Process for purifying an aqueous liquid stream comprising monomeric Ε-caprolactam

Abstract

A process for purifying an aqueous liquid stream comprising monomeric E-caprolactam, polyamide 6 and one or more organic compounds X, wherein monomeric E-caprolactam has a boiling point Tc and the one or more one organic compounds X have a boiling point Tx > Tc.

Description

Process for purifying an aqueous liquid stream comprising monomeric ε-caprolactam The present invention relates to a highly efficient and, at the same time, flexible process for separating high boiling compounds from a stream which comprises the high boiling compounds and ε-caprolactam; this stream is preferably obtained from the depolymerization of polyamide 6 contained in a solid material, wherein this material is preferably a waste material, more preferably a textile waste material. Further, the present invention relates to a method of controlling this process, and yet further to a plant in which said process and said method are carried out. Polyamide, and in particular polyamide 6 characterized by the formula (–NH–(CH2)5–CO–)n, can be found in numerous materials, such as packaging, engineering plastics from automotive and textile filaments. The latter represents about 40 % of the polyamide 6 global market. At present, only a very small part of the textile filaments is recycled while it represents a significant percentage of the global CO2emissions. There is thus a need to recycle polyamide 6 from such materials. The purification process for ε-caprolactam downstream of the depolymerization step is not a straight-forward task, for example due to the various possible chemical compositions of waste materials comprising polyamide 6 which form the educt materials for the recycling process. It was found that said waste materials will contain certain compounds which, either before or after depolymerization of polyamide 6, lead to a stream comprising ε-caprolactam and compounds having a higher boiling point than ε-caprolactam. Due to possibly different chemical compositions of said waste material, however, these compounds having a higher boiling point than ε-caprolactam will usually differ from time to time, both with regard to the content in the stream to be purified and in chemical nature. Therefore, there is a need for a flexible process which is suitable for purifying crude ε-caprolactam streams comprising said high boiling compounds and which allows for dealing with different qualities of streams to be purified. According to the present, it was found that this task can be accomplished by a process setup which exhibits twoserially arranged stages, wherein each stage exhibits a depolymerization sub-stage, a dewatering sub-stagedownstream of said depolymerization sub-stage and a high boiler separation sub-stage downstream of saiddewatering sub-stage, and wherein after each stage, the residue stream obtained from the high boiler sub-stage is either recycled back or subjected to further treatment or use. Therefore, the present invention relates to a process for purifying an aqueous liquid stream comprising monomeric ε- caprolactam, polyamide 6 and one or more organic compounds X, wherein monomeric ε-caprolactam has a boiling point TC and the one or more one organic compounds X have a boiling point TX > TC, said process comprising(i) providing a stream SM comprising a solid material M comprising polyamide 6;(ii) preparing an aqueous depolymerization mixture MD1 from SM;(iii) subjecting the mixture MD1 to a first depolymerization and purification stage, comprising(iii.1) subjecting the mixture MD1 in a depolymerization unit UR1 to polyamide 6 depolymerization conditionsDR1 comprising a depolymerization temperature TR1 at a depolymerization pressure pR1, obtaining aliquid aqueous product stream SR1 comprising monomeric ε-caprolactam at a concentration cR1(C), polyamide 6 at a concentration cR1(P) and one or more compounds X at a total concentration cR1(X); (iii.2) passing the liquid aqueous stream SR1 into a first water separation unit UWS1, obtaining from SR1 aliquid aqueous product stream SWS1 comprising monomeric ε-caprolactam at a concentration cWS1(C) > cR1(C), polyamide 6 at a concentration cWS1(P) > cR1(P) and one or more compounds X at a total concentration cWS1(X) > cR1(X), and further obtaining at least one aqueous residue stream SR-WS1 comprising separated water; (iii.3) passing the liquid aqueous stream SWS1 into a high boiler separation unit UHS1, obtaining from SWS1 anaqueous product stream SP-HS1 comprising monomeric ε-caprolactam at a concentrationcP-HS1(C) > cWS1(C) and further obtaining from SWS1an aqueous residue stream SR-HS1comprising polyamide 6 at a concentration cR-HS1(P) ≥ cWS1(P) and one or more compounds X at a totalconcentration cR-HS1(X) > cWS1(X);(iv) passing the aqueous residue stream SR-HS1 to further treatment, comprising(iv.1) recycling at least a part of the stream SR-HS1 to (iii), comprising subjecting the at least part of thestream SR-HS1 in the depolymerization unit UR1 to the polyamide 6 depolymerization conditions DR1;and / or (iv.2) subjecting at least a part of the stream SR-HS1 to a second depolymerization and purification stage,comprising (iv.2.1) subjecting the at least part of the stream SR-HS1 in a depolymerization unit UR2 to polyamide6 depolymerization conditions DR2 comprising a depolymerization temperature TR2 at a depolymerization pressure pR2, obtaining a liquid aqueous stream SR2 comprising monomeric ε-caprolactam at a concentration cR2(C), optionally polyamide 6 at a concentration cR2(P) < cR-HS1(P), and one or more compounds X at a total concentration cR2(X); (iv.2.2) passing the liquid aqueous stream SR2 into a second water separation unit UWS2, obtainingfrom SR2a liquid aqueous product stream SWS2comprising monomeric ε-caprolactam at a concentration cWS2(C) > cR2(C), polyamide 6 at a concentration cWS2(P) > cR2(P) and one or more compounds X at a total concentration cWS2(X) > cR2(X), and further obtaining at least one aqueous residue stream SR-WS2comprising separated water; (iv.2.3) passing the liquid aqueous stream SWS2 into a high boiler separation unit UHS2, obtainingfrom SWS2 an aqueous product stream SP-HS2 comprising monomeric ε-caprolactam at a concentration cP-HS2(C) > cWS2(C) and further obtaining from SWS2 an aqueous residue stream SR-HS2 comprising one or more compounds X at a total concentration c R-HS2(X) > cWS2(X) and optionally polyamide 6 at a concentration cR-HS2(P) > cWS2(P); (iv.2.4) passing the aqueous residue stream SR-HS2 to further treatment, comprising(iv.2.4.1) recycling at least a part of the stream SR-HS2 to (iv.2.1), comprising subjectingthe at least part of the stream SR-HS2 in the depolymerization unit UR2 to the polyamide 6 depolymerization conditions DR2; and / or(iv.2.4.2) passing at least a part of the stream SR-HS2 to a further use.According to (i), the solid material M comprised in the stream SM preferably comprises, more preferably consists of, a waste material, wherein said waste material more preferably comprises, more preferably consists of, one or more of at least one textile waste material and at least one engineering plastics waste material, more preferably comprises,more preferably consists of at least one textile waste material.Preferably from 10 to 99 weight-%, more preferably from 30 to 98.5 weight-%, more preferably from 50 to 98 weight-%, more preferably from 80 to 98 weight-% of the solid material M consist of polyamide 6.In addition to polyamide 6, the solid material M preferably comprises one or more further organic polymeric compounds, more preferably including, but not limited to, one or more of at least one elastane; at least one polyamide 6.6; at least one semiaromatic polyamide including one or more of polyamide 6T and polyamide 6I; at least one polyethylene terephthalate; at least one polyurethane; at least one polyester; at least one polyether; at least one polyvinyl chloride; at least one natural fiber material such as wool and cotton; at least one cellulose material; at least one natural elastomer; at least one synthetic elastomer; at least one copolymer of two or more of said polymeric compounds including statistical copolymers, gradient copolymers, alternating copolymers, block copolymers, and graft copolymers; and at least one rubber material comprising one or more of at least one natural rubber material and at least one synthetic rubber material. Prior to being provided to the process of the present invention, the waste material can be suitably sorted. In this regard, it is possible to spread the collected textile waste material on a conveyor, which spreading can be carried out either manually and / or mechanically. Thereafter, the respectively spread textile waste material is subjected to sorting, either by composition and / or by color. Sorting can be carried out either manually and / or optically. If carried out optically, the sorting preferably comprises an infrared sorting, more preferably a near-infrared sorting and / or a mid- infrared sorting. Optionally, prior to sorting, the textile waste material can be subjected to a suitable metal removing step. If a metal removing step is carried out, ferrous elements are preferably separated, for example by suitable magnetic means, and / or non-ferrous elements are preferably separated, for example by suitable eddy current separating means. After said sorting, the respectively obtained textile waste material can be subjected to a further treatment, such as cutting and / or milling. Generally, the solid material M can be provided according to any suitable method. Preferably according to the present invention, providing the solid material M comprises providing the solid material M in a delivering unit whichpreferably comprises one or more of at least one big bag station and at least one a bulk container station; passingthe provided solid material M via a first connecting line from the delivering unit to a material collecting unit, preferably a collecting drum, wherein the first connecting line preferably comprises one or more of at least one material receiving and discharge unit, at least one first material feeding unit, and at least one first particle separation unit; passing the solid material M from the material collecting unit via a second connecting line to a melting unit UM asdescribed herein, wherein the second connecting line preferably comprises one or more of at least one second material feeding unit, at least one second particle separation unit, and at least one metal detector. Optionally of preferably, the solid material M may be provided in the form of granules, wherein the particle size distribution of said granules is preferably characterized by one or more of the following pairs of values, preferably by two or more of the following pairs of values, more preferably by the following three pairs of values:- a D10 value of the particle width in the range of from in the range of from 0.1 to 15 mm and a D10 value of theparticle length in the range of from 0.3 to 15 mm;- a D50 value of the particle width in the range of from in the range of from 0.2 to 20 mm and a D50 value of theparticle length in the range of from 0.5 to 20 mm;- a D90 value of the particle width in the range of from in the range of from 0.3 to 30 mm and a D90 value of theparticle length in the range of from 0.8 to 30 mm. According to (ii), the aqueous depolymerization mixture is prepared. While there are no specific restrictions in this regard, it is preferred that preparing the aqueous depolymerization mixture MD1comprises- melting in a melting unit UM the solid material M comprised in the stream SM having a temperature TSM at apressure pSM, obtaining a liquid stream SM;- admixing in a pre-reaction unit UPR the liquid stream SM with an aqueous stream SW having a temperature TSWat a pressure pSW, obtaining the depolymerization mixture MD1 having a temperature TMD1 at a pressure pMD1.The pre-reaction unit UPR preferably comprises, more preferably consists of, a mixing unit, preferably a static mixing unit, and wherein the melting unit UM comprises, preferably consists of an extruder, preferably a single-screw extruder or a twin-screw extruder. Further, it is preferred that SW and SM are admixed in UPR at a mixing ratio (mW / kg) / (mP / kg) in the range of from 1:1 to 20:1, more preferably in the range of from 2:1 to 15:1, more preferably in the range of from 5:1 to 10:1, wherein mW is the amount of water comprised in SW and mP is the amount of polyamide 6 comprised in SM. Preferably according to the process of the present invention, the polyamide 6 depolymerization conditions DR1according to (iii.1) comprise a depolymerization pressure pR1in the range of from 40 to 140 bar, more preferably in the range of from 40 to 125 bar, more preferably in the range of from 40 to 110 bar; and a depolymerization temperature TR1 in the range of from 230 to 335 °C, preferably in the range of from 250 to 320 °C, more preferably in the range of from 270 to 310 °C. As far as this process design is concerned, it is preferred that 0.8 ≤ TMD1 / TR1 ≤ 1.05 and 0.9 ≤ pMD1 / pR1 ≤ 1.05; 0.6 ≤ TSM / TMD1 ≤ 1.2 and 0.9 ≤ pSM / pMD1 ≤ 1.05; and 0.8 ≤ TSW / TMD1 ≤ 1.2 and 0.9 ≤ pSW / pMD1 ≤ 1.05.Preferably, the depolymerization unit UR1 comprises z chemical reactors R1i, i=1…z1, wherein z1 is in the range offrom 1 to 10, preferably in the range of from 1 to 8, more preferably in the range of from 1 to 6, more preferably in therange of from 1 to 5, more preferably in the range of from 1 to 4, more preferably in the range of from 1 to 3. If z1 > 1,is preferred that at least 2 reactors R1i, more preferably all z1 reactors R1i, are serially coupled, wherein- the depolymerization mixture MD1 is fed into R1i, with i = 1;- an aqueous liquid stream S1i containing ε-caprolactam dissolved in water is removed from reactor R1i and fedinto the reactor R1(i+1), with i < z1;- an aqueous liquid stream S1z containing ε-caprolactam dissolved in water is removed from the reactor R1z1 asthe stream SR1; wherein in every reactor R1i, a depolymerization temperature TR1iat a depolymerization pressure pR1iis maintained, wherein, independently of each other, TR1iis in the range of from 230 to 330 °C and pR1iis in the range of from 40 to 140 bar, preferably wherein TR1iis in the range of from 250 to 320 °C and pR1iis in the range of from 40 to 125 bar, more preferably wherein TR1iis in the range of from 270 to 310 °C and pR1iis in the range of from 40 to 110 bar. For z1> 1, it is preferred that the z1reactors R1iare vertically arranged, with R11being the top-most reactor and R1z1being the bottom-most reactor, wherein S1iobtained from R1iis transferred to R1(i+1)by gravity, preferably by gravity only. More preferably, at least 1, preferably all z1reactors R1i, are continuous stirred tank reactors (CSTR). Preferably, every continuous stirred tank reactor R1ihas, independently from each other, from 2 to 6 compartments, more preferably from 2 to 5 compartments, more preferably from 2 to 4 compartments, said compartments preferably being serially, more preferably being serially and vertically arranged, wherein 2 adjacent compartments are separated by a divider which comprises at least one flow-through opening. Preferably at least one compartment comprised in a reactor R1i comprises at least one agitator, wherein more preferably every compartment of every reactor R1i comprises at least one agitator, wherein more preferably, every compartment of every reactor R1icomprises one agitator, and the process comprises agitating the depolymerization mixture in a given compartmentfor at least part of the time during subjecting to depolymerization conditions in said compartment. Preferably, the polyamide 6 depolymerization conditions further comprise a total residence time tR1 of the aqueous depolymerization mixture in the unit UR1, preferably in the z1reactors R1i, more preferably in the z1continuous stirred tank reactors, wherein at least 85 weight-%, preferably at least 90 weight-%, more preferably at least 95 weight-% of the aqueousdepolymerization mixture have a tR1 in the range of from 30 to 90 min. More preferably, the residence time of anaqueous depolymerization mixture in a reactor R1iis tR1iand 0.90 ≤ (tR1i / tR1(i+1)) ≤ 1.10, more preferably 0.95 ≤ (tR1i / tR1(i+1)) ≤ 1.05. Preferably according to the present invention, no polyamide 6 depolymerization catalyst such as a mineral acidand / or a zinc salt such as zinc chloride, zinc acetate or zinc triflate is used for preparing the depolymerization mixtureMD1, is contained in the depolymerization mixture MD1 to be subjected to depolymerization conditions in UR1, and ispresent during depolymerization in UR1. Preferably, the liquid aqueous stream SR1 according to (iii.1) has a temperature in the range of from 230 to 330 °C, preferably in the range of from 250 to 320 °C, more preferably in the range of from 270 to 310 °C. Further preferably,in the liquid aqueous stream SR1 according to (iii.1), the weight ratio of water relative to the sum of monomeric ε- caprolactam, polyamide 6 and the at least one compound X, m(W) / (m(C)+(m(P)+(X)), is in the range of from 5:1 to15:1, preferably in the range of from 6:1 to 10:1, more preferably in the range of from 7:1 to 9:1. Preferably from 98 to100 weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the stream SR1 consist of monomeric ε-caprolactam, polyamide 6, the one or more compounds X, and water.According to the present invention, the term „polyamide 6“ which is comprised in the stream SR-HS1 encompassespolymeric polyamide 6 as well as any oligomeric polyamide 6. Said oligomeric polyamide 6 can be comprised alreadyin the depolymerization mixture MD1 subjected to depolymerization conditions according to (iii.1), and generally, isformed from polyamide 6 in the first depolymerization stage carried out according to (iii.1). Further, it may be possiblethat some oligomeric polyamide 6 is formed during the first water separation stage according to (iii.2). Further, theterm “oligomeric polyamide 6” encompasses any oligomers starting from dimers and, therefore, includes ε- caprolactam dimer, ε-caprolactam trimer, ε-caprolactam tetramer, ε-caprolactam pentamer, ε-caprolactam hexamer, and so forth, wherein the oligomers may exhibit a linear and / or a cyclic structure. Regarding the chemical nature of the high boiler compounds X, a comparatively high uncertainty exists, simply in view of the unpredictable chemical composition of the materials subjected to depolymerization and, finally, high boiler separation according to the present invention. However, when developing the process of the present invention, numerous elaborate experiments were carried out, and it was found that in a majority of situations, the one or more compounds X preferably comprise at least one of- at least one aromatic amine which includes at least one of an aromatic monoamine, an aromatic diamine, anaromatic triamine and an aromatic tetramine;- at least one aliphatic amine which includes at least one of an aliphatic monoamine, an aliphatic diamine andan aliphatic triamine;- at least one aliphatic amide;- at least one aromatic alcohol which includes at least one of an aromatic monool and an aromatic diol;- at least one aliphatic alcohol which includes at least one of an aliphatic monool and an aliphatic diol;- at least one aromatic acid;- at least one and aliphatic acid;- at least other compound selected from the group consisting of one or more cleavage products of dyes such asoptionally chlorinated aromatic diamines, one or more water-soluble oligomeric cellulose cleavage products, and one or more water-soluble oligomers of terephthalic acid and hexamethylenediamine. Yet further, it was found that- the at least one aromatic amine preferably includes one or more of 4,4’-methylenedianiline (MDA), isomersthereof such as 2,4’-methylenedianiline and 2,2’-methylenedianiline, and polymethylen polyphenylen polyamines (pMDA);- the at least one aliphatic amine and the at least one aliphatic amide preferably include one or more ofhexamethylenediamine adipate, 6-aminocaproic acid and oligomers thereof, including 6-aminocaproic acid dimer and higher oligomers such as 6-aminocaproic acid trimer, 6-aminocaproic acid tetramer, 6- aminocaproic acid pentamer, 6-aminocaproic acid hexamer, N'-(6-aminohexyl)hexane-1,6-diamine, N- methylhexane-1,6-diamine, 6-amino-hexanamide, derivatives of ε–caprolactam other than ε–caprolactam oligomers and having a boiling point higher than ε–caprolactam such as 1-(6-aminohexyl)azepan-2-one;- the at least one aliphatic alcohol preferably includes one or more of butanediol and oligomers thereof,including butanediol dimer and higher oligomers such as butanediol trimer, including polytetrahydrofuran;- the at least one aromatic acid and the at least one aliphatic acid preferably include one or more of terephthalicacid and adipic acid. According to (iii.2), the liquid aqueous stream SR1is passed into a first water separation unit UWS1. Preferably, (iii.2) comprises(iii.2.1) passing the liquid aqueous stream SR1 into a water evaporation unit UWS1A, obtaining from SR1 a liquidaqueous product stream SWS1Acomprising monomeric ε-caprolactam at a concentration cWS1A(C) > cR1(C), polyamide 6 at a concentration cWS1A(P) > cR1(P) and one or more compounds X at a concentration cWS1A(X) > cR1(X), and further obtaining from SR1one or more aqueous vapor streams SR-WS1A;(iii.2.2) passing the liquid aqueous stream SWS1A into a water separation unit UWS1B, obtaining from SWS1A thestream SWS1 and further obtaining from SWS1A one or more aqueous streams SR-WS1B. Preferably according to the present invention, the water evaporation unit UWS1A comprises two or more water evaporation sub-units, more preferably two or more serially coupled water evaporation sub-units. More preferably,every water evaporation comprises, more preferably consists of, a flash drum. According to the present invention, itis preferred that the water separation unit UWS1B comprises a film evaporator, more preferably a falling film evaporator. The liquid aqueous stream SWS1according to (iii.2) has a temperature preferably in the range of from 75 to 120 °C, more preferably in the range of from 80 to 110 °C, more preferably in the range of from 85 to 100 °C. In the liquid aqueous stream SWS1, the weight ratio of water relative to the sum of monomeric ε-caprolactam, polyamide 6 and the at least one compound X, m(W) / (m(C)+(m(P)+(X)), is preferably in the range of from 0.13:1 to 0.4:1, more preferablyin the range of from 0.14:1 to 0.3:1, more preferably in the range of from 0.15:1 to 0.2:1. Preferably from 98 to 100weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the stream SWS1 consist of monomeric ε-caprolactam, polyamide 6, the one or more compounds X, and water. According to the present invention, it is preferred that at least one of the product stream SP-HS1 which is obtained from the first high boiler separation stage and the product stream SP-HS2 which is obtained from the second high boilerseparation stage is passed to a further water separation stage for further concentrating the respective stream with regard to monomeric ε-caprolactam. Therefore, the process of the present invention preferably further comprises(v) passing- the aqueous product stream SP-HS1 obtained according to (iii.1), comprisingmonomeric ε-caprolactam at the concentration cP-HS1(C) and water at a concentration cP-HS1(W);and / or -the aqueous product stream SP-HS2 obtained according to (iv.2.3), comprising monomeric ε-caprolactamat the concentration cP-HS2(C) and water at a concentration cP-HS2(W) to a third water separation unit UWS3, obtaining a product stream SP-WS3 comprising monomeric ε-caprolactam at a concentration cP-WS3(C) > cP-HS1(C) and water at a concentration cP-WS3(W) < cP-HS1(W), and further obtaining at least one aqueous residue stream SR-WS3comprising water at a concentration cR-WS3(W) > cP-HS1(W). Preferably, in the product stream SP-WS3, cP-WS3(C) + cP-WS3(W) is in the range of from 98.5 to 100 weight-%, more preferably in the range of from 99 to 100 weight-%, more preferably in the range of from 99.9 to 100 weight-%, based on the total weight of the stream SP-WS3, wherein in the stream SP-WS3, the weight ratio of monomeric ε-caprolactam relative to water is preferably at least 4:1, more preferably at least 5:1, more preferably at least 6:1, with values of at least 7:1 or at least 8:1 or at least 9:1 or at least 10:1 being conceivable.With regard to the setup of the high boiler separation carried out in according to (iii.3), no specific limitations exist. Inthe context of the present invention, three preferred ways of carrying out said high boiler separation are preferred. In detail:According to a first alternative with regard to (iii.3), it is preferred that the high boiler separation unit UHS1 according to(iii.3) is an evaporation unit, (iii.3) comprising(iii.3.1) passing the stream SWS1 into the unit UHS1, preparing in the unit UHS1 from the stream SWS1 an evaporationmixture MHS1having an evaporation temperature THS1at an evaporation pressure pHS1with THS1> TWS1, wherein the one or more one organic compounds X have a boiling point TBXand monomeric ε-caprolactam has a boiling point TBCwith TBX> THS1≥ TBCat the evaporation pressure pHS1;(iii.3.2) removing the stream SP-HS1 from the unit UHS1, the stream SP-HS1 having a temperature TP-HS1 withTP-HS1 ≤ THS1;(iii.3.3) removing the stream SR-HS1 from the unit UHS1, the stream SR-HS1 having a temperature TR-HS1 withTR-HS1 = TP-HS1. In the context of said first alternative, pHS1 is preferably in the range of from 50 to 200 mbar and THS1 is preferably in the range of from 220 to 330 °C, more preferably in the range of from 240 to 320 °C, more preferably in the range of from 260 to 310 °C; wherein preparing the mixture MHS1 in the unit UHS1 according to (iii.3.1) more preferably comprises- heating the stream SWS1 passed into the unit UHS1 from the temperature TWS1 to the evaporation temperatureTHS1 via internal heating means HINT1 arranged within the unit UHS1, thereby obtaining the evaporation mixture MHS1; or- passing, in addition to the stream SWS1, a stream SX1 into the unit UHS1, the stream SX1 having a temperatureTX1 > TWS1, admixing the stream SX1 and the stream SWS1 and heating the obtained mixture to the temperature THS1 via internal heating means HINT1 arranged within the unit UHS1, thereby obtaining the evaporation mixture MHS1, wherein the process further separating the stream SX1 from the stream SR-HS1, wherein the stream SX1 has the temperature TX = TR-HS1; or- passing, in addition to the stream SWS1, a stream SY1 into the unit UHS1, the stream SY1 having a temperatureTY1> THS1, and admixing the stream SWS1and the stream SY1, thereby obtaining the evaporation mixture MHS1, wherein the process further comprises separating a stream SX1from the stream SR-HS1, wherein the stream SX1has a temperature TX1= THSR1; and subjecting the stream SX1to heating via external heating means HEXT1arranged outside the unit UHS1, obtaining the stream SY1having the temperature TY1; and wherein preferably TY1≥ (THS1+ 10 K), more preferably TY1≥ (THS1+ 20 K), more preferably TY1≥ (THS1+ 30 K).Further in the context of said first alternative, the process preferably further comprises subjecting the stream SP-HS1 tocooling in a cooling unit, obtaining from said cooling unit a cooled stream SP-HS1, more preferably obtaining a cooledand partially condensed stream SP-HS1, and wherein the cooled stream SP-HS1 has a temperature TP-HS1 preferably in the range of from 160 to 320 °C, more preferably in the range of from 165 to 310 °C, more preferably in the range of from 170 to 300 °C. With regard to said first alternative, it is preferred that the water separation unit UWS3 as defined herein comprises two or more water separation sub-units, more preferably two water separation sub-units UWS3A and UWS3B, more preferably two serially coupled water separation sub-units UWS3Aand UWS3Bwith UWS3Bbeing arranged downstream ofUWS3A. Preferably, the water separation sub-unit UWS3A comprises, more preferably consists of, a droplet separator,more preferably selected from the group consisting of a hydrocyclone, a demister plate, and an absorption tower,more preferably a hydrocyclone; and the water separation sub-unit UWS3Bpreferably comprises, more preferably consists of, a distillation column. According to a second alternative with regard to (iii.3), it is preferred that the high boiler separation unit UHS1 according to (iii.3) is a stripping unit, (iii.3) comprising(iii.3.1) passing the stream SWS1 and an aqueous stripping gas stream SG01 into the unit UHS1, wherein theaqueous stripping gas stream SG01 has a temperature TG01 with TG01 > TWS1;(iii.3.2) bringing the stream SWS1 and the stream SG01 in the unit UHS1 at stripping conditions into contact with eachother, wherein the stripping conditions comprise a stripping pressure pHS1 and wherein at the strippingpressure pHS1, the one or more one organic compounds X comprised in the stream SWS1 have a boiling point TBX and monomeric ε-caprolactam has a boiling point TBC < TBX;(iii.3.3) removing the stream SP-HS1 from the unit UHS1, the stream SP-HS1 having a temperature TP-HS1 withTWS1 < TP-HS1 < TG01;(iii.3.4) removing the stream SR-HS1 from the unit UHS1, the stream SR-HS1 having a temperature TP-HS1 withTWS1 < TR-HS1 < TG01. In the context of said second alternative, it is preferred that from 95 to 100 weight-%, more preferably from 98 to 100 weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.8 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the aqueous stripping gas stream SG01consist of water; and that TG01is preferably at least 250 °C, more preferably in the range of from 250 to 500 °C, more preferably in the range of from 300 to 450 °C. With regard to said second alternative, it is preferred that the water separation unit UWS3as defined herein comprises two or more water separation sub-units, more preferably two water separation sub-units UWS3Aand UWS3B, more preferably two serially coupled water separation sub-units UWS3Aand UWS3Bwith UWS3Abeing arranged upstream ofUWS3B. Preferably, the water separation sub-unit UWS3A comprises, preferably consists of, a scrubbing unit, andwherein the water separation sub-unit UWS3B comprises, preferably consists of, a distillation column. According to a third alternative with regard to (iii.3), it is preferred that the high boiler separation unit UHS1 according to (iii.3) is a stripping unit, (iii.3) comprising(iii.3.1) passing the stream SWS1 and a non-aqueous stripping gas stream SG01 into the unit UHS1, wherein the non-aqueous stripping gas stream SG01 comprises at least one inert gas G1 and has a temperature TG01 with TG01 > TWS1;(iii.3.2) bringing the stream SWS1 and the stream SG01 in the unit UHS1 at stripping conditions into contact with eachother, wherein the stripping conditions comprise a stripping pressure pHS1 and wherein at the strippingpressure pSHS1, the one or more one organic compounds X comprised in the stream SWS1have a boiling point TBXand monomeric ε-caprolactam has a boiling point TBC< TBX;(iii.3.3) removing the stream SP-HS1 from the unit UHS1, the stream SP-HS1 having a temperature TP-HS1 withTWS1< TP-HS1< TG01;(iii.3.4) removing the stream SR-HS1 from the unit UHS1, the stream SR-HS1 having a temperature TR-HS1 withTWS11 < TR-HS1 < TG01. In the context of said third alternative, it is preferred that the at least one inert gas G1 comprises one or more of nitrogen and carbon dioxide, more preferably nitrogen, wherein more preferably, at least 99 weight-%, morepreferably at least 99.5 weight-%, more preferably at least 99.9 volume -% of the at least one inter gas G1 consist ofnitrogen, wherein more preferably from 95 to 100 weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the non-aqueous stripping gas stream SG01 consist of the at least one inertgas G1; and wherein TG01 is at least 250 °C, preferably in the range of from 250 to 500 °C, more preferably in the range of from 300 to 450 °C.With regard to said second alternative, it is preferred that the water separation unit UWS3 as defined herein comprises,more preferably consists of, a distillation column. According to the present invention, a residue stream SR-HS1 is obtained from the first high boiler separation unit. Preferably, the stream SR-HS1 has a temperature in the range of from 220 to 330 °C, more preferably in the range offrom 235 to 315 °C, more preferably in the range of from 250 to 300 °C. In the stream SR-HS1, the weight ratio ΦR-HS1of the polyamide 6 relative to the one or more compounds X, m(P) / m(X), is preferably in the range of from 0.2:1 to 99:1, more preferably in the range of from 0.8:1 to 95:1, more preferably in the range of from 1:1 to 90:1. Preferably from 95 to 100 weight-%, more preferably from 98 to 100 weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.8 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the residue stream SR-HS1consist of polyamide 6, the one or more compounds X, optionally water, and optionally monomeric ε-caprolactam, wherein preferably from 0 to 5 weight-%, more preferably from 0 to 4 weight-%, more preferably from 0 to 3 weight-% of the residue stream SR-HS1consist of water and monomeric ε-caprolactam. As mentioned herein, the process of the present invention is characterized by a high flexibility, in particular with regard to controlling certain process paths depending on the composition of individual streams which in turn depends on the specific composition of the solid material M and the waste material comprising polyamide 6 and the resulting composition of the streams obtained from the first depolymerization unit UR1, subsequently from the first water separation unit UWS1 and, finally, from the first high boiler separation unit UHS1. This applies in particular to the residue stream SR-HS1. Therefore, the present invention preferably relates to the process as described above, wherein, if in the stream SR-HS1, the weight ratio ΦR-HS1 of the polyamide 6 relative to the one or more compounds X, ΦR-HS1= m(P) / m(X), is greater than or equal to a pre-defined threshold value ΦR-HS1(T1), the process preferably further comprises(iv.1) recycling at least a part of the stream SR-HS1 to (iii), comprising subjecting at least part of the stream SR-HS1,preferably the stream SR-HS1, in the depolymerization unit UR1to the polyamide 6 depolymerization conditions DR1. The respective threshold value ΦR-HS1(T1) can be chosen according to the specific needs of the overall processdesign. By way of example, threshold values in the range of from 1:1 to 90:1 such as from 1:1 to 10:1 or from 10:1 to20:1 or from 20:1 to 30:1 or from 30:1 to 40:1 or from 40:1 to 50:1 or from 50:1 to 60:1 or from 60:1 to 70:1 or from70:1 to 80:1 or from 80:1 to 90:1 are conceivable. Preferred ranges may be from 1:1 to 5:1 or from 1:1 to 4:1 or from1:1 to 3:1 or from 1:1 to 2:1.According to (iv.1), at least a part of the stream SR-HS1 is recycled to the first depolymerization stage according to (iii) as a portion of the depolymerization mixture MD1. While there are no specific restrictions how said recycle stream is passed back to UR1, it may be preferred that it is passed directly in the reactor R1, preferably in the reactor R11 as described herein. However, it is also conceivable to admix said recycle stream with any suitable stream upstream of the reactor R1, preferably in the reactor R11, for example with one or more of:(r1) the stream leaving the static mixing unit as described herein;(r2) the stream SM comprising a solid material M, provided according to (i) and comprising polyamide 6 asdescribed herein, wherein the combined stream is then subjected to melting in the melting unit UM asdescribed herein;(r3) the solid material M which has been provided in a delivering unit which preferably comprises one or more of atleast one big bag station and at least one bulk container station, as described herein, in particular before therespectively provided solid material SMis subjected to granulation from which granulation the solid material SMis obtained in the form of granules, preferably in the form of granules wherein the particle size distribution of said granules is preferably characterized by one or more of the following pairs of values, preferably by two or more of the following pairs of values, more preferably by the following three pairs of values as described herein: -a D10 value of the particle width in the range of from in the range of from 0.1 to 15 mm and a D10 valueof the particle length in the range of from 0.3 to 15 mm; -a D50 value of the particle width in the range of from in the range of from 0.2 to 20 mm and a D50 valueof the particle length in the range of from 0.5 to 20 mm; -a D90 value of the particle width in the range of from in the range of from 0.3 to 30 mm and a D90 valueof the particle length in the range of from 0.8 to 30 mm.In case the at least a part of the stream SR-HS1 is recycled according to one or more of (r2) and (r3), it is preferred thatprior to admixing with the stream SM according to (r2) or with the solid material M according to (r3), the recycle stream exhibiting a temperature preferably in the range of from 220 to 330 °C, more preferably in the range of from 235 to 315 °C, more preferably in the range of from 250 to 300 °C, is subjected to cooling, preferably at ambientpressure, to a temperature less than 150 °C, preferably at most 100 °C, more preferably at most 75 °C, morepreferably at most 50 °C. When cooling to said temperatures, at least part of the recycle stream, preferably the entirerecycle stream is solidified. After said solidification, it is preferred that the obtained solid is subjected to suitablecomminution to obtain a comminuted material. Preferably, said comminuted material exhibits an average diameter inthe range of from 0.1 to 30 mm, more preferably in the range of from 0.5 to 15 mm, more preferably in the range offrom 1 to 10 mm, more preferably in the range of from 2 to 7.5 mm, more preferably in the range of from 3 to 5 mm.According to the recycling according to (r2) and (r3), it is preferred that said recycled comminuted material isadmixed with the non-recycled solid material M at a mixing ratio ΦMRM = (mM / kg) / (mRM / kg) in the range of from 15:1 to4:3, more preferably in the range of from 12:1 to 5:3, more preferably in the range of from 10:1 to 6:3, wherein mM isthe amount of non-recycled solid material SM and mRM is the amount of solid recycled material; ranges of ΦMRM offrom 9.5:1 to 6.5:3 or from 9:1 to 7:3 may be more preferred.If, on the other hand, the weight ratio ΦR-HS1 of the polyamide 6 relative to the one or more compounds X, ΦR-HS1 = m(P) / m(X), in the stream SR-HS1 is smaller than a pre-defined threshold value ΦR-HS1(T2) with ΦR-HS1(T2) < ΦR-HS1(T1), the process preferably further comprises(iv.3) passing at least part of the stream SR-HS1, preferably the stream SR-HS1,to further use.According to the present invention, passing to further use according to (iv.3) preferably includes one or more of subjecting to pyrolysis, subjecting to a hydrogenation reaction, subjecting to incineration, and subjecting to one ormore suitable depolymerization reactions other than the depolymerization reactions according to UR1 and UR2.If, however, the weight ratio ΦR-HS1of the polyamide 6 relative to the one or more compounds X, ΦR-HS1= (m(P) / m(X),in the stream SR-HS1, is smaller than a pre-defined threshold value ΦR-HS1(T1) and greater than or equal to a pre-definedthreshold value ΦR-HS1(T2) with ΦR-HS1(T2) < ΦR-HS1(T1), the process preferably further comprises(iv.2) subjecting at least a part of the stream SR-HS1, preferably the stream SR-HS1, to a second depolymerization andpurification stage. Preferably, (iv.2) comprises preparing from the at least part of the stream SR-HS1a depolymerization mixture MD2, andsubjecting the mixture MD2 in a depolymerization unit UR2 to polyamide 6 depolymerization conditions DR2. Morepreferably, preparing said depolymerization mixture MD2 comprises admixing the at least part of the stream SR-HS1 with an aqueous stream Saq at a mixing ratio ΦWP = (mW / kg) / (mP / kg) in the range of from 1:1 to 20:1, more preferably in the range of from 2:1 to 15:1, more preferably in the range of from 5:1 to 10:1, wherein mW is the total amount of water comprised in SR-HS1 and Saq, and mP is the amount of polyamide 6 comprised in the at least a part of the streamSR-HS1. Generally, there are no specific restrictions from which source the aqueous stream Saq is taken. Preferably, atleast a part of the aqueous stream Saq consists of one or more of at least a part of at least one stream SWS1 obtained according to (iii.2), at least a part of at least one stream SWS2 obtained according to (iv.2.2), and at least a part of at least one stream SR-WS3obtained according to (v) as defined in embodiment 15, wherein the at least a part of at least one stream SWS1preferably comprises, more preferably is at least a part of the one or more aqueous streams SWS1Bobtained according to (iii.2.2) as defined herein. Therefore, according to the process of the present invention, it ispossible to re-use one or more aqueous streams obtained in the course of the process to prepare the aqueousdepolymerization mixture MD2. Preferably according to the process of the present invention, the polyamide 6 depolymerization conditions DR2 according to (iv.2.1) comprise a depolymerization pressure pR2 in the range of from 40 to 140 bar, more preferably in the range of from 40 to 125 bar, more preferably in the range of from 40 to 110 bar; and a depolymerizationtemperature TR2 in the range of from 230 to 335 °C, preferably in the range of from 250 to 320 °C, more preferably inthe range of from 270 to 310 °C.Preferably, the depolymerization unit UR2 comprises z chemical reactors R2i, i=1…z2, wherein z2 is in the range offrom 1 to 10, preferably in the range of from 1 to 8, more preferably in the range of from 1 to 6, more preferably in the range of from 1 to 5, more preferably in the range of from 1 to 4, more preferably in the range of from 1 to 3, more preferably 1 or 2. If z2 > 1, is preferred that at least 2 reactors R2i, more preferably all z2 reactors R2i, are serially coupled, wherein- the depolymerization mixture MD2 is fed into R2i, with i = 1;- an aqueous liquid stream S2i containing ε-caprolactam dissolved in water is removed from reactor R2i and fedinto the reactor R2(i+1), with i < z2;- an aqueous liquid stream S2z2 containing ε-caprolactam dissolved in water is removed from the reactor R2z2 asthe stream SR2; wherein in every reactor R2i, a depolymerization temperature TR2iat a depolymerization pressure pR2iis maintained, wherein, independently of each other, TR2iis in the range of from 230 to 330 °C and pR2iis in the range of from 40 to 140 bar, preferably wherein TR2iis in the range of from 250 to 320 °C and pR2iis in the range of from 40 to 125 bar, more preferably wherein TR2iis in the range of from 270 to 310 °C and pR2iis in the range of from 40 to 110 bar. For z2> 1, it is preferred that the z2reactors R2iare vertically arranged, with R21being the top-most reactor and R2z2being the bottom-most reactor, wherein S2iobtained from R2iis transferred to R2(i+1)by gravity, preferably by gravity only. More preferably, at least 1, preferably all z2reactors R2i, are continuous stirred tank reactors (CSTR). Preferably, every continuous stirred tank reactor R2i has, independently from each other, from 2 to 6 compartments, more preferably from 2 to 5 compartments, more preferably from 2 to 4 compartments, said compartments preferably being serially, more preferably being serially and vertically arranged, wherein 2 adjacent compartments are separated by a divider which comprises at least one flow-through opening. Preferably at least one compartment comprised in a reactor R2i comprises at least one agitator, wherein more preferably every compartment of every reactor R2i comprises at least one agitator, wherein more preferably, every compartment of every reactor R2i comprises one agitator, and the process comprises agitating the depolymerization mixture in a given compartment for at least part of the time during subjecting to depolymerization conditions in said compartment. Preferably, the polyamide 6 depolymerization conditions further comprise a total residence time tR2of the aqueous depolymerization mixture in the unit UR2, preferably in the z2reactors R2i, more preferably in the z2continuous stirred tank reactors, wherein at least 85 weight-%, preferably at least 90 weight-%, more preferably at least 95 weight-% of the aqueous depolymerization mixture MD2have a tR2in the range of from 30 to 90 min. More preferably, the residence time of an aqueous depolymerization mixture in a reactor R2iis tR2iand 0.90 ≤ (tR2i / tR2(i+1)) ≤ 1.10, more preferably 0.95 ≤ (tR2i / tR2(i+1)) ≤ 1.05. Preferably according to the present invention, no polyamide 6 depolymerization catalyst such as a mineral acidand / or a zinc salt such as zinc chloride, zinc acetate or zinc triflate is used for preparing the depolymerization mixtureMD2, is contained in the depolymerization mixture MD2 to be subjected to depolymerization conditions in UR2, and ispresent during depolymerization in UR2.According to the present invention, it is preferred that z2 ≤ z1, more preferably z2 < z1, more preferably z2 = 1.Preferably, the liquid aqueous stream SR2 according to (iv.2.1) has a temperature in the range of from 230 to 330 °C, preferably in the range of from 250 to 320 °C, more preferably in the range of from 270 to 310 °C. Further preferably, in the liquid aqueous stream SR2 according to (iv.2.1), the weight ratio of water relative to the sum of monomeric ε- caprolactam, polyamide 6 and the at least one compound X, m(W) / (m(C)+(m(P)+(X)), is in the range of from 5:1 to15:1, preferably in the range of from 6:1 to 12:1, more preferably in the range of from 6.5:1 to 10.5:1. Preferably from98 to 100 weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the stream SR1 consist of monomeric ε-caprolactam, polyamide 6, the one or more compounds X, and water. According to (v.2.2), the liquid aqueous stream SR2is passed into a second water separation unit UWS2. Preferably, (iv.2.2) comprises(iv.2.2.1) passing the liquid aqueous stream SR2 into a water evaporation unit UWS2A, obtaining from SR2 a liquidaqueous product stream SWS2Acomprising monomeric ε-caprolactam at a concentration cWS2A(C) > cR2(C), polyamide 6 at a concentration cWS2A(P) > cR2(P) and one or more compounds X at a concentration cWS2A(X) > cR2(X), and further obtaining from SR2one or more aqueous vapor streams SR-WS2A;(iv.2.2.2) passing the liquid aqueous stream SWS2A into a water separation unit UWS2B, obtaining from SWS2A thestream SWS2 and further obtaining from SWS2A one or more aqueous streams SR-WS2B. Preferably according to the present invention, the water evaporation unit UWS2A comprises two or more waterevaporation sub-units, more preferably two or more serially coupled water evaporation sub-units. More preferably,every water evaporation comprises, more preferably consists of, a flash drum. According to the present invention, itis preferred that the water separation unit UWS2B comprises a film evaporator, more preferably a falling filmevaporator. The liquid aqueous stream SWS2according to (iv.2.2) has a temperature preferably in the range of from 75 to 120 °C, more preferably in the range of from 80 to 110 °C, more preferably in the range of from 85 to 100 °C. In the liquid aqueous stream SWS2, the weight ratio of water relative to the sum of monomeric ε-caprolactam, polyamide 6 and the at least one compound X, m(W) / (m(C)+(m(P)+(X)), is preferably in the range of from 0.13:1 to 0.4:1, more preferably in the range of from 0.14:1 to 0.3:1, more preferably in the range of from 0.15:1 to 0.2:1. Preferably from 98 to 100 weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the stream SWS2 consist of monomeric ε-caprolactam, the one or more compounds X, optionally water, and optionally polyamide 6. With regard to the setup of the high boiler separation carried out in according to (iv.2.3), no specific limitations exist. Generally, it may be preferred to use the same or essentially the same apparatus setup as in the first high boilerseparation stage according to (iii.3). In the context of the present invention, three preferred ways of carrying out said second high boiler separation are preferred. In detail:According to a first alternative with regard to (iv.2.3), it is preferred that the high boiler separation unit UHS2 accordingto (iv.2.3) is an evaporation unit, (iv.2.3) comprising(iv.2.3.1) passing the stream SWS2 into the unit UHS2, preparing in the unit UHS2 from the stream SWS2 anevaporation mixture MHS2 having an evaporation temperature THS2 at an evaporation pressure pHS2 with THS2 > TWS2, wherein the one or more one organic compounds X have a boiling point TBX and monomeric ε-caprolactam has a boiling point TBC with TBX > THS2 ≥ TBC at the evaporation pressure pHS2;(iv.2.3.2) removing the stream SP-HS2 from the unit UHS2, the stream SP-HS2 having a temperature TP-HS2 withTP-HS2≤ THS2;(iv.2.3.3) removing the stream SR-HS2 from the unit UHS2, the stream SR-HS2 having a temperature TR-HS2 withTR-HS2= TP-HS2. In the context of said first alternative, pHS2is preferably in the range of from 50 to 200 mbar and THS2is preferably in the range of from 220 to 330 °C, more preferably in the range of from 240 to 320 °C, more preferably in the range of from 260 to 310 °C; wherein preparing the mixture MHS2 in the unit UHS2 according to (iv.2.3.1) more preferably comprises- heating the stream SWS2 passed into the unit UHS2 from the temperature TWS2 to the evaporation temperatureTHS2 via internal heating means HINT2 arranged within the unit UHS2, thereby obtaining the evaporation mixture MHS2; or- passing, in addition to the stream SWS2, a stream SX2 into the unit UHS2, the stream SX2 having a temperatureTX2 > TWS2, admixing the stream SX2 and the stream SWS2 and heating the obtained mixture to the temperature THS2via internal heating means HINTarranged within the unit UHS2, thereby obtaining the evaporation mixture MHS2, wherein the process further separating the stream SX2 from the stream SR-HS2, wherein the stream SX2has the temperature TX2= TR-HS2; or- passing, in addition to the stream SWS2, a stream SY2 into the unit UHS2, the stream SY2 having a temperatureTY2 > THS2, and admixing the stream SWS2 and the stream SY2, thereby obtaining the evaporation mixture MHS2, wherein the process further comprises separating a stream SX2 from the stream SR-HS2, wherein the stream SX2 has a temperature TX2 = THSR2; and subjecting the stream SX2 to heating via external heating means HEXT2 arranged outside the unit UHS2, obtaining the stream SY2 having the temperature TY2; and wherein preferably TY2 ≥ (THS2 + 10 K), more preferably TY2 ≥ (THS2 + 20 K), more preferably TY2 ≥ (THS2 + 30 K).Preferably, the process further comprises subjecting the stream SP-HS2 to cooling in a cooling unit, obtaining from saidcooling unit a cooled stream SP-HS2, preferably obtaining a cooled and partially condensed stream SP-HS2, and whereinthe cooled stream SP-HS2 has a temperature TP-HS2 preferably in the range of from 160 to 320 °C, more preferably in the range of from 165 to 310 °C, more preferably in the range of from 170 to 300 °C. Further in the context of said first alternative, the process preferably further comprises subjecting the stream SP-HS2 to cooling in a cooling unit, obtaining from said cooling unit a cooled stream SP-HS2, more preferably obtaining a cooled and partially condensed stream SP-HS2, and wherein the cooled stream SP-HS2 has a temperature TP-HS2 preferably in the range of from 160 to 320 °C, more preferably in the range of from 165 to 310 °C, more preferably in the range of from 170 to 300 °C. With regard to said first alternative, it is preferred that the water separation unit UWS3as defined herein comprises two or more water separation sub-units, more preferably two water separation sub-units UWS3Aand UWS3B, more preferably two serially coupled water separation sub-units UWS3Aand UWS3Bwith UWS3Bbeing arranged downstream ofUWS3A. Preferably, the water separation sub-unit UWS3A comprises, more preferably consists of, a droplet separator,more preferably selected from the group consisting of a hydrocyclone, a demister plate, and an absorption tower, more preferably a hydrocyclone; and the water separation sub-unit UWS3Bpreferably comprises, more preferably consists of, a distillation column. According to a second alternative with regard to (iv.2.3), it is preferred that the high boiler separation unit UHS2 according to (iv.2.3) is a stripping unit, (iv.2.3) comprising(iv.2.3.1) passing the stream SWS2 and an aqueous stripping gas stream SG02 into the unit UHS2, wherein theaqueous stripping gas stream SG01 has a temperature TG02 with TG02 > TWS2;(iv.2.3.2) bringing the stream SWS2 and the stream SG02 in the unit UHS2 at stripping conditions into contact witheach other, wherein the stripping conditions comprise a stripping pressure pHS2 and wherein at the stripping pressure pHS2, the one or more one organic compounds X comprised in the stream SWS2 havea boiling point TBX and monomeric ε-caprolactam has a boiling point TBC < TBX;(iv.2.3.3) removing the stream SP-HS2 from the unit UHS2, the stream SP-HS2 having a temperature TP-HS2 withTWS2< TP-HS2< TG02;(iv.2.3.4) removing the stream SR-HS2 from the unit UHS2, the stream SR-HS2 having a temperature TP-HS2 withTWS2< TR-HS2< TG02. In the context of said second alternative, it is preferred that from 95 to 100 weight-%, more preferably from 98 to 100 weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.8 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the aqueous stripping gas stream SG02 consist of water; and wherein TG02 is at least 250 °C, more preferably in the range of from 250 to 500 °C, more preferably in the range of from 300 to 450 °C. With regard to said second alternative, it is preferred that the water separation unit UWS3 as defined herein comprises two or more water separation sub-units, more preferably two water separation sub-units UWS3A and UWS3B, morepreferably two serially coupled water separation sub-units UWS3A and UWS3B with UWS3A being arranged upstream of UWS3B. Preferably, the water separation sub-unit UWS3A comprises, preferably consists of, a scrubbing unit, and wherein the water separation sub-unit UWS3B comprises, preferably consists of, a distillation column. According to a third alternative with regard to (iv.2.3), it is preferred that the high boiler separation unit UHS2 according to (iv.2.3) is a stripping unit, (iv.2.3) comprising(iv.2.3.1) passing the stream SWS2 and a non-aqueous stripping gas stream SG02 into the unit UHS2, wherein thenon-aqueous stripping gas stream SG02 comprises at least one inert gas G2 and has a temperatureTG02 with TG02 > TWS2;(iv.2.3.2) bringing the stream SWS2 and the stream SG02 in the unit UHS2 at stripping conditions into contact witheach other, wherein the stripping conditions comprise a stripping pressure pHS2and wherein at the stripping pressure pSHS2, the one or more one organic compounds X comprised in the stream SWS2have a boiling point TBXand monomeric ε-caprolactam has a boiling point TBC< TBX;(iv.2.3.3) removing the stream SP-HS2 from the unit UHS2, the stream SP-HS2 having a temperature TP-HS2 withTWS2< TP-HS2< TG02;(iv.2.3.4) removing the stream SR-HS2 from the unit UHS2, the stream SR-HS2 having a temperature TR-HS1 withTWS2< TR-HS2< TG02.In the context of said third alternative, it is preferred that the at least one inert gas G2 comprises one or more ofnitrogen and carbon dioxide, more preferably nitrogen, wherein more preferably, at least 99 weight-%, morepreferably at least 99.5 weight-%, more preferably at least 99.9 volume -% of the at least one inter gas G2 consist ofnitrogen, wherein more preferably from 95 to 100 weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the non-aqueous stripping gas stream SG02 consist of the at least one inert gas G2; and wherein TG02 is at least 250 °C, preferably in the range of from 250 to 500 °C, more preferably in the range of from 300 to 450 °C. With regard to said second alternative, it is preferred that the water separation unit UWS3as defined herein comprises,more preferably consists of, a distillation column.According to the present invention, a residue stream SR-HS2is obtained from the second high boiler separation unit. Preferably, the stream SR-HS2 has a temperature in the range of from 220 to 330 °C, more preferably in the range of from 235 to 315 °C, more preferably in the range of from 250 to 300 °C. In the stream SR-HS2, the weight ratio ΦR-HS2 of the polyamide 6 relative to the one or more compounds X, m(P) / m(X), is preferably in the range of from 0.01:1 to 99:1, more preferably in the range of from 0.02:1 to 90:1, more preferably in the range of from 0.03:1 to 85:1. Preferably from 95 to 100 weight-%, more preferably from 98 to 100 weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.8 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the residue stream SR-HS2 consist of the one or more compounds X, optionally polyamide 6, and optionally water and optionally monomeric ε-caprolactam, wherein preferably from 0 to 5 weight-%,more preferably from 0 to 4 weight-%, more preferably from 0 to 3 weight-% of the residue stream SR-HS2 consist of water and monomeric ε-caprolactam. As for the first high boiler separation step and as already mentioned hereinabove, according to the present invention, the term „polyamide 6“ which is possibly comprised in the stream SR-HS2 encompasses polymeric polyamide 6 as well as any oligomeric polyamide 6. Said oligomeric polyamide 6 can be comprised already in the depolymerization mixture MD2 subjected to depolymerisation conditions according to (iv.2.1), and generally, is formed from polyamide 6 in the second depolymerization stage carried out according to (iv.2.1). Further, it may be possible that some oligomeric polyamide 6 is formed during the second water separation stage according to (v.2.2). Further, the term “oligomeric polyamide 6” encompasses any oligomers starting from dimers and, therefore, includes ε-caprolactam dimer, ε-caprolactam trimer, ε-caprolactam tetramer, ε-caprolactam pentamer, ε-caprolactam hexamer, and so forth, wherein the oligomers may exhibit a linear and / or a cyclic structure. As mentioned herein, the process of the present invention is characterized by a high flexibility, in particular withregard to controlling certain process paths depending on the compositions of individual streams which in turn dependon the specific composition of the solid material M and the waste material comprising polyamide 6 and the resulting composition of the streams. This does not apply only for the first stage of the process, but also for the second stage with regard to streams obtained from the second depolymerization unit UR2, subsequently from the second water separation unit UWS2 and, finally, from the second high boiler separation unit UHS2. This applies in particular to the residue stream SR-HS2. Therefore, the present invention preferably relates to the process as described above, wherein, if in the stream SR-HS2, the weight ratio ΦR-HS2 of the polyamide 6 relative to the one or more compounds X, ΦR-HS2 = m(P) / m(X), is greater than or equal to a pre-defined threshold value ΦR-HS2(T), the process preferably further comprises(iv.2.4.1) recycling at least a part of the stream SR-HS2, preferably the stream SR-HS2, to (iv.2.1), comprisingsubjecting the at least part of the stream SR-HS2in the depolymerization unit UR2to the polyamide 6 depolymerization conditions DR2.The respective threshold value ΦR-HS2(T) can be chosen according to the specific needs of the overall process design.By way of example, threshold values in the range of from 1:1 to 10:1 or from 10:1 to 20:1 or from 20:1 to 30:1 or from 30:1 to 40:1 or from 40:1 to 50:1 or from 50:1 to 60:1 or from 60:1 to 70:1 or from 70:1 to 80:1 or from 80:1 to 90:1 are conceivable. According to (iv.2.4.1), at least a part of the stream SR-HS2 is recycled to the second depolymerization stage accordingto (iv.2.1) as a portion of the depolymerization mixture MD2. While there are no specific restrictions how said recyclestream is passed back to UR2, it may be preferred that it is passed directly in the reactor R1, preferably in the reactor R21 as described herein. However, it is also conceivable to admix sad recycle stream with any suitable stream upstream of the reactor R2, preferably in the reactor R21, for example with the stream Saq or the stream SR-HS1 to bepassed into UR2. Therefore, (iv.2.4.1) preferably comprises one or more of admixing at least part of the stream SR-HS2 with the at least part of the stream SR-HS1, and passing at least part of the stream SR-HS2 directly into the depolymerization unit UR2. If, however, the weight ratio ΦR-HS2 of the polyamide 6 relative to the one or more compounds X, ΦR-HS2 = (m(P) / m(X), in the stream SR-HS2, is smaller than a pre-defined threshold value ΦR-HS2(T), the process preferably further comprises(iv.2.4.2) passing at least a part of the stream SR-HS2, preferably the stream SR-HS2, to further use.According to the present invention, passing to further use according to (iv.2.4.2) preferably includes one or more of subjecting to pyrolysis, subjecting to a hydrogenation reaction, subjecting to incineration, and subjecting to one or more suitable depolymerization reactions other than the depolymerization reactions according to UR1and UR2. With regard to the product stream SP-HS2obtained from UHS2, it is preferred that at least a part thereof is passed to further water separation, preferably to one or more of UWS3Aor to UWS3Bas defined herein. In terms of rendering the process of the present invention still more advantageous, it is preferred that one or more of the at least one aqueous residue stream SR-WS1 according to (iii.2), of the at least one aqueous residue stream SR-WS2according to (iv.2.2), and of the at least one aqueous residue stream SR-WS3 as defined herein is passed back to (ii)as part of the depolymerization mixture MD1. The process of the present invention exhibiting two serially arranged depolymerization-water separation-high boiler separation stages, together with the possibility to recycle the residue streams obtained from the respective high boiler separation stages or to choose other stream paths as described above lead to a very efficient polyamide 6depolymerization characteristic of the overall process. Therefore, the process of the present invention exhibits apolyamide 6 depolymerization efficiency Φ(P) preferably of at least 85 %, more preferably of at least 90 %, more preferably of at least 95 %, wherein Φ(P) / % = 100 x [(mD1(P)-mR-HS2(P)) / mD1(P)] wherein mD1(P) is the mass of polyamide 6 comprised in the depolymerization mixture MD1 to be subjected to depolymerization conditions DR1 according to (iii.1), and wherein mR-HS2(P) is the mass of polyamide 6 comprised inthe stream SR-HS2. Efficiencies of at least 96 % or at least 97 % at least 98 % or at least 99 % are conceivable.Further preferably, the process of the present invention, comprising (v) as defined herein, comprises(vi) passing the product stream SP-WS3 obtained according to (v) into a purification unit UP, obtaining from SP-WS3 astream SCPL exhibiting a concentration cCPL(C) of monomeric ε-caprolactam with cCPL(C) > cP-WS3(C);wherein the purification unit UP comprises a distillation unit UDI, the process comprising feeding the stream SP-WS3 to UDI, obtaining from UDI a stream SDI exhibiting a concentration cDI(C) of monomeric ε-caprolactam with cCPL(C) ≥ cDI(C) > cP-WS3(C) , wherein the purification unit UP preferably further comprises, downstream of the unit UDI, one or more of a crystallization unit UCR and a chemical treatment unit UOD, the process comprising obtaining the stream SCPL from UCR or from UOD. If the purification unit UP further comprises a crystallization unit UCR located downstream of UDI, the process preferably comprises feeding the stream SDI to the crystallization unit UCR, obtaining from UCR a stream SCR being the stream SCPLcomprising ε-caprolactam at a concentration cCR(C) = cCPL(C). If the purification unit UPfurther comprises a chemical treatment unit UODlocated downstream of UDI, the processpreferably comprises feeding the stream SDI to the chemical treatment unit UOD, obtaining from UOD a stream SODbeing the stream SCPLcomprising monomeric ε-caprolactam at a concentration cOD(C) = cCPL(C). If the purification unit UPfurther comprises a chemical treatment unit UODand a crystallization unit UCR, wherein the crystallization unit UCRis located downstream of the distillation unit UDIand the chemical treatment unit UODis locateddownstream of the crystallization unit UCR, the process preferably comprises feeding the stream SDI to thecrystallization unit UCR, obtaining from the crystallization UCR a stream SCR comprising monomeric ε-caprolactam at a concentration cCR(C) with cCR(C) > cDI(C), and feeding the stream SCR to the chemical treatment unit UOD, obtaining from UOD a stream SOD being the stream SCPL comprising monomeric ε-caprolactam at a concentration cOD(C) = cCPL(C). If the purification unit UP further comprises a chemical treatment unit UOD and a crystallization unit UCR, wherein the chemical treatment unit UOD is located downstream of the distillation unit UDI and the crystallization unit UCR is located downstream of the unit UOD, the process preferably comprises feeding the stream SDIto the chemical treatment unit UOD, obtaining from the chemical treatment unit UODa stream SODcomprising monomeric ε-caprolactam at a concentration cOD(C) with cOD(C) > cDI(C), and feeding the stream SODto the crystallization unit UCR, obtaining from UCRa stream SCRbeing the stream SCPLcomprising monomeric ε-caprolactam at a concentration cCR(C) = cCPL(C). Preferably, the chemical treatment in the unit UOD as defined herein comprises(a) providing a preferably liquid stream SDI comprising monomeric ε-caprolactam from the distillation unit UDI or apreferably liquid stream SCR comprising monomeric ε-caprolactam from the crystallization unit UCR, saidstream SDI or said stream SCR further comprising one or more oxidizable organic impurity compounds Y, wherein the stream SDI or the stream SCR exhibits a weight ratio rYC of the one or more organic compounds Y relative to monomeric ε-caprolactam;(b) providing a stream SPM comprising at least one permanganate;(c) preparing an oxidation reaction educt mixture MOE from the stream SDI and the stream SPM, or from the streamSCR and the stream SPM, and subjecting the mixture MOE to oxidation reaction conditions, obtaining an oxidation reaction product stream SP comprising monomeric ε-caprolactam, further comprising one or more oxidation products Z obtained from the oxidation of at least a part of the one or more compounds Y, andoptionally further comprising a part of the one or more organic compounds Y, wherein the stream SP exhibits a weight ratio rYCP of organic compound Y relative to monomeric ε-caprolactam with 0 ≤ rYCP < rYC and furtherexhibits a weight ratio rZCP of the one or more products Z relative to monomeric ε-caprolactam with rZCP > 0;(d) separating at least a part of the one or more oxidation products Z and optionally at least a part of organiccompound Y from the stream SP, obtaining the stream SOD; wherein the process optionally further comprises providing a stream SOHcomprising at least one hydroxide, wherein the oxidation reaction educt mixture MOEaccording to (c) is prepared from the stream SUDor the stream SCR, and from the stream SPMand the stream SOH; wherein separating at least a part of the one or more oxidation products Z and optionally at least a part of organic compound Y from the stream SPaccording to (d) preferably comprises subjecting the stream SPobtained according to (c) to distillation in a distillation unit UDT, comprised in the chemical treatment unit UOD, obtaining from thedistillation unit UDT a stream SDT comprising monomeric ε-caprolactam as the stream SOD, wherein the unit UDTcomprises one or more distillation columns, preferably one or two distillation columns, wherein at least one column is optionally configured as side stream column or as divided wall column. The process of the present invention may further comprise a downstream polymerization stage in which the ultimate product stream comprising monomeric ε-caprolactam obtained from the stages as defined above is subjected to suitable polyamide 6 polymerization conditions. Therefore, the present invention also relates to a process as defined above, further comprising(α) providing the stream SP-WS3, preferably the stream SCPL;(β) passing the stream SP-WS3, preferably the stream SCPL to a polyamide 6 production plant UPA6;(γ) subjecting the stream SP-WS3, preferably the stream SCPL to ε-caprolactam polymerization conditions, obtainingfrom UPA6a polyamide 6 material MPand a stream comprising water and one or more ε-caprolactam oligomers;(δ) optionally subjecting to stream comprising water and one or more ε-caprolactam oligomers to concentrationwith respect to the one or more ε-caprolactam oligomers in at least one concentration stage, obtaining a concentrated stream comprising water and one or more ε-caprolactam oligomers;(ε) passing the optionally concentrated stream comprising water and one or moreε-caprolactam oligomers into at least one of the melting unit UM as defined herein and the water separation unit UWS1, preferably the water separation unit UWS1B as defined herein. Preferably, the optionally concentrated stream comprising water and one or more ε-caprolactam oligomers according to (ε) further comprises monomeric ε-caprolactam. Further preferably, said integrated process comprises(γ) subjecting the stream SP-WS3, preferably the stream SCPL in UPA6 to ε-caprolactam polymerization conditions,obtaining from UPA6 a polyamide 6 material MP and a stream SEW comprising water at a concentration cEW(W), monomeric ε-caprolactam at a concentration cEW(C), and one or more ε-caprolactam oligomers at a total concentration cEW(O);(δ) subjecting the stream SEW to concentration, comprising(δ.1) subjecting the stream SEW to concentration in a first concentration unit UC1, obtaining from UC1 aconcentrated stream SC1 comprising water at a concentration cC1(W), monomeric ε-caprolactam at a concentration cC1(C), and one or more ε-caprolactam oligomers at a total concentration cC1(O), with cC1(W) < cEW(W), cC1(C) > cEW(C) and cC1(O) > cEW(O), and further obtaining from UC1 an aqueous stream SW1comprising water at a concentration cW1(W) > cEW(W); (δ.2) subjecting the stream SC1 to concentration in a second concentration unit UC2, obtaining from UC2 aconcentrated stream SC2comprising one or more ε-caprolactam oligomers at a total concentration cC2(O), with cC2(O) > cC1(O), and further obtaining from UC2 an aqueous stream SW2 comprising water ata concentration cW2(W) and monomeric ε-caprolactam at a concentration cW2(C), with cW2(W) > cW1(W) and cW2(C) > cW1(C);(ε) passing the stream SC2 to the sub-unit UM and the stream SW2 to the separation unit UWS1, preferably UWS1B.As described above, the stream SEW which is obtained from the polyamide 6 polymerization plant UPA6 comprises water, monomeric ε-caprolactam and one or more ε-caprolactam oligomers. Usually, this aqueous stream SEW further comprises one or more further organic compounds other than monomeric ε-caprolactam and one or more ε- caprolactam oligomers. Therefore, it is preferred that the stream SEW further comprises one or more organic compounds V other than monomeric ε-caprolactam and oligomers thereof at a total concentration cEW(V), the process according to (δ) comprising(δ.1) subjecting the stream SEW to concentration in a first concentration unit UC1, obtaining from UC1 a concentratedstream SC1 comprising water at a concentration cC1(W), monomeric ε-caprolactam at a concentration cC1(C), one or more ε-caprolactam oligomers at a total concentration cC1(O) and one or more organic compounds V at atotal concentration cC1(V), with cC1(W) < cEW(W), cC1(C) > cEW(C), cC1(O) > cEW(O) and cC1(V) > cEW(V), andfurther obtaining from UC1an aqueous stream SW1comprising water at a concentration cW1(W) > cEW(W);(δ.2) subjecting the stream SC1 to concentration in a second concentration unit UC2, obtaining from UC2 aconcentrated stream SC2comprising one or more ε-caprolactam oligomers at a total concentration cC2(O) and one or more organic compounds V at a total concentration cC2(V), with cC2(O) > cC1(O) and cC2(V) > cC1(V), and further obtaining from UC2 an aqueous stream SW2 comprising water at a concentration cW2(W) and monomeric ε-caprolactam at a concentration cW2(C), with cW2(W) > cW1(W) and cW2(C) > cW1(C). More preferably according to the present invention, (γ) comprises(γ.1) passing the stream SP-WS3, preferably the stream SCPL, and preferably an aqueous stream SAQ0 to apolymerization stage ST0, obtaining from ST0 a polyamide 6 crude product stream SPA1 and an aqueous stream SWA1;(γ.2) passing the stream SPA1 and preferably an aqueous stream SAQ1 to a granulation stage ST1, obtaining fromST1 a crude granulated polyamide 6 material MPA2 and an aqueous stream SWA2;(γ.3) passing the material MPA2 and preferably an aqueous stream SAQ2 to an extraction stage ST2, obtaining fromST2 a purified granulated polyamide 6 material MPA3 and an aqueous stream SWA3;(γ.4) passing the material MPA3 to a drying stage ST3, obtaining from ST3 the polyamide 6 material MP and anaqueous stream SWA4. In particular regarding the process of the present invention comprising (γ.1) to (γ.4) above, it is preferred that thestream SW1 obtained from UC1 according to (δ) is passed back to the polyamide 6 production plant UPA6. Morepreferably, the stream SW1is passed back to UPA6as at least part of one or more of the streams SAQ0, SAQ1and SAQ2. Assuming that some of the polyamide 6 material obtained from the production plant UPA6does not meet thespecifications, the process may preferably further comprise passing at least some of said material MPR to the unit UM.The method for controlling the process The present invention not only relates to the process as defined herein, but also to a method of controlling said process. In particular, the present invention relates to a method for controlling a process as defined herein, said process being carried out in a chemical plant, wherein the plant comprises(1.1) the first depolymerization unit UR1;(1.2) the first water separation unit UWS1 arranged downstream of UR1;(1.3) the first high boiler separation unit UHS1 arranged downstream of UWS1;(1.4) the second depolymerization unit UR2 arranged downstream of UHS1;(1.5) the second water separation unit UWS2 arranged downstream of UR2;(1.6) the second high boiler separation unit UHS2 arranged downstream of UR2;(2.1) means for analyzing the chemical composition of the stream SR-HS1;(2.2) means for analyzing the chemical composition of the stream SR-HS2;(3.1) controllable means for passing at least a part of the stream SR-HS1, preferably the stream SR-HS1, either to UR1and / or to UR2and / or to further use;(3.2) controllable means for passing at least a part of the stream SR-HS2, preferably the stream SR-HS2, either to UR2and / or to further use;wherein the method for controlling the process carried out in the plant comprises(a.1) defining threshold values ΦR-HS1(T1) and ΦR-HS1(T2) with ΦR-HS1(T2) < ΦR-HS1(T1) of the weight ratio ΦR-HS1 of thepolyamide 6 relative to the one or more compounds X in the stream SR-HS1;(a.2) determining in the course of the process at a time ta the value of ΦR-HS1;(a.3) determining at the time ta the values ΔΦR-HS1(T1) = ΦR-HS1 - ΦR-HS1(T1) andΔΦR-HS1(T2) = ΦR-HS1 - ΦR-HS1(T2);(a.4) controlling at the time ta the means according to (3.1) so that for a period of time Δta starting at ta(a.4.1) if ΔΦR-HS1(T1) ≥ 0, the process comprises recycling at least a part of the stream SR-HS1, preferablythe stream SR-HS1, to (iii), comprising subjecting at least a part of the stream SR-HS1, preferably thestream SR-HS1, in the depolymerization unit UR1 to the polyamide 6 depolymerization conditions DR1; (a.4.2) if ΔΦR-HS1(T1) < 0 and ΔΦR-HS1(T2) ≥ 0, the process comprises subjecting at least a part of thestream SR-HS1, preferably the stream SR-HS1, to a second depolymerization and purification stage according to (iv.2); (a.4.3) if ΔΦR-HS1(T2) < 0, the process comprises passing at least a part of the stream SR-HS1, preferably thestream SR-HS1, to further use;(b.1) defining a threshold value ΦR-HS2(T) of the weight ratio ΦR-HS2 of the polyamide 6 relative to the one or morecompounds X in the stream SR-HS2;(b.2) determining in the course of the process at a time tb the value of ΦR-HS2;(b.3) determining at the time tb the value ΔΦR-HS2(T) = ΦR-HS2 - ΦR-HS2(T);(b.4) controlling at the time tb the means according to (3.2) so that for a period of time Δtb starting at tb(b.4.1) if ΔΦR-HS2(T) ≥ 0, the process comprises recycling at least a part of the stream SR-HS2, preferablythe stream SR-HS2, to (iv.2.1), comprising subjecting at least a part of the stream SR-HS2, preferably the stream SR-HS2, in the depolymerization unit UR2to the polyamide 6 depolymerization conditions DR2; (b.4.2) if ΔΦR-HS2(T) < 0, the process comprises passing at least a part of the stream SR-HS2, preferably thestream SR-HS2, to further use. Preferably according to said method, the plant further comprises(2.3) means for analyzing the chemical composition of the stream SP-HS2;(3.3) controllable means for passing at least a part of the stream SP-HS2, preferably the stream SR-HS1, either to UWS3Aand / or to UWS3B; and the method for controlling the process carried out in the plant preferably further comprises(c.1) defining a threshold value ΦP-HS2(T) of the weight ratio ΦP-HS2 of the water contained in the stream SP-HS2relative to the total weight of the stream SR-HS2;(c.2) determining in the course of the process at a time tc the value of ΦP-HS2;(c.3) determining at the time tc the value ΔΦP-HS2(T) = ΦP-HS2 – ΦP-HS2(T);(c.4) controlling at the time tc the means according to (3.3) so that for a period of time Δtc starting at tc(c.4.1) if ΔΦP-HS2(T) ≥ 0, the process comprises passing at least a part of the stream SP-HS2, preferably thestream SP-HS2, to UWS3A; (c.4.2) if ΔΦR-HS2(T) < 0, the process comprises passing at least a part of the stream SP-HS2, preferably thestream SP-HS2, to UWS3B. Preferably, said method is at least partially computer-implemented, wherein more preferably, the chemical plant further comprises(4) a computer-supported system for controlling at least the means according to (3.1) and (3.2), and optionallyaccording to (3.3). More preferably, the computer-supported system is further used for determining at least one of ΔΦR-HS1(T1) and ΔΦR-HS1(T12) according to (a.3) and ΔΦR-HS2(T) according to (b.3), and optionally ΔΦP-HS2(T) according to (c.3). The plant The present invention not only relates to the process and the method as defined herein, but also to a plant for carrying out said process and said method. In particular, the present invention relates to a plant comprising(1.1) a first depolymerization unit UR1, and preferably a melting unit UM arranged upstream of UR1;(1.2) a first water separation unit UWS1 arranged downstream of UR1;(1.3) a first high boiler separation unit UHS1 arranged downstream of UWS1;(1.4) a second depolymerization unit UR2 arranged downstream of UHS1;(1.5) a second water separation unit UWS2 arranged downstream of UR2;(1.6) a second high boiler separation unit UHS2 arranged downstream of UR2;(1.7) preferably a third water separation unit UWS3 arranged downstream of UHS1 and UHS2, UWS3 preferablycomprising two water separation sub-units UWS3A and UWS3B;(1.8) preferably a purification unit UP arranged downstream of UWS3, UP preferably comprises a distillation unit UDI,wherein the purification unit UP more preferably further comprises, downstream of the unit UDI, one or more of a crystallization unit UCR and a chemical treatment unit UOD;(1.9) optionally a polyamide 6 production plant UPA6, preferably arranged downstream of UP;(2.1) means for analyzing the chemical composition of the stream SR-HS1;(2.2) means for analyzing the chemical composition of a stream SR-HS2;(2.3) optionally means for analyzing the chemical composition of the stream SP-HS2;(3.1) controllable means for passing the stream SR-HS1 either to UR1 and / or to UR2 and / or to further use;(3.2) controllable means for passing the stream SR-HS2 either to UR2 and / or to further use;(3.3) optionally controllable means for passing at least a part of the stream SP-HS2, preferably the stream SP-HS21,either to UWS3Aand / or UWS3B;(4) preferably a computer-supported system for controlling at least the means according to (3.1) and (3.2), andoptionally (3.3). Further, the present invention relates to a computer program comprising instructions which, when the program is executed by the computer-supported system (4) as defined herein, cause the system to perform the method as defined herein. Still further, the present invention relates to a non-transient computer-readable medium containing instructions which, when executed by one or more processors, cause the one or more processors to perform the program as defined herein.Further, the present invention relates to a stream SCPL comprising highly purified ε-caprolactam, the stream SCPLbeing obtainable or obtained by a process as defined herein. Further, the present invention relates to the use of saidstream SCPL as an educt material for a chemical process, preferably for a polymerization reaction, more preferably for preparing polyamide 6.Further, the present invention relates to a method for preparing polyamide 6, comprising(A) preparing a stream SCPL according to a process as defined herein;(B) subjecting the stream SCPL, optionally after storing, to polyamide 6 polymerization conditions.Further, the present invention relates to polyamide 6, obtainable or obtained by said method. Further, the present invention relates to a process as defined herein, further comprising providing at least part of thestream SCPL to a polyamide 6 production unit UPA6, wherein the polyamide 6 produced in UPA6 is preferably providedas a feedstock to a textile material producing unit UTP, from which unit UTP(A) a textile material MTE is obtained which is brought onto the market, wherein, after the lifetime TMTE of saidtextile material MTE, it is at least partially collected as textile waste material in a textile material collecting unit UTC;(B) remaining material MRE is obtained as textile waste material;wherein at least part of the textile waste material according to (A), or at least part of the textile waste materialaccording to (B), or at least part of the textile waste material according to (A) and at least part of the textile waste material according to (B) is suitably provided as solid material M according to (i). Further, the present invention relates to a process as defined herein, further comprising providing at least part of thestream SCPL to a polyamide 6 production unit UPA6, wherein the polyamide 6 produced in UPA6 is preferably providedas a feedstock to an engineering plastics material producing unit UEP, from which unit UEP(A) an engineering plastics material MEP is obtained which is brought onto the market, wherein, after the lifetimeTMEPof said engineering plastics material MEP, it is at least partially collected as engineering plastics waste material in an engineering plastics material collecting unit UEC;(B) remaining material MRE is obtained as engineering plastics waste material;wherein at least part of the engineering plastics waste material according to (A), or at least part of the engineering plastics waste material according to (B), or at least part of the engineering plastics waste material according to (A) and at least part of the engineering plastics waste material according to (B) is suitably provided as solid material M according to (i).Further, the present invention relates to the use of the stream SCPL as defined above for preparing polyamide 6, saiduse preferably further comprising employing said polyamide 6 as a feedstock for preparing one or more of a textile material and an engineering plastics material, more preferably for preparing a textile material.Further, the present invention relates to a method for preparing polyamide 6, said method comprising employing the stream SCPL as defined above as a starting material, wherein said method preferably further comprises employingsaid polyamide 6 as a feedstock for preparing one or more of a textile material and an engineering plastics material,more preferably for preparing a textile material. In the course of the process according to the present invention, it may become necessary to purify one or more of theapparatus involved, in particular apparatus employed in process states where residue streams might be involved,such as in steps (iii.3) and (iv.2.3), i.e. apparatus employed in the high boiler separation stages where, in particular, oligomeric and / or polymeric residues may deposit in or on said apparatus. Such apparatus include, but are not limited to, pipes, tubes, pumps, vessels, reactors, columns, drums, valves, heat exchangers, droplet separators, and the like. Preferred solvents respectively used may include one or more of diethylene glycol, mixtures of adipic acid and water such as a 1:1 mixture, polyethylene glycol such as PEG 400, N-methyl-2-pyrrolidone (NMP), and (monomeric) ε-caprolactam. NMP, for example, may turn out to be suitable in particular at higher temperatures.Further conceivable compounds which may be used for said purification task include solvents which arecharacterized by a specific Hansen parameter space wherein the Hansen parameter D (dispersion / van der Waals) is in the range of from 16.0 to 18.0, the Hansen parameter P (polarity) is in the range of from 6.5 to 13.0 and the Hansen parameter H (hydrogen bonding) is in the range of from 7.5 to 17.5. Compounds characterized by said specific Hansen parameter space include, but are not limited to: Hansen parameter compound DP HN,N-Dimethylacetoacetamid 17.8 12.9 9.74-Methylthiazole 18.6 6.9 7.61-Propanol 16.0 6.8 17.4Methylglycol 16.0 8.2 15.0Diacetin 16.4 8.9 14.22,5-Dimethylisosorbid 17.6 7.1 7.5According to a further aspect, the present invention relates to a process for purifying an aqueous liquid stream comprising monomeric ε-caprolactam, polyamide 6 and one or more organic compounds X, wherein monomeric ε- caprolactam has a boiling point TC and the one or more one organic compounds X have a boiling point TX > TC, said process comprising(i) providing a stream SM comprising a solid material M comprising polyamide 6;(ii) preparing an aqueous depolymerization mixture MD1 from SM, comprising(ii.1) melting in a melting unit UM the solid material M comprised in the stream SM having a temperature TSMat a pressure pSM, obtaining a liquid stream SM;(ii.2) admixing in a pre-reaction unit UPR the liquid stream SM with an aqueous stream SW having atemperature TSW at a pressure pSW, obtaining the depolymerization mixture MD1 having a temperature TMD1 at a pressure pMD1.(iii) subjecting the mixture MD1 to a depolymerization and purification stage, comprising(iii.1) subjecting the mixture MD1 in a depolymerization unit UR1 to polyamide 6 depolymerization conditionsDR1 comprising a depolymerization temperature TR1 at a depolymerization pressure pR1, obtaining a liquid aqueous product stream SR1 comprising monomeric ε-caprolactam at a concentration cR1(C), polyamide 6 at a concentration cR1(P) and one or more compounds X at a total concentration cR1(X); (iii.2) passing the liquid aqueous stream SR1 into a water separation unit UWS1, obtaining from SR1 a liquidaqueous product stream SWS1comprising monomeric ε-caprolactam at a concentration cWS1(C) > cR1(C), polyamide 6 at a concentration cWS1(P) > cR1(P) and one or more compounds X at a total concentration cWS1(X) > cR1(X), and further obtaining at least one aqueous residue stream SR-WS1comprising separated water; (iii.3) passing the liquid aqueous stream SWS1 into a high boiler separation unit UHS1, obtaining from SWS1 anaqueous product stream SP-HS1comprising monomeric ε-caprolactam at a concentration cP-HS1(C) > cWS1(C) and further obtaining from SWS1an aqueous residue stream SR-HS1comprising polyamide 6 at a concentration cR-HS1(P) ≥ cWS1(P) and one or more compounds X at a totalconcentration cR-HS1(X) > cWS1(X);(iv) recycling the stream SR-HS1 to (iii), comprising- subjected the aqueous residue stream SR-HS1 obtained according to (iii.3) to cooling, obtaining an atleast partially, preferably an entirely solidified residue stream SR-HS1; -subjecting the solidified residue stream SR-HS1 to comminution, obtaining a comminuted material;- admixing said comminuted material as recycled solid material M with non-recycled solid material M ata mixing ratio ΦMRM = (mM / kg) / (mRM / kg) wherein mM is the amount of non-recycled solid material andmRMis the amount of solid recycle material obtaining the stream SMaccording to (i), wherein mMis the amount of non-recycled solid material SM and mRM is the amount of recycled solid material M.With regard to said further aspect of the present invention, according to (iv), the recycle stream SR-HS1, exhibiting atemperature preferably in the range of from 220 to 330 °C, more preferably in the range of from 235 to 315 °C, more preferably in the range of from 250 to 300 °C, is subjected to cooling, preferably at ambient pressure, to atemperature less than 150 °C, preferably at most 100 °C, more preferably at most 75 °C, more preferably at most 50°C. When cooling to said temperatures, at least part of the recycle stream, preferably the entire recycle stream is solidified. After said solidification, the obtained solid is subjected to suitable comminution to obtain a comminutedmaterial. Preferably, said comminuted material exhibits an average diameter in the range of from 0.1 to 30 mm,preferably in the range of from 0.5 to 15 mm, more preferably in the range of from 1 to 10 mm, more preferably inthe range of from 2 to 7.5 mm, more preferably in the range of from 3 to 5 mm. Said comminuted recycle material is admixed with the non-recycled solid material M at a mixing ratio ΦMRM preferably in the range of from 15:1 to 4:3,more preferably in the range of from 12:1 to 5:3, more preferably in the range of from 10:1 to 6:3, wherein mM is the amount of non-recycled solid material SM and mRM is the amount of solid recycle material; ranges of from 9.5:1 to 6.5:3 or from 9:1 to 7:3 may be more preferred. According to this further aspect of the present invention, the process preferably further comprises(v) passing the aqueous product stream SP-HS1 obtained according to (iii.1), comprising monomeric ε-caprolactamat the concentration cP-HS1(C) and water at a concentration cP-HS1(W) to a water separation unit UWS3, obtaining a product stream SP-WS3 comprising monomeric ε-caprolactam at a concentration cP-WS3(C) > cP-HS1(C) and water at a concentration cP-WS3(W) < cP-HS1(W), and further obtaining at least one aqueous residue stream SR-WS3comprising water at a concentration cR-WS3(W) > cP-HS1(W); wherein in the product stream SP-WS3, cP-WS3(C) + cP-WS3(W) is preferably in the range of from 98.5 to 100 weight-%, more preferably in the range of from 99 to 100 weight-%, more preferably in the range of from 99.9 to 100 weight-%, based on the total weight of the stream SP-WS3, wherein in the stream SP-WS3, the weight ratio of monomeric ε- caprolactam relative to water is preferably at least 4:1, more preferably at least 5:1, more preferably at least 6:1. Further preferably according to this further aspect of the present invention, the process further comprises, after (v),(vi) passing the product stream SP-WS3 obtained according to (v) into a purification unit UP, obtaining from SP-WS3 astream SCPL exhibiting a concentration cCPL(C) of monomeric ε-caprolactam with cCPL(C) > cP-WS3(C); wherein the purification unit UP comprises a distillation unit UDI, the process comprising feeding the stream SP-WS3 to UDI, obtaining from UDI a stream SDI exhibiting a concentration cDI(C) of monomeric ε-caprolactam withcCPL(C) ≥ cDI(C) > cP-WS3(C); and wherein the purification unit UP optionally or preferably further comprises one ormore of a chemical treatment unit UOD and a crystallization unit UCR. Still further preferably according to this further aspect, the present invention relates to a process, comprising(α) providing the stream SP-WS3, preferably the stream SCPL, as described above;(β) passing the stream SP-WS3, preferably the stream SCPL, to a polyamide 6 production plant UPA6;(γ) subjecting the stream SP-WS3, preferably the stream SCPL, to ε-caprolactam polymerization conditions, obtainingfrom UPA6a polyamide 6 material MPand a stream comprising water and one or more ε-caprolactam oligomers;(δ) optionally subjecting the stream comprising water and one or more ε-caprolactam oligomers to concentrationwith respect to the one or more ε-caprolactam oligomers in at least one concentration stage, obtaining aconcentrated stream comprising water and one or more ε-caprolactam oligomers;(ε) passing the optionally concentrated stream comprising water and one or more ε-caprolactam oligomers into atleast one of the melting unit UM as defined herein and the water separation unit UWS1 as defined herein, preferably the water separation unit UWS1B as defined herein. According to another aspect, the present invention relates to a process, preferably the process as described herein, said process comprising the step of converting a part of the stream SR-HS1 and / or at least a part of the stream SR-HS2and / or the stream SCPL and / or a chemical material obtainable by or obtained by the process as described herein toobtain a product Ω; and further relates to a process comprising the step of using the plant as described herein toobtain a stream SR-HS1, a stream SR-HS2, a stream SCPL and a chemical material, and preferably converting a part ofthe stream SR-HS1 and / or at least a part of the stream SR-HS2 and / or the stream SCPL and / or the chemical material toobtain a product Ω.Preferably, the product Ω is selected from:- building block or monomer; or- polymer, preferably polymer A, polymer composition, preferably polymer composition A, or polymer product,preferably polymer product A; or- industrial use polymer, industrial use surfactant, descaling compound, industrial use biocide, industrial usesolvent, industrial use dispersant, composition thereof or formulation thereof; or- agrochemical composition, agrochemical formulation auxiliary or agrochemically active ingredient; or- active pharmaceutical ingredient or intermediate thereof, pharmaceutical excipient, animal feed additive,human food additive, dietary supplements, aroma chemical or aroma composition; or- aqueous polymer dispersion, preferably polyurethane or polyurethane – poly(meth)acrylate hybrid polymerdispersion, emulsion, binder for paper and fiber coatings, UV-curable acrylic polymer for hot melts and coatings polyisocyanates, hyperbranched polyester polyol, polymeric dispersant for inorganic binder compositions, unsaturated polyester polyol or 100% curable composition; or- cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter, further cosmetic ingredient or composition orformulation thereof; or- polymer B, polymer composition B, coating composition, other functional composition, foil, molded body,coating or coated substrate.Regarding this process from which the product Ω, is obtained, it is preferred:that the content of the part of the stream SR-HS1and / or the at least a part of the stream SR-HS2and / or the stream SCPLand / or the chemical material in the product Ω is 1 weight-% or more, preferably 2 weight-% or more, more preferably5 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 90weight-% or more, more preferably 95 weight-% or more;and / or that the content of the part of the stream SR-HS1 and / or the at least a part of the stream SR-HS2 and / or the stream SCPLand / or the chemical material in the product Ω is 100 weight-% or less, preferably 95 weight-% or less, morepreferably 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 content is determined based on identity preservationand / or segregation and / or mass balance and / or book and claim chain of custody models, preferably based on massbalance, preferably the International Sustainability and Carbon Certification (ISCC) standard.The publication Prior Art Disclosure; Issue 684; paragraphs

[1000] to

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

[1000] to

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

[1000] to

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

[1000] to

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

[2001] to

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

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

[2009] and

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

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

[3035] to

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

[3008] to

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

[3001] to

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

[3006] to

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

[3045] to

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

[3056] to

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[6014] entitled “Process for the preparation of aqueous polyurethane dispersions” and section [6017)] entitled “Aqueous UV-curable polyurethane dispersions, their preparation and use and compositions containing them” of Reference RF1.Composition(s) and uses of aqueous polymer dispersion(s) and of polymeric dispersant(s) are defined in more detail in the following sections of Reference RF1: section

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

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

[6006] entitled “Binders for paper coating” section

[6007] entitled “Binders for fiber bonding” section

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

[8000] to

[8005] of Reference RF1. The present invention 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 ofembodiments 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.A process for purifying an aqueous liquid stream comprising monomeric ε-caprolactam, polyamide 6 and oneor more organic compounds X, wherein monomeric ε-caprolactam has a boiling point TC and the one or moreone organic compounds X have a boiling point TX > TC, said process comprising(i) providing a stream SM comprising a solid material M comprising polyamide 6;(ii) preparing an aqueous depolymerization mixture MD1 from SM;(iii) subjecting the mixture MD1 to a first depolymerization and purification stage, comprising(iii.1) subjecting the mixture MD1 in a depolymerization unit UR1 to polyamide 6 depolymerizationconditions DR1 comprising a depolymerization temperature TR1 at a depolymerization pressurepR1, obtaining a liquid aqueous product stream SR1comprising monomeric ε-caprolactam at a concentration cR1(C), polyamide 6 at a concentration cR1(P) and one or more compounds X at a total concentration cR1(X); (iii.2) passing the liquid aqueous stream SR1 into a first water separation unit UWS1, obtaining from SR1a liquid aqueous product stream SWS1comprising monomeric ε-caprolactam at a concentration cWS1(C) > cR1(C), polyamide 6 at a concentration cWS1(P) > cR1(P) and one or more compounds X at a total concentration cWS1(X) > cR1(X), and further obtaining at least one aqueous residue stream SR-WS1comprising separated water; (iii.3) passing the liquid aqueous stream SWS1 into a high boiler separation unit UHS1, obtaining fromSWS1 an aqueous product stream SP-HS1 comprising monomeric ε-caprolactam at a concentrationcP-HS1(C) > cWS1(C) and further obtaining from SWS1 an aqueous residue stream SR-HS1comprising polyamide 6 at a concentration cR-HS1(P) ≥ cWS1(P) and one or more compounds X ata total concentration cR-HS1(X) > cWS1(X);(iv) passing the aqueous residue stream SR-HS1 to further treatment, comprising(iv.1) recycling at least a part of the stream SR-HS1 to (iii), comprising subjecting the at least part of thestream SR-HS1 in the depolymerization unit UR1 to the polyamide 6 depolymerization conditions DR1; and / or(iv.2) subjecting at least a part of the stream SR-HS1 to a second depolymerization and purificationstage, comprising (iv.2.1) subjecting the at least part of the stream SR-HS1 in a depolymerization unit UR2 topolyamide 6 depolymerization conditions DR2 comprising a depolymerizationtemperature TR2 at a depolymerization pressure pR2, obtaining a liquid aqueous stream SR2 comprising monomeric ε-caprolactam at a concentration cR2(C), optionally polyamide 6 at a concentration cR2(P) < cR-HS1(P), and one or more compounds X at a total concentration cR2(X); (iv.2.2) passing the liquid aqueous stream SR2 into a second water separation unit UWS2,obtaining from SR2 a liquid aqueous product stream SWS2 comprising monomeric ε- caprolactam at a concentration cWS2(C) > cR2(C), polyamide 6 at a concentration cWS2(P) > cR2(P) and one or more compounds X at a total concentrationcWS2(X) > cR2(X), and further obtaining at least one aqueous residue stream SR-WS2 comprising separated water; (iv.2.3) passing the liquid aqueous stream SWS2 into a high boiler separation unit UHS2,obtaining from SWS2 an aqueous product stream SP-HS2 comprising monomeric ε-caprolactam at a concentration cP-HS2(C) > cWS2(C) and further obtaining from SWS2 an aqueous residue stream SR-HS2 comprising one or more compounds X at a total concentration cR-HS2(X) > cWS2(X) and optionally polyamide 6 at a concentration cR-HS2(P) > cWS2(P); (iv.2.4) passing the aqueous residue stream SR-HS2 to further treatment, comprising(iv.2.4.1) recycling at least a part of the stream SR-HS2 to (iv.2.1), comprisingsubjecting the at least part of the stream SR-HS2in the depolymerization unit UR2to the polyamide 6 depolymerization conditions DR2; and / or (iv.2.4.2) passing at least a part of the stream SR-HS2 to a further use.2. The process of embodiment 1, wherein according to (i), the solid material M comprised in the stream SMcomprises, preferably consists of, a waste material, wherein said waste material more preferably comprises, more preferably consists of, one or more of at least one textile waste material and at least one engineering plastics waste material, more preferably comprises, more preferably consists of at least one textile waste material.3. The process of embodiment 2, wherein from 10 to 99 weight-%, preferably from 30 to 98.5 weight-%, morepreferably from 50 to 98 weight-%, more preferably from 80 to 98 weight-%, of the solid material M consist of polyamide 6.4. The process of embodiment 3, wherein, in addition to polyamide 6, the solid material M comprises one ormore further organic polymeric compounds, preferably including, but not limited to, one or more of at least one elastane; at least one polyamide 6.6; at least one semiaromatic polyamide including one or more of polyamide6T and polyamide 6I; at least one polyethylene terephthalate; at least one polyurethane; at least one polyester; at least one polyether; at least one polyvinyl chloride; at least one natural fiber material such as wool and cotton; at least one cellulose material; at least one natural elastomer; at least one synthetic elastomer; at least one copolymer of two or more of said polymeric compounds including statistical copolymers, gradient copolymers, alternating copolymers, block copolymers, and graft copolymers; and at least one rubber material comprising one or more of at least one natural rubber material and at least one synthetic rubber material.5. The process of any one of embodiments 1 to 4, wherein according to (ii), preparing the aqueousdepolymerization mixture MD1 comprises- melting in a melting unit UM the solid material M comprised in the stream SM having a temperature TSMat a pressure pSM, obtaining a liquid stream SM;- admixing in a pre-reaction unit UPR the liquid stream SM with an aqueous stream SW having atemperature TSW at a pressure pSW, obtaining the depolymerization mixture MD1 having a temperatureTMD1 at a pressure pMD1.The process of any one of embodiments 1 to 5, wherein the polyamide 6 depolymerization conditions DR1according to (iii.1) comprise a depolymerization pressure pR1 in the range of from 40 to 140 bar, preferably in the range of from 40 to 125 bar, more preferably in the range of from 40 to 110 bar; and a depolymerization temperature TR1in the range of from 230 to 335 °C, preferably in the range of from 250 to 320 °C, more preferably in the range of from 270 to 310 °C.The process of any one of embodiments 1 to 6, wherein the liquid aqueous stream SR1 according to (iii.1) hasa temperature in the range of from 230 to 330 °C, preferably in the range of from 250 to 320 °C, more preferably in the range of from 270 to 310 °C.The process of any one of embodiments 1 to 7, wherein in the liquid aqueous stream SR1 according to (iii.1),the weight ratio of water relative to the sum of monomeric ε-caprolactam, polyamide 6 and the at least one compound X, m(W) / (m(C)+(m(P)+(X)), is in the range of from 5:1 to 15:1, preferably in the range of from 6:1 to 10:1, more preferably in the range of from 7:1 to 9:1.The process of any one of embodiments 1 to 8, wherein from 98 to 100 weight-%, preferably from 99 to 100weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the stream SR1 consist of monomeric ε-caprolactam, polyamide 6, the one or more compounds X, and water.The process of any one of embodiments 1 to 9, wherein the one or more compounds X comprise at least oneof- at least one aromatic amine which includes at least one of an aromatic monoamine, an aromaticdiamine, an aromatic triamine and an aromatic tetramine;- at least one aliphatic amine which includes at least one of an aliphatic monoamine, an aliphaticdiamine and an aliphatic triamine;- at least one aliphatic amide;- at least one aromatic alcohol which includes at least one of an aromatic monool and an aromatic diol;- at least one aliphatic alcohol which includes at least one of an aliphatic monool and an aliphatic diol;- at least one aromatic acid;- at least one and aliphatic acid;- at least other compound selected from the group consisting of one or more cleavage products of dyessuch as optionally chlorinated aromatic diamines, one or more water-soluble oligomeric cellulosecleavage products, and one or more water-soluble oligomers of terephthalic acid and hexamethylenediamine.The process of any one of embodiments 1 to 10, wherein (iii.2) comprises(iii.2.1) passing the liquid aqueous stream SR1 into a water evaporation unit UWS1A, obtaining from SR1 aliquid aqueous product stream SWS1A comprising monomeric ε-caprolactam at a concentration cWS1A(C) > cR1(C), polyamide 6 at a concentration cWS1A(P) > cR1(P) and one or more compounds X at a concentration cWS1A(X) > cR1(X), and further obtaining from SR1 one or more aqueous vapor streams SR-WS1A;(iii.2.2) passing the liquid aqueous stream SWS1A into a water separation unit UWS1B, obtaining from SWS1Athe stream SWS1and further obtaining from SWS1Aone or more aqueous streams SR-WS1B.The process of any one of embodiments 1 to 11, wherein the liquid aqueous stream SWS1 according to (iii.2)has a temperature in the range of from 75 to 120 °C, preferably in the range of from 80 to 110 °C, more preferably in the range of from 85 to 100 °C.The process of any one of embodiments 1 to 12, wherein in the liquid aqueous stream SWS1, the weight ratioof water relative to the sum of monomeric ε-caprolactam, polyamide 6 and the at least one compound X, m(W) / (m(C)+(m(P)+(X)), is in the range of from 0.13:1 to 0.4:1, preferably in the range of from 0.14:1 to 0.3:1, more preferably in the range of from 0.15:1 to 0.2:1.The process of any one of embodiments 1 to 13, wherein from 98 to 100 weight-%, preferably from 99 to 100weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the stream SWS1 consist of monomeric ε-caprolactam, polyamide 6, the one or more compounds X, and water.The process of any one of embodiments 1 to 14, further comprising(v) passing- the aqueous product stream SP-HS1 obtained according to (iii.1), comprising monomeric ε-caprolactam at the concentration cP-HS1(C) and water at a concentration cP-HS1(W); and / or -the aqueous product stream SP-HS2 obtained according to (iv.2.3), comprising monomeric ε-caprolactam at the concentration cP-HS2(C) and water at a concentration cP-HS2(W)to a third water separation unit UWS3, obtaining a product stream SP-WS3 comprising monomeric ε- caprolactam at a concentration cP-WS3(C) > cP-HS1(C) and water at a concentration cP-WS3(W) < cP-HS1(W), and further obtaining at least one aqueous residue stream SR-WS3 comprising water at a concentration cR-WS3(W) > cP-HS1(W); wherein in the product stream SP-WS3, cP-WS3(C) + cP-WS3(W) is preferably in the range of from 98.5 to 100 weight-%, more preferably in the range of from 99 to 100 weight-%, more preferably in the range of from 99.9to 100 weight-%, based on the total weight of the stream SP-WS3, wherein in the stream SP-WS3, the weight ratio of monomeric ε-caprolactam relative to water is preferably at least 4:1, more preferably at least 5:1, more preferably at least 6:1.16. The process of any one of embodiments 1 to 15, wherein the high boiler separation unit UHS1 according to(iii.3) is an evaporation unit, (iii.3) comprising (iii.3.1) passing the stream SWS1 into the unit UHS1, preparing in the unit UHS1 from the stream SWS1 anevaporation mixture MHS1 having an evaporation temperature THS1 at an evaporation pressure pHS1 with THS1 > TWS1, wherein the one or more one organic compounds X have a boiling point TBX andmonomeric ε-caprolactam has a boiling point TBCwith TBX> THS1≥ TBCat the evaporation pressure pHS1; (iii.3.2) removing the stream SP-HS1 from the unit UHS1, the stream SP-HS1 having a temperature TP-HS1 withTP-HS1≤ THS1; (iii.3.3) removing the stream SR-HS1 from the unit UHS1, the stream SR-HS1 having a temperature TR-HS1 withTR-HS1= TP-HS1.17. The process of embodiment 16, wherein pHS1 is in the range of from 50 to 200 mbar and THS1 is in the range offrom 220 to 330 °C, preferably in the range of from 240 to 320 °C, more preferably in the range of from 260 to310 °C; wherein preparing the mixture MHS1 in the unit UHS1 according to (iii.3.1) preferably comprises -heating the stream SWS1 passed into the unit UHS1 from the temperature TWS1 to the evaporationtemperature THS1 via internal heating means HINT1 arranged within the unit UHS1, thereby obtaining the evaporation mixture MHS1; or -passing, in addition to the stream SWS1, a stream SX1 into the unit UHS1, the stream SX1 having atemperature TX1 > TWS1, admixing the stream SX1 and the stream SWS1 and heating the obtained mixture to the temperature THS1via internal heating means HINT1arranged within the unit UHS1, thereby obtaining the evaporation mixture MHS1, wherein the process further separating the stream SX1from the stream SR-HS1, wherein the stream SX1has the temperature TX= TR-HS1; or -passing, in addition to the stream SWS1, a stream SY1 into the unit UHS1, the stream SY1 having atemperature TY1 > THS1, and admixing the stream SWS1 and the stream SY1, thereby obtaining theevaporation mixture MHS1, wherein the process further comprises separating a stream SX1 from the stream SR-HS1, wherein the stream SX1 has a temperature TX1 = THSR1; and subjecting the stream SX1 toheating via external heating means HEXT1 arranged outside the unit UHS1, obtaining the stream SY1 having the temperature TY1; and wherein preferably TY1 ≥ (THS1 + 10 K), more preferably TY1 ≥ (THS1 + 20 K), more preferably TY1 ≥ (THS1 + 30 K).18. The process of embodiment 16 or 17, further comprising subjecting the stream SP-HS1 to cooling in a coolingunit, obtaining from said cooling unit a cooled stream SP-HS1, preferably obtaining a cooled and partially condensed stream SP-HS1, and wherein the cooled stream SP-HS1 has a temperature TP-HS1 preferably in the range of from 160 to 320 °C, more preferably in the range of from 165 to 310 °C, more preferably in the rangeof from 170 to 300 °C.19. The process of any one of embodiments 16 to 18, wherein the water separation unit UWS3 as defined inembodiment 15 comprises two or more water separation sub-units, preferably two water separation sub-units UWS3A and UWS3B, more preferably two serially coupled water separation sub-units UWS3A and UWS3B with UWS3B being arranged downstream of UWS3A.20. The process of embodiment 19, wherein the water separation sub-unit UWS3A comprises, preferably consistsof, a droplet separator, preferably selected from the group consisting of a hydrocyclone, a demister plate, and an absorption tower, more preferably a hydrocyclone; and wherein the water separation sub-unit UWS3Bcomprises, preferably consists of, a distillation column.21. The process of any one of embodiments 1 to 15, wherein the high boiler separation unit UHS1 according to(iii.3) is a stripping unit, the process according to (iii.3) comprising (iii.3.1) passing the stream SWS1 and an aqueous stripping gas stream SG01 into the unit UHS1, wherein theaqueous stripping gas stream SG01 has a temperature TG01 with TG01 > TWS1; (iii.3.2) bringing the stream SWS1 and the stream SG01 in the unit UHS1 at stripping conditions into contactwith each other, wherein the stripping conditions comprise a stripping pressure pHS1 and wherein at the stripping pressure pHS1, the one or more one organic compounds X comprised in the stream SWS1 have a boiling point TBX and monomeric ε-caprolactam has a boiling point TBC < TBX;(iii.3.3) removing the stream SP-HS1 from the unit UHS1, the stream SP-HS1 having a temperature TP-HS1 withTWS1< TP-HS1< TG01; (iii.3.4) removing the stream SR-HS1 from the unit UHS1, the stream SR-HS1 having a temperature TP-HS1 withTWS1< TR-HS1< TG01.22. The process of embodiment 21, wherein from 95 to 100 weight-%, preferably from 98 to 100 weight-%, morepreferably from 99 to 100 weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.8 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the aqueous stripping gas stream SG01 consist of water; and wherein TG01 is at least 250 °C, more preferably in the range of from 250 to 500 °C, more preferably in the range of from 300 to 450 °C.23. The process of embodiment 21 or 22, wherein the water separation unit UWS3 as defined in embodiment 15comprises two or more water separation sub-units, preferably two water separation sub-units UWS3A andUWS3B, more preferably two serially coupled water separation sub-units UWS3A and UWS3B with UWS3A being arranged upstream of UWS3B.24. The process of embodiment 23, wherein the water separation sub-unit UWS3A comprises, preferably consistsof, a scrubbing unit, and wherein the water separation sub-unit UWS3B comprises, preferably consists of, adistillation column.25. The process of any one of embodiments 1 to 15, wherein the high boiler separation unit UHS1 according to(iii.3) is a stripping unit, the process according to (iii.3) comprising (iii.3.1) passing the stream SWS1 and a non-aqueous stripping gas stream SG01 into the unit UHS1, whereinthe non-aqueous stripping gas stream SG01 comprises at least one inert gas G1 and has atemperature TG01with TG01> TWS1;(iii.3.2) bringing the stream SWS1 and the stream SG01 in the unit UHS1 at stripping conditions into contactwith each other, wherein the stripping conditions comprise a stripping pressure pHS1and wherein at the stripping pressure pSHS1, the one or more one organic compounds X comprised in the stream SWS1have a boiling point TBXand monomeric ε-caprolactam has a boiling point TBC< TBX; (iii.3.3) removing the stream SP-HS1 from the unit UHS1, the stream SP-HS1 having a temperature TP-HS1 withTWS1 < TP-HS1 < TG01; (iii.3.4) removing the stream SR-HS1 from the unit UHS1, the stream SR-HS1 having a temperature TR-HS1 withTWS11 < TR-HS1 < TG01.26. The process of embodiment 25, wherein the at least one inert gas G1 comprises one or more of nitrogen andcarbon dioxide, preferably nitrogen, wherein more preferably, at least 99 weight-%, more preferably at least 99.5 weight-%, more preferably at least 99.9 volume -% of the at least one inter gas G1 consist of nitrogen,wherein more preferably from 95 to 100 weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the non-aqueous stripping gas stream SG01consist of the at least one inert gas G1; and wherein TG01is at least 250 °C, preferably in the range of from 250 to 500 °C, more preferably in the range of from 300 to 450 °C.27. The process of embodiment 25 or 26, wherein the water separation unit UWS3 as defined in embodiment 15comprises, preferably consists of, a distillation column.28. The process of any one of embodiments 1 to 27, wherein the stream SR-HS1 has a temperature in the range offrom 220 to 330 °C, preferably in the range of from 235 to 315 °C, more preferably in the range of from 250 to 300 °C.29. The process of any one of embodiments 1 to 28, wherein in the stream SR-HS1, the weight ratio ΦR-HS1 of thepolyamide 6 relative to the one or more compounds X, m(P) / m(X), is in the range of from 0.2:1 to 99:1,preferably in the range of from 0.8:1 to 95:1, more preferably in the range of from 1:1 to 90:1.30. The process of any one of embodiments 1 to 29, wherein from 95 to 100 weight-%, preferably from 98 to 100weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.8 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the residue stream SR-HS1consist of polyamide 6, the one or more compounds X, optionally water, and optionally monomeric ε- caprolactam, wherein preferably from 0 to 5 weight-%, more preferably from 0 to 4 weight-%, more preferably from 0 to 3 weight-% of the residue stream SR-HS1 consist of water and monomeric ε-caprolactam.31. The process of any one of embodiments 1 to 30, wherein, if in the stream SR-HS1, the weight ratio ΦR-HS1 of thepolyamide 6 relative to the one or more compounds X, ΦR-HS1 = m(P) / m(X), is greater than or equal to a pre-defined threshold value ΦR-HS1(T1), the process comprises(iv.1) recycling at least a part of the stream SR-HS1 to (iii), comprising subjecting at least part of the streamSR-HS1, preferably the stream SR-HS1, in the depolymerization unit UR1to the polyamide 6 depolymerization conditions DR1.32. The process of any one of embodiments 1 to 30, wherein, if in the stream SR-HS1, the weight ratio ΦR-HS1 of thepolyamide 6 relative to the one or more compounds X, ΦR-HS1 = m(P) / m(X), is smaller than a pre-definedthreshold value ΦR-HS1(T2) with ΦR-HS1(T2) < ΦR-HS1(T1), the process further comprises (iv.3) passing at least part of the stream SR-HS1, preferably the stream SR-HS1,to further use.33. The process of any one of embodiments 1 to 30, wherein, if in the stream SR-HS1, the weight ratio ΦR-HS1 of thepolyamide 6 relative to the one or more compounds X, ΦR-HS1 = (m(P) / m(X), is smaller than a pre-defined threshold value ΦR-HS1(T1) and greater than or equal to a pre-defined threshold value ΦR-HS1(T2) with ΦR-HS1(T2) < ΦR-HS1(T1), the process comprises (iv.2) subjecting at least a part of the stream SR-HS1, preferably the stream SR-HS1, to a seconddepolymerization and purification stage.34. The process of embodiment 33, wherein (iv.2.1) comprises preparing from the at least part of the streamSR-HS1a depolymerization mixture MD2, and subjecting the mixture MD2in a depolymerization unit UR2to polyamide 6 depolymerization conditions DR2.35. The process of embodiment 34, wherein preparing the mixture MD2 comprises admixing the at least part of thestream SR-HS1 with an aqueous stream Saq at a mixing ratio ΦWP = (mW / kg) / (mP / kg) in the range of from 1:1 to 20:1, more preferably in the range of from 2:1 to 15:1, more preferably in the range of from 5:1 to 10:1, wherein mW is the total amount of water comprised in SR-HS1 and Saq, and mP is the amount of polyamide 6 comprised in SR-HS1.36. The process of embodiment 35, wherein at least a part of the stream Saq consists of one or more of at least apart of at least one stream SWS1 obtained according to (iii.2), at least a part of at least one stream SWS2 obtained according to (iv.2.2), and at least a part of at least one stream SR-WS3 obtained according to (v) as defined in embodiment 15, wherein the at least a part of at least one stream SWS1 preferably comprises, more preferably is at least a part of the one or more aqueous streams SWS1B obtained according to (iii.2.2) as defined in embodiment 11.37. The process of any one of embodiments 1 to 36, wherein the the polyamide 6 depolymerization conditions DR2according to (iv.2.1) comprise a depolymerization pressure pR2in the range of from 40 to 140 bar, preferably in the range of from 40 to 125 bar, more preferably in the range of from 40 to 110 bar; and a depolymerization temperature TR2in the range of from 230 to 335 °C, preferably in the range of from 250 to 320 °C, more preferably in the range of from 270 to 310 °C.38. The process of any one of embodiments 1 to 37, wherein the liquid aqueous stream SR2 according to (iv.2.1)has a temperature in the range of from 230 to 330 °C, preferably in the range of from 250 to 320 °C, more preferably in the range of from 270 to 310 °C.39. The process of any one of embodiments 1 to 38, wherein in the liquid aqueous stream SR2 according to(iv.2.1), the weight ratio of water relative to the sum of monomeric ε-caprolactam, polyamide 6 and the at least one compound X, m(W) / (m(C)+(m(P)+(X)), is in the range of from 5:1 to 15:1, preferably in the range of from 6:1 to 12:1, more preferably in the range of from 6.5:1 to 10.5:1.40. The process of any one of embodiments 1 to 39, wherein from 98 to 100 weight-%, preferably from 99 to 100weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the stream SR2consist of monomeric ε-caprolactam, polyamide 6, the one or more compounds X, and water.41. The process of any one of embodiments 1 to 40, wherein (iv.2.2) comprises(iv.2.2.1) passing the liquid aqueous stream SR2 into a water evaporation unit UWS2A, obtaining from SR2 aliquid aqueous product stream SWS2Acomprising monomeric ε-caprolactam at a concentration cWS2A(C) > cR2(C), polyamide 6 at a concentration cWS2A(P) > cR2(P) and one or more compounds X at a concentration cWS2A(X) > cR2(X), and further obtaining from SR2 one or more aqueous vapor streams SR-WS2A; (iv.2.2.2) passing the liquid aqueous stream SWS2A into a water separation unit UWS2B, obtaining fromSWS2A the stream SWS2 and further obtaining from SWS2A one or more aqueous streams SR-WS2B.42. The process of any one of embodiments 1 to 41, wherein the liquid aqueous stream SWS2 according to (iv.2.2)has a temperature in the range of from 75 to 120 °C, preferably in the range of from 80 to 110 °C, more preferably in the range of from 85 to 100 °C.43. The process of any one of embodiments 1 to 42, wherein in the liquid aqueous stream SWS2, the weight ratioof water relative to the sum of monomeric ε-caprolactam, polyamide 6 and the at least one compound X, m(W) / (m(C)+(m(P)+(X)), is in the range of from 0.13:1 to 0.4:1, preferably in the range of from 0.14:1 to 0.3:1, more preferably in the range of from 0.15:1 to 0.2:1.44. The process of any one of embodiments 1 to 43, wherein from 98 to 100 weight-%, preferably from 99 to 100weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the stream SWS2consist of monomeric ε-caprolactam, the one or more compounds X, optionally water, and optionally polyamide 6.45. The process of any one of embodiments 1 to 44, wherein the high boiler separation unit UHS2 according to(iv.2.3) is an evaporation unit, (iv.2.3) comprising(iv.2.3.1) passing the stream SWS2 into the unit UHS2, preparing in the unit UHS2 from the stream SWS2 anevaporation mixture MHS2 having an evaporation temperature THS2 at an evaporation pressure pHS2 with THS2 > TWS2, wherein the one or more one organic compounds X have a boiling pointTBX and monomeric ε-caprolactam has a boiling point TBC with TBX > THS2 ≥ TBC at the evaporation pressure pHS2; (iv.2.3.2) removing the stream SP-HS2 from the unit UHS2, the stream SP-HS2 having a temperature TP-HS2with TP-HS2 ≤ THS2; (iv.2.3.3) removing the stream SR-HS2 from the unit UHS2, the stream SR-HS2 having a temperature TR-HS2with TR-HS2 = TP-HS2.46. The process of embodiment 45, wherein pHS2 is in the range of from 50 to 200 mbar and THS2 is in the range offrom 220 to 330 °C, preferably in the range of from 240 to 320 °C, more preferably in the range of from 260 to 310 °C; wherein preparing the mixture MHS2in the unit UHS2according to (iv.2.3.1) preferably comprises -heating the stream SWS2 passed into the unit UHS2 from the temperature TWS2 to the evaporationtemperature THS2 via internal heating means HINT2 arranged within the unit UHS2, thereby obtaining the evaporation mixture MHS2; or -passing, in addition to the stream SWS2, a stream SX2 into the unit UHS2, the stream SX2 having atemperature TX2 > TWS2, admixing the stream SX2 and the stream SWS2 and heating the obtained mixture to the temperature THS2 via internal heating means HINT arranged within the unit UHS2, thereby obtaining the evaporation mixture MHS2, wherein the process further separating the stream SX2 from the stream SR-HS2, wherein the stream SX has the temperature TX2 = TR-HS2;or -passing, in addition to the stream SWS2, a stream SY2 into the unit UHS2, the stream SY2 having atemperature TY2 > THS2, and admixing the stream SWS2 and the stream SY2, thereby obtaining the evaporation mixture MHS2, wherein the process further comprises separating a stream SX2 from the stream SR-HS2, wherein the stream SX2 has a temperature TX2 = THSR2; and subjecting the stream SX2 to heating via external heating means HEXT2 arranged outside the unit UHS2, obtaining the stream SY2 having the temperature TY2; and wherein preferably TY2 ≥ (THS2 + 10 K), more preferably TY2 ≥ (THS2 + 20 K), more preferably TY2 ≥ (THS2 + 30 K).47. The process of embodiment 45 or 46, further comprising subjecting the stream SP-HS2 to cooling in a coolingunit, obtaining from said cooling unit a cooled stream SP-HS2, preferably obtaining a cooled and partially condensed stream SP-HS2, and wherein the cooled stream SP-HS2has a temperature TP-HS2preferably in the range of from 160 to 320 °C, more preferably in the range of from 165 to 310 °C, more preferably in the range of from 170 to 300 °C.48. The process of any one of embodiments 45 to 47, wherein the water separation unit UWS3 as defined inembodiment 15 comprises two or more water separation sub-units, preferably two water separation sub-units UWS3A and UWS3B, more preferably two serially coupled water separation sub-units UWS3A and UWS3B with UWS3B being arranged downstream of UWS3A.49. The process of embodiment 48, wherein the water separation sub-unit UWS3A comprises, preferably consistsof, a droplet separator, preferably selected from the group consisting of a hydrocyclone, a demister plate, and an absorption tower, more preferably a hydrocyclone; and wherein the water separation sub-unit UWS3B comprises, preferably consists of, a distillation column.50. The process of any one of embodiments 1 to 44, wherein the high boiler separation unit UHS2 according to(iv.2.3) is a stripping unit, the process according to (iv.2.3) comprising (iv.2.3.1) passing the stream SWS2 and an aqueous stripping gas stream SG02 into the unit UHS2, whereinthe aqueous stripping gas stream SG01has a temperature TG02with TG02> TWS2; (iv.2.3.2) bringing the stream SWS2 and the stream SG02 in the unit UHS2 at stripping conditions into contactwith each other, wherein the stripping conditions comprise a stripping pressure pHS2 and wherein at the stripping pressure pHS2, the one or more one organic compounds X comprised in the stream SWS2 have a boiling point TBX and monomeric ε-caprolactam has a boiling pointTBC < TBX; (iv.2.3.3) removing the stream SP-HS2 from the unit UHS2, the stream SP-HS2 having a temperature TP-HS2with TWS2 < TP-HS2 < TG02; (iv.2.3.4) removing the stream SR-HS2 from the unit UHS2, the stream SR-HS2 having a temperature TP-HS2with TWS2 < TR-HS2 < TG02.The process of embodiment 50, wherein from 95 to 100 weight-%, preferably from 98 to 100 weight-%, morepreferably from 99 to 100 weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.8 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the aqueous stripping gas stream SG02 consist of water; and wherein TG02 is at least 250 °C, more preferably in the range of from 250 to 500 °C, morepreferably in the range of from 300 to 450 °C.The process of embodiment 50 or 51, wherein the water separation unit UWS3 as defined in embodiment 15comprises two or more water separation sub-units, preferably two water separation sub-units UWS3A and UWS3B, more preferably two serially coupled water separation sub-units UWS3Aand UWS3Bwith UWS3Abeingarranged upstream of UWS3B.The process of embodiment 52, wherein the water separation sub-unit UWS3A comprises, preferably consistsof, a scrubbing unit, and wherein the water separation sub-unit UWS3Bcomprises, preferably consists of, a distillation column.The process of any one of embodiments 1 to 44, wherein the high boiler separation unit UHS2 according to(iv.2.3) is a stripping unit, the process according to (iv.2.3) comprising(iv.2.3.1) passing the stream SWS2 and a non-aqueous stripping gas stream SG02 into the unit UHS2,wherein the non-aqueous stripping gas stream SG02 comprises at least one inert gas G2 andhas a temperature TG02 with TG02 > TWS2;(iv.2.3.2) bringing the stream SWS2 and the stream SG02 in the unit UHS2 at stripping conditions into contactwith each other, wherein the stripping conditions comprise a stripping pressure pHS2 and wherein at the stripping pressure pSHS2, the one or more one organic compounds X comprised in the stream SWS2 have a boiling point TBX and monomeric ε-caprolactam has a boiling point TBC< TBX;(iv.2.3.3) removing the stream SP-HS2 from the unit UHS2, the stream SP-HS2 having a temperature TP-HS2with TWS2< TP-HS2< TG02;(iv.2.3.4) removing the stream SR-HS2 from the unit UHS2, the stream SR-HS2 having a temperature TR-HS1with TWS2< TR-HS2< TG02.The process of embodiment 54, wherein the at least one inert gas G2 comprises one or more of nitrogen andcarbon dioxide, preferably nitrogen, wherein more preferably, at least 99 weight-%, more preferably at least99.5 weight-%, more preferably at least 99.9 volume -% of the at least one inter gas G2 consist of nitrogen,wherein more preferably from 95 to 100 weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the non-aqueous stripping gas stream SG02 consist of the at least one inert gasG2; and wherein TG02 is at least 250 °C, preferably in the range of from 250 to 500 °C, more preferably in therange of from 300 to 450 °C.56. The process of embodiment 54 or 55, wherein the water separation unit UWS3 as defined in embodiment 15comprises, preferably consists of, a distillation column.57. The process of any one of embodiments 1 to 56, wherein the stream SR-HS2 has a temperature in the range offrom 220 to 330 °C, preferably in the range of from 235 to 315 °C, more preferably in the range of from 250 to 300 °C.58. The process of any one of embodiments 1 to 57, wherein in the stream SR-HS2, the weight ratio ΦR-HS2 of thepolyamide 6 relative to the one or more compounds X, ΦR-HS2 = m(P) / m(X), is in the range of from 0.01:1 to99:1, preferably in the range of from 0.02:1 to 90:1, more preferably in the range of from 0.03:1 to 85:1.59. The process of any one of embodiments 1 to 58, wherein from 95 to 100 weight-%, preferably from 98 to 100weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.8 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the residue stream SR-HS2consist of the one or more compounds X, optionally polyamide 6, and optionally water and optionally monomeric ε-caprolactam, wherein preferably from 0 to 5 weight-%, more preferably from 0 to 4 weight-%, more preferably from 0 to 3 weight-% of the residue stream SR-HS2 consist of water and monomeric ε- caprolactam.60. The process of any one of embodiments 1 to 59, wherein, if in the stream SR-HS2, the weight ratio ΦR-HS2 of thepolyamide 6 relative to the one or more compounds X, ΦR-HS2 = m(P) / m(X), is greater than or equal to a pre- defined threshold value ΦR-HS2(T), the process comprises (iv.2.4.1) recycling at least a part of the stream SR-HS2, preferably the stream SR-HS2, to (iv.2.1), comprisingsubjecting the at least part of the stream SR-HS2 in the depolymerization unit UR2 to the polyamide 6 depolymerization conditions DR2.61. The process of embodiment 60, wherein (iv.2.4.1) comprises one or more of admixing at least part of thestream SR-HS2with the at least part of the stream SR-HS1, and passing at least part of the stream SR-HS2directly into the depolymerization unit UR2.62. The process of any one of embodiments 1 to 60, wherein, if in the stream SR-HS2, the weight ratio ΦR-HS2 of thepolyamide 6 relative to the one or more compounds X, ΦR-HS2 = m(P) / m(X), is smaller than a pre-defined threshold value ΦR-HS2(T), the process comprises (iv.2.4.2) passing at least a part of the stream SR-HS2, preferably the stream SR-HS2, to further use.63. The process of any one of embodiments 1 to 62, further comprising passing at least a part of the streamSP-HS2 to UWS3A or to UWS3B as defined in embodiments 19 and 20; or to UWS3A or to UWS3B as defined in embodiments 23 and 24; or to UWS3 as defined in embodiment 27.64. The process of any one of embodiments 1 to 63, further comprising recycling one or more of the at least oneaqueous residue stream SR-WS1 according to (iii.2), of the at least one aqueous residue stream SR-WS2 according to (iv.2.2), and of the at least one aqueous residue stream SR-WS3 according to (v) as defined in embodiment 15, back to (ii) as part of the depolymerization mixture MD1.65. The process of any one of embodiments 1 to 64, exhibiting a polyamide 6 depolymerization efficiency Φ(P) ofat least 85 %, preferably of at least 90 %, more preferably of at least 95 %, wherein Φ(P) / % = 100 x [(mD1(P)-mR-HS2(P)) / mD1(P)] wherein mD1(P) is the mass of polyamide 6 comprised in the depolymerization mixture MD1to be subjected to depolymerization conditions DR1according to (iii.1), and wherein mR-HS2(P) is the mass of polyamide 6 comprised in the stream SR-HS2.66. The process of any one of embodiments 1 to 65, comprising (v) as defined in embodiment 15, the processfurther comprising (vi) passing the product stream SP-WS3 obtained according to (v) into a purification unit UP, obtaining fromSP-WS3 a stream SCPL exhibiting a concentration cCPL(C) of monomeric ε-caprolactam with cCPL(C) > cP-WS3(C); wherein the purification unit UP comprises a distillation unit UDI, the process comprising feeding the stream SP- WS3 to UDI, obtaining from UDI a stream SDI exhibiting a concentration cDI(C) of monomeric ε-caprolactam with cCPL(C) ≥ cDI(C) > cP-WS3(C), wherein the purification unit UPpreferably further comprises, downstream of the unit UDI, one or more of a crystallization unit UCRand a chemical treatment unit UOD, the process comprising obtaining the stream SCPLfrom UCRor from UOD.67. The process of embodiment 66, wherein the purification unit UP further comprises a crystallization unit UCRlocated downstream of UDI, the process comprising feeding the stream SDI to the crystallization unit UCR, obtaining from UCR a stream SCR being the stream SCPL comprising ε-caprolactam at a concentration cCR(C) = cCPL(C).68. The process of embodiment 66, wherein the purification unit UP further comprises a chemical treatment unitUOD located downstream of UDI, the process comprising feeding the stream SDI to the chemical treatment unit UOD, obtaining from UOD a stream SOD being the stream SCPL comprising monomeric ε-caprolactam at a concentration cOD(C) = cCPL(C).69. The process of embodiment 66, wherein the purification unit UP further comprises a chemical treatment unitUOD and a crystallization unit UCR, wherein the crystallization unit UCR is located downstream of the distillation unit UDI and the chemical treatment unit UOD is located downstream of the crystallization unit UCR, the process comprising feeding the stream SDI to the crystallization unit UCR, obtaining from the crystallization UCR a stream SCR comprising monomeric ε-caprolactam at a concentration cCR(C) with cCR(C) > cDI(C), and feeding the stream SCR to the chemical treatment unit UOD, obtaining from UOD a stream SOD being the stream SCPL comprising monomeric ε-caprolactam at a concentration cOD(C) = cCPL(C).70. The process of embodiment 66, wherein the purification unit UP further comprises a chemical treatment unitUODand a crystallization unit UCR, wherein the chemical treatment unit UODis located downstream of the distillation unit UDIand the crystallization unit UCRis located downstream of the unit UCR, the process comprising feeding the stream SDIto the chemical treatment unit UOD, obtaining from the chemical treatment unit UODa stream SODcomprising monomeric ε-caprolactam at a concentration cOD(C) with cOD(C) > cDI(C), and feeding the stream SODto the crystallization unit UCR, obtaining from UCRa stream SCRbeing the stream SCPLcomprising monomeric ε-caprolactam at a concentration cCR(C) = cCPL(C).71. The process of any one of embodiments 66 to 70, wherein the chemical treatment in the unit UOD comprises(a) providing a preferably liquid stream SDI comprising monomeric ε-caprolactam from the distillation unitUDI or a preferably liquid stream SCR comprising monomeric ε-caprolactam from the crystallization unitUCR, said stream SDI or said stream SCR further comprising one or more oxidizable organic impuritycompounds Y, wherein the stream SDI or the stream SCR exhibits a weight ratio rYC of the one or more organic compounds Y relative to monomeric ε-caprolactam; (b) providing a stream SPM comprising at least one permanganate;(c) preparing an oxidation reaction educt mixture MOE from the stream SDI and the stream SPM, or from thestream SCRand the stream SPM, and subjecting the mixture MOEto oxidation reaction conditions, obtaining an oxidation reaction product stream SPcomprising monomeric ε-caprolactam, further comprising one or more oxidation products Z obtained from the oxidation of at least a part of the one or more compounds Y, and optionally further comprising a part of the one or more organic compounds Y, wherein the stream SP exhibits a weight ratio rYCP of organic compound Y relative to monomeric ε-caprolactam with 0 ≤ rYCP < rYC and further exhibits a weight ratio rZCP of the one or more products Z relative to monomeric ε-caprolactam with rZCP > 0;(d) separating at least a part of the one or more oxidation products Z and optionally at least a part oforganic compound Y from the stream SP, obtaining the stream SOD; wherein the process optionally further comprises providing a stream SOH comprising at least one hydroxide, wherein the oxidation reaction educt mixture MOE according to (c) is prepared from the stream SUD or the stream SCR, and from the stream SPM and the stream SOH;wherein separating at least a part of the one or more oxidation products Z and optionally at least a part of organic compound Y from the stream SP according to (d) preferably comprises subjecting the stream SP obtained according to (c) to distillation in a distillation unit UDT, comprised in the chemical treatment unit UOD,obtaining from the distillation unit UDT a stream SDT comprising monomeric ε-caprolactam as the stream SOD,wherein the unit UDT comprises one or more distillation columns, preferably one or two distillation columns, wherein at least one column is optionally configured as side stream column or as divided wall column.The process of any one of embodiments 1 to 71, preferably according to any one of embodiments 66 to 71,comprising(α) providing the stream SP-WS3, preferably the stream SCPL;(β) passing the stream SP-WS3, preferably the stream SCPL to a polyamide 6 production plant UPA6;(γ) subjecting the stream SP-WS3, preferably the stream SCPL to ε-caprolactam polymerization conditions,obtaining from UPA6a polyamide 6 material MPand a stream comprising water and one or more ε- caprolactam oligomers;(δ) optionally subjecting to stream comprising water and one or more ε-caprolactam oligomers toconcentration with respect to the one or more ε-caprolactam oligomers in at least one concentration stage, obtaining a concentrated stream comprising water and one or more ε-caprolactam oligomers;(ε) passing the optionally concentrated stream comprising water and one or moreε-caprolactam oligomers into at least one of the melting unit UM as defined in embodiment 5 and thewater separation unit UWS1, preferably the water separation unit UWS1B as defined in embodiment 11.A method for controlling a process according to any one of embodiments 1 to 72, said process being carriedout in a chemical plant,wherein the plant comprises(1.1) the first depolymerization unit UR1;(1.2) the first water separation unit UWS1 arranged downstream of UR1;(1.3) the first high boiler separation unit UHS1 arranged downstream of UWS1;(1.4) the second depolymerization unit UR2 arranged downstream of UHS1;(1.5) the second water separation unit UWS2 arranged downstream of UR2;(1.6) the second high boiler separation unit UHS2 arranged downstream of UR2;(2.1) means for analyzing the chemical composition of the stream SR-HS1;(2.2) means for analyzing the chemical composition of the stream SR-HS2;(3.1) controllable means for passing at least a part of the stream SR-HS1, preferably the stream SR-HS1, eitherto UR1 and / or to UR2 and / or to further use;(3.2) controllable means for passing at least a part of the stream SR-HS2, preferably the stream SR-HS2, eitherto UR2 and / or to further use; wherein the method for controlling the process carried out in the plant comprises(a.1) defining threshold values ΦR-HS1(T1) and ΦR-HS1(T2) with ΦR-HS1(T2) < ΦR-HS1(T1) of the weight ratio ΦR-HS1 of the polyamide 6 relative to the one or more compounds X in the stream SR-HS1;(a.2) determining in the course of the process at a time ta the value of ΦR-HS1;(a.3) determining at the time ta the values ΔΦR-HS1(T1) = ΦR-HS1 - ΦR-HS1(T1) andΔΦR-HS1(T2) = ΦR-HS1 - ΦR-HS1(T2);(a.4) controlling at the time ta the means according to (3.1) so that for a period of time Δta starting at ta(a.4.1) if ΔΦR-HS1(T1) ≥ 0, the process comprises recycling at least a part of the stream SR-HS1,preferably the stream SR-HS1, to (iii), comprising subjecting at least a part of the stream SR-HS1, preferably the stream SR-HS1, in the depolymerization unit UR1 to the polyamide 6depolymerization conditions DR1; (a.4.2) if ΔΦR-HS1(T1) < 0 and ΔΦR-HS1(T2) ≥ 0, the process comprises subjecting at least a part ofthe stream SR-HS1, preferably the stream SR-HS1, to a second depolymerization and purification stage according to (iv.2);(a.4.3) if ΔΦR-HS1(T2) < 0, the process comprises passing at least a part of the stream SR-HS1,preferably the stream SR-HS1, to further use;(b.1) defining a threshold value ΦR-HS2(T) of the weight ratio ΦR-HS2 of the polyamide 6 relative to the one ormore compounds X in the stream SR-HS2;(b.2) determining in the course of the process at a time tb the value of ΦR-HS2;(b.3) determining at the time tb the value ΔΦR-HS2(T) = ΦR-HS2 - ΦR-HS2(T);(b.4) controlling at the time tb the means according to (3.2) so that for a period of time Δtb starting at tb(b.4.1) if ΔΦR-HS2(T) ≥ 0, the process comprises recycling at least a part of the stream SR-HS2,preferably the stream SR-HS2, to (iv.2.1), comprising subjecting at least a part of the stream SR-HS2, preferably the stream SR-HS2, in the depolymerization unit UR2 to the polyamide 6 depolymerization conditions DR2; (b.4.2) if ΔΦR-HS2(T) < 0, the process comprises passing at least a part of the stream SR-HS2,preferably the stream SR-HS2, to further use.The method of embodiment 73,wherein the plant further comprises(2.3) means for analyzing the chemical composition of the stream SP-HS2;(3.3) controllable means for passing at least a part of the stream SP-HS2, preferably the stream SR-HS1, eitherto UWS3A and / or to UWS3B; wherein the method for controlling the process carried out in the plant further comprises(c.1) defining a threshold value ΦP-HS2(T) of the weight ratio ΦP-HS2 of the water contained in the streamSP-HS2 relative to the total weight of the stream SR-HS2;(c.2) determining in the course of the process at a time tc the value of ΦP-HS2;(c.3) determining at the time tc the value ΔΦP-HS2(T) = ΦP-HS2 – ΦP-HS2(T);(c.4) controlling at the time tc the means according to (3.3) so that for a period of time Δtc starting at tc(c.4.1) if ΔΦP-HS2(T) ≥ 0, the process comprises passing at least a part of the stream SP-HS2,preferably the stream SP-HS2, to UWS3A; (c.4.2) if ΔΦR-HS2(T) < 0, the process comprises passing at least a part of the stream SP-HS2, preferablythe stream SP-HS2, to UWS3B.The method of embodiment 73 or 74, being at least partially computer-implemented.The method of embodiment 75, wherein the chemical plant further comprises(4) a computer-supported system for controlling at least the means according to (3.1) and (3.2), andoptionally according to (3.3).The method of embodiment 76, wherein the computer-supported system is further used for determining atleast one of ΔΦR-HS1(T1) and ΔΦR-HS1(T12) according to (a.3) and ΔΦR-HS2(T) according to (b.3), and optionallyΔΦP-HS2(T) according to (c.3).A plant for carrying out the process of any one of embodiments 1 to 72 and the method according to any oneof embodiments 73 to 77, said plant comprising(1.1) a first depolymerization unit UR1, and preferably a melting unit UM arranged upstream of UR1;(1.2) a first water separation unit UWS1 arranged downstream of UR1;(1.3) a first high boiler separation unit UHS1 arranged downstream of UWS1;(1.4) a second depolymerization unit UR2 arranged downstream of UHS1;(1.5) a second water separation unit UWS2 arranged downstream of UR2;(1.6) a second high boiler separation unit UHS2 arranged downstream of UR2;(1.7) preferably a third water separation unit UWS3 arranged downstream of UHS1 and UHS2, UWS3 preferablycomprising two water separation sub-units UWS3A and UWS3B;(1.8) preferably a purification unit UP arranged downstream of UWS3, UP preferably comprises a distillationunit UDI, wherein the purification unit UPmore preferably further comprises, downstream of the unit UDI, one or more of a crystallization unit UCRand a chemical treatment unit UOD;(1.9) optionally a polyamide 6 production plant UPA6, preferably arranged downstream of UP;(2.1) means for analyzing the chemical composition of the stream SR-HS1;(2.2) means for analyzing the chemical composition of a stream SR-HS2;(2.3) optionally means for analyzing the chemical composition of the stream SP-HS2;(3.1) controllable means for passing the stream SR-HS1 either to UR1 and / or to UR2 and / or to further use;(3.2) controllable means for passing the stream SR-HS2 either to UR2 and / or to further use;(3.3) optionally controllable means for passing at least a part of the stream SP-HS2, preferably the streamSR-HS1, either to UWS3A and / or UWS3B;(4) preferably a computer-supported system for controlling at least the means according to (3.1) and (3.2),and optionally (3.3).79. A computer program comprising instructions which, when the program is executed by the computer-supportedsystem (4) as defined in embodiments 76 and 78, cause the system to perform the method according to anyone of embodiments 73 to 75.80. A non-transient computer-readable medium containing instructions which, when executed by one or moreprocessors, cause the one or more processors to perform the program according to embodiment 79.81. A stream SCPL comprising highly purified ε-caprolactam, the stream SCPL being obtainable or obtained by aprocess according to any one of embodiments 66 to 71.82. Use of the stream SCPL according to embodiment 81 as an educt material for a chemical process, preferablyfor a polymerization reaction, more preferably for preparing polyamide 6.83. A method for preparing polyamide 6, comprising(A) preparing a stream SCPL according to a process according to any one of embodiments 66 to 71;(B) subjecting the stream SCPL, optionally after storing, to polyamide 6 polymerization conditions.84. Polyamide 6, obtainable or obtained by a method according to embodiment 83.85. The process of any one of embodiments 66 to 71, further comprising providing at least part of the stream SCPLto a polyamide 6 production unit UPA6, wherein the polyamide 6 produced in UPA6 is preferably provided as afeedstock to a textile material producing unit UTP, from which unit UTP(A) a textile material MTE is obtained which is brought onto the market, wherein, after the lifetime TMTE ofsaid textile material MTE, it is at least partially collected as textile waste material in a textile material collecting unit UTC; (B) remaining material MRE is obtained as textile waste material;wherein at least part of the textile waste material according to (A), or at least part of the textile waste material according to (B), or at least part of the textile waste material according to (A) and at least part of the textile waste material according to (B) is suitably provided as solid material M according to (i).86. The process of any one of embodiments 66 to 71, further comprising providing at least part of the stream SCPLto a polyamide 6 production unit UPA6, wherein the polyamide 6 produced in UPA6 is preferably provided as afeedstock to an engineering plastics material producing unit UEP, from which unit UEP(A) an engineering plastics material MEP is obtained which is brought onto the market, wherein, after thelifetime TMEP of said engineering plastics material MEP, it is at least partially collected as engineering plastics waste material in an engineering plastics material collecting unit UEC; (B) remaining material MRE is obtained as engineering plastics waste material;wherein at least part of the engineering plastics waste material according to (A), or at least part of the engineering plastics waste material according to (B), or at least part of the engineering plastics waste material according to (A) and at least part of the engineering plastics waste material according to (B) is suitablyprovided as solid material M according to (i).87. Use of the stream SCPL according to embodiment 81 for preparing polyamide 6, said use preferably furthercomprising employing said polyamide 6 as a feedstock for preparing one or more of a textile material and an engineering plastics material, more preferably for preparing a textile material.88. A method for preparing polyamide 6, said method comprising employing the stream SCPL according toembodiment 81 as a starting material, wherein said method preferably further comprises employing said polyamide 6 as a feedstock for preparing one or more of a textile material and an engineering plastics material, more preferably for preparing a textile material.89. A process, preferably according to any one of embodiments 1 to 71, comprising the step of converting a partof the stream SR-HS1and / or at least a part of the stream SR-HS2and / or the stream SCPLand / or a chemical material obtainable by or obtained by the process according to any one of embodiments 1 to 71 to obtain a product Ω.90. A process comprising the step of using the plant according to embodiment 78 to obtain a stream SR-HS1, astream SR-HS2, a stream SCPL and a chemical material, and preferably converting a part of the stream SR-HS1 and / or at least a part of the stream SR-HS2 and / or the stream SCPL and / or the chemical material to obtain aproduct Ω.91. The process of embodiment 89 or 90, wherein the product Ω is selected from:- building block or monomer; or- polymer, preferably polymer A, polymer composition, preferably polymer composition A, or polymerproduct, preferably polymer product A; or -industrial use polymer, industrial use surfactant, descaling compound, industrial use biocide, industrialuse solvent, industrial use dispersant, composition thereof or formulation thereof; or -agrochemical composition, agrochemical formulation auxiliary or agrochemically active ingredient; or- active pharmaceutical ingredient or intermediate thereof, pharmaceutical excipient, animal feedadditive, human food additive, dietary supplements, aroma chemical or aroma composition; or -aqueous polymer dispersion, preferably polyurethane or polyurethane – poly(meth)acrylate hybridpolymer dispersion, emulsion, binder for paper and fiber coatings, UV-curable acrylic polymer for hot melts and coatings polyisocyanates, hyperbranched polyester polyol, polymeric dispersant for inorganic binder compositions, unsaturated polyester polyol or 100% curable composition; or- cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter, further cosmetic ingredient orcomposition or formulation thereof; or -polymer B, polymer composition B, coating composition, other functional composition, foil, moldedbody, coating or coated substrate.92. The process of any one of embodiments 89 to 91,wherein the content of the part of the stream SR-HS1 and / or the at least a part of the stream SR-HS2 and / or the stream SCPL and / or the chemical material in the product Ω is 1 weight-% or more, preferably 2 weight-% ormore, 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; and / or wherein t the content of the part of the stream SR-HS1 and / or the at least a part of the stream SR-HS2 and / or thestream SCPL and / or the chemical material in the product Ω is 100 weight-% or less, preferably 95 weight-% orless, 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 content is determined based on identity preservation and / or segregation and / or mass balance and / or book and claim chain of custody models, preferably based on mass balance, preferably the International Sustainability and Carbon Certification (ISCC) standard. It is explicitly noted that the above-disclosed 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. The term „bar“ as used in the context of the present invention refers to the absolute pressure, also referred to as „bar(abs)“ or as “bara”. The term “textile material” as used herein covers textile raw materials and non-textile raw materials that are processed by various methods into linear, planar and spatial structures. It concerns the linear textile structures produced from them, such as yarns, twisted yarns and ropes, the sheet-like textile structures, such as woven fabrics, knitted fabrics, braids, stitch-bonded fabrics, nonwovens and felts, and the three-dimensional textile structures, i.e. body structures, such as textile hoses, stockings or textile semi-finished products; and it further concerns those finished products which, using the aforementioned products, are brought into a saleable condition by making up, opening up and / or other operations for onward transmission to the processor, the trade or the end consumer. The term “textile waste material” as used herein covers a textile material as defined above, the inherent value of which has been consumed from the perspective of its current holder and, thus, is an end-of-life material for said holder. The term “engineering plastics” as used herein refers to high-performance plastics grades which possess physical properties enabling them to perform for prolonged use in structural applications, over a wide temperature range,under mechanical stress, and in difficult chemical and physical environments used for example to fabricate plastic parts replacing traditional engineering materials like metals and ceramics. Engineering plastics specifically apply inthe fabrication of mechanical parts across several industries such as automotive, medical, electrical and electronics,aerospace, construction and consumer products. The term “engineering plastics waste material” as used herein covers an engineering plastics material as defined above, the inherent value of which has been consumed from the perspective of its current holder and, thus, is an end-of-life material for said holder.The present invention is further illustrated by the Figures 1 to 8 as described hereinbelow.Short description of the FiguresFigure 1 shows a process according to present invention. According to this process, an aqueousdepolymerization mixture MD1 which is prepared from a stream SM comprising a solid material M comprisingpolyamide 6 (preparation of MD1 not shown), is passed into a depolymerization unit UR1 and subjected there todepolymerization conditions DR1. Preferably, the solid material M comprised in the stream SM comprises, preferablyconsists of, a waste material, wherein said waste material more preferably comprises, more preferably consists of, one or more of at least one textile waste material and at least one engineering plastics waste material, morepreferably comprises, more preferably consists of at least one textile waste material. From said depolymerization inthe unit UR1, a liquid aqueous product stream SR1 is obtained which comprises monomeric ε-caprolactam at a concentration cR1(C), polyamide 6 at a concentration cR1(P) and one or more compounds X at a total concentration cR1(X). Said liquid aqueous stream SR1 is passed into a first water separation unit UWS1, and from UWS1, a liquid aqueous product stream SWS1 comprising monomeric ε-caprolactam at a concentration cWS1(C) > cR1(C), polyamide 6at a concentration cWS1(P) > cR1(P) and one or more compounds X at a total concentration cWS1(X) > cR1(X) isobtained. Further from UWS1, an aqueous residue stream SR-WS1 comprising separated water is obtained. The liquid aqueous stream SWS1 is then passed into a high boiler separation unit UHS1, and from UHS1, an aqueous product stream SP-HS1comprising monomeric ε-caprolactam at a concentration cP-HS1(C) > cWS1(C) is obtained. Further from UHS1, an aqueous residue stream SR-HS1is obtained which comprises polyamide 6 at a concentrationcR-HS1(P) ≥ cWS1(P) and one or more compounds X at a total concentration cR-HS1(X) > cWS1(X).The aqueous residue stream SR-HS1obtained from the high boiler separation unit UHS1is then passed to further treatment. This further treatment according to the present invention comprises- recycling at least a part of the stream SR-HS1, wherein said recycling comprises subjecting the at least part ofthe stream SR-HS1 in the depolymerization unit UR1 to the polyamide 6 depolymerization conditions DR1;- subjecting at least a part of the stream SR-HS1 to a second depolymerization and purification stage (explainedin detail in the following);- passing at least part of the stream SR-HS1 to further use (not shown), wherein said further use may compriseone or more of subjecting to pyrolysis, subjecting to a hydrogenation reaction, subjecting to incineration, and subjecting to one or more suitable depolymerization reactions other than those in UR1 and UR2.According to the present invention, the decision which further treatment is carried out is preferably made on theweight ratio ΦR-HS1 of the polyamide 6 relative to the one or more compounds X, ΦR-HS1 = m(P) / m(X), depending on the value of this weight ratio ΦR-HS1 relative to a respective pre-defined threshold value. If the residue stream SR-HS1 is passed to a second depolymerization and purification stage, it is passed into a second depolymerization unit UR2 and subjected there to polyamide 6 depolymerization conditions DR2, and from UR2, a liquid aqueous stream SR2 comprising monomeric ε-caprolactam at a concentration cR2(C), optionally polyamide 6 at a concentration cR2(P) < cR-HS1(P), and one or more compounds X at a total concentration cR2(X) is obtained. Said liquid aqueous stream SR2is passed into a second water separation unit UWS2, and from UWS2, a liquid aqueous product stream SWS2comprising monomeric ε-caprolactam at a concentration cWS2(C) > cR2(C), polyamide 6 at aconcentration cWS2(P) > cR2(P) and one or more compounds X at a total concentration cWS2(X) > cR2(X) is obtained.Further from UWS2, an aqueous residue stream SR-WS2comprising separated water is obtained. The liquid aqueous stream SWS2is then passed into a second high boiler separation unit UHS2, and from UHS2, an aqueous product stream SP-HS2comprising monomeric ε-caprolactam at a concentration cP-HS2(C) > cWS2(C) is obtained. Further from UHS2, an aqueous residue stream SR-HS2is obtained which comprises one or more compounds X at a total concentration cR-HS2(X) > cWS2(X) and optionally polyamide 6 at a concentration cR-HS2(P) > cWS2(P). The aqueous residue stream SR-HS2 obtained from the high boiler separation unit UHS2 is then passed to further treatment. This further treatment according to the present invention comprises- recycling at least a part of the stream SR-HS2, wherein said recycling comprises subjecting the at least part ofthe stream SR-HS2 in the depolymerization unit UR2 to the polyamide 6 depolymerization conditions DR2;- passing at least part of the stream SR-HS2,to further use, wherein said further use may comprise one or more ofsubjecting to pyrolysis, subjecting to a hydrogenation reaction, subjecting to incineration, and subjecting to one or more suitable depolymerization reactions other than those in UR1 and UR2.According to the present invention, the decision which further treatment is carried out is preferably made on theweight ratio ΦR-HS2of the polyamide 6 relative to the one or more compounds X, ΦR-HS1= m(P) / m(X), depending on the value of this weight ratio ΦR-HS2relative to a respective pre-defined threshold value.Figure 2 shows a process according to present invention. Further according to the process as shown anddescribed in Figure 1, this process further comprises passing the aqueous product stream SP-HS1 obtained from thefirst high boiler separation unit UHS1 and comprising monomeric ε-caprolactam at the concentration cP-HS1(C) and water at a concentration cP-HS1(W); and / or passing the aqueous product stream SP-HS2 obtained from the first second boiler separation unit UHS2 and comprising monomeric ε-caprolactam at the concentration cP-HS2(C) and water at a concentration cP-HS2(W) to a third water separation unit UWS3, from which third water separation unit UWS3 a product stream SP-WS3 comprising monomeric ε-caprolactam at a concentration cP-WS3(C) > cP-HS1(C) and water at aconcentration cP-WS3(W) < cP-HS1(W), and at least one aqueous residue stream SR-WS3 comprising water at a concentration cR-WS3(W) > cP-HS1(W) are obtained.Figure 3 shows a process according to present invention. Further according to the process as shown inFigure 2, this process further comprises certain further recycling paths preferably realized in the process of thepresent invention. In particular, it is shown that one or more of the at least one aqueous residue stream SR-WS1obtained from the first water separation unit UWS1, of the at least one aqueous residue stream SR-WS2 obtained fromthe first water separation unit UWS2, and of the at least one aqueous residue stream SR-WS3 obtained from the firstwater separation unit UWS2, are recycled to UR1 as part of the depolymerization mixture MD1.Figure 4 shows a process according to present invention. Further according to the process as shown inFigure 3, this process further comprises a two-stage water separation unit UWS3 wherein UWS3 comprises two waterseparation sub-units UWS3Aand UWS3B, preferably two serially coupled water separation sub-units UWS3Aand UWS3B.Figure 5 shows a process according to present invention. Further according to the process as shown inFigure 3, this process further comprises passing product stream SP-WS3 obtained from the third water separation unitUWS3into a purification unit UP, from which purification unit UPa stream SCPLis obtained which exhibits a concentration cCPL(C) of monomeric ε-caprolactam with cCPL(C) > cP-WS3(C). Said purification unit UP comprises a distillation unit UDI, and the process comprising feeding the stream SP-WS3 to UDI, obtaining from UDI a stream SDI exhibiting a concentration cDI(C) of monomeric ε-caprolactam with cCPL(C) ≥ cDI(C) > cP-WS3(C). Preferably according to the present invention, said purification unit UP preferably further comprises, downstream of the unit UDI, one or more of a crystallization unit UCR and a chemical treatment unit UOD; in this case, the process comprises obtaining the stream SCPL from UCR or from UOD.Figure 6 shows a process according to present invention. Further according to the process as shown inFigure 5, this process further comprises passing the stream SCPL to a polyamide 6 production plant UPA6. In saidpolyamide 6 production plant UPA6, the stream SCPL to is subjected to ε-caprolactam polymerization conditions. FromUPA6, a polyamide 6 material MPis obtained (not shown).Figure 7 shows a process according to present invention. Further according to the process as shown inFigure 6, this process further comprises passing the polyamide 6 material MP, after its lifetime, back as part of thesolid material M and as starting material to be subjected to depolymerization conditions in UR1.Figure 8 shows a process according to a further aspect of the present invention. According to this furtheraspect, the residue stream SR-HS1 is recycled to the depolymerization unit UR1, wherein, in first stage, the liquidresidue stream SR-HS1 obtained from the high boiler separation unit is cooled (UCOO) wherein, from cooling, thesolidified stream SR-HS1 is obtained. This solid material is then subjected to comminution (UCOM), from which comminution a comminuted material is obtained as recycle solid material (SRM). Together with non-recycled solidmaterial (SNM), the solid material M is formed which, in the form of the stream SM, is subjected to melting in themelting unit UM. The respectively obtained liquid stream SM is then admixed with aqueous stream SW which, preferably according to the present invention, is formed by at least one of the aqueous recycle streams SR-WS1 and SR-WS3 (in Fig.8, both streams SR-WS1 and SR-WS3 are used to form the stream SW). As a further component, the stream SW passed into the pre-reaction unit UPR may comprise a fresh, non-recycled aqueous stream (not shown). Withregard to the stream SP-WS3, the unit UP, the stream SCPL, the unit UPA6 and the dotted arrow from UPA6 to UR1,reference is made to the respective descriptions of the Figures 2 to 6 above.

Claims

Claims1. A process for purifying an aqueous liquid stream comprising monomeric ε-caprolactam, polyamide 6 and oneor more organic compounds X, wherein monomeric ε-caprolactam has a boiling point TC and the one or more one organic compounds X have a boiling point TX > TC, said process comprising (i) providing a stream SM comprising a solid material M comprising polyamide 6;(ii) preparing an aqueous depolymerization mixture MD1 from SM;(iii) subjecting the mixture MD1 to a first depolymerization and purification stage, comprising(iii.1) subjecting the mixture MD1 in a depolymerization unit UR1 to polyamide 6 depolymerizationconditions DR1comprising a depolymerization temperature TR1at a depolymerization pressure pR1, obtaining a liquid aqueous product stream SR1comprising monomeric ε-caprolactam at a concentration cR1(C), polyamide 6 at a concentration cR1(P) and one or more compounds X at a total concentration cR1(X); (iii.2) passing the liquid aqueous stream SR1 into a first water separation unit UWS1, obtaining from SR1a liquid aqueous product stream SWS1comprising monomeric ε-caprolactam at a concentration cWS1(C) > cR1(C), polyamide 6 at a concentration cWS1(P) > cR1(P) and one or more compounds X at a total concentration cWS1(X) > cR1(X), and further obtaining at least one aqueous residue stream SR-WS1 comprising separated water; (iii.3) passing the liquid aqueous stream SWS1 into a high boiler separation unit UHS1, obtaining fromSWS1 an aqueous product stream SP-HS1 comprising monomeric ε-caprolactam at a concentration cP-HS1(C) > cWS1(C) and further obtaining from SWS1 an aqueous residue stream SR-HS1 comprising polyamide 6 at a concentration cR-HS1(P) ≥ cWS1(P) and one or more compounds X ata total concentration cR-HS1(X) > cWS1(X); (iv) passing the aqueous residue stream SR-HS1 to further treatment, comprising(iv.1) recycling at least a part of the stream SR-HS1 to (iii), comprising subjecting the at least part of thestream SR-HS1in the depolymerization unit UR1to the polyamide 6 depolymerization conditions DR1; and / or (iv.2) subjecting at least a part of the stream SR-HS1 to a second depolymerization and purificationstage, comprising (iv.2.1) subjecting the at least part of the stream SR-HS1 in a depolymerization unit UR2 topolyamide 6 depolymerization conditions DR2 comprising a depolymerization temperature TR2 at a depolymerization pressure pR2, obtaining a liquid aqueous stream SR2 comprising monomeric ε-caprolactam at a concentration cR2(C), optionally polyamide 6 at a concentration cR2(P) < cR-HS1(P), and one or more compounds X at a total concentration cR2(X); (iv.2.2) passing the liquid aqueous stream SR2 into a second water separation unit UWS2,obtaining from SR2 a liquid aqueous product stream SWS2 comprising monomeric ε- caprolactam at a concentrationcWS2(C) > cR2(C), polyamide 6 at a concentration cWS2(P) > cR2(P) and one or more compounds X at a total concentration cWS2(X) > cR2(X), and further obtaining at least one aqueous residue stream SR-WS2 comprising separated water; (iv.2.3) passing the liquid aqueous stream SWS2 into a high boiler separation unit UHS2,obtaining from SWS2 an aqueous product stream SP-HS2 comprising monomeric ε- caprolactam at a concentration cP-HS2(C) > cWS2(C) and further obtaining from SWS2 an aqueous residue stream SR-HS2 comprising one or more compounds X at a total concentration cR-HS2(X) > cWS2(X) and optionally polyamide 6 at a concentration cR-HS2(P) > cWS2(P); (iv.2.4) passing the aqueous residue stream SR-HS2 to further treatment, comprising(iv.2.4.1) recycling at least a part of the stream SR-HS2 to (iv.2.1), comprisingsubjecting the at least part of the stream SR-HS2in the depolymerization unit UR2to the polyamide 6 depolymerization conditions DR2; and / or (iv.2.4.2) passing at least a part of the stream SR-HS2 to a further use.

2. The process of claim 1, wherein according to (i), the solid material M comprised in the stream SM comprises,preferably consists of, a waste material, wherein said waste material more preferably comprises, more preferably consists of, one or more of at least one textile waste material and at least one engineering plastics waste material, more preferably comprises, more preferably consists of at least one textile waste material; wherein preferably from 10 to 99 weight-%, more preferably from 30 to 98.5 weight-%, more preferably from 50 to 98 weight-%, more preferably from 80 to 98 weight-%, of the solid material M consist of polyamide 6;wherein, in addition to polyamide 6, the solid material M preferably comprises one or more further organic polymeric compounds, more preferably including, but not limited to, one or more of at least one elastane; at least one polyamide 6.6; at least one semiaromatic polyamide including one or more of polyamide 6T and polyamide 6I; at least one polyethylene terephthalate; at least one polyurethane; at least one polyester; at least one polyether; at least one polyvinyl chloride; at least one natural fiber material such as wool and cotton; at least one cellulose material; at least one natural elastomer; at least one synthetic elastomer; at least one copolymer of two or more of said polymeric compounds including statistical copolymers, gradient copolymers, alternating copolymers, block copolymers, and graft copolymers; and at least one rubber material comprising one or more of at least one natural rubber material and at least one synthetic rubber material.

3. The process of claim 1 or 2, wherein the one or more compounds X comprise at least one of- at least one aromatic amine which includes at least one of an aromatic monoamine, an aromaticdiamine, an aromatic triamine and an aromatic tetramine; -at least one aliphatic amine which includes at least one of an aliphatic monoamine, an aliphaticdiamine and an aliphatic triamine; -at least one aliphatic amide;- at least one aromatic alcohol which includes at least one of an aromatic monool and an aromatic diol;- at least one aliphatic alcohol which includes at least one of an aliphatic monool and an aliphatic diol;- at least one aromatic acid;- at least one and aliphatic acid;- at least other compound selected from the group consisting of one or more cleavage products of dyessuch as optionally chlorinated aromatic diamines, one or more water-soluble oligomeric cellulose cleavage products, and one or more water-soluble oligomers of terephthalic acid and hexamethylenediamine.

4. The process of any one of claims 1 to 3, further comprising(v) passing- the aqueous product stream SP-HS1 obtained according to (iii.1), comprising monomeric ε-caprolactam at the concentration cP-HS1(C) and water at a concentration cP-HS1(W); and / or -the aqueous product stream SP-HS2 obtained according to (iv.2.3), comprising monomeric ε-caprolactam at the concentration cP-HS2(C) and water at a concentration cP-HS2(W) to a third water separation unit UWS3, obtaining a product stream SP-WS3comprising monomeric ε- caprolactam at a concentration cP-WS3(C) > cP-HS1(C) and water at a concentration cP-WS3(W) < cP-HS1(W), and further obtaining at least one aqueous residue stream SR-WS3comprising water at a concentration cR-WS3(W) > cP-HS1(W).

5. The process of any one of claims 1 to 4, wherein in the stream SR-HS1, the weight ratio ΦR-HS1 of the polyamide6 relative to the one or more compounds X, m(P) / m(X), is in the range of from 0.2:1 to 99:1, preferably in the range of from 0.8:1 to 95:1, more preferably in the range of from 1:1 to 90:1; wherein preferably from 95 to 100 weight-%, more preferably from 98 to 100 weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.8 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the stream SR-HS1 consist of polyamide 6, the one or morecompounds X, optionally water, and optionally monomeric ε-caprolactam, wherein more preferably from 0 to 5 weight-%, more preferably from 0 to 4 weight-%, more preferably from 0 to 3 weight-% of the stream SR-HS1consist of water and monomeric ε-caprolactam.

6. The process of any one of claims 1 to 5,^ wherein, if in the stream SR-HS1, the weight ratio ΦR-HS1 of the polyamide 6 relative to the one or morecompounds X, ΦR-HS1 = m(P) / m(X), is greater than or equal to a pre-defined threshold value ΦR-HS1(T1), the process comprises (iv.1) recycling at least a part of the stream SR-HS1 to (iii), comprising subjecting at least part of thestream SR-HS1, preferably the stream SR-HS1, in the depolymerization unit UR1 to the polyamide 6 depolymerization conditions DR1; ^or wherein, if in the stream SR-HS1, the weight ratio ΦR-HS1 of the polyamide 6 relative to the one or morecompounds X, ΦR-HS1 = (m(P) / m(X), is smaller than a pre-defined threshold value ΦR-HS1(T1) andgreater than or equal to a pre-defined threshold value ΦR-HS1(T2) with ΦR-HS1(T2) < ΦR-HS1(T1), the process comprises (iv.2) subjecting at least a part of the stream SR-HS1, preferably the stream SR-HS1, to a seconddepolymerization and purification stage; ^or wherein, if in the stream SR-HS1, the weight ratio ΦR-HS1 of the polyamide 6 relative to the one or morecompounds X, ΦR-HS1 = m(P) / m(X), is smaller than a pre-defined threshold value ΦR-HS1(T2) with ΦR- HS1(T2) < ΦR-HS1(T1), the process further comprises (iv.3) passing at least part of the stream SR-HS1, preferably the stream SR-HS1, to further use.

7. The process of any one of claims 1 to 6,^ wherein the high boiler separation unit UHS2 according to (iv.2.3) is an evaporation unit, the processaccording to (iv.2.3) comprising (iv.2.3.1) passing the stream SWS2 into the unit UHS2, preparing in the unit UHS2 from the streamSWS2an evaporation mixture MHS2having an evaporation temperature THS2at an evaporation pressure pHS2with THS2> TWS2, wherein the one or more one organic compounds X have a boiling point TBXand monomeric ε-caprolactam has a boiling point TBCwith TBX> THS2≥ TBCat the evaporation pressure pHS2; (iv.2.3.2) removing the stream SP-HS2 from the unit UHS2, the stream SP-HS2 having a temperatureTP-HS2 with TP-HS2 ≤ THS2; (iv.2.3.3) removing the stream SR-HS2 from the unit UHS2, the stream SR-HS2 having a temperatureTR-HS2 with TR-HS2 = TP-HS2: wherein preparing the mixture MHS2 in the unit UHS2 according to (iv.2.3.1) preferably comprises -heating the stream SWS2 passed into the unit UHS2 from the temperature TWS2 to the evaporationtemperature THS2 via internal heating means HINT2 arranged within the unit UHS2, thereby obtaining the evaporation mixture MHS2; or -passing, in addition to the stream SWS2, a stream SX2 into the unit UHS2, the stream SX2 having atemperature TX2> TWS2, admixing the stream SX2and the stream SWS2and heating the obtained mixture to the temperature THS2via internal heating means HINTarranged within the unit UHS2, thereby obtaining the evaporation mixture MHS2, wherein the process further separating the stream SX2 from the stream SR-HS2, wherein the stream SX has the temperature TX2 = TR-HS2; or -passing, in addition to the stream SWS2, a stream SY2 into the unit UHS2, the stream SY2 having atemperature TY2 > THS2, and admixing the stream SWS2 and the stream SY2, thereby obtaining the evaporation mixture MHS2, wherein the process further comprises separating a stream SX2 from the stream SR-HS2, wherein the stream SX2 has a temperature TX2 = THSR2; and subjecting the stream SX2 to heating via external heating means HEXT2 arranged outside the unit UHS2, obtaining the stream SY2 having the temperature TY2; and wherein preferablyTY2 ≥ (THS2 + 10 K), more preferably TY2 ≥ (THS2 + 20 K), more preferably TY2 ≥ (THS2 + 30 K); ^or wherein the high boiler separation unit UHS2 according to (iv.2.3) is a stripping unit, the processaccording to (iv.2.3) comprising (iv.2.3.1) passing the stream SWS2 and an aqueous stripping gas stream SG02 into the unit UHS2,wherein the aqueous stripping gas stream SG01 has a temperature TG02 with TG02 > TWS2; (iv.2.3.2) bringing the stream SWS2 and the stream SG02 in the unit UHS2 at stripping conditions intocontact with each other, wherein the stripping conditions comprise a stripping pressure pHS2 and wherein at the stripping pressure pHS2, the one or more one organic compounds X comprised in the stream SWS2 have a boiling point TBX and monomeric ε-caprolactam has a boiling point TBC< TBX; (iv.2.3.3) removing the stream SP-HS2 from the unit UHS2, the stream SP-HS2 having a temperatureTP-HS2with TWS2< TP-HS2< TG02; (iv.2.3.4) removing the stream SR-HS2 from the unit UHS2, the stream SR-HS2 having a temperatureTP-HS2with TWS2< TR-HS2< TG02; ^or wherein the high boiler separation unit UHS2 according to (iv.2.3) is a stripping unit, the processaccording to (iv.2.3) comprising (iv.2.3.1) passing the stream SWS2 and a non-aqueous stripping gas stream SG02 into the unit UHS2,wherein the non-aqueous stripping gas stream SG02 comprises at least one inert gas G2 and has a temperature TG02 with TG02 > TWS2; (iv.2.3.2) bringing the stream SWS2 and the stream SG02 in the unit UHS2 at stripping conditions intocontact with each other, wherein the stripping conditions comprise a stripping pressure pHS2 and wherein at the stripping pressure pSHS2, the one or more one organic compounds X comprised in the stream SWS2 have a boiling point TBX and monomeric ε- caprolactam has a boiling point TBC < TBX; (iv.2.3.3) removing the stream SP-HS2 from the unit UHS2, the stream SP-HS2 having a temperatureTP-HS2with TWS2< TP-HS2< TG02; (iv.2.3.4) removing the stream SR-HS2 from the unit UHS2, the stream SR-HS2 having a temperatureTR-HS1with TWS2< TR-HS2< TG02.

8. The process of any one of claims 1 to 7, wherein in the stream SR-HS2, the weight ratio ΦR-HS2 of the polyamide6 relative to the one or more compounds X, ΦR-HS2 = m(P) / m(X), is in the range of from 0.01:1 to 99:1,preferably in the range of from 0.02:1 to 90:1, more preferably in the range of from 0.03:1 to 85:1; wherein preferably from 95 to 100 weight-%, more preferably from 98 to 100 weight-%, more preferably from 99 to 100 weight-%, more preferably from 99.5 to 100 weight-%, more preferably from 99.8 to 100 weight-%, more preferably from 99.9 to 100 weight-% of the residue stream SR-HS2 consist of the one or more compounds X, optionally polyamide 6, and optionally water and optionally monomeric ε-caprolactam, wherein more preferably from 0 to 5 weight-%, more preferably from 0 to 4 weight-%, more preferably from 0 to 3 weight-% of the residue stream SR-HS2 consist of water and monomeric ε-caprolactam.

9. The process of any one of claims 1 to 8, wherein,if in the stream SR-HS2, the weight ratio ΦR-HS2 of the polyamide 6 relative to the one or more compounds X, ΦR-HS2 = m(P) / m(X), is greater than or equal to a pre-defined threshold value ΦR-HS2(T), the process comprises (iv.2.4.1) recycling at least a part of the stream SR-HS2, preferably the stream SR-HS2, to (iv.2.1), comprisingsubjecting the at least part of the stream SR-HS2 in the depolymerization unit UR2 to the polyamide 6 depolymerization conditions DR2; and if in the stream SR-HS2, the weight ratio ΦR-HS2 of the polyamide 6 relative to the one or more compounds X,ΦR-HS2 = m(P) / m(X), is smaller than a pre-defined threshold value ΦR-HS2(T), the process comprises (iv.2.4.2) passing at least a part of the stream SR-HS2, preferably the stream SR-HS2, to further use.

10. The process of any one of claims 1 to 9, further comprising passing at least a part of the stream SP-HS2 to UWS3as defined in claim 4.

11. The process of any one of claims 1 to 10, exhibiting a polyamide 6 depolymerization efficiency Φ(P) of at least85 %, preferably of at least 90 %, more preferably of at least 95 %, wherein Φ(P) / % = 100 x [(mD1(P)-mR-HS2(P)) / mD1(P)] wherein mD1(P) is the mass of polyamide 6 comprised in the depolymerization mixture MD1to be subjected to depolymerization conditions DR1according to (iii.1), and wherein mR-HS2(P) is the mass of polyamide 6 comprised in the stream SR-HS2.

12. The process of any one of claims 1 to 11, comprising (v) as defined in claim 4, the process further comprising(vi) passing the product stream SP-WS3 obtained according to (v) into a purification unit UP, obtaining fromSP-WS3 a stream SCPL exhibiting a concentration cCPL(C) of monomeric ε-caprolactam with cCPL(C) > cP-WS3(C); wherein the purification unit UP comprises a distillation unit UDI, the process comprising feeding the stream SP-WS3 to UDI, obtaining from UDI a stream SDI exhibiting a concentration cDI(C) of monomeric ε-caprolactam with cCPL(C) ≥ cDI(C) > cP-WS3(C) , wherein the purification unit UPpreferably further comprises, downstream of the unit UDI, one or more of a crystallization unit UCRand a chemical treatment unit UOD, the process comprising obtaining the stream SCPLfrom UCRor from UOD.

13. A method for controlling a process according to any one of claims 1 to 12, said process being carried out in achemical plant, wherein the plant comprises (1.1) the first depolymerization unit UR1;(1.2) the first water separation unit UWS1 arranged downstream of UR1;(1.3) the first high boiler separation unit UHS1 arranged downstream of UWS1;(1.4) the second depolymerization unit UR2 arranged downstream of UHS1;(1.5) the second water separation unit UWS2 arranged downstream of UR2;(1.6) the second high boiler separation unit UHS2 arranged downstream of UR2;(2.1) means for analyzing the chemical composition of the stream SR-HS1;(2.2) means for analyzing the chemical composition of the stream SR-HS2;(3.1) controllable means for passing at least a part of the stream SR-HS1, preferably the stream SR-HS1, eitherto UR1 and / or to UR2 and / or to further use;(3.2) controllable means for passing at least a part of the stream SR-HS2, preferably the stream SR-HS2, eitherto UR2 and / or to further use;wherein the method for controlling the process carried out in the plant comprises(a.1) defining threshold values ΦR-HS1(T1) and ΦR-HS1(T2) with ΦR-HS1(T2) < ΦR-HS1(T1) of the weight ratioΦR-HS1of the polyamide 6 relative to the one or more compounds X in the stream SR-HS1;(a.2) determining in the course of the process at a time ta the value of ΦR-HS1;(a.3) determining at the time ta the values ΔΦR-HS1(T1) = ΦR-HS1 - ΦR-HS1(T1) andΔΦR-HS1(T2) = ΦR-HS1 - ΦR-HS1(T2);(a.4) controlling at the time ta the means according to (3.1) so that for a period of time Δta starting at ta(a.4.1) if ΔΦR-HS1(T1) ≥ 0, the process comprises recycling at least a part of the stream SR-HS1,preferably the stream SR-HS1, to (iii), comprising subjecting at least a part of the stream SR-HS1, preferably the stream SR-HS1, in the depolymerization unit UR1 to the polyamide 6 depolymerization conditions DR1; (a.4.2) if ΔΦR-HS1(T1) < 0 and ΔΦR-HS1(T2) ≥ 0, the process comprises subjecting at least a part ofthe stream SR-HS1, preferably the stream SR-HS1, to a second depolymerization and purification stage according to (iv.2);(a.4.3) if ΔΦR-HS1(T2) < 0, the process comprises passing at least a part of the stream SR-HS1,preferably the stream SR-HS1, to further use;(b.1) defining a threshold value ΦR-HS2(T) of the weight ratio ΦR-HS2 of the polyamide 6 relative to the one ormore compounds X in the stream SR-HS2;(b.2) determining in the course of the process at a time tb the value of ΦR-HS2;(b.3) determining at the time tb the value ΔΦR-HS2(T) = ΦR-HS2 - ΦR-HS2(T);(b.4) controlling at the time tb the means according to (3.2) so that for a period of time Δtb starting at tb(b.4.1) if ΔΦR-HS2(T) ≥ 0, the process comprises recycling at least a part of the stream SR-HS2,preferably the stream SR-HS2, to (iv.2.1), comprising subjecting at least a part of the stream SR-HS2, preferably the stream SR-HS2, in the depolymerization unit UR2 to the polyamide 6 depolymerization conditions DR2; (b.4.2) if ΔΦR-HS2(T) < 0, the process comprises passing at least a part of the stream SR-HS2,preferably the stream SR-HS2, to further use;wherein the plant preferably further comprises (2.3) means for analyzing the chemical composition of the stream SP-HS2;(3.3) controllable means for passing at least a part of the stream SP-HS2, preferably the stream SR-HS1, eitherto UWS3A and / or to UWS3B; andwherein the method for controlling the process carried out in the plant preferably further comprises (c.1) defining a threshold value ΦP-HS2(T) of the weight ratio ΦP-HS2 of the water contained in the streamSP-HS2 relative to the total weight of the stream SR-HS2; (c.2) determining in the course of the process at a time tc the value of ΦP-HS2;(c.3) determining at the time tc the value ΔΦP-HS2(T) = ΦP-HS2 – ΦP-HS2(T);(c.4) controlling at the time tc the means according to (3.3) so that for a period of time Δtc starting at tc(c.4.1) if ΔΦP-HS2(T) ≥ 0, the process comprises passing at least a part of the stream SP-HS2,preferably the stream SP-HS2, to UWS3A; (c.4.2) if ΔΦR-HS2(T) < 0, the process comprises passing at least a part of the stream SP-HS2, preferablythe stream SP-HS2, to UWS3B; wherein more preferably, said method is at least partially computer-implemented and the chemical plantfurther comprises (4) a computer-supported system for controlling at least the means according to (3.1) and (3.2), andoptionally according to (3.3).

14. A plant for carrying out the process according to any one of claims 1 to 12 and the method according to claim13, said plant comprising (1.1) a first depolymerization unit UR1, and preferably a melting unit UM arranged upstream of UR1;(1.2) a first water separation unit UWS1 arranged downstream of UR1;(1.3) a first high boiler separation unit UHS1 arranged downstream of UWS1;(1.4) a second depolymerization unit UR2 arranged downstream of UHS1;(1.5) a second water separation unit UWS2 arranged downstream of UR2;(1.6) a second high boiler separation unit UHS2 arranged downstream of UR2;(1.7) preferably a third water separation unit UWS3 arranged downstream of UHS1 and UHS2, UWS3 preferablycomprising two water separation sub-units UWS3Aand UWS3B; (1.8) preferably a purification unit UP arranged downstream of UWS3, UP preferably comprises a distillationunit UDI, wherein the purification unit UP more preferably further comprises, downstream of the unit UDI, one or more of a crystallization unit UCR and a chemical treatment unit UOD; (1.9) optionally a polyamide 6 production plant UPA6, preferably arranged downstream of UP;(2.1) means for analyzing the chemical composition of the stream SR-HS1;(2.2) means for analyzing the chemical composition of a stream SR-HS2;(2.3) optionally means for analyzing the chemical composition of the stream SP-HS2;(3.1) controllable means for passing the stream SR-HS1 either to UR1 and / or to UR2 and / or to further use;(3.2) controllable means for passing the stream SR-HS2 either to UR2 and / or to further use;(3.3) optionally controllable means for passing at least a part of the stream SP-HS2, preferably the stream SR-HS1, either to UWS3A and / or UWS3B; (4) preferably a computer-supported system for controlling at least the means according to (3.1) and (3.2),and optionally (3.3).

15. A process, preferably the process according to any one of claims 1 to 12, comprising the step of convertingthe stream SL1 obtainable or obtained by the process according to any one of claims 1 to 12 and / or the stream SCPL obtainable or obtained by the process according to claim 12 and / or a chemical material obtainable or obtained by the process according to any one of claims 1 to 12 to obtain a product Ω; and / or a processcomprising the step of using the plant according to claim 14 to obtain a stream SR-HS1, a stream SR-HS2, a stream SCPLand a chemical material, and preferably converting a part of the stream SR-HS1and / or at least a part of the stream SR-HS2 and / or the stream SCPL and / or the chemical material to obtain a product Ω.

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