Method and pre-processing arrangement for pre-processing a foam mix for feeding a reactor of a recycling process for recovering raw materials and respective computer program

Abstract

Method (100) for pre-processing a foam mix for feeding a reactor of a recycling process, which comprises performing a first sorting step (102) for selecting, target foam pieces that comprise target foam material that is suitable for the reactor, transporting (104) the selected target foam pieces to a shredding unit, shredding (106), the selected target foam pieces to form shredded foam elements, performing a second sorting step (108) for selecting target foam elements from the shredded foam elements, transporting (110) the selected target foam elements to a milling unit; and milling (112) the selected target foam elements to form target foam flakes suitable for feeding to the reactor.

Description

[0001] Method and pre-processing arrangement for pre-processing a foam mix for feeding a reactor of a recycling process for recovering raw materials and respective computer program

[0002] Description

[0003] The present invention is directed to a method for pre-processing a foam mix for feeding a reactor of a recycling process for recovering raw materials, to a pre-processing arrangement and to a computer program.

[0004] Currently, in the field of foam recycling, innovative alternatives are being developed and deployed that are categorized as chemical recycling (vs. mechanical recycling). This will take the plastic resin back to its base state - for instance in the case of polystyrene foam (PS foam), back to a styrene monomer, or in the case of polyurethane foam (PU foam) back to the aromatic diisocyanates (e.g. TDI, MDI) and Polyol. TDI is typically used to make flexible polyurethane foam for furniture, bedding, carpet underlay and other products. MDI is primarily used to make rigid polyurethane foams used as insulation for homes, but may also be present in flexible foam formulations.

[0005] An example of typical pre-processing steps for foam recycling, in particular for polystyrene foams, are summarized in the website https: / / www.recyclefoam.org / about-foam-recycling. Foam residues are either placed in the same container as other recyclables or are taken to a dedicated drop-off center. From there, the recyclables are delivered to a sorting facility or material recovery facility (MRF) where the foam is either separated from other recyclables (mechanically or manually) or are kept separated from the other recyclables. The foam pieces are delivered to a grinder or shredder from where they are transferred to a densifies or press, where the loose foam elements are compacted for storage or transportation to the recycling facility. Another example of the steps of a pre-processing method for a polystyrene foam mix can be found in the website https: / / www.homeforfoam.com / recycling.

[0006] In a mechanical recycling process, the foam flakes are typically mixed with a binding agent and the mixture is steamed and pressed, for instance in a cylindrical press, a process with is antibacterial and actives the binding agent. After the pressed cylinder has dried, it can be peeled to a desired thickness. The rolls are ultimately cut to size into a recycled foam product, for instance as fall absorbing plates or sound or heat isolating material.

[0007] Polyurethane is one of the most important materials of the wide-ranging and diverse family of polymers and plastics. It can be solid or have an open cellular structure. In this case it is referred to as foam. Foams, in turn, can be flexible or rigid. Polyurethane is typically manufactured by reacting polyols and diisocyanates, both products derived from crude oil. A series of additives are then added to produce high-quality PU foam products. The nature of the additives depends on the application the foam will be used for, which include, among others, bedding, furniture, and automotive.

[0008] In the case of flexible PU-foam, the main application for mechanical recycling is re-bounded foams, e.g. for carpet underlays. Mainly post industrial waste, rather than post costumer waste, flex foams are shredded, and the single pieces are glued together with a PU-adhesive and pressed to form a carpet underlay. Mechanical recycling processes are described, for instance, in documents US 5290818 A, US 6136870 A or US 9410026 B1 .

[0009] The brochure "The end-of-life of flexible polyurethane foam from mattresses and furniture. An overview of regulatory drivers, recycling technologies and remaining challenges” issued by the European Association of Flexible Polyurethane Foam Block Manufacturers (https: / / europur.org / wp-content / uploads / 2022 / 04 / EoL-Brochure-2021- EUROPUR.pdf), August 2021, in particular in Part II, addresses the evolution of recycling technologies, namely mechanical recycling, chemical recycling and thermochemical recycling.

[0010] The scientific publication by M. Grdadolnik et al. titled Insight into Chemical Recycling of Flexible Polyurethane Foams by Acidolysis, ACS Sustainable Chem. Eng. 2022, 10, 3, 1323-1332 describes an exemplary chemical recycling process for polyurethane foams.

[0011] Other examples of chemical recycling processes are disclosed, for instance in documents DE 102016122275 A1, DE 102013106364 A1, WO 2021023889 A1, and US 20220251328 A1.

[0012] In the particular and exemplary case of mattress manufacturing plants, several types of materials are used when manufacturing mattresses. Many mattresses include parts such as fabric covers, polyurethane foam padding, and metal springs. Mattress factories also generate grades of by-products such as LDPE Mattress Bags and Old Corrugated Containers OCC. Mattress plant recycling services aim to recycle or reuse all of these materials. Some recycling services solely address end of life materials discarded by the general public. However, mattress factory recycling services offer waste management solutions for scrap materials generated from manufacturing operations.

[0013] End-of-Life PU foams made from flexible PU foam waste (e.g., mattresses, upholstered furniture, car seats, etc.) consist of a mixture of different PU foam types, referred to herewithin as PU foam materials, whose composition may contain a variety of compositions (standard foam, high resilient foam, viscoelastic etc.) and / or additives, such a fillers, flame retardants, styrene-acrylonitrile (SAN), dyes, etc. Producing a high-quality product from an unsorted feed mixture, in particular for a chemical recycling process, is therefore not possible. Various problems occur if the target foam material is not properly sorted, especially for chemical recycling. Firstly, low quality product is expected when no proper sorting is carried out beforehand, particularly in the case of high-quality chemical recycling, whose ultimate goal is to provide polyols with virgin-polyol quality that are suitable as 1:1 substitutes thereof. This results in most cases in an off-specification product after the chemical recycling. Further, technical damage of the different process steps during chemical recycling can happen, if the stream of unsuitable material is not sorted properly. The chemical reaction conditions cannot be optimized in terms of energy preservation and product conversion. Low throughput and high retention times are the consequence of feeding non-suitable foam material to the reactor. Without a sorting step, the quality of the products resulting from a chemical recycling process is typically poor, as undetermined compositions or the presence of undetermined additives lead to unknown side reaction products. Besides, product yield deteriorates with different foam materials and additives, as post-processing yield, such as phase separation and filtration, is influenced by the additives.

[0014] For example, PU foam can be recycled chemically into the basic feed stocks of PU e.g. into Polyols and Isocyanates. A promising feedstock for this process is end of life material e.g. PU foam mattresses. For chemical reasons, it does make sense to separate PU foam mattresses into mattresses made from standard foam, viscoelastic foam, high resilient (HR) foam, etc. Further discriminations e.g. according to SAN content or flame retardant content optimizes the performance and product qualities that can be achieved in a chemical recycling process. To achieve a homogeneous feed material of high content of standard Polyols suitable for a high-quality chemical recycling process it is necessary to pre-process the mattress feed stock. Pre-processes can include operation steps such as transportation, sorting, shredding, baling, feeding to reactors. A critical problem that has not been solved up to now is to optimize the combination of these process steps in a way that the pre-processing reaches the maximum economic efficiency. Compared to treatment processes for other (non-foam) recycling materials for PU foams special problems arise due to the low density of the material and the large dimensions of the material, making an efficient handling mandatory to be economically successful.

[0015] The approach to studying the pre-processing method has been derived by developing and combining different kind of technological concepts. These concepts assume that the foam pieces are collected, typically at collection and presorting facilities and then compressed into bales. So the pre-processing starts with the reception of end-of-life foam pieces, which can include foam articles for instance upholstered furniture, foam boards, e.g. for insulation purposes, automobile seats, mattresses, etc. and ends with the start of the foam recycling process. In general, different approaches have been investigated, which include: a) collecting foam articles or pieces, coarse shredding these foam pieces, sorting to separate a particular type or types of foam (the so-called target foam material) from other foam types, fine shredding of positively sorted foam and feeding the foam flakes to a recycling reactor; b) collection of foam articles or pieces, sorting the non-shredded articles or pieces using robotic systems, fine shredding the positive sorted foam pieces and feeding the fine shredded foam elements to a recycling reactor; c) upon reception of the end-of-life foam articles and pieces, sorting the foam articles to separate the pieces with target foam material from the remaining foam pieces, baling the target foam pieces, transporting the bales to the recycling plant, unbaling the foam pieces fine shredding the foam pieces and feeding the fine shredded foam pieces to the recycling reactor.

[0016] However, these available pre-processing methods have disadvantages that include unnecessary bailing and transportations costs for foam pieces not suitable for the recycling process, high costs associated to dosing of foam pieces (e.g. mattresses) via robotic systems, or low product quality due to a high inhomogeneity of foam materials fed to the reactor.

[0017] It is therefore an object of the present invention to provide a method of pre-processing a foam mix that enables a general reduction of the recycling costs and, in particular in the case of chemical recycling, results in a higher yield.

[0018] According to a first aspect of the present invention, a method for pre-processing a foam mix for feeding a reactor of a recycling process for recovering raw materials is presented. The foam mix comprises a plurality of foam pieces, which may comprise also complete foam articles, such as mattresses. The method comprises the steps of:

[0019] - performing a first sorting step for selecting, from the foam mix, target foam pieces that comprise target foam material that is suitable for the reactor;

[0020] - transporting the selected target foam pieces to a shredding unit;

[0021] - shredding, at the shredding unit, the selected target foam pieces to form shredded foam elements;

[0022] - performing a second sorting step for selecting target foam elements from the shredded foam elements;

[0023] - transporting the selected target foam elements to a milling unit;

[0024] - milling, at the milling unit, the selected target foam elements to form target foam flakes that are suitable for the reactor. Optionally, the method of the first aspect may comprise the step of feeding the target foam flakes to the reactor for recovering raw materials.

[0025] According to the invention, a foam mix including one or more foam pieces, which can be whole foam articles such as mattresses, vehicle seats, upholstered chairs or sofas, or portions thereof corresponds to the starting material. Two separate sorting steps are performed. The first sorting step is done prior to the shredding step to separate those foam pieces that comprise the target foam material that suits a predetermined recycling process. Those foam pieces that are not selected are separated and no longer take part in the pre-processing method of the first aspect, and the transport costs associated thereto are reduced, especially in cases where the first transporting step involves the transport of the foam pieces from a material recover facility to the recycling plant by truck, rail, air or ship transport.

[0026] Foam, also referred to as foamed plastic, is a synthetic resin converted into a sponge-like mass with a closed-cell or open-cell structure, either of which may be flexible or rigid. Foam is used for a variety of products, including cushioning materials, air filters, furniture, toys, thermal insulation, sponges, plastic boats, panels for buildings, lightweight beams, etc. Under appropriate conditions almost every thermosetting or thermoplastic resin can be converted into a foam. Plastics that are commonly foamed include vinyls, polystyrene, polyethylene, phenolics, silicones, cellulose acetate and urethanes, such as polyurethane (PU). PU foams is typically used in the fabrication of mattresses and upholstery. Different types of PU foams include, for instance, standard PU foam, high resilience (HR) PU foam, viscoelastic PU foam, etc. Depending on foam parameters such as the density or chemical compositions, PU foams are available as, for example, and non-restrictively, charcoal foam, dry fast foam, high density foam, lux foam (evlon foam), latex-rubber foam, rebond foam, etc , which are all open-cell Polyurethane foams.

[0027] However, foam pieces may comprise a mixture of foam materials and some of the selected foam pieces may include foam materials that are not suitable for the recycling process. Thus, a second sorting step is carried out after the target foam pieces are shredded. Shredded foam pieces are referred to as foam elements. This enables a better sorting of the foam pieces, for minimizing the risk of feeding to the reactor foam material other than the target foam material, which is the foam material or foam materials that are suitable for the recycling process. Feeding unsuitable foam material to the recycling process can result in a contamination of the reactor or of the process and thus in a decrease of the yield and in an increase of the costs.

[0028] Thus, the pre-processing method of the first aspect of the invention offers an optimal balance in terms of cost reduction and yield improvement compared to known pre-processing method or strategies.

[0029] In the following, developments of the method of the first aspect of the invention will be described.

[0030] In a development the method further comprises the step of:

[0031] - pressing the selected target foam pieces for forming pressed target foam pieces prior to the step of transporting the selected target foam pieces, as pressed target foam pieces to the shredding unit.

[0032] This is particularly advantageous for pre-processing that involves transporting the selected foam pieces comprising target foam material by means of truck, railway, airplane or ship transport since the volume of the selected foam pieces is reduced during the pressing step.

[0033] Alternatively, or additionally, another development of the method of the first aspect includes pressing the selected target foam elements for forming pressed target foam elements prior to the step of transporting the selected target foam elements as pressed target foam elements to the milling unit. This is particularly advantageous in developments where the transporting step after the second involves the use of truck, railway, airplane or ship transport.

[0034] Alternatively, or additionally, another development of the method of the first aspect includes pressing the target foam flakes for forming pressed target foam flakes prior to the step of feeding the target foam flakes, as pressed target foam flakes, to the reactor. This is particularly advantageous in developments of the pre-processing methods that require a transport (e.g. road, rail, air or sea transport) of the target foam flakes from the milling unit to the recycling reactor. In a particular development the method includes pressing the target foam flakes, in particular using an extruder. This is particularly advantageous for controlling dosage of target foam flakes into the reactor, especially when the reactor vessel of the reactor is pressurized.

[0035] In a preferred development the step of shredding the selected target foam pieces results in shredded foam elements with a maximum dimension in the range of 100 mm to 500 mm. Additionally, or alternatively, in another development, the step of milling the selected target foam elements results in milled target foam flakes with a maximum dimension smaller than 120 mm preferably smaller than 90 mm even more preferable smaller than 70 mm.

[0036] Preferably, in a development, the first sorting step and / or the second sorting step is, or are, performed using one or more of optical sorting methods, in particular one or more optical sorting methods selected from the group consisting of a near-infrared spectroscopy based method, a medium-infrared spectroscopy based method, a Raman spectroscopy based method, a UV-VIS spectroscopy based method, an optical camera based method, a laser induced breakdown spectroscopy method an X-ray fluorescence based method and a THz spectroscopy based method.

[0037] Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) is the measurement of the interaction of infrared radiation with matter by absorption, emission, or reflection. It is used to study and identify chemical substances or functional groups in solid, liquid, or gaseous forms. It can be used to characterize new materials or identify and verify known and unknown samples.

[0038] The infrared portion of the electromagnetic spectrum is usually divided into three regions; the near-, mid- and far- infrared, named for their relation to the visible spectrum. The higher-energy near-IR, approximately 14,000-4,000 cm-1 (0.7-2.5 pm wavelength) can excite overtone or combination modes of molecular vibrations. The mid-infrared, approximately 4,000-400 cm-1 (2.5-25 pm) is generally used to study the fundamental vibrations and associated rotational-vibrational structure. For instance, near infrared spectroscopy (NIRS) is a spectroscopic method that uses the near-infrared region of the electromagnetic spectrum (approximately from 700 nm to 2500 nm). Typical applications include medical and physiological diagnostics, and control quality. Near-infrared spectroscopy is not a particularly sensitive technique, but it can be very useful in probing bulk material with little or no sample preparation. Instrumentation for NIRS includes a source, a detector, and a dispersive element (such as a prism, or, more commonly, a diffraction grating) to allow the intensity at different wavelengths to be recorded. The instrumentation is very similar to that used for the UV-visible and mid-IR ranges.

[0039] UV-VIS spectroscopy refers to absorption spectroscopy or reflectance spectroscopy in part of the ultraviolet and the full, adjacent visible regions of the electromagnetic spectrum. Being relatively inexpensive and easily implemented, this methodology is widely used in diverse applied and fundamental applications. The only requirement is that the sample absorb in the UV-VIS region, i.e. be a chromophore. Absorption spectroscopy is complementary to fluorescence spectroscopy. Parameters of interest, besides the wavelength of measurement, are absorbance (A) or transmittance (%T) or reflectance (%R), and its change with time. UV / VIS spectroscopy is routinely used in analytical chemistry for the quantitative determination of diverse analytes or sample, such as transition metal ions, highly conjugated organic compounds, and biological macromolecules.

[0040] Raman spectroscopy is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. Raman spectroscopy is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified. Typically, a sample is illuminated with a laser beam. Electromagnetic radiation from the illuminated spot is collected with a lens and sent through a monochromator. Elastic scattered radiation at the wavelength corresponding to the laser line (Rayleigh scattering) is filtered out by either a notch filter, edge pass filter, or a band pass filter, while the rest of the collected light is dispersed onto a detector.

[0041] Laser induced breakdown spectroscopy is a type of atomic emission spectroscopy which uses a highly energetic laser pulse as the excitation source. The laser is focused to form a plasma, which atomizes and excites samples. The formation of the plasma only begins when the focused laser achieves a certain threshold for optical breakdown, which generally depends on the environment and the target material.

[0042] X-ray fluorescence (XRF) refers to the emission of characteristic "secondary" (or fluorescent) X-rays from a material that has been excited by being bombarded with high-energy X-rays or gamma rays. The phenomenon is widely used for elemental analysis and chemical analysis.

[0043] Terahertz spectroscopy detects and controls properties of matter with electromagnetic fields that are in the frequency range between a few hundred gigahertz and several terahertz (abbreviated as THz). In many-body systems, several of the relevant states have an energy difference that matches with the energy of a THz photon. Therefore, THz spectroscopy provides a particularly powerful method in resolving and controlling individual transitions between different many-body states.

[0044] In a preferred development, the first sorting step is performed using a handheld near infrared spectroscopy device.

[0045] In a development, the first sorting step and / or the second sorting step comprises:

[0046] - performing a first analysis step for determining first composition data of a sample foam piece or sample foam element under analysis, the first composition data being indicative of a composition of the sample foam piece or sample foam element;

[0047] - performing a second analysis step for determining second composition data of the sample foam piece or sample foam element, the second composition data being indicative of the composition of the sample foam piece or sample foam element; and - selecting the sample foam piece as a target foam piece or the sample foam element as target foam element upon determining that the first composition data and the second composition data are indicative of the target foam material.

[0048] The composition data is data that is indicative of the composition of the foam piece under analysis, from which information regarding the type of foam material and / or contained additives can be inferred, based on which the suitability of the foam piece for the predetermined recycling process, i.e. whether the foam piece comprises or not the target foam material, can be decided.

[0049] In a development the first analysis step for determining the first composition data and the second analysis step for determining the second composition data are performed using different analytical methods. For instance, the first composition data is indicative of a type of polyurethane foam of the sample foam piece or sample foam element and the second composition data is indicative of a type of additive and / or impurity of the sample foam piece or the sample foam element, in particular a type of additive selected from a group consisting of water, inorganic fillers, flame retardants, styrenes (in particular styrene acrylonitrile), silicon stabilizers, crosslinker, chain extenders, monools, antioxidants, defoamers, catalysts and dyes.

[0050] The above-mentioned SAN content of the introduction generally may embrace content of "graft polyols” often also termed polymer polyols. Polymer polyols mean dispersions of polymers, mostly aery lonitrile-sty rene copolymers, in particular stabilized by the co-polymerization of macromers in a polyether polyol matrix. The graft polyols used for the preparation of polyurethane foams usually have a hydroxy value in the range from 15 to 120 mg KOH / g. They may be present in the polyurethane foams in an amount of up to 25 wt.%.

[0051] Alternatively, or additionally, the second composition data can be indicative of dust, dirt, humidity, microbial contamination or fungal contamination. In another development, the first composition data is indicative of a type of additive and / or impurity and the second composition data is indicative of a type of foam.

[0052] Water represents in many cases the additive with a highest content, sometimes forming up to 70% of the total amount of additives. Typically it reacts to CO2 during the foaming process.

[0053] In particular for flexible polyurethane foams, the fillers promote an increase in density and resistance to compression. However, they reduce the resilience and contribute to the increase in permanent deformation. In addition, properties such as tear strength are significantly affected by the introduction of fillers. Accordingly, it is necessary to determine the correct concentration of the filler in the polymer matrix, so as to obtain a product of reliable quality. Some notable fillers include inorganic materials such as calcium carbonate, dolomite, aluminum silica, titanium dioxide, chalk and talc while some of the organic materials used as filler are SAN, carbon black and natural fibers. Silicone stabilizer or surfactants for PU foams are typically grafted copolymers which consist of a polydimethylsiloxane backbone and polyethylene oxide-co-propylene oxide pendant groups. Some silicone stabilizers include siloxanes with polyetherol sidechains. Stabilizers are typically used as surfactants to stabilize the foam cells in the flexible polyurethane foaming process. It increases the compatibility of raw materials, decrease surface tension in polyurethane foam systems, improve emulsification and nucleation, prevent coalescence and stabilize cell membranes.

[0054] The chemical nature of the PU, the high air permeability, and the high inner surface area of the foam structure cause this material to be highly flammable. Consequently, the application of flame retardants to flexible PU foams is an important issue. The use of halogenated flame retardants is not considered optimal, in part due to the high emission level and the possible phase-out by the European Risk Assessment Body. Consequently, melamine as a nonhalogenated flame retardant is applied more and more frequently. Other flame retardants include, but are not limited to formaldehyde-based retardants and phosphorus-based retardants. Also, expandable graphite may be used as flame retardant.

[0055] Typically, the addition of crosslinking additives, or crosslinkers, to PU foams serves to reduce or eliminate deterioration under humid aging conditions of these foams, in particular those made using non-fugitive tertiary amine urethane catalysts. Examples of cross-linkers, in particular for high resilient (HR) PU foams include glycerine, diethanolamine, and sorbitol.

[0056] Chain extenders are typically low molecular weight diols or diamines that react with diisocyanates to build polyurethane molecular weight and increase the block length of the hard segment. Much like the diisocyanates, chain extenders can be either aliphatic or aromatic. Examples of chain extenders, in particular for VE foams, include butandiol and methylpropanediol.

[0057] Generally, for ensuring a safe production of PU foams, a foam stabilizer possesses weak uniformizing power and a defoaming agent is required for the purpose of controlling the formation of open cells. Commonly used defoaming agents include insoluble oils, polydimethylsiloxanes and other silicones, certain alcohols, stearates and glycols.

[0058] There are mainly two types of catalysts used in polyurethane technology, i.e. amine catalysts and organometallics. Amine catalysts generally catalyze the isocyanate-water reaction better than the isocyanate-polyol reaction, while organometallics are considered as gel catalysts although they additionally influence blowing reactions. The amine catalysts, especially tertiary amines, are the most common organic base catalysts in the synthesis of polyurethanes. One of the most commonly used tertiary amine catalyst is 1 ,4-diazobicyclo[2,2,2]octane (DABCO). It catalyzes both isocyanate-polyol and isocyanate-water reactions. One of the drawbacks of using tertiary amines is their offensive fishlike odor and high volatility. Increasing environmental concerns toward decreasing of emissions of volatile organic compounds (VOC) have contributed to the development of nonfugitive catalysts. In another. Tertiary amines are typically present in small concentrations, e.g., under 0.5% of the total foam and they are typically volatile and no longer detectable in the final foam. In addition, metal-catalysts are also used in PU foam manufacturing. For instance tin-organic compounds (mostly DBTL dibutyltin dilaurate) are now only permitted in very small quantities by the testing institutes (including their degradation products). However, alternative tin compounds are currently being used.

[0059] Further, the analytical sorting methods can be advantageously used to sort out, material which is covered with or contains unacceptable dirt, dust, or microbial or fungal layers, irrespectively of the material having the right foam composition for the recycling process. In this cases the composition data is indicative of the presence of said unacceptable dirt, dust, or microbial or fungal material.

[0060] Additionally, or alternatively, in a further development of the method of the first aspect of the invention, the first sorting step, the second sorting step or both the first and the second sorting steps comprise:

[0061] - determining a composition of a sample foam piece or a sample foam element at a first location, thereby obtaining first composition data indicative of the composition of the sample foam piece or sample foam element at said first location;

[0062] - determining a composition of the sample foam piece or the sample foam element at a non-overlapping second location different than the first location, thereby obtaining second composition data indicative of the composition of the sample foam piece or of the sample foam element at the second location; and

[0063] - selecting the sample foam piece as a target foam piece or the sample foam element as a target foam element upon determining that the composition data obtained at the first location and the second location is indicative of the target foam material.

[0064] This is particularly advantageous in the case of foam with a mixed composition that includes sections made of the target foam material and other sections of non-target foam material.

[0065] In a development, the method further comprises determining respective composition data indicative of the composition of the sample foam piece at three or more different non overlapping locations and selecting the sample foam piece as a target foam piece upon determining that at least predetermined percentage of the determined composition data is indicative of the target foam material. For instance, in an exemplary and non-restricting development, the sample foam piece is analyzed at four different non-overlapping locations and the sample foam piece is selected as a target foam piece upon determining that at least 75%, i.e., three out of the four determined composition data, are indicative of the target foam material. In a more preferred development, a sample foam piece is selected as a target foam piece upon determining that at least 80%, at least 85%, at least 90% or are least 95% of the determined composition data, are indicative of the target foam material. In a most preferred development, the sample foam piece is selected as a target foam piece upon determining that all determined composition data are indicative of target foam material. Preferably, the pre-processing method of the first aspect is for feeding target foam flakes to a reactor of a chemical recycling process, in particular for feeding PU-containing target foam flakes to a reactor for recovering TDA and polyol as raw materials for the fabrication of recycled PU foam.

[0066] The method of the first aspect of the invention can be advantageously used for pre-processing a plastic mix, additionally or alternatively comprising other types of non-foam plastic. In different developments, the foam mix can be a polyurethane mix, a flexible polyurethane mix, or a mattress mix.

[0067] A second aspect of the present invention is formed by a pre-processing arrangement. The pre-processing arrangement, also referred to herewithin as the arrangement, is suitable for pre-processing a foam mix following a method according to the first aspect, in particular for feeding a reactor of a recycling process for recovering raw materials. The pre-processing arrangement comprises a first sorting unit that is configured to select, from the foam mix, target foam pieces comprising target foam material that is suitable for the reactor. The arrangement also comprises a first transporting unit configured to receive the selected target foam pieces and to transport the selected target foam pieces to a shredding unit, wherein the shredding unit is configured to shred the selected target foam pieces to form shredded foam elements. The arrangement also comprises a second sorting unit that is configured to select target foam elements from the shredded foam elements. The arrangement further comprises a second transporting unit that is configured to receive the selected target foam elements and to transport the selected target foam elements to a milling unit, wherein the milling unit is configured to mill the selected target foam elements to form target foam flakes.

[0068] The pre-processing arrangement of the second aspect of the invention thus shares the advantages of the method for pre-processing a foam mix of the first aspect, or of any of its developments.

[0069] In the context of the present invention the shredded foam elements, respectively target foam elements, in particular mean shredded PU foam elements. Shredded PU foam elements embrace generally a "comminuted polyurethane or polyisocyanurate foam or the like foam material”. Preferably this means the material is obtained from a foam, and the comminuted polyurethane or polyisocyanurate is for example used in shredded form, i.e. in the form of granules, flakes, as an agglomerate, or as a powder.

[0070] The polyurethane or polyisocyanurate foams can be comminuted by conventional methods, for example by shredding, e.g. in a rotation mill or rotary mill at room temperature, to a particle size of ordinarily less than 500 mm, for example to a particle size in the range of from 10 to 500 mm, preferably to a particle size of less than 20 mm, or ground, e.g. by known cold grinding processes.

[0071] Preferably, for a milled foam a particle size of less than 5 mm is selected, for example a particle size in the range of 0.01 mm to 5 mm, and preferably in the range of 0.01 mm to 1 mm. The properties of the polyurethane or polyisocyanurate foams might vary in broad ranges. Preferably, polyurethane foams are used in the process of the present invention. According to a further embodiment, the present invention is also directed to the process as disclosed above, wherein the polyurethane foams are selected from the group consisting of polyisocyanate derived polyurethane foams.

[0072] The polyurethane or polyisocyanurate foams used in the present invention are preferably obtained from items produced from polyurethane foams at a time after use for the purpose for which they were manufactured or polyurethane foam waste from production processes.

[0073] Before subjecting to the process of the present invention, the items may be subjected to sorting steps and / or to mechanical comminution. That is, further sorting and bringing the items into appropriate sizes, e.g. by shredding, sieving or separation by rates of density, i.e. by air, a liquid or magnetically.

[0074] Optionally, these fragments may then undergo processes to eliminate impurities, e.g. paper labels. Furthermore, steps to remove blowing agents may be included in the process. Suitable methods are in principle known to the person skilled in the art.

[0075] Herein, the term "polyurethane foam waste” includes end-of-life polyurethane foams and production rejects of PU foams or waste generated through further processing of PU foams. In this context, the term "spent polyurethane foam” denotes an item produced from a polyurethane foam at a time when it has already been used for the purpose for which it was manufactured. "Production rejects of polyurethane foams" denotes polyurethane foam waste occurring in production processes of PU foams.

[0076] Generally, polyurethane foams are produced by a reaction between a polyisocyanate component and a polyol component. Typically, further materials, in particular additives, such as flame retardants (e.g. phosphorous-based), polymerization catalysts (e.g. tertiary amines), fillers and surfactants as siloxanes can be added in the production process of the polymers.

[0077] The properties of a polyurethane foam are influenced by the chemistry of polyisocyanate and polyol components used and the recipe applied in polymerization. For example, the starting materials may influence the crosslinking density of the polymers in a three-dimensional network. Rigid polyurethane are typically obtained from monomers with a comparably low molecular weight and high functionality creating a highly crosslinked, dense network.

[0078] Industrially and consequently in large quantities, especially methylene-di(phenylisocyanate) (MDI) or its polymeric forms or tolylene 2,4 and 2, 6-diisocy anate (TDI) are used as polyisocyanate components for the production of PU rigid foams and PU flexible foams. For a representative composition of these PU foams, see for example US 9,023,907 B2, WO 2015 / 121057 and WO 2013 / 139781. Organic polyisocyanates that can be used in the preparation of polyurethanes are any of the known organic di- and polyisocyanates, preferably aromatic polyfunctional isocyanates.

[0079] Suitable polyisocyanate components used for the production of the polyurethanes or polyisocyanurates comprise any of the polyisocyanates known for the production of polyurethanes or polyisocyanurates. These comprise the aliphatic, cycloaliphatic, and aromatic difunctional or poly-functional isocyanates known from the prior art, and also any desired mixtures thereof. Examples are diphenylmethane 2, 2'-, 2,4'-, and 4,4'-diisocyanate, the mixtures of monomeric diphenylmethane diisocyanates with diphenyl-methane diisocyanate homologs having a larger number of rings (polymer MDI), isophorone diisocyanate (IPDI) and its oligomers, tolylene 2,4- and 2,6-diisocyanate (TDI), and mixtures of these, tetramethylene diisocyanate and its oligomers, hexa-methylene diisocyanate (HD I) and its oligomers, naphthylene diisocyanate (NDI), and mixtures thereof.

[0080] Preferably, tolylene 2,4- and / or 2,6-diisocynate (TDI) or a mixture thereof, monomeric diphenyl-methane diisocyanates, and / or diphenylmethane diisocyanate homologs having a larger number of rings (polymer MDI), and mixtures of these. Other possible isocyanates are mentioned by way of example in "Kunststoffhandbuch [Plastics handbook], volume 7, Polyurethane [Polyurethanes]", Carl Hanser Verlag, 3rd edition 1993, chapter 3.2 and 3.3.2.

[0081] The organic di- and polyisocyanates may be used individually or in the form of mixtures.

[0082] Common polyols used in huge quantities are, e.g., selected from the group consisting of polyether polyols, polyester polyols, polyetherester polyols and mixtures thereof.

[0083] Polyetherols are by way of example produced from epoxides, for example propylene oxide and / or ethylene oxide, or from tetrahydrofuran with starter compounds exhibiting hydrogen-activity, for example aliphatic alcohols, phenols, amines, carboxylic acids, water, or compounds based on natural substances, for example sucrose, sorbitol or mannitol, with use of a catalyst. Mention may be made here of basic catalysts and double-metal cyanide catalysts, as described by way of example in WO 2006 / 034800, EP 0090444, or WO 2005 / 090440.

[0084] Polyesterols are by way of example produced from aliphatic or aromatic dicarboxylic acids and polyhydric alcohols, polythioether polyols, polyesteramides, hydroxylated polyacetals, and / or hydroxylated aliphatic polycarbonates, preferably in the presence of an esterification catalyst. Other possible polyols are mentioned by way of example in "Kunststoffhandbuch [Plastics handbook], volume 7, Polyurethane [Polyurethanes]", Carl Hanser Verlag, 3rd edition 1993, chapter 3.1. In the following, developments of the arrangement of the second aspect will be disclosed.

[0085] In a development, the arrangement is confined within a single plant or building complex, and the first transporting unit and / or the second transporting unit comprise a conveying system, such as a conveyor belt or a sucking and / or blowing unit, to transport the corresponding selected target foam pieces and / or the selected target foam elements to the shredding unit and / or to the milling unit. In an alternative development, the pre-processing arrangement is distributed in two or more different location and the first transporting unit and / or the second transporting unit include a road-based transporting unit (e.g., a truck), a rail-based transporting unit (e.g., a train), an air-based transporting unit (e.g., a cargo plane) and / or a sea-based transporting unit (e.g., a container ship).

[0086] In a development, the pre-processing arrangement of the invention further comprises a first pressing unit and / or a second pressing unit and / or a third pressing unit. In particular the first pressing unit is arranged and configured to press the selected target foam pieces to form pressed target foam pieces, the second pressing unit is configured to press the selected target foam elements to form pressed target foam elements, and the third pressing unit is configured to press the target foam flakes to form pressed target foam flakes. This is particularly advantageous in the case of a distributed arrangement with more than one location, since it reduces the volume of the foam to be transported between two different locations, and therefore also the transport costs. In a preferred development, the third pressing unit comprises a extruder, which is preferably configured to feed the pressed target foam flakes to the reactor or the recycling process.

[0087] In a preferred development of the pre-processing arrangement the shredding unit is configured to provide shredded foam elements with a maximum dimension in the range of 100 mm to 500 mm. The shredding unit may comprise an adjuster unit for adjusting the size of the foam elements. The adjuster unit may comprise a mesh with a fixed or a variable diameter size. Here, only shredded foam pieces that fit through the mesh are provided as foam elements. The size of the foam elements after having been shredded at the shredding unit is set in dependence on the requirements of the second sorting unit and the second transporting unit. A larger foam element size is associated with less sorting effort of the second sorting unit, since there will be less foam elements to sort. However it increases the chance of having foam elements with a mixture of suitable foam materials and unsuitable foam materials for the predetermined recycling process or reactor.

[0088] Additionally or alternatively, the milling unit is configured to provide milled target foam flakes maximum dimension smaller than 120 mm preferably smaller than 90 mm even more preferable smaller than 70 mm.

[0089] Further, in another development of the arrangement of the invention the first sorting unit and / or the second sorting unit is, or are, selected from a group consisting of a near-infrared spectroscopy device, a medium-infrared spectroscopy device, a UV-VIS spectroscopy device, an optical camera, a laser induced breakdown spectroscopy device, a Raman spectroscopy device, an X-ray fluorescence device and a THz spectroscopy device. The choice of the sorting unit depends on the type of target foam material, since different target foam materials may be better identified using a particular sorting unit based on a given suitable operation principle.

[0090] Advantageously, and preferably, in a development, the first sorting unit is a handheld near infrared spectroscopy device. An operator can therefore easily select the target foam pieces from the incoming target mix irrespectively of the size of the piece. According to a third aspect of the invention a computer program is presented. The computer program comprises instructions which, when executed by a control device of a pre-processing arrangement, cause the pre-processing arrangement to carry out the method of the first aspect of the invention. The control device of the pre-processing arrangement can be a single processing unit located at the recycling facility or may be distributed among different processing units located at different locations and exchanging the necessary data for operation via suitable data network.

[0091] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0092] The embodiments of the invention are described in the following on the basis of the drawing in comparison with the state of the art, which is also partly illustrated. The latter is not necessarily intended to represent the embodiments to scale. The drawing is, where useful for explanation, shown in schematized and / or slightly distorted form. With regard to additions to the teaching immediately recognizable from the drawing, reference is made to the relevant prior art. It should be kept in mind that numerous modifications and changes can be made to the form and detail of an embodiment without deviating from the general concept of the invention. The features of the invention disclosed in the description, in the drawing and in the claims may be essential for a further development of the invention, either individually or in any combination. In addition, all combinations of at least two of the features disclosed in the description, drawing and / or claims fall within the scope of the invention.

[0093] The general concept of the invention is not limited to the exact form or detail of the preferred embodiments shown and described below or to a subject matter, which would be limited in comparison to the subject matter as claimed in the claims.

[0094] For specified design ranges, values within specified limits of the ranges are also dis-closed as limit values and thus are arbitrarily applicable and claimable.

[0095] The following drawing shows in:

[0096] Fig. 1 a flow diagram of an exemplary method for pre-processing a foam mix in accordance with a first embodiment of the invention;

[0097] Fig. 2 a flow diagram of an exemplary method for pre-processing a foam mix in accordance with a second embodiment of the invention;

[0098] Fig. 3 a schematic block diagram of a pre-processing arrangement in accordance with a third embodiment of the invention;

[0099] Fig. 4 a schematic block diagram of a pre-processing arrangement in accordance with a fourth embodiment of the invention; and Fig. 5 a schematic block diagram of a pre-processing arrangement in accordance with a fifth embodiment of the invention.

[0100] Fig. 1 shows a flow diagram of an exemplary method 100 for pre-processing a foam mix in accordance with a first embodiment of the invention. For the discussion of the features mentioned in the discussion of the method steps of Figs. 1 and 2, the reader is referred to the discussion of pre-processing arrangements of Figs. 3, 4 are 5. The method 100 is suitable for pre-processing a foam mix 202, for example, for feeding a reactor 250 of a recycling process, in particular a chemical recycling process for recovering raw materials. The method 100 includes, in a step 102, performing a first sorting step for selecting, from the foam mix 202, target foam pieces 206 that comprise target foam material 207 that is suitable for the reactor 250. The selected target foam pieces may, at this stage, also comprise other foam materials, such as foam materials that are not suitable for the reactor, Those foam pieces that are not selected are not further part of the pre-processing process and may, for example, be pressed and transported for another recycling process. The selected target foam pieces 206 are then transported, in a step 104, to a shredding unit 210. This transporting step 104 can be for instance carried out by means of a conveyor belt system, by a road, rail, air or sea-based transport unit such as a truck, a train, an airplane or a ship, or by any combination thereof. The selected target foam pieces 206 are then shredded, in a step 106 to form shredded foam elements, also referred to as foam elements, and which are the result of shredding foam pieces or foam articles, and which have a similar size, in dependence on the used shredding unit. From the shredded foam elements, target foam elements 216 are then selected by performing a second sorting step 108, which are then transported, in a step 110, to a milling unit. Those foam elements that, according to the second sorting step 108 do not qualify as target foam elements 216 are excluded from the subsequent steps to guarantee that they are not fed to the reactor. The selected target foam elements 216 are milled to form target foam flakes, which, in an optional step 114, are fed into the reactor 250 of the recycling process.

[0101] Fig. 2 shows a flow diagram of an exemplary method 100B for pre-processing a foam mix in accordance with a second embodiment of the invention. For the sake of clarity, those method steps of the method 100B of Fig.2 that have a similar or identical function to those of method 100 of Fig. 1 will be referred to using the same reference numbers. This exemplary method 100B is preferred in cases where the first sorting step 102 and the shredding step 106 are performed in different facilities where a transporting step 104 of the selected target foam pieces by road, train, sea or air is required, and / or in cases where the second sorting step 108 and the milling step 112 are performed in different facilities where a transporting step 110 of the target foam elements by road, train, sea or air is required and / or in cases where the milling step 112 and the optional step of feeding 114 the target foam flakes to the reactor are performed in different facilities where a transport by road, train, sea or air is required. The method 100B therefore includes one, two or three pressing steps, namely a first pressing step 116A, wherein the selected target foam pieces 207 are pressed for forming pressed target foam pieces 207b prior to the step of transporting 104 the selected target foam pieces 207, as pressed target foam pieces 207b, to the shredding unit 210 and / or a second pressing step 116B, wherein the selected target foam elements 216 are pressed for forming pressed target foam elements 216B prior to the step of transporting 110 the selected target foam elements 216 as pressed target foam elements 216B to the milling unit 220, and / or a third pressing step 116C, wherein the target foam flakes 222 are pressed for forming pressed target foam flakes 222B prior to the step of feeding the target foam flakes 222 as pressed target foam flakes 222B to the reactor 250.

[0102] In particular, the first and / or the second sorting steps 102, 108 is, or are, performed using one or more of optical sorting methods, in particular one or more optical sorting methods selected from the group consisting of a nearinfrared spectroscopy based method, a medium-infrared spectroscopy based method, a Raman spectroscopy based method, a UV-VIS spectroscopy based method, an optical camera based method, a laser induced breakdown spectroscopy method an X-ray fluorescence based method and a THz spectroscopy based method.

[0103] Infrared spectroscopy (IR spectroscopy or vibrational spectroscopy) is the measurement of the interaction of infrared radiation with matter by absorption, emission, or reflection. It is used to study and identify chemical substances or functional groups in solid, liquid, or gaseous forms. It can be used to characterize new materials or identify and verify known and unknown samples.

[0104] The infrared portion of the electromagnetic spectrum is usually divided into three regions; the near-, mid- and far- infrared, named for their relation to the visible spectrum. The higher-energy near-IR, approximately 14,000-4,000 cm-1 (0.7-2.5 pm wavelength) can excite overtone or combination modes of molecular vibrations. The mid-infrared, approximately 4,000-400 cm-1 (2.5-25 pm) is generally used to study the fundamental vibrations and associated rotational-vibrational structure. For instance, near infrared spectroscopy (NIRS) is a spectroscopic method that uses the near-infrared region of the electromagnetic spectrum (approximately from 700 nm to 2500 nm). Typical applications include medical and physiological diagnostics, and control quality. Near-infrared spectroscopy is not a particularly sensitive technique, but it can be very useful in probing bulk material with little or no sample preparation. Instrumentation for NIRS includes a source, a detector, and a dispersive element (such as a prism, or, more commonly, a diffraction grating) to allow the intensity at different wavelengths to be recorded. The instrumentation is very similar to that used for the UV-visible and mid-IR ranges.

[0105] UV-VIS spectroscopy refers to absorption spectroscopy or reflectance spectroscopy in part of the ultraviolet and the full, adjacent visible regions of the electromagnetic spectrum. Being relatively inexpensive and easily implemented, this methodology is widely used in diverse applied and fundamental applications. The only requirement is that the sample absorb in the UV-VIS region, i.e. be a chromophore. Absorption spectroscopy is complementary to fluorescence spectroscopy. Parameters of interest, besides the wavelength of measurement, are absorbance (A) or transmittance (%T) or reflectance (%R), and its change with time. UVA / IS spectroscopy is routinely used in analytical chemistry for the quantitative determination of diverse analytes or sample, such as transition metal ions, highly conjugated organic compounds, and biological macromolecules.

[0106] Raman spectroscopy is a spectroscopic technique typically used to determine vibrational modes of molecules, although rotational and other low-frequency modes of systems may also be observed. Raman spectroscopy is commonly used in chemistry to provide a structural fingerprint by which molecules can be identified. Typically, a sample is illuminated with a laser beam. Electromagnetic radiation from the illuminated spot is collected with a lens and sent through a monochromator. Elastic scattered radiation at the wavelength corresponding to the laser line (Rayleigh scattering) is filtered out by either a notch filter, edge pass filter, or a band pass filter, while the rest of the collected light is dispersed onto a detector.

[0107] Laser induced breakdown spectroscopy is a type of atomic emission spectroscopy which uses a highly energetic laser pulse as the excitation source. The laser is focused to form a plasma, which atomizes and excites samples. The formation of the plasma only begins when the focused laser achieves a certain threshold for optical breakdown, which generally depends on the environment and the target material.

[0108] X-ray fluorescence (XRF) refers to the emission of characteristic "secondary" (or fluorescent) X-rays from a material that has been excited by being bombarded with high-energy X-rays or gamma rays. The phenomenon is widely used for elemental analysis and chemical analysis.

[0109] Terahertz spectroscopy detects and controls properties of matter with electromagnetic fields that are in the frequency range between a few hundred gigahertz and several terahertz (abbreviated as THz). In many-body systems, several of the relevant states have an energy difference that matches with the energy of a THz photon. Therefore, THz spectroscopy provides a particularly powerful method in resolving and controlling individual transitions between different many-body states.

[0110] Fig. 3 shows a schematic block diagram of a pre-processing arrangement 200 in accordance with a third embodiment of the invention. The pre-processing arrangement 200 is suitable for pre-processing a foam mix 202, for example a flexible foam mix 202, in particular a polyurethane (PU) mix for feeding a reactor 250 of a recycling process, for instance a chemical recycling process for recovering raw materials 252, such as TDA and polyols in the case of TDI-based PU foam. In the case of a MDI-based PU foam or a TDI / MDI mixed foam, then MDA is also obtained. Typically, in the recycling process, the amine is converted back to the corresponding isocyanate in a downstream step, generally after a dedicated reprocessing and purification chain.

[0111] The pre-processing arrangement 200 comprises a first sorting unit 204A that is configured to select, from the foam mix 202 that comprises one or more foam pieces 205, 206A, 206B, probably comprising different types of foam materials, those foam pieces 206A, 206B comprising target foam material 207 that is suitable for the reactor 250, and which are referred to as target foam pieces.

[0112] The first sorting unit can comprise, for instance, a near-infrared spectroscopy device 204.1, a medium-infrared spectroscopy device 204.2, a UV-VIS spectroscopy device 204.3, an optical camera 204.4, a laser induced breakdown spectroscopy device 204.5, a Raman spectroscopy device 204.6, an X-ray fluorescence device 204.7 or a THz spectroscopy device 204.8. The selected target foam pieces 206 which have been selected based on its content of target foam material 207 are then transported by a first transporting unit 208 that is configured to receive the selected target foam pieces 206 and to transport the selected target foam pieces 206 to a shredding unit 210. The transporting unit 108 of Fig. 1 is exemplarily configured as a conveyor belt, but may also be any of the transporting units previously described. The shredding unit 210 is configured to shred the selected target foam pieces 206 to form shredded foam elements 212. The shredding unit 210 may for instance comprise a cylindrical chamber with a cylindrical rotating element co-axially arranged inside the chamber to rotate along the common longitudinal axis. The rotating element has cutting and / or gripping elements distributed along its surface. The inner wall of the cylindrical chamber may also comprise cutting and / or gripping elements. A gap between the inner wall of the chamber and the rotating element allows the introduced foam piece to move. When engaged by the cutting or gripping elements, the foam pieces are cut or tore. A filtering mesh allows those shredded pieces with a predetermined size to exit the shredding unit 210. These are referred to as foam elements 212.

[0113] The foam elements 212 are provided to a second sorting unit 204B configured to select target foam elements 216 from the shredded foam elements 212. Since the target foam pieces may still comprise foam material 211 other that the suitable target foam material 207, some of the shredded foam elements that undergo the analysis of the second sorting unit may not qualify as target foam elements 216 and are separated.

[0114] As in the case of the first sorting unit 204A, the second sorting unit 204B can comprise, for instance, a near-infrared spectroscopy device 204.1, a medium-infrared spectroscopy device 204.2, a UV-VIS spectroscopy device 204.3, an optical camera 204.4, a laser induced breakdown spectroscopy device 204.5, a Raman spectroscopy device 204.6, an X-ray fluorescence device 204.7 or a THz spectroscopy device 204.8. The first sorting unit does not have to be the same type of device as the second sorting unit.

[0115] A second transporting unit 218 is configured to receive the selected target foam elements 216 and to transport the selected target foam elements 216 to a milling unit 220. The milling unit 220 is configured to mill the selected target foam elements 216 to form target foam flakes 222 that are suitable, both in size and in composition, to be fed to the reactor 250.

[0116] The milling unit and the shredding unit can be based on a similar technology, although the average size of the target foam flakes is smaller than the average size of the shredded foam elements.

[0117] Fig. 4 shows a schematic block diagram of a pre-processing arrangement 200B in accordance with a fourth embodiment of the invention. The following discussion will focus on those features distinguishing the arrangement 200B of Fig. 4 from the arrangement 200 of Fig. 3. Those features of the arrangements 200 and 200B that have an identical or similar functionality will be referred to using the same reference number and the reader is referred to the discussion of Fig. 3 above. The pre-processing arrangement 200B further comprising a first pressing unit 224, a second pressing unit 226 and a third pressing unit 228, wherein the first pressing unit 224 is configured to press the selected target foam pieces 207 to form pressed target foam pieces 207B, the second pressing unit 226 is configured to press the selected target foam elements 216 to form pressed target foam elements 216B, and the third pressing unit 228 is configured to press the target foam flakes 222 to form pressed target foam flakes 222B. This configuration is particularly advantageous when the transporting units 208 and 218 involve a long distance transport, for instance, by road, rail, air or overseas, or where the reactor 250 is not located in the same location as the pre-processing arrangement. In a particular preferred example, the target foam flakes are pressed using an extruder, as the third pressing unit 2. Advantageously the pressed target foam flakes are then fed to the reactor. This is particularly advantageous for controlling dosage of target foam flakes into the reactor, especially when the reactor vessel of the reactor is pressurized.

[0118] Fig. 5 shows a schematic block diagram of a pre-processing arrangement 200C in accordance with a fifth embodiment of the invention. The following discussion will focus on those features distinguishing the arrangement 200C of Fig. 5 from the arrangement 200 of Fig. 3 and the arrangement 200B of Fig. 4. Those features of the arrangements 200 and 200B and 200C that have an identical or similar functionality will be referred to using the same reference number and the reader is referred to the discussion of Figs. 3 and 4 above.

[0119] In the exemplary arrangement 200C of Fig. 5, the first sorting unit is a handheld near infrared spectroscopy device 204.11.

[0120] The arrangements 200, 200B and 200C can be configured as pre-processing arrangements for pre-processing a mattress mix as a foam mix.

[0121] In summary, the invention is directed to a method for pre-processing a foam mix for feeding a reactor of a recycling process, which comprises performing a first sorting step for selecting, target foam pieces that comprise target foam material that is suitable for the reactor, transporting the selected target foam pieces to a shredding unit, shred-ding, the selected target foam pieces to form shredded foam elements, performing a second sorting step for selecting target foam elements from the shredded foam elements, transporting the selected target foam elements to a milling unit; and milling the selected target foam elements to form target foam flakes suitable for feeding to the reactor.

[0122] Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

[0123] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single unit or device may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.

Claims

Claims1 . Method (100, 100B) for pre-processing a foam mix (202) for feeding a reactor (250) of a recycling process for recovering raw materials (252), the method comprising the steps of:- performing a first sorting step (102) for selecting, from the foam mix (202), target foam pieces (206) that comprise target foam material (207) that is suitable for the reactor (250);- transporting (104) the selected target foam pieces (206) to a shredding unit (210);- shredding (106), at the shredding unit (210), the selected target foam pieces (206) to form shredded foam elements (212);- performing a second sorting step (108) for selecting, from the shredded foam elements (212) target foam elements (216) that comprise the target foam material (207);- transporting (110) the selected target foam elements (216) to a milling unit (220);- milling (112), at the milling unit (220), the selected target foam elements (216) to form target foam flakes (222) that are suitable for feeding into the reactor.

2. The method (100, 100B) of claim 1 , further comprising the step of: pressing (116A) the selected target foam pieces (207) for forming pressed target foam pieces (207b) prior to the step of transporting (104) the selected target foam pieces (207) as pressed target foam pieces (207b) to the shredding unit (210) and / or pressing (116B) the selected target foam elements (216) for forming pressed target foam elements (216B) prior to the step of transporting (110) the selected target foam elements (216) as pressed target foam elements (216B) to the milling unit (220).

3. The method (100, 100B) of claim 1 or 2, further comprising the step of pressing (116C) the target foam flakes (222) for forming pressed target foam flakes (222B) prior to an optional step (114) of feeding the target foam flakes (222) as pressed target foam flakes (222b) to the reactor (250).

4. The method (100, 100B) of any of the preceding claims, wherein the step of shredding (106) the selected target foam pieces results in shredded foam elements (212) with a maximum dimension in the range of 100 mm to 500 mm.

5. The method (100, 100B) of any of the preceding claims, wherein the step of milling (112) the selected target foam elements (216) results in milled target foam flakes (222) with a maximum dimension smaller than 120 mm preferably smaller than 90 mm even more preferable smaller than 70 mm.

6. The method (100, 100B) of any of the preceding claims, wherein the first sorting step (102) and / or the second sorting step (108) is performed using one or more of optical sorting methods, in particular one or more optical sorting methods selected from the group consisting of a near-infrared spectroscopy based method, a midinfrared spectroscopy based method, a Raman spectroscopy based method, a UV-VIS spectroscopy based method, an optical camera based method, a laser induced breakdown spectroscopy method an X-ray fluorescence based method and a THz spectroscopy based method.

7. The method (100, 100B) of any of the preceding claims, wherein the first sorting step (104) is performed using a handheld near infrared spectroscopy device (204.11).

8. Pre-processing arrangement (200, 200B, 200C) for pre-processing a foam mix (202) for feeding a reactor of a recycling process (250) for recovering raw materials (252), the pre-processing arrangement (200) comprising: a first sorting unit (204A) configured to select, from the foam mix (202), target foam pieces (206A, 206B) comprising target foam material (207) that is suitable for the reactor (250);- a first transporting unit (208) configured to receive the selected target foam pieces (206) and to transport the selected target foam pieces (206) to a shredding unit (210); wherein the shredding unit (210) is configured to shred the selected target foam pieces (206) to form shredded foam elements (212);- a second sorting unit (204B) configured to select target foam elements (216) from the shredded foam elements (212);- a second transporting unit (218) configured to receive the selected target foam elements (216) and to transport the selected target foam elements (216) to a milling unit (220); wherein the milling unit (220) is configured to mill the selected target foam elements (216) to form target foam flakes (222).

9. The pre-processing arrangement (200, 200B, 200C) of claim 8, further comprising a first pressing unit (224) and / or a second pressing unit (226) and / or a third pressing unit (228), wherein the first pressing unit (224) is configured to press the selected target foam pieces (207) to form pressed target foam pieces (207B), the second pressing unit (226) is configured to press the selected target foam elements (216) to form pressed target foam elements (216B), and the third pressing unit (228) is configured to press the target foam flakes (222) to form pressed target foam flakes (222B).

10. The pre-processing arrangement (200, 200B, 200C) of claim 8 or 9, wherein the shredding unit (210) is configured to provide shredded foam elements (212) with a maximum dimension in the range of 100 mm to 500 mm.11 . The pre-processing arrangement (200, 200B, 200C) of claim 8 or 9, wherein the milling unit (220) is configured to provide milled target foam flakes (222) with a maximum dimension smaller than 120 mm preferably smaller than 90 mm even more preferable smaller than 70 mm.

12. The pre-processing arrangement (200, 200B, 200C) of any of the claims 8 to 11, wherein the first sorting unit (204A) and / or the second sorting unit (204B) is or are selected from a group consisting of a near-infrared spectroscopy device (204.1), a mid-infrared spectroscopy device (204.2), a UV-VIS spectroscopy device (204.3), an optical camera (204.5), a laser induced breakdown spectroscopy device (204.5), a Raman spectroscopy device (204.6), an X-ray fluorescence device (204.7) and a THz spectroscopy device (204.8).

13. The pre-processing arrangement (200, 200B, 200C) of any of the claims 8 to 12, wherein the first sorting unit is a handheld near infrared spectroscopy device (204.11).

14. Computer program comprising instructions which, when executed by a control device of a pre-processing arrangement, cause the pre-processing arrangement to carry out the method of any of the claims 1 to 7.

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