Device for processing polymer materials

Abstract

The invention relates to a device for processing polymer materials, comprising a container (100), wherein the container (100) is equipped with a stuffing tool (300a, 300b,...) for generating a stuffing pressure on the material in the direction of a container opening (500) in order to discharge the material. The device comprises a multi-screw extruder (1), and a control device is provided in order to control the rotational speed N(PCU) of the stuffing tool (300a, 300b,...) and / or the rotational speed n(ex) of the screws (3a, 3b,...) such that the ratio (V) of the stuffing number S(PCU) of the container (100) to the transport number t(ex) of the extruder (1) V = S(PCU) / t(ex), where V ≤ 10, the following applying for the stuffing number S(PCU) [1 / min]: S(PCU) = N(PCU) * A(PCU) and the following applying for the transport number t(ex) in [1 / min]: t(ex) = g(ex) * n(ex) * a(ex).

Description

[0001] Device for processing polymer materials

[0002] The invention relates to a device and a method for processing or preparing polymer materials, in particular thermoplastic waste plastic, for recycling purposes according to the preambles of claims 1 and 18.

[0003] It is known from the prior art, for example, that a passive feeding element, such as a hopper, or an active feeding element, such as a screw conveyor, is used to introduce a material to be processed into the feed opening of an extruder. However, the materials must possess a certain flowability for this purpose, e.g., bottle refining, but also agglomerates or granules. A large number of materials, e.g., film shreds, fiber shreds, but also ground PET bottles, generally do not have these free-flowing properties, or not to a sufficient degree. Therefore, active feeding systems are advantageously used, which forcefully convey the material into the extruder, for example, a screw conveyor directly coupled to the extruder. Even more advantageous is the upstream integration of a cutting compactor or a preconditioning unit (PCU), which regularly provides very good equalization or...can create material preparation.

[0004] Such devices, comprising a combination of a container, a cutting compactor or preconditioning unit (PCU), and an attached extruder, for the pretreatment and processing of polymer waste, are known in a variety of configurations. These are usually containers with rotating tools directly coupled to the extruder. The mixing and grinding tools circulating within the container or PCU also support the filling or feeding process of the attached extruder. This processing step in the PCU, which precedes the extrusion process, also serves, among other things, to modify the shape and properties of the polymer materials accordingly.In the pretreatment unit, the thermoplastic materials undergo processes including mixing, heating, softening, compaction, pre-degassing, drying, dehumidification, cutting, comminution, crystallization, and / or homogenization, and their bulk density is increased. However, the materials are not melted at this stage. The polymers pretreated in this way are then fed into the extruder to be compacted, and 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. Extruders in various configurations, such as single-screw or multi-screw extruders for processing and melting polymeric materials, are also known from the prior art.

[0005] The extrusion process is generally most efficient when the screw filling level is consistent and sufficiently high. The feeding process of the extruder is therefore sensitive and significantly influences the final result and the quality of the recyclates. For example, unfavorable feed characteristics of the extruder can lead to a pumping effect in the throughput, i.e., a change in the throughput over time, which is detrimental to reliable operation and the quality of the recyclates. Consequently, numerous attempts have been made in the prior art to improve the feed characteristics and feeding of extruders.

[0006] In the processing of thermoplastic materials, especially in the reprocessing of industrial or post-consumer waste, materials are often processed whose original form, e.g., films, bottles, die-cut grids, cups, fibers, nonwovens, textiles, etc., is transformed into a transportable form through pre-processing, shredding, or washing. Single-screw extruders, i.e., extruders with only one rotating screw, are very frequently used for processing such materials.

[0007] However, multi-screw extruders, especially twin-screw extruders, are often advantageous for processing such materials. This is particularly true when refining or special cleaning steps are required on the polymer. Twin-screw or multi-screw extruders are therefore advantageously used primarily to achieve specific material qualities and to compound these materials.

[0008] In twin-screw extruders, two screws rotate side by side in a roughly oval-shaped cylinder or bore, either in the same or opposite directions. The material to be processed is fed into the extruder via the feed opening, then melted under pressure and material compression, and conveyed downstream in the cylinder. The melt is subsequently fed to a die or extruded from the extruder.

[0009] In co-rotating twin-screw extruders, two parallel cylindrical or two conical screws rotate side by side in a cylinder or housing with the same direction and speed of rotation. The transport processes, or conveying principle, in the screw elements of a co-rotating twin-screw extruder are based on the so-called drag conveying principle, i.e., the transfer of the material from one screw to the other within the engagement area of ​​the screws. Accordingly, twin-screw extruders, unlike single-screw extruders, are regularly operated only partially filled. This results in a certain degree of forced conveying, as well as good mixing through redistribution and surface renewal, and ensures that a homogeneous melt with the necessary temperature and pressure is conveyed into the downstream die.

[0010] In counter-rotating twin-screw extruders, two cylindrical or parallel screws, or two conical screws, rotate in opposite directions. The clearance between the screws is typically somewhat tight, and the tendency for wear is correspondingly higher. Counter-rotating twin-screw extruders are also generally operated partially filled, partly to prevent excessive pressure build-up and the associated material wear on the screws and barrels.

[0011] Multi-screw extrusion systems are generally fed gravimetrically, and sometimes volumetrically, to maintain a largely constant fill level within the extrusion system. This invariably results in a partially filled screw in the feed area of ​​multi-screw extruders. A single-screw extruder, on the other hand, is fundamentally capable of producing largely constant fill levels along the screw from a "full hopper," i.e., with a fully filled screw in the feed area.

[0012] As previously explained, the material fed into the extruder is immediately transported further downstream, resulting in a torque curve for the extruder drive that depends on the fill level. The aim is generally to keep the extruder's torque curve, or the fill level of the partially filled extruder (usually defined in kg / revolution), as constant as possible. This ensures high-quality polymer melting without shear peaks that could lead to overheating of the polymer melt. Excessive filling of the extruder, i.e., insufficient fill level, can lead to throughput losses and shear peaks, as well as poorly homogenized polymers. Therefore, maintaining a constant extruder fill level is advantageous for the quality of the recyclates and for economic efficiency. Despite all efforts and preventative measures, it is still possible that, for example,The bulk density variations cannot be sufficiently balanced over time. While mixing the materials in the PCU does have a dampening effect on any bulk density fluctuations of the input materials to a certain (small) degree, such mixing alone, and often even intensive pretreatment of the materials in the PCU, is insufficient in many cases. Maintaining a sufficiently constant bulk density over extended periods then proves impossible. Instead, the bulk density of the processed materials fluctuates over time, rising and falling from an average value. This is detrimental and also causes the disadvantages described above. Unfavorable settings can manifest themselves, for example, in significant effects that are detrimental to feeding behavior and material quality, among other things.

[0013] The object of the present invention is therefore to provide a device of the type mentioned at the outset with which the fill level of the extruder can be kept as constant as possible, or with which the feed behavior and the feeding of the screw are supported in the best possible way, and which makes the extruder or its feed behavior and fill level, for example, more tolerant of operational material differences and influences.

[0014] This problem is solved by the characterizing features of claim 1.

[0015] The device is designed for processing or preparing polymer materials, in particular thermoplastic waste plastic for recycling purposes, with at least one container or cutting compactor for the material to be processed, wherein at least one, preferably several, rotatable tools for moving, mixing, heating and optionally comminuting the material are arranged in the container, wherein a container opening is formed in the container, in particular in a side wall of the container, through which the pretreated material can be discharged from the interior of the container, wherein at least one of the tools is arranged in the area of ​​the container opening and a packing tool is or serves as a packing tool for generating a packing pressure or force on the material in the direction of the container opening for the discharge of the material from the container, wherein the device includes at least one extruder orThe multi-screw extruder for processing and melting the material discharged from the container comprises at least two screws rotatable in a common housing, in particular a twin-screw extruder, wherein the extruder is directly connected to the container for receiving the material discharged from the container opening.

[0016] According to the invention, a control device is provided for setting and controlling the rotational speed N(PCll) of the at least one packing tool and / or for controlling the rotational speed n(ex) of the at least two screws, wherein the control device is designed and / or configured to control the rotational speed N(PCll) of the at least one packing tool and / or the rotational speed n(ex) of the screws in such a way that the ratio (V) between a packing number S(PCll) of the container and a transport number t(ex) of the extruder is:

[0017] V = S(PCU) / t(ex)

[0018] V < 10, in particular V < 8, preferably V < 5, preferably V < 1, is,

[0019] - where the following applies to the filling number S(PCll) [1 / min]:

[0020] S(PCll) = N(PCll) * A(PCll) where

[0021] N(PCll) the rotational speed of the lowest or closest tamping tool(s) [U / rnin] and

[0022] A(PCll) specifies the number of feeding tools, and the following applies to the feed rate t(ex) in [1 / min]: t(ex) = g(ex) * n(ex) * a(ex) where g(ex) is the number of threads or flights of the screws, n(ex) is the screw speed [rpm], and a(ex) is the number of screws. By controlling the speed of the at least one feeding tool or the speed of the at least two screws according to the invention, the feeding of the screw is advantageously supported, and it is advantageously possible to keep the fill level of the extruder constant and to make it more tolerant of operational material variations and influences. Furthermore, it is possible to consider and compensate for the properties of the material entering the extruder, e.g., with regard to moisture, density, and material temperature, and this can be done directly in the PCU.

[0023] Accordingly, devices or process controls with high rotational speed N(PCll) of the stuffing tools, e.g., with a peripheral speed of 40 m / s or above, or with large extruders operated at low rotational speed n(ex) and a single-pass feed, are critical and disadvantageous. In such configurations, the values ​​for V are regularly above 10 and the desired advantages cannot be achieved.

[0024] Furthermore, achieving cost-effective throughput is advantageous. Accordingly, larger twin-screw extruders should be operated at a correspondingly higher speed n(ex), for example, at approximately 400 rpm or more, to make the most of the larger size and thus also the higher investment costs of the larger extruder. If, for example, a twin-screw extruder were operated at a low speed n(ex) of only 100 rpm, this would be more expensive in terms of investment than a single-screw extruder that would deliver similar throughput. Against this background, operating twin-screw extruders at very low speeds is also disadvantageous.

[0025] The control unit is designed or configured to control either only the rotational speed N(PCU) of at least one packing tool, only the rotational speed n(ex) of the screws, or both rotational speeds. This can be achieved, for example, by controlling the drive(s). In any case, the control unit adjusts the rotational speed(s) of the packing tool and / or the screws so that the required ratio of V < 10 between the fictitious packing number S(PCU) of the container and the fictitious transport number t(ex) of the extruder is achieved. This can be set once at the beginning or, for example, it can be a continuous control process in which the rotational speed(s) are constantly readjusted. For instance, a value is set at the beginning and can then be readjusted during operation, possibly also taking into account various other parameters, such as...The temperature of the material in the PCU, the torque of the PCU, the torque of the extruder, the temperature of the melt, etc., are all relevant factors. For the purposes of this definition, a tamping tool is any rotating or periodically circulating element or tool within the container that generates a relevant tamping pressure or force on the material inside the container, moving it towards the container opening, in order to expel the material through the opening or to assist in such expulsion. It is irrelevant how the tamping tool acts on the material, i.e., whether it merely moves the material or applies energy, or whether it also cuts or crushes the material. The decisive factor is the tamping or pressure effect on the material towards the container opening.

[0026] To fulfill this purpose, the tamping tool is positioned within a certain proximity or height range relative to the container opening. Tools positioned too far above or below the container opening do indeed act on the material, causing it to rotate, heat, and / or break it up, but they do not generate any tamping pressure or force towards the container opening that would force the material out through the opening. These tools are therefore not tamping tools.

[0027] Elements or tools are or act particularly advantageously as stuffing tools when they are arranged in the area of ​​< 50%, in particular < 30%, of the height of the container opening above the uppermost edge or point of the container opening and of < 50%, in particular < 30%, of the height of the container opening below the lowermost edge or point of the container opening, preferably in the area between the uppermost and the lowermost edge or point of the container opening.

[0028] Furthermore, it is advantageous if the tamping tool is located within a certain distance of the container opening. Elements or tools are or act as tamping tools, in particular, if the radially outermost end of the tamping tool, located closest to the container wall, and especially the ends of all tamping tools, has a radial distance of < 50%, and in particular < 30%, of the container radius from the container opening or the container wall.

[0029] The tamping tools can be arranged one above the other in one or more discrete height levels, particularly in the defined height range above and below the container opening. Simultaneously, several tamping tools can be provided on each of these height levels. In this context, a tamping tool is defined as any element or tool that exerts a periodic, radial force on the material towards the container opening—i.e., a relevant tamping effect—when it is moved past the container opening. This includes any individual element that generates, or is capable of generating, a periodic, focused filling pressure or pressure surge in the direction of the container opening during operation. The number A of tamping tools is determined and calculated in this way.

[0030] For example, a rotating disc within the area of ​​influence of the container opening can be provided, equipped with individual knives at one or more positions around its circumference. Each knife repeatedly passes the container opening as it rotates, generating a sharp pressure pulse each time it passes. Each knife is thus an individual tamping tool, and the number A of tamping tools corresponds to the number of individual knives. If there are several such discs with knives arranged one above the other within the relevant area of ​​influence, then all knives on all discs are also considered individual tamping tools. Discs outside this area are not considered, and neither they nor their knives are included in the number A.

[0031] For example, if there are two rotating discs in the relevant area of ​​effect and detection, e.g., approximately + / - 50% above or below the container opening, of which the first disc has six knives and the second disc has three knives, then the number A of the tamping tools would be nine.

[0032] This also applies analogously to other tool types, e.g., rotating axes from which beams or paddles extend laterally. Each individual beam that passes within the relevant height range of the container opening and is long enough, i.e., extends radially far enough outwards towards the container wall, and exerts a focused pressure pulse, counts as a single tamping tool for determining the number A. If, for example, three superimposed beam systems rotate within the relevant height range of the container opening, each with two, four, or six individual beams extending radially from a central axis, the total number A of tamping tools is twelve.

[0033] Tamping tools arranged or built discretely along a radial or radial curve or line belong together and are counted as a single tamping tool (A=1). In the device according to Fig. 5, for example, a disk is provided with three curved, longer knives arranged on this disk; accordingly, the number of tamping tools here is A=3. Even if these were not continuous curved knives, i.e., knives with a continuous blade, but rather several discrete small knives or blade sections arranged side by side in a curved line, thereby forming the curved knife, this would still only be a single tamping tool, and A=3 would still apply.

[0034] In order to be counted as a separate tamping tool, i.e., to increase A by 1, there must advantageously be a minimum distance or a minimum angle of > 25° between the tools when viewed around the circumference.

[0035] Figures 7 to 12, which are described in more detail below, show examples of how to calculate A.

[0036] The advantageous design and control of the device allows the fill level of the extruder to be kept very constant, the feeding behavior of the screw to be further improved with good throughput and stable throughput consistency, and the quality of the final polymer materials to be further increased.

[0037] According to an advantageous design, the consideration arises to also adapt the extruder itself, or especially the critical area of ​​the feeding or intake of the extruder, in a constructive manner, or to design it in such a way that the intake behavior and the feeding of the screw are further supported.

[0038] The device includes an extruder or multi-screw extruder for processing and melting polymeric materials, with at least two rotatable screws arranged side-by-side in a common housing. Specifically, a twin-screw extruder with exactly two screws is provided. In its typical basic design, this extruder has an upstream feed section where the material to be processed is introduced into the extruder, and a downstream extrusion section located further downstream in the material conveying direction, where the material is melted. Accordingly, the extruder housing has at least one feed opening in its outer wall in the feed section for introducing the material to be processed into the grasping area of ​​the screws. In the downstream extrusion section, there is largely, i.e., via the...along the longitudinal course of the extrusion area, a screw gap that is essentially constant and smaller or narrower up to the screw exit, surrounding the screws completely or on all sides, between the outer diameters or the enveloping surfaces of the screws and the inner wall of the housing.

[0039] In this context, "constant" means that the screw gap does not change significantly along the extrusion section, i.e., up to the screw exit, and remains essentially the same. For extruders with cylindrical screws, the extrusion section therefore corresponds to the parallel part of the extruder.

[0040] In this context, "narrow" means a small distance to the inner wall relative to the screw diameter, usually a distance of only a few tenths of a mm to the cylinder or a distance of less than 1 mm when new.

[0041] The screw gap does not need to be identical, constant, and narrow at every single point or in every section of the extrusion area; rather, it should be observed along the entire length of the extrusion area. Deviations in small sections or partial changes or enlargements of the screw gap in specific areas, such as in the degassing area or at additional inlet openings, are not relevant. Despite such deviations, a constant and narrow screw gap is maintained throughout the entire extrusion area. In particular, larger screw gaps between the cylinder and screw may occur in sections, for example, in areas of any additional feed where melt is already present, or in areas where melt is being degassed. In all these areas, melt is already present in the extrusion section.molten material is present, in contrast to the area of ​​the pocket described below, where no melting has yet occurred or melting is avoided.

[0042] The housing advantageously features a pocket extending along a partial longitudinal section of the extruder, or in a region near the feed opening, extending along the screws. This pocket has a screw gap between the outer diameters of the screws and the inner wall of the housing that is larger than the screw gap in the extrusion section. Accordingly, the pocket ends at the transition to the extrusion section, from which point the screws are separated from the inner wall only by the constant, narrow screw gap. The pocket thus advantageously extends to the point where the screw gap remains consistently small all the way to the screw exit, or, in extruders with cylindrical screws, to the parallel section of the extruder.The overall screw gap is therefore larger in the pocket area than in the downstream extrusion area, where the screw gap is consistently small.

[0043] Accordingly, the intake area within the pocket is significantly larger in diameter compared to the outer diameter of the screws. This makes it advantageously possible to introduce additional material, including lighter materials, into this space, beyond the screw's filling volume, and in particular to pack, trickle in, or convey.

[0044] The enlarged intake area, pocket, or screw gap can also be formed only in a circumferential section around the screws. Preferably, however, the enlarged screw gap extends around the entire circumference of the screws or over large parts or areas of the screw circumference. The pocket thus preferably surrounds the screws completely on all sides. Approximately similar or uniform distances or screw gaps between the screws and the inner wall are preferred on all sides.

[0045] The pocket and the enlarged screw gap within it advantageously allow more material to be fed into the extruder than the screws could convey. Due to the distance between the cylinder and the screw, and the enlarged screw gap in the pocket area, some of the material can escape or flow back if the screws become overloaded—meaning the subsequent, closely spaced section of the screws cannot accommodate the excess material. Such an overload can occur, for example, due to changes in the material, such as a higher bulk density or improved flowability. The correspondingly enlarged space of the pocket in the extruder's feed area thus also acts as a compensating element. This prevents both underfeeding and overfeeding of the extruder.

[0046] It is essential that no significant melting processes occur in this area of ​​the pocket during operation; that is, the material or particles retain a certain degree of granularity. Partial softening may occur, but the material must not melt, and certainly not be completely melted, as this would cause the conveying process to stop. In this context, a multi-screw extruder, particularly a twin-screw extruder, offers several advantages. These include favorable feeding characteristics and a higher throughput for a given screw diameter at a defined rotational speed. Furthermore, it provides good conveying performance, short residence times, a narrow residence time range, good self-cleaning of the screws, good dispersion and homogenization properties, flexible geometry design due to its modular construction, and good process control.

[0047] The advantageous design of the extruder allows its fill level to be kept very constant, and the feeding behavior of the screw can be further improved with good throughput and stable throughput consistency, and the quality of the final polymer materials can also be further increased.

[0048] According to a further advantageous embodiment, it can be provided that the longest or maximum length LE of the inlet opening, measured parallel to the conveying direction or in the longitudinal direction of the axial longitudinal axes of the screws or parallel to these longitudinal axes, is in the range of 0.2 Da < LE < 15 Da.

[0049] "Da" is defined as the outer diameter of the screw closest to the feed opening, measured at the point of the feed opening furthest downstream in the conveying direction. This definition of Da also applies to all other uses of Da presented here.

[0050] According to a further advantageous embodiment, the longest or maximum width BE or height of the feed opening, measured perpendicular to the conveying direction or perpendicular to the axial longitudinal axes of the screws, is in the range of 0.1 Da < BE < 3 Da. The width is not measured along the curvature of the cylinder or the curved path of the opening, but rather as the clear width or height on a straight line directly between the opposite edges; it is therefore the absolute width or height of the opening in side view or projected onto the central section plane of the extruder.

[0051] This refers to the longest or maximum dimension of the longitudinal or lateral extent of the feed opening. The exact shape of the feed opening is not defined or specified; it can be, for example, rectangular, square, round, or oval. Feed openings without corners, particularly oval, elliptical, or circular, are preferred for optimal feed behavior. In a particularly advantageous embodiment, as previously described, the pocket has an inner diameter that is larger along its entire length compared to the screw gap in the extrusion area. The inner diameter Ti of the pocket is defined and determined as follows:

[0052] The screws are arranged side by side, and the axial longitudinal axes of all screws define a common plane or lie in a common plane. This is particularly advantageous in embodiments where exactly two identical cylindrical or conical screws are arranged symmetrically next to each other in the housing.

[0053] The inner diameter Ti of the pocket is then defined and measured as the length of a straight line perpendicular to this plane and intersecting the longitudinal axis of the screw nearest or adjacent to the intake opening, between the opposing areas of the inner wall of the housing. From these inner diameters Ti of the pocket determined in this way, the inner diameter Ti with the greatest length is then selected and used.

[0054] This largest inner diameter Ti satisfies the condition Ti = k * Di, where: 1.7 < k < 9.6. “Di” is defined as the inner (core) diameter of the screw closest to the feed opening, as is Da, measured at the point furthest downstream of the feed opening in the conveying direction.

[0055] Local deviations in small sections of the circumference, or partial changes or enlargements, e.g., small bulges or channels in the housing or pocket, are not relevant. If such structures are present, the imaginary extension of the line of the inner wall is essentially used to determine the inner diameter Ti of the pocket.

[0056] For parallel twin screws, the ratio between Da and Di is regularly specified by the manufacturers and is a performance characteristic for, among other things, throughput, torque, etc.

[0057] In a further advantageous embodiment, the pocket has a length range LT extending from the downstream point of the intake opening in the conveying direction or along the axial axes of the screws to the downstream end of the pocket. This length range LT is in the range of 0.2 Da < LT < 10 Da.

[0058] The special design of the feed opening and the pocket allows for an extremely consistent fill level in the extruder. This further improves the screw feeding behavior and increases both throughput and throughput consistency. The extruder, and indeed the entire system consisting of the cutter compactor and extruder, becomes significantly more stable and efficient. Furthermore, the quality of the resulting polymer materials can be further enhanced, and operational efficiency can be improved.

[0059] According to an advantageous embodiment, the length LE of the feed opening is in the range of 0.3 Da < LE < 10 Da. Furthermore, it is advantageously provided that the width (BE) of the feed opening (4) is in the range of 0.1 Da < BE < 2 Da. In this way, a particularly favorable feed behavior is ensured.

[0060] According to an advantageous embodiment, it is provided that for screws with Da < 100 mm: 1.7 < k < 3 and / or that for screws with Da > 100 mm: 3 < k < 9. These values ​​offer favorable conditions for smaller or larger screw diameters, respectively.

[0061] According to a further advantageous embodiment, the length range LT of the pocket is in the range of 0.5 Da < LT < 6 Da. This allows for particularly advantageous processing of the material.

[0062] In the downstream section of the feed area, a transition zone can advantageously be provided that adapts the geometry of the pocket from the feed area to the extrusion area. This adaptation to the screw diameter can begin as early as in the feed area. That is, downstream along the screw, the diameter of the pocket is smaller than upstream. This creates a shell, particularly a conical one, or the housing is designed to taper, for example, conically, to facilitate easier flow of the materials in the extrusion direction. When designing such a transition zone, particularly a conical one, further compaction of the material is advantageously achieved.

[0063] In this context, it is advantageous if the length section LT of the pocket, starting from the most downstream point of the feed opening in the conveying direction or in the longitudinal direction of the axial axes of the screws to the downstream end of the pocket, is continuously tapered at a uniform angle or conically tapered for at least a portion of > 50%, preferably > 70%, particularly > 80%, even more preferably > 90% or > 95% of the length of the length section LT, preferably over substantially the entire length of the length section LT. According to a further structurally advantageous embodiment, the feed opening is located laterally on the extruder and / or opens only into the grasping area of ​​one of the screws, with the central longitudinal axis of the feed opening intersecting the central longitudinal axes of the screws being particularly well-defined.

[0064] A particularly advantageous design results when the extruder is configured as a twin-screw extruder with exactly two cylindrical screws aligned parallel to each other. Alternatively, but also advantageous for corresponding applications, it is possible for the two screws to each be conical.

[0065] The two screws are advantageously arranged symmetrically next to each other. In cylindrical screws, the longitudinal axes of the screws are parallel to each other and to the longitudinal axis of the housing. In conical screws, the longitudinal axes of the screws are at an angle to each other. In both cases, a longitudinal axis of the housing runs between the screws or their longitudinal axes.

[0066] Depending on the requirements, it is advantageous if the screws are designed as screws that rotate in the same direction or in opposite directions.

[0067] Furthermore, it is advantageous if the worms are designed as interlocking or combing worms, wherein the axial distance between the worms or the central longitudinal axes over their entire length is smaller than the (outer) worm diameter Da.

[0068] Such designs regularly result in, among other things, a tendency towards further improved occupancy rates, improved support, a narrower dwell time range, and good process control.

[0069] The tools or tamping tools in the PCU are advantageously discs, rods or beams, in particular with knives arranged on them.

[0070] If tools or stuffing tools are arranged in several tool planes, especially several discs on top of each other, they can, but do not have to, be the same size, i.e. they can also have different dimensions or diameters compared to each other.

[0071] For the feeding behavior, it has also proven advantageous if, in the area upstream of the container opening or in the area upstream of the feed opening or feeding opening of the extruder, the direction of rotation of the tool or plugging tool of the lowest level runs essentially opposite to the conveying direction of the extruder. Such arrangements are already known in principle, for example from EP 2 558 263 B1 or EP 2689 908 B1, and are incorporated into the present disclosure by reference.

[0072] It is particularly advantageous if the longitudinal axis of the screw or the longitudinal axis of the screw closest to the feed opening, or the inner wall of the housing, or the outer surface 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.

[0073] Furthermore, it is advantageous if the opening in the PCU is directly connected to the inlet opening without any significant distance or transfer path, e.g., without a screw conveyor. This enables efficient and gentle material transfer.

[0074] An advantageous device is further characterized in that the container is cylindrical or conical. However, the container need not necessarily 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 excess container height is not utilized and therefore has no further influence on material processing.

[0075] An advantageous device is characterized in that the extruder is connected tangentially to the container and / or that the housing of the extruder has a feed opening located on its end face or in its shell wall for the material to be captured by the screw or screws of the extruder, and the feed opening is connected to the container opening.

[0076] 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) or tamping 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 tamping 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.

[0077] In this context, it is also advantageous to provide that the tool or tamping tool, or, if several tools or tamping tools are arranged one above the other, the lowest tool or tamping tool closest to the bottom, as well as the opening, are positioned at a short distance from the bottom surface, particularly 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 at its edge. 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.

[0078] A particularly advantageous device is one comprising a cutting compactor or a preconditioning unit (PCU) with at least one mixing, comminuting, or packing tool rotatable or rotating about a rotary axis, and with a container opening formed in the side wall of the cutting compactor in the region of the height of the lowest packing tool closest to the bottom. A twin-screw extruder is tangentially connected to this container opening, into which the pretreated material is fed.

[0079] To solve the objective problem, a further method for processing or preparing polymer materials, in particular thermoplastic waste plastic for recycling purposes, is provided, wherein the materials to be processed are moved, mixed, heated and optionally crushed in at least one container or cutting compactor by at least one, preferably several, tools rotatable about a rotary axis, wherein at least one of the tools is arranged in the area of ​​a container opening and a stuffing tool is used to generate a stuffing pressure or force on the material in the direction of the container opening for the discharge of the material from the container, and wherein the polymer materials, which are present in lumpy or particulate form, are subsequently discharged from the container via the container opening and into an extruder directly connected to the container.Multi-screw extruders with at least two screws rotatable in a common housing, in particular a twin-screw extruder, are used to compact and melt or agglomerate the material.

[0080] According to the invention, this method provides that the rotational speed N(PCll) of the at least one packing tool and / or the rotational speed n(ex) of the at least two screws is / are adjustable and controllable and is / are adjusted and controlled such that the ratio (V) between a packing number S(PCll) of the container and a transport number t(ex) of the extruder is: V = S(PCll) / t(ex), V < 10, in particular V < 8, preferably V < 5, preferably V < 1 , is

[0081] - where for the packing number S(PCU) [1 / min]: S(PCll) = N(PCll) * A(PCll), where N(PCll) is the rotational speed of the lowest or bottom-closest packing tool (e) [U / rnin] and A(PCll) is the number of packing tools, and where for the transport number t(ex) in [1 / min]: t(ex) = g(ex) * n(ex) * a(ex), where g(ex) is the number of threads of the screws, n(ex) is the rotational speed of the screws [u / min] and a(ex) is the number of screws.

[0082] Such a process allows the aforementioned advantages to be achieved, in particular good feeding behavior and a constant fill level of the extruder.

[0083] Either only the rotational speed N(PCll) of at least one packing tool or only the rotational speed n(ex) of the screws is controlled or set, or both rotational speeds are regulated. This can be achieved, for example, by controlling the drives. In any case, the control device sets the rotational speed(s) so that the required ratio V of < 10 between the fictitious packing number S(PCll) of the container and the fictitious transport number t(ex) of the extruder is achieved.

[0084] In particular, it is advantageous if the method is carried out with a device according to the invention as described above.

[0085] 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.

[0086] Fig. 1a shows an embodiment of an advantageous extruder in a partial sectional view from above.

[0087] Fig. 1b shows the extruder according to Fig. 1a in a partial sectional view from the side. Fig. 2 shows an advantageous extruder in a perspective view.

[0088] Fig. 3 shows an advantageous extruder in a perspective partial sectional view.

[0089] Fig. 4a shows a cross-section of an advantageous extruder in the extrusion area C.

[0090] Fig. 4b shows a cross-section of the extruder in the transition area B.

[0091] Fig. 4c shows a cross-section of the extruder in the feed area A.

[0092] Figs. 5a and 5b show a device according to the invention or cutting compressor-extruder combination with cylindrical screws from above and from the side.

[0093] Figs. 6a and 6b show an alternative device according to the invention or cutting compactor-extruder combination with conical screws from above and from the side.

[0094] Figures 7 to 12 show examples of how to calculate A, each in a side sectional view and in a top view.

[0095] The illustrations in Figures 1 to 12 are only schematic.

[0096] Figs. 1a and 1b show an exemplary advantageous embodiment of an advantageous multi-screw extruder 1 as part of a device or cutting compressor-extruder combination according to the invention, which is then combined or connected with a container or a PCU to form the device according to the invention.

[0097] The present is a co-rotating twin-screw extruder 1 with two identical, cylindrical, parallel screws 3a, 3b, which are arranged symmetrically to each other, intermeshing or interlocking, next to each other in a common housing 2 for rotation.

[0098] Fig. 1a shows a top view of the extruder 1. It is a partial sectional view in which the housing 2 is partially cut open, providing a view into the interior of the housing 2 of the two adjacent screws 3a and 3b.

[0099] Fig. 1b also shows a partial sectional view of the same extruder 1 from the side, and the lateral feed opening 4 and the screw 3a closest to or adjacent to the feed opening 4 can be seen.

[0100] Inside the housing 2, i.e., within the inner walls 8, an internal chamber 15 is formed. The screws 3a, 3b arranged in the internal chamber 15 are set into rotation by a drive 31, shown on the left in the figures, located upstream of the conveying direction 6, with the same direction and speed of rotation. The direction and speed of rotation of the screws 3a, 3b are variably adjustable and can be set by a control device (not shown).

[0101] A housing longitudinal axis 40, i.e. the axis of the housing 2 running along the conveying direction 6, runs from above (Fig. 1a, 5a, 6a) centrally between the two screws 3a, 3b and parallel to the longitudinal axes 3a', 3b' and from the side (Fig. 1b, 5b, 6b) in the plane of the screws 3a, 3b and the longitudinal axes 3a', 3b'.

[0102] The extruder 1 has a feed area A into which the materials to be processed, usually polymer materials intended for recycling, are introduced. Within this feed area A, the feed opening 4 is formed in the outer wall of the housing 2, through which the material to be processed is fed into the intake area of ​​the screws 3a, 3b. In this case, the feed opening 4 is located laterally on the extruder 1 and opens into the intake area of ​​the screw 3a.

[0103] Downstream, an extrusion section C is formed. In this section, the screw gap 7, formed between the outer diameters of the screws 3a, 3b and the inner wall 8 of the housing 2, is largely very narrow at approximately 0.2 mm and largely constant. The melting of the polymer material and the formation of a polymer melt also take place in this extrusion section C. It is understood that there may be sections or positions where the screw gap 7 is locally larger; however, such local variations are negligible here, and the entire length of the extrusion section C is to be considered, in which the screw gap 7 is, on average, consistently small.

[0104] In the feed area A, the housing 2 is extended or enlarged in a region around the feed opening 4, or has a pocket 5 extending over a certain longitudinal section of the extruder 1 along the screws 3a, 3b. Along the entire length of the pocket 5, there is a screw gap 7' that is larger than the screw gap 7 of the extrusion area C, or rather, screw gaps 7' that are enlarged circumferentially around the screws 3a, 3b are formed. This means that the radial distance between the outer diameter of the screws 3a, 3b and the inner wall 8 of the housing 2 is sometimes significantly increased in the region of the pocket 5. The screw gaps 7' are essentially very similar throughout, i.e., the screws 3a, 3b are approximately the same distance from the inner wall 8 in every cross-section. During operation, the material does not yet melt in the region of the pocket 5.The end 11 of the pocket 5 is located at the beginning of the extrusion area C seen in the conveying direction 6, i.e. where the screws 3a, 3b are only partially or completely separated from the inner wall 8 by the largely narrow and constant screw gap 7.

[0105] The inlet opening 4 has a certain longitudinal extent as well as a certain width and height extent. In this case, the geometric shape of the inlet opening 4 is essentially rectangular; however, round or oval shapes without corners are also advantageous.

[0106] In the present example, the longest length LE of the feed opening 4 is approximately 3 Da. The length LE is measured in the conveying direction or longitudinal direction 6 of the longitudinal axes 3a' and 3b' of the screws 3a and 3b, respectively, parallel to these axes. "Da" is the outer diameter of the screw 3a that is closest to the feed opening 4, i.e., the adjacent screw 3a. "Da" is measured in the area of ​​the feed opening 4, specifically at the point 9 of the feed opening 4 furthest downstream when viewed in the conveying direction 6, i.e., at the furthest downstream endpoint 9 of the feed opening 4.

[0107] The longest width or height BE of the inlet opening 4 is approximately 2 Da in this case. The width BE is measured in the transverse direction 12, perpendicular to the conveying direction 6, and at right angles to the axial longitudinal axes 3a', 3b' of the screws 3a, 3b. The same definition of Da applies here as given above. The longest width BE is not measured along the curved opening or along the radius of curvature, but corresponds to the direct or clear height or the distance between the opposing edges of the inlet opening 4.

[0108] As previously described, the pocket 5 has an increased inner diameter Ti along its entire length. The inner diameter Ti of the pocket 5 is determined and measured as follows: The axial axes 3a' and 3b' of the screws 3a and 3b define a common plane 13 and lie within it. The inner diameter Ti is then defined and measured as the length of a straight line perpendicular to this plane 13, intersecting the longitudinal axis 3a' of the screw 3a nearest to the feed opening 4, through the inner area 15 between the opposing surfaces of the inner wall 8 (top and bottom in Fig. 4c) of the housing 2. The largest inner diameter Ti of the pocket is selected and determined by a specific relationship between a factor k multiplied by the inner diameter Di of the screw 3a closest to the feed opening 4.Analogous to Da, Di is also determined or measured at point 9 of the intake opening 4, which is furthest downstream in the conveying direction 6.

[0109] Pocket 5 further possesses a specific length range LT, which begins at the downstream point 9 of the feed opening 4, continues in the conveying direction or longitudinal direction 6 of the screws 3a, 3b, and extends to the end 11 of pocket 5. The end 11 of pocket 5 is located where the enlarged screw gap 7' no longer exists, but where the parallel section of the extruder 1 or the extrusion section C begins, and the screw gap 7 is essentially small and constant. In the present example, the length range LT is approximately 6 Da, where Da is defined above as the diameter of the screw 3a closest to the feed opening 4 at point 9.

[0110] The length range LT of the pocket 5 lies within a transition region B of the extruder 1. Length range LT is therefore the downstream portion of the pocket 5, and in this region, the housing 2 tapers from its enlarged configuration within the pocket 5 to the small screw gap 7 in the extrusion region C. This is achieved by the housing 2 being designed with a conical taper in sections. In a first section immediately downstream of the feed opening 4, the screw gap 7' remains constant, and the housing 2 is cylindrical. Only after approximately 20 to 30% of length range LT does the reduction of the enlarged screw gap 7' begin, followed by a conical section extending to the end 11 of the pocket 5. Preferably, the conical section terminates as close as possible, or even directly, behind the end or point 9 of the feed opening 4.

[0111] As shown in Figures 1a and 1b, the pocket 5 is enlarged all around the screws 3a, 3b, or the screw gap 7' is enlarged all around, and corresponding approximately equal radial distances or essentially similar screw gaps 7' exist between the screws 3a, 3b and the inner wall 8 in the area of ​​the pocket 5. However, it is also possible that only parts of the pocket 5 are enlarged, meaning that the pocket 5 is only spaced from the screws 3a, 3b in a certain circumferential area, but not in others.

[0112] Fig. 2 shows a schematic and not-to-scale perspective view of the relevant area of ​​an embodiment of an advantageous twin-screw extruder 1. The drive 31, which drives the two screws 3a and 3b, is shown on the far left. The material to be processed enters the intake area of ​​the nearest screw 3a via the feed opening 4. In this area, or in the intake area A, the housing 2 is enlarged and forms the pocket 5. Downstream of this, the conically tapered transition area B is visible, in which the screw gap 7' decreases and becomes a very small, constant screw gap 7 in the extrusion area C at the end 11 of the pocket 5.

[0113] Fig. 3 shows a perspective view of an embodiment from an opposite direction, with part of the housing 2 graphically removed. The inner area 15 of the housing 2 or pocket 5, the tapered transition area B, and the subsequent extrusion area C are also visible here.

[0114] The same explanations apply to Figures 2 and 3 as to Figures 1a and 1b.

[0115] Figures 4a, 4b, and 4c show cross-sections through an advantageous extruder 1 or through the housing 2, and also through the screws 3a, 3b, at different positions at right angles to the longitudinal axes 3a', 3b' or to the housing longitudinal axis 40.

[0116] Fig. 4a shows a cross-section in the extrusion area C. The very small screw gap 7 of < 1 mm is visible, which does not change essentially over the extrusion area C.

[0117] Fig. 4b shows a cross-section in the transition region B, specifically in the area of ​​the conical taper. Here, the screw gap 7' is already enlarged compared to the screw gap 7. This cross-section is therefore already located in the area of ​​the pocket 5, and there is a certain distance or space between the inner wall 8 and the screws 3a, 3b.

[0118] Fig. 4c shows a cross-section in the area of ​​pocket 5, specifically in the area of ​​the feed opening 4. The screw gaps 7' have reached their maximum size here, and the inner diameter Ti of pocket 5 is also largest in this area. The plane 13, spanned by the longitudinal axes 3a' and 3b', is visible. The inner diameter Ti passes through the longitudinal axis 3a' of the screw 3a and is perpendicular to plane 13.

[0119] In schematic figures 5a and 5b, an advantageous embodiment of a complete device according to the invention for processing or preparing polymer materials, in particular thermoplastic waste plastic for recycling purposes, is shown from two different perspectives, from above and from the side.

[0120] The basic structure and basic function of such a cutting compactor-extruder combination is well known, for example from EP 2 558 263 or EP 2 689 908, and is only briefly described below.

[0121] The complete device comprises a cylindrical container or cutting compactor or preconditioning unit (PCU) 100 for receiving the polymer material to be processed. Such a container 100 is, for example, already well known from EP 123 771. The container 100 is circularly cylindrical with a flat bottom surface and a cylindrical side wall 400 oriented vertically to it.

[0122] Rotating tools 300a and 300b are arranged in container 100. Specifically, these are flat carrier discs, arranged at a short distance from the bottom surface, rotating about a pivot axis 200, and aligned parallel to the bottom surface. Cutting edges are mounted on the top of the carrier disc. The carrier disc is driven to rotate by a motor via an axis located below container 100. The pivot axis 200 is located on the central longitudinal axis of container 100.

[0123] Tools 300a and 300b are used, among other things, for moving, mixing, heating, and comminuting the material present in container 100. Accordingly, the thermoplastic materials in container 100 are mixed, heated, softened, compacted, pre-degassed, dried, dehumidified, cut, comminuted, crystallized, and / or homogenized, and their bulk density is increased. The rotation of tools 300a and 300b creates a mixing vortex within the material, which remains in container 100 for a certain residence time and is pretreated accordingly.

[0124] In the present embodiment, only tools 300a are provided in a single tool level. These tools are, serve, or act as packing tools 300a. At the level of this lowest tool level, a container opening 500 is formed in the side wall of the container 100. The housing 2 or the feed opening 4 of the extruder 1 is tangentially connected to this container opening 500, thereby bringing the polymer material pre-treated in the container 100 into the extruder 1 or into the intake area of ​​the screws 3a, 3b, specifically in the area of ​​the pocket 5. This extruder 1 is designed analogously to Figures 1a and 1b, and the corresponding descriptions are adopted here. Especially with multi-screw extruders, the feed is particularly sensitive, and consistent feeding at as uniform a level as possible is especially important.The present method of introducing the pre-treated material into the pocket 5 of the twin-screw extruder 1 is particularly advantageous. The direction of rotation of the tools 300a of the lowest level (arrow) runs in the area of ​​the container opening 500 or the opening 4 essentially opposite to the conveying direction 6 of the extruder 1.

[0125] A control device (not shown) serves to adjust and control the rotational speed N(PCll) of at least one tamping tool 300a, 300b. The same control device also serves to adjust and control the rotational speed n(ex) of at least two screws 3a, 3b, as well as to coordinate the rotational speeds with each other or their ratio to each other.

[0126] The outer edges of the tamping tools 300a extend relatively close to the side wall 400. The tamping tools 300a, or the knives, are located at approximately the same height or plane as the central longitudinal axes 3a', 3b' of the screws 3a, 3b of the extruder 1.

[0127] In practical operation, the plastic material to be processed, usually in the form of plastic waste, bottles, or films, is placed in the container 100. There, the plastic material is shredded and mixed by the rotating tool 300a, 300b, etc., and in the process is heated and softened by the applied mechanical friction energy, but not melted. After a certain residence time in the container 100, the softened but not melted material is discharged from the container 100 through the opening 500 and fed into the pocket 5 of the extruder 1, thus partially feeding the extruder 1.

[0128] In this context, the term "stuffing tool 300a" ​​refers to each individual element or tool 300a that exerts a periodic, radial force on the material towards the container opening, i.e., a relevant stuffing effect, when it is moved past the container opening 500; in other words, each individual element or tool that can generate a periodic, pointed filling pressure or pressure surge in the direction of the container opening 500.

[0129] The single disc, as shown here, lies within the relevant effective and detection range of approximately + / - 50% above or below the container opening 500. Each of the three curved knives, spaced approximately 120° apart, in the device according to Fig. 5 is thus a tamping tool 300a, and the number A of tamping tools 300a corresponds to the number of individual knives. Specifically, the number A of tamping tools 300a is therefore 3. If the knives were rows of individual small, discrete knives arranged in a curved line analogous to the curved blades, this would not change anything; these discrete knives would be considered a single tamping tool, and the number A would still be 3.

[0130] The rotational speed N(PCll) of at least one tamping tool 300a, 300b and the rotational speed n(ex) of at least two augers 3a, 3b can be controlled or adjusted via the control unit. This is done via the control of the respective motors or drives.

[0131] The rotational speeds N(PCll) and n(ex) are set or controlled in such a way that the required ratio V between the fictitious packing number S(PCll) and the fictitious transport number t(ex) yields a value below 10.

[0132] In schematic figures 6a and 6b, a further advantageous embodiment of a complete device according to the invention is shown in views from above and from the side, respectively.

[0133] The same principles apply to Figures 6a and 6b as to Figures 5a and 5b. In contrast, the direction of rotation of the tools or plugging tools 300a (arrow) is reversed compared to Figure 5a. Furthermore, the direction of rotation of the screws 3a and 3b is opposite to each other. Additionally, the screws 3a and 3b are not cylindrical, but conical. Accordingly, the longitudinal axes 3a' and 3b' are not parallel to each other, and the extruder 1 is also not parallel to, but conically adapted to, the path of the screws 3a and 3b in the extrusion area C. The inner diameter Ti is determined analogously, and the largest inner diameter of the pocket is located in Figure 6b on the far left, upstream of the feed opening 4. However, the control and regulation of the rotational speeds of the plugging tools and the screws is carried out analogously to Figure 5.

[0134] Figures 7 to 12 show exemplary devices for calculating A, each in a side sectional view and a top view. These highly schematic figures are designed analogously to Figure 5, for which reference is made to the corresponding explanations.

[0135] Figures 7a and 7b show several tools or tamping tools 300a, 300b in two directly superimposed planes, with all tools rotating in the region of the container opening 500 and thus being tamping tools. The tamping tools are spaced angularly apart from each other around their circumference. The upper tamping tools 300b each consist of three knives lying directly next to each other in a straight radial line; these knives belong together and are each considered as only one knife. The number A of tamping tools is therefore 8.

[0136] Figures 8a and 8b similarly show several tamping tools 300a, 300b in two superimposed planes. Each tamping tool 300b consists of three knives arranged side by side in a curved line; these knives belong together and are each considered a single knife. The number A of tamping tools is therefore also 8.

[0137] Figures 9a and 9b also show several tools 300a, 300b in two superimposed planes, but here only the angularly spaced tools 300b of the upper plane rotate in front of the container opening 500 and act as tamping tools, while the lower tools 300a do not and are therefore not tamping tools. The number A of tamping tools is accordingly determined only by the upper plane and is 3.

[0138] Figures 10a and 10b also show several tamping tools 300a, 300b in one plane, each with a knife and distal paddle. Each knife and paddle are arranged next to each other in a radial line and therefore each counts as a single tamping tool. Thus, there are four pairs of angularly opposed tamping tools. The number A of tamping tools is therefore 4.

[0139] Figures 11a and 11b show several tamping tools 300a, 300b in two superimposed planes, where all tools are tamping tools and rotate in the area of ​​the container opening 500. A beam with two ends 300b rotates at the top, and a disc with three blades 300a rotates at the bottom. The number A of tamping tools is therefore 5.

[0140] In Figures 12a and 12b, analogous to Figure 11, several tamping tools 300a, 300b are shown in three superimposed planes, where all tools are tamping tools and rotate in the area of ​​the container opening 500. At the top, two beams with two ends each 300b rotate, and at the bottom, a disc with three blades 300a rotates. The number A of tamping tools is therefore 7. Example:

[0141] The following experiment was carried out on an exemplary test setup according to the invention. This involved a PCU (Preconditioning Unit) / twin-screw extruder combination with the following system configuration:

[0142] In the system configuration (comparable approximately to the schematic device shown in Figures 5a and 5b), a preconditioning unit (PCU), a container, or a cutting compactor was used, each with a tamping tool and a drive with variable speed. A single (lower) tool level was installed, located in the area of ​​the container opening or the extruder feed point.

[0143] A control device was provided with which the rotational speed N(PCU) of the tamping tools and the rotational speed n(ex) of the screws could each be set or controlled so that the required ratio V between the fictitious tamping number S(PCU) and the fictitious transport number t(ex) yielded a value of less than 1.

[0144] The container or PCU used here had the following relevant dimensions or parameters:

[0145] Number of tamping tools (A(PCU)): 3

[0146] Speed ​​N(PCU) of the tamping tools: 700 rpm; fictitious tamping rate S(PCU): 2100 rpm

[0147] The twin-screw extruder used here had the following relevant dimensions and parameters: Number a(ex) of screws (3a, 3b): 2

[0148] Frequency g(ex) of the screws (3a, 3b): 3 Rotational speed n(ex) of the screws (3a, 3b): 400 rpm Fictitious transport rate t(ex): 2400 rpm

[0149] Length (LE) of the inlet opening (4): 2.38 Da or 150 mm

[0150] Width (BE) of the feed opening (4): 1.11 Da or 70 mm; outer diameter Da of the screws (3a, 3b): 63 mm; inner diameter Di of the screws (3a, 3b): approx. 40 mm; largest inner diameter (Ti) of the pocket (5): 80 mm; length range (LT) of the pocket (5): 6 Da or 378 mm; two identical cylindrical screws, parallel, co-rotating, intermeshing

[0151] This resulted in a ratio V of 0.88.

[0152] The selected rotational speed of the tools in the PCU also ensured that the energy input into the material was such that a specific material temperature was reached. This temperature was measured using systems that either penetrated the material or measured it non-contact from the side or top. This temperature was essentially determined by the polymer being introduced. It was essential 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 within the PCU, and furthermore facilitated the melting process in the extruder, as the material was thoroughly 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.

[0153] Moist HDPE film was used as the test material. This material was obtained from used packaging. It was first shredded and then pre-cleaned in a washing plant.

[0154] It was found that the selected rotational speeds allowed the extruder's fill level to be kept very constant and sufficiently high. The feeding behavior of the twin-screw extruder, the throughput, and the throughput consistency were significantly improved. The quality of the HDPE granules obtained in this way was also very satisfactory. All the recycled material met the optical and mechanical requirements. Various products were made from the regranulate produced.

[0155] Recycled material is mixed with the new material and processed back into films.

Claims

Patent claims:

1. Device for processing or preparing polymer materials, in particular thermoplastic waste plastic for recycling purposes, especially for carrying out the method according to claim 18, with at least one container or cutting compactor (100) for the material to be processed, wherein at least one, preferably several, rotating about an axis in the container (100). (200) Rotatable tools (300a, 300b, ...) are arranged for moving, mixing, heating, and optionally comminuting the material, wherein a container opening (500) is formed in the container (100), in particular in a side wall (400) of the container (100), through which the pretreated material can be discharged from the interior of the container (100), wherein at least one of the tools (300a, 300b, ...) is arranged in the region of the container opening (500) and is a packing tool (300a, 300b, ...) for generating a packing pressure or force on the material in the direction of the container opening (500) for discharging the material from the container (100), wherein the device includes at least one extruder or multi-screw extruder (1) for processing and melting the material discharged from the container (100), with at least two screws rotatable in a common housing (2). (3a, 3b, ...), in particular a twin-screw extruder (1), wherein the extruder (1) is directly connected to the container (100) for receiving the material discharged from the container opening (500) of the container (1), characterized in that a control device is provided for adjusting and controlling the rotational speed N(PC11) of the at least one packing tool (300a, 300b, ...) and / or for controlling the rotational speed n(ex) of the at least two screws (3a, 3b, ...), wherein the control device is designed and / or configured to control the rotational speed N(PC11) of the at least one packing tool (300a, 300b, ...) and / or the rotational speed n(ex) of the screws (3a, 3b, ...) such that the ratio (V) between a packing number S(PC11) of the container (100) and a transport number t(ex) of the extruder (1) is:. V = S(PCU) I t(ex) V < 10, in particular V < 8, preferably V < 5, preferably V < 1, is, - where the following applies to the filling number S(PCll) [1 / min]: S(PCll) = N(PCll) * A(PCll) where N(PCll) the rotational speed of the lowest or closest tamping tools (300a, 300b, ...) [rpm] and A(PCll) specifies the number of tamping tools (300a, 300b, ...), and where the transport number t(ex) in [1 / min] is given by: t(ex) = g(ex) * n(ex) * a(ex) where g(ex) specifies the number of threads of the screws (3a, 3b ,...), n(ex) the rotational speed of the screws (3a, 3b, ...) [rpm] and a(ex) the number of screws (3a, 3b ,...).

2. Device according to claim 1, characterized in that the at least one stuffing tool (300a, 300b, ...) is arranged in the area of ​​< 50%, in particular < 30%, of the height of the container opening (500) above the uppermost edge or point of the container opening (500) and of < 50%, in particular < 30%, of the height of the container opening (500) below the lowermost edge or point of the container opening (500), preferably in the area between the uppermost and the lowermost edge or point of the container opening (500).

3. Device according to one of claims 1 to 2, characterized in that the radially outermost, container wall-adjacent end of the at least one tamping tool (300a, 300b, ...), in particular the ends of all tamping tools (300a, 300b, ...), has a radial distance of < 50%, in particular < 30%, of the radius of the container (100) from the container opening (500).

4. Device according to one of claims 1 to 3, characterized in that the extruder (1) comprises a feed section (A) for introducing the material to be processed into the extruder (1), and a further downstream extrusion section (C) for melting the material, wherein the housing (2) in the feed section (A) has at least one feed opening (4) formed in its outer wall for introducing the material to be processed into the gripping area of ​​the screws (3a, 3b, ...), wherein in the extrusion section (C) there is a largely constant narrow screw gap (7) between the outer diameters of the screws (3a, 3b, ...) and the inner wall (8) of the housing (2), wherein the housing (2) in the feed section (A) or in an area around the feed opening (4) has a section extending over a partial longitudinal section of the extruder (1) along the screws (3a, 3b, ...) extending, pocket (5) wherein the pocket (5) has an enlarged screw gap (7') along its entire longitudinal length, compared to the screw gap (7) in the extrusion area (C), between the outer diameters of the screws (3a, 3b, ...) and the inner wall (8) of the housing (2).

5. Device according to one of claims 1 to 4, characterized in that the end (11) of the pocket (5) is located at the transition to the extrusion area (C), from which the screws (3a, 3b, ...) are spaced apart on all sides only by the screw gap (7) from the inner wall (8).

6. Device according to one of claims 1 to 5, characterized in that the longest length (LE) of the feed opening (4) measured in the conveying direction or in the longitudinal direction (6) of the axial longitudinal axes (3a', 3b', ...) of the screws (3a, 3b, ...) is in the range of 0.2 Da < LE < 15 Da, where Da is the outer diameter of the screw (3a, 3b) that is closest to the feed opening (4), measured at the point (9) of the feed opening (4) furthest downstream in the conveying direction.

7. Device according to one of claims 1 to 6, characterized in that the longest width (BE) of the inlet opening (4) measured in the transverse direction (12) transverse to the conveying direction (6) or transverse to the axial longitudinal axes (3a', 3b', ...) of the screws (3a, 3b, ...) is in the range of 0.1 Da < BE < 3 Da.

8. Device according to one of claims 1 to 7, characterized in that the pocket (5) has an enlarged inner diameter (Ti) along its entire longitudinal length, wherein the screws (3a, 3b, ...) are arranged side by side and the axial longitudinal axes (3a', 3b', ...) of the screws (3a, 3b, ...) define a common plane (13) or lie in a common plane (13), wherein the inner diameter (Ti) of the pocket (5) is defined and measured as the length of a straight line perpendicular to this plane (13) and intersecting the longitudinal axis (3a') of the screw (3a) nearest or adjacent to the intake opening (4) between the opposing regions of the inner wall (8) of the housing (2), wherein the following applies to the largest inner diameter (Ti) of the pocket (5): Ti = k * Di where: 1 ,7 < k < 9,6 where Di is the inner diameter of the screw (3a, 3b, ...) that is closest to the intake opening (4), measured at the point (9) of the intake opening (4) furthest downstream in the conveying direction.

9. Device according to one of claims 1 to 8, characterized in that the pocket (5) has a length range (LT) starting from the most downstream point (9) of the intake opening (4) in the conveying direction or in the longitudinal direction (6) of the axial longitudinal axes (3a', 3b', ...) of the screws (3a, 3b, ...) to the downstream end (11) of the pocket (5), wherein the length range (LT) is in the range of 0.2 Da < LT < 10 Da.

10. Device according to one of claims 1 to 9, characterized in that the length (LE) of the inlet opening (4) is in the range of 0.3 Da < LE < 10 Da.

11. Device according to one of claims 1 to 10, characterized in that the width (BE) of the inlet opening (4) is in the range of 0.1 Da < BE < 2 Da.

12. Device according to one of claims 1 to 11, characterized in that for determining the inner diameter (Ti) for Da < 100 mm: 1.7 < k < 3 and / or that for Da > 100 mm: 3 < k < 9.

13. Device according to one of claims 1 to 12, characterized in that the length range (LT) of the pocket (5) is in the range of 0.5 Da < LT < 6 Da.

14. Device according to one of claims 1 to 13, characterized in that the length region (LT) of the pocket (5) is formed conically and / or continuously tapered at a uniform angle, starting from the point (9) furthest downstream of the inlet opening (4) in the conveying direction or in the longitudinal direction (6) of the axial longitudinal axes (3a', 3b', ...) of the screws (3a, 3b, ...) to the end (11) of the pocket (5) located downstream therefrom, at least in a partial section of > 50%, in particular > 80%, preferably > 90% of the length of the length region (LT), in particular substantially over the entire length of the length region (LT).

15. Device according to one of claims 1 to 14, characterized in that the feed opening (4) is formed laterally on the extruder (1) and / or opens only into the capture area of ​​one of the screws (3a, 3b, ...), wherein it is particularly provided that the central longitudinal axis of the feed opening (4) intersects the central longitudinal axes (3a', 3b', ...) of the screws (3a, 3b, ...).

16. Device according to one of claims 1 to 15, characterized in that the extruder (1) is designed as a twin-screw extruder with two cylindrical screws (3a, 3b) aligned parallel to each other, rotating in the same or opposite directions and interlocking, or with two conical screws (3a, 3b) rotating in the same or opposite directions and interlocking.

17. Device according to one of claims 1 to 16, characterized in that a passive feed element, in particular a funnel, and / or an active feed element, in particular a screw feeder, is provided for introducing the material to be processed into the feed opening (4), wherein it is particularly provided that the active and / or the passive feed element is directly connected to the extruder (1).

18. A method for processing or preparing polymer materials, in particular thermoplastic waste plastic, for recycling purposes, wherein the materials to be processed are moved, mixed, heated and optionally crushed in at least one container or cutting compactor (100) by at least one, preferably several, rotatable tools (300a, 300b, ...) about a rotary axis (200), wherein at least one of the tools (300a, 300b, ...) is arranged in the area of ​​a container opening (500) and is a packing tool (300a, 300b, ...) for generating a packing pressure or force on the material in the direction of the container opening (500) for ejecting the material from the container (100). and wherein the polymer materials, which are in lumpy or particulate form, are subsequently discharged from the container (100) via the container opening (500) and fed into an extruder or multi-screw extruder (1) directly connected to the container (100) with at least two screws (3a, 3b, ...) rotatable in a common housing (2), in particular a twin-screw extruder (1), in order to be compacted and melted or agglomerated there, characterized in that the rotational speed N(PC11) of the at least one packing tool (300a, 300b, ...) and / or the rotational speed n(ex) of the at least two screws (3a, 3b, ...) is / are adjustable and controllable and is / are adjusted and controlled such that the ratio (V) between a packing number S(PC11) of the container (100) and a transport number t(ex) of the extruder (1): V = S(PCU) / t(ex) V < 10, in particular V < 8, preferably V < 5, preferably V < 1, is, - where the following applies to the filling number S(PCll) [1 / min]: S(PCll) = N(PCll) * A(PCll) where N(PCll) the rotational speed of the lowest or closest tamping tool (300a, 300b, ...) [rpm] and A(PCll) specifies the number of tamping tools (300a, 300b, ...), and where the transport number t(ex) in [1 / min] is given by: t(ex) = g(ex) * n(ex) * a(ex) where g(ex) specifies the number of threads of the screws (3a, 3b ,...), n(ex) the rotational speed of the screws (3a, 3b, ...) [rpm] and a(ex) the number of screws (3a, 3b ,...). 8 / 12 9 / 12 10 / 12 11 / 12 12 / 12

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