Process and apparatus for increasing intrinsic viscosity of polycondensates

Abstract

Process and apparatus for processing of polycondensates, in particular for recycling processing of contaminated polycondensates, comprising the following processing steps: a) initially charging the polycondensates / materials to be processed, in particular in a container, b) at least partially, especially completely, melting the polycondensates, in particular by extruding in an extruder, and preparing a polymer melt, c) mixing the polymer melt, d) cooling the polymer melt, e) treating the mixed and cooled polymer melt in a melt reactor, in particular for polycondensation / postcondensation, to increase the intrinsic viscosity and / or to purify the polymer melt.

Description

[0001] METHOD AND DEVICE FOR INCREASING THE INTRINSIC VISCOSITY OF POLYCONDENSATES

[0002] The present invention relates to a method and a device for processing polycondensates or materials containing polycondensates, in particular for recycling processing of contaminated polycondensates, according to claim 1 and claim 12, respectively.

[0003] Essentially, it involves a process sequence or a device sequence that can be used in the processing of recycled materials consisting of or containing thermoplastic polycondensates. Polycondensates are the products of polycondensation, in which monomers with at least two reactive functional groups are linked to form a polymer by cleavage of low-molecular-weight compounds. Along with chain polymerization and polyaddition, polycondensation is one of the most important polymerization reactions.

[0004] The polycondensates that frequently occur during recycling include, in particular, PET, PET-G, PET-A and their copolymers, PA, PC, polycondensates from renewable raw materials such as PLA, but also other ester compounds that polymerize or polycondense under temperature and vacuum.

[0005] During recycling, the polycondensates, which are solid in their use state, are first converted into a polymer melt, particularly using an extrusion system, e.g., a well-known PCU (preconditioning unit) / cutter-compactor-extruder system, where the PCU can be placed under vacuum or inert gases. The melt can be filtered and then transferred via a melt cooler to a melt reactor - MSP (melt state process) reactor or LSP (liquid state process) reactor - where a reaction, particularly (post-)polycondensation, and / or purification of the polymers takes place. The melt treated in this way is then fed to a downstream device that either produces granules or semi-finished products such as fibers, filaments, tapes, preforms for the production of bottles or containers, or films with corresponding downstream processes.

[0006] Such processes and devices are known from the state of the art and are generally suitable for the recycling of polycondensates. Polycondensates, such as polyethylene terephthalates, are sensitive and subject to various degradation processes, e.g., hydrolytic degradation, thermal degradation, or thermo-oxidative degradation. Thermal degradation is primarily a problem in melt-phase processes and leads, for example, to a decrease in intrinsic viscosity (IV), the formation of carboxyl end groups or acetaldehyde, or the yellowing of the polymer, etc. Oxygen further accelerates and intensifies these degradation reactions, forming free radicals.

[0007] High melt temperatures often negatively impact the quality of the final polymers, causing, among other things, 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 components. This reverses or counteracts some of the efforts of upstream processes aimed at improving material quality, such as pretreatment, filtration, and degassing.

[0008] In this context, the property of polycondensates is exploited: damage caused during production and / or use of the products—for example, shortening of the polymer chains due to thermal and / or hydrolytic degradation, or the penetration of foreign substances into the polymer—is relatively easy to "repair," for example, through repolymerization. This allows the same or almost the same properties as the original product to be restored. Some properties can even be improved through such treatment, for example, the mechanical properties, but also the reduction of foreign substances that, for example, have previously migrated into the polymer during use.

[0009] The influencing of the properties of used polycondensate products is widely known and can be achieved through polycondensation reactions or purification by diffusion, before melting, during melting, or after the melting process in the liquid or solid phase. Solid-state post-condensation reactors (SSP reactors) or melt reactors (MSP or LSP reactors) are typically used for this purpose.

[0010] Solid-state postcondensation (SSP) is a process for the further condensation of polycondensates to increase their molecular weight under the most gentle conditions possible. The granulated polycondensate is post-treated under inert gas or vacuum. Compared to melt polycondensation, this process has the advantage of a lower reaction temperature and therefore less discoloration of the polycondensates. Furthermore, it avoids viscosity problems, which can be serious in a polycondensate melt. However, SSP treatment typically requires more time, e.g., 10–20 hours compared to approximately 1 hour for MSP or LSP treatment. The systems are therefore larger and less flexible. Variable viscosities (iV) in the input are more difficult to control.

[0011] Melt polycondensation under vacuum also exploits the inherent property of polycondensates, especially PET, to (re)condense in the melt phase, which leads to an increase in the IV value and the efficient removal of volatile impurities. Compared to SSP, the reaction rate in the melt is significantly higher than in the solid phase.

[0012] When treating materials from the field of industrial or post-consumer waste processing using a melt and melt reaction treatment, the following problem often arises due to the different properties of the input materials, in particular differences in viscosity, contamination, ingredients, etc.:

[0013] During transfer to the melt, e.g. through an extrusion system, it is often not possible or not sufficient attention is paid to achieving a narrow temperature distribution in the melt. This is partly due to the melting process, partly to the mechanical filtration of the melt, whereby different melt temperatures are generated depending on the polymer properties and the degree of contamination. In some cases, low-viscosity parts of the melt remain colder, while high-viscosity parts of the melt are subjected to more energy in the form of shear, for example in the extruder screw or during filtration, and therefore heat up more rapidly. These viscosity differences are very often already present in the input material and are sometimes unknown, unrecognizable, or not taken into account. However, this leads to problems in the processing and to reduced quality of the end products.

[0014] It is therefore an object of the present invention to provide a method and a device for the advantageous processing of polycondensates or materials containing polycondensates, with which increased process reliability and increased quality of the end products can be achieved. In particular, the intrinsic viscosity of the material is to be increased and the content of impurities or contaminants is to be reduced. This object is achieved according to the invention by a method for processing polycondensates or materials containing polycondensates, in particular for the recycling processing of contaminated polycondensates, e.g. PET, PA, PC or PLA, wherein the method comprises the following processing steps: a) Introduction of the polycondensates orMaterials, in particular in a container, b) at least partial, in particular complete, melting of the polycondensates, in particular by extrusion in an extruder, and creation of a polymer melt, c) mixing the polymer melt, d) tempering, in particular cooling, the polymer melt, e) treating the mixed and tempered, in particular cooled, polymer melt in a melt reactor, in particular for polycondensation or post-condensation, to increase the intrinsic viscosity and / or to purify the polymer melt.

[0015] Analogously, the objective object is achieved according to the invention by a device for processing polycondensates or materials containing polycondensates, in particular for the recycling processing of contaminated polycondensates, wherein the device comprises: a melting device for melting the polycondensates to be processed and for creating a polymer melt, a mixing device downstream of the melting device for mixing the polymer melt, a tempering device downstream of the melting device, in particular a cooling device, for tempering, in particular reducing, the temperature of the polymer melt, a melt reactor connected thereto for treating the mixed and tempered, in particular cooled, polymer melt, in particular for polycondensation or post-condensation, for increasing the intrinsic viscosity and / or for cleaning the polymer melt.

[0016] When recycling different or inhomogeneous materials, different material flows come together, e.g., from the packaging of containers and bottles, which have a high initial viscosity, with materials from the thermoforming film sector, which have a lower melt viscosity, and / or with fibrous materials, which have a very low viscosity. For some PET blends, this results in an average core melt temperature of 275 °C, with a considerable range of + / - 20 °C.

[0017] When a polycondensate melt is treated in a melt reactor, for example an MSP reactor, a reaction and / or purification is carried out under temperature, residence time and with the removal of moisture, oxygen, glycol or other substances.

[0018] If such polymerization or post-condensation is carried out in the melt reactor, the molecular chain distribution becomes narrower the narrower the temperature spectrum of the input melt and the narrower the residence time spectrum in the melt reactor.

[0019] The residence time spectrum in the melt reactor is kept as narrow as possible by appropriate measures, such as conveying systems, level measurements, etc. Furthermore, applying a vacuum and / or purging with inert gases ensures that the reaction proceeds largely uniformly throughout the reactor.

[0020] 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.

[0021] Furthermore, it has proven advantageous to select the absolute temperature of the melt as it enters the melt reactor as low as reasonably possible. While this reduces the reaction rate and increases the time required in the reaction system, it leads to greater process reliability and better final quality. The influence of temperature on reaction rates is subject to an exponential relationship, whereas the change over residence time follows only a linear relationship. By setting a lower melt temperature, the viscosity range or molecular chain distribution can be kept narrower, since short-chain polymer components, i.e., polymer components with lower viscosity, polymerize faster than long-chain molecules at a given temperature.

[0022] It is also important to note that, in addition to the desired polycondensation reactions, various undesirable side reactions occur in the melt reactor, which negatively impact the quality of the final polymer. These side reactions are also considerably less frequent at lower temperatures. Residence time increases these side reactions, but temperature has an exponential effect, meaning that the number of undesirable side reactions increases disproportionately at higher temperatures.

[0023] A particularly undesirable substance in this context is acetaldehyde. Acetaldehyde imparts a fruity apple flavor, especially in beverage bottles, which is extremely undesirable in water packaging. Such byproducts can also have a negative impact on processability.

[0024] The melt viscosity range of the final products is also regularly subject to stringent requirements. For virgin materials, a range of + / - 0.002 dl / g is a common value. Due to the high use of recyclates, this range must also be maintained during reprocessing.

[0025] The varying content of residual catalysts, fillers, etc. influences the reaction rate and, to some extent, the diffusion rate. For these reasons, it is also advantageous to set the lowest practical reaction temperature and temperature range.

[0026] Another typical situation during recycling is the retention of residues of migrating substances, contaminants, etc. in the polymer. These foreign or impure substances regularly lead to a loss of quality in the produced material. For example, a material discolors significantly more at elevated temperatures than with extended exposure times.

[0027] Accordingly, several factors must be taken into account, especially

[0028] - that an increase in the temperature of the melt is often detrimental and undesirable for the subsequent process,

[0029] - that inconsistent and excessively high melt temperatures often lead to quality problems, and / or

[0030] - that a homogenized, mixed, and tempered, especially cooled, melt is often advantageous for improved product quality, thus enabling a constant discharge volume and a homogeneous viscosity distribution. According to the invention, a special combination of extruder, melt mixer, and melt tempering unit, in particular a melt cooler, and a melt reactor, is provided. The requirements and preparation of the melt for a process in an MSP / LSP melt reactor are particularly delicate and demanding – corresponding preparation and adjustment of the melt parameters is accordingly more important and more difficult than, for example, for an SSP.

[0031] For this reason, the invention proposes, when processing polycondensates, particularly from secondary raw material sources, using a melt reactor, to ensure uniformity, tempering, particularly lowering, and narrowing of the melt temperature upstream of the melt reactor. Particular attention must be paid to this, especially given the elevated temperatures regularly encountered in the melt reactor. All of this is ensured by the method and device according to the invention.

[0032] The homogenization of the temperature is to be understood both temporally and spatially, ie the temperature should be as constant as possible over a longer period of time, ie from several minutes to hours, and the local deviation perpendicular to the flow direction should also be as small as possible.

[0033] In every channel system, a certain temperature distribution, or a radial temperature gradient from the inside to the outside, exists perpendicular to the flow direction. Higher throughputs require corresponding channel cross-sections, resulting in local temperature inhomogeneity perpendicular to the flow direction. Local transverse mixing of the melt is therefore advantageous.

[0034] During the continuous process, particularly during the extrusion process, there are also temporal temperature changes. For example, filter cleaning results in temporarily increased shear in the extruder, leading to temporally elevated temperatures. Different material forms, such as regrind, partially crystallized fibers, thick fibers, highly drawn fibers, and even iV differences in the starting material, also cause the material to be sheared differently in the extruder, which also leads to further temporal temperature inhomogeneities and resulting viscosity fluctuations during the process.

[0035] Temperature uniformity: Targeted temperature control reduces the temporal component of temperature deviations. Temperature range reduction: The melt temperature has a distribution across the channel and a distribution over time that is determined by the preceding influences and / or the material components. Mixing reduces this temperature range, as does temperature control.

[0036] In this context, the term "tempering" refers to adjusting the temperature of the melt to the desired or advantageous temperature. This can involve a reduction or an increase in temperature. The tempering device or melt / tempering mixer is accordingly suitable, designed, controlled, and / or intended for cooling and / or heating.

[0037] Tempering advantageously involves a reduction in temperature or cooling. This preferably takes place in a suitable cooling device or in a melt / cooling mixer.

[0038] However, there are also situations in which a – usually rather small – increase in temperature is advantageous or necessary, usually only by a few degrees. This is the case, for example, when the temperature upstream of the cooler is too low, and the melt needs to be heated. For example, if the melt is too cold from the upstream extrusion process because it is very fluid and therefore requires less energy input into the extruder. Accordingly, tempering then involves raising the temperature or heating. This is advantageously carried out in a suitably suitable and designed tempering device or the melt / tempering mixer.

[0039] In the method according to the invention, the processing steps are advantageously carried out in the specified order a) to e).

[0040] However, it is particularly advantageous if steps c) and d) are carried out simultaneously or in a common process step, i.e. if the polymer melt is mixed and tempered, in particular cooled, at the same time.

[0041] In order to improve the purification, it is advantageous if, before steps c) and d), the polymer melt is filtered to remove unmelted components and / or impurities.

[0042] Product quality is also improved by degassing the filtered polymer melt before steps c) and d). Particularly efficient and advantageous mixing and a generally advantageous narrow residence time range are achieved when the polymer melt is mixed distributively.

[0043] It is advantageous for product quality if the polymer melt is mixed and / or tempered, in particular cooled, in such a way that the temperature distribution in the polymer melt, in particular in the phase from before mixing or tempering, in particular cooling, to immediately before the melt reactor, preferably in the phase from the start of melting during extrusion to before the melt reactor, in particular over the entire process, is < + / - 10° C, in particular < + / - 5° C, preferably < + / - 1 ° C. This also makes it possible to achieve a narrow viscosity range or molecular chain distribution.

[0044] In order to achieve high product quality and greater process reliability and to avoid side reactions, it is further advantageous if the polymer melt is tempered, in particular cooled, in such a way that the temperature of the polymer melt immediately before or upon entry into 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).

[0045] In this context, it is also advantageous and the advantages just mentioned can be achieved if the polymer melt is tempered, in particular cooled, in such a way that the temperature of the polymer melt immediately before or upon entry into the melt reactor is only relatively slightly, i.e. by 1 - 10%, above the melting range of the polymer.

[0046] An advantageous process control provides for special steps right at the beginning of the processing process, namely that the polycondensates or materials are comminuted and / or heated before melting according to step b), in particular during step a), wherein it is preferably provided that the polycondensates or materials are heated and permanently mixed while maintaining their lumpiness and flowability, and optionally degassed, softened, dried, increased in viscosity and / or crystallized.

[0047] A further advantageous and efficient method implementation consists in that at least the processing steps c), d) and e), in particular all the provided processing steps, follow one another immediately and directly in time and space, without any further intervening processing steps. In the device according to the invention, it can advantageously be provided that the melt reactor is spatially directly and directly connected in the conveying direction to the mixing device or the tempering device, in particular the cooling device, without any further intervening functional unit, or is downstream of the mixing device or the tempering device, in particular the cooling device, and is coupled one after the other in terms of process.

[0048] An effective and advantageous device provides that the melting device is an extruder, wherein the extruder comprises in particular a melt filter and / or a degassing zone.

[0049] An advantageous overall arrangement for achieving high-quality end products is characterized in that a cutter-compactor is arranged upstream of the melting device, in particular a cutter-compactor-extruder combination being provided for comminuting and / or heating the polycondensates or materials. The cutter-compactor is preferably designed and suitable for heating and continuously mixing the polycondensates or materials while maintaining their lumpiness and flowability, and optionally for degassing, softening, drying, increasing their viscosity, and / or crystallizing them.

[0050] An efficient and advantageous device provides that the mixing device is a distributive mixer.

[0051] It is particularly advantageous in this context if the mixing device is simultaneously the tempering device, in particular the cooling device, wherein in particular a melt tempering mixer or melt tempering / mixer, preferably a melt cooling mixer or melt cooler / mixer, is provided.

[0052] An MSP reactor or an LSP reactor is advantageously provided as the melt reactor.

[0053] For the intended use according to the invention, the exact design of the melt reactor is relatively unimportant. It can advantageously be a melt reactor according to the design described in DE 1745541, but also according to the design described in DE 4013912 or DE 4126425.

[0054] Common to all melt reactors is the attempt to significantly increase the melt's surface area under reduced pressure or in an inert gas flow, triggering a polycondensation reaction to lengthen the polymer chains and thus optimize the polymer's mechanical properties for reuse in a final product. Furthermore, the diffusion process enables the removal of undesirable substances that may have entered the polymer during previous use. This makes it possible to reuse these polymers in applications where food contact compatibility, odor tolerance, and skin compatibility are essential. The reaction products or diffusion products are removed either by vacuum or by the inert gas flow.

[0055] In order to achieve good product quality, it is advantageous if the mixing device and / or the tempering device, in particular the cooling device, or the melt tempering mixer, preferably the melt cooling mixer, are controllable or regulated 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 this temperature distribution is achieved in the area upstream of the mixer or tempering device, in particular the cooler, up to immediately upstream of the melt reactor, preferably in the area of ​​the melting unit or the extruder up to upstream of the melt reactor, in particular in the entire system or device.

[0056] To achieve and maintain good product quality and greater process reliability, it is advantageous if the mixing device and / or the temperature control device, in particular the cooling device, are controllable or regulated such that the temperature of the polymer melt immediately before or upon entry into 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 range can be achieved in the final product.

[0057] In order to also achieve these advantages, it can advantageously be provided that the mixing device and / or the tempering device, in particular the cooling device, are controllable or controlled in such a way that the temperature of the polymer melt immediately before / upon entry into the melt reactor is 1-10% above the melting range of the polymer.

[0058] From a plant engineering perspective, it may be advantageous to use feed pumps for the melt both upstream of the temperature controller, especially the cooler or mixer, and downstream of the temperature controller, especially the cooler or mixer, and / or downstream of the melt reactor to overcome any pressure differences. However, care must be taken to ensure that this does not lead to a significant temperature increase upstream of the melt reactor, especially due to a pump downstream of the temperature controller, especially the cooler / mixer.

[0059] The core temperature of the melt is advantageously selected according to the desired residence time and reaction rate in the melt reactor or reaction vessel. Experience has shown that, in general, the lowest possible core temperature should be attempted.

[0060] The temperature control medium, in particular the cooling medium, of the melt temperature control system, in particular the melt cooling system, e.g., the melt cooler / mixer, is regulated according to the core temperature of the melt. For this purpose, the temperature can be recorded both before and after the melt temperature control system, in particular the melt cooling system. In advantageous temperature control systems, in particular the cooling system, the temperature of the melt can also be measured in the temperature control section, in particular the cooling section. This temperature is used to adjust the temperature control medium, in particular the cooling medium.

[0061] It is advantageous if the melt temperature is sufficiently representative. For example, the melt temperature in a supply pipe can differ considerably between the wall and the center of the pipe. Therefore, it is recommended and useful to measure the temperature both at the wall and in the center of the pipe. The thicker the pipe, the more useful it is to measure at multiple points across the cross-section.

[0062] Advantageous embodiments of the method and device according to the invention are illustrated and explained below using non-limiting, more general and more specific embodiments:

[0063] The recycling of PET materials from a wide variety of sources is often desired, for example from leftover filaments, fiber residues, thermoforming films (e.g. cheese or sausage packaging, tool or electronic packaging), PET bottle material (e.g. water bottles or soft drinks), etc. The viscosity range is usually considerable and amounts to approximately 0.5 dl / g (for fibers) to 0.79 dl / g (for bottle ground material).

[0064] Such an inhomogeneous input material mix results in a correspondingly broad molecular chain distribution and a broad viscosity range. Furthermore, such mixtures rarely contain exactly the same components, meaning the quantitative proportions of the different materials vary and are constantly changing.

[0065] During the melting process, the particles, usually smaller particles in the form of polymer flakes, fibers, or films, experience varying shear stresses depending on their mechanical properties (size, stretching, thickness, etc.) and their viscous properties. This leads to a broad melt temperature distribution, e.g., 276 °C + / - 20 °C (after the extruder), with the adverse effects described above that accompany such a broad and varying temperature distribution. After the filter, the melt temperature distribution is still approximately 277 °C + / - 15 °C. After the melt cooler / mixer, the melt temperature distribution is 260 °C + / - 3 °C, although a range of less than 3 °C is also achievable. Thus, even before the melt reactor, the temperature of the melt is evened out, lowered, and narrowed across its width.

[0066] Example PET (A-PET) for packaging and fibers: Melt temperature ranges PET

[0067] Melting temperature of PET: > 250 °C, typically 256 °C

[0068] Melt temperature during recycling: typically 275 °C to 310 °C (depending on the process, contamination and filtration fineness) Target temperature range before LSP: 260 °C to 270 °C + / - 3 °C

[0069] Cooling in the range of: 5 to 25% (at reference temperature 260 °C)

[0070] Viscosity lift depending on melt temperature:

[0071] The residence time t in the melt reactor is constant.

[0072] The inlet viscosity before the melt reactor is 0.5 dl / g.

[0073] Melt temperature: 270 °C viscosity reached 0.53 dl / g

[0074] Melt temperature: 280 °C viscosity reached 0.57 dl / g

[0075] Melt temperature: 290 °C viscosity reached 0.62 dl / g

[0076] An advantageous schematic of an advantageous device, arrangement, or system 1 is shown in Fig. 1, and an exemplary method is also explained with reference to Fig. 1. This is an exemplary schematic representation illustrating the essential components and units of this device. Accordingly, this representation makes no claim to the final accuracy of all structural details and proportions.

[0077] Not shown in Fig. 1 is an optional container in the form of a conventional cutter-compactor or preconditioning unit (PCU). In this case, this could be arranged to the right, in front of, or upstream of the extruder. Such a cutter-compactor or container is filled with the recycled polymer material to be processed. The polymer material is placed in the container, comminuted using mixing and comminution tools, mixed, and heated until softened, although usually not melted. The sticky polymer particles remain in lumps. In addition, the material undergoes pretreatment, for example, drying, precompaction, and, depending on the material, increasing its viscosity.

[0078] When processing secondary raw materials from polycondensates, an extrusion process is used to melt the polycondensates, depending on the shape of the materials (e.g., fibers, granules, agglomerates, film chips, thick-walled ground material, etc.). The secondary raw materials can originate from various sources and be contaminated with solids or liquids, such as cotton fibers or spinning aids, which may consist of oils. Furthermore, these materials often have different viscosities in their molten state.

[0079] In the lowest section of this cutter-compactor or container, the extruder 2, visible in Fig. 1, can be connected tangentially. The material is discharged from the container and transferred into the extruder 2, where it is captured by the screw. In the front section of the extruder 2, the left section in Fig. 1, the material is melted and plasticized under increased pressure.

[0080] Single-screw extrusion systems or multi-screw extrusion systems, such as twin-screw extrusion systems, can be used for this melting process. The well-known PCU extruder system has proven particularly effective, allowing some unwanted substances to be evaporated in the PCU, and the material to be densified and heated or softened. This system also features forced extruder feeding, which is particularly advantageous for poorly flowing fiber materials. The extruder then melts the material, optionally degassing the polymers. This process can also be supported by vacuum or inert gases in the PCU. The melt is then filtered in a filtration unit 3, which removes solid and gel-like components from the melt.

[0081] Downstream of the filtration unit 3, and following this melting process and the first purification step, the melt is transferred, usually via a melt pump (not shown), to the melt cooler / mixer 4. This is designed to reduce any temperature inhomogeneities that occur, both spatially and temporally. At the same time, the average melt temperature is lowered. This is necessary because, among other things, the variation in the different input materials results in different melt temperatures. Furthermore, the filtration process also leads to temporal or spatial inhomogeneities.

[0082] After the temperature of the melt has been lowered and equalized in the melt cooler / mixer 4, the melt is transferred to the melt reactor 5.

[0083] After undergoing the reaction or purification process in melt reactor 5, the molten material then enters a discharge unit and can be further processed, such as granulation, if necessary. It can also be directly transformed into a final or semi-finished product, e.g., fibers, films, bottle preforms, etc.

[0084] The cooling medium is adjusted in terms of 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 reached. As can be seen in Fig. 1, at least the melt temperature 1 is recorded here and the tempering medium is adjusted so that the desired temperature is reached. This can be checked using the melt temperature 2. The temperature can be measured at different locations within the line, at the outermost edge and / or in the middle of the pipe. For very high system throughputs, it is advantageous to install thicker lines and / or multiple lines. With thick lines, the temperature is advantageously recorded at several points within the pipe.The temperature measurement is ideally carried out using several temperature recording devices, whereby the temperature is recorded representatively over the cross-section of the inlet and / or outlet channel.

[0085] By measuring the temperature distribution within the inlet and outlet lines, both the mixing quality and the cooling rate can be checked. Mixing quality is indicated by the narrower temperature distribution, and cooling quality by the reduction in the average temperature.

[0086] Comparative tests:

[0087] The following tests were conducted on an exemplary test system according to the invention. This was an INTAREMA 80 TE PCU / extruder combination equipped with a SW 4 / 134 melt filter according to the following system configuration:

[0088] The processed materials consisted of fiber waste from various areas of a spinning mill. Start-up waste (lumps), undrawn fibers, monofilaments, and drawn fibers were used. Furthermore, the fibers had different spinning oil contents ranging from 0.3 to 2 wt%. The initial moisture contents also varied, in some cases reaching 10 wt% or more.

[0089] The material was pre-shredded using a single-screw shredder. Alternatively, mills can also be used for this purpose. Using the PCU / extruder combination, the fibers were compacted, dried, and heated. After a suitable residence time in the PCU, they were transferred to the single-screw extruder. After melting, the material was degassed and passed through the melt filter unit.

[0090] The filtered melt was then pumped to the melt cooler / mixer via the melt pump. The cooler / mixer used in this case was a static mixer without moving elements. The cooler / mixer was heated and cooled using thermal oil. The melt temperature was recorded both upstream of the cooler / mixer and downstream to verify the effectiveness of the unit. Furthermore, the viscosity was measured downstream of the melt reactor. Particular attention was paid to the stability of the viscosity over time.

[0091] For comparison, the melt cooler / mixer was removed and the melt was transferred directly into the melt reactor.

[0092] The melt reactor was a horizontal disc reactor, similar to the design described in DE 1745541. The polymer mass is repeatedly passed through the reaction chamber in free-falling streams. Rotating discs draw the polymer mass from a sump, and the polymer mass flows back in as a thin film. This process achieves a very large surface area relative to the volume of the reaction mass, allowing the released reaction products to evaporate quickly and promoting a polymer reaction.

[0093] The disc reactor was pressurized to a vacuum of 6 mbar. The discs rotated at 1 rpm. The average residence time of the material in the reactor was approximately 60 min.

[0094] After leaving the reactor, the material was granulated in the strand granulation.

[0095] The results were as follows:

[0096] Without melt cooler / mixer:

[0097] Throughput of approximately 350 kg / h. A mixture of PET bottle waste, fibers, and thermoforming film was used as input material.

[0098] Operating time approx. 10h

[0099] The melt temperature was recorded upstream of the melt reactor (Fig. 2, lower curve). The temperature of the polymer mass was measured using a temperature sensor immersed approximately 20 mm into the melt stream. The average inlet temperature was approximately 288 °C. The melt temperature fluctuation range was approximately 35 °C.

[0100] The intrinsic viscosity was measured inline after the melt reactor and was on average approximately 0.69 dl / g with a fluctuation range of approximately 0.07 dl / g (Fig. 2, upper curve).

[0101] With melt cooler / mixer:

[0102] Throughput of approx. 350 kg / h.

[0103] The same mixture of PET waste from bottles, fibers and thermoforming films was used as input material.

[0104] Operating time approx. 20h

[0105] The melt temperature was recorded before the mixer / cooler (Fig. 3, middle curve) and after the mixer / cooler (Fig. 3, bottom curve). The temperature of the melt was measured using a temperature sensor immersed approximately 20 mm into the mass flow. The average inlet temperature was approximately 293 °C. The melt cooled to an average of 260 °C.

[0106] The intrinsic viscosity was measured inline after the melt reactor and averaged approximately 0.65 dl / g. The fluctuation range was completely eliminated, thus exceeding the industry standard of + / - 0.002 dl / g (Fig. 3, top curve).

[0107] This clearly shows the advantageous homogenization, predominant lowering and broadening of the melt temperature and the intrinsic viscosity.

Claims

Patent claims 1. A method for processing polycondensates or materials containing polycondensates, in particular for the recycling and processing of contaminated polycondensates, comprising the following processing steps: a) placing 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 creating a polymer melt, c) mixing the polymer melt, d) tempering, in particular cooling, the polymer melt, e) treating the mixed and tempered, in particular cooled, polymer melt in a melting reactor, in particular for polycondensation or post-condensation, for increasing the intrinsic viscosity and / or for purifying the polymer melt.

2. Method according to claim 1, characterized in that the processing steps are carried out in the specified order.

3. 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 that the polymer melt is mixed and tempered, in particular cooled, simultaneously.

4. Method according to one of claims 1 to 3, characterized in that, prior to steps c) and d), the polymer melt is filtered to remove unmelted components and / or impurities.

5. Method according to one of claims 1 to 4, characterized in that degassing of the filtered polymer melt takes place before steps c) and d).

6. Method according to one of claims 1 to 5, characterized in that the polymer melt is mixed distributively.

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

8. Method according to 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 entry into the melting 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. Method according to one of claims 1 to 8, characterized in that the polymer melt is tempered, in particular cooled, such that the temperature of the polymer melt immediately before or upon entry into the melting reactor is 1-10% above the melting range of the polymer.

10. Method according to any one of claims 1 to 9, characterized in that the polycondensates or materials are comminuted and / or heated before melting according to step b), in particular during step a), wherein it is preferably provided that the polycondensates or materials are heated and continuously mixed while retaining their granularity and flowability, and optionally degassed, softened, dried, increased in viscosity and / or crystallized.

11. Method according to one of claims 1 to 10, characterized in that at least the processing steps c), d) and e), in particular all provided processing steps, follow each other immediately and directly in time and space, each without any further intervening processing step.

12. Device for processing polycondensates or materials containing polycondensates, in particular for recycling and processing contaminated polycondensates, comprising a melting device (2) for melting the polycondensates to be processed and for producing a polymer melt, a mixing device (3) downstream of the melting device (2) for mixing the polymer melt, a temperature control device, in particular a cooling device, (4) following the melting device (2) for temperature control, in particular reduction, of the temperature of the polymer melt, a melting reactor (5) connected thereto for treatment of the mixed and temperature-controlled, in particular cooled, polymer melt, in particular for polycondensation or post-condensation, for increasing the intrinsic viscosity and / or for purifying the polymer melt.

13. Device according to claim 12, characterized in that the melting reactor (5) is spatially connected directly and immediately, without any further interposed functional unit, in the conveying direction to the mixing device (3) or the temperature control device, in particular cooling device, (4) or is connected downstream of the mixing device (3) or the temperature control device, in particular cooling device, (4) and is coupled in series in a process-related manner.

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

15. Device according to one of claims 12 to 14, characterized in that a cutting compressor (1) is connected upstream of the melting device (2), wherein in particular a cutting compressor-extruder combination is provided, for comminuting and / or heating the polycondensates or materials, wherein the cutting compressor (1) is preferably configured and suitable for heating and continuously mixing the provided polycondensates or materials while maintaining their granularity and flowability, and optionally degassing, softening, drying, increasing their viscosity and / or crystallizing them.

16. Device according to one of claims 12 to 15, characterized in that the mixing device (3) is a distributive mixer.

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

18. Device according to one of claims 12 to 17, characterized in that the melting reactor (5) is an LSP reactor or an MSP reactor.

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

20. Device according to one of claims 12 to 19, characterized in that the mixing device (3) and / or the temperature control device, in particular cooling device, (4) are controllable or controlled such that the temperature of the polymer melt immediately before or at the entry into the melting 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 cooling device, (4) or before the temperature control mixer, in particular cooling mixer.

21. Device according to one of claims 12 to 20, characterized in that the mixing device (3) and / or the temperature control device, in particular cooling device, (4) are controllable or controlled such that the temperature of the polymer melt immediately before / upon entry into the melting reactor (5) is 1-10% above the melting range of the polymer.

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