending on how the cutter-compactor's tools introduce the pretreated material into the feed opening of the conveyor or extruder or support this process. This depends, among other things, on the direction of rotation of the screw and the direction of rotation of the tools. In this context, it has proven advantageous if, in the area upstream of the container opening or in the area upstream of the feed opening or feeding opening of the conveyor or extruder, the direction of rotation of the tool of the lowest level runs essentially opposite to or in the opposite direction to the conveying direction of the conveyor or extruder. Such arrangements are already known in principle, for example from EP 2 558 263 B1 or EP 2 689 908 B1, and are incorporated into the present disclosure by reference.

[0054] It is particularly advantageous if the longitudinal axis of the conveyor or the screw or the longitudinal axis of the screw closest to the intake opening or the inner wall of the housing or the envelope of the screw runs tangentially to the inside of the side wall of the container, wherein the screw is preferably connected to a drive at its front end and conveys at its opposite front end to an outlet opening arranged at the front end of the housing, in particular an extruder head.

[0055] It is also advantageous if the opening in the PCU is directly connected to the intake opening without any long distance or transfer path, such as a conveyor screw. This allows for effective and gentle material transfer.

[0056] An advantageous device is further characterized by the container being cylindrical or conical. However, the container does not necessarily have to be circularly cylindrical, although this shape is advantageous for practical and manufacturing reasons. Container shapes deviating from the circular cylindrical shape, such as truncated conical containers or cylindrical containers with an elliptical or oval outline, can be converted to a circular cylindrical container of the same capacity, assuming that the height of this fictitious container is equal to its diameter. Container heights that significantly exceed the resulting mixing vortex (taking the safety distance into account) are disregarded, since this excessive container height is not utilized and therefore no longer has any influence on material processing.

[0057] An advantageous device is characterized in that the conveyor or extruder is connected tangentially to the container and / or that the housing of the conveyor or extruder has an intake opening located on its front side or in its casing wall for the material to be picked up by the screw or screws of the conveyor or extruder, and the intake opening is connected to the container opening.

[0058] In a further advantageous embodiment, the receiving container can be substantially cylindrical, with a flat base surface and a cylindrical side wall aligned vertically thereto. Furthermore, it is structurally simple if the axis of rotation of the tool(s) coincides with the central axis of the receiving container. In a further advantageous embodiment, the axis of rotation of the tool(s) or the central axis of the container is aligned vertically and / or perpendicular to the base surface. This also applies analogously to conical containers. These special geometries optimize the feed behavior in a structurally stable and simply constructed device.

[0059] In this context, it is also advantageous to provide that the tool, or, if several tools are arranged one above the other, the lowest tool closest to the ground, as well as the opening are arranged a short distance from the floor surface, in particular in the region of the lowest quarter of the height of the receiving container. The distance is defined and measured from the lowest edge of the opening or the feed opening to the container floor in the edge area of ​​the container. Since the corner edge is usually rounded, the distance is measured from the lowest edge of the opening along the imaginary extensions of the side wall downwards to the imaginary extension of the container floor outwards. Suitable distances are 10 to 400 mm.

[0060] Furthermore, it is advantageous for machining if the radially outermost edges of the tool reach close to the side wall of the container.

[0061] Particularly advantageous is a device comprising a cutter-compactor or a preconditioning unit (PCU) with at least one mixing or comminuting tool that can rotate or rotate about a rotational axis, and with a container opening formed in the side wall of the cutter-compactor at the height of the lowest tool closest to the ground. A twin-screw extruder, into which the pretreated material is introduced, is tangentially connected to this container opening.

[0062] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings. The invention is schematically illustrated in the drawings using non-limiting exemplary embodiments and is described below by way of example with reference to the drawings.

[0063] Fig. 1 shows a first embodiment of a device according to the invention.

[0064] Fig. 2 shows a further embodiment of a device according to the invention.

[0065] Fig. 3 shows yet another embodiment of a device according to the invention. Fig. 4 shows the result of a comparative test not according to the invention.

[0066] Fig. 5 shows the result of a comparative test.

[0067] Fig. 1 shows a first advantageous embodiment of an apparatus according to the invention for processing or reprocessing polymer materials, in particular thermoplastic waste plastic for recycling purposes. The basic structure and basic mode of operation of such a cutter-compactor-extruder combination is well known, for example, from EP 2 558 263 or EP 2 689 908, and will be described only briefly below. Furthermore, it should be noted that the illustrations in Figures 1 to 3 are only schematic.

[0068] The device shown in Fig. 1 comprises a cylindrical container or cutter-compactor or a preconditioning unit (PCU) 1 for receiving the polymer material to be processed. Such a container 1 is already well known, for example, from EP 123 771. The container 1 is cylindrical with a flat bottom surface and a cylindrical side wall 4 aligned vertically thereto.

[0069] A rotatable or rotating tool 3a is arranged in the container 1. The tool 3a here is a flat carrier disk with knives 7 mounted on its upper side, arranged at a short distance from the base surface, rotating about an axis of rotation and aligned parallel to the base surface. The carrier disk is driven to rotate by a motor 300a via an axis 2a, wherein the motor 300a is located below the container 1. The axis of rotation or the axis 2a is arranged in the central longitudinal axis or center axis of the container 1. The tool 3a serves, among other things, to move, mix, heat and comminute the material present in the container 1. Accordingly, the thermoplastic materials are mixed, heated, softened, compacted, pre-degassed, dried, dehumidified, cut, comminuted, crystallized and / or homogenized in the container 1, and their bulk density is increased.By rotating the tool 3a, a mixing vortex is formed in the material and the material remains in the container 1 for a certain residence time and is pretreated there accordingly.

[0070] At the level of the single tool 3a in this case, or at the level of the lowest tool level 30a, a container opening 5 is formed in the side wall 4 of the container 1. The housing or feeding opening of a conveyor 6, in this case a compressing twin-screw extruder 6, is tangentially connected to this container opening 5. Especially with multi-screw extruders, the intake or feeding process is particularly sensitive, and constant feeding at as consistent a level as possible is particularly important.

[0071] The outer edges of the tool 3a extend relatively close to the side wall 4, approximately 5% of the radius. The screw of the extruder 6, located near the container opening 5, is adapted to the contour of the inner wall 4 of the container 1 and set back. No part of the extruder 6 protrudes into the interior of the container 1. The tools 3a and the blades 7 are located at approximately the same height or level as the central longitudinal axis of the extruder 6.

[0072] In practical operation, the plastic material to be processed, usually in the form of plastic waste, bottles, or foil, is introduced into container 1. The introduced plastic material is, among other things, crushed and mixed by the rotating tool 3a, and is thereby heated and softened, but not melted, by the introduced mechanical friction energy. After a certain residence time in container 1, the softened, but not melted, material is discharged from container 1 through container opening 5 and fed to extruder 6, or the extruder 6 is fed in this way.

[0073] In the present embodiment, the extruder 6 is a conventional co-rotating twin-screw extruder known per se, in which the softened plastic material is melted in a first zone, subsequently compressed, and the polymer melt then exits or is granulated on the opposite side. According to the invention, a measuring device (not shown here) is provided for measuring the torque of the extruder 6 or the two extruder screws. Such torque measuring devices for extruders are known. Furthermore, a control device (also not shown) is provided for controlling the rotational speed of the tool 3a, which is in communication or data communication with the measuring device. This 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.The torque of the extruder 6 is continuously measured at defined, suitably short time intervals or distances and the data is transmitted to the control device in order to be able to react quickly and continuously to changes and to adjust the speed of the tool 3a.

[0074] In the present case, the speed of the tool 3a is controlled in such a way that the torque of the extruder 6 remains essentially constant and the fluctuations in the torque are less than + / - 5%.

[0075] By adjusting the speed of the tool 3a in this way, the stuffing cycles in the extruder 6 are directly influenced and the filling level of the screw flights of the extruder 6 and, subsequently, the torque of the extruder 6 changes accordingly. In this way, the filling level of the extruder 6 can be kept very constant (see also Example 1 below).

[0076] The device of Fig. 2 is constructed largely analogously to the device of Fig. 1, but has two tools 3a, 3b in the container 1 in two superimposed tool planes 30a, 30b, specifically two carrier disks with knives arranged parallel to each other.

[0077] The lower tool 3a or the lowest tool level 30a is arranged in the area or at the height of the container opening 5 or the feed opening of the twin-screw extruder 6. The upper tool 3b or the upper tool level 30a is arranged in the middle to upper area of ​​the container 1.

[0078] The tools 3a, 3b in the two tool levels 30a, 30b can be rotated independently of one another and at different speeds via two separate drives 300a, 300b arranged below and above the container 1. According to the invention, the speed of the lower tool 3a in the lowest tool level 30a is controlled as a function of the torque of the extruder 6.

[0079] To compensate for different parameters in the input material and ensure good processing, it can be advantageous if the speed of the other, overlying tool 3b can be adjusted independently of the torque of the extruder 6. These tools 3b can, for example, rotate at a fixed or freely adjustable speed, or at a speed dependent on other parameters, which is not dependent on the torque of the conveyor or extruder or is not torque-controlled via the control device.

[0080] This is implemented in the exemplary embodiment shown in Fig. 2, and the rotational speed of the upper tool 3b in the tool plane 30b above it is controlled or adjusted independently of, or rather not dependent on, the torque of the extruder 6. Here, the temperature of the material in the area of ​​the upper tool plane 30b is measured, and the rotational speed of the upper tool 3b is controlled or adjusted depending on this material temperature. However, this is only to be understood as an exemplary option (see also Example 2 below).

[0081] The device according to Fig. 3 is again analogous to the device in Fig. 2. The only difference is that in Fig. 3, both tools 3a and 3b are driven from below, i.e., via motors or drives 300a, 300b, both of which are arranged below the container 1. The rotation or drive axes 2a and 2b are concentrically located within one another.

[0082] Try:

[0083] The following tests were each conducted on an exemplary test system according to the invention. This was a PCU (preconditioning unit) / twin-screw extruder combination equipped with an SW 4 / 134 melt filter according to the system configuration shown below (PCU configuration 1 or 2).

[0084] The test material used in each case was HDPE bottle granules. This material was obtained from used containers from the hygiene sector, e.g., shampoo bottles, or from cleaning products, e.g., household cleaners. This material was first shredded and then pre-cleaned in a washing system. The basic properties or parameters of this material are that it is free-flowing, but it has varying bulk densities and moisture contents.

[0085] Each of the test systems had a measuring device for measuring the extruder's torque and a control device connected to the measuring device for controlling the tool's speed. The control device was programmed, designed, and configured to control the tool's speed depending on the torque of the conveyor or extruder.

[0086] Example 1 :

[0087] In PCU configuration 1 (comparable to a device according to Fig. 1), a preconditioning unit (PCU) or a container or a cutter / compactor was used, which had a tool with a variable-speed drive. A single (lower) tool level was constructed here, which was located in the area of ​​the container opening or in the area of ​​the extruder inlet. The speed of this tool was thus controlled according to the invention as a function of the extruder torque.

[0088] PCU configuration 1 :

[0089] By adjusting the tool speeds in this way, the extruder filling level could be kept constant even in this configuration 1. The extruder's feeding behavior, throughput, and throughput consistency were also improved, and the quality of the resulting PE polymer materials was very high.

[0090] Example 2:

[0091] In PCU configuration 2 (comparable to a device according to Fig. 2 or Fig. 3), a PCU was used which had two variable speed drives.

[0092] A first lower tool level (filling level) was located in the extruder inlet area, and the speed of the tools on this level was influenced and controlled by the extruder torque. According to the invention, the speed of this tool was thus controlled as a function of the extruder torque.

[0093] A second tool level was located above the first tool level or filling level. This was equipped with a second drive with a variable speed. This second tool level (which could also consist of several tool levels one above the other) was responsible for the advantageous processing of the incoming material. The speed of the tools on this tool level was controlled so that the energy was introduced into the material in such a way that a specific material temperature was reached. The material temperature was measured using measuring systems that protruded into the material or recorded the temperature non-contacting from the side or top. This temperature was essentially determined by the introduced polymer. The aim was to ensure that the incoming material chips reached a specific temperature close to the softening temperature of the polymer.This ensured a certain degree of pre-compaction, thus evening out the bulk density, and also facilitated the melting process in the extruder, as the material was heated to near its softening point. Since the softening temperatures of the thermoplastic polymers used here are in the range where water evaporates, the residual moisture in the incoming material was also removed.

[0094] PCU configuration 2:

[0095] The result is shown in Fig. 5, where the torque of the extruder is plotted as a function of the tool speed.

[0096] Fig. 5 shows the change in extruder torque as a function of the speed of the tools in the lowest tool level of the PCU. In this experiment, the speed of the tools in the lowest tool level of the PCU was varied as a function of the extruder torque. The PCU did not have to directly address the requirements of the incoming material, such as moisture content, compaction, and material temperature, as this was handled by the upper tool in the upper tool level with its own drive.

[0097] Clearly visible in Fig. 5 is the advantageously uniform, almost non-fluctuating extruder torque. This allowed the extruder's fill level to be kept extremely constant and sufficiently high. The feeding behavior of the twin-screw extruder, as well as the throughput and throughput consistency, were improved. The quality of the HDPE granules obtained in this way was very satisfactory.

Claims

Patent claims:

1. A method for processing or preparing polymer materials, in particular thermoplastic waste plastic for recycling purposes, wherein the polymer materials to be processed are moved, mixed, heated and optionally comminuted in a container or cutter-compactor (1) by at least one rotatable or rotating tool (3a, 3b), optionally a plurality of rotatable or rotating tools (3a, 3b), and wherein the polymer materials in lumpy or particulate form are then discharged from the container (1) and introduced into a conveyor (6), in particular an extruder (6), preferably a twin-screw or multi-screw extruder, in particular in order to be compacted and melted or agglomerated there, characterized in that the torque of the conveyor (6) is measured and the speed of the tool or at least one of the tools (3a, 3b) is controlled or adjusted as a function of the torque of the conveyor (6).is changed.

2. Method according to claim 1, characterized in that the torque of the conveyor (6) is continuously measured at defined, in particular regular, intervals.

3. Method according to one of claims 1 to 2, characterized in that the conveyor (6) is operated at a fixed speed.

4. Method according to one of claims 1 to 3, characterized in that with increasing torque of the conveyor (6) the speed of the tool (3a, 3b) is reduced and / or that with decreasing torque of the conveyor (6) the speed of the tool (3a, 3b) is increased.

5. Method according to one of claims 1 to 4, characterized in that the control of the speed of the tool (3a, 3b) is carried out in such a way that the torque of the conveyor (6) remains constant or the fluctuations in the torque are less than + / - 5%.

6. Method according to one of claims 1 to 5, characterized in that the control of the speed of the tool (3a, 3b) is carried out in such a way that the filling level of the conveyor (6) remains constant or the fluctuations in the filling level are small / less than + / - 10%.

7. Method according to one of claims 1 to 6, characterized in that the control of the speed of the tool (3a, 3b) is carried out in such a way that the speed of the tool (3a, 3b) does not fall below a certain minimum speed.

8. Method according to one of claims 1 to 7, characterized in that the rotational speed of the tool (3a, 3b) is additionally adjustable, in particular increaseable, independently of the torque of the conveyor (6).

9. Method according to one of claims 1 to 8, characterized in that the tools (3a, 3b) are arranged in the container in at least two superimposed tool planes (30a, 30b).

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

11. Method according to one of claims 9 to 10, characterized in that the tools (3a, 3b) in the individual tool levels (30a, 30b) can be rotated independently of one another and at different speeds, in particular via separate drives (300a, 300b).

12. Method according to one of claims 9 to 11, characterized in that the rotational speed of the tool (3a) in the lowest tool level (30a) is controlled as a function of the torque of the conveyor (6).

13. Method according to one of claims 9 to 12, characterized in that the rotational speed of the tool (3a) in the lowest tool level (30a) is controlled as a function of the torque of the conveyor (6) and the rotational speed of the tool or tools (3b) in the other tool level(s) (30b) above is controlled or adjusted independently of the torque of the conveyor (6).

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

15. Method according to one of claims 9 to 14, characterized in that the speed of the tool or tools (3b) in the other tool level(s) (30b) above is controlled so that a certain material temperature is reached in this area and / or that the temperature of the material in this area is measured and the speed of the tool or tools (3b) in the other tool level(s) (30b) above is controlled or changed depending on this material temperature.

16. Device for processing or preparing polymer materials, in particular thermoplastic waste plastic for recycling purposes, in particular for carrying out the method according to claim 1, with at least one container or cutter-compactor (1) for the material to be processed, wherein in the container (1) at least one tool (3a, 3b) which can be rotated or turned about an axis of rotation (2), optionally a plurality of rotatable or rotating tools (3a, 3b), is or are arranged for moving, mixing, heating and optionally comminuting the material, wherein in the container (1), in particular in a side wall (4) of the container (1), in particular in the region of the orthe height of the lowest or ground-nearest tool (3a), a container opening (5) is formed through which the pretreated 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), characterized in that a measuring device is provided for measuring the torque of the conveyor (6), that a control device which is in communication connection with the measuring device is provided for controlling the rotational speed of the tool (3a, 3b) or at least one of the tools (3a, 3b), wherein the control device is designed or configured to control the rotational speed of the tool (3a, 3b) as a function of the torque of the conveyor (6).

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

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

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

20. Device according to one of claims 16 to 19, characterized in that the control device is designed to adjust the speed of the tool (3a, 3b) so that the torque of the conveyor (6) remains constant or is halvable or the fluctuations in the torque are less than + / - 5%.

21. Device according to one of claims 16 to 20, characterized in that the control device is designed to adjust the speed of the tool (3a, 3b) so that the filling level of the conveyor (6) remains constant or can be halved or the fluctuations in the filling level are small / less than + / - 10%.

22. Device according to one of claims 16 to 21, characterized in that the control device is designed to adjust the speed of the tool (3a, 3b) so that the speed of the tool (3a, 3b) does not fall below a certain minimum speed.

23. Device according to one of claims 16 to 22, characterized in that the rotational speed of the tool (3a, 3b) is additionally adjustable, in particular increaseable, independently of the torque of the conveyor (6).

24. Device according to one of claims 16 to 23, characterized in that in the container (1) several, at least two, tools (3a, 3b) are arranged in different tool levels (30a, 30b) or at different distances from the bottom surface or lowest region of the container (1) and that the tools (3a, 3b) in the container (1) are arranged in at least two superimposed tool levels (30a, 30b).

25. Device according to one of claims 16 to 24, characterized in that the tool (3a) or the lowest tool (3a) or the lowest tool level (30a) in the area or at the height of the container opening (5) or the feed opening of the conveyor (6) connected to the container opening (5).

26. Device according to one of claims 24 to 25, characterized in that the tools (3a, 3b) in the individual tool levels (30a, 30b) can be rotated independently of one another and at different speeds, in particular via separate drives (300a, 300b).

27. Device according to one of claims 24 to 26, characterized in that the rotational speed of the tool (3a) in the lowest tool level (30a) can be controlled by the control device as a function of the torque of the conveyor (6).

28. Device according to one of claims 24 to 27, characterized in that the speed of the tool (3a) in the lowest tool level (30a) can be controlled by the control device as a function of the torque of the conveyor (6) and the speed of the tool or tools (3b) in the other tool level(s) (30b) above it can be controlled or adjusted independently of the torque of the conveyor (6).

29. Device according to one of claims 24 to 28, characterized in that the rotational speeds of all tools (3a, 3b) in each tool plane (30a, 30b) can be controlled by the control device in dependence on the torque of the conveyor (6), independently of one another.

30. Device according to one of claims 24 to 29, characterized in that the speed of the tool or tools (3b) in the other tool level(s) (30b) located above is controlled so that a certain material temperature is reached in this area and / or that the speed of the tool or tools (3b) in the other tool level(s) (30b) located above is controllable or variable depending on this material temperature.

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

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