EP4688737A1 - Highly integrated caprolactam recycling process - Google Patents

Highly integrated caprolactam recycling process

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Publication number
EP4688737A1
EP4688737A1 EP24716281.1A EP24716281A EP4688737A1 EP 4688737 A1 EP4688737 A1 EP 4688737A1 EP 24716281 A EP24716281 A EP 24716281A EP 4688737 A1 EP4688737 A1 EP 4688737A1
Authority
EP
European Patent Office
Prior art keywords
stream
weight
unit
range
ppm
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP24716281.1A
Other languages
German (de)
French (fr)
Inventor
Stefan Blei
Faissal-Ali El-Toufaili
Hannah Stephanie MANGOLD
Caroline Beyer
Florian Richter
Bart Vander Straeten
Vikram Ravikumar
Esther Matyka LARYEA
Bao Liu
Dag Wiebelhaus
Volker Neu
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
BASF SE
Original Assignee
BASF SE
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by BASF SE filed Critical BASF SE
Publication of EP4688737A1 publication Critical patent/EP4688737A1/en
Pending legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D201/00—Preparation, separation, purification or stabilisation of unsubstituted lactams
    • C07D201/02—Preparation of lactams
    • C07D201/12—Preparation of lactams by depolymerising polyamides
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07D—HETEROCYCLIC COMPOUNDS
    • C07D223/00—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom
    • C07D223/02—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom not condensed with other rings
    • C07D223/06—Heterocyclic compounds containing seven-membered rings having one nitrogen atom as the only ring hetero atom not condensed with other rings with hetero atoms or with carbon atoms having three bonds to hetero atoms with at the most one bond to halogen, e.g. ester or nitrile radicals, directly attached to ring carbon atoms
    • C07D223/08—Oxygen atoms
    • C07D223/10—Oxygen atoms attached in position 2
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
    • C08J11/00—Recovery or working-up of waste materials
    • C08J11/04—Recovery or working-up of waste materials of polymers
    • C08J11/10—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation
    • C08J11/18—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material
    • C08J11/28—Recovery or working-up of waste materials of polymers by chemically breaking down the molecular chains of polymers or breaking of crosslinks, e.g. devulcanisation by treatment with organic material by treatment with organic compounds containing nitrogen, sulfur or phosphorus
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02W—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT
    • Y02W30/00—Technologies for solid waste management
    • Y02W30/50—Reuse, recycling or recovery technologies
    • Y02W30/62—Plastics recycling; Rubber recycling

Definitions

  • the present invention relates to a highly integrated recycling process, specifically for recycling E- caprolactam from a solid material which comprises a polymer prepared from c-caprolactam, specifically polyamide 6.
  • Polyamide and in particular polyamide 6 being characterized by the formula (-NH-(CH2)5-CO-) n , can be found in numerous materials, such as packaging, engineering plastics from automotive and textile filaments. The latter represents about 40 % of the polyamide 6 global market. At present, only a very small part of the textile filaments is recycled while it represents a significant percentage of the global CO2 emissions. Thus, there is a need to recycle polyamide 6 from such materials. Processes for alkaline depolymerizing a polyamide exists. However, such processes have a certain CO2 footprint and are energy-intensive. Therefore, there is a need to provide an improved process for depolymerizing a polyamide able to overcome these issues.
  • waste material comprising polyamide 6 is subjected to hydrolytic depolymerization and the respectively obtained liquid aqueous stream is advantageously treated to combine heat integration aspects as well as water recovery aspects in order to render the overall process as efficient and economically advantageous as possible.
  • the present invention relates to a recycling process for recovering c-caprolactam from a solid material M comprising polyamide 6, the process comprising
  • a stream S M which comprises the solid material.
  • the solid material M comprises, more preferably consists of, waste material, wherein said waste material more preferably comprises, more preferably consists of, one or more of at least one textile waste material and at least one engineering plastics waste material, more preferably comprises, more preferably consists of at least one textile waste material.
  • the solid material M may comprise, in addition to polyamide 6, at least one further polymeric compound, wherein the at least one further polymeric compound preferably comprises one or more of at least one polyamide 6.6; at least one polyethylene terephthalate; at least one polyurethane; at least one polyester; at least one polyether; at least one polyvinyl chloride; at least natural fiber material such as wool and cotton; at least one cellulose material; at least one natural elastomer; at least one synthetic elastomer; at least one copolymer of two or more of said polymeric compounds including statistical copolymers, gradient copolymers, alternating copolymers, block copolymers, and graft copolymers; and at least one rubber material comprising one or more of at least one natural rubber material and at least one synthetic rubber material.
  • the at least one further polymeric compound preferably comprises one or more of at least one polyamide 6.6; at least one polyethylene terephthalate; at least one polyurethane; at least one polyester; at least one poly
  • the solid material M is in the form of granules, wherein the mean diameter of the granules is preferably in the range of from 0.5 to 10 mm, more preferably in the range of from 1 to 7 mm, more preferably in the range of from 2 to 4 mm.
  • an aqueous depolymerization mixture is prepared based on SM. While there are no specific restrictions how this depolymerization mixture is prepared, it may be preferred to providing the stream SM, to provide a liquid aqueous stream Sw, wherein preferably from 90 to 100 weight-% of Sw consist of water, to feed the stream SM and the liquid aqueous stream Sw into the chemical reaction unit UR according to (iii), to obtaining the aqueous depolymerization mixture in U R .
  • the depolymerization mixture which is subjected to polyamide 6 depolymerization conditions according to (iii) exhibits a mixing ratio m w /kg : m P /kg, defined as the amount of water contained in Sw, mw, relative to the mass of polyamide 6 contained in the solid material M, m?, 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 .
  • the depolymerization mixture is subjected to polyamide 6 depolymerization conditions in the reaction unit UR.
  • Said depolymerization conditions comprise a polyamide 6 depolymerization temperature T D and a polyamide 6 depolymerization pressure p D , wherein T D is in the range of from 230 to 330 °C and p D 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 T D is in the range of from 270 to 310 °C and p D is in the range of from 40 to 110 bar.
  • SR is removed from R z ; wherein in every reactor R, a polyamide 6 depolymerization temperature TDI at a polyamide 6 depolymerization pressure poi is maintained, wherein, independently of each other, TDI is in the range of from 230 to 330 °C and poi is in the range of from 40 to 140 bar, preferably wherein TDI is in the range of from 250 to 320 °C and p D j is in the range of from 40 to 125 bar, more preferably wherein T D j is in the range of from 270 to 310 °C and p D j is in the range of from 40 to 110 bar.
  • maintaining a depolymerization temperature TDI in a reactor R comprises heating the reactor contents of R, more preferably indirectly heating the reactor contents of R, wherein more preferably, maintaining a depolymerization temperature TDI in a reactor R comprises heating the reactor contents of R by passing a heating medium through a heating jacket of R.
  • the heating medium is preferably hot oil.
  • Other heating media known by the skilled person can be used for passing through the heating jacket of R.
  • the z reactors R are vertically arranged, with Ri being the top-most reactor and R z being the bottom-most reactor, wherein Sj obtained from R is transferred to R+i by gravity, more preferably by gravity only.
  • the overall residence time in the chemical reaction unit UR is in the range of from 15 to 160 minutes, more preferably in the range of from 20 to 120 minutes, more preferably in the range of from 25 to 100 minutes, more preferably in the range of from 30 to 90 minutes.
  • the aqueous liquid stream S R has a temperature T R in the range of from 230 to 330 °C, more preferably in the range of from 250 to 320 °C, more preferably in the range of from 270 to 310 °C.
  • no polyamide 6 depolymerization catalyst such as a mineral acid and/or a zinc salt such as zinc chloride, zinc acetate or zinc triflate is added for preparing the depolymerization mixture.
  • said one or more decomposition products from the one or more elastanes preferably include at least one of aniline, butanediol, butanediol oligomers including, for example, butandediol dimer and butanediol trimer, and 4,4’-methylenedianiline (MDA) and isomers thereof such as 2,4’-methylenedianiline and 2,2’-methylenedianiline.
  • aniline butanediol
  • butanediol oligomers including, for example, butandediol dimer and butanediol trimer
  • MDA 4,4’-methylenedianiline
  • the liquid aqueous stream SR is passed into an evaporation unit UE, obtaining from SR a liquid aqueous stream SL comprising e-caprolactam dissolved in water at a concentration C S L with C S L > C S R, and further obtaining from S R one or more aqueous vapor streams Sv.
  • the evaporation unit UE comprises two or more evaporation sub-units, the process comprising obtaining at least at least two vapor streams Svi and Sv2, passing the vapor stream Svi to at least one heat-consuming unit and passing the vapor stream Sv2 to at least one heatconsuming unit, wherein the vapor streams Svi and Sv2 differ from each other in either pressure and/or temperature.
  • n > 1 wherein for j ⁇ n, the process comprises passing the aqueous liquid stream Si_j obtained from the evaporation sub-unit UEG) as feed stream into the evaporation sub-unit U E G+1 ) ⁇ More preferably, the n evaporation sub-units U E G) are serially coupled. More preferably, n > 1 , wherein for j ⁇ n, T V (j+i) ⁇ T V j; Pv ⁇ j+i) ⁇ Pvj! T L (j+i) ⁇ T L j; and p L (j+i) ⁇ PLJ.
  • the process comprises passing the aqueous liquid stream S R through a heat exchanging unit upstream of UE, obtaining from this heat exchanging unit a cooled stream S R .
  • the purification unit UP comprises one or more of a heat-consuming water separation unit Uws, a heat-consuming distillation unit U D and a heat-consuming crystallization unit Uc, preferably two or more of a heat-consuming water separation unit U ws , a heat-consuming distillation unit U D and a heat-consuming crystallization unit U c , more preferably a heatconsuming water separation unit Uws, a heat-consuming distillation unit UD and a heat-consuming crystallization unit Uc, wherein at least part of the heat consumed in one or more of Uws, UD and Uc is provided by at least one of the one or more streams Sv.
  • the purification unit UP comprises a heat-consuming water separation unit Uws, a heat-consuming distillation unit UD and a heat-consuming crystallization unit Uc, wherein Uws is located upstream of UD and UD is located upstream of Uc.
  • the process comprises feeding the stream SL comprising e-caprolactam at a concentration CSL to Uws, obtaining from Uws a stream Sows comprising e-caprolactam at a concentration Cuws, feeding the stream Sows to the distillation unit UD, obtaining from U D a stream SUD comprising e-caprolactam at a concentration CUD, feeding the stream SUD into the crystallization unit U c , and obtaining from U c a stream SCPL comprising e-caprolactam at a concentration C S CPL, wherein C S L ⁇ Cuws ⁇ CUD ⁇ C S CPL.
  • At least one stream Sv is used for providing at least a part of the heat consumed in Uws.
  • at least one of said streams Sv is at least partially condensed.
  • at least one stream Sv is used for providing at least a part of the heat consumed in UD.
  • at least one of said streams Sv is at least partially condensed.
  • at least one stream Sv is used for providing at least a part of the heat consumed in U c .
  • water is separated from the liquid aqueous stream SL.
  • a stream Suws is preferably obtained, being purified with respect to £-caprolactam, wherein Suws is preferably passed to a further downstream purification sub-unit, more preferably to the purification sub-unit UD.
  • at least one of the one or more aqueous streams SRW according to (v) is obtained which is then preferably fed to the water treatment unit Uw.
  • the water separation unit Uws comprises at least two heat-consuming water separation sub-units Uwsi and Uws2, preferably two serially coupled heat-consuming water separation sub-units U W si and U W s2, wherein the stream S L is fed into U W si and wherein at least part of the heat consumed in one or more of Uwsi and U W s2 is provided by at least one of the one or more streams Sv.
  • the process comprises one or more of (ii-1 ) and (ii-2) preferably (ii-1) and (ii-2):
  • Uwsi is an evaporation unit, preferably comprising a film evaporator, more preferably a falling film evaporator, wherein said film evaporator is more preferably equipped with heating means to provide heat for evaporation.
  • the unit Uwsi may comprise two or more evaporation sub-units, preferably two or more serially coupled evaporation sub-units.
  • Uws2 comprises, more preferably consists of, a distillation column equipped with heating means to provide heat for distillation.
  • At least one aqueous stream SRWI is obtained from Uwsi and further preferably, at least one aqueous stream SRW2 is obtained from U W s2- More preferably, at least one of S RWi and S RW 2, more preferably S RWi and S RW 2, are fed into the water treatment unit U W -
  • a separation unit Ui is arranged downstream of Uwsi and upstream of Uws2, which serves for separating impurities from the aqueous stream comprising £-caprolactam obtained from Uwsi before it is passed to the second purification sub-unit Uws2.
  • the process preferably comprises obtaining from Uwsi an aqueous stream Suwsi, feeding the stream Suwsi into the separation unit Ui, obtaining from Ui an aqueous stream Sui, and feeding the stream Sui into the unit U W s2, wherein in Ui, one or more of impurities are separated from Suwsi, thereby obtaining from Ui an impurity stream Si, said impurities preferably comprising at least one impurity comprised in SR according to (ii).
  • the process more preferably comprises
  • preparing the aqueous liquid mixture ME according to (a) comprises mixing the stream Suwsi with the stream Sn .
  • the evaporation in the evaporation unit E1 according to (b) is preferably carried out in one or more stirred vessels, or in one or more film evaporators, or in one or more stirred vessels and in one or more film evaporators; wherein the evaporation in the evaporation unit E1 according to (b) is more preferably carried out in one or more continuous stirred-tank reactors, or in one or more falling film evaporators, or in one or more continuous stirred-tank reactors and in one or more falling film evaporators; wherein the evaporation in the evaporation unit E1 according to (b) is more preferably carried out in one or more continuous stirred-tank reactors, wherein more preferably, if evaporation in E1 is carried out in
  • the purification sub-unit UD it is preferred that it comprises at least one distillation column, preferably two or three distillation columns, more preferably two or three serially coupled distillation columns. According to the present invention, it is preferred that at least part of the heat consumed in one or more of said distillations columns is provided by at least one of the streams Sv from which at least one at least partially condensed stream Svw2 is obtained which is preferably passed to the unit Uw.
  • At least a part of at least one stream Sv is passed as heating medium through a heat exchanger of at least one distillation column of UD, preferably through a heat exchanger of each of the two or three distillation columns of UD, more preferably through a heat exchanger used for sump evaporation of each of the two or three distillation columns of UD.
  • the respectively obtained stream SUD which is obtained from U D and which is further purified with respect to e-caprolactam is then preferably passed to a crystallization unit Uc from which the final stream SCPL is obtained.
  • a crystallization unit Uc from which the final stream SCPL is obtained.
  • the specific design of the crystallization unit Uc is concerned, no specific restrictions exists.
  • at least part of the heat consumed in Uc is at least partially provided by at least one stream Sv, wherein based on Sv, at least one at least partially condensed stream Svws is obtained which is preferably passed to the unit Uw.
  • (vi) comprises
  • the water treatment unit Uw comprises a water recovery unit UWR and a waste water unit Uww, wherein (vi.1 ) further comprises
  • 91 to 100 weight-% more preferably from 92 to 100 weight-%, more preferably from 95 to 100 weight-% of Sw consist of water.
  • suitable pre-treat at least one of the streams Sw such as by changing the temperature, preferably heating, and/or by changing the pressure, preferably increasing the pressure.
  • fresh water is added to the process in order to compensate any water losses.
  • fresh water can be added, for example, to at least one of the streams and/or directly to the unit UR.
  • At least one solid-liquid separation unit is arranged downstream of the reaction unit UR, wherein preferably at least one of the streams SL and SR is passed through at least one solid-liquid separation unit prior to being passed to the next downstream unit.
  • such solid-liquid separation unit comprises one or more of a centrifuge, a decanter, a decanter centrifuge, and a filter.
  • the stream SCPL is preferably passed to a polyamide 6 production unit UPP, wherein the polyamide 6 produced in UPP is preferably at least partially provided as a feedstock to a textile material producing unit U T p, wherein the textile material M T produced in U T p is preferably brought onto the market, and wherein, after the life-time TMT of said textile material, it is preferably collected as textile waste material in a textile material collecting unit UTC and preferably suitably provided from UTC to UR as SM, preferably via a unit UM , wherein UM preferably comprises one or more silos, and/or one or more hoppers, and/or one or more truck unloading stations, and/or one or more big bag unloading station.
  • the stream S M either comprises material MT and does not comprise MR; or comprises material MR and does not comprise material MT; or comprises material MT and material MR.
  • one or more streams SNCPL can be additionally passed to UPP, wherein SNCPL comprises non-recycled e-caprolactam, i.e. £-caprolactam from a conventional source.
  • one or more streams S N PA6 can be additionally passed to U T p, wherein S N PA6 comprises non-recycled polyamide 6, i.e. polyamide 6 from a conventional source.
  • the present invention also relates to crystallized e-caprolactam, i.e. the stream SCPL as such, obtainable or obtained by a process as described above.
  • said crystallized e-caprolactam exhibits an APHA color (sometimes also referred to as Hazen), determined as described Reference Example 1 , of at most 5, preferably of at most 4, more preferably of at most 3, more preferably of at most 2, more preferably of at most 1.5, more preferably of at most 1.
  • an APHA color sometimes also referred to as Hazen
  • said crystallized e-caprolactam exhibits a purity, determined as described in Reference Example 2, of at least 99.8 weight-%, preferably of at least 99.9 weight-%, more preferably of at least 99.95 weight-%, based on the total weight of SCPL.
  • the crystallized e-caprolactam obtainable or obtained by the process of the present invention exhibits an £-caprolactam oligomer content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; and/or a 6-aminocaproic acid content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight- ppm.
  • the crystallized £-caprolactam obtainable or obtained by the process of the present invention exhibits a triisopropyl borate content in the range of from 0 to 100 weight-ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight- ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm.
  • the crystallized e-caprolactam obtainable or obtained by the process of the present invention exhibits a polytetrahydrofuran content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight- ppm; and/or an aniline content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; and/or a methylene diphenyl diamine (MDA), isomers and oligomers content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; and/or a butanediol content
  • e-caprolactam oligomer encompasses e-caprolactam dimer and higher oligomers, such as e-caprolactam trimer, e-caprolactam tetramer, e-caprolactam pentamer, e-caprolactam hexamer;
  • 6-aminocaproic acid encompasses 6-aminocaproic and oligomers thereof, including 6-aminocaproic acid dimer and higher oligomers such as 6-aminocaproic acid trimer, 6-aminocaproic acid tetramer, 6-aminocaproic acid pentamer, 6-aminocaproic acid hexamer;
  • aniline encompasses aniline as such and further encompasses derivatives thereof, such as aniline containing one or more methyl groups, and/or one or more halogen residues, and/or one or more additional amino groups, and/or one or more benzyl groups, where
  • Methylene dianiline as described hereinunder is not an aniline derivative according to the present invention: the term “methylene dianiline” encompasses 4,4’-methylenedianiline (MDA) and isomers thereof such as 2,4’-methylenedianiline and 2,2’-methylenedianiline; the term “butanediol” encompasses butanediol as such and oligomers thereof, including butanediol dimer and higher oligomers such as butanediol trimer; the term “ethylene glycol” encompasses ethylene glycol as such and oligomers thereof, including diethylene glycol and higher oligomers such as triethylene glycol.
  • MDA 4,4’-methylenedianiline
  • isomers thereof such as 2,4’-methylenedianiline and 2,2’-methylenedianiline
  • butanediol encompasses butanediol as such and oligomers thereof, including butanediol dimer and
  • the respective content refers to an individual compound encompassed by the respective general term.
  • the term “an c-caprolactam oligomer content in the range of from 0 to 10 weight-ppm” refers to an E- caprolactam dimer content in the range of from 0 to 10 weight-ppm, an c-caprolactam trimer content in the range of from 0 to 10 weight-ppm, an c-caprolactam tetramer content in the range of from 0 to 10 weight-ppm, an c-caprolactam pentamer content in the range of from 0 to 10 weight-ppm, an e-caprolactam hexamer content in the range of from 0 to 10 weight-ppm, etc.
  • the present invention also relates to the use of SCPL, obtainable or obtained by a process as described above, for preparing a polymeric material, preferably for preparing polyamide 6, said use preferably further comprising employing said polymeric material, preferably said polyamide 6 as a feedstock for preparing a textile material.
  • the present invention relates to the process as described above, which process further comprises providing the stream SCPL to a polyamide 6 production unit U PP, wherein the polyamide 6 produced in UPP is preferably provided as a feedstock to a textile material producing unit UTP, from which unit UTP
  • a textile material MT is obtained which is brought onto the market, wherein, after the lifetime TMT of said textile material M T , it is at least partially collected as textile waste material in a textile material collecting unit UTC ;
  • (B) remaining material MR is obtained as textile waste material; wherein at least part of the textile waste material according to (A), or at least part of the textile waste material according to (B), or at least part of the textile waste material according to (A) and at least part of the textile waste material according to (B) is suitably provided to UR as SM, preferably via UM.
  • the present invention relates to the process as described above, which process further comprises providing the stream SCPL to a polyamide 6 production unit U PP, wherein the polyamide 6 produced in UPP is preferably provided as a feedstock to an engineering plastics material producing unit UTP, from which unit UTP
  • an engineering plastics material MT is obtained which is brought onto the market, wherein, after the life-time TMT of said engineering plastics material MT, it is at least partially collected as engineering plastics waste material in an engineering plastics material collecting unit UTC;
  • (B) remaining material MR is obtained as engineering plastics waste material; wherein at least part of the engineering plastics waste material according to (A), or at least part of the engineering plastics waste material according to (B), or at least part of the engineering plastics waste material according to (A) and at least part of the engineering plastics waste material according to (B) is suitably provided to UR as SM, preferably via UM.
  • the collected textile waste material Downstream of the unit UTC and upstream of the unit UR, preferably upstream of the unit UM, the collected textile waste material can be suitably sorted.
  • the collected textile waste material can be spread on a conveyor, which spreading can be carried out either manually and/or mechanically.
  • the respectively spread textile waste material is subjected to sorting, either by composition and/or by color.
  • Sorting can be carried out either manually and/or optically. If carried out optically, the sorting preferably comprises an infrared sorting, more preferably a near-infrared sorting and/or a mid-infrared sorting.
  • the textile waste material prior to sorting, can be subjected to a suitable metal removing step.
  • ferrous elements are preferably separated, for example by suitable magnetic means, and/or non-ferrous elements are preferably separated, for example by suitable eddy current separating means.
  • the respectively obtained textile waste material can be subjected to a further treatment, such as cutting and/or milling, prior to being fed to UR, preferably prior to being fed to U R via U M .
  • the present invention relates the crystallized e-caprolactam, obtainable or obtained as stream SCPL by a process as described above, wherein said crystallized e-caprolactam exhibits one or more of the following properties: an APHA color, determined as described Reference Example 1 , of at most 5, preferably of at most 4, more preferably of at most 3, more preferably of at most 2, more preferably of at most 1.5, more preferably of at most 1 ; a purity, determined as described in Reference Example 2, of at least 99.8 weight-%, preferably of at least 99.9 %, more preferably of at least 99.95 %.
  • said crystallized e-caprolactam exhibits one or more of the following properties: an e-caprolactam oligomer content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a 6-aminocaproic acid content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight- ppm.
  • said crystallized e-caprolactam further exhibits the following property: a triisopropyl borate content in the range of from 0 to 100 weight-ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight- ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm.
  • said crystallized e-caprolactam in case the solid material M described above comprises one or more elastanes, exhibits one or more of the following properties: a polytetrahydrofuran content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight- ppm; an aniline content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a methylenediphenyl diamine (MDA), isomers and oligomers content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a butanediol content in the range of from 0 to 500 weight-ppm, more
  • MDA methyl
  • the present invention relates to the use of SCPL, obtainable or obtained by a process as described above, for preparing polyamide 6, wherein said use preferably further comprises employing said polyamide 6 as a feedstock for preparing one or more of at least one textile material and at least one engineering plastics material, more preferably for preparing at least one textile material.
  • the present invention relates to the use of a process as described above for preparing high-purity e-caprolactam from a solid material M, preferably a waste material comprising polyamide 6 and preferably one or more elastanes, said high-purity e-caprolactam exhibiting one or more of the following properties: an e-caprolactam oligomer content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a 6-aminocaproic acid content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight- ppm; a triisopropyl borate content in the range of from 0 to 100 weight-ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from
  • the present invention relates to the use of SCPL, obtainable or obtained by a process as described above, preferably of SCPL as described above, for preparing one or more of a polymer and a polymer product; or to a method for preparing one or more of a polymer and a polymer product, said method comprising employing SCPL, obtainable or obtained by a process as described above, preferably of SCPL as described above, as a starting material.
  • the present invention relates to said use or said method, wherein the polymer, or the polymer product, or the polymer and the polymer product is or are in the form of at least one of a granulate, a strand, a rod, a plate, a pipe, a foil, a layer, a film, a sheet, a fiber, a filament, a coating, an extruded article, a molded article, a soft foam, a half-rigid foam and a rigid foam.
  • the present invention relates to said use or said method, wherein the polymer, or the polymer product, or the polymer and the polymer product comprises or comprise polyamide 6 and optionally at least one further polymeric compound, said polyamide 6 being at least partially obtainable or obtained from SCPL, said SCPL being obtainable or obtained by a process according to any one of embodiments 1 to 14, preferably being SCPL according to any one of embodiments 17 to 20, wherein the at least one further polymeric compound preferably comprises one or more of at least one polyamide 6.6; at least one polyethylene terephthalate; at least one polyurethane; at least one polyester; at least one polyether; at least one polyvinyl chloride; at least natural fiber material such as wool and cotton; at least one cellulose material; at least one natural elastomer; at least one synthetic elastomer; at least one copolymer of two or more of said polymeric compounds including statistical copolymers, gradient copolymers, alternating copolymers, block copolymers, and graft
  • the present invention relates to said use or said method, wherein the polymer, or the polymer product, or the polymer and the polymer product is or are one of the following or a part of one of the following: a part of a car, preferably a cylinder head cover, an engine cover, a housing for a charge air cooler, a charge air cooler flap, an intake pipe, an intake manifold, a connector, a gear wheel, a fan wheel, a cooling water box, a housing or a housing part for a heat exchanger, a coolant cooler, a charge air cooler, a thermostat, a water pump, a radiator, a fastening part or a part of a battery system for electromobility, a dashboard, a steering column switch, a seat, a headrest, a center console, a transmission component, a door module, a car exterior for an A, a B, a C or a D pillar cover, a spoiler, a door handle, an exterior mirror, a wind
  • the present invention relates to said use or said method, wherein the polymer, or the polymer product, or the polymer and the polymer product contains or contain polyamide 6, obtainable or obtained from SCPL, said SCPL being obtainable or obtained by a process according to embodiment 28, in an amount of 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight-% or more, more preferably 15 weight-% or more, more preferably 30 weight- % or more, more preferably 40 weight-% or more, more preferably 60 weight-% or more, more preferably 80 weight-% or more, more preferably 90 weight-% or more, more preferably 95 weight-% or more; and/or in an amount of 100 weight-% or less, preferably 95 weight-% or less, more preferably 90 weight-% or less, more preferably 50 weight-% or less, more preferably 25 weight-% or less, more preferably 10 weight-% or less.
  • the present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated.
  • every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to "The process of any one of embodiments 1 , 2 and 3".
  • the following set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.
  • the solid material M comprises, more preferably consists of, waste material, wherein said waste material more preferably comprises, more preferably consists of, one or more of at least one textile waste material and at least one engineering plastics waste material, more preferably comprises, more preferably consists of at least one textile waste material, wherein preferably from 10 to 100 weight-%, more preferably from 30 to 100 weight-%, more preferably from 50 to 100 weight-%, more preferably from 80 to 100 weight-%, of M consist of polyamide 6, wherein if the polyamide 6 content of the solid material M is less than 100 weight-%, the solid material M optionally additionally comprises one or more elastanes. 3.
  • the purification unit UP comprises one or more of a heat-consuming water separation unit Uws, a heat-consuming distillation unit U D and a heat-consuming crystallization unit U c , preferably two or more of a heatconsuming water separation unit Uws, a heat-consuming distillation unit U D and a heatconsuming crystallization unit Uc, more preferably a heat-consuming water separation unit Uws, a heat-consuming distillation unit UD and a heat-consuming crystallization unit Uc, wherein at least part of the heat consumed in one or more of Uws, UD and Uc is provided by at least one of the one or more streams Sv.
  • (i-3) obtaining at least one at least partially condensed aqueous stream Svws from Uc; the process further comprising feeding one or more Svwi, Svw2 and Svws; preferably two or more Svwi, Svw2 and Svws; more preferably Svwi, Svw2 and Svws into the water treatment unit Uw as defined in claim 3.
  • the purification unit UP comprises a heat-consuming water separation unit Uws, a heat-consuming distillation unit U D and a heatconsuming crystallization unit Uc, the process comprising feeding the stream SL comprising £-caprolactam at a concentration CSL to Uws, obtaining from Uws a stream Uws comprising E- caprolactam at a concentration Cuws, feeding the stream Suws to the distillation unit U D , obtaining from U D a stream SUD comprising c-caprolactam at a concentration CUD, and feeding the stream SUD into the crystallization unit Uc, and obtaining from Uc a stream SCPL comprising c-caprolactam at a concentration CSCPL, wherein CSL ⁇ Cuws ⁇ CUD ⁇ CSCPL.
  • the water separation unit Uws comprises at least two heat-consuming water separation sub-units Uwsi and Uws2, preferably two serially coupled heat-consuming water separation sub-units Uwsi and Uws2, wherein the stream SL is fed into Uwsi and wherein at least part of the heat consumed in one or more of Uwsi and Uws2 is provided by at least one of the one or more streams Sv.
  • Crystallized e-caprolactam obtainable or obtained as stream SCPL by a process according to any one of embodiments 1 to 14, exhibiting one or more of the following properties: an APHA color, determined as described Reference Example 1 , of at most 5, preferably of at most 4, more preferably of at most 3, more preferably of at most 2, more preferably of at most 1 .5, more preferably of at most 1 ; a purity, determined as described in Reference Example 2, of at least 99.8 weight-%, preferably of at least 99.9 %, more preferably of at least 99.95 %.
  • SCPL obtainable or obtained by a process according to any one of embodiments 1 to 15, preferably of S C PL according to any one of embodiments 17 to 20, for preparing polyamide 6, said use preferably further comprising employing said polyamide 6 as a feedstock for preparing one or more of at least one textile material and at least one engineering plastics material, more preferably for preparing at least one textile material.
  • spandex is also referred to as “spandex”, and common brand names for spandex include Lycra, Elaspan, Acepora, Creora, Inviya, Roica, Dorlastan, Linel or ESPA.
  • the term “textile material” covers textile raw materials and non-textile raw materials that are processed by various methods into linear, planar and spatial structures. It concerns the linear textile structures produced from them, such as yarns, twisted yarns and ropes, the sheet-like textile structures, such as woven fabrics, knitted fabrics, braids, stitch-bonded fabrics, nonwovens and felts, and the three-dimensional textile structures, i.e. body structures, such as textile hoses, stockings or textile semi-finished products; and it further concerns those finished products which, using the aforementioned products, are brought into a saleable condition by making up, opening up and/or other operations for onward transmission to the processor, the trade or the end consumer.
  • the term “textile waste material” covers a textile material as defined above, the inherent value of which has been consumed from the perspective of its current holder and, thus, is an end-of-life material for said holder.
  • X is a chemical element and A, B and C are concrete elements such as Li, Na, and K, or X is a temperature and A, B and C are concrete temperatures such as 10 °C, 20 °C, and 30 °C.
  • X is one or more of A and B” disclosing that X is either A, or B, or A and B, or to more specific realizations of said feature, e.g. “X is one or more of A, B, C and D”, disclosing that X is either A, or B, or C, or D, or A and B, or A and C, or A and D, or B and C, or B and D, or C and D, or A and B and C, or A and B and D, or B and C and D, or A and B and C and D, or A and B and C and D, or A and B and C and D, or A and B and C and D, or A and B and C and D.
  • a waste material stream SM comprising polyamide 6 is passed into reaction unit UR where the waste material is subjected to polyamide 6 depolymerization conditions (depolymerisation via hydrolysis in an aqueous medium).
  • a liquid aqueous stream SR is obtained and removed which comprises e-caprolactam and one or more impurities.
  • This stream SR is then passed to an evaporation unit U E from which a liquid aqueous stream S L and one or more aqueous vapor streams S v are obtained and removed; in Fig. 1 , only one vapor stream S v is shown.
  • the stream S L has a higher e-caprolactam concentration than the stream SR.
  • the stream SL is then passed to a heat-consuming purification unit UP where a further purification with regard to e-caprolactam occurs.
  • a product stream SCPL is finally obtained which comprises e-caprolactam at a concentration which is significantly higher than the e-caprolactam concentration of the stream SL.
  • at least a part of the heat consumed in the purification unit U P is at least partially provided by at least one of the one or more vapor streams S v and based on S v , one or more at last partially condensed aqueous streams Svw are obtained and removed from U P ; only one stream Svw is shown in Fig. 1.
  • one or more aqueous streams SR are obtained from SL. At least one stream Svw is then at least partially recycled to the reaction unit UR, and also at least one stream SRW is at least partially recycled to the reaction unit U R.
  • Figure 2 shows a process including the complete recycling loop
  • stream SCPL is passed to a polyamide 6 production unit UPP where it is employed as starting material.
  • a polyamide 6 production unit UPP where it is employed as starting material.
  • one or more further streams SNCPL can be additionally passed to U PP , said streams comprising non-recycled s-caprolactam, i.e. s-caprolactam from a conventional source.
  • the respectively prepared polyamide 6 material is then passed to a unit UTP where it is used as a starting material for preparing a material comprising polyamide 6, preferably a textile material comprising polyamide 6.
  • one or more further streams S N PA6 can be additionally passed to U T p, said streams comprising non-recycled polyamide 6, i.e. polyamide 6 from a conventional source.
  • further streams comprising one or more starting materials other than polyamide 6 can be passed to UTP.
  • the material, preferably the textile material MT obtained from UTP then goes into the market and remains there for a given lifetime TMT.
  • the respective end-of-life material is suitably collected in a collecting unit UTC, preferably a textile material collecting unit, from which it is suitably passed as stream the SM or as part of the stream S M to the reaction unit U R preferably via a unit U M for providing the stream S M to U R .
  • Such unit U M usually comprises any apparatus by which the preferably solid material M can be suitably passed to the reaction unit UR.
  • UM comprises apparatuses such as one or more silos, one or more hoppers, one or more truck unloading stations, one or more big bag unloading station, and the like.
  • M R is obtained from the production process, i.e. material which is not comprised in MT.
  • M R may be in the form textile cuttings.
  • This material can be fed, either via UTC and/or directly via UM , to UR as the stream SM or as part of stream SM.
  • This recycle loop as shown in Fig. 2 also applies to any of Figs. 3 to 6 below, however, is not explicitly shown there.
  • Figure 3 shows a process with a preferred water treatment stage
  • the process as shown in this Fig. 3 shows a preferred treatment of the streams S V w and S RW as already shown in Figs. 1 and 2.
  • the streams Svw and SRW are passed into a water treatment unit Uw from which a stream Sw is obtained which is then (at least partially) recycled as aqueous stream Sw (or part thereof) to the reaction unit U R. Further from Uw, one or more waste water streams Sww are obtained which are not recycled to the process.
  • the water treatment unit Uw comprises a water recovery unit UWR and optionally a waste water unit Uww.
  • the streams Svw and SRW are passed into the water treatment unit Uw where they are suitably purified and/or suitably collected in order to obtain the one or more aqueous recycle streams. Streams which are obtained from such purification may then be passed to the waste water treatment unit Uww.
  • FIG. 4 shows a process with a preferred heat-consuming purification unit UP
  • the process as shown in Fig. 4 shows a preferred way of purifying the stream SL with respect to £-caprolactam.
  • the stream SL is first passed to a water separation unit from which the one or more streams S RW are obtained which are then preferably passed to the water treatment unit Uw as already shown in Fig. 2 and, according to a preferred design, in Fig. 3.
  • at least one of the streams Sv is passed to Uws for at least partially meeting the heat demand of Uws; based on this at least one stream Sv passed to Uws, one or more at least partially condensed streams Svwi are obtained and preferably further passed to the water treatment Uw.
  • the stream Sows comprising e-caprolactam is then preferably passed to a distillation unit UD for further purification with respect to e-caprolactam. Further, at least one of the streams S v is passed to U D for at least partially meeting the heat demand of U D ; based on this at least one stream S v passed to U D , one or more at least partially condensed streams S V w2 are obtained and preferably further passed to the water treatment Uw.
  • the stream SUD comprising £-caprolactam is then preferably passed to a crystallization unit Uc for further purification with respect to £-caprolactam.
  • At least one of the streams Sv is passed to Uc for at least partially meeting the heat demand of Uc; based on this at least one stream Sv passed to Uc, one or more at least partially condensed streams Svws are obtained and preferably further passed to the water treatment Uw.
  • FIG. 5 shows a process with a preferred water separation unit Uws
  • Fig. 5 shows a preferred way of separating water from the stream SL in the water separation unit U W s.
  • the stream S L is first passed to a first stage of water separation, carried out in the unit Uwsi.
  • a stream comprising c-caprolactam is then passed to an intermediate treatment stage Ui where impurities may be removed.
  • the thus purified stream obtained from Ui is then further passed to a second stage of water separation, carried out in the unit Uws2.
  • a stream Suws2 comprising E- caprolactam is obtained which corresponds to the stream Sows as shown in Fig. 4 and which is then preferably passed to the distillation unit U D.
  • a stream Si comprising the respectively separated impurities is removed which, depending on the amount and/or the chemical nature of the impurities, may be put to further use.
  • one or more aqueous streams SRWI are obtained which are then preferably passed to the water treatment unit Uw as already shown in Fig. 2 and, according to a preferred design, in Fig. 3.
  • one or more aqueous streams SRW2 are obtained which are then preferably passed to the water treatment unit Uw as already shown in Fig. 2 and, according to a preferred design, in Fig. 3.
  • At least one of the streams Sv is passed to Uwsi for at least partially meeting the heat demand of Uwsi; based on this at least one stream Sv passed to U W si, one or more at least partially condensed streams Svwn are obtained and preferably further passed to the water treatment U W -
  • at least one of the streams S v is passed to U W s2 for at least partially meeting the heat demand of U s2; based on this at least one stream Sv passed to U s2, one or more at least partially condensed streams Svwi2 are obtained and preferably further passed to the water treatment Uw.
  • FIG. 6 shows a process with a preferred use of different vapour streams Sv
  • Fig. 6 shows, based on the preferred process design according to Fig. 5, a further preferred way of providing heat to the purification unit Up.
  • one or more vapour streams Svi and one or more vapour streams Sv2 are obtained from the evaporation unit U E which, for example, may comprise two or more evaporation sub-units (not shown), wherein the one or more streams Svi have pressures and temperatures which differ from the pressures and temperatures of the streams Sv2.
  • the streams Svi and Sv2 can be used for providing heat to units with different heat demands.
  • the streams Svi are used for providing at least part of the heat consumed by U wsi and Uc whereas the streams S V 2 are used for providing at least part of the heat consumed by U W s2 and UD. Accordingly, based on the streams Svi, one or more at least partially condensed streams Svwn and Svws are obtained and preferably further passed to the water treatment Uw. Further accordingly, based on the streams Sv2, one or more at least partially condensed streams Svwi2 and Svw2 are obtained and preferably further passed to the water treatment Uw.
  • the Hazen units are defined as the color of a solution containing, in 1 I water, 1 mg platinum in the form of hexachloroplatinum(IV) acid in the presence of 2 mg cobalt(ll) chloride hexahydrate.
  • the Hazen units correspond to the APHA units.
  • a standard solution of 500 Hazen units as prepared as follows: 1.000 g cobalt(ll) chloride hexahydrate (CoCI 2 • 6 H 2 O) and 1.245 g potassium hexachloroplatinate(IV) (K 2 PtCI 6 ) are dissolved in 100 ml hydrochloric acid having a of 1 .19 g/ml. The solution is transferred into a 1000 ml volumetric flask which is filled to the calibration mark. Thus solution contains 500 mg platinum and corresponds to 500 Hazen units.
  • e-caprolactam 50 ⁇ 0.1 g e-caprolactam are dissolved in a 250 Erlenmeyer flask in 50 ml distilled water. The solution is mixed and left until the air bubbles have disappeared.
  • the purity of the crystallized £-caprolactam and the respective amounts of impurities was determined via GC-FID/MS using GC (Agilent 7890A) coupled with two MSDs (Agilent 5975C) for electron impact ionisation and chemical ionisation.
  • the respective are-% values obtained from the measurement was extrapolated to the respective weight-% I weight-ppm values as follows: the diol compounds mentioned above are calibrated in the GC and then measured quantitatively, i.e. in weight-%. By subtracting these measured weight-% values from 100 weight-%, the purity of the crystallized SCPL is obtained.

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Abstract

The present invention relates to a recycling process for recovering ε-caprolactam from a solid material M comprising polyamide 6, comprising (i) providing a stream SM comprising the solid material M; (ii) preparing an aqueous depolymerization mixture based on SM; (iii) subjecting the depolymerization mixture prepared according to (ii) to polyamide 6 depolymerization conditions in a reaction unit UR, obtaining a liquid aqueous stream SR comprising ε-caprolactam dissolved in water at a concentration CSR, the stream SR further comprising one or more impurities; (iv) passing the liquid aqueous stream SR into an evaporation unit UE, obtaining from SR a liquid aqueous stream SL comprising ε-caprolactam dissolved in water at a concentration CSL with CSL > CSR, and further obtaining from SR one or more aqueous vapor streams Sv; (v) passing the aqueous stream SL into a heat-consuming purification unit UP, obtaining from SL a stream SCPL comprising ε-caprolactam at a concentration CSCPL with CSCPL >> CSL, and further obtaining from SL one or more aqueous 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 from the at least one stream Sv at least one at least partially condensed aqueous stream Svw; (vi) recycling at least one stream Svw at least partially and at least one stream SRW at least partially to the reaction unit UR.

Description

Highly integrated caprolactam recycling process
The present invention relates to a highly integrated recycling process, specifically for recycling E- caprolactam from a solid material which comprises a polymer prepared from c-caprolactam, specifically polyamide 6.
Polyamide, and in particular polyamide 6 being characterized by the formula (-NH-(CH2)5-CO-)n, can be found in numerous materials, such as packaging, engineering plastics from automotive and textile filaments. The latter represents about 40 % of the polyamide 6 global market. At present, only a very small part of the textile filaments is recycled while it represents a significant percentage of the global CO2 emissions. Thus, there is a need to recycle polyamide 6 from such materials. Processes for alkaline depolymerizing a polyamide exists. However, such processes have a certain CO2 footprint and are energy-intensive. Therefore, there is a need to provide an improved process for depolymerizing a polyamide able to overcome these issues.
Accordingly, a highly integrated recycle process is needed to achieve the above-mentioned goal. Thus, according to the present invention, a process is provided wherein waste material comprising polyamide 6 is subjected to hydrolytic depolymerization and the respectively obtained liquid aqueous stream is advantageously treated to combine heat integration aspects as well as water recovery aspects in order to render the overall process as efficient and economically advantageous as possible.
Therefore, the present invention relates to a recycling process for recovering c-caprolactam from a solid material M comprising polyamide 6, the process comprising
(i) providing a stream SM comprising the solid material M;
(ii) preparing an aqueous depolymerization mixture based on SM ;
(iii) subjecting the depolymerization mixture prepared according to (ii) to polyamide 6 depolymerization conditions in a reaction unit UR, obtaining a liquid aqueous stream SR comprising c-caprolactam dissolved in water at a concentration CSR, the stream SR further comprising one or more impurities;
(iv) passing the liquid aqueous stream SR into an evaporation unit UE, obtaining from SR a liquid aqueous stream SL comprising c-caprolactam dissolved in water at a concentration CSL with CSL > CSR, and further obtaining from SR one or more aqueous vapor streams Sv;
(v) passing the aqueous stream SL into a heat-consuming purification unit UP, obtaining from SL a stream SCPL comprising c-caprolactam at a concentration CSCPL with
CSCPL » CSL, and further obtaining from SL one or more aqueous 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 from the at least one stream Sv at least one at least partially condensed aqueous stream Svw!
(vi) recycling at least one stream SVw at least partially to the reaction unit UR and at least one stream SRW at least partially to the reaction unit UR. According to (i), a stream SM is provided which comprises the solid material. Preferably, the solid material M comprises, more preferably consists of, waste material, wherein said waste material more preferably comprises, more preferably consists of, one or more of at least one textile waste material and at least one engineering plastics waste material, more preferably comprises, more preferably consists of at least one textile waste material. Preferably from 10 to 99 weight-%, more preferably from 30 to 98.5 weight-%, more preferably from 50 to 98 weight-%, more preferably from 80 to 98 weight-%, of M consist of the polyamide; or preferably from 10 to 100 weight-%, more preferably from 30 to 100 weight-%, more preferably from 50 to 100 weight-%, more preferably from 80 to 100 weight-%, of M consist of the polyamide. If the polyamide 6 content of the solid material M is less than 100 weight-%, it may be preferred that the solid material M additionally comprises one or more elastanes. Generally, the solid material M may comprise, in addition to polyamide 6, at least one further polymeric compound, wherein the at least one further polymeric compound preferably comprises one or more of at least one polyamide 6.6; at least one polyethylene terephthalate; at least one polyurethane; at least one polyester; at least one polyether; at least one polyvinyl chloride; at least natural fiber material such as wool and cotton; at least one cellulose material; at least one natural elastomer; at least one synthetic elastomer; at least one copolymer of two or more of said polymeric compounds including statistical copolymers, gradient copolymers, alternating copolymers, block copolymers, and graft copolymers; and at least one rubber material comprising one or more of at least one natural rubber material and at least one synthetic rubber material.
Preferably, the solid material M is in the form of granules, wherein the mean diameter of the granules is preferably in the range of from 0.5 to 10 mm, more preferably in the range of from 1 to 7 mm, more preferably in the range of from 2 to 4 mm.
According to (ii), an aqueous depolymerization mixture is prepared based on SM. While there are no specific restrictions how this depolymerization mixture is prepared, it may be preferred to providing the stream SM, to provide a liquid aqueous stream Sw, wherein preferably from 90 to 100 weight-% of Sw consist of water, to feed the stream SM and the liquid aqueous stream Sw into the chemical reaction unit UR according to (iii), to obtaining the aqueous depolymerization mixture in UR. Preferably, the depolymerization mixture which is subjected to polyamide 6 depolymerization conditions according to (iii) exhibits a mixing ratio mw/kg : mP/kg, defined as the amount of water contained in Sw, mw, relative to the mass of polyamide 6 contained in the solid material M, m?, 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 .
According to (iii), the depolymerization mixture is subjected to polyamide 6 depolymerization conditions in the reaction unit UR. Said depolymerization conditions comprise a polyamide 6 depolymerization temperature TD and a polyamide 6 depolymerization pressure pD, wherein 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.
Preferably, the chemical reaction unit UR comprises z chemical reactors R, i=1 ...z, wherein z is in the range of from 1 to 10, more preferably in the range of from 2 to 8, more preferably in the range of from 2 to 6, more preferably in the range of from 2 to 5, more preferably in the range of from 2 to 4, more preferably 3 or 4. Preferably, z>1 and at least two reactors R, more preferably the z reactors R, are serially coupled, wherein, if the z reactors R are serially coupled, the solid material M and Sw are preferably fed into R, i=1 ; an aqueous liquid stream Sj containing e-caprolactam dissolved in water is removed from R and fed into R+i , i<z;
SR is removed from Rz; wherein in every reactor R, a polyamide 6 depolymerization temperature TDI at a polyamide 6 depolymerization pressure poi is maintained, wherein, independently of each other, TDI is in the range of from 230 to 330 °C and poi is in the range of from 40 to 140 bar, preferably wherein TDI is in the range of from 250 to 320 °C and pDj is in the range of from 40 to 125 bar, more preferably wherein TDj is in the range of from 270 to 310 °C and pDj is in the range of from 40 to 110 bar. Preferably, maintaining a depolymerization temperature TDI in a reactor R comprises heating the reactor contents of R, more preferably indirectly heating the reactor contents of R, wherein more preferably, maintaining a depolymerization temperature TDI in a reactor R comprises heating the reactor contents of R by passing a heating medium through a heating jacket of R. The heating medium is preferably hot oil. Other heating media known by the skilled person can be used for passing through the heating jacket of R. Preferably, for z>1 , the z reactors R are vertically arranged, with Ri being the top-most reactor and Rz being the bottom-most reactor, wherein Sj obtained from R is transferred to R+i by gravity, more preferably by gravity only.
Preferably, the overall residence time in the chemical reaction unit UR is in the range of from 15 to 160 minutes, more preferably in the range of from 20 to 120 minutes, more preferably in the range of from 25 to 100 minutes, more preferably in the range of from 30 to 90 minutes.
Preferably, the aqueous liquid stream SR has a temperature TR in the range of from 230 to 330 °C, more preferably in the range of from 250 to 320 °C, more preferably in the range of from 270 to 310 °C.
Preferably according to the present invention, no polyamide 6 depolymerization catalyst such as a mineral acid and/or a zinc salt such as zinc chloride, zinc acetate or zinc triflate is added for preparing the depolymerization mixture.
If the solid material M comprises one or more elastanes, the aqueous liquid stream SR contains one or more decomposition products which are formed from the one or more elastanes, for example in the course of the depolymerization reaction in U R. Additionally or alternatively, one or more decomposition products form the one or more elastanes may also be formed in a melting unit upstream of the reaction unit UR, in which melting unit the solid material M is suitably melted, leading to a liquid stream which is then passed into UR. In this case, preparing an aqueous depolymerization mixture based on SM according to step (ii) of the process of the present invention may preferably comprise
(11.1) melting in a melting unit the solid material M provided according to (i), obtaining a liquid stream, wherein the melting unit preferably comprises a kneader or an extruder, more preferably an extruder, and wherein the melting temperature is preferably in the range of from 230 to 330 °C, more preferably in the range of from 250 to 320 °C, more preferably in the range of from 270 to 310 °C;
(11.2) providing a liquid aqueous stream;
(11.3) admixing in a pre-reaction unit the stream obtained according to (ii.1 ) with the stream provided according to (ii.3), obtaining a liquid reaction feed stream, wherein the pre-reaction unit preferably comprises a mixing unit, more preferably a static mixing unit;
(11.4) feeding the stream obtained according to (i.3) as depolymerization mixture into the chemical reaction unit UR.
By way of example, said one or more decomposition products from the one or more elastanes preferably include at least one of aniline, butanediol, butanediol oligomers including, for example, butandediol dimer and butanediol trimer, and 4,4’-methylenedianiline (MDA) and isomers thereof such as 2,4’-methylenedianiline and 2,2’-methylenedianiline.
According to (iv), the liquid aqueous stream SR is passed into an evaporation unit UE, obtaining from SR a liquid aqueous stream SL comprising e-caprolactam dissolved in water at a concentration CSL with CSL > CSR, and further obtaining from SR one or more aqueous vapor streams Sv.
Preferably, the evaporation unit UE comprises two or more evaporation sub-units, the process comprising obtaining at least at least two vapor streams Svi and Sv2, passing the vapor stream Svi to at least one heat-consuming unit and passing the vapor stream Sv2 to at least one heatconsuming unit, wherein the vapor streams Svi and Sv2 differ from each other in either pressure and/or temperature. More preferably, the process comprises subjecting the aqueous liquid stream SR to depressurization in an evaporation unit UE comprising n evaporation sub-units UEG), 1 j n with n > 1 , obtaining from each sub-unit UEG) an aqueous vapor stream Sv, and an aqueous liquid stream Si_j comprising e-caprolactam dissolved in water, wherein Sv, has a temperature Tv, and a pressure pvj and wherein Si_j has a temperature Ti_j and a pressure pi_j, wherein at least one evaporation sub-unit UEG), more preferably every evaporation sub-unit UEG) comprises, more preferably consists of, a flash drum. Preferably, n > 1 , wherein for j < n, the process comprises passing the aqueous liquid stream Si_j obtained from the evaporation sub-unit UEG) as feed stream into the evaporation sub-unit UEG+1 )■ More preferably, the n evaporation sub-units UEG) are serially coupled. More preferably, n > 1 , wherein for j < n, TV(j+i) < TVj; Pv<j+i) < Pvj! TL(j+i) < TLj; and pL(j+i) < PLJ. Optionally, the process comprises passing the aqueous liquid stream SR through a heat exchanging unit upstream of UE, obtaining from this heat exchanging unit a cooled stream SR.
According to (v), the aqueous stream SL is passed into a heat-consuming purification unit U P, obtaining from SL a stream SCPL comprising e-caprolactam at a concentration CSCPL with CSCPL » CSL, and further obtaining from SL one or more aqueous 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 from the at least one stream Sv at least one at least partially condensed aqueous stream SVw- The abbreviation “»” as used in this context illustrates that the concentration CSCPL is significantly higher than the concentration CSL, wherein, preferably, the stream SCPL ultimately obtained from the purification unit UP comprises, preferably consists of, substantially pure e-caprolactam.
Preferably, the purification unit UP comprises one or more of a heat-consuming water separation unit Uws, a heat-consuming distillation unit U D and a heat-consuming crystallization unit Uc, preferably two or more of a heat-consuming water separation unit Uws, a heat-consuming distillation unit UD and a heat-consuming crystallization unit Uc, more preferably a heatconsuming water separation unit Uws, a heat-consuming distillation unit UD and a heat-consuming crystallization unit Uc, wherein at least part of the heat consumed in one or more of Uws, UD and Uc is provided by at least one of the one or more streams Sv. More preferably, the purification unit UP comprises a heat-consuming water separation unit Uws, a heat-consuming distillation unit UD and a heat-consuming crystallization unit Uc, wherein Uws is located upstream of UD and UD is located upstream of Uc.
Preferably according to the present invention, wherein the purification unit UP comprises a heatconsuming water separation unit Uws, a heat-consuming distillation unit UD and a heat-consuming crystallization unit Uc, the process comprises feeding the stream SL comprising e-caprolactam at a concentration CSL to Uws, obtaining from Uws a stream Sows comprising e-caprolactam at a concentration Cuws, feeding the stream Sows to the distillation unit UD, obtaining from U D a stream SUD comprising e-caprolactam at a concentration CUD, feeding the stream SUD into the crystallization unit Uc, and obtaining from Uc a stream SCPL comprising e-caprolactam at a concentration CSCPL, wherein CSL < Cuws < CUD < CSCPL.
Preferably, at least one stream Sv is used for providing at least a part of the heat consumed in Uws. By providing said heat to Uws, at least one of said streams Sv is at least partially condensed. Alternatively or additionally, at least one stream Sv is used for providing at least a part of the heat consumed in UD. By providing said heat to UD, at least one of said streams Sv is at least partially condensed. Alternatively or additionally, at least one stream Sv is used for providing at least a part of the heat consumed in Uc. By providing said heat to Uc, at least one of said streams Sv is at least partially condensed. Therefore, the process preferably comprises 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 aqueous stream SVwi from UwS;
(i-2) obtaining at least one at least partially condensed aqueous stream Svw2 from UD;
(i-3) obtaining at least one at least partially condensed aqueous stream Svws from Uc; wherein it is more preferred that one or more Svwi, Svw2 and Svws; preferably two or more Svwi,
Svw2 and Svws; more preferably Svwi, Svw2 and Svws are fed into the water treatment unit Uw.
In the water separation unit Uws, water is separated from the liquid aqueous stream SL. From SL having been passed into Uws, a stream Suws is preferably obtained, being purified with respect to £-caprolactam, wherein Suws is preferably passed to a further downstream purification sub-unit, more preferably to the purification sub-unit UD. Further, from Uws and based on SL, at least one of the one or more aqueous streams SRW according to (v) is obtained which is then preferably fed to the water treatment unit Uw.
More preferably, the water separation unit Uws comprises at least two heat-consuming water separation sub-units Uwsi and Uws2, preferably two serially coupled heat-consuming water separation sub-units UWsi and UWs2, wherein the stream SL is fed into UWsi and wherein at least part of the heat consumed in one or more of Uwsi and UWs2 is provided by at least one of the one or more streams Sv. More preferably, the process comprises one or more of (ii-1 ) and (ii-2) preferably (ii-1) and (ii-2):
(ii-1) obtaining at least one at least partially condensed aqueous stream Svwn from Uwsi; (ii-2) obtaining at least one at least partially condensed aqueous stream Svwi2 from Uws2.
While not being restricted to any specific purification units, it is preferred according to the present invention that Uwsi is an evaporation unit, preferably comprising a film evaporator, more preferably a falling film evaporator, wherein said film evaporator is more preferably equipped with heating means to provide heat for evaporation. Optionally, the unit Uwsi may comprise two or more evaporation sub-units, preferably two or more serially coupled evaporation sub-units. Preferably, Uws2 comprises, more preferably consists of, a distillation column equipped with heating means to provide heat for distillation. Preferably, at least one aqueous stream SRWI is obtained from Uwsi and further preferably, at least one aqueous stream SRW2 is obtained from UWs2- More preferably, at least one of SRWi and SRW2, more preferably SRWi and SRW2, are fed into the water treatment unit UW-
It is further preferred that downstream of Uwsi and upstream of Uws2, a separation unit Ui is arranged which serves for separating impurities from the aqueous stream comprising £-caprolactam obtained from Uwsi before it is passed to the second purification sub-unit Uws2. Therefore, the process preferably comprises obtaining from Uwsi an aqueous stream Suwsi, feeding the stream Suwsi into the separation unit Ui, obtaining from Ui an aqueous stream Sui, and feeding the stream Sui into the unit UWs2, wherein in Ui, one or more of impurities are separated from Suwsi, thereby obtaining from Ui an impurity stream Si, said impurities preferably comprising at least one impurity comprised in SR according to (ii). According to the present invention, it is preferred that in Ui, an £-caprolactam oligomeric compound is separated from the stream Suwsi- Regarding the separation of impurities in Ui, the process more preferably comprises
(a) preparing an aqueous liquid mixture ME comprising the stream Suwsi obtained from Uwsi;
(b) subjecting the mixture ME according to (a) to evaporation conditions in an evaporation unit Ei , obtaining an aqueous vapor stream Sui and an aqueous liquid stream Si;
(c) dividing the stream Si according to (b) into a first stream Sn and a second stream S12, wherein Sn and S12 have the same chemical composition as Si;
(d) optionally passing the stream S|2 obtained according to (c) to a suitable downstream treatment stage; wherein preparing the aqueous liquid mixture ME according to (a) comprises mixing the stream Suwsi with the stream Sn . The evaporation in the evaporation unit E1 according to (b) is preferably carried out in one or more stirred vessels, or in one or more film evaporators, or in one or more stirred vessels and in one or more film evaporators; wherein the evaporation in the evaporation unit E1 according to (b) is more preferably carried out in one or more continuous stirred-tank reactors, or in one or more falling film evaporators, or in one or more continuous stirred-tank reactors and in one or more falling film evaporators; wherein the evaporation in the evaporation unit E1 according to (b) is more preferably carried out in one or more continuous stirred-tank reactors, wherein more preferably, if evaporation in E1 is carried out in more than one continuous stirred-tank reactors, the continuous stirred-tank reactor are arranged in parallel.
Regarding the purification sub-unit UD, it is preferred that it comprises at least one distillation column, preferably two or three distillation columns, more preferably two or three serially coupled distillation columns. According to the present invention, it is preferred that at least part of the heat consumed in one or more of said distillations columns is provided by at least one of the streams Sv from which at least one at least partially condensed stream Svw2 is obtained which is preferably passed to the unit Uw. More preferably, at least a part of at least one stream Sv is passed as heating medium through a heat exchanger of at least one distillation column of UD, preferably through a heat exchanger of each of the two or three distillation columns of UD, more preferably through a heat exchanger used for sump evaporation of each of the two or three distillation columns of UD.
The respectively obtained stream SUD which is obtained from UD and which is further purified with respect to e-caprolactam is then preferably passed to a crystallization unit Uc from which the final stream SCPL is obtained. Regarding the specific design of the crystallization unit Uc is concerned, no specific restrictions exists. Preferably, at least part of the heat consumed in Uc is at least partially provided by at least one stream Sv, wherein based on Sv, at least one at least partially condensed stream Svws is obtained which is preferably passed to the unit Uw.
Regarding the recycling according to (vi), it is preferred that (vi) comprises
(vi.1 ) feeding the at least one stream SVw, preferably at least one of the one or more streams Svwi, Svw2 and Svws, more preferably at least one of the one or more streams Svwn, Svwi2, Svw2 and Svws, more preferably all streams Svwi, Svw2 and Svws, more preferably all streams Svwn, Svwi2, Svw2 and Svws, and the at least one stream SRW, preferably at least one of the one or more streams SRWI and SRW2, more preferably all streams SRWI and SRW2, into a water treatment unit Uw, obtaining from Uw at least one aqueous recycle stream Sw;
(vi.2) recycling the at least one aqueous stream Sw at least partially to the reaction unit UR.
More preferably, the water treatment unit Uw comprises a water recovery unit UWR and a waste water unit Uww, wherein (vi.1 ) further comprises
(vi.1 .1) feeding the at least one stream SVw, preferably at least one of the one or more streams Svwi, Svw2 and SVw3, more preferably at least one of the one or more streams Svwn, Svwi2, Svw2 and Svws, more preferably all streams Svwi, Svw2 and Svws, more preferably all streams Svwn, Svwi2, Svw2 and Svws, and the at least one stream SRW, preferably at least one of the one or more streams SRWI and SRW2, more preferably all streams SRWI and SRW2, into the water recovery unit UWR, obtaining from UWR the at least one aqueous recycle stream Sw and at least one aqueous stream Ssw;
(vi .1 .2) feeding the at least one stream Ssw to the waste water unit Uww, obtaining from Uww, at least one waste water stream Sww-
According to the present invention, it is preferred that from 91 to 100 weight-%, more preferably from 92 to 100 weight-%, more preferably from 95 to 100 weight-% of Sw consist of water. Prior to being passed into UR, it is conceivable to suitable pre-treat at least one of the streams Sw, such as by changing the temperature, preferably heating, and/or by changing the pressure, preferably increasing the pressure.
Yet further according to the present invention, it may be preferred that at least one suitable stage, fresh water is added to the process in order to compensate any water losses. Such fresh water can be added, for example, to at least one of the streams and/or directly to the unit UR.
According to the process of the present invention, it may be preferred that downstream of the reaction unit UR, at least one solid-liquid separation unit is arranged, wherein preferably at least one of the streams SL and SR is passed through at least one solid-liquid separation unit prior to being passed to the next downstream unit. Preferably, such solid-liquid separation unit comprises one or more of a centrifuge, a decanter, a decanter centrifuge, and a filter.
According to the present invention, and based on the ultimately purified e-caprolactam stream SCPL, a full recycle loop can be realized. In particular, this is due to the excellent color properties and purity of the crystallized e-caprolactam obtained as stream SCPL. According to this recycle loop, the stream SCPL is preferably passed to a polyamide 6 production unit UPP, wherein the polyamide 6 produced in UPP is preferably at least partially provided as a feedstock to a textile material producing unit UTp, wherein the textile material MT produced in UTp is preferably brought onto the market, and wherein, after the life-time TMT of said textile material, it is preferably collected as textile waste material in a textile material collecting unit UTC and preferably suitably provided from UTC to UR as SM, preferably via a unit UM , wherein UM preferably comprises one or more silos, and/or one or more hoppers, and/or one or more truck unloading stations, and/or one or more big bag unloading station. Yet further, it is also possible that in the course of producing the textile material in either the unit UTP mentioned above and/or in one or more other production units, remaining material which cannot not be used and which comprises polyamide 6, e.g. in the form of textile cuttings, is obtained; such remaining material MR is also referred to as “textile waste material” in the context of the present invention, and this textile waste material MR can also be used as the solid material M or as a part of the solid material M and can be provided to the reaction unit UR preferably either via the unit UTc and/or the unit U M. Specifically, according to the present invention, the stream SM either comprises material MT and does not comprise MR; or comprises material MR and does not comprise material MT; or comprises material MT and material MR.
If desired and /or necessary, and as shown in Fig. 2, one or more streams SNCPL can be additionally passed to UPP, wherein SNCPL comprises non-recycled e-caprolactam, i.e. £-caprolactam from a conventional source. Further, if desired and /or necessary, and as shown in Fig. 2, one or more streams SNPA6 can be additionally passed to UTp, wherein SNPA6 comprises non-recycled polyamide 6, i.e. polyamide 6 from a conventional source.
According to a further aspect, the present invention also relates to crystallized e-caprolactam, i.e. the stream SCPL as such, obtainable or obtained by a process as described above.
Preferably, said crystallized e-caprolactam exhibits an APHA color (sometimes also referred to as Hazen), determined as described Reference Example 1 , of at most 5, preferably of at most 4, more preferably of at most 3, more preferably of at most 2, more preferably of at most 1.5, more preferably of at most 1.
Preferably, said crystallized e-caprolactam exhibits a purity, determined as described in Reference Example 2, of at least 99.8 weight-%, preferably of at least 99.9 weight-%, more preferably of at least 99.95 weight-%, based on the total weight of SCPL.
It is preferred that the crystallized e-caprolactam obtainable or obtained by the process of the present invention exhibits an £-caprolactam oligomer content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; and/or a 6-aminocaproic acid content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight- ppm.
Furthermore, it is preferred that the crystallized £-caprolactam obtainable or obtained by the process of the present invention exhibits a triisopropyl borate content in the range of from 0 to 100 weight-ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight- ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm.
In particular in case the solid material M provided according to (i) comprises one or more elastanes, it is preferred that the crystallized e-caprolactam obtainable or obtained by the process of the present invention exhibits a polytetrahydrofuran content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight- ppm; and/or an aniline content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; and/or a methylene diphenyl diamine (MDA), isomers and oligomers content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; and/or a butanediol content in the range of from 0 to 500 weight-ppm, more preferably in the range of from 0 to 300 weight-ppm, more preferably in the range of from 0 to 100 weight-ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight-ppm; and/or an ethylene glycol content in the range of from 0 to 500 weight-ppm, more preferably in the range of from 0 to 300 weight-ppm, more preferably in the range of from 0 to 100 weight- ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight-ppm.
In this context of the present invention, the term “e-caprolactam oligomer” encompasses e-caprolactam dimer and higher oligomers, such as e-caprolactam trimer, e-caprolactam tetramer, e-caprolactam pentamer, e-caprolactam hexamer; the term “6-aminocaproic acid” encompasses 6-aminocaproic and oligomers thereof, including 6-aminocaproic acid dimer and higher oligomers such as 6-aminocaproic acid trimer, 6-aminocaproic acid tetramer, 6-aminocaproic acid pentamer, 6-aminocaproic acid hexamer; the term “aniline” encompasses aniline as such and further encompasses derivatives thereof, such as aniline containing one or more methyl groups, and/or one or more halogen residues, and/or one or more additional amino groups, and/or one or more benzyl groups, wherein examples of such aniline derivatives may include N-methyl aniline and aminotoulene. Methylene dianiline as described hereinunder is not an aniline derivative according to the present invention: the term “methylene dianiline” encompasses 4,4’-methylenedianiline (MDA) and isomers thereof such as 2,4’-methylenedianiline and 2,2’-methylenedianiline; the term “butanediol” encompasses butanediol as such and oligomers thereof, including butanediol dimer and higher oligomers such as butanediol trimer; the term “ethylene glycol” encompasses ethylene glycol as such and oligomers thereof, including diethylene glycol and higher oligomers such as triethylene glycol.
In each case, the respective content refers to an individual compound encompassed by the respective general term. For example with respect to the c-caprolactam oligomer content, the term “an c-caprolactam oligomer content in the range of from 0 to 10 weight-ppm” refers to an E- caprolactam dimer content in the range of from 0 to 10 weight-ppm, an c-caprolactam trimer content in the range of from 0 to 10 weight-ppm, an c-caprolactam tetramer content in the range of from 0 to 10 weight-ppm, an c-caprolactam pentamer content in the range of from 0 to 10 weight-ppm, an e-caprolactam hexamer content in the range of from 0 to 10 weight-ppm, etc.
According to a further aspect, the present invention also relates to the use of SCPL, obtainable or obtained by a process as described above, for preparing a polymeric material, preferably for preparing polyamide 6, said use preferably further comprising employing said polymeric material, preferably said polyamide 6 as a feedstock for preparing a textile material.
Further, the present invention relates to the process as described above, which process further comprises providing the stream SCPL to a polyamide 6 production unit U PP, wherein the polyamide 6 produced in UPP is preferably provided as a feedstock to a textile material producing unit UTP, from which unit UTP
(A) a textile material MT is obtained which is brought onto the market, wherein, after the lifetime TMT of said textile material MT, it is at least partially collected as textile waste material in a textile material collecting unit UTC;
(B) remaining material MR is obtained as textile waste material; wherein at least part of the textile waste material according to (A), or at least part of the textile waste material according to (B), or at least part of the textile waste material according to (A) and at least part of the textile waste material according to (B) is suitably provided to UR as SM, preferably via UM.
Further, the present invention relates to the process as described above, which process further comprises providing the stream SCPL to a polyamide 6 production unit U PP, wherein the polyamide 6 produced in UPP is preferably provided as a feedstock to an engineering plastics material producing unit UTP, from which unit UTP
(A) an engineering plastics material MT is obtained which is brought onto the market, wherein, after the life-time TMT of said engineering plastics material MT, it is at least partially collected as engineering plastics waste material in an engineering plastics material collecting unit UTC;
(B) remaining material MR is obtained as engineering plastics waste material; wherein at least part of the engineering plastics waste material according to (A), or at least part of the engineering plastics waste material according to (B), or at least part of the engineering plastics waste material according to (A) and at least part of the engineering plastics waste material according to (B) is suitably provided to UR as SM, preferably via UM.
Downstream of the unit UTC and upstream of the unit UR, preferably upstream of the unit UM, the collected textile waste material can be suitably sorted. In this regard, it is possible to spread the collected textile waste material on a conveyor, which spreading can be carried out either manually and/or mechanically. Thereafter, the respectively spread textile waste material is subjected to sorting, either by composition and/or by color. Sorting can be carried out either manually and/or optically. If carried out optically, the sorting preferably comprises an infrared sorting, more preferably a near-infrared sorting and/or a mid-infrared sorting. Optionally, prior to sorting, the textile waste material can be subjected to a suitable metal removing step. If a metal removing step is carried out, ferrous elements are preferably separated, for example by suitable magnetic means, and/or non-ferrous elements are preferably separated, for example by suitable eddy current separating means. After said sorting, the respectively obtained textile waste material can be subjected to a further treatment, such as cutting and/or milling, prior to being fed to UR, preferably prior to being fed to UR via UM.
Still further, the present invention relates the crystallized e-caprolactam, obtainable or obtained as stream SCPL by a process as described above, wherein said crystallized e-caprolactam exhibits one or more of the following properties: an APHA color, determined as described Reference Example 1 , of at most 5, preferably of at most 4, more preferably of at most 3, more preferably of at most 2, more preferably of at most 1.5, more preferably of at most 1 ; a purity, determined as described in Reference Example 2, of at least 99.8 weight-%, preferably of at least 99.9 %, more preferably of at least 99.95 %.
Optionally or preferably, said crystallized e-caprolactam exhibits one or more of the following properties: an e-caprolactam oligomer content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a 6-aminocaproic acid content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight- ppm.
Optionally or preferably, said crystallized e-caprolactam further exhibits the following property: a triisopropyl borate content in the range of from 0 to 100 weight-ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight- ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm.
Optionally or preferably, said crystallized e-caprolactam, in case the solid material M described above comprises one or more elastanes, exhibits one or more of the following properties: a polytetrahydrofuran content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight- ppm; an aniline content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a methylenediphenyl diamine (MDA), isomers and oligomers content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a butanediol content in the range of from 0 to 500 weight-ppm, more preferably in the range of from 0 to 300 weight-ppm, more preferably in the range of from 0 to 100 weight-ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight-ppm; and/or an ethylene glycol content in the range of from 0 to 500 weight-ppm, more preferably in the range of from 0 to 300 weight-ppm, more preferably in the range of from 0 to 100 weight- ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight-ppm.
Further, the present invention relates to the use of SCPL, obtainable or obtained by a process as described above, for preparing polyamide 6, wherein said use preferably further comprises employing said polyamide 6 as a feedstock for preparing one or more of at least one textile material and at least one engineering plastics material, more preferably for preparing at least one textile material.
Still further, the present invention relates to the use of a process as described above for preparing high-purity e-caprolactam from a solid material M, preferably a waste material comprising polyamide 6 and preferably one or more elastanes, said high-purity e-caprolactam exhibiting one or more of the following properties: an e-caprolactam oligomer content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a 6-aminocaproic acid content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight- ppm; a triisopropyl borate content in the range of from 0 to 100 weight-ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight- ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a polytetrahydrofuran content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight- ppm; an aniline content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a methylenediphenyl diamine (MDA), isomers and oligomers content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a butanediol content in the range of from 0 to 500 weight-ppm, more preferably in the range of from 0 to 300 weight-ppm, more preferably in the range of from 0 to 100 weight-ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight-ppm; and/or an ethylene glycol content in the range of from 0 to 500 weight-ppm, more preferably in the range of from 0 to 300 weight-ppm, more preferably in the range of from 0 to 100 weight- ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight-ppm.
Yet further, the present invention relates to the use of SCPL, obtainable or obtained by a process as described above, preferably of SCPL as described above, for preparing one or more of a polymer and a polymer product; or to a method for preparing one or more of a polymer and a polymer product, said method comprising employing SCPL, obtainable or obtained by a process as described above, preferably of SCPL as described above, as a starting material.
Yet further, the present invention relates to said use or said method, wherein the polymer, or the polymer product, or the polymer and the polymer product is or are in the form of at least one of a granulate, a strand, a rod, a plate, a pipe, a foil, a layer, a film, a sheet, a fiber, a filament, a coating, an extruded article, a molded article, a soft foam, a half-rigid foam and a rigid foam.
Yet further, the present invention relates to said use or said method, wherein the polymer, or the polymer product, or the polymer and the polymer product comprises or comprise polyamide 6 and optionally at least one further polymeric compound, said polyamide 6 being at least partially obtainable or obtained from SCPL, said SCPL being obtainable or obtained by a process according to any one of embodiments 1 to 14, preferably being SCPL according to any one of embodiments 17 to 20, wherein the at least one further polymeric compound preferably comprises one or more of at least one polyamide 6.6; at least one polyethylene terephthalate; at least one polyurethane; at least one polyester; at least one polyether; at least one polyvinyl chloride; at least natural fiber material such as wool and cotton; at least one cellulose material; at least one natural elastomer; at least one synthetic elastomer; at least one copolymer of two or more of said polymeric compounds including statistical copolymers, gradient copolymers, alternating copolymers, block copolymers, and graft copolymers; and at least one rubber material comprising one or more of at least one natural rubber material and at least one synthetic rubber material.
Yet further, the present invention relates to said use or said method, wherein the polymer, or the polymer product, or the polymer and the polymer product is or are one of the following or a part of one of the following: a part of a car, preferably a cylinder head cover, an engine cover, a housing for a charge air cooler, a charge air cooler flap, an intake pipe, an intake manifold, a connector, a gear wheel, a fan wheel, a cooling water box, a housing or a housing part for a heat exchanger, a coolant cooler, a charge air cooler, a thermostat, a water pump, a radiator, a fastening part or a part of a battery system for electromobility, a dashboard, a steering column switch, a seat, a headrest, a center console, a transmission component, a door module, a car exterior for an A, a B, a C or a D pillar cover, a spoiler, a door handle, an exterior mirror, a windscreen wiper, a windscreen wiper protection housing, a decorative grill, a cover strip, a roof rail, a window frame, a sunroof frame, an antenna panel, a headlight, a taillight, an airbag, and/or a cushion; a cloth, an apparel, preferably a shirt, trousers, a pullover, a boot, a shoe, a shoe sole, a tight and/or or jacket; an electrical part, preferably an electrical component, an electronic passive component, an electronic active component, a printed circuit board, a housing component, a foil, a line, a switch such as a microswitch, a plug, a socket, a distributor, a relay, a resistor, a capacitor, an inductor, a bobbin, a lamp, a diode such as an LED, a transistor, a connector, a regulator, an integrated circuit (IC), a processor, a controller, a memory, a sensor, a microbutton, a semiconductor, a reflector housing for example for light-emitting diodes, a fastener for an electrical and/or an electronic component, a spacer, a bolt, a strip, a slide-in guide, a screw, a nut, a film hinge, a snap hook (snap-in), and/or a spring tongue; a consumer and/or a pharmaceutical product, preferably a tennis string, a climbing rope, a bristle, a brush, an artificial grass, a 3D printing filament, a grass trimmer, a zipper, a hook and loop fastener, a paper machine clothing, an extrusion coating, a fishing line, a fishing net, an offshore line and rope, a vial, a syringe, an ampoule, a bottle, a sliding element, a spindle nut, a chain conveyor, a plain bearing, a roller, a wheel, a gear, a roller, a ring gear, a screw and spring damper, a hose, a pipeline, a cable sheathing, a socket, a switch, a cable tie, a fan wheel, a carpet, a box and/or a bottle for cosmetics, a mattress, a cushion, an insulation; a packaging for the food industry, preferably a mono- and/or multi-layer blown film, a cast film (mono- and/or multi-layer), a biaxially stretched film, a laminating film.
Yet further, the present invention relates to said use or said method, wherein the polymer, or the polymer product, or the polymer and the polymer product contains or contain polyamide 6, obtainable or obtained from SCPL, said SCPL being obtainable or obtained by a process according to embodiment 28, in an amount of 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight-% or more, more preferably 15 weight-% or more, more preferably 30 weight- % or more, more preferably 40 weight-% or more, more preferably 60 weight-% or more, more preferably 80 weight-% or more, more preferably 90 weight-% or more, more preferably 95 weight-% or more; and/or in an amount of 100 weight-% or less, preferably 95 weight-% or less, more preferably 90 weight-% or less, more preferably 50 weight-% or less, more preferably 25 weight-% or less, more preferably 10 weight-% or less. The present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated. In particular, it is noted that in each instance where a range of embodiments is mentioned, for example in the context of a term such as "The process of any one of embodiments 1 to 3", every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to "The process of any one of embodiments 1 , 2 and 3". Further, it is explicitly noted that the following set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.
1. A recycling process for recovering e-caprolactam from a solid material M comprising polyamide 6, the process comprising
(i) providing a stream SM comprising the solid material M;
(ii) preparing an aqueous depolymerization mixture based on SM ;
(iii) subjecting the depolymerization mixture prepared according to (ii) to polyamide 6 depolymerization conditions in a reaction unit UR, obtaining a liquid aqueous stream SR comprising e-caprolactam dissolved in water at a concentration CSR, the stream SR further comprising one or more impurities;
(iv) passing the liquid aqueous stream SR into an evaporation unit UE, obtaining from SR a liquid aqueous stream SL comprising e-caprolactam dissolved in water at a concentration CSL with CSL > CSR, and further obtaining from SR one or more aqueous vapor streams Sv;
(v) passing the aqueous stream SL into a heat-consuming purification unit UP, obtaining from SL a stream SCPL comprising e-caprolactam at a concentration CSCPL with CSCPL » CSL, and further obtaining from SL one or more aqueous 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 from the at least one stream Sv at least one at least partially condensed aqueous stream Svw;
(vi) recycling at least one stream Svw at least partially to the reaction unit UR and at least one stream SRW at least partially to the reaction unit UR.
2. The process of embodiment 1 , wherein the solid material M comprises, more preferably consists of, waste material, wherein said waste material more preferably comprises, more preferably consists of, one or more of at least one textile waste material and at least one engineering plastics waste material, more preferably comprises, more preferably consists of at least one textile waste material, wherein preferably from 10 to 100 weight-%, more preferably from 30 to 100 weight-%, more preferably from 50 to 100 weight-%, more preferably from 80 to 100 weight-%, of M consist of polyamide 6, wherein if the polyamide 6 content of the solid material M is less than 100 weight-%, the solid material M optionally additionally comprises one or more elastanes. 3. The process of embodiment 1 or 2, wherein the recycling according to (vi) comprises (vi.1 ) feeding the at least one stream Svw and the at least one stream SRW into a water treatment unit Uw, obtaining from Uw at least one aqueous recycle stream Sw;
(vi.2) recycling the at least one aqueous stream Sw at least partially to the reaction unit UR.
4. The process of embodiment 3, wherein the water treatment unit Uw comprises a water recovery unit UWR and a waste water unit Uww, wherein (vi.1 ) further comprises
(vi.1 .1) feeding the at least one stream Svw and the at least one stream SRW into the water recovery unit UWR, obtaining from UWR the at least one aqueous recycle stream Sw and at least one aqueous stream Ssw;
(vi .1 .2) feeding the at least one stream Ssw to the waste water unit Uww, obtaining from Uww, at least one waste water stream Sww.
5. The process of any one of embodiments 1 to 4, wherein the purification unit UP comprises one or more of a heat-consuming water separation unit Uws, a heat-consuming distillation unit UD and a heat-consuming crystallization unit Uc, preferably two or more of a heatconsuming water separation unit Uws, a heat-consuming distillation unit U D and a heatconsuming crystallization unit Uc, more preferably a heat-consuming water separation unit Uws, a heat-consuming distillation unit UD and a heat-consuming crystallization unit Uc, wherein at least part of the heat consumed in one or more of Uws, UD and Uc is provided by at least one of the one or more streams Sv.
6. The process of embodiment 5, 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 aqueous stream Svwi from Uws;
(i-2) obtaining at least one at least partially condensed aqueous stream Svw2 from UD;
(i-3) obtaining at least one at least partially condensed aqueous stream Svws from Uc; the process further comprising feeding one or more Svwi, Svw2 and Svws; preferably two or more Svwi, Svw2 and Svws; more preferably Svwi, Svw2 and Svws into the water treatment unit Uw as defined in claim 3.
7. The process of embodiment 5 or 6, wherein at least one of the streams SRW is obtained from Uws.
8. The process of any one of embodiments 1 to 7, wherein the purification unit UP comprises a heat-consuming water separation unit Uws, a heat-consuming distillation unit U D and a heatconsuming crystallization unit Uc, the process comprising feeding the stream SL comprising £-caprolactam at a concentration CSL to Uws, obtaining from Uws a stream Uws comprising E- caprolactam at a concentration Cuws, feeding the stream Suws to the distillation unit UD, obtaining from UD a stream SUD comprising c-caprolactam at a concentration CUD, and feeding the stream SUD into the crystallization unit Uc, and obtaining from Uc a stream SCPL comprising c-caprolactam at a concentration CSCPL, wherein CSL < Cuws < CUD < CSCPL. 9. The process of any one of embodiments 1 to 8, wherein the water separation unit Uws comprises at least two heat-consuming water separation sub-units Uwsi and Uws2, preferably two serially coupled heat-consuming water separation sub-units Uwsi and Uws2, wherein the stream SL is fed into Uwsi and wherein at least part of the heat consumed in one or more of Uwsi and Uws2 is provided by at least one of the one or more streams Sv.
10. The process of embodiment 9, comprising one or more of (ii-1 ) and (ii-2) preferably (ii-1 ) and (ii-2):
(ii-1 ) obtaining at least one at least partially condensed aqueous stream Svwn from Uwsi; (ii-2) obtaining at least one at least partially condensed aqueous stream Svw/12 from Uws2.
11 . The process of embodiment 10, wherein at least one aqueous stream SRWI is obtained from Uwsi and at least one aqueous stream SRW2 is obtained from Uws2, and wherein at least one of SRWI and SRW2, preferably SRWi and SRW2 are fed into Uw.
12. The process of any one of embodiments 9 to 11 , wherein downstream of U wsi and upstream of Uws2, a separation unit Ui is located, the process comprising obtaining from Uwsi an aqueous stream Suwsi, feeding the stream Suwsi into the separation unit Ui, obtaining from Ui an aqueous stream Sui, and feeding the stream Sui into the unit Uws2, wherein in Ui, one or more of impurities are separated from Suwsi, thereby obtaining from Ui an impurity stream Si, said impurities preferably comprising at least one impurity comprised in SR according to (ii).
13. The process of any one of embodiments 1 to 12, wherein the evaporation unit UE comprises two or more evaporation sub-units, the process comprising obtaining at least two vapor streams Svi and Sv2, passing the vapor stream Svi to at least one heat-consuming unit and passing the vapor stream Sv2 to at least one heart-consuming unit, wherein the vapor streams Svi and Sv2 differ from each other in either pressure and/or temperature.
14. The process of any one of embodiments 1 to 13, wherein downstream of UR, at least one solid-liquid separation unit is arranged, wherein preferably at least one of the streams SL and SR is passed through at least one solid-liquid separation unit prior to being passed to the next downstream unit.
15. The process of any one of embodiments 1 to 14, further comprising providing the stream SCPL to a polyamide 6 production unit U PP, wherein the polyamide 6 produced in UPP is preferably provided as a feedstock to a textile material producing unit UTP, from which unit UTP
(A) a textile material MT is obtained which is brought onto the market, wherein, after the life-time TMT of said textile material MT, it is at least partially collected as textile waste material in a textile material collecting unit UTC; (B) remaining material MR is obtained as textile waste material; wherein at least part of the textile waste material according to (A), or at least part of the textile waste material according to (B), or at least part of the textile waste material according to (A) and at least part of the textile waste material according to (B) is suitably provided to UR as SM, preferably via UM . The process of any one of embodiments 1 to 14, further comprising providing the stream SCPL to a polyamide 6 production unit UpP, wherein the polyamide 6 produced in UPP is preferably provided as a feedstock to an engineering plastics material producing unit UTp, from which unit UTP
(A) an engineering plastics material MT is obtained which is brought onto the market, wherein, after the life-time TMT of said engineering plastics material MT, it is at least partially collected as engineering plastics waste material in an engineering plastics material collecting unit UTC;
(B) remaining material MR is obtained as engineering plastics waste material; wherein at least part of the engineering plastics waste material according to (A), or at least part of the engineering plastics waste material according to (B), or at least part of the engineering plastics waste material according to (A) and at least part of the engineering plastics waste material according to (B) is suitably provided to U R as SM, preferably via UM. Crystallized e-caprolactam, obtainable or obtained as stream SCPL by a process according to any one of embodiments 1 to 14, exhibiting one or more of the following properties: an APHA color, determined as described Reference Example 1 , of at most 5, preferably of at most 4, more preferably of at most 3, more preferably of at most 2, more preferably of at most 1 .5, more preferably of at most 1 ; a purity, determined as described in Reference Example 2, of at least 99.8 weight-%, preferably of at least 99.9 %, more preferably of at least 99.95 %. The crystallized e-caprolactam of embodiment 17, exhibiting one or more of the following properties: an e-caprolactam oligomer content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a 6-aminocaproic acid content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm. The crystallized e-caprolactam of embodiment 17 or 18, exhibiting the following property: a triisopropyl borate content in the range of from 0 to 100 weight-ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm. The crystallized c-caprolactam of any one of embodiments 17 to 19, preferably wherein the solid material M as defined in embodiment 2 comprises one or more elastanes, said crystallized c-caprolactam exhibiting one or more of the following properties: a polytetrahydrofuran content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; an aniline content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight- ppm; a methylenediphenyl diamine (MDA), isomers and oligomers content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a butanediol content in the range of from 0 to 500 weight-ppm, more preferably in the range of from 0 to 300 weight-ppm, more preferably in the range of from 0 to 100 weight-ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight-ppm; and/or an ethylene glycol content in the range of from 0 to 500 weight-ppm, more preferably in the range of from 0 to 300 weight-ppm, more preferably in the range of from 0 to 100 weight-ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight-ppm. Use of SCPL, obtainable or obtained by a process according to any one of embodiments 1 to 15, preferably of SCPL according to any one of embodiments 17 to 20, for preparing polyamide 6, said use preferably further comprising employing said polyamide 6 as a feedstock for preparing one or more of at least one textile material and at least one engineering plastics material, more preferably for preparing at least one textile material. Use of a process according to any one of embodiments 1 to 14 for preparing high-purity E- caprolactam from a solid material M, preferably from a waste material comprising polyamide 6 and preferably one or more elastanes, said high-purity c-caprolactam exhibiting one or more of the following properties: an £-caprolactam oligomer content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a 6-aminocaproic acid content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a triisopropyl borate content in the range of from 0 to 100 weight-ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a polytetrahydrofuran content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; an aniline content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight- ppm; a methylenediphenyl diamine (MDA), isomers and oligomers content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a butanediol content in the range of from 0 to 500 weight-ppm, more preferably in the range of from 0 to 300 weight-ppm, more preferably in the range of from 0 to 100 weight-ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight-ppm; and/or an ethylene glycol content in the range of from 0 to 500 weight-ppm, more preferably in the range of from 0 to 300 weight-ppm, more preferably in the range of from 0 to 100 weight-ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight-ppm. Use of SCPL, obtainable or obtained by a process according to any one of embodiments 1 to 14, preferably of SCPL according to any one of embodiments 17 to 20, 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, said method comprising employing SCPL, obtainable or obtained by a process according to any one of embodiments 1 to 14, preferably of SCPL according to any one of embodiments 17 to 20, as a starting material. The use or the method of embodiment 23, wherein the polymer, or the polymer product, or the polymer and the polymer product is or are in the form of at least one of a granulate, a strand, a rod, a plate, a pipe, a foil, a layer, a film, a sheet, a fiber, a filament, a coating, an extruded article, a molded article, a soft foam, a half-rigid foam and a rigid foam. The use or the method of embodiment 23 or 24, wherein the polymer, or the polymer product, or the polymer and the polymer product comprises or comprise polyamide 6 and optionally at least one further polymeric compound, said polyamide 6 being at least partially obtainable or obtained from SCPL, said SCPL being obtainable or obtained by a process according to any one of embodiments 1 to 14, preferably being SCPL according to any one of embodiments 17 to 20, wherein the at least one further polymeric compound preferably comprises one or more of at least one polyamide 6.6; at least one polyethylene terephthalate; at least one polyurethane; at least one polyester; at least one polyether; at least one polyvinyl chloride; at least natural fiber material such as wool and cotton; at least one cellulose material; at least one natural elastomer; at least one synthetic elastomer; at least one copolymer of two or more of said polymeric compounds including statistical copolymers, gradient copolymers, alternating copolymers, block copolymers, and graft copolymers; and at least one rubber material comprising one or more of at least one natural rubber material and at least one synthetic rubber material.
26. The use or the method of any one of embodiments 23 to 25, wherein the polymer, or the polymer product, or the polymer and the polymer product is or are one of the following or a part of one of the following: a part of a car, preferably a cylinder head cover, an engine cover, a housing for a charge air cooler, a charge air cooler flap, an intake pipe, an intake manifold, a connector, a gear wheel, a fan wheel, a cooling water box, a housing or a housing part for a heat exchanger, a coolant cooler, a charge air cooler, a thermostat, a water pump, a radiator, a fastening part or a part of a battery system for electromobility, a dashboard, a steering column switch, a seat, a headrest, a center console, a transmission component, a door module, a car exterior for an A, a B, a C or a D pillar cover, a spoiler, a door handle, an exterior mirror, a windscreen wiper, a windscreen wiper protection housing, a decorative grill, a cover strip, a roof rail, a window frame, a sunroof frame, an antenna panel, a headlight, a taillight, an airbag, and/or a cushion; a cloth, an apparel, preferably a shirt, trousers, a pullover, a boot, a shoe, a shoe sole, a tight and/or or jacket; an electrical part, preferably an electrical component, an electronic passive component, an electronic active component, a printed circuit board, a housing component, a foil, a line, a switch such as a microswitch, a plug, a socket, a distributor, a relay, a resistor, a capacitor, an inductor, a bobbin, a lamp, a diode such as an LED, a transistor, a connector, a regulator, an integrated circuit (IC), a processor, a controller, a memory, a sensor, a microbutton, a semiconductor, a reflector housing for example for light-emitting diodes, a fastener for an electrical and/or an electronic component, a spacer, a bolt, a strip, a slide-in guide, a screw, a nut, a film hinge, a snap hook (snap-in), and/or a spring tongue; a consumer and/or a pharmaceutical product, preferably a tennis string, a climbing rope, a bristle, a brush, an artificial grass, a 3D printing filament, a grass trimmer, a zipper, a hook and loop fastener, a paper machine clothing, an extrusion coating, a fishing line, a fishing net, an offshore line and rope, a vial, a syringe, an ampoule, a bottle, a sliding element, a spindle nut, a chain conveyor, a plain bearing, a roller, a wheel, a gear, a roller, a ring gear, a screw and spring damper, a hose, a pipeline, a cable sheathing, a socket, a switch, a cable tie, a fan wheel, a carpet, a box and/or a bottle for cosmetics, a mattress, a cushion, an insulation; a packaging for the food industry, preferably a mono- and/or multi-layer blown film, a cast film (mono- and/or multi-layer), a biaxially stretched film, a laminating film.
27. The use or the method of any one of embodiments 23 to 26, wherein the polymer, or the polymer product, or the polymer and the polymer product contains or contain polyamide 6, obtainable or obtained from SCPL, said SCPL being obtainable or obtained by a process according to embodiment 28, in an amount of 1 weight-% or more, preferably 2 weight-% or more, more preferably 5 weight-% or more, more preferably 15 weight-% or more, more preferably 30 weight-% or more, more preferably 40 weight-% or more, more preferably 60 weight-% or more, more preferably 80 weight-% or more, more preferably 90 weight-% or more, more preferably 95 weight-% or more; and/or in an amount of 100 weight-% or less, preferably 95 weight-% or less, more preferably 90 weight-% or less, more preferably 50 weight-% or less, more preferably 25 weight-% or less, more preferably 10 weight-% or less.
As far as the embodiment 27 is concerned, 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, more preferably the International Sustainability and Carbon Certification (ISCC) standard. As far as the embodiments 23 to 27 are concerned, preparing the polymer, the polymer product, or the polymer and the polymer product may comprise one or more synthesis steps and can be performed by conventional synthesis and technics well known to the person skilled in the art. Examples of the synthesis steps 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.
The term „bar“ as used in the context of the present invention refers to „bar(abs)”, i.e. bar (absolute), sometimes also referred to as “bara”.
The term “elastane” as used herein is also referred to as “spandex”, and common brand names for spandex include Lycra, Elaspan, Acepora, Creora, Inviya, Roica, Dorlastan, Linel or ESPA.
The term “textile material” covers textile raw materials and non-textile raw materials that are processed by various methods into linear, planar and spatial structures. It concerns the linear textile structures produced from them, such as yarns, twisted yarns and ropes, the sheet-like textile structures, such as woven fabrics, knitted fabrics, braids, stitch-bonded fabrics, nonwovens and felts, and the three-dimensional textile structures, i.e. body structures, such as textile hoses, stockings or textile semi-finished products; and it further concerns those finished products which, using the aforementioned products, are brought into a saleable condition by making up, opening up and/or other operations for onward transmission to the processor, the trade or the end consumer. The term “textile waste material” covers a textile material as defined above, the inherent value of which has been consumed from the perspective of its current holder and, thus, is an end-of-life material for said holder.
The term “engineering plastics” as used herein refers to high-performance plastics grades which possess physical properties enabling them to perform for prolonged use in structural applications, over a wide temperature range, under mechanical stress, and in difficult chemical and physical environments used for example to fabricate plastic parts replacing traditional engineering materials like metals and ceramics. Engineering plastics specifically apply in the fabrication of mechanical parts across several industries such as automotive, medical, electrical and electronics, aerospace, construction and consumer products. The term “engineering plastics waste material” as used herein covers an engineering plastics material as defined above, the inherent value of which has been consumed from the perspective of its current holder and, thus, is an end-of-life material for said holder.
In the context of the present invention, a term “X is one or more of A, B and C”, wherein X is a given feature and each of A, B and C stands for specific realization of said feature, is to be understood as disclosing that X is either A, or B, or C, or A and B, or A and C, or B and C, or A and B and C. In this regard, it is noted that the skilled person is capable of transfer to above abstract term to a concrete example, e.g. where X is a chemical element and A, B and C are concrete elements such as Li, Na, and K, or X is a temperature and A, B and C are concrete temperatures such as 10 °C, 20 °C, and 30 °C. In this regard, it is further noted that the skilled person is capable of extending the above term to less specific realizations of said feature, e.g. “X is one or more of A and B” disclosing that X is either A, or B, or A and B, or to more specific realizations of said feature, e.g. “X is one or more of A, B, C and D”, disclosing that X is either A, or B, or C, or D, or A and B, or A and C, or A and D, or B and C, or B and D, or C and D, or A and B and C, or A and B and D, or B and C and D, or A and B and C and D.
The present invention is illustrated by the following figures and reference examples.
Short description of the figures
List of abbreviations
Units
UM Unit for providing feed stream SM
UR Reaction I depolymerisation unit
UE Evaporation unit
UP Purification unit
Uw Water treatment unit
UWR Water recovery unit
Uww Waste water unit
Uws Water separation unit
UWsi Upstream water separation unit
UWs2 Downstream water separation unit
Ui Intermediate separation
UD Distillation unit Uc Crystallization unit
UPP PA6 material production unit
UTP Textile material production unit
UTC Textile material collection unit
Streams
SM PA6 waste material stream
SR Product stream obtained from depolymerisation
SL Liquid stream obtained from evaporation unit comprising CPL (e-caprolactam)
SCPL Final solid CPL product
Sv One or more aqueous vapour streams obtained from evaporation unit
Svi Aqueous vapour stream obtained from evaporation unit
Sv2 Aqueous vapour stream obtained from evaporation unit
Svw One or more at least partially condensed streams obtained from Sv
Svwi Condensed stream obtained from Uws
Svwn Condensed stream obtained from UWSi
Svwi2 Condensed stream obtained from Uws2
Svw2 Condensed stream obtained from UD
Svws Condensed stream obtained from Uc
SRW One or more aqueous streams (reaction water streams)
SRWI Aqueous streams obtained from Uwsi
SRW2 Aqueous streams obtained from Uws2
Sw Recycle water stream obtained from water removal unit UWR
Ssw Stream separated in UWR to be passed to waste water system Uww
Sww Waste water stream
Sows CPL containing stream, obtained from water separation unit Uws
Su si CPL containing stream, obtained from water separation sub-unit Uwsi
Su s2 CPL containing stream, obtained from water separation sub-unit U s2
Sui CPL containing stream, obtained from impurity separation unit Ui
SUD CPL containing stream, obtained from distillation unit UD
Si Stream comprising impurities, obtained from Ui
SNCPL Non-recycle CPL stream
SNPA6 Non-recycle PA6 stream
Others
TMT Lifetime of textile material MT
MT Textile material produced in UTp
MR Material comprising polyamide 6, remaining from production in UTp Figure 1 shows a process according to present invention
According to this process, a waste material stream SM comprising polyamide 6 is passed into reaction unit UR where the waste material is subjected to polyamide 6 depolymerization conditions (depolymerisation via hydrolysis in an aqueous medium). From the reaction unit UR, a liquid aqueous stream SR is obtained and removed which comprises e-caprolactam and one or more impurities. This stream SR is then passed to an evaporation unit U E from which a liquid aqueous stream SL and one or more aqueous vapor streams Sv are obtained and removed; in Fig. 1 , only one vapor stream Sv is shown. The stream SL has a higher e-caprolactam concentration than the stream SR. The stream SL is then passed to a heat-consuming purification unit UP where a further purification with regard to e-caprolactam occurs. From the stream SL which is fed into U P, a product stream SCPL is finally obtained which comprises e-caprolactam at a concentration which is significantly higher than the e-caprolactam concentration of the stream SL. According to the process of the present invention, at least a part of the heat consumed in the purification unit U P is at least partially provided by at least one of the one or more vapor streams Sv and based on Sv, one or more at last partially condensed aqueous streams Svw are obtained and removed from UP; only one stream Svw is shown in Fig. 1. Yet further from the purification unit UP, one or more aqueous streams SR are obtained from SL. At least one stream Svw is then at least partially recycled to the reaction unit UR, and also at least one stream SRW is at least partially recycled to the reaction unit U R.
Figure 2 shows a process including the complete recycling loop
The process according to Fig. 2 shows the further use of the stream SCPL, i.e. the purified s-caprolactam. According to the present invention, stream SCPL is passed to a polyamide 6 production unit UPP where it is employed as starting material. If need be, one or more further streams SNCPL can be additionally passed to UPP, said streams comprising non-recycled s-caprolactam, i.e. s-caprolactam from a conventional source. The respectively prepared polyamide 6 material is then passed to a unit UTP where it is used as a starting material for preparing a material comprising polyamide 6, preferably a textile material comprising polyamide 6. If need be, one or more further streams SNPA6 can be additionally passed to UTp, said streams comprising non-recycled polyamide 6, i.e. polyamide 6 from a conventional source. Depending on the type of material prepared in UTP, also further streams comprising one or more starting materials other than polyamide 6 can be passed to UTP. The material, preferably the textile material MT obtained from UTP then goes into the market and remains there for a given lifetime TMT. Thereafter, the respective end-of-life material is suitably collected in a collecting unit UTC, preferably a textile material collecting unit, from which it is suitably passed as stream the SM or as part of the stream SM to the reaction unit UR preferably via a unit UM for providing the stream SM to UR. Such unit UM usually comprises any apparatus by which the preferably solid material M can be suitably passed to the reaction unit UR. Preferably, UM comprises apparatuses such as one or more silos, one or more hoppers, one or more truck unloading stations, one or more big bag unloading station, and the like. Further in Fig. 2, it is shown that in the production unit UTP, remaining material M R is obtained from the production process, i.e. material which is not comprised in MT. By way of example, M R may be in the form textile cuttings. This material can be fed, either via UTC and/or directly via UM , to UR as the stream SM or as part of stream SM. This recycle loop as shown in Fig. 2 also applies to any of Figs. 3 to 6 below, however, is not explicitly shown there.
Figure 3 shows a process with a preferred water treatment stage
The process as shown in this Fig. 3 shows a preferred treatment of the streams SVw and SRW as already shown in Figs. 1 and 2. According to this process, the streams Svw and SRW are passed into a water treatment unit Uw from which a stream Sw is obtained which is then (at least partially) recycled as aqueous stream Sw (or part thereof) to the reaction unit U R. Further from Uw, one or more waste water streams Sww are obtained which are not recycled to the process. Preferably, the water treatment unit Uw comprises a water recovery unit UWR and optionally a waste water unit Uww. Preferably, the streams Svw and SRW are passed into the water treatment unit Uw where they are suitably purified and/or suitably collected in order to obtain the one or more aqueous recycle streams. Streams which are obtained from such purification may then be passed to the waste water treatment unit Uww.
Figure 4 shows a process with a preferred heat-consuming purification unit UP
The process as shown in Fig. 4 shows a preferred way of purifying the stream SL with respect to £-caprolactam. According to this process, the stream SL is first passed to a water separation unit from which the one or more streams SRW are obtained which are then preferably passed to the water treatment unit Uw as already shown in Fig. 2 and, according to a preferred design, in Fig. 3. Further, at least one of the streams Sv is passed to Uws for at least partially meeting the heat demand of Uws; based on this at least one stream Sv passed to Uws, one or more at least partially condensed streams Svwi are obtained and preferably further passed to the water treatment Uw. The stream Sows comprising e-caprolactam is then preferably passed to a distillation unit UD for further purification with respect to e-caprolactam. Further, at least one of the streams Sv is passed to UD for at least partially meeting the heat demand of UD; based on this at least one stream Sv passed to UD, one or more at least partially condensed streams SVw2 are obtained and preferably further passed to the water treatment Uw. The stream SUD comprising £-caprolactam is then preferably passed to a crystallization unit Uc for further purification with respect to £-caprolactam. Further, at least one of the streams Sv is passed to Uc for at least partially meeting the heat demand of Uc; based on this at least one stream Sv passed to Uc, one or more at least partially condensed streams Svws are obtained and preferably further passed to the water treatment Uw.
Figure 5 shows a process with a preferred water separation unit Uws
The process as shown in Fig. 5 shows a preferred way of separating water from the stream SL in the water separation unit UWs. According to this process, the stream SL is first passed to a first stage of water separation, carried out in the unit Uwsi. From Uwsi, a stream comprising c-caprolactam is then passed to an intermediate treatment stage Ui where impurities may be removed. The thus purified stream obtained from Ui is then further passed to a second stage of water separation, carried out in the unit Uws2. From said unit Uws2, a stream Suws2 comprising E- caprolactam is obtained which corresponds to the stream Sows as shown in Fig. 4 and which is then preferably passed to the distillation unit U D. From the intermediate unit Ui, a stream Si comprising the respectively separated impurities is removed which, depending on the amount and/or the chemical nature of the impurities, may be put to further use. According to this process, one or more aqueous streams SRWI are obtained which are then preferably passed to the water treatment unit Uw as already shown in Fig. 2 and, according to a preferred design, in Fig. 3. Further according to this process, one or more aqueous streams SRW2 are obtained which are then preferably passed to the water treatment unit Uw as already shown in Fig. 2 and, according to a preferred design, in Fig. 3. Preferably, at least one of the streams Sv is passed to Uwsi for at least partially meeting the heat demand of Uwsi; based on this at least one stream Sv passed to UWsi, one or more at least partially condensed streams Svwn are obtained and preferably further passed to the water treatment UW- Preferably, at least one of the streams Sv is passed to UWs2 for at least partially meeting the heat demand of U s2; based on this at least one stream Sv passed to U s2, one or more at least partially condensed streams Svwi2 are obtained and preferably further passed to the water treatment Uw.
Figure 6 shows a process with a preferred use of different vapour streams Sv
The process as shown in Fig. 6 shows, based on the preferred process design according to Fig. 5, a further preferred way of providing heat to the purification unit Up. According to this process, one or more vapour streams Svi and one or more vapour streams Sv2 are obtained from the evaporation unit U E which, for example, may comprise two or more evaporation sub-units (not shown), wherein the one or more streams Svi have pressures and temperatures which differ from the pressures and temperatures of the streams Sv2. Accordingly, the streams Svi and Sv2 can be used for providing heat to units with different heat demands. By way of example and as shown in Fig. 6, the streams Svi are used for providing at least part of the heat consumed by U wsi and Uc whereas the streams SV2 are used for providing at least part of the heat consumed by UWs2 and UD. Accordingly, based on the streams Svi, one or more at least partially condensed streams Svwn and Svws are obtained and preferably further passed to the water treatment Uw. Further accordingly, based on the streams Sv2, one or more at least partially condensed streams Svwi2 and Svw2 are obtained and preferably further passed to the water treatment Uw.
Reference Examples
Reference Example 1 : Determination of the APHA color of crystallized c-caprolactam
The APHA color was determined by according to ISO 8112. In principal, the extinction E of a 50 % by weight aqueous e-caprolactam solution is determined in a cuvette of length I = 5 cm at a wavelength A = 390 nm and expressed in Hazen units (platinum-cobalt scale). For doing this, the measured extinction E is multiplied by the factor f = 150.
The Hazen units (platinum-cobalt scale) are defined as the color of a solution containing, in 1 I water, 1 mg platinum in the form of hexachloroplatinum(IV) acid in the presence of 2 mg cobalt(ll) chloride hexahydrate. The Hazen units correspond to the APHA units. A standard solution of 500 Hazen units as prepared as follows: 1.000 g cobalt(ll) chloride hexahydrate (CoCI2 • 6 H2O) and 1.245 g potassium hexachloroplatinate(IV) (K2PtCI6) are dissolved in 100 ml hydrochloric acid having a of 1 .19 g/ml. The solution is transferred into a 1000 ml volumetric flask which is filled to the calibration mark. Thus solution contains 500 mg platinum and corresponds to 500 Hazen units.
50 ± 0.1 g e-caprolactam are dissolved in a 250 Erlenmeyer flask in 50 ml distilled water. The solution is mixed and left until the air bubbles have disappeared. The 2 cuvettes of the spectrophotometer (which is suitable for measurements at a wavelength A = 390 nm) are filled with distilled water, placed in the beam path, and the spectrophotometer is adjusted at A = 390 nm to E = 0. Then, the distilled water is removed from the sample cuvette, followed by filling this cuvette with the £-caprolactam solution. Then, the extinction E of this solution is determined at A = 390 nm (E390) against the comparative cuvette containing distilled water.
The color number X (Hazen units, platinum-cobalt scale) is calculated as X = E » f = 150 » E390. X is rounded to the next integer.
Reference Example 2: Determination of the purity of crystallized £-caprolactam
The purity of the crystallized £-caprolactam and the respective amounts of impurities was determined via GC-FID/MS using GC (Agilent 7890A) coupled with two MSDs (Agilent 5975C) for electron impact ionisation and chemical ionisation.
According to the present invention, it was found that, if impurities are present in SCPL, and in particular in case one or more elastanes are contained in the solid material M, diol compounds such as butanediol and ethylene glycol, and optionally oligomers thereof, are the predominat impurities. Due to the finding that the process of the present leads to SCPL compositions containing other impurities only at very low weight-ppm values, these other impurities could be neglected as far as the calculation of the purity of crystallized £-caprolactam is concerned.
The respective are-% values obtained from the measurement was extrapolated to the respective weight-% I weight-ppm values as follows: the diol compounds mentioned above are calibrated in the GC and then measured quantitatively, i.e. in weight-%. By subtracting these measured weight-% values from 100 weight-%, the purity of the crystallized SCPL is obtained.

Claims

Claims
1. A recycling process for recovering e-caprolactam from a solid material M comprising polyamide 6, the process comprising
(i) providing a stream SM comprising the solid material M;
(ii) preparing an aqueous depolymerization mixture based on SM;
(iii) subjecting the depolymerization mixture prepared according to (ii) to polyamide 6 depolymerization conditions in a reaction unit UR, obtaining a liquid aqueous stream SR comprising e-caprolactam dissolved in water at a concentration CSR, the stream SR further comprising one or more impurities;
(iv) passing the liquid aqueous stream SR into an evaporation unit UE, obtaining from SR a liquid aqueous stream SL comprising e-caprolactam dissolved in water at a concentration CSL with CSL > CSR, and further obtaining from SR one or more aqueous vapor streams Sv;
(v) passing the aqueous stream SL into a heat-consuming purification unit UP, obtaining from SL a stream SCPL comprising e-caprolactam at a concentration CSCPL with CSCPL » CSL, and further obtaining from SL one or more aqueous 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 from the at least one stream Sv at least one at least partially condensed aqueous stream Svw;
(vi) recycling at least one stream Svw at least partially to the reaction unit UR and at least one stream SRW at least partially to the reaction unit UR.
2. The process of claim 1 , wherein the solid material M comprises, more preferably consists of, waste material, wherein said waste material more preferably comprises, more preferably consists of, one or more of at least one textile waste material and at least one engineering plastics waste material, more preferably comprises, more preferably consists of at least one textile waste material, wherein preferably from 10 to 100 weight-%, more preferably from 30 to 100 weight-%, more preferably from 50 to 100 weight-%, more preferably from 80 to 100 weight-%, of M consist of polyamide 6, wherein if the polyamide 6 content of the solid material M is less than 100 weight-%, the solid material M optionally additionally comprises one or more elastanes.
3. The process of claim 1 or 2, wherein the recycling according to (vi) comprises
(vi.1 ) feeding the at least one stream Svw and the at least one stream SRW into a water treatment unit Uw, obtaining from Uw at least one aqueous recycle stream Sw;
(vi.2) recycling the at least one aqueous stream Sw at least partially to the reaction unit UR.
4. The process of claim 3, wherein the water treatment unit Uw comprises a water recovery unit UWR and a waste water unit Uww, wherein (vi.1 ) further comprises
(vi.1.1) feeding the at least one stream Svw and the at least one stream SRW into the water recovery unit UWR, obtaining from UWR the at least one aqueous recycle stream Sw and at least one aqueous stream Ssw; (vi .1 .2) feeding the at least one stream SSw to the waste water unit Uww, obtaining from Uww, at least one waste water stream Sww.
5. The process of any one of claims 1 to 4, wherein the purification unit UP comprises one or more of a heat-consuming water separation unit Uws, a heat-consuming distillation unit U D and a heat-consuming crystallization unit Uc, preferably two or more of a heat-consuming water separation unit Uws, a heat-consuming distillation unit UD and a heat-consuming crystallization unit Uc, more preferably a heat-consuming water separation unit U ws, a heatconsuming distillation unit UD and a heat-consuming crystallization unit Uc, wherein at least part of the heat consumed in one or more of Uws, UD and Uc is provided by at least one of the one or more streams Sv; wherein the process preferably further comprises one or more of (i-1 ), (i-2) and (i-3); more 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 aqueous stream Svwi from Uws;
(i-2) obtaining at least one at least partially condensed aqueous stream Svw2 from UD;
(i-3) obtaining at least one at least partially condensed aqueous stream SVw3 from Uc; the process preferably further comprising feeding one or more Svwi, SVw2 and Svws! preferably two or more Svwi, Svw2 and Svws; more preferably Svwi, Svw2 and Svws into the water treatment unit Uw as defined in claim 3.
6. The process of claim 5, wherein at least one of the streams SRW is obtained from Uws.
7. The process of any one of claims 1 to 6, wherein the purification unit UP comprises a heatconsuming water separation unit Uws, a heat-consuming distillation unit U D and a heatconsuming crystallization unit Uc, the process comprising feeding the stream SL comprising £-caprolactam at a concentration CSL to Uws, obtaining from Uws a stream Uws comprising £-caprolactam at a concentration Cuws, feeding the stream Sows to the distillation unit UD, obtaining from UD a stream SUD comprising £-caprolactam at a concentration CUD, feeding the stream SUD into the crystallization unit Uc, and obtaining from Uc a stream SCPL comprising £-caprolactam at a concentration CSCPL, wherein CSL < Cuws < CUD < CSCPL.
8. The process of any one of claims 1 to 7, wherein the water separation unit Uws comprises at least two heat-consuming water separation sub-units Uwsi and Uws2, preferably two serially coupled heat-consuming water separation sub-units Uwsi and Uws2, wherein the stream SL is fed into Uwsi and wherein at least part of the heat consumed in one or more of Uwsi and Uws2 is provided by at least one of the one or more streams Sv.
9. The process of claim 8, comprising one or more of (ii-1) and (ii-2) preferably (ii-1 ) and (ii-2): (ii-1) obtaining at least one at least partially condensed aqueous stream Svwn from Uwsi! (ii-2) obtaining at least one at least partially condensed aqueous stream SVwi2 from UWs2-
10. The process of claim 9, wherein at least one aqueous stream SRWi is obtained from UWsi and at least one aqueous stream SRW2 is obtained from Uws2, and wherein at least one of SRWI and SRW2, preferably SRWi and SRW2 are fed into Uw.
11 . The process of any one of claims 8 to 10, wherein downstream of Uwsi and upstream of Uws2, a separation unit Ui is located, the process comprising obtaining from Uwsi an aqueous stream Suwsi, feeding the stream Suwsi into the separation unit Ui, obtaining from Ui an aqueous stream Sui, and feeding the stream Sui into the unit Uws2, wherein in Ui, one or more of impurities are separated from Suwsi, thereby obtaining from Ui an impurity stream Si, said impurities preferably comprising at least one impurity comprised in SR according to (ii).
12. The process of any one of claims 1 to 11 , wherein the evaporation unit U E comprises two or more evaporation sub-units, the process comprising obtaining at least two vapor streams Svi and Sv2, passing the vapor stream Svi to at least one heat-consuming unit and passing the vapor stream SV2 to at least one heat-consuming unit, wherein the vapor streams Svi and SV2 differ from each other in either pressure and/or temperature.
13. The process of any one of claims 1 to 12, further comprising providing the stream SCPL to a polyamide 6 production unit UPP, wherein the polyamide 6 produced in U PP is preferably provided as a feedstock to a textile material producing unit UTP, from which unit UTP
(A) textile material MT is obtained which is brought onto the market, wherein, after the lifetime TMT of said textile material MT, it is at least partially collected as textile waste material in a textile material collecting unit UTc;
(B) remaining material MR is obtained as textile waste material; wherein at least part of the textile waste material according to (A), or at least part of the textile waste material according to (B), or at least part of the textile waste material according to (A) and at least part of the textile waste material according to (B) is suitably provided to UR as SM, preferably via a feeding unit UM.
14. Crystallized e-caprolactam, obtainable or obtained as stream SCPL by a process according to any one of claims 1 to 12, exhibiting one or more of the following properties: an APHA color of at most 5, preferably of at most 4, more preferably of at most 3, more preferably of at most 2, more preferably of at most 1 .5, more preferably of at most 1 ; a purity of at least 99.8 weight-%, preferably of at least 99.9 %, more preferably of at least 99.95 %; and preferably exhibiting one or more of the following properties: an e-caprolactam oligomer content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a 6-aminocaproic acid content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a triisopropyl borate content in the range of from 0 to 100 weight-ppm, more preferably in the range of from 0 to 50 weight-ppm, more preferably in the range of from 0 to 10 weight-ppm; and preferably further exhibiting one or more of the following properties, more preferably wherein the solid material M as defined in claim 2 comprises one or more elastanes: a polytetrahydrofuran content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; an aniline content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight- ppm; a methylenediphenyl diamine (MDA), isomers and oligomers content in the range of from 0 to 10 weight-ppm, more preferably in the range of from 0 to 5 weight-ppm, more preferably in the range of from 0 to 1 weight-ppm; a butanediol content in the range of from 0 to 500 weight-ppm, more preferably in the range of from 0 to 300 weight-ppm, more preferably in the range of from 0 to 100 weight-ppm; and/or an ethylene glycol content in the range of from 0 to 500 weight-ppm, more preferably in the range of from 0 to 300 weight-ppm, more preferably in the range of from 0 to 100 weight-ppm.
15. Use of SCPL, obtainable or obtained by a process according to any one of claims 1 to 12, preferably of SCPL according to claim 14, for preparing polyamide 6, said use preferably further comprising employing said polyamide 6 as a feedstock for preparing one or more of at least one textile material and at least one engineering plastics material, more preferably for preparing at least one textile material.
EP24716281.1A 2023-03-31 2024-03-27 Highly integrated caprolactam recycling process Pending EP4688737A1 (en)

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