Separation of impurities in a process for hydrolytic depolymerization of polyamides.

Abstract

The present invention relates to a process for the preparation of at least one ε-caprolactam oligomer compound CPO, comprising a flow S comprising said at least one CPO and an ε-caprolactam monomer compound CPM. R The present invention relates to a method for separating

Description

[Technical field]

[0001] The present invention relates to a process for separating at least one oligomeric compound of ε-caprolactam CPO from a stream comprising said at least one CPO and monomeric ε-caprolactam compounds CPM. [Background technology]

[0002] Polyamides, specifically those of the formula (-NH-(CH2)5-CO-) n Polyamide 6, characterized by , can be found in many materials such as packaging, automotive engineering plastics, and fiber filaments. The latter accounts for about 40% of polyamide 6 in the world market. Currently, only a small portion of fiber filaments is recycled, but it accounts for a significant proportion of global CO2 emissions. For this reason, there is a need to recycle polyamide 6 from such materials. Methods exist for the alkaline depolymerization of polyamides. However, such methods have a certain CO2 footprint and are energy intensive. Therefore, there is a need to improve methods for depolymerizing polyamides that can eliminate these problems. Summary of the Invention [Problem to be solved by the invention]

[0003] Surprisingly, it has been found that the method of the invention allows for an efficient separation of ε-caprolactam oligomers from ε-caprolactam monomeric compounds compared to known methods, and in particular allows for an improved reuse of solid materials comprising polyamides, such as textile waste, in particular after hydrolytic depolymerization of polyamides. Thus, the use of the method according to the invention for separating at least one ε-caprolactam oligomer compound CPO from a stream SR comprising at least one CPO and an ε-caprolactam monomeric compound CPM makes it possible to reduce the CO2 footprint. [Means for solving the problem]

[0004] The present invention therefore provides a process for the preparation of at least one oligomeric compound of ε-caprolactam CPO from a stream S comprising said at least one CPO and an ε-caprolactam monomeric compound CPM. R 1. A method for separating a compound comprising the steps of: (i) Concentration c R (CPM) is the flow of aqueous liquid containing CPM dissolved in water, S R providing a CPM having a boiling point T CPM S R is the concentration c R (CPO), wherein the CPO is selected from the group consisting of T CPO >T CPM The boiling point T CPO having the steps of: (ii) The flow S provided by (i) R A mixture of aqueous liquids M E preparing a (iii) Mixture M according to (ii) E is subjected to evaporation conditions in an evaporation unit E1 to produce a water vapor flow S V1 and the aqueous liquid flow S L1 A step of obtaining S V1 But, c V1 (CPM)>c R (CPM) is the concentration c V1 (CPM) includes CPM, S L1 But, c L1 (CPO)>c R (CPO) is the concentration c L1 (CPO) containing at least one CPO and c L1 (CPM) <c R (CPM) is the concentration c L1 (CPM) includes CPM,steps; Flow S due to (iv)(iii) L1 The first flow S L11 and the second flow S L12 and dividing the L11 and S L12 S L1 having the same chemical composition as, step; (v) The flow S obtained by (iv) L12 and passing the resulting mixture through a downstream processing stage; (ii) Aqueous liquid mixture M E The step of preparing a flow S R Flow S L11 and mixing the resulting mixture with

[0005] In the context of the present invention, the term "oligomeric compounds of ε-caprolactam" (CPO) encompasses all non-monomeric compound forms of ε-caprolactam oligomers, i.e. all oligomeric compound forms of ε-caprolactam including polyamide 6.

[0006] Preferably, the flow S prepared according to (i) R has a temperature in the range of 100 to 150°C, more preferably in the range of 110 to 145°C, and more preferably in the range of 120 to 140°C.

[0007] Preferably, - Flow S prepared by (i) R indicates a CPM concentration in the range of 15 to 90 mass%, more preferably in the range of 20 to 75 mass%, more preferably in the range of 25 to 60 mass%, and a CPO concentration in the range of 0.5 to 10 mass%, more preferably in the range of 0.5 to 7 mass%, more preferably in the range of 0.5 to 4 mass%, - The flow S obtained by (iii) V1 indicates a CPM concentration in the range of 65 to 99% by mass, more preferably in the range of 65 to 90% by mass, more preferably in the range of 65 to 80% by mass, and the flow S obtained by (iii) V1 more preferably, the CPO concentration is in the range of 0 to 0.4 mass%, more preferably, in the range of 0 to 0.3 mass%, and more preferably, in the range of 0 to 0.2 mass%, - The flow S obtained by (iii) L1indicates a CPM concentration in the range of 0.1 to 10 mass%, more preferably in the range of 0.5 to 7.5 mass%, more preferably in the range of 1 to 5 mass%, and a CPO concentration in the range of 1 to 10 mass%, more preferably in the range of 1.5 to 10 mass%, more preferably in the range of 2 to 10 mass%.

[0008] Preferably, the mixture of aqueous liquids M E According to a first alternative for the preparation of E The step of preparing a stream S R Flow S L11 The flow S obtained from (iv) before mixing with L11 to a temperature in the range of 200 to 270°C, more preferably in the range of 210 to 270°C, and more preferably in the range of 220 to 270°C.

[0009] Preferably, according to the first alternative, the flow S L11 Heating the flow S L11 Preferably, according to the first alternative, in (ii), the flow S prepared in (i) is passed through a heat exchanger H1. R and the flow S obtained by heating L11 are mixed in the evaporation unit E1. Preferably, according to the first alternative, the stream S R Flow S L11 The stream S prepared by (i) is mixed with R is not heated.

[0010] According to said first alternative, it is conceivable that one or more heat exchangers are used, preferably upstream of H1. Preferably, no further heat exchangers are used upstream of H1.

[0011] Aqueous liquid mixture M E The first alternative for the preparation of is specifically illustrated in FIG.

[0012] Preferably, the mixture of aqueous liquids M EAccording to a second alternative for the preparation of E The step of preparing the flow S R The flow S obtained from (iv) L11 and heating the combined stream to a temperature in the range of 200-270°C, more preferably in the range of 210-270°C, more preferably in the range of 220-270°C.

[0013] Preferably, the heating of the combined stream comprises heating the combined stream S L11 Preferably, the flow S R Flow S L11 The stream S prepared by (i) is mixed with R is not heated. According to said second alternative, it is conceivable that one or more heat exchangers are used, preferably upstream of H1. Preferably, no further heat exchangers are used upstream of H1.

[0014] Aqueous liquid mixture M E The first alternative for the preparation of is specifically illustrated in FIG.

[0015] In the context of the present invention, preferably, the evaporation in the evaporation unit E1 according to (iii) is carried out in one or more stirred vessels, or in one or more membrane evaporators, or in one or more stirred vessels and one or more membrane evaporators. More preferably, the evaporation in the evaporation unit E1 according to (iii) is carried out in one or more continuous stirred tank reactors, or in one or more falling film evaporators, or in one or more continuous stirred tank reactors and one or more falling film evaporators. More preferably, the evaporation in the evaporation unit E1 according to (iii) is carried out in one or more continuous stirred tank reactors, more preferably, if the evaporation in E1 is carried out in more than one continuous stirred tank reactor, the continuous stirred tank reactors are arranged in parallel.

[0016] Preferably, the stirred vessel(s) and the membrane evaporator(s) are equipped with heating means for indirectly providing heat for the evaporation taking place in E1, the method comprising the step of passing a heating medium through said heating means, said heating means being more preferably a heating jacket.

[0017] Preferably, the evaporation conditions according to (iii) are E Evaporation temperature T E1 Including T E1 is in the range of 200 to 270°C, more preferably in the range of 210 to 270°C, more preferably in the range of 220 to 270°C, and the evaporation conditions according to (iii) are evaporation pressure p E1 Further, p E1 is more preferably less than 1 bar (abs).

[0018] Preferably, p E1 is in the range of 10 to 900 mbar (abs), more preferably in the range of 10 to 850 mbar (abs), and more preferably in the range of 10 to 800 mbar (abs).

[0019] Preferably, the evaporation conditions according to (iii) are such that the residence time in the evaporation unit E1 is t E1 Further includes t E1 The evaporation time is in the range of 1 minute to 5 hours, more preferably in the range of 5 minutes to 4 hours, and more preferably in the range of 10 minutes to 3 hours. More preferably, the evaporation conditions in (iii) are E Evaporation temperature T E1 Including T E1 is in the range of 200 to 270 ° C, more preferably in the range of 210 to 270 ° C, more preferably in the range of 220 to 270 ° C; (iii) is the evaporation condition, evaporation pressure p E1 Further, p E1 is more preferably less than 1 bar (abs), more preferably in the range of 10 to 900 mbar (abs), more preferably in the range of 10 to 850 mbar (abs), more preferably in the range of 10 to 800 mbar (abs); and the evaporation conditions according to (iii) are such that the residence time t E1 Further includes tE1 is in the range of 1 minute to 5 hours, more preferably in the range of 5 minutes to 4 hours, and more preferably in the range of 10 minutes to 3 hours.

[0020] Preferably, in (iv), the flow S L1 is the mass ratio m(S L12 ):m(S L11 ), the first flow S L11 and the second flow S L12 and is divided into

[0021] Preferably, the downstream processing stage according to (v) comprises one or more of the following: - Evaporation unit; - Flow S L12 a depolymerization unit for depolymerizing at least one of the at least one ε-caprolactam oligomer compounds CPO contained in the at least one ε-caprolactam oligomer compound CPO; - Flow S L12 a separation unit for separating at least one solid residue from the - Flow S L12 a treatment unit for treating at least one solid residue contained in the - Flow S L12 an incineration stage for incinerating at least one solid residue contained in

[0022] Preferably, the downstream processing stage according to (v) comprises an evaporation unit, and said method comprises the steps of: (vi) Flow S L12 is subjected to evaporation conditions in an evaporation unit E2 to produce a water vapor flow S V2 and the liquid flow S L2 A step of obtaining S V2 is c V2 (CPM)>c L12 (CPM), concentration c V2 (CPM) including CPM and c V2 (CPO) <c L12 (CPO), concentration c V2 (CPO) including CPO;S L2 But, cL2 (CPO) ≧ c L12 (CPO), concentration c L2 (CPO), comprising at least one CPO; (vii) The flow S obtained by (vi) L2 passing the resulting signal through downstream processing stages; Further includes:

[0023] Liquid flow S L2 is preferably a non-aqueous liquid stream, i.e. a liquid stream having a water content of max. 0.01% by weight, preferably max. 0.005% by weight, preferably max. 0.002% by weight, more preferably max. 0.001% by weight.

[0024] Preferably, - The flow S obtained by (vi) V2 indicates a CPM concentration in the range of 50 to 100 mass%, more preferably in the range of 60 to 100 mass%, more preferably in the range of 80 to 100 mass%, and a CPO concentration in the range of 0 to 0.5 mass%, more preferably in the range of 0 to 0.3 mass%, more preferably in the range of 0 to 0.1 mass%; - The flow S obtained by (vi) L2 indicates a CPO concentration in the range of 1 to 10 mass %, more preferably in the range of 1.5 to 10 mass %, and more preferably in the range of 2 to 10 mass %.

[0025] Preferably, the evaporation in the evaporation unit E2 according to (vi) is carried out in one or more stirred vessels, or in one or more film evaporators, or in one or more stirred vessels and one or more film evaporators. More preferably, the evaporation in the evaporation unit E2 according to (vi) is carried out in one or more film evaporators. More preferably, the evaporation in the evaporation unit E2 according to (vi) is carried out in one or more wiped film evaporators, more preferably, if the evaporation in E2 is carried out in more than one wiped film evaporator, the wiped film evaporators are arranged in parallel.

[0026] It is conceivable that the evaporation in the evaporation unit E2 according to (vi) takes place in one or more kneaders.

[0027] Preferably, the stirred vessel(s) and the membrane evaporator(s) are equipped with heating means for indirectly providing heat for the evaporation taking place in E2, the method comprising the step of passing a heating medium through said heating means, said heating means being more preferably a heating jacket.

[0028] Preferably, the evaporation conditions according to (vi) are L12 Evaporation temperature T E2 Including T E2 is in the range of 200 to 300°C, more preferably in the range of 215 to 300°C, more preferably in the range of 230 to 300°C, and the evaporation conditions according to (vi) are evaporation pressure p E2 Further, p E2 is more preferably less than 1 bar (abs).

[0029] Preferably, p E2 is in the range of 10 to 900 mbar (abs), more preferably in the range of 10 to 850 mbar (abs), and more preferably in the range of 10 to 800 mbar (abs).

[0030] Preferably, the evaporation conditions according to (vi) are such that the residence time in the evaporation unit E2 is t E2 Further includes t E2 is in the range of 1 second to 5 minutes, more preferably in the range of 5 seconds to 4 minutes, more preferably in the range of 10 seconds to 3 minutes. More preferably, the evaporation conditions according to (vi) are L12 Evaporation temperature T E2 Including T E2 is in the range of 200 to 300 ° C, more preferably in the range of 215 to 300 ° C, more preferably in the range of 230 to 300 ° C, and the evaporation conditions according to (vi) are evaporation pressure p E2 Further, p E2is more preferably less than 1 bar (abs), more preferably in the range of 10 to 900 mbar (abs), more preferably in the range of 10 to 850 mbar (abs), more preferably in the range of 10 to 800 mbar (abs), and the evaporation conditions according to (vi) are the residence time t E2 Further includes t E2 is in the range of 1 second to 5 minutes, more preferably in the range of 5 seconds to 4 minutes, and more preferably in the range of 10 seconds to 3 minutes.

[0031] Preferably, the downstream processing stage according to (vii) comprises one or more of the following: - Flow S L2 a depolymerization unit for depolymerizing at least one of the oligomeric compounds CPO of ε-caprolactam contained in the at least one depolymerization unit; - Flow S L2 a separation unit for separating at least one solid residue from the - Flow S L2 a treatment unit for treating at least one solid residue contained in the - Flow S L2 an incineration stage for incinerating at least one solid residue contained in

[0032] Preferably, the method further comprises the steps of: (viii) Water vapor flow S V1 , more preferably the water vapor flow S V1 and water vapor flow S V2 , more preferably the water vapor flow S V1 and the water vapor flow S V2 The combined flow is then passed through a water removal unit W to separate the CPM from the water. U wherein the water removal unit preferably comprises at least one distillation column, more preferably 1 to 3 distillation columns, more preferably 2 or 3 distillation columns, more preferably 3 distillation columns, and the water removal unit W U comprises more than one distillation column, the distillation columns are more preferably arranged in series.

[0033] Preferably, the bottoms stream of at least one distillation column, more preferably the bottoms stream of the most downstream distillation column, is recycled to the evaporation unit E1.

[0034] Preferably, the flow S according to (i) R The step of providing (i.1) Aqueous liquid mixture M containing CPM and CPO dissolved in water WC preparing a solution comprising: (i.1.1) Aqueous liquid flow S W Providing (i.1.2) providing a solid material M containing a polyamide prepared from ε-caprolactam, (i.1.3) A solid material M prepared according to (i.1.2) and a stream of aqueous liquid S prepared according to (i.1.1) W preparing a mixture with (i.1.4) From the mixture prepared by (i.1.3), an aqueous liquid mixture M containing polyamide dissolved in water is obtained. WP preparing (i.1.5) The aqueous liquid mixture M prepared by (i.1.4) WP Chemical reactor unit R U The aqueous liquid mixture M containing CPM and CPO dissolved in water was subjected to depolymerization conditions in WC The process of obtaining The steps include: (i.2) Optionally, the aqueous mixture M obtained according to (i.1.5) WC Pressure reducing unit D U The steam flow S VD , as well as the aqueous liquid flow S C To obtain S C comprising CPM and CPO dissolved in water; (i.3) Optionally, the aqueous mixture M obtained according to (i.1.5) WC or the aqueous liquid stream S obtained by (i.2) C Solid-liquid separation unit SLU The solid-liquid separation is performed through the sieve to obtain an aqueous liquid stream S containing CPM and CPO dissolved in water. L obtaining a step; (i.4) (i.1.5) WC or by (i.2) a stream of aqueous liquid S C or by (i.3) the aqueous liquid stream S L From at least two evaporation subunits E U1 and E U2 Evaporation unit E equipped with U and separating water by evaporation in at least one steam stream S VE and the aqueous liquid flow S R obtaining a Includes.

[0035] Preferably, the solid material M provided by (i.1.2) comprises waste material, more preferably consists only of waste material, said waste material preferably comprising textile waste.

[0036] Preferably, the aqueous liquid stream S containing ε-caprolactam dissolved in water according to (i.1) WC The steps of preparing the composition include the following steps: (i.1.1) Aqueous liquid flow S W (Here, 50 mass% to 100 mass% S W consists of water, and S W is the temperature T SW T SW >T P providing a (i.1.2) A solid material M containing a polyamide prepared from ε-caprolactam, where M is at a temperature T M T M <T P and T P is the melting point of the polyamide; (i.1.3) A solid material M provided by (i.1.2) and a stream of aqueous liquid S provided by (i.1.1) Wpreparing an aqueous mixture of a solid material M provided by (i.1.2) and a liquid aqueous stream S provided by (i.1.1); W , the chemical reactor R U to obtain said mixture; (i.1.4) from the mixture prepared by (i.1.3), an aqueous liquid mixture M containing polyamide dissolved in water WP comprising a solid material M provided by (i.1.2) and a liquid aqueous stream S provided by (i.1.1) W Chemical reactor R U to obtain said mixture; (i.1.5) The mixture of aqueous liquid prepared by (i.1.4) is fed to a chemical reactor unit R U The aqueous liquid stream M containing ε-caprolactam dissolved in water is subjected to depolymerization conditions in WC The depolymerization conditions are a depolymerization pressure p D Depolymerization temperature T D Including T M <T D <T SW A process that is Includes.

[0037] Preferably, T D The heating temperature is in the range of 230 to 320°C, more preferably in the range of 250 to 300°C, and more preferably in the range of 250 to 295°C or 270 to 295°C.

[0038] Preferably, T SW The heating temperature is in the range of 250 to 350°C, more preferably in the range of 260 to 330°C, and more preferably in the range of 290 to 325°C.

[0039] Liquid aqueous flow S W (T SW The excess heat from the reactor unit R melts the solid material M containing the polyamide (solid material M is preferably in the form of granules) and provides the necessary reaction enthalpy. All additional heat required to maintain the reaction temperature is provided by the reactor unit R UThe heating may be provided via a heating jacket using hot oil, as described in more detail below.

[0040] Preferably, ΔT=T SW -T P The temperature is in the range of 10 to 70°C, more preferably in the range of 10 to 50°C, and more preferably in the range of 10 to 30°C.

[0041] Preferably, p D is in the range of 40 to 120 bar, more preferably in the range of 50 to 100 bar, and more preferably in the range of 60 to 90 bar.

[0042] Preferably, in the mixture prepared according to (i.1.3), at least 75% by weight, more preferably 75-100% by weight, more preferably 85-100% by weight, more preferably 95-100% by weight of the polyamide contained in the solid material M is contained in liquid form.

[0043] Preferably, S provided by (i.1.1) W The total mass of the mixture is 91 to 100 mass%, more preferably 92 to 100 mass%, and even more preferably 95 to 100 mass%.

[0044] Preferably, the solid material M provided by (i.1.2) comprises waste material, more preferably consists solely of waste material, said waste material preferably comprising textile waste.

[0045] Preferably, 10 to 99 mass%, more preferably 30 to 98.5 mass%, more preferably 50 to 98 mass%, more preferably 80 to 98 mass% of M consists of polyamide, or preferably, 10 to 100 mass%, more preferably 30 to 100 mass%, more preferably 50 to 100 mass%, more preferably 80 to 100 mass% of M consists of polyamide.

[0046] Preferably, M is in the form of granules, and the average diameter of the granules is more preferably in the range of 0.5 to 10 mm, more preferably in the range of 1 to 7 mm, and more preferably in the range of 2 to 4 mm.

[0047] (i.1.4), M and S W are preferably the mass m of the polyamide contained in M P relative to the amount of water m contained in S1 W defined as and in the mixing ratio m in the range of 1:1 to 20:1, more preferably in the range of 2:1 to 15:1, and more preferably in the range of 5:1 to 10:1 W / kg:m P / kg, and is supplied to R U .

[0048] Preferably, the chemical reactor unit R U comprises z chemical reactors R i (where i = 1... z, and z is in the range of 1 to 10, more preferably in the range of 2 to 8, more preferably in the range of 2 to 6, more preferably in the range of 2 to 5, more preferably in the range of 2 to 4, more preferably 3 or 4, and more preferably 4).

[0049] Preferably, z > 1, and at least two reactors R i , more preferably z reactors R i are connected in series.

[0050] Preferably, the z reactors R i are connected in series, and at this time, - (i.1.4), M WP is supplied to R i (where i = 1); - The stream S of the aqueous liquid containing ε-caprolactam dissolved in water i is removed from R i and supplied to R i+1 (where i < z); - According to (i.1.5), M WC is removed from R z ; All reactors Ri In the depolymerization pressure p Di At the depolymerization temperature T Di are maintained, and then, independently of each other, T Di is in the range of 230 to 320°C, more preferably in the range of 250 to 300°C, and more preferably in the range of 270 to 295°C, and p Di is more preferably in the range of 40 to 120 bar, more preferably in the range of 50 to 100 bar, and more preferably in the range of 60 to 90 bar.

[0051] Preferably, the reactor R i Depolymerization temperature T Di Maintaining R i and more preferably heating the reactor contents of R i and more preferably, indirectly heating the reactor contents of reactor R i Depolymerization temperature T Di Maintaining the heating medium R i By passing it through the heating jacket of R i The heating medium is preferably hot oil. However, R i It should be noted that other heating media known to those skilled in the art can be used to pass through the heating jacket of the.

[0052] Preferably, z reactors R i are arranged vertically, R1 is the top reactor, and R z is the bottom reactor and R i S obtained from i is caused by gravity, or more preferably by gravity alone, R i+1 Move to.

[0053] Preferably, at least one, more preferably z reactors R i is configured as a non-stirred reactor or a non-circulating reactor, more preferably as a non-stirred reactor and a non-circulating reactor.

[0054] The system preferably operates without an agitator and a circulation pump, which avoids difficult sealing, i.e. high pressure sealing, in the agitator and pump.

[0055] As mentioned above, mixing is preferably ensured by feeding a constant amount of water stepwise during the ongoing reaction time and feeding the liquid solution from reactor R1 to reactors R2 and R3, for example by gravity, after a portion of the reaction time has elapsed.

[0056] Preferably, reactors R1 to R y-1 is operated in batch mode, and reactor R y ~R z is operated in a continuous mode, y>1, and y≦z, and more preferably y is z.

[0057] Preferably, reactors R1 to R y-1 More preferably, one or more of the reactors R1 to R y-1 The residence time in the container is in the range of 5 to 40 minutes, more preferably in the range of 10 to 30 minutes, and more preferably in the range of 15 to 25 minutes.

[0058] Preferably, the reactor R y The residence time in (y is more preferably z) is in the range of 1 second to 40 minutes, more preferably in the range of 2 seconds to 30 minutes, more preferably in the range of 3 seconds to 25 minutes.

[0059] Preferably, the overall residence time in the chemical reactor unit is in the range of 15 to 160 minutes, more preferably in the range of 30 to 120 minutes, more preferably in the range of 45 to 100 minutes, more preferably in the range of 60 to 80 minutes.

[0060] More preferably, four identical chemical reactors R1-R4 are arranged in series: the first three reactors R1-R3 are preferably operated in batch mode, all of said reactors having low residence times, and the last reactor R4 is in continuous mode to allow continuous feeding of downstream process steps.

[0061] SW and M and S in respect of the supply of W In order, R i More preferably, the mixture is supplied to S W R i is fed to S W R containing i M is supplied to S. After time T has elapsed, i is R i is removed from R i+1 are supplied to.

[0062] Preferably, the aqueous mixture M obtained according to (i.1.5) according to (i.2) WC Pressure reducing unit D U The step of exposing to reduced pressure within the (i.2.1) Aqueous liquid flow M WC is supplied as a feed stream to the first evaporation subunit DU11 to produce a water vapor flow S VD11 , and a stream of aqueous liquid containing ε-caprolactam dissolved in water S L11 obtaining an aqueous liquid stream M WC is optionally passed through at least one solid-liquid separation unit F1; (i.2.2) Aqueous liquid flow S L11 is supplied as a feed stream to the second evaporation subunit DU12 to produce a water vapor flow S VD12 , and a stream of aqueous liquid containing ε-caprolactam dissolved in water S C obtaining an aqueous liquid stream S L11 is optionally passed through at least one solid-liquid separation unit F2, Here, (ii.1) is M WC Passing through F1, and S L11 and (ii.1) is more preferably at least one of WC Passing through F1, and S L11 This is specifically illustrated in FIG. VD11 and S. VD12 The combination of VD is equivalent to.

[0063] Preferably, at least one of the solid-liquid separation unit F1 and the solid-liquid separation unit F2, more preferably the solid-liquid separation unit F1 and the solid-liquid separation unit F2, is a filtration unit, F1 more preferably has a mesh size in the range of 0.5 to 5 mm, more preferably in the range of 1 to 3 mm, and F2 more preferably has a mesh size in the range of 0.5 to 5 mm, more preferably in the range of 1 to 3 mm.

[0064] Preferably, in (i.4), at least two evaporation subunits E U1 and E U2 are connected in series, and the water vapor flow S VE1 E U1 and the water vapor flow S VE2 E U2 and E U2 From the flow, a stream of aqueous liquid containing ε-caprolactam dissolved in water, S R and more preferably, the evaporation unit E U E is two evaporation units U1 and E U2 Equipped with Preferably, 75 to 100% by weight of the aqueous liquid stream fed to the evaporation according to (i.4) consists exclusively of water and ε-caprolactam, said stream having a water concentration of c H2O and preferably has an ε-caprolactam concentration c in the range of 5 to 20 mass%. CPL The method includes: VE1 and S VE2 At least a portion of at least one of the aqueous liquid flows S W wherein said recycling step preferably comprises the step of recycling the stream S VE1 and S VE2 The method includes condensing at least one of the following: VE1 and S. VE2 The combination with S VE is equivalent to.

[0065] Preferably, the liquid flow S according to (vii) L2The steps of passing the sample through downstream processing stages include the following steps: (vii.1) Flow S L2 The first flow S L21 and the second flow S L22 and a step of dividing the mixture into S L21 and S L22 S L2 having the same chemical composition as; (vii.2) Flow S L21 The chemical reactor unit R according to (i.1.5) U The process of reusing (recycling) (vii.3) Flow S L22 passing the resulting mixture through a downstream processing stage; Includes.

[0066] Preferably, the downstream processing stage according to (vii.3) comprises: - Flow S L22 a separation unit for separating at least one solid residue from the - Flow S L22 a treatment unit for treating at least one solid residue contained in - Flow S L22 at least one incineration stage for incinerating solid residues contained in The present invention includes one or more of the following:

[0067] The present invention is further described by the following set of embodiments and combinations of embodiments resulting from the indicated dependencies and back-references. In particular, in each instance where a range of embodiments is mentioned, for example, in the context of the term, for example, "the method of any one of embodiments 1-3", it is to be noted that all embodiments within this range are meant to be explicitly disclosed to those skilled in the art, that is, the wording of this term should be understood by those skilled in the art as being synonymous with "the method of any one of embodiments 1, 2, and 3". Furthermore, it is to be clearly noted that the following set of embodiments represents a properly structured part of the general description directed to the preferred aspects of the present invention, and thus properly supports the claims of the present invention, but does not express it.

[0068] 1. At least one oligomeric compound of ε-caprolactam CPO is eluted into a stream S comprising at least one CPO and an ε-caprolactam monomeric compound CPM. R 1. A method for separating a compound comprising the steps of: (i) Concentration c R (CPM) is the flow of aqueous liquid containing CPM dissolved in water, S R preparing a CPM having a boiling point T CPM S R is the concentration c R (CPO), further comprising at least one CPO, CPO >T CPM The boiling point T CPO having the steps of: (ii) The flow S prepared by (i) R Aqueous liquid mixture M E preparing a (iii) Mixture M according to (i) E is subjected to evaporation conditions in an evaporation unit E1 to produce a water vapor flow S V1 and the aqueous liquid flow S L1 A step of obtaining S V1 But, c V1 (CPM)>c R (CPM) is the concentration c V1(CPM) includes CPM, S L1 But, c L1 (CPO)>c R (CPO) is the concentration c L1 (CPO) containing at least one CPO and c L1 (CPM) <c R (CPM) is the concentration c L1 (CPM) including CPM, steps, Flow S due to (iv)(iii) L1 The first flow S L11 and the second flow S L12 and dividing the L11 and S L12 S L1 having the same chemical composition as (v) The flow S obtained by (iv) L12 and passing the resulting mixture through a downstream processing stage; (ii) Aqueous liquid mixture M E The step of preparing a flow S R Flow S L11 The method of claim 1, further comprising mixing the

[0069] 2. Flow S prepared by (i) R has a temperature in the range of 100 to 150°C, preferably in the range of 110 to 145°C, more preferably in the range of 120 to 140°C.

[0070] 3.- Flow S prepared by (i) R has a CPM concentration in the range of 15 to 90 mass%, preferably in the range of 20 to 75 mass%, more preferably in the range of 25 to 60 mass%, and a CPO concentration in the range of 0.5 to 10 mass%, preferably in the range of 0.5 to 7 mass%, more preferably in the range of 0.5 to 4 mass%; - The flow S obtained by (iii) V1 has a CPM concentration in the range of 65 to 99% by mass, preferably in the range of 65 to 90% by mass, more preferably in the range of 65 to 80% by mass, and the flow S obtained by (iii) V1preferably has a CPO concentration in the range of 0 to 0.4 mass%, preferably in the range of 0 to 0.3 mass%, more preferably in the range of 0 to 0.2 mass%, - The flow S obtained by (iii) L1 has a CPM concentration in the range of 0.1 to 10 mass%, preferably in the range of 0.5 to 7.5 mass%, and more preferably in the range of 1 to 5 mass%, and a CPO concentration in the range of 1 to 10 mass%, preferably in the range of 1.5 to 10 mass%, and more preferably in the range of 2 to 10 mass%. The method of embodiment 1 or 2.

[0071] 4. Aqueous liquid mixture M according to (ii) E The step of preparing a flow S R Flow S L11 The flow S obtained from (iv) before mixing with L11 to a temperature in the range of 200 to 270 °C, preferably in the range of 210 to 270 °C, more preferably in the range of 220 to 270 °C.

[0072] 5. Flow S L11 Heating the flow S L11 The method of embodiment 4, comprising passing the above-mentioned mixture through a heat exchanger H1.

[0073] 6. In (ii), the flow S provided by (i) R and the flow S obtained by heating L11 The process of embodiment 4 or 5, wherein the above-mentioned components are mixed in the evaporation unit E1.

[0074] 7. Flow S R Flow S L11 Before mixing with the flow S provided by (i), R The method of any one of embodiments 4 to 6, wherein the is not heated.

[0075] 8.(ii) Aqueous liquid mixture M E The step of preparing a flow S R The flow S obtained from (iv) L11and heating the combined stream to a temperature in the range of 200-270 °C, preferably in the range of 210-270 °C, more preferably in the range of 220-270 °C.

[0076] 9. Heating the combined stream above produces stream S L11 The method of embodiment 8, comprising passing the above-mentioned mixture through a heat exchanger H1.

[0077] 10. Flow S R Flow S L11 The stream S prepared by (i) is mixed with R 10. The method of embodiment 8 or 9, wherein the is not heated.

[0078] 11. The process of any one of the preceding embodiments, wherein the evaporation in the evaporation unit E1 according to (iii) is carried out in one or more stirred vessels, or in one or more membrane evaporators, or in one or more stirred vessels and one or more membrane evaporators, the evaporation in the evaporation unit E1 according to (iii) is preferably carried out in one or more continuous stirred tank reactors, or in one or more falling film evaporators, or in one or more continuous stirred tank reactors and one or more falling film evaporators, the evaporation in the evaporation unit E1 according to (iii) is more preferably carried out in one or more continuous stirred tank reactors, more preferably in case the evaporation in E1 is carried out in more than one continuous stirred tank reactor, the continuous stirred tank reactors are arranged in parallel.

[0079] 12. The method of embodiment 11, wherein the one or more stirred vessels and the one or more membrane evaporators are provided with a heating means for indirectly providing heat for the evaporation carried out in E1, and the method comprises passing a heating medium through said heating means, said heating means being preferably a heating jacket.

[0080] 13.(iii) The evaporation conditions for mixture M E Evaporation temperature T E1 Including T E1is in the range of 200 to 270°C, preferably in the range of 210 to 270°C, more preferably in the range of 220 to 270°C, and the evaporation conditions according to (iii) are an evaporation pressure p E1 Further, p E1 The method of any one of embodiments 1 to 12, preferably embodiment 11 or 12, wherein the pressure is preferably less than 1 bar (abs).

[0081] 14.p E1 is in the range of 10 to 900 mbar (abs), more preferably in the range of 10 to 850 mbar (abs), more preferably in the range of 10 to 800 mbar (abs).

[0082] 15.(iii) Evaporation conditions in the evaporation unit E1 with residence time t E1 Further includes t E1 The method of any one of embodiments 1 to 14, preferably any one of embodiments 11 to 14, wherein the heating time is in the range of 1 minute to 5 hours, preferably in the range of 5 minutes to 4 hours, more preferably in the range of 10 minutes to 3 hours.

[0083] 16.In (iv), the flow S L1 is in the range of 0.01:1 to 0.02:1. L12 ):m(S L11 ) the first flow S L11 and the second flow S L12 16. The method of any one of embodiments 1 to 15, wherein the method is divided into:

[0084] 17.(v) A downstream processing stage according to - Evaporation unit; - Flow S L12 a depolymerization unit for depolymerizing at least one of the at least one ε-caprolactam oligomer compounds CPO contained in the at least one ε-caprolactam oligomer compound CPO; - Flow S L12 a separation unit for separating at least one solid residue from the - Flow S L12 a treatment unit for treating at least one solid residue contained in the - Flow S L12 and an incineration stage for incinerating at least one solid residue included in the at least one solid residue.

[0085] 18. The downstream processing stage according to (v) comprises an evaporation unit, and the process further comprises: (vi) Flow S L12 is subjected to evaporation conditions in an evaporation unit E2 to produce a water vapor flow S V2 and the liquid flow S L2 A step of obtaining S V2 But, c V2 (CPM)>c L12 (CPM) is the concentration c V2 (CPM) including CPM, and c V2 (CPO) <c L12 (CPO) is the concentration c V2 (CPO) including CPO, where S L2 But, c L2 (CPO) ≧ c L12 (CPO) with concentration c L2 (CPO), comprising at least one CPO; (vii) The flow S obtained by (vi) L2 18. The method of any one of the preceding embodiments, further comprising passing the product through a downstream processing stage.

[0086] 19.- The flow S obtained by (vi) V2 has a CPM concentration in the range of 50 to 100 mass%, preferably in the range of 60 to 100 mass%, more preferably in the range of 80 to 100 mass%, and a CPO concentration in the range of 0 to 0.5 mass%, preferably in the range of 0 to 0.3 mass%, more preferably in the range of 0 to 0.1 mass%; - The flow S obtained by (vi) L2 has a CPO concentration in the range of 1 to 10 mass%, preferably in the range of 1.5 to 10 mass%, and more preferably in the range of 2 to 10 mass%. The method of embodiment 18.

[0087] 20. The process of embodiment 18 or 19, wherein the evaporation in the evaporation unit E2 according to (vi) is carried out in one or more stirred vessels, or in one or more membrane evaporators, or in one or more stirred vessels and one or more membrane evaporators, and the evaporation in the evaporation unit E2 according to (vi) is preferably carried out in one or more membrane evaporators, and the evaporation in the evaporation unit E2 according to (vi) is more preferably carried out in one or more wiped film evaporators, and more preferably, if the evaporation in E2 is carried out in more than one wiped film evaporator, the wiped film evaporators are arranged in parallel.

[0088] 21. The method of embodiment 20, wherein the one or more stirred vessels and the one or more membrane evaporators are equipped with heating means for indirectly providing heat for the evaporation carried out in E2, and the method comprises a step of passing a heating medium through said heating means, said heating means being preferably a heating jacket.

[0089] 22.(vi) Evaporation condition is the flow S L12 Evaporation temperature T E2 Including T E2 is in the range of 200 to 300°C, preferably in the range of 215 to 300°C, more preferably in the range of 230 to 300°C, and the evaporation conditions according to (vi) are evaporation pressure p E2 Further, p E2 22. The method of any one of embodiments 18-21, wherein the pressure is preferably less than 1 bar (abs).

[0090] 23.p E2 23. The method of embodiment 22, wherein the pressure is in the range of 10 to 900 mbar (abs), more preferably in the range of 10 to 850 mbar (abs), more preferably in the range of 10 to 800 mbar (abs).

[0091] 24.(vi) Evaporation conditions are determined by residence time t E2 Further includes t E2 The method of any one of embodiments 18 to 23, wherein the heating time is in the range of 1 second to 5 minutes, preferably in the range of 5 seconds to 4 minutes, and more preferably in the range of 10 seconds to 3 minutes.

[0092] 25.(vii) A downstream processing stage according to - Flow S L2 a depolymerization unit for depolymerizing at least one of the oligomeric compounds CPO of ε-caprolactam contained in the at least one depolymerization unit; - Flow S L2 a separation unit for separating at least one solid residue from the - Flow S L2 a treatment unit for treating at least one solid residue contained in the - Flow S L2 at least one incineration stage for incinerating solid residues contained in The method of any one of embodiments 18 to 24, comprising one or more of:

[0093] 26.(viii) Water vapor flow S V1 , preferably a flow of water vapor S V1 and water vapor flow S V2 , more preferably the water vapor flow S V1 and the water vapor flow S V2 The combined flow is then passed through a water removal unit W to separate the CPM from the water. U wherein the water removal unit preferably comprises at least one distillation column, more preferably 1 to 3 distillation columns, more preferably 2 or 3 distillation columns, more preferably 3 distillation columns, and the water removal unit W U comprises more than one distillation column, the distillation columns are preferably arranged in series. The method of any one of embodiments 1 to 25, preferably any one of embodiments 18 to 25, further comprising:

[0094] 27. The process of embodiment 26, wherein the bottoms stream of at least one distillation column, preferably the bottoms stream of the most downstream distillation column, is recycled to the evaporation unit E1.

[0095] 28.Flow S according to (i) R providing (i.1) Aqueous liquid mixture M containing CPM and CPO dissolved in water WC preparing a (i.1.1) Aqueous liquid flow S W preparing a (i.1.2) providing a solid material M containing a polyamide prepared from ε-caprolactam, (i.1.3) A solid material M prepared according to (i.1.2) and a stream of aqueous liquid S prepared according to (i.1.1) W preparing a mixture with (i.1.4) From the mixture prepared by (i.1.3), an aqueous liquid mixture M containing polyamide dissolved in water is obtained. WP preparing (i.1.5) The aqueous liquid mixture M prepared by (i.1.4) WP Chemical reactor unit R U The aqueous liquid mixture M containing CPM and CPO dissolved in water was subjected to depolymerization conditions in WC obtaining a compound according to the present invention; (i.2) Optionally, the aqueous mixture M obtained according to (i.1.5) WC Pressure reducing unit D U The steam flow S VD , as well as the aqueous liquid flow S C To obtain S C comprising CPM and CPO dissolved in water; (i.3) Optionally, the aqueous mixture M obtained according to (i.1.5) WC or the aqueous liquid stream S obtained by (i.2) C Solid-liquid separation unit SL U The solid-liquid separation is performed through the sieve to obtain an aqueous liquid stream S containing CPM and CPO dissolved in water. L obtaining a step; (i.4) (i.1.5) WC or by (i.2) a stream of aqueous liquid S Cor by (i.3) the aqueous liquid stream S L From at least two evaporation subunits E U1 and E U2 Evaporation unit E equipped with U and separating water by evaporation in at least one steam stream S VE and the aqueous liquid flow S R Steps to get The method of any one of embodiments 1 to 27, comprising:

[0096] 29. The method of embodiment 28, wherein the solid material M prepared by (i.1.2) preferably comprises waste material, more preferably consists only of waste material, said waste material preferably comprising textile waste material.

[0097] 30. When embodiment 28 or 29 depends on any one of embodiments 18 to 25, in (vii), the liquid flow S L2 passing the resulting mixture through a downstream processing stage, the downstream processing stage comprising the steps of: (vii.1) Flow S L2 The first flow S L21 and the second flow S L22 and a step of dividing the mixture into S L21 and S L22 S L2 having the same chemical composition as (vii.2) Flow S L21 into the chemical reactor unit according to (i.1.5), (vii.3) Flow S L22 passing the resulting mixture through a downstream processing stage; 30. The method of embodiment 28 or 29, comprising:

[0098] 31. A downstream processing stage according to (vii.3) - Flow S L22 a separation unit for separating at least one solid residue from the - Flow S L22 a treatment unit for treating at least one solid residue contained in the - Flow S L22 and an incineration stage for incinerating at least one solid residue included in the at least one solid residue.

[0099] In the context of the present invention, the term "polyamide prepared from ε-caprolactam" as used herein refers to a polyamide having the formula: (-NH-(CH)-CO-) n It should be noted that the term "polyamide 6" refers to a polyamide 6 characterized by the following: In the context of the present invention, the ε-caprolactam monomer compound CPM is an ε-caprolactam monomer. The term "bar", when used in the context of the present invention, refers to "bar(abs)", i.e. bar (absolute value), sometimes also referred to as "bara".

[0100] The term "fibrous materials" encompasses fibrous and non-fibrous raw materials that are processed by various methods into linear, planar and spatial structures. It relates to linear fibrous structures, such as threads, yarns and ropes, sheet-like fibrous structures, such as woven fabrics, knitted fabrics, braids, stitch-bonded fabrics, nonwoven fabrics and felts, produced from fibrous materials, as well as three-dimensional fibrous structures, i.e. body structures, such as textile hoses, stockings or textile semi-finished products, and also to finished products made saleable by construction, opening up and / or other operations to proceed to processors, traders or final consumers using the aforementioned products.

[0101] The term "textile waste" encompasses textile material, as defined above, whose inherent value has been consumed from the perspective of its current owner and which is therefore end-of-life material for said owner.

[0102] In the context of the present invention, the term "X is one or more of A, B and C", where X is a given characteristic and each of A, B and C represents a specific realization of said characteristic, should be understood as disclosing that X is either A, or B, or C, or A and B, or A and C, or B and C, or A and B and C. In this regard, it should be noted that those skilled in the art can translate the above abstract terms into concrete examples, e.g., X is a chemical element and A, B and C are specific elements such as Li, Na, and K, or X is a temperature and A, B and C are specific temperatures such as 10°C, 20°C, and 30°C. In this regard, it is further noted that one skilled in the art may expand the above terms to less specific realizations of said features, such as, for example, "X is one or more of A and B" disclosing that X is either A, or B, or A and B, or to more specific realizations of said features, such as, for example, "X is one or more of A, B, C, and D" disclosing that X is either A, or B, or C, or D, or A and B, or A and C, or A and D, or B and C, or B and D, or C and D, or A and B and C, or A and B and D, or B and C and D, or A and B and C and D. [Brief description of the drawings]

[0103] [Figure 1]Figure 1 is a schematic diagram of a production unit used in the method according to a preferred embodiment of the present invention. The production unit comprises an evaporation unit E1, a splitting means D, and a mixing means M. A stream SR of an aqueous liquid containing CPM dissolved in water at a concentration cR (CPM), where CPM has a boiling point TCPM, SR further contains at least one CPO at a concentration cR (CPO), and CPO has a boiling point TCPO where TCPO > TCPM. When the stream SR of the aqueous liquid is mixed with a stream SL11, a mixture ME of the aqueous liquid is obtained. When the mixture ME of the aqueous liquid is supplied to evaporation conditions in the evaporation unit E1, a stream SV1 of water vapor and a stream SL1 of the aqueous liquid are obtained. SV1 contains CPM at a concentration cV1 (CPM) where cV1 (CPM) > cR (CPM). SL1 contains at least one CPO at a concentration cL1 (CPO) where cL1 (CPO) > cR (CPO) and contains CPM at a concentration cL1 (CPM) where cL1 (CPM) < cR (CPM). The stream SL1 of the aqueous liquid is split into two streams SL11 and SL12. SL11 and SL12 have the same chemical composition as SL1. The stream SL12 of the aqueous liquid passes through a downstream process not shown in Figure 1, and the stream SL11 of the aqueous liquid is recycled and mixed with SR. [Diagram 2] Figure 2 is a schematic diagram of a production unit used in the method according to a preferred embodiment of the present invention. As in Figure 1, the production unit comprises an evaporation unit E1 and a splitting means D. However, compared to Figure 1, the production unit further comprises a heat exchanger H1 but does not comprise a mixing means M. The stream SR of the aqueous liquid is supplied to the evaporation unit E1, and the stream SL11 of the aqueous liquid passes through H1 for heating before being recycled (reused) as a feed component to E1. Thus, ME is formed within E1. Apart from the said difference, the method illustrated in Figure 2 is implemented as the method illustrated in Figure 1. [Diagram 3]Figure 3 is a schematic diagram of a production unit used in the method according to a preferred embodiment of the present invention. The method illustrated in Figure 3 represents an alternative to the method illustrated in Figure 2. As in Figure 1, the production unit comprises an evaporation unit E1, a splitting means D, and a mixing means M. However, compared to Figure 1, the production unit further comprises a heat exchanger H1, which is arranged downstream of the mixing means M and upstream of E1. For this reason, H1 heats the combined stream to a temperature preferably in the range of 200 to 270 °C, more preferably in the range of 210 to 270 °C, even more preferably in the range of 220 to 270 °C. Apart from said differences, the method illustrated in Figure 3 is implemented as the method illustrated in Figure 1. [Figure 4] Figure 4 is a schematic diagram of a production unit used in the method according to a preferred embodiment of the present invention. As in Figure 3, the production unit comprises an evaporation unit E1, a splitting means D, a mixing means M, and a heat exchanger H1. However, compared to Figure 3, the production unit further comprises a second evaporation unit E2. When a stream SL12 of an aqueous liquid is subjected to evaporation conditions within the second evaporation unit E2, a stream SV2 of water vapor and a stream SL2 of liquid are obtained. SV2 contains CPM at a concentration cV2(CPM) such that cV2(CPM) > cL12(CPM), and CPO at a concentration cV2(CPO) such that cV2(CPO) < cL12(CPO). SL2 contains at least one CPO at a concentration cL2(CPO) such that cL2(CPO) ≥ cL12(CPO). The liquid stream SL2 passes through a downstream processing stage not shown in Figure 4. Apart from said differences, the method illustrated in Figure 4 is implemented as the method illustrated in Figure 3. [Diagram 5]Figure 5 is a schematic diagram of a production unit used in the method according to a preferred embodiment of the present invention. As in Figure 4, the production unit comprises an evaporation unit E1, a splitting means D, a mixing means M, a heat exchanger H1 and a second evaporation unit E2. However, in comparison with Figure 4, the production unit further comprises a water removal unit WU for separating CPM from water. The water removal unit WU comprises three distillation columns arranged in series. The bottom stream of the most downstream distillation column is recycled to the evaporation unit E1. The water vapor stream SV1 and the water vapor stream SV2 are mixed and the combined stream passes through the water removal unit WU. Apart from said differences, the method illustrated in Figure 5 is implemented as the method illustrated in Figure 4. [Figure 6] Figure 6 is a schematic diagram of a production unit used in a method according to a preferred embodiment of the invention. As in Figure 5, the production unit comprises an evaporation unit E1, a splitting means D, a mixing means M, a heat exchanger H1, a second evaporation unit E2 and a water removal unit WU for separating CPM from water. However, in comparison with Figure 5, the production unit further comprises upstream of M and E1 a chemical reactor unit RU, a decompression unit DU, a solid-liquid separation in a solid-liquid separation unit SLU, and an evaporation unit EU with at least two evaporation subunits EU1 and EU2. When a solid material M containing polyamide prepared from ε-caprolactam and an aqueous liquid stream SW are fed to depolymerization conditions in the chemical reactor unit RU, a mixture of aqueous liquids MWC is obtained, which comprises CPM and CPO dissolved in water. When the mixture of aqueous liquids MWC passes through the decompression unit DU, a steam stream SVD and an aqueous liquid stream SC are obtained. SC, which comprises CPM and CPO dissolved in water. The aqueous liquid stream SC is subjected to solid-liquid separation by passing it through a solid-liquid separation unit SLU, resulting in an aqueous liquid stream SL comprising CPM and CPO dissolved in water. Water is then separated from the aqueous liquid stream SL by evaporation in EU comprising EU1 and EU2, resulting in a water vapor stream SVE and an aqueous liquid stream SR. The aqueous liquid stream SR is then treated as in the method illustrated in FIG. 5. [Figure 7]Figure 7 is a schematic diagram of a production unit used in a method according to a preferred embodiment of the invention. As in Figure 6, the production unit comprises an evaporation unit E1, a splitting means D, a mixing means M, a heat exchanger H1, a second evaporation unit E2 and a water removal unit WU for separating CPM from water, and upstream of M and E1, the production unit further comprises a chemical reactor unit RU, a decompression unit DU, a solid-liquid separation in a solid-liquid separation unit SLU, and an evaporation unit EU with two evaporation subunits EU1 and EU2. The method illustrated in Figure 7 is carried out as the method illustrated in Figure 6, except that the liquid stream SL2 is split into two streams, a first stream SL21 and a second stream SL22. SL21 and SL22 have the same chemical composition as SL2. Stream SL21 is reused as a component of the aqueous liquid stream SW. The liquid stream SL22 passes through downstream processing stages not shown in Figure 7. [Figure 8]Figure 8 is a schematic diagram of a part of a production unit used in a method according to a preferred embodiment of the invention, i.e. the part providing SR. Said part of the production unit comprises a reaction unit RU, a depressurization unit DU, a solid-liquid separation unit SLU and an evaporation unit E1 with two evaporation subunits EU1 and EU2, said two units being connected in series as illustrated in Figure 8. As previously described, a solid material M comprising polyamide and an aqueous liquid stream SW are fed into the reactor unit RU and are subjected to depolymerization conditions comprising a depolymerization temperature TD at a depolymerization pressure pD. An aqueous liquid stream MWC is removed from the bottom of the RU, the MWC comprising ε-caprolactam dissolved in water. Feeding the aqueous liquid stream MWC into the depressurization unit DU gives a steam stream SVD and an aqueous liquid stream SC comprising ε-caprolactam dissolved in water. The steam stream SVD is recycled as a component of the aqueous liquid stream SW, preferably after being at least partially condensed. When the aqueous liquid stream SC passes through the solid-liquid separation unit SLU, an aqueous liquid stream SSLU is obtained comprising ε-caprolactam dissolved in water. The aqueous liquid stream SL is then fed to evaporation in E1, specifically SL is fed to EU1. A water vapor stream SVE1 is obtained from EU1 and a water vapor stream SVE2 is obtained from EU2. The water vapor streams SVE1 and SVE2 are recycled, preferably by condensation, as components of the aqueous liquid stream SW. Furthermore, an aqueous liquid stream SR1 comprising ε-caprolactam dissolved in water is removed from EU1 and fed to EU2, and an aqueous liquid stream SR comprising ε-caprolactam dissolved in water is obtained and removed from EU2. The aqueous liquid stream SR is then further processed as disclosed above and illustrated in figures 1 to 7. [Figure 9]Figure 9 is a schematic diagram of a part of a production unit used in a method according to a preferred embodiment of the invention, i.e. the part providing SR. Said part of the production unit comprises a reaction unit RU, a depressurization unit DU, a solid-liquid separation unit SLU and an evaporation unit E1 with two evaporation subunits EU1 and EU2, said two units being connected in series as illustrated in Figure 9. The depressurization unit DU comprises a depressurization subunit DU11, a depressurization subunit DU12 and two solid-liquid separation units F1 and F2. The aqueous liquid stream MWC removed from the bottom of the RU passes through a solid-liquid separation unit F1, preferably a filtration unit F1, preferably with a mesh size in the range of 0.5-5 mm, more preferably in the range of 1-3 mm, and is then fed to the subunit DU11 to obtain a water vapor stream SVD11 and an aqueous liquid stream SLD11 comprising ε-caprolactam dissolved in water. The aqueous liquid stream SLD11 then passes through a solid-liquid separation unit F2, preferably a filtration unit F2, preferably with a mesh size in the range of 0.5-5 mm, more preferably in the range of 1-3 mm, and is then fed as a feed stream to a second pressure reduction subunit DU12 to obtain a water vapor stream SVD12 and an aqueous liquid stream SC comprising ε-caprolactam dissolved in water. The water vapor streams SVD11 and SVD12 are recycled as components of the aqueous liquid stream SW, preferably after at least partial condensation. Downstream of DU, the method is implemented as the method of FIG. 8. [Explanation of symbols]

[0104] D...Dividing means D U ...Decompression unit DU11 Pressure Reducing Subunit DU12 Pressure Reducing Subunit E1... Evaporation unit E2: Second evaporation unit E U ...Evaporation unit E U1 Evaporation subunit EU2 Evaporation subunit F1 Solid-liquid separation unit F2 Solid-liquid separation unit H1...Heat exchanger M...Mixing means, solid materials M E ...Water-based liquid mixtures M WC ...Aqueous liquid flow M WP ...Water-based liquid mixtures R1: Chemical reactor R2: Chemical reactor R3: Chemical reactor R4: Chemical reactor R i Chemical reactors R U Chemical Reactor Unit R y Chemical reactors R Z Chemical reactors S1...Aqueous liquid flow S C ...Aqueous liquid flow S i ...Aqueous liquid flow S L ...Aqueous liquid flow S L1 ...Aqueous liquid flow S L2 Liquid flow S L11 ...Aqueous liquid flow S L12 ...Aqueous liquid flow S L21 First flow S L22 ...Second flow S LD11 ...Aqueous liquid flow SLU: Solid-liquid separation unit SL U Solid-liquid separation unit S R ...Aqueous liquid flow S R1 ...Aqueous liquid flow S SLU ...Aqueous liquid flow S V1 ...Water vapor flow S V2 ...Water vapor flow S VD ...Water vapor flow S VD11 ...Water vapor flow S VD12 ...Water vapor flow S VE ...Water vapor flow S VE1 ...Water vapor flow S VE2 ...Water vapor flow S W ...Aqueous liquid flow S WC ...Aqueous liquid flow W U ...Water removal unit

Claims

1. A flow S containing at least one ε-caprolactam oligomer compound CPO and an ε-caprolactam monomer compound CPM. Ｒ A method for separating from, (i) Concentration c Ｒ Step of providing a flow S of an aqueous liquid containing CPM dissolved in water at (CPM), wherein CPM has a boiling point T Ｒ and S ＣＰＭ further contains said at least one CPO of (CPO), and CPO has a boiling point T Ｒ at concentration c Ｒ where T ＣＰＯ > T ＣＰＭ and has a boiling point T ＣＰＯ ; Flow S provided by (ii)(i) Ｒ A mixture M of aqueous liquids containing Ｅ Steps to prepare: (iii)(i) The mixture M Ｅ Evaporation unit E １ Exposed to evaporation conditions inside, the water vapor flow S Ｖ１ and the flow of aqueous liquid S Ｌ１ A step to obtain S Ｖ１ However, c Ｖ１ (CPM) > c Ｒ (CPM) is the concentration c Ｖ１ (CPM) includes CPM, S Ｌ１ However, c Ｌ１ (CPO) > c Ｒ (CPO) is a concentration c Ｌ１ (CPO) includes at least one CPO, and c Ｌ１ (CPM) < c Ｒ (CPM) is the concentration c Ｌ１ (CPM) so CPM is included in the step; Flow S by (iv)(iii) Ｌ１ The first flow S Ｌ１１ And the second flow S Ｌ１２ The step of dividing into S Ｌ１１ and S Ｌ１２ is S Ｌ１ A step having the same chemical composition; The flow S obtained by (v)(iv) Ｌ１２ The step includes passing it through a downstream processing stage, (ii) A mixture of aqueous liquids M Ｅ The step of preparing the flow S Ｒ The flow S Ｌ１１ A method that includes mixing with

2. - Flow S provided by (i) Ｒ However, it exhibits a CPM concentration in the range of 15 to 90% by mass, and a CPO concentration in the range of 0.5 to 10% by mass. - Flow S obtained by (iii) Ｖ１ However, it showed a CPM concentration in the range of 65-99% by mass. - Flow S obtained by (iii) Ｌ１ However, it exhibits a CPM concentration in the range of 0.1 to 10% by mass, and a CPO concentration in the range of 1 to 10% by mass. The method according to claim 1.

3. (ii) The aqueous liquid mixture M Ｅ The step of preparing is flow S Ｒ Flow S Ｌ１１ Before mixing with (iv), the flow S obtained from (iv) Ｌ１１ The method according to claim 1 or 2, further comprising heating to a temperature in the range of 200 to 270°C.

4. The aforementioned flow S Ｌ１１ Heating the flow S Ｌ１１ (ii) includes passing the flow S provided by (i) through the heat exchanger H1, wherein (ii) Ｒ and the flow S obtained from heating Ｌ１１ However, the evaporation unit E １ Mixed inside, or (ii) The aqueous liquid mixture M Ｅ The step of preparing is provided by (i) and flow S Ｒ The flow S obtained from (iv) Ｌ１１ This includes mixing with and heating the combined flow to a temperature in the range of 200 to 270°C, wherein heating the combined flow is performed by the flow S Ｌ１１ to the heat exchanger H １ Including passing through The method according to claim 3.

5. The method according to claim 1, (iii) The evaporation unit E １ A method in which evaporation occurs within one or more stirred vessels, or within one or more membrane evaporators, or within one or more stirred vessels and one or more membrane evaporators.

6. The method according to claim 5, The evaporation conditions according to (iii) are for mixture M Ｅ Evaporation temperature T Ｅ１ Includes, T Ｅ１ However, the temperature range is 200-270°C, and the evaporation conditions according to (iii) are such that the evaporation pressure p Ｅ１ Methods that further include the above.

7. The method according to claim 5 or 6, The evaporation conditions according to (iii) are as follows: Evaporation unit E １ dwell time t within Ｅ１ It further includes, Ｅ１ However, the method ranges from 1 minute to 5 hours.

8. The method according to claim 1, In (iv), flow S Ｌ１ However, the mass ratio m(S) is in the range of 0.01:1 to 0.02:

1. Ｌ１２ ): m(S Ｌ１１ ) with the first flow S Ｌ１１ And the second flow S Ｌ１２ A method of dividing into two parts.

9. The method according to claim 1, The downstream processing stage according to (v) is - Evaporation unit; - Flow S Ｌ１２ A depolymerization unit for depolymerizing at least one ε-caprolactam oligomer compound CPO contained in; - Flow S Ｌ１２ A separation unit for separating at least one solid residue from; - Flow S Ｌ１２ A processing unit for processing at least one solid residue contained therein; - Flow S Ｌ１２ A method comprising one or more incineration stages for incinerating at least one solid residue contained in a.

10. The method according to claim 1, The downstream processing stage according to (v) includes an evaporation unit, and the method is (vi) Flow S Ｌ１２ Evaporation unit E ２ Exposed to evaporation conditions inside, the water vapor flow S Ｖ２ and liquid flow S Ｌ２ A step to obtain S Ｖ２ However, c Ｖ２ (CPM) > c Ｌ１２ (CPM) is the concentration c Ｖ２ (CPM) CPM, and c Ｖ２ (CPO) <c Ｌ１２ (CPO) is a concentration c Ｖ２ (CPO) includes CPO, S Ｌ２ However, c Ｌ２ (CPO) ≥ c Ｌ１２ (CPO) is a concentration c Ｌ２ (CPO) includes at least one CPO, The flow S obtained by (vii)(vi) Ｌ２ A method further comprising the step of passing the data through a downstream processing stage.

11. The method according to claim 10, Evaporation unit E by (vi) ２ A method in which evaporation occurs within one or more stirred vessels, or within one or more membrane evaporators, or within one or more stirred vessels and one or more membrane evaporators.

12. A method according to claim 10 or 11, The evaporation conditions according to (vi) are for the flow S Ｌ１２ and include the evaporation temperature T Ｅ２ where T Ｅ２ is in the range of 200 to 300 °C, and the evaporation conditions according to (vi) further include the evaporation pressure p Ｅ２ A method.

13. A method according to claim 10 or 11, The evaporation conditions according to (vi) are for evaporation unit E ２ dwell time t within Ｅ２ It further includes, Ｅ２ However, the method is in the range of 1 second to 5 minutes.

14. A method according to claim 10 or 11, The downstream processing stage by (vii) - Flow S Ｌ２ A depolymerization unit for depolymerizing at least one ε-caprolactam oligomer compound CPO contained in; - Flow S Ｌ２ A separation unit for separating at least one solid residue from; - Flow S Ｌ２ A processing unit for processing at least one solid residue contained therein; - Flow S Ｌ２ A method comprising one or more incineration stages for incinerating at least one solid residue contained in a.

15. The method according to claim 10, (viiii) Water vapor flow SV1, water removal unit W for separating CPM from water Ｕ Steps to pass through Methods that further include the above.

16. The method according to claim 1, Flow S due to (i) Ｒ The steps provided are, (i.1) A mixture M of aqueous liquid containing CPM and CPO dissolved in water. ＷＣ The steps for preparing the following: (i.1.1) Flow of aqueous liquid S Ｗ A process to provide; (i.1.2) A step of preparing a solid material M containing a polyamide prepared from ε-caprolactam; (i.1.3) A solid material M prepared according to (i.1.2) and a flow of aqueous liquid S provided according to (i.1.1) Ｗ A step of preparing a mixture with; (i.1.4) From the mixture prepared according to (i.1.3), an aqueous liquid mixture M containing polyamide dissolved in water is obtained. ＷＰ The process of preparing; (i.1.5) Aqueous liquid mixture M prepared according to (i.1.4) ＷＰ to chemical reactor unit R Ｕ A mixture M of aqueous liquids containing CPM and CPO dissolved in water, which are subjected to depolymerization conditions inside the chamber. ＷＣ process to obtain Steps including; (i.2) Optionally, the aqueous mixture M obtained by (i.1.5) may be used. ＷＣ to pressure reduction unit D Ｕ Exposed to reduced pressure inside, the water vapor flow S ＶＤ , and the flow of aqueous liquid S Ｃ It is about obtaining S Ｃ A step comprising CPM and CPO dissolved in water; (i.3) Optionally, the aqueous mixture M obtained by (i.1.5) may be used. ＷＣ Or (i.2) the aqueous liquid flow S obtained by Ｃ Solid-liquid separation unit SL Ｕ The solid-liquid is separated by passing the liquid through a filter, and the resulting aqueous liquid flow S contains CPM and CPO dissolved in water. Ｌ Steps to obtain (i.4) (i.1.5) Mixture M of aqueous liquid obtained ＷＣ From, or the aqueous liquid flow S obtained by (i.2) Ｃ From, or the aqueous liquid flow S obtained by (i.3) Ｌ Therefore, at least two evaporation subunits E Ｕ１ and E Ｕ２ Easy Evaporation Unit E Ｕ Water is separated by evaporation inside, creating at least one water vapor flow S ＶＥ and the flow of aqueous liquid S Ｒ A method that includes the step of obtaining.

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