Heat integration in a process for hydrolytically depolymerizing a polyamide

The present invention relates to a heat-integrated process for hydrolytically depolymerizing a polyamide prepared from c-caprolactam.

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. There is thus a need to recycle polyamide 6 from such materials. Processes for alkaline depolymerizing a polyamide exists. Further, the processes in the art are energy-intensive processes. Thus, there is a need to provide an improved process for depolymerizing a polyamide able to overcome these issues.

Surprisingly, it was found that the process of the present invention according to which polyamide is hydrolytically depolymerized is more robust and is more cost effective. Further, the process of the present invention permits to reduce the overall energy consumption compared to known processes for depolymerization of a polyamide which also permits to reduce costs. Hence, using a heat-integrated process for depolymerizing a polyamide according to the present invention permits to reduce the CO2 footprint.

Therefore, the present invention relates to a heat-integrated process for hydrolytically depolymerizing a polyamide prepared from c-caprolactam, said polyamide being contained in a solid material M, the process comprising

(i) preparing an aqueous liquid stream SR comprising c-caprolactam dissolved in water, comprising

(1.1) providing the solid material M comprising the polyamide, and providing a aqueous liquid stream Sw;

(1.2) preparing a mixture of the solid material M and the aqueous liquid stream Sw provided according to (i.1);

(1.3) preparing an aqueous mixture MA comprising the polyamide dissolved in water from the mixture prepared according to (i.2);

(1.4) subjecting the aqueous mixture MA prepared according to (i.3) to depolymerization conditions comprising a depolymerization temperature TD at a depolymerization pressure PD in a chemical reactor unit Ru, obtaining a liquid aqueous reaction mixture MR in Ru, MR comprising c-caprolactam dissolved in water, wherein TD is in the range of from 230 to 320 °C and PD is in the range of from 40 to 120 bar;

(1.5) removing an aqueous liquid stream SR from Ru, SR comprising c-caprolactam dissolved in water, wherein said aqueous liquid stream SR has a pressure PR in the range of from 40 to 120 bar and a temperature TR in the range of from 230 to 320 °C;

(1.6) optionally passing the aqueous liquid stream SR through a heat exchanging unit HUo, obtaining an aqueous liquid stream SLO having a temperature TLO with TLO < TR and having a pressure pi_o in the range of from 40 to 120 bar;

(ii) subjecting the aqueous liquid stream SR obtained according to (i .5), or the aqueous liquid stream SLO obtained according to (i.6), to depressurization in an evaporation unit EU, obtaining from EU at least one aqueous vapor stream Sv having a temperature Tv in the range of from 100 to 230 °C, and at least one aqueous liquid stream SL comprising E- caprolactam dissolved in water;

(iii) passing at least one aqueous vapor stream Sv obtained according to (ii), having a temperature Tv, through a heat exchanging unit HU, thereby heating in HU at least one stream ST having a temperature TST, obtaining a cooled aqueous stream Sv, Scv, having a temperature Tcv with Tcv < Tv and at least one heated stream ST, SHT, having a temperature THST with THST > TST;

(iv) separating c-caprolactam from at least one aqueous liquid stream SL obtained according to

(ii) in at least one heat consuming purification unit PU, wherein the heat consumed in PU is at least partially provided by at least one heated stream SHT;

(v) recycling at least one aqueous liquid stream SRE obtained from at least one heat consuming purification unit PU according to (iv) into Ru, preferably as part of the aqueous liquid stream Sw according to (i.1 ).

Preferably, the mixture prepared according to (i.2) is prepared in the chemical reactor unit Ru.

Preferably, according to (i.5), the aqueous liquid stream SR has a pressure PR in the range of from 50 to 100 bar, more preferably in the range of from 60 to 90 bar.

Preferably, according to (i.5), the aqueous liquid stream SR has a temperature TR in the range of from 250 to 310 °C, more preferably in the range of from 270 to 300 °C.

Preferably, the solid material M provided according to (i.1) comprises, more preferably consists of, waste material, wherein said waste material more preferably comprises textile waste material.

Preferably, the process comprises

(ii) subjecting the aqueous liquid stream SR obtained according to (i.5), or the aqueous liquid stream SLO obtained according to (i.6), to depressurization in an evaporation unit EU comprising n evaporation sub-units EU (j), 1 < j < n with n > 1 , obtaining from each sub-unit EU(j) an aqueous vapor stream SvG) and an aqueous liquid stream SLG) comprising c-caprolactam dissolved in water, wherein SvG) has a temperature TvG) and a pressure pvG) and wherein SLG) has a temperature TLG) and a pressure PLG);

(iii) passing at least one aqueous vapor stream SvG) obtained according to (ii) and having a temperature TvG) in the range of from 100 to 230 °C, through a heat exchanging unit HUG), thereby heating in HUG) a stream STG) having a temperature TSTG), obtaining a cooled aqueous stream SvG), ScvG), having a temperature TcvG) with TcvG) < TvG) and at least one heated stream STG), SHTG), having a temperature THSTG) with THSTG) > TSTG);

(iv) separating c-caprolactam from at least one aqueous liquid stream SLG) obtained according to (ii) in at least one heat consuming purification unit PU, wherein the heat consumed in PU is at least partially provided by at least one heated stream SHTG);

(v) recycling at least one aqueous liquid stream SRE obtained from at least one heat consuming purification unit PU according to (iv) into Ru, more preferably as part of the aqueous liquid stream Sw according to (i.1); wherein at least one evaporation sub-unit EU (j), more preferably every evaporation sub-unit EU (j) according to (ii) comprises, more preferably consists of, a flash drum.

Preferably, according to (ii), the aqueous liquid stream SR obtained according to (i .5), or the aqueous liquid stream SLO obtained according to (i.6), is subjected to depressurization in the evaporation unit EU(1); and, according to (iv), e-caprolactam is separated from the aqueous liquid stream Si_(n) obtained according to (ii) in at least one heat consuming purification unit PU.

Preferably, n > 1 , and wherein for j < n, the process comprises passing the aqueous liquid stream SLG) obtained from the evaporation sub-unit EUG) as feed stream into the evaporation sub-unit EUG+1). More preferably, the n evaporation sub-units EUG) ^are serially coupled.

Preferably, n > 1 , and wherein for j < n, TvG+1) < TvG); PvG+1) < PvG); TLG+1 ) < G); and PLG+1 ) < PLG)-

Preferably, pv(n) is in the range of from 0.90 to 1.5 bar, more preferably in the range of from 0.95 to 1.1 bar; Tv(n) is in the range of from 90 to 110 °C, more preferably in the range of from 95 to 100 °C; pi_(n) is in the range of from 0.90 to 1.5 bar, more preferably in the range of from 0.95 to 1 .1 bar; and K(n) is in the range of from 90 to 110°C, more preferably in the range of from 95 to 105 °C.

Heat exchange upstream of EU according to (i.6)

Preferably, n is in the range of from 1 to 3, more preferably n = 1 or n = 2, more preferably n = 1.

The process preferably comprises passing the aqueous liquid stream SR through a heat exchanging unit HUo according to (i.6), obtaining an aqueous liquid stream SLO having a temperature Ko with Ko < TR and having a pressure PLO in the range of from 40 to 120 bar; and subjecting the aqueous liquid stream SLO obtained according to (i.6) to depressurization according to (ii).

Preferably, Ko is in the range of from 130 to 150 °C, more preferably in the range of from 120 to 140 °C and a pressure PLO is in the range of from 40 to 120 bar, more preferably in the range of from 50 100 bar, more preferably in the range of from 60 to 90 bar.

Preferably, the aqueous vapor stream Sv(n) obtained from EU(n) has a pressure pv(n) in the range of from 0.95 to 1.5 bar, more preferably in the range of from 1.0 to 1 .4 bar, and a temperature K(n) in the range of from 90 to 110 °C, more preferably in the range of from 95 to 100 °C; and the aqueous liquid stream Si_(n) obtained from EU(n) has a pressure pi_(n) in the range of from 0.95 to 1 .5 bar, more preferably in the range of from 1 .0 to 1 .4 bar, and a temperature K(n) in the range of from 90 to 110 °C, more preferably in the range of from 95 to 100 °C. Preferably, for n = 1 according to a preferred aspect, the aqueous vapor stream Sv(1 ) obtained from EU(1 ) has a pressure pv(1 ) in the range of from 0.95 to 1.5 bar, more preferably in the range of from 1 .0 to 1 .4 bar, and a temperature Tv(1 ) in the range of from 90 to 110 °C, more preferably in the range of from 95 to 100 °C; and the aqueous liquid stream Si_(1 ) obtained from EU(1 ) has a pressure pi_(1 ) in the range of from 0.95 to 1.5 bar, more preferably in the range of from 1 .0 to 1 .4 bar, and a temperature K(1 ) in the range of from 90 to 110 °C, more preferably in the range of from 95 to 100 °C.

Preferably, according to (iv), c-caprolactam is separated from the aqueous liquid stream Si_(1 ) obtained according to (ii) in at least one heat consuming purification unit PU, wherein the heat consumed in PU is at least partially provided by the heated stream SHT(1 ).

Preferably, the process further comprises recycling the cooled aqueous stream Scv(1 ) into Ru, more preferably as part of the aqueous liquid stream Sw according to (i.1 ).

The presence of a heat exchanger upstream of the evaporation unit EU according to an alternative of the present invention is shown in Figure 1.

No heat exchange upstream of EU(1)

Alternatively, the aqueous liquid stream SR is preferably not passed through a heat exchanging unit HUo according to (i.6), and, according to (ii), the aqueous liquid stream SR obtained according to (i.5) is subjected to depressurization in an evaporation unit EU.

Preferably, n is in the range of from 2 to 5, more preferably in the range of from 2 to 4, more preferably n = 2 or n = 3.

Preferably, the process comprises

(ii) subjecting the aqueous liquid stream SR obtained according to (i.5) to depressurization in an evaporation unit EU comprising n evaporation sub-units EU (j), obtaining from the subunit EU (j) an aqueous vapor stream SvG) and an aqueous liquid stream SLG) comprising E- caprolactam dissolved in water, wherein SvG) has a temperature TvG) and a pressure pvG) and wherein SLG) has a temperature TLG) and a pressure PLG); wherein for j < n, the aqueous liquid stream SLG) obtained from the evaporation sub-unit EUG) is passed as feed stream into the evaporation sub-unit EUG+1 ); wherein for j < n, TvG+1 ) < TvG); PvG+1 ) < PvG); G+1 ) < KG); and p _L G+1 ) < PLG); wherein pv(n) is in the range of from 0.95 to 1.5 bar, more preferably in the range of from 1 .0 to 1 .4 bar; Tv(n) is in the range of from 90 to 110 °C, more preferably in the range of from 95 to 100 °C; PL(H) is in the range of from 0.95 to 1.5 bar, more preferably in the range of from 1.0 to 1 .4 bar; and K(n) is in the range of from 90 to 110°C, more preferably in the range of from 95 to 105 °C;

(iii) passing at least the aqueous vapor stream Sv(n) obtained according to (ii) through the heat exchanging unit HU(n), thereby heating in HU(n) the stream S-r(n) having a temperature Tsi-(n), obtaining the cooled aqueous stream Sv(n), Scv(n), having a temperature Tcv(n) with Tcv(n) < Tv(n) and the heated stream S-r(n), SHi-(n), having a temperature THsi-(n) with THST(H) > TST(H);

(iv) separating c-caprolactam from the aqueous liquid stream Si_(n) obtained according to (ii) in at least one heat consuming purification unit PU, wherein the heat consumed in PU is at least partially provided by at least one of the heated streams SHTG);

(v) recycling at least one aqueous liquid stream SRE obtained from at least one heat consuming purification unit PU according to (iv) into Ru, more preferably as part of the aqueous liquid stream Sw according to (i.1 ).

Preferably, according to (iii), at least the aqueous vapor streams SvG) for j = 2...n obtained according to (ii) are passed through the heat exchanging units HUG), j ⁼ 2...n.

The absence of a heat exchanger upstream of the evaporation unit EU according to an alternative of the present invention is shown in Figures 2-5. Said alternative is further detailed in the following.

According to a first preferred aspect, the process preferably comprises

(ii) subjecting the aqueous liquid stream SR obtained according to (i.5) to depressurization in an evaporation unit EU comprising n evaporation sub-units EUG), obtaining from the subunit EUG) an aqueous vapor stream SvG) and an aqueous liquid stream SLG) comprising E- caprolactam dissolved in water, wherein SvG) has a temperature TvG) and a pressure pvG) and wherein SLG) has a temperature TLG) and a pressure PLG); wherein the aqueous liquid stream SR is passed as feed stream into the evaporation subunit EU(1 ); wherein for j < n, the aqueous liquid stream SLG) obtained from the evaporation sub-unit EUG) is passed as feed stream into the evaporation sub-unit EUG+1 ); wherein for j < n, TvG+1 ) < TvG); PvG+1 ) < PvG); G+1) < KG); and p _L G+1 ) < PLG); wherein pv(n) is in the range of from 0.95 to 1.5 bar, more preferably in the range of from 1 .0 to 1 .4 bar; Tv(n) is in the range of from 90 to 110 °C, more preferably in the range of from 95 to 100 °C; PL(H) is in the range of from 0.95 to 1.5 bar, more preferably in the range of from 0.95 to 1 .4 bar; and K(n) is in the range of from 90 to 110°C, more preferably in the range of from 95 to 105 °C;

(iii) passing the aqueous vapor streams SvG) obtained according to (ii) through the heat exchanging units HUG), thereby heating in HUG) the stream STG) having a temperature TSTG), obtaining the cooled aqueous stream SvG), ScvG), having a temperature TcvG) with TcvG) < KG) ^ar| d the heated stream STG), SHTG), having a temperature THSTG) with THSTG) > TSTG); (iv) separating e-caprolactam from the aqueous liquid stream Si_(n) obtained according to (ii) in at least one heat consuming purification unit PU, wherein the heat consumed in PU is at least partially provided by at least one of the heated streams SHTG);

(v) recycling at least one aqueous liquid stream SRE obtained from at least one heat consuming purification unit PU according to (iv) into Ru, more preferably as part of the aqueous liquid stream Sw according to (i.1).

Preferably, according to said first aspect, n = 2 and pv(1) is in the range of from 7.5 to 18 bar, more preferably in the range of from 8 to 16 bar;

Tv(1) is in the range of from 160 to 210 °C, more preferably in the range of from 170 to 200 °C; PL(1 ) is in the range of from 7.5 to 18 bar, more preferably in the range of from 8 to 16 bar; and TL(1 ) is in the range of from 160 to 210 °C, more preferably in the range of from 170 to 200 °C.

Alternatively, preferably, n = 3 and pv(1) is in the range of from 19 to 31 bar, more preferably in the range of from 20 to 30 bar;

Tv(1) is in the range of from 205 to 240 °C, more preferably in the range of from 210 to 235 °C; PL(1 ) is in the range of from 19 to 31 bar, more preferably in the range of from 20 to 30 bar; and TL(1 ) is in the range of from 205 to 240 °C, more preferably in the range of from 210 to 135 °C; pv(2) is in the range of from 7.5 to 18 bar, more preferably in the range of from 8 to 16 bar;

Tv(2) is in the range of from 160 to 210 °C, more preferably in the range of from 170 to 200 °C; PL(2) is in the range of from 7.5 to 18 bar, more preferably in the range of from 8 to 16 bar; and TL(2) is in the range of from 160 to 210 °C, more preferably in the range of from 170 to 200 °C; or pv(1) is in the range of from 7.5 to 18 bar, more preferably in the range of from 8 to 16 bar;

Tv(1) is in the range of from 160 to 210 °C, more preferably in the range of from 170 to 200 °C; PL(1 ) is in the range of from 7.5 to 18 bar, more preferably in the range of from 8 to 16 bar; and TL(1 ) is in the range of from 160 to 210 °C, more preferably in the range of from 170 to 200 °C; pv(2) is in the range of from 1 .5 to 7 bar, more preferably in the range of from 2 to 7 bar;

Tv(2) is in the range of from 115 to 165 °C, more preferably in the range of from 120 to 165 °C; PL(2) is in the range of from 1 .5 to 7 bar, more preferably in the range of from 2 to 7 bar; and TL(2) is in the range of from 115 to 165 °C, more preferably in the range of from 120 to 165 °C.

According to said first preferred aspect, the process preferably further comprises recycling at least one of the cooled aqueous streams ScvG), more preferably all cooled aqueous streams ScvG) obtained according to (iii) into Ru, more preferably as part of the aqueous liquid stream Sw according to (i.1).

Said first aspect of the present invention is shown in Figure 2.

According to a second preferred aspect, the process preferably comprises

(ii) subjecting the aqueous liquid stream SR obtained according to (i.5) to depressurization in an evaporation unit EU comprising n evaporation sub-units EUG), obtaining from the sub- unit EU(j) an aqueous vapor stream SvG) and an aqueous liquid stream SLG) comprising E- caprolactam dissolved in water, wherein SvG) has a temperature TvG) and a pressure pvG) and wherein SLG) has a temperature TLG) and a pressure PLG); wherein the aqueous liquid stream SR is passed as feed stream into the evaporation subunit EU(1); wherein for j < n, the aqueous liquid stream SLG) obtained from the evaporation sub-unit EUG) is passed as feed stream into the evaporation sub-unit EUG+1); wherein for j < n, TvG+1) < TvG); PvG+1) < PvG); G+1) < G); and p _L G+1 ) < PLG); wherein pv(n) is in the range of from 0.95 to 1.5 bar, more preferably in the range of from 1 .0 to 1 .4 bar; Tv(n) is in the range of from 90 to 110 °C, more preferably in the range of from 95 to 100 °C; PL(H) is in the range of from 0.95 to 1.5 bar, more preferably in the range of from 1.0 to 1 .4 bar; and K(n) is in the range of from 90 to 110°C, more preferably in the range of from 95 to 105 °C;

(iii) passing the aqueous vapor streams SvG), j > 1 , obtained according to (ii) through the heat exchanging units HUG), thereby heating in HUG) the stream STG) having a temperature TSTG), obtaining the cooled aqueous stream SvG), ScvG), having a temperature TcvG) with TcvG) < KG) ^ar| d the heated stream STG), SHTG), having a temperature THSTG) with THSTG) > TSTG);

(iv) separating c-caprolactam from the aqueous liquid stream SL(O) obtained according to (ii) in at least one heat consuming purification unit PU, wherein the heat consumed in PU is at least partially provided by at least one of the heated streams SHTG);

(v) recycling at least one aqueous liquid stream SRE obtained from at least one heat consuming purification unit PU according to (iv) into Ru, more preferably as part of the aqueous liquid stream Sw according to (i.1); wherein x % of the stream Sv(1) obtained according to (ii) are admixed with at least one of the streams SRE according to (v), 0 < x < 100; wherein, if x * 100, the process comprises dividing the stream Sv(1) into a substream Svi(1) and a substream Sv2(1), Svi(1) constituting x % of the stream Sv(1) and Sv2(1) constituting (100-x) % of the stream Sv(1), and admixing Svi(1) with at least one of the streams SRE according to (v).

Preferably, for x * 100, the substream Sv2(1) is passed through the heat exchanging unit HU(1), thereby heating in HU(1) the stream ST(1 ) having a temperature TST(1 ), obtaining the cooled aqueous stream Svi(1), Scv(1), having a temperature Tcv(1) with Tcv(1) < Tvi(1) and the heated stream ST(1 ), SHT(1 ), having a temperature THST(1 ) with THST(1 ) > TST(1 ).

Said second aspect is shown in Figures 3 and 5. Said aspect is further detailed in the following.

As a first alternative of the second aspect of the present invention, preferably 25 < x < 100, more preferably 50 < x < 100, more preferably 75 < x < 100, wherein more preferably, x = 100.

Preferably, according to said first alternative of the second aspect, n = 3 and pv(1) is in the range of from 19 to 31 bar, more preferably in the range of from 20 to 30 bar;

Tv(1) is in the range of from 205 to 240 °C, more preferably in the range of from 210 to 235 °C; PL(1 ) is in the range of from 19 to 31 bar, more preferably in the range of from 20 to 30 bar; and TL(1 ) is in the range of from 205 to 240 °C, more preferably in the range of from 210 to 135 °C; pv(2) is in the range of from 7.5 to 18 bar, more preferably in the range of from 8 to 16 bar;

Tv(2) is in the range of from 160 to 210 °C, more preferably in the range of from 170 to 200 °C; PL(2) is in the range of from 7.5 to 18 bar, more preferably in the range of from 8 to 16 bar; and TL(2) is in the range of from 160 to 210 °C, more preferably in the range of from 170 to 200 °C; or pv(1) is in the range of from 7.5 to 18 bar, more preferably in the range of from 8 to 16 bar;

Tv(1) is in the range of from 160 to 210 °C, more preferably in the range of from 170 to 200 °C; PL(1 ) is in the range of from 7.5 to 18 bar, more preferably in the range of from 8 to 16 bar; and TL(1 ) is in the range of from 160 to 210 °C, more preferably in the range of from 170 to 200 °C; pv(2) is in the range of from 1 .5 to 7 bar, more preferably in the range of from 2 to 7 bar;

Tv(2) is in the range of from 115 to 165 °C, more preferably in the range of from 120 to 165 °C; PL(2) is in the range of from 1 .5 to 7 bar, more preferably in the range of from 2 to 7 bar; and TL(2) is in the range of from 115 to 165 °C, more preferably in the range of from 120 to 165 °C.

According to said first alternative, preferably, admixing x % of the stream Sv(1) obtained according to (ii) with at least one of the streams SRE according to (v) comprises bubbling x % of the stream Sv(1) into the at least one aqueous liquid stream SRE.

According to said first alternative, the process preferably further comprises recycling at least one of the cooled aqueous streams ScvG), more preferably all cooled aqueous streams ScvG) obtained according to (iii) into Ru, more preferably as part of the aqueous liquid stream Sw according to (i.1).

Said first alternative of the second aspect of the present invention is shown in Figure 3.

According to a second alternative of the second aspect of the present invention, preferably, 1 < x < 20, more preferably 2 < x < 15, more preferably 5 < x < 10.

According to said second alternative, preferably, n = 2 and pv(1) is in the range of from 7.5 to 18 bar, more preferably in the range of from 8 to 16 bar;

Tv(1) is in the range of from 160 to 210 °C, more preferably in the range of from 170 to 200 °C; PL(1 ) is in the range of from 7.5 to 18 bar, more preferably in the range of from 8 to 16 bar; and TL(1 ) is in the range of from 160 to 210 °C, more preferably in the range of from 170 to 200 °C.

Preferably, according to said second alternative, admixing x % of the stream Sv(1) obtained according to (ii) with at least one of the streams SRE according to (v) comprises passing the substream Svi(1) through a heat exchanging unit HURE, thereby cooling the substream Svi(1), wherein in the heat exchanging unit HURE, at least one of the streams SRE is heated prior to being recycled into Ru according to (v).

Preferably, according to said second alternative, when x = 100, the process comprises passing the substream Sv2(1 ) through a heat exchanging unit HU(1), thereby cooling the substream Sv2(1 ), obtaining a cooled stream Scv(1 ), wherein more preferably the stream Scv(1 ) is recycled into Ru, more preferably as part of the aqueous liquid stream Sw according to (i.1 ).

Preferably, the process according to said second alternative preferably further comprises recycling at least one of the cooled aqueous streams ScvG), more preferably all cooled aqueous streams ScvG) obtained according to (iii) into Ru, more preferably as part of the aqueous liquid stream Sw according to (i.1 ).

Said second alternative of the second aspect of the present invention is shown in Figure 5.

According to a third alternative of the second aspect of the present invention, the process preferably comprises

(ii) subjecting the aqueous liquid stream SR obtained according to (i.5) to depressurization in an evaporation unit EU comprising n evaporation sub-units EUG), obtaining from the subunit EUG) an aqueous vapor stream SvG) and an aqueous liquid stream SLG) comprising E- caprolactam dissolved in water, wherein SvG) has a temperature TvG) and a pressure pvG) and wherein SLG) has a temperature TLG) and a pressure PLG); wherein the aqueous liquid stream SR is passed as feed stream into the evaporation subunit EU(1 ); wherein for j < n, the aqueous liquid stream SLG) obtained from the evaporation sub-unit EUG) is passed as feed stream into the evaporation sub-unit EUG+1 ); wherein for j < n, TvG+1 ) < TvG); PvG+1 ) < PvG); G+1 ) < G); and p _L G+1 ) < PLG); wherein pv(n) is in the range of from 0.95 to 1 .5 bar, more preferably in the range of from 1 .0 to 1 .4 bar; Tv(n) is in the range of from 90 to 110 °C, more preferably in the range of from 95 to 100 °C; PL(H) is in the range of from 0.95 to 1.5 bar, more preferably in the range of from 1 .0 to 1.4 bar; and K(n) is in the range of from 90 to 110°C, more preferably in the range of from 95 to 105 °C;

(iii) passing the aqueous vapor streams SvG) obtained according to (ii) through the heat exchanging units HUG), thereby heating in HUG) the stream STG) having a temperature TSTG), obtaining the cooled aqueous stream SvG), ScvG), having a temperature TcvG) with vG) < KG) ^ar| d the heated stream STG), SHTG), having a temperature THSTG) with THSTG) > TSTG);

(iv) separating c-caprolactam from the aqueous liquid stream SL(O) obtained according to (ii) in at least one heat consuming purification unit PU, wherein the heat consumed in PU is at least partially provided by at least one of the heated streams SHTG); (v) recycling at least one aqueous liquid stream SRE obtained from at least one heat consuming purification unit PU according to (iv) into Ru, more preferably as part of the aqueous liquid stream Sw according to (i.1); wherein at least one of the streams SLG), prior to being passed as feed stream into the evaporation sub-unit EU(j+1) according to (ii), is passed through a heat exchanging unit HURE, thereby cooling the SLG), wherein in the heat exchanging unit HURE, at least one of the streams SRE is heated prior to being recycled into Ru according to (v).

According to said third alternative, preferably, the at least one of the streams SLG) which is passed through the heat exchanging unit HURE is the stream SL(1 ).

According to said third alternative, preferably, n = 2 and pv(1) is in the range of from 7.5 to 18 bar, more preferably in the range of from 8 to 16 bar;

Tv(1) is in the range of from 160 to 210 °C, more preferably in the range of from 170 to 200 °C; PL(1 ) is in the range of from 7.5 to 18 bar, more preferably in the range of from 8 to 16 bar; and TL(1 ) is in the range of from 160 to 210 °C, more preferably in the range of from 170 to 200 °C.

Preferably, according to said third alternative, the process further comprises recycling at least one of the cooled aqueous streams ScvG), more preferably all cooled aqueous streams ScvG) obtained according to (iii) into Ru, more preferably as part of the aqueous liquid stream Sw according to (i.1).

Said third alternative of the second aspect of the present invention is shown in Figure 4.

Heat-consuming purification units PU / PU (i)

In the context of the present invention, preferably, according to (iv), the at least one heat consuming purification unit PU comprises a heat consuming purification unit PU(1), or a heat consuming purification unit PU(2), or a heat consuming purification unit PU(1) and a heat consuming purification unit PU(2), more preferably a heat consuming purification unit PU(1) and a heat consuming purification unit PU(2), wherein the purification unit PU(1) comprises at least one film evaporator, more preferably at least one falling film evaporator, more preferably two falling film evaporators, more preferably two serially coupled falling film evaporators, wherein in PU(1), water is separated from an aqueous stream comprising e-caprolactam dissolved in water; the purification unit PU(2) comprises at least one distillation column, more preferably two or three distillation columns, more preferably two or three serially coupled distillation columns, wherein in PU(2), water is removed from an aqueous stream comprising e-caprolactam dissolved in water.

Preferably, the process comprises passing at least a part of at least one heated stream SHT 3S heating medium through a heating jacket of the at least one film evaporator of PU(1). Preferably, the process comprises passing at least a part of at least one heated stream S^as heating medium through a heat exchanger of an evaporator of at least one distillation column of PU(2), more preferably through a heat exchanger of each of the two or three distillation columns of PU(2), more preferably through a heat exchanger used for sump evaporation of each of the two or three distillation columns of PU(2).

Preferably, the process comprises passing at least a part of at least one heated stream S^as heating medium through a heating jacket of the at least one film evaporator of PU(2).

Preferably, according to (iv), separating e-caprolactam from at least one aqueous liquid stream SL, more preferably Si_(n), obtained according to (ii), SL having a water concentration CL(H2O), in at least one heat consuming purification unit PU according to (iv) comprises

(iv.1) passing said at least one aqueous liquid stream SL through a solid-liquid separation SLU, obtaining an aqueous liquid stream SLSLU comprising e-caprolactam dissolved in water, SLSLU having a water concentration CLSLU(H2O), and further obtaining a solid;

(iv.2) passing the at least one aqueous liquid stream SL, preferably the aqueous liquid stream SLSLU obtained according to (iv.1 ), through the purification unit PU(1), obtaining an aqueous liquid stream SLRUI , SLPUI having a water concentration CLPUI (H2O), wherein CLPUI (H ₂ O) < C (H ₂ O), more preferably C PUI (H ₂ O) < C SLU(H ₂ O);

(iv.3) passing the aqueous liquid stream SLPUI obtained according to (iv.2) through a separation unit OSU, obtaining an aqueous liquid stream SLOSU, SLOSU having a water concentration CLOSU(H2O), wherein, in OSU, oligomers of e-caprolactam which are comprised in SLPUI are separated from SLPUI ;

(iv.4) passing the aqueous liquid stream SLPUI obtained according to (iv.2), preferably the aqueous liquid stream CLOSU(H2O) obtained according to (iv.3), through the purification unit PU(2), obtaining a liquid stream CLPU2(H2O) having a water concentration CLPU2(H2O), wherein CLPU2(H2O) « CLPUI (H2O), more preferably CLPU2(H2O) « Cosu(H2O).

Solid-liquid separation unit

Preferably, the solid-liquid separation SLU according to (iv.1 ) comprises, more preferably consists of, one or more of a centrifuge, a decanter, a decanter centrifuge, and a filter, more preferably one or more of a decanter and a decanter centrifuge.

Preferably, the separation OSU according to (iv.3) comprises a stirred tank reactor and a film evaporator, more preferably a wipe film evaporator, wherein, more preferably, the stirred tank reactor and a film evaporator are serially coupled.

The present invention is further illustrated by the following set of embodiments and combinations of embodiments resulting from the dependencies and back-references as indicated. In particular, it is noted that in each instance where a range of embodiments is mentioned, for example in the context of a term such as "The process of any one of embodiments 1 to 4", every embodiment in this range is meant to be explicitly disclosed for the skilled person, i.e. the wording of this term is to be understood by the skilled person as being synonymous to "The process of any one of embodiments 1 , 2, 3 and 4". Further, it is explicitly noted that the following set of embodiments represents a suitably structured part of the general description directed to preferred aspects of the present invention, and, thus, suitably supports, but does not represent the claims of the present invention.

1 . A heat-integrated process for hydrolytically depolymerizing a polyamide prepared from E- caprolactam, said polyamide being contained in a solid material M, the process comprising

(i) preparing an aqueous liquid stream SR comprising c-caprolactam dissolved in water, comprising

(1.1) providing the solid material M comprising the polyamide, and providing a aqueous liquid stream Sw;

(1.2) preparing a mixture of the solid material M and the aqueous liquid stream Sw provided according to (i.1);

(1.3) preparing an aqueous mixture MA comprising the polyamide dissolved in water from the mixture prepared according to (i.2);

(1.4) subjecting the aqueous mixture MA prepared according to (i.3) to depolymerization conditions comprising a depolymerization temperature TD at a depolymerization pressure PD in a chemical reactor unit Ru, obtaining a liquid aqueous reaction mixture MR in Ru, MR comprising c-caprolactam dissolved in water, wherein TD is in the range of from 230 to 320 °C and PD is in the range of from 40 to 120 bar;

(1.5) removing an aqueous liquid stream SR from Ru, SR comprising c-caprolactam dissolved in water, wherein said aqueous liquid stream SR has a pressure PR in the range of from 40 to 120 bar and a temperature TR in the range of from 230 to 320 °C;

(1.6) optionally passing the aqueous liquid stream SR through a heat exchanging unit HUo, obtaining an aqueous liquid stream SLO having a temperature TLO with TLO < TR and having a pressure pi_o in the range of from 40 to 120 bar;

(ii) subjecting the aqueous liquid stream SR obtained according to (i.5) or the aqueous liquid stream SLO obtained according to (i.6) to depressurization in an evaporation unit EU, obtaining from EU at least one aqueous vapor stream Sv having a temperature Tv in the range of from 100 to 230 °C, and at least one aqueous liquid stream SL comprising c-caprolactam dissolved in water;

(iii) passing at least one aqueous vapor stream Sv obtained according to (ii), having a temperature Tv, through a heat exchanging unit HU, thereby heating in HU at least one stream ST having a temperature TST, obtaining a cooled aqueous stream Sv, Scv, having a temperature Tcv with Tcv < Tv and at least one heated stream ST, SHT, having a temperature THST with THST > TST;

(iv) separating c-caprolactam from at least one aqueous liquid stream SL obtained according to (ii) in at least one heat consuming purification unit PU, wherein the heat consumed in PU is at least partially provided by at least one heated stream SHT;

(v) recycling at least one aqueous liquid stream SRE obtained from at least one heat consuming purification unit PU according to (iv) into Ru, preferably as part of the aqueous liquid stream Sw according to (i.1 ).

2. The process of embodiment 1 , wherein according to (i .5), the aqueous liquid stream SR has a pressure PR in the range of from 50 to 100 bar, preferably in the range of from 60 to 90 bar.

3. The process of embodiment 1 or 2, wherein according to (i .5), the aqueous liquid stream SR has a temperature TR in the range of from 250 to 310 °C, more preferably in the range of from 270 to 300 °C.

4. The process of any one of embodiments 1 to 3, wherein the solid material M provided according to (i.1) comprises, preferably consists of, waste material, wherein said waste material preferably comprises textile waste material.

5. The process of any one of embodiments 1 to 4, comprising

(ii) subjecting the aqueous liquid stream SR obtained according to (i.5) or the aqueous liquid stream SLO obtained according to (i.6) to depressurization in an evaporation unit EU comprising n evaporation sub-units EUG), 1 < j < n with n > 1 , obtaining from each sub-unit EU(j) an aqueous vapor stream SvG) and an aqueous liquid stream SLG) comprising e-caprolactam dissolved in water, wherein SvG) has a temperature TvG) and a pressure pvG) and wherein SLG) has a temperature TLG) and a pressure PLG);

(iii) passing at least one aqueous vapor stream SvG) obtained according to (ii) and having a temperature TvG) in the range of from 100 to 230 °C, through a heat exchanging unit HUG), thereby heating in HUG) a stream STG) having a temperature TSTG), obtaining a cooled aqueous stream SvG), ScvG), having a temperature TcvG) with TcvG) < TvG) and at least one heated stream STG), SHTG), having a temperature THSTG) with THSTG) ^> TSTG);

(iv) separating e-caprolactam from at least one aqueous liquid stream SLG) obtained according to (ii) in at least one heat consuming purification unit PU, wherein the heat consumed in PU is at least partially provided by at least one heated stream SHTG);

(v) recycling at least one aqueous liquid stream SRE obtained from at least one heat consuming purification unit PU according to (iv) into Ru, preferably as part of the aqueous liquid stream Sw according to (i.1 ); wherein at least one evaporation sub-unit EUG), preferably every evaporation sub-unit EUG) comprises, more preferably consists of a flash drum.

6. The process of embodiment 5, wherein according to (ii), the aqueous liquid stream SR obtained according to (i.5) or the aqueous liquid stream SLO obtained according to (i.6) is subjected to depressurization in the evaporation unit EU(1 ); and wherein according to (iv), e-caprolactam is separated from the aqueous liquid stream SL(D) obtained according to (ii) in at least one heat consuming purification unit PU.

7. The process of embodiment 5 or 6, wherein n > 1 , and wherein for j < n, the process comprises passing the aqueous liquid stream SLG) obtained from the evaporation sub-unit EU(j) as feed stream into the evaporation sub-unit EU(j+1 ).

8. The process of any one of embodiments 5 to 7, wherein n > 1 , and wherein for j < n, TvG+1 ) < KG); PvG+1 ) < PvG); KG+1 ) < KG); and PLG+1 ) < PLG)-

9. The process of any one of embodiments 5 to 8, wherein pv(n) is in the range of from 0.90 to 1.5 bar, preferably in the range of from 0.95 to 1.1 bar; Tv(n) is in the range of from 90 to

110 °C, preferably in the range of from 95 to 100 °C; pi_(n) is in the range of from 0.90 to 1 .5 bar, preferably in the range of from 0.95 to 1.1 bar; and K(n) is in the range of from 90 to 110°C, preferably in the range of from 95 to 105 °C.

10. The process of any one of embodiments 5 to 9, wherein n is in the range of from 1 to 3, preferably n = 1 or n = 2, more preferably n = 1 .

11 . The process of embodiment 10, comprising passing the aqueous liquid stream SR through a heat exchanging unit HUo according to (i.6), obtaining an aqueous liquid stream SLO having a temperature Ko with Ko < TR and having a pressure pi_o in the range of from 40 to 120 bar; and subjecting the aqueous liquid stream SLO obtained according to (i.6) to depressurization according to (ii).

12. The process of embodiment 11 , wherein Ko is in the range of from 130 to 150 °C, preferably in the range of from 120 to 140 °C and a pressure PLO in the range of from 40 to 120 bar, preferably in the range of from 50 to 100 bar, more preferably in the range of from 60 to 90 bar.

13. The process of any one of embodiments 10 to 12, wherein the aqueous vapor stream Sv(n) obtained from EU(n) has a pressure pv(n) in the range of from 0.95 to 1.5 bar, preferably in the range of from 1 .0 to 1 .4 bar, and a temperature K(n) in the range of from 90 to 110 °C, preferably in the range of from 95 to 100 °C; and wherein the aqueous liquid stream SL(O) obtained from EU(n) has a pressure PL(O) in the range of from 0.95 to 1.5 bar, preferably in the range of from 1 .0 to 1 .4 bar, and a temperature K(n) in the range of from 90 to 110 °C, preferably in the range of from 95 to 100 °C.

14. The process of any one of embodiments 10 to 13, wherein according to (iv), £-caprolactam is separated from the aqueous liquid stream SL(1 ) obtained according to (ii) in at least one heat consuming purification unit PU, wherein the heat consumed in PU is at least partially provided by the heated stream SHT(1 ). The process of any one of embodiments 10 to 14, further comprising recycling the cooled aqueous stream Scv(1 ) into Ru, preferably as part of the aqueous liquid stream Sw according to (i.1 ). The process of any one of embodiments 5 to 9, wherein the aqueous liquid stream SR is not passed through a heat exchanging unit HUo according to (i.6), wherein according to (ii), the aqueous liquid stream SR obtained according to (i.5) is subjected to depressurization in an evaporation unit EU. The process of embodiment 16, wherein n is in the range of from 2 to 5, preferably in the range of from 2 to 4, more preferably n = 2 or n = 3. The process of embodiment 17, comprising

(ii) subjecting the aqueous liquid stream SR obtained according to (i.5) to depressurization in an evaporation unit EU comprising n evaporation sub-units EU(j), obtaining from the sub-unit EU(j) an aqueous vapor stream SvG) and an aqueous liquid stream SLG) comprising e-caprolactam dissolved in water, wherein SvG) has a temperature TvG) and a pressure pvG) and wherein SLG) has a temperature TLG) and a pressure PLG); wherein for j < n, the aqueous liquid stream SLG) obtained from the evaporation subunit EUG) is passed as feed stream into the evaporation sub-unit EUG+1 ); wherein for j < n, TvG+1 ) < TvG); PvG+1 ) < PvG); G+1 ) < KG); and p _L G+1 ) < PLG); wherein pv(n) is in the range of from 0.95 to 1.5 bar, preferably in the range of from 1 .0 to 1 .4 bar; Tv(n) is in the range of from 90 to 110 °C, preferably in the range of from 95 to 100 °C; PL(H) is in the range of from 0.95 to 1.5 bar, preferably in the range of from 1.0 to 1.4 bar; and K(n) is in the range of from 90 to 110°C, preferably in the range of from 95 to 105 °C;

(iii) passing at least the aqueous vapor stream Sv(n) obtained according to (ii) through the heat exchanging unit HU(n), thereby heating in HU(n) the stream S-r(n) having a temperature Tsi-(n), obtaining the cooled aqueous stream Sv(n), Scv(n), having a temperature Tcv(n) with Tcv(n) < Tv(n) and the heated stream S-r(n), SHi-(n), having a temperature KsT(n) with KsT(n) > Tsi-(n);

(iv) separating e-caprolactam from the aqueous liquid stream SL(O) obtained according to (ii) in at least one heat consuming purification unit PU, wherein the heat consumed in PU is at least partially provided by at least one of the heated streams SHTG);

(v) recycling at least one aqueous liquid stream SRE obtained from at least one heat consuming purification unit PU according to (iv) into Ru, preferably as part of the aqueous liquid stream Sw according to (i.1 ). The process of embodiment 18, wherein according to (iii), at least the aqueous vapor streams SvG) for j = 2...n obtained according to (ii) are passed through the heat exchanging units H U(j), j = 2...n. The process of any one of embodiments 16 to 19, comprising

(ii) subjecting the aqueous liquid stream SR obtained according to (i.5) to depressurization in an evaporation unit EU comprising n evaporation sub-units EU(j), obtaining from the sub-unit EU(j) an aqueous vapor stream SvG) and an aqueous liquid stream SLG) comprising e-caprolactam dissolved in water, wherein SvG) has a temperature TvG) and a pressure pvG) and wherein SLG) has a temperature TLG) and a pressure PLG); wherein the aqueous liquid stream SR is passed as feed stream into the evaporation sub-unit EU(1); wherein for j < n, the aqueous liquid stream SLG) obtained from the evaporation subunit EUG) is passed as feed stream into the evaporation sub-unit EUG+1); wherein for j < n, TvG+1) < TvG); PvG+1) < PvG); G+1) < KG); and p _L G+1 ) < PLG); wherein pv(n) is in the range of from 0.95 to 1.5 bar, preferably in the range of from 1 .0 to 1 .4 bar; Tv(n) is in the range of from 90 to 110 °C, preferably in the range of from 95 to 100 °C; PL(H) is in the range of from 0.95 to 1.5 bar, preferably in the range of from 0.95 to 1.4 bar; and K(n) is in the range of from 90 to 110°C, preferably in the range of from 95 to 105 °C;

(iii) passing the aqueous vapor streams SvG) obtained according to (ii) through the heat exchanging units HUG), thereby heating in HUG) the stream STG) having a temperature TSTG), obtaining the cooled aqueous stream SvG), ScvG), having a temperature TcvG) with TcvG) < KG) and the heated stream STG), SHTG), having a temperature THST ) with THST ) > TG);

(iv) separating e-caprolactam from the aqueous liquid stream SL(O) obtained according to (ii) in at least one heat consuming purification unit PU, wherein the heat consumed in PU is at least partially provided by at least one of the heated streams SHTG);

(v) recycling at least one aqueous liquid stream SRE obtained from at least one heat consuming purification unit PU according to (iv) into Ru, preferably as part of the aqueous liquid stream Sw according to (i.1). The process of embodiment 20, wherein n = 2 and wherein pv(1) is in the range of from 7.5 to 18 bar, preferably in the range of from 8 to 16 bar;

K(1) is in the range of from 160 to 210 °C, preferably in the range of from 170 to 200 °C;

PL(1 ) is in the range of from 7.5 to 18 bar, preferably in the range of from 8 to 16 bar; and

K(1) is in the range of from 160 to 210 °C, preferably in the range of from 170 to 200 °C. The process of embodiment 20, wherein n = 3 and wherein pv(1) is in the range of from 19 to 31 bar, preferably in the range of from 20 to 30 bar;

K(1) is in the range of from 205 to 240 °C, preferably in the range of from 210 to 235 °C;

PL(1 ) is in the range of from 19 to 31 bar, preferably in the range of from 20 to 30 bar; and

K(1) is in the range of from 205 to 240 °C, preferably in the range of from 210 to 135 °C; pv(2) is in the range of from 7.5 to 18 bar, preferably in the range of from 8 to 16 bar;

Tv(2) is in the range of from 160 to 210 °C, preferably in the range of from 170 to 200 °C; PL(2) is in the range of from 7.5 to 18 bar, preferably in the range of from 8 to 16 bar; and TL(2) is in the range of from 160 to 210 °C, preferably in the range of from 170 to 200 °C; or wherein pv(1) is in the range of from 7.5 to 18 bar, preferably in the range of from 8 to 16 bar;

Tv(1) is in the range of from 160 to 210 °C, preferably in the range of from 170 to 200 °C; PL(1 ) is in the range of from 7.5 to 18 bar, preferably in the range of from 8 to 16 bar; and TL(1 ) is in the range of from 160 to 210 °C, preferably in the range of from 170 to 200 °C; pv(2) is in the range of from 1 .5 to 7 bar, preferably in the range of from 2 to 7 bar;

Tv(2) is in the range of from 115 to 165 °C, preferably in the range of from 120 to 165 °C;

PL(2) is in the range of from 1.5 to 7 bar, preferably in the range of from 2 to 7 bar; and K(2) is in the range of from 115 to 165 °C, preferably in the range of from 120 to 165 °C.

23. The process of any one of embodiments 20 to 22, further comprising recycling at least one of the cooled aqueous streams ScvG), preferably all cooled aqueous streams ScvG) obtained according to (iii) into Ru, preferably as part of the aqueous liquid stream Sw according to (i.1).

24. The process of any one of embodiments 16 to 19, comprising

(ii) subjecting the aqueous liquid stream SR obtained according to (i.5) to depressurization in an evaporation unit EU comprising n evaporation sub-units EUG), obtaining from the sub-unit EUG) ^an aqueous vapor stream SvG) and an aqueous liquid stream SLG) comprising e-caprolactam dissolved in water, wherein SvG) has a temperature TvG) and a pressure pvG) and wherein SLG) has a temperature TLG) and a pressure PLG); wherein the aqueous liquid stream SR is passed as feed stream into the evaporation sub-unit EU(1); wherein for j < n, the aqueous liquid stream SLG) obtained from the evaporation subunit EUG) is passed as feed stream into the evaporation sub-unit EUG+1); wherein for j < n, TvG+1) < TvG); PvG+1) < PvG); G+1) < KG); and p _L G+1 ) < PLG); wherein pv(n) is in the range of from 0.95 to 1.5 bar, preferably in the range of from 1 .0 to 1 .4 bar; Tv(n) is in the range of from 90 to 110 °C, preferably in the range of from 95 to 100 °C; PL(H) is in the range of from 0.95 to 1.5 bar, preferably in the range of from 1.0 to 1.4 bar; and K(n) is in the range of from 90 to 110°C, preferably in the range of from 95 to 105 °C;

(iii) passing the aqueous vapor streams SvG), j > 1 , obtained according to (ii) through the heat exchanging units HUG), thereby heating in HUG) the stream STG) having a temperature TSTG), obtaining the cooled aqueous stream SvG), ScvG), having a temperature TcvG) with TcvG) < KG) and the heated stream STG), SHTG), having a temperature THSTG) with THSTG) > TSTG);

(iv) separating e-caprolactam from the aqueous liquid stream SL(O) obtained according to (ii) in at least one heat consuming purification unit PU, wherein the heat consumed in PU is at least partially provided by at least one of the heated streams SHTG);

(v) recycling at least one aqueous liquid stream SRE obtained from at least one heat consuming purification unit PU according to (iv) into Ru, preferably as part of the aqueous liquid stream Sw according to (i.1); wherein x % of the stream Sv(1) obtained according to (ii) are admixed with at least one of the streams SRE according to (v), 0 < x < 100; wherein, if x * 100, the process comprises dividing the stream Sv(1) into a substream Svi(1) and a substream Sv2(1), Svi(1) constituting x % of the stream Sv(1) and Sv2(1) constituting (100-x) % of the stream Sv(1), and admixing Svi(1) with at least one of the streams SRE according to (v). The process of embodiment 24, wherein for x * 100, the substream Sv2(1 ) is passed through the heat exchanging unit HU(1), thereby heating in HU(1) the stream ST(1 ) having a temperature TST(1 ), obtaining the cooled aqueous stream Svi(1), Scv(1), having a temperature Tcv(1) with Tcv(1) < Tvi(1) and the heated stream ST(1 ), SHT(1 ), having a temperature THST(1 ) with THST(1 ) > TST(1 ). The process of embodiment 24 or 25, wherein 25 < x < 100, preferably 50 < x < 100, more preferably 75 < x < 100, wherein more preferably, x = 100. The process of any one of embodiments 24 to 26, wherein n = 3 and wherein pv(1) is in the range of from 19 to 31 bar, preferably in the range of from 20 to 30 bar; Tv(1) is in the range of from 205 to 240 °C, preferably in the range of from 210 to 235 °C; PL(1 ) is in the range of from 19 to 31 bar, preferably in the range of from 20 to 30 bar; and TL(1 ) is in the range of from 205 to 240 °C, preferably in the range of from 210 to 135 °C; pv(2) is in the range of from 7.5 to 18 bar, preferably in the range of from 8 to 16 bar;

Tv(2) is in the range of from 160 to 210 °C, preferably in the range of from 170 to 200 °C; PL(2) is in the range of from 7.5 to 18 bar, preferably in the range of from 8 to 16 bar; and TL(2) is in the range of from 160 to 210 °C, preferably in the range of from 170 to 200 °C; or wherein pv(1) is in the range of from 7.5 to 18 bar, preferably in the range of from 8 to 16 bar;

Tv(1) is in the range of from 160 to 210 °C, preferably in the range of from 170 to 200 °C; PL(1 ) is in the range of from 7.5 to 18 bar, preferably in the range of from 8 to 16 bar; and TL(1 ) is in the range of from 160 to 210 °C, preferably in the range of from 170 to 200 °C; pv(2) is in the range of from 1.5 to 7 bar, preferably in the range of from 2 to 7 bar;

Tv(2) is in the range of from 115 to 165 °C, preferably in the range of from 120 to 165 °C; PL(2) is in the range of from 1 .5 to 7 bar, preferably in the range of from 2 to 7 bar; and TL(2) is in the range of from 115 to 165 °C, preferably in the range of from 120 to 165 °C. The process of any one of embodiments 24 to 27, wherein admixing x % of the stream Sv(1) obtained according to (ii) with at least one of the streams SRE according to (v) comprises bubbling x % of the stream Sv(1) into the at least one aqueous liquid stream SRE. The process of any one of embodiments 24 to 28, further comprising recycling at least one of the cooled aqueous streams ScvG), preferably all cooled aqueous streams ScvG) obtained according to (iii) into Ru, preferably as part of the aqueous liquid stream Sw according to (i.1). The process of embodiment 24 or 25, wherein 1 < x < 20, preferably 2 < x < 15, more preferably 5 < x < 10. The process of embodiment 30, wherein n = 2 and wherein pv(1) is in the range of from 7.5 to 18 bar, preferably in the range of from 8 to 16 bar;

Tv(1) is in the range of from 160 to 210 °C, preferably in the range of from 170 to 200 °C; PL(1 ) is in the range of from 7.5 to 18 bar, preferably in the range of from 8 to 16 bar; and TL(1 ) is in the range of from 160 to 210 °C, preferably in the range of from 170 to 200 °C. The process of embodiment 30 or 31 , wherein admixing x % of the stream Sv(1 ) obtained according to (ii) with at least one of the streams SRE according to (v) comprises passing the substream Svi(1) through a heat exchanging unit HURE, thereby cooling the substream Svi(1), wherein in the heat exchanging unit HURE, at least one of the streams SRE is heated prior to being recycled into Ru according to (v). The process of any one of embodiments 30 to 32, further comprising recycling at least one of the cooled aqueous streams ScvG), preferably all cooled aqueous streams ScvG) obtained according to (iii) into Ru, preferably as part of the aqueous liquid stream Sw according to (i.1). The process of any one of embodiments 16 to 19, comprising

(ii) subjecting the aqueous liquid stream SR obtained according to (i.5) to depressurization in an evaporation unit EU comprising n evaporation sub-units EUG), obtaining from the sub-unit EUG) ^an aqueous vapor stream SvG) and an aqueous liquid stream SLG) comprising e-caprolactam dissolved in water, wherein SvG) has a temperature TvG) and a pressure pvG) and wherein SLG) has a temperature TLG) and a pressure PLG); wherein the aqueous liquid stream SR is passed as feed stream into the evaporation sub-unit EU(1); wherein for j < n, the aqueous liquid stream SLG) obtained from the evaporation subunit EUG) is passed as feed stream into the evaporation sub-unit EUG+1); wherein for j < n, TvG+1) < TvG); PvG+1) < PvG); G+1) < KG); and p _L G+1 ) < PLG); wherein pv(n) is in the range of from 0.95 to 1.5 bar, preferably in the range of from 1 .0 to 1 .4 bar; Tv(n) is in the range of from 90 to 110 °C, preferably in the range of from 95 to 100 °C; PL(H) is in the range of from 0.95 to 1.5 bar, preferably in the range of from 1.0 to 1.4 bar; and Ti_(n) is in the range of from 90 to 110°C, preferably in the range of from 95 to 105 °C;

(iii) passing the aqueous vapor streams SvG) obtained according to (ii) through the heat exchanging units HUG), thereby heating in HU(j) the stream STG) having a temperature TSTG), obtaining the cooled aqueous stream SvG), ScvG), having a temperature TcvG) with TcvG) < TvG) and the heated stream STG), SHTG), having a temperature THSTG) with THSTG) > TSTG);

(iv) separating e-caprolactam from the aqueous liquid stream Si_(n) obtained according to (ii) in at least one heat consuming purification unit PU, wherein the heat consumed in PU is at least partially provided by at least one of the heated streams SHTG);

(v) recycling at least one aqueous liquid stream SRE obtained from at least one heat consuming purification unit PU according to (iv) into Ru, preferably as part of the aqueous liquid stream Sw according to (i.1); wherein at least one of the streams SLG) , P ^r i° ^r to being passed as feed stream into the evaporation sub-unit EUG+1) according to (ii), is passed through a heat exchanging unit HURE, thereby cooling the SLG), wherein in the heat exchanging unit HURE, at least one of the streams SRE is heated prior to being recycled into Ru according to (v). The process of embodiment 34, wherein the at least one of the streams SLG) which is passed through the heat exchanging unit HURE is the stream SL(1 ). The process of embodiment 34 or 35, wherein n = 2 and wherein pv(1) is in the range of from 7.5 to 18 bar, preferably in the range of from 8 to 16 bar;

Tv(1) is in the range of from 160 to 210 °C, preferably in the range of from 170 to 200 °C;

PL(1 ) is in the range of from 7.5 to 18 bar, preferably in the range of from 8 to 16 bar; and

TL(1 ) is in the range of from 160 to 210 °C, preferably in the range of from 170 to 200 °C. The process of any one of embodiments 34 to 36, further comprising recycling at least one of the cooled aqueous streams ScvG), preferably all cooled aqueous streams ScvG) obtained according to (iii) into Ru, preferably as part of the aqueous liquid stream Sw according to (i.1). The process of any one of embodiments 1 to 37, wherein according to (iv), the at least one heat consuming purification unit PU comprises a heat consuming purification unit PU(1), or a heat consuming purification unit PU(2), or a heat consuming purification unit PU(1) and a heat consuming purification unit PU(2), preferably a heat consuming purification unit PU(1) and a heat consuming purification unit PU(2), wherein the purification unit PU(1) comprises at least one film evaporator, preferably at least one falling film evaporator, more preferably two falling film evaporators, more preferably two serially coupled falling film evaporators, wherein in PU(1), water is separated from an aqueous stream comprising e-caprolactam dissolved in water; the purification unit PU(2) comprises at least one distillation column, preferably two or three distillation columns, more preferably two or three serially coupled distillation columns, wherein in PU(2), water is removed from an aqueous stream comprising E- caprolactam dissolved in water.

39. The process of embodiment 38, comprising passing at least a part of at least one heated stream SHT as heating medium through a heating jacket of the at least one film evaporator of PU(1).

40. The process of embodiment 38 or 39, comprising passing at least a part of at least one heated stream SHT as heating medium through a heat exchanger of an evaporator of at least one distillation column of PU(2), preferably through a heat exchanger of each of the two or three distillation columns of PU(2), more preferably through a heat exchanger used for sump evaporation of each of the two or three distillation columns of PU(2).

41 . The process of any one of embodiments 38 to 40, comprising passing at least a part of at least one heated stream SHT as heating medium through a heating jacket of the at least one film evaporator of PU(2).

42. The process of any one of embodiments 38 to 41 , wherein according to (iv), separating E- caprolactam from at least one aqueous liquid stream Si_, preferably Si_(n), obtained according to (ii), SL having a water concentration CL(H2O), in at least one heat consuming purification unit PU according to (iv) comprises

(i v.1 ) preferably passing said at least one aqueous liquid stream SL through a solid-liquid separation SLU, obtaining an aqueous liquid stream SLSLU comprising c-capro- lactame dissolved in water, SLSLU having a water concentration CLSLU(H2O), and further obtaining a solid;

(iv.2) passing the at least one aqueous liquid stream SL, preferably the aqueous liquid stream SLSLU obtained according to (iv.1), through the purification unit PU(1), obtaining an aqueous liquid stream SLRUI , SLPUI having a water concentration CLPUI (H ₂ O), wherein C PUI (H ₂ O) < c _L (H ₂ O), preferably C PUI (H ₂ O) < C SLU(H ₂ O);

(iv.3) preferably passing the aqueous liquid stream SLPUI obtained according to (iv.2) through a separation unit OSU, obtaining an aqueous liquid stream SLOSU, SLOSU having a water concentration CLOSU(H2O), wherein in OSU, oligomers of E- caprolactam which are comprised in SLPUI are separated from SLPUI ;

(iv.4) passing the aqueous liquid stream SLPUI obtained according to (iv.2), preferably the aqueous liquid stream CLOSU(H2O) obtained according to (iv.3), through the purification unit PU(2), obtaining a liquid stream CLPU2(H2O) having a water concentration CLPU2(H2O), wherein CLPU2(H2O) « CLPUI (H2O), preferably CLPU2(H2O) << COSU(H ₂ O).

43. The process of any one of embodiments 1 to 42, wherein the solid-liquid separation SLU according to (iv.1 ) comprises, preferably consists of, one or more of a centrifuge, a decanter, a decanter centrifuge, and a filter, preferably one or more of a decanter and a decanter centrifuge.

44. The process of embodiment 42 or 43, wherein the separation OSU according to (iv.3) comprises a stirred tank reactor and a film evaporator, preferably a wipe film evaporator, wherein more preferably, the stirred tank reactor and a film evaporator are serially coupled.

In the context of the present invention, it is noted that the term „polyamide prepared from £-caprolactam“ as used herein refers to „polyamide 6“ being characterized by the formula (-NH-(CH ₂ ) ₅ -CO-)n.

The term „bar“ as used in the context of the present invention refers to „bar(abs)”, i.e. bar (absolute), sometimes also referred to “bara”.

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.

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. ‘ 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. Description of the figures

Figure 1 is a schematic representation of a production unit used for the process according to preferred embodiments of the invention.

The production unit comprises a reactor unit Ru, an evaporation unit EU, a heat consuming purification unit PU and two heat exchanging units HUo and HU. The solid material M comprising the polyamide and an aqueous liquid stream Sw are fed into the reactor unit Ru and subjected to depolymerization conditions comprising a depolymerization temperature TD at a depolymerization pressure poas detailed in the foregoing. An aqueous liquid stream SR is removed from the bottom of Ru, SR comprising c-caprolactam dissolved in water, wherein said aqueous liquid stream SR has a pressure PR in the range of from 40 to 120 bar and a temperature TR in the range of from 230 to 320 °C. The aqueous liquid stream SR is passed through the heat exchanging unit HUo obtaining an aqueous liquid stream SLO having a temperature TLO with TLO < TR and having a pressure pi_o in the range of from 40 to 120 bar. The aqueous liquid stream SLO is subjected to depressurization in the evaporation unit EU. An aqueous vapor stream Sv having a temperature Tv in the range of from 100 to 230 °C is removed from the top of EU and an aqueous liquid stream SL comprising c-caprolactam dissolved in water is removed from the bottom of EU. The aqueous vapor stream Sv, having a temperature Tv, is passed through a heat exchanging unit HU, a cooled aqueous stream Scv, having a temperature Tcv with Tcv < Tv, is removed from HU and a heated stream ST, SHT, having a temperature THST with THST > TST, is also removed from HU. The heated stream ST is used for providing a part of the heat consumed in the heat consuming purification unit PU. The aqueous stream SL comprising c-caprolactam dissolved in water is fed into PU for separating c-caprolactam from SL. An aqueous liquid stream SRE (water) is removed from PU and recycled as part of the aqueous liquid stream Sw. In particular, water is passed through HUo for heating and then fed to RU as part of the aqueous liquid stream Sw. The cooled stream Scv (water) is similarly recycled as part of the aqueous liquid stream Sw. PU comprises a heat consuming purification unit PU(1) and a heat consuming purification unit PU(2), wherein the purification unit PU (1 ) comprises at least one film evaporator and wherein the purification unit PU(2) comprises at least one distillation column. At least one stream (x) comprising c-caprolactam is removed from PU as well as at least one stream (y) comprising impurities and substantially free of, preferably free of, c-caprolactam.

Figure 2 is a schematic representation of a production unit used for the process according to preferred embodiments of the invention.

The production unit comprises a reactor unit Ru, an evaporation unit EU comprising three subunits EU(1), EU(2) and EU(3), a heat consuming purification unit PU and three heat exchanging units HU(1), HU(2) and HU(3). The solid material M comprising the polyamide and an aqueous liquid stream Sw are fed into the reactor unit Ru and subjected to depolymerization conditions comprising a depolymerization temperature TD at a depolymerization pressure po as detailed in the foregoing. An aqueous liquid stream SR is removed from the bottom of Ru, SR comprising E- caprolactam dissolved in water, wherein said aqueous liquid stream SR has a pressure PR in the range of from 40 to 120 bar and a temperature TR in the range of from 230 to 320 °C. The aqueous liquid stream SR is subjected to depressurization in the evaporation sub-unit EU(1). An aqueous vapor stream Sv(1) is removed from the top of EU(1) and an aqueous liquid stream SL(1 ) comprising e-caprolactam dissolved in water is removed from the bottom of EU(1), wherein Sv(1) has a temperature Tv(1) and a pressure pv(1) and wherein Si_(1 ) has a temperature Ti_(1 ) and a pressure pi_(1 ). The aqueous vapor stream Sv(1), having a temperature Tv(1) in the range of from 100 to 230 °C, is passed through a heat exchanging unit HU(1), a cooled aqueous stream Scv(1), having a temperature Tcv(1) with Tcv(1) < Tv(1), is removed from HU(1) and a heated stream SHT(1 ) is also removed from HU(1). The heated stream SHT(1 ) is used for providing a part of the heat consumed in the heat consuming purification unit PU. The aqueous stream Si_(1 ) comprising e-caprolactam dissolved in water is fed in the evaporation sub-unit EU(2). An aqueous vapor stream Sv(2) is removed from the top of EU(2) and an aqueous liquid stream SL(2) comprising e-caprolactam dissolved in water is removed from the bottom of EU(2), wherein Sv(2) has a temperature Tv(2) and a pressure pv(2) and wherein SL(2) has a temperature TL(2) and a pressure PL(2). The aqueous vapor stream Sv(2), having a temperature Tv(2) in the range of from 100 to 230 °C, is passed through a heat exchanging unit HU(2), a cooled aqueous stream Scv(2), having a temperature Tcv(2) with Tcv(2) < Tv(2), is removed from HU(2) and a heated stream SHT(2) is also removed from HU (2). The heated stream SHT(2) is used for providing a part of the heat consumed in the heat consuming purification unit PU. The aqueous stream SL(2) comprising e-caprolactam dissolved in water is fed in the evaporation sub-unit EU(3). An aqueous vapor stream Sv(3) is removed from the top of EU(3) and an aqueous liquid stream SL(3) comprising E- caprolactam dissolved in water is removed from the bottom of EU(3), wherein Sv(3) has a temperature Tv(3) and a pressure pv(3) and wherein SL(3) has a temperature TL(3) and a pressure PL(3). The aqueous vapor stream Sv(3), having a temperature Tv(3) in the range of from 100 to 230 °C, is passed through a heat exchanging unit HU(3), a cooled aqueous stream Scv(3), having a temperature Tcv(3) with Tcv(3) < Tv(3), is removed from HU(3) and a heated stream SHT(3) is also removed from HU (3). The heated stream SHT(3) is used for providing a part of the heat consumed in the heat consuming purification unit PU. The aqueous stream SL(3) comprising £-caprolactam dissolved in water is fed into PU for separating £-caprolactam from SL(3). An aqueous liquid stream SRE (water) is removed from PU and recycled as part of the aqueous liquid stream Sw. The cooled streams Scv(1), Scv(2) and Scv(3) (water) are recycled as part of the aqueous liquid stream Sw. Prior to be recycled, these cooled streams can be passed through an optional heat exchanger shown in Figure 2. PU comprises a heat consuming purification unit PU(1) and a heat consuming purification unit PU(2), wherein the purification unit PU(1) comprises at least one film evaporator and wherein the purification unit PU(2) comprises at least one distillation column. At least one stream (x) comprising £-caprolactam £-caprolactam is removed from PU as well as at least one stream (y) comprising impurities and substantially free of, preferably free of, £-caprolactam.

Figure 3 is a schematic representation of a production unit used for the process according to preferred embodiments of the invention.

The production unit comprises a reactor unit Ru, an evaporation unit EU comprising three sub- units EU(1), EU(2) and EU(3), a heat consuming purification unit PU, two heat exchanging units HU (2) and HU (3) and a water unit WU (a closed loop water system) in which stream Sv(1 ) is bubbled in the liquid water stream). The solid material M comprising the polyamide and an aqueous liquid stream Sw are fed into the reactor unit Ru and subjected to depolymerization conditions comprising a depolymerization temperature TD at a depolymerization pressure po as detailed in the foregoing. An aqueous liquid stream SR is removed from the bottom of Ru, SR comprising e-caprolactam dissolved in water, wherein said aqueous liquid stream SR has a pressure PR in the range of from 40 to 120 bar and a temperature TR in the range of from 230 to 320 °C. The aqueous liquid stream SR is subjected to depressurization in the evaporation sub-unit EU(1 ). An aqueous vapor stream Sv(1 ) is removed from the top of EU(1 ) and an aqueous liquid stream Si_(1 ) comprising e-caprolactam dissolved in water is removed from the bottom of EU(1 ), wherein Sv(1 ) has a temperature Tv(1 ) and a pressure pv(1 ) and wherein Si_(1 ) has a temperature TL(1 ) and a pressure pi_(1 ). The aqueous vapor stream Sv(1 ), having a temperature Tv(1 ) in the range of from 100 to 230 °C, is passed through the water unit WU and water is recycled as part of Sw. The aqueous stream Si_(1 ) comprising e-caprolactam dissolved in water is fed in the evaporation sub-unit EU(2). An aqueous vapor stream Sv(2) is removed from the top of EU(2) and an aqueous liquid stream SL(2) comprising e-caprolactam dissolved in water is removed from the bottom of EU(2), wherein Sv(2) has a temperature Tv(2) and a pressure pv(2) and wherein SL(2) has a temperature TL(2) and a pressure PL(2). The aqueous vapor stream Sv(2), having a temperature Tv(2) in the range of from 100 to 230 °C, is passed through a heat exchanging unit HU(2), a cooled aqueous stream Scv(2), having a temperature Tcv(2) with Tcv(2) < Tv(2), is removed from HU (2) and a heated stream SHT(2) is also removed from HU (2). The heated stream SHT(2) is used for providing a part of the heat consumed in the heat consuming purification unit PU. The aqueous stream SL(2) comprising e-caprolactam dissolved in water is fed in the evaporation sub-unit EU(3). An aqueous vapor stream Sv(3) is removed from the top of EU(3) and an aqueous liquid stream SL(3) comprising e-caprolactam dissolved in water is removed from the bottom of EU(3), wherein Sv(3) has a temperature Tv(3) and a pressure pv(3) and wherein SL(3) has a temperature TL(3) and a pressure pi_(3). The aqueous vapor stream Sv(3), having a temperature Tv(3) in the range of from 100 to 230 °C, is passed through a heat exchanging unit HU(3), a cooled aqueous stream Scv(3), having a temperature Tcv(3) with Tcv(3) < Tv(3), is removed from HU (3) and a heated stream SHT(3) is also removed from HU (3). The heated stream SHT(3) is used for providing a part of the heat consumed in the heat consuming purification unit PU. The aqueous stream SL(3) comprising e-caprolactam dissolved in water is fed into PU for separating e-caprolactam from SL(3). An aqueous liquid stream SRE (water) is removed from PU and recycled as part of the aqueous liquid stream Sw after having been passed through WU. The cooled streams Scv(2) and Scv(3) (water) are recycled as part of the aqueous liquid stream Sw by passing through WU, and optionally through a heat exchanger downstream of WU (shown in Figure 3). PU comprises a heat consuming purification unit PU(1 ) and a heat consuming purification unit PU(2), wherein the purification unit PU(1 ) comprises at least one film evaporator and wherein the purification unit PU(2) comprises at least one distillation column. At least one stream (x) comprising e-caprolactam is removed from PU as well as at least one stream (y) comprising impurities and substantially free of, preferably free of, e-caprolactam. Figure 4 is a schematic representation of a production unit used for the process according to preferred embodiments of the invention.

The production unit comprises a reactor unit Ru, an evaporation unit EU comprising two sub-units EU(1 ) and EU(2), a heat consuming purification unit PU and three heat exchanging units HU(1 ), HU(2) and HURE. The solid material M comprising the polyamide and an aqueous liquid stream Sw are fed into the reactor unit Ru and subjected to depolymerization conditions comprising a depolymerization temperature TD at a depolymerization pressure po as detailed in the foregoing. An aqueous liquid stream SR is removed from the bottom of Ru, SR comprising e-caprolactam dissolved in water, wherein said aqueous liquid stream SR has a pressure PR in the range of from 40 to 120 bar and a temperature TR in the range of from 230 to 320 °C. The aqueous liquid stream SR is subjected to depressurization in the evaporation sub-unit EU (1 ). An aqueous vapor stream Sv(1 ) is removed from the top of EU(1 ) and an aqueous liquid stream Si_(1 ) comprising E- caprolactam dissolved in water is removed from the bottom of EU(1 ), wherein Sv(1 ) has a temperature Tv(1 ) and a pressure pv(1 ) and wherein Si_(1 ) has a temperature Ti_(1 ) and a pressure pi_(1 )- The aqueous vapor stream Sv(1 ), having a temperature Tv(1 ) in the range of from 100 to 230 °C, is passed through a heat exchanging unit HU(1 ), a cooled aqueous stream Scv(1 ), having a temperature Tcv(1 ) with Tcv(1 ) < Tv(1 ), is removed from HU(1 ) and a heated stream SHT(1 ) is also removed from H U (1 ). The heated stream SHT(1 ) is used for providing a part of the heat consumed in the heat consuming purification unit PU. The aqueous stream Si_(1 ) comprising c-caprolactam dissolved in water is passed through a heat exchanging unit HURE prior to be fed in the evaporation sub-unit EU(2). An aqueous vapor stream Sv(2) is removed from the top of EU(2) and an aqueous liquid stream SL(2) comprising c-caprolactam dissolved in water is removed from the bottom of EU(2), wherein Sv(2) has a temperature Tv(2) and a pressure pv(2) and wherein SL(2) has a temperature TL(2) and a pressure PL(2). The aqueous vapor stream Sv(2), having a temperature Tv(2) in the range of from 100 to 230 °C, is passed through a heat exchanging unit HU(2), a cooled aqueous stream Scv(2), having a temperature Tcv(2) with Tcv(2) < Tv(2), is removed from HU (2) and a heated stream SHT(2) is also removed from HU (2). The heated stream SHT(2) is used for providing a part of the heat consumed in the heat consuming purification unit PU. The aqueous stream SL(2) comprising c-caprolactam dissolved in water is fed into PU for separating e-caprolactam from SL(2). An aqueous liquid stream SRE (water) is removed from PU and recycled as part of the aqueous liquid stream Sw by passing through HURE. The cooled streams Scv(1 ) and Scv(2) (water) are recycled as part of the aqueous liquid stream Sw by passing through HURE, and optionally through a heat exchanger downstream of HURE (shown in Figure 4). PU comprises a heat consuming purification unit PU(1 ) and a heat consuming purification unit PU(2), wherein the purification unit PU(1 ) comprises at least one film evaporator and wherein the purification unit PU(2) comprises at least one distillation column. At least one stream (x) comprising £-caprolactam is removed from PU as well as at least one stream (y) comprising impurities and substantially free of, preferably free of, £-caprolactam. Figure 5 is a schematic representation of a production unit used for the process according to preferred embodiments of the invention.

The production unit comprises a reactor unit Ru, an evaporation unit EU comprising two sub-units EU(1 ) and EU(2), a heat consuming purification unit PU and three heat exchanging units HU(1 ), HU(2) and HURE. The solid material M comprising the polyamide and an aqueous liquid stream Sw are fed into the reactor unit Ru and subjected to depolymerization conditions comprising a depolymerization temperature TD at a depolymerization pressure po as detailed in the foregoing. An aqueous liquid stream SR is removed from the bottom of Ru, SR comprising c-caprolactam dissolved in water, wherein said aqueous liquid stream SR has a pressure PR in the range of from 40 to 120 bar and a temperature TR in the range of from 230 to 320 °C. The aqueous liquid stream SR is subjected to depressurization in the evaporation sub-unit EU (1 ). An aqueous vapor stream Sv(1 ) is removed from the top of EU(1) and an aqueous liquid stream Si_(1 ) comprising E- caprolactam dissolved in water is removed from the bottom of EU(1 ), wherein Sv(1 ) has a temperature Tv(1 ) and a pressure pv(1 ) and wherein Si_(1 ) has a temperature Ti_(1 ) and a pressure pi_(1 )- The aqueous vapor stream Sv(1 ) is divided in two sub-streams Svi(1 ) and Sv2(1 ). Svi(1 ) constituting x % of the stream Sv(1 ) and Sv2(1 ) constituting (100-x) % of the stream Sv(1 ), with x * 100. Svi(1 ) is passed through a heat exchanging unit HURE and admixed with SRE to be recycled as part of the aqueous liquid stream Sw. Sv2(1 ) is passed through a heat exchanging unit HU(1 ), a cooled aqueous stream Scv(1 ), having a temperature Tcv(1 ) with Tcv(1 ) < Tv(1 ), is removed from HU(1 ) and a heated stream SHT(1 ) is also removed from HU(1 ). The heated stream SHT(1 ) is used for providing a part of the heat consumed in the heat consuming purification unit PU. The aqueous stream Si_(1 ) comprising c-caprolactam dissolved in water is fed in the evaporation sub-unit EU(2). An aqueous vapor stream Sv(2) is removed from the top of EU(2) and an aqueous liquid stream SL(2) comprising c-caprolactam dissolved in water is removed from the bottom of EU(2), wherein Sv(2) has a temperature Tv(2) and a pressure pv(2) and wherein SL(2) has a temperature TL(2) and a pressure PL(2). The aqueous vapor stream Sv(2), having a temperature Tv(2) in the range of from 100 to 230 °C, is passed through a heat exchanging unit HU(2), a cooled aqueous stream Scv(2), having a temperature Tcv(2) with Tcv(2) < Tv(2), is removed from HU (2) and a heated stream SHT(2) is also removed from HU (2). The heated stream SHT(2) is used for providing a part of the heat consumed in the heat consuming purification unit PU. The aqueous stream SL(2) comprising c-caprolactam dissolved in water is fed into PU for separating c-caprolactam from SL(2). An aqueous liquid stream SRE (water) is removed from PU and recycled as part of the aqueous liquid stream Sw by passing through HURE. The cooled streams Scv(1 ) and Scv(2) (water) are recycled as part of the aqueous liquid stream Sw by passing through HURE, and optionally through a heat exchanger downstream of HURE (shown in Figure 5). PU comprises a heat consuming purification unit PU(1 ) and a heat consuming purification unit PU(2), wherein the purification unit PU (1 ) comprises at least one film evaporator and wherein the purification unit PU(2) comprises at least one distillation column. At least one stream (x) comprising c-caprolactam is removed from PU as well as at least one stream (y) comprising impurities and substantially free of, preferably free of, c-caprolactam.