PLANT AND METHOD FOR THE RECYCLING OF CONTAMINATED POLYOLEFINS

Description

Technical field

[0001] The invention relates to a recycling plant and a recycling process for contaminated polyolefins, in particular for HDPE from packaging material such as beverage containers. State of the art

[0002] With population-driven resource consumption increasing, recycling processes are gaining importance, particularly for polymers used in packaging. However, this reuse is severely limited for food packaging, as the recycled materials must be suitable for direct food contact again. This requires that any contaminants in the material do not transfer to the food in unacceptable quantities. The constantly tightening legal requirements in the food sector restrict the use of recycled material and—depending on the type of polymer—lead to very poor recycling rates, especially in the packaging sector. While PET packaging is relatively unproblematic in this respect, and the material from PET bottles can (to a limited extent) be used again for the production of PET bottles, there is a need for improvement with polyolefins such as HDPE.On the one hand, the large number of different HDPE packaging materials makes recycling difficult, and on the other hand, the removal of contaminants from the material of HDPE bottles is a problem that has not yet been satisfactorily solved.

[0003] The measured reduction of a presumed maximum possible contamination ("challenge test" concentration) to a residual concentration serves as a measure of the cleaning performance of a recycling process, allowing different recycling processes to be evaluated and compared. Some of the processes evaluated so far are indeed suitable for cleaning HDPE material, but they take so long that economic viability is not possible.

[0004] German patent application DE 42 07 370 A1 discloses a process for removing pesticides from plastic containers contaminated with pesticides, particularly those made of polyethylene. This allows the plastic containers to be recycled. The process involves shredding the plastic into strips and combining them with a solvent, causing the plastic to swell and extracting the pesticide. The pesticide-contaminated solvent is then separated from the plastic by sieving. After sieving, the plastic strips are degassed. This requires heating the solvent, which is achieved by applying heat.

[0005] US patent 5,368,796 discloses a method for cleaning polyethylene films. The films are shredded and transferred to a solvent bath containing an organic solvent. Additional cleaning is achieved by friction, for example, by intensive stirring in the bath. The solvent is separated from the shredded film by boiling.

[0006] From DE 10 2004 002 159 A1, a process is known in which polymers are freed from impurities by bringing the polymers into contact with a liquefied gas or a supercritical fluid, which serves as a solvent for the impurities. By reducing the pressure, the solvent can be separated from the polymer. Only after separation is the solvent completely depressurized, causing the gas to become gaseous or the fluid to become subcritical. This allows the impurities to be separated from the solvent.

[0007] US patent 2002 / 0128394 A1 describes a process for producing a polypropylene mixture. This involves reacting high molecular weight polymers with a first solvent and low molecular weight polymers with a second solvent. This results in the formation of two liquid phases.

[0008] A polypropylene fraction can be separated from one of the liquid phases. Degassing yields a polypropylene mixture.

[0009] German patent DE 42 33 740 A1 discloses a process which enables the separation of cross-linked polyethylene from metal-containing composite parts by swelling the polyethylene. The swelling leads to the separation of the composite.

[0010] WO 03 / 106546 A1 shows a system consisting of a stirred tank and a connected filter vessel. In the stirred tank, a plastic contaminated with heavy metals is dissolved in a solvent, and the heavy metals are filtered out of the solution in the filter vessel. Object of the invention

[0011] It is an object of the present invention to provide an alternative recycling process for contaminated polyolefins, wherein the purified polyolefin material obtained by the process is preferably suitable for use in food packaging. Furthermore, the process should be economically feasible. Further advantages of the present invention will become apparent from the following description. Description of the invention

[0012] The above-mentioned problem is solved by a method according to claim 1 and a recycling plant according to claim 9.

[0013] Among other things, a recycling process for contaminated polyolefins is disclosed, wherein a contaminated polyolefin material is swollen in the presence of a solvent, whereby impurities present in the polyolefin material dissolve in the solvent, and the solvent and the impurities dissolved in the solvent are removed from the polyolefin material.

[0014] Also disclosed is a recycling plant for recycling contaminated polyolefins with a swelling reactor, for example in the form of a stirred tank or a cascade of stirred tanks or a tubular reactor, containing a solvent, wherein the solvent is a solvent with a lower polarity than water, wherein the swelling reactor is designed to swell a contaminated polyolefin material in the presence of the solvent in order to convert the polyolefin material into

[0015] to dissolve existing impurities in the solvent. Downstream of the swelling reactor (or as part of the swelling reactor), the recycling plant includes a section for removing the solvent and the impurities dissolved in the solvent from the polyolefin material, in order to obtain a purified polyolefin material.

[0016] The following features are described, which are to be considered (individually) as preferred features, even if they are not explicitly designated as such. The features are to be disclosed separately (as part of any process and / or any system) and – insofar as they are not mutually exclusive – in any combination. This includes the possibility of simultaneously implementing all described features.

[0017] Of particular interest as a polyolefin that can be purified using the method and / or recycling plant described in this document is HDPE (high-density polyethylene). Therefore, this polymer is used below as an example to explain the invention. However, the disclosures relating to HDPE are also disclosed alternatively for polyolefins in general and, in particular, for the preferred polyolefins mentioned in this document.

[0018] Contaminants, especially those consisting of nonpolar molecules, can migrate into the HDPE matrix and accumulate there in very high concentrations. They are released from the HDPE matrix only very slowly, even when high temperatures (100-300°C) and a steep concentration gradient are used to remove these contaminants during the recycling process.

[0019] The present invention aims to modify HDPE so that it releases impurities more easily and with less technical effort. This is achieved by exploiting the swelling properties of polyolefins: A swollen polymer is generally more voluminous, with larger molecular distances and a lower density. Therefore, it allows impurities to diffuse outwards much faster than a non-swollen polymer, assuming the same concentration gradient of the impurities. Furthermore, two additional effects can significantly enhance the cleaning effect. Firstly, a swollen polymer can be mechanically squeezed like a sponge, thereby removing many of the impurities it contains. Secondly, impurities are carried away when the solvent used for swelling is removed.

[0020] Therefore, a recycling process for contaminated polyolefins is disclosed, which can be carried out in a recycling plant such as the plant described in this document.

[0021] The recycling process involves the removal of contaminants from a contaminated polyolefin material, particularly from areas far from the surface of the contaminated polyolefin material.

[0022] The removal of impurities from contaminated polyolefin material involves swelling the contaminated polyolefin material in the presence of a solvent and / or using a solvent. During this process, impurities present in the polyolefin material dissolve in the solvent. The solvent and the impurities dissolved in the solvent can then be removed from the polyolefin material together and / or simultaneously.

[0023] The recycling process can meet all the criteria of the European Food Safety Authority (EFSA) in accordance with EU Regulation EC282 / 2008 and EU Regulation 1935 / 2004 and their amendments.

[0024] The recycling performance of the recycling process can be assessed by the CEF Panel (EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids) using a so-called challenge test. In this test, the polyolefin material is contaminated with predetermined contaminants at predetermined concentrations, and the concentrations of these contaminants are measured after the recycling process. The recycling process can significantly reduce or even completely remove common contaminants such as benzene, toluene, and / or xylene. The recycling process can also significantly reduce or even completely remove specific contaminants such as di-tert-butylhydroxyltoluene (BHT), phenylcyclohexane, methyl stearate, zinc stearate, trichloroethane, trichloromethane, butyl salicylate, methyl palmitate, lindane, and / or benzophenone.Naturally, the concentration of contaminants that may be present in the solvents used can also be greatly reduced or even completely removed.

[0025] The recycling process yields purified polyolefin material that is at least partially suitable for food contact. This purified polyolefin material can then be used for packaging suitable for food products.

[0026] The contaminated polyolefin material may be made from one or more polyolefins and / or contain a total polyolefin content of at least 60, 80 or 90 percent by weight.

[0027] The one or more polyolefins may advantageously be PP (polypropylene) and / or PE (polyethylene), in particular LDPE (low-density polyethylene) and / or LLDPE (linear low-density polyethylene) and / or HDPE (high-density polyethylene) and / or UHMWPE (ultra-high molecular weight polyethylene), with HDPE being preferred.

[0028] Alternatively or additionally, one or more of the polyolefins can be a thermoplastic elastomer or a plastomer.

[0029] Preferably, the polyolefin material contains less than 20 or 10 percent by weight of foreign polymers such as barrier layers.

[0030] The contaminated polyolefin material is preferably in solid form, especially when swelling.

[0031] The contaminated polyolefin material may have been processed into pieces (for example, "flakes") before swelling and / or may already be in the form of pieces when swelling, with the pieces preferably having a maximum dimension (distance between the furthest points) of no more than 40, 30, or 25 millimeters and / or at least 0.25, 0.5, or 1 millimeter. This facilitates swelling and, due to the large surface area, mass transfer and thus purification. Preferably, at least 90 or 95 percent by weight of the contaminated polyolefin material has this form.

[0032] The contaminated polyolefin material can be separated from foreign substances such as glue or paper before swelling and, if necessary, sorted by color.

[0033] The contaminated polyolefin material preferably originates from food packaging, especially bottles.

[0034] According to one theory, the impurities present in the contaminated polyolefin material are so-called "NIAS" ("non-intentionally added substances").

[0035] The impurities present in the contaminated polyolefin material may (in particular in the majority and / or in a proportion of at least 40, 60 or 80 percent by weight of the impurities) comprise molecules that are nonpolar or substantially nonpolar and / or have at least 5, 8 or 10 and / or at most 70, 50 or 40 carbon atoms and / or have a molecular weight of at least 20 Daltons and at most 1000 Daltons.

[0036] Alternatively or additionally, the impurities present in the contaminated polyolefin material (especially in the majority and / or in a proportion of at least 40, 60 or 80 percent by weight of the impurities) may include substances from one or more of the following groups of substances: aliphatic saturated hydrocarbons, aliphatic unsaturated hydrocarbons, aliphatic hydrocarbons with functional groups, aromatic hydrocarbons, aromatic hydrocarbons with functional groups, fragrances (especially terpenes such as limonene), flavorings.

[0037] The impurities present in the contaminated polyolefin material may (in particular in the majority and / or in a proportion of at least 40, 60 or 80 percent by weight of the impurities) include molecules that fall under the term MOSH (Mineral Oil Saturated Hydrocarbons) and / or the term MOAH (Mineral Oil Aromatic Hydrocarbons).

[0038] Swelling of the contaminated polyolefin material in the presence of the solvent results in the production of a swollen polyolefin material.

[0039] The swelling is preferably carried out until the volume of the contaminated polyolefin material has increased by at least 0.3, 0.5 or 0.8 and / or at most 40, 20 or 7 percent, with a volume increase of 1 to 5 percent being particularly preferred.

[0040] Preferably, the contaminated polyolefin material is swollen at a temperature of at least 0, 100 or 150 degrees Celsius and / or at most about 10°C below the melting temperature of the respective polyolefin.

[0041] Furthermore, it is advantageous if the contaminated polyolefin material is swollen under overpressure, especially at a pressure of at least 1, 50 or 100 bar and / or at most 1000, 500 or 250 bar.

[0042] Alternatively or additionally, it can be provided that the contaminated polyolefin material is swollen in the presence of a solvent, the solvent being in a liquid state or in a supercritical state.

[0043] The contaminated polyolefin material can be allowed to swell for at least 0.5, 1 or 2 hours and / or at most 10, 5 or 3 hours.

[0044] It is advantageous to agitate the polyolefin material and / or the solvent during swelling (especially relative to each other). For example, the polyolefin material and / or the solvent can be stirred.

[0045] According to one variant, the swelling of the contaminated polyolefin material is carried out using a percolation process (continuous flow process). In this process, the solvent flows past the contaminated polyolefin material, which then absorbs the solvent. The flow of the solvent past the polyolefin material ensures that locally contaminated solvent flows off and is replaced by less contaminated solvent.

[0046] In another variant, the swelling of the contaminated polyolefin material is carried out using an immersion process. In this process, the contaminated polyolefin material is immersed in the solvent, and the polyolefin material and solvent are preferably stirred. This facilitates the equalization of the impurity concentration in the solvent.

[0047] In another variant, the swelling of the contaminated polyolefin material is carried out while the polyolefin material and the solvent are passed in countercurrent flow. Preferably, the solvent has a lower concentration of impurities at all times during the mass transfer than the contaminated polyolefin material with which it is in contact, so that the concentration gradient always decreases from the polyolefin phase towards the solvent phase. For this purpose, uncontaminated or only slightly contaminated solvent is fed in at the point where the "leached" contaminated polyolefin material is withdrawn. Conversely, at the point where the contaminated polyolefin material is fed in, the solvent, now laden with impurities, is withdrawn. This is done in process engineering equipment known to those skilled in the art, preferably tubular reactors or stirred tank reactor cascades.

[0048] The solvent containing dissolved impurities is also referred to in this document as the "contaminated solvent". The contaminated solvent can be purified and reused as a solvent in the process, in particular for swelling the contaminated polyolefin material, whereby the purification of the contaminated solvent can be carried out, for example, by distillation or rectification.

[0049] The solvent can be a solvent of low polarity or a nonpolar solvent. On the one hand, the solvent can preferably be less polar than water, preferably as polar as or less polar than acetone. On the other hand, the solvent can be as polar as or more polar than n-hexane.

[0050] According to one version, the solvent is an alkane, in particular n-hexane or n-heptane.

[0051] Preferably, the solvent and the contaminated polyolefin material have a RED ("relative energy difference") according to Hansen (source: Charles M. Hansen: Hansen Solubility Parameters: A User's Handbook, 2nd edition, CRC Press, Boca Raton, 2007, ISBN 0-8493-7248-8) of at most 3, 2, or 1.

[0052] The solvent used in the present process can consist of a single type of solvent or of several types of solvents, i.e., a solvent mixture. Preferably, the solvent consists of at least 80, 90, or 95 percent by weight of one type of solvent, for example n-hexane, as this makes it easier to purify.

[0053] If the solvent contains more than one type of solvent, it is preferred that the boiling points of two of the solvent types used differ by at least 2, 5, or 10 degrees Celsius and / or at most 100, 50, or 30 degrees Celsius, so that they can be easily separated by distillation. It is further preferred that the solvents do not form an azeotrope.

[0054] Removing the solvent and / or impurities dissolved in the solvent from the polyolefin material can advantageously involve mechanical compression of the swollen polyolefin material, resulting in a pressed polyolefin material. For example, a screw press or a belt filter press can be used for the mechanical compression of the swollen polyolefin material. By mechanical compression, at least 60, 80, or 90 percent of the solvent and / or impurities dissolved in the solvent can be advantageously removed from the polyolefin material.

[0055] The swollen polyolefin material preferably has a volume that is at least 0.3, 0.5 or 0.8 and / or at most 40, 20 or 7 percent larger than the non-swollen polyolefin material and / or the squeezed polyolefin material.

[0056] According to one variant, the process step in which the polyolefin material is swollen and the process step in which the swollen polyolefin material is subjected to mechanical compression can each be performed once. Alternatively, the aforementioned process steps can be performed multiple times (for example, two, three, or more times each) during the process and / or with the same polyolefin material.

[0057] It can be provided, for example, that the swollen polyolefin material is subjected to mechanical compression, whereby a portion (in particular at least 30, 20, or 10 percent) of the (contaminated) solvent present in the swollen polyolefin material is removed from the polyolefin material. Subsequently, the resulting compressed polyolefin material can be swollen again in the presence of a solvent (i.e., the same, a different, or a purified solvent), whereby any remaining impurities present in the polyolefin material dissolve in the solvent. Afterward, the resulting swollen polyolefin material can be subjected to mechanical compression once more. According to one variant, the solvent can be purified after one or each mechanical compression before being used again for swelling. According to another variant, this purification can be omitted.

[0058] The recycling process and / or the removal of the solvent (preferably with impurities dissolved in the solvent) from the polyolefin material may include (first) drying of the polyolefin material (especially the pressed polyolefin material) in a dryer, whereby solvent remaining in the polyolefin material is evaporated, resulting in a dried polyolefin material.

[0059] Although this does not have to be the first drying of the polyolefin material, this drying is referred to as "(first) drying" (only) to distinguish it from the "second drying" described below.

[0060] It is advantageous to expose the polyolefin material to a gas, particularly an inert gas such as nitrogen, for (initial) drying. The evaporated solvent can then be recovered from the gas, for example, using a cold trap.

[0061] It is also conceivable that the (first) drying is carried out under vacuum and / or in a vacuum dryer and / or that it is carried out under reduced pressure, in particular at a pressure of less than 1 (fine vacuum), 300 (rough vacuum) or 1013 (negative pressure) mbar absolute.

[0062] The (first) drying is expediently carried out at a temperature that is (preferably at least 5 or 10 degrees Celsius and / or at most 50, 30 or 20 degrees Celsius) below the melting temperature (peak temperature according to ISO11357-3-2013) of the polyolefin material and / or the gas with which the polyolefin material is exposed for (first) drying has such a temperature.

[0063] It is advisable to carry out the (first) drying at a temperature that is above the boiling point of the solvent and / or the impurities remaining in the polyolefin material.

[0064] The (first) drying is preferably carried out at a pressure of at least 1, 300 or 1013 mbar absolute and / or at most the vapor pressure of the solvent at the corresponding drying temperature.

[0065] The (first) drying is preferably carried out for a duration of at least 60, 30 or 10 minutes and / or at most 30, 20, or 10 hours.

[0066] The dryer used for the (first) drying of the polyolefin material can be, for example, a drum dryer or a fluidized bed dryer.

[0067] The recycling process and / or the removal of impurities from the contaminated polyolefin material can involve melting and extruding the polyolefin material (especially the dried polyolefin material). The polyolefin can then be granulated to obtain polyolefin granules.

[0068] For extrusion, an extruder with a degassing zone is preferably used. This allows any solvent remaining in the polyolefin material to be removed.

[0069] Furthermore, it may be stipulated that the polyolefin material undergoes melt filtration.

[0070] When removing the solvent and / or impurities from the polymer material, beneficial additives may also be removed. Therefore, it may be necessary to add one or more additives (especially essentially the same additives that were previously removed) to the molten polyolefin material. These one or more additives could, for example, be one or more process stabilizers such as antioxidants.

[0071] The recycling process and / or the removal of impurities from the contaminated polyolefin material can include (second) drying, in particular vacuum drying, of the polyolefin material (especially the polyolefin granules). The drying can be carried out, for example, in a solid-state polycondensation reactor (SSP reactor).

[0072] Although this does not necessarily have to be the second drying of the polyolefin material, this drying is referred to as "(second) drying" (only) to distinguish it from the "first drying" described above.

[0073] Preferably, the (second) drying is carried out under reduced pressure (especially at a pressure below 1013 mbar (atmospheric pressure under standard conditions)) and / or under vacuum below 50 mbar. Alternatively, the (second) drying can be carried out under increased pressure, especially at a pressure up to the vapor pressure of the respective solvent at the corresponding drying temperature, and / or the polyolefin material can be exposed to a gas, especially an inert gas such as nitrogen, for drying purposes.

[0074] The (second) drying is expediently carried out at a temperature that is (preferably at least 5 or 10 degrees Celsius and / or at most 50, 30 or 20 degrees Celsius) below the melting temperature (peak temperature according to ISO11357-3-2013) of the polyolefin material and / or the gas with which the polyolefin material is optionally exposed for drying has such a temperature.

[0075] The (second) drying is preferably carried out at a pressure of at least 1mbar, 5mbar or 50mbar and / or at most 1bar, 10bar or 100bar.

[0076] The (second) drying is preferably carried out for a duration of at least 1 minute, 5 minutes or 10 minutes and / or at most 30 hours, 20 hours, or 10 hours.

[0077] Furthermore, drying can take place in an atmosphere consisting of at least 99, 98, 98, or 90 percent nitrogen by volume.

[0078] Disclosed is also a recycling plant for recycling contaminated polyolefins, in particular for carrying out the recycling process disclosed in this document and / or for removing contaminants from contaminated polyolefin material. The polyolefin material may, in particular, be the polyolefin material described above in connection with the recycling process.

[0079] According to one theory, the recycling plant could be an upgraded or converted PET recycling plant, i.e., a plant for recycling polyethylene terephthalate.

[0080] The recycling plant includes a swelling reactor, for example, in the form of a stirred tank reactor, a cascade of stirred tank reactors, or a tubular reactor. The swelling reactor contains a solvent, which is a solvent with lower polarity than water and / or the solvent described above in connection with the recycling process. The swelling reactor is designed to cause the contaminated polyolefin material to swell in the presence of the solvent in order to dissolve or wash out any impurities present in the polyolefin material.

[0081] The swelling reactor is configured to swell the contaminated polyolefin material in the presence of the solvent at or during the temperature, pressure, and / or time described above in connection with the process. The swelling reactor is characterized by its ability to swell the contaminated polyolefin material at a pressure between 1 and 1000 bar, and preferably between 1 and 250 bar, using the solvent. In particular, the swelling reactor can be configured to swell the contaminated polyolefin material at a temperature approximately 10°C below the melting point of the respective polyolefin material.

[0082] Furthermore, the swelling reactor is designed to agitate the polyolefin material during the swelling process, particularly by stirring. For this purpose, the swelling reactor may, for example, include a stirrer.

[0083] The swelling reactor may be designed to achieve the swelling of the polyolefin material by means of a percolation process, an immersion process, or by passing the polyolefin material and the solvent in countercurrent flow, particularly as described above in connection with the recycling process.

[0084] The recycling plant has a downstream (i.e., located below) section of the plant for removing the solvent and the impurities dissolved in the solvent from the polyolefin material.

[0085] In particular, such a plant component may include a filter for filtering out the solvent and / or means for pressing out the swollen polyolefin material.

[0086] Advantageously, the recycling plant has one or more separation stages and / or washing stages upstream of the swelling reactor (i.e., arranged upstream of it).

[0087] These can be designed to separate foreign materials, such as paper labels, from the polyolefin material.

[0088] The recycling plant may advantageously include one or more of the following separation stages (especially upstream of the source reactor in the specified order): metal separator (for separating magnetic and / or non-magnetic metals); label remover (for removing labels); ballistic sorter (for removing films); bottle sorter (for sorting by color); manual sorting stage; air classifier (for example, for removing labels and sleeves); float-sink separation stage (separation by sinking in water); sorting stage using NIR spectroscopy (near-infrared spectroscopy; for separating foreign plastics and / or dust).

[0089] The recycling plant may advantageously include one or more of the following washing stages (especially upstream of the source reactor in the specified order): Washing stage with water and, if necessary, one or more surfactants such as an alkaline solution; Washing stage with hot water (for example, to remove paper and cardboard); Washing stage for final washing with water and / or for neutralizing the alkaline solution.

[0090] After separation and / or washing, the polymer material can be dried before being fed into the swelling reactor. Preferably, a dryer is arranged between the separation and / or washing stages upstream of the swelling reactor and the swelling reactor itself.

[0091] The recycling plant may include a mill for shredding products made from the polyolefin material, such as containers and closures. Preferred particle sizes are specified above in connection with the process, with processing into flakes being particularly preferred.

[0092] The mill can, for example, be located downstream of one or more of the separation stages mentioned above and / or upstream of one or more of the washing stages mentioned above. In particular, the washing of the polymer material can take place after comminution.

[0093] Furthermore, the recycling plant may have a dryer downstream of the swelling reactor, as described above in connection with the (first) drying process.

[0094] A downstream plant section for purifying the solvent, in particular by means of distillation or rectification, and for returning the purified solvent to the swelling reactor is preferably also provided.

[0095] Finally, a purified polyolefin material is disclosed, produced by a process described in this document and / or by means of a recycling plant described in this document, wherein the purified polyolefin material is preferably in the form of granules.

[0096] Terms in this document should preferably be understood as they would be understood by a person skilled in the art. If several interpretations are possible in a given context, each interpretation should preferably be disclosed individually. In particular, in the event of any ambiguity, the preferred definitions listed in this document may be used as an alternative or supplement.

[0097] When this document refers to the removal of impurities dissolved in the solvent from the polyolefin, this also includes, alternatively, the removal of impurities present in the polyolefin. This is because purification steps such as SSP are capable of removing not only impurities dissolved in the solvent from the polyolefin, but also those that are not dissolved in the polyolefin.

[0098] Furthermore, the subsequent patent claims are additionally disclosed by reference to any one of the preceding patent claims ("according to one of the preceding claims"), even if they are not claimed in this form. Brief description of the drawings

[0099] They show: Fig. 1 ad a recycling process (flowchart in 4 parts in the order 1a, 1b, 1c, 1d) Implementation of the invention

[0100] The invention is explained below by way of example with reference to the drawings.

[0101] In the Figs. 1a to 1d The process for recycling contaminated polyolefins is illustrated. The process essentially consists of four parts: In the first part (shown in Fig. 1a ) the polyolefin material is sorted and then shredded.

[0102] In a second part (shown in Fig. 1bThe shredded polyolefin material is then washed, dried and, if necessary, sorted again.

[0103] In a third part (shown in Fig. 1c Impurities are removed from the washed and dried polyolefin material by swelling it with a solvent, causing the impurities present in the polyolefin material to dissolve in the solvent. Subsequently, the solvent and the dissolved impurities are first mechanically separated from the polyolefin material, and then any remaining solvent is removed in a dryer.

[0104] In a fourth part (shown in Fig. 1d ) After passing through an optional further sorting step, the polyolefin material is melted, extruded, granulated and fed into an SSP reactor where it is subjected to vacuum treatment.

[0105] Fig. 1aThe polyolefin material to be cleaned comes, for example, from containers, especially bottles, and closures, and can be delivered to the recycling plant in bales. The bales are broken down at the recycling plant (11). The containers are fed to a first metal separator (12), which removes magnetic metal (12a). The containers then pass through a label removal stage (13) before being fed to a ballistics sorter (14), which removes films (14a). In a second metal separator (15), non-magnetic metals (15a) are separated, followed by color sorting in a color bottle sorter (16), which removes containers of a different color (16a) and collects them in a mixed fraction (16b).Finally, the sorted containers are cut into flakes in a mill (18), which are separated from remaining labels and sleeves (19a) in an air classifier (19).

[0106] Fig. 1bThe flakes are washed with water and surfactants such as an alkali (21), separated by density in a separation stage (22), and foreign polymers such as PET, PC, and / or PVC (22a) are removed. A subsequent wash in hot water (23) removes paper and cardboard fibers (23a), which are collected as sludge. If an alkali was used beforehand, a second wash can also serve to neutralize the alkali (24). After passing through the washing stages, the flakes are dried and fed into an air classifier (25). Any remaining foreign plastics (26a) can be identified using an NIR spectrometer (26), allowing them to be removed. Finally, the flakes are packaged (27) and tested (28). If the flakes fail the test, they are rejected as bulky material (28a). If the flakes pass the test, they are processed further (29).

[0107] Fig. 1cA solvent (n-heptane in this example) is added to the flakes, and the flakes are initially mixed with the solvent by stirring (31). Under increased pressure and temperature, the flakes absorb the solvent, i.e., they swell (32). Solvent not absorbed by the flakes is removed by a filter, and the flakes are then pressed (33), thereby removing the solvent and dissolved impurities (33a) from the flakes. The aforementioned steps are repeated one (or more) times (34, 35, 36) to remove any remaining impurities (36a) from the flakes. Finally, the pressed flakes are dried (37), whereby any solvent remaining in and on the flakes, along with any remaining volatile impurities (37a), evaporates.The solvent and impurities can be separated using a cold trap, whereby the impurities can be burned off in a burner (37). The dried flakes are then tested again (38). Only those flakes that pass the test are processed further (33), the rest are sorted out as bulk material (38a).

[0108] Fig.1d The flakes (41), which have been collected in a silo (42), are optionally fed to a (third) metal separator (43) in which flakes of metal (43a) are removed. The flakes are then melted, extruded, and granulated (44), the extrusion of which may include melt degassing (44a) to remove residual solvent and / or volatile impurities.

[0109] The polyolefin granules (44c) produced by granulation can be collected and packaged (44b). These granules, which may not yet be suitable for use in the food sector (44c), can be tested (44d). If they pass the test, they are released for use in food packaging (50), and if they fail, they are rejected (bulky material, 49a). Alternatively, the polyolefin material can be tested after granulation (45). If the color of the granules does not meet the requirements, additives can be added (45b), and the modified polyolefin material can be returned to the silo (42). If the granules pass the test (45), they can be made available directly for applications outside the food sector (45a) or fed into an SSP reactor (46) where they undergo vacuum treatment.The treated granules are collected (47) and intended for use in the food sector (48), and are tested for this purpose (49) before being released (50). If the test is passed, the product is released (50); if it fails, it is sorted out as bulky goods (49a).

Claims

1. A recycling process for contaminated polyolefins, including removal of contaminants from a contaminated polyolefin material (11), wherein - a contaminated polyolefin material (11) is swelled by means of a solvent (31,34), to dissolve contaminants present in the polyolefin material in the solvent, and - the solvent and the contaminants in the solvent are removed from the polyolefin material (33a,36a) - characterized in that the removal of the contaminants dissolved in the solvent from the polyolefin material includes a compression of the swollen polyolefin material (33,36), through which a majority of the solvent is pressed out of the swollen polyolefin material, with the pressed-out polyolefin material preferably dried thereafter in a drier (37), through which solvent remaining in the pressed-out polyolefin material is vaporized (37a).

2. The process of claim 1, characterized in that the polyolefin material in essence consists of polyethylene or polypropylene.

3. The process of one of the foregoing claims, characterized in that the polyolefin material is melted and extruded (44), preferably with an extruder having a degasification zone being used for this (44a), to remove residual solvent from the polyolefin material, with the polyolefin material then being granulated to extrusion (44), through which a polyolefin granulate is obtained.

4. The process of claim 3, characterized in that the polyolefin granulate is heated in a solid-state condensation reactor (SSP reactor) (46), preferably with this occurring in a vacuum.

5. The process of one of the foregoing claims, characterized in that the contaminated polyolefin material, preferably present in the form of containers, before being swelled in the presence of the solvent, is comminuted to flakes (18), and foreign materials, for example paper or metal, are separated out of the polyolefin material via one or more sorting processes in a dry condition (19) and / or through one or more washing steps in water (21).

6. The process of one of the foregoing claims, characterized in that the contaminated polyolefin material is swollen by means of the solvent (32) at a temperature of about 10 °C below the melting temperature of the particular polyolefin material, and at a pressure between 1 and 1000 bar, for at least 5 minutes, with the polyolefin material being moved during this, especially stirred.

7. The process of one of the foregoing claims, characterized in that the contaminated polyolefin material is swollen by means of the solvent (32), with the volume of the contaminated polyolefin material increasing through the swelling by at least 1 percent.

8. The process of one of the foregoing claims, characterized in that the solvent is a solvent having lower polarity than water, with the solvent preferably being an alkane, especially an n-hexane or n-heptane.

9. A recycling system for the recycling of contaminated polyolefins, featuring: - a swelling reactor, for example in the form of a stirring vessel (32,35), a stirring vessel cascade, or a tube reactor, containing a solvent, with the solvent being a solvent with a lower polarity than water, with the swelling reactor being so configured as to swell a contaminated polyolefin material in the presence of the solvent (32,35), to dissolve contaminants present in the polyolefin material in the solvent, - a system component (33) placed downstream of the swelling reactor, for removal of the solvent and the contaminants dissolved in the solvent, from the polyolefin material characterized in that the swelling reactor (32,35) is so configured so as to swell the contaminated polyolefin material by means of the solvent at a pressure between 1 and 1000 bar and preferable between 1 and 250 bar and during this, to move the polyolefin material, especially by stirring and that the system component (33) placed downstream of the swelling reactor for removal of the solvent from the polyolefin material, and of contaminants dissolved in the solvent, includes means for compression of the swollen polyolefin material and / or a drier.

10. The recycling system of claim 9, characterized in that - it is an upgraded or converted PET recycling system, and / or - the recycling system has separation and washing stages (19,22,23) placed upstream of the swelling reactor (32,35) for separating out foreign materials such as paper labels, from the polyolefin material, as well as a drier (37) placed downstream of the swelling reactor.

11. The recycling system of one of claims 9 or 10, characterized by an extruder with a granulator (44) placed downstream of the swelling reactor (32,35) for melting, extruding and granulating of the polyolefin material, as well as an SSP reactor (46) placed downstream of the granulator.

12. The recycling system of one of claims 9 to 11, characterized by a system component placed downstream of the swelling reactor (32,35) for purification of the solvent, especially by means of distillation or rectification, and for recycling the purified solvent back into the swelling reactor.

13. The recycling system of one of claims 9 to 12, characterized in that the swelling reactor (32,35) is so configured so as to swell the contaminated polyolefin material by means of the solvent at a temperature of about 10 °C below the melting temperature of the particular polyolefin material and during this, to move the polyolefin material, especially by stirring.

14. The recycling system of one of claims 9 to 13 for conducting the process of one of claims 1 to 8.