Method for selecting, from a foam mix comprising one or more foam pieces, target foam pieces, method and pre-processing arrangement for pre-processing a foam mix for feeding a reactor of a recycling process and respective computer program

Abstract

Method (102) for selecting, from a foam mix comprising one or more foam pieces, target foam pieces that comprise target foam material that is suitable for a predetermined recycling process, the method (102) comprising the steps of: performing a first analysis step (102A) for determining first composition data of a sample foam piece, the first composition data being indicative of a composition of the sample foam piece, performing a second analysis step (1028) for determining second composition data of the sample foam piece, the second composition data being indicative of the composition of the sample foam piece; and selecting (102C) the sample foam piece as a target foam piece upon determining that the first composition data and the second composition data are indicative of the target foam material.

Description

[0001] Method for selecting, from a foam mix comprising one or more foam pieces, target foam pieces, method and preprocessing arrangement for pre-processing a foam mix for feeding a reactor of a recycling process and respective computer program

[0002] Description

[0003] The present invention is directed to a method for selecting, from a foam mix comprising one or more foam pieces, target foam pieces that comprise target foam material suitable for a predetermined recycling process. The invention is further directed to a method for pre-processing a foam mix, 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 be also 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 compaction unit, densifier 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. In the case of flexible PU-foam, the main application for mechanical recycling is rebounded 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.

[0008] 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.orq / wp-content / upioads / 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.

[0009] 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. 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.

[0010] 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.

[0011] 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 pres- ence 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.

[0012] 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.

[0013] Document EP 3957453 A1 discloses a method for separating waste polyurethane foams, wherein for each polyurethane sample of a supply stream at least one respective spectrum is recorded by near-infrared spectroscopy. Each polyurethane sample of the supply stream is classified by a machine learning classification algorithm into a respective class of at least two classes, and the supply stream is separated into at least two streams according to the classification into the respective class, each class corresponding to a type of polyurethane.

[0014] Document EP 3957454 A1 discloses a method for separating waste polymer foams, wherein for each polymer sample of a waste supply stream at least one respective primary spectrum is recorded. In a primary separation step, each polymer sample of the supply stream is classified by a primary machine learning classification algorithm such that the supply stream is separated into at least two primary streams according to the classification. In a secondary separation step, each polymer sample of a first primary stream is classified by a secondary machine learning classification algorithm such that the first primary stream is separated into at least two secondary streams.

[0015] Document EP 4104994 A1 discloses a method for sorting flexible polyurethane foams into categories of conventional flexible polyurethane foams, high resilience flexible polyurethane foams, and viscoelastic flexible polyurethane foams by mid-infrared spectroscopy. Calibration samples of the different classes of foams are used to define a first library that allows distinguishing viscoelastic polyurethane foams and a second library that allows distinguishing conventional from HR polyurethane foams.

[0016] DE 102019215878 A1 discloses a method for sorting foam particles and / or measuring the quantity of foam particles. Further disclosed are a foaming device and a device for producing particle foam parts, which are combined with a device for sorting foam particles and / or measuring the quantity of foam particles.

[0017] A critical problem that has not been solved up to now is to optimize the combi-nation 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.

[0018] It is an object of the present invention to provide an optimized method for sorting target foam pieces that enables a general reduction of the recycling costs and, in particular in the case of chemical recycling, results in a higher yield and higher product quality.

[0019] According to a first aspect of the present invention a method for selecting, from a foam mix comprising one or more foam pieces, target foam pieces that comprise target foam material that is suitable for a predetermined recycling process is disclosed. The method of the first aspect of the invention comprises the steps of:

[0020] - in a first analysis step, determining first composition data of a sample foam piece by means of a first analysissetting, the first composition data being indicative of a composition of the sample foam piece;

[0021] - in a second analysis step, determining second composition data of the sample foam piece by means of a second analysis-setting, the second composition data being indicative of the composition of the sample foam piece; and

[0022] - selecting the sample foam piece as a target foam piece upon determining that the first composition data and the second composition data are indicative of the target foam material.

[0023] Typical sorting methods involve the use of sensors, e.g. optical sensors, to detect and identify the foam material before deciding if the foam material has an acceptable quality or not for the predetermined recycling process, i.e. if the foam material qualifies as a target foam material. However, due to the variety of different compositions and layered or packed material design, the detection and sorting process is sometimes falsified and some foam pieces can be regarded as having sufficient quality although it might comprise a layer or section of unacceptable foam material. If such a composite foam piece is fed to the recycling process it can cause severe trouble or spoil the product quality.

[0024] Thus, according to the invention, by combining at least two analysis steps, it is possible to better analyse the sample foam piece currently being sorted and improve the compositional homogeneity of the selected target foam pieces through a more accurate sorting. The combination of at least two analysis steps can increase the yield of the target foam material for the recycling process, since they enable a reduction of the contamination by the presence of foam materials not suitable for the recycling process. Due to the resulting lower impurities in the material stream, the product quality of the recycling process can be significantly increased.

[0025] Foam, also referred to as foamed plastic, is a synthetic resin converted into a spongelike mass with a closed-cell or open-cell structure, either of which may be flexible or rigid.

[0026] 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 foam include, for instance, standard PU foam, high resilience PU foam, viscoelastic PU foam, etc.. Depending on foam parameters such as the density, resilience 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] 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.

[0028] The composition data is determined by means of an analysis-setting, which refer to any analysis method or analysis device suitable for obtaining the composition data.

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

[0030] The first analysis-setting and the second analysis-setting are, in a preferred development, different analysis-settings. However, in an alternative development, the first analysis-setting and the second analysis-setting are the same analysis-setting.

[0031] In a development, the method further comprises performing at least a third analysis step for determining at least a third composition data indicative of a composition of the sample foam piece and selecting the sample foam piece as a target foam piece upon determining that all determined composition data is indicative of the target foam material. In an alternative development, the sample foam piece is selected 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, four different analysis steps are performed 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, is indicative of the target foam material.

[0032] In another 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. This enables a better qualification or even quantification of the composition of the foam piece under analysis, i.e. the current sample foam piece, which is typically not possible when applying only one analytical method.

[0033] In yet another development the first composition data is indicative of a type of foam, in particular of a type of polyurethane foam of the sample foam piece and the second composition data is indicative of a type of additive and / or impurity of the sample foam piece. Preferably, in another development, the second composition data is indicative of one or more additives selected from a group consisting of water, inorganic fillers, such as, but not limited to CaC03, organic fillers, flame retardants, styrenes (in particular styrene acrylonitrile), silicon stabilizers, crosslinker, chain extenders, monools, such as phenoxyethanol, antioxidants, defoamers, catalysts and dyes.

[0034] 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.

[0035] 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 acrylonitrile-styrene 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.%.

[0036] 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.

[0037] 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.

[0038] 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.

[0039] 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 non-halogenated 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. 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 crosslinkers, in particular for high resilient (HR) PU foams include glycerine, diethanolamine, and sorbitol.

[0040] 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 di isocyanates, chain extenders can be either aliphatic or aromatic. Examples of chain extenders, in particular for VE foams, include Butandiol and Methylpropanediol.

[0041] 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.

[0042] 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 tinorganic 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.

[0043] Further, the optical 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 pro-cess. In these cases the composition data is indicative of the presence of said unacceptable dirt, dust, or microbial or fungal material.

[0044] In yet another development the first analysis step for determining the first composition data and / or the second analysis step for determining the second composition data is performed by one or more analytical 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 THz spectroscopy based method, a UV-Vis spectroscopy based method, an optical-cameras based method, a laser induced breakdown spectroscopy method and an X-ray fluorescence based method. 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.

[0045] 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 nearinfrared 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.

[0046] 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.

[0047] 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.

[0048] 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. 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.

[0049] 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.

[0050] Preferably, in a development the first analysis step for determining the first composition data is performed using a handheld near infrared spectroscopy device.

[0051] The method of the first aspect of the invention thus enables a high-quality sorting process. Any process that requires to sort out unsuitable foam pieces will benefit from this method. For instance, mattress recycling process, in particular a chemical recycling process, will benefit from a more stable feed supply, leading to a more stable chemical recycling process with a higher yield. Further, the recycled raw materials, such as polyol and TDI, will have a higher purity and a more stable composition, which will enable to replace virgin material with the recycled raw materials during the production of new mattresses. Additionally, shutdowns, cleaning efforts or repair works in the chemical recycling process can be reduced by providing a higher quality material to the reactor.

[0052] According to a second aspect of the invention, a method for pre-processing a foam mix for feeding a reactor of a recycling process is disclosed. The method comprising the steps of

[0053] - performing steps of the method for selecting target foam pieces of the first aspect of the invention;

[0054] - transporting the selected target foam pieces to a shredding unit;

[0055] - shredding, at the shredding unit, the selected target foam pieces to form shredded foam elements;

[0056] - feeding the shredded foam elements to the reactor for recovering raw materials.

[0057] Alternatively, or additionally a method for pre-processing a foam mix also in accordance with the invention comprises the steps of:

[0058] - - receiving the foam fix comprising foam pieces and transporting said foam pieces to a shredding unit;

[0059] - - shredding, at the shredding unit, the foam pieces to form shredded foam elements;

[0060] - - performing steps of the method of the first aspect of the invention for selecting, among the shredded foam element, target foam elements comprising the target foam element.

[0061] In this particular development, the foam containing objects to be sorted are the shredded foam elements, and the result of the sorting step are selected target foam elements. Preferably, in a development of the method of the second aspect, the method for selecting target foam pieces and / or target foam elements, i.e., generally speaking, foam objects comprising target foam material, is performed twice, once using foam pieces as input, before shredding the selected target foam pieces, and a second time using foam elements as input, before feeding the selected target foam elements to the reactor.

[0062] The method for pre-processing a foam mix of the second aspect thus shares the advantages of the method for selecting target foam pieces (or target form elements) of the first aspect of the invention.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] 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.

[0068] 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.

[0069] 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. 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.

[0070] 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.

[0071] 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.

[0072] Industrially and consequently in large quantities, especially methylenedi(phenylisocyanate) (MDI) or its polymeric forms or toluene-2,4-diisocyanate and toluene-2,6-diisocyanate (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.

[0073] Organic polyisocyanates that can be used in the preparation of polyurethanes are any of the known organic di- and polyisocyanates, preferably aromatic polyfunctional isocyanates.

[0074] 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’-diisocy anate, the mixtures of monomeric diphenylmethane diisocyanates with diphenylmethane diisocyanate homologs having a larger number of rings (polymer MDI), isophorone diisocyanate (IPDI) and its oligomers, toluene-2,4-diisocyanate and toluene-2,6-diisocyanate (TDI), and mixtures of these, tetramethylene diisocyanate and its oligomers, hexa-methylene diisocyanate (HDI) and its oligomers, naphthylene diisocyanate (NDI), and mixtures thereof.

[0075] Preferably, toluene-2,4-diisocyanate and / or toluene-2,6-diisocynate (TDI) or a mixture thereof, monomeric diphenylmethane 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. The organic di- and polyisocyanates may be used individually or in the form of mixtures.

[0076] Common polyols used in huge quantities are, e.g., selected from the group consisting of polyether polyols, polyester polyols, polyetherester polyols and mixtures thereof.

[0077] 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 ex-ample in WO 2006 / 034800, EP 0090444, or WO 2005 / 090440.

[0078] 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 "Kun- ststoffhandbuch [Plastics hand-book], volume 7, Polyurethane [Polyurethanes]", Carl Hanser Verlag, 3rd edition 1993, chapter 3.1 .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. 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.

[0079] The method of the second 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.

[0080] A third aspect of the present invention is directed to a pre-processing arrangement for pre-processing a foam mix for feeding a reactor of a recycling process for recovering raw materials.

[0081] The pre-processing arrangement of the third aspect comprising at least one target foam selection unit that configured to select, from the foam mix, target foam pieces comprising target foam that is suitable for the reactor. The target foam selection unit comprises a foam composition determination unit that configured to perform a first analysis step for determining first composition data of a sample foam piece, the first composition data being indicative of a composition of the sample foam piece and to perform a second analysis step for determining second composition data of the sample foam piece, the second composition data being indicative of the composition of the sample foam piece; and a processing unit configured to receive the first composition data and the second composition data and to determine that sample foam piece is a target foam piece when both the first composition data and the second composition data are indicative of the target foam material. In a development, the target foam selection unit is arranged in a single device. In an alternative development, the foam composition determination unit is signally connected, e.g. via a wired or a wireless connection, to the processing unit. In yet another development, the foam composition determination unit comprises a first device for performing the first analysis step and a second device for performing the second analysis step, both of which are signally connected (wired, or wirelessly) to the processing unit, which may be integrated with one of the devices or be an external processing unit.

[0082] Depending on where the target foam selection unit is placed within the arrangement, a target foam selection unit according to the invention can be also used to perform a first analysis step for determining first composition data of a sample foam element, the first composition data being indicative of a composition of the sample foam element and to perform a second analysis step for determining second composition data of the sample foam element, the second composition data being indicative of the composition of the sample foam element. Here, the processing unit is configured to receive the first composition data and the second composition data and to determine that sample foam element is a target foam element when both the first composition data and the second composition data are indicative of the target foam material.

[0083] In another development, the pre-processing arrangement of the third aspect further comprises a transporting unit that is configured 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 for feeding to the reactor.

[0084] In yet another development, the pre-processing arrangement of the third aspect additionally comprises a foam element selection unit that is configured to select, from the shredded foam elements, shredded target foam elements comprising target foam that is suitable for the reactor. The foam element selection unit is preferably configured as target foam selection unit in which the input material are foam elements provided by the shredding unit. In particular, in a development, the foam element selection unit comprises a foam composition determination unit configured to perform an additional first analysis step for determining first composition data of a sample foam element, the first composition data being indicative of a composition of the sample foam element, and to perform an additional second analysis step for determining second composition data of the sample foam element, the second composition data being indicative of the composition of the sample foam element. Further, the processing unit, which can be a dedicated processing unit or the processing unit of the target foam selection unit, is configured to receive the first additional composition data and the second additional composition data and to determine that the sample foam element is a target foam element when both the first composition data and the second composition data are indicative of target foam.

[0085] The inclusion of two sorting steps, namely one for foam pieces and another one for foam elements, enables an optimal balance in terms of cost reduction and yield improvement compared to known pre-processing method or strategies. Also, the quality of the resulting products is improved. In another development the target foam selection unit and / or the foam element selection unit comprise a first composition determination unit that is configured to determine the first com-position data and a second composition determination unit configured to determine the second composition data.

[0086] Preferably, in a development, the foam composition determination unit and / or the first composition determination unit and / or the second composition determination 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 Raman spectroscopy device, a THz spectroscopy device, a laser induced breakdown spectroscopy device and an X-ray fluorescence device.

[0087] A fourth aspect of the present invention is formed by a computer program comprising instructions which, when executed by a control unit of a target foam selection unit cause the target foam selection unit to perform the method of the first aspect of the invention.

[0088] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

[0089] 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.

[0090] 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.

[0091] 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.

[0092] The following drawing shows in:

[0093] Fig. 1 a flow diagram of an exemplary method for pre-processing a foam mix that includes a method for selecting target foam pieces that comprise target foam material in accordance with a first embodiment of the invention; Fig. 2 a flow diagram of another exemplary method for pre-processing a foam mix that includes a method for selecting target foam elements that comprise target foam material in accordance with a first embodiment of the invention;

[0094] Fig. 3 a flow diagram of an exemplary method for pre-processing a foam mix in accordance with a third embodiment of the invention;

[0095] Fig. 4 a schematic block diagram of a pre-processing arrangement in accordance with a fourth embodiment of the invention;

[0096] Fig. 5 a schematic block diagram of a pre-processing arrangement in accordance with a fifth embodiment of the invention;

[0097] Fig. 6A a schematic block diagram of an exemplary target foam selection unit in accordance with a sixth embodiment of the invention; and

[0098] Fig. 6B a schematic block diagram of another exemplary target foam selection unit in accordance with a seventh embodiment of the invention.

[0099] Fig. 1 shows a flow diagram of an exemplary method 100 for pre-processing a foam mix that includes a method 102 for selecting target foam pieces that comprise target foam material in accordance with a first embodiment of the invention. The following discussion will also make reference to the features of exemplary pre-processing arrangements that are shown in Figs. 4 and 5 and described below with more detail. The method 102 for selecting target foam pieces thus forms a first step of the method 100 for pre-processing the foam mix. The method 102 is suitable for selecting, from a foam mix 202 comprising one or more foam pieces 206A, 206B, 203 (see Fig. 4), target foam pieces 206 that comprise target foam material 207 that is suitable for a predetermined recycling process. The method 102 comprises, in a first step 102A, performing a first analysis step for determining first composition data CD1 of a sample foam piece 202C (see e.g. Fig 6A and the corresponding discussion below), the first composition data being indicative of a composition of the sample foam piece 202C. The method also comprises, in a step 102B, performing a second analysis step for determining second composition data CD2 of the sample foam piece 202C, the second composition data being indicative of the composition of the sample foam piece 202C, The method 102 also comprises, in a step 102C, selecting the sample foam piece 202C as a target foam piece 206 upon determining that the first composition data CD1 and the second composition data CD2 are indicative of the target foam material 207.

[0100] Once the target foam piece has been selected according to the method 102, the pre-processing method 100 of Fig. 1 further includes, in a step 104, transporting the selected target foam pieces to a shredding unit 210, in a step 106, shredding the selected target foam pieces 206 to form shredded foam elements 212 and, in an optional step 108, feeding the shredded foam elements 212 into the reactor 150. Fig. 2 shows a flow diagram of another exemplary method 100B for pre-processing a foam mix 202 that includes a method 107 for selecting target foam elements 206 that comprise target foam material 207 in accordance with a second embodiment of the invention. In the method 100B of Fig. 2, performing the method 102 described above is optional, as indicated by the discontinuous line. If the method 102 is not performed, the foam pieces of the foam mix are all transported, in a step 104 to the shredding unit. If the method 102 is performed, only the selected target foam pieces are transported in the step 104. The foam pieces that reach the shredding unit are shredded, in a step 106 to form shredded foam elements. Now, the method 107 for selecting target foam elements, or in other words, foam elements comprising target foam material, is carried out before feeding the selected target foam elements the reactor in an optional step 108.

[0101] The method 107 comprises performing a first analysis step 107A for determining first composition data CD 1 of a sample foam element 212B, the first composition data being indicative of a composition of the sample foam element 212B. The method also comprises performing a second analysis step 107B for determining second composition data CD2 of the sample foam element 212B, the second composition data being indicative of the composition of the sample foam element 212B. The method 107 also comprises, in a step 107C, selecting the sample foam element 212B as a target foam element 216 upon determining that the first composition data CD1 and the second composition data CD2 are indicative of the target foam material 207.

[0102] Fig. 3 shows a flow diagram of an exemplary method 100C for pre-processing a foam mix 202. The method 100C 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, comprises the following steps. In a step 102, the method 102 includes 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. This method step corresponds to the method for selecting a target foam piece described with reference to Fig. 1 above. 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 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, a sucking and / or blowing unit, 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 107. This second sorting step corresponds to the method 107 for selecting target foam elements as discussed with reference to Fig. 2 above. The selected target foam elements are then transported, in a step 110, to a milling unit. Those foam elements that, according to the second sorting step 107, 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. 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 107 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 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 100C 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. In particular the step of pressing the target foam flakes, in preferably performed 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.

[0103] Fig. 4 shows a schematic block diagram of a pre-processing arrangement 200 in accordance with a fourth embodiment of the invention. The pre-processing arrangement 200 is suitable for pre-processing a foam mix 202 for feeding a reactor 250 of a recycling process for recovering raw materials 250. The reactor 250 is exemplarily, but not necessarily, a chemical reactor for chemically recycling PU foam.

[0104] The pre-processing arrangement 200 comprises a target foam selection unit 204, configured to select, from the foam mix 202, target foam pieces 206 comprising target foam 207 that is suitable for the reactor 250. An exemplary target foam selection unit 204 is shown in Fig. 6A. The target foam selection unit 204 of Fig. 6A comprises a foam composition determination unit 205 that is configured to perform a first analysis step (see 102A) for determining first composition data CD1 of a sample foam piece of the foam mix 202, the first composition data being indicative of a composition of the sample foam piece, i.e. the foam piece currently under analysis, and to perform a second analysis step (see 102B) for determining second composition data CD2 of the sample foam piece, the second composition data being indicative of the composition of the sample foam piece. The target foam selection unit 204 also comprises a processing unit 209 that is configured to receive the first composition data CD1 and the second composition data CD2 and to determine that sample foam piece is a target foam piece 206 when both the first composition data and the second composition data are indicative of target foam. If the first composition data CD1 and the second composition data CD2 are not indicative of the target foam material 207 the sample foam piece (see 203) is not selected and is removed from the pre-processing arrangement 200.

[0105] Preferably, the first composition data CD1 is indicative of a type foam, in particular of a type of polyurethane foam of the sample foam piece, and the second composition data is indicative of a type of additive of the sample foam piece, in particular indicative of one or more additives, 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. Additionally, or alternatively, the first composition data and / or the second composition data is indicative of the presence of an impurity or contamination, such as unacceptable dirt, dust, or microbial or fungal layers.

[0106] The pre-processing arrangement 200 further comprises a transporting unit 208 that is configured 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 for feeding to the reactor.

[0107] Fig. 5 shows a schematic block diagram of a pre-processing arrangement 200B in accordance with another embodiment of the invention. The pre-processing arrangement 200B is also suitable for pre-processing a foam mix 202, for example a flexible foam mix, 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. The raw materials to be recovered are typically 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.

[0108] The pre-processing arrangement 200B comprises a first sorting unit 20A that is configured to select, from the foam mix 202 that comprises one or more foam pieces 203, 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. The first sorting unit 204A corresponds to the target foam selection unit 204 described with reference to Fig. 4. The foam composition determination unit 205 of the target foam selection unit 204A 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 foam composition determination unit 205 of the target foam selection unit 204A may also comprise two of the above- mentioned devices, each configured to determine a respective one of the first and the second composition data.

[0109] 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 208 of Fig. 1 is exemplarily configured as a conveyor belt. The shredding unit 210 is configured to shred the selected target foam pieces 206 to form shredded foam elements 212. The shred-ding 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.

[0110] 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. The second sorting unit can be also configured as a target foam selection unit, such as the one described with reference to Fig. 4 204A.

[0111] Due to its position in the pre-processing arrangement 200B of Fig. 5, the second sorting unit 204B is referred to as a foam element selection unit 204B and comprises a foam composition determination unit (analogous to the foam composition determination unit 205 of Fig. 4) that is configured to perform an additional first analysis step (see 107A) for determining first composition data CD1 of a sample foam element, i.e. a foam element under currently under analysis. The first composition data CD1 is indicative of a composition of the sample foam element. It is also configured to perform an additional second analysis step (see 107B) for determining second composition data CD2 of the sample foam element, the second composition data being indicative of the composition of the sample foam element. The foam element selection unit 204B also comprises a processing unit (analogous to the processing unit 209 of Fig. 4) configured to receive the first composition data CD1 and the second composition data CD2 and to determine that sample foam element is a target foam element 216 when both the first composition data CD1 and the second composition data CD2 are indicative of target foam 207.

[0112] Since the target foam pieces 206 may still comprise foam material 211 other than 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.

[0113] 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.

[0114] 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.

[0115] 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. Preferably, the milled target foam flakes have a maximum dimension smaller than 120 mm preferably smaller than 90 mm even more preferable smaller than 70 mm. The arrangements 200, and 200B can be configured as pre-processing arrangements for pre-processing a mattress mix as a foam mix.

[0116] Fig. 6A shows a schematic block diagram of an exemplary target foam selection unit 204A or foam element selection unit 204B in accordance with a sixth embodiment of the invention.

[0117] The target foam selection unit 204A or foam element selection unit 204B comprise a foam composition determination unit 205 that configured to perform the first analysis step (102A or 107A) for determining first composition data CD1 of a sample foam piece 202C or of a sample foam element 212B. Again, the first composition data CD1 is indicative of a composition of the corresponding sample foam piece 202C or element 212B under analysis. The composition determination unit determination unit 205 is also configured to perform a second analysis step (see 102B or 107B) for determining second composition data CD2 of the sample foam piece 202C or element 212B, where the second composition data CD2 is indicative of the composition of the sample foam piece 202C or element 212C under analysis. The first and second composition data CD1 and CD2 are sent to the processing unit 209, which is configured to receive the first composition data CD1 and the second composition data CD2 and to determine that sample foam piece 202C or the sample foam element 212B is a target foam piece 206 or a target foam element 216, when both the first composition data CD1 and the second composition data CD2 are indicative of target foam 207.

[0118] In the exemplary case shown in Fig. 6A, the target foam selection unit 204A or foam element selection unit 204B comprise a first composition determination unit 205a configured to determine the first composition data CD1 and a second composition determination unit 205b configured to determine the second composition data CD2. Optionally, the target foam selection unit 204A or foam element selection unit 204B may comprise at least a third composition determination unit 205c configured to determined third composition data CD3. The first composition determination 205a unit and / or the second composition determination unit 205b can be 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 Raman spectroscopy device, a THz spectroscopy device, a laser induced breakdown spectroscopy device and an X- ray fluorescence device.

[0119] Preferably, the first composition data CD1 is indicative of a type foam, in particular of a type of polyurethane foam PUx of the sample foam piece 202C or of the sample foam element 212B and the second composition data is indicative of a type of additive Ax of the sample foam piece 202C or of the sample foam element 212B. The second composition data can also be indicative of an impurity or a contamination.

[0120] Preferably, the first and the second composition data are obtained from a common location on the sample under analysis, as it is shown in Fig. 4. In an alternative embodiment more than one non-overlapping locations of the sample foam piece 202C and / or the sample foam element 212B are analysed to obtain a better spatial resolution. Fig. 6B shows a schematic block diagram of another exemplary target foam selection unit foam element selection unit 204C in accordance with a seventh embodiment of the invention. In the target foam selection unit foam element selection unit 204C the individual composition determination units 205a, 205b, and, if applicable, 205c, are independent devices, that communicate the determined composition data to the processing unit 209 via a wired or wireless connection.

[0121] In summary, the invention is directed to a method for selecting, from a foam mix comprising one or more foam pieces, target foam pieces that comprise target foam material that is suitable for a predetermined recycling process, the method comprising the steps of performing a first analysis step for determining first composition data of a sample foam piece, the first composition data being indicative of a composition of the sample foam piece, performing a second analysis step for determining second composition data of the sample foam piece, the second composition data being indicative of the composition of the sample foam piece; and selecting the sample foam piece as a target foam piece upon determining that the first composition data and the second composition data are indicative of the target foam material.

[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.

[0124] A single unit or device may fulfil 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.

[0125] Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS1 . Method (102) for selecting, from a foam mix (202) comprising one or more foam pieces (202), target foam pieces (206, 206A, 206B) that comprise target foam material (207) that is suitable for a predetermined recycling process, the method (102) comprising the steps of:- in a first analysis step (102A), determining first composition data (CD1 ) of a sample foam piece (202C) by means of a first analysis-setting, the first composition data being indicative of a composition of the sample foam piece (202C);- in a second analysis step (102B), determining second composition data (CD2) of the same sample foam piece (202C) by means of a second analysis-setting, the second composition data being indicative of the composition of the sample foam piece (202C); and- selecting (102C) the sample foam piece (202C) as a target foam piece (206) upon determining that the first composition data (CD1) and the second composition data (CD2) are indicative of the target foam material (207); wherein the first composition data (CD1) is indicative of a type of foam, in particular of a type of polyurethane foam (PUx), of the sample foam piece (202C) and the second composition data is indicative of a type of additive (Ax) and / or impurity of the sample foam piece (202C).

2. The method (102) of claim 1 , further comprising performing at least a third analysis step for determining at least a third composition data (CD3) indicative of a composition of the sample foam piece (202C) and selecting the sample foam piece (202C) as a target foam piece (206) upon determining that at least a predetermined number of the determined composition data, in particular all of the determined composition data (CD1 , CD2, CD3), is indicative of the target foam material (207).

3. The method (102) of claim 1 or 2, wherein the first analysis step (102A) for determining the first composition data (CD1) and the second analysis step (102B) for determining the second composition data (CD2) are performed using different analytical methods.

4. The method (102) of any of the preceding claims, wherein the first composition data (CD1) and the second composition data (CD2) are obtained from more than one non-overlapping locations of the sample foam piece (202C).

5. The method (102) of any of the preceding claims, wherein the second composition data (CD2) is indicative of one or more additives (Ax) 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 and / or wherein the second composition data (CD2) is indicative of one or more impurities selected from a group consisting of dust, dirt, microbial contamination and fungal contamination.

6. The method (102) of any of the preceding claims, wherein the first analysis step (102A) for determining the first composition data (CD1) and / or the second analysis step (102B) for determining the second composition data (CD2) is performed by one or more analytical 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 THz spectroscopy based method, a UV-Vis spectroscopy based method, an optical-cameras based method, a laser induced breakdown spectroscopy method and an X-ray fluorescence based method.

7. The method (102) of any of the preceding claims, wherein the first analysis step (102A) for determining the first composition data (CD1) is performed using a handheld near infrared spectroscopy device (204).

8. A method (100, 100B, 100C) for pre-processing a foam mix (202) for feeding a reactor (250) of a recycling process, the method (100, 100B, 100C) comprising the steps of:- performing the method (102) of any of the preceding claims 1 to 7 for selecting target foam pieces (206) from the foam mix (202);- 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); and optionally- feeding (108) the shredded foam elements (222) to the reactor (250) for recovering raw materials (252); or comprising the steps of:- transporting the foam mix (202) comprising one or more foam pieces (206A, 206B, 203) to a shredding unit (210);- shredding (106), at the shredding unit (210), the foam pieces to form shredded foam elements (212);- performing the method (107) of any of the preceding claims 1 to 7 on the shredded foam elements for selecting shredded target foam elements upon determining that the first composition data (CD1) and the second composition data (CD2) are indicative of target foam material (207); and- optionally feeding (108) the selected shredded target foam elements (222) to the reactor (250) for recovering raw materials (252); or comprising the steps of- performing the method (102) of any of the preceding claims 1 to 7 for selecting target foam pieces from the foam mix;- 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 the method (107) of any of the preceding claims 1 to 7 on the shredded foam elements for selecting shredded target foam elements upon determining that the first composition data (CD1) and the second composition data (CD2) are indicative of target foam material (207); and- optionally feeding (108) the selected shredded target foam elements (222) to the reactor (250) for recovering raw materials (252).

9. Pre-processing arrangement (200, 200b, 200c) for pre-processing a foam mix for feeding a reactor of a recycling process for recovering raw materials, the pre-processing arrangement (200) comprising at least one target foam selection unit (204, 204b) configured to select, from the foam mix (202), target foam pieces (206A, 206B) comprising target foam (207) that is suitable for the reactor (250), the target foam selection unit (204) comprising:- a foam composition determination unit (205) configured to perform a first analysis step (102a) for determining first composition data (CD1) of a sample foam piece (202C), the first composition data being indicative of a composition of the sample foam piece (202C) being indicative of a type of foam, in particular of a type of polyurethane foam (PUx) of the sample foam piece (202C), and to perform a second analysis step (102b) for determining second composition data (CD2) of the same sample foam piece (202C), the second composition data being indicative of the composition of the sample foam piece (202C) being indicative of a type of additive (Ax) and / or impurity of the sample foam piece (202C); and- a processing unit (209) configured to receive the first composition data (CD1) and the second composition data (CD2) and to determine that sample foam piece (202C) is a target foam piece when both the first composition data and the second composition data are indicative of target foam.

10. The pre-processing arrangement of claim 9, further comprising:- a transporting unit (208) configured 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) for feeding to the reactor.

11. The pre-processing arrangement of claim 10, further comprising a foam element selection unit (204B) that is configured to select, from the shredded foam elements (212), shredded target foam elements (216) comprising target foam (207) that is suitable for the reactor (250).

12. The pre-processing arrangement of claim 11 , wherein the foam element selection unit (204B) comprises:- a foam composition determination unit (205) configured to perform an additional first analysis step (107a) for determining first composition data (CD1) of a sample foam element (212B), the first composition data being indicative of a composition of the sample foam element (212B), and to perform an additional second analysis step (107b) for determining second composition data (CD2) of the sample foam element (212B), the second composition data being indicative of the composition of the sample foam element (212B); and- a processing unit (209) configured to receive the first composition data (CD1 ) and the second composition data (CD2) and to determine that sample foam element (212b) is a target foam element (216) when both the first composition data (CD1) and the second composition data (CD2) are indicative of target foam (207).

13. The pre-processing arrangement of claim 9 or 12, wherein the target foam selection unit (204A) and / or the foam element selection unit (204B) comprise:- a first composition determination unit (205a) configured to determine the first com-position data (CD1); and- a second composition determination unit (205b) configured to determine the second composition data (CD2).

14. The pre-processing arrangement of any of the claims 9, 12 or 13, wherein foam composition determination unit (205) and / or the first composition determination (205a) unit and / or the second composition determination unit(205b) is or are selected from a group consisting of a near-infrared spectroscopy device (204.1), a mediuminfrared spectroscopy device (204.2), a UV-Vis spectroscopy device (204.3), an optical camera (204.4), a Raman spectroscopy device (204.5), a THz spectroscopy device (204.6), a laser induced breakdown spectroscopy device (204.7) and an X-ray fluorescence device (204.8).

15. Computer program comprising instructions which, when executed by a control unit of a target foam selection unit cause the target foam selection unit to perform the method of any of the preceding claims 1 to 7.

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