Procedure for the treatment of waste containing synthetic materials

Abstract

A process for recycling waste containing synthetic materials, comprising at least one target polymer and at least one substance to be separated, wherein a) the waste containing synthetic materials is mixed with at least one swelling agent, to swell the at least one target polymer to form a polymer gel as a first phase with a polymer content of > 30% by weight, referred to the total mass of the target polymer and the swelling agent contained in the polymer gel, and b) at least one impurity that is not soluble in the first phase is separated from the polymer gel by filtration, using a sieve with a mesh size of 1 to 1000 μm as the filtration device, and the swollen polymer gel is conveyed through the sieve, wherein the target polymer is selected from the group consisting of polystyrenes, polyolefins, polyesters, polycarbonates, polyamides and their copolymers, as well as combinations or mixtures thereof; and The insoluble impurity is selected from the group consisting of fillers and reinforcing substances, inert impurities, foreign polymers, duromeric adhesive layers or foams, and heavy metal pigments, the polymer gel having a dynamic viscosity in the range of 100 mPas to 10,000 Pas, measured in accordance with ISO 6721-10: 1999.

Description

Procedure for the treatment of waste containing synthetic materials The invention relates to a process for recycling waste containing synthetic materials. The invention also relates to the use of the process. Synthetic materials are often used in composite materials, with the specific materials being chosen for the particular composite. For example, in modern flexible packaging materials, complex and highly functional multilayer composites are used as multilayer films to achieve a wide range of functionalities, such as sealing capabilities, selective permeation properties, and mechanical and optical properties tailored to the specific application requirements. In this case, mixtures are used with special additives or with additives with filler and reinforcing materials, composite materials of synthetic material-synthetic material and composite materials of synthetic material-metal or composite materials of synthetic material-non-metal, in general composite materials of synthetic / non-synthetic material. During the production and after-use of products containing synthetic materials, large quantities of synthetic waste are generated. This waste holds significant potential for valuable materials, which should be harnessed for resource efficiency. Given this, the recycling quotas specified in EU directives (Packaging, WEEE, and ELV directives) also require at least partial recycling of synthetic materials, including the large quantities of mixed composite waste and shredder residues. However, recycling materials from this waste containing synthetic material is not yet state-of-the-art due to its high content of contaminants, such as halogenated aromatic compounds and heavy metals, and the variety of materials. Because of the diversity of polymers, contaminants, and impurities in this mixed and composite waste, highly efficient sorting, separation, and processing of synthetic material would be necessary to produce high-quality recycled materials that meet new product specifications. This required separation technique is not currently available for the waste containing the aforementioned synthetic material. Conventional waste separation processes for pure synthetic materials with external contamination, based on differences in density, electrostatic properties, fragility, spectroscopic and optical properties, etc., fail in this case. Thermal and raw material procedures have been developed for the disposal of composite waste containing contaminants and disruptive substances (pyrolysis such as Haloclean and others or SUSTEC Schwarze Pumpe; Hornung, A.; Bockhorn, H.; Hornung, U. (1999): Gradual gasification of plastic mixtures from household and electronic waste collections. VDI Reports No. 1492, p. 687 et seq.; Uddin, MA; Bhaskar, T.; Kaneko, J.; Muto, A.; Sakata, Y.; Matsui, T. (2002) "Dehydrohalogenation during pyrolysis of brominated flame retardant containing high impact-resistant polystyrene (HIPS. Br) mixed with poly(vinyl chloride) (PVC). Fuel 81, pp. 1819-1825"; SVZ (2001): We close the circle. Fact sheet from the Center of Recycling of Secondary Raw Materials Schwarze Pump (SVZ) .The disadvantage is that, at best, new petrochemical raw materials are produced or only the calorific value of synthetic materials is utilized. Alternatively, approaches to material recycling have been published that, despite the complex management of multi-stage procedures, lead to recycled materials of mixed, undefined, and therefore inferior synthetic material, the so-called downstream recycling (document US 2007 / 0054106 A1). Various solvent-based recycling procedures (Selektive Extraktion: Maurer, A., Schlummer, M. (2004) "Good as new. Recycling plastics from WEEE and packaging waste". Waste Management World, May-June 2004, pp 33-43; and documents EP 0949293 A2 or JP 2000146540 or DE 19927523 A1 or Bruce E. Naumann's base patent: document DE 69033888 T2), which obtain high added value due to their high cleaning performance. The disadvantage of these solution procedures is the high solvent currents which, with the usual low concentrations of synthetic material solutions (Naumann explicitly mentions a polymer loading of 5-20%), add up to approximately 10 times the mass flow of the recycled material. These large quantities of solvents must be recovered within the process in an energy-intensive manner. Recovery is achieved through thermal drying of the purified polymer solution, evaporation, and distillation—procedures that are very costly in terms of both operating and investment costs. As disadvantageous as the low polymer loads (uneconomical operation) are the large proportions of undissolved filter residues that are contaminated with a lot of solvent, which must be washed subsequently in several stages and in which the foreign polymers or residual substances are often very swollen due to this long exposure time and must be dried in an energy-intensive way for further treatment. These disadvantages of the state of the art ultimately lead to solvent-based recycling procedures only being cost-effective for large flow rates (> 1,000 kg / h) and, if possible, in continuous operation of 3 or 4 shifts, since the high investment costs are only amortized with large yields (scale factor) and frequent start-up and shutdown of the installation, especially in the distillation and solvent recovery area (process stages that are typically run continuously), is time-consuming and energy-intensive and therefore expensive. Based on this, the mission of the present invention is to enable economical and simplified recycling of waste containing synthetic materials. Document DE 102005 026451 A1 refers to a process for recycling synthetic materials, whereby a target polymer is produced as a gel-like precipitation product from which the soluble and insoluble constituents are separated. EP 1616 903 A1 reveals a device for filtering polystyrene resin in a gel state containing foreign matter. This device involves bringing polystyrene resin residues into contact with a solvent to produce a gel. The foreign matter is then separated by filtration. Document WO 94 / 12565 A1 relates to a procedure for separating the composite material from the per se soluble synthetic material with other materials, with which it comes into contact with a swelling agent and swells, and then the synthetic material is removed from the rest of the composite material by a mechanical procedure in a swollen state. This problem is solved by the process for recycling waste containing synthetic material according to claim 1. Claim 11 relates to the use of the process. The other dependent claims relate to preferred embodiments. According to the invention, a process for recycling waste containing synthetic materials containing at least one target polymer and at least one substance to be separated (valuable or disruptive substance), wherein a) the residue containing synthetic material is mixed with at least one swelling agent under swelling of at least one target polymer to form a polymer gel as a first phase with a polymer content of > 30% by weight, based on the total mass of the target polymer and the swelling agent contained in the polymer gel, and b) at least one substance insoluble in the first phase is separated from the polymer gel by filtration, where a sieve with a mesh size of 1 to 1000 pm is used as a filtration device and the swollen polymer gel is conveyed through the sieve, The target polymer is selected from the group consisting of polystyrenes, polyolefins, polyesters, polycarbonates, polyamides and their copolymers, as well as combinations or mixtures thereof; and The insoluble impurity is selected from the group consisting of fillers and reinforcing materials, inert contaminants, foreign polymers, thermosetting adhesive layers or foams, and heavy metal pigments, the polymer gel having a dynamic viscosity in the range of 100 mPas to 10,000 Pas, measured in accordance with ISO 6721-10: 1999. In the case of the process according to the invention, it is possible to work with smaller quantities of solvent, based on the polymer yield, and with simple groups that are cost-effective even with low yields. It is important to maintain the advantages of the dissolution process, namely, a high cleaning potential by removing dissolved polymers at the molecular level, while reducing the disadvantages (complex multi-stage process with high energy and investment costs). By selectively swelling the target polymer, viscosity is reduced. This is important for improving filtration, i.e., the separation of insoluble substances. Diffusion rates are also increased, which is important for better extraction of soluble substances. In or after step a) of the procedure according to the invention, a liquid phase of the swelling agent or phase that is immiscible with the polymer gel is preferably formed as the second phase in which at least one substance is dissolved. Compared to known dissolution processes, selective swelling is distinguished by at least one of the following characteristics: 1. The swollen polymer gels produced have a higher polymer content, typically > 30%, in particular > 50%. 2. The viscosity of the swollen target polymers is clearly higher than that of the known polymer solutions. 3. While known polymer solutions are homogeneously single-phase and can be homogeneously diluted with the addition of solvent, target polymers with selective swelling agents behave differently: the target polymer only swells to a certain point, meaning the resulting polymer gel no longer absorbs any more swelling agent. A heterogeneous mixture of two gel phases and excess swelling agent forms. Here, the possibility of separating the substances is offered: the highly viscous gels can be filtered under pressure and the excess swelling agent contains soluble substances and can be easily separated from the gel, making multi-stage or countercurrent extraction possible. Operating costs can be reduced due to the small quantities of solvent or blowing agents in circulation, which are evaporated and processed by thermal distillation. Only a fraction (10-50%) of the thermal energy requirement for the closed solvent cycle is needed. Valuable insoluble substances, impurities, and harmful components (both external and internal), such as fillers and reinforcing agents, inert contaminants, foreign polymers, thermosetting adhesive layers or foams, heavy metal pigments, etc., can be more easily separated by filtration (at higher flow rates) at a lower temperature due to their lower viscosity (compared to filtration of the molten material). The lower temperature means less quality loss, e.g., due to thermo-oxidative damage. Furthermore, fewer processing stabilizers are required. Finer sieves are also used. The pressure drop across the sieve is lower, therefore elastomeric contaminants are separated more effectively by filtration; that is, they are less "squeezed" through the sieve. Swollen polymer gel can be conveyed through a sieve at a lower pressure than molten polymer.Due to the lower shear stress, the chains remain intact. There is also significantly less thermo-mechanical stress on the organic impurities and foreign polymers being separated: reduced cross-contamination (e.g., by PVC) and, consequently, significantly less material damage and molecular weight reduction. The original properties and quality of the target polymer are preserved. The separated foreign polymers are also of high quality and unchanged due to the gentle treatment, making subsequent recycling possible. Valuable substances, impurities, and soluble contaminants, such as unwanted old additives and their reaction products, as well as low-molecular-weight polymer degradation products, oligomers, and residual monomers, can be efficiently extracted from the swollen target polymer due to significantly higher diffusion rates. This minimizes the long temperature and time load that is often otherwise required for vacuum degassing, e.g., for PS (polystyrene) or for solid-phase post-condensation of PET (polyethylene terephthalate) or PA (polyamide), and reduces undesirable thermally induced side reactions, such as decomposition and monomer removal, or, e.g., acetaldehyde formation in the case of PET. It is also advisable to use a 5-10% swelling agent as a filtration aid. Low molecular weight contaminants are then removed by vacuum degassing in-line or downstream. The separation effect and reduced internal friction are beneficial in this case. The advantages include a simplified procedure compared to the dissolution-precipitation process, which achieves a polymer content of 40-50% even with very high purification yields. Instead of four or five process stages in four or five different units (dissolution, filtration, optional extraction, precipitation, and drying), the precipitation stage is eliminated, and all impurity removal stages by selective swelling (swelling, filtration, optional extraction, and drying) are carried out in a single unit (an extruder with degassing and dosing of the swelling agent before melt filtration). Furthermore, due to the smaller circulating masses resulting from the use of less solvent, the equipment is smaller while maintaining the same polymer yield. This significantly reduces investment costs, enabling cost-effective operation even with lower yields and allowing for recycling tailored to customer requirements. Furthermore, the extruders offer excellent scalability, ensuring a safe and low-risk market entry. The polymer gel is preferably dried by removing the swelling agent and converted into a polymer granule, returning the swelling agent removed from the polymer gel to the process, optionally in purified form. In this case, the polymer gel exhibits a dynamic viscosity in the range of 100 mPas to 10,000 Pas (measured according to ISO 6721-10: 1999). It is also preferable that waste containing synthetic materials be mixed with the blowing agent and melted in an extruder. This particularly facilitates the blowing of the target polymer. Furthermore, it is particularly preferred that the polymer gel have a polymer content of > 50% by weight, in particular 70 to 90% by weight, based on the total mass of the polymer and swelling agent contained in the polymer gel. This allows for filtration at a pressure ranging from 0.5 bar to 300 bar. Consequently, the polymer gel is subjected to lower shear stress during filtration. Due to this lower shear stress, the polymer chains, particularly those of the target polymer, remain intact. Preferably, the filtration temperature is maintained within the range of 20 °C to 300 °C. As a result, both the target polymer and the filter material are exposed to the lowest possible thermal stress, thus improving effective recycling. The diffusion coefficient of the substances dissolved in the procedure according to the invention can be in the range of 3.0 *10-12 cm2 / s to 1.0 *10-9 cm2 / s. The following data may apply to gel filtration: Diffusion coefficient for DEHP on PS at 1 ppm DEHP and 80 °C: 3.281 *10-12 cm2 / s, from Migratest® Lite, FA-BES Diffusion coefficient of DEHP in S at 20% DEHP and 80 °C: 1.2 *10-10 cm2 / s Diffusion coefficient of DEHP in S at 30% DEHP and 80 °C: 5.5 *10-10 cm2 / s Diffusion coefficient of DEHP in S at 40% DEHP and 80 °C: 1.4 *10-9 cm2 / s (Hellwege, Knappe and Loge, Kolloid-Zeitschrift, vol. 179 (1), p. 40 et seq.) The substances that can be separated are halogenated substances, in particular fluorinated, chlorinated, brominated or mixed halogenated aromatic hydrocarbons, or aliphatic hydrocarbons, with special preference polychlorinated or polybrominated aromatic hydrocarbons or flame retardants. In addition, valuable substances and / or impurities, non-metals, composite materials, glass, fillers, foreign synthetic materials, and inert organic or inorganic components can be separated as substances. Halogen-free liquids are preferably used as swelling agents, particularly water, alcohols, aldehydes, ketones, acids, alkalis, aliphatic hydrocarbons, aromatic hydrocarbons, esters, ethers, heterocycles, or mixtures thereof. The appropriate swelling agent can be selected depending on the target polymer and the substances to be separated. Furthermore, in the process according to the invention, the substances insoluble in the swelling agent can preferably be collected as a filter cake in the filtration device. For this purpose, a device can be used to separate waste substances containing synthetic materials containing target polymers, which has a feed for the waste containing synthetic materials, an extruder, a device for dosing the swelling agent, a filtration device, and a device for removing the swelling agent. This device may also include a pre-mounted mixer. Additionally, it may feature a granulation unit, which converts the purified polymer into a form that is easy to process. Furthermore, the device may have a rotating filtration device, in particular a rotating sieve, for example, for continuous discharge of the filter cake. Additionally, the procedure is used for recycling composite waste, packaging waste, electroplating waste, additive compositions, multilayer composite materials, synthetic / synthetic composite materials, synthetic / non-synthetic composite materials, and in particular synthetic / metal composite materials and synthetic / non-metal composite materials, according to the invention. The object according to the application will be explained in more detail with reference to the following Figures 1 to 3, without restricting it to these variants. Figure 1 shows a schematic diagram for molten filtration of swollen electroplating waste. Figure 2 shows a diagram illustrating the increase in melt viscosity due to the proportion of solvent in the grinding material. Figure 3 shows the pressure dependence of the percentage of swelling agent content in ABS. Figure 1 schematically illustrates the process cycle. Electroplating waste processed into grinding media is melted in an extruder, and a defined quantity of solvent is added upstream of the melt filter. Alternatively, dosing takes place in an upstream mixer. The resulting low-viscosity melt is then filtered using a high-capacity continuous melt filter, e.g., from Ettlinger. The solvent is subsequently removed from the melt in a vacuum degassing dome, and the polymer is granulated at the end of the extrusion screw. The filter cake, with its high chromium, nickel, and copper content, is continuously discharged via a rotary filter system and is available for the chemical etching processes described in the prior art to recycle the metals. Figure 2 shows the increase in melt viscosity of synthetic waste materials as a function of solvent content in the grinding media. ABS (acrylonitrile butadiene styrene copolymer) grinding media was mixed with varying amounts of an unlabeled solvent, and the melt flow index (MFI) was determined as a measure of viscosity. Due to the expected decrease in viscosity, measurements were performed at lower temperatures of 190 and 200 °C instead of the standard MFI conditions for ABS (220 °C, 10 kg). Figure 2 clearly demonstrates the effect of solvent dosage: a 5% solvent dosage leads to an increase in MFI by a factor of 3–4, and a 10% dosage to an increase by a factor of 8.5. To estimate the reduced pressure drop across a filter caused by the addition of a swelling agent, an ABS grade was mixed with 0, 5, and 10% swelling agent, and the MFI was measured at 200 °C under different loading weights (or pressures). This is shown in Figure 3. With increasing swelling agent content, an average MFI of 13.3 ± 1.8 g / 10 min remained constant under lower loading weights or pressures. In this example, the addition of a 10% swelling agent corresponds to a pressure reduction of 5.

Claims

1. A process for recycling waste containing synthetic materials, comprising at least one target polymer and at least one substance to be separated, wherein (a) the waste containing synthetic materials is mixed with at least one swelling agent to swell the at least one target polymer to form a polymer gel as a first phase with a polymer content of > 30% by weight, based on the total mass of the target polymer and the swelling agent contained in the polymer gel, and (b) at least one impurity that is not soluble in the first phase is separated from the polymer gel by filtration, using a sieve with a mesh size of 1 to 1000 pm as the filtration device, and the swollen polymer gel is conveyed through the sieve, wherein the target polymer is selected from the group consisting of polystyrenes, polyolefins, polyesters, polycarbonates, polyamides and their copolymers,as well as their combinations or mixtures; and the insoluble impurity is selected from the group consisting of fillers and reinforcing substances, inert impurities, foreign polymers, duromeric adhesive layers or foams, and heavy metal pigments, the polymer gel having a dynamic viscosity in the range of 100 mPas to 10,000 Pas, measured in accordance with ISO 6721-10:1999.

2. A process according to the preceding claim, characterized in that during or after step a), a liquid phase of the swelling agent, which is not miscible with the polymer gel, is formed as a second phase in which at least one substance is dissolved.

3. A process according to any one of the preceding claims, characterized in that the polymer gel is dried by removing the swelling agent and is converted into a polymer granule,1. Recirculating the blowing agent removed from the polymer gel back into the process in purified form.

2. A process according to any one of the preceding claims, characterized in that the waste containing synthetic materials is melted in an extruder.

3. A process according to any one of the preceding claims, characterized in that the polymer gel has a melt flow index (MFR), measured according to ISO 1133, in the range of 1 to 100 g / 10 min.

4. A process according to any one of the preceding claims, characterized in that the polymer gel has a polymer content of >50% by weight, in particular 70 to 90% by weight, based on the total mass of the polymer and blowing agent contained in the polymer gel.

5. A process according to any one of the preceding claims,characterized in that a temperature in the range of 20 °C to 300 °C is maintained during filtration.

8. A process according to any of the preceding claims, characterized in that the separating substances are halogenated substances, in particular fluorinated, chlorinated, brominated, or mixed halogenated aromatic hydrocarbons, or aliphatic hydrocarbons, especially polychlorinated or polybrominated aromatic hydrocarbons, or flame retardants.

9. A process according to any of the preceding claims, characterized in that halogen-free liquids are used as swelling agents, in particular water, alcohols, aldehydes, ketones, acids, alkalis, aliphatic hydrocarbons, aromatic hydrocarbons, esters, ethers, heterocyclic compounds, or mixtures thereof.

10. A process according to any of the preceding claims,characterized in that the substances insoluble in the swelling agent are collected in the form of a filter cake in the filtration device.

11. Use of the process according to any one of claims 1 to 10 for recycling composite waste, packaging waste, electroplating waste, additive compositions, multilayer composite materials, synthetic / synthetic composite materials, synthetic / non-synthetic composite materials, in particular synthetic / metal composite materials, synthetic / non-metal composite materials.

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