Water removal in a process for hydrolytically depolymerizing a polyamide

Patent metadata

Field	Value
Publication number	US-2025223417-A1
Application number	US-202318852637-A
Country	US
Kind code	A1
Filing date	Mar 30, 2023
Priority date	Apr 1, 2022
Publication date	Jul 10, 2025
Grant date	—

Abstract

The present invention relates to a water-efficient process for hydrolytically depolymerizing a polyamide prepared from ε-caprolactam.

First claim

1 .- 17 . (canceled)

18 . A water-efficient process for hydrolytically depolymerizing a polyamide prepared from ε-caprolactam, said polyamide being comprised in a solid material M, the process comprising
(i) preparing an aqueous liquid stream S WC containing ε-caprolactam dissolved in water, comprising
(i.1) providing the solid material M containing the polyamide;
(i.2) providing an aqueous liquid stream S W ;
(i.3) preparing an aqueous mixture of the solid material M provided according to (i.1) and the aqueous liquid stream S W provided according to (i.2);
(i.4) subjecting the aqueous mixture prepared according to (i.3) to depolymerization conditions in a chemical reactor unit R U , obtaining the aqueous liquid stream S WC containing ε-caprolactam dissolved in water;

(ii) separating water from the aqueous liquid stream S WC by evaporation in at least two evaporation units, obtaining at least one aqueous vapor stream S V , wherein at least a part of at least one aqueous vapor stream S V is recycled into step (i.2) as a component of the aqueous liquid stream S W .

19 . The process of claim 18 , wherein preparing an aqueous liquid stream S WC containing ε-caprolactam dissolved in water according to (i) comprises
(i.1) providing the solid material M containing the polyamide, M having a temperature T M , wherein T M <T P , T P being the melting point of the polyamide;
(i.2) providing the aqueous liquid stream S W , wherein from 50 weight-% to 100 weight-% of S W consist of water and wherein S W has a temperature T SW , wherein T SW >T P ;
(i.3) preparing an aqueous mixture of the solid material M provided according to (i.1) and the aqueous liquid stream S W provided according to (i.2), comprising feeding the solid material M provided according to (i.1) and the liquid aqueous stream S W provided according to (i.2) into a chemical reactor unit R U , obtaining said mixture;
(i.4) subjecting the aqueous liquid mixture prepared according to (i.3) to depolymerization conditions in the chemical reactor unit R U , obtaining the aqueous liquid stream S WC containing ε-caprolactam dissolved in water, wherein the depolymerization conditions comprise a depolymerization temperature T D at a depolymerization pressure p D , wherein T M <T D <T SW .

20 . The process of claim 18 , wherein ΔT=T SW −T P and ΔT is in the range of from 10 to 70° C.

21 . The process of claim 18 , wherein from 91 to 100 weight-% of S W provided according to (i.2) consist of water.

22 . The process of claim 18 , wherein (ii) comprises
(ii.1) optionally feeding the aqueous liquid stream S WC as a feed stream to a first evaporation unit EU 1 , obtaining at least one aqueous vapor stream S V1 , and an aqueous liquid stream S L1 comprising ε-caprolactam dissolved in water; (ii.2) optionally feeding the aqueous liquid stream S WC or the aqueous liquid stream S L1 to a solid-liquid separation unit, SLU, obtaining an aqueous liquid stream S SLU comprising ε-caprolactam dissolved in water; (ii.3) feeding the aqueous liquid stream S WC or the aqueous liquid stream S L1 or the aqueous liquid stream S SLU to evaporation in at least two evaporation units EU 2 and EU 3 , wherein an aqueous vapor stream S V2 is obtained from EU 2 and an aqueous vapor stream S V3 is obtained from EU 3 , and wherein from EU 3 , an aqueous liquid stream S L3 comprising ε-caprolactam dissolved in water is obtained; wherein preferably from 75 to 100 weight-% of the aqueous liquid stream which is fed to evaporation according to (ii.3) consist of water and ε-caprolactam, said stream exhibiting a water concentration c H2O ; the process further comprising recycling at least a part of at least one of streams S V2 and S V3 into step (i.2) as a component of the aqueous liquid stream S W .

23 . The process of claim 22 , wherein (ii) comprises
(ii.1) feeding the aqueous liquid stream S WC as a feed stream to a first evaporation unit, EU 1 , obtaining at least one aqueous vapor stream S V1 , and an aqueous liquid stream S L1 comprising ε-caprolactam dissolved in water; (ii.2) optionally feeding the aqueous liquid stream S L1 to a solid-liquid separation unit SLU, obtaining an aqueous liquid stream S SLU comprising ε-caprolactam dissolved in water; (ii.3) feeding the aqueous liquid stream S L1 or the aqueous liquid stream S SLU to evaporation in at least two evaporation units EU 2 and EU 3 , wherein an aqueous vapor stream S V2 is obtained from EU 2 and an aqueous vapor stream S V3 is obtained from EU 3 , and wherein from EU 3 , an aqueous liquid stream S L3 comprising ε-caprolactam dissolved in water is obtained.

24 . The process of claim 23 , wherein (ii.1) comprises
(ii.1.1) feeding the aqueous liquid stream S WC as a feed stream to a first evaporation sub-unit EU 11 , obtaining an aqueous vapor stream S V11 , and an aqueous liquid stream S L11 comprising ε-caprolactam dissolved in water; (ii.1.2) feeding the aqueous liquid stream S L11 as a feed stream to a second evaporation sub-unit EU 12 , obtaining an aqueous vapor stream S V12 , and the aqueous liquid stream S L1 comprising ε-caprolactam dissolved in water.

25 . The process of claim 24 , wherein (ii.1) comprises
(ii.1.1) feeding the aqueous liquid stream S WC as a feed stream to a first sub-evaporation unit, EU 11 , obtaining an aqueous vapor stream S V11 , and an aqueous liquid stream S L11 comprising ε-caprolactam dissolved in water, wherein prior to feeding to EU 11 , the aqueous liquid stream S WC is optionally passed through at least one solid-liquid separation unit F 1 ; (ii.1.2) feeding the aqueous liquid stream S L11 as a feed stream to a second sub-evaporation unit, EU 12 , obtaining an aqueous vapor stream S V12 and the aqueous liquid stream S L1 comprising ε-caprolactam dissolved in water, wherein prior to feeding to EU 12 , the aqueous liquid stream S L11 is optionally passed through at least one solid-liquid separation unit F 2 ; wherein (ii.1) comprises at least one of passing S WC through F 1 and passing S L11 through F 2 , wherein (ii.1) preferably comprises passing S WC through F 1 and passing S L11 through F 2 .

26 . The process of claim 22 , wherein (ii.3) comprises
(ii.3.1) feeding the aqueous liquid stream S L1 or the aqueous liquid stream S SLU , to evaporation in a first evaporation unit EU 2 , obtaining an aqueous vapor stream S V2 and an aqueous liquid stream S L21 , wherein the concentration of ε-caprolactam in the stream S L21 is c CPLL21 with c CPLL21 >c CPL , and wherein the concentration of water in the stream S V2 is c H2OV2 with c H2OV2 >c H2O ; (ii.3.2) feeding at least a part of the aqueous liquid stream S L21 to evaporation in a second evaporation unit EU 3 , obtaining an aqueous vapor stream S V3 and an aqueous liquid stream S L31 , wherein the concentration of ε-caprolactam in the stream S L31 is c CPLL31 with c CPLL31 >c CPLL21 , and wherein the concentration of water in the stream S V3 is c H2OV2 with c H2OV2 >c H2OL21 .

27 . The process of claim 28 , wherein the evaporation unit EU 2 comprises a film evaporator.

28 . The process of claim 27 , the process comprising passing at least a part of at least one aqueous vapor stream S V through the heating means of the film evaporator comprised in EU 3 .

29 . The process of claim 26 , wherein (ii.3.2) comprises feeding at least a part of the aqueous liquid stream S L21 to evaporation in a second evaporation unit EU 3 , obtaining an aqueous vapor stream S V3 , and obtaining an aqueous liquid stream S L31 and a liquid stream S L32 , wherein the concentration of ε-caprolactam in the stream S L31 is

Assignees

• Basf Se

Inventors

• Blei Stefan
• El-Toufaili Faissal-Ali
• Gauer Jochen
• Hetz-Hunsinger Alexander
• Kotanjac Zeljko
• Ravikumar Vikram Raghavendhar

Classifications

• C08J2377/02

  Polyamides derived from omega-amino carboxylic acids or from lactams thereof (C08J2377/10 takes precedence) · CPC title

• Y02W30/62

  Plastics recycling; Rubber recycling · CPC title

• C08J11/14 Primary

  by treatment with steam or water · CPC title

• C07D201/12 Primary

  by depolymerising polyamides · CPC title