Method and device for increasing intrinsic viscosity of polycondensates

Abstract

The invention relates to a method and a device for processing polycondensates, in particular for recovering processing contaminated polycondensates, comprising the following processing steps: a) presenting the polycondensates or materials to be processed, in particular in a container, b) at least partially, in particular completely melting the polycondensates, in particular by extrusion in an extruder, and producing a polymer melt, the invention relates to a method for producing a polymer melt, comprising the following steps: a) preparing a polymer melt, c) mixing the polymer melt, d) cooling the polymer melt, e) disposing the mixed and cooled polymer melt in a melt reactor, in particular for polycondensation or post-condensation, in order to increase the intrinsic viscosity and / or to purify the polymer melt.

Description

Technical Field

[0001] The present invention relates to a method for processing polycondensates or materials containing polycondensates, in particular for recycling contaminated polycondensates, according to claim 1, and an apparatus for processing polycondensates or materials containing polycondensates, in particular for recycling contaminated polycondensates, according to claim 12. Background Art

[0002] Basically, it is a process sequence or an apparatus sequence which can be used when processing recycling materials consisting of or containing thermoplastic polycondensates. Polycondensates are understood to be products of polycondensation in which monomers having at least two reactive functional groups are linked to form polymers by cleavage of low molecular weight compounds. Polycondensation is one of the most important polymerization reactions, in addition to chain polymerization and polyaddition.

[0003] Polycondensates that frequently occur during the recycling process include in particular PET, PET-G, PET-A and their copolymers, PA, PC, polycondensates consisting of recycled raw materials (such as PLA), but also other ester compounds that polymerize or polycondense under temperature and vacuum.

[0004] During the recycling process, the polycondensate which is solid in the state of use is first converted into a polymer melt, in particular by means of an extrusion system, for example by means of the known PCU (pre-treatment unit) / cutting compressor-extruder system, wherein the PCU can be placed under vacuum or inert gas. The melt can be filtered and then subsequently transferred via a melt cooler to a melt reactor (MSP (melt state process) reactor or LSP (liquid state process) reactor), where a reaction, in particular (post) polycondensation and / or purification of the polymer takes place. The melt thus treated is then supplied to a subsequent device which produces granules, or semi-finished products such as fibers, filaments, tapes, preforms or films for producing bottles or containers are produced online using corresponding subsequent devices.

[0005] Such methods and apparatuses which are suitable in principle for recycling polycondensates are known from the prior art.

[0006] Polycondensates such as polyethylene terephthalate are sensitive and undergo various degradation processes, such as hydrolytic, thermal or thermooxidative degradation. Thermal degradation is primarily a problem in the process during the melting phase and leads, for example, to a drop in the intrinsic viscosity, the formation of carboxyl end groups or acetaldehyde or yellowing of the polymer, etc. These degradation reactions are additionally accelerated and intensified by oxygen with the formation of free radicals.

[0007] High mass temperatures or melt temperatures generally lead to negative effects on the quality of the final polymer and in particular lead to molecular chain shortening, undesirable gel formation or particles in the melt and polymer combustion. The high temperatures also promote the decomposition of polymers or components. As a result, some of the efforts of the upstream processes for improving the quality of the material (such as pretreatment, filtration, degassing) are reversed or offset again.

[0008] In this regard, the properties of polycondensates are utilized, i.e. damage caused during the manufacture and / or use of the product (e.g. shortening of the polymer chains due to thermal and / or hydrolytic degradation, or penetration of foreign substances into the polymer) can be "repaired" relatively easily, for example by repolymerization. This can produce the same or almost the same properties as the initial product. Some properties can even be improved by this treatment, such as mechanical properties, but also a reduction in foreign substances that have previously migrated into the polymer during use.

[0009] The influence of the properties of the polycondensate products used is known to a large extent and can be carried out by purification by diffusion in the liquid phase or in the solid phase before, during or after the polycondensation reaction or before melting. For this purpose, solid phase post-condensation reactors (solid-state SSP reactors) or melt reactors (MSP or LSP reactors) are usually used.

[0010] Solid phase post-condensation (SSP) is a method for further condensing polycondensates in order to increase their molar mass under conditions that are as mild as possible. Here, the pelletized polycondensate is reprocessed under inert gas or vacuum. The advantage of this method compared to melt polycondensation is the lower reaction temperature and, therefore, less discoloration of the polycondensate. In addition, it avoids viscosity problems, which can be severe in polycondensate melts. However, SSP processing usually requires more time, for example 10-20 hours, compared to about 1 hour in MSP or LSP processing. As a result, the system is larger and less flexible. Different viscosities at the input (iV) can be more difficult to adjust.

[0011] Melt polycondensation under vacuum can also utilize the inherent properties of polycondensates (especially PET) to (re)polycondense in the melt phase, which leads to increased IV values ​​and effective removal of volatile interfering substances. Compared with SSP, the reaction rate in the melt is significantly higher than that in the solid phase.

[0012] In the case of the disposal of materials from the field of processing industrial or post-consumer waste by means of melt and melt reaction disposal, the following problems often arise due to the different characteristics of the input materials, in particular due to differences in viscosity, contamination, composition, etc.:

[0013] When transferring into the melt, for example by means of an extrusion system, it is often not possible or insufficiently considered to achieve a narrow temperature distribution of the melt. This is partly within the scope of the melting process and partly within the scope of the mechanical filtration of the melt, wherein, depending on the polymer properties and the degree of contamination, different melt temperatures are produced. Partly, the low-viscosity part of the melt remains relatively cold, while the high-viscosity part of the melt, for example in the extruder screw or during filtration, obtains greater energy in the form of shear and thus heats up more strongly. These viscosity differences are often already present in the input material and are sometimes not known or recognizable or are not taken into account. However, this leads to problems in the processing and reduces the quality of the final product. Summary of the invention

[0014] The object of the present invention is therefore to provide a method and a device for the advantageous processing of polycondensates or materials containing polycondensates, with which method / device an increased process reliability and an increased quality of the end product can be achieved. In particular, the intrinsic viscosity of the material should also be increased or the content of interfering substances or dirt should be reduced.

[0015] According to the invention, this object is achieved by a method for processing polycondensates or materials containing polycondensates, in particular for recycling contaminated polycondensates such as PET, PA, PC or PLA, wherein the method comprises the following processing steps:

[0016] a) presenting polycondensates or materials to be processed, in particular in containers,

[0017] b) at least partially, in particular completely, melting the polycondensate, in particular by extrusion in an extruder, and forming a polymer melt,

[0018] c) mixing the polymer melt,

[0019] d) temperature control, in particular cooling, of the polymer melt,

[0020] e) treating the mixed and temperature-controlled, in particular cooled, polymer melt in a melt reactor, in particular for polycondensation or postcondensation, in order to increase the intrinsic viscosity and / or to purify the polymer melt.

[0021] Similarly, according to the invention, this object is achieved by a device for processing polycondensates or materials containing polycondensates, in particular for recycling contaminated polycondensates, wherein the device comprises:

[0022] - a melting device for melting the polycondensate to be processed and producing a polymer melt,

[0023] a mixing device following the melting device, which serves to mix the polymer melt,

[0024] a temperature control device, in particular a cooling device, downstream of the melting device, which serves to control the temperature, in particular to reduce the temperature, of the polymer melt,

[0025] A melt reactor connected to the temperature control device, which serves to process the mixed and temperature-controlled, in particular cooled, polymer melt, in particular for polycondensation or postcondensation in order to increase the intrinsic viscosity and / or to purify the polymer melt.

[0026] When reprocessing different or inhomogeneous materials, for example different material streams from can and bottle packaging (which have a high initial viscosity) are mixed with materials from the deep-drawing film sector (which have a low viscosity in the melt) and / or with fiber materials (which have a very low viscosity). This results in average core temperatures of the melt of 275° C. with a significant belt width of + / -20° C. in certain PET blends.

[0027] When the polycondensate melt is processed in a melt reactor (eg, an MSP reactor), the reaction and / or purification is carried out at temperature, residence time, and with the removal of moisture, oxygen, glycol, or other materials.

[0028] If such a polymerization or postcondensation is carried out in a melt reactor, the molecular chain distribution becomes all the narrower the temperature spectrum of the input melt and the narrower the residence time spectrum in the melt reactor.

[0029] By means of suitable measures (e.g. conveying devices, fill level measuring devices, etc.), the residence time spectrum in the melt reactor is kept within as narrow a range as possible. Furthermore, by applying a vacuum and / or flushing with inert gas it is ensured that the reaction proceeds largely uniformly along the reactor. Considering that the reaction rate of a chemical reaction approximately doubles with a temperature increase of 10° C., it is advantageous if the melt has a narrow temperature distribution when entering the melt reactor.

[0030] Furthermore, it has proven to be advantageous to select the absolute temperature of the melt as low as possible when it enters the melt reactor. Although this reduces the reaction rate and prolongs the time required in the reaction system, this leads to higher process reliability and better final quality. The reaction rate is affected exponentially by the temperature, while the residence time changes linearly. Thus, the viscosity band width or the molecular chain distribution can also be kept narrower by setting a lower temperature for the melt, since the short-chain polymer fraction (i.e. the polymer fraction with a lower viscosity) polymerizes faster than the long-chain molecules at a certain temperature.

[0031] It should also be noted that, in addition to the desired polycondensation reaction, various undesirable side reactions occur in the reaction in the melt reactor, which have a negative impact on the quality of the final polymer. These side reactions are also significantly less effective at lower temperatures. The residence time has an increasing effect on these side reactions, but the temperature has an exponential effect on this, i.e., at higher temperatures, the number of undesirable side reactions increases disproportionately.

[0032] Acetaldehyde is a particularly undesirable interfering substance in this regard. In particular, in the beverage bottle sector, acetaldehyde causes a fruity apple taste, which is extremely undesirable when packaging water. However, this byproduct also has a negative impact on processability.

[0033] The band width of the melt viscosity of the final product is also usually subject to high requirements. Thus, in virgin materials, a band width of + / -0.002 dl / g is a common value. Due to the high use of recycled materials, this band width must be maintained even during reprocessing.

[0034] Different contents of residual catalyst, filler material, etc. influence the reaction rate and partially also the diffusion rate. For this reason, it is also advantageous to set the lowest reasonable reaction temperature and temperature range.

[0035] Another situation that typically occurs during recycling is the presence of residual migratory substances, dirt, etc. in the polymer. These foreign or interfering substances often lead to quality defects in the produced material. Thus, at elevated temperatures, the material, for example, changes color significantly more than over a longer period of time.

[0036] Accordingly, several factors must be considered, especially

[0037] - an increase in the temperature of the melt is generally disadvantageous and undesirable for the subsequent processes,

[0038] - Non-uniform and excessively high melt temperatures often lead to quality issues, and / or

[0039] A homogenized, mixed and temperature-controlled, in particular cooled, melt is generally advantageous for improved product quality and thus makes it possible to achieve a constant discharge volume and a uniform viscosity distribution.

[0040] According to the invention, there is a special combination of extruder, melt mixer and melt temperature controller (especially melt cooler) and melt reactor. The prerequisites or preparation of the melt for the process in the melt reactor MSP / LSP are particularly delicate or demanding (the corresponding preparation and setting of the melt parameters are correspondingly more important and more difficult than for SSP).

[0041] For this reason, it is proposed according to the invention that when processing polycondensates, in particular polycondensates from secondary raw materials, by means of a melt reactor, the temperature of the melt is equalized, controlled (in particular lowered) and reduced in width before the melt reactor. It is precisely the elevated temperatures that are often present in the melt reactor that must be paid special attention to. All of this can be ensured by the method according to the invention and the device according to the invention.

[0042] Temperature equalization may be understood here both in time and in location, ie the temperature should be as constant as possible over a longer period of time (ie from a few minutes to a few hours) and local or regional deviations transversely to the flow direction should also be as small as possible.

[0043] In each channel system, there is a certain temperature distribution transversely to the flow direction or a radial temperature gradient from the inside to the outside. In the case of higher outputs, corresponding channel cross sections are required, and this results in local temperature inhomogeneities transversely to the flow direction. Therefore, local transverse mixing of the melt is advantageous.

[0044] However, in the course of continuous processes, especially due to extrusion processes, there are also temperature changes over time, for example, due to filter cleaning, there are briefly higher shears in the extruder, which temporarily lead to temperature increases. Due to different material forms (such as ground material, partially crystallized fibers, coarse fibers, highly drawn fibers) and IV differences in the starting material, the material in the extruder is also sheared differently, which also leads to further temperature inhomogeneities over time and resulting viscosity fluctuations during the course of the process.

[0045] Temperature equalization: Reduction of the temporal component of temperature deviations through targeted temperature control.

[0046] Temperature width reduction: The melt temperature has a distribution transversely to the channel and over time that is determined by previous influencing factors and / or material composition. Mixing reduces this temperature width, but so does tempering.

[0047] The term "tempering" is currently understood to mean adapting the temperature of the melt to a desired or advantageous temperature. This can be a reduction in temperature or an increase in temperature. The tempering device or melt / tempering mixer is accordingly adapted, designed, controlled and / or arranged for cooling and / or heating.

[0048] Advantageously, tempering is a temperature reduction or cooling. This is advantageously carried out in a corresponding cooling device or melt / cooling mixer.

[0049] However, there are situations in which at most a relatively small increase in temperature is also advantageous or necessary, usually only by a few degrees. For example, if the temperature before the cooler is too low and the melt must be heated, for example, if the melt has become too cold due to the preceding extrusion process, since the melt is very thin and the energy input in the extruder is therefore low. Accordingly, temperature control is then an increase in temperature or heating. This is advantageously carried out in a correspondingly suitable and designed temperature control device or melt / temperature control mixer.

[0050] In the method according to the invention, the processing steps are advantageously carried out in the order specified a) to e).

[0051] However, it is particularly advantageous if steps c) and d) are carried out simultaneously or in a common process step, ie the polymer melt is mixed and tempered, in particular cooled, simultaneously.

[0052] To improve the purification, it is advantageous if, before steps c) and d), the polymer melt is filtered in order to remove unmelted components and / or impurities.

[0053] An improvement in the product quality also results if, prior to steps c) and d), a degassing of the filtered polymer melt is carried out.

[0054] Particularly effective and advantageous mixing and a fundamentally advantageous, narrow residence time spectrum are achieved if the polymer melts are mixed distributively.

[0055] It is advantageous for product quality if the polymer melt is mixed and / or tempered, in particular cooled, such that the temperature distribution in the polymer melt, in particular before mixing or tempering, in particular cooling, up to the stage immediately before the melt reactor, preferably in the stage from melting during extrusion up to the stage before the melt reactor, in particular in the entire process sequence is <+ / -10° C., in particular <+ / -5° C., preferably <+ / -1° C. In this way, a narrow viscosity band width or molecular chain distribution can also be achieved.

[0056] In order to achieve a high product quality and a high process reliability and to avoid side reactions, it is further advantageous if the polymer melt is temperature-controlled, in particular cooled, in such a way that the temperature of the polymer melt immediately before or when entering the melt reactor is 5 to 25% lower than the temperature of the polymer melt immediately before mixing and temperature-controlled, in particular cooling, or before steps c) and d).

[0057] In this context, it is also advantageous and possible to achieve the advantages just mentioned if the polymer melt is tempered, in particular cooled, in such a way that its temperature immediately before or upon entering the melt reactor is only relatively slightly, namely by 10%, above the melting range of the polymer.

[0058] An advantageous method utilizes a special step already at the beginning of the processing method, namely comminuting and / or heating the polycondensate or material before melting according to step b), especially during step a), wherein it is preferably provided that the polycondensate or material is heated and permanently mixed while maintaining its blockiness and bulkiness and, if necessary, degassed, softened, dried, its viscosity increased and / or crystallized.

[0059] Another advantageous and efficient method implementation is that at least processing steps c), d) and e), in particular all processing steps provided, are carried out immediately and directly one after the other in terms of time and location, in each case without further intervening processing steps.

[0060] In the device according to the invention, it can be advantageously provided that the melt reactor is connected to a mixing device or a temperature control device, in particular a cooling device, in spatial proximity and directly in the conveying direction without further intervening functional units, or is connected downstream of a mixing device or a temperature control device, in particular a cooling device, and is coupled in sequence in terms of process.

[0061] An effective and advantageous arrangement provides that the melting device is an extruder, wherein the extruder comprises, in particular, a melt filter and / or a degassing zone.

[0062] An overall arrangement which is advantageous for achieving a high-quality end product is characterized in that a cutter compressor is connected upstream of the melting device, wherein in particular a cutter compressor-extruder combination is provided for comminuting and / or heating the polycondensate or material. The cutter compressor is preferably designed and suitable for heating and permanently mixing the polycondensate or material being supplied while maintaining its blockiness and bulkiness, and, if necessary, degassing, softening, drying, increasing its viscosity and / or crystallizing it.

[0063] An efficient and advantageous arrangement provides that the mixing device is a distributing mixer.

[0064] In this context, it is particularly advantageous if the mixing device is simultaneously a temperature control device, in particular a cooling device, wherein in particular a melt temperature control mixer or a melt temperature control mixer / mixer, preferably a melt cooling mixer or a melt cooler / mixer, is provided.

[0065] As melt reactor, an MSP reactor or an LSP reactor is advantageously provided. The specific design of the melt reactor is relatively unimportant for the intended use according to the invention. The melt reactor can be a melt reactor according to the design of DE 1745541, but can also be a melt reactor according to the design of DE 4013912 or DE 4126425.

[0066] Common to all melt reactors is the attempt to greatly increase the melt in terms of its surface area under reduced pressure conditions or in an inert gas stream and to initiate the polycondensation reaction in order to extend the polymer chains and thus optimize the mechanical properties of the polymer when it is reused in the end product. In addition, the diffusion process enables the removal of undesirable materials that may have entered the polymer as a result of previous use. This provides the possibility of reusing these polymers in applications in which food suitability, odor and skin compatibility must be ensured. The reaction products or diffusion products are removed by negative pressure or by an inert gas stream.

[0067] In order to achieve good product quality, it is advantageously provided that the mixing device and / or the temperature control device (in particular the cooling device) or the melt temperature control mixer (preferably the melt cooling mixer) is controllable or controlled in such a way that the temperature distribution in the polymer melt is <+ / -10° C., in particular <+ / -5° C., preferably <+ / -1° C. In this context, it is particularly advantageous if such a temperature distribution is achieved in the region immediately upstream of the mixer or temperature control device, in particular the cooler, up to the melt reactor or upstream thereof, preferably in the region of the melting unit or the extruder up to upstream of the melt reactor, in particular in the entire system or device.

[0068] In order to achieve and set a good product quality and higher process reliability, it is advantageously provided that the mixing device and / or the temperature control device, in particular the cooling device, can be controlled or controlled in such a way that the temperature of the polymer melt immediately before or when entering the melt reactor is 5-25% lower than the temperature of the polymer melt immediately before the mixing device and the temperature control device, in particular the cooling device, or before the temperature control mixer, preferably the cooling mixer. In this way, side reactions can be reduced and a narrow IV width can be obtained in the end product.

[0069] In order to also achieve these advantages, it can be advantageously provided that the mixing device and / or the temperature control device, in particular the cooling device, can be controlled or is controlled in such a way that the temperature of the polymer melt immediately before / when entering the melt reactor is 1-10% above the melting range of the polymer.

[0070] From the perspective of plant technology, it can be provided that a feed pump for the melt is used upstream of a temperature controller, in particular a cooler or a mixer, and downstream of a temperature controller, in particular a cooler or a mixer and / or downstream of the melt reactor in order to overcome possible pressure differences. However, care must be taken again that no significant temperature increase occurs upstream of the melt reactor, in particular due to any pump downstream of the temperature controller, in particular the cooler / mixer.

[0071] The core temperature of the melt is advantageously selected in accordance with the desired residence time and the desired reaction rate in the melt reactor or reaction vessel. It has been found that generally an attempt should be made to set the lowest possible core temperature.

[0072] In this case, the temperature control medium, in particular the cooling medium, of the melt temperature control system, in particular the melt cooling system (e.g., melt cooler / mixer) is adjusted in accordance with the core temperature of the melt. For this purpose, the temperature can be recorded before and after the melt temperature control system, in particular the melt cooling system. In advantageous temperature control systems, in particular cooling systems, the temperature of the melt can also be measured in the temperature control section, in particular the cooling section. This temperature is used to set the temperature control medium, in particular the cooling medium.

[0073] Advantageously, the melt temperature is sufficiently representative. Thus, the melt temperature in the feed pipe differs significantly at the wall of the pipe or in the central part of the pipe. It is therefore advisable and reasonable to measure the temperature at the wall as well as in the center of the pipe. The thicker the line, the more reasonable it is to measure at multiple points on the cross section.

[0074] Advantageous embodiments of the method according to the invention and of the device according to the invention are described and explained below on the basis of more general and more specific examples which should be understood as non-limiting:

[0075] It is often desirable to reprocess PET materials from completely different sources, for example from residual filaments, residual fibers, deep-drawn films (e.g. cheese or sausage packaging, tool or electronic device packaging), PET bottle material (e.g. water bottles or soft drinks), etc. The viscosity band width is usually significant here and is about 0.5 dl / g (in the case of fibers) to 0.79 dl / g (in the case of bottle mill stock).

[0076] In such inhomogeneous input material mixtures, a correspondingly wide molecular chain distribution or a wide viscosity band width is produced. In addition, such mixtures are rarely characterized by identical components, i.e. the quantitative proportions of different materials are different and furthermore continuously change.

[0077] During the melting process, the particles (mostly smaller particles in the form of polymer flakes, fibers or films) are subjected to different shear loads depending on their mechanical properties (size, stretching, thickness, etc.) and viscosity properties. This leads to a wide melt temperature distribution, for example: 276°C + / - 20°C (after the extruder), which has the disadvantages described at the beginning, which are associated with this wide and changing temperature distribution. After the filter, the melt temperature distribution is still about 277°C + / - 15°C. After the melt cooler / mixer, the melt temperature distribution is 260°C + / - 3°C, wherein a band width of less than 3°C can also be achieved. Therefore, the temperature of the melt is equalized, reduced and the width is reduced before the melt reactor.

[0078] Examples of PET used for packaging and fiber (A-PET):

[0079] PET melt temperature range

[0080] PET melt temperature: >250°C, typically 256°C

[0081] Typical melt temperature during recovery: 275°C to 310°C (depending on method, contamination and filter fineness)

[0082] Target temperature range before LSP: 260°C to 270°C + / - 3°C

[0083] Cooling range: 5% to 25% (at reference temperature 260°C)

[0084] The viscosity increase depends on the melt temperature:

[0085] The residence time t in the melt reactor is constant.

[0086] The input viscosity before the melt reactor was 0.5 dl / g.

[0087] Melt temperature: 270℃ Viscosity 0.53dl / g

[0088] Melt temperature: 280℃ Viscosity 0.57dl / g

[0089] Melt temperature: 290℃ Viscosity 0.62dl / g BRIEF DESCRIPTION OF THE DRAWINGS

[0090] exist Figure 1 An advantageous schematic diagram of an advantageous device or assembly or apparatus 1 is shown in FIG. Figure 1 An exemplary method is explained. It is an exemplary schematic diagram for illustrating the most important components and units of the device. Accordingly, this illustration does not guarantee the final accuracy of all design details and proportions. DETAILED DESCRIPTION

[0091] exist Figure 1 Not depicted is an optional container in the form of a conventional cutting compressor or pre-processing unit (PCU). Currently, this container can be arranged to the right of the extruder or before it or upstream of it. Such a cutting compressor or container is filled with the recycled polymer material to be processed. The polymer material is presented in the container, crushed by mixing and crushing tools, mixed and heated until softened, but usually not melted. The blockiness of the viscous polymer particles remains unchanged. In addition, the material is pre-treated and, for example, dried, pre-compressed and, depending on the material, the viscosity is increased.

[0092] When processing secondary raw materials from polycondensates, the extrusion process used to melt the polycondensates is pre-determined by the shape of the current material (such as fibers, granules, agglomerates, film fragments, thick-walled mill stock, etc.). The secondary raw materials can originate from different sources and can be contaminated with solid and liquid substances (such as cotton fibers or spinning aids), which may consist of oil. In addition, these materials often have different viscosities in the molten state.

[0093] exist Figure 1 The extruder 2 which can be seen in the figure can be connected tangentially to the cutting compressor or the lowermost area of ​​the container. The material is discharged from the container and transferred to the extruder 2 and is caught there by the screw. Figure 1 In the frontmost section on the left, the material melts and plasticizes under increasing pressure.

[0094] In this melting process, a single screw extrusion system or a multi-screw extrusion system (such as a twin screw) can be used. Here, the known PCU extruder system has proven to be particularly successful, since it enables the undesired substances to be partially gasified in the PCU, compressing and heating or softening the material. In addition, this system also has a forced feeding of the extruder, which is particularly advantageous in fiber materials with poor flowability. The extruder then melts the material, optionally it degases the polymer. In addition, the process can be supported by means of negative pressure or inert gas in the PCU.

[0095] The melt is subsequently filtered in a filter unit 3 , which removes solid components but also gel-like components from the melt.

[0096] Downstream of the filter unit 3 and immediately following the filter unit 3 and after the process of melting and the first purification step, the melt is mostly conveyed to a melt cooler / mixer 4 via a (not shown) melt pump. The melt cooler / mixer has the task of visibly reducing the temperature inhomogeneities that occur not only spatially but also temporally. At the same time, the average melt temperature is reduced. This is necessary because, in particular, the dispersion of different input materials leads to different melt temperatures. In addition, the filtering process can also lead to temporal or local inhomogeneities.

[0097] After the temperature of the melt is reduced and equalized in the melt cooler / mixer 4 , the melt is transferred to the melt reactor 5 .

[0098] After the reaction process or purification process in the melt reactor 5, the molten material reaches the output unit and can be further processed if necessary, such as granulation. However, it can also be directly formed into a final product or semi-finished product, such as in the form of fibers, films, preforms, etc.

[0099] The cooling medium is set in terms of its quantity, temperature and / or speed by measuring the melt temperature before or after the melt cooler / mixer 4 so that the desired target temperature is achieved. Figure 1 As can be seen in the figure, at least one melt temperature 1 is detected here, and the temperature control medium is set so that the desired temperature is reached. This temperature can be controlled using the melt temperature 2. The temperature measurement can be performed at different locations in the line, at the outermost edge and / or in the center of the tube. In the case of very high plant outputs, it is advantageous to install thicker lines and / or multiple lines. In the case of thicker lines, it is advantageous to detect the temperature at multiple locations in the tube. Ideally, the temperature measurement is performed using multiple temperature detection devices, wherein the temperature is typically detected in the cross section of the inflow and / or outflow channel.

[0100] By measuring the temperature distribution within the feed and discharge lines, the mixing quality and cooling rate can be tested. Mixing quality can be identified by a narrower temperature distribution, and cooling quality can be identified by a decrease in the average temperature.

[0101] Comparative test:

[0102] The following tests were performed on an exemplary test device according to the invention. This was a PCU / extruder combination INTAREMA 80TE equipped with a melt filter SW4 / 134 according to the following device configuration:

[0103]

[0104]

[0105] The material processed hereby consists of fiber waste from different areas of the spinning mill. Start-up waste (lumps), undrawn fibers, monofilaments and drawn fibers were used. In addition, the fibers had different proportions of spinning oil in the range of 0.3 to 2 weight percent. The input moisture content was also different, in some cases it was 10 weight percent and more.

[0106] The material is pre-comminuted by means of a single-shaft pulverizer. Alternatively, a grinding mill can also be used for this purpose.

[0107] With the aid of the PCU / extruder combination, the fibers are compressed, dried and heated and after a corresponding residence time in the PCU they are transferred to a single-screw extruder. After melting, the material is degassed and guided through a melt filtration device.

[0108] The filtered melt is then conveyed to the melt cooler / mixer via a melt pump. The cooler / mixer used is a static mixer without moving elements. The temperature of the cooler / mixer is controlled with thermal oil, which can be heated as well as cooled. The melt temperature is detected not only before the cooler / mixer but also afterward in order to check the effectiveness of the unit. In addition, the viscosity is measured after the melt reactor. In this case, special attention is paid to the stability of the viscosity over time.

[0109] For comparison purposes, the melt cooler / mixer was removed and the melt was transferred directly to the melt reactor.

[0110] The melt reactor is a horizontal disk reactor, similar to the one according to DE 1745541, in which the polymer mass is guided several times through the reaction chamber as a free-falling veil. Here, the rotating disk draws the polymer mass out of the sump and the polymer mass flows back again as a thin film. This method achieves a very large surface area relative to the reaction mass, which allows the released reaction products to evaporate in a short time and promotes the polymer reaction.

[0111] The disk reactor is currently loaded with a negative pressure of 6 mbar. The disk rotates at a rotation speed of 1 rpm. The average residence time of the material in the reactor is about 60 min.

[0112] After leaving the reactor, the material is granulated in an extrusion granulation unit.

[0113] The results are as follows:

[0114] Without Melt Cooler / Mixer:

[0115] The output is about 350kg / h.

[0116] A mixture of PET waste from bottles, fibers and deep-drawn films was used as input material.

[0117] Running time: about 10 hours

[0118] The melt temperature before the melt reactor was recorded ( Figure 2 , lower curve). The temperature of the polymer mass was measured using a temperature sensor immersed about 20 mm into the melt stream. The average input temperature was about 288° C. The fluctuation width of the melt temperature was about 35° C.

[0119] The intrinsic viscosity was measured online after the melt reactor and averaged about 0.69 dl / g with a fluctuation width of about 0.07 dl / g ( Figure 2 , the upper curve).

[0120] With melt cooler / mixer:

[0121] The output is about 350kg / h.

[0122] The input material was a homogeneous mixture of PET waste from bottles, fibers and deep-drawn films.

[0123] Running time: about 20h

[0124] The melt temperature before the mixer / cooler was recorded ( Figure 3 , middle curve) and the melt temperature after the mixer / cooler ( Figure 3 , the bottom curve). The temperature of the mass was measured using a temperature sensor immersed about 20 mm in the mass flow. The average input temperature was about 293°C. The melt cooled to an average of 260°C.

[0125] The intrinsic viscosity is measured online after the melt reactor and averages about 0.65 dl / g. The fluctuation width can be completely eliminated and is therefore better than the industry standard of + / - 0.002 dl / g ( Figure 3 , the top curve).

[0126] The advantageous balancing of the temperature and intrinsic viscosity of the melt, the reduction in the dominant properties and the reduction in the width can be clearly seen here.

Claims

1. A method for processing polycondensates or materials containing polycondensates, in particular for recycling contaminated polycondensates, comprising the following processing steps: a) presenting polycondensates or materials to be processed, in particular in containers, b) at least partially, in particular completely, melting the polycondensate, in particular by extrusion in an extruder, and producing a polymer melt, c) mixing the polymer melt, d) temperature control, in particular cooling, of the polymer melt, e) treating the mixed and temperature-controlled, in particular cooled, polymer melt in a melt reactor, in particular for polycondensation or postcondensation, in order to increase the intrinsic viscosity and / or to purify the polymer melt.

2. The method according to claim 1, characterized in that The processing steps are performed in the order specified.

3. The method according to claim 1 or 2, characterized in that Steps c) and d) are carried out simultaneously or in a common process step, or the polymer melt is mixed and tempered, in particular cooled, simultaneously.

4. The method according to any one of claims 1 to 3, characterized in that Prior to steps c) and d), the polymer melt is filtered in order to remove unmelted components and / or contaminants.

5. The method according to any one of claims 1 to 4, characterized in that Prior to steps c) and d), degassing of the filtered polymer melt is carried out.

6. The method according to any one of claims 1 to 5, characterized in that The polymer melts are distributively mixed.

7. The method according to any one of claims 1 to 6, characterized in that The polymer melt is mixed and / or tempered, in particular cooled, in such a way that the temperature distribution in the polymer melt is <+ / -10° C., in particular <+ / -5° C., preferably <+ / -1° C.

8. The method according to any one of claims 1 to 7, characterized in that The polymer melt is tempered, in particular cooled, such that the temperature of the polymer melt immediately before or upon entering the melt reactor is 5-25% lower than the temperature of the polymer melt immediately before mixing and tempering, in particular cooling, or before steps c) and d).

9. The method according to any one of claims 1 to 8, characterized in that The polymer melt is temperature-controlled, in particular cooled, in such a way that the temperature of the polymer melt before or upon entering the melt reactor is 1-10% above the melting range of the polymer.

10. The method according to any one of claims 1 to 9, characterized in that Before melting according to step b), in particular during step a), the polycondensate or material is comminuted and / or heated, wherein it is preferably provided that the polycondensate or material is heated and permanently mixed while retaining its blockiness and bulkiness and, if necessary, degassed, softened, dried, increased in viscosity and / or crystallized.

11. The method according to any one of claims 1 to 10, characterized in that At least the processing steps c), d) and e), in particular all processing steps provided, are carried out immediately in time and in place and directly one after the other in each case without further intervening processing steps.

12. A device for processing polycondensates or materials containing polycondensates, in particular for recycling contaminated polycondensates, comprising: a melting device (2) for melting the polycondensate to be processed and producing a polymer melt, a mixing device (3) subsequent to the melting device (2) for mixing the polymer melt, a temperature control device, in particular a cooling device (4), downstream of the melting device (2) for controlling the temperature, in particular reducing the temperature of the polymer melt, A melt reactor (5) connected to the temperature control device, which is used to process the mixed and temperature-controlled, in particular cooled, polymer melt, in particular for polycondensation or postcondensation in order to increase the intrinsic viscosity and / or to purify the polymer melt.

13. The device according to claim 12, characterized in that The melt reactor (5) is connected to the mixing device (3) or the temperature control device, in particular the cooling device (4) in the conveying direction in a spatially adjacent and direct manner without any further interposed functional units, or is connected downstream of the mixing device (3) or the temperature control device, in particular the cooling device (4), and is coupled in sequence in terms of process.

14. The device according to any one of claims 12 to 13, characterized in that The melting device (2) is an extruder, wherein the extruder comprises, in particular, a melt filter and / or a degassing zone.

15. The device according to any one of claims 12 to 14, characterized in that The melting device (2) is preceded by a cutting compressor (1), wherein in particular a cutting compressor-extruder combination is provided for comminuting and / or heating the polycondensate or material, wherein the cutting compressor (1) is preferably designed and suitable for heating and permanently mixing the polycondensate or material being fed while maintaining its blockiness and bulkiness, and, if necessary, for degassing, softening, drying, increasing its viscosity and / or crystallizing it.

16. The device according to any one of claims 12 to 15, characterized in that The mixing device (3) is a distributing mixer.

17. The device according to any one of claims 12 to 16, characterized in that The mixing device (3) is simultaneously a temperature control device, in particular a cooling device (4), wherein in particular a melt cooling mixer is provided.

18. The device according to any one of claims 12 to 17, characterized in that The melt reactor (5) is a LSP reactor or a MSP reactor.

19. The device according to any one of claims 12 to 18, characterized in that The mixing device (3) and / or the temperature control device, in particular the cooling device (4), can be controlled or is controlled in such a way that the temperature distribution in the polymer melt is <+ / -10°C, in particular <+ / -5°C, preferably <+ / -1°C.

20. The device according to any one of claims 12 to 19, characterized in that The mixing device (3) and / or the temperature control device, in particular the cooling device (4) can be controlled or is controlled in such a way that the temperature of the polymer melt immediately before entering the melt reactor (5) or when entering the melt reactor (5) is 5-25% lower than the temperature of the polymer melt immediately before the mixing device (3) and the temperature control device, in particular the cooling device (4) or before the temperature control mixer, in particular the cooling mixer.

21. The device according to any one of claims 12 to 20, characterized in that The mixing device (3) and / or the temperature control device, in particular the cooling device (4), can be controlled or is controlled in such a way that the temperature of the polymer melt immediately before / on entering the melt reactor (5) is 1-10% above the melting range of the polymer.

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