Extruder for processing polymer materials

Abstract

The invention relates to an extruder or multi-screw extruder (1) for processing and melting polymeric materials, in particular a twin-screw extruder (1), comprising at least two screws (3a, 3b,...) which can rotate in a common housing (2); a feed region (A) for introducing the material to be processed into the extruder (1); and an extrusion region (C), which is located further downstream, for melting the material. The housing (2) has, in the feed region (A), at least one feed opening (4) which is formed in the lateral wall of the housing and is intended for introducing the material to be processed into the active region of the screws (3a, 3b,...); in the extrusion region (C), a narrow screw gap (7) is formed largely between the outer diameters of the screws (3a, 3b,...) and the inner wall (8) of the housing (2), said screw gap being essentially constant up to the screw outlet; the housing (2) has, in the feed region (A) or in a region around the feed opening (4), a pocket (5) which extends over a longitudinal portion of the extruder (1) along the screws (3a, 3b,...); the pocket (5) has, over its entire longitudinal extent, a screw gap (7') between the outer diameters of the screws (3a, 3b,...) and the inner wall (8) of the housing (2), said screw gap being wider than the screw gap (7) in the extrusion region (C); the end (11) of the pocket (5) lies at the transition into the extrusion region (C), starting from which the screws (3a, 3b,...) are only spaced apart from the inner wall (8) on all sides by the screw gap (7); and at least one resistance element (20) for generating a resistance for the material is formed or provided between ≤ 3 Da upstream of the end (11) of the pocket and ≤ 5 Da downstream of the end (11) of the pocket, Da being the outer diameter of the screw (3a) lying closest to the feed opening (4), measured at the point (9) of the feed opening (4) lying farthest downstream in the conveying direction (6).

Description

[0001] Extruders for processing polymer materials

[0002] The invention relates to an extruder or multi-screw extruder for processing and melting polymeric materials according to the preamble of claim 1. The invention further relates to a device according to claim 21, comprising such an extruder connected to a container or a preconditioning unit (PCU) for processing or preparing polymeric materials, in particular thermoplastic waste plastic for recycling purposes.

[0003] Single-screw and multi-screw extruders for processing and melting polymeric materials are well known in a wide variety of designs.

[0004] Devices comprising a combination of a container, a cutting and compacting unit (PCU), and an attached extruder for the pretreatment and processing of polymer waste, particularly various thermoplastic materials, are also well-known. These are typically containers with rotating tools directly connected to the extruder. The mixing and grinding tools circulating within the container or PCU also support the filling and feeding process of the attached extruder. This pre-processing step in the PCU, preceding the extrusion process, is also responsible, among other things, for modifying the shape and properties of the polymer materials accordingly.In the pretreatment unit, the thermoplastic materials undergo various processes, including mixing, heating, softening, compacting, pre-degassing, drying, dehumidifying, cutting, comminuting, crystallizing, and / or homogenizing, 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.

[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 of rotation and rotational speed. 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, on the one hand, in a certain degree of forced conveying, and on the other hand, in good mixing through redistribution and surface renewal, and a homogeneous melt with the necessary temperature and pressure is conveyed into the subsequent die. In counter-rotating twin-screw extruders, two cylindrical or...Parallel or two conical screws rotating in opposite directions. The clearance between the screws is usually somewhat tight, and the tendency for wear is correspondingly higher. Counter-rotating twin-screw extruders are also generally operated partially filled, partly to avoid excessive pressure build-up and the associated material wear on the screws and barrels.

[0010] 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.

[0011] As previously explained, the material fed into the extruder is immediately transported 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 material underfilling 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 both the quality of the recyclates and for cost-effectiveness.

[0012] Despite all efforts and the implementation of measures, it is possible that, for example, the bulk density variations cannot be sufficiently balanced over time.

[0013] Against this background, the idea arises to constructively adapt the extruder itself, or especially the critical area of ​​the feeding or intake of the extruder, or to design it in such a way that the intake behavior and the feeding of the screw are supported.

[0014] The object of the present invention is therefore to provide an extruder 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 feeding of the screw are supported in the best possible way, and which, for example, is also more tolerant of operational material differences and influences.

[0015] This problem is solved by the features of claim 1.

[0016] Accordingly, an extruder or multi-screw extruder is provided for processing and melting polymeric materials, with at least two rotatable screws located side by side in a common housing. In particular, a twin-screw extruder with exactly two screws is provided.

[0017] In its typical basic design, this extruder has an upstream intake area where the material to be processed is introduced into the extruder, and a downstream extrusion area where the material is melted.

[0018] Accordingly, the extruder housing has at least one intake opening formed in its casing wall in the intake area for introducing the material to be processed into the grasping area of ​​the screws.

[0019] In the downstream extrusion area, there is largely, i.e., along the longitudinal course of the extrusion area, a screw gap that is essentially constant and small or narrow, surrounding the screws on all sides, extending to the screw exit, between the outer diameters or the enveloping surfaces of the screws and the inner wall of the housing.

[0020] In this context, "constant" means that the screw gap does not change significantly in position 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.

[0021] 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.

[0022] The screw gap does not need to be identical, constant, or 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. For screws positioned off-center within the cylinder, the screw gap is referenced to a specific position.In all these areas, melt or molten material is already present in the extrusion area, in contrast to the area of ​​the pocket described below, where no melting has yet taken place.

[0023] According to the invention, the housing has, in the feed area or in a region near the feed opening, a pocket extending along a partial longitudinal section of the extruder along the screws, or is designed as such. This pocket has, along its entire length, 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 area. Accordingly, the end of the pocket is located at the transition to the extrusion area, from which point the screws are separated from the inner wall only by the constant, narrow screw gap. Advantageously, the pocket extends to the point from which the screw gap remains consistently small to the screw exit, or, in the case of 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.

[0024] 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 thus into the screw's working area, particularly for stuffing, trickling in, or conveying.

[0025] The enlarged feed area, pocket, or screw gap can also be formed only in a large partial area 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 on all sides are preferred. The pocket and the enlarged screw gap or space there advantageously allow more material to be fed into the extruder than the screws could convey. Due to the spacing of the cylinder from the screw or the enlarged screw gap in the pocket area, some of the material can be expelled if the screws become overloaded.The closely spaced section of the screw feeder can no longer accommodate the material – it either displaces or flows back. Such overfilling can occur, for example, due to a change 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 serves as a compensating element. This prevents both underfeeding and overfeeding of the extruder.

[0026] It is essential that no significant melting processes occur in this area of ​​the bag during operation; that is, the material or particles must retain a certain degree of lumpiness. Partial softening may occur, but the material must not melt, and certainly not be completely melted, as this would bring the conveying process to a standstill.

[0027] Such a multi-screw extruder, and in particular a twin-screw extruder, offers a number of advantages in this context. 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.

[0028] According to the invention, it is further provided that in the area from < 3 Da before the end of the pocket to < 5 Da after the end of the pocket, at least one resistance element or blocking element is formed or arranged to generate resistance for the material or to create a backflow effect. The resistance generated by such a resistance element has proven advantageous for the feeding behavior and the throughput of the extruder. Furthermore, this advantageously separates the feed zone from the other process zones, or limits the feed area of ​​the screw in the pocket-shaped or conical area of ​​the cylinder downstream of the resistance element or blocking element. Depending on the resistance or backflow effect, the resistance element may also act as a blocking element."Da" here refers to 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.

[0029] The unique design of the extruder, screws, and bag according to the invention allows for an extremely consistent fill level in the extruder. The screw feeding behavior is further improved, and both throughput and throughput consistency increase. The extruder, and indeed the entire system consisting of the cutting 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 increased.

[0030] The resistance element can be formed or arranged at any position within the specified area. According to an advantageous embodiment, the resistance element is formed or arranged in the area of ​​< 1 L / Da upstream of the end of the pocket and / or in the area of ​​< 1 L / Da downstream of the end of the pocket.

[0031] The resistance element(s) can be designed in any way; in any case, it is advantageous if the resistance element is designed to generate a flow resistance or back pressure and to create a negative pressure gradient along the conveying direction to initiate the melting process of the material.

[0032] According to an advantageous embodiment, the resistance element is designed as a screw element or screw section or part of the respective screw, in particular of both screws, for example as a section with a changed pitch.

[0033] In this context, it is advantageous if the resistance element is a counter- or reverse-conveying element, or a screw element or screw section with a pitch opposite to that of the respective screw. Such elements have the greatest backwater effect on the material and act as, or are referred to as, barrier elements. However, it can also be advantageous if the resistance element is a conveying element, or a screw element or screw section with a pitch in the same direction as, but different (i.e., smaller) than, that of the respective screw.

[0034] It can also be advantageous if the resistance element is a conveying-neutral element or a screw element with a neutral or no slope.

[0035] Furthermore, it can be advantageous if the resistance element is designed with a mixing effect, for example as a kneading block or toothed mixing element.

[0036] Likewise, it can be advantageous if, alternatively or additionally, at least one or more resistance elements are provided which are not formed as part or section of the screws or on the screws, but are arranged or formed on or on the housing, preferably on the inside of the housing, and project inwards into the interior of the housing or into the screw gap or into the pocket or into the enlarged screw gap.

[0037] In one exemplary variant of such a resistance element, elements are provided that can either be inserted through the housing from the outside into the interior of the housing or are formed on the inner wall of the housing and protrude inwards from there.

[0038] These elements can, for example, be pin-shaped or designed as elements with a flat or planar extent, such as webs, plates, or the like. These elements can advantageously be distributed regularly around the circumference.

[0039] Furthermore, the length or depth to which these elements protrude into the interior of the housing can vary. These elements may extend only into the (enlarged) screw gap up to the outer radii of the screws, thus reducing the area of ​​the screw gap. However, these elements can also be longer and protrude beyond Da, i.e., into the area of ​​the screws themselves, in which case the screws have corresponding clearances to ensure collision-free rotation.

[0040] For feeding, it has proven advantageous if the augers in the area downstream of the intake opening up to the beginning of the resistance element have uniform gradients, particularly in the range of 0.4 to 1.6 Da.

[0041] In this context, it is preferred that the augers in the area downstream of the feed opening up to the beginning of the resistance element are designed as box profiles, shear-flank profiles, or earth-mixing profiles. The geometry of the conveying elements is advantageously selected according to the bulk density of the material being processed: For heavy bulk materials or high bulk density, conveying elements or augers with earth-mixing or shear-flank profiles are advantageously used; for light materials or low bulk density, box profiles (rectangular profiles) are advantageous: from 10 to 350 kg / m³ 3 predominantly box sections from 100 - 400 kg / m 3 predominantly shear flank profiles and over 250 kg / m 3 predominantly standard profiles / earth mixture profiles.

[0042] It has proven advantageous if the length of the resistance element is 0.1 Da to 8 Da, preferably 0.1 Da to 6 Da, and particularly 0.3 Da to 5 Da. Lengths between 4 and 6 Da can also be advantageous; a counter-rotating resistance element as a worm section can advantageously be approximately 0.3 to 0.35 Da long.

[0043] According to an advantageous embodiment, the resistance element begins in the region of < 3 Da before the end of the pocket, extends beyond the end of the pocket, and ends in the region of > 0.1 Da, preferably 0.2 Da, to < 5 Da after the end of the pocket. Accordingly, the resistance element is also present in the transition area from the pocket to the extrusion area.

[0044] In an advantageous embodiment, the resistance element or locking element accordingly begins at the earliest 3 L / Da before the end of the conical transition or the end of the pocket, projects beyond this transition by at least 0.1 L / Da into the extrusion area and ends at the latest 5 L / Da after the conical transition or the end of the pocket.

[0045] In another advantageous embodiment, the resistance element or blocking element begins directly at the conical transition or at the end of the pocket, thus separating the intake zone from the other process zones.

[0046] In this context, it is also advantageous if the resistance element extends downstream to a maximum of a degassing area or a degassing opening or to a melt transport area, i.e., into an area where there is only a narrow screw clearance, where largely only melt is present, and where only conveying elements, i.e., no mixing elements, are provided.

[0047] In an advantageous embodiment, the resistance element is formed from a sequence of, in particular up to four, screw elements or screw sections or zones with decreasing drag capacity. This sequence promotes the melting of the plastic. The decreasing drag capacity of the screw elements leads to complete filling of the screw flights and thus to better introduction of the shear forces, which results in higher dissipation.

[0048] Furthermore, it has proven advantageous if the screws or screw profiles are single-, double- or triple-start, preferably double-start.

[0049] A particularly flexible variant advantageously provides that the screws within the housing are axially displaceable, specifically by a maximum of + / - 3 Da, i.e., in or against the extrusion direction. Accordingly, the screws can all be linearly displaced by the same distance in their axial direction. This allows for rapid adaptation of the area at the end of the pocket or in the conical transition, which is partly responsible for filling the screw, to different material requirements. In this way, the position of the resistance element can be variably adjusted and adapted to the conditions, especially to different bulk density variations. The screws are then shifted to achieve the maximum possible throughput.

[0050] In a particularly advantageous embodiment, as previously described, the pocket has an increased inner diameter 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:

[0051] 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.

[0052] 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.

[0053] 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.

[0054] In a further advantageous embodiment, the pocket has a length range LT extending from the downstream point of the feed 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, preferably 0.5 Da < LT < 6 Da. This allows for particularly advantageous material processing.

[0055] 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 material in the extrusion direction. When designing such a transition zone, particularly a conical one, further compaction of the material is advantageously achieved.

[0056] In this context, it is advantageous if the length range LT of the pocket, starting from the point furthest downstream of the inlet opening in the conveying direction or in the longitudinal direction of the axial axes of the screws to the end of the pocket located downstream therefrom, is continuously tapered or conically tapered at a uniform angle for at least a partial section of > 50%, preferably > 70%, in particular > 80%, even more preferably > 90% or > 95% of the length of the length range LT, preferably over substantially the entire length of the length range LT.

[0057] According to a further structurally advantageous embodiment, it is provided that the feed opening is formed laterally on the extruder and / or opens only into the capture area of ​​one of the screws, wherein it is particularly provided that the central longitudinal axis of the feed opening intersects the central longitudinal axes of the screws.

[0058] 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.

[0059] 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.

[0060] Depending on the requirements, it is advantageous if the screws are designed as screws that rotate in the same direction or in opposite directions.

[0061] 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.

[0062] 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.

[0063] According to a further structurally advantageous embodiment, a passive feeding element, in particular a hopper, and / or an active feeding element, in particular a screw conveyor, are provided for introducing the material to be processed into the feed opening of the extruder, wherein it is particularly provided that the active and / or the passive feeding element is directly connected to the extruder. The feeding elements also influence the feeding process and the bulk densities.

[0064] The materials to be processed can thus be fed into the extruder via a passive hopper, which is located either on the side or at the top of the extruder. However, it has been shown that this is only sufficient for a limited number of materials. The materials must primarily possess a certain flowability, for example, bottle refining, but also agglomerates or granules.

[0065] A significant number of materials, such as film shreds, fiber shreds, and even ground PET bottles, typically lack these free-flowing properties or do not possess them to a sufficient degree. Therefore, active feeding systems are advantageously used, which forcefully convey the material into the extruder. For example, a screw conveyor with one or more screws can be used and, for instance, directly coupled to the extruder. While this achieves satisfactory results, it is often only partially successful in compensating for the bulk density variations of the materials being processed over time. Even more advantageous is the upstream use of a cutting compactor or a power control unit (PCU), which can consistently achieve very good compensation.

[0066] In this context, an advantageous device for processing or preparing polymer materials, in particular thermoplastic waste plastic for recycling purposes, is provided with at least one container or cutting compactor for the material to be processed, wherein at least one rotatable or rotating tool, optionally several rotatable or rotating tools, for moving, mixing, heating and optionally comminuting the material is / are arranged in the container, wherein in the container, in particular in a side wall of the container, in particular in the area of ​​theat the height of the lowest or closest tool, a container opening is formed through which the pretreated material can be discharged from the interior of the container, and with at least one extruder according to the invention for receiving the material discharged from the container, wherein it is particularly provided that the extruder is directly connected to the container.

[0067] A structurally advantageous embodiment provides that several, at least two, tools are arranged in the container in different tool planes or at different distances from the bottom surface or lowest area of ​​the container, and that the tools are arranged in the container in at least two superimposed tool planes.

[0068] Furthermore, it is advantageous if the single tool or the lowest tool or the lowest tool level is located in the area or at the level of the container opening, and if necessary also at the level of the feed opening of the extruder connected to it.

[0069] Multi-screw extruders can also be advantageously coupled directly to a polymer processing unit (PCU) or a cutting compactor for processing polymer materials. In this configuration, the lowest tooling level of the hopper, preferably consisting of a disk onto which tools can be mounted and located in the extruder opening area, feeds the pre-treated materials into the extrusion device. The number of feeding cycles of the tools in the lowest tooling level at the extruder opening also influences the fill level of the extruder. Furthermore, the average bulk density of the materials in the PCU, particularly in the lowest section of the PCU, corresponding to the average compaction, also contributes to the fill level.

[0070] This makes it possible to consider and compensate for the properties of the material entering the extruder, such as moisture content, density, and material temperature, directly in the PCU. Unfavorable settings can manifest themselves, for example, in significant fluctuations in extruder torque and die speed, which can negatively impact feeding behavior and material quality.

[0071] Even the mere mixing of the materials in the PCU has a dampening effect, to a certain (small) degree, on any bulk density fluctuations of the input materials. However, mixing alone, and often even intensive pretreatment of the materials in the PCU, is insufficient in some cases, and it is not always possible to maintain a sufficiently constant bulk density over extended periods solely through this method. Instead, the bulk density of the processed materials fluctuates over time, rising and falling from an average value. This is already a disadvantage and causes the described drawbacks. These can be compensated for by the extruder design according to the invention.

[0072] The tools in the PCU are advantageously discs, rods or beams, especially with knives arranged on them.

[0073] If tools are arranged in several tool planes, especially several discs stacked on top of each other, they can, but do not have to, be the same size; they can also have different dimensions or diameters.

[0074] The way the cutting compactor tools introduce the pre-treated material into the extruder's feed opening, or support this process, is also advantageous for the feeding behavior. This depends, among other things, on the direction of rotation of the screw and the tools. In this context, it has proven advantageous if, in the area upstream of the hopper opening or the feed opening of the extruder, the direction of rotation of the tool on 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 2 689 908 B1, and are incorporated into the present disclosure by reference. It is particularly advantageous if the longitudinal axis of the screw or the tool is oriented in the direction of rotation of the tool on the lowest level.the longitudinal axis of the screw closest to the feed opening or the inner wall of the housing or the envelope of the screw runs tangentially to the inside of the side wall of the container, wherein preferably the screw is connected to a drive at its end face and conveys at its opposite end face to an outlet opening arranged at the end face of the housing, in particular an extruder head.

[0075] Furthermore, it is advantageous if the opening in the PCU is directly connected to the inlet opening without any extended distance or transfer section, such as a screw conveyor. This enables efficient and gentle material transfer.

[0076] 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.

[0077] 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.

[0078] In a further advantageous embodiment, the receiving container can be essentially cylindrical with a flat bottom surface and a cylindrical side wall oriented vertically to it. It is also structurally simple if the axis of rotation of the tool(s) coincides with the central axis of the receiving container. In a further advantageous embodiment, the axis of rotation of the tool(s) or the central axis of the container is oriented vertically and / or perpendicular to the bottom surface. This also applies analogously to conical containers. These special geometries optimize the feeding behavior in a structurally stable and simple device.

[0079] In this context, it is also advantageous to provide that the tool, or, if several tools are arranged one above the other, the lowest tool closest to the bottom, as well as the opening, are 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.

[0080] Furthermore, it is advantageous for machining if the radially outermost edges of the tool extend close to the side wall of the container.

[0081] A particularly advantageous device is one with a cutting compactor or a preconditioning unit (PCU) comprising at least one mixing or comminuting tool rotatable or rotating about a rotary axis and a container opening formed in the side wall of the cutting compactor at the height of the lowest, bottom-adjusted tool. A twin-screw extruder is tangentially connected to this container opening, into which the pretreated material is fed.

[0082] 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.

[0083] Fig. 1a shows an embodiment of an extruder according to the invention in a partial sectional view from above.

[0084] Fig. 1b shows the extruder according to Fig. 1a in a partial sectional view from the side.

[0085] Fig. 2 shows an extruder according to the invention in a perspective view.

[0086] Fig. 3 shows an extruder according to the invention in a perspective partial sectional view. Fig. 4a shows a cross-section of an extruder according to the invention in the extrusion area C.

[0087] Fig. 4b shows a cross-section of the extruder in the transition area B.

[0088] Fig. 4c shows a cross-section of the extruder in the feed area A.

[0089] Figs. 5a and 5b show a cutting compressor-extruder combination according to the invention with cylindrical screws from above and from the side.

[0090] Figs. 6a and 6b show an alternative cutting compactor-extruder combination with conical screws from above and from the side.

[0091] The illustrations in Figures 1 to 6 are only schematic.

[0092] Figs. 1a and 1b show an exemplary advantageous embodiment of a multi-screw extruder 1 according to the invention. In this case, it 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.

[0093] 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.

[0094] 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.

[0095] Inside the housing 2, i.e., within the inner walls 8, an inner chamber 15 is formed. The screws 3a, 3b arranged in the inner chamber 15 are set into rotation with the same direction and speed of rotation by means of a drive 31, shown on the left in the figures, located upstream of the conveying direction 6.

[0096] 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'.

[0097] 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.

[0098] 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.

[0099] 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, no melting of the material occurs in the region of the pocket 5.

[0100] 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.

[0101] The feed opening 4 has a certain longitudinal extent as well as a certain width and height. In this case, the geometric shape of the feed opening 4 is essentially rectangular; however, round or oval shapes without corners are also advantageous. In this 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.

[0102] 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.

[0103] 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 or adjacent to the inlet 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.

[0104] The largest inner diameter Ti of the pocket is selected or determined according to the invention by a specific relationship between a factor k multiplied by the inner diameter Di of the screw 3a that is closest to the feed opening 4. Analogously to Da, Di is also determined or measured at the point 9 of the feed opening 4 furthest downstream in the conveying direction 6.

[0105] 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.

[0106] 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 in 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.

[0107] 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, i.e., that the pocket 5 is only spaced from the screws 3a, 3b in a certain circumferential area, but not in others, or that the screws 3a, 3b are mounted off-center.

[0108] In the area of ​​the end 11 of the pocket 5, in the present case in the area of ​​about 0.2 Da before the end 11 of the pocket 5 to about 0.3 Da after the end 11 of the pocket 5, a resistance element 20 or blocking element is formed to generate a resistance for the material or to form a backflow effect.

[0109] The resistance element 20 is configured as a screw element, screw section, or partial section of each of the two screws 3a and 3b, specifically as a section with a modified pitch. In this case, the resistance element 20 is a counter- or reverse-conveying screw section with a pitch opposite to that of the respective screw 3a or 3b. Accordingly, the resistance element 20 generates flow resistance or backpressure and creates a negative pressure gradient along the conveying direction 6 to initiate the melting process of the material.

[0110] The resistance element 20 is approximately 0.5 Da long and extends over the end 11 of the pocket 5 into the extrusion area downstream.

[0111] Fig. 2 shows a schematic and not-to-scale perspective view of the relevant area of ​​an embodiment of a twin-screw extruder 1 according to the invention. 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 according to the invention. 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.

[0112] Fig. 3 shows a perspective view of an embodiment from an opposite direction, with part of the housing 2 graphically removed. Visible here as well are the inner region 15 of the housing 2 or the pocket 5, the tapered transition region B and the subsequent extrusion region C, as well as the resistance element 20 provided in the region of the end 11 of the pocket, which is also designed here as a section with a opposite pitch.

[0113] The same explanations apply analogously to Figures 2 and 3 as to Figures 1a and 1b.

[0114] Figures 4a, 4b, and 4c show cross-sections through an extruder 1 according to the invention, or through the housing 2, and also through the screws 3a, 3b, at different positions at right angles to the longitudinal axes 3a', 3b' and to the housing longitudinal axis 40.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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.

[0119] 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.

[0120] 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 cylindrical with a flat bottom surface and a cylindrical side wall 400 oriented vertically to it.

[0121] A rotatable or rotating tool 300a, 300b is arranged in the container 100. The tool 300a, 300b is a flat carrier disc, arranged at a short distance from the bottom surface, rotating about a rotation axis 200, and aligned parallel to the bottom surface. Blades are mounted on its upper surface. The carrier disc is driven to rotate by a motor via an axis, the motor being located below the container 100. The rotation axis 200 is arranged in the central longitudinal axis of the container 100.

[0122] The tools 300a and 300b are used, among other things, for moving, mixing, heating, and comminuting the material present in the container 100. Accordingly, the thermoplastic materials in the 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 the tools 300a and 300b creates a mixing vortex within the material, which remains in the container 100 for a certain residence time and is pretreated accordingly.

[0123] At the level of the single tool 300a, 300b in this case, or at the level of the 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 pretreated in the container 100 into the extruder 1 or into the intake area of ​​the screws 3a, 3b, specifically in the region of the pocket 5. This extruder 1 is designed analogously to Figures 1a and 1b, and the corresponding descriptions are adopted here. Especially in multi-screw extruders, the feed is particularly sensitive, and consistent feeding at as uniform a level as possible is crucial. The present method of introducing the pretreated material into the pocket 5 of the twin-screw extruder 1 is particularly advantageous.The direction of rotation of the tool 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.

[0124] The outer edges of the tool 300a, 300b extend relatively close to the side wall 400. The tools 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.

[0125] 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.

[0126] 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.

[0127] The same principles apply to Figures 6a and 6b as to Figures 5a and 5b. The difference is that the direction of rotation of the tool 300a (arrow) is reversed compared to Figure 5a. Furthermore, the direction of rotation of the screws 3a and 3b is opposite to each other. In addition, 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 shape 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 Fig. 6b on the far left, upstream of the inlet opening 4. A further difference is that the resistance element 20, which causes a backwater pressure, is in each case a conveying-neutral screw section of the two screws 3a, 3b with neutral or no pitch, or as a disc-shaped element.

[0128] Example:

[0129] 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:

[0130] In the system configuration (comparable approximately to the schematic device according to Figs. 5a and 5b), a preconditioning unit (PCU), a container, or a cutting compactor was used, each with a tool featuring a variable-speed drive. A single (lower) tool level was installed, positioned in the area of ​​the container opening or the extruder feed point.

[0131] The twin-screw extruder used here had the following specific features:

[0132] Dimensions and parameters: 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

[0133] Position and length of the resistance element (20): Start: approx. 0.2 Da before the end of the pocket; End: approx. 3.8 Da after the end of the pocket; Length: approx. 4 Da

[0134] Type of resistance element (20): screw section with

[0135] Counter-slope and kneading blocks two identical cylindrical worms, parallel, running in the same direction, interlocking

[0136] The rotational speed of the tools in the PCU was regulated to ensure 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 already 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.

[0137] HDPE bottle regrind was used as the test material. This material was obtained from used containers from the hygiene sector, e.g., shampoo bottles, or the cleaning sector, e.g., household cleaners. This material was first shredded and then pre-cleaned in a washing plant. The fundamental properties or parameters of this material are that it is free-flowing, but exhibits varying bulk densities and moisture contents.

[0138] It was found that the extruder's fill level could be maintained very consistently and at a sufficiently high level. 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. Bottles for household cleaners were blown from the regranulate, and varying amounts of recycled material were blended with virgin material.

Claims

Patent claims:

1. Extruder or multi-screw extruder (1) for processing and melting polymeric materials with at least two screws (3a, 3b, ...) rotatable in a common housing (2), in particular twin-screw extruder (1), with a feed area (A) for introducing the material to be processed into the extruder (1), and a further downstream extrusion area (C) for melting the material, wherein the housing (2) has at least one feed opening (4) formed in its outer wall in the feed area (A) for introducing the material to be processed into the capture area of ​​the screws (3a, 3b, ...), wherein in the extrusion area (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), characterized in that the housing (2) in the feed area (A) orin an area around the feed opening (4) a pocket (5) extending over a partial longitudinal section of the extruder (1) along the screws (3a, 3b, ...) has, wherein the pocket (5) has, along its entire longitudinal length, a screw gap (7') that is enlarged 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), wherein 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 on all sides only by the screw gap (7) from the inner wall (8) and that in the area from < 3 Da before the end (11) of the pocket (5) to < 5 Da after the end (11) of the pocket (5) at least one resistance element (20) is formed or arranged to generate a resistance for the material, where Da is the outer diameter of the screw (3a) that is closest to the feed opening (4), measured at the point (9) of the feed opening (4) furthest downstream in the conveying direction (6).

2. Extruder (1) according to claim 1 , characterized in that the resistance element (20) is formed or arranged in the area of ​​< 1 L / Da upstream of the end (11) of the pocket (5) and / or in the area of ​​< 1 L / Da downstream of the end (11) of the pocket (5).

3. Extruder (1) according to one of claims 1 to 2, characterized in that the resistance element (20) is designed to generate a flow resistance and to form a negative pressure gradient along the conveying direction (6) to initiate the melting process of the material.

4. Extruder (1) according to one of claims 1 to 3, characterized in that the resistance element(s) (20) is / are designed as a screw element or screw section or part of the respective screw (3a, 3b, ...) and / or that the resistance element(s) (20) is / are arranged or formed on or on the housing (2), preferably on the inside of the housing (2), and projects / project inwards into the interior of the housing (2) or into the screw gap (7) or into the pocket (5) or into the enlarged screw gap (7').

5. Extruder (1) according to one of claims 1 to 4, characterized in that the resistance element (20) is designed with a mixing effect, for example as a kneading block or toothed mixing element.

6. Extruder (1) according to one of claims 1 to 5, characterized in that the resistance element (20) is a recirculating element or a screw element or screw section with a pitch opposite to the respective screw (3a, 3b, ...).

7. Extruder (1) according to one of claims 1 to 5, characterized in that the resistance element (20) is a conveying element or a screw element or screw section with a pitch in the same direction as the respective screw (3a, 3b, ...), or that the resistance element (20) is a conveying-neutral element or a screw element with a neutral or no pitch.

8. Extruder (1) according to one of claims 1 to 7, characterized in that the screws (3a, 3b, ...) have uniform pitches in the area downstream of the feed opening (4) up to the beginning of the resistance element (20), in particular in the range of 0.4 to 1.6 Da.

9. Extruder (1) according to one of claims 1 to 8, characterized in that the screws (3a, 3b, ...) in the area downstream of the feed opening (4) up to the beginning of the resistance element (20) are designed as box profiles, shear flank profiles or earth mixer profiles.

10. Extruder (1) according to one of claims 1 to 9, characterized in that the length of the resistance element (20) is 0.1 Da to 8 Da, preferably 0.1 Da to 6 Da, in particular 0.3 Da to 5 Da.

11. Extruder (1) according to one of claims 1 to 10, characterized in that the resistance element (20) begins in the region of < 3 Da, in particular < 1 Da, before the end (11) of the pocket (5), extends beyond the end (11) of the pocket (5), and ends in the region of > 0.1 Da, preferably > 1 Da, to < 5 Da after the end (11) of the pocket (5).

12. Extruder (1) according to one of claims 1 to 11 , characterized in that the resistance element (20) extends downstream to a maximum extent to a degassing area or to a melt transport area.

13. Extruder (1) according to one of claims 1 to 12, characterized in that the resistance element (20) is formed from a sequence of, in particular up to 4, screw elements or screw sections or zones with decreasing drag capacity.

14. Extruder (1) according to one of claims 1 to 13, characterized in that the screws (3a, 3b, ...) are single-, double- or triple-flight, preferably double-flight.

15. Extruder (1) according to one of claims 1 to 14, characterized in that the screws (3a, 3b, ...) are axially displaceable in the housing (2), in particular by a maximum of + / - 3 Da.

16. Extruder (1) according to one of claims 1 to 15, characterized in that the pocket (5) has a length range (LT) extending from the point furthest downstream (9) of the feed 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, wherein the length range (LT) is in the range of 0.2 Da < LT < 10 Da, preferably in the range of 0.5 Da < LT < 6 Da.

17. Extruder (1) according to one of claims 1 to 16, characterized in that the length region (LT) of the pocket (5) extending from the most downstream point (9) of the feed 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) is 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 range (LT), is conical and / or continuously tapered at a uniform angle.

18. Extruder (1) according to one of claims 1 to 17, 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, ...).

19. Extruder (1) according to one of claims 1 to 18, 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.

20. Extruder (1) according to one of claims 1 to 19, characterized in that a passive feed element, in particular a hopper, 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).

21. Device for processing or preparing polymer materials, in particular thermoplastic waste plastic for recycling purposes, with at least one container or cutting compactor (100) for the material to be processed, wherein at least one rotatable or rotating tool (300a, 300b, ...), optionally several rotatable or rotating tools (300a, 300b, ...), for moving, mixing, heating and optionally comminuting the material is / are arranged in the container (100), in particular in a side wall (400) of the container (100), in particular in the area of ​​theat the height of the lowest or bottom-adjusted tool (300a), a container opening (500) is formed through which the pretreated material can be discharged from the interior of the container (100), and with at least one extruder (1) according to one of claims 1 to 20, for receiving the material discharged from the container (100), wherein it is particularly provided that the extruder (1) is directly connected to the container (100).

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