Extruder for processing polymer materials

Abstract

An extruder or multi-screw extruder (1) for processing and melting polymer materials, comprising at least two screws (3a, 3b,...) which are rotatable in a common housing (2), in particular a twin-screw extruder (1), having an intake region (A) for feeding the material to be processed into the extruder (1), and an extrusion region (C) further downstream for melting the material, wherein the intake region (A) of the housing (2) has at least one intake opening (4) which is provided in the lateral wall of the housing and is designed for feeding the material to be processed into the engagement region of the screws (3a, 3b,...), characterized in that the housing (2) has, in the intake region (A) or in a region around the intake opening (4), a pocket (5) extending along the screws (3a, 3b,...) over a partial longitudinal portion of the extruder (1), and in that the housing (2) has, at least in a longitudinal portion of the pocket (5) in the region between two directly adjacent screws (3a, 3b,...) or in the region of material transfer from one screw to the adjacent screw, at least one gusset (20) projecting into the interior region (15) of the housing (2) and extending 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 22, 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 generally somewhat smaller, and the tendency to 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, considerations arise as to constructively adapt the extruder, for example also in the critical area of ​​feeding or intake, or to design it in such a way that the intake behavior and the feeding of the screws are thereby 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 and, for example, also become 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 for processing and melting polymeric materials is provided, 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 advantageously a screw gap that is essentially constant and small or narrow, surrounding the screws completely or on all sides, extending to the screw outlet, 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 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, 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 still present 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 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 a pocket. This pocket advantageously 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. The pocket thus advantageously 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 part 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] In this context, according to the invention, in an extruder or multi-screw extruder with a pocket, it is provided that in the housing, at least in one area or longitudinal section of the pocket, in the area between two directly adjacent screws or in the material transfer area from one screw to the adjacent screw, at least one gusset projecting into the interior of the housing and running in or along the conveying direction is formed.

[0029] The gussets ensure that each individual screw is enclosed by the cylinder to a slightly greater extent than would be the case without them. These gussets are located, for example, in the feed area or the conical transition area, forming a local pocket-like area in the material transfer zone from one screw to the next. This creates a slight build-up of material, thereby positively influencing the conveying effect. The gussets thus advantageously support the transfer of material from screw to screw, enhance the conveying action of the screws, and also aid in guiding the screws within the housing. In addition to axially conveying the particles in the feed area, the gussets also assist in the transfer of particles from one screw to another. This is particularly beneficial for very light bulk materials with densities of less than 350 kg / m³. 3With the help of at least one wedge, at least in the conical transition area, it is very possible to maintain a stable flow.

[0030] The inventive 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.

[0031] In this context, it is advantageously provided that the gusset(s) is / are defined and formed from the inner wall of the housing, in particular by the intersecting inner walls of the, in particular axially parallel, bores for the worms or the worm chambers, wherein the intersection point or the intersection line of the inner walls forms the gusset(s) or defines its / their upper edge, height or shape.

[0032] An advantageous embodiment for the infeed behavior provides that at least one gusset has a substantially wedge-shaped form, roughly triangular in cross-section, with two concavely curved, in particular circularly curved, side surfaces and an upper edge, in particular straight, linear or non-curved.

[0033] In an advantageous embodiment, it is provided that the wedge(s) is / are symmetrical to its height, i.e., for example, having two similarly curved side surfaces.

[0034] For some types of material, it is also advantageous if the two side surfaces of the wedges are curved or aligned parallel or concentrically to the snails or their enveloping surfaces.

[0035] It is advantageous if the gusset is not too thin in order to adequately absorb the lateral forces of the screw and the material. A smooth curve transitioning from the outer diameter of the pocket to the inner cylinder diameter is also beneficial, as it helps maintain a certain degree of self-cleaning. However, it can also be advantageous to design the transition at an angle to increase conveying in the extrusion direction, although this will result in a slightly reduced level of self-cleaning within the system.

[0036] Alternatively, or for other types of material, it can be advantageous if the side surfaces of the wedges are not curved or aligned parallel or concentrically to the screws or their casings, and if the distance between the side surfaces and the screws decreases towards the top edge, i.e., if the wedge(s) approach the screws. This increases the conveying efficiency and makes it possible to achieve a higher conveying rate, especially in the conical section of the cylinder. This is particularly beneficial for very light materials below 100 kg / m³. 3 This conveying system is particularly advantageous for materials such as highly stretched fibers, but also for very thin film chips with a film thickness of less than 100 micrometers, such as biaxially stretched polypropylene or polyester.

[0037] The closer the gusset gets to the screw, the more two separate pocket-like areas are formed within the housing, facilitating a direct transfer from one screw to the other. The formation of these pocket-like areas allows for material exchange within the extruder; during transfer, this creates a buffer zone or conveying zone.

[0038] The lighter the incoming material is in its bulk density, the more suitable gussets near the screw are, because light material often needs more compression and guidance through the pronounced gussets.

[0039] In an advantageous embodiment, the gusset(s) is / are formed only on one side of the inner wall of the housing, or on only a single inner wall or position of the inner wall, and the opposite side of the inner wall is free of gussets or a flat connection without gussets is formed there between the two screw chambers. In a twin-screw extruder, in this case there is only a single gusset.

[0040] In an alternative embodiment, which is advantageous for certain types of material, several, e.g., two, gussets are formed on diametrically opposed inner walls or positions of the housing. In particular, it can be advantageous if each gusset is assigned a directly opposite gusset, especially one running between the same screws, on the opposite side of the inner wall or at a position opposite it in the housing.

[0041] In this context, it is advantageous for the infeed behavior of certain materials if the opposing wedges are identical and / or symmetrically arranged.

[0042] For other types of material, it is alternatively advantageous if the opposing gussets are designed differently, and in particular have different heights and / or radii of curvature or curvature shapes.

[0043] In this context, an advantageous embodiment provides that the wedge(s) is / are arranged symmetrically between two snails and / or in the plane of symmetry between two directly adjacent snails.

[0044] Furthermore, an advantageous arrangement can be designed such that the screws are arranged side by side and the axial longitudinal axes of the screws define a common plane or lie in a common plane, wherein the wedge(s) is / are formed on a straight line / plane perpendicular to and intersecting this plane between the opposing inner walls of the housing. In particular, it can be provided that this straight line / plane runs through the midpoint or bisector of the distance between the longitudinal axes, especially in the case of screws with the same diameters.

[0045] It is also advantageous if the gusset(s) extend at least to the end of the pocket. It is also possible for the gusset(s) to extend further into the extrusion area and even to the end of the extruder or the exit opening.

[0046] An advantageous embodiment further provides that the length of at least one wedge lies in a range from L=0.1 Da to L=15 Da, preferably from L=0.5 Da to L=9 Da.

[0047] Furthermore, it is advantageous if at least one gusset extends over the entire length of the pocket. Another advantageous embodiment provides that the at least one gusset extends only from the point furthest downstream of the inlet opening in the conveying direction, and the area upstream of this point is free of gussets.

[0048] According to an advantageous embodiment, it is further 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 present uses of Da.

[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, especially oval, elliptical, or circular ones, are preferred in terms of feed behavior.

[0052] 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:

[0053] The screws are arranged side by side, and the axial 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. 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 feed opening, between the opposing areas of the inner wall of the housing. Of 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 this context, it is advantageous if the gusset height Zh of the gusset(s), measured as the normal distance of the upper edge of the gusset to the plane spanned by the longitudinal axes of the screws, is designed as follows or lies within this range: (h+screw gap) < Zh < Ti / 2, where h 2 = There 2 / 4 - (Da-Di) 2 / 4. h is the normal distance between the plane spanned by the longitudinal axes of the screws (13 in Fig. 4c) and the screw circle or the intersection of the screw circles, measured in the area between the screws, specifically in the line / plane (23 in Fig. 4c) normal to the plane 13 above. h is thus determined by the diameters of the screws and represents the lower limit at which a collision with the screws would occur. The gap height Zh is therefore defined by the largest inner diameter Ti and by the distance (h + screw gap). Ti depends on Di and changes along the axis in the conical region. For two screws with the same diameter, the gap height Zh is defined at the normal that passes through the center of the two screw axes. For screws with different diameters, the largest Da and the smallest Di are used in the formulas.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] In this context, it is further advantageous if it is provided that at least one gusset extends over the entire length range LT.

[0059] The special design of the pocket, the gussets, and, if applicable, the feed opening, 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.

[0060] According to an advantageous embodiment, the length LE of the infeed opening is further provided that it is in the range of 0.3 Da < LE < 10 Da. Furthermore, it is advantageously provided that the width (BE) of the infeed opening (4) is in the range of 0.1 Da < BE < 2 Da. In this way, a particularly advantageous infeed behavior is ensured.

[0061] 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.

[0062] 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.

[0063] 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 material compaction is advantageously achieved. In this context, it is also advantageous if at least one gusset extends over the entire transition zone.

[0064] 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 or conically tapered at a uniform angle 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. Advantageously, at least one gusset is formed in this region.

[0065] In an advantageous embodiment, the gusset(s) extend continuously across the infeed area A, the transition area B, and the extrusion area C to the extruder outlet. The gusset(s) advantageously extend across the entire area or over the entire length of the pocket, over the end of the pocket into the extrusion area, and to the end of the extruder.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] Depending on the requirements, it is advantageous if the screws are designed as co-rotating or counter-rotating screws. Furthermore, it is advantageous if the screws are designed as interlocking or combing screws, whereby the axial distance between the screws or the central longitudinal axes is smaller than the (outer) screw diameter Da over their entire length.

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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 method is satisfactory, it often only compensates to a certain extent for the bulk density variations of the materials being processed over time.

[0074] Even more advantageous is the upstream use of a cutting compactor or a PCU, which can regularly provide very good compensation.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] 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 within the PCU (Production Control Unit). Unfavorable settings can manifest, for example, as significant fluctuations in extruder torque and die speed, which can negatively impact feeding behavior and material quality. Even simply mixing the materials within the PCU has a dampening effect, to a certain (small) degree, on any bulk density fluctuations in the input materials. However, mixing alone, and often even intensive pretreatment of the materials within 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 these methods.Rather, 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.

[0080] The tools in the PCU are advantageously discs, rods or beams, especially with knives arranged on them.

[0081] 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.

[0082] 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 is 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.

[0083] 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 material at its opposite end face to an outlet opening, in particular an extruder head, located at the end face of the housing. It is further advantageous if the opening in the PCU is connected directly and immediately to the feed opening without a longer distance or transfer section, e.g., a conveying screw. This enables efficient and gentle material transfer.

[0084] 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.

[0085] 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.

[0086] 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.

[0087] 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.

[0088] Furthermore, it is advantageous for machining if the radially outermost edges of the tool extend close to the side wall of the container.

[0089] 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 in the region of the height of the lowest, bottom-adjusted tool. A twin-screw extruder is tangentially connected to this container opening, into which the pretreated material is fed.

[0090] 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.

[0091] Fig. 1a shows an embodiment of an extruder according to the invention in a partial sectional view from above.

[0092] Fig. 1b shows the extruder according to Fig. 1a in a partial sectional view from the side.

[0093] Fig. 2 shows an extruder according to the invention in a perspective view.

[0094] Fig. 3 shows an extruder according to the invention in a perspective partial sectional view.

[0095] Fig. 4a shows a cross-section of an extruder according to the invention in the extrusion area C.

[0096] Fig. 4b shows a cross-section of the extruder in the transition area B.

[0097] Fig. 4c shows a cross-section of the extruder in the feed area A.

[0098] Figs. 5a and 5b show a cutting compressor-extruder combination according to the invention with cylindrical screws from above and from the side.

[0099] Figs. 6a and 6b show an alternative cutting compactor-extruder combination with conical screws from above and from the side.

[0100] Figures 7 to 13 a, b, c show advantageous designs of various spandrels. The representations in the figures are schematic only.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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'.

[0106] 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.

[0107] Further 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 polymeric 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.

[0108] 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.

[0109] 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.

[0110] 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.

[0111] 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. The longest width or height BE of the feed opening 4 is, in this case, approximately 2 Da. 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 for 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 intake opening 4.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] In the embodiment according to Figs. 1a and 1b, two opposing wedges 20 are formed; for illustrative reasons, these are only shown schematically in Fig. 1b. The location and position of the wedges 20 are also shown in the following figures.

[0118] 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.

[0119] 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. The descriptions for Figs. 2 and 3 are analogous to those for Figs. 1a and 1b.

[0120] Figures 2 and 3 further show that in the housing 2, in a longitudinal section of the pocket 5, in the area between the two directly adjacent screws 3a, 3b, or in the material transfer area from one screw 3a to the adjacent screw 3b, a gusset 20 is formed, projecting into the inner area 15 of the housing 2 and extending in the conveying direction 6. Accordingly, two gussets are formed at diametrically opposed positions on the inner walls 8, extending over the entire area of ​​the pocket 5 to the extruder outlet. The detailed design of these gussets is shown in Figures 4a, 4b, and 4c and is described there in more detail.

[0121] 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.

[0122] 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.

[0123] 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.

[0124] 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.

[0125] It can be seen that in the housing 2, in a longitudinal section of the pocket 5 in the area between the two directly adjacent screws 3a, 3b, or in the material transfer area from one screw 3a to the adjacent screw 3b, two gussets 20 are formed projecting into the inner area 15 of the housing 2 and extending in the conveying direction 6. The two gussets 20 are defined and formed by the intersecting inner walls 8 of the axially parallel bores or screw chambers, with the points of intersection or lines of intersection of the inner walls 8 forming the gussets 20 and defining their heights or upper edges 22.

[0126] The wedges 20 each have an essentially elongated wedge-shaped form, approximately triangular in cross-section, with two concave circularly curved inwards side surfaces 21 and a straight, non-curved upper edge 22.

[0127] The opposing wedges 20 are designed symmetrically to their height and are arranged identically and symmetrically to each other.

[0128] In the present embodiment, the side surfaces 21 of the wedges 20 are curved or aligned parallel or concentrically to the worms 3a, 3b or their enveloping surfaces. Accordingly, the distance between the side surfaces 21 and the worms 3a, 3b remains constant everywhere, including in the direction of the upper edge 22.

[0129] The two wedges 20 are arranged symmetrically in the material transfer area between the two screws 3a, 3b and in the plane of symmetry 23 between the two directly adjacent screws 3a, 3b. It is thus provided that the screws 3a, 3b are arranged side by side and their axial longitudinal axes 3a', 3b' define a common plane 13 or lie in a common plane 13, with the wedges 20 being formed on a plane 23 between the opposing inner walls 8, which is oriented normal to this plane 13 and intersects the midpoint or bisector of the distance between the longitudinal axes 3a', 3b'.

[0130] In the present example, the gussets 20 extend continuously over the entire length of the pocket 5, i.e. over the intake area A, the transition area B to the end 11 of the pocket 5 and also beyond, in and over the entire extrusion area C to the extruder exit.

[0131] The wedge height Zh of wedge 20 lies in the range of: (h+snail gap) < Zh < Ti / 2, where h 2 = There 2 / 4 - (Da-Di) 2 / 4. The wedge height Zh is the perpendicular distance of the upper edge 22 of the wedge 20 to the plane 13 spanned by the longitudinal axes 3a', 3b' of the screws 3a, 3b, and lies in the plane 23, which is perpendicular to plane 13. In this case, with equal screw diameters, it lies midway between the longitudinal axes 3a', 3b'. h is the perpendicular distance between the plane 13 spanned by the longitudinal axes 3a', 3b' of the screws 3a, 3b and the screw circle or the intersection of the screw circles of the screws 3a, 3b, also measured in plane 23. h thus represents the lower limit for the wedge height Zh at which a collision with the screws would occur. The gusset height Zh is shown in Fig. 4c only as an example and also applies analogously in Fig. 4a, 4b or Fig. 7-13.

[0132] 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.

[0133] 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.

[0134] 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.

[0135] 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.

[0136] The tools 300a, 300b serve, among other things, to move, mix, heat, and comminute 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, 300b creates a mixing vortex in the material, which remains in the container 100 for a certain residence time and is pretreated accordingly. 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, whereby the polymer material being pretreated in the container 100 is fed into the extruder 1 or theis brought into the capture area of ​​the screws 3a, 3b, specifically in the area of ​​the pocket 5. This extruder 1 is designed analogously to Figs. 1a and 1b, 2, 3 and 4a, 4b or 4c, and the corresponding descriptions are adopted here. The inventive gussets 20 are also present here and extend in the schematic figures over the entire length of the pocket and the rest of the extruder.

[0137] Especially in multi-screw extruders, the feeding process is particularly sensitive, and consistent feeding at a level that remains constant is crucial. The present method of introducing the pre-treated material into pocket 5 of the twin-screw extruder 1 is particularly advantageous. The direction of rotation of the tool 300a on the lowest level (arrow) runs, in the area of ​​the hopper opening 500 or opening 4, essentially opposite to the conveying direction 6 of the extruder 1.

[0138] 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.

[0139] 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.

[0140] In schematic Figures 6a and 6b, a further advantageous embodiment of a complete device according to the invention is shown in top and side views, respectively. The specifications for Figures 6a and 6b are analogous to those for Figures 5a and 5b. In contrast, 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 contours 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. The two opposing gussets 20 are analogous to those in Figure 5.

[0141] Figures 7 to 13 show different variants and configurations of the wedges 20. These illustrations are analogous to Figures 4a, 4b, and 4c, and the corresponding details and reference numerals are adopted. In all figures, the wedges 20 are located in the material transfer area between the screws 3a and 3b, or symmetrically to the plane 23.

[0142] In Fig. 7a, b and c, two identical wedges 20 are formed symmetrically opposite each other between the screws 3a, 3b, the side surfaces 21 of which are curved or aligned parallel or concentric to the screws 3a, 3b or their enveloping surfaces.

[0143] In Fig. 8a, b and c, two identical wedges 20 are formed, symmetrically opposite each other between the worms 3a, 3b, whose side surfaces 21 differ from Fig.

[0144] 7 are not curved or aligned parallel or concentric to the spirals 3a, 3b or their envelopes and the distance between the side surfaces 21 and the spirals 3a, 3b decreases in the direction towards the top edge 22.

[0145] In Fig. 9a, b and c, wedges 20 analogous to Fig. 8 are shown with differently shaped, more strongly curved side surfaces 21.

[0146] Figures 10, 11 and 12 correspond analogously to Figures 7, 8 and 9 with the respective difference that here not two opposing gussets, but only a single, one-sided gusset 20 is formed and the opposite inner wall is free of gussets 20 or is flat.

[0147] Fig. 13 shows a mixed variant with two opposing, different wedges 20. The side surfaces 21 of the upper wedges 20 are curved in a circular arc and are parallel or concentric to the screws 3a, 3b or their enveloping surfaces. The side surfaces 21 of the lower wedges 20 are curved differently and more strongly, and are not parallel or concentric to the screws 3a, 3b or their enveloping surfaces. The distance between the side surfaces 21 and the screws 3a, 3b decreases towards the upper edge 22, and the curvature becomes increasingly pronounced.

[0148] Example:

[0149] 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:

[0150] In the system configuration (comparable to the device shown in Figures 4 and 5), 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.

[0151] The twin-screw extruder used here had the following specific features:

[0152] Dimensions or parameters:

[0153] Length (LE) of the inlet opening (4): 2.38 Da or 150 mm

[0154] 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

[0155] Screws: two identical cylindrical screws, parallel, running in the same direction, interlocking

[0156] Wedges: two identical, opposing wedges extending the entire length of the pocket, within the extrusion area, to the extruder exit. The rotational speed of the tools in the PCU was controlled to ensure that the energy input into the material was such that a specific material temperature was reached. The material 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 tempered close to 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.

[0157] 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.

[0158] 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 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) has at least one feed opening (4) formed in its outer wall in the feed section (A) for introducing the material to be processed into the capture area of ​​the screws (3a, 3b, ...), characterized in that the housing (2) has a feed opening (4) in the feed section (A) or in an area around the feed opening (4) extending over a partial longitudinal section of the extruder (1) along the screws (3a, 3b, ...) extending, pocket (5), and that in the housing (2) at least in a longitudinal section of the pocket (5) in the area between two directly adjacent screws (3a, 3b, ...) or in the material transfer area from one screw to the adjacent screw at least a gusset (20) projecting into the interior area (15) of the housing (2), extending in the conveying direction (6), is formed.

2. Extruder (1) according to claim 1, characterized in that in the extrusion area (C) there is a narrow screw gap (7) between the outer diameters of the screws (3a, 3b, ...) and the inner wall (8) of the housing (2) which is essentially constant up to the extruder or screw outlet, wherein the pocket (5) has a screw gap (7') that is larger than 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) along its entire longitudinal length.

3. Extruder (1) according to claim 1 or 2, 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).

4. Extruder (1) according to one of claims 1 to 3, characterized in that the gusset(s) (20) is / are defined and formed from the inner wall (8) of the housing (2), in particular by the intersecting inner walls (8) of the, in particular axially parallel, bores or screw chambers, wherein the intersection point of the inner walls (8) forms the gusset(s) (20).

5. Extruder (1) according to one of claims 1 to 4, characterized in that the at least one gusset (20) has a substantially wedge-shaped form with two concavely curved inwards, in particular circularly curved, side surfaces (21) and a, in particular straight, upper edge (22).

6. Extruder (1) according to one of claims 1 to 5, characterized in that the gussets (20) are symmetrical to their height.

7. Extruder (1) according to one of claims 1 to 6, characterized in that the side surfaces (21) of the gussets (20) are curved or aligned parallel or concentric to the screws (3a, 3b, ...) or their enveloping surfaces.

8. Extruder (1) according to one of claims 1 to 6, characterized in that the side surfaces (21) of the gussets (20) are not curved or aligned parallel or concentric to the screws (3a, 3b, ...) or their enveloping surfaces and the distance between the side surfaces (21) and the screws (3a, 3b, ...) decreases in the direction of the upper edge (22).

9. Extruder (1) according to one of claims 1 to 8, characterized in that the at least one gusset (20) is formed only on one side of the inner wall (8) of the housing (2) and the opposite side of the inner wall (8) is free of gussets (20) or a planar connection is formed there between the two screw chambers.

10. Extruder (1) according to one of claims 1 to 8, characterized in that several gussets (20) are formed on diametrically opposed inner walls (8), in particular that each gusset (20) is assigned a gusset (20) directly opposite and running between the same screws (3a, 3b, ...) on the opposite side of the inner wall (8).

11. Extruder (1) according to one of claims 1 to 10, characterized in that the opposing gussets (20) are identical and / or symmetrically arranged.

12. Extruder (1) according to one of claims 1 to 10, characterized in that the opposing gussets (20) are designed differently, and in particular have different heights.

13. Extruder (1) according to one of claims 1 to 12, characterized in that the wedge(s) (20) is / are arranged symmetrically between the screws (3a, 3b, ...) and / or in the plane of symmetry between two directly adjacent screws (3a, 3b, ...) and / or that 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 wedge(s) (20) is / are formed on a straight line / plane (23) oriented normal to and intersecting this plane (13) between the opposing inner walls (8) of the housing (2) and in particular through the midpoint or bisector of the distance between the longitudinal axes (3a', 3b', ...). ...) proceeds.

14. Extruder (1) according to one of claims 1 to 13, characterized in that the gusset(s) (20) extend to the end (11) of the pocket (5). 15 Extruder (1) according to one of claims 1 to 14, characterized in that the length of the at least one gusset (20) is in a range of L=0.1 Da to L=15 Da, preferably from L=0.5 Da to L=9 Da, and / or that the at least one gusset (20) extends over the entire length of the pocket (5) and in particular also over the entire extrusion area (C) to the extruder outlet.

16. Extruder (1) according to one of claims 1 to 15, characterized in that the at least one wedge (20) extends from the point furthest downstream (9) of the feed opening (4) in the conveying direction (6).

17. Extruder (1) according to one of claims 1 to 16, characterized in that the pocket (5) has an enlarged inner diameter (Ti) along its entire longitudinal path, 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.

18. Extruder (1) according to one of claims 1 to 17, characterized in that the gusset height (Zh) of the gusset(s) (20), measured in the straight line / plane (23) normal to the plane (13) or as the normal distance of the upper edge (22) of the gusset (20) to the plane (13) spanned by the longitudinal axes (3a', 3b', ...) of the screws (3a, 3b, ...), is designed as follows: (h+snail gap (7) < Zh < Ti / 2 where h 2 = There 2 / 4 - (Da-Di) 2 / 4 where h is the normal distance between the plane (13) and the spiral circle or the intersection point of the spiral circles of the spirals (3a, 3b) measured in the line / plane (23).

19. Extruder (1) according to one of claims 1 to 18, characterized in that the pocket (5) has a length range (LT) extending from the furthest 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), wherein the length range (LT) is in the range of 0.2 Da < LT < 10 Da, in particular 0.5 Da < LT < 6 Da, and that it is particularly provided that the at least one gusset (20) extends over the entire length range (LT).

20. Extruder (1) according to one of claims 1 to 19, characterized in that the length region (LT) of the pocket (5) starting 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 conically and / or continuously tapered at a uniform angle for at least a partial section of > 50%, in particular > 80%, preferably > 90% of the length of the length region (LT), and in particular over the entire length of the length region (LT), and that it is provided in particular that the at least one gusset (20) extends over the tapered section of the length region (LT).

21. Extruder (1) according to one of claims 1 to 20, characterized in that the extruder (1) is designed as a twin-screw extruder with two cylindrical screws (3a, 3b) arranged 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.

22. 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-adjacent 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 21, 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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