A recycling process for recovering epsilon-caprolactam from a solid material

Abstract

The present invention relates to a recycling process for recovering ε-caprolactam from a solid material W comprising polyamide 6, the process comprising pyrolyzing the solid material W and subsequently subjecting to further treatments for recovering the valuable ε-caprolactam.

Description

[0001] A recycling process for recovering epsilon-caprolactam from a solid material

[0002] The present invention relates to a recycling process for recovering c-caprolactam from a solid material W comprising polyamide 6, the process comprising pyrolyzing the solid material W and subsequently subjecting to further treatments for recovering the valuable c-caprolactam.

[0003] Currently, plastic waste is still largely landfilled or incinerated for heat generation. Chemical recycling is an attractive way to convert waste plastic material into useful chemicals. An important technique for chemically recycling plastic waste is pyrolysis. The pyrolysis is a thermal degradation of plastic waste in an inert atmosphere and yields value added products such as pyrolysis gas, liquid pyrolysis oil and char (residue), wherein pyrolysis oil is the major product. The pyrolysis gas and char can be used as fuel for generating heat, e.g. for reactor heating purposes. The pyrolysis oil can be used as source for syngas production and / or processed into chemical feedstock such as ethylene, propylene, C4 cuts, etc. for example in a (steam) cracker.

[0004] Typically, the plastic waste is mixed plastic waste composed of different types of polymers. The polymers are often composed of carbon and hydrogen in combination with other elements such as chlorine, bromine, fluorine, sulfur, oxygen and nitrogen that complicate recycling efforts. The elements other than carbon and hydrogen may be harmful during the further processing of the crude pyrolysis oil, since they may deactivate or poison catalysts used in the further processing of the pyrolysis oil or cause corrosion. In mixed plastic waste, polyamides are often present such as polyamide 6. Such polyamide 6 is valuable and being able to recover its monomer, E- caprolactam, from mixed plastic waste materials is of great interest at the present time.

[0005] Therefore, there is a need to provide a recycling process for recovering c-caprolactam from a solid material W comprising polyamide 6. Indeed, there is a need when degrading solid waste material to recover valuable products which can be re-used in the industry, while using an economic process.

[0006] WO 2023 / 144338 A1 and WO 2023 / 144339 A1 relate to a process for the recovery of caprolactam from polyamide 6 comprising fishing nets.

[0007] WO 2023 / 144337 A1 relates to a process for the recovery of c-caprolactam from Nylon 6 comprising multi-component material, in particular multi-layered film. Further, D3 relates to a plant configured to carry out the process. D4 discloses a process for depolymerizing nylon 6 and recovering caprolactam from the depolymerized products by extraction with alkyl phenolic compounds.

[0008] US 5 990 306 A relates to a process for the preparation of purified caprolactam comprising the depolymerization of polyamide containing carpet.

[0009] Perez Barbara Alejandra et aL, “Insights into co-pyrolysis of polyethylene terephthalate and polyamide 6 mixture through experiments, kinetic modelling and machine learning”, Chemical Engineering Journal, Vol. 468, 143637 (2023) relates to the pyrolysis of polyethylene terephthalate (PET), polyamide 6, and mixtures thereof.

[0010] The object underlying the present invention is to provide a recycling process for recovering c- caprolactam from a solid material W comprising polyamide 6, preferably from solid waste material to recover valuable products which can be re-used in the industry, while using an economic process.

[0011] According to the present invention, it was found that the process of the present invention permits to recycle solid material W comprising polyamide 6 by efficiently recovering c-caprolactam from a pyrolysis liquid.

[0012] Therefore, the present invention relates to a recycling process for recovering c-caprolactam from a solid material W comprising polyamide 6, the process comprises

[0013] (i) providing the solid material W;

[0014] (ii) subjecting the solid material W provided according to (i) to, preferably non-hydrous, pyrolysis in a pyrolysis reactor unit RU(P), obtaining a mixture MP comprising an aqueous phase PA(1) comprising e-caprolactam, an organic phase PO(1) comprising c-caprolactam;

[0015] (iii) isolating c-caprolactam from MP obtained according (ii), (iii) comprising

[0016] (111.1) passing the mixture MP obtained according to (ii) in a separation unit SU, obtaining a liquid stream S1 comprising PO(1 ) and a liquid stream S2 comprising PA(1);

[0017] (111.2) separating c-caprolactam from the liquid stream S2 obtained according to (iii.1 ), in a purification unit PU.

[0018] Therefore, the present invention also relates to a process for preparing a polymer or a polymer product, comprising the steps of recovering c-caprolactam from a solid material W according to the above process, and

[0019] (iv) converting the liquid stream S1 obtained according to (iii.2), or the liquid stream S11 obtained according to (iii.3) as defined below to a polymer or a polymer product; wherein (iii) further comprises

[0020] (111.3) subjecting the stream S1 obtained according to (iii.1 ) to extraction with water and optionally a base B in at least one extraction zone ZE, obtaining a liquid stream S11 , depleted in £-caprolactam compared to S1 , comprising PO(1 ) and an aqueous liquid stream S3 comprising c-caprolactam dissolved in water;

[0021] (111.4) separating c-caprolactam from the liquid stream S3 obtained according to (iii.3), in a purification unit, preferably in the purification unit PU used in (iii.2).

[0022] Therefore, the present invention also relates to a process for preparing a polymer or a polymer product, comprising the step of converting at least one monomer, preferably obtained from the liquid stream S1 obtained according to (iii.2), or the liquid stream S11 obtained according to (iii.3) as defined below, to a polymer or a polymer product, wherein (iii) in the above process further comprises (111.3) subjecting the stream S1 obtained according to (iii.1 ) to extraction with water and optionally a base B in at least one extraction zone ZE, obtaining a liquid stream S11 , depleted in £-caprolactam compared to S1 , comprising PO(1 ) and an aqueous liquid stream S3 comprising e-caprolactam dissolved in water;

[0023] (111.4) separating £-caprolactam from the liquid stream S3 obtained according to (iii.3), in a purification unit, preferably in the purification unit PU used in (iii.2).

[0024] Preferably, the pyrolysis is non-hydrous, i.e. no water is added to W prior to pyrolysis and / or no water is present in W at the start of the pyrolysis.

[0025] Preferably the solid material W comprises polyamide 6 in an amount of at least 0.25 weight-%, more preferably at least 1 weight-%, more preferably in the range of from 1 to 95 weight-%, more preferably in the range of from 2 to 80 weight-%, more preferably in the range of from 3 to 60 weight-%, based on the weight of W.

[0026] Preferably the solid material W comprises, in addition to polyamide 6, one or more polyolefins.

[0027] Preferably the one or more polyolefins comprise, more preferably consist of, polyethylene (HDPE, LDPE), polymethylpentene (PMP), polybutene-1 (PB-1), polyisobutylene (PIB), polypropylene, polystyrene, and copolymers thereof.

[0028] Preferably from 40 to 99 weight-%, more preferably from 50 to 90 weight-%, more preferably from 60 to 90 weight-% of the solid material W comprises one or more polyolefins.

[0029] Preferably the solid material W comprises a solid waste material, wherein said waste material preferably comprises one or more of plastic waste material and textile waste material.

[0030] Preferably the solid material W being a solid waste material includes pre-consumer waste material and post-consumer waste material.

[0031] In the context of the present invention, the term “pre-consumer waste material” refers to waste material obtained from the manufacturers (such as scraps), retailers, and so on.

[0032] In the context of the present invention, the terms “plastic waste material” or “mixed plastic waste material” refers to plastic waste material containing different kinds of plastic objects. Often plastic is sorted before it is used for treatment / recycling, such as the plastic waste material can be only plastic bags or plastic foils to be treated or recycled. This can be done upfront by different companies. However, in the context of the present invention, there is potentially less need for such presorting requirement, the mixed plastic waste material or plastic waste material is municipal plastic waste material as obtained from households, such as a mixture of plastic bags, plastic packaging, plastic tubes, etc. In the context of the present invention, the term “plastic waste material” refers to any plastic material discarded after use, namely the plastic material has reached the end of its useful life and is considered post-consumer waste. The plastic waste material can be pure polymeric plastic waste material, mixed plastic waste material or film waste material, including soiling, adhesive materials, fillers, residues etc. The plastic waste material may have a nitrogen content, a sulfur content, a halogen content and optionally also a heavy metal content. The plastic waste can originate from any plastic material containing source.

[0033] Accordingly, the term “plastic waste material” includes industrial and domestic plastic waste material and includes used tires and agricultural and horticultural plastic material.

[0034] Typically, plastic waste material is a mixture of different plastic materials, including hydrocarbon plastics, namely polyolefins such as polyethylene (HDPE, LDPE), polymethylpentene (PMP), polybutene-1 (PB-1), polyisobutylene (PIB), polypropylene, polystyrene, and copolymers thereof, and polymers comprising carbon atoms, hydrogen atoms, and other elements such as chlorine, fluorine, oxygen, nitrogen, sulfur, silicone, etc., for example chlorinated plastics, such as polyvinylchloride (PVC), polyvinylidene chloride (PVDC), etc., nitrogen-containing plastics, such as polyamides (PA), polyurethanes (PU), acrylonitrile butadiene styrene (ABS), etc., oxy- gen-containing plastics such as polyesters, e.g., polyethylene terephthalate (PET), polycarbonate (PC), etc.), silicones and / or sulfur bridges crosslinked rubbers. PET plastic waste is often sorted out before pyrolysis since PET has a profitable resale value. Accordingly, the plastic waste material to be pyrolyzed often contains less than about 10 wt.-%, preferably less than about 5 wt.-%, more preferably less than 1 weight-%, more preferably substantially no PET based plastic waste on the dry weight of the plastic waste material.

[0035] Typically, the plastic waste material may further comprise additives, such as processing aids, plasticizers, flame retardants, pigments, light stabilizers, lubricants, impact modifiers, antistatic agents, antioxidants, etc. These additives may comprise elements other than carbon and hydrogen. For example, bromine is mainly found in connection to flame retardants. Metal compounds may be used as lightfast pigments and / or stabilizers in plastics. Cadmium, zinc, and lead may be present in heat stabilizers and slip agents used in plastics manufacturing. The plastic waste material can also contain residues. Residues in the sense of the invention are contaminants adhering to the plastic waste material. The sum of additives and residues is usually present in an amount of less than 50 wt.-%, preferably less than 30 wt.-%, more preferably less than 20 wt.- %, more preferably less than 10 wt.-%, based on the total weight of the dry weight plastic waste material.

[0036] Examples of rubber comprised in the plastic waste material include end-of-life tires, rubber waste produced during manufacturing processes and discarded rubber containing products such as latex examining gloves. End-of-life tires comprise further ingredients such as textiles and organic and inorganic additives which may be separated from the rubber portion of end-of- life tires prior to pyrolysis. Pyrolysis oils obtained by pyrolysis of (predominantly) end-of-life tires are also known as tire pyrolysis oils (TPO). In the context of the present invention, the term “textile waste material” refers to waste materials from clothing, carpet, furniture, fishing nets, woven textiles and tissues.

[0037] Pyrolysis (ii)

[0038] Preferably the pyrolysis according to (ii) is performed by thermal cracking and / or catalytic cracking.

[0039] For catalytic cracking, the catalyst can be one or more of an alkali metal carbonate compound, such as potassium carbonate, an alkali metal hydroxide compound, such as sodium hydroxide, an alkali metal oxide, an alkaline earth metal carbonate compound, an alkaline earth metal hydroxide compound, such as calcium hydroxide (Ca(OH)2), an alkaline earth metal oxide, such as calcium oxide (CaO), and an acidic catalyst, such as alumina, zeolites, alumina-silicates or alumina-bound zeolites.

[0040] Preferably the pyrolysis according to (ii) is performed at a temperature in the range of from 250 to 800 °C, more preferably in the range of from 300 to 700 °C, more preferably in the range of from 350 to 650 °C, more preferably in the range of from 400 to 600 °C.

[0041] According to one embodiment of the present invention, pyrolysis is preferably carried out at temperatures above 400 °C, more preferably above 425 °C, more preferably above 450°C, most preferably above 475°C. These lower limits can be combined with the above upper limits to give preferred temperature ranges.

[0042] Preferably the pyrolysis according to (ii) is performed at a pressure in the range of from 0.1 to 5 bar(abs), more preferably in the range of from 0.9 to 1.5 bar(abs).

[0043] Preferably the pyrolysis according to (ii) is performed under atmosphere exempt of oxygen.

[0044] Preferably, the reactor used for the pyrolysis is ventilated with nitrogen.

[0045] Preferably the pyrolysis reactor unit RU(P) is selected from the group consisting of a fluidized bed, a moving bed, a fixed bed, an entrained flow, an auger, a screw reactor, an extruder, a stirred tank reactor, a rotary kiln and combinations thereof.

[0046] Preferably the fluidized bed is bubbling, turbulent, fast or circulating.

[0047] Preferably (ii) comprises

[0048] (11.1) subjecting W to pyrolysis in a pyrolysis reactor unit RU(P), obtaining an intermediate gas stream G;

[0049] (11.2) subjecting the intermediate gas stream G to condensation in a gas-liquid separation unit, obtaining a mixture MP comprising an aqueous phase PA(1) comprising e-caprolactam, an organic phase PO(1) comprising e-caprolactam.

[0050] Preferably the condensation according to (ii.2) is performed at a temperature in the range of from 20 to 300 °C, more preferably in the range of from 70 to 110 °C.

[0051] Preferably the condensation according to (ii.2) is performed at a pressure in the range of from 0.8 to 1.2 bar(abs), more preferably in the range of from 1 to 1.2 bar (abs).

[0052] Preferably the gas-liquid separation unit used in (ii.2) is a condenser, a scrubber or a quench, more preferably a condenser.

[0053] The non-condensable “permanent” gases exiting the gas-liquid separation unit can be used to generate process heat / electricity by burning in a gas burner, gas motor or combined heat and power plant. The flue gases of this combustion might need to be cleaned according to emission laws to remove dust, ashes and other components.

[0054] In the context of the present invention, the organic phase PO(1) obtained according to (ii) comprising e-caprolactam is commonly called as a pyrolysis oil.

[0055] Preferably from 40 to 90 weight-%, more preferably from 45 to 80 weight-% of W is recovered as the mixture MP comprising the organic phase PO(1) and the aqueous phase PA(1).

[0056] Preferably more than 40 weight-% of PA 6 comprised in W is recovered as £-caprolactam.

[0057] Preferably from 50 to 99.9 weight-%, more preferably from 70 to 98 weight-%, more preferably from 80 to 95 weight-%, of £-caprolactam comprised in MP is in the aqueous phase PA(1) obtained according to (ii).

[0058] Preferably from 98 to 100 weight-%, more preferably from 99 to 100 weight-%, of the £-capro- lactam comprised in the aqueous phase PA(1) obtained according to (ii) is dissolved.

[0059] Separation (iii.1 ) in SU

[0060] Preferably passing the mixture MP obtained according to (ii) in a separation unit SU, obtaining a liquid stream S1 comprising PO(1) and a liquid stream S2 comprising PA(1) according to (iii.1) comprises

[0061] (111.1.1 ) passing the mixture MP obtained according to (ii) in a solid-liquid separation sub-unit SU1 comprised in SU for removing solids comprised in MP, obtaining a liquid mixture MP1 depleted in solids compared to MP;

[0062] (111.1.2) passing the liquid mixture MP1 obtained according to (iii.1.1) in a liquid-liquid separation sub-unit SU2 comprised in SU, SU2 being located downstream of SU1 , obtaining the liquid stream S1 comprising PO(1) and the liquid stream S2 comprising PA(1). Preferably the solid-liquid separation sub-unit SU1 is one or more of a filter, a settler and a centrifuge, more preferably a filter.

[0063] Optionally, a filter aid can be added to MP before filtration.

[0064] Optionally, a portion of S1 obtained according to (iii.1) is recycled to RU(P).

[0065] Preferably, the separation in SU1 according to (iii.1 .1) is performed at a temperature in the range of from 5 to 150°C, more preferably in the range of from 60 to 95 °C, more preferably in the range of from 75 to 90 °C.

[0066] Preferably, (iii.1 .1) comprises bringing in contact water with the mixture MP obtained according to (ii), and optionally with a base B0, and passing MP with water, and the optional B0, in the solid-liquid separation sub-unit SU1 comprised in SU for removing solids comprised in MP, obtaining a liquid mixture MP1 depleted in solids compared to MP.

[0067] According to said alternative, preferably, according to (iii.1 .1), bringing in contact water with the mixture MP obtained according to (ii) is performed at a temperature in the range of from 10 to 200 °C, more preferably in the range of from 10 to 90 °C.

[0068] Preferably, according to (iii.1.1 ), the weight ratio of water to MP is in the range of from 0.05:1 to 2:1 , more preferably in the range of from 0.1 :1 to 1.5:1 , more preferably in the range of from 0.1 :1 to 1 .2: 1 , more preferably in the range of from 0.1 :1 to 0.5: 1 .

[0069] Preferably the base B0 used in (iii.1.1) is one or more of an alkali metal compound, an alkaline earth metal compound and ammonia, more preferably B0 is an alkali metal compound being one or more of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, calcium hydroxide, calcium oxide and calcium carbonate, more preferably one or more of potassium hydroxide, sodium hydroxide, potassium carbonate and sodium carbonate, more preferably one or more of potassium hydroxide and sodium hydroxide, more preferably potassium hydroxide or sodium hydroxide.

[0070] Preferably, (iii.1.2) comprises bringing in contact water with the liquid mixture MP1 obtained according to (iii.1 .1) and passing MP1 with water in the liquid-liquid separation sub-unit SU2 comprised in SU, SU2 being located downstream of SU1 , obtaining the liquid stream S1 comprising PO(1) and the liquid stream S2 comprising PA(1).

[0071] Preferably, according to (iii.1.2), bringing in contact water with the liquid mixture MP1 obtained according to (iii.1 .1) is performed at a temperature in the range of from 10 to 200 °C, more preferably in the range of from 10 to 90 °C.

[0072] Preferably, according to (iii), the weight ratio of water to MP1 is in the range of from 0.05:1 to 2:1 , more preferably in the range of from 0.1 :1 to 1.5:1 , more preferably in the range of from 0.1 :1 to 1 .2: 1 , more preferably in the range of from 0.1 :1 to 0.5: 1 .

[0073] Optionally, (iii.1 .2) comprises bringing in contact water and a base B0 with the liquid mixture MP1 obtained according to (iii.1.1 ) and passing MP1 with B0 and water in the liquid-liquid separation sub-unit SU2 comprised in SU, SU2 being located downstream of SU1 , obtaining the liquid stream S1 comprising PO(1) and the liquid stream S2 comprising PA(1), wherein the pH of the aqueous phase PA(1) in S2 is in the range of from 3 to 13, preferably in the range of from 7 to 10.

[0074] Preferably, the base B0 used in (iii.1.2) is one or more of an alkali metal compound, an alkaline earth metal compound and ammonia, more preferably B0 is an alkali metal compound being one or more of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, calcium hydroxide, calcium oxide and calcium carbonate, more preferably one or more of potassium hydroxide, sodium hydroxide, potassium carbonate and sodium carbonate, more preferably one or more of potassium hydroxide and sodium hydroxide, more preferably potassium hydroxide or sodium hydroxide.

[0075] Preferably, the liquid-liquid separation sub-unit SU2 is one or more of a decanter, a hydrocyclone, a settler tank and a centrifuge, more preferably a decanter or a settler tank.

[0076] Preferably the separation in SU2 according to (iii.1 .2) is performed at a temperature in the range of from 5 to 150 °C, more preferably in the range of from 60 to 95 °C, more preferably in the range of from 75 to 90 °C.

[0077] Preferably, water used in (iii.1) is demineralized water.

[0078] Preferably, water used in (iii.1) is recycled water.

[0079] Purification (iii.2) in PU

[0080] Preferably, the purification unit PU comprises one or more of a distillation unit and a crystallization unit.

[0081] Distillation

[0082] Preferably, (iii.2) comprises subjecting the stream S2 obtained according to (iii.1 ) to distillation in a distillation unit comprised in PU, obtaining e-caprolactam separated from S2.

[0083] Preferably the distillation according to (iii.2) is performed at a temperature in the range of from 60 to 600 °C, preferably of from 70 to 400 °C.

[0084] Preferably, the distillation according to (iii.2) is performed at a pressure in the range of from 0.0025 to 1 bar (abs). Preferably, the distillation is carried out at a temperature in the range of about 60 °C to about 600 °C, more preferably from about 70 °C to about 400 °C, more preferably from about 70 °C to about 360 °C (the temperature ranges refer to atmospheric pressure of 1 .013 bar). The corresponding operating pressure of the at least one distillation column preferably ranges from about 0.001 bar(abs) to about 4 bar (abs), more preferably from about 0.001 bar(abs) to about 0.98 bar (abs), more preferably from about 0.01 bar(abs) to about 0.05 bar (abs). The temperature is adjusted accordingly in case the pressure is * 1.013 bar.

[0085] Two distillation columns

[0086] Preferably, (iii.2) comprises

[0087] (111.2.1 ) subjecting the stream S2 obtained according to (iii.1) to distillation in a first distillation column D1 comprised in the distillation unit, obtaining a bottom stream S2(1) comprising £-caprolactam and one or more compounds different to e-caprolactam and a top stream S2(2) comprising water;

[0088] (111.2.2) subjecting the bottom stream S2(1) obtained according to (iii.2.1) to distillation in a second distillation column D2, D2 being located downstream of D1 , obtaining a bottom stream S2(11) comprising the one or more compounds different to E- caprolactam and a top stream S2(21) comprising c-caprolactam.

[0089] Preferably the one or more compounds different to c-caprolactam comprised in S2(1) and in S2(11) are high boiling compounds.

[0090] In the context of the present invention, the term “high boiling compounds” refers to compounds other than c-caprolactam having a boiling point which is of about, or higher than, the boiling point of £-caprolactam. Such compounds have for example a boiling point of at least 230 °C or of at least 270 °C. Similarly, the term “low boiling compounds” refers to compounds other than £-caprolactam having a boiling point which is of about, or lower than, the boiling point of £-capro- lactam. Such compounds have for example a boiling point of at most 230 °C or of at most 270 °C.

[0091] Such step is illustrated in Figure 3.

[0092] Preferably, the first distillation column D1 is operated at a pressure > 0.98 bar (abs). Preferably, the first distillation column at a temperature in the range of from about 100 °C to about 120 °C. Such step may permit to recover low boiling components which might otherwise be difficult to recover from lower pressures.

[0093] Preferably, the second distillation column D2 is operated with a reduced pressure. It is preferably a “vacuum distillation”.

[0094] Preferably, the second distillation column D2 is operated at a pressure in the range of from about 0.0025 bar (abs) to about 0.005 bar (abs). Preferably the second distillation column D2 is operated at a temperature in the range of from about 130 °C to about 200 °C.

[0095] Preferably, S2(21) comprises more than 85 weight-% of c-caprolactam comprised in S2.

[0096] One distillation column

[0097] Preferably, (iii.2) comprises

[0098] (iii.2.1 ’) subjecting the stream S2 obtained according to (iii.1) to distillation in a distillation unit being a divided wall distillation column comprised in PU, obtaining a bottom stream S2(1 ’) comprising one or more compounds different to c-caprolactam, a middle stream S2(2’) comprising c-caprolactam and a top stream S2(3’) comprising water.

[0099] This alternative is illustrated in Figure 4.

[0100] Preferably, the one or more compounds different to c-caprolactam comprised in S2(1’) are high boiling compounds.

[0101] Preferably, the top stream S2(3’) further comprises low boiling compounds.

[0102] Preferably, the divided wall distillation column is operated at a pressure in the range of about 0.1 bar (abs) to about 0.2 bar (abs).

[0103] Preferably, the top stream S2(3’) is obtained at a temperature in the range of from about 40 °C to about 60 °C.

[0104] Preferably, the middle stream S2(2’) is obtained at a temperature in the range of from about 180 °C to about 220 °C.

[0105] Preferably, the bottom stream S2(1’) is obtained at a temperature of at least 220 °C.

[0106] Preferably, S2(2’) comprises more than 85 weight-% of c-caprolactam comprised in S2.

[0107] Optionally, (iii.2) further comprises subjecting the c-caprolactam separated from S2 obtained from the distillation, preferably subjecting the top stream S2(12) comprising c-caprolactam obtained according to (iii.2.2) or the middle stream S2(2’) comprising c-caprolactam obtained according to (iii.2. T), to crystallization in a crystallization unit comprised in PU, obtaining solid E- caprolactam. One of these alternatives is illustrated in Figure 5.

[0108] Crystallization

[0109] Preferably, (iii.2) comprises (iii.2.1 ”) subjecting the stream S2 obtained according to (iii.1) to crystallization in a crystallization unit CU comprised in PU, obtaining crystallized c-caprolactam.

[0110] This is illustrated for example in Figure 8.

[0111] Preferably, the crystallization according to (iii.2.1”) is performed at a temperature in the range of from 5 to 70 °C.

[0112] Preferably, the crystallization according to (iii.2.1”) is performed at a pressure in the range of from 0.001 to 5 bar(abs), more preferably of from 0.01 to 1.1 bar(abs).

[0113] Preferably, the crystallized c-caprolactam is separated from the non-crystallized portion by filtration.

[0114] Preferably according to (iii.2.1”), in addition to the crystallized c-caprolactam, a stream SW is obtained and removed from CU, SW comprising water.

[0115] Optionally, the stream SW is recycled and used as a source of water for the process of the present invention, for example in (iii.1 ), more preferably in (iii.1.1) and / or (iii.1.2).

[0116] The crystals / solid (c-caprolactam rich phase), i.e. crystallized c-caprolactam obtained according to (iii.2.1”), can be subjected to an elevated temperature to obtain a liquid with a vapor pressure that can be subjected to a distillation unit to increase the yield of c-caprolactam. Preferably, E- caprolactam is obtained as an overhead product and the remaining high boiling compounds as a bottom product. Preferably, the distillation is performed at a temperature in the range of from 130 °C to 200 °C and at a pressure in the range of from 0.0025 bar(abs) to 0.005 bar(abs). This is for example illustrated by Figure 8.

[0117] In general, c-caprolactam can be crystallized from c-caprolactam-water mixtures in suitable means for crystallization such as for example crystallization units. For example, the c-caprolac- tam-water mixture can be cooled down whereby the solubility of c-caprolactam in water is reduced and the crystallization of c-caprolactam is initiated, c-caprolactam can also be crystallized using evaporative cooling crystallization processes disclosed in P. J. Diepen, O. S. L. Bruinsma, G. M. Van Rosmalen: Melt crystallization by controlled evaporative cooling. The £-caproclactam- water system in batch operation; Chemical Engineering Science, Vol. 55, 2000, 3575-3584 and the references cited therein. Optimization of such a crystallization process can be made by a skilled person based on its common general knowledge.

[0118] Preferably, (iii.2) further comprises

[0119] (iii.2.2”) subjecting the crystallized e-caprolactam obtained according to (iii.2.1”) to drying, obtaining a mixture ML comprising c-caprolactam;

[0120] (iii.2.3”) subjecting ML obtained according to (iii.2.2”) to distillation in a distillation column D3, obtaining a top stream ML(1) comprising c-caprolactam and a bottom stream ML(2) comprising one or more compounds other than e-caprolactam.

[0121] Preferably, (iii.2) further comprises subjecting the non-crystallized portion of S2 obtained according to (iii.2.1”) to distillation in a distillation unit, obtaining e-caprolactam separated from said portion of S2.

[0122] Preferably, the distillation according to (iii.2) is performed at a temperature in the range of from 120 to 300 °C. Preferably, the distillation according to (iii.2) is performed at a pressure in the range of from 2 mbar (abs) to 1 bar (abs). With this distillation, e-caprolactam is obtained as an overhead product along with low boiling compounds and the high boiling compounds are obtained as a bottom product.

[0123] Preferably, less than 20 weight-%, more preferably less than 15 weight- % of e-caprolactam comprised in MP is contained in S1.

[0124] Extraction (iii.3)

[0125] Preferably, (iii) further comprises

[0126] (111.3) subjecting the stream S1 obtained according to (iii.1 ) to extraction with water and optionally a base B in at least one extraction zone ZE, obtaining a liquid stream S11 , depleted in £-caprolactam compared to S1 , comprising PO(1 ) and an aqueous liquid stream S3 comprising £-caprolactam dissolved in water;

[0127] (111.4) separating £-caprolactam from the liquid stream S3 obtained according to (iii.3), in a purification unit, preferably in the purification unit PU used in (iii.2).

[0128] Preferably, (iii.3) comprises

[0129] (111.3.1 ) introducing S1 into ZE;

[0130] (111.3.2) bringing in contact S1 with water and a base B into ZEat a temperature in the range of from 10 to 200 °C, obtaining a mixture ME comprising an aqueous phase PA(2) and the organic phase PO(1), the pH of the aqueous phase PA(2) of ME being in the range of from 7 to 11 ;

[0131] (111.3.3) separating PA(2) from PO(1), obtaining a liquid stream S11 , depleted in £-caprolactam compared to S1 , comprising PO(1) and an aqueous liquid stream S3 comprising £-ca- prolactam dissolved in water.

[0132] Preferably, the base B is one or more of an alkali metal compound, an alkaline earth metal compound and ammonia.

[0133] Preferably, B is an alkali metal compound being one or more of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate and sodium bicarbonate, more preferably one or more of potassium hydroxide, sodium hydroxide, potassium carbonate and sodium carbonate, more preferably one or more of potassium hydroxide and sodium hydroxide, more preferably potassium hydroxide or sodium hydroxide. Preferably, water used in (iii.3) is demineralized water.

[0134] Preferably, according to (iii.3), the weight ratio of water to S1 is in the range of from 0.05:1 to 2:1 , more preferably in the range of from 0.1 :1 to 1.5:1 , more preferably in the range of from 0.1 :1 to 1 .2: 1 , more preferably in the range of from 0.1 :1 to 0.5: 1 .

[0135] Preferably, the process further comprises

[0136] (iv) converting the liquid stream S1 obtained according to (iii.2), or the liquid stream S11 obtained according to (iii.3) as defined herein, obtaining a monomer, a polymer or a polymer product.

[0137] The converting step(s) to obtain the monomer, polymer or polymer product may comprise one or more synthesis steps and can be performed by conventional synthesis and technics well known to a person skilled in the art. Independent of the person skilled in the art to assess novelty and inventive step of the independent claim(s), the person skilled in the art to perform the converting step(s) is preferably from the technical field(s) pyrolysis, gasification, remonomeriza- tion, depolymerization, synthesis, production of monomers, polymers and polymer compounds, and / or its further processing (e.g. extrusion, injection molding). Examples of the step(s) of the conversion is / are described in “Industrial Organic Chemistry”, 3. volume, Wiley-VCH, 1997, ISBN: 978-3-527-28838-0, „Kunststoffhandbuch“, 11 volumes in 17 sub-volumes, Carl Hanser Verlag; especially volume 6, „Polyamide“, 1. edition, 1966, volume 7, „Polyurethane", 3. edition, 1993, and volume 8, “Polyester”, 1. edition 1973; “Industrial Organic Chemistry”, 3. volume, Wiley-VCH, 1997, ISBN: 978-3-527-28838-0, “Injection Molding Reference Guide, 4th edition, CreateSpace Independent Publishing Platform, 2011 , ISBN: 978-1466407824, EP0989146 (A1 ), EP1460094 (A1), W02006034800 (A1), EP1529792 (A1 ), W02006042674 (A1), EP0364854 (A2), US5506275 (A), EP0897402 (A1), WO2015082316 (A1), WO2021021855 (A1 ), WO2021126938 (A1), W02021021902 (A1 ), WO2021092311 (A1), W02008155271 (A1), WO2013139827 (A1), each of which is incorporated herein by reference.

[0138] Preferably, the monomer is a di- or polyol; more preferably butandiol; an aldehyde; more preferably formaldehyde; a di- or polyisocyanate; more preferably methylene diphenyl diisocyanate (MDI), polymeric methylene diphenyl diisocyanate (pMDI), toluene diisocyanate (TDI), hexamethylenediisocyanate (HDI) or isophoronediisocyanate (I PDI); an amide; more preferably caprolactam; an alkene; more preferably styrene, ethene and / or norbornene; an alkyne, a (dijester; more preferably methyl methacrylate; a mono or diacid; more preferably adipic acid or terephthalic acid; a diamine; more preferably hexamethylenediamine, nonanediamine; or a sulfone; more preferably 4,4'-dichlorodiphenyl sulfone.

[0139] Preferably, the polymer is and / or the polymer product comprises a polyamide (PA); preferably PA6 or PA66; a polyisocyanate polyaddition product; preferably polyurethane (PU), thermoplastic polyurethane (TPU), a polyurea or a polyisocyanurate (PIR); a low-density polyethylene (LDPE), a high-density polyethylene (HDPE), polyethylene (PE), a polypropylene (PP), a polyvinyl chloride (PVC), a polyvinyl acetate (PVA), a polystyrene (PS), a poly acrylonitrile butadiene styrene (ABS), a poly styrene acrylonitrile (SAN), a poly acrylate styrene acrylonitrile (ASA), a polytetrafluoroethylene (PTFE), a poly(methyl acrylate) (PMA), a poly(methyl methacrylate) (PMMA), a polybutadiene (BR, PBD), a poly(cis-1 ,4-isoprene), a poly(trans-1 ,4-isoprene), a polyoxymethylene (POM), a polyethylene terephthalate (PET), a polybutylene terephthalate (PBT), a polybutylene adipate co-terephthalate (PBAT), a polyester (PES), a polyether sulfone (PESU), polyhydroxyalkanoate (PH A), a poly-3-hydroxybutyrate (P3HB), a poly-4-hydroxybutyrate (P4HB), a polyhydroxyvalerate (PHV), a polyhydroxyhexanoate (PHH), a polyhydroxyoctanoate (PHO), a polylactic acid (PLA), a polysulfone (PSU), a polyphenylene sulfone (PPSU), a polycarbonate (PC), a polyether ether ketone (PEEK), a poly(p-phenylene oxide) (PPO), a poly(p- phenylene ether) (PPE); or copolymer or mixture thereof.

[0140] Preferably the polymer and / or the polymer product is / are or is / are a part of: a part of a car; preferably a cylinder head cover, an engine cover, a housing for charge air cooler, a charge air cooler flap, an intake pipe, an intake manifold, a connector, a gear wheel, a fan wheel, a cooling water box, a housing, a housing part for heat exchanger, a coolant cooler, a charge air cooler, a thermostat, a water pump, a radiator, a fastening part, a part of battery system for electro-mobility, a dashboard, a steering column switch, a seat, a headrest, a center console, a transmission component, a door module, an A, B, C or D pillar cover, a spoiler, a door handle, an exterior mirror, a windscreen wiper, a windscreen wiper protection housing, a decorative grill, a cover strip, a roof rail, a window frame, a sunroof frame, an antenna panel, a headlight and taillight, a cylinder head cover, intake manifold, an airbag, a cushion, or a coating; a cloth; preferably a shirt, trousers, a pullover, a boot, a shoe, a shoe sole, a tight or a jacket; an electrical part; preferably an electrical or electronic passive or active component, a circuit board, a printed circuit board, a housing component, a foil, a line, a switch, a plug, a socket, a distributor, a relay, a resistor, a capacitor, an inductor, a bobbin, a lamp, a diode, a LED, a transistor, a connector, a regulator, an integrated circuit (IC), a processor, a controller, a memory, a sensor, a micro-switch, a micro-button, a semiconductor, a reflector housing for light-emitting diodes (LED), a fastener for electrical or electronic component, a spacer, a bolt, a strip, a slide-in guide, a screw, a nut, a film hinge, a snap hook (snap-in), or a spring tongue; a consumer, agricultural or pharmaceutical product; preferably a tennis string, a climbing rope, a bristle, a brush, an artificial grass, a 3D printing filament, a grass trimmer, a zipper, a hook and a loop fastener, a paper machine clothing, an extrusion coating, a fishing line, a fishing net, an offshore line and rope, a vial, a syringe, an ampoule, a bottle, a sliding element, a spindle nut, a chain conveyor, a plain bearing, a roller, a wheel, a gear, a roller, a ring gear, a screw and a spring dampers, a hose, a pipeline, a cable sheathing, a socket, a switch, a cable tie, a fan wheel, a carpet, a box or bottle for cosmetics, a mattress, a cushion, an insulation, a detergent, a dishwasher tabs or a powder, a shampoo, a body wash, a shower gel, a soap, a fertilizer, a fungicide, or a pesticide; a packaging for the food industry; preferably a mono- or multi-layer blown film, a mono- or multi-layer cast film, a biaxially stretched film, or a laminating film; or a part of a construction; preferably a rotor blade, an insulating material, a frame, a housing, a wall, a coating, or a separating wall.

[0141] Preferably, the recycled content in the liquid stream S1 obtained according to (iii.2), or the liquid stream S11 obtained according to (iii.3) as defined herein, or the monomer, the polymer or the polymer product obtained according to (iv) as defined herein, stemming from the solid material W, is 1 weight-% or more, 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. More preferably, the recycled content is determined based on identity preservation and / or segregation and / or mass balance and / or book and claim chain of custody models, more preferably based on mass balance, more preferably the International Sustainability and Carbon Certification (ISCC) standard.

[0142] Alternatively, preferably the recycled content in a product stream comprising the liquid stream S1 obtained according to (iii.2), or the liquid stream S11 obtained according to (iii.3) as defined herein, or the monomer, the polymer or the polymer product obtained according to (iv) as defined herein, stemming from the solid material W, is 100 weight-% or less, more 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. More preferably the recycled content is determined based on identity preservation and / or segregation and / or mass balance and / or book and claim chain of custody models, more preferably based on mass balance, more preferably the International Sustainability and Carbon Certification (ISCC) standard.

[0143] The present invention further relates to a method for preparing a monomer, a polymer or a polymer product, the method comprising converting the liquid stream S1 obtained according to (iii.2) of the recycling process of the present invention, or the liquid stream S11 obtained according to (iii.3) as defined herein of the recycling process of the present invention, obtaining said monomer, polymer or polymer product. In the context of this method, the definitions relative to step (iv) of the process of the present invention, such as the definition of the monomer, the polymer, etc., apply to said method as well.

[0144] The present invention further relates to a unit for carrying out the recycling process according to the present invention, the unit comprising a pyrolysis reactor unit RU(P); an inlet means for introducing W into RU(P); an outlet means for removing MP from RU(P); a separation unit SU; an inlet means for introducing MP into SU; an outlet means for removing S1 from MP; an outlet means for removing S2 from MP; a purification unit PU; an inlet means for introducing S2 into PU; an outlet means for removing e-caprolactam from PU.

[0145] Preferably the unit further comprises at least one extraction zone ZE comprising a means for extracting; an inlet means for introducing S1 into ZE; an outlet means for removing S11 from ZE;an outlet means for removing S3 from ZE;an inlet means for introducing S3 into PU.

[0146] In the context of the present invention, it is noted that the components of the units disclosed herein above as to the unit are similar to those described relative to the process.

[0147] According to the present invention, and based on a purified e-caprolactam stream obtained according to (iii) of the process according to the present invention, a full recycle loop can be realized. According to this recycle loop, the purified e-caprolactam stream is preferably passed to a polyamide 6 production unit UPP. The polyamide 6 produced in U PP is for example at least partially provided as a feedstock to a textile material producing unit UTP, wherein the textile material MTproduced in UTP is preferably brought onto the market, and wherein, after the life-time TMT of said textile material, it is preferably collected as textile waste material in a textile material collecting unit UTc and preferably suitably provided from UTC to mix with plastic waste material obtaining the solid waste material W. Yet further, it is also possible that in the course of producing the textile material in either the unit UTP mentioned above and / or in one or more other production units, remaining material which cannot not be used and which comprises polyamide 6, e.g. in the form of textile cuttings, is obtained; such remaining material M R is also referred to as “textile waste material” in the context of the present invention, and this textile waste material can also be used as the solid material W or as a part of the solid material W and can be provided according to (i) of the process of the present invention. In the context of the present invention, the polyamide 6 produced in UPPcan be used for the production of any products and textile represents only an example among others. In this regard, as to the production of polyamide 6, examples of processes are disclosed in Ullmann’s Encyclopedia of Industrial Chemistry, Polyamides (Ben Herzog et aL), Ed. 2020 Wiley-VCH Verlag GmbH & Co. KGaA.

[0148] If desired and / or necessary, one or more streams SNCPL can be additionally passed to UPP, wherein SNCPL comprises non-recycled e-caprolactam, i.e. e-caprolactam from a conventional source. Further, if desired and / or necessary, one or more streams SNPA6 can be additionally passed to UTp, wherein SNPAS comprises non-recycled polyamide 6, i.e. polyamide 6 from a conventional source.

[0149] According to a further aspect, the present invention also relates to the use of e-caprolactam, obtainable or obtained by a process as described above, for preparing a polymeric material, preferably for preparing polyamide 6. For example, said use may comprise employing said polymeric material, preferably said polyamide 6, as a feedstock for preparing a textile material. The present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated. In particular, it is noted that in each instance where a range of embodiments is mentioned, for example in the context of a term such as "The process of any one of embodiments 1 to 4", every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to "The process of any one of embodiments 1 , 2, 3 and 4". Further, it is explicitly noted that the following set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.

[0150] 1 . A recycling process for recovering e-caprolactam from a solid material W comprising polyamide 6, the process comprises

[0151] (i) providing the solid material W;

[0152] (ii) subjecting the solid material W provided according to (i) to, preferably non-hydrous, pyrolysis in a pyrolysis reactor unit RU(P), obtaining a mixture MP comprising an aqueous phase PA(1) comprising e-caprolactam, an organic phase PO(1) comprising e-caprolactam;

[0153] (iii) isolating e-caprolactam from MP obtained according (ii), (iii) comprising

[0154] (111.1) passing the mixture MP obtained according to (ii) in a separation unit SU, obtaining a liquid stream S1 comprising PO(1 ) and a liquid stream S2 comprising PA(1 );

[0155] (111.2) separating e-caprolactam from the liquid stream S2 obtained according to (iii.1 ), in a purification unit PU.

[0156] 2. The process of embodiment 1 , wherein the solid material W comprises polyamide 6 in an amount of at least 0.25 weight-%, preferably at least 1 weight-%, more preferably in the range of from 1 to 95 weight-%, more preferably in the range of from 2 to 80 weight-%, more preferably in the range of from 3 to 60 weight-%, based on the weight of W.

[0157] 3. The process of embodiment 1 or 2, wherein the solid material W comprises, in addition to polyamide 6, one or more polyolefins.

[0158] 4. The process of any one of embodiments 1 to 3, wherein the solid material W comprises a solid waste material, wherein said waste material preferably comprises one or more of plastic waste material and textile waste material.

[0159] 5. The process of any one of embodiments 1 to 4, wherein the pyrolysis according to (ii) is performed by thermal cracking and / or catalytic cracking.

[0160] 6. The process of any one of embodiments 1 to 5, wherein the pyrolysis according to (ii) is performed at a temperature in the range of from 250 to 800 °C, preferably in the range of from 300 to 700 °C, more preferably in the range of from 350 to 650 °C, more preferably in the range of from 400 to 600 °C.

[0161] 7. The process of any one of embodiments 1 to 6, wherein the pyrolysis according to (ii) is performed at a pressure in the range of from 0.1 to 5 bar(abs), preferably in the range of from 0.9 to 1.5 bar(abs).

[0162] 8. The process of any one of embodiments 1 to 7, wherein the pyrolysis according to (ii) is performed under atmosphere exempt of oxygen.

[0163] 9. The process of any one of embodiments 1 to 8, wherein the pyrolysis reactor unit RU(P) is selected from the group consisting of a fluidized bed, a moving bed, a fixed bed, an entrained flow, an auger, a screw reactor, an extruder, a stirred tank reactor and a rotary kiln and combinations thereof.

[0164] 10. The process of any one of embodiments 1 to 9, wherein (ii) comprises

[0165] (11.1) subjecting W to pyrolysis in a pyrolysis reactor unit RU(P), obtaining an intermediate gas stream G;

[0166] (11.2) subjecting the intermediate gas stream G to condensation in a gas-liquid separation unit, obtaining a mixture MP comprising

[0167] - an aqueous phase PA(1) comprising e-caprolactam,

[0168] - an organic phase PO(1) comprising e-caprolactam.

[0169] 11. The process of embodiment 10, wherein the condensation according to (ii.2) is performed at a temperature in the range of from 20 to 300 °C, more preferably in the range of from 70 to 110 °C.

[0170] 12. The process of embodiment 10 or 11 , wherein the gas-liquid separation unit used in (ii.2) is a condenser, a scrubber or a quench, more preferably a condenser.

[0171] 13. The process of any one of embodiments 1 to 12, wherein from 50 to 99.9 weight-%, preferably from 70 to 98 weight-%, more preferably from 80 to 95 weight-%, of e-caprolactam comprised in MP is in the aqueous phase PA(1) obtained according to (ii).

[0172] 14. The process of any one of embodiments 1 to 13, wherein passing the mixture MP obtained according to (ii) in a separation unit SU, obtaining a liquid stream S1 comprising PO(1) and a liquid stream S2 comprising PA(1) according to (iii.1) comprises

[0173] (111.1.1) passing the mixture MP obtained according to (ii) in a solid-liquid separation subunit SU1 comprised in SU for removing solids comprised in MP, obtaining a liquid mixture MP1 depleted in solids compared to MP;

[0174] (111.1.2) passing the liquid mixture MP1 obtained according to (iii.1.1) in a liquid-liquid separation sub-unit SU2 comprised in SU, SU2 being located downstream of SU1 , obtaining the liquid stream S1 comprising PO(1) and the liquid stream S2 comprising PA(1).

[0175] 15. The process of embodiment 14, wherein the solid-liquid separation sub-unit SU1 is one or more of a filter, a settler and a centrifuge, preferably a filter.

[0176] 16. The process of embodiment 14 or 15, wherein (iii.1.1 ) comprises bringing in contact water with the mixture MP obtained according to (ii) and passing MP with water in the solid-liquid separation sub-unit SU1 comprised in SU for removing solids comprised in MP, obtaining a liquid mixture MP1 depleted in solids compared to MP.

[0177] 17. The process of embodiment 14 or 15, wherein (iii.1.2) comprises bringing in contact water with the liquid mixture MP1 obtained according to (iii.1.1) and passing MP1 with water in the liquid-liquid separation sub-unit SU2 comprised in SU, SU2 being located downstream of SU1 , obtaining the liquid stream S1 comprising PO(1 ) and the liquid stream S2 comprising PA(1).

[0178] 18. The process of embodiment 17, wherein (iii.1.2) comprises bringing in contact water and a base BO with the liquid mixture MP1 obtained according to (iii.1.1) and passing MP1 with BO and water in the liquid-liquid separation sub-unit SU2 comprised in SU, SU2 being located downstream of SU1 , obtaining the liquid stream S1 comprising PO(1) and the liquid stream S2 comprising PA(1), wherein the pH of the aqueous phase PA(1) in S2 is in the range of from 3 to 13, preferably in the range of from 7 to 10; wherein the base B0 is preferably one or more of an alkali metal compound, an alkaline earth metal compound and ammonia, more preferably B0 is an alkali metal compound being one or more of potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium bicarbonate, sodium bicarbonate, calcium hydroxide, calcium oxide and calcium carbonate, more preferably one or more of potassium hydroxide, sodium hydroxide, potassium carbonate and sodium carbonate, more preferably one or more of potassium hydroxide and sodium hydroxide, more preferably potassium hydroxide or sodium hydroxide.

[0179] 19. The process of any one of embodiments 16 to 18, wherein water used in (iii.1.2) is demineralized water.

[0180] 20. The process of any one of embodiments 14 to 19, wherein the liquid-liquid separation subunit SU2 is one or more of a decanter, a hydrocyclone, a settler tank and a centrifuge, preferably a decanter or a settler tank.

[0181] 21 . The process of any one of embodiments 1 to 13, wherein the separation in SU2 according to (iii.1.2) is performed at a temperature in the range of from 5 to 150 °C, preferably in the range of from 60 to 95 °C, more preferably in the range of from 75 to 90 °C. The process of any one of embodiments 1 to 21 , wherein the purification unit PU comprises one or more of a distillation unit and a crystallization unit. The process of any one of embodiments 1 to 22, wherein (iii.2) comprises subjecting the stream S2 obtained according to (iii.1) to distillation in a distillation unit comprised in PU, obtaining e-caprolactam separated from S2. The process of embodiment 23, wherein the distillation according to (iii.2) is performed at a temperature in the range of from 60 to 600 °C, preferably of from 70 to 400 °C. The process of embodiment 23 or 24, wherein (iii.2) comprises

[0182] (111.2.1 ) subjecting the stream S2 obtained according to (iii.1) to distillation in a first distillation column D1 comprised in the distillation unit, obtaining a bottom stream S2(1 ) comprising e-caprolactam and one or more compounds different to e-capro- lactam and a top stream S2(2) comprising water;

[0183] (111.2.2) subjecting the bottom stream S2(1) obtained according to (iii.2.1) to distillation in a second distillation column D2, D2 being located downstream of D1 , obtaining a bottom stream S2(11) comprising the one or more compounds different to e-ca- prolactam and a top stream S2(21 ) comprising e-caprolactam. The process of embodiment 23 or 24, wherein (iii.2) comprises

[0184] (iii.2. T) subjecting the stream S2 obtained according to (iii.1) to distillation in a distillation unit being a divided wall distillation column comprised in PU, obtaining a bottom stream S2(1 ’) comprising one or more compounds different to e-caprolactam, a middle stream S2(2’) comprising e-caprolactam and a top stream S2(3’) comprising water. The process of any one of embodiments 1 to 22, wherein (iii.2) comprises

[0185] (iii.2.1”) subjecting the stream S2 obtained according to (iii.1) to crystallization in a crystallization unit comprised in PU, obtaining crystallized e-caprolactam separated from the non-crystallized portion of S2. The process of embodiment 27, wherein the crystallization according to (iii.2.1”) is performed at a temperature in the range of from 5 to 70 °C. The process of any one of embodiments 1 to 28, wherein (iii) further comprises

[0186] (111.3) subjecting the stream S1 obtained according to (iii.1 ) to extraction with water and optionally a base B in at least one extraction zone ZE, obtaining a liquid stream S11 , depleted in e-caprolactam compared to S1 , comprising PO(1) and an aqueous liquid stream S3 comprising e-caprolactam dissolved in water;

[0187] (111.4) separating e-caprolactam from the liquid stream S3 obtained according to (iii.3), in a purification unit, preferably in the purification unit PU used in (iii.2). The process of embodiment 29, wherein (iii.3) comprises

[0188] (111.3.1) introducing S1 into ZE;

[0189] (111.3.2) bringing in contact S1 with water and a base B into ZEat a temperature in the range of from 10 to 200 °C, obtaining a mixture ME comprising an aqueous phase PA(2) and the organic phase PO(1), the pH of the aqueous phase PA(2) of ME being in the range of from 7 to 11 ;

[0190] (111.3.3) separating PA(2) from PO(1), obtaining a liquid stream S11 , depleted in e-capro- lactam compared to S1 , comprising PO(1) and an aqueous liquid stream S3 comprising e-caprolactam dissolved in water. The process of embodiment 29 or 30, wherein the base B is one or more of an alkali metal compound, an alkaline earth metal compound and ammonia. The process of any one of embodiments 29 to 31 , wherein, according to (iii.3), the weight ratio of water to S1 is in the range of from 0.05:1 to 2:1 , preferably in the range of from 0.1 :1 to 1.5:1 , more preferably in the range of from 0.1 :1 to 1.2:1 , more preferably in the range of from 0.1 :1 to 0.5:1. The process of any one of embodiments 1 to 32, comprising:

[0191] (iv) converting the liquid stream S1 obtained according to (iii.2), or the liquid stream S11 obtained according to (iii.3) as in any one of embodiments 29 to 32, obtaining a monomer, a polymer or a polymer product. The process of embodiment 33, wherein the monomer is a di- or polyol; preferably bu- tandiol; an aldehyde; preferably formaldehyde; a di- or polyisocyanate; preferably methylene diphenyl diisocyanate (MDI), polymeric methylene diphenyl diisocyanate (pMDI), toluene diisocyanate (TDI), hexamethylenediisocyanate (HDI) or isophoronediisocyanate (IPDI); an amide; preferably caprolactam; an alkene; preferably styrene, ethene and / or norbornene; an alkyne, a (di)ester; preferably methyl methacrylate; a mono or diacid; preferably adipic acid or terephthalic acid; a diamine; preferably hexamethylenediamine, nonanediamine; or a sulfone; preferably 4,4'-dichlorodiphenyl sulfone. The process of embodiment 33, wherein the polymer is and / or the polymer product comprises a polyamide (PA); preferably PA6 or PA66; a polyisocyanate polyaddition product; preferably polyurethane (PU), thermoplastic polyurethane (TPU), a polyurea or a polyiso- cyanurate (PIR); a low-density polyethylene (LDPE), a high-density polyethylene (HDPE), polyethylene (PE), a polypropylene (PP), a polyvinyl chloride (PVC), a polyvinyl acetate (PVA), a polystyrene (PS), a poly acrylonitrile butadiene styrene (ABS), a poly styrene acrylonitrile (SAN), a poly acrylate styrene acrylonitrile (ASA), a polytetrafluoroethylene (PTFE), a poly(methyl acrylate) (PM A), a poly(methyl methacrylate) (PM MA), a polybutadiene (BR, PBD), a poly(cis-1 ,4-isoprene), a poly(trans-1 ,4-isoprene), a polyoxymethylene (POM), a polyethylene terephthalate (PET), a polybutylene terephthalate (PBT), a polybutylene adipate co-terephthalate (PBAT), a polyester (PES), a polyether sulfone (PESU), polyhydroxyalkanoate (PH A), a poly-3-hydroxybutyrate (P3HB), a poly-4-hydroxybutyrate (P4HB), a polyhydroxyvalerate (PHV), a polyhydroxyhexanoate (PHH), a polyhydroxyoctanoate (PHO), a polylactic acid (PLA), a polysulfone (PSU), a polyphenylene sulfone (PPSU), a polycarbonate (PC), a polyether ether ketone (PEEK), a poly(p-phenylene oxide) (PPO), a poly(p-phenylene ether) (PPE); or copolymer or mixture thereof. The process of embodiment 33 or 35, wherein the polymer and / or the polymer product obtained according to (iv) is / are or is / are a part of: a part of a car; preferably a cylinder head cover, an engine cover, a housing for charge air cooler, a charge air cooler flap, an intake pipe, an intake manifold, a connector, a gear wheel, a fan wheel, a cooling water box, a housing, a housing part for heat exchanger, a coolant cooler, a charge air cooler, a thermostat, a water pump, a radiator, a fastening part, a part of battery system for electro-mobility, a dashboard, a steering column switch, a seat, a headrest, a center console, a transmission component, a door module, an A, B, C or D pillar cover, a spoiler, a door handle, an exterior mirror, a windscreen wiper, a windscreen wiper protection housing, a decorative grill, a cover strip, a roof rail, a window frame, a sunroof frame, an antenna panel, a headlight and taillight, a cylinder head cover, intake manifold, an airbag, a cushion, or a coating; a cloth; preferably a shirt, trousers, a pullover, a boot, a shoe, a shoe sole, a tight or a jacket; an electrical part; preferably an electrical or electronic passive or active component, a circuit board, a printed circuit board, a housing component, a foil, a line, a switch, a plug, a socket, a distributor, a relay, a resistor, a capacitor, an inductor, a bobbin, a lamp, a diode, a LED, a transistor, a connector, a regulator, an integrated circuit (IC), a processor, a controller, a memory, a sensor, a micro-switch, a micro-button, a semiconductor, a reflector housing for light-emitting diodes (LED), a fastener for electrical or electronic component, a spacer, a bolt, a strip, a slide-in guide, a screw, a nut, a film hinge, a snap hook (snap-in), or a spring tongue; a consumer, agricultural or pharmaceutical product; preferably a tennis string, a climbing rope, a bristle, a brush, an artificial grass, a 3D printing filament, a grass trimmer, a zipper, a hook and a loop fastener, a paper machine clothing, an extrusion coating, a fishing line, a fishing net, an offshore line and rope, a vial, a syringe, an ampoule, a bottle, a sliding element, a spindle nut, a chain conveyor, a plain bearing, a roller, a wheel, a gear, a roller, a ring gear, a screw and a spring dampers, a hose, a pipeline, a cable sheathing, a socket, a switch, a cable tie, a fan wheel, a carpet, a box or bottle for cosmetics, a mattress, a cushion, an insulation, a detergent, a dishwasher tabs or a powder, a shampoo, a body wash, a shower gel, a soap, a fertilizer, a fungicide, or a pesticide; a packaging for the food industry; preferably a mono- or multi-layer blown film, a mono- or multi-layer cast film, a biaxially stretched film, or a laminating film; or a part of a construction; preferably a rotor blade, an insulating material, a frame, a housing, a wall, a coating, or a separating wall. The process of any one of embodiments 1 to 36, wherein the recycled content in the liquid stream S1 obtained according to (iii.2), or the liquid stream S11 obtained according to (iii.3) as in any one of embodiments 29 to 32, or the monomer, the polymer or the polymer product obtained according to (iv) as in any one of embodiments 33 to 36, stemming from the solid material W, is 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; or wherein the recycled content in a product stream comprising the liquid stream S1 obtained according to (iii.2), or the liquid stream S11 obtained according to (iii.3) as in any one of embodiments 29 to 32, or the monomer, the polymer or the polymer product obtained according to (iv) as in any one of embodiments 33 to 36, stemming from the solid material W, is 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; and wherein the recycled content is preferably determined based on identity preservation and / or segregation and / or mass balance and / or book and claim chain of custody models, more preferably based on mass balance, more preferably the International Sustainability and Carbon Certification (ISCC) standard. A unit for carrying out the recycling process according to any one of embodiments 1 to 37, the unit comprising a pyrolysis reactor unit RU(P); an inlet means for introducing W into RU(P); an outlet means for removing MP from RU(P); a separation unit SU; an inlet means for introducing MP into SU; an outlet means for removing S1 from MP; an outlet means for removing S2 from MP; a purification unit PU; an inlet means for introducing S2 into PU; an outlet means for removing e-caprolactam from PU; the unit preferably further comprising at least one extraction zone ZE comprising a means for extracting; an inlet means for introducing S1 into ZE; an outlet means for removing S11 from ZE;an outlet means for removing S3 from ZE;an inlet means for introducing S3 into PU. Use of e-caprolactam, obtainable or obtained by a process according to any one of embodiments 1 to 32, for preparing polyamide 6. It is explicitly noted that the above set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.

[0192] In the context of the present invention, a term “X is one or more of A, B and C”, wherein X is a given feature and each of A, B and C stands for specific realization of said feature, is to be understood as disclosing that X is either A, or B, or C, or A and B, or A and C, or B and C, or A and B and C. In this regard, it is noted that the skilled person is capable of transfer to above abstract term to a concrete example, e.g. where X is a chemical element and A, B and C are concrete elements such as Li, Na, and K, or X is a temperature and A, B and C are concrete temperatures such as 10 °C, 20 °C, and 30 °C. In this regard, it is further noted that the skilled person is capable of extending the above term to less specific realizations of said feature, e.g. “X is one or more of A and B” disclosing that X is either A, or B, or A and B, or to more specific realizations of said feature, e.g. “X is one or more of A, B, C and D”, disclosing that X is either A, or B, or C, or D, or A and B, or A and C, or A and D, or B and C, or B and D, or C and D, or A and B and C, or A and B and D, or B and C and D, or A and B and C and D.

[0193] The present invention is further illustrated by the following examples.

[0194] Examples

[0195] Analytics - Caprolactam analysis

[0196] Solid samples were placed in the drying cabinet at 70°C to melt. The sample (approx. 100 mg) was weighed using a disposable pipette and an internal standard (6-10 mg dimethyl adipate) was added, then diluted with isopropanol (6 mL). Cloudy samples and samples with suspended particles were filtered with a 0.20 pm disposable filter before analysis. The e-caprolactam content of the sample was analyzed using a gas chromatograph (carrier gas: hydrogen). The method is based on a temperature program that heats up from 150°C to 300°C. A column from Phenomenex was used, which has a ZB 5HT stationary phase.

[0197] Analytics - PA6 content in mixed plastic waste (mechanical analysis)

[0198] The different plastics fractions were sorted mechanically. Identification of the plastics species was done by scanning the material with a NIR and / or VIS spectrometer.

[0199] Experiments

[0200] Example 1

[0201] A mixed plastic waste solid material W (sorting fraction MPO323; polyolefin-rich plastic waste) with a polyamide 6 content of 0.35 wt.-% determined as above, was pyrolyzed in a pyrolysis reactor (stirred tank reactor with approx. 5 L volume) at a wall temperature of 490 °C (resulting inner temperatures were up to 450 °C) and at a pressure of 1.2 bar(abs) under atmosphere exempt of oxygen. 800 g / h W were fed in 200g portions every 15 min. Upon condensation of the reactor effluent in two sequential condensers (first heated to 80 °C and second at room temperature) a total mass fraction of 56.7 wt.-% regarding the starting material W was obtained as liquid mixture MP. The mixture MP comprises an aqueous phase and an organic phase (oil). Solid-liquid-separation was conducted to generate filtrate for further experiments. A heated filter with 20 cm2area and a 0.2 pm PTFE membrane was used for filtration. After MP heated to 80 °C was added in portions of 700 g the filter was pressurized with 1 bar. Average filtration time was 1h and solid content 0.2 wt.-%. Liquid-Liquid-separation was performed in a 1.3 L heated and initially agitated glass vessel with volumetric scale at 70 °C. The aqueous phase (PA) amounted relative to the organic phase (PO) 0.12 kg (PA) / kg (PO).

[0202] The e-caprolactam content of the organic phase was analyzed to be 0.21 wt.% whereas in the aqueous phase it amounted 0.63 wt.-%. The total £-caprolactam (CPL) content of MP was determined and was equal to 0.26 wt.-% so that the £-caprolactam yield regarding the starting material W accounted 0.14 wt.-%.

[0203] Example 2

[0204] A mixed plastic waste solid material W (sorting fraction MPO323 comprising an added polyamide 6 content of 10 weight-%) was pyrolyzed in a pyrolysis reactor (stirred tank reactor with approx. 5 L volume) at a wall temperature of 490 °C (resulting inner temperatures were up to 450 °C) and at a pressure of 1.2 bar(abs) under atmosphere exempt of oxygen. 800 g / h W were fed in 200g portions every 15 min. Upon condensation of the reactor effluent in two sequential condensers (first heated to 80°C and second at room temperature) a total mass fraction of 63.8 wt.-% regarding the starting material W was obtained as liquid mixture MP. The mixture MP comprises an aqueous phase and an organic phase (oil). Solid-liquid-separation was conducted to generate filtrate for further experiments. A heated filter with 20 cm2area and a 0.2 pm PTFE membrane was used for filtration. After MP heated to 80 °C was added in portions of 700 g the filter was pressurized with 1 bar(abs). Average filtration time was 1 h and solid content 0.2 wt.-%. Liquid-Liquid-separation was performed in a 1.3 L heated and initially agitated glass vessel with volumetric scale at 70°C. The aqueous phase (PA) amounted relative to the organic phase (PO) 0.5 kg (PA) / kg(PO).

[0205] The £-caprolactam content of the organic phase was analyzed to be 1 .75 wt.-% whereas in the aqueous phase it amounted 23 wt.-%. The total £-caprolactam (CPL) content of MP was determined and was equal to 8.83 wt.-% so that the £-caprolactam yield regarding the starting material W accounted 5.63 wt.-%.

[0206] This yield increase of 5.49 wt.-% (= 5.63 - 0.14) compared to comparative example 1 suggests that from the 10 wt.-% added polyamide 6 (PA6) 54.9 % were pyrolyzed to e-caprolactam. To improve the accuracy of the calculations for Ex.2, the yield increase upon addition was related to the added amount of PA6. This yield increase of 5.49 wt.-% compared to Example 1 suggests that from the 10 wt.-% added polyamide 6 (PA6) 54.9 % were pyrolyzed to caprolactam. This value is in good accordance with the value based on the determined PA6- content in MPO323 which accounts 54.64 wt.-%. Furthermore, the calculated CPL pyrolysis yield of the PA-content in MPO323 is with 41.3 wt.-% in a similar range regarding the determination accuracy.

[0207] Table 1

[0208] CPL-yield calculation pyrolysis

[0209] Subsequently, the aqueous phase (PA resp. stream S2) was subjected to a first distillation in a rotary evaporator at 120 °C and 950 mbar(abs), obtaining a first distillate and bottoms, said bottoms comprising the majority of c-caprolactam (essentially all c-caprolactam comprised in stream S2, a loss of 0.2 % only) - the yield of c-caprolactam in bottoms after the first distillation was 86.8 % (= obtained CPL in bottoms / CPL contained in MP after pyrolysis). Further, said bottoms was subjected to a second distillation in a short path distillation apparatus (kugelrohr type also known as ball tube) at a temperature starting from 130 °C up to 200 °C and at 2.5 mbar(abs), obtaining a second distillate comprising the majority of c-caprolactam and bottoms. Said distillate was then subjected to condensation at - 78°C and at 2.5 mbar(abs) and E- caprolactam was obtained with a yield of 74.1 % (= obtained CPL after the second distillation I condensation / CPL contained in MP after pyrolysis). The purity of c-caprolactam was 70.3% (see Table 2 below). Table 2

[0210] CPL-yield in the work-up of the mixture MP obtained from pyrolysis of MPO323&PA6 (Ex.2) comprising a liquid aqueous phase and a liquid organic phase

[0211] Example 3

[0212] The pyrolysis reactor outlet MP of Example 2 was adjusted with NaOH to different pH values in the aqueous phase. For this, water was added before in a ratio of 0.5kg / kg(MP). After phase separation the e-caprolactam content in both phases was measured and the distribution coefficient calculated from the molar amounts.

[0213] Table 3

[0214] Distribution coefficients for e-caprolactam at different pH values

[0215] The distribution coefficient for e-caprolactam K = (concentration(CPL) in aqueous phase I con- centration(CPL) in organic phase) increases with the pH constantly. Apart from increasing the amount of the aqueous phase its pH increase can be used to reduce the CPL-content of the organic phase.

[0216] Description of the figures

[0217] Figure 1 is a schematic representation of a unit for carrying out the recycling process according to embodiments of the present invention. The unit comprises a pyrolysis reactor unit RU(P), a separation unit SU and a purification unit PU. A solid material W comprising polyamide 6 is provided and subjected to pyrolysis in RU(P), obtaining a mixture MP comprising an aqueous phase PA(1) and an organic phase PO(1), both phases comprises e-caprolactam, preferably from 50 to 99.9 weight-%, more preferably from 70 to 98 weight-%, more preferably from 80 to 95 weight-%, of c-caprolactam comprised in MP is in the aqueous phase PA(1). The mixture MP is passed in SU, obtaining a liquid stream S1 comprising PO(1) and a liquid stream S2 comprising PA(1). S2 is subsequently subjected to purification in PU for separating c-caprolactam from the liquid stream S2.

[0218] Figure 2 is a schematic representation of a unit for carrying out the recycling process according to embodiments of the present invention. The unit comprises a pyrolysis reactor unit RU(P), a gas-liquid separation unit GLSU, a separation unit SU comprising a solid-liquid separation sub-unit SU1 and a liquid-liquid separation sub-unit SU2, and a purification unit PU. A solid material W comprising polyamide 6 is provided and subjected to pyrolysis in RU(P), obtaining an intermediate gas stream G. The stream G is subjected to condensation in GLSU, obtaining a mixture MP comprising an aqueous phase PA(1) and an organic phase PO(1), both phases comprises c-caprolactam, preferably from 50 to 99.9 weight-%, more preferably from 70 to 98 weight-%, more preferably from 80 to 95 weight-%, of c-caprolactam comprised in MP is in the aqueous phase PA(1). The mixture MP is passed in SU, obtaining a liquid stream S2 comprising PA(1). In particular, MP is passed in SU1 comprised in SU for removing solids comprised in MP, obtaining a liquid mixture MP1 depleted in solids compared to MP. Subsequently, MP1 is passed in SU2 comprised in SU, obtaining a liquid stream S1 comprising PO(1) and a liquid stream S2 comprising PA(1). S2 is subsequently subjected to purification in PU for separating E- caprolactam from the liquid stream S2.

[0219] Figure 3 is a schematic representation of the purification unit PU according to embodiments of the present invention. The purification PU comprises a distillation unit comprising a first distillation column D1 and a second distillation unit D2. The stream S2 removed from the separation unit SU (not shown in Fig. 3) is subjected to distillation in D1 comprised in PU, obtaining a bottom stream S2(1) comprising c-caprolactam and one or more compounds different to c-capro- lactam and a top stream S2(2) comprising water. The bottom stream S2(1) is subsequently subjected to distillation in D2, D2 being located downstream of D1 , obtaining a bottom stream S2(11) comprising the one or more compounds different to c-caprolactam and a top stream S2(12) comprising c-caprolactam. Optionally, a stream S3 (not shown in Fig. 3) obtained from an extraction zone ZE (not shown in Fig. 3) is subjected to distillation as S2 in PU.

[0220] Figure 4 is a schematic representation of the purification unit PU according to embodiments of the present invention. The purification PU comprises a distillation unit being a divided wall distillation column. The stream S2 removed from the separation unit SU (not shown in Fig. 4) is subjected to distillation in the distillation unit comprised in PU, obtaining a bottom stream S2(1’) comprising heavy boiling compounds, a middle stream S2(2’) comprising c-caprolactam and a top stream S2(3’) comprising water and light boiling compounds. Optionally, a stream S3 (not shown in Fig. 4) obtained from an extraction zone ZE (not shown in Fig. 4) is subjected to distillation as S2 in PU. Figure 5 is a schematic representation of the purification unit PU according to embodiments of the present invention. The purification PU comprises a distillation column D being a divided wall distillation column, and a crystallization unit CU. The stream S2 removed from the separation unit SU (not shown in Fig. 5) is subjected to distillation in D, obtaining a bottom stream S2(1 ’) comprising heavy boiling compounds, a middle stream S2(2’) comprising e-caprolactam and a top stream S2(3’) comprising water and light boiling compounds. The stream S2(2’) is subjected to crystallization in CU, obtaining solid e-caprolactam (CPL) and a liquid stream SL. Optionally, a stream S3 (not shown in Fig. 5) obtained from an extraction zone ZE (not shown in Fig. 5) is subjected to distillation as S2 in PU.

[0221] Figure 6 is a schematic representation of a unit for carrying out the recycling process according to embodiments of the present invention. The unit comprises a pyrolysis reactor unit RU(P), a gas-liquid separation unit GLSU, a separation unit SU comprising a solid-liquid separation sub-unit SU1 and a liquid-liquid separation sub-unit SU2, an extraction zone ZEand a purification unit PU. A solid material W comprising polyamide 6 is provided and subjected to pyrolysis in RU(P), obtaining an intermediate gas stream G. The stream G is subjected to condensation in GLSU, obtaining a mixture MP comprising an aqueous phase PA(1) and an organic phase PO(1), both phases comprises e-caprolactam, preferably from 50 to 99.9 weight-%, more preferably from 70 to 98 weight-%, more preferably from 80 to 95 weight-%, of e-caprolactam comprised in MP is in the aqueous phase PA(1 ). The mixture MP is passed in SU, obtaining a liquid stream S2 comprising PA(1). In particular, MP is passed in SU1 comprised in SU for removing solids comprised in MP, obtaining a liquid mixture MP1 depleted in solids compared to MP. Subsequently, MP1 is passed in SU2 comprised in SU, obtaining a liquid stream S1 comprising PO(1) and a liquid stream S2 comprising PA(1). S1 is then subjected to extraction with water and optional a base B in ZE, obtaining a liquid stream S11 , depleted in e-caprolactam compared to S1 , comprising PO(1) and an aqueous liquid stream S3 comprising e-caprolactam in water. S2 is subsequently subjected to purification in PU for separating e-caprolactam from the liquid stream S2. Further, S3 is also subjected to purification, in particular in PU as well.

[0222] Figure 7 is a schematic representation of the purification unit PU according to embodiments of the present invention. The purification PU comprises a distillation column D being a divided wall distillation column, an extraction unit EX and a crystallization unit CU. The stream S2 removed from the separation unit SU (not shown in Fig. 3) is subjected to distillation in D, obtaining a bottom stream S2(1 ’) comprising heavy boiling compounds, a middle stream S2(2’) comprising e-caprolactam and a top stream S2(3’) comprising water and light boiling compounds. The stream S2(2’) is subjected to extraction in EX with water and optionally a base, obtaining a stream S21 (1 ) comprising e-caprolactam (polar phase) and a stream S21 (2) comprising one or more compounds other than e-caprolactam (unpolar phase). The stream S21 (1 ) is subsequently subjected to crystallization in CU, obtaining solid e-caprolactam (CPL) and a liquid stream SL comprising water. Optionally, a stream S3 (not shown in Fig. 7) obtained from an extraction zone ZE (not shown in Fig. 7) is subjected to distillation as S2 in PU. Figure 8 is a schematic representation of the purification unit PU according to embodiments of the present invention. The purification PU comprises a crystallization unit CU, a drying unit UD and a distillation column D3. The stream S2 removed from the separation unit SU (not shown in Fig. 8) is subjected to crystallization in CU, obtaining a stream SC comprising solid E- caprolactam and a liquid stream SW comprising mostly water. The stream SC is further dried (heated) in UD, obtaining a stream ML comprising c-caprolactam (upon heating to above 70°C in liquid form). The stream ML is subjected to distillation in D3, obtaining a top stream ML(1) comprising c-caprolactam and a bottom stream ML(2) comprising one or more compounds other than £-caprolactam. Optionally, a stream S3 (not shown in Fig. 8) obtained from an extraction zone ZE (not shown in Fig. 8) is subjected to crystallization as S2 in PU. The stream SW may be recycled and used as a source of water for the process of the present invention, for example in 111.1.1 and / or 111.1.2

[0223] Cited literature

[0224] P. J. Diepen, O. S. L. Bruinsma, G. M. Van Rosmalen: Melt crystallization by controlled evaporative cooling. The caprolactam-water system in batch operation; Chemical Engineering Science, Vol. 55, 2000, 3575-3584

[0225] Ullmann’s Encyclopedia of Industrial Chemistry, Polyamides (Ben Herzog et al.), Ed. 2020 Wiley-VCH Verlag GmbH & Co. KGaA

[0226] “Industrial Organic Chemistry”, 3. volume, Wiley-VCH, 1997, ISBN: 978-3-527-28838-0 „Kunststoffhandbuch“, 11 volumes in 17 sub-volumes, Carl Hanser Verlag; especially volume 6, „Polyamide“, 1st edition, 1966, volume 7, „Polyurethane", 3. edition, 1993, and volume 8, “Polyester”, 1st edition 1973; “Industrial Organic Chemistry”, 3. volume, Wiley- VCH, 1997, ISBN: 978-3-527-28838-0

[0227] “Injection Molding Reference Guide, 4th Edition, CreateSpace Independent Publishing Platform, 2011 , ISBN: 978-1466407824 EP0989146 A1 EP1460094 A1

[0228] W02006034800 A1 EP 1529792 A1 W02006042674 A1 EP0364854 A2 US5506275 A EP0897402 A1 WO2015082316 A1 WO2021021855 A1 WO2021126938 A1 W02021021902 A1 WO2021092311 A1 W02008155271 A1 WO2013139827 A1

Claims

Claims1. A recycling process for recovering e-caprolactam from a solid material W comprising polyamide 6, the process comprises(i) providing the solid material W;(ii) subjecting the solid material W provided according to (i) to, preferably non-hydrous, pyrolysis in a pyrolysis reactor unit RU(P), obtaining a mixture MP comprising- an aqueous phase PA(1) comprising e-caprolactam, an organic phase PO(1) comprising e-caprolactam;(iii) isolating e-caprolactam from MP obtained according (ii), (iii) comprising(111.1) passing the mixture MP obtained according to (ii) in a separation unit SU, obtaining a liquid stream S1 comprising PO(1) and a liquid stream S2 comprising PA(1);(111.2) separating e-caprolactam from the liquid stream S2 obtained according to (iii.1), in a purification unit PU.

2. The process of claim 1 , wherein the solid material W comprises polyamide 6 in an amount of at least 0.25 weight-%, preferably at least 1 weight-%, more preferably in the range of from 1 to 95 weight-%, more preferably in the range of from 2 to 80 weight-%, more preferably in the range of from 3 to 60 weight-%, based on the weight of W.

3. The process of claim 1 or 2, wherein the solid material W comprises a solid waste material, wherein said waste material preferably comprises one or more of plastic waste material and textile waste material; wherein preferably the solid material W comprises, in addition to polyamide 6, one or more polyolefins.

4. The process of any one of claims 1 to 3, wherein the pyrolysis according to (ii) is performed by thermal cracking and / or catalytic cracking.

5. The process of any one of claims 1 to 4, wherein the pyrolysis according to (ii) is performed at a temperature in the range of from 250 to 800 °C, preferably in the range of from 300 to 700 °C, more preferably in the range of from 350 to 650 °C, more preferably in the range of from 400 to 600 °C; wherein the pyrolysis according to (ii) is preferably performed at a pressure in the range of from 0.1 to 5 bar(abs), more preferably in the range of from 0.9 to 1.5 bar(abs).

6. The process of any one of claims 1 to 5, wherein (ii) comprises(11.1) subjecting W to pyrolysis in a pyrolysis reactor unit RU(P), obtaining an intermediate gas stream G;(11.2) subjecting the intermediate gas stream G to condensation in a gas-liquid separation unit, obtaining a mixture MP comprising- an aqueous phase PA(1) comprising e-caprolactam,- an organic phase PO(1) comprising e-caprolactam. wherein the condensation according to (ii.2) is performed at a temperature preferably in the range of from 20 to 300 °C, more preferably in the range of from 70 to 110 °C.

7. The process of any one of claims 1 to 6, wherein from 50 to 99.9 weight-%, preferably from 70 to 98 weight-%, more preferably from 80 to 95 weight-%, of e-caprolactam comprised in MP is in the aqueous phase PA(1 ) obtained according to (ii).

8. The process of any one of claims 1 to 7, wherein passing the mixture MP obtained according to (ii) in a separation unit SU, obtaining a liquid stream S1 comprising PO(1) and a liquid stream S2 comprising PA(1), according to (iii.1 ) comprises(111.1 .1) passing the mixture MP obtained according to (ii) in a solid-liquid separation subunit SU1 comprised in SU for removing solids comprised in MP, obtaining a liquid mixture MP1 depleted in solids compared to MP;(111.1.2) passing the liquid mixture MP1 obtained according to (iii.1.1) in a liquid-liquid separation sub-unit SU2 comprised in SU, SU2 being located downstream of SU1 , obtaining the liquid stream S1 comprising PO(1) and the liquid stream S2 comprising PA(1); wherein (iii.1 .1 ) preferably comprises bringing in contact water with the mixture MP obtained according to (ii) and passing MP with water in the solid-liquid separation sub-unit SU1 comprised in SU for removing solids comprised in MP, obtaining a liquid mixture MP1 depleted in solids compared to MP.

9. The process of any one of claims 1 to 8, wherein (iii.2) comprises subjecting the stream S2 obtained according to (iii.1) to distillation in a distillation unit comprised in PU, obtaining e-caprolactam separated from S2; wherein (iii.2) preferably comprises(111.2.1 ) subjecting the stream S2 obtained according to (iii.1) to distillation in a first distillation column D1 comprised in the distillation unit, obtaining a bottom stream S2(1 ) comprising e-caprolactam and one or more compounds different to e-capro- lactam and a top stream S2(2) comprising water;(111.2.2) subjecting the bottom stream S2(1) obtained according to (iii.2.1) to distillation in a second distillation column D2, D2 being located downstream of D1 , obtaining a bottom stream S2(11) comprising the one or more compounds different to e-ca- prolactam and a top stream S2(12) comprising e-caprolactam; or wherein (iii.2) preferably comprises(iii.

2. T) subjecting the stream S2 obtained according to (iii.1) to distillation in a distillation unit being a divided wall distillation column comprised in PU, obtaining a bottom stream S2(1 ’) comprising one or more compounds different to e-caprolactam, a middle stream S2(2’) comprising e-caprolactam and a top stream S2(3’) comprising water.

10. The process of any one of claims 1 to 8, wherein (iii.2) comprises(iii.2.1 ”) subjecting the stream S2 obtained according to (iii.1) to crystallization in a crystallization unit CU comprised in PU, obtaining crystallized e-caprolactam; wherein the crystallization according to (iii.2.1”) is performed at a temperature preferably in the range of from 5 to 70 °C; wherein, preferably, according to (iii.2.1”), in addition to the crystallized e-caprolactam, a stream SW comprising water is obtained and removed from CU, optionally SW being recycled as a source of water for (iii.1 ).11 . The process of any one of claims 1 to 10, wherein (iii) further comprises(111.3) subjecting the stream S1 obtained according to (iii.1 ) to extraction with water and optionally a base B in at least one extraction zone ZE, obtaining a liquid stream S11 , depleted in e-caprolactam compared to S1 , comprising PO(1) and an aqueous liquid stream S3 comprising e-caprolactam dissolved in water;(111.4) separating e-caprolactam from the liquid stream S3 obtained according to (iii.3), in a purification unit, preferably in the purification unit PU used in (iii.2).

12. A process for preparing a polymer or a polymer product, comprising the steps of recovering e-caprolactam from a solid material W according to claim 11 , and(iv) converting the liquid stream S1 obtained according to (iii.2), or the liquid stream S11 obtained according to (iii.3) as defined in claim 14 to a polymer or a polymer product.

13. A process for preparing a polymer or a polymer product, comprising the step of converting at least one monomer, preferably obtained from the liquid stream S1 obtained according to (iii.2), or the liquid stream S11 obtained according to (iii.3) as defined in claim 14, to a polymer or a polymer product; wherein the monomer is preferably a di- or polyol; preferably butandiol; an aldehyde, preferably formaldehyde; a di- or polyisocyanate, preferably methylene diphenyl diisocyanate (MDI), polymeric methylene diphenyl diisocyanate (pMDI), toluene diisocyanate (TDI), hexamethylenediisocyanate (HDI) or isophoronediisocyanate (IPDI); an amide, preferably caprolactam; an alkene, preferably styrene, ethene and / or norbornene; an alkyne, a (di)ester, preferably methyl methacrylate; a mono or diacid, preferably adipic acid or terephthalic acid; a diamine, preferably hexamethylenediamine, nonanediamine; or a sulfone, preferably 4, 4'-dichlorodiphenyl sulfone; wherein the polymer is and / or the polymer product preferably comprises a polyamide (PA), preferably PA6 or PA66; a polyisocyanate polyaddition product, preferably polyurethane (PU), thermoplastic polyurethane (TPU), a polyurea or a polyisocyanurate (PI R); a low-density polyethylene (LDPE), a high-density polyethylene (HDPE), polyethylene (PE), a polypropylene (PP), a polyvinyl chloride (PVC), a polyvinyl acetate (PVA), a polystyrene (PS), a poly acrylonitrile butadiene styrene (ABS), a poly styrene acrylonitrile (SAN), a poly acrylate styrene acrylonitrile (ASA), a polytetrafluoroethylene (PTFE), a poly(methyl acrylate) (PM A), a poly(methyl methacrylate) (PM MA), a polybutadiene (BR, PBD), apoly(cis-1 ,4-isoprene), a poly(trans-1 ,4-isoprene), a polyoxymethylene (POM), a polyethylene terephthalate (PET), a polybutylene terephthalate (PBT), a polybutylene adipate coterephthalate (PBAT), a polyester (PES), a polyether sulfone (PESU), polyhydroxyalkanoate (PH A), a poly-3-hydroxybutyrate (P3HB), a poly-4-hydroxybutyrate (P4HB), a polyhydroxyvalerate (PHV), a polyhydroxyhexanoate (PHH), a polyhydroxyoctanoate (PHO), a polylactic acid (PLA), a polysulfone (PSU), a polyphenylene sulfone (PPSU), a polycarbonate (PC), a polyether ether ketone (PEEK), a poly(p-phenylene oxide) (PPO), a poly(p- phenylene ether) (PPE); or copolymer or mixture thereof; wherein the polymer and / or the polymer product obtained according to (iv) preferably is / are or is / are a part of: a part of a car; preferably a cylinder head cover, an engine cover, a housing for charge air cooler, a charge air cooler flap, an intake pipe, an intake manifold, a connector, a gear wheel, a fan wheel, a cooling water box, a housing, a housing part for heat exchanger, a coolant cooler, a charge air cooler, a thermostat, a water pump, a radiator, a fastening part, a part of battery system for electro-mobility, a dashboard, a steering column switch, a seat, a headrest, a center console, a transmission component, a door module, an A, B, C or D pillar cover, a spoiler, a door handle, an exterior mirror, a windscreen wiper, a windscreen wiper protection housing, a decorative grill, a cover strip, a roof rail, a window frame, a sunroof frame, an antenna panel, a headlight and taillight, a cylinder head cover, intake manifold, an airbag, a cushion, or a coating; a cloth; preferably a shirt, trousers, a pullover, a boot, a shoe, a shoe sole, a tight or a jacket; an electrical part; preferably an electrical or electronic passive or active component, a circuit board, a printed circuit board, a housing component, a foil, a line, a switch, a plug, a socket, a distributor, a relay, a resistor, a capacitor, an inductor, a bobbin, a lamp, a diode, a LED, a transistor, a connector, a regulator, an integrated circuit (IC), a processor, a controller, a memory, a sensor, a micro-switch, a micro-button, a semiconductor, a reflector housing for light-emitting diodes (LED), a fastener for electrical or electronic component, a spacer, a bolt, a strip, a slide-in guide, a screw, a nut, a film hinge, a snap hook (snap-in), or a spring tongue; a consumer, agricultural or pharmaceutical product; preferably a tennis string, a climbing rope, a bristle, a brush, an artificial grass, a 3D printing filament, a grass trimmer, a zipper, a hook and a loop fastener, a paper machine clothing, an extrusion coating, a fishing line, a fishing net, an offshore line and rope, a vial, a syringe, an ampoule, a bottle, a sliding element, a spindle nut, a chain conveyor, a plain bearing, a roller, a wheel, a gear, a roller, a ring gear, a screw and a spring dampers, a hose, a pipeline, a cable sheathing, a socket, a switch, a cable tie, a fan wheel, a carpet, a box or bottle for cosmetics, a mattress, a cushion, an insulation, a detergent, a dishwasher tabs or a powder, a shampoo, a body wash, a shower gel, a soap, a fertilizer, a fungicide, or a pesticide; a packaging for the food industry; preferably a mono- or multi-layer blown film, a mono- or multi-layer cast film, a biaxially stretched film, or a laminating film; ora part of a construction; preferably a rotor blade, an insulating material, a frame, a housing, a wall, a coating, or a separating wall.

14. The process of any one of claims 1 to 13, wherein the recycled content in the liquid stream S1 obtained according to (iii.2), or the liquid stream S11 obtained according to (iii.3) as in claim 14, or the monomer, the polymer or the polymer product obtained according to (iv) as in any one of claims 15 to 18, stemming from the solid material W, is 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; or wherein the recycled content in a product stream comprising the liquid stream S1 obtained according to (iii.2), or the liquid stream S11 obtained according to (iii.3) as in claim 14, or the monomer, the polymer or the polymer product obtained according to (iv) as in any one of claims 15 to 18, stemming from the solid material W, is 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; and preferably wherein the recycled content is determined based on identity preservation and / or segregation and / or mass balance and / or book and claim chain of custody models, more preferably based on mass balance, more preferably the International Sustainability and Carbon Certification (ISCC) standard.

15. A unit for carrying out the recycling process according to any one of claims 1 to 14, the unit comprising a pyrolysis reactor unit RU(P); an inlet means for introducing W into RU(P); an outlet means for removing MP from RU(P); a separation unit SU; an inlet means for introducing MP into SU; an outlet means for removing S1 from MP; an outlet means for removing S2 from MP; a purification unit PU; an inlet means for introducing S2 into PU; an outlet means from removing e-caprolactam from PU; the unit preferably further comprising at least one extraction zone ZE comprising a means for extracting; an inlet means for introducing S1 into ZE; an outlet means for removing S11 from ZE;an outlet means for removing S3 from ZE;an inlet means for introducing S3 into PU.

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