Highly integrated process for preparing polyamide 6 from polyamide 6 containing waste

Abstract

An integrated process for preparing polyamide 6, comprising (i) providing a stream SMR comprising a solid material MR comprising polyamide 6, wherein the solid material MR comprises a waste material; (ii) preparing from the stream SMR in a depolymerisation and purification unit UDP a stream SCPL comprising purified ε-caprolactam, the unit UDP comprising at least one depolymerization sub-unit UD; (iii) passing the stream SCPL to a polyamide 6 production unit UPA; (iv) subjecting the stream SCPL in UPA to ε-caprolactam polymerization conditions, obtaining from UPA a polyamide 6 material MP and a stream comprising water and one or more ε-caprolactam oligomers; (v) optionally subjecting to stream comprising water and one or more ε-caprolactam oligomers to concentration 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; (vi) passing the optionally concentrated stream comprising water and one or more ε-caprolactam oligomers into at least one of the depolymerization sub-units UD according to (ii).

Description

Highly integrated process for preparing polyamide 6 from polyamide 6 containing wasteThe present invention relates to a highly integrated process for preparing polyamide 6.US 4,107,160 A relates to relates to an apparatus and a continuous process for the recovery of caprolactam from solid polycaprolactam waste and / or polycaprolactam extraction water.JP 2023 / 108237 A relates to a recycling method for producing a recycled polyamide resin by using a depolymerisation solution containing caprolactam and oligomers as a raw material for polymerization.The present invention relates to a highly integrated process for preparing polyamide 6 in a polyamide 6 production unit wherein polyamide 6 is prepared by polymerizing E-caprolactam. TheE-caprolactam educt stream which is used in the polyamide 6 production unit is prepared in a depolymerization and purification unit where a polyamide 6 containing material is depolymerized to give a crude E-caprolactam stream which is then purified to give the E-caprolactam educt stream. From said polyamide 6 production unit, a recycle stream is passed back to the depolymerization and purification unit, and at least one, preferably more components of this stream are suitably separated and, according to preferred processes of the present invention, passed to different stages carried out in the depolymerization and purification unit. Yet further, according to a further preferred process of the present invention, off-spec polyamide 6 material from the polyamide 6 production unit is suitably recycled to the depolymerization and purification unit.Therefore, the present invention relates to an integrated process for preparing polyamide 6, comprising(I) providing a stream SMR comprising a solid material MR comprising polyamide 6, wherein the solid material MR comprises a waste material;(ii) preparing from the stream SMR in a depolymerisation and purification unit UDP a stream SCPL comprising purified E-caprolactam, the unit UDP comprising at least one depolymerization sub-unit UD;(ill) passing the stream SCPL to a polyamide 6 production unit UPA;(iv) subjecting the stream SCPL in UPA to E-caprolactam polymerization conditions, obtaining from UPA a polyamide 6 material MP and a stream comprising water and one or moreE-caprolactam oligomers;(v) optionally subjecting to stream comprising water and one or more E-caprolactam oligomers to concentration with respect to the one or more E-caprolactam oligomers in at least one concentration stage, obtaining a concentrated stream comprising water and one or more E-caprolactam oligomers;(vi) passing the optionally concentrated stream comprising water and one or more E-caprolactam oligomers into at least one of the depolymerization sub-units UD according to (ii).Preferably, the optionally concentrated stream comprising water and one or more E-caprolactam oligomers according to (vi) further comprises E-caprolactam, i.e. monomeric E-caprolactam.Preferably according to the present invention, the process comprises(iv) subjecting the stream SCPL in UPA to E-caprolactam polymerization conditions, obtaining from UPA a polyamide 6 material MP and a stream SEW comprising water at a concentration CEW(W), E-caprolactam at a concentration CEW(C), and one or more E-caprolactam oligomers at a total concentration CEW(O);(v) subjecting the stream SEW to concentration, comprising(v.1 ) subjecting the stream SEW to concentration in a first concentration unit Uci, obtaining from Uci a concentrated stream Sci comprising water at a concentration Cci(W),E-caprolactam at a concentration Cci(C), and one or more E-caprolactam oligomers at a total concentration cci(O), with Cci(W) < CEW(W), CCI(C) > CEW(C) andCci(O)> CEW(O), and further obtaining from Uci an aqueous stream Swi comprising water at a concentration Cwi(W) > CEW(W);(v.2) subjecting the stream Sci to concentration in a second concentration unit Uc2, obtaining from Uc2 a concentrated stream Sc2 comprising one or more E-caprolactam oligomers at a total concentration cc2(O), with cc2(O) > cci(0), and further obtaining from Uc2 an aqueous stream Sw2 comprising water at a concentration cw2(W) and E-caprolactam at a concentration Cw2(C), with cw2(W) > Cwi(W) and cw2(C) > Cwi(C);(vi) passing the stream Sc2 into the depolymerisation and purification unit UDP.As described above, the stream SEW which is obtained from the polyamide 6 polymerization unit UPA comprises water, monomeric E-caprolactam and one or more E-caprolactam oligomers. Usually, this aqueous stream SEW furher comprises one or more further organic compounds other than monomeric E-caprolactam and one or more E-caprolac- tam oligomers. Therefore, it is preferred that the stream SEW further comprises one or more organic compounds X other thanE-caprolactam and oligomers thereof at a total concentration CEW(X), the process according to (v) comprising(v.1 ) subjecting the stream SEW to concentration in a first concentration unit Uci, obtaining from Uci a concentrated stream Sci comprising water at a concentration Cci(W),E-caprolactam at a concentration Cci(C), one or more E-caprolactam oligomers at a total concentration Cci(O) and one or more organic compounds X at a total concentration cci (X), with Cci(W) < CEW(W), CCI (C) > CEW(C), CCI(O)> CEW(O) and Cci(X)> CEW(X), and further obtaining from Uci an aqueous stream Swi comprising water at a concentration Cwi(W) > CEW(W);(v.2) subjecting the stream Sci to concentration in a second concentration unit Uc2, obtaining from Uc2 a concentrated stream Sc2 comprising one or more E-caprolactam oligomers at a total concentration cc2(O) and one or more organic compounds X at a total concentration Cc2(X), with cc2(O) > Cci(O) and cc2(X) > Cci(X), and further obtaining from Uc2 an aqueous stream Sw2 comprising water at a concentration cw2(W) and E-caprolac- tam at a concentration Cw2(C), with cw2(W) > Cwi(W) and cw2(C) > Cwi(C).Generally, the apparatus or the apparatuses used as concentration unit Uci is or are not subject to any particular design, provided that the inventive concentration of the aqueous stream obtained from UPA, preferably the stream SEW, can be suitably carried out. Preferably, the concentration unit Uci comprises one or more of a vessel with internal, external, or both internal and external heat exchange; and a falling film heat exchanger.Generally, the apparatus or the apparatuses used as concentration unit Uc2 is or are not subject to any particular design, provided that the inventive concentration of the stream Sci which is passed into Uc2 can be suitably carried out. Preferably, the concentration unit Uc2 comprises one or more of a vessel with internal, external, or both internal and external heat exchange; and a thin film evaporator.As far as the polymerization unit UPA is concerned, no specific limitations exist, provided that the aqueous stream, preferably the stream SEW, and the polyamide 6 material MP are suitably obtained. Preferably according to the present invention, the polymerization is carried out as a hydrolytic chain polymerization. Yet further, the polymerization unit UPA preferably further comprises one or more further downstream stages including, but not limited to, one or more of at least one purification stage such as an extraction stage, at least one molding stage such as a granulation stage, and at least one drying stage. Preferably according to the present invention, (iv) comprises(iv.1 ) passing the stream SCPL and preferably an aqueous stream SAQO to a polymerization stage STo, obtaining from STo a polyamide 6 crude product stream SPAI and an aqueous stream SWAI;(iv.2) passing the stream SPAI and preferably an aqueous stream SAQI to a granulation stage ST 1, obtaining from STi a crude granulated polyamide 6 material MPA2 and an aqueous stream SWA2;(iv.3) passing the material MPA2 and preferably an aqueous stream SAQ2 to an extraction stage ST2, obtaining from ST2 a purified granulated polyamide 6 material MPA3 and an aqueous stream SWAS;(iv.4) passing the material MPA3 to a drying stage ST3, obtaining from ST3 the polyamide 6 material MP and an aqueous stream SWA4.Preferably according to the present invention, according to (iv.1 ), one or more suitable additives A are passed to the polymerization stage STo, including, but not restricted to, at least one filler such as titania, zinc oxide, silica, montmorillonite, and multi-walled carbon nanotubes; at least one flame retardant such as zinc borate, magnesium hydroxide, boehmite, and aluminum diethyl phosphinate; at least one reinforcing agent such as glass fiber and carbon fiber; and / or at least one end-capping agent such as amine end-capping agents and carboxyl end-capping agents. Typical amine end-capping agent include at least one monofunctional acid such as adipic acid, acetic acid, propionic acid, benzoic acid, stearic acid and / or terephthalic acid. Typical carboxyl end-capping agent include at least one monofunctional amine such as hexaneamine, cyclohexylamine and benzylamine, and / or at least one oligo- or polyfunctional amine such as triacetone diamine and one or more polyetheramines. It is preferred that at least one organic compound X comprised in the stream SEW is either a non-reacted organic additive A as described above or an organic compound which is obtained during polymerization from one or more additives A and E-caprolactam and / or an E-caprolactam oligomerization or polymerization product.Preferably, the stream SEW comprises at least part of the stream SWA3 and optionally one or more of at least a part of the stream SWAI and at least part of the stream SWA2. Further preferably, the process comprises passing at least a part of the stream SWA4 obtained from drying according to (iv.4) to the extraction stage according to (iv.3).As described above, the concentration carried out in Uci results in the stream Sci which is, compared to the Uci feed stream, preferably the stream SEW, concentrated in E-caprolactam, one or more E-caprolactam oligomers and preferably one or more organic compounds X, and further results in the stream Swi which is, compared to the Uci feed stream, preferably the stream SEW, concentrated in water. In particular regarding the process of the present invention comprising (iv.1 ) to (iv.4) above, it is preferred that the stream Swi obtained from Uci according to (v.1) is passed back to the polyamide 6 production unit UPA. More preferably, the stream Swi is passed back to UPA as at least part of one or more of the streams SAQO, SAQI and SAQ2.Regarding the depolymerization and purification unit UDP, there are no specific restrictions how the depolymerization and the downstream purification of the crude E-caprolactam stream obtained from said depolymerization is carried out, provided that from UDP, an E-caprolactam stream SCPL is obtained which fulfills the specifications necessary to be subjected to polyamide 6 polymerization conditions in UPA. With regard to the depolymerization carried out in the depolymerization sub-unit UD, it is preferred that it is a hydrolytic depolymerization, wherein more preferably, no polyamide 6 depolymerization catalyst such as a mineral acid and / or a zinc salt such as zinc chloride, zinc acetate or zinc triflate is used for said depolymerisation.Preferably, the depolymerisation and purification unit UDP comprises, downstream of the at least one depolymerization sub-unit UD, a water separation sub-unit UP2 for separating water fromE-caprolactam. In this case, it is preferred that the process further comprises passing the stream Sw2 obtained from Uc2 according to (v.2) to UP2.Preferably, the depolymerisation and purification unit UDP comprises, upstream of the at least one depolymerization sub-unit UD, a melting and mixing sub-unit UM. In this case, it is preferred that the process further comprises passing the stream Sc2 to the sub-unit UM and further comprises passing the stream SMR to the sub-unit UM, obtaining from UM a stream which passed to UD.According to the present invention, the depolymerisation and purification unit UDP preferably comprises a mixing and melting sub-unit UM where an aqueous depolymerisation mixture is prepared which is passed to the depolymerisation sub-unit UD. Preferably, preparing the aqueous depolymerization mixture in UM comprises melting in a melting subunit the solid material MR, obtaining a liquid stream and admixing in a pre-reaction sub-unit said liquid stream with an aqueous stream, thus obtaining a liquid stream and feeding this liquid stream as depolymerization mixture into the sub-unit UD. The pre-reaction sub-unit preferably comprises, more preferably consists of, a mixing unit, preferably a static mixing unit, and the melting sub-unit comprises, preferably consists of an extruder, preferably a single-screw extruder or a twin-screw extruder.Generally, it cannot be ruled out that some of the polyamide 6 material obtained from UPA does not meet the desired specification. For such a scenario, the process of the present invention allows for advantageously recycling such material, referred to herein as material MPR to the unit UDP. Therefore, it is preferred that if some of the polyamide 6 material MP obtained from the production unit UPA does not meet the specifications, the process further comprises passing at least some of said material MPR to the depolymerisation and purification unit UDP for depolymerization, more preferably passing at least some of said material MPR to the mixing and melting sub-unit UM. These specifications of MP preferably include, for example for the use of producing textile fibers, in particular suitable for high speed spinning methods, one or more of the relative viscosity, for example determined according to ISO 307; by way of example, typical values for in- spec materials MP are in the range of from 2.4 to 2.5; the moisture content, for example determined according to ISO 15512; by way of example, typical values for in- spec materials MP are at most 0.1 % (m / m); the content of hot water extractable compounds, for example determined according to ISO 6427; by way of example, typical values for in-spec materials MP are at most 0.6 % (m / m); the viscosity number, for example determined according to ISO 307 via the Huggins method; by way of example, typical values for in-spec materials MP are in the range of from 120 to 150 ml / g; the color number such as the APHA value, for example determined according to ISO 8112; by way of example, typical values for in-spec materials MP are at most 5; the melting point, for example determined according to ISO 3146; by way of example, typical values for in- spec materials MP are at about 220 °C; the density, for example determined according to ISO 1183; by way of example, typical values for in-spec materials MP are in the range of from 1 .1 to 1 .2 g / cm3; the specific chip number; by way of example, typical values for in-spec materials MP are at about 80 counts / g; the bulk density; by way of example, typical values for in-spec materials MP are in the range of from 650 tom 800 kg / m3; the pellet size; by way of example, typical values for in-spec materials MP are in the range of from 2.0 to 2.5 mm; the pellet shape; by way of example, a typical shape is a cylindrical form; the water absorption, for example determined analogously to ISO 62; by way of example, typical values for in- spec materials MP are in the range of from 8 to 9 %; the humidity absorption, for example determined analogously to ISO 62; by way of example, typical values for in-spec materials MP are in the range of from 2 to 3 %; the titania content; depending on the specific use of the material MP, typical values for in-spec materials MP are either in the range of from 0 to 0.05 weight-% (for example for producing bright textile fibers) or in the range of from 0.2 to 0.4 weight-% (for example for producing semi dull textile fibers) or in the range of from 1 to 2 weight-% (for example for producing full dull textile fibers);the content of amino end groups; typical values for in-spec materials MP are in the range of from 40 to 47 mmol / kg.Depending on the specific further use of the material MP, one of said specifications deviating from a pre-determined value or range may be sufficient to qualify the respective material as an off-spec material MPR. Further, also depending on the specific further use of the material MP, one or more of said specifications deviating from a pre-determined value or range may not be detrimental as long as one or more other specifications meet a pre-determined value or are in a pre-determined range; thus, although one or more of said specifications deviate from a pre-determined value or range, the respective material MP can be an in-spec material nevertheless.Further regarding the unit UDP, it is preferred that it comprises, downstream of UD and upstream of UP2, a first purification sub-unit UPI, and downstream of UP2, a third purification stage UP3. In this case, it is preferred that the process further comprises passing the E-caprolactam stream obtained from UD to UPI, obtaining from UPI an E-caprolactam stream which is passed to UP2, obtaining from UP2 an E-caprolactam stream which is passed to UP3, obtaining from UP3 the stream SCPL.As far as the solid material MR is concerned, it is preferred that it comprises, more preferably consists of, 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 MR consist of the polyamide; or preferably from 10 to 100 weight-%, more preferably from 30 to 100 weight-%, more preferably from 50 to 100 weight-%, more preferably from 80 to 100 weight-%, of MR consist of the polyamide. If the polyamide 6 content of the solid material MR is less than 100 weight-%, it may be preferred that the solid material MR additionally comprises one or more elastanes. Generally, the solid material MR may comprise, in addition to polyamide 6, at least one further polymeric compound, wherein the at least one further polymeric compound preferably comprises one or more of at least one polyamide 6.6; at least one polyethylene terephthalate; at least one polyurethane; at least one polyester; at least one polyether; at least one polyvinyl chloride; at least 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 unit UDP, the collected textile 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 metalremoving 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 MR can be provided according to any suitable method. Preferably according to the present invention, providing the solid material M comprises providing the solid material MR in a delivering unit which preferably comprises one or more of at least one big bag station and at least one a bulk container station; passing the provided solid material MR via a first connecting line 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 MR from the material collecting unit via a second connecting line to the unit UM, 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. Preferably, the solid material MR is 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 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 value of 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 value of the particle length in the range of from 0.8 to 30 mm.As far as the hydrolytic depolymerization in the sub-unit UD is concerned, it is preferred that the depolymerization pressure PD is 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 the depolymerisation temperature TD is in the range of from 230 to 335 °C, more preferably in the range of from 250 to 320 °C, more preferably in the range of from 270 to 310 °C. Preferably, the unit UD comprises z chemical reactors R, 1=1 ...z, wherein z is in the range of from 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. If z > 1 , is preferred that at least 2 reactors R, more preferably all z reactors R, are serially coupled, wherein in every reactor R, a depolymerization temperature TDI at a depolymerization pressure PDI is maintained, wherein, independently of each other, TDI is in the range of from 230 to 330 °C and PDI is in the range of from 40 to 140 bar, preferably wherein TDI is in the range of from 250 to 320 °C and PDI is in the range of from 40 to 125 bar, more preferably wherein TDI is in the range of from 270 to 310 °C and PDI is in the range of from 40 to 110 bar. For z > 1, it is preferred that the z reactors R are vertically arranged, with Ri being the top-most reactor and Rzbeing the bottom-most reactor, wherein Si obtained from R is transferred to +i by gravity, preferably by gravity only. More preferably, at least 1, preferably all z reactors R, are continuous stirred tank reactors (CSTR). Preferably, every continuous stirred tank reactor R 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 R; comprises at least one agitator, wherein more preferably every compartment of every reactor R comprises at least one agitator, wherein more preferably, every compartment of every reactor R 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 to of the aqueous depolymerization mixture in the sub-unit UD, preferably in the z reactors R, more preferably in the z continuous stirred tank reactors, wherein at least 85 weight-%, preferably at least 90 weight-%, more preferably at least 95 weight-% of the aqueous depolymerization mixture have a to in the range of from 30 to 90 min. More preferably, the residence time of an aqueous depolymerization mixture in a reactor R is toi and 0.90 < (toi I bi+i) 1 .10, more preferably 0.95 < (toi I bi+i) < 1.05.Preferably according to the present invention, the purification sub-unit URI comprises a water separation sub-unit Uws and, downstream thereof, a high boiler separation sub-unit Ui. In the sub-unit UWS, at least part of the water comprised in the aqueous stream obtained from the sub-unit UD is separated off. The resulting crude E-caprolactam stream is then passed to the high boiler separation unit Ui where one or more impurities are separated off; said impurities preferably comprise at least one organic compound having a higher boiling point than E-caprolactam. With regard to the specific apparatus design of the sub-unit Uws, it is preferred that it comprises one or more of a falling film evaporator, a flash tank, a forced circulation evaporator, and a distillation column, more preferably one or more of a falling film evaporator and a flash tank, more preferably a falling film evaporator and a flash tank. As far as the high boiler separation unit Ui is concerned, no specific restrictions exist provided that in said unit Ui, compounds can be at least partially separated which have a higher boiling point than E-caprolactam. It was found that the waste material which are most preferably used as the solid material MR will contain certain compounds which, either prior to or after depolymerization of polyamide 6 in the sub-unit UD lead to a stream comprising E-caprolactam and compounds having a higher boiling point than E-caprolactam. Due to possibly different chemical compositions of said waste material, however, these compounds having a higher boiling point than E-caprolactam will usually differ from time to time, both with regard to the content in the stream to be purified and in chemical nature. Preferably, the sub-unit Ui comprises an evaporation sub-unit arranged upstream of a further separation unit, wherein more preferably, the evaporation unit comprises a stirred reactor, more preferably a stirred tank reactor, more preferably a continuous stirred tank reactor, and the further separation unit comprises, more preferably consists of, a droplet separator, preferably selected from the group consisting of a hydrocyclone, a demister plate, and an absorption tower, more preferably a hydrocyclone.As far as the purification sub-unit UP2 is concerned, it is preferred that it is a water separation which, more preferably, comprises one or more of a falling film evaporator, a flash tank and a distillation column, more preferably a distillation column.Preferably, the purification sub-unit UP3 comprises one or more of a distillation sub-unit UDI and a crystallization subunit UCR, more preferably comprises a distillation sub-unit UDI and a crystallization sub-unit UCR, wherein the stream SCPL is preferably obtained from the crystallization sub-unit UCR which is preferably arranged downstream of the distillation sub-unit UDI. Regarding the sub-unit UDI, it is preferred that it comprises at least one distillation column, preferably two or three distillation columns, more preferably two or three serially coupled distillation columns. The respectively obtained stream which is obtained from UDI is passed to the crystallization sub-unit UCR from which the finally purified stream SCPL is obtained.Depending on, for example, the individual operating hours of the unit UDP on the one hand and the unit UPA on the other hand, it is possible that for different operating hours, either the stream Sci and / or the stream SCPL is or are passed, prior to being passed to the respective unit, to a suitable buffer unit. Therefore, for such cases, it is preferred that downstream of Uci and upstream of Uc2, the stream Sci is passed to a buffer unit UBCI and downstream of UDP and upstream of UPA, the stream SCPL is passed to a buffer unit UBCPL.From a general point of view, the process of the present invention represents the core of the polyamide 6 production and recycling loop. Therefore, the process of the present invention preferably further comprises providing the material MP obtained from UPA as a feedstock to a polyamide containing material producing unit UTP, from which unit UTP a polyamide containing material MT is obtained which is brought onto the market, wherein, after a life-time TMT of said material MT, it is at least partially collected as waste material and passed to UDP as at least part of SMR, wherein the material MT is preferably one or more of a textile material and an engineering plastics material, preferably a textile material.Yet further, the present invention also relates to an integrated polyamide 6 plant for carrying out the process of the present invention as described herein, wherein the integrated polyamide 6 plant comprises a depolymerization and purification unit UDP and a polyamide 6 production unit UPA, a transportation line LCPL for passing a purified E-capro- lactam from UDP to UPA and at least transportation line Ls for passing an aqueous recycle stream from UPA to UDP.Preferably, the transportation line Ls comprises two concentration units Uci and Uc2, wherein Uci is arranged downstream of UPA and Uc2 is arranged downstream of Uci and upstream of UDP. Further preferably, said integrated polyamide 6 plant further comprises a transportation line Lwi from Uci to UPA for passing an aqueous stream Swi obtained from Uci to UPA. Preferably, downstream of Uc2, the transportation line Ls comprises at least two sub-lines Lw2 and Lc2 for passing an aqueous stream Sw2 obtained from Uc2 to UDP via Lws2 and for passing a concentrated stream Sc2 from Uc2 to UDP via Lc2. Regarding the transportation line LCPL, it is preferred that it comprises a buffer unit UBCPL and the transportation line Ls comprises a buffer unit UBCI, wherein UBCI is preferably arranged downstream of Uci and upstream of Uc2. Further preferably, the integrated polyamide 6 plant further comprises a transportation line LMPR for passing a polyamide material MPR obtained from UPA to UDP.According to a further aspect, the present invention relates to a process, preferably to the process as described above, which comprises the step of converting the polyamide 6 material MP obtainable or obtained by the process as described herein or the material MPR obtainable or obtained by the process as described herein or the stream SMR obtainable or obtained by the process as described herein or a chemical material obtainable by or obtained by the process as described herein to obtain a product Q. Yet further, the present invention relates to a process comprising the step of using the integrated polyamide 6 plant as described herein to obtain a polyamide 6 material MP; and preferably converting the polyamide 6 material MP to obtain a product Q.Preferably, the product Q 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 cleaning polymer, cleaning surfactant, descaling compound, cleaning biocide or composition 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 polymer 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 or composition or formulation 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 Q, is obtained, it is preferred: that the content of MP and / or MPR and / or SMR and / or the chemical material in the product Q is 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight-% or more, more preferably 15 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 60 weight-% or more, more preferably 80 weight-% or more, more preferably 90 weight-% or more, more preferably 95 weight-% or more; and / or that the content of MP and / or MPR and / or SMR and / or the chemical material in the product Q is 100 weight-% or less, preferably 95 weight-% or less, more preferably 90 weight-% or less, more preferably 50 weight-% or less, more preferably 25 weight-% or less, more preferably 10 weight-% or less; and preferably wherein the content is determined based on identity preservation and / or segregation and / or mass balance and / or book and claim chain of custody models, preferably based on mass balance, preferably the International Sustainability and Carbon Certification (ISCC) standard.The publication Prior Art Disclosure; Issue 684; paragraphs

[1000] to

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

[1000] to

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

[1000] to

[8005] ,The term "building block”, as used in the context of the product Q 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 dioxid, 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 Q 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 Q herein, comprises organic reagents, which are applied for formation of compounds with higher molecular complexity. The intermediate compound can be selected for example from the group consisting of phosgene, polyisocyanates and propylene oxide. The polyisocyanates are in particular aromatic di- and polyisocyanates, preferably toluene diisocyanate (TDI) and / or diphenylmethane diisocyanate (MDI).The building block and the monomer and typical converting step(s) to obtain the building block or monomer are described in more detail in paragraphs

[1000] to

[1012] of Reference RF1.The term "polymer A”, as used in the context of the product Q 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 Q 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 Q 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 Q 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 Q 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 Q 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 Q 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 Q 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 Q 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 Q herein, typically relates to a composition comprising an agrochemically active ingredient and at least one agrochemical formulation auxiliary. Examples of agrochemical compositions, active ingredients and auxiliaries are described in more detail in Reference RF1, paragraph

[4001] , The agrochemical composition may take the form of any customary formulation. The agrochemical compositions are prepared in a known manner, e.g. described by Mollet and Grubemann, Formulation technology, Wiley VCH, Weinheim, 2001; or Knowles, New developments in crop protection product formulation, Agrow Reports DS243, T&F Informa, London, 2005. The converting step(s) to obtain the agrochemically active ingredients and auxiliaries may be conducted in analogy to the production step(s) of their analogues that are based on petrochemicals or other precursors that are not gained by recycling processes. In addition, conversion to compounds mentioned in sections "Polymer” and "Cosmetic surfactant, emollient, wax, 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 Q 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 Q 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 Q 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 or polyvinylimidazole / polyvinylpyr- rolidone-copolymer. Animal feed additives, human food additives and dietary supplements are defined in more detailin 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 Q 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 defined in more detail in paragraph

[5003] of Reference RF1 . The converting step(s) to obtain the aroma chemical and aroma composition may comprise one or more synthesis steps and can be performed by conventional synthesis and techniques well known to a person skilled in the art.The term "aqueous polymer dispersion”, as used in the context of the product Q herein, comprises aqueous compositions) 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 composite particles, 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 Q 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 polyure- thane(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 Q 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 in coating compositions” section

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

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

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

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

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

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

[6012] entitled "Preparation of organic solvent based hyperbranched polyester polyols” of Reference RF1 . Coating compositions) 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®, solvent-based coating composition(s) comprising said unsaturated polyester polyol 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 Q herein, comprises preferably in particular hydraulically setting compositions and compositions comprising calcium sulfate and is defined in more detail in section

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

[6021] of Reference RF1.The term "cosmetic surfactant”, as used in the context of the product Q 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 Q 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 Q 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 Q 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 Q 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 Q herein, comprises any ingredient suitable for making a cosmetic formulation. Several sources disclose cosmetically acceptable ingredients. E. g. the database Cosing on the internet pages of the European Commission discloses cosmetic ingredients and the International Cosmetic Ingredient Dictionary and Handbook, edited by the Personal Care Products Council (PCPC), discloses cosmetic ingredients. The term "composition and / or formulation thereof' with reference to the cosmetic surfactant, emollient, wax, cosmetic polymer, UV filter and / or further cosmetic ingredient refers to personal care and / or cosmetic compositions or formulations defined in more detail in paragraph

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

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

[8000] to

[8005] of Reference RF1.The present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated. In particular, it is noted that in each instance where a range of embodiments is mentioned, for example in the context of a term such as "The process of any one of embodiments 1 to 4", every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to "The process of any one of embodiments 1, 2, 3 and 4". Further, it is explicitly noted that the following set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.1 . An integrated process for preparing polyamide 6, comprising(i) providing a stream SMR comprising a solid material MR comprising polyamide 6, wherein the solid material MR comprises a waste material;(ii) preparing from the stream SMR in a depolymerisation and purification unit UDP a stream SCPL comprising purified E-caprolactam, the unit UDP comprising at least one depolymerization sub-unit UD;(ill) passing the stream SCPL to a polyamide 6 production unit UPA;(iv) subjecting the stream SCPL in UPA to E-caprolactam polymerization conditions, obtaining from UPA a polyamide 6 material MP and a stream comprising water and one or more E-caprolactam oligomers;(v) optionally subjecting to stream comprising water and one or more E-caprolactam oligomers to concentration with respect to the one or more E-caprolactam oligomers in at least one concentration stage, obtaining a concentrated stream comprising water and one or more E-caprolactam oligomers;(vi) passing the optionally concentrated stream comprising water and one or more E-caprolactam oligomers into at least one of the depolymerization sub-units UD according to (ii).2. The process of embodiment 1 , wherein the optionally concentrated stream comprising water and one or more E-caprolactam oligomers further comprises E-caprolactam.3. The process of embodiment 2, wherein the process comprises(iv) subjecting the stream SCPL in UPA to E-caprolactam polymerization conditions, obtaining from UPA a polyamide 6 material MP and a stream SEW comprising water at a concentration CEW(W), E-caprolactam at a concentration CEW(C), and one or moreE-caprolactam oligomers at a total concentration CEW(O);(v) subjecting the stream SEW to concentration, comprising(v.1 ) subjecting the stream SEW to concentration in a first concentration unit Ud, obtaining from Uci a concentrated stream Sci comprising water at a concentration Cci(W), E-caprolactam at a concentration cci (C), and one or more E-caprolactam oligomers at a total concentration cci (0), with Cci(W) < CEW(W),CCI (C) > CEW(C) and Cci(0)> CEW(O), and further obtaining from Uci an aqueous stream Swi comprising water at a concentration Cwi(W) > CEW(W);(v.2) subjecting the stream Sci to concentration in a second concentration unit Uc2, obtaining from Uc2 a concentrated stream Sc2 comprising one or more E-caprolactam oligomers at a total concentration Cc2(0), with CC2(O) > cci (0), and further obtaining from Uc2 an aqueous stream Sw2 comprising water at a concentration cw2(W) and E-caprolactam at a concentration Cw2(C), with Cw2(W) > Cwi(W) and Cw2(C) > Cwi(C);(vi) passing the stream Sc2 into the depolymerisation and purification unit UDP.4. The process of embodiment 3, wherein the stream SEW further comprises one or more organic compounds X other than E-caprolactam and oligomers thereof at a total concentration CEW(X), the process comprising(v.1 ) subjecting the stream SEW to concentration in a first concentration unit Uci, obtaining from Uci a concentrated stream Sci comprising water at a concentration Cci(W),E-caprolactam at a concentration Cci(C), one or more E-caprolactam oligomers at a total concentration Cci(O) and one or more organic compounds X at a total concentration cci (X), with Cci(W) < CEW(W), CCI(C) > CEW(C), CCI(O)> CEW(O) and cci(X)> CEW(X), and further obtaining from Uci an aqueous stream Swi comprising water at a concentration Cwi(W) > CEW(W);(v.2) subjecting the stream Sci to concentration in a second concentration unit Uc2, obtaining from Uc2 a concentrated stream Sc2 comprising one or more E-caprolactam oligomers at a total concentration cc2(O) and one or more organic compounds X at a total concentration cc2(X), with cc2(O) > Cci(O) and cc2(X) > cci (X), and further obtaining from Uc2 an aqueous stream Sw2 comprising water at a concentration cw2(W) and E-caprolactam at a concentration Cw2(C), with cw2(W) > Cwi(W) and OW2(C) > Cwi(C).5. The process of embodiment 3 or 4, wherein the concentration unit Uci comprises one or more of a vessel with internal, external, or both internal and external heat exchange; and a falling film heat exchanger.6. The process of any one of embodiments 3 to 5, wherein the concentration unit Uc2 comprises one or more of a vessel with internal, external, or both internal and external heat exchange; and a thin film evaporator.7. The process of any one of embodiments 3 to 6, wherein (iv) comprises(iv.1 ) passing the stream SCPL and preferably an aqueous stream SAQO to a polymerization stage STo, obtaining from STo a polyamide 6 crude product stream SPAI and an aqueous stream SWAI;(iv.2) passing the stream SPAI and preferably an aqueous stream SAQI to a granulation stage ST 1, obtaining from STi a crude granulated polyamide 6 material MPA2 and an aqueous stream SWA2;(iv.3) passing the material MPA2 and preferably an aqueous stream SAQ2 to an extraction stage ST2, obtaining from ST2 a purified granulated polyamide 6 material MPA3 and an aqueous stream SWAS;(iv.4) passing the material MPA3 to a drying stage ST3, obtaining from ST3 the polyamide 6 material MP and an aqueous stream SWA wherein the stream SEW comprises at least part of the stream SWA3 and optionally one or more of at least a part of the stream SWAI and at least part of the stream SWA2; wherein the process preferably further comprises passing at least a part of the stream SWA4 obtained from drying according to (iv.4) to the extraction stage according to (iv.3).8. The process of embodiment 7, further comprising passing the stream SWAI obtained from Uci according to (v.1) back to the polyamide 6 production unit UPA.9. The process of embodiment 8, wherein the stream Swi is passed back to UPA as at least part of one or more of the streams SAQO, SAQI and SAQ2.10. The process of any one of embodiments 3 to 9, wherein the depolymerisation and purification unit UDP comprises, downstream of the at least one depolymerization sub-unit UD, a water separation sub-unit UP2 for separating water from E-caprolactam, the process further comprising passing the stream Sw2 obtained from Uc2 according to (v.2) to UP2.11 . The process of any one of embodiments 3 to 10, wherein the depolymerisation and purification unit UDP comprises, upstream of the at least one depolymerization sub-unit UD, a melting and mixing sub-unit UM, wherein the process further comprises passing the stream Sc2 to the sub-unit UM and further comprises passing the stream SMR to the sub-unit UM, obtaining from UM a stream which passed to UD.12. The process of any one of embodiments 3 to 11, wherein some of the polyamide 6 material obtained from the production unit UPA does not meet the specifications, the process further comprising passing at least some of said material to the depolymerisation and purification unit UDP for depolymerization, preferably passing at least some of said material to UM.13. The process of any one of embodiments 3 to 12, wherein the depolymerisation and purification unit UDP comprises, downstream of UD and upstream of UP2, a first purification sub-unit UPI, and downstream of UP2, a third purification stage UP3, wherein the process further comprising passing the stream obtained from UD to UPI, obtaining from UPI a stream which is passed to UP2, obtaining from UP2 the stream which is passed to UP3, obtaining from UP3 the stream SCPL.14. The process of any one of embodiments 3 to 13, wherein downstream of Uci and upstream of Uc2, the stream Sci is passed to a buffer unit UBCI and downstream of UDP and upstream of UPA, the stream SCPL is passed to a buffer unit UBCPL.15. The process of any one of embodiments 3 to 14, further comprising providing the material MP obtained from UPA as a feedstock to a polyamide containing material producing unit UTP, from which unit UTP a polyamide containing material MT is obtained which is brought onto the market, wherein, after a life-time TMT of said material MT, it is at least partially collected as waste material and passed to UDP as at least part of SMR, wherein the material MT is preferably one or more of a textile material and an engineering plastics material, preferably a textile material.16. An integrated polyamide 6 plant for carrying out the process according to any one of embodiments 1 to 15, the integrated polyamide 6 plant comprising a depolymerization and purification unit UDP and a polyamide 6 production unit UPA, a transportation line LCPL for passing a purified E-caprolactam from UDP to UPA and at least transportation line Ls for passing an aqueous recycle stream from UPA to UDP.17. The integrated polyamide 6 plant of embodiment 16, wherein the transportation line Ls comprises two concentration units Uci and Uc2, wherein Uci is arranged downstream of UPA and Uc2 is arranged downstream of Uci and upstream of UDP.18. The integrated polyamide 6 plant of embodiment 17, further comprising a transportation line Lwi from Uci to UPA for passing an aqueous stream Swi obtained from Uci to UPA.19. The integrated polyamide 6 plant of embodiment 17 or 18, wherein downstream of Uc2, the transportation line Ls comprises at least two sub-lines Lw2 and Lc2 for passing an aqueous stream Sw2 obtained from Uc2 to UDP via LWS2 and for passing a concentrated stream Sc2 from Uc2 to UDP via Lc2.20. The integrated polyamide 6 plant of any one of embodiments 17 to 19, wherein the transportation line LCPL comprises a buffer unit UBCPL and the transportation line Ls comprises a buffer unit UBCI, wherein UBCI is preferably arranged downstream of Uci and upstream of Uc2.21. The integrated polyamide 6 plant of any one of embodiments 16 to 20, further comprising a transportation line LMPR for passing a polyamide material MPR obtained from UPA to UDP.22. A process, preferably according to any one of embodiments 1 to 15, comprising the step of converting the polyamide 6 material MP obtainable or obtained by the process according to any one of embodiments 1 to 15 or the material MPR obtainable or obtained by the process according to embodiment 12 or the stream SMR obtainable or obtained by the process according to embodiment 15 or a chemical material obtainable by or obtained by the process according to any one of embodiments 1 to 15 to obtain a product Q.23. A process comprising the step of using the integrated polyamide 6 plant according to any one of embodiments 16 to 21 to obtain a polyamide 6 material MP; and preferably converting the polyamide 6 material MP to obtain a product Q.24. The process of embodiment 22 or 23, wherein the product Q 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; orcleaning polymer, cleaning surfactant, descaling compound, cleaning biocide or composition 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 polymer 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 or composition or formulation thereof; or polymer B, polymer composition B, coating composition, other functional composition, foil, molded body, coating or coated substrate.25. The process of any one of embodiments 22 to 24, wherein the content of MP and / or MPR and / or SMR and / or the chemical material in the product Q is 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight-% or more, more preferably 15 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 60 weight-% or more, more preferably 80 weight-% or more, more preferably 90 weight-% or more, more preferably 95 weight-% or more; and / or wherein the content of MP and / or MPR and / or SMR and / or the chemical material in the product Q is 100 weight- % or less, preferably 95 weight-% or less, more preferably 90 weight-% or less, more preferably 50 weight-% or less, more preferably 25 weight-% or less, more preferably 10 weight-% or less; and preferably wherein the 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.According to the present invention, the term "one or more E-caprolactam oligomers” and the term "at least one s-ca- prolactam oligomer” preferably refer to at least one of E-caprolactam dimer, E-caprolactam trimer, E-caprolactam tetramer, E-caprolactam pentamer, E-caprolactam hexamer and E-caprolactam heptamer.The term "textile material” 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” covers atextile 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 in the context of the product Q 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 in the 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 in the context of the product Q 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.Short description of the figuresList of abbreviationsUDP Depolymerization and purification unit, for depolymerizing and purifying E-caprolactamUD Depolymerization sub-unit, comprised in UDPUPA Polyamide 6 production unit, for polymerizing polyamide 6 from E-caprolactamUci Concentration unit downstream of UPA and upstream of Uc2Uc2 Concentration unit downstream of Uci and upstream of UDPUBCI Buffer unit for temporarily storing SciUBCPL Buffer unit for temporarily storing SCPLUM Melting and mixing sub-unit comprised in UDP upstream of UDUPI E-caprolactam purification sub-unit comprised in UDP downstream of UD and upstream of UP2UP2 Water separation sub-unit for separating water from E-caprolactam, comprised in UDPUP3 E-caprolactam purification sub-unit comprised in UDP downstream of UD. SCPL is obtained from UP3UTP Polyamide 6 containing material MT producing unit, downstream of UPASMR Stream comprising a solid material MRSCPL Stream comprising purified E-caprolactam, obtained from UDPS Stream comprising water and one or more E-caprolactam oligomers, obtained from UPASEW Stream comprising water, E-caprolactam, one or more E-caprolactam oligomers and optionally one or more organic compounds X other than E-caprolactam and oligomers thereof, obtained from UPASCI Concentrated stream comprising water and one or more E-caprolactam oligomers, obtained from Uci based on SEWSc2 Concentrated stream comprising water and one or more E-caprolactam oligomers, obtained from Uc2 based on SciSwi Aqueous stream, obtained from Uci in addition to SciSw2 Aqueous stream, obtained from Uc2 in addition to Sc2SPAI Crude E-caprolactam product stream, obtained from stage SToSPA2 Crude E-caprolactam product stream, obtained from stage ST 1SPA3 Crude E-caprolactam product stream, obtained from stage ST2SWAI Aqueous stream, obtained from stage STo, optionally part of SEWSWA2 Aqueous stream, obtained from stage ST 1, optionally part of SEWSWA3 Aqueous stream, obtained from stage ST2, preferably at least part of SEWSWA4 Aqueous stream, obtained from stage ST3, preferably passed back to stage ST2SAQO Aqueous stream, derived from Swi, to be passed into stage SToSAQI Aqueous stream, derived from Swi, to be passed into stage ST1SAQ2 Aqueous stream, derived from Swi, to be passed into stage ST2SWM Make-up water stream, to be passed into UMSWR Uop-internal water recycle stream(s), obtained from purification stages, recycled to UM SCPLO E-caprolactam feed stream to UPA from sources other than UDPSTo E-caprolactam polymerization stage, carried out in UPAST1 E-caprolactam granulation stage, carried out in UPA downstream of SToST2 E-caprolactam extraction stage, carried out in UPA downstream of ST 1ST3 E-caprolactam drying stage, carried out in UPA downstream of ST1. From ST3, MP is preferably obtainedMR Solid material comprising polyamide 6, comprised in stream SMRMP Polyamide 6 material, obtained from UPAMPR off-spec polyamide 6 material, obtained from UPAMT Polyamide 6 containing material, obtained from UTPTMT Lifetime of polyamide 6 containing material MTFigure 1 shows a process according to present invention. According to this process, a stream SMR comprising a solid material MR which in turn comprises polyamide 6 is passed into a depolymerisation and purification unit UDP which comprises a depolymerisation sub-unit UD. Preferably, the solid material comprises a waste material, preferably one or more of a textile waste material and an engineering plastics waste material, more preferably a textile waste material. Upstream of UD, SMR may be passed to further one or more suitable pre-treatment stages, indicated by the dotted arrow. In UD, depolymerization of the polyamide 6 comprised in the material MR takes place, and a respective stream is obtained from UD which is then further passed through UDP (as indicate by the dotted arrow), resulting in a purified E-caprolactam stream SCPL which is passed as an educt stream to a polyamide 6 production unitUPA where E-caprolactam comprised in SCPL is suitably polymerized to obtain a polyamide 6 material MP which is removed from UPA. Further from the UPA, a stream S is obtained which comprises at least water and one or more s-ca- prolactam oligomers. This stream S is suitably passed back to the depolymerization and purification unit UDP, thus realizing an integrated depolymerization-polymerization process.Figure 2 shows a process according to present invention. Further according to the process as shown in Figure 1, this process comprises two concentration stages carried out in the concentration units Uci and Uc2. A stream SEW,1,e. a stream comprising at least water and one or more E-caprolactam oligomers, is obtained from UPA (cf the stream S according to Figure 1) and passed to the concentration unit Uci where it is concentrated at least with respect to one or more E-caprolactam oligomers to give the (concentrated) stream Sci, wherein during centration in Uci , water is separated and obtained as aqueous stream Swi. The stream Sci is then passed to the concentration unit Uc2 where it is further concentration, at least with respect to one or more E-caprolactam oligomers, to give the respectively concentrated stream Sc2. During centration in Uc2, water is separated and obtained as aqueous stream Sw2. The concentrated stream Sc2 is suitably passed back to the depolymerization and purification unit UDP, thus realizing an integrated depolymerization-polymerization process.Figure 3 shows a process according to present invention. Further according to the process as shown in Figure2, this process illustrates two further preferred integration methods. First, the aqueous stream Swi which is obtained from the concentration unit Uci is suitably passed back to UPA as educt stream in one or more stages carried out in UPA. Second, the aqueous stream Swi which is obtained from the concentration unit Uci is suitably passed as educt stream to a purification unit UP2, namely a water separation sub-unit comprised in UDP which serves for separating water from a crude E-caprolactam stream and which is located downstream of the de-polymerization sub-unit UD.Figure 4 shows a process according to present invention. Further according to the process as shown in Figure3, this process illustrates a preferred setup of the polyamide 6 production unit UPA. According to this preferred design, the purified E-caprolactam stream SCPL which is obtained from the depolymerization and purification unit UDP is passed to an E-caprolactam polymerization stage STo in UPA. The polyamide 6 containing product stream SPAI is then suitably passed to an E-caprolactam granulation stage STI ■ The respectively obtained granules stream SPA2 is then suitably passed to an E-caprolactam extraction stage ST2 for polyamide 6 purification purposes. The respectively obtained purified granules stream SPAS is then suitably passed to an E-caprolactam drying stage STS comprising one or more suitably drying sub-stages, from which drying the polyamide 6 material MP is obtained. From at least one of the stages STo, ST 1 and ST2, preferably from at least two of these stages, more preferably from each of these stages, a respective aqueous stream (SWAI, SWA2, SWAS) is obtained. At least the stream SWA3 is, at least partially, removed from UPA as the stream SEW, optionally (as indicated by the dotted arrows) together with at least a part of SWAI and / or SWA2. Yet further, the aqueous stream Swi which is obtained from concentrating the stream SEW in Uci is passed back as one or more educt steams to UPA, wherein a first part may be passed into stage STO, a second part may be passed into stage STI, and a third part may be passed into stage STS. Still further preferred a process design according towhich an aqueous stream SWA4 is obtained from the drying stage STS, wherein this aqueous stream SWA4 is passed back to the extraction stage ST2.Figure 5 shows a process according to present invention. Further according to the process as shown in Figure 3 and Figure 4 (the preferred design of UPA is not shown in Figure 5), this process illustrates a further preferred design according to which two buffer units are present, one for suitably buffering the supply of the stream SCPL from UDP to UPA (the buffer unit UBCPL), one for suitably buffering the supply of the stream Sci from the concentration unit Uci to the concentration unit Uc2 (the buffer unit UBCI).Figure 6 shows a process according to present invention. Further according to the process as shown in Figure 3, Figure 4 (the preferred design of UPA is not shown in Figure 6) and Figure 5, a preferred setup of the depolymerisation and purification unit UDP is shown. According to this setup, the stream SMR and the stream Sc2 concentrated at least with respect to one or moreE-caprolactam oligomers are both suitably passed into a melting and mixing sub-unit UM where the educt stream for the downstream, preferably hydrolytic, depolymerization sub-unit UD is suitably prepared. Downstream of UD, a first purification sub-unit UPI is installed which preferably comprises at least one or more of a water separation stage and a high boiler separation stage (organic compounds having a higher boiling point than E-caprolactam). From UPI, the respectively purified E-caprolactam stream is passed to the second purification sub-unit UP2 into which, as described in the context of Figure 3, also the aqueous stream SW2 is passed which preferably comprises, in addition to water, (non-polymerized) E-caprolactam which was comprised in the stream SEW, separated from SEW in Uci and comprised and Sci, and further separated from Sci in Uc2. From said second purification sub-unit UP2, the obtained crude s-ca- prolactam is then passed to a third purification sub-unit UP3 which preferably comprises one or more of a distillation stage and a crystallization stage, wherein from UP3, the purified stream SCPL is obtained which is then passed to UPA.Figure 7 shows a process according to present invention. Further according to the process as shown in Figure 6, this process includes a recycle line for polyamide 6 materials MPR which are obtained from UPA and which are not subject to further processing into a further valuable product, for example due to not meeting one or more desired specifications. According to the integrated process of the present invention, such a material MPR is passed back to UDP, preferably to the mixing and melting sub-unit UM where it is suitably made part of the educt stream which is passed to the depolymerisation sub-unit UD.Figure 8 shows how a process according to present invention is the core of a highly advantageous recycle loop of materials comprising polyamide 6. In particular, Figure 8 shows that the polyamide 6 material MP obtained from UPA is passed to a unit UTP where a polyamide 6 containing material MT is produced. Such a material MT is then, after its lifetime, suitably collected and then suitably passed as an educt material, as component of the stream SMR, to the integrated depolymerization-polymerization process of the present invention.Figure 9 shows further optional and advantageous aspects of the process of the present invention. As far as the unit UDP is concerned, two Uop-internal recycle streams are shown, in particular two aqueous recycle streams SWR which are obtained from one or more stages purification stages, in particular purifications stages carried out in UPI and UP2. Further, a stream SWM is shown which is passed to UDP, in particular UM, SWM being a water make-up stream which is used to compensate any unavoidable water losses when carrying out the process of the present invention, in spite of all integration measures including the water recycling measures. Yet further, a stream SCPLO is shown which is an E-caprolactam educt stream to be passed to UPA and which may be used in addition to SCPL and which may be of any nature, be it from another waste depolymerization process, from a conventional source, or from a biobased process comprising, for example, an artificial enzyme-catalyzed cascade or the like.

Claims

Claims1 . An integrated process for preparing polyamide 6, comprising(i) providing a stream SMR comprising a solid material MR comprising polyamide 6, wherein the solid material MR comprises a waste material;(ii) preparing from the stream SMR in a depolymerisation and purification unit UDP a stream SCPL comprising purified E-caprolactam, the unit UDP comprising at least one depolymerization sub-unit UD;(ill) passing the stream SCPL to a polyamide 6 production unit UPA;(iv) subjecting the stream SCPL in UPA to E-caprolactam polymerization conditions, obtaining from UPA a polyamide 6 material MP and a stream comprising water and one or more E-caprolactam oligomers;(v) optionally subjecting to stream comprising water and one or more E-caprolactam oligomers to concentration with respect to the one or more E-caprolactam oligomers in at least one concentration stage, obtaining a concentrated stream comprising water and one or more E-caprolactam oligomers;(vi) passing the optionally concentrated stream comprising water and one or more E-caprolactam oligomers into at least one of the depolymerization sub-units UD according to (ii).

2. The process of claim 1 , wherein the optionally concentrated stream comprising water and one or more s-ca- prolactam oligomers further comprises E-caprolactam.

3. The process of claim 2, wherein the process comprises(iv) subjecting the stream SCPL in UPA to E-caprolactam polymerization conditions, obtaining from UPA a polyamide 6 material MP and a stream SEW comprising water at a concentration CEW(W), E-caprolactam at a concentration CEW(C), and one or moreE-caprolactam oligomers at a total concentration CEW(O);(v) subjecting the stream SEW to concentration, comprising(v.1 ) subjecting the stream SEW to concentration in a first concentration unit Ud, obtaining from Uci a concentrated stream Sci comprising water at a concentration Cci(W), E-caprolactam at a concentration cci (C), and one or more E-caprolactam oligomers at a total concentration cci (0), with Cci(W) < CEW(W),CCI (C) > CEW(C) and Cci(0)> CEW(O), and further obtaining from Uci an aqueous stream Swi comprising water at a concentration Cwi(W) > CEW(W);(v.2) subjecting the stream Sci to concentration in a second concentration unit Uc2, obtaining from Uc2 a concentrated stream Sc2 comprising one or more E-caprolactam oligomers at a total concentration Cc2(0), with CC2(O) > cci (0), and further obtaining from Uc2 an aqueous stream Sw2 comprising water at a concentration cw2(W) and E-caprolactam at a concentration Cw2(C), with Cw2(W) > Cwi(W) and Cw2(C) > Cwi(C);(vi) passing the stream Sc2 into the depolymerisation and purification unit UDP.

4. The process of claim 3, wherein the stream SEW further comprises one or more organic compounds X other than E-caprolactam and oligomers thereof at a total concentration CEW(X), the process comprising(v.1) subjecting the stream SEW to concentration in a first concentration unit Uci, obtaining from Uci a concentrated stream Sci comprising water at a concentration Cci(W), E-caprolactam at a concentration Cci(C), one or more E-caprolactam oligomers at a total concentration Cci(O) and one or more organic compounds X at a total concentration cci (X), with Cci(W) < CEW(W), Cci(C) > CEW(C), CCI(O)> CEW(O) and cci(X)> CEW(X), and further obtaining from Uci an aqueous stream Swi comprising water at a concentration Cwi(W) > CEW(W);(v.2) subjecting the stream Sci to concentration in a second concentration unit Uc2, obtaining from Uc2 a concentrated stream Sc2 comprising one or more E-caprolactam oligomers at a total concentration cc2(O) and one or more organic compounds X at a total concentration cc2(X), with cc2(O) > Cci(O) and cc2(X) > cci (X), and further obtaining from Uc2 an aqueous stream Sw2 comprising water at a concentration cw2(W) and E-caprolactam at a concentration Cw2(C), with cw2(W) > Cwi(W) and cw2(C) > Cwi(C); wherein the concentration unit Uci preferably comprises one or more of a vessel with internal, external, or both internal and external heat exchange; and a falling film heat exchanger; and wherein the concentration unit Uc2 preferably comprises one or more of a vessel with internal, external, or both internal and external heat exchange; and a thin film evaporator.

5. The process of claim 3 or 4, wherein (iv) comprises(iv.1 ) passing the stream SCPL and preferably an aqueous stream SAQO to a polymerization stage STo, obtaining from STo a polyamide 6 crude product stream SPAI and an aqueous stream SWAI;(iv.2) passing the stream SPAI and preferably an aqueous stream SAQI to a granulation stage ST 1, obtaining from STi a crude granulated polyamide 6 material MPA2 and an aqueous stream SWA2;(iv.3) passing the material MPA2 and preferably an aqueous stream SAQ2 to an extraction stage ST2, obtaining from ST2 a purified granulated polyamide 6 material MPA3 and an aqueous stream SWAS;(iv.4) passing the material MPA3 to a drying stage ST3, obtaining from ST3 the polyamide 6 material MP and an aqueous stream SWA wherein the stream SEW comprises at least part of the stream SWA3 and optionally one or more of at least a part of the stream SWAI and at least part of the stream SWA2; wherein the process more preferably further comprises passing at least a part of the stream SWA4 obtained from drying according to (iv.4) to the extraction stage according to (iv.3).

6. The process of claim 5, further comprising passing the stream Swi obtained from Uci according to (v.1) back to the polyamide 6 production unit UPA, preferably wherein the stream Swi is passed back to UPA as at least part of one or more of the streams SAQO, SAQI and SAQ2.

7. The process of any one of claims 1 to 6, wherein the depolymerisation and purification unit UDP comprises a mixing and melting sub-unit UM where an aqueous depolymerisation mixture is prepared, which is passed to the depolymerisation sub-unit UD.

8. The process of any one of claims 3 to 7, wherein the depolymerisation and purification unit UDP comprises, downstream of the at least one depolymerization sub-unit UD, a water separation sub-unit UP2 for separating water from E-caprolactam, the process further comprising passing the stream Sw2 obtained from Uc2 according tO (V.2) tO UP2.

9. The process of any one of claims 3 to 8, wherein the depolymerisation and purification unit UDP comprises, upstream of the at least one depolymerization sub-unit UD, a melting and mixing sub-unit UM, wherein the process further comprises passing the stream Sc2 to the sub-unit UM and further comprises passing the stream SMR to the sub-unit UM, obtaining from UM a stream which passed to UD.

10. The process of any one of claims 3 to 9, wherein some of the polyamide 6 material obtained from the production unit UPA does not meet the specifications, the process further comprising passing at least some of said material to the depolymerisation and purification unit UDP for depolymerization, preferably passing at least some of said material to UM.

11. The process of any one of claims 3 to 10, wherein the depolymerisation and purification unit UDP comprises, downstream of UD and upstream of UP2, a first purification sub-unit UPI, and downstream of UP2, a third purification stage UP3, wherein the process further comprising passing the stream obtained from UD to UPI, obtaining from UPI a stream which is passed to UP2, obtaining from UP2 the stream which is passed to UP3, obtaining from UP3 the stream SCPL.

12. The process of any one of claims 3 to 11, wherein downstream of Uci and upstream of Uc2, the stream Sci is passed to a buffer unit UBCI and downstream of UDP and upstream of UPA, the stream SCPL is passed to a buffer unit UBCPL.

13. The process of any one of claims 1 to 12, further comprising providing the material MP obtained from UPA as a feedstock to a polyamide containing material producing unit UTP, from which unit UTP a polyamide containing material MT is obtained which is brought onto the market, wherein, after a life-time TMT of said material MT, it is at least partially collected as waste material and passed to UDP as at least part of SMR, wherein the material MT is preferably one or more of a textile material and an engineering plastics material, preferably a textile material.

14. An integrated polyamide 6 plant for carrying out the process according to any one of claims 1 to 13, the integrated polyamide 6 plant comprising a depolymerization and purification unit UDP and a polyamide 6 production unit UPA, a transportation line LCPL for passing a purified E-caprolactam from UDP to UPA and at least transportation line Ls for passing an aqueous recycle stream from UPA to UDP; wherein the transportation line Ls comprises two concentration units Uci and Uc2, wherein Uci is arranged downstream of UPA and Uc2 is arranged downstream of Uci and upstream of UDP, said integrated polyamide 6 plant more preferably further comprising a transportation line Lwi from Uci to UPA for passing an aqueous stream Swi obtained from Uci to UPA, wherein downstream of Uc2, the transportation line Ls more preferably comprises at least two sub-lines Lw2 and Lc2 for passing an aqueous stream Sw2 obtained from Uc2 to UDP via LWS2 and for passing a concentrated stream Sc2 from Uc2 to UDP via Lc2; wherein more preferably, the transportation line LCPL comprises a buffer unit UBCPL and the transportation line Ls comprises a buffer unit UBCI, wherein UBCI is preferably arranged downstream of Uci and upstream of Uc2; said integrated polyamide 6 plant preferably further comprising a transportation line LMPR for passing a polyamide material MPR obtained from UPA to UDP.

15. A process, preferably according to any one of claims 1 to 13, comprising the step of converting the polyamide 6 material MP obtainable or obtained by the process according to any one of claims 1 to 13 or the material MPR obtainable or obtained by the process according to claim 10 or the stream SMR obtainable or obtained by the process according to claim 13 or a chemical material obtainable by or obtained by the process according to any one of claims 1 to 13 to obtain a product Q; and / or a process comprising the step of using the integrated polyamide 6 plant according to claim 14 to obtain a polyamide 6 material MP; and preferably converting the polyamide 6 material MP to obtain a product Q.

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