Apparatus and method for processing materials

Abstract

The present invention relates to an apparatus for processing materials that contain or consist of polymeric materials, in particular for recycling contaminated thermoplastic polymers. The apparatus comprises an extruder (2) having a screw (10) for melting the material, a first filtration unit (3) for filtering the melt and a degassing zone (5) for degassing the melt. According to the invention, at the extruder outlet (9), a melt pump (6) is connected to said degassing zone (5) or after or downstream of the screw (10).

Description

[Technical field]

[0001] The present invention relates to an apparatus and a method for treating material comprising or consisting of polymeric material or for recycling contaminated thermoplastic polymers according to the preamble of claim 1 or claim 19. [Background technology]

[0002] A known and proven sequence of steps in the processing of secondary raw materials is the extrusion, filtration and pelletization of the thermoplastic material to be treated.

[0003] A known effective principle is to first heat or soften the thermoplastic polymer in a cutter compactor or preconditioning unit (PCU), then transfer it to an extruder where it is melted, and then the melt is filtered and degassed, and possibly filtered again, for example to produce granules, where the first melt filtration is provided before or even far upstream of the degassing by the extruder. A high quality final product with a high proportion of recycled granules can thus be achieved.

[0004] The control of known devices or methods is, for example, as follows: In a cutter compactor or preconditioning unit (PCU), the polymeric material to be processed is crushed, mixed, heated, dried, precompressed and, if necessary, buffered. An extruder, which is directly tangentially connected to the cutter compactor, is continuously charged with the heated and softened precompressed material. In this extruder screw, the material is plasticized. The melt leaves the extruder at one end of the plasticization zone, is cleaned in an automatic self-cleaning filter and is returned again to the part of the extruder located downstream of the filter. In this part of the extruder, i.e. after the first melt filter, a final homogenization of the melt takes place. In the subsequent degassing zone, filtration and degassing of the homogenized melt takes place. The melt is then fed via the discharge zone of the extruder to the respective equipment, for example a granulator. Optionally, it is also possible to arrange a second melt filtration section after the discharge zone and before the equipment. Such an equipment is, for example, shown in FIG. 1 and will be described in more detail below. Such filtering, homogenization and degassing allows difficult to process materials such as heavily printed foils and / or wet materials to be processed.

[0005] However, this is already evident in the case of a single filtration stage, but when two filtration stages are provided or used, it means in particular that a pressure increase occurs in the melt and the melt temperature can become very high, especially at one end of the extrusion system, specifically before the tool.

[0006] Especially when recycling polymers, double or double filtration is often used. This may be necessary when recycling particularly highly contaminated polymers, for example, to remove contaminants or gels from the material stream to be processed, which may require different separation methods. This purification for quality improvement is always connected with a pressure increase. Here, in particular, if the pressure is increased only by the melt, high melt temperatures occur in the case of extruders.

[0007] However, high bulk or melt temperatures have a negative impact on the quality of the polymer. They lead, among other things, to increased consumption of stabilizers, shortening of molecular chains, and undesirable gel formation and combustion of particles and polymers in the melt. Decomposition of the polymer or inclusions also occurs due to high temperatures. This negates or fails some of the efforts made upstream to improve material quality.

[0008] From the prior art it is also basically known to provide a gear pump in the region of the distal end of the extruder which conveys the melt. Summary of the Invention [Problem to be solved by the invention]

[0009] It is therefore an object of the present invention to realize an apparatus and a method which allows for an easy improvement of the resulting material quality. [Means for solving the problem]

[0010] The present invention solves this problem in an apparatus for processing material comprising or consisting of polymeric material, in particular for recycling contaminated thermoplastic polymers, comprising at least one extruder having at least one screw for melting the material, at least one first filtration unit for filtering the melt and at least one degassing zone for degassing the melt, by the features set out in the characterizing part of claim 1.

[0011] According to the invention, at the extruder outlet, connected to or arranged or provided in the venting zone or after or downstream of the screw, is at least one melt pump or device for pumping the polymer melt.

[0012] This therefore means that the melt pump is located after the extruder outlet or downstream relative to the extruder or screw, and thus necessarily after or downstream relative to the degassing zone, i.e. the melt pump is connected to the degassing zone in the melt flow direction, the melt pump may be located immediately after the degassing zone or indirectly behind it, i.e. at some distance after the degassing zone.

[0013] Such melt pump arrangement provides increased pressure and simultaneously reduced bulk temperature, thereby mitigating the above-mentioned drawbacks and improving material quality.

[0014] The low bulk temperatures in this region have a correspondingly positive effect on the melt quality. Another advantage is the low tendency to produce undesirable odors and discolorations, which are more likely in higher temperature systems, especially when using cellulose-destroying materials such as paper or wood. Such melt pump arrangements are particularly advantageous, for example, when recycling typical supermarket foils made of LDPE / LLDPE and partly with high residual moisture, especially when these foils are contaminated with paper impurities, e.g. wood chips from labels or pallets, as well as foreign polymers, dust, etc. Here, even a temperature increase of just a few degrees has a particularly destructive and harmful effect.

[0015] In particular, this is advantageous in the case of difficult to process polymeric materials and where applications require gentle processing of the polymer and high filtration performance.

[0016] Furthermore, degassing can also be particularly efficient and powerful, since the pressure increase and the temperature increase are decoupled by the downstream melt pump, so that the highest temperature in the entire system does not occur at the end of the screw or before the second filtration unit, but already before the degassing, which prevents subsequent outgassing of the melt components, which has a positive effect on the quality of the melt and the regenerated granulate.

[0017] Therefore, there is an advantage that the pressure increase by the melt pump relieves the extruder from the task of increasing the pressure, and the pressure increase can be carried out in an extremely short period of time, making it possible to make the device more compact and realize it in a space-saving manner.

[0018] A further advantage of this melt pump pressure increase is that the extruder speed can be optimally adapted to the polymer without compromising throughput.

[0019] Furthermore, the lower bulk temperature also significantly reduces energy consumption.

[0020] Furthermore, since only purified and degassed melt flows through the melt pump in this manner, the service life of the melt pump components is also advantageous.

[0021] In this respect, it is preferred that the melt pump is connected in close spatial proximity and directly to the degassing zone in the conveying direction, without any further functional units in between, or is connected to the lower stage of the degassing zone and connected one after the other in process terms. By "functional unit" is meant here a unit which acts, for example mechanically, on the melt or which acts on a processing step. Here, the term "close and direct" is understood to mean that the melt pump is located immediately beside or behind the degassing zone, and no actual processing units, such as filters, homogenizers or the like, are provided between the melt pump and the degassing zone. Passive connections, transition pieces or transition pipes may be provided without any interference. Instead of locating a pressure increase zone or discharge metering zone within the extruder, a melt pump can be conveniently located directly and closely behind the degasser to provide the pressure increase required, for example, for an additional filtration stage.

[0022] It may also be advantageous that the extruder does not have a metering zone for increasing the pressure of the melt in the area downstream of the first filtration unit, in particular in the area downstream of the degassing zone, and / or that a melt pump replaces the metering zone. That is, screw extruders are relatively inefficient when pressure needs to be increased or when the melt needs to be pumped. For this reason too, it is advantageous to omit the last pressure increase stage (metering zone) of the extruder after degassing, especially before the second filtration, and replace it with a melt pump. The melt pump is therefore connected immediately after or immediately downstream of the degassing unit or degassing zone of the extruder screw. Thus, excessively high bulk temperatures do not impair or cancel the quality improvement achieved by filtration.

[0023] Alternatively, it would be equally effective if the melt pump is not located immediately after the degassing zone, but rather there is a spacing between the degassing section and the melt pump.

[0024] In this regard, it is advantageous if the screw extends continuously in the region between the center of the last venting port of the venting zone located most downstream in the conveying direction and the extruder outlet, i.e., there is a residual screw or conveying means between the venting section and the melt pump. It is therefore advantageous to provide a continuous screw from the inlet to the extruder outlet, i.e., on both sides of the venting section.

[0025] In this respect, it is further advantageous if the melt pump is connected at a distance of not more than 20 D from the degassing section, and it is particularly advantageous if it is arranged to have a certain minimum distance, i.e. the distance is in the range of 5-20 D, preferably in the range of 5-15 D, more preferably in the range of 8-11 D. Here, D means the outer diameter of the extruder screw, i.e., measured at the rearmost vent hole of the downstream most venting zone in the conveying direction, where the venting zone is formed with at least one vent hole. The distance between the vent and the melt pump is defined here as the distance between the center of the rearmost vent of the most downstream venting zone in the conveying direction and the melt pump, as described above. In particular, the location of the most upstream active conveying means or conveying functional part of the melt pump is considered here, i.e. the start or inlet channel of the melt pump where the melt enters the pump or is received by the conveying means or pump action. This distance is understood as the "melt flow distance", i.e. measured along the direction of the path that the melt moves or takes in the device, or is considered as the distance between units arranged along the conveying or flow direction of the melt.

[0026] Here, a particularly advantageous device is defined as follows. An apparatus for processing a material comprising or consisting of a polymeric material, in particular for recycling contaminated thermoplastic polymers, comprising an extruder (2) having a screw (10) for melting the material, a first filtration unit (3) for filtering the melt and a degassing zone (5) for degassing the melt, At the extruder outlet (9), a melt pump (6) is connected to a degassing zone (5) downstream or after the screw (10), The screw (10) continues in the region between the center of the last degassing port (11) of the degassing zone (5) located most downstream in the conveying direction and the extruder outlet (9), or a residual screw (14) or conveying means is provided in this region; The melt pumps (6) are connected at intervals (13) of 5 to 20D, preferably in the range of 5 to 15D, and more preferably in the range of 8 to 11D; D is the outer diameter of the screw (10) of the extruder (2) measured at the rearmost vent (11) of the venting zone (5) located most downstream in the conveying direction, The spacing (13) is defined as the distance between the center of the rearmost vent (11) of the degassing zone (5) located most downstream in the conveying direction and the position of the melt pump (6), in particular the most upstream active conveying means or conveying functional component of the melt pump (6).

[0027] In this context, experiments have shown that the shortest screw length, i.e. after degassing, results in the lowest temperature rise. However, the conveying capacity of the screw is strongly influenced by material fluctuations that occur during the recycling process. This can be evidenced, for example, by retention in the degassing area and can also lead to material discharge at the degassing port. This leads to material losses as well as losses in degassing performance and thus to quality deterioration. In view of this background, it is useful for the residual screw to have a certain minimum length, even if this leads to an increase in the bulk temperature.

[0028] The recycling plant is designed to be extremely versatile overall in terms of its requirements profile and must be able to process a variety of polymers with different viscosities and sliding properties. To ensure this versatility, a minimum length of the discharge screw is also advantageous. Various experiments with different materials have shown that this allows a versatile configuration to be realized that combines operational safety with the lowest possible temperature rise.

[0029] Thus, an apparatus with the above mentioned characteristics, especially with the defined minimum spacing, allows on the one hand a flexible application, but at the same time a very stable process and, due to the low bulk temperatures, a particularly gentle treatment of the polymer melt, which leads to an improved quality of the melt and of the regenerated granules.

[0030] In this regard, one advantageous configuration is one in which the ratio of the length of the first upstream portion of the screw, from the first filtration unit to the center of the front degassing port of the most upstream degassing zone, to the length of the second upstream portion of the screw, from the center of the rearmost degassing port of the most downstream degassing zone to the end of the screw or the extruder outlet, i.e., the remaining screw length, is in the range of 0.1 to 3, specifically in the range of 0.3 to 2.

[0031] It is advantageous if the length of the first upstream part of the screw between the first filtration unit and the front degassing port of the most upstream degassing zone is in the range of 1 to 15D, in particular in the range of 3 to 10D.

[0032] Furthermore, it is advantageous if the length of the second upstream portion of the screw between the rearmost degassing port of the most downstream degassing zone and the extruder outlet, or the length of the remaining screw, is in the range of 3 to 12D, specifically in the range of 4 to 10D, and preferably in the range of 5 to 8D.

[0033] Thus, according to the above-mentioned advantageous embodiment, the melt pump does not necessarily have to be connected in close spatial proximity and directly to the degassing zone in the conveying direction without any further functional units in between, but can also be arranged at the above-mentioned distance, and it is expedient if the extruder screw or the remainder of the screw also continues in the region behind this degassing zone.

[0034] In this regard, it is advantageous if the cross-sectional area of ​​the root of the screw or the remaining screw is expanded or contracted by no more than 50%, preferably no more than 20%, in particular no more than 5%, in the region between the center of the last degassing port of the degassing zone located most downstream in the conveying direction and the extruder outlet, i.e. up to the end of the extruder screw, by no more than 50%, preferably no more than 20%, in particular no more than 5%. The smaller the change in the core cross-sectional area, i.e., the smaller the compression, the less shear the material will experience. If the core cross-sectional area is too large, the material will be compressed, leading to an undesirable temperature increase. For certain materials, for example, if the amount of material to be degassed is large, a small compression may be effective.

[0035] According to one useful configuration, it is further advantageous that the inclination of the screw or the remaining screw is increased or decreased, preferably kept constant, in the region between the center of the rearmost venting port located most downstream in the conveying direction and the extruder outlet by no more than 3 L / D, preferably no more than 1.5 L / D, in particular no more than 0.5 L / D. Here, L / D refers to the general ratio of the (effective) length of the screw to the diameter of the screw. The smaller the change in inclination, the less shear the material will experience. If the gas ballast of the melt is very high, a small compression can "squeeze" the material, i.e. force the gas back into the venting section.

[0036] Furthermore, the screw or residual screw may be determined by the product of the screw depth, web width, gear width, and flight inclination, i.e. P=t*b*B*S (B=Sg*b), t is the depth, b is the web width, B is the thread width, S is the (thread) slope, g is the number of threads on the screw. The product is In the region between the center of the last vent of the venting zone located most downstream in the conveying direction and the extruder outlet, it is advantageous to change by 30% or less, preferably 15% or less, in particular 5% or less, preferably 3% or less, in particular not to change at all. This allows to reduce the introduction of shear into the material. In some cases, advantageous changes in compression can be achieved not only by changing the core cross-sectional area, but also, for example, by carrying out multiple steps, changing the inclination or increasing the web width, which leads to a certain degree of increase in the degree of compression.

[0037] An apparatus having the last mentioned characteristics not only has the advantages mentioned above (possibly on an enhanced scale), but also allows for great flexibility in its application, at the same time a very high process stability and a particularly gentle treatment of the polymer melt, which results in an improved quality of the melt and of the regenerated granulate.

[0038] According to a further advantageous embodiment, a second filtration unit is connected to the melt pump in the conveying direction or downstream of the melt pump, particularly in close spatial proximity and directly, without any further functional units in between. In particular, when recycling highly contaminated polymers, double or double filtration is often necessary, for example to remove contaminants or gels from the material stream to be processed. This second filtration is always associated with a pressure increase, which would lead to high melt temperatures in the extruder if the pressure were increased only by the melt. Therefore, the configuration of the melt pump according to the invention is particularly advantageous when a second filtration unit is provided. The melt pump thus performs the necessary pressure increase for the second filtration unit. The extruder is relieved of this task, which allows it to be realized in a shorter length. This significantly reduces the residence time, the bulk temperature and the energy consumption.

[0039] The device is particularly practical and advantageous if a discharge unit for discharge connected downstream of the second filtration unit in the conveying direction and / or at least one post-treatment unit for processing the melt, such as a granulation unit, is provided.

[0040] It is also advantageous for the quality of the material if a container is provided for feeding the material to be processed, in particular for crushing and / or heating, to which an extruder is connected. Particularly advantageously, mixing and / or crushing tools are provided in the container for mixing and possibly crushing the material while continuously maintaining its massiness and flowability, and also for possibly heating and softening the material. In a particularly advantageous embodiment, the container is configured to be a conventional cutter compactor or a PCU or preconditioning unit.

[0041] A particularly advantageous constructional apparatus is characterized in that the extruder is a single-screw extruder having a single screw.

[0042] It is also advantageous if a gear pump is provided as the melt pump.

[0043] In order to better homogenize the melt and to improve its quality, it is advantageous, in particular, if a homogenization unit for homogenizing the melt is provided behind the first filtration unit and before the degassing zone in the conveying direction, in particular a screw or part of a screw or extruder, which is configured in such a way that the melt is sheared and mixed therein or is subjected to intensive shear and tensile stresses, resulting in a strong acceleration of the melt.

[0044] Structurally particularly advantageous apparatuses are configured in such a way that at least some units of the extruder, i.e. the degassing zone and the melt pump, in particular all units present in the apparatus, are arranged essentially linearly or axially one after the other or on a common longitudinal axis.

[0045] However, according to the invention, a cascade installation is also possible, where a first extruder melts the polymeric material, where the melt is also filtered. The material is then transferred to a second extruder, where it is degassed. In this configuration, the melt pump is located directly and closely adjacent to the degassing zone of the second extruder.

[0046] The present invention further achieves the problem stated in the opening paragraph by a method for treating materials which contain or consist of polymeric materials, in particular for recycling contaminated thermoplastic polymers, which method comprises the steps of: a) providing the material to be treated, in particular in a vessel; b) at least partially, in particular completely melting the material, in particular in an extruder; c) performing a first filtration of the melt to remove unmelted components and / or impurities; d) degassing the filtered melt; e) increasing the pressure of the melt with a melt pump; f) discharging and / or post-treating the melt, in the order listed. According to the invention, the increase in the melt pressure is performed after the degassing of the melt or is performed in tandem with the degassing of the melt.

[0047] A device having the above-mentioned characteristics is preferably used for this purpose.

[0048] As mentioned above, the method according to the invention allows for an increase in melt pressure and a concomitant reduction in bulk temperature, thereby reducing the above mentioned drawbacks and improving the quality of the material.

[0049] Thus, this method provides the advantages mentioned above.

[0050] An even better material quality can be achieved in particular by carrying out a homogenization step of the filtered melt after the first filtration of the melt according to step c) and before the degassing of the melt according to step d).

[0051] The second filtration of the melt is particularly necessary in the case of highly contaminated polymers. It is therefore advantageous if, after increasing the pressure of the melt according to step e), the second filtration of the melt is carried out immediately and directly, in particular without any further processing steps in between. However, if a second filtration of the melt is carried out, a pressure increase is necessary, in which case the risk of an increase in the bulk temperature increases. It is therefore particularly advantageous in this case to increase the pressure by the method according to the invention or by a melt pump.

[0052] A particularly advantageous pretreatment is to grind and / or heat the material prior to the melting according to step b), in particular during step a), preferably to heat and continuously mix the material whilst maintaining its massiness and flowability, optionally to degas it, soften it, dry it, increase its viscosity and / or crystallize it.

[0053] It is particularly advantageous if at least process steps b), d) and e), in particular all process steps provided, are carried out in immediate and direct succession in time and space without any further process steps in between.

[0054] It is advantageous if there is a distance between the degassing section and the pressure build-up section, i.e. the melt pump, of not more than 20 D, in particular in the range of 5 to 20 D, preferably in the range of 5 to 15 D, more preferably in the range of 8 to 11 D, D being the outer diameter of the screw of the extruder used, measured at the last degassing port of the most downstream degassing zone in the conveying direction, this distance being defined as the distance between the center of the last degassing port of the most downstream degassing zone in the conveying direction and the position of the melt pump, in particular of the most upstream active conveying means or conveying functional part of the melt pump.

[0055] In this connection, it is particularly advantageous if the screw root cross-sectional area, the screw inclination and / or the product of the screw depth, web width, flight width and flight inclination are configured according to the features of claim 6, 7 or 8 or are preferably as constant as possible in the region between the center of the last venting port of the most downstream venting zone in the conveying direction and the extruder outlet. [Brief description of the drawings]

[0056] The invention will now be described with reference to non-limiting embodiments. [Figure 1] FIG. 1 shows a known device in the prior art. [Diagram 2] FIG. 1 shows an apparatus according to the present invention. [Diagram 3] FIG. 2 shows another device according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0057] For comparison, Fig. 1 shows a known device in the prior art. This figure is a schematic diagram to explain the most important components and units of this device. Therefore, this figure does not claim final accuracy of all structural details and proportions.

[0058] Figure 1 shows a vessel 1 in the form of a conventional cutter compactor or preconditioning unit (PCU). In this case, the vessel 1 is filled from the left side via a belt conveyor with the recycled polymeric material to be processed. The polymeric material is fed into the vessel 1, crushed by mixing and crushing tools, mixed and heated until soft, but usually without melting. The agglomeration of the sticky polymer particles is maintained. In addition, the material is pre-treated, e.g. dried, pre-compacted and, depending on the material, e.g. the viscosity is increased.

[0059] Tangentially connected to the bottom of the cutter compactor or vessel 1 is extruder 2. Extruder 2 is a single screw extruder with a single screw 10. Material is discharged from vessel 1 and transferred into extruder 2 where it is received by screw 10. At the front of extruder 2 the material is subjected to an increase in pressure where it is melted and plasticized.

[0060] The melt is subsequently filtered in a first filtration unit 3. For this purpose, the melt is withdrawn from the extruder 2 at one end of the plasticization zone, clarified in the automatic and self-cleaning first filtration unit 3 and then returned again to the part of the extruder 2 which is located downstream of the filtration unit 3.

[0061] Downstream of and connected to the filtration unit 3, a homogenization unit can be provided for homogenizing the melt, which can be part of the extruder screw 10 configured to shear and mix the melt, subjecting it to concentrated shear and tensile stresses.

[0062] Further, a degassing zone 5 is arranged for degassing the melt. In this region, the extruder screw 10 has a reduced core diameter, which allows the melt to relax and the pressure to drop. The degassing zone 5 is provided with two degassing ports 11, through which the exhausted gas escapes.

[0063] Downstream of the degassing zone 5 there is a discharge metering zone 12, in which the core diameter of the screw 10 increases again and the pressure on the melt increases. This is necessary in order to prepare the melt for discharge into the subsequent second filtration unit 7. However, this pressure increase also increases the temperature of the melt, which, as mentioned above, has a negative effect on the quality of the final product. Downstream of the second filtration unit 7 the molten material reaches a discharge unit 8 and is possibly further processed, for example granulated.

[0064] In contrast, Figure 2 illustrates an example of an apparatus according to the present invention. Like Figure 1, this figure is a schematic diagram, not drawn to scale and without showing great detail.

[0065] The left hand portion of the apparatus shown in Figure 1 is nearly identical to the apparatus of Figure 1, and more precisely, is identical up to the inclusion of a degassing unit 5. However, in Figure 2, the extruder screw 10 terminates just after the degassing zone 5, where the extruder outlet 9 is provided.

[0066] Therefore, only a short residual screw 14 is shown in Figure 2, and the distance between the degassing zone 5 and the melt pump 6 (here, for example a gear pump) is short. The melt pump 6 continues to pump the melt, thereby effectively increasing the pressure in the subsequent second filtration unit 7, which is provided similarly to Figure 1. However, due to the presence of the melt pump 6, the temperature of the melt does not increase excessively, and both the temperature difference and the absolute value of the bulk temperature are kept low.

[0067] Melt pump 6 is spatially connected to extruder outlet 9 or degassing zone 5 via a short residual screw 14. Thus, the melt discharged from extruder 2 or degassing zone 5 passes via residual screw 14 into the area of ​​melt pump 6 and is received by the conveying elements of melt pump 6.

[0068] To ensure a reliable transfer of the melt from the extruder 2 to the melt pump 6, it is possible to provide several short passive transition nozzles without departing from the principles of the present invention, particularly to compensate for diameter differences between the units. Such non-functional units do not detract from the embodiment of the present invention.

[0069] The distance 13 between the last vent 11 of the venting zone 5 and the melt pump 6 is approximately 3D for the exemplary embodiment shown in Figure 2. However, no actual dimensions or proportions can be derived from Figure 2, especially for the distance 13, since the diameter of the screw 10 or the extruder 2 is shown enlarged for better understanding.

[0070] In any case, the distance 13 is measured between the center of the rearmost or most downstream vent port 11 in the conveying direction and the start of the melt pump 6, i.e., the most upstream conveying functional component of the melt pump 6. In other words, the distance 13 is the length of the remainder screw 14 plus any passive additional components (if any) between the remainder screw 14 and the melt pump 6. The outer diameter D of the screw 2 associated with the distance 13 is taken or measured at the position of the rearmost vent port 11.

[0071] The screw 10 does not change any more from the rearmost vent 11, i.e. the characteristics and shape of the screw 10 or the remaining screw 14 remain unchanged until the extruder outlet 9. In particular, the root cross-sectional area and the slope of the flight of the screw 10 remain constant. The product of the depth, web width, gear width and slope are also constant in the area after the rearmost vent 11.

[0072] A further embodiment of the present invention is shown in Figure 3. This figure is also a schematic diagram, not to scale and without showing great detail.

[0073] FIG. 3 shows an apparatus similar to that of FIG. 2, but the length of the remaining screw 14, i.e., the length of the screw 10 in the region downstream of the rearmost vent port 11, is slightly longer, and therefore the distance between the vent zone 5 and the melt pump 6 is also larger than in the apparatus of FIG. 2.

[0074] Thus, in this embodiment, the length of the remaining screw 10 in the region downstream of the rearmost vent port 11, i.e., the residual screw 14, is about 7D. The distance 13 between the center of the rearmost vent port 11 of the degassing zone 5 located most downstream in the conveying direction and the melt pump 6 is about 10D (neither is shown to exact dimensions). Here, D is the outer diameter of the screw 10 of the extruder 2, always measured at the rearmost venting port 11 of the venting zone 5 located most downstream in the conveying direction.

[0075] The inclination of the flight of the remaining screw 14 downstream of the vent 11 is constant at about 1 L / D and is therefore the same as the inclination of the flight at the location of the vent 11. The inclination of the flight of the screw 10 is therefore kept constant in the region between the center of the rearmost vent 11, which is located most downstream in the conveying direction, and the extruder outlet 9.

[0076] Therefore, the cross-sectional area or depth of the root of the screw 10 is also approximately constant in the region between the center of the rearmost degassing port 11 located at the most downstream side in the conveying direction and the extruder outlet 9.

[0077] The embodiment according to FIG. 3 is a very versatile embodiment, i.e. applicable to a wide variety of polymers, providing an advantageous combination of stability and operational safety, as well as a low temperature rise, providing a high quality end product.

[0078] The following comparative experiments were carried out for different plant configurations, more precisely for plant configuration 1 (comparative example) similar to FIG. 1 and for plant configuration 2 with melt pump similar to FIG. 2 or 3. The process parameters and the input materials were also kept constant. The same materials were used in both cases: LLD-PE foil or HD-PE foil made from post-consumer waste. Plant configuration 1 - comparative example (without melt pump)

[0079] The equipment configuration is an Intarema 1108 TVE PCU / extruder combination. [Table 1] [Table 2] Equipment configuration 2: Configuration equipped with melt pump according to the present invention

[0080] This setup was also an Intarema 1108 TVE PCU / extruder combination, however the melt pump was located at the extruder outlet downstream of the venting section, i.e. at the following distance from the last venting port (defined above): - SP_V0: Approximately 3D - SP_V1: Approx. 8D - SP_V2: Approx. 10D - SP_V3: Approx. 12D That is, the area behind or downstream of the degassing section still continues with the extruder screw or remainder screw, i.e., extends close to the melt pump. [Table 3] [Table 4] result

[0081] In each case, the bulk temperature T1 just before the first melt filter (LF) was compared to the bulk temperature T2 just before the granulator (HG) after the second melt filter. Additionally, possible material losses due to degassing were also evaluated. [Table 5] [Table 6]

[0082] It can be seen that in configuration 2 according to the invention, a smaller temperature rise (smallest at SP_V0) was recorded and also that the absolute temperature was lower (both compared to installation configuration 1 without a melt pump).

[0083] Furthermore, it was found that the shortest screw length after degassing (SP_V0) results in the lowest temperature rise. However, the conveying capacity of the screw is strongly influenced by the material fluctuations that occur during the recycling process. This is evidenced, for example, by the retention of material up to the degassing zone, which leads to material discharge at the degassing port, as well as material losses and poor degassing performance. This further leads to poor quality of the final product. Therefore, some minimum length of the residual screw was tolerated here, even if it resulted in an increase in bulk temperature. Therefore, in order to ensure the required versatility of the recycling equipment, i.e., the ability to process various polymers with different viscosities and sliding properties, it is advantageous for the discharge screw behind the degassing section to have a certain minimum length. Various experiments with these different materials have shown that the SP_V2 case proves to be the most versatile configuration, offering an advantageous combination of operational safety and the lowest temperature rise.

Claims

1. An apparatus for processing a material comprising or consisting of a polymeric material, in particular for recycling contaminated thermoplastic polymers, comprising an extruder (2) having a screw (10) for melting said material, a first filtration unit (3) for filtering the melt and a degassing zone (5) for degassing the melt, 10. An apparatus according to claim 9, characterized in that a melt pump (6) is connected to said degassing zone (5) or after or downstream of said screw (10) at the extruder outlet (9).

2. 3. The apparatus according to claim 2, characterized in that the melt pump (6) is connected in close spatial proximity and directly to the degassing zone (5) in the conveying direction without any further functional units between them or is connected downstream of the degassing zone (5) and connected in tandem with it in terms of process.

3. 3. The apparatus according to claim 1, wherein the melt pumps (6) are connected with a distance (13) of less than or equal to 20 D, in particular in the range of 5 to 20 D, preferably in the range of 5 to 15 D, preferably in the range of 8 to 11 D, D being the outer diameter of the screw (10) of the extruder (2), measured at the rearmost degassing port (11) of the most downstream degassing zone (5) in the conveying direction, the distance (13) being defined as the distance measured between the center of the rearmost degassing port (11) of the most downstream degassing zone (5) in the conveying direction and the position of the melt pump (6), in particular of the most upstream active conveying means or conveying functional component of the melt pump (6).

4. 4. The apparatus according to claim 1, characterized in that the extruder (2) does not have a metering zone increasing the pressure of the melt in the region downstream of the first filtration unit (3), in particular in the region downstream of the degassing zone (5), and / or the melt pump (6) replaces a metering zone.

5. 5. The device according to claim 1, wherein a second filtering unit is connected to the melt pump in the conveying direction, in particular in close spatial proximity and directly, without any further functional units between the melt pump and the second filtering unit.

6. 6. An apparatus according to claim 1, characterized in that the root cross-sectional area of ​​the screw (10) is expanded or contracted by at most 50%, preferably at most 20%, in particular at most 5%, in the region between the center of the last vent (11) of the venting zone (5) located most downstream in the conveying direction and the extruder outlet (9), preferably kept constant.

7. 7. Apparatus according to claim 1, characterized in that the inclination of the screw (10) is increased or decreased by at most 3 L / D, preferably at most 1.5 L / D, in particular at most 0.5 L / D, preferably kept constant, in the region between the center of the last vent (11) of the venting zone (5) located most downstream in the conveying direction and the extruder outlet (9).

8. The product of the depth, web width, gear width and flight inclination of the screw (10), i.e. P=t*b*B*S (B=S-g*b), t is the depth, b is the web width, B is the thread width, S is the (thread) slope, g is the number of gears of the screw. The product is 8. Apparatus according to claim 1 , characterized in that in the region between the centre of the last vent (11) of the venting zone (5) situated furthest downstream in the conveying direction and the extruder outlet (9), the temperature varies by at most 30%, preferably at most 15%, in particular 5%, preferably at most 3%, in particular does not vary at all.

9. The device according to any one of claims 1 to 8, characterized in that it is provided with a discharge unit (8) for discharge, which is connected downstream of the second filtration unit (7) in the conveying direction, and / or at least one post-treatment unit (8) for processing the melt, for example a granulation unit.

10. 10. Apparatus according to any one of claims 1 to 9, characterized in that it comprises a container (1) for supplying the material to be treated, in particular for crushing and / or heating, to which the extruder (2) is connected, preferably comprising a mixing and / or crushing device in the container (1) for mixing and optionally crushing the material while continuously maintaining its massiness and flowability, and optionally heating and softening the material, the container (1) being preferably a cutter compactor.

11. Apparatus according to any one of the preceding claims, characterized in that the extruder (2) is a single-screw extruder equipped with a single screw (10).

12. 12. The apparatus according to claim 1, characterized in that as the melt pump (6) a gear pump is provided.

13. 13. The apparatus according to claim 1, characterized in that a homogenization unit for homogenizing the melt is provided behind the first filtration unit (3) in the conveying direction and before the degassing zone (5), in particular a screw or part of the screw (10) or of the extruder (2), in which the screw or part of the screw (10) or of the extruder (2) is configured in such a way that the melt is sheared and mixed therein or is subjected to intensive shear and tensile stresses, resulting in a strong acceleration of the melt.

14. 14. The device according to claim 1, characterized in that at least the units (2), (5) and (6), in particular all units (2) to (8) present, are arranged axially one after the other or on a common longitudinal axis.

15. 15. Apparatus according to claim 1, characterized in that the screw (10) also continues in the region between the center of the last degassing port (11) of the degassing zone (5) which is furthest downstream in the conveying direction and the extruder outlet (9) or is provided in said region with a residual screw (14) or conveying means, the melt pump (6) being connected with a spacing (13) ranging from 5 to 20D, preferably from 5 to 15D, preferably from 8 to 11D, D being the outer diameter of the screw (10) of the extruder (2), measured at the last degassing port (11) of the degassing zone (5) which is furthest downstream in the conveying direction, the spacing (13) being defined as the distance measured between the center of the last degassing port (11) of the degassing zone (5) which is furthest downstream in the conveying direction and the position of the active conveying means or conveying functional component which is furthest upstream of the melt pump (6), in particular the melt pump (6).

16. 16. Apparatus according to any one of claims 1 to 15, characterized in that the ratio between the length of the portion of the screw (10) between the first filtration unit (3) and the frontmost degassing port which is located most upstream of the degassing zone (5) and the length of the portion of the screw (10) between the rearmost degassing port (11) which is located most downstream of the degassing zone (5) and the extruder outlet (9) or the length of the remaining screw (14) is in the range of 0.1 to 3, in particular in the range of 0.3 to 2.

17. 17. Apparatus according to any one of the preceding claims, characterized in that the length of the section of the screw (10) between the first filtration unit (3) and the most upstream front deaeration port of the deaeration zone (5) is in the range of 1 to 15 D, in particular in the range of 3 to 10 D.

18. 18. Apparatus according to any one of the preceding claims, characterized in that the length of the part of the screw (10) between the rearmost venting port (11) most downstream of the venting zone (5) and the extruder outlet (9), or the length of the remaining screw (14), is in the range of 3 to 12 D, in particular in the range of 4 to 10 D, preferably in the range of 5 to 8 D.

19. A method for treating materials comprising or consisting of polymeric materials, in particular for recycling contaminated thermoplastic polymers, preferably using a device according to any one of claims 1 to 18, comprising the steps of: a) providing said material to be treated, in particular in a vessel; b) at least partially, in particular completely melting said material, in particular in an extruder; c) performing a first filtration of the melt to remove unmelted components and / or impurities; d) degassing the filtered melt; e) increasing the pressure of the melt with a melt pump; f) discharging and / or post-treating the melt, in the order listed:

5. The method of claim 1, wherein the step of increasing the pressure of the melt is performed after the step of degassing the melt, and the steps are sequential.

20. 20. Method according to claim 19, characterized in that after the first filtration of the melt according to step c) and before the degassing of the melt according to step d), a step of homogenizing the filtered melt is performed.

21. 21. The method according to any one of claims 19 to 20, characterized in that after increasing the pressure of the melt according to step e), a second filtration of the melt is carried out immediately and directly, in particular without any further processing steps in between.

22. 22. The method according to any one of claims 19 to 21, characterized in that prior to melting according to step b), in particular during the process of step a), the material is ground and / or heated, preferably heated and continuously mixed while maintaining its massiness and flowability, and optionally degassed, softened, dried, its viscosity increased and / or crystallized.

23. 23. The method according to any one of claims 19 to 22, characterized in that at least process steps b), d) and e), in particular all process steps provided, are carried out in immediate and direct succession in time and space without any further process steps in between.

24. 24. The method according to claim 19, characterized in that the melt pump (6) is connected with a distance (13) of less than or equal to 20 D, in particular in the range of 5 to 15 D, preferably in the range of 5 to 20 D, preferably in the range of 8 to 11 D, D being the outer diameter of the screw (10) of the extruder (2), measured at the rearmost venting opening (11) of the most downstream venting zone (5) in the conveying direction, the distance (13) being defined as the distance between the center of the rearmost venting opening (11) of the most downstream venting zone (5) in the conveying direction and the position of the melt pump (6), in particular of the most upstream active conveying means or conveying functional component of the melt pump (6).

25. 25. The method according to claim 19, characterized in that the root cross-sectional area of ​​the screw (10), the inclination of the screw (10) and / or the product of the depth, web width, gear width and flight inclination of the screw (10) are configured according to the features of claims 6, 7 or 8 in the region between the center of the rearmost degassing port (11) of the degassing zone (5) located most downstream in the conveying direction and the extruder outlet (9).

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