Neutral hydrolysis of polycaprolactam fragments in automotive shredder residue for recovering caprolactam

Abstract

A method for recycling caprolactam from an automotive shredder residue comprising polycaprolactam comprising: a) mixing the automotive shredder residue with water, whereby a mixture 1 containing polycaprolactam and water is obtained; b) depolymerizing the polycaprolactam present in the mixture 1 without addition of a depolymerization catalyst at a temperature of 200°C to 600°C, preferably 300 to 400 °C and a pressure of 30 to 200 bar, preferably 40 to 140 bar to produce a mixture 2 comprising caprolactam; c) recovering the caprolactam.; and caprolactam obtainable by the method according to the present invention and the use of an automotive shredder residue comprising polycaprolactam and glass fibers for recycling caprolactam in the absence of a depolymerization catalyst.

Description

Neutral hydrolysis of polycaprolactam fragments in automotive shredder residue for recovering caprolactamDescriptionThe present invention relates to a method for recycling caprolactam from an automotive shredder residue comprising polycaprolactam comprising: a) mixing the automotive shredder residue with water, whereby a mixture 1 containing polycaprolactam and water is obtained; b) depolymerizing the polycaprolactam present in the mixture 1 without addition of a depolymerization catalyst at a temperature of 200°C to 600°C, preferably 300 to 400 °C and a pressure of 30 to 200 bar, preferably 40 to 140 bar to produce a mixture 2 comprising caprolactam; c) recovering the caprolactam.The present invention further relates to caprolactam obtainable by the method according to the present invention and the use of an automotive shredder residue comprising polycaprolactam and glass fibers for recycling caprolactam in the absence of a depolymerization catalyst.Automotive shredder residue (ASR) holds significant relevance in the context of recycling due to its composition and environmental impact. ASR is a typical byproduct of the shredding process used to recycle end-of-life vehicles, and it consists usually of various materials such as plastics, rubber, glass, textiles, and metals that cannot be easily separated. This complex mixture poses challenges for traditional recycling methods. However, ASR has gained attention as an alternative energy source through technologies like thermal treatment. By converting ASR into energy, it reduces the reliance on fossil fuels and contributes to a more sustainable future. Additionally, efforts are being made to improve the recycling efficiency of ASR by developing advanced sorting and separation techniques, which would enhance the recovery of valuable materials and minimize its environmental impact. Overall, the relevance of ASR recycling lies in its potential to promote resource conservation, reduce landfill waste, and support the development of innovative recycling solutions.EP0692356 A1 suggests to recycle automotive shredder residue by preparing a composite material comprising ASR and a virgin polymer.Vijayan, S.K.; Kibria, M.A.; Uddin, M.H.; Bhattacharya, S. “Pretreatment of Automotive Shredder Residues, Their Chemical Characterisation, and Pyrolysis Kinetics.” Sustainability 2021 , 13, 10549 suggests to recycle automotive shredder residue by pyrolysis.Ezzat El Halabi, Mike Third, and Matthew Doolan “Machine-based dismantling of end of life vehicles: A life cycle perspective” Procedia, 29 (2015) 651-655 suggest to recycle automotive shredder residue by machine based dismantling.Juliana Argente Caetano, Valdir Schalch, Javier Mazariegos Pablos “Characterization and recycling of the fine fraction of automotive shredder residue (ASR) for concrete paving blocks production” Clean Technologies and Environmental Policy (2020) 22:835-847 suggest to recycle ASR by solidification with cement, gravel and sand for paving blocks production.Won-Seok Yang et al. “Utilization of automobile shredder residue (ASR) as a reducing agent for the recovery of black copper” Korean J. Chem. Eng., 33(4), 1267-1277 (2016) suggests to recycle ASR by using it instead of lump coal as a reducing agent in the copper production.It is an object of the present invention to find a simple and inexpensive method for recycling automotive shredder residue (ASR), especially for recycling the polymers comprising glass fibers, more especially polycaprolactam comprising glass fibers in ASR.The object is achieved by a method for recycling caprolactam from an automotive shredder residue comprising polycaprolactam comprising: a) mixing the automotive shredder residue with water, whereby a mixture 1 containing polycaprolactam and water is obtained; b) depolymerizing the polycaprolactam present in the mixture 1 without addition of a depolymerization catalyst at a temperature of 200°C to 600°C, preferably 300 to 400 °C and a pressure of 30 to 200 bar, preferably 40 to 140 bar to produce a mixture 2 comprising caprolactam; c) recovering the caprolactam.The object is further achieved by caprolactam obtainable by the method according to the present invention and the use of an automotive shredder residue comprising polycaprolactam and glass fibers for recycling caprolactam in the absence of a depolymerization catalyst.It has been found by the inventors that the value product caprolactam can be recycled from polycaprolactam comprising ASR by the inventive process. It has especially been found that no separation of glass fibers and optionally further insolubles is necessary before the depolymerization. By said process a simple and inexpensive method for recycling automotive shredder residue is therefore provided.The automotive shredder residue may be obtainable, preferably is obtained, by shredding vehicles. Preferably, the automotive shredder residue is obtainable by depollution of the vehicles, dismantling the vehicles, shredding the vehicles, and separating metal particles from the shredded vehicles.The vehicles are typically end-of-life vehicles (also called “ELV”), which are typically at least 15 years old. The vehicles can be passenger cars, light-duty or heavy-duty trucks, motorbikes, autility vehicle, an agricultural vehicle, or recreational vehicles. The vehicle can be an electric vehicle, such as a fully electric vehicle or a hybrid electric vehicle.In depollution of vehicles hazardous liquids such as fuel, lubricating oil, coolants, brake fluids and batteries can be removed from the vehicles prior to shredding.The dismantling of vehicles may comprise selective removal of parts, such as engines, gearboxes, tires, glass and plastics, for being reused as spare parts for the second-hand market. The dismantling may also comprise the removal of larger plastic components, such as bumpers, dashboard, fluid containers for recycling the plastics separately.The ASR may comprise further waste from other sources. For examples, garbage from the last owners may remain in the trunk or interior of the vehicles. The advantage of the present process is that it can handle broadly varying compositions of the ASR.The shredding can be made with a vehicle shredder machine. Vehicle shredder machines are manufactured in different sizes. Typically, a vehicle shredder machine comprises a heavy fastturning rotor, which may revolve in a vertical or a horizontal plane and is often equipped with swinging hammers. The vehicle shredder machine tears and shreds the car hulk until its parts are reduced to fragments with a desired fragment size, such as up to 30 cm, preferably 1 mm to 15 cm. Then the fragments may pass through grids and leave the rotor housing.After shredding, the metal fragments such as ferrous and non-ferrous metal fragments can be separated from the shredded vehicles. The ferrous metal fragments can be removed by magnetic separators. The non-ferrous metal fragments can be separated from the shredded vehicles by eddy current separators, by heavy media sink / float units which separate on the basis of density, or by manual sorting. Typically, 60 - 90 wt% of the vehicle weight is metal, which can be separated from the shredded vehicle.The automotive shredder residue may represent about 10 - 40 wt%, preferably from 15 - 35, and in particular from 20 - 30 wt% of the original vehicle weight.The automotive shredder residue may comprise fragments of various polymeric vehicle parts, such as fragments of bumpers, interior panels, dashboard, cable insulation, fuel tank, electrical insulation, flexible foam seating, foam insulation panels, automotive suspension bushings, electrical potting compounds, car body parts, pillar coverings, spoilers polymer parts coated with automotive paint, wheel covers, gears, bushes, cams, bearings, weatherproof coatings, interior and exterior trims, fuel systems, gear housings, headlamp retainer, engine cover, connector housings, door handles, carburetor components, exterior mirror components, windscreen wiper components, windscreen wiper protective housings, decorative grilles, cover strips, roof rails, window frames, sliding roof frames, antenna cladding covers, front and rear lights, radiator grilland body exterior parts, engine covers, cylinder head covers, intake pipes, cylinder head covers, engine covers, housings for charge air coolers, charge air cooler valves.The automotive shredder residue may comprise fragments of various polymeric vehicle parts, such as fragments of- bumpers, interior panels, dashboard, cable insulation, where these fragments are often made of polypropylene;- fuel tank, electrical insulation, where these fragments are often made of polyethylene;- flexible foam seating, foam insulation panels, automotive suspension bushings, electrical potting compounds, hard plastic parts, transmission mounts, motor mounts, seals, impact foam parts, where these fragments are often made of polyurethane;- body parts, dashboards, wheel covers, where these fragments are often made of acryloni- trile-butadiene-styrene;- gears, bushes, cams, bearings, charge air coolers, cylinder head covers, oil pans, engine cooling systems, thermostat and heater housings, exhaust systems including mufflers and housings for catalytic converters, air intake manifolds, timing chain belt front covers, where these fragments are often made of nylon 6 or nylon 6.6.;- interior and exterior trims, fuel systems, small gears, where these fragments are often made of polyoxymethylene;- wiper arm and gear housings, headlamp retainer, connector housings, where these fragments are often made of polyethylene terephthalate; and- door handles, bumpers, carburetor components, where these fragments are often made of polybutylene terephthalate.The automotive shredder residue may comprise at least 30 wt%, preferably at least 40 wt%, and in particular at least 50 wt% of the fragments of the polymeric vehicle parts. In another form the automotive shredder residue may comprise at least 70 wt%, preferably at least 80 wt%, and in particular at least 90 wt% of the fragments of the polymeric vehicle parts.The automotive shredder residue may comprise at least 20 wt%, preferably at least 30 wt%, and in particular at least 40 wt% of the fragments of the polymeric vehicle parts, which are black polymeric vehicle parts. In another form the automotive shredder residue may comprise at least 70 wt%, preferably at least 80 wt%, and in particular at least 90 wt% of the fragments of the polymeric vehicle parts, which are black polymeric vehicle parts. The black polymeric vehicle parts usually comprise carbon black pigments.The automotive shredder residue may comprise up to 15 wt%, preferably up to 10 wt%, and in particular up to 5 wt% of metal fragments, such as ferrous and non-ferrous metal particles.The automotive shredder residue may comprise up to 15 wt%, preferably up to 10 wt%, and in particular up to 5 wt% of wood and cardboard.The automotive shredder residue may comprise up to 15 wt%, preferably up to 10 wt%, and in particular up to 5 wt% of glass fragments, e.g. broken window glass fragments.The automotive shredder residue can be separated into a shredder light fraction (also called SLF) and a shredder heavy fraction (also called SHF). The separation of the SLF and the SHF can be achieved by air classification. Another air classification can be made by the rotary movement of the vehicle shredder machine may create a fanning action that can blow out the shredder light fraction, and the shredder heavy fraction may leave the vehicle shredder machine through a grid.The SLF can be present in an amount of 55 - 90 wt%, preferably 65 - 85 wt%, and in particular at 70 - 80 wt% of the automotive shredder residue. The SHF may represent the remaining amount to 100 wt%.The SHF can be present in an amount of 10 - 45 wt%, preferably 15 - 35 wt%, and in particular at 20 - 30 wt% of the automotive shredder residue. The SLF may represent the remaining amount to 100 wt%.The SLF usually contains a lower weight percentage of rubber particles than the SHF. The SLF usually contains a lower weight percentage of glass particles than the SHF. The SLF usually contains a lower weight percentage of metal particles than the SHF.The SLF usually contains a higher weight percentage of polyurethane foam particles than the SHF.The SLF usually contains a lower weight percentage of solid and sand than the SHF.Figure 1 shows a possible flow scheme with a suitable process sequence for obtaining the automotive shredder residue and for obtaining caprolactam by the inventive process. Starting from the vehicles, followed by optional depollution, followed by optional dismantling, followed by shredding the vehicles, followed by optional separating the metal fragments from the shredded vehicle, then the ASR is obtained, followed by optional separation of the ASR in shredder light fraction and shredder heavy fraction. The depolymerization comprises the mixing with water, followed by the depolymerization to produce caprolactam, followed by the recovery of caprolactam and optionally by the polymerization of caprolactam to produce polycaprolactam.Generally, the ASR comprises inorganic and organic material.The polymeric vehicle parts (plastics) are considered as organic material.The metal fragments (metal), such as ferrous and non-ferrous metal particles and wire are considered as inorganic material.The wood and cardboard are considered as organic material.The glass fragments (glass), e.g. broken window glass fragments are considered as inorganic material.The ASR may further comprise dirt in form of soil and sand. If dirt is present, it is generally present in an amount of at least 1 wt%, preferably at least 3 wt%, more preferably at least 5 wt%. The dirt is considered as inorganic material.Further, non-identified other components may be present in the ASR. If non-identified other components are present, they are generally present in an amount of at least 3 wt%, preferably at least 5 wt%, more preferably at least 10 wt%. The non-identified other components are considered as organic material.Preferably, the ASR (automotive shredder residue) comprises at least 5 wt%, preferably 8 to 40 wt%, more preferably 10 to 35 wt% of inorganic material. The inorganic material preferably comprises glass, metal and dirt. The glass is preferably present at least in part in form of glass fibers. The metal is preferably present at least in part in form wire or ferrous and non-ferrous metal particles.Further preferably, the glass fibers are at least in part present in the polycaprolactam, i.e. as reinforcing material. The polycaprolactam is preferably present in the ASR in form of reinforced polycaprolactam.Further preferably, the ASR comprises at least 60 wt%, preferably 60 to 92 wt%, more preferably 65 to 90 wt% of organic material comprising plastics. The organic material preferably comprises rubber, wood, plastics including polycaprolactam, polyurethane, and at least one of paper and cardboard. In another preferred form, the ASR comprises at least 30 wt%, preferably at least 50 wt%, and in particular at least 70 wt% of polycaprolactam.Preferably, the plastics comprise at least 2 wt%, preferably 4 to 40 wt%, more preferably 5 to 30 wt% polycaprolactam. In another preferred form, the plastics comprise at least 30 wt%, preferably at least 50, and in particular at least 70 wt% polycaprolactam.The ASR that is used in step a) has been obtained by the steps mentioned above, generally known in the art.Step a)The step a) comprises mixing the ASR (automotive shredder residue) with water, whereby a mixture 1 containing polycaprolactam and water is obtained.The automotive shredder residue (ASR) is known in the art and defined above. In the inventive method it is generally possible to employ the complete ASR, a shredder light fraction (SLF) and / or a shredder heavy fraction (SHF).The polycaprolactam (also described as polyamide 6, PA6, nylon 6, poly-e-caproamide) is any polycaprolactam present in ASR. Generally, the polycaprolactam in step a) has a viscosity number of 90 to 350 ml / g, preferably from 100 to 240 ml / g. The viscosity number (VN) of the polyamides and polyamide compositions according to the present invention is determined according to EN ISO 307:2019 in sulphuric acid (0.5% [m / v] of polycaprolactam in 96 wt.-% [m / m] sulphuric acid at 25 °C), unless indicated otherwise.The polycaprolactam in the automotive shredder residue is generally reinforced polycaprolactam comprising at least partly the glass fibers mentioned above. The reinforced polycaprolactam preferably comprises 5 to 50 wt%, more preferably 10 to 40 wt%, most preferably 15 to 35 wt% of glass fibers, based on the total amount of polycaprolactam and glass fibers.The glass fibers are generally chopped fibers, also called short fibers, having a length in the range from 0.1 to 1 mm, long fibers having a length in the range from 1 to 50 mm, and continuous fibers having a length l>50 mm. Continuous fibers are used in the form of rovings or fabric in fiber-reinforced plastics.Also available are ground glass fibers, the length of which after grinding is typically in the range from 70 to 200 pm.Particular preference being given to glass fibers in the form of rovings or in the forms of chopped glass as described above.Preferred examples of glass fibers are chopped long glass fibers having an average starting length to be determined by laser diffraction-particle size analysis (laser granulometry / laser diffractometry) according to ISO 13320:2009 in the range from 1 to 50 mm, more preferably in the range from 1 to 10 mm, most preferably in the range from 2 to 7 mm. Most preferred glass fibers have an average fiber diameter to be determined by laser diffractometry according to ISO 13320:2009 in the range from 7 to 18 pm, more preferably in the range from 9 to 15 pm.The glass fibers may be modified with a suitable size system or an adhesion promoter / adhesion promoter system. Preference is given to using a size system or an adhesion promoter based on silane, to improve compatibility with the thermoplastic. Suitable size systems and adhesion promoter / adhesion promoter systems are known by a person skilled in the art.The glass fibers present in the ASR, as a result of the processing, may be shorter in the composition than the glass fibers originally used and described above. Thus, the arithmetic average ofthe glass fiber length after processing, to be determined by high-resolution X-ray computed tomography, is frequently only in the range from 150 pm to 300 pm.Generally, any type of glass fibers may be present (e.g. E, A, C, D, ECR, AR, R, S-2). Particular preference being given to glass fibers in the form of E glass.The mixing of the ASR with water can be done conventionally, such as by adding the water to the ASR, or by adding the ASR to the water. The water can be introduced cold (e.g. 0.5 °C to 25°C) or hot (e.g. > 25°C to < 100°C).The mixing is typically carried out for at least 10 min, 30 min, 1 , 2, 3, 4, 5, 6, 7, 8, 9, or 10 hours and it may take up to 72, 48, or 24 hours. A preferred mixing time is 10 Min. to 3 hours. The exact mixing time will depend on the size of the automotive shredder residue and the polycaprolactam present.The mixing can be carried out at temperatures in the range from 0.5 to <100°C, preferably at 10 to 50 °C, more preferably at 15 to 30 °C, most preferably at 20 to 25 °C. The pressure is preferably 1 bar to 3 bar, more preferably atmospheric pressure (e.g. at 1 bar (1.01325 bar)).Generally, it is also possible to carry out the mixing above 100°C, e.g. > 100°C to 200°C. In this case, the mixing is carried out at elevated pressure (e.g. > 1bar, such as > 1 bar to 3 bar).Preferably, the mixing is carried out at a temperature of 15 to 30°C, preferably 20 to 25°C and atmospheric pressure (e.g. 1 bar (1.01325 bar)).The mixing is generally done in any vessel or tank. Stirring is possible but not mandatory. Suitable vessels and tanks are known in the art. Preferably, the mixing is done directly in the device suitable for the depolymerization in step b). Suitable devices are known in the art.The weight ratio of the water to the polycaprolactam (without glass fibers) in step a) is generally in the range from 1 :1 to 30:1 , preferably 2:1 to 20:1 , more preferably from 7:1 to 15:1.Step a) can be operated in a batch mode, in a semi-continuous mode or in a continuous mode, all of which are known to the skilled person. Preferably, step a) is operated in a batch mode.Suitable devices for carrying out step a) (e.g. mixer) are known by a person skilled in the art.Step b)Step b) comprises depolymerizing the polycaprolactam present in the mixture 1 without addition of a depolymerization catalyst at a temperature of 200°C to 600°C, preferably 250 to 400 °C and a pressure of 30 to 200 bar, preferably 40 to 140 bar to produce a mixture 2 comprising caprolactam. Generally, the pressure is a function of the temperature.Processes for depolymerization of polycaprolactam are generally known.Generally, the depolymerization of polycaprolactam into caprolactam monomers comprises a hydrolytic degradation step, usually at elevated temperature, generally in the presence of water and a recovery step of the formed monomer for example by steam distillation. The hydrolytic degradation step can be performed in both the presence and the absence of a catalyst. According to the process of the present invention, the depolymerization is carried out without addition of a depolymerization catalyst.In step b) of the inventive process the polycaprolactam is depolymerized by heating with steam, preferably superheated steam, generally with a nominal temperature of 200°C to 600°C, preferably 300 to 400 °C and a pressure of 30 to 200 bar, preferably 40 to 140 bar.It has been found by the inventors that a depolymerization of polycaprolactam ist possible directly from a mixture of ASR and water, without separating the polycaprolactam or plastics from the ASR before depolymerization. It has further been found that a “neutral” depolymerization, without addition of a depolymerization catalyst, is possible. The inventive process is therefore extremely convenient and efficient.The depolymerization in step b) is generally carried out for 0.1 hour to 24 hours, preferably 0.2 hour to 8 hours, more preferably 0.5 hours to 3 hours.Suitable devices (depolymerization reactors / hydrolyzer) for carrying out the depolymerization step b) are known by a person skilled in the art.Feeding steam to the depolymerization reactor according to step b) of the present invention allows, optionally without further heating, to obtain a vapor stream comprising caprolactam and water. The weight to weight ratio of caprolactam to water in said vapor stream can be adjusted by modifying the amount of water used in step a).During the depolymerization in step b) typically at least 60 wt% of the polycaprolactam, preferably 80-100 wt%, are depolymerized into caprolactam.Step c)Step c) comprises recovering the caprolactam. The caprolactam is generally recovered directly from mixture 2,.Preferably, the mixture 2 obtained in step b) is cooled before the recovering in step c). Preferably, the mixture is cooled to a temperature of < 100°C, more preferably to 98°C to 20°C.Generally, any method known in the art for the separation of caprolactam from water can be used in step c), e.g. extraction, flash separation, e.g. evaporation or distillation. Preferably, the caprolactam is recovered by evaporation or distillation, more preferably by distillation.It is possible to separate all or a part of insolubles present in mixture 2, e.g. by filtration or centrifugation, before the separation of the caprolactam from water.Preferably, in the recovering step c) water is removed from the mixture 2, followed by recovering the caprolactam. More preferably, at least 75 wt% of the water present in mixture 2 is removed prior to the recovering of caprolactam, preferably by evaporation or distillation. The recovering steps mentioned before are known by a person skilled in the art.Step c) is operated in a batch mode, in a semi-continuous mode or in a continuous mode, all of which are known to the skilled person. Preferably, step c) is operated in a batch mode.Following step c), in general substantially pure caprolactam is obtained. The recovered caprolactam can be used in all applications, wherein virgin caprolactam is used. The recovered caprolactam may be useful for preparing polycaprolactam and other uses requiring the use of substantially pure caprolactam.In another form the method comprises the step: converting the plastic fragment mix obtainable by or obtained by the method according to the invention to obtain a product PRF1.More specifically, the method comprises the additional step of: converting the caprolactam obtainable by or obtained by the method according to the invention to obtain a product PRF1 .The product PRF1 may be selected from: i) building block or monomer; or ii) polymer, preferably polymer A, polymer composition, preferably polymer composition A, or polymer product, preferably polymer product A; or iii) industrial use polymer, industrial use surfactant, descaling compound, industrial use biocide, industrial use solvent, industrial use dispersant, composition thereof or formulation thereof; or iv) agrochemical composition, agrochemical formulation auxiliary or agrochemically active ingredient; or v) active pharmaceutical ingredient or intermediate thereof, pharmaceutical excipient, animal feed additive, human food additive, dietary supplements, aroma chemical or aroma composition; or vi) aqueous polymer dispersion, preferably polyurethane or polyurethane - poly(meth)acry- late hybrid polymer dispersion, emulsion, binder for paper and fiber coatings, UV-curable acrylicpolymer for hot melts and coatings polyisocyanates, hyperbranched polyester polyol, polymeric dispersant for inorganic binder compositions, unsaturated polyester polyol or 100% curable composition; or vii) cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter, further cosmetic ingredient or composition or formulation thereof; or viii) polymer B, polymer composition B, coating composition, other functional composition, foil, molded body, coating or coated substrate.The content of the caprolactam obtained by the method according to the invention in the product PRF1 can be 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight- % or more, more preferably 15 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 60 weight-% or more, more preferably 80 weight-% or more, more preferably 90 weight-% or more, more preferably 95 weight-% or more, based on the total content of caprolactam in the product PRF1 .In further embodiments, the content of the caprolactam obtained by the method according to the invention in the product PRF1 can be 100 weight-% or less, preferably 95 weight-% or less, more preferably 90 weight-% or less, more preferably 50 weight-% or less, more preferably 25 weight-% or less, more preferably 10 weight-% or less, based on the total content of caprolactam in the product PRF1 .Preferably this content is determined based on identity preservation and / or segregation and / or mass balance and / or book and claim chain of custody models, preferably based on mass balance, preferably the International Sustainability and Carbon Certification (ISCC) standard.The publication Prior Art Disclosure; Issue 684; paragraphs

[1000] to

[8005] ; ISSN: 2198-4786; published: February 12, 2024 will be regarded as Reference RF1 , which is incorporated herein by reference in its entirety. Preferably, the product PRF1 is a product as described in Reference RF1 ; paragraphs

[1000] to

[8005] , Preferably, the method described herein is further a method for the production of a product, preferably product PRF1.The converting step to obtain the product PRF1 preferably comprises one or more step(s) as described below and can be performed by conventional methods well known to a person skilled in the art. The converting step preferably comprises one or more step(s) selected from: recycling, preferably depolymerizing, gasifying, pyrolyzing, and / or steam cracking; and / or purifying, preferably crystallizing, (solvent) extracting, distilling, evaporating, hydrotreating, absorbing, adsorbing and / or subjecting to ion exchanger; and / or assembling, preferably foaming, synthesizing, chemical conversion, chemically transforming, polymerizing and / or compounding; and / or forming, preferably foaming, extruding and / or molding; and / or finishing, preferably coating and / or smoothing.In addition, the one or more step(s) are described in detail in Reference RF1 ; paragraphs

[1000] to

[8005] ,The term “building block”, as used herein, comprises compounds, which are in a gaseous or liquid state under standard conditions of 0°C and 0.1 MPa. Building blocks are typically used in chemical industry to form secondary products, which provide a higher structural complexity and / or higher molecular weight than the building block on which the secondary product is based. The building block is preferably selected from the group consisting of hydrogen, carbon monoxide, carbon dioxide, ethylene oxide, ethylene glycols, syngas comprising a mixture of hydrogen and carbon monoxide, alkanes, alkenes, alkynes and aromatic compounds. The alkanes, alkenes, alkynes and aromatic compounds comprise in particular 1 to 12 carbon atoms, respectively.The term “monomer”, as used herein, comprises molecules, which can react with each other to form polymer chains by polymerization. The monomer is preferably selected from the group consisting of (meth)acrylic acid, salts of (meth)acrylic acid; in particular sodium, potassium and zinc salts; (meth)acrolein and (meth)acrylates. (Meth)acrylates comprising 1 to 22 carbon atoms are preferred, in particular comprising 1 to 8 carbon atoms. The terms (meth)acrylic acid, (meth)acrolein or (meth)acrylate relate to acrylic acid, acrolein or acrylate and also to methacrylic acid, methacrolein or methacrylate, where applicable. Further, the monomer can be selected from hexamethylenediamine (HMD) and adipic acid.The building block can further be an intermediate compound. The term “intermediate compound”, as used herein, comprises organic reagents, which are applied for formation of compounds with higher molecular complexity. The intermediate compound can be selected for example from the group consisting of phosgene, polyisocyanates and propylene oxide. The polyisocyanates are in particular aromatic di- and polyisocyanates, preferably toluene diisocyanate (TDI) and / or diphenylmethane diisocyanate (MDI).The building block and the monomer and typical converting step(s) to obtain the building block or monomer are described in more detail in paragraphs

[1000] to

[1012] of Reference RF1.The term “polymer A”, as used herein, comprises thermoplastic, e.g., polyamide or thermoplastic polyurethane, thermoset, e.g., polyurethane, elastomer, e.g., polybutadiene, or a copolymer or a mixture thereof and is defined in more detail in paragraphs

[2001] to

[2007] of Reference RF1 .The term “polymer composition A”, as used herein, comprises all compositions comprising a polymer as described above and one or more additive(s), e.g. reinforcement, colorant, modifier and / or flame retardant, and is defined in more detail in paragraph

[2008] of Reference RF1. The term “polymer product A”, as used herein, comprises any product comprising the polymer A and / or polymer composition A as described above and is defined in more detail in paragraphs

[2009] and

[2010] of Reference RF1.The step(s) to obtain the polymer, preferably polymer A, polymer composition, preferably polymer composition A or polymer product, preferably polymer product A is / are described in more detail in paragraph

[2011] of Reference RF1.The term “industrial use polymer”, as used herein, comprises rheology, polycarboxylate, alkox- ylated polyalkylenamine, alkoxylated polyalkylenimine, polyether-based, dye inhibition and soil release cleaning polymers defined in more detail in paragraphs

[3035] to

[3044] of Reference RF1. The term “industrial use surfactant”, as used herein, comprises non-ionic, anionic and amphoteric industrial use surfactants defined in more detail in paragraphs

[3008] to

[3034] of Reference RF1. The term “industrial use descaling compound”, as used herein, comprises nonphosphate based builders (NPB) and phosphonates (CoP) described in more detail in paragraphs

[3001] to

[3005] of Reference RF1. The term “industrial use biocide”, as used herein, refers to a chemical compound that kills microorganisms or inhibits their growth or reproduction defined in more detail in paragraphs

[3006] to

[3007] of Reference RF1. The term “industrial use solvent”, as used herein, comprises alkyl amides, alkyl lactamides, alkyl esters, lactate esters, alkyl diester, cyclic alkyl diester, cyclic carbonates, aromatic aldehydes and aromatic esters defined in more detail in paragraphs

[3045] to

[3055] of Reference RF1. The term “industrial use dispersant”, as used herein, comprises anionic and non-ionic industrial use dispersants defined in more detail in paragraphs

[3056] to

[3058] of Reference RF1 . The term “composition and / or formulation thereof’ with reference to the industrial use polymers, industrial use surfactants, descaling compounds and / or industrial use biocides refers to industrial use compositions and / or institutional use products and / or fabric and home care products and / or personal care products defined in more detail in paragraph

[3059] of Reference RF1 . The converting step(s) to obtain the industrial use polymer, industrial use surfactant, descaling compound and / or industrial use biocide are defined in more detail in paragraph

[3060] of Reference RF1. The converting steps to obtain the industrial use composition or formulation of the industrial use polymer, industrial use surfactant, descaling compound and / or industrial use biocide are defined in more detail in paragraph

[3061] of Reference RF1 .The term “agrochemical composition”, as used herein, typically relates to a composition comprising an agrochemically active ingredient and at least one agrochemical formulation auxiliary. Examples of agrochemical compositions, active ingredients and auxiliaries are described in more detail in Reference RF1 , paragraph

[4001] ,The agrochemical composition may take the form of any customary formulation. The agrochemical compositions are prepared in a known manner, e.g. described by Mollet and Grubemann, Formulation technology, Wiley VCH, Weinheim, 2001 ; or Knowles, New developments in crop protection product formulation, Agrow Reports DS243, T&F Informa, London, 2005. The converting step(s) to obtain the agrochemically active ingredients and auxiliaries may be conducted in analogy to the production step(s) of their analogues that are based on petrochemicals or other precursors that are not gained by recycling processes. In addition, conversion to compounds mentioned in sections “Polymer” and “Cosmetic surfactant, emollient, wax, cosmeticpolymer, UV filter, further cosmetic ingredient or compositions or formulations thereof’ may be performed as described in these sections as well as the respective paragraphs in Reference RF1.The term active pharmaceutical ingredients and / or intermediates thereof, as used herein, comprises substances that provide pharmacological activity or other direct effect in the diagnosis, cure, mitigation, treatment, or prevention of disease, or to affect the structure or any function of the body. Intermediates thereof are isolated products that are generated during a multi-step route of synthesis of an active pharmaceutical ingredient. The term pharmaceutical excipients, as used herein, comprises compounds or compound mixtures used in compositions for various pharmaceutical applications, which are not substantially pharmaceutically active on itself. Active pharmaceutical ingredients and / or intermediates thereof and pharmaceutical excipients are defined in more detail in paragraph

[5001] of Reference RF1.The converting step(s) to obtain the active pharmaceutical ingredients and / or intermediates thereof and pharmaceutical excipients may comprise one or more synthesis steps and can be performed by conventional synthesis and techniques well known to a person skilled in the art.The terms animal feed additives, human food additives, dietary supplements, as used herein, comprises Vitamins, Pro-Vitamins and active metabolites thereof including intermediates and precursors, especially Vitamin A, B, E, D, K and esters thereof, like acetate, propionate, palmitate esters or alcohols thereof like retinol or salts thereof and any combinations thereof; Tetraterpenes, especially isoprenoids like carotenoids and xanthophylls including their intermediates and precursors as well as mixtures and derivates thereof, especially beta carotene, Canthaxan- thin, Citranaxanthin, Astaxanthin, Zeaxanthin, Lutein, Lycopene, Apo-carotenoids, and any combinations thereof; organic acids, especially formic acid, propionic acid and salts thereof, such as sodium, calcium or ammonium salts, and any combinations thereof, such as but not limited to mixtures of formic acid and sodium formiate, propionic acid and ammonium propionate, formic acid and propionic acid, formic acid and sodium formiate and propionic acid, propionic acid and sodium propionate and formic acid and sodium formiate; glycerides of carboxylic acids and short and medium chain fatty acids, conjugated linoleic acids, such as omega-6 fatty acid (C18:2) methyl ester and 1 ,2-propandiol and beverage stabilizers, such as polyvinylpyrroli- done-polymer or polyvinylimidazole / polyvinylpyrrolidone-copolymer. Animal feed additives, human food additives and dietary supplements are defined in more detail in paragraph

[5002] of Reference RF1.The converting step(s) to obtain the animal feed additives, human food additives, dietary supplements may comprise one or more synthesis steps and can be performed by conventional synthesis and techniques well known to a person skilled in the art.The terms aroma chemical and aroma composition as used herein, comprise a volatile organic substance with a molecular weight between 70-250 g / mol comprising a functional group with a carbon skeleton of C5-C16 carbon atoms comprising linear, branched, cyclic, for example with aring size of C5-C18, bicyclic or tricyclic aliphatic chains and but not necessarily one or more unsaturated structural elements like double bonds, triple bonds, aromatics or heteroaromatics and preferably the one or more additional functional groups are selected from alcohol, ether, ester, ketone, aldehyde, acetal, carboxylic acid, nitrile, thiol, amine. In one aspect, the aroma chemical is a terpene-based aroma chemical, for example selected from monoterpenes and monoterpenoids, sesquiterpenes and sesquiterpenoids, diterpenes, triterpenes or tetraterpenes. Aroma chemicals can be combined with further aroma chemicals to give an aroma composition. Aroma chemicals and aroma compositions are defined in more detail in paragraph

[5003] of Reference RF1.The converting step(s) to obtain the aroma chemical and aroma composition may comprise one or more synthesis steps and can be performed by conventional synthesis and techniques well known to a person skilled in the art.The term “aqueous polymer dispersion”, as used herein, comprises aqueous composition(s) comprising dispersed polymer(s) and is defined in more detail in the section

[6001] entitled “aqueous polymer dispersion” of Reference RF1 . The dispersed polymer(s) may be selected from acrylic emulsion polymer(s), styrene acrylic emulsion polymer(s), styrene butadiene dispersions), aqueous dispersion(s) comprising composite particles, acrylate alkyd hybrid dispersions), polyurethane(s) (including UV-curable polyurethanes) and polyurethane - poly(meth)acrylate hybrid polymer(s). The term “emulsion polymer”, as used herein, comprises polymer(s) made by free-radical emulsion polymerization. Aqueous polyurethane dispersion(s) are defined in more detail in the section

[6002] entitled “Polyurethane dispersions” of Reference RF1 . UV-curable polyurethane(s) is / are defined in more detail in the section

[6017] of Reference RF1. Polyurethane - poly(meth)acrylate hybrid polymer(s) is / are defined in more detail in the section

[6016] of Reference RF1 .The term “polymeric dispersant”, as used herein, comprises preferably polymer(s) comprising polyether side chain, in particular polycarboxylate ether polymer(s) and polycondensation produces) defined in more detail in paragraph

[6020] entitled “Polymeric dispersant” of Reference RF1.The converting (polymerization) step(s) to obtain the aqueous polymer dispersion(s) comprising emulsion polymer(s) is / are defined in more detail in the section

[6003] entitled “Emulsion polymerization” of Reference RF1.The converting (polymerization) step(s) to obtain the aqueous polyurethane dispersion(s) is / are defined in more detail in the section

[6014] entitled “Process for the preparation of aqueous polyurethane dispersions” and section

[6017] entitled “Aqueous UV-curable polyurethane dispersions, their preparation and use and compositions containing them” of Reference RF1 . Composition(s) and uses of aqueous polymer dispersion(s) and of polymeric dispersant(s) are defined in more detail in the following sections of Reference RF1 : section

[6004] entitled “Uses of aqueous polymer dispersions”, section

[6005] entitled “Binders for architectural and construction coatings”section

[6006] entitled “Binders for paper coating” section

[6007] entitled “Binders for fiber bonding” section

[6008] entitled “Adhesive polymers and adhesive compositions” section

[6015] entitled “Aqueous polyurethane dispersions suitable for use in coating compositions” section

[6016] entitled “Aqueous polyurethane - poly(meth)acrylate hybride polymer dispersions suitable for use in coating compositions” section

[6017] entitled “Aqueous UV-curable polyurethane dispersions, their preparation and use and compositions containing them” section

[6018] entitled “Inorganic binder compositions comprising polymeric dispersants and their use”

[6019] 100% curable coating compositionsUV-crosslinkable poly(meth)acrylate(s) and its / their uses are defined in more detail in section

[6009] entitled “UV-crosslinkable poly(meth)acrylates for use in UV-curable solvent-free hotmelt adhesives and their use for making pressure-sensitive self-adhesive articles” of Reference RF1.Polyisocyanate(s), composition(s) comprising them and their uses are defined in more detail in section

[6010] entitled “Polyisocyanates” of Reference RF1 .Hyperbranched polyester polyol(s) and its / their uses are defined in more detail in section

[6011] entitled “Organic solvent based hyperbranched polyester polyols suitable for use in coating compositions” of Reference RF1 . The converting step(s) to obtain the hyperbranched polyester polyols is / are defined in more detail in the section

[6012] entitled “Preparation of organic solvent based hyperbranched polyester polyols” of Reference RF1 . Coating composition(s) comprising hyperbranched polyester polyol(s), polyisocyanate(s) and additive(s) and substrate(s) coated therewith are defined in more detail in section

[6013] entitled “Organic solvent based two component coating compositions comprising hyperbranched polyester polyols and polyisocyanates” of Reference RF1.Unsaturated polyester polyol(s), solvent-based coating composition(s) comprising said unsaturated polyester polyol(s) and substrate(s) for coating with said coating composition(s) are defined in more detail in section

[6018] entitled “Organic solvent based coating composition comprising unsaturated polyester polyols” of Reference RF1 .100% curable coating composition(s) is / are defined in more detail in section

[6019] of Reference RF1 .Polymeric dispersant(s) for inorganic binder compositions is / are defined in more detail in section

[6020] of Reference RF1 . The inorganic binder composition(s) comprising the polymeric dispersants and their use are defined in more detail in section

[6021] of Reference RF1 . The converting step(s) to obtain the polymeric dispersant(s) are defined in more detail in section

[6020] of Reference RF1 . The term “inorganic binder composition” comprising the polymeric dispersants), as used herein, comprises preferably in particular hydraulically setting compositionsand compositions comprising calcium sulfate and is defined in more detail in section

[6021] of Reference RF1 entitled “Inorganic binder compositions comprising the polymeric dispersant and their use”. Specific building material formulation(s) comprising polymeric dispersant(s) or building product(s) produced by a building material formulation comprising a polymeric dispersant are disclosed in more detail in section

[6021] of Reference RF1.The term “cosmetic surfactant”, as used herein, comprises non-ionic, anionic, cationic and amphoteric surfactants and is defined in more detail in paragraph

[7002] of Reference RF1 . The term “emollient”, as used herein, refers to a chemical compound used for protecting, moisturizing, and / or lubricating the skin and is defined in more detail in paragraph

[7003] of Reference RF1 . The term “wax”, as used herein, comprises pearlizers and opacifiers and is defined in more detail in paragraph

[7004] of Reference RF1. The term “cosmetic polymer”, as used herein, comprises any polymer that can be used as an ingredient in a cosmetic formulation and is defined in more detail in paragraph

[7005] of Reference RF1 . The term “UV filter”, as used herein, refers to a chemical compound that blocks or absorbs ultraviolet light and is defined in more detail in paragraph

[7006] of Reference RF1 . The term “further cosmetic ingredient”, as used herein, comprises any ingredient suitable for making a cosmetic formulation. Several sources disclose cosmetically acceptable ingredients. E. g. the database Cosing on the internet pages of the European Commission discloses cosmetic ingredients and the International Cosmetic Ingredient Dictionary and Handbook, edited by the Personal Care Products Council (PCPC), discloses cosmetic ingredients. The term “composition and / or formulation thereof’ with reference to the cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter and / or further cosmetic ingredient refers to personal care and / or cosmetic compositions or formulations defined in more detail in paragraph

[7007] of Reference RF1. The converting step(s) to obtain the cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter or further cosmetic ingredient is / are defined in more detail in paragraph

[7008] of Reference RF1 .The terms “polymer B”, “polymer composition B”, “coating composition”, “other functional composition”, “foil”, “molded body”, “coating” and “coated substrate” are well known to the person skilled in the art and are defined in more detail from paragraph

[8000] to

[8005] of Reference RF1.The present invention further relates to caprolactam obtainable by the method according to the present invention.Further, the present invention relates to the use of an automotive shredder residue comprising polycaprolactam and glass fibers for recycling caprolactam, preferably by carrying out the method according to the present invention.Suitable automotive shredder residue (ASR) and polycaprolactam are described before.ExamplesExample 1 - Preparation of ASR SamplesTo prepare the model ASR-1 to ASR-3 the single components are collected from a local ELV collector company (an authorized treatment facility which depollutes ELV) from various about 15 year old passenger cars. For example, glass is the glass from front windshields and rear windows, dirt is collected as attached to the car exterior, PUR foam is collected from the seat foam, and plastic is collected from selected plastic parts of the cars, such as wheel covers, dashboard, wiper arm, door handle, gears, and bushes, where the type of polymer is known.The ASR-1 to ASR-3 samples are prepared in 5 kg batches by weighing in the components and by shredding the components listed in Table 1 first by hand with a hammer and metal scissors, followed by shredding with a four-shaft shredder (like Model “JFS 8080” from Jogindra, India with main blade rotation diameter 245 mm, assistant rotation diameter 270 mm, 42 main blades, 20 assistant blades, 25 rpm main axle rotation speed, 120-200 kg / hr capacity). The maximum fragment size is 10 cm.The amount of polycaprolactam in the ASR-1 to ASR-3 was adjusted to 40 wt% based on the weight of the “Plastics” component listed in Table 1 .The amount of inorganic particles corresponds to the amount of dirt, glass, metal, and partially “Others” in Table 1 .Table 1 : Composition of model ASR (amounts in wt%)Example 2 - Preparation of SLF and SHF SamplesTo prepare the model shredder light fractions SLF-1 to SLF-3 and the shredder heavy fractions SHF-1 to SHF-3 the single components are collected from a local ELV collector company as described in Example 1 .The samples are prepared in 5 kg batches by weighing in the components and by shredding the components listed in Tables 2 and 3 first by hand with a hammer and metal scissors, followed by shredding with a four-shaft shredder. The maximum fragment size is 10 cm.Table 2: Composition of SLF (amounts in wt%)Table 3: Composition of SHF (amounts in wt%)Example 3 - Depolymerizing ASR-1 to ASR-3The ASR-1 to ASR-3 samples from Example 1 are used for depolymerization.The samples comprise 10 wt% polycaprolactam based on the weight of the “Plastics” component listed in Table 1 . For example, a 100 g sample of ASR-1 contains 35 wt% plastics, which is 35 g, of which are 10 wt% polycaprolactam, which is 3,5 g.In an autoclave, 100 g of either ASR-1 , ASR-2 or ASR-3 is heated to 310°C with 500 g of water for 1 .5 hours. After cooling, the solids are removed by filtration, and the water is evaporated in vacuo at temperatures < 80 °C, caprolactam is then removed from the reaction mixture by distillation at 150 °C in vacuo.About 2,8 g caprolactam are obtained after distillation, which corresponds to about 80 % of the expected yield of 3,5 g.Example 4 - Depolymerizing SLF-1 to SLF-3The SLF-1 to SLF-3 samples from Example 2 (Table 2) are used for depolymerization.The samples comprise 5 wt% polycaprolactam based on the weight of the “Plastics” component listed in Table 2.For example, a 100 g sample of SLF-3 contains 29 wt% plastics, which is 29 g, of which are 5 wt% polycaprolactam, which is 1 ,45 g polycaprolactam.In an autoclave 100 g of either SLF-1 , SLF-2 or SLF-3 is heated to 310°C with 500 g of water for 1 .5 hours. Caprolactam is then removed from the reaction mixture by distillation as described in Example 3.About 1 ,1 g caprolactam are obtained after distillation, which corresponds to about 76 % of the expected yield of 1 ,45 g.Example 5 - Depolymerizing SHF-1 to SHF-3The SHF-1 to SHF-3 samples from Example 2 (Table 3) are used for depolymerization.The samples comprise 20 wt% polycaprolactam based on the weight of the “Plastics” component listed in Table 2.For example, a 100 g sample of SHF-3 contains 32 wt% plastics, which is 32 g, of which are 20 wt% polycaprolactam, which is 6,4 g polycaprolactam.In an autoclave 100 g of either SHF-1 , SHF-2 or SHF-3 is heated to 310°C with 500 g of water for 1 .5 hours. Caprolactam is then removed from the reaction mixture by distillation as described in Example 3.About 5,3 g caprolactam are obtained after distillation, which corresponds to about 83 % of the expected yield of 6,4 g.

Claims

Claims1 . A method for recycling caprolactam from an automotive shredder residue comprising polycaprolactam comprising: a) mixing the automotive shredder residue with water, whereby a mixture 1 containing polycaprolactam and water is obtained; b) depolymerizing the polycaprolactam present in the mixture 1 without addition of a depolymerization catalyst at a temperature of 200°C to 600°C, preferably 300 to 400 °C and a pressure of 30 to 200 bar, preferably 40 to 140 bar to produce a mixture 2 comprising caprolactam; c) recovering the caprolactam.

2. The method of claim 1 , where the automotive shredder residue is obtainable by shredding vehicles.

3. The method of claim 1 or 2, where the automotive shredder residue comprises at least 5 wt%, preferably 8 to 40 wt%, more preferably 10 to 35 wt% of inorganic material.

4. The method of claim 3, where the inorganic material comprises glass, metal and dirt.

5. The method of claim 4, where the glass is present at least in part in form of glass fibers.

6. The method of claim 5, where the glass fibers are at least in part present in the polycaprolactam in form of reinforced polycaprolactam.

7. The method of any one of claims 1 to 6, where the automotive shredder residue comprises at least 60 wt%, preferably 60 to 92 wt%, more preferably 65 to 90 wt% of organic material comprising plastics.

8. The method of claim 7, where the organic material comprises rubber, polyurethane, wood, plasics including polycaprolactam, and at least one of paper and cardboard.

9. The method of claim 7 or 8, where the plastics comprise at least 2 wt%, preferably 4 to 40 wt%, more preferably 5 to 30 wt% polycaprolactam.

10. The method of any one of claims 1 to 9, where the weight ratio of water to polycaprolactam in step a) is in the range from 1 :1 to 30:1 , preferably 2:1 to 20:1 , more preferably 7:1 to 10:1.11 . The method of any one of claims 1 to 10, where the mixture 2 obtained in step b) is cooled before the recovering in step c).

12. The method of any one of claims 1 to 10, where in the recovering step c) water is removed from the mixture 2, followed by recovering the caprolactam.

13. The method of claim 13, where at least 75 wt% of the water present in mixture 2 is re- moved prior to the recovering of caprolactam, preferably by evaporation or distillation.

14. The method of claim 12 or 13, where the caprolactam is recovered by distillation.

15. Method, preferably according to any one of claims 1 to 14, comprising the step: - converting the caprolactam obtainable by or obtained by the method according to any one of claims 1 to 14 to obtain a product PRF1.

16. Caprolactam obtainable by the method according to any one of claims 1 to 14.

17. Use of an automotive shredder residue comprising polycaprolactam and glass fibers for recycling of caprolactam in the absence of a depolymerization catalyst, preferably by carrying out the method according to any one of claims 1 to 14.

Images