Process for recovering chemicals in process for recycling blend textiles

Abstract

To solve drawbacks of known processes of recycling polyester-cotton textiles and to provide a method of increasing the purity of polyester monomers recovered from a depolymerizing solution and from other solutions and mixtures resulting from known textile recycling depolymerization processes.SOLUTION: The invention provides a process to recover NaOH, polyester monomers, dyes and byproducts from an alkaline depolymerization liquor resulting from a depolymerization reaction of polyester in a blend textile. The process comprises concentrating a solution in a mixture comprising water, solid NaOH, dyes and other liquid products, extracting ethylene glycol from the mixture, dissolving solid NaOH, recovering solid dyes and recovering terephthalic acid.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a process for recovering chemicals, including dyes, obtained in the recycling process of blended textile products. More specifically, the present invention relates to a process for recovering and isolating NaOH, polyester monomers and dyes obtained in the recycling process of polyester blended textile fabrics by alkaline depolymerization of polyester. The process of the present invention is particularly suitable for recycling processes for recovering and recycling cellulose staple fibers from textiles containing polyester filaments or fibers and cellulose staple fibers, especially cotton staple fibers. The present invention also relates to a process for recovering vat dyes from textile products. [Background technology]

[0002] The textile industry has a significant impact on the environment due to its large use of petrochemicals and natural resources, and due to the current trend of increasing consumption while shortening the lifespan of clothing. In the fashion sector, recycling waste textiles from textiles, used clothes, apparel, etc. is a major challenge. The cost of recycling waste textiles includes not only the recovery of waste textiles, but also the definition of a suitable method of waste textile processing that is economically sustainable on a large scale. Polyester, e.g. polyethylene terephthalate (PET) fibers, and cotton are the most widely used man-made and natural fibers. Known methods of processing waste textiles include removing polyester from waste textiles by depolymerization and recovering the depolymerization products for further processing, e.g. to obtain reusable polyester again.

[0003] Patent Document 1 describes a method for recycling waste polycotton textile products, i.e. textile products containing cotton and polyester components, in which the textile products are subjected to a depolymerization reaction of the polyester component by basic hydrolysis, such as in a sodium hydroxide solution. The recovery of terephthalic acid is carried out through the steps of terephthalic acid precipitation, terephthalic acid separation, terephthalic acid washing, crystallization, and terephthalic acid drying.

[0004] Patent document 2 in the name of the present applicant, filed on February 13, 2023, and incorporated herein by reference, discloses a process for recycling polycotton textile articles, in particular textiles and garments, comprising polyester filaments or polyester fibers and cellulose staple fibers, in particular cotton staple fibers.

[0005] The process of Patent Document 2 includes a step of depolymerizing the polyester with an alkaline depolymerization solution, so that the polyester is decomposed into monomers and the structure of the cellulose fibers substantially corresponds to the structure of the original polycotton fabric minus the polyester portion, and also includes a step of bleaching the treated textile with a bleaching solution after depolymerization of the polyester, and a step of washing the treated textile with a washing solution after bleaching the treated textile.

[0006] In particular, the invention of Patent Document 2 relates to a process for recycling waste blended textile products containing polyester fibers and cellulose fibers, preferably cotton fibers, which process involves depolymerization of the polyester in a basic aqueous solution and includes the following steps: a) providing a quantity of said textile product into a reaction chamber; b) supplying the basic depolymerization solution in a constant amount according to a liquor ratio in the range of 1 / 2 to 1 / 20, where the weight of the textile product is the weight of the solution; c) circulating the amount of depolymerization solution through the textile to depolymerize the polyester into its corresponding monomers and remove the polyester monomers from the textile; d) removing the depolymerization solution from the reaction chamber; Here, the temperature of the depolymerization solution in step c) is 101°C to 160°C, preferably 120°C to 160°C, and more preferably 130°C to 140°C. where e) the solution is circulated through the textile article while the textile article is stationary to provide a treated textile article comprising staple cellulosic fibers, preferably staple cotton fibers, substantially free of polyester material. The reaction is carried out for 100 to 150 minutes, more preferably 120 minutes, with the depolymerization solution being pumped through the textile product in the reactor and the textile product being held stationary, i.e., static.

[0007] In other words, in the process of Patent Document 2, the ester bond of the polyester is converted into a monomer (disodium terephthalate (Na 2 A depolymerization solution is fed into the reaction chamber for depolymerizing polyester fibers of the waste blended textile article, which are kept stationary in the reaction chamber, under reaction conditions that allow the cleavage of the fibers into cellulose acetate (TP), ethylene glycol (EG), and ethylene glycol (EG), so that dyes, particularly indigo dyes and other vat dyes, are substantially stripped or removed from the textile and the depolymerization of the staple cellulose fibers in the textile is dramatically reduced. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] International Publication No. 2022 / 195433 [Patent Document 2] European Patent Application No. 23156251 Summary of the Invention [Problem to be solved by the invention]

[0009] The depolymerization solution, or reaction solution, as well as the bleaching and cleaning solutions, contain NaOH, TPA, Na 2 These include chemicals such as TP, EG, and dyes such as indigo dyes, reactive dyes, and sulfur dyes.

[0010] The solutions (depolymerization solution, bleach solution, cleaning solution) can be reused multiple times in the process, with the chemicals (i.e., Na 2 The concentrations of the above chemicals (TPA, EG, and dyes) are increased. Applicant has found that an increase in the number of cycles has a positive effect on the processability of the solution to recover the above chemicals, including the dyes.

[0011] Furthermore, the applicant has noticed that if the chemical recovery process is carried out after multiple repetitions with the aforementioned solutions (depolymerization solution, bleaching solution, washing solution), the chemical recovery efficiency is improved since more of the compounds to be treated are present in the solution, which can be seen in terms of reduced process costs, labor costs and energy consumption.

[0012] A common problem when recycling PET fibers from polycotton textile products, especially from clothing and textiles, is the presence of further products, in particular the presence of certain amounts of dyes, together with the monomers TPA and EG in the depolymerization reaction mixture.

[0013] Another problem is the recovery of NaOH from the reaction mixture (liquid) for reuse in further processes, especially in the same recycle cycle.

[0014] It is therefore an object of the present invention to overcome the above-mentioned drawbacks of known processes for recycling polyester-cotton textiles, and to provide a method for increasing the purity of polyester monomers recovered from depolymerization solutions and from other solutions and mixtures resulting from known textile recycling depolymerization processes.

[0015] Another object of the present invention is to recover NaOH, polyester monomers and indigo dyes or indigo type dyes present in the depolymerization solutions (including the bleaching and washing solutions) obtained in the process of US 2007 / 0139963. The recovery process can be carried out separately for the different solutions or after recovering the depolymerization, bleaching and washing solutions as one processing solution. [Means for solving the problem]

[0016] The above object is achieved herein by a process as defined in claim 1. Preferred embodiments are defined in the dependent claims. A further object of the invention is a process for recovering vat dyes from textile products as defined in claim 12.

[0017] The starting material for the process of the present invention is a mixture resulting from a process of depolymerizing the polyester part of a textile product using a depolymerization solution containing NaOH. After the depolymerization process, the monomers terephthalic acid (TPA) and ethylene glycol (EG) are produced. In addition, this solution contains dyes, in particular vat dyes, i.e. indigo dyes and indigooid or indigo-type dyes, which are present in the cotton or cellulose part of the textile product and which have been removed from the surface of the textile product and remain in the depolymerization solution. In some cases, other widely used polyesters such as polypropylene terephthalate (PPT), polytrimethylene terephthalate (PTT), polybutylene terephthalate (PBT), or mixtures of these polyesters may be present. In this case, the polyesters are hydrolyzed by the process to produce the corresponding monomers, i.e. NaOH. 2 This results in TPA, butanediol, propylenediol, and trimethylene glycol.

[0018] The term "textile goods" as used herein refers to textiles, garments, yarns, and fibers. Textiles may be woven, knitted, or nonwoven. Garments include any apparel item, such as t-shirts, pants, jeans, jackets, shirts, sportswear, etc. An exemplary polycotton yarn is a core-spun yarn having a polyester core and a cotton sheath containing staple cotton fibers. Blended nonwoven fabrics contain nonwoven polyester filaments on a cotton or cellulosic substrate.

[0019] The term "cellulosic fibers" is used herein to define cotton fibers, cotton derivative fibers, modified cotton fibers, and other fibers typically used in yarns, such as linen, flax, jute, hemp, ramie, kenaf, sisal, and henequen fibers. Cotton and cellulose fibers are generally in the form of staple fibers in yarns. Viscose and other man-made cellulose fibers and filaments fall within the definition of cellulosic fibers herein. In both cases, the cotton or cellulose fibers are not reduced to pulp but are recovered in their original state (e.g., in the intact form of staple fibers in yarns).

[0020] The term "depolymerization solution" or "depolymerization liquor" (DL) is used herein to define an aqueous mixture (or liquor) containing NaOH (average concentration of NaOH is about 3% by weight) to a pH of about 13 and monomers resulting from the alkaline depolymerization reaction of polyester fibers of waste textile products. The DL is a mixture of disodium terephthalate (Na 2 The DL contains ethylene glycol (EG) and TPA (tetrahydrofuran (TPA)). As the waste textiles originate from dyed textiles or garments, the DL may also contain indigo and indigoid dyes which have been stripped from the textiles, for example by the mechanical action of the depolymerization solution on the textiles, and may also contain cellulose fibres and other reaction products. Other dyes that may be included in the DL include hydrolysis reactive dyes, sulphur dyes etc.

[0021] In one embodiment, the present invention provides a method for determining whether a Na ions are present between a dissolved salt in an aqueous solution and a solid salt. 2 To change the physical state of TPA, the alkaline pH of the depolymerization solution was selectively changed to Na 2 The solution pH is changed to recover TPA. The liquid impurities are removed from the solid salts, and the solid impurities are separated as dissolved salts in the aqueous solution. 2 Removed from TPA.

[0022] In another embodiment, the present invention relates to a method for the preparation of a medicament ... 2 Na from an aqueous solution containing TPA (dissolved) 2The present invention relates to a process for recovering NaOH from the depolymerization liquor for use in further depolymerization processes of blended fiber articles by precipitating TPA as a solid salt.

[0023] The process of the present invention includes the steps of providing an aqueous alkaline depolymerization liquor, typically having a pH of about 13; concentrating said liquor to obtain a lubricant product (i.e., a muddy mixture having a solids content of 40% to 80% by weight), which is a mixture containing water, solid NaOH, and the solid and liquid products of the depolymerization reaction (including dye); extracting EG or other glycols from the lubricant mixture using an organic solvent; and first extracting NaOH from the lubricant mixture. 2 and then changing the pH of the undissolved solid portion remaining from the extraction of EG to dissolve the TPA and then precipitate the TPA as a sodium salt or acid. Vat dyes, particularly indigo and indigoid dyes, are recovered from said undissolved solid phase. Alternatively, the process of the present invention can also recover sulphur dyes. Disperse dyes present in the depolymerisation liquor may usually be dissolved in the liquid organic phase.

[0024] According to one aspect of the invention, the process of the invention comprises: a) evaporating a portion of the water from the aqueous alkaline depolymerization liquor to obtain a concentrated mixture comprising a depolymerization reaction product; b) Liquid phase containing EG, water and NaOH, and NaOH, Na 2 extracting said mixture with an organic solvent to obtain a solid phase containing TPA, water and, optionally, a dye; c) at least Na in the solid portion 2 A step of dissolving TPA in an alkaline solution having a pH range of 9.5 to 11.0, and allowing a solid content including a dye to be present in the alkaline solution; d) separating the solids, including the dye, from the alkaline solution to obtain a purified alkaline solution and a solid dye; e) precipitating TPA from the purified alkaline solution; and f) recovering EG and NaOH from the liquid portion.

[0025] According to one embodiment, the aqueous depolymerization solution is concentrated under vacuum at a temperature below 100° C. to obtain a concentrated mixture having a lubricating solid, i.e., muddy, consistency, until the solids content of the resulting concentrated mixture is in the range of 40% to 80% by weight, e.g., about 50% to 65% by weight. Advantageously, the water evaporated in this step can be reused in the process, e.g., by adding NaOH and Na to the alkaline solution in which the dye is still present as solid particles that can be removed from the solution. 2 To dissolve the TPA, it can be added to the concentrated crude mixture after the organic solvent extraction step.

[0026] In one embodiment, NaOH is added to the purified alkaline solution to produce Na 2 The TPA is precipitated. NaOH is preferably added to the purified alkaline solution as a concentrated solution up to 20% by weight to obtain a NaOH solution suitable for use in the depolymerization process of blended textiles and textiles. A suitable NaOH solution for the process described in US Pat. No. 5,999,433 is a 48 Baume NaOH solution.

[0027] Thus, Na 2 The advantage of this step of alkaline precipitation of TPA is that it can be easily converted to disodium terephthalate (Na 2 After removal of the TPA by methods known per se, such as filtration or centrifugation, the remaining alkaline solution is suitable for recycling in the conventional process of depolymerization.

[0028] According to another embodiment, HCl is added to the purified alkaline solution to precipitate TPA as an acid, in which case the resulting solution contains water and NaCl.

[0029] Advantageously, the organic solvent used to extract the glycol monomer, for example ethylene glycol, from the eluate solid obtained after evaporation of the water is selected from methanol, ethanol, isopropyl alcohol, ethyl acetate, in other words, the organic solvent used in this step is suitable to remove the glycol monomer, some water and some NaOH dissolved in the water from the concentrated mixture previously obtained.

[0030] According to one embodiment, the solvent in the obtained organic phase containing solvent, EG, water and NaOH is evaporated to obtain a liquid phase and NaOH. The advantage of the process of the present invention is that the NaOH can be recycled by using it for further depolymerization reactions of the blended fiber products. Usually, the purity of NaOH is 60-70%.

[0031] According to one embodiment, the liquid phase disclosed above is distilled to separate the solvent from the mixture of EG (or other glycol monomer) and water, said solvent being advantageously reused in further extractions according to step b).

[0032] Further aspects and advantages of the present invention will now be explained in more detail with reference to the accompanying drawings, given as non-limiting examples, in which: [Brief description of the drawings]

[0033] [Figure 1] 1 is a flowchart of an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0034] As can be seen in the flow chart of FIG. 1, the process for recovering NaOH and polyester monomers resulting from the alkaline depolymerization reaction of polyester in a blended textile article includes the steps of providing an aqueous alkaline depolymerization liquor 1 containing polyester monomers, NaOH and optionally a dye, evaporating water from said aqueous alkaline depolymerization liquor to obtain a concentrated lump-like mixture 2 containing water, solid NaOH, dye and the solid and liquid products of the depolymerization reaction, extracting EG from said concentrated lump-like mixture with an organic solvent, and altering the pH of the solid phase remaining from the EG extraction to first dissolve TPA and then precipitate TPA as the sodium salt or acid.

[0035] A depolymerization liquid 1 obtained from an alkaline depolymerization process of a blended textile product is initially provided. This liquid contains all the products and reagents used in this process, except for the cellulose and non-polyester fibers of the textile product. This liquid 1 is heated (step b) under vacuum, i.e., reduced pressure, to a temperature below 100°C, preferably in the range of 50°C to 95°C, most preferably in the range of 75°C to 85°C. In one embodiment, the typical pressure is 100mmHg to 700mmHg, preferably 250mmHg to 700mmHg. Water is evaporated from the depolymerization liquid 1 until the depolymerization liquid has a solid content of about 50% to 80% by weight and a thick lubricating mixture with a mud-like viscosity. The evaporated water 0 is recovered for further use in the process.

[0036] The enriched mixture 2 is extracted with an organic solvent (step b) to obtain a liquid organic phase 3 and a solid phase 4. The liquid phase contains the organic solvent, the extracted ethylene glycol (EG), water and NaOH, and the solid phase 4 contains NaOH, Na 2 These include TPA, vat dyes such as indigo dyes and indigoid dyes (if present in the textile article). The organic solvent is a polar solvent and is preferably selected from methanol, ethanol, isopropyl alcohol, ethyl acetate and mixtures thereof. The preferred solvent is isopropanol.

[0037] The extraction is preferably carried out at room temperature. After extraction, the solid portion is preferably separated from the liquid phase by centrifugation, for example at 4500-5000 rpm, to obtain an undissolved solid portion 4 and a liquid organic phase portion 3. In one embodiment, the undissolved solid portion 4 is dried, for example in an oven at 60-70° C., to remove any organic solvents that may be present.

[0038] The liquid organic phase containing the solvent, EG, water and NaOH is recovered and evaporated under vacuum (preferably 250 mmHg to 700 mmHg) at 50°C to 80°C, preferably 65°C to 75°C to remove EG, solvent and water. The remaining solid contains NaOH6 with a purity of at least 60% by weight, usually at least 70% by weight. The remaining weight portion usually contains impurities such as polyester fragments or cellulose fragments that are not fully depolymerized. The NaOH thus obtained can be purified. The solid NaOH can be used to increase the NaOH content of the initial depolymerization liquid 1 without purification. Furthermore, it can also be used in the depolymerization reaction of blended fiber products, as previously disclosed with reference to Patent Document 2, without purification. The impurities resulting from this step do not affect the depolymerization process.

[0039] The liquid organic phase 5, comprising solvent 7, EG and water 8, is then distilled to separate the solvent 7 from the EG and water 8. Advantageously, the recovered solvent 7 is used in the extraction step b), i.e. again to extract the lubricating solid 2 obtained from step a) of the process. Preferably, the liquid portion 5 is distilled at 65° C. to 75° C., preferably at 82.5° C., to obtain the solvent 7 and the EG / water mixture 8. The ethylene glycol is recovered from the mixture 8 by methods known per se in the art, for example by fractional distillation, by separating the EG 15 from the water 14. The water 14 is advantageously reused in the process of the invention.

[0040] After extraction, the undissolved portion, i.e., Na 2 The mixture of TPA, NaOH, and dye is preferably dissolved in NaOH and Na2 The dye is treated with an aqueous alkaline solution having a pH sufficiently low to dissolve the TPA. A suitable pH range is between 9.5 and 11.0, preferably the pH is about 10. In this state, the insoluble vat dyes, particularly the indigo and indigoid dyes, are separated and recovered by filtration or centrifugation (step d). The separated dye 10 is washed several times with water and dried in an oven. The water used to wash the dye is recovered and reused in the process.

[0041] The purity of the vat dyes thus obtained is at least 95%. The purity of the dyes is measured by spectroscopy (UV-Vis). The purified dyes are suitable for reduction to a soluble, e.g. leuco, form for use in dyeing processes.

[0042] NaOH and TPA disodium salt (Na 2 To recover terephthalic acid (TPA) from the alkaline solution 11 containing TPA, the pH of this alkaline solution is altered in step e. Two possible methods for recovering TPA are provided:

[0043] In the first step (e2), TPA is precipitated in acid form by adding an acid such as HCl, acetic acid, sulfuric acid, etc. until the pH reaches about 2, and the precipitated TPA is separated, for example by filtration or centrifugation, and dried to obtain solid TPA 13'.

[0044] Alternatively, this process can be carried out by adding NaOH to the purified alkaline solution 11 to obtain Na 2 Advantageously, the method further comprises the step e1) of precipitating TPA. 2 Precipitation of TPA is achieved by adding concentrated NaOH solution until the NaOH concentration is 20 wt %.

[0045] Preferably, solid Na 2The TPA 13 is separated from the alkaline solution 11, for example by filtration or centrifugation, and washed several times with water. The remaining alkaline solution 16 contains water and NaOH and can be used for the depolymerization reaction of the blended fiber article.

[0046] The present invention is further disclosed with reference to the following examples, which are provided for illustrative and non-limiting purposes.

[0047] Example 1 2.5 L of the depolymerization solution with pH 13.29 and initial NaOH content of 3.06 wt.% (obtained from 25 consecutive cycles of the depolymerization process described in Patent Document 2) was evaporated under vacuum at 90° C. This process yielded a slurry-like solid with a weight of 708 g and a solid content of 62%. The desired components were extracted by a two-step extraction method using methanol and IPA. The amount of the solvent used was calculated as follows: Amount of solvent (ml) = Amount of solid (g) × 2.5 After extraction, the liquid and solid phases were separated by centrifugation at approximately 5000 rpm for 15 minutes. The recovered organic solvent was 94% of the initial solvent amount, and the dry solid was 37% of the initial solid amount. The solvent was then evaporated under vacuum at 70°C to obtain 98 grams (82% yield) of NaOH (65% purity). The recovered organic solvent (95% recovery) was distilled at 82.5°C, allowing the recovery of pure organic solvent for reuse in the extraction process. After distillation, the mixture of water and EG was further fractionated to separate 37.67 grams of EG. The solid residue obtained after extraction was dissolved in water at pH 10 and 4 grams of indigo dye was precipitated and collected by centrifugation. The purity of the dye was determined by spectroscopy (UV-Vis).The pH of the dissolved portion was adjusted to pH 2 with HCl and 100.87 grams of TPA was precipitated and recovered by centrifugation.

[0048] Example 2 The depolymerization solution, bleach solution and wash solution were collected and mixed after 30 cycles each in the process described in US Pat. No. 5,993,436. From the mixture, 2200 ml of solution was removed and concentrated to a slurry by vacuum evaporation at 90° C. After evaporation, 596 grams of solids with a solid content of 50% were obtained. The same procedure as described in Example 1 above was then carried out. The amounts of TPA, EG, NaOH and indigo dye recovered were 62.04 g TPA, 22.7 g EG, 58 g NaOH (62% purity, 85% yield) and 2.4 g indigo dye (solid, colored form, 96% purity), respectively. In conclusion, the present invention provides a method for the preparation of polyester monomers (TPA, Na 2 The present invention provides a process for recycling the liquid resulting from the depolymerization of polyester filaments in a blended fabric (i.e., depolymerization solution) to separate and recover the dimethyl ether (TPA, EG and other glycols), NaOH and indigo dyes or other vat dyes.

[0049] The present invention also provides a process for recovering vat dyes, particularly indigo dyes, from waste textiles. According to this embodiment, textiles, preferably waste textiles, are treated with an alkaline solution by passing a stream of the alkaline solution through the textile while maintaining the textile in a stationary state to remove the vat dye from the textile, and recovering or separating the insoluble vat dye from the resulting solution.

[0050] Typically, the alkaline solution is pumped through a vessel containing the waste textile product and circulated through the waste textile product several times. Suitable alkaline solutions for the removal process of vat dyes, preferably indigo dyes and indigoid dyes, are in particular the alkaline solutions as disclosed in paragraphs

[0004] to

[0006] . The pH of the suitable alkaline solutions is 10 to 14. The preferred concentration of NaOH in the solution is 33 g / L to 237 g / L NaOH, preferably 36 g / L to 43 g / L NaOH.

Claims

1. 1. A process for the recovery of NaOH, dye-containing polyester monomers resulting from alkaline depolymerization of polyester in blended textiles, comprising the steps of: providing an aqueous alkaline depolymerization solution (1) containing polyester monomers, NaOH, and optionally dyes; concentrating said aqueous alkaline depolymerization solution (1) to a concentrated mixture (2) containing water, solid NaOH, and solid and liquid products of the depolymerization reaction; extracting EG from said concentrated mixture (2) with an organic solvent; and modifying the pH of the solid portion (4) remaining from the extraction of EG in order to first dissolve TPA and then precipitate TPA as its sodium salt or acid.

2. a) evaporating a portion of the water from said aqueous alkaline depolymerization liquid (1) to obtain said concentrated mixture (2) containing a depolymerization reaction product; b) A liquid phase (3) containing EG, water and NaOH, and a mixture of NaOH, Na ２ extracting said concentrated mixture (2) with an organic solvent to obtain a solid fraction (4) containing TPA and, optionally, a dye; c) at least Na in the solid portion (4) ２ A step of dissolving TPA in an alkaline solution having a pH of 9.5 to 11.0, and causing a solid content (10) containing a dye to be present in the alkaline solution; d) separating the dye-containing solids (10) from the alkaline solution to obtain a purified alkaline solution (11) and a solid dye; e) precipitating TPA from the purified alkaline solution (11).

3. In addition, Na ２ 3. The process of claim 2, further comprising a step e1) of adding NaOH to the purified alkaline solution (11) to precipitate TPA (12).

4. The process for recovering chemical substances according to claim 2, further comprising the step e2) of adding HCl to said purified alkaline solution (11) to precipitate TPA (13').

5. The solid Na ２ The process for recovering chemical substances according to claim 3, characterized in that TPA (13) is separated from the purified alkaline solution, and the purified alkaline solution is used in the depolymerization reaction of blended fiber products.

6. 3. The chemical recovery process according to claim 1 or 2, characterized in that the organic solvent is selected from methanol, ethanol, isopropyl alcohol, ethyl acetate, and mixtures thereof.

7. The process for recovering chemical substances according to claim 1 or 2, characterized in that the organic phase (3) containing the solvent, EG, water and NaOH is evaporated to produce a liquid portion (5) and NaOH (6), which is used in the depolymerization reaction of the blended fiber product.

8. 8. Chemical recovery process according to claim 7, characterized in that the liquid portion (5) is distilled to produce a solvent (7) and a mixture of EG and water (8), said solvent being reused in the extraction step b).

9. The water evaporated from the aqueous alkaline depolymerization liquid (1) is added to the solid portion (4), and the Na in the solid portion (4) is ２ 3. The process for recovering chemical substances according to claim 1 or 2, characterized in that TPA is dissolved.

10. 3. The process for recovering chemical substances according to claim 1 or 2, characterized in that water is evaporated from the aqueous alkaline depolymerization liquid (1) under vacuum at a temperature below 100°C, so that the solid content of the resulting concentrated mixture (2) is 50-80% by weight.

11. 3. The chemical recovery process of claim 2, wherein the dye is a vat dye, and further comprising the steps of reducing the dye present in the solids of step d) of claim 2 to a soluble form in a reaction solution and filtering the remaining solids from the solution to recover the dye.

12. 1. A process for recovering vat dyes, particularly indigo dyes, from textile articles, comprising the steps of treating the textile article with an alkaline solution by passing a stream of alkaline solution through the textile article while maintaining the textile article in a static state, thereby removing insoluble vat dye from the textile article, and separating the insoluble vat dye from the resulting alkaline solution.

13. 13. The vat dye recovery process of claim 12, wherein said textile comprises polyester filaments, further comprising the steps of depolymerizing said polyester into corresponding polyester monomers and separating said monomers from said insoluble dye.

14. 14. The vat dye recovery process according to claim 12 or 13, wherein the alkaline solution is pumped through a vessel containing the waste textile product and circulated through the waste textile product multiple times.

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