Method and apparatus for processing polymeric materials

Abstract

The present invention relates to a method and an apparatus for processing or treating polymeric materials, in particular thermoplastic waste, for the purpose of recycling, in which the polymeric material to be treated is moved, mixed, heated, and optionally pulverized by at least one rotatable member or rotary blade member (3a, 3b), preferably several rotatable members or rotary blade members (3a, 3b), in a receiving vessel or cutter compactor (1), and the polymeric material in the form of small pieces or granules is then removed from the receiving vessel (1) and sent to a conveyor (6) or extruder (6), preferably a twin-screw or multi-screw extruder, where it is, among other things, compressed, melted, or agglomerated. According to the present invention, the torque of the conveyor (6) is measured, and the rotation speed of the several rotatable members or rotary blade members or at least one rotatable member or rotary blade member is controlled or changed depending on the torque of the conveyor (6).

Description

[Technical Field]

[0001] The present invention relates to a method and an apparatus for processing or treating polymeric materials, in particular thermoplastic waste intended for recycling, as set out in the preamble of original claim 1 or 16. [Background technology]

[0002] Methods and apparatus for processing polymeric materials, particularly various thermoplastic resins, in combination with a containment vessel or preconditioning unit (PCU) and a connected conveyor, particularly an extruder, are well known.

[0003] In this case, a device for pre-treating the polymeric material, such as a known cutter compactor or pre-treatment unit (PCU), is usually installed upstream of the extrusion system. It is typically a container equipped with a rotating blade and directly connected to the extruder. The processing steps in the PCU upstream of the extrusion process also serve to appropriately change the shape and properties of the polymeric material. For this reason, it is useful to introduce energy into the polymeric material. In the pre-treatment unit, the thermoplastic material can be mixed, heated, softened, reduced in volume, pre-degassed, dried, dewatered, cut, reduced in volume, pre-degassed, dried, dewatered, cut, crushed, crystallized, and / or homogenized indefinitely to increase its bulk density.

[0004] The pretreated polymer is then introduced into an extruder where it is compressed and in particular melted. Such coalescing devices have been known for many years, for example from EP 2 558 263 or EP 2 689 908.

[0005] The mixing and crushing blade elements rotating in the receiving vessel or PCU also support the intake or feeding process of the conveyor or extruder connected to the receiving vessel. Both the conveying and extrusion processes are usually very efficient when the screw intake state is constant and sufficiently high. Therefore, the intake area of ​​the conveyor or extruder is a sensitive area that has a major impact on the final result or quality of the recycled material to be achieved. In this regard, for example, the distance of the mixing and crushing blade elements to the screw of the conveyor or extruder, the shape and size of the intake opening, and the rotation direction of the mixing and crushing blade elements relative to the conveying direction of the conveyor or extruder play an important role. On the conveyor or extruder side, the shape of the screw flights, the shape of the screw base, and the free opening surface of the screw flights also play an important role.

[0006] Poor intake performance of the conveyor or extruder, for example, can lead to pumping of the volumetric throughput, i.e., variations in throughput over time, which negatively impacts reliable processing and the quality of the recycled material.

[0007] In this respect, the prior art has not attempted to adjust the intake or feed area of ​​the conveyor or extruder, which is a sensitive point, or to design this point so that the feed action and the feed zone of the screw are kept as good as possible and are able to react to material changes caused by, for example, operating conditions.

[0008] In addition to single-screw extruders, twin-screw or multi-screw extruders may also be used, especially to achieve special material grades or to mix several materials. These extruders are also directly connected to the PCU. In this case, the lowermost blade surface of the container, which can be fitted with a blade and preferably comprises a disk located in the area of ​​the extruder intake, pushes the pre-treated polymer material into the extrusion device.

[0009] The number of cycles of the rotary blade members of the lowest rotary blade member face in the region of the inlet of the conveyor or the inlet of the extruder generally has a significant effect on the inlet condition of the conveyor or the extruder. Furthermore, the average bulk density of the polymer material in the PCU, especially in the lowest region of the PCU, also affects the inlet condition according to the average degree of volume reduction. It is relatively unimportant whether the conveyor or the extruder takes in the side or gusset region of the twin screw or in which direction of rotation of the rotary blade members the inlet of the conveyor or the extruder takes in.

[0010] The polymer material fed into the conveyor or extruder is immediately sent forward, resulting in a torque curve of the driver of the conveyor or extruder that corresponds to the intake state. Usually, it is desired to keep the torque curve of the conveyor or extruder, i.e., the intake state of the conveyor or extruder, as constant as possible. This allows for a qualitatively good melting of the polymer material without the occurrence of shear peaks that could overheat the molten polymer. An extremely insufficient intake of the conveyor or extruder, i.e., an extremely low intake, can result in throughput losses and shear peaks, as well as in insufficient polymer homogenization. Therefore, a constant intake of the polymer material into the conveyor or extruder is desirable for the quality and economic efficiency of the recycled polymer material.

[0011] Figure 4 shows an example of undesirable extruder torque variations as a function of the rotational speed of the rotary blade members. In this example, the rotational speed of the rotary blade members was varied to meet the needs of the entrained polymer material in terms of moisture, volume reduction and material temperature in the PCU, but variations in the extruder torque and the rotational speed of the rotary blade members occurred, which had a significant negative impact on the entrainment operation and material quality.

[0012] Simply mixing the polymeric material in the PCU can have some (albeit small) effect of suppressing the bulk density fluctuations of the incorporated polymeric material. However, mixing alone, and often even intensive pre-treatment of the material in the PCU, is sometimes not sufficient, and it is not always possible to keep the bulk density sufficiently constant over time. Instead, the bulk density of the processed polymeric material will fluctuate over time, both above and below a mean value. This is already undesirable and leads to the problems mentioned above. Summary of the Invention [Problem to be solved by the invention]

[0013] It is therefore an object of the present invention to provide a method and an apparatus of the type mentioned at the outset, in which the intake conditions of the conveyor or extruder can be kept as constant as possible. [Means for solving the problem]

[0014] The object of the present invention is solved by a method as set out in the characterizing clause of claim 1. There is therefore provided a method for processing or treating polymeric material, in particular thermoplastic waste intended for recycling, in which the polymeric material treated in a receiving vessel, cutter compactor or pre-treatment unit (PCU) is treated, moved, mixed, heated and preferably comminuted by at least one rotatable blade member, i.e. a rotary blade member, preferably by a plurality of rotatable blade members, i.e. a rotary blade member, and the polymeric material is subsequently removed from the receiving vessel in small pieces or granules and introduced into a conveyor or extruder, in particular where it is compacted, melted or agglomerated.

[0015] According to the invention, the torque of the conveyor or extruder is measured and the rotational speed of the rotary blade member or at least one rotary blade member is controlled or varied in response to the measured torque of the conveyor or extruder.

[0016] The object of the present invention is achieved by a method as set forth in the characterizing part of claim 16. Thus, an apparatus for processing or treating polymeric materials, in particular thermoplastic waste intended for recycling, particularly suitable for carrying out the method set forth in claim 1, is provided, which comprises at least one container, cutter compactor or pre-treatment unit for the material to be treated, wherein at least one rotary blade member or a plurality of rotary blade members or rotatable blade members, which are rotated or freely rotatable about a rotation axis, are provided in the container for moving, mixing, heating and, if necessary, pulverizing the material to be treated, and wherein the container is provided with a container outlet through which the pre-treated material can be removed from the container. The container outlet is formed in a side wall of the container, in particular in the region or at the height of the rotary blade member located in its lowest position or near the bottom wall. Furthermore, at least one conveyor or extruder is provided to receive the material removed from the container through the container outlet.

[0017] According to the invention, in order to control the rotational speed of the rotary blade member or at least one rotary blade member by providing a measuring device for measuring the torque of the conveyor or extruder, a controller is provided having a communication link or data link with the measuring device, the controller being adapted or arranged to control the rotational speed of the rotary blade member in response to the torque of the conveyor or extruder. Thus, the controller controls the rotational speed of the rotary blade member in response to the torque of the conveyor or extruder measured by the measuring device.

[0018] Thus, the present invention proposes to directly influence, control, or adjust the rotational speed at which the rotary blade members rotate within the PCU or storage vessel based on the torque of the conveyor or extruder. By adjusting the rotational speed of the rotary blade members in this way, the intake cycle of the conveying or extrusion system is directly affected, and the torque of the conveyor or extruder, in turn, varies depending on the intake conditions of the screw passage of the conveyor or extruder. As a result, the intake conditions of the conveyor or extruder can be kept constant. The screw intake operation is improved, and the throughput as well as the process stability are improved. This makes the combined cutter compactor and conveyor or extruder system more stable and efficient. Furthermore, the quality of the resulting polymer material can be improved, and the economic operating efficiency is increased.

[0019] Basically, the above-mentioned effects apply to all types of conveyors or extruders, i.e. not only to compression screws for extruders or agglomerators, but also to non-compressing or low-compressing screws that have a predominantly or exclusively conveying function, and produce the above-mentioned effects.

[0020] In this specification, the term "conveyor" should be understood to refer to systems with a compressing screw, i.e., with an agglomerating or plasticizing effect, as well as to systems with a non-compressing or decompressing screw.

[0021] As used herein, the terms "extruder" and "extruder screw" refer not only to conveyors or screw-type conveyors in which the polymeric material is wholly or partially melted, i.e., a typical extruder, but also to conveyors or screw-type conveyors that only agglomerate but do not melt the softened polymeric material. Such agglomerating screws only compress and shear the polymeric material, but do not plasticize it. Thus, agglomerating screws deliver material at the outlet that is not completely melted, but consists only of superficially molten particles that are bonded together as if by sintering. However, in either case, the screw applies pressure to compress the polymeric material during conveying.

[0022] Systems for measuring the torque of conveyors or extruders are known. For example, in an extruder, a torque detection unit is provided in the connection area between the output shaft of the transmission and the shaft of the extruder to detect, without contact, the torque that can be transmitted to the extruder by the output shaft of the transmission and the connection area. Other systems for continuously monitoring the torque of conveyors and extruders are also known, such as torque sensors based on the magnetostrictive principle. These systems are primarily used to detect and eliminate possible overload conditions and to operate the extruder at its load limit in order to increase the driving force or torque density, for example.

[0023] The torque of the conveyor or extruder is preferably measured continuously at predetermined, in particular regular, time intervals, and therefore, in a preferred embodiment, the measuring device is characterized in that it is configured to measure the torque of the conveyor or extruder continuously at predetermined, in particular regular, time intervals.

[0024] This means that in practicing the present invention, the torque of the conveyor or extruder can be measured at predetermined times or at predetermined time intervals, the data can be sent to a controller, and the rotational speed of the rotary blade member can be rapidly and continuously adjusted in response to torque changes.

[0025] Preferably, the conveyor or extruder is operated at a constant rotational speed. Therefore, in a preferred embodiment, the controller is configured to operate the conveyor or extruder at a constant rotational speed.

[0026] When a conveyor or extruder is operated at a constant rotation speed nEx = constant [rpm], the intake cycle per rotation speed nEx changes as the rotation speed nW [rpm] of the rotary blade member changes, which changes the intake degree of the screw passage and, ultimately, the torque MEx [Nm] of the conveyor or extruder.

[0027] It is preferable that the rotation speed of the rotary blade member is decreased as the torque of the conveyor or extruder increases, or that the rotation speed of the rotary blade member is increased as the torque of the conveyor or extruder decreases. Therefore, in a preferred embodiment, the controller is configured to decrease the rotation speed of the rotary blade member as the torque of the conveyor or extruder increases and / or to increase the rotation speed of the rotary blade member as the torque of the conveyor or extruder decreases.

[0028] The rotation speed nWE [rpm] of the rotary blade member in the PCU is defined as a function of the torque MEx [Nm] of the conveyor or extruder. Therefore, as the torque of the conveyor or extruder increases, slowing down the rotation speed of the rotary blade member reduces the number of intake cycles, thereby lowering the intake degree of the conveyor or extruder, i.e., the screw conveying path of the conveyor or extruder. This results in a reduction in the torque of the conveyor or extruder. Such control can be mapped by a PID controller.

[0029] Preferably, the rotation speed of the rotary blade member is controlled so that the torque of the conveyor or extruder is constant or the torque of the conveyor or extruder varies by less than ±5%, preferably less than ±3%. Thus, a preferred embodiment is characterized in that the controller adjusts the rotation speed of the rotary blade member so that the torque of the conveyor or extruder remains constant, i.e. can be made constant, or the torque of the conveyor or extruder varies by less than ±5%, preferably less than ±3%.

[0030] In this way it is achieved that the torque curve of the conveyor or extruder is as constant as possible and avoids the occurrence of peaks or large variations.

[0031] The rotation speed of the rotary blade member is preferably controlled so that the intake of the conveyor or extruder remains constant or fluctuates by less than ±10%, preferably less than ±5%. Therefore, a preferred embodiment is characterized in that the controller is configured to adjust the rotation speed of the rotary blade member so that the intake of the conveyor or extruder remains constant, i.e. can be made constant, or fluctuates by less than ±10%, preferably less than ±5%.

[0032] As mentioned above, it is also desirable in terms of the quality of the final product and economic efficiency to keep the incorporation of the conveyor or extruder, i.e. the screw of the conveyor or extruder, as constant as possible, for example, evaluated in kg / rev. The incorporation of the conveyor or extruder can be determined or calculated by practical means or can be measured, for example, by pressure measurement or ultrasonic measurement in the screw, as described in Austrian Patent Specification No. 505618.

[0033] However, the processing or conditioning of polymeric materials may be responsive to factors other than incorporation into a conveyor or extruder. Various parameters in the incorporation material, such as, for example, large variations in moisture content, may require the rotational speed of the rotary blade member to be kept relatively high to introduce sufficient energy into the polymeric material at a given set-up of the rotary blade member to, for example, maintain evaporation of moisture and achieve compression. This may limit the flexibility of the rotational speed of the rotary blade member.

[0034] Preferably, the rotation speed of the rotary blade member is controlled so that it does not fall below a predetermined minimum rotation speed. Therefore, a preferred aspect is characterized in that the controller is configured to adjust the rotation speed of the rotary blade member so that it does not fall below the predetermined minimum rotation 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 is constantly injected into the material being processed.

[0036] In order to compensate for various parameters of the incoming material and ensure a good processing, it is preferable that the rotation speed of the rotary blade member can be adjusted, in particular increased, independently of the torque of the conveyor or extruder. Therefore, it is preferable that the rotation speed of the rotary blade member can be adjusted, in particular increased, independently of the torque of the conveyor or extruder. This increases the processing flexibility, for example, allowing adaptation to different materials to be processed. In particular, there are cases where, for some reason, the rotation speed of the rotary blade member needs to be increased and cannot be reduced, because this would result in insufficient energy being introduced into the material to be processed.

[0037] The rotary blade members are preferably provided on at least two rotary blade member surfaces arranged above and below the container. Therefore, a preferred embodiment is characterized in that a plurality of, at least two, rotary blade members are provided on different rotary blade member surfaces within the container, i.e., at different distances from the bottom surface or the lowest region of the container, and the rotary blade members are provided on at least two rotary blade member surfaces arranged above and below the container.

[0038] The material to be processed is usually added from the top of the container, passes through the container from top to bottom while being heated, softened, and mixed for a predetermined residence time, and then is taken into a conveyor or extruder at the bottom. The rotary blade members are at different heights or distances from the bottom of the container to facilitate good processing and increase flexibility.

[0039] The lowest rotary blade member surface is preferably provided in an area or at a height where the inlet of the conveyor or extruder is located. Therefore, it is preferable that the lowest rotary blade member surface is provided in an area or at a height where the inlet of the conveyor or extruder or the inlet of the conveyor or extruder connected to the outlet of the storage container is located. This ensures efficient intake by the conveyor or extruder.

[0040] Preferably, the rotary blade members on each rotary blade member surface can be rotated independently at different rotational speeds, in particular by separate drivers. Therefore, it is preferable that the rotary blade members on each rotary blade member surface can be rotated independently at different rotational speeds, in particular by separate drivers. This also increases processing flexibility. For this purpose, two or more drivers can be used to accommodate the respective rotational speeds. The rotary blade members may be driven from above, below, or from the side.

[0041] Preferably, the rotation speed of the rotary blade member at the lowermost rotary blade member surface is controlled in accordance with the torque of the conveyor or extruder. Therefore, a preferred embodiment is characterized in that the rotation speed of the rotary blade member at the lowermost rotary blade member surface can be controlled by a controller in accordance with the torque of the conveyor or extruder.

[0042] In this embodiment, the rotational speed of the rotary blade member of the lowest rotary blade member surface, i.e., the rotary blade member in the area of ​​the inlet of the conveyor or extruder, is controlled in response to the torque of the conveyor or extruder. The rotational speed of the rotary blade members of the rotary blade member surfaces above this may be controlled in response to the torque of the conveyor or extruder, but this is not required. In other words, the rotary blade members of the upper rotary blade member surfaces may rotate at a constant or adjustable rotational speed without being controlled in response to the torque of the conveyor or extruder or by a controller.

[0043] Thus, for example, polymer material in the upper region of the container can be processed at a high rotational speed and therefore a correspondingly high energy input, i.e., at a high temperature, while in the lower region of the PCU, the rotational speed of the rotary blade element is adjusted to maintain a constant torque or intake state of the conveyor or extruder. This allows a certain degree of freedom, i.e., separation, between the material processing in the container and the intake to the conveyor or extruder.

[0044] It is also a preferred embodiment that only the rotation speed of the rotary blade member on the lowest rotary blade member surface is controlled in accordance with the torque of the conveyor or extruder, and the rotation speeds of the rotary blade members on other rotary blade member surfaces above the lowest rotary blade member surface are controlled or adjusted independently of the torque of the conveyor or extruder. Therefore, it is a preferred embodiment that only the rotation speed of the rotary blade member on the lowest rotary blade member surface is controlled by a controller in accordance with the torque of the conveyor or extruder, and the rotation speeds of the rotary blade members on other rotary blade member surfaces above the lowest rotary blade member surface are controlled or adjusted independently of the torque of the conveyor or extruder.

[0045] Therefore, in this embodiment, it is essential, not optional, that the rotational speed of the upper rotary blade member is not controlled in response to the torque of the conveyor or extruder, but rather is controlled independently of the torque.

[0046] In another preferred embodiment, the rotation speeds of all the rotary blade members on each rotary blade member surface are controlled independently of one another in response to the torque of the conveyor or extruder. Therefore, one preferred embodiment is characterized in that the rotation speeds of all the rotary blade members on each rotary blade member surface are controlled independently of one another by a controller in response to the torque of the conveyor or extruder.

[0047] Therefore, this is an aspect characterized in that the rotational speeds of all the rotary blade members on all the rotary blade member surfaces are torque-controlled individually and independently of one another.

[0048] Another preferred embodiment is to control the rotation speed of the rotary blade member on the surface of another upper rotary blade member so that a predetermined temperature is achieved in this region. It is also preferred to measure the temperature of the polymer material in this region and control or adjust the rotation speed of the rotary blade member on the surface of another upper rotary blade member in accordance with the temperature of the polymer material. Therefore, another preferred embodiment is to control the rotation speed of the rotary blade member on the surface of another upper rotary blade member in accordance with the temperature of the polymer material so that a predetermined temperature is achieved in this region, and / or to control or adjust the rotation speed of the rotary blade member on the surface of another upper rotary blade member in accordance with the temperature of the polymer material.

[0049] The rotary blade member is preferably disk-shaped, rod-shaped or bar-shaped, and in particular is provided with a blade.

[0050] The blades are provided on a plurality of rotary blade member surfaces, in particular on a plurality of disk surfaces, and do not necessarily have to be of the same size, but may have different dimensions or diameters.

[0051] In one preferred embodiment, the conveyor is equipped with at least one compression screw and configured as a single-screw extruder. Furthermore, it is highly preferred that the conveyor has multiple compression screws. It is particularly preferred that the conveyor is a twin-screw extruder, in particular a synchronous twin-screw extruder. In fact, achieving a good incorporation degree is highly preferred in twin-screw extruders or multi-screw extruders. In particular, in intermeshing synchronous twin-screw or multi-screw extruders, regardless of whether the screws have parallel or conical paths, especially in the feed region, the number of incorporation cycles at the lowest rotary blade member face in the region of the extruder inlet particularly influences the incorporation degree of the extruder system, resulting in a torque curve for the extruder driver depending on the incorporation degree.

[0052] For the intake operation, it is particularly important how the rotary blade members of the cutter compactor push the pre-treated polymer material into the inlet of the conveyor or extruder and support this pushing operation. This depends, inter alia, on the direction of rotation of the screw of the conveyor or extruder and the direction of rotation of the rotary blade members. In this respect, it has proven advantageous for the direction of rotation of the rotary blade members of the lowest rotary blade member face to be opposite or substantially opposite to the conveying direction by the conveyor or extruder in the area before the outlet of the receiving vessel or in the area before the inlet or inlet of the conveyor or extruder. Such configurations are already known, for example, from EP 2 558 263 or EP 2 689 908, the disclosures of which are incorporated herein by reference.

[0053] In particular, the longitudinal axis of the conveyor or extruder, or the longitudinal axis of the screw closest to the inlet or inner wall of the housing, i.e., the screw envelope, preferably extends tangent to the inside of the side wall of the container, in which case the screw is preferably connected at its front end to the driver and delivers at its opposite end to an outlet at the front end of the screw housing, in particular at the head of the extruder.

[0054] It is further preferred that the outlet provided on the PCU is directly connected to the inlet, for example to a screw type conveyor, without any long gap or transition distance, which allows for efficient and gentle material conveyance.

[0055] In a further preferred embodiment, the container is characterized by a cylindrical or conical shape. However, it is not essential that the container be cylindrical, although this shape is preferred for practical and technical manufacturing reasons. Containers with shapes that deviate from cylindrical shapes, such as frusto-conical containers or cylindrical containers with elliptical or oval contours, can be converted into cylindrical containers of the same volume, assuming that the height of this virtual container is equal to its diameter. Container heights that significantly exceed the naturally occurring mixing vortex (taking into account safety distances) can be ignored, since this excess container height is not utilized and therefore does not affect material processing.

[0056] In a preferred embodiment, the conveyor or extruder is connected tangentially to the container and / or the housing of the conveyor or extruder is provided at its front end or in its jacket wall with an inlet for the polymer material to be taken up by the screw of the conveyor or extruder, which inlet is connected to the outlet of the container.

[0057] In a further preferred embodiment, the container has a substantially cylindrical shape with a flat bottom and a cylindrical sidewall extending perpendicular to the bottom. The structure is also simpler when the rotation axis of the rotary blade member coincides with the central axis of the container. In a more preferred embodiment, the rotation axis of the rotary blade member or the central axis of the container extends vertically and / or perpendicular to the bottom. This also applies to conical containers. Such a shape optimizes the intake operation in a structurally stable and simplified device.

[0058] In the present invention, a preferred embodiment is that the rotary blade member, or if multiple rotary blade members are provided one above the other, the lowest rotary blade member closest to the bottom of the container is provided together with the outlet port close to the bottom of the container, particularly in the lowest region occupying one-fourth of the height of the container. This distance is measured from the lowest edge of the outlet or inlet port to the bottom of the container at the edge region of the container. Since the edges of the container are usually rounded, this distance is measured from the lowest edge of the outlet port along a line extending downward from the side wall of the container to a line extending outward from the bottom of the container. A suitable distance is 10 to 400 mm.

[0059] Furthermore, it is preferable that the radially outermost end of the rotary blade member be adjacent to the side wall of the container.

[0060] Highly preferred is an apparatus having a cutter compactor or pre-processing unit (PCU) with at least one rotatable or rotating mixing or grinding element and with a container outlet formed in the side wall of the cutter compactor in the region of the height of the lowest rotary blade element adjacent to the bottom of the container.

[0061] The twin screw extruder is connected tangentially to the outlet of a receiving vessel into which the pretreated polymeric material is taken. [Brief explanation of the drawings]

[0062] Further specific advantages and embodiments of the present invention will become apparent from the following description and the accompanying drawings, which show the invention diagrammatically by way of non-limiting exemplary embodiments and which will be described in more detail with reference to the accompanying drawings, in which: [Figure 1] 1 shows a first embodiment of the device according to the invention; [Figure 2] 3 shows another embodiment of the device according to the invention. [Figure 3] 3 shows yet another embodiment of the device according to the present invention. [Figure 4] 4 shows the results of a comparative test not according to the present invention. [Figure 5] The results of the comparative test are shown below. DETAILED DESCRIPTION OF THE INVENTION

[0063] Figure 1 shows a first preferred embodiment of an apparatus according to the invention for processing or treating polymeric materials, in particular thermoplastic waste intended for recycling. The basic structure and basic function of such a combined cutter-compactor and extruder system are known, for example from EP 2 558 263 or EP 2 689 908, and will therefore be described in a very brief manner below. It should be noted that the illustrations in Figures 1 to 3 are purely schematic.

[0064] The apparatus shown in Figure 1 comprises a cylindrical container, cutter compactor or pre-treatment unit (PCU) 1 for containing the polymeric material to be treated. This container 1 is already known, for example from EP 123 771. The container 1 is cylindrical with a flat bottom and a cylindrical sidewall jacket 4 extending perpendicularly to the bottom.

[0065] A rotatable rotary blade member, i.e., rotary blade member 3a, is provided within storage container 1. Rotary blade member 3a is a flat support disk provided at a slight distance from the bottom surface, and is positioned parallel to the bottom surface, with a plurality of blade portions 7 attached to its upper surface. The support disk is rotatably driven by motor 300a via shaft 2a, which is provided below storage container 1. Rotational shaft 2a is positioned on the longitudinal axis, i.e., central axis, of storage container 1.

[0066] In particular, the rotary blade member 3a moves, mixes, heats, and pulverizes the material to be processed within the container 1. For this reason, the thermoplastic material is generally mixed, heated, softened, reduced in volume, pre-degassed, dried, dehumidified, cut, pulverized, crystallized, and / or homogenized within the container 1, and the bulk density of the thermoplastic material is reduced. The rotation of the rotary blade member 3a creates a mixing vortex in the material to be processed, and the material is pre-heated by remaining in the container 1 for a predetermined residence time.

[0067] The side wall 4 of the container 1 is formed with a container outlet 5 at the level of the rotary blade members 3a, in the example embodiment at the level of the lowest rotary blade member face 30a. The housing or inlet of a conveyor 6, which in the embodiment is a twin-screw type compression extruder 6, is connected tangentially to the container outlet 5. In particular in multi-screw type extruders, the intake is very sensitive, so a constant feed at the most stable height is particularly important.

[0068] The outer end of the rotary blade member 3a is quite close (about 5% of the radius of rotation) to the side wall 4. In the region where the discharge outlet 5 of the container is formed, the screw of the extruder 6 approaching the container is positioned so as to be recessed from the contour of the inner wall 4 of the container 1 so as to conform to the contour of the inner wall. No part of the extruder 6 protrudes into the interior of the container 1. The rotary blade member 3a or blade portion 7 is substantially at the same height or plane as the longitudinal centerline of the extruder 6.

[0069] During operation, the material to be processed, usually in the form of plastic waste, plastic bottles, or plastic film, is introduced into the container 1. The introduced plastic material is crushed and mixed by the rotary blade member 3a, among other things, and is heated and softened without being melted by the mechanical friction energy generated during the crushing and mixing process. After a predetermined residence time in the container 1, the softened but not melted material is removed from the container 1 through the outlet 5 of the container and fed to the extruder 6, i.e., the extruder 6 is fed in this way.

[0070] In this exemplary embodiment, extruder 6 is a well-known conventional synchronized twin-screw extruder in which the softened plastic material is melted in a first zone and then compressed, and the resulting polymer melt is extruded or pelletized opposite the intake end.

[0071] The present invention provides a measurement device (not shown) for measuring the torque of the extruder 6, i.e., the twin-screw extruder. Such torque measurement devices for extruders are known. The present invention also specifies a measurement device (also not shown) equipped with a communication or data link for controlling the rotational speed of the rotary blade member 3a. The controller controls the rotational speed of the rotary blade member 3a in response to the torque of the extruder 6 measured by the measurement device. In an embodiment, the torque of the extruder 6 is continuously measured at predetermined, suitably short time intervals, and the measured data is transmitted to the controller, which rapidly and continuously adjusts the rotational speed of the rotary blade member 3a in response to changes in the data.

[0072] In this embodiment, the rotation speed of the rotary blade member 3a is controlled so that the torque of the extruder 6 is substantially constant and the torque fluctuation is less than ±5%.

[0073] By adjusting the rotation speed of the rotary blade member 3a, the intake cycle of the extruder 6 is directly influenced, so that the torque of the extruder 6 varies depending on the intake level of the screw passage of the extruder 6. In this way, the intake level of the extruder 6 can be kept very constant (see also Example 1 below).

[0074] The device in Figure 2 is generally similar to the device in Figure 1, but the storage container 1 contains two support disks with the upper and lower rotary blade member surfaces 30a and 30b of the two rotary blade members 3a and 3b, specifically, with the blade portions arranged parallel to each other.

[0075] The lower rotary blade member 3a or the lowest rotary blade member surface 30a is provided in an area or height where the discharge port 5 of the storage container, i.e., the intake port of the twin-screw extruder 6, is located. The upper rotary blade member 3b, i.e., the upper rotary blade member surface 30a, is provided in a central area near the upper area of ​​the storage container 1.

[0076] The rotary blade members 3a, 3b on the two rotary blade member surfaces 30a, 30b may be rotated separately at different rotational speeds by two separate drivers 300a, 300b provided below and above the container 1.

[0077] The rotation speed of the lower rotary blade member 3 a on the lowermost rotary blade member surface 30 a is controlled in accordance with the torque of the extruder 6 .

[0078] In order to be able to compensate for different parameters of the material being fed and to ensure good processing, the rotation speed of the upper rotary blade member 3b is preferably adjustable independently of the torque of the extruder 6. The upper rotary blade member 3b may for example rotate at a rotation speed that is constant, arbitrarily adjustable or independent of the parameters of the material being fed and that is not dependent on the torque of the conveyor or extruder, i.e. is not subject to torque control by a controller.

[0079] This is achieved in the exemplary embodiment shown in Figure 2, where the rotational speed of the upper rotary blade member 3b in the upper rotary blade member surface 30b is controlled and adjusted independently of the torque of the extruder 6. In this embodiment, the temperature of the material to be treated is measured in the area of ​​the upper rotary blade member surface 30b, and the rotational speed of the upper rotary blade member 3b is controlled or changed depending on the temperature of the material to be treated. However, this control is only one exemplary option (see also Example 2 below).

[0080] The device shown in Fig. 3 is similar to the device in Fig. 1. The only difference is that in Fig. 3, both rotary blade members 3a, 3b are driven from below by motors or drivers 300a, 300b provided below the container 1. The rotary or drive shafts 2a, 2b are coaxial. [Example]

[0081] The following tests were each carried out on a test system according to an embodiment of the present invention, which is a combined system of a PCU (Preconditioning Unit) and a twin-screw extruder equipped with a melt filter SW4 / 134, having the following system configuration (PCU configuration 1 or 2):

[0082] The test materials used were crushed high-density polyethylene bottles. The test materials were obtained from sanitary containers such as used shampoo bottles or cleaning agent containers such as used household detergent bottles. The test materials were first crushed and then pre-washed in a washing machine. The basic properties or parameters of the test materials were good fluidity, but they had different bulk densities and moisture contents.

[0083] Each prototype equipment was equipped with a measuring device for measuring the torque of the extruder and a controller connected to the measuring device for controlling the rotation speed of the rotary blade member. The controller was programmed, designed, and set to control the rotation speed of the rotary blade member in response to the torque of the conveyor, i.e., the extruder.

[0084] Example 1 In PCU structure 1 (corresponding to the device shown in Figure 1), the pre-processing unit (PCU), i.e., the cutter compactor, was a container having a rotary blade member with a drive whose rotation speed was variable. The rotary blade member was configured so that one (lower) rotary blade member surface was provided in the area of ​​the outlet of the container, i.e., the intake area to the extruder. The rotation speed of the rotary blade member was controlled according to the torque of the extruder in accordance with the present invention.

[0085] TIFF2025539520000002.tif69151

[0086] As described above, by controlling the rotation speed of the rotary blade member, the degree of filling of the extruder could be kept constant in this PCU structure 1. The extruder intake state, throughput, and processing stability were also improved, and the quality of the obtained high-density polyethylene polymer was extremely high.

[0087] Example 2 In PCU configuration 2 (corresponding to the device shown in FIG. 2 or FIG. 3), a PCU with two variable speed drives was used.

[0088] The first, or lower, rotary blade member face (intake position) was positioned in the intake area of ​​the extruder, and the rotational speed of the rotary blade member of the lower rotary blade member face was controlled by the torque of the extruder. Thus, the rotational speed of the lower rotary blade member was controlled in response to the torque of the extruder in accordance with the present invention.

[0089] A second rotary blade surface, located above the first rotary blade surface, i.e., the intake surface, was provided above the first rotary blade surface. The second rotary blade surface was driven by a variable-speed second driver. The second rotary blade surface (multiple rotary blade surfaces may be provided one above the other) contributed to the efficient processing of the intake material. The rotational speed of the rotary blade members of the second rotary blade surface was controlled so that the energy applied to the polymer material reached a predetermined material temperature. The temperature of the polymer material was measured using a measurement system inserted into the polymer material or non-contact-detecting the temperature from the side or above. The detected temperature could be considered to be the temperature of the polymer added. It was necessary to ensure that the added polymer pieces reached a temperature near the softening point of the polymer. This ensured the desired pre-volume reduction, i.e., homogenization of the bulk density, and further facilitated melt processing in the extruder because the entire amount of the material to be processed reached a temperature near the softening point. The softening point of the thermoplastic polymer material used was in the range where evaporation of water occurred, so that residual moisture in the input polymer material was also removed.

[0090] TIFF2025539520000003.tif69152

[0091] The results are shown in Figure 5. It can be seen that the torque of the extruder is a function of the rotation speed of the rotary blade member.

[0092] 5, it can be seen that the torque fluctuation of the extruder is a function of the rotational speed of the rotary blade member at the lowest rotary blade member surface of the PCU. In this test, the rotational speed of the rotary blade member at the lowest rotary blade member surface of the PCU was thus varied according to the torque of the extruder. During this process, the conditions of the input material in the PCU, such as moisture content, volume reduction rate, and temperature of the material to be processed, were controlled by the upper rotary blade member at the height of the upper rotary blade member equipped with a dedicated driver, so no one had to pay direct attention to these.

[0093] It can be clearly seen in Figure 5 that the extruder has a good uniform torque with little or no torque fluctuation. Thus, the degree of filling of the extruder remains very constant and is sufficiently high. The intake, throughput and processing consistency of the twin-screw extruder are improved. The quality of the high-density polyethylene granules thus obtained is very satisfactory.

Claims

1. 1. A method for processing or treating polymeric materials, in particular thermoplastic waste for the purpose of recycling, in which the polymeric material treated in a receiving vessel or cutter compactor (1) is treated, moved, mixed, heated and preferably pulverized by at least one rotatable blade member (3a, 3b), preferably by a plurality of rotatable blade members (3a, 3b), and the polymeric material is subsequently removed from the receiving vessel (1) in the form of small pieces or granules and introduced into a conveyor (6), in particular an extruder (6), preferably a twin-screw or multi-screw extruder, and in particular compressed, melted or agglomerated in the conveyor or extruder, a method for measuring the torque of the conveyor (6) and controlling or varying the rotation speed of the rotary blade member or of the at least one rotary blade member (3a, 3b) depending on the torque of the conveyor (6).

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

3. 3. A method according to claim 1 or 2, characterized in that the conveyor (6) is operated at a constant rotational speed.

4. 4. The method according to claim 1, wherein the rotation speed of the rotary blade members (3a, 3b) is reduced as the torque of the conveyor (6) increases, and / or the rotation speed of the rotary blade members (3a, 3b) is increased as the torque of the conveyor (6) decreases.

5. 5. The method according to claim 1, wherein the rotation speed of the rotary blade members (3a, 3b) is controlled so that the torque of the conveyor (6) is constant or the fluctuation of the torque is less than ±5%.

6. 6. The method according to claim 1, wherein the rotation speed of the rotary blade members (3a, 3b) is controlled so that the intake rate of the conveyor (6) is constant or the fluctuation of the intake rate is less than ±10%.

7. 7. The method according to claim 1, wherein the rotational speed of the rotary blade members (3a, 3b) is controlled so that the rotational speed of the conveyor (6) does not fall below a predetermined minimum rotational speed.

8. 8. A method according to any one of claims 1 to 7, characterized in that the rotation speed of the rotary blade members (3a, 3b) can be adjusted, preferably increased, without depending on the torque of the conveyor (6).

9. 9. The method according to claim 1, wherein the rotary blade members (3a, 3b) are provided in the container with at least two upper and lower rotary blade member faces (30a, 30b).

10. 10. The method according to any one of claims 1 to 9, characterized in that the rotating element (3a) or the lowest rotating element surface (30a) is provided in the region or at the height of the inlet of the conveyor (6) or the outlet of the container (5).

11. 11. The method according to claim 9 or 10, characterized in that the rotary blade members (3a, 3b) in the individual rotary blade member faces (30a, 30b) are rotated independently of each other at different rotational speeds, in particular by separate drivers (300a, 300b).

12. 12. The method according to any one of claims 9 to 11, characterized in that the rotation speed of the rotating member (3a) at the lowest rotating member surface (30a) is controlled depending on the torque of the conveying machine (6).

13. 13. The method according to any one of claims 9 to 12, characterized in that the rotation speed of the rotating member (3a) on the lowest rotating member surface (30a) is controlled in response to the torque of the conveyor (6), and the rotating blade member or members (3b) on the upper rotating blade member surface (30b) are controlled or adjusted independently of the torque of the conveyor (6).

14. 14. The method according to any one of claims 9 to 13, characterized in that the rotational speeds of all the rotary blade members (3a, 3b) on each of the rotary blade member faces (30a, 30b) are controlled independently and separately from each other in response to the torque of the conveyor (6).

15. 15. The method according to any one of claims 9 to 14, characterized in that the rotary blade members (3b) on the upper rotary blade member surface (30b) are controlled so that a predetermined material temperature is achieved in the area where the rotary members are located and / or the temperature of the material is measured in that area and the rotation speed of the rotary blade member or rotary members (3b) on the upper rotary blade member surface (30b) is controlled depending on the material temperature.

16. 1. An apparatus for processing or treating polymeric materials, in particular thermoplastic waste, for the purpose of recycling, in particular for carrying out the method according to claim 1, at least one receiving vessel or cutter compactor (1) for the material to be processed, At least one rotary blade member (3a, 3b) or a plurality of rotatable blade members or rotary blade members (3a, 3b) rotated or freely rotatable about a rotation axis (2) are provided in the container (1) for moving, mixing, heating and, if necessary, pulverizing the material to be treated; The container (1) has a container outlet (5) formed in a side wall (4) of the container (1) or in the region or height of the lowest or bottom wall of the rotary blade member (3a), through which pre-treated material can be removed from the inside of the container (1), and the device is provided with at least one conveyor (6), in particular an extruder (6), for receiving the material removed from the container (1), A measuring device for measuring the torque of the conveying machine (6) is provided, and a controller having a communication link with the measuring device and controlling the rotational speed of the rotary blade members (3a, 3b) or at least one of the rotary blade members (3a, 3b) is provided, and the controller is configured to control or be able to control the rotational speed of the rotary blade members (3a, 3b) in accordance with the torque of the conveying machine (6).

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

18. 18. Apparatus according to claim 16 or 17, characterized in that the controller is arranged to operate the conveyor (6) at a constant rotational speed.

19. 19. Apparatus according to any one of claims 16 to 18, characterized in that the controller is configured to reduce the rotational speed of the rotary blade members (3a, 3b) as the torque of the conveyor (6) increases and / or to increase the rotational speed of the rotary blade members (3a, 3b) as the torque of the conveyor (6) decreases.

20. 20. Apparatus according to any one of claims 16 to 19, characterized in that the controller is configured to adjust the rotational speed of the rotary blade members (3a, 3b) so that the torque of the conveyor (6) remains constant or is reduced by half, or so that the torque fluctuates by less than ±5%.

21. 21. Apparatus according to any one of claims 16 to 20, characterized in that the controller is configured to adjust the rotational speed of the rotary blade members (3a, 3b) so that the intake state of the conveyor (6) remains constant or is reduced by half, or so that the intake state fluctuates by less than ±10%.

22. 22. Apparatus according to any one of claims 16 to 21, characterized in that the controller is configured to adjust the rotational speed of the rotary blade members (3a, 3b) so that the rotational speed of the rotary blade members (3a, 3b) does not fall below a predetermined rotational speed.

23. 23. Apparatus according to any one of claims 16 to 22, characterized in that the rotational speed of the rotary blade members (3a, 3b) can be adjusted, preferably increased, without depending on the torque of the conveyor (6).

24. 24. The device according to any one of claims 16 to 23, characterized in that at least two plurality of rotary blade members (3a, 3b) are provided in the container (1) on different rotary blade member surfaces (30a, 30b) or at different distances from the bottom surface or lowest region of the container (1), and the rotary blade members (3a, 3b) are provided on at least two rotary member surfaces (30a, 30b) one above the other in the container.

25. 25. The device according to any one of claims 16 to 24, characterized in that the rotary blade member (3a), the lowest rotary blade member (3a) or the lowest rotary blade member surface (30a) is provided in the area or at the height of the outlet (5) of the storage container or the inlet of the conveyor (6) connected to the outlet (5) of the storage container.

26. 26. An apparatus according to claim 24 or 25, characterized in that the rotary blade members (3a, 3b) in each rotary blade member surface (30a, 30b) are rotated independently of each other at different rotational speeds, in particular by separate drivers (300a, 300b).

27. 27. The device according to any one of claims 24 to 26, wherein the rotation speed of the rotating member (3a) at the lowest rotating member surface (30a) is controlled by the controller in response to the torque of the conveyor (6).

28. 28. An apparatus according to any one of claims 24 to 27, characterized in that the rotational speed of the rotating member (3a) on the lowest rotating member surface (30a) is controlled in response to the torque of the conveyor (6), and the rotating blade member or multiple rotating members (3b) on the upper rotating blade member surface (30b) are controlled or adjustable without being dependent on the torque of the conveyor (6).

29. 29. An apparatus according to any one of claims 24 to 28, characterized in that the rotational speeds of all the rotary blade members (3a, 3b) on each of the rotary blade member surfaces (30a, 30b) are controlled independently and separately from one another in response to the torque of the conveyor (6).

30. 30. An apparatus according to any one of claims 24 to 29, characterized in that the rotary blade members (3b) in the upper rotary blade member surface (30b) are controlled so that a predetermined material temperature is achieved in the area where they are located and / or the rotation speed of the rotary blade member or rotary members (3b) in the upper rotary blade member surface (30b) is controlled or changed depending on the material temperature.

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

Images