TW202506641A - Process for hydrolytically depolymerizing a polyamide - Google Patents

Abstract

A process for hydrolytically depolymerizing a polyamide 6 comprised in a solid material M, the process comprising providing the solid material M; melting in a melting unit U _Mthe solid material M, obtaining a liquid stream S _Mhaving a temperature T _SMat a pressure p _SM; providing a liquid aqueous stream S _Whaving a temperature T _SWat a pressure p _SW; admixing in a pre-reaction unit U _PRthe stream S _Mwith the stream S _W, obtaining a liquid reaction feed stream S _Fhaving a temperature T _SFat a pressure p _SF; feeding the stream S _Finto a chemical reaction unit U _R; subjecting the stream S _Fin the reaction unit U _Rto polyamide 6 depolymerization conditions comprising a polyamide 6 depolymerization temperature T _Dat a polyamide 6 depolymerization pressure p _D, obtaining in U _Ran aqueous depolymerization mixture comprising ε-caprolactam dissolved in water; removing an aqueous liquid reactor exit stream S _Rfrom U _R, the stream S _Rcomprising ε-caprolactam dissolved in water; wherein 0.8 ≤ T _SF/T _D≤ 1.05 and 0.9 ≤ p _SF/p _D≤ 1.05.

Description

Method for hydrolyzing and depolymerizing polyamide

The present invention relates to a method for hydrolytically depolymerizing polyamide prepared from ε-caprolactam and a device for implementing the method for hydrolytically depolymerizing polyamide prepared from ε-caprolactam, and preferably for implementing the above-mentioned method.

Polyamides, and in particular polyamide 6 characterized by the formula (-NH-( _CH2 ) ₅ -CO-) _n , can be found in many materials, such as packaging, automotive engineering plastics and textile filamentary fibers. The latter accounts for about 40% of the global market for polyamide 6. Currently, only a very small part of textile filamentary fibers is recycled, while they account for a significant percentage of global _CO2 emissions. There is therefore a need to recover polyamide 6 from such materials. There are methods for alkaline depolymerization of polyamides. Therefore, there is a need to provide improved methods for depolymerizing polyamides that can overcome these problems.

According to the present invention, it was found that when the depolymerization reaction actually takes place upstream of the chemical reaction unit, a special sequence of melting units and pre-reaction units is realized, an efficient depolymerization reaction of polyamide 6 by hydrolysis can be achieved. In addition, it was found that if a special design of the chemical reaction unit is realized, the method can be made more efficient. Based on this, and in combination with a special sequence of stages upstream and especially downstream of the chemical reaction unit that allows water recovery and extremely efficient use of process heat, the present invention can provide an advantageous overall method for recovering polyamide 6-containing materials.

Therefore, the present invention relates to a method for hydrolyzing and depolymerizing polyamide 6 contained in a solid material M, the method comprising: (i) providing the solid material M; (ii) melting the solid material M provided according to (i) in a melting unit _UM to obtain a liquid stream SM having a temperature T _SM at a pressure p _SM ; (iii) providing a liquid water stream _SW having a temperature T _SW at a pressure p _SW ; (iv) mixing the stream _SM obtained according to (ii) with the stream SW provided according to (iii) in a pre-reaction unit U _PR to obtain a liquid reaction feed stream _SF having a temperature T _SF at a pressure p _SF ; (v) feeding the stream _SF obtained according to (iv) into a chemical reaction unit _UR ; (vi) mixing the stream SF in the reaction unit U _{PR with the stream SW provided according to (iii) to obtain a liquid reaction feed stream SF having a temperature T SF at a pressure p SF ;} subjecting the stream _SF to polyamide 6 depolymerization conditions in _{a reactor UR} , said polyamide 6 depolymerization conditions comprising a polyamide 6 depolymerization temperature _TD at a polyamide ₆ depolymerization pressure PD, to obtain an aqueous depolymerization mixture in a reactor _UR , said aqueous depolymerization mixture comprising ε-caprolactam dissolved in water; (vii) removing an aqueous liquid reactor exit stream _SR from the _UR , said stream _SR comprising ε-caprolactam dissolved in water; wherein 0.8 ≤ _TSF / _TD ≤ 1.05 and 0.9 ≤ _pSF / _pD ≤ 1.05.

Preferably according to the present invention, for preparing the stream _SF to be subjected to the hydrolytic polyamide 6 depolymerization conditions according to (vi), no polyamide 6 depolymerization catalyst, such as inorganic acids (such as one or more of hydrochloric acid, nitric acid, sulfuric acid and phosphoric acid) and/or zinc salts (such as zinc chloride, zinc acetate or zinc trifluoromethanesulfonate) is added.

Preferably, 0.6 ≤ T _SM /T _SF ≤ 1.05 and 0.9 ≤ p _SM /p _SF ≤ 1.05. According to the present invention, preferably may be one or more of the following ranges: 0.6 ≤ T _SM /T _SF ≤ 0.7; 0.7 ≤ T _SM /T _SF ≤ 0.8; 0.8 ≤ T _SM /T _SF ≤ 0.9; 0.9 ≤ T _SM /T _SF ≤ 1.0; 1.0 ≤ T _SM /T _SF ≤ 1.05.

More preferably, 0.8 ≤ T _SW /T _SF ≤ 1.3 and 0.9 ≤ p _SW /p _SF ≤ 1.05. Further according to the present invention, one or more of the following ranges may be preferred: 0.8 ≤ T _SW /T _SF ≤ 0.9; 0.9 ≤ T _SW /T _SF ≤ 1.0; 1.0 ≤ T _SW /T _SF ≤ 1.1; 1.1 ≤ T _SW /T _SF ≤ 1.2; 1.2 ≤ T _SW /T _SF ≤ 1.3.

With regard to the pre-reaction unit U _PR according to (iv), there are no special restrictions, provided that a liquid reaction feed stream _SF having a temperature T _SF at a pressure p _SF is available. Preferably, the pre-reaction unit U _PR according to (iv) comprises and preferably consists of a mixing unit, wherein the mixing unit is preferably a static mixing unit. The term "static mixing unit" as used herein refers to an arrangement of several mixing elements, which are installed in a pipe or duct and operate with essentially no moving parts and preferably no moving parts at all. According to the invention, it is preferred that the mixing unit is configured as a suitable pipe junction for a pipe for the flow _SM and a pipe for the flow _SW , wherein no special mixing elements are present.

According to the present invention, preferably according to (iv), _SW and _SM are mixed in _UPR at a mixing ratio ( _mW /kg)/(mP/ _kg ) in a range of from 1:1 to 20:1, more preferably in a range of from 2:1 to 15:1, and more preferably in a range of from 5:1 to 10:1, wherein _mW is the amount of water contained in _SW and _mP is the amount of polyamide 6 contained in _SM . Preferred ranges are, for example, from 5:1 to 6:1, or from 6:1 to 7:1, or from 7:1 to 8:1, or from 8:1 to 9:1, or from 9:1 to 10:1.

With regard to the melting unit U _M according to (ii), there are no particular restrictions, provided that a liquid stream S _M having a temperature T _SM at a pressure p _SM is available. Preferably, the melting unit U _M according to (ii) comprises an extruder or an extruder, more preferably an extruder, wherein more preferably, the melting unit U _M according to (ii) consists of an extruder, wherein more preferably, the extruder is more preferably a single-screw extruder or a twin-screw extruder, more preferably a twin-screw extruder. More preferably, the solid material M provided according to (i) and having a temperature below T _SM is fed into the extruder and melted therein while being conveyed through the extruder. The temperature of the solid material fed into the extruder preferably has a temperature in the range from 10 to 50°C, more preferably in the range from 15 to 40°C, more preferably in the range from 20 to 30°C. Further preferably, the solid material is fed into the extruder at a pressure in the range from 0.75 to 5 bar, more preferably in the range from 0.85 to 3 bar, more preferably in the range from 0.95 to 1.5 bar. For the melting material M, the extruder is preferably equipped with suitable heating means to heat the material M respectively, wherein the liquid stream _SM has a temperature T _SM when leaving the extruder. The suitable heating means can be arranged in a way that the extruder exhibits one heating zone or more than one heating zone. It is conceivable that the extruder has more than one feeding zone for feeding the solid material M. Further according to the invention, the extruder can be operated starve-fed or flood-fed.

Preferably, the melting unit U _M (preferably an extruder) is equipped with a degassing system for removing one or more gases during the melting process in the extruder. Although it is generally conceivable that the extruder has more than one degassing zone, it is preferred to have one degassing zone. Preferably, the degassing zone is located immediately before the pressure build-up in the discharge zone of the extruder. If the melting unit U _M (preferably an extruder) is equipped with a degassing system, the method preferably comprises removing a gas flow S _GM from U _M during the melting according to (ii). Preferably, the gas stream S _GM has a temperature T _GM at a pressure p _GM , wherein 0.95 ≤ T _GM /T _SM ≤ 1.05, preferably 0.95 ≤ T _GM /T _SM ≤ 1.0. Preferably according to the present invention, the stream S _GM obtained from the melting unit U _M is subjected to washing in the washing unit U _S , preferably to one or more of wet washing and dry washing, more preferably to wet washing, wherein the wet washing preferably comprises passing the gas stream S _GM into a washing column, preferably filling the washing column. Before being subjected to washing, the flow S _GM obtained from the melting unit _UM is preferably subjected to cooling, preferably in a vacuum system, through which the flow S _GM is preferably removed from the melting unit _UM .

According to the invention, the stream _SM has a pressure _pSM , wherein the pressure _pSM is preferably in the range of 0.9 ≤ _pSM / _pSF ≤ 1.05 and wherein _pSF is in the range of 0.9 ≤ _pSF / _pD ≤ 1.05. As discussed below, the polyamide 6 depolymerization pressure _pD is preferably in the range of from 40 to 140 bar. Thus, according to the invention, the pressure _pSM is preferably higher, preferably significantly higher, than the pressure at which the solid material M is fed into the melting unit _UM and preferably into the extruder. According to the invention, it is conceivable that this pressure increase is achieved in the extruder itself. However, it is particularly preferred that the pressure increase is achieved by means of a suitable compression device which is contained in the melting unit U _M , for example a compression device which is arranged downstream of the extruder. According to this preferred arrangement, it is preferred that the liquid stream leaving the extruder is at substantially the same pressure as the solid material fed into the extruder, wherein the liquid stream is then suitably compressed in the compression device so that the stream S _M has a temperature T _SM at a pressure p _SM . Preferably according to the present invention, the compression device comprises and preferably consists of at least one suitable gear pump, wherein if more than one gear pump is installed, it is preferred that at least two gear pumps are arranged in series.

Further according to the invention, preferably the liquid stream _SM leaving the melting unit _UM is passed through a filter unit _UF before being mixed with the liquid water stream _SW according to (iv). Preferably, the filter unit _UF is arranged downstream of the melting unit _UM and upstream of the reaction unit _UR , the filter unit _UF preferably being a filter unit _UF for separating particles from the liquid stream _SM , said particles having a particle size in the range from 100 to 500 microns, preferably in the range from 200 to 400 microns, wherein the method comprises passing the liquid stream _SM through _UF before mixing according to (iv). Furthermore, if the melting unit U _M comprises a compression device as described above, it is preferred that the liquid flow (preferably obtained from the extruder) is passed through the filtering device U _F before the liquid flow (preferably obtained from the extruder) passes through the compression device.

Further according to the invention, the melting unit U _M may comprise more than one melting device, preferably more than one extruder, wherein for example two or more extruders may be arranged in parallel.

Regarding the depolymerization conditions of polyamide 6 according to (vi), preferably, _TD is in the range of from 230 to 330 ° C and _p is in the range of from 40 to 140 bar, more preferably, _TD is in the range of from 250 to 320 ° C and _p is in the range of from 40 to 125 bar, and more preferably, _TD is in the range of from 270 to 310 ° C and _p is in the range of from 40 to 110 bar.

Thus, a preferred range for _TD is, for example, from 270 to 280 °C or from 280 to 290 °C or from 290 to 300 °C or from 300 to 310 °C, and a preferred range for _pD is, for example, from 40 to 55 bar or from 55 to 70 bar or from 70 to 85 bar or from 85 to 100 bar or from 100 to 110 bar.

According to the present invention, the reaction unit _UR according to (v) comprises at least one reactor in which the liquid stream _SF is subjected to the depolymerization conditions according to (vi). Preferably, the reaction unit _UR according to (v) comprises z chemical reactors R _i , i=1 ... z, wherein z is in the range from 1 to 10, preferably in the range from 1 to 8, more preferably in the range from 1 to 6, more preferably in the range from 1 to 5, more preferably in the range from 1 to 4, more preferably in the range from 1 to 3. More preferably, the reaction unit _UR according to (v) comprises 3 reactors R ₁ , R ₂ and R ₃ .

If the reaction unit _UR according to (v) comprises more than one reactor R _i , i.e. if z > 1, preferably at least 2 reactors R _i , preferably all z reactors R _i are connected in series, wherein - according to (v), a stream _SF is fed to R _i , where i = 1; - a liquid aqueous stream S _i containing ε-caprolactam dissolved in water is removed from the reactor R _i and fed to the reactor R _i+1 , where i <z; - according to (vii), a liquid aqueous stream S _z containing ε-caprolactam dissolved in water is removed from the reactor R _z as stream _SR ; wherein in each reactor R _i a depolymerization temperature T _Di is maintained at a depolymerization pressure p _Di , wherein, independently of one another, T _Di is in the range from 230 to 330 ° C and p Di is 230 ° C. to 330 ° C. _Di is in the range of from 40 to 140 bar, preferably wherein T _Di is in the range of from 250 to 320 °C and p _Di is in the range of from 40 to 125 bar, more preferably wherein T _Di is in the range of from 270 to 310 °C and p _Di is in the range of from 40 to 110 bar. Regarding the preferred arrangement of the three reactors R ₁ , R ₂ and R ₃ , it is preferred that these three reactors are connected in series, wherein - according to (v), the stream _SF is fed to R ₁ ; - a liquid aqueous stream S ₁ containing ε-caprolactam dissolved in water is removed from the reactor R ₁ and fed to the reactor R ₂ ; - a liquid aqueous stream S ₂ containing ε-caprolactam dissolved in water is removed from the reactor R ₂ and fed to the reactor R ₃ ; - according to (vii), a liquid aqueous stream S ₃ containing ε-caprolactam dissolved in water is removed from the reactor R ₃ as stream _SR ; wherein in the reactor R ₁ , a depolymerization temperature T _D1 is maintained at a depolymerization pressure p _D1 , wherein T wherein _{T D1} is in the range of from 230 to 330 ° C and p _D1 is in the range of from 40 to 140 bar, preferably wherein T _D1 is in the range of from 250 to 320 ° C and p _D1 is in the range of from 40 to 125 bar, more preferably wherein T _D1 is in the range of from 270 to 310 ° C and p _D1 is in the range of from 40 to 110 bar; wherein a preferred range of T _D1 is, for example, from 270 to 280 ° C or 280 to 290 ° C or 290 to 300 ° C or 300 to 310 ° C, and a preferred range of p _D1 is, for example, from 40 to 55 bar or from 55 to 70 bar or from 70 to 85 bar or from 85 to 100 bar or from 100 to 110 bar; wherein in reactor R ₂ , the depolymerization pressure p A depolymerization temperature T _D2 at _a pressure of 230 to 330 ° C. and p _D2 is in the range of 40 to 140 bar, preferably T _D2 is in the range of 250 to 320 ° C. and p _D2 is in the range of 40 to 125 bar, more preferably T _D2 is in the range of 270 to 310 ° C. and p _D2 is in the range of 40 to 110 _bar ; wherein a preferred range of T _D2 is, for example, from 270 to 280 ° C. or 280 to 290 ° C. or 290 to 300 ° C. or 300 to 310 ° C., and a preferred range of p _D2 is, for example, from 40 to 55 bar or from 55 to 70 bar or from 70 to 85 bar or from 85 to 100 bar or from 100 to 110 bar; wherein in the reactor R ₃ , maintaining a depolymerization temperature T _D3 under a depolymerization pressure p _D3 , wherein T _D3 is in the range of from 230 to 330 ° C and p _D3 is in the range of from 40 to 140 bar, preferably wherein T _D3 is in the range of from 250 to 320 ° C and p _D3 is in the range of from 40 to 125 bar, more preferably wherein T _D3 is in the range of from 270 to 310 ° C and p _D3 is in the range of from 40 to 110 bar; wherein a preferred range for T _D3 is, for example, from 270 to 280 ° C or 280 to 290 ° C or 290 to 300 ° C or 300 to 310 ° C, and for p Preferred ranges for _D3 are, for example, from 40 to 55 bar, or from 55 to 70 bar, or from 70 to 85 bar, or from 85 to 100 bar, or from 100 to 110 bar.

According to the present invention, it is preferred that for z>1, the z reactors _Ri are arranged vertically, wherein _Ri is the uppermost reactor and _Rz is the lowermost reactor, wherein _Si obtained from _Ri is transferred to Ri ₊₁ by gravity, and preferably only by gravity. With regard to the preferred arrangement of three reactors _R1 , _R2 and _R3 , it is preferred that the reactors _R1 , _R2 and _R3 are arranged vertically, wherein _Ri is the uppermost reactor and _R3 is the lowermost reactor, wherein _Si obtained from _Ri is transferred to _R2 by gravity, and preferably only by gravity, and wherein _S2 obtained from _R2 is transferred to _R3 by gravity, and preferably only by gravity.

Regarding the specific design of one or more reactors _Ri , it is preferred that at least one reactor _Ri is a stirred tank reactor, and more preferably all of the reactors are stirred tank reactors. Regarding the preferred arrangement of three reactors _R1 , _R2 and _R3 , it is preferred that the reactors _R1 , _R2 and _R3 are stirred tank reactors.

Although there is no general limitation on the specific design of the stirred tank reactor, according to the present invention, it is particularly preferred that at least one stirred tank reactor _Ri , and preferably each stirred tank reactor _Ri independently has preferably from 2 to 6 compartments, more preferably from 2 to 5 compartments, and more preferably from 2 to 4 compartments, the compartments are preferably arranged in series, and more preferably in series and vertically, wherein two adjacent compartments are separated by a partition comprising at least one co-current opening. Preferably, at least one compartment contained in the reactor _Ri comprises at least one agitator, wherein more preferably, each compartment of each reactor _Ri comprises at least one agitator, wherein more preferably, each compartment of each reactor _Ri comprises one agitator, wherein the method comprises stirring the depolymerization mixture in a given compartment at least part of the time during the depolymerization conditions in the compartment. Regarding the preferred arrangement of the three reactors _R1 , _R2 and _R3 , it is more preferred that the stirred tank reactor _R1 has 3 compartments arranged vertically and continuously, each compartment of which contains a stirrer, the stirred tank reactor _R2 has 3 compartments arranged vertically and continuously, each compartment of which contains a stirrer, and the stirred tank reactor _R3 has 3 compartments arranged vertically and continuously, each compartment of which contains a stirrer. Special reference is made to FIG. 5 of the present invention and the related description thereof.

Alternatively, with regard to the particular design of the stirred tank reactor, it is particularly preferred according to the present invention that at least one stirred tank reactor _Ri and preferably each stirred tank reactor _Ri independently of one another has preferably from 2 to 6 compartments, more preferably from 2 to 5 compartments, more preferably from 2 to 4 compartments, the compartments preferably being arranged in series, and more preferably in series and vertically, wherein the reactor _Ri comprises at least one agitator and wherein 2 adjacent compartments are formed by one or more suitable components of the agitator, such as blades comprised in the agitator, and are separated by them, wherein the method comprises stirring the depolymerization mixture in the reactor compartment for at least part of the time during which it is subjected to depolymerization conditions in a given compartment. In this regard, and further with respect to the preferred arrangement of the three reactors _R1 , _R2 and _R3 , it is preferred that the stirred tank reactor _R1 has 2 compartments formed by suitable components of the stirrer contained in _R1 and equally divided therefrom, which are arranged vertically and continuously, the stirred tank reactor _R2 has 2 compartments formed by suitable components of the stirrer contained in _R2 and equally divided therefrom, which are arranged vertically and continuously, and the stirred tank reactor _R3 has 2 compartments formed by suitable components of the stirrer contained in _R3 and equally divided therefrom, which are arranged vertically and continuously.

Preferably according to the present invention, the depolymerization conditions of polyamide 6 according to (vi) further comprise a total residence time t _D of the aqueous depolymerization mixture in the unit _UR , preferably in the z reactors R _i , more preferably in the z stirred tank reactors, wherein at least 85% by weight, preferably at least 90% by weight, more preferably at least 95% by weight of the aqueous depolymerization mixture has a t _D in the range of 30 to 90 min. The term "total residence time" as used hereinbefore and hereinafter in the present invention refers to the sum of the residence times in all the above-mentioned chemical reactors R _i . In particular, for z > 1, it is preferred that the residence time of the aqueous depolymerization mixture in the reactor _Ri is _tDi and wherein 0.90 ≤ ( _tDi /tDi ₊₁ ) ≤ 1.10, preferably 0.95 ≤ ( _tDi /tDi ₊₁ ) ≤ 1.05. Thus, according to the present invention, it is preferred to achieve a narrow residence time distribution. Regarding the preferred arrangement of the three reactors _R1 , _R2 and _R3 , it is preferred that the residence time of the aqueous depolymerization mixture in reactor _R1 is _tD1 , the residence time of the aqueous depolymerization mixture in reactor _R2 is _tD2 , and the residence time of the aqueous depolymerization mixture in reactor _R3 is _tD3 , and wherein 0.90 ≤ ( _tD1 / _tD2 ) ≤ 1.10, preferably 0.95 ≤ ( _tD1 / _tD2 ) ≤ 1.05, and wherein 0.90 ≤ ( _tD2 / _tD3 ) ≤ 1.10, preferably 0.95 ≤ ( _tD2 / _tD3 ) ≤ 1.05.

Preferably according to the invention, at least one of the reactors _Ri , and preferably all the reactors _Ri, has one or more outlet means for removing a gas stream from the respective reactor _Ri , i.e. outlet means for degassing the respective reactor _Ri . Thus, the method of the invention preferably comprises removing a respective gas stream S _Gi from at least one reactor _Ri , and preferably from all z reactors _Ri , the given gas stream S _Gi having a temperature T _Gi at a pressure p _Gi , wherein 0.95 ≤ T _Gi /T _Di ≤ 1.05. Regarding the preferred arrangement of three reactors _R1 , _R2 and _R3 , the method further preferably comprises removing a gas stream _SG1 from _R1 , _SG1 having a temperature _TG1 at a pressure _pG1 , wherein _0.95≤TG1 / _TD1≤1.05 , removing a gas stream _SG2 from _R2 , _SG2 having a temperature _TG2 at a pressure _pG2 , wherein _0.95≤TG2 / _TD2≤1.05 , and removing a gas stream _SG3 from _R3 , _SG3 having a temperature _TG3 at a pressure _pG3 , wherein _0.95≤TG3 / _TD3≤1.05 . According to the present invention, it is preferred that the method further comprises merging at least one of the gas streams S _Gi , more preferably all of the gas streams S _Gi , more preferably the gas streams S _G1 , S _G2 and S _G3 with the above-mentioned gas stream S _GM , preferably before subjecting the gas stream S _GM to the above-mentioned washing.

Generally speaking, there is no particular limitation on how to provide the solid material M according to (i). Preferably, providing the solid material M according to (i) comprises (i.1) providing the solid material M in a delivery unit U _MD , wherein U _MD preferably comprises one or more of at least one ton bag feeding station and at least one bulk container station; (i.2) passing the solid material M provided according to (i.1) from the unit U _MD into a material collecting unit U _MC , preferably a collecting bucket, through a first connecting line, wherein the first connecting line preferably comprises one or more of the following: at least one material receiving and discharging unit U _MRD , at least one first material feeding unit U _FMF and at least one first particle separation unit U _FMPS ; (i.3) passing the solid material M from the unit U _MC into the unit U _M through a second connecting line. , wherein the second connection circuit preferably includes one or more of the following: at least one second material feeding unit _USMF , at least one second particle separation unit _USMSPS and at least one metal detector.

Preferably, the first connection line according to (i.2) comprises at least one unit U _MRD , preferably at least one hopper, more preferably at least one one-zone hopper, and further comprises at least one unit U _FMF , preferably at least one rotary feeder, and preferably further comprises at least a particle separation unit U _FMPS , more preferably at least one filter, more preferably at least one screen filter.

Further preferably, for passing the solid material M from the unit U _MD into the unit U _MC through the first connecting line, at least one gas flow _SG is passed through the first connecting line, and the at least one gas flow preferably includes and is more preferably composed of air or lean air, wherein before passing through the first connecting line, it is preferably filtered, compressed and cooled, and is more preferably pre-treated by filtering, compression and cooling.

Further preferably, the second connection line according to (i.3) comprises at least two units _USMF , preferably comprising a rotary feeder and a loss-in-weight feeder, wherein more preferably the rotary feeder is arranged upstream of the loss-in-weight feeder, and further comprises a unit _USMSPS , preferably comprising a vibrating screen.

Preferably, according to (i), the solid material M is provided in the form of particles and preferably provided to U _M , wherein the particle size distribution of the particles is preferably characterized by one or more of the following pairs of values, preferably by two or more of the following pairs of values, and more preferably by the following three pairs of values: - a D10 value of particle width in the range of 0.3 to 15 mm, and a D10 value of particle length in the range of 0.3 to 15 mm; - a D50 value of particle width in the range of 0.5 to 20 mm, and a D50 value of particle length in the range of 0.5 to 20 mm; - a D90 value of particle width in the range of 0.8 to 30 mm, and a D90 value of particle length in the range of 0.8 to 30 mm.

Better value pairs are for example: -             D10 value of particle width, which is in the range of 2 to 4 mm, and D10 value of particle length, which is in the range of 3.5 to 5.5 mm; -             D50 value of particle width, which is in the range of 2.5 to 4.5 mm, and D50 value of particle length, which is in the range of 4 to 7 mm; -             D90 value of particle width, which is in the range of 3 to 5 mm, and D90 value of particle length, which is in the range of 4.5 to 8.5 mm.

The term "particles" used hereinbefore and hereinbefore in the present invention includes particles which are optionally preformed, and also includes chopped pieces.

In the solid material M provided according to (i), preferably 10 to 100 wt %, more preferably 30 to 100 wt %, more preferably 50 to 100 wt %, more preferably 60 to 100 wt %, more preferably 70 to 100 wt %, more preferably 80 to 100 wt % consists of polyamide 6. If the content of polyamide 6 in the solid material M is less than 100 wt %, the solid material M may preferably further comprise one or more elastanes. Generally speaking, the solid material M may contain at least one other polymer compound in addition to polyamide 6, wherein the at least one other polymer compound preferably contains one or more of the following: at least one polyamide 6.6; at least one semi-aromatic polyamide including one or more of polyamide 6T and polyamide 6I; at least one polyethylene terephthalate; at least one polyurethane; at least one polyester; at least one polyether; at least one poly Vinyl chloride; at least one natural fiber material, such as wool and cotton; at least one cellulose material; at least one natural elastomer; at least one synthetic elastomer; at least one copolymer of two or more of the polymer compounds, including statistical copolymers, gradient copolymers, alternating copolymers, block copolymers and graft copolymers; and at least one rubber material, including at least one natural rubber material and at least one synthetic rubber material. In addition, in addition to polyamide 6, the solid material M may further include one or more of the following: at least one pigment material and at least one glass fiber material.

Preferably, the solid material M provided according to (i) comprises and preferably consists of the following: waste, preferably one or more of textile waste and engineering plastic waste, more preferably textile waste. Generally speaking, the solid material M provided according to (i) can be composed of a single material or a plurality of different materials, that is, it is composed of w chemical materials _Mj , where j=1..w and w≥1. Further according to the present invention, preferably at least one of the chemical materials _Mj , more preferably each chemical material _Mj comprises and preferably consists of waste, and the waste preferably comprises and preferably consists of at least one textile waste. If w>1, the respective two or more materials may have different chemical compositions without any particular restrictions, provided that the solid material M exhibits the composition discussed above.

According to the present invention, the liquid water stream _SW provided according to (iii) is preferably composed of water in an amount of from 90 to 100 wt%, more preferably from 91 to 100 wt%, more preferably from 92 to 100 wt%, more preferably from 93 to 100 wt%, more preferably from 94 to 100 wt%, more preferably from 95 to 100 wt%. The best range may be from 96 to 100 wt%, from 97 to 100 wt%, from 99 to 100 wt%, or from 99 to 100 wt%.

Preferably according to the invention, providing the liquid water stream _SW according to (iii) comprises generating a water stream comprising at least part of the water contained in the stream _SR , and feeding at least part of the generated water stream back to the chemical reaction unit _UR as the water stream _SW or as part thereof.

Regarding the recovery of the water, for example, the method may comprise subjecting the stream _SR obtained from the chemical reaction unit _UR to hot water separation, optionally after subjecting _SR to filtration, to obtain the water stream _SX ; and feeding at least part of the water stream _SX back to the chemical reaction unit _UR as part of the water stream _SW , wherein the hot water separation preferably comprises one or more of distillation and falling film evaporation. Preferably, generating the water stream _SX may comprise distilling the stream _SR obtained from the reaction unit _UR , optionally after subjecting _SR to filtration, to obtain the stream _SX . The distillation can preferably be carried out in a distillation column at a bottom temperature preferably in the range of from 70 to 140° C., more preferably in the range of from 80 to 120° C., more preferably in the range of from 90 to 110° C. and at a top pressure preferably in the range of from 0.5 to 1.5 bar, more preferably in the range of from 0.7 to 1.2 bar, more preferably in the range of from 0.8 to 1.1 bar, wherein the stream _SX is obtained at the top of the distillation column. Furthermore, the distillation can preferably comprise subjecting the vapor top stream to condensation to obtain a liquid stream _SX , wherein at least a portion of the liquid stream _SX is fed back to the chemical reaction unit _UR as part of the water stream _SW . Preferably, the liquid stream _SX obtained from the condensation can be split into two streams, wherein the first stream obtained by the split is fed back to the chemical reaction unit _UR as part of the water stream _SW and the second stream is fed back to the top of the distillation column, wherein the volume ratio of the first stream to the second stream is preferably in the range of from 10:1 to 0.5:1, more preferably in the range of from 7:1 to 1:1, and more preferably in the range of from 5:1 to 2:1.

Regarding the recovery of water, it is preferred to use a method according to the present invention, wherein according to (vii), the stream _SR comprises ε-caprolactam dissolved in water at a concentration of c _SR , and the stream _SR further comprises one or more impurities, and the method further comprises (viii) passing the liquid water stream _SR to an evaporation unit _UE , obtaining a liquid water stream _SL from _SR , the liquid water stream _SL comprising ε-caprolactam dissolved in water at a concentration of c _SL , wherein c _SL > c _SR , and further obtaining one or more water vapor streams _{SV from SR ;} (ix) passing the water stream _SL to a heat-consuming purification unit _UP , obtaining a stream _SCPL from _SL , the stream _SCPL comprising ε-caprolactam at a concentration of c _SCPL , wherein c _SCPL >> c _SL , and further obtaining from _SL one or more water streams _SRW , wherein at least part of the heat consumed in _UP is provided by at least one of the one or more streams _SV , thereby obtaining at least one at least partially condensed water stream _SVW from at least one stream _SV ; (x) at least partially recycling at least one stream _SVW to the reaction unit _UR and at least partially recycling at least one stream _SRW to the reaction unit _UR .

The recovery according to (x) preferably comprises (x.1) feeding at least one stream _SVW and at least one stream _SRW to a water treatment unit _UW to obtain at least one water recovery stream _SW from _UW ; (x.2) at least partially recovering at least one water stream _SW to the reaction unit _UR .

The water treatment unit U _W preferably includes a water recovery unit U _WR and a waste water unit U _WW , wherein (x.1) preferably further includes (x.1.1) feeding at least one stream _SVW and at least one stream _SRW to the water recovery unit U _WR to obtain at least one water recovery stream _SW and at least one water stream S _SW from U _WR ; (x.1.2) feeding at least one stream S _SW to the waste water unit U _WW to obtain at least one waste water stream S _WW from U _WW .

The purification unit _UP preferably comprises one or more of a heat-consuming water separation unit U _WS , a heat-consuming distillation unit _UD and a heat-consuming crystallization unit _UC , more preferably two or more of the heat-consuming water separation unit U _{WS ,} the heat-consuming distillation unit _UD and the heat-consuming crystallization unit _UC , more preferably the heat-consuming water separation unit U _WS , the heat-consuming distillation unit UD and the heat-consuming crystallization unit _UC , wherein at least part of the heat consumed in one or more of U _WS , _UD and _UC is provided by at least one of the one or more streams _SV .

For such a purification unit _UP , the method preferably includes one or more of (a-1), (a-2) and (a-3); more preferably at least two or more of (a-1), (a-2) and (a-3); more preferably (a-1), (a-2) and (a-3): (a-1) obtaining at least one at least partially condensed water stream _SVW1 from U _WS ; (a- ₂ ) obtaining at least one at least partially condensed water stream _SVW2 from UD; (a-3) obtaining at least one at least partially condensed water stream _SVW3 from _UC ; wherein the method further includes one or more of _SVW1 , _SVW2 and _SVW3 ; preferably two or more of _SVW1 , _SVW2 and _SVW3 ; more preferably _SVW1 , _SVW2 and SVW3 _VW3 is fed to the water treatment unit U _W as defined in Specific Example 29.

Preferably, at least one of the equal flows S _RW is obtained from U _WS .

Preferably, the purification unit _UP comprises a heat-consuming water separation unit U _WS , a heat-consuming distillation unit _UD and a heat-consuming crystallization unit _UC , wherein the method comprises feeding a stream _SL to U _WS , the stream _SL comprising ε-caprolactam having a concentration of c _SL , obtaining a stream U _WS from U _WS , the stream U _WS comprising ε-caprolactam having a concentration of c _UWS , feeding the stream _SUWS to the distillation unit _UD , obtaining a stream S _UD from _UD , the stream S _UD comprising ε-caprolactam having a concentration of c _UD , feeding the stream S _UD to the crystallization unit _UC and obtaining a stream _SCPL from _UC , the stream _SCPL comprising ε-caprolactam having a concentration of c _SCPL , wherein c _SL < c _UWS < c _UD ＜ c _SCPL .

Preferably, the water separation unit U _WS comprises at least two heat-consuming water separation units U _WS1 and U _WS2 , more preferably two heat-consuming water separation units U _WS1 and U _WS2 connected in series, wherein the stream _SL is preferably fed into U _WS1 , and wherein at least part of the heat consumed in one or more of U _WS1 and U _WS2 is preferably provided by at least one of one or more streams _SV .

For such a water separation unit U _WS , the method preferably comprises one or more of (b-1) and (b-2), preferably (b-1) and (b-2): (b-1) obtaining at least one at least partially condensed water stream S _VW11 from U _WS1 ; (b-2) obtaining at least one at least partially condensed water stream S _VW12 from U _WS2 .

Further for such a water separation unit U _WS , it is preferred that at least one water flow _SRW1 is obtained from U _WS1 and at least one water flow _SRW2 is obtained from U _WS2 , and wherein at least one of _SRW1 and _SRW2 , preferably _SRW1 and _{SRW2 ,} is fed into U _W .

Further, for such a water separation unit U _WS , it is preferred that the separation unit U _I is located downstream of U _WS1 and upstream of U _WS2 , wherein the method preferably comprises obtaining a water flow S _UWS1 from U _WS1 , feeding the flow S _UWS1 into the separation unit U _I , obtaining a water flow S _UI from U _I , and feeding the flow S _UI into the unit U _WS2 , wherein in U _I , one or more of the impurities are separated from S _UWS1 , thereby obtaining an impurity flow S _I from U _I , and the impurities preferably include at least one impurity included in _SR according to (vii).

Preferably, the evaporation unit _UE comprises two or more evaporation subunits, wherein the method preferably comprises obtaining at least two steam streams S _V1 and S _V2 , passing the steam stream S _V1 into at least one heat consuming unit and passing the steam stream S _V2 into at least one heat consuming unit, wherein the steam streams S _V1 and S _V2 are different from each other in pressure and/or temperature.

Preferably, at least one solid-liquid separation unit is arranged downstream of _UR , wherein preferably at least one of the streams _SL and _SR is passed through at least one solid-liquid separation unit before passing into the next downstream unit.

According to the present invention, preferably the solid material M provided according to (i) comprises, and preferably consists of, waste materials, preferably one or more of textile waste materials and engineering plastic waste materials, and more preferably textile waste materials.

With regard to the above-mentioned stream _SCPL , i.e. the purified ε-caprolactam stream, it is preferred that this stream _SCPL be passed to _the polyamide 6 production unit _UPP , where it is used as starting material. If desired, one or more further streams _SNCPL comprising non-recycled ε-caprolactam, i.e. ε-caprolactam from known sources, may be passed to _UPP in addition. The separately prepared polyamide 6 material may then preferably be passed to _the unit _UTP , where it is used as starting material for the preparation of a material comprising polyamide 6, preferably a textile material comprising polyamide 6. If desired, one or more further streams _SNPA6 can additionally be passed to the _UTP , which streams comprise non-recycled polyamide 6, i.e. polyamide 6 from known sources. Depending on the type of material prepared in the _UTP , further streams comprising one or more starting materials other than polyamide 6 can be passed to the _UTP . The materials obtained from the _UTP , and preferably textile materials _MT , then preferably enter the market and remain there for a given life _TMT . Afterwards, the respective end-of-life materials are suitably collected in a collection unit _UTC , and preferably a textile material collection unit, from which they are suitably passed in the form of solid material M, or in the form of a portion of solid material M, as described above, optionally after selection as described herein.

Therefore, according to the present invention, the method may preferably further comprise providing a flow S _CPL to a polyamide 6 production unit U _PP , wherein the polyamide 6 produced in U _PP is preferably provided in the form of raw material to a textile material production unit U _TP , and from the unit U _TP (A) a textile material _MT is obtained, the textile material _MT is brought to the market, wherein after the life span T _MT of the textile material MT, it is at least partially collected in the form of textile waste in a textile material collection unit U _TC ; (B) the remaining material MR is obtained in the form of textile waste; wherein the remaining material _MR is provided to the textile material _production unit U TP via U _M to U TP; _R suitably provides at least part of the textile waste according to (A), or at least part of the textile waste according to (B), or at least part of the textile waste according to (A) and at least part of the textile waste according to (B).

Therefore, the present invention also relates to a use of _SCPL which can be or is obtained by the above method, which is used for preparing polyamide 6. The use preferably further comprises using the polyamide 6 as a raw material for preparing textile materials.

In addition, the present invention also relates to a method for preparing polyamide 6, which comprises using _SCPL which can be or is obtained by the method as described above as a starting material, wherein the method preferably further comprises using the polyamide 6 as a raw material for preparing a textile material.

According to the present invention, the method may further include providing a stream S _CPL to a polyamide 6 production unit U _PP , wherein the polyamide 6 produced in U _PP is preferably provided as a raw material to an engineering plastic material production unit U _EP , and (A) obtaining an engineering plastic material _ME from the unit U _EP , the engineering plastic material _ME is put on the market, wherein, after the life span T _ME of the engineering plastic material _ME , it is at least partially collected as engineering plastic waste in an engineering plastic material collection unit U _EC ; (B) obtaining the remaining material M _R in the form of engineering plastic waste; wherein the remaining material M R is provided to U _R in the form of S _M (preferably by U _M ) suitably provides at least a portion of the engineering plastic waste according to (A), or at least a portion of the engineering plastic waste according to (B), or at least a portion of the engineering plastic waste according to (A) and at least a portion of the engineering plastic waste according to (B).

Therefore, the present invention also relates to a use of _SCPL that can be or is obtained by the method as described above, which is used to prepare polyamide 6. The use preferably further comprises using the polyamide 6 as a raw material for preparing engineering plastic materials.

In addition, the present invention also relates to a method for preparing polyamide 6, which comprises using _SCPL that can be or is obtained by the above method as a starting material, wherein the method preferably further comprises using the polyamide 6 as a raw material for preparing an engineering plastic material.

According to another aspect, the present invention relates to an integrated process for preparing polyamide 6, comprising (α) preparing a stream _SCPL comprising purified ε-caprolactam according to the process as described _{herein; (β) passing the stream SCPL into} a polyamide 6 production unit _UPA ; (γ) subjecting the stream _SCPL to ε-caprolactam polymerization conditions in _UPA , obtaining polyamide 6 material _MP and a stream comprising water and one or more ε-caprolactam oligomers from _UPA ; (δ) optionally subjecting a stream comprising water and one or more ε-caprolactam oligomers to concentration for the one or more ε-caprolactam oligomers in at least one concentration stage to obtain a concentrated stream comprising water and the one or more ε-caprolactam oligomers; (ε) passing the optionally concentrated stream comprising water and the one or more ε-caprolactam oligomers into at least one of the melting unit _UM and the water ionization unit U _WS2 described herein.

Preferably, the optionally enriched stream comprising water and one or more ε-caprolactam oligomers according to (ε) further comprises ε-caprolactam, i.e. monomeric ε-caprolactam. Further preferably, the integrated method comprises (γ) subjecting the stream S _CPL to ε-caprolactam polymerization conditions in U _PA , obtaining from U _PA a polyamide 6 material _MP and a stream S EW comprising water having a concentration c _EW (W), ε-caprolactam having a concentration c _EW (C), and one or more ε-caprolactam oligomers having a total concentration c _EW (O); (δ) subjecting the stream S _EW to concentration, which comprises (δ.1) subjecting the stream _{S EW} to concentration in a first concentration unit U _C1 , obtaining from U _C1 a stream comprising water having a concentration c _C1 (W), ε-caprolactam having a concentration c _C1 (C), and one or more ε-caprolactam oligomers having a total concentration c _C1 (O) a concentrated stream S _C1 of one or more ε-caprolactam oligomers, wherein c _C1 (W) < c _EW (W), c _C1 (C) > c _EW (C), and c _C1 (O) > c _EW (O), and further obtaining a water stream S _W1 comprising water having a concentration of c _W1 (W) > c _EW (W) from U _C1 ; (δ.2) subjecting the stream S _C1 to concentration in a second concentration unit U _{C2, obtaining a concentrated stream S C2 of} one or more ε-caprolactam oligomers having a total concentration of c _C2 (O) from U _C2 , wherein c _C2 (O) > c _C1 (O), and further obtaining water comprising a concentration of c _W2 (W), and a concentration of c _W2 (W) from U _C2 . (C) an aqueous stream _SW2 of ε-caprolactam, wherein _cW2 (W) > _cW1 (W) and _cW2 (C) > _cW1 (C); (ε) passing the stream _SC2 into the subunit _UM and passing the stream _SW2 into the subunit _UWS2 .

As described above, the water stream S _EW obtained from the polyamide 6 polymer units U _PA comprises water, monomers ε-caprolactam, and one or more ε-caprolactam oligomers. Typically, this water stream S _EW further comprises one or more other organic compounds in addition to monomers ε-caprolactam and one or more ε-caprolactam oligomers. Therefore, it is preferred that the stream S _EW further comprises one or more organic compounds X other than ε-caprolactam and its oligomers with a total concentration of c _EW (X), and the method according to (δ) comprises (δ.1) subjecting the stream S _EW to concentration in a first concentration unit U _C1 , and obtaining from U _C1 a concentrated stream S _C1 comprising water with a concentration of c _C1 (W), ε-caprolactam with a concentration of c _C1 (C), one or more ε-caprolactam oligomers with a total concentration of c _C1 (O), and one or more organic compounds X with a total concentration of c _C1 (X), wherein c _C1 (W) < c _EW (W), c _C1 (C) > c _EW (C), c _C1 (O) > c _EW (O) and c _C1 (X) > c _EW (X), and further obtaining a water stream S _W1 comprising water having a concentration of c _W1 (W) > c _EW (W) from U _C1 ; (δ.2) subjecting the stream S _C1 to concentration in a second concentration unit U _C2 , obtaining a concentrated stream S C2 comprising one or more ε-caprolactam oligomers having a total concentration of c _C2 (O) and one or more organic compounds X having a total concentration of c _C2 (X) from U _C2 , wherein c _C2 (O) > c _C1 (O) and c _C2 (X) > c _C1 (X), and further obtaining a water stream S _W2 comprising water having a concentration of c _W2 (W) and ε-caprolactam having a concentration of c _W2 (C) from U _C2 , wherein c _W2 (W) > c _W1 (W) and c _W2 (X) > c C1 (X _). (C) ＞ c _W1 (C).

More preferably, according to the present invention, (γ) comprises (γ.1) passing the stream S _CPL and the preferred water stream S _AQ0 into a polymerization stage ST ₀ to obtain a crude polyamide 6 product stream S _PA1 and a water stream S _WA1 from ST ₀ ; (γ.2) passing the stream S _PA1 and the preferred water stream S _AQ1 into a granulation stage ST ₁ to obtain a crude granulated polyamide 6 material _MPA2 and a water stream S _WA2 from ST ₁ ; (γ.3) passing the material _MPA2 and the preferred water stream S _AQ2 into an extraction stage ST ₂ to obtain a purified granulated polyamide 6 material _MPA3 and a water stream S _WA3 from ST ₂ ; (γ.4) passing the material _MPA3 into a drying stage ST 3 to obtain a purified granulated polyamide 6 material MPA3 and a water stream S WA3 from ST ₂ ; ₃ Obtain polyamide 6 material _MP and water flow S _WA4 .

In case some of the polyamide 6 material obtained from the production unit U _PA does not meet the specifications, the method may preferably further comprise passing at least some of this material M _PR into the unit U _M .

As described above, the method of the present invention is preferably a continuous method. However, one or more method steps can be performed in batch mode, and one or more steps can be performed in semi-continuous mode.

The present invention is further described by the following group of specific examples and the combination of specific examples generated by the indicated dependent and reverse references. In particular, it should be noted that in each case where a series of specific examples is mentioned, such as the context before and after the term "a method as in any one of the specific examples 1 to 4", each specific example in this series is intended to be clearly disclosed to those skilled in the art, that is, those skilled in the art should understand the wording of this term as synonymous with "a method as in any one of the specific examples 1, 2, 3 and 4". In addition, it is clearly pointed out that the following group of specific examples represent a properly organized part of the general description of the preferred aspects of the present invention, and therefore properly support but do not represent the scope of the patent application of the present invention.

1. A method for hydrolyzing and depolymerizing a polyamide 6 contained in a solid material M, the method comprising: (i) providing a solid material M; (ii) melting the solid material M provided according to (i) in a melting unit _UM to obtain a liquid stream _SM having a temperature T _SM at a pressure p _SM ; (iii) providing a liquid water stream _SW having a temperature T _SW at a pressure p _SW ; (iv) mixing the stream SM obtained according to (ii) with the stream _SW provided according to (iii) in a pre-reaction unit _UPR to obtain a liquid _reaction feed stream _SF having a temperature T _SF at a pressure p _SF ; (v) feeding the stream _SF obtained according to (iv) into a chemical reaction unit _UR ; (vi) subjecting the stream SF to a reaction in the reaction unit _{UR; (vii} ) removing an aqueous liquid reactor exit stream _SR from the _UR , the stream SR comprising ε- _caprolactam dissolved in water; wherein 0.8 _{≤ T SF / TD ≤ 1.05} and 0.9 ≤ _{p SF} / p _D ≤ _1.05 .

2. The method of specific example 1, wherein 0.6 ≤ T _SM /T _SF ≤ 1.05 and 0.9 ≤ p _SM /p _SF ≤ 1.05.

3. The method of specific example 1, wherein 0.8 ≤ T _SW /T _SF ≤ 1.3 and 0.9 ≤ p _SW /p _SF ≤ 1.05.

4. A method according to any one of embodiments 1 to 3, wherein the pre-reaction unit U _PR according to (iv) comprises and preferably consists of a mixing unit, which is preferably a static mixing unit.

5. The method of any one of specific examples 1 to 4, wherein according to (iv), _SW and _SM are mixed in the U _PR at a mixing ratio of (mW/ _kg )/(mP/kg) in the range of from 1:1 to 20:1, preferably in the range of from 2:1 to 15:1, and more preferably in the range of from 5: ₁ to 10:1, wherein _mW is the amount of water contained in _SW and _mP is the amount of polyamide 6 contained in _SM .

6. The method according to any one of embodiments 1 to 5, wherein the melting unit _UM comprises, and preferably consists of, an extruder, which is preferably a single-screw extruder or a twin-screw extruder.

7. The method of any one of embodiments 1 to 6, preferably embodiment 6, wherein the melting unit U _M is equipped with a degassing system, wherein the method comprises removing a gas flow S _GM from U _M during the melting according to (ii), the gas flow S _GM having a temperature T _GM at a pressure p _GM , wherein 0.95 ≤ T _GM /T _SM ≤ 1.05.

8. The method of embodiment 7, wherein the gas stream S _GM removed from U _M is subjected to washing in a washing unit U _S , preferably subjected to one or more of wet washing and dry washing, more preferably subjected to wet washing, wherein the wet washing preferably comprises passing the gas stream S _GM into a washing column, preferably into a packed washing column.

9. The method according to any one of embodiments 1 to 8, wherein a filter unit _UF is arranged downstream of the melting unit U _M and upstream of the reaction unit _UR , the filter unit _UF being preferably a filter unit _UF for separating particles from the liquid stream _SM , the particles having a particle size in the range from 100 to 500 μm, preferably in the range from 200 to 400 μm, wherein the method comprises passing the liquid stream _SM through U _F before mixing according to (iv).

10. The method of any one of embodiments 1 to 9, wherein according to (vi), _TD is in the range of 230 to 330 °C and _p is in the range of 40 to 140 bar, preferably _TD is in the range of 250 to 320 °C and _p is in the range of 40 to 125 bar, more preferably _TD is in the range of 270 to 310 °C and _p is in the range of 40 to 110 bar.

11. The method of any one of embodiments 1 to 10, wherein the reaction unit _UR according to (v) comprises z chemical reactors R _i , i=1…z, wherein z is in the range from 1 to 10, preferably in the range from 1 to 8, more preferably in the range from 1 to 6, more preferably in the range from 1 to 5, more preferably in the range from 1 to 4, and more preferably in the range from 1 to 3.

12. The method of embodiment 11, wherein if z > 1, at least 2 reactors _Ri , preferably z reactors Ri _, are connected in series, wherein - according to (v), the stream _SF is fed to _Ri , wherein i = 1; - a liquid aqueous stream S _i containing ε-caprolactam dissolved in water is removed from the reactor _Ri and fed to the reactor Ri ₊₁ , wherein i <z; - according to (vii), the liquid aqueous stream S _z containing ε-caprolactam dissolved in water is removed from the reactor R _z as the stream _SR ; wherein in each reactor _Ri , a depolymerization temperature T _Di is maintained at a depolymerization pressure p _Di , wherein, independently of one another, T _Di is in the range from 230 to 330 ° C, and p _Di is in the range of from 40 to 140 bar, preferably wherein T _Di is in the range of from 250 to 320 °C and p _Di is in the range of from 40 to 125 bar, more preferably wherein T _Di is in the range of from 270 to 310 °C and p _Di is in the range of from 40 to 110 bar.

13. The method of embodiment 12, wherein for z > 1, the z reactors R _i are arranged vertically, wherein R ₁ is the uppermost reactor and R _z is the lowermost reactor, wherein S _i obtained from R _i is transferred to R _i+1 by gravity, and preferably only by gravity.

14. The method of any one of embodiments 11 to 13, wherein at least one, and preferably z, reactors R _i are stirred tank reactors.

15. The method of embodiment 14, wherein each stirred tank reactor _Ri independently has from 2 to 6 compartments, preferably from 2 to 5 compartments, more preferably from 2 to 4 compartments, the compartments are preferably arranged in series, and more preferably in series and vertically, wherein two adjacent compartments are separated by a partition comprising at least one co-current opening.

16. The method of embodiment 15, wherein at least one compartment contained in the reactor _Ri comprises at least one agitator, wherein preferably each compartment of each reactor _Ri comprises at least one agitator, wherein more preferably each compartment of each reactor _Ri comprises one agitator, wherein the method comprises stirring the depolymerization mixture in a given compartment at least part of the time during the exposure to depolymerization conditions in the compartment.

17. The method of any one of embodiments 1 to 16, and preferably any one of embodiments 11 to 16, and more preferably the method of embodiment 15 or 16, wherein the polyamide 6 depolymerization conditions according to (vi) further comprise a total residence time t _D of the aqueous depolymerization mixture in the unit _UR , preferably in the z reactors R _i , and more preferably in the z stirred tank reactors, wherein at least 85 wt.%, preferably at least 90 wt.%, and more preferably at least 95 wt.% of the aqueous depolymerization mixture has a t _D in the range from 30 to 90 min.

18. The method of embodiment 17, wherein the method up to embodiment 17 is according to any one of embodiments 11 to 16, wherein z > 1, preferably according to embodiment 15 or 16, wherein z > 1, wherein the residence time of the aqueous depolymerization mixture in the reactor _Ri is _tDi , and wherein 0.90 ≤ ( _tDi /tDi ₊₁ ) ≤ 1.10, preferably 0.95 ≤ ( _tDi /tDi ₊₁ ) ≤ 1.05.

19. The method according to any of embodiments 11 to 18, comprising removing a respective gas stream S _Gi from at least one reactor R _i , and preferably from all z reactors R _i , the given gas stream S _Gi having a temperature T _Gi at a pressure p _Gi , wherein 0.95 ≤ T _Gi /T _Di ≤ 1.05.

20. The method of embodiment 19, further comprising merging at least one of the gas streams S _Gi , and preferably all of the gas streams S _Gi , with the gas stream S _GM as defined in embodiment 7 before the gas stream S _GM as defined in embodiment 8 is subjected to scrubbing.

21. A method as in any one of specific examples 1 to 20, wherein providing the solid material M according to (i) comprises (i.1) providing the solid material M in a delivery unit _UMD , wherein _UMD preferably comprises one or more of at least one ton bag feeding station and at least one bulk container station; (i.2) passing the solid material M provided according to (i.1) from the unit _UMD into a material collecting unit _UMC , preferably a collecting bucket, through a first connecting line, wherein the first connecting line preferably comprises one or more of the following: at least one material receiving and discharging unit _UMRD , at least one first material feeding unit _UFMMF , and at least one first particle separation unit _UFMPS ; (i.3) passing the solid material M from the unit _UMC into the unit _UM through a second connecting line , wherein the second connection circuit preferably includes one or more of the following: at least one second material feeding unit _USMF , at least one second particle separation unit _USMSPS , and at least one metal detector.

22. The method according to embodiment 21, wherein the first connection line according to (i.2) comprises at least one unit U _MRD , preferably at least one hopper, more preferably at least one one-zone hopper, and further comprises at least one unit U _FMF , preferably at least one rotary feeder, and preferably further comprises at least a particle separation unit U _FMPS , more preferably at least one filter, more preferably at least one screen filter.

23. A method as in specific example 21 or 22, wherein for passing the solid material M from the unit _UMD into the unit _UMC through a first connecting line, at least one gas stream _SG is passed through the first connecting line, the at least one gas stream preferably comprises, and more preferably consists of, air or lean air, wherein before being transmitted through the first connecting line, the at least one gas stream is preferably pre-treated by at least one of filtering, compression and cooling, and more preferably by filtering, compressing and cooling.

24. A method as in any one of specific examples 21 to 23, wherein the second connection line according to (i.3) comprises at least two units _USMF , preferably a rotary feeder and a loss-in-weight feeder, wherein more preferably, the rotary feeder is arranged upstream of the loss-in-weight feeder, and further comprises a unit _USMSPS , preferably a vibrating screen.

25. The method of any one of embodiments 1 to 24, wherein according to (i), the solid material M is provided in the form of particles, and preferably provided to _UM , wherein the particle size distribution characteristics of the particles are preferably one or more of the following pairs of values, preferably two or more of the following pairs of values, and more preferably three of the following pairs of values: - a D10 value of the particle width in the range of 0.3 to 15 mm, and a D10 value of the particle length in the range of 0.3 to 15 mm; - a D50 value of the particle width in the range of 0.5 to 20 mm, and a D50 value of the particle length in the range of 0.5 to 20 mm; - a D90 value of the particle width in the range of 0.8 to 30 mm; The particle length D90 value is in the range of 0.8 to 30 mm.

26. A method as described in any one of specific examples 1 to 25, wherein from 10 to 100% by weight, preferably from 30 to 100% by weight, more preferably from 50 to 100% by weight, more preferably from 60 to 100% by weight, more preferably from 70 to 100% by weight, more preferably from 80 to 100% by weight of the solid material M consists of polyamide 6.

27. The method according to any one of embodiments 1 to 26, wherein providing the liquid water stream _SW according to (iii) comprises generating a water stream comprising at least part of the water comprised in the stream _SR , and feeding at least part of the generated water stream back to the chemical reaction unit _UR as the water stream _SW or as a part thereof.

28. The method of any one of embodiments 1 to 27, wherein according to (vii), the stream _SR comprises ε-caprolactam dissolved in water at a concentration c _SR , the stream _SR further comprising one or more impurities, the method further comprising (viii) passing the liquid water stream _SR into an evaporation unit _UE to obtain a liquid water stream _SL from _SR , the liquid water stream _SL comprising ε-caprolactam dissolved in water at a concentration c _SL , wherein c _SL > c _SR , and further obtaining one or more water vapor streams _{SV from SR ;} (ix) passing the water stream _SL into a heat-consuming purification unit _UP to obtain a stream _SCPL from _SL , the stream _SCPL comprising ε-caprolactam at a concentration c _SCPL , wherein c _SCPL >> c _SL , and further obtaining from _SL one or more water streams _SRW , wherein at least part of the heat consumed in _UP is provided by at least one of the one or more streams _SV , thereby obtaining at least one at least partially condensed water stream _SVW from the at least one stream _SV ; (x) at least partially recycling at least one stream _SVW to the reaction unit _UR and at least partially recycling at least one stream _SRW to the reaction unit _UR .

29. The method of embodiment 28, wherein the recovery according to (x) comprises (x.1) feeding the at least one stream _SVW and the at least one stream _SRW to a water treatment unit _UW to obtain at least one water recovery stream _SW from _UW ; (x.2) at least partially recovering the at least one water stream _SW to the reaction unit _UR .

30. A method as in specific example 29, wherein the water treatment unit U _W comprises a water recovery unit U _WR and a waste water unit U _WW , wherein (x.1) further comprises (x.1.1) feeding the at least one stream _SVW and the at least one stream _SRW to the water recovery unit U _WR to obtain the at least one water recovery stream _SW and the at least one water stream S _SW from U WR; ₍ x.1.2) feeding the at least one stream S _SW to the waste water unit U _WW to obtain at least one waste water stream S _WW from U _WW .

31. A method as described in any one of specific examples 28 to 30, wherein the purification unit _UP comprises one or more of a heat-consuming water separation unit U _WS , a heat-consuming distillation unit _UD , and a heat-consuming crystallization unit _UC , preferably two or more of the heat-consuming water separation unit U _WS , the heat-consuming distillation unit _UD , and the heat-consuming crystallization unit _UC , and more preferably the heat-consuming water separation unit U _WS , the heat-consuming distillation unit _UD , and the heat-consuming crystallization unit _UC , wherein at least part of the heat consumed in one or more of U _WS , _UD and _UC is provided by at least one of the one or more streams _SV .

32. The method of embodiment 31, comprising one or more of (i-1), (i-2), and (i-3); preferably at least two or more of (i-1), (i-2), and (i-3); more preferably (i-1), (i-2), and (i-3): (i-1) obtaining at least one at least partially condensed water stream _SVW1 from U _WS ; (i-2) obtaining at least one at least partially condensed water stream _SVW2 from _UD ; (i-3) obtaining at least one at least partially condensed water stream _SVW3 from _UC ; the method further comprising one or more of _SVW1 , _SVW2 , and _SVW3 ; preferably two or more of _SVW1 , _SVW2 , and _SVW3 ; more preferably _SVW1 , _SVW2 , and SVW3; _VW3 is fed to the water treatment unit U _W as defined in Specific Example 29.

33. The method of embodiment 31 or 32, wherein at least one of the streams S _RW is obtained from U _WS .

34. The method of any one of embodiments 28 to 33, wherein the purification unit _UP comprises a heat-consuming water separation unit U _WS , a heat-consuming distillation unit _UD and a heat-consuming crystallization unit _UC , the method comprising feeding the stream _SL to U _WS , the stream _SL comprising ε-caprolactam having a concentration of _{c SL ,} obtaining from U _WS a stream U _WS comprising ε-caprolactam having a concentration of c _UWS , feeding the stream _SUWS to the _distillation unit _UD , obtaining from _UD a stream S _UD comprising ε-caprolactam having a concentration of c _UD , feeding the stream S _UD to the crystallization unit _UC , and obtaining from _UC a stream _SCPL comprising ε- _caprolactam having a concentration of c ε-caprolactam of _SCPL , where c _SL ＜ c _UWS ＜ c _UD ＜ c _SCPL .

35. A method as in any one of specific examples 28 to 34, wherein the water separation unit U _WS comprises at least two heat-consuming water separation units U _WS1 and U _WS2 , preferably two heat-consuming water separation units U _WS1 and U _WS2 connected in series, wherein the stream _SL is fed into U _WS1 and wherein at least part of the heat consumed in one or more of U _WS1 and U _WS2 is provided by at least one of the one or more streams _SV .

36. The method of embodiment 35, comprising one or more of (ii-1) and (ii-2), and preferably (ii-1) and (ii-2): (ii-1) obtaining at least one at least partially condensed water stream S _VW11 from U _WS1 ; (ii-2) obtaining at least one at least partially condensed water stream S _VW12 from U _WS2 .

37. The method of embodiment 36, wherein at least one water stream _SRW1 is obtained from U _WS1 and at least one water stream _SRW2 is obtained from U _WS2 , and wherein at least one of _SRW1 and _SRW2 , and preferably _SRW1 and _SRW2 , is fed into U _W.

38. A method as in any one of specific examples 35 to 37, wherein the separation unit _UI is located downstream of U _WS1 and upstream of U _WS2 , the method comprising obtaining a water flow S _UWS1 from U _WS1 , feeding the flow S _UWS1 to the separation unit _UI , obtaining a water flow S _UI from _UI , and feeding the flow S _UI to the unit U _WS2 , wherein in _UI , one or more of the impurities are separated from S _UWS1 , thereby obtaining an impurity flow S _i from _UI , the impurities preferably comprising at least one impurity comprised in _SR according to (vii).

39. A method as in any one of specific examples 28 to 38, wherein the evaporation unit _UE comprises two or more evaporation subunits, the method comprising obtaining at least two steam streams S _V1 and S _V2 , passing the steam stream S _V1 into at least one heat consumption unit, and passing the steam stream S _V2 into at least one heat consumption unit, wherein the steam streams S _V1 and S _V2 differ from each other in pressure and/or temperature.

40. The method of any one of embodiments 28 to 39, wherein at least one solid-liquid separation unit is arranged downstream of _UR , wherein at least one of the streams _SL and _SR preferably passes through the at least one solid-liquid separation unit before entering the next downstream unit.

41. The method of any one of embodiments 28 to 40, further comprising providing the stream S _CPL to a polyamide 6 production unit U _PP , wherein the polyamide 6 produced in the U PP is preferably provided in the form of raw material to a textile material production unit U _TP , from which unit U _TP (A) a textile material MT is obtained, which is brought to the market, wherein after a lifetime T _MT of the textile material _MT , it is at least partially collected in the form of textile waste in a textile material collection unit U _TC ; (B) remaining material MR is obtained in the form of textile waste; wherein the polyamide 6 produced in the U _PP is preferably provided in the form of raw material to a textile material production unit U _TP , from which unit U _TP (A) a textile material MT is obtained, which is brought to the market, wherein after a lifetime T MT of the textile material _MT , it is at least partially collected in the form of textile waste in a textile material collection unit U _TC ; _R suitably provides at least part of the textile waste according to (A) or at least part of the textile waste according to (B) or at least part of the textile waste according to (A) and at least part of the textile waste according to (B).

42. The method according to any one of embodiments 1 to 41, wherein from 90 to 100 wt. %, preferably from 91 to 100 wt. %, more preferably from 92 to 100 wt. %, more preferably from 93 to 100 wt. %, more preferably from 94 to 100 wt. %, more preferably from 95 to 100 wt. % of the liquid water stream _SW provided according to (iii) consists of water.

43. A method as in any one of specific examples 1 to 42, which is a continuous method, a semi-continuous method or a batch method.

44. A method as in any one of specific examples 1 to 43, wherein the solid material M provided according to (i) comprises, and preferably consists of: waste, preferably one or more of textile waste and engineering plastic waste, more preferably textile waste.

45. A use of S _CPL that can be or is obtained by the method of any one of specific examples 28 to 44, which is used to prepare polyamide 6, and the use preferably further comprises using the polyamide 6 as a raw material for preparing one or more of textile materials and engineering plastic materials, and more preferably for preparing textile materials.

46. A method for preparing polyamide 6, the method comprising using _SCPL which can be or is obtained by the method of any one of specific examples 28 to 44 as a starting material, wherein the method preferably further comprises using the polyamide 6 as a raw material for preparing one or more of a textile material and an engineering plastic material, and more preferably for preparing a textile material.

47. Use of _SCPL obtainable by the method of any one of embodiments 28 to 44 for preparing one or more of a polymer and a polymer product; or a method for preparing one or more of a polymer and a polymer product, the method comprising using _SCPL obtainable by the method of any one of embodiments 28 to 44 as a starting material.

48. The use or method of embodiment 47, wherein the polymer, or the polymer product, or the polymer and the polymer product are in the form of at least one of a particle composition, a strand, a rod, a sheet, a tube, a foil, a layer, a film, a sheet, a fiber, a filamentary fiber, a coating, an extrusion, a molding, a flexible foam, a semi-rigid foam, and a rigid foam.

49. The use or method of embodiment 47 or 48, wherein the polymer, or the polymer product, or the polymer and the polymer product comprises polyamide 6 and, if necessary, at least one other polymer compound, wherein the at least one other polymer compound preferably comprises one or more of the following: at least one polyamide 6.6; at least one semi-aromatic polyamide including one or more of polyamide 6T and polyamide 6I; at least one polyethylene terephthalate; at least one polyurethane; at least a polyester; at least one polyether; at least one polyvinyl chloride; at least one natural fiber material, such as wool and cotton; at least one cellulose material; at least one natural elastomer; at least one synthetic elastomer; at least one copolymer of two or more of the polymer compounds, including statistical copolymers, gradient copolymers, alternating copolymers, block copolymers and graft copolymers; and at least one rubber material, including one or more of at least one natural rubber material and at least one synthetic rubber material.

50. The use or method of any one of specific examples 47 to 49, wherein the polymer, or the polymer product, or the polymer and the polymer product, is one of the following or a part of one of the following: -     ... wheel), fan wheel, cooling water tank, housing or housing parts of heat exchanger, refrigerant cooler, charge air cooler, thermostat, water pump, radiator, fastener parts of electric vehicle or battery system parts, instrument panel, steering column switch, seat, headrest, center console, transmission component, door module, A, B, C or D pillar cover for automobile exterior, spoiler, door handle, exterior rearview mirror, windshield wiper, windshield wiper protective housing, decorative grille, cover strip, sunroof track, window frame, sunroof frame, skylight, headlight, taillight, airbag and/or seat cushion; -          Fabrics, ready-made garments, preferred shirts, trousers, pullovers, boots, shoes, soles, tights and/or jackets; -            Electrical parts, preferably electrical components, electronic passive components, electronic active components, printed circuit boards, housing parts, foils, wiring, switches such as micro switches, plugs, sockets, distributors, relays, resistors, capacitors, inductors, reels, lamps, diodes such as LEDs, transistors, connectors, regulators, integrated circuits (ICs), processors, controllers, memories, sensors, micro buttons, semiconductors, reflector housings, such as for light-emitting diodes, fasteners, washers, bolts, strips, slide-in guides, screws, nuts, leaf slings, spring hooks (snap-in) and/or spring tongues for electrical and/or electronic components; -        Consumer and/or pharmaceutical products, preferred tennis strings, climbing ropes, bristles, brushes, artificial turf, 3D printing filaments, lawn mowers, zippers, Velcro, paper machine covers, extrusion coatings, fishing lines, fishing nets, offshore lines and ropes, vials, syringes, ampoules, bottles, sliding elements, spindle nuts, chain conveyors, sliding bearings, rollers, rollers, gears, rollers, toroidal gears, screws and spring dampers, hoses, pipes, cable sheaths, sockets, switches, cable ties, fan wheels, carpets, cosmetic boxes and/or bottles, mattresses, cushions, insulation materials; -        For packaging in the food industry, preferably single-layer and/or multi-layer blown films, cast films (single-layer and/or multi-layer), biaxially oriented films, and laminated films.

51. The use or method of any one of specific examples 47 to 50, wherein the polymer, or the polymer product, or the polymer and the polymer product contains 1 wt% or more, preferably 2 wt% or more, better 5 wt% or more, better 15 wt% or more, better 30 wt% or more, better 40 wt% or more, better 60 wt% or more, better 80 wt% or more, better 90 wt% or more, better 95 wt% or more; and/or 100 wt% or less, preferably 95 wt% or less, better 90 wt% or less, better 50 wt% or less, better 25 wt% or less, better 10 wt% or less of polyamide 6.

In relation to specific example 51, the respective amounts are preferably determined based on identity preservation, and/or segregation, and/or mass balance, and/or book and claim chain of custody models, more preferably based on mass balance, and more preferably the International Sustainability and Carbon Certification (ISCC) standard.

With respect to specific examples 47 to 51, the preparation of the polymer, the polymer product, or the polymer and the polymer product may comprise one or more synthetic steps and may be performed by using techniques well known to those skilled in the art of synthesis and invention. Examples of synthetic procedures are described in Industrial Organic Chemistry, ^3rd volume, Wiley-VCH, 1997; ISBN: 978-3-527-28838-0; Kunststoffhandbuch, 11 volumes in 17 sub-volumes, Carl Hanser Verlag, especially volume 6, Polyamide, ^1st edition, 1966; Injection Molding Reference Guide, 4th edition, CreateSpace Independent Publishing Platform, 2011, ISBN: 978-1466407824; WO 2008/155271 A1 and WO 2013/139827 A1, each of which is incorporated herein by reference.

As used in this article, the term "ba" refers to "abs", which is bara (absolute), sometimes also called "bara".

As used herein, the term "textile material" covers both textile and non-textile materials that are processed into linear, planar and three-dimensional structures by a variety of methods. It relates to linear textile structures, such as yarns, twists and ropes, sheet-like textile structures, such as woven fabrics, knits, braids, stitched bonded fabrics, non-woven fabrics and felts, and three-dimensional textile structures, i.e. body structures, such as textile hoses, stockings or textile semi-finished products, made therefrom; and it further relates to the use of the above-mentioned products to bring them into a salable state by sewing, laying and/or other operations for onward delivery to processors, traders, or final consumers. The term "textile waste" as used herein covers textile materials as defined above, the inherent value of which has been consumed from the perspective of its current owner and is therefore end-of-life material for that owner.

As used herein, the term "engineering plastics" refers to high performance plastic grades that possess physical properties that enable them to be used in structural applications, over a wide temperature range, under mechanical stresses, and in difficult chemical and physical environments for extended periods of time for use, for example, in the manufacture of plastic parts that replace traditional engineering materials such as metals and ceramics. Engineering plastics are particularly used in the manufacture of mechanical parts in several industries such as automotive, medical, electrical and electronic, aerospace, construction, and consumer products. As used herein, the term "engineering plastic scrap" encompasses engineering plastic materials as defined above whose inherent value has been consumed from the perspective of their current owner and which are therefore end-of-life materials to that owner.

The term "elastane" used herein is also referred to as "spandex" and common trade names of spandex include Lycra, Elaspan, Acepora, Creora, Inviya, Roica, Dorlastan, Linel or ESPA.

In the context of the present invention, the term "X is one or more of A, B and C" (where X is a given feature and each of A, B and C represents a specific embodiment of the feature) should be understood to disclose that X is A, or is B, or is C, or is A and B, or is A and C, or is B and C, or is A and B and C. In this regard, it should be noted that a person skilled in the art is able to convert the above abstract terms into concrete examples, such as where 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 should be further noted that one skilled in the art is able to extend the above terms to less specific implementations of the feature, such as “X is one or more of A and B” discloses that X is A or B, or A and B, or to more specific realizations of the feature, such as “X is one or more of A, B, C, and D” discloses that X is A, or is B, or is C, or is D, or is A and B, or is A and C, or is A and D, or is B and C, or is B and D, or is C and D, or is A and B and C, or is A and B and D, or is B and C and D, or is A and B and C and D.

Preferred aspects of the present invention are further illustrated in Figures 1 to 14, as described in the brief description of the figures.

(1): vertically arranged three-compartment reactor _Ri (2): outlet means for degassing reactor (3): outlet means for removing liquid reaction mixture from _Ri (4): outlet means for feeding a liquid stream into _Ri , such as feeding stream S _F into R ₁ : inlet device (5): heating jacket (6.1): top compartment (6.2): middle compartment (6.3): bottom compartment (7.1): stirrer in the top compartment (7.2): stirrer in the middle compartment (7.3): stirrer in the middle compartment (8): drive unit (9.1) for the stirrer according to (7.1) to (7.3): partition (9.2) with a co-current opening between the top compartment and the middle compartment: partition (10.1) with a co-current opening between the middle compartment and the bottom compartment: inlet device (10.2) for passing a heating medium into the heating jacket (5): outlet device M, _MT , _MR for removing a heating medium from the heating jacket (5): materials _R1 , _R2 , _R3 :Reactors S ₁ , S ₂ , S ₃ , _SCPL , _SF , SG ₍₁₎ , SG ₍₂₎ , _SG(3) , _SG1 , _SG2 , _SG3 , S _GM , S _I , _SL , _SM , S _NCPL , _SNPA6 , _SR , _SRW , _SRW1 , SRW2 , _{S SW ,} S _UD , S _UI , S _UWS , S _UWS1 , S _UWS2 , S _V , S _V1 , S _V2 , S _VW , S _VW1 , S _VW2 , S _VW3 , S _VW11 , S _VW12 , S _w , S _WW : Stream U _C , U _D , U _E , U _F , U _FMF (1), U _FMF (2.1), U _FMF (3), U _FMF (4), U _FMPS (1), U _FMPS (2.1), U _I , U _MRD (2.1), U _MRD (2.3), U _MRD (4), U _M , U _MC , U _MD , U _P , U _PP , U _PR , U _R , U _S , U _SMF (1), U _SMF (2), U _SMPS , U _TC , U _TP , U _W , U _WR , U _WS , U _WS1 , U _WS2 , U _WW : unit

Figures 1-4 and 6-14 illustrate the process according to the present invention.

FIG5 shows a preferred design of a reactor R _i used according to the present invention.

[Figure 1] illustrates the process according to the invention. A suitably provided solid material M comprising polyamide 6 is fed into a melting unit _UM , from which a liquid stream _SM is obtained and which is further passed into a pre-reaction unit U _PR , where it is mixed with a liquid water stream _SW . The liquid stream _SF obtained from the unit _{U PR} is then passed into _a reaction unit _UR , where it is subjected _to polyamide 6 depolymerization conditions to obtain an aqueous depolymerization mixture comprising ε-caprolactam dissolved in water. An aqueous liquid reactor exit stream _SR comprising ε-caprolactam dissolved in water is then removed from the unit _UR .

[FIG. 2] illustrates the process according to the invention. In addition to the process design shown in FIG. 1, the melting unit _UM according to FIG. 2 is equipped with a degassing system. Via this degassing system, a gas stream _SGM is removed, which is obtained when the solid material M is melted in _UM . _{This stream SGM is} then passed to the washing unit _US .

FIG. 3 illustrates a process according to the invention. In addition to the process design shown in FIG. 2 , a filtering unit U _F is arranged downstream of the melting unit U _M and upstream of the reaction unit _UR . The stream S _M obtained from the unit U _M passes through this filtering unit and downstream of U _F as a suitably filtered stream S _M into the pre-reaction unit U _PR .

FIG. 4 illustrates a process according to the invention. Compared to the process design shown in FIG. 3 , a preferred design of a reaction unit _UR is shown. According to this preferred design, the unit _UR consists of three reactors R ₁ , _{R 2 and} R _{3 ,} which are arranged in _series and _which are preferably arranged vertically. The stream S _SF obtained from the pre-reaction unit U _PR is fed to the reactor _{R 1} , where it is subjected to polyamide 6 depolymerization conditions and _{a liquid water stream S 1 is} obtained therefrom, which comprises _ε -caprolactam dissolved in water and further comprises undepolymerized polyamide ₆ . The stream _S1 is then passed (preferably only by gravity) to _the reactor _R2 , in which it is subjected to polyamide 6 depolymerization conditions and from which a liquid aqueous stream _S2 is obtained, which _comprises ε-caprolactam dissolved in water and further comprises non-depolymerized polyamide 6. The stream _S2 is then passed ₍ preferably only by gravity) to the reactor _R3 , in which it is subjected to polyamide 6 depolymerization conditions and from which a liquid aqueous stream _S3 is obtained, which comprises ε-caprolactam dissolved in water _. This stream _S3 is then removed from the reaction unit _UR as stream _SR .

[FIG. 5] shows a preferred design of a reactor _Ri used according to the present invention. If more than one reactor _Ri is used, as described above before and after FIG. 4, it is preferred that each reactor _Ri exhibits this preferred design. FIG. 5 shows a reactor _Ri that is a stirred tank reactor. In FIG. 5 , the following symbols are used: (1) vertically arranged three-compartment reactor _Ri (2) outlet device for the degassing reactor (3) outlet device for removing the liquid reaction mixture from _Ri (4) inlet device for feeding a liquid stream into _Ri , for example, for feeding stream _SF into _R1 (5) heating jacket (6.1) top compartment (6.2) middle compartment (6.3) bottom compartment (7.1) stirrer for the top compartment (7.2) stirrer for the middle compartment (7.3) stirrer for the middle compartment (8) drive unit (9.1) for the stirrer according to (7.1) to (7.3) A partition (9.2) with a downstream opening between the top compartment and the middle compartment A partition (10.1) with a downstream opening between the middle compartment and the bottom compartment Inlet means (10.2) for passing a heating medium into the heating jacket (5) Outlet means for removing a heating medium from the heating jacket (5)

[Fig. 6] illustrates a process according to the invention. Compared to the process design shown in Fig. 4, a preferred design is shown for providing a solid material M. According to Fig. 6, the solid material is provided in a delivery unit M _{MD ,} which may comprise, for example, one or more big bag stations and/or one or more bulk container stations. From the unit U _MD , the material is then passed to a suitable material collection _unit M _MC , which preferably comprises and more preferably consists of a drum. From the unit M _MC , the material is then suitably passed to a melting unit U _M.

[Figure 7] illustrates a process according to the invention. Compared to the process design shown in Figure 6, a better process is shown how to pass solid material from a delivery unit U _MD via a first connection line to a collection unit U _MC . The unit U _MD according to Figure 7 comprises, for example, a bulk container station, from which the material M is passed to a particle separation unit U _FMPS (1), and two ton bag feeding stations, wherein from the first ton bag feeding station, the material M is passed to a particle separation unit U _FMPS (2.1) and wherein from the second ton bag feeding station, the material M is passed to a particle separation unit U _FMPS (2.2). From U _FMPS (1), the material M is then passed through a feeding unit U _FMF (1) (e.g. a rotary feeder) and, via U _FMF (1), passed into and, if necessary, distributed to receiving and discharge devices U _MRD (3) (preferably a hopper) and U _MRD (4) (preferably a hopper). Furthermore, from U _FMPS (2.1), the material M is then passed into a receiving and discharge device U _MRD (2.1) (preferably a hopper) and, from U _MRD (2.1), passed through a feeding unit U _FMF (2.1) (e.g. a rotary feeder) and, via U _FMF (2.1), passed into and, if necessary, distributed to the receiving and discharge devices U _MRD (3) and U _MRD (4). Similarly, from U _FMPS (2.2), the material M is then passed into the receiving and discharge device U _MRD (2.2) (preferably a hopper), and from U _MRD (2.2) through the feeding unit U _FMF (2.2) (such as a rotary feeder), and via U _FMF (2.2), it is passed into and distributed as required to the receiving and discharge devices U _MRD (3) and U _MRD (4). From U _MRD (3) and/or U _MRD (4), the material M is then passed via the unit U _FMF (3) (preferably a rotary feeder) and/or the unit U _FMF (4) (preferably a rotary feeder) into the collecting unit U _MC . 7 , gas streams _SG (1), _SG (2) and _{SG (} 3) are shown which are passed into respective parts of the first connecting line to ( _{pneumatically} ) transport material M to respective downstream units as shown. Before passing into respective parts of the first connecting line, at least one of the gas _streams and preferably all of the gas streams are preferably subjected to gas filtration, followed by compression and subsequent cooling (not shown).

[Figure 8] illustrates the process according to the present invention. Compared with the process design shown in Figure 6, a preferred process is shown for passing the solid material from the collecting unit U _MC (preferably including a collecting bucket) into the melting unit U _M via a second connecting line. According to Figure 8, the solid material M is passed from the unit U _MC through the first feeding unit _USMF (1) (such as a rotary feeder) into the particle separation unit U _SMPS (such as a vibrating screen). From U _SMPS , the material M is then passed into the second feeding unit _USMF (2) (preferably a loss-in-weight feeding device, such as a loss-in-weight screw), and then the material M is appropriately passed from it into the melting unit U _M. Preferably, the preferred process upstream of unit U _M shown in Figure 8 should be viewed in conjunction with the preferred process shown in Figure 6.

FIG. 9 illustrates a process according to the invention. Compared to the process design shown in FIG. 4 , it is further shown that gas streams S _Gi are obtained in and removed from the reactors R _i contained in the unit _UR . These gas streams, in particular S _G1 , S _G2 and S _G3 , are then suitably combined and passed to the washing unit _US . It should be noted that it is also possible to pass the streams S _Gi separately to the unit _US (alternative solution not shown). It is further conceivable to combine one or more of the streams S _Gi with the gas stream S _GM obtained from the melting unit _UM before feeding into _US (alternative solution not shown).

[Figure 10] illustrates a process according to the invention. Figure 10 shows the sequence of stages downstream of a preferred reaction unit _UR , and the preferred water recovery via stream _SW . According to the process of Figure 10, a liquid water stream _S3 is obtained from the last reactor _R3 of the unit _{UR and} removed as a stream _SR , which contains ε-caprolactam and one or more impurities. This stream _SR is then passed to an evaporation unit _UE , from which _a liquid water stream _SL and one or more water vapor streams _SV are obtained and removed; only one vapor stream _SV is shown in Figure 10. Stream _SL has a higher ε-caprolactam concentration than stream _SR . The stream _SL is then passed to a heat-consuming purification unit _UP , in which further purification of the ε-caprolactam is carried out. From the stream _SL fed into _UP , a product stream _SCPL is finally obtained, which comprises ε-caprolactam in a concentration significantly higher than that of _the stream _SL . According to the process of the invention, at least part of the heat consumed in the purification unit _UP is provided at least partly by at least one of the one or more vapour streams _SV , and based on _SV , one or more last partially condensed water streams _SVW are obtained and removed from _UP ; only one stream _SVW is shown in FIG. 10 . From the purification unit _UP , one or more water streams _SRW are obtained from _SL . At least one stream _SVW is then at least partially recycled to the reaction unit _UR , and at least one stream _SRW is also at least partially recycled to the reaction unit _UR , wherein, for the purpose of recycling, the streams _SVW and _SRW are passed to a water treatment unit _UW , from which a stream _SW is obtained, _which is then _recycled (at least partially) as a water stream _SW (or part thereof) to the reaction unit _UR . From _UW , one or more wastewater streams _SWW are further obtained, which are not recycled to the process. Preferably, the water treatment unit _UW comprises a water recovery unit _UWR and, if necessary _, a wastewater unit _UWW . Preferably, the streams _SVW and _SRW are passed to the water treatment unit _UW where they are suitably purified and/or suitably collected to _obtain one or more water recovery streams. The streams obtained from such purification can then be passed to the wastewater treatment unit _UWW from which a wastewater stream _SWW is _obtained .

[Figure 11] illustrates a process according to the invention. The process according to Figure 11 shows further uses of the stream _SCPL , i.e. purified ε-caprolactam. According to the invention, the stream _SCPL is preferably passed to a polyamide 6 production unit _UPP , in which it is used as starting material. If necessary, one or more additional streams _SNCPL containing non-recycled ε-caprolactam, i.e. ε-caprolactam from known sources, may be passed to _UPP in _addition . The respectively prepared polyamide 6 material is then passed to a unit _UTP , _in which it is used as starting material for the preparation of a material containing polyamide 6, preferably a textile material containing polyamide 6. If desired, one or more further streams _SNPA6 can additionally be passed into _UTP , which streams comprise non-recycled polyamide 6, i.e. polyamide 6 from known sources. Depending on the type of material prepared in _UTP , further streams comprising one or more starting materials other than polyamide 6 can also be passed into _UTP . The materials obtained from _UTP , preferably textile materials _MT, then enter the market and remain therein for a given life _TMT . Afterwards, the respective end-of-life materials are suitably collected in a collecting unit _UTC , preferably a textile material collecting unit, from which they are suitably passed as a stream _SM or part of a stream _SM into the reaction unit _UR , preferably via the unit _UM in order to provide the stream _SM to _UR . Such a unit _UM usually comprises means for suitably passing preferably solid material M into the reaction unit _UR . Preferably, _UM comprises means such as one or more storage silos, one or more hoppers, one or more truck unloading stations, one or more big bag unloading stations, etc. Further in FIG. 11 , in the production unit UT _P , residual material _MR is obtained from this production process, i.e. material not included in _MT . _MR may be in the form of textile cuttings, for example. This material may be fed to _UR via _UTC and/or directly via _UM as the stream _SM or as part of the stream _SM , preferably according to the process described in FIGS. 6 , 7 and 8 above.

[Figure 12] illustrates a process according to the invention. Compared to Figure 11, a preferred design of the unit _UP is shown, i.e. the process shown in Figure 12 shows a preferred way for purifying the ε-caprolactam stream _SL . According to this process, the stream _SL is first passed into a water separation unit _UWS , from which one or more streams _SRW are _obtained , and then these streams _SRW are preferably passed into a water treatment unit _UW , as shown in Figure 11. Furthermore, at least one of the streams _SV is passed to U _WS in order to at least partially satisfy the heat demand of U _WS ; based on the at least one stream _SV passed to U _WS , one or more at least partially condensed streams _SVW1 are obtained and preferably passed further to the water treatment unit U _W , in particular U _WR . The stream _SUWS comprising ε-caprolactam is then preferably passed to a distillation unit _UD for further purification of ε-caprolactam. Furthermore, at least one of the streams _SV is passed to _UD in order to at least partially satisfy the heat demand of _UD ; based on the at least one stream _SV passed to _UD , one or more at least partially condensed streams _SVW2 are obtained and preferably passed further to the water treatment unit U _W , in particular U _WR . The ε-caprolactam-containing stream S _UD is then preferably passed to a crystallization unit _UC for further purification of the ε-caprolactam. In addition, at least one of the streams _SV is passed to _UC to at least partially satisfy the heat demand of _UC ; based on this at least one stream _SV passed to _UC , one or more at least partially condensed streams _SVW3 are obtained and are preferably further passed to the water treatment unit U _W , in particular U _WR .

[Figure 13] illustrates a process according to the invention. Compared to Figure 13, a preferred design of the unit U _WS is shown, i.e. the process shown in Figure 13 shows a preferred way of separating water by a self-flowing stream _SL . According to this process, the stream _SL is first passed to the first stage of water separation implemented in the unit U _WS1 . Then the stream _SUWS1 containing ε-caprolactam is passed from U _WS1 to the intermediate treatment stage U _I , in which impurities can be removed. Then _the purified stream _SUI obtained from U _I is further passed to the second stage of water separation implemented in the unit U _WS2 . From the unit U _WS2 , a stream _SUWS2 comprising ε-caprolactam is obtained, which stream _SUWS2 corresponds to the stream _SUWS shown in FIG. 12 and which is then preferably passed to the distillation unit _UD . From the intermediate unit U _I , a stream S _I is removed comprising the respectively separated impurities _, which can be further used based on the amount and/or chemical properties of the impurities. According to this process, one or more water streams _SRW1 are obtained, which are then preferably passed to a water treatment unit U _W , in particular U _WR . Further according to this process, one or more water streams _SRW2 are obtained, which are then preferably passed to the water treatment unit U _W , in particular U _WR . Preferably, at least one of the streams _SV is passed to U _WS1 to at least partially meet the heat demand of U _WS1 ; based on the at least one stream _SV passed to U _WS1 , one or more at least partially condensed streams _SVW11 are obtained, and preferably they are further passed to the water treatment U _W , especially U _WR . Preferably, at least one of the streams _SV is passed to U _WS2 to at least partially meet the heat demand of U _WS2 ; based on the at least one stream _SV passed to U _WS2 , one or more at least partially condensed streams _SVW12 are obtained, and preferably they are further passed to the water treatment U _W , especially U _WR .

FIG. 14 illustrates a process according to the invention. Compared to FIG. 13 , in addition to the preferred recovery loop shown in FIG. 11 above, and the treatment of the gas stream S _Gi obtained in and removed from the reactors R ₁ , R ₂ and R ₃ shown in FIG. 9 above.

M: Solid material

S _F : Liquid reaction feed flow

S _M :Liquid Flow

_SR : Aqueous liquid reactor outlet stream

S _W : Liquid water flow

U _M : Melting Unit

U _PR : Pre-reaction unit

_UR : Reaction Unit

Claims (15)

A method for hydrolyzing and depolymerizing a polyamide 6 contained in a solid material M, the method comprising: (i) providing the solid material M; (ii) melting the solid material M provided according to (i) in a melting unit _UM to obtain a liquid stream _SM having a temperature T _SM at a pressure p _SM ; (iii) providing a liquid water stream _SW having a temperature T _SW at a pressure p _SW ; (iv) mixing the stream _SM obtained according to (ii) with the stream _SW provided according to (iii) in a pre-reaction unit _UPR to obtain a liquid reaction feed stream _SF having a temperature T _SF at a pressure p _SF ; (v) feeding the stream _SF obtained according to (iv) into a chemical reaction unit _UR ; (vi) subjecting the stream SF to a reaction in the reaction unit _UR . _(vii) removing from the _UR an aqueous liquid _reactor exit stream _SR , the stream SR comprising ε- _caprolactam dissolved in water; wherein 0.8 _≤ T _SF / _TD ≤ 1.05 and 0.9 ≤ _{p SF} / p _D ≤ 1.05. The method of claim 1, wherein 0.6 ≤ T _SM /T _SF ≤ 1.05 and 0.9 ≤ p _SM /p _SF ≤ 1.05 and wherein 0.8 ≤ T _SW /T _SF ≤ 1.3 and 0.9 ≤ p _SW /p _SF ≤ 1.05. The method of claim 1 or 2, wherein the pre-reaction unit U _PR according to (iv) comprises and preferably consists of a mixing unit, the mixing unit is preferably a static mixing unit, wherein according to (iv), _SW and _SM are mixed in U _PR at a mixing ratio (m W /kg) / (m P /kg) preferably in the range of from 1:1 to 20:1, more preferably in the range of from 2: ₁ to 15:1, more preferably in the range of from 5:1 to ₁₀ :1, wherein m _W is the amount of water contained in _SW and m _P is the amount of polyamide 6 contained in _SM ; wherein the melting unit U _M comprises and preferably consists of an extruder, the extruder is preferably a single-screw extruder or a twin-screw extruder, wherein the melting unit U M _M is preferably equipped with a degassing system, the method preferably comprising removing a gas stream S _GM from U _M during the melting according to (ii), the gas stream S _GM having a temperature T _GM at a pressure p _GM , wherein preferably 0.95 ≤ T _GM /T _SM ≤ 1.05, wherein the gas stream S _GM removed from U _M is preferably subjected to a washing in a washing unit _US . A method as claimed in any one of claims 1 to 3, wherein a filter unit _UF is arranged downstream of the melting unit U _M and upstream of the reaction unit _UR , the filter unit _UF being preferably a filter unit U _F for separating particles from the liquid flow _SM , the particles having a particle size in the range from 100 to 500 μm, preferably in the range from 200 to 400 μm, wherein the method comprises passing the liquid flow _SM through U _F before mixing according to (iv). A method as claimed in any one of claims 1 to 4, wherein according to (vi), _TD is in the range of from 230 to 330 °C and _pD is in the range of from 40 to 140 bar, preferably wherein _TD is in the range of from 250 to 320 °C and _pD is in the range of from 40 to 125 bar, more preferably wherein _TD is in the range of from 270 to 310 °C and _pD is in the range of from 40 to 110 bar. A method according to any one of claims 1 to 5, wherein the reaction unit _UR according to (v) comprises z chemical reactors R _i , i=1...z, wherein z is in the range from 1 to 10, preferably in the range from 1 to 8, more preferably in the range from 1 to 6, more preferably in the range from 1 to 5, more preferably in the range from 1 to 4, more preferably in the range from 1 to 3, wherein if z > 1, at least 2 reactors R _i , preferably z reactors R _i are connected in series, wherein - according to (v), the stream S _SF is fed to R _i , wherein i=1; - a liquid water stream S _i containing ε-caprolactam dissolved in water is removed from the reactor R _i and fed to the reactor R _i+1 , wherein i <z; - According to (vii), the liquid aqueous stream _Sz containing ε-caprolactam dissolved in water is removed from the reactor _Rz as the stream _SR ; wherein in each reactor _R1 a depolymerization temperature TDi is maintained at a depolymerization pressure _pDi , wherein, independently of one another, _TDi is in the range from 230 to 330°C and pDi is in the range from 40 to 140 bar, preferably wherein TDi is in the range from 250 to 320°C and pDi is in the range from 40 to 125 bar, more preferably wherein _TDi is in the range from 270 to 310°C and _pDi is in the range from 40 to 110 bar, wherein for z>1, the z reactors R1 are preferably arranged vertically, wherein _R1 is the uppermost reactor and Rz is the lowermost reactor, wherein the liquid aqueous stream Sz containing ε-caprolactam dissolved in water is removed from the reactor Rz as the stream SR; wherein in each reactor R1 a depolymerization temperature TDi is maintained at a depolymerization pressure _pDi , wherein, independently of one another, _TDi is in the range from 230 to 330°C and pDi is in the range from 40 to 140 bar, preferably wherein TDi is in the range from 250 to 320°C and _pDi is in the range from 40 to 125 bar, more preferably wherein TDi is in the range from 270 to 310°C and pDi is in the range from 40 to 110 bar, wherein for z>1, the z reactors _R1 are preferably arranged vertically, wherein _R1 is the uppermost reactor and _R2 is the lowermost reactor, wherein the liquid aqueous stream Sz containing ε-caprolactam dissolved in water is removed from the reactor Rz as the stream SR The _Si obtained by _i is transferred to Ri ₊₁ , preferably by gravity, more preferably only by gravity. The method of claim 6, wherein at least one and preferably z reactors R _i are stirred tank reactors, wherein preferably each stirred tank reactor R _i has preferably 2 to 6 compartments, more preferably 2 to 5 compartments, more preferably 2 to 4 compartments independently of each other, the compartments are preferably arranged in series and more preferably in series and vertically, wherein two adjacent compartments are separated by a partition comprising at least one co-current opening, wherein preferably at least one compartment contained in the reactor R _i comprises at least one agitator, wherein preferably each compartment of each reactor R _i comprises at least one agitator, wherein more preferably, each reactor R i _i comprises a stirrer, wherein the method comprises stirring the depolymerization mixture in a given compartment for at least part of the time during the depolymerization conditions in the compartment; wherein the polyamide 6 depolymerization conditions according to (vi) preferably further comprise a total residence time t _D of the aqueous depolymerization mixture in the unit _UR , more preferably in the z reactors R _i , more preferably in the z stirred tank reactors, wherein at least 85% by weight, preferably at least 90% by weight, more preferably at least 95% by weight of the aqueous depolymerization mixture has a t _D in the range from 30 to 90 min; wherein for z > 1, the residence time of the aqueous depolymerization mixture in the reactor R _i is t _Di and wherein preferably 0.90 ≤ (t _Di / t _Di+1 ) ≤ 1.10, better 0.95 ≤ (t _Di / t _Di+1 ) ≤ 1.05. A method as claimed in claim 6 or 7, comprising removing respective gas streams S _Gi from at least one reactor R _i and preferably from all z reactors R _i , wherein the given gas stream S _Gi has a temperature T _Gi at a pressure p _Gi , wherein 0.95 ≤ T _Gi /T _Di ≤ 1.05, the method preferably further comprising merging at least one of the gas streams S _Gi and preferably all the streams S _Gi with the gas stream S _GM as defined in claim 3 before subjecting the gas stream S _GM to washing as defined in claim 3. The method of any one of claims 1 to 8, wherein providing the solid material M according to (i) comprises (i.1) providing the solid material M in _a delivery unit _UMD , wherein _UMD preferably comprises one or more of at least one big bag station and at least one bulk container station; (i.2) passing the solid material _M provided according to (i.1) from the unit _UMD into a material collection unit _UMC , preferably a collection bucket, through a first connection line, wherein the first connection line preferably comprises one or more of the following: at least one material receiving and discharging unit _UMRD , at least one first material feeding unit _UFMF and at least one first particle separation _{unit UFMPS} ; (i.3) passing the solid material M from the unit _UMC into the unit _UM through a second connection line , wherein the second connection line preferably includes one or more of the following: at least one second material feeding unit _USMF , at least one second particle separation unit _USMPS and at least one metal detector; wherein the first connection line according to (i.2) preferably includes at least one unit U _MRD , preferably at least one hopper, more preferably at least one one-zone hopper, and preferably further includes at least one unit U _FMF , preferably at least one rotary feeder, and preferably further includes at least particle separation unit U _FMPS , more preferably at least one filter, more preferably at least one screen filter; wherein for passing the solid material M from the unit U _{M D} into the unit U _MC through the first connection line, it is preferred that at least one gas stream S _G is transmitted through the first connecting line, the at least one gas flow preferably comprises and is more preferably composed of air or lean air, wherein before being transmitted through the first connecting line, the at least one gas flow is preferably pre-treated by at least one of filtering, compression and cooling and is more preferably filtered, compressed and cooled; wherein the second connecting line according to (i.3) preferably comprises at least two units _USMF , preferably comprises a rotary feeder and a loss-in-weight feeder, wherein more preferably, the rotary feeder is arranged upstream of the loss-in-weight feeder, and further comprises a unit _USMSP , preferably a vibrating screen. A method as claimed in any one of claims 1 to 9, wherein according to (i), the solid material M is provided in the form of particles and is preferably provided to U _M , wherein the particle size distribution of the particles is preferably characterized by one or more of the following pairs of values, preferably by two or more of the following pairs of values, and more preferably by the following three pairs of values: - a D10 value of the particle width in the range of 0.3 to 15 mm, and a D10 value of the particle length in the range of 0.3 to 15 mm; - a D50 value of the particle width in the range of 0.5 to 20 mm, and a D50 value of the particle length in the range of 0.5 to 20 mm; - a D90 value of the particle width in the range of 0.8 to 30 The particle length D90 value is in the range of from 0.8 to 30 mm; wherein preferably from 10 to 100 wt %, more preferably from 30 to 100 wt %, more preferably from 50 to 100 wt %, more preferably from 60 to 100 wt %, more preferably from 70 to 100 wt %, more preferably from 80 to 100 wt % of the solid material M consists of the polyamide 6. The method of any one of claims 1 to 10, wherein from 90 to 100 wt. %, preferably from 91 to 100 wt. %, more preferably from 92 to 100 wt. %, more preferably from 93 to 100 wt. %, more preferably from 94 to 100 wt. %, more preferably from 95 to 100 wt. % of the liquid water stream _SW provided according to (iii) consists of water. A method as claimed in any one of claims 1 to 11, wherein the solid material M provided according to (i) comprises and preferably consists of: waste, preferably one or more of textile waste and engineering plastic waste, more preferably textile waste. A method as claimed in any one of claims 1 to 12, wherein according to (vii), the stream _SR comprises ε-caprolactam dissolved in water at a concentration of c _SR , the stream _SR further comprising one or more impurities, the method further comprising (viii) passing the liquid water stream _SR into an evaporation unit _UE to obtain a liquid water stream _SL from _SR , the liquid water stream _SL comprising ε-caprolactam dissolved in water at a concentration of c _SL , wherein c _SL > c _SR , and further obtaining one or more water vapor streams _{SV from SR ;} (ix) passing the water stream _SL into a heat-consuming purification unit _UP to obtain a stream _SCPL from _SL , the stream _SCPL comprising ε-caprolactam at a concentration of c _SCPL , wherein c _SCPL >> c _SL , and further obtaining one or more water streams _SRW from _SL , wherein at least part of the heat consumed in _UP is provided by at least one of the one or more streams _SV , thereby obtaining at least one at least partially condensed water stream _SVW from at least one of the streams _SV ; (x) at least partially recycling at least one stream _SVW to the reaction unit _UR and at least partially recycling at least one stream _SRW to the reaction unit _UR . The method of claim 13, further comprising providing the stream S _CPL obtained according to (ix) to a polyamide 6 production unit U _PP , wherein the polyamide 6 produced in the U _PP is preferably provided in the form of raw material to a textile material production unit U _TP , from which unit U _TP (A) a textile material _{MT is obtained, the textile material MT is brought to the market, wherein after the life span T MT of the textile material MT, it is at least partially collected in the form of textile waste in a textile material collection unit U TC; (B) the remaining material MR is obtained in the} form of textile waste; wherein the remaining material _MR is provided to a textile material production unit U _{TP via U M R} suitably provides at least part of the textile waste according to (A) or at least part of the textile waste according to (B) or at least part of the textile waste according to (A) and at least part of the textile waste according to (B). A use of S _CPL which can be or is obtained by the method of claim 16, which is used to prepare one or more of a polymer and a polymer product, wherein the polymer or the polymer product or the polymer and the polymer product are in the form of at least one of a particle-composed object, a strand, a rod, a sheet, a tube, a foil, a layer, a film, a sheet, a fiber, a filamentary fiber, a coating, an extrusion, a molding, a flexible foam, a semi-rigid foam and a rigid foam; and wherein the polymer or the polymer product or the polymer and the polymer product comprise polyamide 6 and, if necessary, at least one other polymer compound, wherein the at least one other polymer compound preferably comprises one or more of the following: at least one polyamide 6.6; at least one a semiaromatic polyamide including one or more of polyamide 6T and polyamide 6I; at least one polyethylene terephthalate; at least one polyurethane; at least one polyester; at least one polyether; at least one polyvinyl chloride; at least one natural fiber material, such as wool and cotton; at least one cellulose material; at least one natural elastomer; at least one synthetic elastomer; at least one copolymer of two or more of the polymer compounds, including statistical copolymers, gradient copolymers, alternating copolymers, block copolymers and graft copolymers; and at least one rubber material, including one or more of at least one natural rubber material and at least one synthetic rubber material; The polymer or the polymer product or the polymer and the polymer product are preferably one of the following or a part of one of the following: - automotive parts, preferably cylinder head cover, engine hood, charge air cooler housing, charge air cooler flap, intake pipe, intake manifold, connector, gear wheel), fan wheel, cooling water tank, housing or housing parts of heat exchangers, refrigerant coolers, charge air coolers, thermostats, water pumps, radiators, fastener parts of electric vehicles or parts of battery systems, instrument panels, steering column switches, seats, headrests, center consoles, transmission components, door modules, A, B, C or D pillar covers for vehicle exteriors, spoilers, door handles, exterior rearview mirrors, windshield wipers, windshield wiper protective housings, decorative grilles, cover strips, sunroof rails, window frames, sunroof frames, roof panels, headlights, taillights, airbags and/or seat cushions; - Fabrics, ready-made garments, preferred shirts, trousers, pullovers, boots, shoes, soles, tights and/or jackets; - Electrical parts, preferably electrical components, electronic passive components, electronic active components, printed circuit boards, housing parts, foils, wiring, switches such as micro switches, plugs, sockets, distributors, relays, resistors, capacitors, inductors, reels, lamps, diodes such as LEDs, transistors, connectors, regulators, integrated circuits (ICs), processors, controllers, memories, sensors, micro buttons, semiconductors, reflector housings, such as for light-emitting diodes, fasteners, washers, bolts, strips, slide-in guides, screws, nuts, leaf slings, spring hooks (snap-in) and/or spring tongues for electrical and/or electronic components; - Consumer and/or pharmaceutical products, preferred tennis strings, climbing ropes, bristles, brushes, artificial turf, 3D printing filaments, lawn mowers, zippers, Velcro, paper machine covers, extrusion coatings, fishing lines, fishing nets, offshore lines and ropes, vials, syringes, ampoules, bottles, sliding elements, spindle nuts, chain conveyors, sliding bearings, rollers, rollers, gears, rollers, toroidal gears, screws and spring dampers, hoses, pipes, cable sheaths, sockets, switches, cable ties, fan wheels, carpets, cosmetic boxes and/or bottles, mattresses, cushions, insulation materials; - For packaging in the food industry, preferably single-layer and/or multi-layer blown films, cast films (single-layer and/or multi-layer), biaxially oriented films, and laminated films.

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