AT526989B1 - Method and apparatus for processing or preparing polymer materials - Google Patents

Abstract

The invention relates to a method and a device for processing polymer materials, wherein the polymer materials to be processed are moved, mixed, heated, and optionally comminuted in a container (1) by at least one rotating tool (3a, 3b), and wherein the polymer materials, in their lumpy or particulate form, are 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, wherein the torque of the conveyor (6) is measured and the rotational speed of the tool, or at least one of the tools (3a, 3b), is controlled or changed as a function of the torque of the conveyor (6). The invention is characterized in that the tools (3a, 3b) are arranged in the container in at least two superimposed tool planes (30a, 30b) and the rotational speeds of all tools (3a, 3b) in each tool plane (30a, 30b) are controlled independently of one another as a function of the torque of the conveyor (6).

Description

Description

METHOD AND DEVICE FOR PROCESSING POLYMER MATERIALS

[0001] The invention relates to a method and an apparatus for processing or preparing polymer materials, in particular thermoplastic waste plastic for recycling purposes, according to the preambles of claim 1 and claim 14 respectively.

[0002] Methods and devices in which a combination of a container or a preconditioning unit (PCU) and a conveyor connected thereto, in particular an extruder, is used for the processing of polymer waste, in particular of different thermoplastic polymers, are well known.

[0003] Often, devices for pretreating the materials to be processed are connected upstream of an extrusion system, for example, known cutting compactors or preconditioning units (PCUs), which 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 others, of modifying the shape and properties of the polymer materials accordingly. Introducing energy into the material is advantageous in this process. In the pretreatment unit, the thermoplastic materials are, among other things, mixed, heated, softened, compacted, pre-degassed, dried, dehumidified, cut, crushed, crystallized, and/or homogenized, and their bulk density is increased.

[0004] The polymers thus pretreated are then fed into an extruder to be compacted, in particular melted. Such combination devices have been known for a long time, for example from EP 2 558 263 or EP 2 689 908.

[0005] The mixing and grinding 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 and extrusion processes are generally most efficient when the screw filling level is constant and sufficiently high. The feeding area of the conveyor or extruder is therefore sensitive and has a significant influence on the final result and the quality of the recyclates. In this context, factors such as the distance of the mixing and grinding tools from the conveyor or extruder screw, the shape and size of the feeding opening, and the direction of rotation of the mixing tools relative to the conveying direction of the conveyor or extruder play a role. On the conveyor or extruder side, factors such as the profile of the screw flight, the shape of the screw base, and the free open area of the screw channel are also important. If the feed behavior of the conveyor or extruder is unfavorable, the volumetric throughput can, for example, pump, i.e., the throughput can change over time, which is detrimental to reliable operation and the quality of the recyclates.

[0006] Therefore, in the prior art there has been no shortage of attempts to either constructively adapt or design the sensitive area of the feeding or infeed of a conveyor or extruder in such a way as to best support the infeed behavior and feeding of the screw and, for example, to make it more tolerant of operational material differences.

[9007] In particular, to achieve special material qualities and also to compound these materials, twin-screw or multi-screw extruders are used in addition to 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 disk onto which tools can be mounted and is located in the area of the extruder opening, feeds the pretreated materials into the extrusion device.

[0008] The number of packing cycles of the tools of the lowest tool level in the area of the conveying opening or extruder opening generally has a particular influence on the fill level of the

Conveyor or extruder. Furthermore, the average bulk density of the materials in the PCU, especially in the lowest part of the PCU, is partly responsible for the fill level, corresponding to the average compaction. It is relatively irrelevant whether the conveyor or extruder is filled from the side or in the area of the twin screw's cleavage, or with which direction of rotation the tools fill the conveying or extruder opening.

[0009] The material drawn into the conveyor or extruder is immediately conveyed further, resulting in a torque profile of the conveyor or extruder drive that depends on the fill level. The aim is generally to keep the torque profile of the conveyor or extruder, or the fill level of the conveyor or extruder, as constant as possible. This results in high-quality polymer melting without shear peaks that could lead to overheating of the polymer melt.

[0010] Excessive underfilling of the conveyor or extruder, i.e., insufficient fill level, can lead to throughput losses and shear peaks, and can also result in poorly homogenized polymers. Therefore, maintaining a constant fill level of the conveyor or extruder is advantageous for the quality of the recyclates and for economic efficiency.

[0011] Figure 4 shows an example of an unfavorable change in the torque of the extruder as a function of the rotational speed of the die. Here, for example, the rotational speed of the die was varied in an attempt to meet the requirements of the incoming material with regard to moisture, density, and material temperature in the PCU, which resulted in significant fluctuations in the torque of the extruder and the rotational speed of the die, which were detrimental to the feeding behavior and material quality, among other things.

[0012] Even the mere mixing of the materials in the PCU has a dampening effect, to a certain (small) degree, on any bulk density fluctuations of the input materials. However, mixing alone, and often even intensive pretreatment of the materials in the PCU, is insufficient in some cases, and it is not always possible to maintain a sufficiently constant bulk density over a longer period. Rather, the bulk density of the processed materials fluctuates over time from an average value up and down. This is already a disadvantage and causes the described drawbacks.

[0013] JP 2002059021 A and WO 2012164424 A2 describe devices of this type and methods carried out with them. In each case, a rotating tool is used for shredding waste materials, and the shredded material is subsequently processed further, in particular in an extruder. The torque of the extruder is measured, and the rotational speed of the shredding tool is controlled as a function of the torque.

[0014] It is therefore an object of the present invention to provide a method or device of the type mentioned at the outset with which the fill level of the conveyor or extruder can be kept as constant as possible.

[0015] This problem is solved by the characterizing features of claim 1. Accordingly, a method for processing or preparing 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 cutting 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, which are present in lumpy or particulate form, are subsequently discharged from the container and introduced into a conveyor or extruder, in particular to be further compacted and melted or agglomerated there, wherein the torque of the conveyor or extruder is measured, and the rotational speed of the tool or at least one of the tools is controlled or changed as a function of the measured torque of the conveyor or extruder.

[0016] According to the invention, it is provided that the tools are arranged in the container in at least two superimposed tool planes and that the rotational speeds of all tools in each tool plane depend on the torque of the conveyor, independently

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They can be controlled separately from each other.

[0017] This problem is solved analogously by the characterizing features of claim 14. Accordingly, a device for processing or preparing 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 cutting compactor or a preconditioning unit (PCU) for the material to be processed, wherein at least one rotatable or rotating tool, optionally several rotatable or rotating tools, for moving, mixing, heating and optionally comminuting the material is/are arranged in the container, 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, especially in the region or at the height of the lowest or bottom-adjacent tool. Furthermore, at least one conveyor or extruder is provided for receiving the material discharged from the container via the container opening.

[0018] Furthermore, it is provided that a measuring device for measuring the torque of the conveyor or extruder is provided, and that a control device in communication or data communication with the measuring device is provided for controlling the rotational speed of the tool or at least one of the tools, wherein 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.

[0019] According to the invention, it is provided that several, at least two, tools are arranged in the container in different tool planes or at different distances from the bottom surface or lowest area of the container, and that the tools are arranged in the container in at least two superimposed tool planes, and that the rotational speeds of all tools in each tool plane can be controlled independently of each other by the control device depending on the torque of the conveyor.

[0020] According to the invention, it is therefore proposed to directly influence, control, or change the rotational speed of the tool(s) in the PCU or in the container via the torque of the conveyor or extruder. The adjusted tool rotational speeds directly influence the feeding cycles into the conveyor or extruder system, thereby changing the fill level of the screw flights of the conveyor or extruder and, consequently, the torque of the conveyor or extruder. In this way, the fill level of the conveyor or extruder can be kept constant. The screw feeding behavior is improved, and the throughput and throughput consistency are also enhanced. The overall system of cutting compactor and conveyor or extruder becomes more stable and efficient as a result. Furthermore, the quality of the polymer materials obtained can be increased, and operational efficiency can be improved.

[0021] In principle, the effects mentioned are relevant and present in all conveyors or extruders, that is, not only in compressing screws for extruders or agglomerators, but also in non- or less compressing screws with a predominant or pure conveying function.

[0022] The general term “conveyor” is understood to include both systems with non-compressing or decompressing screws and systems with compressing screws, i.e., extruder screws with agglomerating or plasticizing effect.

[0023] In this text, the terms “extruder” and “extruder screw” are understood to mean conveyors and conveying screws with which the material is completely or partially melted, i.e., classic extruders, but also conveyors and conveying screws with de-

The softened material is only agglomerated, but not melted. With such agglomerating screws, the material is only briefly subjected to strong compression and shearing, but not plasticized. The agglomerating screw therefore delivers material at its outlet that is not completely molten, but consists of particles that are only partially melted on their surface and are fused together, similar to sintering. In both cases, however, pressure is exerted on the material during conveying via the screw, thus compacting it.

[0024] Systems for measuring the torque of conveyors or extruders are known. For example, in extruders, a torque detection unit can be arranged in the connection area between the gearbox output shaft and the extruder shaft for non-contact detection of the torque transmitted to the extruder shaft via the gearbox output shaft and the connection area. Other systems for continuously monitoring the torques of conveyors or extruders are also known, for example, torque sensors based on the principle of magnetostriction. Such systems primarily serve to detect and eliminate possible overload situations in order to operate the extruder, for example, closer to its load limits in order to increase the drive power or the torque density.

[0025] 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.

[0026] This means that the torque is measured during the duration of the process either at predefined times or at defined time intervals and the data are 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.

[0027] 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.

[0028] If the conveyor or extruder runs at a fixed speed nEx = const [rpm], then with a variable speed of the tools nW [rpm], different packing cycles result per speed nEx. Thus, the fill level of the screw flights changes and consequently the torque of the conveyor or extruder MEx [Nm].

[0029] Advantageously, as the torque of the conveyor or extruder increases, the rotational speed of the tool is reduced, and conversely, as the torque of the conveyor or extruder decreases, the rotational speed of the tool is increased. An advantageous device is accordingly characterized in that the control device is designed and configured to reduce the rotational speed of the tool as the torque of the conveyor or extruder increases and/or to increase the rotational speed of the tool as the torque of the conveyor or extruder decreases.

[0030] The rotational speed of the tools nWE [rpm] in the PCU is defined as a function of the torque of the conveyor or extruder MEx [Nm]. Accordingly, if the rotational speed of the tools decreases with increasing torque of the conveyor or extruder, this leads to fewer feed cycles and thus to a lower fill level of the conveyor or extruder or the screw flights of the conveyor or extruder. This in turn leads to a decrease in the torque of the conveyor or extruder. This can be implemented accordingly by a PID controller.

[0031] Advantageously, the rotational speed of the tool is controlled such that the torque of the conveyor or extruder remains constant or the fluctuations in torque are less than +/- 5%, preferably less than +/- 3%. An advantageous device is accordingly characterized in that the control device is designed to...

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The speed of the tool should be adjusted so that the torque of the conveyor or extruder remains constant or is half-barred, or the fluctuations in torque are less than +/- 5%, preferably less than +/- 3%.

[0032] In this way, it can be achieved that the torque profile of the conveyor or extruder is kept as constant as possible and peaks or larger changes are avoided.

[0033] Advantageously, the rotational speed of the tool is controlled such that the fill level of the conveyor or extruder remains constant, or that 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 rotational speed of the tool so that the fill level of the conveyor or extruder remains constant or is half-barred, or that the fluctuations in the fill level are small/less than +/- 10%, preferably less than +/- 5%.

[0034] As mentioned in the introduction, it is also advantageous with regard to the quality of the end product and economic efficiency to keep the fill level of the conveyor or extruder, or of the screw(s) of the conveyor or extruder, e.g., defined in kg/revolution, as constant as possible. The fill level of the conveyor or extruder can be determined or calculated in a practical manner, or can be measured, for example, by pressure measurement in the screw or by ultrasonic measurement, as described, for example, in AT 505618 B1.

[0035] In some cases, however, material preparation follows different rules than the feeding of the conveyor or extruder. For example, different parameters in the input material, such as highly variable moisture content, may necessitate keeping the rotational speed of the tools relatively high in order to introduce sufficient energy into the material with a given tool setup, e.g., to maintain both the evaporation of moisture and to achieve compaction. This can restrict the degree of freedom of the tool rotational speed.

[0036] Advantageously, the speed of the tool is controlled such 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 so that the speed of the tool does not fall below a certain minimum speed.

[0037] In this way, it is ensured that the torque of the conveyor or extruder is kept as constant as possible, while at the same time ensuring that sufficient energy is always introduced into the material being processed.

[0038] To compensate for different parameters in the input material and to ensure good processing, it can be advantageous if the rotational speed of the tool is also adjustable, and in particular can be increased, independently of the torque of the conveyor or extruder. An advantageous device is accordingly characterized in that the rotational speed of the tool is also adjustable, and in particular can be increased, independently of the torque of the conveyor or extruder.

[0039] This allows for greater flexibility in machining and makes it possible, for example, to react to differences in the materials being machined. In particular, for certain requirements the rotational speed of the tools must be higher and cannot be reduced, as otherwise too little energy would be transferred into the material.

[0040] According to the invention, the tools are arranged in the container in at least two superimposed tool planes. A device according to the invention is accordingly characterized in that several, at least two, tools are arranged in the container in different tool planes or at different distances from the bottom surface or lowest area of the container, and that the tools are arranged in the container in at least two superimposed tool planes.

[0041] Often, the material to be processed is fed into the top of the container, passes through the container from top to bottom during a certain residence time, and is heated, softened, and mixed in the process, and is then discharged into the conveyor or extruder at the bottom. Tools at different heights or distances from the bottom facilitate advantageous processing and increase flexibility.

[0042] Advantageously, the lowest tool level is arranged in the area or at the level 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 level of the container opening or the feed opening of the conveyor or extruder connected to the container opening.

[0043] This ensures effective filling of the conveyor or extruder.

[0044] 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.

[0045] This also increases the flexibility of the machining process. For this purpose, two or more different drives can be used, the speed of which can be controlled accordingly. It is possible to drive the tools from above, from below, or from the circumference.

[0046] 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.

[0047] In this way, the rotational speed of the tools of the lowest tool level, i.e., in the area of the filling opening of the conveyor or extruder, is controlled as a function of the torque of the conveyor or extruder. The rotational speed of the tools of the other higher tool levels can be controlled as a function of the torque of the conveyor or extruder, but need not be; that is, these tools can also rotate at a defined or adjustable speed that does not depend on the torque of the conveyor or extruder or is not torque-controlled via the control device.

[0048] In this way, for example, the polymer material in the upper part of the container can be processed at higher rotational speeds and correspondingly higher energy input, i.e., at higher temperatures. In the lower part of the PCU, the rotational speed of the tools 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 a decoupling of the material preparation in the container from the feeding of the conveyor or extruder.

[0049] Advantageously, it can also be provided that the rotational speed of the tool is controlled only in the lowest tool level as a function of the torque of the conveyor or extruder, and that the rotational speed of the tool(s) in the other tool level(s) above is controlled or set independently of the torque of the conveyor or extruder. An advantageous device is accordingly characterized in that the rotational speed of the tool can be controlled by the control device only in the lowest tool level as a function of the torque of the conveyor or extruder, and that the rotational speed of the tool(s) in the other tool level(s) above is controlled or set independently of the torque of the conveyor or extruder.

[0050] Here, therefore, it is not optional but mandatory that the rotational speed of the tools of the other higher tool levels is not controlled depending on the torque of the conveyor or extruder, but differently.

[0051] According to the invention, the rotational speeds of all tools in each tool plane are controlled independently of one another as a function of the torque of the conveyor or extruder. A device according to the invention is accordingly characterized in that the rotational speeds of all tools in each tool plane can be controlled independently of one another by the control device as a function of the torque of the conveyor or extruder.

[0052] Accordingly, the rotational speeds of all tools in all tool planes are torque-controlled, but each is independently or individually adjustable.

[0053] Advantageously, it can also be provided that the rotational speed of the tool(s) 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 rotational speed of the tool(s) in the other tool level(s) above is controlled or changed as a function of this material temperature. An advantageous device is accordingly characterized in that the rotational speed of the tool(s) in the other tool level(s) above is controlled such that a specific material temperature is reached in this area and/or that the rotational speed of the tool(s) in the other tool level(s) above is controllable or changeable as a function of this material temperature.

[0054] The tools are advantageously discs, rods or beams, in particular with knives arranged on them.

[0055] If tools are arranged in several tool planes, in particular several disks one above the other, they can, but do not have to, be the same size, i.e. they can also have different dimensions or diameters.

[0056] 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 especially 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 therefore particularly advantageous with twin-screw extruders or multi-screw extruders. Especially with co-rotating, intermeshing two- or multi-screw extruders—regardless of whether the screws have a parallel or conical orientation, particularly in the feed area—the number of packing 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 is dependent on the fill level.

[0057] For the feeding behavior, it is also advantageous how the tools of the cutting compactor 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 of the conveyor or extruder, the direction of rotation of the tool of the lowest level is essentially opposite 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.

[0058] It is particularly advantageous if the longitudinal axis of the conveyor or screw or the longitudinal axis of the screw closest to the feed 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 preferably the screw is connected to a drive at its end face and conveys at its opposite end face to an outlet opening arranged at the end face of the housing, in particular an extruder head.

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[0059] It is further advantageous if the opening in the PCU is connected directly and immediately to the feed opening without a longer distance or transfer section, e.g., a screw conveyor. This enables effective and gentle material transfer.

[0060] An advantageous device is further characterized in that the container is cylindrical or conical. However, the container does not necessarily have to have a circular cylindrical shape, although this shape is advantageous for practical and manufacturing reasons. Container shapes deviating from the circular cylindrical shape, such as frustoconical containers or cylindrical containers with an elliptical or oval base, can be converted to a circular cylindrical container of the same capacity, assuming that the height of this hypothetical container is equal to its diameter. Container heights that significantly exceed the resulting mixing vortex (taking into account the safety distance) are disregarded, since this excessive container height is not utilized and therefore no longer has any influence on the material processing.

[0061] 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 inlet opening located on its end face or in its shell wall for the material to be captured by the screw or screws of the conveyor or extruder, and the inlet opening is connected to the container opening.

[0062] In a further advantageous embodiment, the receiving container can be essentially cylindrical with a flat bottom surface and a cylindrical side wall oriented vertically to it. It is also 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 oriented vertically and/or perpendicular to the bottom surface. This also applies analogously to conical containers. These special geometries optimize the feeding behavior in a structurally stable and simple device.

[0063] 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 bottom, as well as the opening, are arranged at a short distance from the bottom surface, in particular in the area 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 bottom of the container in the edge region of the container. Since the corner edge is usually rounded, the distance is measured from the lowest edge of the opening along the imaginary downward extension of the side wall to the imaginary outward extension of the container bottom. Suitable distances are 10 to 400 mm.

[0064] Furthermore, it is advantageous for machining if the radial outermost edges of the tool extend close to the side wall of the container.

[0065] A device with a cutting compactor or a preconditioning unit (PCU) is particularly advantageous, comprising at least one mixing or comminuting tool rotatable or rotating about a rotational axis and a container opening formed in the side wall of the cutting compactor in the region of the height of the lowest, bottom-adjusted tool. A twin-screw extruder is tangentially connected to this container opening, into which the pretreated material is introduced.

[0066] Further advantages and embodiments of the invention will become apparent from the description and the accompanying drawings. The invention is schematically illustrated therein by means of non-limiting exemplary embodiments in the drawings and is described below by way of example with reference to the drawings.

[0067] Fig. 1 shows a first embodiment of a device.

[0068] Fig. 2 shows another embodiment of a device according to the invention.

[0069] Fig. 3 shows a further embodiment of a device according to the invention. [0070] Fig. 4 shows the result of a comparison test not according to the invention. [0071] Fig. 5 shows the result of a comparison test.

[0072] Figure 1 shows a first advantageous embodiment of a device for processing or preparing polymer materials, in particular thermoplastic waste plastic, for recycling purposes. The basic structure and basic operation of such a cutting, compacting, and extruding combination is well known, for example from EP 2 558 263 or EP 2 689 908, and is only briefly described below. It should also be noted that the illustrations in Figures 1 to 3 are only schematic.

[0073] The device shown in Fig. 1 comprises a cylindrical container or cutting compactor or preconditioning unit (PCU) 1 for receiving the polymer material to be processed. Such a container 1 is, for example, already well known from EP 123 771. The container 1 is cylindrical with a flat bottom surface and a cylindrical side wall 4 oriented vertically to it.

[0074] A rotatable or rotating tool 3a is arranged in the container 1. The tool 3a is a flat carrier disc, arranged at a short distance from the bottom surface, rotating about an axis of rotation, and aligned parallel to the bottom surface. Blades 7 are mounted on its upper surface. The carrier disc is driven to rotation by a motor 300a via an axis 2a, the motor 300a being located below the container 1. The axis of rotation, or axis 2a, is arranged in the central longitudinal axis of the container 1.

[0075] The tool 3a serves, among other things, to move, mix, heat, and comminute the material present in the container 1. Accordingly, the thermoplastic materials in the container 1 are mixed, heated, softened, compacted, pre-degassed, dried, dehumidified, cut, comminuted, crystallized, and/or homogenized, and their bulk density is increased. The rotation of the tool 3a creates a mixing vortex in the material, and the material remains in the container 1 for a certain residence time, where it is pretreated accordingly.

[0076] 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, here a compressing twin-screw extruder 6, is tangentially connected to this container opening 5. Especially with multi-screw extruders, the feed or feeding is particularly sensitive, and consistent feeding at as uniform a level as possible is especially important.

[0077] The outer edges of the tool 3a extend relatively close to, approximately 5% of the radius, the side wall 4. The screw of the extruder 6 closest to the container is adapted to the contour of the inner wall 4 of the container 1 and set back in the area of the container opening 5. 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 plane as the central longitudinal axis of the extruder 6.

[0078] In practical operation, the plastic material to be processed, usually in the form of plastic waste, bottles, or films, is placed in the container 1. The plastic material is shredded and mixed by the rotating tool 3a, among other things, and is heated and softened by the applied mechanical friction energy, but not melted. After a certain residence time in the container 1, the softened but not melted material is discharged from the container 1 through the opening 5 and fed to the extruder 6.

[0079] 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, compression then takes place and the polymer melt then exits or is granulated on the opposite side.

[0080] According to the invention, a measuring device (not shown) 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, which communicates with the measuring device and exchanges data for controlling the rotational speed of the tool 3a. 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, appropriately short time intervals, and the data is transmitted to the control device in order to react quickly and continuously to changes and to adjust the rotational speed of the tool 3a.

[0081] In the present case, the rotational speed of the tool 3a is controlled in such a way that the torque of the extruder 6 remains essentially constant and the fluctuations of the torque are less than +/- 5%.

[0082] By adjusting the rotational speeds of the tool 3a in this way, the packing cycles in the extruder 6 are directly influenced, and the fill level of the screw flights of the extruder 6 changes accordingly, and consequently, so does the torque of the extruder 6. In this way, the fill level of the extruder 6 can be kept very constant (see also Example 1 below).

[0083] The device of Fig. 2 is largely analogous 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 discs with knives arranged parallel to each other.

[0084] The lower tool 3a, or the lowest tool level 30a, is arranged in the area or at the level 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.

[0085] The tools 3a, 3b in the two tool planes 30a, 30b can be rotated independently of each other and at different speeds via two separate drives 300a, 300b arranged below and above the container 1.

[0086] According to the invention, the rotational speed of the lower tool 3a in the lowest tool level 30a is controlled as a function of the torque of the extruder 6.

[0087] To compensate for different parameters in the input material and to ensure good processing, it can be advantageous if the rotational speed of the other, upstream tool 3b is adjustable 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 does not depend on the torque of the conveyor or extruder or is not torque-controlled via the control device.

[0088] This is implemented in the exemplary embodiment shown in Fig. 2, and the rotational speed of the upper tool 3b in the tool level 30b above it is controlled or set independently, i.e., not dependent on the torque of the extruder 6. Here, the temperature of the material in the area of the upper tool level 30b is measured, and the rotational speed of the upper tool 3b is controlled or changed depending on this material temperature. However, this is only to be understood as an exemplary option (see also Example 2 below).

[0089] The device according to Fig. 3 is again analogous to the device of Fig. 2. The only difference is that in Fig. 3 both tools 3a and 3b are driven from below, i.e., by motors or drives 300a, 300b, both of which are arranged below the container 1. The rotary or drive axes 2a and 2b are concentrically arranged within each other.

[0090] Attempts:

[0091] The following experiments were each carried out on an exemplary test setup. This was a PCU (Preconditioning Unit) / twin-screw

Extruder combination, equipped with a melt filter SW 4/134 according to the system configuration shown below (PCU configuration 1 or 2).

[0092] HDPE bottle regrind was used as the test material in each case. This material was obtained from used containers from the hygiene sector, e.g., shampoo bottles, or from the cleaning sector, e.g., household cleaners. This material was first shredded and then pre-cleaned in a washing plant. The basic properties or parameters of this material are that it is free-flowing, but has varying bulk densities and also varying moisture contents.

[0093] Each of the experimental setups had a measuring device for measuring the torque of the extruder and a control device connected to the measuring device for controlling the rotational speed of the tool. The control device was programmed, designed, and configured to control the rotational speed of the tool as a function of the torque of the conveyor or extruder.

EXAMPLE 1:

[0094] In PCU configuration 1 (comparable to a device according to Fig. 1), a preconditioning unit (PCU), a container, or a cutting compactor was used, which had a tool with a drive that was variable in speed. A single (lower) tool level was set up here, which was arranged in the area of the container opening or in the area of the extruder feed. According to the invention, the speed of this tool was thus controlled as a function of the torque of the extruder.

PCU CONFIGURATION 1:

PCU-

Configuration 1 Device Type Remark

EREMA

PCU (container) 1300 mm diameter, a drive with variable speed

twin snail running parallel

63 mm screw diameter, made in China

Extrusion unit

Melt filter RTF 4/134 EREMA, filtration 150 µm gear

Maag SP 45 melt pump, HG 152 granulation melt pump, EREMA hot-discharge granulation

[0095] By adjusting the rotational speeds of the tools in this way, the fill level of the extruder could already be kept constant with this configuration 1. The feeding behavior of the extruder, the throughput and the throughput consistency were also improved, and the quality of the resulting PE polymer materials was very high.

EXAMPLE 2:

[0096] In the PCU configuration 2 (comparable to a device according to Fig. 2 or Fig. 3) a PCU was used which had two drives with variable speeds.

[0097] A first lower tool level (filling level) was arranged in the area of the extruder feed, and the rotational speed of the tools of this tool level was influenced and controlled by the torque of the extruder. According to the invention, the rotational speed of this tool was therefore controlled as a function of the torque of the extruder.

[0098] A second, overlying tool level was located above the first tool level

11719

The filling level was arranged in a second, variable-speed drive. This second tool level (which could also consist of several superimposed tool levels) was responsible for the advantageous preparation of the incoming material. The rotational speed of the tools in this tool level was regulated so that the energy input into the material was such that a specific material temperature was reached. The material temperature was measured using measuring systems that protruded into the material or measured the temperature contactlessly from the side or from above. This temperature was essentially determined by the polymer being introduced. It was important to ensure that the incoming material chips reached a specific temperature close to the polymer's softening point. This ensured a certain degree of pre-compaction, thus homogenizing the bulk density, and furthermore, 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 of the incoming material was also removed.

PCU CONFIGURATION 2:

PCU-

Configuration 2 Device Type Remark

EREMA

PCU 1300 mm diameter, two drives with variable speed

twin snail running parallel

63 mm screw diameter, made in China

Extrusion unit

Melt filter RTF 4/134 EREMA, filtration 150 µm gear

Maag SP 45 melt pump, HG 152 granulation melt pump, EREMA hot-discharge granulation

[0099] The result is shown in Fig. 5, namely the torque of the extruder as a function of the tool rotational speed.

[00100] Figure 5 shows the change in extruder torque as a function of the rotational speed of the tools in the lowest tool level of the PCU. In this experiment, the rotational speed of the tools in the lowest tool level of the PCU was varied as a function of the extruder torque. It was therefore not necessary to directly address the requirements of the incoming material, e.g., moisture, density, and material temperature in the PCU, as these were handled by the upper tool in the upper tool level with its own drive.

[00101] As can be clearly seen in Fig. 5, the extruder's advantageously uniform torque exhibits little to no fluctuation. This allowed the extruder's fill level to be kept extremely constant and sufficiently high. The feeding behavior of the twin-screw extruder, the throughput, and the throughput consistency were improved. The quality of the HDPE granules obtained in this way was very satisfactory.

Claims (27)

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 crushed in a container or cutting compactor (1) by at least one rotatable or rotating tool (3a, 3b), optionally several rotatable or rotating tools (3a, 3b), and wherein the polymer materials, which are present in lumpy or particulate form, are 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 particular to be compacted and melted or agglomerated there, wherein the torque of the conveyor (6) is measured and the rotational speed of the tool or at least one of the tools (3a, 3b) is controlled or changed as a function of the torque of the conveyor (6), characterized in that the tools (3a, 3b) are arranged in the container in at least two superimposed tool planes (30a, 3b). 30b) are arranged and the rotational speeds of all tools (3a, 3b) in each tool plane (30a, 30b) are controlled independently of each other as a function of the torque of the conveyor (6). 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 when the torque of the conveyor (6) increases, the speed of the tool (3a, 3b) is reduced and/or when the torque of the conveyor (6) decreases, the speed of the tool (3a, 3b) is increased. 5. Method according to one of claims 1 to 4, characterized in that the speed of the tool (3a, 3b) is controlled in such a way that the torque of the conveyor (6) remains constant or the fluctuations of the torque are less than +/- 5%. 6. Method according to one of claims 1 to 5, characterized in that the speed of the tool (3a, 3b) is controlled in such a way that the fill level of the conveyor (6) remains constant or the fluctuations in the fill level are small/less than +/- 10%. 7. Method according to one of claims 1 to 6, characterized in that the speed of the tool (3a, 3b) is controlled 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 tool (3a) or the lowest tool level (30a) is arranged in the area or at the level of the feed opening of the conveyor (6) or the container opening (5). 10. Method according to one of claims 8 to 9, characterized in that the tools (3a, 3b) in the individual tool planes (30a, 30b) can be rotated independently of each other and at different speeds, in particular via separate drives (300a, 300b). 11. Method according to one of claims 8 to 10, 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). 12. Method according to one of claims 8 to 11, characterized in that the rotational speed 13. 14. 15. 16. 17. 18. AT 526 989 B1 2026-04-15 the speed of the tool (3a) in the lowest tool level (30a) is controlled depending on the torque of the conveyor (6) and the speed of the tool or tools (3b) in the other tool level(s) above (30b) is controlled or set independently of the torque of the conveyor (6). Method according to one of claims 8 to 12, characterized in that the rotational speed of the tool(s) (3b) in the other overlying tool level(s) (30b) is controlled such 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 rotational speed of the tool(s) (3b) in the other overlying tool level(s) (30b) is controlled or changed as a function of this material temperature. Device for processing or preparing polymer materials, in particular thermoplastic waste plastic for recycling purposes, especially for carrying out the method according to claim 1, with at least one container or cutting compactor (1) for the material to be processed, wherein at least one rotatable or rotating tool (3a, 3b), optionally several rotatable or rotating tools (3a, 3b), is/are arranged in the container (1) for moving, mixing, heating and optionally comminuting the material, wherein a container opening (5) is formed in the container (1), in particular in a side wall (4) of the container (1), in particular in the area of or at the height of the lowest or bottom-adjacent tool (3a), 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), wherein a measuring device for measuring the torque of the conveyor (6) is provided, wherein a control device in communication with the measuring device is provided for controlling the 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 speed of the tool (3a, 3b) as a function of the torque of the conveyor (6), characterized in that several, at least two, tools (3a, 3b) are arranged in the container (1) in different tool planes (30a, 30b) or at different distances from the bottom surface or lowest area of the container (1) and that the tools (3a, 3b) are arranged in the container (1) in at least two superimposed tool planes (30a, 30b) and that the rotational speeds of all tools (3a, 3b) in each tool plane (30a, 30b) can be controlled independently of each other by the control device depending on the torque of the conveyor (6). Device according to claim 14, characterized in that the measuring device is designed to continuously measure the torque of the conveyor (6) at defined, in particular regular, intervals. Device according to one of claims 14 to 15, characterized in that the control device is designed to operate the conveyor (6) at a fixed speed. Device according to one of claims 14 to 16, 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. Device according to one of claims 14 to 17, 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 half bar or the fluctuations of the torque are less than +/- 5%. 14119 19. Device according to one of claims 14 to 18, characterized in that the control device is designed to adjust the speed of the tool (3a, 3b) so that the fill level of the conveyor (6) remains constant or is half-barred or the fluctuations in the fill level are small/less than +/- 10%. 20. Device according to one of claims 14 to 19, 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. 21. Device according to one of claims 14 to 20, 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). 22. Device according to one of claims 14 to 21, characterized in that the tool (3a) or the lowest tool (3a) or the lowest tool level (30a) is arranged in the area or at the level of the container opening (5) or the feed opening of the conveyor (6) connected to the container opening (5). 23. Device according to claim 22, characterized in that the tools (3a, 3b) in the individual tool planes (30a, 30b) can be rotated independently of each other and at different speeds, in particular via separate drives (300a, 300b). 24. Device according to one of claims 22 to 23, 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). 25. Device according to one of claims 22 to 24, 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) and the rotational speed of the tool or tools (3b) in the other tool level(s) above (30b) can be controlled or adjusted independently of the torque of the conveyor (6). 26. Device according to one of claims 22 to 25, characterized in that the rotational speed of the tool(s) (3b) in the other overlying tool level(s) (30b) is regulated such that a certain material temperature is reached in this area and/or that the rotational speed of the tool(s) (3b) in the other overlying tool level(s) (30b) is controllable or variable depending on this material temperature. 27. Device according to one of claims 14 to 26, characterized in that the conveyor (6) is an extruder (6) with at least two screws, in particular a twin-screw extruder. This includes 4 sheets of drawings.