Device and method for processing materials

Abstract

The invention relates to a device and a method for processing materials that contain or consist of polymer materials, in particular for processing, during recycling, soiled thermoplastic polymers. The device comprises an extruder (2) having a screw (10) for melting the materials, also having a first filtering unit (3) for filtering the melt and a degassing zone (5) for degassing the melt. According to the invention, a melt pump (6) is connected, at the extruder outlet (9), to the degassing zone (5) or after or downstream of the screw (10).

Description

[0001] Device and method for processing materials

[0002] The invention relates to a device and a method for processing materials containing or consisting of polymeric materials or for recycling processing of contaminated thermoplastic polymers according to the preamble of claims 1 and 19, respectively.

[0003] When processing secondary raw materials, a well-known and proven sequence of steps involves extrusion, filtration and granulation of the thermoplastic materials to be processed.

[0004] A known advantageous concept involves first heating or softening the thermoplastic polymers in a cutter-compactor or preconditioning unit (PCU), then transferring them to an extruder and melting them there. The melt is then filtered and degassed, possibly filtered again, and then, for example, pellets are produced. The first melt filtration is arranged before or upstream of the extruder degassing unit. This allows for the production of end products of high quality and a high proportion of regranulates.

[0005] A known device or process, for example, provides the following: In a cutter-compactor or preconditioning unit (PCU), the polymer material to be treated is shredded, mixed, heated, dried, pre-compacted, and optionally buffered. An extruder directly connected tangentially to the cutter-compactor is continuously filled with the heated and softened, pre-compacted material. The material is plasticized in the extruder screw. The melt is discharged from the extruder at the end of the plasticizing zone, cleaned in an automatic, self-cleaning filter, and returned to the section of the extruder located downstream of the filter. In this section of the extruder, i.e., after the first melt filter, the final homogenization of the melt takes place. In the subsequent degassing zone, the filtered and homogenized melt is degassed.The melt is then fed via the extruder's discharge zone to the respective tool, e.g., a pelletizer. Optionally, a second melt filtration system can be arranged downstream of the discharge zone and upstream of the tool. Such a device is shown, for example, in Fig. 1 and will be described in more detail below.

[0006] Through this type of filtration, homogenization, and degassing, even difficult-to-process materials such as heavily printed films and / or moist materials can be processed. However, it has been shown that even with a single filtration stage, but especially when two filtration stages are planned or used, a pressure increase in the melt occurs, and the melt temperature can be very high, especially at the end of the extrusion system, especially upstream of the die.

[0007] Especially in the recycling of polymers, double filtration is often used. This can be particularly necessary when recycling highly contaminated polymers, for example, to remove contaminants and gels from the material stream being processed, which may require different separation methods. This quality-enhancing purification is always associated with an increase in pressure. This process, especially when pressure is generated solely with the melt, generates high melt temperatures in the case of an extruder.

[0008] However, high melt or melt temperatures negatively impact the quality of the polymers. High melt or melt temperatures result in, among other things, increased consumption of stabilizers, shortening of molecular chains, undesirable gel formation, or even burning of particles and polymer in the melt. High temperatures also promote the decomposition of the polymer or its constituents. This reverses or counteracts some of the efforts of upstream processes to improve material quality.

[0009] It is also generally known from the prior art to provide gear pumps that convey the melt in the area of ​​the distal end of an extruder.

[0010] The object of the present invention is therefore to provide a device and a method with which the resulting material quality can be easily improved.

[0011] The invention solves this problem in a device for processing materials containing or consisting of polymeric materials, in particular for recycling and processing contaminated thermoplastic polymers, comprising at least one extruder with at least one screw for melting the materials, with at least one first filtration unit for filtering the melt and at least one degassing zone for degassing the melt, by the characterizing features of claim 1.

[0012] According to the invention, at least one melt pump or a device for pumping the polymer melt is connected or arranged or provided at the extruder outlet to the devolatilization zone or after or downstream of the screw.

[0013] This means that the melt pump is located behind the extruder outlet, or downstream of the extruder or screw, and thus necessarily also behind or downstream of the vent zone. The melt pump is therefore connected to the vent zone in the direction of melt flow. The melt pump can be located directly behind the vent zone or indirectly behind it, i.e., at a certain distance behind the vent zone.

[0014] By arranging the melt pump in this way, a pressure increase is achieved while simultaneously reducing the melt temperature, which reduces the above-mentioned disadvantages and results in improved material quality.

[0015] The lower melt temperature in this range has a correspondingly positive effect on melt quality. Another advantage is the reduced tendency to develop undesirable odors or discoloration, which can be more pronounced in higher-temperature systems, especially in applications involving cellulose impurities such as paper or wood. This is particularly advantageous when recycling typical supermarket films made of, for example, LDPE / LLDPE, some of which have high residual moisture content, especially when these films are contaminated with paper, e.g., labels, wood particles from pallets, etc., or with foreign polymers, dust, etc. Here, even a temperature increase of just a few degrees can have a particularly disruptive and detrimental effect.

[0016] This is particularly advantageous for difficult-to-treat polymer materials and when the application requires polymer-friendly processing and strong filtration performance.

[0017] The downstream melt pump also allows for particularly efficient and powerful degassing, as it decouples pressure and temperature buildup. As a result, the highest temperature in the entire system occurs before the degassing stage, rather than at the end of the screw or before the second filtration unit. This counteracts the subsequent gasification of melt components and positively impacts the quality of the melt and regranulate. The pressure buildup by the melt pump advantageously relieves the extruder of the pressure buildup task, allowing the pressure buildup to be significantly shorter, making the device more compact and space-saving.

[0018] A further advantage of the pressure build-up by the melt pump is that the extruder speed can be optimally adjusted to the polymer - without any loss of throughput.

[0019] Furthermore, a lower mass temperature also significantly reduces energy consumption.

[0020] Furthermore, only cleaned and degassed melt flows through the melt pump, which is an advantage for the service life of this component.

[0021] In this context, it is advantageous if the melt pump is spatially and directly connected to the degassing zone in the conveying direction, without any further functional unit in between, or is connected downstream of the degassing zone and coupled in series in terms of process.

[0022] A “functional unit” is understood to be a unit that acts on the melt, e.g. mechanically, or carries out a processing step.

[0023] The term "immediately and directly" is to be understood in this case to mean that the melt pump is located directly next to or behind the degassing zone, and that no actual processing units, such as filters, homogenizers, or the like, are provided between the melt pump and the degassing zone. Passive connecting or transition pieces or pipes do not interfere and may be present.

[0024] The direct and immediate arrangement of the melt pump after degassing, instead of a pressure boosting zone in the extruder or a discharge metering zone, results in an advantageous increase in the required pressure, for example for a possible additional filter stage.

[0025] It can also be advantageous if the extruder downstream of the first filtration unit, particularly downstream of the devolatilization zone, is free of a metering zone that increases the melt pressure, and / or if the melt pump replaces a metering zone. A screw extruder is relatively inefficient when it is intended to increase pressure or pump melt. For this reason, too, it is advantageous to omit the last pressure-increasing stage (metering zone) of an extruder after devolatilization, and particularly before a second filtration, and replace it with a melt pump. The melt pump is therefore coupled directly and immediately downstream of or downstream of the devolatilization unit or devolatilization zone of the extrusion screw. This ensures that the quality improvement achieved by filtration is not offset or negated by excessively high melt temperatures.

[0026] Alternatively, it is also advantageous if the melt pump is not located directly behind the degassing zone, but if there is a certain distance between the degassing and the melt pump.

[0027] In this context, it is advantageous if the screw continues continuously in the area between the center of the rearmost vent of the vent zone, located furthest downstream in the conveying direction, and the extruder outlet, i.e., if there is a residual screw or conveying elements between the vent and the melt pump. Therefore, a continuous screw is advantageously provided from the inlet to the extruder outlet, i.e., on both sides of the vent.

[0028] In this context, it is further advantageous if the melt pump is connected at a distance from the degassing unit of maximum <= 20 D. A certain minimum distance is particularly advantageous, i.e., the distance is provided to be 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.

[0029] D refers to the outer diameter of the screw of the extruder, measured at the rearmost vent opening of the vent zone located furthest downstream in the conveying direction, wherein at least one vent opening is formed in the vent zone.

[0030] The distance between the vent opening and the melt pump mentioned here is defined as the distance measured between the center of the rearmost vent opening of the vent zone, which is located furthest downstream in the conveying direction, and the melt pump. Particular attention is paid to the position of the most upstream active conveying element or the most upstream conveying active parts of the melt pump, i.e. the beginning or the inlet-side passages of the melt pump, where the melt enters the pump or is captured by the conveying elements or the pumping action. The distance is understood as the "melt flow distance", i.e. measured along or in the direction of the path that the melt travels or takes in the device, or as the distance between the units along the conveying or flow direction of the melt.

[0031] A particularly advantageous device can be defined as follows: Device for processing materials containing or consisting of polymeric materials, in particular for the recycling processing of contaminated thermoplastic polymers, comprising an extruder (2) with a screw (10) for melting the materials, with a first filtration unit (3) for filtering the melt and a devolatilization zone (5) for devolatilizing the melt, wherein a melt pump (6) is connected to the extruder outlet (9) at or after the devolatilization zone (5) after or downstream of the screw (10), wherein the screw (10) also continues in the area between the middle of the rearmost devolatilization opening (11) of the devolatilization zone (5) located furthest downstream in the conveying direction and the extruder outlet (9) or a residual screw (14) orConveying elements are provided, and wherein the melt pump (6) is connected at a distance (13) of 5 to 20 D, preferably in the range from 5 to 15 D, preferably in the range from 8 to 11 D, wherein D is the outer diameter of the screw (10) of the extruder (2) measured at the rearmost vent (11) of the vent zone (5) located furthest downstream in the conveying direction, and wherein the distance (13) is defined as the distance measured between the center of the rearmost vent (11) of the vent zone (5) located furthest downstream in the conveying direction and the melt pump (6), in particular the position of the furthest upstream active conveying element or the furthest upstream conveying active parts of the melt pump (6).

[0032] In this context, experiments have shown that the shortest screw after degassing results in the smallest temperature increase. However, the screw's conveying capacity is significantly influenced by the material fluctuations that occur during recycling. This can manifest itself, for example, in a backflow into the degassing area and can even lead to material discharge at the degassing opening. In addition to the material loss, this also results in a loss of degassing performance, which in turn leads to reduced quality. Against this backdrop, it is advantageous to provide a certain minimum length for the remaining screw, even if this leads to a certain increase in the melt temperature.

[0033] Recycling plants are designed to be very universal in terms of their requirements and must be able to process different polymers with different viscosities and sliding properties. To ensure this universality, a minimum length of the discharge screw is also advantageous. Various tests with different materials have shown that this allows for a universal design that combines operational reliability with the lowest possible temperature rise.

[0034] A device with the aforementioned features, especially with the specified minimum clearances, is thus both flexible in its application and highly process-stable. Thanks to its low melt temperature, it achieves particularly gentle treatment of the polymer melt. This increases the quality of both the melt and the regranulate.

[0035] An advantageous embodiment provides in this context that the ratio of the length of a first upstream section of the screw from the first filtering unit to the center of the most upstream front vent of the vent zone to the length of a second upstream section of the screw from the center of the most downstream rear vent of the vent zone to the end of the screw or to the extruder outlet, i.e. to the length of the remaining screw, is in the range from 0.1 to 3, in particular in the range from 0.3 to 2.

[0036] It is advantageous if the length of the first upstream section of the screw between the first filtration unit and the most upstream front degassing opening of the degassing zone is in the range of 1 to 15 D, in particular in the range of 3 to 10 D.

[0037] Furthermore, it is advantageous if the length of the second upstream section of the screw between the furthest downstream rearmost vent of the vent zone and the extruder outlet, or the length of the remaining screw, 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.

[0038] According to the advantageous embodiments mentioned above, the melt pump does not necessarily have to be spatially connected directly and immediately to the venting zone in the conveying direction, without any further functional unit in between, but the aforementioned distance can be provided. Advantageously, the extruder screw or the residual screw also continues in this area after the venting zone. In this context, it is advantageous if the inner core cross-section of the screw or residual screw - specifically in the area between the center of the rearmost venting opening of the venting zone, located furthest downstream in the conveying direction, and the extruder outlet - i.e. up to the end of the extruder screw - is increased or reduced by <= 50%, preferably by <= 20%, in particular by <= 5%, and preferably remains constant.The smaller the change in the core cross-section, e.g., the compression, the less shear is introduced into the material. If the core cross-section increases too much, this results in compression of the material, which would lead to an undesirable temperature increase. For certain materials, a small amount of compression may be beneficial, e.g., when there is a large amount of substance to be degassed.

[0039] According to an advantageous embodiment, it is further provided that the pitch of the screw or residual screw - in the area between the middle of the rearmost vent of the vent zone furthest downstream in the conveying direction and the extruder outlet - increases or decreases by <= 3 L / D, preferably by 1.5 <= L / D, in particular by <= 0.5 L / D, and preferably remains constant. L / D is understood to be the usual ratio of the (active) length of the screw to the diameter of the screw. The smaller the change in the pitch, the less shear is introduced into the material. If the melt has a very high gas ballast, a small compression can "squeeze out" the material, i.e. force gas back into the vent.

[0040] Furthermore, it is advantageous if the screw or the remaining screw is designed in such a way that the product of depth, web width, flight width and flight pitch of the screw, namely

[0041] P = t * b * B * S, where B = S - g*b with t ... depth b ... web width

[0042] B ... aisle width

[0043] S ... (flight) pitch g ... number of flights of the screw in the area between the center of the rearmost vent of the vent zone, located furthest downstream in the conveying direction, and the extruder outlet, changes by <= 30%, preferably by <= 15%, in particular by <= 5%, preferably by <= 3%, in particular not at all. This can reduce the introduction of shear into the material. A change in compression that is advantageous in certain cases can be achieved not only by changing the core cross-section; multiple flights, a change in pitch or an increase in the flight width, for example, also lead to a certain increase in compression.

[0044] A device with the latter features not only offers the aforementioned advantages, in some cases even to a greater extent, but is also very flexible in its application, while at the same time being very process-stable and achieving particularly gentle treatment of the polymer melt. This improves the quality of the melt and the regranulate.

[0045] According to a further advantageous embodiment, a second filtration unit is connected to the melt pump, in particular spatially immediately and directly, without any further interposed functional unit, in the conveying direction or downstream of the melt pump. Especially when recycling more heavily contaminated polymers, double filtration 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 an increase in pressure, and if pressure is generated only with melt, high melt temperatures are generated in the case of an extruder. The inventive arrangement of the melt pump is therefore particularly advantageous when a second filtration unit is provided. The melt pump thus takes over the necessary pressure build-up for the second filtration unit.The extruder is relieved of this task and can therefore be designed for a shorter duration. This significantly reduces residence time, melt temperature, and energy consumption.

[0046] A practically advantageous device is obtained if a discharge unit for discharge and / or at least one subsequent processing unit for processing the melt, for example a granulation unit, is provided, in particular downstream of a second filtering unit in the conveying direction.

[0047] It is also advantageous for material quality if a container is provided for storing, in particular for comminuting and / or heating, the materials to be processed, to which the extruder is connected. It is particularly advantageous if the container contains mixing and / or comminuting tools for mixing and, if necessary, comminuting the materials while permanently maintaining their lumpiness and flowability, and, if necessary, heating and softening the materials. A particularly advantageous embodiment provides for the container to be a conventional cutter-compactor or a PCU (preconditioning unit).

[0048] A particularly advantageous device from a structural point of view is characterized in that the extruder is a single-screw extruder with a single screw.

[0049] It is also advantageous if a gear pump is used as the melt pump.

[0050] For better homogenization of the melt and to increase the quality, it is advantageous if, in particular in the conveying direction after the first filtration unit and before the degassing zone, a homogenization unit is provided for homogenizing the melt, in particular a screw or a section of the screw or of the extruder, which is designed such that the melt is sheared and mixed therein or is subjected to intensive shear stress and tensile stress and is strongly accelerated.

[0051] A device which is particularly advantageous in terms of design provides that at least the units of the extruder, the degassing zone and the melt pump, in particular all units provided in the device, if present, are arranged essentially linearly or axially one behind the other or lie on a common longitudinal axis.

[0052] However, the invention also allows for a cascaded system, in which a first extruder melts the polymer material and the melt is also filtered there. The material is then transferred to a second extruder and degassed there. In this arrangement, the melt pump is located directly adjacent to the degassing zone of the second extruder.

[0053] The invention further achieves the object stated at the outset with a method for processing materials containing or consisting of polymeric materials, in particular for the recycling processing of contaminated thermoplastic polymers, which comprises the following processing steps in the specified order: a) introduction of the materials to be processed, in particular in a container, b) at least partial, in particular complete, melting of the materials, in particular in an extruder, c) first filtration of the melt to remove unmelted components and / or impurities, d) degassing of the filtered melt, e) increasing the pressure of the melt by means of a melt pump, f) discharge and / or subsequent processing of the melt.

[0054] According to the invention, the increase in the pressure of the melt takes place after the degassing of the melt or after the degassing of the melt and is coupled in series in terms of the process.

[0055] Advantageously, a device with the features described above is used for this purpose.

[0056] As previously described, the process according to the invention achieves an increase in the pressure of the melt while simultaneously reducing the melt temperature, thereby reducing the above-mentioned disadvantages and resulting in improved material quality.

[0057] In this way, the advantages mentioned above are achieved in the process.

[0058] A further improved material quality can be achieved in particular by homogenizing 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).

[0059] A second filtration of the melt is necessary, especially for heavily contaminated polymers. Accordingly, it is advantageous if, after increasing the melt pressure according to step e), a second filtration of the melt is carried out, particularly immediately and directly, without any further intermediate processing step. However, if a second filtration of the melt is carried out, an increase in pressure is necessary, and this is precisely when the risk of increasing the melt temperature is increased. In this case, it is therefore particularly advantageous to increase the pressure using the method according to the invention or using a melt pump.

[0060] A particularly advantageous preparation provides that the materials are comminuted and / or heated prior to melting according to step b), in particular during step a), wherein it is preferably provided that the materials are heated and continuously mixed while maintaining their lumpiness and flowability, and optionally degassed, softened, dried, increased in viscosity, and / or crystallized. It is particularly advantageous if at least processing steps b), d), and e), in particular all the intended processing steps, follow one another immediately and directly in time and place, without any further intervening processing step.

[0061] It is advantageous if there is a distance of <= 20 D, in particular in the range from 5 to 20 D, preferably in the range from 5 to 15 D, preferably in the range from 8 to 11 D, between devolatilization and pressure increase, i.e. melt pump, where D is the outer diameter of the screw of the extruder used, measured at a rearmost devolatilization opening of a devolatilization zone located furthest downstream in the conveying direction, and where the distance is defined as the distance measured between the center of the rearmost devolatilization opening of the devolatilization zone located furthest downstream in the conveying direction and the melt pump, in particular the position of the furthest upstream active conveying element or the furthest upstream conveying active parts of the melt pump.

[0062] In this context, it is particularly advantageous if the inner core cross-section of the screw, the pitch of the screw, and / or the product of depth, flight width, flight width and flight pitch of the screw in the area between the center of the rearmost vent opening of the vent zone located furthest downstream in the conveying direction and the extruder outlet is designed according to the features of claims 6, 7 and 8, respectively, or are preferably as constant as possible.

[0063] The invention will now be described with reference to non-limiting embodiments.

[0064] Fig. 1 shows a device known from the prior art.

[0065] Fig. 2 shows a device according to the invention.

[0066] Fig. 3 shows another device according to the invention.

[0067] Fig. 1 shows a device known from the prior art for comparison. This is a schematic representation to illustrate the key components and units of this device. Accordingly, this representation makes no claim to final accuracy of all design details and proportions. Fig. 1 shows a container 1 in the form of a classic cutter-compactor or preconditioning unit (PCU). In this case, the container 1 is filled from the left via a conveyor belt with the recycled polymer material to be processed. The polymer material is placed in the container 1, crushed using mixing and crushing tools, mixed, and heated until softened, although usually not melted. The lumpiness of the sticky polymer particles is retained.In addition, the material undergoes pre-treatment and is, for example, dried, pre-compacted and, depending on the material, the viscosity is increased.

[0068] An extruder 2 is tangentially connected to the lowermost section of the cutter-compactor or container 1. The extruder 2 is a single-screw extruder with a single screw 10. The material is discharged from the container 1 and transferred to the extruder 2, where it is captured by the screw 10. In the front section of the extruder 2, the material is melted and plasticized under increased pressure.

[0069] The melt is then filtered in a first filtration unit 3. For this purpose, the melt is discharged from the extruder 2 at the end of the plasticizing zone, cleaned in the automatic and self-cleaning first filtration unit 3, and then returned to the section of the extruder 2 located downstream of the filtration unit 3.

[0070] Downstream of and adjacent to the filtration unit 3, a homogenization unit for homogenizing the melt can be provided. This can be a section of the extruder screw 10 designed to shear and mix the melt and subject it to intense shear and tensile stress.

[0071] Adjacent to this is the degassing zone 5 for degassing the melt. The extruder screw 10 has a reduced core diameter in this area, which relaxes the melt and reduces the pressure. Two degassing openings 11 are located in the degassing zone 5, through which the escaping gas can escape.

[0072] Downstream of the degassing zone 5 is the discharge metering zone 12, where the core diameter of the screw 10 increases again and the pressure on the melt is increased. This is necessary to prepare the melt for discharge into the subsequent second filtration unit 7. However, this increase in pressure also increases the temperature of the melt, which has the previously mentioned adverse effects on the quality of the final products. Downstream of the second filtration unit 7, the molten material then enters the discharge unit 8 and can be further processed, for example, by granulation.

[0073] In comparison, Fig. 2 shows a sketch of an exemplary device according to the invention. Like Fig. 1, this is a schematic overview representation, not proportional or to scale, and not detailed down to the last detail.

[0074] The left part of the device according to Fig. 1 is essentially identical to the device according to Fig. 1 , up to and including the degassing unit 5. In Fig. 2, however, the extruder screw 10 ends shortly after the degassing zone 5 and the extruder outlet 9 is located there.

[0075] Accordingly, in Fig. 2, there is only a short residual screw 14, and the distance from the degassing zone 5 to the melt pump 6, here, for example, a gear pump, is short. The melt pump 6 continues to pump the melt, thus efficiently increasing the pressure for the subsequent second filtration unit 7, which is provided analogously to Fig. 1. However, by providing the melt pump 6, the temperature of the melt is not excessively increased, and both the temperature differences and the absolute melt temperatures remain lower.

[0076] The melt pump 6 is spatially connected to the extruder outlet 9 or to the degassing zone 5 via a short residual screw 14. The melt exiting the extruder 2 or the degassing zone 5 accordingly enters the sphere of the melt pump 6 via the residual screw 14 and is captured by the conveying components of the melt pump 6.

[0077] To ensure a smooth transition of the melt from extruder 2 to melt pump 6, it is possible, without deviating from the inventive concept, to provide short passive transition nozzles, particularly to compensate for differences in the diameters of the units. Such non-functional units do not impair the inventive design.

[0078] The distance 13 between the rearmost vent opening 11 of the vent zone 5 and the melt pump 6 is approximately 3 D in the exemplary embodiment according to Fig. 2. In view of the fact that the diameter of the screw 10 or of the extruder 2 is shown in an enlarged manner for clarity, no real dimensions and ratios can be derived from Fig. 2, in particular not with regard to the distance 13. The distance 13 is in any case measured between the center of the rearmost or furthest downstream vent opening 11 as seen in the conveying direction and the beginning of the melt pump 6, i.e. the furthest upstream, conveying-active parts of the melt pump 6. The distance 13 therefore comprises the length of the remaining screw 14 plus, if present, any passive adapter pieces, e.g. between the remaining screw 14 and the melt pump 6.The outer diameter D of the screw 2 relevant for the distance 13 is taken or measured at the position of the rearmost degassing opening 1 1.

[0079] The screw 10 no longer changes from the rearmost vent 11, i.e., the characteristics and geometries of the screw 10 or the remaining screw 14 remain unchanged up to the extruder outlet 9. In particular, the inner core cross-section and the pitch of the screw 10 remain constant. The product of depth, flight width, flight width, and pitch also remains constant in the area from the rearmost vent 11.

[0080] Fig. 3 shows a further embodiment of the invention. This is also a schematic overview, not proportional or to scale, and not detailed in every detail.

[0081] Fig. 3 shows a device analogous to Fig. 2, but the length of the remaining screw 14, i.e. the length of the screw 10 in the area downstream of the rearmost vent opening 11, is somewhat longer, and thus the distance between the vent zone 5 and the melt pump 6 is also greater than in the device according to Fig. 2.

[0082] Thus, in this embodiment, the length of the remaining screw 10 in the region downstream of the rearmost vent opening 11, i.e. the remaining screw 14, is approximately 7 D. The distance 13 between the center of the rearmost vent opening 11 of the vent zone 5, which is located furthest downstream in the conveying direction, and the melt pump 6 is approximately 10 D (both not shown to scale).

[0083] D is always the outer diameter of the screw 10 of the extruder 2 measured at the rearmost vent opening 11 of the vent zone 5 located furthest downstream in the conveying direction.

[0084] The pitch of the remaining screw 14 downstream of the vent opening 11 is constant at approximately 1 L / D and is therefore the same as at the location of the vent opening 11. The pitch of the screw 10 thus remains constant in the area between the center of the rearmost vent opening 11 located furthest downstream in the conveying direction and the extruder outlet 9.

[0085] The inner core cross-section or the depth of the screw 10 is also essentially constant in the area between the center of the rearmost vent opening 11 located furthest downstream in the conveying direction and the extruder outlet 9.

[0086] The embodiment according to Fig. 3 is a very universal design, i.e. it can be used for different polymers, which advantageously combines stability and operational reliability with only a small temperature increase and delivers high quality of the end products.

[0087] Comparative tests:

[0088] The following comparative tests were conducted on different plant configurations: plant configuration 1 analogous to Fig. 1 (comparison) and plant configuration 2 with a melt pump analogous to Figs. 2 and 3, respectively. The process parameters and the input materials were kept constant. The materials used in each case were LLDPE films and HDPE films from post-consumer waste.

[0089] Plant configuration 1 - comparison (without melt pump):

[0090] This is a PCU / extruder combination “Intarema 1108 TVE”:

[0091] Plant configurations 2 - according to the invention with melt pump:

[0092] This is the same PCU / extruder combination "Intarema 1108 TVE." However, a melt pump was placed downstream of the vent at the extruder exit, at the following distances from the rearmost vent opening (as defined previously):

[0093] - SP_V0: approx. 3 D

[0094] - SP_V1 : approx. 8 D

[0095] - SP_V2: approx. 10 D

[0096] - SP_V3: approx. 12 D

[0097] In the area behind or downstream of the degassing, the extruder screw or residual screw continued up to close to the melt pump. Result:

[0098] In each case, the melt temperature T1 directly before the first melt filter (LF) was compared with the melt temperature T2 directly before granulation (HG) after the second melt filter. Furthermore, any material loss due to degassing was assessed.

[0099] It can be seen that in the configurations 2 according to the invention, lower temperature increases were recorded (lowest at SP_V0) and furthermore it can be seen that the absolute temperatures were also lower - in each case compared to the plant configuration 1 without melt pump.

[0100] It has also been shown that while the shortest screw after degassing (SP_V0) results in the smallest temperature increase, the screw's conveying capacity is significantly influenced by the material fluctuations that occur during recycling. This is evident, for example, in a material backlog all the way into the degassing area, which leads to material discharge at the degassing opening and, in addition to material loss, also to a loss of degassing performance. This subsequently leads to reduced quality of the final products.

[0101] Therefore, a certain minimum length of the remaining screw was accepted, even if this leads to an increase in the melt temperature.

[0102] In order to ensure the required universality of recycling plants, i.e. the ability to process different polymers with different viscosities and sliding properties, a certain minimum length of the discharge screw behind the degassing is advantageous.

[0103] From the various tests with different materials, the SP_V2 version has proven to be the most universal design, which advantageously combines operational reliability and the lowest temperature rise.

Claims

Patent claims 1. Device for processing materials containing or consisting of polymeric materials, in particular for recycling and processing contaminated thermoplastic polymers, comprising an extruder (2) with a screw (10) for melting the materials, with a first filtration unit (3) for filtering the melt and a degassing zone (5) for degassing the melt, characterized in that a melt pump (6) is connected at the extruder outlet (9) to the degassing zone (5) or after or downstream of the screw (10).

2. Device according to claim 2, characterized in that the melt pump (6) is spatially connected directly and immediately, without any further intervening functional unit, to the degassing zone (5) in the conveying direction or is connected downstream of the degassing zone (5) and is coupled in sequence in a process.

3. Device according to one of claims 1 to 2, characterized in that the melt pump (6) is connected at a distance (13) of <= 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, wherein D is the outer diameter of the screw (10) of the extruder (2) measured at the rearmost degassing opening (11 ) of the degassing zone (5) located furthest downstream in the conveying direction, and wherein the distance (13) is defined as the distance measured between the center of the rearmost degassing opening (11 ) of the degassing zone (5) located furthest downstream in the conveying direction and the melt pump (6), in particular the position of the most upstream active conveying element or the most upstream conveying active parts of the melt pump (6).

4. Device according to one of claims 1 to 3, characterized in that the extruder (2) is free of a metering zone which increases the pressure of the melt in the area downstream of the first filtration unit (3), in particular in the area downstream of the degassing zone (5), and / or that the melt pump (6) replaces a metering zone.

5. Device according to one of claims 1 to 4, characterized in that the melt pump (6) is connected, in particular spatially directly and immediately, without further an intermediate functional unit, in the direction of conveyance a second filter unit (7) is connected.

6. Device according to one of claims 1 to 5, characterized in that the inner core cross-section of the screw (10), in the area between the center of the rearmost degassing opening (1 1 ) of the degassing zone (5) located furthest downstream in the conveying direction and the extruder outlet (9), is increased or decreased by <= 50%, preferably by <= 20%, in particular by <= 5%, preferably remains constant.

7. Device according to one of claims 1 to 6, characterized in that the pitch of the screw (10), in the area between the center of the rearmost degassing opening (11) of the degassing zone (5) located furthest downstream in the conveying direction and the extruder outlet (9), increases or decreases by <=3 L / D, preferably by 1.5 <= L / D, in particular by <= 0.5 L / D, preferably remains constant.

8. Device according to one of claims 1 to 7, characterized in that the product of depth, web width, thread width and thread pitch of the screw (10) is namely P = t * b * B * S, where B = S - g*b with t ... depth b ... web width B ... aisle width S ... (pitch)g ... number of flights of the screw in the area between the center of the rearmost degassing opening (11) of the degassing zone (5) located furthest downstream in the conveying direction and the extruder outlet (9), changes by <= 30%, preferably by <= 15%, in particular by <= 5%, preferably by <= 3%, in particular not at all.

9. Device according to one of claims 1 to 8, characterized in that a discharge unit (8) is provided, in particular a second filtration unit (7) downstream in the conveying direction, for discharge and / or at least a subsequent processing unit (8) for processing the melt, for example a granulation unit.

10. Device according to one of claims 1 to 9, characterized in that a container (1 ) is provided for feeding, in particular for comminution and / or heating, the materials to be processed, to which the extruder (2) is connected, and that preferably it is provided that mixing and / or comminution tools are provided in the container (1 ) for mixing and optionally comminution of the materials while permanently maintaining their granularity and flowability, and optionally heating and softening the materials, wherein the container (1 ) is preferably a cutting compactor.

11. Device according to one of claims 1 to 10, characterized in that the extruder (2) is a single-screw extruder with a single screw (10).

12. Device according to one of claims 1 to 11, characterized in that a gear pump is provided as the melt pump (6).

13. Device according to one of claims 1 to 12, characterized in that, in particular in the conveying direction after the first filtration unit (3) and before the degassing zone (5), a homogenization unit is provided for homogenizing the melt, in particular a screw or a section of the screw (10) or of the extruder (2), which is designed in such a way that the melt is sheared and mixed therein or is subjected to intensive shear stress and tensile stress and is strongly accelerated.

14. Device according to one of claims 1 to 13, characterized in that at least the units (2), (5) and (6), in particular all units (2) to (8) as far as present, are arranged axially one behind the other or lie on a common longitudinal axis.

15. Device according to one of claims 1 to 14, characterized in that the screw (10) continues in the area between the center of the rearmost degassing opening (11) of the degassing zone (5) located furthest downstream in the conveying direction and the extruder outlet (9), or a residual screw (14) or conveying elements are provided in this area, and that the melt pump (6) is connected at a distance (13) of 5 to 20 D, preferably in the range of 5 to 15 D, preferably in the range of 8 to 11 D, wherein D is the outer diameter of the screw (10) of the extruder (2) measured at the rearmost degassing opening (11) of the degassing zone (5) located furthest downstream in the conveying direction, and wherein the distance (13) is the distance measured between the center of the rearmost degassing opening (11) of the degassing zone (5) located furthest downstream in the conveying direction and the extruder outlet (9). is defined at the rearmost degassing opening (11) of the degassing zone (5) and the melt pump (6), in particular the position of the most upstream active conveying element or the most upstream conveying active parts of the melt pump (6).

16. Device according to one of claims 1 to 15, characterized in that the ratio of the length of the section of the screw (10) between the first filtration unit (3) and the foremost degassing opening of the degassing zone (5) located furthest upstream to the length of the section of the screw (10) between the rearmost degassing opening (11) of the degassing zone (5) located furthest downstream to the extruder outlet (9), or to 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. Device according to one of claims 1 to 16, characterized in that the length of the section of the screw (10) between the first filtration unit (3) and the foremost degassing opening of the degassing zone (5) located furthest upstream is in the range of 1 to 15 D, in particular in the range of 3 to 10 D.

18. Device according to one of claims 1 to 17, characterized in that the length of the section of the screw (10) between the furthest downstream rearmost degassing opening (11) of the degassing 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 processing materials containing or consisting of polymeric materials, preferably using a device according to any one of claims 1 to 18, in particular for the recycling and processing of contaminated thermoplastic polymers, comprising the following processing steps in the specified order: a) feeding the materials to be processed, in particular into a container, b) at least partial, in particular complete, melting of the materials, in particular in an extruder, c) initial filtration of the melt to remove unmelted components and / or impurities, d) degassing of the filtered melt, e) increasing the pressure of the melt by a melt pump, f) discharge and / or subsequent processing of the melt. characterized in that the increase in the pressure of the melt is downstream of the degassing of the melt and is coupled sequentially in a process.

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), the filtered melt is homogenized.

21. Method according to 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 takes place, in particular immediately and directly, without any further intermediate processing step.

22. Method according to one of claims 19 to 21, characterized in that the materials are crushed and / or heated before melting according to step b), in particular during step a), wherein it is preferably provided that the materials are heated and continuously mixed while retaining their lumpiness and flowability, and optionally degassed, softened, dried, increased in viscosity and / or crystallized.

23. Method according to one of claims 19 to 22, characterized in that at least the processing steps b), d) and e), in particular all provided processing steps, follow each other immediately and directly in time and space, without any further intervening processing step.

24. Method according to any one of claims 19 to 23, characterized in that the melt pump (6) is connected at a distance (13) of <= 20 D, in particular in the range of 5 to 15 D, preferably in the range of 5 to 20 D, preferably 8 to 11 D, wherein D is the outer diameter of a screw (10) of an extruder (2) measured at the rearmost degassing opening (11) of a degassing zone (5) located furthest downstream in the conveying direction, and wherein the distance (13) is defined as the distance measured between the center of the rearmost degassing opening (11) of the degassing zone (5) located furthest downstream in the conveying direction and the melt pump (6), in particular the position of the most upstream active conveying element or the most upstream conveying active parts of the melt pump (6).

25. Method according to one of claims 19 to 24, characterized in that the inner core cross-section of the screw (10), the pitch of the screw (10), and / or the The product is designed according to the features of claims 6, 7 and 8, and consists of the depth, web width, channel width and channel pitch of the screw (10) in the area between the center of the rearmost degassing opening (11) of the degassing zone (5) located furthest downstream in the conveying direction.

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